Bulkhead insert for an internal combustion engine

An engine includes a cylinder block defining at least one main bearing bulkhead adjacent to a cylinder, and a crankshaft rotatably housed within the block by a main bearing. A bulkhead insert has a cap portion, and an insert portion provided within the bulkhead. The insert portion has having first and second end regions connected by first and second straps. Each strap having a flanged beam cross section. The first and second ends of the insert portion are configured to connect a main bearing cap column to a cylinder head column. Each of the first and second end regions define at least one protrusion having a surface substantially normal to engine combustion and reactive loads. The cap portion is configured to mate with the first end region at the main bearing cap column and support the main bearing.

TECHNICAL FIELD

Various embodiments relate to a bulkhead insert for an internal combustion engine.

BACKGROUND

An internal combustion engine has an engine block defining one or more cylinders. A cylinder head attaches to the block to form combustion chambers with the cylinders of the block. The block may form bulkheads between adjacent cylinders that provide structural support for the engine and separation between the cylinders. Typically, the engine block and the head are fastened or bolted together, for example, using head bolts that extend along and through head bolt columns. As the engine operates, the translational motion of the pistons within the cylinders is transformed into a rotational motion of a crankshaft. The crankshaft may be connected to the engine block and is supported for rotation by main crankshaft bearings. The crankshaft may be generally opposed to the engine head and may have a series of fasteners, such as main bearing bolts, that retain the crankshaft in the main bearings and adjacent to the block. As the engine operates, the head bolts and the main bearing bolts are loaded due to forces on the engine caused by combustion within the cylinders, and their corresponding reactive loads or forces. These forces may cause significant stress and fatigue on the engine and on the engine block.

SUMMARY

In an embodiment, an engine is provided with a cylinder block defining at least one main bearing bulkhead adjacent to a cylinder, and a crankshaft rotatably housed within the block by a main bearing. The engine has a bulkhead insert with an insert portion and a cap portion. The insert portion is provided within the bulkhead and having first and second end regions connected by first and second straps. Each strap has a flanged beam cross section. The first and second ends of the insert portion are configured to connect a main bearing cap column to a cylinder head column. Each of the first and second end regions define at least one protrusion having a surface substantially normal to engine combustion and reactive loads. The cap portion is configured to mate with the first end region at the main bearing cap column and support the main bearing.

In another embodiment, an engine main bearing structure is provided with a bulkhead insert for connecting a main bearing cap column to a head column. The insert has first and second ends connected by a pair of straps. Each strap has an I-beam cross-section. Each end defines at least one protrusion having a surface normal to engine combustion and reactive loads. The first end is shaped to support a crankshaft main bearing, and the second end is configured to receive head bolts.

In yet another embodiment, a method of forming an engine includes providing a bulkhead insert in a tool. The bulkhead insert is configured to connect a main bearing cap column to a cylinder head column and has first and second straps. Each strap has a flanged beam cross section. The insert defines protrusions having surfaces substantially normal to engine combustion and reactive loads. An engine block is formed having a bulkhead containing the bulkhead insert in the tool.

DETAILED DESCRIPTION

In various examples, an internal combustion engine is provided with an insert positioned within a bulkhead region of a cylinder block. The bulkhead insert provides additional structural strength to the engine by directly connecting the head bolt column to the main bearing column, or the engine head bolts to the main bearing bolts. The bulkhead insert may be provided with members such as straps that extend between the head bolts and the main bearing bolts. The straps may have an I-beam cross-section, or another flanged, beam cross-section that provides an increased load carrying capability. The two straps of the insert may be connected to one another by an arch connection that provides a continuous connection between the straps for even load distribution. The arch connection may be without a corner or similar discontinuity that would otherwise provide additional stress points in the insert.

The structure of the insert provides for compact packaging for use in the engine block, while enabling higher loads to be carried through the insert compared to the bulkhead alone. As engine design moves towards smaller block sizes and more compact structures, the size of an insert also decreases and the corresponding packaging constraints on the bulkhead insert increases. As engine design moves towards weight reduction, the engine block may be made from alternative materials such as an aluminum alloy, a composite material, and the like. The bulkhead insert may be made from a different material from the block, e.g. an iron alloy, to provide the desired strength for the engine and act as the primary load carrying structure within the bulkhead and between the head bolts and main bearing bolts, while being sized for the limited packaging space.

The bulkhead insert may be provided with additional structural features that provide surfaces that are inclined relative to or generally normal to the combustion and reactive forces within the engine during operation to absorb these loads into the insert along the natural load path and dissipate the loads from concentrating in localized areas near the main bearing cap bolt column or boss and the head bolt column or boss. In one example, the bulkhead insert is provided as a near-net-shape, cast, ferrous insert that is positioned within an engine block die for an aluminum casting. The insert provides support for the crankshaft main bearing, and is fracture split to also provide the main bearing cap.

The insert provides a tie strap configuration to connect the head bolt columns to the main bearing cap columns. This insert then becomes a cast-in-place bulkhead insert of which the combustion loads are carried through the stronger insert material opposed to the bulkhead of the block. The insert provides increased load carrying capabilities. A conventional cylinder block bulkhead width is defined by peak combustion loads that the bulkhead and the crank main journal connection need to carry in addition to a safety factor for block durability and life. The engine block provides a packaging constraint with cylinder bore size and cylinder bore spacing. A cast-in-place bulkhead insert according to the present disclosure nests within the bulkhead width in the fore-aft direction known as the crank axis or longitudinal axis of the engine, and is partially encapsulated within the block bulkhead width starting from centerline of crank bore upwards to cover the entire head bolt column end and connecting strap of the insert. The insert also provides main bearing bolt columns that are integrated into the bulkhead insert. The size and shape of the connecting strap and insert provides an increased load carrying member for the bulkhead. The shape of the connecting strap of the insert may be further constrained based on packaging of the cylinder block lubrication circuit. Additionally, the insert provides the needed strength for smaller, compact engine block designs with narrower bulkheads.

FIG. 1illustrates a schematic of an internal combustion engine20. The engine20has a plurality of cylinders22, and one cylinder is illustrated. The engine20may include multiple cylinders arranged in various manners, including an inline configuration and a V-configuration. The engine20has a combustion chamber24associated with each cylinder22. The cylinder22is formed by cylinder walls32and piston assembly34. The piston assembly34is connected to a crankshaft36. The combustion chamber24is in fluid communication with the intake manifold38and the exhaust manifold40. An intake valve42controls flow from the intake manifold38into the combustion chamber30. An exhaust valve44controls flow from the combustion chamber30to the exhaust manifold40. The intake and exhaust valves42,44may be operated in various ways as is known in the art to control the engine operation.

A fuel injector46delivers fuel from a fuel system directly into the combustion chamber30such that the engine is a direct injection engine. A low pressure or high pressure fuel injection system may be used with the engine20, or a port injection system may be used in other examples. An ignition system includes a spark plug48that is controlled to provide energy in the form of a spark to ignite a fuel air mixture in the combustion chamber30. In other embodiments, other fuel delivery systems and ignition systems or techniques may be used, including compression ignition.

The engine20includes a controller and various sensors configured to provide signals to the controller for use in controlling the air and fuel delivery to the engine, the ignition timing, the power and torque output from the engine, and the like. Engine sensors may include, but are not limited to, an oxygen sensor in the exhaust manifold40, an engine coolant temperature, an accelerator pedal position sensor, an engine manifold pressure (MAP sensor, an engine position sensor for crankshaft position, an air mass sensor in the intake manifold38, a throttle position sensor, and the like.

In some embodiments, the engine20is used as the sole prime mover in a vehicle, such as a conventional vehicle, or a stop-start vehicle. In other embodiments, the engine may be used in a hybrid vehicle where an additional prime mover, such as an electric machine, is available to provide additional power to propel the vehicle.

Each cylinder22operates under a four-stroke cycle including an intake stroke, a compression stroke, an ignition stroke, and an exhaust stroke. In other examples, the engine may operate using a two-stroke cycle. During the intake stroke, the intake valve42opens and the exhaust valve44closes while the piston assembly34moves from the top of the cylinder22to the bottom of the cylinder22to introduce air from the intake manifold to the combustion chamber. The piston assembly34position at the top of the cylinder22is generally known as top dead center (TDC). The piston assembly34position at the bottom of the cylinder is generally known as bottom dead center (BDC).

During the compression stroke, the intake and exhaust valves42,44are closed. The piston34moves from the bottom towards the top of the cylinder22to compress the air within the combustion chamber24.

Fuel is then introduced into the combustion chamber24and ignited. In the engine20shown, the fuel is injected into the chamber24and is then ignited using spark plug48. In other examples, the fuel may be ignited using compression ignition.

During the expansion stroke, the ignited fuel air mixture in the combustion chamber24expands, thereby causing the piston34to move from the top of the cylinder22to the bottom of the cylinder22. The movement of the piston assembly34causes a corresponding movement in crankshaft36and provides for a mechanical torque output from the engine20. The combustion process causing the expansion stroke results in loads and forces on the engine20. A force on the engine caused by the combustion event in the chamber24imparts a force on the face50of the piston34, and at least a portion of the force travels down the connecting rod52to the main bearing and crankshaft36. This force on the main bearing may be referred to as a reactive force. The combustion event within the chamber24also causes a force on the cylinder head62, which loads attachment points, such as head bolts, between the engine head62and a cylinder block60. The force on the cylinder head and head bolts may be referred to as a combustion force.

During the exhaust stroke, the intake valve42remains closed, and the exhaust valve44opens. The piston assembly34moves from the bottom of the cylinder to the top of the cylinder22to remove the exhaust gases and combustion products from the combustion chamber24by reducing the volume of the chamber24. The exhaust gases flow from the combustion cylinder22to the exhaust manifold40and to an aftertreatment system such as a catalytic converter.

The intake and exhaust valve42,44positions and timing, as well as the fuel injection timing and ignition timing may be varied for the various engine strokes.

The engine20may have a cylinder block60that forms the cylinders22. A cylinder head62is connected to the block60. The head62encloses the combustion chamber24and also supports the various valves42,44, and intake and exhaust systems38,40. A head gasket or another sealing member may be positioned between the block60and the head62to seal the combustion chamber24.

FIG. 2illustrates a portion of the engine20according to an example. The engine20is illustrated as an in-line, three cylinder engine, although other configurations are also contemplated. The engine20is shown as a sectional view with the section line taken in a plane through the rotational axis of the crankshaft.

The engine block60is shown with a deck face70that is configured to mate with a corresponding deck face of a cylinder head62or a head gasket. The block60has attachment features72to connect the cylinder head62. In the example shown, the cylinder head62is connected to the block60using fasteners such as cylinder head bolts into threaded bores in head bolt columns72.

A bulkhead74is formed by the block60between adjacent cylinders22and between a cylinder22and end of the block60. The bulkhead74typically has a pair of cylinder head columns72associated with it, although only one is shown in the present Figure due to the view.

An insert80is provided in the bulkhead74of block60. The insert80provides a support structure for a main bearing for a crankshaft36. The insert80has a main bearing cap82(or cap portion) that attaches to a cap end region84of the insert80to encircle a main bearing and rotatably support the crankshaft36. The pistons of the engine20may be connected to the crankshaft36between the main bearing caps82.

The insert80has attachment features86to connect the main bearing cap82to the cap region84. In the example shown, the main bearing cap82is connected to the remainder of the insert80using main bearing bolts into threaded bores in main bearing bolt columns86. These main bearing bolt columns86may also be provided in or adjacent to the bulkhead74of the engine20.

A crankcase (not shown) may be provided and is connected to the block60to generally enclose the crankshaft, contain lubricant, etc. The crankcase is generally opposed to the deck face70in the present example, as the crankshaft is generally opposed to the cylinder head.

FIG. 3illustrates a cross sectional view of the engine20taken through the bulkhead74. The block60is formed with a bulkhead insert80within the bulkhead74. The insert80may be formed as a single integral component and then divided or split after the block60is cast or formed, or before the block60is formed. The insert80has an insert portion90and a cap portion82. The insert portion90is generally provided within the bulkhead74and has a first end region84(or cap end region) and a second end region92. The first and second end regions84,92are connected by first and second straps94,96.

The insert80has a main bearing cap82or cap portion82. The cap portion82has a surface98that is shaped to support at least a portion of a main bearing100for a crankshaft36. The end region84of the insert portion90also has a surface102that is shaped to support another portion of the main bearing100for the crankshaft36. The surfaces98,102encircle the main bearing100. The cap82connects and mates with the end region along part line162.

The first and second end regions84,92of the insert80are configured to provide a connection between the main bearing cap columns86and the cylinder head columns72.

The cap portion82and the end region84of the insert portion90define an attachment feature106for each main bearing cap column86. In the present example, the attachment feature106is a bore, such as a tapped bore, that is sized to receive a main bearing bolt or other fastener to connect the cap portion82to the insert portion90. All or a portion of the bore may be tapped. Tapped regions of the bore may be located in both portions82,90, or only in one portion90. Therefore, the main bearing bolts connect only to the insert80and any loads are transferred directly through the insert. Loads on the remainder of the block60may therefore be indirect.

The end regions92of the insert portion90define an attachment feature108for each cylinder head column72. In the present example, the attachment feature108is a bore, such as a tapped bore, that is sized to receive a head bolt or other fastener to connect the cylinder head62to the insert portion90and the block60. The attachment feature108may extend from the deck face70though the bulkhead74and to the insert80. The attachment feature108also extends upwardly though a corresponding cylinder head62. All of the bore may be tapped or only a portion of the bore may be tapped. Tapped regions of the bore may be located in both portion90and the block60, or only in one portion90. Therefore, the head bearing bolts connect only to the insert80and any loads are transferred directly through the insert. Loads on the remainder of the block60may therefore be indirect.

A force is imparted on the engine due to a combustion event in the combustion chamber24of the engine20. Due to the combustion event, the head bolts108experience a reactive force, shown by arrows132, opposing the combustion force, as the fasteners108are connecting the cylinder head to the cylinder block. Due to the combustion event, reactive forces132load the fasteners which are threaded into the end region92of the insert portion90of the insert80. The force travels through the first and second straps94,96of the insert portion90where the combustion force reacts on the cap portion82of the main bearing. The combustion force or load is imparted onto the main bearing shell and main bearing cap portion82, and is generally shown by arrow134. Main bearing bolts86or main bearing cap fasteners apply a clamp load by threading into bulkhead insert along the main bearing column and oppose the force134.

FIG. 4illustrates a perspective view of the insert80. As can be seen fromFIGS. 3-4, the insert80has a series of surface features110on the first end region84. The surface features110may be a series of protrusions, teeth, or serrations. Each protrusion110has a surface112that is inclined to and/or is substantially normal to engine combustion and reactive loads. The orientation of these surfaces112assists in the transfer of loads to the insert80.

The insert80also has a series of surface features114on the second end region84. The surface features114may be a series of protrusions, teeth, or serrations. Each protrusion114has a surface116that is inclined to and/or is substantially normal to engine combustion and reactive loads. The orientation of these surfaces116assists in the transfer of loads to the insert80.

As can be seen fromFIG. 4, the surface features110,114may have depth to them such that they extend along the longitudinal axis122of the engine20. The longitudinal axis122is illustrated inFIG. 3, and extends through the centers of adjacent cylinders in engine20according to the present example. The transverse axis124and vertical axis126are also illustrated. The vertical axis may or may not be aligned with a gravitational force on the engine20.

The faces or normal surfaces112,116may be generally or substantially parallel with one another. In other examples, the faces112,116may be angled or inclined relative to one another.

In further examples, the surface features110,114may be positioned in other locations on the insert80. The surface features110,114may also be provided in other shapes and dimensions. The surface features110,114may be other macro-tribology surface features, and may include various specified roughnesses. Alternatively, the insert80may have serrations110,114as well as additional macro-tribology surface features to stabilize against engine combustion and reactive loads during engine operation and use.

In further examples, only one set of surface features110,114may be provided, or more than two sets may be provided. The surface features are illustrated as being similar to one another on either side of the first end region and on either side of the second end region; however, the surface features may vary in size, shape, and number in various locations on the insert80.

The insert80may be provided with a drilled or otherwise formed passage for engine fluids. For example, passage120is formed in the insert80to provide flow of a lubricant to the main bearing100.

Referring generally toFIGS. 3-5, the straps94,96extend outwardly from the first end region84and generally away from one another. The straps94,96may form a symmetrical or asymmetrical V-shape for example. A portion of the second end region92is provided at an end of each strap94,96and includes the cylinder head bolt columns108.

The straps94,96are illustrated as being asymmetrical, and this configuration may be used for an engine20having an offset crankshaft. An offset crankshaft is a crankshaft36that is offset from the centerline of the cylinders, or offset from axis122. For an offset crankshaft, each straps94,96may have a different length, different shape or arch, and different cross-sectional area or shape. The straps94,96need to generally carry the same load between the end region84and a respective head bolt column108, and the straps94,96are dimensioned to carry substantially equal loads. For example, with an offset crankshaft36, one strap may need to be dimensioned differently than the other strap based on the load path being angled. The straps94,96may also need to have varying dimensions from one another due to torsional forces during engine operation, such as those caused by twist in the crankshaft36.

The insert80may be provided with a continuous arch130extending between the two straps94,96. This continuous arch130is adjacent to the first end region84of the insert80. The continuous arch130is provided to reduce or eliminate steps, corners, or other discontinuities that may cause a stress point in the insert80leading to fatigue, cracking, and other issues under repeated load and engine use. The arch130structure provides for a smooth load distribution and load path through the insert80.

FIG. 5illustrates a cross sectional view of the insert80taken in a plane parallel to axes122,124, and illustrates the cross-section of the straps94,96. As shown inFIG. 5, the cross-sectional area of one strap is substantially equal to a cross-sectional area of the other strap. In other examples, the cross-sectional areas of each strap94,96may be different from one another.

The straps94,96are illustrated as having a flanged, beam-shaped cross-section, and in the example shown, have an I-beam cross-section. Although an I-beam is a preferred cross-section, other beam sections may be used and include a C-shaped beam shape, an L-shaped beam shape, a T-shaped beam shape, and the like. The flanged beam cross-section is used for the straps94,96to increase the strength of each member. Without this shape, the straps94,96may have insufficient strength as the cross-sectional area is limited by the packaging constraints of the engine and the narrow bulkhead region74.

The I-beam shapes of each strap94,96have a center section140with a first end flange142and a second end flange144. The center section140connects to an intermediate region of each of the end flanges142,144. The I-beams are illustrated as being generally symmetrical; however the I-beams may be asymmetrical with one or more of the sections140,142,144connected at an offset relative to the other.

The beam shape for each strap94,96may be same or may vary from one another. For example, the center sections140may have the same or different lengths or widths, the end flanges may have the same or different lengths and widths, and/or the center sections140may connect to each end flange142,144at the same or different points.

FIG. 6illustrates a process or a method150for forming and/or assembling an engine, such as engine20according to an embodiment. Various embodiments of the method150may include greater or fewer steps, and the steps may be performed in another order than illustrated.

An insert80is formed at step152. In the example shown, the insert80is cast and comprises iron, a ferrous alloy, and the like. In other examples, the insert80is formed from another suitable material with a greater strength than the block60material. The insert80may be cast using a near net shape casting process, and may be cast using a high pressure or low pressure process. The insert is formed with the surface features and tribology features as described above, and in further examples, additional surface features may be provided by a machining process or the like. The insert80is also formed with various touch points and locators appropriate for the method of engine block60manufacture as described below. In other examples, the insert80may be formed using other appropriate manufacturing techniques, including, but not limited to, casting, powder metallurgy techniques, forging, machining, die casting and heat treating, etc.

The insert80is positioned within a tool for forming the engine block60at step154. The tool is provided according to the manufacturing technique for the engine block60, and may include various dies, molds, slides, and the like. The tool may also include various inserts or cores to provide other features of the block60. The insert may be coated before being placed in the tool to provide an improved bond with the block60. The insert may also be machined or cubed, etc. before placement in the tool.

The engine block60is formed at step156. The engine block60is formed according to the manufacturing technique appropriate for the primary material of the block60. In one example, the engine block60is cast as an aluminum or aluminum alloy around the insert(s)80as a casting process. The engine block60may be cast using a high pressure casting process or a low pressure casting process, and may be a sand casting, a die casting, and the like. In another example, the engine block is molded or injection molded as a composite material around metal insert(s)80.

As can be seen from the description, the insert80is typically formed of a different material than the block60. The insert80may be formed from a higher strength material, while the block60may be formed from a material with reduced weight, higher thermal conductivity, and the like. The structure of the insert80may additionally allow for a lower strength material, lighter block60to be provided than would otherwise be available in an engine without insert(s)80in the bulkhead(s).

The block60is removed from the tool and may be machined or otherwise post-processed at step158to form various features of the block60. For example, the block60may be machined to form the deck face70, etc. Additionally, the block60may be machined, or drilled and tapped, to form the head bolt bores into the block and insert. The insert80may be machined, or drilled and tapped, to form the main bearing cap bores. The block and insert may be machined to form various cooling or lubrication passages in the engine20, such as passage120.

The insert80is split or divided at step160to form the insert portion90and the cap portion82. In one example, the insert80is fracture split, which may include forming a fracture line or locator using a process such as laser etching or scoring. The insert80is cranked or split after the fracture split line is defined. After the split, the insert80has a cap portion82and an insert portion90with mating surfaces formed by the split that mate along the split line162as shown inFIGS. 3 and 4. The split line162may be linear, non-linear, symmetric, asymmetric, or otherwise shaped.

By splitting the insert80after the block60has been formed and by forming the block material generally up to where the fracture line162is going to be placed, several advantages are realized, which include removing a saddle and lock width machining process that is typically present with a fracture split design, and eliminating bi-material machining which causes shortened tool life, and has the potential for increased scrap rates.

As the insert portion90and the cap portion82are formed from the same material, the engine20may operate with reduced noise, vibration, and harshness as the two components have a common coefficient of thermal expansion.

Although the surface features and macro-tribology features are positioned on the insert80to interact with combustion and reaction loads during engine operation, they may also have a secondary benefit of stabilizing the insert80within the block60, and maintaining the bond between the insert portion90and the block60while the insert80is being split and machined.

After the insert80is split, additional machining may be conducted, for example, to machine the bore for the crankshaft bearing, e.g. to machine surfaces98,102.

In addition to a straightforward split of the insert80as shown, it is also envisioned that the split may include the addition of a groove on the cap portion82and a mating protrusion on the insert portion90, or vice versa. The groove and protrusion would mate when the insert80is reassembled to assist in locating the cap portion82when the main bearing fasteners are inserted, and may also assist the main bearings in any torsional or side loads on the cap portion82.

The engine20is assembled at step162, and may include placing the engine20into a vehicle. The cylinder head62is connected to the block60using head bolts connected to the insert80at attachment points108. The main bearings and crankshaft36are positioned within surface102, and the cap portion98is then located. The main bearing bolts are used to connect the cap portion82to the insert portion90via attachment points86. The insert80is therefore mechanically connected or fastened to both the head bolts and main bearing bolts to provide a load path therebetween.