Cylinder head assembly and axially located igniter sleeve for same

A cylinder head assembly includes a cylinder head having a top deck, a fire deck, and an igniter post extending upward from the fire deck. An igniter sleeve is within an igniter bore in the cylinder head and includes a locating surface clamped against an upward facing stop surface of the cylinder head. A tip coolant clearance is defined axially between a sleeve tip and the fire deck, and a body coolant clearance is defined peripherally between the igniter sleeve and the cylinder head and is continuously circumferential of the igniter sleeve axially between the sleeve tip and a coolant cavity formed in the cylinder head.

TECHNICAL FIELD

The present disclosure relates generally to an igniter sleeve, and more particularly to locating and supporting an igniter sleeve in a cylinder head assembly.

BACKGROUND

Internal combustion engines are well-known and in widespread use throughout the world for diverse purposes such as vehicle propulsion, production of rotational power in a great many machines, and electrical power generation. Most modern internal combustion engines include a cylinder block having combustion cylinders therein, and a cylinder head that includes intake and exhaust conduits, and valves controlling the opening and closing of the intake and exhaust conduits. Depending upon the engine type, an igniter such as a sparkplug, a prechamber sparkplug or another prechamber ignition device, may be supported in the cylinder head. Spark-ignition technologies are often used in gaseous fuel or gasoline engines. The internal geometry of the cylinder head is commonly complex to provide multiple coolant passages for conveying a coolant through the cylinder head to dissipate heat from combustion, including dissipating heat from sparkplugs or other ignition devices.

Cylinder head geometry, materials, and construction generally, have been varied in many ways over the years in efforts to optimize cooling efficacy. Where components overheat, various problems in the nature of cracking, thermal fatigue, combustion problems, and even seizure of moving parts or melting of materials can occur. Poor cooling efficacy can limit the manner in which an engine can be operated, or enhance it if efficacy is high. Certain modern engines are desirably relatively power dense, and inferior capacity for heat rejection can limit the available engine power output, for example.

U.S. Pat. No. 10,385,800 to Hyde et al., commonly owned, is directed to a cylinder head assembly, cylinder head, and method. Hyde et al. propose a cylinder head assembly including an igniter mount and a sleeve abutting the igniter mount within an igniter bore, such that the sleeve and cylinder head form an igniter cooling passage or moat circumferential of the igniter mount. The disclosed configuration apparently improves heat dissipation and reduces likelihood of pre-ignition. While Hyde et al. may have various applications, there is always room for improvement and development of alternative strategies.

SUMMARY

In one aspect, a cylinder head assembly includes a cylinder head having a top deck, a fire deck, an igniter post extending upward from the fire deck, an upward facing stop surface arranged axially between the top deck and the fire deck, a coolant cavity formed between the top deck and the fire deck, and an igniter bore defining a bore center axis and including an upper bore section extending through the top deck, and a lower bore section formed in the igniter post. The cylinder head assembly further includes an igniter sleeve having an upper sleeve end within the upper bore section, a lower sleeve end positioned upon the igniter post and having a sleeve tip, and a locating surface clamped against the upward facing stop surface. A tip coolant clearance is defined axially between the sleeve tip and the fire deck and extends circumferentially around the igniter post. A body coolant clearance is defined peripherally between the igniter sleeve and the cylinder head, and the body coolant clearance is continuously circumferential of the igniter sleeve axially between the sleeve tip and the coolant cavity.

In another aspect, an igniter sleeve includes an elongate sleeve body defining a center axis extending between an upper sleeve end and a lower sleeve end having a sleeve tip. The elongate sleeve body includes a cylindrical body wall between the upper sleeve end and the lower sleeve end, a conical body wall within the lower sleeve end and having an inner igniter clamping surface, and a cylindrical tip wall forming a tip opening extending through the sleeve tip. The elongate sleeve body further includes a seal shoulder, and a seal groove formed adjacent to the seal shoulder and circumferential of the center axis, a locating surface axially between the seal shoulder and one of the upper sleeve end or the lower sleeve end and structured to clamp against an upward facing stop surface in a cylinder head, and a downward facing tool engagement surface.

In still another aspect, an igniter sleeve includes an elongate sleeve body defining a center axis extending between an upper sleeve end and a lower sleeve end including a sleeve tip. The elongate sleeve body includes a cylindrical body wall between the upper sleeve end and the lower sleeve end, a conical body wall adjoining the cylindrical body wall and located within the lower sleeve end, and a cylindrical tip wall adjoining the conical body wall and forming a tip opening extending through the sleeve tip. Each of the cylindrical body wall, the conical body wall, and the cylindrical tip wall is axisymmetric about the center axis. The elongate sleeve body further includes a peripheral shoulder, and a downward facing locating surface upon the peripheral shoulder.

DETAILED DESCRIPTION

Referring toFIG.1, there is shown an internal combustion engine system10, according to one embodiment. Engine system10includes an engine12having an engine housing14with a plurality of combustion cylinders16formed therein. A plurality of pistons18are within cylinder16and coupled with a crankshaft20in a generally conventional manner. Cylinders16can include any number in any suitable arrangement such as an inline pattern, a V-pattern, or still another. Engine system10may further include a fuel supply (not shown) which may be a gaseous fuel supply having a stored volume of a gaseous fuel, such as cryogenically stored natural gas with attendant vaporization and pressurization equipment, a stored volume of pressurized gas, or various other gas supply configurations such as connections to a line gas supply or the like. Suitable gaseous fuels can include not only natural gas but also methane, ethane, mine gas, landfill gas, biogas, or still others. In other embodiments, engine system10could be a liquid fuel arrangement, a dual fuel arrangement, or still another. In a practical implementation strategy engine system10can be prechamber spark-ignited, however, other spark-ignition strategies or compression-ignition strategies could be employed in different embodiments. Engine system10can be deployed in any application, including for electrical power generation, operation of a pump or a compressor, or for vehicle propulsion, to name a few examples.

Engine12further includes a cylinder head assembly22attached to engine housing14, and a head gasket26sandwiched between cylinder head assembly22and engine housing14. Cylinder head assembly22includes a cylinder head24and may be one of a plurality of substantially identical cylinder heads24each associated with one cylinder16. In other arrangements, cylinder head assembly22could include a slab cylinder head associated with multiple cylinders according to generally known configurations. Coolant channels28fluidly connect between engine housing14and cylinder head24to convey a flow of liquid engine coolant through cylinder head24for cooling of components therein. Engine valves30are supported in cylinder head24, and are visible in the counterpart cylinder head assembly shown on the right side of the drawing inFIG.1. Description and discussion herein of operation or structure of any one element in the singular should be understood to refer by way of analogy to similar elements in analogous components. Moreover, description or discussion of any one embodiment is to be understood to refer by way of analogy to any other embodiment except where stated otherwise or apparent from the context.

Engine valves30will typically be actuated to operate engine system10in a conventional four-cycle pattern, and in an implementation include two conventionally operated exhaust valves and two conventionally operated intake valves per cylinder, as will be familiar to those skilled in the art. As will be further apparent from the following description, engine system10generally, and cylinder head assembly22in particular, is uniquely configured for efficient installation and removal of certain components as well as improved cooling efficacy as compared to certain known designs.

Cylinder head assembly22further includes an igniter sleeve38having an igniter40supported therein. Igniter40may include a prechamber sparkplug igniter, having a prechamber tip42within cylinder16with one or more outlets46formed therein that communicate flame jets to cylinder16to ignite a main charge of fuel therein. A main gaseous fuel charge can be delivered by way of fumigation, port injection, direct injection, or combinations of these. One or more spark electrodes44are within prechamber tip42to produce a spark that ignites a mixture of fuel and air in prechamber tip42. In a practical implementation, a prechamber ignition charge of fuel and air is pushed into prechamber tip42in response to movement of piston18toward a top dead center position in cylinder16. In other embodiments, a prechamber sparkplug or other prechamber ignition device could be directly supplied with a fuel and/or air for prechamber ignition.

Referring also now toFIG.2, cylinder head24includes a top deck48, a fire deck50, and an igniter post52extending upward from fire deck50. Igniter post52supports and positions igniter sleeve38, as further discussed herein. Cylinder head24further includes an upward facing stop surface54arranged axially between top deck48and fire deck50. The term “axially” in this instance refers to directions along a common axis of cylinder head24and igniter sleeve38, later described. Cylinder head24also includes a coolant cavity56formed between top deck48and fire deck50, and an igniter bore58defining a bore center axis60and including an upper bore section62extending through top deck48, and a lower bore section64formed in igniter post52. A plurality of exhaust conduits66are also provided in cylinder head24and extend through coolant cavity56to intake and exhaust openings in fire deck50to enable an exchange of heat with coolant circulated therein. Igniter post52can include a generally cylindrical upwardly projecting protrusion formed by casting and/or machining in cylinder head24and centered on bore center axis60. Igniter sleeve38may likewise be centered on bore center axis60.

Referring also now toFIG.3, igniter sleeve38includes an upper sleeve end68within upper bore section62, and a lower sleeve end70positioned upon igniter post52and having a sleeve tip72. Sleeve tip72includes a tip axial end surface74. Igniter sleeve38is also understood to include an elongate sleeve body88defining a center axis90extending between upper sleeve end68and lower sleeve end70and colinear with bore center axis60. Elongate sleeve body88may also include a cylindrical body wall92between upper sleeve end68and lower sleeve end70, a conical body wall94within lower sleeve end70and adjoining cylindrical body wall92, and having an igniter clamping surface96against which igniter40is clamped when cylinder head assembly22is assembled for service. Elongate sleeve body88may also include a cylindrical tip wall98adjoining conical body wall94and forming a tip opening100extending through sleeve tip72, with cylindrical tip wall98positioned peripherally and circumferentially around igniter post52. Cylindrical body wall92, conical body wall94, and cylindrical tip wall98may be axisymmetric about center axis90. Cylindrical tip wall98may be interference-fitted with igniter post52in some embodiments, with the interference fit forming a combustion seal. During assembly, igniter sleeve38can be heated prior to installation upon igniter post52to enable formation of an interference fit by shrink fitting. Analogously igniter post52could be chilled prior to installation of igniter sleeve38thereon to facilitate formation of an interference fit, according to known principles.

Igniter sleeve38and elongate sleeve body88, referred to at times interchangeably herein, may include an inner sleeve surface102sized and shaped to complimentarily accept igniter40, and an outer sleeve surface104, much of which is directly exposed to a flow of coolant through coolant cavity56as further discussed herein. Outer sleeve surface104and inner sleeve surface102are each in part upon cylindrical body wall92, conical body wall94, and cylindrical tip wall98, and oriented parallel to one another upon the respective walls92,94and98. Igniter sleeve38further includes a locating surface76clamped against upward facing stop surface54. Locating surface76defines an axial positioning of igniter sleeve38in cylinder head24, such that igniter sleeve38can be installed downwardly into cylinder head24until locating surface76contacts upward facing stop surface54to establish a positioning of igniter sleeve38for service in cylinder head24.

It can also be seen fromFIG.2that a tip coolant clearance78is defined axially between sleeve tip72and fire deck50and extends circumferentially around igniter post52. Tip coolant clearance78may form, or be part of, a coolant moat that enables coolant to flow in direct heat transference contact with igniter sleeve38and igniter post52to dissipate heat of fire deck50, igniter40, igniter post52, and igniter sleeve38. The flow of coolant into and through tip coolant clearance78can be an active pumped flow such as with dedicated coolant channels or holes opening to or near tip coolant clearance78, or by way of passive flow based on fluid connection with coolant cavity56. It can also be noted a body coolant clearance80is defined peripherally between igniter sleeve38and cylinder head24. Body coolant clearance80may be continuously circumferential of igniter sleeve38axially between sleeve tip72and coolant cavity56in some embodiments to provide an unobstructed upward flow of coolant.

In the embodiment illustrated inFIGS.1-3, locating surface76is a downward facing outer igniter sleeve surface, thus part of outer sleeve surface104, and spaced axially from sleeve tip72. In other embodiments locating surface76could be positioned elsewhere, and could be part of sleeve tip72. Downward facing means generally facing a direction of fire deck50, not necessarily directly or solely downward facing. Also in the embodiment illustrated inFIGS.1-3locating surface76engages with upward facing stop surface54formed in or near top deck48. In other embodiments a mid-deck region could be provided in cylinder head24and could include an upward facing stop surface. In still other instances an upward facing stop surface could be formed near, or potentially as part of, fire deck50. Body coolant clearance80fluidly connects tip coolant clearance78to other parts of coolant cavity56and thus enables coolant flow to be substantially in pervasive heat transference contact with outer surface104of igniter sleeve38vertically upward to such point at which outer surface104is obscured within or sealed from top deck48within upper bore section62. It can also be noted inFIGS.2and3in particular that igniter sleeve38includes a peripheral shoulder82and locating surface76is formed on peripheral shoulder82. Igniter sleeve38may also include one or more seal shoulders84defining one or more seal grooves86adjacent to respective seal shoulders84. Seal grooves86may be equipped with O-ring seals, and peripheral shoulder82may be located axially between the one or more stop shoulders84and lower sleeve end70. Depending upon the construction of an igniter sleeve a peripheral shoulder with a locating surface formed thereon may be located axially between one or more seal shoulders and an upper sleeve end.

Referring now toFIG.4, there is shown an igniter sleeve138according to another embodiment, and including an upper sleeve end168and a lower sleeve end170. Igniter sleeve138includes a locating surface176upon a peripheral shoulder182. Igniter sleeve138also includes a seal shoulder184and a seal groove186formed adjacent to seal shoulder184. An O-ring seal187is within seal groove186. Igniter sleeve138also includes internal threads189functioning as tool engagement surfaces that can be engaged by a removal tool to withdraw igniter sleeve138from a cylinder head. In igniter sleeve138peripheral shoulder182is located axially between seal shoulder184and lower sleeve end170. Internal threads189may include downward facing tool engagement surfaces as contemplated herein.

Referring now toFIG.5, there is shown an igniter sleeve238according to another embodiment. Igniter sleeve238includes a locating surface276that engages against a stop surface254. Stop surface254is formed on igniter post252. A suitable O-ring seal, another type of seal such as a gasket seal, or a metal-metal seal could be formed by or between locating surface276and stop surface254.

Referring now toFIG.6, there is shown an igniter sleeve338according to yet another embodiment. Igniter sleeve338includes a sleeve tip372, and an inside seal groove373formed in an inner surface of sleeve tip372. A sealing element375, such as an O-ring seal, is between sleeve tip372and igniter post352and forms a combustion seal. Sealing element375can be understood as radially between sleeve tip372and igniter post352, whereas in other embodiments a sealing element could be positioned axially between a respective sleeve tip and igniter post.

Referring now toFIG.7, there is shown an igniter sleeve438according to yet another embodiment. Igniter sleeve438includes a sleeve tip472positioned upon an igniter post452, and engaged by way of internal threads453of sleeve tip472and external threads455of igniter post452. In this embodiment igniter sleeve438can be threaded into engagement with igniter post452, with a combustion seal being formed as a metal-metal seal between the threads of the respective components, or by way of a separate sealing element radially or axially between the respective components.

Referring now toFIG.8, there is shown an igniter sleeve538according to yet another embodiment. Igniter sleeve538is positioned upon an igniter post452and includes a sleeve tip572attached to and sealed with igniter post552by way of a weld577. Weld577can include mixed solidified materials of igniter sleeve538and igniter post552, such as may be achieved by laser welding or another type of welding peripherally around the mated interface of sleeve tip572and igniter post552.

Referring now toFIG.9, there is shown an igniter sleeve638according to yet another embodiment. Igniter sleeve638includes an upper body section639having external threads655formed thereon. A cylinder head624includes internal threads653mated with external threads655. An igniter post652of cylinder head624receives a sleeve tip672, and a combustion seal679such as a gasket is sandwiched between igniter sleeve638and an igniter post652. Engagement of internal threads653and external threads655clamps igniter sleeve638into cylinder head624.

Referring now toFIG.10, there is shown an igniter sleeve738according to yet another embodiment. Igniter sleeve738includes a downward facing tool engagement surface710. A slot712through a body wall (not numbered) is formed in part by downward facing tool engagement surface710, extending between inner and outer surfaces of igniter sleeve738. For disassembly, a removal tool can be positioned in slot712and engaged against downward facing tool engagement surface710such that upward force can be applied to igniter sleeve738and the same removed from a cylinder head. Slot(s)712could be T-shaped as shown, L-shaped, or have still another configuration. Igniter sleeve738also differs from other embodiments in that a plurality of protrusions739are formed thereon and structured to clamp against an upward facing stop surface in a cylinder head. Protrusions739thus can be understood to include locating surfaces functioning analogously to those described in other embodiments, but rather than a body coolant clearance continuously circumferential of igniter sleeve738, a body coolant clearance would be discontinuous and interrupted by way of protrusions739.

Referring back toFIG.3, igniter sleeve38also includes downward facing tool engagement surfaces110. In contrast to a slot arrangement, igniter sleeve38includes a hole112formed in part by downward facing tool engagement surfaces110.

INDUSTRIAL APPLICABILITY

Referring to the drawings generally, but returning focus to the embodiment ofFIGS.1-3, during service engine system10will operate to convey gaseous fuel and air into each of cylinders16. As each respective piston18moves toward a top dead center position in a compression stroke the respective engine valves30will be closed, enabling gaseous fuel and air to be urged into the respective prechamber tip42. At a desired timing, spark electrode44is energized to produce an electrical spark that triggers ignition of the fuel and air in prechamber tip42. Combustion of the fuel and air produces hot jets of combustion gases conveyed out through outlets46and into the respective cylinder16to trigger ignition of a main charge of gaseous fuel and air therein. Ignition and combustion of the main charge urges the respective piston18downward according to well known principles.

Also during operation, engine coolant is conveyed through coolant cavity56, and caused to flow through tip coolant clearance78, exchanging heat with materials of igniter post52and lower sleeve end70. The coolant flows upward from tip coolant clearance78through body coolant clearance80into coolant cavity56, and is thenceforth discharged from cylinder head24to return to a coolant tank typically by way of a heat exchanger or the like.

Known sparkplug sleeves employ various methods for sealing and assembly. Such known strategies typically suffer from a variety of drawbacks relating to cooling efficacy as well as installation and/or removal. The present disclosure provides an igniter sleeve configured where a positive stop is provided at a location that does not obstruct coolant flow into or out of a moat region around an igniter post. As described herein possible positive stop locations can be along upper body regions of an igniter sleeve, such as that specifically shown in the embodiments ofFIGS.1-3and4. In other embodiments, a positive stop location can be provided on an inner diameter region of an igniter sleeve, such as in the embodiments ofFIGS.7and9. Sealing between an igniter sleeve and a cylinder head may be accomplished by using O-ring grooves in the igniter sleeve or cylinder head, laser or friction welding, or a threaded interface. A downward load can be generated by applying a clamping load above an igniter using a clamp secured to a top deck surface, or by way of a threaded engagement between the igniter sleeve and the cylinder head as describe herein. Further, heating the igniter sleeve or freezing the cylinder head can reduce a required assembly force. Tool engagement surface features contemplated herein for removing an igniter sleeve for servicing or replacement can include holes, slots, internal or external ledges or shoulders, or threads, for example.