Engine cover having a retainer to secure an engine accessory

A cam cover for a cylinder head of an internal combustion engine which has an aperture in the cam cover adapted to permit spark plug installation into the cylinder head and two tabs protruding vertically from the cam cover adapted to retain a boss extending from an ignition coil is disclosed. The ignition coil has a portion adapted to fit over the spark plug and an orifice through the boss. The cam cover also has a recess between the tabs with the recess extending into the cam cover which is adapted to accept a self-tapping screw in the event of a tab failure. The tabs have a varying cross-section along their length such that they allow the orifice to be slid over the tabs by them squeezing together and then snapping into place when the orifice clears the ramps on the side of the tabs.

BACKGROUND

1. Technical Field

The present development relates to retaining ignition coils or other engine accessories on covers of internal combustion engines.

2. Background Art

Spark-ignition engines typically have one spark plug/ignition coil per cylinder. The spark plug is typically threaded into the cylinder head through an aperture in the cam cover. The ignition coil is assembled over the tip of the spark plug that extends away from the combustion chamber. The ignition coil has a boss that defines an orifice through which a threaded fastener engages the cam cover to retain the coil in place. In some cases, a fastener may be inserted into a tapped hole in the cam cover. The threaded fastener and threaded plug are more costly and necessitate additional parts for each cylinder of the engine.

U.S. Pat. No. 6,609,508 B2 discloses a U-shaped retaining clip for attaching an ignition coil assembly to a cam cover. This design obviates the need for a threaded fastener. However, it requires a modification of existing cam covers and requires that the ignition coil engage the U-shaped retaining clip which necessitates a change in the design of the coil. Furthermore, no servicing procedure is disclosed in the event that one of the plastic elements fails, for example, during maintenance operations.

The above limitations and disadvantages are addressed by the present development as summarized below.

SUMMARY

A cam cover for a cylinder head of an internal combustion engine defines an aperture for installing a spark plug in the cylinder head. Two tabs extend outwardly from the cam cover at a location near the aperture. A boss extending from an ignition coil receives the two tabs to retain the ignition coil on the spark plug in a snap-fit relationship.

According to an embodiment of the present disclosure, a standard ignition coil from the prior art with no modifications is used. By using a standard ignition coil standardization of parts across engine and vehicle lines is facilitated. In some prior art applications, a brass insert is provided in the cam cover to mate with the threaded fastener as well as a cylindrical aluminum insert in the mounting hole in the coil. The present development obviates the need for the brass insert, the threaded fastener, and the aluminum insert per ignition coil and for each engine accessory using this embodiment.

A method for replacing a coil installed on a cam cover of a cylinder head is disclosed in which tabs protruding from the cam cover are squeezed together to facilitate removing the coil by sliding the orifice of the coil boss over the tabs. A replacement coil is installed by placing the orifice of the replacement coil boss over the tabs, placing the replacement coil over a spark plug mounted into the cylinder head, and pressing down on the replacement coil thereby squeezing the tabs together to allow the replacement coil to be coupled with the spark plug.

In the event that a tab is damaged, the replacement coil is installed by placing the orifice of the coil over the cam cover surface, pressing the coil over a spark plug mounted in the cylinder head, threading a self-tapping screw through the orifice of the coil boss, and screwing the self-tapping screw into a recess formed in the cam cover.

Much of the discussion above is directed to an application involving a spark plug coil secured to a cam cover. However, the present development may apply to other engine accessories. For example, it is known to have sensors and actuators mounted within a cam cover or any engine cover. An aperture is provided in the cam cover through with the wires travel to the sensor or actuator enclosed between the cam cover and cylinder head or through any cover. A non-limiting list of examples includes: a camshaft position sensor, a variable valve timing actuator, and a valve lift actuator in regards to a cam cover. In regards to other covers, a non-exhaustive list may include: temperature, pressure, humidity, Hall effect, position, and magnetic sensors as well as piezoelectric, hydraulic, and solenoid actuators.

The above, as well as other advantages of the present development will become apparent to those skilled in the art from the detailed description when considered in the light of the accompanying drawings.

DETAILED DESCRIPTION

An internal combustion engine may have one or two cylinder heads which form the upper portion on the combustion chamber for three to six cylinders depending on whether the engine is configured as an I-4, I-6, V-6, or V-8 engine. Intake and exhaust valves permit fresh air to enter the combustion chambers and exhaust to exit the combustion chambers are actuated by a valvetrain mechanism in the cylinder head. A cover encloses and seals the valvetrain from the outside. The cover is generally referred to as a valve cover with reference to either a cam-in-block or an engine with an overhead camshaft. The term “cam cover” used herein applies to what is commonly referred to as: a valve cover, a rocker arm cover, or a cam cover.

Referring toFIG. 1, a cam cover1is mounted on cylinder head2via fasteners3. Ignition coils4protrude through cam cover1through apertures defined in cam cover1. Ignition coils4couple with spark plugs (not visible) mounted in cylinder head2. Ignition coils4have connectors5provided for making electrical connection to ignition coils4. Ignition coils4also have bosses6extending outwardly from ignition coils4with retaining orifices7defined in bosses6for securing ignition coils4to cam cover1. Cam cover1seals a non-combustion side8of cylinder head2, keeping lubricant for the rocker arms and other moving parts within the space between cylinder head2and cam cover1.

Referring toFIG. 2, a cam cover10is shown with an installed coil12according to one embodiment of the present disclosure. Coil12has a connector receptacle14to which a wiring connector may be connected. Coil12has a boss16that defines an orifice18. Tabs20extend outwardly from cam cover10through orifice18to retain coil12.

Referring toFIG. 3, coil12is aligned with, but not installed on cam cover10. Cam cover10defines an aperture22through which a spark plug24is installed. Coil12fits over spark plug24as orifice18is fitted over tabs20. The distance between centerlines of coil12and orifice18is the same as the distance between the centerline of aperture22and the center of tabs20.

When properly aligned, coil12engages spark plug24as orifice18engages tabs20. When orifice18is first brought into contact with tabs20, orifice18slides over distal sections25of tabs20. As orifice18of boss16is lowered further, orifice18engages a ramp of engagement section26of tabs20and can be lowered no further without tabs20moving. By applying a force on boss16, tabs20bend toward each other to fit through orifice18. When orifice18of boss16clears engagement section26of tabs20, tabs20return to their original, undeformed, vertical position when orifice18engages body sections27of tabs20. A radially extending surface28holds boss16and coil12in place on cam cover10

Continuing to refer toFIG. 3, tabs20are of constant cross section along the length of distal sections25. Proceeding further down the length, the cross section increases along engagement sections26, in one embodiment the cross section increases monotonically in a direction toward cam cover10. As shown inFIG. 4, engagement sections26appear to increase in width linearly along the length, i.e., forming a ramp. This is a non-limiting example. In one embodiment, engagement sections26have a feature to facilitate grabbing the tabs with a tool so that they can be squeezed together for removal of the coil or other engine accessory. In embodiments with such a grabbing feature on engagement section26, distal section52may be omitted. Engagement sections26may be any shape, i.e., which allows orifice18to be guided over tabs20and then snap back after orifice18clears engagement sections so that the coil or other accessory is secured in place. Proximate section27has a constant cross section with the outside dimension being about the same or slightly less than the inside dimension of orifice18. The length of body section27, indicated as L inFIG. 3, is at least as long as the height of boss16, indicated at H inFIG. 3, so that engagement sections26clear boss and snap to their original vertical shape to hold boss16in place.

InFIG. 4, an installed coil is shown. According to an embodiment of the present development, removal of coil12or spark plug24requires the removal of boss16from tabs20. A pliers26can be used to push tabs20together while pulling up on coil12for removal. When coil12is removed, spark plug24can be accessed. When removing coil12, tabs20may be damaged or broken. If the tabs are found inadequate to retain coil12, a service fix, as shown inFIG. 5, includes a self-tapping screw30. At least distal section25and engagement section26of tabs20are removed to accommodate self-tapping screw30. Cavity28, provided in cam cover10to accommodate self-tapping screw30, can be seen inFIGS. 3 and 4.

Plan views of one alternative embodiment of tabs50are shown inFIGS. 6 and 7. InFIG. 7, tabs50are in an unsqueezed state, in which a gap of X exists between the two tabs50. The distal section52has a diameter equal to or slightly less than D, the diameter of the orifice56with which tabs50engage. Tabs50also have engagement sections54, which, as shown inFIG. 7, have a broadest dimension from the edge of one tab to the other of W. InFIG. 8, the tabs are shown squeezed together. In such a configuration, a width of the outside edges of engagement sections54is D or less so that engagement sections54can be placed over an orifice of diameter D. As squeezed together, the width of the two distal sections52is D minus X.

InFIG. 3, coil12is engaged with spark plug24and retaining orifice18of boss16couples with tabs20. According to other embodiments of the disclosure, other accessories can be coupled with tabs similar to tabs20, but supplied at a different location on the cam cover or on any engine cover. Engine accessory may be one of: a camshaft position sensor, a variable valve timing actuator, and a valve lift actuator. In such a case, an aperture is provided for an operative end of the accessory to gain access inside the cam cover.

Embodiments of the present disclosure in which the tabs are integral with the cover is appropriate for situations in which the mold for the cover is being newly designed or redesigned. However, in the middle of a production run, redesigning the mold to integrate the tabs may be prohibitively expensive. Thus, according to an alternative embodiment, shown inFIG. 8, cover40having an aperture42to provide access for an accessory and having a cylindrical cavity is coupled with an adapter46. Cover40may be a cover of the prior art in which cylindrical cavity44might have been fitted with a brass insert so that a conventional bolt could be used to secure the accessory. According to the present development, adapter46has a connection section48having a diameter roughly equal to the diameter of cylindrical cavity44. Adapter46has tabs50which include proximate section52, engagement section54, and distal section56. Defined in the top of connection section48is a drive feature60. In the embodiment ofFIG. 8, the drive feature is a flathead key. Alternatively, drive feature48may be keyed to permit it to mate with other known drivers, such as Allen, TORX, Phillips, etc.

A plan view of adapter46is shown inFIG. 9in which distal section56and engagement section54can be viewed. Connection section48has a groove (or key)60defined in an end closest to the tabs. InFIG. 10, adapter46is slid into cylindrical cavity of cover40and a tool61is inserted in groove60. A torque applied to tool61is transmitted through groove60to rotate adapter46. By rotating adapter46with respect to cover40, frictional forces causes the rubbing surfaces to heat up and melt. Upon cooling, adapter46is coupled with cover40. This process is commonly known as spin welding. The coupled adapter26and cover are shown inFIG. 11.

Also shown inFIG. 11is that proximate section52extends outwardly from cover40is length, L. Accessory64has height H, at least in the vicinity of retaining orifice63. Accessory64is held in place by engagement sections54of adapter46by sliding retaining orifice63over adapter46. Referring now toFIG. 12, accessory64is shown installed on cover40. Accessory has a sensor65which gains access inside of cover40through aperture42(which is not called out inFIG. 12since it is filled with sensor65). Sensor65can be any known type of sensor. Alternatively, element65is an actuator. To seal the accessory at the aperture in cover40, an O-ring66can be provided in groove66. Alternatively, any other type of known sealing configuration can be provided. The snap-fit relationship of the tabs of adapter40with accessory64provides sufficient downward force to deform the O-ring or other seal.

Another embodiment of an adapter68is shown inFIG. 13. Connection section70comprises threads. Cylindrical cavity44of cover40has a diameter D. The threads on connection section have a major diameter, M, which is greater than D, and a minor diameter, m, which is less than D. Adapter68has tabs72which include: a proximate section74, engagement section76, and distal section78. Connection section70has a drive feature80formed in the end of connection feature closer to tabs72. Drive feature80can be any keyed arrangement such as: flat head, TORX, Allen, Phillips, etc, but shown as a flat head inFIG. 13. The threads on connection section70are self-tapping threads. By inserting adapter68into cylindrical cavity44as far as possible; placing a tool, such as tool61ofFIG. 10into drive feature80; and rotating adapter68by such a tool, the self-tapping threads engage with the surface surrounding cylindrical cavity44. Adapter68is pulled into cavity44until the threads are fully engaged.

Embodiments of the disclosure can be practiced otherwise than as specifically illustrated and described with departing from its spirit or scope. For example, while the present development has been described for mounting an ignition coil, those skilled in the art will appreciate that the present development can be used to attach various types of components within the scope of the development.