Variable operating valve apparatus for an internal combustion engine

A variable operating valve apparatus for an internal combustion engine that provides for improved combustion performance without enlarging the size of the cylinder head in the transverse direction. The variable valve mechanism includes a camshaft axially supported by the cylinder head, three-dimensional cams formed on the camshaft, a rocker shaft actuator able to displace the rocker shaft in the axial direction according to engine operating conditions, and a lift volume setting mechanism that changes the amount of valve lift dependent on the extent of positional change of the rocker shaft in the axial direction. The camshaft is at least axially supported on the intake port side of the cylinder head, a fuel injector (which injects fuel into the intake port) is installed to the part of the intake sidewall at the intake port of the cylinder head, and a concave part is formed into the intake sidewall above the fuel injector extending inward toward the camshaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable valve mechanism for an internal combustion engine. More specifically, the present invention relates to a variable valve mechanism that allows a fuel injector to be installed at a location that provides for improved combustion performance, without increasing the width of the engine's cylinder head.

2. Description of Background Information

A variable valve mechanism has been applied to engines used in automotive vehicles as manner of variably controlling the extent and duration of valve lift for a valve that opens and closes an intake port leading to a combustion chamber. Furthermore, a fuel injector is provided to lower undesirable exhaust gas emissions.

The prior art includes a variable valve mechanism, of the type applied to an engine, that includes a camshaft that synchronously rotates with a crankshaft, a solid cam with an axially changing profile formed on the camshaft, an actuator that changes the position of the cam profile in the axial direction in response to engine operating conditions, a swinging rocker arm equipped with components that contact multiple valves, a sub-rocker arm supporting a roller follower that rotatably contacts the solid cam, and a sub-rocker support part that supports the swinging movement of the sub-rocker on the rocker arm (see for example, Japanese Published Patent Application H5-18221, pages 3-4 and FIG. 1).

Japanese Published Patent Application H10-18823 (see pages 3-4 and FIG. 1) discloses another type of variable valve mechanism that includes a solid cam camshaft that incorporates a variable low to high-speed profile that changes continuously along the axial direction, an actuator that changes the axial position of the camshaft in relation to engine operating conditions, and an arm that moves in synchronization with two or more adjacent valves and whose movement is dependent on the profile of the solid cam. The aforesaid arm incorporates a follower mechanism that follows positional changes in the linear contact angle of the rotating solid cam through a follower in contact therewith, and two or more contact members that press against the ends of two or more valves.

Japanese Published Application 2002-147241 (see pages 3-4 and FIG. 4) discloses another type of engine in which there is a positional relationship between a fuel injector and a cylinder head.

Currently known variable valve mechanisms of the type applied to internal combustion engines, such as those noted in Japanese Published Patent Application H5-18221 and Japanese Published Patent Application H10-18823, describe a mechanism that includes a camshaft onto which a three-dimensional cam (hereafter referred to as a 3D cam) is formed having a profile that varies along the axial direction, and valves that open and close according to the rotation of the 3D cam, wherein the amount of valve lift varies depending on the positional relationship between the 3D cam and valve stem. These variable valve mechanisms described by Japanese Published Patent Application H5-18221 and Japanese Published Patent Application H10-18823 employ a mechanism in which the valve is driven by the rotational movement of the 3D cam being transferred to the valve through a rocker arm.

Moreover, some internal combustion engines place the fuel injector as close to the combustion chamber as possible in an effort to lower exhaust gas emissions and improve combustion performance. For example, the fuel injector shown in Japanese Published Application 2002-147241 is located in the middle at the top of the cylinder in order to inject fuel directly into the combustion chamber.

These known variable valve mechanisms exhibit an undesirable characteristic in that the use of 3D cams to open and close valves through rocker arms has the effect of increasing the width (the transverse direction at a right angle to the axial centerline of the camshaft) of the cylinder head. Furthermore, increasing the width of the cylinder head makes it more difficult to locate the injector (which sprays fuel into the intake port leading to the combustion chamber) close to the combustion chamber.

In order to solve the shortcomings of the prior art, the present invention proposes a variable valve mechanism that axially supports the camshaft, on which a 3D cam is formed, at least on the intake port side of the cylinder head, locates the fuel injector in the part of the intake sidewall bordering the intake port of the cylinder head, and provides for a concave part, formed in the intake sidewall, that extends inward toward the intake camshaft at a location above the fuel injector. This structure prevents the sidewall from obstructing the installation of the fuel injector to the cylinder head, and allows the fuel injector to be located in closer proximity to the combustion chamber.

SUMMARY OF THE INVENTION

Accordingly, one aspect of the present invention is to provide a variable valve mechanism. The variable valve mechanism includes a camshaft, which is axially supported by an engine cylinder head, onto which a three-dimensional cam is formed to a profile that changes along the axial direction. The camshaft is axially supported at least on an intake port side of the cylinder head. The variable valve mechanism also includes a rocker shaft actuator that changes an axial position of a rocker shaft in response to engine operating conditions, a valve lift volume setting mechanism configured to alter an amount of lift of a valve dependent on the extent of axial movement of the rocker shaft, a fuel injector installed on a part of an intake sidewall bordering the intake port of the cylinder head, in which the fuel injector is configured to spray fuel into an intake port, and a concave part formed in the intake sidewall and extending inward toward the camshaft at a location above the fuel injector.

The concave part is formed at least on a part of said intake sidewall directly opposite a fuel injector harness connector. The fuel injector is installed at the intake sidewall so as to incline the harness connector in a direction away from a sprocket attached to an axial end of the camshaft. The camshaft is axially supported by the cylinder head so that a maximum lift profile of the three-dimensional cam is oriented toward an end of the camshaft to which the sprocket is attached, in which the profile is the part of the cam that applies a maximum valve lift.

According to another aspect of the present invention, a variable valve mechanism for an internal combustion engine is provided. The variable valve mechanism includes a camshaft, axially supported by an engine cylinder head, in which the camshaft includes a three-dimensional cam having a profile that varies along a length of the cam. The variable valve mechanism also includes a rocker shaft having an axial position that changes in response to engine operating conditions, a valve lift volume setting mechanism configured to alter the lift of a valve in response to an amount of axial movement of the rocker shaft, and a fuel injector, configured to spray fuel into an intake port, attached at an intake sidewall, in which the intake sidewall includes a concavity adjacent the fuel injector.

The concavity may include an angular depression extending inward in the direction of the camshaft. Further, the concavity may be formed opposite a connector associated with the fuel injector. Still further, the connector may be angled away from a sprocket on the camshaft. The camshaft may include a maximum lift profile portion that is oriented toward a sprocket end side of the camshaft.

According to another aspect of the present invention, a variable valve mechanism for an internal combustion engine is provided. The variable valve mechanism includes a camshaft, axially supported by an engine cylinder head, in which the camshaft includes a three-dimensional cam having a profile that varies along a length of the cam. The variable valve mechanism also includes a rocker shaft having an axial position that changes in response to engine operating conditions, a valve lift volume setting mechanism configured to alter the lift of a valve in response to an amount of axial movement of the rocker shaft, and a fuel injector, configured to spray fuel into an intake port, attached at an intake sidewall. A connector and a fuel rail, each being associated with the fuel injector are attached to a rearward end of a casing of said fuel injector. As a result, the connector and the fuel rail are not obstructed by the intake side wall.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The variable valve mechanism invention described by the present invention specifies a concave part that allows for the non-obstructed installation of a fuel injector into the intake sidewall of a cylinder head without interference therewith, thereby allowing the fuel injector to be located in closer proximity to the combustion chamber.

As a result, the variable valve mechanism allows the fuel injector to be placed at a location beneficial to combustion performance, without increasing the width of the cylinder head in the transverse direction, even though the camshaft, onto which three-dimensional cams are formed, is axially supported on the intake port side of the cylinder head.

FIGS. 1 through 8will now be referred to with respect to a first embodiment of the present invention.FIG. 3illustrates an engine2which is installed to a vehicle (not shown in the drawing), a cylinder block4, a cylinder head6, a cylinder8, a piston10, a head chamber12, and a combustion chamber14. The engine2includes the cylinder head6and the cylinder block4, in which the cylinder head6is attached to the cylinder block4at a lower head surface16. A head cover (not shown in the drawing) attaches to an upper surface18of the cylinder head6. The combustion chamber14is defined by the cylinder8and the piston10in the cylinder block4, and the head chamber12in the cylinder head6.

The engine2is a four-cylinder engine in which each of the four cylinders8is located in linear alignment with an adjacent cylinder, each cylinder8being equipped with two intake and two exhaust valves (four-valve engine).

As shown in theFIG. 1, the cylinder head6of the engine2is formed to an approximate rectangular shape with the four cylinders8being arranged in linear alignment in the lengthwise (L) direction as opposed to the shorter transverse (W) direction. A front wall20and a rear wall22are located at the respective front (F) and rear (R) sides of engine2in the lengthwise (L) direction, and an intake sidewall24and an exhaust side wall26are located on their respective sides of the engine2in the transverse (W) direction. As shown inFIG. 4, a spark plug28is installed in the center of the cylinder head6along the transverse (W) direction facing the head chamber12. A plug guide tube30, which is installed over the spark plug28, rises to a point above the upper head surface18.

As shown inFIG. 3, intake and exhaust ports36and38, respectively, are formed within the intake sidewall24and the exhaust sidewall26of the cylinder head6, and respectively lead to intake and exhaust valve orifices32and34, respectively, which are formed in the head chamber12of the combustion chamber14. A fuel injector40is installed at the intake sidewall24and sprays fuel into the combustion chamber14through the intake port36. As illustrated inFIG. 4, a nozzle44of a fuel injector casing42is inclined toward the intake port36through its placement within an injector installation orifice46formed in the intake sidewall24. A rearward end48of the fuel injector casing42connects to a fuel rail50. A harness connector52is attached to the fuel injector casing42near the rearward end48in proximity to the intake sidewall24.

The engine2is equipped with a variable valve mechanism54which includes an intake valve56and an exhaust valve58that operate to respectively open and close the intake and the exhaust ports36and38, respectively, of the cylinder head6. Moreover, in this embodiment, the engine2is a four-valve engine in which each cylinder8is equipped with two intake valves56and two exhaust valves58.

As illustrated inFIG. 3, an intake valve head60and an exhaust valve head62, which are formed on the ends of the intake valve56and the exhaust valve58, respectively, move with a motion that opens and closes the intake and the exhaust valve orifices32and34, respectively. An intake valve stem64and an exhaust valve stem66are movably supported along their axial direction by an intake valve stem guide68and an exhaust valve stem guide70of the cylinder head6.

The intake and exhaust valves56and58are equipped with intake and exhaust spring retainers76and78, respectively, that are installed to intake valve stem tip72of the intake valve stem64, and exhaust valve stem tip74of the exhaust valve stem66, respectively. An intake valve spring84is compressed between the intake retainer76and an intake spring seat80, and an exhaust valve spring86is compressed between the exhaust retainer78and an exhaust spring seat82on the cylinder head6. The pressure generated by the intake valve spring84and the exhaust valve spring86is applied in a direction whereby the intake valve64seals off the intake port36, and the exhaust valve70seals off the exhaust port38from the combustion chamber14.

Referring toFIGS. 1 and 2, an intake camshaft90and an exhaust camshaft92are axially supported by multiple camshaft support structures88over the upper head surface18of the cylinder head6in parallel alignment in the lengthwise (L) direction. Each camshaft support structure88includes a first camshaft housing94which is installed to the upper head surface18oriented in the transverse (W) direction and aligned with the other first camshaft housings94at opposing sides of each cylinder8in the lengthwise direction (L), and a second camshaft housing96which is attached to each first camshaft housing94, thus holding the camshaft90and the exhaust camshaft92there between. The camshaft support structure88is attached to the upper surface18of the cylinder head6by housing bolts98.

The camshaft support structures88, which axially support the intake and exhaust camshafts90and92between first and second camshaft housings94and96, locate the intake camshaft90toward the outward extending side of the intake port36, and the exhaust camshaft92toward the outward extending side of the exhaust port38in the transverse direction (W). An intake cam sprocket100and an exhaust cam sprocket102are respectively attached to the axial ends of the intake camshaft90and the exhaust camshaft92, that extend forward past the front wall20of the cylinder head6(“F” direction of the engine2).

The intake cam sprocket100and the exhaust cam sprocket102are driven by a timing chain (not shown in the drawings) that runs off of a sprocket on the crankshaft, and are covered by a chain case (not shown in the drawings) attached to case mounting flanges104which extend outward in the transverse (W) direction from the front wall20of the cylinder head6.

Moreover, a rear housing106is formed as an integral part of the first camshaft housing94nearest to rear wall22of cylinder head6, and extends rearward (in the “R” direction of the engine2) from the rear wall22. An intake cam thrust receiver108(seeFIG. 8) and an exhaust cam thrust receiver (not shown in the drawings) are installed around the rear extremities of the intake and the exhaust camshafts90and92that extend rearward from the rear housing106(in the “R” direction of the engine2).

The intake camshaft thrust receiver mechanism108and the exhaust cam thrust receiver mechanism include an intake cam support member114and an exhaust cam support flange (the latter not shown in the drawings) which are pressed into the rear housing106around the respective rearward protruding ends of the intake and exhaust camshafts90and92(the latter not shown inFIG. 8) which extend outward from the rear housing106. The intake cam support member114and the exhaust cam support flange are respectively located adjacent to an intake cam thrust bearing112and an exhaust cam thrust bearing (the latter not shown in the drawings) and the intake cam thrust washer110and an exhaust cam thrust washer (the latter not shown in the drawings). The intake cam thrust receiver mechanism108and the exhaust cam thrust receiver mechanism are provided to absorb axial thrust pressure from 3D intake and exhaust cams116and118, respectively, (to be described subsequently), and thus prevent the intake and exhaust camshafts90and92from moving in the axial direction while rotating.

The variable valve mechanism54applied to the engine2includes camshafts which are axially supported by the cylinder head6and onto which 3D cams are formed with profiles that vary in the axial direction. At least one camshaft, onto which 3D cams are formed, is axially supported at the intake port36side of the cylinder head6.

As illustrated inFIG. 1, the intake camshaft90, which is axially supported on the intake port36side, is a single shaft incorporating four integrally formed 3D intake cams116, one 3D intake cam116being located at each cylinder8. Likewise, the exhaust camshaft92, which is supported on the exhaust port38side, is a single shaft incorporating four integrally formed 3D exhaust cams118, one 3D exhaust cam118being located at each cylinder8. Each 3D intake cam116incorporates an axially varying lift profile that includes a maximum lift profile116F and a minimum lift profile116R, which are able to respectively actuate the intake valve56to a maximum and minimum lift volume respectively. Likewise, each 3D exhaust cam118incorporates an axially varying lift profile that includes a maximum lift profile118F and a minimum lift profile118R which actuate the exhaust valve58to a maximum and minimum lift volume, respectively.

The first camshaft housing94of the camshaft support structure88locates the intake camshaft90and the exhaust camshaft92in parallel alignment along opposing sides of the spark plug guide tubes30which are aligned along the center line of the cylinder head6. An intake rocker shaft120and an exhaust rocker shaft122are movably supported in the axial direction, and fixedly supported in the radial direction. As can be seen inFIGS. 6 and 7, intake and exhaust rocker shaft actuators124and126are installed to the end of the rear housing106(direction “R”) that extends rearward from the first camshaft housing94installed to the rear wall22of the cylinder head6. The actuators124and126operate in response to engine conditions in order to set the axial positions of the intake and exhaust rocker shafts120and122, respectively.

As shown inFIGS. 6 through 8, the intake and exhaust rocker shaft actuators124and126include a motor case128installed to the rear housing106, intake and exhaust rocker shaft male gear members130and132, respectively, which are integrally formed as male threads around the respective ends of the intake and exhaust rocker shafts120and122, and which extend into the motor case128. The intake and exhaust rocker shaft actuators124and126also include intake and exhaust rocker shaft female gear members134and136, respectively, which are formed as internally (female) threaded sleeves, movably supported by the motor case128in the radial direction but fixedly supported in the axial direction, whose female threads mesh with the male threads of the intake and exhaust rocker shaft male gear members130and132, respectively. The intake and exhaust rocker shaft actuators124and126further include intake and exhaust rocker shaft relay gears138and140, respectively, that radially extend from the circumference of the intake and exhaust rocker shaft female gear members134and136, respectively.

Further, the intake and exhaust rocker shaft actuators124and126include intake pinion gear142and an exhaust pinion gear (not shown in the drawings) that mesh with the intake and exhaust rocker shaft relay gears138and140, respectively, and include intake and exhaust (FIG. 1) rocker shaft actuator motors144and146, respectively, which are installed to the motor case128and which drive the intake pinion gear142and the exhaust pinion gear, respectively.

The intake and exhaust rocker shaft actuators124and126provide a mechanism through which the intake and exhaust rocker shaft motors144and146are able to rotatably drive the intake and exhaust rocker shaft female gear members134and136through the intake pinion gear142and the exhaust pinion gear respectively driving intake and the exhaust rocker shaft relay gears138and140, thus axially displacing an intake rocker shaft120and an exhaust rocker shaft122through the respective rotational movements applied to the intake and exhaust rocker shaft male gear members130and132.

As shown inFIGS. 7 and 8, in the interior of the motor case128, an intake cam sensor trigger148and an exhaust cam sensor trigger (not shown in the drawings), formed as integral components, are attached to the intake cam support member114and the exhaust cam support flange (not shown in the drawings) that attach to the ends of the intake and exhaust camshafts90and92, respectively, extending from the rear housing106. The intake cam sensor trigger148and the exhaust cam sensor trigger respectively activate intake and exhaust cam angle sensors150and152(FIG.4), respectively, which are installed to motor case128, to provide a cam position detection function.

As illustrated inFIGS. 3 through 6, an intake valve lift volume setting mechanism154, which applies an amount of lift to the intake valves dependent on the axial position of the intake rocker shaft120, is located between the 3D intake cam116on the intake camshaft90and the intake valve stem tip72on the end of the intake valve56. In a similar structure, an exhaust valve lift volume setting mechanism156, which applies an amount of lift to the exhaust valves dependent on the axial position of the exhaust rocker shaft122, is located between the 3D exhaust cam118on the exhaust camshaft92and the exhaust valve stem tip74on the end of the exhaust valve58.

The intake valve lift volume setting mechanism154includes first intake rocker arm158whose fulcrum end is pivotably supported by and axially movable on the intake rocker shaft120, and whose non-fulcrum end contacts the intake valve stem tip72. The intake valve lift volume setting mechanism154further includes a second intake rocker arm160which contacts the first rocker arm158, and whose fulcrum end is pivotably supported by the intake rocker shaft120, but is not axially movable thereon.

The first intake rocker arm158is an approximately U-shaped member, positioned between adjacent first camshaft housings94, whose fulcrum end intersects with and is pivotably supported by the intake rocker shaft120while allowing the axial movement of the intake rocker shaft120therein. Two intake valve adjuster screws162are attached to the middle part of the first intake rocker arm158that runs parallel with the intake rocker arm shaft120, contact the intake valve stem tips72, and are secured by intake valve adjuster nuts164.

The second intake rocker arm160is a linear member located between the fulcrum ends of the U-shaped first intake rocker arm158and held in position on the intake rocker shaft120by stop flanges166. The second intake rocker arm160is thus able to radially pivot but not axially slide on the intake rocker shaft120. An intake roller168, which rides against the 3D intake cam116, is rotatably supported by and axially movable on the intake roller shaft170which is attached to the center of each end of the U-shaped first intake rocker arm158.

An abbreviated description of the exhaust valve lift volume setting mechanism156will be offered, as mechanism156is structurally similar to the intake valve lift volume setting mechanism154. The exhaust valve lift volume setting mechanism156is an approximately U-shaped first exhaust rocker arm172and a straightly structured second exhaust rocker arm174. The fulcrum end of the first exhaust rocker arm172is pivotably supported by and axially movable on the exhaust rocker shaft122. The tip (non-fulcrum) end incorporates two exhaust valve adjuster screws176and corresponding exhaust valve adjuster nuts178. The fulcrum end of the second exhaust rocker arm174is pivotably supported by the exhaust rocker shaft122and is held in a fixed axial position thereon by stop flanges180. An exhaust roller182, which is the contacting member to the 3D exhaust cam118, is axially supported by exhaust roller shaft184whose ends are fixedly attached to the second exhaust rocker arm174.

The intake and exhaust valve lift volume setting mechanisms154and156provide a manner through which the amount of lift applied to the intake and exhaust valves56and58can be altered by changing the position where intake and exhaust rollers168and182, respectively, contact the profiles of 3D intake and exhaust cams116and118, respectively. The positions of the intake and exhaust rollers168and182can be changed by the mechanism through which the intake and exhaust rocker shaft actuators124and126move the intake and exhaust rocker shafts120and122in the axial direction.

As shown inFIGS. 1 and 4, the variable valve mechanism54of the engine2axially supports the intake camshaft90, onto which the 3D intake cams116are formed, at least at the intake port36side of the cylinder head6. The fuel injector40, which sprays fuel into the intake port36, is installed to the part of the intake sidewall24bordering the intake port36of the cylinder head6. A concave part186is formed as a portion of the intake sidewall24that indents toward the intake camshaft90above the fuel injector40.

The concave part186is formed as an inwardly curved depression in the intake sidewall24at least at a location opposite to the harness connector52of the fuel injector40. The fuel injector40is installed to the intake sidewall24with the harness connector52inclined, with respect to the fuel injector casing42, in a direction away from the intake cam sprocket100(i.e. toward the rear (R) of the engine2) which is attached to the axial end of the intake camshaft90. The intake camshaft90is axially supported by the cylinder head6and oriented to place the maximum intake lift profile116F (which is the part of the 3D intake cam116that applies maximum valve lift) toward the front (F) of the engine2in respect to the minimum intake lift profile116R (which may apply zero lift), that is, on the side of the engine2nearer to the intake cam sprocket100which is attached to the end of the intake camshaft90.

The following discussion will explain the operation of the invention. The variable valve mechanism54, which is incorporated into the engine2, is able to vary the amount of lift applied to the intake and exhaust valves56and58by virtue of the intake and exhaust valve lift volume setting mechanisms154and156and the mechanism through which the intake and exhaust rocker shaft actuators124and126change the position of the intake and exhaust rocker arm shafts120and122in the axial direction, thus changing the positions of the intake and exhaust roller168and182on the profiles of the 3D intake and exhaust cam116and118, respectively.

The variable valve mechanism54provides for axial support of the intake camshaft90, onto which the 3D intake cams116are formed, at least on the intake port36side of the cylinder head6. The fuel injector40, which sprays fuel into the intake port36, is installed to the part of the intake sidewall24bordering the intake port36of the cylinder head6. The concave part186is formed within the portion of the intake sidewall24located above the fuel injector40and extends inwardly in a direction toward the intake camshaft90.

Thus structured, the variable valve mechanism54allows the fuel injector40to be installed to the intake sidewall24without obstruction as a result of the provision of the concave part186. As shown inFIG. 4, the fuel injector40can be located in closer proximity to the combustion chamber14in order to shorten distance “A” between the intake orifice32of the combustion chamber14and the nozzle44of the fuel injector40.

Even though the variable valve mechanism54provides for support of the intake camshaft90(onto which the 3D intake cams116are formed) at the intake port36side of the cylinder head6, this structure allows the fuel injector40to be placed at a location beneficial to combustion performance without increasing width “B” of the cylinder head6.

Moreover, as the variable valve mechanism54provides for at least the formation of the concave part186in the intake sidewall24opposite the harness connector52of the fuel injector40, the part of the intake sidewall24above the harness connector52and the fuel injector40may be formed to a shape that does not adversely affect the combustion performance of the cylinder head6.

Furthermore, the variable valve mechanism54provides for the installation of the fuel injector40to the intake sidewall24so that the harness connector52inclines away from the intake cam sprocket100which is installed to the axial end of the intake camshaft90, and further provides for the axial support of the intake camshaft90in the cylinder head6so that the maximum lift profile116F, which is the part of the 3D intake cam116that provides the greatest amount of valve lift, is located nearer the intake cam sprocket100side of the intake camshaft90, the sprocket100being attached to the end of the intake camshaft90.

If the fuel injectors40were to be installed to the intake sidewall24with the harness connectors52inclined in a direction toward the intake sprocket100(i.e. toward the front of the engine2), the harness connector52on the forward-most fuel injector40, that is, the harness connector of the fuel injector installed to the part of the intake sidewall24nearest to the front wall20of the cylinder head6, would interfere with the case mounting flange104which protrudes outward in the transverse (W) direction from the front wall20. However, because the harness connector52is inclined toward the rear (direction “R”) of the engine2, it does not interfere with the case mounting flange104nor the part of the intake sidewall24located above the harness connector52and the fuel injector40. Furthermore, by providing a gap between the minimum intake lift profile116R and the intake sidewall24, it becomes possible to form the concave part186in the intake sidewall24at a location opposing the harness connector52of the fuel injector40.

FIG. 9describes a second embodiment of the invention. In this second embodiment of the variable valve mechanism54, the fuel injector40is installed to the intake sidewall24of the cylinder head6, the harness connector52is installed to the rearward end48of the fuel injector casing42of the fuel injector40, and the fuel rail50is installed to the rearward end48of the fuel injector casing42opposite to the intake sidewall24.

In this second embodiment of the variable valve mechanism54, the harness connector52and the fuel rail50, which are connected to the fuel injector casing42of the fuel injector40, are located farther away from the intake sidewall24as compared to their positions in the first embodiment, thus preventing the harness connector52and the fuel rail50from being obstructed by the intake sidewall24of the cylinder head6, and thus allowing distance “A” (the distance between the nozzle44of the fuel injector40and the intake orifice32of the combustion chamber14) to be reduced to a length shorter than that of the corresponding distance “A” in the first embodiment. The fuel injector40can thus be positioned closer to the combustion chamber14.

As a result, the second embodiment of the variable valve mechanism54makes it possible to install the fuel injector40at a location conducive to improved combustion performance without widening width “B” of the cylinder head6.

FIG. 10describes a third embodiment of the invention. In this third embodiment of the variable valve mechanism54, the concave part186is formed as an angular depression extending inward toward the intake camshaft90, in the part of the intake sidewall24located above the fuel injector40, in order to reduce the width of gap “D” that extends along the profile of the 3D intake cam116from the maximum intake lift profile116F to the minimum intake lift profile116R.

In this third embodiment of the variable valve mechanism54, the concave part186is formed as an inward extending angular contour of the intake sidewall24at the fuel injector40. The concave part186reduces the width of gap “D” adjacent to the profile of the 3D intake cam116, and thus not only makes it possible to locate the fuel injector40nearer to the combustion chamber14, but to provide sufficient space between the intake sidewall24and the harness connector52of the fuel injector40.

As a result, the third embodiment of the variable valve mechanism54provides for easy installation of the harness connector52and allows for the placement of the fuel injector40at a location beneficial to combustion performance.

The present disclosure relates to subject matter contained in priority Japanese Application No. 2002-372285, filed on Dec. 24, 2002, which is herein expressly incorporated by reference in its entirety.