Cam phaser cover assembly

Information

  • Patent Grant
  • 6386167
  • Patent Number
    6,386,167
  • Date Filed
    Friday, June 29, 2001
    23 years ago
  • Date Issued
    Tuesday, May 14, 2002
    22 years ago
Abstract
An improved splined cam phaser includes four assemblies: a sprocket assembly, an inner hub assembly, a cover assembly, and a piston assembly. The joined assemblies provide phaser function at reduced manufacturing cost. The cover assembly, at least in part, is stamped from sheet stock and is net formed to receive a seal.
Description




TECHNICAL FIELD




The present invention relates to a cam phaser apparatus for controllably varying the phase relationship between the crankshaft and the camshaft of an internal combustion engine; more particularly, to a cam phaser having concentric splined elements counter-rotatable by a splined piston therebetween; and most particularly, to a splined cam phaser wherein the parts are optimized for ease and economy of manufacture, reduced phaser size, and improved phaser performance.




BACKGROUND OF THE INVENTION




Splined cam phasers are well known in the automotive art; see, for example, U.S. Pat. No. 5,588,404. In principle, a phaser assembly is relatively simple. A first rotatable element is fixedly mounted to the end of a camshaft of an engine and turns synchronously therewith. The first element has helical splines on its outer surface. A second rotatable element surrounds the first element concentrically and has a drive wheel, pulley, or sprocket adapted to be driven by the crankshaft of the engine. On its inner surface, the second element has helical splines opposite-handed from the splines on the first element. A generally cylindrical piston is positioned in a closed annular space between the two elements. The piston has helical splines on both its inner surface and its outer surface which mesh with the splines on the first and second elements. The piston is controllably driven axially in either direction by programmably-directed hydraulic pressure against one or the other side of the piston, causing the first and second elements to counter-rotate with respect to each other and thereby varying the relative timing of the valves with respect to the pistons by changing the rotational phase relationship between the crankshaft and the camshaft. Preferably, the first element is provided at its outer end with a sectored timing wheel, also referred to herein as a target wheel, to permit automatic monitoring of the cam position at all times.




The prior art cam phaser can be difficult and expensive to manufacture. Typically, all moving parts are individually machined from steel forgings. The target wheel, which carries the compressive force of the major assembly bolt, is optimally formed by investment casting, a very expensive forming method. The layout of the parts and seals does not lend itself to formation by less expensive known methods, for example, by powdered metal forming, preferably by powdered steel. Further, the internal passages in various parts, required to present hydraulic fluid to one or the other face of the piston, typically are formed labor-intensively by cutting and drilling.




Therefore, what is needed in the art is an improved splined cam phaser wherein the cost of manufacture is minimized by minimizing the number of machined parts.




What is also needed in the art is an improved splined cam phaser wherein the target wheel may be stamped inexpensively from sheet steel stock.




Further needed in the art is an improved splined cam phaser wherein the axial length is reduced.




Still further needed in the art is an improved splined cam phaser wherein the speed of response is improved.




Finally, what is needed in the art is an improved splined cam phaser wherein the position of the cam shaft sprocket relative to the crank shaft can be set after assembly of the splined cam shaft phaser.




SUMMARY OF THE INVENTION




Briefly described, an improved splined cam phaser in accordance with the invention comprises four assemblies: a sprocket assembly, an inner hub assembly, a cover assembly, and a piston assembly. The joined assemblies provide an improved phaser function over that of the prior art phaser. The component parts of the assemblies are [carefully] re-configured from the analogous parts of the prior art phaser to permit much of the improved phaser to be manufactured inexpensively by powdered metal forming or by stamping from sheet metal, in contrast with a prior art cam phaser wherein all parts are formed expensively either by machining from forged blanks or by investment casting. These changes reduce the cost of manufacture, reduce the weight and axial length, and improve the speed of response, all of which are important customer acceptance criteria. In addition, the irregularly shaped and larger capacity oil passages of the present invention, which require no machining after forming, permit further improvement in speed of response time of the phaser assembly. Further, the proportions of some parts are altered such that all radial and axial loads are borne by a single bearing in place of two bearings in the prior art phaser, thereby reducing variability in axial alignment of the component parts.




The present invention overcomes the problems of the prior art by providing a cam phaser with a lighter, less expensive sheet metal cover. The invention uses a sheet metal cover to replace the conventional cast and machined cover by rearranging the load distribution of the cam phaser. Instead of the cover bearing the load, the invention places the load on an inner hub. With the load redistributed, the cover is made with less expensive materials and processes. In the preferred embodiment, the cover is made of sheet metal or net casting. The cover, while providing a seal for the pressure chamber that actuates the piston, no longer bears the load of the camshaft. A target wheel, also of sheet metal, is an optional component that is mounted on the outside of the cover. The target wheel has indicia for generating signals representative of the angular position of the cam phaser. Those signals are used to control the setting of the angle of the cam phaser.




With the present invention all the components of the cover and the inner hub are net shaped as originally manufactured thereby eliminating the cost of additional machining. The added machining of o-ring grooves is also eliminated. Likewise, targets are net cast into the sheet metal cover or are easily stamped rather than machined into a cast cover.




Further, with the present invention the manufacturing of the piston is simplified and the cost reduced by eliminating the need to machine grooves for the o-ring seals in the piston skirt.











BRIEF DESCRIPTION OF THE DRAWINGS




The foregoing and other objects, features, and advantages of the invention, as well as presently preferred embodiments thereof, will become more apparent from a reading of the following description in connection with the accompanying drawings in which:





FIG. 1

is a cross-sectional view of a prior art spline-type cam phaser substantially as disclosed in U.S. Pat. No. 5,588,404;





FIG. 2

is a cross-sectional view of an improved spline-type cam phaser in accordance with the invention;





FIG. 3

is an exploded cross-sectional view of the sprocket assembly of the cam phaser shown in

FIG. 2

;





FIG. 4

is an assembled cross-sectional view of the exploded sprocket assembly show in

FIG. 3

;





FIG. 5

is an exploded cross-sectional view of the inner hub assembly of the cam phaser shown in

FIG. 2

;





FIG. 6

is an assembled cross-sectional view of the exploded inner hub assembly shown in

FIG. 5

;





FIG. 7

is an exploded cross-sectional view of the cover assembly of the cam phaser shown in

FIG. 2

;





FIG. 8

is an assembled cross-sectional view of the exploded cover assembly shown in

FIG. 7

;





FIG. 9

is an exploded cross-sectional view of the cam phaser shown in

FIG. 2

, showing the combining of the assemblies shown in

FIGS. 4

,


6


, and


8


with a piston assembly;





FIG. 10

is an assembled cross-sectional view of the exploded assemblies shown in

FIG. 9

,

FIG. 10

being substantially identical with

FIG. 2

;





FIG. 11

is a plan view of a sprocket wheel shown in

FIG. 3

;





FIG. 12

is a plan view of a target wheel shown in

FIG. 7

;





FIG. 13

is a cross-sectional view of an alternative embodiment of a phase control piston wherein a non-load-bearing portion of the piston is formed from a plastic polymer; and





FIG. 14

is an elevational view of the phase control piston shown in FIG.


13


.











DESCRIPTION OF THE PREFERRED EMBODIMENT




The improvements and benefits conferred by a cam phaser in accordance with the invention may be best understood by first considering a prior art cam phaser.




Referring to

FIG. 1

, numeral


10


generally indicates a portion of the valve gear of an internal combustion engine including a camshaft


12


conventionally carrying a plurality of valve-actuating cams (not shown) and mounted for rotation in the cylinder head or other portion of a multi-camshaft engine (not shown). Camshaft


12


includes at one end an enlarged cylindrical journal


14


, which may be a bearing journal, on the end of which is fixedly mounted a prior art variable cam phaser


16


formed in accordance with the prior art, substantially as disclosed in U.S. Pat. No. 5,588,404 issued Dec. 31, 1996 to Lichti et al., the relevant disclosure of which is hereby incorporated by reference.




Cam phaser


16


includes an outer drive member in the form of a pulley


18


(although a chain sprocket, gear, or other suitable drive device could equally well be used). The pulley


18


includes an outer rim


20


, adapted to be driven by a toothed timing belt (not shown). As the belt drives pulley


18


, the cam phaser


16


transfers its rotary motion to the camshaft


12


. The angular position of the cam phaser


16


with respect to the camshaft is adjusted to vary the opening and closing of the valves. That adjustment is made to increase or reduce horsepower and/or fuel efficiency. Rim


20


is connected by a web


22


with a tubular portion


24


extending axially to one side of the web and having at an outer end a cylindrical external bearing surface


26


. Within the portion


24


and extending from the outer end adjacent bearing surface


26


are internal right hand helical splines


28


.




Pulley


18


is supported for relative rotation upon a coaxial driven hub assembly comprising an assembly of a hub flange


30


and a hub


32


. The hub flange includes an end having a circular recess


34


in which the end of the camshaft journal


14


is received. A flange


36


extends outwardly from the recess


34


and terminates outwardly in an enlarged cylindrical journal


38


that slidably engages an internal bearing surface


40


of tubular portion


24


. Adjacent to the flange


36


and opening away from the camshaft


12


, the hub flange


30


includes a recess


42


adjacent an external guiding surface


44


containing a piston seal ring


46


. Adjacent the guiding surface


44


, a shoulder


48


extends inwardly to a smaller diameter tubular portion


50


on which the hub


32


is supported.




Hub


32


comprises a tubular body provided, on an outer diameter, with external left hand helical splines


52


. On its inner diameter, hub


32


includes a raised portion


54


carried by tubular portion


50


, an end face


56


engaging the shoulder


48


, and an annular shoulder


58


that is engaged by an outwardly flared flange


60


formed by a thin wall end of the tubular portion


50


of the hub flange. Further outward, in the direction away from the camshaft, the hub


32


inner diameter forms a slightly enlarged internal locating surface


62


having a retaining groove


64


toward its inner end.




An annular cover


66


having a central opening and a generally U-shaped annular cross-section is mounted on the outer ends of the hub


32


and tubular portion


24


. The cover includes an outer wall


68


with an inner surface engaging the bearing surface


26


of the tubular portion


24


and an inner wall


70


having an outer surface engaging the internal locating surface


62


of the hub. An inward extension of the inner wall forms a shoulder


72


against which is clamped the head


74


of a central fastener in the form of an attaching bolt


76


. The bolt extends through openings in the cover


66


and the hub flange


30


into a hollow center


78


of the camshaft


12


wherein it is threadably engaged in a manner not shown. An annular end wall


80


of the cover extends between the outer and inner walls


68


,


70


and encloses an annular space within the cam phaser. Within this space are located a first annular phase control piston


82


and a second annular lash control piston


84


.




The first piston


82


divides the annular space into an annular pressure chamber


86


adjacent the cover


66


and an annular return chamber


88


between the flange


36


and the piston


82


. Piston


82


includes a ring of external right hand helical splines


90


engaging the internal splines


28


within the tubular portion


24


of the pulley. Additionally, there is a ring of internal left hand helical splines


92


that engage the external helical splines


52


of the hub


32


. Accordingly, axial motion of the piston


82


causes a change in the angular orientation or phase relation between pulley


18


and the hub


32


, as well as the associated camshaft


12


to which the hub is attached. Changing the phase relationship produces a corresponding change in the time when the valves open and close.




A large helical coil compression spring


94


is seated against the flange


36


of the hub flange and is received in a recess


96


of the piston


82


for biasing the piston in a direction toward the annular cover


66


, tending to return the camshaft to a predetermined position, such as a retarded or advanced position for valve actuation. The spring


94


lies within the return chamber


88


formed on the camshaft side of the piston. A piston seal ring


100


seated in a groove in a guiding surface


102


of the piston


82


engages a cylinder surface


104


within the tubular portion


24


of the pulley


18


. Piston seal ring


100


and piston seal ring


46


in the guiding surface


44


of flange


60


, which engages a cylindrical surface of the piston, limit the leakage of oil between the pressure chamber


86


and the return chamber


88


.




Piston


82


alters the phase of the camshaft. When piston


82


moves in a direction against the bias of spring


94


, it retards the camshaft timing, by forcing pressurized engine oil (or hydraulic fluid) through passages


108


in the camshaft and


110


in the hub flange which communicate with drain passage


114


in the camshaft. Passage


112


is connected to a pressurized oil supply for forcing piston


82


in an advance direction. Suitable seals are provided to prevent the leakage of pressure and drain oil from the interior of the cam phaser to external surfaces of pulley


18


.




The annular lash control piston


84


is located in the pressure chamber


86


between the piston


82


and cover


66


. This piston includes external and internal helical splines like those of piston


82


and also engaging the corresponding splines


28


,


52


of the pulley and hub respectively. The splines of the two pistons are preferably formed with machined end surfaces of the pistons in engagement with one another so that the helices of the splines are continuous when the pistons are engaged. An annular groove


120


in the phase control piston


82


, opening toward the facing surface of the lash control piston


84


, receives a cylindrical compression spring, preferably in the form of a wave spring


122


. Spring


122


urges the lash control piston


84


away from the phase control piston


82


and takes up the lash in the splines between the associated pulley and hub. In this lash control action, the pistons


82


,


84


function in the same manner as known split gears used for lash control in gear drives.




Prior to assembly of the cam phaser, the hub flange


30


has its tubular portion


50


extending axially. This component is then assembled together with the hub


32


, pistons


82


,


84


, and pulley


18


. Hub


32


is not fixed to the hub flange but is rotatable on the tubular portion


50


, so that the pulley


18


with splined pistons and hub may be rotated relative to the hub flange


30


in order to properly time the pulley to the hub flange with the compression spring


94


fully extended. The outer end of the tubular portion


50


is then deformed, such as by staking or rolling, to form the flange


60


shown in FIG.


1


. Flange


60


engages shoulder


58


of the hub, locking the components in their desired orientations. The cover


66


may then be installed and is retained by a retaining ring


124


until assembly of the unit to an engine camshaft.




Thereafter, the pre-timed mechanism is installed on a camshaft


12


as in

FIG. 1. A

conventional pin (not shown) may be used to orient the hub flange


30


to the camshaft for proper timing. Bolt


76


is threaded through the openings into the camshaft and tightened so as to lock the cover, hub, hub flange, and camshaft elements into fixed relation. This manner of assembly permits the manufacture and assembly of the splined components to be carried out without regard to any requirement for orientation or fixed relation of the internal and external splines other than the splines on the two pistons which are formed together. This allows timing of the elements to be conducted only after assembly of the mechanism components in the manner just described.




Referring to

FIGS. 2-14

, an improved splined cam phaser


126


embodying the invention includes a generally tubular inner hub assembly


128


comprising a generally cylindrical inner hub


130


and a hub flange


132


. See

FIGS. 5 and 6

. The hub flange


132


includes a recess


134


for receiving the flat end of a camshaft


12


having advance and retard oil passages


136


,


138


formed therein and a central threaded bore


140


for receiving bolt


76


to mount the inner hub assembly


128


onto the camshaft


12


. The hub flange


132


has an oversize central bore


142


for passage of the bolt


76


and first and second passages


144


,


146


mating with the advance and retard oil passages


136


,


138


, respectively in the camshaft


12


to admit oil to the advance and retard oil galleries of phaser


126


. The hub flange


132


has a cylindrical outer wall portion


148


having an axially extensive outer guide surface


150


and an axially extensive inner piston guide surface


152


. The oversize bore


142


in the hub flange is sized to receive in interference fit a boss


154


on the inner hub


130


, the boss sealably mating with the end of the camshaft


12


to prevent leakage between the oil supply passages


136


and


138


. A portion of the inner hub


130


distal from the camshaft comprises a longitudinal gear


156


having external left hand helical splines


52


. A shouldered step


158


in the inner hub adjacent the gear


156


receives a formed ring


160


for retaining an inner piston seal


162


. The axial bore


164


in inner hub


130


is assymetrically enlarged through its distal portion to provide an oil passage


166


to the pressure chamber, as discussed below. The inner hub


130


and hub flange


132


are press fit together to define an annular return chamber


88


therebetween, as shown in

FIGS. 5 and 6

. The hub flange


132


is configured so that it may be easily formed inexpensively by powdered metal forming in known fashion, such forming including net shaping of the oil passages


144


,


146


. The inner hub


130


is preferably formed by machining of a forged blank and can be alternately formed from powdered metal.




In the present invention, the several functions of prior art annular cover


66


are divided among several inexpensively formed new components which are assemblable into a cover assembly


168


which is less expensive to manufacture than investment-cast cover


66


. Cover assembly


168


comprises an outer hub


170


and cover


218


, and an optional timing wheel


172


as shown in

FIGS. 7 and 8

. The outer hub


170


has an axial bore


174


for accommodating bolt


76


and is supported concentrically within a wider-diameter outer portion


176


of the inner hub


130


, to which it is attached for joint rotation by a pin


178


. An annular space


180


between the inner hub


130


and the outer hub


170


defines an annular passage for pressurized oil from the assymetric axial bore


164


in the inner hub to the pressure chamber. The outer hub


170


is provided with an axial outer recess


182


for receiving the head


74


of the bolt


76


and with a short axial boss


184


having parallel sides surrounding the recess for receiving timing wheel


172


which is preferably stamped from sheet steel. Timing wheel


172


permits continuous measurement of the phase of the camshaft relative to the crankshaft by an external sensor (not shown). The timing wheel


172


has a non-circular central opening


186


having parallel sides


188


, as shown in

FIG. 12

, which is matable with the boss


184


on the outer hub


170


. The timing wheel


172


may have both radial and axial flange portions


190


,


192


as desired, and is readily and inexpensively formed by stamping or deep drawing from sheet metal. The outer hub


170


is also configured for inexpensive and reliable forming by powdered metal techniques. The cover


218


is provided with a central recess


220


which surrounds the outer hub


170


and which has a lip


222


for engaging a step


224


on the outer hub


170


. Preferably, an O-ring


226


is captured between lip


222


and step


224


to provide a rotating seal of the pressure chamber


86


. The cover


218


is readily and inexpensively formed by stamping or deep drawing from sheet metal.




An advantage of the present cam phaser configuration is that the juncture of the cover with the sprocket flange is no longer a rotary bearing which can adversely affect axial alignment. Prior art cover


66


is fixed to the camshaft by bolt


76


and rotates therewith against hub flange


24


(surface


26


in FIG.


1


). Cover


66


serves also as a timing wheel. In the present invention, cover


218


is fixed to the sprocket flange


200


and instead rotates with the sprocket and crankshaft, there being a new rotary seal


226


, such as an o-ring, between cover


218


and outer hub


170


. Outer hub


170


bears the axial load formerly borne by cover


66


. This improvement, and the associated reduction in fabrication costs of the improved timing wheel assembly, is possible because there is no secondary axial guiding surface


26


as in prior art phaser


16


, due to the axially longer primary guiding surface


150


/


210


formed in inner hub assembly


128


and sprocket assembly


194


, respectively, as discussed in more detail below.




Concentrically surrounding the inner hub assembly


128


is a sprocket assembly


194


comprising a generally flat toothed sprocket wheel


196


for receiving a timing chain (not shown). The sprocket assembly has a central opening


198


and a generally cylindrical sprocket flange


200


having a shouldered portion


202


, as shown in FIG.


3


. The protion


202


is fit into the sprocket wheel opening


198


to form the sprocket assembly


194


, as shown in FIG.


4


. The sprocket wheel


196


is provided with a plurality of holes


204


for bolting the wheel to the flange via matching holes


206


in flange


200


. Preferably, the holes in the sprocket wheel are radially slotted to permit precise timing adjustment of the phaser by slight rotation of the sprocket wheel past the sprocket flange during final assembly. As shown in

FIG. 9

, during assembly, the sprocket flange


200


is disposed radially apart from the inner hub assembly


128


to form an annular space


208


therebetween, as discussed further below. The sprocket flange


200


is preferably formed by machining of a forged blank. The sprocket wheel


196


is readily formed inexpensively by known powdered metal forming techniques, wherein powdered metal is compressed and solidified in a mold to yield a rigid, durable part.




A portion of the inner wall of the sprocket flange proximal to the camshaft is a smooth cylindrical guiding surface


210


for rotatably mating with the cylindrical outer surface


150


of the hub flange


132


to form an axially-extensive single bearing for carrying all imposed radial loads and for maintaining axial alignment of the hub assembly and the sprocket assembly. The portion of the inner wall of the sprocket flange distal from the camshaft is provided with internal right hand helical splines


28


.




In the annular space


208


between the sprocket flange and the hub assembly is disposed a piston assembly


211


comprising an annular phase control piston


82


and an annular lash control piston


84


. The pistons are provided on their outer and inner surfaces, respectively, with external right hand helical splines


90


and internal left hand helical splines


92


for meshingly engaging the corresponding splines


28


,


52


on the sprocket flange and the hub assembly, respectively. An intermediate annular chamber


120


between the pistons holds a wave spring


122


for urging the pistons apart to take up lash in the splines. The pistons divide the annular space


208


into an annular pressure chamber


86


and an annular return chamber


88


. The phase control piston


82


has an inner skirt


212


which is slidably sealed against the piston seal


162


in the seal ring


160


, and an outer seal ring


214


and outer piston seal


216


which is slidably disposed against the inner guide surface


152


of the outer wall portion


148


. The pressure chamber


86


is closed by the inverted cup-shaped cover


218


which is an element of the cover assembly


168


which is sealingly attached as by crimping to the outer end of the sprocket flange


200


.




Referring to

FIGS. 13 and 14

, the cost and weight of annular phase control piston


82


may be reduced by substituting a moldable plastic polymer, for example, Nylon 6/6 available from E.I. DuPont de Nemours, Wilmington, Del. USA, for a non-load-bearing portion of the piston. In alternative embodiment


82




a


, the load-bearing splined portion


82




b


is machined from a forged metal blank, as in piston


82


, but without the skirt portion. A flange


83


is provided as a lock for plastic skirt


85


which is conveniently overmolded onto piston


82




b


in known insert molding fashion to yield embodiment


82




a.






Within the return chamber


88


is disposed a helical coil compression spring


94


for biasing the pistons to a full advance position. The spring


94


is seated at its proximal end in an annular recess


42


in the hub flange and at its distal end in an annular recess


96


in the phase control piston.




To complete fabrication of the improved phaser


126


, as shown in

FIG. 9

, the piston assembly


211


and compression spring


94


are installed onto the inner hub assembly


128


and the two assemblies are inserted into the sprocket assembly


194


through the central opening


228


in the sprocket flange


200


. A snap ring


230


is installed in the groove


232


formed between the sprocket flange


200


and the hub flange


132


to retain the inner hub assembly


128


in the sprocket assembly


194


. The cover assembly


168


including the O-ring


226


and cover


218


is inserted into the recess


176


(

FIG. 5

) in the inner hub assembly


128


, the two assemblies being rotationally aligned to permit a pin


178


to be inserted therebetween. The radial flange


234


on the cover


218


is then sealed to the sprocket flange


200


as by roll crimping or welding. The cover


168


is retained in the phaser by bolt


76


.




The operation of a cam phaser in accordance with the invention is substantially identical with that of the prior art cam phaser as disclosed in the incorporated reference.




A splined cam phaser in accordance with the invention has several important advantages over the prior art cam phaser.




First, an inner hub assembly


128


that includes a separate hub flange


132


and an inner hub


130


replaces the complex conventional hub flange


30


. The prior art hub flange


30


is entirely machined from a complex forged blank and is very expensive to fabricate. The present inner hub


130


is also machined from a forging, but the forging is much less complex and the machining is much less expensive. The inner hub


130


is configured to permit powdered metal forming, at significant savings in fabrication cost.




Second, the axially short external guiding surface


44


on the prior art hub flange


30


is reconfigured as an axially extensive external guiding surface


150


on hub flange


132


. The axial length is sufficient that all radial loads may be borne on this one bearing surface, eliminating the need for a second external bearing surface


26


as on the prior art hub flange


30


. In the prior art phaser


16


, variances in the first and second bearings are additive, whereas in the improved phaser all variance is contained in a single bearing. Thus, total bearing variance is reduced and axial alignment of the component parts is significantly improved.




Third, the hub flange


132


is conveniently configured such that the oil passages


144


,


146


are net formed in the flange during powdered metal fabrication thereof, thus eliminating the complex and expensive drilling and machining of oil passages required by the prior art hub flange. As the oil passage are net formed, no secondary or finish machining is required, thus reducing cost.




Fourth, eliminating the second bearing removes the need for great structural strength and rigidity in annular cover


66


, which is also needed to support the axial load imposed by the bolt head


74


without being deformed. Cover


66


is formed very expensively by investment casting. In phaser


126


, cover


66


is reconfigured as cover assembly


168


having three separate parts: the outer hub


170


, the cover


218


, and the optional timing wheel


172


. The cover and timing wheel are readily stamped, punched, or deep drawn by a shaped ram or form from sheet metal in known fashion, and the outer hub is readily formed by powdered metal forming, all at a great reduction in cost over prior art cover


66


. Axial length of the phaser is also reduced by obviating the need for a thick cover. Reduction in mass of the cover also reduces inertia and thus improves speed of response of the phaser.




Fifth, the inner piston seal is provided by a separate grooved ring


160


, for supporting seal


162


, the ring being pressed into a shouldered step


158


in inner hub


130


. This permits easy machining of the inner hub to form the hub splines


52


before installation of the ring with no required allowance in length of the inner hub to accommodate a machining transition zone between the splines and the seal groove. This improvement reduces the minimum axial length of the phaser.




Sixth, an integral O-ring groove to accommodate an O-ring


226


as an inner seal to the annular pressure chamber


86


is formed between a step


224


on the outer hub and the lip


222


on the cover. Thus, the need to machine an o-ring groove to seal the the annular pressure chamber is eliminated.




Seventh, timing of the phaser may be performed after assembly by relative rotation of the sprocket wheel


196


and sprocket flange


200


as described above. Thus, no post assembly staking of the outer hub to the inner hub, as in the prior art phaser, is required.




Eighth, the annular phase control piston may be formed partially of a plastic polymer to reduce cost and weight.




It will be seen from the above that, in contrast with the prior art cam phaser, only the splined components of the improved cam phaser are formed by machining from forged blanks (the inner hub, the sprocket flange, and the two pistons). All other structural parts may be formed by other inexpensive processes from inexpensive starting materials, thus reducing the cost of manufacture, improving ease of assembly, reducing size and weight, and improving response performance.




From the foregoing description, it will be apparent that there has been provided an improved splined cam phaser, wherein the cost and ease of fabrication is very significantly reduced, size is reduced, and speed of response is improved. Variations and modifications of the herein described cam phaser, in accordance with the invention, will undoubtedly suggest themselves to those skilled in this art. Accordingly, the foregoing description should be taken as illustrative and not in a limiting sense.



Claims
  • 1. A variable cam phaser for attachment to a camshaft of an internal combustion engine for varying the phase relationship between the camshaft and a crankshaft by application of variable force to the phaser, comprising:a) input drive means for receiving input rotary motion from said crankshaft and for transmitting said input rotary motion to said camshaft; b) sprocket flange means adjustably mounted to said input drive means and rotatable therewith and having first-handed internal helical splines on a portion of a radial inner surface thereof distal from said camshaft; c) inner hub flange means connectable to said camshaft for transmitting the rotary motion from said input drive means to the camshaft, said inner hub flange means having a hub portion and a flange portion disposed within said sprocket flange means, said flange portion extending axially over a portion of said radial inner surface of said sprocket flange means proximal to said camshaft to define an axially extensive bearing therebetween, said inner hub flange means having second-handed external helical splines extending into a first annular space opposite said first-handed internal helical splines on said sprocket flange means; d) outer hub means coupled to said inner hub flange means to define a second annular space between said outer hub means and said hub portion of said inner hub flange means and further a third annular space between said outer hub means and the distal portion of said sprocket flange means; e) annular piston means disposed within said second annular space and dividing said space into a first compression chamber distal from said camshaft and a second compression chamber proximal to said camshaft, said annular piston means having external helical splines in meshable relationship with said splines on said sprocket flange means and having internal helical splines in meshable relationship with said splines on said inner hub means, said piston means being operable upon application of fluid pressure in one of said first and second compression chambers to move in a direction toward the other of said chambers to act on the splines and thereby radially displace said inner hub flange means and said sprocket flange means with respect to each other to adjust the phase between the crankshaft and the camshaft; and f) a cover assembly including a cover sealably mounted to an outer end of said sprocket flange means and to an outer surface of said outer hub means to enclose said first compression chamber, said cover having a central opening therethrough for receiving said outer hub means and being connected to said outer hub means for rotation therewith, wherein the cover comprises stamped metal.
  • 2. The variable cam phaser of claim 1, further comprising a timing wheel mounted on the outer hub means.
  • 3. A variable cam phaser in accordance with claim 1, wherein said cover further includes a seal disposed between said cover and said outer hub means.
  • 4. The variable cam phaser of claim 3, wherein the outer hub means comprises a stepped portion for receiving said seal.
  • 5. The variable cam phaser of claim 3, wherein the cover comprises a lip for receiving said seal.
  • 6. The variable cam phaser of claim 1, wherein the outer hub means comprises cast or powdered metal.
  • 7. A variable cam phaser in accordance with claim 2, wherein said timing wheel is formed from sheet metal by a process selected from the group consisting of punching, stamping, and deep drawing.
US Referenced Citations (6)
Number Name Date Kind
5588404 Lichti et al. Dec 1996 A
5870983 Sato et al. Feb 1999 A
5875751 Strauss et al. Mar 1999 A
5970930 Scheidt et al. Oct 1999 A
6089198 Goppelt et al. Jul 2000 A
6116200 Abts et al. Sep 2000 A