Patent Application
20150275707
The present invention relates to an internal combustion engine with a camshaft phaser which uses pressurized oil to vary the phase relationship between a crankshaft and a camshaft of the internal combustion engine; more particularly to such an internal combustion engine which includes a drive belt for transmitting rotational motion from the crankshaft to the camshaft; and still even more particularly to such an internal combustion engine which includes a sealing arrangement to seal the drive belt from the oil used to vary the phase relationship between the crankshaft and the camshaft.
A typical vane-type camshaft phaser for changing the phase relationship between a crankshaft and a camshaft of an internal combustion engine generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is selectively supplied to either the advance chambers or the retard chambers and vented from the other of the advance and retard chambers in order to rotate the rotor within the stator and thereby change the phase relationship between the camshaft and the crankshaft. Some camshaft phasers include a valve spool within the camshaft phaser in order to selectively supply and vent oil to and from the advance and retard chambers as necessary in order to achieve the desired phase relationship between the camshaft and the crankshaft. When the oil is vented from either the advance chambers or the retard chambers, the oil is typically drained out of the camshaft phaser and allowed to reach a drive member, such as a chain, gear, or belt, which transfers rotational motion from the crankshaft to the camshaft phaser. While this may be acceptable to some drive members, particularly chains and gears, other drive members, particularly belts, may not tolerate exposure to oil.
U.S. Pat. No. 5,361,735 to Butterfield et al. teaches a camshaft phaser having a flexible diaphragm at one axial end thereof to prevent oil from the camshaft phaser from reaching the drive belt. The flexible diaphragm is positioned between a valve spool and an actuator which alters the position of the valve spool. Consequently, the actuator pushes on the valve spool through the flexible diaphragm during operation. Since the flexible diaphragm is rotating at the rotational speed of the camshaft during operation and the rotational actuator is rotationally stationary, durability issues with the flexible diaphragm may result, particularly if there is misalignment in concentricity between the actuator and the center of the flexible diaphragm.
What is needed is a camshaft phaser which minimizes or eliminates one or more the shortcomings as set forth above.
Briefly described, an internal combustion engine includes a crankshaft rotatable about a crankshaft axis and a camshaft rotatable by the crankshaft about a camshaft axis. The internal combustion engine also includes an oil supply, an engine cover, and a drive member disposed within the engine cover for transferring rotational motion from the crankshaft to the camshaft. A camshaft phaser is disposed within the engine cover for controllably varying the phase relationship between the crankshaft and the camshaft. The camshaft phaser includes an input member driven by the drive member, an output member rotatable with the camshaft wherein the output member is rotatable relative to the input member by oil from the oil supply thereby varying the phase relationship between the crankshaft and the camshaft, and a valve spool within the camshaft phaser and moveable therein between 1) an advance position to direct oil from the oil supply to cause the input member to rotate relative to the output member to advance the camshaft relative to the crankshaft and 2) a retard position to direct oil from the oil supply to cause the input member to rotate relative to the output member to retard the camshaft relative to the crankshaft. An actuator moves the valve spool between the advance position and the retard position and a sealing arrangement defines a dry zone with one of the engine cover and the actuator to isolate the drive member from oil used to rotate the output member relative to the input member.
Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.
This invention will be further described with reference to the accompanying drawings in which:
Referring to
With continued reference to
Stator 30 is generally cylindrical and includes a plurality of radial chambers 48 (only one radial chamber 48 is labeled in
Rotor 32 includes a central hub 54 with a plurality of vanes 56 extending radially outward therefrom and a central through bore 58 extending axially therethrough. The number of vanes 56 is equal to the number of radial chambers 48 provided in stator 30. Rotor 32 is coaxially disposed within stator 30 such that each vane 56 divides each radial chamber 48 into advance chambers 60 and retard chambers 62. The radial tips of lobes 50 are mateable with central hub 54 in order to separate radial chambers 48 from each other. Each of the radial tips of lobes 50 and the tips of vanes 56 may include one of a plurality of wiper seals 64 to substantially seal adjacent advance chambers 60 and retard chambers 62 from each other.
Back cover 34 is sealingly secured, using cover bolts 66, to the axial end of stator 30 that is proximal to camshaft 16. A back cover seal 68, for example only, an o-ring, may be provided between back cover 34 and stator 30 in order to provide an oil-tight seal between the interface of back cover 34 and stator 30. Tightening of cover bolts 66 prevents relative rotation between back cover 34 and stator 30. Back cover 34 includes a back cover central bore 70 extending coaxially therethrough. The end of camshaft 16 is received coaxially within back cover central bore 70 such that camshaft 16 is allowed to rotate relative to back cover 34. In an alternative arrangement, camshaft phaser pulley 52 may be integrally formed or otherwise attached to back cover 34 rather than to stator 30 as described previously.
Similarly, front cover 36 is sealingly secured, using cover bolts 66, to the axial end of stator 30 that is opposite back cover 34. A front cover seal 72, for example only, an o-ring, may be provided between front cover 36 and stator 30 in order to provide an oil-tight seal between the interface of front cover 36 and stator 30. Cover bolts 66 pass through back cover 34 and stator 30 and threadably engage front cover 36, thereby clamping stator 30 between back cover 34 and front cover 36 to prevent relative rotation between stator 30, back cover 34, and front cover 36. In this way, advance chambers 60 and retard chambers 62 are defined axially between back cover 34 and front cover 36.
Camshaft phaser 22 is attached to camshaft 16 with camshaft phaser attachment bolt 40 which extends coaxially through central through bore 58 of rotor 32 and threadably engages camshaft 16, thereby clamping rotor 32 securely to camshaft 16. In this way, relative rotation between stator 30 and rotor 32 results in a change in phase relationship or timing between crankshaft 12 and camshaft 16.
With continued reference to
Oil supply 44 provides a supply of pressurized oil to valve spool 42 through radial camshaft passages 80 which communicate with a camshaft counterbore 82 which forms a camshaft annular oil passage 84 with a portion of camshaft phaser attachment bolt 40. The oil then passes from camshaft annular oil passage 84 to an axial rotor oil passage 86 which extends axially into rotor 32. The oil is subsequently communicated to an annular rotor oil supply groove 88 which extends radially outward from central through bore 58 and intersects axial rotor oil supply passage 86. Annular rotor oil supply groove 88 is axially aligned with bolt oil supply passages 90 which extend radially through camshaft phaser attachment bolt 40 from valve bore 78. In this way, oil from oil supply 44 is supplied to valve spool 42.
Valve spool 42 includes a body 92 that is generally cylindrical, hollow, and dimensioned to provide annular clearance between body 92 and valve bore 78 of camshaft phaser attachment bolt 40. Valve spool 42 also includes an advance land 94 extending radially outward from body 92 for selectively blocking fluid communication between bolt oil supply passages 90 and advance bolt passages 96 which extend radially outward through camshaft phaser attachment bolt 40 from valve bore 78 and communicate with advance oil passages 74 of rotor 32 through an annular rotor advance oil groove 98 which extends radially outward from central through bore 58. Advance land 94 fits within valve bore 78 of camshaft phaser attachment bolt 40 in a close fitting relationship to substantially prevent oil from passing between advance land 94 and valve bore 78. Valve spool 42 also includes a retard land 100 extending radially outward from body 92 for selectively blocking fluid communication between bolt oil supply passages 90 and retard bolt passages 102 which extend radially outward through camshaft phaser attachment bolt 40 from valve bore 78 and communicate with retard oil passages 76 of rotor 32 through an annular rotor retard oil groove 104 which extends radially outward from central through bore 58. Retard land 100 is spaced axially from advance land 94 and fits within valve bore 78 of camshaft phaser attachment bolt 40 in a close fitting relationship to substantially prevent oil from passing between retard land 100 and valve bore 78.
Valve spool 42 is axially moveable within valve bore 78 with input from actuator 46 and a spool spring 106 which is positioned axially between valve spool 42 and the bottom of valve bore 78. When actuator 46 is in an unenergrized state of operation as shown in
Conversely, when actuator 46 is in an energized state of operation as shown in
Drive member 26 may not be compatible with the oil supplied to camshaft phaser 22, consequently, a dry zone 110 may be formed within engine cover 28. Drive member 26 is located within dry zone 110 which is substantially free of the oil supplied to camshaft phaser 22. Dry zone 110 is formed by a sealing arrangement which may comprise an engine cover to camshaft phaser seal 112 and an engine to camshaft phaser seal 114. The sealing arrangement will be described in greater detail in the paragraphs that follow.
Referring now to
Engine to camshaft phaser seal 114 provides a seal between camshaft support 18 and back cover 34. A camshaft support bore 124, which is cylindrical, extends into camshaft support 18 in a coaxial relationship with camshaft 16. Engine to camshaft phaser seal 114 includes an engine to camshaft phaser seal supporting body 126 which is ring shaped and secured coaxially within camshaft support bore 124, for example, by a press fit. Engine to camshaft phaser seal supporting body 126 may be made of a rigid material, for example, metal or plastic. Engine to camshaft phaser seal 114 also includes an engine to camshaft phaser seal lip seal 128 which extends radially inward from engine to camshaft phaser seal supporting body 126. Engine to camshaft phaser seal lip seal 128 may be molded and bonded to engine to camshaft phaser seal supporting body 126 and may be made of an elastomeric or rubber-like material, for example only, Nitrile Butadiene Rubber (NBR), Viton®, or silicone. Engine to camshaft phaser seal 114 may also include an engine to camshaft phaser seal dust lip seal 130 which extends radially inward from engine to camshaft phaser seal supporting body 126 and may be made from the same material as engine to camshaft phaser seal lip seal 128. Engine to camshaft phaser seal dust lip seal 130 protects engine to camshaft phaser seal lip seal 128 from external contamination that may have undesirable effects on engine to camshaft phaser seal lip seal 128. Back cover 34 includes a back cover sealing body 132 for radially mating with engine to camshaft phaser seal lip seal 128. Back cover sealing body 132 is ring-shaped and extends axially away from back cover 34 into camshaft support bore 124 in a coaxial relationship with camshaft support bore 124. Back cover sealing body 132 is sized to elastically deform engine to camshaft phaser seal lip seal 128 when assembled in order to provide an oil-tight seal between back cover sealing body 132 and engine to camshaft phaser seal lip seal 128.
Engine cover 28 includes an engine cover bore 134 extending therethrough in a substantially coaxial relationship with camshaft 16. Actuator 46 is received coaxially within engine cover bore 134 and is fixed to engine cover 28 to prevent relative rotation between engine cover 28 and actuator 46. An engine cover to actuator seal 136, which may be an O-ring as shown, is disposed between actuator 46 and engine cover 28. In this way, oil that is vented from advance chambers 60 and retard chambers 62 through the end of valve bore 78 is prevented from exiting engine cover 28 between the interface of engine cover 28 and actuator 46. It should be noted that engine cover to actuator seal 136 is a static seal, unlike engine cover to camshaft phaser seal 112 and engine to camshaft phaser seal 114 which are dynamic seals, since there is no relative movement between engine cover 28 and actuator 46.
With continued reference to
Alternatively, as shown in
While not shown, it should now be understood that camshaft phaser 22 may include a bias spring that either partially or completely offsets the natural retarding torque induced by the overall valve train friction, balances performance times, or helps return the phaser to a default position of rotor 32 within stator 30. The bias spring may be grounded at one end thereof to front cover 36 and may be attached at the other end thereof to rotor 32 for biasing rotor 32 relative to stator 30.
While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
