Patent Grant
9784144
The present invention relates to a camshaft phaser for varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine; more particularly to such a camshaft phaser which is a vane-type camshaft phaser; even more particularly to a vane-type camshaft phaser which includes a control valve in which the position of the control valve determines the phase relationship between the crankshaft and the camshaft; and still even more particularly to such a camshaft phaser which uses torque reversals of the camshaft to actuate the camshaft phaser.
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 one of the advance and retard chambers and vacated from the other of the advance chambers and retard chambers by a phasing oil control valve in order to rotate the rotor within the stator and thereby change the phase relationship between the camshaft and the crankshaft. One such camshaft phaser is described in U.S. Pat. No. 8,534,246 to Lichti et al., the disclosure of which is incorporated herein by reference in its entirety and hereinafter referred to as Lichti et al. As is typical for phasing oil control valves, the phasing oil control valve of Lichti et al. operates on the principle of direction control, i.e. the position of the oil control valve determines the direction of rotation of the rotor relative to the stator. More specifically, when a desired phase relationship between the camshaft and the crankshaft is determined, the desired phase relationship is compared to the actual phase relationship as determined from the outputs of a camshaft position sensor and a crankshaft position sensor. If the actual phase relationship, does not match the desired phase relationship, the oil control valve is actuated to either 1) an advance position to supply oil to the retard chambers and vent oil from the advance chambers or 2) a retard position to supply oil to the advance chambers and vent oil from the retard chambers until the actual phase relationship matches the desired phase relationship. When the actual phase relationship matches the desired phase relationship, the oil control valve is positioned to hydraulically lock the rotor relative to the stator. However, leakage from the advance chambers and the retard chambers or leakage from the oil control valve may cause the phase relationship to drift over time. When the drift in phase relationship is detected by comparing the actual phase relationship to the desired phase relationship, the oil control valve must again be actuated to either the advance position or the retard position in order to correct for the drift, then the oil control valve is again positioned to hydraulically lock the rotor relative to the stator after the correction has been made. Consequently, the position of the rotor relative to the stator is not self-correcting and relies upon actuation of the phasing oil control valve to correct for the drift.
U.S. Pat. No. 5,507,254 to Melchior, hereinafter referred to as Melchior, teaches a camshaft phaser with a phasing oil control valve which allows for self-correction of the rotor relative to the stator as may be necessary due to leakage from the advance chamber or from the retard chamber. Melchior also teaches that the valve spool defines a first recess and a second recess separated by a rib such that one of the recesses acts to supply oil to the advance chamber when a retard in timing of the camshaft is desired while the other recess acts to supply oil to the retard chamber when an advance in the timing of the camshaft is desired. The recess that does not act to supply oil when a change in phase is desired does not act as a flow path. However, improvements are always sought in any art.
What is needed is a camshaft phaser which minimizes or eliminates one or more the shortcomings as set forth above.
Briefly described, a camshaft phaser is provided for controllably varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine. The camshaft phaser includes an input member connectable to the crankshaft of the internal combustion engine to provide a fixed ratio of rotation between the input member and the crankshaft; an output member connectable to the camshaft of the internal combustion engine and defining an advance chamber and a retard chamber with the input member; a valve spool coaxially disposed within the output member such that the valve spool is rotatable about an axis relative to the output member and the input member, the valve spool defining a supply chamber and a vent chamber with the output member; an actuator which rotates the valve spool in order to change the position of the output member relative to the input member by 1) supplying oil from the supply chamber to the advance chamber and venting oil from the retard chamber to the vent chamber when retarding the phase relationship of the camshaft relative to the crankshaft is desired and 2) supplying oil from the supply chamber to the retard chamber and venting oil from the advance chamber to the vent chamber when advancing the phase relationship between the camshaft relative to the crankshaft is desired; and a phasing check valve which is displaceable axially between 1) an open position which allows oil to flow from the vent chamber to the supply chamber and 2) a closed position which prevents oil from flowing from the supply chamber to the vent chamber.
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:
In accordance with a preferred embodiment of this invention and referring to
Camshaft phaser 12 generally includes a stator 18 which acts as an input member, a rotor 20 disposed coaxially within stator 18 which acts as an output member, a back cover 22 closing off one axial end of stator 18, a front cover 24 closing off the other axial end of stator 18, a camshaft phaser attachment bolt 26 for attaching camshaft phaser 12 to camshaft 14, and a valve spool 28. The rotational position of valve spool 28 relative to stator 18 determines the rotational position of rotor 20 relative to stator 18, unlike typical valve spools which move axially to determine only the direction the rotor will rotate relative to the stator. The various elements of camshaft phaser 12 will be described in greater detail in the paragraphs that follow.
Stator 18 is generally cylindrical and includes a plurality of radial chambers 30 defined by a plurality of lobes 32 extending radially inward. In the embodiment shown, there are three lobes 32 defining three radial chambers 30, however, it is to be understood that a different number of lobes 32 may be provided to define radial chambers 30 equal in quantity to the number of lobes 32.
Rotor 20 includes a rotor central hub 36 with a plurality of vanes 38 extending radially outward therefrom and a rotor central through bore 40 extending axially therethrough. The number of vanes 38 is equal to the number of radial chambers 30 provided in stator 18. Rotor 20 is coaxially disposed within stator 18 such that each vane 38 divides each radial chamber 30 into advance chambers 42 and retard chambers 44. The radial tips of lobes 32 are mateable with rotor central hub 36 in order to separate radial chambers 30 from each other. Each of the radial tips of vanes 38 may include one of a plurality of wiper seals 46 to substantially seal adjacent advance chambers 42 and retard chambers 44 from each other. While not shown, each of the radial tips of lobes 32 may also include one of a plurality of wiper seals 46.
Rotor central hub 36 defines an annular valve spool recess 48 which extends part way into rotor central hub 36 from the axial end of rotor central hub 36 that is proximal to front cover 24. As a result, rotor central hub 36 includes a rotor central hub inner portion 50 that is annular in shape and bounded radially inward by rotor central through bore 40 and bounded radially outward by annular valve spool recess 48. Also as a result, rotor central hub 36 includes a rotor central hub outer portion 52 that is bounded radially inward by annular valve spool recess 48 and is bounded radially outward by the radially outward portion of rotor central hub outer portion 52 from which lobes 32 extend radially outward. Since annular valve spool recess 48 extends only part way into rotor central hub 36, annular valve spool recess 48 defines an annular valve spool recess bottom 54 which is annular in shape and extends between rotor central hub inner portion 50 and rotor central hub outer portion 52. As shown, the outer circumference of rotor central hub inner portion 50 may be stepped, thereby defining a valve spool recess shoulder 56 that is substantially perpendicular to camshaft axis 16 and faces toward front cover 24.
Back cover 22 is sealingly secured, using cover bolts 60, to the axial end of stator 18 that is proximal to camshaft 14. Tightening of cover bolts 60 prevents relative rotation between back cover 22 and stator 18. Back cover 22 includes a back cover central bore 62 extending coaxially therethrough. The end of camshaft 14 is received coaxially within back cover central bore 62 such that camshaft 14 is allowed to rotate relative to back cover 22. Back cover 22 may also include a sprocket 64 formed integrally therewith or otherwise fixed thereto. Sprocket 64 is configured to be driven by a chain that is driven by the crankshaft of internal combustion engine 10. Alternatively, sprocket 64 may be a pulley driven by a belt or any other known drive member known for driving camshaft phaser 12 by the crankshaft. In an alternative arrangement, sprocket 64 may be integrally formed or otherwise attached to stator 18 rather than back cover 22.
Similarly, front cover 24 is sealingly secured, using cover bolts 60, to the axial end of stator 18 that is opposite back cover 22. Cover bolts 60 pass through back cover 22 and stator 18 and threadably engage front cover 24; thereby clamping stator 18 between back cover 22 and front cover 24 to prevent relative rotation between stator 18, back cover 22, and front cover 24. In this way, advance chambers 42 and retard chambers 44 are defined axially between back cover 22 and front cover 24. Front cover 24 includes a front cover central bore 66 extending coaxially therethrough and a recirculation chamber 68 which is annular in shape and extending coaxially thereinto from the side of front cover 24 which is adjacent to stator 18.
Camshaft phaser 12 is attached to camshaft 14 with camshaft phaser attachment bolt 26 which extends coaxially through rotor central through bore 40 of rotor 20 and threadably engages camshaft 14, thereby clamping rotor 20 securely to camshaft 14. More specifically, rotor central hub inner portion 50 is clamped between the head of camshaft phaser attachment bolt 26 and camshaft 14. In this way, relative rotation between stator 18 and rotor 20 results in a change in phase or timing between the crankshaft of internal combustion engine 10 and camshaft 14.
Oil is selectively transferred to advance chambers 42 from retard chambers 44, as result of torque applied to camshaft 14 from the valve train of internal combustion engine 10, i.e. torque reversals of camshaft 14, in order to cause relative rotation between stator 18 and rotor 20 which results in retarding the timing of camshaft 14 relative to the crankshaft of internal combustion engine 10. Conversely, oil is selectively transferred to retard chambers 44 from advance chambers 42, as result of torque applied to camshaft 14 from the valve train of internal combustion engine 10, in order to cause relative rotation between stator 18 and rotor 20 which results in advancing the timing of camshaft 14 relative to the crankshaft of internal combustion engine 10. Rotor advance passages 74 may be provided in rotor 20 for supplying and venting oil to and from advance chambers 42 while rotor retard passages 76 may be provided in rotor 20 for supplying and venting oil to and from retard chambers 44. Rotor advance passages 74 extend radially outward through rotor central hub outer portion 52 from annular valve spool recess 48 to advance chambers 42 while rotor retard passages 76 extend radially outward through rotor central hub outer portion 52 from annular valve spool recess 48 to retard chambers 44. Transferring oil to advance chambers 42 from retard chambers 44 and transferring oil to retard chambers 44 from advance chambers 42 is controlled by valve spool 28 and recirculation check valves 78, as will be described in detail later, such that valve spool 28 is disposed coaxially and rotatably within annular valve spool recess 48.
Rotor 20 and valve spool 28, which act together to function as a valve, will now be described in greater detail with continued reference to
Annular spool base 90 includes oil make-up passages 102 extending axially therethrough which provide fluid communication between respective vent chambers 100 and oil make-up chamber 92. Oil make-up chamber 92 receives pressurized oil from an oil source 104, for example, an oil pump of internal combustion engine 10, via a rotor supply passage 106 formed in rotor 20 and also via a camshaft supply passage 108 formed in camshaft 14. An oil make-up check valve 110 is located within rotor supply passage 106 in order to prevent oil from back-flowing from oil make-up chamber 92 to oil source 104 while allowing oil to be supplied to oil make-up chamber 92 from oil source 104.
Annular spool top 94 includes spool vent passages 112 extending axially therethrough which provide fluid communication between respective vent chambers 100 and recirculation chamber 68. It should be noted that oil make-up chamber 92 and recirculation chamber 68 are in constant fluid communication with each other via oil make-up passages 102, vent chambers 100, and spool vent passages 112, and consequently, recirculation chamber 68 and oil make-up chamber 92 are maintained at a common pressure. It should also be noted that the surface area of the face of annular spool base 90 that defines in part oil make-up chamber 92 is substantially the same as the surface area of the face of annular spool top 94 that faces toward recirculation chamber 68, thereby causing equal and opposite hydraulic loads in oil make-up chamber 92 and recirculation chamber 68, and also thereby preventing an unbalanced axial load on valve spool 28. Annular spool top 94 also includes spool supply passages 114 extending axially therethrough which provide fluid communication between respective supply chambers 98 and recirculation chamber 68. Recirculation check valves 78 are configured to allow oil to flow from recirculation chamber 68 to respective supply chambers 98 through respective spool supply passages 114. Recirculation check valves 78 are also configured to prevent oil to flow from respective supply chambers 98 to recirculation chamber 68 through respective spool supply passages 114.
Valve spool 28 also includes a valve spool drive extension 116 which extends axially from annular spool top 94 and through front cover central bore 66. Valve spool drive extension 116 and front cover central bore 66 are sized to interface in a close sliding fit which permits valve spool 28 to rotate freely relative to front cover 24 while substantially preventing oil from passing between the interface of valve spool drive extension 116 and front cover central bore 66. Valve spool drive extension 116 is arranged to engage an actuator 118 which is used to rotate valve spool 28 relative to stator 18 and rotor 20 as required to achieve a desired rotational position of rotor 20 relative to stator 18 as will be described in greater detail later. Actuator 118 may be, by way of non-limiting example only, an electric motor which is stationary relative to internal combustion engine 10 and connected to valve spool drive extension 116 through a gear set or an electric motor which rotates with camshaft phaser 12 and which is powered through slip rings. One such actuator and gear set is show in U.S. patent application Ser. No. 14/613,630 to Haltiner filed on Feb. 4, 2015, the disclosure of which is incorporated herein by reference in its entirety. Actuator 118 may be controlled by an electronic controller (not shown) based on inputs from various sensors (not shown) which may provide signals indicative of, by way of non-limiting example only, engine temperature, ambient temperature, intake air flow, manifold pressure, exhaust constituent composition, engine torque, engine speed, throttle position, crankshaft position, and camshaft position. Based on the inputs from the various sensors, the electronic controller may determine a desired phase relationship between the crankshaft and camshaft 14, thereby commanding actuator 118 to rotate valve spool 28 relative to stator 18 and rotor 20 as required to achieve the desired rotational position of rotor 20 relative to stator 18.
Each recirculation check valve 78 includes a recirculation check valve body 120 defining a tapered recirculation check valve seating surface 122 which selectively seats with annular spool top 94 to block a respective spool supply passage 114 and which selectively unseats from annular spool top 94 to open a respective spool supply passage 114 such that each recirculation check valve 78 opens inward into a respective spool supply passage 114. Each recirculation check valve body 120 extends through a respective spool supply passage 114 and includes a retention aperture 124 extending therethrough in a direction substantially perpendicular to camshaft axis 16. Each recirculation check valve body 120 is retained and biased toward engagement with a recirculation check valve plate 126 which is annular in shape and which is fixed to the face of annular spool top 94 which faces toward front cover 24. Recirculation check valve plate 126 defines respective recirculation check valve arms 128 associated with a respective recirculation check valve body 120. Each recirculation check valve arm 128 is defined by a recirculation check valve plate slot 130 such that each recirculation check valve arm 128 is arcuate in shape and extends through a respective retention aperture 124. Recirculation check valve arms 128 are resilient and compliant such that recirculation check valve arms 128 bias recirculation check valve bodies 120 toward seating with annular spool top 94. In order to accommodate flexure of recirculation check valve arms 128 which allows recirculation check valve bodies 120 to unseat from annular valve spool top 94, annular valve spool top 94 is provided with valve spool top recess 132 which is annular in shape and extends axially into the face of annular valve spool top 94 which faces toward front cover 24. In this way, recirculation check valves 78 are displaceable axially between an open position which allows oil to flow from vent chambers 100 to supply chambers 98 and a closed position which prevents oil from flowing from supply chambers 98 to vent chambers 100. It should be noted that recirculation check valves 78 open into respective supply chambers 98.
Rotor 20 may include an air purge passage 134 in order to purge air from oil that is supplied to oil make-up chamber 92. Air purge passage 134 extends through rotor 20 from oil make-up chamber 92 to the face of rotor 20 that faces toward back cover 22. A restriction orifice 136 is located within air purge passage 134 and is sized to minimize the volume of oil that can flow therethrough in order to prevent air purge passage 134 from significantly detracting from the flow of oil from vent chambers 100 to supply chambers 98 while still permitting air to be purged. Back cover 22 includes a back cover annular recess 138 which faces toward rotor 20 and extends radially inward from back cover central bore 62 such that back cover annular recess 138 is in fluid communication with air purge passage 134. Air that is communicated to back cover annular recess 138 is allowed to escape between the radial clearance between camshaft 14 and back cover central bore 62.
Operation of camshaft phaser 12 will now be described with continued reference to
As shown in
Conversely, as shown in
It is important to note that oil exclusively flows from supply chambers 98 to whichever of advance chambers 42 and retard chambers 44 need to increase in volume in order to achieve the desired phase relationship of rotor 20 relative to stator 18 while oil exclusively flows to vent chambers 100 from whichever of advance chambers 42 and retard chambers 44 need to decrease in volume in order to achieve the desired phase relationship of rotor 20 relative to stator 18. In this way, only one set of recirculation check valves 78 are needed, acting in one direction within valve spool 28 in order to achieve the desired phase relationship of rotor 20 relative to stator 18. Consequently, it is not necessary to switch between sets of check valves operating in opposite flow directions or switch between an advancing circuit and a retarding circuit. In the case of the position control valve described herein, a unidirectional flow circuit is defined within valve spool 28 when valve spool 28 is moved to a position within rotor 20 to allow either flow from advance chambers 42 to retard chambers 44 or from retard chambers 44 to advance chambers 42 where the flow circuit prevents flow in the opposite directions. Consequently, the flow circuit is defined by valve spool 28 which is simple in construction and low cost to produce.
In operation, the actual rotational position of rotor 20 relative to stator 18 may drift over time from the desired rotational position of rotor 20 relative to stator 18, for example only, due to leakage from advance chambers 42 and/or retard chambers 44. Leakage from advance chambers 42 and/or retard chambers 44 may be the result of, by way of non-limiting example only, manufacturing tolerances or wear of the various components of camshaft phaser 12. An important benefit of valve spool 28 is that valve spool 28 allows for self-correction of the rotational position of rotor 20 relative to stator 18 if the rotational position of rotor 20 relative to stator 18 drifts from the desired rotational position of rotor 20 relative to stator 18. Since the rotational position of valve spool 28 relative to stator 18 is locked by actuator 118, rotor advance passages 74 and rotor retard passages 76 will be moved out of alignment with valve spool lands 96 when rotor 20 drifts relative to stator 18. Consequently, oil will flow to advance chambers 42 from retard chambers 44 and oil will flow from advance chambers 42 to retard chambers 44 as necessary to rotate rotor 20 relative to stator 18 to correct for the drift until each valve spool land 96 is again aligned with respective rotor advance passages 74 and rotor retard passages 76.
It should be noted that oil that may leak from camshaft phaser 12 is replenished from oil provided by oil source 104. Replenishing oil is accomplished by oil source 104 supplying oil to recirculation chamber 68 via camshaft supply passage 108, rotor supply passage 106, oil make-up chamber 92, oil make-up passages 102, vent chambers 100, and spool vent passages 112. From recirculation chamber 68, the oil may be supplied to advance chambers 42 or retard chambers 44 as necessary by one or more of the processes described previously for advancing, retarding, or correcting for drift.
While clockwise rotation of rotor 20 relative to stator 18 respectively has been described as advancing camshaft 14 and counterclockwise rotation of rotor 20 relative to stator 18 has been described as retarding camshaft 14, it should now be understood that this relationship may be reversed depending on whether camshaft phaser 12 is mounted to the front of internal combustion engine 10 (shown in the figures) or to the rear of internal combustion engine 10.
In accordance with another preferred embodiment of this invention and referring to
Camshaft phaser 212 generally includes a stator 218 which acts as an input member, a rotor 220 disposed coaxially within stator 218 which acts as an output member, a back cover 222 closing off one axial end of stator 218, a front cover 224 closing off the other axial end of stator 218, a camshaft phaser attachment bolt 226 for attaching camshaft phaser 212 to camshaft 214, and a valve spool 228. The rotational position of valve spool 228 relative to stator 218 determines the rotational position of rotor 220 relative to stator 218, unlike typical valve spools which move axially to determine only the direction the rotor will rotate relative to the stator. The various elements of camshaft phaser 212 will be described in greater detail in the paragraphs that follow.
Stator 218 is generally cylindrical and includes a plurality of radial chambers 230 defined by a plurality of lobes 232 extending radially inward. In the embodiment shown, there are three lobes 232 defining three radial chambers 230, however, it is to be understood that a different number of lobes 232 may be provided to define radial chambers 230 equal in quantity to the number of lobes 232.
Rotor 220 includes a rotor central hub 236 with a plurality of vanes 238 extending radially outward therefrom and a rotor central through bore 240 extending axially therethrough. The number of vanes 238 is equal to the number of radial chambers 230 provided in stator 218. Rotor 220 is coaxially disposed within stator 218 such that each vane 238 divides each radial chamber 230 into advance chambers 242 and retard chambers 244. The radial tips of lobes 232 are mateable with rotor central hub 236 in order to separate radial chambers 230 from each other. Each of the radial tips of vanes 238 may include one of a plurality of wiper seals 246 to substantially seal adjacent advance chambers 242 and retard chambers 244 from each other. While not shown, each of the radial tips of lobes 232 may also include one of a plurality of wiper seals 246.
Rotor central hub 236 defines an annular valve spool recess 248 which extends part way into rotor central hub 236 from the axial end of rotor central hub 236 that is proximal to front cover 224. As a result, rotor central hub 236 includes a rotor central hub inner portion 250 that is annular in shape and bounded radially inward by rotor central through bore 240 and bounded radially outward by annular valve spool recess 248. Also as a result, rotor central hub 236 includes a rotor central hub outer portion 252 that is bounded radially inward by annular valve spool recess 248 and is bounded radially outward by the radially outward portion of rotor central hub outer portion 252 from which lobes 232 extend radially outward. Since annular valve spool recess 248 extends only part way into rotor central hub 236, annular valve spool recess 248 defines an annular valve spool recess bottom 254 which is annular in shape and extends between rotor central hub inner portion 250 and rotor central hub outer portion 252.
Back cover 222 is sealingly secured, using cover bolts 260, to the axial end of stator 218 that is proximal to camshaft 214. Tightening of cover bolts 260 prevents relative rotation between back cover 222 and stator 218. Back cover 222 includes a back cover central bore 262 extending coaxially therethrough. The end of camshaft 214 is received coaxially within back cover central bore 262 such that camshaft 214 is allowed to rotate relative to back cover 222. Back cover 222 may also include a sprocket 264 formed integrally therewith or otherwise fixed thereto. Sprocket 264 is configured to be driven by a chain that is driven by the crankshaft of internal combustion engine 210. Alternatively, sprocket 264 may be a pulley driven by a belt or other any other known drive member known for driving camshaft phaser 212 by the crankshaft. In an alternative arrangement, sprocket 264 may be integrally formed or otherwise attached to stator 218 rather than back cover 222.
Similarly, front cover 224 is sealingly secured, using cover bolts 260, to the axial end of stator 218 that is opposite back cover 222. Cover bolts 260 pass through back cover 222 and stator 218 and threadably engage front cover 224; thereby clamping stator 218 between back cover 222 and front cover 224 to prevent relative rotation between stator 218, back cover 222, and front cover 224. In this way, advance chambers 242 and retard chambers 244 are defined axially between back cover 222 and front cover 224. Front cover 224 includes a front cover central bore 266 extending coaxially therethrough.
Camshaft phaser 212 is attached to camshaft 214 with camshaft phaser attachment bolt 226 which extends coaxially through rotor central through bore 240 of rotor 220 and threadably engages camshaft 214, thereby clamping rotor 220 securely to camshaft 214. More specifically, rotor central hub inner portion 250 is clamped between the head of camshaft phaser attachment bolt 226 and camshaft 214. In this way, relative rotation between stator 218 and rotor 220 results in a change in phase or timing between the crankshaft of internal combustion engine 210 and camshaft 214.
Oil is selectively transferred to advance chambers 242 from retard chambers 244, as result of torque applied to camshaft 214 from the valve train of internal combustion engine 210, i.e. torque reversals of camshaft 214, in order to cause relative rotation between stator 218 and rotor 220 which results in retarding the timing of camshaft 214 relative to the crankshaft of internal combustion engine 210. Conversely, oil is selectively transferred to retard chambers 244 from advance chambers 242, as result of torque applied to camshaft 214 from the valve train of internal combustion engine 210, in order to cause relative rotation between stator 218 and rotor 220 which results in advancing the timing of camshaft 214 relative to the crankshaft of internal combustion engine 210. Rotor advance passages 274 may be provided in rotor 220 for supplying and venting oil to and from advance chambers 242 while rotor retard passages 276 may be provided in rotor 220 for supplying and venting oil to and from retard chambers 244. Rotor advance passages 274 extend radially outward through rotor central hub outer portion 252 from annular valve spool recess 248 to advance chambers 242 while rotor retard passages 276 extend radially outward through rotor central hub outer portion 252 from annular valve spool recess 248 to retard chambers 244. Transferring oil to advance chambers 242 from retard chambers 244 and transferring oil to retard chambers 244 from advance chambers 242 is controlled by valve spool 228 and recirculation check valves 278, as will be described in detail later, such that valve spool 228 is disposed coaxially and rotatably within annular valve spool recess 248.
Rotor 220 and valve spool 228, which act together to function as a valve, will now be described in greater detail with continued reference to
Valve spool outer portion 228b includes a valve spool outer portion base 314 located axially between valve spool inner portion 228a and front cover 24 and also includes a valve spool drive extension 316 which extends axially away from valve spool outer portion base 314 and through front cover central bore 266. Valve spool outer portion base 314 is annular in shape and sized to mate radially with rotor central hub outer portion 254 in a close sliding interface such that valve spool outer portion base 314 is able to freely rotate within annular valve spool recess 248 while substantially preventing oil from passing between the interface of valve spool outer portion base 314 and annular valve spool recess 248. Valve spool outer portion 228b also includes a valve spool outer portion central through bore 317 which extends axially therethrough such that valve spool outer portion central through bore 317 is centered about camshaft axis 216. Valve spool outer portion central through bore 317 is sized to mate radially with rotor central hub inner portion 250 in a close sliding interface such that valve spool outer portion base 314 is able to freely rotate relative to camshaft phaser rotor 220 while substantially preventing oil from passing between the interface of valve spool outer portion central through bore 317 and rotor central hub inner portion 250. Valve spool outer portion 228b is sealingly secured to valve spool inner portion 228a with valve spool screws 315 which extend through valve spool outer portion base 314 and threadably engage valve spool inner portion 228a, thereby substantially preventing oil from passing between the interface of valve spool outer portion base 314 and valve spool inner portion 228a and rotationally fixing valve spool inner portion 228a to valve spool outer portion 228b. Fixing valve spool outer portion 228b to valve spool inner portion 228a also prevents axial pressure from generating a thrust load between valve spool 228 and front cover 224 and also between valve spool 228 and rotor 220. Valve spool drive extension 316 is arranged to engage an actuator 318 which is used to rotate valve spool 228 relative to stator 218 and rotor 220 as required to achieve a desired rotational position of rotor 220 relative to stator 218 as will be described in greater detail later. Actuator 318 may be, by way of non-limiting example only, an electric motor which is stationary relative to internal combustion engine 210 and connected to valve spool drive extension 316 through a gear set or an electric motor which rotates with camshaft phaser 212 and which is powered through slip rings. One such actuator and gear set is show in U.S. patent application Ser. No. 14/613,630 to Haltiner filed on Feb. 4, 2015, the disclosure of which is incorporated herein by reference in its entirety. Actuator 318 may be controlled by an electronic controller (not shown) based on inputs from various sensors (not shown) which may provide signals indicative of, by way of non-limiting example only, engine temperature, ambient temperature, intake air flow, manifold pressure, exhaust constituent composition, engine torque, engine speed, throttle position, crankshaft position, and camshaft position. Based on the inputs from the various sensors, the electronic controller may determine a desired phase relationship between the crankshaft and camshaft 214, thereby commanding actuator 318 to rotate valve spool 228 relative to stator 218 and rotor 220 as required to achieve the desired rotational position of rotor 220 relative to stator 218.
Each recirculation check valve 278 may be integrally formed as part of a recirculation check valve plate 326 which is annular in shape and sized to fit within recirculation chamber 294 such that the thickness of recirculation check valve plate 326 is less than the depth of recirculation chamber 294. Each recirculation check valve 278 may be located at the free end of a recirculation check valve arm 328 which is defined by a recirculation check valve slot 330 formed through recirculation check valve plate 326. Recirculation check valve arms 328 are resilient and compliant such that recirculation check valve arms 328 recirculation check valves 278 toward seating with valve spool inner portion 228a. In this way, each recirculation check valve 278 acts as a reed valve that opens into recirculation chamber 294 and can be easily and economically formed, by way of non-limiting example only, by stamping sheet metal stock, i.e. recirculation check valves 278, recirculation check valve plate 326, and recirculation check valve arms 328 can be integrally formed as a single piece. Recirculation check valve plate 326 may be radially indexed and retained within recirculation chamber 294 by recirculation check valve plate screws 331 which extend through recirculation check valve plate 326 and threadably engage valve spool inner portion 228a.
Rotor 220 may include a rotor vent passage 334 in order to vent oil that may leak to be axially between valve spool inner portion 228a and valve spool recess bottom 254. Rotor vent passage 334 extends through rotor 220 from valve spool recess bottom 254 to the face of rotor 220 that faces toward back cover 222. Back cover 222 includes a back cover annular recess 338 which faces toward rotor 220 and extends radially inward from back cover central bore 262. Oil that is communicated to back cover annular recess 338 is allowed to escape between the radial clearance between camshaft 214 and back cover central bore 262. Similarly, oil that may leak to be axially between valve spool outer portion 228b and front cover 224 is allowed to escape between the radial clearance between front cover central bore 266 and valve spool drive extension 316. In this way, opposing axial faces of valve spool inner portion 228a and valve spool outer portion 228b are vented, thereby preventing an unbalanced axial force from being applied to valve spool 228.
Operation of camshaft phaser 212 will now be described with continued reference to
As shown in
Conversely, as shown in
It is important to note that oil exclusively flows from supply chambers 298 to whichever of advance chambers 242 and retard chambers 244 need to increase in volume in order to achieve the desired phase relationship of rotor 220 relative to stator 218 while oil exclusively flows to vent chambers 300 from whichever of advance chambers 242 and retard chambers 244 need to decrease in volume in order to achieve the desired phase relationship of rotor 220 relative to stator 218. In this way, only one set of recirculation check valves 278 are needed, acting in one direction within valve spool 228 in order to achieve the desired phase relationship of rotor 220 relative to stator 218. Consequently, it is not necessary to switch between sets of check valves operating in opposite flow directions or switch between an advancing circuit and a retarding circuit. In the case of the position control valve described herein, a unidirectional flow circuit is defined within valve spool 228 when valve spool 228 is moved to a position within rotor 220 to allow either flow from advance chambers 242 to retard chambers 244 or from retard chambers 244 to advance chambers 242 where the flow circuit prevents flow in the opposite directions. Consequently, the flow circuit is defined by valve spool 228 which is simple in construction and low cost to produce.
In operation, the actual rotational position of rotor 220 relative to stator 218 may drift over time from the desired rotational position of rotor 220 relative to stator 218, for example only, due to leakage from advance chambers 242 and/or retard chambers 244. Leakage from advance chambers 242 and/or retard chambers 244 may be the result of, by way of non-limiting example only, manufacturing tolerances or wear of the various components of camshaft phaser 212. An important benefit of valve spool 228 is that valve spool 228 allows for self-correction of the rotational position of rotor 220 relative to stator 218 if the rotational position of rotor 220 relative to stator 218 drifts from the desired rotational position of rotor 220 relative to stator 218. Since the rotational position of valve spool 228 relative to stator 218 is locked by actuator 318, rotor advance passages 274 and rotor retard passages 276 will be moved out of alignment with valve spool lands 296 when rotor 220 drifts relative to stator 218. Consequently, oil will flow to advance chambers 242 from retard chambers 244 and oil will flow from advance chambers 242 to retard chambers 244 as necessary to rotate rotor 220 relative to stator 218 to correct for the drift until each valve spool land 296 is again aligned with respective rotor advance passages 274 and rotor retard passages 276.
It should be noted that oil that may leak from camshaft phaser 212 is replenished from oil provided by oil source 304. Replenishing oil is accomplished by oil source 304 supplying oil to recirculation chamber 294 via bolt supply passage 308, rotor supply passage 306, oil make-up groove 292, and valve spool recirculation passages 302. From recirculation chamber 294, the oil may be supplied to advance chambers 142 or retard chambers 144 as necessary by one or more of the processes described previously for advancing, retarding, or correcting for drift. It should be noted that a portion of bolt supply passage 308 which is downstream of oil make-up check valve 310 is not visible in the figures, but may extend generally radially outward through camshaft phaser attachment bolt 226 to rotor supply passage 306.
While clockwise rotation of rotor 220 relative to stator 218 respectively has been described as advancing camshaft 214 and counterclockwise rotation of rotor 220 relative to stator 218 has been described as retarding camshaft 214, it should now be understood that this relationship may be reversed depending on whether camshaft phaser 212 is mounted to the front of internal combustion engine 210 (shown in the figures) or to the rear of internal combustion engine 210.
The arrangement of recirculation check valves 78 and recirculation check valves 278 as well as recirculation chamber 68 and recirculation chamber 294 as described herein provide for economical manufacture and compactness of camshaft phaser 12 and camshaft phaser 212 respectively.
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.
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| Number | Date | Country |
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| 2487227 | Jul 2012 | GB |
| Number | Date | Country | |
|---|---|---|---|
| 20170022849 A1 | Jan 2017 | US |
