Patent Grant
9366162
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 use with an internal combustion engine for controllably varying the phase relationship between a crankshaft and a camshaft in the 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 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 allows oil to flow from the vent chamber to the supply chamber and 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, annular valve spool recess bottom 54 may be stepped, thereby defining a valve spool recess shoulder 56 that is substantially perpendicular to camshaft axis 16.
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 other 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 front cover counter bore 68 extending coaxially thereinto from the side of front cover 24 which is adjacent to stator 18. A front cover annular projection 70 extends axially from the bottom of front cover counter bore 68 toward rotor 20 such that front cover annular projection 70 in parts defines front cover central bore 66 and such that front cover annular projection 70 defines, together with front cover counter bore 68, a front cover annular recess 72.
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 by 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 phasing 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. It should be noted that phasing check valves 78 are shown in
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
Valve spool 28 also includes a valve spool band 110 which radially surrounds outer supply chambers 102 and outer vent chambers 104 such that valve spool band 110 is sealingly secured to annular spool dividing wall 92 and annular spool top 90. A reservoir 112 is defined radially between valve spool band 110 and front cover counter bore 68 and also axially between annular spool top 90 and front cover 24. Valve spool band 110 includes a plurality of valve spool band supply passages 114 extending radially therethrough and a plurality of valve spool band vent passages 116 extending radially therethrough. Each valve spool band supply passage 114 provides fluid communication between a respective outer supply chamber 102 and reservoir 112 while each valve spool band vent passage 116 provides fluid communication between a respective outer vent chamber 104 and reservoir 112. Each valve spool band supply passage 114 includes a respective phasing check valve 78 which allows oil to flow from reservoir 112 to respective outer supply chambers 102 while preventing oil from flowing from outer supply chambers 102 to reservoir 112 as will be described in greater detail later.
Annular spool base 88 includes oil make-up passages 120 extending axially therethrough which provide fluid communication between respective inner vent chambers 98 and an annular volume 122 defined axially between annular valve spool recess bottom 54 and annular spool base 88. Annular volume 122 receives pressurized oil from an oil source 124, for example, an oil pump of internal combustion engine 10, via a rotor supply passage 126 formed in rotor 20 and also via a camshaft supply passage 129 formed in camshaft 14.
Valve spool 28 also includes a valve spool drive extension 128 which extends axially from annular spool top 90 and through front cover central bore 66. Valve spool drive extension 128 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 128 and front cover central bore 66. Valve spool drive extension 128 is arranged to engage an actuator 130 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 130 may be, by way of non-limiting example only, an electric motor which is stationary relative to camshaft phaser 12 and connected to valve spool drive extension 128 through a gear set or an electric motor which rotates with camshaft phaser 12 and which is powered through slip rings. Actuator 130 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 130 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.
A valve spool ring 132 is located radially between valve spool 28 and the portion of annular valve spool recess 48 defined by rotor central hub outer portion 52. Valve spool ring 132 is fixed to rotor 20, for example only, by press fitting valve spool ring 132 with annular valve spool recess 48, such that relative rotation between valve spool ring 132 and rotor 20 is prevented. Valve spool ring 132 is sized to substantially prevent oil from passing between the interface between valve spool ring 132 and annular valve spool recess 48. Valve spool ring 132 includes a plurality of valve spool ring advance passages 134 and a plurality of valve spool ring retard passages 136 which extend radially therethrough. Each valve spool ring advance passage 134 is aligned with a respective rotor advance passage 74 while each valve spool ring retard passage 136 is aligned with a respective rotor retard passage 76. Each valve spool ring advance passage 134 and each valve spool ring retard passage 136 is sized to be equal to the width of valve spool inner lands 94, and the spacing between valve spool ring advance passages 134 and valve spool ring retard passages 136 matches the spacing between valve spool inner lands 94. Valve spool inner lands 94 engage the inner circumference of valve spool ring 132 to substantially prevent oil from passing between the interfaces of valve spool inner lands 94 and valve spool ring 132 while allowing valve spool 28 to rotate within valve spool ring 132 substantially uninhibited. Consequently, inner supply chambers 96 and inner vent chambers 98 are fluidly segregated and fluid communication into and out of advance chambers 42 and retard chambers 44 is substantially prevented when valve spool inner lands 94 are aligned with valve spool ring advance passages 134 and valve spool ring retard passages 136 to block valve spool ring advance passages 134 and valve spool ring retard passages 136.
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 inner supply chambers 96 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 inner vent chambers 98 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 phasing 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 130, valve spool ring advance passages 134 and valve spool ring retard passages 136 will be moved out of alignment with valve spool inner lands 94 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 inner land 94 is again aligned with respective valve spool ring advance passages 134 and valve spool ring retard passages 136.
It should be noted that oil that may leak from camshaft phaser 12 is replenished from oil provided by oil source 124. Replenishing oil is accomplished by oil source 124 supplying oil to reservoir 112 via camshaft supply passage 129, rotor supply passage 126, annular volume 122, oil make-up passages 120, inner vent chambers 98, vent chamber connecting passages 108, outer vent chambers 104, and valve spool band vent passages 116. From reservoir 112, 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.
It should be noted that opposing axial ends of valve spool 28 are at a common pressure because reservoir 112 and annular volume 122 are in constant fluid communication via oil make-up passages 120, inner vent chambers 98, vent chamber connecting passages 108, outer vent chambers 104, and valve spool band vent passages 116. Maintaining opposing axial ends of valve spool 28 at a common pressure prevents hydraulic pressure from applying an axial load to valve spool 28.
While camshaft phaser 12 has been described as including valve spool ring 132, it should now be understood that valve spool ring 132 may be omitted. If valve spool ring 132 is omitted, then valve spool inner lands 94 interface directly with the surface of annular valve spool recess 48 defined by rotor central hub outer portion 52. Furthermore, rotor advance passages 74 and rotor retard passages 76 need to be equal to the width of valve spool inner lands 94 when valve spool ring 132 is omitted, and the spacing between rotor advance passages 74 and rotor retard passages 76 matches the spacing between valve spool inner lands 94.
While phasing check valves 78 have been described in the embodiment herein as being located within outer supply chambers 102, it should now be understood that phasing check valves 78 could be located in numerous other locations which prevent flow from inner supply chambers 96 to inner vent chambers 98. By way of non-limiting example only, phasing check valves 78 could be located between reservoir 112 and outer vent chambers 104. In another configuration, outer supply chambers 102 may be commonly connected to a first common passage and outer vent chambers 104 may be commonly connected to a second common passage where one or more phasing check valves 78 allow flow from the second common passage to the first common passage while preventing flow from the first common passage to the second common passage.
While clockwise rotation of rotor 20 relative to stator 18 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.
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.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5507254 | Melchior | Apr 1996 | A |
| 5645017 | Melchior | Jul 1997 | A |
| 5649506 | Melchior | Jul 1997 | A |
| 7523728 | Berndorfer | Apr 2009 | B2 |
| 8156906 | Takenaka | Apr 2012 | B2 |
| 8534246 | Lichti et al. | Sep 2013 | B2 |
| 20070017463 | Mott et al. | Jan 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 2487227 | Jul 2012 | GB |
