CAMSHAFT-PHASING DRIVE WITH WEDGE ACTUATORS

Abstract: A phase-adjusting drive for engine camshafts and the like includes, in a preferred embodiment, a sprocket (16) driving a camshaft-­ attached hub (27) through paired wedge packs (40) that transfer torque and maintain a lash-free connection. A plunger (46) actuated by engine oil pressure and a co-acting drive spring (62) axially move alternate active wedges (44) to oppositely vary the arcuate lengths of the wedge packs (40) and thereby change the phase angle between the sprocket (16) and the camshaft attached to the hub (27).

Description: This invention relates to a phase-adjusting drive as specified in the preamble of claim 1, for example as disclosed in GB-A-2 151 333. It relates especially to camshaft phasing devices for varying the timing of valve actuation by an engine-driven camshaft. It is known in the art relating to engine valve gear to provide various means for varying valve timing as desired for the control of engine performance and efficiency. Among the various types of variable valve-timing devices employed have been camshaft phasing devices, often in the form of drive pulleys and the like incorporating phase-changing means for varying the phase between a rotatably driving input member such as a gear, pulley or sprocket and a rotatably driven output member such as a camshaft. Summary of the Invention A phase-adjusting drive according to the present invention is characterised by the features specified in the characterising portion of claim 1. The present invention provides an especially compact and effective form of phase-adjusting (hereinafter termed as "phasing") drive which, in a preferred embodiment, is applied in an engine camshaft drive to vary the phase or timing of a driven camshaft relative to a driving member, such as a sprocket, that is driven in timed relation to an engine crankshaft or the like. The phasing drive of the invention employs the concept of paired wedges, or wedge packs, positioned in opposing fashion and movable together to positively control phase changes in either direction. Preferably multiple wedges are used in each pack to multiply the angular phase change obtained from a small axial movement of actuating means such as a hydraulic piston. A preferred embodiment of the invention provides a compact camshaft-connected, phase-adjusting drive including the additional features of (1) arcuately-oriented paired wedge packs having alternately-engaged, oppositely-facing passive and active wedges with helical engaging surfaces, (2) a hydraulic plunger for oppositely actuating the active wedges axially in the two packs in advancing and retarding motions to arcuately expand or contract the wedge packs, (3) helically-sided wedges with passive end wedges having one flat side for engaging the drive and driven members on non-helical drive surfaces to reduce machining complexity, and (4) the use of net-formed (e.g. powder metal) wedges to remove the need to machine the helical surfaces. These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings, in which: In the drawings: Figure 1 is a pictorial view, partially in cross-section, showing a phase-adjusting camshaft drive (phaser) and camshaft assembly according to the invention; Figure 2 is an exploded pictorial view of the phaser of Figure 1; Figure 3 is a cross-sectional view of the phaser of Figure 1 prior to assembly with a camshaft; Figure 4 is a schematic view illustrating the operation and arrangement of the wedge packs of the invention; and Figure 5 is a cross-sectional view of an engine assembly including an alternative embodiment of phaser for use in a timing belt drive arrangement and illustrating oil-control means for both embodiments. Detailed Description Referring now to the drawings in detail, numeral 10 generally indicates an internal combustion engine of a type having a camshaft 11 driven by a crankshaft (not shown) through a chain 14 or other suitable drive means. The camshaft carries a plurality of cams or lobes (not shown) for actuating the cylinder intake and/or exhaust valves (not shown) of the engine in known manner. On the front, driven, end of the camshaft there is a phase adjuster 15 that includes a sprocket 16. The sprocket comprises a drive member with a peripheral drive portion, i.e, wheel 18, that is toothed and is drivably engaged by the chain 14 for rotatably driving the sprocket 16 on an axis 19 that is co-axial with the camshaft 11. Within the wheel 18 is a central portion 20 having an axial cylindrical opening 22. A pair of stops 23 are provided in and extend inwardly from the periphery of the opening 22 at circumferentially-spaced locations. The stops each have generally oppositely-facing, longitudinally-extending inner and outer side surfaces 24, 26. A driven hub 27 is fixed to the front end of the camshaft by a central screw 28 and a pin 30 or other means for fixing their phase relationship. Adjacent to mounted end 31, the hub 27 defines an internal cylinder 32 at the far end of which are two pairs of arcuately-spaced, longitudinally-extending upper and lower arms 33, 34, respectively. The arms also have generally oppositely facing longitudinally extending inner and outer side surfaces 35, 36. An external cylindrical surface of the hub cylinder portion 32 and arms 33, 34 forms a journal 37, received in the opening 22 of the sprocket for oscillatably supporting the sprocket 15. An oil passage 38 in the end 31 of the hub connects with a mating feed passage 39 in the camshaft for a purpose to be subsequently described. The cylinder 32 portion and arms 33, 34 which define journal 37 of the hub are received within the opening 22 of the sprocket central portion with the outer side surfaces 36 of the lower arms 34 spaced arcuately from the outer side surfaces 26 of the stops 23. A pair of arcuately lengthenable and shortenable wedge packs 40 are disposed, each one extending arcuately between and engaging the side surface 26 of a respective one of the stops and the opposing side surface 36 of the co-operating arm. A cover 41, threadably or otherwise retained on the end of the sprocket central portion 20, retains the wedge packs 40 within opening 22 and adjacent the cylinder 32 of the hub 27. A retaining ring 42 is received in an annular groove 42′ of the sprocket and engages an annular shoulder 42″ of the hub to maintain it in assembly with the sprocket. However, the ring 42 could be made integral with the sprocket or any other suitable retaining means could be used. Each of the wedge packs 40 controls the minimum arcuate spacing between its respective stop and arm side surfaces, and the packs are arranged so that when one is arcuately lengthened, the other is equally shortened. Thus, the arcuate distances between the two stops and their co-operating arms are changed in equal and opposite amount and the phase angles between the chain driven sprocket 16 and the camshaft-connected hub 27 are thereby altered. Each of the wedge packs 40 (see Figure 4) is made up of several passive wedges 43 having narrow ends facing axially in one direction alternating with active wedges 44 having their narrow ends facing axially in the opposite direction. The engaging surfaces of the wedges are preferably helical, although alternate sides of the wedges could be axially directed if desired and could thereby be made flat (planar). The helical angle, i.e, lead, of the wedges is sufficiently shallow that torque loads tend to lock the wedge packs by internal friction rather than to urge the wedges to retract and shorten the arcuate length of the packs. The length of the passive wedges essentially extends from the hub cylinder 32 to the cover 41 so that motion of the passive wedges 43 is limited to an arcuate path about the axis 19. However, the active wedges 44 are substantially shorter, allowing them room for axial motion as well as arcuate. Passive end wedges 45 in the wedge packs 40 preferably have flat axially-extending outer surfaces which engage the side surfaces 26, 36 of the sprocket stops and hub arms. This avoids any need for machining helical surfaces on the sprocket and hub. If desired, the end wedges, stops and arms could have helical engaging surfaces. Alternatively, the wedge packs could be rearranged to use active wedges having one flat side as the end wedges. A plunger 46 is disposed within the sprocket opening 22 for limited reciprocatable movement along the axis 19. The plunger includes a piston portion 47 which is reciprocably received in the cylinder 32 and carries a split seal ring 48 or other means to limit oil leakage thereby. The piston 47 and the end 31 of the hub define a chamber 50 with which the oil passage 38 connects. Adjacent the piston portion 47 is an enlarged (in this embodiment) actuating portion 51 that includes an annular groove 52 partly defining an outer flange 54 having opposite outwardly-opening, radial recesses 55. The recesses receive mating protrusions 56 of a pair of spring retainers 58 that are press-fitted into adjacent portions of the groove 52. The retainers 58 are slotted to receive outwardly flared ends of semi-annular leaf type drive springs 59 lying within the groove 52. Both the retainers and the flared ends of spring 59 extend radially between the upper arms 33 or lower arms 34 to prevent their rotation relative to the hub 27. Also within the groove 52 are individual fingers 60 extending radially inwards from each of the active wedges 44 of the wedge packs 40 which are on opposite sides of the plunger 46 intermediate the spring retainers 58. The drive springs 59 are positioned to engage the fingers 60 and advance the active wedges 44 of the two packs to their engaged positions, thus expanding the packs to take up the clearance between the wedges and the surfaces 26, 36. The fingers of each pack are thus urged to positions adjacent opposite sides of the plunger groove 52. A coil return spring 62 extends between the cover 41 and an annular recess 63 in the end of the plunger actuating portion 51 to bias the piston 47 into the cylinder 32 and to compress the chamber 50. A threaded opening 64 is provided in the centre of the plunger to allow access to the hub retaining screw 28. The opening 64 is closed by a threaded plug 66 to enclose the chamber 50. Figure 4 shows schematically a linear representation of the arcuate relationship of the two wedge packs 40 and the associated plunger groove 52. The packs have a minimum arcuate length X and a maximum arcuate length Y. The fingers 60 of the active wedges are urged by the drive springs 59 (represented by bent arrows) to expand the packs 40 to take up the clearance in the available space which totals X + Y. Movement of the plunger groove 52 leftward as shown in Figure 4 shortens the upper pack 40 while the lower pack is lengthened an equivalent amount by the action of its drive spring 59. In operation, the return spring 62 normally forces the plunger piston 47 into the cylinder 32, fully expanding (arcuately lengthening) one of the wedge packs 40 and contracting (arcuately shortening) the other to move the camshaft 11 into a desired phase relation with the engine crankshaft and pistons, not shown. In one embodiment, this would retard the timing of the engine valves or, preferably, the inlet valves to improve low-speed operation of the engine. As the engine speed and/or load increases to a predetermined condition, engine oil pressure is supplied to the chamber 50 through the feed passage 39 and oil passage 38. The oil pressure is sufficient to overcome the force of the return spring 62 and to move the plunger to its furthest position towards the cover 41. A side of the plunger groove 52 thereby engages the fingers 60 of the expanded wedge pack forcing them to retract and allow the pack to be arcuately shortened. At the same time, the drive spring engaging the fingers of the other (contracted) wedge pack urges them in an advancing direction to expand and arcuately lengthen the pack until all the clearance is taken up. This changes the phase relation of the hub and sprocket and, thereby, the camshaft and crankshaft, preferably advancing the camshaft timing to provide improved operation of the engine in a mid range/high load condition. In order to resume the retard position, the oil pressure is removed and the return spring 62 returns the mechanism to the initial condition and camshaft timing. Any desired manner of supplying oil to and discharging oil from the chamber 50 for actuating the plunger could be used. As shown schematically in Figure 5, a preferred embodiment employs a three-way valve, such as a solenoid-actuated spool valve 67. Any suitable form and location of the valve and solenoid could be employed. In this embodiment, the valve 67 is placed so that, in the retard position shown, it blocks the flow of oil from an oil pressure gallery 68 to the chamber 50 whilst maintaining communication of the chamber 50 with a discharge passage 70. The connection is through the oil passage 38 and feed passage 39 to an oil groove 71 in the camshaft bearing 72. The groove 71 in turn communicates with a connecting passage 74 which connects with the valve 67. When the solenoid is actuated, the valve moves to cut-off communication with the discharge passage 70 and to open the passage 38 to flow of oil under pressure from the gallery 68 to the chamber 50. In this manner, the oil flow required to actuate the mechanism is limited to that needed to expand the chamber 50 when the valve 67 is actuated and no oil flow is required except when the timing is being changed in a chamber-expanding direction. This reduces the size and power requirement of the engine oil pump and is in contrast to some other forms of hydraulic timing control which allow oil under pressure to bleed off through an orifice as long as the respective pressure chamber is in a contracted condition and only blocks the flow when expansion of the chamber is desired. Figure 5 further discloses an alternative embodiment of phase adjuster, i.e, phaser, according to the invention, which is generally indicated by numeral 75. The device is similar to the embodiments of Figures 1-4 but, instead of a sprocket 16, uses a toothed pulley 76 driven by a re-inforced rubber-like timing belt 78. To prevent the undesirable escape of oil onto the timing belt 78, the unit includes a cover 79 having a central access opening closed by sealed plug 80. Oil which leaks past the plunger piston 47 into the space adjacent the cover 79, wedge packs 40 and spring 62 is returned through internally-connecting drain passages 82, 83, 84 in hub 86, and drain passages 87, 88 in a camshaft thrust flange 90 to an annular space 91 surrounding a thrust surface 92. From space 91, the oil drains to an engine sump, not shown. The remainder of the camshaft mounting and oil supply systems in the engine 10 are like those of the first described embodiment.

Claims: A phase-adjusting drive (15) comprising: a drive member (16) rotatable on an axis (19); a driven member (27) rotatable on said axis (19); cam means comprising first and second wedge means (40), movable relative to one another, spaced radially from the axis (19) and positioned between the drive and driven members in such a manner as to control the phase-relationship between the drive and driven members when said wedge means (40) are moved in opposite directions; and actuating means for moving said cam means, said wedge means comprise first and second wedge packs (40) spaced radially from the axis (19) and positioned between the drive and driven members in such a manner as to control in opposite directions the angular phase-relationship between the drive and driven members; characterised in that said actuating means (46,47,51,52,60) arcuately contracts one of the wedge packs (40) whilst coincidentally arcuately expanding the other of the wedge packs (40) to positively vary the angular phase-relationship of the drive and driven members to one another. A phase-adjusting drive according to claim 1, characterised in that each wedge pack (40) includes passive wedges (43), which are movable only in arcuate paths, alternatively engaged by active wedges (44) which are movable together in paths having both arcuate and transverse portions, each wedge pack (40) having at least two active wedges (44) therein to multiply the phase-adjusting motion of said wedge packs (40). A phase-adjusting drive according to claim 2, characterised in that the transverse portions of the paths of motion of the active wedges (44) are in directions generally parallel to said axis (19). A phase-adjusting drive according to claim 2, characterised in that said wedges (43,44) have lead angles which are sufficiently shallow as to cause friction-locking of the wedge packs (40) against torque-induced phase changes between the drive and driven members. A phase-adjusting camshaft drive according to claim 1, characterised in that said drive member (16) includes a peripheral drive portion (18) adapted to be engaged by a driving means (14) and a central portion (20) having an axial cylindrical opening (22) with at least one stop (23) extending inwards from the periphery of the opening (22) and including generally oppositely-facing longitudinally-extending first and second stop surfaces (24,26); said driven member is a driven hub member (27) connectable with a camshaft (11) for rotation on said axis (19), said hub member (27) including an internal cylinder (32) and a plurality of arms (33,34) extending longitudinally from arcuately-spaced portions adjacent one end of the cylinder (32), at least the arms (33,34) of the hub member (27) being received within the opening (22) of the drive member (16) and being arcuately spaced from the first and second stop surfaces (24,26); said first and second wedge packs (40) are spaced radially from the axis (19) with each of the packs (40) extending arcuately between one of the stop surfaces (24,26) of the drive member (16) and one of the arms (33,34) of the hub member (27) to control in both directions changes in the angular phase-relationship between the drive member (16) and the hub (27), each of said wedge packs (40) including alternately-engaged, oppositely-facing wedges (43,44) movable in advancing and retracting motions relative to one another to lengthen or shorten the arcuate length of each pack (40); and said actuating means (46,47,51,52,60) retracts the wedges (44) of one of the wedge packs (40) to arcuately shorten said one pack whilst coincidentally advancing the wedges (44) of the other wedge pack (40) to arcuately lengthen said other pack, thereby adjusting the arcuate spacing between the hub arms (33,34) and their associated stop surfaces (24,26) of the drive member (16) so as to positively vary the phase-relationship of the drive and driven members. A phase-adjusting camshaft drive according to claim 5, characterised in that said wedges (43,44) have lead angles which are sufficiently shallow as to cause friction locking of the wedge packs (40) against torque-induced phase changes between the drive and driven members. A phase-adjusting camshaft drive according to claim 5, characterised in that each wedge pack (40) includes end wedges (45) having straight outer sides engaging the stop surfaces (24,26) and arms (33,34), the engaged surfaces of which extend parallel with said axis (19). A phase-adjusting camshaft drive according to claim 5, characterised in that each wedge pack (40) includes passive and active wedges (43,44), the passive wedges (43) being movable only in arcuate paths and the active wedges (44) also being movable in arcuate paths as well as being movable transverse thereto in either an advancing motion or a retracting motion, each wedge pack (40) having at least two active wedges (44) to multiply the phase-adjusting motion of the wedge pack (40). A phase-adjusting camshaft drive according to claim 8, characterised in that the actuating means includes a plunger (46) reciprocably received in said internal cylinder (32) of the hub (27), resilient means (62) urging the plunger (46) in one actuating direction, and means (38,39) for admitting pressure fluid to the cylinder (32) to force the plunger (46) in an opposite direction, the plunger (46) further including means (51,52) engaging the active wedges (44) for simultaneously moving them in said advancing and retracting motions. A phase-adjusting camshaft drive according to claim 8, characterised in that the wedges (43,44) each have at least one helical surface, the wedges (43,44) being formed to size to avoid machining of the helical surfaces.

Inventors: ELPHICK, THOMAS G., KOVACEVICH, KENNETH ANTHONY, LICHTI, THOMAS HOWARD, NIEMIEC, MICHAEL JOSEPH, SHOST, MARK ANTHONY, WAYDELIS, RONALD ANDREW
Applicants: GENERAL MOTORS CORPORATION
Application year: 1990
Main classification: F01L1
IPC codes: F01L1, F16D3