Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/02—Valve drive
  • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
  • F01L1/047—Camshafts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/02—Valve drive
  • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
  • F01L1/08—Shape of cams
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
  • F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
  • F01L13/0036—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
  • F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
  • F01L13/0057—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque by splittable or deformable cams
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H53/00—Cams or cam-followers, e.g. rollers for gearing mechanisms
  • F16H53/02—Single-track cams for single-revolution cycles; Camshafts with such cams
  • F16H53/04—Adjustable cams
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L2301/00—Using particular materials
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L2303/00—Manufacturing of components used in valve arrangements

Definitions

• the invention relates to improvements for camshaft assemblies of internal combustion engines with switchable cam lobes that can be selectively engaged or disengaged, so that different valve timings can be achieved according to operating requirements; such camshaft assemblies are described in UK patent application GB 0106891.5.
• the broadest aspect of the invention is as set out in Claim 1 and comprises a slideable cam lobe which can be selectably latched in 2 positions substantially perpendicular to the main axis of the camshaft so that the slideable cam lobe can be withdrawn and latched within the lift curve of a pair of adjacent cams, so that these adjacent cams then control the valve lift, as well as the slideable cam being latched in a second position to provide the controlling valve lift.
• Figure 1 shows an isometric view of the proposed complete camshaft assembly for lifting poppet valves.
• Figure 2 shows a longitudinal sectional view of a part of the proposed camshaft assembly for poppet valve actuation.
• Figure 3 is an isometric view of a detachable cam lobe.
• Figure 4 is an isometric view of a detachable cam lobe locking clip.
• Figure 5 is shows the detail of the locking tang of the cam lobe locking clip of Fig.4.
• Figure 6 shows a longitudinal elevation of one slideable cam lobe latched to the cam shaft at its lifting or active position.
• Figure 7 shows the transverse cross section through one slideable cam lobe latched to the cam shaft at its full lift or active position.
• Figure 8 shows the cross section through one slideable cam lobe latched to the cam shaft at its zero lift or inactive position, with the adjacent lower lift cams lifting the tappet or cam follower.
• Figures 9 shows the slideable cam lobe in transition between inactive and active positions.
• Figure 10 shows a transverse cross section of a second embodiment of the invention with the slideable cam at full lift, ie active.
• Figure 11 shows a transverse cross section of a third embodiment of the invention with the slideable cam at full lift, ie active.
• Figure 12 shows a cross section of a third embodiment of the invention with the slideable cam latched to be inactive
• Figure 13 shows a cross section of a fourth embodiment of the invention with the slideable cam latched to be inactive.
• the lifting mechanism for providing each valve with 2 possible lifts and periods comprises essentially 3 cams, ie 2 fixed outboard cams 101 and 102 of identical profiles which provide the low lift for the poppet valve, and one slideable and latchable inboard cam 103 which provides the high lift for the poppet valve.
• cams when made active by the mechanism, would bear directly against a tappet which is in contact with the poppet valve, but the tappets and the valves have been omitted for clarity.
• Other similar slideable cams are shown by 104-110 inclusive, ie 8 in total for this particular camshaft.
• Each of the slideable cams comprises 2 parts, ie the main lifting portion, ie 103-110, and a clip, eg 127, 128, 129, 130, 131, 132, 133 & 134, which holds the slideable cams to the cam axle, ie the longitudinal shaft 100.
• 111, 112 and 113 are commonly referred to as the noses of the appropriate cams, ie the point of maximum lift on each cam, whilst 114, 115 and 116 are the base circle areas, ie the points of zero lift of each cam.
• the fixed low lift cams 201 & 202, 205 & 206, 207 & 208, 209 & 210, 211 & 212, 213 & 214, 215 & 216, 217 & 218 are shown grouped in pairs and integral with the cam axle 204, the slideable and latchable cams, which are not shown, occupying the spaces, referred to as axle slots, between the pairs of fixed cams, ie 228, 229, 230, 231, 232, 233, 234 and 235.
• An oil feed gallery 219 receives oil from the engine oil circuit and this oil can access the latching mechanisms of the slideable cams via drillings 220, 221, 222, 223, 224, 225, 226 and 227, the exact shape, number and dispostions of these drillings depending upon the particular embodiment of this invention.
• the cam axle which can be a single piece, and its fixed cams can be of cast iron, chill cast iron, spheroidal graphite nodular iron, steel, or forged steel, or forged metal matrix composites such as steel alloys reinforced with dispersed ceramic particles, eg titanium diboride particles, or forged aluminium alloys reinforced with ceramics, eg dispersed silicon carbide particles, which ideally have a particle size equal or smaller than 3 microns.
• the fixed cams could be coated, in one embodiment, with a fusable tungsten steel coating.
• one embodiment of the latchable and slideable lobe 300 has a cam profile 303 around a substantial periphery of the cam lobe, holes 301 & 302 to receive latching means, a formed slot 308, the parallel sides of which engage with the parallel sides of the axle slots, and means for fixing a retaining mechanism for the cam lobe onto the cam axle.
• the fixing means are slots 304, 305, 306 and 307 which accommodate tongues and locking tangs of a clip, which will be described with reference to Figure 4.
• the major 2 sides of the formed slot of the slideable cam lobe are substantially parallel to each other and to the corresponding sides of the axle slot to which they are fitted.
• the other sides of the slideable cam are also substantially parallel to the major planes of the 2 lower lift cams adjacent to the axle slot, and are therefore substantially orthogonal to major axis of the cam axle.
• the slideable cam lobe may be of a sintered material, cast, chill cast material, forged material, or a metal matrix composite material which is either forged or cast.
• the material can be cast iron, chill cast iron, a steel, forged aluminium alloys, forged aluminium alloys reinforced with dispersed ceramic silicon carbide particles which may be smaller than 3 microns, cast aluminium alloys reinforced with structured and/or woven ceramic fibres, such as alumina.
• the material can also be a steel reinforced with dispersed ceramic particles, eg titanium diboride.
• the profiled functional surface of slideable cam can be coated with a hard fusable material, such as a tool steel, or a tungsten steel alloy coating.
• this retaining clip 400 secures the slideable cam 309, shown in Fig.3, to the camshaft axle 204 shown in Fig.2.
• the clip is manufactured from a steel or a spring steel pressing which has rails 401, 402, 403 & 404 which engage in corresponding slots (304-307 inclusive) in the slideable cam shown in Fig.3.
• the clip is automatically locked in position by the tangs 405 and another on the B side which is not visible; these tangs can be released with a tool to allow clip removal.
• the side rails are part of 2 side members 407 and 408 which bridge the open end of the slideable cam, thus retaining the slideable cam to the cam axle.
• the bridging, retention and locking functions can be achieved from stiff steel wire, or the slideable cam can be secured by a cross rivet which has a head at one end and a means for locking the rivet at the other end.
• Such locking may include a riveting head, a circlip or a deformable or cripping washer.
• the slideable cam lobe can be retained by crimping, swaging or bending relatively flexible portions of the slideable lobe in the non lifting area of the slideable cam lobe, so that the bent portions overlap the cam axle slot and limit the maximum travel of the slideable cam on the cam axle in one direction.
• the retaining clip In order for the slideable cam to function satisfactorily in both active and inactive modes, the retaining clip, or any other retention embodiment, must have a maximum effective radius in the areas A & B, about the rotational axis of the cam axle, which is less than the base circle radius of the adjacent low lift cams, and the maximum effective height of the clip, in the area around C, must be shorter than the effective radius across A or B by an amount which is substantially the difference in maximum lift between the high and low lift cams. This ensures that the high lift slideable cam can be parked in the inactive position without the retaining means or clip fouling the tappet.
• a consequence of this base circle geometry of the slideable cam is that the slideable cam profile has to be generated from a smaller base circle radius than the profile for the fixed cams.
• 505 is a side member of the retaining clip of Fig.4, 502 being the base of the clip; the retaining rails are not visible in this section.
• the locking tang 503 can be seen engaging in a corner relief 504 of the slideable cam 501, effectively retaining the slideable cam 501 to the cam axle 500.
• the tang 503 is bendable about the base 502 of the clip so that the clip can be inserted and removed from the slideable cam by elastically bending the tangs.
• Fig.5 shows the clip and slideable cam in the effective zero lift position, the peripheral extremity of the clip 502 having a radius which is less than the base circle radius of the adjacent low lift cams, as depicted in part by 510.
• the high lift (inboard) slideable cam 601 is seen between the 2 fixed outer lower lift cams 602 & 603, latched in its high lift position and lifting the tappet 606.
• the retaining clip 604 is visible, as is one latching pin hole 605, of this particular embodiment.
• this embodiment uses a single cross pin 702 to perform the latching of the high lift slideable cam 707 to the cam axle 706, in both full lift and effective no lift positions.
• a high level oil pressure in the oil gallery 709 acts on the collar of the spring carrier 702c with adequate force to compress the spring 703 and move the pin 702 into the hole 711, thus locking the high lift cam 707 to the cam axle 706.
• Alternative embodiments can have springs which are in tension.
• the latching of the slideable cam in its high lift position takes place whilst the cam assembly for the particular valve is in its base circle period, ie the only force acting on the slideable cam is a the centrifugal force which pulls the cam 707 radially outwards from the cam axle 706 along the cam axis YY.
• This outward motion of the slideable cam, during the base circle period will occur when the cam is rotated 90-270 degrees relative to the position shown in Fig.7; there is adequate time, during the base circle period and up to engine speeds of about 4000-5000rpm, for the centrifugal force to accelerate the slideable cam from its inactive position to its latched active position, and be in position for the immediate valve lift event.
• the slideable cam is usually arranged so that its cam profile has at least one matching lift point, relative to the fixed low lift cams, during the opening phase of the valve lift, and one matching lift point, relative to the fixed low lift cams, during the closing phase of the valve lift.
• These matching lifts may be in the opening and closing ramp phases of the valve lift profiles.
• the spring force from the spring 703 is adequate to overcome a lower level oil pressure in the oil gallery 709, moving the pin 702 towards the face 707a of the cam 707.
• the higher and lower oil pressures in the galleries are achieved by some switching device in the engine oil circuit, such as an electrical solenoid valve.
• the hole 701 in the slideable cam is then moved progressively by the action of the tappet forces on the cam until the hole 701 aligns with the pin end 702b.
• the pin 702 can now engage the hole 701 to lock the cam 707 in its effective zero lift position, ie the cam 707 is now masked by the two lower lift side cams 712 (only one of these side cams is visible in this view, Fig.8).
• the retaining clip 708, described with reference to Fig.6, acts as a second level safety device to ensure that the cam 707 cannot leave contact with the cam axle 706.
• FIG. 7 Another feature of the embodiment shown in Fig. 7 are the support rings 704 and 705 that are fitted to the cam axle holes 716 and 717.
• the support ring 704 acts as a reaction stop to the spring 703 and prevents excessive bending of the pin 702 when engaged in the cam hole 711.
• the support ring 705 acts prevents excessive bending of the pin 702 when engaged in the cam hole 701.
• the hole 711 can have an enlarged eccentric diameter relative to the locking pin 702 , such that there is clearance between the pin side and the unloaded side of the slideable cam 707 holes, ie 71 la.
• the eccentricity of the full lift latching pin hole in the slideable cam is towards the base circle diameter direction of the cam.
• the latching pin 702 also has means for providing a reaction surface 702c to the spring 703, and this reaction surface 702c also forms a collar, and partial seal, for the oil pressure in gallery 709, ie the collar is a sliding fit with the latching pin hole 716 in the cam axle, h the embodiment of Figs.7-9, the collar 702c also has a sleeve portion 702d which helps reduce oil loss from the pressurised supply in gallery 709.
• Other embodiments of this collar are a crimped washer, or a ring fitted with interference to the pin 702.
• the rate and preload of the spring 703 in Figs.7-9 is such that it can be substantially compressed by the higher oil pressure in the gallery 709, allowing the pin to be moved towards the surface 715 of the cam 707, whilst there is adequate spring force to overcome the lower oil pressure and move the pin towards the surface 707a of the cam 707.
• the ends of the pin 702a and 702b may be bevelled or chamfered to allow a more progressive entry into the holes 701 and 711.
• transverse hole 799 through the slideable cam 707 which may be of any desired profile.
• This transverse hole could have a substantial cross section of material between it and the cam slot in the slideable cam.
• the latchable high lift cam 707 does not need a no lift or "base circle” cam portion, as the base circle portion of the latchable cam is effectively provided by the base circle diameters of the 2 adjacent cams (Fig.6, 602 and 603, also Fig.8, 712).
• Fig.8 additionally shows that for the latchable higher lift cam profile to be totally inactive, allowing for tolerances in the mechanism, then the latching geometry of the high lift cam is arranged so that the distance, on the centreline of the slideable cam, from the nose 800 of the slideable cam to the axis through the latching hole(s) 701 in the slideable cam, used to keep the cam in its inactive position, is less than the distance from the nose 801 of the fixed low lift cams to the centreline of the major axes of the latching pins 802. For reference, this distance difference is called the retraction offset.
• the latching pin 702 has exited from the high lift latching hole 711 of the cam 707, and this allows the slideable cam to be displaced by the reaction force in the tappet such that the slideable cam moves towards its effective zero lift latched position, which is fully achieved when the latching pin 702 reaches the centreline of the hole 701.
• the cam nose 902 of the slideable cam 707 reaches the same height as the cam nose of the adjacent low lift cams
• the chamfered pin end 727 engages a transverse groove 901 in the sliding face 707a of the cam 707; the aperture of the zero lift latching pin hole is contained within the width of this groove.
• the width of the transverse groove, from the centreline of the latching tube hole to the edge of the groove furthest from the cam nose, is such that it at least equals the retraction offset.
• the force from the spring 703 on the latching pin 711 acts on the inclined surface of the transverse groove 901, forcing the chamfered pin end to slide outwards from the centreline XX of the cam and thus pulling the slideable cam so that the nose of the slideable cam 902 is forced below the noses of the 2 adjacent low lift cams.
• This ensures that the nose of the high lift cam is clearly inactive, and is necessary to accommodate tolerance accumulations in the mechanisms and camshaft assembly.
• the magnitude of the additional retraction of the slideable cam relative to the cam noses of the fixed cams is defined in the section with reference to Fig.8, and is applied also to the entry chamfer 901.
• this embodiment incorporates an additional, or redundant, safety latch pin 1001 fitted to the slideable cam 707, and acted upon by the spring 1002.
• the support collar 1005 is set back from the face 1007 of the cam axle so that there exists a recess 1004, which is slightly larger in size than the profile of the additional latch pin 1001. This allows the slideable cam to be latched simultaneously on both sides of the cam axle, thus reducing any tipping of the cam 707 relative to the cam axle 706.
• the spring 1002 reacts against an abutment 1003, which in this embodiment is a plug or cap 1003 fitted with interference into the hole 1008.
• this embodiment uses 2 latching pins 11001 and 11002 which engage holes 11016 and 11017 for the active operation of the high lift cam, whilst the inactive position is achieved with the pins 11001 and 11002 latched into holes 11011 and 11012 which are in the latching tube 11010 which is rigidly attached to the moveable cam 11009.
• a valve in the engine's oil circuit controls the oil pressure to the gallery 11013 to "low” or "high” pressure levels.
• the spring forces exerted by the springs 11005 and 11006 are adequate to overcome the oil pressure force acting on the pin areas 11014 & 11015 in direct contact with the oil and the pins are forced inwards so that the pin ends 11025 & 11026 protrude into the line of travel of the latching tube 11010, unlatching the upper slideable cam from the axle 11027.
• the reaction of the tappet forces the slideable cam to move along the surfaces 11028 and 11029 until the end of the cam tube 11030 comes into contact the pin ends 11025 and 11026.
• the cam tube 11030 has a bevelled or radiused end 11031 which encourages the pins 11001 and 11002 to be displaced outwards whilst the cam tube slides further into the body of the cam axle 11027.
• the pins ends 11025 & 11026 then engage into the holes 11011 & 11012 of the latching tube, effectively locking the upper cam into its "zero lift" position, as shown in Fig.12.
• the holes in the latching tube can have chamfers.
• the slideable cam in its active position uses the base circle diameter 11025 of the adjacent low lift cams.
• seal 11008 fitted to either the cam tube 11010 or the cam axle 11027 and support collars 11003 and 11004 to guide the latching pins 11001 and 11002.
• the seal could be an elastomeric type O-ring which fits into a groove in the cam tube 11010 or alternatively fits into a groove in the cam axle 11027.
• the slideable cam can be retained to the cam axle by fixing clip 11040 which can be of same types as described with reference to previous sections describing Figs. 4 and 5.
• this shows the slideable cam 11009 latched to the cam axle 11027 in the effective zero lift position; the proportions, profile and dimensions of the slideable cam, relative to the adjacent low lift cam, are such to ensure that that the slideable cam, when in its inactive position, can be nested within the profile of the adjacent low lift cams.
• the latching geometry of the slideable high lift cam is arranged so that the distance, on the centreline of the slideable cam, from the nose of the slideable cam 12003 to the axis through the latching holes in the slideable cam tube (11041, Fig.l 1), used to keep the cam in its inactive position, is less than the distance from the nose of the fixed low lift cams 12002 to the centreline of the major axes of the latching pins 12004.
• a further feature of the embodiment, shown in Figs. 11 & 12, is the use of conical ended latching pins 12055 and 12056 (Fig.12) to engage with the holes 12057 and 12058 in the cam tube 12052.
• This conical engagement feature enables the slideable cam to be latched below the surfaces of the adjacent fixed cam 12002.
• the latching tube may have a chamfered transverse groove, larger in width than the diameter of the latching hole, and orthogonal to the latching hole for the inactive cam position, the groove extending mainly on the side of the latching hole furthest from the cam nose.
• the groove width extending from the centreline of the latching hole(s) in the latching tube towards the retaining clip portion of the slideable cam lobe, is equal to or greater than the difference between the distances, on the centreline of the slideable cam, from the nose of the slideable cam to the axis through the latching holes in the cam tube, used to keep the cam in its inactive position, and the distance from the nose of the fixed low lift cams to the centreline of the major axes of the latching pins
• the cam tube 11010 which is rigidly joined to the slideable cam 11009, may be realized in alternative forms, eg a hollow tube pressed into the slideable cam, or a tube which is sintered as part of a sintered slideable cam, or a hollow cam tube may be secured (Fig.12) by having a swaged portion in the hollow cam tube with enlarged diameter 12022, relative to the main body of the tube 12021 , on one side of one of a substantially horizontal surface 12050 of the slideable cam, with a fixing circlip 12051, on the other side of the same horizontal surface of the slideable, or alternatively the tube is joined to the slideable cam by swages in the cam tube above and below the said horizontal surface.
• some clearance may be provided between the outer diameter of the cam tube 12052 and the diameter of the hole 12053 in the slideable cam, thus allowing some compliance, to compensate for tolerance stacks, between the axes of the hole in the cam axle 12054 and the cam tube 12052.
• this embodiment is a variation of that proposed with reference to Fig.12, in that the cam tube 13001 is attached to the slideable cam 13009 by means of the retaining clip 13004.
• the cam tube in this embodiment, can be attached orthogonally to the retaining clip by several means, eg by having a swaged portion in the hollow cam tube with enlarged diameter 13002, relative to the main body of the tube 13001, on one side of one of the substantially horizontal surfaces of the clip, with a fixing circlip 13003 on the other side of the same horizontal surface 13004 of the clip, or alternatively the tube is joined to the retaining clip by swages in the cam tube above and below the said horizontal surface.
• the previously described assemblies may be used in any type of internal combustion engine which uses camshafts to open poppet valves.
• the poppet valve actuation may be through bucket tappets, or finger or roller followers.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Valve-Gear Or Valve Arrangements (AREA)

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• 2002
  • 2002-06-21 GB GB0214361A patent/GB2385888B/en not_active Expired - Fee Related
• 2003
  • 2003-06-17 WO PCT/GB2003/002594 patent/WO2004001199A2/en not_active Ceased
  • 2003-06-17 AU AU2003277971A patent/AU2003277971A1/en not_active Abandoned
  • 2003-06-17 EP EP03740744A patent/EP1534938A2/de not_active Withdrawn

Non-Patent Citations (1)

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