US20080035085A1 - Method and apparatus for controlling a switchable cam follower - Google Patents
Method and apparatus for controlling a switchable cam follower Download PDFInfo
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- US20080035085A1 US20080035085A1 US11/503,776 US50377606A US2008035085A1 US 20080035085 A1 US20080035085 A1 US 20080035085A1 US 50377606 A US50377606 A US 50377606A US 2008035085 A1 US2008035085 A1 US 2008035085A1
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- Prior art keywords
- hydraulic
- gallery
- lash adjuster
- hla
- engine
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- 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
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- 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
- F01L1/20—Adjusting or compensating clearance
- F01L1/22—Adjusting or compensating clearance automatically, e.g. mechanically
- F01L1/24—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically
- F01L1/2405—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically by means of a hydraulic adjusting device located between the cylinder head and rocker arm
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- 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
- F01L13/0005—Deactivating valves
Definitions
- the present invention relates to variable valve activation mechanisms for combustion valves of internal combustion engines; more particularly, to methods and apparatus for controllably supplying activating engine oil to such variable valve activation mechanisms including switchable cam followers; and most particularly, to an improved hydraulic lash adjuster and control scheme for such controllable valve actuation.
- a typical prior art selective valve deactivation mechanism includes a switchable cam follower such as an articulated two-step deactivation roller finger follower (DRFF) disposed between an engine camshaft lobe and a valve stem.
- the DRFF includes a hydraulically-actuated lock pin to engage or disengage the articulated members.
- the lock pin is engaged between the articulated members by a return spring, such that the valve train is in high-lift mode by default at shutdown or other times as desired.
- the lock pins are disengaged by application of high pressure hydraulic fluid, typically engine oil provided by the engine's oil distribution system to overcome the return spring.
- the DRFF is pivoted on a hydraulic lash adjuster (HLA) at an end opposite to the valve-engaging end.
- HLA hydraulic lash adjuster
- the HLA is mounted rotatably about its axis in a residence bore in the engine, typically in the engine head.
- the HLA is supplied with engine oil from a molded or bored engine gallery to feed the lash adjuster mechanism therein, and oil also flows from the HLA to the DRFF through a central opening in the ball head of the HLA and a mating passage in the DRFF.
- the lock pin spring overcomes the oil pressure and the DRFF is in high-lift mode.
- the oil pressure is increased via a regulating oil control valve (ROCV) to a higher pressure sufficient to cause the lock pin to be retracted, placing the DRFF in low-lift or no-lift mode.
- the engine oil gallery thus doubles as a switching gallery and an oil supply gallery for top engine functions such as camshaft bearings.
- the function may be provided by a combination of a three-way on/off valve in the switching gallery coupled to a pressure relief valve and an in-line flow restrictor to maintain low switching pressure at between about 0.3 bar and about 0.8 bar.
- this approach can be difficult to package on existing engine block or head arrangements because of the common oil gallery shared by the HLAs and the cam bearings.
- HLA arrangement that may be packaged in an existing head wherein the camshaft bearings are lubricated via an existing first oil gallery and the HLA switching and lash adjusting functions are satisfied, at least in part, from a second, independently controlled oil gallery remote from the first oil gallery, and wherein the first and second galleries are readily purged of air.
- an internal combustion engine is equipped to supply the camshaft bearings with pressurized oil via a first dedicated oil gallery independently of the hydraulic lash adjusters and any valve deactivation devices which are supplied from a second dedicated oil gallery.
- the galleries are connected and a small-orifice flow restriction is placed either in a connecting passage between the first and second galleries or within the HLAs themselves.
- the primary engine oil gallery is as in the prior art, to minimize required retooling of engine molds.
- An improved hydraulic lash adjuster, formed in accordance with the invention is identical with a prior art HLA except that the prior art annular oil distribution groove in the outer surface of the body is eliminated to prevent communication of the primary engine oil gallery with the HLA.
- the secondary gallery is formed remotely from the first oil gallery in the HLA residence bore in the engine, and the HLA is prevented from rotating within the residence bore.
- the HLA can communicate for actuation with only the new, second oil gallery.
- FIG. 1 a is a schematic drawing of a first prior art oil supply system, showing a single-feed HLA supplied by a single oil gallery via a regulating oil control valve;
- FIG. 1 b is an elevational cross-sectional drawing of a prior art single-feed HLA useful in the system shown in FIG. 1 a;
- FIG. 2 a is a schematic drawing of a second prior art oil supply system, showing a dual-feed HLA supplied by a conventional oil gallery and a switching oil gallery via a three-way on/off valve;
- FIG. 2 b is an elevational cross-sectional view of a portion of a prior art valve train as shown schematically in FIG. 2 a;
- FIG. 3 is a schematic drawing of a third prior art oil supply system, showing a single-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery;
- FIG. 4 is a schematic drawing of the third prior art oil supply system shown in FIG. 3 , in high-pressure (low valve lift) mode;
- FIG. 5 is an elevational cross-sectional view of a first embodiment of an improved HLA in accordance with the invention, which improved HLA is suitable for use in the first improved oil supply system shown in FIGS. 6 and 7 ;
- FIG. 6 is a schematic drawing of a first improved oil supply system in accordance with the invention, showing an improved single-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery, the two galleries being hydraulically connected but functionally isolated via a flow restriction;
- FIG. 7 is a schematic drawing of the first improved oil supply system in accordance with the invention shown in FIG. 6 , in high-pressure (low valve lift) mode;
- FIG. 8 is an elevational cross-sectional view of a second embodiment of an HLA in accordance with the invention.
- FIG. 9 is a schematic drawing of a second improved oil supply system in accordance with the invention, showing an improved dual-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery, the two galleries being hydraulically connected but functionally isolated via a flow restriction in each HLA in the engine; and
- FIG. 10 is a schematic drawing of the second improved oil supply system in accordance with the invention shown in FIG. 9 , in high-pressure (low valve lift) mode.
- a first prior art oil supply system 100 includes a pressurizing pump 102 which draws intake hydraulic fluid 104 from a sump 106 .
- Fluid 104 is typically engine oil and sump 106 is typically an engine crankcase.
- Pressurized output oil 108 from pump 102 is directed through a regulating oil control valve (ROCV) 110 which regulates pressure in a conventional oil gallery 112 to about 0.5 bar.
- Pressurized oil is supplied from gallery 112 to cam bearings 114 and to a conventional hydraulic lash adjuster 116 disposed rotatably about its axis in a residence bore 115 in an engine head 117 .
- An outer annular groove 119 in HLA body 120 coincides with first port 118 , and HLA 116 thus is free to rotate about its longitudinal axis while oil is supplied to port 118 from groove 119 at any angular orientation of the HLA.
- ROCV 110 is controlled by an engine control module (not shown).
- the “normal” (“low”) operating pressure 134 as noted above is about 0.5 bar.
- ROCV 110 opens to permit higher oil pressure 136 (which may be the same as pressure 108 or not) to flow to HLA 116 and thence into the DRFF.
- higher oil pressure is also felt by cam bearings 114 .
- a low oil pressure 134 required for full valve activation can rob the cam bearings 114 of adequate oil flow.
- a second prior art oil supply system 200 includes pressurizing oil pump 102 which draws intake oil 104 from sump 106 , as in prior art system 100 ( FIG. 1 a ).
- Pressurized output oil 108 from pump 102 is fed through a first flow restriction 240 into a conventional oil gallery 112 at an unregulated intermediate pressure 242 sufficient to lubricate cam bearings 114 and fill the low-pressure reservoir 228 and lash adjusting mechanism 230 of a second prior art HLA 216 disposed in a residence bore 215 in an engine head 217 .
- a second (switching) gallery 244 is provided in engine head 217 in parallel with conventional gallery 112 and communicates with a switchable cam follower such as DRFF 246 via a passage 248 independent of low-pressure reservoir 228 .
- first flow restriction 240 is simply a small-diameter port where the oil feed passes through the engine head gasket.
- a three-way on/off valve 250 controlled by an engine control module (not shown) governs flow of oil into switching gallery 244 .
- Oil flow into switching gallery 244 is either at high pressure 108 or a very low pressure 254 .
- a bypass “bleed” 252 preferably is provided to maintain a slight charge pressure 254 in switching gallery 244 , as is desirable for some valve deactivation systems.
- Prior art system 200 desirably divorces the lash adjusting and cam bearing lubrication functions from the valve deactivation functions.
- the presence of conventional oil gallery 112 where formed in existing engine heads leaves little room for the addition of a switching gallery 244 adjacent thereto.
- a longer HLA is required, having in some designs a two-piece plunger, and the volume of the low-pressure reservoir is quite small, making an engine equipped with this system vulnerable to cold-starting clatter.
- a third prior art oil supply system 300 includes pressurizing oil pump 102 which draws intake oil 104 from sump 106 , as in prior art systems 100 and 200 ( FIGS. 1 a and 2 a ).
- pressurized output oil 108 from pump 102 is fed through a first flow restriction 240 into a conventional oil gallery 112 at an unregulated intermediate pressure 242 sufficient to lubricate cam bearings 114 .
- the HLA is entirely divorced from gallery 112 .
- a second gallery 244 is provided in engine head 217 adjacent conventional gallery 112 and supplies an HLA 316 similar to HLA 116 , filling the low-pressure reservoir and lash adjusting mechanism via a single feed.
- a three-way on/off valve 350 governs flow of oil into switching gallery 244 .
- Oil flow into switching gallery 244 is either at low pressure 334 ( FIG. 3 , DRFF engaged for high valve lift)) or high pressure 108 ( FIG. 4 , DRFF disengaged for no or low valve lift).
- three-way valve 350 is only either open or closed, a second flow restriction 352 around valve 350 and a pressure relief valve 356 maintains low pressure 334 in switching gallery 244 , preferably about 0.5 bar similar to pressure 134 as in first system 100 for lash adjusting functions of HLA 316 .
- valve 350 opens to oil pressure 108 and closes to relief valve 356 .
- Third prior art system 300 achieves the objective of divorcing cam bearing lubrication from HLA activities while utilizing a substantially unmodified production HLA such as HLA 116 ( FIGS. 1 a and 1 b ).
- HLA 116 FIGS. 1 a and 1 b
- the presence of the conventional oil gallery 112 where formed in existing engine heads leaves little room for the addition of a switching gallery 244 adjacent thereto.
- the first and second galleries and the HLA are not readily purged of air and may have dead legs at various points therein.
- a first improved oil supply system 400 in accordance with the invention is similar to but improves upon prior art system 300 .
- Improved system 400 includes pressurizing oil pump 102 which draws intake oil 104 from sump 106 as in prior art system 300 ( FIGS. 3 and 4 ).
- pressurized output oil 108 from pump 102 is fed through a first flow restriction 240 into a conventional oil gallery 112 at an unregulated intermediate pressure 242 sufficient to lubricate cam bearings 114 .
- HLA 416 is entirely divorced from gallery 112 .
- a second gallery 244 is provided in engine head 217 in addition to the conventional gallery 112 and supplies an improved HLA 416 similar to conventional HLA 116 , filling the low-pressure reservoir and lash adjusting mechanism via a single feed.
- HLA 416 differs from HLA 116 in having no annular oil supply groove 119 formed in the unfeatured cylindrical exterior of HLA body 420 ; and further, HLA 416 is prevented from free rotation in the HLA residence bore 215 ( FIG. 2 b ) in engine head 217 by inclusion of an anti-rotation flat or other obvious mechanical preventer as known in the art.
- the HLA fill port 418 in body 420 is inaccessible to the conventional oil gallery 112 disposed in an existing head in which HLA 416 might be retrofitted and is positioned to communicate with only second gallery 244 for all HLA oil supply functions.
- a three-way on/off valve 350 governs flow of oil into switching gallery 244 .
- Oil flow into switching gallery 244 is either at low pressure 434 ( FIG. 6 , DRFF engaged for high valve lift)) or high pressure 108 ( FIG. 7 , DRFF disengaged for no or low valve lift).
- Switching gallery 244 is open to pressure relief valve 356 . Referring to FIG. 7 , when high pressure oil to HLA 416 is desired, valve 350 opens switching gallery 244 to a second position to oil pressure 108 and closes switching gallery 244 to relief valve 356 .
- First improved oil supply system 400 achieves the objective of divorcing cam bearing lubrication from HLA activities while utilizing a minimally modified production HLA such as HLA 116 ( FIGS. 1 a and 1 b ), and while accommodating a conventional oil gallery passage in a current head.
- System 400 also provides several other important advantages not available in the prior art.
- the conventional oil gallery 112 and the switching oil gallery 244 are formed in engine head 217 on opposite sides of HLA 416 . This arrangement makes it relatively easy to form the two galleries in an existing engine head mold with minimal required retooling of the mold.
- the arrangement also provides maximal flow separation of the two galleries within the residence bore of the HLA and thus minimizes hydraulic cross-talk between the two galleries, whereas in the prior art ( FIG. 2 b ) the two galleries, being adjacent and on the same side of the residence bore, are separated by only a few millimeters of bore wall.
- a second improved oil supply system 500 in accordance with the invention is similar to first improved system 400 , differing only in the implementation of a pressure reducing flow restriction between the two galleries.
- system 400 the ends of the conventional and switching galleries 112 , 244 are joined via a connector 453 containing flow restrictor 452 .
- oil flows from the conventional gallery through restrictor 452 and into the switching gallery.
- Pressure relief valve 356 and flow restrictor 452 are sized to regulate the pressure in the switching gallery to the desired 0.5 bar pressure.
- air from gallery 112 is swept by pressurized oil through connector 453 where it joins with air in gallery 244 and both are purged through relief valve 356 .
- system 500 the ends of galleries 112 , 244 are not joined except through the final HLA in an engine bank; thus there are still no dead flow legs.
- the pressure reducing flow restrictions are located in the body of the HLA rather than in connector 453 as in system 400 .
- Each HLA 516 ( FIG. 8 ) is identical to HLA 416 except that an orifice or flow restriction 552 is provided through HLA body 520 in communication with conventional oil gallery 112 .
- oil flows from the conventional gallery through the flow restriction into the HLA low pressure chamber and switching gallery and eventually out the pressure relief valve.
- the pressure relief valve and flow restrictors are sized to regulate the pressure in the switching gallery to the desired 0.5 bar pressure. This eliminates having to manufacture connector 453 containing restriction 452 of system 400 .
- Air in gallery 112 is purged into low-pressure reservoir 528 and thence out of the HLA via tip opening 532 .
- Continued purging from gallery 112 through HLA 516 drives air in port 518 and switching gallery 244 out through three-way valve 350 and relief valve 356 ( FIGS. 8 and 9 ).
- the low pressure limit for default operation of an associated DRFF can be set lower than for a prior art ROCV system, which aids switching performance;
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Lubrication Of Internal Combustion Engines (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
Abstract
An internal combustion engine is equipped to supply the camshaft bearings with pressurized oil via a first dedicated oil gallery independently of the hydraulic lash adjusters (HLAs) and any valve deactivation devices which are supplied from a second dedicated oil gallery. The galleries may be connected at their downstream ends and a flow restriction is placed in a connecting passage or within each HLA. An improved HLA is similar to a prior art HLA except that the prior art annular oil distribution groove in the outer surface of the HLA body is eliminated to prevent communication of the primary engine oil gallery with the HLA. The secondary gallery is formed remotely from the first oil gallery in the HLA residence bore in the engine, and the HLA is prevented from rotating within the residence bore.
Description
- The present invention relates to variable valve activation mechanisms for combustion valves of internal combustion engines; more particularly, to methods and apparatus for controllably supplying activating engine oil to such variable valve activation mechanisms including switchable cam followers; and most particularly, to an improved hydraulic lash adjuster and control scheme for such controllable valve actuation.
- Mechanisms for varying the valve timing and/or lift of combustion valves in internal combustion engines are well known. A typical prior art selective valve deactivation mechanism includes a switchable cam follower such as an articulated two-step deactivation roller finger follower (DRFF) disposed between an engine camshaft lobe and a valve stem. The DRFF includes a hydraulically-actuated lock pin to engage or disengage the articulated members. In one example of a DRFF, the lock pin is engaged between the articulated members by a return spring, such that the valve train is in high-lift mode by default at shutdown or other times as desired. The lock pins are disengaged by application of high pressure hydraulic fluid, typically engine oil provided by the engine's oil distribution system to overcome the return spring. The DRFF is pivoted on a hydraulic lash adjuster (HLA) at an end opposite to the valve-engaging end. The HLA is mounted rotatably about its axis in a residence bore in the engine, typically in the engine head. The HLA is supplied with engine oil from a molded or bored engine gallery to feed the lash adjuster mechanism therein, and oil also flows from the HLA to the DRFF through a central opening in the ball head of the HLA and a mating passage in the DRFF. When oil is supplied through the engine gallery at low pressure, the lock pin spring overcomes the oil pressure and the DRFF is in high-lift mode. To overcome the lock pin spring, the oil pressure is increased via a regulating oil control valve (ROCV) to a higher pressure sufficient to cause the lock pin to be retracted, placing the DRFF in low-lift or no-lift mode. The engine oil gallery thus doubles as a switching gallery and an oil supply gallery for top engine functions such as camshaft bearings.
- A problem arises in using a single oil gallery in such a dual mode in that the pressure logic of a deactivation application mandates that oil pressure in the gallery be low (lock pin engaged, valves actuated) at the highest engine speeds and load conditions. Under these conditions, the camshaft bearings, which are oiled from the same gallery, are subjected to highest load and lowest oil flow which can result in premature bearing wear or outright failure.
- One known approach to preventing this problem is to provide a second gallery adjacent the first gallery specifically for supplying the DRFF and to relegate the primary gallery to satisfying the lash adjustment and camshaft bearing lubrication requirements. This approach avoids the necessity for an ROCV, which is both bulky and expensive, but it requires significant changes in the prior art HLA design to provide independent oil feeds for the lash adjustment and switching functions. See, for example, U.S. Pat. No. 7,047,925, depicting a dual feed HLA. Such designs significantly reduce the volume of the HLA low-pressure chamber, raising concerns for potential noise upon cold start of the engine. Further, it can be difficult and expensive to provide two adjacent galleries so close together within the engine block; and further, significant leakage can occur between the two galleries along the wall of the HLA residence bore.
- Instead of using a ROCV, the function may be provided by a combination of a three-way on/off valve in the switching gallery coupled to a pressure relief valve and an in-line flow restrictor to maintain low switching pressure at between about 0.3 bar and about 0.8 bar. However, this approach can be difficult to package on existing engine block or head arrangements because of the common oil gallery shared by the HLAs and the cam bearings.
- What is needed in the art is an HLA arrangement that may be packaged in an existing head wherein the camshaft bearings are lubricated via an existing first oil gallery and the HLA switching and lash adjusting functions are satisfied, at least in part, from a second, independently controlled oil gallery remote from the first oil gallery, and wherein the first and second galleries are readily purged of air.
- It is a principal object of the present invention to separate the camshaft oil supply requirements from the HLA oil supply requirements while using a common engine oil pressurizing pump.
- It is a further object of the present invention to readily and automatically purge all oil galleries of air.
- It is a still further object of the present invention to require the minimum changes in prior art engine casting molds by utilizing the existing HLA oil supply gallery and providing a second oil supply gallery.
- Briefly described, an internal combustion engine is equipped to supply the camshaft bearings with pressurized oil via a first dedicated oil gallery independently of the hydraulic lash adjusters and any valve deactivation devices which are supplied from a second dedicated oil gallery. To improve air purging of both galleries, the galleries are connected and a small-orifice flow restriction is placed either in a connecting passage between the first and second galleries or within the HLAs themselves. In an aspect of the present invention, the primary engine oil gallery is as in the prior art, to minimize required retooling of engine molds. An improved hydraulic lash adjuster, formed in accordance with the invention, is identical with a prior art HLA except that the prior art annular oil distribution groove in the outer surface of the body is eliminated to prevent communication of the primary engine oil gallery with the HLA. The secondary gallery is formed remotely from the first oil gallery in the HLA residence bore in the engine, and the HLA is prevented from rotating within the residence bore. Thus, the HLA can communicate for actuation with only the new, second oil gallery. Forming the improved HLA requires only the omission of the prior art annular oil groove in the HLA body and provision for non-rotation of the improved HLA.
- The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
-
FIG. 1 a is a schematic drawing of a first prior art oil supply system, showing a single-feed HLA supplied by a single oil gallery via a regulating oil control valve; -
FIG. 1 b is an elevational cross-sectional drawing of a prior art single-feed HLA useful in the system shown inFIG. 1 a; -
FIG. 2 a is a schematic drawing of a second prior art oil supply system, showing a dual-feed HLA supplied by a conventional oil gallery and a switching oil gallery via a three-way on/off valve; -
FIG. 2 b is an elevational cross-sectional view of a portion of a prior art valve train as shown schematically inFIG. 2 a; -
FIG. 3 is a schematic drawing of a third prior art oil supply system, showing a single-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery; -
FIG. 4 is a schematic drawing of the third prior art oil supply system shown inFIG. 3 , in high-pressure (low valve lift) mode; -
FIG. 5 is an elevational cross-sectional view of a first embodiment of an improved HLA in accordance with the invention, which improved HLA is suitable for use in the first improved oil supply system shown inFIGS. 6 and 7 ; -
FIG. 6 is a schematic drawing of a first improved oil supply system in accordance with the invention, showing an improved single-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery, the two galleries being hydraulically connected but functionally isolated via a flow restriction; -
FIG. 7 is a schematic drawing of the first improved oil supply system in accordance with the invention shown inFIG. 6 , in high-pressure (low valve lift) mode; -
FIG. 8 is an elevational cross-sectional view of a second embodiment of an HLA in accordance with the invention; -
FIG. 9 is a schematic drawing of a second improved oil supply system in accordance with the invention, showing an improved dual-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery, the two galleries being hydraulically connected but functionally isolated via a flow restriction in each HLA in the engine; and -
FIG. 10 is a schematic drawing of the second improved oil supply system in accordance with the invention shown inFIG. 9 , in high-pressure (low valve lift) mode. - The advantages and benefits of an oil supply system in accordance with the invention may be better appreciated by first considering three prior art systems.
- Referring to
FIGS. 1 a and 1 b, a first prior artoil supply system 100 includes a pressurizingpump 102 which draws intakehydraulic fluid 104 from asump 106.Fluid 104 is typically engine oil andsump 106 is typically an engine crankcase. Pressurizedoutput oil 108 frompump 102 is directed through a regulating oil control valve (ROCV) 110 which regulates pressure in aconventional oil gallery 112 to about 0.5 bar. Pressurized oil is supplied fromgallery 112 tocam bearings 114 and to a conventionalhydraulic lash adjuster 116 disposed rotatably about its axis in a residence bore 115 in anengine head 117. Oil enters HLA 116 through afirst port 118 inHLA body 120, thence into an innerannular groove 122 formed inplunger 124, thence through asecond port 126 inplunger 124 which opens into a low-pressure reservoir 128. Fromreservoir 128, oil flows both intolash adjusting mechanism 130 and also out ofHLA 116 through athird port 132 which mates with a rocker arm or finger follower mechanism (not shown, but seeFIG. 2 b). An outerannular groove 119 inHLA body 120 coincides withfirst port 118, andHLA 116 thus is free to rotate about its longitudinal axis while oil is supplied toport 118 fromgroove 119 at any angular orientation of the HLA. ROCV 110 is controlled by an engine control module (not shown). The “normal” (“low”)operating pressure 134 as noted above is about 0.5 bar. When deactivation of an associated switchable cam follower such a DRFF is desired,ROCV 110 opens to permit higher oil pressure 136 (which may be the same aspressure 108 or not) to flow toHLA 116 and thence into the DRFF. Of course, the higher oil pressure is also felt bycam bearings 114. As noted above, at high engine speed or high engine load alow oil pressure 134 required for full valve activation can rob thecam bearings 114 of adequate oil flow. - Referring now to
FIGS. 2 a and 2 b, a second prior artoil supply system 200 includes pressurizingoil pump 102 which drawsintake oil 104 fromsump 106, as in prior art system 100 (FIG. 1 a).Pressurized output oil 108 frompump 102 is fed through afirst flow restriction 240 into aconventional oil gallery 112 at an unregulatedintermediate pressure 242 sufficient to lubricatecam bearings 114 and fill the low-pressure reservoir 228 and lashadjusting mechanism 230 of a secondprior art HLA 216 disposed in aresidence bore 215 in anengine head 217. A second (switching)gallery 244 is provided inengine head 217 in parallel withconventional gallery 112 and communicates with a switchable cam follower such asDRFF 246 via apassage 248 independent of low-pressure reservoir 228. In some engine systems,first flow restriction 240 is simply a small-diameter port where the oil feed passes through the engine head gasket. - There is no ROCV in this second prior art system. Rather, a three-way on/off
valve 250 controlled by an engine control module (not shown) governs flow of oil into switchinggallery 244. Oil flow into switchinggallery 244 is either athigh pressure 108 or a verylow pressure 254. Although the three-way valve 250 is only either open or closed, a bypass “bleed” 252 preferably is provided to maintain aslight charge pressure 254 in switchinggallery 244, as is desirable for some valve deactivation systems. -
Prior art system 200 desirably divorces the lash adjusting and cam bearing lubrication functions from the valve deactivation functions. However, the presence ofconventional oil gallery 112 where formed in existing engine heads leaves little room for the addition of aswitching gallery 244 adjacent thereto. Further, a longer HLA is required, having in some designs a two-piece plunger, and the volume of the low-pressure reservoir is quite small, making an engine equipped with this system vulnerable to cold-starting clatter. - Referring to
FIGS. 3 and 4 , a third prior artoil supply system 300 includes pressurizingoil pump 102 which drawsintake oil 104 fromsump 106, as inprior art systems 100 and 200 (FIGS. 1 a and 2 a). As insystem 200,pressurized output oil 108 frompump 102 is fed through afirst flow restriction 240 into aconventional oil gallery 112 at an unregulatedintermediate pressure 242 sufficient to lubricatecam bearings 114. However, the HLA is entirely divorced fromgallery 112. Asecond gallery 244 is provided inengine head 217 adjacentconventional gallery 112 and supplies anHLA 316 similar toHLA 116, filling the low-pressure reservoir and lash adjusting mechanism via a single feed. - Again, there is no ROCV in this third prior art system. Rather, a three-way on/off
valve 350 governs flow of oil into switchinggallery 244. Oil flow into switchinggallery 244 is either at low pressure 334 (FIG. 3 , DRFF engaged for high valve lift)) or high pressure 108 (FIG. 4 , DRFF disengaged for no or low valve lift). Although three-way valve 350 is only either open or closed, asecond flow restriction 352 aroundvalve 350 and apressure relief valve 356 maintainslow pressure 334 in switchinggallery 244, preferably about 0.5 bar similar topressure 134 as infirst system 100 for lash adjusting functions ofHLA 316. When high pressure toHLA 316 is desired,valve 350 opens tooil pressure 108 and closes torelief valve 356. - Third
prior art system 300 achieves the objective of divorcing cam bearing lubrication from HLA activities while utilizing a substantially unmodified production HLA such as HLA 116 (FIGS. 1 a and 1 b). However, the presence of theconventional oil gallery 112 where formed in existing engine heads leaves little room for the addition of aswitching gallery 244 adjacent thereto. Further, the first and second galleries and the HLA are not readily purged of air and may have dead legs at various points therein. - Referring now to
FIGS. 5 , 6, and 7, a first improvedoil supply system 400 in accordance with the invention is similar to but improves uponprior art system 300.Improved system 400 includes pressurizingoil pump 102 which drawsintake oil 104 fromsump 106 as in prior art system 300 (FIGS. 3 and 4 ). As insystem 300,pressurized output oil 108 frompump 102 is fed through afirst flow restriction 240 into aconventional oil gallery 112 at an unregulatedintermediate pressure 242 sufficient to lubricatecam bearings 114.HLA 416 is entirely divorced fromgallery 112. Asecond gallery 244 is provided inengine head 217 in addition to theconventional gallery 112 and supplies animproved HLA 416 similar toconventional HLA 116, filling the low-pressure reservoir and lash adjusting mechanism via a single feed. As shown inFIG. 5 , however,HLA 416 differs fromHLA 116 in having no annularoil supply groove 119 formed in the unfeatured cylindrical exterior ofHLA body 420; and further,HLA 416 is prevented from free rotation in the HLA residence bore 215 (FIG. 2 b) inengine head 217 by inclusion of an anti-rotation flat or other obvious mechanical preventer as known in the art. Thus, theHLA fill port 418 inbody 420 is inaccessible to theconventional oil gallery 112 disposed in an existing head in whichHLA 416 might be retrofitted and is positioned to communicate with onlysecond gallery 244 for all HLA oil supply functions. - As in
prior art embodiment 300, there is no ROCV in first improvedoil supply system 400. Rather, a three-way on/offvalve 350 governs flow of oil into switchinggallery 244. Oil flow into switchinggallery 244 is either at low pressure 434 (FIG. 6 , DRFF engaged for high valve lift)) or high pressure 108 (FIG. 7 , DRFF disengaged for no or low valve lift). Although the three-way valve 350 is only either open or closed, asecond flow restriction 452 in a connectingpassage 453 between the distal ends 455,457 respectively ofconventional oil gallery 112 and switchingoil gallery 244, which distal ends are not connected in the prior art embodiments, combined with apressure relief valve 356 ingallery 244 maintainslow pressure 434 in switchinggallery 244, preferably about 0.5 bar similar topressure 134 as infirst system 100 for lash adjusting functions ofHLA 316, when three-way valve 350 is closed to highpressure oil flow 108 in a first position.Switching gallery 244 is open topressure relief valve 356. Referring toFIG. 7 , when high pressure oil toHLA 416 is desired,valve 350 opens switchinggallery 244 to a second position tooil pressure 108 and closes switchinggallery 244 torelief valve 356. - First improved
oil supply system 400 achieves the objective of divorcing cam bearing lubrication from HLA activities while utilizing a minimally modified production HLA such as HLA 116 (FIGS. 1 a and 1 b), and while accommodating a conventional oil gallery passage in a current head. -
System 400 also provides several other important advantages not available in the prior art. First, any air bubbles in either of the oil galleries are automatically purged throughpressure relief valve 356 when the system is in low pressure mode as shown inFIG. 6 . Second, becausegalleries connector 453, there are no dead legs in the flow path and thus all air is purged, unlike the prior art systems wherein each of the oil galleries has a dead terminal leg. Third, theconventional oil gallery 112 and the switchingoil gallery 244 are formed inengine head 217 on opposite sides ofHLA 416. This arrangement makes it relatively easy to form the two galleries in an existing engine head mold with minimal required retooling of the mold. The arrangement also provides maximal flow separation of the two galleries within the residence bore of the HLA and thus minimizes hydraulic cross-talk between the two galleries, whereas in the prior art (FIG. 2 b) the two galleries, being adjacent and on the same side of the residence bore, are separated by only a few millimeters of bore wall. - Referring now to
FIGS. 8 , 9, and 10, a second improvedoil supply system 500 in accordance with the invention is similar to firstimproved system 400, differing only in the implementation of a pressure reducing flow restriction between the two galleries. - As just described, in
system 400 the ends of the conventional and switchinggalleries connector 453 containingflow restrictor 452. In the low pressure mode (FIG. 6 ), oil flows from the conventional gallery throughrestrictor 452 and into the switching gallery.Pressure relief valve 356 and flow restrictor 452 are sized to regulate the pressure in the switching gallery to the desired 0.5 bar pressure. In addition, air fromgallery 112 is swept by pressurized oil throughconnector 453 where it joins with air ingallery 244 and both are purged throughrelief valve 356. - In
system 500, the ends ofgalleries connector 453 as insystem 400. - Each HLA 516 (
FIG. 8 ) is identical toHLA 416 except that an orifice or flowrestriction 552 is provided throughHLA body 520 in communication withconventional oil gallery 112. Thus, referring toFIG. 9 , oil flows from the conventional gallery through the flow restriction into the HLA low pressure chamber and switching gallery and eventually out the pressure relief valve. The pressure relief valve and flow restrictors are sized to regulate the pressure in the switching gallery to the desired 0.5 bar pressure. This eliminates having to manufactureconnector 453 containingrestriction 452 ofsystem 400. Air ingallery 112 is purged into low-pressure reservoir 528 and thence out of the HLA viatip opening 532. Continued purging fromgallery 112 throughHLA 516 drives air inport 518 and switchinggallery 244 out through three-way valve 350 and relief valve 356 (FIGS. 8 and 9 ). - An added advantage of
systems FIGS. 7 and 10 ) the flow restrictions (452, 552) are slightly back flushed, which can help to keep the orifice from becoming plugged with engine debris in long-term use. As insystem 400,HLA 516 must be prevented from rotation to keep the supply ports in the HLA registered with the proper oil gallery. - The benefits of improved oil distribution systems in accordance with the invention may be summarized as follows:
- a) they utilize a smaller, faster, and less expensive on/off OCV than the ROCV of the prior art;
- b) they utilize two separate oil galleries to avoid cam bearing lubrication concerns, especially in valve-deactivation applications;
- c) the conventional and switching oil galleries are in communication for excellent purging of air and have no dead legs;
- d)) the conventional and switching oil galleries are on opposite sides of the residence bore for the HLA;
- e) the low pressure limit for default operation of an associated DRFF can be set lower than for a prior art ROCV system, which aids switching performance;
- f) The conventional oil gallery remains positioned as in prior art engines, requiring minimal retooling of engine molds; and
- g) although a modified HLA is required, the necessary changes involve less risk than for the prior art
dual feed system 200; further, only the HLA body requires modification, so the advantages of the prior art single-piece plunger can be retained. - While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.
Claims (12)
1. In an internal combustion engine having at least one camshaft bearing, at least one hydraulic lash adjuster disposed in a residence bore formed in said engine, and at least one switchable cam follower actuated by hydraulic fluid fed from the hydraulic lash adjuster, a system for controllably supplying hydraulic fluid to the camshaft bearing and to the hydraulic lash adjuster, comprising:
a) a first hydraulic gallery in said engine for supplying said hydraulic fluid at a first pressure from a pressurized source to said camshaft bearing;
b) a second hydraulic gallery in said engine for supplying said hydraulic fluid at a second pressure from said pressurized source to said hydraulic lash adjuster.
c) a valve for variably connecting said second hydraulic gallery to said pressurized source; and
d) a fluid connector in fluid communication with said first and second hydraulic galleries, said connector including a flow-restricting orifice,
wherein said first and second hydraulic galleries are independently disposed on sides of said residence bore, and
wherein said hydraulic lash adjuster includes a hydraulic lash adjuster mechanism, said lash adjuster further comprising a low pressure chamber in fluid communication with the hydraulic lash adjuster mechanism and the switchable cam follower.
2. A system in accordance with claim 1 wherein said valve is a three-way on/off valve.
3. A system in accordance with claim 2 further comprising a pressure relief valve in fluid communication with said three-way on/off valve for selective connection to said second hydraulic gallery.
4. A system in accordance with claim 3 wherein a first position of said three-way on/off valve prohibits flow of said hydraulic fluid from said pressurized source through said valve to said second hydraulic gallery, and wherein a second position of said three-way on/off valve permits flow of said hydraulic fluid from said pressurized source through said valve to said second hydraulic gallery.
5. A system in accordance with claim 1 wherein said hydraulic fluid is engine oil supplied from an engine sump.
6. A system in accordance with claim 1 wherein said fluid connecting passage is connected between the distal ends of said first and second hydraulic galleries.
7. A system in accordance with claim 1 wherein said flow-restricting orifice is formed in a body of said hydraulic lash adjuster.
8. A system in accordance with claim 7 wherein the first gallery intersects the resident bore and is in flow communication with said low pressure chamber through said orifice.
9. A system in accordance with claim 1 wherein said flow-restricting orifice is disposed in a connecting passage, said connecting passage connecting said first and second hydraulic galleries.
10. A system in accordance with claim 1 wherein said hydraulic lash adjuster includes a body having a cylindrical outer surface unfeatured by an annular groove.
11. A system in accordance with claim 8 wherein one of said hydraulic lash adjuster or said resident bore includes an anti-rotation feature whereby axial rotation of said body relative to said resident bore is limited.
12. A multiple-cylinder internal combustion engine comprising:
a) at least one camshaft bearing;
b) at least one hydraulic lash adjuster disposed in a residence bore formed in said engine;
c) at least one switchable cam follower actuated by hydraulic fluid fed from said hydraulic lash adjuster; and
d) a system for controllably supplying hydraulic fluid to said camshaft bearing and to said hydraulic lash adjuster, including
a first hydraulic gallery in said engine for supplying said hydraulic fluid from a pressurized source to said camshaft bearing;
a second hydraulic gallery in said engine for supplying said hydraulic fluid from said pressurized source to said hydraulic lash adjuster.
a valve for variably connecting said second hydraulic gallery to said pressurized source; and
a fluid connector in fluid communication with said first and second hydraulic galleries, said connector including a flow-restricting orifice,
wherein said first and second hydraulic galleries are independently disposed on sides of said residence bore, and
wherein said hydraulic lash adjuster includes a hydraulic lash adjuster mechanism, said lash adjuster further comprising a low pressure chamber in fluid communication with the hydraulic lash adjuster mechanism and the switchable cam follower.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/503,776 US20080035085A1 (en) | 2006-08-14 | 2006-08-14 | Method and apparatus for controlling a switchable cam follower |
EP07075619A EP1892387A1 (en) | 2006-08-14 | 2007-07-20 | Method and apparatus for controlling a switchable cam follower |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US11/503,776 US20080035085A1 (en) | 2006-08-14 | 2006-08-14 | Method and apparatus for controlling a switchable cam follower |
Publications (1)
Publication Number | Publication Date |
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US20080035085A1 true US20080035085A1 (en) | 2008-02-14 |
Family
ID=38727282
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US11/503,776 Abandoned US20080035085A1 (en) | 2006-08-14 | 2006-08-14 | Method and apparatus for controlling a switchable cam follower |
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US (1) | US20080035085A1 (en) |
EP (1) | EP1892387A1 (en) |
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US20160102585A1 (en) * | 2014-10-10 | 2016-04-14 | Schaeffler Technologies AG & Co. KG | Switching oil gallery de-aeration |
US20160281551A1 (en) * | 2015-03-23 | 2016-09-29 | Ford Global Technologies, Llc | Hydraulic circuit for valve deactivation |
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Owner name: DELPHI TECHNOLGIES, INC., MICHIGAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HENDRIKSMA, NICK J.;REEL/FRAME:018202/0728 Effective date: 20060801 |
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