US 6,308,671 B1
`(10) Patent N0.:
`(12) United States Patent
`
`Reed et al.
`(45) Date of Patent:
`Oct. 30, 2001
`
`USOO6308671B1
`
`(54) METHOD OF INCREASING TORQUE AND/
`OR REDUCING EMISSIONS BY VARYING
`THE TIMING OF INTAKE AND/0R
`EXHAUST VALVES
`
`(75)
`
`Inventors: Dennis C. Reed, Plymouth; Martin
`Muller, Ann Arbor; Edward George
`Himes, Novi, all of MI (US); Bart
`Hubert Schreurs, Athus (BE);
`J00n-H0 Y00, Ann Arbor, MI (US)
`
`(73) Ass1gnee: Delphl Technologles, Inc., Troy, MI
`(US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by0 days.
`
`($) Notice:
`
`(21) Appl. NO‘: 09/658,596
`(22) Filed
`Sep. 11, 2000
`(51)
`Int. Cl.7
`........... F01L 1/34; F02D 9/10
`
`(52) US. Cl.
`.................
`1233/9015; 123/399; 123/478
`(58) Field of Search .............................. 123/90.15, 90.16,
`123/90.17, 90.18, 90.31, 399, 478; 701/103,
`104
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`........... 123/399
`6,006,725 * 12/1999 Stefanopoulou et al.
`6,182,636 *
`2/2001 Russell et al.
`....................... 123/399
`
`* cited by examiner
`
`.
`.
`.
`.
`.
`Primary Examiner—We11un L0
`(74) Attorney, Agent, or Firm—Vincent A. Cichosz
`(57)
`ABSTRACT
`
`A method of improving the operating characteristics of an
`internal combustion engine equipped with electronic throttle
`control employs variable cam timing to vary the phasing of
`the intake valves and/or exhaust valves so as to achieve
`lower feed gas emissions and improved fuel economy while
`delivering as closely as possible the desired torque. The
`method can be implemented using a fuel-lead strategy or an
`air-lead strategy. Whenever a change is requested in the
`amount of torque, the method responds by adjusting the
`amount of fuel flow, the spark timing, the position of the
`throttle and/or the pos1tions of the intake valves and/or the
`exhaust valves SO as to deliver the desired torque. The
`method adjusts those operating parameters in a way that
`improves the ability of the engine to deliver the desired
`torque, produce less feed gas emissions, idle more stably,
`and consume less fuel.
`
`6,000,375 * 12/1999 Isobe .................................... 123/322
`
`10 Claims, 8 Drawing Sheets
`
`”0
`
`Calculate
`Des‘ircd 'l'orquc
`
`
`[00
`
`/
`
`'20
`Desired lorqlic
`320
`
`Acliinl 0R Desired N.
`‘
`\
`Dilution
`(juiwium
`Dcsu’cd l‘llcl Dulcnnine
`
`
`DCSH’CL‘ Fuel
`Iv’uul / Cyl
`
`
`
`
`Dcslicd Fuel
`lzufl‘llllud Fuel / L‘vl
`I30
`
`iso
`Haired All" Rat\m
`L.._
`Culciilale
`Calculate Fuel
`
`Desired Air
`Injector l‘iilsu Widili
`
`
`
`140
`-\
`Desired Aii
`
`7m
`lingiiie Speed
`\\ ,
`
`ClllClllillL‘ Voluincn lC
`lhmulc Position
`MAP
`Oalculale i)CSiICll
`
`
`lingiiic |,ii.id
`
`lilliciciiuy
`Huromelcr
`bagd an duiud awning: 4——
`
`
`Vlilulllullll}““16“”le
`
`imam»- spat-ii
`
`
`
`
`
`
`Desii ml
`[Exhaust and lnnikz:
`(allurinisu in“
`
`230
`liii ’lllc SEEli ,,
`.
`.
`liii '11“: Load
`
`Aliilirl)‘sii'l
`5
`lixlinusl Lind lnlukc
`k u
`H I
`i
`
`~.
`I
`. __
`j
`.
`Aclllzll Ulk
`Linn I liiier l as
`,V l'
`I'
`_
`
`l..i Lll tin.
`Dcsncd
`A
`
`Hilulwu M,
`
`
`Desired 'l'liroille posinoii
`1-70
`\
`l
`.
`~
`,
`.
`. \4.’
`
`
`ALlunl 'llirolllt. l osiliuii AdjllSl—> '1'! 111*!) "1'
`
`"all; Eli": m“
`Desnedlixlitiiisl
`H0
`and “mm. Cum
`Engine Speed
`
`.
`
`
`Calculate Desuud ltxllzlllsl
`l’liiiser l’osiiions
`.
`j
`.
`_
`Engine lertiue
`And liiliikc Caini Hum ~_.,
`
`
`l’usiniiiis _.,._.
`,
`Coolant 'l'eiiip
`Baroiiiclric l’rcssni
`220
`200
`lixliniisl
`Acliinl
`(imnk l‘ulscs
`mill liilnl'i- l'nm
`
`
`—"‘—‘—V Cniculinc Acluiil lixhnnsl l’hnserl’osiliuns
`min n.
`Vclunl‘i’lL
`Cam Pulses
`
`And lnlnkc (fiiin l’linsci
`Em ci 1 Mg
`based an Mimi aw pox,
`l’lisiliims
`
`
`
`EnginL Spud
`A‘TV‘LEH'I 1.70 Vt
`
`
`VW EX1007
`
`US. Patent No. 6,557,540
`
`VW EX1007
`U.S. Patent No. 6,557,540
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 1 0f 8
`
`US 6,308,671 B1
`
`FIGURE 1
`
`(ECM)
`
`t
`
`eo1rEtnoC
`
`c1
`
`rM
`
`00
`
`nlu
`
`nd
`
`ec1
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 2 0f 8
`
`US 6,308,671 B1
`
`R
`
`.3
`
`E
`
`mm
`
`mm
`
`533$03
`
`
`
`gammaamu
`
`A3HouoondHHonk
`
`“093.350ofinH
`
`noun—EHMO”35¢an
`
`2
`
`NmmeHh
`
`E
`
`RogueI
`
`
`
`ummamflmoofidHhm.HondamHuman—memoHanna—ammmIHamcwm
`
`
`
`m:ExIHonnam”25530mm23.95mm
`
`Ew
`
`
`
`
`
`:65£3.62Houucoo039nm
`
`IE
`Homnmm30v:wmhxo
`
`
`
`“325m.325
`
`
`
`Hmsmuudnmanna033
`
`
`
`
`
`noncwmEfiésow...HQ303-(wm
`
`amp...
`
`Manama5de
`
`wnsumuumflou.H2@xmudH
`
`Amauv
`
`
`
`
`
`HomflamoHdumenmfioBufimaoou
`
`
`
`
`
`GHSmmOHm0350an“Vacuum;
`
`
`
`
`
`HemawmGOHuHuomoduuouafi.
`
`
`
`amtHOE—0mUoOn—mwHOHAo>3..
`
`
`
`
`
`
`
`
`
`
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 3 0f 8
`
`US 6,308,671 B1
`
`FIGURE 3
`
`HO
`
`I 00
`
`Calculate
`
`
`Desired 'l'orque
`
`
`320
`Desired 'l'orqne
`\
`Actual OR Desired
`
`
`Calculate
`Desu'cd Fuel
`Deteniune
`
`Dilution
`
`
`
`Desired Fuel
`l’uel / Cyl
`
`
`
`
`Desired Fuel
`Requu'ed Fuel 1 CV].
`
`Desired A/l“ Ratio\
`
`Calculate
`Calculate l-‘uel
`
`
`
`Desired Air
`injector Pulse Width
`
`
`
`
`
`Desired Air
`
` 7,”)
`
`I
`
`lingine Speed
`\
`Calculate Voilllllclllt.‘
`Calculate Desired
`Volumetric lillicieacy
`
`
` MAP
`
`
`Throttle Position
`lingnie Load
`lillicrency
`
`Barometer
`
`54541 on desired cmmjojr +—_
`Desued
`
`
`lixhaust and Intake
`Cam i'lmscr 1'01
`
`n
`:20
`1
`
`I30
`
`140
`\\
`
`lJ'O
`
`Desired 'l'lu‘otlle position
`
`\
`
`
`Actual 'l'lirottle Position
`Adjust
`—‘—> 'l'ltrottle Position
`
`with ETC
`
`
`Engine Speed
`
`230
`
`
`lingine Speed-n
`
` [Engine Load
`Actual or Desired
`lixhaust and Intake
`Actual UR
`
`Cain l’haser l’os.
`Calculate
`Desired
`
`Dilution
`
`
`Dilution>
`
`H0
`l’liaser Positions Engine Speed
`
`
`Calculate Desired lixliaust
`
`
`
`And Intake Cam l’hasct‘
`Engine Torque
`
`
`
`Positions
`
`
`Coolant Temp
`
`Baroirielric Pressur
`
`
`Desired Exhaust
`and Intake Cam
`
`
`100
`22.0
`lixhaust
`Actual
`
`
`Crank l’ulses
`
`mul [ntaki- (Tarn
`Calcv 1+2 Votundrit.
`l’haser Positions
`——‘—"~—‘—} Calculate Actual lixlianst
`
`
`
`Cam Pulses
`And Intake Cain l’liaser
`Ef'FicianB
`
`
`
`
`Positions
`[taxed on nail/mi mm pas.
`
`
`
`
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 4 0f 8
`
`US 6,308,671 B1
`
`F IGURE 4
`
`"r
`
`IOO
`\~’
`
`
`Volumetric lillicienev
`
`MAl’ . MAl‘. or lMl“l’
`
`Determine Mass
`Air Flow
`
`lA'l'RPM, . Coolant 'l'enip, Ultl't) etc.MW
`
`
`I to
`360
`
`
`Calculate
`
`
`Desired 'l'orque
`
`
`370
`
`
`
`l)esited littct
`Determine
`Calculate
`Actual 0R Desired
`All" Ratio
`l-‘uel ltlvl
`
`
`
`
`Desired Fuel
`Dilution
`
`
`Desired lr‘tiel
`Required Fuel / (:yl
`
`130
`l)esrred A/l" Ratio
`Calculate
`Culutlutu l'uul
`
`
`Desired Air
`Injector Pulse Width
`
`
`
`Desired Air
`I40
`
`
`
`
`2' l 0
`lingine Speed
`lingine Speed
`N
`
`
`
`Calculate Volumetric
`
`
`Calculate Desired
`Volumetric litliciency
`
`
`lingnie Load
`lillictcncy based on
`
`
`MAP
`.
`.
`.
`.
`
`lhrottlc POSIIIOH
`
`Barometer
`desire cam angles
`4——-——-
`
`
`Destretl lixliaust and
`Desired 'l‘ltrottle position
`Intake Cain
`
`150
`l’liaser l’osrtions
`Actual 'lhrottle Position
` Adjust
`
`Throttle Position
`
`
`’
`I (
`With 1'.
`
`lingnte Load
`
`
`Actual or Desired
`
`lixliuust and lnttike
`Adm] ()R
`
`
`\,
`.
`,
`.
`~
`~.
`J
`. -.
`')
`‘
`L tliIJllllll.
`(.nm 1 Itaser l (is.
`Desired
`D'lmw“
`Dilution
`
`
`
`
`
`
`Desired I orqttt:
`
`A” How
`
`120
`
`l‘nLim, S )LLVJ
`
`l)'siret| lixli'tu 'I
`‘ :| 1m}; . 6 ‘3
`M L
`I
`L
`L 4“)
`l’ltaser l’osrtions
`>
`
`iqo
`
`,
`.
`,
`lLtlglm: hpL‘Cd
`
`
`Calculate Desired lixliunst
`
`Engine 'l‘ortltte
`And Intake Cant l’linser
`Positions
`
`
`Coolant 'l'emp
`
`Barometric Pressu
`Volumetric lilliciency
`Actual
`lixltaust
`
`220
`200
`
`
`
`and intake Cum
`
`
`|-'.n one Speed
`Crank l’ulses
`l-‘liaser Positions
`
`Calculate Volumetric
`Calculate Actual llxliaust
`
`
`
`.
`‘
`:
`.
`.
`\.
`I u.
`And Intake Cam l’ltaser
`lingtuc
`Anti-till
`”[1“an based 0”
`(.nm 1 tilses
`Positions
`
`Aclmil cum angles ““5
`
`
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 5 0f 8
`
`US 6,308,671 B1
`
`FIGURE 5
`
`HO
`
`IH
`
`
`Main
`
`
`Torque
`
`Pedal Position
`~—-——#~+
`
`Engine Speed
`
`Select
`
`Torque
`
`
`Cruise Control
`
`
`
`
`Traction Control
`
`"
`
`UL:
`
`Desired 'I'orque
`
`
`
`
`
`SUM
`
`/'\\
`
`v'F—‘—’ Torque /
`
`Additional accessory loads
`—————>
`
`US
`
`Vehicle Speed
`
`
`Transmission
`
`
`
`Engine Speed
`"orque
`
`
`
`l l4-
`
`.1
`
`Additional
`
`__
`
`__r__,,_, _.
`
`Torque
`
`.
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 6 0f 8
`
`US 6,308,671 B1
`
`ON
`
`ON
`
`ON
`
`cw
`
`CV
`
`ON
`
`ON
`
`ON
`
`ON
`
`or
`
`or
`
`or
`
`cm
`
`wv
`
`Cw
`
`av
`
`av
`
`3‘
`
`NN
`
`mm
`
`mm
`
`0v
`
`vv
`
`a.»
`
`NV
`
`ov
`
`hm
`
`om
`
`om
`
`mm
`
`on
`
`av
`
`3.
`
`cv
`
`av
`
`3.
`
`COO
`
`OOCCOC
`
`ODOOOOOOO
`
`DDODOOCCO
`
`Elm03w
`Samocow
`Sam00mm
`
`or
`
`we
`
`ON
`
`ON
`
`on
`
`9..
`
`on
`
`om
`
`om
`
`mmmmmmcoo
`
`c—E
`
`mm
`
`0?
`
`NNNNNF‘DCD
`
`SideconSimCommSEN—oowmSEEOCTN
`
`
` oooEmmacomEamoomr2mmCome
`
`or
`
`cm
`
`mm
`
`0?
`
`av
`
`me
`
`aw
`
`em
`
`on
`
`O?
`
`0v
`
`DOD
`
`CD
`
`Np
`
`on
`
`0?
`
`cm
`
`wmmDOHm
`
`
`
`2amcom
`
`
`
`mDOEOHa}EMEE<E
`
`2mmocmmSEEcomv
`
`SEEe36
`
`SEE000?
`
`or3OP
`
`OF
`
`or
`
`c—
`
`ooo
`
`we
`
`m—
`
`m?
`
`m—
`
`or
`
`m—
`
`m—
`
`m;
`
`mp
`
`mmIceman
`
`008059..ahmsoocxcm
`
`onoEov
`
`OBEN
`
`
`
`@3500SON.
`
`mtoomSon
`
`
`
`0.850.»tom
`
`octoowtcop
`
`mNSeaman
`
`mNroQom
`
`mNECEOV
`
`cmxcomzow
`
`QDBN
`
`QNQBOOZOM
`
`mtccwSoc
`
`meBow—‘om
`
`octoomtoor
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 7 0f 8
`
`US 6,308,671 B1
`
`FIGURE 7
`
`
`
`
`FIGURE 8
`
`

`

`US. Patent
`
`Oct. 30, 2001
`
`Sheet 8 0f 8
`
`US 6,308,671 B1
`
`mmmDDHm
`
`0000000000200952
`000000000.550350
`0?CF0?0r00002500300
`00CV0v000vm:0wNw0.w0\000:0\.
`0000Eonmm0—090—0030050
`000m0w0r0m0—Nr000.050900
`0N0090..or00OmNBoEoV
`mm000f0?0p000mamtoowam
`cw0m0—or0?000035m
`SEE000055000mm.2mm000mSEE00cmSTE000mSEE000w55000gElm000MDOEOFokawiixxfi
`
`
`
`
`
`E01090Sam00002am0000Eni0000SEC09?2mm003.Sam000vmDUZObfi.EwEE/«E
`
`
`
`
`
`O0000mmVa0550
`
`00000m00n0930030
`
`00o000mmummBoEov
`
`00000ONmu0.5050900
`
`000000m20900050
`
`000000m0035038000000ONmm0.3500205
`
`000000000050350
`
`000000000200029:
`
`

`

`US 6,308,671 B1
`
`1
`METHOD OF INCREASING TORQUE AND/
`OR REDUCING EMISSIONS BY VARYING
`THE TIMING OF INTAKE AND/OR
`EXHAUST VALVES
`
`FIELD OF THE INVENTION
`
`The present invention relates, in general, to an internal
`combustion engine of the type equipped with an electronic
`throttle control system and a variable valve timing
`mechanism(s), and of the type controlled by a torque based
`management system. More particularly, the invention per-
`tains to a method of increasing engine torque and/or of
`reducing engine emissions by varying the phasing of either
`the intake valves or the exhaust valves or both.
`
`BACKGROUND OF THE INVENTION
`
`The following background information is provided to
`assist the reader to understand one of the many environ-
`ments in which the invention will typically be used. Upon
`reading this document, the reader will appreciate that the
`invention may also be applied or adapted to environments
`other than that described below.
`
`FIG. 1 illustrates one cylinder of an electronically con-
`trolled multi-cylinder engine that is equipped with a mecha-
`nism capable of varying the timing of the opening and
`closing of the intake and exhaust valves. While the engine 1
`is operating, air at atmospheric pressure is drawn into an
`inlet 2 through a filter 3 and into an intake duct 4. The
`incoming air then flows into a throttle body 5 in which is
`disposed a throttle valve 6. The throttle valve 6 typically
`takes the form of a rotatable plate.
`Controlled by an electronic throttle control (ETC) system,
`the throttle plate 6 has its position adjusted regularly to allow
`an amount of air appropriate to present conditions to pass
`through the throttle body 5 and thereafter into an intake
`manifold 7. The throttle control system typically features a
`pedal sensor 8, a throttle position sensor (TPS) 9, a motor 10
`and an electronic control module (ECM) 11. The pedal
`sensor 8 enables the ECM 11 to monitor the position of the
`accelerator pedal, and thus to determine whether the driver
`wants the vehicle to maintain, increase or decrease torque.
`The TPS sensor 9 enables the ECM 11 to monitor the
`
`angular position that the throttle plate 6 occupies in the
`throttle body 5. Pursuant to prior art algorithms, the ECM 11
`uses the input from these sensors, as well as other sensors,
`such as those shown in FIG. 2, to control the engine 1 so that
`it delivers the desired torque according to the conditions
`under which the vehicle is operating. In doing so, the ECM
`11 controls via motor 10 the position of the throttle plate 6,
`and thus the quantity of air that is drawn into the intake
`manifold 7.
`
`From the intake manifold 7 the incoming air then passes
`to an intake duct 12 that leads to the cylinder 13. Meanwhile,
`fuel from a fuel tank 14 is pumped via a pump 15 through
`a pipe 16 to a fuel injector 17. According to known practice,
`the ECM 11 uses data from several sensors to calculate the
`
`injector pulse width, i.e., the electrical signal that the ECM
`11 uses to activate the fuel injector 17 for a time appropriate
`to current conditions. Activated via a drive circuit, the fuel
`injector 17 injects the precise amount of fuel into the intake
`duct 12. There, the fuel mixes with the inlet air coming from
`the intake manifold 7.
`
`As noted in greater detail infra, a cam timing mechanism
`drives the intake valve 18 to the open position in timed
`relationship with the intake cycle of cylinder 13. During the
`intake cycle, a low pressure condition develops within the
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`combustion chamber 19 due to the downward movement of
`a piston 20 within the cylinder 13. The low pressure draws
`the fuel-air mixture from the intake duct 12 past the intake
`valve 18 and into the combustion chamber 19. For the
`subsequent compression cycle, the action of the cam timing
`mechanism(s), as noted infra, closes the intake and exhaust
`valves 18 and 21 at the top of the cylinder 13. During the
`compression cycle itself, as is well known,
`the upward
`movement of the piston 20 compresses the air-fuel mixture
`in the combustion chamber 19 of the cylinder 13.
`During the combustion cycle,
`the fuel-air mixture is
`ignited and exploded to produce power. Operating according
`to the spark sequence controlled by an electronic spark
`timing system, the ECM 11 causes the air-fuel mixture to be
`ignited in the combustion chamber 19. More specifically, the
`combustion cycle is initiated, at the appropriate time, by a
`spark driven across the spaced electrodes of a spark plug 22.
`The explosive force of the combustion drives the piston 20
`downward within cylinder 13. The downward thrust of the
`piston 20 is imparted via connecting rods 23 as a torque
`upon a crankshaft 24 of the engine 1. Combined with the
`torque it receives from the other pistons in the engine 1, the
`crankshaft 24 drives the wheels and the accessory loads, etc.,
`of the motor vehicle, as is generally understood in the art.
`For the exhaust cycle, a cam timing mechanism drives the
`exhaust valve 21, at
`the appropriate time,
`to the open
`position. During the exhaust cycle, the upward movement of
`the piston 20 forces the exhaust gases produced by com-
`bustion past
`the exhaust valve 21 and into an exhaust
`manifold 25. An exhaust pipe 26 then channels the exhaust
`gases to a catalytic converter 27. A catalyst within the
`converter 27 aids the oxidization of unburned constituents,
`such as carbon monoxide (CO) and hydrocarbons (HC), and
`the reduction of nitrogen oxides (NOX). From the converter
`27,
`the purified exhaust gases are conveyed typically
`through a muffler and then through a tail pipe to atmosphere.
`The ECM 11 monitors and controls the operation of the
`engine 1 through many data sensors, switches and control
`devices, some of: which are shown in FIGS. 1 and 2. In
`addition to the pedal and TPS sensors 8 and 9, the data
`sensors include an intake air temperature (IAT) sensor 28, a
`coolant temperature sensor (CTS) 29, a manifold absolute
`pressure (MAP) sensor 30, a vehicle speed sensor (VSS) 31,
`an oxygen (022) sensor 32, and an engine speed (RPM)
`sensor 33. On some vehicles, additional data sensors are
`used. These include a wide range air-fuel (WRAF) sensor
`34, a barometric pressure (BARO) sensor 35, and a mass air
`flow (MAF) sensor 36. The devices and subsystems that the
`ECM 11 controls,
`include the electronic throttle control
`system, the electronic spark timing system, the fuel injection
`system and the cam timing mechanisms.
`The data sensors generate electrical signals, typically in
`analog form, indicative of the parameters they are intended
`to measure. The IAT sensor 28 typically measures the
`temperature of the air in the inlet 2 of the engine 1. The CTS
`sensor 29 senses the temperature of the coolant that flows in
`channels 37 around the cylinders to keep the engine cool.
`The MAP sensor 30 measures the absolute air pressure in the
`intake manifold 7. The VSS, sensor 31 generates a pulse
`representing the actual speed of the vehicle. The O2 sensor
`32 is typically mounted to the exhaust system downstream
`of the converter 27 so that its head lies exposed to the stream
`of exhaust gases produced by the engine 1. It senses the free
`oxygen concentration in the exhaust gases, and conveys a
`corresponding signal to the ECM 11. Typically exposed to
`the exhaust gases upstream of the converter 27, the WRAF
`sensor 34 measures the air-fuel ratio. It is used on some
`
`

`

`US 6,308,671 B1
`
`3
`vehicles to measure directly the ratio of air to fuel for
`purposes of controlling the delivery of fuel to the engine 1.
`The ECM 11 uses the signals from the O2 and WRAF
`sensors 32 and 34 to control more precisely the fuel-air
`mixture to achieve stoichiometry. This correction process is
`known as closed loop operation.
`On vehicles equipped with BARO and MAF sensors, the
`BARO sensor 35 measures the pressure of the ambient air
`and provides data to the ECM 11 as to pressure changes due
`to altitude and weather. The MAF sensor 36 measures the
`rate at which the air mass flows into the intake manifold 7.
`For vehicles not equipped with a BARO sensor 35, the ECM
`11 is programmed to estimate the barometric pressure using
`data from various other sensors according to well-known
`practice. For vehicles not equipped with a MAF sensor 36,
`the ECM 11 estimates the air mass flow rate using data from
`the various other sensors, as is also known in the art.
`The analog signals generated by the data sensors are
`conveyed to the ECM 11 where an A/D converter 40
`converts them into digital signals. This conversion is nec-
`essary because the central processing unit (CPU) 41 of the
`ECM 11 can only manipulate digital information. Along
`with the input received by the interface (I/F) 42, the digital
`sensor data is conveyed to input registers in the ECM 11.
`Using the data it reads from the registers, the CPU 41 not
`only performs the mathematical computations and logic
`functions necessary to calculate inter alia the spark timing,
`the cam timing and the proper fuel-air mixture, but also
`provides control signals through drive circuits 43—47, The
`CPU 41 performs all of its functions according to the
`programming code stored in its associated memory devices.
`The memory devices include random access memory
`(RAM) 48 and read only memory (ROM) 49 inclusive of
`programmable ROM (PROM). The CPU 41 uses RAM 48 to
`temporarily store information such as the data received from
`the data sensors, the diagnostic codes and the results of its
`calculations. The ROM 49 is where the calibration data and
`
`fuel delivery algorithms are typically stored along with
`various lookup tables and control algorithms that collec-
`tively constitute the programming code. The elements in the
`ECM 11 are connected to one another through a system bus
`50 containing address, data and control buses.
`Used primarily to maintain the engine 1 at idle, the idle
`speed control (ISC) system includes the ECM 11 and an idle
`air control (IAC) valve 51. The IAC valve 51 is situated in
`a flow path parallel to that through the throttle body 5. Upon
`closure of the throttle plate 6 and feedback from the VSS
`sensor 31 indicating the vehicle has stopped, the ISC system
`compares the actual engine speed with a target engine speed
`it derives according to known practice. Based on the differ-
`ence between the target and actual values, the ISC system
`controls the IAC valve 51 via drive circuit 43 so as to adjust
`the rate at which air flows into the engine 1 and thereby
`attain the target idle speed.
`The electronic spark timing (EST) system includes the
`ECM 11, the RPM sensor 33 and a distributor module 55.
`The RPM sensor 33 generates a pulse for every 30 degrees
`that the crankshaft 24 rotates, thereby providing a measure
`of the speed, or revolutions per minute (rpm), at which the
`engine 1 is operating. Through the data sensors, the ECM 11
`monitors the speed and other operating conditions of the
`engine 1, and, from those parameters, calculates the proper
`spark timing. According to the spark timing sequence, the
`ECM 11 then directs the distributor module 55 via drive
`
`circuit 44 to distribute to each of the spark plugs 22, at the
`appropriate time, the energy required to achieve combustion.
`The fuel injection system includes the ECM 11 and the
`fuel injector 17. Operating according to known principles,
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`the ECM 11 uses data from several sensors to calculate the
`target air-fuel ratio. The mass of intake air per engine
`revolution is calculated from the mass flow rate of intake air
`measured by the MAF sensor 36 and the engine speed
`detected by the RPM sensor 33. Alternatively, it may also be
`estimated using data from other sensors, such as the MAP
`sensor 30 and the RPM sensor 33. Using the mass of intake
`air per engine revolution, the ECM 11 then determines the
`injector pulse width warranted by the current operating
`conditions. The ECM 11 continually adjusts the injector
`pulse width to correct for changes in various parameters,
`such as in the readings taken from the TPS, IAT, O2 and
`WRAF sensors, so as to maintain as closely as possible the
`target air-fuel ratio. At a given angle in the operational cycle
`of the crankshaft 24, the ECM 11 then directs drive circuit
`45 to inject fuel from the fuel
`injector 17 for the time
`dictated by the injector pulse width.
`Most four cycle engines are designed so that the intake
`and exhaust valves operate (i.e., open and close) in a fixed
`angular relationship to the angular position of the crank-
`shaft. Many engines use only a single camshaft to control the
`opening and closing of the intake and exhaust valves. The
`newer, more advanced engines often use a dual cam
`arrangement, i.e., one camshaft to control the open/close
`timing of the intake valves and another camshaft to govern
`the open/close timing of the exhaust valves. In either case,
`each valve is biased by a spring to the closed position.
`Affixed to the camshaft(s) are as many cams as there are
`valves, with the cams for the intake valves being oriented at
`one angle and the cams for the exhaust valves being oriented
`at another angle. Because a camshaft rotates at half the speed
`of the crankshaft, each intake cam causes its corresponding
`intake valve to be open (against the bias of the spring) and
`closed at fixed intervals during the operational cycle of the
`crankshaft. Similarly, each exhaust cam causes its corre-
`sponding exhaust valve to be open and closed at fixed
`intervals.
`
`The term “standard cam timing” refers to the opening and
`closing of the intake and/or exhaust valves at such fixed
`intervals. In engines that employ standard cam timing, a
`compromise must be reached between how smooth will the
`engine run at idle, how much torque will it be able to deliver
`at medium to high speeds, the toxicity of its emissions, aid
`how much fuel will
`the engine consume.
`It
`involves a
`decision as to when and how long the intake and exhaust
`valves should be open at the same time (i.e., valve overlap).
`The amount and phasing of valve overlap is a trade-off
`between stable idling and the amount of power that will be
`available at medium to high speeds. It also is a trade-off
`between engine performance, emissions and fuel economy.
`The automotive industry is now investigating the use of
`variable cam timing (VCT) schemes to improve the overall
`performance of an engine without the strict compromises
`required by standard cam timing techniques. VCT allows the
`timing of the camshafts, and thus the opening and closing of
`the valves, to be optimized over a wider range of operating
`conditions. It offers the possibility of improved performance
`at medium to full loads coupled with reduced emissions and
`improvements in fuel economy.
`Referring to FIG. 1, the opening and closing of intake
`valve 18 is controlled by a cam 70 attached to an intake
`camshaft 71. A cam 80 attached to a camshaft 81 likewise
`
`controls the opening and closing of exhaust valve 21. As the
`pistons reciprocate within their respective cylinders,
`the
`torque they impart to the crankshaft 24 via the connecting
`rods 23 also drives a timing pulley 60. Each camshaft at its
`end also has a pulley, with camshaft 71 having timing pulley
`
`

`

`US 6,308,671 B1
`
`5
`61 and camshaft 81 having timing pulley 62. A timing belt
`63 connects the timing pullers 60, 61 and 62. Consequently,
`as the crankshaft 24 rotates, it also drives the camshafts 71
`and 81, with the cams 70 and 80 thereon opening and closing
`the intake and exhaust valves 18 and 21 at predetermined
`angles in the operational cycle of the crankshaft 24. A
`crankshaft sensor 56 generates a set number of pulses (e.g.,
`58 pulses) for each rotation of the crankshaft 2,4. Similarly,
`there are two camshaft sensors 57 and 58. Each camshaft
`
`sensor 57 and 58 generates a set number of pulses (e.g., 4
`pulses) for each rotation of its respective camshaft 71 and
`81.
`
`5
`
`10
`
`The dual cam engine shown in FIG. 1 has two continu-
`ously variable cam timing mechanisms 72 and 82, one for
`the intake valves and the other for the exhaust valves.
`
`15
`
`Controlled by the ECM 11, each VCT mechanism enables its
`respective camshaft to be phase-shifted relative to the crank-
`shaft 24 as a function of the conditions under which the
`
`engine 1 is operating. Also referred to as cam phasers, VCT
`mechanisms take a variety of forms such as the vane type or
`helical gear type cam phasers. The latter is discussed below
`for illustrative purposes.
`Situated between the camshaft 71 and the timing pulley
`61, the intake VCT mechanism 72 turns the camshaft 71 and
`timing pulley 61 relative to each other. More specifically, the
`intake cam phaser 72 uses the camshaft 71 and timing pulley
`61 as external gears and interconnects them via an interme-
`diate helical gear. Through drive circuit 46, the ECM 11
`controls a valve 73 that affects the hydraulic pressure acting
`upon the helical gear. It also uses feedback from sensors 56
`and 57 to monitor the angular relationship between the
`crankshaft 24 and the intake camshaft 71. By changing the
`hydraulic pressure via valve 73, the ECM 11 can move the
`helical gear axially, and thus alter the angular relationship
`between the intake camshaft 71 and the timing pulley 61 as
`well as the crankshaft 24. In doing so, the ECM 11 can adjust
`the open/close timing of the intake valve 18.
`The exhaust VCT mechanism 82 is situated between the
`
`camshaft 81 and the timing pulley 62. Like the intake cam
`phaser 72, the exhaust cam phaser 82 uses the camshaft 81
`and timing pulley 62 as external gears and interconnects
`them via an intermediate helical gear. Through drive circuit
`47, the ECM 11 controls a valve 83 that affects the hydraulic
`pressure acting upon this helical gear. It also uses feedback
`from sensors 56 and 58 to monitor the angular relationship
`between the crankshaft 24 and the exhaust camshaft 81. By
`changing the hydraulic pressure via valve 83, the ECM 11
`can move this helical gear axially, and thus alter the angular
`relationship between the exhaust camshaft 81 and the timing
`pulley 62 as well as the crankshaft 24. In doing so, the ECM
`11 can adjust the open/close timing of the exhaust valve 21.
`Using VCT mechanisms,
`the open/close timing of the
`intake and exhaust valves 18 and 21 can be optimized to
`improve the overall performance of the engine 1. In dual
`overhead cam (DOHC) engines, there are four possible types
`of VCT: (1) phasing only the intake cam (Intake Only); (2)
`phasing only the exhaust cam (Exhaust Only); (3) phasing
`the intake and exhaust cams equally (Dual Equal); and (4)
`phasing the intake and exhaust cams independently (Dual
`Independent). The Dual Equal strategy is also applicable to
`single overhead cam (SOHC) engines.
`It is well known that use of a VCT mechanism on only the
`intake camshaft 71 improves engine operation. This
`involves varying the open/close timing of the intake valve
`18, as compared to standard cam timing, when the engine 1
`is operating at part load. For example, by advancing the
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`opening of the intake valve 18, the valve overlap is extended
`into the exhaust stroke. This means that the intake valve 18
`starts to open near the end of the exhaust stroke. Viewing
`FIG. 1, this allows the piston 20,
`in its upward exhaust
`stroke, to push a small amount of the exhaust gases back into
`the intake duct 12. On the subsequent (downward) intake
`stroke, this exhaust gas is then re-ingested into the cylinder
`13 for combustion with the fuel-air mixture. By advancing
`the closing of the intake valve 18, the intake valve 18 closes
`earlier in the compression stroke. This means that less of the
`fuel-air mixture is pushed back into the intake duct 12,
`thereby enabling more power to be produced during com-
`bustion.
`
`The benefits of intake cam phasing are well known. First,
`it reduces NOx emissions. This is due to what is referred to
`as increased residual dilution. The re-ingested exhaust gases
`(i.e., the diluent) lowers the temperature at which combus-
`tion occurs, thereby reducing the amount of NOx emissions.
`The extent of the NOx reduction depends on the load and
`speed of the engine. Second, it reduces HC emissions. The
`last portion of the exhaust gases ejected from cylinder 13
`during the exhaust stroke is rich in unburned HC. It is this
`portion of the exhaust gases that is re-ingested during the
`intake stroke and subsequently burned. Advanced intake
`cam timing also increases the torque output by the engine at
`medium to high speeds, improves fuel economy and enables
`the engine to be operated more stably at idle.
`It is also well known that use of a VCT mechanism on
`
`only the exhaust camshaft 81 has a significant effect on
`emissions. This involves varying the close/open timing of
`the exhaust valve 21, as compared to standard cam timing,
`when the engine 1 is operating at part load. For example, by
`delaying the closing of the exhaust valve 21,
`the valve
`overlap is extended into the intake stroke. This means that
`the exhaust valve 21 stays open at the start of the intake
`stroke. Viewing FIG. 1, this allows the piston 20, in its
`downward intake stroke,
`to draw a small amount of the
`exhaust gases from the exhaust manifold 25 not only back
`into the cylinder 13 but also into the intake duct 12 due to
`vacuum. Along with the fuel-air mixture, this exhaust gas is
`then burned in the combustion chamber 19 during the
`combustion cycle.
`The benefits of exhaust cam phasing are well known.
`First, it also reduces NOx emissions due to increased residual
`dilution. Second, HC emissions are reduced because the
`HC-rich portion of the exhaust gases is drawn back into the
`cylinder 13. Delayed exhaust cam timing also improves fuel
`economy and enables the engine to be operated more stably
`at idle. In addition, exhaust cam phasing can be used as a
`substitute for an external exhaust gas recirculation (EGR)
`system, as it performs the same function. The cost of
`equipping a vehicle with an exhaust cam phaser can be less
`than that for a conventional EGR system.
`US. Pat. No. 5,713,317 to Yoshioka describes a method
`of controlling a VCT mechanism through which to vary the
`open/close timing of a valve. It purports to optimize the
`valve timing so as to improve the output of the engine at high
`altitudes while it
`is operating under high loads. It also
`purports to reduce the fuel consumption and emissions of the
`engine at high altitudes as it operates under low to medium
`loads. The method essentially controls the amount of
`residual dilution (i.e., re-ingested exhaust gases). In doing
`so, the Yoshioka reference teaches advance of the intake
`valve only, in a way that attempts to compensate for the
`effects of altitude.
`
`US. Pat. No. 5,755,202 to Stefanopoulou et al. teaches
`the use of a Dual Equal VCT strategy on a vehicle equipped
`
`

`

`US 6,308,671 B1
`
`7
`with ETC and a torque based engine control system. Accord-
`ing to the method, the range of torque that can be demanded
`of the engine is divided into five regions, namely, negligible,
`small, moderate, high and maximum. The engine control
`system chooses the particular cam timing schedule to use
`according to the region into which the actual torque demand
`falls. For example, in the negligible torque region, standard
`cam timing is used to maintain the engine at, a stable idle.
`In the small torque region, the timing scheme falls between
`standard and fully retarded cam phasing, with the exact
`timing dependent on the magnitude of the torque demand. I