(12) United States Patent
`(10) Patent N0.:
`US 6,681,752 B1
`
`Kreikemeier et al.
`(45) Date of Patent:
`Jan. 27, 2004
`
`USUO6681752B1
`
`(54) FUEL INJECTION SYSTEM METHOD AND
`APPARATUS USING OXYGEN SENSOR
`SIGNAL CONDITIONING T0 MODIFY AIR/
`FUEL RATIO
`
`4,502,444 A
`4,526,001 A
`4500419 A
`4,980,834 A
`5,762,055 A
`
`3/1985 Rubbo et a1.
`7/1985 Burns 3 a1~
`“1980 Ninomiya et a1-
`12/1990 Ikeda et a1.
`6/1998 Yainashita et al.
`
`(75)
`
`Inventors: Michael L Kreikemeier, Belgrade, MT
`(US); Chad D Beauregard, Belgrade,
`MT (US)
`
`2,2001 weISbmd a a1"
`6’189’523 B1
`Primary Examiner—Bibhu Mohanty
`(74) Attorney, Agent, or Firm—Allan Jacobson
`
`(73) Assignee: Dynojet Research Company, North
`Las Vegas, NV (US)
`,
`‘
`,
`.
`.
`SHDJCCI. to any dISCIalmer’. the term 0f thls
`patent 1s extended or adjusted under 35
`USL. 154(b) by 0 days.
`
`.
`NOUCCZ
`
`)
`
`*
`
`(
`
`(21) APP1~ N05 10/212:475
`y,
`-
`.
`,
`(fl) Flled'
`Aug. 5’ 2002
`(51)
`Int. Cl.7 ................................................ F02D 41/00
`(52) US, Cl.
`________________________________________ 123/683; 123/687
`(58) Field of Search ................................. 123/683, 687,
`123/674, 672
`
`(56)
`
`References Cited
`
`U'S' PATENT DOCUMENTS
`4,143,623 A
`3/1979 Norimatsu et a1.
`4,163,433 A
`8/1979 Fujushiro
`4,202,301 A
`5/1980 Early et a1.
`4,263,652 A
`4/1981 l-lenrich
`
`ABSTRACT
`(57)
`AInethod and apparatus for externally modifying the opera-
`tion of a closed loop electronic fuel injection control system
`that is normally used with a standard oxygen sensor, which
`method and apparatus includes replacing the standard oxy-
`gen sensor with a Wide band oxygen sensor. The signal from
`the Wide band oxygen sensor is processed in a first signal-
`conditioning module and coupled to the input of the elec-
`tronic fuel
`injection control system. The first signal-
`conditioning module simulates the appearance of a standard
`oxygen sensor to the electronic fuel injection control system.
`In a second embodiment, a method and apparatus for exter—
`nauy modifying the operation of a closed loop electronic
`fuel injection control system that is normally used with a
`Wide band oxygen sensor, includes intercepting the signal
`from the Wide band oxygen sensor in a second signal—
`conditioning module. The second signal-conditioning mod-
`ule receives a first current from the Wide band oxygen sensor
`and provides a second current to the electronic fuel injection
`control system.
`
`19 Claims, 6 Drawing Sheets
`
`20
`
`13
`
`
`
`WIDE BAND SIGNAL
`ENGINE CONTROL UNIT
`
`CONDITIONING MODULE
`UTILIZING RICH-LEAN SIGNAL
`
`
`
`
`
`
`FUEL INJECTOR
`
`14
`
`WIDE BAND
`
`OXYGENNSENSOR
`
`12"
`INTAKE AIR
`
`E1B
`
`EXHAUST
`
`FORD Ex. 1028, page 1
`IPR2019-01400
`
`FORD Ex. 1028, page 1
` IPR2019-01400
`
`

`

`US. Patent
`
`Jan. 27, 2004
`
`Sheet 1 0f 6
`
`US 6,681,752 B1
`
`FIG.
`
`1
`
`20
`
`(PRIOR ART)
`ENGINE CONTROL UNIT
`
`FUEL INJECTOR
`14
`
`18
`
`EXHAUST
`
`UTILIZING RICH-LEAN SIGNAL OXYGEN SENSOR
`
`FIG.
`
`1A
`
`100A
`
`OXYGEN SENSOR VOLTAGE
`
`0.8 VOLTS - 1003 l
`0.5 VOLTS -
`
`0.2 VOLTS
`
`I I
`
`109A
`
`102
`
`FUEL FLOW
`
`1023
`A A A A
`“"Nl"
`""'
`“I"
`
`""
`
`
`
`15.0
`
`103
`
`AIR FUEL RATIO
`
`TIME
`
`FORD Ex. 1028, page 2
`IPR2019-01400
`
`FORD Ex. 1028, page 2
` IPR2019-01400
`
`

`

`US. Patent
`
`Jan. 27, 2004
`
`Sheet 2 0f 6
`
`US 6,681,752 B1
`
`I: [13.
`
`E?
`
`(PRIOR ART)
`
`22
`
`
`
`ENGINE CONTROL UNIT UTILIZING
`AIR-FUEL RATIO SIGNAL
`
`
`
`FUEL 11N4JECT0R
`OXYGENNSENSOR
`
`‘
`INTAIEE AIR
`EXHiAEUST
`L— '
`)
`j
`
`WIDE BAND
`
`
`
`10
`
`F211;.
`
`£54
`
`(PRIOR ART)
`
`RICH
`
`TARGET AIR FUEL RATIO
`
`
`
`FORD Ex. 1028, page 3
`IPR2019-01400
`
`FORD Ex. 1028, page 3
` IPR2019-01400
`
`

`

`US. Patent
`
`Jan. 27, 2004
`
`Sheet 3 0f 6
`
`US 6,681,752 B1
`
`FIG.
`
`5'
`
`13
`
`ENGINE CONTROL UNIT
`UTILIZING RICH-LEAN SIGNAL
`
`WIDE BAND SIGNAL
`CONDITIONING MODULE
`
`20
`
`
`
`
`
`OXYGENUSENSOR
`
`
`WIDE BAND
`
`E18
`
`EXHAUST
`
`FUEL INJECTOR
`14
`
`INTAKE AIR
`
`10
`
`
`
`FIG. 3A
`
`TARGET AIR FUEL RATIO
`
`WIDE BAND OXYGEN SENSOR CURRENT
`v v
`
`110
`
`”2
`
`14.7: 1
`(DNA)
`
`ENA-
`
`—2mA-
`
`
`
`OUTPUT 0F WIDE BAND SIGNAL CONDITIONING MODULE
`mm" “4“ — 114B— “4
`0.5 VOLTS
`0.2 VOLTS
`118A -
`
`143
`
`115
`
`A FUEL FLOW
`v
`
`I
`1153
`
`RESULTANT AIR-FUEL RATIO
`
`113
`
`TIME
`
`FORD Ex. 1028, page 4
`IPR2019-01400
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`FORD Ex. 1028, page 4
` IPR2019-01400
`
`

`

`US. Patent
`
`Jan. 27, 2004
`
`Sheet 4 0f 6
`
`US 6,681,752 B1
`
`FIG. 3B
`
`TARGET AIR FUEL RATIO
`
`14 7:1
`(OmA)
`
`14.7:1
`(OmA)
`12.8 1
`
`i
`:
`~.
`-----
`96$
`
`_ m
`..........
`. ......
`.
`.......
`-2InA
`,
`:
`\309
`5
`5
`
`OUTPUT 0F WIDE BAND SIGNAL CONDITIONING MODULE
`
`0.8 vans
`313 _ RICH
`0.5 VOLTS
`
`0.2 VOLTS
`
`
`
`3M
`
`EMA
`
`RESULTANT AIR-FUEL RATIO
`
`TIME
`
`FORD Ex. 1028, page 5
`IPR2019-01400
`
`FORD Ex. 1028, page 5
` IPR2019-01400
`
`

`

`US. Patent
`
`Jan. 27, 2004
`
`Sheet 5 0f 6
`
`US 6,681,752 B1
`
`FIG. 4
`
`22
`
`
`ENGINE CONTROL UNIT
`UTILIZING AIR-FUEL SIGNAL
`
`
`
`13A
`
`
`
`
`
`
`WIDE BAND SIGNAL
`CONDITIONING MODULE
`
`WIDE BAND
`OXYGEN SENSOR
`
`EXHAUST
`
`FORD Ex. 1028, page 6
`IPR2019-01400
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`FORD Ex. 1028, page 6
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`

`

`US. Patent
`
`1B2.h
`
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`
`FORD Ex. 1028, page 7
`IPR2019-01400
`
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` IPR2019-01400
`
`
`

`

`US 6,681,752 B1
`
`1
`FUEL INJECTION SYSTEM METHOD AND
`APPARATUS USING OXYGEN SENSOR
`SIGNAL CONDITIONING TO MODIFY AIR/
`FUEL RATIO
`
`FIELD OF THE INVENTION
`
`The present invention relates to control systems for con-
`trolling the air to fuel ratio in an internal combustion engine.
`BACKGROUND OF THE INVENTION
`
`1O
`
`2
`presence of excess oxygen in the exhaust gasses. For air/fuel
`mixtures richer than 14.7 the standard oxygen sensor outputs
`a value of about 0.8 volts indicating oxygen depletion in the
`exhaust gasses. In the region around stoichiometric,
`the
`transition between 0.2 and 0.8 volts is relatively abrupt. The
`standard oxygen sensor is also referred to as a rich/lean
`sensor.
`
`The signal output of the standard oxygen sensor is an
`input signal to the ECU. In closed loop mode, the signal
`from the standard oxygen sensor is used by the ECU to
`control the amount of fuel sent to the fuel injectors so as to
`maintain an air to fuel ratio of 14.7. Specifically, a threshold
`of 0.5 volts is established. When the oxygen sensor output
`falls below 0.5,
`the fuel
`flow to the fuel
`injectors is
`increased. When the oxygen sensor output rises above 0.5,
`the fuel flow to the fuel injectors is decreased. The air/fuel
`ratio moves above and below the stoichiometric value of
`14.7 as the signal from the standard oxygen sensor to the
`ECU fluctuates between 0.2 and 0.8 volts.
`
`Closed loop systems typically operate in open loop mode
`part of the time, where the signal from the standard oxygen
`sensor is not used. Open loop mode is needed when the
`operator demands more horsepower from the engine, such as
`would be needed for acceleration when passing another
`vehicle. In open loop mode, the ECU outputs fuel flow
`control signals in accordance with an internally stored fuel
`map, while ignoring the feedback signal from the standard
`oxygen sensor.
`The prior art technique of adding an external product to
`modify the fuel flow signal from the ECU is not effective in
`closed loop mode. When the external add-on product
`attempts to adjust
`the fuel flow to a value other than
`prescribed by the ECU, the ECU (which is still involved in
`fuel flow management and operating in closed loop mode)
`quickly readjusts its output in an attempt to fluctuate about
`a stoichiometric mixture. In other words, the add—on product
`and the ECU in closed loop mode conflict with each other.
`And as indicated above, the oxygen sensor output tran-
`sition around stoichiometric is abrupt. Furthermore,
`the
`characteristics of a standard oxygen sensor outside of its
`narrow stoichiometric range of operation are unstable.
`Although it is possible to intercept and condition the signal
`from a standard oxygen sensor, it is not a reliable way to
`adjust the air/fuel ratio to a value other than that prescribed
`by the ECU responsive to the standard oxygen sensor. The
`abrupt transition and unstable characteristics make it difii—
`cult to use the output of the standard oxygen sensor to
`achieve air/fuel ratios other than the stoichiometric value of
`14.7:1.
`
`SUMMARY OF THE INVENTION
`
`invention is embodied in a method and
`The present
`apparatus for externally modifying the operation of a closed
`loop electronic fuel injection control system to effectively
`modify the engine fuel delivery profile (effective engine fuel
`map) to enhance engine performance.
`the present
`In accordance with a first embodiment
`invention,
`the operation of a closed loop electronic fuel
`injection control system normally used with a standard
`oxygen sensor, is modified using an external apparatus to
`effectively modify the engine fuel delivery profile. The
`standard oxygen sensor is replaced with a wide band oxygen
`sensor that is capable of sensing exhaust gas properties as a
`measure of the actual air/fuel ratio of the intake combustion
`mixture over a broad range of air/fuel ratio values. The
`signal from the wide band oxygen sensor is intercepted,
`
`FORD Ex. 1028, page 8
`IPR2019-01400
`
`Internal combustion engines mix air and fuel in a pre-
`scribed ratio to facilitate combustion. Engine performance
`and economy is affected by the air/filel ratio. In particular, a
`stoichiometric air/fuel mixture achieves optimum fuel
`economy. For gasoline, a stoichiometric air/fuel mixture is
`14.7 parts air to 1 part fuel by weight. Air/fuel ratios richer
`than stoichiometric (e.g. less than 14.7:1) result in increased
`engine power output at the expense of fuel economy. Air to
`fuel ratios leaner than stoichiometric (e.g. greater than
`14.7:1) can lead to engine performance problems.
`Some internal combustion engines mix fuel and air in a
`carburetor using a spray nozzle to inject fuel droplets into an
`air stream passing into the engine cylinders. However,
`modern internal combustion engines use an electronic fuel
`injection system to replace the carburetor as a more accurate
`and reliable fuel delivery system.
`In an electronic fuel
`injection system, fuel and air are mixed in the engine intake
`manifold by spraying fuel droplets through a fuel injector
`directly into the air flow. An engine control unit (ECU)
`maintains the desired air to fuel ratio by controlling the
`amount of fuel injected by the fuel injectors. The ECU is
`operated either closed loop mode or open loop mode.
`Some prior art electronic fuel injection systems operated
`only in open loop mode. In open loop mode, air and fuel are
`delivered to the engine in accordance with a table of target
`air/fuel ratios internally stored in the ECU. The stored table,
`also known as a fuel map,
`is based on engine operating
`conditions such as throttle position, engine RPM (speed in
`revolutions per minute), engine temperature, air temperature
`and ambient air pressure. The fuel map determines the fuel
`delivery profile for the engine. It is known in the art that
`modifyng the fuel map can enhance engine performance
`and/or fuel economy.
`However, modifying the internally stored fuel map may
`require replacement of memory components in ECU, unless
`the ECU memory is electrically re-prograrnmable, which is
`not
`typical.
`It
`is known in the art
`to enhance engine
`performance by modifying the fuel flow signals provided by _
`
`the ECU to the fuel injectors. That is, the internal fuel map
`of the ECU is e ectively modified by externally intercepting
`
`
`and modifying 1e fuel flow control signals from the ECU to
`the fuel supply system. The net resulting engine fuel map is,
`in effect, a new fuel delivery profile for the engine,
`Some electronic fuel injection control systems operate in
`a closed loop mode in which the air/fuel ratio is directly
`sensed and used in an adaptive feedback control system. To
`sense the air/fuel ratio, a typical fuel
`injection system
`includes a standard oxygen (02) sensor placed in the exhaust
`flow of the engine. Unused (unburned) oxygen in the
`exhaust gasses indicates a leaner air/fuel mixture (i,e., too
`much oxygen for the amount of fuel). Lack of oxygen in the
`exhaust gases indicates a richer air/fuel mixture (i.e., not
`enough oxygen for the amount of fuel).
`For air/fuel mixtures leaner than 14.7, the standard oxy—
`gen sensor outputs a value of about 0.2 volts indicating the
`
`15
`
`30
`
`4O
`
`45
`
`60
`
`FORD Ex. 1028, page 8
` IPR2019-01400
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`

`

`US 6,681,752 B1
`
`3
`processed in a first signal-conditioning module and coupled
`to the input of a first type of ECU normally used with a
`standard oxygen sensor. The first
`type of ECU is pro-
`grammed to seek a stoichiometric target air/fuel ratio for
`each closed loop engine operating condition.
`For each engine operating condition (throttle position,
`RPM, etc.) the first signal—conditioning module determines
`a new target air/fuel ratio. When the signal from the wide
`band oxygen sensor indicates the new target air/fuel ratio,
`the first signal conditioning module outputs a signal simu-
`lating the output of a standard oxygen sensor at stoichio—
`metric air/fuel ratio to said first type of ECU normally used
`with a standard oxygen sensor. That is, at the new target
`air/fuel ratio, the first signal-conditioning module outputs a
`signal that moves between 0.2 and 0.8 volts, thereby simu-
`lating the output of a standard oxygen sensor, so that it
`appears to the first type of ECU as a standard oxygen sensor
`operating at a stoichiometric air/fuel ratio.
`In such manner, a new engine fuel delivery profile is
`provided by the first signal-conditioning module in a fuel
`injection control system having said first
`type of ECU
`normally used with a standard oxygen sensor.
`In accordance with a second embodiment of the present
`invention,
`the operation of a closed loop electronic fuel
`injection control system that normally utilizes a wide band
`oxygen sensor in conjunction with a second type of ECU, is
`modified using a second signal-conditioning module to
`effectively modify the engine fuel delivery profile (effective
`engine fuel map) to enhance engine performance. The signal
`from the wide band oxygen sensor is intercepted and pro-
`cessed in said second signal-conditioning module. The out-
`put of the second signal-conditioning module is coupled to
`the input of said second type of ECU normally used to
`receive signals from a Wide band oxygen sensor.
`For each engine operating condition (throttle position,
`RPM, etc.), the second type of ECU has a programmed
`target air/fuel ratio in its internally stored fuel map. For each
`of those same engine operating conditions (throttle position,
`RPM, etc.), the second signal-conditioning module stores a
`corresponding new target air/fuel ratio. The second signal
`conditioning module determines when the signal from the
`wide band oxygen sensor represents the new target air/fuel
`ratio, and substitutes a signal representing the originally
`programmed target air/fuel ratio value as an input signal to
`the second type of ECU. That is, at the new target air/fuel
`ratio, the second signal-conditioning module outputs a cur-
`rent signal that simulates the output of a wide band oxygen
`sensor operating at the originally programmed target air/fuel
`ratio. Thus, the second signal—conditioning module appears
`to the second type of ECU as a wide band oxygen sensor
`operating at the originally programmed target air/fuel ratio.
`In such manner, a new engine fuel delivery profile is
`provided by the second signal conditioning module in a fuel
`injection control system having said second type of ECU
`normally used with a wide band oxygen sensor.
`BRIEF DESCRlP’l‘lON OF THE DRAWING
`
`MG. 1 is a block diagram of a closed loop fuel injection
`control system using a standard oxygen sensor in accordance
`with the prior art.
`FIG. 1A is a timing diagram illustrating the operation of
`the fuel injection control system of FIG. 1 using a standard
`oxygen sensor in accordance with the prior art.
`FIG. 2 is a block diagram of a closed loop fuel injection
`control system using a wide band oxygen sensor in accor—
`dance with the prior art.
`
`5
`
`10
`
`15
`
`30
`
`40
`
`45
`
`60
`
`4
`FIG. 2A is a timing diagram illustrating the operation of
`the fuel injection control system of FIG. 2 using a wide band
`oxygen sensor in accordance with the prior art.
`FIG. 3 is a block diagram of a closed loop fuel injection
`control system in accordance with the present invention.
`FIGS. 3A and 3B are timing diagrams illustrating the
`operation of the fuel injection control system of FIG. 3 in
`accordance with the present invention.
`FIG. 4 is a block diagram of a closed loop fuel injection
`control system in accordance with a second embodiment of
`the present invention.
`FIG. 4A is a timing diagram illustrating the operation of
`the fuel injection control system of FIG. 4 in accordance
`with the present invention.
`FIG. 5 is a schematic diagram, partially in block form, of
`a wide band signal-conditioning circuit embodying the
`present invention.
`DETAILED DESCRIPTION
`
`A typical closed loop fuel injection system using a stan—
`dard oxygen sensor is shown in FIG. 1. The overall system
`includes an internal combustion engine 10 having an intake
`air channel 12 and an exhaust channel 18, a standard oxygen
`sensor 16, a fuel injector 14 and an electronic control unit
`20. Under control of the ECU 20, the fuel injector 14 sprays
`fuel droplets to mix with the intake air 12. The standard
`oxygen sensor 16 is placed in the exhaust channel 18 in the
`path of the engine exhaust gasses.
`In normal operation, the standard oxygen sensor 16 pro-
`vides ECU 20 with an indication of the presence of oxygen
`in the exhaust gasses, which provides information about the
`intake gas mixture entering the engine. If oxygen is present
`the output of sensor 16,
`the output
`is 0.2 volts. As the
`concentration of oxygen approaches zero, the output voltage
`jumps to 0.8 volts. Thus, a typical standard oxygen sensor
`outputs 0.8 volts when the intake air/fuel ratio is rich (less
`than 14.7) and outputs 0.2 volts when the intake air/fuel ratio
`is lean (greater than 14.7). The characteristics of the standard
`oxygen sensor (having a rich/lean signal output) is not stable
`is enough to be used to control the air/fuel ratio at a steady
`14.7: 1. Instead, the standard oxygen sensor is used primarily
`as an indicator of whether the intake mixture is too rich or
`too lean, relative to stoichiometric.
`As illustrated in the timing diagram of FIG. 1A, ECU 20
`increases fuel flow through the fuel injectors 14 until the
`standard oxygen sensor voltage output 100 rises above the
`0.5 volts axis 100A. After the standard oxygen sensor output
`voltage 100 is above the 0.5 volt axis for a prescribed length
`of time, the ECU 20 begins to decrease 102A the fuel flow
`through the fuel
`injectors. The fuel
`flow continues to
`decrease until the standard oxygen sensor output voltage 100
`drops below the 0.5 volts axis 100B. After the standard
`oxygen sensor voltage output 100 is below the 0.5 volt axis
`for a prescribed length of time,
`the ECU 20 begins to
`increase 102B the fuel flow through the fuel injectors. The
`result is that the standard oxygen sensor output voltage 100
`moves back and forth between 0.8 volts and 0.2 volts
`representing a too rich or too lean intake mixture, respec-
`tively.
`The air/fuel mixture does not stabilize at 14.721 precisely.
`Instead the air/fuel continually switches between rich and
`lean on each side of 14.721. The sawtooth shape of the
`resultant air/fuel ratio graph 103 is a result of the ECU 20
`“hunting” to establish a stoichiometric intake air/fuel ratio.
`Wide Band Oxygen Sensor
`A typical closed loop fuel injection system using a wide
`band oxygen sensor is shown in FIG. 2. The overall system
`
`FORD Ex. 1028, page 9
`IPR2019-01400
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`FORD Ex. 1028, page 9
` IPR2019-01400
`
`

`

`includes an internal combustion engine 10 having an intake
`air channel 12 and an exhaust channel 18, a wide band
`oxygen sensor 17, a fuel injector I4 and an electronic control
`unit 22. Under control of the ECU 22, the fuel injector 14
`sprays fuel droplets to mix with the intake air 12. The Wide
`band oxygen sensor 17 is placed in the exhaust channel 18,
`in the path of the engine exhaust gasses.
`Awide band oxygen sensor 17 senses the presence of fuel
`as well as oxygen in the exhaust gasses. That is, the wide
`band oxygen sensor 17 is capable of measuring the quantity
`of unburned fuel or unused oxygen present in the exhaust
`gasses 18. If oxygen is present in the exhaust gasses 18, the
`sensor 17 output current is positive and proportional to the
`concentration of oxygen. If unburned fuel is present in the
`exhaust gasses 18 the sensor 17 output current is negative
`and proportional to the unburned fuel concentration. If there
`is no oxygen or unburned fuel in the exhaust 18, the sensor
`17 output current is zero, which implies that the engine
`intake air/fuel ratio is at the stoichiometric (14.7: 1) ratio.
`A wide band oxygen sensor permits a fuel
`injection
`control system to provide a range of closed loop operations
`(other than stoichiometric) that include best power settings
`for various conditions, such as passing or cruising, as well
`as for optimum fuel economy or optimum emission control
`settings. The wide band oxygen sensor 17 allows the ECU
`22 to control fuel flow to a specific programmed target
`air/fuel ratio rather than to fluctuate above and below a
`stoichiometric air/fuel
`ratio determined by the inherent
`characteristic of a standard oxygen sensor of (16 in FIG. 1).
`A closed loop fuel injection system using a wide band
`oxygen sensor as in FIG. 2 operates difierently as compared
`to a closed loop fuel injection system using a standard
`oxygen sensor as in FIG. 1. In the case of a standard oxygen
`sensor in FIG. 1, a stoichiometric air/fuel ratio is achieved
`by increasing (or decreasing) fuel flow to the fuel injectors
`until the standard oxygen sensor switches output. Thus, with
`a standard oxygen sensor in FIG. 1 there is a “hunting” about
`a stoichiometric air/fuel ratio. In the case of a wide band
`oxygen sensor in FIG. 2,
`target air/fuel ratios from the
`internally stored fuel map are achieved by increasing (or
`decreasing) fuel flow to the fuel injectors until the pro-
`grammed target air/fuel ratio is sensed by the wide band
`oxygen sensor 17. A closed loop fuel
`injection control
`system (as in FIG. 2) operates in accordance with feedback
`control system principles to achieve rapid and stable con-
`vergence Without hunting about
`the programmed target
`air/fuel ratio.
`FIG. 2A illustrates the operation of a closed loop fuel
`injection system using a wide band oxygen sensor. As shown _
`in FIG. 2A, the ECU 22 responsive to its internal fuel map
`attempts to adjust the air/fuel ration to a desired target
`air/fuel ratio 104. In particular, the target air/fuel ratio 104
`goes from a stoichiometric mixture of 14.7:1 to a richer
`mixture of 12.821. The ECU 22 gradually increases fuel
`flow. As a result, the current output 106 of the wide band
`oxygen sensor goes from 0 to —1 milliamperes. The transi-
`tion between Wide band oxygen sensor current output levels
`106 is gradual rather than abrupt, as is the transition of the
`air/fuel ratio 108 as it goes from stoichiometric 14.7:1 to a
`richer 1281.
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`FIG. 3 illustrates the use of a wide band signal-
`conditioning module 13 for externally modifying the opera-
`tion of a closed loop electronic fuel injection control system
`having an ECU 20 that normally receives the rich/Iean signal
`from a standard oxygen sensor. The overall system includes
`an internal combustion engine 10 having an intake air
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`3
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`US 6,681,752 B1
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`6
`channel 12 and an exhaust channel 18, a fuel injector 14 and
`an electronic control unit 20.
`
`The unmodified system of FIG. 1 uses a standard oxygen
`sensor 16. In accordance with the present invention, a wide
`band oxygen sensor 17 in FIG. 2 replaces the standard
`oxygen sensor 16 of FIG. 1 in the exhaust channel 18. In
`addition, the signal from the wide band oxygen sensor 17 is
`processed in a wide band signal conditioning module 13.
`The output of the wide and signal conditioning module 13 is
`coupled to ECU 20.
`FIG. 3A illustrates the operation of the system of FIG. 3
`to achieve the (stoichiometric) target air/fuel ratio 110. The
`output of the wide band signal conditioning module 114 is
`either at 0.2 volts or at 0.8 volts. In such manner, the wide
`band signal conditioning module 13 simulates the output of
`a standard oxygen sensor to the ECU 20.
`As illustrated in the timing diagram of FIG, 3A, ECU 20
`increases fuel flow through the fuel injectors 14 until the
`Wide band oxygen sensor voltage output 114 rises above the
`0.5 volts axis 114A. After the wide band oxygen sensor
`output voltage 114 is above the 0.5 volt axis for a prescribed
`length of time, the ECU 20 begins to decrease the fuel flow
`116A through the fuel injectors. The fuel flow continues to
`decrease until the wide band oxygen sensor output voltage
`114 drops below the 0.5 volts axis 114B. After the Wide band
`oxygen sensor voltage output 114 is below the 0.5 volt axis
`for a prescribed length of time,
`the ECU 20 begins to
`increase the fuel flow 116B through the fuel injectors.
`The result is that the fuel flow to the fuel injectors is
`increased and decreased about an average value of fuel flow
`representing the amount of fuel necessary to achieve a
`stoichiometric air/fuel ratio. The air/fuel mixture does not
`stabilize at 14.7:1 precisely. Instead, the air/fuel ratio con-
`tinually switches between rich and lean on either side of
`14.7:1. The sawtooth shape of the air/fuel ratio graph 118 is
`a result of the ECU 20 “hunting” to establish a stoichiomet—
`ric intake air/fuel ratio. At the stoichiometric target value
`110, the output 112 of the wide band oxygen sensor varies
`slightly above and below (i.e., hunts about) the axis repre-
`senting zero output current.
`The wide band signal conditioning module appears to the
`ECU 20 to be a standard oxygen sensor. The wide band
`signal conditioning module output voltage 114 moves back
`and forth between 0.8 volts and 0.2 volts signaling a too rich
`or too lean intake mixture to the ECU 20. At the same time,
`the output 112 of the wide band oxygen sensor varies
`slightly above and below the axis representing a stoichio-
`metric air/fuel ratio (zero output current).
`FIG. 3B shows what happens when the target air/fuel ratio
`303 is changed to a new target air/fuel ratio. In particular, the
`stoichiometric value 304 of the new target air/fuel ratio
`changes to a different value 306 for the new target air/fuel
`ratio. In response, the wide band signal conditioning module
`13 (FIG. 3) signals the ECU 20 that the air/fuel mixture is
`lean 310A. In response, ECU 20 increases 314A the fuel
`flow to the fuel injectors. ECU 20 continues to increase the
`fuel flow to the fuel injectors until the output of the wide
`band signal conditioning module 13 indicates that the air/
`fuel mixture is rich 313.
`
`In response, ECU 20 decreases the fuel flow to the fuel
`injectors until the output of the wide band signal condition-
`ing module 13 indicates that the air/fuel mixture is lean 315.
`The new fuel flow level 316 is generally higher than the
`prior fuel flow level 314. As a result, the new air/fuel ratio
`320 is generally lower than the prior air/fuel ratio 318. In
`such manner, the air/fuel ratio is set at a richer (12.8) level.
`
`FORD Ex. 1028, page 10
`IPR2019-01400
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`FORD Ex. 1028, page 10
` IPR2019-01400
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`US 6,681,752 B1
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`7
`At the stoichiometric value 304, the output of the wide
`band oxygen sensor varies slightly above and below (i.e.,
`hunts about) the axis 307 representing zero output current.
`In comparison, at the new target air/fuel ratio 306, the output
`308 of the wide band oxygen sensor varies slightly above
`and below (i.e., hunts about) the axis 309 representing minus
`1 milliampere output current (corresponding to an air/fuel
`ratio of 12.8).
`Although the new target air/fuel ratio of 12.8 has been
`achieved, the ECU 20 receives output signals from the wide
`band signal conditioning module 13 representing an air/fuel
`ratio of 14.7 (stoichiometric) of a standard oxygen sensor.
`The wide band signal conditioning module 13 tricks the
`ECU 20 into achieving a richer air/fuel ratio by appearing to
`be a standard oxygen sensor operating at a stoichiometric
`air/fuel ratio value.
`FIG. 4 illustrates the use of a wide band signal-
`conditioning module 13A for externally modifying the
`operation of a closed loop electronic fuel injection control
`system having an ECU 22 that normally receives the output
`current of a wide band oxygen sensor. The overall system
`includes an internal combustion engine 10 having an intake
`air channel 12 and an exhaust channel 18, a fuel injector 14
`and an electronic control unit 22.
`
`An unmodified system (FIG. 2) uses a wide band oxygen
`sensor 17 coupled to an ECU 22 of the type that is normally
`connected to a wide band oxygen sensor 17. In accordance
`with the present invention, the signal from the wide band
`oxygen sensor 17 is disconnected from ECU 22 and pro-
`cessed in a wide band signal conditioning module 13A (FIG.
`4). The output of the wide and signal conditioning module
`13A is coupled to ECU 22.
`The timing diagram of FIG. 4A illustrates the operation of
`the fuel injection control system of MG. 4 for two cases:
`normal and modified. For normal (unmodified) operation,
`the wide band signal conditioning module 13A is absent.
`Waveforms depicted as a solid line, 404, 406, 408, 410, 412,
`414, 418, 420 pertain to normal unmodified operation.
`Waveforms shown as dotted lines, 407, 416, 422 pertain to
`modified operation, For modified operation, the connection
`between the wide band oxygen sensor 17 and ECU 22 (FIG.
`2) is broken, and the wide band signal conditioning module
`13A (FIG. 4) is inserted between the wide band oxygen
`sensor 17 and the ECU 22.
`
`In normal operation, without wide band signal condition-
`ing module 13A present, the target air/fuel ratio goes from
`a first level 404 representing a first engine operating condi-
`tion to a second level 406 representing a second engine
`operating condition. In response, ECU 22 increases the fuel
`flow to the fuel injectors lowering the air/fuel ratio from a
`first level 418 to a second level 420. At the same time, the
`oxygen sensor current goes down from a first level 412 to a
`second level 414. The wide band signal conditioning module
`13A not being present, the oxygen sensor current output 414
`is equal to the ECU 22 oxygen sensor current input current
`410.
`
`In accordance with the present invention, the insertion of
`the wide band signal conditioning module 13A modifies the
`fuel delivery profile for the engine. In particular, for the
`second level 406 of target air/fuel ratio, the presence of the
`wide band signal conditioning module 13A causes a new
`target air/fuel ratio 407 to be achieved. In order to achieve
`a new target air/fuel ratio 407,
`the signal conditioning
`module 13A amplifies the current from the wide band
`oxygen sensor by a multiplication factor (percentage
`increase or decrease) determined by the ratio between the
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`original target fuel map and the desired modified fuel map.
`The wide band oxygen sensor current level is multiplied in
`the signal conditioning module 13A by the above multipli-
`cation factor to become a more negative value 416.
`The ECU 22 is deceived because it receives a modified
`oxygen sensor current output level from the wide band
`signal conditioning module 13A in lieu of the actual oxygen
`sensor current level. Although the ECU 22 thinks the air/fuel
`ratio is at a level according to its internal programming, the
`actual resulting air/fuel ratio 422 is lower, representing a
`richer air/fuel mixture. A new target air/fuel ratio 407 has
`been achieved, while the ECU 22 receives output signals
`from the wide band signal conditioning module 13A repre-
`senting the originally programmed target air/fuel ratio. The
`Wide band signal conditioning module 13A tricks the ECU
`22 into achieving a new target air/fuel ratio by appearing to
`be a Wide band oxygen sensor operating at the originally
`programmed air/fuel ratio value.
`The block diagram of FIG. 5 represents a preferred
`embodiment of a wide band signal conditioning module 13
`in MG. 3. Wide band signal conditioning module is used in
`conjunction with a first type of ECU (20 from FIG. 3) that
`normally utilizes an air/fuel ratio signal from a standard
`oxygen sensor. The wide band signal—conditioning module
`13 comprises sensor control circuitry 434, a resistor network
`R2, R3, a micro—controller