United States Patent
`
`[19]
`
`[11] Patent Number:
`
`4,845,630
`
`Stephens
`
`[45] Date of Patent:
`
`Jul. 4, 1989
`
`[54]
`
`METHOD AND APPARATUS FOR
`CALCULATING CORRECTED VEHICLE
`FUEL ECONOMY
`
`[75]
`
`Inventor: Donald L. Stephens, La Conner,
`Wash.
`
`[73]
`
`Assignee:
`
`Paccar Inc., Bellevue, Wash.
`
`[21]
`
`Appl. No.: 29,271
`
`[22]
`
`[51]
`[52]
`
`[5 8]
`
`[56]
`
`Filed:
`
`Mar. 23, 1987
`
`Int. Cl.4 ................................................ G01F 9/00
`US. Cl. ...................................... 364/442; 73/113;
`73/1 14
`Field of Search .............. 73/112, 113, 114, 117.3;
`364/442, 565, 424; 340/52 R
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`a
`
`8/1926 Brown .
`1,595,960
`3,153,143 10/1964 Fogarty .
`3,686,935
`8/1972 May ....................................... 73/112
`9/1975 Walker et a1.
`......... 73/114
`3,908,451
`
`9/1977 Harvey .........
`.. 364/442 X
`4,050,295
`
`4,113,046 9/1978 Arpino ......
`180/105 E
`...... 73/117.3
`4,129,034 12/1978 Niles et a1.
`
`4,173,887 11/1979 Fiala ................... 73/114
`
`.. 340/754
`4,210,908
`7/1980 Sakakibara
`1/1981 Crump, Jr. ........... 235/615
`4,247,757
`
`..... 340/52 F
`4,354,173 10/1982 Kuhn et a1.
`..... 73/112 X
`4,475,380 10/1984 Colovas et a1.
`
`4,564,905
`1/1986 Masada et al.
`364/442 X
`
`4,570,226 2/ 1986 Aussedat .................. 364/442
`.................. 340/52 R
`4,647,902 3/ 1987 Teshima et a1.
`
`FOREIGN PATENT DOCUMENTS
`
`.
`
`8927 3/ 1980 European Pat. Off.
`W083/01686 5/1983 PCT Int’l Appl.
`.
`894760 12/1981 U.S.S.R.
`.
`1472991
`5/1977 United Kingdom .
`2015739A 9/1979 United Kingdom .
`2052744A 1/ 1981 United Kingdom .
`2127545A 4/ 1984 United Kingdom .
`2150295A 6/1985 United Kingdom .
`
`Primary Examiner—Gary Chin
`Attorney, Agent, or Firm—Seed and Berry
`
`[57]
`
`ABSTRACT
`
`A method and apparatus for calculating a corrected fuel
`economy rate. A fuel-consuming engine that propels a
`ground vehicle has at least one fuel rate sensor for mea-
`suring the fuel consumption rate of the engine. The
`apparatus further comprises a sensor for measuring the
`distance travelled by the ground vehicle. Digital count-
`ers accumulate pulse counts from the sensors and the
`pulse counts are processed by a microprocessor to cal-
`culate the distance travelled by the ground vehicle, the
`fuel consumed by the engine, and the change of the
`kinetic energy of the vehicle. The microprocessor then
`corrects the fuel consumed by subtracting the weighted
`change of the kinetic energy of the vehicle over the
`sampling period. Themicroprocessor then calculates
`the ratio of the distance travelled to the corrected fuel
`consumed to produce a corrected fuel economy rate, or
`its reciprocal. The ratio can be displayed on a digital
`display.
`
`32 Claims, 4 Drawing Sheets
`
`APPLE 1021
`
` 1
`
`APPLE 1021
`
`1
`
`

`

`US. Patent
`
`Jul. 4, 1989
`
`Sheet 1 of 4
`
`4,845,630
`
`E\\_____._______
`
`mzHfifimE
`
`
`
`mHmmEaE
`
`a:
`
`szsmmE
`
`Emma»:
`
`32
`
`__
`
`—.
`
`.J.53
`"'-Em:
`--gamma
`
`2
`
`
`
`
`

`

`US. Patent
`
`Jul. 4, 1989
`
`Sheet 2 of4
`
`4,845,630
`
`SET VEHICLE PARAMETERS
` 100
`
`RAXLE=X.XXX ; 313mm,)“;
`GPHZRO=X.XX:NTEEHT:XX:
`PPGAL:XXXXX ; Husm=x.xx:
`KEm=X.XXXE-08;scv=xxxxx_
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`SET SAMPLE PERTH] A
`TIMBER 0F SAMPLES
`
`VCLOCK : X.XXX
`KEUNT : XX
`
`102
`
`FIG. 2A
`
`
`
`104
`
`CALCUATE EUEFFICIENTS
`
`
` mm : mama/12)
`5230 x RAXLE . NTEETH
`
`
`_ FLDSCN
`KFUEL . PPSAL
`
`_
`KEGH a= ecu
`
`KEG ‘
`32.174
`
`
`
`
`
`INITIALIZE FUEL s. DISTANCE sums
`PUB. (I) = BPHZRU ”MIX/.1500.
`DIST(1)=U
`I:I-l
`
`
`
`
`
`“18
`
`
`
`3
`
`

`

`US. Patent
`
`Jul. 4, 1989
`
`Sheet 3 of4
`
`4,845,630
`
`112
`
`115
`
` RESET FLAG: CALClLATE FUEL
`81 DISTANCE INCREMENTS
`IFLAG : 0
`DELGA : KFUB. * FCOUNTS
`DELHI : K030 * VCflJNTS
`
`
`
`
`
`
` J:KC(lJNTS+l
`
`
`" FIG. 2B
`
`PUSH UP FUEL & DISTANCE STACKS
`
`FUEL (J) '= FUEL (J—l)
`DIST (J) = DIST (H)
`J _= H
`
`_
`
`
`
`122
`
`
`
`
`
`
`
`
`UPDATE TOTAL FUEL & DISTANCE
`HJEL(1):HJB.(I)+DELGA
`UIST(1):DIST(1)+DE.HI
`
`‘25
`
`4
`
`

`

`US. Patent
`
`Jul. 4, 1989
`
`Sheet 4 of4
`
`4,845,630
`
`CALClLATE HEIDI-[TED FUEL USED
`DURING LAST INTERVAL AND
`HEIGHTS) DISTANCE TRAVELED A
`SPEED [AJRING LAST IND INTERVALS
`
`128
`
`FIG 2C
`‘
`
`HFUEL :(FUE1.(1)- FUEL (KCWNT)
`NDISTI : (DISTH) ~ DIST (KCIlJNT)
`HSPEDI : HDISTI / VCLDCK
`HDISTZ : (DIST(2) - DISTIKCDJNT +1)
`ISPEDZ : HDIST2 / VCLDCK
`
`HFUEL - KEG * (HSPEDT ** 2 - HSPED2 1:: 2 )
`
`)lKEDUNT
`)/KCDLNT
`
`)
`
`/KCDUNT
`
`CALELLATE [DHREETED NPG
`
`— I30
`
`mean = ____!DIL____
`
`5
`
`

`

`1
`
`4,845,630
`
`METHOD AND APPARATUS FOR CALCULATING
`CORRECTED VEHICLE FUEL ECONOMY
`
`TECHNICAL FIELD
`
`This invention relates generally to a method and
`apparatus for calculating the fuel economy of a vehicle
`and more particularly to a method and apparatus for
`calculating a fuel economy which is corrected for
`changes in the kinetic energy of the vehicle.
`BACKGROUND OF THE INVENTION
`
`Fuel economy is of great concern among operators of
`fleets of vehicles, particularly trucks used for hauling
`loads over a wide range of speeds on highways. The
`truck driver interested in maximizing fuel economy can
`be particularly aided by a continual display of the cur-
`rent fuel economy of the truck. The truck driver can use
`this information to develop and maintain driving habits
`which maximize fuel economy.
`It has been known to use the manifold vacuum of an
`internal combustion engine propelling a vehicle to serve
`as an indicator of the fuel economy being achieved by
`that vehicle. Manifold vacuum is, however, a highly
`erratic variable and is dependent upon outside condi-
`tions such as atmospheric pressure. For these reasons,
`manifold vacuum does not provide an accurate or stable
`reading, greatly reducing its value as an indicator of
`engine fuel economy.
`'
`It has also long been known in the art to measure the
`engine fuel consumption rate and speed of the vehicle to
`calculate an instantaneous measure of fuel economy.
`These instantaneous measures of fuel economy are also
`highly erratic, but can be smoothed by means of elec-
`tronic signal processing to produce a more stable and
`usable measure of fuel economy.
`In US. Pat. No. 4,354,173, issued to Kuhn et a1., an
`apparatus for indicating the fuel economy of a motor
`vehicle includes sensors for detecting engine speed,
`distances travelled by the vehicle, and the engine throt-
`tle. In addition, an accelerometer is coupled to the dis-
`tance sensor to determine the vehicle acceleration. The
`signals from these sensors are combined to produce a
`signal indicative of the fuel economy of the vehicle and
`useful to alert the vehicle operator when, for example,
`the vehicle’s transmission should be shifted.
`,
`In US. Pat. No. 4,113,046, Arpino discloses of a
`method and an apparatus for indicating the fuel econ-
`omy of a vehicle during acceleration. The apparatus
`uses a throttle rate signal in combination with an accel-
`eration signal to generate an efficiency signal. This
`efficiency signal drives an indicator to show whether
`the vehicle is accelerating efficiently. The efficiency
`signal can also be used in a vehicle speed control device
`to automatically control the acceleration of the vehicle.
`The prior art does not disclose a fuel economy mea-
`surement system which accounts for changes in the fuel
`economy that are due to changes in the vehicle’s kinetic
`energy as the vehicle acelerates or decelerates. There-
`fore, fuel economy indication systems that do not ac-
`count for changes in the kinetic energy produce mis-
`leading signals whose behavior can be annoying to a
`driver who is attempting to maximize fuel economy.
`The present invention provides an apparatus for cor-
`recting fuel economy measurements to account for
`changes in the kinetic energy og the vehicle. This appa-
`ratus is extremely simple and does not require sensors to
`
`2
`measure throttle position, rate of change of throttle
`position, or vehicle acceleration.
`DISCLOSURE OF THE INVENTION
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`The primary object of the invention is to provide a
`method and apparatus for calaulating a fuel economy
`measurement which is corrected for changes in the fuel
`consumption due to changes in the kinetic energy of the
`vehicle as the vehicle is accelerated or decelerated.
`
`It is another object of the invention to provide a fuel
`economy measurement apparatus that calculates a fuel
`economy measurement that is a closer approximation to
`the true fuel economy of the vehicle.
`It is still another object of the invention to provide a
`system that can display a fuel economy measurement
`that varies smoothly with accelerations and decelera-
`tions of the vehicle.
`
`In general, the method of the present invention mea-
`sures intervals of time, intervals of the distance trav-
`elled by the vehicle, and the fuel consumed by the vehi-
`cle’s engine in an interval of time or distance. The
`method further comprises the steps of calculating a
`corrected fuel consumption of the engine over an inter-
`val of time or distance by subtracting a weighted differ-
`ence of the kinetic energy of the vehicle at the end and
`the beginning of the interval of time or distance from
`the measured fuel consumption over the interval of time
`or distance. The method further cpmprises calculating a
`ratio of the distance travelled by the vehicle over the
`interval of time or distance to the corrected fuel con-
`
`sumption.
`Since both fuel consumption (fuel used/distance trav-
`eled) and fuel economy (distance traveled/fuel used)
`are commonly used, and since these measures are recip-
`rocally related, it can br seen that this invention applies
`to both.
`
`The fuel economy measurement apparatus of the
`present invention comprises means for measuring inter-
`vals of time, means for measuring intervals of distance
`travelled by the ground vehicle, and means for measur—
`ing the fuel consumed by the engine in an interval of
`time or distance. The apparatus further comprises
`means for calculating a corrected fuel economy of the
`engine over the interval of time or distance by subtract-
`ing a weighted difference of the kinetic energy of the
`ground vehicle at the end and the beginning of the
`interval of time or distance from the measured fuel
`
`consumption over the interval of time or distance and
`for further calculating a ratio of the distance travelled
`by the ground vehicle over the interval of time or dis-
`tance to the corrected fuel consu,ption, or its reciprocal.
`The means for calculating can be a microprocessor that
`is connected to a random access memory (RAM) and a
`read-only memory (ROM), such as an electrically pro-
`grammable ROM (EPROM). In further embodiments,
`the present invention can further comprise a display
`device to present the corrected fuel economy rate to the
`truck driver.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`65
`
`FIG. 1 is a schematic diagram of a preferred embodi-
`ment of the apparatus of the present invention.
`FIGS. 2A—2C are a block diagram of a computer
`program that operates with the apparatus shown in
`FIG. 1.
`
`6
`
`

`

`3
`
`4,845,630
`
`BEST MODES FOR CARRYING OUT THE
`INVENTION
`
`One embodiment of the apparatus of the present in-
`vention is shown in FIG. 1. Corrected fuel economy
`apparatus 10 comprises fuel consumption sensors 12 and
`14, incremental distance sensor 16, and circuitry 18.
`Fuel consumption sensors 12 and 14 are connected to
`the fuel system 20 of the engine propelling the vehicle
`and incremental distance sensor 16 is attached at a point
`on the vehicle where it can measure rotations of one of
`the vehicle’s wheels. It is convenient to attach incre-
`mental distance sensor 16 to an axle driveshaft or trans-
`mission output shaft of the vehicle.
`Fuel system 20 is schematically shown to be the injec-
`tion system of a six cylinder diesel engine intended for
`use in heavy-duty trucks. Such an engine is built by the
`Caterpillar Co. The fuel system comprises a fuel supply
`circuit 22 that receives fuel under pressure from a fuel
`pump (not shown) that is connected to the vehicle’s fuel
`tank (not shown). The fuel supply circuit is connected
`to fuel injectors 24 and returns the fuel to the fuel sup-
`ply system. The directions of fuel flow in the fuel supply
`circuit are shown by arrows.
`Fuel consumption sensors 12 and 14 are connected
`into fuel supply circuit 22 in order to measure the rate at
`which fuel is supplied to and returned from the the fuel
`supply circuit, respectively. The fuel consumption sen-
`sors can be FloScan fuel sensors that produce a pulsed
`signal in accordance with the volume of fuel passing
`through the sensor. The frequency of the pulses pro-
`duced by the fuel consumption sensors is proportional
`to the rate at which the fuel is flowing through the
`sensors. For the application shown in FIG. 1, the fuel
`consumption sensors are chosen to produce approxi-
`mately 48,000 pulses per gallon of fuel.
`Approximately one-fourth to one-third of the fuel
`passing through fuel consumption sensor 12 does not
`return to pass through fuel consumption sensor 14. The
`amount of fuel being supplied to the engine is propor-
`tional
`to the difference between the frequencies of
`pulses produced by the two fuel consumption sensors.
`In another diesel engine application, such as a Cum-
`mins engine, where a more nearly constant fraction of
`the fuel supplied to the fuel supply circuit is injected, an
`accurate measure of the fuel consumed by the engine
`can be obtained by monitoring the frequency produced
`by fuel consumption sensor 12. Accordingly, fuel con-
`sumption sensor 14 can be dispensed with in such appli-
`cations, and the fuel returning from the fuel supply
`circuit can be returned to the fuel supply system along
`the “return ” line. If only fuel consumption sensor 12 is
`to be used, the flow sensor can be chosen to produce
`fewer (e.g., 19200) pulses per gallon of fuel. At typical
`idle fuel delivery rates, this single flow sensor will pro-
`duce approximately 40 pulses per second.
`In other diesel applications, such as electronically
`controlled injection engines, the engine electronic con-
`troller can supply a signal that measures fuel flow.
`In still other internal-combustion engine applications,
`such as a spark-ignited engine, the fuel consumed by the
`engine can be determined by the fuel flow to the fuel
`system, such as a carburetor.
`Incremental distance sensor 16, being attached to
`measure the rotations of a wheel of the vehicle, can
`comprise a toothed wheel 28 and a magnetic sensor 30
`for producing a pulse each time a tooth of the toothed
`wheel passes the magnetic sensor.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`3O
`
`35
`
`4O
`
`45
`
`50
`
`55
`
`65
`
`4
`Circuitry 18 contains signal processing circuitry, a
`circuit for counting the pulses produced by the fuel
`consumption and incremental distance sensors, a micro-
`processor for performing the required calculations, and
`memory and a clock to serve the microprocessor. Sig-
`nal conditioning circuits 32—36 receive the pulsed sig-
`nals produced by sensors 12—16, respectively, and pro-
`duce pulsed signals at the same respective frequencies.
`These pulsed signals are sent to a programmable timer/-
`counter 38 which, under the control of microprocessor
`40, accumulates pulse counts. The programmable ti-
`mer/counter can, for example, be an Intel 8254, which
`contains three identical 16‘bit timer/counters 42—46.
`Each counter can count, independently of the others,
`from O to 65535. Counters 42—46 are operated to accu-
`mulate the count of pulses respectively received from
`signal consitioning circuits 32-36. When microproces-
`sor 40, which can be an Intel 8031, attempts to read the
`contents of one of the counters, the signal on the chip
`select line 48 is set to a logic “0” and an appropriate
`address is sent over address lines 50 to read/write logic
`52. When it desires to read the designated counter, the
`microprocessor sets read line 54 to a logic “0” state,
`thereby sending a signal to control word register 56.
`Signals from the control word register cause the
`counter designated by address lines 56 to load its cur-
`rent count into a special register. This count data is then
`transferred via internal bus 58 to data bus buffer 60, and
`then to the microprocessor over 8-bit data bus 62. The
`16-bit count read from the designated counter must be
`transferred to the microprocessor in two 8-bit bytes.
`Microprocessor 40 is also connected to a read-only
`memory (ROM) 64, a clock 66, and a random access
`memory (RAM) 68. ROM 64 can be, for example, an
`electrically programmable ROM (EPROM). The ROM
`contains the program for controlling the microproces-
`sor and the RAM is used to store data generated and
`required by the program. Microprocessor 40 and ROM
`64 can be replaced by a microcontroller, which can be
`programmed to serve the same function. Accordingly,
`the microcontroller can be regarded as an equivalent of
`the combination of microprocessor 40 and ROM 64.
`Finally, the microprocessor drives display device 70
`which displays the corrected fuel economy calculated
`by the microprocessor. The corrected value displayed
`by display device 70 can be the average of the corrected
`fuel economy over a period of time, for example, 5
`seconds. Other averaging schemes to prevent erratic
`readings will be apparent to those skilled in the art.
`The calculations performed by microprocessor 40 on
`the data provided by sensors 12—16 correct the fuel
`consumed by the engine to account for that fraction of
`the “fuel” consumed which is converted to or from
`kinetic energy. The fuel consumed by the engine when
`the vehicle is travilling at a constant speed is an exact
`measure of the energy required to move the vehicle
`along the highway at that speed. If, however, the vehi-
`cle accelerates, some of the energy produced by the
`consumption of fuel is converted to the form of kinetic
`energy. It is “stored” in this form and can later be used
`to move the vehicle along the highway. Subtracting the
`quantity of fuel that corresponds to the kinetic energy
`“stored” from the total fuel consumed leaves only the
`fuel consumed in moving the vehicle down the high-
`way. If the sensors are read periodically by micro-
`processor 40, the change in kinetic energy is measured
`by the difference between the squares of the speeds
`measured at the most recent sample and the next most
`
`7
`
`

`

`4,845,630
`
`5
`recent sample. The difference between the squares of
`the successive samples of the velocity must be multi-
`plied by half the mass of the vehicle in order to dimen-
`sionally convert the difference to a kinetic energy dif-
`ference. The mass (or, equivalently, the weight) of the
`vehicle must be known to the same order of accuracy as
`the desired correction.
`'
`Other methods of calculation may produce the same
`result. For example, the difference of velocities over the
`measured distance divided by the elapsed time,
`(V 1 —V2)/t, gives the average acceleration. Multiplying
`by the mass gives M (V 1—V2)/t, the average force to
`accelerate the vehicle. Multiplying this by the average
`velocity, (V 1+V2)/2, gives M (V 1—V2) (V 1+V2)/2t,
`the power needed to produce the acceleration, and
`multiplying this by the elapsed time t gives M(V1——V2)
`(V 1+V2)/2,
`the energy needed. If these factors are
`multiplied,
`the result is MV12/2—MV22/2, which is
`obviously the difference on kinetic energies over the
`distance traveled.
`
`The weighting factor that should be applied to the
`change in the kinetic energy must increase the kinetic
`energy change to account for the fuel that would be
`used at real engine and drive train efficiencies to propel
`the vehicle if, for example, the kinetic energy were not
`available during coasting. It must also convert the en-
`ergy value to an equivalent weight of fuel. The required
`factor is: (fuel consumption/unit change of kinetic en-
`ergy). This correCtion factor can be calculated as a
`function of vehicle speed and weight and stored as a
`table in ROM 64.
`
`Turning now to FIG. 2A—2C, the operation of one
`version of a computer program for microprocessor 40
`(in FIG. 1) will be described. The purpose of these
`calculations is to compute the corrected fuel consump-
`tion rate given by the formula:
`
`distance travelled
`Corrected Fuel Economy = —.__________
`(fuel consumed) — Keq (V12 — V22)
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`'
`45
`
`6
`factors involve the vehicle parameters that were estab-
`lished in block 100.
`Blocks 106, 108, and 110 form a logic loop for initial-
`izing the fuel and distance arrays which are stored in the
`RAM. The first KCOUNT entries in the FUEL and
`DIST arrays are initialized. The FUEL array is initial-
`ized to a value equal to the amount of fuel burned at the
`estimated initializing fuel burn rate in a single sample
`period. The DIST array is initialized to zero.
`The logic loop comprising blocks 112 and 116 and
`subroutine SENSOR 114 is iterated, with block 112
`receiving the outputs produced by subroutine SENSOR
`114. Subroutine SENSOR produces values of IFLAG,
`VCOUNTS, and FCOUNTS. IFLAG is held at zero
`until VCLOCK seconds have elapsed. At this point,
`IFLAG is set equal to 1 and the values of VCOUNTS
`and FCOUNTS are stored in memory. VCOUNTS and
`FCOUNTS respectively record the number of pulses
`produced by the incremental distance sensor and by the
`fuel sensor during the sample period of VCLOCK sec-
`onds. After the value of IFLAG has been set equal to 1,
`decision block 116 allows the program to progress to
`block 118, which resets the value of IFLAG and calcu-
`lates the incremental number of gallons and miles that
`were produced in the last VCLOCK seconds. These
`incremental values are produced by multiplying the
`coefficients KFUEL and KODO by the values of
`FCOUNTS and VCOUNTS,
`respectively. Blocks
`120-124 form a logic loop which pushes each of the
`values in the FUEL and DIST arrays up by one posi-
`tion.
`The program escapes from this loop when all current
`values in the arrays have been pushed up by one posi-
`tion and the program then enters block 126. Block 126
`adds the latest incremental amount of fuel consumed
`and distance travelled to the previous accumulated
`FUEL and DIST values, respectively. The samples in
`the FUEL and DIST arrays are taken VCLOCK sec-
`onds apart.
`Control passes next to block 128 where the fuel con-
`sumed over the last KCOUNT - 1 sampling periods
`(WFUEL) and the distance travelled over the last
`KCOUNT - 1 sampling periods (VDISTl) is calculated.
`In addition, two pairs of distance and speed variables
`are calculated in block 128. One weighted distance
`(WDISTI),
`the distance
`covered over
`the
`last
`KCOUNT - 1 sampling periods, is divided by the num-
`ber of samples and the weighted speed over the last
`KCOUNT - 1 sampling periods is calculated by divid-
`ing WDISTI by the duration of a single sampling per-
`iod. Similarly, another weighted distance variable
`(WDIST2) is calculated over the next most recent
`KCOUNT - 1 sampling periods and normalized by the
`number of periods. WSPED2 is calculated by dividing
`the average distance travelled in each sampling period
`of the next KCOUNT - 1 most recent sampling preiods
`by the number of seconds in each sampling period to
`produce a speed. Control then passes to block 130.
`In block 130 the corrected fuel economy rate is com-
`puted by dividing the most recent per-sampling period
`distance covered over the last KCOUNT - 1 sampling
`periods by the difference between the per-sampling
`interval average of fuel used in the last kcount - 1 sam—
`pling intervals and the weighted difference between the
`squares of the two speed variables calvulated in block
`128. This is the value that is then converted by micro-
`processor 40 and displayed on display 70 (FIG. 1). Con-
`trol of the program then returns to the logic loop
`
`where Keq is the weighting factor times half the vehicle
`mass and V1 and V2 are speeds at the end and beginning
`of the distance travelled, respectively.
`In initialization of block 100, quantities are ascribed
`to certain vehicle parameters. These include the axle .
`radius (RAXLE), the rolling radius of the vehicle’s tires
`(ROLRAD), an initial estimate of the time rate of fuel
`consumption (GPHZRO), the number of teeth on the
`toothed wheel of
`the distance increment
`sensor
`(NTEETH), the number of pulses per gallon produced
`by the fuel consumption sensor (PPGAL), the fuel burn
`ratio of the engine’s fuel system (FLOSCR), the fuel
`equivalent for change in kinetic energy per unit vehicle
`mass (KEQm), and the gross combined vehicle weight
`(GCW). Many of these variables may be reset in value.
`For example, the gross combined vehicle weight value
`is resettable by the operator.
`'
`In sample period initialization block 102, the sample
`period of the distance increment and fuel sensors and
`the number of samples used in the weighting calcula-
`tions for fuel and distance are specified. For a particular
`type of vehicle, the parameters initialized in blocks 100
`and 102 can be stored in ROM 64 (FIG. 1). In block 104,
`the program calculates conversion factors for
`the
`odometer, the fuel sensor, and the change from vehicle
`kinetic energy to equivalent fuel. These conversion
`
`50
`
`55
`
`65
`
`8
`
`

`

`4,845,630
`
`7
`formed by blocks 112 and 116 and subroutine SENSOR
`114. This logic loop collects a new set of VCOUNTs
`and FCOUNTS and uses these data to update the cor-
`rected fuel economy rate, MPGCOR.
`If the program whose block diagram is shown in 5
`FIGS. 2A-2C is intended to be used with an engine
`requiring only a single fuel consumption sensor (see
`FIG.
`1), e.g.,
`a Cummins engine,
`the value of
`FCOUNTS can be read directly from counter 42 which
`is connected to fuel consumption sensor 12 through 10
`signal conditioning circuit 32. If, on the other hand, the
`engine requires both fuel consumption sensors 12 and
`14, FCOUNTS will be calculated by microprocessor 40
`as the difference between the counts read from counters
`42 and 44.
`
`15
`
`While the computer program described by the flow
`chart in FIGS. 2A—2C relies on samples taken over
`sampling periods that have a fixed time duration, one
`skilled in the art will appreciate that a computer pro-
`gram for microprocessor 40 in FIG. 1 could alterna-
`tively sample the time and distance variables as func-
`tions of fixed increments in distance. In this latter case,
`the independent variable for the calculations is distance
`rather than the more conventionally used time variable.
`Various averaging methods are well known to those
`skilled in the art and are frequently used on display
`devices for such purposes as smothing or quickening the
`response, or for minimizing the effect of inherent errors
`such as are encountered with digital data. These meth-
`ods may be used in this device. Clearly, their use or
`non-use is not germane to the essence of the invention,
`which is the accounting for vehicle kinetic energy in the
`claculation of vehicle fuel efficiency.
`I claim:
`
`20
`
`25
`
`30
`
`35
`
`8
`means for producing signals that measure a predeter-
`mined interval of time, the interval having a begin-
`ning and an end;
`means for producing signals that measure a distance
`traveled by the vehicle in the interval of time;
`means for producing signals that measure the fuel
`consimed by the engine in the interval of time; and
`means for receiving the time interval, distance trav-
`eled and fuel consumption signals and calculating a
`corrected fuel consumption of the engine in the
`interval of time by subtracting a weighted differ»
`ence of the kinetic energies of the ground vehicle at
`the end and at the beginning of the interval of time
`from the measured fuel consumed in the interval of
`time, and for calculating a value of a ratio of ‘the
`distance traveled by the ground vehicle in the in-
`terval of time and the corrected fuel consumption.
`4. The fuel economy measurement apparatus of claim
`3 wherein the means for calculating is a microprocessor.
`5. The apparatus of claim 4, further comprising read-
`only memory (ROM) for storing a program for the
`microprocessor and random-access memory (RAM) for
`storing one or more values of data generated by the
`program, wherein the ROM and RAM are connected to
`the microprocessor.
`6. The fuel economy measurement apparatus of claim
`5 wherein the microprocessor calculates the difference
`of the kinetic energies of the ground vehicle at the end
`and the beginning of the interval of time, based on
`stored values of the measured fuel consumption rate
`over the interval of time.
`7. A fuel economy measurement apparatus for use in
`a ground vehicle, propelled by an engine that consumes
`a fuel, comprising:
`means for producing signals that measure a predeter-
`mined interval of time, the interval having a begin-
`ning and an end;
`means for producing signals that measure a distance
`traveled by the ground vehicle in the interval of
`time;
`means for producing signals that measure the fuel
`consumed by the engine in the interval of time;
`a microprocessor for receiving the time interval,
`distance travelled, and fuel consumption signals
`and calculating a corrected fuel consumption of the
`engine in the interval of time by subtracting a
`weighted difference of the kinetic energies of the
`ground vehicle at the end and the beginning of the
`interval of time from the measured fuel consumed
`in the interval of time, and for calculating a value
`of a ratio of the distance traveled by the ground
`behicle in the interval of time and the corrected
`fuel consumption; and
`means for displaying the value of the ratio.
`8. The fuel economy measurement apparatus of claim
`7 wherein the display means is a digital display.
`9. A method of measuring a corrected fuel economy
`rate of a fuel«consuming engine in a ground vehicle, the
`method comprising the steps of:
`(A) producing signals that measure a predetermined
`interval of time, the interval having 'a beginning
`and an end;
`(B) producing signals that measure a distance trav-
`eled by the ground vehicle in the interval of time;
`(C) producing signals that measure the fuel consumed
`by the engine in the interval of time;
`(D) receiving the time interval, distance traveled, and
`fuel consumption signals and calculating the kinetic
`
`1. A vehicle fuel economy meter for adjusting the
`value of a distance traveled by the vehicle per unit of
`fuel consumed by the vehicle, including means for mea-
`suring the speed of the vehicle during a measurement
`period, means for measuring the change of kinetic en- 40
`ergy of the vehicle from measured speeds of the vehicle,
`and electronic circuitry for adjusting the value in which
`the value is increased by the change of kinetic energy of
`the vehicle during the measurement period when the
`vehicle speed is increasing from a lower value to a 45
`higher value, and correspondingly decreased during the
`measurement period when the vehicle speed is decreas-
`ing from a higher value to a lower value.
`2. A vehicle fuel economy meter for adjusting the
`value of a distance traveled by the vehicle per unit of 50
`fuel consumed by the vehicle, including means for mea-
`suring the speed of the vehicle during a measurement
`period, means for measuring the change of kinetic en-
`ergy of the vehicle from measured speeds of the vehicle,
`and electronic circuitry for adjusting the value in which
`the consumed fuel equivalent of the change of vehicle
`kinetic energy in the distance traveled is a fuel decreas-
`ing factor in the calculation of the distance traveled per
`unit of fuel consumed for an increasing vehicle speed
`from a lower value to a higher value and in which the
`consumed fuel equivalent of the change of vehicle ki-
`netic energy in the distence traveled is fuel increasing
`factor in the calculation of distance traveled per unit of
`fuel consumed for a decreasing vehicle speed from a
`higher value to a lower value.
`3. A fuel economy measurement apparatus for use in
`a ground vehicle propelled by an engine that consumes
`a fuel, comprising:
`
`60
`
`65
`
`55
`
`9
`
`

`

`4,845,630
`
`10
`
`15
`
`20
`
`25
`
`9
`energy of the ground vehicle at the end and at the
`beginning of the time interval;
`(E) calculating a corrected fuel consumption of the
`engine in the interval of time by subtracting a
`weighted difference of the kinetic energies. of the 5
`ground vehicle at the end and at the beginning of
`the interval of time from the measured fuel con-
`sumption in the interval of time; and
`(F) calculating a value of a ratio of the corrected fuel
`consumption and the distance traveled by the
`ground vehicle in the interval of time.
`10. The method of claim 9, further comprising the
`step of displaying the calculated ratio.
`11. A fuel economy measurement apparatus for use in
`a ground vehicle propelled by an engine that consumes
`a fuel, comprising:
`means for producing signals that measure a predeter-
`mined interval of distance traveled by the ground
`vehicle, the interval having a beginning and an end;
`means for producing signals that measure the fuel
`consumed by the engine in the interval of distance;
`and
`means for receiving signals that measure the predeter-
`mined interval of distance traveled by the ground
`vehicle and the signals that measure the fuel con-
`sumed by the engine in the interval of distance and
`calculating a corrected fuel consumption of the
`engine in the interval of distance by subtracting a
`weighted differenc