WO1983001686A1

WO1983001686A1 - Method and device for measuring the energy loss for vehicles driven by an internal-combustion engine

Info

Publication number: WO1983001686A1
Application number: PCT/SE1981/000320
Authority: WO
Inventors: Anders Bosson Hedberg
Original assignee: Anders Bosson Hedberg
Priority date: 1980-05-14
Filing date: 1981-11-02
Publication date: 1983-05-11
Also published as: EP0092543A1; SE451904B; SE8003651L

Abstract

The efficiency of practical engines for transportation varies strongly with RPM and powerlevel. Under dynamic driving conditions, that is to say with speed-changes and hilly roads, there are good possibilities to adjust the way of driving so that the mileage is influenced. The principle of measuring and presenting the fuel used per driven distance is known. Such a device usually gives information that is at best difficult to use and sometimes directly missleading under dynamical driving conditions. The explanation is, that the meter only registers the used fuel-energy and does not take into consideration the energy that has been stored e.g. in the form of increased speed of the vehicle, and which can be used later for propelling the vehicle. In the proposed invention the instantaneously measured fuel consumption per driven unit of length is corrected with different forms of stored energy per driven unit of length. This gives a measure of at every moment used total-energy per driven unit of length. Presented to the driver, this gives a good guidance for choice of a way of driving which results in considerable fuel saving. In one embodiment of the invention the energy-consumption is calculated as, by flowmeter (1) measured flow of fuel to the engine from which is subtracted terms corresponding to the potential and kinetic energy stored in the vehicle. The data for the stored energy is calculated from data from accelerometer (10) which measures the acceleration of the vehicle plus the component of the earth's gravitation that is parallel to the road surface. The signals from relevant sensors are treated in processing unit (2) and the resulting value of the instantaneous energy-consumption per driven unit of length is presented on display unit (17) for the driver.

Description

METHODANDDEVICEFORMEASURINGTHE ENERGYLOSSFORVEHICLESDRIVEN BYANINTERNAL-COMBUSTIONENGINE

The invention is a process and a device for producing a decision- variable that gives the driver possibilities for choosing such running conditions and parameters for the engine and vehicle under dynamical driving conditions that makes possible a considerable increased milage. The decision-variable consists of a calculation of the instantaneously consumed total energy per driven unit of lenght.

Normally engines for vehicles has to work under very varying loads and speeds. However, only within rather narrow limits are they capable of converting the chemical energy in the fuel into useful mechanical energy with acceptible efficency. As an example see fig 1, which for a typical Otto-cycle engine shows the specific fuel consumption (g/k h) as a function of engine speed and torque. The specific fuel consumption varies between 280 g/kWh and 600 g/kWh. This is one of the reasons why the milage for a car is so greatly influences by the drivers vay of handling the accelerator (that is choice of delivered torque). It can be seen that both a high and a low torque gives high specific consumption. As a comment: driving with constant speed on level road does not give the driver any possibility to choose torque, it is only given as a result of the speed.

There are good possibilities for influencing the working-parameters for the engine when changing speed and climbing hills, that is under dynamical driving conditions, and perhaps especially under urban driving. The efficiency of a engine is under most circumstances strongly dependent on delivered torque and engine speed (the running parameters of the engine).

The principle to measure and indicate the fuel consumption per driven unit of lenght is known and applied to some cars. Such a conventional fuel-consumption-indicator gives information which is difficult to use (and sometimes directly missleading) for driving in the most fuel- saving way under typical urban driving conditions with many inescapable speedchanges.

As an example: at every aceleration (or hill climbing ) the conventional FCI (fuel consumption indicator) indicates high consumption. Since trying to minimize the indicated consumption would demand avoiding acceleration urban driving would be a very slow transport indeed. The reason for this impossible situation is that the conventional FCI does not take into account the usefulness of an increased speed.

To make it possible for the driver to judge the waste of energy at acceleration and hill-climbing more information is required than information about consumed fuel and covered distance. During acceleration and hill-climbing the consumed fuel has been converted to losses in the engine and futher part of it has been used to overcome friction in the transmission and tyres/road-surface and futher to overcome the air resistance. These parts are converted to heat and are lost to the environment.

Futiiermore part of the energy-content of the fuel has been used to change the kinetic and potential energy of the vehicle . This energy has not yet been wasted, it has only been converted from chemically to mechanically stored energy vhich still is at the disposition to move the vehicle without any futher fuel consumption. In those cases where there are possibilities to choose running parameters ( eg. by choosing different gears or by transferring energy into other temporarily storable energy forms) a indicator which shows the real losses gives the possibilities for adjusting the driving conditions so that the efficiency becomes the best possible. Consumed energy for a given utility function (eg covered distance) is calculated as consumed fuel minus that part of the temporarily stored energy of every other kind which can be used for useful functions. The conversion factor between amount of fuel and stored energy is for instance choosen to correspond to the best efficiency of the engine and transmission.

The purpouse of the invention is, to present for the driver at every moment such information that ^'is useful guidance in the choice of such driving parameters for the engine that considerable reduction of used fuel during various driving conditions is achieved. The data which is best suited to give guidance for choice of driving parameters comes from a calculation of the instantainously consumed total energy per covered unit of lenght. The desired result is obtained by the process according to patent claim 1 -5 or a device according to patent-claim 6 - 9.

One embodiment of the invention is described with reference to the attached drawings. Fig 1 shows the specific fuel consumption (g/kWh) for a typical Otto engine as function of tourque and engine-speed. Data for this figure is obtained from ref. 1 for the general features and ref. 2 for specific data in some points. Fig. 2 is a diagram showing sensors, datapaths, processing unit and indicators and display according to this invention.

The principle for the process according to the invention is that sensors collect information about interior and exterior variables for the vehicle. This information is processed in a processing unit and the result, wasted energy per driven distance = IND is presented on a display for the driver.

The relation for the processing is presented in eqvation 1.

Eq.1: IND = (B-b)/s - K2- (m/s)/A-ds -K3'U'I«t/s s

-K2.H.(v1^Z- v0²)/s - K2-Z-(n1²- nO* )/s - k6.

IND is the display-value presented to the driver s iSOistance covered during the measuring interval B is to the carburetor or equivalent delivered fuel during the measuring interval.

OMPI b is during the measuring interval in the carburetor temporarily stored fuel (eg in the acceleration pump).

K2 is the conversion factor from mechanical energy to amount of fuel. m is the total mass of the vehicle, in certain cases including a virtual mass corresponding to the angular momentum of the wheels.

A is the sum of the acceleration of the vehicle and the earth gravitational acceleration projected on the speed vector. In a simplified process and for certain uses the earth gravitational acceleratin can be excluded, in this case the potential energy of the vehicle is left out.* In this case term 2 is more simply calulated according to the formula

2*(v1² - vO )-m/2

K3 is a function of battery voltage and includes charging efficiency and conversion factors.

U is the battery voltage.

I is the charging current to the battery. t is the time-duration of the measuring interval.

H is the summed angular momentum of the wheels etc. v1 is speed of the vehicle at the end of the measuring interval. vo is speed of the vehicle at the start of the measuring interval.

_ is the angular momentum for the rotating Darts of the engine. n1 is the rotating speed of the engine at the end of the measuring interval, no is the rotating speed of the engine at the start of the measuring interval.

Term 1 consists of used fuel per driven unit of lenght during the measuring interval.

Term 2 gives the change in the sum of potential and kinetic energy per driven unit of lenght during the measuring interval.( In certain cases the potential energy can be neglected).

Term 3 is energy stored in battery per driven unit of lenght under the measuring interval. This term can in many cases be neglected but where it is of importance one must take into account the charge-retention and efficiency of the battery..

Term -4 is the change during the measuring interval in kinetic energy per driven unit of lenght in the form of rotational energy in wheels etc. This can often be approximated with a virtual mass that is added to the total mass m of the vehicle. Under hill-climbing this approximation gives a small error which usually can be neglected .

Term 5 is the change during the measuring interval in rotational energy in the rotating parts of the engine and transmission per driven unit of lenght. This should be included up to the amount that this stored energy could be used for propelling t^'he vehicle forward without consuming any fuel. Normally the internal friction of the engine is so great that it instead has a breaking effect, and in this case this term should not be included.

Term 6 etc. are other forms of during the measuring interval per driven unit of lenght stored energy which later can be put to useful work thereby saving fuel.

For^'an embodiment according to patent-claim 7 terms 1 and 2 are choosen to be included in the calculation. Term 4 is . approximated with a virtual mass that is added to the mass of the vehicle.

The fuelflow to the engine is measured by flowmeter 1 which

_* produces binary electrical pulses, and every puls represents a certain amount of fuel, in the order of 0.1 ml. The processing unit 2 contain registers, of which 4 is used to accumulate the total number of fuel pulses 3, and register 5 is used to count the fuel pulses 3 under the measuring interval. Covered distance is measured by a magnetic or optical encoder

6 which is mounted between the speedometercable and the speedometer. Encoder 6 delivers a binary electrical way-pulse

7 each time a cog on a cogged wheel mounted on the speedometer-cable passes. Every way-pulse 7 represents a covered distance ds. The way-puses 7 are accumulated booth totally in register

8 and also during the measuring interval in register 9, all in processing unit 2.

I Accelerometer 10 is mounted and adjusted in such a way that it only measures the acceleration along an axis parallel . to the road-surface and along the longitudinal axis of the vehicle.

The output-signal 11 from the. accelerometer 10 is a binary coded 8 bit word including a sign bit.

Every time a way-pulse 7 arrives to the processing unit 2 accelerometer-signal 11 is read and added to the contents of register

12 in the processing unit 2.

For correct calculation of used fuel a correction has to be made with the amount of fuel temporarily stored in any acceleration-pump. On that pump is mounted an position-encoder 13 which converts the position of the pump-membrane into a binary signal 14 with 4 bits resolution. The position of the pump-membrane is read by the processing unit 2 at the end of every measuring interval.

Register 18 in the processing unit 2 is a real-time clock that is used for control.

For the selection of programs in the processing unit 2 and for setting relevant parameters a control-panel 15 is connected to the processing unit 2.

Indication of the choosen program is done by signals form the processing unit 2 on a number of signal-lamps 16.

The result of the calulations done in processing unit 2 is presented as figures on digital display unit 17. The processing unit can have several different programs.

At the start of the system it is possible to store any changes of the

_* parameters of the equation into registers specially included for that purpose. This is done wit a special program which is choosen with control-panel 15.

The parameter that could have to be adjusted often is the total weight of the vehicle, as it varies with the load.

This weight is for instance adjusted with a number corresponding to the deviation from a standard weight. The duration of the measuring interval dt x 2 seconds can be specified with the exponent n, which is stored in a register 20. The measuring interval is calculated and put into register 19.

In what follows only the principle for the program that

OMPI calculates the instantanious total energy-consumption per driven km will be presented.

At the start the measuring interval duration time in register 19 is copied to register 18. This register 18 is then counted down by a clock-puls every dt seconds.

At the start a zero is stored in : register 4 for the total number of fuel-pulses, register 5 for the number of fuel-pulses during the measuring interval, reister 12 for the accumulated acceleration, register 8 for the total number of way-pulses and register 9 for the number of way-pulses during the measuring interval.

Now the^" measuring interval starts and during this fuel-pulses 3 are counted into registers 4 and 5, way-pulses are counted into registers 8 and 9. For every clock-puls dt register 18 is counted down one unit and also at that time the acceleration-signal 11 is added to the accumulated value in register 12. Futhermore register 18 is tested, when it reaches zero the calculation and presentation-cycle is started. Else the collection cycle continues and fuel-pulses 3, way-pulses 7 and clock-pulses are registered.

The calculation and presentation-cycle starts when register 18 has reached zero. Then until the next fuelrpulse arrives the way-pulses are registered. This eliminates a rounding error which might be considerable as each fuel-pulse represents a relatively great amount of fuel. By choosing such a small ds that makes the number of way-pulses during the measuring interval great enough, the rounding error due to the way-pulses can be reduced enough in comparison with other sources of uncertainty.

When the expected fuel-pulse arrives all wanted information is in the registers of the processing unit and the wanted estimation of the energy-consumption per km is obtained by calculation according to eq. 1. After that the numerical value of the energy-consumption is fed to the display unit 17 where it will remain during the next measuring interval.

This next measuring interval starts with initiation of all registers involved and the cycle starts all over again. Example: During a fast acceleration when the engine works with 70 % - 90% of maximum power the engine operate with best^" efficiency, that is to say that the greatest possible part of the energy-content of the fuel is converted into mechanical work at the wheels. Of this mechanical energy the main part is transformed into kinetic energy in the form of speed of the vehicle and is preserved as such. The proposed invention would indicate a relatively low consumption of energy/km, since it takes into account that a major part of the used fuel has been converted into kinetic energy which is stored in the vehicle and which is at our disposition to propel the vehicle forward without any futher fuel-consumption. A conventional fuel-consumption-indicator would indicate a large fuel-consumption/km during the acceleration-phase. If we use the conventional fuel-consumption- indicator to indicate how to save fuel we would be coaxed to accelerate the vehicle very slowly to make the meter show a low consumption ( the invention would then indicate greater energy-consumption than in the first case ). Under these circumstances the engine works with low part-load and consequently has bad efficiency. Only a minor part of the energy-content of the fuel is converted into useful mechanical work at the wheels. This means that, for a certain useful work done more fuel has to be spent than in the first case, when the engine was allowed to work with best efficiency. This example suggests that the information from the proposed invention, gives the driver the possibility to choose such way of driving ( choice of gear, level of acceleration etc ) that the engine works with best efficiency. That is to say that the engine is made to operate under such circumstances so that maximum of the energy-content of the fuel is converted into useful mechanical work.

The required correction of the readings from a conventional fuel-consumption-indicator to make it into energy-consumption, ^* can be considerable. Field experiment with a prototype of the invention in a Saab-95 shows that at almost full acceleration in gear 4 at 80 km/h a conventional fuel-

OMPI consumptionmeter indicates 18 liter/100km while the invention indicates 7 liter/100km. As can be seen the correction for the kinetic energy is considerable.

Experiments with acceleration from 0 - 50 km/h shows an variation of 556 in used fuel for different driving strategies and also that a strategy based on the invention gives low consumption. Conclusion: the invention gives the information that enables the driver to choose such working conditions for the engine which results in a considerable fuel-saving.

Claims

PATENT CLAIMS1) Process for engine-driven vehicles for producing such information which gives the driver possibilities to choose such running parameters for the engine and vehicle under dynamical driving conditions that a saving of fuel is obtained, the said information is obtained through processing incoming measuring-signals in a processing unit and the said information consists of a in the processing unit calculated value of the instantaneously consumed energy per driven unit of lenght, characterized in, that during the measuring interval driven distance is measured, that during the same measuring interval to the engine delivered fuel is measured, whereby a first approximation of the instantaneously consumed energy per driven unit of lenght for the vehicle is calculated,- that during the same measuring interval the speed-change of the vehicle in the driving direction is measured through which by suitable treatment a calculation of in the vehicle stored or given-off kinetic energy is obtained, that the measured values are brought to a processing unit (2), that the processing unit is arranged to subtract from, respectively add to, the through measurement of fuel-amount obtained first approximation of the instantaneously consumed energy per driven unit of lenght, a term which corresponds to the through measurment of the speed-change obtained calculation of the in the vehicle stored, respectively given-off kinetic energy per driven unit of length._-2) Process according to claim 1, characterized by, that under the same measuring interval the gain in height (above see- level) of the vehicle is measured, through which a calculation of in the vehicle stored or given-off potential energy is obtained, that the measured values are brought to a processing unit (2), that the processing unit is arranged to subtract form, respectively add to, the, according to claim 1 calculated instantaneously consumed energy per driven unit of lenght, a term corresponding to the through measurement of the gain of height of the vehicle, obtained calculation of in the vehicle stored or given-off potential energy per driven unit of lenght. 3) Process according to claim 1, characterized in, that during the measuring interval the acceleration of the vehicle in the driving direction plus the component of the earths gravitational acceleration is measured, ' through which by suitable treatment a calculation of in the vehicle stored or given-off sum of kinetic and potential energy' is obtained, that the measured value are brought to a processing unit (2), that the processing unit is arranged to subtract from, respectively add to, the through measurement of fuel-amount obtained first approximation of the instantaneously consumed energy per driven unit of lenght, a term which corresponds to the through measurement of the acceleration obtained calculation of the in the vehicle stored, respectively given- off sum of kinetic and potential energy per driven unit of length.4) Process according to any of the preceding claims, characterized in, that during the measuring interval the change in stored fuel between the sensor of fuel-flow and the cylinders of the engine is measured, that the measured value is brought to processing unit (2), that the processing unit is arranged to adjust the calculated value of instantainously consumed energy per driven unit of lenght with a term corresponding to per driven unit of lenght stored or given-off amount of fuel between the sensor of fuel-flow and * the cylinders of the engine.5) Process according to any of the preceding claims, characterized in, that during the measuring interval to or from the electrical batteries of the vehicle taken electrical charge and battery voltage are measured, that the measured values are brought to processing unit (2), that the processing unit is arranged to adjust the calculated value of instantainously consumed energy per driven unit of lenght with a term corresponding to per driven unit of lenght stored or given-off electical energy in the batteries, the energy obtained form the measurment of the charging current and voltage of the batteries. 6) A device for embodiment of the process according to claim 1, characterized in, that it contains timegiver clock, that it contains sensor (6) from which signal the driven distance can be calculated, that it contains sensor (1) from which signal the flow of fuel to the engine can be calculated, that it contains sensor ( 10 alternatively 6) from which signal the change in the velocity of the vehicle can be calculated, that -it contains means for conveying the sensor-signals to a processing unit (2), that the processing unit (2) is arranged so that it, on the basis of said sensor-signals, during every measuring interval calculates the consumed energy per driven unit of lenght for the vehicle, where the consumed energy per driven unit of lenght is calculated as consumed fuel-energy reduced with, respectively increased with, in the vehicle stored, respectively given-off, kinetic energy. *7) A device for the embodiment of the process according to claim 3, characterized in, that it contains sensor (6) from which signal the driven distance can be calculated, that it contains sensor (1) from which signal the flow of fuel to the engine can be calculated, * that it contains sensor (10) from which signal the vehicle- acceleration plus the component of the earths gravitational acceleration parallel to the roadsurface can be calculated, that it contains means for conveying the sensor-signals to a processing unit (2), that the processing unit (2) is arranged so that, on the basis of said sensor-signals during every measuring interval, it calculates the consumed energy per driven unit of lenght for the vehicle, where the consumed energy per driven unit of lenght is calculated as consumed fuel-energy reduced with, respectively increased with in the vehicle stored, respectively given-off sum of potential and kinetic energy.OMPI 8) A device constructed according to any of the preceding claims, characterized in, that it contains sensors form which signals the changes in the energy stored in the electrical batteries can be calculated, that it contains means for conveying the sensor-signals to a processing unit (2), that the processing unit (2) is arranged so that it, on the basis of said sensor-signals, adjusts the calculation according to any of the preceding claims of the consumed energy per driven unit of length under the measuring interval with a term corresponding to the change in energy-content of the batteries per driven unit of lenght.9) A device constructed according to any of the preceding claims, characterized in, that to the processing unit (2) a display-unit (17) of digital or • analog type is connected, that this shows the calculated result of consumed energy per driven unit of lenght during the measuring interval.Refereses:

1. AIP Conference Proceedings no 25 Efficient use of Energy Fig. 4.3

2. Shop manual for Saab-95.