EP1299863A1

EP1299863A1 - System for working economy

Info

Publication number: EP1299863A1
Application number: EP01941399A
Authority: EP
Inventors: Klas GÖTHE
Original assignee: DRIVEC AB
Current assignee: DRIVEC AB
Priority date: 2000-06-14
Filing date: 2001-06-14
Publication date: 2003-04-09
Also published as: AU2001274756A1; WO2001097176A1; SE0002224D0; SE0002224L

Abstract

Arrangement at an internal combustion engine for reducing the energy consumption of the engine, and providing information to a user of the engine related to the energy consumption of the engine. The arrangement comprises a control unit and one or more sensors to measure physical parameters of the engine during operation, where the control unit is adapted to generate an output signal, based on the measured parameters, which is compensated for external factors, such as load changes, wherein the output signal comprises said information; and means for transferring said output signal to at least a presentation means.

Description

SYSTEM FOR WORKING ECONOMY

Technical field

The invention relates to a system for minimising the costs for operation and maintenance of internal combustion engines, and more specifically, but not exclusively, internal combustion engines which are mounted in vehicles and even more specifically heavy vehicles.

Prior art

An internal combustion engine has a varying efficiency depending on at which motor speed the engine is working. Generally speaking, an internal combustion engine has a motor speed interval in which the engine has an optimum efficiency. Operation outside this interval results in a lower efficiency and consequently losses in form of increased fuel consumption and an increased wear of the engine and in the case of a car also the tyres. A system for reducing the fuel consumption of engines is disclosed in EP-646708 Bl . This patent relates to an apparatus for reducing the supply of fuel to the engine a while after full throttle has been performed and maintained by automatically controlling a fuel supply means. The reduction of the fuel supply is adjusted so that the motor speed of the engine will not be reduced significantly at constant load. However, the reduction is performed in a fixed step and the driver of the vehicle receives no further indications of an erroneous driving behaviour. The system has no memory function in that it does not take an earlier driving behaviour into account, i.e. it is the instantaneous fuel consumption that is affected.

Summary of the invention An object with the present invention is to provide a significant improvement of the total economy of an internal combustion engine. An object with the present invention is more specifically to reduce the fuel consumption, reduce the wear of the engine, reduce the discharge of ecologically harmful substances through the exhaust fumes and in the case of a car also reduce the wear of the tyres of the vehicle. A further object is to improve the driver's driving behaviour by reading objective data from the vehicle by means of a control unit during operation, process the data and generate an output signal which is presented to the driver of the vehicle, e.g. through presentation means in form of a display. The output signal may further be used to generate a control signal to the fuel supply means of the engine .

Other objects, advantages and features of the present invention will be clear from the following detailed description, the appended claims, and the figures.

Short description of the figures

The invention will be disclosed in more detail in the following with reference to the appended schematic drawings, in which

Fig 1 is a schematic block diagram of the system according to the invention,

Fig 2 is a flow chart of the method according to the invention, and

Fig 3 is a graph of a torque curve of an internal combustion engine with the economical region indicated.

Detailed description of the invention The invention is based on a system which measures the relevant factors that control the consumption of energy and the working economy of an engine 1 and transforms these factors to quantifiable data. By a combination of measurement, registration, interpretation and reaction on relevant information, the system provides conditions for optimal use of provided engine energy. Data are transferred into easily interpretable symbols which can trigger corrective measures in systems that supervise the way to assimilate the consumed energy and which otherwise affect the working economy. The system is characterised in that corrective measures can be taken based on stored as well as momentary information. Corrective measures may be triggered by both human and intelligent mechanical control systems.

The fields of application of the system are mainly in the transport sector with special emphasis on vehicles intended for transport of goods and people by sea and land. The system is characterised in that through continuos measuring, registration and transformation to easily interpreted information it facilitates the corrective measures that in every moment are necessary to provide for an optimum use of provided energy.

A feature when presenting data is that only the information which shall give rise to a corrective measure is presented. This kind of selective presentation is specially adapted for maximising the human ability to perceive and react to relevant information during a long period. To enhance this ability, the information is presented on a display 2 which is adapted to be placed where it is easily observed. A feature of the information which is presented on the above-mentioned display unit 2 is that it is arranged in a manner which makes it possible for a person, who shall interpret and react on the provided information, to survey the process momentarily and during a period back in time. With this principle of continuos presentation, both the information which leads to corrective measures and the confirmation that the measure has been performed are documented together with the result thereof. Another characteristic in the way of providing information is that the relevant information is presented in a form which prioritise a reflex-based perception of information and as a consequence thereof reflex-based reactions on this information instead of information that calls for an intellectual effort in form of registration, evaluation, and transformation to an adequate measure.

The relevant factors are normally derived from the measuring and registration systems 3 that are located in the actual engine or vehicle.

Another characteristic for the way to register and evaluate data is a built-in method for every specific unit to revise the need of kinetic energy on a running basis due to the influence of external factors. Thereby it is possible to distinguish between the energy that has been supplied to the engine 1 for compensating for the influence of external, non-affectable factors, such as wind, topography, and load, and energy that has been supplied for affectable factors such as speed, motor speed, and output power. The calculation is performed by a control unit 4, which has been developed for this purpose, using a specific formula for the energy consumption.

When calculating the operating parameters of an engine 1, an increase of the motor speed at a constant gear range i.e. acceleration, will call for further supply of energy. If the acceleration is followed by retardation, this may involve an uneconomical use of energy. In this system a method has been developed which calculates and presents the supplied amount of kinetic energy during the course of acceleration. The model considers the size of the variation over time, the output value of the variation, and the mass that shall be transported. The calculation model includes a time factor during which the new speed shall be maintained and during which the supplied energy shall be used.

If the system registers retardation within the time specified for use according to the above, this will be registered as a negative deviation in both the registration system and on the display 2. The amount of negative deviation increases with the time of retardation and the amount of retardation. The system is also characterised by a technique to indicate a best possible use of the engine 1 and/or whether it generates the expected power at defined combinations of motor speed, throttle and load by detecting substances in the exhaust fumes. The concentration of the detector substance constitutes a measure of the capacity of the engine 1 to deliver power and the driving behaviour of the driver respectively.

We have a vehicle unit (control unit) which can be programmed by means of an external PC 5 for every vehicle. The control unit is preferably programmed in a high level language, such as C, and has an external memory 6 (eeprom, ram or the like) that stores all vehicle data.

What is programmed in the memory 6 is:

- Power curve (kW) - Torque curve (Nm)

- Fuel cost (g/kW) for different loads

- White, green, yellow, blue, and red zone in the motor speed region

- Gear box, engine, and final gear - Acceleration constants, i.e. at which amplitude we will consider a motor speed increase as an acceleration

- Corresponding retardation constants.

The energy supplied to the vehicle at a speed increase is the theoretical kinetic energy multiplied by an efficiency. This is not an absolute measure but merely a relative measure that increases exponentially with the speed:

Wk = v² * m / 2 It does not matter which mass we choose as the relationship is linear and we are only interested in a relative measure. The supplied energy according to the above is called the invested energy and is presented as an amplitude on a bar on the display 2. The maximum value of the bar corresponds to the energy that the driver supplies to the vehicle when he performs a speed increase from 0 to 90 km/h during a time interval t. The invested energy is reduced with a percentage rate rl and a fixed rate r2 per second;

Winvest = Winvest - Winvest * rl (k) - r2 (k)

At every speed, a specific power is needed to maintain e.g. a vehicle at a constant speed. The power need is a function of the total load; for example physical load, air resistance, roll resistance, and topography. These factors represent an unavoidable energy loss, which the driver has no influence on with the exception of speed selection, as the air resistance is exponentially dependent on the speed according to;

F = Cd * v * v * A * p / 2

The present invention calculates the total load at every instance. At acceleration and retardation the mass may be derived from the time it takes for a specific engine 1 to obtain a specific speed increase or retardation. The calculated optimum need for power, which determines an unavoidable loss factor k of the vehicle, is continuously compared with the load point of the engine 1. An engine 1 can generate a specific power at different loads where every load has a specific efficiency. Operation of the engine 1 at a higher efficiency results in a better economy. A load point is a function of motor speed and torque. The efficiency at the actual load point is continuously compared with all possible load points that generate the same power and with their efficiency. The difference between the efficiency of the actual load point and the load point with the highest efficiency is continuously monitored. A difference between the actual load point and the optimum load point generates an error message . The interest rates rl and r2 are in their simplest form a constant multiplied by the loss factor k. The interest rates may however be calculated from more complex relationships, e.g. an acceleration of the vehicle at a poor efficiency of the engine 1 may result in a longer reduction period than if the acceleration occurs at an optimum efficiency (correct motor speed interval) .

When the vehicle is retarding, the kinetic energy loss of the vehicle is calculated and if there still is invested energy (an investment not yet written of) , the kinetic energy reduction is presented in the diagram on the display 2;

W_lost = Winvest - ΔWk. If W_lost < 0 then W_lost = W_invest . W_invest will never become negative.

W_lost will be weighted and presented in the diagram.

To estimate the load we calculate the change in motor speed during an acceleration with regard to the throttle and power curve. If we supply x kW to the engine during the time period t from motor speedl to motor speed2 we can calculate the momentary load.

The momentary load is used to know which gear with the highest efficiency the driver may choose without loosing speed (too low power output) . The economy zone (green zone) shrinks at high load. The economy zone normally lies between approximately 1200 and 1700 rpm, but if the load is high the green zone may shrink to 1400 - 1700 rpm. The zone normally shrinks from low rpm up to higher rpm with increased load. However, the green zone might expand to e.g. 1000 - 1700 if the load decreases.

The control unit 4 stores in two different locations how many seconds the engine 1 has been operating in every motor speed during its working life. The motor speed value when the engine 1 has been operating with supply of fuel (throttle) is stored in one location and the motor speed spectrum without restrictions is stored in the other location. This is done in order to be able to distinguish between running the engine at too high motor speeds and motor braking.

Motor speed, speed, throttle and economy (curve) is stored four times per second in a memory unit tied to the driver. The data are subsequently used for evaluation of the driving. The evaluation is preferably made in a PC 5 where the programme supplies the driver with feedback of how good/bad he drives and advise of how he might improve his way of driving.

The best way to reach an optimum use of supplied kinetic energy to engine driven vehicles is to; a. influence the driver to drive economically by: providing continuous feedback during driving indicating to the driver if he is driving correctly or not. At incorrect behaviour, the system calls for corrective measures or a control unit triggers an automatic correction. registering driving behaviour so that it may be followed up, evaluated, and corrected by means of information, education, and incentive. providing a basis for systems that may give stimulus towards a correct driving behaviour. detecting substances in the exhaust fumes that show a high correlation with an uneconomical driving behaviour. b. see to that the engine 1 is in a condition which provides best power by; evaluating the power need of the engine 1 and calling for measures when negative deviations occur. notifying when it is time to perform service based on driving distance and/or operating time. - detecting substances in the exhaust fumes, which exhibit a high correlation with poor combustion and satisfying engine performance. c. plan the driving time so as to reduce or eliminate the factors, which influence the driving economy negatively.

The judgements of a correct or incorrect behaviour are based on how the torque of the specific engine 1 is used in dependence of load, speed change, and speed. Tracer substances in the exhaust fumes provide a complementary basis for forming a judgement. The aim is to minimise the motor speed at every load and speed. This is true for engines equipped with EDC . For engines without EDC the demand is added that the throttle shall not provide more energy/fuel than the engine 1 can make use of. The system is based on a control unit 4. This control unit 4 is in turn divided into two units, the vehicle unit and the driver unit. The vehicle unit is coupled to and configured for every specific vehicle. The driver unit is a driver specific unit, which goes along with the driver when he drives another car or if the driving pattern of the driver shall be transferred to an analysis and/or follow up programme .

The vehicle unit measures three parameters from the car by means of sensors; motor speed, speed, and throttle. The throttle is measured per thousand where a completely released throttle pedal corresponds to 0 and a fully depressed throttle pedal corresponds 1000.

From these three parameters it is possible to measure and register: — Acceleration

- Retardation

- Estimated (momentary) load. Load is the weight, air resistance, roll resistance etc. of the vehicle . - Output power of the motor

- Motor brake

- Gear position

- Supplied kinetic energy

- Used kinetic energy All fundamental data regarding motor speed and speed are collected from the measuring equipment of the vehicle; throttle information is collected by means of a specific sensor 3 for vehicles without EDC. Measurement and registration take place continuously, preferably four times per second.

Besides measured variables, the vehicle unit stores constants and graphs, which are specified for every type of engine, such as:

- Torque curve — Power curve

- Fuel cost curve

- Ideal motor speed (where the engine produces power at a lowest cost)

- Different motor speed zones (specified by the manufacturer) , white, green, orange, blue, and red zone

- Highest motor speed that is economically defensible during acceleration.

- Lowest motor speed that is economically defensible during acceleration. The system is further based on registering of information in four basic blocks :

Block 1 - Limits, registers and reports when appointed limits are exceeded whit regards to the factors: - speed

- motor speed

- throttle (vehicles without EDC)

- operation outside "green zone" according to the recommendations by the manufacturer - amount of indication substances in the exhaust fumes Possible additional functions are:

- warning of exceeded driving time

- warning of exceeded service time Block 2 - Driving patterns, register and report deviations from recommended driving patterns:

- wrong gear (time)

- to fast/slow acceleration

- use of power, i.e. how an increase in speed and/or supply of power is used.

- expected power consumption compared to actual power consumption. Negative deviation is marked as a possible engine trouble.

- discharge of indication gas Block 3 - Disposal of time, registers and reports direct driving behaviours :

- no load time

- driving time

- breaks - distance covered

- number of starts and stops

- gear change patterns

Block 4 - Engine history, registers the total engine time of the vehicle in different motor speed regions differentiated into the categories: - η ourney

- no load time

- engine brake

- energy supply at constant speed and acceleration respectively

Also registered are:

- distance travelled

- engine time at different speed intervals

- time for service and performed service respectively based on engine time and distance travelled. Block 1 comprises data that are objective and may hence be used as concrete goals. Block 1 and 2 are shown on a display when deviation occurs and are classified as an incorrect behaviour which may be followed up and attended by the driver .

Block 2 constitutes the part of the registration which is based on judgements of what is more or less right or wrong. Even for these judgements, goals may be formulated and followed up. There is, however, no absolute truth which results in that the objectives may be differentiated and adapted to the vehicle fleet, way of transportation, and the education level of the driver. Errors that may occur and measures against them are disclosed below.

Block 3 describes how the driving time is distributed among different activities during the time every driver makes use of the vehicle. Basic data in this block may both be used for planning driving routes as well as setting goals for activities that the driver may influence.

Block 4 describes the history of the vehicle and act as a basis for forming a judgement of its technical standard and useful life.

The driver shall always be informed of deviations that are registered as an incorrect behaviour. The indication on the driver unit is for this purpose designed so that only deviations are shown and that the magnitude of the error signal is in proportion to the size of the error. By the combination of the signal strength and that the signal only shows an incorrect behaviour, the possibility for the driver to observe and react on reflex even in complex traffic situations will increase.

The principle is simple; the change of the appearance of the area on the display calls for attention while the amount of change controls the impulse and the extent of reaction. Since the driver unit accounts for the most recent driving, preferably 30 seconds, the driver may follow the effect of the corrective measure.

All factors that control the driving behaviour are accounted for individually or in relevant combinations. In an evaluation programme that has been developed, the behaviour of the driver is evaluated. Incorrect behaviours are shown and evaluated with reference to nature and significance. In order to achieve a balanced judgement, the error frequency is put in relation to the time, which has been defined as "correct driving behaviour" . The driving pattern is shown with the driving time or driving distance as a basis.

Situations that may occur and the measures that are possible according to the invention will be presented below.

During an acceleration phase a driver may chose to switch gear so that he uses all gears, i.e. switch gear from 1, 2, 3, 4 ... highest gear. The acceleration will take longer time. The driver may change gear at the wrong motor speed, for example at a too high motor speed (a high cost per kW used) , or operate at gears that lie at a too low motor speed. This will lead to a low use of power at a high cost per kW. We say that every gear change costs energy. An expensive acceleration (per time unit) during a short time pays off better than an acceleration that is somewhat cheaper per time unit during a longer time. In order for the driver not to change gear too often we want him to start the acceleration at the lowest motor speed where the torque is the greatest and accelerate to a motor speed where the power is the greatest and the fuel economy per kW does not increase appreciably. This is at the motor speeds which were mentioned above (highest motor speed during an acceleration and lowest motor speed during an acceleration, respectively) . When the driver has reached the highest motor speed, we calculate how many gear steps he may perform in order to reach the lowest motor speed during an acceleration.

We also take the momentary load into consideration, which we measure by calculating the time it takes for the engine to increase in motor speed at full throttle. If it turns out that the vehicle needs a high motor power in order to change the speed, that is the vehicle is very heavy loaded, we will compensate the gear change tip so that the vehicle obtains a high enough power in order to continue the acceleration.

When travelling at constant speed, the driver may chose a too low gear in order to keep the speed. The motor speed will then lie in a region where every provided kW costs more than necessary. The driver may also choose a gear which is too high and even in this case every kW costs more than necessary. We want the driver to operate the vehicle as close as possible to the optimum motor speed, that is where every kW costs as little as possible. We calculate which gear that lies as close as possible to the optimum motor speed and tip-off the driver to change gear as many steps as necessary (in one gear change) . Also in this case we make sure that the vehicle will obtain a motor speed that is powerful enough not to demand the driver to change gear at every small extra load, such as head wind.

If a driver does not plan his route, this will result in that he drives the vehicle with continuous accelerations and retardations as a consequence. Acceleration before a red light where the driver must stop is a typical example of an unnecessary acceleration.

Every acceleration costs fuel and wear. Therefore, we see an acceleration as an investment in speed, which must pay off. We calculate the amount of energy that the driver invests in the speed of the vehicle and presents this in form of a bar on the screen. The investment which is exponential in relation to the speed, is gradually reduced until it is paid off, which means that the acceleration was well founded. For example, if the driver accelerates the vehicle before the red light and thereafter brakes, he will take out the investment before it is paid off and will receive a loss that is presented as a graph on the driver unit.

When a vehicle approaches a hill, the driver may immediately select a lower gear in order to climb the hill with a high power without losing speed. The driver may shift gear every half step up the hill in order to always use the highest power.

We may detect the hill in that the driver increases the throttle but loses in speed. Once again, every gear change costs energy. We do not want the driver to change gear before he really needs to, it is better to lose a little speed and keep the gear than to switch to a lower gear and keep a constant speed. When and if the motor speed has sunk to the lowest motor speed which is cost effective, it is time to change gear; we will then inform about a lowest gear that has a motor speed below the highest motor speed within the green zone. At this point the motor generates the highest power that does not compromise with the fuel cost per kW taken out and hopefully the vehicle will climb the hill with this gear; if not, the driver shall once again not switch to a lower gear until he is about to leave the green zone . An experienced driver that has climbed the same hill many times should know at which gear the truck will manage to climb the hill. If so is the case, he shall increase the speed a bit before the hill and not change gear until the driver unit tells him to but instead of switching down to the gear that lies highest in the green zone, the driver will use his experience and immediately switch to a gear that he knows will manage to climb the hill (if the motor speed is within the green zone) . Here the driver's experience is better than the tip from the driver unit since it does not know how long the slope is. A driver who does not follow the gear change tips but instead uses his experience will not receive a "punishment" on the display since the driver unit assumes that the driver knows what he is doing. If the driver's procedure to change gear was incorrect, this will be discovered in the analysis programme as the PC can analyse data that are not presented in real time but "looks" ahead and knows how long the slope is.

It is always incorrect to drive with the engine in a motor speed that lies outside our specified motor speed range if at the same time fuel is supplied to the engine and it is loaded.

The disclosure above is directed towards a preferred embodiment in form of a vehicle. In an alternative embodiment, which is possible within the scope of the invention, the invention is used to increase the working economy of for example a power plant that is operated by an internal combustion engine. In this case the load changes depend on variable energy needs of the consumers, which make use of the energy from the power plant . An example of poor working economy in this context is to increase the energy production in the power plant when it is known, for example through market surveys of the consumption habits of the consumers, that the energy consumption will decrease within a near future .

Claims

1. A method of improving the working economy of a system comprising an internal combustion engine (1) by producing such information that gives the operator of the system the possibility to choose running parameters for parts of the system to reduce the fuel consumption of the engine, where said information is related to the energy invested for the operation of the system and obtained by processing information from one or more sensors (3), characterized by the steps of: determining a loss-factor corresponding to the inevitable energy loss per unit of time of the system, reducing the information related to said invested energy for the operation of the system by said loss-factor during a predetermined time interval, determining if the momentum of the system is decreasing, and wherein a decrease in momentum of the system before the invested energy is used will generate a signal corresponding to the energy loss of the system, released by said decrease in momentum of the system.

2. A method according to claim 1, wherein the system is a vehicle.

3. A method according to claim 2, wherein the vehicle is a car, truck, bus, or any other land based vehicle.

4. A method according to claim 2, wherein the vehicle is a boat.

5. A method according to any preceding claim, wherein the loss-factor is fixed to a pre-deter ined value.

6. A method according to claims 1-4, wherein the loss- factor is determined during operation of the system.

7. A method according to claim 6, wherein the loss- factor is determined from the load of the system.

8. A method according to claims 6 or 7, wherein a signal is generated corresponding to the determined loss- factor.

9. A method according to any preceding claim, wherein said information is presented to the operator of the system in the form of a graph on a display (2) .

10. An apparatus for improving the working economy of a system comprising an internal combustion engine (1), said apparatus comprising a control unit (4), where the control unit is adapted to receive signals from one or more sensors

(3), characterized in that the control unit (4) is adapted to: determine a loss-factor corresponding to the inevitable energy loss per unit of time of the system, reduce the information related to said invested energy for the operation the system by said loss-factor during a predetermined time interval, determine if the momentum of the system is decreasing, and generate a signal corresponding to the energy loss of the system, released by said decrease in momentum of the system, if a decrease in momentum is detected before the invested energy is used.

11. An apparatus according to claim 10, wherein the system is a vehicle.

12. An apparatus according to claim 11, wherein the vehicle is a car, truck, bus, or any other land based vehicle.

13. An apparatus according to claim 11, wherein the vehicle is a boat.

14. An apparatus according to claims 10-13, wherein the control unit (4) is adapted to use a loss-factor that is fixed to a pre-determined value.

15. An apparatus according to claims 10-13, wherein the control unit (4) is adapted to determine the loss- factor during operation of the system.

16. An apparatus according to claim 15, wherein the control unit (4) is adapted to determine the loss-factor from the load of the system.

17. An apparatus according to claims 15 or 16, wherein the control unit (4) is adapted to generate a signal that corresponds to the determined loss-factor.

18. An apparatus according to claims 10-17, wherein the control unit (4) is adapted to present said information to the operator of the system in form of a graph on a display (2) .