EP1155291A1 - Monitoring the performance of a vehicle - Google Patents

Abstract

A vehicle performance monitoring system is provided in which engine 'on' and 'off' and engine speed, and also road speed, are detected by detectors (18, 20) and the signals indicative of these parameters are fed to a processor (22). A further signal representing the level of the fuel in the vehicle's fuel tank, and which indirectly represents the amount of fuel used by the vehicle, is obtained from a level indicator (32) and fed to the processor (22). The processor using the information to product data pertaining to fuel consumption, times during which the engine is idling, over-revving of the engine, engine start times, engine shut down times and vehicle speed.

Description

MONITORING THE PERFORMANCE OF A VEHICLE

FIELD OF THE INVENTION

THIS INVENTION relates to the monitoring of the performance of a

vehicle. It also relates to fuel level indicators.

BACKGROUND TO THE INVENTION

Fuel is a major day-to-day expense in any business which uses

vehicles. This is particularly true of trucking operations. Failure properly to account

for fuel can impact severely on the profitability of the business. Spilling of fuel at the

time of filling, fuel spilling over due to the temperature increase which occurs when

the fuel is transferred from a storage tank to the truck's tank, inaccurate recording in

the "diesel book" and theft all contribute to fuel losses. Insofar as theft is concerned,

it is well known that fuel is often stolen from trucks after they leave their depot. This

is particularly true on long hauls where road conditions, traffic volumes and detours

can greatly influence the quantity of fuel actually consumed for a journey. Because

wide variations in consumption are common place from journey to journey, and from

driver to driver on the same route, it is difficult to tell if a quantity of fuel has been

taken from the fuel tank.

Various devices are available which monitor parameters such as

speed, acceleration and deceleration of a vehicle, the time for which the engine is on and the time for which the engine is off. These provide useful information on the

journey undertaken, and on the driver's performance, but do not contribute to solving

the problems involved in accounting for fuel.

To enable any fuel usage control system to be implemented, it is

necessary to know how much fuel has passed through the fuel tank, and how much

fuel is in the tank. Hence the present invention also relates to fuel level indicators

for fuel tanks.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided a

system for monitoring the fuel consumption of an engine fitted to a vehicle which

comprises indicator means for producing an output signal indicative of the fuel level

in a fuel tank, means for providing a signal representing the distance covered by the

vehicle, and a processor to which each of said signals is fed and which processes

said signals to provide a result indicative of fuel consumption.

Said indicator means can include a visual read out from which the

volume of fuel in the tank can be read. Said indicator means can also include a

visual read out which can be re-set to zero and which indicates the volume of fuel

taken from the tank since the last time the read-out was re-set.

In one form said indicator means includes a resistance wire in a circuit to which a d.c. voltage is applied and a float which rises and falls with fuel level in

the fuel tank, movements of said float varying the length of said resistance wire

which is in the circuit and hence the current which flows therethrough. In a specific

embodiment the indicator means comprises a first resistance wire, a second

resistance wire and a conductive element carried by the float, said element bridging

between said wires and sliding up and down the wires as the float moves, those

portions of the resistance wires that are above the float being in said circuit.

The system can further include means for detecting engine speed and

producing a signal indicative of engine speed, and means for feeding the signal

indicative of engine speed to said processor. It can also include means for detecting

transmission speed and producing a signal indicative of transmission speed, and

means for feeding the signal indicative of transmission speed to said processor.

The system can also include a manually operated means in the vehicle

cab for providing a signal to the processor which signal represents a maximum

permitted vehicle speed, the processor having means for comparing said signal

representing maximum permitted vehicle speed with the signal indicative of

transmission speed and producing an output signal if the transmission speed

exceeds the maximum permitted speed, and an audio and/or visual warning device

in the vehicle cab to which said output signal is fed.

According to another aspect of the present invention there is provided a fuel level indicator comprising first and second vertically extending resistance

wires which are spaced apart horizontally and extend parallel to one another, an

electrically conductive link connecting the lower ends of said resistance wires, a d.c.

source connected across the upper ends of said resistance wires, a float the vertical

position of which varies in dependence on fuel level in the tank, the float including an

electrically conductive bridging element which joins said resistance wires, and

means for detecting the changes in current which occurs as the float moves

vertically and varies the lengths of the resistance wires which are above the float.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how

the same may be carried into effect, reference will now be made, by way of example,

to the accompanying drawings in which:

Figure 1 diagrammatically illustrates a monitoring system for a vehicle.

Figure 2 is a diagrammatic plan view of a vehicle with the system of Figure 1

fitted;

Figure 3 is a side elevation of the vehicle;

Figure 4 is a pictorial view of a fuel level indicator;

Figure 5 is a circuit diagram; and

Figure 6 is a pulse diagram.

DETAILED DESCRIPTION OF THE DRAWINGS ln Figure 1 an internal combustion engine fitted to a vehicle is

designated 10, its power output shaft is designated 12, an automatic gearbox, or

clutch and manual gearbox, is designated 14, and the drive shaft to the wheels of

the vehicle is designated 16.

Sensors 18 and 20 detect the rates at which the shafts 12 and 16

respectively are rotating and, of course, detect when they are static. In the case of

the shaft 12 this means that the engine 10 is switched-off and in the case of the

shaft 16 it means that the vehicle is stationary. Each sensor 18, 20 can comprise a

magnet fixed to the shaft and a magnetically operated switch adjacent the shaft.

Thus the switch is opened and closed once per revolution of the shaft, and provides

a series of pulses at a rate indicative of shaft speed. Alternatively the sensors can

switch a current a number of times per revolution e.g. eight times, thereby

generating a number of pulses per revolution. In another form the sensor can

generate an a.c. signal having a frequency which varies with the rate of rotation. An

interface to convert the a.c. signal to a digital signal is required with this latter

construction.

The signals from the sensors 18 and 20 are fed to a microprocessor 22

along lines 24 and 26 respectively.

The fuel tank of the vehicle is shown at 28. Fuel flows from the tank 28

to the engine 10 along the fuel pipe 30. A fuel level indicator is shown at 32, this providing a signal indicative of the fuel level in the tank 28. The output signal from

the indicator 32 is fed along a line 34 to the microprocessor 22. If the signal from

the indicator 32 is analogue, an interface for converting it to digital form is required

between the indicator 32 and the microprocessor 22.

The vehicle can, to increase its operating range, have a so-called bulk

tank 36 which is above the level of the tank 28. The tanks 28 and 36 are

interconnected by a feed pipe 38 having a solenoid operated valve 40 in it. The

valve 40 is connected to the microprocessor 22 by a line 42. The tank 36 has, at the

upper end thereof, a switch 44 which operates to indicate that the tank 36 is full.

The switch 44 is connected to the processor 22 by the line 46.

It is preferred that both tanks 28, 36 be filled through a filler opening of

the tank 36. In this form it must be possible to hold the valve 40 open whilst the

tanks are being filled. Alternatively, each tank 28, 36 can have its own filler opening.

A positioning system (such as that referred to as the GPS system) can

be fitted to the vehicle. The signal receiving antenna is shown at 48 and its

connection to the microprocessor 22 is shown at 50.

The information stored in the processor 22 can be downloaded onto a

mainframe computer or P.C. via a port 52. The processor 22 itself serves mainly to

compact the information being received. Average readings over a period of time, and not all the data that is received, are stored in the processor 22.

It is also possible to connect the port 52 to a unit which can provide the

information to the depot by a radio frequency link for "on the road" monitoring. It is

also possible to use a magnetically operated unit, or a unit that uses an infrared link,

onto which the information is downloaded for subsequent downloading onto the

depot's computer. It is also possible to use mobile phone technology to download

the information onto the mobile phone network and thence to the depot's computer.

The layout on a mechanical horse of the system described above is

illustrated in Figures 2 and 3. Neither the fifth wheel nor the trailer that the horse

tows is illustrated.

Prior to the start of a journey, the tanks 28, 36 are filled. The indicator

32 provides a signal to the processor 22 which eventually indicates that the tank 28

is full. No indication of how much fuel is in the tank 36 is given until the switch 44

closes indicating that the tank 36 is full.

To calibrate the tank 28, bearing in mind that tanks are manufactured

in many different shapes, it is possible to feed fuel to the tank through a fuel flow

meter which constantly measures the volume which has been fed to the tank. The

instantaneous volume read from the meter is compared with the reading being given

by the fuel level indicator 32. By storing this information in the microprocessor 22, all subsequent readings of the indicator 32 represent fuel volume in the tank even if

fuel level and fuel volume are not in a linear relationship due to tank shape.

Starting of the engine 10 produces a signal from the sensor 18 and this

initiates a cycle during which information is stored in the microprocessor 22.

Switching-off of the engine 10 terminates the cycle. In the event that the engine

remains on continuously for a predetermined time, for example, 20 minutes, expiry

of this period terminates one cycle and commences another. This ensures that the

data being recorded can be correlated with the location of the vehicle on the road.

This assists in analysis because, for example, a set of readings which looks

incorrect may be interpreted in an entirely different manner if it is known the vehicle

was in a mountain pass.

By using the distance travelled and fuel consumed it is possible to

provide consumption figures. By storing consumption figures over a period of time,

any extraordinary change in the consumption figure can be detected and repairs

made and/or remedial action taken.

By storing information obtained from the GPS (Global Positioning

System) it is possible to detect that the vehicle departed from its normal route.

The processor can also detect over-revving of the engine and when

the vehicle has been braked hard. By the end of each cycle, the system has recorded sufficient

information to determine the time for which the engine was running, kilometres

travelled, average RPM, peak RPM, fuel used, cost of the fuel used during the cycle,

a cost with other factors included to give a total cost for the cycle, number of stops

exceeding a predetermined length of time etc. All these can be calculated in the

depot computer from the information downloaded from the microprocessor 22.

When the reading from the indicator 32 shows that the tank 28 is

almost empty, the valve 40 is opened and fuel flows from the tank 36 to the tank 28.

The indicator 32 detects the increasing level in the tank 28. In the event that the

tank 28 refills completely, the signal from the indicator 32 which shows that the tank

28 is full causes the valve 40 to be closed. If the reading from the indicator 32

ceases to indicate that the fuel level in the tank 28 is increasing then, after a short

delay, the valve 40 is closed. As soon as the tank 36 has been emptied into the

tank 28, the processor 22 is able to calculate how much fuel was on the truck when

it commenced its journey.

The speed of the vehicle, which can be derived from the rate at which

pulses are arriving from the sensor 20, can be displayed in the vehicle cab. The

display in the cab can include a facility which enables the drive to input a chosen

speed to the processor. The speed inputted will normally be the maximum permitted

speed in the zone through which the vehicle is travelling. In the event that vehicle

speed, as determined by the sensor 20, exceeds the preset speed, the driver is given an audio and/or visual warning in the cab. The fact that the warning has been

activated is recorded in the processor.

It will be understood that by comparing current information with

historical, stored information, any significant deviations from the norm can be

detected.

The indicator 32 can be of any construction which will provide accurate

readings of the fuel level in the tank 28. The indicator 32 shown in Figure 4 works

on the basis of movement of a float 54 up and down two vertically extending

resistive wires 56. The float 54 is guided by a vertical guide rod 58 which passes

through a central hole 60 in the float. The wires 56 pass through slots 62 in the float

54. A pair of electrically conductive bridging elements (not shown) are provided

inside the float. These elements are of a resiliently flexible metal and the wires 56

pass between the portion of these elements which are in the slots 62. The resilience

of the metal, and the positioning of the elements, causes the elements to bear on

the wires 56 to make electrical contact but not with sufficient pressure to inhibit up

and down movements of the float.

The wires 56 extend down from an upper cap 64 to a bottom bar 64

which are held spaced apart by the rod 58. The wires 56 are anchored to the bar 66

and either the bar 66, or an additional wire (not shown) connected between the

wires 56, electrically connects the lower ends of the wires 56 to one another. The wires 56 pass through bushes (not shown) which insulate the

wires 56 from the cap 64. Fitted to the cap 64 is an enclosure 68 which contains

electronics for recording the output of the indicator 32. The line 34 extends from the

enclosure 68 to the microprocessor 22.

The enclosure 68 has two displays 70 and 72. The display 70

indicates the volume of fuel in the tank. The display 72 indicates the change in

volume since the last reading. This indicates how much fuel has been removed from

the tank since the last reading. A re-set button (not shown), preferably only

accessible to an authorized person, is provided for resetting the display 72 to zero.

The indicator 32 is fitted to the tank 28 with the cap 64 in an opening in the top of

the tank (see Figure 3). The rod 58, wires 56 and float 54 are inside the tank 28,

and the enclosure 68 is visible from outside the tank 28.

A constant current is applied to the wires 56 from a constant current

source 58 (see Figure 5). As the float 54 rises and falls, the lengths of the wires 56

which are above the bridge constituted by the bridging elements, and which are thus

in the circuit, varies. There is consequently a change in resistance which is

proportional to the level of the fuel in the tank and therefore proportional to the

volume of fuel in the tank. The wires 56 are represented in Figure 5 by the variable

resistance symbol. The change in current which results from the application of a

constant voltage to a resistance which varies in magnitude is detected by an

amplifier 60. The upper ends of the wires 56 are both connected to the constant current source 58. The input point of the amplifier is connected to earth via a

capacitor 62.

A recent trend is not to have the bulk tank 36 but to have a second

main tank which lies ahead of, or to the rear of, the tank 28. These tanks are

independent of one another and each must have its own a fuel level indicator. For

this layout the system must be capable of processing information on two channels

so that information can be received from each tank. Whilst the current in channel 1

is on, as shown by the upper line in Figure 6, the current in channel 2 is off, as

shown by the lower line in Figure 6. The current in channel 1 passes through the

wires 56 of the detector 32 of one tank and the current of channel 2 passes through

the wires 56 of the detector 32 of the other tank.

Experimental work has shown that pulsing each channel once per

second for a period of up to 10 milliseconds gives acceptable results. It is also

desirable to switch the current on and allow the circuit to stabilize for say 6 to 10

microseconds seconds before activating the amplifier and using the voltage at point

P as the input to the amplifier. This voltage is amplified and fed along line 34 to the

microprocessor via an interface which converts it to digital form.

It is also possible, instead of feeding a signal to the amplifier and

feeding the amplified signal to the microprocessor 22, to generate a frequency signal

proportional to the voltage. The frequency signal is read by the microprocessor as an indication of float level.

The float 54 is within a vertical housing (not shown) to which the fuel

has limited access. Slopping of the fuel in the tank thus has a minimal effect on the

level in the tube and consequently the float does not bob up and down if the fuel in

the tank slops whilst the truck is moving.

It is possible to replace the switch 44 of the tank 36 by a detector 32,

or to provide a detector 32 in addition to the switch 44.

Claims

CLAIMS:

1. A system for monitoring the fuel consumption of an engine fitted to a

vehicle which comprises indicator means for producing an output signal indicative of

the fuel level in a fuel tank, means for providing a signal representing the distance

covered by the vehicle, and a processor to which each of said signals is fed and

which processes said signals to provide a result indicative of fuel consumption.

2. A system as claimed in claim 1 , wherein said indicator means includes

a visual read out from which the volume of fuel in the tank can be read.

3. A system as claimed in claim 2, wherein said indicator means also

includes a visual read out which can be re-set to zero and which indicates the

volume of fuel taken from the tank since the last time the read-out was re-set.

4. A system as claimed in claim 1 , 2 or 3, wherein said indicator means

includes a resistance wire in a circuit to which a d.c. voltage is applied and a float

which rises and falls with fuel level in the fuel tank, movements of said float varying

the length of said resistance wire which is in the circuit and hence the current which

flows therethrough.

5. A system as claimed in claim 1 , 2 or 3, wherein the indicator means

comprises a first resistance wire, a second resistance wire and a conductive element carried by a float which rises and falls with fuel level in the tank, said element

bridging between said wires and sliding up and down the wires as the float moves,

those portions of the resistance wires that are above the float being in said circuit, a

d.c. voltage in use being applied to the resistance wires and conductive element.

6. A system as claimed in claim 1 or 2 and including means for detecting

engine speed and producing a signal indicative of engine speed, and means for

feeding the signal indicative of engine speed to said processor.

7. A system as claimed in claim 1 and including means for detecting

transmission speed and producing a signal indicative of transmission speed, and

means for feeding the signal indicative of transmission speed to said processor.

8. A system as claimed in claim 7 and including manually operated

means in the vehicle cab for providing a signal to the processor which signal

represents a maximum permitted vehicle speed, the processor having means for

comparing said signal representing maximum permitted vehicle speed with the

signal indicative of transmission speed and producing an output signal if the

transmission speed exceeds the maximum permitted speed, and an audio and/or

visual warning device in the vehicle cab to which said output signal is fed.

9. A fuel level indicator comprising first and second vertically extending

resistance wires which are spaced apart horizontally and extend parallel to one another, an electrically conductive link connecting the lower ends of said resistance

wires, a d.c. source connected across the upper ends of said resistance wires, a

float the vertical position of which varies in dependence on fuel level in the tank, the

float including an electrically conductive bridging element which joins said resistance

wires, and means for detecting the changes in current which occurs as the float

moves vertically and varies the lengths of the resistance wires which are above the

float.