Fuel consumption rate detecting apparatus for a vehicle

Apparatus for measuring the distance traveled by a vehicle per unit quantity of fuel. The apparatus includes a generator for generating a voltage signal proportional to the speed of the vehicle, apparatus for generating a pulse signal proportional to the volume of fuel consumed by the vehicle and a switching device for cycling between open and closed positions in response to the pulse signal. An energy storage device, electrically connected to the generator and the switching device is provided. The energy storage device stores a charge from the voltage signal when the switching device is in the open position and discharges the stored charge when the switching device is in the closed position, thereby generating a fuel consumption signal representing distance traveled per unit quantity of fuel of the vehicle. Also provided is an indicator, electrically connected to the energy storage device for indicating fuel efficiency of the vehicle in response to the fuel consumption signal. The indicator has a dynamic damping for causing it to respond to an average voltage of the fuel consumption signal.

TECHNICAL FIELD 
The present invention relates to fuel consumption rate or fuel efficiency 
measuring systems. More particularly, the present invention relates to 
apparatus for measuring the distance traveled by a vehicle per unit of 
quantity of fuel. 
BACKGROUND ART 
Providing an instantaneous visual indication of the fuel efficiency or fuel 
consumption rate of a vehicle to the operator of the vehicle can be very 
important. Particularly when the fuel being consumed is very expensive or 
when a certain distance must be traveled with a fixed amount of fuel. 
Generally known apparatus have been proposed for measuring fuel efficiency 
of a vehicle by performing a calculation of the vehicle distance traveled 
per unit of fuel. The calculation of vehicle distance traveled per unit of 
fuel is provided to an indicator such as a meter in the form of an 
electrical signal. The electrical signal causes the meter to move 
providing an indication of fuel efficiency or consumption. Representative 
of such apparatus are U.S. Pat. Nos. 2,250,125, 2,422,240, 2,941,397, 
3,058,340, 3,118,302, 3,635,079, 3,812,710, 3,908,451, 3,967,097, 
4,008,607, 4,012,949 and 4,054,781. 
The apparatus disclosed by the above-referenced patents do not provide 
simple and easy to use apparatus which can provide an instantaneous 
measure of the fuel efficiency of a vehicle in miles per gallon. 
DISCLOSURE OF INVENTION 
The present invention provides apparatus for measuring the distance 
traveled by a vehicle per unit quantity of fuel which is simple and easy 
to use. 
Further, the present invention provides apparatus for measuring the 
distance traveled by a vehicle per unit quantity of fuel which can be used 
in any type of vehicle such as an automobile, boat, airplane or the like. 
Still further, the present invention provides apparatus for providing an 
instantaneous measurement of the fuel efficiency of the fuel consumption 
rate of a vehicle per distance traveled. 
The apparatus of the present invention includes a generator for generating 
a voltage signal proportional to the speed of a vehicle, apparatus for 
generating a pulse signal proportional to the volume of fuel consumed and 
a switching device for cycling between open and closed positions in 
response to the pulse signal. 
The apparatus of the present invention further provides an energy storage 
device electrically connected to the generator and the switching device. 
The energy storage device stores a charge from the voltage signal when the 
switching device is in the open position and discharges the stored charge 
when the switching device is in the closed position. The energy storage 
device as a result of the charging and discharging operation generates a 
fuel consumption signal representing distance traveled per unit quantity 
of fuel of the vehicle. 
The energy storage device may be provided by a capacitor and the apparatus 
for generating a pulse signal may be provided by a fluid flow meter. The 
fluid flow meter may be in the form of a rotary vane flow meter. 
The apparatus of the present invention further includes an indicator device 
electrically connected to the energy storage device for receiving the fuel 
consumption signal generated by the energy storage device. The indicator 
device includes dynamic damping of a sufficient level to cause it to 
respond to an average voltage of the fuel consumption signal generated by 
the energy storage device. The indicator device provides a visual 
indication of the fuel efficiency of the vehicle. 
The present invention as described above outputs the fuel consumption 
signal as a voltage signal proportional to miles traveled per gallon of 
fuel by implementing the following equation: 
##EQU1## 
where K is the calibration factor of the apparatus and V equals miles per 
gallon.

BEST MODE FOR CARRYING OUT THE INVENTION 
The present invention provides apparatus for measuring the distance 
traveled by a vehicle per unit quantity of fuel. The present invention 
outputs a voltage signal which provides an instantaneous measurement of 
the fuel efficiency or fuel consumption rate of a vehicle. The measurement 
is visually indicated to the operator of the vehicle. 
In order to provide a measurement of the distance traveled by a vehicle per 
unit quantity of fuel a measurement of the fuel flow rate and the speed of 
the vehicle is needed. FIG. 1 illustrates the apparatus of the present 
invention in this regard. 
The apparatus of the present invention shown in FIG. 1 includes a 
tachometer generator 10 for generating a voltage signal proportional to 
the speed of a vehicle. The vehicle is not shown. The tachometer generator 
is a magnetic type generator which produces its own electrical voltage 
signal as a result of the movement of apparatus of the vehicle operably 
connected thereto. The tachometer generator 10 may be driven by the 
speedometer of the vehicle. For example, the speedometer cable in an 
automobile may be connected to the tachometer generator to thereby 
generate a voltage signal proportional to the speed of the vehicle. 
The apparatus of the present invention also includes a fluid flow meter 12 
for generating a pulse signal proportional to the volume of the fuel 
flowing from a fuel supply 13 to the engine 14 of the vehicle. The fuel 
flowing into the engine is consumed by combustion to generate locomotive 
force to drive the vehicle. 
The fluid flow meter 12 may be provided by a rotary vane flow meter having 
a plurality of rotating vanes 15. The rotating vanes 15 are turned by the 
flow of fuel through the fluid flow meter 12. A position sensor 16 senses 
the rotation of the vanes 15 corresponding to a unit volume of fuel. Thus 
an electrical pulse is generated each time a unit volume of fuel flows 
through the fluid flow meter 12. In order to provide an accurate 
indication of the flow of fuel in the fluid flow meter 12 the effects of 
friction on the rotating vanes 15 must be eliminated. Therefore, the 
rotating vanes 15 must be mounted for frictionless rotation. 
A switching device 17 is provided in the apparatus of the present 
invention. The switching device 17 may be a transistor or the like which 
is coupled to the fluid flow meter 12 through a switch driver 18. The 
switch driver 18 receives the pulse signal generated by the fluid flow 
meter 12 and causes the switching device 17 to cycle between open and 
closed positions in response thereto. 
An energy storage device 20 is also provided in the apparatus of the 
present invention. The energy storage device 20 is electrically connected 
to the tachometer generator 10 and the switching device 17. The energy 
storage device stores a charge from the voltage signal provided by the 
tachometer generator 10 when the switching device 17 is in the open 
position and discharges the charge stored therein when the switching 
device 17 is in the closed position. By the charging and discharging 
operation, the energy storage device 20 generates a fuel consumption 
signal representing distance traveled per unit quantity of fuel of the 
vehicle. The energy storage device 20 may be implemented by a capacitor. 
The fuel consumption signal is in the form of a saw tooth wave voltage 
signal. 
The apparatus of the present invention further includes an indicator device 
22 such as a meter electrically connected to the energy storage device 20. 
An amplifier 24 is connected between the energy storage device 20 and the 
meter 22. The amplifier 24 amplifies the fuel consumption signal generated 
by the energy storage device 20. The meter 22 is dynamically damped at a 
sufficient level to cause it to respond to an average voltage of the fuel 
consumption signal generated by the energy storage device 20. 
The apparatus of the present invention, as described above and as 
illustrated in FIG. 1, implements the following equation: 
##EQU2## 
where K is the calibration factor of the meter. 
The tachometer generator 10 provides a voltage proportional to speed in 
miles per second. The fluid flow meter 12 provides a pulse signal 
proportional to quantity of fuel consumed in seconds per gallon. Thus, if 
the signals outputted by the tachometer generator 10, which provides a 
voltage proportional to miles per second and the fluid flow meter 12 which 
provides a pulse signal representative of seconds per gallon, are 
multiplied, as shown in the equation, then the signal resulting therefrom 
would indicate fuel efficiency in miles per gallon. 
Applying the pulse signal from the fluid flow meter 12 to the switching 
device 17 and the voltage signal from the tachometer generator 10 to the 
capacitor 20 accomplishes the multiplication of the signals in order to 
output a signal representative of miles per gallon in accordance with the 
above equation. The miles per gallon voltage signal is provided to the 
meter 22 through the amplifier 24 to provide a visual indication of fuel 
efficiency of the vehicle to the operator thereof. 
FIG. 2 illustrates the various signals provided in the apparatus of the 
present invention. As can be seen in FIG. 2, the fluid flow meter 
generates a series of pulses 30 which are provided to the switch driver 
18. The switch driver 18 controls the switching device 17. The pulses 30 
provided to the switch driver 18 causes the switching device 17 to 
momentarily close on each pulse. The momentary closure of the switching 
device 17 connects the capacitor 20 to ground potential thereby 
discharging the capacitor 20 to ground potential. 
Opening of the switching device 17 causes the capacitor 20 to be charged by 
the voltage signal 32 generated by the tachometer generator 10. The 
capacitor 20 charges at a rate proportional to the voltage signal 32 
applied thereto by the tachometer generator 10. 
The fuel consumption signal output from the capacitor 20, due to the 
charging and discharging of the capacitor 20, is in the form of a saw 
tooth wave voltage signal 34. The saw tooth wave voltage signal 34 is 
amplified by the amplifier 24 and applied to the meter 22. The meter 22 is 
heavily damped in order to indicate an average voltage of the saw tooth 
wave voltage signal 34 output from the capacitor 20. 
FIG. 2 further illustrates that the saw tooth wave voltage signal 34 being 
applied to the amplifier 24 from the capacitor 20 is a function of both 
the voltage signal 32 outputted by the tachometer generator 10 and the 
time between closures of the switch device 17 caused by pulse signal 30. 
For example, if the time between pulses of the pulse signal 30 from the 
fluid flow meter drops to half of its previous value at time t.sub.2 and 
the voltage signal 32 output by the tachometer generator 10 remains 
constant, then the fuel consumption is indicated as being cut in half in 
the saw tooth wave voltage signal 34 output by the capacitor 20. In other 
words, the average value of the saw tooth wave voltage signal 34 applied 
to the amplifier 24 from the capacitor 20 is reduced to half, thereby 
indicating the miles per gallon having changed to half of its original 
value. 
Further, as shown in FIG. 2, if as shown between times t.sub.3 and t.sub.4 
the pulse signal 30 output from the fluid flow meter 12 is changed back to 
its original value but the voltage signal 32 from the tachometer generator 
10 is reduced to half its original signal, then the charging rate of the 
capacitor 20 is now at half of its previous value. Thus, the saw tooth 
wave voltage signal 34 output to the amplifier 24 is half its original 
value shown in time t.sub.1 to t.sub.2. 
The apparatus of the present invention as described above and as shown in 
FIG. 1 can be used in any type of vehicle in order to provide a measure of 
the fuel efficiency or the fuel consumption rate of the vehicle. 
Therefore, the apparatus of the present invention can be used on boats, 
automobiles, airplanes or any other such vehicle where an instantaneous 
measurement of fuel efficiency is needed. 
Further, the apparatus of the present invention can be used in any 
application where a mere indication of a distance quantity such as shaft 
rotation relative to the flow of a fluid measured in volumes such as 
gallons is needed. Such an indication need not be related to fuel 
efficiency but can be related to, for example, revolutions per gallon of 
fluid. 
While the present invention has been described in terms of its preferred 
embodiment, it should be noted that numerous modifications may be made 
thereto without departing from the spirit and scope of the invention as 
defined in the appended claims. For example, the present invention may be 
used in any application which may require apparatus for measuring the 
distance traveled by a vehicle per unit quantity of fuel. It is intended 
that all such modifications fall within the scope of the appended claims.