Fuel economy display for vehicles

• US 5,693,876 A
• Filed: 05/31/1996
• Issued: 12/02/1997
• Est. Priority Date: 05/31/1996
• Status: Expired due to Fees

• Current Assignee: Freightliner Corporation
• Original Assignee: Freightliner Corporation
• Inventors: Ehlbeck, James M., Ghitea, Nicolae Jr.
• Primary Examiner(s): Dombroske, George M.
• Application Number:
  US08/655,841
• Time in Patent Office: 550 Days
• Field of Search: 73/113, 73/114, 73/116, 73/117.2, 73/117.3, 340/439
• US Class Current: 73/114.53
• CPC Class Codes: G01F 9/023 with electric, electro-mechanic or electronic means

Abstract

An improved fuel economy device computes a filtered rate of change of instantaneous fuel economy or a filtered instantaneous fuel economy and repetitively updates a graphical display depicting the current fuel economy. The fuel economy can be displayed as a percentage of a target fuel economy, programmed by the driver or other operator of the vehicle.

Claims

1. An improved fuel economy device for a vehicle comprising:

a speed measuring device operable to measure speed of the vehicle;

a fuel rate measuring device operable to measure fuel rate;

a control unit in communication with the speed measuring device and the fuel rate measuring device, the control unit operable to receive the speed and fuel rate, and operable to compute and repetitively update a filtered rate of change of instantaneous fuel economy using at least a first predefined filter coefficient; and

a display device in communication with the control unit, the display device operable to graphically display the filtered rate of change of instantaneous fuel economy;

wherein the display device includes a bar graph display with a first and second region and a reference point between the first and second region, the bar graph display being operable to display a portion of the first region to reflect a positive change in the filtered rate of change in instantaneous fuel economy, and being operable to display a portion of the second region to reflect a negative filtered rate of change in the instantaneous fuel economy.

2. The device of claim 1 wherein the control unit is operable to limit the filtered rate of change of instantaneous fuel economy to a predefined maximum limit;

and

wherein the display device is operable to display the limited filtered rate of change of instantaneous fuel economy such that the change in the illuminated portion, from one update of the display to the next, is limited to a predefined number of display elements in the bar graph display.

3. The device of claim 1 wherein the control unit is operable to compute a filtered instantaneous fuel economy at periodic intervals;

and

wherein the display device is operable to display and periodically update the filtered instantaneous fuel economy.

4. The device of claim 1 wherein the speed measuring device comprises a speed sensor and an engine electronic control unit, and the fuel rate measuring device comprises a fuel rate control and the engine control unit;

wherein the engine electronic control unit is operable to compute the fuel rate and the speed of the vehicle;

and wherein the engine electronic control unit is in communication with the control unit and is operable to transfer a first message including the speed and a second message including the fuel rate to the control unit.

5. The device of claim 4 wherein the engine electronic control unit and the control unit are coupled together via a serial communication bus.

6. The device of claim 1 wherein the control unit is operable to compute the filtered rate of change of instantaneous fuel economy by adding a first weighted rate of change of instantaneous fuel economy, weighted by a first filter coefficient, to a weighted value of a previously computed filtered rate of change of instantaneous fuel economy, weighted by a second filter coefficient, to compute a first sum value, and dividing the first sum value by a constant approximating the sum of the first and the second filter coefficients wherein at least one of the first or second filter coefficients is not equal to one.

7. An improved fuel economy device for a vehicle comprising:

a speed measuring device operable to measure speed of the vehicle;

a fuel rate measuring device operable to measure fuel rate of the vehicle;

a control unit in communication with the speed measuring device and the fuel rate measuring device, the control unit operable to receive the speed and fuel rate, and operable to compute and repetitively update a filtered instantaneous fuel economy, and a short term average of the filtered instantaneous fuel economy computed over a predefined period; and

a display device in communication with the control unit, the display device operable to graphically display the filtered instantaneous fuel economy or the short term average fuel economy as a percentage of a user programmable target fuel economy.

8. The device of claim 7 wherein the control unit is operable to compute the filtered instantaneous fuel economy by summing a first weighted value comprising a current instantaneous fuel economy, weighted by a first filter coefficient, and a second weighted value comprising a previously computed filtered instantaneous fuel economy, weighted by a second filter coefficient, and dividing the sum of the first and second weighted values by a constant value, wherein at least one of the first or second filter coefficients is not equal to one.

9. The device of claim 7 wherein the control unit is operable to compute the short term average fuel economy by summing the filtered instantaneous fuel economy over a number of intervals and dividing the sum by the number of intervals.

10. The device of claim 7 wherein the control unit is operable to compute the percentage of target fuel economy by subtracting the programmed target fuel economy from either the short term average fuel economy or the filtered instantaneous fuel economy to compute a difference, and dividing the difference by the programmed target fuel economy.

11. The device of claim 10 wherein display device is operable to display the percentage of the target fuel economy in a bar graph with a first portion of the bar graph representing a negative percentage, and a second portion of the bar graph representing a positive percentage.

12. The device of claim 7 wherein the programmed target fuel economy is user programmable via an input device coupled to the control unit.

13. The device of claim 12 wherein the control unit is operable to control the display device to display set-up data for the programmed target fuel economy, and is operable to display the programmed target fuel economy in response to inputs entered at the input device.

14. A method for computing fuel economy in a vehicle comprising:

measuring road speed of the vehicle;

measuring fuel rate of the vehicle;

computing a current instantaneous fuel economy by dividing the road speed by the fuel rate;

computing a current rate of change in instantaneous fuel economy;

weighting the current rate of change in instantaneous fuel economy by a first filter coefficient;

weighting a previously computed filtered rate of change of fuel economy by a second filter coefficient;

summing the result of the first and second weighting steps;

dividing the result of the summing step by a predefined constant to find a current filtered rate of change of instantaneous fuel economy;

converting the current filtered rate of change of instantaneous fuel economy into a graphical quantity for display;

displaying the graphical quantity such that the current filtered rate of change of instantaneous fuel economy is conveyed to a driver of the vehicle; and

repeating the above steps to update the display of the current filtered rate of change of instantaneous fuel economy at discrete intervals.

15. The method of claim 14 wherein the processing step includes:

limiting the displayed value of the current filtered rate of change of instantaneous fuel economy when a difference between the current filtered instantaneous fuel economy and a previously displayed rate of change of instantaneous fuel economy exceeds a threshold.

16. The method of claim 14 wherein the first and second filter coefficients are user programmable values.

17. A method for computing fuel economy in a vehicle comprising:

measuring road speed of the vehicle;

measuring fuel rate of the vehicle;

computing a current instantaneous fuel economy by dividing the road speed by the fuel rate;

weighting the current instantaneous fuel economy by a first filter coefficient;

weighting a previously computed, filtered instantaneous fuel economy by a second filter coefficient;

summing the result of the first and second weighting steps;

dividing the result of the summing step by a predefined constant to find a current filtered instantaneous fuel economy;

converting the current filtered instantaneous fuel economy into a graphical quantity representing current fuel economy;

graphically displaying the current fuel economy as a percentage of a predefined target fuel economy; and

repeating the above steps to update the display at discrete intervals.

18. The method of claim 17 further including:

averaging the current filtered instantaneous fuel economy over a predefined number of intervals, wherein the number of intervals is one to compute the current instantaneous fuel economy and greater than one to compute the short term average fuel economy; and

wherein the converting step includes converting the current filtered instantaneous fuel economy or the short term average fuel economy into a graphical quantity representing current fuel economy.

19. The method of claim 17 wherein the predefined target fuel economy is programmable by a driver and by a service tool.

20. A method for computing fuel economy in a vehicle comprising:

measuring road speed of the vehicle;

measuring fuel rate of the vehicle;

computing a current instantaneous fuel economy by dividing the road speed by the fuel rate;

computing a current value of fuel economy by digitally filtering the current and one or more previous values of instantaneous fuel economy;

computing a current value of displayed fuel economy by converting the current value of the fuel economy into a graphical quantity for display on a display device;

comparing the current value of the displayed fuel economy with a previously displayed value of the fuel economy to determine the difference between the current and previous values of displayed fuel economy;

limiting the current value of the displayed fuel economy if the difference between the current and previous values of the displayed fuel economy is greater than a predefined threshold;

displaying the current value of the displayed fuel economy on the display device;

repeating the above steps to update the display of the current displayed fuel economy at discrete intervals.

21. An improved fuel economy device for a vehicle comprising:

a speed measuring device operable to measure speed of the vehicle;

a fuel rate measuring device operable to measure fuel rate of the vehicle;

a control unit in communication with the speed measuring device and the fuel rate measuring device, the control unit operable to receive the speed and fuel rate, and operable to compute and repetitively update a filtered instantaneous fuel economy, or a short term average of the filtered instantaneous fuel economy computed over a predefined period; and

a display device in communication with the control unit, the display device operable to numerically display the filtered instantaneous fuel economy or the short term average fuel economy as a percentage of a user programmable target fuel economy and the filtered instantaneous or short term average fuel economy.