GB1602129A

GB1602129A - Odometer

Info

Publication number: GB1602129A
Application number: GB21924/77A
Authority: GB
Original assignee: DIGITAL CAR INSTR
Current assignee: DIGITAL CAR INSTR
Priority date: 1977-05-24
Filing date: 1977-05-24
Publication date: 1981-11-04
Also published as: FR2392362A1; IT1095645B; IT7823733A0

Description

(54) ODOMETER (71) We, DIGITAL CAR INSTRU MENTATION LTD., formerly Funtpon Limited, a British Company of 30, Bonville Road, Brislington Trading Estate, Bristol BS4 5QH, England, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to apparatus for a vehicle, such as a motor car, to record and display the total distance travelled by the vehicle.

The conventional odometer in a motor car comprises a mechanical counter driven by a cable that is connected to the vehicle drive system so that it rotates at a rate dependent on vehicle speed. Because of mechanical failures in the conventional odometer, electrical odometers have been proposed in which a transducer is provided that produces electrical pulses at a rate dependent on vehicle speed, and a counter is provided to count these pulses and activate display means according to the total pulse count so as to produce a a visual display of the total distance travelled.

The lack of a drive cable in such electrical odometers makes them more reliable and gives greater flexibility in fitting, but these advantages have been offset in many proposals by providing electro-mechanical counters and display means that are themselves unreliable or costly to provide, for example, stepping motors that are indexed by the pulses and operate mechanical counters. In other electrical odometers, electrical counters and display means have been proposed, thereby completely avoiding problems of mechanical wear and unreliability in these components.

However, these odometers have then been completely dependent on their electrical power supply. Power has to be supplied to them at all times, even when the vehicle is not in use, and any power failure results in a complete loss of record of total distance travelled.

An object of the present invention is to pro vide an improved electrical odometer that keeps a permanent record of the total distance travelled.

An odometer according to the present invention comprises processing circuitry for receiving electrical pulses at a rate proportional to vehicle speed and processing them electronically so as to produce a pulse count corresponding to the total distance travelled, display means that is fed an electrical representation of said pulse count and produces a corresponding visual display of the total distance travelled, and a nonvolatile memory in which said pulse count is recorded and which is read by the processing circuitry to provide a pulse count from which counting proceeds, at least upon connection of power to the processing circuitry, the processing circuitry being such as to receive an electrical signal indicative of whether or not the electrical ignition system of said vehicle is switched on, and operating to record said pulse count in the memory each and every time the ignition is switched off.

The use of a non-volatile memory to record said pulse count ensures that the count recorded in the memory is retained in the event of a failure in the power supply to the odometer, counting being re-commenced from this recorded count upon re-connection of power to the odometer.

The pulse count can also be recorded in the memory in the event of power failure.

The memory may be of the electrostatic type or of the magnetic bubble type, both being non-volatile in that they operate to retain a record independently of a power supply.

An odometer according to the invention will now be described by way of example with reference to the accompanying drawing.

A transducer 1, which may be an electric, magnetic or optical transducer, is fitted to a vehicle transmission system so as to produce electrical pulses at a rate proportional to the vehicle speed. These pulses are fed via a line 2 to a processor 3 in which they are divided down to give one pulse per tenth of a mile (or kilometre). The division ratio is pro grammable by external links or inputs 4 to the processor that facilitate the use of the odometer with vehicles of different types, for example, having different axle ratios. The pulses of the divided pulse train are then counted by the processor under the control of a counter programme sequence, the result of the count being held in an internal register.

At a preset programme time, the pulse count in said internal register is read out via a multiplexed display sequence onto digital display means 5 having a seven digit, seven segment display. Also, during the counter programme sequence, the pulse count is presented several times via an input line 6 to a non-volatile memory 7, but this pulse count is only written into the memory when the vehicle ignition is switched off. An ignition indication signal is fed to the processor 3 via a line 8 and when this signal goes low at ignition switch-off, the processor produces control signals on lines 9 and clock signals on line 10, that cause the pulse count to be written into the memory 7.

When the vehicle ignition is switched on, the ignition indication signal on line 8 goes high and this causes the processor to read the pulse count from the memory 7, this count being stored in said internal register of the processor. Thus, as the vehicle travels1 the pulse count proceeds from that value read into the internal register from the memory 7 at ignition switch on.

The processor 3 is powered by the vehicle battery via the positive supply line 11 and vehicle earth. In the event of power failure, the processor is triggered by the ignition indication signal going low. A capacitor 12 connected across the power lines maintains the supply voltage long enough for the processor to write the pulse count into the memory 7.

When normal operation resumes, this pulse count in memory 7 is then read out into said internal register of the processor for counting to proceed.

In an alternative embodiment of the inven tion, the capacitor 12 could be omitted in which case the processor does not write the pulse count into the memory 7 on power failure. However, on resumption of normal operation the processor writes the last re corded pulse count from memory 7 into said internal register of the processor, and counting proceeds from that count. In this case, some of the distance travelled will not be recorded but the error will be acceptably small.

The non-volatile memory 7 is of the electrostatic type and comprises an electrically alterable read-only memory (EAROM). Al ternatively, the memory may be a Diffmoss random access memory or a magnetic bubble memory. A d.c.-d.c. convertor is supplied to power the memory if the normal battery voltage is not sufficient.

The processor 3 may be a microprocessor with an external programme read-only memory, for example, IE 8080, or may be a micro-computer with an internal programme read-only memory.

A capacitor 13 sets the clock rate for the processor 3, but can be replaced by a crystal device.

The processor 3 also operates to produce a journey distance travelled under the control of a driver of the vehicle who can operate a reset switch 14 and a display switch 15. The reset switch 14 when operated by a driver serves to reset a second register that is provided internally of the processor 3 and which, like said first mentioned internal register, counts the divided pulses. Thus, the second internal register keeps a count corresponding to the distance travelled by the vehicle since the register was last reset. The display switch 15, when operated, causes the processor to read out the pulse count in the second register so that it is displayed on the display means 5 for a predetermined time before the normal total distance display is re-established.If desired, the processor 3 can be arranged so as to write the pulse count in the second internal register into the memory 7 in the same way as it does the pulse count in the first internal register as described above.

In an alternative embodiment of the invention display means separate to the display means 5, may be provided to display the journey distance travelled.

The processor 3 is also controlled by a side-light signal which, when the side-lights are switched on, causes the processor to increase the frequency or alter the mark/space ratio at which the display means 5 is multiplexed so as to decrease the brightness of the display for night-time driving.

The display means 5 is powered from a d.c.-d.c. converter 16.

The illustrated circuitry also processes the transducer pulses to give an indication of the vehicle speed.

Processor 3 produces a train of pulses at a frequency proportional to the frequency of the transducer pulses, and this is fed via a line 17 to a capacitor 18 that acts as a digitalanalogue converter supplying current to a meter 19 so that the latter gives a reading of vehicle speed. The resistors 20, 21, form a shunt across the meter that allows it to be calibrated. In an alternative embodiment, the meter 18 can be replaced by digital display means driven by the processor 3 like the display means 5.

The resistors 22, 23 connected between the positive supply line 11 and the switches 14, 15 are pulldown resistors. The diodes and resistors connected to the input connections to the processor, as shown in the drawing, and the capacitor 12, all serve to suppress supply transients.

WHAT WE CLAIM IS:- 1. An odometer comprising processing circuitry for receiving electrical pulses at a rate proportional to vehicle speed and processing them electronically so as to produce a pulse count corresponding to the total distance travelled, display means that is fed an electrical representation of said pulse count and produces a corresponding visual display of the total distance travelled, and a non-volatile memory in which said pulse count is recorded and which is read by the processing circuitry to provide a pulse count from which counting proceeds, at least upon connection of power to the processing circuitry, the processing circuitry being such as to receive an electrical signal indicative of whether or not the electrical ignition system of said vehicle is switched on, and operating to record said pulse count in the memory each and every time the ignition is switched off.

2. An odometer as claimed in claim 1 in which said pulse count is recorded in said memory in the event of failure in the power supply to the processing circuitry.

3. An odometer as claimed in either of the preceding claims in which the processing circuitry operates to read the pulse count in the memory each and every time ignition is switched on.

4. An odometer as claimed in any one of the preceding claims in which the processing circuitry includes a store in which said pulse count is stored and which produces said electrical representation for the display means, the pulse count in the store being recorded in the memory and the store receiving the pulse count read out of the memory.

5. An odometer as claimed in any one of the preceding claims in which the memory is an electrostatic memory.

6. An odometer as claimed in claim 5 in which the memory is an electrically alterable read-only memory.

7. An odometer as claimed in any one of the preceding claims in which the processing circuitry includes means that divides the rate of said electrical pulses and counts the corresponding divided pulses.

8. An odometer as claimed in any one of the preceding claims in which the processing circuitry comprises a processor to process the electrical pulses and to write into and read from said memory.

9. An odometer as claimed in any one of the preceding claims in which the processing circuitry includes a manually operable reset switch and is such as to process said received pulses to produce a pulse count corresponding to the distance travelled after operation of the reset switch and to display this on display means.

10. An odometer as claimed in claim 9 in which said distance travelled after operation of the reset switch is displayed on the same display means as said total distance travelled, a manually operable display switch being provided so that when operated it causes the former to be displayed.

11. An odometer as claimed in claim 9 or 10 in which said pulse count corresponding to the distance travelled after operation of the reset switch is recorded periodically in the memory and is read out of the memory to provide a pulse count from which counting proceeds, at least upon connection of power to the processing circuitry.

12. A vehicle fitted with an odometer as claimed in any one of the preceding claims.

13. An odometer substantially as herein described with reference to the accompanying drawings.

14. A vehicle fitted with an odometer substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. to the processor, as shown in the drawing, and the capacitor 12, all serve to suppress supply transients. WHAT WE CLAIM IS:-

1. An odometer comprising processing circuitry for receiving electrical pulses at a rate proportional to vehicle speed and processing them electronically so as to produce a pulse count corresponding to the total distance travelled, display means that is fed an electrical representation of said pulse count and produces a corresponding visual display of the total distance travelled, and a non-volatile memory in which said pulse count is recorded and which is read by the processing circuitry to provide a pulse count from which counting proceeds, at least upon connection of power to the processing circuitry, the processing circuitry being such as to receive an electrical signal indicative of whether or not the electrical ignition system of said vehicle is switched on, and operating to record said pulse count in the memory each and every time the ignition is switched off.