GB2032113A

GB2032113A - Device for displaying the residual distance of travel of a motor vehicle

Info

Publication number: GB2032113A
Application number: GB7926345A
Authority: GB
Original assignee: Mannesmann VDO AG
Current assignee: Mannesmann VDO AG
Priority date: 1978-08-17
Filing date: 1979-07-27
Publication date: 1980-04-30
Also published as: DE2836083A1; GB2032113B; GB2104661B; IT7925013A0; IT1122451B; GB2104661A; FR2433794A1; FR2433794B1

Abstract

A device for displaying the distance a motor vehicle can travel with a given quantity of fuel present in the tank has a supply resistor datum source (1) for measuring the quantity of fuel in a fuel tank (3) by means of a float (4), a variable resistor (5) whose resistance is varied by the position of the throttle halve (9) of the engine, a pre-set variable resistor (6) representing the average fuel consumption of the engine, a transistor (7) whose base is controlled by a voltage from an engine speed datum source (10) and a moving coil display instrument (8) and a constant current source (13). The display instrument (8) gives at any instant the distance which the vehicle can travel before the fuel tank is empty. The float level sensor may be replaced by a capacitive level sensor (Fig. 2) and the constant current source may be replaced by a current source whose output is varied from a predetermined value given by the average fuel consumption as a function of the position of the throttle valve and the speed of the engine (Fig. 3). <IMAGE>

Description

SPECIFICATION Device for displaying the residual distance of travel of a motor vehicle.

The invention relates to a device for displaying the distance a motor vehicle can travel with a given quantity of fuel present in the fuel tank taking into account the fuel consumption of the motor vehicle.

Devices of this type are already known wherein the fuel consumption is metered by means of a through-flow meter and the so-called residual distance of travel can be ascertained from the quantity of fuel left in the tank and the speed of the vehicle. A microprocessor is provided for calculating the residual distance from the above information. It is true that such devices supply a precise indication of the particular residual distance of travel, but they require considerable outlay and are costly, and this limits their application to motor vehicles of the luxury class.

According to the present invention there is provided a device for displaying the distance a motor vehicle can travel with a given quantity of fuel present in the fuel tank, including: means for detecting the quantity of fuel in the tank; means for detecting the fuel consumption at any given instant; means for detecting the speed of the vehicle; and a display instrument, the current supplied to the display instrument being determined by the above detecting means as well as the average fuel consumption for the vehicle, whereby the display instrument indicates the distance which the vehicle will travel with the present quantity of fuel.

In the above determination, the starting point is the specific average fuel consumption for the particular motor vehicle, which is modified by the mode of travel manifesting itself in the particular throttle valve position. Instead of using the throttle valve position, it is also possible to use the accelerator pedal position for modifying the motor vehicle-specific average consumption. With such a device, it becomes possible (as tests have shown) to accurately determine the particular residual distance of travel with a minimum outlay.The outlay is extremely small, there being in fact merely required an element converting the throttle valve or accelerator pedal movement into a resistance variation, the said element being for example a potentiometer, a further resistor which, for setting the motor vehicle specific average consumption, is also adjustable, and also a constant current source which may consist only of one or two transistors and a few further components. A special supply resistor datum source is necessary only in a very few cases, since such is already available in the majority of motor vehicles. Finally, a display instrument is required.

A further substantial improvement in the accuracy of the determination of the residual distance of travel can be achieved in that there may be provided, in the branch containing the display instrument, a resistor whose resistance varies as a function of the speed of the motor vehicle. In this way it is possible to take into account an increase or reduction in the fuel consumption arising from the conditions under which the motor vehicle is driven, such as occurs for example due to a varying load on the vehicle, due to gradients and also to the prevailing wind speed and direction. Advantageously, there may be provided as the resistor, the emitter-collector section of a transistor the base electrode of which has applied to it a velocity-dependent control voltage.In the case of motor vehicles having an electrical or electronic tachometer, this control voltage can be directly extracted from the tachometer, so that no supplementary datum source generating a velocity-dependent signal is required.

According to a further feature, the supply resistance datum source and the constant current source feeding it may be replaced by a capacitive supply datum source. Such a capacitive supply datum source comprises a sensor in the form of a capacitance which forms an oscillationdetermining element in an oscillator circuit, and, depending on the quantity of fuel present in the fuel tank, varies the frequency of the oscillator.

The frequency of the oscillator which varies as a function of the level of fuel left in the tank is then converted into an analog voltage signal. Such supply datum sources have the advantage that they are more precise than known supply resistance datum sources. By using such a datum source, the accuracy of the device can be further enhanced.

In a further alternative, the constant current source and the resistors contained in the branch containing the display instrument may be replaced by a current source feeding the supply resistance datum source, the current of which varies from a predetermined value given by the average fuel consumption as a function of the throttle valve position and possibly the speed of the motor vehicle. This embodiment represents a solution which is again possible but which requires a somewhat larger outlay in respect of components than does the previously described embodiment, so that it will be employed only in special cases.

The present invention will now be described in detail by way of example with reference to the accompanying drawing, wherein: Figure 1 is a circuit diagram of one preferred form of device having a supply resistance datum source, Figure 2 is a circuit diagram of a second form of device having a capacitive supply datum source, and Figure 3 is a circuit diagram of a further alternative form of device having a variable current source.

Referring first to Fig. 1, the device comprises a supply resistor datum source 1 controlled by a float 4 resting on the liquid level 2 in a container 3. A variable resistor 5 is provided in parallel with the resistance datum source 1 and a variable resistor 6, the emitter-collector path of a transistor 7 and a moving coil instrument 8 are connected in series with the variable resistor 5. The variable resistor 5 has a value of resistance varied by the position of the throttle valve 9. With this resistor 5, a modification of the specific average consumption as determined by the variable resistor 6 can be effected.A modification of the average consumption dependent on the speed of the vehicle is effected via the transistor 7, the resistance of the emitter-collector path being controlled by a speed-dependent voltage signal from a speed datum source 10 which is applied to the base electrode of the transistor 7. The two branches 11 and 12 of the circuit are connected to a constant current source 13.

Referring now to Fig. 2, the supply resistor datum source 1 and the constant current source 13 are replaced by a capacitive filling level metering device 14. The metering device 14 comprises a capacitive sensor 1 5 extending over the entire height of the container 3 and which forms an oscillation-determining element of an oscillator 1 6. The output of the oscillator 1 6 is connected via a rectifier 1 7 to the series-circuit consisting of the resistors 5 and 6, the transistor 7 and of the moving coil instrument 8.

Referring lastly to Fig. 3, the supply resistor datum source 1 and the moving coil instrument 8 are connected in parallel with each other and are fed from a source of current 1 8 the current of which varies from a predetermined value given by the average fuel consumption as a function of the position of the throttle valve 9, and the particular speed of the motor vehicle.

Claims

1. A device for displaying the distance a motor vehicle can travel with a given quantity of fuel present in the fuel tank, including: means for detecting the quantity of fuel in the tank; means for detecting the fuel consumption at any given instant; means for detecting the speed of the vehicle; and a display instrument, the current supplied to the display instrument being determined by the above detecting means as well as the average fuel consumption for the vehicle, whereby the display instrument indicates the distance which the vehicle will travel with the present quantity of fuel.

2. A device according to claim 1, wherein the fuel quantity detecting means comprises a supply resistor datum source controlled by a float, and fed by a constant current source.

3. A device according to claim 2, wherein the fuel consumption detecting means comprises a variable resistor whose resistance is modified by the position of throttle valve of the engine, said resistor being connected between the constant current source and the display instrument.

4. A device according to claim 3, wherein the means for detecting the speed of the vehicle comprises a transistor whose collector-emitter path is in series with the display instrument, the base electrode of which receives a voltage from a speed datum source.

5. A device according to claim 1, wherein the fuel quantity detecting means comprises an oscillator and a capacitative filling level metering device having a capacitative sensor forming an oscillation determining element of the oscillator.

6. A device according to claim 5, wherein between the output of the oscillator and the display instrument there is provided in series a first variable resistor, whose resistance is varied in accordance with the position of the throttle of the engine for detecting the fuel consumption, a second pre-set variable resistor whose resistance is representative of the average fuel consumption, and a third variable resistor device whose resistance is varied in accordance with the speed of the engine.

7. A device according to claim 6, wherein said third resistor device is a transistor whose coilector-emitter path is in series with the other variable resistors and the display instrument, the base electrode of said transistor receiving a voltage from a speed datum source.

8. A device according to claim 2, wherein said constant current source has its current varied from a predetermined value given by the average fuel consumption as a function of the position of the throttle valve and the speed of the engine, and feeds both the supply datum source and the display instrument in parallel.

9. A device for displaying the distance a motor vehicle can travel with a given quantity of fuel present in the tank, constructed substantially as herein described with reference to and as illustrated in Fig. 1, or Fig. 2, or Fig. 3 of the accompanying drawing.