GB2072906A - Device for measuring the distance covered by a vehicle - Google Patents

Abstract

A device for indicating the distance covered by a vehicle including a mechanical counter (5) connected to a vehicle component such as a shaft in a gear box (2), which rotates in accordance with the distance covered, the counter including a number of interconnected counter wheels (8) to produce a decimal total, means for scanning (15) or sensing the instantaneous positions of the counter wheels (8), a converter (6) which receives the scanned data and converts it to digital output signals, and a digital indicator (7) electrically connected to the converter (6). <IMAGE>

Description

SPECIFICATION Device for measuring the distance covered by a vehicle This invention relates to a device for measuring and indicating the distance covered by a vehicle, of the type including a mechanical counter for logging the distance covered.

In existing vehicles equipped with this type of indicator, the style and arrangement of the indicator in the vehicle, for example on the dashboard, cannot be freely selected, because the drive to the indicator device, which is usually in the form of a flexible cable, considerably Limits the available area in which it can be fitted. Moreover, it has been found that the counter not only requires a substantial amount of room but also does not permit free uniform construction with the other indicating instruments on the vehicle.

Adaptation to the other indicating instruments is difficult or impossible, particularly in the case of digital indicator devices as has often been customary in recent times. By contrast indicator devices are also known in which the distance covered is electronically logged and-transmitted to a digital indicator device by electronic means. In such indicator devices assembled from several electronic components there is however the problem that the distance logged may be eradicated when there is a failure of the current supply or when one of the electronic components is replaced.

The main object of the invention is to avoid the aforementioned drawbacks, and to provide a vehicle distance indicator device for which the choice of position is independent of the drive cable, which requires little space, and whose output data can be continuously logged and indicated digitally.

Broadly stated the invention consists in a device for indicating the distance covered by a vehicle, including a mechanical counter for logging the distance covered, the counter including counter wheels which are driven in accordance with the rotation of a vehicle wheel, a scanner located on the counter and arranged to sense the position of the counter wheels, a converter which senses the scanned data and an indicator device connected to the converter and having a digital display device for the scanned data.

By means of the scanner and the electrical transmission to a digital indicator device, the data scanned by the counter can be readily reproduced and clearly read. Moreover, the usual flexible drive shaft can be eliminated, and this makes it possible to select freely the mounting and arrangement of the indicator device in the vehicle at any chosen location. A further advantage is that only a small amount of space in the vehicle is required for the indicator device and better readability is provided by the freedom to select the stylistic design of the figures on the display. As the mechanical counter is retained, the storage capacity of the counter is reliably maintained with no time limit, even if the electrical digital indication should break down.

In order to log the distance covered, the wheels of the counter may have contact elements to engage with sliding contacts of the scanner and produce output switching signals or instructions according to the digital code, which may be on the binary code or Gray code, or so-called excessthree code system.

According to one preferred feature of the invention the wheels of the counter may be sensed by a device which avoids direct contact therewith, one advantage being that wear between the counter wheels and the scanner is avoided.

Thus, in one form of the invention the counter wheels have electrically conductive elements which are opposed by components of the scanner arranged to operate on the inductance principle so as to transmit output signals on a digital coded basis.

It is also possible that the wheels of the counter may have electrically conductive elements opposed by components of the scanner which operate on the capacitance system to transmit digital output signals. For example, the induction component may be a coil-co-operating with an oscillator. Alternatively the component may consist of a Hall generator. The scanner may also be arranged to operate on optical principles.

The digital coded switching instructions delivered by the scanner are preferably converted in the converter into digital signals which can be read in the indicator device.

In order to be able to determine the distance covered even in the event of failure of the transmission of data to the indicator device the wheels of the counter preferably have visually readable figures by which the distance can be read off, in addition to their electrical contact elements.

Space-saving and practical accommodation in the vehicle can be achieved if the counter with the scanning device is located close to a component which rotates when the vehicle is moving, such as a shaft in the gear box, and is connected to the converter and the digital indicator device. As a result of locating the counter close to a rotating component, the use of a universally flexible drive shaft is unnecessary, and moreover, unauthorised manipulation of the counter can be completely precluded.

The invention may be performed in various ways and one specific embodiment will now be described by way of example with reference to the accompanying drawing, in which: Figure 1 is a diagrammatic side view of a vehicle with an indicator device and a counter according to the invention, Figure 2 is a diagram illustrating the arrangement of a converter which co-operates with the indicator device, a scanning device, and a part of a counter, Figure 3 is a diagram illustrating part of a modified arrangement somewhat similar to that of Figure 2, Figures 4 to 6 are diagrammatic views on an enlarged scale of several different forms of a counter wheel combined with a scanning device of the type illustrated in Figure 3, and Figure 7 is a diagrammatic side view of a wheel of the counter.

The vehicle shown diagrammatically in Figure 1 has an engine 1 with a gear box 2, and arranged to drive the vehicle wheels 4 via a propeller shaft 3, as illustrated. To the gear box 2 is fastened a counter 5, which is driven for example by one of the shafts of the gear box, and logs the distance covered by the vehicle. An indicator device 7, located in an instrument panel of the vehicle for example, is connected via a converter 6 to the counter 5.

As can be seen from Figure 2, the diagrammatically illustrated counter 5 has a number of counter wheels 8 corresponding to the desired decimals (only one of which wheels is illustrated however). The counter wheels 8 are rotatably mounted in a housing 9 and are driven in the usual way and operated in successive steps.

Each counter wheel 8 comprises a contact drum 10 and a figure disc 1 and each drum 10 has four adjacent rings 12, each contact elements 1 3 which are arranged in accordance with the binary code system for example, and represent the numerals 0 to 9. Sliding contacts 14 bear against each of the rings 12, and are connected to a scanning device 1 5, in which the sensed positions of the contact elements 13 are logged and conveyed as binary coded data to the converter 6 via lines 1 6. In the converter 6 the data concerning the distance covered which is delivered by the scanning device 1 5 is converted into signals which are transmitted via line 1 7 and shown as a digital reading on the display panel of the indicator device 7.

In the embodiment illustrated in Figure 3, the same reference numbers, with an added suffix, are used as in the example of Figure 2. The partly illustrated counter 5 has a counter wheel 8, whose contact drum 10' carries four adjacently situated rings 12' each composed of electrically nonconductive material with metal elements 13' selected and arrange for instance, according to the binary code system, to reproduce the numbers 0 to 9. Components 14' of the scanning device 15 oppose each of the rings 1 2' at a slight spacing, so as to avoid making contact with the rings.

In the example illustrated diagramatically in Figure 4, the component 14' indicated in dot and dash lines, contains a coil 18, which lies within the oscillatory circuit of an oscillator which is accommodated ip tiie scanning device 1 5.

If when the counter wheel rotates, the metal elements 13' of the ring 12' pass the coil 18, the inductance of the coil 1 8 is varied instantaneously such that the oscillations of the oscillator are simultaneously varied or interrupted. These interruptions are conveyed, for example as binarily coded data, via the lines 1 6 to the converter 6 shown in Figure 2, and displayed in a readable manner in the indicator device 7.

In the example illustrated diagrammatically in Figure 5, each component 14' of the scanner contains an electrode 1 9 of a capacitor 20 which is located in the oscillatory circuit of an oscillator.

In this case, when the electrically conductive elements 13', each of which form the other electrode of the respective capacitor 20, pass the capacitance of the capacitor is so varied that a variation in the oscillations of the oscillator occurs.

These variations in oscillation are likewise conveyed as binary coded data via the lines 1 6 to the converter 6 (Figure 2).

The component 14' shown in the example of Figure 6 contains a semiconductor element 21 and the one pole 22 of a permanent magnet acting as a component of a Hail generator which is accommodated in the scanner 1 5. The other pole of the permanent magnet is formed by the plates 13'. When the plates 13' pass, the semiconductor element 21, which at this moment is situated between the two poles 22 and 13', is magnetically influenced so that current flows for a brief period. This so-called Hall current is conveyed as binary coded data via the lines 1 6 to the converter 6 (Figure 2) as in the aforementioned examples.

The view shown in Figure 3 indicates that part of the figure disc 11 of a counter wheel 8 projects as a segment of a circle from the housing 9. As a result of this arrangement, the figures provided on the counter wheels 8, and therefore the distance covered, can also be read off visually.

The use of a mechanical counter which logs the distance covered and retains it indefinitely is thereforo particularly advantageous if any disturbances should occur in the scanning device 15, in the converter 6 or in the digital indicator device 7, or if one of these components has to be replaced. Moreover, the vehicle battery can, if required, be disconnected without any misgivings, as the record of the distance covered is not eradicated.

The invention is not confined to the illustrated examples. Although arranging the counter on the gear box is of advantage, for the type of speedometer normally provided on a vehicle, the counter may be mounted at a different point on the vehicle and connected to any wheel on the vehicle which rotates in accordance with the distance covered. It is also possible for the figure discs 11 to be of drum shape on their outer circumference where the figures are situated, instead of having the space-saving flat shape illustrated. It is also possible for the scanning of the counter to be performed by optical means, for example by means of a light source and a photoelectric element. In this case, however, special precautions must be taken to provide a suitable light cover or shield to avoid the risk of error or interference.

Claims (11)

1. A device for indicating the distance covered by a vehicle, including a mechanical counter for logging the distance covered, the counter including counter wheels which are driven in accordance with the rotation of a vehicle wheel, a scanner located on the counter and arranged to sense the position of the counter wheels, a converter which receives the scanned data and an indicator device connected to the converter and having a digital display device for the scanned data.

2. A device as claimed in Claim 1, in which the counter wheels of the counter have electrical contact elements to be engaged by sliding contacts of the scanner, which produce digital output signals.

3. A device as claimed in Claim 1, in which the counter wheels of the counter have electrical elements opposed to electrical components of the scanner and arranged to interact by electrical inductance so as to transmit digital output signals.

4. A device as claimed in Claim 3, in which the electrical component of the scanner is a coil which cooperates with an oscillator.

5. A device as claimed in Claim 3, in which the electrical component of the scanner is a Hall generator

6. A device as claimed in Claim 1, in which the counter wheels of the counter have electrical elements opposed to electrical components of the scanner and arranged to interact by electrical capacitance so as to transmit digital output signals.

7. A device as claimed in any of the preceding claims, in which the coded output signals from the scanner are converted in the converter into signals which can be read digitally in the indicator device.

8. A device as claimed in any of the preceding claims, in which the counter wheels of the counter have visually readable figures in addition to electrical contact elements.

9. A device as claimed in any of the preceding claims, in which the counter with the scanner is located close to a component of the vehicle, which rotates when the vehicle is moving, and is connected to the converter and the indicator device.

10. A distance indicating device substantially as described with reference to the accompanying drawing.

11. A vehicle including a distance indicating device, as claimed in any of the preceding claims.