GB2068119A - Instantaneous consumption indicator for a vehicle driven by an internal combustion engine - Google Patents

Abstract

A fuel consumption indicator for a motor vehicle comprises a pneumatic element connected to the intake passage of the engine with a diaphragm (3) subjected to the pressure difference between the atmosphere and the partial vacuum in the passage. The diaphragm is mechanically connected to a movable slider (9) which closes different electric circuits depending on the position of the diaphragm. The display means (27) comprises lamps selectively energised by separate ones of the different circuits to indicate the approximate fuel consumption. Some of the lamps may be energised through more than one of the circuits, connected in series with different resistances R1, R2 to vary the intensity of the light. <IMAGE>

Description

SPECIFICATION instantaneous consumption indicator for a vehicle driven by an internal combustion engine The invention relates to instantaneous fuel consumption indicators for motor vehicles driven by internal combustion engines of the type comprising a pneumatic element or motor connected to the intake passage of the engine and having a movable wall subjected to the depression which prevails in said passage and whose position depends on said depression and comprising dispiay means adapted to be located in the passenger space of the vehicle in a position where it can be seen by the driver of the vehicle.

Such indicators are intended to provide an approximative indication to the driver, rather than a precise indication in litres/hr; such an indication is sufficient in mest cases. Mest of them are hased on the rela Non which existe betwsen the depression Ap in the intake passage dewnstrean of the driver controlled enrothe or butterfly valve and the consumption C.

Migh emounts obdepression int eht intake manifold sowespone @@ iovy sonsumption and the reverse is @@@@ @ue in alcady operation. For example, the indi @@@@ üsclesed in French specification 1,164,738 @@@@@es a pneuma@is elementcarried by the dash @@@ @@@@@ @@the venicle and the movable wall thereof, formed by a deiormable diaphragm, is hitched to a deedie movahie in front of a dial comprising two @ones of different appearance, for example of differ en@@ ours, one chwhich corresponds to consumptions iess unen a predeiermined value, the other to consumptions above said vaiue.

Buch a consumption indicator requires a pneumaic connection (generaily a hose) conveying the depression; to the dashboard of the vehicle. The con :ection is cumbersome, which is serious in a one where space is limited; there exists risks of malfunc- ion ciue to twisting of the hose connection unless precautions are taken during mounting. display by a movable needle does not sufficiently attract the driver's attention.

According to the invention, there 5 provided an indicator of the hereinbefore type wherein the movable wall of said pneumatic element, which is placed in the vicinity of the engine, is mechanically connecked to a movable member of contact means which close different electric circuits depending on the position of said wall and said display means comprise at least two separate light sources, typically of different colours, ded by separate ones of said different circuits.

The light sources will typically be low-voltage lighting lamps, of the type used for alarm for example in a particular embodiment, the movable member comprises a slider which slidably contacts a printed-circuit board and is arranged to connect a metal earth track to one of several second metal tracks belonging to said different circuits; the pneumatic element and the contact may be mounted in a common case connected to the manifold of the engine by a short pipe length and to the display means placed on the dashboard by electric line means provided with a pluggable connector; such contact means are compact, easily positioned, even if limited space is available, and the connection to the display means is easy to provide by means of a flexible cable.

The indicator may be completed vvith means supplying a signal indicating that the gearbox is engaged in an intermediate gear ratio; in an elaborate form, this intermediate gear ratio signal may only be supplied above a predetermined speed of the engine.

The invention will be better understood from the following description of a particular embodiment, given by way of example only. the description refers to the accompanying drawings in which: figure 1 shows a curve 20 representing the varia ion of the consumption c as a function of the speed T1 end curves 21,22,23,24 defining the ranges of depression in the manifold corresponding to the lighting of different control warning lights, or to the Nghting of the same warning light with different Intensi@es; Figure 2 is a cross-sectional view opf the pneumatic elernent and of the contact means to which it is coupled; figure 8 is a partial view, from the lef of Figure 2, showing the lead-out of the electrocal connections of the contact means to the dashboard;; Figure 4 is a top view of the contact areas of contact means adapted to light successively two indicator larnps, one of which with three different intensities, the mabile slider being shown in nroken line in a position where no warning larmp is lit (idling and low load of the engine); Figure 5 is a side view of the contact means of Figure 4.

For clarity, it will be assumed in the following description that the indicator comprises display means having two light sources and is arranged so that: - the two sources are switched off when the depression Ap is greater than a first value, 500 mb for example; - one source is switched on with a low brightness when Ap is less than the first value, corresponding to curve 21 of Figure 1, but higher than a second value, corresponding to curve 22; -the same source is switched on, with increased brightness when curves 22, then 23, are exceeded; - finally, the other source, of a colour attracting attention (orange for example), is switched on when the depression becomes lower than another value, corresponding to curve 24(300 mb for example).

Referring to Figure 1, in which curves 21 to 24 indicate the consumption C as a function of speed N, in steady operation and at a constant depression, there appears a relation between depression Ap and consumption C. Curves 21 to 24 may be compared with curves 25 and 26, which correspond respectively to operation when the butterfly is closed and the engine acts as a retarder, and to full-load operation, The shape of curve 20 (consumption in steady operation for the upper ratio) makes appear a strong increase in consumption when the depression is Bow.

The indicator illustrated in Figure 2 comprises a pneumatic element and contact means which consti tutes an assembly connected to the intake manifold by a vacuum pipe and to a display unit by a flexible electric cable.

The pneumatic element 1 (Figure 2) comprises a casing in which a diaphragm 4clamped between rigid cups 5 and 6 defines two chambers 2 and 3.

Work chamber 2 is connected to the part of the intake pipe of the engine situated downstream of the driver actuated throttle member by a connector 7 and a flexible pipe. Chamber 3 is connected to atmospheric pressure. When a depression is transmitted to chamber 2, it tends to move diaphragm 4 towards the right in Figure 2, against the progressively increasing force of a return spring 8.

The movable wall of pneumatic element 1, formed by diaphragm 4 and cups 5 and 6, is mechanically connected to the mobile siider 9 of an electric contactor 10. Electric contactor 10 is connected by electrical connecting lines to light sources of a display unit 27 carried by the dashboard of the vehicle. The connecting lines may be contained in a flexible cable chown schematicaly at 28 (Figure 2), provided with an end connector plug 30 having insertable contacts 29.

Contactor 10 comprices. in a case which may be common with that of pneumatic element 1, an insulating support 11 having conducting tracks thereon. The suport Tay be ofatyps similar two usual eingle-face printed-circuit boards.Referring to Figures 4 and 5, where the shape of slider 9 is shown schematically in broken line, slider 9 rubs on support 11 and cooperates with a first ground track 12 and with a plurality of second tracks, including in succession when slider 9 moves: -a track 13, connected to a track 14 for closing an electric circuit including a first source (gree lamp for example) of the dashboard, a resistor R1 and a resistor R2 (connected in series with resistor R1) and an electric source (battery for example); -atrack 15, connected to track 14 through resistor R2 only; track 14; - a track 1-6 closing a circuit comprising a second light source (orange lamp for example) of display unit 27 to the dashboard of the vehicle and the electric source 4, without a resistor.

The colour of the lamps may obviously be chosen arbitrarily.

The device operates as follows: When a high depression (exceeding 500 mb for example) is transmitted to pneumatic element 1 (during idling and low engine load), diaphragm 4 is maintained in its right hand position in Figure 2.

Consequently, slider 9 is in contactwiththe insulating plastic part of the printed circuit, as shown in Figure 4; contactor 10 does not close an electrical connection and no lamp is lit: that situation corres ponds to a low-consumption range (Figure 1).

If the engine is being loaded, depression Ap decreases and diaphragm 4 moves leftwards (in Fig ure 2); slider 9 contacts the metal coated parts and connects tracks 12 and 13; the circuit lighting the green lamp between tracks 12 and 14 is closed through the series resistors R1 and R2: the voltage at the terminals of this green lamp is then low and there is a gleam indicating the operation is in the lower zone of an average consumption range (between curves 21 and 22 in Figure 1).

If the depression further decreases, slider9 moves further leftwards of Figure 2 and connects track 12 and track 15; then, the circuit for lighting the green lamp between tracks 12 and 14 is closed through resistor R2 only: the voltage at the terminals of the green lamp will be higher and the light intensity greater, indicating an intermediate part of the average consumption range (between 22 and 23 in Figure 1).

If the depression is further reduced, slider 9 connectstracks 12 and 14 directly. The green lamp is subjected to maximum voltage and will be fully illuminated indicating to the driver that he is in the upper part of the average consumption range (between 23 and 24).

Finally, if the engine is heavily loaded (with the throttle practically wide open for example), slider 9 connects tracks 12 and 16 and closes the circuit lighting the orange lamp. The full voltage Is applied to the lamp which has maximum brightness indicating high consumption (between 24 and 26).

Thus, it can be seen that the device of the inven- tion, while quite simple, gives the driver the possibili ',rC3 eslimets wit-h suicient accuracy te instan taneous consumption of his vehicle.

As mentioned earlier, it may be useful to display the gear ra -io in which the gearbox is engaged, at least when to speed of the engine is higher than a given threshold, since in formal use the lowest consumptions are obtained when using the highest possible ratio of the gearbox.

In a simple embodiment, display is obtained by an additional signal emitted when the gearbox is engaged in an intermediate ratio. This signal may be audible or visual: in the latter case, it may consist in winking of pre green lamp orofthe orange lamp, or in the lighting up of an additional warning light In an other embodiment, the gearbox intermediate ratio signal is only supplied when the engine rotates at a speed higher than a threshold, for example 2500 RPM The attention of the driver is thus drawn to the evel of his fuel consumption, maximum fuel-sparing being obtained when all warning lights are out.

An advantage, which results from the very principle of the indicator, resides in the fact that the display unit may be disposed at a considerable distance from the pneumatic depression sensor and from the associated electric elements (contacts, resistors).

The pneumatic sensor may be disposed under the bonnet, near the engine, whereas the display unit, taking up little space, may be disposed directly in the dashboard of the vehicle and may be reduced to simple telltale lamps {miniature lamps placed behind coloured screens).

When the indicator is arranged for being responsive to the depression downstream of the driver controlled throttle (for instance in the intake manifold, as in the embodiment of Figure 2), it may be used whatever the type of fuel delivery system. When the fuel supply system of the engine is of a type in which the rate of airflowtaken by the engine is measured by an auxiliary throttle located upstream of the driver controlled throttle and which is progressively and automatically opened by a pneumatic element subjected to the pressure which prevails in the intake passage between the throttles, that pneumatic element may be shared with the indicator. Such an auxiliary throttle element in the form of a butterfly or piston is currently used in carburettors of the constant depression type and in fuel injection systems.

Then, the movable member of the contact means may be driven by the movable wall of the pneumatic element which fulfils two functions: first, it measures the airflow and indirectly meters the fuel flow; second, it provides an input signal to the consumption indicator.

Numerous modified embodiments of the invention are possible. For example, more than two warning lights may be provided if necessary and/orvariable brightness may be omitted.

Claims (8)

1. An instantaneous fuel consumption indicator of the type set forth, wherein the movable wal; of said pneumatic element, placed in the vicinity of the engine, is mechanically connected to a movable member of contact means which close different electric circuits depending on the position of said wall and said display means comprises at least two separate light sources fed by separate ones of said different circuits.

2. Indicator according to claim 1, wherein said contact means comprises a slider slidably received on a printed-circuit board and is arranged to connect a earth track to one of several second electrically conductive tracks belonging to different circuits.

3. Indicator according to claim 1 or 2, wherein one at least of the light sources is arranged to be supplied by either of a plurality of said circuits which are supplied by the same electric source and have different resistances.

4. Indicator according to claim 3, wherein the display means comprises two light sources one of which indicates high consumption when lit and is supplied by a circuit closed when the depression in the manifold is less than a first predetermined value and the other of which indicates a moderate consumption when lit and is supplied by the other cir cuit.

5. Indicator according to any one of the preceding claims, wherein said pneumatic element comprises a casing in which said movable wall includes a deformable diaphragm subjected to the opposed action of a return spring and of the depression which prevails in the engine manifold.

6. Indicator according to any one of the preceding claims, wherein the pneumatic element and the contact means are mounted in a common casing connected to the manifold by a short vacuum pipe and to the display means placed on the dashboard of the vehicle by an electric cable provided with an end connector.

7. Indicator according to any one of the preceding claims, further comprising means indicating whether the gearbox of the vehicle is engaged in an intermediate ratio.

8. Indicator according to claim 1, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.