GB2084328A

GB2084328A - Compensated Fluid Flow Rate Device

Info

Publication number: GB2084328A
Application number: GB8028869A
Authority: GB
Original assignee: Rover Co Ltd
Current assignee: Rover Co Ltd
Priority date: 1980-09-06
Filing date: 1980-09-06
Publication date: 1982-04-07
Also published as: GB2084328B

Abstract

A fuel flow transducer with a non-linear output is made more accurate by use of a correction pulse generator 11, the output from which is combined by gate 12 with the pulsed output from the transducer to produce a signal more nearly representative of the true flow speed. The correction pulse generator, in one embodiment, has an output frequency related to the output frequency of the transducer, or may have a constant pulse frequency. The connected signal is then used, with a signal indicative of the speed of a motor vehicle, to produce a display 17 of the rate of fuel consumption of the vehicle. The display is updated in response to receipt of a given number of pulses representative of either fuel volume consumed or distance travelled. <IMAGE>

Description

SPECIFICATION Device for Indicating the Flow Rate of Fluids This invention relates to devices for indicating the flow rate of fluids, and particularly, but not exclusively to a fuel consumption indicator for a vehicle.

Vehicle fuel consumption indicators that are to be fitted to mass production vehicles tend to be inaccurate at some rates of flow due to non-linear output characteristics, of typical flow speed transducers available in the price range suitabie for mass filament. This non-linearity can be corrected by the use of microprocessor systems, but these tend to be complex and costly.

According to the present invention there is provided a device for indicating the flow rate of fluids, comprising a flow transducer means for sensing the flow speed and producing a pulsed output proportional to the sensed speed of flow, a correction pulse generator for producing pulses to correct for the error between the flow speed sensed by said transducer and the actual speed of said fluid, and means for receiving outputs from said flow transducer means and said correction pulse generator for displaying a quantity substantially proportional to said flow speed.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a device for indicating the fluid flow rate in accordance with the invention arranged to serve as an electronic fuel consumption indicator for a vehicle; Figure 2 is a block diagram of the fuel consumption indicator of Figure 1, but shown in the form of conventional logic components and integrated circuits; Figure 3 is a block diagram similar to Figure 2 but of a modified device in accordance with the invention; and Figure 4 is a block diagram similar to Figures 2 and 3, but of a further modified device in accordance with the invention.

Figure 1 shows the basic arrangement of a fuel consumption indicator which receives a pulsed output from a known type of fuel flow transducer (not shown), the frequency of which output is proportional to the speed of flow. The output is, however, non-linear in relation to the actual flow rate, the tendency being for the sensed flow rate to be substantially lower than the actual output at low rates of flow, becoming increasingly accurate as the flow rate increases.

As shown, pulses from the fuel flow transducer are combined with pulses from a correction pulse generator 11 by means of an exclusive On gate 1 2 which eliminates miscounting. In the present embodiment the correction pulse generator operates at a constant pulse frequency equivalent to a known quantity of fuel per hour, since this provides the requisite relatively large proportion of correction pulses at low fuel flow rates, the correction pulses forming a progressively smaller proportion of the total pulses at higher flow rates.

In a modified embodiment the correction pulse generator generates pulses at any given moment at a frequency which is a function of the pulse frequency of the fuel flow transducer means; this arrangement can more accurately correct the error in the output of particular flow transducers.

The combined pulses from the flow transducer and the correction pulse generator are divided by a divider 13, the output of which is fed to a counter 14, partly by way of a pulse generator 1 5.

A road speed transducer of known type (not shown) produces pulses at a frequency proportional to the speed of the vehicle to which the fuel consumption indicator is fitted. Thus each pulse represents a predetermined distance travelled since the last pulse. The roadspeed pulses are divided by a divider 16, and fed to counter 14.

Counter 14 counts the divided roadspeed pulses for a period determined by the number of fuel flow pulses received by the divider. After a predetermined number of fuel flow pulses, representative of a predetermined quantity of fuel, have been received by the divider, it transmits a pulse to counter 14 and pulse generator 15, causing counter 14 to display on a 4 digit LED display 1 7 a figure equal to the number of roadspeed pulses counted during the period in which the predetermined quantity of fuel has flowed. Dividers 13 and 1 6 ensure that the figure corresponds to the fuel consumption rate in conventional units such as miles per gallon.The pulse generator 1 5 then resets the counter 14 and the divider 13 to zero, while the display continues to show the same figure until a further pulse from divider 1 3 causes the above described process to be repeated and the display is updated.

Figure 2 shows the arrangement of Figure 1 in terms of conventional logic notation and standard integrated eircuits, and corresponding components are numbered as in Figure 1. As will be seen, counter 14 is arranged to drive a four digit display wherein each digit is made up of a combination from seven possible segments.

Provision is made to dim the LED for convenience when driving at night.

Figure 3 shows a modified fuel consumption indicator arranged in accordance with the invention which, while similar to that of Figures 1 and 2, incorporates means 18 to ensure that a minimum predetermined period of one second elapses after one up-date before a further up-date occurs. This is provided in the form of an AND gate one input to which is by way of a monostable providing a delayed output after a preceding output pulse from the AND gate to up-date the display. By means of this arrangement a more rapid display up-date at low fuel flow rates is obtainable without the penalty of a too rapid update at higher fuel flows, which results in a stabilisation of the up-date period over the full range of fuel flow rates encountered in the vehicle.

While Figures 1, 2 and 3 all illustrate arrangements for providing a display of distance travelled per unit fuel consumed, Figure 4 illustrates an arrangement, incorporating the improvement of Figure 3, but whereby a display of fuel consumed per unit distance travelled is obtained. As will be seen, the arrangement has reversed sensor functions in terms of inputs to the counter, and includes a phase locked loop which increases the fuel pulse rate.

Claims

1. A device for indicating the flow rate of fluids, comprising a flow transducer means for sensing the flow speed and producing a pulsed output proportional to the sensed speed of flow, a correction pulse generator for producing pulses to correct for the error between the flow speed sensed by said transducer and the actual speed of said fluid, and means receiving outputs from said flow transducer means and said correction pulse generator for displaying a quantity substantially proportional to said flow speed.

2. A device as claimed in claim 1, including means for measuring the distance travelled by a motor vehicle, said flow transducer means sensing the fuel flow rate, and said display means displaying a quantity relating the fuel consumed to the distance travelled.

3. A device as claimed in claim 1 or 2, wherein said correction pulse generator generates pulses at a constant frequency.

4. A device as Claimed in claim 1 qr 2, wherein said correction pulse generator generates pulses at a frequency which is a function of the pulse frequency of the output of said flow transducer means.

5. A device as claimed in any preceding claim, wherein said display means provides a digital display which is up-dated when a predetermined number of pulses representative of flow have been received by said display means since the preceding update.

6. A device as claimed in claim 2 or claim 3 or e 4 when dependant on claim 2, wherein said display means provides a digital display which is up-dated when a predetermined distance travelled has been measured by said measuring means since the preceding up-date.

7. A device as claimed in claim 5 or 6, wherein means are provided to ensure that a minimum predetermined period elapses after one up-date before a further up-date occurs.

8. A device substantially as hereinbefore described with reference to Figures 1 and 2, Figure 3 or Figure 4 of the accompanying drawings.