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The invention refers to a device for measuring the fuel comsumption of
liquid-fuel engines, the power yield of which varies according to
operating conditions, especially with fuel consumption of automotive
engines.
In the case of one known apparatus of this kind, fuel measurement occurs by
means of a device with two chambers for measuring quantities; the chambers
are separated by a diaphragm, and magnetic valves transfer the running
fuel back and forth between the chambers; after each chamber in turn is
filled, the diaphragm is moved by the fuel, and activates the magnetic
valves on the one hand, and a counter on the other.
In the case of another known apparatus, fuel measurement occurs by means of
a measuring pipe governed by magnetic valves with an equalizing container
of equal volume; the sinking liquid surface is traced by means of a
reflecting light beam, and the required switching actions are triggered
photo-electrically. Since timing is done simultaneously it is possible to
then derive fuel consumption with respect to a unit of time or, within
otherwise constant conditions of test, power etc.
The known apparatuses thus described have some disadvantages which
substantially reduce their applications. Thus, for example the minimal
quantity of flow-through which produces the smallest indicated measure of
sufficient accuracy is about 10 cm.sup.3 ; this entails undesirable long
periods of measurement (of up to several minutes) in case of measuring
very small quantities of flow-through of less than 0.1 liter/h. Another
disadvantage is that the known gauges do not permit to measure consumption
of injection systems with two different levels of pressure and such that
the return flow cannot be shunted before the gauge. A further
disadvantage, especially of the devices involving a material pipe, lies in
their dimensions, as well as the fact that they measure by sensing a
freely mobile liquid surface; this feature permits the use only in test
stations and excludes a permanent installation in vehicles in an
application as a gauge with a dash-board readout.
It is the purpose of the present invention to create a gauge for fuel
consumption that produces accurate measurements in a short period of time
for minimal quantities of flow-through, and which can be installed in
vehicles with a dashboard display and which permits measurement of the
consumption of carburetor-as well as fuel-injected engines.
The apparatus for which protection is sought consists of: one metering unit
each for fuel transport and/or fuel return including
(a) One gear which rotates freely in a circular chamber,
(b) Holes, extending at a tangent into the circular chamber, and serving as
inlets and outlets for fuel,
(c) One component each for transmitting light, installed in the walls of
the chamber in the area covered by the teeth of the ring gear,
(d) One infra-red transmitter and infra-red receiver external of the
chamber on one optical axis with the components for light transmission,
and
(e) One measuring unit connected to the infra-red receiver and consisting
mainly of a pulse transformer or comparison circuit, respectively.
The invention provides, for the first time, a flow-through gauge which does
not work intermittently on the basis of a given minimal quantity of fuel,
but which produces exact values for quantities of less than 10 cm.sup.3
and, hence, exact test results for times of test of much less than one
minute. Because of the construction as a flow-through gauge with a
comparison measure of return flow, it is possible to measure small
quantities of 10 ml/h. and less, even though the device is dimensioned for
large quantities; similarly, it can measure large quantities with a
corresponding reduction of the measured return flow. The set operates with
high degree of accuracy. The occurrence of errors, for example through a
threshold, is excluded due to the increase flow-through in both metering
units even with smallest quantities of consumption. The sets are small
externally, and are thus suitable for a fixed installation in vehicles
with connection to a dash-board indicator. The use of an infra-red
transmitter to generate the measuring signal assures a valid measure even
in case of coloured fuels.
The gauge applies the same methods to measuring fuel consumption of
carburetor-as well as fuel-injected engines. To handle the latter type, it
is only necessary to position a lock valve at the engine-side connector of
the forward-flow meter unit and to open a direct connection between the
return connector of the injection pump and the return metering unit; thus
it is possible simply to switch the device from measuring carburetor
engines to injection engines by closing, and respectively opening the two
connections.
To exclude error due to air bubbles carried in the fuel, it is advantageous
to insert, between the pump and forward-flow meter unit, a gas extractor
chamber equipped with a magnetic valve governed by the level of liquid,
for example, by change of resistance or capacitance. In the case of gauges
for fuel-injected engines, or combined gauges, it is useful to equip the
gas extractor chamber with an additional valve activated by a diaphragm,
the pressure side of which is connected to the engine-side connector of
the return meter unit, and the off-load chamber of which is connected with
the tank-side connector of the return meter unit. By these means it is
possible to limit the excess fuel delivered to the injector pump to remain
below a maximum which can be adjusted at the diaphragm valve; as soon as
the desired surplus quantity is exceeded the diaphragm valve opens, and
thus the surplus quantity of fuel exceeding the maximum, can flow back to
the tank, or fuel line, resp., while bypassing the metering units.
The electronic measuring unit consists, in its simplest form, of a simple
pulse transforming circuit as a mono-stable vibrator, the input of which
is connected with the infra-red receiver through a pnp transistor in
emitter configuration, and with the infra-red transmitter over an npn
transistor in collector configuration as well as a resistor. This
arrangement produces a coupling between the infra-red tansmitter and
receiver, which leads to a pulse to the transmitter that depends on the
light signal received by the infra-red receiver, and hence to greater
steepness of both flanks of the pulses originating from the infra-red
receiver which are then used as input pulses for the mono-stable vibrator.
Moreover, it is useful to equip the pulse transformer with a calibrating
circuit consisting essentially of a potentiometer, to adjust the width of
pulses. This circuit permits compensation for unavoidable production
tolerances of the metering gear which would entail a need to individually
calibrate the indicator with respect to the corresponding metering unit.
In configurations with only one metering unit e.g. as a gauge with
indicator mounted in the dashboard of a vehicle with normally spirated
engine, the indicator is connected directly to the mono-stable vibrator.
If the gauge is to be configured for comparison measures, i.e. with
separate metering units for forward fuel flow and return flow of fuel,
then an adjustment of pulse width is required to account for the return
flow. The output sides of the pulse transformer are connected to a
difference circuit over each of these circuits: a transistor stage for
obtaining constant pulse amplitudes, a condenser stage to integrate over
pulses, and an amplifier which transforms the impedance. The difference
circuit produces the test voltage for the indicator. One of both
transistor circuits may contain a variable resistor for calibration
against the other stage; also, the difference circuit may be followed by a
variable resistor to adjust the maximum of the output signal.
The invention is illustrated, by way of example, in the accompanying
drawings, in which:
FIG. 1 is a plan view of the measuring device for the combined measuring of
fuel consumption of carburetted or fuel-injected engines;
FIG. 2 is a cross section through FIG. 1 taken on the line A--A thereof;
FIG. 3 is a cross section through FIG. 1 taken on the line B--B thereof;
FIG. 4 is a circuit diagram designed to evaluate metering results; and
FIGS. 5a and 5b are block diagrams or one individual gauge each for
measuring of carburetted engines and fuel injected engines respectively.
Referring to the drawings, the combined gauge for measuring fuel
consumption of carburetted engines or fuel-injected engines, respectively,
includes pump-side forward flow connector indicated at 1, 1a, the engine
side forward flow connector indicated at 2, the engine side return flow
connector indicated at 3, and the tank-side return flow connector
indicated at 4. The remainder of the unit consist of a flow-through
metering unit each for forward and return flow, which consist (see FIGS. 2
and 3) of freely rotating gears 6, 6a positioned in a circular chamber 5,
5a, holes 7, 7a and 8a drilled at a tangent and opening into the circular
chambers 6, 6a to form fuel entries and outlets into, and from, the
chambers, one lens element 9, 10 and 9a, 10a each located in the wall of a
chamber in the zones of the teeth of the gears 6, 6a; one infra-red diode
11, 11a; and one photo diode 12, 12a both of which are on the same optical
axis as the lenses 9, 10 and 9a, 10.
The axes of the gear wheels are indicated at 13 and 13a. The engine-side
connectors of both metering units are liquid-connected by means of a
transverse aperture 14. A lock valve 15, 16, is positioned in the
transverse hole 14 on the one hand, and the engine-side connector for the
return from an injector pump 3, on the other hand.
Further, a gas extractor chamber 19 is installed ahead of the forward flow
metering unit and is equipped with a magnetic valve 18 which is governed
by a resistor 17. The gas extractor chamber 19 is equipped with a valve
21, activated by a diaphragm 20 (FIG. 1); the off-load chamber 22 of the
valve 21 is connected by means of hole 23 with the tank-side connector of
the return metering unit, and its pressure chamber 24 is connected with
the engine-side connector 3 of the return metering unit by means of a hole
25.
The measuring device illustrated in the drawing operates as follows:
In the case of measurement of fuel consumption of carburetted engines,
valve 15 is opened and connector 3 is closed by means of valve 16 or any
other suitable method. Connector la is linked with the ouput sides of the
fuel pump, connector 2 the carburetor, and connector 4 with the suction
pipe of the fuel pump. Fuel entering through connector la is de-gassed in
chamber 19, and any gas extracted (see FIG. 2) is collected in the dome of
chamber 19 and escapes through valve 18. Opening of the magnetic valve 18
is governed by resistor 17 which triggers the switch through a change in
resistance in response to a lowering of the liquid level below that of the
resistor 17. Fuel flowing out of the extractor chamber 19 through forward
flow inlet 1 and the tangential hole 7 into chamber 5, combined with the
outflow of fuel through hole 8, rotates the gear wheel 6 with a speed
proportional to the velocity of fuel flow; each time a tooth of the wheel
crosses the optical axis, the infra-red signal is interrupted which
triggers a pulse in the photo transistor. Hence, the number of pulses from
the photo transistor is directly proportional to the volume of fluid
flowing through the metering unit. By means of simple integration over
pulses it is thus possible to determine the volume of fuel flowing through
and to express it as a function of any suitable variable (time, distance,
etc.). Such a gauge thus satisfies accuracy requirements for dashboard
instruments.
In the case of the gauge shown in the drawing which produces comparison
measures for separate forward and return flows, a volume of fluid reduced
by the quantity consumed (flowing out of connector 2) is returned into the
tank through the return flow measuring unit 5a-12a. This measuring unit
(5a-12a) works on the same principle as the forward flow unit, so that the
portion of fluid that has reached the carburetor through connector 2 can
be computed from the difference of both measurements.
Measurement of consumption of fuel-injected engines occurs analogously,
however, by means of a closed valve 15 and an open valve 16 and linking
connector 3 with the return from the injector pump, the fuel flow is
routed over the injector pump to the return flow metering unit instead of
going directly through the transverse hole 14. In this case the diaphragm
regulator is used to adjust the return flow corresponding to the excess
flow to an arbitrary maximum value of, e.g., 35 liter/h. For this purpose
the pressure which builds up in the return line in front of the metering
unit (which acts as a restrictor) is transmitted over the connecting line
25 (FIGS. 1 and 3) to the pressure chamber 24 of the diaphragm valve; as
soon as it exceeds the closing force of, e.g., 0.1 atu, which is pre-set
at the diaphragm valve 21, the pressure opens valve 21 and thereby opens
the gas extractor 19 through the relief chamber 22 and hole 23 to give
access to the return line. As a result, fuel is diverted directly to the
tank with a corresponding reduction of the forward flow and the return
quantity, until valve 21 closes again in response to falling pressure in
the return line and in pressure chamber 24.
Referring to FIG. 4, the infra-red diode (D.sub.1) and photo transistor
(T.sub.1) of the forward flow metering unit are identified with the same
reference numbers as in FIG. 1. The photo transistor 12 is connected
through transistor T.sub.3 in an emitter configuration with a mono-stable
vibrator V.sub.1, such that transistor T.sub.2 with input resistor R.sub.2
is coupled; transistor T.sub.2 is in a collector configuration in series
with the infra-red diode. Coupling of transistors T.sub.2 and T.sub.3
causes a current to flow through the infra-red diode the change of which
is proportional to the light intensity at the photo transistor T.sub.1,
leading to a change in the steepness of pulses from the photo transistor,
which are otherwise closer to sine form. The pulses, which are still in
approximate wave form are converted to rectangular pulses by the
mono-stable vibrator V.sub.1 ; the potentiometer R.sub.3 which is in
parallel with the vibrator V.sub.1 permits to calibrate the width of
pulses to compensate for unavoidable production variability in the speed
of measuring wheels.
The measuring circuit for return flow is analogous -- it is not shown in
detail but identified as "Part B." The only difference is that for Part B,
a calibration for production tolerances is not required, as the adjustment
occurs only with respect to the relationship of both fuel metering units.
The constant-time rectangular pulses produced by the mono-stable vibrator
V.sub.1 of both metering units are integrated separately in one condenser
circuit each (R.sub.6, R.sub.7, C.sub.2, resp. R.sub.8, R.sub.9, and
C.sub.3), connected over transistors T.sub.5, resp. T.sub.6, which are
used for ensuring constant pulse amplitude; the condensor circuits are
linked with the comparison circuit V.sub.5 over one amplifier each
V.sub.3, resp. V.sub.4 which transforms impedances. The comparison circuit
V.sub.5 produces an output voltages at both condensors; this is the test
voltage for the indicator which may be an analogue meter 26 or a digital
indicator 27.
The potentiometer R.sub.5 in the integrating circuit T.sub.5, C.sub.3,
R.sub.9, V.sub.3 serves to calibrate the entire stage, whereas the
variable resistor R.sub.10 in the output circuit permits to adjust the
maximum with respect to the final indicator, thus allowing for a simple
calibration.
The modules of circuitry identified in the diagram as Parts A, B and C are
individually tested modules, each of which has a voltage regulator
V.sub.2, resp. V.sub.6. In case of application of the unit as a flow gauge
for large quantities it will be sufficient to connect module Part A. For
simple reading of quantities, it is sufficient to connect this output to a
pulse counter with digital read-out, however, one may also link up an
integrator to obtain a test voltage suitable for analogue read-out.
The drawing illustrates the invention by way of a combined gauge for
measuring consumption of carburetted and fuel-injected engines. However,
it is also possible to design individual gauges to measure either
carburetted or fuel injected engines, to be used as bench sets or in
dashboard applications in vehicles. In that case the device is simplified
in that only the parts required for the task are included. FIG. 5
illustrates, similarly to FIG. 1, one device each for carburetted (5a) and
fuel-injected (5b) engines by means of block diagrams, using reference
numbers corresponding to those employed in FIG. 1. The only difference is
that the gauge for carburetted engines has in place of the lock valve, a
calibrated hole or restrictor 14a; since the return flow is also constant
and calibrated, a metering unit in the return flow can be dispensed with.
The measuring circuitry computes the actual forward flow against a pre-set
volume representing the return flow within the circuit and which
corresponds to the calibrated return flow.
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