Note: Descriptions are shown in the official language in which they were submitted.
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VEHICLE FUEL TANK MANAGEMENT
The invention relates to an engine management system
arrangement typically for a passenger vehicle.
In petrol (gasoline) cars an electronic engine
management system is provided which controls the
operation of fuel injectors supplying fuel to the engine
so as to maximise effectiveness in dependence on load,
speed and other sensed conditions.
In bi-fuel vehicles such as for petrol and natural gas
there is a need to provide electronic engine management
systems for both fuels.
The present invention is concerned with utilising an
engine management system to assist in refuelling such a
bi-fuel vehicle with gas.
According to the invention there is provided a multiple
fuel vehicle management system for operating a motor
vehicle on either gas or liquid fuel during normal road
use and including means for controlling an automatic
refill cycle to fill a gas tank at high pressure from a
low pressure gas supply in response to sensed
information from sensors within the vehicle.
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Further according to the invention there is provided a
method of managing the operation of a multiple fuel
motor vehicle, including the steps of operating the
vehicle on either gas or liquid fuel during normal road-
use and controlling the vehicle when stationary to
provide an automatic refill cycle following receipt of
an initiating signal, the cycle including the steps of
sensing the presence of a gas supply the source and
filling a gas tank with high pressure gas derived from a
low pressure source.
According to a further aspect of the invention there is
provided a program on a carrier for controlling the
operation of gas fuel utilisation vehicle in use, the
program providing a refuelling cycle includes the steps
of detecting the presence of a source of low pressure
gas fuel, detecting the pressure of gas stored within a
tank mounted on the vehicle, determining whether tank
pressure is such as to be capable of replenishment,
providing an operation signal for a compressor to power
up a compressor during a period required to replenish
stored gas fuel and terminating the power up when
detecting pressure meets requirements.
The invention is now described by way of example with
reference to the accompanying drawings in which:
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Figure 1 shows a bi-fuel vehicle with facilities for gas
refuelling with an on-board compressor;
Figure 2 shows aspects of the vehicle in more detail-
including the electronic control mechanism for all three
operations with a single unit;
Figure 3A and 3B shows the flowchart associated with the
refuelling operation; and
Figure 4 shows a more detailed configuration of the on-
board gas compression of the supply.
In a petrol vehicle an engine management arrangement
including an electronic control unit (ECU) controls fuel
injectors which ECU controls the fuel intake and engine
speed and so on, by utilising vehicle sensors and
actuators at various points within the vehicle.
Where bi-fuel capability is required, compressed natural
gas is utilised in addition to the petrol (gasoline) or
diesel liquid fuel.
The arrangement of Figure 1 shows a bi-fuel vehicle 100
with the capability of gas refuelling with on-board
compression and control. The vehicle includes an engine
block 7 with both petrol injectors 2 and gas injectors 6
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associated with an inlet manifold 3. In addition to
accommodating the injectors 2 and 6 the manifold will
accommodate the suction intakes from the brake servo,
petrol tank vapour canister-discharge, engine crankcase
ventilation and the like. Such a manifold is described
in more detail in our copending patent application. A
throttle 5 regulates the air intake to the engine under
the control of the ECU 4.
Gas will pass from gas tank 27 through pipe 15 to the
injectors 2 and petrol will pass from petrol tank 8
through pipe 16 to injectors 6. The petrol tank 8 is
refilled via filler point 14.
The gas stored in tank 27 is at high pressure (typically
200 bar) and this is obtained from a low pressure
source, typically a domestic natural gas source 17 at 1
bar and is made available to the vehicle via a low
pressure quick release hose 12 coupled to the gas
filling point 13 mounted on the vehicle. This low
pressure gas passes through hose 36 and is converted
into high pressure via the compressor 28 mounted in the
region of the gas tank 27. The compressor is operated
using vehicle power as described in more detail below.
The petrol tank 8 at least partially surrounds the gas
tank 27 to act as impact buffer and to provide dual
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fuels storage from a compact source of storage. The gas
tank could typically have a capacity of 17 litres and
the petrol tank a capacity of 50 litres.
The ECU 4 is configured to provide three modes of
operation. The first is to control the provision of
vehicle power using petrol as the fuel. The second is
to control the provision of vehicle power using gas as
the fuel. The third is to control the provision of
vehicle power to drive the compressor refuelling
sequence.
The manner in which this can be achieved is described in
more detail with reference to Figure 2.
In an ECU, used for petrol vehicle control the device
receives information from vehicle sensors and uses this
information to control the petrol injectors. The ECU
determines the flowrate of air via the throttle and the
correct amount of petrol for each cylinder intake stroke
dependent on sensed information. The quantity of fuel
is determined from stored information, known as mapping
or calibration, of the engine speed and load,
temperature, throttle position, ignition timing,
air/fuel ratio, exhaust emissions and other powertrain
sensors specific to the model of engine fitted.
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Such an arrangement is replicated in the present
configuration by the control/processor 22 and the
storage area 23. The control 22 together with stored
mapping controls the petrol injectors via electric-
connections 19. The throttle has the electrical
connection 43. The known engine sensors mentioned above
are shown collectively as being received by input 44.
In the present vehicle, however, two other operations
are envisaged and to keep down costs and size as well as
to maximise control effectiveness, these have been
incorporated into the same ECU 4, by the provision of
additional storage areas 24 and 25 and extended
programming control. The same control 22 (e.g. a
microprocessor) can be utilised for all three functions
as now described. For the sake of simplicity any
interfacing for the sensors and power output stages for
actuating the controls are omitted.
For gas operation, the petrol injectors 2 are no longer
used and the gas injectors 6 come into play. The gas
supplied to the injectors will typically be at a
pressure of 7 bar, having been reduced from the tank
pressure via regulator 20.
The gas injectors operate in a similar manner to the
petrol injectors, but the amount of gas fuel mixing with
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the air will be different for the same set of
circumstances. To accommodate this change, a separate
mapping store 24 is provided. The existing engine
sensors can be employed to provide intelligence on-
conditions to allow the gas mapping to be effective.
Hence the throttle position will be different but the
throttle position sensor will provide an output via
electrical cable 43 to the control 22. The injectors 6
will be pulsed to open a needle valve against spring
pressure using an internal electromagnetic coil within
the injector housing via control cable 19.
The control 22 can be programmed to make the decision as
to which fuel is the most appropriate and this can be
determined from sensed parameters such as load, speed
and fuel capacity remaining. Sensor 27a is provided to
supply information on gas pressure indicative of volume
in the tank 27 via cable 42.
In such an embodiment, the switchover of fuel will be
effected without any noticeable change of handling of
the vehicle by the driver. It may be preferable,
however, to include an indicator device 45 to display to
the driver what fuel source is currently employed.
In addition to the bi-fuel operation, the vehicle has
the capability to allow refuelling at a convenient gas
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supply source at the driver's house, for example. The
driver can initiate the gas refill cycle once the
vehicle is parked and the low pressure hose is connected
to the gas filling point as detected by sensor 13a via-
lead 41. The ECU 4 controls operation of the compressor
28 via lead 46. The compressed gas begins to fill the
tank 27 and pressure information is available to the ECU
from sensor 27a via lead 42. The cycle can be arranged
to be automatic so that replenishment is effected
without further intervention from the driver once manual
initiation is instigated using the stored sequence
information stored in store 25 within the ECU 4.
A flow chart shown in Figure 3A and 3B illustrates the
steps and decisions programmed into the ECU 4 to allow
the automatic sequence to operate.
Although not shown on the flow chart, for simplification
the presence of the low pressure quick release hose and
other parameters could in practice be continuously
monitored during the cycle. After the manual initiation
by means of a designated switch the program follows a
sequence of steps and checks to ensure safe operation
automatically. The detection of an error will trigger
an audible/visual alarm. The visual alarm could
comprise a display unit with indicia relating to the
particular detected event. This could be incorporated
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in an expanded display 45. Hence in operation, for
example if the hose is determined not to be connected
this will result in an indication or prompt on the
display.
The on-board compressor arrangement utilised during the
automatic cycle is described in more detail in Figure 4.
The compressor 28 is a two stage compressor of the type
disclosed in our copending patent application. It
includes a body portion 50 which includes a first
cylindrical chamber 51 and a second smaller cylindrical
chamber 52. Rams A and B are connected by rod 54 and
hydraulic fluid under pressure simultaneously pushes
piston A and pulls piston B during part of the
operational cycle. This allows gas received externally
via coupling 13 and duct 36 to be drawn into chamber 51.
On completion of the stroke, the hydraulic pressure
rises rapidly and a spool valve 34 switches and causes
hydraulic fluid to force the rod 54 in the reverse
direction so compressing the gas in chamber 51.
The compressed gas passes via conduit 55 and valve 56
into the now open chamber 52 to provide a second stage
of compression, once the hydraulic fluid reverses flow
on actuation of the spool valve into its second bi-
stable position. After the second stage of compression
the compressed gas is allowed to exit to the storage
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tank 27. The hydraulic fluid spool valve 34 ensures
that correct passage of the hydraulic fluid is
maintained. The power to drive the hydraulic fluid is
provided by an electric motor 30 via a belt 31 to-
hydraulic pump 29 under the control of the ECU 4. Fluid
passes to the compressor 28 under the switching action
of spool valve 34 to allow second stage compression of
the gas whilst the first stage intake is occurring and
vice versa.
The compressor may be cooled internally by liquid in a
reservoir 35 passing through a radiator 32 and filter 33
in the vehicle engine cooling system. This may be
simplified by using a hydraulic pump 29 designed to
operate with a glycol based fluid so that the coolant in
the engine cooling system can be used directly to power
and cool the compressor without the need for an
intermediate fluid or secondary cooling circuit.
The electrical power is provided by the engine running
to generate electricity via an alternator (not shown).
This avoids draining the battery. It would also be
possible to utilise a hydraulic pump directly linked to
the engine as in the manner employed with a power
steering pump.
The on-board arrangement utilising the common ECU avoids
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long recharging times when a low pressure source of
natural gas is available. A recharge cycle of 30
minutes or less is possible.
Typical gas flowrates and pressures for the on-board
compressor for a passenger road vehicle are given in the
following table.
Gas Refuelling - Engine Driven Two
Stage Gas Compressor
Gas Flow Rate L/min 128
Gas Discharge Pressure Bar 225
Delivered gas volume in '-~ hour L 3,840
cycle
Equivalent petrol volume in 1-~ L 4.65
hour
cycle
Hydraulic oil flowrate L/min 15.7
Compressor interstage pressure Bar 15
Peak hydraulic pressure Bar 268
Hydraulic power input (peak) kW 7.01
The arrangement shown in the example is for a naturally
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aspirated engine. This arrangement could also be
applied to turbocharged or blown systems, where air is
forced through the manifold by an external fan or blower
rather than being drawn into the engine by suction from-
the engine cylinders as each piston performs an intake
stroke, or to more recent engine technologies which
employ air ram and direct fuel injection.
The vehicle ECU will normally be programmed to use the
compressed natural gas as the preferred fuel but in use
where operational load or speed requirements favour the
liquid fuel (e. g. petrol) the system automatically
switches over without noticeable loss of power.
When changing between fuels under load, the ECU can be
programmed to switch in steps such that the gas
injectors switch over in sequence rather than all
together to ensure an smooth changeover over several
engine revolutions between each injector switching.
Hence the switchover may occur over 30 or more
revolutions.
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