Device for temporarily storing volatile fuel constituents and supplying them at a controlled rate to the intake pipe of an internal combustion engine

A device for temporarily storing the volatile fuel constituents contained in the empty space (11) of a fuel tank (10) and supplying them at a controlled rate to the intake pipe (1) of an internal combustion engine (2). A shut-off valve (8) is accommodated in a line (3) that extends through a volatile fuel constituent absorber (9) to the intake pipe of the engine. A sensor (4) accommodated in the line generates a first signal representing the mass flow. An auxiliary component (6) generates a second signal quantitatively representing the valve position of the shut-off valve and compares the first and second signals. The auxiliary component has at least one accessory means (7) for displaying deviations between the first and second signals.

BACKGROUND OF THE INVENTION 
The present invention concerns a device for temporarily storing volatile 
fuel constituents and supplying them at a controlled rate to the intake 
pipe of an internal combustion engine, wherein a shut-off valve is 
accommodated in a line that extends through a volatile fuel absorber to 
the intake pipe of an engine. 
A device of this type is known from the German Patent No. 3,802,664 and the 
U.S. Pat. No. 4,901,702. The device is intended to prevent the volatile 
fuel constituents, always present in the empty space at the top of an 
internal combustion engine's fuel tank, from escaping into the atmosphere. 
The device comprises a special venting line between this space and the 
atmosphere which accommodates a reservoir containing a volatile fuel 
absorber. The absorber usually comprises a permeable mass of activated 
carbon that can temporarily store a considerable volume of volatile fuel. 
The absorber is regenerated by forcing fresh air through it while the 
engine is operating normally. The device therefore also comprises a line 
that connects the reservoir with the engine's intake pipe. It is also 
known to control the mass flow through this line leading to an internal 
combustion engine's intake pipe by means of one or more valves. An 
auxiliary valve is interposed directly upstream of a shut-off valve. The 
auxiliary valve can be closed off by a vacuum-controlled regulator 
governed by the difference between the pressure in a control chamber and 
atmospheric pressure. 
It should be emphasized that controlling the rate at which volatile 
constituents are supplied to the intake pipe of an internal combustion 
engine is of significant importance. It is a prerequisite to unrestricted 
exploitation of the advantages of such a device. When problems with mass 
flow occur in a device of this type, which device comprises many 
individual components, it is impossible to detect and correct them. A 
malfunction on the part of the device has a negative effect on the 
environment due to the creation of engine exhaust pollutants. Uncombusted 
hydrocarbons can escape into the atmosphere as a result of a defective 
line without being noticed by those operating the internal combustion 
engine. The efficiency of the engine can also be affected negatively by 
malfunctions on the part of the device, especially in the form of rough 
engine operation. 
SUMMARY OF THE INVENTION 
A principal object of the present invention is to improve a device of the 
aforesaid type by controlling the rate of flow of the mass of volatile 
fuel components that travel through the line into the intake pipe of an 
internal combustion engine. Taken in conjunction with the regulation of 
the various phases of operation of an internal combustion fuel to the 
combustion chambers accompanied by inclusion of the volatile fuel 
constituents, thereby considerably reducing the potential for 
environmental pollution by the engine. 
This object, as well as other objects which will become apparent from the 
discussion that follows, are achieved, in accordance with the present 
invention, by providing (1) a sensor in the volatile fuel line that 
generates a signal representing the mass flow, (2) an auxiliary component 
that generates another signal quantitatively representing the valve 
position of the shut-off valve, and that compares the first and second 
signals; and (3) at least one accessory means of displaying discrepancies 
between the first and the second signal. 
The device in accordance with the present invention for controlling the 
supply of volatile fuel constituents to the intake pipe of an internal 
combustion engine makes it possible to monitor and affect the mass flow of 
volatile fuel constituents into the intake pipe. Using the sensor with an 
auxiliary component, which can for example be a mechanism for activating 
the shut-off valve, and with accessory means of displaying irregularities 
in the mass flow, it is possible to detect early and to eliminate any 
malfunctions that may occur in the system. When the flow through the 
sensor and into the intake pipe deviates slightly from a reference flow 
that has been defined for ideal operating conditions on the part of the 
internal combustion engine, due to deposits in the auxiliary valve for 
example, the controls will, by regulating the shut-off valve, be able to 
vary the supply of the gas to the intake pipe. The mass flows that act as 
a reference for comparison with the actual mass flows of volatile fuel 
constituents can in a practical way be plotted in a graph associated with 
the auxiliary component. 
The references for the mass flow into the internal combustion engine's 
intake pipe can constantly be compared by the auxiliary component with the 
actual flow by way of the signal obtained by the sensor. If the 
discrepancies between the two values exceed an arbitrarily prescribed 
tolerance, the auxiliary component will activate the shut-off valve. How 
rapidly the shut-off valve responds to a control signal from the auxiliary 
component is decisive for adaptation to the dynamic procedures within the 
device. The more rapidly the shut-off valve responds to a control signal 
from the auxiliary component, the more advantageous will be the 
effectiveness of the device in relation to exhaust emissions and the 
efficiency of the internal combustion engine. When discrepancies between 
the reference and actual values for the mass flow can no longer be 
compensated, this situation can be determined from the accessory which 
provides the display. 
According to a preferred feature of the invention, the sensor is upstream 
of the absorber and the shut-off valve. The advantage is that the sensor 
is easily accessible and is not near the intake pipe. If any defect in the 
form of a leaking or disconnected hose occurs at any point in the device, 
the volatile mass flowing through the sensor will decrease. The resulting 
discrepancy between the actual and reference values will be detected by 
the auxiliary component and, if the discrepancy cannot be corrected, 
displayed on the display. 
According to another preferred feature of the invention, the sensor can 
transmit a signal to the shut-off valve to activate it by way of the 
auxiliary component. The shut-off valve continuously transmits a signal to 
the auxiliary component as long as the internal combustion engine is in 
operation. The signal from the sensor activates the shut-off valve by way 
of an auxiliary component, for example in the form of a control device. 
According to still another preferred feature of the present invention, the 
auxiliary component can accommodate means of suppressing the display of 
discrepancies which are less than an arbitrarily prescribed threshold. The 
accessory means, which can be a display for example, will accordingly 
provide the information only in the event of critical discrepancies 
between the reference value and the actual value of the mass flowing 
through the line into the internal combustion engine's intake pipe. This 
approach provides a better overview in monitoring the device's operation 
and makes it easier to control. 
The preferred embodiments of the present invention will now be described 
with reference to the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A device for supplying volatile fuel constituents to the intake pipe of an 
internal combustion engine at a controlled rate operates as described in 
the aforementioned German Patent No. 3,802,664 and U.S. Pat. No. 
4,901,702, for example. 
In addition to the components described in that patent, a sensor 4 is 
positioned upstream of an absorber 9 containing granulated active carbon 
and a shut-off valve 8. Sensor 4 communicates by way of a signal line 5 
with an auxiliary component 6 in the form of an electronic control unit 
and supplies it with a signal representing the actual state of mass flow. 
A graph of the mass-flow reference parameters can be stored in the control 
unit 6. Once a discrepancy between the actual and reference values has 
attained a certain magnitude, this discrepancy is displayed on an accessor 
means 7. Meanwhile, the control unit 6 activates a shut-off valve 8 in an 
attempt to make the two values coincide. If this attempt is successful, 
the display on accessory means 7 is removed. The control unit 6 can also 
accommodate additional means that will not allow shut-off valve 8 to be 
activated and a display to be indicated on accessory means 7 until a 
prescribed interval of time has elapsed subsequent to the occurrence of 
the discrepancy. This arrangement provides time for minor irregularities 
in the device, or operations already carried out in relation to shut-off 
valve 8, to stabilize. 
FIG. 2 illustrates the structure and operation of the auxiliary component 
or engine control unit 6. This unit includes a conventional engine control 
which receives various temperatures, the engine RPM, the injected fuel 
quantity and/or values from the lamda probe as inputs. The output values 
of the engine control include the desired value, which can be stored in 
the performance graph of the engine control unit, and a correction value 
which influences the desired value. The correction unit shown in FIG. 2 
is, in actuality, a part of the engine control unit. Its purpose is to 
adjust the desired value stored in the performance graph in dependence 
upon the input data that reflect the operating condition of the engine, 
for example the engine RPM, and various temperatures measured at different 
points. 
The corrected value is subtracted from the desired value at a node 12 to 
produce a corrected desired value. This corrected value is supplied to a 
subtraction node 13 which also receives the actual value from the sensor 
4. The corrected desired value is also supplied to a comparator 14 which 
causes the accessory means 7 to display a discrepancy when a prescribed 
threshold value is exceeded. 
Simultaneously, the difference between the actual and the corrected desired 
value are passed through a regulator and amplifier to actuate the shut-off 
valve 8. 
The engine data, which are shown as input signals to the engine control 
unit in FIG. 2, are received as actual values, are stored in the engine 
control and compared with the fixed desired value stored in the 
performance graph by means of at least one comparator (included in the 
engine control and therefore not separately shown in FIG. 2). Deviations 
from the desired value may be caused by lamda deviations (for example, a 
too-rich mixture), by strongly varying ambient temperatures or other by 
external influences. If the actual values do not correspond to the desired 
values which are stored in the performance graph, the correction comes 
into play and influences the fixed desired value. This corrected desired 
value forms the output signal of the subtraction node 12 which is compared 
with the actual value of the mass flow through the shut-off valve 8. 
There has thus been shown and described a novel device for supplying 
volatile fuel components at a controlled rate to the intake pipe of an 
internal combustion engine which fulfills all the objects and advantages 
sought therefor. Many changes, modifications, variations and other uses 
and applications of the subject invention will, however, become apparent 
to those skilled in the art after considering this specification and the 
accompanying drawings which disclose the preferred embodiment thereof. All 
such changes, modifications, variations and other uses and applications 
which do not depart from the spirit and scope of the invention are deemed 
to be covered by the invention, which is to be limited only by the claims 
which follow.