EP0191170A1 - Fuel vapour purging device for a fuel tank - Google Patents

Abstract

Device for venting fuel tanks in internal combustion engines or the like, fuel vapors being formed being taken up in a buffer store containing an activated carbon filter and being released into the intake area of the internal combustion engine depending on the operating conditions. The delivery takes place via an electrically controlled tank ventilation valve by continuously changing its passage cross section, which is achieved by changing the duty cycle of the control pulse sequence for this valve. The duty cycle can be determined in the sense of a pure control from a map as a function of the speed and load of the internal combustion engine, or taking into account preferably averaged lambda values, the aim being to reduce the passage cross section of the tank ventilation valve when the mixture becomes richer. Furthermore, an adaptive feedforward control is provided which intervenes in the calculation of the fuel quantity to be supplied or in the calculation of the fuel injection signal with a correction value (ATE) and switches to limit value control when predetermined mixture proportions are reached. The basic adaptation in the lambda control circuit for the fuel supply calculation is only released if the fuel quantities from the tank ventilation are negligible.

Description

State of the art

The invention relates to a device according to the preamble of the main claim. In internal combustion engines, it is known for tank ventilation that, due to and depending on certain parameters (fuel temperature, quantity, vapor pressure, air pressure, flushing quantity ...), fuel vapors not only vent to the outside, but rather feed them to the internal combustion engine, usually so that a buffer filled with activated carbon is provided, which absorbs the fuel vapors that form, for example when the vehicle is stationary, and feeds it to the intake area of the internal combustion engine via a line. In this context, it is also known to increase the possible increase in exhaust gas emissions by such an additional quantity of fuel / air mixture attributable to the tank ventilation prevent or keep it small by allowing the tank ventilation only in certain operating states of the internal combustion engine (see Bosch "Motronic" - technical description C5 / 1 from August 1981-, DE-OS 28 29 958).

The intermediate storage container containing the activated carbon filter is able to store fuel vapors up to a certain maximum amount, the filter being flushed during engine operation by the vacuum developed by the internal combustion engine in the intake tract, for which purpose the filter has an opening to the outside air. Therefore, if you only allow the buffer to be flushed under certain operating conditions, an additional fuel-air mixture that can be traced back to this tank ventilation results, which, as a mixture that has not been measured or cannot be measured with reasonable effort, results in the fuel metering signal that is normally produced very precisely with a high degree of computation a fuel injection system, the duration of the injection control command t _i - and the resulting quantity of fuel supplied to the internal combustion engine falsifies. Such, in particular also the driving behavior influencing under certain conditions, additional fuel amount ^g in extreme cases as Tankentlüftun may consist of almost 100% air or 100% fuel vapor SGE mixed well, is also not acceptable when going through the influence of this disturbance variable pneumatic actuators directly relates to the intake manifold pressure developed by the internal combustion engine or the supply of the tank ventilation mixture through an electronic on / off control for particularly sensitive loads drive conditions, such as idle, completely excluded.

The invention is therefore based on the object of providing a device which can supply the tank ventilation mixture, which cannot be predetermined in terms of its proportions or quantities, to the intake tract of the respective internal combustion engine in such a way that, on the one hand, there is effective ventilation of the buffer store, and on the other hand but does not have any disruptive influence on the operation of the internal combustion engine, especially in the case of fuel metering devices operating under the influence of a lambda control, for example fuel injection systems or controlled carburetors or the like, no disturbance variables are superimposed in such a way that the control is brought to a stop or in the case of adaptive ones Pilot control systems due to longer-term deviations in the controller output, which are nevertheless only due to the additional influence of the tank ventilation mixture, pilot control corrections are introduced that permanently disrupt the adaptation behavior.

Advantages of the invention

The invention solves this problem with the characterizing features of the main claim and has the decisive advantage that the tank ventilation influence is removed from the area of arbitrary connections and is deliberately fine-tuned to the respective internal combustion engine behavior with continuous change of the maximum quantity to be supplied, in particular The area of the tank ventilation is also controlled and regulated depending on the lambda regulation of the operating mixture which is already present in internal combustion engines, so that negative influences are neither possible on the driving behavior nor on the regulation.

It is particularly advantageous to control the tank ventilation in the sense of a pre-control from a load-speed map, this pre-control then being made even more dependent on the lambda control factor.

Advantageous further developments and improvements of the device specified in the main claim are possible through the measures listed in the subclaims. It is particularly advantageous to introduce an additional limit control, or one that is effective alone in connection with the load-speed characteristic map, around the limit of a minimum permissible lambda control factor and, finally, an adaptive precontrol of the tank ventilation, which adjusts to one at start, overrun cutoff and with inactive lambda control Minimum value is set, and also also a limit control around the limit of a minimum permissible adaptation value.

In this case, caused by the tank ventilation deviation of the control factor from the set point causes a runaway of a correction value, which then so in the calculation of the injection signal, _it hi applied to a fuel injection system, is taken into account that compensated irrespective of load and speed, a constant fuel or air flow becomes. In this way it is possible to determine the influence of the tank ventilation on the lambda control and the associated adaptation of the pilot control switch off the fuel injection signal. With changes in the tank ventilation mixture composition and with load changes, an impairment of driving behavior can therefore be avoided.

It is also advantageous that the tank ventilation valve in the tank ventilation line between the filter and the suction tract is periodically controlled by the associated control unit, the period resulting from the change between opening and closing the valve and a variation of this ratio of opening time to closing time (which corresponds to the duty cycle corresponds to the tank ventilation control) a corresponding adjustment of the tank ventilation mixture quantity can be achieved. In this way, depending on the lambda control factor, tank ventilation can also be incorporated and implemented in the overall behavior of the internal combustion engine over a wide range.

drawing

Embodiments of the invention are shown in the drawing and are explained in more detail in the following description. 1 shows the basic principle of tank ventilation with tank ventilation valve with a continuously changeable opening cross section and electronic control unit, FIG. 2 shows the approximately linear course of the characteristic curve of the tank ventilation valve over the pulse duty factor of the control pulse sequence, FIG. 3 shows a tank ventilation characteristic Field for precontrolling the duty cycle of the control pulse sequence for the tank ventilation valve via load and speed, Fig. 4 shows the characteristic curve of the mean value of the lambda control factor for lambda control-dependent control of the tank ventilation, Fig. 5 characteristic curves of the duty cycle, tank ventilation and lambda control factor over time in each case with pure control via the tank ventilation map and additionally with a control dependent on the mean value of the lambda control factor, Fig. 6 shows the characteristic curve of the duty cycle of the control pulse sequence, the tank ventilation and the average value of the lambda control factor over time with pilot control via the tank ventilation map and Additional limit control, Fig. 7 schematically shows the block diagram of the tank ventilation with pilot control map and optional additional intervention of a lambda control-dependent control and a limit control, Fig. 8 shows another schematic block diagram of an adaptive tank Ventilation control with possible influence on the fuel quantity supplied by the internal combustion engine, Fig. 9 curves over the time of the tank ventilation curve, the duty cycle of the control pulse sequence, the adaptive pilot control for tank ventilation and the lambda control factor and Fig. 10 the area of the tank ventilation adaptation in the load speed diagram.

Description of the embodiments

In Fig. 1, a fuel tank or tank 10 is ge shows which is ventilated and vented exclusively via an activated carbon filter located in a temporary storage container 11, the fuel evaporating from the tank being stored in the activated carbon filter up to a limited maximum amount. This stored fuel is then sucked into the engine while the internal combustion engine is running - only the intake area 12 with the throttle valve 12a is shown in FIG. 1. The metering of the fuel extracted from the area of the tank ventilation or of the fuel air mixture formed there, the proportions of which cannot be determined, takes place via a special tank ventilation valve 13 such that in all operating states of the system there is no impairment of driving behavior and exhaust gas behavior and no impairment of the control circuits involved in the fuel metering and adaptive systems occurs.

The control of the tank ventilation valve 13 takes place on its magnetic part 13a by a control unit 14, which outputs a control pulse sequence with a variable pulse duty factor TV, whereby a suitable variation of the opening cross section of the tank ventilation system 13 can be set. The characteristic curve of the tank ventilation valve 13 between the minimum flow rate Qmin and Qmax over the pulse duty factor can be approximately linear, possibly also exponential, which can be included in the calculation.

The following information relates to the specific numerical data of a suitable tank ventilation valve depending on the duty cycle of the control pulse sequence continuously variable passage cross section.

The tank ventilation valve is advantageously based on the solenoid principle, which is open when de-energized and controlled by a suitable pulse frequency pulse sequence of 10 Hz. This results in a maximum throughput of 2 <Q54 m ³ / h and a minimum throughput at the same pressure difference of 0 <Q ≦ 0.1 m ³ / h, with a pressure difference Ap = 20 mbar, in this preferred exemplary embodiment the one that can be produced via the pulse duty factor Variation between Qmin and Qmax is 1:20. A corresponding characteristic curve is shown qualitatively in FIG. 2.

For the other functions of the tank ventilation TE, reference is made to the block diagram of FIG. 7; Here, a first embodiment, which is also of independent importance from other, possibly supplementary and supportive control and regulation options for tank ventilation, includes the control of the tank ventilation valve via a tank ventilation map or pilot control map, which is dependent on the load (shown as pilot control Injection pulse t _L here a fuel injection system) and the speed n via 4x4 support points with the possibility of interpolation each outputs quantized duty cycle variables and feeds, for example, a multiplier 15 for the tank ventilation valve control. In the illustration in FIG. 7, such a pilot control map is denoted by 16 and is shown in FIG. 3 as a diagram, the map is to be interpreted so that the percentage enrichment of the current supplied to the internal combustion engine combustion ^g EMI ULTRASONIC at a given TE-mixture in all areas is the same.

In this context, it is pointed out that the following explanations essentially relate to the application of the tank ventilation to a fuel injection system, so that common names for the injection are used in the following. As a result, however, the invention is not restricted to the assignment to a fuel injection system, but rather includes the possibility of use with any fuel metering devices for internal combustion engines.

The duty cycle of the control pulse sequence for the tank ventilation valve can be quantized continuously or in steps of, for example, 10% each in the range between 0 and 100%. In Fig. 7, the control of the further processing point 15 from the pilot control map 16 is shown via a switch S1, which is useful so that in certain operating states (idling, overrun cut-off) the tank ventilation can be completely prevented, if necessary, or also to do without to allow the pilot control map control to take effect other control and regulating methods to be explained below.

7 also shows the lambda control loop for generating the fuel metering signal for better understanding the internal combustion engine 17, in this case, a spark-ignition internal combustion engine (Otto motor) having fuel injection, wherein in a multiplier 18, from the output signal of a load sensor, not shown, for example, an air flow meter and a rotation _- generated number generator a load signal, namely, an injection time signal t and a further, downstream multiplier stage 19, ultimately for the control of the injection valve or valves. A correction factor F _{R is} applied to the injection time duration at the multiplier stage 19, which is generated as a lambda correction factor behind a comparator 20 from the actual lambda value generated by the lambda probe 21 and a lambda target value from a lambda controller 22.

In an advantageous embodiment of the present invention, this lambda correction factor F _R , which is present anyway on the basis of the lambda control loop, is used in order to make possible a lambda control-dependent control of the tank ventilation as well.

For this purpose, the averaged value F _{R of} the lambda correction factor generated via an interposed low-pass filter 23 is used and also reaches the multiplication point 15 for the TE valve control via a characteristic curve block 24.

The characteristic curve of the tank ventilation change or influencing above the mean value of the lambda control is again shown separately in FIG. 4 and comprises four support points with interpolation, the The basic function is that an increasing enrichment of the tank ventilation mixture (TE mixture) is recognized via the mean value F _{R of} the lambda correction factor, since this shifts to lower values, and the tank ventilation is closed accordingly by a corresponding change in the duty cycle of the control pulse sequence for the tank ventilation valve becomes.

Finally, the block diagram of FIG. 7 also contains a second possible variant for characteristic curve mean value control, which can be used as an alternative to this and comprises limit value regulation of the mean value of the lambda correction factor. For this purpose, a further comparison point 25 is provided, to which a limit value F _{RGW of} the mean value of the lambda correction factor is supplied, together with the actual value mean value F _{R of} the correction factor. Via a switch S2, the comparison result is sent to a comparator 26, which decides whether the mean value F _{R of} the correction factor is above or below the predetermined limit value; depending on the result, a downstream integrator 27 is driven as an I controller for limit value control with appropriate polarity, the output signal of which is then likewise fed to the multiplication point 15.

The functions resulting from the possible tank ventilation control method are explained below with the aid of the diagram profiles in FIGS. 5 and 6.

The diagrams show on the left 5 shows the states which result from the pilot control map 16 with pure control; assume that the duty cycle of the controller is at 0.25 due to the speeds and load values; occurs at a predetermined time t ₁ (see diagram b) of Fig. 5) a sudden increase in the fuel content in the TE mixture (illustrated by three different curves (1); (2); (3)), then the reacts Control via the pilot control map thereon not at all and the lambda correction factor F _R only shifts correspondingly in the direction of lean chemical mixing as a result of the "fuel cloud" (theoretical jump function) in the TE mixture (see c) of FIG. 5), ie the regulator is emaciated.

This is different with the diagram courses on the right side of FIG. 5; If you also assume a duty cycle of 0.25 from the map control here, then the influence of the F _R -dependent control results in lower duty cycle values, depending on the fuel cloud in the TE mixture, as in (2) and (3) shown; this change in the duty cycle results from the pilot control component above the characteristic block of the mean value lambda control and also shows a less severe drop in the lambda correction factor F _R in c).

The effect of the limit value control, shown in the diagrams of FIG. 6 at a), b) and c) without an F _F -dependent control, is such that the tank ventilation TE via the duty cycle of the control pulse sequence from the pilot control map of the tank ventilation KFTE of the block 16 (maximum) is open (Numerical value at a) in FIG. 6: TV = 0.25) until the TE fuel enrichment to an assumed value of 100% in this case results at time t ₁ (see b) of FIG. 6).

According to the characteristic curve at c) of FIG. 6 for the lambda correction factor (= solid line following a triangular curve, the mean value F _{R of} the correction factor being shown in dashed lines in this diagram), the enrichment which is now brought about by the tank venting shifts the mean value F _R beyond the limit value GW, which occurs at time t ₂ . From here, the pulse duty factor of the control pulse sequence is then (increasingly) closed via the I controller 27, that is to say decreases until the mean value F has returned to the limit value by the time t ₃ ; From this point in time, the pulse duty factor increases again in accordance with the adjustment of the I-controller 27, whereby multiple oscillations, as shown at c) in FIG. 6, can also result around the limit value GW until the cloud formation has subsided at the time t ₄ and mean F _R and duty cycle return to the previous values.

It is understood that the time constant of the I-controller 27 for the tank ventilation must be greater than the time constant of the I-controller of the Lambda control for the fuel metering or the calculation of the fuel injection pulses known per se, one for the entire speed / load range constant time constant is sufficient for the tank ventilation. Furthermore, it should for the I-controller, a Maximalbegrenzun ^g I _TEmax provided and the quantization of the I controller be about four times finer than the output quantization for the duty cycle.

The overall function of the tank ventilation in accordance with the block diagram of FIG. 7 can therefore look like the two following formulas alternatively indicate and the alternatively provided additional control options occur via the mean value of the lambda control or the limit value control in addition to the map control:

• 1. Die Ausgabe des Tastverhältnisses TV ist unterbunden (TV = 0), also die Tankentlüftung gesperrt, wenn
  • a) die Lambda-Regelung der Brennkraftmaschine selbst unwirksam ist,
  • b) der Betriebszustand Schubabschneiden vorliegt oder
  • c) gegebenenfalls bei Leerlauf.
• 2. Erfolgt die Kraftstoffzuführung oder -dosierung, etwa bei einer Kraftstoffeinspritzanlage mit adaptiver Vorsteuerung der Lambda-Regelung (LRA), dann würden diese beiden Funktionen (LRA und TE) sich gegenseitig beeinflussen und zu einem Fehlverhalten führen. Die TE ist daher abzuschalten, wenn LRA aktiv ist oder umgekehrt, die adaptive Lambda-Regelung ist abzuschalten, wenn die Tankentlüftung TE aktiv ist.
• 3. Dabei können noch folgende Bedingungen gelten:
  • a) Bei Start mit Motortemperatur T_MOT ^< 30° und T_ANS < 30° ist die Tankentlüftung TE für ca. 10 Minuten geschlossen; währenddessen ist die erwähnte adaptive Vorsteuerung der Lambda-Regelung (LRA) aktiv.
  • b) Es schließt sich eine TE-Phase von ca. 5 Minuten an, dann wird TE mit Änderungsbegrenzung geschlossen. Unter Beachtung des Korrekturfaktors FR wird dann, wenn die Abweichung ΔF_R > 5 % vom Normalwert F_R = 1 ist, die LRA aktiviert und abgewartet, bis ΔF_R ^< 5 % ist oder maximal 5 Minuten vergangensind. Anschließend kann die TE wieder mit Änderungsbegrenzung zugelassen werden.

The following boundary conditions must generally be observed as switch-on conditions:

• 1. The output of the duty cycle TV is prevented (TV = 0), ie the tank ventilation is blocked when
  • a) the lambda control of the internal combustion engine itself is ineffective,
  • b) the operating status of thrust cutting is present or
  • c) if necessary at idle.
• 2. If the fuel supply or metering takes place, for example in a fuel injection system with adaptive pilot control of the lambda control (LRA), then these two functions (LRA and TE) influence each other and lead to misconduct. The TE must therefore be switched off when LRA is active or vice versa, the adaptive lambda control must be switched off when the tank ventilation TE is active.
• 3. The following conditions may also apply:
  • a) When starting with engine temperature T _MOT ^< 30 ° and T _ANS <30 °, the tank ventilation TE is closed for approx. 10 minutes; the aforementioned adaptive feedforward control of the lambda control (LRA) is active in the meantime.
  • b) A TE phase of approx. 5 minutes follows, then TE is closed with a change limit. Taking the correction factor FR into account, if the deviation ΔF _R > 5% from the normal value F _R = 1, the LRA is activated and waited until ΔF _R ^< 5% or a maximum of 5 minutes have passed. The TE can then be permitted again with a change limit.

A further, preferred embodiment of the present invention includes the possibility of additionally adaptively designing the tank ventilation TE, in simple terms, to design the components, switching means, regulating and control processes involved in the tank ventilation in such a way that what the tank ventilation brings to the mixture for the internal combustion engine , is subtracted from the actual mixture formation (basic adaptation), so to speak, which is also a particular advantage Such mixture preparation systems and fuel injection systems, which themselves have an adaptive feedforward control for lambda control and in which tank ventilation can therefore cause certain difficulties insofar as this adaptive feedforward control (basic adaptation) takes the longer-term deviations of the controller output (lambda controller) as a measure for one Correction of the pilot control used - the invention in the configuration to be explained below enables the advantages of adapting the pilot control in the lambda circuit to be maintained and extended to the tank ventilation.

The block diagram of FIG. 8 therefore shows schematically and without going into special detailed solutions, in the upper area the lambda control circuit for the mixture preparation, for example by a fuel injection system with basic adaptation, and in the lower part the extension of the basic principle to adaptive pilot control of the tank ventilation. The same elements and components as in the block diagram of FIG. 7 are provided with the same reference numerals, since the adaptive pilot control of the tank ventilation continues to use at least partial areas of the block diagram representation of FIG. 7, for example the basic principle of the pilot control map 16 when certain limit values are reached or there , where a TE feedforward control adaptation is not used, which will be explained further below with reference to the representation of FIG. 10.

8 is that of the actual value setpoint comparison point 20 for the output signal of the lambda probe downstream lambda controller again designated 22; the lambda correction factor F _R is led to an intervention point 19 ', where, multiplicatively or additively, preferably multiplicatively, an effective injection time period t _L · π _i · F _i generated by other components of the mixture preparation system, for example a fuel injection system, is supplied.

A further intervention in the injection period then takes place at 30; this intervention serves or is represented representatively for adapting the pilot control (basic adaptation). For this purpose, the output signal F _R of the lambda controller is smoothed 22 via a low-pass filter 23, that is subjected to averaging and the smoothed or average value signal F _R of the correction factor is run according to a comparison point 31 via a switch S3 to the base adaptation block 32, which typically is a controller. In a downstream multiplier block 33 there is also a multiplication by a normalized speed value; memory (not shown) can also be provided, which temporarily stores the value of the basic pre-control adaptation, for example, for periods during which a lambda signal is not available, for example due to an inactive lambda probe.

The controller 32 for the basic adaptation adjusts its output variable for the multiplicative or additive factor resulting at the point of engagement 30, which originates from it, until the mean value of the output variable of the lambda controller 22 matches the setpoint at the comparison point 31, which is preferably the assumes neutral value 1, corresponds. It is understood that these pilot control basic adaptation various correction values - proportional to speed, drehzahlunabhän- gi ^g, which can be engaged depending on the load state of the internal combustion engine additively or multiplicatively correcting the calculated injection time period comprise, what is not shown.

The adaptive pilot control of the tank ventilation, which is assigned to the pilot control adaptation of the injection duration, initially comprises a logic circuit or sequence control circuit, which is represented at 34 as representative of all conceivable embodiments, also as a software version, and an associated block 35 for the TE adaptation, which alternatively, the mean value of the lambda correction factor F _{R is} applied via the switch S3 already mentioned. Therefore, in this exemplary embodiment the control factor F _{R is} used to intervene in the tank ventilation, an adaptation to the load value t _L , for example additively, would of course also be conceivable.

Furthermore, to block 35 for TE adaptation information from block 34 of the sequence control TE, mainly via the duty cycle of the control pulse sequence for the tank ventilation valve 13, active lambda control, transition to pilot control map and the like. The result of a limit value detection block 36 from the output of the TE adaptation block 35, at which a value of the adaptive pilot control for tank ventilation (ATE) is present, is whether this correction factor ATE (adaptation value) has a negative threshold value (ATEmin) or has reached a positive threshold value ATEpos, which threshold values can also be referred to as fat or lean. The adaptation value ATE passes through an intermediate multiplier 37, at which, in order that the two intervention values of the basic adaptation and the TE adaptation are equivalent, a standardized speed value is supplied, and via a switch S4 to a further intervention point 38 in the course of the preparation where multiplicative or additive interventions can be made.

A multiplier 39 with a speed value n is then connected downstream, so that a fuel / time-air mass / time mixture information is obtained at an addition point 40, which is then fed to the TE mixture at point 41.

In this case, the tank ventilation line 42 carrying the TE mixture from the tank ventilation valve 13 in front of the throttle valve can be connected to the intake tract of the internal combustion engine, as a result of which the amount of the extracted TE mixture remains approximately constant while the cross section of the TE valve 13 remains the same, since the negative pressure in front of the throttle valve is approximately constant and the amount increases with the root of the negative pressure. In fact, the negative pressure varies somewhat over load and speed even in front of the throttle valve, so that the opening of the TE valve 13 in the map 16 KFTE = f (n, t _L ) mentioned earlier must be corrected somewhat in order to obtain a constant amount Q _TE to reach. A constant amount is also helpful for adaptive control as it is through an additive correction worth can be compensated. As mentioned, the following equations apply:

If the TE mixture was likewise introduced behind the throttle valve - this will be discussed further below with the aid of a table - the vacuum and thus the quantity would vary considerably more so that especially when idling, where the tank ventilation can be particularly troublesome, this amount of TE would be the greatest and with increasing load, where it is less and less disturbing, the amount of flushing would be less and less.

Based on the block diagram of FIG. 8, the following basic functions apply.

The deviation of the lambda control factor from the target value F _R = 1 causes a correction value to run away, which is included in the calculation of the injection signal in addition to the air quantity, as explained further above, so that a constant fuel or air quantity is independent of load and speed is compensated (adaptive feedforward control). 8 then results for

The tank ventilation is activated at the start, when the overrun is switched off and set to a minimum value when the lambda control is inactive; a defined mixture should enable starting and reinsertion after overrun fuel cutoff.

The further course of the adaptive pilot control in the case of tank ventilation in accordance with the block diagram of FIG. 8, including the information from the pilot control map, is explained in more detail below with the aid of the curves of FIG. 9 "time course of the tank ventilation"; these functional details are therefore part of the overall inventive concept for tank ventilation.

If the lambda control is active, that is to say the switch S5 in front of the lambda controller 22 is closed, a corresponding signal also reaching the sequence control 34, then the TE control starts softly and the duty cycle of the tank ventilation TVTE becomes, as in b) in 9, shown in a ramp shape, but with change limitation 1, increased starting from a predetermined minimum value TVTEmin1. The slope of the duty cycle of the control pulse sequence for the TE valve is chosen so that the pilot control to be explained further below can compensate for the resulting disturbance in the mixture balance of the internal combustion engine in good time.

The deviation of the lambda control factor caused by this change - compare the curve at a), where a fuel share in the TE mixture of 100% (as required) is assumed at the time of the TVTE increase, from the target value F _{R =} 1 (compare 9) in the direction bold causes the correction value to run away, which then

is included in the calculation of the injection signal in such a way that a constant amount of fuel or air is compensated for regardless of load and speed, so that the adaptive pilot control results in tank ventilation - see 9 also shows the course of the adaptation value ATE at c) in FIG. 9, which rises to a maximum negative value ATEmax and, as already explained further above in the block diagram in FIG. 8, acts on the lambda control as adaptive pilot control in the case of tank ventilation.

The pulse duty factor is increased until the adaptation value ATE has reached a minimum negative threshold value ATEmin, which can also be referred to as a lean stop in relation to the adaptation value. A limit control then starts. In addition, the duty cycle TVTE may already have reached a pre-control stop value at t ₁ , which can result from the pre-control map; the pulse duty factor is therefore no longer changed until time t ₂ , at which the negative threshold value ATEmin is reached. Then, starting at t ₂ , the pulse duty factor TVTE is decremented until it falls below the threshold mentioned again (in the positive direction). From then on, the duty cycle is incremented again until the threshold is exceeded again in the negative direction, etc. In this way, there is a continuous oscillation (limit control) around the negative minimum value (predetermined lean stop), with the change limitation in the adjustment of the duty cycle like an integral Share (ITE) works, therefore it surrenders

In general, the fuel from the intermediate store decreases with increasing operating time, so that with this limit value control the pilot control value from the characteristic map 16 is reached and therefore the pulse duty factor remains constant for a predetermined period of time during which the adaptation value ATE runs from the negative stop in the positive direction .

If the adaptation value reaches a positive threshold value ATEmax (fat stroke), then this means that the filter has been rinsed sufficiently - the two threshold values are sent to the sequence control 34 via the threshold value block 36 - and the pulse duty factor is then gradually changed to a second one from time t ₃ Minimum value TVTEmin2 driven.

At the same time and after reaching this minimum value, it is then possible to enable the basic adaptation via block 32 (= adaptation without TE) by switching switch S3 for a predetermined (programmable) time (on the order of a few minutes).

After this time has elapsed, the TE mixture is checked by the control process just explained beginning in block 34 with the regulation of the duty cycle from the beginning - it should also be pointed out here that the reduction of the duty cycle with a change limit 2 to the minimum value TVTEmin2 er follows, which enables a faster change in the duty cycle to small passage cross-sections of the tank ventilation valve.

This adaptation of the tank ventilation pre-control is expediently limited to a load-speed range which is effective only below an air volume threshold, as shown in FIG. 10, since it can only be calculated precisely enough in this range. Moreover, the adapted value ATE is expediently only stored in a memory, not mentioned, assigned to block 35 of the TE adaptation, when the engine is running — for use, for example, in the case of an inactive 2-probe in the meantime — deleted again when the engine is switched off.

The TE precontrol adaptation is interrupted above the range indicated in FIG. 10, and the last adapted value ATE is temporarily stored in the memory (not shown) assigned to block 35. Above the effective range of the TE pilot control adaption according to Fig. 10, so much tank ventilation mixture can be output via the KFTE map that the influence on the lambda control can be neglected (the TE amount is proportional to the air volume), so that in this section the Basic adaptation can also be effective during the tank ventilation - in other words, the switch S3 is switched to the block 32 in this case, which can also be done by the sequence control 34 by evaluating the corresponding load and speed information.

ständnis anhand eines Blockschaltbilds unter Verwendung von Einzelkomponenten erläutert wurde, auch eine softwaremäßige Ausführung der erfindungsgemäßen Einrichtung mittels eines Mikrorechners oder Mikrocomputers ohne weiteres innerhalb des erfindungsgemäßen Rahmens liegt und durchgeführt werden kann; eine solche Ausführungsform stellt für den Fachmann auf dem Gebiet der Kraftstoffzumessung bei Brennkraftmaschinen kein Problem dar; da er notfalls auch Fachleute auf dem Gebiet der Datenverarbeitungstechnik heranziehen kann.The sequence control for the activation of the tank ventilation valve in the form of a flow chart indicated on the next page 25 specifies the function of the sequence control 34 in software terms. It is therefore understood that, although the invention is intended to improve the

was explained on the basis of a block diagram using individual components, and a software version of the device according to the invention by means of a microcomputer or microcomputer is easily within the scope of the invention and can be carried out; such an embodiment is not a problem for the person skilled in the field of fuel metering in internal combustion engines; because if necessary he can also call in specialists in the field of data processing technology.

The following variants of the pre-control of the tank ventilation are also mentioned and are clearly summarized in the table on page 30.

1. To achieve a constant amount of TE per time (variant 1.1), the tank ventilation line in front of the throttle valve is fed to the intake tract, as already explained earlier. In this case, since the amount of extracted TE mixture is approximately constant with the cross-section of the tank ventilation valve remaining the same, in order to implement the functions and values mentioned above, it only needs to have a comparatively small variability to comply with the minimum and maximum values, which is around 1:20.

The other alternatives for pilot control are summarized according to the various evaluation criteria in the form of the table-like decision matrix mentioned earlier (p. 30).

Variation 1:8 folgt:

2. In order to achieve a constant relative TE error (Var. 1.2), the tank ventilation in front of the throttle valve is also initiated here. The map is designed so that the TE quantity is proportional to the air volume (up to a certain maximum air volume, approx. 10 times the idling volume). Then the relative error in this load and speed range is constant. However, the flush volume in the idle area is relatively small; with:

Variation 1: 8 follows:

3. To achieve a constant TE quantity per revolution (Var. 2.1), the tank ventilation would have to be introduced behind the throttle valve in the intake manifold, although the vacuum would vary considerably more. With increasing negative pressure, the flow is then no longer laminar, but in any case turbulent, until the critical pressure ratio is reached, at which the flow reaches the speed of sound; at a supercritical pressure ratio, the quantity is constant. The calculation for this is complex, and the following information is only a rough estimate based on the assumption that the Bernoulli equation holds.

On the one hand, the TE valve has to cope with a much larger variation to the above To comply with minimum and maximum quantities, namely one

On the other hand, in order to ensure that the error caused by the tank ventilation per revolution is constant, the tank ventilation map should have a greater variation, which is helpful for an additive adaptation - here additive to t _L ).

The following then approximately applies:

4. To achieve a constant pilot control value (variant 2.2), the tank ventilation is also initiated in the intake manifold, i.e. behind the throttle valve, whereby with the simplest pilot control, a fixed value instead of the map, the vacuum and thus the quantity would vary much more, so that straight in the idle and start-up area, where the tank ventilation is particularly troublesome, the tank ventilation amount would be greatest, and with increasing load, where the tank ventilation is always on niger disturbing, the amount of flushing would decrease, as is known from the previous system. In an air volume measuring system, the error would depend on various variables such as load (from air volume) and speed; an adaptation is therefore particularly complex, the following roughly applies:

Variants 1.1 and 1.2 are suitable for systems that generate an approximately constant pressure drop in front of the throttle valve (air volume meter with damper). Systems with a very low pressure drop, especially when idling (HLM, Alpha / n, P / n) can only be covered with variant 2.1. If this variant 2.1 of the pre-control of the TE has to be selected (additive to t _L ), appropriate measures must be taken. The TE adaptation is then added to t _{L 'and} the adaptation range is then to be limited by a t _L threshold.

All features shown in the description, the following claims and the drawing can be essential to the invention both individually and in any combination with one another.

Claims (23)

1. Device for venting fuel tanks in internal combustion engines or the like. With an intermediate storage (fuel carbon filter container) absorbing fuel vapors and means for the controlled delivery of the tank ventilation mixture (TE mixture) to the internal combustion engine as a function of selected operating conditions, characterized in that the passage opening cross section of an electrically controlled tank ventilation valve (13) connected between the intermediate store (11) and the internal combustion engine (17) can be changed continuously depending on the operating conditions. 2. Apparatus according to claim 1, characterized in that the tank ventilation valve (13) as a solenoid valve (solenoid) is driven by a clocked, in its duty cycle of a control circuit (14) for changing the passage opening cross-section control pulse train. 3. Apparatus according to claim 1 or 2, characterized in that the setting of the duty cycle (TVTE) of the control pulse sequence for the tank vent tion valve (13) at least partially via a pilot control map of load (t _L ) and speed (n) between predetermined values (0% - 100%; TVTEmin1, TVTEmin2, TVTEmax). 4. The device according to claim 3, characterized in that the pilot control map (KFTE) comprises at least 4x4 support points with the possibility of interpolation and is designed so that the percentage enrichment of the combustion mixture is continuously the same for a given TE mixture. 5. Device according to one of claims 1 to 4, characterized in that at least additionally a lambda control-dependent control of the passage opening cross section or the duty cycle of the control pulse sequence of the tank ventilation valve (13) is provided. 6. The device according to claim 5, characterized in that the lambda control-dependent control of the duty cycle (TVTE) takes place along an average characteristic of the lambda control factor (F _R ) such that an increasing enrichment of the TE mixture above the average value of the lambda Control factor (FR) is recognized and the tank ventilation is closed accordingly by reducing the pulse duty factor accordingly. 7. The device according to one or more of claims 1 to 6, characterized in that, as an alternative to the characteristic-dependent control over the mean of the lambda correction factor according to claim 6, a limit value regulation of the pulse duty factor (TVTE) of the control pulse sequence is carried out, wherein if a predetermined limit value ( F _RGW ) is changed by the mean value of the lambda control factor (FR) the duty cycle in the sense of a reduction in the opening cross section and when exceeded in the sense of an increase in the opening cross section. 8. The device according to one or more of claims 1 to 7, characterized in that the tank ventilation adaptively taking into account the lambda control factor (F _R ) or additionally the load (t _L ), speed (n) by influencing the calculated value of the Amount of fuel to be supplied to the internal combustion engine is made. 9. The device according to claim 8, characterized in that the adaptation takes place multiplicatively or additively per time (on air quantity Q _L ) or additively on injection quantity / stroke (on load signal t _L ). 10. The device according to claim 8 or 9, characterized in that when utilizing longer-term deviations (averaging) of the lambda controller output as a measure for a correction of an adaptive, calculated fuel supply pilot quantity, the controller output between the basic adaptation block (32) for correcting the calculated fuel quantity and the tank ventilation adaptation block (35) for an adaptation value (ATE) of the tank ventilation can be switched over at least at certain values of air volume flow rate and speed such that the basic adaptation remains unaffected by the tank ventilation. 11. The device according to one of claims 1 to 4, characterized in that a duty cycle values for the control pulse sequence of the tank ventilation valve stored map control block (16) is provided, which is a function of load (t _L ) and speed (n) predetermined values of Outputs duty cycle and supplies an intervention point (multiplier 15). 12. The apparatus of claim 5 or 6, characterized in that the point of engagement (multiplier 15) is supplied with a further output signal of a characteristic block (24), which creates predetermined values of the duty cycle as a function of the course of the mean value (F _R ) of the lambda control factor for sole evaluation or in combination with the information in the input tax map. 13. The apparatus according to claim 7, characterized in that a comparison point (25) is provided, which is a limit value (F _RGW ) of the mean value of the lambda control factor and this is supplied with a downstream comparator (26) for sign determination and an integrator ( 27), which generates a changing pulse duty factor for the control pulse sequence in a continuous adjustment with a predetermined constant and feeds it to the point of engagement (multiplier stage 15), alternatively to the characteristic-dependent adjustment and, if necessary, in addition for evaluating the input tax map. 14. The apparatus of claim 8, 9 or 10, characterized in that a sequence control circuit (34) for the adaptive pilot control for tank ventilation and a controlled by this tank ventilation adaptation block (35) is provided, the evaluation of a preferably averaged value of the lambda Control factor (F _R ) creates a pre-control adaptation value (ATE) and conveys the calculation sequence for the fuel quantity to be supplied to the internal combustion engine (injection signal) in such a way that a constant fuel or air quantity per time is compensated for regardless of load and speed. 15. The apparatus according to claim 14, characterized in that a given predetermined maximum and minimum values (ATE _max , ATE _min ) of the adaptive pilot correction value for tank ventilation (ATE) more responsive and the sequence control (34) in the sense of a correspondingly directed change in the duty cycle (TVTE) controls. 16. The device according to any one of claims 13, 14 or 15, characterized in that when the lambda control is active, the pulse duty factor (TVTE) of the control pulse sequence for the tank ventilation valve (13) is increased in a ramp shape with a predetermined first change limit from a minimum value (TVTE _min1 ) , until a negative maximum threshold value (ATEmin lean stop) of the adaptation value (ATE) is reached with the resulting reduction the duty cycle of the control pulse sequence until the threshold value is undershot and then gradually increased to form a continuous oscillation around the negative minimum threshold value (ATEmin) - limit value control. 17. The apparatus according to claim 16, characterized in that when the adaptation value (ATE) rises continuously from the negative stop in the positive direction, the pulse duty factor (TVTE) of the control pulse sequence is kept constant at a predetermined value, preferably from the pilot control map (16), and when it is reached a positive maximum stop value (ATEma _x ) a change in the pulse duty factor, preferably with a second steeper change limitation, is initiated, with simultaneous release of the basic adaptation in the lambda control circuit of the fuel quantity calculation (injection signal calculation). 18. The apparatus of claim 17 or 16, characterized in that after release of the basic adaptation (adaptation without fuel tank venting) for a fixed, predetermined, programmable time, recheck the Tankentlüftun ^g sgemisches Aufregelung effected by the duty cycle. 19. Device according to one of claims 14 to 18, characterized in that the tank ventilation pre-control adaptation to a predetermined, effective below a certain air flow rate limit and below a certain speed limit Load-speed range is limited, and above this range, on interruption of the tank-venting precontrol adaptation, and release of the basic adaptation for the _K raftstoffmengenberechnung (injection signal computing), the determination of the duty cycle for the release of the tank venting mixture on the map stored in dependence occurs to the speed and load. 20. The apparatus according to claim 19, characterized in that during the transition from the area of the tank ventilation pre-control adaptation into the controlled map area of the tank ventilation mixture addition, the last adaptation value (ATE) is temporarily stored, with which the adapted tank ventilation pre-control starts after returning to the adaptation area. 21. The apparatus according to claim 16 to 18, characterized in that the TE amount is formed proportional to the amount of air, and the adaptation has a multiplicative effect, 22. The apparatus of claim 16 to 18, characterized in that the TE amount is formed independently of the speed additively per stroke and the adaptation acts additively on TL. 23. The device according to claim 22, characterized in that the upper range of the adaptation is limited by a TL threshold.

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