DE2848310A1 - FUEL CONTROL SYSTEM WITH AN EXHAUST GAS SENSOR, FOR COMBUSTION MACHINES - Google Patents

Description

CONTENT ^ BROSE ^ BROSE'Ä « D-8023 Munich-Pullach, Wiener Str. 2; Tel. (08917 9330 71; Telex 52-2147 bros d; Cables: «Pater,! Bus- Munich

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Applicant: THE BENDIX CORPORATION, Southfield, Michigan 48o75, USA

Fuel control system with an exhaust gas sensor, for Internal combustion engines

lh _F characters - _,,. _. Day: ⁷ «NOV. 197

Yourrel .: 56l4 / 15-A _Date: Vln / hO

DESCRIBES JNG

The invention relates generally to fuel control systems with an exhaust gas sensor located in the exhaust gas of an internal combustion engine is arranged to determine the content of constituents in the exhaust gas, and specifically relates to optimization techniques for economical fuel utilization Use of such fuel control systems.

There are a number of different embodiments of air / fuel ratio regulators for internal combustion engines. Generally, regulators of this type adjust the amount of fuel to match that of the internal combustion engine sucked air is mixed in order to achieve an optimal mixture of these two components, which in the Cylinders are burned. Various operating parameters of the machine can be recorded and different Way to calculate the desired ratio, however it will generally be the speed, the absolute pressure in the suction pipe and the temperature most often used.

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The air / fuel mixture that is normally desired or is sought, the stoichiometric or λ = 1, ö .und due to the salient advantages of a relatively good economic utilization of the fuel and the exhaust gas control. Precise regulation of the air / fuel ratio around the stoichiometric point is required in such regulators namely if three-way catalytic converters are used, as these are only effective in a very narrow window or Working band range of the air / fuel ratio. F. is also It is known that extended lean side operation of an engine can destroy the converter and cause degradation the conversion or the conversion efficiency can. An air / fuel ratio regulator with an open loop operation is therefore a simple MfiglichVe.it that Air / fuel ratio close to the stoichiometric value to be considered an electronic fuel injection system, an electronic carburetor system or others Air / fuel control devices.

However, it is evident that an open loop controller cannot works correctly at all times for all manufactured machines due to tolerances, wear and tear, maintenance, Change in environmental conditions and due to others changeable Criteria. In order for these regulators to achieve more precise control of the air / fuel ratio with open operation, became a self-adapting control or regulation according to a closed control loop with these controllers with an open Retrieb brought into use. An advantageous closed loop control system that controls the air / fuel ratio regulates to the stoichiometric value and is quite successful, consists of one which has an oxygen sensor contains, which is arranged in the exhaust gas of the machine to be controlled.

The oxygen sensor generates two voltage values, of which one is relatively high and the lack of oxygen in the exhaust gas

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or a rich or rich air / fuel ratio indicates, while the other is relatively low and the ^ ehlen of oxygen in the gas or a lean air / fuel ratio. Switching between these two values takes place by a relatively sharp slope at the stoichiometric point as the air / fuel ratio passes through it.

To provide an integral control based on this switching point a limit cycle oscillation is generated, whereby the air / Fuel ratio is moved below and above the stoichiometric point in a narrow band, the mean value of which is the stoichiometric point Point is. An example of a fuel control system using closed control loop in which an oxygen sensor is used is explained in US Pat. No. 3,815,556.

I · '

Since the slope of the sensor signal is ^{not infinite when switching at the stoichiometric point * 1} , a change in the mean value of the air / fuel ratio away from the stoichiometric point, either towards the rich side or towards the lean side, can be obtained by setting the sensor voltage with a threshold value compares which indicates the desired air / fuel ratio. The change or variation is, however, somewhat limited by the slope of the waveform of the "} ^Θ ίΐΡι switching point, and the better the sensor is (steeper curve), the lower the achievable change or variation. In addition, the desired air / fuel ratios, the set by the threshold value, unreliable as the sensor is subject to aging and the characteristic curve of the sensor changes. Rs constant adjustment of the system is required in order to maintain a predetermined or desired air / fuel ratio Control loop is described in TIS-PS 3 87 ^ 171.

Another known system uses asymmetric integration to operate a (^ closed loop system in rich or lean air / fuel ratios using a stoichiometric probe.

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These systems can then provide a means of controlling the air / fuel ratio for specific conditions. For example, an internal combustion engine can be operated much more economically on a leaner air / fuel ratio than the stoichiometric ratio during many operating times. With constant travel conditions, if no unnatural loads or acceleration requirements occur, the machine can work smoothly or smoothly on air / fuel ratios that are approx. IR: 1 or higher. The operation of the machine also requires less fuel if, in addition to operating on an average air / fuel ratio, which is the stolchlometric ratio, a control system could switch to different average air / fuel ratios depending on the setting of certain conditions, but _t 1 .the desirable control is maintained with the help of a 0_ sensor.

Only the present invention provides a method and apparatus for operating a fuel control system according to a closed loop control, in which a normally stoichiometric sensor at a medium air / fuel ratio is used, which is either on the stoichiometric point or can deviate from it.

Tn preferably includes. Br ^ nstoffrepelnyr.tom with closed Control loop an oxygen sensor that generates a signal with a level when it detects the presence of oxygen detects in the exhaust gas and generates a signal with a second level when it detects the lack of oxygen in the exhaust gas. It will furthermore, a comparison stage is used, the threshold voltage of which lies between the two levels, in order to carry out the switching operation of the non-preloaded sensor for an exhaust gas component, which is representative of a stoichiometric air / fuel ratio is. An integrator receives the output of the comparison stage and generates an integral control signal for an air / fuel ratio controls the air / fuel ratio depending on the detection of the switching process

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of the sensor.

Air / fuel ratios that are not stoiohiometric, a constant presetting current is applied to the oxygen sensor by a current source in order to change the waveform of its switching characteristics to change. Me bias according to the lean side becomes by changing the waveform jump from the bold intended for the lean area, so that this Fuel conditions occurs. A preload accordingly the rich area is provided by changing the waveform sequence from a rich to a lean area (occurrence), in that this occurs with richer air / fuel ratio Rf> n, never the position of the bias current determines the change in the air / Fuel ratio from the stoichiometric value and polarity determines the direction of this change.

In another specific embodiment of the invention The power source is powered by economic travel circuitry controlled, never includes travel circuitry an acceleration detector circuit for detecting changes in speed or rotational speed produced by a trip detector circuit are fed, which between large slow changes indicating accelerations or decelerations, and indicate large load changes and between relatively small rapid changes that occur during an essentially

differs.

constant for>r> steadiness and load conditions auftrnto ^r </ F3n sampling switch works depending on the ice detector and enables the power source to bias the air / fuel ratio to the lean side, during the determination of a travel condition and also the air / fuel ratio bias the stoichiometric fourth during non-travel conditions.

It is therefore an object of the invention to operate a closed loop fuel control system using a normally stoichiometric sensor at air / fuel ratios that are either rich, lean, or at stoichiometric ”

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It is also the object of the invention to specify a circuit arrangement, due to the economic din during the travel conditions Fuel utilization is improved.

The solution to this problem never emerges from claim 1.

In the following, the invention is explained in more detail using exemplary embodiments with reference to the drawings. Show it:

Figure 1 is a system block diagram of an air / fuel ratio control system with the feature of improved economy at travel speed or travel conditions with Features according to the invention;

^ igur ?. an inverted side view, in section, of an oxygen sensor installed in the exhaust pipe dps systems according to Pig. I is arranged;

Figures Diagrams showing the pre-stressed and non-pre-stressed-3A-E reproduce th waveforms of the digger of Fig. 1;

FIG. ^{1 is} a graph of the air / fuel ratio (λ) as a function of the bias current for the sensor shown in FIG. 2;

Figure ^ is a diagram showing steady state Tmfl / fuel ratio waveforms for the system according to ^ ig. 1 as a result Fig. 5 illustrates the sensor waveform shape of Fipr;

Figures waveforms of various signals following in the system fiA-E Fig. 1 occur when this is in an economic Travel mode arheitet;

FIG. 7 is a detailed circuit diagram of the circuit arrangement for similarly labeled blocks of the system according to FIG. 1.

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■ Figure 1 shows an advantageous air / fuel ratio control system with features according to the invention. The system includes in part an engine Io and an air / fuel (A / ^w ) ratio controller 12 which changes the air / fuel ratio as a function of an air / fuel ratio control signal with variable pulse width via a control line 11 of a controllable mixing device (not illustrated) such as an electronic injection system or an electronically controlled carburetor. Such a variable pulse width signal controller 12 can control the mixing device either by regulating the amount of air or the amount of fuel supplied to the engine.

The air / fuel ratio controller 12 is preferably of the open loop type that controls the parameters such as
temperature, MAP and RPM (N) from the fascine 1o above
the speed sensor 2R or the sensor line 15 receives in order to calculate the desired air / fuel ratio from these variables. The speed sensor 28 can in a preferred manner
consist of a tachometer which receives an input variable from a toothed gear wheel, which is connected to a sieve rotating part of the machine Io. As is conventional, the controller 12 has a programmed program through which
a dependent air / fuel ratio is generated for each value of the measured engine variable. n _Pr air / fuel ratio controller 12 can either digital or analog op: be designed with regard to its calculation device to the
Provide air / fuel ratio control signal, in the preferred embodiment, however, an analog computing device is present, which generates a basic pulse width for an electronic fuel injection system, on the base of the
RPM and MAP variables and corrections
derselhen. Fin analog computer of this ^m yps is more detailed 1n the US Pf? · *> 7Vi ofift described.

A further input variable to the air / fuel ratio controller consists of an integral control signal corresponding to a closed loop, which is supplied via line 17 by an integrator lh. The integrator lh develops the control

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signal to an output, where the signal increases over time with a constant sequence or decreases there with a constant sequence _s to change the pulse width of the air / fuel ratio controller 12 in the sense of a closed control loop. The integrator m switches from an increasing rise curve or ramp-shaped curve to a decreasing ramp-shaped curve and back again, which happens as a function of the output variable of a comparison variable 16 which has one of two levels. The comparison stage 16 switches or changes the level at a point at which the waveform voltage of an oxygen sensor 2o exceeds a reference input voltage to the comparison stage IFi at the connection IR. The input reference voltage of the comparison stage is preferably known as a voltage which leads to a uniform result, even under conditions in which the waveform or the sensor is subject to aging.

Normally a non-biased oxygen sensor occupies 2o a signal output voltage that occurs at rich air / fuel ratios is relatively high when there is little or no oxygen in the exhaust gas and generates a low signal when an increase or an excess of oxygen is contained in the exhaust gas products. The sensor waveform switches or runs between the high and the low level in a narrow transition region hot almost stoichiometric value, while the air / fuel Ratio regulator 12 increases or decreases the air / fuel ratio of the engine through this point. Of the Switching point or stoichlometric point is determined by the transport lag of the system is delayed because of the change in the air / fuel ratio on the mixing device only through the sensor it is determined after which the combustion products reach the sensor according to this change. This delay and the Integration sequence of the integrator 1 * 1 represent the amplitude and the frequency of the characteristic Orenz oscillation cycle.

According to an important aspect of the invention, v-ann dip waveform of the oxygen sensor can be modified to a non-stoloichiometric one To realize the air / fuel ratio in the machine Io, by the oxygen sensor Po via an adjustable constant current source 22 preloaded x ^ ird. The power source 22 can by

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it sends different currents through the sensor 2o, in addition are used to modify the waveform and thus the comparison stage 16 generates its level change, either with rich or lean air / fuel ratios, which depends on the size of the bias current and its direction is, and can generate a stoichiometric switch point when the bias current source 22 is not turned on.

According to a further important aspect of the invention, the current source 22 can be controlled in a preferred embodiment on and off, specifically by means of a sampling switch 3'l, which is operationally connected to the output of a travel detector 32 and an acceleration detector 3o is connected. The acceleration detector, which shows any changes or fluctuations in the speed changes of the machine, receives a Input speed signal from the speed sensor 2fi, which shows the current Speed d4r machine indicates. It is known to be small rapid fluctuations or changes and increases in the speed of the engine due to changes in the air / fuel ratio from the injectors, with small sudden decreases also going such information. Fs is further known that larger slow increases or decreases in speed are mainly due to the from Transitions initiated by the driver arise, such as acceleration, Delays or load changes.

The acceleration detector 3o thus differentiates the number of revolutions Output variable N of the speed sensor 28 indicating per minute, to generate an acceleration waveform from which the Travel detector 32 can determine that the machine Io is essentially on constant load and speed works. This type of business is referred to as a travel business and presents itself during the major portion of the operational life of the machine. During a travel phase in the operation of the machine, the air / Lean fuel ratio for economical operation be chosen as that of the stoichiometric point in order to achieve optimal economy, this leaning effect is possible because the machine during the Relseb-

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drive only requires a fraction of the output power. While under these conditions, the driving characteristics are not noticeably changed if the air / fuel ratio is 1B: 1 or slightly higher can also be chosen for longer periods of time.

During the time when the sampling ^{switch 3 1} I receives an output from the travel detector 32 indicating this condition, the power source 22 is energized and changes the waveform of the oxygen sensor so that the waveform is changed to a lean condition or condition at the point at which the reference voltage of the comparison stage 16 is passed, conversely, the sampling switch 34 is assigned a time constant which, if the opposite state of acceleration or deceleration is detected by the travel detector 32, continuously tries to disable the circuit and restore the travel operation . During acceleration and deceleration conditions, the power source 22 is disabled and the oxygen sensor loop operates as normal on an air / fuel ratio that is substantially close to the stoichiometric ratio.

A travel company as explained earlier would be certain Destroy catalyst converters that receive exhaust gas from exhaust pipe 18 of the engine, to avoid any destruction of converter 24 during To prevent this mode of operation is an override control unit ? ß provided, which bypasses or bypasses the exhaust gas around the converter, (usually the bypass control unit consists of a double acting solenoid valve (not shown) which normally closes the bypass path. The output size of the Sampling switch 34 can be used like this Fig. 1 schematically illustrates to open the bypass route during travel operations.

Figure 2 shows, in cross section, the oxygen sensor, generally is denoted by 2o and is arranged in the exhaust system 18 of the engine Io. The exhaust combustion products contained in the exhaust pipe unburned hydrocarbons, oxides of nitrogen and carbon together with oxygen, which are close to the oxygen

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sensor 2o are pre-routed. Peroxidiihlpr? O has a draw opening 21, which is located in an insulator base grain 10 and receives gases from the surrounding atmosphere, which consist essentially of 79 % nitrogen and 21 % oxygen of O ^. The oxygen sensor 20 also contains a solid electrolyte oxygen ion conductor 23 made of ZrCK or similar material, which contains an inner electrode 25 made of a noble metal, preferably made of platinum. On the outer surface of the solid electrolyte conductor 23, a catalyst electrode 27 is provided, which preferably contains a noble metal such as platinum. A protective cover made of an oxide 29, in the preferred embodiment a porous cover or coating made of MgO ALpO spinel covers the entire outer active unit of the sensor 2o. All layers, 23, 25, 27, 29 are permeable or porous to molecules or oxygen ions and the two platinum conductor layers 25, 27 have connections 31 and 33 in order to collect the flow of electrons. An oxygen sensor of this type is commercially available from Bendix-Autolite of Ostoria, Ohio, model number X-7 *} 1. A variable constant current source 22 (direction and magnitude) is also provided to bias the sensor by connecting it to electrodes 23,25.

In theory, the oxygen sensor will operate when 0 _? Molecules become oxygen ions with the addition of four electrons on the surface of the electrode 25, so that the oxygen ions then diffuse into the solid electrolyte 29. Since the partial pressure of the oxygen on the electrode surface 25 is higher than on the electrode surface 27, the oxygen ions move freely through the solid electrolyte of the other catalyst electrode 27. At this point the oxygen ions give electrons ah and combine to form 0 molecules again . Fin net electron current thus flows from electrode P5 to electrode 27 with a polarity which is displayed as a function of the difference in the partial pressure of 0 ″ in the exhaust gas in relation to the 0 partial pressure in the surrounding atmosphere. An increase in the difference in partial pressures between the electrodes usually increases the voltage generated. Generally, a net partial pressure of

-22

O ₀ in the exhaust gas of approx

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Voltage of approx. 1.0 V emits. When the net pressure of oxygen increases, the output voltage of the sensor ah falls and becomes less than 0.1 - 0.2 V when the partial pressure is Io or more.

Since the voltage generated by the Op sensor 2o is a function of the difference in partial pressures at electrode 25 and electrode 27, the waveform of the sensor can be modified by artificially applying either a higher or a lower O ^ partial pressure to the Electrode 27 generated than that due to the O _? - (it still occurs in the exhaust gas.

The bias current of the current source 22 is used to supply electrons to one of the electrodes 25, 27 in order to either pump 0 molecules away from the electrode 27, thereby reducing the O 2 partial pressure, or by 0 _? - To pump molecules to the electrode 27, whereby the Op partial pressure is increased there. ν

When a lean bias is desired, electrons become sent to the electrode 27 and the oxygen ions generated thereby migrate through the permeable ZrOp layer and become 0_- Molecules at the electrode 25, so that at the electrode 27 of the 0 partial pressure is reduced. If the "sensor 2o with switching begins to go from rich to lean, the Op partial pressure at electrode 27 begins to rise, but it does rise not as fast as the exhaust gas rises, as oxygen molecules are transported away from the electrode. the waveform of the same therefore does not reach the switching point at the stoichiometric point, but is delayed until the increasing Pressure covers the pressure loss due to the bias current.

When switching from lean to fat, the pressure at the electrode 27 drops; it must, but not to the stoichiometric one Drop in pressure so that the sensor can switch because the bias current already 0 “already transported away from the area, so that the transition will take place earlier.

Conversely, when a bias voltage corresponding to the rich region is desired, electrons are supplied to the electrode 25.

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As a result, 0_ molecules are ionized on this and become an electrode 27 transported, where they increase the 0 partial pressure. If then during the transitions of the sensor when the exhaust gas from switches rich to lean and the Op partial pressure at the electrode 27 is increased, the additional preload pressures cause an earlier one Switching the sensor or the waveform. Fin cyclical course from the lean to the rich side when the O_ partial pressure at the electrode 27 is decreased, shows a delay in the SehaltVorgang, until after the result of the decrease in the operating pressure overcomes the surgical preload pressure that was developed there.

The bias current causes a greater precise change in the partial pressure of 0_ on the exhaust side of the sensor, since the Concentrations of O_ there are generally much lower lie. The 0 - pressure on the atmospheric side of the sensor remains essentially unchanged even during the preload. Alternatively can also be an Op reference pressure instead of atmospheric pressure be used.

The preceding description explains at least a theoretical one Mechanism by which the effect of the pre-stressed feeler can be explained. However, the subject matter of the invention is not limited to any mechanism and one or more phenomena can of course be exploited, by which the physical responsiveness of the burrower under a preload can be changed.

Figure 3 shows the change of a waveform with a bias current impressed on the lean air / fuel ratio sensor 2o. Curve C shows a non-preloaded sensor, in which the transition from a rich to a lean mixture takes place sharply with a maximum increase, whereby the reference voltage intersects the curve at approximately an air / fuel ratio which is stoiehiometric, or A = 1, O. Curve D was generated by adding a bias current to the sensor and illustrates that the waveform transition occurs later or at a leaner air / fuel ratio λ = 1.1 than curve C. The next curve F.

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shows for the same reference threshold and for one larger bias flow an even leaner air / fuel ratio λ = 1.2, which occurs when the comparison stage l6 switches at this value. Rs it should also be mentioned that the curve E has a smaller slope than the curve C or the curve D.

It can thus be stated as a general rule that ?, for increasing bias currents for the sensor 2o the transitions with greater Shifting from the non-biased waveform will occur, with smaller slopes. It is believed that the decrease in the slope due to the change sequence of the Partial pressures is caused on the sensor, which is reduced by the pressure provided by the bias currents. The transition from lean to rich for a sensor biased into lean operation is a mirror image of that illustrated in FIG. 3 Waveforms represent the waveforms that lead instead of lagging a non-biased waveform. With others V / ort, the feeler follows the same biased waveform upwards as it moves it downwards. «

For a non-biased waveform, it is desirable that the transition from tiber 9o% of the maximum value Io% of the value is done within about 5o milliseconds. The actual waveform for any probe will depend on the probe shape from its environment, including the sequence in which the integrator changes the air / fuel ratio. The curves shown in FIG. 3 depend on the time and can only be assigned to a time parameter if the sequence of changes in the air / fuel ratio is known and the system carries out a regulation according to a closed control loop.

For a rich air / fuel ratio or preload, again referred to Fig. 3, in which the curve C shows the transition from a lean to a rich air / fuel mixture for a non-preloaded sensor illustrated. Curve "B" and curve A illustrate two waveforms in which the sensor is biased with different currents, as on earlier

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Position was explained. The polarity of the bias current of waveforms B and A has been reversed which is ftr but equivalent for bias voltage, respectively for waveforms P and E was provided. It should be noted that the waves of A has a smaller slope and occurs at a richer or richer λ than the waveforms B and C. As the Bias currents, richer air / fuel ratios are possible.

Figure h illustrates the bias current for the sensor as a function of the change in air / fuel ratio caused by the bias current. A positive bias is defined to be an O _? Induced change that runs counter to that caused by the partial pressures of the probe, while a negative bias is defined as O _p migration, similar to that caused by the partial pressures. Positive bias currents increase the air / fuel ratio and negative bias currents decrease the air / fuel ratio, as shown in FIG. The relationship is symmetrical, as one would expect for positive and negative bias currents, since the amount of oxygen carried by the bias current is proportional to the amount of electrons delivered to the electrodes of the probe. The curve is further logarithmic in terms of the change in X since the probe follows the Nernst calculation which says that the output voltage is a logarrythmic function of the ratio of the partial pressures of O _p which modifies the bias voltage. In general, air / fuel ratios can be as high as 3o: 1 or X =? or as low as Io: 1 λ = 0.7 can be achieved with this technique.

According to an essential feature of the invention, p. illustrates a method to bias a 0 sensor to thereby obtain either a rich or lean air / fuel ratio from an integral regulator. It has also been shown that dip control of the air / fuel ratio depends on the size and polarity of the bias current supplied to ^{the 17 UhIPr.} It is assumed in this description that the sensor is at an essentially constant operating temperature, that is to say approximately the temperature of the exhaust gas.

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The waveforms according to Pig. 5, the output of the integrator 14 illustrate in its ftrenzzyklus which controls the air / fuel ratio control, as explained previously. Waveform C represents a non-biased air / fuel ratio waveform that is symmetrical about the air / fuel ratio λ = 1 or the stoichiometric ratio. The TMg. 5 shows new steady state conditions of the bias current provided for a while. For waveform D that corresponds to the waveform with the same reference numerals of ^ ig. 3, the air / fuel ratio switches to a later point 62 and therefore requires additional space in the lean area or zone of the air / fuel ratio. As a result, the total or average air / fuel ratio is biased to the non-stoichiometric value of approx. 1.1 in terms of time. Similarly, for., Waveform E at 64, an additional delay in the switching time is provided. As a result, any even leaner air / fuel ratio than an average overall ratio will be developed.

For switching to the rich air / fuel ratios, waveforms A and B are shown in FIG. 5, which correspond to the waveforms identified by the same reference characters in FIG. As before, point 6o is the generalized switch point for waveform C that results in a stoichiometric air / fuel ratio as an overall mean. Point 66 illustrates where waveform B crosses the switching point due to the delay caused by the bias current, and similarly, waveform A illustrates yet another delay 68 where the waveform is biased with even greater current.

Fs can thus be recognized by pretensioning the burrower with a constant current with either positive or negative polarity different fourths of air / fuel ratios, which are not stoichiometric can be obtained in a simple and reproducible manner. This system thus enables a method of changing the air / fuel ratio over a continuous range of fats,

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lean and stoichiometric values by dividing the integrator I ¹ I with the biased waveforms of the pip ;. 3 is controlled.

Figures 6 and 7 illustrate an economical travel system, in which the method of a variable bias current for the O_ sensor is used, which is now in detail should be explained. The acceleration detector 3o comprises a circuit arrangement with filter stages Rl, 01; R2.02; R3.03; and an amplifier Al. The resistor Rl between the speed signal input terminal 13 and a terminal of the capacitance 01 is switched on, the other connection of the capacitance being connected to ground, forms a low-pass filter with the capacitance, which attenuates or suppresses high frequency disturbances from the speed sensor. At the connection point of the low-pass filter is a connection of a resistor R2 and a Capacitance 02 turned on, which is connected at the other terminal to the inverting input of the amplifier A1. Form R2, C2 a differentiating stage that differentiates the speed component of the sensor signal and an acceleration signal at the output of the amplifier Al generated.

The amplifier Al, which has a filter stage with a capacity 03 and a resistor R3 connected in parallel between its output and the inverting input forms a active low-pass filter whose non-inverting input terminal is connected to Hasse or Earth. In cooperation with the low-pass filter Rl, 01 reduces the active filter stage any interference or high frequency components outside of the desired Acceleration band and amplifies the differentiated signal.

As can be seen better from waveform 6A, there is Acceleration signal N from a high-frequency component with a small amplitude, which reproduces acceleration quantities and deceleration quantities, which are caused by individual cylinder deviations and / or changing air / fuel ratios are caused, which are generally referred to as the roughness of the machine will. This roughness signal becomes a larger, more slowly fluctuating signal with large amplitude changes in speed superimposed or speed, as we do by superimposed

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speed accelerations, decelerations and / or load changes is produced.

Acceleration signal N arrives at terminal I of a window or bandwidth comparison stage 15, which operates as a two-mode comparison stage with an upper threshold voltage + V or which arrives at terminal H \ and with a lower threshold voltage -V which goes to terminal T _? reaches, by comparing the output voltage of the re-acceleration detector 3o to the terminal I with the two threshold voltages, the comparison stage generates one of three output variables. When the input voltage I is higher than the threshold voltage + V, a relatively low output is produced at the output terminal H. If the input voltage I is lower than the threshold voltage -V, a relatively low voltage is produced at the output terminal L, and if the input voltage is between the two threshold voltages, a relatively low voltage is produced at the output terminal G, while the outputs L and H have a high voltage lie. The lower and the upper threshold value can be different and can be adjusted, <

that they are tailored to the travel mode of a particular machine are. Such a window or bandwidth comparison stage, as described above, can be made from a conventional Apparatus commercially available from Burr-Brown-Research Corporation of Tucson, Arizona under model no. IlI ^ is available.

The output port H and the output port L are connected to the Combined connection point, which is formed at one terminal of a resistor R'l, the other terminal of which with a positive supply voltage + V is connected. Fs can thus be seen that this connection point is performing an OR function, where large acceleration values or deceleration values are relative generate low output voltage at the connection point, like the one in Fipr. 6B is shown.

At andnron times when the tension between the?, Wri thresholds

values, as indicated by a relatively high voltage for the bandwidth comparison stage and shown in Fig. FiR is, a travel condition is determined and a travel signal is derived therefrom. The output connection G can be used for this Signals to various other parts of this or other circuits and is connected to ground or earth via a resistor R15. It can be seen that the state of travel or the output of the comparison stage 15, which is a relatively high voltage provides to occur for a considerable period of time, as can be seen by the broken lines which 4Specify the mode of operation of the machine in this condition or condition.

The block 3 * 1 of FIG. 7 illustrates a circuit arrangement with the sampling switch which comprises a monostable multivibrator 17, 4 which receives the output of the bandwidth comparison stage 32 at an input connection A, the waveform of the monostable multivibrator 17 is never shown in F ± .g. 6n shown. If the bandwidth comparison stage detects a state that lies outside the travel range window or the travel range bandwidth, the monostable multivibrator immediately generates a relatively low voltage signal by switching to the unstable state. The monostable multivibrator then finally comes out of its unstable state and back into its stable state or its high voltage state. Her monostable multivibrator checks every time period to determine whether the Ban fiber ».I ten pre-match stage r>Inf> r Hn1 snhodlnp.unp; has found again. In its asynchronous ^p .et; r1 phase, however, the monostable multivibrator is kept at a low value by the low value of the bandwidth comparison stage 32.

At any point in time after a number of timing cycles, for example at point 72, the bandwidth comparison stage 32 determines the presence of further travel strain, and the monostable multivibrator returns to its stable state and to a relatively low voltage state until another acceleration / approximately event outside the ^p enr> ters or bandwidth is determined, for example at 7 ¹ I.

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The monostable multivibrator 17 has a time constant for the unstable state, which is long enough to ensure that the small oscillations of the acceleration signal around the threshold voltages do not oscillate in the System can lead. The system is thus subject to hysteresis when changing from an acceleration mode into a travel mode to ensure that the travel condition exists prior to reducing the system to the lean side, however, while creating a stoichiometric condition and is maintained for the time constant of the monostable multivibrator immediately after reaching the threshold values. Even though Now that a single direction hysteresis is shown, it is evident that there are two phenomena of flysteresis can be implemented if necessary.

In the sampling switch 3 * 1, a non-inverting former comparison stage is also included, which summarizes an amplifier A2, which is connected between a negative voltage, and ground or ground. Rier amplifier A2 has a low value resistor R7, which supplies a reference voltage from a variable sliding contact which is connected to a positive voltage source + V. Never feed from the monostable multivibrator 17 to the non-inverting connection of amplifier A? happens via a pair of plate resistors R ¹ O, R6. The divider resistors take a ¹ ^ part of the output voltage of the monostable multivibrator and if a comparison is made with the threshold value developed by the resistor R7, the amplifier A2 produces a negative output voltage if the voltage is greater than the threshold value, and a relatively small exhaust tension if it is less than the threshold value. For signals that are above the threshold value, a self-coupling resistor RlH is provided between the output and the inverting input terminal in order to bring the signal into a switching form of a predetermined voltage level, as shown in Pip. 6ü is shown »

The voltage level of the sample extraction switch switches the current from the power source 22 off and on to either a naperes T.uft /

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Generate fuel ratio when a travel condition is encountered or a stoichiometric air / fuel ratio to generate when accelerations, or decelerations Load changes were detected. The one at the output connector of the The voltage level provided by amplifier A2 is used to set the air / fuel ratio for deflection of the system on to adjust the lean side. It should also be noted that the travel signal can be used to convey the air / Change fuel ratio in any of the aforementioned systems.

The block 22 in FIG. 7 illustrates a bipolar controllable constant current source which biases the O ~ sensor 2o via a * ³ power line 21. The constant current source 22 includes two sets of matched transistor pairs QJ, Qp and L-Q., »Qn. Each set forms a variable constant current source with opposite polarity. For a positive bias, the base of the transistor Q ₇ and the collector of the same are brought together at the connection point which is formed at the base of a transistor Qj. A bias resistor R8 is also connected between a control input λ and the connection point. The transistor CK is its collector is connected to the current line 21 and its emitter is connected to a voltage source + V via a resistor RIl. By supplying a negative polarity to the control terminal Λ, different current values are dissipated via the diode which is applied to the transistor Q and the resistor RR The amount of current drawn off depends on the voltage value that is applied at \ , and is transferred in a mirror image through the transistor O ^ to the power supply line 21, namely from the voltage source + V and the resistor RIl as a positive bias current + i.

Similarly, for a negative bias voltage, a transistor o _o has its collector connected to the power supply line 21 and its emitter connected to a negative power supply -V via a transmitter resistor Rio. The input of the transistor O._ runs via a bias resistor RQj which is held between the control terminal X and the spin base. A transistor connected as a diode 0 of which

9 0 9 8 2 3 / η 5 G 3

Base and collector connected, is also connected to the base of transistor Q._ at this point and is also connected to a negative power supply or voltage -V at an emitter junction. Similar to the positive power supply, a positive control voltage at the terminal λ causes a current to flow through the resistor R9 and the transistor Q ₁ , which is represented in the transistor Q ₂ as a negative bias current -i.

It can thus be seen that for any desired air / Fuel ratio can be fed to the sensor via the power line 21 from the power source 22, a bias current. The size and the polarity of the bias current depend on the polarity and the magnitude of the voltage supplied to the control terminal X. will. Advantageously, use is made of this power source of the travel signal circuitry, the one turns positive bias current on and off to drive the system air / fuel ratio into the lean range, as shown in Fig. 6E.

Her output of the sensor 2o in FIG. 7 is connected to the inverting input connection of an amplifier A3 which comprises part of the comparison stage 16, to be precise via an input resistor R15 ¹ . The input resistance R15 ¹ has a sufficient size or resistance value so that the bias current to the sensor 2o is not influenced. The threshold value of the comparison stage 16 is developed at the connection point of the series circuit from the divider resistor R18 and a variable divider resistor R17. The divider combination is connected between the positive voltage connection + V and the ground or earth.

The anti-parallel connected diodes D1 and D2 form a parallel combination between the output of the amplifier A3 and the inverting input and ensure a voltage limitation of the Voltage excursions from the output terminal. For the transitions of the

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Sensor 2o, the output voltage of amplifier A3 is approx. + o, 6V or -o, 6V.

A knee voltage is applied to the inverting input terminal of the amplifier A3 through an output resistor R16 and an amplifier A5 which is equivalent in magnitude but opposite in polarity to an offset voltage of the waveform. The offset voltage caused by the IR voltage drop across the sensor of the bias current, as the ^p has NHLer a particular operating resistance. However, this offset voltage does not affect the shape of the curves in FIG. 3, but only causes a level shift which, however, can be canceled.

The size of the shift, positive or negative, depends on the size of the bias current, since the sensor maintains a substantially constant low resistance at operating temperatures. The Aufsetζspannung is therefore related to the voltage at terminal X by a certain gain constant. The amplifier A5 generates this knee voltage by receiving the voltage from the terminal X via the non-inverting input terminal and multiplying it by the gain constant of the amplifier. The gain constant can be adjusted by changing the variable resistor R22 connected between the output and inverting input terminal of amplifier A ¹ S in relation to a fixed resistor R21 connected between the inverting input terminal and ground is switched.

If the comparison stage determines that the voltage of the O_ sensor exceeds the visual threshold, it produces a relatively low one Voltage and if the voltage supplied by the O ^ sensor is less than the threshold, it generates a relatively high voltage.

The output variable of the comparison stage Iß is via an input resistor Rl3 the non-inverting input terminal one

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Integrating amplifier AH pressed, the positive or the non-inverting terminal of which is connected to ground or earth. An integrating capacitance C4 is connected between the output and the inverting input terminal to produce voltage changes in relation to the levels provided by the comparison stage. For an input variable corresponding to a lower value or level from the comparison stage, which indicates that a rich air / fuel mixture has been detected by the O ^ sensor, the integration stage generates a relatively increasing ramp-shaped voltage, the slope of which depends on the time constants of CA and Rl 3 is dependent. The integrating amplifier A4 alternately generates a falling, ramp-shaped waveform for periods of time when the output variable of the comparison amplifier A3 is relatively high in terms of voltage and also with the same slope as the rising, ramp-shaped waveform or voltage.

It can also be seen that for any set Bias current for the sensor 2o the threshold value of the comparison stage 16 can be adjusted to the mean air / fuel ratio of the system change over quite a range due to the decreasing slope of the voltage of the probe at its transition area between a high voltage output and a low voltage output. Larger bias currents, in terms of either a fatter or a lean ratio, provide a means for a far-reaching setting, when the slope of the transition decreases.

For example, a set positive bias current, which allows the system to operate along the curve ^ of FIG. 3, in conjunction with an NPN transistor 7? can be used to change the mean air / fuel ratio. The transistor is usually biased in an on state because its base is connected to a positive supply voltage * V through a bias resistor R2o. The transistor 72 is also connected to its collector with the positive supply voltage + V via a variable resistor

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P.19 is connected and its emitter is connected to the Schwpllenwert connection point of amplifier A3 connected. A negative voltage applied to the base terminal keeps transistor 72 off the end.

By transmitting the travel signal via the output of the amplifier A2 _z around terminal 7o, switching between a stoichiometric ratio and a lean air / fuel ratio is realized. In the absence of travel conditions, the output of amplifier A2 allows transistor 72 to remain on and resistor R19 can be adjusted to operate at the stoichiometric point of curve E in FIG. If a travel condition is detected, the negative voltage of amplifier A2 turns transistor 72 off and a lower threshold value then results. The lower threshold set by resistor R17 can realize operation along curve E at any desired lean air / fuel ratio.

In summary, the invention thus creates an economical working travel operating system for an internal combustion engine, which contains the following devices: a speed sensor 28, which is coupled to a rotating part of the machine Io and generates a speed signal which indicates the speed of the in · operation machine located; an acceleration detector 3o, which responds to the speed signal to determine the (Irfiße and the direction to determine changes in the speed of the machine and to generate an acceleration signal provide which indicates these changes; a travel detector 32 that receives the acceleration signal and generates a travel signal when the acceleration signal is substantially constantly indicative of a travel condition for the machine, at a relatively constant speed and prevailing operating conditions; and finally, a power source 22 responsive to the travel signal to control the air / fuel ratio of the Set machine leaner than the stoichiometric air / Fuel ratio during the operating modes of the Machine when a travel condition or condition is detected.

30 8823/0563.

Although a preferred embodiment of the invention
As illustrated and described in detail, it will be apparent that those skilled in the art can make a number of changes and modifications to the various portions of the system without departing from the scope of the present invention.

All recognizable in the description and in the drawings
The technical details shown are important for the invention.

909023/05 (53

Claims (1)

D-8023 Munich-Pullach. Wiener Str. 2; Tel. (089) 7 93 30 71; Te.ex 5i12U7 bros d; Cables: "Patentibus" Munich Applicant: THE BENDIX CORPORATION, Southfield, Michigan 48o75, USA Your reference: Paris file: 5614/15-A rag: Nov. 7th 1.Q7R Yourrel .: Date: _v In / hf5 PATENT CLAIMS (l / method for operating an internal combustion engine with an air / fuel ratio controller with closed loop control and with an oxygen burner for the implementation an economical travel mode, characterized in that a travel condition of at least one Operating parameters of the machine determined that a relatively constant engine speed and relatively constant Shows machine load; that a travel signal is generated as a function of the determination of a travel condition and the air / fuel ratio of the internal combustion engine is set to a leaner value than the stoichiometric value when the travel condition is present and that this setting by controllable or adjustable pretensioning of the oxygen sensor is taken from a power source responsive to the travel signal. 2. The method according to claim 1, characterized in that the setting of the air / fuel ratio of the internal combustion engine to the stoichiometric value is made when a travel condition is not present and that 909823/0563 2843310 this by means of controllable pre-tensioning of the oxygen sensor the power source. 3. ^ experience according to claim 2, characterized in that the T, uft / fuel ratio on the stoichiometric value for is held for a predetermined period of time when the Travel signal is detected. H. The method according to claim 3, characterized in that in order to maintain the air / fuel ratio a sample is taken from the travel signal after the predetermined period of time has elapsed and that the stoichiometric air / fuel ratio is again maintained for the predetermined time period if by sampling it is determined that there is no travel signal, and that the lean air / fuel ratio is switched back if the travel signal is present at the end of a sampling. ^r j. Method according to Claim 1, characterized in that the following procedure is used for the nt ^ llen of the travel condition and for the generation of the travel signal 1n: that the _rotational teeth of the machine are determined by a rotating part of the machine and a Prehzahlsignal is generated which represents the n rP number; differentiating the speed signal with respect to time and _{providing an n P} acceleration signal thereon representing the magnitude and direction of changes in the speed signal; and that the acceleration signal is compared with a threshold value, and the heat signal is generated if the absolute magnitude of the acceleration signal is less than the absolute fourth of the threshold value. 6. The method according to claim 5, characterized in that during the comparison process the acceleration signal is compared with a positive threshold value and with a negative threshold value, whereof the positive threshold is different from the negative threshold, and that the travel signal is generated when the absolute The magnitude of the acceleration signal is smaller than the threshold ^values 909823/0563 7. A fuel control system Piner to the realization wirtschaftIi Reisebetriehes for an internal combustion engine, for implementing the method according to one or more of the preceding claims, characterized in that the system contains a speed sensing, the rotating ^m eil of the machine is pekoppelt to one and a the ("Provides speed signal reproducing the speed or speed of the machine in operation; since ⁰ · an acceleration detector responding to the speed signal of the speed sensor is provided in order to determine the Or'iRp and the 'direction of the speed changes of the machine and an acceleration signal which reproduces the changes to generate; riaß a travel detector receives the acceleration si p; na] and provides pin Rpise signal when the acceleration signal of the "aschine is essentially constant and thus a ^p eisostatus of the" machine with a relatively constant low speed or speed and sustained load conditions indications; that ^M 1 lt-el responsive to the ice chip are provided in order to set the air / fuel ratio of the machine leaner than the stoichiometric ratio during operating states of the machine when a travel condition is determined. ^. A fuel control system according to claim 7 »characterized dadurcb that a sampling switch is provided which receives the ^ eisesip-nal and the 'Finstellmittel for the air / ^R race-fuel ratio control for making the air / fuel ratio of the engine set leaner than the stoichiometric ratio when the Roise signal is present and the air / fuel ratio of the -adenine; ated on cien stoichiometriscnen ^T changes when the Fieisesignal Tehlt. Q. fuel recycling system according to claim ^, characterized in that that the sampling switch has a stable state and an unstable state with a predetermined duration, that the switch can be brought into its unstable state, when the travel signal is absent, and in its stable State is returned when the predetermined period of time has passed and the travel signal is present. 909823/0563 BATH 10. Fuel control system according to claim R, characterized in that that the internal combustion engine with a catalyst converter is equipped to reduce the harmful exhaust gases of the internal combustion engine, with the converter between the Ahgasrohr and the atmosphere is on and working effectively when the air / fuel ratio of the engine is essentially at the stoichiometric value that further an override device is provided to divert the exhaust gases around the transducer to atmosphere when the engine is on non-stoichiometric Air / fuel ratio works. 11. fuel control system according to claim lo, characterized in that that the bypass device is responsive to the travel signal and bypasses the exhaust gas around the transducer during a travel condition and oine "t winning the exhaust gas through the converter during nioht-Rn 1 rspbndtn / runf ^ n 'ermttgl loht. 1?. Fuel control system according to Claim 7 » characterized in that the acceleration detector contains a differentiating device which receives the speed signal and generates a derivative function from the speed signal and outputs this derivative function as an acceleration signal. 13. ^ fuel control system according to claim 12, characterized in that daP. the acceleration detector contains a filter device, to remove high-frequency control signals from the speed signal or to attenuate. l'f. Fuel control system according to Claim 12, characterized in that that the travel detector contains a comparison stage which provides the travel signal when the acceleration signal is smaller than a positive threshold and greater than a negative threshold. 15. Fuel control system according to claim 7, characterized in that that the device for setting the air / fuel ratio includes: an exhaust gas sensor which is arranged in the exhaust system of the internal combustion engine and a signal with a waveform 909823/0563 generated, which has a voltage-wise high first level, when the presence of oxygen in the exhaust gas is detected becomes, and has a second low voltage level when a Lack of oxygen in the exhaust gas is found to be the sensor a fast switching process between the first level and the Performs second level at a transition point which has a relatively steep rise and which is substantially at a stoichiometric air / fuel ratio is located; one Integration stage to increase the air / fuel ratio, when the waveform is relatively high in voltage and above a threshold, and around the air / fuel ratio to zoom out when the waveform voltage is relatively low and is less than the threshold. If). Fuel control system according to claim 15, characterized in that that the integrating stage contains an execution for changing the threshold value as a function of the travel signal, to achieve a leaner air / fuel ratio during a travel operation as the stoichiometrisehe to provide and around during Non-travel conditions a stoichiometric air / fuel ratio to be provided. 17. Fuel control system according to claim 15, characterized in that that the integrating stage has a device for delaying the integrating stage when reducing the air / fuel ratio for a predetermined time after a transition of the teacher of one contains a high voltage level to a low voltage level, that the delay means is responsive to the travel signal to provide a leaner stoichiometric air / fuel ratio than to provide the stoichiometric during the travel operation and to provide a stoichiometric air / fuel ratio during a Do not provide for travel security. lR. That the integrating stage contains a Asymmetriereinrichtunr fuel control system according to claim 15, characterized in that to bev7irken order that the integrator _m the air / fuel ratio olge 11 of a larger ^ or increase speed as it decreases the air / fuel ratio or reduced daP> the 909823/0563 BATH ORIGINAL Asymmetry device responds to the travel signal to a leaner air / fuel ratio than the stoichiometrlsohe to provide during a travel operation and to provide a stoichiometric air / fuel ratio xt during a non-travel operation to be provided. 19 · Fuel control system according to claim 15, characterized in that a current biasing device is provided to controllably supply the biasing current to the sensor, the biasing current causing the sensor to delay the generation of the transition from the first voltage level to the second voltage level, and that the current biasing device is responsive to the RpL se signal for providing a leaner air / fuel ratio than stoichiometric during a travel operation and for providing a stoichiometric air / fuel ratio during a non-travel operation. 2o. Fuel control system according to Claim 15 and 1Q, characterized in that that a device for changing the threshold value is provided that this Finrichtung for changing the threshold value and the current biasing means are responsive to the price signal in combination to provide a leaner air / fuel ratio than to provide the stoichiometric during a travel operation and to provide a stoichiometric air / fuel ratio to be provided during a non-travel company. 909823/0563