EP0033939A2 - Device for regulating the fuel supply via the idling nozzle to internal-combustion engines - Google Patents

Abstract

In a device for regulating the fuel supply to internal-combustion engines via an electromagnetically controlled idling nozzle, in which the fuel supply via the idling nozzle can be switched off when the engine is in overrun mode by means of a switch actuated directly or indirectly by the accelerator pedal, a further, speed-dependent switch controlled by an electronic device is provided in parallel with the said switch, the speed-dependent switch being closed when the engine speed decreases into a range corresponding to the idling speed, with the result that the idling nozzle is switched on again and opened. In such an arrangement, the engine speeds are determined and evaluated via the voltage output by the generator of the vehicle, but due to the differing shape of the characteristics of individual generators this is not sufficiently accurate and, accordingly, leads to differing switching instants. According to the object on which the application is based, the arrangement mentioned at the outset is to be designed in such a way that the reclosing instant in the idling-speed range is maintained with the greatest possible accuracy. This object is achieved by virtue of the fact that reclosing is performed by a pulse control, in which the pulses are taken from the ignition device (4) of the engine. The pulses used are therefore directly proportional to the engine speed and maximum accuracy is achieved. <IMAGE>

Description

The invention relates to a device for regulating the fuel supply to internal combustion engines via an electromagnetically controlled idle nozzle, in which the fuel supply can be switched off via the idle nozzle when the engine is in push mode by means of a switch actuated directly or indirectly by the accelerator pedal, with an electronic device paralleling this switch Controlled further speed-dependent switch is located, which is closed when the engine speed drops into a range corresponding to the idling speed, so that the idling nozzle is switched on again and opens.

Devices of this type have the purpose of saving gasoline which is still supplied but not required when the engine is in the pushing mode via the idling nozzle. The idle nozzle is therefore in front of these directions designed as an idle mixture shutoff valve.

In a known arrangement of the type mentioned at the outset, the engine speeds are determined and evaluated via the voltage output by the alternator of the vehicle. A disadvantage of this arrangement, however, is that on the one hand the accuracy of the evaluation depends on the shape of the characteristic due to the different course of the characteristics of the individual alternators, and that on the other hand the drive of the alternator in a vehicle is subject to fluctuations, for example due to the non-positive power transmission by means of the V-belt . This leads to inaccurate and different switching times.

An increased accuracy is required, however, because when switching on above the optimal idling speed, the gasoline savings that can be achieved with the present arrangement are reduced again, since this keeps the idling nozzle open for too long and since when switching on below the optimal idling speed, there is a risk that the engine either stops or runs so out of round that it is exposed to increased wear.

It is therefore desirable that when the accelerator is withdrawn, i.e. when the engine comes into overrun and the engine speed drops and if the fuel supply is interrupted via the parallel switch, the electronic control system switches it back on as precisely as possible at the optimal idling speed.

The invention is accordingly based on the object of designing an arrangement of the type mentioned at the outset in such a way that the point in time at which the motor is switched on again is observed with the greatest possible accuracy in the idling speed range.

This object is achieved in that the restart is carried out by a pulse control, the pulses being picked up by the ignition device of the engine.

With this arrangement it is achieved that pulses are used which are directly proportional to the respective engine speed and which cannot deviate from it in any way. For this reason, a maximum degree of accuracy is achieved with the arrangement according to the invention, and the switch-on time for a four-stroke engine is precisely determined to half a revolution, since two pulses are delivered per revolution.

It is particularly advantageous if the pulses in front of the ignition coil, in particular at the breaker contact of the distributor of the ignition system, are tapped, since the voltages occurring there are low and are therefore easy to process.

In order to be able to control the electromagnetic idle nozzle (the idle mixture shut-off valve) in a simple manner by means of the pulses, it is advantageous if the pulses via a pulse shaper, an amplifier stage and a phase rotation and stabilization device are fed to a digital-to-analog converter (for "pulse smoothing") and if the analog values thus formed are fed to a threshold switch (window discriminator) which acts on a relay coil of the parallel switch via an amplifier. The threshold value switch is advantageously adjustable in terms of the size of the threshold value, for example via a variable resistor, so that the idling speed, which differs from engine to engine, can be precisely specified at the threshold value switch.

By means of the threshold switch, the lower threshold value corresponding to the reclosing time is set precisely and, in addition, a range is set in which the speed can remain when the engine is started. This range corresponds to approximately 300 to 900 rpm. This hysteresis range is necessary to prevent the valve from fluttering, i.e. constant opening and closing.

The changing signal of the threshold switch is fed to the coil of the idle mixture cut-off valve via an amplifier and a switching relay.

The arrangement described above works for normal idle mixture shutoff valves. However, this function is hampered by certain shut-off valves, which due to their design are the sub pressure in the carburetor intake pipe are more exposed and which are kept closed by this vacuum. For such valves, it is necessary to apply an additional force in order to be able to open them, which according to the invention occurs by briefly increasing the voltage acting on the idle mixture shutoff valve during the restart process.

For this purpose, it is further provided according to the invention that the signal of the threshold switch corresponding to the point in time at which it is switched on is fed to an electronic switch which closes as a result and is connected upstream of a capacitor charging stage which is acted upon by a push-pull voltage converter.

When the signal corresponding to the lower idling speed and thus the reclosing time reaches the electronic switch, this switch is closed, so that the capacitor previously charged via the push-pull voltage converter can discharge via this electronic switch and supply its increased voltage to the idling mixture shut-off valve.

The capacitor is charged when the switching signal corresponding to the upper speed in the hysteresis range of the threshold switch is fed to a second electronic switch, which then closes and enables the capacitor to be charged by means of the push-pull voltage converter.

The arrangement described above is based on an idle mixture shut-off valve which is designed such that the idle nozzle closes when the current is switched off. In certain vehicles, however, an idle mixture cut-off valve is provided which works in reverse by opening the idle nozzle when the current is switched off, in order to ensure that the idle power of the engine is retained in the event of damage to the winding or the like. In this case, the arrangement must be designed in such a way that if the speed drops below the threshold value corresponding to the reclosure time, the parallel switch opens and is not closed.

It is advantageous if the switch which can be actuated by the accelerator pedal is arranged directly on the carburetor and can be actuated by means of the throttle valve axis. For this purpose, the throttle valve axis is expediently provided with a circle segment acting on a lever of the switch in order to keep the switch, which is designed as a pressure switch, actuated over a predetermined range of rotation of the throttle valve.

Since under certain circumstances the discharge time of the capacitor may be too short to exert a sufficient opening force, the invention provides in a modified embodiment that the signal of the threshold value switch corresponding to the reclosing time at the optimal idling speed is via a monostable /

The flip-flop is supplied to an electronic switch which closes as a result and which supplies an increased voltage to the coil of the idling mixture shut-off valve. In this way it becomes possible to supply the increased voltage to the idling mixture shut-off valve for a longer time than is possible with the previously described capacitor charging stage, so that its opening can be reached in any case. In particular, in this embodiment, depending on the use of the voltage source, the voltage can be varied in terms of its size and can be adjusted to the force required to open the various idle mixture shut-off valves of different designs.

• Fig. 1 zeigt in schematischer Darstellung eine Ausführungsform der erfindungsgemäßen Anordnung.
• Fig. 2 ist das Blockschaltbild der erfindungsgemäßen Anordnung nach Fig. 1.
• Fig. 3 ist das detaillierte Schaltbild der Anordnung nach Fig. 2.
• Fig. 4 ist ein Blockschaltbild ähnlich Fig. 2 bei einer abgewandelten Ausführungsform.
• Fig. 5 ist das detaillierte Schaltbild der Anordnung nach Fig. 4.

However, it is advantageous here if the increased voltage is generated by a push-pull voltage converter, which supplies its voltage via the electronic switch to the coil of the idling mixture shut-off valve after it has been closed.

• Fig. 1 shows a schematic representation of an embodiment of the arrangement according to the invention.
• FIG. 2 is the block diagram of the arrangement according to the invention according to FIG. 1.
• FIG. 3 is the detailed circuit diagram of the arrangement according to FIG. 2.
• FIG. 4 is a block diagram similar to FIG. 2 in a modified embodiment.
• FIG. 5 is the detailed circuit diagram of the arrangement according to FIG. 4.

According to FIG. 1, a carburetor 1 is provided with an electromagnetically controlled idle mixture shut-off valve 2, which is acted upon by an electronic device 3, which will be explained in detail later in connection with FIGS. 2 and 3. The electronic circuit 3 is supplied by the ignition device 4 of the motor vehicle directly proportional pulses of the engine speed. Arranged on the carburetor 1 is a microswitch 5, the actuating lever 6 of which is acted upon by a circular segment 7, which is arranged on the throttle valve axis 8 in order to keep the microswitch 5, which is designed as a pressure switch, actuated over a predetermined range of rotation of the throttle valve of the carburetor 1.

The microswitch 5 can thus be actuated by the accelerator pedal, the idle mixture shut-off valve being switched off when the vehicle engine is in the push mode by means of this switch.

9 with a fuse of the device 3 and 10 denotes a plug connection to the vehicle electrical system.

Fig. 2 shows the device 3 in the block diagram. The pulses supplied by the breaker contacts 11 of the ignition device 4 are fed to a pulse shaper 12, in which they are shaped into rectangular pulses and then passed through an amplifier stage 13 and a phase rotation and stabilization device 14 into a digital-to-analog converter 15, in which they are used "Pulse smoothing" can be converted into analog values.

The analog values thus formed, which are directly proportional to the engine speed, are fed to a threshold switch 16 (a window discriminator).

Via a connecting line 24 and an amplifier 18, the threshold switch 16 acts on a relay 22 with a switch 22a which is parallel to the microswitch 5 which can be actuated by the throttle valve axis. When one or both switches 5 and 22a are closed, the coil 23 of the idle mixture shut-off valve is acted on, so that the idle nozzle opens.

When using an idle mixture shut-off valve, which closes the idle nozzle when the current is switched off, the switch 22a is open in the rest position and the switch 5 is closed in the rest position.

• Bei einer Betätigung des Gaspedals wird der mittels der Drosselklappenachse 8 betätigbare Schalter 5 geschlossen und damit das Leerlaufgemiscbabschaltventil 2 geöffnet. Die infolge der Drehzahlsteigerung vom Digital-Analog-Umwandler 15 kommenden und der Drehzahl entsprechenden Analogwerte beaufschlagen über den Schwellwertschalter 16 und den Verstärker 18 die Spule 22 des Schalters 22a, so daß dieser geöffnet wird.

The arrangement described works as follows:

• When the accelerator pedal is actuated, the switch 5, which can be actuated by means of the throttle valve axis 8, is closed and the idling mixture shutoff valve 2 is thus opened. The result of the speed increase Analog values coming from the digital-to-analog converter 15 and corresponding to the rotational speed act on the coil 22 of the switch 22a via the threshold switch 16 and the amplifier 18, so that the latter is opened.

When accelerating, switch 5 is immediately opened again, while switch 22a also remains open until the engine idle speed is reached. In this area, which can be extended over a long period of time when the engine is in overrun mode, both switches 5 and 22a are open, so that the coil 23 of the idling mixture shut-off valve 2 is without current and the valve is closed. The fuel supply via the idle nozzle is therefore interrupted in this area.

By means of the threshold switch 16, the application of the relay 22 is switched off at a precisely set point in time corresponding to the optimal idling speed, so that the switch 22a now closes again and the idling nozzle is consequently opened.

In order to avoid a constant opening and closing of the idle mixture cut-off valve when the engine speed is increased again, the threshold switch 16 is provided with a hysteresis area, which has the effect that the relay 22 is not yet acted upon again when the speed increases, but only when this occurs Speed increase the hysteresis area is left.

FIG. 2 also shows a device with which it is possible to briefly apply an increased voltage to the coil 23 of the idling mixture shut-off valve in order to overcome the retaining force due to the negative pressure in the carburetor intake pipe. This device consists of an electronic switch 17 which is connected upstream of a capacitor charging stage 21 which is acted upon by a push-pull voltage converter 19 and an electronic switch 20 connected downstream of the latter. The electronic switch 17 in turn acts on the coil 23 of the idle mixture shut-off valve 2.

• Das dem Wiedereinschaltzeitpunkt bei optimaler Leerlaufdrehzahl entsprechende Signal des Schwellwertschalters 16 wird dem elektronischen Schalter 17 zugeführt, der hierdurch geschlossen wird, wodurch sich der zuvor aufgeladene Kondensator der Kondensatoraufladestufe 21 über den Schalter 16 und die Leitung 26 entladen kann, so daß eine erhöhte Spannung der Spule 23 zugeführt wird.

This arrangement works as follows:

• The signal of the threshold switch 16 corresponding to the reclosing time at an optimal idling speed is supplied to the electronic switch 17, which is thereby closed, whereby the previously charged capacitor of the capacitor charging stage 21 can discharge via the switch 16 and the line 26, so that an increased voltage of the coil 23 is supplied.

The capacitor of the capacitor charging stage 21 is charged when the switching signal corresponding to the upper speed of the hysteresis range of the threshold switch 16 is supplied to the second electronic switch 20, which then closes, so that the capacitor is now charged by means of the push-pull voltage converter can.

FIG. 3 is the detailed circuit diagram of the arrangement according to FIG. 2. The individual modules corresponding to the blocks in FIG. 2 are outlined in dashed lines and provided with the reference symbols according to FIG. 2 in order to facilitate the overview. The variable resistor for setting the size of the threshold value of the threshold switch 16 is denoted by 25 in FIG. 3.

An integrated component IC1 essentially consists of a monostable multivibrator, which converts the input pulses taken directly from the interrupter 11 into rectangular pulses of constant duration. The output signal acts on a load resistor R5 and on a voltage divider R6 / R7.

The current for a moving coil measuring device (tachometer) to be connected if necessary is set at resistor R5.

After a voltage divider, the signal at transistor T1 is amplified again and a phase shift is carried out. At transistor T2, whose operating voltage is stabilized to 12 V by Zener diodes, pulses with a positive amplitude occur via a load resistor R12. These pulses are fed via a diode D4 to an integrating stage consisting of the resistor R13 and the capacitor C4. Resistor R14 is the discharge resistor for C4.

Depending on the number of pulses of the same duration, the corresponding voltage level is set at the integration stage.

This voltage level is fed to a further integrated module IC2. This is a Schmitt trigger with an adjustable threshold and a fixed hysteresis. The threshold value can be set externally using a trimmer R16. This sets the reclosing time of the idle mixture shut-off valve.

The operating voltage is increased from 12 V to a galvanically isolated voltage of 25 V via the push-pull voltage converter 19. This voltage is rectified via diodes D6 to D9. The DC voltage is supplied to a capacitor C7 via a charging resistor R27, provided that the transistor T4 is driven with a low signal from the output of the integrated component IC2. At this time, the speed is above the threshold of the switching point set on the integrated module IC2.

As long as the engine is in overrun mode and its speed is above the idling speed, the idle mixture shut-off valve is not activated by the electronics. If the engine speed approaches the idling speed, the switching threshold of the integrated module IC2 is undershot, so that its output 14 drives the transistor T5. The capacitor charge of C7 (25 V) is used to overexcitation of the idle mixture shut-off valve. The the necessary holding voltage of 12 V is provided by the relay contact of relay 22, which is simultaneously excited by transistor T3.

The overexcitation of 25 V for 3 ms is required in the manner described for special designs of the idle mixture shut-off valve so that the nozzle needle sucked in by the negative pressure that builds up in the carburetor is torn loose.

FIG. 4 is a block diagram similar to FIG. 2 in a modified embodiment. In this embodiment, the supply of an increased voltage by a capacitor is replaced by the supply of voltage by means of a voltage source 29, which can be a push-pull voltage converter, in particular the push-pull voltage converter from the embodiment according to FIGS. 2 and 3. This voltage source is preceded by an electronic switch 28 which is controlled directly by the threshold switch 16 via a monostable multivibrator 27. Thus, if the signal of the threshold switch 16 corresponding to the reclosing time at the optimal idling speed is fed via the monostable multivibrator 27 to the electronic switch 28 that closes as a result, the voltage of the voltage source 29 is supplied to the coil 23 of the idling mixture shutoff valve 2.

FIG. 5 shows the detailed circuit diagram for this modified embodiment, the assemblies corresponding to the blocks in FIG. 4 again being outlined with dashed lines and provided with the reference symbols according to FIG. 4. 5, the flip-flop 27 is provided with an integrated component IC3 to which the voltage is supplied by the threshold switch 16 and which controls the electronic switch 28.

Claims (18)

1 _t device for regulating the fuel supply to internal combustion engines via an electromagnetically controlled idling nozzle, in which the fuel supply via the idling nozzle when the engine is in push mode can be switched off by means of a switch actuated directly or indirectly by the accelerator pedal, with another controlled by an electronic device parallel to this switch speed-dependent switch, which is closed when the engine speed drops into a range corresponding to the idling speed, so that the idling nozzle is switched on and opens again, characterized in that the switching on is carried out by a pulse control, the pulses from the ignition device (4) of the Motors can be tapped. 2. Device according to claim 1, characterized in that the pulses are tapped before the ignition coil. 3. Apparatus according to claim 2, characterized in that the pulses at the interrupter contact (11) of the distributor of the ignition system (4) are tapped. 4. Device according to one of claims 1 to 3, characterized in that the pulses via a pulse shaper (12), an amplifier stage (13) and a phase rotation and stabilization device (14) are supplied to a digital-to-analog converter (15). 5. The device according to claim 4, characterized in that the analog values are supplied to a threshold switch (16) which acts on a relay coil (22) of the parallel switch (22a) via an amplifier (18). 6. The device according to claim 5, characterized in that the threshold switch is adjustable with respect to the size of the threshold value corresponding to an optimal idling speed. 7. The device according to claim 6, characterized in that the setting of the threshold value via a variable resistor (25). 8. The device according to claim 5 to 7, characterized in that the threshold switch (16) has a hysteresis range above the threshold value corresponding to the optimal idle speed, in which the activation of the idle nozzle (the idle mixture shut-off valve) is maintained when the speed increases. 9. The device according to claim 8, characterized in that the hysteresis range a speed range of about 300 to 900 U / min. corresponds. 10. Device according to one of the preceding claims, characterized in that the coil (23) of the idle mixture shut-off valve (2) acting voltage is briefly increased during the restart process. 11. The device according to claim 10, characterized in that the reclosing time at the optimal idle speed signal of the threshold switch (16) is a closing electronic switch (17) is supplied, which is connected upstream of a capacitor charging stage (21) by a push-pull voltage converter (19) is applied. 12. The apparatus according to claim 11, characterized in that the capacitor charging during the discharge of the capacitor (C7) stage (21) resulting increased voltage of the coil (23) of the idle mixture shutoff valve (2) is supplied. 13. The apparatus of claim 11 and 12, characterized in that the switching signal corresponding to the upper speed of the hysteresis range in the threshold switch (16) is fed to a second electronic switch (20) which is arranged between the push-pull voltage converter (19) and the capacitor charging stage (21) and then closes, so that the capacitor (C7) is charged by means of the push-pull voltage converter (19). 14. The apparatus according to claim 10, characterized in that the reclosing time at the optimal idle speed corresponding signal of the threshold switch (16) via a monostable multivibrator (27) is fed to a closing electronic switch (28), which increases the voltage of the coil (23) of the idle mixture shut-off valve (2). 15. The apparatus according to claim 14, characterized in that the increased voltage is generated by a push-pull converter (29). 16. The device according to one of the preceding claims with an idle mixture shut-off valve, which opens when the current is switched off, characterized in that when the engine speed drops below the threshold value corresponding to the reclosure time, the parallel switch (22a) opens and that the switch (5 ) is closed in the rest position. 17. Device according to one of the preceding claims, characterized in that the switch (5) which can be actuated by the accelerator pedal is arranged directly on the carburetor (1) and can be actuated by means of the throttle valve axis (8). 18. The apparatus according to claim 17, characterized in that the throttle valve axis (8) is provided with a circular segment (7) acting on a lever (6) of the switch to actuate the switch (5) designed as a pressure switch over a predetermined range of rotation of the throttle valve to keep.

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