DE3320359A1 - METHOD FOR CONTROLLING THE FUEL SUPPLY TO AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

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04/17/1983 ch / dö

ROBERT BOSCH GMBH, 7OOO STUTTGART 1

Method for controlling the supply of fuel to an internal combustion engine

State of the art

The invention is based on a method for controlling the fuel supply to an internal combustion engine an idle shutdown device in the overrun area according to the genre of the main claim. Such a method is from DE-OS (R ^ 356 of

Applicant) known. Such a method makes it possible to brake an engine equipped with an internal combustion engine Motor vehicle in push mode. With such procedures it is generally disadvantageous that after the end of pushing operation because of the sudden resumption of the Fuel supply occurs a jolt and thereby the comfort and, to a certain extent, safety is impaired while driving. The method mentioned at the beginning with the associated device avoids torque jumps in that the interruption the fuel supply at the beginning and the restart

the fuel supply at the end of the overrun mode not suddenly, but rather smoothly. For this purpose ■ the fuel supply is set according to a Function either reduced or strengthened again. The achieved relatively high driving comfort is but bought with a high and costly effort in switching means.

Advantages of the invention

The inventive method with the characterizing Features of the main claim has the advantage that a sufficiently comfortable driving behavior with relatively little switching effort and thereby conditional small construction volume and cost ratio is achieved. In addition, the method according to the invention also with carburettor engines - and can be used particularly advantageously there.

The corresponding advantages are with a device with the characterizing features of the independent claim achievable. It is particularly advantageous that in addition to the ground line and the voltage line only three further connecting lines and a single one - into one of the named connecting lines inserted - switching device are required.

Through the measures listed in the subclaims are advantageous developments and improvements of the method specified in the main claim and the facility specified in the ancillary claim possible.

It has thus been found to be advantageous, depending on the upper speed threshold, the idle fuel quantity en neither feed nor switch off completely or switch on intermittently. This allows easily achieve a smooth and practically unnoticeable transition to push mode.

Another advantage is the introduction of the lower speed threshold, which means a smooth termination of the push mode and a smooth and jolt-free transition into allows idling.

The driving comfort is further increased by the introduction of a blocking time; when changing gears, during This blocking time of the internal combustion engine continues to be supplied with the idle fuel quantity.

The device comprises a number of building blocks known in principle, which are more useful and advantageous Way are interrelated. The logical connection of the blocks and others Details and advantageous configurations can be found in the description in conjunction with the drawings and to be taken from the claims.

drawing

An exemplary embodiment of the invention is shown in the drawing and is detailed in the following description explained. Figure 1 shows the device according to the invention in a block diagram, Figure 2 is a circuit diagram with the individual assemblies and FIG. 3 a function diagram.

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Description of the embodiment

In the block diagram according to FIG. 1, an accelerator pedal 11, an ignition device 12 and an idle shut-off valve 13 are initially shown as known elements of a motor vehicle. An accelerator pedal switch lk is mechanically connected to the accelerator pedal 11. Usually, the winding of the idle shut-off valve 13 lies between a terminal 15 and a ground connection represents the output of the overrun cut-off device l8. An input 19 of the overrun cut-off device l8 is connected to an ignition device 12, a second input 21 of the overrun cut-off device l8 is at one end of the accelerator pedal switch lk. The other end of the accelerator pedal switch lk is connected to ground l6.

FIG. 2 shows the individual modules and components of the overrun cut-off device 18. Only elements that are essential for the function are indicated. An input voltage divider with a series connection of a diode 22 and a resistor 23 and a parallel connection of a resistor 2k and a capacitor 25 is connected between the input and the ground connection 16 is used as a speed sensor.

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Next is n .. one for a lower speed threshold first threshold level 27 is provided, which essentially the series circuit of a voltage comparator 28 and two inverters 29 and 31 comprises. The non-inverting one The input of the voltage coraparator 28 is connected to a fixed voltage divider with the resistors 52 and 33 to one Supply line 34 with screened voltage as well as over a series circuit of a resistor 35 and a diode 36 at the output of the second inverter 31 · Der inverting input of the span comparator 28 is connected to the collector of the pre-stage transistor 26, which in turn has a work resistance 37 on the Supply line 34 and a capacitor 38 on Mass l6 lies. The voltage comparator 28 is provided with a load resistor 39 and a blocking capacitor 4l Mistake.

A second threshold value stage 42 is provided for the upper speed _{threshold n o} , which, connected in series, comprises a voltage comparator 43 and two inverters 44 and 45. The voltage comparator 43 has a load resistor 46 and a blocking capacitor 47. The non-inverting input of the ^ pannungskomparators 43 is again connected to the tap of a fixed voltage divider with the resistors 48 and 49 and via a series circuit of a resistor 5I and a diode 52 with the output of the second inverter 45 connected.

The screened voltage is applied to line 34 from the clamp 15 via a filter resistor 53 in connection with a filter capacitor 54 and a Zener diode 55.

».18721

The connection 21 of the accelerator pedal switch Ik is connected to the input of a switching preliminary stage 56. Within the switching pre-stage 56, the connecting line is led via resistors 57 and 58 to the base of a switching pre-stage transistor 59. Between the junction of the two resistors 57 and 58 and the ground connection 16 there is a Zener diode 61, and between the input of the switching pre-stage and the emitter of the transistor 59 there is a resistor 62. The emitter of the transistor 59 is connected directly to the connection 15.

The collector of the transistor 59 of the switching preliminary stage 56 is connected to the input of a switching output stage 63. There is also a switching point C cited later in the functional description. The switching output stage 63 comprises an output stage transistor 6 ^ and a base series resistor 65> which is at the input of the switching output stage 63. The emitter of the output stage transistor 6k is connected to the ground connection l6, and a switching relay 66 is inserted between the collector of the transistor 6k and the terminal 15 as a working resistance. The winding of the switching relay 66 is bridged in the usual way with a freewheeling diode 67.

The relay 66 of the switching output stage 63 is in operative connection with a switch 68, the connections of which on the one hand at terminal 15 and on the other hand via a diode 69 at ground connection l6 and at connection 17 the overrun cut-off device l8. The diode 69 serves as a freewheeling diode for the idle shut-off valve

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A one-shot multivibrator 71 is also provided, which has a negating AND circuit 72 and an inverter 73 includes. The input of the inverter 73 is via a resistor 7 ^ to ground l6 and a capacitor connected to the output of the AND circuit 72. The output of the inverter 73 is directly connected to an input the AND circuit 72 connected.

The other input of the AND circuit 73 and thus the input of the monostable multivibrator 71 is via a Switching point D, which will be required later, is applied to the output of a negating AND circuit 76. Next is one second negating AND circuit 77 is provided. One input of the AND circuit 76 is connected to an input of the AND circuit 77 and "also with the connection point of the two resistors 57 and 58 of the switching preliminary stage 56 are connected. Further is this connecting line to the input of an astable multivibrator 78 and a negating AND circuit 79 led. The other input of the AND circuit 79 is connected to the output of the monostable multivibrator 71; the output of the AND circuit 79 is via a diode 71 at the switching point C and thus at the input of the switching output stage 63 · The other input of the AND circuit 76 is at the output of the first threshold stage 27 and at the same time at one input of a negating AND circuit 82 «The other input of AND circuit 77 is present a switching point G mentioned again later and at the output of the second threshold value stage 42. The output the AND circuit 77 is at a switching point F and at the input of a further negating AND circuit The other input of the further AND circuit 83 is connected to the output of the AND circuit 82; the The output of the further AND circuit 83 is at the input

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an inverter 8k. A line leads from the output of the inverter 84 via a diode 85 to the switching point C and thus to the input of the switching output stage 63. The switching point C is also connected via a diode 86 to a switching point A, which in turn is connected to the connecting line between the inverter 29 and the inverter 31 of the first threshold value stage 27 is connected.

The astable flip-flop 78 comprises two inverting ones AND circuits 87 and 88. The AND circuit 88 is connected as an inverter, its input is connected to the output of the AND circuit 87 and connected to one end of a resistor 89. From the other end of the resistance 89 leads a capacitor 91 to the output of the inverter 88 and a resistor 92 to the other input of the AND circuit 87. The output of the AND circuit and thus the output of the astable trigger circuit 78 is connected to the other Input of the AND circuit 82.

Figure 3 is a functional diagram. FIG. 3a shows, depending on the time t, the speed curve η for a transition to overrun mode. The speed decreases from a value above the speed n_. First, the speed η falls below the upper threshold value n _Q , then the lower threshold value n. And then stabilizes at an idling value. The position of the throttle valve is sketched in FIG. 3b. Initially the throttle valve is open. If gas is removed, the throttle valve is at time t. closed and remains closed, Figure 3c shows the position of the idle valve. The idle valve is initially open, it remains open beyond the time t. After a blocking period has elapsed, which extends from time t to time t _o

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extends, the throttle valve is closed at time t _p * If the speed η falls below the speed threshold n _o at time t, the idle valve is

5 *

intermittently open and closed. If the speed η falls below the lower threshold value n. At the time t. , the idle valve is fully opened again and stays open. In Figure 3 is the idle fuel amount shown. It is "fully supplied" by time t, completely switched off from time t to time t_, from time t_ to time t ^ zu fed to a part and from time t. on again fully made available.

The following is the mode of action of the invention Facility including the associated procedure.

Three speed states of the internal combustion engine are evaluated by the two threshold value switches 27 and k2. Depending on the current speed of the internal combustion engine, on the position of the accelerator pedal 11 and on whether a shift is currently taking place, there are five cases.

Terms and Conditions

General conditions can be specified for some switching points. The following are in a first column the switching points, in a second column the speed conditions and in a third number the resulting ones Voltage potentials listed.

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■ i Switching point M - Ufctf a - 3320359 A3 ... 18721 Switching point I ⁿ < ⁿ ! L potential ⁿ > ⁿ 4 H potential Switching point G η <n ₂ L potential ⁿ > ⁿ 2 H potential H potential astable level 78 is working L potential astable level 78

does not work

The measuring point M represents the release input for the astable trigger circuit 78.

FaTT I- idling while stationary

When the internal combustion engine is idling at a standstill Motor vehicle, the speed η is below the lower Speed threshold n. In the first threshold level 27 becomes from the resistor 37 and the capacitor 38 one first time constant TT and from the resistor 39 and the capacitor ^ tI a second time constant "C

2 effective; for the second threshold level 42 comes from the resistor 46 and the capacitor 47 a time constant "C-. Under the conditions.

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the switching point A in Figure 2 is at H potential. The transistor 64 of the switching output stage 63 thus becomes conductive controlled, the relay 66 is energized, the switching contact is closed and that

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Idle shutoff valve 13 energized. The supply of the idle fuel quantity is not disturbed. The accelerator pedal switch Ik controlled by the accelerator pedal 11 is open and has no influence

Case II - vehicle runs on gas

If the accelerator pedal 11 is actuated, the speed η of the internal combustion engine increases. Usually, when a corresponding predetermined speed is exceeded, the shut-off valve 13 is de-energized and the idle fuel quantity is shut off. According to the invention, however, the gasification of an idle fuel quantity is involved in the air / fuel mixture formation process up to a medium speed range of approximately η = 3,000 revolutions / minute. For this purpose, the transistor 59 of the switching preliminary stage 56 is controlled to be conductive via the accelerator pedal switch lk. The switching point C goes to Η potential via the collector of the transistor 59. The transistor 64 of the switching output stage 63 thus also becomes conductive, the relay 66 picks up and the idle shut-off valve 13 is kept in the current-carrying state via the switch 68.

Case III - the vehicle is accelerated and gear changes are made

During a shift, the driver generally takes his foot off the accelerator pedal 11. The speeds η are generally above the two speed thresholds n. And n _o . In this case, the overrun fuel cut-off would normally commence and the speed η of the internal combustion engine would drop very sharply. To prevent this from happening is

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according to the invention the monostable multivibrator 71 is provided. The monostable multivibrator 71 can emit a pulse of about half a second duration, during which time switching point C is held at H potential. The transistor Sk of the switching stage 63 and thus also the idle cut-off valve 13 are thus kept energized. The monostable multivibrator 71 then emits the pulse when an edge HL occurs at switching point D. This is the case under the condition described. The switching point M then has H potential when the accelerator pedal switch Ik is open. The switching point M serves - as already mentioned above - as a release for the astable multivibrator 78 and also as a release for the AND circuit 79

Case IV - The vehicle is held in push

If the speed of the internal combustion engine is between the values n. And n_, the switching point A is at L potential. The transistor 59 of the switching preliminary stage 56 is blocked. The one-shot multivibrator 71 emits its mentioned pulse. If the accelerator pedal switch lk is still open after that, a new switching condition is added: the switching point E has H potential, the switching point G has L potential and leads the switching point F to H potential. In this way, however, the AND circuit 83 is now controlled to be conductive. The switching pulses of the astable multivibrator 38 are switched through to the switching point C, the transistor Sk of the switching stage 63 is switched on and off intermittently. A ratio of 1: 1 is provided as the pulse duty factor. The idle shut-off valve 13 is also switched on and off intermittently by the transistor Sk via the relay 66

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switches. As soon as the speed η falls below the speed threshold η in overrun mode, the switching point receives E from the first speed threshold 27 and an L potential thus influences the AND circuit 82 so that the switching point C remains at Η potential. This becomes the intermittent Signal converted into a permanent switch-on signal.

Case V - Vehicle is kept pushing at high speeds

If the speed η of the internal combustion engine is above the upper speed threshold n ", the astable trigger circuit 78 can no longer be effective after the pulse emitted by the monostable trigger circuit 71 has elapsed, since the switching point G is at H potential and the switching point F is at L- Potential lies. The idle shut-off valve 13 is de-energized. If the speed η of the internal combustion engine then falls below the upper threshold value n _o , the astable trigger circuit 78 is enabled again. The idle cut-off valve 13 is switched on and off again intermittently. If the speed η continues to fall, namely to below the lower threshold value τι. , the idle shut-off valve 13 remains switched on continuously.

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Claims (1)

R. I i
04/17/1983 ch / dö 721 ROBERT BOSCH GMBH, 7OOO STUTTGART 1 Method and device for controlling the fuel supply an internal combustion engine Expectations Iy method of controlling fuel delivery to a Internal combustion engine with an idling shutdown device in the push mode, with the fuel supply reduced depending on operating parameters at the beginning of overrun according to a predetermined function and is increased at the end of the push mode according to a preselected function, characterized in that that an upper speed threshold (n ") is provided and in overrun mode above the upper one Speed threshold (n ") the idle fuel quantity turned off completely. 2. The method according to claim 1, characterized in that in the overrun mode below the upper speed threshold (n _o ) of the internal combustion engine, a predeterminable part of the idling fuel quantity is supplied. . 18721 3. Device according to claim 2, characterized in that that the supply of the idling amount of fuel is intermittent takes place between full amount and complete shutdown. k » Method according to one of the preceding claims, characterized in that a lower speed threshold (n.) is also provided and the full idle fuel quantity is supplied to the internal combustion engine below the lower speed threshold (n) in overrun mode. 5. The method according to any one of the preceding claims, characterized in that immediately after the onset of pushing operation for a definable blocking time the internal combustion engine still has full idling power amount of substance is supplied. 6. The method according to claim 5 for an internal combustion engine with a downstream change gear, characterized characterized in that the locking time begins with a gear change. 7. Device for performing the method according to one of claims 1 to 6, characterized in that that in the supply line of the electrical power for the idle shut-off valve (13) an overrun cut-off device (L8) inserted and an accelerator pedal switch (1 * 0) controlled by the accelerator pedal (11) is provided and the Overrun cut-off device (18) for the purpose of controlling it to the accelerator pedal switch (1 * 0 and to a speed sensor (Ignition device 12 of the internal combustion engine) is connected. R. 8. Device according to claim 7 »characterized in that the overrun cut-off device (L8) has a first, from Speed sensor (12) controllable, threshold value stage (27) to form the lower speed threshold (s) and one connected to it, the idle shut-off valve (13) controlling, switching output stage (63) includes. 9. Device according to claim 7 or 8, characterized in that that the overrun cut-off device (l8) has a second threshold value stage which can be controlled by the speed sensor (12) (42) for forming the upper speed threshold (n_) and a switching output stage (63) controlled by it comprises 10. Device according to one of claims 7 to 9 »characterized in that the overrun cut-off device (l8) one of the accelerator pedal holder (1 * 0 controllable and the Switching state of a switching output stage (63) controlling switching preliminary stage (56) contains. 11. Device according to one of claims 8 to 10, characterized in that a monostable flip-flop (71) is provided, the input of which with an output of the first threshold value stage (27) and the output of which the input of the switching output stage (63) is connected. 12. Device according to claim 10, characterized in that the input of the monostable flip-flop (71) continues can be controlled by the accelerator pedal switch (1 * 0. 13. Device according to one of claims 7 to 12, characterized in that the overrun cut-off device (18) comprises an astable toggle stage (78) controllable by the accelerator pedal switch (lk ) and a switching output stage (63) controllable by it.