EP0614003B1 - Method for controlling the deceleration of an internal combustion engine - Google Patents

Description

The invention relates to a method for controlling the overrun operation of an internal combustion engine according to the preamble of claim 1.

Such a method is known from US-A-5 119 781 and is used in particular to control the fuel supply to an internal combustion engine before and after the overrun operation.

For reasons of the increasingly urgent saving of fuel and to reduce pollutant emissions, it is known in the control of modern internal combustion engines to reduce the fuel in overrun mode or to switch it off completely.

Thrust operation is generally spoken of when the speed of the internal combustion engine exceeds a certain, predetermined value when the throttle valve is closed. Overrun operation can also be recognized if the throttle valve is not completely closed, but falls below a predetermined opening angle and the speed is above the value that would normally be set for the respective accelerator pedal position.

Since there is generally a jump in torque during the transition from overrun mode to overrun cutoff (overrun cutoff) and vice versa, which may be noticeable in the vehicle as a jerk, it is customary to adjust the ignition angle in the "late" direction in order to reduce the torque. At the same time, an actuator (idle filling actuator), that doses the combustion air when the throttle valve is closed, adjusted to a position that only allows a small air flow.

This method has the disadvantage that the ignition angle cannot always be adjusted to the value required for the desired torque reduction in the "late" direction, and the idle filling actuator cannot always be concluded that the air flow is sufficiently small without over-evacuating the intake manifold or one Fear of the internal combustion engine to fear.

The consequence of this is that, when the overrun mode is switched over after overrun fuel cutoff, the internal combustion engine often still delivers so much torque that the sudden shutdown of the fuel supply leads to a sudden jump in torque.

On the other hand, in the opposite case, namely when changing from overrun cut-off to overrun or partial load, when the throttle valve is opened from its closed position, the ignition angle is suddenly changed in the direction of "late" when the fuel injection is started and then with the aid of a ramp function on the Ignition angle provided for normal engine operation is adjusted.

From DE-PS 28 01 790 a method and a device for controlling the fuel supply at the beginning and after the overrun operation is known, with which the operating behavior of the internal combustion engine can be improved during the said transitions. If the accelerator pedal returns to its zero position, the throttle valve also reaches its idle position, which signals the start of coasting operation at a speed above a certain threshold value. There follows a certain period of time during which the fuel supply is maintained and the fuel supply then follows a predetermined one Function reduced to be switched off abruptly afterwards. At the end of the overrun operation, the fuel metering suddenly increases to a value that results in an ignitable mixture, but the resulting torque is not yet too great. After the sudden increase in fuel metering, the fuel supply is then brought up to the normal value according to a selectable function.

US-A-4 276 863 describes an apparatus for controlling the supply of fuel to the cylinders of an internal combustion engine. In order to achieve a smooth torque transition when the injection is restarted after a delay in the internal combustion engine, individual cylinders are switched on in stages depending on the speed of the internal combustion engine. Depending on the firing order of the individual cylinders, a predetermined sequence is observed both when switching off and when switching on the fuel supply.

From DE-A-27 39 223 it is known to store various models for the interruption of the fuel delivery to the cylinders in a fuel injection system for an internal combustion engine. The pre-selected interruption schedule depends on the power demanded by the engine.

The invention has for its object to provide a method of the type mentioned for an internal combustion engine with several cylinders so that soft torque transitions from overrun to overrun shutdown and vice versa can be realized in a simple manner.

The solution to this problem characterizes claim 1. Advantageous further developments can be found in the subclaims.

It is by selectively suppressing injection pulses for individual cylinders according to specified masking patterns It is possible to significantly reduce the torque jump during the transition from overrun mode to overrun cut-off, since the torque slowly degrades.

The restart jolt at the end of the overrun can also be avoided by gradually switching on the injection for the cylinders. In addition to increased driving comfort, these measures make the vehicle safer to handle even in the limit areas of push operation.

• Figur 1 ein vereinfachtes Blockschaltbild einer Brennkraftmaschine, bei der das erfindungsgemäße Verfahren angewendet wird,
• Figur 2 ein Flußdiagramm zur Steuerung der Kraftstoffzufuhr während des Übergangs von Teillast nach Schubabschaltung,
• Figur 3 mögliche Ausblendmuster für eine Vierzylinder-Brennkraftmaschine und
• Figur 4 eine Abfolge ausgewählter Ausblendmuster für den Betriebsübergang nach Figur 2.

An embodiment of the invention is shown in the drawing and is explained in more detail with reference to the following description. Show it:

• FIG. 1 shows a simplified block diagram of an internal combustion engine in which the method according to the invention is applied,
• FIG. 2 shows a flow chart for controlling the fuel supply during the transition from partial load to overrun fuel cutoff.
• Figure 3 possible masking pattern for a four-cylinder internal combustion engine and
• FIG. 4 shows a sequence of selected masking patterns for the transfer of operations according to FIG. 2.

In the block diagram of an internal combustion engine shown in simplified form in FIG. 1, only those parts are shown which are necessary for understanding the method according to the invention. The reference number 10 denotes an internal combustion engine with four cylinders Z1 to Z4. An injection valve EV1 to EV4 is assigned to each of these cylinders, which inject fuel in a predetermined sequence into individual intake pipes of the respective cylinders (sequential fuel injection). The injection valves are parts of a fuel circuit, not shown, which in a manner known per se consists of a fuel tank, a pressure regulator, a fuel pump, a fuel filter and corresponding lines. The internal combustion engine 10 receives the combustion air via an air filter 11, an intake duct 12 and a throttle valve block 13. This throttle valve block 13 contains a throttle valve, a throttle valve switch and / or a throttle valve opening angle sensor. To determine the intake air mass, an air mass meter 14 is provided in the intake duct 12, which can be implemented either as a hot-film air mass meter or as a hot-wire air mass meter. A three-way catalytic converter 16 is provided in an exhaust gas duct 15 for separating out the constituents HC, CO and NO _x contained in the exhaust gases. To detect the oxygen concentration in the exhaust gas, a lambda probe 17 is inserted in the exhaust gas duct 15 upstream of the three-way catalytic converter 16. Furthermore, a sensor 18 for detecting the engine speed and a coolant temperature sensor are located at suitable points on the internal combustion engine 19 available. The outputs of the sensors mentioned and the inputs of the actuators mentioned are connected via interfaces to corresponding inputs and outputs of an electronic control device 20.

Such electronic control devices for internal combustion engines, which in addition to fuel injection can also take on a multitude of other tasks (e.g. ignition control), are known per se, so that only the structure and its mode of operation associated with the present invention are dealt with below. The heart of the electronic control device 20 is a microcomputer, which controls the required functions according to a defined program. With the help of the signals supplied by the sensors (air mass meter 14, speed sensor 18) and processed in corresponding circuits, a basic injection time or basic injection time is calculated and, depending on further operating parameters, corrections of this basic injection time are carried out in such a way that a fuel-air mixture is generally used by using the lambda control is achieved, which corresponds to the stoichiometric ratio (λ = 1).

For example, the internal combustion engine is in partial load operation and the driver of the vehicle takes his foot in front of the accelerator pedal, i.e. the throttle valve closes completely and the speed of the internal combustion engine is above a limit value, so overrun mode is recognized and the fuel supply to the internal combustion engine can be prevented.

As an alternative to evaluating the throttle valve position as a thrust criterion, the position of the accelerator pedal 21 can also be used.

The process sequence for switching off the fuel in overrun mode is described with reference to FIG. 2.

In a first step S1, both the position of the throttle valve and the current speed n of the internal combustion engine are read. For this purpose, the throttle valve block 13 according to FIG. 1 can either contain a throttle valve position sensor or, in the simplest case, a throttle valve switch, the output signal of which, like the signal from the speed sensor 18, is supplied to the electronic control device 20. Subsequently, in step S2 it is queried whether the throttle valve is closed and the current speed n of the internal combustion engine is above a limit value GW1. This limit value GW1 can be stored, for example, as a function of the machine temperature and the coolant temperature, in a map 23 of a memory in the electronic control device 21. If one of the queries is negative, there is no overrun operation and the injection pulses TI are passed on unchanged to the injection valves EV1-EV4 in step S7. If both queries are positive, overrun mode is recognized in step S3 and overrun cutoff is activated in step S4. For this purpose, masking patterns are read out from a memory 22 of the electronic control device 20, according to the structure of which the injection pulses TI for individual cylinders Z1 to Z4 of the internal combustion engine 10 are selectively suppressed in step S5.

In FIG. 3, the 16 possible blanking patterns A to P are shown using the example of a four-cylinder internal combustion engine. The cylinders Z1 to Z4 are plotted in their usual firing order from left to right. A filled (black) square signals an injection pulse for the injection valve assigned to the respective cylinder, while an empty (white) square means that the injection pulse for the respective injection valve is suppressed. With blanking pattern P, all cylinders Z1 to Z4 are therefore supplied with fuel (normal driving operation), with blanking pattern A, the fuel supply is completely prevented (overrun cutoff). Combinations between these two fade-out patterns are either one (Pattern B, C, E, I), two (pattern D, F, G, J, K) or three injectors (pattern H, L, N, O) are activated. These masking patterns are stored in a read-only memory (ROM) 22 of the electronic control device 22, it being possible for reasons of capacity to store two of these masking patterns as one byte. For the possible operating state transitions of the internal combustion engine (overrun cut-off ---> idling, overrun cut-off ---> partial load, partial load ---> overrun cut-off, idling ---> overrun cut-off), the 16 possible skip patterns in a four-cylinder internal combustion engine result in a consequence of masking patterns (5 patterns in the exemplary embodiment) defined and read out in accordance with the respective operating state change.

In a 4-stroke internal combustion engine with four cylinders, this means that the individual blanking patterns are read out at intervals of one working cycle (720 ° KW revolution). A possible sequence of skip patterns is indicated in FIG. 4 for the partial load operating transition after overrun fuel cutoff, as was described with reference to FIG. 2. Starting from masking pattern P, according to which all four cylinders Z1, Z3, Z4 and Z2 are supplied with fuel sequentially, cylinder Z2 is switched off after 720 ° KW, cylinder Z3 is also switched off after another 720 ° KW etc. Is the last masking pattern (here Pattern A) processed, ie the last byte read out, the transition function is executed. In the example of the fuel cut-off, the injection of all four cylinders remains switched off after the last blanking pattern has been carried out. In the example of reinsertion, ie the change of operating mode, overrun cut-off ---> idling or overrun cut-off ---> partial load, the injection of all four cylinders remains switched on after execution of the last blanking pattern. The sequences of fade-out patterns are defined separately for the respective transitions, ie in the example given a selection of five fade-out patterns is selected from the 16 possible patterns. At the individual transitions, the Fade-out patterns can still be differentiated according to the applied speed, the speed change speed (speed gradient) and the respective throttle valve angle or throttle valve gradient.

If an engine operating state change occurs during the processing of a skip pattern, the further execution of the previously read sequence of skip patterns is stopped and the corresponding skip pattern (ie the byte sequence) is run "backwards". If, for example, the transition after overrun cut-off is active and the driver of the vehicle presses the accelerator pedal again, the sequence of skip patterns is not run through to the end, but back to the beginning. In this case, the transition function is ended when the first masking pattern of this sequence is read in again and executed as an injection sequence.
Entry into a transition function is not linked to a cylinder number, ie the first masking pattern does not necessarily have to begin with cylinder Z1. The sequence of blanking patterns is started regardless of the cylinder numbering if the criteria for thrust detection or for thrust end are met.

The method according to the invention can of course also be used for internal combustion engines with a different number of cylinders, for example for 6-cylinder internal combustion engines. In this case there are 64 possible masking patterns.

Claims (4)

1. Method for controlling the fuel supply to an internal combustion engine (10)

   - with a plurality of cylinders (Z1-Z4) and successive injections into the cylinders in a predetermined sequence in the overrun operation range,

   - operating parameters (DKW,n) of the internal combustion engine being detected and the beginning and end of overrun operation being detected when these operating parameters meet particular conditions,

   - the fuel supply to the cylinders (Z1-Z4) being reduced in accordance with a selectable function when overrun begins and being released again in accordance with a selectable function at the end of overrun,

   - once overrun operation has been detected the injections for individual cylinders (Z1-Z4) being suppressed in a predetermined sequence and

   - once the end of overrun has been detected the injections for individual cylinders (Z1-Z4) restarting in another predetermined sequence,

   - the sequences being determined by a temporal sequence of individual masking patterns (A-P) stored in a memory of an electronic control device (20),

   characterized in that when a change in the operating state of the internal combustion engine (10) occurs during the processing of a sequence of masking patterns (A-P), the current masking pattern (A-P) is not continued to the end but, instead, once the change in the operating state has been detected, the current masking pattern (A-P) and the sequence of masking patterns (A-P) are then run through backwards.
2. Method according to Claim 1, characterized in that the masking patterns (A-P) are determined as a function of the respective speed (n) applied or of the speed gradient of the internal combustion engine (10).
3. Method according to Claim 1, characterized in that the masking patterns (A-P) are determined as a function of the respective throttle-valve angle (DKW) applied or of its gradient.
4. Method according to Claim 1, characterized in that the processing of a sequence of masking patterns (A-P) is started independently of the cylinder numbering (Z1-Z2) when the criteria for overrun detection or the end of overrun are met.

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