DE10341577B3 - Overrun control system for internal combustion engine of road vehicle has one or more programmed to control volume flow regulation valve and stop injection when overrun condition is sensed - Google Patents

Abstract

A first, start (S1) step and a control input (B) trigger a second step (S2) which monitors whether the engine is pulling or on the overrun. It sends signals to a third step (S3) which checks the result after a delay (T-W) and to the high-pressure fuel pump (S4) which switches off a marker (M). A fifth step (S5) produces a threshold signal (FUP-SW) which is dependent on engine speed (N). The actual fuel pressure (FUP-AV) is read on the sixth step (S6). The threshold and actual values are compared in the seventh step (S7). Signals are sent to the third and eighth (S8) steps. A minimum injection period (MFF-MIN) is specified. The ninth step (S9) specifies the frequency of fuel supply (ANZ-LEAK).

Description

The The invention relates to a method and a device for controlling an internal combustion engine with a fuel supply, the a flow control valve includes.

One increasing proportion of internal combustion engines has injectors on, which are arranged directly on the combustion chamber. Such internal combustion engines with direct fuel injection have in conjunction with a very high fuel pressure in the fuel supply of the injectors the advantage that they are highly efficient and therefore fuel efficient can be operated. To is in the fuel supply in one direction, for example Gasoline internal combustion engines a pressure of up to about 200 bar generated. To produce this high Pressure have corresponding feeders for fuel a low-pressure pump, which promotes fuel from a tank and this promotes into a low-pressure circuit in which a pressure from 3 to 6 bar prevails.

On the output side the low-pressure circuit, a high-pressure pump is provided, which regularly from the crankshaft of the internal combustion engine is driven. The high pressure pump promotes the fuel into a fuel storage, which at normal Operation of the engine fuel at a pressure of 150 to 200 bar stores. Injectors are with the fuel tank operatively connected and are fueled by this. Upstream of the High pressure pump is in the low pressure circuit a flow control valve provided by means of which the flow, that of the high-pressure pump supplied is, can be adjusted. This has the advantage of being on a otherwise necessary regulator valve at the output of the fuel storage, which is supplied by the high pressure pump, can be dispensed with and also on a return line from the regulator valve to the low pressure circuit. The efficiency of a such fuel supply device is higher as that of a Kraftstoffzuführvorrichtung with a regulator valve on Output of the fuel storage. Thus, the fuel consumption can be the internal combustion engine by the use of a fuel supply without Lower regulator valve.

The Volume flow control valve, however, has a leakage of, for example 0.01 liters / minute with the result that even in operating conditions in where no fuel required is, the fuel mass flow caused by the leakage, is conveyed to the high-pressure pump and from this into the fuel tank.

in the Shifting operation of the internal combustion engine, i. if the actual Speed of the crankshaft of the internal combustion engine is higher as the driver desired Speed, in modern internal combustion engines is the regular fuel supply to the combustion chambers the cylinder is switched off. This measure reduces on the one hand the fuel consumption and causes the other one in push mode desired Braking effect of the engine. The shift operation is further defined by that the output from the crankshaft output torque is negative.

Further is in the push mode of the internal combustion engine and the throttle in its closed position brought with the result that only a very small air mass in the respective cylinder of the internal combustion engine passes. At a longer push operation the leakage causes an uncontrolled increase in the fuel pressure in the fuel storage.

In the DE 198 58 468 A1 a method for controlling the fuel supply in a gasoline engine with direct injection is described. To control fueling during a fuel cutoff mode, the amount of oxygen stored in the catalyst or the temperature of the catalyst is determined and intermittently supplied with fuel to the engine so that the fuel in the catalyst is reacted and excess oxygen therein is reduced.

From the DE 199 33 198 A1 a method for pressure control on an injection device for liquid fuels is known in which from a fuel tank, the fuel is conveyed by means of a backing pump via the delivery line and a high-pressure pump in a pressure accumulator, which is in communication with at least one injection nozzle, wherein the pressure in the pressure accumulator over a controllable pressure holding valve is controlled. The amount of fuel flow to the high-pressure pump is controlled in dependence on the flow rate through the pressure-holding valve in such a way that with an increase in the flow rate discharged through a discharge line of the pressure-holding valve, the inflow quantity to the high-pressure pump is reduced.

The The object of the invention is a method and a device to provide for controlling an internal combustion engine, the one or the uncontrolled increase in pressure in sliding operation of the internal combustion engine prevented in the fuel tank.

The object is solved by features of the independent claims. Advantageous embodiments of the invention are in the Unteransprü marked.

The Invention is characterized in that in an internal combustion engine with a fuel supply device, which comprises a volume flow control valve, in the detected shift operation the regular fuel supply to the combustion chambers the cylinder is switched off. The frequency of an isolated Fuel supply to the combustion chambers the cylinder hangs off of a size that a predetermined minimum injection period characterized and depends on one of the leakage of the flow control valve characterizing Size. This has the advantage that the desired Fuel mass accurate is zumessbar, even if a very small leakage of the flow control valve consists. For example, only in every fifth or tenth cylinder segment Fuel in one of the combustion chambers meted out.

One Cylinder segment is defined as the crankshaft angle for a Divided duty cycle of a cylinder of an internal combustion engine by the number of cylinders. A cylinder segment is thus at an internal combustion engine with four cylinders 180 ° and in an internal combustion engine with six cylinders 120 ° crankshaft angle. An uncontrolled pressure increase in the fuel tank during a very long-lasting overrun, leading to damage in the fuel tank to lead can be avoided in a simple way.

In an advantageous embodiment of the method for controlling the Internal combustion engine hangs the frequency the fuel supply to the combustion chambers from a fuel pressure in the fuel storage. The advantage is that the fuel pressure anyway is recorded and thus available as a measure and so easy and reliable It can be ensured that the fuel pressure has certain values does not exceed.

In a further advantageous embodiment of the invention is the Size that characterized a predetermined minimum injection period, a the minimum fuel mass characterizing size, the while an injection process is edible.

This has the advantage that the frequency the fuel supply is so simple and accurate can be determined, as the minimum fuel mass characterizing quantity which is acceptable during an injection, decisively is for the fuel mass balance in the fuel storage and thus for the fuel pressure.

In a further advantageous embodiment of the invention is the the minimum fuel mass characterizing size is a minimum Fuel mass flow through the injector during a Cylinder segment with feed of fuel in the combustion chamber. This has the advantage that the calculation processes in a device for controlling the internal combustion engine frequently Basis of corresponding mass flows can be done and thus the frequency the fuel supply to the combustion chambers is easy to calculate, especially since the regular Fuel mass flow, due to the leakage of the flow control valve enters the fuel storage, depending on the particular control parameter of the volume flow control valve is stored in a characteristic.

In A further advantageous embodiment of the invention is based on detected an error of the volume flow control valve when the frequency the fuel supply to the combustion chambers exceeds a predetermined threshold. This has the advantage that at the same time a simple diagnosis of the flow control valve possible is.

In a further advantageous embodiment of the invention takes place the fuel supply during the Expansion or Ausschiebetaktes. This has the advantage of being unburned Air / fuel mixture in the exhaust system of the internal combustion engine reaches and there especially in the range of a catalytic converter inflamed. This exothermic reaction contributes This helps to heat up the catalytic converter and thus also while of the shift operation to maintain its operating temperature or at least can almost maintain. So can in a subsequent Normal operation of the internal combustion engine, in which a load on the internal combustion engine is applied, the exhaust gases in the catalytic converter immediately with a high Efficiency to be converted.

embodiments The invention are explained below with reference to the schematic drawings. It demonstrate:

1 an internal combustion engine with direct injection of the fuel into the combustion chamber,

2 a flowchart of a program for controlling the internal combustion engine according to 1 in push mode.

elements same construction and function are cross-figurative with the same Provided with reference numerals.

An internal combustion engine ( 1 ) comprises an intake tract 1 , an engine block 2 , a cylinder head 3 and an exhaust tract 4 , The engine block 2 includes a plurality of cylinders having pistons and connecting rods via which they are connected to a crankshaft 21 are coupled.

The cylinder head 3 includes a valvetrain with an inlet valve, an outlet valve and valve actuators. The cylinder head 3 further comprises an injection valve 34 and a spark plug. Alternatively, the injection valve 34 also in the intake tract 1 be arranged.

Further, a feeder 5 intended for fuel. It includes a fuel tank 50 that is via a first fuel line with a low pressure pump 51 connected is. On the output side is the low-pressure pump 51 towards an inlet 53 a high pressure pump 54 operatively connected. Furthermore, the output side of the low-pressure pump 51 a mechanical regulator 52 provided, which on the output side via a further fuel line to the tank 50 connected is. The mechanical regulator 52 is preferably a simple spring-loaded valve in the manner of a check valve, wherein the spring constant is chosen so that in the inlet 53 a predetermined low pressure of, for example 3 to 6 bar is not exceeded. The low pressure pump 51 is preferably designed so that it always delivers a sufficiently high amount of fuel during operation of the internal combustion engine, which ensures that the predetermined low pressure is not exceeded.

The feed 53 is to the high pressure pump 54 guided, which output the fuel to a fuel tank 55 promotes. The high pressure pump 54 is usually from the crankshaft 21 or the camshaft driven and thus promotes a constant fuel volume at constant speed of the crankshaft in the fuel tank 55 ,

The injectors 34 are with the fuel storage 55 operatively connected. The fuel thus becomes the injectors 34 over the fuel storage 55 fed.

In the flow of the high-pressure pump 54 that is, upstream of the high pressure pump 54 , is a volume flow control valve 56 provided by means of which the flow adjusted who can, which is supplied to the high-pressure pump. By a corresponding control of the volume flow control valve 56 can be ensured in the fuel tank 55 always the desired fuel pressure prevails without an electromagnetic regulator on the output side of the fuel tank 54 must be provided with a corresponding return line in the low pressure circuit.

Furthermore, the internal combustion engine is a control device 6 assigned, which in turn are assigned sensors that detect different quantities and each determine the measured value of the measured variable. The control device 6 determined depending on at least one of the measured variables manipulated variables, which are then converted into corresponding control signals for controlling actuators by means of appropriate actuators.

The sensors are a pedal position sensor, which detects the position of an accelerator pedal, a crankshaft angle sensor, which detects a crankshaft angle and which is then assigned a rotational speed N, an air mass meter, which detects the air mass flow MAF, and a pressure sensor 58 , which determines the fuel pressure FUP_AV in the fuel reservoir 55 detected. Depending on the embodiment of the invention, any subset of the sensors or additional sensors may be present.

The actuators are, for example, as intake or exhaust valves, the injectors 34 , a spark plug, a throttle valve or the volume flow control valve 56 educated.

A program for controlling the internal combustion engine in coasting mode is started in a step S1 ( 2 ). In step S1, variables are initialized to predetermined values.

In a step S2 is checked whether the operating state BZ of the internal combustion engine, the shift operation SCH is. If this is not the case, then the condition of the step S2 again after a predetermined waiting time T_W, the Program in a persisted in a step S3, tested.

However, if the condition of step S2 is met, then in one step 54 a flag M1 with the. Value OFF used. This flag M1 is then used, for example, by a function for determining the injection period TI, and causes the regular injection, that is, injection in each cylinder segment of the internal combustion engine, to be inhibited.

In a step S5 becomes a threshold value FUP_SW of the fuel pressure dependent of the rotational speed N, preferably determined by means of map interpolation.

In a step S6, the actual fuel pressure FUP_AV read in from the fuel pressure sensor is read 58 is determined.

In a step S7, it is checked whether the actual fuel pressure FUP_AV is greater than the threshold value FUP_SW of the fuel pressure. If the condition of step S7 is not met, the processing in step S3 is continued. However, if the condition of step S7 is fulfilled, then in a step S8, a minimum fuel mass flow MFF_MIN to be measured is dependent on a mi nimalen injection period TI_MIN, the actual fuel pressure FUP_AV and preferably an air mass flow MAF determined.

The minimum injection time TI_MIN is predetermined such that when the minimum injection time TI_MIN is exceeded, a precise metering by the injection valve 34 is possible. If the minimum injection time TI_MIN is not reached, precise metering of the fuel is not guaranteed due to the complex dynamic processes during the needle stroke.

In a step S9, a frequency ANZ_LEAK of the fuel meterings is calculated from the quotient of the leakage through the volume flow control valve 56 conditioned fuel mass flow MFF_VCV and the minimum edible fuel mass flow MFF_MIN determined. All fuel mass flows and also the air mass flow are based on the fuel mass or air mass per cylinder segment.

The fuel mass flow MFF_VCV caused by the leakage of the flow control valve 56 is conditional, is preferably dependent on a control variable of the volume flow control valve 56 , for example, the current, stored in a characteristic.

Preference is then given to the step 59 in a step S20, it is checked whether the frequency ANZ_LEAK of the fuel meterings is greater than a further threshold value SW_W, which is preferably selected such that it is only exceeded if an error of the volume flow control valve 56 is present. If the condition of step S20 is satisfied, in a step S22, an error of the volume flow control valve 56 recognized and performed a corresponding diagnostic function, which may include, for example, a limp home mode of the internal combustion engine. The program is subsequently terminated in a step S23.

is does not satisfy the condition of step S20, then in one step S11 a counter LEAK_CTR increased by the value 1. In a step S13, it is checked whether the counter LEAK_CTR is greater than a maximum value LEAK_CTR_MAX.

If this is the case, then in a step S15 the injection time period TI is occupied by the minimum injection time period TI_MIN. A function to control the injector 34 then generates a corresponding actuating signal, which causes that through the injection valve 34 Fuel for the minimum injection period TI_MIN is metered into the combustion chamber of the cylinder. Alternatively, it is also possible to set an injection period that differs from the minimum injection time period TI_MIN, which ensures that the minimum fuel mass flow MFF_MIN to be measured is metered.

In a step S17, the counter LEAK_CTR initialized to zero again. Subsequently, the processing is in the step S2 continued.

alternative can the frequency ANZ_LEAK of the fuel metering in the step S9 additionally dependent on a correction value is determined, which depends on the deviation of the actual Fuel pressure FUP_AV of the threshold value FUP_SW of the fuel pressure. For example, the frequency ANZ_LEAK increased if the actual Fuel pressure much higher is lower than the threshold FUP_SW or the frequency ANZ_LEAK be in the opposite case. Furthermore, the maximum value LEAK_CTR_MAX elevated and then in step S15 with the injection period TI a correspondingly larger value are occupied as the minimum injection period TI_MIN.

Claims (7)

Method for controlling an internal combustion engine in coasting with a fuel supply device ( 5 ), which is a volume flow control valve ( 56 ), in which - in the detected shift operation (SCH), the regular fuel supply to the combustion chambers of the cylinder is switched off and - the frequency (ANZ_LEAK) of a sporadic fuel supply to the combustion chambers is dependent on a size that characterizes a minimum injection period (TI_MIN), and depends on one the leakage of the volume flow control valve ( 56 ) characterizing size. Method for controlling an internal combustion engine according to the preceding claim, characterized in that the frequency (ANZ_LEAK) of the fuel supply to the combustion chambers depends on a fuel pressure (FUP_AV) in a fuel reservoir ( 55 ). Method according to one of the preceding claims, characterized characterized in that the size, the characterized a predetermined minimum injection period (TI_MIN), is a variable characterizing the minimum fuel mass, the while an injection process is edible. Method according to the preceding claim, characterized in that the variable characterizing the minimum fuel mass is a minimum fuel mass flow (MFF_MIN) through the injection valve ( 34 ) during a cylinder segment when fuel is supplied to the combustion chamber. Method according to one of the preceding claims, characterized characterized in that an error of the volume flow control valve is detected when the frequency (ANZ_LEAK) exceeds a predetermined further threshold value (SW_W). Method according to one of the preceding claims, characterized characterized in that the fuel supply during the expansion or Ausschiebetaktes takes place. Device for controlling an internal combustion engine in coasting mode with a fuel supply device, which comprises a volume flow control valve ( 56 ), wherein the device comprises - first means, which switch off the regular fuel supply to the combustion chambers of the cylinders in the detected shift operation (SCH), and - second means, which determine the frequency of a singulated fuel supply to the combustion chambers, depending on a variable, the predetermined minimum injection duration (TI_MIN), and of a the leakage of the flow control valve ( 56 ) characterizing size.