EP0828069A2 - Method and apparatus for monitoring the flow restrictor of the fuel supply of an engine - Google Patents

Abstract

The monitoring method monitors the through flow limiters (180-183) arranged respectively between the fuel storage vessel (160) and each fuel injector (120-123) of a four cylinder IC engine (100) across a common fuel supply rail. Each limiter prevents a fuel flow to each cylinder, if the injected fuel amount exceeds a specific value. In determined operations for monitoring the through flow limiter, the injector is controlled in such a manner, that the injector releases an injected amount of fuel, which exceeds the specified limiting value. Then emanating from the reaction of the engine, is monitored whether the through flow limiter stops the flow of fuel.

Description

State of the art

The invention relates to a method and a device to monitor a flow restrictor Fuel metering system of an internal combustion engine.

From the unpublished DE-OS 196 05 417 is a Fuel metering system of an internal combustion engine, known which the fuel is injected into from a storage unit the individual combustion chambers of the internal combustion engine are reasonable is. Is between the memory and the respective combustion chamber a flow restrictor is arranged, the fuel flow stops when the fuel flow a certain Limit exceeds. Monitoring the Flow limiter is not with this device intended.

Resin, soiling or damage to outside, the flow limiter can function be disturbed. If corresponding faults are not recognized, this leads to an impermissibly high amount of injected fuel. This in turn causes one Overloading the engine and can up to Destroy them.

A defect in the flow restrictor cannot be done easily can be recognized, as this is usually only in the System takes effect. In normal operation it is usually out of function.

Object of the invention

The invention is based, the Flow limiter of a fuel metering system if possible easy to monitor for functionality.

Advantages of the invention

With the procedure according to the invention it is possible a defect in the flow limiter is simple and safe of a fuel metering system.

Advantageous and expedient configurations and Further developments of the invention are in the subclaims featured.

drawing

The invention is described below with reference to the drawing illustrated embodiment explained. 1 shows 2 shows a block diagram of the device according to the invention, FIG. 2 a flow chart for explaining the invention Procedure, Figure 3 different signals over time t applied and Figure 4 is a flow diagram of another Embodiment of the procedure according to the invention.

Description of the embodiments

In the following, the device according to the invention is based on the example a self-igniting internal combustion engine, where the fuel metering by means of a solenoid valve is controlled. The embodiment shown in Figure 1 relates to a so-called common rail system. The invention Approach is not on these systems limited.

With 100 an internal combustion engine is referred to an intake line 105 receives fresh air and emits 110 exhaust gases via an exhaust pipe.

The internal combustion engine shown is a four-cylinder internal combustion engine. Every cylinder the Internal combustion engine is an injector 120, 121, 122 and 123 assigned. The injectors are connected via solenoid valves 130, 131, 132 and 133 fuel metered. The fuel arrives from a so-called rail 135 via the injectors 120, 121, 122 and 123 into the cylinders of internal combustion engine 100.

Is between the rail 135 and the injectors 120 to 123 flow restrictors 180, 181, 182 and 183, respectively arranged. Preferably, the injector and the Flow limiter a structural unit. Of the Flow limiter can alternatively between each Solenoid valve and the rail or between the solenoid valve and the respective injector.

The flow restrictors are designed such that they Connection between the Rail 135 and the injectors interrupt if through this line within a certain time unit more than a predetermined Amount of fuel flows. This amount is chosen so that it is larger than the largest when operating correctly occurring quantity. It is therefore larger than the full load quantity or the starting quantity. The amount is also chosen so that it is less than the amount at which the Internal combustion engine is damaged.

The fuel in the rail 135 is from a high pressure pump 145 brought to an adjustable pressure. The high pressure pump 145 is connected to a via a solenoid valve 150 Fuel delivery pump 155 connected. The fuel delivery pump 155 is in with a fuel reservoir 160 in Connection.

The valve 150 comprises a coil 152. The solenoid valves 130, 131, 132 and 133 include coils 140, 141, 142 and 143 that be supplied with current by means of an output stage 175 can. The output stage 175 is preferably in a control unit 170 arranged, which corresponds to the coil 152 controls.

Furthermore, a sensor 177 is provided which detects the pressure in the Rail 135 detects and a corresponding signal to the control unit 170 directs.

An error detection 176 evaluates various signals and In the event of a fault, power is applied to the 175 output stage and the valve 152 with a corresponding signal.

Control unit 170 is connected to one via two switching means Ubat supply voltage in connection. The first Switching means 190 connects the supply voltage Ubat via a so-called terminal 15 (KL15) with the control device 170. A second switching means 192 connects the Ubat supply voltage via a so-called terminal 30 (KL30) with control unit 170.

The switching means 190 is the Ignition switch by the driver when starting the Internal combustion engine is operated. When operating the This switch is in his internal combustion engine closed position.

The connection point between the switching means 190 and the Control device 170, which is also referred to as terminal 15, is also available via the winding of a relay 194 Mass in connection.

When the internal combustion engine is operating, the switching means is 190 closed, relay 194 energized and switch 192 also closed. When switching off the internal combustion engine opens the switching means 190. This stops the current flow prevented by relay 194. The relay 194 is like this designed that it still for a while Hold switch 192 in its closed state. Thereby control unit 170 will continue to operate for a certain time Power supplied. This time is usually called Designated caster. Usually run during this time various test programs.

Such a device is for example from the DE-OS 38 02 770 (US-A 4 905 645) is known.

This facility now works as follows. The fuel delivery pump 155 delivers the fuel from the reservoir via valve 150 to high pressure pump 145. The high pressure pump 145 builds a predefinable pressure in the rail 135 on. Usually in Rail 135 for systems for spark ignition internal combustion engines pressure values of about 30 up to 100 bar and with self-igniting internal combustion engines Pressure values of about 1000 to 2000 bar achieved.

By energizing the coils 140 to 143, the corresponding Solenoid valves 130 to 133 controlled. The control signals for the coils, the start of injection starts and the injection end of the fuel through the injectors 120 to 123 fixed.

If an error occurs with such a system, this can it is, for example, a defect in the area of Control unit 170, the high pressure part and / or the injection valves act, it must be ensured that the Internal combustion engine comes to a safe stop.

In particular in systems in which the high-pressure pump 145 is driven directly by the internal combustion engine, and thus the high-pressure pump 145 when the internal combustion engine is running Continually promoting is a shutdown of the High pressure pump 145 not possible. Therefore, by others Measures are taken to ensure that the pressure in the high pressure part quickly dismantled and / or the fuel supply is prevented.

This is particularly necessary if in the high pressure part a leak occurs and the fuel is broken by a High pressure injector permanently in a cylinder reached. In these cases, the fuel supply be prevented. Reaches the injected Amount of fuel the value at which the corresponding Flow limiter responds, this prevents the further fuel supply to the faulty injector. The flow limiter preferably interrupts the Fuel flow if that in a given unit of time injected fuel amount a threshold exceeds.

If error monitoring 175 detects an error, it switches the error monitor 175 to an emergency driving program. This means that valve 150 is in its closed state brought. This ensures that no other Fuel is provided by the pump 115.

As a further or alternative measure, the Solenoid valves 140, 141, 142 and 143 controlled such that the fuel metering in an angular position Release the crankshaft in which the injection does not Contributes to the torque of the internal combustion engine. It is particularly advantageous if the fuel metering is released in the area of bottom dead center. This means the fuel metering takes place immediately before Open the exhaust valves of the internal combustion engine. Here the injectors are controlled so that such Amount of fuel is metered that the flow restrictor disconnect.

To check the flow limiter, as in FIG. 2 proceeded illustrated. At certain intervals, Step 200 the position of the switching means 190 as signal SN read. Then in step 205 this signal SN compared with the previous switch position SA. are the two switching positions are the same, so in step 210 the old switch position with the new switch position overwritten. We will connect after a waiting period the new position SN of the switching means 190 in step 200 read.

Query 205 recognizes that the position of the Switching means 190 has changed, this means that Switching means 190 has been opened, so a test program processed to check the flow limiter. In In a first step 220, the injectors become like this controlled to meter such a quantity of fuel, that the flow limiters respond. Preferably only increases the amount for a metering, then it will be reduced to the usual value.

In the subsequent step 225, the speed N becomes the Internal combustion engine detected. In step 230, a Time counter t increased. The query 235 checks whether the value of the time counter is greater than a time threshold tW. Is if this is not the case, step 225 and Step 230 processed.

Query 235 recognizes that the time counter t is greater than that Is the threshold value tW, the query 240 follows. The query 240 checks whether the speed N is less than a Speed threshold is NS. If this is the case, it ends Program in step 245. Query 240 recognizes that the Speed is greater than the threshold value NS, then in Step 250 recognized for errors and a corresponding one Fault memory set or the fault is the driver displayed.

As an alternative and / or in addition to query 240, a Query 260 may be provided. Query 260 checks whether the speed N has dropped since the control. For this a speed value NA was stored in step 220. The Query 260 checks whether the current speed value N is less than the old speed value NA. Is that the case, the program ends in step 265. Recognizes the query 240 that the current speed N is greater than the old one Speed value is NA, then in step 250 there is an error recognized and a corresponding error memory set or the error is displayed to the driver.

Queries 240 and 260 recognize whether the flow restrictors have addressed, and turned off the internal combustion engine has come to a standstill.

It is particularly advantageous if the injection in one Angular range occurs in which they make no contribution to the Torque delivers. Such an angular range lies immediately before the bottom dead center of each Cylinders.

According to the invention after switching off the Internal combustion engine by the driver's operability the flow limiter checked. For this, the injector controlled individually and / or jointly such that the Injector releases a flow of fuel that causes the flow limiter interrupts the fuel flow and the internal combustion engine comes to a standstill. The Functionality of the flow limiter is recognized when the speed after a waiting time tW after the Control of the injectors drops and / or below a threshold.

In a further embodiment, it is checked whether the Speed of a single cylinder from a given one Mean deviates. In Figure 3 is the course of the speed N and the position S of the switch 190 over time t applied. Switching means 190 is up to time t1 closed, the speed assumes a value NL that for example corresponds to the idling speed. To the At time t1, the driver opens switch 190 by Switch off internal combustion engine. From that point falls the speed drops to zero according to a predetermined function.

In Figure 3a, the drop in the correct function of the Flow limiter applied. In the illustrated Embodiment, the speed drops linearly over time.

If one of the flow restrictors is not working properly, so the speed increases due to the combustion in the corresponding cylinder at short notice. To this short-term increase in speed and thus a faulty Detecting the flow limiter becomes as in FIG. 4 proceeded illustrated.

In the wake, which accordingly, as described in Figure 2, is recognized, it is recognized whether one of the Flow limiter is not working correctly. In a first In step 400, a counter L is set to 1. Then in Step 410 is for the drive signal AL of the Lth Cylinder corresponding to step 220 such a value AMAX chosen that the corresponding flow limiter responds.

The subsequent step 415 detects the Speed N. In step 420, the setpoint NS for the Speed is predefined at least depending on the time t. Here, the expected course of the speed at Switching off is taken into account.

The subsequent query 430 checks whether the in Step 415 measured speed N from the expected speed NS deviates. In particular, it is checked whether the measured Speed N is greater than the expected value NS. Is this the Case, ie the speed deviates from its expected Value, the device detects in step 440 Flow restrictor error.

If this is not the case, step 450 follows Counter L increased by one. The subsequent query 460 checks that all flow restrictors have been checked that means whether the injection quantity has increased for all cylinders has been. If the query recognizes that the counter L assumes a value that is greater than the number of cylinders ZZ, the program ends in step 470. Otherwise it is done the jump to step 410 and the check of the follows next cylinder.

Claims (6)

Method for monitoring a flow restrictor Fuel metering system of an internal combustion engine, the Flow limiter the fuel flow between one Fuel storage, an injector and / or the Internal combustion engine stops when the injected Amount of fuel exceeds a predetermined limit, being in certain operating states to check the Flow limiter the injector is controlled in such a way that the injector has an injected amount of fuel releases that exceeds the specified limit, and that based on the reaction of the internal combustion engine it is checked whether the flow restrictor limits the fuel flow prevents. A method according to claim 1, characterized in that the check is carried out in the wake. Method according to one of the preceding claims, characterized characterized in that for checking the speed of the Internal combustion engine is evaluated. Method according to one of the preceding claims, characterized characterized in that an error is detected when the Speed deviates from an expected value. Method according to one of the preceding claims, characterized characterized in that an error is detected when the Speed does not drop and / or greater than a threshold is. Device for monitoring a flow limiter a fuel metering system of an internal combustion engine, wherein the flow restrictor is the fuel flow between one Fuel storage, an injector and / or the Internal combustion engine stops when the injected Amount of fuel exceeds a predetermined limit, with Means for review in certain operating conditions of the flow limiter control the injector so that the injector releases an injected amount of fuel, which exceeds the specified limit, and with with Means based on the reaction of the Check the internal combustion engine, whether the flow limiter Prevents fuel flow.

Images