EP1856394B1 - Method and device for monitoring an internal combustion engine injection device - Google Patents

Description

The invention firstly relates to a method for operating an injection device of an internal combustion engine, according to the preamble of the independent claim. The invention further relates to a device and a computer program for carrying out the method according to the invention.

State of the art

From the DE 199 08 352 A1 Method for monitoring an injection device of an internal combustion engine is known in which a mechanical and an electrical malfunction of an injection device are detected by evaluating signals of a misfire detection, and in which an error response is initiated as a function of the detected malfunction.

In the prior art injection valves for a high-pressure as well as low-pressure fuel direct injection are basically known. In particular, injector are also known in which the dosage of injected into the combustion chambers of the internal combustion engine fuel quantity is not only possible over the opening period of the valve, but also by varying the stroke of the nozzle needle of the injector. The injection valves are typically designed as solenoid valves or piezo valves.

Injectors measure the fuel mass to be injected into the cylinder, which is needed for clean and efficient combustion in the engine. The control of the injection valves is typically carried out via a power output stage, wherein the injection is preferably triggered by a so-called low-side switch of the power amplifier.

The power amplifier is monitored during operation so that short circuits can be detected and responded to battery voltage and ground of the power amp.

Furthermore, it is also known to monitor software and hardware errors, for example in a control unit.

From the DE 103 05 178 A1 A method for operating an injection valve of an internal combustion engine is already known in which by monitoring a proper function of the internal combustion engine soiled injection valves are detected and suitable cleaning measures are initiated. To check the proper functioning of the pressure in a fuel tank and on the other hand, the cylinder is monitored for dropouts out. Furthermore, the torque behavior is controlled and checked by targeted enrichment and simultaneous monitoring of the lambda value, whether the injectors are working properly. When a detected contamination measures for cleaning the injector are initiated.

Advantages of the invention

In contrast, the method according to the invention for operating an injection device has the advantage that at least two malfunctions of an injection device are detected by evaluating signals of a misfire detection, so that suitable fault reactions can be initiated in an advantageous manner as a function of the detected malfunction. This has the particular advantage that cleaning attempts on an injection valve can be omitted, for example, in the event of an electrical fault in the injection device.

Furthermore, a monitoring device of an injection device (5) of an internal combustion engine is advantageously provided in which a detection means detects signals of a misfire detection, wherein the monitoring device recognizes at least two malfunctions of the injection device by evaluating the signals of the misfire detection, and in that the monitoring device has an error response as a function of the detected malfunction initiates.

It is provided to check by evaluating a fuel pressure, whether a malfunction of the injection device is present. Thus, it is ensured in an advantageous manner that error responses are only initiated if an additional evaluation independent of the misfire detection also recognizes a malfunction of the injection device. Thus, the security of error detection is advantageously increased.

According to the invention, it is provided that when a misfire of a cylinder is detected and the fuel pressure drops below a threshold value, a mechanical malfunction of the injection device is detected. So that's beneficial only error reactions can be initiated, which are suitable to fix mechanical errors.

In case of dropouts of cylinders, which are assigned to a power amplifier bank of the injection device and a drop in the fuel pressure below a threshold, an electrical malfunction of the injection device is detected. This has the advantage that specific measures can be introduced that are suitable for eliminating electrical errors of the injection device.

The measures listed in the dependent claims advantageous refinements and improvements of the independent claim method are possible.

Furthermore, it is advantageous that, in the event of a recognized electrical fault, an output stage (45) controlling the injection valves (40) is additionally checked for electrical errors. This advantageously makes it possible to further narrow down the cause of the electrical malfunction and to initiate specific fault reactions.

In particular, it is advantageous that the internal combustion engine is operated in an emergency mode as a function of the malfunction as an error reaction.

Furthermore, it is advantageous to model this procedure according to the invention in a method and a computer program product.

drawings

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the drawings.

• Figur 1 schematisch eine Brennkraftmaschine mit einer Einspritzvorrichtung,
• Figur 2 schematisch eine Endstufenschaltung für zwei Einspritzventile,
• Figur 3 schematisch ein Ablaufschema eines erfmdungsgemäßen Verfahrens,
• Figur 4 schematisch eine erfindungsgemäße Vorrichtung.

Show it:

• FIG. 1 schematically an internal combustion engine with an injection device,
• FIG. 2 schematically an output stage circuit for two injectors,
• FIG. 3 schematically a flow chart of a method according to the invention,
• FIG. 4 schematically a device according to the invention.

Description of the embodiments

The invention is based on the idea to check an injection device of an internal combustion engine with regard to both mechanical and electrical function and to initiate error-specific error response or auxiliary measures in the case of malfunctions of the injection device.

The invention is suitable for both low pressure and high pressure fuel injection systems, regardless of the embodiments in the embodiments.

In FIG. 1 schematically a multi-cylinder internal combustion engine 1 is shown with an injection device 5, wherein four injectors 40 and one of the cylinder 110 are exemplified. The injection device 5 comprises a first and second fuel pump 10, 20, a pressure accumulator 30, injectors 40, an output stage 45, a fuel tank 50 and a pressure sensor 60. The first fuel pump 10 pumps fuel from a fuel tank 50 in the direction of a second fuel pump 20. Die first fuel pump 10 is adapted to generate a low pressure. The second fuel pump 20 delivers the fuel into a pressure accumulator 30 and increases the low pressure provided by the first fuel pump 10 to a high pressure. The pressure accumulator 30, often referred to as fuel storage, rail or common rail is in turn connected to four injection valves 40. Via a pressure sensor 60, at least the pressure in the pressure accumulator 30 is monitored.

By way of example, one of the four injection valves 40 is shown in connection with a cylinder 110 of the internal combustion engine 1. In the cylinder 110, a piston 120 is movably arranged. The cylinder has a combustion chamber 100, which is delimited inter alia by the piston 120, an inlet valve 150, an outlet valve 160. It can too a plurality of inlet and / or outlet valves 150, 160 may be provided. In the area of Ein - and

Exhaust valves 150, 160 protrude into an injection valve 40 and a spark plug 200 into the combustion chamber 100. The injection valves 40 allow a direct introduction of fuel into the combustion chamber 100 and are driven by the output stage 45. About the spark plug 200, the fuel in the combustion chamber 100 can be ignited. Furthermore, a suction pipe 155 preferably supplies air to the intake valve 150 and, by opening the intake valve 150, the air enters the combustion chamber 110. By opening the exhaust valve 160, exhaust gases are preferably directed into an exhaust pipe 165.

FIG. 2 schematically shows as part of an output stage 45, a circuit of a power amplifier bank for two injectors EV1, 2 as actuators, which are shown symbolically in the present example as resistors. Of course, capacitive or inductive actuators may be provided, which are designed, for example. As a piezo or solenoid valve.

Both actuators EV1,2 are each connected to a connection on the so-called highside via a high-side switching element HSL with a supply line. On the other terminal side of the actuators EV1, 2, the so-called lowside, the connection of the first actuator EV1 is connected to a first lowside switching element GLS1 and the connection of the second actuator EV2 is connected to a second lowside switching element GLS2, wherein the two switching elements GLS1, GLS2 switch the two actuators EV1,2 to a common lowside supply line.

FIG. 3 schematically shows a flow chart of a method according to the invention.

In a first step 510 it is checked whether dropouts have been recognized. If no dropouts are observed, it can be assumed that no injector is permanently open and the check in step "no error" 700 is ended.

If dropouts have been detected, it is checked in a second step 520 whether the fuel pressure p has fallen below a threshold value. If the fuel pressure is above the threshold value, it is to be assumed that, despite the misfire, no injection valve is permanently open and the further check is terminated in the step "no error" 700.

If the threshold value is undershot, it is checked in a third and fourth step 530, 540, whether dropouts occur only on one cylinder or on all cylinders of a power amplifier bank.

If dropouts occur only on one cylinder, it can be assumed that the injection valve of the respective cylinder is permanently open due to a mechanical malfunction. It is branched into the step "mechanical error" 620.

If it is necessary to observe dropouts on all cylinders that are assigned to a power amplifier bank, it can be assumed that the injection valves of this cylinder bank are permanently open due to an electrical malfunction. It is branched into the step "electrical error" 610.

In further process steps, not shown, appropriate error responses can now be initiated on the basis of the identified malfunctions.

The invention is based on the consideration that in a permanently open injection valve 40, a very large amount of fuel from the fuel reservoir 30 is injected into a combustion chamber of a cylinder of the internal combustion engine. This then has the following effects:

The fuel mass flowing through a permanently open injection valve causes the fuel pump is no longer able to keep the pressure in the pressure accumulator constant. The fuel pressure in the fuel tank drops. For a given system, a fuel pressure threshold may now be set that is typically less than the fuel pressure for a permanently open injector. A falling below such a threshold value is thus to be regarded as a fault feature for a permanently open injection valve.

Furthermore, no combustible mixture is generated by the excessive injected fuel mass in the affected cylinder more, the combustion is suspended, it comes to so-called dropouts. These dropouts are detected by a misfire detection. Dropouts are thus a necessary feature in the presence of a permanently open injection valve.

If both dropouts and pressure drops are to be observed, it can be assumed that the injection valve is permanently open. In this case, it is additionally possible to distinguish whether there is a mechanical or electrical fault of the injection device.

With a mechanical malfunction of the injector, i. For example, if the valve pin sticks due to dirt, fuel is injected permanently into this cylinder and the remaining cylinders operate normally. Dropouts are therefore observed only for this cylinder.

If there is an electrical malfunction of the injection device, for example due to a faulty drive signal of the output stage, this leads to dropouts on all cylinders which are assigned to the faulty power amplifier bank. So in the case of a four-cylinder internal combustion engine typically set two cylinders. For example, this indicates in FIG. 2 shown first actuator or injector actuator 1 on the lowside a short circuit to ground, so the first injector actuator 1 is permanently open. However, since the entire current flows through the first injection valve actuator 1, no current is available for opening the valve for the second injection valve actuator 2, the second injection valve remains closed. In this respect, misfires occur on one cylinder due to a large amount of fuel and on the other cylinder due to a fuel shortage.

Thus, it is already possible to detect electrical or mechanical malfunctions of the injection device solely by evaluating the signals of the misfire detection. With the evaluation of the fuel pressure is checked whether the misfires of the internal combustion engine caused by a malfunction of the injector or possibly have another cause.

Based on the detected malfunction suitable error responses can now be initiated. If, for example, there is a mechanical malfunction, an attempt can be made to purge the injection valve with fuel or to release it mechanically by targeted activation of the injection valve.

In the event of a detected electrical malfunction, it may be provided, for example, to further limit the electrical fault in further test steps and, if necessary, to take further precautions depending on the electrical fault.

In particular, it may be provided to initiate emergency measures coordinated with a detected fault, for example by changing operating modes of the internal combustion engine or adjusting injection parameters. For example, it may be provided as an emergency measure to turn off the faulty power amplifier bank in the event of a detected electrical fault. However, other emergency measures are also conceivable.

FIG. 4 1 shows an embodiment of a monitoring device 400 according to the invention of an injection device 5. A detection means 420 is part of the device 400 according to the invention in the example shown. Schematically, a fuel reservoir 30 which is in connection with an injection valve 40 is shown. The injection valve 40 protrudes into a cylinder 110 of the internal combustion engine. By means of a pressure sensor 320, a fuel pressure p in the fuel reservoir 30 is detected with the aid of a pressure sensor 60. Furthermore, a misfire detection 310 is connected to the cylinder 110. Signals of the pressure detection 320 and the misfire detection 310 are forwarded to the detection means 420. The monitoring device 400 evaluates the detected signals and, if appropriate, initiates suitable error responses as a function of the detected malfunction.

In a further embodiment, it can also be provided to construct the monitoring device 400 according to the invention as part of an engine control unit; in particular, the pressure detection 320 and the misfire detection 310 can also be part of an engine control unit. Of course, other combinations are conceivable.

Claims (6)

1. Method for monitoring an injection device (5) of an internal combustion engine,
   wherein a mechanical and an electrical malfunction of an injection device are detected by evaluating signals of a misfire detection means,
   and a fault reaction is initiated in accordance with the detected malfunction,
   characterized
   in that, when a misfire is detected in just one cylinder and the fuel pressure drops below a threshold value, a mechanical malfunction of the injection device is detected, and
   in that, when there are misfires in all the cylinders (110) which are assigned to an output stage bank of the injection device (5) and the fuel pressure drops below a threshold value (SW), an electrical malfunction of the injection device (5) is detected.
2. Method according to Claim 1, characterized in that by evaluating a fuel pressure it is checked whether a malfunction of the injection device is occurring.
3. Method according to Claim 1, characterized in that, when an electrical fault is detected, an output stage (45) which actuates the injection valves (40) is additionally checked for electrical faults.
4. Method according to at least one of the preceding claims, characterized in that the internal combustion engine is operated in an emergency operating mode as a fault reaction in accordance with the malfunction.
5. Monitoring device of an injection device (5) of an internal combustion engine, in which a sensing means senses signals of a misfire detection means, wherein the monitoring device detects a mechanical and an electrical malfunction of an injection device by evaluating signals of the misfire detection means,
   and the monitoring device initiates a fault reaction in accordance with the detected malfunction,
   characterized
   in that, when a misfire is detected in just one cylinder and the fuel pressure drops below a threshold value, the monitoring device detects a mechanical malfunction of the injection device, and
   in that, when there are misfires in all the cylinders (110) which are assigned to an output stage bank of the injection device (5) and the fuel pressure drops below a threshold value (SW), the monitoring device detects an electrical malfunction of the injection device (5).
6. Computer program product with program code which is stored on a machine-readable carrier, for carrying out the method according to one of Claims 1 to 4 when the program is run on a computer or control unit.

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