JP3947071B2 - Diagnosis method and apparatus for pressure damper - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for diagnosing a pressure damper disposed in a fuel metering system of an internal combustion engine. The fuel metering system includes a pre-conveying pump that conveys fuel from a fuel container to a low-pressure region, and a high-pressure pump that conveys fuel from a low-pressure region to a high-pressure region.
[0002]
The invention further relates to a computer program executed on a computing device, in particular a microprocessor.
[0003]
Furthermore, the present invention relates to a pressure damper diagnostic device arranged in a fuel metering system of an internal combustion engine. The fuel metering system includes a pre-conveying pump that conveys fuel from a fuel container to a low-pressure region, and a high-pressure pump that conveys fuel from a low-pressure region to a high-pressure region.
[0004]
Finally, the present invention relates to a fuel metering system for an internal combustion engine that performs fuel injection. The fuel metering system includes a pre-conveying pump that conveys fuel from a fuel container to a low-pressure region, and a high-pressure pump that conveys fuel from a low-pressure region to a high-pressure region. A pressure damper is disposed in the low pressure region.
[0005]
[Prior art]
From the prior art, internal combustion engines are known in which fuel is injected directly into the intake pipe or into the combustion chamber. In order to inject fuel directly into the combustion chamber of the internal combustion engine, a fuel metering system configured in two stages is usually used. This fuel metering system has a pre-conveying pump, usually configured as an electromagnetic force pump (EKP). The pre-conveying pump conveys fuel from the fuel container to the low pressure region. In the low pressure region the fuel is present at a relatively low pressure of the level of about 3 to 4 bar. Fuel is conveyed from the low pressure region to the high pressure region by a high pressure pump. In the high pressure region, the fuel is present at a pressure of about 120 to 150 bar for gasoline internal combustion engines and at a pressure of about 1200 to 1500 bar for diesel engines. The so-called common rail fuel metering system has a high pressure reservoir in the high pressure region. Fuel can be stored in this high pressure reservoir at a relatively high pressure. From the high pressure region, fuel is directly injected into the combustion chamber of the internal combustion engine via an electrically controllable injector.
[0006]
In such a two-stage fuel metering system, pressure fluctuations that pulsate strongly in the low pressure region occur. This pulsation occurs especially in fuel metering systems in which the high-pressure pump is configured as an individual cylinder piston pump. The cause of the pulsation is a control end impact of the high pressure pump controlled as necessary. The frequency of the pulsation depends on the rotation speed of the high pressure pump.
[0007]
In order to avoid unacceptably loading the low pressure region, it is known to arrange a pressure damper in the low pressure region. A pressure damper for a fuel metering system is known from DE 38443840 A1. The pressure damper disclosed therein can reduce pressure peaks. This is done by connecting a damper and a fuel-filled chamber acting on the air cushion and compressing the air cushion. The pressure damper can be placed in front of or in the high pressure pump, or in the low pressure region. The pressure damper attenuates the pulsation in the low pressure region until the load in the low pressure region is significantly reduced. Based on the reduced load, for example, conventional joining techniques can be used for the low-pressure circuit. If the pressure damper fails, an unacceptable load on the low-pressure circulation circuit is expected, which impairs the durability of the connection, especially in the low-pressure region. In particular, in some cases, functional filling and high-pressure pump transport are hindered.
[0008]
The fuel metering system known from the prior art cannot diagnose a pressure damper that has failed in the low pressure region. If the pressure damper fails, it must be prepared that the low pressure bonding technology will fail before the expected life. This requires high construction costs and maintenance costs to ensure the functional capability of the low pressure circulation circuit.
[0009]
[Patent Document 1]
DE3843840A1
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide means for diagnosing a pressure damper during operation of an internal combustion engine.
[0011]
[Means for Solving the Problems]
This problem is solved starting from the method described at the outset, by detecting and evaluating the pressure profile in the low pressure region and using the detected pressure profile for the diagnosis of the pressure damper.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention makes it possible for the first time to diagnose the pressure damper of a fuel metering system during operation of the internal combustion engine. The advantage of this is that the low-pressure circuit can be constructed with inexpensive standard techniques. As long as the pressure damper is functioning, the pulsations in the low pressure region are attenuated. If a failure of the pressure damper is diagnosed, a corresponding measure can be started for the protection of the low-pressure circuit.
[0013]
The main point of the present invention is that the on-board diagnostic function can monitor the pressure damper in the low pressure region of the fuel metering system during the operation of the internal combustion engine and diagnose the failed pressure damper at an early stage. If the error function of the pressure damper is diagnosed, the replacement of the element can be signaled. Inexpensive elements can be used by means of on-board diagnosis in the low-pressure circulation circuit, and at that time, the usability of the system is not reduced.
[0014]
According to an advantageous refinement of the invention, it is proposed to measure the pressure profile in the low-pressure region with a pressure sensor arranged in the low-pressure region. To be precise, the pressure value is measured with respect to time, and the passage of pressure is detected based on the pressure value. The two-stage fuel metering system known from the prior art is highly vulnerable to high temperatures. For this reason, when the temperature is high, the preload in the low pressure region must be increased to maintain the required function. It is also conceivable that the means for increasing the preload comprise a low pressure sensor for detecting the preload. The pressure sensor included in the fuel metering system for increasing the preload can also be used to measure the pressure profile in the low pressure region within the diagnostic method of the invention.
[0015]
According to an advantageous embodiment of the invention, it is proposed to form a differential pressure course from the difference between the target pressure course for the low pressure region and the detected pressure course within the framework of the evaluation of the pressure course in the low pressure region. The The target pressure course can be obtained, for example, from a device for controlling the preload.
[0016]
The absolute value of the detected pressure course or differential pressure course is preferably formed in the frame of the evaluation of the pressure course in the low-pressure region.
[0017]
According to another advantageous refinement of the invention, it is proposed to use the detected amplitude of the pressure profile in the low-pressure region or the amplitude of the differential pressure profile for the diagnosis of the pressure damper. Advantageously, a pressure damper failure is diagnosed when the amplitude of the pressure profile or the differential pressure profile detected in the low pressure region exceeds a predetermined threshold for a predetermined time. The predetermined time can be selected to be small so that a failure of the pressure damper is diagnosed once the amplitude exceeds a predetermined threshold.
[0018]
However, in order to avoid misdiagnosis as much as possible, the amplitude must exceed a threshold for a relatively long time, thereby diagnosing a failure of the late pressure damper.
[0019]
Furthermore, the steady pressure difference between the pressure course in the low pressure region and the target pressure course in the low pressure region is taken into account in the diagnostic frame of the pressure damper. Advantageously, vibrations having a natural frequency in the low pressure region are filtered out of the detected pressure profile. The natural frequency in the low pressure region can be detected as a premise of the diagnostic method of the present invention. By filtering out the natural frequency vibration in the low pressure region from the detected pressure profile, this vibration is prevented from causing misdiagnosis. Diagnosis is advantageously not performed when filtering out the natural frequency oscillations of the low-pressure circulation circuit from the detected pressure profile.
[0020]
The method of the invention is particularly preferably realized in the form of a computer program. This computer program is especially executed on a microprocessor. Here, this computer program is suitable for carrying out the method of the invention when executed on a calculator. In this case, the invention is realized by a computer program, which is therefore suitable for carrying out this as well as the method of the invention.
[0021]
According to an advantageous embodiment of the invention, the computer program is stored in a storage element, in particular ROM, RAM or flash memory. The storage element is connected to the calculator via a communication connection. In order to implement the computer program, the computer program is transmitted from the storage element to the calculator on a command-by-instruction basis or as a whole.
[0022]
As a further solution to the problem of the method of the present invention, starting from a diagnostic device of the type mentioned at the outset, this device detects and evaluates the pressure course in the low pressure region and uses the detected pressure course to diagnose the pressure damper. Suggested to use.
[0023]
In an advantageous refinement of the invention, the diagnostic device comprises means for performing the method of the invention. The diagnostic device comprises, for example, a calculator, in particular a microprocessor, which is connected to the storage element via a communication connection. A computer program is stored in the storage element, and the computer program is executed on a computer to implement the method of the present invention.
[0024]
Finally, the object of the invention is as a further solution, starting from a fuel metering system of the type mentioned at the outset, means for the fuel metering system to detect the pressure course in the low pressure region, and the detected pressure course It is proposed to have means for evaluating the pressure and means for diagnosing the pressure damper based on the detected pressure course.
[0025]
The pressure profile in the low pressure region can be modeled for example on the basis of sensor signals or other parameters used in the control device for the internal combustion engine. Similarly, the pressure course can be measured by suitable measuring means.
[0026]
In an advantageous refinement of the invention, it is proposed that the fuel metering system comprises means for carrying out the method of the invention.
[0027]
【Example】
Further features, applicability and advantages of the present invention will become apparent from the description of the embodiments of the present invention.
[0028]
FIG. 1 shows a fuel metering system 1 of the present invention. This fuel metering system delivers fuel to the internal combustion engine 2. The fuel metering system 1 is configured as a two-stage system having a low pressure region ND and a high pressure region HD. Furthermore, it has the pre-conveyance pump 3, This pre-conveyance pump is comprised as an electromagnetic fuel pump, for example, and conveys fuel from the fuel container 4 to the low voltage | pressure area | region ND. The fuel transported by the pre-transport pump 3 is supplied to the high-pressure pump 6 through the filter element 5. The high-pressure pump 6 is configured, for example, as an individual cylinder / piston pump that is controlled as necessary, and conveys fuel from the low-pressure region ND to the high-pressure region HD. A high pressure reservoir 7 is arranged in the high pressure region HD. Fuel is accumulated in the high-pressure reservoir with an injection pressure pr and is directly injected into the combustion chamber 9 of the internal combustion engine 2 through the injection valve 8 as necessary.
[0029]
Based on the action of the high-pressure pump 6 controlled as necessary, a typical pulsation is induced in the low-pressure region ND, the frequency of which depends on the rotational speed of the high-pressure pump 6. The amplitude of this pulsation is so high that the low-pressure circuit ND cannot actually be driven by the conventional joining technique. In order to attenuate the pulsation, the pressure damper 10 is arranged in the low pressure region ND at the high pressure pump 6 or immediately before the high pressure pump 6. The pressure damper 10 attenuates the pressure peak. This is done by connecting the damper and a chamber filled with fuel 10a acting on the air cushion 10b and compressing the air cushion. Various embodiments of the pressure damper 10 are known from DE 38443840 A1 and are cited here.
[0030]
In order to be able to diagnose the pressure damper 10 during the operation of the internal combustion engine 1, the pressure sensor 11 is arranged in the low pressure region ND according to the invention. This pressure sensor records the pressure course pn in the low pressure region ND and further supplies a corresponding signal to the control device 12 of the fuel metering system 1. The control device 12 controls the fuel metering system 1. The control device 12 is connected to the pre-conveying pump 3 and the high-pressure pump 6 through the control line.
[0031]
The control device 12 has a storage element 13 in which a computer program is stored. This computer program is executed on the calculator 14 of the control device 12, in particular on a microprocessor, and is suitable for carrying out the diagnostic method of the invention. In order to execute the computer program, this computer program is transmitted from the storage element 13 to the calculator 14 on a command-by-instruction basis or as a whole via the communication connection 15.
[0032]
The method of the present invention will be described based on the flowchart shown in FIG. The method starts at function block 20. In the function block 21, the pressure pn in the low pressure region ND is measured by the pressure sensor 11. In the function block 22, a differential pressure is formed from the difference between the target pressure pnsoll for the low pressure region ND and the measured pressure pn. The target pressure passage pnsoll is used by the control device 12, for example.
[0033]
In the function block 23, the differential pressure profile is filtered by a bandpass filter. Thereby, the natural frequency vibration of the low pressure region ND of the fuel metering system 1 can be filtered out. As a precondition for this, the natural frequency of the low pressure region ND is detected. This type of vibration occurs, for example, in a fuel metering system with a mechanically controlled low-pressure circulation circuit, or a fuel metering system with a system for increasing the preload, or when the pre-feed pump 3 fails. . In the function block 23, the natural frequency of the low-pressure circulation circuit is filtered out. At this time, the diagnosis of the pressure damper 10 is not performed.
[0034]
In the function block 24, an absolute value course is formed. This is done by forming an absolute value of the differential pressure course that has passed through the band.
[0035]
In function block 25, further filtering is performed. This filtering is performed to smooth the absolute value course. The absolute value course of the differential pressure course passed through the band and smoothed is shown as pd. In inquiry block 26 it is checked whether the elapsed pd is greater than / equal to a predetermined threshold ps for a predetermined duration ts. Both the threshold ps and the duration ts can be adapted to different fuel metering systems 1. If the elapsed time pd exceeds the threshold value ps for at least the duration ts, a failure of the pressure damper 10 is diagnosed in the function block 27. At function block 28, the method of the present invention ends.
[0036]
If the elapsed pd is below or equal to the threshold value ps or exceeds the threshold value ps for a duration shorter than the duration ts, the function block 29 diagnoses that the pressure damper 10 is not faulty. The function block 29 branches again to the function block 21, where the instantaneous pressure pn in the low pressure region ND is again measured. This method is performed periodically. A value for the pressure pn is measured at each cycle, so that the pressure course pn can be detected from the individual pressure values after a plurality of cycles.
[0037]
Before the measured pressure profile pn is evaluated in the function blocks 23 to 29, it must be ensured that there is no steady deviation from the target pressure profile pnsoll in the low pressure zone ND. If such a steady deviation exists, this triggers a diagnosis of a failure of the pressure damper 10 as well. For this reason, the differential pressure profile is monitored without absolute value formation and without filtering. Stationary error monitoring is performed at inquiry block 30. If a stationary error is identified, a fault in the low-pressure circuit ND is estimated and the method of the invention ends.
[0038]
In the upper part of FIG. 3, the pressure course pn measured in the low pressure region ND and the target pressure course pnsoll are shown for the pressure damper 10 without failure. From the lower part of FIG. 3, it can be seen that the smoothed and bandpass filtered absolute value pd of the passage of the differential pressure remains clearly below the threshold value ps.
[0039]
FIG. 4 shows the pressure profile pn measured for the failed pressure damper 10. From the upper part of FIG. 4, a large pulsation with a pressure lapse pn is apparent. From the lower part of FIG. 4, it can be seen that the amplitude of the pressure course pd is above the threshold value ps, exceeding the duration ts.
[Brief description of the drawings]
FIG. 1 illustrates a fuel metering system of the present invention in accordance with an advantageous embodiment.
FIG. 2 shows the diagnostic method of the present invention according to an advantageous implementation failure.
FIG. 3 shows the pressure course in the low pressure region of the fuel metering system of FIG. 1 when the pressure damper is normal.
FIG. 4 shows the pressure course in the low pressure region of the fuel metering system of FIG. 1 when the pressure damper is faulty.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel metering system 2 Internal combustion engine 3 Pre-conveying pump 4 Fuel container 5 Filter element 6 High pressure pump 7 High pressure reservoir 8 Injection valve 9 Combustion chamber ND Low pressure area HD High pressure area

Claims (14)

A method for diagnosing a pressure damper (10) arranged in a low pressure region (ND) of a fuel metering system (1) of an internal combustion engine (2),
The fuel metering system (1) includes a pre-conveying pump (3) that conveys fuel from a fuel container (4) to a low pressure region (ND), and a high pressure that conveys fuel from a low pressure region (ND) to a high pressure region (HD). In the type having a pump (6),
Detecting and evaluating the pressure course (pn) in the low pressure region (ND);
A diagnostic method characterized in that the detected pressure course (pn) is used for the diagnosis of the pressure damper (10). The method according to claim 1, wherein the pressure profile (pn) in the low pressure region (ND) is measured by a pressure sensor (11) arranged in the low pressure region (ND). Within the framework of the evaluation of the pressure course (pn) in the low pressure zone (ND), a differential pressure course is formed from the difference between the target pressure course (pnsoll) and the detected pressure course (pn) for the low pressure zone (ND). The method according to claim 1 or 2. The absolute value of the detected pressure course (pn) or differential pressure course is formed within the framework of the evaluation of the pressure course (pn) in the low pressure region (ND). Method. 5. The method according to claim 1, wherein the amplitude of the pressure profile (pn) or the differential pressure profile detected in the low pressure region (ND) is used for the diagnosis of the pressure damper (10). A failure of the pressure damper (10) is detected when the amplitude of the pressure course (pn) or the amplitude of the differential pressure course detected in the low pressure region (ND) exceeds a predetermined threshold (ps) for a predetermined duration (ts). 6. The method of claim 5, wherein the method is diagnosed. 2. The steady pressure difference between the pressure course (pn) in the low pressure zone (ND) and the target pressure course (pnsoll) for the low pressure zone (ND) is taken into account in the diagnostic frame of the pressure damper (10). 7. The method according to any one of items 6 to 6. The method according to claim 1, wherein the natural frequency oscillation in the low-pressure region (ND) is filtered out from the detected pressure course (pn). In a computer program running on a calculator (14), in particular a microprocessor,
9. When the computer program is executed on a calculator (14), it is suitable for carrying out the method according to any one of claims 1 to 8,
A computer program characterized by the above. Computer program according to claim 9, wherein the computer program is stored in a storage element (13), in particular in ROM, RAM or flash memory. A diagnostic device for a pressure damper (10) arranged in a low pressure region (ND) of a fuel metering system (1) of an internal combustion engine (2),
The fuel metering system (1) includes a pre-conveying pump (3) that conveys fuel from a fuel container (4) to a low pressure region (ND), and a high pressure that conveys fuel from a low pressure region (ND) to a high pressure region (HD). In a device of the type having a pump (6),
The device (12) is characterized by detecting and evaluating the pressure course (pn) in the low pressure region (ND) and using the detected pressure course (pn) for diagnosis of the pressure damper (10). Diagnostic device. 12. The device according to claim 11, wherein the device (12) comprises means for carrying out the method according to any one of claims 2-8. A fuel metering system (1) for an internal combustion engine that performs fuel injection,
The fuel metering system (1) transports fuel from a fuel container (4) to a low pressure region (ND) and a fuel from a low pressure region (ND) to a high pressure region (HD). A high-pressure pump (6),
In a fuel metering system of the type in which a pressure damper (10) is arranged in the low pressure region (ND),
The fuel metering system (1) comprises means (11) for detecting the pressure course (pn) in the low pressure region (ND), means (12) for evaluating the detected pressure course (pn), Means for diagnosing the pressure damper (10) based on the detected pressure course (pn),
A fuel metering system characterized by that. 14. The fuel metering system (1) according to claim 13, wherein the fuel metering system (1) comprises means for carrying out the method according to any one of claims 2 to 8.

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