EP1818536A2 - Method and device for surveillance of at least one glow plug of a motor vehicle - Google Patents

Method and device for surveillance of at least one glow plug of a motor vehicle Download PDF

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Publication number
EP1818536A2
EP1818536A2 EP07100987A EP07100987A EP1818536A2 EP 1818536 A2 EP1818536 A2 EP 1818536A2 EP 07100987 A EP07100987 A EP 07100987A EP 07100987 A EP07100987 A EP 07100987A EP 1818536 A2 EP1818536 A2 EP 1818536A2
Authority
EP
European Patent Office
Prior art keywords
glow plug
time
threshold value
current
dependent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP07100987A
Other languages
German (de)
French (fr)
Other versions
EP1818536A3 (en
Inventor
Hans-Peter Bauer
Rainer Moritz
Ulrich Kawa
Frank Lehmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
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Robert Bosch GmbH
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Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP1818536A2 publication Critical patent/EP1818536A2/en
Publication of EP1818536A3 publication Critical patent/EP1818536A3/en
Ceased legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P19/00—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition
    • F02P19/02—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition electric, e.g. layout of circuits of apparatus having glowing plugs
    • F02P19/027—Safety devices, e.g. for diagnosing the glow plugs or the related circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P17/00—Testing of ignition installations, e.g. in combination with adjusting; Testing of ignition timing in compression-ignition engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/20—Output circuits, e.g. for controlling currents in command coils
    • F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
    • F02D2041/2031—Control of the current by means of delays or monostable multivibrators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/20—Output circuits, e.g. for controlling currents in command coils
    • F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
    • F02D2041/2058—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit using information of the actual current value
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/20—Output circuits, e.g. for controlling currents in command coils
    • F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
    • F02D2041/2058—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit using information of the actual current value
    • F02D2041/2062—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit using information of the actual current value the current value is determined by simulation or estimation

Definitions

  • the invention relates to a method and a device for monitoring an at least one glow plug of a motor vehicle.
  • glow plugs in motor vehicles are monitored by comparing the current flowing through the glow plugs with a predetermined fixed threshold. If the current consumption through the glow plug is less than the threshold, the glow plug is rated as faulty.
  • Analog circuits use comparators or differential amplifiers for this purpose.
  • Microcomputer-based Glühzeit tenuieri determine via an analog-to-digital converter corresponding to the current through the glow plug digital value and compare this with a stored digital threshold.
  • the problem is that the current profile of the glow plug after application of the supply voltage is highly time-dependent.
  • the monitoring of the glow plug based on a fixed current value therefore only allows a very rough rating.
  • a time-dependent variable which characterizes the current flowing through the at least one glow plug for fault detection is compared with at least one time-dependent threshold value, and is detected for errors when the time-dependent variable is greater and / or less than the threshold value is, can be detected much more safely and effectively for errors. It is particularly advantageous if the time-dependent threshold value is determined by means of a simulation of the glow plug. As a result, the effort in the context of the application of the control unit can be significantly reduced.
  • the time-dependent threshold value or the time-dependent threshold values have the same characteristic time profile as the current of the glow plug to be monitored.
  • a particularly simple and inexpensive replica of the glow plug is a so-called RC circuit.
  • the glow plug is essentially simulated by a capacitor. The charge contained in the capacitor corresponds to the energy content and thus to a first approximation of the temperature of the glow plug.
  • a particularly accurate and precise replica of the glow plug results in replicating a microcomputer circuit is used. In such a microprocessor circuit, a corresponding time characteristic or a programmed function may be included.
  • the comparison between the time-dependent threshold value and the time-dependent variable is carried out by means of an analog comparison circuit. As a result, the circuit complexity and the programming effort in the control unit can be significantly reduced and there is a simple and cost-effective solution available.
  • FIG. 1 shows the essential elements of the device according to the invention.
  • a glow plug 100 is connected in series with a current measuring means 120 and a switching means 110 between the two terminals of a supply voltage.
  • a current measuring means 120 and a switching means 110 is provided for each glow plug.
  • a common switching means 110 and / or a common current measuring means 120 is provided for a plurality of glow plugs or all glow plugs of an internal combustion engine.
  • the illustrated embodiment, in which each glow plug is associated with a current measuring means 120 and a switching means 110 offers the advantage that the glow plugs can be individually controlled and the current flowing through the respective glow plug can be evaluated. If several glow plugs are combined to form a group, or if all the glow plugs are actuated together and / or the current evaluated together, this offers the advantage that more expensive elements, for example the switching means, can be saved, thus resulting in considerable cost savings.
  • a control unit 130 which, in addition to other components not shown, includes an evaluation 133, a control 135 and an error detection 137.
  • the driver 135 controls the switching means 110 to supply a desired energy to the glow plug.
  • the evaluation 133 evaluates the voltage drop across the current measuring means 120 to determine the current flowing through the glow plug.
  • the current measuring means 120 is preferably designed as an ohmic resistor.
  • the voltage drop at the current measuring means 120 is supplied to an amplifier 140 which provides its output signal to the evaluation 133. Furthermore, the output signal of the measuring amplifier 140 reaches a comparator 150, at whose second input the output signal of a threshold value input 160 is present.
  • the glow plugs have a very low resistance at the beginning of the current supply. As a result, a very large current flows at the beginning of the current supply. By heating the glow plug increases their resistance, which in turn causes the current drops.
  • An exemplary course of the current over the time of an annealing process is plotted in FIG. 2 with a solid line. If the current deviates significantly from this curve, then a fault in the range of the control or a defect of the glow plug can be assumed.
  • a lower threshold value IU is specified, below which error is detected.
  • the value of the lower threshold IU assumes, by way of example, the dot-dash line in FIG. If the current falls below this value, then a defect is detected.
  • an upper threshold value 10 is specified, which assumes the profile indicated by a dashed line in FIG. If the current exceeds this value, a defect is assumed as well. It is particularly advantageous if both a lower and an upper threshold value are predetermined and detected for errors when the current is outside the tolerance band defined by the two threshold values.
  • control unit 130 may be omitted and only a measuring amplifier 140 and a comparator 150 and a threshold value 160 may be provided, which evaluates the voltage drop across the measuring resistor 120.
  • a circuit may be constructed in particular analog. D. h only analogous components are provided which take over the functionalities.
  • Threshold value 160 is essentially formed by an RC circuit in this embodiment. This consists of a series circuit of a resistor 201 and a capacitor 205, which is arranged between the ground terminal and the connection point between the current measuring means 120 and the switching means 110. Ie. Essentially, a voltage proportional to the voltage drop across the glow plug 100 is applied to the capacitor 205. Furthermore, there is a series circuit of the resistor 201 and further resistors 202, 203 and 204. This series circuit is arranged between the ground terminal and the connection point between switching means 110 and current measuring means 120 respectively.
  • the input signal to the comparator 150a is tapped.
  • the signal for a second comparator 150b is tapped.
  • the two comparators 150a and 150b correspond to the comparator 1150 shown in FIG. 1.
  • two comparators are provided so that a threshold value query with a lower and an upper threshold value is possible.
  • one of the two comparators and one of the three resistors 202, 203 or 204 can be dispensed with. In this embodiment, only a comparison with a threshold value is then possible. It is essential that the voltage divider and the series circuit of capacitor 205 and resistor 201 are supplied with the same voltage applied to the glow plug to be monitored.
  • the voltage drop corresponding to the current flowing through the glow plug is compared with the voltage drop across the capacitor 205. Whereby not the total voltage but the voltage divided by the voltage divider consisting of the resistors 202, 203 and 204 is evaluated. At the outputs of the comparators 150a and 150b, there is a respective signal which, depending on the comparison, indicates an error or indicates a fault-free operation.
  • the circuit shown in Figure 3 represents a simple replica of the glow plug.
  • the voltage across the capacitor depends on the charge of the capacitor.
  • the capacitor acts integrating and summing up the energy introduced into the glow plug. This is achieved by applying a voltage proportional to the voltage drop across the glow plug to the capacitor 205.
  • the state of charge or the voltage across the capacitor 205 is a measure of the temperature or the resistance of the glow plug.
  • the time behavior of the output voltage of the voltage divider which is formed by the resistors 202, 203 and 204, corresponds to the time behavior of the fault-free current through the glow plug.
  • the lower and / or upper threshold values can be specified.
  • the embodiment shown in FIG. 3 represents an analogous possibility of realization. It is particularly advantageous if the threshold value specification 160 forms part of the control unit 130. In this case, it is possible to realize the threshold value specification digitally. For example, it may be provided that the threshold value is stored as a characteristic curve in a memory of the control unit 130. In each case, a characteristic for the upper and / or lower threshold can be provided. In this case, the comparison is also made in a comparator, which is in the form of a digital circuit or a computer.
  • FIG. 4 shows a further embodiment of the replica of the glow plug according to the invention, from which threshold values for the current, in particular an upper current threshold value IO and a lower current threshold value IU, are formed.
  • the references 135, 110, 120, 100 and 140 again designate the drive 135, the switching means 110, the current measuring means 120 and the amplifier 140, which are already known from FIG.
  • the replica of the glow plug takes place here again by an RC element, which is formed by the resistor 201 and the capacitance 205. In contrast to FIG. 3, however, here the RC element is connected between the drive 135 and a ground connection.
  • the RC element 201, 205 is energized and it forms at the tap between the resistor 201 and the capacitor 205, a voltage which behaves like the voltage at the glow plug 100.
  • the voltage divider 202, 203, 204 then comparison voltages are formed, which are proportional to an upper threshold for the current IO and proportional to a lower current threshold IU.
  • the tapped between the resistors 202 and 203 voltage is proportional to the upper threshold IO.
  • the tapped between the resistors 203 and 204 voltage is proportional to the lower threshold IU.
  • the voltage proportional to the upper threshold value IO is supplied to a comparator 150a whose other input is connected to the output of the amplifier 140. As soon as the voltage drop across the resistor 120, which is evaluated by the comparator 140, exceeds the comparison voltage for the upper current threshold value IO, a corresponding signal is generated by the comparator 150a, which represents an error signal. Accordingly, the comparator 150b generates a signal when the voltage drop across the measuring means 120, which is evaluated by the comparator 140, falls below the comparison voltage for the lower measured current value IU.
  • the threshold values IO and IU are calculated on the basis of different input variables according to a programmed function. For example, provision may be made for the threshold values to be calculated according to a function based on predefined parameters, the time and the supply voltage applied to the glow plug. Such a calculation is preferably carried out by means of a computer.
  • the output signal of the controller 135 is used to calculate the threshold values. This means based on the drive signal of the switching means, which is preferably present as a time-dependent PWM signal, the threshold value is calculated. This can be realized both analogously by means of an RC circuit and also digitally by means of a computer.
  • a corresponding computer may be part of the control unit 130.

Abstract

The method involves comparing a time-dependent parameter characterizing the current (IO) flowing through at least one glow plug with at least one time-dependent threshold value (IU) to detect a fault. It involves detecting a fault if the time-dependent parameter is greater than and/or les than the threshold value. The threshold value is determined by simulating a glow plug. An independent claim is also included for an arrangement for monitoring at least one glow plug in motor vehicle.

Description

Stand der TechnikState of the art

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zur Überwachung einer wenigstens einer Glühkerze eines Kraftfahrzeugs.The invention relates to a method and a device for monitoring an at least one glow plug of a motor vehicle.

Üblicherweise werden Glühkerzen in Kraftfahrzeugen dadurch überwacht, dass der durch die Glühkerzen fließende Strom mit einem vorgegebenen festen Schwellenwert verglichen wird. Ist die Stromaufnahme durch die Glühkerze kleiner als der Schwellenwert, wird die Glühkerze als fehlerhaft bewertet. Analoge Schaltungen verwenden hiefür Komparatoren oder Differenzverstärker. Mikrocomputerbasierte Glühzeitsteuergeräte ermitteln über ein analog-digital-Konverter einen dem Strom durch die Glühkerze entsprechenden digitalen Wert und vergleichen diesen mit einem abgespeicherten digitalen Schwellenwert.Conventionally, glow plugs in motor vehicles are monitored by comparing the current flowing through the glow plugs with a predetermined fixed threshold. If the current consumption through the glow plug is less than the threshold, the glow plug is rated as faulty. Analog circuits use comparators or differential amplifiers for this purpose. Microcomputer-based Glühzeitsteuergeräte determine via an analog-to-digital converter corresponding to the current through the glow plug digital value and compare this with a stored digital threshold.

Problematisch ist, dass der Stromverlauf der Glühkerze nach Anlegen der Versorgungsspannung stark zeitabhängig ist. Die Überwachung der Glühkerze auf Basis eines festen Stromwerts erlaubt daher nur eine sehr grobe Bewertung.The problem is that the current profile of the glow plug after application of the supply voltage is highly time-dependent. The monitoring of the glow plug based on a fixed current value therefore only allows a very rough rating.

Offenbarung der ErfindungDisclosure of the invention

Dadurch, dass eine zeitabhängige Größe, die den durch die wenigstens eine Glühkerze fließenden Strom charakterisiert zur Fehlererkennung mit wenigstens einem zeitabhängigen Schwellenwert verglichen wird, und auf Fehler erkannt wird, wenn die zeitabhängige Größe größer und/oder kleiner als er Schwellenwert ist, kann wesentlich sicher und effektiver auf Fehler erkannt werden. Besonders vorteilhaft ist es, wenn zeitabhängige Schwellenwert mittels einer Nachbildung der Glühkerze ermittelt wird. Dadurch kann der Aufwand im Rahmen der Applikation des Steuergeräts deutlich reduziert werden.Characterized in that a time-dependent variable which characterizes the current flowing through the at least one glow plug for fault detection is compared with at least one time-dependent threshold value, and is detected for errors when the time-dependent variable is greater and / or less than the threshold value is, can be detected much more safely and effectively for errors. It is particularly advantageous if the time-dependent threshold value is determined by means of a simulation of the glow plug. As a result, the effort in the context of the application of the control unit can be significantly reduced.

Bei einer vereinfachten Ausführungsform ist lediglich vorgesehen, dass überprüft wird, ob der Strom kleiner als der zeitabhängige Schwellenwert ist. Bei einer alternativen Ausführungsform ist vorgesehen, dass auf Fehler erkannt wird, wenn der Strom größer als der zeitabhängige Schwellenwert ist. Bei einer besonders vorteilhaften Ausführungsform ist vorgesehen, dass zwei zeitabhängige Schwellenwerte vorgegeben werden, die ein Toleranzband bilden. Liegt der gemessene Strom außerhalb dieses Toleranzbandes wird auf Fehler erkannt.In a simplified embodiment, it is merely provided that it is checked whether the current is smaller than the time-dependent threshold value. In an alternative embodiment, it is provided that errors are detected when the current is greater than the time-dependent threshold value. In a particularly advantageous embodiment, it is provided that two time-dependent threshold values are predetermined, which form a tolerance band. If the measured current is outside this tolerance band, an error is detected.

Besonders vorteilhaft ist, wenn der zeitabhängige Schwellenwert bzw. die zeitabhängigen Schwellenwerte den gleichen charakteristischen zeitlichen Verlauf aufweisen, wie der Strom der zu überwachenden Glühkerze. Eine besonders einfache und kostengünstige Nachbildung der Glühkerze stellt eine so genannte RC-Schaltung dar. Bei dieser wird die Glühkerze im Wesentlichen durch einen Kondensator nachgebildet. Die in dem Kondensator enthaltene Ladung entspricht dem Energiegehalt und damit in erster Näherung der Temperatur der Glühkerze. Eine besonders genaue und präzise Nachbildung der Glühkerze ergibt sich, zur Nachbildung eine Mikrocomputerschaltung verwendet wird. In einer solchen Mikroprozessorschaltung kann eine entsprechende zeitliche Kennlinie oder eine programmierte Funktion beinhaltet sein. Besonders vorteilhaft ist es, wenn der Vergleich zwischen dem zeitabhängigen Schwellenwert mit der zeitabhängigen Größe mittels einer analogen Vergleichsschaltung erfolgt. Dadurch kann der Schaltungsaufwand bzw. der Programmieraufwand im Steuergerät deutlich reduziert werden und es steht eine einfache und kostengünstige Lösung zur Verfügung.It is particularly advantageous if the time-dependent threshold value or the time-dependent threshold values have the same characteristic time profile as the current of the glow plug to be monitored. A particularly simple and inexpensive replica of the glow plug is a so-called RC circuit. In this case, the glow plug is essentially simulated by a capacitor. The charge contained in the capacitor corresponds to the energy content and thus to a first approximation of the temperature of the glow plug. A particularly accurate and precise replica of the glow plug results in replicating a microcomputer circuit is used. In such a microprocessor circuit, a corresponding time characteristic or a programmed function may be included. It is particularly advantageous if the comparison between the time-dependent threshold value and the time-dependent variable is carried out by means of an analog comparison circuit. As a result, the circuit complexity and the programming effort in the control unit can be significantly reduced and there is a simple and cost-effective solution available.

Zeichnungdrawing

Die Ausführungsbeispiele der Erfindung sind in de Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigen:

Figur 1
wesentliche Elemente einer Vorrichtung zur Überwachung wenigstens einer Glühkerze,
Figur 2
den zeitlichen Verlauf des Stromwerts und der Schwellenwerte über der Zeit und
Figur 3
eine detaillierte Darstellung einer Nachbildung und
Figur 4
eine weitere Ausführungsform der erfindungsgemäßen Nachbildung der Glühstiftkerze.
The embodiments of the invention are illustrated in de drawing and explained in more detail in the following description. Show it:
FIG. 1
essential elements of a device for monitoring at least one glow plug,
FIG. 2
the time course of the current value and the thresholds over time and
FIG. 3
a detailed presentation of a replica and
FIG. 4
a further embodiment of the replica of the glow plug according to the invention.

Beschreibung der AusführungsbeispieleDescription of the embodiments

In Figur 1 sind die wesentlichen Elemente der erfindungsgemäßen Vorrichtung dargestellt. Eine Glühkerze 100 ist in Reihe mit einem Strommessmittel 120 und einem Schaltmittel 110 zwischen den beiden Anschlüssen einer Versorgungsspannung geschaltet. In dem dargestellten Ausführungsbeispiel ist für jede Glühkerze ein Strommessmittel 120 und ein Schaltmittel 110 vorgesehen. Bei einer Ausgestaltung der erfindungsgemäßen Vorrichtung kann auch vorgesehen sein, das für mehrere Glühkerzen oder alle Glühkerzen einer Brennkraftmaschine ein gemeinsames Schaltmittel 110 und/oder ein gemeinsames Strommessmittel 120 vorgesehen ist. Die dargestellte Ausführungsform, bei dem jeder Glühkerze ein Strommessmittel 120 und ein Schaltmittel 110 zugeordnet ist, bietet den Vorteil, dass die Glühkerzen einzeln angesteuert und der durch die jeweilige Glühkerze fließende Strom ausgewertet werden kann. Sind mehrere Glühkerzen zu einer Gruppe zusammengefasst, bzw. werden alle Glühkerzen gemeinsam angesteuert und/oder der Strom gemeinsam ausgewertet, so bietet dies den Vorteil, dass teurere Elemente beispielsweise die Schaltmittel eingespart werden können und sich damit eine erhebliche Kostenersparnis ergibt.FIG. 1 shows the essential elements of the device according to the invention. A glow plug 100 is connected in series with a current measuring means 120 and a switching means 110 between the two terminals of a supply voltage. In the illustrated embodiment, a current measuring means 120 and a switching means 110 is provided for each glow plug. In one embodiment of the device according to the invention can also be provided that a common switching means 110 and / or a common current measuring means 120 is provided for a plurality of glow plugs or all glow plugs of an internal combustion engine. The illustrated embodiment, in which each glow plug is associated with a current measuring means 120 and a switching means 110, offers the advantage that the glow plugs can be individually controlled and the current flowing through the respective glow plug can be evaluated. If several glow plugs are combined to form a group, or if all the glow plugs are actuated together and / or the current evaluated together, this offers the advantage that more expensive elements, for example the switching means, can be saved, thus resulting in considerable cost savings.

Des Weiteren ist eine Steuereinheit 130 vorgesehen, die neben weiteren nicht dargestellten Bauelementen eine Auswertung 133, eine Ansteuerung 135 und eine Fehlererkennung 137 umfasst. Die Ansteuerung 135 steuert das Schaltmittel 110 an, um der Glühkerze eine gewünschte Energie zuzuführen. Die Auswertung 133 wertet die am Strommessmittel 120 abfallende Spannung aus, um den Strom, der durch die Glühkerze fließt, zu ermitteln. Das Strommessmittel 120 ist vorzugsweise als Ohmscher Widerstand ausgebildet. Der Spannungsabfall am Strommessmittel 120 wird ein Verstärker 140 zugeführt, der sein Ausgangssignal der Auswertung 133 zur Verfügung stellt. Des Weiteren gelangt das Ausgangssignal des Messverstärkers 140 zu einem Komparator 150, an dessen zweiten Eingang das Ausgangssignal einer Schwellenwertvorgabe 160 anliegt.Furthermore, a control unit 130 is provided which, in addition to other components not shown, includes an evaluation 133, a control 135 and an error detection 137. The driver 135 controls the switching means 110 to supply a desired energy to the glow plug. The evaluation 133 evaluates the voltage drop across the current measuring means 120 to determine the current flowing through the glow plug. The current measuring means 120 is preferably designed as an ohmic resistor. The voltage drop at the current measuring means 120 is supplied to an amplifier 140 which provides its output signal to the evaluation 133. Furthermore, the output signal of the measuring amplifier 140 reaches a comparator 150, at whose second input the output signal of a threshold value input 160 is present.

Üblicherweise weisen die Glühkerzen zu Beginn der Bestromung einen sehr geringen Widerstand auf. Dies hat zur Folge, dass zu Beginn der Bestromung ein sehr großer Strom fließt. Durch die Aufheizung der Glühkerze erhöht sich deren Widerstand, was wiederum dazu führt, dass der Strom abfällt. Ein beispielhafter Verlauf des Stroms über der Zeit eines Glühvorgangs ist in Figur 2 mit einer durchgezogenen Linie aufgetragen. Weicht der Strom von diesem Verlauf deutlich ab, so ist von einem Fehler im Bereich der Ansteuerung oder ein Defekt der Glühkerze auszugehen.Usually, the glow plugs have a very low resistance at the beginning of the current supply. As a result, a very large current flows at the beginning of the current supply. By heating the glow plug increases their resistance, which in turn causes the current drops. An exemplary course of the current over the time of an annealing process is plotted in FIG. 2 with a solid line. If the current deviates significantly from this curve, then a fault in the range of the control or a defect of the glow plug can be assumed.

Erfindungsgemäß ist nun vorgesehen, dass ein unterer Schwellenwert IU vorgegeben wird, mit dessen Unterschreiten auf Fehler erkannt wird. Der Wert des unteren Schwellenwerts IU nimmt beispielhaft den in Figur 2 strichpunktierten Verlauf an. Fällt der Strom unter diesen Wert ab, so wird auf Defekt erkannt. Bei einer Ausführungsform kann vorgesehen sein, dass ein oberer Schwellenwert 10 vorgegeben wird, der den in Figur 2 mit einer gestrichelten Linie bezeichneten Verlauf annimmt. Überschreitet der Strom diesen Wert, so wird ebenfalls von einem Defekt ausgegangen. Besonders vorteilhaft ist es, wenn sowohl ein untere als auch ein oberer Schwellenwert vorgegeben wird und auf Fehler erkannt wird, wenn der Strom außerhalb des durch die beiden Schwellenwerte definierten Toleranzbandes liegt.According to the invention, it is now provided that a lower threshold value IU is specified, below which error is detected. The value of the lower threshold IU assumes, by way of example, the dot-dash line in FIG. If the current falls below this value, then a defect is detected. In one embodiment, it may be provided that an upper threshold value 10 is specified, which assumes the profile indicated by a dashed line in FIG. If the current exceeds this value, a defect is assumed as well. It is particularly advantageous if both a lower and an upper threshold value are predetermined and detected for errors when the current is outside the tolerance band defined by the two threshold values.

Bei einer vereinfachten Ausführungsform kann die Steuereinheit 130 entfallen und lediglich ein Messverstärker 140 sowie ein Komparator 150 und eine Schwellenwertvorgabe 160 vorgesehen sein, die den Spannungsabfall am Messwiderstand 120 auswertet. Eine solche Schaltung kann insbesondere analog aufgebaut sein. D. h es sind lediglich analoge Bauelemente vorgesehen, die die Funktionalitäten übernehmen.In a simplified embodiment, the control unit 130 may be omitted and only a measuring amplifier 140 and a comparator 150 and a threshold value 160 may be provided, which evaluates the voltage drop across the measuring resistor 120. Such a circuit may be constructed in particular analog. D. h only analogous components are provided which take over the functionalities.

In Figur 3 sind wesentliche Elemente der Figur 1, insbesondere die Schwellwertvorgabe 160, detailliert dargestellt. Bereits in Figur 1 beschriebene Elemente sind mit entsprechenden Bezugszeichen bezeichnet. Die Schwellenwertvorgabe 160 wird in dieser Ausführungsform im Wesentlichen durch eine RC-Schaltung gebildet. Diese besteht aus einer Reihenschaltung eines Widerstandes 201 und eines Kondensators 205, die zwischen dem Masseanschluss und dem Verbindungspunkt zwischen dem Strommessmittel 120 und dem Schaltmittel 110 angeordnet ist. D. h. im Wesentlichen liegt an dem Kondensator 205 eine zu dem Spannungsabfall an der Glühkerze 100 proportionale Spannung an. Des weiteren besteht eine Reihenschaltung aus dem Widerstand 201 und weiteren Widerständen 202, 203 und 204. Diese Reihenschaltung ist entsprechend zwischen dem Massenanschluss und dem Verbindungspunkt zwischen Schaltmittel 110 und Strommessmittel 120 angeordnet. Am Verbindungspunkt zwischen den Widerständen 202 und 203 wird das Eingangssignal für den Komparator 150a abgegriffen. An dem Verbindungspunkt zwischen den Widerständen 203 und 204 wird das Signal für einen zweiten Komparator 150b abgegriffen. Die beiden Komparatoren 150a und 150b entsprechen dem in Figur 1 dargestellten Komparator 1150. In der Ausführungsform gemäß einer Figur 3 sind zwei Komparatoren vorgesehen, damit eine Schwellenwertabfrage mit einen unteren und einen oberen Schwellenwert möglich ist. Bei einer vereinfachten Ausführungsform kann einer der beiden Komparatoren sowie einer der drei Widerstände 202, 203 oder 204 entfallen. Bei dieser Ausführungsform ist dann nur ein Vergleich mit einem Schwellenwert möglich. Wesentlich ist, dass der Spannungsteiler und die Reihenschaltung aus Kondensator 205 und Widerstand 201 mit der gleichen Spannung beaufschlagt werden, die an der zu überwachenden Glühkerze anliegt.In FIG. 3, essential elements of FIG. 1, in particular the threshold value specification 160, are shown in detail. Already described in Figure 1 elements are designated by corresponding reference numerals. Threshold value 160 is essentially formed by an RC circuit in this embodiment. This consists of a series circuit of a resistor 201 and a capacitor 205, which is arranged between the ground terminal and the connection point between the current measuring means 120 and the switching means 110. Ie. Essentially, a voltage proportional to the voltage drop across the glow plug 100 is applied to the capacitor 205. Furthermore, there is a series circuit of the resistor 201 and further resistors 202, 203 and 204. This series circuit is arranged between the ground terminal and the connection point between switching means 110 and current measuring means 120 respectively. At the connection point between the resistors 202 and 203, the input signal to the comparator 150a is tapped. At the connection point between the resistors 203 and 204, the signal for a second comparator 150b is tapped. The two comparators 150a and 150b correspond to the comparator 1150 shown in FIG. 1. In the embodiment according to FIG. 3, two comparators are provided so that a threshold value query with a lower and an upper threshold value is possible. In a simplified embodiment, one of the two comparators and one of the three resistors 202, 203 or 204 can be dispensed with. In this embodiment, only a comparison with a threshold value is then possible. It is essential that the voltage divider and the series circuit of capacitor 205 and resistor 201 are supplied with the same voltage applied to the glow plug to be monitored.

Erfindungsgemäß wird der Spannungsabfall, der dem Strom entspricht der durch Glühkerze fließ, mit dem Spannungsabfall an dem Kondensator 205 verglichen. Wobei hierbei nicht die Gesamtspannung, sondern die mit dem Spannungsteiler bestehend aus den Widerständen 202, 203 und 204 geteilte Spannung ausgewertet wird. An den Ausgängen der Komparatoren 150a und 150b liegt jeweils ein Signal an, das abhängig von dem Vergleich ein Fehler anzeigt oder einen fehlerfreien Betrieb anzeigt.According to the invention, the voltage drop corresponding to the current flowing through the glow plug is compared with the voltage drop across the capacitor 205. Whereby not the total voltage but the voltage divided by the voltage divider consisting of the resistors 202, 203 and 204 is evaluated. At the outputs of the comparators 150a and 150b, there is a respective signal which, depending on the comparison, indicates an error or indicates a fault-free operation.

Die in Figur 3 dargestellte Schaltung stellt eine einfache Nachbildung der Glühkerze dar. Die Spannung am Kondensator hängt von der Ladung des Kondensators ab. Der Kondensator wirkt integrierend und summiert, die in die Glühkerze eingebrachte Energie auf. Dies wird dadurch erreicht, dass am Kondensator 205 eine zum Spannungsabfall an der Glühkerze proportionale Spannung anliegt. Der Ladezustand bzw. die Spannung am Kondensator 205 ist ein Maß für die Temperatur bzw. den Widerstand der Glühkerze. Durch geeignete Wahl der Werte des Kondensators und der Widerstände wird erreicht, dass das zeitliche Verhalten der Ausgangsspannung des Spannungsteilers, der durch die Widerstände 202, 203 und 204 gebildet wird, dem zeitlichen Verhalten des fehlerfreien Stroms durch die Glühkerze entspricht. Durch eine entsprechende Aufteilung der Widerstandswerte können die unteren und/oder oberen Schwellenwerte vorgegeben werden.The circuit shown in Figure 3 represents a simple replica of the glow plug. The voltage across the capacitor depends on the charge of the capacitor. The capacitor acts integrating and summing up the energy introduced into the glow plug. This is achieved by applying a voltage proportional to the voltage drop across the glow plug to the capacitor 205. The state of charge or the voltage across the capacitor 205 is a measure of the temperature or the resistance of the glow plug. By suitably selecting the values of the capacitor and the resistors, it is achieved that the time behavior of the output voltage of the voltage divider, which is formed by the resistors 202, 203 and 204, corresponds to the time behavior of the fault-free current through the glow plug. By a corresponding division of the resistance values, the lower and / or upper threshold values can be specified.

Die in Figur 3 dargestellte Ausführungsform stellt eine analoge Realisierungsmöglichkeit dar. Besonders vorteilhaft ist es, wenn die Schwellwertvorgabe 160 ein Bestandteil der Steuereinheit 130 bildet. In diesem Fall ist es möglich, die Schwellwertvorgabe digital zu realisieren. So kann beispielsweise vorgesehen sein, dass der Schwellenwert als Kennlinie in einem Speicher der Steuereinheit 130 abgelegt ist. Dabei können jeweils eine Kennlinie für den oberen und/oder den unteren Schwellwert vorgesehen sein. In diesem Fall erfolgt der Vergleich ebenfalls in einem Komparator, der in Form einer Digitalschaltung oder eines Rechners ausgebildet ist.The embodiment shown in FIG. 3 represents an analogous possibility of realization. It is particularly advantageous if the threshold value specification 160 forms part of the control unit 130. In this case, it is possible to realize the threshold value specification digitally. For example, it may be provided that the threshold value is stored as a characteristic curve in a memory of the control unit 130. In each case, a characteristic for the upper and / or lower threshold can be provided. In this case, the comparison is also made in a comparator, which is in the form of a digital circuit or a computer.

In der Figur 4 wird eine weitere Ausführungsform der erfindungsgemäßen Nachbildung der Glühstiftkerze gezeigt, aus der dann Schwellwerte für den Strom, insbesondere ein oberer Stromschwellenwert IO und ein unterer Stromschwellwert IU gebildet werden. Mit dem Bezugszeichen 135, 110, 120, 100 und 140 sind wieder die Ansteuerung 135, das Schaltmittel 110, das Strommessmittel 120 und der Verstärker 140 bezeichnet, die bereits aus der Figur 1 bekannt sind. Die Nachbildung der Glühkerze erfolgt hier wieder durch ein RC-Glied, welches von dem Widerstand 201 und der Kapazität 205 gebildet wird. Im Unterschied zur Figur 3 ist hier jedoch das RC-Glied zwischen der Ansteuerung 135 und einem Masseanschluss geschaltet. Sobald von der Ansteuerung 135 ein entsprechendes Ansteuersignal zum Durchschalten des Schaltmittels 110 erzeugt wird, wird auch das RC-Glied 201, 205 mit Strom beaufschlagt und es bildet sich am Abgriff zwischen dem Widerstand 201 und dem Kondensator 205 eine Spannung aus, die sich wie die Spannung an der Glühkerze 100 verhält. Durch den Spannungsteiler 202, 203, 204 werden dann Vergleichsspannungen gebildet, die proportional zu einem oberen Schwellwert für den Strom IO und proportional zu einem unteren Stromschwellwert IU sind. Die zwischen den Widerständen 202 und 203 abgegriffene Spannung verhält sich proportional zum oberen Schwellwert IO. Die zwischen den Widerständen 203 und 204 abgegriffene Spannung verhält sich proportional zu dem unterem Schwellwert IU. Die Spannung proportional zum oberen Schwellwert IO wird einem Komparator 150a zugeleitet, dessen anderer Eingang mit dem Ausgang des Verstärkers 140 verbunden ist. Sobald die über den Widerstand 120 abfallende Spannung, die von dem Komparator 140 ausgewertet wird, die Vergleichsspannung für den oberen Stromschwellwert IO überschreitet wird von dem Komparator 150a ein entsprechendes Signal erzeugt, welches ein Fehlersignal darstellt. Entsprechend erzeugt der Komparator 150b ein Signal, wenn die am Messmittel 120 abfallende Spannung, die vom Komparator 140 ausgewertet wird, die Vergleichsspannung für den unteren Strommesswert IU unterschreitet.FIG. 4 shows a further embodiment of the replica of the glow plug according to the invention, from which threshold values for the current, in particular an upper current threshold value IO and a lower current threshold value IU, are formed. The references 135, 110, 120, 100 and 140 again designate the drive 135, the switching means 110, the current measuring means 120 and the amplifier 140, which are already known from FIG. The replica of the glow plug takes place here again by an RC element, which is formed by the resistor 201 and the capacitance 205. In contrast to FIG. 3, however, here the RC element is connected between the drive 135 and a ground connection. Once from the control 135 a corresponding Drive signal is generated for switching through the switching means 110, the RC element 201, 205 is energized and it forms at the tap between the resistor 201 and the capacitor 205, a voltage which behaves like the voltage at the glow plug 100. By the voltage divider 202, 203, 204 then comparison voltages are formed, which are proportional to an upper threshold for the current IO and proportional to a lower current threshold IU. The tapped between the resistors 202 and 203 voltage is proportional to the upper threshold IO. The tapped between the resistors 203 and 204 voltage is proportional to the lower threshold IU. The voltage proportional to the upper threshold value IO is supplied to a comparator 150a whose other input is connected to the output of the amplifier 140. As soon as the voltage drop across the resistor 120, which is evaluated by the comparator 140, exceeds the comparison voltage for the upper current threshold value IO, a corresponding signal is generated by the comparator 150a, which represents an error signal. Accordingly, the comparator 150b generates a signal when the voltage drop across the measuring means 120, which is evaluated by the comparator 140, falls below the comparison voltage for the lower measured current value IU.

Bei einer weiteren Ausführungsform kann vorgesehen sein, dass die Schwellenwerte IO und IU ausgehend von verschiedenen Eingangsgrößen gemäß einer programmierten Funktion berechnet werden. So kann beispielsweise vorgesehen sein, dass die Schwellenwerte ausgehend von fest vorgegebenen Parametern, der Zeit und der an der Glühkerze anliegenden Versorgungsspannung gemäß einer Funktion berechnet werden. Eine solche Berechnung erfolgt vorzugsweise mittels eines Rechners.In a further embodiment it can be provided that the threshold values IO and IU are calculated on the basis of different input variables according to a programmed function. For example, provision may be made for the threshold values to be calculated according to a function based on predefined parameters, the time and the supply voltage applied to the glow plug. Such a calculation is preferably carried out by means of a computer.

Ferner kann vorgesehen sein, dass zur Berechnung der Schwellenwerte das Ausgangssignal der Steuerung 135 verwendet wird. Dies bedeutet ausgehend von dem Ansteuersignal des Schaltmittels, das vorzugsweise als zeitabhängiges PWM-Signal vorliegt, wird der Schwellenwert berechnet. Dies kann sowohl analog mittels eines RC-Schaltung als auch digital mittels eines Rechners realisiert sein.Furthermore, it can be provided that the output signal of the controller 135 is used to calculate the threshold values. This means based on the drive signal of the switching means, which is preferably present as a time-dependent PWM signal, the threshold value is calculated. This can be realized both analogously by means of an RC circuit and also digitally by means of a computer.

Ein entsprechender Rechner kann Teil der Steuereinheit 130 sein.A corresponding computer may be part of the control unit 130.

Claims (7)

Verfahren zur Überwachung wenigstens einer Glühkerze eines Kraftfahrzeugs, wobei eine zeitabhängige Größe, die den durch wenigstens eine Glühkerze fließenden Strom charakterisiert, zur Fehlererkennung mit wenigstens einem zeitabhängigen Schwellenwert verglichen wird, wobei auf Fehler erkannt wird, wenn die zeitabhängige Größe größer und/oder kleiner als der Schwellenwert ist, dadurch gekennzeichnet, dass der zeitabhängige Schwellenwert mittels einer Nachbildung der Glühkerze ermittelt wird.Method for monitoring at least one glow plug of a motor vehicle, wherein a time-dependent variable which characterizes the current flowing through at least one glow plug is compared with at least one time-dependent threshold for fault detection, wherein errors are detected if the time-dependent variable is greater than and / or less than the threshold value, characterized in that the time-dependent threshold value is determined by means of a replica of the glow plug. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass der zeitabhängige Schwellenwert den charakteristischen zeitlichen Stromverlauf der entsprechenden Glühkerzentyps besitzt.A method according to claim 1, characterized in that the time-dependent threshold value has the characteristic temporal current profile of the corresponding Glühkerzentyps. Vorrichtung zur Überwachung wenigstens einer Glühkerze eines Kraftfahrzeugs, wobei eine zeitabhängige Größe, die den durch wenigstens eine Glühkerze fließenden Strom charakterisiert, mit Mitteln, die zur Fehlererkennung die zeitabhängige Größe mit wenigstens einem zeitabhängigen Schwellenwert vergleicht, und auf Fehler erkennt, wenn die zeitabhängige Größe größer und/oder kleiner als der Schwellenwert ist, dadurch gekennzeichnet, dass der zeitabhängige Schwellenwert mittels einer Nachbildung der Glühkerze ermittelt wird.A device for monitoring at least one glow plug of a motor vehicle, wherein a time-dependent variable that characterizes the current flowing through at least one glow plug, with means that compares the time-dependent variable with at least one time-dependent threshold for error detection, and detects errors when the time-dependent variable is larger and / or is smaller than the threshold value, characterized in that the time-dependent threshold value is determined by means of a simulation of the glow plug. Vorrichtung nach Anspruch 3, dadurch gekennzeichnet, dass die Nachbildung mittels einer analogen RC-Schaltung gebildet wird.Apparatus according to claim 3, characterized in that the replica is formed by means of an analog RC circuit. Vorrichtung nach Anspruch 4, dadurch gekennzeichnet, dass die RC-Schaltung mit derselben Spannung UV verbunden ist, welche auch an der Glühkerze anliegt.Apparatus according to claim 4, characterized in that the RC circuit is connected to the same voltage UV, which also rests on the glow plug. Vorrichtung nach Anspruch 3, dadurch gekennzeichnet, dass die Nachbildung mittels einer eines Rechners gebildet wird.Apparatus according to claim 3, characterized in that the replica is formed by means of a computer. Vorrichtung nach Anspruch 6, dadurch gekennzeichnet, dass der Rechner eine abgespeicherten Kennlinie oder programmierten Funktion beinhaltet.Apparatus according to claim 6, characterized in that the computer includes a stored characteristic or programmed function.
EP07100987.2A 2006-02-08 2007-01-23 Method and device for surveillance of at least one glow plug of a motor vehicle Ceased EP1818536A3 (en)

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WO2009097922A1 (en) * 2008-02-04 2009-08-13 Robert Bosch Gmbh Method for monitoring at least one glow plug of an internal combustion engine and corresponding device
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CN102224468B (en) * 2008-11-21 2014-02-12 西门子公司 Method and measurement device for determining condition of electric igniter of gas turbine burner and ignition device for gas turbine burner
EP2290224A3 (en) * 2009-08-20 2015-10-21 Toyota Jidosha Kabushiki Kaisha Glow plug deterioration determination system
EP2759771A4 (en) * 2011-09-20 2015-12-30 Bosch Corp Glow plug diagnostic method and glow plug drive control device
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US9683240B2 (en) 2011-10-31 2017-06-20 Philip Morris Products S.A. Modulating beta-damascenone in plants

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