EP1493969A2 - Method for operating a glow ignition device of a car heater at startup of the car heater - Google Patents

Abstract

The method for the operating of an incandescent igniter element of a vehicle's heater in the starting phase entails the recording a value in dependence upon a heating capacity of the igniter element (12), comparing this value with a reference, and if the value is less than the reference increasing the heating capacity of the incandescent igniter element. In the first stage the value which is in dependence upon the heating capacity is based on a voltage applied to the igniter element and current flowing through it.

Description

The present invention relates to a method for operating a Glühzündelements a vehicle heater when starting the vehicle heater.

The Glühzündelemente used in Fahrzeugheizeinrichtungen, the Example Glühzündstifte, have the problem that they are production-related a comparatively strong dispersion in their electrical resistance exhibit. This can result in energizing such a glow plug by applying a voltage due to the existing Ohm resistance is a current and thus an electric heating power set in a trap under a required for ignition Heating power is, in the other case, however, at the same voltage clearly above the heating power required for ignition. In the former Trap is basically the problem that even under consideration other operating parameters, such as ambient temperature, a heater may not ignite while in the second Trap excessive consumption of electrical energy and thus a Excessive load on an on-board system is present and possibly the glow plug is destroyed by overload.

It is the object of the present invention to provide a method of operation a Glühzündelements a vehicle heater when starting the Provide vehicle heater, with which a reliable and efficient startup operation becomes possible.

a) Ermitteln einer mit einer Heizleistung des Glühzündelements im Zusammenhang stehenden Größe,

b) Vergleichen der mit der Heizleistung im Zusammenhang stehenden Größe mit einer Referenz,

c) dann, wenn die Größe kleiner als die Referenz ist, Erhöhen der Heizleistung des Glühzündelements.

According to the invention, this object is achieved by a method for operating a Glühzündelements a vehicle heater in a starting phase of the vehicle heater, comprising the steps:

a) determining a value associated with a heating power of the Glühzündelements,

b) comparing the quantity related to the heating power with a reference,

c) when the size is smaller than the reference, increasing the heating power of Glühzündelements.

It is essential in the method according to the invention that it is checked that How much power is applied in the starting phase. In particular, too determined empirically in association with particular heaters can determine how high the heating power must be in order to achieve ignition according to the invention, then a performance adjustment can take place, so that production-related and aging-related performance fluctuations can be compensated for the Glühzündelementen.

According to a particularly advantageous aspect, it can be provided that in step a) the amount related to the heating power based on a voltage applied to the Glühzündelement and a current flowing over the Glühzündelement current is determined.

Because in general also due to the easier controllability, the heating power by specifying a specific duty cycle or duty cycle, ie pulsed application of a voltage to a Glühzündelement, is set or adjusted, according to another aspect of Present invention proposed that in step c) the heating power by increasing a duty cycle applied to the Glühzündelement Voltage is increased. It is then further advantageous if the Voltage is a voltage averaged over time and when the current is is an average current over time. Such an average voltage or such an average current may be in various ways calculated, determined or presented. So that can actually over the value acquired over time is calculated by averaging. Furthermore, for example, by providing circuitry a low-pass filter system to ensure that in the event of voltage or current monitoring of the pulsed voltage or current value in one more or less constant "averaged" or "effective" voltage or be converted into a corresponding stream.

Since it is crucial for the safe ignition, how large the electrical resistance a energized by applying a voltage Glühzündelements is in the hot state, it is proposed according to a further aspect of the invention, that at least step c) for the first time after expiration of a first predetermined time since the beginning of energizing the Glühzündelements is carried out.

In general, a correct operation of a Glühzündelements or cause a heating device equipped with it so that after a determinable, for example, heater-dependent period of time the ignition occurs. According to another aspect of the invention therefore suggested that after expiration of a second predetermined Time period is checked if an ignition has occurred. It can be provided be that if no ignition is made since the beginning of the Excitation of Glühzündelements applied heating energy with a reference energy is compared. Depending on whether the heating energy is greater or smaller than the reference energy, it is then possible that if the heating energy is greater than the reference energy, in the presence of a Fuel supply problem is closed, or that if the heating energy is less than the reference energy, in the presence of a Ignition energy problem is closed.

a) Ermitteln einer mit einer Heizleistung des Glühzündelements im Zusammenhang stehenden Größe,

b) Vergleichen der mit der Heizleistung im Zusammenhang stehenden Größe mit einer Referenz,

c) dann, wenn die Größe mehr als ein vorbestimmtes Ausmaß von der Refefenz abweicht, Verändern der Heizleistung derart, dass die Größe sich in Richtung Referenz verändert.

According to a further aspect, the present invention relates to a method for operating a Glühzündelements a vehicle heater in a starting phase of the vehicle heater, comprising the steps:

a) determining a value associated with a heating power of the Glühzündelements,

b) comparing the quantity related to the heating power with a reference,

c) when the size deviates more than a predetermined amount from the ref, changing the heating power so that the size changes in the direction of reference.

Fig. 1

in vereinfachter Art und Weise eine Heizeinrichtung mit einem zum Zünden der Verbrennung vorgesehenen Glühzündelement und einer zugeordneten Ansteuerschaltung;

Fig. 2

ein Flussdiagramm, das die erfindungsgemäße Vorgehensweise in der Startphase der in Fig. 1 gezeigten Heizeinrichtung veranschaulicht;

Fig. 3

ein Diagramm, das über der Zeit aufgetragen den über ein Glühzündelement fließenden Strom und die dabei sich einstellende Temperatur veranschaulicht.

The present invention will be described below in detail with reference to the accompanying drawings. It shows:

Fig. 1

in a simplified manner, a heating device with a planned Glühzündelement for igniting the combustion and an associated drive circuit;

Fig. 2

a flow chart illustrating the procedure according to the invention in the starting phase of the heating device shown in Figure 1.

Fig. 3

a graph plotted over time illustrates the current flowing through a Glühzündelement and thereby adjusting temperature.

A system in which a procedure according to the invention can be implemented is indicated generally at 10 in FIG. As an elementary component, this heating system 10 a Glühzündelement 12, for example, a Glühzündstift on. At this Glühzündelement 12 can be applied via a switching transistor 14, such as field effect transistor, provided by an electrical power supply system voltage U _Batt . This may be, for example, a DC voltage provided by an on-board voltage system. A microprocessor 16, which is also fed via a fixed voltage supply 18 from the on-board voltage system, controls the transistor 14 via a drive line 20 to turn this pulsed conductive or non-conductive and thus by specifying a specific duty cycle or duty cycle, ie a specific An / Off ratio to apply a pulsed voltage to the Glühzündelement 12 when it is to be energized. The application of a pulsed voltage results in a correspondingly pulsed current flow, whereby, depending on the duty cycle, a corresponding averaged or effective voltage or current value results.

The microprocessor 16 determines this applied to Glühzündstift 12 average or effective voltage by tapping the applied voltage via a low-pass filter 22, with the result that the applied itself rectangular voltage in a more or less constant averaged or effective voltage value U _GS converted and as such is input to the microprocessor 16. In a corresponding manner, the microprocessor uses a low-pass filter 24 on the transistor 14, the current flowing at voltage applied, and this corresponding pulsed current is converted by tapping a low-pass filter in a more or less constant average or effective Glühstiftstrom I _GS . In order to also have information about the available on-board voltage, the microprocessor 16 further picks up this on-board voltage U _Bett via a low-pass filter 26, this low-pass filter essentially having the task of averaging or, for example, generating voltage fluctuations during the detection when the generator is running smooth.

In Fig. 3, the heating and operating characteristics of such Glühzündelements 12 is shown in principle. In this Fig. 3 represent the curves I ₁ and I _2, the currents applied over time, which flow over two different Glühzündelemente having different electrical resistances, at a predetermined voltage of, for example, 8.5 volts. Thus, the curve I _{1 represents} the current flow in a Glühzündelement having a ohmic cold resistance (room temperature) of 0.42 Ω. The curve I ₂ represents the course of a Glühzündelements having an ohmic resistance of 0.6 Ω. In association with the curves I ₁ and I ₂ , the curves T ₁ and T _{2 represent} the temperatures occurring in each case in the region of such Glühzündelements. Due to the higher current, the Glühzündelement having the current profile I ₁ generates a higher heat output and thus a higher temperature T ₁ , while the Glühzündelement with the current waveform I ₂ due to the lower current and the correspondingly lower heating power will lead to a correspondingly lower temperature T ₂ .

In order to obtain a reliable ignition, it also depends on the concrete constructive structure of a heater and of course also depending on environmental conditions, required, sufficient Provide heating power. On the other hand leads to a too high heating power excessively high and not required temperatures, so that Although ignition may occur, but the on-board power supply is excessively loaded and possibly the Glühzündelement be destroyed can. To be in a system, as dargstellt in Fig. 1, in an efficient way and how to obtain a safe ignition of a heater, can the invention described below with reference to FIG Procedure be made.

It should first be assumed in the procedure according to the invention that at the time t = 0, the excitation of Glühzündelements 12 begins in step S1 by applying a voltage U _start . Here, this voltage U corresponding to the _start of the previously already mentioned, detected by the microprocessor 16 or detectable already averaged over the low-pass filter 22 and the effective voltage, which can be obtained by setting a certain duty cycle. It can be done so that initially worked with a voltage U _GS , which will not be sufficient even under favorable environmental conditions to obtain an ignition. It is then, represented by a step S2, first a predetermined period of time t1 waited in the increased by heating the Glühzündelements 12 and correspondingly increasing ohmic resistance of the voltage value I _{GS has} dropped to an approximately constant value. This time period t1 can, for example, in the range of 10 s. lie. If this period has expired, then the current I _GS and the voltage U _GS as well as the voltage U _Batt can be determined or detected by the microprocessor.

After the step S2, it is then determined in a step S3 whether a time t2 has elapsed since the energization of the Glühzündelements 12. It is initially assumed that this time t2, which is longer than the previously mentioned time t1, has not yet elapsed. In steps S13 and S14 it is then checked whether the current I _GS or the voltage U _GS exceed predetermined maximum values I _max and U _max . If this is the case, a fault is concluded in a step S15 and a step S7 is undertaken, in which the duty cycle is reduced, in order consequently to apply a correspondingly reduced effective or average voltage to the Glühzündelement 12. The maximum voltage U _max involved in step S 14 can be determined, for example, by the voltage U _Batt provided by the power supply, for example the on-board voltage system minus a safety limit U *, which can correspond to expected voltage drop in the on-board voltage system at the transistor 14 when the Glühzündelements 12 are energized. U _max can thus reflect the maximum achievable voltage at Glühzündelement 12. I _max may represent the maximum allowable current through the Glühzündelement 12.

If both the voltage U _GS and the current I _{GS are} smaller than the predetermined limit values, then the heating power P _ist generated at the glow element 12 _is determined by multiplying the previously detected current or voltage values I _GS and U _GS in a step S4. This heating power P _ist is then compared with a setpoint power P _soll . This setpoint power P _soll can be specified in a specific heater and, of course, can also be changed as a function of different ambient parameters, in particular the outside temperature. If the determined or detected heating power P _{ist is} smaller than the required power P _soll required for reliable ignition, the voltage applied to the glow-ignited element 12 is increased in step S6 by increasing the duty cycle, ie increasing the on / off ratio , also increases the effective or average voltage U _GS . Here, for example, can proceed so that either a defined increase in the duty cycle is given, which then has a certain increase in Glühzündelementenspannung U _GS result, or that a predetermined increase of this voltage U _{GS is} obtained by appropriate setting or adjusting a certain duty cycle , If this increase in increment or voltage increase has occurred, the system returns to step S2 in order to carry out the procedure described above again. This is done so often or until it is determined in step S4 that now the heating power P _is greater than the target power P _soll , so that step S4 to step S7 is taken. There is reduced by duty cycle reduction, the effective or average voltage U _GS , whereupon stepping back to step S2 to perform the procedure described above, the monitoring of the heating power again.

The sequence of steps S2 to S6 or S7 thus ensures that it is independent of which concrete ohmic resistance a Glühzündelement 12, always by appropriate adjustment of the duty cycle the required heating power is provided, which ensures safe ignition without excessive consumption of electrical energy. Thus, you can above all, production-related fluctuations in the Glühzündelementen be compensated.

In step S3, the answer to the question is as to whether the elapsed time is smaller when the given time t2 is for example 90 s, no, then the Procedure to a step S8 in which evaluated the flame detection becomes. For example, the flame detection may be based on a temperature sensor take place, which is when an ignition is made and a Flame occurs, reports a significant increase in temperature. This flame detection Of course it can also run from the beginning of the start phase, if it is already detected before expiration of the time t2, that the ignition has occurred, including the energization of Glühzündelements 12 to finish.

If, after the expiry of the time t2, it has been detected that a flame has occurred and thus the ignition has taken place, then in a step S9 the starting phase is ended and no further voltage is applied to the glow-ignited element 12. However, if the answer in step S8 is no, the time integral of the heating power is formed up to the time t2 in a step S10 and compared with a reference energy E _min . This reference energy E _min can be determined as an energy value that is at least required to ignite a heater. If the heating energy applied in the starting phase is greater than this reference energy E _min , then it is determined in a step S11 that there is a fault in the fuel delivery and a corresponding check is to be carried out, since, although sufficient heating has been carried out, but no ignition has taken place , This is an indication that there was little or no fuel.

If it is determined in step S10 that the heating energy is less than the reference energy E _min , then it is determined in a step S12 that too little ignition energy or heating energy has been applied, which may be due to a defect of the Glühzündelements or too high an impedance Glühzündelement.

With the procedure according to the invention, care can be taken that even with glow-ignited elements, which have a certain dispersion in their have electrical resistance, in a reliable and economical way and a heater can be started. It goes without saying that in this procedure or in the present invention still different other aspects can be considered. So, for example for the switching transistor 14 both in terms of current detection as well as the voltage detection a correction value metrologically be determined, which may therefore be necessary in particular since Such transistors, due to their physical structure, in relevant voltage range comparatively high detection inaccuracies in the current or voltage detection of up to 20%. This deviation can be detected and in the microprocessor 16 then be deposited as a corresponding correction value. Furthermore is it goes without saying that this transistor is on overload, on short circuit or interruption can be monitored. It is also possible that in the procedure according to the invention, the heating power not with a setpoint is compared, but with a setpoint range, within which reliable ignition is to be expected. Falls the heating power out of this setpoint range, then the invention Measures of the duty cycle reduction or duty cycle increase taken.

An advantageous aspect of the present invention is that Glühzündelemente same type or so equipped heaters in different voltage environments can be used. It must only be ensured that, for example, by specifying a certain duty cycle on Glühzündelement at the beginning of the startup procedure applied or effective voltage is comparatively small, so that by appropriate increase of the duty cycle then the required Heating power can be approached from below. Of course The present invention may also be used in conjunction with permanently attached ones Voltage can be used at which a power adjustment then by voltage increase and not by Tastgradveränderung is reached. Further, the procedure of the present invention may be the same be that initially a comparatively high voltage is applied, which has a correspondingly high heat output. If this is above the reference power, can change accordingly of the duty cycle, namely reduction of the duty cycle, the desired, for example, for a particular heater optimal heating from above be approached.

Claims (10)

Method for operating a Glühzündelements a vehicle heater in a starting phase of the vehicle heater, comprising the steps: a) determining a quantity (P _ist ) associated with a heat output of the Glühzündelements (12), b) comparing the quantity related to the heating power (P _ist ) with a reference (P _soll ), c) when the size (P _ist ) is smaller than the reference (P _soll ), increasing the heating power of the Glühzündelements (12). A method according to claim 1, characterized in that in step a) the amount related to the heating power (P _is ) based on a voltage applied to the Glühzündelement (12) voltage (U _GS ) and over the Glühzündelement (12) flowing current (I _GS ) is determined. A method according to claim 1 or 2, characterized in that in step c) the heating power is increased by increasing a duty cycle of the Glühzündelement (12) voltage applied (U _GS ). Method according to claim 2 or 3, characterized in that the voltage (U _GS ) is a voltage averaged over time and that the current (I _GS ) is a current averaged over time. Method according to one of Claims 1 to 4, characterized in that at least step c) is carried out for the first time after a first predetermined period of time (t1) has elapsed since the start of energizing the glow-igniting element (12). Method according to one of claims 1 to 5, characterized in that after the latest expiration of a second predetermined period of time (t2) is checked whether an ignition has occurred. A method according to claim 6, characterized in that when no ignition is performed, the heat energy applied since the start of energization of Glühzündelements (12) is compared with a reference energy (E _min ). A method according to claim 7, characterized in that , when the heating energy is greater than the reference energy (E _min ), is closed for the presence of a fuel supply problem. A method according to claim 7 or 8, characterized in that , when the heating energy is less than the reference energy (E _min ), is closed on the presence of an ignition energy problem. Method for operating a Glühzündelements a vehicle heater in a starting phase of the vehicle heater, comprising the steps: a) determining a quantity (P _ist ) associated with a heat output of the Glühzündelements (12), b) comparing the property with the heating power in connection with a reference size (P _soll), c) if the quantity (P _ist ) deviates more than a predetermined amount of the reference (P _soll ), changing the heating power such that the quantity (P _is ) changes in the direction of reference.

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