EP1645803B1 - Process to start a heating apparatus, and in particular a vehicle heater. - Google Patents

Description

The present invention relates to a method for starting a heater, in particular vehicle heater.

Such heaters used for example as auxiliary heaters or auxiliary heaters in motor vehicles are particularly critical in the starting phase in terms of pollutant emissions. Therefore, there is generally a desire to keep this starting phase as short as possible. For this purpose, it is known, for example, after generating a start command, first in a preconditioning phase by preheating an ignition element and, if necessary, operating further heating devices for the combustion or the ignition, ie starting the combustion, to create favorable conditions. After this Vorkonditionierungsphase then fuel is fed, for example, with the maximum, so maximum delivery capacity. It should be noted that the term "delivery rate" is used here to refer to the quantity of fuel fed in per unit time, which could also be referred to as the fuel flow. This fuel mixes with the naturally supplied combustion air in parallel, so that an ignitable mixture is formed, which is ignited in ideal circumstances within a few seconds. Since the fuel feed is generally time-controlled in known heaters, that is, this maximum amount of fuel is fed for a predetermined time, before then transferred to normal operation, but there is a problem that in the case where the provided mixture does not ignite, a excessive fuel accumulation is generated in the area of the heater. The consequence of this may be that liquid fuel from the heater or a combustion chamber of the same runs out or liquid fuel is ejected via the exhaust system in a subsequent restart attempt.

The DE 100 50 611 C1 discloses a method for starting a fuel-operated vehicle heater, wherein in the event that in a first ignition phase, the occurrence of a flame is not detected, is started after a first ignition phase subsequent rinse phase with a second ignition phase. In the first ignition phase, a comparatively large fuel delivery rate is started and gradually reduced, while in the second ignition phase beginning after the purge phase, a comparatively small fuel delivery stage is started and gradually increased.

The DE 198 20 192 A1 discloses a method for igniting a gas-fired burner, in which, if after a predetermined period of gas supply, the occurrence of a flame has not been detected, the gas supply is interrupted and in a subsequent ignition phase after a time interval in which the gas delivery remains adjusted trying again to start the combustion.

The DE 43 23 221 C1 discloses a method for starting a fuel-fired heater, in which, when in a first ignition phase, the occurrence of a flame is not detected, then blown in a subsequent free-blowing phase of existing in a combustion chamber fuel, whereupon in a subsequent second ignition phase attempting to start the combustion by taking up the fuel delivery again.

The JP 02 044122 A discloses a method of starting a burner in which, when the start of a flame is detected in the starting phase, the opening of a fuel supply adjusting proportional valve is changed from the slow ignition opening and this state is maintained for a predetermined period of time ,

It is the object of the present invention to provide a method for starting a heater, in particular vehicle heater, with the In a reliable way, a fuel supersaturation in a heater can be avoided.

According to the invention this object is achieved by a method for starting a heater, in particular vehicle heater, in which method in a first ignition phase fuel is fed with a first Zünd-flow rate in the heater and then if detected before the expiration of a maximum period of the first ignition no ignition is, from the first ignition phase, a second ignition phase is entered, in which fuel is fed with a second ignition delivery in the heater, which is smaller than the first ignition delivery.

It can be provided that, when an ignition is detected before the expiration of a maximum period of the first ignition phase, a stabilization phase is started in which fuel is fed with a stabilizing flow rate in the heater, and then, if before the expiration of the maximum time the first firing phase no ignition is detected, the second firing phase is started, in which fuel is fed to the second Zünd-flow rate in the heater, which second firing rate is less than the first firing rate and as the stabilizing flow rate.

In the method according to the invention is thus checked whether after the start of the fuel feed in the starting phase within a predetermined time, the ignition takes place, so the fuel / air mixture has started to burn. If this is the case, ie if there is a correct, fast starting process, then in a subsequent stabilization phase the flame is given the opportunity to spread further and to switch to a stable combustion state. However, if it is detected that there is no correct ignition, ie the fuel / air mixture has not started to burn, then a second ignition phase is entered, in which an attempt is still made to start the combustion, but with reduced fuel supply. In this way, a supersaturation of the heater with fuel in the Starting phase can be avoided. This not only reduces the risk of leaking liquid fuel from a heater, but also leads to more favorable conditions, in the event that a start attempt must be terminated unsuccessfully and a new start attempt must be started.

In the method according to the invention, it can further be provided that when an ignition is detected when the second ignition phase has started before a maximum duration of the second ignition phase has elapsed, the stabilization phase is started. Thus, if the ignition in the second ignition phase with reduced fuel supply, then in the subsequent stabilization phase, the flame can continue to spread and stabilize.

It is also proposed that, when the second ignition phase is started, no ignition is detected before the maximum duration of the second ignition phase has expired, the fuel supply is terminated.

The stabilization flow rate fed into the heater during the stabilization phase can essentially correspond to the first ignition flow rate introduced in the first ignition phase. Furthermore, it is proposed that the first ignition delivery amount corresponds to the maximum delivery quantity. This means that in the first ignition phase, a fuel is operated in the heater or a combustion chamber of the same feeding system with maximum capacity.

In order to ensure that conditions exist at the beginning of the first ignition phase which on the one hand enable ignition in principle or on the other hand ensure faster ignition, it can also be provided in the method according to the invention that the first ignition phase is started after a combustion chamber pre-conditioning phase has elapsed.

Fig. 1

die über der Zeit aufgetragene Fördermenge bei Durchführung eines nicht erfindungsgemäßen Verfahrens bei einem korrekt ablaufenden Startvorgang;

Fig. 2

ein Fördermenge-Zeit-Diagramm bei einem Startvorgang, bei dem die Zündung erst in einer zweiten Zündphase erfolgt;

Fig. 3

ein weiteres der Fig. 1 entsprechendes Fördermenge-ZeitDiagramm, bei welchem auch in der zweiten Zündphase keine Zündung erfolgt;

Fig.4

in prinzipieller Darstellung ein Heizgerät, bei welchem das erfindungsgemäße Verfahren zum Einsatz kommen kann.

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

Fig. 1

the applied over the time flow rate when performing a method not according to the invention in a correct starting process;

Fig. 2

a delivery-time diagram during a starting process, in which the ignition takes place only in a second ignition phase;

Fig. 3

another one Fig. 1 corresponding delivery time-time diagram, in which also in the second ignition phase no ignition takes place;

Figure 4

in a schematic representation of a heater in which the inventive method can be used.

Before referring to the Fig. 2 and 3 the timing or the various possible variations of the method according to the invention will be described with reference to the Fig. 4 describes the structure of a heater in which the inventive method can be used.

This generally designated 10 heater has a combustion chamber housing 12 in which a combustion chamber 14 is formed. Into this combustion chamber 14, the fuel required for the combustion is fed via a fuel feed pump 16. Further, a Combustion air blower 18 is provided, which feeds the air required for mixture formation in the combustion chamber 14.

In the illustrated construction according to the principle of an evaporator burner, a porous evaporator medium 20 is provided in the combustion chamber housing 12, for example in a region near the bottom thereof. This porous evaporator medium 20 receives the initially liquid fuel, distributes it in its volume range, in particular under Kapillarförderwirkung, and gives the fuel in a vaporous configuration at its combustion chamber 14 side facing in this. In order to support this fuel evaporation, the porous evaporator medium 20 may be associated with an electrically operable heater 22 which, by increasing the temperature in the region of the porous evaporator medium 20, especially in the starting phase, ensures faster and more intense fuel evaporation. Furthermore, in the region of the combustion chamber 14, an ignition device 24, for example a Glühzündstift provided. This generates locally high temperatures that a surrounding mixture of fuel vapor and combustion air can be ignited. Furthermore, a flame detection element 26 is provided, which can detect whether an ignition has taken place in the combustion chamber 14, that is, the combustion has started and thus a flame has occurred. This flame detection element 26 can detect optically, but can also detect the temperature present in the region of the combustion chamber 14 or the combustion chamber housing 12, which of course also allows a conclusion as to whether an ignition has taken place and thus combustion has been started or not ,

The heater 10 is further associated with a drive device 28. This controls the operation of the various system components of the heater 10. Thus, this controls the fuel pump 16, as well as the combustion air blower 18 to initiate the required amount of combustion air and fuel to the combustion chamber 14 at the required time. Also the electrically energizable heater 22 and the ignition member 24 are under the control of the drive device 26. At the same time receives these inputs, for example, the detection signal of the flame detection element 26th

It should be noted that in the Fig. 4 shown heater 10 only by way of example stands for a variety of different possible variations. It is understood that in various areas of this heater 10, the structure may be different than shown. However, it is important for the present invention that there are system areas which can initiate combustion air and fuel following combustion in a combustion chamber, which can generate the thermal conditions required for ignition, and which permit a conclusion as to whether ignition has taken place or not Combustion is present or not.

To start such a heater 10, the procedure is as follows:

After generating a start command, for example, following a control program or by manually entering a user, first in the Fig. 1 Started with t _v conditioning phase started. In this conditioning phase, the thermal conditions required for successfully starting the heater 10 are generated in the region of the heater 10, in particular the combustion chamber 14. In particular, this involves the excitation of the ignition device 24 so that it is heated, for example, in its region projecting into the combustion chamber 14 and then provides the conditions required for ignition in this region. The electrically energizable heating device 22 can also be operated in order to preheat the porous evaporator medium 20 and the region of the combustion chamber 14 or the combustion chamber housing 12 surrounding it. For this conditioning phase t _v , a fixed period of time may be predetermined, wherein This fixed period of time may also depend on external conditions such. B. the ambient temperatures. Lower ambient temperatures may require a longer conditioning phase.

After the end of the conditioning phase t _v at a time 1, a first ignition phase t _Z1 is then started. From the beginning of this first ignition phase, fuel is directed toward the combustion chamber 14 by corresponding activation of the fuel pump 16, ie, in the case illustrated, it is introduced into the porous evaporator medium 20 and then vaporized in the direction of the combustion chamber 14. In order to make the entire starting procedure as short as possible, the fuel pump 16 can be operated in this first ignition phase t _Z1 so that the first ignition delivery quantity fed in this phase corresponds to a maximum possible delivery quantity m _max . It goes without saying that combustion air is also conveyed in the direction of the combustion chamber 14 parallel to the fuel feed. This combustion air feed can for example also be started during the conditioning phase t _v .

In the case of an ideally or correctly starting procedure, the ignition should take place even before the expiration of a maximum possible period of time t _Z1 'of the first ignition phase t _Z1 , which should lead to a corresponding output of the flame detection element 26. In the in Fig. 1 shown example, this ignition takes place at time 2. With occurring ignition and thus starting combustion then the first ignition phase t _{Z1 is} completed. Since the ignition has already started, 2 is then entered into a stabilization phase t _s at this time. In this stabilization phase, fuel is conveyed with a stabilizing flow rate in the direction of the combustion chamber 14. This stabilizing flow rate may correspond, for example, to the first ignition flow. That is, even in the stabilization phase t _s , the fuel pump 16 can be controlled so that it operates at maximum flow rate m _max .

After a predetermined period of time of this stabilization phase t _s , in case of Fig. 1 So at time 3, then is transferred to the normal combustion mode, which means that fuel is fed with a flow rate m _betr toward the combustion chamber 14. Here, a corresponding adjustment of the flow rate of the combustion air blower 18 can be made in order to provide the ideal fuel / air ratio for the then running combustion can.

In Fig. 2 the case is shown in which, even after the expiration of the maximum duration t _Zt1 'of the first ignition phase t _Z1, the occurrence of an ignition could not yet be detected. That is, at the time 2, which is the duration t _Z1 'after the time 1, there is no combustion. According to the invention, a second ignition phase t _{Z2 is} then entered in this case. In this second ignition phase t _Z2 fuel is passed with a second ignition delivery in the direction of the combustion chamber 14, which corresponds to a delivery rate m _min in the example shown. This second ignition delivery is smaller than the first ignition delivery and is also smaller than the stabilization delivery, which corresponds to the first ignition delivery in the example shown.

With continued fuel feed and possibly adjusted combustion air feed is then monitored by means of the flame detection element 26 continues to determine whether combustion occurs, so the ignition takes place or not.

In the in Fig. 2 In the example shown, the occurrence of the ignition and thus the start of combustion are signaled at time 3 and even before the expiry of a maximum possible time period t _Z2 'of the second ignition phase t _Z2 by a corresponding sensor signal of the flame detection element 26 of the control device 28. The second ignition phase t _Z2 is then terminated and the stabilization phase t _s , which then follows this second ignition phase t _{Z2, is} entered. In this stabilization phase t _s , fuel with the stabilizing flow rate is then fed back into the combustion chamber 14 in order to ensure the fastest possible spread and thus also to support combustion stabilization in the combustion chamber 14. Here it can be provided that, even if the second ignition phase t _{Z2 has} previously passed through, the stabilization phase t _s corresponds to that which occurs in the Fig. 1 illustrated sequence is present, ie in the case in which the entry into the second ignition phase t _{Z2 was} not required. This means that in the in Fig. 2 shown example in the stabilization phase t _s with that flow rate, here m _max , is promoted, which was present in the first ignition phase t _Z1 . However, it is also conceivable in principle, in the stabilization phase _s t to the effect of differentiating whether from the first ignition phase t _Z1 in the stabilization period t _s has been entered, or from the second ignition phase t _Z2. After the end of the stabilization phase t _s at time 4, the normal combustion mode is then transferred and fuel with the delivery amount m _{betr is} conveyed. It should be noted here that in the example shown, this provided for the normal combustion plant flow rate m _{betr is} greater than the provided in the start phase for the second ignition phase t _Z2 second ignition flow rate m _min . However, this does not have to be the case. The in the in Fig. 2 Of course, the flow rate to be used at the time of subsequent normal operating phase will depend on which heating power has to be provided.

In Fig. 3 the case is shown in which when performing the start procedure according to the invention after the completion of the first ignition phase t ₁ with the time t _Z1 'and also the complete expiry of the second ignition phase t _Z2 with their maximum time t _Z2 ' the occurrence of the ignition is not yet could be recognized. In this case, the fuel supply is then completely terminated according to the invention with the end of the second ignition phase t _z2 , that is to say at time 2. That is to say, the two ignition phases t _Z1 and t _Z2 , together with their respective maximum time periods t _Z1 'and t _Z2 ', together define a safety time interval starting at the beginning of the fuel feed in at time 1. So if no ignition takes place within this safety time interval, then a continued Prevented fuel supply and thus prevents fuel supersaturation in the combustion chamber. It can then be initiated, for example, after a predetermined waiting interval, a renewed startup process, in which initially attempted again by starting the conditioning phase t _v to provide the necessary or necessary for ignition conditions in the combustion chamber 14. If the multiple pass of this procedure still does not lead to the ignition, then, for example after four or five attempts, a restart attempt can be inhibited and instead a warning message generated, since then the probability of a defect in any of the system areas is high.

Various advantages can be achieved with the previously described procedure according to the invention for starting a heater used in a vehicle, for example as a parking heater or auxiliary heater. Thus, as already explained above, significantly less fuel is introduced into the combustion chamber when the start procedure is carried out than has hitherto been customary. The risk of leakage of liquid fuel in the absence of ignition or the ejection of unburned fuel in a subsequent starting process can thus be reduced. Furthermore, the reduced fuel supply improves the chances of a successful second or subsequent start attempt if the first attempt did not result in ignition. Further, regardless of whether the ignition in the first ignition phase, ie at a larger fuel flow rate, or in the second ignition phase, ie at lower fuel flow rate, occurs, the stabilization phase is followed, the flame is given in each case, the possibility under suitable conditions then spread as quickly as possible and stabilize. It has also been found that with respect to the total duration of the two ignition phases in the procedure according to the invention with lowering the fuel supply in the second ignition phase, the probability of a successful ignition is higher than in the case in which over these two phases or corresponding time period maximum possible Amount is encouraged.

In an alternative variate of the method according to the invention, for example, when the ignition is detected before the expiration of the first ignition phase t _Z1 , this time of detection but already comparatively close to the expiration of the maximum possible time t _Z1 'this first ignition phase t _Z1 , for example in the last quarter of this maximum possible period of time t _Z1 ', the entry into the stabilization phase t _{s be} dispensed with and instead be transferred directly into the normal combustion mode. The reason for this may be that a comparatively large amount of fuel is introduced into the combustion chamber immediately before the ignition occurs, which can then be burned on entry into the normal combustion mode with reduced fuel feed and thus contributes to flame stabilization.

Claims (7)

1. A procedure for starting a heating device, in particular a vehicle heating device, said procedure comprising, during a first ignition phase (t_z1), the insertion of a first ignition supply volume (m_max) of fuel into said heating device, and then, if ignition does not take place before the end of a maximum period (t_z1') of said first ignition phase (t_z1), the transition from the first ignition phase to a second ignition phase (t_z2), where a second ignition supply volume (m_min) of fuel is inserted into said heating device, the latter being smaller than said first ignition supply volume (m_max).
2. The procedure according to claim 1, characterized in that

   - when an ignition is detected before the expiry of a maximum period (t_z1') of said first ignition phase (t_z1), a stabilising phase (t_s) will be started, where a stabilising supply volume (m_max) of fuel is inserted into said heating device,

   - when no ignition is detected before the expiry of a maximum period (t_z1') of said first ignition phase (t_z1), there will be a transition from the first ignition phase to said second ignition phase (t_z2) where a second ignition supply volume (m_min) of fuel will be inserted into said heating device, said second ignition supply volume (m_min) being smaller than said first ignition supply volume (m_max) and said stabilising supply volume (m_max).
3. The procedure according to claim 2,
   characterized in that said stabilising phase (t_s) will be started when an ignition is detected with said second ignition phase (t_z2) having been started and before the expiry of a maximum period (t_z2') of said second ignition phase (t_z2).
4. The procedure according to claim 2 or 3,
   characterized in that said fuel supply will be stopped when no ignition is detected with said second ignition phase (t_z2) having been started and before the expiry of a maximum period (t_z2') of said second ignition phase (t_z2).
5. The procedure according to one of claims 2 to 4,
   characterized in that said stabilising supply volume (m_max) substantially corresponds to said first ignition supply volume (m_max).
6. The procedure according to one of claims 1 to 5,
   characterized in that said first ignition supply volume (m_max) corresponds to a maximum supply volume.
7. The procedure according to one of claims 1 to 6,
   characterized in that said first ignition phase (t_z1) is started after expiry of a combustion chamber preconditioning phase (t_v).

Images