JP2010281535A - Discharge ignition device for burner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge ignition device for a burner capable of surely igniting a fuel sprayed from the burner in comparison with a conventional one. <P>SOLUTION: In this discharge ignition device for the burner in which a pair of cathode bar 5 and anode bar 6 is disposed in a state that their tips are adjacent to each other at a small interval, and which is constituted to ignite the fuel 4 sprayed from the burner by generating spark discharge 7 between both tips, the cathode bar 5 is projected to be longer than the anode bar 6 toward the spraying direction of the fuel 4, and the anode bar 6 is disposed closest at a position retracting from a tip side of the cathode bar 5 to a basic end side by a required length. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a discharge ignition device for a burner.

  Conventionally, in a diesel engine, a particulate filter is provided in the middle of an exhaust pipe through which exhaust gas flows, and particulate matter (particulate matter) contained in the exhaust gas is collected through the particulate filter. In this type of particulate filter, an oxidation catalyst having Pt, Pd or the like as an active species is integrally supported, and the collected particulates are self-combusted from an exhaust temperature as low as possible. .

  However, in the operating region where the exhaust temperature is low, the trapped amount exceeds the processing amount of the particulates, so if the operating state continues at such a low exhaust temperature, the regeneration of the particulate filter proceeds well. First, the particulate filter may fall into an overcollected state.

  For this reason, as shown in FIG. 7, a burner 2 is provided in front of the particulate filter 1, and high-temperature exhaust gas 3 generated by the combustion of the burner 2 is introduced into the particulate filter 1, whereby the particulate filter 1 It has hitherto been proposed to regenerate the particulate filter 1 by actively raising the catalyst bed temperature to burn out the collected particulates.

  Here, the ignition of the fuel 4 sprayed from the burner 2 is performed by spark discharge by the equal-length cathode rods 5 and anode rods 6 arranged symmetrically so that the tips of each other are closest to each other immediately before the burner 2. In addition, the spark discharge is continuously performed continuously during the spraying of the fuel 4 from the viewpoint of stably maintaining the combustion of the burner 2.

  In other words, when the burner 2 is installed in the exhaust system of the automobile, the driving state changes greatly as the automobile repeats acceleration / deceleration, the flow rate of the exhaust gas 3 also fluctuates greatly, and the burner 2 may be misfired. However, if the spark discharge is continuously performed continuously during the spraying of the fuel 4, misfire of the burner 2 can be avoided and the combustion can be maintained stably. .

  In addition, as the prior art document information related to the technique of raising the temperature of the particulate filter or the like using the burner as described above, for example, the following Patent Document 1 and Patent Document 2 already exist.

JP-A-5-86845 JP-A-6-167212

  However, as shown in an enlarged view in FIG. 8, when the spark discharge 7 is performed by the equal-length cathode rod 5 and the anode rod 6 that are symmetrically arranged so that the front ends of the burner 2 are closest to each other, The spark discharge 7 bends in an arc shape in the spray direction of the fuel 4 due to the influence of the spray of the fuel 4 and the discharge length is extended to reduce the energy density. Therefore, the spray of the fuel 4 from the burner 2 is ignited. In cold areas where the outside air temperature is low, especially when the atomization of the fuel 4 is not sufficient, the fuel 4 is not vaporized well, so that the ignition is likely to be difficult.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a burner discharge ignition device that can ignite fuel spray from the burner more reliably than before.

  In the present invention, a pair of electrode rods are arranged so that the tips of each other are close to each other with a slight gap therebetween, and a spark discharge is generated between the two tips so that the fuel spray from the burner can be ignited. A burner discharge ignition device constructed, wherein one electrode rod extends longer than the other electrode rod in the direction of fuel spraying and is retracted by a required length from the distal end side to the proximal end side of one electrode rod. The other electrode rod is arranged so as to be closest to each other.

  Thus, in this way, the discharge position of one electrode rod slightly shifts in the fuel spray direction due to the influence of fuel spray from the burner, but the shortest distance from the discharge position to the other electrode rod. Since a spark discharge occurs between them, arc-shaped bending as in the case of symmetrically arranging conventional equal-length electrode rods does not occur, so the discharge length of the spark discharge becomes shorter than before and the energy density increases, fuel from the burner It becomes possible to make the ignition to the spray easy.

  Also, from the viewpoint of maintaining stable combustion of the burner, when spark discharge is continuously performed continuously during fuel spraying, once the sprayed fuel ignites, the tip of one electrode rod close to the flame The side becomes red hot, the heat is transmitted to the discharge position, the vicinity of the discharge position becomes a high temperature state, and the vaporization of the fuel spray near the discharge position is promoted. The ignitability is also greatly improved.

  At this time, one electrode rod has a heat capacity that is longer than the other electrode rod, and once it is warmed, it is in a condition that its high temperature state is easy to continue. The high temperature state in the vicinity of the discharge position due to the heat transmitted from the tip end side of the rod is relatively easily maintained.

  Further, in the present invention, it is preferable that at least one of the electrode bars is constituted by a glow plug, and in this way, a discharge voltage is applied between both electrodes after the electrode bar constituted by the glow plug is energized. By applying the, the electrode rod composed of the glow plug is preheated in red, and a large amount of fuel spray guided here can be surely vaporized.

  Once the sprayed fuel has ignited, as described above, heat transfer from the tip side of one electrode rod close to the flame and the heat capacity of one electrode rod have increased (especially in the glow In the case of a plug, it is possible to maintain the vicinity of the discharge position at a high temperature state due to the large heat capacity), so that energization to the glow plug may be stopped.

  According to the burner discharge ignition device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, the energy density of the spark discharge can be increased by making the discharge length as short as possible even under the influence of the fuel spray from the burner, The tip of one of the electrode rods is brought close to a flame so that the vicinity of the discharge position is maintained at a high temperature by heat transfer, so that the vaporization of the fuel spray near the discharge position can be promoted. On the other hand, ignition can be performed more reliably than before.

  (II) According to the invention described in claim 2 of the present invention, the electrode rod constituted by the glow plug is preheated by energization in advance, and a large amount of fuel spray guided to the electrode rod is surely vaporized. Therefore, it is possible to vaporize the fuel well from the first time at the start and easily ignite the fuel.Even if the atomization of the fuel is not sufficient at the start especially in a cold district where the outside temperature is low, It is possible to reliably ignite the fuel spray.

It is the schematic which shows an example of the form which implements this invention. It is the graph which compared the relationship between ignition time and spraying flow velocity with a prior art example. It is the graph which compared the relationship between the 2nd ignition time and elapsed time with a prior art example. It is the schematic which shows another form example of this invention. It is the graph which compared the relationship between ignition time and external temperature by the presence or absence of a glow plug. It is the graph which compared the relationship between the ignition time at the time of starting, and the spray flow rate with the presence or absence of a glow plug. It is the schematic which shows a prior art example. It is the schematic which expands and shows the principal part of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 to 3 show an example of an embodiment for carrying out the present invention, and portions denoted by the same reference numerals as those in FIGS. 7 and 8 represent the same items.

  As shown in FIG. 1, in this embodiment, as in the conventional example of FIGS. 7 and 8, the pair of cathode rods 5 and anode rods 6 are arranged so that their tips are close to each other with a slight gap therebetween. Are arranged so that the spark discharge 7 is caused between the two tips and the fuel 4 sprayed from the burner 2 (see FIG. 7) can be ignited. It differs greatly in that the anode rod 6 is arranged so as to extend longer than the anode rod 6 in the direction and the closest to the anode rod 6 at a position retracted by a required length from the distal end side to the proximal end side of the cathode rod 5.

  That is, in such a configuration, the discharge position of the cathode bar 5 slightly shifts in the fuel spray direction due to the influence of the spray of the fuel 4 from the burner 2, but with the anode bar 6 at the shortest distance from the discharge position. Since a spark discharge occurs in the meantime, the arc-shaped bending as in the case where the conventional cathode rods 5 and anode rods 6 having the same length are symmetrically arranged is not generated, so that the discharge length of the spark discharge 7 becomes shorter than before and the energy density is reduced. As a result, the ignition of the fuel 4 sprayed from the burner 2 can be facilitated.

  Further, in the case where the spark discharge 7 is continuously performed continuously during the spraying of the fuel 4 from the viewpoint of stably maintaining the combustion of the burner 2, once the sprayed fuel 4 is ignited, the cathode rod close to the flame. 5 is red hot, the heat is transmitted to the discharge position, the vicinity of the discharge position becomes a high temperature state, and the vaporization of the spray of the fuel 4 near the discharge position is promoted. The ignitability is also greatly improved by promoting vaporization.

  At this time, the cathode bar 5 has a heat capacity that is longer than that of the anode bar 6, and once heated, the high temperature state is easily maintained. The high temperature state in the vicinity of the discharge position due to the heat transmitted from the side is relatively easily maintained.

  In fact, according to the verification experiment by the present inventor, as shown in FIG. 2, when the ignition time during operation is taken on the vertical axis and the spray flow velocity is taken on the horizontal axis, the cathode rods 5 and anode rods 6 having the same length are arranged. Compared with the curve A of the conventional example used, it was confirmed that the curve B of the present embodiment can ignite within a relatively short time even at a higher spray flow rate (in the example of FIG. This is shown in an example of extending about 30 mm longer than the anode rod 6 in the spraying direction of the fuel 4).

  Furthermore, as shown in FIG. 3, when the vertical ignition time is the second ignition time during continuous operation and the horizontal axis is the elapsed time from the first time, the equal length cathode rod 5 and anode rod 6 were used. Compared with the curve A of the conventional example, it was confirmed that the curve B of the present embodiment example has an extremely short ignition time as the elapsed time from the first time is shorter (in FIG. 2, the cathode rod 5 is the fuel). In this example, it is projected about 30 mm longer than the anode rod 6 in the spraying direction 4).

  FIG. 4 shows another embodiment of the present invention. In the example shown here, the cathode bar 5 is constituted by a glow plug, and in this way, it is constituted by a glow plug. By applying a discharge voltage between the two electrodes after energizing the cathode bar 5, the cathode bar 5 composed of the glow plug is preheated in advance, and a large amount of fuel 4 introduced here It is possible to reliably vaporize the spray.

  Once the sprayed fuel 4 is ignited, as described above, the heat transfer from the tip side of the cathode bar 5 close to the flame and the heat capacity of the cathode bar 5 are increased (especially the glow plug). In such a case, since the vicinity of the discharge position can be maintained at a high temperature by the large heat capacity), the energization to the glow plug may be stopped.

  Therefore, in the case of this embodiment, the energy density of the spark discharge 7 can be increased by reducing the discharge length as much as possible even under the influence of the spray of the fuel 4 from the burner 2, and the cathode rod 5 Since the tip side is brought close to the flame and the vicinity of the discharge position is maintained in a high temperature state by heat transfer, the vaporization of the fuel 4 in the vicinity of the discharge position can be promoted, so the spray of the fuel 4 from the burner 2 can be promoted. On the other hand, ignition can be performed more reliably than before.

  In addition, since the cathode rod 5 composed of a glow plug is preheated by energization in advance, the spray of a large amount of fuel 4 guided to the cathode rod 5 can be surely vaporized. The fuel 4 can be easily vaporized and easily ignited, and even when the atomization of the fuel 4 is not sufficient at the start-up particularly in a cold district where the outside air temperature is low, the fuel 4 is reliably sprayed. Ignition can be performed.

  In fact, according to a verification experiment by the present inventor, as shown in FIG. 5, when the ignition time at the start is plotted on the vertical axis and the outside air temperature is plotted on the horizontal axis, the curve X is compared with the curve X when no glow plug is used. Thus, it was confirmed that the curve Y of the present embodiment can be ignited in a relatively short time from a lower outside air temperature.

  Further, as shown in FIG. 6, when the ignition time at the start is plotted on the vertical axis and the spray flow velocity is plotted on the horizontal axis, the curve Y of the present embodiment is compared with the curve X when the glow plug is not employed. It was confirmed that ignition was possible in a relatively short time even at a higher spray flow rate.

  The burner discharge ignition device of the present invention is not limited to the above-described embodiment, and the target to be heated by the burner is not necessarily limited to the particulate filter. The catalyst may be an oxidation catalyst arranged in the preceding stage, or may be various catalysts having an active temperature range above a predetermined temperature, such as a NOx storage reduction catalyst, a selective reduction catalyst, a three-way catalyst, etc. Contrary to the illustrated example, one electrode rod may be an anode rod, the other electrode rod may be a cathode rod, and an AC voltage may be applied. The electrode rod may be composed of a glow plug, or the other electrode rod may be composed of a glow plug contrary to the illustrated example, and other types may be used without departing from the scope of the present invention. Of course, changes can be made.

1 particulate filter 2 burner 3 exhaust gas 4 fuel 5 cathode rod (one electrode rod)
6 Anode rod (the other electrode rod)
7 Spark discharge

Claims (2)

  For a burner configured such that a pair of electrode rods are arranged so that the tips of each other are close to each other with a slight gap therebetween, and a spark discharge is generated between the two tips to ignite fuel spray from the burner. A discharge ignition device in which one electrode rod extends longer than the other electrode rod in the fuel spray direction and is retracted by a required length from the distal end side to the proximal end side of one electrode rod. Is arranged so as to be closest to each other.   2. The discharge ignition device for a burner according to claim 1, wherein at least one of the electrode rods is constituted by a glow plug.

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