JP2012057517A - Control method of post-process burner system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of a post-process burner system capable of minimizing accumulation of soot in a burner and occurrence of HC slip, maintaining high combustion performance by preventing occurrence of a faulty ignition, and achieving high reliability.SOLUTION: When an exhaust brake 19 operates during combustion of fuel in the burner, fuel injection from a fuel injection nozzle 15 in the burner is stopped.

Description

  The present invention relates to a method for controlling an aftertreatment burner system.

  Conventionally, in a diesel engine, a particulate filter is provided in the middle of an exhaust pipe through which exhaust gas flows, and particulates (particulate matter) contained in the exhaust gas are collected through the particulate filter. However, under normal diesel engine operating conditions, there are few opportunities to obtain exhaust temperatures that are high enough for the particulates to self-combust. Therefore, an oxidation catalyst with Pt, Pd, etc. as the active species is used as the particulate filter. It is made to carry integrally.

  That is, if such a particulate filter carrying an oxidation catalyst is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates are burned and removed even at a lower exhaust temperature than in the past. It becomes possible.

  However, even when such a particulate filter is employed, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, so that the operation state at such a low exhaust temperature. If this continues, there is a possibility that the particulate filter will fall into an overcollected state without the regeneration of the particulate filter proceeding well.

  Therefore, a flow-through type oxidation catalyst is attached to the upstream of the particulate filter, and when the amount of particulate accumulation increases, fuel is added to the exhaust gas upstream of the oxidation catalyst to force the particulate filter. It is considered to play.

  In other words, if fuel is added to the exhaust gas upstream of the oxidation catalyst, the added fuel (HC) undergoes an oxidation reaction while passing through the preceding oxidation catalyst. The catalyst bed temperature of the particulate filter immediately after that is raised, the particulates are burned out, and the particulate filter is regenerated.

  However, the catalyst bed in which the oxidation catalyst in the previous stage can exhibit sufficient catalytic activity in a vehicle with an operation state in which the operation state with a low exhaust temperature continues for a long time such as an urban route bus that travels only on a congested road There is a problem that the particulate filter cannot be efficiently regenerated within a short time because it is difficult to raise the temperature to the temperature and the oxidation reaction of the added fuel in the oxidation catalyst is not activated.

  Therefore, in recent years, a burner is provided on the inlet side of the particulate filter, and the catalyst is warmed early regardless of the operating state of the vehicle due to combustion of the burner, and the collected particulates are incinerated. Efficient reproduction within a short time has been studied.

  FIG. 3 shows a basic configuration of a conventional aftertreatment burner system. Reference numeral 1 denotes a diesel engine equipped with a turbocharger 2, and an intake 4 guided from an air cleaner 3 passes through an intake pipe 5 and the turbocharger 2. , The intake air 4 pressurized by the compressor 2a is sent to the intercooler 6 to be cooled, and the intake air 4 is further guided from the intercooler 6 to the intake manifold 7 to each cylinder of the diesel engine 1. 8 (the case of in-line 6 cylinders is illustrated in FIG. 3), and the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 passes through the exhaust manifold 10. It is sent to the turbine 2b of the turbocharger 2, and is sent to the exhaust pipe 11 after driving the turbine 2b.

  A particulate filter 12 (exhaust purification material) that integrally carries an oxidation catalyst is provided in the middle of the exhaust pipe 11 while being held by a muffler 13, and in the front stage of the particulate filter 12. A burner 14 for injecting and burning an appropriate amount of fuel is provided.

  The burner 14 is provided with a fuel injection nozzle 15 responsible for fuel spraying of the burner 14 and an ignition plug 16 for igniting the fuel injected from the fuel injection nozzle 15. A fuel atomizer 17 for atomizing fuel introduced from a fuel tank (not shown) with atomizing air supplied from an air tank is connected to the spark plug 16 by energization. An ignition coil 18 for generating sparks is connected.

  The exhaust pipe 11 upstream of the burner 14 is provided with an exhaust brake 19 that causes the diesel engine 1 to act as a compressor by closing the exhaust pipe 11 during braking.

  In addition, a combustion air supply pipe 20 for extracting a part of the intake air 4 from the downstream of the compressor 2a of the turbocharger 2 and leading it to the burner 14 as combustion air is branched and connected to the intake pipe 5. A combustion air cutoff valve 21 is provided in the middle of the air supply pipe 20.

  The fuel injection from the fuel injection nozzle 15 is controlled by an operation signal 17a output to the fuel atomizer 17 from a control device 22 constituting an engine control computer (ECU: Electronic Control Unit). The spark is controlled by an ignition signal 18a output from the control device 22 to the ignition coil 18, and the opening / closing of the combustion air shut-off valve 21 is controlled by a valve opening signal 21a output from the control device 22. It has become so.

  Here, when an operation request for the burner 14 is generated, as shown in FIG. 4, the combustion air shut-off valve 21 is opened, and a part of the intake air 4 from the downstream of the compressor 2a of the turbocharger 2 is opened. It is extracted and guided to the burner 14 as combustion air, and sparking at the spark plug 16 (see FIG. 3) is started, and fuel injection from the fuel injection nozzle 15 is turned on and started. 14, the fuel is burned.

  Examples of the general technical level related to the post-processing burner system as described above include Patent Document 1 and Patent Document 2.

JP 2009-91909 A JP 2010-43563 A

  By the way, in the conventional post-processing burner system, when the accelerator is off with the exhaust brake switch (not shown) in the cab turned on, as shown in FIG. 4, the exhaust brake 19 is turned on, that is, closed. Even so, the combustion of the fuel in the burner 14 is continued as it is.

  However, during the operation of the exhaust brake 19, the rotation of the turbine 2b of the turbocharger 2 decreases, and the amount of intake air 4 extracted from the downstream of the compressor 2a and guided to the burner 14 as combustion air decreases. The combustion of the fuel in the burner 14 becomes a fuel rich state, misfire or incomplete combustion occurs, soot is excessively deposited on the spark plug 16 or the fuel injection nozzle 15 inside the burner 14, and HC slip increases, resulting in poor ignition. There was a problem that a vicious cycle of becoming easy to occur occurs and the combustion performance deteriorates.

  In view of such circumstances, the present invention can minimize the accumulation of soot and HC slip in the burner, prevent the occurrence of poor ignition, maintain high combustion performance, and improve reliability. It is an object of the present invention to provide a control method for an aftertreatment burner system that can be realized.

In the present invention, an exhaust brake and an exhaust purification material are provided in the middle of an exhaust pipe, a burner is provided upstream of the exhaust purification material, and a part of the intake air is extracted from the downstream of the compressor of the turbocharger and burned. A control method for a post-treatment burner system that is guided as working air and that can heat the exhaust purification material by combustion of fuel in the burner,
When the exhaust brake is operated during combustion of fuel in the burner, the fuel injection in the burner is stopped, and the control method of the aftertreatment burner system is characterized.

  According to the above means, the following operation can be obtained.

  During the operation of the exhaust brake, the rotation of the turbine of the turbocharger decreases, and the amount of intake air drawn out from the downstream of the compressor and guided to the burner as combustion air decreases, but during combustion of fuel in the burner, When the exhaust brake is activated, the fuel injection in the burner is stopped, so that the combustion of fuel in the burner does not become a fuel rich state, so that incomplete combustion is less likely to occur and soot is ignited inside the burner. Excessive accumulation on the plug and the fuel injection nozzle can be avoided, HC slip does not increase, ignition failure is less likely to occur, and there is no concern about deterioration in combustion performance.

  In the control method of the aftertreatment burner system, until the continuous operation time of the exhaust brake exceeds the set time, the fuel injection in the burner is only stopped, the combustion air is supplied to the burner and the ignition plug is used. When the continuous operation time of the exhaust brake exceeds a set time, not only the fuel injection in the burner, but also the supply of combustion air to the burner and the spark in the spark plug are stopped, The burner can be extinguished. In this way, if the exhaust brake is released before the continuous operation time of the exhaust brake exceeds the set time, supply of combustion air to the burner and ignition Since the spark at the plug continues, it is possible to immediately restart the combustion of fuel in the burner simply by restarting the stopped fuel injection. In addition, it is possible to minimize exhaust gas temperature drop before and after exhaust brake operation and prevent regeneration of exhaust purification material and prolonged temperature rise control, while the vehicle runs on a long and gentle downhill When the continuous operation time of the exhaust brake exceeds the set time, not only the fuel injection in the burner but also the supply of combustion air to the burner and the spark in the spark plug are stopped, and the burner Since the fire is extinguished, it is possible to reset the burner without forcibly extending the operation.

  According to the control method of the post-processing burner system of the present invention, soot accumulation inside the burner and occurrence of HC slip can be minimized, high ignition performance can be maintained by preventing the occurrence of poor ignition, An excellent effect of improving the reliability can be achieved.

It is a timing chart of the combustion air shut-off valve, the fuel injection nozzle, and the exhaust brake in the embodiment of the control method of the aftertreatment burner system of the present invention. It is a flowchart which shows the flow of control in the Example of the control method of the post-process burner system of this invention. It is a whole schematic block diagram which shows the basic composition of the conventional post-processing burner system. It is a timing chart of the combustion air shut-off valve, the fuel injection nozzle, and the exhaust brake in the conventional aftertreatment burner system.

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

  1 and 2 show an embodiment of a control method for a post-processing burner system according to the present invention. In the figure, the same reference numerals as those in FIGS. Although the construction is the same as that of the conventional one shown in FIGS. 3 and 4, the feature of this embodiment is that the exhaust brake 19 operates during combustion of fuel in the burner 14, as shown in FIGS. In this case, the fuel injection in the burner 14 is stopped.

  Here, when an operation request for the burner 14 is generated, the combustion air shut-off valve 21 is opened (see step S1) as shown in the flowchart of FIG. 2, and the intake air 4 from the downstream of the compressor 2a of the turbocharger 2 is opened. Is extracted and guided to the burner 14 as combustion air, and sparking at the spark plug 16 is turned on (see step S2) and fuel injection from the fuel injection nozzle 15 is turned on. (See step S3), fuel is burned in the burner 14 and combustion control is performed (see step S4), and regeneration control for forcibly regenerating the particulate filter 12 or downstream thereof To promote activation by raising the bed temperature of various catalysts (selective reduction catalysts that reduce and purify NOx using urea water or HC as a reducing agent) Is performed (see step S5), it is determined whether or not the regeneration condition or the temperature increase condition has been cleared (see step S6), and when the regeneration condition or the temperature increase condition is cleared, The fuel injection from the fuel injection nozzle 15 is turned off and finished (see step S7), the spark at the spark plug 16 is turned off and finished (see step S8), and the combustion air shut-off valve 21 is turned off. The combustion air is closed (see step S9), the supply of the combustion air to the burner 14 is terminated, the burner 14 is extinguished (see step S10), a flag to be described later is turned off (see step S11), and the burner 14 The operation of is terminated.

  In the present embodiment, in step S6, when the regeneration condition or the temperature raising condition is not cleared, it is determined whether or not the exhaust brake 19 is operating (see step S12). When the brake 19 is operating, only the fuel injection from the fuel injection nozzle 15 is turned OFF and temporarily stopped (see step S13), and a flag for judging the state of fuel injection is turned ON ( It is determined whether or not the continuous operation time of the exhaust brake 19 exceeds the set time (X [sec]) (see step S15), and the continuous operation time of the exhaust brake 19 is set to the set time (see step S15). X [sec]) is not exceeded, it is repeatedly determined in step S12 whether or not the exhaust brake 19 is in operation. When the operation of the brake 19 is released, it is determined whether or not the flag is ON (see step S16). If the flag is ON, the process returns to step S3. Thus, the stopped fuel injection is resumed, and the combustion of fuel in the burner 14 is resumed. Incidentally, when the flag is OFF in the step S16, that is, when the exhaust brake 19 is not operated and the fuel injection from the fuel injection nozzle 15 is continued while being ON, Returning to step S5, regeneration control of the particulate filter 12 or temperature increase control of various catalysts arranged downstream thereof is repeatedly performed.

  On the other hand, when the continuous operation time of the exhaust brake 19 exceeds the set time (X [sec]) in step S15, the spark in the spark plug 16 is turned off in step S8 and the process ends. In step S10, the combustion air shut-off valve 21 is closed, supply of combustion air to the burner 14 is terminated in step S10, the burner 14 is extinguished, the flag is turned off in step S11, and the burner 14 is activated. Is to be terminated.

  Next, the operation of the above embodiment will be described.

  During the operation of the exhaust brake 19, the rotation of the turbine 2b of the turbocharger 2 decreases, and the amount of intake air 4 extracted from the downstream of the compressor 2a and guided to the burner 14 as combustion air decreases. When the exhaust brake 19 is activated during the combustion of the fuel at 14, the process proceeds from step S12 to step S13 in FIG. 2, and only the fuel injection from the fuel injection nozzle 15 is turned OFF, as shown in FIG. Thus, since the fuel injection in the burner 14 is stopped, the combustion of the fuel in the burner 14 does not become a fuel rich state, and incomplete combustion is less likely to occur. Excessive accumulation on the nozzle 15 can be avoided, HC slip does not increase, and ignition failure is less likely to occur. But worry is not necessary to decrease.

  Further, in this embodiment, until the continuous operation time of the exhaust brake 19 exceeds the set time (X [sec]), a loop of step S12 → step S13 → step S14 → step S15 → step S12 in FIG. Only by stopping the fuel injection in the burner 14, the supply of combustion air to the burner 14 (see step S1 in FIG. 2) and the spark in the spark plug 16 (see step S2 in FIG. 2) are continued. Therefore, if the operation of the exhaust brake 19 is canceled before the continuous operation time of the exhaust brake 19 exceeds the set time (X [sec]), step S12 → step S16 → step in FIG. By simply resuming the stopped fuel injection by the flow of S3, the combustion of fuel in the burner 14 is immediately resumed. Can be, a temperature decline of the exhaust gas in the exhaust brake 19 actuated back and forth with minimal, it is possible to prevent a prolonged playback and warm-up control of the particulate filter 12 as an exhaust gas purifying material.

  On the other hand, when the vehicle runs on a long and gentle downhill, if the continuous operation time of the exhaust brake 19 exceeds the set time (X [sec]), not only the fuel injection in the burner 14 but also the fuel injection in FIG. The flow of step S15 → step S8 → step S9 → step S10 stops the supply of combustion air to the burner 14 and the spark at the spark plug 16, and the burner 14 is extinguished. It becomes possible to reset once without forcibly prolonging.

  However, in this case, since the regeneration condition or the temperature raising condition in step S6 in FIG. 2 is not cleared, an operation request for the burner 14 is output again.

  In this way, soot accumulation inside the burner 14 and occurrence of HC slip can be minimized, high ignition performance can be maintained by preventing the occurrence of poor ignition, and reliability can be improved.

  The control method of the post-treatment burner system of the present invention is not limited to the above-described embodiment, and is not limited to the case where the exhaust purification material immediately after the burner is a particulate filter, but is selective even in the presence of oxygen. A selective reduction catalyst having the property of reacting NOx with a reducing agent, and oxidizing the NOx in the exhaust gas when the exhaust air-fuel ratio is lean, temporarily storing it in the form of nitrate, and the oxygen concentration in the exhaust gas Various exhaust purification catalysts such as NOx occlusion reduction catalyst having the property of decomposing and releasing NOx through the intervention of unburned HC, CO, etc. when it is reduced, and replacing it with a particulate filter as an exhaust purification material, Alternatively, after a configuration in which a burner is used to raise the temperature of the exhaust purification catalyst to the active temperature range when it is cold when it is separately arranged downstream of the particulate filter. Needless to say, various changes can be made without departing from the scope of the present invention, such as being similarly applicable to the processing burner system.

DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Turbocharger 2a Compressor 2b Turbine 11 Exhaust pipe 12 Particulate filter (exhaust purification material)
14 Burner 15 Fuel Injection Nozzle 16 Spark Plug 17 Fuel Atomizer 17a Actuation Signal 18 Ignition Coil 18a Ignition Signal 19 Exhaust Brake 20 Combustion Air Supply Pipe 21 Combustion Air Shut-off Valve 21a Opening Signal 22 Controller X Setting Time

Claims (2)

An exhaust brake and an exhaust purification material are arranged in the middle of the exhaust pipe, a burner is provided upstream of the exhaust purification material, and a part of the intake air is drawn into the burner from the downstream of the turbocharger compressor and led as combustion air. , A control method for a post-processing burner system that allows the exhaust purification material to be heated by combustion of fuel in the burner,
A control method for a post-processing burner system, wherein fuel injection in the burner is stopped when the exhaust brake is operated during combustion of fuel in the burner.   Until the continuous operation time of the exhaust brake exceeds the set time, the fuel injection in the burner is only stopped, the supply of combustion air to the burner and the sparking at the spark plug continue, and the exhaust brake continues The post-processing of claim 1, wherein when the operating time exceeds a set time, not only the fuel injection in the burner but also the supply of combustion air to the burner and the spark at the spark plug are stopped to extinguish the burner. Burner system control method.

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