JP4258871B2 - Exhaust gas purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an exhaust gas purification device in which a purification means for reducing a predetermined component in exhaust gas of an engine is arranged in an exhaust passage of an engine of an automobile.
[0002]
[Prior art]
  2. Description of the Related Art It is generally known that secondary air for assisting in the oxidation of HC (hydrocarbon) and CO is supplied to an exhaust passage in an exhaust gas purification device for an engine.
[0003]
  In Japanese Patent Laid-Open No. 9-125939, a fuel combustor is provided to increase the catalyst temperature by supplying the exhaust gas to the upstream side of the catalyst in the engine exhaust passage before engine operation. It describes that a heat exchanger for heating is provided on the downstream side of the catalyst, and the air for air conditioning is heated by the exhaust gas of the combustor by operating the combustor when the air conditioning temperature is low.
[0004]
  Japanese Patent Application Laid-Open No. H8-40049 describes that a combustion heater is used for heating the passenger compartment of an automobile, and that heat is radiated outside the vehicle when the temperature of the heat medium heated by the combustion heater exceeds a predetermined value. Has been.
[0005]
[Problems to be solved by the invention]
  If secondary air is supplied to the exhaust passage in the exhaust gas purification device, it will be advantageous for the oxidation of HC and CO, but if the secondary air is low temperature, the exhaust gas will be cooled by it and the purification performance of the catalyst etc. Gets worse. On the other hand, if the secondary air is heated, the problem of deterioration in purification performance can be avoided, but a combustor for heating the secondary air is required separately. Further, if a combustor for heating as described in the above publication is provided, it is possible to quickly raise the temperature of the catalyst and to heat the vehicle interior. Once the exhaust gas of this combustor is allowed to flow through the engine exhaust passage, Since heat is exchanged in the exhaust passage, the heating efficiency is lowered.
[0006]
[Means for Solving the Problems]
  Therefore, in the invention of this application, the heater exhaust gas is used for purification of exhaust gas.
[0007]
  That is, the invention of this application is an exhaust gas purification apparatus in which a purification means for reducing a predetermined component in exhaust gas of an engine is arranged in an exhaust passage of an automobile engine.
  A combustion heater for heating the air supplied to the passenger compartment;
  Gas supply means for supplying heater exhaust gas discharged from the combustion heater to be used for heating the air to a portion upstream of the purifying means in the exhaust passage;,
Detection means for detecting a state relating to purification of the purification means, and control means for controlling the operation of the gas supply means based on the state of the purification means detected by the detection meansAnd.
[0008]
  Therefore, according to the present invention, the combustion heater can be used effectively for heating air conditioning air, which is the original purpose, and can be used for purifying engine exhaust gas. That is, by supplying the heater exhaust gas to a portion upstream of the exhaust passage purification means, the temperature of the engine exhaust gas can be increased, and further the temperature of the purification means can be increased. It becomes advantageous for purification.Moreover, the heater exhaust gas can be supplied to the purification means at an appropriate time when the purification means works effectively, which is advantageous for purification of the engine exhaust gas.
[0009]
  When the combustion heater burns a combustible gas that is leaner than the stoichiometric air-fuel ratio and heats the passenger compartment supply air, the exhaust gas contains a large amount of oxygen. Accordingly, when this heater exhaust gas is supplied to the exhaust passage of the engine, it becomes hot secondary air, which is advantageous for oxidative purification of HC and CO in the engine exhaust gas.
[0010]
  Next, the purifying means converts NO in the engine exhaust gas to NO.₂In the case of an oxidation catalyst that oxidizes rapidly, this oxidation catalyst can be activated quickly by the heater exhaust gas. Particularly, when the heater exhaust gas contains a large amount of oxygen, it is advantageous for oxidation of NO by the oxidation catalyst. become.
[0011]
  Next, as the purifying means, a catalyst having at least an oxidizing function out of an oxidizing function and a reducing function is employed, and as the detecting means, a temperature at which it can be determined whether or not the catalyst is in an active state. Is used so that the heater exhaust gas is supplied to the catalyst when the state of the catalyst detected by the detection means is not active. If one that controls the operation of the gas supply means is employed, the catalyst can be heated by the heater exhaust gas to achieve its early activation. In particular, the combustion heater produces a combustible gas that is leaner than the stoichiometric air-fuel ratio. When burning, oxygen contained in the heater exhaust gas can be effectively used for the oxidation reaction on the catalyst.
[0012]
  Next, the combustion heater employs a combustion gas that burns a combustible gas that is leaner than the stoichiometric air-fuel ratio and heats the air supplied to the passenger compartment, and absorbs HC in the exhaust gas of the engine as the purification means. HC absorbing material is used, and as the detecting means, a device that detects a parameter such as a temperature that can grasp whether the HC absorbing material is in a state of desorbing the absorbed HC is adopted. As the control means, when the state of the HC absorbent detected by the detection means is in a state of desorbing HC, the gas discharged from the heater is supplied to the HC absorbent. If one that controls the operation of the supply means is employed, the desorbed HC can be efficiently oxidized and decomposed by hot secondary air. In particular, if the HC absorbent supports a catalytic metal having an oxidation catalyst function, the desorbed HC can be more efficiently oxidized and decomposed.
[0013]
  Next, as the above-mentioned combustion type heater, one that burns a combustible gas that is leaner than the stoichiometric air-fuel ratio and heats the cabin supply air is adopted,
  The purification means includes a catalyst having at least an oxidation function among an oxidation function and a reduction function, and an HC absorbent that is disposed downstream of the catalyst and absorbs HC in the exhaust gas of the engine,
  As the detection means, a catalyst state detection means for detecting whether or not the catalyst is in an active state, and whether or not the HC absorbent is in a state of desorbing the absorbed HC. An absorbent state detection means for detecting,
  As the control means, when the catalyst state detected by the catalyst state detection means is not active, the heater exhaust gas is supplied to the catalyst, and the HC detected by the absorbent state detection means. The gas supply means is operated so that the heater exhaust gas is supplied to the exhaust passage between the catalyst and the HC absorbent when the state of the absorbent is in the state of desorbing HC. If you adopt something to control,
  The catalyst can be heated with the heater exhaust gas for early activation, and oxygen contained in the exhaust gas can be used effectively for the oxidation reaction on the catalyst, and from the HC absorbent. The desorbed HC can be efficiently oxidized and decomposed by hot secondary air. In particular, if the HC absorbent supports a catalyst having an oxidation catalyst function, the desorbed HC can be more efficiently oxidized and decomposed.
[0014]
  next,Purifying means disposed in an exhaust passage of an automobile engine for reducing predetermined components in the exhaust gas of the engine, a combustion heater for heating air supplied to the passenger compartment, and heating of the air from the combustion heater In the exhaust gas purifying apparatus, comprising: a gas supply means for supplying heater exhaust gas used and exhausted to a portion of the exhaust passage upstream of the purifying means.The engine is operated with a lean air-fuel mixture at a predetermined ratio or more than the stoichiometric air-fuel ratio in at least a part of the operation region, and NOx in the exhaust gas of the engine operated with the lean is reduced as the purification means. Gas introduction means for introducing engine exhaust gas into the combustion heater from the exhaust passage upstream of the NOx reduction catalyst in order to obtain oxygen for burning the fuel of the combustion heater by using a catalyst to be purified. If the engine exhaust gas is used for combustion of the combustion heater and the exhaust gas is supplied to the NOx reduction catalyst, the NOx reduction catalyst can be activated early and the oxygen concentration Engine exhaust gas with a high flow rate changes to exhaust gas with a low oxygen concentration by combustion in the combustion heater and flows to the NOx reduction catalyst It is advantageous for the reduction of NOx by the catalyst.
[0015]
  Next, when an oxidation catalyst is provided in the exhaust passage upstream of the NOx reduction catalyst, the gas introduction means supplies the engine exhaust gas from the exhaust passage upstream of the oxidation catalyst to the combustion heater. In this case, the engine exhaust gas having a high oxygen concentration can be sent to the combustion heater without consuming the oxygen in the engine exhaust gas by the oxidation catalyst, which is advantageous for combustion in the heater. Since the exhaust gas after combustion in the heater has a low oxygen concentration, NOx reduction purification by the NOx reduction catalyst is performed efficiently.
[0016]
  next,Purifying means disposed in an exhaust passage of an automobile engine for reducing predetermined components in the exhaust gas of the engine, a combustion heater for heating air supplied to the passenger compartment, and heating of the air from the combustion heater In the exhaust gas purifying apparatus, comprising: a gas supply means for supplying heater exhaust gas used and exhausted to a portion of the exhaust passage upstream of the purifying means.The engine is operated with a lean air-fuel mixture at a predetermined ratio or more than the stoichiometric air-fuel ratio in at least a part of the operation region, and as the purification means, absorbs NOx in the exhaust gas of the engine operated with the lean The exhaust passage upstream of the catalyst is used to obtain oxygen for burning the fuel of the combustion heater by using a NOx absorbent that releases NOx when the oxygen concentration in the exhaust gas decreases. Provided with gas introduction means for introducing engine exhaust gas into the combustion heater, and using the engine exhaust gas for combustion of the combustion heater, the exhaust gas is supplied to the NOx absorbent to release NOx. According to the present invention, since the exhaust gas having a high oxygen concentration is changed to the exhaust gas having a low oxygen concentration by combustion in the combustion heater, NOx absorption is performed. Which is advantageous to the release of NOx from the wood.
[0017]
  When providing an oxidation catalyst in the exhaust passage upstream of the NOx absorbent, the gas introduction means introduces engine exhaust gas into the combustion heater from the exhaust passage upstream of the oxidation catalyst. What should I do?
[0018]
  Next, when the gas supply means supplies the heater exhaust gas generated by the combustion with the engine exhaust gas to the NOx absorbent, the engine is operated with an air-fuel mixture whose air-fuel ratio is smaller than the lean. For example, the oxygen concentration of the engine exhaust gas supplied to the NOx absorbent is further reduced, which is more advantageous for the release of NOx from the NOx absorbent. This also means that the engine exhaust gas supplied to the NOx absorbent is oxygen equivalent to the exhaust gas when the engine is operated at λ = 1 without operating the engine at λ = 1 (theoretical air-fuel ratio). This means that it is not necessary to greatly change the air-fuel ratio of the engine for releasing NOx from the NOx absorbent, which is advantageous for preventing sudden change in engine output torque.
[0019]
【The invention's effect】
  As described above, according to the invention of this application, the combustion heater that heats the air supplied to the passenger compartment, and the heater exhaust gas that is used for heating the air from the combustion heater is discharged from the engine. A gas supply means for supplying a portion of the exhaust passage upstream of the purification means;Detection means for detecting a state relating to purification of the purification means; and control means for controlling the operation of the gas supply means based on the state of the purification means detected by the detection means;Because it is equipped with, combustion heater can be effectively used for heating air conditioning air, which is the original purpose,The heater exhaust gas can be supplied to the purification means at an appropriate time when the purification means works effectively, which is advantageous for purification of engine exhaust gas.In particular, when the combustion heater burns a combustible gas leaner than the stoichiometric air-fuel ratio and heats the air supplied to the passenger compartment, the heater exhaust gas becomes hot secondary air, and the engine This is advantageous for oxidative purification of HC and CO in the exhaust gas.
[0020]
  Further, according to the present invention, an oxidation catalyst is employed as the purifying means, and the heater exhaust gas is supplied to the oxidation catalyst as hot secondary air when the catalyst is not in an active state. This catalyst can be heated with the heater exhaust gas to achieve its early activation, and is advantageous for promoting the oxidation reaction on the catalyst.
[0021]
  Further, when the HC absorbent is employed as the purifying means, and the HC absorbent is in a state of detaching the absorbed HC, the heater exhaust gas is supplied to the HC absorbent as hot secondary air. According to the supply, HC desorbed from the HC absorbent can be efficiently oxidized and decomposed.
[0022]
  Further, the exhaust gas of the engine operated by the lean air-fuel mixture is introduced into the combustion heater from the exhaust passage upstream of the NOx reduction catalyst and used for combustion of the fuel of the heater, and the heater exhaust gas is used as the NOx. According to what is supplied to the reduction catalyst, the NOx reduction catalyst can be activated early and the oxygen concentration of the engine exhaust gas supplied to the NOx reduction catalyst becomes low. It is advantageous for the reduction of.
[0023]
  Further, the exhaust gas of the engine operated by the lean air-fuel mixture is introduced into the combustion heater from the exhaust passage upstream of the NOx absorbent and used for the combustion of the fuel of the heater, and the heater exhaust gas is used as the NOx. According to what is supplied to the absorbent, the oxygen concentration of the engine exhaust gas supplied to the NOx absorbent is reduced, which is advantageous for the release of NOx from the NOx absorbent.
[0024]
  In particular, when the heater exhaust gas generated by the combustion with the engine exhaust gas is supplied to the NOx absorbent, the NOx absorbent is operated if the engine is operated with an air / fuel ratio smaller than the lean air / fuel ratio. The oxygen concentration of the engine exhaust gas supplied to the engine becomes further lower, which is more advantageous for the release of NOx from the NOx absorbent, and greatly changes the air-fuel ratio of the engine for the release of NOx from the NOx absorbent. This is no longer necessary, which is advantageous for preventing sudden changes in engine output torque.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
  <Embodiment 1>
  FIG. 1 shows the overall configuration of an exhaust gas purification device for an engine 1 of an automobile. A direct connection three-way catalyst 3, an HC trap material (HC absorber) 4 for absorbing HC in exhaust gas, and an exhaust passage 2 of the engine 1 A three-way catalyst 5 is provided in order from the upstream side. Reference numeral 6 denotes a combustion heater for heating the passenger compartment, and reference numeral 7 denotes a gas supply means for supplying gas discharged from the combustion heater 6 to the exhaust passage 2. The three-way catalysts 3 and 5 purify HC, CO and NOx (nitrogen oxides) in the engine exhaust gas, and thus have an oxidation catalyst function and a reduction catalyst function.
[0027]
  The automobile may be an engine car driven only by the engine 1 or a so-called hybrid car driven by a combination of the engine 1 and an electric motor. The engine 1 is a gasoline engine operated mainly at λ = 1. The direct-coupled three-way catalyst 3 is directly connected to the exhaust manifold of the engine 1, and is composed of, for example, a mixture of a material in which Pt and Rh are supported on an alumina base material and ceria. The HC trap material 4 is made of, for example, a material in which Pd is supported on zeolite. The three-way catalyst 5 is composed of the same catalyst as the direct-coupled three-way catalyst 3.
[0028]
  The combustion heater 6 is configured by connecting a fuel tank 10 to a combustor 9 as shown in FIG. The combustor 9 includes a mixing chamber 12 that mixes fuel (for example, light oil) and air (outside air) sent from a fuel tank 10 by a fuel pump 11, a combustion chamber 13 that burns the air-fuel mixture, and a fan 14 for the mixing. Further, an ignition plug (not shown) for combustion is provided, and a heat medium jacket 15 is formed around the combustion chamber 13. The amounts of the fuel and air are adjusted so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio.
[0029]
  In FIG. 2, reference numeral 16 denotes a heat medium (for example, water) circulation path, and the jacket 15, the heater core 19 disposed in the passenger compartment air-conditioning air duct 17, and the heat medium circulation pump 20 are sequentially connected by a pipe. It consists of The air duct 17 is provided with a damper 21 and a blower 22 for switching between an inside air introduction state and an outside air introduction state on the upstream side of the heater core 19. Dampers 23 to 26 for switching and supplying air are provided. Thus, a gas supply pipe 27 for supplying the gas used for heating the heat medium (accordingly, for heating air-conditioning air) from the combustion chamber 13 to the engine exhaust passage 2 is extended.
[0030]
  The gas supply pipe 27 constitutes the gas supply means 7. As shown in FIG. 1, the gas supply pipe 27 is branched in the middle, and one of the gas supply pipes 27 is upstream of the directly connected three-way catalyst 3 in the exhaust passage 2. The other end of the exhaust passage 2 is connected to a portion between the directly connected three-way catalyst 3 and the HC trap material 4. A gas supply position for supplying the heater exhaust gas discharged from the combustion type heater 6 to the engine exhaust passage 2 and an atmospheric discharge position for releasing it to the atmosphere are provided on the upstream side of the branch portion of the gas supply pipe 27. A first valve 29 for switching to a direct connection catalyst upstream position for supplying the heater exhaust gas to the upstream side of the direct connection three-way catalyst 3, the direct connection three-way catalyst 3, and the HC trap material 4. A second valve 30 is provided for switching to the upstream position of the trap material supplied between the two.
[0031]
  Thus, in order to control the operation of the valves 29 and 30 of the combustion heater 6 and the gas supply means 7, the control means 31 using a microcomputer and the occupant determine and operate whether or not the vehicle compartment heating is necessary. A heater switch 32 and detection means 33 for detecting the temperature of the HC trap material 4 are provided.
[0032]
  Even if the temperature sensor that directly measures the temperature of the HC trap material 4 is used as the detection means 33, the exhaust gas temperature, the engine water temperature, or the engine intake air amount that can estimate the temperature of the HC trap material 4 is detected. It may be a sensor. Since the exhaust gas temperature and the engine water temperature have a corresponding relationship that is substantially proportional to the temperature of the HC trap material 4, they can be used for control as they are. With respect to the engine intake air amount, the temperature of the HC trap material 4 is estimated based on the total intake air amount from the start of the engine. In the case of a hybrid vehicle, the temperature of the HC trap material 4 may be estimated based on the time from when the engine 1 is started and the average value of the traveling speed.
[0033]
  The specific flow of control is shown in FIG. First, data (switch ON (ON) / OFF (OFF), detection data, heating request level, etc.) is input from the heater switch 32, detection means 33, etc., and the combustion heater 6 is based on the state of the heater switch 32. ON / OFF is set (steps A1 to A4). Subsequently, the temperature Tt of the HC trap material 4 is estimated based on the data of the detection means 33 (step A5). When the trap material temperature Tt is equal to or lower than the predetermined temperature Tto, the output of the combustion heater 6 is set if the heater switch 32 is ON, and the heater switch 32 is set ON if the heater switch 32 is OFF. The output of the combustion heater 6 is set (steps A5 to A9).
[0034]
  Here, a temperature (for example, 150 ° C.) at which the HC trap material 4 starts to desorb the absorbed HC is given to the predetermined temperature Tto. This temperature Tto is also a temperature at which the direct-coupled three-way catalyst 3 starts to show substantial activity. Moreover, the output setting of the combustion type heater 6 is performed based on the environment such as the degree of heating requirement and the in-vehicle temperature set by the occupant using a switch or the like.
[0035]
  Then, after setting the first valve 29 to the gas supply position and the second valve 30 to the directly connected catalyst upstream position, the heater ON / OFF setting, the output setting and the valve setting are executed, that is, the combustion type The heater 6 and valves 29 and 30 are actuated (steps A10 and A11).
[0036]
  When the temperature Tt of the HC trap material 4 is higher than the above Tto and below the predetermined temperature Tt1, the setting of the combustion heater 6 similar to the above steps A7 to A9 is performed, and the first valve 29 is set to the gas supply position. The second valve 30 is set to the trap material upstream position, and the setting is executed (steps A12 to A16). Here, the predetermined temperature Tt1 is a temperature (for example, 250 ° C.) at which the three-way catalyst 5 in the subsequent stage starts to show activity.
[0037]
  Also, when the temperature Tt of the HC trap material 4 exceeds the predetermined temperature Tt1, if the heater switch 32 is set to ON, the heater output is set, and the second valve 30 is set to the atmospheric discharge position. Those settings are executed (steps A17 to A19).
[0038]
  As described above, when the engine 1 is cold or when the engine 1 is stopped, the direct-coupled three-way catalyst 3 is not at a temperature at which it is substantially active, and the HC trap material 4 is not When the absorbed HC has not been desorbed, the relatively high-temperature gas used for heating the heat medium of the combustion heater 6 reaches the upstream side of the directly connected three-way catalyst 3 in the exhaust passage 2. Supplied. Accordingly, air-conditioning air can be heated by the operation of the combustion heater 6, and the directly connected three-way catalyst 3 can be heated by the exhaust gas from the combustion heater 6, so that the catalyst 3 can be activated early. This is advantageous for purifying engine exhaust gas. Further, even when the heater switch 32 is OFF, it is forcibly set to ON and the combustion heater 6 operates, which is advantageous in avoiding exhausting the engine exhaust gas without purification. become.
[0039]
  The output of the combustion heater 6 is set based on the environment such as the degree of heating requirement and the temperature inside the vehicle. In order to improve the exhaust gas purification performance, the amount of fuel and air supplied to the combustion heater 6 should be increased. It may be.
[0040]
  When the temperature reaches the temperature at which the HC trap material 4 desorbs the absorbed HC, the heater exhaust gas is supplied to a portion of the exhaust passage 2 between the directly connected three-way catalyst 3 and the HC trap material 4. When HC is desorbed from the HC trap material 4, this HC is oxidized and purified by the catalytic metal Pd of the trap material 4, but the heater exhaust gas is high in temperature and contains a large amount of oxygen. It can be said that the secondary air, and when the HC is desorbed from the HC trap material 4, the hot secondary air promotes the oxidative purification of HC.
[0041]
  In the above embodiment, the heater exhaust gas is released to the atmosphere when the temperature of the HC trap material 4 exceeds Tt1, but is supplied between the direct-coupled three-way catalyst 3 and the HC trap material 4. The oxidation of HC desorbed from the HC trap material 4 may be promoted.
[0042]
  <Embodiment 2>
  In the present embodiment, the automobile may be the above-described engine car or a hybrid car. However, the engine is a predetermined ratio or more (for example, A / A) more than the stoichiometric air-fuel ratio like a diesel engine or a so-called lean burn gasoline engine. FIG. 4 shows a case having a region operated lean in F> 16). That is, an oxidation catalyst 35 and a NOx reduction catalyst 36 are provided in order from the upstream side in the exhaust passage 2 of the engine 1, and the exhaust gas of the combustion heater 6 is supplied to the upstream side of the oxidation catalyst 35 by the gas supply means 7. It is supplied by a tube 27.
[0043]
  As the oxidation catalyst 35, for example, a catalyst in which Pd is supported on a mixture of alumina and ceria is used. As the NOx reduction catalyst 36, for example, a catalyst in which Pt is supported on zeolite is used. A gas supply pipe 27 of the gas supply means 7 is provided with a valve 37 that switches between a position for supplying the heater exhaust gas to the exhaust passage 2 and a position for releasing it to the atmosphere. The combustion heater 6 and the valve 37 are controlled by the control means 31 based on the outputs of the heater switch 32 and the detection means 33.
[0044]
  In the case of this embodiment, when it is detected by the detection means 33 that the oxidation catalyst 35 has not reached the temperature at which the oxidation catalyst 35 is substantially active, the control means 31 turns the combustion heater 6 on / off of the heater switch 32. Regardless, the valve 37 is forcedly operated and the heater exhaust gas is supplied to the exhaust passage 2.
[0045]
  Accordingly, the oxidation catalyst 35 can be activated early when the engine is cold, and the oxidation reaction in the oxidation catalyst 35 is promoted by the heater exhaust gas having a large amount of oxygen, so that HC and CO in the engine exhaust gas can be efficiently purified. it can.
[0046]
  The heater exhaust gas may also be supplied between the oxidation catalyst 35 and the NOx reduction catalyst 36 in the exhaust passage 2.
[0047]
  Further, instead of the oxidation catalyst 35, a NO oxidation catalyst (for example, a catalyst in which Ag is supported on alumina) is used, and NOx reduction catalyst is used as NOx reduction catalyst.₂N₂For example, a catalyst suitable for reducing the catalyst, for example, a catalyst in which Ag is supported on zeolite, or a catalyst in which Pt is supported on zeolite by ion exchange may be used.
[0048]
  <Embodiment 3>
  As shown in FIG. 5, the present embodiment is a case where the same oxidation catalyst 35 and the NOx reduction catalyst 36 are sequentially provided in the exhaust passage 2 from the upstream side in the same engine 1 as in the second embodiment. The use of the combustion heater 6 is different.
[0049]
  That is, in this embodiment, in order to obtain oxygen for burning the fuel of the combustion type heater 6, gas introduction means 39 for introducing engine exhaust gas into the combustion type heater 6 from the upstream side portion of the oxidation catalyst 35 in the exhaust passage 2. The gas supply means 7 supplies gas discharged from the combustion heater 6 to a portion of the exhaust passage 2 between the oxidation catalyst 35 and the NOx reduction catalyst 36. In the gas introduction pipe 40 constituting the gas introduction means 39, the valve position is switched between an E gas introduction position where engine exhaust gas is introduced into the combustion heater 6 and an outside air introduction position where outside air is introduced into the combustion heater 6. The first valve 41 is provided, and the gas supply pipe 27 constituting the gas supply means 7 is switched to an H gas supply position for supplying the heater exhaust gas to the exhaust passage 2 and an H gas release position for releasing it to the atmosphere. 42 is provided.
[0050]
  Further, a portion of the exhaust passage 2 upstream of the oxidation catalyst 35 has a passage diameter smaller than the passage diameter downstream of the oxidation catalyst 35 and is curved, and the exhaust gas flow path in the upstream portion. The resistance is larger than that of the downstream portion.
[0051]
  In order to control the operation of the combustion heater 6 and the valves 41 and 42, a control means 31, a heater switch 32, and a detection means 43 are provided. The detecting means 43 is for determining whether or not the temperature Tn of the NOx reduction catalyst 36 is substantially the active temperature Tno, and this is the same as in the case of the detecting means of the first embodiment. A sensor that detects the engine water temperature, the exhaust gas temperature, or the engine intake air amount, or a sensor that directly detects the temperature of the NOx reduction catalyst 36 is used. Further, the control means 31 includes an engine operation region determination unit.
[0052]
  The operation region determination unit determines whether or not the engine 1 is in an operation region where it is difficult to purify NOx by the NOx reduction catalyst 36. The determination includes a sensor (engine speed sensor, engine engine) that detects the engine operation state. Load sensor). That is, it is difficult for the NOx reduction catalyst 36 to purify NOx when the amount of NOx in the engine exhaust gas is large and when the oxygen concentration in the engine exhaust gas is high, and the air-fuel ratio of the engine is high lean (for example, A / F> 30) is an operation region in which the oxygen concentration in the engine exhaust gas is high, and when the engine load is high, the amount of NOx in the engine exhaust gas is large. Determined.
[0053]
  A specific flow of control is shown in FIG. First, data (switch ON / OFF, detection data, heating request level, etc.) is input from the heater switch 32, the detection means 43, etc., and the ON / OFF of the combustion heater 6 is set based on the state of the heater switch 32. (Steps B1 to B4). Subsequently, the temperature Tn of the NOx reduction catalyst 36 is estimated based on the data of the detection means 43 (step B5).
[0054]
  When the catalyst temperature Tn is equal to or higher than the predetermined temperature Tno, it is determined whether or not the engine operating state is in a region where it is difficult to purify NOx (steps B6 and B7). In the NOx purification difficult region, if the heater switch 32 is ON, the output of the combustion type heater 6 is set. If the heater switch 32 is OFF, the heater switch 32 is set to ON and the combustion type heater 6 is set. The output is set (steps B8 to B10).
[0055]
  Then, it is checked whether the ignition timer t has counted the set time to or longer. If it has not been set, the timer t is counted, the first valve 41 is set to the outside air introduction position, and the second The valve 42 is set to the H gas release position, and the settings of the combustion heater 6 and the valves 41 and 42 are executed (steps B11 to B15). If the timer t has counted the set time to or longer, the first valve 41 is set to the E gas introduction position, the second valve 42 is set to the H gas supply position, and these settings are executed (step B16). → B17 → B15).
[0056]
  When the catalyst temperature Tn does not reach the predetermined temperature Tno, or when the engine operating state is not in the NOx purification difficulty region, if the heater switch 32 is ON, the heater output is set and the ignition timer t is set. Counting is performed, and if the heater switch 32 is OFF, the count of the ignition timer t is canceled (set to zero) (steps B18 to B20).
[0057]
  The ignition timer t is used to improve the ignitability of the combustion heater 6 by introducing outside air with a large amount of oxygen into the combustion heater 6 instead of engine exhaust gas when the combustion heater 6 is started. ~ 2 seconds are given.
[0058]
  Accordingly, when the NOx reduction catalyst 36 is at a temperature at which the NOx reduction catalyst 36 is substantially active and the engine operating state is in a region where it is difficult to purify NOx, part of the engine exhaust gas bypasses the oxidation catalyst 35 and burns the combustion heater. 6, oxygen in the exhaust gas is used for fuel combustion by the heater 6, and is supplied to the NOx reduction catalyst 36 as exhaust gas with a small amount of oxygen. For this reason, the NOx reduction catalyst 36 is heated by the heater exhaust gas and activated, and the oxygen concentration of the engine exhaust gas supplied to the catalyst 36 becomes low, which is advantageous for NOx reduction purification.
[0059]
  In the NOx purification difficult region, when the combustion heater 6 is not operating, outside air is temporarily introduced to the heater 6 to improve its ignitability, but when the heater is already operating. , T ≧ to, the engine exhaust gas is promptly introduced into the combustion heater 6.
[0060]
  In the NOx purification difficult region, the amount of fuel supplied to the combustion heater 6 may be increased in order to improve the purification performance of the NOx reduction catalyst 36.
[0061]
  When the first valve 41 is set to the outside air introduction position in order to improve the ignitability in the NOx purification difficult region, the NOx reduction catalyst 36 is actively heated by the heater exhaust gas with the second valve 42 set as the H gas supply position. You may make it promote the activity.
[0062]
  In this embodiment, the exhaust gas flow resistance of the exhaust gas upstream of the oxidation catalyst 35 in the exhaust passage 2 is increased to bypass the exhaust gas to the combustion heater 6. A valve for forcibly bypassing the exhaust gas by reducing or reducing the gas amount may be provided upstream or downstream of the oxidation catalyst 35 in the exhaust passage 2.
[0063]
  Further, in the present embodiment, the oxidation catalyst 35 is provided, but even when the oxidation catalyst 35 is not provided, a part or all of the exhaust gas is introduced into the combustion heater 6 for combustion in the NOx purification difficult region. You may make it supply to a NOx reduction catalyst after using.
[0064]
  <Embodiment 4>
  As shown in FIG. 7, in this embodiment, in the same engine 1 as in the second embodiment, the exhaust gas passage 2 has a direct-coupled three-way catalyst (low temperature active catalyst) 3 and a NOx absorption catalyst 45 in the upstream as in the first embodiment. In this case, the use of the combustion heater 6 is similar to that of the third embodiment.
[0065]
  The NOx absorption catalyst 45 is formed by forming an inner coat layer having an alumina base material, Pt and Ba, and an outer coat layer having a zeolite base material and Pt on a carrier. In this catalyst, Ba absorbs NOx when the oxygen concentration in the exhaust gas is high (when the engine is operated at a lean ratio (for example, A / F> 16) or more than the stoichiometric air-fuel ratio), and the exhaust gas NOx absorbent that desorbs absorbed NOx when the oxygen concentration in it decreases (especially when λ = 1), Pt is a catalytic metal that reduces and decomposes NOx desorbed from Ba, and is supported on zeolite Made Pt NO in exhaust gas NO₂Oxidizes to make it easy to absorb into Ba.
[0066]
  In this embodiment, gas introduction means 39 for introducing engine exhaust gas into the combustion heater 6 from the upstream side of the three-way catalyst 3 in the exhaust passage 2 to obtain oxygen for burning the fuel of the combustion heater 6; Gas supply means 7 is provided for supplying gas discharged from the combustion heater 6 to a portion of the exhaust passage 2 between the three-way catalyst 3 and the NOx absorption catalyst 45. As in the third embodiment, the gas introduction pipe 40 constituting the gas introduction means 39 is provided with a first valve 41 that switches between the E gas introduction position and the outside air introduction position, and the gas supply pipe constituting the gas supply means 7. 27 is provided with a second valve 42 that switches between an H gas supply position and an H gas discharge position.
[0067]
  In order to control the operation of the combustion heater 6 and the valves 41 and 42, a control means 31, a heater switch 32, and a detection means 43 are provided. The detection means 43 is for determining whether or not the temperature Tn of the NOx absorption catalyst 45 is substantially the active temperature Tno, and is substantially the same as the detection means 43 of the third embodiment. is there. Further, the control means 31 includes a NOx trap amount estimation unit for estimating the NOx trap (absorption) amount TR of the NOx absorption catalyst 45, which estimates the amount TR based on the elapsed time from the start of the trap.
[0068]
  A specific flow of control is shown in FIG. First, data (switch ON / OFF, detection data, heating request level, etc.) is input from the heater switch 32, the detection means 43, etc., and the ON / OFF of the combustion heater 6 is set based on the state of the heater switch 32. Then, the temperature Tn of the NOx absorption catalyst 45 is estimated based on the data of the detection means 43 (steps C1 to C5). Subsequently, it is determined whether or not the engine exhaust gas is being bypassed to the combustion heater 6. If not, the NOx trap amount TR is integrated (steps C6 and C7). Whether or not bypassing is in progress is determined by whether or not a bypass timer t1 described later is operating (t10> t1> 0).
[0069]
  When the catalyst temperature Tn is equal to or higher than the predetermined temperature Tno and the NOx trap amount TR is equal to or higher than the predetermined trap amount (saturated trap amount of the NOx absorbent or a trap amount somewhat smaller than that) TRO, the NOx trap amount TR The counting is canceled and the timer t1 is counted to bypass the engine exhaust gas to the combustion heater 6 (steps C8 to C11).
[0070]
  The bypass timer t1 is set to the scheduled bypass time t10 (for example, several seconds.
Until the time t10> to), if the heater switch 32 is ON, the output of the combustion heater 6 is set. If the heater switch 32 is OFF, the heater switch 32 is set ON and the combustion heater 6 is turned on. The output is set (steps C12 to C15).
[0071]
  Then, it is determined whether or not the ignition timer t has counted the set time to or longer, and if it is not longer than the set time, the ignition timer t is counted, the first valve 41 is set to the outside air introduction position, The second valve 42 is set to the H gas release position, and the settings of the combustion heater 6 and the valves 41 and 42 are executed (steps C16 to C20). When the ignition timer t counts the set time to or longer, the first valve 41 is set to the E gas introduction position, the second valve 42 is set to the H gas supply position, and these settings are executed ( Along with steps C21 → C22 → C20), the air-fuel ratio of the engine 1 is changed from a high lean state (for example, A / F ≧ 22) to a low lean state (for example, A / F = 16). If it is already bypassed in step C6, the count of the bypass timer t1 is continued, and the above processing is performed until it reaches the scheduled bypass time t10 (step C6 → C11).
[0072]
  When the catalyst temperature Tn has not reached the predetermined temperature Tno, the NOx trap amount TR has not reached the planned trap amount TRO, or the bypass timer t1 has reached the planned bypass time t10 (bypass end). If the heater switch 32 is ON, the heater output is set and the ignition timer t is counted when the heater switch 32 is ON. If the heater switch 32 is OFF, the count of the ignition timer t is canceled ( To zero) (steps C23 to C26).
[0073]
  Therefore, when the NOx trapping catalyst 45 is at a temperature at which the NOx trapping catalyst 45 is substantially active, if the amount of NOx trap is saturated or close to it, a part of the engine exhaust gas bypasses the three-way catalyst 3 and burns. Oxygen in the exhaust gas introduced into the heater 6 is used for fuel combustion by the heater 6 and becomes an exhaust gas with a small amount of oxygen (equivalent exhaust gas when the engine 1 is operated at λ = 1) and NOx. It is supplied to the absorption catalyst 45. For this reason, the NOx absorption catalyst 45 begins to desorb the absorbed NOx, and the desorbed NOx is reduced and purified efficiently. Further, since the NOx trap amount is not accumulated during the exhaust gas bypass, it is possible to avoid that the next bypass starts before the planned trap amount is reached. In addition, since it is not necessary to set the air-fuel ratio of the engine 1 to λ = 1 at once from the high lean state, a sudden change in the engine output torque can be avoided.
[0074]
  Exhaust air is temporarily introduced to the heater 6 to improve ignitability when the combustion heater 6 is not operating, and engine exhaust is performed on condition that t ≧ to when the combustion heater 6 is already operating. In this embodiment, the three-way catalyst 3 in the exhaust passage 2 may be configured such that the gas is promptly introduced into the combustion heater 6 and the amount of fuel supplied to the combustion heater 6 may be increased when the engine exhaust gas is bypassed. The exhaust gas flow resistance of the upstream portion of the exhaust gas is increased and the exhaust gas is bypassed to the combustion heater 6, but a valve for forcibly bypassing the exhaust gas is provided as a three-way catalyst in the exhaust passage 2. 3 is the same as in the third embodiment in that the bypass may be performed even when the three-way catalyst 3 is not provided.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an exhaust gas purification apparatus according to a first embodiment.
FIG. 2 is a circuit diagram showing an example of a combustion heater.
FIG. 3 is a flowchart of control in the same form.
FIG. 4 is a block diagram showing a configuration of an exhaust gas purifying apparatus according to a second embodiment.
FIG. 5 is a block diagram showing a configuration of an exhaust gas purifying apparatus according to a third embodiment.
FIG. 6 is a flowchart of control in the same form.
FIG. 7 is a block diagram showing a configuration of an exhaust gas purifying apparatus according to a fourth embodiment.
FIG. 8 is a flowchart of control in the same form.
[Explanation of symbols]
    1 engine
    2 Exhaust passage
    3 Directly connected three-way catalyst
    4 HC trap material
    5 Three-way catalyst
    6 Combustion heater
    7 Gas supply means
  27 Gas supply pipe
  29 1st valve
  30 Second valve
  31 Control means
  32 Heater switch
  33 Detection means
  35 Oxidation catalyst
  36 NOx reduction catalyst
  37 Valve
  39 Gas introduction means
  40 Gas inlet pipe
  41 1st valve
  42 Second valve
  43 Detection means
  44 Operating region determination means
  45 NOx absorption catalyst
  46 NOx trap amount estimation means

Claims (11)

In an exhaust gas purification apparatus in which a purification means for reducing a predetermined component in the exhaust gas of the engine is arranged in an exhaust passage of an automobile engine,
A combustion heater for heating the air supplied to the passenger compartment;
A gas supply means for supplying a heater exhaust gas used for heating the air from the combustion heater to an upstream side of the purification means in the exhaust passage ;
Detection means for detecting a state relating to purification of the purification means;
An exhaust gas purification apparatus comprising: control means for controlling the operation of the gas supply means based on the state of the purification means detected by the detection means . In the exhaust gas purification device according to claim 1,
The combustion heater is an exhaust gas purification device that heats the air supplied to the passenger compartment by burning a combustible gas that is leaner than the stoichiometric air-fuel ratio. In the exhaust gas purifying device according to claim 1 or 2,
It said purifying means, an exhaust gas purification apparatus is an oxidation catalyst for oxidizing NO of the engine exhaust gas to NO _2. In the exhaust gas purification device according to claim 1 ,
The purification means is a catalyst having at least an oxidation function among an oxidation function and a reduction function,
The detection means is for detecting whether or not the catalyst is in an active state,
The control means controls the operation of the gas supply means so that the heater exhaust gas is supplied to the catalyst when the state of the catalyst detected by the detection means is not active. apparatus. In the exhaust gas purification device according to claim 1 ,
The combustion heater is for heating the air supplied to the passenger compartment by burning a combustible gas that is leaner than the stoichiometric air-fuel ratio,
The purification means is an HC absorbent that absorbs HC in the exhaust gas of the engine,
The detection means is for detecting whether or not the HC absorbent is in a state of desorbing the absorbed HC,
The control means supplies the gas so that the heater exhaust gas is supplied to the HC absorbent when the state of the HC absorbent detected by the detection means is in a state of detaching HC. An exhaust gas purification device for controlling the operation of the means. In the exhaust gas purification device according to claim 1 ,
The combustion heater is for heating the air supplied to the passenger compartment by burning a combustible gas that is leaner than the stoichiometric air-fuel ratio,
The purification means includes a catalyst having at least an oxidation function among an oxidation function and a reduction function, and an HC absorbent that is disposed downstream of the catalyst and absorbs HC in the exhaust gas of the engine,
As the detection means, a catalyst state detection means for detecting whether or not the catalyst is in an active state, and whether or not the HC absorbent is in a state of desorbing the absorbed HC. An absorbent state detection means for detecting,
The control means supplies the heater exhaust gas to the catalyst when the state of the catalyst detected by the catalyst state detection means is not active, and the HC detected by the absorbent state detection means. The gas supply means is operated so that the heater exhaust gas is supplied to the exhaust passage between the catalyst and the HC absorbent when the state of the absorbent is in the state of desorbing HC. The exhaust gas purification device to control. A purification means disposed in an exhaust passage of an automobile engine for reducing a predetermined component in the exhaust gas of the engine;
A combustion heater for heating the air supplied to the passenger compartment;
An exhaust gas purifying apparatus comprising a gas supply means for supplying a heater exhaust gas discharged from the combustion heater used for heating the air to a portion upstream of the purifying means in the exhaust passage ;
The engine is operated by a lean air-fuel mixture at a predetermined ratio or more than the stoichiometric air-fuel ratio in at least a part of the operation region,
The purification means is a catalyst that reduces and purifies NOx in the exhaust gas of the engine operated lean.
Gas introduction means for introducing engine exhaust gas into the combustion heater from the exhaust passage upstream of the catalyst in order to obtain oxygen for burning the fuel of the combustion heater;
An exhaust gas purification device in which the gas supply means supplies heater exhaust gas generated by combustion with the engine exhaust gas to the catalyst. In the exhaust gas purifying device according to claim 7 ,
An oxidation catalyst is provided in the exhaust passage upstream of the catalyst for reducing and purifying NOx,
The exhaust gas purification device, wherein the gas introduction means introduces engine exhaust gas into the combustion heater from the exhaust passage upstream of the oxidation catalyst. A purification means disposed in an exhaust passage of an automobile engine for reducing a predetermined component in the exhaust gas of the engine;
A combustion heater for heating the air supplied to the passenger compartment;
An exhaust gas purifying apparatus comprising a gas supply means for supplying a heater exhaust gas discharged from the combustion heater used for heating the air to a portion upstream of the purifying means in the exhaust passage ;
The engine is operated by a lean air-fuel mixture at a predetermined ratio or more than the stoichiometric air-fuel ratio in at least a part of the operation region,
The purification means is a NOx absorbent that absorbs NOx in the exhaust gas of the engine operated lean and releases the NOx when the oxygen concentration in the exhaust gas decreases,
Gas introduction means for introducing engine exhaust gas into the combustion heater from the exhaust passage upstream of the catalyst in order to obtain oxygen for burning the fuel of the combustion heater;
An exhaust gas purification apparatus in which the gas supply means supplies heater exhaust gas generated by combustion with the engine exhaust gas to the NOx absorbent so as to release NOx from the NOx absorbent. In the exhaust gas purifying device according to claim 9 ,
An oxidation catalyst is provided in the exhaust passage upstream of the NOx absorbent,
The exhaust gas purification device, wherein the gas introduction means introduces engine exhaust gas into the combustion heater from the exhaust passage upstream of the oxidation catalyst. In the exhaust gas purifying device according to claim 9 ,
An exhaust gas purification apparatus in which the engine is operated by an air-fuel mixture having a smaller air-fuel ratio than lean when the gas supply means supplies heater exhaust gas generated by combustion with the engine exhaust gas to the NOx absorbent.

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