JP2010096005A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of immediately raising a temperature of a reduction catalyst arranged at the exhaust gas downstream side of a filter while preventing the thermal damage of a reducing agent injection valve or the thermal degradation of the reduction catalyst caused by a high temperature. <P>SOLUTION: In the exhaust emission control device for the internal combustion engine, a particulate filter arranged in an exhaust passage in the internal combustion engine and trapping an exhaust particulate in exhaust gas, the reducing agent injection valve injecting a reducing agent into the exhaust passage, and the reduction catalyst reducing NOx in exhaust gas by using the reducing agent are arranged sequentially from an exhaust gas upstream side. The exhaust emission control device includes: the exhaust passage having a first passage and a second passage which are branched at a side upstream of the reducing agent injection valve and merged at a side downstream of the reducing agent injection valve and upstream of the reduction catalyst; the reducing agent injection valve arranged in the first passage; a heating means arranged in the second passage and heating exhaust gas flowing in the second passage; and a control section for controlling the heating means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine in which a particulate filter, a reducing agent injection valve, and a reduction catalyst are sequentially provided from the exhaust upstream side.

The exhaust gas discharged from the internal combustion engine contains exhaust particulates (hereinafter referred to as “PM”) and nitrogen oxides (hereinafter referred to as “NO _X ”). For this reason, conventionally, a particulate filter (hereinafter simply referred to as “filter”) for collecting PM and a reduction catalyst for reducing NO _x are provided in the exhaust passage of the internal combustion engine, and the exhaust gas. Exhaust gas purification devices that perform this purification have been put into practical use. As one aspect of this reduction catalyst, there is a reduction catalyst that selectively reduces NO _{x in} exhaust gas by using a reducing agent supplied on the upstream side of the reduction catalyst.

  Here, the filter has a problem that clogging occurs when the amount of collected PM increases. Therefore, when a filter is used, regeneration control is performed in which the collected PM is burned to regenerate the filter. As a method for controlling the regeneration of the filter, for example, an oxidation catalyst is provided on the upstream side of the exhaust of the filter, and an oxidation reaction is caused by supplying unburned fuel (HC) to the oxidation catalyst by a method such as controlling the operating state of the internal combustion engine. There is known a method for burning PM collected by a filter using exhaust heat generated by this oxidation reaction. In addition to this, there is a method in which a heating means such as a burner or a heating wire is provided on the upstream side of the filter, and the regeneration of the filter is performed by operating the heating means when performing regeneration control.

  When an oxidation catalyst is provided on the upstream side of the filter and the operation state of the internal combustion engine is controlled so that the exhaust gas contains unburned fuel and supplied to the oxidation catalyst, the regeneration control requires a considerable amount of exhaust gas. Temperature is required. Therefore, in an exhaust gas purification apparatus provided with a filter, a reduction catalyst, and a reducing agent injection valve, the filter may be provided on the exhaust upstream side of the reducing agent injection valve and the reduction catalyst. In addition, if the reduction catalyst is provided upstream of the filter, PM may adhere to the reduction catalyst. Therefore, as shown in FIG. 10, the filter 300 is more than the reducing agent injection valve 301 and the reduction catalyst 302. May also be provided upstream of the exhaust (see, for example, Patent Document 1).

On the other hand, when the temperature of the reduction catalyst is lower than the activation temperature, the reduction efficiency of NO _x is remarkably lowered. When the temperature of the reduction catalyst is low, the reduction of NO _x is efficiently performed. There is a risk that unpurified exhaust gas will not be released and released into the atmosphere. For this reason, for example, when the internal combustion engine is cold started, under the operating conditions where the temperature of the reduction catalyst does not reach the activation temperature, the temperature increase control of the reduction catalyst is performed as necessary.

  As a method for controlling the temperature increase of the reduction catalyst, a method using oxidation heat by an oxidation catalyst provided on the exhaust gas upstream side of the reduction catalyst and a method using heating means have been proposed. For example, as shown in FIG. 11, an exhaust purification apparatus that includes heating means such as a heater 303, a reducing agent injection valve 304, and a reduction catalyst 305 sequentially from the upstream side of the exhaust gas is an example that does not include a filter. Is disclosed (for example, Patent Document 2).

JP 2008-138583 A (FIG. 1) Japanese Patent Laying-Open No. 2005-256727 (FIG. 1)

By the way, in the exhaust gas purification device in which the filter is provided on the upstream side of the reduction catalyst as in the exhaust gas purification device described in Patent Document 1, before the exhaust gas discharged from the internal combustion engine reaches the reduction catalyst. It is configured to pass through the filter. In such an exhaust purification device, even if an oxidation catalyst or heating means is provided upstream of the filter, and the temperature of the exhaust gas is raised by the same method as the filter regeneration control, and the temperature increase control of the reduction catalyst is attempted, Since the heat capacity is relatively large and the filter is easily deprived of heat, it may take time to activate the reduction catalyst at an elevated temperature. In particular, the reduction catalyst also has a relatively large heat capacity, and it takes a long time to activate the reduction catalyst due to the relatively large amount of heat required for the reduction catalyst to be activated. . As a result, it takes time to efficiently reduce NO _{x in} the exhaust gas, and unpurified exhaust gas is released into the atmosphere during that time.

  On the other hand, in an exhaust purification device in which a filter is provided on the upstream side of the reduction catalyst, in order to efficiently raise the temperature of the reduction catalyst, a burner or the like is provided upstream of the reduction catalyst as described in Patent Document 2. Although it is considered effective to provide a heating means, the reducing agent injection valve is vulnerable to high temperatures, and if the heating means is provided upstream of the reducing agent injection valve, the heating means may cause thermal damage to the reducing agent injection valve. is there. In addition, when the heating means is provided downstream of the reducing agent injection valve and upstream of the reduction catalyst, the reducing agent injection valve and the reduction catalyst are not provided extremely separated from each other. May be directly exposed to the heating means, resulting in thermal degradation of the reduction catalyst.

  Therefore, as a result of earnestly examining the above problems, the inventor of the present invention branches the upstream side of the reducing agent injection valve and joins the downstream side of the reducing agent injection valve and the upstream side of the reduction catalyst. It has been found that such a problem can be solved by providing a passage and a second passage, including a reducing agent injection valve in one first passage and a heating means in the other second passage. It has been completed. That is, the present invention provides an internal combustion engine exhaust capable of quickly raising the temperature of the reduction catalyst provided downstream of the filter exhaust while preventing thermal damage to the reducing agent injection valve and thermal degradation of the reduction catalyst due to high temperatures. An object is to provide a purification device.

According to the present invention, a particulate filter that is provided in an exhaust passage of an internal combustion engine and collects exhaust particulates in exhaust gas, a reducing agent injection valve that injects a reducing agent into the exhaust passage, and a reducing agent are used. In an exhaust gas purification apparatus for an internal combustion engine in which a reduction catalyst for reducing NO _{x in} exhaust gas is sequentially provided from the exhaust upstream side, the exhaust passage branches on the upstream side of the reducing agent injection valve, and the reducing agent injection The first passage and the second passage that join downstream from the valve and upstream from the reduction catalyst are provided, and the reducing agent injection valve is provided in the first passage, and is provided in the second passage. An exhaust gas purification apparatus for an internal combustion engine, characterized by comprising a heating means for heating the exhaust gas flowing through the second passage and a control unit for controlling the heating means, solves the above-mentioned problems can do.

  Further, in configuring the exhaust gas purification apparatus for an internal combustion engine according to the present invention, it is preferable that the first passage and the second passage branch on the downstream side of the particulate filter and the upstream side of the reducing agent injection valve.

  In configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, the flow rate ratio of the exhaust gas flowing through the second passage may be 50% or less with respect to the entire flow rate of the exhaust gas discharged from the internal combustion engine. preferable.

  Further, in configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, it is preferable that the heating means is a burner, and the second passage includes a flame collision portion that causes the flame radiated from the burner to collide.

  In configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, the control unit determines whether the temperature of the reduction catalyst is equal to or higher than a predetermined threshold, and the determination result by the catalyst temperature determination unit And a heating means control section that controls the heating means based on the above.

  In configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, the control unit controls the output of the heating means so that the combustion temperature of the burner as the heating means becomes 600 ° C. or more when the heating means is operated. Is preferred.

  In configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, it is preferable that the control unit includes a heating unit operation determination unit that determines whether the heating unit can be operated based on the operating state of the internal combustion engine.

  Further, in configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, when the heating means is a burner, the heating means operation determination unit determines whether or not the burner may be misfired during the operation of the burner. When it is determined that the burner may misfire, it is preferable that the heating means controller stops the burner.

According to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the first passage and the second passage that branch upstream from the reducing agent injection valve and merge downstream from the reducing agent injection valve and upstream from the reduction catalyst. The exhaust passage is branched into this passage, and a heating means for heating the exhaust gas is provided in a second passage different from the first passage provided with the reducing agent injection valve. Therefore, the heat quantity of the exhaust gas heated to high temperature by the heating means is not taken away by the filter, and the high temperature exhaust gas efficiently flows into the reduction catalyst, and the temperature of the reduction catalyst is quickly raised.
In addition, since the second passage different from the first passage provided with the reducing agent injection valve is provided with a heating means for heating the exhaust gas, the reducing agent injection valve is changed to a high temperature exhaust gas. It is not exposed and the reduction catalyst is not directly exposed to the heating means. Therefore, thermal damage of the reducing agent injection valve and thermal deterioration of the reduction catalyst are prevented.

  In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the first passage and the second passage branch on the downstream side of the filter and the upstream side of the reducing agent injection valve, thereby allowing all exhaust gas to pass through the filter. Therefore, PM does not adhere to the reduction catalyst or be released into the atmosphere.

  Further, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, when the flow rate ratio of the exhaust gas flowing through the second passage is 50% or less, the reduction injected from the reducing agent injection valve provided in the first passage. There is no possibility of significantly reducing the agent splitting and evaporation effects, and it is possible to prevent the exhaust gas having a very high temperature from flowing into the reduction catalyst during the operation of the heating means.

  Further, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, when the heating means is a burner, the second passage is provided with a flame collision part, so that the reduction catalyst is directly exposed to the flame radiated from the burner. Is prevented.

  Further, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, the control unit includes the catalyst temperature determination unit and the heating means control unit, so that the exhaust gas can be heated according to the necessity of raising the temperature of the reduction catalyst. it can. Therefore, the temperature of the reducing catalyst can be raised quickly while preventing thermal damage of the reducing agent injection valve and thermal deterioration of the reducing catalyst.

  Further, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, the control unit controls the output of the burner so that the combustion temperature becomes 600 ° C. or higher, whereby unburned fuel is injected from the burner. Is prevented. Therefore, adhesion of unburned fuel to the reduction catalyst and release of unburned fuel into the atmosphere are prevented.

  Further, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the control unit includes a predetermined heating means operation determination unit, so that it is not necessary to raise the temperature of the reduction catalyst even when the temperature of the reduction catalyst is lower than the threshold value. It is possible to suppress the operation of the heating unit in a situation where it is difficult to ensure the stability of the operation of the heating unit or the heating unit.

  Further, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, when the heating means is a burner, the heating means control section stops the burner when the heating means operation determination section determines that the burner may misfire. This prevents the occurrence of misfire during the operation of the burner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be specifically described below with reference to the drawings as appropriate. However, this embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.
In addition, in each figure, what has attached | subjected the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

[First Embodiment]
1. FIG. 1 shows an overall configuration of an internal combustion engine exhaust purification device (hereinafter simply referred to as “exhaust purification device”) 10 according to a first embodiment of the present invention. ing.
The exhaust purification device 10 includes an exhaust passage 12 connected to an internal combustion engine 11. The exhaust passage 12 includes an upstream exhaust passage 12a and a downstream exhaust passage 12b, and a first passage 13 and a second passage branch between the upstream exhaust passage 12a and the downstream exhaust passage 12b. 14 is connected by an exhaust gas adjusting unit 50 having 14. The upstream side exhaust passage 12a and the exhaust gas adjustment unit 50, and the downstream side exhaust passage 12b and the exhaust gas adjustment unit 50 are connected to each other by mounting flanges 15a, 15b, 15c, and 15d provided at end portions, respectively.

  An oxidation catalyst 19 and a filter 20 are provided in the upstream exhaust passage 12a from the upstream side. In addition, a reduction catalyst 21 is provided in the downstream exhaust passage 12b, and temperature sensors 24 and 25 are attached to the upstream side and the downstream side of the reduction catalyst 21, respectively. Further, in the exhaust gas adjusting unit 50, a reducing agent injection valve 27 is provided in the first passage 13, and a burner 70 as a heating unit is provided in the second passage 14. The exhaust purification device 10 includes a control unit 30 that controls the reducing agent injection valve 27 and the burner 70.

The filter 20 provided in the upstream side exhaust passage 12a is for collecting PM in the exhaust gas. For example, a known filter including a honeycomb structure filter made of a ceramic material is used. .
The oxidation catalyst 19 provided on the exhaust upstream side of the filter 20 is mainly used for regeneration control of the filter 20 and oxidizes unburned fuel contained in the exhaust gas by controlling the operation state of the internal combustion engine 11. The PM collected by the filter 20 is burned by this oxidation heat. As the oxidation catalyst 19, for example, a known oxidation catalyst is used, for example, a catalyst in which platinum is supported on alumina and a predetermined amount of rare earth element such as cerium is added.

The reduction catalyst 21 provided in the downstream side exhaust passage 12 b reduces NO _x in the exhaust gas using the reducing agent supplied from the reducing agent injection valve 27. Examples of the reduction catalyst 21 include a porous carrier containing strontium or barium as an active component, an alkaline earth metal such as magnesium, a rare earth metal such as cerium and lanthanum, a noble metal such as platinum and rhodium, and the like. In addition, a known reduction catalyst is used. The reduction catalyst 21 has a characteristic that the reduction efficiency of NO _x decreases when the catalyst temperature is lower than the activation temperature.

2. Exhaust Gas Adjusting Unit (1) Overall Configuration of Exhaust Gas Adjusting Unit FIGS. 2A to 2B, 3 and 4 show details of the configuration of the exhaust gas adjusting unit 50 in the exhaust emission control device of the present embodiment. It shows. FIG. 2B is a view of the exhaust gas adjusting unit 50 of FIG. 3 is a ZZ sectional view of FIG. 2A, and FIG. 4 is a YY sectional view of FIG.
The exhaust gas adjusting unit 50 is connected to an exhaust gas introduction chamber 51 communicating with the upstream side exhaust passage 12 a and a first opening 51 a provided in a part of the exhaust gas introduction chamber 51. A pipe 56, a burner cover 52 connected in communication with a second opening 51 b provided in a part of the exhaust gas introduction chamber 51, and a junction pipe 57 connected to the L-shaped pipe 56 and the burner cover 52. It has.

  A plurality of exhaust gas introduction holes 57a and 57b are provided in a portion arranged in the L-shaped tube 56 and a portion arranged in the burner cover 52 in the outer periphery of the merge pipe 57 (see FIG. 4). reference). Therefore, of the exhaust gas flowing into the exhaust gas introduction chamber 51, the exhaust gas flowing from the first opening 51a to the L-shaped tube 56 side flows into the merge pipe 57 from the plurality of exhaust gas introduction holes 57a, and downstream. It is led to the side exhaust passage 12b. In the exhaust purification apparatus of the present embodiment, the first passage 13 is configured by the L-shaped tube 56 and the merging tube 57. On the other hand, of the exhaust gas flowing into the exhaust gas introduction chamber 51, the exhaust gas flowing on the burner cover 52 side from the second opening 51b flows into the junction pipe 57 from the plurality of exhaust gas introduction holes 57b. In the exhaust gas purification apparatus of the present embodiment, the second passage 14 is constituted by the burner cover 52.

(2) Configuration of First Passage Reducing agent injection valve 27 is fixed to the end of merging pipe 57 constituting first passage 13 opposite to the end on the downstream exhaust passage 12b side. The reducing agent injection valve 27 provided in the first passage 13 of the exhaust gas adjusting unit 50 is for supplying the reducing agent into the exhaust gas upstream of the reduction catalyst. An ON-OFF valve whose opening / closing is controlled by ON / OFF is used. The reducing agent injection valve 27 includes an electromagnetic control portion and a resin portion for achieving a precise valve opening operation.

As the reducing agent injected by the reducing agent injection valve 27, for example, an aqueous urea solution is used. When the urea aqueous solution is used as a reducing agent, the urea aqueous solution supplied into the exhaust gas is decomposed by the exhaust heat and ammonia is generated. Then, ammonia and NO _x in the exhaust gas undergo a reduction reaction in the reduction catalyst, and the NO _x is purified into nitrogen (N ₂ ) and water (H ₂ O). The reducing agent that can be used is not limited to one that generates ammonia, and unburned fuel (HC) may be used depending on the type of the reduction catalyst.

  In the exhaust purification apparatus of the present embodiment, the reducing agent injection valve 27 is arranged so that the central axis of the reducing agent injection shape injected from the reducing agent injection valve 27 coincides with the axis of the merging pipe 57. The reducing agent injection valve 27 injects the reducing agent in the axial direction of the merge pipe 57. Since the reducing agent injection valve 27 is arranged in this way, the reducing agent can be injected along the flow direction of the exhaust gas flowing through the first passage 13, and the reducing agent is uniformly distributed in the exhaust gas. In addition, the heat dissipation of the reducing agent injection valve 27 is made efficient. However, the arrangement position of the reducing agent injection valve 27 is not limited to the end of the merging pipe 57.

  Further, in the exhaust purification apparatus of the present embodiment, a mixer 18 for promoting the mixing and diffusion of the exhaust gas and the reducing agent is provided at the connection portion with the lower exhaust passage 12b which is the terminal portion of the first passage 13. Is provided. The form of the mixer 18 is not particularly limited, and various mixers are used. The position where the mixer 18 is provided is not particularly limited as long as it is downstream of the reducing agent injection valve 27 and upstream of the reduction catalyst. For example, a mixer may be provided between the connection portion of the L-shaped tube 56 and the junction tube 57 and the connection portion of the burner cover 52 and the junction tube 57.

  However, when the mixer 18 is provided on the downstream side of the connection portion of the burner cover 52 and the junction pipe 57 as in the exhaust gas adjustment unit 50 used in the exhaust purification apparatus of the present embodiment, the temperature of the reduction catalyst is increased. In this case, not only the reducing agent but also the amount of heat of the high-temperature exhaust gas that has passed through the second passage 14 can be diffused. Further, when the mixer 18 is provided at this position, the crystallized reducing agent can be dissolved by the amount of heat of the high-temperature exhaust gas even if the reducing agent crystal is generated in the mixer 18.

(3) Configuration of the second passage (3) -1 Heating means As the heating means provided in the second passage 14 of the exhaust gas adjusting unit 50, a heating wire, a burner or the like is used. In the purification device, a burner 70 is used. As shown in FIG. 3, the burner 70 provided in the exhaust purification apparatus of this embodiment has a glow plug 72 for heating fuel disposed in the axial hole 71 a of the nozzle 71. This is an air assist burner 70 that supplies fuel and air to the gap between the heating portion 73 and the nozzle 71 on the front end side. By using the glow plug 72 as the fuel ignition means, the fuel temperature is raised and the viscosity of the fuel is lowered, so that atomization of the fuel and promotion of fuel ignition are promoted.

  In the exhaust purification system of this embodiment, a low-power piston pump (not shown) is used as means for supplying air to the burner 70. If it is a low output piston pump, there is no possibility of lowering the exhaust temperature even if the piston pump is driven while the burner 70 is not ignited. Further, with the air assist burner 70, it is easy to remove the contamination generated in the gap between the nozzle 71 and the heating unit 73 by supplying air when the burner 70 is stopped, and to clean the gap. However, the heating means that can be used is not limited to the example described above.

  Further, the burner 70 has an exhaust gas temperature value detected by a temperature sensor (24 in FIG. 1) upstream of the reduction catalyst, or a temperature sensor (not shown) provided in the burner cover 52 or the first passage 13. Fuel is supplied so that the combustion temperature of the burner 70 estimated based on the temperature becomes 600 ° C. or higher. In a state where the estimated combustion temperature is 600 ° C. or higher, a large amount of unburned fuel is not discharged mixed with the flame. Release into the atmosphere is prevented.

(3) -2 Burner Cover The burner 70 is attached to the burner cover 52 so that the tip of the nozzle 71 faces the burner cover 52. As shown in FIGS. 3 and 4, the burner cover 52 includes a first small chamber 52 a provided on the exhaust gas introduction chamber 51 side, and a second small chamber 52 b to which a flame radiated from the burner 70 is guided. A large chamber 52c that communicates with the second small chamber 52b, and a communication chamber 52d that communicates with the large chamber 52c and guides the exhaust gas to the connecting pipe 57 that is a part of the first passage 13. The burner cover 52 bends the inflow direction and the outflow direction of the exhaust gas by 90 degrees.

  A cylindrical combustion tube 53 is disposed in the large chamber 52 c in the burner cover 70, and an exhaust gas introduction passage 54 is provided on the outer peripheral surface of the cylindrical combustion tube 53. It faces the first small chamber 52a provided on the exhaust gas introduction chamber 51 side. The exhaust gas introduction passage 54 of the cylindrical combustion tube 53 is offset from the central axis of the cylindrical combustion tube 53, and the exhaust gas flowing into the cylindrical combustion tube 53 through the exhaust gas introduction passage 54 causes the cylindrical combustion tube 53. A swirl flow is formed inside. Therefore, the mixing of the calorie | heat amount of the flame radiated | emitted by the burner 70 and exhaust gas, and promotion of combustibility are achieved.

  One end of the cylindrical combustion tube 53 is fixed to the side wall of the burner cover 52 so as to surround the burner 70, and the other end of the cylindrical combustion tube 53 faces the second small chamber 52b. As described above, the axial direction of the cylindrical combustion tube 53 forms 90 degrees with the inflow direction of the exhaust gas to the burner cover 52, and the outflow direction of the exhaust gas from the burner cover 52 also forms 90 degrees.

  In the exhaust gas adjusting section 50 in which the second passage 14 is configured in this way, the exhaust gas introduced into the cylindrical combustion tube 53 from the first small chamber 52a enters the second small chamber 52b while forming a swirl flow. Proceed toward. When the exhaust gas heated by the burner 70 in the cylindrical combustion pipe 53 is guided to the second small chamber 52b, it collides with the side wall of the burner cover 52 as the flame collision portion 55, and then flows into the large chamber 52c. It flows through 52d and is guided to the joining portion 17 with the first passage 13.

  Since the burner cover 52 is configured as described above and the exhaust passage from the burner 70 to the reduction catalyst is not linear, when the exhaust gas is heated using the burner 70, the burner 70 emits radiation. Even when the fired flame extends for a long time, it collides with the flame collision portion 55, so that the reduction catalyst is prevented from being directly exposed to the flame. Therefore, thermal degradation of the reduction catalyst is prevented.

(4) Configuration of Merged Portion As shown in FIG. 4, a merged tube 57 constituting the first passage 13 in the merged portion 17 of the first passage 13 and the second passage 14 of the exhaust gas adjusting unit 50. A plurality of exhaust gas introduction holes 57b are provided on the outer peripheral surface of the burner, and a burner cover 52 constituting the second passage 14 is connected so as to cover the outside. Since the joining portion 17 of the first passage 13 and the second passage 14 is configured in this manner, the high-temperature exhaust gas flowing through the second passage 14 with respect to the exhaust gas flowing through the first passage 13. Gas flows in from the 360 degree ambient direction. Therefore, the high-temperature exhaust gas flowing from the second passage 14 is sufficiently mixed with the exhaust gas flowing in the first passage 13, and the heat amount of the reducing agent and the exhaust gas with respect to the entire inlet surface of the reduction catalyst. Flows evenly.

  In the exhaust purification apparatus of the present embodiment, the first passage 13 and the second passage 14 are branched on the downstream side of the filter, but the branched portion may be on the upstream side of the filter. However, if the first passage 13 and the second passage 14 are branched on the downstream side of the filter, the entire amount is exhausted even during a period in which a part of the exhaust gas flows through the second passage 14 and is heated by the burner 70. Exhaust gas passes through the filter. Therefore, the exhaust particulates are prevented from adhering to the burner 70 and the reduction catalyst in the second passage 14 or being released into the atmosphere.

3. Control Unit Next, the control unit 30 provided in the exhaust emission control device of the present embodiment will be described with reference to FIG. FIG. 5 shows a configuration example represented by functional blocks with respect to the operation control of the burner 70 in the control unit 30.

  The control unit 30 is a catalyst temperature calculation unit (indicated as “catalyst temperature calculation” in FIG. 5) that calculates the temperature of the reduction catalyst, and a catalyst that determines whether or not the temperature of the reduction catalyst is equal to or higher than a predetermined threshold value. A temperature determination unit (denoted as “catalyst temperature determination” in FIG. 5) and a burner operation determination unit (denoted as “burner operation determination” in FIG. 5) for determining whether or not the burner 70 is operable based on the operating state of the internal combustion engine )), And a burner control unit (indicated as “burner control” in FIG. 5) for controlling the output of the burner 70 based on the determination results of the catalyst temperature determination unit and the burner operation determination unit. Yes. Each of these units is specifically realized by executing a program by a microcomputer (not shown).

  The catalyst temperature calculation unit is a part that estimates the temperature Tcat of the reduction catalyst by calculation based on the sensor value Tgu of the temperature sensor 24 upstream of the reduction catalyst and the sensor value Tgl of the temperature sensor 25 downstream of the reduction catalyst. The calculated temperature of the reduction catalyst is output to the catalyst temperature determination unit. However, the estimation method of the temperature Tcat of the reduction catalyst is not limited to the example described above.

  The catalyst temperature determination unit is a part that determines whether or not the temperature of the reduction catalyst is equal to or higher than a predetermined threshold and estimates whether or not the reduction catalyst is in an activated state. In the exhaust purification apparatus of the present embodiment, the catalyst temperature determination unit determines whether or not the temperature Tcat of the reduction catalyst calculated by the catalyst temperature calculation unit is lower than the activation temperature Tact. Since the activation temperature Tact of the reduction catalyst is generally a value of about 200 to 250 ° C., the threshold value is selected and set within a range of 200 to 250 ° C., for example, depending on the characteristics of the reduction catalyst used.

  The burner operation determination unit is a portion that determines whether the burner 70 can be operated based on the operating state of the internal combustion engine. Even if the reduction catalyst is not in the activated state, there is a case where it is not desired to operate the burner 70, so the burner operation determination unit determines whether the burner 70 can be operated. In the exhaust purification device of the present embodiment, the burner operation determination unit detects the rotational speed Ne of the internal combustion engine, the fuel injection amount Q to the internal combustion engine, and the like, and considers the rotational speed Ne, the fuel injection amount Q, and the like. The operating state of the internal combustion engine is estimated, and whether or not the burner 70 can be operated is determined.

For example, because the vehicle is a like when using the engine brake during traveling, in the case of the NO _X flow rate is small operating state discharged from the internal combustion engine is not necessary to raise the temperature of the reduction catalyst downhill, burner operation The determination unit instructs to wait for the operation of the burner 70. Further, when the exhaust gas flow rate or flow rate increases due to a sudden increase in the rotational speed Ne of the internal combustion engine, the burner 70 may misfire, so the burner operation determination unit instructs the burner 70 to wait.
From the viewpoint of preventing misfire prevention of the burner 70, an exhaust flow rate sensor or an exhaust flow rate sensor is attached to the upstream exhaust passage, the second passage, or the like, and based on these sensor values, is there a risk of misfire of the burner 70? The burner operation determination unit can be configured to determine whether or not. Further, a temperature sensor may be disposed on the exhaust downstream side of the burner 70, and it may be directly determined whether or not a flame is emitted from the burner 70 based on the sensor value of the temperature sensor.

  The burner control unit is basically a part that outputs a drive signal for the burner 70 when it is necessary to raise the temperature of the reduction catalyst based on the determination result of the catalyst temperature determination unit. Further, in the exhaust purification apparatus of the present embodiment, the burner control unit detects the temperature of the exhaust gas heated to a high temperature by the burner 70, and applies the burner 70 to the burner 70 so that the detected exhaust gas temperature becomes 600 ° C. or higher. Control the fuel supply. However, when an instruction to wait for the operation of the burner is output from the burner operation determination unit, the burner control unit makes the operation of the burner 70 stand by regardless of the temperature of the reduction catalyst.

4). Next, an example of a routine of the control method of the exhaust purification device 10 shown in FIG. 1 will be specifically described based on the flowcharts of FIGS. 6 and 7. This routine is always executed while the internal combustion engine 11 is being started.

  First, in step S11 after the start, the temperature Tcat of the reduction catalyst 21 is calculated, and then the process proceeds to step S12 to determine whether or not the temperature Tcat of the reduction catalyst 21 is lower than the activation temperature Tact. When the temperature Tcat of the reduction catalyst 21 is lower than the activation temperature Tact, the process proceeds to step S13, whereas when the temperature Tcat of the reduction catalyst 21 is equal to or higher than the activation temperature Tact, the process proceeds to step S18.

If it is determined that the temperature Tcat of the reduction catalyst 21 is lower than the activation temperature Tact, the rotational speed Ne, the fuel injection amount Q, etc. of the internal combustion engine 11 are read in step S13, and the rotational speed Ne, the fuel injection amount Q, etc. are read in step S14. After estimating the operating state of the internal combustion engine 11 based on this, it is determined whether or not the burner 70 is operated in step S15.
If it is determined in step S15 that the burner 70 is to be operated, the process proceeds to step S16 to determine whether or not the burner 70 is currently operating. If it is determined in step S16 that the burner 70 is not operating, the burner 70 is operated in step S17, heating of the exhaust gas is started, and this routine is terminated. Then, it returns to step S11 again and the temperature Tcat of the reduction catalyst 21 is calculated. On the other hand, if it is determined in step S16 that the burner 70 is already operating, the routine is terminated without proceeding to step S17, and the process returns to step S11.

When it is determined in step S15 that the burner 70 is not operated, the process proceeds to step S18 to determine whether the burner 70 is currently operating. If it is determined in step S18 that the burner 70 is already operating, the process proceeds to step S19, the operation of the burner is stopped and this routine is terminated, and then the process returns to step S11. On the other hand, if it is determined in step S18 that the burner 70 is not in operation, this routine is terminated and the process returns to step S11.
If it is determined in step S12 that the temperature Tcat of the reduction catalyst 21 is equal to or higher than the activation temperature Tact, the process proceeds directly to step S18, and after the routine is completed through steps S18 to S19 described above. The process returns to step S11.

Thus, until it is determined in step S12 that the temperature Tcat of the reduction catalyst 21 is equal to or higher than the activation temperature Tact, whether or not the burner 70 needs to be operated in step S13 to step S19 and the misfire of the burner 70 are determined. The exhaust gas is heated while considering whether or not there is a risk of this, and the temperature of the reduction catalyst 21 is increased by the exhaust heat.
When it is determined in step S12 that the temperature Tcat of the reduction catalyst 21 is equal to or higher than the activation temperature Tact, if the burner 70 is operating in steps S18 to S19, the burner 70 is stopped and this routine is terminated. .

FIG. 7 shows an example of a control flow when the internal combustion engine 11 is stopped.
When a stop signal for the internal combustion engine 11 is input, it is first determined in step S20 whether or not the burner 70 is operating. If it is determined that the burner 70 is in operation, the process proceeds to step S21 to stop the operation of the burner, and this routine is terminated. On the other hand, if it is determined in step S20 that the burner 70 is not in operation, the present routine is terminated as it is.

As described above, in the exhaust purification device 10 of the present embodiment, when the temperature of the reduction catalyst 21 needs to be raised, the exhaust gas is heated by the burner 70 provided in the second passage. The reduction catalyst 21 is immediately activated to be heated while preventing damage and thermal deterioration of the reduction catalyst, and the reduction of NO _{x in} the exhaust gas is started early. Further, the exhaust purification device 10 of the present embodiment is configured such that the ratio of the flow rate of exhaust gas flowing through the second passage 14 to the total amount of exhaust gas discharged from the internal combustion engine 11 is 50% or less, Since the flow rate of the exhaust gas flowing to the first passage 13 side does not become excessively small, the effect of splitting and evaporating the reducing agent injected by the reducing agent injection valve 27 provided in the first passage 13 is remarkable. There is no decline.
Further, the exhaust purification device 10 of the present embodiment stops the burner 70 when it is determined that the burner 70 may be misfired based on the operating state of the internal combustion engine 11 when the burner 70 is in operation. The misfire of the burner 70 is avoided.

[Second Embodiment]
The exhaust gas purification apparatus according to the second embodiment of the present invention has the same configuration as that of the first embodiment, except that the configuration of the exhaust gas adjusting unit is different from that of the first embodiment. Hereinafter, the exhaust emission control device of the present embodiment will be described focusing on the configuration of the exhaust gas adjusting unit.

FIGS. 8A to 8B and FIGS. 9A to 9B show the configuration of the exhaust gas adjusting unit 100 provided in the exhaust purification apparatus of the present embodiment. 8B is a view of the exhaust gas adjusting unit 100 of FIG. 8A as viewed in the direction of arrow P, and FIG. 9A is a QQ cross-sectional view of FIG. (B) is RR sectional drawing of Fig.8 (a).
The exhaust gas adjusting unit 100 includes a casing 101 provided with an exhaust gas introduction port 101a. A burner cover 102 and a junction pipe 103 are accommodated in the casing 101.

  A gap 105 is formed between the burner cover 102 and the casing 101, and exhaust gas that does not flow into the burner cover 102 flows through the gap 105 and is guided to the junction pipe 103. A plurality of exhaust gas introduction holes 103 a are provided in a portion of the outer periphery of the merge pipe 103 disposed in the gap 105. Therefore, the exhaust gas flowing through the gap 105 between the burner cover 102 and the casing 101 and led to the merging pipe 103 flows into the merging pipe 103 from the plurality of exhaust gas introduction holes 103a, and is led to the downstream exhaust passage 12b. It is burned. In the exhaust purification apparatus of the present embodiment, the first passage 113 is constituted by the gap 105 and the merge pipe 103.

  Further, the reducing agent injection valve 27 is fixed to an end portion of the confluence pipe 103 constituting the first passage 113 on the side opposite to the end portion on the downstream side exhaust passage 12b side. The central axis of the injection shape of the reducing agent injected from the reducing agent injection valve 27 coincides with the axis of the merging pipe 103, and the reducing agent injection valve 27 injects the reducing agent toward the axial direction of the merging pipe 103. To do. Further, in the exhaust gas adjustment unit 100 used in the exhaust purification device of the present embodiment, the lower portion that is the terminal portion of the first passage 113 is the same as the exhaust gas adjustment unit used in the exhaust purification device of the first embodiment. A mixer 18 is disposed at a connection portion with the side exhaust passage 12b.

  The burner cover 102 includes a first small chamber 102 a provided on the exhaust gas inlet 101 a side of the casing 101, a second small chamber 102 b to which a flame radiated from the burner 70 is guided, and a second small chamber. A large chamber 102c that communicates with 102b and in which the cylindrical combustion tube 53 is disposed, and a communication chamber 102d that communicates with the large chamber 102c and guides exhaust gas to the joining portion 117 with the first passage 113, The burner cover 102 bends the exhaust gas inflow direction and the outflow direction at 90 degrees. In the exhaust gas purification apparatus of the present embodiment, the second passage 114 is constituted by the first small chamber 102a, the second small chamber 102b, the large chamber 102c, and the communication chamber 102d.

  In the large chamber 102c of the burner cover 102, a cylindrical combustion tube 53 provided with an exhaust gas introduction passage 54 with an end 54a facing the first small chamber 102a is provided, as in the exhaust gas adjusting portion of the first embodiment. One end of the cylindrical combustion tube 53 is fixed to the side wall of the burner cover 102 so as to surround the burner 70, and the other end faces the second small chamber 102b.

  In the exhaust gas adjusting unit 100 used in the exhaust purification apparatus of this embodiment, the burner 70 is attached to the casing 101 so that the tip of the nozzle 71 faces the large chamber 102c of the burner cover 102. Even when the flame radiated from the burner 70 extends for a long time, it collides with the flame collision portion 55, so that the reduction catalyst is not directly exposed to the flame, and thermal degradation of the reduction catalyst is prevented.

  A plurality of exhaust gas introduction holes 103 b are also provided in a portion of the outer periphery of the merge pipe 103 constituting the first passage 113 disposed in the communication chamber 102 d of the burner cover 102. Therefore, the exhaust gas flowing through the second passage 114 flows into the joining pipe 103 via the plurality of exhaust gas introduction holes 103b on the outer periphery of the joining pipe 103 disposed in the communication chamber 102d, and enters the first passage 113. Mixed with exhaust gas flowing through.

As described above, the exhaust gas adjusting unit 100 used in the exhaust gas purification apparatus according to the present embodiment has the second passage 114 in which the exhaust gas is heated when the temperature of the reduction catalyst needs to be increased. It has a double pipe structure provided inside. Therefore, the second passage 114 through which the high-temperature exhaust gas heated by the burner 70 passes is not exposed to the outside, and the surface temperature of the exhaust gas adjusting unit 100 is kept relatively low. As a result, the influence of heat on the outside of the exhaust purification device is reduced, and safety is further improved.
Furthermore, since the second passage 114 through which the high-temperature exhaust gas heated by the burner 70 flows is surrounded by the first passage 113, the exhaust gas adjusting unit 100 used in the exhaust purification device of the present embodiment is The heat loss of the exhaust gas flowing through the second passage 114 is reduced. Therefore, the heating efficiency of the exhaust gas by the burner 70 is improved, and the fuel consumption during the operation of the burner 70 is reduced.

1 is a schematic diagram showing an overall configuration of an exhaust gas purification apparatus for an internal combustion engine according to a first embodiment of the present invention. It is an external view for demonstrating the structure of the exhaust-gas adjustment part with which the exhaust gas purification apparatus of 1st Embodiment is equipped. It is sectional drawing for demonstrating the internal structure of the exhaust-gas adjustment part with which the exhaust gas purification apparatus of 1st Embodiment is equipped. It is another sectional view for explaining an internal configuration of an exhaust gas adjusting part with which the exhaust emission control device of the first embodiment is provided. It is a block diagram which shows the structural example of the control part of the exhaust gas purification apparatus of an internal combustion engine. It is a flowchart which shows an example of the control method of the exhaust gas purification device of an internal combustion engine. It is a flowchart which shows an example of the control method of the exhaust gas purification apparatus when an internal combustion engine stops. It is an external view for demonstrating the structure of the exhaust-gas adjustment part with which the exhaust gas purification apparatus of 2nd Embodiment is equipped. It is sectional drawing for demonstrating the internal structure of the exhaust-gas adjustment part with which the exhaust gas purification apparatus of 2nd Embodiment is equipped. It is a figure for demonstrating the structure of the conventional exhaust gas purification apparatus of an internal combustion engine. It is a figure for demonstrating the structure of the conventional exhaust gas purification apparatus of an internal combustion engine.

Explanation of symbols

10: exhaust purification device, 11: internal combustion engine, 12: exhaust passage, 12a: upstream exhaust passage, 12b: downstream exhaust passage, 13: first passage, 13a: bent portion, 14: second passage, 15a 15b, 15c, 15d: mounting flange, 17: junction, 18: mixer, 19: oxidation catalyst, 20: particulate filter, 21: reduction catalyst, 24/25: temperature sensor, 27: reducing agent injection valve, 30 : Control unit, 50: exhaust gas adjusting unit, 51: exhaust gas introduction chamber, 51a: first opening, 51b: second opening, 52: burner cover, 52a: first small chamber, 52b: second Small chamber, 52c: large chamber, 52d: communication chamber, 53: cylindrical combustion pipe, 54: exhaust gas introduction passage, 54a: end, 55: flame collision section, 56: L-shaped pipe, 57: junction pipe, 57a 57b: exhaust gas introduction hole, 70 Heating means (burner), 71: nozzle, 71a: axial hole, 72: glow plug, 73: heating unit, 100: exhaust gas adjusting unit, 101: casing, 101a: exhaust gas inlet, 102: burner cover, 103 : Confluence pipe, 103a and 103b: exhaust gas introduction hole, 105: gap, 113: first passage, 114: second passage, 117: confluence portion

Claims (8)

A particulate filter provided in the exhaust passage of the internal combustion engine for collecting exhaust particulates in the exhaust gas, a reducing agent injection valve for injecting a reducing agent into the exhaust passage, and the exhaust gas using the reducing agent in the exhaust gas a reduction catalyst for reducing NO _X in an exhaust purification device of an internal combustion engine which is sequentially provided from the exhaust upstream side,
The exhaust passage includes a first passage and a second passage that branch on the upstream side of the reducing agent injection valve and merge on the downstream side of the reducing agent injection valve and the upstream side of the reduction catalyst. The reducing agent injection valve is provided in the first passage,
An exhaust gas purification system for an internal combustion engine, comprising: a heating unit provided in the second passage for heating the exhaust gas flowing through the second passage; and a control unit for controlling the heating unit. apparatus.   2. The exhaust gas purification of an internal combustion engine according to claim 1, wherein the first passage and the second passage are branched downstream of the particulate filter and upstream of the reducing agent injection valve. apparatus.   The exhaust gas purification of the internal combustion engine according to claim 1 or 2, wherein a flow rate ratio of the exhaust gas flowing through the second passage is set to 50% or less of a flow rate ratio of the exhaust gas discharged from the internal combustion engine. apparatus.   4. The internal combustion engine according to claim 1, wherein the heating unit is a burner, and the second passage includes a flame collision unit that collides a flame radiated from the burner. Engine exhaust purification system.   The control unit is a catalyst temperature determination unit that determines whether or not the temperature of the reduction catalyst is equal to or higher than a predetermined threshold, and a heating unit control that controls the heating unit based on a determination result by the catalyst temperature determination unit The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust gas purification device is an internal combustion engine.   The said control part controls the output of the said heating means so that the combustion temperature of the said burner as the said heating means may be 600 degreeC or more at the time of the action | operation of the said heating means. An exhaust emission control device for an internal combustion engine according to claim 1.   The exhaust control device for an internal combustion engine according to claim 5 or 6, wherein the control unit includes a heating means operation determination unit that determines whether the heating means is operable based on an operating state of the internal combustion engine. . When the heating means is the burner, the heating means operation determination unit determines whether or not the burner may misfire during the operation of the burner,
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 5 to 7, wherein when it is determined that the burner may misfire, the heating means control unit stops the burner. .

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