JP2012052474A - Exhaust emission control device and sensor for exhaust purification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat insulating performance of an inspection filter in an exhaust emission control device and a sensor for exhaust purification.SOLUTION: The exhaust emission control device for improving insulating performance of an inspection filter includes: a main particulate capturing filter disposed in a main exhaust line of an internal combustion engine; and a sensor comprising an inspection filter disposed in a sub-exhaust line branched from the main exhaust line and an outer cylinder covering the inspection filter. An outer circumference part of the outer cylinder has a heat insulating structure.

Description

  The present invention relates to an exhaust gas purification device and an exhaust gas purification sensor for an internal combustion engine, and more particularly to an inspection filter installed in a sub exhaust line branched from a main exhaust line of an internal combustion engine in which a main particulate trapping filter is installed, and its filter The present invention relates to an exhaust purification device including a sensor including an outer cylinder that covers an inspection filter, and an exhaust purification sensor used in the exhaust purification device.

  2. Description of the Related Art Conventionally, there has been an exhaust purification device that uses a particulate particulate filter (DPF) made of a porous ceramic to capture particulates (PM) mainly composed of C (carbon) discharged from a diesel engine. Are known. In this conventional exhaust purification apparatus, PM gradually accumulates in the DPF as the diesel engine is continuously used. For this reason, it is possible to prevent PM from being released into the atmosphere from the diesel engine side, and it is possible to purify the exhaust gas.

  If cracks or the like occur in the DPF, PM may leak to the exhaust line downstream of the DPF. As a measure for preventing cracks and the like in the DPF, it is effective to oxidize and remove PM in the DPF at an appropriate timing. Therefore, in order to measure the amount of PM accumulated in the DPF, a sub exhaust line connected to the upstream side of the DPF and taking in part of the exhaust gas discharged from the internal combustion engine as a sample gas is provided, and the PM is disposed on the sub exhaust line. It is conceivable to provide an inspection filter as a sensor (see, for example, Patent Document 1).

  Such a PM sensor can measure the pressure difference before and after the inspection filter and obtain the amount of PM in the auxiliary exhaust line. Furthermore, it is possible to diagnose PM leakage to the downstream side of the DPF or obtain the amount of PM deposited on the DPF.

European Patent No. 1914537

  By the way, the PM sensor inspection filter is disposed on the exhaust line and is exposed to the exhaust gas, so that PM accumulates. However, if PM exceeds a certain amount on the inspection filter, the sub-exhaust It becomes difficult to introduce sample gas into the line, and the detection accuracy decreases. Therefore, it is conceivable to provide a removal device such as an electric heater in the inspection filter in order to oxidize and remove the PM deposited on the inspection filter.

  In order to operate a removal device such as an electric heater, it is necessary to supply electric power from the vehicle battery. In order to efficiently oxidize and burn PM in the inspection filter using the removal device, an inspection is required. It is not appropriate that the filter structure has a structure that allows heat from the removal device to escape. In addition, if a large amount of PM accumulates on the inspection filter, the amount of heat generated when removing the PM from the inspection filter increases, which may cause damage to the inspection filter. Although it is effective to remove PM from the filter every time a small amount of PM is deposited, it is desirable to suppress the input power per one as much as possible.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an exhaust purification device and an exhaust purification sensor that have improved heat insulation performance in a test filter.

  The above object is obtained from a main particulate trap filter installed in a main exhaust line of an internal combustion engine, an inspection filter installed in a sub exhaust line branched from the main exhaust line, and an outer cylinder covering the inspection filter. An exhaust purification device comprising: a sensor, wherein the outer peripheral portion of the outer cylinder has a heat insulating structure.

  Further, the above object is to purify exhaust gas comprising a test filter and an outer cylinder covering the test filter, which are installed in a sub exhaust line branched from the main exhaust line of the internal combustion engine in which the main particulate trapping filter is installed. This is achieved by an exhaust gas purification sensor in which the outer peripheral portion of the outer cylinder has a heat insulating structure.

  In the inventions of these aspects, the outer peripheral portion of the outer cylinder that covers the inspection filter installed in the auxiliary exhaust line has a heat insulating structure. Therefore, it is possible to improve the heat insulation performance of the inspection filter.

  In the above exhaust purification apparatus, based on the differential pressure detection means for detecting the pressure difference generated between the upstream side and the downstream side of the inspection filter in the auxiliary exhaust line, and the detection result by the differential pressure detection means. And removing means for burning and removing the fine particles captured by the inspection filter.

  In the above-described exhaust purification device or exhaust purification sensor, the outer peripheral portion of the outer cylinder may be constituted by a double pipe as a heat insulating structure.

  In this case, the outer peripheral part of the outer cylinder may have an air layer surrounded between the inner wall and the outer wall of the double pipe.

  Moreover, the outer peripheral part of the said outer cylinder is good also as having a vacuum layer enclosed between the inner wall and outer wall of a double tube.

  Furthermore, the outer peripheral part of the outer cylinder may have a heat insulating mat surrounded between the inner wall and the outer wall of the double pipe.

  ADVANTAGE OF THE INVENTION According to this invention, the heat insulation performance in an exhaust gas purification apparatus and an exhaust gas purification sensor can be improved.

1 is an overall configuration diagram of an exhaust emission control device according to an embodiment of the present invention. It is a principal part block diagram of the exhaust gas purification apparatus which is one Example of this invention. It is a principal part block diagram of the exhaust gas purification apparatus which is a modification of this invention. It is a principal part block diagram of the exhaust gas purification apparatus which is a modification of this invention. It is a whole block diagram of the exhaust gas purification apparatus which is a modification of this invention.

  Hereinafter, a specific embodiment of an exhaust emission control device according to the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an exhaust emission control device 10 according to an embodiment of the present invention.

  An exhaust purification device (also referred to as an exhaust gas purification device or an exhaust gas purification device) 10 of this embodiment is provided on a main exhaust line 14 connected to an internal combustion engine (particularly a diesel engine) 12, as shown in FIG. A diesel oxidation catalyst (DOC) 16 and a main particulate capture filter (DPF) 18 are provided. The DOC 16 is a catalyst for removing easily oxidized carbon monoxide and hydrocarbons contained in exhaust gas (also referred to as exhaust gas) discharged from the internal combustion engine 12. The DPF 18 is a filter that can capture particulate matter (PM) contained in the exhaust gas discharged from the internal combustion engine 12.

  The exhaust purification device 10 of the present embodiment is a device for purifying exhaust gas discharged from the internal combustion engine 12 to the atmosphere, and a failure occurs in the DPF 18 so that an amount of PM equal to or greater than a threshold is on the main exhaust line 14. When this leaks to the downstream side of the DPF 18, it is possible to detect this failure and perform an alarm, blinking of the lamp, lighting, and the like. The exhaust purification device 10 includes a PM sensor 20 as an exhaust purification sensor for detecting a failure of the DPF 18.

  FIG. 2 is a block diagram of the main part of the exhaust emission control device 10 according to one embodiment of the present invention. A sub exhaust line 22 provided separately from the main exhaust line 14 communicating with the atmosphere is connected to the DPF 18 downstream of the main exhaust line 14. The sub exhaust line 22 is branched from the main exhaust line, and a part of the exhaust gas can flow in. The sub exhaust line 22 has a channel cross-sectional area smaller than the channel cross-sectional area of the main exhaust line. The PM sensor 20 is disposed in the sub exhaust line 22 and detects PM leakage of the DPF 18 based on the amount of PM accumulated in the sub exhaust line 22 or the concentration of PM in the exhaust gas flowing through the sub exhaust line 22. judge.

  The PM sensor 20 includes an inspection filter 28 provided on the sub exhaust line 22 and an outer cylinder that covers the inspection filter 28. The PM sensor 20 may be configured to further include a differential pressure gauge, a flow meter, and a temperature measurement unit. A suction means (not shown) such as a pump is connected to the auxiliary exhaust line 22 downstream of the inspection filter 28. Part of the exhaust gas in the main exhaust line 14 that has passed through the DPF 18 is drawn into the sub exhaust line 22 side by being sucked by a pump or the like, and passes through the inspection filter 28.

  The inspection filter 28 is a filter for calculating the amount of PM accumulated in the sub exhaust line 22 or the concentration of PM contained in the exhaust gas exhausted from the internal combustion engine 12, and captures PM. Is possible. The inspection filter 28 is made of a material such as porous ceramic similar to the DPF 18, and is formed in a cylindrical shape or other than a cylindrical shape (for example, a square 1 cell, a 3 × 3 cell, or the like). The inspection filter 28 has a soot storage capacity smaller than the soot storage capacity of the DPF 18.

  A differential pressure gauge (not shown) of the PM sensor 20 is an electrical signal corresponding to a differential pressure ΔP between the inlet and outlet of the inspection filter 28 in the auxiliary exhaust line 22 (that is, a pressure difference between the upstream side and the downstream side). For example, a known pressure gauge such as a diaphragm type, a gauge type, a bellows type, and a thermal type. The differential pressure gauge is electrically connected to an arithmetic unit mainly composed of a microcomputer. The output of the differential pressure gauge is supplied to this calculation unit. The calculation unit detects a pressure difference ΔP generated between the upstream side and the downstream side of the inspection filter 28 in the auxiliary exhaust line 22 based on the output signal of the differential pressure gauge.

  A part of the sub exhaust line 22 is formed by a cylindrical outer cylinder (canister) 24 that constitutes at least a part of a pipe that guides the exhaust gas flowing in from the main exhaust line 14 side to the inspection filter 28 side. The canister 24 is fixed on the auxiliary exhaust line 22 by a cylindrical jig 26. The canister 24 is made of a high-strength member such as stainless steel, and is attached to the jig 26 by welding or the like. The inspection filter 28 is held by the cylindrical jig 26 or the canister 24 with a mat or ceramic paste.

  The canister 24 covers the outer peripheral side of the cylindrical inspection filter 28 extending in the axial direction, and guides the exhaust gas flowing in from the main exhaust line 14 side to the inspection filter 28. The end of the inspection filter 28 protrudes toward the exhaust gas inflow side on the inner peripheral side of the canister 24. For this reason, when the exhaust gas containing PM is guided to the inspection filter 28 on the auxiliary exhaust line 22, the PM accumulates on the outer peripheral side of the inspection filter 28.

  A heater 32 is disposed on the inner peripheral side of the inspection filter 28. The heater 32 is a heating wire, a sheath heater, a ceramic heater, or the like, and is heated by supplying electric power from a battery mounted on a vehicle or the like on which the internal combustion engine 12 is mounted. The heater 32 heats the entire inspection filter 28 to a predetermined temperature (for example, 600 ° C.), thereby burning PM accumulated on the outer wall of the inspection filter 28 to regenerate the inspection filter 28. The timing of power supply to the heater 32 is controlled based on the detection result of the pressure difference ΔP in the auxiliary exhaust line 22 by the arithmetic unit, the travel distance or travel time of the vehicle.

  Next, operation | movement of the exhaust gas purification apparatus 10 of a present Example is demonstrated.

  In this embodiment, the exhaust gas discharged from the internal combustion engine 12 flows through the main exhaust line 14 and passes through the DPF 18 and then is released to the atmosphere, or flows into the sub exhaust line 22 and enters the PM sensor 20. be introduced. The PM in the exhaust gas introduced into the PM sensor 20 is adsorbed and deposited on the inspection filter 28 of the PM sensor 20.

  The calculation unit detects a pressure difference ΔP generated between the upstream side and the downstream side of the inspection filter 28 in the auxiliary exhaust line 22 based on the output signal of the differential pressure gauge. Then, based on the pressure difference ΔP, the amount of PM deposited on the inspection filter 28 or the concentration of PM in the exhaust gas flowing through the auxiliary exhaust line 22 is calculated, and based on the calculated amount or concentration of PM, The presence or absence of PM leakage from the DPF 18 is determined. As a result of the determination, if it is determined that PM leakage from the DPF 18 has occurred, an alarm, lamp blinking, lighting, or the like is performed. Therefore, it is possible to calculate the PM accumulation amount of the inspection filter 28 to determine whether or not the DPF 18 has failed, and to notify the driver of the vehicle or the like on which the exhaust purification device 10 is mounted when the failure is determined.

  The calculation unit also determines whether the amount of PM deposited on the inspection filter 28 based on the pressure difference ΔP calculated as described above is equal to or greater than a predetermined threshold value. The predetermined threshold is set to the minimum value of the PM accumulation amount that requires the regeneration of the inspection filter 28. When it is determined that the PM accumulation amount is equal to or greater than the predetermined threshold, power is supplied from the battery to the heater 32 to heat the inspection filter 28.

  When the inspection filter 28 is heated by the operation of the heater 32, the PM deposited on the inspection filter 28 is burned, whereby the inspection filter 28 is regenerated. Therefore, even if PM accumulates excessively on the inspection filter 28, the PM can be burned by the action of the heater 32 to regenerate the inspection filter 28.

  By the way, in order to regenerate the inspection filter 28 by burning the accumulated PM, it is necessary to supply power to the heater 32 from the battery. In this regard, in order to efficiently oxidize and burn the deposited PM in the inspection filter 28, the heat insulation performance of the inspection filter 28 and its surroundings is ensured so that heat from the heater 32 is efficiently transmitted to the inspection filter 28. Is desirable. Hereinafter, the characteristic part of a present Example is demonstrated.

  In the present embodiment, the canister 24 constituting a part of the auxiliary exhaust line 22 is provided in a cylindrical shape so as to cover the outer peripheral side of the inspection filter 28, but the outer periphery of the canister 24 has an inner wall (small diameter). Part) and an outer wall (large diameter part), it is comprised by the double tube which forms internal space. The double pipe of the canister 24 extends in the axial direction from the exhaust gas inlet of the canister 24 to the attachment position of the canister 24 and a jig 26 for fixing the canister 24 on the auxiliary exhaust line 22. Yes. In the outer peripheral portion of the canister 24, an air layer 34 filled with air may be formed between the inner wall and the outer wall.

  In the PM sensor 20, the outer peripheral portion of the canister 24 has a heat insulating effect by a double tube that sandwiches the air layer 34 and the like. For this reason, since heat from the heater 32 inside the canister 24 is difficult to escape to the outside of the canister 24, the temperature of the inspection filter 28 arranged inside the canister 24 is easily raised by the operation of the heater 32, and the inspection filter 28 Is easily maintained at a high temperature.

  Therefore, according to the present embodiment, it is possible to improve the heat insulation performance of the PM sensor 20 (particularly the inspection filter 28), and as a result, the PM deposited on the inspection filter 28 by the operation of the heater 32. Can be efficiently oxidized and removed.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope described in the claims.

  For example, in the above embodiment, the PM sensor 20 as shown in FIG. 2 is used. However, the present invention is not limited to this, and the PM sensor 50 as shown in FIG. 3 may be used. .

  That is, the PM sensor 50 as an exhaust purification sensor for detecting a failure of the DPF 18 is configured by an inspection filter 28 provided on the sub exhaust line 22 and an outer cylinder (canister) 52 that covers the inspection filter 28. ing. A part of the sub exhaust line 22 is formed by a canister 52. The canister 52 is a cylindrical member that constitutes at least a part of a pipe that guides the exhaust gas flowing in from the main exhaust line 14 side to the inspection filter 28 side. The inspection filter 28 is held on the inner peripheral side of the canister 52 by a support member 54 provided at one end of the canister 52 and a support member 56 provided at the other end of the canister 52.

  The canister 52 covers the outer peripheral side of the cylindrical inspection filter 28 extending in the axial direction, and guides the exhaust gas flowing in from the main exhaust line 14 side to the inspection filter 28. The end of the inspection filter 28 protrudes toward the exhaust gas inflow side on the inner peripheral side of the canister 52. For this reason, when exhaust gas containing PM is guided to the inspection filter 28 on the sub exhaust line 22, PM accumulates on the outer peripheral side of the inspection filter 28.

  A heater may be provided on the inner peripheral side of the inspection filter 28. This heater is a heating wire, a sheath heater, a ceramic heater, or the like that is heated by power supplied from a battery mounted on a vehicle or the like in which the internal combustion engine 12 is mounted. This heater has a role of heating the entire inspection filter 28 to a predetermined temperature (for example, 600 ° C.). When the inspection filter 28 is heated to a predetermined temperature by the heater, the PM deposited on the outer wall of the inspection filter 28 is burned to regenerate the inspection filter 28. The timing of power supply to the heater is controlled based on the detection result of the pressure difference ΔP in the auxiliary exhaust line 22 by the calculation unit, the travel distance or travel time of the vehicle.

  In the structure of the PM sensor 50 of this modification, the canister 52 that constitutes a part of the auxiliary exhaust line 22 is provided so as to cover the outer peripheral side of the inspection filter 28. The outer periphery of the canister 52 is It is comprised by the double tube which forms internal space with an inner wall and an outer wall. The double pipe of the canister 52 extends in the axial direction from the exhaust gas inlet of the canister 52 to the exhaust gas discharge jig to which the canister 52 is fixed. In the outer peripheral portion of the canister 52, an air layer 58 filled with air may be formed between the inner wall and the outer wall.

  In such a PM sensor 50, the outer peripheral portion of the canister 52 has a heat insulating action by a double pipe with an air layer or the like interposed therebetween, and therefore heat from the heater inside the canister 52 is difficult to escape to the outside of the canister 52. The temperature of the inspection filter 28 disposed inside the heater is easily raised by the operation of the heater, and the inspection filter 28 is easily maintained at a high temperature. Therefore, also in this modification, it is possible to obtain the same effect as the above-described embodiment.

  In the above embodiment, the PM sensor 20 is formed with the air layer 34 filled with air between the inner wall and the outer wall of the double pipe on the outer peripheral portion of the canister 24. 4A, as the PM sensor 100, a vacuum layer 102 having a pressure lower than the atmospheric pressure is formed between the inner wall and the outer wall of the double tube at the outer peripheral portion of the canister 24. As shown in FIG. It is good to do. In such a structure, the outer peripheral portion of the canister 24 also has a heat insulating effect by the vacuum layer 102. For this reason, according to this modification, the heat from the heater 32 inside the canister 24 is less likely to escape to the outside of the canister 24 compared to the above-described embodiment, so the PM sensor 100 (particularly the inspection filter 28). ) Can be further improved, and an effect equal to or higher than that of the above-described embodiment can be obtained.

  Further, although the air layer 34 filled with air is formed as the PM sensor 20 between the inner wall and the outer wall of the double pipe on the outer peripheral portion of the canister 24, the present invention is not limited to this. As shown in FIG. 4B, as the PM sensor 200, a heat insulating mat 202 such as glass wool, alumina mat, ceramic fiber or the like may be inserted between the inner wall and the outer wall of the double pipe on the outer periphery of the canister 24. Good. In such a structure, the outer peripheral portion of the canister 24 also has a heat insulating action by the heat insulating mat 202. For this reason, according to this modification, the heat from the heater 32 inside the canister 24 is difficult to escape to the outside of the canister 24 compared to the above-described embodiment, so the PM sensor 200 (particularly the inspection filter 28). ) Can be further improved, and an effect equal to or higher than that of the above-described embodiment can be obtained.

  Further, in the above embodiment, the auxiliary exhaust line 22 connected to the downstream side of the DPF 18 of the main exhaust line 14 is provided, and the PM sensor 20 is disposed in the auxiliary exhaust line 22 to determine PM leakage from the DPF 18. Although the present invention is a system of the exhaust purification device 10, the present invention is not limited to this, and as shown in FIG. 5, a sub exhaust line 302 connected to the DPF 18 upstream side of the main exhaust line 14 is provided, and the sub exhaust line is provided. The PM sensor 304 may be disposed in the 302 and applied to the system of the exhaust gas purification apparatus 300 that measures the amount of PM accumulated in the DPF 18 or the concentration of PM in the exhaust gas flowing through the main exhaust line 14. The auxiliary exhaust line 302 may be connected to the upstream side of the DPF 18 of the main exhaust line 14 on the upstream side and to the downstream side of the DPF 18 of the main exhaust line 14 on the downstream side.

  Also in this modified example, if the outer peripheral portion of the canister 24 that covers the outer peripheral side of the inspection filter 28 of the PM sensor 304 is configured by a double tube that forms an internal space with the inner wall and the outer wall, the canister 24 can be used. Since the outer peripheral portion has a heat insulating action, it is possible to obtain the same effect as the above-described embodiment.

10,300 Exhaust purification device 12 Internal combustion engine 14 Main exhaust line 18 DPF
20, 50, 100, 200, 304 PM sensor 22, 302 Sub exhaust line 24, 52 Canister 28 Filter for inspection 32 Heater 34, 58 Air layer 54, 56 Support member 102 Vacuum layer 202 Thermal insulation mat

Claims (11)

A main particle capturing filter installed in a main exhaust line of an internal combustion engine, a test filter installed in a sub exhaust line branched from the main exhaust line, and a sensor comprising an outer cylinder covering the test filter. An exhaust purification device comprising:
An exhaust emission control device, wherein an outer peripheral portion of the outer cylinder has a heat insulating structure. Differential pressure detection means for detecting a pressure difference generated between the upstream side and the downstream side of the inspection filter in the auxiliary exhaust line;
Based on the detection result by the differential pressure detection means, removing means for burning and removing the fine particles captured by the inspection filter;
The exhaust emission control device according to claim 1, comprising:   The exhaust gas purification apparatus according to claim 1 or 2, wherein an outer peripheral portion of the outer cylinder is configured by a double pipe as a heat insulating structure.   The exhaust gas purification apparatus according to claim 3, wherein an outer peripheral portion of the outer cylinder has an air layer surrounded between an inner wall and an outer wall of the double pipe.   The exhaust gas purification apparatus according to claim 3, wherein an outer peripheral portion of the outer cylinder has a vacuum layer surrounded between an inner wall and an outer wall of the double pipe.   The exhaust gas purification apparatus according to claim 3, wherein an outer peripheral portion of the outer cylinder has a heat insulating mat surrounded between an inner wall and an outer wall of the double pipe. An exhaust purification sensor comprising a test filter and an outer cylinder covering the test filter installed in a sub exhaust line branched from a main exhaust line of an internal combustion engine in which a main particulate trapping filter is installed,
An exhaust gas purification sensor, wherein an outer peripheral portion of the outer cylinder has a heat insulating structure.   The exhaust gas purification sensor according to claim 7, wherein the outer peripheral portion of the outer cylinder is constituted by a double pipe as a heat insulating structure.   The exhaust gas purification sensor according to claim 8, wherein an outer peripheral portion of the outer cylinder has an air layer surrounded between an inner wall and an outer wall of the double pipe.   The exhaust gas purification sensor according to claim 8, wherein the outer peripheral portion of the outer cylinder has a vacuum layer surrounded by an inner wall and an outer wall of the double pipe.   The exhaust gas purification sensor according to claim 8, wherein the outer peripheral portion of the outer cylinder has a heat insulating mat surrounded between the inner wall and the outer wall of the double pipe.

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