JP5531459B2 - PM sensor - Google Patents

Description

  The present invention relates to a PM sensor for detecting breakage of a diesel particulate filter (DPF) that removes particulate matter in exhaust gas.

  Currently, in vehicles, diesel particulate filters (hereinafter referred to as DPF) that remove particulate matter (hereinafter referred to as PM) such as soot in exhaust gas are used as exhaust gas aftertreatment. Has been. When the function is lost due to damage or damage to the DPF during use, PM is released into the atmosphere.

  In OBD (On Board Diagnosis), which was legalized in 2003 in California, USA, detection of DPF breakage is obligatory, and along with this, development of a PM sensor to detect DPF breakage is underway. Yes.

  As shown in FIG. 6, the PM sensor 61 is provided on the downstream side of the DPF 63 provided in the exhaust passage 62 of the engine E.

  In the conventional PM sensor 61, PM (煤) 64 is ionized at a high voltage (for example, 2000 to 7000 V) using one electrode arranged on the upstream side, and an ion current is produced on the other electrode arranged on the downstream side. Is measured (see, for example, Patent Document 1).

  When the DPF 63 is damaged, the PM 64 flows into the exhaust passage on the downstream side of the DPF 63, and the ion current is detected by the PM sensor 61. That is, it is possible to detect damage to the DPF 63 by detecting the PM 64 on the downstream side of the DPF 63 using the PM sensor 61.

JP 2006-153716 A

  However, the above-described PM sensor was originally used for detecting smoke in a factory or the like, and various problems occur if this is applied to a vehicle as it is.

  For example, when mounted on a vehicle, the PM sensor is required to be small, but the conventional PM sensor uses a high voltage of 2000 to 7000 V, so the apparatus becomes very large. Moreover, since the apparatus becomes large, the cost is high and the weight is increased, which is not preferable.

  Furthermore, since the conventional PM sensor uses a high voltage, there are safety and insulation problems. Furthermore, the conventional PM sensor may cause radio noise or the like due to the use of a high voltage, and is considered unsuitable for vehicles.

  Accordingly, an object of the present invention is to provide a PM sensor that solves the above-described problems, is small in size and low in cost, and can detect damage to the DPF.

The present invention was devised to achieve the above object,
A PM sensor for detecting particulate matter in exhaust gas,
A base that is disposed in an exhaust passage of the vehicle and adheres the particulate matter; two electrodes that are formed on the surface of the base so as to face each other at a predetermined interval; and electrical continuity between the two electrodes. It is a PM sensor provided with a detection unit that detects and detects the presence or absence of adhesion of the particulate matter.

  The base is disposed in the exhaust passage on the downstream side of a diesel particulate filter (DPF) that removes particulate matter in the exhaust gas, and the detection unit detects electrical continuity between the electrodes. Then, it is good to detect the breakage of the diesel particulate filter.

  The base includes a built-in electric heater for burning particulate matter adhering to the base, and the base is energized when the engine is started or at regular intervals during engine operation. You may provide the reproduction | regeneration part which burns the particulate matter adhering to the stand.

  A ceramic glow plug may be used as the base, and the electrodes may be formed on the surface of the ceramic glow plug.

  According to the present invention, it is possible to provide a PM sensor that is small in size and low in cost and capable of detecting damage to a DPF.

It is a figure which shows PM sensor which concerns on one embodiment of this invention, (a) is a schematic perspective view, (b) is a front view when arrange | positioning in an exhaust passage. It is explanatory drawing for demonstrating the operation | movement principle of PM sensor of FIG. It is a figure which shows PM sensor which concerns on one embodiment of this invention, (a) is a schematic perspective view, (b) is the sectional side view. In this invention, it is a perspective view which shows the modification of the shape of the electrode of PM sensor. In this invention, it is a top view which shows the modification of the shape of the electrode of PM sensor. It is explanatory drawing explaining the conventional PM sensor.

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

  FIG. 1A is a schematic perspective view of a PM sensor according to the present embodiment, and FIG. 1B is a front view when the PM sensor is arranged in an exhaust passage.

  As shown in FIGS. 1A and 1B, the PM sensor 1 includes a substantially rectangular parallelepiped base 2 for adhering PM (soot) in exhaust gas, and a predetermined interval on the surface of the base 2. 2 and the two electrodes 3 and 4 formed to face each other, and a detection unit 5 that detects electrical continuity between the electrodes 3 and 4.

  The PM sensor 1 is for detecting breakage of the DPF (not shown), and the base 2 is disposed in the exhaust passage 11 on the downstream side of the DPF. The base 2 is made of ceramic, for example.

  The two electrodes 3 and 4 are formed on the surface facing the upstream side of the base 2 in the exhaust direction. The electrodes 3 and 4 include a linear portion 6 formed in a linear shape and a circular tip portion 7 formed at one end portion of the linear portion 6, and are spaced apart by a predetermined distance so that the tip portions 7 face each other. Formed.

  The distance between the electrodes 3 and 4 is, for example, about several mm, and the sensitivity can be improved as the distance between the electrodes 3 and 4 is reduced. The other ends of the straight portions 6 of the electrodes 3 and 4 are electrically connected to an ECM 8 mounted on the vehicle via a cable 12. The electrodes 3 and 4 are made of stainless steel, for example, and are formed by vacuum deposition or the like.

  The detection unit 5 detects whether or not PM is attached (deposited) to the base 2 between the electrodes 3 and 4 by detecting electrical conduction between the electrodes 3 and 4. Specifically, whether or not the electrodes 3 and 4 are electrically connected by constantly applying a predetermined voltage between the electrodes 3 and 4 and constantly monitoring the current between the electrodes 3 and 4. Is detected.

  The base 2 has a built-in electric heater 9 for burning PM adhering to the base 2. The electric heater 9 is electrically connected to the ECM 8 via the cable 13.

  The PM sensor 1 includes a regeneration unit 10 that energizes the electric heater 9 at the start of the engine or at regular intervals during engine operation (running) to burn the PM adhering to the base 2.

  Since the DPF does not capture 100% of the PM, even if the DPF is normal, if it is operated for a long time, the PM will adhere to the base 2 between the electrodes 3 and 4, and the DPF is actually damaged. In spite of this, there is a possibility that the DPF is erroneously detected as damaged.

  Therefore, in the present embodiment, the regeneration unit 10 energizes the electric heater 9 at the start of the engine or at regular intervals during engine operation, so that the PM 20 attached to the base 2 is burned.

  More specifically, the regenerating unit 10 accumulates the engine operating time, energizes the electric heater 9 at regular intervals during engine operation, and periodically burns PM. Try not to accumulate. Further, the regeneration unit 10 energizes the electric heater 9 when starting the engine, and burns the PM adhering to the base 2 also when starting the engine.

  As for the time interval during which the regeneration unit 10 energizes the electric heater 9 while the engine is running, it is measured in advance how much PM adheres to the base 2 while the engine is running. It may be set to a time interval (for example, about 3 to 4 hours) that does not detect the electrical continuity. The detection unit 5 and the reproduction unit 10 are mounted on the ECM 8.

Next, the operation principle of the PM sensor 1 will be described. When the DPF is damaged or damaged and its function is lost, the PM flows into the exhaust passage 11 on the downstream side of the DPF. As shown in FIG. 2, the PM 20 that has flowed out adheres to the surface of the base 2 facing upstream in the exhaust direction, and at this time, the PM 20 also adheres to the base 2 between the electrodes 3 and 4.

  Since PM20 (煤) is mainly made of carbon, it has conductivity. Therefore, when a certain amount of PM 20 adheres and accumulates on the base 2 between the electrodes 3 and 4, the electrodes 3 and 4 are electrically short-circuited and the electrodes 3 and 4 are electrically connected. The detector 5 detects electrical continuity between the electrodes 3 and 4 and detects breakage of the DPF. When detecting the breakage of the DPF, the detection unit 5 turns on, for example, a MIL (Malfunction Indicator Lamp).

  Thus, in the PM sensor 1, when the DPF is damaged, the drained PM 20 is accumulated on the base 2 between the electrodes 3 and 4, and the DPF is electrically connected between the electrodes 3 and 4. Detects damage.

  The operation of the present embodiment will be described.

  In PM sensor 1 concerning this embodiment, base 2 for making PM20 adhere, two electrodes 3 and 4 formed facing the surface of base 2 at predetermined intervals, and both electrodes 3 and 4 And a detector 5 for detecting the presence or absence of PM20 by detecting electrical continuity therebetween.

  By arranging the PM sensor 1 in the exhaust passage 11 on the downstream side of the DPF, it is possible to detect the PM 20 flowing out downstream of the DPF when the DPF is damaged, and it is possible to detect the damage of the DPF. The PM sensor 1 cannot measure the amount of PM20, but the OBD legalized in 2003 mentioned above does not specify the amount of PM20 and only requires detection of DPF breakage. Therefore, it is not necessary to measure the amount of PM20.

  The PM sensor 1 does not require a large-scale device as in the conventional method, and has a simple configuration in which the electrodes 3 and 4 are formed on the surface of the base 2, so that it is smaller and lower in cost than the conventional one. .

  In the PM sensor 1, the electric heater 9 is built in the base 2, and the electric heater 9 is energized when the engine is started or at regular intervals during engine operation to burn the PM 20 attached to the base 2. It has been removed.

  Thereby, since PM20 adhering to the base 2 can be removed every time the engine is started, detection can be started in a state where PM20 is not adhering to the base 2 between the electrodes 3 and 4. Further, by removing the PM 20 attached to the base 2 at regular intervals while the engine is operating, the PM 20 may accumulate on the base 2 between the electrodes 3 and 4 even when traveling for a long time. This eliminates the possibility of erroneously detecting that the DPF is damaged even though the DPF is not damaged.

  Another embodiment of the present invention will be described.

  A PM sensor 31 shown in FIG. 3A uses a ceramic glow plug 32 as a base 2 and both electrodes 3 and 4 are formed on the surface of the ceramic glow plug 32.

  As shown in FIG. 3B, a heating element 33 made of a ceramic resistor is provided inside the ceramic glow plug 32. By energizing the heating element 33, the surface of the ceramic glow plug 32 is provided. The attached PM 20 can be burned.

  When the PM sensor 31 is attached to the exhaust passage 11, a boss portion or the like is provided in the exhaust passage 11, and a screw portion 34 of the ceramic glow plug 32 is screwed into the boss portion or the like to form the electrodes 3 and 4. It is good to attach so that a part may face in exhaust passage 11.

  Since the ceramic glow plug 32 is rotated when the ceramic glow plug 32 is attached to the exhaust passage 11, no matter what angle the ceramic glow plug 32 is fixed, the electrodes 3 and 4 are positioned upstream of the exhaust direction. It is desirable to form a plurality of electrodes 3, 4 in the circumferential direction of the ceramic glow plug 32.

  Thus, by using the ceramic glow plug 32 for the base 2, the PM sensor 31 can be easily attached to the exhaust passage 11.

  In the above-described embodiment, the case where the electrodes 3 and 4 are composed of the straight portion 6 and the circular tip portion 7 has been described. However, the shape of the electrodes 3 and 4 is not limited thereto, and can be arbitrarily set.

  For example, like the PM sensor 41 shown in FIG. 4, the tip 7 of the electrodes 3, 4 may be formed in a ring shape over the entire circumferential direction of the surface of the ceramic glow plug 32 as the base 2. As a result, regardless of the angle at which the ceramic glow plug 32 is fixed, the electrodes 3 and 4 can be arranged upstream in the exhaust direction.

  Further, as shown in FIG. 5, the electrodes 3 and 4 are formed in a comb-like shape including a plurality of linear portions 51 arranged in parallel and a connection portion 52 connecting the ends of the linear portions 51, You may make it arrange | position so that the linear part 51 of the electrode 3 and the linear part 51 of the electrode 4 may alternate. Thereby, since the area of the part which the electrode 3 and the electrode 4 oppose increases, a sensitivity can be improved.

  In the above embodiment, the case where the PM sensors 1, 31, 41 are used for the purpose of detecting the breakage of the DPF has been described. It can also be used for the purpose of detecting abnormalities in the system. In this case, PM sensors 1, 31, 41 are provided in the exhaust passage of the vehicle, and black smoke (that is, PM) generated when an abnormality occurs in the fuel system of the vehicle is detected by the PM sensors 1, 31, 41. What is necessary is just to make it detect.

DESCRIPTION OF SYMBOLS 1 PM sensor 2 Base 3, 4 Electrode 5 Detection part 8 ECM
9 Electric heater 10 Reproduction part 11 Exhaust passage

Claims (4)

A PM sensor for detecting particulate matter in exhaust gas,
A base that is disposed in an exhaust passage of the vehicle and adheres the particulate matter; two electrodes that are formed on the surface of the base so as to face each other at a predetermined interval; and electrical continuity between the two electrodes. A detection unit for detecting and detecting the presence or absence of adhesion of the particulate matter,
The opposing tip portions of the two electrodes are formed in a circular shape ,
The PM sensor , wherein the base is formed in a columnar shape, and the two electrodes are continuously provided over the entire circumferential direction of the surface of the base . The base is disposed in the exhaust passage on the downstream side of a diesel particulate filter (DPF) that removes particulate matter in the exhaust gas,
2. The PM sensor according to claim 1, wherein the detection unit detects a breakage of the diesel particulate filter by detecting electrical continuity between the electrodes. The base has a built-in electric heater for burning particulate matter adhering to the base,
When starting the engine, at least one of the predetermined time intervals during engine operation, by supplying an electric current to the electric heater, PM sensor according to claim 1 or 2, including a reproduction section for burning the particulate matter adhering to the base . The PM sensor according to claim 1, wherein a glow plug is used as the base, and the electrodes are formed on a surface of the glow plug.

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