JP2011064611A - Deposit amount detector and detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deposit amount detector and a detection system capable of improving detection sensitivity. <P>SOLUTION: The deposit amount detector includes: a dielectric body 31 being arranged in an exhaust passage U through which the exhaust gas of an internal combustion engine moves and having a main surface 31a; a pair of electrodes 33a, 33b arranged on the main surface 31a of the dielectric body 31 so as to face each other in a planar view; a cover layer 32 arranged on the main surface 31a of the dielectric body 31 so as to cover the pair of the electrodes 33a, 33b; and a deposit amount calculation unit 4 for calculating the deposit amount of particle-like materials included in the exhaust gas deposited on the main surface 31a of the dielectric body 31 based on the change of the electrostatic capacitance between the pair of the electrodes 33a, 33b. A plurality of air holes C are formed on the cover layer 32. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a deposition amount detection device and a detection system for detecting a deposition amount of particulate matter contained in exhaust gas.

  As a deposition amount detection device that detects the deposition amount of particulate matter (PM) contained in exhaust gas, for example, a so-called capacitance type that detects the deposition amount by using a change in capacitance. (See, for example, Patent Documents 1 and 2).

JP 2001-33412 A Special Table 2000-517426

  However, in the above conventional accumulation amount detection device, the accumulation amount of the particulate matter is simply calculated based on the change in the capacitance between the pair of electrodes. There has been a problem that the rate of change in capacitance between the case where particulate matter is deposited is small and the detection sensitivity is poor.

  The present invention has been made in view of the above problems, and an object thereof is related to a deposition amount detection device and a detection system capable of improving detection sensitivity.

  In order to achieve the above object, a deposition amount detection apparatus according to the present invention is provided in an exhaust passage through which exhaust gas of an internal combustion engine moves, and is arranged so as to face a dielectric having a main surface in a plan view. A pair of electrodes provided on the main surface of the dielectric, a cover layer provided on the main surface of the dielectric so as to cover the pair of electrodes, and particulate matter contained in the exhaust gas are the dielectric. A deposition amount calculation unit that calculates a deposition amount deposited on the main surface of the substrate based on a change in capacitance between the pair of electrodes, wherein the cover layer has a plurality of pores formed therein. Yes.

  The accumulation amount detection device and the detection system of the present invention have an effect that detection sensitivity can be improved.

FIG. 1 is a block diagram showing a schematic configuration of a detection system according to the present embodiment. FIG. 2 is a perspective view illustrating a schematic configuration of the accumulation amount detection sensor according to the present embodiment. FIG. 3 is a plan view showing a schematic configuration of the accumulation amount detection sensor when the cover layer is omitted. 4 is a cross-sectional view taken along a cutting line II shown in FIG. FIG. 5 is a diagram illustrating a result of measurement by simulation. FIG. 6 is a cross-sectional view showing the same part as in FIG. 4, and is a view showing a preferred embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a detection system 1 according to the present embodiment. As shown in FIG. 1, a detection system 1 according to the present embodiment is provided in a combustion apparatus that uses petroleum fuel such as a vehicle (automobile or the like) (not shown). A detection sensor 3, a deposition amount calculation unit 4, a flow rate sensor 5, a flow rate calculation unit 6, an ECU (Electronic Control Unit) 7, and a control unit 8 are provided. Here, the accumulation amount detection sensor 3 and the accumulation amount calculation unit 4 constitute an embodiment of the accumulation amount detection device according to the present invention.

  The filter device 2 is provided in the exhaust passage U and is a device for collecting particulate matter contained in the exhaust gas moving through the exhaust passage U. The filter device 2 is composed of, for example, a DPF (Diesel Particulate Filter). That is, exhaust gas is generated when an internal combustion engine such as a diesel engine, piston engine, gas turbine engine, or the like burns, and, as indicated by an arrow in FIG. 1, a silencer (downstream) from the internal combustion engine (upstream). ) To the exhaust passage U. The exhaust gas that has passed through the silencer is released to the outside. Here, as the particulate matter contained in the exhaust gas, for example, simple solid carbon fine particles linked in tufts, a polymer hydrocarbon called SOF (Soluble Organic Fraction), or sulfates are included. Can be mentioned. Since the particulate matter is deposited in the human respiratory tract and lungs, it can adversely affect the human body and cause air pollution. Therefore, the particulate matter is collected in the filter device 2.

  The accumulation amount detection sensor 3 is a sensor for detecting the accumulation amount of particulate matter contained in the exhaust gas, and is provided in the exhaust passage U on the downstream side (muffler side) from the filter device 2. .

  FIG. 2 is a perspective view showing a schematic configuration of the accumulation amount detection sensor 3 according to the present embodiment. As shown in FIG. 2, the accumulation amount detection sensor 3 according to the present embodiment has a rectangular parallelepiped appearance and is provided on a base B provided in the exhaust passage U. The accumulation amount detection sensor 3 may be directly provided in the exhaust passage U without providing the base B. Moreover, although the accumulation amount detection sensor 3 according to the present embodiment has a rectangular parallelepiped appearance, it is not limited thereto, and may be a round bar shape, a plate shape, or the like, and the shape is not particularly limited.

  The accumulation amount detection sensor 3 includes a dielectric 31 and a cover layer 32. FIG. 3 is a plan view showing a schematic configuration of the accumulation amount detection sensor 3 when the cover layer 32 is omitted. Here, FIG. 3 is a plan view seen from the direction of arrow N in FIG. 4 is a cross-sectional view taken along a cutting line II shown in FIG.

  The dielectric 31 is provided in the exhaust passage U through which the exhaust gas of the internal combustion engine moves, and has a main surface 31a. In the present embodiment, the main surface 31a of the dielectric 31 is a surface substantially perpendicular to the longitudinal direction of the exhaust passage U (the direction of the arrow N in FIG. 2), and is affected by the wind of the exhaust gas. It becomes a surface. For this reason, particulate matter that could not be collected by the filter device 2 is deposited on the main surface 31 a of the dielectric 31. Here, as the dielectric 31, for example, an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, a silicon carbide sintered body, a silicon nitride sintered body, or a glass ceramic sintered body is used. Ceramics such as the body can be mentioned.

  The cover layer 32 is provided on the main surface 31a of the dielectric 31 so as to cover the first electrode 33a and the second electrode 33b. In addition, the 1st electrode 33a and the 2nd electrode 33b are a pair of electrodes, The shape is a comb-tooth shape in planar view, as shown in FIG. The first electrode 33a and the second electrode 33b are provided on the main surface 31a of the dielectric 31 so as to mesh with each other through a predetermined gap. Here, the 1st electrode 33a and the 2nd electrode 33b consist of metal materials, such as silver, copper, gold | metal | money, platinum, palladium, tungsten, molybdenum, or manganese, for example. Thus, since the first electrode 33a and the second electrode 33b are comb-like in a plan view and are provided on the main surface 31a of the dielectric 31 so as to mesh with each other through a predetermined gap, The effect is easily exhibited, and the detection sensitivity of the deposition amount detection device is improved.

  The first electrode 33a and the second electrode 33b are not particularly limited in shape as long as they are provided on the main surface 31a of the dielectric 31 so as to face each other in plan view. For example, the shape of the first electrode 33a and the second electrode 33b may be a meander shape or a double helix shape other than the above-described comb shape. Even in such a shape, the edge effect is easily exhibited, so that the detection sensitivity of the deposition amount detection device is improved.

  The cover layer 32 has a plurality of closed pores C as shown in FIG. In the present embodiment, all of the plurality of pores formed in the cover layer 32 are closed pores C. That is, since a plurality of airs having a dielectric constant of approximately “1” are formed in the cover layer 32, the dielectric constant of the cover layer 32 is compared with the case where a plurality of closed pores C are not formed in the cover layer 32. , Get lower. Thus, since the dielectric constant of the cover layer 32 becomes low, the detection sensitivity of the deposition amount detection device is improved. This reason will be described later.

  In addition, a heating element 34 is embedded in the dielectric 31. The heating element 34 generates heat in response to an instruction from a heating element control unit (not shown). When the heating element 34 generates heat, the particulate matter deposited on the main surface 31a of the dielectric 31 is burned out. Thereby, the particulate matter deposited on the main surface 31a of the dielectric 31 can be cleaned. Note that the timing at which the heating element control unit causes the heating element 34 to generate heat is not particularly limited. For example, when the amount of particulate matter deposited on the main surface 31a of the dielectric 31 exceeds a threshold value, the heating element controller may cause the heating element 34 to generate heat or generate heat at regular intervals. The body control unit may cause the heating element 34 to generate heat. When there is no need to clean the particulate matter deposited on the main surface 31 a of the dielectric 31, the heating element 34 may not be embedded in the dielectric 31.

  The deposition amount calculation unit 4 uses the deposition amount in which the particulate matter contained in the exhaust gas is deposited on the main surface 31a of the dielectric 31 as a change in capacitance between the first electrode 33a and the second electrode 33b. Calculate based on The accumulation amount calculation unit 4 outputs the calculated accumulation amount to the control unit 8.

  By the way, in order to improve the detection sensitivity of the deposition amount detection device, it is necessary that the rate of change in capacitance between the case where the particulate matter is not deposited and the case where the particulate matter is deposited is large. . Therefore, the inventors fix the dielectric constant of the dielectric 31 to “9”, the dielectric constant of the particulate matter to “6”, and the dielectric constant of the cover layer 32 to “6”, “9”, “12”. ”,“ 15 ”, the rate of change in capacitance when the particulate matter is not deposited (thickness 0 mm) and when the particulate matter is deposited (thickness 0.1 mm) Was measured by simulation. The result is shown in FIG.

  As shown in FIG. 5, it can be seen that the lower the dielectric constant of the cover layer 32, the greater the rate of change in capacitance. The rate of change in capacitance (%) is calculated by dividing the amount of change in capacitance by the value of capacitance when particulate matter is not deposited and multiplying the result by 100. Is done. That is, in order to improve the detection sensitivity of the deposition amount detection device, it is necessary to lower the dielectric constant of the cover layer 32. In other words, it is necessary to reduce the dielectric constant between the first electrode 33a and the second electrode 33b in a cross-sectional view.

  Here, the lower the dielectric constant of the cover layer 32, the larger the rate of change in capacitance is for the following reason. That is, when the dielectric constant of the cover layer 32 is lowered, the dielectric constant of the cover layer 32 is relatively lower than that of the particulate matter. That is, the ratio of the dielectric constant of the particulate matter to the sum of the dielectric constant of the cover layer 32 and the dielectric constant of the particulate matter increases. Therefore, the lower the dielectric constant of the cover layer 32, the greater the change rate of the capacitance, and the detection sensitivity of the deposition amount detection device is improved.

  For this reason, in this embodiment, by forming a plurality of closed pores C in the cover layer 32, the dielectric constant of the cover layer 32, that is, the dielectric constant between the first electrode 33a and the second electrode 33b is lowered. . Therefore, the deposition amount detection device according to the present embodiment can improve the detection sensitivity as compared with the conventional deposition amount detection device.

  In the above description, the case where all of the plurality of pores formed in the cover layer 32 are closed pores C has been described. However, the present invention is not limited to this. That is, some of the plurality of pores formed in the cover layer 32 may be open pores. However, when open pores are formed in the cover layer 32, particulate matter may adhere to the first electrode 33a and the second electrode 33b through the open pores, and the first electrode 33a and the second electrode 33b may be corroded. There is. For this reason, when forming open pores in the cover layer 32, the first electrode 33a and the second electrode 33b need to be configured using a metal material having high corrosion resistance, such as gold or platinum. It is. In other words, when all of the plurality of pores formed in the cover layer 32 are closed pores C as in the present embodiment, corrosion resistance is used as a constituent material of the first electrode 33a and the second electrode 33b. It is not necessary to select a material with high properties, and the degree of freedom in material selection is improved.

In order to further reduce the dielectric constant of the cover layer 32, the cover layer 32 is preferably made of a low dielectric constant material. Examples of the low dielectric constant material include silicon dioxide (SiO ₂ ), high heat-resistant epoxy resin, SiOF, and SiOC. When the cover layer 32 is configured using a low dielectric constant material, the deposition amount detection apparatus according to the present embodiment can further improve the detection sensitivity.

  Further, in order to further reduce the dielectric constant between the first electrode 33a and the second electrode 33b, as shown in FIG. 6, the cover layer 32 individually covers the first electrode 33a and the second electrode 33b. It is preferably provided on the main surface 31 a of the dielectric 31. That is, since air having a dielectric constant of approximately “1” is interposed between the first electrode 33a and the second electrode 33b, the dielectric constant between the first electrode 33a and the second electrode 33b is further reduced. If it does in this way, the deposition amount detection apparatus concerning this embodiment can further improve detection sensitivity.

  The flow rate sensor 5 is a sensor for detecting the flow rate of the exhaust gas that moves through the exhaust passage U, and is provided in the exhaust passage U upstream of the filter device 2 (internal combustion engine side). Examples of the flow sensor 5 include a flow sensor using a thermal flow method. Note that the method of the flow sensor 5 is not particularly limited as long as the flow rate of the exhaust gas can be detected.

  The flow rate calculation unit 6 calculates the flow rate of the exhaust gas moving through the exhaust passage U based on the information detected by the flow rate sensor 5. The flow rate calculation unit 6 outputs the calculated exhaust gas flow rate to the control unit 8.

  The flow rate sensor 5 and the flow rate calculation unit 6 are an embodiment of the flow rate detection device according to the present invention.

  The ECU 7 is a controller that controls an ignition system and a combustion system in the internal combustion engine. For example, the ECU 7 reduces or increases the rotational speed of the internal combustion engine or controls the ignition timing of the internal combustion engine, etc., according to an instruction from the control unit 8 described later. That is, the ECU 7 can control the number of particulate matter contained in the exhaust gas by controlling the ignition system and the combustion system in the internal combustion engine.

  Based on the flow rate of the exhaust gas calculated by the flow rate calculation unit 6 and the deposition amount of the particulate matter calculated by the deposition amount calculation unit 4, the control unit 8 includes, in the exhaust gas moved per unit time, An uncollectable amount indicating how much particulate matter that could not be collected by the filter device 2 was included is calculated. The control unit 8 instructs the ECU 7 based on the calculated uncollectable amount. For example, the control unit 8 instructs the ECU 7 to reduce the number of particulate matter contained in the exhaust gas if the calculated uncollectable amount is equal to or greater than a threshold value. The control unit 8 may simply display the calculated uncollectable amount on the display without instructing the ECU 7.

DESCRIPTION OF SYMBOLS 1 Detection system 2 Filter apparatus 3 Deposit amount detection sensor 31 Dielectric 31a Main surface 32 Cover layer 33a First electrode 33b Second electrode 4 Deposit amount calculation part 5 Flow rate sensor 6 Flow rate calculation part 8 Control part C Closed pore

Claims (7)

A dielectric provided in an exhaust passage through which exhaust gas of the internal combustion engine moves, and having a main surface;
A pair of electrodes provided on the principal surface of the dielectric so as to face each other in plan view;
A cover layer provided on the main surface of the dielectric so as to cover the pair of electrodes;
A deposition amount calculation unit that calculates a deposition amount in which particulate matter contained in the exhaust gas is deposited on the main surface of the dielectric based on a change in capacitance between the pair of electrodes; ,
A deposition amount detection device in which a plurality of pores are formed in the cover layer.   The accumulation amount detection apparatus according to claim 1, wherein all of the plurality of pores formed in the cover layer are closed pores. Some of the plurality of pores formed in the cover layer are open pores,
The deposition amount detection device according to claim 1, wherein the electrode is made of gold or platinum.   The said cover layer is a deposition amount detection apparatus as described in any one of Claims 1-3 provided in the main surface of the said dielectric material so that each of said pair of electrodes may be covered separately.   The deposition amount detection apparatus according to claim 1, wherein a heating element is embedded in the dielectric. A filter device that is provided in the exhaust passage and collects particulate matter contained in the exhaust gas;
A control system comprising: a deposition amount detection device according to any one of claims 1 to 5 that detects a deposition amount of particulate matter that could not be collected by the filter device. A flow rate detection device for detecting a flow rate of exhaust gas moving in the exhaust passage;
Based on the flow rate of the exhaust gas detected by the flow rate detection device and the deposition amount of the particulate matter detected by the deposition amount detection device, in the exhaust gas moved per unit time, the filter device The control system according to claim 6, further comprising a control device that calculates an uncollectable amount indicating how much particulate matter that could not be collected was contained.

Images