JP6409436B2 - Diagnostic equipment - Google Patents

Description

  The present invention relates to a diagnostic device, and more particularly to a diagnostic device for a PM sensor that detects particulate matter (hereinafter referred to as PM) contained in exhaust gas.

  Conventionally, an electrical resistance type PM sensor is known as a sensor for detecting PM in exhaust discharged from an internal combustion engine. An electrical resistance type PM sensor uses a pair of conductive electrodes facing each other on the surface of an insulating substrate, and the electrical resistance value changes depending on the conductive PM (mainly soot component) adhering to these electrodes. The PM amount is estimated (see, for example, Patent Document 1).

  Further, as a failure diagnosis device for an electric resistance type PM sensor, a device that compares the regeneration times of two PM sensors with each other and determines a failure when the difference between the regeneration times of these sensors is larger than a predetermined value is proposed. (For example, refer to Patent Document 2).

JP2012-83210A JP 2009-144512 A

  By the way, in the failure diagnosis apparatus for the electrical resistance PM sensor described above, the diagnosis is limited to the sensor regeneration period, and the diagnosis cannot be performed during the sensor regeneration interval period in which the electrical resistance value does not change. For this reason, there is a possibility that the PM sensor malfunction or function deterioration cannot be detected at an early stage.

  An object of the disclosed diagnostic device is to detect a PM sensor malfunction and functional deterioration early and in real time.

  The disclosed diagnostic device includes at least a pair of electrode members that are disposed in an exhaust passage of an internal combustion engine and that include a cell that collects particulate matter in exhaust gas and that is disposed opposite to the cell so as to form a capacitor. A plurality of sensors provided with estimation means for estimating the amount of particulate matter in the exhaust based on the capacitance between the pair of electrode members, and based on the amount of particulate matter estimated by the plurality of sensors And an abnormality determining means for determining abnormality of the plurality of sensors.

  According to the disclosed diagnostic apparatus, it is possible to detect functional failure and functional deterioration of the PM sensor early and in real time.

It is a schematic block diagram which shows an example of the exhaust system of the engine to which the diagnostic apparatus which concerns on 1st embodiment was applied. It is a typical fragmentary sectional view showing PM sensor of a diagnostic device concerning a first embodiment. It is a functional block diagram which shows the electronic control unit of the diagnostic apparatus which concerns on 1st embodiment. (A), (B) is a figure explaining the sensor regeneration time of each PM sensor, (C) is a figure explaining the comparison of the PM amount estimated value of each PM sensor. (A) is a typical perspective view which shows the sensor part of PM sensor which concerns on 2nd embodiment, (B) is a typical exploded perspective view which shows the sensor part of PM sensor which concerns on 2nd embodiment. . It is a typical fragmentary sectional view showing PM sensor of a diagnostic device concerning other embodiments.

  Hereinafter, based on an accompanying drawing, a diagnostic device concerning each embodiment of the present invention is explained. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[First embodiment]
FIG. 1 is a schematic configuration diagram illustrating an example of an exhaust system of a diesel engine (hereinafter simply referred to as an engine) 100 to which the diagnostic device according to the first embodiment is applied. In the exhaust pipe 110 of the engine 100, an oxidation catalyst 210, a particulate filter (hereinafter referred to as DPF) 220, and the like are provided in order from the exhaust upstream side. The diagnostic device of the present embodiment is configured by disposing two PM sensors 10 (10A, B) in the exhaust pipe 110 upstream of the DPF 220, respectively. The number of PM sensors 10 is not limited to two, but may be three or more. Further, the arrangement position of the PM sensors 10 </ b> A and 10 </ b> B may be the exhaust pipe 110 on the downstream side of the DPF 220.

  Next, a detailed configuration of the PM sensors 10A and 10B according to the present embodiment will be described based on FIG.

  The PM sensors 10A and 10B include a case member 11 inserted into the exhaust pipe 110, a pedestal part 20 for attaching the case member 11 to the exhaust pipe 110, a sensor part 30 accommodated in the case member 11, and an electronic control unit. (Hereinafter referred to as ECU) 40.

  The case member 11 is formed in a bottomed cylindrical shape with the bottom side (the lower end side in the illustrated example) closed. The length L in the cylinder axis direction of the case member 11 is formed to be substantially the same as the radius R of the exhaust pipe 110 so that the bottom cylindrical wall portion protrudes to the vicinity of the axial center CL of the exhaust pipe 110. ing. In the following description, the bottom side of the case member 11 is the front end side, and the side opposite to the bottom side is the base end side of the case member 11.

A plurality of inlets 12 arranged at intervals in the circumferential direction are provided in the cylindrical wall portion on the distal end side of the case member 11. In addition, a plurality of outlets 13 arranged at intervals in the circumferential direction are provided in the base end side cylindrical wall portion of the case member 11. The total opening area S ₁₂ of the inlet 12 is smaller than the total opening area S ₁₃ of the outlet _{13 (S 12 <S 13)} . That is, in the exhaust flow velocity V ₁₂ of the inlet 12 near slower than the exhaust flow velocity V ₁₃ near guide outlet 13 (V ₁₂ <V _13), the pressure P ₁₂ in the inlet 12 side pressure outlet 13 side It is higher than the _{P 13 (P 12> P 13} ). As a result, exhaust gas is smoothly taken into the case member 11 from the inlet 12, and at the same time, exhaust gas in the case member 11 is smoothly led out into the exhaust pipe 110 from the outlet 13.

  The pedestal portion 20 includes a male screw portion 21 and a nut portion 22. The male screw portion 21 is provided at the base end portion of the case member 11 and closes the base end side opening of the case member 11. The male screw portion 21 is screwed with a female screw portion of a boss portion 110 </ b> A formed in the exhaust pipe 110. The nut portion 22 is, for example, a hexagonal nut, and is fixed to the upper end portion of the male screw portion 21. The male screw portion 21 and the nut portion 22 are formed with through holes (not shown) through which conductive wires 32A, 33A described later are inserted.

  The sensor unit 30 includes a filter member 31, a plurality of pairs of electrodes 32 and 33, and an electric heater 34.

  The filter member 31 is formed, for example, by alternately plugging the upstream side and the downstream side of a plurality of cells forming a lattice-like exhaust flow path partitioned by porous ceramic partition walls. The filter member 31 is held on the inner peripheral surface of the case member 11 via a cushion member 31A in a state in which the flow path direction of the cell is substantially parallel to the axial direction of the case member 11 (vertical direction in the drawing). . The PM in the exhaust gas taken into the case member 11 from the introduction port 12 flows from the cell plugged on the downstream side into the cell plugged on the upstream side, so that the surface of the partition wall It is collected in the hole. In the following description, a cell whose downstream side is plugged is referred to as a measurement cell, and a cell whose upstream side is plugged is referred to as an electrode cell.

  The electrodes 32 and 33 are, for example, conductive metal wires, and are alternately inserted from the downstream side (non-plugged side) into the electrode cells facing each other across the measurement cell to form a capacitor. These electrodes 32 and 33 are connected to a capacitance detection circuit (not shown) built in the control unit 40 via conductive lines 32A and 33A, respectively.

  The electric heater 34 is, for example, a heating wire and constitutes the regenerating means of the present invention. The electric heater 34 generates heat by energization and heats the measurement cell, thereby performing so-called filter regeneration (hereinafter also referred to as sensor regeneration) in which PM accumulated in the measurement cell is removed by combustion. For this reason, the electric heater 34 is formed by being bent into a continuous S-shape, and straight portions parallel to each other are inserted into each measurement cell along the flow path.

  Next, details of the ECU 40 of the present embodiment will be described with reference to FIG. The ECU 40 includes a sensor regeneration control unit 41A corresponding to the PM sensor 10A, a sensor regeneration control unit 41B corresponding to the PM sensor 10B, a PM amount estimation calculation unit 42A corresponding to the PM sensor 10A, and a PM corresponding to the PM sensor 10B. A quantity estimation calculation unit 42B and a sensor abnormality determination unit 43 are provided as functional elements. These functional elements are described as being included in the ECU 40 that is an integral piece of hardware, but may be provided in separate hardware. The sensor regeneration control units 41A and 41B and the PM amount estimation calculation units 42A and 42B have the same function, and will be described below together.

  The sensor regeneration control units 41A and 41B are an example of the regeneration means of the present invention, and turn on the electric heater 34 according to the capacitance Cp between the electrodes 32 and 33 detected by a capacitance detection circuit (not shown). The sensor regeneration to be energized) is executed. The electrostatic capacitance Cp between the electrodes 32 and 33 is expressed by the following formula 1 where the dielectric constant ε of the medium between the electrodes 32 and 33, the area S of the electrodes 32 and 33, and the distance d between the electrodes 32 and 33 are expressed. .

  In Formula 1, the surface areas S of the electrodes 32 and 33 are constant, and when PM is collected by the filter member 31, the dielectric constant ε and the distance d change, and the capacitance Cp also changes accordingly. That is, a proportional relationship is established between the capacitance Cp between the electrodes 32 and 33 and the amount of PM deposited on the filter member 31.

When the electrostatic capacity Cp between the electrodes 32 and 33 reaches a predetermined electrostatic capacity upper limit threshold _{CP_max} indicating the PM upper limit accumulation amount of the filter member 31, the sensor regeneration control units 41A and 41B _turn on the electric heater 34. Sensor regeneration is started (see FIGS. 4A and 4B). This sensor regeneration is continued until the capacitance Cp falls to a predetermined capacitance lower limit threshold _{CP_min} indicating complete removal of PM.

Estimating the PM amount calculation unit 42A, B is an example of a means for estimating the present invention, based on the variation amount of capacitance [Delta] Cp _n between regeneration interval T _n (next sensor reproduction start from the sensor reproduction end), the exhaust The total PM amount m _{PM_sum} is estimated.

PM quantity m _{PM_n} to be trapped by the filter member 31 between regeneration interval T _n is obtained by Equation 2 below obtained by multiplying the first coefficient β to the variation amount of capacitance [Delta] Cp _n.

The PM amount estimation calculation units 42A and _{42B exhaust the air} flowing into the filter members 31 of the sensors 10A and 10B based on the following equation 3 that sequentially accumulates the PM amount m _{PM_n} between the regeneration intervals T _n calculated from the equation 2. The total PM amount m _{PM_sum} is calculated in real time.

The sensor abnormality determination unit 43 is an example of the abnormality determination unit of the present invention, and is input from the total PM amount m _{PM_sum_A} of the PM sensor 10A input from the PM amount estimation calculation unit 42A and the PM amount estimation calculation unit 42B. By comparing the total PM amount m _{PM_sum_B} of the PM sensor 10B, the abnormality of the PM sensors 10A and 10B is determined.

When abnormality such as functional failure or functional deterioration occurs in one or both of the PM sensors 10A and 10B, as shown in FIG. 4C, the total PM amount m _{PM_sum_B} of the PM sensor 10A and the total PM amount of the PM sensor 10B _{Deviation from} m _{PM_sum_B} occurs. Sensor abnormality determination unit 43, as well as calculating the deviation Delta] m _PM of these total amount of PM m _{PM_sum_A} and total PM amount m _{PM_sum_B} in real time, the deviation Delta] m _PM exceeds a predetermined threshold value, PM sensor 10A, abnormal B is It is determined that it has occurred.

  Next, the effect of the diagnostic apparatus according to the present embodiment will be described.

  In the conventional technology that compares the output values of two electric resistance type PM sensors with each other, diagnosis cannot be performed during the regeneration interval period in which the electric resistance value between the electrodes does not change, and the PM sensor malfunctions or deteriorates. There are issues that cannot be detected early and in real time.

  On the other hand, in the diagnostic apparatus according to the present embodiment, each PM sensor 10A, B detects the amount of PM in real time based on the capacitance Cp between the electrodes 32, 33 having good sensitivity even during the regeneration interval period. By comparing the output values of the PM sensors 10A, B, the abnormality of the PM sensors 10A, B is determined. Therefore, according to the diagnostic device of the present embodiment, it is possible to detect the functional failure and functional deterioration of the PM sensors 10A and 10B early and in real time.

[Second Embodiment]
Next, based on FIG. 5, the detail of the diagnostic apparatus which concerns on 2nd embodiment is demonstrated. The diagnostic device according to the second embodiment is a PM type in which the sensor unit 30 is a stacked type in the PM sensors 10A and 10B according to the first embodiment. Since other components have the same structure, detailed description and illustration are omitted.

  5A is a perspective view of the sensor unit 60 according to the second embodiment, and FIG. 5B is an exploded perspective view of the sensor unit 60. The sensor unit 60 includes a plurality of filter layers 61 and a plurality of first and second electrode plates 62 and 63.

  The filter layer 61 is, for example, plugged alternately upstream and downstream of a plurality of cells that are partitioned by partition walls such as porous ceramics to form an exhaust passage, and these cells are arranged in parallel in one direction. It is formed in a rectangular parallelepiped shape. The PM contained in the exhaust gas flows into the cell C2 whose upstream side is plugged from the cell C1 whose downstream side is plugged, as indicated by a broken line arrow in FIG. 5B. Thus, it is collected on the partition wall surface and pores of the cell C1. In the following description, the cell flow path direction is the length direction of the sensor section 60 (arrow L in FIG. 5A), and the direction orthogonal to the cell flow path direction is the width direction of the sensor section 60 (FIG. 5). (A) Arrow W).

  The first and second electrode plates 62 and 63 are, for example, plate-like conductive members, and are formed so that the outer dimensions in the length direction L and the width direction W are substantially the same as those of the filter layer 61. The first and second electrode plates 62 and 63 are alternately stacked with the filter layer 61 interposed therebetween, and are connected to a capacitance detection circuit (not shown) built in the ECU 40 via conductive lines 62A and 63A, respectively. ing.

  That is, the first electrode plate 62 and the second electrode plate 63 are disposed to face each other, and the filter layer 61 is sandwiched between the electrode plates 62 and 63, so that the entire cell C1 forms a capacitor. . As described above, in the second embodiment, the entire cell C1 is made the capacitor by the flat electrode plates 62 and 63, so that the electrode surface area S can be effectively secured, and the detectable capacitance absolute It becomes possible to increase the value. Further, since the inter-electrode distance d becomes the cell pitch and is made uniform, variations in the initial capacitance can be effectively suppressed.

  When the PM accumulated in the cell C1 is burned and removed, a voltage is directly applied to the electrode plates 62 and 63, or a heater substrate (not shown) is interposed between the filter layer 61 and the electrode plates 62 and 63. Just set up.

[Others]
The present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented without departing from the spirit of the present invention.

  For example, as shown in FIG. 6, in the PM sensors 10 </ b> A and 10 </ b> B of the first embodiment, the positions of the inlet 12 and the outlet 13 are switched to reverse the flow of exhaust gas introduced into the case member 11. It may be. In this case, the filter member 31 may be stored in the case member 11 by being inverted.

10A, B PM sensor 11 Case member 12 Inlet port 13 Outlet port 20 Base portion 21 Male screw portion 22 Nut portion 30 Sensor portion 31 Filter member 32, 33 Electrode 34 Electric heater 40 ECU
41A, B sensor regeneration control unit 42A, B PM amount estimation calculation unit 43 sensor abnormality determination unit

Claims (5)

A filter member including a cell that is disposed in an exhaust passage of an internal combustion engine and collects particulate matter in exhaust gas is provided with at least a pair of electrode members that are disposed opposite to each other with the cell interposed therebetween to form a capacitor. A plurality of sensors provided with estimation means for estimating the amount of particulate matter in the exhaust based on the capacitance between the electrode members;
An abnormality determining means for determining an abnormality of the plurality of sensors based on the amount of particulate matter estimated by the plurality of sensors ,
The plurality of sensors are arranged in the exhaust passage upstream or downstream of the particulate filter,
Each of the plurality of sensors includes a regeneration unit that performs sensor regeneration for burning and removing the collected particulate matter when the amount of the particulate matter collected by the filter member reaches a predetermined value.
The estimation means calculates the amount of particulate matter collected by the filter member during the sensor regeneration interval from the amount of change in capacitance between the pair of electrodes during the sensor regeneration interval, and calculates each sensor regeneration By sequentially integrating the amount of particulate matter between intervals, the amount of particulate matter in the exhaust is estimated in real time,
The abnormality determining unit is a diagnostic device that determines that an abnormality occurs when a difference between the amount of particulate matter estimated by one sensor and the amount of particulate matter estimated by another sensor exceeds a predetermined threshold . When the capacitance between the pair of electrode members reaches an upper limit threshold, the regeneration means performs sensor regeneration until it decreases to the lower limit threshold,
The estimation means is configured such that the amount of particles collected by the filter member during the sensor regeneration interval from the amount of change in capacitance until the capacitance between the pair of electrodes rises from the lower limit threshold value to the upper limit threshold value. The diagnostic apparatus according to claim 1, wherein the substance amount is calculated . The plurality of sensors are formed in a cylindrical shape so that the filter member is accommodated in the cylinder, and exhaust gas introduced into the cylinder from the opening at one end is allowed to pass through the filter member to be outside the cylinder from the other end opening. diagnostic apparatus according deriving casing member to claim 1 or 2 comprising, respectively. The filter member is a filter layer in which a plurality of the cells are arranged in parallel in one direction, and the pair of electrode members are flat plate-like first and second electrode plates facing each other with the filter layer interposed therebetween. 4. The diagnostic device according to any one of 3 . The plurality of first electrode plates, the second electrode plates, and the filter layers, respectively, and the plurality of first and second electrode plates are alternately stacked with the plurality of filter layers sandwiched one by one. 4. The diagnostic device according to 4 .

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