JP2016109512A - Sensor and control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor having a fuel property discriminating function and capable of accurately discriminating the fuel property and a control device of an internal combustion engine.SOLUTION: A sensor arranged in an exhaust passage 110 of an internal combustion engine 100 and detecting the amount of a particulate substance contained in an exhaust gas provides at least a pair of electrodes 32, 33 sandwiching a cell and facing each other on a filter member 31 arranged in the exhaust passage 110 and collecting the particulate substance in the exhaust gas, and is composed of a capacitance type sensor having estimation means 42 for estimating the amount of the particulate substance in the exhaust gas based on the capacitance between the pair of electrodes 32, 33, and includes a fuel property discrimination part 2 for discriminating a fuel property on the basis of the amount of the particulate substance estimated by the estimation means 42.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor and a control device for an internal combustion engine, and more particularly to a PM sensor for detecting particulate matter (hereinafter referred to as PM) contained in exhaust gas and a control device for an internal combustion engine.

  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).

  By the way, when controlling an internal combustion engine, it is desired to perform appropriate control according to the fuel to be used. Specifically, even when a fuel other than standard fuel, for example, biofuel or poor fuel, is used, it is desired to perform appropriate control according to the fuel property to be used.

  In Patent Document 2, in the PM sensor arranged on the downstream side of the particulate filter, when the PM amount at the time of sensor regeneration completion after refueling is detected, and this value is larger than the PM amount at the time of sensor regeneration completion before refueling Discloses that the cause is a decrease in cetane number due to fuel supply.

JP2012-83210A JP 2011-185095 A

  However, in Patent Document 2, although a decrease in cetane number can be determined, for example, determination using biofuel is difficult, and determination of fuel properties is insufficient.

  In Patent Document 2, the specific structure of the PM sensor is not disclosed, and it is considered that a general electric resistance type PM sensor is used. Since the electric resistance type PM sensor has a simple structure that attaches PM to each electrode, there is a possibility that a part of the PM adhering to the electrode may be detached, especially in an operation state where the exhaust flow rate increases, thereby ensuring the estimation accuracy. There is a problem that cannot be done. Further, since the electrical resistance value between the electrodes does not change until the electrodes are connected to each other due to the deposition of PM, there is a problem that the amount of PM cannot be accurately estimated during the period until the electrodes are connected by PM. For this reason, the electric resistance PM sensor cannot be expected to accurately determine the fuel property.

  Accordingly, an object of the present invention is to provide a sensor and an internal combustion engine control device that solve the above-described problems, have a fuel property discrimination function, and can accurately discriminate the fuel property.

  The present invention was devised to achieve the above object, and is a sensor that is disposed in an exhaust passage of an internal combustion engine and detects the amount of particulate matter contained in the exhaust, and is disposed in the exhaust passage. A filter member including a cell that collects particulate matter in the exhaust is provided with at least a pair of electrodes that are arranged opposite to each other with the cell interposed therebetween to form a capacitor, and the exhaust is performed based on the capacitance between the pair of electrodes. A sensor having an electrostatic capacity type sensor having an estimation unit for estimating the amount of particulate matter in the sensor, and having a fuel property determination unit for determining a fuel property based on the amount of particulate matter estimated by the estimation unit. is there.

  According to the present invention, it is possible to provide a sensor having a fuel property determination function and capable of accurately determining a fuel property.

(A) is a schematic block diagram which shows an example of the exhaust system of the diesel engine to which PM sensor which concerns on one Embodiment of this invention was applied, (B) is a functional block diagram of an electronic control unit. It is a typical fragmentary sectional view showing PM sensor of a diagnostic device concerning one embodiment of the present invention. (A) is a typical perspective view which shows the sensor part of PM sensor which concerns on one modification of this invention, (B) is a typical disassembled perspective view which shows the sensor part of the PM sensor. It is a typical fragmentary sectional view showing PM sensor concerning one modification of the present invention.

  Hereinafter, a sensor according to an embodiment of the present invention (hereinafter referred to as a PM sensor) will be described with reference to the accompanying drawings. 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.

  FIG. 1A is a schematic configuration diagram illustrating an example of an exhaust system of a diesel engine (hereinafter simply referred to as an engine) to which a PM sensor according to the present embodiment is applied, and FIG. 1B is a diagram of an electronic control unit. It is a functional block diagram.

  As shown in FIG. 1A, an oxidation catalyst 210, a particulate filter (hereinafter referred to as DPF) 220, and the like are provided in the exhaust passage (exhaust pipe) 110 of the engine 100 in order from the exhaust upstream side. . The diagnostic device of the present embodiment is configured by arranging the PM sensor 10 in the exhaust passage 110 upstream of the DPF 220. The number of PM sensors 10 is not limited and may be two or more. In addition, the arrangement position of the PM sensor 10 may be the exhaust passage 110 on the downstream side of the DPF 220.

  Next, a detailed configuration of the PM sensor 10 will be described.

  As shown in FIG. 2, the PM sensor 10 includes a case member 11 inserted into the exhaust passage 110, a pedestal portion 20 for attaching the case member 11 to the exhaust passage 110, and a sensor portion 30 accommodated in the case member 11. And.

  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 of the case member 11 in the cylinder axis direction is formed to be substantially the same as the radius R of the exhaust passage 110 so that the bottom cylindrical wall portion protrudes to the vicinity of the axial center CL of the exhaust passage 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} ). Thereby, exhaust gas is smoothly taken into the case member 11 from the inlet 12, and at the same time, the exhaust gas in the case member 11 is smoothly led out into the exhaust passage 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 passage 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 downstream to the cell plugged upstream, 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 an electronic control unit (ECU) 40 of the vehicle via conductive wires 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 sensor regeneration (filter regeneration) for burning and removing PM accumulated in the measurement cell. 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.

  As shown in FIG. 1B, the PM sensor 10 includes a sensor regeneration control unit 41 and a PM amount estimation calculation unit 42. The sensor regeneration control unit 41 and the PM amount estimation calculation unit 42 are mounted on the ECU 40. Note that the sensor regeneration control unit 41 and the PM amount estimation calculation unit 42 may be mounted on a hardware unit configured separately from the ECU 40. The ECU 40 constitutes a control device for an internal combustion engine according to the present embodiment, and is configured to control the engine 100 including fuel injection timing.

  The sensor regeneration control unit 41 performs sensor regeneration that turns on (energizes) the electric heater 34 in accordance with the capacitance Cp between the electrodes 32 and 33 detected by a capacitance detection circuit (not shown). 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 surface 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 deposition amount of the filter member 31, the sensor regeneration control unit 41 _turns on the electric heater 34 to perform sensor regeneration. (See FIG. 3). 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 42 is an example of a means for estimating the present invention, together with obtaining the capacitance Cp between the electrodes 32 and 33, on the basis of the variation amount of capacitance [Delta] Cp _n in the period to be measured, The total PM amount m _{PM_sum} in the exhaust is estimated.

PM quantity m _{PM_n} to be trapped by the filter member 31 between any period 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 unit 42 sequentially accumulates the PM amount m _{PM_n} of the period T _n calculated from Equation 2, based on the following Equation 3, the total PM amount m in the exhaust gas flowing into the filter member 31 of the PM sensor 10. _{Calculate PM_sum} in real time.

  The PM sensor 10 further includes a fuel property determination unit 2.

  The fuel property determination unit 2 is configured to determine the fuel property based on the PM amount estimated by the PM amount estimation calculation unit 42 serving as an estimation unit.

  The fuel property determination unit 2 maps a reference particulate matter amount (referred to as a reference PM amount) that is a PM amount discharged from the engine 100 when a standard fuel that is a reference for determining a fuel property is used for each driving situation. A fuel property map 3 is provided, a reference PM amount corresponding to the current driving situation is obtained with reference to the fuel property map 3, and the obtained reference PM amount and the PM amount estimated by the PM amount estimation calculation unit 42 (estimated) (Referred to as “PM amount”).

  For example, in a fuel with a large amount of hydrocarbons, the amount of PM discharged from the engine 100 increases, so the estimated PM amount becomes larger than the reference PM amount. Moreover, since biofuel has a large oxygen content, when biofuel is used, the amount of PM discharged from the engine 100 decreases, and the estimated PM amount becomes smaller than the reference PM amount. Therefore, in the present embodiment, the fuel property determination unit 2 determines the fuel property of the currently used fuel depending on whether the estimated PM amount is larger or smaller than the reference PM amount.

  The fuel property map 3 is created by obtaining a reference PM amount for each possible operating situation by an experiment or a calculation using a PM deposition model in advance. Here, the engine speed and the engine load are used as parameters representing the driving situation, the PM amount discharged from the engine 100 at a predetermined time is calculated for each engine speed and the engine load, and the reference PM amount is obtained. Map 3 was created. However, the parameter indicating the driving situation is not limited to this, and for example, three or more parameters may be used.

  The fuel property determining unit 2 refers to the fuel property map 3 to obtain a reference PM amount corresponding to the current driving situation, and at the same time, a predetermined amount (a predetermined amount used when calculating the reference PM amount by the PM amount estimation calculating unit 42). The estimated PM amount that is the amount of PM deposited on the filter member 31 at a time equal to the time) is obtained, and the magnitude relationship between the reference PM amount and the estimated PM amount and the difference (deviation) between the two are output as fuel property data.

  The fuel property determination unit 2 may be configured not to determine the fuel property when the amount of PM discharged from the engine 100 is not stable, for example, when the vehicle is started.

  The fuel property data output from the fuel property determination unit 2 is input to the fuel property correspondence control unit 4 mounted on the ECU 40. The fuel property response control unit 4 constitutes a control device for an internal combustion engine according to the present embodiment.

  The fuel property correspondence control unit 4 controls the engine 100 including the fuel injection timing according to the fuel property determined by the fuel property determination unit 2, that is, the fuel property data input from the fuel property determination unit 2. is there.

  For example, when the fuel property control unit 4 has a large amount of hydrocarbons and the estimated PM amount is larger than the reference PM amount, and the difference between the reference PM amount and the estimated PM amount is larger than a predetermined threshold, According to the degree of the deviation, the fuel injection timing correction control is performed so that the fuel injection is performed at a timing earlier than the fuel injection timing when the standard fuel is used.

  In addition to the fuel injection timing correction control, the fuel property response control unit 4 may be configured to perform, for example, fuel injection amount correction control according to the fuel property. The engine 100 is configured to be controlled so that the amount of NOx in the exhaust gas is optimized.

  The effect of this embodiment is demonstrated.

  In the PM sensor 10 according to the present embodiment, at least a pair of electrodes 32 that are disposed opposite to each other with a cell interposed between a filter member 31 that includes a cell that is disposed in the exhaust passage 110 and collects PM in the exhaust, and forms a capacitor. , 33, and a capacitance type sensor having a PM amount estimation calculation unit 42 for estimating the PM amount in the exhaust gas based on the capacitance between the pair of electrodes 32, 33, and a PM amount estimation calculation unit A fuel property determination unit 2 for determining the fuel property based on the PM amount estimated by 42 is provided.

  In the conventional electric resistance type PM sensor, there is a possibility that a part of the PM is detached in an operation state in which the exhaust gas flow rate increases, and the electric resistance value between the electrodes changes until the electrodes are connected to each other by the deposition of PM. Therefore, there is a problem that the amount of PM cannot be accurately estimated.

  On the other hand, in the PM sensor 10 according to the present embodiment, the PM amount is estimated based on the capacitance change amount between the electrodes 32 and 33 having good sensitivity, and the PM in the exhaust gas is filtered. Since it is configured to be surely collected by the member 31, the amount of PM in the exhaust gas discharged from the engine 100 can be estimated with high accuracy. Therefore, by further including the fuel property determination unit 2 that determines the fuel property based on the estimated amount of PM, the PM sensor 10 having a fuel property determination function and capable of accurately determining the fuel property can be realized.

  By accurately discriminating the fuel properties, the engine 100 can be controlled in accordance with the fuel properties, and optimal engine control corresponding to not only the standard fuel but also biofuel, poor fuel, and the like is possible.

  In particular, when biofuel is used as the fuel, there is a possibility that the amount of NOx in the exhaust gas increases and exceeds the regulation value. However, according to this embodiment, the use of biofuel is discriminated early. It is possible to perform optimal engine control according to the fuel properties, and to appropriately control the NOx amount in the exhaust gas.

  Note that when the amount of PM in the exhaust gas is large, fuel consumption may be deteriorated, but it is also possible to improve fuel consumption by performing optimal engine control in accordance with fuel properties.

  Further, according to the PM sensor 10 according to the present embodiment, the PM amount and the fuel property can be estimated at the same time, and the cost is low as compared with the case where each function is realized by another device.

  Further, in the PM sensor 10 of the present embodiment, the case member 11 that houses the sensor unit 30 has its tip projecting to the vicinity of the axial center CL where the exhaust flow velocity is the fastest in the exhaust passage 110. An inlet 12 that takes in exhaust gas into the case member 11 is provided in the cylindrical wall portion on the distal end side of the case member 11. In addition, a outlet port 13 having an opening area larger than that of the inlet 12 is provided in the base end side cylindrical wall portion of the case member 11. That is, according to the PM sensor 10 of the present embodiment, the introduction port 12 is disposed in the vicinity of the axial center CL of the exhaust passage 110 where the exhaust flow rate is fast, and the opening area of the outlet port 13 is increased, so that the introduction port 12 and the introduction port 12 are guided. A large static pressure difference from the outlet 13 can be secured, and the flow of exhaust gas passing through the sensor unit 30 can be effectively promoted.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

  For example, the specific configuration of the PM sensor 10 is not limited to the above embodiment, and a stacked type sensor unit 60 may be used as shown in FIGS.

  The sensor unit 60 includes a plurality of rectangular parallelepiped filter layers 61 in which cells that are alternately plugged on the upstream side and the downstream side are arranged in parallel in one direction, and a plurality of first plates made of a plate-like conductive member. And the second electrode plates 62 and 63, and the first and second electrode plates 62 and 63 are alternately stacked with the filter layer 61 interposed therebetween. The first and second electrode plates 62 and 63 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.

  By arranging the first electrode plate 62 and the second electrode plate 63 to face each other and sandwiching the filter layer 61 between the electrode plates 62 and 63, the electrode surface area S can be effectively secured and detected. It is possible to increase the absolute capacitance 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 is burned and removed, a voltage is directly applied to the electrode plates 62, 63, or a heater substrate (not shown) is interposed between the filter layer 61 and the electrode plates 62, 63. do it.

  In addition, as shown in FIG. 4, the positions of the inlet 12 and the outlet 13 may be interchanged so that the flow of exhaust gas introduced into the case member 11 is reversed. In this case, the filter member 31 may be stored in the case member 11 by being inverted.

2 Fuel property determination unit 3 Fuel property map 4 Fuel property response control unit 10 PM sensor (sensor)
40 ECU
42 PM amount estimation calculation unit (estimating means)
100 engine (internal combustion engine)
110 Exhaust passage

Claims (3)

A sensor that is disposed in an exhaust passage of an internal combustion engine and detects the amount of particulate matter contained in the exhaust,
A filter member including a cell that is disposed in the exhaust passage and collects particulate matter in the exhaust is provided with at least a pair of electrodes that are opposed to each other with the cell interposed therebetween to form a capacitor, and between the pair of electrodes. It consists of a capacitance type sensor equipped with an estimation means for estimating the amount of particulate matter in the exhaust based on the capacitance,
A sensor comprising a fuel property determining unit for determining a fuel property based on the amount of particulate matter estimated by the estimating means. The fuel property determination unit is a fuel property map in which a reference particulate matter amount, which is the amount of particulate matter discharged from the internal combustion engine when a standard fuel serving as a reference for determining fuel properties is used, is mapped for each operating situation. The fuel property map is determined by comparing the reference particulate matter amount corresponding to the current operating state with reference to the fuel property map and the particulate matter amount estimated by the estimation means. The sensor according to claim 1. A sensor according to claim 1 or 2,
A fuel property response control unit that controls the internal combustion engine including fuel injection timing according to the fuel property determined by the fuel property determination unit;
A control apparatus for an internal combustion engine, comprising:

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