JP2016161369A - Fine particle measurement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain calibration in a fine particle measurement system.SOLUTION: A fine particle measurement system includes: a measurement signal generation circuit for outputting a measurement signal correlating with a fine particle amount in the exhaust gas of an internal combustion engine; a fine particle amount determination part for determining the fine particle amount based on the measurement signal; a signal receiving part for receiving a predetermined signal showing that a state relating to the internal combustion engine is in a predetermined state where the fine particle amount is considered to be a known amount; and a calibration execution part for correcting either the deviation of the measurement signal when the fine particle amount is the known amount or the deviation of the fine particle amount specified based on the measurement signal when the fine particle amount is the known amount. The calibration execution part executes the calibration when the predetermined signal is received by the signal reception part.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fine particle measurement system for measuring the amount of fine particles such as soot contained in a gas.

  2. Description of the Related Art Conventionally, a fine particle measurement system that measures the amount of fine particles such as soot contained in exhaust gas of an internal combustion engine such as a diesel engine is known (Patent Document 1). The fine particle measurement system of Patent Document 1 generates ions by corona discharge, charges the fine particles in the exhaust gas with the generated ions, captures ions that are not used for charging the fine particles, and based on the amount of captured ions. (In other words, based on the amount of ions charged and not captured by the fine particles), the amount of fine particles in the exhaust gas is measured. The amount of captured ions correlates with the amount of ions used for charging, and the amount of ions used for charging correlates with the amount of particulates in the exhaust gas. The amount of particulates in the exhaust gas stream can be measured from the amount. In such a fine particle measurement system, sufficient insulation is required between the electrode for corona discharge and the electrode for capturing ions not used for charging. Therefore, the insulation between the electrodes is ensured by surrounding the wiring connected to each electrode with a resin insulating member.

JP 2013-195069 A

  However, the insulating member used in the fine particle measuring system of Patent Document 1 deteriorates with age due to, for example, soot and water adhering to the gas to be measured, and its insulating property is lowered. Therefore, the insulating member is connected to each electrode. There is a risk of leakage current between the wirings. When a leak current occurs, there is a problem in that the measurement accuracy of the amount of fine particles decreases because the value of the current flowing through the electrode for capturing ions changes. For this reason, in such a case, it is required to calibrate by correcting the deviation of the measured value. However, in the past, the actual situation is that sufficient contrivance has not been made for calibration in the fine particle measurement system. Such a problem is not limited to the case where ions are generated by corona discharge to charge the particles, but is a common problem when ions are charged to the particles by any method.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

  (1) According to one aspect of the present invention, a measurement signal generation circuit that outputs a measurement signal that correlates with the amount of particulates in exhaust gas from an internal combustion engine; a particulate amount determination unit that determines the amount of particulates based on the measurement signal; A signal receiving unit that receives a predetermined signal indicating that the state relating to the internal combustion engine is a predetermined state in which the amount of fine particles can be regarded as a known amount; and the case where the amount of fine particles is the known amount; A calibration execution unit that corrects any one of the deviation of the measurement signal and the deviation of the fine particle amount specified based on the measurement signal when the fine particle amount is the known amount; A fine particle measurement system comprising: the fine particle measurement system, wherein the calibration execution unit executes the correction when the predetermined signal is received by the signal reception unit. According to the fine particle measurement system of this embodiment, when the amount of fine particles is in a predetermined state that can be regarded as a known amount, any one of the deviation of the measurement signal and the fine particle amount is corrected. It is possible to accurately specify the deviation of the measurement signal or the deviation of the amount of fine particles and perform the correction with high accuracy. For this reason, calibration of the particle measurement system can be executed to suppress a decrease in the measurement accuracy of the particle amount.

  (2) In the fine particle measurement system of the above aspect, the known amount may be zero. According to the particulate measurement system of this aspect, since the correction is performed in a state in which the measurement signal can be regarded as zero or the amount of particulates can be zero, any deviation between the deviation of the measurement signal and the amount of particulates is easy. Can be specified. In addition, since it is assumed that the measurement signal or the amount of fine particles obtained in such a state is caused by the leakage current between the electrodes, the amount of fine particles corresponding to the leakage current value or the leakage current value can be accurately specified.

  (3) In the particulate measurement system of the above aspect, the predetermined state may be a state in which the internal combustion engine is driven and fuel supply to the internal combustion engine is interrupted. According to the particulate measurement system of this aspect, since the correction is performed in a state where the measurement signal can be regarded as zero, any one of the deviation of the measurement signal and the deviation of the amount of particulates can be easily specified.

  (4) In the fine particle measurement system of the above aspect, the calibration execution unit may execute the correction after a predetermined period has elapsed since the signal reception unit received the predetermined signal. According to the particulate measurement system of this aspect, since the correction is executed after a predetermined period has elapsed since the reception of the predetermined signal, the correction is performed in a state where the particulates in the internal combustion engine are almost discharged after the fuel supply is shut off. Can be executed. For this reason, the correction | amendment error resulting from the microparticles | fine-particles which remain | survive in an internal combustion engine can be suppressed.

  (5) In the fine particle measurement system of the above aspect, the predetermined state may be a state in which driving of the internal combustion engine is stopped. According to the particulate measurement system of this aspect, since the correction is performed in a state in which the measurement signal can be regarded as zero or the amount of particulates can be zero, any deviation between the deviation of the measurement signal and the amount of particulates is easy. Can be specified. In addition, since it is assumed that the measurement signal or the amount of fine particles obtained in such a state is caused by the leakage current between the electrodes, the amount of fine particles corresponding to the leakage current value or the leakage current value can be accurately specified.

  (6) In the fine particle measurement system of the above aspect, an ion generation unit that generates ions by corona discharge; a charging chamber for charging at least a part of the fine particles in the exhaust gas using the ions; An ion capture unit that captures at least a part of the ions that have not been used for charging, and the measurement signal generation circuit includes an amount of the ions generated from the ion generation unit, and an ion capture unit. The measurement signal may be output based on a current value corresponding to a difference from the amount of the captured ions. According to the particulate measurement system of this embodiment, since ions are generated by corona discharge, very high insulation is required between the power supply circuit to the discharge electrode and the circuit through which a current corresponding to the difference in the amount of ions flows. . This is because leakage voltage tends to occur because the voltage fed (applied) to the discharge electrode in order to cause corona discharge is easily generated, while the current corresponding to the difference in ion amount is very large. This is because the influence of the leakage current on the current corresponding to this difference is large and it is necessary to prevent this influence from occurring. In such a configuration, even when the insulation between the circuits is deteriorated due to aging or the like, it is possible to suppress a decrease in the measurement accuracy of the amount of fine particles by performing the above-described correction.

  The present invention can be realized in various modes, and can be realized in the form of, for example, a particulate sensor, a particulate detection method, an internal combustion engine equipped with a particulate measurement system, and a vehicle equipped with the internal combustion engine. it can.

It is explanatory drawing which shows schematic structure of the vehicle to which the particulate-measurement system as one Embodiment of this invention is applied. 3 is an explanatory diagram schematically showing a schematic configuration of a tip end portion 100e of the particle sensor 100. FIG. 3 is a block diagram showing a schematic configuration of an electric circuit unit 700. FIG. 6 is a block diagram showing a configuration of a measurement signal generation circuit 740. FIG. It is a flowchart which shows the procedure of the fine particle amount determination process in this embodiment. It is a flowchart which shows the procedure of the calibration process in this embodiment. It is a flowchart which shows the procedure of the calibration process in 2nd Embodiment.

A. First embodiment:
A1. System configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration of a vehicle to which a particulate measurement system as an embodiment of the present invention is applied. FIG. 1A is an explanatory diagram illustrating a schematic configuration of a vehicle 500 on which the particulate measurement system 10 is mounted. FIG. 1B is an explanatory diagram illustrating a schematic configuration of the particulate measurement system 10 attached to the vehicle 500. The particulate measurement system 10 includes a particulate sensor 100, a cable 200, and a sensor driving unit 300, and measures the amount of particulates such as soot contained in exhaust gas discharged from the internal combustion engine 400. The internal combustion engine 400 is a power source of the vehicle 500 and is configured by a diesel engine or the like.

  The vehicle 500 includes various sensors 406 provided at various parts in the vehicle 500 in addition to the particle sensor 100. From these sensors 406, measured values of parameters relating to driving of the internal combustion engine 400 are supplied to the vehicle control unit 420. The parameters relating to the driving of the internal combustion engine 400 have a broad meaning including operating condition parameters of the internal combustion engine 400 and environmental parameters that change due to the operation of the internal combustion engine 400. The operating condition parameters of the internal combustion engine 400 include, for example, the rotational speed of the internal combustion engine 400, the fuel injection amount, the speed of the vehicle 500, the torque of the internal combustion engine 400, the exhaust pressure of the internal combustion engine 400, the intake pressure of the internal combustion engine 400, EGR This corresponds to the degree of opening / closing (when an EGR valve (Exhaust Gas Recirculation valve) is provided), the amount of intake air to the internal combustion engine 400, the ignition timing, and the like. Examples of the environmental parameter that changes due to the operation of the internal combustion engine 400 include the exhaust gas temperature of the internal combustion engine 400.

  The particulate sensor 100 is attached to an exhaust gas pipe 402 extending from the internal combustion engine 400, and is electrically connected to the sensor driving unit 300 by a cable 200. In the present embodiment, the particulate sensor 100 is attached to the exhaust gas pipe 402 on the downstream side of the filter device 410 (for example, DPF (Diesel particulate filter)). The fine particle sensor 100 outputs a signal correlated with the amount of fine particles contained in the exhaust gas to the sensor driving unit 300.

  The sensor driving unit 300 drives the particulate sensor 100 and measures the amount of particulate contained in the exhaust gas based on a signal input from the particulate sensor 100. In the present embodiment, “the amount of fine particles” means “the fine particle mass concentration” proportional to the mass of fine particles contained in the unit volume of exhaust gas and “the number of fine particles” proportional to the number of fine particles contained in the unit volume of exhaust gas. Measured as “concentration”. Note that only one of “mass concentration of fine particles” and “number concentration of fine particles” may be measured. In addition to these, for example, it may be measured as a value proportional to the surface area of the fine particles contained in the unit volume of the exhaust gas. The sensor driving unit 300 outputs a signal indicating the amount of fine particles contained in the exhaust gas to the vehicle control unit 420. The vehicle control unit 420 determines the combustion state of the internal combustion engine 400, the amount of fuel supplied from the fuel supply unit 430 to the internal combustion engine 400 via the fuel pipe 405, and the like in accordance with a signal input from the sensor drive unit 300. To control. The vehicle control unit 420 is configured to warn the driver of the vehicle 500 of deterioration or abnormality of the filter device 410, for example, when the amount of fine particles contained in the exhaust gas is larger than a predetermined upper limit (threshold value). May be. In addition, the vehicle control unit 420 transmits various information related to driving of the vehicle to the sensor driving unit 300. Specifically, for example, a fuel cut signal indicating a state in which fuel injection is stopped, a signal indicating an ignition state (ON or OFF), and the like are applicable. Electric power is supplied from the power supply unit 440 to the sensor driving unit 300 and the vehicle control unit 420.

  As shown in FIG. 1B, the particulate sensor 100 includes a cylindrical tip 100e. The tip 100e is inserted on the inside of the exhaust gas pipe 402 on the outer surface of the exhaust gas pipe 402. It is fixed. Here, the tip 100e of the particulate sensor 100 is inserted substantially perpendicular to the extending direction DL of the exhaust gas pipe 402. On the surface of the casing CS of the distal end portion 100e, an inflow hole 45 for taking in the exhaust gas into the casing CS and an exhaust hole 35 for discharging the taken in exhaust gas to the outside of the casing CS are provided. Part of the exhaust gas flowing through the exhaust gas pipe 402 is taken into the casing CS of the tip portion 100e through the inflow hole 45. The fine particles contained in the taken-in exhaust gas are charged by ions (here, cations) generated by the fine particle sensor 100. The exhaust gas containing the charged fine particles is discharged to the outside of the casing CS through the discharge hole 35. The internal configuration of the casing CS and the specific configuration of the particulate sensor 100 will be described later.

  A cable 200 is attached to the rear end portion 100r of the particle sensor 100. The cable 200 has a configuration in which a first wiring 221, a second wiring 222, a signal line 223, and an air supply pipe 224 are bundled. The first wiring 221, the second wiring 222, and the signal line 223 are electrically connected to an electric circuit unit 700 described later. The air supply pipe 224 is connected to an air supply unit 800 described later.

  The sensor driving unit 300 includes a sensor control unit 600, an electric circuit unit 700, and an air supply unit 800. The sensor control unit 600 and the electric circuit unit 700 and the sensor control unit 600 and the air supply unit 800 are electrically connected, respectively.

  The sensor control unit 600 includes a microcomputer and a memory, and controls the electric circuit unit 700 and the air supply unit 800. The sensor control unit 600 includes a fine particle amount determination unit 610, a calibration execution unit 620, a map storage unit 630, a current value storage unit 640, a fine particle amount storage unit 650, and a correction value storage unit 660.

  The fine particle amount determination unit 610 determines the fine particle amount with reference to a fine particle amount map mp1 stored in the map storage unit 630 based on a signal (a measurement signal Sesc described later) input from the electric circuit unit 700. FIG. 1B schematically shows the setting contents of the fine particle amount map mp1. In the fine particle amount map mp1, a correspondence relationship between a signal input from the electric circuit unit 700 and the fine particle amount is set in advance. Details of the fine particle amount map mp1 and details of the method of determining the fine particle amount will be described later. In addition, the particulate amount determination unit 610 outputs a signal representing the amount of particulates contained in the exhaust gas to the vehicle control unit 420. The fine particle amount determining unit 610 corresponds to the fine particle amount determining unit and the signal receiving unit in the claims.

  The calibration execution unit 620 corrects the deviation of the signal input from the electric circuit unit 700 by executing a calibration process described later. Details of such signal shift will be described later. The current value storage unit 640 stores a current value derived from a signal input from the electric circuit unit 700 in a particle amount determination process described later. The fine particle amount storage unit 650 stores the fine particle amount determined in the fine particle amount determination process described later. The correction value storage unit 660 stores a correction value used in a particle amount determination process described later. The correction value storage unit 660 stores zero as an initial value of the correction value in advance. This correction value can be changed by a calibration process described later.

  The electric circuit unit 700 supplies power for driving the particle sensor 100 via the first wiring 221 and the second wiring 222. In addition, a signal correlating with the amount of fine particles contained in the exhaust gas is input from the fine particle sensor 100 to the electric circuit unit 700 via the signal line 223. The electric circuit unit 700 outputs a signal corresponding to the amount of fine particles contained in the exhaust gas to the sensor control unit 600 using the signal input from the signal line 223. Specific contents of these signals will be described later.

  The air supply unit 800 includes a pump (not shown), and supplies high-pressure air to the particulate sensor 100 via the air supply pipe 224 based on an instruction from the sensor control unit 600. The high-pressure air supplied from the air supply unit 800 is used when measuring the amount of fine particles by the fine particle sensor 100. Instead of supplying air by the air supply unit 800, another type of gas may be supplied to the particle sensor 100.

  FIG. 2 is an explanatory diagram schematically showing a schematic configuration of the tip 100e of the particle sensor 100. As shown in FIG. The distal end portion 100e has a configuration in which an ion generation unit 110, an exhaust gas charging unit 120, and an ion trapping unit 130 are provided in a casing CS. That is, in the casing CS, the three processing units 110, 120, and 130 are arranged in this order from the base end side (upper side in FIG. 2) to the front end side (lower side in FIG. 2) of the tip end part 100e. Are lined up along the axial direction. The casing CS is formed of a conductive member, and is connected to the secondary side ground SGL (FIG. 3) via the signal line 223 (FIG. 1).

  The ion generation unit 110 is a processing unit for generating ions (here, cations) to be supplied to the exhaust gas charging unit 120, and includes an ion generation chamber 111 and a first electrode 112. The ion generation chamber 111 is a small space formed inside the casing CS. The air supply hole 55 and the nozzle 41 are provided on the inner peripheral surface, and the first electrode 112 protrudes inside. It has been. The air supply hole 55 communicates with the air supply pipe 224 (FIG. 1) and supplies high-pressure air supplied from the air supply unit 800 (FIG. 1) to the ion generation chamber 111. The nozzle 41 is a minute hole (orifice) provided in the vicinity of the central portion of the partition wall 42 that partitions the exhaust gas charging unit 120, and ions generated in the ion generation chamber 111 enter the charging chamber 121 of the exhaust gas charging unit 120. Supply. The first electrode 112 has a rod-like outer shape, and a base end portion thereof is fixed to the casing CS via the ceramic pipe 25 in a state in which the tip end portion is close to the partition wall 42. The first electrode 112 is connected to the electric circuit portion 700 (FIG. 1) via the first wiring 221 (FIG. 1).

  The ion generator 110 applies a DC voltage (for example, 2 to 3 kV) using the power supplied from the electric circuit unit 700 with the first electrode 112 as an anode and the partition wall 42 as a cathode. The ion generator 110 generates a positive ion PI by generating a corona discharge between the tip of the first electrode 112 and the partition wall 42 by applying this voltage. The positive ions PI generated in the ion generation unit 110 are jetted into the charging chamber 121 of the exhaust gas charging unit 120 through the nozzle 41 together with the high-pressure air supplied from the air supply unit 800 (FIG. 1). It is preferable that the jet speed of the air jetted from the nozzle 41 is about the speed of sound.

  The exhaust gas charging unit 120 is a part for charging the fine particles S contained in the exhaust gas with the cation PI, and includes a charging chamber 121. The charging chamber 121 is a small space adjacent to the ion generation chamber 111 and communicates with the ion generation chamber 111 via the nozzle 41. The charging chamber 121 communicates with the outside of the casing CS via the inflow hole 45 and communicates with the trapping chamber 131 of the ion trapping unit 130 via the gas flow path 31. The charging chamber 121 is configured such that when air containing positive ions PI is ejected from the nozzle 41, the inside becomes negative pressure, and exhaust gas outside the casing CS flows through the inflow hole 45. The air containing the cation PI ejected from the nozzle 41 and the exhaust gas flowing in from the inflow hole 45 are mixed inside the charging chamber 121. At this time, the cation PI supplied from the nozzle 41 is charged to at least a part of the fine particles S contained in the exhaust gas flowing in from the inflow hole 45. The air containing the charged fine particles S and the cations PI that have not been charged is supplied to the trapping chamber 131 of the ion trap 130 via the gas flow path 31.

  The ion trap 130 is a part for trapping ions that have not been used for charging the fine particles S, and includes a trap chamber 131 and a second electrode 132. The capture chamber 131 is a small space adjacent to the charging chamber 121 and communicates with the charging chamber 121 via the gas flow path 31. Further, the capture chamber 131 communicates with the outside of the casing CS via the discharge hole 35. The second electrode 132 has a substantially rod-shaped outer shape whose upper end is tapered, and the longitudinal direction of the second electrode 132 is in the casing CS such that the longitudinal direction is along the flow direction of the air flowing through the gas flow path 31 (the extending direction of the casing CS). It is fixed. The second electrode 132 is connected to the electric circuit portion 700 (FIG. 1) via the second wiring 222 (FIG. 1). A voltage of about 100 V is applied to the second electrode 132 and functions as an auxiliary electrode that assists in capturing positive ions that have not been charged by the fine particles S. Specifically, a voltage is applied to the ion trap 130 with the second electrode 132 as an anode and the casing CS constituting the charging chamber 121 and the trap chamber 131 as a cathode. As a result, the positive ions PI that have not been used for charging the fine particles S receive a repulsive force from the second electrode 132 and are deflected in a direction away from the second electrode 132. The positive ions PI whose traveling direction is deflected are captured by the capture chamber 131 functioning as a cathode and the inner peripheral wall of the gas flow path 31. On the other hand, the fine particles S charged with the cation PI receive a repulsive force from the second electrode 132 as in the case of the cation PI alone, but the mass thereof is larger than that of the cation PI, so Smaller than a single cation PI. Therefore, the charged fine particles S are discharged from the discharge hole 35 to the outside of the casing CS according to the flow of the exhaust gas.

  The fine particle sensor 100 outputs a signal indicating a change in current according to the amount of positive ions PI captured by the ion capturing unit 130. The sensor control unit 600 (FIG. 1) determines the amount of particulates contained in the exhaust gas based on the signal output from the particulate sensor 100.

  FIG. 3 is a block diagram illustrating a schematic configuration of the electric circuit unit 700. The electric circuit unit 700 includes a primary power supply circuit 710, an insulating transformer 720, a corona current measurement circuit 730, a measurement signal generation circuit 740, a first rectifier circuit 751, and a second rectifier circuit 752. ing.

  The primary power supply circuit 710 boosts the DC voltage supplied from the power supply unit 440 and supplies the boosted DC voltage to the insulation transformer 720 and drives the insulation transformer 720. The primary power supply circuit 710 includes a discharge voltage control circuit 711 and a transformer drive circuit 712. The discharge voltage control circuit 711 includes a DC / DC converter, and the supply voltage to the insulation transformer 720 can be arbitrarily changed under the control of the sensor control unit 600. For example, the supply voltage is controlled such that the current value of the input current Iin supplied to the first electrode 112 of the particle sensor 100 via the first wiring 221 becomes a target current value (for example, 5 μA). Practically done. This control method will be described later. Thereby, in the ion generation part 110, the generation amount of the cation PI generated by corona discharge can be made constant.

  The transformer drive circuit 712 includes a switch circuit capable of switching the direction of the current flowing through the primary coil of the insulation transformer 720, and drives the insulation transformer 720 by switching the switch circuit. In this embodiment, the transformer drive circuit 712 is configured as a push-pull circuit, for example, but may be configured as a circuit of another system such as a half-bridge system or a full-bridge system.

  The insulation transformer 720 performs voltage conversion on the power supplied from the primary side power supply circuit 710 and supplies the converted power (here, AC power) to the secondary side rectifier circuits 751 and 752. The insulation transformer 720 can set different amplification factors for the power supplied to the first rectifier circuit 751 and the power supplied to the second rectifier circuit 752 depending on the secondary coil configuration. Is possible. The insulation transformer 720 of this embodiment is configured such that the primary side coil and the secondary side coil are not in physical contact and are coupled magnetically. The primary side circuit of the insulating transformer 720 includes the sensor control unit 600 and the power supply unit 440 in addition to the primary side power supply circuit 710. The secondary side circuit of the insulating transformer 720 includes the particle sensor 100 and rectifier circuits 751 and 752. The corona current measurement circuit 730 and the measurement signal generation circuit 740 are circuits that extend between the primary side circuit and the secondary side circuit of the isolation transformer 720, and are electrically connected to both circuits, respectively. . As will be described later, the corona current measurement circuit 730 has a gap between a circuit portion electrically connected to the primary side circuit of the isolation transformer 720 and a circuit portion electrically connected to the secondary side circuit. It is physically insulated. Here, the ground (ground potential) indicating the reference potential of the primary side circuit is also referred to as “primary side ground PGL”, and the ground indicating the reference potential of the secondary side circuit is also referred to as “secondary side ground SGL”. The end of the primary side coil of the insulating transformer 720 is connected to the primary side ground PGL, and the end of the secondary side coil is connected to the secondary side ground SGL. The casing CS of the particle sensor 100 is connected to the secondary side ground SGL via the signal line 223 and the shunt resistor 230. In the particulate measurement system 10, the primary side ground PGL and the secondary side ground SGL are electrically insulated by an insulating member. Such an insulating member is made of, for example, ceramic or resin, and has high insulating properties (for example, about 1 teraohm).

  The rectifier circuits 751 and 752 convert the AC power output from the insulating transformer 720 into DC power. The first rectifier circuit 751 is connected to the first electrode 112 of the particle sensor 100 via the first wiring 221 and the short protection resistor 753. The second rectifier circuit 752 is connected to the second electrode 132 of the particle sensor 100 via the second wiring 222 and the short protection resistor 754.

  The corona current measurement circuit 730 is connected to both ends of the shunt resistor 230 on the signal line 223 through wirings 761 and 762, and is connected to the sensor control unit 600 through the wiring 763. The corona current measurement circuit 730 outputs a signal Sdc + trp indicating the current value of the current (Idc + Itrp) flowing on the signal line 223 from the casing CS toward the secondary side ground SGL to the sensor control unit 600. Here, the “signal indicating the current value” is not limited to a signal directly indicating the current value, but also a signal indirectly indicating the current value. For example, a signal that can specify a current value by applying an arithmetic expression or a map to information obtained from the signal is also included in the “signal indicating the current value”.

  The sensor control unit 600 controls the discharge voltage control circuit 711 according to the signal Sdc + trp input from the corona current measurement circuit 730. The outline of control of the discharge voltage control circuit 711 by the sensor control unit 600 will be described later.

  The measurement signal generation circuit 740 measures a current Ic corresponding to the current Iesc (hereinafter referred to as “leakage current Iesc”) of the positive ion PI that has flown outside without being captured by the ion trap 130. The measurement signal generation circuit 740 is connected to the secondary-side signal line 223 via the wiring 771 and is connected to the primary-side sensor control unit 600 via the wiring 772. Further, the measurement signal generation circuit 740 is connected to the primary side ground PGL via the wiring 773. The measurement signal generation circuit 740 outputs the measurement signal Sesc to the sensor control unit 600. The measurement signal generation circuit 740 may generate a low sensitivity measurement signal and a high sensitivity measurement signal and output them to the sensor control unit 600, respectively. In this case, one of the low sensitivity measurement signal and the high sensitivity measurement signal may be the measurement signal Sesc.

The relationship of the following formula (1) is established between the currents flowing through the tip 100e of the particle sensor 100.
Iin = Idc + Itrp + Iesc (1)
Here, Iin is an input current of the first electrode 112, Idc is a discharge current flowing through the casing CS via the partition wall 42, and Itrp is a trap corresponding to the charge amount of the cation PI trapped in the casing CS. Iesc is a leakage current corresponding to the charge amount of the cation PI that has flown outside without being captured by the ion trap 130.

Since the discharge current Idc and the trapping current Itrp flow from the casing CS to the secondary side ground SGL via the signal line 223, the total current (Idc + Itrp) flows through the shunt resistor 230 on the signal line 223. Here, the current value of (Idc + Itrp) is substantially equal to the current value of the input current Iin. Leakage current IIesc of formula (1) is approximately 1/10 of approximately ⁶ times the magnitude of the current flowing through the signal line 223 (Idc + Itrp), in order to be substantially ignored when monitoring the fluctuation of the input current Iin is there. Since the current value of the input current Iin is equal to the current value of the corona discharge of the ion generator 110, it can be said that the current value of the current (Idc + Itrp) flowing through the signal line 223 is substantially equal to the current value of the corona discharge. From this, it can be said that the corona current measurement circuit 730 outputs a signal Sdc + trp indicating the corona discharge current value of the ion generator 110 to the sensor controller 600. In response to this, the sensor control unit 600 controls the discharge voltage control circuit 711 so that the current value of the input current Iin becomes the target current in accordance with the signal Sdc + trp input from the corona current measurement circuit 730. .

The leakage current Iesc is equal to the difference between the input current Iin and the current flowing through the shunt resistor 230 (Idc + Itrp).
Iesc = Iin− (Idc + Itrp) (2)
A current Ic corresponding to the leakage current Iesc flows through the measurement signal generation circuit 740. The measurement signal generation circuit 740 generates a measurement signal Sesc corresponding to the current Ic and outputs it to the sensor control unit 600. The particle amount determination unit 610 of the sensor control unit 600 determines the amount of particles contained in the exhaust gas based on the measurement signal Sesc.

A2. Configuration example of measurement signal generation circuit:
FIG. 4 is a block diagram illustrating a configuration of the measurement signal generation circuit 740. The measurement signal generation circuit 740 includes an amplifier circuit 741, a negative feedback resistor 742, and a resistor 743. An operational amplifier can be used as the amplifier circuit 741. The inverting input terminal of the amplifier circuit 741 is connected to the secondary side ground SGL via the resistor 743, the wiring 771, and the signal line 223. As shown in FIG. 3, the signal line 223 is connected to the casing CS of the particle sensor. A power supply Vref that applies a constant reference voltage (for example, 0.5 V) to the primary side ground PGL is connected to the non-inverting input terminal of the amplifier circuit 741 via a wiring 773. In the following description, the same reference numeral “Vref” is used to represent the reference voltage of the power supply Vref. When the reference voltage Vref is input to the non-inverting input terminal of the amplifier circuit 741, the potential difference between the two input terminals of the amplifier circuit 741 is brought close to a potential difference range where errors (such as errors due to bias current and offset voltage) are unlikely to occur. Can be adjusted. As will be described in detail later, a current Ic corresponding to the leakage current Iesc (FIG. 3) of the particle sensor 100 flows through the inverting input terminal of the amplifier circuit 741. This current Ic is converted into a voltage E1 by the amplifier circuit 741. The signal Sesc indicating the voltage E1 is supplied as a measurement signal to the sensor control unit 600 via the wiring 772.

  The reason why the current Ic flowing through the inverting input terminal of the amplifier circuit 741 becomes a current corresponding to the leakage current Iesc of the particle sensor 100 is as follows. When the leakage current Iesc is generated, the reference potential of the secondary side ground SGL is lower than the reference potential of the primary side ground PGL according to the magnitude of the leakage current Iesc. This is because energy (power) supplied to the particle sensor 100 from the primary circuit including the primary power supply circuit 710 (FIG. 3) and energy (power) output from the particle sensor 100 via the signal line 223. This is because a difference in energy corresponding to the leakage current Iesc occurs. If a difference occurs between the reference potential of the secondary ground SGL and the reference potential of the primary ground PGL due to the generation of the leakage current Iesc, the compensation current Ic corresponding to this difference is applied to the inverting input terminal of the amplifier circuit 741. Flows. This compensation current Ic is equal to the leakage current Iesc and is a current that compensates for the difference between the reference potential of the secondary side ground SGL and the reference potential of the primary side ground PGL. Therefore, the measurement signal generation circuit 740 can generate the voltage E1 (and the measurement signal Sesc) representing the leakage current Iesc by performing IV conversion of the compensation current Ic.

The output voltage E1 of the amplifier circuit 741 is given by the following equation (3).
E1 = Ic × R1 + Vref (3)
Here, Ic is a compensation current, R1 is a resistance value of the negative feedback resistor 742, and Vref is a reference voltage of the amplifier circuit 741.

  In the sensor control unit 600, the fine particle amount determination unit 610 determines the fine particle amount contained in the exhaust gas with reference to the fine particle amount map mp1 based on the measurement signal Sesc supplied from the measurement signal generation circuit 740. As shown in FIG. 1B, the fine particle amount map mp1 is a two-dimensional map showing the correspondence between the measurement signal Sesc and the fine particle amount. In FIG. 1B, the horizontal axis indicates the amount of fine particles, and the vertical axis indicates the measurement signal Sesc. More precisely, the vertical axis indicates the current value of the current Ic corresponding to the voltage level of the measurement signal Sesc. As shown in the fine particle amount map mp1, the measurement signal Sesc and the fine particle amount are proportional to each other. When the amount of fine particles is zero, the current value of the measurement signal Sesc is zero. The fine particle amount determination unit 610 can determine the amount of fine particles by specifying a current value corresponding to the supplied measurement signal Sesc and referring to the fine particle amount map mp1 based on the current value.

  However, if the insulating property of the insulating member disposed between the primary side ground PGL and the secondary side ground SGL decreases due to aging or the like, leakage occurs between the primary side ground PGL and the secondary side ground SGL. An electric current can be generated. When the leak current is generated, the difference between the reference potential of the secondary side ground SGL and the reference potential of the primary side ground PGL changes from the initial value, so that the value of the leakage current Iesc changes. As a result, the magnitude (voltage) of the measurement signal Sesc deviates from the original value, and an error occurs in the determined amount of fine particles. For example, although the fine particles are not present in the exhaust gas, the leakage current Iesc is detected as a non-zero value, and the detected fine particle amount may not become zero. Further, since the insulating property of the insulating member changes with time, the value of the leakage current Iesc also changes with time, and as a result, the amount of deviation in the magnitude of the measurement signal Sesc also changes with time. Therefore, the measurement error of the amount of fine particles may gradually increase. Therefore, in the fine particle measurement system 10 of the present embodiment, a fine particle amount determination process described later is executed and corrected using a current value derived based on the measurement signal Sesc, and a correction process described later is executed and used for correction. By updating the correction value, a decrease in the measurement accuracy of the fine particle amount is suppressed.

A3. Fine particle amount determination processing:
FIG. 5 is a flowchart showing the procedure of the fine particle amount determination process in the present embodiment. In the fine particle measurement system 10, when an ignition-on signal is received from the vehicle control unit 420, a fine particle amount determination process is executed. The fine particle amount determination unit 610 identifies the current value of the current Ic corresponding to the voltage level of the measurement signal Sesc and stores it in the current value storage unit 640 (step S105). The fine particle amount determination unit 610 corrects the current value specified in step S105 using the correction value stored in the correction value storage unit 660 (step S110). As described above, the initial value of this correction value is zero, and the correction value can be updated by a calibration process. By setting this correction value to an appropriate value, a signal corresponding to the original amount of fine particles can be obtained even if the measurement signal Sesc shifts due to a decrease in insulation properties of the insulating member.

  The fine particle amount determining unit 610 refers to the fine particle amount map mp1 to determine the fine particle amount based on the corrected current value (step S115). The fine particle amount determination unit 610 stores the fine particle amount determined in step S115 in the fine particle amount storage unit 650 (step S120). After step S120 is completed, the process returns to step S105 described above. Therefore, identification of the current value corresponding to the measurement signal Sesc and determination of the amount of fine particles are repeatedly executed. The fine particle amount measurement process is executed until an ignition off signal is received.

A4. Calibration process:
FIG. 6 is a flowchart showing the procedure of the calibration process in the present embodiment. This calibration process is a process for setting (updating) the correction value used in the fine particle amount determination process described above to an appropriate value. In the present embodiment, the deviation of the measurement signal Sesc when the amount of fine particles in the exhaust gas is essentially zero is specified, and a correction value that cancels this deviation is determined. In the present embodiment, the calibration process is executed every time the vehicle 500 travels a predetermined distance (for example, 5000 kilometers).

  The calibration execution unit 620 is on standby until a fuel cut signal is received from the vehicle control unit 420 (step S205). When the fuel cut signal is received (step S205: YES), the calibration execution unit 620 waits for a predetermined period (step S210). The fuel cut signal is a signal indicating that the fuel supply to the internal combustion engine 400 is interrupted, and is output, for example, when the vehicle 500 is traveling downhill and the driver is not stepping on the accelerator pedal. The The vehicle control unit 420 outputs a fuel cut signal when detecting that the fuel injection amount is zero. When the fuel cut signal is received, since the fuel is not supplied to the internal combustion engine 400, there is a low possibility that fine particles are present in the exhaust gas. In other words, the fuel cut signal indicates that the amount of fine particles in the exhaust gas can be regarded as zero. In addition, since the process waits for a predetermined period in step S210, it is highly possible that most of the fine particles remaining in the internal combustion engine 400 have been discharged during that time. That is, by performing steps S205 and S210, the possibility that the amount of fine particles in the exhaust gas is zero in the exhaust gas pipe 402 can be increased. The predetermined period of step S210 is preferably set by determining the time from when the fuel injection amount becomes zero until the amount of fine particles discharged from the internal combustion engine 400 becomes zero by experiments or the like. Note that step S210 may be omitted. In the present embodiment, the fuel cut signal corresponds to a predetermined signal in the claims.

  The calibration execution unit 620 acquires the current value stored in the current value storage unit 640 for a predetermined number of consecutive times (N times) after step S210 is completed (step S215). As described above, since the current value is repeatedly stored in the current value storage unit 640 by the fine particle amount determination process, the calibration execution unit 620 can acquire the current value for a predetermined continuous number of times. The predetermined number of consecutive times can be set to an arbitrary number. Further, the accuracy of calibration can be improved by setting the predetermined number of continuous times to a larger number.

  The calibration execution unit 620 determines whether or not the fuel cut signal has been canceled while the N current values acquired in step S215 are stored in the current value storage unit 640 (step S220). For example, when the current value is stored in the current value storage unit 640 in association with the current value in step S105 of the fine particle amount determination process described above, the release of the fuel cut signal is detected. The time associated with the current value stored last in N times is compared to the time associated with the acquired current value, and the time associated with the last stored current value is longer than the time when the fuel cut signal is released. If it is before, it may be determined that the fuel cut signal is not released while the current values for N times are stored in the current value storage unit 640. Note that by determining whether or not the fuel cut signal has been released between the completion of step S210 and the completion of step S215, the fuel cut is performed while the current values for N times are stored in the current value storage unit 640. Judgment may be made by considering whether or not the signal is released.

  When it is determined that the fuel cut signal has been released while the current values for N times are stored in the current value storage unit 640 (step S220: YES), the process returns to step S205 described above. On the other hand, when it is determined that the fuel cut signal is not released while the current values for N times are stored in the current value storage unit 640 (step S220: NO), the calibration execution unit 620 The average value of the N current values acquired in S215 is calculated (step S225). When the fuel cut signal is not canceled, the current value is essentially zero because the amount of fine particles in the exhaust gas can be regarded as zero. However, when a leak current is generated due to a decrease in insulating properties of the insulating member, a current corresponding to the leak current is detected. Further, by obtaining the average value of N times, it is possible to accurately identify the current value corresponding to the leakage current without errors. Note that if the fuel cut signal is canceled while the current values for N times are stored in the current value storage unit 640, it is not possible to assume that the amount of fine particles in the exhaust gas is zero. In addition to the electric current to be generated, the electric current caused by the fine particles in the exhaust gas is also detected. For this reason, since the accuracy of specifying the current value corresponding to the leak current is lowered, the process returns to step S205 as described above, and step S225 and subsequent steps are not executed. As described above, the calibration accuracy can be further improved by setting the predetermined number of consecutive times (N times) in step S215 to a larger number. However, if the predetermined number of consecutive times is set to a very large value, the possibility that the fuel cut signal is canceled increases. For this reason, for example, an average time during which the fuel cut signal is continuously output is obtained, and a predetermined number of continuous times (N times) is appropriately set, such as setting the number of times the current value can be measured within the time as a predetermined number of continuous times. It is preferable to set to a different value.

  The calibration execution unit 620 overwrites the correction value stored in the correction value storage unit 660 with the average value calculated in step S225 (step S230). Therefore, when the fine particle amount determination process is executed after the execution of step S230, the current value can be corrected using the latest correction value in step S110. That is, the latest leakage current can be canceled and the current value caused by the fine particles in the exhaust gas can be accurately derived. After completion of step S230, the calibration process ends.

  According to the fine particle measurement system 10 of the first embodiment described above, the correction value is obtained based on the current value obtained while receiving the fuel cut signal, and the voltage of the measurement signal Sesc is obtained using the correction value. The current value of the current Ic corresponding to the level is corrected. Receiving the fuel cut signal means that the amount of fine particles in the exhaust gas can be regarded as zero. Therefore, the current value obtained in such a state is estimated not as a current value due to fine particles in the exhaust gas but as a leak current value due to a decrease in insulating properties of the insulating member. In the particulate measurement system 10, the current value of the current Ic corresponding to the voltage level of the measurement signal Sesc is corrected based on the leakage current value. Therefore, the leakage current value is canceled and the current value caused by particulates in the exhaust gas is accurately obtained. Can be derived. For this reason, it can suppress that the detection accuracy of the amount of particulates in exhaust gas falls.

  In addition, since the correction value is determined based on the current value obtained after waiting for a predetermined period after receiving the fuel cut signal, most of the fine particles remaining in the internal combustion engine 400 are discharged and the amount of fine particles in the exhaust gas is zero. The correction value can be determined based on the current value obtained in a state where there is a high possibility that For this reason, the correction value corresponding to the leakage current can be accurately obtained.

  Further, by obtaining the average value of the current values for N times, it is possible to specify the current value corresponding to the leakage current with high accuracy without errors. In addition, when the fuel cut signal is canceled while the current values for N times are stored in the current value storage unit 640, the process returns to step S105 without obtaining a correction value, so that the amount of particulates in the exhaust gas is zero. It can suppress that a correction value is determined based on the measured value obtained when it is not in the state which can be considered to exist. As a result, the correction value can be determined with high accuracy.

  Further, in the fine particle measurement system 10, since ions are generated by corona discharge, a member having a very high insulating property (resistance value) is required as an insulating member between the primary side ground PGL and the secondary side ground SGL. As described above, even if the insulating property of the insulating member is deteriorated due to aging or the like, according to the particle measuring system 10 of the present embodiment, the amount of particles in the exhaust gas can be obtained with high accuracy.

B. Second embodiment:
FIG. 7 is a flowchart showing the procedure of the calibration process in the second embodiment. Since the configuration of the particle measurement system of the second embodiment is the same as the configuration of the particle measurement system 10 of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof is omitted. The calibration process of the second embodiment is different from the calibration process of the first embodiment in that step S205a is executed instead of step S205, and step S220 is omitted. Since other procedures in the calibration process of the second embodiment are the same as those of the first embodiment, the same procedures are denoted by the same reference numerals, and detailed description thereof is omitted. The fine particle amount determination process in the second embodiment is the same as the fine particle amount determination process in the first embodiment, and thus detailed description thereof is omitted.

  As shown in FIG. 7, in the calibration process of the second embodiment, the calibration execution unit 620 first waits until it receives an ignition off signal from the vehicle control unit 420 (step S205a). When the ignition-off signal is received, the above-described steps S210 and S215 are executed. When the ignition-off signal is received, since the driving of the internal combustion engine 400 is stopped, the possibility that fine particles are present in the exhaust gas is low. In other words, the ignition-off signal indicates that the amount of fine particles in the exhaust gas can be regarded as zero, similar to the fuel cut signal described above. In addition, since the system waits for a predetermined period as in the first embodiment (step S210), it is highly possible that most of the fine particles remaining in the internal combustion engine 400 have been discharged during that time. That is, similarly to the first embodiment, by executing steps S205a and S210, the possibility that the amount of fine particles in the exhaust gas is zero in the exhaust gas pipe 402 can be increased. The ignition off signal corresponds to a predetermined signal in the claims.

  Here, when the ignition-off signal is received, the above-described fine particle amount determination processing is completed. Therefore, in step S215 of the second embodiment, the current value of the current Ic corresponding to the voltage level of the measurement signal Sesc is specified and stored in the current value storage unit 640 (that is, similar to step S105 of the fine particle amount determination process). Is executed a predetermined number of times. After completion of step S215, the above-described steps S225 and S230 are executed. In addition, each process of 2nd Embodiment can be performed by driving the particle | grain measurement system 10 by the electric power feeding from the battery which is not illustrated, for example.

  The fine particle measurement system of the second embodiment described above has the same effect as the fine particle measurement system 10 of the first embodiment.

C. Variations:
C1. Modification 1:
In each embodiment, the fine particles S are charged by generating cations PI by corona discharge and mixing the cations PI with the exhaust gas flowing into the charging chamber. However, the present invention is not limited to this. For example, the present invention is applied to a fine particle measuring system 10 having a charged portion in a sensor body that makes charged particles charged with fine particles S by attaching particles on the surface of the electrode and applying a high voltage to the electrode. (See, for example, US Patent Publication US2012 / 0312074A1 and US Patent Publication US2013 / 0219990A1).

C2. Modification 2:
In each embodiment, the fine particle amount determination process and the calibration process are executed as separate routines, but may be executed as a single routine. In this case, the single routine can be regarded as a fine particle amount determination process or a calibration process. That is, the correction value may be updated in the fine particle amount determination process, or the current value may be corrected in the calibration process.

C3. Modification 3:
In each embodiment, the fine particle amount determination process and the calibration process are both executed by the sensor control unit 600, but at least one of these processes may be executed by the vehicle control unit 420. For example, the fine particle amount determination process may be executed by the sensor control unit 600 (fine particle amount determination unit 610), and the calibration process may be executed by the vehicle control unit 420. In this configuration, in step S <b> 215 of the calibration process, the vehicle control unit 420 may acquire N current values from the sensor control unit 600. In step S230, the vehicle control unit 420 transmits the average value calculated in step S225 to the sensor control unit 600, and the sensor control unit 600 overwrites and stores the received average value in the correction value storage unit 660. That's fine. In this configuration, the vehicle control unit 420 corresponds to a signal reception unit and a calibration execution unit in the claims.

C4. Modification 4:
In each embodiment, the correction value is determined based on the current value obtained in a state where the amount of fine particles in the exhaust gas can be regarded as zero, but in a state where it can be regarded as any known amount instead of zero. The correction value may be determined based on the obtained current value. In this configuration, the current value when the amount of fine particles in the exhaust gas is a known amount in a state where the insulation of the insulating member is not deteriorated (that is, in a state where no leakage current is generated) is obtained in advance. The difference between the current value and the average value of the current values obtained in step S225 is preferably determined as a correction value. In this configuration, the vehicle control unit 420 transmits a predetermined signal indicating that the amount of fine particles in the exhaust gas can be regarded as a known amount to the sensor driving unit 300 (calibration execution unit 620). However, it is preferable to wait for reception of such a signal instead of step S205. The output of the predetermined signal described above is, for example, specified in advance a relationship between a parameter relating to driving of the internal combustion engine 400 such as the fuel injection amount and the rotational speed of the internal combustion engine 400 and the amount of fine particles in the exhaust gas. It is preferable that the parameter relating to the driving of 400 is executed when the amount of fine particles in the exhaust gas becomes a value corresponding to a known amount.

C5. Modification 5:
In each embodiment, the current value of the measurement signal Sesc is corrected in the fine particle amount determination process, and the correction value used for the correction is updated in the calibration process. However, the present invention is not limited to this. For example, in the fine particle amount determination process, the fine particle amount is determined based on the current value of the measurement signal Sesc, and the determined fine particle amount is corrected. In the calibration process, the correction value used for correcting the fine particle amount is updated. Also good. In this configuration, for example, the amount of fine particles is obtained based on a current value obtained in a state where the amount of fine particles in exhaust gas can be regarded as zero, and the amount of fine particles is determined as a correction value. Since the amount of fine particles obtained in this state is essentially zero, the amount of fine particles obtained as a value other than zero corresponds to the amount of fine particles corresponding to an error obtained due to a cause such as a leak current. Therefore, in the fine particle amount determination process, the fine particle amount can be obtained with high accuracy by subtracting the fine particle amount corresponding to the error from the fine particle amount determined based on the current value of the measurement signal Sesc.

C6. Modification 6:
In step S115 of the fine particle amount determination process of each embodiment, the fine particle amount is determined with reference to the fine particle amount map, but instead of such a map, a relationship indicating the relationship between the voltage value of the measurement signal Sesc and the fine particle amount. The amount of fine particles may be determined by calculation using an equation.

C7. Modification 7:
In each embodiment, the fuel cut signal and the ignition off signal are used as signals indicating that the amount of fine particles in the exhaust gas can be regarded as zero. However, the present invention is not limited to these signals, and other signals are used. May be used. For example, in the configuration in which so-called idling stop control is performed in the vehicle 500 to stop driving of the internal combustion engine 400 when the vehicle speed becomes a predetermined value or less, a signal indicating that the idling stop control is on, You may use as a signal which shows that it is in the state which can be considered that the amount of fine particles in exhaust gas is zero. A signal indicating that the fuel injection amount is zero may be used as a signal indicating that the amount of fine particles in the exhaust gas can be regarded as zero.

C8. Modification 8:
In the first embodiment, when the fuel cut signal is canceled in the middle of acquiring the current value for a predetermined number of times, the process returns to step S205, but instead of returning to step S205, the fuel cut signal is canceled. An average value of current values (current values corresponding to the number of times equal to or less than N−1) obtained by the calculation may be obtained, and the current value may be overwritten as a correction value.

C9. Modification 9:
In the embodiment, the fine particle measurement system 10 is mounted on the vehicle 500 and measures the amount of fine particles contained in the exhaust gas of the internal combustion engine 400, but the present invention is not limited to this. Fine particles contained in the exhaust gas of any other internal combustion engine such as an internal combustion engine mounted on an arbitrary moving body such as a ship or a stationary internal combustion engine may be measured.

C10. Modification 10:
In the embodiment, the calibration process is executed each time the vehicle 500 travels a predetermined distance, but the present invention is not limited to this. For example, when an ignition-on signal is received from the vehicle control unit 420, the calibration process may be started simultaneously with the start of the fine particle amount determination process. That is, it may be executed once in one operation (period from ignition on to off). Further, for example, the time may be measured by a timer (not shown), and the calibration process may be executed every time a predetermined period (for example, 30 days) elapses.

  The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Fine particle measurement system 25 ... Ceramic pipe 31 ... Gas flow path 35 ... Discharge hole 41 ... Nozzle 42 ... Partition wall 45 ... Inflow hole 55 ... Air supply hole 100 ... Fine particle sensor 100e ... Tip part 100r ... Rear end part 110 ... Ion generation Part 111 ... Ion generation chamber 112 ... First electrode 120 ... Exhaust gas charging part 121 ... Charging chamber 130 ... Ion trap part 131 ... Trapping chamber 132 ... Second electrode 200 ... Cable 221 ... First wiring 222 ... Second Wiring 223 ... Signal line 224 ... Air supply pipe 230 ... Shunt resistance 300 ... Sensor drive part 400 ... Internal combustion engine 402 ... Exhaust gas pipe 405 ... Fuel pipe 406 ... Sensor 410 ... Filter device 420 ... Vehicle control part 430 ... Fuel supply part 440 ... Power supply unit 500 ... Vehicle 600 ... Sensor control unit 610 ... Fine particle amount determination unit 620 ... Calibration Execution unit 630 ... Map storage unit 640 ... Current value storage unit 650 ... Particle amount storage unit 660 ... Correction value storage unit 700 ... Electrical circuit unit 710 ... Primary power supply circuit 711 ... Discharge voltage control circuit 712 ... Transformer drive circuit 720 ... Insulation Transformer 730 ... Corona current measurement circuit 740 ... Measurement signal generation circuit 741 ... Amplification circuit 742 ... Negative feedback resistor 743 ... Resistance 751 ... First rectifier circuit 752 ... Second rectifier circuit 753 ... Short protection resistor 754 ... For short protection Resistance 761, 763 ... Wiring 771-773 ... Wiring 800 ... Air supply part CS ... Casing DL ... Stretching direction E1 ... Voltage F ... Arrow Ic ... Current, compensation current Idc ... Discharging current Iin ... Input current Iesc ... Current, leakage current Itrp ... Capture current PI ... Positive ion PGL ... Primary side ground S ... Fine particle Sesc ... Measurement signal Sdc + trp ... No. SGL ... Secondary side ground Vref ... Power supply, reference voltage

Claims (6)

A measurement signal generating circuit for outputting a measurement signal correlated with the amount of fine particles in the exhaust gas of the internal combustion engine;
A fine particle amount determining unit that determines the fine particle amount based on the measurement signal;
A signal receiving unit that receives a predetermined signal indicating that the state relating to the internal combustion engine is a predetermined state in which the amount of fine particles can be regarded as a known amount;
Any of the deviation of the measurement signal when the amount of fine particles is the known amount and the deviation of the amount of fine particles specified based on the measurement signal when the amount of fine particles is the known amount A calibration execution unit for correcting deviations;
A particulate measurement system comprising:
The calibration execution unit executes the correction when the predetermined signal is received by the signal reception unit;
A fine particle measuring system characterized by that. The fine particle measurement system according to claim 1,
The known quantity is zero;
A fine particle measuring system characterized by that. The fine particle measurement system according to claim 2,
The predetermined state is a state in which the internal combustion engine is driven and fuel supply to the internal combustion engine is shut off.
A fine particle measuring system characterized by that. The fine particle measurement system according to claim 3,
The calibration execution unit executes the correction after a predetermined period has elapsed since the signal reception unit received the predetermined signal.
A fine particle measuring system characterized by that. The fine particle measurement system according to claim 2,
The predetermined state is a state in which the driving of the internal combustion engine is stopped.
A fine particle measuring system characterized by that. In the fine particle measurement system according to any one of claims 1 to 5,
An ion generator that generates ions by corona discharge;
A charging chamber for charging at least some of the fine particles in the exhaust gas using the ions;
An ion capturing part for capturing at least a part of the ions that were not used for charging the fine particles;
Further comprising
The measurement signal generation circuit outputs the measurement signal based on a current value corresponding to a difference between the amount of the ions generated from the ion generation unit and the amount of the ions captured by the ion capturing unit. To
A fine particle measuring system characterized by that.

Images