JP2019032188A - Particle detection apparatus and vehicle - Google Patents

Abstract

To reduce an influence of fluctuation in a corona discharge voltage and the like when corona discharge is used for particle detection, thereby precisely measuring an ion current that is a prerequisite for detecting fine particles.SOLUTION: A discharge voltage is applied to a corona discharge electrode provided in a measurement chamber in which exhaust gas flows to cause corona discharge, fine particles in exhaust are charged with ions generated by the corona discharge, and an ion current responsive signal corresponding to a magnitude of an ion current changing in accordance with an amount of the charged fine particles is obtained to detect the fine particles in the exhaust gas. At this time, an influence of disturbance caused by a transient operation state of a heat engine is removed from the ion current responsive signal and the fine particles are detected based on the ion current responsive signal from which at least a part of the influence of the disturbance is removed.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fine particle detection device for detecting fine particles and a vehicle equipped with the fine particle detection device.

  In a vehicle equipped with an internal combustion engine that burns fuel containing hydrocarbons, particulate matter (PM) containing carbon may be generated in the exhaust gas as the hydrocarbons burn. In order to limit the discharge of fine particles containing carbon to the atmosphere, a fine particle detection device that detects fine particles (PM) in exhaust gas has been proposed. A device using corona discharge is known as such a fine particle detection device (for example, see Patent Document 1 below). In the particle detector using corona discharge, a corona current is controlled to generate a certain amount of ions by corona discharge. Since some of these ions adhere to the fine particles to charge the fine particles, the amount of fine particles can be measured by measuring the ionic current generated when the charged fine particles go outside, that is, to the atmosphere.

JP 2014-219225 A

  The technique of fine particle measurement described in Patent Document 1 is excellent in that the ion current is measured after stabilizing the corona current and the amount of fine particles is measured. Impedance may fluctuate greatly, which may affect measurement accuracy.

  Such fluctuations in discharge impedance may occur when the amount of exhaust increases suddenly, such as when the internal combustion engine is transient, assuming that the particulate matter in the exhaust is measured in the environment where the particulate measuring device is placed, for example, the exhaust passage of the vehicle. Or when the amount of fine particles increases rapidly. Such fluctuations in impedance are so great that they cannot be removed or smoothed by stabilizing the corona current.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

(1) As a first aspect of the present invention, there is provided a particulate detection device for detecting particulates in the exhaust of a heat engine that accompanies combustion. The fine particle detection device includes a corona discharge unit that generates a corona discharge by applying a discharge voltage to a corona discharge electrode provided in a measurement chamber through which the exhaust flows, and ions generated by the corona discharge. An ion current signal output unit that charges fine particles in the exhaust gas and outputs an ion current corresponding signal corresponding to the magnitude of the ion current that varies depending on the amount of charged fine particles, and the operation of the heat engine from the ion current corresponding signal. Based on the disturbance removal unit that removes at least a part of the influence of the disturbance caused by the state being in a transient state, and the ion current corresponding signal from which at least a part of the influence of the disturbance is removed, the amount of fine particles in the gas A detection unit that performs detection.

  Such a particle detector removes at least a part of the influence of disturbance caused by the operating state of the heat engine in a transient state from the ion current corresponding signal corresponding to the magnitude of the ion current that changes depending on the amount of charged particles. The amount of particulates in the exhaust of the heat engine can be detected based on the ion current corresponding signal from which at least a part of the influence of the disturbance is removed.

(2) The fine particle detection apparatus further includes a receiving unit that receives a transient signal indicating a transient state of the heat engine, and the disturbance removing unit temporarily outputs [1] an ion current corresponding signal according to the transient signal received by the receiving unit. Masking processing, [2] processing to integrate or average the ion current corresponding signal, and [3] correction coefficient calculated to remove or mitigate the influence of disturbance due to the transient state. And [4] a process of offsetting the ion current corresponding signal using an offset value determined so as to remove or mitigate the influence of the disturbance due to the transient state. In this way, it is possible to easily remove or mitigate the influence of the disturbance due to the transient state of the heat engine from the ion current corresponding signal.

(3) As a second aspect of the present invention, a vehicle including an internal combustion engine is provided. In this vehicle, at least the discharge electrode of the fine particle detection device is provided in an exhaust passage of an internal combustion engine that is a heat engine, and the reception unit of the fine particle detection device receives a transient signal from an operation control unit that controls the operation of the internal combustion engine. May be received. If it carries out like this, when detecting fine particles in exhaust gas of an internal combustion engine as vehicles, it can be judged certainly whether an internal combustion engine is in a transitional state.

(4) In such a vehicle, a notification unit that performs notification that can be recognized by the driver, and a notification that uses the notification unit when it is determined that the amount of particles detected by the particle detection device is greater than or equal to a predetermined threshold value. And a control unit for performing the above. In this way, the driver can be notified when the detected amount of fine particles is equal to or greater than a predetermined threshold. As a result, it becomes easier to avoid the risk that the driver continues to operate without knowing the state of the internal combustion engine and continues to emit exhaust gas containing fine particles.

(5) As a third aspect of the present invention, a method for detecting particulates in the exhaust of a heat engine that accompanies combustion is provided. In this method, a corona discharge is generated by applying a discharge voltage to a corona discharge electrode provided in a measurement chamber through which exhaust flows, and ions generated by the corona discharge are used to charge fine particles in the exhaust. An ion current corresponding signal corresponding to the magnitude of the ion current that changes depending on the amount of fine particles to be generated is output, and the influence of the disturbance caused by the operating state of the heat engine being in a transient state is removed from the ion current corresponding signal. Based on the ion current corresponding signal from which at least a part of the influence is removed, the amount of fine particles in the gas is detected. Therefore, it is possible to detect the amount of particulates in the exhaust of the heat engine based on the ion current corresponding signal from which at least a part of the influence of the disturbance generated when the operation of the heat engine is in a transient state is removed.

It is explanatory drawing for demonstrating the whole structure of the microparticle detection apparatus which concerns on embodiment. It is explanatory drawing which shows schematic structure of a sensor drive part and a sensor among fine particle detection apparatuses. It is explanatory drawing which showed typically schematic structure of the front-end | tip part of a microparticle sensor. It is explanatory drawing which illustrated schematic structure of the electric circuit part. It is a circuit diagram which shows the circuit structure of an ion current detection circuit. It is a flowchart which shows the outline | summary of a microparticle measurement process routine. It is a graph which shows the correlation with the noise in a corona discharge voltage and ion current detection. It is a flowchart which shows the ion current measurement process routine in 1st Embodiment. It is a flowchart which shows the ion current measurement process routine in 2nd Embodiment. It is a flowchart which shows the ion current measurement process routine in 3rd Embodiment. It is a flowchart which shows the ion current measurement process routine in 4th Embodiment.

A. First embodiment:
A1) Hardware configuration of the whole particle detector:
FIG. 1A is an explanatory diagram illustrating an overall configuration of the particle detection device 10 according to the embodiment, particularly a schematic configuration of a vehicle 50 on which the particle detection device 10 is mounted. FIG. 1B is an explanatory diagram illustrating a schematic configuration of the particle detection device 10 attached to the vehicle 50.

  As shown in FIG. 1A, the particulate detection device 10 according to the embodiment includes a particulate sensor 100, a cable 20, and a sensor drive unit 30, and is exhausted from an internal combustion engine 40 as a heat engine (hereinafter referred to as a heat engine). The amount of fine particles such as soot contained in the EG is measured. The internal combustion engine 40 is a power source of the vehicle 50, and is a diesel engine in this embodiment. Of course, other heat engines such as engines using other fuels such as gasoline and alcohol can be used.

  The particulate sensor 100 is attached to an exhaust gas pipe 62 extending from the internal combustion engine 40 and detects particulates such as soot in the exhaust gas pipe 62 using corona discharge. The particle sensor 100 is electrically connected to the sensor driving unit 30 by the cable 20. In the present embodiment, the particulate sensor 100 is attached to the exhaust gas pipe 62 on the downstream side of the filter device 41 (for example, DPF (Diesel particulate filter)). The fine particle sensor 100 outputs a signal correlated to the amount of fine particles contained in the exhaust gas EG, which is a gas, to the sensor driving unit 30.

  The sensor driving unit 30 drives the particle sensor 100 and detects the amount of particles in the exhaust gas EG based on a signal input from the particle sensor 100. The “amount of fine particles in the exhaust gas EG” detected by the sensor driving unit 30 may be a value proportional to the total surface area of the fine particles in the exhaust gas EG or a value proportional to the total mass of the fine particles. May be. Alternatively, it may be a value (fine particle concentration) proportional to the number of fine particles contained in the unit volume of the exhaust gas EG. In this case, the amount of exhaust gas EG that has passed through the particle sensor 100 is separately measured. The amount of exhaust gas EG passing through the particulate sensor 100 is obtained from the output of a flow rate sensor (not shown) provided in the exhaust gas pipe 62 or estimated by a known method using a plurality of parameters relating to the driving state of the vehicle. Can do.

  The sensor drive unit 30 is electrically connected to the vehicle control unit 42 on the vehicle 50 side, and outputs a signal indicating the detected amount of fine particles in the exhaust gas EG to the vehicle control unit 42. In addition, the sensor driving unit 30 can receive a signal related to the driving state of the vehicle 50 from the vehicle control unit 42. The vehicle control unit 42 controls the entire vehicle 50 and is connected to each unit using a network such as CAN to exchange data. The vehicle control unit 42 inputs / outputs a signal to / from the sensor driving unit 30, instructs the operation of the sensor driving unit 30, and conversely inputs a signal from the sensor driving unit 30, and fuels via the fuel pipe 61. The combustion state of the internal combustion engine 40 is controlled, for example, by adjusting the amount of fuel supplied from the supply unit 43 to the internal combustion engine 40. In addition, the vehicle control unit 42 has a function as a diagnosis for detecting an abnormality of the vehicle and recording the state, and an informing unit such as a lamp for notifying the driver when any abnormality is detected. 55. For example, when the amount of fine particles in the exhaust gas EG is larger than a predetermined amount, the driver of the vehicle 50 is warned by driving the notification unit 55 about the deterioration or abnormality of the filter device 41. A battery 44 is mounted on the vehicle and supplies power to each part of the vehicle. Each circuit to be described later may include a power supply circuit, and provides a voltage necessary for the operation as needed based on the power from the battery 44.

  As shown in FIG. 1B, the particle sensor 100 includes a cylindrical tip portion 100e, and the tip portion 100e is fixed to the outer surface of the exhaust gas pipe 62 in a state where the tip portion 100e is inserted inside the exhaust gas pipe 62. Yes. Here, the tip 100e of the particulate sensor 100 is inserted substantially perpendicular to the extending direction DL of the exhaust gas pipe 62. An inflow hole 145 for taking in the exhaust gas EG into the casing CS and an exhaust hole 135 for discharging the taken out exhaust gas EG to the outside of the casing CS are provided on the surface of the casing CS of the distal end portion 100e. . Part of the exhaust gas EG flowing through the exhaust gas pipe 62 is taken into the casing CS of the tip end portion 100e through the inflow hole 145. Fine particles contained in the taken-in exhaust gas EG are charged by ions (here, cations) generated in the fine particle sensor 100. The exhaust gas EG containing charged fine particles is discharged to the outside of the casing CS through the discharge hole 135. The fine particle sensor 100 detects the amount of fine particles using an ion current generated by discharging charged fine particles to the outside. The internal configuration of the casing CS and the specific configuration of the particulate sensor 100 will be described later.

  A cable 20 is attached to the rear end portion 100r of the particle sensor 100. The cable 20 has a configuration in which a first wiring 21, a second wiring 22, a signal line 23, and an air supply pipe 24 are bundled. The wirings 21 and 22 and the signal line 23 and the air supply pipe 24 constituting the cable 20 are each constituted by a flexible member. The first wiring 21, the second wiring 22, and the signal line 23 are electrically connected to the electric circuit unit 70 of the sensor driving unit 30, and the air supply pipe 24 is connected to the air supply unit 80. .

  The sensor driving unit 30 includes a control unit 60, an electric circuit unit 70, and an air supply unit 80. Electrical signals can be exchanged between the control unit 60 and the electric circuit unit 70 and between the control unit 60 and the air supply unit 80 after providing necessary electrical insulation. ing.

  The control unit 60 includes a microcomputer and controls the electric circuit unit 70 and the air supply unit 80. In addition, the control unit 60 detects the amount of fine particles in the exhaust gas EG from the signal input from the electric circuit unit 70, and outputs a signal representing the amount of fine particles in the exhaust gas EG to the vehicle control unit 42. The exchange of signals with the vehicle control unit 42 is performed by a communication interface 66 built in the control unit 60. The communication interface 66 can output a signal to the vehicle control unit 42 or receive a signal from the vehicle control unit 42. In the case of receiving a signal, the communication interface 66 is enabled as a receiving unit. In addition, the control unit 60 also detects an abnormality in the electric circuit unit 70. The abnormality detection process performed by the control unit 60 will be described in detail later.

  The electric circuit unit 70 supplies power for driving the particle sensor 100 via the first wiring 21 and the second wiring 22. In addition, the electric circuit unit 70 receives a signal correlated with the corona current from the particle sensor 100 through the signal line 23. The electric circuit unit 70 uses the signal input from the signal line 23 to stabilize the corona current, and then sends a signal corresponding to the ion current corresponding to the amount of fine particles in the exhaust gas EG to the control unit 60. Output. Specific contents of these signals will be described later.

  The air supply unit 80 includes a pump (not shown), and supplies high-pressure air to the particulate sensor 100 via the air supply pipe 24 based on an instruction from the control unit 60. The controller 60 can vary the amount of air supplied to the particulate sensor 100 by controlling the air supply unit 80. The high-pressure air supplied from the air supply unit 80 is used when driving the particulate sensor 100. Note that the type of gas supplied by the air supply unit 80 may be other than air.

A2) Configuration of particulate sensor:
FIG. 2 is an explanatory diagram schematically showing a schematic configuration of the tip portion 100e of the particle sensor 100. As shown in FIG. The entire tip portion 100e of the particulate sensor 100 is disposed inside the exhaust gas pipe 62 and is exposed to the exhaust gas EG. The tip 100e of the particle sensor 100 includes an ion generator 110, an exhaust gas charging unit 120, and an ion trap 130. In the casing CS, the three mechanism parts of the ion generation part 110, the exhaust gas charging part 120, and the ion trapping part 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). (In other words, along the axial direction of the particle sensor 100). The casing CS is formed of a conductive member, and, as will be described later with reference to FIG. 3, through the signal line 23 (FIG. 1B), in the electric circuit unit 70, the secondary is connected through the shunt resistor R <b> 1. It is connected to the side ground SGL.

  The ion generation unit 110 is a mechanism 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 as a corona discharge electrode. It is configured. The ion generation chamber 111 is a small space formed inside the casing CS, and an air supply hole 155 and a nozzle 124 are provided on the inner peripheral surface, and the first electrode 112 is protruded inside. It has been. This configuration corresponds to a corona discharge unit. The air supply hole 155 communicates with the air supply pipe 24 (FIG. 1B) and supplies high-pressure air supplied from the air supply unit 80 (FIG. 1B) to the ion generation chamber 111. The nozzle 124 is a minute hole (orifice) provided in the vicinity of the central portion of the partition wall 142 that partitions the exhaust gas charging unit 120, and ions generated in the ion generation chamber 111 are transferred to the charging chamber 121 of the exhaust gas charging unit 120. Supply. The first electrode 112 has a rod-like outer shape, and the base end portion is fixed to the casing CS via the ceramic pipe 25 so that the tip end portion is close to the partition wall 142. The first electrode 112 is connected to the electric circuit unit 70 via the first wiring 21 (FIG. 1B). Details thereof will be described later.

  The ion generation unit 110 is applied with a DC voltage (for example, 2 to 3 kV) by the electric circuit unit 70 using the first electrode 112 as an anode and the partition wall 142 as a cathode. In the ion generator 110, corona discharge is generated between the tip of the first electrode 112 and the partition wall 142 by application of this voltage. In the corona discharge, a part of molecules constituting the air around the first electrode 112 is ionized. As a result, cations PI are generated around the first electrode 112. The positive ions PI generated in the ion generator 110 are jetted into the charging chamber 121 of the exhaust gas charging unit 120 through the nozzle 124 together with the high-pressure air supplied from the air supply unit 80 (FIG. 1B). It is preferable that the injection speed of the air injected from the nozzle 124 is about the speed of sound.

  The exhaust gas charging unit 120 is a part for charging fine particles contained in the exhaust gas EG 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 through the nozzle 124. In addition, the charging chamber 121 communicates with the outside of the casing CS via the inflow hole 145 and communicates with the capture chamber 131 of the ion capture unit 130 via the gas flow path 134. The charging chamber 121 is configured such that when air containing positive ions PI is ejected from the nozzle 124, the inside becomes negative pressure and the exhaust gas EG outside the casing CS flows through the inflow hole 145. Therefore, the air containing the positive ions PI ejected from the nozzle 124 and the exhaust gas EG flowing in from the inflow hole 145 are mixed inside the charging chamber 121. At this time, at least a part of the soot S (fine particles) contained in the exhaust gas EG flowing from the inflow hole 145 is charged by the cation PI supplied from the nozzle 124. The air containing the charged soot S and the cation PI that has not been charged is supplied to the trapping chamber 131 of the ion trap 130 via the gas flow path 134.

  In FIG. 2, the positive ion PI is shown as “+” in “◯”, and “◯” in which 煤 S is hatched. Since the cation PI cannot be visually recognized, the illustration is a schematic for understanding. Further, the size of the ridge S is also for explanation, and in actuality, there are many cases of about 0.1 μm to several tens of μm. The size of the soot S, which is a fine particle, varies depending on the type of internal combustion engine 40 used, its fuel, the state of combustion, and the like. Note that the entire space including the ion generation chamber 111, the charging chamber 121, and the trapping chamber 131, or a part thereof, functions as a measurement chamber.

  The ion capturing part 130 is a part for capturing ions that are not used for charging the soot S (fine particles), and includes a capturing 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 through the gas flow path 134. Further, the capture chamber 131 communicates with the outside of the casing CS through the discharge hole 135.

  The second electrode 132 has a substantially rod-like outer shape, and is fixed to the casing CS such that the longitudinal direction is along the flow direction of the air flowing through the gas flow path 134 (the extending direction of the casing CS). The second electrode 132 is connected to the electric circuit unit 70 via the second wiring 22 (FIG. 1B). The second electrode 132 functions as an auxiliary electrode that assists in the capture of cations that have not been subjected to charging of the soot S. Specifically, the ion trapping unit 130 is applied with a voltage of about 100 V by the electric circuit unit 70 with the second electrode 132 as an anode and the casing CS constituting the charging chamber 121 and the trapping chamber 131 as a cathode. Yes. As a result, the positive ions PI that are not used for charging the soot S receive a repulsive force from the second electrode 132 and are easily moved away from the second electrode 132. The positive ions PI whose movement direction is away from the second electrode 132 are captured by the capture chamber 131 functioning as the cathode and the inner peripheral wall of the gas flow path 134. On the other hand, the soot S charged with the cation PI receives repulsion from the second electrode 132 in the same manner as the cation PI alone, but its mass is much larger than that of the cation PI. The influence given to the direction is smaller than that of a single cation PI. Therefore, the charged soot S is discharged from the discharge hole 135 to the outside of the casing CS according to the flow of the exhaust gas EG.

  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 control unit 60 (FIG. 1B) detects the amount of soot S contained in the exhaust gas EG based on the signal output from the particulate sensor 100. A method for calculating the amount of soot S contained in the exhaust gas EG from the signal output from the particulate sensor 100 will be described later.

A3) Configuration of electric circuit section:
Next, the electrical circuit unit 70 and the connection between the electrical circuit unit 70 and the particle sensor 100 will be described with reference to FIG. FIG. 3 is an explanatory diagram showing the overall electrical configuration of the particle detection apparatus 10. The electric circuit unit 70 includes a driver 71, an insulating transformer 72, a corona current measurement circuit 73, an ion current measurement circuit 74 corresponding to an ion current signal output unit, first, second, and third rectifier circuits 81, 82,12. The electric circuit unit 70 is roughly divided into a primary side and a secondary side of the insulating transformer 72 with the insulating transformer 72 interposed therebetween. The primary side and the secondary side operate by independent power sources. The primary power supply is supplied as a stabilized voltage by a power supply unit 46 connected to the battery 44. The control unit 60 and the like as well as the circuits 75 and 76 of the driver 71 are operated by a DC power source supplied from the power source unit 46 to the driver 71. This power supply is shown as Vp in a circle mark in each figure including FIG. Since there are a plurality of types of power sources on the secondary side, they will be described separately.

  In the insulating transformer 72 of the present embodiment, the primary side winding and the secondary side winding are not in electrical contact with each other physically. For this reason, as long as insulation failure does not occur, the primary side and the secondary side of the insulation transformer 72 are completely separated. In FIG. 3, a broken line indicates a boundary between the primary side and the secondary side of the electric circuit unit 70. The primary side circuit of the insulation transformer 72 includes the control unit 60 and the power supply unit 46 in addition to the driver 71. The secondary circuit of the insulating transformer 72 includes the fine particle sensor 100 and the first, second, and third rectifier circuits 81, 82, and 12. The corona current measurement circuit 73 and the ion current measurement circuit 74 are circuits that straddle between the primary side circuit and the secondary side circuit of the insulation transformer 72 and are electrically connected to both circuits, respectively. . As will be described later, the corona current measuring circuit 73 includes a circuit portion that is electrically connected to the primary side circuit of the insulating transformer 72 and a circuit portion that is electrically connected to the secondary side circuit. However, as will be described later, both are electrically insulated by a photocoupler.

  The electrically insulated primary side and secondary side individually define a ground potential (ground potential) and are provided with ground wiring. Here, the ground indicating the reference potential of the primary side circuit is referred to as “primary side ground PGL”, and in FIG. In addition, the ground indicating the reference potential of the secondary circuit is referred to as “secondary ground SGL”, and is similarly indicated by “▼” in FIG. In the insulating transformer 72, the terminal tap of the secondary winding is connected to the secondary ground SGL. The ion current measurement circuit 74 is connected to the primary side ground PGL. Since the primary-side power source is the vehicle-mounted battery 44, the primary-side ground PGL is connected to the chassis of the vehicle. Therefore, the primary side ground PGL is also referred to as a chassis ground PGL.

  The driver 71 is a circuit that adjusts the power supplied to the primary side winding of the insulating transformer 72, and includes a discharge voltage control circuit 75 and a transformer drive circuit 76. The driver 71 forms a push-pull type power supply circuit together with the primary side of the insulating transformer 72 by the cooperation of the discharge voltage control circuit 75 and the transformer drive circuit 76. The discharge voltage control circuit 75 has a built-in DC / DC converter (not shown) having a variable output voltage, boosts the power supply voltage Vp output from the power supply unit 46, and supplies this to the center tap of the primary winding of the insulating transformer 72. Apply to PT1. The output voltage of the DC / DC converter can be adjusted by the control unit 60. The transformer drive circuit 76 includes two switching elements connected to the taps PT2, PT3 at both ends of the primary winding of the insulating transformer 72, respectively. The switching element is interposed between the primary side ground PGL of the driver 71 and the taps PT2 and PT3. The transformer drive circuit 76 converts the DC voltage supplied from the discharge voltage control circuit 75 into AC by repeatedly turning on and off these two switching elements alternately at several tens of KHz. The insulation transformer 72 converts the AC voltage applied to the primary side from the winding ratio of the primary side and secondary side coils to generate a secondary side voltage. The circuit configuration on the secondary side of the insulating transformer 72 will be described later.

  The discharge voltage control circuit 75 incorporates a circuit that detects energy applied to the primary side of the insulating transformer 72. This circuit is a circuit that detects energy applied to the primary side of the insulation transformer 72 from the voltage on the primary side of the insulation transformer 72 and the current that flows when the voltage is applied. The magnitude of the detected energy can be read from the control unit 60. By reading this energy, the controller 60 estimates the energy output to the secondary side of the insulating transformer 72, and as a result, the output voltage of the first rectifier circuit 81, that is, the corona discharge voltage used for corona discharge. Vec can be estimated. The corona discharge voltage Vec may be directly measured by providing a voltage detector in the first rectifier circuit 81. In that case, in order to ensure insulation between the primary side and the secondary side, the measured value may be transmitted to the primary side control unit 60 via an insulating element such as a photocoupler.

  The control unit 60, which is another circuit that operates at the power supply voltage Vp generated by the power supply unit 46, incorporates a microprocessor, RAM, ROM, and the like, and executes a program stored in advance in the internal ROM, thereby enabling fine particles Controls the overall operation of the detection apparatus 10. The control unit 60 executes the program stored in the ROM to control the discharge voltage control circuit 75 and the transformer drive circuit 76 built in the driver 71, and at the same time, the energy application circuit of the discharge voltage control circuit 75 described above. The detection value and the measurement results of the corona current measurement circuit 73 and the ion current measurement circuit 74 are acquired, and the amount of fine particles is detected. The fine particle amount detection process executed by the control unit 60 will be described in detail later.

  As described above, the insulation transformer 72 constitutes a push-pull type power supply circuit. The voltage on the secondary side of the insulating transformer 72 is determined according to the voltage supplied to the primary side and the ratio of the number of turns of the primary side winding and the secondary side winding. The secondary winding is provided with a plurality of taps, and a total of three types of AC voltages can be extracted with respect to the secondary side ground SGL. The output of the tap with the highest turns ratio is connected to the first rectifier circuit 81, and the output of the tap with the next highest turns ratio is connected to the second rectifier circuit 82. The output of the tap having the lowest winding ratio is connected to the third rectifier circuit 12.

The first and second rectifier circuits 81 and 82 rectify the alternating current of each voltage output from the insulating transformer 72 and convert it into direct current. The first rectifier circuit 81 is composed of a multistage charge pump, and boosts the voltage converted to direct current to a voltage about 10 times. As shown in FIG. 3, the output (DC) of the first rectifier circuit 81 is connected to the first electrode 112 via the short protection resistor 83, and the converted DC voltage is converted into the first wiring 21. And applied to the first electrode 112 via That is, the DC voltage applied by the first rectifier circuit 81 is substantially the discharge voltage at the first electrode 112, and the DC current supplied from the first rectifier circuit 81 is input to the first electrode 112. the input current I _in. The second rectifier circuit 82 rectifies the AC voltage boosted by the insulating transformer 72. The second rectifier circuit 82 is connected to the second electrode 132 via the short protection resistor 84 and applies the rectified DC voltage to the second electrode 132 via the second wiring 22. When the voltage applied to the first electrode 112 is adjusted by the discharge voltage control circuit 75, the voltage applied to the second electrode 132 is accompanied by a change in the voltage applied to the first electrode 112. Change.

  The third rectifier circuit 12 generates a drive voltage Vcc for a secondary side amplifier or the like. The third rectifier circuit 12 employs a forward method, receives an alternating current of a predetermined voltage from the insulating transformer 72, rectifies this, and converts it into a direct voltage. Since the converted DC voltage is not completely DC, it is output after being stabilized by a stabilization circuit using a highly accurate three-terminal regulator or the like. This is used as a power supply voltage for operating the corona current measuring circuit 73 and the ion current measuring circuit 74. This is referred to as a drive voltage Vcc, and in FIG.

The corona current measurement circuit 73 is a circuit for detecting a current value of a discharge current (corona current) that flows due to corona discharge generated in the ion generator 110, and the ion current measurement circuit 74 is captured by the ion trap 130. This is a circuit that measures the ion current by supplying a current (I _c ) corresponding to the positive ion PI flowing out from the primary side to the secondary side circuit. The operation of both the circuits 73 and 74 will be described below including the connection with the particle sensor 100.

A4) Configuration of corona current measurement circuit and ion current measurement circuit:
The signal line 23 from the casing CS of the particle sensor 100 is connected to the input line 95 of the ion current measuring circuit 74 inside the electric circuit unit 70, and this signal line is a shunt resistor corresponding to the voltage conversion unit. It is connected to the secondary side ground SGL via R1. Both ends of the shunt resistor R1 are connected to the secondary side of the corona current measuring circuit 73 by wirings 91 and 92. A current (I _dc + I _trp ) from the casing CS via the signal line 23 and an ionic current (I _c ) from the ionic current measuring circuit 74 flow into the shunt resistor R1 toward the secondary side ground SGL. Therefore, the total current (I _all = I _dc + I _trp + I _c ) flows through the shunt resistor R1. Here, the current I _dc is a current flowing from the first electrode 112 to the casing CS through the partition wall 142 by corona discharge, and the current I _trp corresponds to the charge of the cation PI trapped in the casing CS. Current. The current I _c is the current I _esc corresponding to the charge of the cation PI that is used for charging the soot S among the cations PI generated by the corona discharge and is taken out of the casing CS together with the exhaust gas EG. Equivalent to. When the positive ion PI is taken away together with the soot S, a current corresponding to the current I _esc is supplied from the ion current measuring circuit 74. This is because the charge corresponding to the cation PI carried away falls to the ground somewhere and returns to the chassis of the vehicle 50, that is, to the power supply unit 46 on the primary side. In other words, a current I _c equal to the current I _esc corresponding to the positive ion PI taken away together with the kite S is supplied from the primary side power supply voltage Vp to the secondary side ground SGL via the ion current measuring circuit 74. As a result, the discharge input current I _in supplied from the first rectifier circuit 81 to the first electrode 112 via the first wiring 21 and the total current I _all recovered from the particle sensor 100 are obtained. The current balance in the electric circuit unit 70 is balanced. Therefore, this current I _c is hereinafter referred to as ion current I _c .

The above-described total current I _all corresponding to the measurement current flows through the shunt resistor R1. Therefore, a voltage generated by multiplying the total current I _all by the resistance value of the shunt resistor R1 is generated at both ends of the shunt resistor R1. The corona current measurement circuit 73 includes an amplifier (not shown) that amplifies the voltage across the shunt resistor R1, and a photocoupler (not shown) that optically insulates the output voltage of the amplifier and outputs the output voltage to the outside. The input side of the amplifier and the photocoupler is operated by the drive voltage Vcc. On the other hand, the output side of the photocoupler is connected to the control unit 60 by a wiring 93. The output side of the photocoupler is operated by the power supply voltage Vp on the primary side. Therefore, the secondary side of the corona current measurement circuit 73 is completely insulated from the primary side. In the above description, the corona current measuring circuit 73 amplifies the voltage across the shunt resistor R1 as an analog signal, optically insulates it, and outputs it to the control unit 60. May be converted into a digital signal, insulated by a photocoupler, and output to the control unit 60 side as a digital signal. Such conversion into a digital signal includes, for example, a built-in oscillator that generates a triangular wave in the corona current measuring circuit 73, and compares the output of the amplifier with the voltage signal of the triangular wave, so that the output of the amplifier can be determined according to the output voltage. It can be realized by a configuration of converting into a digital signal with a high duty. Alternatively, after the output of the amplifier is converted into a parallel or serial digital signal by an A / D converter, each signal may be insulated by a photocoupler.

The output of the corona current measurement circuit 73 is input to the control unit 60 through the input port P1 by the wiring 93. That is, the control unit 60 can detect the total current I _all used for corona discharge. As described above, the input current I _in from the electric circuit 70 is supplied to the first electrode 112 of the fine particle sensor 100 are all used in corona discharge, to balance the total current I _all. Therefore, when detecting the amount of fine particles in the fine particle sensor 100, the control unit 60 passes the discharge voltage control circuit 75 of the driver 71 and the transformer drive circuit 76 so that the total current I _all becomes constant. The effective value of the AC voltage applied to the primary winding of the insulating transformer 72 is feedback-controlled. As a result, the input current I _in supplied to the first electrode 112 through the first wire 21 is kept constant.

The input current I _in can be adjusted by the control unit 60 controlling the voltage applied to the primary side of the insulating transformer 72. The control unit 60 controls the voltage applied to the primary side of the insulation transformer 72 via the discharge voltage control circuit 75, thereby controlling the amount of positive ions PI generated by corona discharge in the ion generation unit 110. be able to. Discharge voltage voltage control using the control circuit 75, upon detection of the particulate amount, the target current value input current I _in is set in advance (for example, 5 .mu.A) is performed such that, when estimating the particulate diameter , So that at least two different voltages are applied to the first electrode 112.

A5) Ion current measurement circuit details:
Next, the configuration and operation of the ion current measuring circuit 74 will be described in detail. The ion current measurement circuit 74 is configured as an operational amplifier, and amplifies the ion current I _c with a predetermined amplification degree. This output is input to the analog input port ADC1 of the control unit 60 via the wiring 94. The control unit 60 converts the signal of the analog input port ADC1 with a built-in analog / digital converter and reads it, thereby knowing the magnitude of the ion current I _c and detecting the amount of fine particles in the exhaust gas EG. The detected amount of fine particles is output to the vehicle control unit 42 and used for outputting a warning to the driver, switching the operating conditions of the internal combustion engine 40, or the like. The ion current measurement circuit 74 receives a control signal from the control unit 60. This control signal is input from the output ports Q3 and Q4 of the control unit 60 to the ion current measuring circuit 74 via the wirings 96 and 97.

  The circuit configuration of the ion current measuring circuit 74 is shown in FIG. The ion current measuring circuit 74 includes an amplifier circuit including an operational amplifier 35 that constitutes a previous stage conversion circuit (voltage-current conversion circuit) and an operational amplifier 36 that constitutes a subsequent stage differential amplifier. Further, the ion current measuring circuit 74 includes a negative voltage generating circuit 39 that generates a negative voltage Vn based on a charge pump principle, two operational amplifiers 37 and 38 that generate an offset voltage, and resistors R3, R4, and R13 that set an offset voltage. , R14, resistors R6 to R9 for setting the gain of the operational amplifier 36 functioning as a differential amplifier, other resistors R0, R5, R10 to R12, a transistor Tr11, and the like. In the following description, the resistance value of each resistor is expressed using the resistor symbols (for example, R3 to R12).

  This ion current measuring circuit 74 is roughly composed of an operational amplifier 35 and resistors R0 and R5 and operates as a conversion circuit, an operational amplifier 38 and resistors R13 and R14, and operates as an offset voltage applying circuit. 36 and 37, resistors R3, R4, R6 to R10, and a portion operating as an amplifier circuit and a negative voltage generating circuit 39. Of these, the portion that operates as an amplifier circuit is more specifically composed of an operational amplifier 37 and resistors R3 and R4, and is composed of a circuit that outputs a shift voltage, and an operational amplifier 36 and resistors R6 to R9, and performs voltage amplification. It consists of a circuit.

  For convenience of explanation, the negative voltage generation circuit 39 will be described first. The negative voltage generation circuit 39 is a circuit that generates a negative voltage of about −0.6 V from the drive voltage Vcc (+5 V). The negative voltage generation circuit 39 includes a switching transistor Tr21, capacitors C21 and C22 for accumulating charges, diodes D21, D22 and D23 for selectively accumulating the generated positive and negative voltages in the capacitor C22, and necessary resistances. The devices R21 to R24 are provided.

  As shown in FIG. 4, the base terminal of the transistor Tr <b> 21 is connected to the output port Q <b> 4 of the control unit 60 via the resistor R <b> 21 and the wiring 97. The collector terminal of the transistor Tr21 is connected to the drive voltage Vcc via a current limiting resistor R23. A resistor R22 is interposed between the base and emitter of the transistor Tr21. Rectifier diodes D21 and D22 are connected to the collector of the transistor Tr21 via a capacitor C21. Accordingly, when the output port Q4 of the control unit 60 is switched between the high level (+ 5V) and the low level (0V), the transistor Tr21 is turned on / off. When the transistor Tr is off, a circuit of resistor R23-capacitor C21-diode D21-primary side ground PGL can be formed from the drive voltage Vcc, and charge is accumulated in the capacitor C21 with the transistor Tr21 side of the capacitor C21 being plus. The Next, when the transistor Tr21 is turned on, the positive side of the capacitor C21 is connected to the primary side ground PGL via the transistor Tr21, so that the diodes D21 and D22 side of the capacitor C21 have a negative potential. For this reason, the capacitor C22 is charged via the diode D22 and the voltage stabilizing resistor R24 connected in series with the diode D22. Since the capacitor C22 is charged through the diode D22, the side opposite to the side connected to the ground PGL has a negative potential.

  The above operation occurs every time the output port Q4 of the control unit 60 is switched between the high level and the low level. As a result, a negative voltage can be continuously extracted from the side opposite to the ground side of the capacitor C22. Since the diode D23 is connected in parallel to the capacitor C22, the voltage output from the capacitor C22 is limited by the forward voltage (about 0.6 V) of the diode D23. That is, the voltage output from the capacitor C22 is stabilized at -0.6V. This voltage is referred to as a negative voltage Vn, and is indicated by “−” in “」 ”in FIG.

  Of the positive and negative power supply terminals, the operational amplifiers 35 and 36 of the ion current measuring circuit 74 have a positive voltage side connected to the drive voltage Vcc and a negative voltage side connected to the negative voltage Vn. As for the operational amplifiers 37 and 38, the negative voltage side may be ground (0 V). Since the two operational amplifiers 37 and 38 have a voltage follower circuit configuration and output a predetermined voltage (2.5 V in this embodiment), the voltage dividing resistance ratio of the voltage dividing resistors R3 and R4 and R13 and R14 This is because a desired voltage can be obtained simply by changing the value. The operational amplifier 37 having a voltage follower circuit configuration outputs the voltage connected to its input terminal as it is. The voltage on the input side is a value obtained by dividing the drive voltage Vcc by the resistance values of the two resistors R3 and R4, that is, Vcc × R4 / (R3 + R4). The output voltage of the operational amplifier 37 is called a shift voltage Vbs.

  Similarly, the operational amplifier 38 outputs a predetermined voltage (2.5 V) using the voltage dividing resistors R13 and R14. The input terminal (+) of the operational amplifier 38 has voltage dividing resistors R13 and R14. In addition to this, since the collector terminal of the transistor Tr11 is also connected, the output voltage of the operational amplifier 38 changes depending on the on / off state of the transistor Tr11. The output port Q3 of the control unit 60 is connected to the base of the transistor Tr11 via the resistor R11 and the wiring 96. A resistor R12 is connected between the base and the emitter of the transistor Tr11. Therefore, when the output port Q3 of the control unit 60 becomes high level (H), the transistor Tr11 is turned on, and the offset voltage Vos that is the output of the operational amplifier 38 becomes 0V. On the other hand, when the output port Q3 of the control unit 60 becomes low level (L), the transistor Tr11 is turned off, and the offset voltage Vos that is the output of the operational amplifier 38 becomes 2.5V.

The output terminal of the operational amplifier 38 that outputs the offset voltage Vos is directly to the input terminal (+) of the operational amplifier 35 that constitutes the conversion circuit (voltage-current conversion circuit), or the input terminal of the operational amplifier 36 that constitutes the amplification circuit ( -) Are connected through a resistor R7. The operational amplifier 35 is connected to the casing CS of the particle sensor 100 via the resistor R0 and the signal line 23 at the input terminal (−). The input terminal (−) is connected to the output terminal of the operational amplifier 35 via the resistor R5. Since the ionic current I _c flowing into the casing CS flows through the resistor R5, the operational amplifier 35 is
Va = R * I _c
According to the relationship, the ion current I _c is converted into the voltage Va. However, since the offset voltage Vos is applied to the input terminal (+) of the operational amplifier 35, the output voltage of the operational amplifier 35 is the offset voltage Vos + voltage Va.

  An amplifier using the operational amplifier 36 is connected to the subsequent stage of the conversion circuit (voltage / current circuit) configured using the operational amplifier 35. The operational amplifier 36 amplifies and outputs the difference between the output of the operational amplifier 35 (offset voltage Vos + voltage Va) and the offset voltage Voss. The positive input terminal (+) is connected to the output of the previous operational amplifier 35 via resistors R8 and R10, and to the shift voltage Vbs which is the output of the operational amplifier 37 via a resistor R9. As described above, the offset voltage Vos is input to the negative input terminal (−) of the operational amplifier 36 through the resistor R7. The amplification degree Gb of the operational amplifier 36 is determined by the ratio of the resistors R6 to R9 connected to the two input terminals (+, −), that is, R9 / R8 = R6 / R7. In an actual circuit, R9 = R6 and R8 = R7.

The output of the operational amplifier 35 in the previous stage constituting the amplifier circuit is the offset voltage Vos + the output voltage Va, but the offset voltage Vos is connected to the negative input terminal (−) of the operational amplifier 36 via the resistor R7. Therefore, the influence of the offset voltage Vos is canceled in the ion current detection circuit 74 as a whole, and the offset voltage Vos does not appear in the output of the operational amplifier 36. However, since the shift voltage Vbs is input to the input terminal (+) of the operational amplifier 36, the output of the operational amplifier 36 is shifted by this shift voltage Vbs. As a result, the output of the operational amplifier 36 is a voltage Gb · Va corresponding to the ion current I _c with the shift voltage Vbs (2.5 V in this embodiment) as the center voltage.

The output of the operational amplifier 36 is input to the analog input port ADC1 of the control unit 60. The output of the operational amplifier 36 read by the control unit 60 is called a detection signal Vion. The control unit 60 reads the detection signal Vion input to the analog input port ADC1 by converting it with a built-in analog / digital converter. Detection signal Vion read, the corona discharge is performed, if there is no abnormality in all circuitry including a fine particle sensor 100 can be handled as a value reflecting the ion current I _c. Therefore, by reading this detection signal Vion, the control unit 60 can detect the amount of fine particles in the exhaust gas. The detected amount of fine particles is output to the vehicle control unit 42 and used for outputting a warning to the driver, switching the operating conditions of the internal combustion engine 40, or the like.

As described above, the detection signal Vion output by the ionic current measuring circuit 74, becomes a value reflecting the ion current I _c corresponding to the quantity of particulate, For this purpose, the corona discharge is performed normally, and corona discharge It is assumed that the detection circuit for the ion current I _c generated based on the above is operating normally. The following configuration is incorporated in the ion current measurement circuit 74 so that such a premise can be verified.

(A) In the ion current measurement circuit 74, the offset voltage Vos can be switched by turning the output port Q3 of the control unit 60 on (high level) and off (low level). When measuring the ion current I _c , the offset voltage Vos that is the output of the operational amplifier 38 is set to 0 V. When determining whether or not the particle sensor 100 is normal, the offset voltage Vos is 2 as necessary. .5V. The determination of whether or not normal will be described in detail later.

(B) The negative voltage generation circuit 39 generates a negative voltage Vn (−0.6 V), which is used as one operating voltage of the operational amplifiers 35 to 36. For this reason, the output of the operational amplifier 35 can take a negative value. Since the shift voltage Vbs (+2.5 V) that is the output of the operational amplifier 37 is input to the subsequent operational amplifier 36 that receives the output of the operational amplifier 35, the output of the ion current measuring circuit 74 is eventually the shift voltage Vbs. The value can be a value equal to or lower than the shift voltage Vbs. Specifically, when the ionic current flows I _c is higher than the shifted voltage Vbs voltage (Va) corresponding to the ion current I _c, no flow ion current I _c, due to an insulation deterioration If a reverse current flows, the voltage becomes lower than the shift voltage Vbs.

  The reason why the measurement by the ion current measuring circuit 74 is not normally performed is that the casing CS of the fine particle sensor 100, that is, the short-circuit between the secondary ground GGL and the chassis ground PGL, the insulation deterioration, or the like occurs. A case may be considered where the insulation of the circuit board of the circuit unit 70 or the insulation transformer 72 is deteriorated and the insulation resistance is significantly reduced. Therefore, based on this knowledge, in the present embodiment, the following particle detection process is executed.

A6) Fine particle detection processing:
FIG. 5 is a flowchart showing a particulate detection processing routine executed by the control unit 60. The control unit 60 starts the processing routine immediately after turning on the power, performs the initialization processing (step S100), and the corona discharge start processing (step S110), and then performs steps S200 to S200 at predetermined intervals. The process of S130 is repeatedly executed.

  The initialization process (step S100) executed by the control unit 60 includes a process for confirming whether each part of the electric circuit unit 70 is abnormal, a process for initializing various parameters used for the particle detection process, and the like. When there is no abnormality in the electric circuit unit 70 and the initialization of the parameters is completed, the control unit 60 starts corona discharge (step S110). Specifically, the control unit 60 drives the discharge voltage control circuit 75 and the transformer drive circuit 76 to drive the primary side of the insulating transformer 72 at a predetermined frequency and output a high voltage to the secondary side. As a result, a high voltage is applied to the first electrode 112 of the particle sensor 100 from the first rectifier circuit 81 provided on the secondary side, and corona discharge is started. Of course, the trap voltage is simultaneously applied to the second electrode 132 of the particle sensor 100 via the second rectifier circuit 82. Further, the third rectifier circuit 12 also operates, and the corona current measurement circuit 73 and the ion current measurement circuit 74 also start to operate after receiving the output voltage.

When the corona discharge is started, the control unit 60 performs a process of inputting a discharge participation parameter (step S200). The discharge participation parameter is a parameter necessary for estimating the corona discharge voltage. In the present embodiment, the detection result from the energy detection circuit in the discharge voltage control circuit 75 and the corona current value I _all output from the corona current measurement circuit 73 are input as the discharge participation parameters. As already described, if a detector or the like for measuring the output voltage of the first rectifier circuit 81, which is a corona voltage, is provided, the corona discharge voltage can be detected by reading the output.

Subsequently, a fluctuation amount calculation process is performed (step S120). The fluctuation amount is a fluctuation amount of the corona discharge voltage Vec obtained from the parameter read in step S120, and is a fluctuation amount ΔVec indicating how much the corona discharge voltage Vec is deviated from the reference value. For the corona discharge voltage Vec, the corona current measurement circuit 73 detects the total current I _all and performs feedback control using the reference voltage as the target voltage. However, since a high voltage is applied to the first electrode 112 to cause corona discharge, the corona discharge voltage Vec fluctuates from the target voltage in a short time. According to actual measurement, if it is an instantaneous value (peak voltage), it may fluctuate up to 1000 volts at the maximum from the target value of feedback control. Various factors including the impedance of the first electrode 112 of the fine particle sensor 100 can be considered as factors affecting the ion current Ic, but the variation ΔVec from the reference voltage of the corona discharge voltage Vec is the detected value of the ion current. On the other hand, it turned out to be noise. This point will be described with reference to FIG. FIG. 6 is a graph showing the relationship between the fluctuation amount ΔVec from the corona voltage reference value and the noise voltage ΔVn superimposed on the detected value of the ionic current, using the impedance of the discharge part of the fine particle sensor 100 as a parameter. Since the ion current Ic is converted into a voltage value when read by the input port ADC1 of the control unit 60, noise with respect to the measured value of the ion current is shown as a noise voltage ΔVn in FIG.

  As can be seen from FIG. 6, even if the impedance of the discharge part of the fine particle sensor 100, that is, the first electrode 112 to which the voltage from the first rectifier circuit 81 is applied, changes in the range of 2 GΩ to 5 GΩ. The correlation between the fluctuation amount ΔVec of the voltage from the reference voltage and the noise voltage ΔVn does not change. For this reason, even if wrinkles adhere to the first electrode 112 and its impedance changes, the relationship between the two can be considered constant. Therefore, the control unit 60 calculates the fluctuation amount ΔVec from the reference voltage of the corona discharge voltage Vec obtained from the discharge participation parameter read in step S200.

  After calculating the fluctuation amount (step S120), an ion current measurement process is executed (step S300). The contents of this process will be described in detail later. In this ion current measurement process, the ion current Ic is measured after mitigating the influence of the above-described corona voltage variation. Therefore, the amount of fine particles is calculated based on the ion current Ic in which the influence due to the fluctuation amount of the corona discharge voltage is mitigated (step S130). As already described, since the ion current Ic corresponds to the amount of ions discharged to the outside of the particle sensor 100 together with the fine particles, if the ion current Ic is accurately obtained, the calculation based on the ion current Ic is performed. The amount of fine particles can be determined with high accuracy. After the above process, if no abnormality is detected, the control unit 60 returns to the above-described step S200, and the processes after step S200 are repeated.

  Next, the ion current measurement process in 1st Embodiment is demonstrated based on FIG. FIG. 7 is a flowchart showing ion current measurement processing in the first embodiment. Since this process is executed by the control unit 60, the control unit 60 functions not only in the first embodiment described below but also in other embodiments as a disturbance removal unit that removes the influence of disturbance. When the processing shown in FIG. 7 is started, the control unit 60 determines whether or not the internal combustion engine 40 of the vehicle is in a transient state based on the signal received from the vehicle control unit 42 (step S310). Since the vehicle control unit 42 controls the operation of the internal combustion engine 40, it is assumed that the internal combustion engine 40 is in a transient state, such as when the output of the internal combustion engine 40 is increased or decreased for acceleration or deceleration of the vehicle. A signal indicating the state is output to the control unit 60. The control unit 60 can determine whether the internal combustion engine 40 is in a transient state by receiving this signal via the communication interface 66.

  If it is determined that the internal combustion engine 40 is in a transient state, nothing is performed and the process is terminated. Therefore, in this case, the measurement of the ion current Ic is not performed. It should be noted that the fluctuation amount obtained in step S120, here the fluctuation amount from the reference voltage of the corona voltage, is not received or received from the vehicle control unit 42 as to whether or not the internal combustion engine 40 is in a transient state. It is determined whether or not ΔVec is greater than a predetermined threshold value V1, and if the amount of variation ΔVec from the reference voltage of the corona discharge voltage Vec is greater than a predetermined threshold value V1, it is determined that the internal combustion engine 40 is in a transient state. The same judgment may be made. When the output of the internal combustion engine 40 fluctuates greatly, the exhaust gas contains a large amount of soot and the like, and the impedance of the first electrode 112 of the particulate sensor 100 changes, resulting in a corona discharge voltage. Because it fluctuates.

  If it is determined in step S310 that the internal combustion engine 40 is not in a transient state, the output from the ion current measurement circuit 74 is read via the input port ADC1, and based on this, the ion current Ic is measured. That is, in this embodiment, it is determined whether or not the internal combustion engine 40 of the vehicle 50 is in a transient state, and when it is determined that the vehicle 50 is not in a transient state, it is determined that the noise voltage ΔVn is small and the influence on the measurement is small. If the ion current is measured and it is determined that the current is in a transient state, the ion current measurement itself is not performed. Therefore, the measured value of the ion current Ic does not include the value in the transient state in which a large noise component is superimposed, and the ion current is detected with high accuracy. For this reason, fine particles can be detected with high accuracy based on the ion current.

B. Second embodiment:
Next, a second embodiment will be described. In the particle detection apparatus 10 of the second embodiment, the hardware configuration and the outline of the particle detection processing shown in FIG. 5 are the same as those of the first embodiment. The particle detector 10 of the second embodiment is different from the first embodiment only in the ion current measurement process (step S300). Therefore, in the following description, the same step number is assigned to the same process as in the first embodiment, and the detailed description thereof may be omitted. The same applies to the third and subsequent embodiments.

  The ion current measurement process in 2nd Embodiment was shown in FIG. In the second embodiment, when the ion current measurement process is started, it is first determined whether or not the internal combustion engine 40 is in a transient state as in the first embodiment (step S310). If it is determined that the internal combustion engine 40 is in a transient state, it is next determined whether or not the variation obtained in step S120, here, the variation ΔVec from the reference voltage of the corona discharge voltage Vec is greater than a predetermined threshold value V2. This is performed (step S312). If the fluctuation amount ΔVec from the reference voltage of the corona discharge voltage Vec obtained in step S120 is larger than the predetermined threshold value V2, next, a process of calculating the offset amount of the entire circuit that measures the ion current Ic from the fluctuation amount ΔVec. Is performed (step S320). Here, the circuit to be measured is from the discharge voltage control circuit 75 and the transformer driving circuit 76 that are the primary side of the electric circuit unit 70 to the first rectifier circuit 81 that is the secondary side, and further to the ion current measuring circuit 74. It is the whole including up to. In order to correct the relationship between the fluctuation amount ΔVec and the noise voltage ΔVn shown in FIG. 6, if the corona discharge voltage Vec is to be offset, the discharge voltage control circuit 75 and the transformer drive circuit 76 apply it to the primary side of the insulating transformer 72. This is because it is necessary to change the energy to be changed.

  After obtaining the offset amount, a process of applying the offset amount to the entire circuit that performs corona discharge is performed (step S330). More specifically, the discharge voltage control circuit 75 and the transformer drive circuit 76 are controlled to perform offset so as to cancel the fluctuation of the corona discharge voltage Vec. Thereafter, a process for measuring the ion current Ic is performed (step S350). On the other hand, if the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is not larger than the predetermined threshold value V2 in the determination in step S312, no processing relating to the offset amount in steps S320 and S330 is performed and the ion current Ic is immediately performed. Is performed (step S312: “YES”, step S350).

  Further, if it is already determined in step S310 that the internal combustion engine 40 is not in a transient state, the process directly proceeds to step S350, and the process of measuring the ionic current Ic is performed. Accordingly, when the internal combustion engine 40 is not in a transient state or when the fluctuation amount ΔVec of the corona discharge voltage from the reference voltage is not larger than the threshold value V2, the ion current Ic is immediately calculated without calculating or giving the offset amount. Measurement will be performed.

  According to the second embodiment described above, if the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is larger than the threshold value V2, the circuit for performing the corona discharge by obtaining the offset amount that cancels this fluctuation amount. Here, the discharge voltage control circuit 75 and the transformer drive circuit 76 are controlled, and the ion current Ic is measured after reducing the fluctuation amount ΔVec. Accordingly, the ion current Ic is not measured in a state where the fluctuation amount ΔVec from the reference voltage of the corona discharge voltage Vec is large including the case where the fluctuation amount ΔVec is originally small and the fluctuation amount is not offset. For this reason, the ion current Ic can be measured with high accuracy, and as a result, the detection of fine particles can be performed with high accuracy.

  In the second embodiment, the process of offsetting the corona discharge voltage is performed only when the internal combustion engine 40 is in a transient state and the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is larger than the threshold value V2. If the internal combustion engine 40 is in a transient state, the offset process may always be performed. Alternatively, if the threshold value V1 larger than the threshold value V2 is set and the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is larger than the threshold value V1, the offset process and the process for measuring the ion current Ic are not performed, and FIG. The illustrated ion current measurement process may be terminated. In this way, when the variation ΔVec of the corona discharge voltage Vec from the reference voltage is too large (ΔVec> V1), the ion current Ic is not measured, so that it is not necessary to perform an excessive offset process.

C. Third embodiment:
Next, a third embodiment will be described. The particle detection apparatus 10 of the third embodiment has the same hardware configuration and the entire processing of the particle detection processing routine shown in FIG. 5 as in the first and second embodiments. In the third embodiment, as shown in FIG. 9, the ionic current measurement process is different from the first and second embodiments. When the ion current measurement process shown in FIG. 9 is started, the control unit 60 first measures the ion current Ic (step S350). Then, it is determined whether or not the internal combustion engine 40 is in a transient state (step S310). If it is determined that the internal combustion engine 40 is in a transient state, it is determined whether or not the variation obtained in step S120, here the variation ΔVec from the reference voltage of the corona discharge voltage Vec is greater than a predetermined threshold V3 ( Step S313).

  If it is determined in step S310 that the internal combustion engine 40 is not in a transient state, or if it is determined in step S313 that the variation ΔVec from the reference voltage of the corona discharge voltage Vec is not greater than a predetermined threshold value V3. No action is taken and the ion current measurement process is terminated. As a result, the ion current Ic measured in step S350 is used as it is for the detection of the amount of fine particles (FIG. 5, step S130).

  On the other hand, if the internal combustion engine 40 is in a transient state and it is determined in step S313 that the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is larger than a predetermined threshold value V3, then this fluctuation amount. Processing for calculating the correction coefficient k from ΔVec is performed (step S360). The correction coefficient k is a coefficient for removing the influence of the noise voltage ΔVn assumed from the relationship shown in FIG. 6 from the ion current Ic measured in step S350. Based on the relationship shown in FIG. 6, it is easy to obtain a relational expression or a lookup table for obtaining the correction coefficient k from the variation ΔVec in advance.

  Subsequently, the ion current Ic is corrected by multiplying the previously measured ion current Ic by the correction coefficient k (step S370). Therefore, if step S370 is executed, the ion current Ic can be handled as a value with the influence of the noise voltage ΔVn removed or reduced.

  According to the third embodiment described above, when the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is larger than the predetermined threshold value V3, the influence of the fluctuation amount ΔVec is alleviated and the ion current Ic is set. The amount of fine particles can be detected with high accuracy. Alleviating the influence of the fluctuation amount Vec means removing the influence or reducing the influence.

D. Fourth embodiment:
Next, a fourth embodiment will be described. The particle detection device 10 of the fourth embodiment has the same hardware configuration and the entire processing of the particle detection processing routine shown in FIG. 5 as in the first to third embodiments. In the fourth embodiment, as shown in FIG. 10, the ion current measurement process is different from those in the first to third embodiments. When the ion current measurement process shown in FIG. 10 is started, the control unit 60 first performs a process of measuring the ion current Ic, similarly to the third embodiment (step S350). Then, it is determined whether or not the internal combustion engine 40 is in a transient state (step S310). If it is determined that the internal combustion engine 40 is in a transient state, the amount of variation obtained in step S120, here, the corona discharge voltage Vec is determined. It is determined whether or not the fluctuation amount ΔVec from the reference voltage is greater than a predetermined threshold value V4 (step S314).

  If it is determined in step S310 that the internal combustion engine 40 is not in a transient state, or if it is determined in step S314 that the variation ΔVec from the reference voltage of the corona discharge voltage Vec is not greater than a predetermined threshold value V4. No action is taken and the ion current measurement process is terminated. As a result, the ion current Ic measured in step S350 is used as it is for the detection of the amount of fine particles (FIG. 5, step S130).

  On the other hand, if it is determined in step S314 that the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is larger than the predetermined threshold value V4, the already measured ion current Ic is filtered (step S380). ). Here, the filter processing for the ion current Ic is expressed as a function F (Ic). As described above, the corona discharge voltage Vce is feedback controlled so as to coincide with the reference voltage. For this reason, even if it deviates from the reference voltage to the plus side or minus side for a short time, it may be considered that the control is performed in the vicinity of the reference voltage if an average over a certain period is taken. For this reason, if the process of integrating the measurement result of the ion current Ic (filter process using a low-pass filter) is performed, the influence of the noise voltage ΔVn can be reduced. The filtering process may be an integration process, or may be a so-called smoothing process in which a measurement value before the previous time is weighted to obtain an average value or an intermediate value. The average may be not only an arithmetic average but also a geometric average or a moving average.

  According to the fourth embodiment described above, when the internal combustion engine 40 is in a transient state and the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is larger than the predetermined threshold value V4, the fluctuation amount ΔVec The influence can be mitigated by filtering.

  In the third and fourth embodiments described above, a threshold value V1 larger than the threshold values V3 and V4 is set, and before the determination in step S313 or S314, the variation amount ΔVec of the corona discharge voltage Vec from the reference voltage is the threshold value V1. If it is larger, the ion current measurement process shown in FIG. 9 or 10 may not be executed. In this way, as described in the second embodiment, when the fluctuation amount ΔVec of the corona discharge voltage Vec from the reference voltage is too large (ΔVec> V1), the measurement of the ion current Ic is not performed. The possibility of using the included ion current Ic for the detection processing of the fine particles can be reduced.

E. Other embodiments:
In the above embodiment, only the processing for detecting fine particles (FIG. 5, step S130) has been described. However, when the amount of detected fine particles is equal to or larger than a predetermined value, the control unit 60 May be output to the vehicle control unit 42 and notified to the driver by the notification unit 55. In this way, the driver can understand that soot and the like are discharged from the internal combustion engine 40 in a predetermined amount or more, and can drive the vehicle 50 more appropriately. For example, it is possible to avoid sudden start, rapid acceleration, etc., and not to increase the amount of soot contained in the exhaust gas.

  In the above-described embodiment, in order to determine that the operating state of the internal combustion engine 40 is in a transient state (in other words, noise is on the measured value of the ionic current), it is a transient state from the vehicle control unit 42. However, the signal indicating the “transient state” may be replaced by another signal. For example, a parameter that greatly affects the behavior of the vehicle 50, and thus the internal combustion engine 40, such as an accelerator pedal or brake pedal depression amount signal is received and differentiated. It may be determined that it is equivalent to “state”. Further, in determining whether or not the operating state of the internal combustion engine 40 is in a transient state, as described above, it is necessary to receive a signal from the vehicle control unit 42 or the like as to whether or not the internal combustion engine 40 is in a transient state. There is no. As described above, even when the fluctuation amount of the corona discharge voltage is measured and the fluctuation amount exceeds a predetermined value (for example, the threshold value V1 described above), it is determined that the operating state of the internal combustion engine 40 is in a transient state. Good. In addition, an internal combustion engine based on one or a combination of various parameters that can withstand corona discharge, such as the amount of change, rate of change, absolute value, etc. of parameters such as the primary side voltage and primary side energy of the insulation transformer 72. It may be determined whether or not 40 is in a transient state. At this time, the determination may be made without receiving a signal indicating whether the internal combustion engine 40 is in a transient state from the vehicle control unit 42 or the like, or the signal from the vehicle control unit 42 or the like may be received and combined to be determined. You may do it.

  In the above embodiment, the correction coefficient k and the like are obtained by using the fluctuation amount ΔVec of the corona discharge voltage. However, other parameters that affect the corona discharge, such as the primary side voltage and the primary side energy of the insulating transformer 72. Using correction values and corrections using directly measured values such as secondary side voltage, secondary side output energy, output voltage of battery 44 and power supply unit 46, or other parameters that affect these values It is also possible to determine whether or not it is necessary. These parameters may be these values themselves, or the amount of change or rate of change thereof.

  In the above embodiment, the particle sensor 100 is provided with the air supply hole 155 and supplied with air from the air supply unit 80. However, the particle sensor 100 does not use such forced flow of air from the outside. It may be a thing. For example, the configuration of the particle detection system described in JP-A-2006-61767 is adopted, and the configuration of the electric circuit unit 70 including the ion current measuring circuit 74 and the control unit 60 of the present application is applied to this circuit unit (reference numeral 200). It is also possible to do. Further, the particle sensor 100 may be configured without the second electrode 132. The second electrode 132 is provided to collect cations that have not adhered to the fine particles without discharging them to the outside of the fine particle sensor 100, but is generated by the discharge at the first electrode 112 that performs corona discharge. By devising the amount of cation produced, the flow path of the exhaust gas EG, etc., it is possible to suppress the discharge of the cation that does not adhere to the fine particles.

In the above embodiment, the control unit 60 determines whether or not to apply a high voltage to the first electrode 112 of the particle sensor 100 and whether to apply the offset voltage Vos to the operational amplifier 35 as a conversion circuit. Yes. On the other hand, a circuit for autonomously switching these assignments is provided, and the control unit 60 detects the state and detects the amount of fine particles by the detection signal V _ion and determines sensor abnormality or the like accordingly. There is no problem even if the configuration is performed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment, Of course, in the range which does not deviate from the summary of this invention, it can implement in a various aspect. A part implemented by hardware in the embodiment can be replaced by software. For example, the discharge voltage control circuit 75 is controlled so that the total current I _all detected by the control unit 60 and the corona current measurement circuit 73 is constant, but a feedback circuit that makes the total current I _all constant is implemented by hardware. It is easy to realize.

DESCRIPTION OF SYMBOLS 10 ... Fine particle detector 12 ... 3rd rectifier circuit 20 ... Cable 21 ... 1st wiring 22 ... 2nd wiring 23 ... Signal line 24 ... Air supply pipe 25 ... Ceramic pipe 30 ... Sensor drive part 31 ... Gas flow path 35-38 ... Operational amplifier 39 ... Negative voltage generation circuit 40 ... Internal combustion engine 41 ... Filter device 42 ... Vehicle control unit 43 ... Fuel supply unit 44 ... Battery 46 ... Power supply unit 50 ... Vehicle 55 ... Notification unit 60 ... Control unit 61 ... Fuel Pipe 62 ... Exhaust gas pipe 66 ... Communication interface 70 ... Electric circuit part 71 ... Driver 72 ... Insulation transformer 73 ... Corona current measurement circuit 74 ... Ion current measurement circuit 75 ... Discharge voltage control circuit 76 ... Transformer drive circuit 80 ... Air supply part 81 ... first rectifier circuit 82 ... second rectifier circuit 83,84 ... short protection resistors 91-94,96 ... wiring 95 ... Force line 100 ... Particulate sensor 100e ... Tip 100r ... Rear end 110 ... Ion generator 111 ... Ion generator chamber 112 ... First electrode 120 ... Exhaust gas charger 121 ... Charge chamber 124 ... Nozzle 130 ... Ion trap 131 ... Capture chamber 132 ... second electrode 134 ... gas flow path 135 ... discharge hole 142 ... partition wall 145 ... inflow hole 155 ... air supply hole ADC1 ... analog input port C21, C22 ... capacitor CS ... casing D21-D24 ... diode EC ... equivalent Circuit PGL ... Primary side ground PT1 ... Center tap PT2, PT3 ... Tap Q1, Q3, Q4 ... Output port R0 ... Resistor R1 ... Shunt resistor R3-R9, R11-R13, R21-R24 ... Resistor Rc, Rp, Rt ... Insulation resistance S ... 煤 SGL ... Secondary side ground Tr ... Trans Star Tr11 ... transistor Tr21 ... transistor

Claims (5)

A particulate detector for detecting particulates in the exhaust of a heat engine with combustion,
A corona discharge part for generating a corona discharge by applying a discharge voltage to a corona discharge electrode provided in a measurement chamber through which the exhaust flows; and
An ion current signal output unit that charges fine particles in the exhaust with the ions generated by the corona discharge and outputs an ion current corresponding signal corresponding to the magnitude of the ion current that varies depending on the amount of charged fine particles;
A disturbance removing unit that removes at least a part of the influence of the disturbance caused by the operation state of the heat engine being in a transient state from the ion current corresponding signal;
And a detection unit that detects the amount of particulates in the exhaust gas based on an ion current corresponding signal from which at least part of the influence of the disturbance has been removed. The fine particle detection device according to claim 1,
A receiver for receiving a transient signal indicating a transient state of the heat engine;
The disturbance removing unit is in accordance with the transient signal received by the receiving unit.
[1] A process of temporarily masking the ion current corresponding signal;
[2] Processing for integrating or averaging the ion current corresponding signal;
[3] A process of correcting the ion current corresponding signal using a correction coefficient calculated so as to remove or mitigate the influence of disturbance due to the transient state;
[4] A process for offsetting the ion current corresponding signal using an offset value determined to remove or mitigate the influence of disturbance due to the transient state,
A particle detector that performs any one of the following. A vehicle equipped with an internal combustion engine,
The fine particle detection device according to claim 2 is provided in an exhaust passage of the internal combustion engine which is the heat engine,
The receiving unit of the particulate detector receives the transient signal from an operation control unit that controls the operation of the internal combustion engine. The vehicle according to claim 3,
A notification unit for performing notification recognizable by the driver;
A vehicle comprising: a control unit that performs notification using the notification unit when it is determined that the amount of the particle detected by the particle detection device is equal to or greater than a predetermined threshold. A method for detecting particulates in the exhaust of a heat engine with combustion,
A corona discharge is generated by applying a discharge voltage to a corona discharge electrode provided in a measurement chamber through which the exhaust flows.
With the ions generated by the corona discharge, the fine particles in the exhaust are charged, and an ion current corresponding signal corresponding to the magnitude of the ion current that changes depending on the amount of the charged fine particles is output.
From the ion current corresponding signal, the influence of disturbance caused by the operating state of the heat engine being in a transient state is removed,
A method for detecting the amount of particulate matter in the exhaust gas based on an ion current corresponding signal from which at least a part of the influence of the disturbance has been removed.

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