JP5333383B2 - Sensor control device - Google Patents

Description

  The present invention relates to a sensor control device that calculates an amount of particulate matter (PM) based on a detection signal of a particulate matter detection sensor.

  Conventionally, various PM sensors (particulate matter detection sensors) for detecting the amount of PM discharged from an engine have been proposed. For example, in the PM sensor of Patent Document 1, a pair of counter electrodes is provided on an insulating substrate, and the resistance between the electrodes changes when PM adheres between the pair of counter electrodes. The detection signal is output. Then, the PM amount is calculated based on the detection signal of the PM sensor.

JP 59-196453 A

  When the amount of PM is calculated based on the detection signal of the PM sensor, the amount of PM is calculated as a mass. To evaluate the amount of PM discharged from the engine, not only the evaluation based on the mass but also the number of particles. Evaluation is considered. In such a case, it is conceivable to calculate the number of PM particles by preliminarily determining the average particle mass of the particulate matter adhering to the PM sensor and dividing the PM amount (mass) by the average particle mass.

  However, it is considered that the PM contained in the exhaust includes those having different sizes (mass and particle size), and the size distribution varies depending on the engine operating state and the like. For this reason, when calculating the number of PM particles, it is difficult to ensure the calculation accuracy, and it is considered that there is a problem that the number of PM particles cannot be accurately grasped.

  An object of the present invention is to provide a sensor control device that can accurately determine the number of particles of particulate matter (PM) discharged from an internal combustion engine.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

A sensor control device according to the present invention includes an adherend portion for adhering conductive particulate matter contained in exhaust gas discharged from an internal combustion engine, and a detection portion including a pair of counter electrodes provided in the adherend portion. And is applied to a particulate matter detection sensor that outputs a detection signal corresponding to a resistance value between the pair of counter electrodes. And in 1st invention, the adhesion amount calculation means which calculates the adhesion amount of the said particulate matter based on the detection signal of the said particulate matter detection sensor, and one particle | grain of the particulate matter adhering to the said to-be-adhered part A plurality of different average particle masses can be set as the average particle mass per hit, a particle mass setting unit for setting any one of the average particle masses, and an adhesion amount of the particulate matter calculated by the adhesion amount calculation unit And particle number calculating means for calculating the number of particles of the particulate matter based on the average particle mass set by the particle mass setting means.

  In short, when the average particle mass used for calculation of the number of particles of the particulate matter is one and is fixed, there is a concern that the calculation accuracy of the number of particles is lowered. That is, it is difficult to ensure the calculation accuracy, considering that there are variations in the particle size of the particulate matter, and that the particulate matter changes depending on the operating state of the internal combustion engine. In this regard, according to the present invention, since the average particle mass of the particulate matter adhering to the adherend can be set from a plurality of average particle masses, the average particle mass can be selectively used, and the number of particles Calculation accuracy can be increased. As a result, the number of particles of particulate matter discharged from the internal combustion engine can be accurately obtained.

  Note that the mass per particle of the particulate matter and the particle size are approximately proportional to each other, and the particle size can be used instead of the mass as an index of the size of the particulate matter. That is, the average particle mass and the average particle size may be treated as the same as the average size per particle of the particulate matter.

In a second aspect of the invention, there is provided a sensor control device in which detection results from the plurality of detection units are respectively input as detection signals, wherein the plurality of detection units have different sizes of attached particulate matter. The particle mass setting means sets the average particle mass for each of the plurality of detection units, and the particle number calculation unit is configured to determine the amount of the particulate matter adhered and the average particle for each of the plurality of detection units. Based on the mass, the number of particles of the particulate matter is calculated for each of the plurality of detection units, and the number of particles of the particulate matter in the exhaust gas is calculated based on the respective calculation results.

  According to the above configuration, since the sizes of the particles to be attached are different in the plurality of detection units, the range of the size of the particles can be limited. Therefore, the calculation accuracy of the number of particles in each detection unit can be increased, and as a result, the number of particulate matter present in the exhaust gas can be calculated with high accuracy.

In the third invention, the particle number calculating means is a part that is a part of the entire range of the size of the particulate matter contained in the exhaust gas based on the detection result of any of the plurality of detection units. The number of particles is calculated for a range of particulate matter.

  According to the above configuration, for example, the number of particles can be calculated only for a light and small range of particulate matter in the entire range of the size of the particulate matter. Specifically, among the detection results of the plurality of detection units, the detection result of the detection unit that minimizes the size range of the particulate matter is used, so that only particles in a light range are targeted. Calculate the number.

According to a fourth aspect of the invention, there is provided an operating state detecting means for detecting an operating state of the internal combustion engine, wherein the particle mass setting means is an average particle of the particulate matter based on the engine operating state detected by the operating state detecting means. Set the mass.

  When the operating state of the internal combustion engine changes, the size distribution of the particulate matter in the exhaust gas is considered to change accordingly. According to the above configuration, when the distribution of the size of the particulate matter changes as the engine operating state changes, the average particle mass can be variably set in accordance with the change. Therefore, the calculation accuracy of the number of particles of the particulate matter can be increased.

As configurations for setting the average particle mass of the particulate matter based on the engine operating state, the following fifth and sixth inventions are conceivable.

In a fifth aspect of the invention, the engine operating state in which the fuel particle size is increased by detecting an engine operating state that is a determining factor of the fuel particle size injected from the fuel injection means of the direct injection internal combustion engine as the operating state. Then, the average particle mass is set to a large value as compared with the engine operating state in which the fuel particle size becomes small.

That is, the fuel particle size (the particle size of the fuel injected from the fuel injection means) changes according to the engine operating state, and the size (mass and particle size) of the particulate matter changes according to the fuel particle size. It is done. In this regard, according to the fifth aspect, the number of particles of the particulate matter can be calculated with high accuracy while suitably reflecting the engine operating state at each time.

  Specifically, the higher the pressure (fuel pressure) of the fuel supplied to the fuel injection means, the smaller the particle size of the fuel. Conversely, the lower the fuel pressure, the larger the particle size of the fuel. Considering this, it is better to set a larger particle mass as the average particle mass of the particulate matter as the fuel pressure is lower. Also, the higher the water temperature of the internal combustion engine, the smaller the fuel particle size, and conversely, the lower the water temperature, the larger the fuel particle size. Considering this, it is better to set a larger particle mass as the average particle mass of the particulate matter as the water temperature is lower.

In the sixth aspect of the invention, the rotational speed of the internal combustion engine is detected as the operating state, and the average particle mass is set to a larger value as the detected rotational speed of the internal combustion engine is higher.

If the rotational speed of the internal combustion engine is different, the “atomization time” from the end of fuel injection to the ignition and combustion in the combustion cycle of the internal combustion engine changes, which may affect the size of the particulate matter. For example, when the rotational speed of the internal combustion engine is high, the atomization time is shortened and particulate matter having a large particle size is discharged into the exhaust passage. In this regard, according to the sixth invention, it is possible to calculate the number of particles of the particulate matter with high accuracy while suitably reflecting the engine speed of each time.

The block diagram which shows the outline | summary of the engine control system in embodiment of invention. The disassembled perspective view which decomposes | disassembles and shows the principal part structure of the sensor element of PM sensor. The electrical block diagram regarding PM sensor. The figure which shows the particle size distribution of adhesion PM about three PM detection parts. The flowchart which shows the calculation procedure of PM particle number. The figure which shows a sensor element and main electrical structures. The flowchart which shows the calculation procedure of PM particle number. (A) is a figure which shows the relationship between a fuel pressure and PM particle size, (b) is a figure which shows the relationship between water temperature and PM particle size, (c) is a figure which shows the relationship between an engine speed and PM particle size. The top view which shows another structure of a sensor element.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. This embodiment monitors the amount of PM (the amount of conductive particulate matter) in the exhaust discharged from the engine in a vehicle engine system including an on-vehicle engine. In particular, a PM sensor is provided in the engine exhaust pipe, and the amount of PM in the exhaust gas is monitored based on the amount of PM attached by the PM sensor. FIG. 1 is a configuration diagram showing a schematic configuration of the present system.

  In FIG. 1, an engine 11 is a direct-injection gasoline engine, and the engine 11 is provided with a fuel injection valve 12 and an ignition device 13 as actuators related to the operation of the engine 11. A fuel supply unit 15 is connected to the fuel injection valve 12 via a fuel pipe 14, and the fuel injection valve 12 directly injects fuel supplied from the fuel supply unit 15 into the engine combustion chamber. The fuel supply unit 15 is a well-known high-pressure fuel supply unit that increases the pressure of the fuel and supplies the fuel to the fuel injection valve 12. The high-pressure pump that increases the pressure of the fuel supplied from the fuel tank, and the high pressure discharged from the high-pressure pump. A delivery pipe or the like is provided as a pressure accumulating section into which fuel is introduced.

  The exhaust pipe 16 of the engine 11 is provided with a three-way catalyst 17 as an exhaust purification device, an A / F sensor 18 is provided on the upstream side of the three-way catalyst 17, and particulate matter detection is provided on the downstream side. A PM sensor 19 as a sensor is provided. In addition, in the present system, the rotation sensor 21 for detecting the engine rotation speed, the intake pressure sensor 22 for detecting the intake pipe pressure, and the fuel pressure in the fuel supply unit 15 (fuel pressure in the delivery pipe) are detected. A fuel pressure sensor 23, a water temperature sensor 24 for detecting the temperature of engine cooling water (engine water temperature), and the like are provided.

  The ECU 25 is mainly composed of a microcomputer (microcomputer) composed of a well-known CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, so that the engine can be operated according to the engine operating state each time. 11 and various peripheral devices are controlled. That is, the ECU 25 inputs signals from the various sensors and the like, calculates the fuel injection amount and ignition timing based on the various signals, and controls the driving of the fuel injection valve 12 and the ignition device 13. Further, the ECU 25 performs fuel pressure control for controlling the fuel pressure in the fuel supply unit 15 (fuel pressure in the delivery pipe). Specifically, the ECU 25 sets the target fuel pressure based on each engine operating state (engine speed and intake pipe pressure), and also provides fuel pressure feedback so that the actual fuel pressure detected by the fuel pressure sensor 23 matches the target fuel pressure. Implement control.

  Further, the ECU 25 calculates the actual PM emission amount (actual PM emission amount) of the engine 11 based on the detection signal of the PM sensor 19, and diagnoses the combustion state of the engine 11 based on the actual PM emission amount. Specifically, if the actual PM emission amount exceeds a predetermined abnormality determination value, it is determined that the PM is excessively discharged and the engine is abnormal.

  In addition, the ECU 25 may be configured to variably control the control mode of the engine 11 based on the actual PM emission amount calculated from the detection result of the PM sensor 19. For example, the fuel injection amount can be controlled based on the actual PM emission amount, the fuel injection timing can be controlled, and the ignition timing can be controlled.

  Next, the configuration of the PM sensor 19 and the electrical configuration related to the PM sensor 19 will be described with reference to FIGS. FIG. 2 is an exploded perspective view showing an essential configuration of the sensor element 31 constituting the PM sensor 19, and FIG. 3 is an electrical configuration diagram regarding the PM sensor 19.

  As shown in FIG. 2, the sensor element 31 has two insulating substrates 32 and 33 each having a long plate shape, and one of the insulating substrates 32 has three PM detections for detecting the amount of PM. The parts 34, 35 and 36 are provided, and the other insulating substrate 33 is provided with a heater part 37 for heating the sensor element 31. The sensor element 31 is configured by laminating insulating substrates 32 and 33 in two layers. The insulating substrate 32 corresponds to the adherend. In the present embodiment, three PM detectors are provided. However, the number of PM detectors is arbitrary as long as it is plural.

  Each of the PM detection units 34 to 36 has a pair of detection electrodes, and the insulating substrate 32 is provided with a pair of detection electrodes 34 a and 34 b as the PM detection unit 34 and a pair of detection electrodes 35 a as the PM detection unit 35. , 35b, and a pair of detection electrodes 36a, 36b as the PM detector 36. The detection electrodes of the PM detectors 34 to 36 are provided apart from each other on the surface of the substrate opposite to the other insulating substrate 33 (heater substrate), and have one or two straight lines that form a straight line. The electrodes are alternately arranged so as to face each other at a predetermined interval. The opposing intervals of the detection electrodes in the PM detection units 34 to 36 are all the same. Moreover, the heater part 37 is comprised by the heat generating body which consists of heating wires, for example.

  However, the shape of the detection electrode of each PM detection unit 34 to 36 is not limited to the above, and a plurality of comb electrodes are provided alternately, a curved shape, one each A pair of electrode portions composed of the above-mentioned lines may be arranged opposite to each other in parallel at a predetermined distance.

  Although not shown, the PM sensor 19 has a holding portion for holding the sensor element 31, and the sensor element 31 is fixed to the exhaust pipe in a state where one end side thereof is held by the holding portion. It is like that. In this case, at least a part including the PM detection units 34 to 36 and the heater unit 37 is located in the exhaust pipe, and the insulating substrate 32 (PM attached portion) in the sensor element 31 faces the exhaust upstream side, The PM sensor 19 is configured to be attached to the exhaust pipe. Thereby, when exhaust gas containing PM flows in the exhaust pipe, the PM adheres to and accumulates on the detection electrodes of the PM detection units 34 to 36 and the periphery thereof on the insulating substrate 32. The PM sensor 19 has a protective cover that covers the protruding portion of the sensor element 31.

  When the PM in the exhaust gas adheres to and accumulates on the insulating substrate 32 of the sensor element 31, the PM sensor 19 having the above configuration causes each resistance value of the PM detection units 34 to 36 (that is, the resistance value between each pair of detection electrodes). Since the change in the resistance value and the change in the resistance value correspond to the PM adhesion amount, the change in the resistance value is used to detect the PM amount.

  As shown in FIG. 3, as an electrical configuration related to the PM sensor 19, a power supply device 41 is connected to one end side of the PM detection units 34 to 36 of the PM sensor 19, and shunt resistors 42, 43, 44 is connected. The power supply device 41 is configured by a booster circuit that boosts the voltage of the in-vehicle battery. For example, the power supply device 41 applies voltages of 50 V, 40 V, and 30 V to the PM detectors 34, 35, and 36, respectively. In each PM detection part 34-36, since the applied voltage is different, the electric field intensity around the electrode is different from each other, and the PM (attachment) collected by each PM detection part 34-36 according to the difference in the electric field intensity. The maximum particle size of (PM) is different. That is, various PMs having different particle sizes are mixed in the exhaust gas. However, since PM having a relatively large particle size has a large mass, it is not collected unless it is a PM detection unit having a high electric field strength. On the other hand, since the PM having a relatively small particle size has a small mass, it is also collected by the PM detection unit having a small electric field strength.

  In addition, if PM which exists in exhaust_gas | exhaustion is electrically charged, it is thought that the collection efficiency to each PM detection part 34-36 is improved. That is, when the PM is charged, the force that the PM is attracted to each of the PM detection units 34 to 36 increases, and the PM is efficiently collected. A configuration may be adopted in which a charging unit having discharge means is provided in the exhaust pipe, and the charging unit is operated to charge the PM. Specifically, ions are generated by corona discharge in the charging portion, and the PM is charged by attaching the ions to the PM. The charged PM is separated and collected at the detection electrodes of the PM detection units 34 to 36 by the action of an electric field.

  Further, in the electric circuit shown in FIG. 3, voltage dividing circuits are configured by the PM detection units 34 to 36 and the shunt resistors 42 to 44, respectively, and the intermediate point voltages thereof are PM detection voltages Vpm1, Vpm2, and Vpm3. To be input. That is, in each PM detection part 34-36, resistance value (interelectrode resistance value) changes according to PM adhesion amount, and PM detection voltage Vpm1-Vpm3 changes according to the change of the resistance value. The PM detection voltages Vpm1 to Vpm3 are input to the microcomputer 45 via an A / D converter (not shown). The microcomputer 45 calculates the PM adhesion amount according to the PM detection voltages Vpm1 to Vpm3.

  A heater power supply 47 is connected to the heater section 37 of the PM sensor 19. The heater power supply 47 is, for example, an in-vehicle battery, and the heater unit 37 is heated by power supply from the in-vehicle battery. In this case, a transistor 48 as a switching element is connected to the low side of the heater unit 37, and heating control of the heater unit 37 is performed when the transistor 48 is turned on / off by the microcomputer 45.

  When energization of the heater unit 37 is started in a state where PM is adhered to the insulating substrate 32, the temperature of the adhered PM rises, and the adhered PM is forcibly burned accordingly. Due to such forced combustion, PM adhering to the insulating substrate 32 is removed by combustion. For example, the microcomputer 45 performs the heating control by the heater unit 37 when a request for forced combustion of PM is generated when the engine is started or when the operation is finished, or when it is determined that the PM adhesion amount has reached a predetermined amount. Note that the PM forced combustion process of the PM sensor 19 regenerates the PM adhesion amount detection function in the PM sensor 19, and is also referred to as a sensor regeneration process in that sense.

  As described above, in the configuration in which the applied voltages in the PM detection units 34 to 36 are different, the PM particle size distribution is different for each PM detection unit, and the particle size distribution is shown in FIG. FIG. 4 shows the particle size distribution of PM (adherent PM) collected for the three PM detectors 34 to 36 with the horizontal axis representing the PM particle size [μm] and the vertical axis representing the number of particles [number]. is there.

As shown in FIG. 4, in each PM detection unit 34 to 36, the higher the applied voltage, the larger the particle size range of the adhered PM is to the upper limit enlargement side, that is, the maximum particle size that can be collected is increased, and the adhesion is accompanied accordingly. The average value (average particle size) of the particle size of PM becomes larger as the PM detection unit has a higher applied voltage. Specifically, in the PM detection unit 34 having an applied voltage of 50 V, PM having a particle size of 0 to 0.5 μm is collected, and the average particle size is 0.25 μm. Moreover, in PM detection part 35 with an applied voltage of 40 V, PM with a particle size of 0 to 0.4 μm is collected, and the average particle size is 0.2 μm. In the PM detector 36 with an applied voltage of 30 V, PM with a particle size of 0 to 0.3 μm is collected, and the average particle size is 0.15 μm. In the present embodiment, the particle size range (0 to 0.5 μm) of the PM detection unit 34 corresponds to the entire range of the size of PM.

  In the present embodiment, focusing on the fact that the size (particle size range) of the adhered PM differs for each PM detection unit 34 to 36, the average particle mass per PM is set for each PM detection unit 34 to 36. At the same time, the number of PM particles is calculated using the average particle mass. Note that the PM particle mass is generally proportional to the PM particle size, and the PM average particle size differs between the PM detectors 34 to 36 as described above. It is different.

  Specifically, the PM adhesion amount at the PM detection unit 34 is Mass_A [mg], the average particle mass is Mean_A [mg], the PM adhesion amount at the PM detection unit 35 is Mass_B [mg], and the average particle mass is Mean_B. Assuming that [mg] is the PM adhesion amount at the PM detection unit 36 and Mass_C [mg] and the average particle mass is Mean_C [mg], the number of PM particles adhering to the PM detection units 34 to 36 is Mass_A / Mean_A. , Mass_B / Mean_B, Mass_C / Mean_C, and the sum of them is used to calculate the number of PM particles in the exhaust gas.

  In addition, when each PM detection part 34-36 is compared, the area of PM adhesion surface differs according to each electrode length differing (refer FIG. 2). Therefore, the number of PM particles in the exhaust gas may be calculated in consideration of the area ratio of the PM detection units 34 to 36. For example, the PM particle number may be calculated by converting the PM detection units 34 to 36 with the same area, and the number of PM particles in the exhaust gas may be calculated based on the sum of the PM particle numbers.

  Incidentally, supplementing the calculation of the PM adhesion amount in the exhaust, basically, the PM adhesion amount is calculated based on the detection result of one of the three PM detection units 34 to 36. In this case, among the three PM detection units 34 to 36, the PM detection units 35 and 36 are limited in the size of the collected PM, but the PM detection unit 34 has a size of the collected PM. There is no limitation, and PM of any size can be collected. Therefore, it is desirable to calculate the PM amount in the exhaust based on the detection result of the PM detection unit 34. However, the PM adhesion amount may be calculated based on the detection results of the three PM detection units 34 to 36.

  FIG. 5 is a flowchart showing the procedure for calculating the number of PM particles, and this process is repeatedly executed by the microcomputer 45 in the ECU 25 at a predetermined cycle.

  In FIG. 5, in step S <b> 11, whether or not the execution condition for calculating the number of particles is satisfied is determined. For example, as an execution condition, it is determined whether or not an abnormality has occurred in the PM sensor 19, and it is assumed that the execution condition is satisfied when there is no abnormality. When step S11 is YES, in step S12, based on the PM detection voltages Vpm1 to Vpm3, the PM adhesion amounts in the PM detection units 34 to 36 are calculated. Moreover, in step S13, the average particle mass in each PM detection part 34-36 is set. At this time, the average particle mass of each of the PM detection units 34 to 36 is set so as to be different depending on the voltage applied to each of the PM detection units 34 to 36.

  Thereafter, in step S14, the number of PM particles is calculated for each PM detection unit 34-36 based on the amount of PM adhesion and the average particle mass in each PM detection unit 34-36, and for each PM detection unit 34-36. The number of PM particles in the exhaust is calculated based on the number of PM particles.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  The PM sensor 19 is provided with three PM detectors 34 to 36 each having a different size range (particle size range) of PM to be adhered, and calculates the PM adhesion amount for each PM detector 34 to 36 and average particles. The mass was set, and the number of PM particles for each of the PM detection units 34 to 36 was calculated based on the PM adhesion amount and the average particle mass. The number of PM particles in the exhaust gas is calculated based on each calculation result. According to such a configuration, in the plurality of PM detection units 34 to 36, the sizes of the PM particles to be attached are different from each other, and therefore the range of the size of the PM particles can be limited. Therefore, the calculation accuracy of the number of PM particles in each of the PM detection units 34 to 36 can be increased, and as a result, the number of PMs present in the exhaust gas can be calculated with high accuracy.

  Here, when the PM sensor has only one PM detection unit, and the average particle mass is one and is fixed, the size of the PM contained in the exhaust gas varies, so the particles There is a concern that the accuracy of calculating the number will be low. In this regard, according to the configuration of the present embodiment, since a plurality of average particle masses for each of the PM detection units 34 to 36 are set, the average particle mass can be properly used, and the calculation accuracy of the number of particles can be improved. .

(Second Embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment. In this embodiment, the PM sensor has one PM detection unit, and the number of PM particles is calculated based on the detection result (PM detection voltage Vpm) of the PM detection unit. In calculating the number of particles, the average particle mass of PM is set based on the engine operating state. That is, the size of PM contained in the exhaust gas can be changed according to the engine operating state every time. Therefore, in the present embodiment, the average particle mass is set in consideration of the fact that the size of PM changes according to the engine operating state every time, thereby improving the calculation accuracy of the number of PM particles.

  FIG. 6 is a diagram showing a sensor element 51 that constitutes the PM sensor 19 in this embodiment, and main electrical configurations.

  As shown in FIG. 6, the sensor element 51 has two insulating substrates 52 and 53 each having a long plate shape. One insulating substrate 52 is provided with a PM detector 54, and the other insulating substrate 52 is insulated. A heater portion 55 is provided on the substrate 53. The insulating substrate 52 corresponds to the adherend. The insulating substrate 52 is provided with a pair of detection electrodes 54a and 54b which are provided apart from each other on the surface of the substrate opposite to the other insulating substrate 53, and PM detection is performed by the pair of detection electrodes 54a and 54b. Part 54 is configured. Each of the detection electrodes 54a and 54b has a comb shape having a plurality of comb teeth, and the detection electrodes 54a and 54b are opposed to each other with a predetermined interval so that the comb teeth of the detection electrodes 54a and 54b are alternately arranged.

  A power supply device 41 is connected to one detection electrode 54a of the PM detection unit 54, and a shunt resistor 42 is connected to the other detection electrode 54b. These power supply device 41 and shunt resistor 42 have already been described (see FIG. 2). In this case, an intermediate voltage between the PM detector 54 and the shunt resistor 42 is input to the microcomputer 45 as the PM detection voltage Vpm (sensor detection value).

  FIG. 7 is a flowchart showing the procedure for calculating the number of PM particles in the present embodiment, and this process is repeatedly executed by the microcomputer 45 at a predetermined cycle.

  In FIG. 7, in step S <b> 21, it is determined whether or not the execution condition for calculating the number of particles is satisfied (similar to S <b> 11 in FIG. 5). After that, in step S22, the PM adhesion amount in the PM detection unit 54 is calculated based on the PM detection voltage Vpm. In step S23, a predetermined operating state parameter representing the engine operating state is acquired. In the present embodiment, the fuel pressure calculated from the detection result of the fuel pressure sensor 23, the water temperature calculated from the detection result of the water temperature sensor 24, and the engine rotation speed calculated from the detection result of the rotation sensor 21 as the operation state parameters Are going to get.

  Thereafter, in step S24, the average particle mass of PM is set based on the current operation state parameter. At this time, the average particle mass of PM is set based on the relationship shown in FIG. More specifically, in FIG. 8, (a) is a diagram showing the relationship between the fuel pressure and the PM particle size (= particle mass per particle), and (b) is the water temperature and the PM particle size (= 1 particle). It is a figure which shows the relationship with the (particulate particle mass). 8A and 8B show a relationship that the PM particle size decreases as the fuel pressure increases, and the PM particle size decreases as the water temperature increases. The fuel pressure and water temperature correspond to the operating state parameters that are the determining factors of the fuel particle size.

  In short, when the fuel pressure is relatively high or when the water temperature is relatively high, the particle size of the fuel injected from the fuel injection valve 12 becomes small, and conversely, when the fuel pressure is relatively low or when the water temperature is relatively low. The particle size of fuel injected from the fuel injection valve 12 increases. In this case, the PM in the exhaust tends to be smaller as the fuel particle size is smaller, and FIGS. 8A and 8B are defined based on the relationship.

  FIG. 8C is a graph showing the relationship between the engine speed and the PM particle size (= particle mass per particle). FIG. 8C shows the relationship that the PM particle size increases as the engine speed increases. If the engine rotational speed is different, the “atomization time” from the end of fuel injection to the ignition and combustion in the engine combustion cycle changes, which may also affect the PM size. For example, when the engine speed is high, the atomization time is short, and PM having a relatively large PM particle size is discharged to the exhaust pipe.

  In addition, the structure using any one parameter or the structure using two parameters may be used in addition to setting the average particle mass of PM using all the three operation state parameters.

  Thereafter, in step S25, the number of PM particles in the exhaust is calculated based on the PM adhesion amount and the average particle mass.

  According to the second embodiment described in detail above, the average particle mass of PM is set based on the engine operating state each time. Therefore, when the magnitude of PM changes with a change in the engine operating state, the average particle mass can be set variably accordingly, and as a result, the calculation accuracy of the number of PM particles can be increased.

  Specifically, fuel pressure and water temperature are determined as operating state parameters that determine fuel particle size, and the average particle mass is smaller in the engine operating state where the fuel particle size becomes larger than in the engine operating state where the fuel particle size becomes smaller. Is set to a large value. Thereby, when the fuel particle size in the engine combustion chamber (particle size of the injected fuel from the fuel injection valve 12) changes in size, while taking into account the change in the size of PM due to the change in the fuel particle size, The number of PM particles can be calculated with high accuracy. Further, the average particle mass is set to a larger value as the engine speed is higher. As a result, when the engine rotation speed changes, the number of PM particles can be calculated with high accuracy while taking into account the change in the magnitude of PM due to the change in the engine rotation speed.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  -In the said 1st Embodiment, it is good also as a structure which can variably set the applied voltage in each PM detection part 34-36. That is, the voltage of each PM detection part 34-36 applied by the power supply device 41 can be made variable, and the difference of the applied voltage in each PM detection part can be changed. For example, the voltage applied to each PM detection unit 34 to 36 is changed based on the engine operating state. At this time, if the magnitude of the PM contained in the exhaust gas tends to increase, the applied voltage of each PM detector 34 to 36 or the applied voltage of the PM detector 34 that has the maximum voltage is changed to the high voltage side. Good.

  -In said 1st Embodiment, based on the detection result in any one of several PM detection parts 34-36, PM of the partial range used as a part among the full range of the magnitude | size of PM contained in exhaust_gas | exhaustion The number of particles may be calculated for. For example, in step S14 in FIG. 5, the number of PM particles is calculated for each PM detection unit 34 to 36 based on the PM adhesion amount and the average particle mass. At this time, the number of PM particles calculated from the detection result of the PM detection unit 36 among the PM detection units 34 to 36 is a light and small range of the entire size range (0 to 0.5 μm) of the PM in the exhaust gas. The number of particles is only PM of (0 to 0.3 μm). Thus, by extracting the number of PM particles calculated from the detection results of the PM detection units 34 to 36, the number of PM particles in a desired size range can be obtained.

  The PM detection unit 34 performs processing for subtracting the PM adhesion amount calculated based on the detection result of the PM detection unit 35 from the PM adhesion amount calculated based on the detection result of the PM detection unit 34. The particle size range of the attached PM is within the particle size range (0 to 0.5 μm) and is not within the particle size range (0 to 0.4 μm) of the attached PM at the PM detector 35, that is, 0.4 to The PM adhesion amount can be calculated for a PM having a particle size range of 0.5 μm, and the number of particles can be calculated for a PM having a particle size range (0.4 to 0.5 μm). Similarly, according to both detection results of the PM detectors 35 and 36, the PM adhesion amount can be calculated for PM in the particle size range of 0.3 to 0.4 μm, and the particle size range (0.3 to 0.4 μm). ), The number of particles can be calculated.

  In the first embodiment, in the configuration in which the processing cycle for calculating the number of PM particles and the processing cycle for calculating the PM adhesion amount are individually determined, and the former processing cycle is longer than the latter processing cycle, PM In the case of calculating the adhesion amount, only one of the three PM detection units 34 to 36 is applied with a voltage (the other two are applied voltage = 0), and only when calculating the number of PM particles, A configuration in which different voltages are respectively applied to the PM detection units 34 to 36 may be employed.

  In the first embodiment, one PM sensor 19 is used, and each PM detection voltage is input to the ECU 25 from the plurality of PM detection units 34 to 36 included in the one PM sensor 19. It is good also as a structure which changes and uses PM sensors and inputs PM detection voltage into ECU25 from these PM sensors, respectively. In this case, each PM sensor only needs to have one PM detection unit (however, it may have a plurality of PM detection units).

  -You may change the structure of the sensor element used in the said 1st Embodiment as follows. FIG. 9 is a plan view showing another configuration of the sensor element. In FIG. 9, for convenience of explanation, the same reference numerals are given to the same components as those of the sensor element 31 shown in FIG. 2, and detailed description thereof is omitted.

  In the sensor element 61 shown in FIG. 9A, the intervals between the detection electrodes are different in each PM detection unit 34 to 36, and the interval d <b> 1 between the detection electrodes of the PM detection unit 34 and the PM detection unit 35. The distance d2 between the detection electrodes and the distance d3 between the detection electrodes of the PM detection unit 36 have a relationship of d1 <d2 <d3.

  According to the said structure, the electric field intensity produced between the detection electrodes of each PM detection part 34-36 can be varied because the space | interval between detection electrodes is different in each PM detection part 34-36. Therefore, regarding the PM adhering to the sensor element 61, the size (particle diameter or mass) of the adhering PM in each PM detection unit 34 to 36 can be varied. In this case, the PM detectors 34 to 36 may have the same applied voltage. In this way, in the configuration in which the applied voltage is the same, a power supply device having a simple configuration can be applied.

  Further, the sensor element 62 shown in FIG. 9B has a temperature gradient (temperature difference) in each PM detection unit 34 to 36 by providing the heater unit 37 at a position biased with respect to the three PM detection units 34 to 36. ). More specifically, the heater unit 37 (heat generating unit) is disposed in correspondence with the PM detection unit 34 located on the most distal side of the insulating substrate 32 among the three PM detection units 34 to 36. And according to the temperature gradient, the magnitude | size (particle size and mass) of adhesion PM in each PM detection part 34-36 is varied, respectively.

  According to the above configuration, since the distance from the heater unit 37 (heat generation unit) is different for each PM detection unit 34 to 36, the temperature of each PM detection unit 34 to 36 is different in the heater heating state. Differences cause different air convection. For example, the higher the temperature of the PM detection unit (PM detection unit 34 in the present embodiment), the faster the air flow and the greater the convection. At this time, in each PM detection part 34-36, the magnitude | size of adhering PM will differ with the difference in the convection which each generate | occur | produces. For example, a relatively large PM (a PM having a large mass) is collected by the PM detector 34 having a large convection, and a relatively small PM (a PM having a small mass) is captured by the PM detector 36 having a small convection. Be collected.

  The sensor element 63 shown in FIG. 9C is provided with heat generating portions 37a, 37b, and 37c corresponding to the three PM detecting portions 34 to 36, respectively, and the heat generating portions 37a to 37c have different heat generation amounts. Thus, a temperature difference (temperature gradient) is added to each PM detector 34 to 36. In this case, the PM detecting unit 34 and its surroundings are heated by the heat generating unit 37a, the PM detecting unit 35 and its surroundings are heated by the heating unit 37b, and the PM detecting unit 36 and its surroundings are heated by the heating unit 37c. For example, the heat generation amount Q1 of the heat generating portion 37a, the heat generation amount Q2 of the heat generating portion 37b, and the heat generation amount Q3 of the heat generating portion 37c have a relationship of Q1> Q2> Q3.

  According to the said structure, in the heater heating state, the temperature of each PM detection part 34-36 differs, respectively, and the convection of a different air arises according to the difference in the temperature. For example, the higher the temperature of the PM detection unit (PM detection unit 34 in the present embodiment), the faster the air flow and the greater the convection. At this time, in each PM detection part 34-36, the magnitude | size of adhering PM will differ with the difference in the convection which each generate | occur | produces. For example, a relatively large PM (a PM having a large mass) is collected by the PM detector 34 having a large convection, and a relatively small PM (a PM having a small mass) is captured by the PM detector 36 having a small convection. Be collected.

  In the configuration of FIG. 9 (c), the PM detectors 34 to 36 can reliably set a temperature difference compared to the configuration of FIG. It is possible to appropriately distribute the adhered PM due to the difference.

  In each of the above embodiments, the average particle mass [mg] is used as an index of the size of PM particles, but the average particle size [μm] can also be used. Since the mass per one PM particle and the particle size are in a substantially proportional relationship, it can be said that using the average particle mass is synonymous with using the average particle size.

  In a configuration in which a PM filter for collecting PM is provided in the engine exhaust pipe, and a PM sensor is provided on at least one of the downstream side and the upstream side, the regeneration timing of the PM filter is determined based on the detection value of the PM sensor. It is good also as a structure to control. Moreover, it is good also as a structure which performs failure diagnosis of PM filter based on the detected value of PM sensor.

  -In the above-mentioned embodiment, although application about a direct-injection type gasoline engine was illustrated, it is applicable also to other types of engines. For example, the present invention can be applied to a diesel engine (particularly, a direct injection type diesel engine), and the present invention can be used for a PM sensor provided in an exhaust pipe of the diesel engine. Alternatively, the PM amount may be detected for a gas other than the engine exhaust.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Fuel injection valve (fuel injection means), 19 ... PM sensor (particulate matter detection sensor), 21 ... Rotation sensor, 23 ... Fuel pressure sensor, 24 ... Water temperature sensor, 25 ... ECU, 32 ... Insulating substrate (attachment portion), 34 to 36 ... PM detection portion, 34a, 34b, 35a, 35b, 36a, 36b ... Detection electrode (counter electrode), 37 ... Heater portion, 45 ... Microcomputer (attachment amount calculation means) , Particle mass setting means, particle number calculation means), 52... Insulating substrate (attached part), 54... PM detection part, 54 a and 54 b.

Claims (6)

It has a target attachment for attaching the conductive particulate matter contained in exhaust gas discharged from the internal combustion engine, and a plurality of detection units comprising a pair of opposing electrodes provided on the object to be adhered portion, each of these A sensor control device applied to a particulate matter detection sensor that outputs a detection signal according to a resistance value between the pair of counter electrodes in the detection unit ,
The plurality of detection units have different size ranges of adhering particulate matter, and each range has a different median value and overlaps within the entire range of the size of the particulate matter in the exhaust gas. Is established,
An adhesion amount calculating means for calculating an adhesion amount of the particulate matter for each of the plurality of detection units based on a detection signal of the particulate matter detection sensor;
A plurality of average particle masses different from each other in the plurality of detection units can be set as the average particle mass per particle of the particulate matter adhering to the adherend, and one of which sets the average particle mass Mass setting means;
Wherein the adhesion amount of the particulate matter for each of the plurality of detection units which is calculated by the adhesion amount calculating means, on the basis of the average particle mass of each particle mass setting the plurality of detection units which is set by means of the plurality of While calculating the number of particles of the particulate matter for each detection unit, a particle number calculating means for calculating the number of particles of the particulate matter based on the respective calculation results ;
Based on each detection signal in the plurality of detection units, a total adhesion amount calculating means for calculating a total adhesion amount that is the amount of the particulate matter adhered to the adherend portion;
A sensor control device comprising: The particle number calculation unit is configured to detect a part of the particulate matter that is a part of the whole range of the particulate matter contained in the exhaust gas based on the detection signal of any of the plurality of detection units. The sensor control device according to claim 1 , wherein the number of particles is calculated. The particle number calculation means uses the detection signals of two detection units that partially overlap the size range of the particulate matter, and the non-overlapping ranges of the non-overlapping ranges that are non-overlapping in the two detection units. The sensor control device according to claim 1, wherein the number of particles is calculated for the particulate matter. Comprising an operating state detecting means for detecting an operating state of the internal combustion engine;
The sensor control apparatus according to any one of claims 1 to 3, wherein the particle mass setting unit sets an average particle mass of the particulate matter based on an engine operation state detected by the operation state detection unit. The internal combustion engine is a direct injection internal combustion engine in which fuel is directly injected into a combustion chamber by fuel injection means,
The operating state detecting means detects an engine operating state that is a determining factor of the particle size of fuel injected from the fuel injection means as the operating state,
5. The sensor control device according to claim 4, wherein the particle mass setting means sets the average particle mass to a larger value in an engine operation state in which the fuel particle size becomes larger than in an engine operation state in which the fuel particle size becomes smaller. . The operating state detecting means detects the rotational speed of the internal combustion engine as the operating state,
6. The sensor control device according to claim 4, wherein the particle mass setting means sets the average particle mass to a larger value as the detected rotational speed of the internal combustion engine is higher.

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