JP2012036816A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably detect an abnormality of a combustion state of an internal combustion engine.SOLUTION: A PM sensor 17 is provided to the exhaust pipe 14 of the engine 11. The PM sensor 17 has an adhesion part to which the PM (conductive particulate matter) contained in the gas is made to adhere and a pair of counter electrodes provided apart from the adhesion part, and outputs a sensor detection signal corresponding to a resistance value between a pair of the counter electrodes. A microcomputer 44 computes the amount of the PM to be discharged from the engine 11 according to the operation state of the engine 11 as an estimated discharge amount and carries out an abnormality diagnosis on the combustion state of the engine 11 on the basis of the estimated computed amount and the sensor detection signal.

Description

  The present invention relates to a control device for an internal combustion engine that calculates the amount of particulate matter (PM) contained in exhaust gas based on a detection signal of a particulate matter detection sensor.

  Conventionally, various types of PM sensors (particulate matter detection sensors) for detecting the amount of PM contained in exhaust gas discharged from an internal combustion 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 is deposited between the pair of counter electrodes, and the resistance between the electrodes is measured. Thus, the PM amount is detected. In this case, as a detection circuit connected to the sensor element, a voltage dividing circuit is configured by an interelectrode resistance that is a resistance between a pair of opposed electrodes and a predetermined shunt resistance, and an intermediate voltage of the voltage dividing circuit is detected by a sensor. It was made to output as a detection signal.

JP 59-196453 A

  By the way, in the internal combustion engine, when a failure of various actuators related to combustion of the internal combustion engine or a deviation of a conforming value in various parameters for controlling the combustion state of the internal combustion engine occurs, the PM emission becomes excessive and the emission is reduced. It is expected to get worse. In this case, since the environment is deteriorated, it is necessary to detect the abnormality in order to take some measures.

  An object of the present invention is to provide a control device for an internal combustion engine that can preferably detect an abnormality in the combustion state of the internal combustion engine.

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

  The present invention is applied to an internal combustion engine in which a particulate matter detection sensor for detecting the amount of conductive particulate matter contained in exhaust gas is provided in an exhaust passage, and based on a sensor detection signal of the particulate matter detection sensor. The present invention relates to a control device for an internal combustion engine that calculates the amount of particulate matter in exhaust gas. The invention according to claim 1 is an estimated amount calculating means for calculating an amount of the particulate matter discharged from the internal combustion engine as an estimated discharged amount based on an operating state of the internal combustion engine, and the estimated amount. And an abnormality diagnosing means for performing an abnormality diagnosis of the combustion state of the internal combustion engine based on the estimated emission amount calculated by the calculating means and the sensor detection signal.

  In the particulate matter detection sensor, the sensor detection signal varies according to the amount of particulate matter in the exhaust gas. The amount of particulate matter in the exhaust gas varies depending on the operating state of the internal combustion engine, but it is possible to grasp in advance the relationship between the operating state and the amount of particulate matter. In the present invention, when an abnormality occurs in the combustion state of the internal combustion engine, the amount of particulate matter in the exhaust gas (estimated emission amount) calculated based on the operation state of the internal combustion engine, and the actual particulate matter detection sensor Focusing on the difference between the detected amount of particulate matter in the exhaust gas (actual emission amount), the abnormality diagnosis of the internal combustion engine is performed using the estimated emission amount and the sensor detection signal as parameters. In this case, even when abnormality occurs in the combustion state of the internal combustion engine and excessive discharge of particulate matter occurs, the excessive discharge state can be grasped by the sensor detection signal of the particulate matter detection sensor. Therefore, it is possible to detect whether there is an abnormality in the internal combustion engine.

  According to a second aspect of the present invention, the abnormality diagnosis unit performs the abnormality diagnosis based on a change in the sensor detection signal during a period in which the estimated discharge amount is zero or substantially zero.

  For example, during idle operation, low load operation, and fuel cut, if the combustion state of the internal combustion engine is normal, the particulate matter discharged from the internal combustion engine is zero or substantially zero. If the amount of particulate matter emission is small, it is easy to detect a deviation between the estimated emission amount and the actual emission amount, and as a result, it is possible to accurately detect whether there is an abnormality in the internal combustion engine.

  Specifically, in a period when the estimated emission amount is zero or substantially zero, a change amount of the actual emission amount calculated based on the sensor detection signal or the sensor detection signal in that period is calculated, and the change amount is determined in advance. An abnormality diagnosis is performed by comparing the amount of change in the normal state. Alternatively, in the above period, the abnormality detection may be performed by calculating the change rate of the sensor detection signal or the actual discharge amount during the period and comparing the calculated change rate with a predetermined normal state change rate. Good.

  According to a third aspect of the present invention, the particulate matter detection sensor includes an adherend portion to which the particulate matter contained in the gas is attached, and a pair of counter electrodes provided at a distance from the adherend portion. And a sensor detection signal corresponding to a resistance value between the pair of counter electrodes is output. Further, the removing means for removing the particulate matter adhering to the adherend portion, and the removal of the particulate matter from the adherent portion, followed by a decrease in the resistance value of the pair of counter electrodes A dead zone time calculating means for calculating a dead zone time that is a dead zone time until the sensor detection signal changes, and an exhaust from the internal combustion engine within the dead zone period based on the estimated emission amount calculated by the estimated amount calculating means. A dead zone emission calculating means for calculating a total amount of the particulate matter to be calculated, wherein the abnormality diagnosis means is a dead zone time calculated by the dead zone time calculating means and the particles calculated by the dead zone emission amount calculating means. The abnormality diagnosis is carried out based on the total amount of the substance.

  In the particulate matter detection sensor, the resistance value between the pair of counter electrodes changes according to the particulate matter attached to the adherend, and the sensor detection signal fluctuates accordingly. At this time, the sensor detection signal does not fluctuate until the counter electrodes are connected via the particulate matter, and is held constant at a value corresponding to the amount of adhesion 0 (dead zone). However, when an abnormality in the combustion state of the internal combustion engine occurs and the particulate matter becomes excessively discharged, the sensor detection signal fluctuates from a value corresponding to the adhesion amount 0 at an earlier time point than normal.

  Focusing on this point, in the present invention, the actual dead zone time from the removal of the particulate matter at the adherend to the fluctuation of the sensor detection signal, and the particulate matter discharged from the internal combustion engine within the dead zone period The presence or absence of abnormality of the internal combustion engine is detected by comparison with the total amount of the engine. Specifically, the abnormality is diagnosed by calculating a threshold value based on the total amount of particulate matter discharged from the internal combustion engine, and comparing the actual dead zone time with the threshold value. Thereby, even when abnormality occurs in the combustion state of the internal combustion engine and excessive discharge of particulate matter occurs, the excessive discharge state can be grasped. In particular, abnormality detection can be performed with high accuracy when the amount of particulate matter discharged from the internal combustion engine rises and changes, such as when the internal combustion engine is heavily loaded or when the load increases.

The block diagram which shows the outline of the engine control system in embodiment of invention. The disassembled perspective view which decomposes | disassembles and shows the principal part structure of a sensor element. The figure which shows the electrical structure regarding PM sensor. The flowchart which shows the abnormality diagnosis process in 1st Embodiment. The time chart for demonstrating more specifically the abnormality diagnosis process of 1st Embodiment. The figure for demonstrating the dead zone of PM sensor. The flowchart which shows the abnormality diagnosis process in 2nd Embodiment. The figure which shows an example of the map for abnormality determination value setting. The time chart for demonstrating more specifically the abnormality diagnosis process of 2nd Embodiment.

(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 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 a fuel injection valve 12, an ignition device 13, and the like are provided as actuators related to the operation of the engine 11. The exhaust pipe 14 of the engine 11 is provided with a three-way catalyst 15 as an exhaust purification device, an A / F sensor 16 is provided on the upstream side of the three-way catalyst 15, and particulate matter detection is provided on the downstream side. A PM sensor 17 as a sensor is provided. In addition, in this system, a rotation sensor 18 for detecting the engine rotation speed, a pressure sensor 19 for detecting the intake pipe pressure, and the like are provided.

  The ECU 20 is mainly composed of a microcomputer comprising a known CPU, ROM, RAM, etc., and executes various control programs stored in the ROM, so that the engine can be operated according to the engine operating state at each time. 11 various controls are executed. That is, the ECU 20 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 20 calculates the actual PM emission amount (actual PM emission amount) of the engine 11 based on the detection signal of the PM sensor 17, 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 20 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 17. 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 17 and the electrical configuration related to the PM sensor 17 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 17, and FIG. 3 is an electrical configuration diagram regarding the PM sensor 17.

  As shown in FIG. 2, the sensor element 31 has two insulating substrates 32 and 33 each having a long plate shape, and one insulating substrate 32 has a PM detector 34 for detecting the amount of PM. The other insulating substrate 33 is provided with a heater portion 35 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.

  The insulating substrate 32 is provided with a pair of detection electrodes 36a and 36b which are provided apart from each other on the surface of the substrate opposite to the other insulating substrate 33. PM detection is performed by the pair of detection electrodes 36a and 36b. Part 34 is configured. The detection electrodes 36a and 36b each have a comb shape having a plurality of comb teeth. The detection electrodes 36a and 36b are opposed to each other with a predetermined interval so that the comb teeth of the detection electrodes 36a and 36b are staggered. Moreover, the heater part 35 is comprised by the heat generating body which consists of heating wires, for example.

  However, the shape of the pair of detection electrodes 36a and 36b is not limited to the above, and a pair of detection electrodes 36a and 36b are provided in a curved shape, or a pair of electrode portions each composed of one line are parallel to each other with a predetermined distance therebetween. It may be arranged oppositely.

  Although not shown, the PM sensor 17 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 unit 34 and the heater unit 35 is disposed 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 17 is configured to be attached to the exhaust pipe. Thus, when exhaust gas containing PM flows through the exhaust pipe, the PM adheres to and accumulates on the detection electrodes 36a and 36b and the periphery thereof on the insulating substrate 32. The PM sensor 17 has a protective cover that covers the protruding portion of the sensor element 31.

  In the PM sensor 17 configured as described above, when PM in the exhaust adheres to and accumulates on the insulating substrate 32 of the sensor element 31, the resistance value of the PM detector 34 (that is, the resistance value between the pair of detection electrodes 36a and 36b) is thereby increased. Since the change and the change in the resistance value correspond to the PM deposition amount, the change in the resistance value is used to detect the PM amount.

  As shown in FIG. 3, as an electrical configuration regarding the PM sensor 17, a sensor power supply 41 is connected to one end side of the PM detection unit 34 of the PM sensor 17, and a shunt resistor 42 is connected to the other end side. The sensor power supply 41 is constituted by a constant voltage circuit, for example, and the constant voltage Vcc is 5V. In this case, a voltage dividing circuit 40 is formed by the PM detection unit 34 and the shunt resistor 42, and an intermediate voltage between them is input to the ECU 20 as a PM detection voltage Vpm (sensor detection value). That is, in the PM detection unit 34, the resistance value Rpm changes according to the PM deposition amount, and the PM detection voltage Vpm changes depending on the resistance value Rpm and the resistance value Rs of the shunt resistor 42. The PM detection voltage Vpm is input to the microcomputer 44 via the A / D converter 43.

Here, when Vcc = 5 V and Rs = 100 kΩ, the PM detection voltage Vpm is obtained by the following equation (1).
Vpm = 5V × 100 kΩ / (100 kΩ + Rpm) (1)
At this time, if the PM deposition amount is 0 (or substantially 0), the resistance value Rpm of the PM detection unit 34 becomes infinite, so Vpm = 0V. Further, when the resistance value Rpm of the PM detection unit 34 is reduced to, for example, 1 kΩ due to PM deposition in the PM detection unit 34, Vpm = 4.95V. Thus, the PM detection voltage Vpm changes according to the amount of PM accumulated in the PM detection unit 34. The microcomputer 44 calculates the PM accumulation amount according to the PM detection voltage Vpm.

  The voltage dividing circuit 40 constitutes a signal output circuit, and the voltage dividing circuit 40 can change the PM detection voltage Vpm with an output range of 0 to 5V. In this case, the output upper limit value of the PM detection voltage Vpm is 5V, more strictly, a voltage value slightly lower than 5V.

  A heater power supply 45 is connected to the heater unit 35 of the PM sensor 17. The heater power supply 45 is, for example, an in-vehicle battery, and the heater unit 35 is heated by power supply from the in-vehicle battery. In this case, a transistor 46 as a switching element is connected to the low side of the heater unit 35, and heating control of the heater unit 35 is performed by the transistor 44 being turned on / off by the microcomputer 44.

  When energization of the heater unit 35 is started in a state where PM is deposited on the insulating substrate 32, the temperature of the deposited PM rises, and the deposited PM is forcibly burned accordingly. Due to such forced combustion, PM deposited on the insulating substrate 32 is removed by combustion. The microcomputer 44, for example, when the engine is started or when the operation is completed, or when it is determined that the PM accumulation amount has reached a predetermined amount, or when the engine operation time or vehicle travel distance from the previous PM forced combustion has reached a predetermined value. When the determination is made, heating control by the heater unit 35 is performed assuming that a forced combustion request for PM has occurred.

  In addition, the ECU 20 is provided with an EEPROM 47 as a backup memory for storing various learning values, abnormality diagnosis values (diagnostic data), and the like.

  In the present embodiment, the PM amount discharged from the engine 11 is calculated as the estimated PM discharge amount based on the operation state of the engine 11, and the calculated estimated PM discharge amount is calculated based on the detection signal of the PM sensor 17. By comparing with the calculated actual PM emission amount (actual PM emission amount) of the engine 11, the abnormality diagnosis of the combustion state of the engine 11 is performed. Hereinafter, the abnormality diagnosis process will be described in detail.

  FIG. 4 is a flowchart showing an abnormality diagnosis process of the engine 11. This process is repeatedly executed by the microcomputer 44 every predetermined time.

  In FIG. 4, in step S <b> 11, it is determined whether or not the driving state of the actuator related to the operation of the engine 11 is normal. Examples of the actuator related to engine operation include a fuel injection valve 12, an ignition device 13, a throttle valve (not shown), and the like. The determination that these actuators are driven normally is performed by inputting the results of abnormality diagnosis of various actuators executed by another routine (not shown).

  When the actuator related to the operation of the engine 11 is normally driven, the process proceeds to step S12, and it is determined whether or not the PM sensor 17 can acquire a valid PM detection voltage Vpm. Here, if the engine 11 has been warmed up, the determination is YES.

  That is, in this embodiment, at the time of starting the engine, it is assumed that a forced combustion request is generated, and the insulating substrate 32 is heated by the heater unit 35, and the PM deposited on the insulating substrate 32 is removed by the forced combustion. Thereafter, assuming that an effective PM detection voltage Vpm can be acquired, control of the engine 11 based on the PM detection voltage Vpm is started. However, in the case of cold start, water is likely to be generated in the exhaust passage, and if the heater is heated while the water is attached to the sensor element 31, the sensor element 31 may be damaged. Therefore, at the time of engine start, PM forced combustion is performed after a predetermined start period has elapsed (after the engine 11 has been warmed up), and control using the PM detection voltage Vpm is prohibited during the start period. I am going to do that.

  If a valid PM detection voltage Vpm can be acquired, the process proceeds to step S13, where the PM amount in the exhaust is calculated based on the operating state of the engine 11, and the calculated PM amount is stored as the estimated PM discharge amount Wr. The estimated PM emission amount Wr calculated here is an instantaneous value of the PM amount discharged from the engine 11 in the current engine operating state. In step S13, parameters relating to the engine operating state such as engine speed, intake air amount, fuel injection amount, fuel injection timing, air-fuel ratio, engine cooling water temperature, ignition timing, valve timing, fuel pressure, etc., and PM discharged from the engine 11 The relationship with the amount is previously determined and stored as a matching map, and the estimated PM emission amount in the current engine operating state is calculated using the matching map. If the engine has an EGR device for returning the exhaust of the engine 11 to the intake system, the EGR rate may be further added to the above parameters.

  In the subsequent step S14, it is determined whether or not the estimated PM discharge amount Wr is zero or a value near zero. This step S14 is also a process for determining that the current operating state of the engine 11 can be regarded as a PM emission amount = 0 from the engine 11. Such engine operating states include idle operation, low load traveling, fuel cut, and the like. When step S14 is NO, the abnormality diagnosis process after step S15 is not executed and this process is terminated.

  In step S13, it is determined whether or not the estimated PM discharge amount Wr as an instantaneous value is 0 or substantially 0. Instead, the rate of change of the integrated value of the estimated PM discharge amount Wr (the slope of the change). ) May be 0 or substantially 0.

  If step S14 is YES, the process proceeds to step S15, and the PM emission amount diagnostic counter Cpm is incremented by one. The PM discharge amount diagnosis counter is a counter for measuring an elapsed time from the time when the estimated PM discharge amount Wr becomes 0 or substantially 0, and when Wr≈0. In step S15, the PM detection voltage Vpm at the time when Wr≈0 is obtained and stored.

  In a succeeding step S16, it is determined whether or not the counter value of the PM discharge amount diagnosis counter Cpm is equal to or larger than a predetermined determination value K1. When the counter value ≧ K1, the process proceeds to step S17, where the PM detection voltage Vpm is acquired, and the change amount ΔVpm of the PM detection voltage Vpm from the time when Wr≈0 is calculated. Here, the difference between the current PM detection voltage Vpm and the PM detection voltage when Wr≈0 is calculated as the change amount ΔVpm.

  In step S18, it is determined whether or not the change amount ΔVpm is equal to or greater than the abnormality determination value KE1. If ΔVpm ≧ KE1, the routine proceeds to step S20, where it is determined that an abnormality has occurred in the combustion state of the engine 11. At this time, abnormality diagnosis data (diag data) indicating combustion abnormality of the engine 11 is stored in the EEPROM 47.

  In step S18, instead of comparing the change amount ΔVpm with the abnormality determination value KE1, the speed of change (slope of change) of the PM detection voltage Vpm is calculated in the period of Wr≈0, and the change of the calculated change is calculated. An abnormality diagnosis may be performed by comparing the speed and the abnormality determination value. The speed of change is determined by dividing the difference between the current PM detection voltage Vpm and the PM detection voltage Vpm at the start of Wr≈0 by the value of the PM discharge amount diagnostic counter Cpm, thereby changing the PM detection voltage Vpm. Calculated as the average speed at the time. Further, the PM discharge amount diagnostic counter Cpm and the change amount ΔVpm may be reset, for example, when NO is determined in at least one of steps S11, S12, and S14, or an abnormality caused by this routine. You may reset after a diagnostic process is complete | finished.

  FIG. 5 is a time chart for more specifically explaining the abnormality determination process of the engine 11 by the PM detection voltage Vpm. In FIG. 5, it is assumed that the engine is started.

  In FIG. 5, at timing t <b> 11, an engine start request is generated and combustion of the engine 11 is started, whereby the engine rotation speed increases and the estimated PM emission amount Wr fluctuates. At timing t12, the PM forced combustion flag is set. Thereby, the heater energization is turned on, and the forced combustion of the deposited PM is started.

  Note that the PM detection voltage Vpm increases with the start of energization of the heater unit 35 because the temperature of the deposited PM deposited on the PM sensor 17 (insulating substrate 32) increases and the interelectrode resistance decreases. This is due to That is, the PM has a temperature characteristic in which the resistance value decreases as the temperature rises. When the resistance value decreases, the PM detection voltage Vpm increases, and Vpm sticks to the output upper limit value. Thereafter, when the deposited PM is removed by forced combustion, the PM detection voltage Vpm decreases due to an increase in the resistance value, and Vpm becomes substantially zero.

  When the PM detection voltage Vpm is changed to a decreasing side, the heater energization is turned off and the PM forced combustion flag is reset because the forced combustion process is completed. In addition, a PM measurement permission flag is set. The heater energization may be turned off after the PM detection voltage Vpm becomes substantially zero.

  After the PM measurement permission flag is set and the effective PM detection voltage Vpm can be acquired, the engine 11 is in an idle operation state (estimated PM emission amount Wr≈0 or the rate of change of its integrated value≈0. If). In this case, the count up of the PM discharge amount diagnosis counter is started at timing t13. When the counter value becomes equal to or greater than the determination value K1, abnormality diagnosis is started. At this time, when the change amount ΔVpm is equal to or greater than the abnormality determination value KE1, it is determined that the combustion state of the engine 11 is abnormal.

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

  Based on the operating state of the engine 11, the amount of PM discharged from the engine 11 is calculated as the estimated PM discharge amount Wr, and the combustion state of the engine 11 is calculated based on the calculated estimated PM discharge amount Wr and the PM detection voltage Vpm. Since the abnormality diagnosis is performed, even when an abnormality occurs in the combustion state of the engine 11 and the PM is excessively exhausted, the excessive exhaust state can be grasped by the sensor detection signal of the PM sensor. Therefore, it is possible to detect whether or not the combustion state of the engine 11 is abnormal.

  Since the abnormality diagnosis is performed based on the change in the PM detection voltage Vpm during the period in which the estimated PM discharge amount Wr is zero or substantially zero, the PM detection voltage Vpm is originally not discharged from the engine 11. By detecting this change, an abnormality in the combustion state of the engine 11 can be accurately detected.

(Second Embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment. In the first embodiment, the abnormality diagnosis of the engine 11 is performed in a period in which the estimated PM emission amount Wr calculated based on the engine operating state is zero or substantially zero. However, in the present embodiment, the estimated PM emission amount Wr is An abnormality diagnosis of the engine 11 is performed during a period in which the engine 11 fluctuates.

  In the PM sensor 17, PM in the exhaust gas adheres to the insulating substrate 32, and the resistance value between the detection electrodes 36 a and 36 b (PM detection unit 34) is established by connecting the pair of detection electrodes 36 a and 36 b via the adhered PM. Resistance value) changes. Therefore, in the PM sensor 17, in the period until the pair of detection electrodes 36a and 36b are connected by the adhesion of PM, the PM detection voltage Vpm does not increase even if the PM deposition amount ≠ 0, and Vpm = 0. It becomes a dead zone that continues.

  FIG. 6 is a diagram for explaining the dead zone of the PM sensor 17. If the exhaust gas contains PM, the PM detection voltage Vpm increases with time. At this time, the relationship between time and Vpm is essentially Vpm = 0 when time = 0 as shown by a broken line, and thereafter Vpm increases with the passage of time. However, when the amount of accumulated PM is detected by the PM sensor 17, as shown by the solid line, the PM detection voltage Vpm becomes 0 during the period from time 0 to t1, and Vpm starts to increase toward t1 at t1. This period from time 0 to t1 is a dead zone.

  By the way, in the state where the PM emission is excessive due to the abnormality of the combustion state of the engine 11, the PM emission amount (estimated PM emission amount Wr) of the engine 11 calculated based on the current engine operating state and the PM detection voltage. There is a deviation from the actual PM discharge amount Wpm calculated based on Vpm, and the actual PM discharge amount (actual PM discharge amount Wpm) is larger than the value calculated as the integrated value of the estimated PM discharge amount Wr. In this case, after the PM combustion removal, a deviation between the estimated PM emission amount Wr and the actual PM emission amount Wpm appears as a difference in dead zone time, and according to the current engine operating state, the PM emission amount becomes a dead zone of the PM sensor 17. Even if it is determined to be a corresponding degree, in reality, more PM than the amount corresponding to the dead zone may be discharged from the engine 11.

  Focusing on this point, in the present embodiment, the dead zone time from when PM on the insulating substrate 32 is burned and removed until the PM detection voltage Vpm starts to rise, and the dead zone is discharged from the engine 11 within the dead zone period. The total amount of the estimated PM emission amount Wr is compared, and an abnormality in the combustion state of the engine 11 is diagnosed based on the comparison result.

  FIG. 7 is a flowchart showing an abnormality diagnosis process of the engine 11. This process is repeatedly executed by the microcomputer 44 every predetermined time. In addition, about the process similar to the said FIG. 4, the same step number as FIG. 4 is attached | subjected and the description is abbreviate | omitted.

  In FIG. 7, in steps S31 and S32, the same processing as in steps S11 and S12 of FIG. 4 is performed, and if step S32 is YES, the process proceeds to step S33.

  In step S33, it is determined whether or not it is immediately after the PM forced combustion process is completed. If YES, the process proceeds to step S35 and starts counting up the counter Cf after PM removal. The PM removal counter Cf is a counter for measuring the elapsed time from the time when the forced combustion process of PM ends (for example, when the heater is turned off).

  When step S33 is NO, it progresses to step S34, it is determined whether the abnormality diagnosis in this routine is being implemented, and if abnormality diagnosis is being performed, it progresses to step S35. In step S34, it is determined as YES if the PM removal counter Cf ≠ 0 is not satisfied.

  In step S36, it is determined whether the PM detection voltage Vpm has changed from 0 to an increase. When Vpm = 0, it is determined that it is the dead zone period of the PM sensor 17, and this routine is terminated as it is. On the other hand, when the PM detection voltage Vpm changes from 0 to a value larger than 0, the process proceeds to step S37. It should be noted that the period from the end of PM forced removal until step S36 becomes YES is the dead zone period in the PM sensor 17, and the post-PM removal counter Cf when the step S36 becomes YES becomes the dead zone time.

  In step S37, using the estimated PM emission amount Wr calculated based on the operating state of the engine 11, an estimated PM integrated value ΣWr is calculated as the total amount of PM emission discharged from the engine 11 within the dead zone period. In step S38, an abnormality determination value KE2 is calculated based on the estimated PM integrated value ΣWr using a predetermined abnormality determination value setting map.

  FIG. 8 is a diagram illustrating an example of the abnormality determination value setting map. According to FIG. 8, as the estimated PM integrated value ΣWr increases (the PM discharge amount of the engine 11 increases), the abnormality determination value KE2 becomes a smaller value.

  In step S39, it is determined whether the post-PM removal counter Cf is less than the abnormality determination value KE2. That is, step S39 is a process for comparing the dead zone time calculated based on the engine operating state and the actual dead zone time calculated based on the PM detection voltage Vpm. If the latter is shorter than the former, YES is determined. It is determined. When Cf <KE2, the routine proceeds to step S41, where it is determined that an abnormality has occurred in the combustion state of the engine 11. At this time, abnormality diagnosis data (diag data) indicating combustion abnormality of the engine 11 is stored in the EEPROM 47.

  FIG. 9 is a time chart for more specifically explaining the abnormality diagnosis process of the engine 11 of the present embodiment. In the figure, the solid line indicates when the engine 11 is normal, and the alternate long and short dash line indicates when the engine 11 is abnormal.

  In FIG. 9, at timing t <b> 21, counting up of the post-PM removal counter Cf is started with the end of the PM forced combustion process. Further, at timing t21, the engine 11 is in a high load operation state, and the estimated PM integrated value ΣWr increases.

  After the timing t21, the engine high load operation state is continued, and the abnormality diagnosis process of the engine 11 is performed during the increase period of the PM emission amount.

  At this time, if the combustion state of the engine 11 is normal, the PM detection voltage Vpm increases at timing t23 as shown by the solid line. At this time, the dead zone time (counter value of Cf) from the timing t21 to the rise timing (t23) of the PM detection voltage Vpm is the abnormality determination value KE2 calculated based on the estimated PM integrated value ΣWr at the rise timing (t23). That's it. On the other hand, if an abnormality occurs in the combustion state of the engine 11, the PM detection voltage Vpm rises at timing t22, as shown by a one-dot chain line. At this time, it is determined that Cf <KE2 and the combustion state of the engine 11 is abnormal.

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

  Specifically, based on the actual dead zone time from when PM on the insulating substrate 32 is removed until the PM detection voltage Vpm starts to rise, and the estimated PM integrated value ΣWr within the dead zone period, specifically, estimation is performed. Since the abnormality determination value KE2 calculated based on the PM integrated value ΣWr is compared with the actual dead zone time, the abnormality of the combustion state of the engine 11 is diagnosed. Even in this case, it is possible to grasp the excessive discharge state. In particular, when the amount of PM discharged from the engine 11 increases and changes, such as when the engine 11 is heavily loaded or when the load increases, abnormality detection can be performed with high accuracy.

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

  An integrated value of the estimated PM discharge amount Wr (instantaneous value) calculated based on the engine operating state at a predetermined time and an increase amount of the PM detection voltage Vpm at the predetermined time (PM deposition on the insulating substrate 32 of the sensor 17) The abnormality diagnosis of the combustion state of the engine 11 is performed by comparison with the amount). In this case, when the PM accumulation amount calculated based on the PM detection voltage Vpm is larger than the integrated value of the estimated PM emission amount Wr calculated based on the engine operating state, it is determined that the combustion state of the engine 11 is abnormal.

  Abnormal diagnosis of the combustion state of the engine 11 by comparing the rate of change of the PM accumulated amount during a predetermined time of the estimated PM discharge amount Wr and the rate of change of the PM accumulated amount deposited on the insulating substrate 32 of the PM sensor 17 To implement. In this case, it is determined that there is an abnormality in the combustion state of the engine 11 when the latter rise change is faster than the former rise change.

  -It is good also as a structure which detects the presence or absence of the abnormality of the actuator which concerns on the combustion state of the engine 11 based on the estimated PM discharge amount Wr and PM detection voltage Vpm.

In the above embodiment, the voltage dividing circuit 40 shown in FIG. 3 is used as the signal output circuit, but this may be changed. For example, the PM detector 34 and the shunt resistor 42 constituting the voltage dividing circuit may be reversely connected, and the PM detector 34 may be provided on the low side and the shunt resistor 42 may be provided on the high side. In this configuration, the PM detection voltage Vpm is obtained by the following equation (2).
Vpm = 5V × Rpm / (Rs + Rpm) (2)
Rpm is the resistance value of the PM detector 34, and Rs is the resistance value of the shunt resistor 42 (for example, 5 kΩ).

  In the above-described embodiment, the heater unit 35 is provided integrally with the insulating substrate 32 as a heating means for forced PM combustion. However, the temperature of the ambient gas of the PM sensor 17 (for example, the temperature in the engine exhaust pipe) is set. It is good also as a structure which raises to the combustion temperature of PM. In this case, for example, a configuration in which the exhaust temperature is raised by engine combustion control, or a configuration in which heating means (a heater or the like) different from the heater unit 35 is provided in the exhaust pipe is adopted.

  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 detection 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, 17 ... PM sensor (particulate matter detection sensor), 20 ... ECU, 32 ... Insulating substrate (attachment part), 34 ... PM detection part, 35 ... Heater part (heating means), 36a, 36b ... Detection Electrode (counter electrode), 40... Voltage dividing circuit, 44... Microcomputer (estimated amount calculation means, abnormality diagnosis means, removal means, dead zone time means, total amount calculation means).

Claims (3)

A particulate matter detection sensor for detecting the amount of conductive particulate matter contained in the exhaust is applied to an internal combustion engine provided in an exhaust passage, and the exhaust gas based on the sensor detection signal of the particulate matter detection sensor In a control device for an internal combustion engine that calculates the amount of particulate matter,
Estimated amount calculating means for calculating the amount of the particulate matter discharged from the internal combustion engine as an estimated discharged amount based on the operating state of the internal combustion engine;
An abnormality diagnosis means for performing an abnormality diagnosis of the combustion state of the internal combustion engine based on the estimated emission amount calculated by the estimated amount calculation means and the sensor detection signal;
A control device for an internal combustion engine, comprising:   2. The control device for an internal combustion engine according to claim 1, wherein the abnormality diagnosis unit performs the abnormality diagnosis based on a change in the sensor detection signal during a period in which the estimated emission amount is zero or substantially zero. The particulate matter detection sensor includes a portion to be attached to which the particulate matter contained in a gas is attached, and a pair of counter electrodes provided to be separated from the portion to be attached, and between the pair of counter electrodes. Output sensor detection signal according to the resistance value of
Removing means for removing the particulate matter adhering to the adherend portion;
Dead zone time calculation for calculating a dead zone time, which is a dead zone time from the removal of the particulate matter in the adherend to a change in the sensor detection signal due to a decrease in the resistance value of the pair of counter electrodes. Means,
Dead zone emission calculation means for calculating the total amount of the particulate matter discharged from the internal combustion engine within the dead zone based on the estimated emission amount calculated by the estimated amount calculation means,
2. The abnormality diagnosis unit according to claim 1, wherein the abnormality diagnosis unit performs the abnormality diagnosis based on a dead band time calculated by the dead band time calculation unit and a total amount of the particulate matter calculated by the dead band discharge amount calculation unit. Control device for internal combustion engine.

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