JP4487979B2 - Electronic control unit - Google Patents

Description

  The present invention estimates, for example, an output error of an oxygen concentration sensor disposed in an engine exhaust system in order to detect an air-fuel ratio or rich / lean of an air-fuel mixture, and corrects the sensor output or determines sensor performance deterioration. The present invention relates to an electronic control device.

  As this type of apparatus, there is a conventional apparatus (first conventional apparatus) that estimates an output error of an oxygen concentration sensor in a fuel cut period during deceleration, for example. Normally, since the exhaust pipe is in the atmospheric state during the fuel cut period, this apparatus uses this period to output an error in the output of the oxygen concentration sensor from, for example, a normal reference value measured in the atmospheric air in advance. (Error of output value) is calculated.

  In addition, there is an apparatus (second conventional apparatus) described in Patent Document 1, for example. In this device, a new air passage for supplying fresh air to the oxygen concentration sensor is newly provided, and while supplying fresh air to the oxygen concentration sensor through the fresh air passage, the output of the oxygen concentration sensor is The output error from the regular reference time (output time error) is calculated.

In addition, there is an apparatus (third conventional apparatus) described in Patent Document 2, for example. In this device, the output of the oxygen concentration sensor when the air-fuel ratio is forcibly switched from rich to lean or from lean to rich is checked. Error) is calculated.
JP-A-5-312032 JP-A-5-256175

  As described above, various devices are known as devices for estimating the output error of the oxygen concentration sensor. However, both devices have drawbacks and still leave room for improvement.

  For example, when the first conventional device is applied to an AT vehicle or the like equipped with an automatic transmission, it is required because there is little chance of fuel cut in low-speed driving (for example, 2 to 30 km / h) such as urban driving. It is difficult to ensure the detection frequency. In addition, the second conventional device requires a fresh air passage that is not provided in a general automobile, and is impractical. Furthermore, in the third conventional apparatus, since the air-fuel ratio is forcibly switched, the drivability may be deteriorated. In particular, when this third conventional device is applied to a diesel engine, it is expected that when the air-fuel ratio is changed, an increase or decrease in the fuel injection amount or EGR amount is expected, resulting in a change in torque shock or combustion noise. There is a concern that the user may feel uncomfortable.

  The present invention has been invented in view of such circumstances, and can be applied to general automobiles or the like, and frequently maintains good drivability. The main object of the present invention is to provide an electronic control device that can estimate an output error of an oxygen concentration sensor and perform sensor output correction and sensor performance deterioration determination.

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

  According to the first aspect of the present invention, there is provided an electronic control device that estimates an output error of an oxygen concentration sensor such as an A / F sensor or an O2 sensor disposed in an exhaust passage of an engine and corrects the sensor output. The PM amount estimating means for estimating the PM amount contained in the exhaust gas around the oxygen concentration sensor, and the PM concentration around the sensor obtained by the PM amount estimating means in the exhaust gas is attached to the oxygen concentration sensor. A sensor attached PM amount estimating means for estimating the PM amount, and an output value of the oxygen concentration sensor is corrected to compensate for a sensor output error based on the sensor attached PM amount estimated by the sensor attached PM amount estimating means. Sensor output correction means.

  In the second aspect of the invention, an electronic device that estimates an output error of an oxygen concentration sensor such as an A / F sensor or an O2 sensor disposed in the exhaust passage of the engine and determines deterioration of the sensor performance. In the control device, the PM amount estimating means for estimating the amount of PM contained in the exhaust gas around the oxygen concentration sensor, and the oxygen concentration sensor based on the PM amount around the sensor obtained by the PM amount estimating means in the exhaust gas Sensor attached PM amount estimating means for estimating the amount of PM attached to the sensor, and sensor deterioration degree determination for determining the degree of performance deterioration of the oxygen concentration sensor based on the sensor attached PM amount estimated by the sensor attached PM amount estimating means And means.

  The oxygen concentration sensor disposed in the exhaust passage causes an error in its output due to exhaust dirt or the like. In particular, in direct injection engines, especially direct injection type diesel engines, the exhaust gas contains a lot of PM (Particulate Matter, particulate matter) such as soot and SOF (soluble organic components), so the sensor is easily contaminated. The output error of the sensor becomes large. As for the mechanism of the output error, when the PM adheres to the sensor (especially the sensor element or the cover in the sensing unit), the inventor uses the oxygen for the combustion of the PM at the time of combustion, so that the locality is detected in the sensing unit. It was thought that oxygen decrease (oxygen deficiency) caused the output error of the sensor. Then, through various experiments, each parameter has a correlation between the PM amount adhering to the sensor and the output error of the sensor, and the relationship between the PM amount around the sensor and the PM amount adhering to the sensor. And by estimating the amount of PM adhering to the sensor from the amount of PM contained in the exhaust gas around the sensor, the sensor output based on the amount of PM adhering to the sensor (corresponding to the output error estimated value of the oxygen concentration sensor) I have come up with a method for correcting and judging sensor performance degradation. The invention according to claim 1 or 2 is invented with such a background, and according to these inventions, the sensor attached PM amount estimating means increases the output error of the oxygen concentration sensor as the sensor attached PM amount. It can be determined with accuracy. In addition, the estimation of the amount of PM contained in the exhaust around the sensor can be performed based on, for example, the engine speed indicated by the rotational speed, the fuel injection amount, the EGR amount, etc. The PM amount estimating means can be easily realized in various operating states. Also, with this method, since there is basically no increase / decrease in the fuel injection amount, the EGR amount, etc., good drivability is maintained. Furthermore, in this method, since the sensor output error estimation itself can basically be performed regardless of the running state of the vehicle, the sensor output error can be estimated with high frequency.

  Thus, according to the first or second aspect of the invention, the output error of the oxygen concentration sensor is estimated at a high frequency while maintaining good drivability, and the sensor output is corrected (claim). 1) and sensor performance deterioration determination (claim 2) can be performed. The present invention (apparatus) can be applied to engines in a wide field (for example, ships and aircrafts) that are not limited to automobiles, but it is particularly useful to be applied (mounted) to automobiles. It is as follows.

  In addition, since various aspects can be considered as an estimation aspect of sensor surrounding PM amount, it is desirable to employ | adopt an optimal aspect according to a use etc. For example, in the case where the PM amount around the sensor has a severe temporal change, it is preferable to obtain (update) a value each time. On the other hand, when the amount of PM around the sensor is basically unchanged, it is also effective to obtain (update) the changed value only when there is a change.

  In addition, these configurations are particularly effective when applied to a configuration in which the oxygen concentration sensor is disposed on the upstream side of an exhaust purification device (a catalyst, a filter, etc., particularly a filter) or a configuration without an exhaust purification device. If the oxygen concentration sensor is on the downstream side of the exhaust gas purification device, the PM in the exhaust gas is removed through the device, so that the sensor is not easily contaminated. However, in general, a sensor for feedback control of the air-fuel ratio and EGR is often provided on the upstream side of the exhaust purification device for the convenience of the control (for example, due to consideration of detection accuracy, responsiveness, etc.). It is in an environment where output errors due to are particularly likely to occur. In this regard, according to the configuration of the first or second aspect, even if the oxygen concentration sensor is in such an installation environment, the output error of the sensor can be kept low. In the case of controlling the fuel ratio, EGR, etc., the controllability is improved.

  According to a third aspect of the present invention, in the electronic control device according to the first or second aspect, the oxygen concentration sensor includes one or more vent holes in a cover for the sensing unit, and is taken into the sensing unit through the vent holes. It is characterized by detecting the oxygen concentration of the exhaust gas.

  Such an oxygen concentration sensor generally has excellent water resistance and is particularly useful when used for an exhaust system sensor. However, in this sensor, exhaust gas is taken in through a vent hole provided in the cover of the sensing unit, and the oxygen concentration is detected for the exhaust gas, so that the vent hole is blocked by PM contained in the exhaust gas. If there is something wrong, there is a concern that the detection accuracy may be greatly lowered. In fact, it has been confirmed by experiments of the invention that this type of oxygen concentration sensor is affected by the amount of PM adhering to the sensor, and the accuracy of the sensor output decreases (output error increases). That is, in such a case, the above-described sensor output correction and sensor performance deterioration determination are particularly required. Further, since the change amount of the sensor output error with respect to the change of the sensor adhesion PM amount becomes large, the estimation accuracy of the sensor output error can be improved. Therefore, as in the invention described in claim 3, the configuration described in claim 1 or 2 is particularly useful when applied to such a case.

  According to a fourth aspect of the present invention, in the electronic control device according to any one of the first to third aspects, the sensor adhesion PM amount estimating means is configured to detect the sensor adhesion based on at least one of an exhaust flow rate and an exhaust temperature. It is characterized by estimating the amount of PM.

  The inventor's experiment confirmed that the sensor-attached PM amount is particularly affected by the exhaust flow rate and the exhaust temperature. Specifically, for example, the sensor adhesion PM amount increases as the exhaust gas temperature increases. The inventor believes that when the exhaust gas temperature is low, the PM particles in the exhaust gas have a higher probability of passing through without being attached to the sensor by receiving thermal energy from the sensor. Further, it has been confirmed by the inventors' experiments that the sensor attached PM amount basically increases as the exhaust flow rate increases. For this reason, in order to accurately estimate the sensor attached PM amount as in the above invention, it is effective to estimate the sensor attached PM amount based on at least one of the exhaust flow rate and the exhaust temperature. However, since the relationship between the exhaust temperature and the amount of PM adhering to the sensor is affected by the exhaust gas flow rate, it is more preferable to estimate the PM amount adhering to the sensor based on both of these parameters.

  By the way, the PM amount distribution in the exhaust passage is not always uniform. For this reason, when there is a bias in the PM amount distribution in the exhaust passage, it is important to selectively estimate the PM amount contained in the exhaust around the oxygen concentration sensor, particularly in the exhaust. For example, when a filter for collecting PM is disposed in the exhaust passage of the engine, the amount of PM contained in the exhaust gas has a distribution different between the upstream side and the downstream side of the filter. In this regard, in the invention according to claim 5, in the apparatus according to any one of claims 1 to 4, the PM amount estimating means in the exhaust gas is in the exhaust gas in the apparatus including the PM removal filter. Based on the PM collection efficiency of the filter, which is the rate at which PM is collected by the filter, and the PM collection amount of the filter, which is the amount of PM collected by the filter, the amount of PM around the sensor It is characterized by estimating.

  Usually, in a PM removal filter such as DPF (Diesel Particulate Filter), the amount of PM collected is obtained from a known method (for example, a differential pressure sensor or the like from the degree of clogging of the filter, for example, as a guide for regeneration processing). ). Further, the PM collection efficiency of the filter is determined by the specifications of the filter and its state (for example, the amount of collected PM). The inventor paid attention to this point and invented an apparatus for estimating the PM amount around the sensor based on these parameters as described above. According to the present invention, the amount of PM contained in the exhaust before collecting the DPF and the amount of PM contained in the exhaust after collecting the DPF are selectively and easily estimated accurately. Become so.

  Specifically, when the oxygen concentration sensor is disposed on the upstream side of the filter, the exhaust PM in the apparatus according to claim 5, as described in claim 6. The amount estimation means substantially calculates the PM amount ΔA around the sensor by a relational expression “ΔA = ΔPM × (100 / C)” (ΔPM: PM collection amount of the filter, C: PM collection of the filter) It is effective to adopt a configuration that is calculated based on efficiency (0 to 100%).

  On the other hand, when the oxygen concentration sensor is disposed downstream of the filter, as described in claim 7, in the apparatus according to claim 5, the PM amount estimating means in exhaust gas Is substantially equal to the relational expression “ΔB = (ΔPM / C) × (100−C)” (ΔPM: PM trapping amount of the filter, C: PM trapping of the filter). It is effective to adopt a configuration that is calculated based on the collection efficiency (0 to 100%).

  Specifically, the PM amount ΔA around the sensor on the upstream side of the filter corresponds to the PM amount contained in the exhaust on the upstream side of the filter, and this and the collection efficiency (C / 100) of the filter The product of multiplication is the amount of PM trapped by the filter (ΔPM). That is, “ΔA × (C / 100) = ΔPM” is obtained, and by converting this, the above-mentioned relational expression “ΔA = ΔPM × (100 / C)” is obtained.

  On the other hand, the PM amount ΔB around the sensor on the downstream side of the filter corresponds to the PM amount contained in the exhaust gas on the downstream side of the filter. That is, the PM amount ΔB around the sensor is obtained by subtracting the PM collection amount (ΔPM) of the filter from the PM amount (ΔA) contained in the exhaust gas upstream of the filter. This can be expressed as “ΔB = ΔA−ΔPM”, ΔA is converted based on the above relational expression, “ΔB = ΔPM × (100 / C) −ΔPM”, and further, The relational expression “ΔB = (ΔPM / C) × (100−C)” is obtained.

  According to the inventions described in the sixth aspect and the seventh aspect, the PM amount around the sensor can be accurately estimated (calculated) with simple control (calculation) using the above relational expression. In addition, the invention according to claim 6 or 7 suffices if the PM amount estimating means in exhaust gas is substantially calculated based on the above relational expression. For example, any coefficient or correction may be added to the relational expression. Even when a term or the like is added or when a parameter in the relational expression is replaced with a substantially identical parameter, the above effect or an effect equivalent to the effect can be basically obtained. Therefore, in these cases, the PM amount (ΔA or ΔB) around the sensor is substantially calculated based on the above relational expression.

  According to an eighth aspect of the present invention, in the apparatus according to any one of the fifth to seventh aspects, the filter is subjected to a regeneration process for removing the collected PM. When the regeneration process is performed on the filter while updating the PM collection efficiency in accordance with the degree of increase in the amount of PM collected with continuous use of the PM, the amount of PM collected with the regeneration process It further comprises a collection efficiency setting means for resetting the value of the PM collection efficiency in response to the decrease in the value.

  The PM collection efficiency of the filter improves as the amount of PM collection increases with continuous use of the filter (the efficiency increases). This is because the collection performance of the filter increases due to clogging. For this reason, it is desirable to update the PM collection efficiency as needed according to the degree of increase in the amount of PM collected. On the other hand, when the clogging of the filter advances due to such an increase in the amount of collected PM, the collection performance will eventually become too high and the flow of exhaust will be hindered. For this reason, in general, the filter is regenerated by performing regeneration processing (for example, combustion processing) on the filter at an appropriate time, thereby removing the collected PM (for example, combustion removal). However, when such a regeneration process is performed, the PM collection efficiency of the filter decreases corresponding to the degree of decrease in the amount of collected PM accompanying the regeneration process. For this reason, it is desirable to reset the value (initial value) in the PM collection efficiency corresponding to the decrease. In this regard, according to the above configuration, by providing the collection efficiency setting means, even when PM is deposited on the filter over time due to continuous use, the deposited PM is Even when the regeneration process is reset (for example, approximately zero is removed), the PM collection efficiency is set to an appropriate value each time.

  When an oxygen concentration sensor is provided in the vicinity of the PM removal filter, etc., the PM adhering to the sensor is basically burned and removed by the combustion heat when the filter is regenerated. In this case, the same can be said not only for the PM collection efficiency but also for the sensor-attached PM amount.

  That is, as in the invention according to claim 9, in the apparatus according to any one of claims 5 to 8, the filter is subjected to a regeneration process for removing the collected PM. Yes, when the regeneration process is performed on the filter while updating the sensor adhesion PM quantity based on the estimated value of the sensor adhesion PM quantity estimation means, the sensor adhesion PM quantity decreases with the regeneration process. A configuration that further includes a sensor adhesion PM amount setting means for resetting the value of the sensor adhesion PM amount corresponding to the above is also effective. Since the sensor output increases as the sensor-attached PM amount is removed, when detecting the degree of decrease in the sensor-attached PM amount accompanying the filter regeneration process, for example, based on the change in sensor output before and after the regeneration process. It is effective to detect this.

  In the invention according to claim 10, in the apparatus according to any one of claims 1 to 9, the oxygen concentration sensor is a sensor with a heater including a heater for heating at least a sensing unit of the sensor, Heater control for heating and removing at least the sensing unit of the sensor by the heater and removing the PM adhering to the sensor to at least the permissible amount when the sensor adhering PM amount by the sensor adhering PM amount estimation means exceeds the permissible amount. Means are provided.

  For the target oxygen concentration sensor, even if its output is corrected or performance degradation is judged, if the sensor remains with PM, the sensor will be replaced when the output error eventually increases Will have to do. In this regard, according to the above configuration, the PM attached to at least the sensing portion of the sensor can be combusted and removed to an allowable amount by the heater provided in the sensor. It becomes possible to use. Of course, when the oxygen concentration sensor is provided in the vicinity of the PM removal filter, the PM adhering to the sensor is basically also burned and removed by the combustion heat during regeneration of the filter. However, in this case as well, there is a problem similar to the above-mentioned problem in the sense that there is a concern that PM exceeding the allowable amount adheres to the sensor in a period shorter than the filter regeneration cycle and an output error occurs in the sensor. The above configuration is also effective in solving these problems.

  The heating temperature is preferably equal to or higher than the self-combustion temperature of PM (about 600 ° C.) and within a range where the oxygen concentration sensor operates normally. Further, since the sensor output increases as the sensor-attached PM amount is removed, when detecting the PM removal amount due to heating of the heater, for example, this can be detected based on a change in sensor output before and after heating. It is valid.

[First Embodiment]
Hereinafter, a first embodiment of an electronic control device according to the present invention will be described with reference to the drawings. The electronic control device according to this embodiment estimates the output error (output value or output timing error) of the oxygen concentration sensor for detecting the air-fuel ratio of the air-fuel mixture, and corrects the sensor output. Device. In this embodiment, this electronic control device is mounted on a common rail fuel injection control system for a vehicle diesel engine (internal combustion engine).

  First, the configuration of this system will be described in detail with reference to FIG.

  FIG. 1 is a configuration diagram illustrating an outline of a vehicle control system in which an electronic control device according to the present embodiment is mounted. As the engine of this embodiment, a multi-cylinder reciprocating engine is assumed. However, in FIG. 1, only one cylinder is shown for convenience of explanation.

  As shown in FIG. 1, this system is constructed by a diesel engine 10 having a common rail fuel injection device, various sensors for controlling the engine 10, an ECU (electronic control unit) 60, and the like. Yes.

  In the engine 10, a piston 13 is accommodated in a cylinder (cylinder) 12 formed in the cylinder block 11, and a reciprocating motion of the piston 13 rotates a crankshaft as an output shaft (not shown). The cylinder block 11 is provided with a cooling water passage (not shown), and the engine 10 is cooled by the cooling water. A cylinder head 15 is fixed to the upper end surface of the cylinder block 11, and a combustion chamber 16 is formed between the cylinder head 15 and the upper surface of the piston 13.

  The cylinder head 15 is formed with an intake port 17 and an exhaust port 18 that open to the combustion chamber 16. The intake port 17 and the exhaust port 18 are respectively an intake valve 21 and an exhaust valve that are driven by a cam (not shown). 22 is opened and closed. The intake port 17 is connected to an intake pipe 23 for sucking outside air, and the exhaust port 18 is connected to an exhaust pipe 24 (exhaust passage) for discharging combustion gas.

  The intake pipe 23 is provided with an air flow meter 31 for detecting the amount of fresh air drawn through an air cleaner (not shown) at the most upstream portion of the intake pipe 23. On the downstream side of the air flow meter 31, an electronically controlled throttle valve 32 whose opening is electronically adjusted by an actuator such as a DC motor, and the opening and movement (opening fluctuation) of the throttle valve 32 are shown. A throttle opening sensor 32a for detecting is further provided.

  On the other hand, the exhaust pipe 24 includes an A / F sensor 33a as a linear detection type oxygen concentration sensor that linearly changes the output with respect to a change in oxygen concentration in the exhaust, and an exhaust temperature sensor 34a that detects the exhaust temperature. Is provided.

  FIG. 2 shows an overview structure and an internal structure of a so-called laminated type A / F sensor with a heater as an example of the A / F sensor 33a. 2A is a side view showing the general shape of the sensor, and FIG. 2B is a sectional view showing the internal structure of the sensor.

  As shown in FIG. 2, the sensor 33a includes a sensor element 331 having an integrated Al2O3 heater (not shown), which is doubled by an outer cover 332 and an inner cover 333 at the tip corresponding to the sensing portion. It is covered with. The outer cover 332 and the inner cover 333 are provided with ventilation holes on the side surfaces (holes 332a and 333a) and the bottom surface (holes 332b and 333b) for taking in exhaust air to be sensed. An oxygen concentration in the exhaust gas taken into the inner cover 333 (sensing unit) is detected by the sensor element 331. The water resistance of the sensor 33a is enhanced by the labyrinth structure formed by the vent holes. The sensor 33a is used in a state where at least the sensing part of the sensor element 331 is heated to the operating temperature (for example, about 700 ° C.) by the heater.

  Further, an oxidation catalyst 35 made of, for example, Pt (platinum) or the like is provided on the downstream side of the exhaust pipe 24 (FIG. 1) provided with such a sensor 33 a, and further on the downstream side of the oxidation catalyst 35. Is provided with a DPF (Diesel Particulate Filter) 36 for collecting PM in the exhaust gas. An exhaust temperature sensor 34b for detecting the exhaust temperature is also provided on the downstream side of the DPF 36, and the temperature (center temperature) of the DPF 36 can be detected based on the detected value of the exhaust temperature sensor 34b. It is like that.

  Here, the DPF 36 includes a filter base material having a cylindrical porous structure in which a heat-resistant ceramic such as cordierite is formed in a honeycomb shape. Exhaust gas from the engine 10 is a porous partition wall of the DPF 36. When passing through, PM in the exhaust gas is collected by the DPF 36. When the amount of collected PM exceeds a predetermined value, the DPF 36 is subjected to a combustion process (regeneration process), and the PM collected in the DPF 36 is burned each time as detoxified carbon dioxide gas. Will be discharged. At this time, HC and CO in the exhaust gas are purified by the catalytic action of the oxidation catalyst 35, so that the DPF 36 is regenerated at a relatively low temperature even when continuously regenerated. The regeneration process of the DPF 36 is performed, for example, by performing post injection of one time or multi-stage injection at a time delayed by a predetermined time from the main fuel injection that is performed to obtain power of the engine 10 (generate output torque). . In the diesel engine, since combustion is performed by self-ignition, the throttle valve 32 is normally held at a constant opening (for example, a fully open state), and the fuel amount is mainly controlled as combustion control. However, when it is necessary to regenerate the DPF 36, it is necessary to keep the exhaust temperature constant. Therefore, the ECU 60 frequently adjusts the opening of the throttle valve 32 in order to finely control the intake air amount. become.

  Further, the exhaust pipe 24 provided with the DPF 36 is provided with a differential pressure sensor 37 that detects a differential pressure between the pressure near the DPF 36 inlet and the pressure near the DPF 36 outlet. The differential pressure detected by the differential pressure sensor 37 corresponds to the pressure loss caused by the DPF 36, and indicates the degree of clogging of the DPF 36 due to the PM collection. For this reason, by referring to this differential pressure, the amount of PM collected by the DPF 36 (PM collection amount) can be detected.

  On the other hand, in the cylinder 12, an electromagnetically driven injector (fuel injection valve) 27 for supplying fuel (light oil) to be used for combustion in the combustion chamber 16 is disposed in the combustion chamber 16. Here, for the sake of convenience, only the injector 27 provided in one cylinder (cylinder 12) is illustrated, but such an injector is provided for each cylinder of the engine 10. Each injector of the engine 10 including the injector 27 is connected to a common rail as a pressure accumulation pipe via a high pressure fuel pipe (not shown), and high pressure fuel is sequentially pumped to the common rail from a fuel pump (not shown). The high-pressure fuel corresponding to the injection pressure is stored. In the engine 10, a required amount of fuel is injected and supplied to each cylinder at any time by opening the injectors. In such a common rail system, the fuel injection pressure is basically not influenced by the operating conditions (for example, rotation speed, load, etc.) of the engine 10, so that the fuel can be supplied at the necessary injection amount / injection pressure when necessary.

  That is, when the engine 10 is in operation, intake air is introduced from the intake pipe 23 into the combustion chamber 16 by the opening operation of the intake valve 21, and is mixed with fuel injected and supplied from the injector 27, and compressed by the piston 13 in the state of air-fuel mixture. Thus, ignition (self-ignition) and combustion occur, and the exhaust valve 22 is opened to discharge the exhausted gas to the exhaust pipe 24.

  Further, this system also includes an EGR device for recirculating a part of the exhaust gas to the intake system as EGR (Exhaust Gas Recirculation) gas. The EGR device basically includes an EGR pipe 41 provided so as to communicate the intake pipe 23 and the exhaust pipe 24, and an electromagnetic valve that adjusts the passage area of the EGR pipe 41 according to the valve opening degree. The EGR valve 42 is used. The EGR pipe 41 is provided with an EGR cooler for cooling the EGR gas passing through the pipe. In this EGR apparatus, based on such a configuration, a part of the exhaust gas is recirculated to the intake system through the EGR pipe 41, and the generation of NOx is reduced by lowering the combustion temperature. Note that the exhaust amount (EGR amount) recirculated to the intake system is adjusted by adjusting the valve opening of the EGR valve 42. When the EGR valve 42 is in the fully closed state, the intake air amount sucked into the combustion chamber 16 is equal to the new air amount newly taken into the intake pipe 23 (intake air amount = new air amount). Since this relationship collapses as the valve opening of the EGR valve 42 changes, the intake air amount is adjusted by cooperative control of the throttle valve 32 and the EGR valve 42 in this system. Basically, the amount of fresh air detected by the air flow meter 31 is controlled to be equal to the exhaust flow rate (the exhaust amount passing through the DPF 36).

  In addition to the above sensors, the vehicle (not shown) is further provided with various sensors for vehicle control. For example, a rotation speed sensor 51 including a crank angle sensor (main rotation speed sensor) and a cylinder discrimination sensor (sub rotation speed sensor) for detecting the engine rotation speed, and an accelerator pedal operation amount (accelerator opening) by a driver are set. An accelerator opening sensor 52 and the like for detection are provided.

  In such a system, the ECU 60 that controls the vehicle as an electronic control device includes a known microcomputer (not shown) and controls the engine 10 based on detection signals sequentially input from the various sensors. The microcomputer mounted on the ECU 60 basically includes a CPU (basic processing device) that performs various operations, a RAM as a main memory, a ROM (read only storage device) as a program memory, and a data storage memory. Are composed of various arithmetic devices and storage devices such as an EEPROM (electrically rewritable nonvolatile memory). In the ROM, various programs related to engine control including a program related to output error estimation, output correction, and sensor performance deterioration determination regarding the A / F sensor 33a are stored in a data storage memory (EEPROM). Each type of control data including engine 10 design data is stored in advance.

  The configuration of the vehicle control system according to the present embodiment has been described in detail above. That is, the vehicle (automobile) on which the engine 10 (FIG. 1) is mounted is controlled by such a system. In this system, for example, the optimum fuel injection amount, injection timing, injection pressure, EGR amount, etc. according to the operating state of the engine 10 are calculated based on the calculation by the ECU 60 and the execution of various programs. Is calculated sequentially based on the engine operation information such as the air-fuel ratio detected by the A / F sensor 33a and the like, and feedback control is performed on the engine 10 based on these calculated parameters. It has been broken.

  As described above, in this embodiment, the output error (output value and output timing) of the A / F sensor 33a (oxygen concentration sensor) disposed in the engine exhaust system for detecting the air-fuel ratio of the air-fuel mixture is detected. The sensor output of the sensor 33a is corrected. Hereinafter, an aspect of the sensor output correction will be described in detail with reference to FIGS.

  FIG. 3 is a flowchart showing a processing procedure for the sensor output correction processing according to the present embodiment, and FIG. 4 is a flowchart showing a processing procedure related to calculation of the sensor adhesion PM amount executed during the processing of FIG. Note that the series of processes in FIG. 3 is basically performed sequentially, for example, at a predetermined cycle or a predetermined crank angle by executing a program stored in the ROM by the ECU 60. In addition, the values of various parameters used in the processes in these drawings are stored as needed in a storage device such as a RAM or EEPROM mounted in the ECU 60, and updated as necessary.

  As shown in FIG. 3, in this series of processes, first, in step S11, the amount of PM collected by the DPF 36 (PM collection amount) is calculated. Specifically, for example, this is calculated based on the differential pressure detected by the differential pressure sensor 37, the exhaust temperature detected by the exhaust temperature sensor 34a, the exhaust flow velocity, and the like. The exhaust flow rate is obtained by converting the fresh air amount detected as a mass flow rate by the air flow meter 31 into a volume flow rate (corresponding to an exhaust flow rate) based on, for example, the exhaust temperature near the outlet of the DPF 36 detected by the exhaust temperature sensor 34b. The volume flow rate is obtained by dividing the volume flow rate by the passage area (volume flow rate / passage area). Further, when calculating the amount of collected PM, the exhaust viscosity and exhaust density calculated based on the exhaust temperature near the outlet of the DPF 36, the operating state of the engine 10 (rotation speed, fuel injection amount, EGR amount, etc.), etc. In addition, it is also possible to detect with higher accuracy by taking the above into consideration. Here, the property of the PM discharged from the engine 10 (for example, ease of adhering to the DPF 36 or the sensor 33a) is estimated from the operating state of the engine 10 (for example, the rotational speed, the fuel injection amount, the EGR amount, etc.). Is possible. For this reason, when obtaining information on PM, it is desirable to refer to the operating state of the engine 10 as appropriate.

  In this way, both the PM trapping amount ΔPM per unit time and the PM trapping amount PMS (= ΣΔPM) which is the sum thereof are calculated. Of these, the amount of PM collected PMS corresponds to the amount of PM currently collected by the DPF 36. As described above, the DPF 36 is subjected to a combustion process (regeneration process) every time the amount of collected PM exceeds a predetermined value, but the amount of collected PM PMS calculated here is calculated. Can also be used when the regeneration process of the DPF 36 is performed. Further, since the PM collection amount PMS decreases when the regeneration process of the DPF 36 is performed, when the DPF 36 is regenerated, a value (initial value) is reset (updated) to the PM collection amount PMS corresponding to the decrease. . Specifically, for example, every time the DPF 36 is regenerated, the PM collection amount PMS is reset to “0 (zero)” as an initial value, or the PM collection amount PMS is decreased by a decrease by the regeneration process. To do.

  Next, in a subsequent step S12, a series of processes of FIG. 4 relating to calculation (estimation) of the PM amount (sensor attached PM amount X1) attached to the A / F sensor 33a is executed.

  That is, as shown in FIG. 4, first, in step S121, the PM collection efficiency C of the DPF 36, which is the ratio at which PM in the exhaust gas is collected by the DPF 36, is calculated. FIG. 5 is a graph showing the relationship between the PM collection efficiency C, the PM collection amount PMS (calculated in step S11 in FIG. 3), and the exhaust flow rate. This graph is obtained as a result of the inventors' experiments and simulations, and shows the basic relationship between these parameters.

  As indicated by the solid line L1a (PM collection amount PMS = small), the one-dot chain line L1b (PM collection amount PMS = medium) and the two-dot chain line L1c (PM collection amount PMS = large) in the graph of FIG. The PM collection efficiency C increases as the PM collection amount PMS of the DPF 36 increases (increases). Further, the PM collection efficiency C decreases as the exhaust flow rate increases (increases). In the present embodiment, based on such a relationship, the PM collection efficiency C of the DPF 36 is changed to the PM collection amount PMS and the exhaust flow rate, and further, the operating state of the engine 10 (rotation speed, fuel injection amount, EGR amount, etc.) and the like. Calculate based on Note that the PM collection efficiency C decreases at the time of regeneration of the DPF 36 in correspondence with the degree of decrease in the PM collection amount PMS accompanying the regeneration process. For this reason, at the time of regeneration of the DPF 36, a value (initial value) is reset (updated) to the PM collection efficiency C corresponding to the decrease. Specifically, for example, every time the DPF 36 is regenerated, the PM collection efficiency C is reset to “0 (zero)” as an initial value, or the PM collection amount PMS corresponding to the decrease in the amount of PM collection PMS accompanying the regeneration process is set. The collection efficiency C is decreased.

  Next, in step S122, the PM amount contained in the exhaust around the A / F sensor 33a, that is, the PM amount contained in the exhaust on the upstream side of the DPF 36, is converted into the PM collection efficiency C of the DPF 36 and the PM collection amount ΔPM. And estimate based on Specifically, for example, the PM amount ΔA around the sensor 33a at that time is expressed by a relational expression “ΔA = ΔPM × (100 / C)” (ΔPM: PM collection amount per unit time, C: PM collection of DPF 36) Calculated based on efficiency (0 to 100%).

  Next, in step S123, a PM adhesion coefficient K, which is a ratio of PM contained in the exhaust around the A / F sensor 33a to adhere to the sensor 33a, is calculated. FIG. 6 is a graph showing the relationship between the PM adhesion coefficient K, the exhaust flow rate, and the exhaust temperature. This graph is obtained as a result of the inventors' experiments and simulations, and shows the basic relationship between these parameters.

  As shown by the solid line L2a (exhaust flow rate = small), the alternate long and short dash line L2b (exhaust flow rate = medium), and the two-dot chain line L2c (exhaust flow rate = large) in the graph of FIG. Basically, the PM adhesion coefficient K (sensor adhesion PM amount) increases. Further, as the exhaust gas temperature detected by the exhaust gas temperature sensor 34a increases, the PM adhesion coefficient K (sensor adhesion PM amount) increases, and eventually saturates in the vicinity of “K = 1”. In addition, at this time, the PM adhesion coefficient K is an increase rate (the slope of the graph) of the PM adhesion coefficient K (sensor adhesion PM amount) with respect to the exhaust temperature in the vicinity of the temperature ST of the A / F sensor 33a (strictly, the temperature around the sensor cover). ) Suddenly increases. The inventor believes that this is because when the exhaust gas temperature is low, the PM particles in the exhaust gas have a higher probability of passing through without being attached to the sensor 33a by receiving thermal energy from the sensor 33a. In the present embodiment, based on such a relationship, the PM adhesion coefficient K is determined based on the exhaust flow rate and exhaust temperature (exhaust temperature around the A / F sensor 33a), and the operating state of the engine 10 (rotation speed, fuel injection amount, EGR). (E.g., amount).

  Next, in step S124, the relational expression “ΔX1 = ΔA · K” is solved, that is, the PM amount ΔA around the sensor 33a per unit time is multiplied by the PM adhesion coefficient K to obtain an A / F sensor per unit time. The sensor attached PM amount ΔX1, which is the amount of PM attached to 33a, is calculated, and the sensor attached PM amount X1 is calculated (estimated) as the sum based on the relational expression “X1 = ΣΔX1”. Here, the sensor adhesion PM amount X1 which is the sum of the sensor adhesion PM amount ΔX1 per unit time is actually adhered to the A / F sensor 33a (especially the sensor element 331 and the covers 332 and 333 in the sensing unit (FIG. 2)). It corresponds to the amount of PM.

  The series of processes in FIG. 4 ends with the calculation process of the sensor adhesion PM amount X1. The A / F sensor 33a is disposed in the vicinity of the DPF 36, and PM adhering to the sensor 33a is also burned and removed by the combustion heat during the regeneration of the DPF 36 described above. For this reason, the sensor attached PM amount X1 is updated when the DPF 36 is regenerated. Specifically, for example, every time the DPF 36 is regenerated, the sensor adhesion PM amount X1 is reset to “0 (zero)” as an initial value, or is reduced by the regenerating process based on a change in sensor output before and after the regenerating process. The sensor attached PM amount X1 is decreased by that amount. And when detecting the decreasing degree of sensor adhesion PM amount X1 accompanying the regeneration process of DPF36, this is detected, for example based on the change of the sensor output before and behind a regeneration process.

  Next, returning to the process of FIG. 3, in step S13, the degree of performance deterioration of the sensor 33a is determined based on the sensor attached PM amount X1 corresponding to the estimated value of the sensor output error for the A / F sensor 33a. . Specifically, it is determined whether or not a condition “sensor attached PM amount X1 <threshold (allowable amount)” is satisfied using a predetermined threshold, and this condition is satisfied (sensor attached PM in step S13). If it is determined that the amount X1 is less than the threshold value), the output error of the A / F sensor 33a is small, that is, the degree of performance deterioration of the sensor 33a is small. Correction is performed on the output value of the sensor 33a.

  That is, first, in step S14, in order to estimate the output error of the A / F sensor 33a more precisely, referring to a predetermined map, a sensor output correction value CAF (sensor sensor as a correction value for the output value of the sensor 33a) Equivalent to output error). FIG. 7 shows an example of the map used here. This map is obtained as a result of experiments or simulations, for example.

  As shown in FIG. 7, this map associates the sensor output correction value CAF with the sensor adhesion PM amount X1, and the smaller the sensor adhesion PM amount X1, the more the sensor adhesion PM amount X1 increases. The local oxygen decrease (oxygen deficiency) due to the burned combustion increases, and the sensor output decreases (output value decreases). For this reason, as the sensor adhesion PM amount X1 increases, the sensor output correction value CAF gradually increases from “1”. However, when the sensor attached PM amount X1 further increases and approaches the combustion limit of the sensor 33a, the oxygen decrease due to the combustion does not occur, and the sensor output correction value CAF is saturated to a constant value. .

  After acquiring the sensor output correction value CAF based on such a map, in the subsequent step S15, the output value of the A / F sensor 33a is corrected to compensate for the sensor output error based on the sensor adhesion PM amount X1. Specifically, the relational expression “Vo = Vo · CAF” is solved, that is, the new output value Vo is calculated and updated by multiplying the original output value Vo of the A / F sensor 33a by the sensor output correction value CAF. To do. Then, with this sensor output correction process, the series of processes in FIG. 3 ends.

  On the other hand, if it is determined in step S13 that the above condition is not satisfied (the sensor adhesion PM amount X1 is equal to or greater than the threshold value), the output error of the A / F sensor 33a is large, that is, the performance of the sensor 33a. Assuming that the degree of deterioration is large, in a subsequent step S16, the heater 33 provided integrally with the sensor element 331 (FIG. 2) is used to apply substantially the entire sensor 33a including the sensor element 331 and the covers 332, 333 to, for example, “800 ° C. The PM is heated and heated to remove almost all of the PM adhering to the sensor 33a. Thus, the A / F sensor 33a is reproduced. In this case, the series of processes shown in FIG. The heating temperature “800 ° C.” of the heater is set to a temperature that is equal to or higher than the self-combustion temperature of PM (about 600 ° C.) and the A / F sensor 33a operates normally.

  By the way, as described above, when the DPF 36 is regenerated, the PM adhering to the sensor 33a is also burned and removed by the combustion heat, and thus the regeneration process of the sensor seems unnecessary. However, since the PM exceeding the allowable value may adhere to the sensor 33a during the period shorter than the regeneration period of the DPF 36 and an output error may occur in the sensor 33a, the sensor 33a is always maintained with high accuracy. Such a sensor regeneration process becomes effective. In fact, in the inventor's test, the sensor 33a was always maintained with high accuracy by performing the regeneration of the sensor 33a at least about 20 times for each regeneration of the DPF 36.

  Thus, in this embodiment, the degree of performance deterioration of the A / F sensor 33a is determined based on the sensor adhesion PM amount X1 by repeatedly executing the series of processes in FIG. 3 (step S13 in FIG. 3). When it is determined that the degree of performance deterioration is large, the A / F sensor 33a is regenerated (step S16 in FIG. 3). When it is determined that the degree of performance deterioration is small, the A / F sensor 33a is reproduced. Is corrected (step S15 in FIG. 3). Further, the PM collection efficiency C is sequentially updated in accordance with the degree of increase in PM collection amount (ΔPM, PMS) accompanying the continuous use of the DPF 36 (step S121 in FIG. 4), and regeneration processing is performed on the DPF 36. In the case of being performed, the value of the PM collection efficiency C is reset in response to the decrease in the PM collection amount PMS accompanying the regeneration process. Thereby, erroneous control based on the sensor output error is suitably prevented.

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

  (1) As an ECU 60 (electronic control unit) that estimates the output error of the A / F sensor 33a and corrects the sensor output or determines the deterioration of the sensor performance, the amount of PM contained in the exhaust around the A / F sensor 33a Program for estimating ΔA (exhaust PM amount estimating means) and program for estimating PM amounts ΔX1, X1 adhering to the A / F sensor 33a based on the PM amount ΔA around the sensor obtained by this program (sensor attached PM) Quantity estimation means), a program (sensor degradation degree judgment means) for judging the degree of performance deterioration of the A / F sensor 33a based on the sensor adhesion PM quantity ΔX1, X1 estimated by this program, and the sensor adhesion PM quantity A program for correcting the output value of the A / F sensor 33a to compensate for the sensor output error based on ΔX1 and X1 (sensor output correction method) Stage). Thereby, even in a general automobile, the output error of the A / F sensor 33a is estimated at a high frequency while maintaining good drivability (drivability), and sensor performance deterioration determination (step S13 in FIG. 3). ) And sensor output correction (step S15 in FIG. 3).

  (2) As the A / F sensor 33a, vents (holes 332a, 333a, 332b, 333b) are provided in the covers 332 and 333 for the sensing unit, and the oxygen concentration of the exhaust gas taken into the sensing unit is detected through the vents. The thing was used. Even if the A / F sensor 33a having a structure with excellent moisture resistance is used, even if the vent hole may be blocked by PM, the configuration including the above-described programs makes it possible to detect errors based on sensor output errors. Control and the like are preferably prevented. Further, since the change amount of the sensor output error with respect to the change of the sensor adhesion PM amount becomes large, the estimation accuracy of the sensor output error can be improved.

  (3) When estimating the sensor adhesion PM amount ΔX1, X1, specifically, when calculating the PM adhesion coefficient K, it is calculated based on the exhaust flow rate and the exhaust temperature, and further on the operating state of the engine 10. (Step S123 in FIG. 4). Since the sensor adhesion PM amount ΔX1, X1 (PM adhesion coefficient K) is strongly influenced by the exhaust gas flow rate and the exhaust temperature (see FIG. 6), in order to accurately estimate the sensor adhesion PM amount ΔX1, X1 A configuration that estimates based on both parameters is particularly effective.

  (4) The PM amount ΔA around the sensor 33a is expressed by a relational expression “ΔA = ΔPM × (100 / C)” (ΔPM: PM collection amount per unit time, C: PM collection efficiency of DPF 36 (0-100) %)). Thereby, the amount of PM contained in the exhaust gas before collecting the DPF 36 can be estimated selectively and easily and accurately.

  (5) The PM collection efficiency C is sequentially updated according to the degree of increase in PM collection amount (ΔPM, PMS) associated with continuous use of the DPF 36, and when regeneration processing is performed on the DPF 36, The program is provided with a program (collection efficiency setting means) for resetting the value of the PM collection efficiency C corresponding to the decrease in the PM collection amount PMS accompanying the regeneration process (step S121 in FIG. 4). As a result, the PM collection efficiency C is set to an appropriate value each time.

  (6) When the regeneration process is performed on the DPF 36 while updating the sensor adhesion PM amount ΔX1, X1, the value of the sensor adhesion PM amount X1 corresponds to the decrease in the sensor adhesion PM amount X1 accompanying the regeneration process. It is set as the structure provided with the program (sensor adhesion PM amount setting means) which resets. Thereby, the sensor adhesion PM amount X1 is set to an appropriate value each time.

  (7) When the sensor adhering PM amount X1 exceeds an allowable amount, the heater of the A / F sensor 33a heats almost the entire sensor 33a to, for example, “800 ° C.” to substantially all the PM adhering to the sensor 33a. It is set as the structure provided with the program (heater control means) which carries out combustion removal. Thereby, it becomes possible to use the sensor 33a continuously over a long period of time.

  (8) With respect to the A / F sensor 33a provided on the upstream side of the oxidation catalyst 35 and the DPF 36, the above-described sensor performance deterioration determination and sensor output correction are performed. As a result, the controllability of the air-fuel ratio and EGR control using the sensor 33a is maintained high.

[Second Embodiment]
Next, a second embodiment that embodies the electronic control device according to the present invention will be described with reference to the drawings. Note that the apparatus according to the present embodiment is also applied to a vehicle control system having a configuration similar to that shown in FIG. However, in the vehicle control system according to the present embodiment, as shown in FIG. 8, for example, in order to correct the sensor output of the A / F sensor 33a (see FIG. 1), a downstream of the DPF 36 is provided separately from the sensor 33a. An A / F sensor 33b is further provided on the side. The A / F sensor 33b is also a stacked type A / F sensor with a heater as schematically shown in FIG. Hereinafter, the electronic control device according to the present embodiment will be described focusing on differences from the first embodiment.

  That is, also in this embodiment, the above-described sensor performance deterioration determination and sensor output correction are performed on the A / F sensor 33a in the same manner as in the first embodiment. However, in the present embodiment, not only the A / F sensor 33a but also the A / F sensor 33b provided on the downstream side of the DPF 36 performs the above-described sensor performance deterioration determination and sensor output correction. Like to do. With reference to FIG. 9 in conjunction with FIG. 3 and the like, the deterioration determination and correction mode for the A / F sensor 33b will be described in more detail below.

  The deterioration determination and correction mode for the A / F sensor 33b is basically the same as the deterioration determination and correction mode for the A / F sensor 33a, that is, the contents illustrated in FIGS. 3 to 7 as the first embodiment. It will be equivalent. However, the content of the sensor adhesion PM amount calculation process (corresponding to the process of step S12 in FIG. 3) is slightly different.

  FIG. 9 is a flowchart showing a processing procedure related to calculation of the PM amount (sensor attached PM amount X2) attached to the A / F sensor 33b, which is executed as the processing of step S12 of FIG.

  As shown in FIG. 9, also in this calculation process, the sensor adhesion PM amount X2 is calculated through steps S221 to S224 according to steps S121 to S124 of FIG. However, in step S222, in order to estimate the PM amount ΔB contained in the exhaust around the A / F sensor 33b, that is, the PM amount contained in the exhaust on the downstream side of the DPF 36, the PM amount around the sensor 33b at this time is estimated. ΔB is based on the relational expression “ΔB = (ΔPM / C) × (100−C)” (ΔPM: PM collection amount per unit time, C: PM collection efficiency (0 to 100%) of DPF 36). To calculate. By doing so, the amount of PM contained in the exhaust gas after collecting the DPF 36 can be estimated selectively and easily and accurately. In this case as well, resetting (updating) the value (initial value) to the PM collection efficiency C corresponding to the decrease during regeneration of the DPF 36 is the same as in the first embodiment.

  In addition, since the A / F sensor 33b in the present embodiment is provided on the downstream side of the oxidation catalyst 35 and the DPF 36, the A / F sensor 33b is less likely to get dirty than the A / F sensor 33a. Therefore, the frequency (number of times) of sensor regeneration processing in step S16 in FIG. 3 can be smaller than that in the case of the sensor 33a. Incidentally, in the inventor's test, the sensor 33b can always be maintained with high accuracy by performing the regeneration of the sensor 33b about 2 to 3 times for each regeneration of the DPF 36.

  As described above, in the present embodiment, the degree of performance deterioration of the A / F sensors 33a and 33b is determined based on the sensor attached PM amounts X1 and X2 by repeatedly executing the series of processes of FIG. Step S13 in FIG. 3) When it is determined that the degree of performance deterioration is large, the A / F sensors 33a and 33b are regenerated (Step S16 in FIG. 3), and it is determined that the degree of performance deterioration is small. In step S15, the output values of the A / F sensors 33a and 33b are corrected (step S15 in FIG. 3). Further, the PM collection efficiency C is sequentially updated according to the degree of increase in PM collection amount (ΔPM, PMS) associated with continuous use of the DPF 36 (steps S121 and S221 in FIGS. 4 and 9). When the regeneration process is performed, the value of the PM collection efficiency C is reset according to the decrease in the PM collection amount PMS accompanying the regeneration process. Thereby, erroneous control based on the sensor output error is suitably prevented.

  According to the present embodiment described in detail above, the following excellent effects can be obtained in addition to the effects similar to or equivalent to the effects (1) to (8).

  (9) Not only the A / F sensor 33a provided on the upstream side of the oxidation catalyst 35 and the DPF 36 but also the A / F sensor 33b provided on the downstream side of the DPF 36, the above-described sensor performance deterioration determination and sensor output Correction was made. As a result, the controllability of the air-fuel ratio, EGR, and the like using these sensors 33a and 33b is maintained at a higher level.

[Other Embodiments]
In each of the above embodiments, a process for detecting whether or not PM is removed by heating in step S16 may be provided after step S16 in FIG. In this way, if the sensor attached PM amount is not reduced, for example, because the heaters of the A / F sensors 33a and 33b have failed, the driver or the like is notified of this by a warning light or other informing device. It becomes possible to improve the security level. Whether or not PM has been removed can be confirmed based on, for example, changes in sensor output before and after the heat treatment.

  In each of the above embodiments, substantially the entire A / F sensors 33a and 33b are heated in step S16 of FIG. 3, but at least the sensing unit is heated (in other words, at least attached to the sensing unit). If PM is removed), at least an effect equivalent to the effect of (7) can be obtained.

  In each of the above embodiments, substantially all of the PM adhering to the sensors 33a and 33b is burned and removed in step S16. However, it is not essential to remove all of the PM, and the sensor adheres to at least an allowable amount. If it is the structure which carries out combustion removal of PM amount, the effect according to the effect of said (7) at least can be acquired.

  In each of the above embodiments, the heater provided in the sensors 33a and 33b is used as the heater for performing the heat treatment in step S16 in order to raise the sensing unit to the operating temperature. However, considering that the set temperature is high, a configuration in which a heater is provided separately is also effective. In this case, it is also effective to provide a heater for the cover of the sensing unit.

  In each of the above embodiments, when estimating the amount of PM adhering to the sensor, more specifically, when calculating the PM adhesion coefficient K, it is calculated based on the exhaust flow rate and the exhaust temperature, and further on the operating state of the engine 10. (Steps S123 and S223 in FIGS. 4 and 9). However, the present invention is not limited to this, and if the sensor attached PM amount is estimated based on at least one of the exhaust gas flow rate and the exhaust gas temperature, an effect equivalent to the effect (3) can be obtained.

  -The A / F sensor 33a (FIG. 1) is not provided upstream of the DPF 36, and only the A / F sensor 33b (FIG. 8) provided downstream of the DPF 36 is used for the above-described sensor performance deterioration determination and sensor output. Correction may be performed. For example, such a configuration is effective when performing learning control based on the qualitative characteristics of the oxygen concentration with respect to the air-fuel ratio.

  In each of the above embodiments, the degree of performance degradation of the A / F sensors 33a and 33b is determined based on the amount of sensor adhesion PM (step S13 in FIG. 3), and the sensor performance is determined according to the degree of performance degradation. Regeneration (step S16 in FIG. 3) and sensor output correction (step S15 in FIG. 3) are performed. However, the present invention is not limited to this. For example, when the degree of performance deterioration is small, output correction and sensor regeneration are not performed, and they are continuously used as they are, and when the degree of performance deterioration is large, output correction may be performed. Further, when the degree of performance deterioration is small, output correction may be performed, and when the degree of performance deterioration is large, appropriate fail-safe processing such as lighting of a warning lamp or storing of a diagnosis code may be performed. In addition, a plurality of threshold values may be used to determine the degree of performance degradation more finely, and processing such as output correction, sensor regeneration, and fail-safe processing may be performed in ascending order of performance degradation. Further, a warning light of a different color may be turned on according to the degree of performance deterioration without performing correction. With such a configuration, the driver or the like can easily grasp the degree of deterioration of the sensor performance from the color of the warning light.

  It is possible to correct the sensor output without making a determination itself about the degree of performance degradation. That is, the determination process in step S13 of FIG. 3 may be omitted, and for example, the sensor output may be corrected sequentially at a predetermined cycle or a predetermined crank angle.

  In each of the above embodiments, the PM amount around the sensor is obtained (updated) sequentially (for example, every predetermined cycle or every predetermined crank angle), but the PM amount around the sensor is basically unchanged. It is also effective to obtain (update) a value after the change only when there is a change.

  In each of the above embodiments, the regeneration process of the DPF 36 is executed each time the amount of collected PM exceeds a predetermined value. However, the execution condition (execution timing) of the regeneration process is arbitrary, for example, periodically You may make it perform. However, the execution itself of the reproduction process is not an essential configuration, and the present invention can be applied to a system that does not execute the reproduction process.

  In each of the above embodiments, various types of software (programs) are used, but similar functions may be realized by hardware such as a dedicated circuit.

  In each of the above embodiments, the case where the present invention is applied to a common rail system of a vehicle diesel engine is mentioned as an example. However, the present invention can be basically applied to a gasoline engine (direct injection engine) as well. it can. In a configuration that does not have a PM removal filter such as DPF, the amount of PM contained in the exhaust gas around the oxygen concentration sensor can be determined only by the engine operating state (for example, rotational speed, fuel injection amount, EGR amount, etc.). It is possible to estimate.

  The structure shown in FIG. 2 is merely an example of the structure of an oxygen concentration sensor that is a target of correction and deterioration determination in the apparatus according to the present invention, and is not limited to this. That is, the present invention is not limited to the linear detection type A / F sensor, and an arbitrary oxygen concentration sensor can be used instead of the A / F sensor. For example, the present invention can be similarly applied to a sensor that changes an output in a binary manner with respect to a change in oxygen concentration, that is, an O 2 sensor that detects rich / lean of an air-fuel ratio.

The block diagram which shows the outline of the vehicle control system to which this apparatus was applied about 1st Embodiment of the electronic control apparatus which concerns on this invention. 1A is a side view showing an outline shape of the A / F sensor according to the first embodiment, and FIG. 2B is a cross-sectional view showing an internal structure of the sensor. The flowchart which shows the process sequence about the correction process of the sensor output which concerns on 1st Embodiment. The flowchart which shows the process sequence which concerns on calculation of the sensor adhesion PM amount performed in the process of FIG. The graph which shows the relationship between PM collection efficiency, PM collection amount, and exhaust flow volume, respectively. The graph which shows the relationship between PM adhesion coefficient, exhaust flow volume, and exhaust temperature, respectively. The graph which shows an example of the map used when calculating | requiring a sensor output correction value. The block diagram which shows the outline of the vehicle control system to which this apparatus was applied about 2nd Embodiment of the electronic controller which concerns on this invention. The flowchart which shows the process sequence about the calculation process of the sensor adhesion PM amount which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Diesel engine, 24 ... Exhaust pipe, 31 ... Air flow meter, 33a, 33b ... A / F sensor, 34a, 34b ... Exhaust temperature sensor, 35 ... Oxidation catalyst, 36 ... DPF (Diesel Particulate Filter), 37 ... Differential pressure Sensor, 60 ... ECU (Electronic Control Unit), 331 ... Sensor element, 332, 333 ... Cover, 332a, 332b, 333a, 333b ... Hole (vent hole).

Claims (10)

In an electronic control device that estimates an output error of an oxygen concentration sensor disposed in an exhaust passage of an engine and corrects the sensor output,
Exhaust gas PM amount estimating means for estimating the amount of PM contained in the exhaust gas around the oxygen concentration sensor;
Sensor adhering PM amount estimating means for estimating the PM amount adhering to the oxygen concentration sensor based on the PM amount around the sensor determined by the exhaust PM amount estimating means;
Sensor output correction means for correcting the output value of the oxygen concentration sensor to compensate for a sensor output error based on the sensor adhesion PM amount estimated by the sensor adhesion PM amount estimation means;
An electronic control device comprising: In an electronic control device that estimates an output error of an oxygen concentration sensor disposed in an exhaust passage of an engine and determines deterioration of the sensor performance,
Exhaust gas PM amount estimating means for estimating the amount of PM contained in the exhaust gas around the oxygen concentration sensor;
Sensor adhering PM amount estimating means for estimating the PM amount adhering to the oxygen concentration sensor based on the PM amount around the sensor determined by the exhaust PM amount estimating means;
Sensor deterioration degree determination means for determining the degree of performance deterioration of the oxygen concentration sensor based on the sensor adhesion PM amount estimated by the sensor adhesion PM amount estimation means;
An electronic control device comprising:   3. The electronic control according to claim 1, wherein the oxygen concentration sensor includes one or a plurality of vent holes in a cover for the sensing unit, and detects an oxygen concentration of exhaust gas taken into the sensing unit through the vent holes. apparatus.   The electronic control unit according to any one of claims 1 to 3, wherein the sensor attached PM amount estimating means estimates the sensor attached PM amount based on at least one of an exhaust flow rate and an exhaust temperature.   A filter for collecting PM is disposed in the exhaust passage of the engine, and the PM amount estimating means for exhaust gas is configured to collect PM in the exhaust gas at a rate at which PM in the exhaust gas is collected. The amount of PM around the sensor is estimated based on the collection efficiency and the amount of PM collected by the filter, which is the amount of PM collected by the filter. The electronic control device described.   The oxygen concentration sensor is disposed on the upstream side of the filter, and when the PM collection amount of the filter is ΔPM and the PM collection efficiency (0 to 100%) of the filter is C, 6. The electronic control according to claim 5, wherein the exhaust gas PM amount estimating means calculates the PM amount ΔA around the sensor based on a relational expression substantially “ΔA = ΔPM × (100 / C)”. apparatus.   The oxygen concentration sensor is disposed on the downstream side of the filter, and when the PM collection amount of the filter is ΔPM and the PM collection efficiency (0 to 100%) of the filter is C, 6. The exhaust gas PM amount estimating means calculates the PM amount ΔB around the sensor substantially based on a relational expression “ΔB = (ΔPM / C) × (100−C)”. The electronic control device described. The filter is subjected to a regeneration process for removing the collected PM,
When the regeneration process is performed on the filter while updating the PM collection efficiency according to the degree of increase in the amount of PM collected with continuous use of the filter, the PM trapping associated with the regeneration process is performed. The electronic control device according to any one of claims 5 to 7, further comprising a collection efficiency setting unit that resets the value of the PM collection efficiency in response to a decrease in the collection amount. The filter is subjected to a regeneration process for removing the collected PM,
When the regeneration process is performed on the filter while updating the sensor adhesion PM amount based on the estimated value of the sensor adhesion PM amount estimation means, it corresponds to a decrease in the sensor adhesion PM amount accompanying the regeneration process. The electronic control device according to claim 5, further comprising a sensor adhesion PM amount setting unit that resets the value of the sensor adhesion PM amount. The oxygen concentration sensor is a sensor with a heater including a heater for heating at least a sensing unit of the sensor,
Heater control for heating and removing at least the sensing unit of the sensor by the heater and removing the PM adhering to the sensor to at least the permissible amount when the sensor adhering PM amount by the sensor adhering PM amount estimation means exceeds the permissible amount. The electronic control device according to claim 1, comprising means.

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