JP2016089764A - Sensor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor control device capable of more appropriately removing PM adhering to a gas sensor provided in an exhaust passage of an internal combustion engine.SOLUTION: A sensor control device 30 for controlling a gas sensor 20 provided in an exhaust passage 13 of an internal combustion engine 10, the gas sensor 20 being provided at a position where exhaust gas of the internal combustion engine 10 is directly supplied, comprises sensor cleaning means for executing sensor cleaning for holding each of a temperature and a flow velocity of the exhaust gas at the position where the gas sensor 20 is provided in the exhaust passage 13 to be equal to or higher than a predetermined value in a predetermined period.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor control device that controls a gas sensor capable of detecting a gas concentration of a specific component in a gas to be detected.

  A sensor control device that controls a sensor element capable of detecting a gas concentration of a specific component in a gas to be detected uses, for example, an exhaust gas (combustion gas) discharged from an in-vehicle engine as a gas to be detected (oxygen concentration in the gas ( The present invention is embodied as an air-fuel ratio detection device that detects air-fuel ratio (A / F). The detection result of the air-fuel ratio is used in an air-fuel ratio control system constituted by an engine ECU or the like, and the stoichiometric combustion control for feedback control of the air-fuel ratio in the vicinity of the stoichiometric (theoretical air-fuel ratio) or the air-fuel ratio in a predetermined lean region Lean combustion control with feedback control is realized.

  In recent years, exhaust gas regulations and abnormality detection regulations (OBD) have been increasingly strengthened, and it is desired to improve controllability such as stoichiometric combustion control. There is a need to expand the air-fuel ratio detection range. In addition, it is important to improve the fuel consumption as well as the exhaust gas emission, and it is also important to feedback control the rich state at the time of high engine load.

  By the way, since the oxygen concentration sensor is provided in the exhaust passage, PM (Particulate Matter) made of SOF (Solution Organic Fraction) or SOOT (soot) in the exhaust gas adheres. At this time, if the ventilation path of the oxygen concentration sensor is blocked by the adhering PM, the responsiveness of the oxygen concentration sensor is lowered, and the accuracy of feedback control is lowered accordingly. As a result, the emission improvement effect and the fuel consumption improvement effect are reduced.

  There exists a sensor control apparatus of patent document 1 as a sensor control apparatus which has the function to remove PM adhering to an oxygen concentration sensor. In the control device described in Patent Document 1, DPF regeneration processing is performed based on the output parameter of the oxygen concentration sensor at the time of fuel cut. At this time, the heat generated by the DPF regeneration process is used to remove PM adhering to the oxygen concentration sensor.

JP 2009-36038 A

  As described above, the sensor control device described in Patent Document 1 uses the output parameter of the oxygen concentration sensor at the time of fuel cut as a condition for shifting to the DPF regeneration process. However, at the time of fuel cut, even if the supply of fuel to the combustion chamber is immediately stopped, exhaust remains in the combustion chamber and the exhaust pipe, so these are discharged, and the oxygen concentration in the exhaust pipe becomes the oxygen concentration in the atmosphere. It takes time to become equivalent to Therefore, in the sensor control device described in Patent Document 1, the frequency of satisfying the condition for shifting to the DPF regeneration process is reduced. In the sensor control device described in Patent Document 1, since the PM adhering to the oxygen concentration sensor is removed by using the heat generated by the DPF regeneration processing, the oxygen concentration sensor decreases with the frequency of shifting to the DPF regeneration processing. The frequency of removal of PM adhering to the surface also decreases. In addition, depending on the amount of heat generated during the DPF regeneration process, PM adhering to the oxygen concentration sensor may not be sufficiently removed, and the responsiveness of the oxygen concentration sensor may deteriorate without limit.

  The present invention has been made in order to solve the above-described problems, and a main object of the present invention is to provide a sensor control device that can more suitably remove PM adhering to a gas sensor provided in an exhaust path of an internal combustion engine. Is to provide.

  The present invention is a sensor control device that controls a gas sensor provided in an exhaust path of an internal combustion engine, and the gas sensor is provided at a position to which exhaust gas of the internal combustion engine is directly supplied, and is provided with a gas sensor in the exhaust path. And a sensor cleaning means for performing sensor cleaning for maintaining the temperature and flow velocity of the exhaust gas at a predetermined position at a predetermined value or more in a predetermined period, respectively.

  When removing PM adhering to the gas sensor using the oxidation heat of the fuel by the catalyst, etc., the amount of generated heat may not be sufficient for PM removal. In this case, the amount of PM adhering to the gas sensor is unlimited. To increase. In this regard, in the above configuration, since the gas sensor is provided at a position where the exhaust gas of the internal combustion engine is directly supplied, the oxidation heat by the catalyst is not required, and the temperature and flow rate of the exhaust gas at the position where the gas sensor in the exhaust path is provided. The PM adhering to the gas sensor can be removed by holding each above a predetermined value.

  In addition, when the exhaust gas temperature is lower than the predetermined value, the SOF is not sufficiently oxidized, and when the exhaust gas flow rate is lower than the predetermined value, the SOOT is not sufficiently removed. In this regard, in the above configuration, the exhaust temperature and the exhaust flow velocity are both controlled to be equal to or higher than a predetermined value. Therefore, SOF can be oxidized by increasing the exhaust gas temperature, and SOOT can be removed by increasing the exhaust gas flow velocity.

It is a lineblock diagram showing the whole system outline concerning an embodiment. (A) is a side view of an A / F sensor, (b) is a sectional view of the A / F sensor. It is a figure which shows the change of the responsiveness of an A / F sensor. It is a figure which shows the relationship between the adhesion amount of PM, and responsiveness of an A / F sensor. It is a figure which shows the relationship between exhaust flow velocity and exhaust temperature, and the removal amount of PM. It is a flowchart which shows the process performed in the system which concerns on embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment embodying a sensor control device of the invention will be described with reference to the drawings. In this embodiment, an engine control system that uses a gas sensor provided in an exhaust pipe of an in-vehicle engine (internal combustion engine) mounted on a vehicle and performs various controls of the engine based on the output of the gas sensor will be described. In this control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount, control the ignition timing, and the like. FIG. 1 is a configuration diagram showing an overall outline of the present system.

  In FIG. 1, an engine 10 is a diesel engine, for example, and includes a fuel injection device 11, an intake pipe 12 for introducing air is connected to an intake port, and an exhaust pipe 13 for sending exhaust is connected to an exhaust port. Has been. The exhaust pipe 13 is sequentially provided with an LNT (Lean NOx Trap: NOx reduction catalyst) 14, a DOC (diesel oxidation catalyst) 15, and a DPF 16 as exhaust purification devices.

  The LNT 14 includes, for example, an alkaline earth material (occlusion material) and platinum, and exhausts when the air-fuel ratio of the gas used for combustion in the engine 10 is a lean air-fuel ratio higher than the stoichiometric air-fuel ratio. NOx stored in the LNT 14 is reduced by a reducing agent (HC or CO) contained in the exhaust gas when the air-fuel ratio of the gas is made to be a rich air-fuel ratio lower than the stoichiometric air-fuel ratio. To purify NOx contained in the exhaust gas.

  The DOC 15 is formed by supporting an oxidation catalyst on a known monolithic carrier, for example, a carrier surface made of a ceramic honeycomb structure such as cordierite. The DOC 15 raises the exhaust temperature by oxidative combustion of the supplied fuel when the DPF 16 is regenerated. Further, NO2 generated by oxidation of NO is used as an oxidant for the particulate matter PM deposited on the subsequent DPF 16 to enable continuous oxidation.

  The DPF 16 has a known wall flow type filter structure. For example, a porous ceramic honeycomb structure made of heat-resistant ceramics such as cordierite is formed, and either the inlet side or the outlet side of a large number of cells serving as gas flow paths are staggered in adjacent cells. Seal the filter to make a filter. At this time, a large number of pores are formed through the cell walls defining the gas flow path, and the particulate matter PM in the exhaust gas introduced into the DPF 16 is captured.

  An A / F sensor 20 is provided at an upstream side of any catalyst in the exhaust pipe 13, that is, at a position where exhaust of the engine 10 is directly supplied, in order to monitor the air-fuel ratio. The A / F sensor 20 outputs an electrical signal that is substantially proportional to the air-fuel ratio of the exhaust.

  In addition, a differential pressure sensor 25 is provided in the exhaust pipe 13 in order to monitor the amount of PM accumulated on the DPF 16. The differential pressure sensor 25 is connected to the upstream side and the downstream side of the DPF 16 via a pressure introduction pipe, and outputs an electrical signal corresponding to the differential pressure.

  The ECU 30 is mainly composed of a microcomputer (microcomputer) composed of a well-known CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, so that the engine can be operated according to the engine operating state every time. 10 various controls are executed. That is, the ECU 30 inputs signals from the various sensors and the like, calculates the fuel injection amount based on the various signals, and controls the fuel injection device 11.

  In particular, regarding fuel injection amount control, the ECU 30 performs air-fuel ratio feedback control based on a detection signal of the A / F sensor 20. That is, the ECU 30 performs feedback control so that the air-fuel ratio detected by the A / F sensor 20 becomes a target air-fuel ratio that is set based on the control state of the engine 10. As the air-fuel ratio control, the ECU 30 performs, for example, stoichiometric feedback control in which the target air-fuel ratio is stoichiometric (theoretical air-fuel ratio) or the vicinity thereof.

  In addition, the ECU 30 acquires an electrical signal output from the differential pressure sensor 25, and determines whether or not a regeneration condition is satisfied because the differential pressure before and after the DPF 16 exceeds a threshold value. That is, it is determined whether or not the regeneration condition that the clogging of the DPF 16 becomes equal to or more than a predetermined value due to the PM accumulated on the DPF 16 is satisfied. If the differential pressure exceeds the threshold value, the regeneration process of the DPF 16 is executed. Specifically, fuel is injected (post-injection) from the fuel injection device 11 after the combustion stroke in the engine 10. The fuel by the post injection does not burn in the engine 10 but flows into the exhaust pipe 13 and is oxidized in the DOC 15. In the DOC 15, oxidation heat is generated by oxidation of the fuel, and PM deposited on the DPF 16 is burned and removed by this oxidation heat.

  Next, the structure of the A / F sensor 20 will be described with reference to FIG. 2A is a side view showing the external structure of the A / F sensor 20, and FIG. 2B is a cross-sectional view showing the internal structure.

  As shown in FIG. 2, the A / F sensor 20 is configured such that a sensor element 21 made of a solid electrolyte laminate is covered twice with an outer cover 22 and an inner cover 23. Here, the sensor element 21 is formed on a substrate made of, for example, alumina (Al 2 O 3) together with a gas shielding layer, a diffusion resistance layer, and the like, and a predetermined voltage is applied to a sensing unit sandwiched between a pair of electrodes. The outer cover 22 and the inner cover 23 that cover the sensor element 21 have vent holes 22a, 23a, 22b, and 23b for taking in exhaust air to be sensed, side surfaces (holes 22a and 23a), and bottom surfaces (holes 22b and 23b). ). The outer cover 22, the inner cover 23, and the vent holes 22a, 23a, 22b, and 23b form a ventilation path. The oxygen concentration in the exhaust gas taken into the inner cover 23 through this ventilation path is detected by the sensor element 21.

  Since the A / F sensor 20 is provided in the exhaust path, and exhaust is used as a sensing target, PM contained in the exhaust adheres to the outer cover 22 and the inner cover 23. If PM adheres, the ventilation path is closed, and the flow rate of the gas (exhaust gas) passing through the ventilation path constituted by the outer cover 22, the inner cover 23, and the ventilation holes 22a, 23a, 22b, and 23b decreases. As a result, the exhaust reaching the sensor element 21 is reduced, and it takes time until the amount of exhaust that has reached the amount necessary for sensing.

  The responsiveness of the A / F sensor 20 will be described with reference to FIG. It is assumed that the actual air-fuel ratio (λ) has changed from the lean side (λ> 1) to the rich side (λ <1) at the first time T1. At this time, the sensor output changes from a voltage indicating lean to a voltage indicating rich with a predetermined response delay. In the figure, the responsiveness of the A / F sensor 20 in a state where PM is not attached is indicated by a solid line, and the responsiveness of the A / F sensor 20 in a state where a predetermined amount of PM is attached is indicated by a broken line. . Further, in order to measure the responsiveness, a threshold value λth is provided, and the time (response time) until the sensor output falls below the threshold value λth from the first time T1 when the actual air-fuel ratio changes from lean to rich is measured. And that time is responsive. In FIG. 3, when PM is not attached, the sensor output is lower than the threshold value λth at the second time T2, and the response is Res1. On the other hand, when a predetermined amount of PM is adhered, the sensor output is lower than the threshold value λth at the third time T3, so the response is Res2 longer than Res1.

  More specifically, as shown in FIG. 4, the responsiveness of the A / F sensor 20 deteriorates in a quadratic curve or linearly in proportion to the amount of PM adhering. For example, in the case where PM is not attached, the response is 0.4 seconds, whereas in the state where 70 μg of PM is attached, the response is deteriorated to 1.6 seconds.

  FIG. 3 illustrates the responsiveness of the A / F sensor 20 when the actual air-fuel ratio (λ) changes from the lean side (λ> 1) to the rich side (λ <1). Similarly, when the air-fuel ratio (λ) changes from the rich side (λ <1) to the lean side (λ> 1), the responsiveness deteriorates.

  Therefore, in order to improve the accuracy of the air-fuel ratio feedback control, it is necessary to remove PM adhering to the A / F sensor 20. However, in this embodiment, since the A / F sensor 20 is provided on the upstream side of any catalyst, the PM adhering to the A / F sensor 20 using the heat generated by the oxidation-reduction reaction in each catalyst. Is difficult to remove.

  Therefore, in this embodiment, the PM attached to the A / F sensor 20 is removed by changing the control state of the engine 10. At this time, removal is performed based on the fact that PM contains SOF and SOOT. That is, since SOF is a sulfate liquid substance having carbon solid fine particles as nuclei, it is removed by oxidation in a high temperature environment. On the other hand, since SOOT is physically attached, it is removed by blowing away by increasing the exhaust flow velocity. That is, SOF can be removed by raising the exhaust gas temperature above a predetermined value, and SOOT can be removed by raising the exhaust gas flow rate above a predetermined value.

  FIG. 5 shows the relationship between the exhaust temperature (° C.) and the exhaust flow velocity (m / s) in the vicinity of the A / F sensor 20 and the PM removal amount (μg) per predetermined time. FIG. 5 shows the PM removal amount (μg) in the case where the control for maintaining the exhaust temperature and the exhaust flow rate at predetermined values for 10 seconds is executed nine times in 15 minutes. As shown in FIG. 5, the PM removal amount increases as the exhaust gas temperature increases, and increases as the exhaust gas flow rate increases. However, when at least one of the exhaust temperature and the exhaust flow rate falls below a predetermined value, the PM removal amount decreases. If PM removal control is performed in a state where at least one of the exhaust temperature and the exhaust flow velocity is below a predetermined value, the frequency needs to be increased. Alternatively, if the frequency is not sufficient, the responsiveness of the A / F sensor 20 is lowered without limit.

  Therefore, in the present embodiment, control is performed so that the exhaust temperature and the exhaust flow velocity are each equal to or higher than a predetermined value. Specifically, when the responsiveness of the A / F sensor 20 exceeds a threshold value, it is determined that the amount of PM attached to the A / F sensor 20 exceeds a predetermined value. Then, the amount of fuel supplied from the fuel injection device 11 is increased, and the exhaust temperature and the exhaust flow velocity are each set to a predetermined value or more. At this time, as shown in FIG. 5, the amount of PM that can be removed per predetermined time greatly increases when the exhaust flow velocity is 12 m / s and the exhaust temperature increases greatly when the temperature is 400 ° C. Therefore, the fuel supply amount is increased so that the exhaust flow velocity at the position where the A / F sensor 20 is provided in the exhaust pipe 13 is 12 m / s or more and the exhaust temperature is 400 ° C. or more. The relationship between the fuel supply amount, the exhaust temperature, and the exhaust flow velocity is determined according to the shape of the exhaust pipe 13 and the mounting position (distance from the exhaust port) of the A / F sensor 20 in the exhaust pipe 13. Therefore, the fuel supply amount may be stored in advance in the memory of the ECU 30 in association with the exhaust flow velocity and the exhaust temperature, and the fuel injection device 11 may be controlled so that the exhaust flow velocity and the exhaust temperature become the above values.

  As described above, when measuring the responsiveness of the A / F sensor 20, the threshold λth is provided to measure the responsiveness when the air-fuel ratio changes from the lean side to the rich side. This is because it takes time until the atmosphere becomes equal to the oxygen concentration in the atmosphere when measuring the responsiveness when the oxygen concentration in the exhaust gas is made equal to the oxygen concentration in the atmosphere by combustion cut. That is, even when the supply of fuel from the fuel injection device 11 is stopped and the fuel cut state is established, the air-fuel mixture remains in the combustion chamber of the engine 10 and it takes time until the entire air-fuel mixture is discharged. In addition, exhaust remains in the exhaust pipe 13, and it takes time until all the exhaust is discharged. In this regard, since the air-fuel ratio is forcibly changed to rich by controlling the fuel injection device 11, the responsiveness of the A / F sensor 20 can be measured under uniform conditions.

  Incidentally, as described above, post-injection is performed when the regeneration process of the DPF 16 is performed. By performing post-injection, the amount of fuel supplied increases, so the air-fuel ratio becomes rich. Therefore, in the present embodiment, the responsiveness of the A / F sensor 20 is detected when post injection is performed in the regeneration process of the DPF 16. When the responsiveness of the A / F sensor 20 is worse than a predetermined value, the amount of fuel supplied from the fuel injection device 11 is increased, and the exhaust temperature and the exhaust flow velocity are increased. Further, it has been experimentally obtained that the amount of PM adhering to the A / F sensor 20 before PM is deposited on the DPF 16 and needs to be regenerated is about 5 μg. Therefore, the PM adhering to the A / F sensor 20 can be more suitably removed by continuing the control to set the exhaust gas flow velocity to 12 m / s or more and the exhaust temperature to 400 ° C. or more for a predetermined time.

  FIG. 6 is a flowchart showing a series of processes executed by the ECU 30 in the present embodiment.

  First, it is determined whether or not the differential pressure acquired by the differential pressure sensor 25 exceeds a predetermined first threshold (S101). At this time, the differential pressure sensor 25 and the ECU 30 cooperate to function as measurement means. The threshold value is a value with which it can be determined that the clogging of the DPF 16 due to PM has sufficiently increased. If the differential pressure does not exceed the first threshold value (S101: NO), it is not necessary to perform the regeneration process of the DPF 16, and thus the series of processes is terminated.

  If the differential pressure exceeds the first threshold value (S101: YES), the ECU 30 functions as a regeneration unit, and controls the fuel injection device 11 to perform post injection, thereby starting the regeneration process of the DPF 16 (S102). . In the regeneration process of the DPF 16, since the air-fuel ratio becomes rich as described above, the ECU 30 functions as a determination unit at the start of execution of the regeneration process, thereby comparing the responsiveness of the A / F sensor 20 with a threshold value. It is determined whether sensor cleaning is necessary (S103). If the responsiveness of the A / F sensor 20 is equal to or less than a predetermined threshold (S103: NO), the decrease in the responsiveness of the A / F sensor 20 due to PM is within an allowable range. On the other hand, if the responsiveness of the A / F sensor 20 is equal to or greater than a predetermined threshold (S103: YES), the necessity for PM removal arises, so the ECU 30 functions as a sensor cleaning unit and controls the fuel injection device 11. Thus, the sensor cleaning is started (104).

  In starting the sensor cleaning, first, it is determined whether or not both the exhaust temperature and the exhaust flow velocity are within a predetermined region (S105). At this time, as described above, the fuel supply amount is associated with the exhaust gas temperature and the exhaust gas flow velocity. Therefore, in this process, it is determined whether or not the fuel supply amount is within a predetermined region.

  If the exhaust temperature and the exhaust flow velocity are both within the predetermined range (S105: YES), the PM attached to the A / F sensor 20 can be removed without changing the control state of the engine 10. There is no need to change the control state. On the other hand, if both the exhaust temperature and the exhaust flow rate are not within the predetermined region (S105; NO), the control state of the engine 10, that is, the fuel supply amount is changed so that the exhaust temperature and the exhaust flow rate are within the predetermined region ( S106).

  Subsequently, it is determined whether or not a predetermined time (for example, 10 seconds) has elapsed since the start of sensor cleaning (S107). If a negative determination is made, the process of S107 is repeated until a positive determination is made. At this time, the sensor cleaning has a time limit for the following reason. That is, in sensor cleaning, the number of revolutions of the engine 10 is forcibly increased by increasing the amount of fuel supplied. As a result, sensor cleaning also has a negative effect that drivability deteriorates. For this reason, a time limit is set for sensor cleaning, and deterioration of drivability is suppressed.

  If a predetermined time has elapsed since the start of sensor cleaning, the control state of the engine 10 is returned to the original control state (S108). Then, it is determined whether or not the differential pressure detected by the differential pressure sensor 25 has become smaller than a predetermined second threshold value that is smaller than the first threshold value (S109). Even when sensor cleaning is not necessary (S103: NO), the process proceeds to S109. The process of S109 is performed to determine whether or not the PM adhering to the DPF 16 has been sufficiently removed by the regeneration process of the DPF 16. If the differential pressure is not smaller than the second threshold value (S109: NO), the removal control is continued because PM removal is insufficient. If the differential pressure is smaller than the second threshold (S109: YES), it is recognized that the PM adhering to the DPF 16 has been sufficiently removed, and the series of processes related to the regeneration process is terminated.

  Note that the flowchart shown in FIG. 6 illustrates a series of processes in which the sensor cleaning is performed only once during the regeneration process of the DPF 16, but the sensor cleaning may be performed a plurality of times during the regeneration process of the DPF 16. Good.

  In the sensor cleaning process, the rotational speed of the engine 10 is forcibly increased, so that drivability may be deteriorated as described above. Therefore, using the output of various sensors provided in the vehicle, it is determined whether the driving state of the vehicle is a suitable state for performing the sensor cleaning process, such as when stopping, accelerating, steady operation, etc. The sensor cleaning process may be executed according to the determination result. In this case, for example, when it is determined in S103 that sensor cleaning is necessary, a process for determining the driving state of the vehicle is executed, and when it is determined that the driving state is suitable for sensor cleaning in the process, What is necessary is just to transfer to the process of S104. Further, if the driving state of the vehicle is changed by an operation by the driver, the sensor cleaning process may be interrupted.

  With the above configuration, the sensor control device according to the present embodiment has the following effects.

  When removing the PM adhering to the A / F sensor 20 using the oxidation heat of the fuel by the catalyst, the oxidation heat may not be sufficient for removing the PM. In this case, the PM adheres to the A / F sensor 20 The amount of PM to increase increases without limit. In this respect, in the present embodiment, since the A / F sensor 20 is provided upstream of any catalyst in the exhaust pipe 13, no oxidation heat is required by the catalyst, and the control state of the engine 10 is changed. The PM adhered to the A / F sensor 20 can be removed.

  When the exhaust gas temperature is lower than the predetermined value, the SOF is not sufficiently oxidized, and when the exhaust gas flow rate is lower than the predetermined value, the SOOT is not sufficiently removed. In the above embodiment, the control state of the engine 10 is changed so that both the exhaust temperature and the exhaust flow velocity are equal to or higher than a predetermined value. Therefore, SOF can be oxidized by increasing the exhaust gas temperature, and SOOT can be removed by increasing the exhaust gas flow velocity.

  The determination of the responsiveness of the A / F sensor 20 is performed during the regeneration process of the DPF 16, that is, on the condition that the air-fuel ratio becomes rich. Therefore, it is possible to determine the responsiveness under the same conditions, and thereby it is possible to more accurately determine that the amount of PM attached to the A / F sensor 20 exceeds the allowable amount.

<Modification>
In the above embodiment, the exhaust flow rate and the exhaust temperature are controlled by the fuel injection amount. However, a sensor for detecting the exhaust flow rate and a sensor for detecting the exhaust temperature are provided in the vicinity of the A / F sensor 20 for detection. The exhaust flow rate and the exhaust temperature may be controlled by feeding back the exhaust flow rate and the exhaust temperature to the fuel injection amount. Thus, even when the exhaust flow rate and the exhaust temperature change due to external factors, the desired exhaust flow rate and exhaust temperature can be obtained.

  In the above embodiment, the amount of fuel supplied from the fuel injection device 11 is changed during sensor cleaning, but the control in sensor cleaning is not limited to this. For example, the ignition timing of the fuel in the engine 10 may be changed by advancing or retarding the exhaust valve and the intake valve, respectively, thereby changing the exhaust temperature and the exhaust flow velocity, and changing the fuel supply amount. And changing the ignition timing may be used together.

  In the above embodiment, the responsiveness of the A / F sensor 20 is determined, and sensor cleaning is performed when the responsiveness is worse than the threshold value. However, the determination of responsiveness is not an essential process. Generally, the amount of PM adhering to the A / F sensor 20 increases in proportion to the amount of PM collected by the DPF 16. That is, if the regeneration process of the DPF 16 is necessary, it is estimated that a predetermined amount of PM is attached to the A / F sensor 20 at that time. At this time, the predetermined amount is a value experimentally obtained in advance (for example, 5 μg as shown in the embodiment). Therefore, even if the sensor cleaning is performed every time the regeneration process of the DPF 16 is performed, or the sensor cleaning is performed every time the regeneration process of the DPF 16 is performed a predetermined number of times, it adheres to the A / F sensor 20 as in the above embodiment. The PM that has been removed can be suitably removed.

  In the above embodiment, the A / F sensor 20 is provided in the exhaust pipe 13, but a sensor other than the A / F sensor 20 may be provided, and even in that case, it relates to the sensor cleaning in the above embodiment. Processing is applicable. Specifically, the present invention can be applied to O2 sensors, NOx sensors, PM sensors, H2 sensors, NH3 sensors, and the like.

  In the above embodiment, the LNT 14, the DOC 15, and the DPF 16 are provided as the catalyst provided in the exhaust pipe 13, but the catalyst provided in the exhaust pipe 13 is not limited thereto. For example, an SCR (Selective Catalytic Reduction Denitration Device: Selective Catalytic Reduction :) or the like may be provided.

  In the above embodiment, the responsiveness of the A / F sensor 20 is determined during the regeneration control of the DPF 16, but the determination timing of the responsiveness of the A / F sensor 20 is not limited to this. That is, as long as rich control is performed, the responsiveness of the A / F sensor 20 can be measured more accurately as in the above embodiment. At this time, examples of the control state in which rich control is performed include NOx reduction catalyst activity control, SOx desulfurization catalyst activity control, and early warm-up control. As described above, the catalyst provided in the exhaust pipe 13 is not limited to the above-described embodiment, and can be selected as necessary. Accordingly, in which control state the rich control is performed, What is necessary is just to select according to the provided catalyst.

  In the above embodiment, the necessity of sensor cleaning is determined using the response time when the air-fuel ratio changes to the rich side, but the response time when the air-fuel ratio changes to the lean side is used. The necessity for sensor cleaning may be determined.

  -In above-mentioned embodiment, although the engine 10 shall be mounted in a vehicle, the mounting object is not restricted to a vehicle.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 13 ... Exhaust pipe, 20 ... A / F sensor, 30 ... ECU.

Claims (5)

A sensor control device (30) for controlling a gas sensor (20) provided in an exhaust path (13) of an internal combustion engine (10),
The gas sensor is provided at a position to which exhaust gas from the internal combustion engine is directly supplied,
A sensor control device, comprising: sensor cleaning means for performing sensor cleaning, which maintains a temperature and a flow rate of exhaust gas at a position where the gas sensor is provided in the exhaust path at a predetermined value or more during a predetermined period. The gas sensor is an air-fuel ratio sensor that detects an air-fuel ratio of exhaust gas,
The determination unit according to claim 1, further comprising: a determination unit that determines whether the sensor cleaning is necessary based on a response time when the air-fuel ratio detected by the gas sensor changes to a rich side or a lean side. Sensor control device. The exhaust path is provided with a filter (16) for collecting particulate matter contained in the exhaust,
Regeneration means for performing a regeneration process for burning the particulate matter collected by the filter when a predetermined regeneration condition is satisfied,
The sensor control apparatus according to claim 2, wherein the determination unit performs the determination at the start of execution of the reproduction process.   4. The sensor control device according to claim 1, wherein the sensor cleaning unit sets a flow rate of exhaust gas to 12 m / s or more and sets a temperature of exhaust gas to 400 ° C. or more. 5.   5. The sensor cleaning unit according to claim 1, wherein the temperature and flow velocity of the exhaust gas are set to a predetermined value or more by increasing the amount of fuel supplied to the internal combustion engine or changing the ignition timing, respectively. The sensor control device according to any one of claims.

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