JP2017214885A - Diagnostic device and diagnostic method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively make a failure diagnosis of an oxidation catalyst and an exhaust pipe injector.SOLUTION: In a diagnostic device for an exhaust emission control system, an exhaust pipe injector 20 and an oxidation catalyst 31 are disposed in this order from the upstream side in an exhaust passage 13 of an engine 10. The diagnostic device includes: a temperature sensor 40 for acquiring a catalyst temperature of the oxidation catalyst 31; and a failure determination section 130 for stopping exhaust pipe injection and starting post injection if the catalyst temperature does not reach a predetermined threshold temperature after the exhaust pipe injection is performed by the exhaust pipe injector 20, and determining failure of at least either one of the oxidation catalyst 31 or the exhaust pipe injector 20, on the basis of whether or not the catalyst temperature reaches the predetermined threshold temperature after the post injection is performed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a diagnostic apparatus and a diagnostic method, and more particularly, to a diagnosis of an exhaust purification system.

  Conventionally, as this type of exhaust purification system, an oxidation catalyst having HC / CO oxidation ability and particulate matter in the exhaust (hereinafter referred to as PM) are collected in the exhaust passage of the engine in order from the exhaust upstream side. -A thing provided with a filter (henceforth a filter) is known. There is a limit to the PM collection capacity of the filter. For this reason, when the PM accumulation amount of the filter reaches a predetermined amount, it is necessary to perform so-called filter regeneration in which PM is burned and removed from the filter (see, for example, Patent Document 1).

JP 2012-072666 A

  Generally, filter regeneration is performed by supplying unburned combustion to the oxidation catalyst by post injection or exhaust pipe injection and raising the exhaust temperature to the PM combustion temperature. At this time, if a failure such as a malfunction of the oxidation catalyst or clogging of the exhaust pipe injector occurs, the exhaust temperature cannot be raised to the PM combustion temperature, which causes a problem of defective filter regeneration. For this reason, there is a request to acquire the failure of the oxidation catalyst and the exhaust pipe injector by some method and notify the driver accordingly.

  It is an object of the disclosed technique to effectively perform failure diagnosis of an oxidation catalyst and an exhaust pipe injector.

  The disclosed technology is a diagnostic apparatus for an exhaust purification system in which an exhaust pipe injector and an oxidation catalyst are arranged in order from an upstream side in an exhaust passage of an engine, the temperature acquisition means for acquiring the catalyst temperature of the oxidation catalyst, and the exhaust pipe After the injector starts the exhaust pipe injection, if the catalyst temperature acquired by the temperature acquisition means does not reach a predetermined threshold temperature, the exhaust pipe injection is stopped and the post-injection to the in-cylinder injector of the engine And determining whether at least one of the oxidation catalyst or the exhaust pipe injector has failed based on whether or not the catalyst temperature acquired by the temperature acquisition means after the post injection reaches a predetermined threshold temperature Means.

  The determination means may determine that the oxidation catalyst is in failure when the catalyst temperature acquired by the temperature acquisition means after the post injection does not reach a predetermined threshold temperature.

  The determination means may determine that the exhaust injector is in failure when the catalyst temperature acquired by the temperature acquisition means after the post injection reaches a predetermined threshold temperature.

  The exhaust purification system includes a filter that collects particulate matter in the exhaust in the exhaust passage downstream of the oxidation catalyst, and the determination unit is a filter that burns and removes the particulate matter deposited on the filter. It is preferable to perform failure determination during regeneration and stop filter regeneration when it is determined that either the oxidation catalyst or the exhaust pipe injector has failed.

  The disclosed technique is a diagnostic method for an exhaust purification system in which an exhaust pipe injector and an oxidation catalyst are arranged in order from an upstream side in an exhaust passage of an engine, and after the exhaust pipe injection is started in the exhaust pipe injector, the oxidation catalyst When the temperature of the exhaust gas does not reach a predetermined threshold temperature, the exhaust pipe injection is stopped and the in-cylinder injector of the engine is started to perform post injection, and the temperature of the oxidation catalyst reaches the predetermined threshold temperature after the post injection. Based on whether or not, a failure of at least one of the oxidation catalyst or the exhaust pipe injector is determined.

  If the temperature of the oxidation catalyst does not reach a predetermined threshold temperature after the post injection, the oxidation catalyst may be determined as a failure.

  If the temperature of the oxidation catalyst reaches a predetermined threshold temperature after the post injection, the exhaust injector may be determined to be faulty.

  According to the disclosed system, failure diagnosis of the oxidation catalyst and the exhaust pipe injector can be performed effectively.

1 is a schematic overall configuration diagram showing an exhaust purification system to which a diagnostic device according to an embodiment of the present invention is applied. It is a timing chart figure explaining the failure judgment processing concerning one embodiment of the present invention. It is a flowchart figure explaining the failure determination process which concerns on one Embodiment of this invention.

  Hereinafter, based on an accompanying drawing, a diagnostic device and a diagnostic method concerning one embodiment of the present invention are explained. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, each cylinder of a diesel engine (hereinafter simply referred to as an engine) 10 is provided with an in-cylinder injector 11 that directly injects fuel into the cylinder. The fuel injection amount and fuel injection timing of these in-cylinder injectors 11 are controlled according to an instruction signal input from an electronic control unit (hereinafter referred to as ECU) 100.

  An exhaust passage 13 for leading the exhaust is connected to the exhaust manifold 12 of the engine 10. In the exhaust passage 13, an exhaust pipe injector 20, an exhaust aftertreatment device 30 and the like are provided in order from the exhaust upstream side.

  The exhaust aftertreatment device 30 is configured by arranging an oxidation catalyst 31 and a filter 32 in order from the exhaust upstream side in a case 30A. Further, a temperature sensor 40 is provided immediately downstream (outlet portion) of the oxidation catalyst 31, and a differential pressure sensor 41 is provided before and after the filter 32.

  The oxidation catalyst 31 is formed, for example, by supporting a catalyst component or the like on the surface of a ceramic carrier such as a cordierite honeycomb structure. When the unburned fuel (HC) is supplied by the post-injection of the in-cylinder injector 11 or the exhaust pipe injection of the exhaust pipe injector 20, the oxidation catalyst 31 oxidizes this and raises the exhaust temperature.

  The filter 32 is formed, for example, by arranging a large number of cells partitioned by porous partition walls along the flow direction of the exhaust gas and alternately plugging the upstream side and the downstream side of these cells. . The filter 32 collects PM in the exhaust gas in the pores and surfaces of the partition walls, and when the PM accumulation amount reaches a predetermined upper limit threshold, the filter regeneration is performed to remove the PM.

  The ECU 100 performs various controls of the engine 10 and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, sensor values of various sensors are input to the ECU 100. The ECU 100 also includes a catalyst temperature increase control unit 110, a filter regeneration control unit 120, and a failure determination unit 130 as some functional elements. Each of these functional elements will be described as being included in the ECU 100 that is an integral piece of hardware, but any one of these may be provided in separate hardware.

  The catalyst temperature increase control unit 110 sets the catalyst temperature to the activation temperature when the temperature of the oxidation catalyst 31 is lower than a predetermined activation temperature (for example, about 200 ° C.) such as when the filter regeneration is started or when the engine 10 is cold started. The temperature rise control of the catalyst is increased to More specifically, if the catalyst outlet temperature detected by the exhaust temperature sensor 40 is lower than the activation temperature, the catalyst temperature increase control unit 110 applies early post injection (close to after injection) to the intake throttle or in-cylinder injector 11. The injection is performed at the timing), and the combustion temperature of the engine 10 is increased to raise the temperature of the oxidation catalyst 31 to the activation temperature range. The catalyst temperature increase control is terminated when the catalyst outlet temperature reaches the activation temperature.

  The filter regeneration control unit 120 estimates the PM accumulation amount of the filter 32 from the differential pressure across the filter detected by the differential pressure sensor 41. When the PM accumulation amount reaches a predetermined upper limit threshold, the PM accumulated on the filter 32 is estimated. Implement filter regeneration control to remove combustion. More specifically, when the PM accumulation amount reaches a predetermined upper limit threshold, the filter regeneration control unit 120 causes the exhaust pipe injector 20 to start exhaust pipe injection, supplies unburned fuel to the oxidation catalyst 31, and the filter 32. The exhaust temperature flowing into the engine is raised to the PM combustion temperature (for example, about 600 ° C.). The filter regeneration control is terminated when the PM accumulation amount decreases to a predetermined lower threshold. In this embodiment, the filter regeneration control is configured so that “automatic regeneration” and “manual regeneration” can be performed. Automatic regeneration refers to regeneration that starts automatically regardless of the operation of the driver when the PM accumulation amount reaches the upper threshold. Manual regeneration warns the driver that filter regeneration is necessary when the PM accumulation amount reaches the upper threshold, and starts when the driver stops the vehicle and turns on an operation button (not shown). Refers to playback.

  The failure determination unit 130 performs failure diagnosis of the exhaust pipe injector 20 and the oxidation catalyst 31 such as clogging of the exhaust pipe injector 20 and malfunction of the oxidation catalyst 31. The diagnosis result acquired by the failure determination unit 130 is output to a display device 140 provided in the cab or a speaker (not shown) to notify the driver. Details of the failure determination process will be described below with reference to FIG.

  The failure determination unit 130 first causes the exhaust pipe injector 20 to start exhaust pipe injection when the temperature of the oxidation catalyst 31 reaches a predetermined first threshold temperature (for example, the activation temperature of the oxidation catalyst 31) by the catalyst temperature increase control. (See time t1 in FIGS. 2A and 2B). When the catalyst outlet temperature detected by the temperature sensor 40 reaches a predetermined second threshold temperature (for example, PM combustion temperature) before a predetermined time ΔT has elapsed from the start of exhaust pipe injection (FIG. 2A )), The failure determination unit 130 determines that both the oxidation catalyst 31 and the exhaust pipe injector 20 are normal. The predetermined time ΔT may be set, for example, based on a time sufficient for the oxidation catalyst 31 to raise the exhaust gas temperature to the PM combustion temperature by the oxidation reaction.

  On the other hand, as shown at time t2 in FIG. 2B, when the catalyst outlet temperature detected by the temperature sensor 40 does not reach the second threshold temperature even when the predetermined time ΔT has elapsed since the start of exhaust pipe injection, The failure determination unit 130 stops the exhaust pipe injection and starts late post injection (injection performed when the exhaust valve is opened) by the in-cylinder injector 11. When the catalyst outlet temperature detected by the temperature sensor 40 reaches the second threshold temperature before the predetermined time ΔT has elapsed from the start of the late post injection (see time t3 in FIG. 2B), It is considered that the HC oxidizing ability of the oxidation catalyst 31 is functioning normally, and the exhaust pipe injector 20 has a failure such as clogging. In this case, failure determination unit 130 determines that oxidation catalyst 31 is normal and exhaust pipe injector 20 is defective.

  On the other hand, as indicated by a broken line in FIG. 2B, the catalyst outlet temperature detected by the temperature sensor 40 does not reach the second threshold temperature even after a predetermined time ΔT has elapsed since the start of late post injection. It is considered that the HC oxidation ability of the oxidation catalyst 31 is not functioning normally. In this case, the failure determination unit 130 determines that the oxidation catalyst 31 is a failure.

  The failure determination process of the present embodiment described in detail above is preferably performed in parallel with “manual regeneration” of the filter 32. Hereinafter, details of the failure determination process performed in parallel with the manual regeneration will be described based on the flow of FIG.

  In step S100, it is determined whether or not the PM accumulation amount of the filter 32 estimated from the sensor value of the differential pressure sensor 41 has reached a predetermined upper limit threshold value. If the determination is affirmative, the process proceeds to step S110. If the determination is negative, the process returns.

  In step S110, it is determined whether or not the manual regeneration button has been turned ON by the driver. If the determination is affirmative, the process proceeds to step S120. If the determination is negative, the process returns.

  In step S120, it is determined whether or not the catalyst outlet temperature detected by the temperature sensor 40 has reached a predetermined first threshold temperature (activation temperature). In negative, it progresses to step S130 and catalyst temperature rising control is performed. If affirmative, step S130 is skipped and the process proceeds to step S140.

  In step S140, exhaust pipe injection of the exhaust pipe injector 20 is started to perform failure determination. In step S150, it is determined whether or not a predetermined time ΔT has elapsed since the start of exhaust pipe injection. If affirmative, the process proceeds to step S160.

  In step S160, it is determined whether or not the catalyst outlet temperature detected by the temperature sensor 40 has reached a predetermined second threshold temperature (PM combustion temperature). If the determination is affirmative, the process proceeds to step S200, where it is determined that both the oxidation catalyst 31 and the exhaust pipe injector 20 are normal, and the filter regeneration control is continued in step S210. When the PM accumulation amount decreases to a predetermined lower limit threshold value in step S220, the present control is thereafter terminated.

  On the other hand, in the case of negative in step S160, at this time, the reason why the exhaust temperature does not rise can be determined as a result of a malfunction of the oxidation catalyst 31 or due to clogging of the exhaust pipe injector 20 or the like. Can not. In this case, the process proceeds to step S170, the exhaust pipe injection is stopped, and the late post injection by the in-cylinder injector 11 is started. Further, in step S180, it is determined whether or not a predetermined time ΔT has elapsed since the start of late post injection. If the determination in step S180 is affirmative, the process proceeds to step S190, and it is determined whether or not the catalyst outlet temperature detected by the temperature sensor 40 has reached a predetermined second threshold temperature (PM combustion temperature).

  If the determination in step S190 is affirmative, the reason why the exhaust temperature has not increased in the processing in steps S140 to 160 described above is that unburned fuel has not been supplied to the oxidation catalyst 31 due to clogging of the exhaust pipe injector 20, or the like. it is conceivable that. In this case, the process proceeds to step S300, where it is determined that the oxidation catalyst 31 is normal and the exhaust pipe injector 20 is out of order, and the filter regeneration control is stopped in step S310. In step S320, the driver is notified (displayed / alarmed) of the diagnosis result, and then this control is terminated. Although the exhaust pipe injector 20 is out of order but the oxidation catalyst 31 is normal, the filter regeneration mainly using late / post injection of the in-cylinder injector 11 is not performed in step S310 without stopping the filter regeneration control. Control may be continued.

  On the other hand, in the case of negative in step S190, the cause of the exhaust temperature not increasing in the processing of the above-described steps S140 to 160 is that the function of the oxidation catalyst 31 is lost regardless of whether exhaust pipe injection or post injection is performed. This is probably because the HC oxidation reaction did not occur. In this case, the process proceeds to step S330, it is determined that the oxidation catalyst 31 is out of order, and the filter regeneration control is stopped in step S310. In step S320, the driver is notified (displayed / alarmed) of the diagnosis result, and then this control is terminated.

  As described above in detail, according to the present embodiment, after the exhaust pipe injector 20 performs the exhaust pipe injection, if the temperature of the oxidation catalyst 31 does not reach the second threshold temperature, the exhaust pipe injection to the in-cylinder injector are performed. 11 and post-injection, and the failure determination of the oxidation catalyst 31 and the exhaust pipe injector 20 is performed based on whether or not the temperature of the oxidation catalyst 31 reaches the second threshold temperature after the late post-injection. ing. That is, even if the failure determination is performed only by the exhaust pipe injection, the failure of the oxidation catalyst 31 or the exhaust pipe injector 20 cannot be isolated, but the failure cause can be determined by switching the exhaust pipe injection to the late / post injection. Can be specified in the oxidation catalyst 31 or the exhaust pipe injector 20, and the driver can be surely notified of an appropriate diagnosis result.

  Further, the failure determination process is performed at the start of filter regeneration, and if any failure occurs in either the oxidation catalyst 31 or the exhaust pipe injector 20, the filter regeneration is stopped. As a result, implementation of useless filter regeneration is effectively suppressed, and deterioration of fuel consumption performance associated with an increase in fuel consumption can be reliably prevented.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, the means for acquiring the temperature of the oxidation catalyst 31 is not limited to the temperature sensor 40 on the outlet side, and the temperature may be acquired or estimated in combination with other sensors. The engine 10 is not limited to a diesel engine, and can be widely applied to an internal combustion engine in addition to a gasoline engine or the like.

DESCRIPTION OF SYMBOLS 10 Engine 11 In-cylinder injector 12 Exhaust manifold 13 Exhaust passage 20 Exhaust pipe injector 30 Exhaust aftertreatment device 31 Oxidation catalyst 32 Filter 40 Temperature sensor 41 Differential pressure sensor 100 ECU

Claims (7)

A diagnostic apparatus for an exhaust purification system in which an exhaust pipe injector and an oxidation catalyst are arranged in order from the upstream side in an exhaust passage of an engine,
Temperature acquisition means for acquiring the catalyst temperature of the oxidation catalyst;
After the exhaust pipe injector starts the exhaust pipe injection, if the catalyst temperature acquired by the temperature acquisition means does not reach a predetermined threshold temperature, the exhaust pipe injection is stopped and the in-cylinder injector of the engine The post-injection is started, and at least one failure of the oxidation catalyst or the exhaust pipe injector is determined based on whether or not the catalyst temperature acquired by the temperature acquisition means after the post-injection reaches a predetermined threshold temperature. And a determination means for determining. The diagnostic device according to claim 1, wherein the determination unit determines that the oxidation catalyst is in failure when the catalyst temperature acquired by the temperature acquisition unit after the post injection does not reach a predetermined threshold temperature. The diagnosis device according to claim 1 or 2, wherein the determination unit determines that the exhaust injector is in failure when the catalyst temperature acquired by the temperature acquisition unit after the post injection reaches a predetermined threshold temperature. The exhaust purification system includes a filter that collects particulate matter in the exhaust in the exhaust passage on the downstream side of the oxidation catalyst,
The determination unit performs a failure determination at the time of filter regeneration that burns and removes particulate matter deposited on the filter, and stops filter regeneration when it is determined that either the oxidation catalyst or the exhaust pipe injector is defective. Item 4. The diagnostic device according to any one of Items 1 to 3. A method for diagnosing an exhaust purification system in which an exhaust pipe injector and an oxidation catalyst are arranged in order from the upstream side in an exhaust passage of an engine,
After the exhaust pipe injector starts exhaust pipe injection, if the temperature of the oxidation catalyst does not reach a predetermined threshold temperature, the exhaust pipe injection is stopped and the in-cylinder injector of the engine is started post injection. A diagnostic method comprising: determining whether at least one of the oxidation catalyst or the exhaust pipe injector has failed based on whether the temperature of the oxidation catalyst reaches a predetermined threshold temperature after the post injection. The diagnostic method according to claim 5, wherein if the temperature of the oxidation catalyst does not reach a predetermined threshold temperature after the post injection, the oxidation catalyst is determined to be a failure. The diagnosis method according to claim 5 or 6, wherein when the temperature of the oxidation catalyst reaches a predetermined threshold temperature after the post injection, the exhaust injector is determined to be in failure.

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