DPF abnormality control device

Abstract

To provide a DPF abnormality control device capable of securely preventing abnormal high-temperature exhaust gas in DPF regeneration and having higher reliability compared to conventional devices, without using mechanical components such as a shield plate.SOLUTION: A first level region 50A in which regeneration control processing of a diesel particulate filter is executed, a second level region 50B in which propriety of the processing to be executed in the first level region is monitored and a third level region 50C in which propriety of the processing to be executed in the second level region is monitored are formed in a central processing unit 50 provided in an engine control unit 100. In the second level region, determination as to whether a DPF inlet temperature sensor is normal or defective is made, and when the DPF inlet temperature sensor is determined to be defective, a control signal for forcedly stopping the DPF regeneration control can be output to a required circuit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a DPF abnormality control device, and more particularly to a device that aims to improve reliability and simplify the configuration in preventing so-called hazards such as fires caused by overheating of a DPF. [Background technology]

[0002] BACKGROUND ART It is well known that a DPF (diesel particulate filter) is used as one of the components that make up an exhaust purification device in an automobile (see, for example, Patent Document 1, etc.). This DPF can lose its functionality due to clogging of the filter over time, so a so-called DPF regeneration is usually performed by intentionally generating high-temperature exhaust gas. However, when performing DPF regeneration, the high-temperature exhaust gases described above are usually discharged into the vicinity of the vehicle, which can cause the surrounding objects to become abnormally overheated. To prevent this, measures such as installing a shield are usually taken to prevent overheating. In addition to direct overheating due to the high-temperature exhaust gases as described above, the DPF itself becomes very hot, and the high heat from the DPF also heats up surrounding components, which in some cases could cause components to ignite or burn, so measures to prevent such situations are also necessary. As measures to prevent or suppress overheating of surrounding components due to such high temperatures of the DPF, various measures have been proposed and put into practical use, including not only so-called hardware measures such as providing a shielding plate as described above, but also software processing measures in electronic control units installed in vehicles.For example, a method that forcibly stops the DPF regeneration operation when the DPF temperature detected by a temperature sensor exceeds a reference value, thereby preventing or suppressing an excessive rise in DPF temperature, can be considered a relatively simple method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-25853 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a configuration that provides mechanical parts such as the shielding plate described above, it is necessary to secure additional installation space in current vehicles, where there is not necessarily ample space for arranging components. This not only increases the burden on the structural design, but also leads to an increase in vehicle weight, ultimately resulting in increased costs, and is therefore by no means a wise solution. Furthermore, in the method of stopping DPF regeneration when an excessively high DPF temperature is detected by software processing as described above, from the perspective of functional safety in the automotive functional safety standard (ISO26262), even if the software processing that detects excessive DPF temperatures does not execute normally for some reason, a configuration is required that ensures that DPF regeneration is stopped instead.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and provides a DPF abnormality control device that reliably prevents abnormally high exhaust temperatures during DPF regeneration without using mechanical components such as a shielding plate, and is more reliable than conventional devices. [Means for solving the problem]

[0006] In order to achieve the above object of the present invention, the DPF abnormality control device according to the present invention comprises: The present invention has an electronic control unit configured to be able to execute a regeneration control process for a diesel particulate filter that traps particulate matter contained in exhaust gas from a motor vehicle, The electronic control unit has a central processing unit capable of executing a plurality of control processes, the central processing unit is formed with a first level area in which a regeneration control process for the diesel particulate filter is executed, a second level area in which the appropriateness of the process executed in the first level area is monitored, and a third level area in which the appropriateness of the process executed in the second level area is monitored, In the second level region, a quality determination is made of a DPF inlet temperature sensor provided at the inlet of the diesel particulate filter, and if the DPF inlet temperature sensor is determined to be defective, a control signal for forcibly stopping the DPF regeneration control can be output to a required circuit. [Effects of the Invention]

[0007] According to the present invention, by performing a quality determination of the DPF inlet temperature sensor in the second level region that monitors the appropriateness of the process in the first level region where the regeneration control process of the diesel particulate filter is executed, it becomes possible to reliably detect abnormalities in DPF regeneration with greater reliability than before, thereby achieving the effect of achieving a significant improvement in the reliability and safety of the device. Furthermore, since the present invention can be realized by modifying or adding software, there is no need to secure installation space for adding new components, making it possible to reduce costs while ensuring reliability and safety. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing an example of the configuration of a DPF abnormality control device according to an embodiment of the present invention. [Figure 2] 1 is a configuration diagram showing an example of the configuration of an engine control unit that constitutes a DPF abnormality control device according to an embodiment of the present invention. [Figure 3] 3 is a flowchart showing the procedure of a DPF abnormality control process executed in the DPF abnormality control device according to the embodiment of the present invention. [Figure 4]FIG. 10 is a characteristic diagram showing an example of change in exhaust model temperature based on an exhaust temperature model and an example of change in exhaust temperature when it is determined that the DPF inlet temperature sensor is faulty in the DPF abnormality control process in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The components, arrangements, etc. described below do not limit the present invention, and various modifications can be made within the scope of the present invention. First, an example of the configuration of a DPF abnormality control device according to an embodiment of the present invention will be described with reference to FIGS. The DPF abnormality control device in the embodiment of the present invention is mainly composed of an engine control unit ("ECU" in FIG. 1) 100 and a plurality of sensors provided in an exhaust purification device 200 (see FIG. 1). The engine control unit 100, which is an electronic control unit, is configured with a central processing unit (represented as "CPU" in FIG. 2) 50, which is made up of a microcomputer having a known and commonly-known configuration, as its main components, and also includes memory elements such as RAM and ROM (not shown), an interface circuit (represented as "I / F" in FIG. 2) 60 for interfacing with an external electronic circuit (not shown) and the like (see FIG. 2).

[0010] This engine control unit 100 receives various signals necessary for controlling the operation of an automobile, such as engine speed, accelerator opening, etc., acquired by sensors and switch opening / closing signals (not shown), and these signals are used to execute fuel injection control processing for the engine (denoted as "ENG" in FIG. 1) 300. Furthermore, various sensor output signals and the like required for exhaust purification control, including DPF regeneration control, are input to the engine control unit 100, and are used for the required control processing (details will be described later).

[0011] The exhaust purification device 200 is configured by, in order from the upstream side of the exhaust pipe 11 connected to the exhaust port of the engine 300, an oxidation catalyst 210, a diesel particulate filter (hereinafter referred to as "DPF") 220, and a selective reduction catalyst 230. The configuration of this exhaust gas purification device 200 itself is basically the same as that of a conventionally well-known device, and is not unique to the present invention.

[0012] The oxidation catalyst 210 has a conventional structure and functions to oxidize hydrocarbons (HC), carbon monoxide (CO), and the like in the exhaust gas. The DPF 220 has a conventional structure for capturing particulate matter in exhaust gas. The selective reduction catalyst 230 is a catalyst that selectively reduces NOx contained in the exhaust gas using a liquid reducing agent supplied from the upstream side by the reducing agent injection valve 240, and its configuration itself is the same as that of a conventional catalyst. The liquid reducing agent used may be, for example, urea or aqueous ammonia.

[0013] In this exhaust purification device 200, an oxidation catalyst inlet temperature sensor (hereinafter referred to as "DOC inlet temperature sensor") 1 is provided near the inlet of the oxidation catalyst 210, a DPF inlet temperature sensor 2 is provided near the inlet of the DPF 220, an exhaust temperature sensor 4 is provided near the outlet of the DPF 220, a selective reduction catalyst inlet temperature sensor (hereinafter referred to as "SCR inlet temperature sensor") 3 is provided near the inlet of the selective reduction catalyst 230, and a NOx sensor 5 is provided near the outlet of the selective reduction catalyst 230. These sensors are just examples, and other sensors such as exhaust sensors and O2 sensors (not shown) are provided at appropriate locations, and the outputs of each are input to the engine control unit 100 as described above and used for exhaust control processing, etc.

[0014] Next, the central processing unit 50 constituting the engine control unit 200 will be described with reference to FIG. 2. The central processing unit 50 in the embodiment of the present invention has a configuration in which the processing execution area in which control processing for various operational controls is executed is divided into three areas: a first level area at level 1 (denoted as "PR1" in FIG. 2) 50A, a second level area at level 2 (denoted as "PR2" in FIG. 2) 50B, and a third level area at level 3 (denoted as "PR3" in FIG. 2) 50C.

[0015] The division of processing execution areas into levels within the central processing unit 50 is based on differences in the functions and processing ranges in software execution. First, the first level region 50A of level 1 is a region where the fuel injection control process of the engine 300, the conventional DPF regeneration control process, the injection control process of the liquid reducing agent by the reducing agent injector 11, and the like are executed.

[0016] Next, the second level area 50B of level 2 is an area that performs the function of monitoring the appropriateness of various processing operations executed in the first level area 50A of level 1. The second level area 50B receives signals that are basically the same as the various sensor output signals that are input to the first level area 50A.

[0017] In addition, the method of determining whether various processing operations in the first level area 50A are appropriate in the second level area 50B can be, for example, a method of determining whether the processing operations in the first level area 50A are appropriate by executing the same control processing in the second level area 50B as that executed in the first level area 50A and determining whether the same processing results are obtained. Any determination method can be adopted, and there is no need to be limited to a specific determination method.

[0018] The third level area 50C at level 3 is an area that performs the function of monitoring whether the processing operation at the second level area 50B at level 2 is appropriate. The monitoring operation of the third level area 50C to check whether the processing operations in the second level area 50B are appropriate is realized, for example, by periodically determining whether the ROM (Read Only Memory) and RAM (Random Access Memory) in the second level area 50B are good or bad, and by performing processing such as confirming the reliability of the second level area 50B.

[0019] In addition, if the third level area 50C determines that the processing operation in the second level area 50B is not normal, the third level area 50C executes the required safety response processing, such as forcibly stopping fuel injection, and outputs a control signal required for forcibly stopping fuel injection, etc., to a required circuit, etc. not shown, via the interface circuit 60.

[0020] FIG. 3 shows a flowchart illustrating the procedure of the DPF abnormality control process executed by the central processing unit 50. Hereinafter, the DPF abnormality control process according to the embodiment of the present invention will be described with reference to this figure. First, it is assumed that the central processing unit 50 executes the same DPF regeneration control as in the conventional case in the first level region 50A. Here, the DPF regeneration control is a process for recovering the function of the DPF 220 by burning soot accumulated in the DPF 220 through fuel combustion for DPF regeneration, which is so-called post-injection.

[0021] On the other hand, the DPF abnormality control process in the embodiment of the present invention described below is executed in the second level area 50B of the central processing unit 50. Hereinafter, the DPF abnormality control process executed in the second level region 50B will be described with reference to FIG. First, a quality determination is made for the DPF inlet temperature sensor 2 (see step S110 in FIG. 3). A suitable method for determining whether the exhaust temperature is good or bad is to use, as a determining factor, the temperature difference between the detection value of the exhaust temperature sensor 4 (hereinafter, for the sake of convenience, referred to as the "actual exhaust temperature sensor value") and the exhaust temperature in the exhaust temperature model calculated based on the exhaust temperature model (hereinafter, for the sake of convenience, referred to as the "model exhaust temperature").

[0022] That is, the temperature difference between the actual exhaust temperature sensor value and the model exhaust temperature is calculated, and if this temperature difference exceeds a reference temperature difference, it is determined that the DPF inlet temperature sensor 2 is defective. FIG. 4 shows characteristic lines that show an example of changes in the actual exhaust gas temperature sensor value and the model exhaust gas temperature when it can be determined that the DPF inlet temperature sensor 2 is defective. In the figure, the solid characteristic line shows an example of change in the actual exhaust gas temperature sensor value, and the two-dot chain characteristic line shows an example of change in the model exhaust gas temperature. In this example, after passing around time ta, the model exhaust temperature rises at roughly the same rate as the temperature rise up to that point, whereas the actual exhaust temperature sensor value, although rising in temperature, shows a change in which the rate of rise is clearly slower compared to the rate of temperature rise up to that point, and the difference with the model exhaust temperature clearly increases.

[0023] When a difference occurs between the actual exhaust temperature sensor value and the model exhaust temperature, it is desirable to determine that the DPF inlet temperature sensor 2 is defective as early as possible from the perspective of ensuring the safety of the device. However, if a slight temperature difference is detected and the DPF inlet temperature sensor 2 is immediately determined to be defective, this may result in an erroneous determination. Therefore, the specific point at which the DPF inlet temperature sensor 2 is determined to be defective should be determined based on test results and simulation results, taking into consideration the specific specifications of the entire device, the specifications of each DPF inlet temperature sensor 2, the characteristics of the exhaust temperature model, etc.

[0024] The exhaust temperature model is not specific to the present invention, but is based on a conventionally known method. The exhaust temperature model in the embodiment of the present invention is configured to calculate a model exhaust temperature using engine speed and fuel injection amount as input parameters. The exhaust gas temperature model is not limited to the one described in the embodiment of the present invention, and various existing models can be selected. Therefore, the input parameters are not limited to the engine speed and fuel injection amount described above.

[0025] Returning to the explanation of Figure 3 again, as described above, if it is determined in step S110 that the DPF inlet temperature sensor 2 is faulty, the process proceeds to step S150, whereas if it is determined that the DPF inlet temperature sensor 2 is normal, the process proceeds to step S120. In step 150, the DPF regeneration is forcibly stopped and an alarm is issued.

[0026] That is, a control signal for stopping the DPF regeneration operation is output from the second level region 50B via the interface circuit 60 to a drive circuit or the like (not shown), thereby forcibly stopping the DPF regeneration operation. Furthermore, to notify the occupant of the DPF regeneration abnormality, a warning control signal required to turn on a warning light (not shown) or to emit an alarm sound is output via the interface circuit 60 to a lighting circuit (not shown) or the like, and an alarm is issued by turning on a warning light or the like.

[0027] On the other hand, in step S120, it is determined whether the DPF inlet temperature detected by the DPF inlet temperature sensor 2 exceeds a first specified temperature. If it is determined that the DPF inlet temperature exceeds the first specified temperature (if YES), the process proceeds to the processing of step S150 described above, whereas if it is determined that the DPF inlet temperature does not exceed the first specified temperature (if NO), the process proceeds to the processing of step S130.

[0028] In step S130, it is determined whether the DPF inlet temperature has exceeded a second specified temperature and this state has continued for a specified time or longer. If it is determined that the DPF inlet temperature exceeds the second specified temperature and that this state has continued for more than the specified time (if YES), the process proceeds to step S160. On the other hand, if it is determined that the DPF inlet temperature exceeds the second specified temperature and that this state has not continued for more than the specified time (if NO), the process proceeds to step S140.

[0029] The first specified temperature and the second specified temperature have a relationship of first specified temperature<second specified temperature. In addition, it is preferable to determine the specific set values ​​for the first specified temperature, the second specified temperature, and the specified time based on test results and simulation results, while taking into consideration the specific specifications of the entire device and the specifications of each DPF inlet temperature sensor 2, etc.

[0030] In step S140, since there is no malfunction in the DPF inlet temperature sensor 2 itself or an abnormality in the DPF inlet temperature, the engine operation continues and the DPF regeneration process can be executed. On the other hand, in step S160, the engine is stopped. That is, a control signal required to stop the engine is output from the second level region 50B via the interface circuit 60 to a drive circuit for a fuel injection valve (not shown) and the like, thereby forcibly stopping the engine.

[0031] In the embodiment of the present invention described above, the quality of the DPF inlet temperature sensor 2 is determined based on the temperature difference between the actual exhaust temperature sensor value and the model exhaust temperature (see step S110 in Figure 3), but the method for determining the quality of the DPF inlet temperature sensor 2 is not limited to this, and other methods may also be used. Here, three examples of other methods are described below. The first example is a method for determining whether the DPF inlet temperature sensor 2 is good or bad based on the correlation between temperatures detected by a plurality of temperature sensors.

[0032] Specifically, for example, a correlation is calculated for the detected temperatures of the DOC inlet temperature sensor 1, the DPF inlet temperature sensor 2, and the SCR inlet temperature sensor 3 as described below, and the quality of the DPF inlet temperature sensor 2 is determined based on whether the deviation is a certain amount or more. That is, if the DOC inlet temperature detected by the DOC inlet temperature sensor 1 is Tdoc, the DPF inlet temperature detected by the DPF inlet temperature sensor 2 is Tdpf, and the SCR inlet temperature detected by the SCR inlet temperature sensor 3 is Tscr, if the inequality shown in Equation 1 below holds, it can be determined that the DPF inlet temperature sensor 2 is faulty.

[0033] (Tdoc+Tscr) / 2-Tdpf>predetermined correlation threshold Equation 1

[0034] That is, this method is a method of comparing the average value of the detection values ​​of the two sensors with the detection value of the DPF inlet temperature sensor 2, and judging whether the DPF inlet temperature sensor 2 is good or bad based on the comparison result. It should be noted that the predetermined correlation threshold value in Equation 1 is preferably determined based on test results and simulation results, while taking into consideration the specifications of the DOC inlet temperature sensor 1, DPF inlet temperature sensor 2, and SCR inlet temperature sensor 3 that are actually used, as well as the specific specifications of the entire device.

[0035] Next, a second example of another technique will be described. In the second example, similarly to the first example described above, the quality of the DPF inlet temperature sensor 2 is determined using the outputs of the DOC inlet temperature sensor 1 and the SCR inlet temperature sensor 3. That is, in this second example, if the difference between the detected temperature of the DPF inlet temperature sensor 2 and the detected temperature of either of the other two sensors 1 and 3 is greater than a predetermined value, it is determined that the DPF inlet temperature sensor 2 is faulty.

[0036] Specifically, if either the following formula 2 or formula 3 is satisfied, it is determined that the DPF inlet temperature sensor 2 is defective.

[0037] Tdoc-Tdpf > first individual threshold value Equation 2

[0038] Tscr-Tdpf > second individual threshold value Equation 3

[0039] Here, as in the first example, it is preferable that the first individual threshold value and the second individual threshold value be determined based on test results and simulation results, while taking into consideration the specifications of the DOC inlet temperature sensor 1, DPF inlet temperature sensor 2, and SCR inlet temperature sensor 3 that are actually used, as well as the specific specifications of the entire device.

[0040] Next, a third example of another technique will be described. This third example is similar to the first and second examples in that the DOC inlet temperature sensor 1 and the SCR inlet temperature sensor 3 are used to determine whether the DPF inlet temperature sensor 2 is good or bad. This third example is a method for determining whether the DPF inlet temperature sensor 2 is defective based on whether the temperatures detected by the DPF inlet temperature sensor 2, DOC inlet temperature sensor 1, and SCR inlet temperature sensor 3 are substantially the same after the engine 300 has completely dissipated heat and is at approximately the same temperature as the ambient temperature after the engine has stopped. That is, in this example, if the temperatures detected by the DPF inlet temperature sensor 2, DOC inlet temperature sensor 1, and SCR inlet temperature sensor 3 are not substantially the same after the engine has stopped, it is determined that the DPF inlet temperature sensor 2 is defective.

[0041] The criteria for determining whether the detected temperatures of the DPF inlet temperature sensor 2, DOC inlet temperature sensor 1, and SCR inlet temperature sensor 3 are approximately the same are preferably determined based on test results and simulation results, while taking into consideration the specifications of the DOC inlet temperature sensor 1, DPF inlet temperature sensor 2, and SCR inlet temperature sensor 3 that are actually used, as well as the specific specifications of the entire device. Furthermore, when taking into consideration variations in the characteristics of each sensor, it is more practical and preferable to use a certain tolerance range as the criterion for this determination rather than using a specific value.

[0042] In the embodiment of the present invention, as described above, the DPF abnormality control process is configured to be executed in the second level region 50B. Therefore, even if the conventional DPF abnormality determination process executed in the first level region 50A does not make a normal abnormality determination for some reason, high-temperature exhaust gases caused by an abnormality in the DPF regeneration process are reliably prevented from being released into the vicinity of the vehicle, making it possible to ensure even greater reliability and safety than before.

[0043] Furthermore, as mentioned above, the operation of the second level area 50B is monitored by the third level area 50C. Therefore, if the DPF abnormality control processing in the second level area 50B described above cannot be executed normally due to an abnormality in the RAM or ROM of the second level area 50B, the third level area 50C executes processing such as forcibly stopping the engine, thereby ensuring the safety and reliability of the vehicle. [Industrial Applicability]

[0044] The present invention can be applied to automobiles where it is desired to reliably prevent abnormally high temperature exhaust gases during DPF regeneration without using mechanical components such as shielding plates. [Explanation of symbols]

[0045] 1...DOC inlet temperature sensor 2...DPF inlet temperature sensor 3...SCR inlet temperature sensor 4...Exhaust gas temperature sensor 5...NOx sensor 50...Central processing unit 100...Engine control unit 200...Exhaust gas purification device 300...Engine

Claims

1. The present invention has an electronic control unit configured to be able to execute a regeneration control process for a diesel particulate filter that traps particulate matter contained in exhaust gas from a motor vehicle, The electronic control unit has a central processing unit capable of executing a plurality of control processes, the central processing unit is formed with a first level area in which a regeneration control process for the diesel particulate filter is executed, a second level area in which the appropriateness of the process executed in the first level area is monitored, and a third level area in which the appropriateness of the process executed in the second level area is monitored, In the second level region, a quality determination is made of a DPF inlet temperature sensor provided at an inlet of the diesel particulate filter, and when the DPF inlet temperature sensor is determined to be defective, a control signal for forcibly stopping the DPF regeneration control can be output to a required circuit, In the second level region, when it is determined that the DPF inlet temperature sensor is normal, it is determined whether or not the DPF inlet temperature exceeds a first specified temperature, and when it is determined that the DPF inlet temperature exceeds the first specified temperature, a control signal for forcibly stopping the DPF regeneration control can be output to a required circuit, When it is determined that the DPF inlet temperature does not exceed a first specified temperature in the second level region, it is determined whether the DPF inlet temperature has exceeded a second specified temperature for a specified time, and when it is determined that the DPF inlet temperature has exceeded the second specified temperature for a specified time, a DPF abnormality control device is configured to be able to output a control signal to a required circuit to forcibly stop the engine.

2. 2. The DPF abnormality control device according to claim 1, wherein the central processing unit is configured to allow execution of DPF regeneration control in the first level region when it is determined that the DPF inlet temperature has not exceeded a second specified temperature for a specified time in the second level region.

Images