JP2010159643A - Method for detecting abnormality of temperature sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely decide whether each temperature sensor normally operates. <P>SOLUTION: In a method for detecting the abnormality of the temperature sensors 6, 7, 8 disposed at three sections or more in a flow direction of exhaust gas 5 to put a plurality of catalysts 3, 4 purifying exhaust gas 5 by making the exhaust gas 5 pass therethrough between the same, detection values of the temperature sensors 6, 7, 8 right after the cooling start of an engine are mutually compared and abnormality of the temperature sensors 6, 7, 8 is determined when the mutual deviation exceeds a reference deviation. The detection values of the rear side temperature sensors 7, 8 are estimated based on detection values of the front side temperature sensors 6, 7 and the abnormality of the temperature sensors 6, 7, 8 is determined when the estimated value has a deviation greater than predetermined reference deviation from the actual measured values by the rear side temperature sensors 7, 8 in combinations of the front and the rear temperature sensor 6, 7 and 7, 8 putting the catalysts 3, 4 therebetween under a stable operation condition of predetermined time or longer during operation of the engine. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an abnormality detection method for a temperature sensor that is provided in an exhaust system and detects the temperature of exhaust gas.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. It has been done conventionally.

  This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the flow paths partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. Although it is necessary to regenerate, in an ordinary diesel engine operation state, there are few opportunities to obtain an exhaust temperature high enough for the particulates to self-combust.

  For this reason, for example, an oxidation catalyst obtained by adding an appropriate amount of a rare earth element such as cerium to a material in which platinum is supported on alumina is integrally supported on a particulate filter and collected in the particulate filter. The oxidation reaction of the particulates is promoted by the oxidation catalyst to lower the ignition temperature, so that the particulates can be burned and removed even at an exhaust temperature lower than that of the prior art.

  However, even in such a case, in the operation region where the exhaust temperature is low, the trapped amount exceeds the processing amount of the particulates, and therefore the operation state at such a low exhaust temperature continues. There is a risk that the particulate filter will fall into an over-collected state without the particulate filter regenerating well, and the particulate filter is forcibly forced by the filter regeneration means at the stage when the amount of particulate accumulation has increased. It is necessary to incinerate the collected particulates by heating.

  This type of filter regeneration means includes means for disposing an oxidation catalyst in the preceding stage of the particulate filter and adding fuel to the upstream side thereof for heating by the heat of oxidation reaction on the oxidation catalyst, and for the stage before the particulate filter. Means and the like for heating by arranging an electric heater and a burner have been developed.

  On the other hand, when purifying exhaust gas from a diesel engine, it is not enough to remove particulates in the exhaust gas. In the middle of the exhaust pipe where the exhaust gas flows, NOx selectively reacts with the reducing agent even in the presence of oxygen. A selective reduction catalyst having the property of causing the NOx (nitrogen oxides) in the exhaust gas on the selective reduction catalyst by adding a necessary amount of the reducing agent upstream of the selective reduction catalyst. ) To reduce the NOx emission concentration.

  Exhaust purification materials such as particulate filters and selective reduction catalysts that pass exhaust gas in this way are used to improve the regeneration control and exhaust purification reaction control. It is necessary to detect the temperature and perform appropriate temperature management (see, for example, Patent Document 1 below).

JP 2003-225657 A

  As described above, the reliability of each temperature sensor is very important in performing appropriate temperature management. However, conventionally, it is not determined whether each temperature sensor is operating normally. First, when an extreme abnormality such as disconnection or short circuit of each temperature sensor occurred, it could only be detected by sticking to the lower limit (in case of disconnection) or upper limit (in case of short circuit) of the detected value.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a temperature sensor abnormality detection method that can reliably determine whether or not each temperature sensor is operating normally.

  The present invention is a method for detecting abnormalities in temperature sensors provided at three or more locations in the exhaust gas flow direction so as to sandwich a plurality of exhaust purification materials that pass through exhaust gas to be purified. The detected values of the individual temperature sensors immediately after the cold start are compared with each other, and when the mutual deviation exceeds a predetermined reference deviation, an abnormality of the temperature sensor is determined, and during the engine operation, a predetermined time or more Estimate the detection value of the rear temperature sensor from the detection value of the front temperature sensor for the temperature sensors before and after sandwiching the exhaust purification material under stable operating conditions, and the estimated value is the actual measurement value of the rear temperature sensor On the other hand, the abnormality of the temperature sensor is determined when the deviation exceeds a predetermined reference deviation.

  That is, when the detected values of the individual temperature sensors are compared with each other immediately after the cold start of the engine, the engine and exhaust system are still cold at this stage. All detected values should be measured at a detected temperature close to the outside temperature, and when the mutual deviation of each temperature sensor exceeds a predetermined standard deviation, an abnormality has occurred in any of the temperature sensors. It is determined that

  At this time, normal temperature sensors have almost the same detected value as the outside air temperature, and therefore, when the detected values of the individual temperature sensors are compared with each other, only one of the measured values of the other temperature sensors is significantly different. Is identified as occurring.

  In addition, under stable operating conditions for a predetermined time or longer during engine operation, the floor temperature of the exhaust purification material is already warmed to the exhaust temperature, and a large change in exhaust temperature does not occur before and after the exhaust purification material. However, the temperature is only lowered by the amount of heat released to the outside air while passing through the exhaust purification material.

  For this reason, if the detection value by the temperature sensor on the front side of the exhaust purification material is known, it is estimated that the exhaust temperature lower by the amount of heat released to the outside air from this detection value is detected by the temperature sensor on the rear side. If both are normal, the measured value of the rear side temperature sensor should be measured at a detected temperature close to the estimated value, and the estimated value for the measured value of the rear side temperature sensor is a predetermined standard. When the deviation exceeds the deviation, it is determined that an abnormality has occurred in either the front or rear temperature sensor.

  At this time, since the rear side temperature sensor corresponds to the front side temperature sensor as viewed from the next-stage exhaust purification material, the same determination is made for the next-stage exhaust purification material, and the next-stage exhaust purification material is sandwiched. If no abnormality is determined in the front and rear temperature sensors, it is determined that an abnormality has occurred in the temperature sensor on the front side of the previous exhaust purification material, and the temperature sensor before and after the next exhaust purification material is sandwiched. If an abnormality is determined, it is specified that an abnormality has occurred in the temperature sensor on the rear side of the preceding exhaust purification material.

  Furthermore, in the present invention, it is only necessary to determine that the engine is cold-started when the coolant temperature at the time of starting the engine is equal to or lower than a predetermined temperature, and the engine speed and the fuel injection amount are within a predetermined operating range. What is necessary is just to determine that it is in the stable driving | running condition when staying for more than time.

  According to the above-described temperature sensor abnormality detection method of the present invention, whether or not each temperature sensor equipped so as to sandwich a plurality of exhaust purification materials is operating normally during cold start and during operation Since it can be determined by both, it is possible to reliably detect that an abnormality has occurred in each temperature sensor, and it is possible to identify which temperature sensor the abnormality has occurred. Can be played.

It is the schematic which shows an example of the form which implements this invention. It is a flowchart which shows the procedure of the concrete abnormality detection by the control apparatus of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show an example of an embodiment for carrying out the present invention. Two types of catalysts 3 and 4 (exhaust purification materials) are provided in a casing 2 interposed in the middle of an exhaust pipe 1 constituting an exhaust system path. Are accommodated in series, and the exhaust gas 5 can be purified by passing the exhaust gas 5 through the catalysts 3 and 4.

  Temperature sensors 6, 7, and 8 are provided at three locations in the flow direction of the exhaust gas 5 so as to sandwich the catalysts 3 and 4, and temperature signals from the temperature sensors 6, 7, and 8 are provided. 6a, 7a, and 8a are input to a control device 9 that also serves as an engine control computer (ECU: Electronic Control Unit).

  Here, the control device 9 includes an accelerator opening signal 10a from an accelerator sensor 10 (load sensor) that detects the accelerator opening as a load of the engine, and a rotation speed from the rotation sensor 11 that detects the rotation speed of the engine. A signal 11a and a water temperature signal 12a from a water temperature sensor 12 for detecting the cooling water temperature of the engine are inputted, and whether or not each of the temperature sensors 6, 7, 8 is operating normally. Confirmation is as follows.

  That is, as shown in the flowchart of FIG. 2, in step S1, it is determined whether or not the cooling water temperature is equal to or lower than a predetermined temperature based on the water temperature signal 12a from the water temperature sensor 12 when the engine is started. As long as it is during cold start, the process proceeds to step S2.

  In step S2, the detected values of the individual temperature sensors 6, 7, 8 immediately after the cold start of the engine are compared with each other. In the next step S3, the mutual deviation between the temperature sensors 6, 7, 8 is predetermined. When the reference deviation is exceeded, the routine proceeds to step S4, where the abnormality of the temperature sensors 6, 7, 8 is determined.

  That is, when the detected values of the individual temperature sensors 6, 7, and 8 are compared with each other immediately after the cold start of the engine, the engine and exhaust system are still cold at this stage. If all 8 are normal, all the detected values should be measured at a detected temperature close to the outside air temperature, and the mutual deviation between the temperature sensors 6, 7, and 8 exceeds a predetermined reference deviation. When any of the temperature sensors 6, 7, 8 is abnormal, it is determined that an abnormality has occurred.

  At this time, the normal temperature sensors 6, 7, and 8 have substantially the same detected value as the outside air temperature, so only one other temperature is compared among the detected values of the individual temperature sensors 6, 7, and 8. It is specified that an abnormality has occurred in the sensor 6, 7, 8, which is greatly different from the measured values.

  For example, when the mutual deviation exceeds the temperature sensor 6 and the temperature sensor 7, if it is confirmed that the mutual deviation does not exceed the comparison between the temperature sensor 7 and the temperature sensor 8, the temperature sensor 6 is abnormal. Is identified as occurring.

  Further, when the mutual deviation between the temperature sensors 6, 7, and 8 does not exceed a predetermined reference deviation in the previous step S3, the operating state of the engine is monitored in step S5 to confirm stable operating conditions for a predetermined time or more. Only when it is done, the process proceeds to step S6.

  Here, in the previous step S5, when the engine speed and the fuel injection amount remain within a predetermined operating region for a predetermined time or more, it is determined that the engine is operating under stable operating conditions. The number is grasped on the basis of the rotation speed signal 11a from the rotation sensor 11, and the fuel injection amount is controlled by the control device 9 also serving as an engine control computer by the accelerator sensor 10 and the accelerator opening signal 10a from the rotation sensor 11. And it is grasped | ascertained in the fuel-injection control system which bears control based on the rotation speed signal 11a.

  In the next step S6, the detected value of the rear temperature sensor 7 is estimated from the detected value of the front temperature sensor 6 with respect to the temperature sensors 6 and 7 before and after the catalyst 3 interposed therebetween, and the catalyst 4 is The detected value of the rear temperature sensor 8 is estimated from the detected value of the front temperature sensor 7 with respect to the temperature sensors 7 and 8 before and after being sandwiched therebetween.

  Further, in the next step S7, for each combination of the temperature sensors 6 and 7 and the temperature sensors 7 and 8 before and after sandwiching the catalysts 3 and 4, the actual measurement of the temperature sensors 7 and 8 on the rear side in each group is performed. The value is compared with the estimated value obtained in the previous step S6, and when the estimated value has a deviation exceeding a predetermined reference deviation with respect to the actually measured value, the process proceeds to step S8 and abnormality of the temperature sensors 6, 7, 8 is detected. If it is determined that the deviation does not exceed the reference deviation, the process proceeds to step S9 where it is determined that the temperature sensors 6, 7, and 8 are normal.

  In other words, under stable operating conditions for a predetermined time or longer during engine operation, the bed temperature of the catalysts 3 and 4 is already warmed to the exhaust temperature, and a large change in exhaust temperature before and after the catalysts 3 and 4 does not occur. The temperature sensors 6 and 7 and the temperature sensors 7 and 7 before and after sandwiching each of the catalysts 3 and 4 are only lowered by the amount of heat released to the outside air while passing through the catalysts 3 and 4. If the detected values of the temperature sensors 6 and 7 on the front side in each set are known with respect to the combination of 8, the exhaust temperature lower by the amount of heat released from the detected value to the outside air is detected by the temperature sensors 7 and 8 on the rear side in each set Presumed to be detected.

  Therefore, if the combination of the temperature sensors 6 and 7 and the temperature sensors 7 and 8 before and after sandwiching the catalysts 3 and 4 is normal, the measured values of the temperature sensors 7 and 8 on the rear side in each group Will be measured at a detected temperature close to the estimated value, and the estimated value has a deviation exceeding a predetermined reference deviation with respect to the actually measured values of the temperature sensors 7 and 8 on the rear side in each set. , It is determined that an abnormality has occurred in any of the corresponding sets.

  At this time, if the determination results of each set are known, it is possible to specify which of the temperature sensors 6, 7, and 8 is abnormal by comparing the determination results with each other. For example, when it is determined that an abnormality has occurred in any of the pair of temperature sensors 6 and 7 before and after sandwiching the catalyst 3, the temperature sensors 7 and 8 before and after sandwiching the catalyst 4 at the next stage. If no abnormality is determined in the pair of the above, it is specified that an abnormality has occurred in the temperature sensor 6 on the front side of the catalyst 3 in the preceding stage, and the temperature sensors 7 and 8 before and after sandwiching the catalyst 4 in the next stage are identified. If an abnormality is determined for the set, it is specified that an abnormality has occurred in the temperature sensor 7 on the rear side of the catalyst 3 in the preceding stage.

  Thus, in this way, whether or not the temperature sensors 6, 7 and 8 equipped so as to sandwich the plurality of catalysts 3 and 4 are operating normally is determined during cold start and during operation. Therefore, it is possible to reliably detect that an abnormality has occurred in each of the temperature sensors 6, 7, 8, and the abnormality has occurred in any of the temperature sensors 6, 7, 8. Can be specified.

  The abnormality detection method for the temperature sensor of the present invention is not limited to the above-described embodiment. The exhaust purification material includes a particulate filter, a selective reduction catalyst, a NOx occlusion reduction catalyst, and an oxidation catalyst. Of course, various modifications can be made without departing from the scope of the present invention.

1 Exhaust pipe (exhaust line)
3 Catalyst (exhaust gas purification material)
4 Catalyst (exhaust gas purification material)
5 Exhaust gas 6 Temperature sensor 6a Temperature signal 7 Temperature sensor 7a Temperature signal 8 Temperature sensor 8a Temperature signal 9 Control device 11 Rotation sensor 11a Rotation number signal 12 Water temperature sensor 12a Water temperature signal

Claims (3)

  A method for detecting abnormalities in temperature sensors provided at three or more locations in the exhaust gas flow direction so as to sandwich a plurality of exhaust gas purification materials that pass exhaust gas to be purified. Immediately after, the detected values of the individual temperature sensors are compared with each other, and when the mutual deviation exceeds a predetermined reference deviation, an abnormality of the temperature sensor is determined, and a stable operating condition for a predetermined time or more during engine operation is determined. Then, the detected value of the rear temperature sensor is estimated from the detected value of the front temperature sensor for the temperature sensors before and after the exhaust purification material is sandwiched, and the estimated value is a predetermined value with respect to the actual measured value of the rear temperature sensor. An abnormality detection method for a temperature sensor, characterized by determining an abnormality of the temperature sensor when the deviation exceeds a reference deviation.   The temperature sensor abnormality detection method according to claim 1, wherein it is determined that the engine is cold-started when a coolant temperature at engine startup is equal to or lower than a predetermined temperature.   The temperature sensor abnormality detection method according to claim 1 or 2, wherein when the engine speed and the fuel injection amount remain in a predetermined operation region for a predetermined time or more, it is determined that the engine is in a stable operation condition. .

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