Control device and control method

Abstract

To execute DPF regeneration control at stable intervals.SOLUTION: An engine ECU is a control device for an exhaust emission control device of an engine. The exhaust emission control device includes a DPF provided in an exhaust passage of the engine to collect PMs included in exhaust gas and a differential pressure sensor that detects differential pressure between an inlet and an outlet of the DPF. In the state where no exhaust gas flows in the exhaust passage and there is no differential pressure, when a zero point of the differential pressure sensor is corrected, the engine ECU sets a detection value obtained by the differential pressure sensor as the zero point if it is not a specific situation where a measurement error of the differential pressure sensor easily exceeds a predetermined range (Step S113), and regards the detection value as a value within the predetermined range to correct the zero point if it is the specific situation and if a detection value exceeding the predetermined range is detected by the differential pressure sensor (Step S114).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This disclosure relates to a control device and a control method, and particularly to a control device for an exhaust gas purification device of an internal combustion engine and a control method by the control device.

Background Art

[0002] Conventionally, there has been an exhaust gas purification device including a particulate matter removal filter (hereinafter referred to as "DPF (Diesel Particulate Filter)") that removes particulate matter (hereinafter referred to as "PM (Particulate Matter)") contained in the exhaust gas from an internal combustion engine. Some are provided with a sensor that detects the differential pressure before and after this DPF (see, for example, Patent Document 1). In this exhaust gas purification device, the amount of PM deposited on the DPF is estimated from the differential pressure detected by the sensor. When the amount of PM reaches a predetermined threshold value, regeneration control for removing PM from the DPF is executed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, depending on the conditions of the exhaust passage (for example, temperature, pressure, humidity) or the state of the differential pressure sensor (for example, initial defect, aging deterioration), the detected value of the differential pressure sensor varies. When the detected value varies to the higher differential pressure side, the interval of the regeneration control of the DPF becomes shorter. For this reason, it may give the user an impression that the regeneration control of the DPF is more frequent than usual, or the fuel consumption deteriorates because fuel is used for the regeneration control. Further, when the detected value varies to the lower differential pressure side, the regeneration control is executed in a state where PM is excessively deposited, so the DPF becomes hotter than normal.

[0005] This disclosure is made to solve the above-described problems, and an object thereof is to provide a control device and a control method capable of executing regeneration control of a DPF at a stable interval.

Means for Solving the Problems

[0006] The control device according to this disclosure is a control device for an exhaust gas purification device of an internal combustion engine. The exhaust gas purification device is provided in an exhaust passage of the internal combustion engine and includes a filter that collects particulate matter contained in exhaust gas and a sensor that detects a differential pressure between an inlet and an outlet of the filter. When calibrating the zero point of the sensor in a state where there is no differential pressure and no exhaust gas is flowing in the exhaust passage, if it is not a specific situation in which the measurement error of the sensor is likely to exceed a predetermined range, the detected value by the sensor is set as the zero point. On the other hand, in the case of a specific situation and when a detected value exceeding the predetermined range is detected by the sensor, the detected value is regarded as a value within the predetermined range and the zero point is calibrated.

[0007] Preferably, the specific situation is a situation where the exhaust passage exceeds a predetermined temperature. More preferably, the temperature of the exhaust passage is the temperature inside the filter.

[0008] More preferably, when the detected value exceeds the upper limit value of the predetermined range, the control device regards the detected value as the upper limit value and sets the upper limit value as the zero point. On the other hand, when the detected value is lower than the lower limit value of the predetermined range, the control device regards the detected value as the lower limit value and sets the lower limit value as the zero point.

[0009] More preferably, in the case of a specific situation and when a detected value not exceeding the predetermined range is detected by the sensor, the control device sets the detected value as the zero point.

[0010] According to another aspect of this disclosure, the control method is a control method by a control device of an exhaust gas purification device for an internal combustion engine. The exhaust gas purification device is provided in an exhaust passage of the internal combustion engine and includes a filter that collects particulate matter contained in exhaust gas, and a sensor that detects a differential pressure between an inlet and an outlet of the filter. The control method includes steps in which when the control device calibrates the zero point of the sensor in a state where there is no differential pressure and no exhaust gas is flowing in the exhaust passage, if it is not a specific situation where the measurement error of the sensor is likely to exceed a predetermined range, the detected value by the sensor is set as the zero point, and if it is a specific situation and a detected value exceeding the predetermined range is detected by the sensor, the detected value is regarded as a value within the predetermined range and the zero point is calibrated.

Advantages of the Invention

[0011] According to this disclosure, it is possible to provide a control device and a control method capable of executing the regeneration control of the DPF at stable intervals.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0014] FIG. 1 is a schematic configuration diagram of an exhaust gas purification device 11 for an internal combustion engine according to this embodiment. The engine 1 is a compression self-ignition type internal combustion engine (diesel engine) equipped with the exhaust gas purification device 11. The engine 1 is an internal combustion engine that injects fuel from a fuel injection valve (injector) 14 into a combustion chamber formed in a cylinder 12 of the engine body 10 and performs compression self-ignition. In this embodiment, the engine 1 has four cylinders. An air cleaner 22, an intercooler 24, and a throttle valve (diesel throttle valve) 26 are provided in the intake passage 20 of the engine 1. The fresh air (air) from which foreign matters have been removed by the air cleaner 22 is supercharged (compressed) by a compressor 32 of a turbocharger 30, cooled by the intercooler 24, supplied to the intake manifold 28, and supplied from the intake port to each combustion chamber.

[0015] The exhaust gas (exhaust gas) discharged from the combustion chamber is collected in an exhaust manifold 50 and discharged to the outside air through an exhaust passage 52. A part of the exhaust gas is also refluxed to the intake manifold 28 through an EGR (Exhaust Gas Recirculation) passage 60. An EGR cooler 62 and an EGR valve 64 are provided in the EGR passage 60.

[0016] In the exhaust passage 52, a turbine 34 of a turbocharger 30, an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 70, and a DPF 72 are provided in this order from the upstream side. The exhaust gas purification device 11 includes the DOC 70 and the DPF 72. The DPF 72 is a filter that collects PM in the exhaust gas and purifies it by appropriately burning and removing the collected PM. Although not shown, a urea addition valve and a selective reduction catalyst may be provided downstream of the DPF 72 of the exhaust gas purification device 11. Instead of, or in addition to, the urea addition valve and the selective reduction catalyst, a NOx storage reduction catalyst (NSR (NOx Storage-Reduction) catalyst) may be provided.

[0017] Fuel is stored in the fuel tank 40. The fuel in the fuel tank 40 is supplied to the high-pressure fuel pump 42 by the feed pump 41, and the high-pressure fuel discharged from the high-pressure fuel pump 42 is pumped to the common rail 44 through the fuel passage 43. The high-pressure fuel stored in the common rail 44 is injected from the injector 14 into the combustion chamber (inside the cylinder).

[0018] A fuel addition valve 80 is provided in the exhaust passage 52 upstream of the oxidation catalyst 70 (in this embodiment, the exhaust passage 52 upstream of the turbine 34). Fuel in the fuel tank 40 is supplied to the fuel addition valve 80 by the feed pump 41 through the fuel passage 45, and when the fuel addition valve 80 opens, fuel is added (injected) into the exhaust passage 52.

[0019] The engine ECU 100 (Electronic Control Unit) includes a CPU 101, a memory 102 composed of a ROM and a RAM, an input / output port for inputting and outputting various signals, etc. It executes predetermined arithmetic processing based on the information stored in the memory 102 and the information from various sensors, and controls the injector 14, the throttle valve 26, the high-pressure fuel pump 42, the fuel addition valve 80, etc.

[0020] As various sensors inputted to the engine ECU 100, for example, there are an engine speed sensor 111, an accelerator pedal sensor 112, an air flow meter 113, an oxidation catalyst temperature sensor 114, a DPF temperature sensor 115, and a differential pressure sensor 116, etc. The engine speed sensor 111 detects the rotational speed NE of the engine 1. The accelerator pedal sensor 112 detects the operation amount of the accelerator pedal (hereinafter also referred to as "accelerator opening") AP by the user. The air flow meter 113 detects the intake air amount (inhaled air amount) Ga of the engine 1. The oxidation catalyst temperature sensor 114 detects the temperature Tc of the oxidation catalyst 70. It is desirable that the oxidation catalyst temperature sensor 114 detects the inlet temperature of the oxidation catalyst 70. The DPF temperature sensor 115 detects the temperature Tf (the bed temperature of the DPF 72) of the DPF 72. The differential pressure sensor 116 detects the pressure difference (hereinafter also referred to as "differential pressure") ΔP in the exhaust passage 52 upstream and downstream of the DPF 72.

[0021] In the engine 1 configured as described above, PM contained in the exhaust gas discharged from the engine 1 is collected by the DPF 72. When the amount of PM deposited on the DPF 72 reaches a predetermined value or more, the engine ECU 100 executes a regeneration control to regenerate the DPF 72 by raising the temperature of the DPF 72 and burning and removing the deposited PM. When executing the regeneration control, in order to raise the temperature of the DPF 72, fuel is added from the fuel addition valve 80. The added fuel causes the oxidation catalyst 70 to generate heat (burn), and the temperature of the exhaust gas flowing into the DPF 72 rises.

[0022] FIG. 2 is a diagram for explaining the problems of this disclosure. Referring to FIG. 2, as shown by graph L1, as the usage period (e.g., driving distance) of a machine (e.g., a vehicle) equipped with engine 1 increases, PM accumulates in DPF 72, so when a predetermined flow rate of exhaust gas flows through exhaust passage 52, the differential pressure of DPF 72 rises from the state of the lowest value. The amount of PM deposited on DPF 72 is estimated based on the differential pressure indicated by the detected value by differential pressure sensor 116. When the differential pressure reaches the regeneration control start threshold value, it is determined that the deposited amount of PM has reached a predetermined threshold value, and the regeneration control of DPF 72 is executed. As a result, by removing the PM inside DPF 72, the differential pressure of DPF 72 at a predetermined flow rate returns to almost the lowest value.

[0023] As shown by graphs L1 and L2, depending on the conditions of exhaust passage 52 (e.g., temperature, pressure, humidity) or the state of differential pressure sensor 116 (e.g., initial defect, aging deterioration), variations occur in the detected value of differential pressure sensor 116. As shown by arrow A1, as a result of the detected value varying to the higher differential pressure side, when the change in the differential pressure detected by differential pressure sensor 116 changes from graph L1 to graph L2, as shown by arrow A2, the interval of the regeneration control of DPF 72 becomes shorter. For this reason, it gives the user the impression that the regeneration control of DPF 72 is more frequent than usual, or the fuel consumption deteriorates because fuel is used for the regeneration control. Also, when the detected value varies to the lower differential pressure side, since the regeneration control is executed in a state where PM has accumulated excessively, DPF 72 becomes hotter than normal.

[0024] Therefore, when engine ECU 100 calibrates the zero point of differential pressure sensor 116 in a state where there is no differential pressure that exhaust gas is not flowing through exhaust passage 52, when it is not a specific situation where the measurement error of differential pressure sensor 116 easily exceeds a predetermined range, while taking the detected value by differential pressure sensor 116 as the zero point, in the case of a specific situation and when a detected value exceeding the predetermined range is detected by differential pressure sensor 116, the zero point is calibrated by regarding the detected value as a value within the predetermined range. Thereby, the regeneration control of DPF 72 can be executed at a stable interval.

[0025] FIG. 3 is a flowchart showing the flow of the differential pressure sensor zero point calibration process in this embodiment. Referring to FIG. 3, this differential pressure sensor zero point calibration process is called and executed from the upper process by the CPU 101 of the engine ECU 100 at a predetermined cycle.

[0026] First, the CPU 101 determines whether the calibration condition is satisfied (step S111). The calibration condition is a condition indicating that calibration is possible. Specifically, it is a condition that the original differential pressure to be detected by the differential pressure sensor 116 is 0. For example, it may be a condition that the exhaust gas is not flowing through the exhaust passage 52 because the engine 1 is not operating, or it may be a condition that the ignition is off.

[0027] If it is determined that the calibration condition is satisfied (YES in step S111), the CPU 101 determines whether the large variation condition of the differential pressure sensor 116 is satisfied (step S112). The large variation condition of the differential pressure sensor 116 is a condition indicating a specific situation where the measurement error of the differential pressure sensor 116 is likely to exceed a predetermined range. For example, it may be a condition that the differential pressure sensor 116 is at a high temperature equal to or higher than a predetermined temperature, or it may be a condition that the inside of the exhaust passage 52 in which the differential pressure sensor 116 is provided is at a high temperature equal to or higher than a predetermined temperature. For example, it may be a condition that the temperature of the differential pressure sensor 116 is outside a predetermined range, or it may be a condition that the temperature inside the exhaust passage 52 in which the differential pressure sensor 116 is provided is outside a predetermined range.

[0028] If it is determined that the large variation condition of the differential pressure sensor 116 is not satisfied (NO in step S112), the CPU 101 sets the value detected by the differential pressure sensor 116 as the zero point (step S113). For example, if the value detected by the differential pressure sensor 116 indicates a differential pressure a (kPa), in order to set this value a (kPa) as the differential pressure 0 (kPa), a (kPa) is subtracted from the detected value. It is assumed that the value obtained by subtracting a (kPa) from the value detected by the differential pressure sensor 116 after this zero point calibration is the measured value of the differential pressure.

[0029] On the other hand, when it is determined that the large variation condition of the differential pressure sensor 116 is satisfied (YES in step S112), if the value detected by the differential pressure sensor 116 exceeds the upper limit value of the median range of the differential pressure sensor 116, the CPU 101 sets the upper limit value as the zero point. If it is below the lower limit value, the CPU 101 sets the lower limit value as the zero point. If it does not exceed the median range, the CPU 101 sets the value detected by the differential pressure sensor as the zero point (step S114). The median range of the differential pressure sensor 116 is the accuracy range at the median of the standard accuracy range of the differential pressure sensor 116.

[0030] For example, assuming that the accuracy range is ±b (kPa). In this case, if the value detected by the differential pressure sensor 116 indicates a differential pressure c (kPa), if c > +b, then since b (kPa) is set to 0 (kPa), the value obtained by subtracting b (kPa) from the value detected after this calibration is used as the measured value of the differential pressure. If c < -b, then since -b (kPa) is set to 0 (kPa), the value obtained by adding b (kPa) to the value detected after this calibration is used as the measured value of the differential pressure. If -b ≤ c ≤ b, then since c (kPa) is set to 0 (kPa), the value obtained by subtracting c (kPa) from the value detected after this calibration is used as the measured value of the differential pressure.

[0031] When it is determined that the calibration condition is not satisfied (NO in step S111), after step S113 or after step S114, the CPU 101 returns the process to be executed to the upper process of the call source of this process.

[0032] [Modification Example] (1) In the above-described embodiment, it is assumed that the engine 1 is provided in a vehicle. However, the present invention is not limited to this, and the engine 1 may be provided in a machine other than a vehicle, for example, a generator or a compressor.

[0033] (2) In the above-described embodiment, the number of times the large variation condition of the differential pressure sensor 116 is satisfied in step S112 of FIG. 3 is counted. When the number of times reaches a predetermined number, it may be notified (for example, the sensor confirmation lamp on the meter panel is lit), or information to that effect may be transmitted to an external server such as the server of the manufacturer of the engine 1. As a result, the user or the person in charge of the manufacturer can know that the number of times the large variation condition of the differential pressure sensor 116 is satisfied has reached the predetermined number, and can take countermeasures accordingly.

[0034] (3) In the above-described embodiment, as shown in step S112 of FIG. 3, when the large variation condition of the differential pressure sensor 116 is satisfied once, zero point calibration is executed in step S114. However, the present invention is not limited to this. When the large variation condition is satisfied a plurality of times, zero point calibration may be executed in step S114 using a representative value (for example, average value, median value, mode value, etc.) of the detected values of the differential pressure sensor 116 for the plurality of times.

[0035] (4) In the above-described embodiment, as shown in step S114 of FIG. 3, if it exceeds the median range, the upper limit value or the lower limit value within the accuracy range is set as the zero point. However, the present invention is not limited to this. A value corresponding to the degree of exceeding may be set as the zero point. For example, assume that the accuracy range is ±b (kPa). In this case, when the value detected by the differential pressure sensor 116 indicates a differential pressure c (kPa), if +2b ≧ c > +b, then b / 2 (kPa) is set to 0 (kPa), so the value obtained by subtracting b / 2 (kPa) from the value detected after this calibration is used as the measured value of the differential pressure. If c > +2b, then b (kPa) is set to 0 (kPa), so the value obtained by subtracting b (kPa) from the value detected after this calibration is used as the measured value of the differential pressure. If -2b ≦ c < -b, then -b / 2 (kPa) is set to 0 (kPa), so the value obtained by adding b / 2 (kPa) to the value detected after this calibration is used as the measured value of the differential pressure. If c < -2b, then -b (kPa) is set to 0 (kPa), so the value obtained by adding b (kPa) to the value detected after this calibration is used as the measured value of the differential pressure.

[0036] (5) The above-described embodiments can be regarded as a disclosure of the exhaust gas purification device 11, the engine 1, or the vehicle. Further, it can be regarded as a disclosure of a control method or a control program executed by a control device of the exhaust gas purification device 11, the engine 1, or the vehicle.

[0037] [Summary] (1) As shown in FIG. 1, the engine ECU 100 is a control device for the exhaust gas purification device 11 of the engine 1. The exhaust gas purification device 11 is provided in the exhaust passage 52 of the engine 1, and includes a DPF 72 that collects PM contained in the exhaust gas, and a differential pressure sensor 116 that detects the differential pressure between the inlet and the outlet of the DPF 72. As shown in FIG. 3, when the engine ECU 100 calibrates the zero point of the differential pressure sensor 116 in a state where there is no differential pressure with no exhaust gas flowing in the exhaust passage 52, if it is not a specific situation where the measurement error of the differential pressure sensor 116 easily exceeds a predetermined range, the detected value by the differential pressure sensor 116 is set as the zero point (for example, step S113). On the other hand, if it is a specific situation and a detected value exceeding the predetermined range is detected by the differential pressure sensor 116, the detected value is regarded as a value within the predetermined range and the zero point is calibrated (for example, step S114).

[0038] Thereby, even when the specific situation continues, the zero point of the differential pressure sensor 116 can be appropriately calibrated, so that the amount of PM deposited on the DPF 72 can be appropriately estimated. As a result, the regeneration control of the DPF 72 can be executed at stable intervals.

[0039] (2) As shown in FIG. 3, the specific situation may be a situation where the exhaust passage 52 exceeds a predetermined temperature. Thereby, even when the situation where the exhaust passage 52 exceeds the predetermined temperature continues, the zero point of the differential pressure sensor 116 can be appropriately calibrated.

[0040] (3) As shown in FIG. 3, the temperature of the exhaust passage 52 in the above (2) may be the temperature inside the DPF 72. Thereby, even when the situation where the temperature inside the DPF 72 continues to exceed a predetermined temperature, the zero point of the differential pressure sensor 116 can be appropriately calibrated.

[0041] (4) As shown in step S114 of FIG. 3, when the detected value exceeds the upper limit value of the predetermined range, the engine ECU 100 may regard the detected value as the upper limit value and set the upper limit value as the zero point. On the other hand, when the detected value is lower than the lower limit value of the predetermined range, the engine ECU 100 may regard the detected value as the lower limit value and set the lower limit value as the zero point. Thereby, the zero point of the differential pressure sensor 116 can be calibrated more appropriately.

[0042] (5) As shown in step S114 of FIG. 3, when it is a specific situation and a detected value that does not exceed the predetermined range is detected by the differential pressure sensor 116, the engine ECU 100 may set the detected value as the zero point. Thereby, the zero point of the differential pressure sensor 116 can be calibrated more appropriately.

[0043] Each embodiment disclosed this time is also planned to be implemented in appropriate combination. And it should be considered that each embodiment disclosed this time is illustrative in all respects and not restrictive. The scope of the present disclosure is shown by the claims rather than the description of the above embodiments, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Signs

[0044] 1 Engine, 10 Engine block, 11 Exhaust gas purification device, 12 Cylinder, 14 Injector, 20 Intake passage, 22 Air cleaner, 24 Intercooler, 26 Throttle valve (Diesel throttle valve), 28 Intake manifold, 30 Turbocharger, 32 Compressor, 34 Turbine, 40 Fuel tank, 41 Feed pump, 42 High-pressure fuel pump, 43, 45 Fuel passages, 44 Common rail, 50 Exhaust manifold, 52 Exhaust passage, 60 EGR passage, 62 EGR cooler, 64 EGR valve, 70 DOC, 72 DPF, 80 Fuel addition valve, 100 ECU, 101 CPU, 102 Memory, 111 Engine speed sensor, 112 Accelerator pedal sensor, 113 Airflow meter, 114 Oxidation catalyst temperature sensor, 115 DPF temperature sensor, 116 Differential pressure sensor.

Claims

1. A control device for an exhaust gas purification device of an internal combustion engine, wherein the exhaust gas purification device includes a filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter contained in exhaust gas, and a sensor for detecting a differential pressure between an inlet and an outlet of the filter, and when the control device calibrates a zero point of the sensor in a state where there is no differential pressure with no exhaust gas flowing in the exhaust passage, if it is not a specific situation in which a measurement error of the sensor is likely to exceed a predetermined range, using a detection value by the sensor as the zero point, while if it is the specific situation and a detection value exceeding the predetermined range is detected by the sensor, calibrating the zero point by regarding the detection value as a value within the predetermined range. A control device.

2. The control device according to claim 1, wherein the specific situation is a situation where the exhaust passage exceeds a predetermined temperature.

3. The control device according to claim 2, wherein the temperature of the exhaust passage is the temperature inside the filter.

4. The control device includes when the detection value exceeds an upper limit value of the predetermined range, regarding the detection value as the upper limit value and using the upper limit value as the zero point, while when the detection value is lower than a lower limit value of the predetermined range, regarding the detection value as the lower limit value and using the lower limit value as the zero point. The control device according to any one of claims 1 to 3.

5. The control device according to claim 4, wherein when it is the specific situation and a detection value not exceeding the predetermined range is detected by the sensor, using the detection value as the zero point.

6. A control method by a control device for an exhaust gas purification device of an internal combustion engine, wherein the exhaust gas purification device includes a filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter contained in exhaust gas, and a sensor for detecting a differential pressure between an inlet and an outlet of the filter, and the control method includes steps in which when the control device calibrates a zero point of the sensor in a state where there is no differential pressure with no exhaust gas flowing in the exhaust passage, if it is not a specific situation in which a measurement error of the sensor is likely to exceed a predetermined range, using a detection value by the sensor as the zero point, and if it is the specific situation and a detection value exceeding the predetermined range is detected by the sensor, calibrating the zero point by regarding the detection value as a value within the predetermined range. A control method.

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