Exhaust system state determination method and exhaust system state determination device

Abstract

When an internal combustion engine (2) mounted in a vehicle is temporarily stopped for a time greater than or equal to a predetermined time while the vehicle is being driven, and the outside air temperature is less than or equal to a predetermined temperature. It is determined that freezing has occurred in either an inlet-side pressure introduction pipe (10) or an outlet-side pressure introduction pipe (11), which is a path through which pressure is introduced into a differential pressure sensor (8) that detects pressure loss in a GPF (5) provided in an exhaust passage (3) of an internal combustion engine (2). As a result, it is possible to accurately determine that the output signal of the differential pressure sensor (8) does not output an accurate value due to freezing during vehicle driving.

Description

Technical Field

[0001] The present invention relates to a method for determining a state of an exhaust system and a device for determining a state of an exhaust system. Background Art

[0002] For example, Patent Document 1 discloses a differential pressure sensor that detects a pressure loss of a gasoline particulate filter provided in an exhaust pipe that introduces exhaust gas from an internal combustion engine.

[0003] In Patent Document 1, with respect to at least one of the upstream piping that transmits the pressure on the upstream side (inlet side) of the gasoline particulate filter to the upstream piping of the differential pressure sensor and the downstream piping that transmits the pressure on the downstream side (outlet side) of the gasoline particulate filter to the downstream piping of the differential pressure sensor, it is determined whether a freezing state (frozen state) in which water freezes inside and can block the pipe occurs.

[0004] In Patent Document 1, when the outside temperature is lower than a preset first threshold value when the ignition switch is turned on, or when the water temperature is lower than a preset second threshold value when the ignition switch is turned on, it is determined that at least one of the upstream piping and the downstream piping is in a frozen state.

[0005] However, Patent Document 1 does not consider refreezing after the frozen state is resolved during driving of the vehicle.

[0006] Therefore, in Patent Document 1, if the frozen state is temporarily determined, it is difficult to determine the frozen state again when the frozen state is eliminated. That is, Patent Document 1 does not envision the situation where the frozen state becomes frozen again after the frozen state is eliminated, and there is room for further improvement in the aspect of accurately determining the frozen state.

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-143595 Summary of the invention

[0008] Regarding the exhaust system of the present invention, when an internal combustion engine mounted on a vehicle is temporarily stopped for a time greater than or equal to a specified time during driving of the vehicle and the outside temperature is less than or equal to a specified temperature, it is determined that ice has occurred in a differential pressure sensor that detects pressure loss of an exhaust gas particulate filter provided in an exhaust passage of the above-mentioned internal combustion engine or in a path that introduces pressure to the differential pressure sensor.

[0009] According to the present invention, during vehicle driving, it is possible to determine with high accuracy that the output signal of the differential pressure sensor does not output an accurate value due to freezing. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is an explanatory diagram schematically showing the outline of an exhaust system to which the present invention is applied.

[0011] Figure 2 This is a timing chart showing the situation of freezing determination.

[0012] Figure 3 This is a flowchart showing the flow of freezing determination. DETAILED DESCRIPTION

[0013] Hereinafter, one embodiment of the present invention will be described in detail based on the drawings. Figure 1 It is an explanatory diagram schematically showing the outline of an exhaust system 1 to which the present invention is applied.

[0014] The exhaust system 1 is mounted on a vehicle and includes an internal combustion engine 2, an exhaust passage 3, a manifold catalyst 4, a GPF 5 (Gasoline Particulate Filter), an underfloor catalyst 6, a muffler 7, a differential pressure sensor 8 for detecting a pressure loss in the GPF 5, and a control unit 9 capable of performing a freezing diagnosis described later.

[0015] The internal combustion engine 2 is a spark ignition type internal combustion engine that uses gasoline as fuel, and is mounted on a vehicle such as an automobile.

[0016] Here, the vehicle equipped with the internal combustion engine 2 is specifically an idle stop vehicle capable of idling stop based on the idle stop control or a hybrid vehicle capable of EV driving in which the internal combustion engine 2 is stopped. That is, the vehicle equipped with the internal combustion engine 2 is a vehicle capable of temporarily stopping the internal combustion engine 2 during driving of the vehicle.

[0017] The idle stop control, for example, stops fuel supply to automatically stop the internal combustion engine 2 if a predetermined automatic stop condition is satisfied, and restarts fuel supply to restart the internal combustion engine 2 if a predetermined automatic restart condition is satisfied during the automatic stop.

[0018] The predetermined automatic stop condition includes, for example, the vehicle speed being less than or equal to a predetermined value, the accelerator opening being less than or equal to a predetermined value, etc. The predetermined automatic restart condition includes, for example, the accelerator opening being greater than a predetermined value, the brake pedal not being depressed, etc.

[0019] A hybrid vehicle is a structure that can achieve EV driving by using only a driving motor (not shown) as a driving source to drive the drive wheels. It can also be a so-called series hybrid vehicle that does not use an internal combustion engine 2 as the power of the vehicle, or a so-called parallel hybrid vehicle that can use an internal combustion engine 2 as the power of the vehicle.

[0020] The manifold catalyst 4 purifies exhaust gas and is composed of, for example, a three-way catalyst. The manifold catalyst 4 is arranged close to a combustion chamber (not shown) of the internal combustion engine 2, for example, just downstream of a converging portion of an exhaust manifold (not shown).

[0021] The GPF 5 and the underfloor catalyst 6 are disposed under the floor of the vehicle interior space separated from the combustion chamber (not shown) of the internal combustion engine 2. That is, the GPF 5 and the underfloor catalyst 6 are disposed separated from the engine room of the vehicle.

[0022] The GPF 5 corresponds to an exhaust particulate filter and collects PM, which is exhaust particulate matter in the exhaust gas. The GPF 5 is arranged on the downstream side of the manifold catalyst 4 .

[0023] The underfloor catalyst 6 purifies exhaust gas and is composed of, for example, a three-way catalyst. The underfloor catalyst 6 is disposed adjacent to the GPF 5 on the downstream side of the GPF 5 .

[0024] The muffler 7 reduces exhaust noise and is disposed on the downstream side of the underfloor catalyst 6 .

[0025] The differential pressure sensor 8 can detect the pressure difference between the exhaust pressure at the inlet of the GPF 5 and the exhaust pressure at the outlet of the GPF 5. The exhaust pressure at the inlet of the GPF 5 is introduced into the differential pressure sensor 8 via the inlet side pressure introduction pipe 10. The exhaust pressure at the outlet of the GPF 5 is introduced into the differential pressure sensor 8 via the outlet side pressure introduction pipe 11. The inlet side pressure introduction pipe 10 and the outlet side pressure introduction pipe 11 correspond to the path for introducing the pressure into the differential pressure sensor 8.

[0026] The control unit 9 is a well-known electronic computer having a CPU, a ROM, a RAM, and an input / output interface. Detection signals (output signals) of various sensors such as the differential pressure sensor 8, the crank angle sensor 12, and a sensor capable of detecting the air-fuel ratio of the internal combustion engine 2 are input to the control unit 9. The crank angle sensor 12 detects the crank angle of the crankshaft of the internal combustion engine 2 and can detect the engine speed of the internal combustion engine 2.

[0027] The control unit 9 can calculate the accumulation amount of exhaust particulates trapped by the GPF 5. Specifically, the control unit 9 compares the first accumulation amount calculated using the output signal of the differential pressure sensor 8 and the second accumulation amount calculated based on the operating state of the internal combustion engine 2, and sets the larger value as the accumulation amount of exhaust particulates accumulated on the GPF 5. Here, the first accumulation amount is the accumulation amount calculated based on the pressure loss of the GPF 5. The second accumulation amount is, for example, the accumulation amount calculated based on a physical model using the air-fuel ratio of the internal combustion engine 2, the history of the internal combustion engine speed, etc.

[0028] In addition, the control unit 9 can control the internal combustion engine 2 and perform various diagnoses.

[0029] The exhaust gas (combusted gas) flowing in the exhaust passage 3 contains moisture. Therefore, the differential pressure sensor 8, the inlet pressure introduction pipe 10, and the outlet pressure introduction pipe 11 are in an environment where moisture exists. Therefore, in an extremely low temperature state where the outside temperature is below freezing, the differential pressure sensor 8, the inlet pressure introduction pipe 10, and the outlet pressure introduction pipe 11, which are the paths for introducing pressure into the differential pressure sensor 8, may freeze. For example, if any one of the differential pressure sensor 8, the inlet pressure introduction pipe 10, and the outlet pressure introduction pipe 11 freezes, even if the differential pressure sensor 8 does not fail, the output signal from the differential pressure sensor 8 may not become the value indicating the differential pressure at that time, and various controls and various diagnoses using the output signal of the differential pressure sensor 8 may cause malfunctions. That is, if the differential pressure sensor 8 and the path for introducing pressure into the differential pressure sensor 8 freeze, even if the differential pressure sensor 8 does not fail, the output signal from the differential pressure sensor 8 may deviate from the original value (true value) that should be output at that time, and various controls and various diagnoses using the output signal of the differential pressure sensor 8 may cause malfunctions.

[0030] If freezing of the differential pressure sensor 8 and the path for introducing pressure to the differential pressure sensor 8 can be determined with high accuracy, malfunctions and misdiagnosis of various controls and diagnoses using the output signal of the differential pressure sensor 8 can be suppressed.

[0031] As various controls using the output signal of the differential pressure sensor 8, there is, for example, a GPF 5 regeneration control based on the amount of exhaust particulate matter deposited in the GPF 5. The output signal of the GPF 5 becomes a value deviated from the true value due to freezing. For example, if the first accumulation amount is calculated as a value greater than the actual value, the GPF 5 regeneration control may not be properly performed, resulting in the deterioration of the GPF 5.

[0032] As various diagnoses using the output signal of the differential pressure sensor 8, for example, there are diagnoses of faults of the differential pressure sensor 8 itself and diagnoses of whether the GPF 5 is installed in the exhaust passage 3 or removed from the exhaust passage 3. If the output signal of the GPF 5 becomes a value deviating from the true value due to freezing, it is possible that the fault diagnosis mistakenly determines that the GPF 5 is faulty. In addition, if the output signal of the GPF 5 becomes a value deviating from the true value due to freezing, it is possible that the GPF 5 is determined to be removed from the exhaust passage 3 even when the GPF 5 is installed in the exhaust passage 3.

[0033] Therefore, in the present invention, freezing judgment of the differential pressure sensor 8 and the path for introducing pressure into the differential pressure sensor 8 is performed with high precision, so that when the output of the differential pressure sensor 8 is abnormal due to freezing, various controls and diagnoses using the output signal of the differential pressure sensor 8 are stopped, thereby avoiding malfunction and misdiagnosis.

[0034] The freezing determination is performed by the control unit 9 as a determination unit. When the internal combustion engine 2 is temporarily stopped for a time period greater than or equal to a prescribed time during driving of the vehicle, and the outside temperature during the period is less than or equal to a prescribed temperature, the control unit 9 determines that any one of the differential pressure sensor 8, the inlet pressure introduction pipe 10, and the outlet pressure introduction pipe 11 is frozen. The above-mentioned prescribed temperature is, for example, 0°C. When any one of the differential pressure sensor 8, the inlet pressure introduction pipe 10, and the outlet pressure introduction pipe 11 is frozen, the control unit 9 determines that the output signal of the differential pressure sensor 8 deviates from the true value, and stops various controls and various diagnoses using the output signal of the differential pressure sensor 8.

[0035] The outside air temperature can be estimated based on, for example, a detection signal of an air flow meter (not shown). Alternatively, a temperature sensor for detecting the outside air temperature may be separately provided and the outside air temperature may be obtained from the temperature sensor.

[0036] Figure 2 It is a timing diagram showing the situation of freezing judgment when the outside air temperature is constant at a temperature less than or equal to the above-mentioned specified temperature. Time t1 is the timing when the internal combustion engine speed of the internal combustion engine 2 becomes "0" (zero) and the internal combustion engine 2 stops during driving of the vehicle. Time t1 is the timing when the refreeze counter of the refreeze judgment timer starts counting (incrementing). That is, the refreeze counter of the refreeze judgment timer starts to increase from time t1. Time t2 is the timing when the value of the refreeze counter reaches the specified refreeze threshold value, and is the timing when it is determined that freezing has occurred in the freezing judgment. The refreeze judgment timer measures the time when the internal combustion engine 2 is temporarily stopped. The value of the refreeze counter substantially represents the elapsed time.

[0037] Here, the refreezing threshold value can be changed according to the outside temperature. Specifically, the refreezing threshold value can be changed so that it becomes smaller as the outside temperature is lower. That is, the time from the time t1 when the internal combustion engine 2 stops to the time t2 when the value of the refreezing counter reaches the prescribed maximum freezing threshold value can be changed so that the lower the outside temperature is, the shorter the time is. The refreezing determination timer is one of the functions of the control unit 9.

[0038] With regard to the exhaust system 1 of this embodiment, it is possible to accurately determine that the output signal of the differential pressure sensor 8 does not output an accurate value due to freezing during vehicle driving. That is, the present invention can accurately determine that at least one of the differential pressure sensor 8 and the path for introducing pressure into the differential pressure sensor 8 is frozen.

[0039] Figure 3 1 is a flowchart showing the flow of freezing determination of the exhaust system 1 according to the above-mentioned embodiment.

[0040] In step S1, it is determined whether or not ice has not occurred in the differential pressure sensor 8 and the path for introducing pressure into the differential pressure sensor 8. If it is determined in step S1 that ice has not occurred, the process proceeds to step S2. If it is determined in step S1 that ice has occurred, the process ends. In addition, when the vehicle is started by key-on, if the outside temperature is less than or equal to the above-mentioned predetermined temperature, it is determined that ice has occurred in the differential pressure sensor 8 and the path for introducing pressure into the differential pressure sensor 8.

[0041] In step S2, it is determined whether the outside temperature is higher than the predetermined temperature. If it is determined in step S2 that the outside temperature is higher than the predetermined temperature, the process proceeds to step S3. If it is determined in step S2 that the outside temperature is lower than or equal to the predetermined temperature, the process proceeds to step S4.

[0042] In step S3 , it is determined that refreezing has not occurred in the differential pressure sensor 8 and the path for introducing pressure into the differential pressure sensor 8 .

[0043] In step S4, it is determined whether the internal combustion engine 2 is in operation (rotating). If it is determined in step S4 that the internal combustion engine 2 is in operation (rotating), the process proceeds to step S3. If it is determined in step S4 that the internal combustion engine 2 is stopped (the engine speed is zero), the process proceeds to step S5.

[0044] In step S5, the refreezing counter of the refreezing determination timer is incremented.

[0045] In step S6, it is determined whether the refreezing counter of the refreezing determination timer is less than the refreezing threshold value. If it is determined in step S6 that the refreezing counter of the refreezing determination timer is less than the refreezing threshold value, the process proceeds to step S3. If it is determined in step S6 that the refreezing counter of the refreezing determination timer has reached the refreezing threshold value, the process proceeds to step S7.

[0046] In step S7 , it is determined that refreezing has occurred in the differential pressure sensor 8 and the path for introducing pressure into the differential pressure sensor 8 , and the refreezing counter of the refreezing determination timer is reset.

[0047] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention.

[0048] For example, the internal combustion engine 2 may be a diesel internal combustion engine. In addition, the exhaust gas particulate filter is not limited to the GPF 5, and may be, for example, a DPF (Diesel Particulate Filter).

[0049] The above-mentioned embodiments relate to a method for determining a state of the exhaust system 1 and a device for determining a state of the exhaust system 1 .

Claims

1. A method for determining the state of an exhaust system, wherein: When an internal combustion engine mounted on a vehicle is temporarily stopped for a time period greater than or equal to a specified time while the vehicle is being driven and the outside temperature is less than or equal to a specified temperature, it is determined that ice has occurred in a differential pressure sensor that detects a pressure loss of an exhaust gas particulate filter provided in an exhaust passage of the internal combustion engine or in a path that introduces pressure to the differential pressure sensor.

2. The exhaust system state determination method according to claim 1, wherein: A timer is provided for measuring the time during which the internal combustion engine is temporarily stopped. The timer measures the time during which the internal combustion engine is temporarily stopped.

3. The exhaust system state determination method according to claim 1, wherein: The temporary stop of the internal combustion engine is referred to as idling stop.

4. The exhaust system state determination method according to claim 1, wherein: The vehicle is a hybrid vehicle capable of autonomous EV driving with the internal combustion engine stopped. The temporary stop of the internal combustion engine is performed during EV driving.

5. The exhaust system state determination method according to claim 1, wherein: The above specified time will change according to the outside temperature.

6. The exhaust system state determination method according to any one of claims 1 to 5, wherein: a first accumulation amount calculated using the output signal of the differential pressure sensor and a second accumulation amount calculated based on the operating state of the internal combustion engine, and the larger value is set as the accumulation amount of exhaust gas particulates accumulated on the exhaust gas particulate filter; When it is determined that freezing has occurred in the differential pressure sensor or in a path for introducing pressure to the differential pressure sensor, calculation of the first accumulation amount is interrupted and the second accumulation amount is set as an accumulation amount of exhaust gas particulates accumulated on the exhaust particulate filter.

7. A device for determining the state of an exhaust system, wherein: The exhaust system state determination device comprises: An exhaust gas particulate filter provided in an exhaust passage of an internal combustion engine mounted on a vehicle; a differential pressure sensor for detecting a pressure loss of the exhaust gas particulate filter; and A determination unit determines that ice has occurred in the differential pressure sensor or a path for introducing pressure to the differential pressure sensor when the internal combustion engine is temporarily stopped for a time period greater than or equal to a predetermined time during driving of the vehicle and the outside temperature is less than or equal to a predetermined temperature.

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