Exhaust system state determination method and exhaust system state determination device

Abstract

When an internal combustion engine (2) mounted in a vehicle temporarily stops for a prescribed time or longer during an operation of the vehicle and the outside temperature is less than or equal to a prescribed temperature, it is determined that icing has occurred on one of a differential pressure sensor (8) that detects a pressure loss of a GPF (5) provided in an exhaust path (3) of the internal combustion engine (2), an inlet-side pressure introduction pipe (10), and an outlet-side pressure introduction pipe (11), the pressure introduction pipes being paths for introducing a pressure into the differential pressure sensor (8). Thus, a failure of the differential pressure sensor (8) to output an output signal of a correct value due to icing during the operation of the vehicle can be determined with high accuracy.

Description

[Technical Field]

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

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

[0003] In Patent Document 1, it is determined whether or not a frozen state (icy state) has occurred in at least one of the upstream piping that transmits the pressure on the upstream side (inlet side) of the gasoline particulate filter to 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 differential pressure sensor, in which water freezes inside and the piping may become blocked.

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

[0005] However, in Patent Document 1, no consideration is given to refreezing after the frozen state is cleared while the vehicle is in operation.

[0006] Therefore, in Patent Document 1, once a frozen state is determined, it becomes difficult to determine the frozen state again when the frozen state is unfrozen. In other words, Patent Document 1 does not anticipate a situation in which the frozen state reoccurs after being unfrozen, and there is room for further improvement in accurately determining the frozen state. [Prior art documents] [Patent documents]

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

[0008] The exhaust system of the present invention determines that icing has occurred in a differential pressure sensor that detects pressure loss in an exhaust particulate filter provided in the exhaust passage of the internal combustion engine or in a path that introduces pressure to the differential pressure sensor when the internal combustion engine mounted on the vehicle is temporarily stopped for a predetermined period of time or longer while the vehicle is in operation and the outside air temperature is below a predetermined temperature.

[0009] According to the present invention, it is possible to accurately determine when the output signal of the differential pressure sensor is not outputting a correct value due to icing while the vehicle is in operation. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram schematically illustrating an exhaust system to which the present invention is applied; [Figure 2] 10 is a timing chart showing the freezing determination process. [Figure 3] 10 is a flowchart showing a procedure for determining whether freezing has occurred. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will now be described in detail with reference to the drawings. Figure 1 is an explanatory diagram that schematically shows an exhaust system 1 to which the present invention is applied.

[0012] 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 (Gasoline Particulate Filter) 5, an underfloor catalyst 6, a muffler 7, a differential pressure sensor 8 that detects pressure loss in the GPF 5, and a control unit 9 that can perform icing diagnosis, which will be described later.

[0013] The internal combustion engine 2 is a spark-ignition internal combustion engine that uses gasoline as fuel and is mounted on a vehicle such as an automobile.

[0014] Here, the vehicle equipped with the internal combustion engine 2 is specifically an idle stop vehicle capable of idling stop by idle stop control or a hybrid vehicle capable of EV running, which runs autonomously with the internal combustion engine 2 stopped. In other words, the vehicle equipped with the internal combustion engine 2 is a vehicle in which the internal combustion engine 2 can be temporarily stopped while the vehicle is being driven.

[0015] The idle stop control, for example, stops fuel supply and automatically stops the internal combustion engine 2 when predetermined automatic stop conditions are met, and resumes fuel supply and restarts the internal combustion engine 2 when predetermined automatic restart conditions are met during the automatic stop.

[0016] The predetermined automatic stop condition is, for example, that the vehicle speed is equal to or less than a predetermined value, that the accelerator pedal stroke is equal to or less than a predetermined value, etc. The predetermined automatic restart condition is, for example, that the accelerator pedal stroke is greater than a predetermined value, that the brake pedal is not depressed, etc.

[0017] The hybrid vehicle is capable of EV running, in which the drive wheels are driven only by a drive motor (not shown), and may be a so-called series hybrid vehicle that does not use the internal combustion engine 2 as a power source for the vehicle, or a so-called parallel hybrid vehicle that can use the internal combustion engine 2 as a power source for the vehicle.

[0018] The manifold catalyst 4 purifies the exhaust gas and is made of, for example, a three-way catalyst. The manifold catalyst 4 is disposed relatively close to the combustion chamber (not shown) of the internal combustion engine 2, for example, immediately downstream of the collecting portion of the exhaust manifold (not shown).

[0019] The GPF 5 and the underfloor catalyst 6 are disposed under the floor of the passenger compartment of the vehicle away from a combustion chamber (not shown) of the internal combustion engine 2. In other words, the GPF 5 and the underfloor catalyst 6 are disposed away from the engine compartment of the vehicle.

[0020] The GPF 5 corresponds to an exhaust particulate filter and traps PM, which is particulate matter in the exhaust gas. The GPF 5 is disposed downstream of the manifold catalyst 4.

[0021] The underfloor catalyst 6 purifies exhaust gas and is made up 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.

[0022] The muffler 7 reduces exhaust noise and is disposed downstream of the underfloor catalyst 6.

[0023] The differential pressure sensor 8 is capable of detecting 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 to the differential pressure sensor 8 via an inlet pressure introduction pipe 10. The exhaust pressure at the outlet of the GPF 5 is introduced to the differential pressure sensor 8 via an outlet pressure introduction pipe 11. The inlet pressure introduction pipe 10 and the outlet pressure introduction pipe 11 correspond to paths for introducing pressure to the differential pressure sensor 8.

[0024] The control unit 9 is a well-known digital computer equipped with a CPU, ROM, 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 is capable of detecting the engine speed of the internal combustion engine 2.

[0025] The control unit 9 is capable of calculating the deposition amount of exhaust particulates trapped in the GPF 5. More specifically, the control unit 9 compares a first deposition amount calculated using the output signal of the differential pressure sensor 8 with a second deposition amount calculated from the operating state of the internal combustion engine 2, and determines the larger value as the deposition amount of exhaust particulates deposited in the GPF 5. Here, the first deposition amount is a deposition amount calculated based on the pressure loss of the GPF 5. The second deposition amount is a deposition amount calculated based on a physical model that uses, for example, the air-fuel ratio of the internal combustion engine 2, the history of the engine speed, etc.

[0026] The control unit 9 controls the internal combustion engine 2 and is also capable of carrying out various diagnoses.

[0027] The exhaust gas (burned gas) flowing through 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 is present. Therefore, in extremely low temperature conditions where the outside air temperature is below freezing, there is a risk that the differential pressure sensor 8 and the inlet pressure introduction pipe 10 and the outlet pressure introduction pipe 11, which are paths for introducing pressure to the differential pressure sensor 8, will freeze. For example, if any 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 is not malfunctioning, the output signal from the differential pressure sensor 8 will not be a value that represents the differential pressure at that time, which may cause problems with various controls and diagnoses that use the output signal from the differential pressure sensor 8. In other words, if the differential pressure sensor 8 or the path that introduces pressure to the differential pressure sensor 8 freezes, even if there is no malfunction in the differential pressure sensor 8, the output signal from the differential pressure sensor 8 will deviate from the original value (true value) that should be output at that time, which may cause problems in various controls and diagnoses that use the output signal of the differential pressure sensor 8.

[0028] If freezing of the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8 can be accurately determined, malfunctions and erroneous diagnoses in various controls and diagnoses that use the output signal of the differential pressure sensor 8 can be suppressed.

[0029] An example of various controls that utilize the output signal of the differential pressure sensor 8 is GPF 5 regeneration control, which is performed based on the amount of exhaust particulate matter accumulated in the GPF 5. If the output signal of the GPF 5 deviates from the true value due to freezing, and for example, the first accumulated amount described above is calculated as a value larger than the actual value, the GPF 5 regeneration control may not be performed appropriately, which may cause deterioration of the GPF 5.

[0030] Various diagnoses that utilize the output signal of the differential pressure sensor 8 include, for example, a fault diagnosis of the differential pressure sensor 8 itself and a diagnosis of whether the GPF 5 is attached to or removed from the exhaust passage 3. If the output signal of the GPF 5 deviates from the true value due to icing, the fault diagnosis may erroneously determine that the GPF 5 is faulty. Furthermore, if the output signal of the GPF 5 deviates from the true value due to icing, the fault diagnosis may erroneously determine that the GPF 5 is removed from the exhaust passage 3, even if the GPF 5 is attached to the exhaust passage 3.

[0031] Therefore, in the present invention, freezing detection is performed accurately to determine whether the differential pressure sensor 8 and the path that introduces pressure to the differential pressure sensor 8 have frozen, and when the output of the differential pressure sensor 8 becomes abnormal due to freezing, various controls and diagnoses that use the output signal of the differential pressure sensor 8 are stopped, thereby avoiding malfunctions and erroneous diagnoses.

[0032] The determination of icing is performed by the control unit 9, which serves as a determination section. If the internal combustion engine 2 is temporarily stopped for a predetermined period of time or longer while the vehicle is in operation and the outside air temperature during that time is equal to or lower than a predetermined temperature, the control unit 9 determines that any of the differential pressure sensor 8, the inlet pressure introducing pipe 10, and the outlet pressure introducing pipe 11 is frozen. The predetermined temperature is, for example, 0°C. If any of the differential pressure sensor 8, the inlet pressure introducing pipe 10, and the outlet pressure introducing pipe 11 is frozen, the control unit 9 determines that the output signal of the differential pressure sensor 8 has deviated from the true value, and stops various controls and diagnoses that use the output signal of the differential pressure sensor 8.

[0033] The outside air temperature can be estimated from a detection signal of an air flow meter (not shown), for example. Alternatively, the outside air temperature may be obtained from a separate temperature sensor that detects the outside air temperature.

[0034] FIG. 2 is a timing chart showing the state of icing determination when the outside air temperature is constant at or below the above-mentioned predetermined temperature. Time t1 is the timing when the engine speed of the internal combustion engine 2 becomes "0" (zero) while the vehicle is in operation and the internal combustion engine 2 stops. Time t1 is the timing when the re-icing counter of the re-icing determination timer starts to count up (increment). In other words, the re-icing counter of the re-icing determination timer increases from time t1. Time t2 is the timing when the value of the re-icing counter reaches a predetermined re-icing threshold, and the timing when it is determined that icing has occurred in the icing determination. The re-icing determination timer measures the time during which the internal combustion engine 2 is temporarily stopped. The value of the re-icing counter essentially represents the elapsed time.

[0035] Here, the re-freezing threshold may be changed according to the outside air temperature. Specifically, the re-freezing threshold may be changed so that it decreases as the outside air temperature decreases. In other words, the time from time t1 when the internal combustion engine 2 is stopped to time t2 when the value of the re-freezing counter reaches a predetermined maximum re-freezing threshold may be changed so that it decreases as the outside air temperature decreases. The re-freezing determination timer is one of the functions of the control unit 9.

[0036] In the exhaust system 1 of this embodiment, it is possible to accurately determine when the output signal from the differential pressure sensor 8 is not outputting a correct value due to icing while the vehicle is in operation. In other words, the present invention can accurately determine when at least one of the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8 is frozen.

[0037] FIG. 3 is a flowchart showing the flow of the icing determination in the exhaust system 1 of the above-described embodiment.

[0038] In step S1, it is determined whether or not there is freezing in the differential pressure sensor 8 and the path that introduces pressure to the differential pressure sensor 8. If it is determined in step S1 that there is no freezing, the routine proceeds to step S2. If it is determined in step S1 that there is freezing, the current routine ends. Note that when the vehicle is started with the key turned on, if the outside air temperature is equal to or lower than the predetermined temperature, it is determined that there is freezing in the differential pressure sensor 8 and the path that introduces pressure to the differential pressure sensor 8.

[0039] In step S2, it is determined whether the outside air temperature is higher than the predetermined temperature. If it is determined in step S2 that the outside air temperature is higher than the predetermined temperature, the process proceeds to step S3. If it is determined in step S2 that the outside air temperature is equal to or lower than the predetermined temperature, the process proceeds to step S4.

[0040] In step S3, it is determined that there is no refreezing in the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8.

[0041] In step S4, it is determined whether the internal combustion engine 2 is operating (rotating). If it is determined in step S4 that the internal combustion engine 2 is operating (rotating), the process proceeds to step S3. If it is determined in step S4 that the internal combustion engine 2 is stopped (engine speed is zero), the process proceeds to step S5.

[0042] In step S5, the refreezing counter in the refreezing determination timer is incremented.

[0043] In step S6, it is determined whether the refreezing counter in the refreezing determination timer is less than the refreezing threshold value. If it is determined in step S6 that the refreezing counter in 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 in the refreezing determination timer has reached the refreezing threshold value, the process proceeds to step S7.

[0044] In step S7, it is determined that the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8 have re-frozen, and the re-freezing counter in the re-freezing determination timer is reset.

[0045] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0046] For example, the internal combustion engine 2 may be a diesel engine. Furthermore, the exhaust particulate filter is not limited to the GPF 5, and may be, for example, a DPF (Diesel Particulate Filter).

[0047] The above-described embodiment relates to a method for determining the state of the exhaust system 1 and a device for determining the state of the exhaust system 1.

Claims

1. A method for determining a state of an exhaust system, which determines that icing has occurred in a differential pressure sensor that detects a pressure loss in an exhaust particulate filter provided in an exhaust passage of an internal combustion engine or in a path that introduces pressure to the differential pressure sensor, when an internal combustion engine mounted on a vehicle is temporarily stopped for a predetermined period of time or more while the vehicle is in operation and the outside air temperature is equal to or lower than a predetermined temperature, a first accumulation amount calculated using the output signal of the differential pressure sensor and a second accumulation amount calculated from the operating state of the internal combustion engine are compared, and the larger value is determined to be the accumulation amount of exhaust particulates accumulated in the exhaust particulate filter; A method for determining the state of an exhaust system, in which, when it is determined that freezing has occurred in the differential pressure sensor or the path that introduces pressure to the differential pressure sensor, calculation of the first accumulation amount is interrupted and the second accumulation amount is set to the accumulation amount of exhaust particulates accumulated in the exhaust particulate filter.

2. a timer that measures the time during which the internal combustion engine is temporarily stopped, 2. The exhaust system state determination method according to claim 1, wherein the timer measures the time during which the internal combustion engine is temporarily stopped.

3. 2. The exhaust system state determination method according to claim 1, wherein the temporary suspension of the internal combustion engine is an idle stop.

4. The vehicle is a hybrid vehicle capable of EV driving, which runs autonomously with the internal combustion engine stopped, The exhaust system state determination method according to claim 1, wherein the internal combustion engine is temporarily stopped during EV driving.

5. 2. The exhaust system state determination method according to claim 1, wherein the predetermined time is changed depending on the outside air temperature.

6. an exhaust 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 particulate filter; a determination unit that determines that icing has occurred in the differential pressure sensor or in a path that introduces pressure to the differential pressure sensor when the internal combustion engine is temporarily stopped for a predetermined period of time or more during operation of the vehicle and the outside air temperature is equal to or lower than a predetermined temperature, a first accumulation amount calculated using the output signal of the differential pressure sensor and a second accumulation amount calculated from the operating state of the internal combustion engine are compared, and the larger value is determined to be the accumulation amount of exhaust particulates accumulated in the exhaust particulate filter; When it is determined that freezing has occurred in the differential pressure sensor or the path that introduces pressure to the differential pressure sensor, the calculation of the first accumulation amount is interrupted and the second accumulation amount is set to the accumulation amount of exhaust particulate matter accumulated in the exhaust particulate filter.

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