Method and apparatus for determining the state of an exhaust system

Abstract

A control unit (9) determines whether icing has occurred in a pressure differential sensor (8) that detects pressure loss of a GPF (5), or in an inlet-side pressure introduction pipe (10) or an outlet-side pressure introduction pipe (11) that are passages through which pressure is introduced to the pressure differential sensor (8). Upon determining that icing has occurred, the control unit (9) sets the count value of an icing cancelation counter to a prescribed initial value, and increases or decreases the count value of the icing cancelation counter from the initial value on the basis of the operating condition of an internal combustion engine (2), and when the count value of the icing cancelation counter reaches a prescribed threshold value for canceling the icing determination, determines that the icing that had occurred in the pressure differential sensor (8), the inlet-side pressure introduction pipe (10), or the outlet-side pressure introduction pipe (11) has melted. The count value of the icing cancelation counter decreases while the internal combustion engine (2) is temporarily stopped, and increases while the internal combustion engine (2) is operating.

Description

Technical Field

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

Background Art

[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 of an internal combustion engine is introduced.

[0003] In Patent Document 1, at least one of an upstream pipe that transmits the pressure on the upstream side (inlet side) of the gasoline particulate filter to the differential pressure sensor and a downstream pipe that transmits the pressure on the downstream side (outlet side) of the gasoline particulate filter to the differential pressure sensor determines whether a freezing state (ice freezing state) in which moisture freezes inside and the pipe is blocked has occurred.

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

[0005] However, in this Patent Document 1, no consideration is given to refreezing after the freezing state is resolved during vehicle operation.

[0006] Therefore, in Patent Document 1, once the freezing state is determined, it becomes difficult to determine the freezing state again when the freezing state is resolved. That is, Patent Document 1 does not assume a scene where it refreezes after the freezing state is resolved, and there is room for further improvement in accurately determining the freezing state.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-143595 [Overview of the project]

[0008] The exhaust system of the present invention determines whether or not ice has formed in a differential pressure sensor that detects the pressure loss of an exhaust particulate filter installed in the exhaust passage of the internal combustion engine, or in the path that introduces pressure to the differential pressure sensor, based on the stopped state of the internal combustion engine installed in the vehicle. If it is determined that ice has formed, the count value of a predetermined release counter is set to a predetermined initial value, and the count value of the release counter is increased or decreased from the initial value based on the operating state of the internal combustion engine. When the count value of the release counter reaches a predetermined threshold, it is determined that the ice that had formed in the differential pressure sensor or in the path that introduces pressure to the differential pressure sensor has melted. Furthermore, the direction of increase or decrease of the count value of the release counter is reversed when the vehicle is running and the internal combustion engine is temporarily stopped compared to when it is running, in which case the vehicle is determined that ice has formed.

[0009] According to the present invention, it is possible to accurately determine the melting of ice that has formed in the differential pressure sensor and the path through which pressure is introduced to the differential pressure sensor while the vehicle is in operation. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram illustrating the general outline of an exhaust system to which the present invention is applied. [Figure 2] A timing chart showing the process of determining whether the ice has formed. [Figure 3] A flowchart showing the process for determining whether something is frozen. [Modes for carrying out the invention]

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 is a schematic diagram illustrating the general outline of 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 5 (Gasoline Particulate Filter), an underbody catalyst 6, a muffler 7, a differential pressure sensor 8 for detecting pressure loss of the GPF 5, and a control unit 9 capable of performing ice formation 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 installed in vehicles such as automobiles.

[0014] Here, the vehicle equipped with the internal combustion engine 2 is specifically an idle-stop vehicle capable of idle-stop control, or a hybrid vehicle capable of EV driving, which is autonomous driving with the internal combustion engine 2 stopped. In other words, the vehicle equipped with the internal combustion engine 2 is a vehicle that can temporarily stop the internal combustion engine 2 while the vehicle is in operation.

[0015] Idle stop control, for example, stops the fuel supply and automatically stops the internal combustion engine 2 when predetermined automatic stop conditions are met, and restarts the 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 conditions are, for example, when the vehicle speed is below a predetermined value, when the accelerator pedal opening is below a predetermined value, etc. The predetermined automatic restart conditions are, for example, when the accelerator pedal opening is greater than a predetermined value, when the brake pedal is not pressed, etc.

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

[0018] The manifold catalyst 4 is for purifying exhaust gas and, for example, consists of 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 converging section of an exhaust manifold (not shown).

[0019] The GPF 5 and the underfloor catalyst 6 are disposed under the floor of the passenger compartment space of the vehicle, which is far from the combustion chamber (not shown) of the internal combustion engine 2. That is, the GPF 5 and the underfloor catalyst 6 are disposed away from the engine room of the vehicle.

[0020] The GPF 5 corresponds to a diesel particulate filter and collects 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 is for purifying exhaust gas and, for example, consists of a three-way catalyst. The underfloor catalyst 6 is disposed downstream of the GPF 5 and adjacent to the GPF 5.

[0022] [[ID=]15] 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 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 paths for introducing pressure into 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) from various sensors such as a differential pressure sensor 8, a 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 can calculate the deposition amount of the exhaust particles collected by the GPF 5. Specifically, the control unit 9 compares the first deposition amount calculated using the output signal of the differential pressure sensor 8 with the second deposition amount calculated from the operating state of the internal combustion engine 2, and sets the larger value as the deposition amount of the exhaust particles deposited on the GPF 5. Here, the first deposition amount is the deposition amount calculated based on the pressure loss of the GPF 5. The second deposition amount is, for example, the deposition amount calculated based on a physical model using the history of the air-fuel ratio and engine speed of the internal combustion engine 2.

[0026] In addition, the control unit 9 can control the internal combustion engine 2 and perform various diagnoses.

[0027] The exhaust gas (combusted 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. Consequently, in extremely low temperature conditions where the outside temperature is below freezing, there is a risk that the differential pressure sensor 8, or the inlet pressure introduction pipe 10 and the outlet pressure introduction pipe 11, which are the paths through which pressure is introduced to the differential pressure sensor 8, may freeze. For example, if any of the differential pressure sensor 8, the inlet pressure introduction pipe 10, or 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 represent the differential pressure at that time, which may cause problems with various controls and diagnostics that utilize the output signal of the differential pressure sensor 8. In other words, if the differential pressure sensor 8 or the path through which pressure is introduced to the differential pressure sensor 8 freezes, even if the differential pressure sensor 8 is not faulty, 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 with various controls and diagnostics that utilize the output signal of the differential pressure sensor 8.

[0028] If the 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 misdiagnoses of various controls and diagnostics that utilize the output signal of the differential pressure sensor 8 can be suppressed.

[0029] One example of control using the output signal of the differential pressure sensor 8 is GPF5 regeneration control, which is performed based on the amount of exhaust particulate matter accumulated in GPF5. If the output signal of GPF5 deviates from the true value due to freezing, and for example the first accumulation amount mentioned above is calculated as a larger value than the actual value, GPF5 regeneration control may not be performed properly, which could lead to deterioration of GPF5.

[0030] Various diagnostics using the output signal of the differential pressure sensor 8 include, for example, fault diagnosis of the differential pressure sensor 8 itself, and 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 freezing, there is a risk that the fault diagnosis may incorrectly determine that the GPF 5 is faulty. Also, if the output signal of the GPF 5 deviates from the true value due to freezing, there is a risk that the GPF 5 may be incorrectly determined to be removed from the exhaust passage 3, even if it is actually attached to the exhaust passage 3.

[0031] Therefore, in this invention, the freezing of the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8 is accurately determined, and when the output of the differential pressure sensor 8 becomes abnormal due to freezing, various controls and diagnoses using the output signal of the differential pressure sensor 8 are stopped to avoid malfunctions and misdiagnoses.

[0032] The freezing determination is performed by the control unit 9, which acts as the determination unit. Based on the stopped state of the internal combustion engine 2 mounted on the vehicle, the control unit 9 determines whether freezing has occurred in, for example, the differential pressure sensor 8, the inlet pressure introduction pipe 10, or the outlet pressure introduction pipe 11. In other words, the control unit 9 determines whether freezing has occurred in the differential pressure sensor 8 or in the path that introduces pressure to the differential pressure sensor 8. Specifically, if the internal combustion engine 2 is stopped for a predetermined time or longer, and the ambient temperature during that time is below a predetermined temperature, it is determined that freezing has occurred in either the differential pressure sensor 8, the inlet pressure introduction pipe 10, or the outlet pressure introduction pipe 11. The predetermined temperature is, for example, 0°C.

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

[0034] Furthermore, when the vehicle is started by turning the key on, if the outside temperature is below the above-mentioned predetermined temperature, it is determined that there is ice in the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8.

[0035] If any of the differential pressure sensor 8, the inlet pressure introduction pipe 10, or the outlet pressure introduction 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 diagnostics that utilize the output signal of the differential pressure sensor 8.

[0036] When the control unit 9 determines that freezing has occurred based on its freezing detection, it sets the count value of a predetermined release counter, the freezing release counter, to a predetermined initial value. The freezing release counter is an index corresponding to the total amount of heat sent from the internal combustion engine 2 to the GPF 5. The control unit 9 then increases or decreases the count value of the freezing release counter from its initial value based on the operating state (operating / paused state) of the internal combustion engine 2. When the count value of the freezing release counter reaches a predetermined freezing release threshold, the control unit 9 determines that the freezing that had occurred in the differential pressure sensor 8 or the path introducing pressure to the differential pressure sensor 8 has melted. In other words, when the count value of the freezing release counter reaches a predetermined freezing release threshold, the control unit 9 determines that no freezing has occurred in the differential pressure sensor 8, the inlet pressure introduction pipe 10, and the outlet pressure introduction pipe 11.

[0037] Here, the initial value of the defreezing counter is set to a predetermined amount less than the defreezing threshold. In other words, the initial value of the defreezing counter is set so that the difference from the defreezing threshold remains constant. Furthermore, the initial value of the defreezing counter is set to a range that is greater than or equal to 0 (zero) and less than the defreezing threshold.

[0038] Furthermore, the defreezing threshold is set so that it does not become 0 (zero) even after subtracting the above predetermined amount.

[0039] The de-icing counter's count value is set to decrease when the vehicle is being driven and the internal combustion engine 2 is temporarily stopped (engine speed is 0 rpm), and to increase when the internal combustion engine 2 is running (engine speed is not 0 rpm). In other words, the de-icing counter's count value is set to increase and decrease in opposite directions when the vehicle is being driven and the internal combustion engine 2 is temporarily stopped versus running.

[0040] Furthermore, the count value of the freeze-deactivation counter can never go below 0 (zero).

[0041] If the control unit 9 determines that no ice has formed in the differential pressure sensor 8, the inlet pressure introduction pipe 10, and the outlet pressure introduction pipe 11, it determines that the output signal of the differential pressure sensor 8 is true and resumes various controls and diagnoses using the output signal of the differential pressure sensor 8.

[0042] In the exhaust system 1 of this embodiment, the melting of ice that has formed in the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8 can be accurately determined while the vehicle is in operation.

[0043] Figure 2 is a timing chart showing an example of how freezing is determined when the ambient temperature remains constant at or below the specified temperature.

[0044] Time t1 is the moment when the internal combustion engine 2 starts operating, with the initial count value of the de-icing counter at 0 (zero).

[0045] Time t2 is the timing when the de-icing counter starts counting up (incrementing) from its initial value. The count value of the de-icing counter increases from time t2. In the range where the engine speed of the internal combustion engine 2 is low, the intake air volume and exhaust volume are also low, so sufficient heat cannot be supplied to the exhaust system 1. Therefore, after restarting the operation of the internal combustion engine 2, the count value of the de-icing counter is kept at its initial value (current value) without increasing or decreasing until time t2 when the engine speed reaches a predetermined speed.

[0046] This allows the exhaust system 1 to determine the melting of ice with greater accuracy.

[0047] Time t3 is the point at which the engine speed reaches a predetermined target speed.

[0048] Time t4 is the moment when the count value of the defreezing counter reaches the defreezing threshold, and the moment when the defreezing check determines that there is no defreezing.

[0049] Time t5 is the moment when the engine speed of internal combustion engine 2 becomes "0" (zero) while the vehicle is in operation, and internal combustion engine 2 stops.

[0050] Time t6 is the timing at which the freezing test determines that freezing has occurred. Time t6 is the timing at which the predetermined time has elapsed from the time when the internal combustion engine 2 stopped. The predetermined time may be set according to the outside temperature, for example, and may be set to be shorter as the outside temperature decreases.

[0051] Specifically, the control unit 9 has a timer that measures the time the internal combustion engine 2 is temporarily stopped, and starts counting up (incrementing) this timer at time t5. Time t6 is the timing when the count value of this timer reaches a predetermined refreezing threshold corresponding to the predetermined time. Note that this refreezing threshold may be changed according to the outside temperature, and may be set to be smaller as the outside temperature decreases.

[0052] Additionally, at time t6, the count value of the defreezing counter is set to its initial value.

[0053] Time t7 is the point at which the defrosting counter's count value decreases to 0 (zero) due to the continued suspension of internal combustion engine 2. In other words, during the period from time t6 to time t7, internal combustion engine 2 is stopped, so the defrosting counter's count value is counted down (decremented) from its initial value and gradually becomes smaller.

[0054] Time t8 is when internal combustion engine 2 started operation.

[0055] Figure 3 is a flowchart showing the flow of ice formation detection in the exhaust system 1 of the above-described embodiment.

[0056] Step S1 determines whether or not freezing has been detected in either the differential pressure sensor 8 or the path through which pressure is introduced to the differential pressure sensor 8. In other words, Step S1 determines whether or not either the differential pressure sensor 8 or the path through which pressure is introduced to the differential pressure sensor 8 has already been detected as being frozen. If freezing is detected in Step S1, proceed to Step S4. If freezing is not detected in Step S1, proceed to Step S2.

[0057] In step S2, it is determined whether freezing has occurred in either the differential pressure sensor 8 or the path that introduces pressure to the differential pressure sensor 8. In other words, in step S2, it is determined whether either the differential pressure sensor 8 or the path that introduces pressure to the differential pressure sensor 8 has refreezed. If it is determined in step S2 that refreezing has occurred, the process proceeds to step S3. If it is determined in step S2 that refreezing has not occurred, the routine is terminated.

[0058] In step S3, the counter value of the freeze release counter is set to an initial value.

[0059] 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 S5. If it is determined in step S4 that the internal combustion engine 2 is stopped (engine speed is zero), the process proceeds to step S8.

[0060] In step S5, the counter value of the freeze release counter is incremented.

[0061] In step S6, it is determined whether the count value of the defreezing counter has reached the defreezing threshold. If it is determined in step S6 that the count value of the defreezing counter has reached the defreezing threshold, the process proceeds to step S7. If it is determined in step S6 that the count value of the defreezing counter has not reached the defreezing threshold, the routine is terminated.

[0062] In step S7, it is determined that the ice in the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8 has been released (melted). In other words, in step S7, it is determined that the ice in the differential pressure sensor 8 and the path through which pressure is introduced to the differential pressure sensor 8 has been released.

[0063] In step S8, the counter value of the defreezing counter is decremented, and this routine ends.

[0064] Although specific embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0065] For example, the internal combustion engine 2 may be a diesel engine. Also, the exhaust particulate filter is not limited to GPF5, but may be a DPF (Diesel Particulate Filter), for example.

[0066] In the embodiment described above, the defreezing counter is set by taking the amount of heat supplied to GPF5 as a positive value and the amount of heat released from GPF5 as a negative value. However, the defreezing counter may also be set by taking the amount of heat supplied to GPF5 as a negative value and the amount of heat released from GPF5 as a positive value.

[0067] Furthermore, even when the internal combustion engine 2 is in operation, the de-icing counter may maintain its current value without increasing or decreasing it during a fuel cut-off period when fuel supply to the internal combustion engine 2 is stopped, or when the vehicle speed is above a predetermined speed. For example, if the de-icing counter is set to a positive value for the amount of heat supplied to the GPF5, the count value of the de-icing counter should be maintained at its current value without increasing it during a fuel cut-off period when fuel supply to the internal combustion engine 2 is stopped, or when the vehicle speed is above a predetermined speed, even when the internal combustion engine 2 is in operation.

[0068] This allows the exhaust system 1 to determine the melting of ice with greater accuracy.

[0069] If the destination of a vehicle equipped with the exhaust system 1 of the present invention is not an extremely cold region, the de-icing counter may be kept at its current value without increasing or decreasing it while the internal combustion engine 2 is temporarily stopped. For example, if the de-icing counter is set to a positive value for the amount of heat supplied to the GPF5, then if the destination of a vehicle equipped with the exhaust system 1 of the present invention is not an extremely cold region, the de-icing counter may be kept at its current value without decreasing it while the internal combustion engine 2 is temporarily stopped.

[0070] If the destination is not an extremely cold region, it is assumed that once the ice is thawed by starting the internal combustion engine 2, the ice will not progress even if the internal combustion engine 2 is temporarily stopped.

[0071] This allows the exhaust system 1 to determine the melting of ice with greater accuracy.

[0072] The initial value of the defrosting counter will be closer to the defrosting threshold the shorter the pause time of the internal combustion engine 2 while it is determined that freezing has occurred. For example, if the defrosting counter is set to a positive value for the amount of heat supplied to GPF5, the initial value of the defrosting counter will be larger the shorter the pause time of the internal combustion engine 2 while it is determined that freezing has occurred.

[0073] This allows the exhaust system 1 to determine the melting of ice with greater accuracy.

[0074] Furthermore, the initial value of the de-icing counter may be set to the value furthest from the de-icing threshold (for example, "0") if the pause time of the internal combustion engine 2 while it is determined that icing has occurred exceeds a predetermined time. In other words, the initial value of the de-icing counter may be set to the value that deviates the most from the de-icing threshold if the pause time of the internal combustion engine 2 while it is determined that icing has occurred exceeds a predetermined time.

[0075] If the internal combustion engine 2 is stopped for a long period of time, for example, if you turn off the ignition key at night to stop the internal combustion engine 2 and turn on the ignition key the next morning to start the internal combustion engine 2, the initial value of the de-icing counter will be affected. Correct There is no need to do so.

[0076] This allows the exhaust system 1 to set the initial value of the de-icing counter to a value that reflects actual usage.

[0077] Furthermore, the defreezing threshold may be set according to the outside temperature. Specifically, the defreezing threshold may be set to decrease as the outside temperature increases, for example.

[0078] 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. Based on the stopped state of the internal combustion engine installed in the vehicle, it is determined whether or not ice has formed in the differential pressure sensor that detects the pressure loss of the exhaust particulate filter installed in the exhaust passage of the internal combustion engine, or in the path that introduces pressure to the differential pressure sensor. If it is determined that freezing has occurred, the count value of a predetermined release counter is set to a predetermined initial value, the count value of the release counter is increased or decreased from the initial value based on the operating state of the internal combustion engine, and when the count value of the release counter reaches a predetermined threshold, it is determined that the freezing that had occurred in the differential pressure sensor or the path that introduces pressure to the differential pressure sensor has melted. The above release counter count value is determined by an exhaust system state determination method in which the direction of increase or decrease is reversed when the internal combustion engine is temporarily stopped and when the vehicle is in operation, provided that the vehicle is determined to be experiencing freezing.

2. A method for determining the state of an exhaust system according to claim 1, wherein if the internal combustion engine is temporarily stopped for a predetermined time or longer while the vehicle is in operation and the outside temperature is below a predetermined temperature, it is determined that ice has formed in the differential pressure sensor or the path through which pressure is introduced to the differential pressure sensor.

3. The exhaust system state determination method according to claim 1 or 2, wherein even when the internal combustion engine is in operation, if the intake air volume is below a predetermined value, fuel supply to the internal combustion engine is stopped during fuel cut-off, or the vehicle speed is above a predetermined speed, the count value of the release counter is kept at the current value without increasing or decreasing.

4. If the destination of the above vehicle is not an extremely cold region, The exhaust system state determination method according to claim 1 or 2, wherein the count value of the above-mentioned release counter is kept at its current value without increasing or decreasing it while the internal combustion engine is temporarily stopped.

5. The exhaust system state determination method according to claim 1 or 2, wherein the initial value of the count value of the release counter is closer to the predetermined threshold value the shorter the time the internal combustion engine is temporarily stopped while it is determined that freezing has occurred.

6. The exhaust system state determination method according to claim 1 or 2, wherein the initial value of the count value of the release counter is the value furthest from the predetermined threshold when the temporary shutdown time of the internal combustion engine during which freezing is determined to have occurred exceeds a predetermined time.

7. The method for determining the state of an exhaust system according to claim 1 or 2, wherein the temporary shutdown of the internal combustion engine is an idle stop.

8. The above vehicle is a hybrid vehicle capable of EV driving, which means it can drive autonomously with the internal combustion engine stopped. The method for determining the state of an exhaust system according to claim 1 or 2, wherein the temporary shutdown of the internal combustion engine is during EV driving.

9. An exhaust particulate filter installed in the exhaust passage of the internal combustion engine mounted on the vehicle, A differential pressure sensor for detecting the pressure loss of the exhaust particulate filter, Based on the stopped state of the internal combustion engine, it is determined whether or not ice has formed in the differential pressure sensor or the path through which pressure is introduced to the differential pressure sensor. The system includes a determination unit that, when it is determined that freezing has occurred, sets the count value of a predetermined release counter to a predetermined initial value, increases or decreases the count value of the release counter from the initial value based on the operating state of the internal combustion engine, and determines that when the count value of the release counter reaches a predetermined threshold, the freezing that had occurred in the differential pressure sensor or the path through which pressure is introduced to the differential pressure sensor has melted. The count value of the above-mentioned release counter is determined by an exhaust system state determination device in which the direction of increase or decrease is reversed when the internal combustion engine is temporarily stopped and when the vehicle is in operation, in which freezing has been determined to have occurred.

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