Dew point control method and system for exhaust gas sensor and vehicle

Abstract

The invention discloses a dew point control method and system for an exhaust gas sensor and a vehicle, and relates to the technical field of automobile emission control. The method provided by the invention comprises the following steps: when the internal combustion engine enters a shutdown stage from an operation stage, selectively executing a control action based on a dew point passing state of an exhaust gas sensor before shutdown: if the dew point passing state is not completed, determining a heat compensation value for subsequent heating; if the dew point passing is completed, shutdown heating is carried out on the sensor in the shutdown stage for heat preservation, physical parameters indicating the condensation risk are monitored, and when the parameters meet reset conditions, the dew point passing state is reset to be uncompleted. By introducing the dynamic control logic combining heat compensation, shutdown heat preservation and risk reset across the start-stop cycle, the waste gas sensor can be effectively prevented from being damaged due to condensation under various working conditions, the reliability of the emission system is remarkably improved, and the service life of the sensor is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the field of automotive electronic control technology, and in particular to a thermal management method for an exhaust gas sensor, and more particularly to a dew point control method and system for an exhaust gas sensor in an intermittent operating mode of an internal combustion engine, and a vehicle comprising the system. Background Art

[0002] In modern automotive emissions control systems, the oxygen sensor (a typical exhaust gas sensor) is a key component for achieving closed-loop fuel control in the engine and ensuring maximum conversion efficiency in the three-way catalytic converter. The core sensing element of an oxygen sensor is typically made of ceramic material, which is very sensitive to liquid water formed by condensation of water vapor at low temperatures. Sudden temperature changes can cause thermal shock, leading to cracking and damage in the ceramic, a phenomenon known as "dew point failure."

[0003] To avoid this problem, existing technologies typically integrate "overdew point control" logic into engine control strategies. Specifically, after a cold start, the control unit heats the oxygen sensor at maximum power, using hot exhaust gas from the exhaust pipe and / or energizing the sensor's built-in heater until its temperature exceeds the dew point of water vapor in the exhaust gas (typically above 100°C). Once "overdew point" is confirmed, the control system assumes the sensor is in a safe state for the remainder of the driving cycle (from key-on to key-off), and no further overdew point detection and protection are performed.

[0004] This strategy is effective in traditional internal combustion engine vehicles because their engines run almost continuously throughout a driving cycle. However, with the rise in hybrid technology, particularly extended-range electric vehicles (REVs), the vehicle powertrain architecture has undergone a fundamental shift. In these vehicles, the internal combustion engine is no longer the sole power source; its primary function is to generate electricity. Consequently, it is frequently and intermittently started and stopped based on battery charge and driving commands. This results in multiple engine starts and stops within a complete driving cycle.

[0005] At this point, the "one-time" over-dew point control strategy in the background technology reveals serious defects:

[0006] 1. Poor adaptability to operating conditions: After the engine is shut down, the exhaust pipe gradually cools, creating conditions for water vapor to condense again. If dew point protection is not re-applied the next time the engine is started, the condensed water can damage the sensor. Existing technologies lack a mechanism for secondary or multiple dew point protection within a single driving cycle.

[0007] 2. Lack of memory and compensation mechanisms: If the engine runs for a very short time (for example, only one minute), it may be forced to shut down before completing the dew point process. Existing technology cannot "remember" the amount of heating completed, and the calculation will restart from zero at the next startup, resulting in energy waste and even the abandonment of heating due to strategic misjudgment, increasing the risk of sensor damage.

[0008] 3. Lack of protection after shutdown: After the engine is shut down, the exhaust heat source disappears, and the sensor is completely exposed to the gradually cooling environment. Existing technologies do not monitor or intervene in the sensor status during the shutdown phase, and can only passively wait for the next condensation to occur.

[0009] The most similar prior art to the present invention, such as Chinese patent application CN119664475A, discloses a method for identifying dew point in a vehicle exhaust system. This method obtains parameters such as real-time exhaust temperature, intake air volume, catalyst temperature, and engine shutdown duration after vehicle startup, and calculates a heat integral value to accurately determine whether the vehicle has entered the dew point phase. This solution contributes to improved accuracy in determining the first dew point crossing. However, this solution still focuses on the "first" vehicle startup phase, and its core issue is how to accurately achieve a single dew point crossing. For hybrid vehicles, particularly extended-range vehicles, which experience multiple starts and stops within a single driving cycle, this prior art does not provide an effective solution. It does not consider the risk of a "secondary dew point crossing" when the engine is shut down after a primary dew point crossing and then restarted after cooling, nor does it address the issue of "heat compensation" when the dew point crossing process is interrupted by a brief period of operation. Therefore, developing a new exhaust gas sensor dew point control strategy that can dynamically adapt and proactively protect against the frequent engine starts and stops in hybrid vehicles has become an urgent technical challenge in the field. Summary of the Invention

[0010] The main purpose of the present invention is to provide a dew point control method, system and vehicle for an exhaust gas sensor, aiming to solve the technical problem in the prior art that the dew point control strategy cannot adapt to the frequent start-stop conditions of the internal combustion engine of a hybrid vehicle, resulting in the exhaust gas sensor being easily damaged by repeated condensation.

[0011] To address the above technical problems, the present invention provides a dew point control method for an exhaust gas sensor, which is applied to a vehicle including an internal combustion engine and the exhaust gas sensor. The internal combustion engine is configured to experience at least one operating phase and a shutdown phase within a driving cycle. The method comprises: when the internal combustion engine enters the shutdown phase from the operating phase, based on the excessive dew point state of the exhaust gas sensor before the shutdown phase, selectively performing one of the following control actions:

[0012] a) if the over-dew point state is incomplete over-dew point, determining a heat compensation value for a subsequent heating process;

[0013] b) if the over-dew point status is completed, performing shutdown heating on the exhaust gas sensor and monitoring at least one physical parameter indicating a condensation risk during the shutdown phase; and resetting the over-dew point status to incomplete when the physical parameter satisfies a preset reset condition.

[0014] By intelligently adopting the strategy of "debt compensation" or "active insulation and risk resetting" based on whether the critical state of over-dew point is achieved each time the internal combustion engine is shut down, the present invention realizes dynamic and continuous protection of the exhaust gas sensor across the start-stop cycle, and solves the interruption point and one-time control logic defects of the background technology.

[0015] As a preferred embodiment of the present invention, in control action a), the heat compensation value is determined based on the difference between a preset target heating energy and the cumulative heating energy applied to the exhaust gas sensor during the previous operating phase. This solution precisely quantifies the unfinished heating task (heat "debt"), providing an accurate basis for the next compensation, thereby improving energy efficiency.

[0016] As a preferred embodiment of the present invention, the method further includes: when the internal combustion engine next enters an operating phase, revising the target heating energy required for dew point overshoot determination based on the heat compensation value. This embodiment ensures that the heat compensation value can be effectively applied to subsequent control, allowing the next dew point overshoot process to begin at a higher "starting point," resulting in faster and more reliable completion.

[0017] As a preferred embodiment of the present invention, in control action b), the heating power for the shutdown heating is determined based on at least one vehicle operating condition parameter and / or environmental state parameter. This solution eliminates the need for blind, constant shutdown heating and instead dynamically adjusts it based on the actual heat dissipation environment (determined by vehicle speed, ambient temperature, and other factors), achieving energy savings while ensuring thermal insulation.

[0018] As a preferred embodiment of the present invention, the vehicle operating condition parameter includes vehicle speed, and the environmental condition parameter includes ambient temperature. The method further includes: determining a wall temperature change rate of an exhaust pipe based on the vehicle speed and ambient temperature; and determining a heating power for the shutdown heating based on the wall temperature change rate, wherein a greater wall temperature change rate indicates a greater heating power. This solution provides a specific and effective method for determining heating power, with clear logic, easy engineering implementation, and the ability to precisely counteract environmentally induced heat dissipation.

[0019] As a preferred embodiment of the present invention, in control action b), the at least one physical parameter indicative of condensation risk includes the rate of change of the exhaust pipe wall temperature and / or the rate of change of the pressure within the exhaust pipe. This approach leverages the physical property that water vapor condensation simultaneously causes sudden changes in both temperature and pressure. By selecting the two core parameters that most directly reflect condensation risk, it improves monitoring accuracy.

[0020] As a preferred solution of the present invention, the preset reset condition includes: the wall temperature change rate and the pressure change rate each remain above their respective preset thresholds for a preset duration. This solution, through dual judgment based on both "dual parameters" and "duration," effectively filters out interference from sensor noise or transient fluctuations, ensuring that the state is reset only when substantial condensation is confirmed, avoiding unnecessary switching of control strategies.

[0021] As a preferred solution of the present invention, the overdew point status is reset to an incomplete overdew point, so that the complete overdew point control process must be re-executed when the internal combustion engine next enters the operating phase. This solution clarifies the ultimate purpose of "status reset", namely, to activate a new and complete overdew point protection, thereby forming a closed loop of control logic.

[0022] The present invention also provides a dew point control system for an exhaust gas sensor, which is applied to a vehicle including an internal combustion engine and the exhaust gas sensor, wherein the internal combustion engine is configured to experience at least one operating phase and a shutdown phase within a driving cycle, and the system includes: a control unit configured to selectively execute control action a) or b) described in the method when the internal combustion engine enters the shutdown phase from the operating phase, based on the excessive dew point state of the exhaust gas sensor before the shutdown phase.

[0023] The system provides a physical carrier for the implementation of the above method through the logic execution of the control unit, which can reliably improve the durability of the vehicle emission system.

[0024] The present invention also provides a vehicle, which includes the dew point control system of any of the above solutions.

[0025] By applying this system to vehicles, especially hybrid or extended-range electric vehicles, the reliability and durability of the entire vehicle can be significantly improved, and the maintenance costs and compliance risks caused by emission system failures can be reduced.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Enhanced sensor protection and extended service life: By introducing dynamic control logic across start-stop cycles, this invention greatly reduces the probability of exhaust gas sensor damage due to thermal shock caused by condensed water, thereby significantly extending its effective service life, whether through "heat compensation" to ensure the final completion of each heating task, or through "shutdown insulation" and "risk reset" to proactively prevent and respond to the occurrence of condensation.

[0028] 2. Improved reliability and stability of the emission control system: This invention ensures that the exhaust gas sensor can quickly and safely enter normal working state after each internal combustion engine start-up, providing reliable signal input for the engine's precise fuel closed-loop control, thereby ensuring that the entire emission control system can always maintain efficient and stable operation under the complex operating conditions of hybrid vehicles.

[0029] 3. Improved intelligence and energy efficiency of control strategies: The present invention can memorize heating history and dynamically adjust shutdown heating power according to the actual heat dissipation environment, avoiding the blind heating from scratch and inaction after shutdown in existing technologies. While achieving better protection effects, it also improves energy utilization efficiency.

[0030] 4. Perfect adaptation to modern hybrid vehicle architecture: The core concept and specific solutions of this invention are specially designed for the intermittent operation characteristics of internal combustion engines in hybrid and extended-range vehicles. They resolve the adaptation contradiction between existing technologies and the power architecture of the new generation of vehicles, and have strong practical significance and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments disclosed in the present invention, the drawings of the embodiments will be briefly introduced below. These drawings are only used for illustrative purposes and are not intended to limit the scope of protection of the present invention.

[0032] Figure 1 It is a flow chart of the conventional engine over-dew point control strategy in the prior art.

[0033] Figure 2 This is a flow chart of a dew point protection optimization (heat compensation) strategy for a dew point condition not exceeding the dew point, provided by an embodiment of the present invention.

[0034] Figure 3 This is a flow chart of a shutdown temperature maintenance (shutdown insulation) strategy after exceeding the dew point, provided by an embodiment of the present invention.

[0035] Figure 4 This is a flow chart of a secondary dew point overshoot (dew point state reset) strategy after the dew point overshoot provided by an embodiment of the present invention.

[0036] Figure 5 Schematic diagram of the structure of the dew point control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following further describes the technical solutions (including preferred technical solutions) of the present invention through accompanying drawings and by enumerating some optional embodiments of the present invention. It should be understood that the embodiments described are merely some, and not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0038] Example 1

[0039] This embodiment provides a dew point control method for an exhaust gas sensor, which is applied to hybrid vehicles, particularly extended-range electric vehicles. The vehicle includes an internal combustion engine 300, an exhaust gas sensor 200 (e.g., an oxygen sensor) disposed in an exhaust pipe 400, and a control unit 100 for executing control logic. The exhaust gas sensor 200 itself includes a sensing element 220 for measuring exhaust gas composition and an electric heating element 210 for heating the exhaust gas. The control unit 100 can be part of a vehicle controller 500 (e.g., a vehicle control unit).

[0040] The core of this method is that during a complete driving cycle (from vehicle power-on to power-off), the control unit 100 continuously tracks the running / shutdown status of the internal combustion engine 300 and the excessive dew point status of the exhaust gas sensor 200. Each time the internal combustion engine 300 is shut down, the control unit 100 intelligently triggers subsequent compensation or protection strategies based on the excessive dew point status before the shutdown.

[0041] The dew point overrun status is a flag maintained by the control unit 100 , and may be, for example, “OK” (indicating that the dew point overrun has been completed) or “NOK” (indicating that the dew point overrun has not been completed or the status has been reset).

[0042] In a typical scenario, the execution flow of this method is as follows:

[0043] Initial stage: The vehicle is powered on and the internal combustion engine 300 is started for the first time. At this time, the exhaust gas sensor 200 is in the over-dew point state of "NOK". The control unit 100 implements a traditional over-dew point heating strategy: the exhaust gas sensor 200 is heated by the high-temperature exhaust gas discharged by the internal combustion engine 300 and the power supply of the heating element 210. The control unit 100 accumulates the total heat applied to the sensor in real time (including exhaust gas heat and electric heating heat). When the accumulated heat reaches a preset target energy integral that is sufficient to make the temperature of the sensor element 220 exceed the dew point, the exhaust gas sensor 200 is heated. , the control unit 100 changes the over-dew point status from “NOK” to “OK”.

[0044] Branch 1: When the internal combustion engine is stopped, the dew point status is "NOK"

[0045] This situation usually occurs when the internal combustion engine 300 has been running for a very short time and has been shut down before completing the above-mentioned initial heating process.

[0046] Reference Figure 2 When the control unit 100 detects that the internal combustion engine 300 is shut down and reads the current over-dew point state as "NOK" through its internal state monitoring module 110, it will execute the heat compensation strategy. The specific steps are as follows:

[0047] 1. The heat compensation module 120 in the control unit 100 is activated. It calculates the cumulative heating energy applied during this operation phase. .

[0048] 2. The heat compensation module 120 is based on the formula , calculate the "residual energy difference" or "heat compensation value" required to complete the dew point .in, It is the standard target energy required to complete a complete dew point crossing.

[0049] 3. The heat compensation value It is stored in the non-volatile memory of the control unit 100 and is bound to the state of the exhaust gas sensor 200 .

[0050] 4. When the internal combustion engine 300 is started next time, the heat compensation module 120 reads the stored , and set a new target heating energy The compensation is indirectly achieved by increasing the total target energy to ensure more thorough heating. The control logic will use this increased Serves as the judgment threshold for whether the dew point is exceeded.

[0051] In this way, the method achieves "memory" of the interrupted heating process, ensures the continuity of energy input, and avoids duplication and waste.

[0052] Branch 2: When the internal combustion engine is stopped, the dew point status is "OK"

[0053] This is a more common operating condition, where the exhaust gas sensor 200 has safely passed the dew point and the internal combustion engine 300 has been shut down normally due to energy management needs. At this point, to prevent condensation from forming again during the shutdown cooling process, the system will enter the active protection phase.

[0054] Reference Figure 3 and Figure 4 When the control unit 100 detects that the internal combustion engine 300 is shut down and the state monitoring module 110 reads that the over-dew point state is "OK", the shutdown insulation strategy and the dew point state reset monitoring strategy will be started at the same time.

[0055] 1. Shutdown and insulation strategy:

[0056] It is executed by the shutdown and heat preservation control module 130 and aims to slow down the cooling speed of the exhaust gas sensor 200 through low-power electric heating.

[0057] First, the module 130 records the exhaust temperature at the moment the internal combustion engine 300 stops, which is used as the initial value T of the wall temperature of the exhaust pipe 400 at that position. pipe .

[0058] Next, the module 130 obtains real-time ambient temperature and vehicle speed information from the vehicle bus (such as the CAN bus).

[0059] Based on these parameters, module 130 calculates the wall temperature change rate under the current conditions according to a preset, calibrated model or lookup table. ( ). The rate of change reflects the current heat dissipation speed.

[0060] Finally, module 130 again uses a table lookup method to select an appropriate electric heating power based on the calculated wall temperature change rate θ and controls heating element 210 to continuously operate at this power. The basic principle is that the faster the heat dissipation (the larger θ), the greater the required insulation heating power.

[0061] 2. Dew point status reset monitoring strategy:

[0062] The dew point status reset module 140 is executed in parallel to determine whether irreversible condensation has occurred, thereby requiring the current "OK" status to be "overturned".

[0063] The module 140 continuously monitors the change rates of two key physical parameters: one is the wall temperature change rate θ mentioned above; the other is the pressure change rate φ ( When a large amount of water vapor condenses into water, a large amount of latent heat of vaporization is released at the same time, causing an abnormal temperature change trend and a sudden drop in pressure due to the rapid decrease in gas volume.

[0064] The module 140 internally sets two thresholds: a temperature change rate threshold θ_max and a pressure change rate threshold φ_max, as well as a duration threshold T_max.

[0065] During the monitoring process, if the module 140 finds that the wall temperature change rate θ and the pressure change rate φ both exceed their respective thresholds (θ > θ_max and φ > φ_max), and this state lasts for a time exceeding T_max, the system determines that a significant condensation event has occurred in the exhaust line 400 .

[0066] Once the reset condition is met, the dew point status reset module 140 will immediately and forcibly change the over-dew point status of the exhaust gas sensor 200 from “OK” to “NOK”.

[0067] This "NOK" state will remain until the next start of the internal combustion engine 300. At that time, the control unit 100 will restart a complete, standard over-dew point heating process due to detecting the "NOK" state, thereby ensuring that the newly generated condensed water is completely removed.

[0068] In an alternative embodiment, the shutdown warm-up strategy can employ more advanced closed-loop control. For example, the exhaust gas sensor 200 typically includes a thermistor for temperature measurement. The shutdown warm-up control module 130 can set a dynamic target warm-up temperature (for example, 20°C above the dew point calculated based on the ambient pressure). Then, using a PID (Proportional-Integral-Derivative) algorithm, it adjusts the power of the heating element 210 in real time to ensure that the sensor's measured temperature remains precisely constant at the target warm-up temperature. This approach is more accurate and energy-efficient than an open-loop lookup table.

[0069] In summary, the method of this embodiment organically combines the three strategies of heat compensation, shutdown insulation, and risk reset by making intelligent decisions at the time of internal combustion engine shutdown, forming a complete exhaust gas sensor dew point protection closed loop that can adapt to all operating conditions of hybrid vehicles, greatly improving the reliability of the system.

[0070] Example 2

[0071] This embodiment provides a method for controlling the dew point of an exhaust gas sensor for a hybrid vehicle. Figure 5 As shown, the method is executed in a control unit 100, which serves as the core control unit. This control unit 100 can be integrated into a vehicle controller 500 (e.g., a vehicle control unit (VCU) or an engine control unit (ECU)). The control unit 100 is connected to various vehicle components and sensors via a vehicle bus or dedicated lines to obtain the information necessary to execute the method. This information includes, but is not limited to, signals from an exhaust gas sensor 200 (an oxygen sensor in this embodiment), the operating status of an internal combustion engine 300, and information such as ambient temperature, vehicle speed, exhaust pipe pressure, and intake pipe pressure obtained by various onboard sensors.

[0072] The specific process of this method can be divided into the following core parts:

[0073] Part 1: Traditional first dew point process

[0074] When the vehicle is started for the first time (for example, the key state changes from Key-Off to Key-On and the internal combustion engine 300 is started), the system first performs a traditional over-dew point determination. This process can be referred to Figure 1 .

[0075] Step 101: The internal combustion engine 300 is started for the first time. The control unit 100 detects that the internal combustion engine 300 switches from a stationary state to a running state.

[0076] Step 102: The control unit 100 determines a target heating energy required to safely exceed the dew point temperature of 100°C based on the physical properties of the exhaust gas sensor 200 (such as its mass, specific heat capacity, etc.), which is recorded as the original target heating energy. This value is usually pre-stored in the memory of the control unit 100 as calibration data.

[0077] Step 103: The control unit 100 starts to calculate and accumulate the total heating energy actually applied to the exhaust gas sensor 200 This energy consists of two parts:

[0078] Exhaust heat energy: The control unit 100 uses its built-in engine combustion model to estimate in real time the heating energy of the engine exhaust on the exhaust gas sensor 200 based on parameters such as engine speed, load, intake volume, and fuel injection volume.

[0079] Electric heating energy: The control unit 100 controls the heating element 210 built into the exhaust gas sensor 200 to perform electric heating at a relatively low and safe power. The electric heating energy is equal to the product of the power and the heating time.

[0080] Step 104: The control unit 100 converts the total heating energy accumulated in real time into With target energy Make a comparison.

[0081] Step 105: If Less than , indicating that the exhaust gas sensor 200 has not yet safely passed the dew point, and the system will continue to perform heating and energy accumulation calculations.

[0082] Step 106: If Greater than or equal to , it is determined that the over-dew point is completed. At this time, the control unit 100 sets an internal over-dew point status flag to "OK".

[0083] Step 107: After the dew point is passed, the control unit 100 immediately uses the maximum heating power that the exhaust gas sensor 200 can withstand to quickly heat it so that its temperature reaches the high temperature required for normal operation (for example, above 350°C) as soon as possible, thereby entering a closed-loop control state.

[0084] Step 108: In the background art, once the dew point is exceeded, in this driving cycle, as long as the key state remains at Key-On, the system defaults the dew point state to "OK" and does not re-determine the dew point.

[0085] For more specific explanation, a numerical example is provided: Assume that according to the calibration, the original target heating energy of a certain type of exhaust gas sensor 200 is After the internal combustion engine 300 is started, at time t1, the engine model calculates that the exhaust gas has provided 800 joules of heat energy. At the same time, the control system electrically heats the heating element 210 at a power of 10 watts for 30 seconds, providing 300 joules of electrical heat energy. At this time, the total heating energy = 800 + 300 = 1100 joules. Since 1100 < 2000, it is determined that the dew point has not been exceeded. At time t2, the exhaust heat energy has accumulated to 1500 joules, and the electric heating energy has accumulated to 600 joules. The total energy = 2100 joules. Since 2100 > 2000, the dew point is determined to have been exceeded.

[0086] However, for a hybrid vehicle, the internal combustion engine 300 may be shut down after the over-dew point status is “OK.” At this point, the core strategy of the present invention begins to intervene.

[0087] The method of the present invention can intelligently select and execute subsequent protection strategies based on the traditional over-dew point process and according to different historical operating conditions before the internal combustion engine is shut down.

[0088] Strategy 1: Heat compensation strategy before dew point, refer to Figure 2

[0089] This strategy is used for the following scenario: the internal combustion engine 300 is shut down shortly after starting, at which time the dew point process in Part 1 has not yet been completed (i.e. < ), the over-dew point status is "NOK" (not completed).

[0090] Step 201: The internal combustion engine 300 is restarted.

[0091] Step 202: The control unit 100 detects that the over-dew point status flag is "NOK" before this startup.

[0092] Step 203: The control unit 100 reads a value called "heat compensation value" from its memory. ". This value is calculated and saved at the last shutdown. It is calculated as follows: ,in, is heating energy for the original target, It is the heating energy completed at the last shutdown moment.

[0093] Step 204: The control unit 100 calculates the new target heating energy for this startup. The calculation formula is: By increasing this compensation amount, it is possible to ensure that the water vapor that may have condensed due to cooling after the last shutdown, as well as the condensed water generated by this startup, are effectively evaporated, making the heating more thorough.

[0094] Step 205: The subsequent heating energy calculation and determination process is similar to the traditional method, except that the determination threshold is changed from a fixed After dynamic correction When the accumulated heating energy exceeds Only when the dew point is exceeded is it determined.

[0095] To explain more concretely, let's continue with the numerical example above: Assume The internal combustion engine 300 starts and runs for 20 seconds before stopping. The accumulated heating energy at this time is =700 joules. Since 700 < 2000, the system determines that the dew point has not been exceeded. At the moment of shutdown, the control unit 100 calculates the heat compensation value = 2000 - 700 = 1300 joules, and the value is stored in the non-volatile memory. A few minutes later, when the internal combustion engine 300 is restarted, the control unit 100 reads = 1300 joules, and calculate the target total energy required for this dew point crossing = 2000 + 1300 = 3300 joules. This higher target ensures more thorough heating, effectively compensating for the negative effects of intermediate cooling stops.

[0096] Strategy 2: Temperature maintenance strategy after the dew point has been exceeded, refer to Figure 3

[0097] This strategy addresses the scenario where internal combustion engine 300 is shut down after exhaust gas sensor 200 has successfully passed the dew point (flag is "OK"). To prevent the exhaust pipe 400 from cooling and causing new condensation during the shutdown period, this strategy actively maintains the temperature.

[0098] Step 301: The control unit 100 detects that the internal combustion engine 300 is shut down, and the current over-dew point status flag is "OK".

[0099] Step 302: The control unit 100 immediately starts to obtain the real-time ambient temperature and vehicle speed from the vehicle bus. If the vehicle speed is not zero, it means that the vehicle is coasting or running purely on electric power. The flowing air will accelerate the cooling of the exhaust pipe 400.

[0100] Step 303: Based on the acquired ambient temperature and vehicle speed, the control unit 100 queries a pre-stored "wall temperature change rate calibration table" in its memory. This table describes the rate of temperature drop on the exhaust pipe 400 wall surface under different external conditions, denoted as θ. The "wall temperature change rate calibration table" is shown in Table 1, and its contents are pre-calibrated.

[0101]

[0102] When the engine has exceeded the dew point, the engine state will inevitably enter the shutdown phase. In order to maintain the state of no water vapor in the exhaust pipe, the oxygen sensor needs to be electrically heated under this working condition to ensure the overall temperature. Therefore, the exhaust pipe wall temperature T needs to be initialized according to the exhaust temperature when the engine was last shut down. pipe , calibrate the wall temperature drop rate according to the ambient temperature and the current vehicle speed, simulate the real-time wall temperature situation, integrate the time, and calculate the wall temperature change rate θ. The specific formula is .

[0103] Step 304: The control unit 100 then queries another "Electric Heating Power Calibration Table During Shutdown" based on the calculated or queried wall temperature change rate θ. This table establishes a relationship between θ and the required compensation heating power. As a general rule, the larger the absolute value of θ (i.e., the faster the cooling), the greater the required electric heating power. The "Electric Heating Power Calibration Table During Shutdown" is shown in Table 2, and the contents of this table are pre-calibrated.

[0104]

[0105] Step 305: The control unit 100 instructs the heating circuit to perform continuous, low-power heating compensation on the heating element 210 according to the calibrated power.

[0106] Strategy 3: Secondary dew point crossing after dew point crossing (status reset) strategy, refer to Figure 4

[0107] This strategy is a supplement and upgrade to Strategy 2. It is used to deal with the risk scenario where, after a long shutdown or frequent starts and stops, low-power heating alone is no longer sufficient to combat heat loss, and condensed water may have accumulated again in the exhaust pipe 400.

[0108] Step 401: The triggering premise of this strategy is the same as that of strategy 2. While executing the temperature maintenance heating of strategy 2, the system starts the monitoring logic of this strategy.

[0109] Step 402: The control unit 100 not only monitors the temperature but also begins to monitor pressure changes. It calculates the pressure changes in the exhaust pipe 400 through the exhaust pipe pressure sensor and the intake pipe pressure sensor (or atmospheric pressure sensor).

[0110] Step 403: The control unit 100 performs differential calculations on the two key physical quantities to obtain their rates of change:

[0111] Wall temperature change rate θ: The calculation method is the same as strategy 2.

[0112] Pressure change rate φ: obtained by integrating the pressure difference between the exhaust pipe and the intake pipe and time, that is, .

[0113] Step 404: The control unit 100 compares the real-time calculated θ and φ with preset thresholds θ_max and φ_max. These two thresholds represent the critical rate of change at which significant water vapor condensation may occur.

[0114] The wall temperature change rate threshold θ_max is selected to identify abnormal temperature drops, or inflection points where the temperature slows down and then accelerates, due to the release of latent heat from large amounts of water vapor condensation. Its absolute value is typically calibrated based on the specific heat capacity characteristics of the sensor and exhaust system; a typical empirical range might be between -5°C / s and -15°C / s. The pressure change rate threshold φ_max is selected to identify pressure drops caused by a sharp decrease in gas volume due to condensation of water vapor into liquid water. Its calibration depends on factors such as the exhaust line volume and engine displacement; a typical empirical range might be between -50 mbar / s and -100 mbar / s. By using the dual parameters and a duration T_max (e.g., 3 seconds) to effectively filter out sensor signal noise and transient fluctuations, ensuring that a status reset is triggered only when significant condensation has occurred.

[0115] Step 405: When the system detects that the change in θ satisfies a first threshold condition (e.g., the absolute value exceeds θ_max), and the change in φ satisfies a second threshold condition (e.g., the absolute value exceeds φ_max), and the duration during which these two conditions are met simultaneously exceeds a preset time duration T_max (e.g., 3 seconds), the control unit 100 makes a high-confidence judgment: a non-negligible amount of liquid water has formed inside the exhaust pipe 400.

[0116] Step 406: Once this judgment is made, the control unit 100 will immediately perform a “dew point status reset” operation, ie, forcibly change the over-dew point status flag from “OK” to “NOK” (over-dew point not completed).

[0117] Step 407: This "NOK" state remains. The next time the internal combustion engine 300 is started, the control unit 100 detects this "NOK" state and, as if it were the vehicle's first cold start, executes a complete, new dew point process (i.e., Part 1) to ensure that condensed water on the sensor is completely removed before high-power heating begins.

[0118] Through the organic combination of these three strategies, the method of the present invention constructs a full-operating-condition, multi-level intelligent protection system to ensure the safety of the exhaust gas sensor.

[0119] Example 3

[0120] This embodiment provides a dew point control system for an exhaust gas sensor, the structure of which can be referred to Figure 5 The system is applied to a hybrid vehicle, and its core is a control unit 100 .

[0121] The control unit 100 can be a standalone controller or a functional unit within a vehicle controller 500 (e.g., an ECU or VCU). Its core comprises a processor and memory. The memory stores computer program instructions and the various calibration data and thresholds described in Example 1. The processor is responsible for executing the program instructions to implement the method of the present invention.

[0122] When executing a program, the processor's functions can be logically divided into multiple modules. Figure 5 The modules shown correspond to:

[0123] State Monitoring Module 110: Responsible for basic control functions, such as performing traditional first-pass dew point determination, routine heating control, and communication with other onboard systems. It continuously monitors the start / stop status of the internal combustion engine 300 and the dew point status flag, and distributes this information to other modules.

[0124] Heat compensation module 120 (implementation strategy 1): This module is configured to: when it is learned from the state monitoring module 110 that "internal combustion engine is started" and "the last time the dew point was not exceeded", read the stored heat compensation value from the memory , calculate the new target heating energy , and based on To control the dew point process.

[0125] Shutdown insulation control module 130 (implementation strategy 2): This module is configured as follows: when it is learned from the status monitoring module 110 that "internal combustion engine is shut down" and "dew point has been exceeded", it obtains the ambient temperature and vehicle speed in real time through the vehicle bus, queries the calibration table in the memory, calculates the required compensation heating power, and outputs a control signal to the heating element 210 to maintain the temperature of the exhaust gas sensor 200.

[0126] Dew Point Status Reset Module 140 (Implementation Strategy 3): This module, activated in parallel with module 130, is configured to continuously acquire temperature and pressure information during shutdown and calculate their rate of change. If the rate of change simultaneously exceeds a threshold for a specified period of time, the module overwrites the dew point status flag maintained in memory by the status monitoring module 110, resetting it to "NOK."

[0127] These modules work together under the unified scheduling of the processor to form a complete control system that can intelligently and reliably complete the dew point control of the exhaust gas sensor of hybrid vehicles.

[0128] The present invention also provides a hybrid vehicle comprising the control system.

[0129] Compared with the prior art, the present invention introduces dynamic control logic across start-stop cycles:

[0130] 1. Enhanced sensor protection and extended service life: Through the "shutdown and heat preservation strategy" and "risk reset strategy", the present invention can proactively prevent or promptly respond to condensation, greatly reducing the probability of exhaust gas sensor damage due to thermal shock caused by condensed water, thereby significantly extending its effective service life and reducing users' maintenance costs.

[0131] 2. Improved reliability and stability of the emissions control system: By ensuring that the exhaust gas sensor quickly and safely enters normal operation after each internal combustion engine start (not just the first time), this invention provides reliable signal input for the engine's precise closed-loop fuel control. This ensures that the entire emissions control system maintains efficient and stable operation under the complex operating conditions of hybrid vehicles, meeting increasingly stringent emissions regulations.

[0132] 3. Improved control strategy intelligence and energy efficiency: Through a "heat compensation strategy," this invention can memorize and compensate for interrupted heating processes, avoiding the blind restart of heating from scratch and inaction after shutdowns in existing technologies, thereby achieving efficient energy utilization. Furthermore, the shutdown heating power is dynamically adjusted based on the actual heat dissipation environment, achieving better protection while also improving energy utilization efficiency.

[0133] 4. Perfect adaptation to modern hybrid vehicle architecture: The core concept and specific solutions of this invention are specially designed for the intermittent operation characteristics of internal combustion engines in hybrid and extended-range vehicles. They resolve the adaptation contradiction between existing technologies and the power architecture of the new generation of vehicles, and have strong practical significance and application value.

[0134] It will be easily understood by those skilled in the art that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, combinations, replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A dew point control method for an exhaust gas sensor, applied to a vehicle comprising an internal combustion engine and the exhaust gas sensor, wherein the internal combustion engine is configured to undergo at least one operating phase and a stopping phase within a driving cycle, characterized in that: The method comprises: When the internal combustion engine enters a shutdown phase from an operating phase, one of the following control actions is selectively performed based on the over-dew point state of the exhaust gas sensor before the shutdown phase: a) if the over-dew point state is incomplete over-dew point, determining a heat compensation value for a subsequent heating process; b) if the over-dew point status is completed, performing shutdown heating on the exhaust gas sensor and monitoring at least one physical parameter indicating a condensation risk during the shutdown phase; and resetting the over-dew point status to incomplete when the physical parameter satisfies a preset reset condition.

2. The method according to claim 1, characterized in that In the control action a), the heat compensation value is determined according to a difference between a preset target heating energy and an accumulated heating energy applied to the exhaust gas sensor in a previous operation stage.

3. The method according to claim 1 or 2, characterized in that The method further comprises: When the internal combustion engine enters the operation phase next time, the target heating energy required for dew point determination is corrected based on the heat compensation value.

4. The method according to claim 1, wherein In the control action b), the heating power of the shutdown heating is determined based on at least one vehicle operating condition parameter and / or environmental state parameter.

5. The method according to claim 4, characterized in that The vehicle operating condition parameter includes vehicle speed, and the environmental state parameter includes ambient temperature; The method further includes: determining a wall temperature change rate of an exhaust pipe according to the vehicle speed and the ambient temperature; and determining a heating power of the shutdown heating according to the wall temperature change rate, wherein the greater the wall temperature change rate, the greater the heating power.

6. The method according to claim 1, characterized in that In the control action b), the at least one physical parameter indicating the condensation risk includes a temperature change rate of a wall of the exhaust pipe and / or a pressure change rate in the exhaust pipe.

7. The method according to claim 6, characterized in that The preset reset condition includes: the wall temperature change rate and the pressure change rate are respectively above their respective preset thresholds for a preset period of time.

8. The method according to claim 1, characterized in that The over-dew point state is reset to an incomplete over-dew point state, so that when the internal combustion engine enters the operation phase next time, a complete over-dew point control process needs to be re-executed.

9. A dew point control system for an exhaust gas sensor, applied to a vehicle comprising an internal combustion engine and the exhaust gas sensor, wherein the internal combustion engine is configured to undergo at least one operating phase and a stopping phase within a driving cycle, characterized in that: The system comprises: a control unit configured to selectively perform one of the following control actions when the internal combustion engine enters a shutdown phase from an operating phase, based on an over-dew point state of the exhaust gas sensor before the shutdown phase: a) if the over-dew point state is incomplete over-dew point, determining a heat compensation value for a subsequent heating process; b) if the over-dew point status is completed, during the shutdown phase, controlling the exhaust gas sensor to perform shutdown heating and monitoring at least one physical parameter indicating a condensation risk; and when the physical parameter satisfies a preset reset condition, resetting the over-dew point status to incomplete.

10. The system according to claim 9, characterized in that The control unit is configured to determine the heat compensation value according to a difference between a preset target heating energy and an accumulated heating energy applied to the exhaust gas sensor in a previous operation phase.

11. The system according to claim 9, wherein: The control unit is configured to determine the heating power of the shutdown heating according to at least one vehicle operating condition parameter and / or environmental state parameter.

12. The system according to claim 11, wherein: The vehicle operating condition parameters include vehicle speed, and the environmental state parameters include ambient temperature; the control unit is specifically configured to: determine the wall temperature change rate of an exhaust pipe based on the vehicle speed and ambient temperature, and determine the heating power of the shutdown heating based on the wall temperature change rate.

13. The system according to claim 9, wherein: The system also includes: a sensor for measuring the exhaust pipe temperature and pressure at the location of the exhaust gas sensor; the control unit is specifically configured to: calculate the wall temperature change rate and pressure change rate of the exhaust pipe as the physical parameters based on the measured values ​​of the temperature and pressure, and reset the over-dew point state when the change rate meets the preset reset condition.

14. A vehicle, characterized in that: A dew point control system for an exhaust gas sensor comprising any one of claims 9-13.

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