A method for calculating oxygen storage capacity in catalyst diagnosis

Abstract

This application discloses a method for calculating oxygen storage capacity in catalytic converter diagnostics. The method is applied to vehicles equipped with an EGR system. The method includes: after identifying that the EGR low flow diagnostic condition is not met, but the catalytic converter diagnostic condition is met, closing the EGR valve in the EGR system and returning the EGR mixing valve to its maximum target position in steps; determining whether the current engine speed or engine load exceeds its corresponding diagnostic range; if the determination result is negative, performing an oxygen purging operation on the catalytic converter; after determining that the oxygen purging operation is completed, performing an oxygen storage operation on the catalytic converter; and updating the OSC calculation result. This application avoids interrupting the EGR low flow diagnostic process due to the EGR valve being closed by using the failure to meet the EGR low flow diagnostic condition as one of the starting conditions for catalytic converter diagnostics.

Description

Technical Field

[0001] This application relates to the technical field of catalysts, and specifically to a method for calculating oxygen storage capacity in catalyst diagnostics. Background Technology

[0002] As one of the most crucial components for reducing vehicle emissions, the catalytic converter's catalytic performance and durability play a vital role in ensuring overall vehicle emissions compliance. Currently, catalytic converter diagnostics are achieved by assessing its oxygen storage capacity. Essentially, this involves calculating the oxygen storage capacity and comparing it to a threshold to determine the catalytic converter's aging coefficient. When the aging coefficient falls below the threshold, a catalytic converter malfunction is reported. The oxygen storage capacity (OSC) is typically calculated during the oxygen-reducing process after the catalytic converter has been emptied of oxygen. The formula is as follows: Where 0.23 represents the mass percentage of oxygen in the air, t1 and t2 are the start and end times of the leaning process, respectively, λ is the air-fuel ratio, and ml_w refers to the mass flow rate of the exhaust gas. It is evident that the air-fuel ratio has a significant impact on OSC calculations during catalytic converter diagnostics.

[0003] Many vehicles now come equipped with an EGR (Exhaust Gas Recirculation) system. If the EGR system suddenly turns on or off during catalytic converter diagnostics, it will inevitably cause large fluctuations in the air-fuel ratio, leading to significant deviations in OSC calculations and even false alarms about catalytic converter malfunctions. Therefore, the current strategy for vehicles with EGR is to close the EGR valve once the catalytic converter diagnostic conditions are met, and then restore EGR control after the OSC calculation is completed.

[0004] However, relevant regulations require that EGR high and low flow rates be diagnosed under certain conditions, and that the EGR valve be opened during low flow rate diagnosis. This leads to the following problems: First, if the catalyst diagnostic conditions are met simultaneously during low flow rate diagnosis, the on-board controller will automatically close the EGR valve, preventing the EGR low flow rate diagnosis from being completed. Second, because the EGR valve is immediately closed when the catalyst is diagnosed, the EGR mixing valve in the EGR system will also be triggered to immediately return to its maximum initial position, ultimately causing the OSC calculation process to be interrupted. Summary of the Invention

[0005] This application provides a method for calculating oxygen storage capacity in catalytic converter diagnostics, which can solve at least one of the above-mentioned problems.

[0006] On one hand, embodiments of this application provide a method for calculating oxygen storage capacity in catalytic converter diagnostics. This method is applied to vehicles equipped with an EGR system, and includes:

[0007] After identifying that the EGR low flow diagnostic condition is not met, and the catalyst diagnostic condition is met, the EGR valve in the EGR system is closed, and the EGR mixing valve is returned to the maximum target position in a stepwise manner.

[0008] Determine whether the current engine speed or engine load exceeds its corresponding diagnostic range;

[0009] If the determination result is negative, the oxygen removal operation of the catalyst shall be performed;

[0010] After determining that the oxygen removal operation is completed, the oxygen storage operation of the catalyst is performed.

[0011] Update the OSC calculation results.

[0012] In some embodiments, the EGR low flow diagnostic conditions include: the EGR flow integral value is greater than the corresponding flow threshold, and the pressure ratio before and after EGR is lower than the corresponding threshold.

[0013] In some embodiments, the catalytic converter diagnostic conditions include: identifying that all catalytic converter diagnostic parameters are within the corresponding preset range, wherein the catalytic converter diagnostic parameters include at least one or more of engine speed, engine load, exhaust flow rate, catalytic converter temperature, exhaust flow rate fluctuation, and catalytic converter temperature fluctuation.

[0014] In some embodiments, the oxygen removal operation is achieved by actively enriching the mixed gas in the catalyst.

[0015] In some embodiments, when the oxygen removal amount is detected to be greater than a preset oxygen removal amount threshold, or the post-oxygenation voltage is detected to be greater than a preset post-oxygenation voltage threshold, the oxygen removal operation is determined to be completed.

[0016] In some embodiments, after identifying that the EGR low flow diagnostic condition is not met, but the catalyst diagnostic condition is met, the method further includes:

[0017] The data source for calculating the engine load was switched from the air flow meter to the intake pressure sensor.

[0018] In some embodiments, after updating the OSC calculation result, the method further includes:

[0019] The data source for calculating the engine load is restored to the air flow meter.

[0020] In some embodiments, after determining whether the current engine speed or engine load exceeds its corresponding diagnostic range, the method further includes:

[0021] When the judgment result is yes, determine whether the current engine speed or engine load exceeds its corresponding hysteresis range.

[0022] If the judgment result is negative, proceed to the step of performing oxygen removal operation on the catalyst.

[0023] Secondly, this application discloses an in-vehicle device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method described in the first aspect.

[0024] Thirdly, this application discloses a storage medium storing a program, which, when executed by a processor, is used to implement the method described in the first aspect.

[0025] The technical solution of this application has at least the following advantages:

[0026] 1. By using the failure to meet the EGR low flow diagnostic condition as one of the starting conditions for catalyst diagnostics, the interruption of EGR low flow diagnostics caused by the closure of the EGR valve during catalyst diagnostics is avoided.

[0027] 2. By switching the data source for calculating engine load from the air flow meter to the intake pressure sensor after entering the catalyst diagnostic process, the influence of disturbances to the air flow meter signal can be eliminated.

[0028] 3. By setting the hysteresis range, the engine speed and engine load can appropriately exceed the upper or lower limit during the catalytic converter diagnosis, which helps to ensure the smooth completion of the catalytic converter diagnosis. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of a low-pressure cooling EGR system provided in an exemplary embodiment of this application;

[0031] Figure 2 This is a flowchart illustrating a method for calculating oxygen storage in catalytic converter diagnostics, provided in an exemplary embodiment of this application.

[0032] Figure 3 This is a schematic diagram used to show that when the EGR is turned off during catalytic converter diagnosis, the engine speed drops to the diagnostic speed limit, eventually leading to frequent opening and closing of the EGR.

[0033] Figure 4This is a diagram used to show that when the EGR is turned off during catalytic converter diagnosis, the exhaust flow fluctuates too much, and the diagnostic process is frequently exited and entered, with the EGR frequently turning on and off.

[0034] Figure 5 This is a flowchart of a method for calculating oxygen storage in catalytic converter diagnostics, provided in an exemplary embodiment of this application. Detailed Implementation

[0035] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0039] refer to Figure 1 This illustrates a schematic diagram of a low-pressure cooled EGR system. Figure 1 As shown, the low-pressure cooled EGR system includes an air filter, compressor, EGR mixing valve, engine intake manifold, engine, engine exhaust manifold, turbocharger, catalytic converter, and exhaust gas recirculation manifold. The gas flow direction within the low-pressure cooled EGR system is as follows: Figure 1As shown by the middle arrow. An air flow meter is installed on the intake pipe at the front end of the air filter. The rear end of the air filter connects to the compressor's intake pipe, and the EGR mixing valve is located in the compressor's intake pipe. The compressor's outlet pipe connects to the engine's intake pipe, and the intercooler, throttle body, intake pressure sensor, and intake temperature sensor (not shown in the figure) are sequentially installed on the engine's intake pipe. Both the intake pressure sensor and the intake temperature sensor are located in the pressure regulating chamber of the engine's intake pipe. The outlet end of the engine's intake pipe connects to the engine. The engine's outlet pipe connects between the engine and the catalytic converter, and the turbocharger is located on the engine's outlet pipe. The inlet end of the exhaust gas recirculation (EGR) pipe connects to the outlet end of the catalytic converter, and the outlet end of the EGR pipe connects to the compressor's intake pipe. The exhaust gas recirculation pipeline is sequentially equipped with an EGR cooler for cooling high-temperature exhaust gas, an EGR valve for regulating the gas in the exhaust gas recirculation pipeline, and an EGR temperature sensor is installed on the inlet and outlet pipes of the EGR valve.

[0040] For vehicles equipped with the aforementioned low-pressure cooled EGR system, the EGR valve will be shut off once the catalytic converter diagnostic conditions are met, and EGR control will be restored after the OSC calculation is completed. However, if the catalytic converter diagnostic is triggered during the EGR low-flow diagnostic period that requires EGR to be activated, the EGR low-flow diagnostic will be interrupted.

[0041] To address the aforementioned issues, this application discloses a method for calculating oxygen storage capacity in catalytic converter diagnostics. This method can be applied to vehicles equipped with the aforementioned low-pressure cooled EGR system and is executed by an on-board controller installed in the vehicle. The on-board controller can be an electronic control unit (ECU) installed in the vehicle.

[0042] Reference Figure 2 The method may include the following:

[0043] S10: Identify whether the diagnostic conditions for low EGR flow are met.

[0044] For example, low EGR flow diagnostic conditions may include: the EGR flow integral value is greater than the corresponding flow threshold, and the pressure ratio before and after EGR is lower than the corresponding threshold.

[0045] S11: Identify whether the catalytic converter diagnostic conditions are met.

[0046] For example, catalytic converter diagnostic conditions may include: identifying that all catalytic converter diagnostic parameters are within corresponding preset ranges, wherein the catalytic converter diagnostic parameters include at least one or more of engine speed, engine load, exhaust flow rate, catalytic converter temperature, and catalytic converter temperature fluctuation. For instance, the catalytic converter diagnostic conditions may be deemed met when the engine speed is within [1500 rpm, 3000 rpm], the engine load is within [30%, 100%], the exhaust flow rate is within [40 kg / h, 150 kg / h], the catalytic converter temperature is within [500℃, 800℃], the exhaust flow rate fluctuation is within 15 kg / h, and the catalytic converter temperature fluctuation is within 20℃.

[0047] If the identification result of S10 is not satisfied, and the identification result of S11 is satisfied, proceed to S20. This application embodiment does not impose specific restrictions on the order of S10 and S11.

[0048] S20: Close the EGR valve in the EGR system and return the EGR mixing valve to the maximum target position in steps.

[0049] For example, the on-board controller can control the EGR valve in the EGR system to close and cause the EGR mixing valve to return to the large target position in steps, that is, to make the EGR mixing valve also become inactive.

[0050] S30: Determine whether the current engine speed or engine load exceeds its corresponding diagnostic range.

[0051] For example, the vehicle controller can obtain the current engine speed and engine load, and compare them with the engine speed diagnostic range and engine load diagnostic range respectively, so as to determine whether the engine speed and engine load exceed their respective diagnostic ranges.

[0052] If the judgment result is negative, proceed to S40.

[0053] S40: Perform oxygen removal operation on the catalyst.

[0054] For example, the on-board controller can control the oxygen removal operation of the catalytic converter to remove residual oxygen from the catalytic converter.

[0055] In some embodiments, oxygen removal can be achieved by actively enriching the gas mixture in the catalytic converter. That is, under the control of the onboard controller, a rich gas mixture can be injected into the catalytic converter to remove residual oxygen.

[0056] In some embodiments, the on-board controller can determine that the oxygen purification operation is complete when the current oxygen purification level is greater than a preset oxygen purification level threshold, or when the post-oxygen voltage is greater than a preset post-oxygen voltage threshold. The oxygen purification level and post-oxygen voltage are obtained through a catalytic converter aging monitoring system in the vehicle, which is prior art and will not be described in detail here.

[0057] S50: After determining that the oxygen removal operation is completed, perform the oxygen storage operation on the catalyst.

[0058] For example, after determining that the oxygen removal operation is completed, the vehicle controller can control the oxygen storage operation of the catalytic converter. This oxygen storage operation can be achieved by using an active mixer to reduce the oxygen content of the catalytic converter; that is, by using a lean mixture to oxygenate the catalytic converter.

[0059] S60: Update OSC calculation results.

[0060] For example, the calculation of oxygen storage capacity (OSC) is usually performed during the dilution process after the catalyst is purged of oxygen, i.e., during the execution of S50. The formula for calculating oxygen storage capacity (OSC) is as follows:

[0061]

[0062] Where 0.23 is the mass percentage of oxygen in the air, t1 and t2 are the start and end times of the leaning process, respectively, λ is the air-fuel ratio, and ml_w refers to the mass flow rate of the exhaust gas, i.e., the exhaust flow rate.

[0063] After the calculation is completed, the on-board controller updates the OSC calculation results and resumes normal control of the low-pressure cooling EGR system.

[0064] By adopting the above technical solution, the failure to meet the EGR low flow diagnostic condition is used as one of the starting conditions for catalyst diagnosis, thus avoiding the interruption of EGR low flow diagnosis caused by the EGR valve being closed during catalyst diagnosis.

[0065] refer to Figure 1 When EGR is closed, the EGR mixing valve returns from its target position (operating position) to its initial position, i.e., the maximum target position. Simultaneously, due to the reduced exhaust gas flow caused by EGR closure, the amount of fresh air needs to be reduced to ensure load stability, and the throttle body also closes less. Because the EGR mixing valve is located downstream of the air filter and the air flow meter is located upstream of the air filter, their proximity means that a rapid action of the EGR mixing valve can disturb the air flow meter signal, leading to greater fluctuations in engine load. These engine load fluctuations cause fluctuations in the air-fuel ratio, which, combined with the reduced throttle opening, results in fluctuations in engine speed. The specific effects can be described as follows: Figure 3 and Figure 4As shown, during catalytic converter diagnostics, closing the EGR valve and triggering the EGR mixing valve to immediately return to its maximum initial position causes fluctuations in engine speed, engine load, or exhaust flow. This interrupts the OSC (Oxygen Storage Capacity) calculation process due to deviation from the diagnostic physical range, resulting in no calculation results. After the interruption, the EGR valve opens normally, and engine speed and load return to a stable state, allowing for quick diagnostic entry. Re-entry into diagnostics again closes the EGR valve, leading to further fluctuations in engine speed and load, causing diagnostic interruptions once more. Ultimately, this cycle of frequent EGR valve opening and closing makes catalytic converter diagnostics difficult to complete. Hybrid vehicles operate under more stable conditions and more easily meet diagnostic conditions such as engine speed and load; therefore, this problem is more likely to occur in hybrid vehicles.

[0066] To address the above problems, in some embodiments, reference is made to... Figure 5 Following S10 above, the following processing may also be included:

[0067] S21: Switch the data source for calculating engine load from the air flow meter to the intake pressure sensor.

[0068] For example, since the intake pressure sensor is located on the pressure regulating chamber of the engine intake manifold, it is less affected by the operation of the EGR mixing valve and the calculated load fluctuation is also smaller. Therefore, the data source for calculating the engine load can be switched from the air flow meter to the intake pressure sensor. In the subsequent S30, the vehicle controller processes the data collected by the intake pressure sensor to obtain the engine load, eliminating the influence caused by the disturbance of the air flow meter signal.

[0069] Furthermore, after updating the OSC calculation results, the data source for calculating engine load can be restored to the air flow meter.

[0070] Optionally, in some embodiments, the following may also be included after S30 described above:

[0071] When the judgment result is yes, determine whether the current engine speed or engine load exceeds its corresponding hysteresis range.

[0072] In addition to pre-stored engine speed diagnostic range and engine load diagnostic range, the vehicle controller also pre-stores engine speed hysteresis range and engine load hysteresis range. Taking the engine speed diagnostic range as an example, if the engine speed diagnostic range is [A,B], then the engine speed hysteresis range can be [A1,A] and [B,B1].

[0073] For example, after identifying that at least one of the current engine speed or engine load exceeds the corresponding diagnostic range, the vehicle controller can further determine whether the current engine speed or engine load exceeds its respective hysteresis range.

[0074] If the judgment result is negative, proceed to S40.

[0075] For example, after the vehicle controller detects that the current engine speed and engine load are within the corresponding hysteresis range, it will also enter S40. By setting the hysteresis range, the engine speed and engine load can appropriately exceed the upper or lower limit during catalytic converter diagnosis, which helps to ensure the smooth completion of catalytic converter diagnosis.

[0076] Optionally, this application also provides an on-board device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the oxygen storage calculation method in catalytic converter diagnosis provided in the above-described method embodiments.

[0077] Optionally, this application also provides a computer-readable storage medium storing at least one instruction, at least one program, a code set, or an instruction set, wherein the at least one instruction, the at least one program, the code set, or the instruction set is loaded and executed by the processor to implement the oxygen storage calculation method in catalytic converter diagnostics provided in the above-described method embodiments.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for calculating oxygen storage capacity in catalytic converter diagnostics, characterized in that, The method is applied to a vehicle equipped with an EGR system, and the method includes: After identifying that the EGR low flow diagnostic condition is not met, and the catalyst diagnostic condition is met, the EGR valve in the EGR system is closed, and the EGR mixing valve is returned to the maximum target position in a stepwise manner. Determine whether the current engine speed or engine load exceeds its corresponding diagnostic range; If the determination result is negative, the oxygen removal operation of the catalyst shall be performed; After determining that the oxygen removal operation is completed, the oxygen storage operation of the catalyst is performed. Update OSC calculation results; The EGR low flow diagnostic conditions include: the EGR flow integral value is greater than the corresponding flow threshold, and the pressure ratio before EGR is lower than the corresponding threshold; the catalyst diagnostic conditions include: the catalyst diagnostic parameters are all identified as being within the corresponding preset range.

2. The method according to claim 1, characterized in that, The catalytic converter diagnostic parameters include at least one or more of the following: engine speed, engine load, exhaust flow rate, catalytic converter temperature, exhaust flow rate fluctuation, and catalytic converter temperature fluctuation.

3. The method according to claim 1, characterized in that, The oxygen removal operation is achieved by actively enriching the mixed gas in the catalyst.

4. The method according to claim 1, characterized in that, When the oxygen removal amount is found to be greater than the preset oxygen removal amount threshold, or the post-oxygenation voltage is greater than the preset post-oxygenation voltage threshold, the oxygen removal operation is determined to be complete.

5. The method according to claim 1, characterized in that, After identifying that the EGR low flow diagnostic condition is not met, but the catalyst diagnostic condition is met, the method further includes: The data source for calculating the engine load was switched from the air flow meter to the intake pressure sensor.

6. The method according to claim 5, characterized in that, Following the update of the OSC calculation results, the following is also included: The data source for calculating the engine load is restored to the air flow meter.

7. The method according to claim 1, characterized in that, After determining whether the current engine speed or engine load exceeds its corresponding diagnostic range, the method further includes: When the judgment result is yes, determine whether the current engine speed or engine load exceeds its corresponding hysteresis range. If the judgment result is negative, proceed to the step of performing oxygen removal operation on the catalyst.

8. An in-vehicle device, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 7.

9. A storage medium storing a program that, when executed by a processor, implements the method as described in any one of claims 1 to 7.

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