A heating control system and method for a catalytic converter

Abstract

The application discloses a heating control system and method of a catalytic converter; the intake air flow into the engine is calculated according to the intake manifold pressure; the heating time length of the catalytic converter is determined according to the intake air flow into the engine, and the catalytic converter is heated according to the heating time length. The application judges the condition of entering the catalytic converter heating during cold start, calculates the engine intake air quantity during each catalytic converter heating stage, calculates the heating time of the catalytic converter after each engine start according to the engine intake air quantity and the catalytic converter deterioration coefficient, makes the catalytic converter quickly reach the effective conversion temperature, effectively reduces the emission and fuel consumption of the catalytic converter during the heating stage in the whole vehicle service period, and guarantees the time control of the catalytic converter heating after each engine start. The application considers the aging of the catalytic converter in the whole vehicle service period, makes the catalytic converter quickly reach the effective conversion temperature, and effectively reduces the emission and fuel consumption of the catalytic converter during the heating stage in the whole vehicle service period.

Description

Technical Field

[0001] This invention belongs to the field of automotive engine control technology, specifically relating to a heating control system and method for a catalytic converter. Background Technology

[0002] To meet the China VI B emission standards, traditional internal combustion engine vehicles are designed with dedicated catalytic converters. These converters only achieve optimal conversion efficiency after exceeding their effective temperature (500℃). Because the catalytic converter temperature does not reach its effective temperature during the initial engine start-up, pollutant emissions constitute a significant portion of total emissions. Therefore, controlling catalytic converter heating is an effective means of reducing pollutant emissions during the start-up phase.

[0003] Among the currently available information, the invention patent with application number "CN202111025602.9" entitled "Method and System for Rapid Ignition Control of Automobile Engine Catalyst" describes a method for rapid ignition control of an automobile engine catalyst. However, this method does not consider the aging effect of the catalyst throughout the entire vehicle's lifespan. Throughout the vehicle's lifespan, as the catalyst ages, its oxygen storage capacity (OSC) continuously decreases, leading to a decline in its ability to treat emission pollutants. Summary of the Invention

[0004] In order to effectively reduce the increase in pollutant emissions caused by catalyst aging, this invention designs a catalyst heating control system and method, which calculates the catalyst heating time based on the engine intake air volume and the catalyst oxygen storage capacity.

[0005] A catalytic converter heating control system for achieving one of the objectives of the present invention includes: a catalytic converter heating intake gas flow calculation module and a first catalytic converter heating control module;

[0006] The catalyst intake flow calculation module is used to calculate the intake flow rate into the engine based on the intake manifold pressure.

[0007] The first catalyst heating control module is used to determine the heating duration of the catalyst based on the intake air flow rate into the engine, and heat the catalyst according to this heating duration.

[0008] A method for controlling catalyst heating to achieve the second objective of this invention includes the following steps:

[0009] Calculate the intake airflow into the engine based on the intake manifold pressure;

[0010] The heating time of the catalytic converter is determined based on the intake air flow rate into the engine, and the catalytic converter is heated according to this heating time.

[0011] Beneficial effects:

[0012] This invention determines the conditions for catalytic converter heating during cold engine starts, calculates the engine intake air volume during each catalytic converter heating stage, and calculates the catalytic converter heating time after each engine start based on the engine intake air volume and the catalytic converter degradation coefficient. This allows the catalytic converter to quickly reach its effective conversion temperature, effectively reducing emissions and fuel consumption during the catalytic converter heating stage throughout the vehicle's lifespan. It also ensures controlled catalytic converter heating time after each engine start. This heating method takes into account catalytic converter aging throughout the vehicle's lifespan, enabling the catalytic converter to quickly reach its effective conversion temperature while effectively reducing emissions and fuel consumption during the catalytic converter heating stage throughout the vehicle's lifespan. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the catalyst heating time control method in the embodiments of the present invention;

[0014] Figure 2 This is a diagram showing the arrangement of the pre / post oxygen sensors and catalyst in the embodiments described in this invention. Detailed Implementation

[0015] The following detailed embodiments are provided to explain the technical solutions of the claims of this invention, so that those skilled in the art can understand the claims. The scope of protection of this invention is not limited to the following specific embodiments. Any modifications made by those skilled in the art that incorporate the technical solutions of the claims but differ from the following detailed embodiments are also within the scope of protection of this invention.

[0016] In the description of this invention, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0017] This application embodiment includes a catalytic converter heating control system, including a catalytic converter heating intake flow calculation module and a first catalytic converter heating control module;

[0018] The catalytic converter intake airflow calculation module is used to calculate the intake airflow into the engine based on the intake manifold pressure.

[0019] The first catalytic converter heating control module is used to determine the heating duration of the catalytic converter based on the intake air flow rate into the engine, and to heat the catalytic converter according to this heating duration.

[0020] The aforementioned heating control system also includes a degradation coefficient (DC) calculation module, used to determine the degradation coefficient (DC) of the catalytic converter based on its current oxygen storage capacity, current engine airflow, and catalytic converter temperature. The degradation coefficient (DC) is used to determine the heating duration of the catalytic converter. The calculation method for the degradation coefficient (DC) includes:

[0021] (1) Calculate the current oxygen storage capacity (Mosc) of the catalyst.

[0022] like Figure 2 As shown, an oxygen sensor is installed before and after the catalytic converter. The front oxygen sensor is a linear oxygen sensor for real-time adjustment, while the rear oxygen sensor is a switch-type oxygen sensor to detect the oxygen content in the exhaust and provide feedback for adjustment. A voltage of less than 0.45V in the rear oxygen sensor indicates a decrease in the oxygen content in the catalytic converter.

[0023] During vehicle operation, under certain operating conditions (front oxygen / rear oxygen exceeds dew point and participates in fuel injection control; and engine load is stable), the engine control unit (ECU) performs catalytic converter diagnosis. During the catalytic converter diagnosis phase, the engine fuel injection will undergo enrichment-leaning-enrichment control. In this process, based on the time difference between the enrichment / leaning signal of the front oxygen sensor and the voltage change of the rear oxygen sensor, as well as the engine air flow, the current oxygen storage capacity Mosc of the catalytic converter is calculated.

[0024] The unit is mg;

[0025] In the formula:

[0026] t1 and t2: These are the start and end times of engine fuel injection thinning, respectively, in seconds.

[0027] λ: Air-fuel ratio;

[0028] ml_w: Mass flow rate of exhaust gas, i.e., exhaust flow rate, in kg / h;

[0029] 0.277778: The coefficient for converting kg / h to g / s;

[0030] 1000: the coefficient for converting g to mg;

[0031] 0.23: The percentage of oxygen by mass in the air;

[0032] (2) Calculate the degradation factor DC of the catalyst based on the current oxygen storage capacity Mosc and the calibrated oxygen storage capacity of the fresh / aged catalyst. The calculation method includes:

[0033] (2.1) Under stable engine operating conditions, obtain the engine air flow rate and catalyst temperature at this time, and obtain the oxygen storage value Mosc_new of the fresh catalyst and the oxygen storage value Mosc_aged of the current aged catalyst from Table 1 and Table 2 respectively based on the air flow rate and temperature.

[0034] The critical value B1 for the degradation coefficient of fresh / aged catalysts is determined, i.e.:

[0035] The degradation calibration factor when the current oxygen storage capacity Mosc of the calibrator is equal to the oxygen storage value Mosc_aged of the aged catalytic converter is B1.

[0036] (2.2) Calculate the deterioration coefficient DC

[0037] When Mosc > Mosc_aged, the calculation method of the deterioration coefficient DC includes:

[0038] DC = (Mosc - Mosc_aged) * (1 - B1) / (Mosc_new - Mosc_aged) + B1

[0039] In the formula, Mosc_new represents the oxygen storage value of a fresh catalytic converter;

[0040] When Mosc < Mosc_aged, the calculation method of the deterioration coefficient DC includes:

[0041] DC = (Mosc / Mosc_aged) * B1

[0042] Store the oxygen storage capacity Mosc and the deterioration coefficient DC of the catalytic converter in the system.

[0043]

[0044] Table 1 Oxygen Storage Capacity Table of Fresh Catalytic Converters

[0045]

[0046] Table 2 Oxygen Storage Capacity Table of Aged Catalytic Converters

[0047] In the above heating control system, there is also a deterioration duration coefficient calculation module, which is used to determine the deterioration duration coefficient C1 according to the catalytic converter deterioration coefficient DC and the temperature at the start of the engine. The deterioration duration coefficient C1 is used to determine the heating duration of the catalytic converter. The determination method of the deterioration duration coefficient C1 includes:

[0048] (1) Set the initial deterioration coefficient DC to 1. During the use of the catalytic converter, it will age continuously, and the deterioration coefficient will also decrease continuously from 1;

[0049] (2) Calculate the deterioration coefficient DC according to the one calculated after meeting the catalytic converter heating condition during the previous operation each time the engine starts;

[0050] (3) Determine the catalytic converter heating duration coefficient C1 through the deterioration coefficient shown in Table 3 and the temperature at the start of the engine.

[0051]

[0052] Table 3 Catalytic Converter Heating Duration Coefficient Table

[0053] The aforementioned heating control system also includes a catalytic converter heating condition determination module, which determines whether to heat the catalytic converter based on the engine start-up water temperature and the interval since the last catalytic converter heating was completed. Heating will only proceed if all conditions are met. In this embodiment, the determination conditions include:

[0054] (1) Determine if the engine start is complete. The determination condition is: the engine start is complete when the engine speed exceeds 800 rpm.

[0055] (2) The engine coolant temperature must be lower than the set value (80℃) when starting;

[0056] (3) The time elapsed since the last catalyst heating was completed must be greater than the set time (600s).

[0057] The heating control system described above also includes a second catalytic converter heating control module, which, when all judgment conditions are met, determines whether the catalytic converter should exit the heating mode based on the engine temperature or the catalytic converter model temperature. When the engine temperature is greater than the set protection temperature or the catalytic converter model temperature is greater than the set temperature, the catalytic converter exits the heating mode. The catalytic converter model temperature is a calibrated temperature obtained based on the actual temperature of the catalytic converter.

[0058] The aforementioned heating control system also includes an engine setting module, used to set the engine accordingly before heating the catalytic converter. In this embodiment, the engine performs the following operations in catalytic converter heating mode:

[0059] (1) Set the engine operating mode according to the engine coolant temperature.

[0060] When the temperature is below 0 degrees, it is set to throttle adjustment mode; when the temperature is 0 degrees and above, it is set to throttle full open mode. When the throttle is fully open, the engine intake is more complete and the catalytic converter can be heated faster.

[0061] (2) Increase the engine idle speed to make the catalyst heat up quickly and reduce the heating time; for example, the normal engine idle speed is 800 rpm, and the engine speed is set to 1400 rpm during the catalyst heating stage.

[0062] (3) Two fuel injections are performed to inject more fuel. Two injections are beneficial for fuel stratification, improve combustion, and reduce emissions. It should be noted that under normal circumstances, it is a single injection. The two injections here correspond to a single fuel injection.

[0063] (4) Increase the engine torque reserve during the catalytic converter heating stage to increase the engine intake air volume and retard the ignition angle;

[0064] (5) The ignition angle is delayed according to the ignition efficiency and emission results, which delays the combustion of the engine. Some of the unburned mixture will enter the catalyst for combustion, which will rapidly increase the temperature of the catalyst.

[0065] In the aforementioned heating control system, the method for determining the catalytic converter heating time based on the engine's intake air flow includes:

[0066] (1) Calculate the intake air flow rate M into the engine based on the intake manifold pressure:

[0067] M = (P EV -P)*F+M1*F1+M2*F1

[0068] In the formula:

[0069] P EV Intake manifold pressure, obtained through a pressure sensor;

[0070] P: Atmospheric pressure after altitude correction;

[0071] F: The set temperature coefficient;

[0072] M1: First intake mass correction load value, the correction load calculated by VVL lift;

[0073] F1: Intake mass coefficient, the ratio of the absolute pressure of the engine intake air to its relative pressure;

[0074] M2: Second intake air mass correction load value, a correction load value obtained based on engine speed, boost pressure coefficient, and intake air temperature and pressure.

[0075] The value of the intake airflow integral M3 is calculated using the following formula.

[0076]

[0077] In the formula, M is the intake air flow rate (kg / h), k is the set stability coefficient, which is set to 1 in this embodiment; t is the engine running time;

[0078] Calculate the value of N using the following formula:

[0079]

[0080] When N is greater than the calibrated value C2 (e.g., 2), the catalytic converter heating is stopped.

[0081] The set value C2 is set according to the actual situation and calibrated by the catalytic converter heating time and WLTC cycle emission results.

[0082] Once the catalytic converter heating activation conditions are met, the catalytic converter heating is activated. The catalytic converter is heated by increasing the idle speed, retarding the ignition angle, and using secondary fuel injection. At the same time, the catalytic converter heating duration is calculated. Once the calculation is completed and it is determined that the conditions for catalytic converter heating to be deactivated are met, the catalytic converter heating mode is deactivated.

[0083] The above method for calculating catalytic converter heating time, in addition to considering special conditions such as engine temperature protection, calculates the catalytic converter heating time based on the air flow integral and the catalytic converter heating time coefficient. This allows the heating time to be calculated according to the oxygen storage capacity of the catalytic converter and different intake air volumes of the engine throughout the vehicle's lifespan, thus corresponding to different heating times. This has good benefits for vehicle emissions and fuel consumption during cold starts.

[0084] The aforementioned heating control system also includes a second catalytic converter heating control module, which is used to determine whether the catalytic converter should exit the heating mode based on the engine temperature or the catalytic converter model temperature. When the engine temperature is higher than the set protection temperature (110°C) or the catalytic converter model temperature is higher than the set temperature (570°C), the catalytic converter will exit the heating mode to avoid damage to the engine or catalytic converter due to excessive temperature. The catalytic converter model temperature is a calibrated temperature obtained based on the actual temperature of the catalytic converter.

[0085] This application also includes a method for controlling the heating of a catalyst, comprising the following steps:

[0086] Calculate the intake airflow into the engine based on the intake manifold pressure;

[0087] The heating time of the catalytic converter is determined based on the intake air flow rate into the engine, and the catalytic converter is heated according to this heating time.

[0088] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A heating control system for a catalytic converter, characterized in that, Comprising: A catalytic converter heating intake air flow calculation module and a first catalytic converter heating control module; The catalytic converter heating intake air flow calculation module is used to calculate the intake air flow entering the engine according to the intake manifold pressure; The first catalytic converter heating control module is used to determine the heating duration of the catalytic converter according to the intake air flow entering the engine, and heat the catalytic converter according to this heating duration; It further includes a deterioration coefficient DC calculation module, which is used to determine the deterioration coefficient DC of the catalytic converter according to the current oxygen storage capacity of the catalytic converter, the current intake air flow of the engine, and the temperature of the catalytic converter. The deterioration coefficient DC is used to determine the heating duration of the catalytic converter; The calculation method of the deterioration coefficient DC includes: When Mosc > Mosc_aged: DC = (Mosc - Mosc_aged) * (1 - B1) / (Mosc_new - Mosc_aged) + B1 When Mosc < Mosc_aged: DC = (Mosc / Mosc_aged) * B1 In the formula: Mosc: represents the current oxygen storage capacity of the catalytic converter; Mosc_aged: represents the oxygen storage value of the current aged catalytic converter, which is calibrated according to the intake air flow of the engine and the temperature of the catalytic converter; Mosc_new represents the oxygen storage value of the fresh catalytic converter, which is calibrated according to the intake air flow of the engine and the temperature of the catalytic converter; B1: deterioration calibration coefficient.

2. The heating control system for the catalyst as described in claim 1, characterized in that, It includes a deterioration duration coefficient calculation module, which is used to determine the deterioration duration coefficient C1 according to the catalytic converter deterioration coefficient DC and the temperature at engine startup. The deterioration duration coefficient C1 is used to determine the heating duration of the catalytic converter.

3. The heating control system for the catalyst as described in claim 2, characterized in that, The method for determining the heating duration of the catalytic converter includes: Calculate the value N according to the following formula: ； In the formula: M3 is the integral value of the intake air flow entering the engine; C1 is the deterioration duration coefficient; When N is greater than the calibration value C2, the catalytic converter heating exits.

4. The heating control system for the catalyst as described in claim 1, characterized in that, It further includes a second catalytic converter heating control module, which is used to determine whether the catalytic converter exits the heating mode according to the engine temperature or the catalytic converter model temperature; when the engine temperature is greater than the set protection temperature or the catalytic converter model temperature is greater than the set temperature, the catalytic converter exits the heating mode; the catalytic converter model temperature is the calibrated temperature obtained according to the actual temperature of the catalytic converter.

5. The heating control system for the catalyst as described in claim 1, characterized in that, It further includes a catalytic converter heating condition judgment module, which is used to judge whether to heat the catalytic converter according to the water temperature at engine startup and the interval time since the last catalytic converter heating completion.

6. The heating control system for the catalyst as described in claim 1, characterized in that, It further includes an engine setting module, which is used to perform corresponding settings on the engine before heating the catalytic converter. The corresponding settings include: increasing the engine idle speed and / or increasing the fuel injection amount and / or increasing the intake air flow entering the engine during the catalytic converter heating stage and / or delaying the engine ignition.

7. A method for heating the catalyst in a heating control system for the catalyst as described in claim 1, characterized in that, Including the following steps: Calculate the intake air flow entering the engine according to the intake manifold pressure; Determine the heating duration of the catalytic converter according to the intake air flow entering the engine, and heat the catalytic converter according to this heating duration.

8. The heating control method for the catalyst as described in claim 7, characterized in that, The calculation method of the intake air flow entering the engine includes: M=(P EV -P)*F+M1*F1+M2*F1 In the formula: M: the intake air flow entering the engine; P EV Intake manifold pressure; P: the atmospheric pressure corrected for altitude; F: the set temperature coefficient; M1: First intake air mass correction load value; F1: Intake mass coefficient; M2: Second intake mass correction load value.

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