CN108644024B - Control method of EGR valve of diesel engine - Google Patents

Control method of EGR valve of diesel engine Download PDF

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Publication number
CN108644024B
CN108644024B CN201810392829.9A CN201810392829A CN108644024B CN 108644024 B CN108644024 B CN 108644024B CN 201810392829 A CN201810392829 A CN 201810392829A CN 108644024 B CN108644024 B CN 108644024B
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egr valve
learning
value
self
ecu
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CN108644024A (en
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张焕岩
吴磊
杨越
李�杰
肖海云
蔡亚
程剑峰
葛娟娟
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Anhui Jianghuai Automobile Group Corp
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Anhui Jianghuai Automobile Group Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/0077—Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2441—Methods of calibrating or learning characterised by the learning conditions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/49—Detecting, diagnosing or indicating an abnormal function of the EGR system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/50—Arrangements or methods for preventing or reducing deposits, corrosion or wear caused by impurities

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust-Gas Circulating Devices (AREA)

Abstract

The invention provides a control method of an EGR valve of a diesel engine, which comprises the following steps: after an ECU of the diesel engine is powered on, judging whether the EGR valve is subjected to first self-learning, and if not, judging whether the EGR valve meets the condition of activating the first self-learning; in the set time, if the ignition key is in an ON gear and the stepping times of the accelerator pedal reach the set times, activating the first self-learning; when an ignition key is in an OFF gear, if the EGR valve meets a self-cleaning condition, self-cleaning is carried out, otherwise, the self-cleaning is finished; after the EGR valve is self-cleaned, the EGR valve is subjected to conventional self-learning. The invention can improve the control precision of the EGR valve and increase the working reliability of the EGR valve.

Description

Control method of EGR valve of diesel engine
Technical Field
The invention relates to the technical field of engine control, in particular to a control method of an EGR valve of a diesel engine.
Background
Egr (exhaust Gas recirculation) is exhaust Gas recirculation, i.e. exhaust Gas exhausted by an engine is reintroduced into an air inlet pipe to be mixed with fresh air and then enters a combustion chamber for combustion. An EGR valve is mounted on the engine for controlling the amount of recirculated exhaust gas entering the intake system. With the increasing upgrading of emission legislation, EGR valves require precise control of the amount of exhaust gas entering the engine. Specifically, the opening degree of the EGR valve is adjusted by an ecu (electronic Control unit), thereby accurately controlling the amount of exhaust gas entering the engine. Therefore, the temperature of the combustion chamber is reduced by the participation of the exhaust gas in the combustion, the combustion environment is improved, the load of the engine is reduced, and the emission of NOx is effectively reduced.
The EGR valve is a key component, and the reliability of its operating performance directly restricts the accuracy of the exhaust gas amount control. Most EGR valves are driven by direct current motors, position sensors are integrated in the EGR valves, and the output opening degree of the position sensors is in a linear relation with feedback voltage. Because the EGR valve is arranged in an exhaust gas environment, in the long-term use process, on one hand, the high-temperature exhaust gas influences the output of the characteristics of the sensor in the EGR valve, and on the other hand, the zero point of the EGR valve drifts along with the passage of time due to the fact that a large amount of carbon deposit and coke are attached to the outer surface of the valve plate, the valve plate is continuously worn and the like. Therefore, it is necessary to newly detect and record the voltage value fed back when the EGR valve is fully opened or fully closed by the ECU, and to newly set the characteristic curve of the sensor output. The process of re-establishing the sensor output characteristic curve is called EGR valve self-learning, whether the EGR valve self-learning is successful or not is directly related to the control precision of the EGR valve, and therefore the emission control of the engine is influenced.
Disclosure of Invention
The invention provides a control method of an EGR valve of a diesel engine, which solves the problem that the control precision of the EGR valve is reduced because the zero point of the EGR valve is influenced by carbon deposition and high-temperature waste gas to drift in the use process of the existing EGR valve of the diesel engine, and can improve the control precision of the EGR valve and increase the working reliability of the EGR valve.
In order to achieve the above purpose, the invention provides the following technical scheme:
a method of controlling an EGR valve of a diesel engine, comprising:
after an ECU of the diesel engine is powered on, judging whether the EGR valve is subjected to first self-learning, and if not, judging whether the EGR valve meets the condition of activating the first self-learning;
in the set time, if the ignition key is in an ON gear and the stepping times of the accelerator pedal reach the set times, activating the first self-learning;
when an ignition key is in an OFF gear, if the EGR valve meets a self-cleaning condition, self-cleaning is carried out, otherwise, the self-cleaning is finished;
after the EGR valve is self-cleaned, the EGR valve is subjected to conventional self-learning.
Preferably, the first self-learning comprises:
the ECU sends PWM waves to control the opening degree of the EGR valve;
when the ECU activates first self-learning, the ECU adjusts the duty ratio of the PWM wave at a first rate, and the duty ratio is rapidly reduced from the first duty ratio to a second duty ratio so that the EGR valve is in a fully-closed state and continues for a certain time, wherein the second duty ratio is a negative value;
acquiring the full-closed position of the EGR valve for multiple times according to the first interval time, and calculating to obtain the average value of signals of the full-closed position;
and judging whether the difference value between the average value of the all-closed position signals and a zero position signal value preset in the ECU is smaller than a preset threshold value, if not, taking the average value of the all-closed position signals as a zero position signal value for the first learning of the EGR valve, and writing the zero position signal value into the ECU.
Preferably, the first self-learning further comprises:
the ECU controls the PWM wave to gradually rise from a second duty ratio to a third duty ratio so that the EGR valve is in a full-open state and continues for a certain time, wherein the third duty ratio is a positive value;
acquiring the full-open position of the EGR valve for multiple times according to the first interval time, and calculating to obtain a mean value of signals of the full-open position;
and judging whether the difference value between the full-open position signal average value and a full-open position signal value preset in the ECU is smaller than a preset threshold value, if not, taking the full-open position signal average value as a full-open position signal value for the first learning of the EGR valve, and writing the full-open position signal value into the ECU.
Preferably, the EGR valve meeting the activated self-cleaning condition comprises:
the ignition key is in an OFF gear, the power supply voltage of the ECU is more than 10V, and the air inlet temperature of the diesel engine is in a range of minus 7-110 ℃.
Preferably, the EGR valve self-cleaning comprises:
when the ECU activates self-cleaning, the ECU sends PWM waves with different duty ratios to control the EGR valve to carry out closing action or starting action so as to lead the EGR valve to generate vibration until the self-cleaning process is finished.
Preferably, the ECU sending PWM waves of different duty ratios to control the EGR valve to close or open includes:
the ECU sends a PWM wave with a fourth duty ratio to enable the EGR valve to finish the starting action of opening to 95% of opening degree, and after the starting action lasts for a certain time, the ECU sends a PWM wave with a fifth duty ratio to enable the EGR valve to finish the closing action of closing to 5% of opening degree, wherein the fourth duty ratio and the fifth duty ratio are opposite in phase;
and repeating the opening action and the closing action within the set time until the set times is reached.
Preferably, the conventional self-learning of the EGR valve comprises:
after the EGR valve is automatically cleaned, the ECU sends the PWM wave with the second duty ratio to enable the EGR valve to be in a full-closed state and to last for a certain time;
and acquiring the full-closed position of the EGR valve for multiple times according to the first interval time, and taking the average value of the full-closed position signals obtained through calculation as a bottom dead center learning value.
Preferably, the conventional self-learning of the EGR valve further comprises:
judging whether the difference value between the bottom dead center learning value and the first learning zero position signal value is smaller than a preset threshold value, and if not, reporting a fault;
judging whether the difference value between the bottom dead center learning value and the last bottom dead center learning value is smaller than a preset threshold value, and if not, reporting a fault; if so, the bottom dead center learned value is written in the ECU.
Preferably, the conventional self-learning of the EGR valve further comprises:
after the learning of the bottom dead center is finished, the ECU sends the PWM wave with the third duty ratio to enable the EGR valve to be in a full-open state and to last for a certain time;
and acquiring the full-open position of the EGR valve for multiple times according to the first interval time, and taking the calculated average value of the full-open position signal as a top dead center learning value.
Preferably, the conventional self-learning of the EGR valve further comprises:
judging whether the difference value between the upper dead point learning value and the first-time learning full-open position signal value is smaller than a preset threshold value, and if not, reporting a fault;
and judging whether the difference value between the top dead center learning value and the last top dead center learning value is smaller than a preset threshold value, if not, reporting a fault, and if so, writing the top dead center learning value into the ECU.
The invention provides a control method of an EGR valve of a diesel engine, which is characterized in that self-learning is carried out for the first time by controlling the EGR valve during power-on, self-cleaning and conventional self-learning are carried out on the EGR valve during power-off, the zero positions of the full-closed position and the full-open position of the EGR valve are kept accurate, the problem that the control precision of the EGR valve is reduced because the zero of the EGR valve is influenced by carbon deposition and high-temperature waste gas to drift in the use process of the existing EGR valve of the diesel engine is solved, the control precision of the EGR valve can be improved, and the working reliability of.
Drawings
In order to more clearly describe the specific embodiments of the present invention, the drawings to be used in the embodiments will be briefly described below.
FIG. 1: the invention provides a flow chart of a control method of an EGR valve of a diesel engine;
FIG. 2: is a first self-learning flow chart provided by the embodiment of the invention;
FIG. 3: is a self-cleaning flow chart provided by the embodiment of the invention;
FIG. 4: is a conventional self-learning flow chart provided by embodiments of the present invention.
Detailed Description
In order to make the technical field of the invention better understand the scheme of the embodiment of the invention, the embodiment of the invention is further described in detail with reference to the drawings and the implementation mode.
The method aims to solve the problems that an EGR valve of the current engine is easy to cause zero drift and control accuracy reduction due to carbon deposition and high-temperature waste gas. The invention provides a control method of an EGR valve of a diesel engine, which is characterized in that self-learning is carried out for the first time by controlling the EGR valve during power-on, self-cleaning and conventional self-learning are carried out on the EGR valve during power-off, the zero positions of the fully-closed position and the fully-open position of the EGR valve are kept accurate, the problem that the control precision of the EGR valve is reduced due to drift of the zero point of the EGR valve caused by carbon deposition and high-temperature waste gas in the use process of the existing EGR valve of the diesel engine is solved, the self-learning precision of the EGR valve can be improved, and the working reliability of.
As shown in fig. 1, a flow chart of a control method for an EGR valve of a diesel engine provided by the present invention includes the following steps:
s1: after an ECU of the diesel engine is powered on, judging whether the EGR valve is subjected to first self-learning, and if not, judging whether the EGR valve meets the condition of activating the first self-learning;
s2: in the set time, if the ignition key is in an ON gear and the stepping times of the accelerator pedal reach the set times, activating the first self-learning;
s3: when an ignition key is in an OFF gear, if the EGR valve meets a self-cleaning condition, self-cleaning is carried out, otherwise, the self-cleaning is finished;
s4: after the EGR valve is self-cleaned, the EGR valve is subjected to conventional self-learning.
Specifically, after the ECU of the diesel engine is powered on, since the default value of the EGR valve is preset in the ECU, the value is used as factory equipment. As shown in fig. 2, the first self-learning judgment is performed, and if the ignition key is in the ON gear after the ECU is powered ON and the accelerator pedal stepping frequency reaches the set frequency within the set time, the first self-learning condition is activated. The EGR valve performs self-learning of a fully closed position and self-learning of a fully open position. As shown in fig. 3, when the ignition key is in the OFF range, the self-cleaning determination is performed, and when the self-cleaning condition is satisfied, the EGR valve is opened and closed a plurality of times to vibrate the EGR valve, thereby realizing self-cleaning. As shown in FIG. 4, after self-cleaning, a conventional self-learning determination is made, and full-closed position self-learning and full-open position self-learning of the EGR valve are started. It should be noted that the EGR valve may be opened and closed by forward and reverse rotation of the motor. Through the self-cleaning and self-learning operations of the EGR valve, the problem that the EGR valve is inaccurate in position due to carbon deposition, manufacturing deviation of different valves, position deviation of the EGR valve in the using process and other factors, calculation deviation of the EGR rate is caused, and influences are generated on combustion and emission of an engine is effectively solved.
The first self-learning comprises:
s21: the ECU sends PWM waves to control the opening degree of the EGR valve;
s22: when the ECU activates first self-learning, the ECU adjusts the duty ratio of the PWM wave at a first rate, and the duty ratio is rapidly reduced from the first duty ratio to a second duty ratio so that the EGR valve is in a fully-closed state and continues for a certain time, wherein the second duty ratio is a negative value;
s23: acquiring the full-closed position of the EGR valve for multiple times according to the first interval time, and calculating to obtain the average value of signals of the full-closed position;
s24: and judging whether the difference value between the average value of the all-closed position signals and a zero position signal value preset in the ECU is smaller than a preset threshold value, if not, taking the average value of the all-closed position signals as a zero position signal value for the first learning of the EGR valve, and writing the zero position signal value into the ECU.
It should be noted that, in order to have the pressing force when the EGR valve is fully closed, the duty ratio of the PWM wave sent from the ECU is a negative value, and therefore, the first duty ratio may be-10%. Meanwhile, when the EGR valve starts to be electrified, the EGR valve is in a closed state, the opening degree is controlled along with the PWM wave sent by the ECU, and the first duty ratio can be a positive value or a negative value and is specifically set according to actual requirements.
Further, the first self-learning further comprises:
s25: the ECU controls the PWM wave to gradually rise from a second duty ratio to a third duty ratio so that the EGR valve is in a full-open state and continues for a certain time, wherein the third duty ratio is a positive value;
s26: acquiring the full-open position of the EGR valve for multiple times according to the first interval time, and calculating to obtain a mean value of signals of the full-open position;
s27: and judging whether the difference value between the full-open position signal average value and a full-open position signal value preset in the ECU is smaller than a preset threshold value, if not, taking the full-open position signal average value as a full-open position signal value for the first learning of the EGR valve, and writing the full-open position signal value into the ECU.
In practical application, after being powered on for 2.5s, the ECU detects that the self-learning value of the full-open or full-closed position is equal to the default value (calibrated in the ECU). The valve is considered to have not been learned at this time. And (3) stepping on the accelerator pedal for more than 50% for 3 times (not more than 3 times) in 15s after power-on, and activating a first self-learning function. When the first self-learning begins, the PWM is turned from the current value to-20% at a rate of 200%/s until after the valve stops moving for 200ms, the position signal is read 5 times (20ms interval, keeping PWM-20%) and the average is calculated and the fully closed position is recorded. After the learning of the full off position is finished, the PWM is gradually increased to 40%, and after the valve stops moving for 200ms, the position signal is read for 5 times (20ms interval, PWM is kept at 40%), and the average value is calculated, and the full on position is recorded. After learning is finished, the result is checked.
The EGR valve meeting an active self-cleaning condition includes:
the ignition key is in an OFF gear, the power supply voltage of the ECU is more than 10V, and the air inlet temperature of the diesel engine is in a range of minus 7-110 ℃.
Specifically, when the self-cleaning device is arranged under the power-off state of the diesel engine, the normal use of the vehicle can not be influenced. Meanwhile, if the temperature of the air inlet is too high, the engine still works, and the temperature is too low, so that the normal starting of the vehicle engine is not facilitated. In practical application, the engine speed and the mileage can be used as conditions for activating self-cleaning, and self-cleaning can be activated when the engine speed is less than a set threshold or the mileage reaches a set mileage threshold. The self-cleaning method effectively eliminates the deposits accumulated on the EGR valve, ensures the stable and reliable working state of the EGR valve and prolongs the service life of the EGR valve.
The EGR valve self-cleaning comprises: when the ECU activates self-cleaning, the ECU sends PWM waves with different duty ratios to control the EGR valve to carry out closing action or starting action so as to lead the EGR valve to generate vibration until the self-cleaning process is finished.
Further, the ECU sends PWM waves with different duty ratios to control the EGR valve to carry out closing action or starting action, and the method comprises the following steps: the ECU sends a PWM wave with a fourth duty ratio to enable the EGR valve to finish the starting action of opening to 95% of opening degree, and after the starting action lasts for a certain time, the ECU sends a PWM wave with a fifth duty ratio to enable the EGR valve to finish the closing action of closing to 5% of opening degree, wherein the fourth duty ratio and the fifth duty ratio are opposite in phase; and repeating the opening action and the closing action within the set time until the set times is reached.
In practical application, after the ignition key is in the off gear, the ECU judges whether the EGR valve has a self-cleaning condition, and the condition requirement can be as follows: the temperature of the inlet air is between-7 ℃ and 110 ℃, the power supply voltage of the ECU is more than 10V, the EGR valve is controlled to be at a 95% position after the power is turned off for 500ms, and the EGR valve is controlled to be at a 5% position when the EGR valve is not moved for 400 ms; when the valve remains unmoved for 400ms, the valve is controlled to the 95% position; this opening and closing process was repeated 8 times, and the whole process was completed in 15s, otherwise the cleaning process was directly exited.
The conventional self-learning of the EGR valve comprises:
s41: after the EGR valve is automatically cleaned, the ECU sends the PWM wave with the second duty ratio to enable the EGR valve to be in a full-closed state and to last for a certain time;
s42: and acquiring the full-closed position of the EGR valve for multiple times according to the first interval time, and taking the average value of the full-closed position signals obtained through calculation as a bottom dead center learning value.
Further, the conventional self-learning of the EGR valve further comprises:
s43: judging whether the difference value between the bottom dead center learning value and the first learning zero position signal value is smaller than a preset threshold value, and if not, reporting a fault;
s44: judging whether the difference value between the bottom dead center learning value and the last bottom dead center learning value is smaller than a preset threshold value, and if not, reporting a fault; if so, the bottom dead center learned value is written in the ECU.
The conventional self-learning of the EGR valve further comprises:
s45: after the learning of the bottom dead center is finished, the ECU sends the PWM wave with the third duty ratio to enable the EGR valve to be in a full-open state and to last for a certain time;
s46: and acquiring the full-open position of the EGR valve for multiple times according to the first interval time, and taking the calculated average value of the full-open position signal as a top dead center learning value.
The conventional self-learning of the EGR valve further comprises:
s47: judging whether the difference value between the upper dead point learning value and the first-time learning full-open position signal value is smaller than a preset threshold value, and if not, reporting a fault;
s48: and judging whether the difference value between the top dead center learning value and the last top dead center learning value is smaller than a preset threshold value, if not, reporting a fault, and if so, writing the top dead center learning value into the ECU.
In practical application, conventional self-learning is carried out after self-cleaning, after 0.1s of self-cleaning, the EGR position is controlled to be 0% in a closed-loop mode, when the control error of the EGR position is less than 10% and lasts for 100ms, the current PWM is converted to PWM of-20% at the rate of 200%/s, and after the control error of the EGR position is maintained for 0.3s, position signal values are read for 5 times (if the position value deviation of a certain point is large, the position signal values are eliminated, and unreasonable deviation value interference caused by accidental factors is avoided), and the position signal values are averaged (at the moment, under-20% PWM control, the reading is carried out every 20ms apart) and are used as the lower dead center learning value. After the bottom dead center is learned, the EGR position is controlled to be 100% in a closed-loop mode, when the control error of the EGR position is less than 15% and lasts for 200ms, the current PWM is converted to 40% PWM at a rate of 200%/s, 0.2s is maintained, and after the control error is finished, the position signal value is read for 6 times (if the position value deviation of a certain point is large, the position signal value is eliminated, unreasonable deviation value interference caused by accidental factors is avoided), and the position signal value is averaged (at the moment, under the control of 40% PWM, each reading is separated by 20ms).
Therefore, the control method of the EGR valve of the diesel engine provided by the invention has the advantages that the EGR valve is controlled to carry out self-learning for the first time during power-on, and the EGR valve is automatically cleaned and conventionally self-learned during power-off, so that the zero positions of the fully-closed position and the fully-open position of the EGR valve are kept accurate, the problem that the control precision of the EGR valve is reduced due to drift of the zero point of the EGR valve caused by carbon deposition and high-temperature waste gas in the use process of the existing EGR valve of the diesel engine is solved, the control precision of the EGR valve can be improved, and the working reliability of the.
The construction, features and functions of the present invention have been described in detail with reference to the embodiments shown in the drawings, but the present invention is not limited to the embodiments shown in the drawings, and all equivalent embodiments modified or modified by the spirit and scope of the present invention should be protected without departing from the spirit of the present invention.

Claims (9)

1. A control method for an EGR valve of a diesel engine, comprising:
after an ECU of the diesel engine is electrified, judging whether the EGR valve is subjected to first self-learning, and if not, judging whether the EGR valve meets the condition of activating the first self-learning;
in the set time, if the ignition key is in an ON gear and the stepping times of the accelerator pedal reach the set times, activating the first self-learning;
when an ignition key is in an OFF gear, if the EGR valve meets a self-cleaning condition, self-cleaning is carried out, otherwise, the self-cleaning is finished;
after the EGR valve is self-cleaned, the EGR valve carries out conventional self-learning;
the first self-learning comprises:
the ECU sends PWM waves to control the opening degree of the EGR valve;
when the ECU activates first self-learning, the ECU adjusts the duty ratio of the PWM wave at a first rate, and the duty ratio is rapidly reduced from the first duty ratio to a second duty ratio so that the EGR valve is in a fully-closed state and continues for a certain time, wherein the second duty ratio is a negative value;
acquiring the full-closed position of the EGR valve for multiple times according to the first interval time, and calculating to obtain the average value of signals of the full-closed position;
and judging whether the difference value between the average value of the all-closed position signals and a zero position signal value preset in the ECU is smaller than a preset threshold value, if not, taking the average value of the all-closed position signals as a zero position signal value for the first learning of the EGR valve, and writing the zero position signal value into the ECU.
2. The method for controlling a diesel EGR valve according to claim 1, wherein the first self-learning further comprises:
the ECU controls the PWM wave to gradually rise from a second duty ratio to a third duty ratio so that the EGR valve is in a full-open state and continues for a certain time, wherein the third duty ratio is a positive value;
acquiring the full-open position of the EGR valve for multiple times according to the first interval time, and calculating to obtain a mean value of signals of the full-open position;
and judging whether the difference value between the full-open position signal average value and a full-open position signal value preset in the ECU is smaller than a preset threshold value, if not, taking the full-open position signal average value as a full-open position signal value for the first learning of the EGR valve, and writing the full-open position signal value into the ECU.
3. The method for controlling the EGR valve of the diesel engine according to claim 2, wherein the EGR valve complying with the active self-cleaning condition includes:
the ignition key is in an OFF gear, the power supply voltage of the ECU is more than 10V, and the air inlet temperature of the diesel engine is in a range of minus 7-110 ℃.
4. The method for controlling the EGR valve of the diesel engine according to claim 3, wherein the EGR valve self-cleaning comprises:
when the ECU activates self-cleaning, the ECU sends PWM waves with different duty ratios to control the EGR valve to carry out closing action or starting action so as to lead the EGR valve to generate vibration until the self-cleaning process is finished.
5. The method for controlling the EGR valve of the diesel engine according to claim 4, wherein the ECU sending PWM waves with different duty ratios to control the EGR valve to perform the closing action or the starting action comprises:
the ECU sends a PWM wave with a fourth duty ratio to enable the EGR valve to finish the starting action of opening to 95% of opening degree, and after the starting action lasts for a certain time, the ECU sends a PWM wave with a fifth duty ratio to enable the EGR valve to finish the closing action of closing to 5% of opening degree, wherein the fourth duty ratio and the fifth duty ratio are opposite in phase;
and repeating the opening action and the closing action within the set time until the set times is reached.
6. The method for controlling the EGR valve of the diesel engine according to claim 5, wherein the conventional self-learning of the EGR valve comprises:
after the EGR valve is automatically cleaned, the ECU sends the PWM wave with the second duty ratio to enable the EGR valve to be in a full-closed state and to last for a certain time;
and acquiring the full-closed position of the EGR valve for multiple times according to the first interval time, and taking the average value of the full-closed position signals obtained through calculation as a bottom dead center learning value.
7. The method for controlling an EGR valve for a diesel engine according to claim 6, wherein the conventional self-learning of the EGR valve further comprises:
judging whether the difference value between the bottom dead center learning value and the first learning zero position signal value is smaller than a preset threshold value, and if not, reporting a fault;
judging whether the difference value between the bottom dead center learning value and the last bottom dead center learning value is smaller than a preset threshold value, and if not, reporting a fault; if so, the bottom dead center learned value is written in the ECU.
8. The method for controlling an EGR valve for a diesel engine according to claim 7, wherein the conventional self-learning of the EGR valve further comprises:
after the learning of the bottom dead center is finished, the ECU sends the PWM wave with the third duty ratio to enable the EGR valve to be in a full-open state and to last for a certain time;
and acquiring the full-open position of the EGR valve for multiple times according to the first interval time, and taking the calculated average value of the full-open position signal as a top dead center learning value.
9. The method for controlling an EGR valve for a diesel engine according to claim 8, wherein the conventional self-learning of the EGR valve further comprises:
judging whether the difference value between the upper dead point learning value and the first-time learning full-open position signal value is smaller than a preset threshold value, and if not, reporting a fault;
and judging whether the difference value between the top dead center learning value and the last top dead center learning value is smaller than a preset threshold value, if not, reporting a fault, and if so, writing the top dead center learning value into the ECU.
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