Method and device for inhibiting engine knock

Abstract

The invention discloses a method and device for restraining engine knock. The method comprises the following steps that the actual EGR rate is calculated according to an EGR model, and a first ignition angle correction value is obtained; a second ignition angle correction value is obtained based on the first ignition angle correction value and the knocking receding angle; a filter coefficient is determined according to the target EGR rate and the actual EGR rate, and a third ignition angle correction value is calculated after filtering is conducted through the filter coefficient; taking the smaller one of the second ignition angle correction value and the third ignition angle correction value to obtain a final ignition angle correction value; and correcting the ignition angle based on the final ignition angle correction value so as to suppress knocking. According to the invention, the stable operation of the engine under various dynamic working conditions is ensured, and the unstable combustion phenomenon caused by knocking is reduced, so that the service life of the engine is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and in particular to a method and a device for suppressing engine knock. Background Art

[0002] In the actual operation of gasoline engines, knock is a common problem that needs to be strictly controlled. Knock is mainly caused by the spontaneous combustion of the end mixture far away from the spark plug before the flame surface reaches it after the spark plug is ignited, forming multiple flame centers. These flame centers spread rapidly and generate strong pressure pulses, causing high-frequency vibration of engine parts and damaging the engine. Traditional ECU (engine control unit) suppresses knock by detecting knock and delaying the ignition angle, but this method may not be accurate enough or respond quickly enough under certain working conditions.

[0003] In order to further improve the combustion efficiency of the engine and reduce emissions, modern engines generally use an exhaust gas recirculation (EGR) system. The EGR system reintroduces part of the exhaust gas into the intake duct, mixes it with fresh air, and then enters the cylinder for combustion, thereby effectively reducing the combustion temperature in the cylinder and reducing the generation of nitrogen oxides (NOx). In the prior art, the ECU calculates the target EGR rate based on the engine speed, required torque, and environmental factors (such as ambient temperature, pressure, etc.), and adjusts the actual EGR rate by controlling the EGR valve. At the same time, the ECU also calculates the ignition angle correction value based on the current EGR rate, speed, and actual engine model torque to optimize the combustion process and reduce knock.

[0004] However, the introduction of the EGR system also brings new challenges, especially in dynamic conditions, such as low-speed full-throttle acceleration, where there is a time difference between the rapid change of the EGR rate and the adjustment of the ignition angle, which can easily lead to an aggravation of the knock problem. Under the forward and backward EGR conditions, the target EGR rate is established very quickly, and there is a certain delay between the establishment and exit of the actual EGR rate; when the actual EGR rate response is delayed and the ignition angle intervenes too quickly, the engine quickly crosses the target EGR rate maximum area. At this time, the ignition angle corrected by the EGR compensation is very large, and the actual EGR is not established in time, which will lead to strong knock in transient conditions, which has a great impact on the life of the engine. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method and device for suppressing engine knock, which can improve the engine knock problem with EGR under various working conditions.

[0006] In order to solve the above technical problems, a technical solution adopted by the present invention is to provide a method for suppressing engine knock, comprising the following steps:

[0007] Calculate the actual EGR rate according to the EGR model and obtain the first ignition angle correction value;

[0008] obtaining a second ignition angle correction value based on the first ignition angle correction value and the knock deceleration angle;

[0009] Determine a filter coefficient according to the target EGR rate and the actual EGR rate, and calculate a third ignition angle correction value after filtering with the filter coefficient;

[0010] taking the smaller of the second ignition angle correction value and the third ignition angle correction value to obtain a final ignition angle correction value;

[0011] The ignition angle is corrected based on the final ignition angle correction value, thereby suppressing knocking.

[0012] Furthermore, the step of calculating the actual EGR rate according to the EGR model and obtaining the first ignition angle correction value specifically includes the following sub-steps:

[0013] Input the EGR flow rate and the opening of the EGR valve into the EGR model to obtain the actual EGR rate;

[0014] Obtain engine torque and engine speed;

[0015] Based on the actual EGR rate, the engine torque and the engine speed, a first ignition angle correction value is obtained;

[0016] The step of obtaining the second ignition angle correction value based on the first ignition angle correction value and the knock deceleration angle specifically includes the following sub-steps:

[0017] Get the current knock retreat angle of the engine;

[0018] Obtaining a first correction factor based on a current knock recession angle of the engine;

[0019] The first ignition angle correction value is multiplied by the first correction factor to obtain a second ignition angle correction value.

[0020] Furthermore, before the step of calculating the actual EGR rate according to the EGR model and obtaining the first ignition angle correction value, the following steps are also included:

[0021] Calculating a target EGR rate and controlling an EGR valve according to the target EGR rate to obtain an actual EGR rate;

[0022] The step of calculating the target EGR rate specifically includes the following sub-steps:

[0023] Acquiring environmental parameters and engine operating parameters under current working conditions, wherein the environmental parameters include environmental pressure and ambient temperature, and the engine operating parameters include engine speed, required torque, water temperature, and intake air temperature;

[0024] Obtaining a basic target EGR rate according to the engine speed and required torque;

[0025] A second correction factor is calculated based on the ambient pressure, ambient temperature, water temperature and intake air temperature;

[0026] The basic target EGR rate is corrected based on the second correction factor to obtain a target EGR rate.

[0027] Furthermore, the step of determining the filter coefficient according to the target EGR rate and the actual EGR rate, and calculating the third ignition angle correction value after filtering with the filter coefficient specifically includes the following sub-steps:

[0028] Calculate the difference between the target EGR rate and the actual EGR rate to obtain an EGR rate difference;

[0029] According to the EGR rate difference, a filter coefficient MAP is searched to obtain a filter coefficient corresponding to the EGR rate difference;

[0030] After filtering using the filter coefficient, a third ignition angle correction value is calculated.

[0031] Further, the filter coefficient MAP is generated by the following method:

[0032] Divide the EGR rate difference into first to Nth EGR rate differences from low to high with a first step length, and divide the filtering coefficients into first to Mth coefficients from low to high with a second step length;

[0033] The engine is controlled to filter with the first to Mth coefficients in sequence under the first EGR rate difference, and the knock condition of the engine is monitored in real time, and the coefficient when the engine knock disappears is determined to be the filter coefficient corresponding to the first EGR rate difference, which is recorded as the first filter coefficient; the engine's EGR rate difference is repeatedly controlled to be the second to Nth EGR rate difference, until the filter coefficients corresponding to the second to Nth EGR rate differences are determined, which are recorded as the second to Nth filter coefficients respectively;

[0034] The first to N th EGR rate differences are respectively integrated with the first to N th filter coefficients to form a filter coefficient MAP.

[0035] Further, the step of taking the smaller of the second ignition angle correction value and the third ignition angle correction value to obtain the final ignition angle correction value specifically includes the following sub-steps:

[0036] The smaller of the second ignition angle correction value and the third ignition angle correction value is taken to obtain a basic ignition angle correction value;

[0037] Calculate the ignition compensation angle according to the engine water temperature and intake air temperature;

[0038] The basic ignition angle correction value is compensated based on the ignition compensation angle to obtain a final ignition angle correction value.

[0039] Furthermore, the step of calculating the ignition compensation angle according to the water temperature and the intake air temperature of the engine specifically includes the following sub-steps:

[0040] Obtain the engine's water temperature, intake air temperature, speed and load;

[0041] Obtaining a water temperature ignition compensation angle based on the water temperature, rotation speed and load;

[0042] Obtaining an intake air temperature ignition compensation angle based on the intake air temperature, speed and load;

[0043] The water temperature ignition compensation angle is added to the intake air temperature ignition compensation angle to obtain the ignition compensation angle.

[0044] Further, the intake air temperature ignition compensation angle includes a first intake air temperature ignition compensation angle and a second intake air temperature ignition compensation angle;

[0045] The step of obtaining the intake temperature ignition compensation angle based on the intake temperature, speed and load specifically includes: judging whether the EGR is in the open state; if the EGR is in the open state, obtaining the first intake temperature ignition compensation angle based on the intake temperature, speed and load under the current operating conditions; if the EGR is in the closed state, obtaining the second intake temperature ignition compensation angle based on the intake temperature, speed and load under the current operating conditions.

[0046] Furthermore, the step of determining whether the EGR is in the on state specifically includes: determining whether the EGR rate is greater than a set first threshold value, if the EGR rate is greater than the set first threshold value, determining that the EGR is in the on state, otherwise, the EGR is in the off state;

[0047] The step of obtaining the first intake temperature ignition compensation angle based on the intake temperature, speed and load under the current working condition specifically includes the following sub-steps:

[0048] Look up a first compensation value table based on the intake air temperature and the rotation speed to obtain a first compensation value;

[0049] Look up the first coefficient table based on the speed and the load to obtain the first coefficient;

[0050] Multiplying the first compensation value by a first coefficient to obtain a first intake air temperature ignition compensation angle;

[0051] The step of obtaining the second intake temperature ignition compensation angle based on the intake temperature, speed and load under the current working condition specifically includes the following sub-steps:

[0052] Look up a second compensation value table based on the intake air temperature and the rotation speed to obtain a second compensation value;

[0053] Look up the second coefficient table based on the speed and the load to obtain the second coefficient;

[0054] The second compensation value is multiplied by the second coefficient to obtain a second intake air temperature ignition compensation angle.

[0055] In order to solve the above technical problems, another technical solution adopted by the present invention is to provide a device for suppressing engine knock, comprising:

[0056] A first calculation module, used for calculating an actual EGR rate according to an EGR model and obtaining a first ignition angle correction value;

[0057] A second calculation module, configured to obtain a second ignition angle correction value based on the first ignition angle correction value and the knock back angle;

[0058] A filtering module, determining a filtering coefficient according to a target EGR rate and an actual EGR rate, and calculating a third ignition angle correction value after filtering by the filtering coefficient;

[0059] A smaller module is used to take the smaller value between the second ignition angle correction value and the third ignition angle correction value to obtain a final ignition angle correction value;

[0060] A correction module is used to correct the ignition angle based on the final ignition angle correction value.

[0061] The method and device for suppressing engine knock of the present invention have at least the following beneficial effects: the present invention preliminarily calculates the correction value of the ignition angle through the actual EGR rate, engine torque and engine speed, and then dynamically adjusts the correction value of the ignition angle in combination with the real-time knock situation of the engine, thereby effectively suppressing engine knock; by adding filtering under dynamic conditions, the filter coefficient is determined according to the difference between the target EGR rate and the actual EGR rate, thereby adjusting the calculation time of the ignition angle correction value accordingly, thereby suppressing the knock caused by the time delay of the actual EGR rate compared to the target EGR rate; when calculating the target EGR rate, not only the basic target EGR rate required for the current working condition calculated according to the speed and required torque is considered, but also various The basic target EGR rate is corrected by environmental parameters to obtain the final target EGR rate, so that the method can adapt to different operating environments and operating conditions; the ignition angle is additionally corrected by the water temperature and the intake air temperature, thereby suppressing the knock caused by the high water temperature and the high intake air temperature; when calculating the intake air temperature ignition compensation angle, the intake air temperature ignition compensation angles when the EGR is turned on and off are distinguished, taking into account the different knock tendencies caused by the intake air temperature under the switch EGR operating conditions, so as to obtain the intake air temperature ignition compensation angle that meets the actual requirements under different EGR operating conditions; the present invention ensures the stable operation of the engine under various dynamic conditions, reduces the unstable combustion phenomenon caused by knock, and thus prolongs the service life of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0063] Figure 1 The flowchart is a method for suppressing engine knock according to an embodiment of the present invention.

[0064] Figure 2 Flowchart for calculating the target EGR rate.

[0065] Figure 3 This is the MAP diagram of the basic target EGR rate.

[0066] Figure 4 for Figure 1 Flowchart of step S2 in FIG.

[0067] Figure 5 for Figure 1 Flow chart of step S3 in FIG.

[0068] Figure 6 MAP diagram of the first correction factor.

[0069] Figure 7 Flowchart for generating filter coefficient MAP.

[0070] Figure 8 It is the MAP diagram of the filter coefficients.

[0071] Fig. 9 for Figure 1 Flow chart of step S5 in FIG.

[0072] Fig.10 for Fig. 9 Flowchart of step S52 in FIG.

[0073] Fig.11 A structural block diagram of an embodiment of a device for suppressing engine knock according to the present invention. DETAILED DESCRIPTION

[0074] The present invention will be further described below in conjunction with the accompanying drawings.

[0075] See also Figure 1 , is a flow chart of an embodiment of a method for suppressing engine knock of the present invention. This embodiment specifically includes the following steps:

[0076] S1. Calculate the target EGR rate and control the EGR valve according to the target EGR rate to obtain the actual EGR rate.

[0077] The EGR rate, or exhaust gas recirculation rate, refers to the ratio of the exhaust gas introduced into the intake system during the combustion process of the engine, mixed with fresh air, and then re-entered the cylinder to participate in combustion.

[0078] See also Figure 2 , the step of calculating the target EGR rate includes the following sub-steps:

[0079] S11. Obtaining environmental parameters and engine operating parameters under current working conditions.

[0080] Specifically, the environmental parameters include environmental pressure and environmental temperature, and the engine operating parameters include engine speed, required torque, water temperature and intake air temperature.

[0081] S12: Obtain a basic target EGR rate according to the engine speed and required torque.

[0082] Specifically, according to the engine speed and required torque, check the MAP of the basic target EGR rate to obtain the basic target EGR rate corresponding to the current working condition. Figure 3 , which is the MAP diagram of the basic target EGR rate, where X represents the speed and Y represents the required torque.

[0083] S13. Obtain a second correction factor.

[0084] Specifically, since the basic target EGR rate is data calibrated by the bench, and the bench calibration data is usually calibrated in a normal temperature environment, close to 0 altitude and under optimal temperature conditions, the target EGR rate of the actual vehicle will be different depending on environmental factors, etc. It is necessary to perform deviation correction on the EGR rate of the current working condition based on the current environmental factors (ambient temperature, ambient pressure, etc.) and the current state of the engine (intake temperature, water temperature, etc.) collected from the actual vehicle. The second correction factor is calculated based on the ambient pressure, ambient temperature, water temperature and intake temperature. This calculation method is a mature algorithm and will not be repeated here.

[0085] S14: Correct the basic target EGR rate to obtain a target EGR rate.

[0086] Specifically, the basic target EGR rate is corrected based on the second correction factor, and the basic target EGR rate is multiplied by the second correction factor to obtain the target EGR rate.

[0087] S2. Calculate the actual EGR rate according to the EGR model and obtain a first ignition angle correction value.

[0088] See also Figure 4 , this step S2 includes the following sub-steps:

[0089] S21. Input the EGR flow rate and the opening of the EGR valve into the EGR model to obtain the actual EGR rate.

[0090] Specifically, the real-time EGR flow rate and the opening of the EGR valve are obtained, and the EGR flow rate and the opening of the EGR valve are input into a pre-calibrated EGR model, and the actual EGR rate is obtained after the model is calculated. The EGR model is used to describe the relationship between the EGR flow rate, the EGR valve opening and the actual EGR rate, which belongs to the prior art and will not be described here.

[0091] S22: Obtain engine torque and engine speed.

[0092] Specifically, by connecting the torque sensor of the torque meter to the engine output shaft, the torque of the engine can be accurately measured; and the speed sensor can be used to accurately detect the speed of the engine.

[0093] S23: Obtain a first ignition angle correction value based on the actual EGR rate, engine torque, and engine speed.

[0094] Specifically, the first ignition angle correction value MAP is checked based on the actual EGR rate, engine torque and engine speed to obtain the first ignition angle correction value under the current working condition. The first ignition angle correction value calculated at this time is the ignition angle correction value under the steady-state working condition. In this embodiment, the first ignition angle correction value MAP is calibrated by a bench.

[0095] S3. Obtain a second ignition angle correction value based on the first ignition angle correction value and the knock deceleration angle.

[0096] Knock retreat angle refers to an adjustment measure taken by the engine management system to deal with or alleviate the knock phenomenon, that is, to delay the ignition angle. When knock occurs, in order to reduce the pressure and temperature in the combustion chamber and prevent the knock from further aggravating, the engine management system will automatically adjust the ignition angle to postpone it, which is the knock retreat angle. When EGR is not working, there is no knock. After EGR is turned on, the engine has obvious knock, which means that the first ignition angle correction value is too large under steady-state conditions. The ignition angle is too large, causing the engine to knock. Usually, the first ignition angle correction value is determined by the initial bench stage of the project, which is not suitable for change in the later stage of the project. Therefore, it is necessary to adjust the first ignition angle correction value according to the current knock retreat angle of the engine.

[0097] See also Figure 5 , this step S3 includes the following sub-steps:

[0098] S31. Obtain the current knock retreat angle of the engine.

[0099] Specifically, the current knock recession angle of the engine is monitored in real time by a knock sensor. The size of the knock recession angle represents the strength of the engine knock. The larger the knock recession angle, the stronger the engine knock. Conversely, the weaker the engine knock.

[0100] S32: Obtain a first correction factor based on the current knock retreat angle of the engine.

[0101] Specifically, the first correction factor MAP is queried according to the engine knock retreat angle to obtain the first correction factor corresponding to the current knock retreat angle. The first correction factor MAP is calibrated by the test bench, see Figure 6 , is the MAP diagram of the first correction factor, where X represents the knock retreat angle and Z represents the first correction factor.

[0102] S33: Correct the first ignition angle correction value to obtain a second ignition angle correction value.

[0103] Specifically, the first ignition angle correction value is multiplied by the first correction factor to obtain a second ignition angle correction value.

[0104] S4. Calculate the third ignition angle correction value.

[0105] A filter coefficient is determined according to the target EGR rate and the actual EGR rate, and the third ignition angle correction value is calculated after filtering by the filter coefficient. Specifically, first, the difference between the target EGR rate and the actual EGR rate is calculated to obtain the EGR rate difference; secondly, the filter coefficient MAP is checked according to the EGR rate difference to obtain the filter coefficient corresponding to the EGR rate difference; finally, the third ignition angle correction value is calculated after filtering by the filter coefficient.

[0106] There is a certain delay between the actual EGR rate and the target EGR rate. For example, when entering the EGR condition, if the requested target EGR rate is 20, the actual EGR rate will gradually increase from 0 to 20, and the EGR rate difference will gradually decrease from 20 to 0. That is, in the dynamic condition, when the target EGR rate is greater than the actual EGR rate, the ignition angle corrected according to the target EGR rate is too large for the actual EGR rate, which will cause knocking. Therefore, it is necessary to calculate the second ignition angle correction value through filtering delay. The ignition angle correction value calculated after the delay is the third ignition angle correction value. At this time, the filter coefficient increases with the increase of the EGR rate difference. Similarly, when exiting the EGR condition, the target EGR rate is less than the actual EGR rate. At this time, the ignition angle needs to be reduced as soon as possible to avoid knocking. Therefore, the filter coefficient is reduced on the basis of entering the EGR condition to shorten the delay calculation time. The filter coefficient decreases with the decrease of the EGR rate difference.

[0107] See also Figure 7 , the generation of the filter coefficient MAP includes the following steps:

[0108] S41, dividing the EGR rate difference and the filtering coefficient.

[0109] Specifically, the determined maximum EGR rate difference is divided into the first to the Mth EGR rate difference from low to high with a first step length, and the filtered coefficient is divided into the first to the Mth coefficient from low to high with a second step length. The first step length and the second step length can be set according to actual conditions. In this embodiment, the first step length is set to 5, and the second step length is set to 0.01.

[0110] S42: Determine a first filter coefficient.

[0111] Specifically, the engine is controlled to filter with the first to Mth coefficients in sequence under the first EGR rate difference, and the engine knock condition is monitored in real time, and the coefficient when the engine knock disappears is determined to be the filter coefficient corresponding to the first EGR rate difference, which is recorded as the first filter coefficient.

[0112] S43, determining the second to Nth filter coefficients in sequence.

[0113] Specifically, the EGR rate difference of the engine is repeatedly controlled to be the second to Nth EGR rate difference, and step S42 is repeatedly executed to determine the filter coefficients corresponding to the second to Nth EGR rate difference values, which are respectively recorded as the second to Nth filter coefficients.

[0114] S44: Form a filter coefficient MAP.

[0115] Specifically, the first to Nth EGR rate differences are respectively integrated with the first to Nth filter coefficients to form a filter coefficient MAP. In this way, the corresponding filter coefficient can be quickly matched in the filter coefficient MAP directly according to the EGR rate difference under the current working condition of the engine. Figure 8 , is a MAP diagram of the filter coefficient in this embodiment, X represents the EGR rate difference, and Z represents the filter coefficient.

[0116] S5. Obtain the final ignition angle correction value.

[0117] See also Fig. 9 , this step S5 includes the following sub-steps:

[0118] S51. Obtain a basic ignition angle correction value.

[0119] Specifically, the smaller of the second ignition angle correction value and the third ignition angle correction value is taken to obtain the basic ignition angle correction value. When the engine is in a dynamic condition, the EGR ignition angle correction value is variable. To avoid knocking under dynamic conditions, the smaller of the second ignition angle correction value and the third ignition angle correction value is taken to obtain the basic ignition angle correction value.

[0120] S52: Calculate the ignition compensation angle according to the water temperature and the intake air temperature of the engine.

[0121] See also Fig.10 , this step S52 includes the following sub-steps:

[0122] S521. Obtain the water temperature, intake air temperature, speed, and load of the engine.

[0123] S522: Obtain a water temperature ignition compensation angle based on the water temperature, rotation speed, and load.

[0124] Water temperature is one of the causes of knocking. When the water temperature is low, the knocking tendency is weak; when the water temperature is high, the knocking tendency is strong. Therefore, it is necessary to make additional corrections to the ignition angle according to the water temperature. In this embodiment, the calculation of the water temperature ignition compensation angle is a mature algorithm, which will not be repeated here.

[0125] S523: Obtain an intake air temperature ignition compensation angle based on the intake air temperature, rotation speed, and load.

[0126] In a high temperature environment, high intake temperature will increase the knock tendency of the engine; when the intake temperature is low, the knock tendency of the engine is reduced. Traditional projects will add additional corrections to the ignition angle at high intake temperatures. For engines with EGR configuration, the knock tendency of the engine is different when the EGR is turned on or off in a high intake temperature environment. For the occasional failure of the EGR valve to work (such as stuck), the ignition angle correction under high intake temperature environment is generally obtained based on the premise of opening EGR, which is not applicable to the high intake temperature ignition angle correction when EGR is turned off.

[0127] In order to obtain an intake air temperature ignition compensation angle that meets actual requirements under different working conditions, in this embodiment, the intake air temperature ignition compensation angles when EGR is turned on and when EGR is turned off are distinguished. The intake air temperature ignition compensation angle includes a first intake air temperature ignition compensation angle and a second intake air temperature ignition compensation angle. Specifically, it is determined whether EGR is in an on state. If EGR is in an on state, the first intake air temperature ignition compensation angle is obtained based on the engine intake air temperature, engine speed and engine load under the current working condition; if EGR is in a closed state, the second intake air temperature ignition compensation angle is obtained based on the engine intake air temperature, engine speed and engine load under the current working condition.

[0128] Among them, the method for judging whether EGR is in the open state is: judging whether the EGR rate is greater than the set first threshold value, if the EGR rate is greater than the set first threshold value, then it is judged that EGR is in the open state, otherwise, EGR is in the closed state. The first threshold value is set according to the actual situation. In this embodiment, the first threshold value is set to 2. The method for obtaining the first intake temperature ignition compensation angle based on the engine intake temperature, engine speed and engine load under the current working condition is: first, based on the engine intake temperature and engine speed, check the first compensation value MAP to obtain the first compensation value; secondly, based on the engine speed and engine load, check the first coefficient MAP to obtain the first coefficient; finally, multiply the first compensation value by the first coefficient to obtain the first intake temperature ignition compensation angle. The method for obtaining the second intake temperature ignition compensation angle based on the engine intake temperature, engine speed and engine load under the current working condition is: first, based on the engine intake temperature and engine speed, check the second compensation value MAP to obtain the second compensation value; secondly, based on the engine speed and engine load, check the second coefficient MAP to obtain the second coefficient; finally, multiply the second compensation value by the second coefficient to obtain the second intake temperature ignition compensation angle. In this embodiment, the first compensation value MAP, the first coefficient MAP, the second compensation value MAP and the second coefficient MAP are all calibrated by a test bench.

[0129] S524: Obtain an ignition compensation angle.

[0130] Specifically, the water temperature ignition compensation angle is added to the intake air temperature ignition compensation angle to obtain the ignition compensation angle.

[0131] S53: Obtain a final ignition angle correction value.

[0132] Specifically, the basic ignition angle correction value is compensated based on the ignition compensation angle, and the ignition compensation angle is subtracted from the basic ignition angle to obtain a final ignition angle correction value.

[0133] S6. Correct the ignition angle based on the final ignition angle correction value to suppress knocking.

[0134] See also Fig.11 , is a structural block diagram of an embodiment of the device for suppressing engine knock of the present invention. The device for suppressing engine knock of this embodiment is used to implement the method for suppressing engine knock as described in the above embodiment. Specifically, the device for suppressing engine knock of this embodiment includes a first calculation module 100, a second calculation module 200, a filtering module 300, a minimization module 400 and a correction module 500. Among them:

[0135] The first calculation module 100 is used to calculate the actual EGR rate according to the EGR model and obtain the first ignition angle correction value. In this embodiment, a calculation module is also provided to calculate the target EGR rate before the first calculation module 100 calculates the actual EGR rate and control the EGR valve according to the target EGR rate to obtain the actual EGR rate.

[0136] The second calculation module 200 is used to obtain a second ignition angle correction value based on the first ignition angle correction value and the knock deceleration angle obtained by the first calculation module 100.

[0137] The filtering module 300 determines a filtering coefficient according to the target EGR rate and the actual EGR rate, and calculates a third ignition angle correction value after filtering with the filtering coefficient.

[0138] The smaller one of the second ignition angle correction value obtained by the second calculation module 200 and the third ignition angle correction value obtained by the filtering module 300 is selected to obtain a final ignition angle correction value.

[0139] The correction module 500 is used to correct the ignition angle based on the final ignition angle correction value obtained by the minimization module 400.

[0140] The present invention preliminarily calculates the correction value of the ignition angle through the actual EGR rate, engine torque and engine speed, and then dynamically adjusts the correction value of the ignition angle in combination with the real-time knock situation of the engine, which can effectively suppress engine knock; by adding filtering under dynamic conditions, the filter coefficient is determined according to the difference between the target EGR rate and the actual EGR rate, so as to adjust the calculation time of the ignition angle correction value accordingly, which can suppress the knock caused by the time delay of the actual EGR rate compared with the target EGR rate; when calculating the target EGR rate, not only the basic target EGR rate required for the current working condition calculated according to the speed and required torque is considered, but also the basic target EGR rate is adjusted in combination with various environmental parameters. Correction is performed to obtain the final target EGR rate, so that the method can adapt to different operating environments and working conditions; the ignition angle is additionally corrected by the water temperature and the intake air temperature, thereby suppressing the knock caused by the high water temperature and the high intake air temperature; when calculating the intake air temperature ignition compensation angle, taking into account the different knock tendencies caused by the intake air temperature under the switch EGR working conditions, the intake air temperature ignition compensation angles when the EGR is turned on and the EGR is turned off are distinguished, so that the intake air temperature ignition compensation angle that meets the actual requirements can be obtained under different EGR working conditions; the present invention ensures the stable operation of the engine under various dynamic working conditions, reduces the unstable combustion phenomenon caused by knock, and thus extends the service life of the engine.

[0141] Finally, it should be noted that the above are only preferred implementations of the present invention, and the patent scope of the present invention is not limited thereto. Any equivalent process or equivalent structural transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for suppressing engine knock, characterized in that: The following steps are involved: Calculate the actual EGR rate according to the EGR model and obtain the first ignition angle correction value; obtaining a second ignition angle correction value based on the first ignition angle correction value and the knock deceleration angle; Determine a filter coefficient according to the target EGR rate and the actual EGR rate, and calculate a third ignition angle correction value after filtering with the filter coefficient; taking the smaller of the second ignition angle correction value and the third ignition angle correction value to obtain a final ignition angle correction value; The ignition angle is corrected based on the final ignition angle correction value, thereby suppressing knocking.

2. The method for suppressing engine knock as claimed in claim 1, characterized in that: The step of calculating the actual EGR rate according to the EGR model and obtaining the first ignition angle correction value specifically includes the following sub-steps: Input the EGR flow rate and the opening of the EGR valve into the EGR model to obtain the actual EGR rate; Obtain engine torque and engine speed; Based on the actual EGR rate, the engine torque and the engine speed, a first ignition angle correction value is obtained; The step of obtaining the second ignition angle correction value based on the first ignition angle correction value and the knock deceleration angle specifically includes the following sub-steps: Get the current knock retreat angle of the engine; Obtaining a first correction factor based on a current knock recession angle of the engine; The first ignition angle correction value is multiplied by the first correction factor to obtain a second ignition angle correction value.

3. The method for suppressing engine knock as claimed in claim 1, characterized in that: Before the step of calculating the actual EGR rate according to the EGR model and obtaining the first ignition angle correction value, the following steps are also included: Calculating a target EGR rate and controlling an EGR valve according to the target EGR rate to obtain an actual EGR rate; The step of calculating the target EGR rate specifically includes the following sub-steps: Acquiring environmental parameters and engine operating parameters under current working conditions, wherein the environmental parameters include environmental pressure and ambient temperature, and the engine operating parameters include engine speed, required torque, water temperature, and intake air temperature; Obtaining a basic target EGR rate according to the engine speed and required torque; A second correction factor is calculated based on the ambient pressure, ambient temperature, water temperature and intake air temperature; The basic target EGR rate is corrected based on the second correction factor to obtain a target EGR rate.

4. The method for suppressing engine knock as claimed in claim 3, characterized in that: The step of determining a filter coefficient according to the target EGR rate and the actual EGR rate, and calculating the third ignition angle correction value after filtering with the filter coefficient specifically includes the following sub-steps: Calculate the difference between the target EGR rate and the actual EGR rate to obtain an EGR rate difference; According to the EGR rate difference, a filter coefficient MAP is searched to obtain a filter coefficient corresponding to the EGR rate difference; After filtering using the filter coefficient, a third ignition angle correction value is calculated.

5. The method for suppressing engine knock as claimed in claim 4, characterized in that: The filter coefficient MAP is generated by the following method: Divide the EGR rate difference from low to high into first to Nth EGR rate difference values ​​with a first step length, and divide the filtering coefficient from low to high into first to Mth coefficients with a second step length; The engine is controlled to filter with the first to Mth coefficients in sequence under the first EGR rate difference, and the knock condition of the engine is monitored in real time, and the coefficient when the engine knock disappears is determined to be the filter coefficient corresponding to the first EGR rate difference, which is recorded as the first filter coefficient; the engine's EGR rate difference is repeatedly controlled to be the second to Nth EGR rate difference, until the filter coefficients corresponding to the second to Nth EGR rate differences are determined, which are recorded as the second to Nth filter coefficients respectively; The first to N th EGR rate differences are respectively integrated with the first to N th filter coefficients to form a filter coefficient MAP.

6. The method for suppressing engine knock as claimed in claim 1, characterized in that: The step of taking the smaller of the second ignition angle correction value and the third ignition angle correction value to obtain the final ignition angle correction value specifically includes the following sub-steps: The smaller of the second ignition angle correction value and the third ignition angle correction value is taken to obtain a basic ignition angle correction value; Calculate the ignition compensation angle according to the engine water temperature and intake air temperature; The basic ignition angle correction value is compensated based on the ignition compensation angle to obtain a final ignition angle correction value.

7. The method for suppressing engine knock as claimed in claim 6, characterized in that: The step of calculating the ignition compensation angle according to the water temperature and the intake air temperature of the engine specifically includes the following sub-steps: Obtain the engine's water temperature, intake air temperature, speed and load; Obtaining a water temperature ignition compensation angle based on the water temperature, rotation speed and load; Obtaining an intake air temperature ignition compensation angle based on the intake air temperature, speed and load; The water temperature ignition compensation angle is added to the intake air temperature ignition compensation angle to obtain the ignition compensation angle.

8. The method for suppressing engine knock as claimed in claim 7, characterized in that: The intake air temperature ignition compensation angle includes a first intake air temperature ignition compensation angle and a second intake air temperature ignition compensation angle; The step of obtaining the intake temperature ignition compensation angle based on the intake temperature, speed and load specifically includes: judging whether the EGR is in the open state; if the EGR is in the open state, obtaining the first intake temperature ignition compensation angle based on the intake temperature, speed and load under the current operating conditions; if the EGR is in the closed state, obtaining the second intake temperature ignition compensation angle based on the intake temperature, speed and load under the current operating conditions.

9. The method for suppressing engine knock as claimed in claim 8, characterized in that: The step of determining whether the EGR is in the on state specifically includes: determining whether the EGR rate is greater than a set first threshold value, if the EGR rate is greater than the set first threshold value, determining that the EGR is in the on state, otherwise, the EGR is in the off state; The step of obtaining the first intake temperature ignition compensation angle based on the intake temperature, speed and load under the current working condition specifically includes the following sub-steps: Look up a first compensation value table based on the intake air temperature and the rotation speed to obtain a first compensation value; Look up the first coefficient table based on the speed and the load to obtain the first coefficient; Multiplying the first compensation value by a first coefficient to obtain a first intake air temperature ignition compensation angle; The step of obtaining the second intake temperature ignition compensation angle based on the intake temperature, speed and load under the current working condition specifically includes the following sub-steps: Look up a second compensation value table based on the intake air temperature and the rotation speed to obtain a second compensation value; Look up the second coefficient table based on the speed and the load to obtain the second coefficient; The second compensation value is multiplied by the second coefficient to obtain a second intake air temperature ignition compensation angle.

10. A device for suppressing engine knock, characterized in that: include: A first calculation module, used for calculating an actual EGR rate according to an EGR model and obtaining a first ignition angle correction value; A second calculation module, configured to obtain a second ignition angle correction value based on the first ignition angle correction value and the knock back angle; A filtering module, determining a filtering coefficient according to a target EGR rate and an actual EGR rate, and calculating a third ignition angle correction value after filtering by the filtering coefficient; A smaller module is used to take the smaller value between the second ignition angle correction value and the third ignition angle correction value to obtain a final ignition angle correction value; A correction module is used to correct the ignition angle based on the final ignition angle correction value.

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