Engine coolant temperature control method for engine with EGR system and engine

Abstract

The application discloses an engine cooling liquid temperature control method and engine with an EGR system, which comprises the following four conditions: (1) determining the first linear interpolation number according to the octane number coefficient of oil products and the engine back angle strength coefficient, and using a larger engine load for interpolation; (2) determining the second linear interpolation number according to the ratio of the actual engine fire path torque to the requested fire path torque and the ratio of the requested fire path torque to the maximum torque of the engine, and using a smaller engine load for interpolation; (3) determining the third linear interpolation number according to the target EGR rate and the ratio of the actual EGR rate to the target EGR rate, and using a smaller engine load for interpolation; (4) determining the fourth linear interpolation number according to the intake air temperature and the vehicle speed, and using a smaller engine load for interpolation; the above four conditions are only executed in one of each control cycle. The application optimizes the target cooling liquid temperature control of the engine with the EGR system, and improves the stability.

Description

Technical Field

[0001] This invention relates to the field of engine control technology, specifically to a method for controlling engine coolant temperature with an EGR system and an engine. Background Technology

[0002] An engine is a power source that converts chemical energy into mechanical energy through combustion, generating a significant amount of heat in the process. From the perspectives of power, economy, and emissions performance, an engine ideally operates at its optimal temperature, thus requiring a suitable cooling system. Setting the target coolant temperature for the engine is crucial for its power, economy, and lifespan. Engine control involves many dimensions, such as engine protection, power, and economy, creating a pressing need for these control measures. Coolant temperature control has a significant impact on these control dimensions, especially after the introduction of EGR systems, which further deteriorate engine combustion stability.

[0003] Currently, the target coolant temperature is determined based on engine speed and engine load (engine load can be characterized by actual fresh air intake density, which refers to the actual fresh air density entering the cylinder). This determination method uses a three-dimensional lookup table, where the horizontal axis represents engine speed and the vertical axis represents engine load. Currently, publicly available methods for controlling the target coolant temperature based on engine speed and engine load all employ linear interpolation. Linear interpolation means that if the engine speed n... EngSpd Falling on n EngSpd1 and n EngSpd2 Between (where n) EngSpd1 and n EngSpd2 (This refers to the engine speed coordinates adjacent to the engine speed on the horizontal axis of the table), then the corresponding n... EngSpd1 and n EngSpd2 The engine speed n is obtained by linear interpolation of the target coolant temperature. EngSpd The corresponding target coolant temperature and the interpolation method for the same engine load are the same. However, to improve power and engine performance protection under transient conditions and achieve more reasonable target coolant temperature control, the interpolation method needs to be optimized. Based on this, an engine coolant temperature control method with an EGR system and an engine are proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the coolant temperature of an engine with an EGR system and an engine in general, thereby solving the problem of deteriorated combustion stability after the introduction of an EGR system into the engine.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for controlling coolant temperature in an engine with an EGR system includes the following four scenarios:

[0007] (1) The number of first linear interpolation N1 is determined based on the octane number coefficient of the oil and the retraction strength coefficient of the engine, and a larger engine load is used for interpolation; wherein, the smaller the octane number coefficient of the oil and the larger the retraction strength coefficient of the engine, the larger the number of first linear interpolation N1 is.

[0008] (2) Based on the actual engine firing torque M SprkTrqAct With the requested fire circuit torque M SprkTrqReq ratio And request fire circuit torque M SprkTrqReq With engine maximum torque M TrqMax ratio The number of second linear interpolation operations, N2, is determined, and interpolation is performed using a smaller engine load; where, The smaller, The larger the value, the larger the number of second linear interpolations N2;

[0009] (3) Based on the target EGR rate r EGRDsrd and actual EGR rate r EGRAct Compared with the target EGR rate r EGRDsrd ratio The number of third linear interpolation operations, N3, is determined, and interpolation is performed using a smaller engine load; where the target EGR rate r EGRDsrd The larger, The larger the value, the larger the number of third linear interpolations N3;

[0010] (4) Based on the intake air temperature T MAT The number of fourth linear interpolation operations, N4, is determined by the vehicle speed v, and interpolation is performed using a smaller engine load; where the intake air temperature T... MAT The lower the value, the larger the vehicle speed v, and the larger the number of fourth linear interpolations N4.

[0011] Only one of the above four scenarios will be executed within each control cycle:

[0012] First, determine if the number of linear interpolations N1 is greater than 2; if yes, then use the number of linear interpolations N1 and apply a larger engine load for interpolation; if not, then:

[0013] Next, determine whether the number of second linear interpolations N2 is greater than 2; if yes, then use the second number of linear interpolations N2, and use a smaller engine load for interpolation; if not, then:

[0014] Continue to determine whether the number of third linear interpolation N3 is greater than 2; if yes, then use the number of third linear interpolation N3 and use a smaller engine load for interpolation; if no, then use the number of fourth linear interpolation N4 and use a smaller engine load for interpolation.

[0015] Furthermore, the number of first linear interpolations N1, the number of second linear interpolations N2, the number of third linear interpolations N3, and the number of fourth linear interpolations N4 are all greater than or equal to 2 and are integers.

[0016] Furthermore, the method of interpolation using a larger engine load is as follows:

[0017] Assuming the current actual engine speed is read as n EngSpd And it falls on n EngSpd1 and n EngSpd2 Between, the current actual engine load is rho and falls between rho1 and rho2; where n EngSpd1 and n EngSpd2 Both rho1 and rho2 are adjacent values ​​in the target coolant temperature table, determined based on engine speed and engine load.

[0018] If there is no engine load value greater than rho2 in the table, the final number of linear interpolation is 2, that is, the target coolant temperature corresponding to the engine load rho is obtained by linear interpolation of rho1 and rho2.

[0019] If there is an engine load value in the table that is larger than rho2, then obtain the number N′ of engine load values ​​that are larger than rho2, and determine the size of the determined number of linear interpolation values ​​and N′+2. If the determined number of linear interpolation values ​​is less than or equal to N′+2, then the final number of linear interpolation values ​​is the determined number of linear interpolation values, that is, the target coolant temperature corresponding to engine load rho is obtained by linear interpolation based on rho1 and the N″-th engine load after rho in the table, where N″ is the determined number of linear interpolation values ​​minus 1. If the determined number of linear interpolation values ​​is greater than N′+2, then the final number of linear interpolation values ​​is N′+2, that is, the target coolant temperature corresponding to engine load rho is obtained by linear interpolation based on rho1 and the largest engine load in the table.

[0020] The rotational speed n is obtained by the above method. EngSpd1 With n EngSpd2 The target coolant temperature corresponding to the engine load rho is then determined by the current actual engine speed n. EngSpd And the engine speed is n EngSpd1 With n EngSpd2 The final target coolant temperature is obtained by linear interpolation of the target coolant temperature corresponding to the engine load rho.

[0021] The method of interpolation using a smaller engine load is the opposite: if there is no engine load value smaller than rho1 in the table, then the final number of linear interpolations is 2, that is, the target coolant temperature corresponding to the engine load rho is obtained by linear interpolation based on rho1 and rho2.

[0022] If there is an engine load value smaller than rho1 in the table, then obtain the number N′ of engine load values ​​smaller than rho1, and determine the size of the determined number of linear interpolation values ​​and N′+2. If the determined number of linear interpolation values ​​is less than or equal to N′+2, then the final number of linear interpolation values ​​is the determined number of linear interpolation values, that is, the target coolant temperature corresponding to engine load rho is obtained by linear interpolation based on rho2 and the N″-th engine load before rho in the table, where N″ is the determined number of linear interpolation values ​​minus 1. If the determined number of linear interpolation values ​​is greater than N′+2, then the final number of linear interpolation values ​​is N′+2, that is, the target coolant temperature corresponding to engine load rho is obtained by linear interpolation based on rho2 and the smallest engine load in the table.

[0023] The rotational speed n is obtained by the above method. EngSpd1 With n EngSpd2 The target coolant temperature corresponding to the engine load rho is then determined by the current actual engine speed n. EngSpd And the engine speed is n EngSpd1 With n EngSpd2 The final target coolant temperature is obtained by linear interpolation of the target coolant temperature corresponding to the engine load rho.

[0024] Furthermore, the engine's retraction angle strength coefficient is... phi Knock For the current detonation delay ignition angle, phi KnockMax The maximum permissible ignition angle for detonation delay.

[0025] Furthermore, the maximum permissible ignition angle for detonation delay is 10°.

[0026] Furthermore, the number of each linear interpolation is determined by looking up a table:

[0027] If the horizontal and vertical axis data of the data to be retrieved are not in the table, the number of linear interpolation values ​​is determined by the method of adjacent linear interpolation. That is, the values ​​in the middle of the table data are determined by linear interpolation, and the values ​​outside the table data are directly equal to the edge values. Here, the values ​​in the middle of the table data indicate that the horizontal and vertical axis data of the data to be retrieved are within the minimum and maximum values ​​of the table coordinate axes, and the values ​​outside the table data indicate that the horizontal and vertical axis data of the data to be retrieved are not within the minimum and maximum values ​​of the table coordinate axes.

[0028] After interpolating from the table, round to the nearest integer.

[0029] Furthermore, after determining the number of first linear interpolations N1, it is determined whether the conditions for self-learning update are met; if so, self-learning update is performed on the number of first linear interpolations N1 to determine the final number of first linear interpolations N1.

[0030] Furthermore, the conditions for self-learning updates are:

[0031] The engine speed is within the preset speed range, and the engine speed fluctuation is within the preset speed fluctuation range;

[0032] The engine load is within the preset load range, and the engine load fluctuation is within the preset load fluctuation range;

[0033] The intake air temperature fluctuation range is within the preset temperature fluctuation range;

[0034] The vehicle speed fluctuation range is within the preset vehicle speed fluctuation range;

[0035] The actual EGR rate fluctuation range is within the preset EGR rate fluctuation range;

[0036] The target EGR rate fluctuation range is within the preset target EGR rate fluctuation range;

[0037] The ratio of the engine's actual firing torque to the target firing torque is within the preset range;

[0038] The number of first linear interpolations N1 was not updated in this driving cycle;

[0039] When all of the above conditions are met, the conditions for self-learning and updating are satisfied.

[0040] Furthermore, the self-learning update process is as follows:

[0041] If the self-learning update conditions are met and the maintenance time exceeds the preset maintenance time, the CNT count for the corresponding operating condition is incremented by 1.

[0042] (1) If the number of CNTs exceeds the preset number under a certain working condition, and the number of knocks does not exceed the preset value, then the first linear interpolation number N1 under the corresponding working condition is updated to 0.85 times and rounded to the nearest whole number. N1 under other working conditions is not updated.

[0043] (2) If the number of CNTs exceeds the preset number under a certain working condition, and only the number of low-intensity knocks does not exceed the preset value, then the number of first linear interpolation N1 under the corresponding working condition is updated to 0.95 times and rounded to the nearest whole number. N1 under other working conditions is not updated.

[0044] (3) If the number of CNTs exceeds the preset number value under a certain working condition, and the number of high-intensity knocks exceeds the preset knock count value, then the first linear interpolation number N1 under the corresponding working condition is updated to 1.2 times and rounded to the nearest whole number. N1 under other working conditions is not updated.

[0045] (4) N1 is not updated in other cases;

[0046] After N1 is updated, CNT is immediately reset to 0, and the updated first linear interpolation number N1 is used in the new driving cycle;

[0047] Same operating conditions mean that the differences in engine speed, load, intake air temperature, vehicle speed, EGR rate, and actual engine torque do not exceed ±2%; and N1 is limited to a number not less than 2.

[0048] An engine that uses the engine coolant temperature control method with an EGR system described in any one of the above to control the engine coolant temperature.

[0049] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0050] This invention optimizes the target temperature control of engine coolant with EGR system from the perspectives of engine protection, power, fuel economy and stability, enabling the engine coolant target temperature to respond quickly according to the engine performance requirements. Attached Figure Description

[0051] Figure 1 This is a flowchart of an engine coolant temperature control method with an EGR system according to an embodiment of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0053] This invention proposes a method for optimizing coolant temperature control in an engine with an EGR system, and an engine thereof. Specifically, this method assumes the engine load rho falls between rho1 and rho2, and does not necessarily use only the target coolant temperatures of rho1 and rho2 for interpolation. The specific steps are as follows:

[0054] The first step is to determine the octane rating of the oil product based on the octane number coefficient (as mentioned in patent CN202010608134.7, "A Method and System for Self-Learning Octane Number of Oil Products").OctaneRatio (same physical meaning) and engine recoil angle strength coefficient (phi Knock For the current detonation delay ignition angle, phi KnockMax To determine the maximum permissible ignition angle for detonation delay (10° in this example), the number of first linear interpolations N1 is determined as shown in Table 1. Detonation delay angle intensity coefficient. The larger the octane rating, the stronger the knocking. To suppress knocking, since the engine coolant temperature tends to decrease with increasing engine load, a larger number of linear interpolation terms are used, and a larger engine load is employed for interpolation. The smaller the octane rating, the worse the fuel quality. To reduce the possibility of knocking, since the engine coolant temperature tends to decrease with increasing engine load, a larger number of linear interpolation terms are used, and a larger engine load is employed for interpolation.

[0055] Table 1. Determination of the Number of First Linear Interpolations N1

[0056]

[0057] In the table above, if the data on the horizontal and vertical axes do not fall within the table (including both the center and the outside of the table), N1 determines the value using adjacent linear interpolation. Values ​​within the center of the table (i.e., values ​​within the minimum and maximum range of the table's coordinate axes) are interpolated using linear interpolation, while values ​​outside the table (i.e., values ​​outside the minimum and maximum range of the table's coordinate axes) are directly equal to the edge value. Finally, after interpolation, the result is rounded to the nearest integer.

[0058] "Using a larger engine load for interpolation" – this needs to be explained as follows: assuming N1 is determined to be 4 based on the table above, and the current actual engine speed is read as n… EngSpd And it falls on n EngSpd1 and n EngSpd2 Between (where n) EngSpd1 and n EngSpd2 All are located on the coordinate axis adjacent to the engine speed, which is determined based on the engine speed and engine load to achieve the target water temperature, i.e., n EngSpd1 and n EngSpd2(There are no other coordinate axis values ​​in between), the engine load rho falls between rho1 and rho2 (where rho1 and rho2 are both on the adjacent coordinate axis of the engine load for the target coolant temperature determined based on engine speed and engine load, that is, there are no other coordinate axis values ​​between rho1 and rho2), and if there are more coordinate axis values ​​larger than rho2 in the engine load coordinate axis for the target coolant temperature determined based on engine speed and engine load, excluding rho1 and rho2: 1) If there is one and only one coordinate axis value larger than rho2, such as rho3, that is, rho3 is greater than rho2, and rho3 is the maximum value of the engine load coordinate axis value for the target coolant temperature determined based on engine speed and engine load, then the target coolant temperature corresponding to the engine load rho is linearly interpolated according to rho1 and rho3. In this case, although N1 = 4, the actual number of interpolations is 3 because there is no larger load available for linear interpolation; 2) If there is more than one coordinate axis value larger than rho2, such as rho3, rho4, etc., i.e., rho3 is greater than rho2, and rho4 is greater than rho3, then the target water temperature corresponding to the engine load rho is linearly interpolated based on rho1 and rho4. The above only illustrates the definition of "using a larger engine load for interpolation" when N1 = 4. The same principle applies when N1 is other values. The N1 value will be updated through self-learning later.

[0059] The second step is to determine the actual firing torque M of the engine. SprkTrqAct With the requested fire circuit torque M SprkTrqReq ratio And request fire circuit torque M SprkTrqReq With engine maximum torque M TrqMax (The maximum torque of the engine can be found in patent CN202010632793.4, "Method for Determining the Maximum Output Torque of a Gasoline Engine") The number of second linear interpolations N2 is determined as shown in Table 2. The smaller the value, the worse the engine's actual power response. To achieve engine torque as quickly as possible, the electrical load is reduced. Since the engine coolant temperature tends to increase as the engine load decreases, a larger number of linear interpolation lines are used, and a smaller engine load is employed for interpolation. A larger value indicates a greater engine power demand. Similarly, to achieve torque capability, the electrical load is reduced, and the coolant temperature is controlled at a relatively high level. Since the engine coolant temperature tends to increase as the engine load decreases, a larger number of linear interpolation lines are used, and interpolation is performed with a smaller engine load.

[0060] Table 2. Determination of the Number of Second Linear Interpolations N2

[0061]

[0062] In the table above, if the data on the horizontal and vertical axes do not fall within the table (including both the center and the outside of the table), N2 determines the value using adjacent linear interpolation. Values ​​within the center of the table (i.e., values ​​within the minimum and maximum range of the table's coordinate axes) are interpolated using linear interpolation, while values ​​outside the table (i.e., values ​​outside the minimum and maximum range of the table's coordinate axes) are directly equal to the edge values. Finally, after lookup and interpolation, rounding is performed.

[0063] "Using a smaller engine load for interpolation" – this needs to be explained as follows: assuming N2 is determined to be 4 based on the table above, and the current actual engine speed is read as n... EngSpd And it falls on n EngSpd1 and n EngSpd2 Between (where n) EngSpd1 and n EngSpd2 All are located on the coordinate axis adjacent to the engine speed, which is determined based on the engine speed and engine load to achieve the target water temperature, i.e., n EngSpd1 and n EngSpd2 (There are no other coordinate axis values ​​in between), the engine load rho falls between rho1 and rho2 (where rho1 and rho2 are both on the adjacent coordinate axis of the engine load for the target coolant temperature determined based on engine speed and engine load, i.e., there are no other coordinate axis values ​​between rho1 and rho2), and if, excluding rho1 and rho2, there are more coordinate axis values ​​smaller than rho1 in the engine load coordinate axis for the target coolant temperature determined based on engine speed and engine load: 1) If there is one and only one coordinate axis value larger than rho2, such as rho0, i.e., rho0 is smaller than rho1, and rho0 is the minimum value of the engine load coordinate axis value for the target coolant temperature determined based on engine speed and engine load, then the target coolant temperature corresponding to the engine load rho is linearly interpolated according to rho0 and rho2. In this case, although N2 = 4, the actual number of interpolations is 3 because there is no smaller load for linear interpolation; 2) If there is more than one coordinate axis value smaller than rho2, such as rho -2 ,rho -1 rho0…, that is, rho0 is less than rho1, rho -1 If it is less than rho0, then according to rho -1 The target water temperature corresponding to the linear interpolation engine load rho and rho2. The above only illustrates the definition of "interpolation using a smaller engine load" when N2=4; the same logic applies to other values ​​of N2.

[0064] The third step is to determine the target EGR rate r. EGRDsrd and actual EGR rate r EGRAct With target EGRr EGRDsrd ratio The number of third linear interpolations, N3, is determined as shown in Table 3. Target EGR rate r EGRDsrd The larger the value, the stronger the engine's anti-knock capability, and the higher the engine coolant temperature can be, thus reducing the electrical load (such as fan operation). Since engine coolant temperature tends to increase as engine load decreases, a larger number of linear interpolation iterations can be performed, while using a smaller engine load for interpolation; similarly... The larger the value, the stronger the engine's anti-knock capability, and the higher the engine coolant temperature can be, thus reducing the electrical load (such as the fan's operation). Since the engine coolant temperature tends to increase as the engine load decreases, a larger number of linear interpolation operations are needed, and interpolation can be performed using a smaller engine load.

[0065] Table 3. Determination of the Number of Third Linear Interpolations N3

[0066]

[0067] In Table N3 above, if the data on the horizontal and vertical axes do not fall within the table (including both the center and the outside of the table), N3 determines them using adjacent linear interpolation. Values ​​within the center of the table (i.e., values ​​within the minimum and maximum range of the table's coordinate axes) are interpolated using linear interpolation, while values ​​outside the table (i.e., values ​​outside the minimum and maximum range of the table's coordinate axes) are directly equal to the edge values. Finally, after interpolation, the values ​​are rounded to the nearest integer.

[0068] "Interpolation is performed using a smaller engine load," which is the same method used to obtain N2.

[0069] The fourth step is to determine the intake air temperature (the temperature of the gas entering the cylinder) T. MAT The number of fourth linear interpolation operations N4 is determined by the vehicle speed v, as shown in Table 4. Intake air temperature T MAT The lower the engine speed (v), the stronger its anti-knock capability, allowing for a higher engine coolant temperature to reduce electrical load (such as fan operation). Since engine coolant temperature tends to increase with lower engine load, a larger number of linear interpolation steps are needed, and a lower engine load is required for interpolation. Similarly, the higher the vehicle speed (v), the stronger the engine's heat dissipation capacity, resulting in stronger anti-knock capability and a higher engine coolant temperature, thus reducing electrical load (such as fan operation). Again, since engine coolant temperature tends to increase with lower engine load, a larger number of linear interpolation steps are needed, and a lower engine load is required for interpolation.

[0070] Table 4. Determination of the Number of Fourth Linear Interpolations N4

[0071]

[0072] In Table N4, if the data on the horizontal and vertical axes do not fall within the table (including both the center and the outside of the table), N4 determines them using adjacent linear interpolation. Values ​​within the center of the table (i.e., values ​​within the minimum and maximum range of the table's coordinate axes) are interpolated using linear interpolation, while values ​​outside the table (i.e., values ​​outside the minimum and maximum range of the table's coordinate axes) are directly equal to the edge values. Finally, after interpolation, the values ​​are rounded to the nearest integer.

[0073] "Interpolation is performed using a smaller engine load," which is the same method used to obtain N2.

[0074] It might be necessary to explain the definition of linear interpolation. Assuming the engine speed is constant, the engine load rho is linearly interpolated using rho1 and rho4. The target coolant temperature corresponding to engine load rho1 is T1, and the target coolant temperature corresponding to engine load rho4 is T4. Therefore, the target coolant temperature T corresponding to engine load rho after applying the linear interpolation rule is:

[0075]

[0076] Linear interpolation is an existing technology. The rotational speed is determined to be n. EngSpd1 With n EngSpd2 The target coolant temperature corresponding to the engine load rho is then determined by the current actual engine speed n. EngSpd And the engine speed is n EngSpd1 With n EngSpd2 The final target coolant temperature is obtained by linear interpolation of the target coolant temperature corresponding to the engine load rho.

[0077] The above four steps are executed only in one way within each control algorithm cycle: if N1 is greater than 2, then only interpolation with the number of interpolation steps N1 is used; if N1 is equal to 2, but N2 is greater than 2, then only interpolation with the number of interpolation steps N2 is used, and so on.

[0078] The next step will detail the self-learning update method for the first interpolation number N1. Self-learning updates can only be performed when the following conditions are met simultaneously:

[0079] (1) The engine speed is within the preset range, which is 850rpm to 6000rpm in this example, and the engine speed fluctuation range is ±20rpm;

[0080] (2) The engine load is within the preset range. In this example, it is 150 mgpl to 3000 mgpl, and the engine load fluctuation range is ±15 mgpl.

[0081] (3) The intake air temperature fluctuation range is within ±3℃;

[0082] (4) The vehicle speed fluctuation range is within ±2km / h;

[0083] (5) The actual EGR rate fluctuates within ±1%;

[0084] (6) The target EGR rate fluctuation range is within ±1%;

[0085] (7) The ratio of the actual engine torque to the target torque is within the preset range, which is ±5% in this example;

[0086] (8) The number of interpolations N1 has not been updated in this driving cycle.

[0087] The first interpolation count N1 is only allowed to be updated after all eight conditions above are met simultaneously and the duration exceeds T (3 seconds in this example). Once the above conditions are met, the number of times CNT meets the conditions under each operating condition (in this example, the method for determining the number of interpolations under the same self-learning operating condition is: the difference between engine speed, load, intake air temperature, vehicle speed, EGR rate, and actual engine torque does not exceed ±2%) is recorded. (CNT is recorded and accumulated separately under different operating conditions, and is immediately reset to 0 after the first interpolation count N1 is updated, or it will also be reset to 0 when CNT reaches the preset value of 10000, and will be accumulated again after the conditions are met):

[0088] 1) If, under a certain working condition, the number of CNTs exceeds the preset value (10000 in this example), and the number of knocks does not exceed the preset value (150 in this example), then N1 under the same working condition will be updated to 0.85 times the value before the N1 update and rounded to the nearest whole number. N1 will not be updated under other working conditions.

[0089] 2) If, under a certain operating condition, the number of CNTs exceeds the preset value (10000 in this example), and the number of low-intensity knocks (the ignition angle is delayed by no more than 2° after a knock in this example) does not exceed the preset value (150 in this example), then N1 under the same operating condition will be updated to 0.95 times the value before the N1 update and rounded to the nearest whole number. N1 will not be updated under other operating conditions.

[0090] 3) If, under a certain operating condition, the number of CNTs exceeds the preset value (10000 in this example), or the number of times high-intensity knock occurs (the ignition angle is delayed by more than 6° after knocking in this example) exceeds the preset value (1500 in this example), then N1 under the same operating condition will be updated to 1.2 times the value before the N1 update and rounded to the nearest whole number. N1 will not be updated under other operating conditions.

[0091] 4) N1 is not updated in other cases.

[0092] It should be noted that N1 is limited to a number not less than 2, and ultimately N1, N2, N3, and N4 are all not less than 2. The operating condition can be pre-entered into the memory, or the current operating condition can be compared with existing operating conditions in the memory, and if it is a new operating condition, it can be stored in the memory.

[0093] After N1 is updated, the updated number of interpolations N1 will be used in the new driving cycle.

[0094] The above completes the description of the coolant temperature control method with an EGR system. A flowchart of the coolant temperature control method with an EGR system of the present invention can be found here. Figure 1 .

[0095] The present invention also provides an engine that uses the engine coolant temperature control method with EGR system described in any one of the above to control the engine coolant temperature.

[0096] It should be noted that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0097] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0098] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling engine coolant temperature with an EGR system, characterized in that, This includes the following four situations: (1) The number of first linear interpolations N1 is determined based on the octane rating of the fuel and the engine back angle strength coefficient, and a larger engine load is used for interpolation; wherein, the smaller the octane rating of the fuel and the larger the engine back angle strength coefficient, the larger the number of first linear interpolations N1; the engine back angle strength coefficient is , The ignition angle is delayed due to the current detonation. Maximum permissible ignition angle delayed for detonation; (2) Based on the actual firing torque of the engine With request fire circuit torque ratio and request fire circuit torque With engine maximum torque ratio The number of second linear interpolation operations, N2, is determined, and interpolation is performed using a smaller engine load; where, The smaller, The larger the value, the larger the number of second linear interpolations N2; (3) Based on the target EGR rate and actual EGR rate Compared with the target EGR rate ratio The number of third linear interpolation operations, N3, is determined, and interpolation is performed using a smaller engine load; where the target EGR rate is... The larger, The larger the value, the larger the number of third linear interpolations N3; (4) Based on the intake air temperature and vehicle speed The fourth linear interpolation number N4 is determined, and interpolation is performed using a smaller engine load; among which, the intake air temperature The lower the speed The larger the value, the larger the number of fourth linear interpolations N4; Only one of the above four scenarios will be executed within each control cycle: First, determine if the number of linear interpolations N1 is greater than 2; if yes, then use the number of linear interpolations N1 and apply a larger engine load for interpolation; if not, then: Next, determine whether the number of second linear interpolations N2 is greater than 2; if yes, then use the second number of linear interpolations N2, and use a smaller engine load for interpolation; if not, then: Continue to determine whether the number of third linear interpolation N3 is greater than 2; if yes, then use the number of third linear interpolation N3 and use a smaller engine load for interpolation; if no, then use the number of fourth linear interpolation N4 and use a smaller engine load for interpolation.

2. The engine coolant temperature control method with EGR system according to claim 1, characterized in that, The number of first linear interpolations N1, second linear interpolations N2, third linear interpolations N3, and fourth linear interpolations N4 are all greater than or equal to 2 and are integers.

3. The engine coolant temperature control method with EGR system according to claim 1, characterized in that, The method for interpolating using a larger engine load is as follows: Assuming the current actual engine speed is read as And fall and Between, the current actual engine load is And fall and Between; among them, and as well as and The target coolant temperature is determined based on adjacent values ​​in the table, which are based on engine speed and engine load. If there is no comparison in the table For large engine load values, the final number of linear interpolation iterations is taken as 2, i.e., according to... and Engine load is obtained through linear interpolation. The corresponding target coolant temperature; If the table contains ratios For larger engine load values, obtain a ratio Number of large engine load values And determine the determined number of linear interpolations and... The size; if the determined number of linear interpolations is less than or equal to Then the final number of linear interpolations is taken as the determined number of linear interpolations, that is, according to... and the table The next The engine load is obtained by linear interpolation of the engine load. The corresponding target coolant temperature, Subtract 1 from the determined number of linear interpolations; if the determined number of linear interpolations is greater than... Then the final number of linear interpolations is taken as According to The engine load is obtained by linear interpolation of the maximum engine load in the table. The corresponding target coolant temperature; The rotational speeds were obtained using the methods described above. and Engine load The corresponding target coolant temperature, and then the current actual engine speed. And engine speed is and Engine load The final target coolant temperature is obtained by linear interpolation of the corresponding target coolant temperature. Conversely, if the table does not specify a method for interpolation using a smaller engine load: For smaller engine load values, the final number of linear interpolations is 2, i.e., according to... and Engine load is obtained through linear interpolation. The corresponding target coolant temperature; If the table contains ratios A smaller engine load value yields a higher value. Number of small engine load values And determine the determined number of linear interpolations and The size; if the determined number of linear interpolations is less than or equal to Then the final number of linear interpolations is taken as the determined number of linear interpolations, that is, according to... and the table The previous chapter The engine load is obtained by linear interpolation of the engine load. The corresponding target coolant temperature, Subtract 1 from the determined number of linear interpolations; if the determined number of linear interpolations is greater than... Then the final number of linear interpolations is taken as According to The engine load is obtained by linear interpolation of the minimum engine load in the table. The corresponding target coolant temperature; The rotational speeds were obtained using the methods described above. and Engine load The corresponding target coolant temperature, and then the current actual engine speed. And engine speed is and Engine load The final target coolant temperature is obtained by linear interpolation of the corresponding target coolant temperature.

4. The engine coolant temperature control method with EGR system according to claim 1, characterized in that, The maximum permissible ignition angle for detonation delay is 10°.

5. The engine coolant temperature control method with EGR system according to claim 1, characterized in that, The number of each linear interpolation is determined by looking up a table: If the horizontal and vertical axis data of the data to be retrieved are not in the table, the number of linear interpolation values ​​is determined by the method of adjacent linear interpolation. That is, the values ​​in the middle of the table data are determined by linear interpolation, and the values ​​outside the table data are directly equal to the edge values. Here, the values ​​in the middle of the table data indicate that the horizontal and vertical axis data of the data to be retrieved are within the minimum and maximum values ​​of the table coordinate axes, and the values ​​outside the table data indicate that the horizontal and vertical axis data of the data to be retrieved are not within the minimum and maximum values ​​of the table coordinate axes. After interpolating from the table, round to the nearest integer.

6. The engine coolant temperature control method with EGR system according to claim 1, characterized in that, After determining the number of first linear interpolations N1, it is determined whether the conditions for self-learning update are met; if so, the number of first linear interpolations N1 is updated through self-learning to determine the final number of first linear interpolations N1.

7. The engine coolant temperature control method with EGR system according to claim 6, characterized in that, The conditions for self-learning updates are: The engine speed is within the preset speed range, and the engine speed fluctuation is within the preset speed fluctuation range; The engine load is within the preset load range, and the engine load fluctuation is within the preset load fluctuation range; The intake air temperature fluctuation range is within the preset temperature fluctuation range; The vehicle speed fluctuation range is within the preset vehicle speed fluctuation range; The actual EGR rate fluctuation range is within the preset EGR rate fluctuation range; The target EGR rate fluctuation range is within the preset target EGR rate fluctuation range; The ratio of the engine's actual firing torque to the target firing torque is within the preset range; The number of first linear interpolations N1 was not updated in this driving cycle; When all of the above conditions are met, the conditions for self-learning and updating are satisfied.

8. The engine coolant temperature control method with EGR system according to claim 6, characterized in that, The self-learning update process is as follows: If the self-learning update conditions are met and the maintenance time exceeds the preset maintenance time, the CNT count for the corresponding operating condition is incremented by 1. (1) If the number of CNTs exceeds the preset number under a certain working condition, and the number of knocks does not exceed the preset value, then the number of first linear interpolation N1 under the corresponding working condition is updated to 0.85 times and rounded to the nearest whole number. N1 under other working conditions is not updated. (2) If the number of CNTs exceeds the preset number under a certain working condition, and only the number of low-intensity knocks does not exceed the preset value, then the number of first linear interpolation N1 under the corresponding working condition is updated to 0.95 times and rounded to the nearest whole number. N1 under other working conditions is not updated. (3) If the number of CNTs exceeds the preset number value under a certain working condition, and the number of high-intensity knocks exceeds the preset knock count value, then the number of first linear interpolation N1 under the corresponding working condition is updated to 1.2 times and rounded to the nearest whole number. N1 under other working conditions is not updated. (4) N1 is not updated in other cases; Wherein, the CNT count represents the cumulative number of times that the self-learning update condition is met and the maintenance time exceeds the preset maintenance time under the corresponding working condition. The CNT count for each working condition is recorded independently. After N1 is updated, CNT is immediately reset to 0, and the updated first linear interpolation number N1 is used in the new driving cycle. Same operating conditions mean that the differences in engine speed, load, intake air temperature, vehicle speed, EGR rate, and actual engine torque do not exceed ±2%; and N1 is limited to a number not less than 2.

9. An engine, characterized in that, The engine uses the engine coolant temperature control method with EGR system as described in any one of claims 1 to 8 to control the engine coolant temperature.

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