JP3718857B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
[Industrial application fields]
  The present invention relates to a control device for an internal combustion engine, and in particular, when the engine water temperature is at least a predetermined water temperature according to engine operating conditions, the target air-fuel ratio of the engine intake mixture is set to a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio. The present invention relates to a control device in an internal combustion engine to be switched.
[0002]
[Prior art]
  Conventionally, as an air-fuel ratio control device which is a control device for an internal combustion engine, there is one as disclosed in, for example, Japanese Patent Laid-Open No. 60-230532.
  This is a means for detecting the specific component concentration in the exhaust gas, and a means for performing closed-loop control of the air-fuel ratio state of the engine to the target air-fuel ratio leaner than the stoichiometric air-fuel ratio in accordance with the specific component concentration detected during engine warm-up. And an air-fuel ratio control apparatus for an internal combustion engine, and means for variably controlling the engine target air-fuel ratio detected by the closed-loop control means according to the engine temperature. Close loop control to the lean target air-fuel ratio, and the target air-fuel ratio can be variably controlled according to the engine temperature, so that the air-fuel ratio during warm-up is controlled to a value according to the degree of fuel atomization state at that time Therefore, an attempt is made to improve the fuel consumption rate during warm-up without adversely affecting the operating characteristics.
[0003]
[Problems to be solved by the invention]
  However, such a system that performs closed loop control of the air-fuel ratio to the lean target air-fuel ratio during engine warm-up has the following problems.
  That is, since the air-fuel ratio is corrected only during warm-up, even if the engine temperature changes after warm-up, the target air-fuel ratio remains constant and the target air-fuel ratio is not changed. However, there is a problem that the amount of NOx emission increases or the engine stability deteriorates.
[0004]
  The present invention has been made paying attention to such conventional problems, and at least when the engine water temperature is equal to or higher than a predetermined water temperature according to the engine operating conditions, the target air-fuel ratio of the engine intake air-fuel mixture is set to be higher than the stoichiometric air-fuel ratio. An internal combustion engine that switches to a lean air-fuel ratio on the lean side. By changing the target value of the control factor during lean combustion operation according to the engine water temperature, it is possible to prevent an increase in NOx emissions after warm-up or to stabilize the engine It is an object of the present invention to provide a control device for an internal combustion engine that can improve the engine speed.
[0005]
[Means for Solving the Problems]
  Therefore, according to the first aspect of the present invention, the operating condition detecting means for detecting the engine operating condition including at least the engine water temperature and the stability for detecting the degree of stability of the engine indicated by the rotational fluctuation in the engine based on the combustion state of the engine. The engine intake air-fuel mixture target when the engine water temperature is equal to or higher than a predetermined water temperature and the engine stability level detected by the stability detection means is higher than the predetermined stability level according to the engine operating conditions. When the air-fuel ratio switching control means for switching the air-fuel ratio to a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, and when the target air-fuel ratio by the air-fuel ratio switching control means is controlled to be switched to the lean air-fuel ratio, the engine operating condition is Based on the control factor correction amount calculation means for calculating the correction amount of the control factor for controlling at least one engine combustion state, and the control factor correction amount calculation means Control amount calculation means for calculating a control amount of the engine control factor based on a control factor correction amount; control factor control means for controlling the control factor based on the control amount calculated by the control amount calculation means; The degree of stability based on the control factor controlled by the control factor control means is higher than the predetermined degree of stability.However, if the degree of stability is high,Related to air-fuel ratio switching control meansSaidSpecified water temperatureTo be lowerAnd a water temperature correction amount calculating means for calculating a water temperature correction amount to be corrected.
[0006]
  Also,Claim 2In the described invention, the learning value of the control factor that controls at least one engine combustion state based on the engine operating condition when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means. The control factor learning value calculating means for calculating the control factor learning value, the rewritable control factor learning value storage means for storing the control factor learning value, and the control factor learning value stored in the control factor learning value storage means And a control factor learned value updating unit that rewrites the control factor learned value calculated by the value calculating unit.
[0007]
  AlsoClaim 3In the described invention, when the engine water temperature is high when the engine ignition timing is included as a control factor for controlling the engine combustion state and the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means. The correction amount related to the ignition timing may be calculated so that the ignition timing is more retarded.
  AlsoClaim 4In the described invention, the control factor for controlling the engine combustion state is set as the target air-fuel ratio of the engine intake air-fuel mixture and the ignition timing of the engine. When the control is switched to the air-fuel ratio, the correction amount related to the target air-fuel ratio is calculated so as to correct to the richer air-fuel ratio as the engine water temperature is lower, and the retarded ignition timing is reached. As described above, the correction amount related to the ignition timing may be calculated.
[0008]
  AlsoClaim 5As the described invention, the stability detecting means includes an engine speed detecting means for detecting the engine speed, and a rotation fluctuation value calculating means for calculating an engine speed fluctuation value based on a detection value of the engine speed detecting means. And the degree of stability of the engine may be detected based on the calculated value of the rotation fluctuation value calculating means.
[0009]
[Action / Effect]
  According to the first aspect of the present invention, when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio, the control amount of the control factor that controls at least one engine combustion state is corrected and calculated to obtain the calculated control amount. The control factor is controlled on the basis of the lean air-fuel ratio when at least the engine water temperature is equal to or higher than the predetermined water temperature and the engine stability level detected by the stability detection means is higher than the predetermined stability level. So that the degree of stability based on the control factor is higher than a predetermined degree of stability.If the degree of stability is high,Related to air-fuel ratio switching control meansSaidSpecified water temperatureTo be lowerBecause it is corrected, the stability caused by the combustion state is further increased.At the same time, the lean operation permission range is expanded to improve fuel efficiency.It becomes possible.
[0010]
  Also,Claim 2According to the described invention, when calculating the control factor correction amount, a new learning value obtained by updating a control factor learning value rewritable by so-called learning can be used as the correction amount, and the control factor is controlled. Controllability is improved.
  Claim 3According to the described invention, when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means, the ignition temperature is corrected so that the ignition timing is retarded more when the engine water temperature is higher. Is done.
[0011]
  In other words, the higher the temperature, the lower the final exhaust temperature of combustion to reduce NOx, and the proper combustion temperature is maintained to burn HC, thereby reducing the amount of generation.
  Also,Claim 4According to the described invention, when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means, the engine water temperature is corrected to become a richer air-fuel ratio as the temperature is lower. At the same time, the ignition timing is corrected so that the ignition timing is retarded.
[0012]
  Also,Claim 5According to the described invention, the degree of stability of the engine is detected based on the calculated value of the rotation fluctuation value calculating means. However, since the rotation fluctuation value reliably reflects the degree of stability of the engine, in a predetermined operating state. By calculating the rotation fluctuation value, the degree of stability of the engine itself can be detected.
[0013]
【Example】
  Embodiments of the present invention will be described below with reference to the drawings.
  FIG. 1 is a diagram showing a system configuration according to an embodiment of the present invention.
  In FIG. 1, an intake passage 2 and an exhaust passage 3 are connected to the engine body 1. The intake passage 2 is provided with an air flow meter 4 for detecting the intake air flow rate, a throttle valve 5 and a fuel injection valve 6. Further, the exhaust passage 3 is an O that detects the oxygen concentration in the exhaust.₂ A sensor 7 is provided. 8 is a throttle sensor for detecting the opening degree of the throttle valve 5, 9 is a crank angle sensor which is an engine speed detecting means for detecting the engine speed, 10 is a water temperature sensor, and 11 is a gear position sensor for detecting the gear position of the transmission. It is.
[0014]
  The control unit 20 has a built-in microcomputer, and executes stability control, which will be described later, so that the engine rotation fluctuation detected based on the engine rotation detection signal from the crank angle sensor 9 becomes the target stability. The control unit 20 includes a memory serving as a storage unit that freely stores and rewrites control data calculated at the time of stability control, and this memory corresponds to a control factor learned value storage unit and a water temperature learned value storage unit. Then, as shown in each flowchart described later, the control unit 20 includes an air-fuel ratio switching control means, a target air-fuel ratio correction amount calculation means, a target air-fuel ratio calculation means, an air-fuel ratio control means, a control factor correction amount calculation means, a control amount. Calculation means, control factor control means, stability detection means, water temperature correction amount calculation means, air-fuel ratio switching determination means, air-fuel ratio switching prohibition means, control factor learning value calculation means, control factor learning value update means, water temperature learning value calculation means Each function of the water temperature learning value update means and the rotation fluctuation value calculation means is provided in software.
[0015]
  Next, the control operation of the present embodiment will be described with reference to FIGS.
  First, FIG. 2 and FIG. 3 are basic control routines according to first to fourth embodiments described below.
  FIG. 2 shows the control amount related to the combustion stabilization of the engine control factor (for example, the fuel injection amount in the first embodiment, the ignition advance angle in the second embodiment) in the stability control of this embodiment, that is, the fuel-air ratio. This is a routine for calculating the correction coefficient Dml and is a function of the control amount calculation means. In this embodiment, this routine detects the engine speed based on the reference signal (REF signal) for each cylinder output from the crank angle sensor, and is executed in the reference signal cycle. In addition, when detecting an engine speed based on the angle signal from a crank angle sensor, it performs by time synchronization.
[0016]
  First, in step 1 (shown by S1 in the figure and the same shall apply hereinafter), the target fuel-air ratio correction coefficient Tdml is set from the map fuel-air ratio Mdml by a target fuel-air ratio correction coefficient setting routine described later.
  From the next step 2, a damper operation for switching the fuel-air ratio is performed. The purpose of this is to prevent a sudden change in torque and to make the driving performance appropriate by gradually switching the air-fuel ratio.
[0017]
  First, in step 2, the latest fuel-air ratio correction coefficient Dml currently stored and held is compared with the target fuel-air ratio correction coefficient Tdml set in step 1, and if Dml ≧ Tdml (YES) ), It is determined that the target is richer, and the process proceeds to step 3 where the stored Dml is the previous value Dml._n-1 The new Dml is obtained by subtracting the preset air-fuel ratio change rate value Ddmll in the lean direction (see FIG. 3), and in step 4, Dml is restricted so that it does not become less than Tdml. However, the fuel-air ratio correction coefficient Dml is updated, and the flow ends.
[0018]
  If Dml ≧ Tdml is not satisfied (NO), it is determined that the vehicle is leaner than the target, and the process proceeds to step 5 where the stored Dml is set to the previous value Dml._n-1 Is added to the preset air-fuel ratio change value Ddmlr in the rich direction to obtain a new Dml (see FIG. 3), and in step 6, Dml is limited so that Dml does not exceed Tdml. However, the fuel-air ratio correction coefficient Dml is updated, and the flow ends.
[0019]
  The fuel-air ratio correction coefficient Dml thus obtained is used for calculating the fuel injection amount.
  Next, a routine for calculating and outputting the fuel injection amount using the fuel-air ratio correction coefficient Dml calculated as described above will be described with reference to the flowchart of FIG. This routine is the function of the control means. This routine is executed every 10 ms. Of course, when the control factor is the ignition timing, the routine is not used.
[0020]
  First, in step 11, the target fuel-air ratio Tfbya is calculated by the following equation using the fuel-air ratio correction coefficient Dml.
  Tfbya = Dml + Ktw + Kas
  Here, Ktw is a water temperature increase correction coefficient, and Kas is a post-startup increase correction coefficient.
  Next, in step 12, the detection signal of the air flow meter 4 is A / D converted and linearized to obtain the intake air flow rate Q.
[0021]
  In step 13, an average value Avtp for a predetermined time is obtained from the basic injection amount Tp (= K × Q / Ne, K is a proportional constant) calculated based on the engine speed Ne and the intake air flow rate Q.
  In step 14, the actual fuel injection amount Ti is obtained by the following equation.
  Ti = Avtp × Tfbya × Ktr × (α + αm) + Ts
  Here, Ktr is a transient correction coefficient, α is an air-fuel ratio feedback correction coefficient, αm is an air-fuel ratio learning correction coefficient, and Ts is an invalid pulse width.
[0022]
  Next, in step 15, fuel cut determination is performed. In step 16, it is determined whether or not the fuel cut condition is satisfied. If NO, the fuel injection amount Ti is stored in the output register in step 17. Prepare for jetting. If YES, step 18 stores Ts in the output register. In addition, except the calculation of Tfbya, it is the same as the calculation processing of the conventional fuel injection amount.
[0023]
  next,First embodiment related to basic control operationWill be described with reference to FIGS.In the first embodiment,The control factor is the target fuel-air ratio correction coefficient Tdml used in the flow of FIG. 2 as the target air-fuel ratio of the engine intake air-fuel mixture, and a routine for calculating the target fuel-air ratio correction coefficient Tdml from the map fuel-air ratio Mdml This will be described with reference to the flowchart of FIG. Note that the target fuel / air ratio correction coefficient Tdml varies depending on the engine water temperature. This routine is executed by a background job (BGJ).
[0024]
  First, in step 21, it is determined whether or not the engine water temperature Tw detected by the water temperature sensor 10 is equal to or higher than a predetermined water temperature Twl #, which is a fixed value. If it is determined that Tw ≧ Twl #, step 21 is performed. Proceed to 22.
  In step 22, the lean condition is determined. This is to determine the region where the lean combustion is desired from the requirements of fuel consumption, exhaust, and drivability, and to determine whether the current operating condition is in that range. Detailed description is omitted here, and the description will be given later. In step 22, a lean flag Flean described later is also determined.
[0025]
  Next, at step 22, if the lean condition or Flean = 1, the routine proceeds to step 23, and the lean fuel-air ratio map MDMLL shown in FIG. 6 is referred to using the engine speed Ne and the basic injection amount Tp, and the result Is Mdml.
  In step 24, a water temperature corrected fuel-air ratio Twdml is calculated from the engine water temperature Tw. For example, as shown in FIG. 7, this is calculated from a table, and the higher the engine water temperature Tw with respect to the reference water temperature (reference fuel / air ratio MDMLL set water temperature), the higher the vaporization performance, and the greater the sensitivity. As a result, the amount of correction increases. Here, since the water temperature corrected fuel-air ratio Twdml is an amount subtracted from the map fuel-air ratio Mdml, the target fuel-air ratio correction coefficient Tdml becomes leaner as the engine water temperature Tw becomes higher than the reference water temperature. The amount is to be corrected.
[0026]
  The reference water temperature is higher than the predetermined water temperature Twl # (Twl # ≦ reference water temperature).
  In step 25, the target fuel / air ratio correction coefficient Tdml is calculated by subtracting the water temperature corrected fuel / air ratio Twdml from the map fuel / air ratio Mdml.
  On the other hand, when the engine water temperature Tw is lower than the predetermined water temperature Twl # which is a fixed value at step 21, that is, when it is determined that Tw <Twl #, and at step 22, it is determined that the lean condition is not satisfied or that Flean = 0. If this is the case, the process proceeds to step 26, and the theoretical air-fuel ratio map MDMLS not including the lean region shown in FIG. 8 is referred to using the engine speed Ne and the basic injection amount Tp, and the result is Mdml.
[0027]
  In step 27, the map fuel-air ratio Mdml is set as the target fuel-air ratio correction coefficient Tdml, and this routine is finished.
  That is, in this routine, learning of the fuel-air ratio as a control factor is also performed.Has been done.
  Therefore, in the first embodiment, when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means, the engine water temperature is corrected to a leaner air-fuel ratio as the temperature increases. Since the NOx emission limit shifts to the lean air-fuel ratio side as the water temperature becomes higher, it becomes possible to keep the NOx emission amount within the limit by the air-fuel ratio correction to the lean side, and to improve the fuel consumption. There is an effect of becoming.
[0028]
  Next, the second embodimentThe control operation will be described with reference to FIGS. In the second embodiment, the control factor is the target ignition timing Tadv as the ignition timing of the engine intake air-fuel mixture, and a routine for calculating the target ignition timing Tadv from the ignition timing Madv corresponding to the map fuel-air ratio is shown in FIG. This will be described with reference to a flowchart. The target ignition timing Tadv varies depending on the engine water temperature. This routine is executed by a background job (BGJ).
[0029]
  First, in step 31, it is determined whether or not the engine water temperature Tw detected by the water temperature sensor 10 is equal to or higher than a predetermined water temperature Twl # that is a fixed value. If it is determined that Tw ≧ Twl #, step 31 is performed. Proceed to 32.
  In step 32, the lean condition is determined. This is to determine the region in which lean combustion is desired based on the requirements of fuel consumption, exhaust, and drivability, and to determine whether the current operating condition is in that range. Detailed description is omitted here, and the description will be given later. In step 32, a lean flag Flean described later is also determined.
[0030]
  Next, at step 32, if the lean condition condition or Flean = 1, the routine proceeds to step 33, where the lean fuel / air ratio point-of-fire advance angle map MADVL (not shown) is used using the engine speed Ne and the basic injection amount Tp. The result is referred to as Madv.
  In step 34, a water temperature corrected ignition advance angle Twadv is calculated from the engine water temperature Tw. For example, as shown in FIG. 10, this is calculated from a table. The higher the engine water temperature Tw with respect to the reference water temperature (reference ignition advance angle MADVL set water temperature), the lower the final exhaust temperature of combustion. In order to reduce NOx and to maintain an appropriate combustion temperature to burn HC and reduce the amount of generation, the water temperature correction ignition advance angle is set larger. Here, the water temperature correction ignition advance angle Twadv is an amount that is subtracted from the map ignition advance angle Madv. Therefore, as the engine water temperature Tw becomes higher than the reference water temperature, the ignition advance angle is retarded. ing.
[0031]
  The reference water temperature is higher than the predetermined water temperature Twl # (Twl # ≦ reference water temperature).
  In step 35, the target ignition advance angle Tadv is calculated by subtracting the water temperature correction ignition advance angle Twadv from the map ignition advance angle Madv.
  On the other hand, when the engine water temperature Tw is lower than the predetermined water temperature Twl # which is a fixed value at step 31, that is, when it is determined that Tw <Twl #, and at step 32, it is determined that the lean condition is not satisfied or that Flean = 0. If YES, the routine proceeds to step 36, where a theoretical air-fuel ratio point-in-time ignition advance map MADVS (not shown) is referenced using the engine speed Ne and the basic injection amount Tp, and the result is taken as Madv.
[0032]
  In step 37, the map ignition advance angle Madv is set as the target ignition advance angle Tadv, and the routine ends. That is, in the routine, learning of the ignition timing as a control factor is also performed, and thus the second embodiment also has a configuration according to the invention of claim 3.
  Therefore, in the second embodiment, when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means, the retarded ignition timing becomes higher as the engine water temperature becomes higher. As a result, the amount of NOx generated can be reduced.
[0033]
  Next, the control operation of the third embodiment according to the first aspect of the present invention will be described with reference to FIGS. Third embodimentThenA lean permission water temperature Twp for judging whether or not to switch the target air-fuel ratio of the engine intake air-fuel mixture to a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratioUpdate. First, a lean permission water temperature Twp calculation permission determination routine for determining whether or not the lean permission water temperature Twp is calculated based on the map fuel-air ratio Mdml will be described with reference to the flowchart of FIG. This routine is executed by a background job (BGJ).
[0034]
  First, in step 41, it is determined whether or not the engine water temperature Tw detected by the water temperature sensor 10 is equal to or higher than the lean allowable water temperature previous value Twp−1 previously calculated by the lean allowable water temperature Twp calculation routine, and Tw ≧ If it is determined that Twp−1, the process proceeds to step 42.
  In step 42, the lean condition is determined. This is to determine the region where the lean combustion is desired based on the demands of fuel consumption, exhaust, and drivability, and to determine whether the current operating condition is in that range. Detailed description is omitted here, and the description will be given later. In step 42, a lean flag Flean described later is also determined.
[0035]
  Next, at step 42, if the lean condition or Flean = 1, the routine proceeds to step 43, and the lean fuel-air ratio map MDMLL shown in FIG. 6 is referred to using the engine speed Ne and the basic injection amount Tp, and the result Is Mdml.
  In step 44, a water temperature corrected fuel-air ratio Twdml is calculated from the engine water temperature Tw. For example, as shown in FIG. 7, this is calculated from a table, and the higher the engine water temperature Tw with respect to the reference water temperature (reference fuel / air ratio MDMLL set water temperature), the higher the vaporization performance, and the greater the sensitivity. As a result, the amount of correction increases. Here, since the water temperature corrected fuel-air ratio Twdml is an amount subtracted from the map fuel-air ratio Mdml, the target fuel-air ratio correction coefficient Tdml becomes leaner as the engine water temperature Tw becomes higher than the reference water temperature. The amount is to be corrected.
[0036]
  In step 45, the target fuel / air ratio correction coefficient Tdml is calculated by subtracting the water temperature corrected fuel / air ratio Twdml from the map fuel / air ratio Mdml.
  In step 46, O₂ It is determined whether or not the difference between the actual fuel / air ratio Ddm calculated based on the value detected by the sensor 7 and the target fuel / air ratio correction coefficient Tdml calculated in step 45 is equal to or less than a predetermined value ε. Thus, it is determined whether or not the lean permission water temperature is appropriate. If | Ddm−Tdml | ≦ ε, the process proceeds to step 47.
[0037]
  In step 47, a lean permission water temperature Twp calculation routine, which will be described later, is executed, a lean permission water temperature Twp is calculated, and the process ends.
  On the other hand, at step 41, the engine water temperature Tw becomes the lean permitted water temperature previous value Twp._n-1(Tw <Twp_n-1), And when it is determined at step 42 that the lean condition is not satisfied or Fleen = 0, the routine proceeds to step 48, where the theoretical air-fuel ratio map MDMLS not including the lean region shown in FIG. Reference is made using Ne and the basic injection amount Tp, and the result is Mdml.
[0038]
  In step 49, the map fuel-air ratio Mdml is set as the target fuel-air ratio correction coefficient Tdml, and this routine is finished. Next, a lean permission water temperature Twp calculation routine for calculating the lean permission water temperature Twp will be described with reference to the flowchart of FIG.
  In step 51, the stability of the engine speed is calculated based on the cycle of the reference signal (REF signal) from the crank angle sensor 9. This calculation method will be described with reference to the flowchart of FIG.
[0039]
  In step 52, the lean permission water temperature correction update amount Dtwh is calculated from the stability. For example, as shown in FIG. 13, this is calculated from a table, but a difference from a predetermined slice level SL1 # is calculated from rotation fluctuation calculation data Lljd obtained by a stability detection routine described later, and stable. If the degree is large, that is, if Lljd <SL1 #, even if the lean permit water temperature is lowered and the shift to lean operation is performed quickly, the drivability is not deteriorated. It is trying to improve.
[0040]
  In step 53, a new lean allowable water temperature Twp is obtained by adding the calculated lean allowable water temperature correction update amount Dtwh to the previous value Twpn-1 in the stored lean allowable water temperature Twp. Further, in step 54, lean In order to limit the permitted water temperature Twp to a predetermined range, the lean permitted water temperature Twp is updated while giving the upper limit TwU # and the lower limit TwD # to the Twp, and the flow ends.
[0041]
  That is, in this routine, normal learning related to the lean permission water temperature as a control factor is performed.
  Here, the effect | action which correct | amends and calculates the lean permission water temperature Twp by the said routine is demonstrated.
  In the engine single unit evaluation, the evaluation is usually performed at a predetermined water temperature (for example, 80 ° C.). However, the water temperature changes in an actual vehicle, and the water temperature may change near 20 ° C. even during mode evaluation.
[0042]
  That is, there is a problem that the result of the evaluation by the single engine evaluation cannot be obtained by the vehicle, which is a very difficult factor for matching.
  On the other hand, when matching is performed at a predetermined water temperature, for example, when the water temperature increases by 15 ° C, the NOx emission amount may be about twice as large. NOx will be discharged.
That is, in order to achieve both the exhaust emission control value and the drivability, it is necessary to secure a predetermined value for the conforming region. If the control factor is not corrected by the water temperature, the range of the water temperature that can be permitted to lean is narrowed, and the fuel efficiency improvement rate due to lean is reduced.
[0043]
  For the above reasons, during lean operation, the target value of the control factor (for example, air-fuel ratio, ignition timing, etc.) due to the water temperature is corrected to suppress the NOx emission, thereby stabilizing the emission (vehicle emission evaluation / testing). Can be obtained).
  In addition, since it becomes possible to expand the permitted water temperature range of lean, it becomes possible to improve fuel efficiency. Therefore, according to the third embodiment, when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio, the control amount of the control factor that controls at least one engine combustion state is corrected, and the calculated control amount is calculated. The control factor is controlled based on the above, but when at least the engine water temperature is equal to or higher than the predetermined water temperature and the degree of stability of the engine detected by the stability detecting means is higher than the predetermined degree of The control to switch to the fuel ratio is performed, and the predetermined water temperature related to the air-fuel ratio switching control means is corrected so that the degree of stability based on the control factor is higher than the predetermined degree of stability. There is an effect that it is possible to further increase.
[0044]
  Next, the stability detection routine of FIG. 14 will be described. In addition, what is shown in FIG. 14 detects the said stability from the rotation fluctuation | variation of an engine.
  First, in step 61, an initial process, for example, a rotation speed conversion process for measuring the output interval (cycle) of the cylinder-specific reference signal every 180 ° for each cylinder and calculating the engine speed from the measured value is performed.
[0045]
  In step 62, filter processing for removing the 0.5th order component of the rotation signal is performed. In step 63, a filter process is performed to remove a component that changes depending on the vehicle speed of the rotation signal. The process is performed in rotation synchronization as described above.
  In step 64, bandpass filter processing is performed. In step 65, the result of the filter processing is stored as rotation fluctuation calculation data Lljd, thereby ending this flow. Here, the stability detection routine shown in FIG.5It has the structure of the described invention.
[0046]
  That is, by adopting the stability detection routine, it is possible to detect the degree of stability of the engine itself.
  next,Of the fourth embodimentThe control operation will be described with reference to FIGS. In the fourth embodiment, the control factor is the target fuel-air ratio correction coefficient Tdml used in the flow of FIG. 2 as the target air-fuel ratio of the engine intake mixture and the target ignition timing Tadv as the ignition timing of the engine intake mixture A routine for calculating the target fuel / air ratio correction coefficient Tdml from the map fuel / air ratio Mdml and calculating the target ignition timing Tadv from the ignition timing Madv corresponding to the map fuel / air ratio will be described with reference to the flowchart of FIG. . The target fuel / air ratio correction coefficient Tdml and the target ignition timing Tadv vary depending on the engine water temperature. This routine is executed by a background job (BGJ).
[0047]
  First, in step 101, it is determined whether or not the engine water temperature Tw detected by the water temperature sensor 10 is equal to or higher than a predetermined water temperature Twl #, which is a fixed value. If it is determined that Tw ≧ Twl #, step 101 is performed. Proceed to 102.
  In step 102, the lean condition is determined. This is to determine the region in which lean combustion is desired from the requirements of fuel consumption, exhaust, and drivability, and to determine whether the current operating condition is in that range. Detailed description is omitted here, and the description will be given later. In step 102, the aforementioned lean flag Flean is also determined.
[0048]
  Next, at step 103, if the lean condition or Flean = 1, the routine proceeds to step 103, and a lean fuel-air ratio map MDMLL (not shown) is referred to using the engine speed Ne and the basic injection amount Tp. The result is Mdml.
  In step 104, a lean fuel-air ratio time-of-fire advance angle map MADVL (not shown) is referred to using the engine speed Ne and the basic injection amount Tp, and the result is designated as Madv.
[0049]
  In step 105, a water temperature corrected fuel-air ratio Twdml is calculated from the engine water temperature Tw. For example, as shown in FIG. 16, this is calculated from a table. The higher the engine water temperature Tw with respect to the reference water temperature (reference fuel / air ratio MDMLL set water temperature), the higher the vaporization performance, and the greater the sensitivity. As a result, the amount of correction increases. Here, since the water temperature corrected fuel-air ratio Twdml is an amount subtracted from the map fuel-air ratio Mdml, the target fuel-air ratio correction coefficient Tdml becomes leaner as the engine water temperature Tw becomes higher than the reference water temperature. The amount is to be corrected.
[0050]
  The reference water temperature is higher than the predetermined water temperature Twl # (Twl # ≦ reference water temperature).
  In step 106, the target fuel-air ratio correction coefficient Tdml is calculated by subtracting the water temperature-corrected fuel-air ratio Twdml from the map fuel-air ratio Mdml.
  Further, in step 107, a water temperature corrected ignition advance angle Twadv is calculated from the engine water temperature Tw. For example, as shown in FIG. 17, this is calculated from a table. Unlike the case where only the ignition timing is corrected alone, the engine water temperature Tw with respect to the reference water temperature (reference ignition advance MADVL set water temperature). As the temperature becomes lower, the water temperature correction ignition advance angle is set larger. Here, the water temperature correction ignition advance angle Twadv is an amount that is subtracted from the map ignition advance angle Madv. Therefore, as the engine water temperature Tw becomes lower than the reference water temperature, the ignition advance angle is retarded. ing.
[0051]
  The reference water temperature is higher than the predetermined water temperature Twl # (Twl # ≦ reference water temperature).
  In step 108, the target ignition advance angle Tadv is calculated by subtracting the water temperature correction ignition advance angle Twadv from the map ignition advance angle Madv. Here, the correction of the ignition timing in steps 107 and 108 will be described with reference to FIG.
[0052]
  FIG. 18 shows the ignition timing with respect to the air-fuel ratio (lean), and shows how the NOx emission limit and the engine stability limit change depending on the engine water temperature. It is clear that the NOx emission limit line and the engine stability limit line shift to a leaner side when the engine water temperature becomes higher (more specifically, the higher the temperature, the narrower the NOx emission limit becomes, and the engine stability limit becomes Wide operating area).
[0053]
  Therefore, in order to clear the exhaust regulations and not cause discomfort to the user, it is necessary to set the target values of the air-fuel ratio and the ignition timing in the operation region surrounded by the restriction values.
  That is, as is apparent from FIG. 18, for example, at 80 ° C. and 40 ° C., the set air-fuel ratio and the ignition timing are different in order to secure a predetermined amount of difference between the NOx emission limit and the engine stability limit. That is, the set point shifts to the retarded angle side when the temperature is low. Therefore, unlike the case of correcting only the ignition timing of FIG. 9, when correcting both the air-fuel ratio and the ignition timing, the correction characteristics of the ignition timing are different.
[0054]
  Returning to the description of the flowchart of FIG.
  On the other hand, if the engine water temperature Tw is lower than the predetermined water temperature Twl # which is a fixed value in step 101, that is, if it is determined that Tw <Twl #, and in step 102, it is determined that the lean condition is not satisfied or that Flean = 0. If YES in step 109, the flow proceeds to step 109, and the theoretical air-fuel ratio map MDMLS not including the lean region is referred to using the engine speed Ne and the basic injection amount Tp, and the result is set as Mdml.
[0055]
  In step 110, a theoretical air-fuel ratio point-in-time ignition advance map MADVS (not shown) is referred to using the engine speed Ne and the basic injection amount Tp, and the result is taken as Madv.
  In step 111, the map fuel / air ratio Mdml is set as the target fuel / air ratio correction coefficient Tdml, and in step 112, the map ignition advance angle Madv is set as the target ignition advance angle Tadv, and the routine is terminated.
[0056]
  That is, in this routine, learning of the fuel-air ratio and ignition timing as control factors is also performed.Has been done.
  Therefore, according to the fourth embodiment, when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means, the richer air-fuel ratio becomes as the engine water temperature becomes lower. 20 and the ignition timing on the retarded angle side, and the NOx emission amount is suppressed to a predetermined range as shown in FIG. 20, thereby preventing an increase in the NOx emission amount and FIG. As shown in Fig. 3, the engine stability limit is also limited to a predetermined width, which can prevent deterioration of drivability, expand the lean combustion operation permission water temperature, enable lean burn, and improve fuel efficiency. It will be planned.
[0057]
  Next, the lean condition determination routine performed in Step 22, Step 32, Step 42, Step 72, and Step 102 will be described with reference to FIG.
  In steps 201 and 202, the state of the idle switch is checked to determine whether or not the idle switch is ON, that is, whether or not the throttle valve is fully closed. When it is OFF, the processing is continued. The routine is terminated with the flag Fleen = 0.
[0058]
  In step 205, Tp, which is a parameter representing the load, is detected. If TpLL ≦ Tp <TpLH, the process is continued. If not, the process branches to step 210 and ends (steps 205 and 206).
  TpLL and TpLH are a lean permission lower limit Tp and a lean permission upper limit Tp (both are fixed values), respectively.
[0059]
  Further, when the engine rotation Ne is detected and NeLL ≦ Ne <NeLH, it is next determined in step 209 whether or not the learning convergence in the routine shown in FIG. 11 is OK. This routine is terminated with the permission flag Flane = 1, that is, the lean operation permission. (Steps 207 to 210).
  If the learning convergence is not OK, the lean operation permission flag Flean = 0, that is, the lean operation is not permitted, and this routine is terminated.
[0060]
  NeLL and NeLH are a lean permission lower limit Ne and a lean permission upper limit Ne (both are fixed values), respectively.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing an embodiment of the present invention.
FIG. 2 is a flowchart showing a basic control routine according to the embodiment;
FIG. 3 is a characteristic diagram for explaining the operation of the basic control routine shown in FIG.
FIG. 4 is a flowchart showing a fuel injection amount calculation routine according to the embodiment.
FIG. 5 is a flowchart showing a routine for calculating a target fuel-air ratio correction coefficient Tdml according to the first embodiment.
FIG. 6 is a characteristic diagram showing a lean fuel-air ratio map according to the first embodiment.
FIG. 7 is a characteristic diagram showing a target water temperature correction fuel / air ratio correction amount table according to the first embodiment;
FIG. 8 is a characteristic diagram showing a theoretical air-fuel ratio map according to the first embodiment.
FIG. 9 is a flowchart showing a target ignition timing Tadv calculation routine according to the second embodiment.
FIG. 10 is a characteristic diagram showing an ignition advance correction table according to the second embodiment.
FIG. 11 is a flowchart showing a lean permission water temperature Twp calculation permission determination routine according to a third embodiment;
FIG. 12 is a flowchart showing a lean permission water temperature Twp calculation routine according to the third embodiment.
FIG. 13 is a characteristic diagram showing a lean permission water temperature correction update amount Dtwh table according to the third embodiment;
FIG. 14 is a flowchart showing a stability detection routine according to the third embodiment.
FIG. 15 is a flowchart showing a routine for calculating and calculating a target fuel-air ratio correction coefficient Tdml and a target ignition timing Tadv according to the fourth embodiment.
FIG. 16 is a characteristic diagram showing a target water temperature correction fuel / air ratio correction amount table according to the fourth embodiment;
FIG. 17 is a characteristic diagram showing a target ignition advance correction table according to the fourth embodiment.
FIG. 18 is a characteristic diagram for explaining the operation according to the fourth embodiment.
FIG. 19 is a flowchart showing a lean condition determination routine;
FIG. 20 is a characteristic diagram for explaining the effect according to the fourth embodiment;
[Explanation of symbols]
1 Engine body
4 Air flow meter
6 Fuel injection valve
8 Throttle sensor
9 Crank angle sensor
10 Water temperature sensor
20 Control unit

Claims (5)

Operating condition detecting means for detecting engine operating conditions including at least the engine water temperature;
Stability detection means for detecting the degree of stability of the engine indicated by rotational fluctuation in the engine based on the combustion state of the engine,
When the engine water temperature is at least a predetermined water temperature according to the engine operating conditions and the stability level of the engine detected by the stability detection means is higher than the predetermined stability level, the target air-fuel ratio of the engine intake air-fuel mixture is set to the theoretical air-fuel ratio. Air-fuel ratio switching control means for switching to a lean air-fuel ratio leaner than the fuel ratio;
A control factor that calculates a correction amount of a control factor that controls at least one engine combustion state based on the engine operating condition when the target air-fuel ratio is controlled to be switched to a lean air-fuel ratio by the air-fuel ratio switching control means Correction amount calculating means;
Control amount calculating means for calculating a control amount of the engine control factor based on the control factor correction amount calculated by the control factor correction amount calculating means;
Control factor control means for controlling the control factor based on the control amount calculated by the control amount calculation means;
While such stability degree based on the control factor which is controlled by the regulator control means is higher than a predetermined stability degree, the higher the stability degree according to the air-fuel ratio switching control means correcting the so specified temperature is lower Water temperature correction amount calculating means for calculating the water temperature correction amount to be performed;
A control apparatus for an internal combustion engine, comprising: A control factor that calculates a learning value of a control factor that controls at least one engine combustion state based on the engine operating condition when the target air-fuel ratio is controlled to be switched to a lean air-fuel ratio by the air-fuel ratio switching control means Learning value calculation means;
Rewritable control factor learning value storage means for storing the control factor learning value;
Control factor learning value update means for rewriting the control factor learning value stored in the control factor learning value storage means to the control factor learning value calculated by the control factor learning value calculation means;
The control device for an internal combustion engine according to claim 1, comprising: Including the ignition timing of the engine as a control factor that controls the engine combustion state,
When the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means, the correction amount related to the ignition timing is set so that the ignition timing becomes more retarded as the engine water temperature becomes higher. 3. The control device for an internal combustion engine according to claim 1, wherein the control device calculates the internal combustion engine. The control factors that control the engine combustion state are the target air-fuel ratio of the engine intake mixture and the ignition timing of the engine,
The control factor correction amount calculating means corrects the air-fuel ratio to a richer side when the engine water temperature is lower when the target air-fuel ratio is controlled to be switched to the lean air-fuel ratio by the air-fuel ratio switching control means. The internal combustion engine according to claim 1 or 2, wherein a correction amount related to the target air-fuel ratio is calculated and a correction amount related to the ignition timing is calculated so that the ignition timing is retarded. Control device. The stability detection means is
An engine speed detecting means for detecting the engine speed;
A rotation fluctuation value calculating means for calculating a rotation fluctuation value of the engine based on a detection value of the engine speed detection means;
The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the engine stability level is detected based on a calculated value of the rotation fluctuation value calculating means.

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