JP6507703B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device that controls the operation of a fuel injection valve that injects fuel into a combustion chamber of an internal combustion engine.

  BACKGROUND Conventionally, a fuel injection control device has been disclosed that injects fuel multiple times (multistage injection) in one combustion cycle. For example, the control device described in Patent Document 1 injects a small amount of fuel (pilot injection) immediately before injecting (main injection) a necessary amount of fuel to obtain a desired torque. As a result, the rate of increase in heat generation due to combustion (main combustion) caused by the main injection is reduced, and combustion noise generated with the main combustion is reduced.

Patent No. 4120556

  However, there is a limit to reducing combustion noise only by pilot injection, and on the other hand, further reduction of combustion noise is desired.

  The present invention has been made in view of the above problems, and an object thereof is to provide a fuel injection control device which promotes reduction of combustion noise.

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the claims and the reference numerals in the parentheses described in this section indicate the correspondence with specific means described in the embodiments to be described later, and do not limit the technical scope of the invention. .

One of the disclosed inventions is a noise generated by combustion in the internal combustion engine (10), which is an acquiring means (S16, S17) for acquiring a physical quantity correlated with noise of a predetermined frequency, and a combustion chamber of the internal combustion engine Split injection control means (control means for controlling the operation of the fuel injection valve (11) for injecting fuel to (10a), for controlling the fuel used in one combustion to be divided and injected in a plurality of times S10, S11, S12, S14), and the split injection control means changes the interval of each split injection to a shorter value as the physical quantity is a larger value of noise, and the injection start timing of each injection And the control of the injection time, the waveform of the portion from the heat generation rate starting to increase with the combustion to the maximum value among the waveforms showing the time change of the heat generation rate related to the combustion in the combustion chamber Rising waveform (Wa) In case the acquisition means is characterized and the heat generation rate to form a rising waveform, to obtain the degree of deviation between the heat generation rate represented by a straight line approximating the rising waveform as a physical quantity.

  Here, when the fuel used in one combustion is divided into a plurality of times and injected at short intervals, combustion of fuel relating to each injection is continuously generated so as to be superimposed, resulting in one integrated combustion. In other words, a waveform (heat generation rate waveform) representing a change in heat release rate caused by each combustion is superimposed on each other as illustrated in FIG. It becomes a waveform. Therefore, by controlling the interval, injection time, number of divisions, and the like of each divided injection, it is possible to control the shape of the heat generation rate waveform related to one combustion. Then, the balance between the desired output torque being exhibited, the reduction of exhaust emissions, and the reduction of combustion noise can be suitably controlled in accordance with the operating state of the internal combustion engine.

  However, when such split injection is performed, pulsations corresponding to the number of splits occur in the heat generation rate waveform. Then, when pulsation occurs in a portion (rising waveform) from the start of rising of the heat generation rate to the maximum value in the heat generation rate waveform, the higher the degree of the pulsation, the predetermined frequency component included in the combustion noise The present inventors obtained the finding that the noise (high frequency noise) of the This high frequency noise can be annoying to the driver if it gets louder than the limit. The present inventor has obtained the following findings in response to this problem. That is, if the intervals of the divided injections are shortened, the pulsation can be reduced and hence high frequency noise can be reduced.

  In view of these points, the above-described invention includes split injection control means for controlling the fuel used in one combustion to be split and injected a plurality of times. Therefore, by controlling the interval, the injection time, the number of divisions, and the like as described above, it is possible to control the shape of the heat generation rate waveform related to one combustion. Thus, the balance between the desired output torque, the reduction of exhaust emissions, and the reduction of combustion noise can be suitably controlled in accordance with the operating state of the internal combustion engine.

  Then, in the above-mentioned invention, the physical quantity which has correlation with high frequency noise is acquired, and the injection start timing and the injection time of each injection are controlled, changing the interval according to the physical quantity. Therefore, the balance can be suitably controlled while preventing the high frequency noise from increasing beyond the limit.

FIG. 1 is a schematic view showing a fuel injection control device according to an embodiment of the present invention. The test result which shows various changes corresponding to injection command pulse in comparison with the case where EGR rate is lower than assumption, and the usual case. The noise test result when the change of FIG. 2 arises. The figure which shows a change of a heat release rate, in-cylinder pressure, etc. when EGR rate is lower than assumption, and pressure correction is implemented. The figure which shows the frequency band of the noise produced in the case of FIG. The figure which shows a change of a heat release rate, in-cylinder pressure, etc. when EGR rate is lower than assumption, and pressure correction and interval correction are implemented. The figure which shows the frequency band of the noise produced in the case of FIG. The flowchart which shows the procedure of the injection control which the microcomputer of FIG. 1 implements. The flowchart which shows the calculation procedure of the combustion feature-value which the microcomputer of FIG. 1 implements.

  Hereinafter, an embodiment of a fuel injection control device according to the present invention will be described with reference to the drawings. The fuel injection control device according to the present embodiment is provided by an electronic control device (ECU 20) shown in FIG. The ECU 20 controls the combustion state of the internal combustion engine 10 by controlling the operation of the fuel injection valve 11, the fuel pump 13, the EGR valve (not shown) and the like included in the internal combustion engine 10. The internal combustion engine 10 and the ECU 20 are mounted on a vehicle, and the vehicle travels with the output of the internal combustion engine 10 as a drive source.

  The high pressure fuel compressed by the fuel pump 13 is supplied to the common rail 12. The common rail 12 maintains the supplied high pressure fuel at a predetermined pressure and distributes the high pressure fuel to each of the fuel injection valves 11 provided in each cylinder. The fuel injection valve 11 has an electromagnetic actuator and a valve body. When a voltage is applied to the electromagnetic actuator from the drive circuit 40, the valve body is opened, and high pressure fuel is injected from the injection hole formed in the fuel injection valve 11 to the combustion chamber 10a. When the voltage application to the electromagnetic actuator is stopped, the valve is closed to stop the fuel injection from the injection hole.

  Therefore, the fuel injection timing T is controlled by the ECU 20 controlling the voltage application start timing. The ECU 20 controls the current application time Tq of voltage application to control the injection period by one valve opening, and in turn controls the injection amount Q of fuel by one valve opening. In addition, the ECU 20 controls the discharge amount of the fuel pump 13 to control the pressure of the fuel accumulated in the common rail 12, and in turn controls the injection pressure Pc of the fuel.

  The microcomputer (microcomputer 30) that the ECU 20 has has the injection timing T, the injection amount Q, the injection pressure Pc, etc., the rotational speed (engine speed) of the output shaft of the internal combustion engine 10, the engine load, and the combustion chamber 10a. Control based on the pressure (in-cylinder pressure) of The engine speed NE is calculated by the microcomputer 30 based on the detection value of the crank angle sensor 15. The engine load is calculated by the microcomputer 30 based on the detection value of the accelerator pedal sensor 16. The in-cylinder pressure is calculated by the microcomputer 30 based on the detection value of the in-cylinder pressure sensor 14.

  The microcomputer 30 calculates various target values representing the injection state of the fuel injected from the fuel injection valve 11 based on the calculated engine rotational speed and engine load. For example, the injection timing T, the injection amount Q (energization time Tq), the number of injections when performing multi-stage injection described in detail below, the number of divisions when performing split injection, etc. are calculated.

  As defined herein, multi-stage injection means injecting fuel multiple times during one combustion cycle into the same cylinder. The multiple injections include a main injection for exerting the combustion torque, a pilot injection for burning before the main injection to reduce NOx, and the like. The split injection as defined herein means that fuel used in one combustion is divided and injected in multiple times. In the example of FIG. 2, as shown to (a) and (b) in the figure, the main injection is divided into four and injected. And the combustion of the fuel which concerns on each injection generate | occur | produces continuously so that it may overlap, and it becomes one accumulation combustion. As a result, the waveform (heat release rate waveform) representing the change in heat release rate caused by each combustion is superimposed on each other as shown in FIG. Become.

  In the case of multistage injection, since the time interval (interval) of each injection is long, for example, after the fuel injected by pilot injection is burned and the heat release rate rises, the heat release rate drops to zero, and then the next main The injected fuel starts combustion and heat release rate starts rising. On the other hand, in the case of split injection, as illustrated in FIG. 2, after the fuel injected at the nth time burns and the heat release rate rises, before the heat release rate falls to zero, The fuel injected at the (n + 1) th time starts combustion and the heat release rate rises again.

  The microcomputer 30 functions as various means described below as the CPU executes arithmetic processing in accordance with the program stored in the memory. By these means, the above-described split injection is performed. That is, the microcomputer 30 functions as the target combustion feature quantity calculation means 31, the basic injection pattern calculation means 32, the heat generation rate calculation means 33, the combustion feature quantity calculation means 34, the final injection pattern calculation means 39 and the following compensation means. The compensation means includes a combustion timing compensation means 35, a combustion amount compensation means 36, a combustion period compensation means 37, and a combustion vibration compensation means 38.

  The target combustion feature quantity calculation means 31 calculates target values of various combustion feature quantities based on the engine speed and the engine load described above. For example, the relationship between the engine rotational speed and the engine load and the optimum value of the combustion characteristic amount is tested and acquired in advance, and the acquired optimum value is mapped in association with the engine rotational speed and the engine load. The map (feature amount map) is stored in advance in a memory of the microcomputer 30. The above optimum value is set in consideration of the balance between the output torque according to the engine load and the engine speed, the exhaust emission, and the combustion noise. The target combustion feature quantity calculation means 31 acquires the optimum value corresponding to the engine speed and the engine load at the present time point from the feature quantity map, and sets the optimum value as the target combustion feature quantity. Specific examples of the combustion characteristic amount include a combustion timing MFB50, a combustion amount J, a combustion period TC, and a combustion vibration amount Sig. Hereinafter, these combustion feature quantities will be described with reference to FIG.

  (A) in FIG. 2 shows an injection command pulse, and when the pulse-on is performed, the energization of the fuel injection valve 11 is instructed to open, and when the pulse-off is performed, the energization-off is instructed to close. (B) shows the injection rate which represented the volume of the fuel injected per unit time. (C) shows the heat release rate which is the amount of heat generated per predetermined crank angle. The area of the heat release rate waveform shown in (c) represents the amount of combustion J. A waveform surrounded by an alternate long and short dash line in the figure, which is a portion where the heat release rate rises with the combustion, is called a rising waveform Wa. When the split injection is performed, pulsations corresponding to the number of splits occur in the heat release rate waveform. In the example of FIG. 2, this pulsation appears in the rising waveform Wa.

  (D) shows a time change of the amount of combustion when the amount of combustion J generated in one combustion is 100%. The crank angle when the amount of combustion reaches 50% is denoted as MFB50, and this MFB50 is regarded as the combustion time. Further, a period from MFB 10 to MFB 90 is regarded as a combustion period TC. (E) shows the pressure change (pressure waveform) of the combustion chamber 10a. Pulsation appears in the portion of the pressure waveform corresponding to the rising waveform. Therefore, pulsation also appears in the change (pressure differential waveform) of the differential value of the pressure waveform shown in (f).

  The solid lines in (c), (d), (e), and (f) indicate changes during normal operation of the internal combustion engine 10. (C) When the injection command pulse shown in (a) is not changed although the EGR rate is lower than that in the normal time, or when the internal combustion engine 10 is transiently operated and the EGR rate falls sharply (c) (D) As shown by dotted lines in (e) and (f), each waveform changes. That is, since the fuel is easily burned when the EGR rate becomes low, as shown in (c), the pulsation of the rising waveform Wa becomes large. That is, the peak value of the pulsation is increased while the frequency of the pulsation remains unchanged. As a result, as shown in (d) and (e), the values of the rising waveform Wa and the pressure waveform increase, and as shown in (e) and (f), the pulsation of the pressure waveform increases. The EGR rate is the ratio of the EGR gas contained in the intake air flowing into the combustion chamber 10a, and the EGR gas is a gas that recirculates part of the exhaust gas to the intake air.

  FIG. 3 is a diagram showing the change in combustion noise when the EGR rate decreases and changes from the solid line to the dotted line in FIG. 2; the solid line in the figure is the normal time and the dotted line is the combustion noise at the low EGR rate. Show. As illustrated, the combustion noise increases as the EGR rate decreases, and in particular, the noise in the 1 kHz to 4 kHz frequency band increases.

  Returning to the explanation of the means that the microcomputer 30 of FIG. 1 exerts, the target combustion feature quantity calculation means 31 makes the value of the approximate straight line f (θ) of the pressure waveform smaller than a predetermined threshold THa (see FIG. 2E). Thus, the target combustion feature is calculated. The threshold value THa is set to increase as time passes, and is expressed by a straight line that rises as shown in FIG. 2 (e). The slope and intercept of this straight line are fixed at predetermined values determined in advance.

  This technical significance is explained below. The magnitude of the combustion noise is highly correlated with the pressure value (rising pressure value) in the rising portion of the pressure waveform, and the combustion noise becomes larger as the rising pressure value is larger. The rising pressure value is highly correlated with the injection pressure Pc, and the rising pressure value becomes larger as the injection pressure Pc is higher. Furthermore, the magnitude of the injection pressure Pc has a high correlation with the combustion period TC, and the injection pressure Pc increases as the combustion period TC decreases. Therefore, the target combustion feature amount calculating means 31 sets the target value of the combustion period TC so that the value of the straight line (approximated straight line) approximating the pressure waveform becomes smaller than the predetermined threshold THa (see FIG. 2E). . The target combustion feature quantity calculation means 31 corresponds to a rise suppression means for controlling the fuel injection state (injection pressure Pc) such that the approximate straight line of the rising waveform Wa is less than the threshold THa.

  Further, the target combustion feature quantity calculation means 31 calculates the target combustion feature quantity so that the amplitude of the pulsation appearing in the rising portion of the pressure waveform becomes smaller than a predetermined threshold value THb (see FIG. 2F). The threshold value THb is set to a value that does not change with the passage of time, and is expressed by a straight line extending horizontally before and after the top dead center TDC crank angle as shown in FIG. 2 (f).

  This technical significance is explained below. The predetermined frequency component (high frequency noise) of the combustion noise is highly correlated with the degree of pulsation appearing in the heat generation rate waveform, and the higher the degree of pulsation, the higher the high frequency noise. The degree of pulsation appearing in the heat generation rate waveform is highly correlated with the interval Int, and the degree of pulsation decreases as the interval Int decreases. Therefore, the target combustion feature quantity calculating means 31 sets the target value of the interval Int so that the peak value of the pulsation appearing in the pressure differential waveform becomes smaller than the predetermined threshold value THb.

  The basic injection pattern calculation means 32 calculates a basic injection pattern based on the target combustion feature quantity calculated by the target combustion feature quantity calculation means 31. The basic injection pattern is the injection pattern specified by the injection command pulse, and specifically, the basic injection pattern is calculated by calculating the basic target values of the injection timing T, the injection amount Q and the interval Int. doing. The basic injection pattern calculation means 32 also calculates the basic target value of the injection pressure Pc based on the target combustion characteristic amount.

  For example, the relationship between the optimal value of the basic injection pattern and the combustion feature is tested in advance and acquired, the acquired optimal value is mapped in association with the combustion feature, and the map (injection pattern map) is It is stored in advance in the memory of the microcomputer 30. The basic injection pattern calculation means 32 acquires an optimum value corresponding to the target combustion feature amount calculated by the target combustion feature amount calculation means 31 from the injection pattern map, and sets the optimum value as a basic injection pattern. The basic target value is set with reference to the injection pressure map for the injection pressure Pc as well.

  The heat release rate calculation means 33 acquires a pressure waveform (see FIG. 2 (e)) based on the in-cylinder pressure detected by the in-cylinder pressure sensor 14, and based on the pressure waveform, a heat release rate waveform (see FIG. 2 (c)) Calculate). Describing this calculation method in detail, the pressure waveform includes a component of change (compressed component) caused by compression of the combustion chamber 10a by the piston and a component of change (combustion component) generated by combustion. There is. The compression component can be identified by the closing timing of the intake valve, the volume of the combustion chamber 10a, or the like. The combustion component can be extracted by subtracting the compression component thus specified from the pressure waveform. The heat release rate waveform can be calculated by multiplying the extracted combustion component by a predetermined gain. Thus, the heat generation rate calculation means 33 calculates the heat generation rate waveform based on the pressure waveform.

  The combustion feature quantity calculation unit 34 calculates a combustion feature quantity related to actual combustion based on the heat generation rate waveform calculated by the heat generation rate calculation unit 33. The combustion characteristic quantities calculated here are the combustion timing MFB 50, the combustion amount J, the combustion period TC, and the combustion vibration amount Sig described above. For example, with regard to the combustion timing MFB50, based on the waveform of the combustion mass ratio MFB calculated from the heat release rate waveform (see FIG. 2D), the crank angle when the amount of combustion reaches 50% is taken as the combustion timing MFB50. calculate. For the combustion period TC, a crank angle from when the combustion amount reaches 10% to 90% is calculated as the combustion period TC based on the waveform of the combustion mass ratio MFB. Since the combustion period TC has a high correlation with the injection pressure Pc, the combustion period TC is used as a detected value used for feedback control of the injection pressure Pc. The combustion amount J is calculated by integrating the heat release rate waveform.

The combustion vibration amount Sig is a value representing the degree of vibration of the rising waveform Wa included in the heat release rate waveform. For example, an equation of a straight line f (θ) = αθ + β (see FIG. 6) obtained by approximating the rising waveform Wa by the least square method or the like is calculated based on the rising waveform Wa. θ represents the crank angle, α represents the slope of the approximate straight line f (θ), and β represents the intercept of the approximate straight line f (θ). The period of the rising waveform Wa used for this calculation is set, for example, from the crank angle (θMFB10) of the MFB 10 to the crank angle (θHRRmax) when the heat generation rate becomes maximum. Then, the degree of deviation between the heat generation rate for each crank angle forming the rising waveform Wa and the approximate straight line f (θ) is calculated as the combustion vibration amount Sig representing the degree of pulsation. For example, the combustion vibration amount Sig is calculated according to the following equation 1.

  The various compensation means calculates a deviation between the target value of the combustion feature amount calculated by the target combustion feature amount calculation means 31 and the actual value of the combustion feature amount calculated by the combustion feature amount calculation means. Further, the compensation means calculates a correction amount for the basic injection pattern calculated by the basic injection pattern calculation means 32 based on the deviation. For example, the deviation or the correction amount according to the deviation is mapped in association with the engine speed and the engine load, and the map (correction map) is stored and updated in the memory of the microcomputer 30. Each compensation means acquires and sets the correction amount corresponding to the current engine speed and engine load from the correction map.

  Specifically, the combustion timing compensation means 35 calculates a correction amount for the injection timing T of the basic injection pattern, based on the deviation between the target value and the actual value of the combustion timing MFB50. The combustion amount compensation means 36 calculates a correction amount for the injection amount Q of the basic injection pattern based on the deviation between the target value and the actual value of the combustion amount J. The combustion period compensation means 37 calculates a correction amount for the injection pressure Pc of the basic injection pattern based on the deviation between the target value and the actual value of the combustion period TC. The combustion vibration compensation means 38 calculates the correction amount for the interval Int of the basic injection pattern based on the deviation between the target value and the actual value of the combustion vibration amount Sig.

  The final injection pattern calculation means 39 corrects the basic injection pattern calculated by the basic injection pattern calculation means 32 based on the correction amount calculated by each compensation means, and calculates the final injection pattern. The final injection pattern is the injection pattern specified by the injection command pulse, and the final injection pattern calculation means 39 in FIG. 4A based on the corrected injection timing T, injection amount Q and interval Int. The injection command pulse shown is generated. The pulse on timing of the injection command pulse is set based on the corrected injection timing T, the pulse on period is set based on the corrected injection amount Q, and the interval between the previous pulse off and the next pulse on is the corrected interval. Set based on Int. Thus, the injection timing T, the injection amount Q and the interval Int are feedback-controlled.

  Furthermore, the final injection pattern calculation means 39 controls the operation of the fuel pump 13 based on the corrected injection pressure Pc. Thus, the pressure (injection pressure Pc) of the fuel supplied from the common rail 12 to the fuel injection valve 11 is feedback controlled. The period of feedback by each compensation means is set to a different value. In this way, it is intended to suppress each feedback control from interfering and hunting.

  If the feedback control for the injection pressure Pc and the interval Int is not performed among the various types of feedback control described above, the following problems occur. That is, for example, when the EGR rate decreases and changes from the solid line to the dotted line in FIG. 2, the approximate straight line f (θ) of the pressure waveform becomes larger than the threshold THa, and the peak value of pulsation appearing in the pressure differential waveform It becomes larger than threshold value THb. Therefore, the combustion noise is increased beyond the allowable range.

  In addition, in the example of FIG. 2, since feedback control is implemented about the injection time T and the injection quantity Q (energization time Tq), the injection time which concerns on the injection after the 2nd time among each injection divided into four The correction is made so that T becomes slower and the current application time Tq becomes longer.

  On the other hand, if the feedback control for the injection pressure Pc is performed and the feedback control for the interval Int is not performed, the following problems occur. That is, for example, when the EGR rate decreases, it changes from the solid line to the dotted line in FIG. That is, when the EGR rate decreases and changes to an environment where combustion is promoted, it is attempted to change as shown by the dotted line in FIG. 2, but feedback control is performed to reduce the injection pressure Pc. As a result, the value of the approximate straight line f (θ) of the rising waveform Wa is suppressed small, and the value of the approximate straight line f (θ) becomes smaller than the threshold THa. Therefore, the noise (low frequency noise) of the frequency band of the part enclosed with the dashed dotted line in FIG. 3 can be reduced as shown in FIG.

  However, since the feedback control is not performed for the interval Int, the pulsation of the rising waveform Wa related to the heat release rate waveform is not sufficiently suppressed, and the peak value of the pulsation appearing in the pressure differential waveform becomes larger than the threshold THb. Yes. Therefore, as shown in FIG. 5, the noise (high frequency noise) in the frequency band of the portion shown by the dashed dotted line in FIG. 5 can not be sufficiently suppressed.

  On the other hand, when feedback control is performed for both the injection pressure Pc and the interval Int, combustion noise is reduced as follows. That is, for example, when the EGR rate decreases, it changes from the solid line to the dotted line in FIG. That is, when the EGR rate decreases and changes to an environment where combustion is promoted, it is attempted to change as shown by the dotted line in FIG. 2, but feedback control is performed to reduce the injection pressure Pc. As a result, the value of the approximate straight line f (θ) of the rising waveform Wa is suppressed to be small, and the value of the approximate straight line f (θ) of the pressure waveform is smaller than the threshold THa. Therefore, the low frequency noise surrounded by the alternate long and short dash line in FIG. 3 can be reduced as shown in FIG. In addition, feedback control is performed to shorten the interval Int. As a result, the pulsation included in the rising waveform Wa is suppressed to a low level, and the peak value of the pulsation appearing in the pressure differential waveform is smaller than the threshold value THb. Therefore, the high and low frequency noise in the portion surrounded by the one-dot chain line in FIG. 5 can be reduced as shown in FIG.

  The drive circuit 40 has a switch element (not shown) for switching on / off of energization to a solenoid coil (not shown) of the fuel injection valve 11. The switch element operates based on the injection command pulse generated by the final injection pattern calculation means 39 to switch on / off of voltage application to each fuel injection valve 11. Thus, the solenoid coil is energized during the pulse-on period of the injection command pulse, and the fuel injection valve 11 is opened to inject the fuel. Therefore, the start timing of the fuel injection is controlled by the timing of the pulse on start. Further, the valve opening time is controlled by the length of the pulse on period, and in turn, the amount of fuel injected by one valve opening (fuel injection amount) is controlled.

  However, it does not open at the same time as the start of pulse-on to inject fuel, but opens a little later than the start of pulse-on to start fuel injection. Furthermore, the self-ignition combustion does not necessarily occur simultaneously with the start of fuel injection, but the self-ignition combustion is delayed after the start of injection. Thus, the delay time from the start of injection to the occurrence of combustion is called an ignition delay time.

  FIG. 8 is a flowchart showing the processing procedure of the microcomputer when executing the above-described feedback control, and this processing is repeatedly executed by the microcomputer 30 at a predetermined cycle while the internal combustion engine 10 is in operation.

  First, at step S10 in FIG. 8, the engine speed and the engine load are acquired, and based on these values, calculation of the target combustion feature amount by the target combustion feature amount calculation means 31 is executed. In the following step S11, calculation of a basic injection pattern by the basic injection pattern calculation means 32 is executed based on the target combustion feature quantity calculated in step S10.

  In the subsequent step S12, setting of correction amounts by the combustion timing compensation means 35, the combustion amount compensation means 36, the combustion period compensation means 37 and the combustion vibration compensation means 38 is performed. That is, based on the engine speed and the engine load acquired in step S10, the correction amount for the basic injection pattern is calculated with reference to the correction map. Furthermore, in step S12, based on these correction amounts, the basic injection pattern calculated in step S11 is corrected to calculate the final injection pattern after correction. That is, the generation of the injection command pulse by the final injection pattern calculation means 39 and the calculation of the target value of the injection pressure Pc are executed.

For example, the final target value of the injection time T is calculated according to the following equation 2.

  Tb in the equation 2 is a target value of the combustion timing according to the basic injection pattern. Kt is a correction gain. MFB50Trg-MFB50 is a deviation between the target value and the actual value of the combustion time.

Further, the final target value of the injection amount Q (n) is calculated according to the following Equations 3 and 4.

  Qb (n) in the equation 3 is the n-th injection amount related to the split injection and is a target value of the injection amount according to the basic injection pattern. Kq is a correction gain. JTrg-J is a deviation between the target value and the actual value of the injection amount. R (n) in Equations 3 and 4 is the nth injection amount ratio related to split injection.

Further, the final target value of the injection pressure Pc is calculated according to the following equation 5.

  Pcb in the equation 5 is a target value of the injection pressure according to the basic injection pattern. Kpc is a correction gain. TCTrg-TC is the deviation between the target value and the actual value of the combustion period, and is a high value of the correlation between the deviation of the target value of the injection pressure and the actual value.

Also, the final target value of the interval Int is calculated according to the following equation 6.

  Intb (n) in the equation (6) is the interval of the nth injection relating to the split injection, and is the target value of the interval according to the basic injection pattern. Kint is a correction gain. SigTrg-Sig is a deviation between the target value and the actual value of the combustion vibration amount.

  In correcting the interval Int in step S12 described above, the injection command pulse is set so that the total injection amount of one set of injection relating to the divided injection does not change. For example, when correcting the interval between the nth injection and the n + 1st injection, at least one of the injection end timing of the nth injection and the injection start timing of the n + 1th injection will be corrected. Then, for example, when the injection end timing of the n-th injection is retarded and corrected, the injection time of the injection will be long and the injection amount will increase unless the injection start timing of the injection is also retarded. It becomes. In view of this point, when correcting the interval Int in step S12, the injection command pulse is set so that the total injection amount does not change.

  In the subsequent step S13, acquisition of a detection signal output from the in-cylinder pressure sensor 14 is started. In the following step S14, the injection command pulse calculated in step S12 is output to the drive circuit 40, and fuel injection from the fuel injection valve 11 is performed. In the subsequent step S15, the acquisition of the detection signal output from the in-cylinder pressure sensor 14 is ended. In the following step S16, calculation of the heat generation rate waveform by the heat generation rate calculation means 33 is executed based on the pressure waveform obtained from the acquired detection signal. In the following step S17, based on the heat release rate waveform calculated in step S16, calculation of the combustion feature amount by the combustion feature amount calculation means 34 is executed.

  The target combustion feature quantity calculation means 31 takes into consideration the balance of output torque, exhaust emission, combustion noise, etc. whether to execute split injection in which fuel used in one combustion is divided and injected in multiple times. Then, the determination is made based on the operating state of the internal combustion engine 10. The procedure of the injection control shown in FIG. 8 is common regardless of whether or not it is the split injection. When it is determined that the split injection is to be performed, the microcomputer 30 when performing the above-described processes of steps S10, S11, S12, and S14 corresponds to a split injection control unit that performs control to split injection. . Further, the microcomputer 30 at the time of executing the processes of steps S16 and S17 corresponds to an acquisition means for acquiring a physical quantity having a correlation with noise of a predetermined frequency, that is, the combustion vibration quantity Sig.

  The details of the process of step S17 will be described with reference to FIG. 9. First, in step S20, the combustion amount J is calculated by integrating and calculating the heat release rate waveform calculated in step S16. In the following step S21, the combustion time is calculated based on the waveform of the combustion mass ratio MFB representing the time change of the combustion amount J. For example, the MFB 50 is calculated as the combustion time. In the following step S22, the combustion period TC is calculated based on the waveform of the combustion mass ratio MFB. For example, the period from MFB 10 to MFB 90 is calculated as the combustion period TC.

  In the following step S23, based on the heat release rate waveform, the value of the maximum heat release rate and the time (θHRRmax) at which the maximum heat release rate is reached are calculated. In the following step S24, an equation of an approximate straight line f (θ) = αθ + β of the rising waveform Wa related to the heat release rate waveform is calculated. For example, the slope of the heat release rate from MFB10 to θHRRmax is taken as α in the above equation. In the following step S25, the amount of combustion vibration Sig is calculated based on the equation of the approximate straight line f (θ) calculated in step S24. That is, as the physical quantity representing the degree of pulsation of the rising waveform Wa related to the heat generation waveform, the combustion vibration amount Sig is calculated according to the above-mentioned equation (1).

  Now, the present inventor has found that the following problems occur with the implementation of split injection. That is, the rising waveform Wa of the heat generation rate waveform has a pulsating shape that repeats rising and falling due to superposition of a plurality of combustions. Then, if the injection state is set so that the approximate straight line f (θ) of the rising waveform Wa is less than the threshold value THa, although combustion noise can be reduced, the pulsation of the rising waveform Wa must be sufficiently reduced. The present inventors obtained the finding that high frequency noise can not be sufficiently reduced. In addition, the inventor recalled that if the split injection interval Int is reduced, the pulsation can be reduced and high frequency noise can be sufficiently reduced.

  In view of these points, in the present embodiment, the acquiring means for acquiring the physical quantity (the combustion vibration amount Sig) having a correlation with the high frequency noise, and the fuel used in one combustion are divided and injected a plurality of times. And d) controlling the divided injection control means. The divided injection control means controls the injection start timing (injection timing T) and the injection time of each injection while changing the divided interval Int of each injection according to the physical quantity. Therefore, high frequency noise can be sufficiently reduced, and reduction of combustion noise can be promoted.

  Further, in the present embodiment, the pulsation degree (combustion vibration amount Sig) of the rising waveform Wa is acquired as a physical quantity having a correlation with high frequency noise. The pulsation degree of the rising waveform Wa is highly correlated with the high frequency noise, so if the pulsation degree of the rising waveform Wa is acquired and the interval Int is controlled based on the acquired value, high frequency noise can be accurately reduced. it can.

  Further, for example, when a sound sensor is used contrary to the present embodiment, high frequency noise can be detected directly. However, since various operation noises other than combustion noise are included in the detection value of the sound sensor as noises, it becomes difficult to realize control of the interval Int which can reduce high frequency noise with high accuracy. On the other hand, in the present embodiment, since the physical quantity (pulsating degree) correlated with high frequency noise is detected using the in-cylinder pressure sensor 14, the physical quantity is detected with high accuracy without being greatly affected by the noise. it can. Thus, control of the interval Int can be realized with high accuracy.

  Furthermore, in the present embodiment, the fuel injection control device further includes a lift suppression unit that controls the fuel injection state so that the approximate straight line f (θ) of the rising waveform Wa related to the heat release rate waveform becomes less than the threshold THa. Therefore, noise can be reduced even for noise in a frequency band different from high frequency noise. For example, the noise in the frequency band shown by the dashed dotted line in FIG. 3 can be reduced by the rise suppression means, and the noise in the frequency band shown by the dashed dotted line in FIG. 5 (high frequency noise) can be reduced by controlling the interval Int.

  Further, in the present embodiment, the rise suppressing means controls the injection pressure Pc so that the approximate straight line f (θ) becomes smaller than the threshold THa. Since the injection pressure Pc is highly correlated with the approximate straight line f (θ), according to the present embodiment for controlling the injection pressure Pc as described above, it is high to control the approximate straight line f (θ) to less than the threshold THa. It can be realized with accuracy.

  Furthermore, in the present embodiment, the divided injection control means does not change the total injection amount of fuel used in one combustion in changing the interval Int according to the physical amount (the combustion vibration amount Sig) correlated with the high frequency noise. To change the interval Int. Therefore, when changing the interval Int in order to reduce high frequency noise, it is suppressed that the total injection amount changes due to the change, so reduction of high frequency noise is desired while making the output torque a desired value. Can.

(Other embodiments)
The preferred embodiments of the invention have been described above, but the invention is not limited to the above-described embodiments, and can be variously modified and implemented as exemplified below. Not only combinations of parts which clearly indicate that combinations are possible in each embodiment, but also combinations of embodiments even if they are not specified unless there is a problem with the combination. Is also possible.

  The thresholds THa and THb shown in FIGS. 6 (e) and 6 (f) may be variably set. Specifically, the allowable value of the noise level may be changed according to the operating state of the internal combustion engine 10, and the threshold values THa and THb may be changed according to the allowable value. For example, when the vehicle is traveling at a high speed, the threshold value THa or THb may be changed to a high value by setting the allowable value of the combustion noise high.

  In the above embodiment, the combustion period TC is acquired, and the injection pressure Pc is corrected based on the deviation between the target value and the actual value of the combustion period TC. On the other hand, the injection pressure Pc may be acquired, and the injection pressure Pc may be corrected based on the deviation between the target value and the actual value of the injection pressure Pc.

  In the above embodiment, the pressure waveform is acquired by the in-cylinder pressure sensor 14, and a physical quantity (the amount of combustion vibration Sig) having a correlation with noise of a predetermined frequency is acquired based on the pressure waveform. On the other hand, a sound sensor that detects combustion noise may be provided, and a noise level of a predetermined frequency may be acquired as the physical quantity based on the detection value of the sound sensor.

  In the embodiment shown in FIG. 1, the control device of the present invention is applied to control of the fuel injection valve 11 of the diesel engine. On the other hand, the control device of the present invention may be applied to fuel injection control of a direct injection type engine which is an ignition ignition type gasoline engine and directly injects fuel into a combustion chamber.

  The means and / or function provided by the ECU 20 (control device) can be provided by software stored in a tangible storage medium and a computer that executes the software, only software, only hardware, or a combination thereof. For example, when the control device is provided by a circuit that is hardware, it can be provided by a digital circuit or analog circuit that includes a number of logic circuits.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 10a ... Combustion chamber, 11 ... Fuel injection valve, S10, S11, S12, S14 ... Division | segmentation injection control means, S16, S17 ... Acquisition means.

Claims (3)

Acquisition means (S16, S17) for acquiring a physical quantity correlated with noise of a predetermined frequency, the noise being generated with combustion in the internal combustion engine (10);
Control means for controlling the operation of a fuel injection valve (11) for injecting fuel into a combustion chamber (10a) of the internal combustion engine, wherein control is performed so that fuel used in one combustion is divided and injected multiple times. Split injection control means (S10, S11, S12, S14)
Equipped with
The divided injection control means controls the injection start timing and the injection time of each of the injections while changing the divided injection intervals to shorter values as the physical quantity is a larger value of the noise .
Among the waveforms representing the temporal change of the heat release rate related to the combustion in the combustion chamber, the waveform of the portion from the heat release rate starting to increase with the combustion to the maximum value is the rising waveform (Wa) In the case of
The fuel injection control device according to claim 1, wherein the acquiring unit acquires, as the physical quantity, a deviation degree between a heat release rate forming the rising waveform and a heat release rate represented by a straight line approximating the rising waveform. The rise suppression which controls the pressure of the fuel supplied to the fuel injection valve so that the value of the heat release rate represented by the straight line which approximated the rise waveform becomes less than a threshold in the whole period in which the rise waveform occurs A fuel injection control device according to claim 1, characterized in that it comprises means (31). The split injection control means, when changing the interval in response to said physical quantity, according to claim 1, characterized in the interval altering so as not to change the total injection quantity of fuel used in the single combustion or the fuel injection control device according to 2.

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