JP2008184915A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

A fuel injection control device for an internal combustion engine capable of sufficiently reducing combustion noise of a fuel injection device for an internal combustion engine, particularly a specific vibration intensity in a specific frequency range.
A distance between each cylinder and a crank angle sensor 19 for outputting a crank angle signal Δθ of a multi-cylinder internal combustion engine, an injection control means A0 for injecting fuel from a fuel injection valve 14 of the internal combustion engine 1, and A combustion sound sensor 6 that detects noise or vibration generated from each cylinder according to combustion, and a combustion detection section #nE that detects that each cylinder is in a combustion state are provided for each cylinder. Based on the combustion detection period setting means A3 to be set, the output of the crank angle sensor, and the detection result of the combustion vibration detection means in the combustion detection section #nE, the identification means A2 for identifying the sound or vibration for each cylinder, and the identification means And correction means A4 for correcting the injection control amount of the injection control means for each cylinder in accordance with the vibration intensity indices RK # 1 to RK # 4 that are identification results of A2.
[Selection] Figure 1

Description

  The present invention relates to an apparatus for controlling fuel injection of an internal combustion engine.

In a fuel injection device of a direct injection engine, for example, a common rail diesel engine, low pressure fuel is increased in pressure by a fuel injection pump, and the high pressure fuel is guided to a fuel injection valve provided in each cylinder via a common rail. Each fuel injection valve controls the injection amount, the injection timing, and the number of injections by opening and closing an electromagnetic needle valve.
By the way, from the viewpoint of exhaust gas regulations in recent years, it is required to further improve the injection amount accuracy so that the amount of fuel injected from the fuel injection valve becomes a target value. In particular, it is required to improve the accuracy of small injection amounts such as pre-injection (including pilot injection) performed prior to main injection (main injection) or after injection (including post-injection) after main injection. ing.

  For example, it is assumed that injection is performed in a pilot injection mode in which a small amount of fuel is injected prior to main injection. In this case, the ignition delay of the fuel of the main injection can be improved by the combustion heat of the fuel by the pilot injection, and the steep combustion can be suppressed, thereby suppressing the noise of the internal combustion engine, NOx in the exhaust, and the like. However, high accuracy is required for the injection timing and injection amount in this case, and if the pilot injection amount is not appropriate, vibration noise due to combustion increases, which may cause discomfort to the user.

  By the way, the conventional noise reduction technology is often implemented in the overall (all frequency range), but in order to further reduce the noise of the diesel engine, it is desirable to reduce the noise aiming at a specific frequency range. . For example, in a fuel injection control device for an internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 2002-47975 (Patent Document 1), a difference in generation time (combustion) of pressure waves during combustion (combustion vibration) that is an interval between pilot injection and main injection is disclosed. It has been proposed to adjust the (interval) to interfere with each other's pressure waves to reduce the in-cylinder pressure (or vibration) in a specific frequency range, and thus reduce noise.

JP 2002-47975 A

  By the way, the fuel injection control device of Patent Document 1 requires a controller that calculates the time difference (combustion interval) between pilot injection and main injection for each cylinder and adjusts so that the combustion pressure waves interfere with each other. Become. For this reason, control will be complicated. Further, when feedback control is performed by this fuel injection control device, an in-cylinder pressure sensor is provided for each cylinder, which tends to increase costs.

  The present invention has been made paying attention to the above-described problems, and can sufficiently reduce the combustion noise of the fuel injection device of the internal combustion engine, in particular, the specific vibration intensity in the specific frequency range, and can improve the thermal efficiency. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can be maintained.

  In order to achieve the above-mentioned object, the invention of claim 1 includes a crank angle sensor for outputting a crank angle signal of a multi-cylinder internal combustion engine, an injection control means for injecting fuel from a fuel injection valve of the internal combustion engine, and each cylinder. The combustion vibration detecting means for detecting the sound or vibration generated from each cylinder according to combustion, and the period for detecting that each cylinder is in the combustion state Based on the detection result of the combustion vibration detecting means in each period set by the combustion detection period setting means set for each period, the output of the crank angle sensor, and the combustion detection period setting means, An identification means for identifying vibrations, and a correction means for correcting the injection control amount of the injection control means for each cylinder according to the identification result of the identification means are provided.

  According to a second aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, the identification means performs frequency analysis on the detection result of the combustion vibration detection means in each period, and the frequency analysis. Based on the analysis result of the means, it is determined whether the intensity index value calculating means for calculating the intensity index value of the sound or vibration and whether the intensity index value calculated by the intensity index value calculating means is within a predetermined range. Determination means, and the correction means corrects the injection control amount for each cylinder so that the intensity index value falls within the predetermined range.

  According to a third aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the second aspect, the injection control amount is a fuel injection amount, and the identifying means compares the intensity index value with a predetermined intensity reference value. Further comprising an intensity comparing means, wherein the correcting means increases the fuel injection amount when the intensity comparing means determines that the intensity index value exceeds the intensity reference value, and the intensity index value is When it is determined that the reference value is not exceeded, correction is made for each cylinder so as to reduce the fuel injection amount.

  According to a fourth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the third aspect, the identification means further comprises an injection amount comparing means for comparing the fuel injection amount with a predetermined injection amount reference value, and the correction. When the fuel injection amount is determined to be greater than the injection amount reference value by the injection amount comparison means, the fuel injection amount is divided into a plurality of times for each cylinder and injected. .

  According to a fifth aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine according to any one of the first to fourth aspects, wherein the injection control means performs the main injection and the pre-injection prior to the main injection. The injection control amount is the injection control amount of the pre-injection, and the correcting means corrects the injection control control amount of the pre-injection for each cylinder.

  According to a sixth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the fifth aspect, the injection control means has the same fuel injection amount for the pre-injection in an operating region where the operating conditions of the internal combustion engine are the same. It is characterized by controlling as follows.

  According to the first aspect of the present invention, it is possible to accurately detect sound or vibration transmitted from all the cylinders by merely installing one combustion vibration detecting means, and to correct the injection control amount using this. Since only one combustion vibration detection means is required, it is possible to reduce the cost, reduce the sound or vibration, and maintain the thermal efficiency.

  According to the second aspect of the present invention, it is possible to more easily identify the sound or vibration for each cylinder by performing frequency analysis on the detection result of the combustion vibration detecting means and calculating the intensity index value.

  In the invention of claim 3, noise generation can be suppressed and fuel consumption can be reduced by increasing or decreasing the fuel injection amount.

  The invention according to claim 4 can suppress generation of vibration noise in each divided injection by dividing the number of injections into a plurality of times.

  In the invention of claim 5, by correcting the injection control amount (fuel injection amount) of the pre-injection, the combustion noise can be further reduced and the thermal efficiency can be maintained more precisely.

  According to the sixth aspect of the present invention, fluctuations in generated torque can be suppressed, and stability and simplification of fuel injection control can be achieved.

FIG. 1 shows a common rail diesel engine (hereinafter simply referred to as engine 1) provided with a fuel injection control device for an internal combustion engine as an embodiment of the present invention.
The engine 1 here is a multi-cylinder engine, and a plurality of, in this case, four cylinders C # 1 to C # 4 are provided in an engine body 4 including a cylinder head 2 and a cylinder block 3.
As shown in FIG. 2, the four cylinders C # 1 to C # 4 of the engine body 4 are sequentially arranged at equal intervals in the engine longitudinal direction X. Each cylinder C # 1 to C # 4 is provided with a fuel injection valve 14, and the fuel injection to each cylinder C # 1 to C # 4 is performed by the injection drive of each fuel injection valve 14. The cylinder head 2 which is the engine body 4 is formed with a sensor support portion 5 at a position which is almost in the middle in the engine longitudinal direction X and does not interfere with the four cylinders C # 1 to C # 4. One combustion sound sensor 6 which is combustion vibration detection means for sequentially detecting the combustion noise of the cylinder as the combustion vibration Vb is attached, and a detection signal (combustion vibration Vb) is input to the controller 7 which will be described later.

  A fuel injection control device for an engine, which constitutes a main part of the present invention, is driven to rotate by the engine 1 and sucks up fuel in a fuel tank 8, a high-pressure pump 11 that increases the pressure of the discharge oil of the low-pressure pump 9, and a high-pressure pump 11 and a plurality of (four in this case) fuel injections that inject the high-pressure fuel accumulated in the common rail 12 into the cylinders C # 1 to C # 4. A valve (hereinafter referred to as a fuel injection valve) 14 and a controller 7 for controlling the high-pressure pump 11 and the plurality of fuel injection valves 14 are provided. In FIG. 1, reference numerals 15 and 16 denote first and second fuel filters attached to the low-pressure fuel supply pipe 17.

The low-pressure pump 9 and the high-pressure pump 11 are unitized as a pump unit 10 and includes a pump shaft 101 connected to a drive shaft (not shown) of the engine 1 via a rotation transmission system. The pump shaft 101 is driven to rotate in synchronization with the engine 1, and a vane type feed pump (low pressure pump 9) (not shown) and a plunger (high pressure pump 11) (not shown) for fuel pumping are linked with the rotation of the pump shaft 101. Each is driven. The low pressure pump 9 pumps the fuel from the fuel tank 8 to a low pressure chamber (not shown), and then the high pressure pump 11 increases the pressure of the low pressure fuel and supplies it to the common rail 12 via the fuel pressure regulator 18. The fuel pressure adjuster 18 is controlled by the controller 7 and can adjust the fuel pressure so that the pressure Pr in the common rail 12 becomes a predetermined value.
A relief pipe 22 is connected to the other end of the common rail 12 via a pressure limiter 21, and the relief pipe 22 is connected to the fuel tank 8. The pressure limiter 21 functions to open when the common rail pressure Pr exceeds a predetermined limit set pressure to suppress an excessive increase in fuel pressure. The leaked fuel from the high pressure pump 11 merges with the relief pipe 22 via the leak pipe 23 and is returned to the fuel tank 8.

  Each fuel injection valve 14 disposed opposite to the combustion chamber of each cylinder C # 1 to C # 4 is connected to a plurality of branch pipes 121 branched from the common rail 12, and injects and supplies high pressure fuel into each combustion chamber. A fuel injection nozzle 24 and an excitation coil 13 as an electromagnetic actuator that drives the fuel injection nozzle 24 are provided. The fuel injection nozzle 24 has a needle valve 26 that opens and closes an injection hole (not shown), a spring (not shown) that urges the needle valve 26 in the valve closing direction, and a nozzle body 27 that accommodates these. The excitation coil 13 of each fuel injection valve 14 is connected to the controller 7.

As shown in FIGS. 3A and 3B, the fuel injection valve 14 operates to perform the pre-injection Tp prior to the main injection (main injection) Tm. That is, the fuel injection valve 14 applies pre-injection and main injection drive pulses Tp and Tm as drive signals from the controller 7 to the excitation coil 13 at predetermined injection timings tp and tm. Injection drive can be performed so as to perform injection of injection amounts (corresponding to pulse widths) Qp and Qm according to the interval between Tp and Tm. In addition, what was shown with the dashed-two dotted line in Fig.3 (a), (b) has shown an example of the injection mode in the case of the 2nd pre-injection mentioned later.
The controller 7 includes an input / output device (not shown), a storage device (ROM, RAM, DRAM, etc.) used for storing control programs and control maps, a central processing unit (CPU), a timer counter (not shown), and the like.

  As shown in FIG. 1, on the input end side (not shown) of the controller 7, an accelerator sensor 31 for detecting an accelerator opening θa, an airflow sensor 32 for detecting an intake air amount Qa, and a crank for detecting a crank angle signal Δθ. Angle sensor 19, cylinder discrimination sensor 33 for detecting cylinder discrimination signal Cs, fuel pressure sensor 34 for detecting common rail pressure Pr, water temperature sensor 35 for detecting water temperature wt, air-fuel ratio sensor 37 for detecting air-fuel ratio A / F, combustion vibration Sensors such as a combustion sound sensor 6 which is a combustion vibration detecting means for detecting Vb are connected. The crank angle signal Δθ here is used by the controller 7 to derive the engine speed Ne.

As shown in FIG. 2, one combustion noise sensor 6 is attached to a sensor support portion 5 (see FIG. 2) at a substantially intermediate position in the engine longitudinal direction X of the cylinder head 2 that is the engine body 4. The position of the combustion sound sensor 6 on the engine body 4 and the detection data will be described later.
Various devices such as the fuel injection valves 14 provided for the cylinders C # 1 to C # 4 and the fuel pressure adjuster 18 of the high-pressure pump 11 are connected to the output end (not shown) of the controller 7. Yes.
The controller 7 exhibits a well-known engine control function and also functions as a fuel injection control device A that characterizes the present invention.

That is, as shown in FIG. 5, the fuel injection control device A functions as injection control means A0, target injection amount setting means A1, identification means A2, combustion detection interval setting means A3, and correction means A4.
Here, the basic function of the fuel injection control device A is performed by the target injection amount setting means A1. The target injection amount setting means A1 takes in the accelerator opening θa, the engine rotational speed Ne, the air-fuel ratio A / F, the water temperature wt, etc., which are engine operation information, for each cylinder of the engine 1. Further, based on the operation information, the basic fuel injection amount INJb is calculated, and correction values QA / F and Qwt such as the air-fuel ratio A / F and the water temperature wt are added to the calculated basic fuel injection amount INJb. Target injection amount QFT (= INJb + QA / F + Qwt) is calculated.
Next, the injection control means A0 controls the fuel injection valves 2 of the cylinders C # 1 to C # 4 to perform fuel injection according to the input of the injection control data.

Here, as shown in FIGS. 3A and 3B, for example, a pre-injection mode (in this case, a pilot injection mode) in which pre-injection Tp is performed prior to main injection (main injection) Tm. The injection control data corresponding to is calculated. That is, here, a fuel injection amount map (not shown) is used, drive pulse intervals Tp and Tm for pre-injection and main injection, injection timings tp and tm, injection amounts (corresponding to pulse widths) Qp and Qm, and common rail pressure. Pr and the like are calculated according to the target injection amount QFT.
Furthermore, the injection control means A0 controls the injection amount Qp of the pre-injection Tp so that the operation conditions based on at least the engine speed Ne and the accelerator opening (engine load) θa are the same in the same operation region. As a result, the variation in the generated torque is suppressed by setting the injection amount Qp of the pre-injection Tp to the same value in the operation region where the operation conditions based on the engine rotational speed Ne and the accelerator opening (engine load) θa are the same. The stability and simplification of injection control can be achieved.

Further, when it is determined that the vibration intensity indicators RK # 1 to RK # 4 (RK # n) by the identification unit A2 described later exceed the predetermined vibration determination value TK, the injection control unit A0 is shown in FIG. As described above, in addition to the increase in the pre-injection amount, the injection timing tp of one pre-injection pulse Tp1 indicated by a two-dot chain line is corrected to a delay of the predetermined value Δt, and one injection of the pre-injection pulse Tp1 indicated by the solid line is corrected. The timing is corrected to tp (← tp−Δt). Thereby, injection control is performed so as to suppress noise generation.
Combustion detection section setting means A3 sets a period for detecting that the combustion chamber C of each cylinder (in cylinders C # 1 to C # 4) is in a combustion state for each cylinder. That is, as shown in FIG. 2, here, the sensor support portion is located at a substantially intermediate position in the engine longitudinal direction X of the cylinder head 2 which is each engine body 4 and at a different distance from each cylinder. One combustion sound sensor (combustion vibration detecting means) 6 for detecting a sound or vibration generated from the cylinder in response to combustion is attached.

As shown in FIG. 2, with respect to the combustion noise sensor 6, the cylinder C # 1 (first cylinder) is L1, the cylinder C # 2 (second cylinder) is L2, and the cylinder C # 3 (third cylinder) is L3. Cylinder C # 4 (fourth cylinder) is provided with a different relative distance of L4. For this reason, the time required for the combustion sound (combustion vibration) Vb generated in each of the cylinders C # 1 to C # 4 to reach the single combustion sound sensor 6 is different from each other.
Taking these points into consideration, the crank angle displacement direction (also the time-series direction) of the combustion detection sections # 1E to # 4E of each cylinder (referred to as #nE as a common symbol for all cylinders) (see FIG. 7B) The preset positions (positions of each cylinder relative to compression top dead center C # 1 TDC to C # 4 TDC) are adjusted in advance for each cylinder C # 1 to C # 4. Specifically, vibration wave transmission shifts due to the relative distances L1 to L4 from each cylinder to a single combustion sound sensor (combustion vibration detecting means) 6 being different for each cylinder can be considered.

  Therefore, in order to correct the transmission deviation of the vibration wave, as shown in FIG. 7B, the combustion of each cylinder C # 1 to C # 4 (each cylinder) with respect to the compression top dead center positions C # 1TDC to C # 4TDC. Deviation amounts δ # 1 to δ # 4 of detection sections # 1E to # 4E are set in advance. As a result, the combustion detection sections # 1E to # 4E in the crank angle displacement direction (also the time series direction) are corrected by setting the deviation amounts δ # 1 to δ # 4. As a result, since the single combustion sound sensor 6 is used, the combustion vibration Vb of each of the cylinders C # 1 to C # 4 (each cylinder) is changed in the crank angle displacement direction (despite the difference in the relative distances L1 to L4. It can also be detected and extracted accurately under the same conditions). In addition, the combustion vibration Vb at a plurality of positions can be detected without time-series deviation by using only one combustion sound sensor 6 here, and the cost of the apparatus can be reduced.

Next, the identification means A2 identifies the sound or vibration for each cylinder based on the output of the crank angle sensor and the detection result of the combustion vibration detection means in each period #nE set by the combustion detection period setting means A3. It has a function to do. The control function of the identification unit A2 is divided into the frequency analysis unit a2-1, the intensity index value calculation unit a2-2, the determination unit a2-3, the intensity comparison unit a2-4, and the injection amount comparison unit a2. -5.
The frequency analysis means a2-1 performs frequency analysis of the combustion vibration Vb in the combustion detection sections # 1E to # 4E for each cylinder (see FIGS. 8A to 8C). Here, after the combustion vibration Vb is collected as data along the crank angle displacement direction (which is also the time series direction), the combustion vibration in the combustion detection sections # 1E to # 4E is specified from these combustion vibration data.

Specifically, when the engine 1 is driven, as shown in FIG. 7B, combustion vibrations Vb from all cylinders (cylinders C # 1 to C # 4) are detected by the combustion sound sensor 6 over time. That is, it is sequentially input for each cylinder along a crank angle displacement direction (also a time series direction) as shown in FIG.
Further, the combustion vibration Vb is collected as data along the crank angle displacement direction, and the combustion detection sections # 1E to # 1 of each cylinder set in advance by the combustion detection section setting means A3 from these combustion vibration data. The data in 4E (denoted by #nE as a common symbol for all cylinders) (see FIGS. 7B and 8B) is denoted by specific combustion vibrations vb # 1 to vb # 4 (denoted by vb # n as a common symbol for all cylinders). ) (See FIG. 8B) and extracted.
Furthermore, the specific combustion vibrations vb # 1 to vb # 4 (vb # n) (see FIG. 8B) of each cylinder are subjected to frequency analysis by Fourier transform, and for example, a result as shown in FIG. 8C is obtained. It has gained.

The intensity index value calculation means a2-2 is a low-frequency data in which the user is likely to feel uncomfortable from the analysis result of the frequency analysis means a2-1, for example, the data shown in FIG. Data of the specific frequency region Ef regulated by the high frequency regions fa to fb (specific frequency fpn) is extracted.
Thereby, vibration intensity indices RK # 1 to RK # 4 (RK # n) (as the area equivalent values between the low and high frequency ranges fa to fb) as the intensity index values that are identification results for identifying the sound or vibration for each cylinder. Is calculated for each cylinder. Thus, the certainty of noise determination is ensured by setting the frequency region in which the user feels uncomfortable as the specific frequency region Ef.

The determination unit a2-3 determines whether or not the vibration intensity index (intensity index value) RK # n calculated by the intensity index value calculation unit a2-2 is within a predetermined range.
Here, the identification means A2 may use intensity comparison means a2-4 instead of the determination means a2-3.
The intensity comparison means a2-4 is a vibration intensity index RK # 1 to RK # 4 (RK # n) (intensity index value) which is an identification result for identifying sound or vibration for each cylinder and a predetermined vibration determination value (intensity reference). Value) Compare with TK. That is, the intensity comparison means a2-4 calculates the deviation | TK-RK # n |.
The identification unit A2 may include an injection amount comparison unit a2-5. This injection amount comparison means a2-5 compares the fuel injection amount of the pre-injection with a predetermined injection amount reference value. That is, the calculated injection amount Qp of the pre-injection Tp is compared with a predetermined division determination value QL1 (injection amount reference value). As will be described later, in the correction means A4, when the injection amount Qp exceeds a predetermined division determination value QL1, the number of pre-injections is divided into two (a plurality of times), and when the number is less than the number of pre-injections. Is set to once.

  Next, the correction means A4 sets the injection control amount, in this case, the pre-injection control amount to the cylinder so that the vibration intensity indicators RK # 1 to RK # 4 (RK # n) fall within a predetermined range (within the vibration determination value TK). Modify every time. That is, the correction means A4 uses the deviation | TK-RK # n | obtained by the intensity comparison means a2-4, and determines that the intensity index value RK # n exceeds the vibration determination value (intensity reference value) TK. When it is determined that the injection amount Qp of the pre-injection Tp is increased, the amount Qp of the pre-injection Tp is corrected to be decreased when it is determined that the intensity index value RK # n does not exceed the intensity reference value TK. Specifically, when deviation | TK−RK # n | exceeds a predetermined value β (a positive number set in advance in consideration of detection error), combustion noise Vb is at a level at which the user feels uncomfortable. Determination is made, and the injection amount Qp of the pre-injection Tp is increased by a predetermined increase value + δq (Qp + δq), and when the injection amount Qp is lower, it is corrected by a predetermined decrease value -δq (Qp-δq). As shown in FIG. 4 (a), the reduction value -δq here is a pre-injection injection pulse width Tp of a predetermined ratio, for example, 0.8% Tp, which is a 20% reduction, and the injection amount is .0. It is set to 8 · Qp to suppress noise generation.

Further, the correcting means A4 divides the number of pre-injections into two times (a plurality of times) when the injection amount Qp exceeds a predetermined division determination value QL1 (injection amount reference value), and the number of pre-injections when below the predetermined amount. Is set to once.
Here, when it is determined that it exceeds, as shown in FIG. 4 (b), the number of injections of the pre-injection Tp is divided into two times (for example, Tp1 + Tp2), and the combustion of these two pre-injections Tp1 + Tp2 interferes with each other Predetermined injection timings tp1 and tp2 that can ensure an interval that does not occur are set. Each pre-injection amount at this time is the same value of 1/2 · Qp twice (refer to the two-dot chain line in FIG. 3), and the total pre-injection amount Qp is almost the same as that in the single injection. Set to As a result, generation of noise due to sound or vibration can be suppressed and injection control in an appropriate pre-injection mode can be maintained, combustion in main injection can be accelerated, and the best thermal efficiency can be maintained.

  Next, each control process of the controller 7 of FIG. 1 will be described along the fuel injection control routine and the pre-injection correction process routine of FIGS. 9 and 10. Each routine is executed by the CPU in the controller 7 at a predetermined time period. For example, the calculation of the pre-injection amount Qp and the main injection amount Qm of each fuel injection valve 14 of 4 cylinders may be started after the injection of each fuel injection valve 14 of 4 cylinders in the previous cycle, or the current cycle Thus, it may be started immediately after the end of injection of the immediately preceding injection cylinder of each of the four cylinders.

  First, in step s1, engine parameters such as the engine rotation speed Ne, the accelerator opening θa, the engine cooling water temperature wt, the intake air amount Qa, and the like are captured. In step s2, the basic fuel injection amount INJb is obtained from a basic fuel injection amount map (not shown) based on data (engine parameters) at the time of driving of the engine 1, and a correction value QA such as an air-fuel ratio A / F, a water temperature wt, etc. / F and Qwt are added to calculate the target injection amount QFT (= INJb + QA / F + Qwt).

In step s3, a pre-injection amount Qp is obtained from the target injection amount QFT and the engine speed Ne. Here, the pre-injection amount Qp is calculated on the basis of a characteristic map (see FIG. 6) or an arithmetic expression created by measurement in advance. Further, here, the main injection amount (main injection) Qm is calculated by subtracting the pre-injection amount Qp from the target injection amount QFT.
In step s4, the injection timing tm of the main injection is calculated based on the engine parameter. Specifically, the relationship between the target injection amount QFT, the engine speed Ne, and the injection timing tm of the main injection is calculated based on a characteristic map or an arithmetic expression created by measuring in advance through experiments or the like. In step s5, the pre-injection timing tp is obtained. Here, the pre-injection timing tp with respect to the injection timing tm of the main injection is determined by a predetermined map (not shown) prepared in advance so as to gradually narrow as the engine speed Ne increases.

Next, in step s6, the crank angle Δθ information at this time is captured, and then in step s7, the combustion vibration Vb is captured from the combustion sound sensor 6, and these data are sequentially stored and held over time.
Further, when step s8 is reached, the compression top dead center positions C # 1TDC to C # 4TDC are reached at the time points in each calculation cycle from the combustion vibration Vb data up to the present as shown in FIG. The cylinder that has reached the combustion stroke is obtained based on the cylinder discrimination signal Cs, and the combustion detection sections # 1E to # 4E (#nE) of the discrimination cylinder are specified. At this time, the combustion detection sections # 1E to # 4E in the crank angle displacement direction of the cylinder that has reached the combustion stroke are set in consideration of the shift amounts δ # 1 to δ #.

  Then, the process proceeds to step s9, and the specific combustion vibrations vb # 1 to vb # 4 (vb # n) in the determined cylinder combustion detection section #nE are calculated (see FIGS. 7B and 8A). . For example, in the case of the third cylinder (third cylinder) C # 3 in FIG. 7B, the combustion vibration Vb in the combustion detection section # 3E from the deviation amount δ # 3 is taken in, and the time ta ( 7 (b)), the specific combustion vibration vb # 3 of the third cylinder (third cylinder) C # 3 is calculated (see FIG. 8 (b)).

  Thereafter, the process proceeds to step s10, where the specified specific combustion vibration data (for example, vb # 3) is subjected to frequency analysis by Fourier transform, and a displacement amount diagram of each frequency on the frequency axis is obtained. Of these, the data of the specific frequency region Ef in the low and high frequency regions fa to fb (specific frequency fpn) as the frequency region where the user is likely to feel uncomfortable as shown in FIG. 8C. Is extracted. Further, here, the area equivalent value surrounded by the low and high frequency regions fa to fb (specific frequency fpn) of the frequency displacement amount diagram which is the data of the specific frequency region Ef is the vibration intensity index RK # n, for example, FIG. In the case of the third cylinder (third cylinder) C # 3, the vibration intensity index RK # 3 is calculated.

Next, when step s11 is reached, here, a vibration determination value (intensity reference value) TK corresponding to the engine rotational speed Ne and the accelerator opening θa that is a load is read from a calculation map (not shown). . The intensity reference value TK that is a vibration determination value is set in advance as a constant value at which the combustion noise Vb feels uncomfortable for the user.
Next, when step s12 is reached, the pre-injection correction process is entered. This pre-injection correction process is performed by the pre-injection correction process routine of FIG.

  In step a1, the absolute value | TK−RK # n | of the deviation of the current vibration intensity index RK # n (specific vibration intensity) with respect to the predetermined vibration determination value TK is calculated, and the deviation exceeds the predetermined value β. It is determined whether or not. Here, if the deviation is less than the predetermined value β, the combustion noise Vb is relatively low, and if it is not at a level at which the user feels uncomfortable, the process returns to step s13 of the fuel injection control routine of FIG. In step s13, the pre-injection amount Qp, the main injection amount (main injection) Qm corresponding to the pre-injection amount Tp, the main injection pulse Tm, the pre-injection timing tp set in the above-described steps s3 and s4, The main injection timing tm is set in the injection driver 28 for each fuel injection valve 14, and this control is terminated.

  In step a1 in the pre-injection correction processing routine of FIG. 10, when the deviation exceeds the predetermined value β, if the combustion noise Vb is at a level where the user feels uncomfortable, the process proceeds to step a2 for processing to reduce this. Here, it is assumed that the current vibration intensity index RK # n (specific vibration intensity) with respect to the predetermined vibration determination value TK is small, and the process proceeds to step a3. Here, since there is no need to lower the level of the combustion noise Vb by pre-injection, the pre-injection amount Qp is corrected by a fixed amount δq, that is, corrected to a pre-injection amount (pre-injection amount) Qp (← Qp−δq). To reduce fuel consumption. Then, the process proceeds to step s13 of the fuel injection control routine of FIG. 9, and the pre-injection amount Qp corrected at step a3 at that time and the main injection amount (main injection) set in steps s3 and s4 described above. ) The injection amount pulses Tp and Tm corresponding to Qm and the injection timings tp and tm are set in the injection driver 28 for each fuel injection valve 14, and this control is terminated.

Returning to step a2 again, the current vibration intensity index RK # n (specific vibration intensity) with respect to the predetermined vibration determination value TK is large (for example, the second cylinder C # 2 in FIGS. 7A and 7B). In other words, if the combustion noise Vb is at a level where the user feels uncomfortable, the process proceeds to step a4.
Here, the pre-injection amount Qp is corrected by a fixed amount δq, that is, set to the corrected pre-injection amount Qp (← Qp + δq). Further, when reaching step a5, here, the pre-injection amount Qp corrected in step a4 is compared with a predetermined division determination value QL1. That is, it is determined whether or not the corrected pre-injection amount Qp exceeds the division determination value QL1 for determining that the single pre-injection amount Qp is relatively large and is usually a noise level at which the user feels uncomfortable.
Here, if the pre-injection amount Qp exceeds the division determination value QL1, the process proceeds to step a6, and if not, the process proceeds to step a7.

In step a6, since the pre-injection amount Qp exceeds the division determination value QL1, the number of injections of the pre-injection amount Qp is divided into two. Here, each pre-injection pulse Tp1, Tp2 (= Tp1) corresponding to each pre-injection amount 1/2 · Qp of the same injection is set, and the combustion of each pre-injection pulse Tp1, Tp2 does not interfere with each other. Predetermined injection timings tp1 and tp2 that can ensure the interval are set as shown in FIG.
Then, the process proceeds to step s13 of the fuel injection control routine of FIG. 9, at which time the pre-injection pulses Tp1 and Tp2 corresponding to the two pre-injection amounts 1/2 · Qp after being corrected in step a6, and the above-mentioned The injection pulse Tm corresponding to the main injection amount (main injection) Qm set in steps s3 and s4, the pre-injection timings tp1, tp2, and the main injection timing tm are set in the injection driver 28 of the fuel injection valve 14, and this End the control of the time.

  On the other hand, when reaching step a7 from step a5, the pre-injection amount Qp is equal to or less than the division determination value QL1, and the process proceeds to step s13 without dividing the number of injections of the pre-injection amount Qp. Here, the pre-injection pulse Tp corresponding to the pre-injection amount Qp (← Qp + δq), which has been increased in step a4, and the injection pulse Tm corresponding to the main injection amount (main injection) Qm set in steps s3 and s4 described above. Then, the pre-injection timing tp and the main injection timing tm are set in the injection driver 28 of the fuel injection valve 14, and this control is terminated.

  Thereafter, when the injection driver 28 of the fuel injection valve 14 set in step s13 reaches a proper time after the crank angle counting process, the pre-injection Tp and the main injection Tm are operated, and in the one-time pre-injection mode, As shown by a solid line in 3 (b), in the two-time pre-injection mode, injection driving is performed as shown by a two-dot chain line in FIG. 3 (b). Thereby, in any case, since the pre-injection correction process (noise reduction process after step s12) is performed, it is possible to appropriately perform the injection drive in a state where the user does not feel uncomfortable with the combustion noise Vb. In addition, the combustion in the main injection (main injection) Tm can be accelerated and the best thermal efficiency can be maintained.

  As described above, in the injection control apparatus for the internal combustion engine of FIG. 1, whether or not the vibration intensity index RK # n (specific vibration intensity) in the specific frequency region Ef exceeds the predetermined vibration determination value (intensity reference value) TK is determined. Noise that can be accurately detected based on the processing of a2, and in which the combustion vibration Vb that is the combustion noise of each cylinder makes the user feel uncomfortable in each processing of steps a6 and a7 that is selectively used based on this Injection control can be performed so as not to exceed the level. In addition, the combustion in the main injection (main injection) Tm can be accelerated and the best thermal efficiency can be maintained.

  Here, only one combustion sound sensor 6 which is a combustion vibration detection means is used, and combustion sounds sequentially transmitted from the four cylinders C # 1 to C # 4 (all cylinders) are detected as the combustion vibration Vb. Cost reduction. Moreover, the positions of the combustion detection sections # 1E to # 4E in the crank angle displacement direction are corrected according to the difference in the relative distances L1 to L4 between the combustion sound sensor (combustion vibration detection means) 6 and each cylinder. The vibration intensity indices RK # 1 to RK # 4 as the specific vibration intensity in the specific frequency region Ef specified by the low and high frequency regions fa to fb (specific frequency fpn) of each cylinder can be accurately detected.

Furthermore, when the injection amount Qp of the pre-injection Tp is large by the processing of steps a5 and a6 in the pre-injection correction processing routine, the pre-injection is performed by dividing the injection into a plurality of times Tp1 and Tp2, so that the single pre-injection amount Noise generation due to excessively high Qp can be suppressed.
Further, by the processing of step a6, when the operating conditions based on the engine rotational speed Ne and the load θa are the pre-injection amount ½ · Qp divided twice in the same operating region, the pre-injection pulses Tp1, Tp2 (= Tp1 ) To the same value, fluctuations in generated torque can be suppressed, and stability and simplification of fuel injection control can be achieved.

1 is a schematic configuration diagram of an engine including an internal combustion engine injection control device according to an embodiment of the present invention. It is a figure which shows the schematic plane of the engine of FIG. 1, and demonstrates the attachment position of a combustion sound sensor. FIG. 2 is a characteristic explanatory diagram of a pre-injection mode performed by the internal combustion engine injection control device of FIG. 1, where (a) is an injection pulse diagram, (b) is an injection amount diagram, and (c) is injection in two pre-injections. FIG. FIG. 2 is an explanatory diagram of injection pulses when pre-injection is performed prior to main injection performed by the injection control device of the internal combustion engine of FIG. 1, where (a) is a reference injection pulse diagram and (b) is a two-time pre-injection amount diagram. (C) is an injection pulse diagram in the case of injection timing correction. It is a functional block diagram of the injection control apparatus of FIG. It is a characteristic view of the pre-injection amount setting map used with the injection control apparatus of FIG. FIG. 2 is a characteristic diagram during processing of combustion vibration of the fuel injection device of FIG. FIG. 3 shows combustion vibration correction characteristics in the fuel injection device of FIG. 1, (a) is a combustion detection section explanatory diagram, (b) is a specific combustion vibration explanatory diagram, and (c) is a calculation explanatory diagram of a vibration intensity index. 2 is a flowchart of a fuel injection control routine of the fuel injection device of FIG. It is a flowchart of the pre-injection correction process routine of the fuel injection device of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 5 Sensor support part 6 Combustion sound sensor (combustion vibration detection means)
7 Controller (Injection control means)
DESCRIPTION OF SYMBOLS 12 Common rail 14 Fuel injection valve 19 Crank angle sensor 31 Accelerator opening sensor 33 Cylinder discrimination | determination sensor 35 Water temperature sensor 37 Air fuel ratio sensor a2-1 Frequency analysis means a2-2 Strength index value calculation means a2-3 Determination means a2-4 Intensity comparison Means a2-5 Injection amount comparison means fpn Specific frequency vb # 1 to vb # 4 Specific combustion vibration | TK-RK # n | Deviation A Fuel injection control device A0 Injection control means A1 Target injection amount setting means A2 Identification means A3 Combustion detection Section setting means A4 Correction means C # 1 to C # 4 Cylinder Ef (fa to fb) Specific frequency region L1 to L4 Relative distance Qp Pre-injection amount Qm Main injection amount (main injection amount)
QFT target injection amount RK # 1 to RK # 4 Vibration intensity index (identification result)
Vb Combustion vibration TK Vibration judgment value (strength reference value)
QL1 split judgment value (injection amount reference value)
# 1E to # 4E Combustion detection section

Claims (6)

A crank angle sensor that outputs a crank angle signal of a multi-cylinder internal combustion engine;
Injection control means for injecting fuel from the fuel injection valve of the internal combustion engine;
Combustion vibration detection means for detecting sound or vibration generated according to combustion from each cylinder, one set at different positions between each cylinder,
Combustion detection period setting means for setting, for each cylinder, a period for detecting that each cylinder is in a combustion state;
Identification means for identifying the sound or vibration for each cylinder based on the output of the crank angle sensor and the detection result of the combustion vibration detection means in each period set by the combustion detection period setting means;
Correction means for correcting the injection control amount of the injection control means for each cylinder according to the identification result of the identification means;
A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1,
The identification means is
Frequency analysis means for frequency analysis of the detection result of the combustion vibration detection means in each period;
Based on the analysis result of the frequency analysis means, intensity index value calculation means for calculating the intensity index value of the sound or vibration,
Determining means for determining whether or not the intensity index value calculated by the intensity index value calculating means is within a predetermined range;
Comprising
The fuel injection control device for an internal combustion engine, wherein the correction means corrects the injection control amount for each cylinder so that the intensity index value falls within the predetermined range. The fuel injection control device for an internal combustion engine according to claim 2,
The injection control amount is a fuel injection amount;
The identification means further comprises intensity comparison means for comparing the intensity index value with a predetermined intensity reference value;
The correction means increases the fuel injection amount when the intensity comparison means determines that the intensity index value exceeds the intensity reference value, and the intensity index value does not exceed the intensity reference value. When judged, the fuel injection control device for an internal combustion engine is modified for each cylinder so as to reduce the fuel injection amount. The fuel injection control device for an internal combustion engine according to claim 3,
The identifying means further comprises an injection amount comparing means for comparing the fuel injection amount with a predetermined injection amount reference value;
When the fuel injection amount is determined by the injection amount comparison unit to exceed the injection amount reference value, the correcting unit divides the fuel injection amount into a plurality of times for each cylinder and injects the fuel. A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4,
The injection control means controls the fuel injection valve in the previous period so as to perform main injection and pre-injection preceding this,
The injection control amount is an injection control amount of the pre-injection,
The fuel injection control device for an internal combustion engine, wherein the correction means corrects the injection control control amount of the pre-injection for each cylinder. The fuel injection control device for an internal combustion engine according to claim 5,
The fuel injection control device for an internal combustion engine, wherein the injection control means controls the fuel injection amount of the pre-injection to be the same in an operating region where the operating conditions of the internal combustion engine are the same.

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