JP5023042B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that injects fuel into a plurality of cylinders and controls fuel injection timing for each cylinder.

  As a conventional fuel injection control device for an internal combustion engine, for example, one disclosed in Patent Document 1 is known. This internal combustion engine is of a direct injection type in which fuel is directly injected into a cylinder. In this fuel injection control device, the intake air amount is sampled a plurality of times at predetermined time intervals for each intake stroke of each cylinder by a single airflow sensor, and these sampling values are integrated. The intake air amount of each cylinder is estimated. The estimated intake air amount is used to calculate the next fuel injection amount of the cylinder.

  Further, when the internal combustion engine is in a transient operation state, the fuel injection amount of the cylinder is calculated using an estimated value of the intake air amount of another cylinder in which fuel injection is performed immediately before the cylinder. Thus, the fuel injection amount is appropriately calculated in response to the change in the intake air amount in the transient operation state.

  Further, an average value of the estimated intake air amounts of the plurality of cylinders is obtained, a deviation of the intake air amount of each cylinder with respect to the average value is calculated, and the fuel injection amount of each cylinder is corrected based on this deviation. Thereby, an appropriate fuel injection amount corresponding to the variation in the intake air amount among the plurality of cylinders is obtained.

  However, in this prior art, since the intake air amount in each intake stroke of each cylinder is estimated by distributing the intake air amount detected by a single air flow sensor to each cylinder, the intake air from the air flow sensor to the cylinder is estimated. There is an error between the intake air amount estimated as described above and the actual intake air amount sucked into the cylinder due to the transfer delay of the air flow and the response delay of the airflow sensor. Therefore, even if the fuel injection amount is calculated from the estimated intake air amount, an appropriate fuel injection amount cannot be obtained. Even if the intake air amount is correctly estimated, the actual combustion state varies depending on the injection characteristics, EGR amount, and compression ratio of the injectors between the cylinders. It is difficult to do.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine capable of appropriately and accurately controlling the combustion state in each cylinder without causing a response delay even in a transient operation state. An object of the present invention is to provide a fuel injection control device.

Japanese Patent No. 2755671

In order to achieve the above object, the invention according to claim 1 is a fuel injection control device for an internal combustion engine 3 that injects fuel into a plurality of cylinders 3b and controls fuel injection timing for each cylinder 3b. Operating state detection means (ECU 2, crank angle sensor 11, accelerator opening sensor 12) for detecting the operating state of the engine 3 (engine speed NE, accelerator pedal opening AP in the embodiment (hereinafter the same in this section)); Combustion that is provided for each cylinder 3b and that detects the pressure in the cylinder 3b as in-cylinder pressure PCYL, and represents the combustion state in the cylinder 3b using the detected in-cylinder pressure PCYL. Combustion state parameter detection means (ECU 2, in-cylinder pressure sensor 10) for detecting the state parameter (actual ignition timing TFACT) for each cylinder 3b, and the detected internal combustion engine 3 Target combustion state parameter setting means (ECU 2, step 4 in FIG. 2, step 43 in FIG. 8) for setting a target combustion state parameter (target ignition timing TFCMD) as a target of the combustion state parameter in accordance with the operating state; Fuel injection timing setting means (ECU 2, steps 11 and 12 in FIG. 2, steps 51 and 52 in FIG. 9) for setting the fuel injection timing in accordance with the operating state of the engine 3, and any one of the cylinders Mean value calculating means (ECU2, FIG. 2) for calculating an average value TFACTAVE of a plurality of combustion state parameters including the combustion state parameters in a plurality of other cylinders 3b in which fuel injection has been performed immediately before the current fuel injection in 3b step 9, the step 47) of FIG. 8, the fuel injection timing of one cylinder 3b, the calculated average value TFACTAVE and the target Fuel injection timing correcting means for correcting in accordance with the deviation DSFAVE the baked state parameters (ECU 2, step 8-11 of FIG. 2), the fuel injection timing of one cylinder, and the combustion state parameter detected in one cylinder Second fuel injection timing correcting means (ECU2, step 7 in FIG. 2, step 46 in FIG. 8) for correcting the deviation according to the deviation DSF from the target combustion state parameter, and filtering means (ECU2, FIG. 2) for filtering the combustion state parameter Step 3 of FIG. 8 and step 42 of FIG. 8 and when the fuel injection timing is corrected by the second fuel injection timing correction means, the filtered combustion state parameter (actual ignition timing filter value TFACTAF) and the target combustion state parameter The fuel injection timing is corrected by the fuel injection timing correction means using the deviation DSF The Rutoki, characterized by using the deviation DSFAVE between the average value TFACTAVE and the target combustion state parameter of the combustion state parameter before being filtered.

According to the fuel injection control device for an internal combustion engine, the in-cylinder pressure detecting means detects the pressure in each cylinder as the in-cylinder pressure, and the detected in-cylinder pressure is used to detect the in-cylinder pressure in the cylinder. A combustion state parameter representing a combustion state is detected for each cylinder. Further, a target combustion state parameter that is a target of the combustion state parameter is set by the target combustion state parameter setting means in accordance with the detected operating state of the internal combustion engine. The fuel injection timing is set by the fuel injection timing setting means in accordance with the operating state of the internal combustion engine. Further, the average value of the plurality of combustion state parameters including the combustion state parameters of the plurality of other cylinders in which the fuel injection is performed immediately before the current fuel injection in any one of the plurality of cylinders by the average value calculating means. Is calculated. Then, the fuel injection timing correction means corrects the fuel injection timing of one cylinder according to the deviation between the average value and the target combustion state parameter. In this way, correction of the fuel injection timing of one cylinder is performed using the average value of the combustion state parameters of a plurality of other cylinders, so that the combustion state of other cylinders is reflected and the influence of temporary noise is exerted. While removing, it is possible to appropriately correct the fuel injection timing of the cylinder. Further, when calculating the average value, the combustion state parameters obtained at the previous fuel injection of one cylinder may be included in the plurality of combustion state parameters, and in this case, the combustion states of all the cylinders are reflected. Thus, the fuel injection timing can be corrected appropriately.

Further, the second fuel injection timing correction means corrects the fuel injection timing according to the deviation between the combustion state parameter of one cylinder and the target combustion state parameter, and the combustion state parameter is filtered by the filtering means. When the fuel injection timing is corrected by the second fuel injection timing correction means, the deviation between the combustion state parameter filtered by the filtering means and the target combustion state parameter is used. Thereby, the deviation used for correction of the fuel injection timing can be appropriately obtained while eliminating the influence of noise included in the detected combustion state parameter. On the other hand, when the fuel injection timing is corrected by the fuel injection timing correction means, the deviation between the average value of the combustion state parameter before filtering and the target combustion state parameter is used. Thus, it is possible to appropriately correct the fuel injection timing while maintaining the responsiveness to the combustion state parameter. Also, by using the average value, the same noise removal effect as using the filtered combustion state parameter can be obtained even if the combustion state parameter before filtering is used. Better response to changes in the combustion state can be obtained. Therefore, even in a transient operation state that tends to change the combustion state, it is possible to control the fuel injection timing appropriately and accurately in each cylinder without causing a response delay. As a result, combustion noise is suppressed, drivability and exhaust gas characteristics are controlled. Can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an internal combustion engine 3 to which the fuel injection control device according to the present embodiment is applied. The internal combustion engine (hereinafter referred to as “engine”) 3 is, for example, an in-line four-cylinder type diesel engine mounted on a vehicle (not shown).

  An intake pipe 4 and an exhaust pipe 5 are connected to a cylinder head 3a of the engine 3 and a fuel injection valve (hereinafter referred to as “injector”) 6 is attached so as to face a piston 3d in the cylinder 3b.

  The injector 6 is sequentially connected to a high-pressure pump and a fuel tank (both not shown) via a common rail. The high-pressure pump boosts the fuel in the fuel tank to a high pressure, and then sends the fuel to the injector 6 via the common rail. The injector 6 injects the fuel into the cylinder 3b. The fuel injection amount and fuel injection timing TI of the injector 6 are controlled by the ECU 2 described later.

  An in-cylinder pressure sensor 10 is integrally attached to the injector 6. The in-cylinder pressure sensor 10 is configured by a ring-shaped piezoelectric element, and outputs a detection signal representing a change amount of pressure in the cylinder 3b (hereinafter referred to as “in-cylinder pressure change amount”) DPV to the ECU 2. The ECU 2 calculates the pressure in the cylinder 3b (hereinafter referred to as “in-cylinder pressure”) PCYL based on the in-cylinder pressure change amount DPV.

  A magnet rotor (not shown) is attached to the crankshaft 3c of the engine 3, and a crank angle sensor 11 is constituted by this magnet rotor and an MRE pickup (not shown). The crank angle sensor 11 outputs a TDC signal and a CRK signal, which are pulse signals, to the ECU 2 as the crankshaft 3c rotates. The CRK signal is output every predetermined crank angle (for example, 1 °).

  The ECU 2 obtains the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3d is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke in each cylinder 3b. In the case of the four-cylinder type as in the present embodiment, Is output at every crank angle of 180 °.

  The engine 3 is provided with a cylinder discrimination sensor (not shown), and this cylinder discrimination sensor outputs a cylinder discrimination signal, which is a pulse signal for discriminating the cylinder 3b, to the ECU 2. The ECU 2 calculates a crank angle CA in each cylinder 3b based on the cylinder discrimination signal, the TDC signal, and the CRK signal. Specifically, the crank angle CA is reset to 0 when the TDC signal is generated, and is incremented every time the CRK signal is generated.

  Further, an accelerator opening sensor 12 is connected to the ECU 2. The accelerator opening sensor 12 detects an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown), and a detection signal is output to the ECU 2.

  The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like. The detection signals from the various sensors 10 to 12 described above are input to the CPU after A / D conversion and shaping by the I / O interface. The ECU 2 determines the operation state of the engine 3 according to the control program stored in the ROM according to these input signals, and the operation of the engine 3 including the fuel injection timing TI of the injector 6 according to the determined operation state. To control.

  In the present embodiment, the ECU 2 includes an operation state detection unit, a combustion state parameter detection unit, a target combustion state parameter setting unit, a fuel injection timing setting unit, a fuel injection timing correction unit, a gain setting unit, a correction prohibition unit, an average value. It corresponds to a calculating means, a filtering means, and a second fuel injection timing correcting means. Hereinafter, various processes executed by the ECU 2 will be described with reference to the drawings.

  2 and 3 show a main flow of control processing of the fuel injection timing TI of the injector 6. This process is executed for each cylinder 3b in synchronization with the generation of the TDC signal described above. Accordingly, in the following description, various parameters detected, calculated, or set for each cylinder 3b are denoted by “#i” instead of the cylinder number (# 1 to # 4) of the cylinder 3b. And

  First, in step 1 (illustrated as “S1”, the same applies hereinafter), an actual ignition timing (hereinafter referred to as “actual ignition timing”) TFACT # i in the cylinder 3b is calculated. The actual ignition timing TFACT # i is calculated as follows.

First, using the in-cylinder pressure PCYL # i detected by the in-cylinder pressure sensor 10, a heat generation rate dQθ # i that is a heat generation amount per crank angle of 1 ° is calculated according to the following equation (1).
dQθ # i = (κ · PCYL # i · 1000 · dVθ # i
+ DPCYL # i · 1000 · Vθ # i)
/ Κ-1 (1)
dQθ: heat generation rate κ: specific heat ratio of the air-fuel mixture PCYL: in-cylinder pressure dVθ: in-cylinder volume change rate dPCYL: in-cylinder pressure change rate Vθ: in-cylinder volume Here, the specific heat ratio κ is set to a predetermined value (eg, 1.34). Is set. The in-cylinder pressure change rate dPCYL is the difference between the current value and the previous value of the in-cylinder pressure PCYL, and the in-cylinder volume change rate dVθ and the in-cylinder volume Vθ are both calculated based on the crank angle CA.

  By integrating the heat generation rate dQθ # i, the heat generation amount from the start of combustion in the cylinder 3b is calculated and stored sequentially. Then, the heat generation amount calculated at the end of the combustion is set as the total heat generation amount, and a heat generation amount corresponding to ½ of the total heat generation amount among the plurality of stored heat generation amounts is obtained. The crank angle CA when the engine is in operation is calculated as the actual ignition timing TFACT # i.

  Next, the calculated actual ignition timing TFACT # i is sequentially stored as the actual ignition timing storage value TFACTREGn in the RAM buffer of the ECU 2 (step 2).

Next, the actual ignition timing filter value TFACTAF # i is calculated by subjecting the calculated actual ignition timing TFACT # i to the filtering process shown in the following equation (2) (step 3).
TFACTAF # i (k)
= Α1 · TFACTAF # i (k−1) + α2 · TFACTAF # i (k−2)
+ ... + αm · TFACTAF # i (km)
+ Β1 · TFACT # i (k−1) + β2 · TFACT # i (k−2)
+... + Βj.TFACT # i (k−j) (2)

  In this equation (2), each discrete data with the symbol (k) indicates that it is discrete data sampled or calculated at a predetermined control period ΔT, and the symbol k is a sampling or calculation cycle of each discrete data. Represents the order. For example, the symbol k indicates a value sampled or calculated at the current control timing, and the symbol k-1 indicates a value sampled or calculated at the previous control timing. The same applies to the above formula. In the following description, the symbol (k) in each discrete data is omitted as appropriate. Α1 to αm and β1 to βj are predetermined filter coefficients, and m and j are filter orders (natural numbers). In this low-pass filter process, a predetermined high frequency is set as the cutoff frequency. As a result, noise included in the calculated actual ignition timing TFACT # i is removed.

  Next, in step 4, the target ignition timing TFCMD is calculated by searching a predetermined map (not shown) according to the required torque PMCMD and the engine speed NE. This required torque PMCMD is calculated by searching a predetermined map (not shown) according to the engine speed NE and the accelerator pedal opening AP.

  Next, a first feedback correction term CFBS # i for the cylinder 3b is calculated (step 5). FIG. 4 shows the subroutine. First, in step 20, the difference (TFCMD-TFACTAF # i) between the calculated target ignition timing TFCMD and the actual ignition timing filter value TFACTAF # i is calculated as the first deviation DSF # i. Next, the map values KP1, KI1, and KD1 are calculated by searching the map of FIG. 5 according to the calculated absolute value | DSF # i | of the first deviation DSF # i, and the proportional term gain KP1. #I, integral term gain KI1 # i and differential term gain KD1 # i are set (step 21). These map values KP1, KI1, and KD1 are set to larger values in order to increase the convergence to the target ignition timing TFCMD as the absolute value | DSF | of the first deviation increases.

Next, in steps 22 to 25, the proportional term FBSP # i, the integral term FBSI # i, and the derivative term FBSD # i are calculated by the PID control algorithm shown in the following equations (3) to (6), and these calculated Are added to each other to calculate the first feedback correction term CFBS # i.
FBSP # i (k) = KP1 # i (k) .DSF # i (k) (3)
FBSI # i (k) = KI1 # i (k) .DSF # i (k) + FBSI # i (k-1)
... (4)
FBSD # i (k) = KD1 # i (k) · {DSF # i (k)
-DSF # i (k-1)} (5)
CFBS # i (k) = FBSP # i (k) + FBSI # i (k) + FBSD # i (k)
... (6)

  Returning to FIG. 2, in Step 6 following Step 5, the target fuel injection timing TICMD is calculated by searching a predetermined map (not shown) according to the required torque PMCMD and the engine speed NE.

  Next, in step 7, the fuel injection timing TI # i is calculated by adding the first feedback correction term CFBS # i to the calculated target fuel injection timing TICMD.

Next, the previous value DSFZ of the first deviation DSF, that is, the difference between the target ignition timing TFCMD and the actual ignition timing filter value TFACTAF in the other cylinder 3b in which fuel injection has been performed immediately before the cylinder 3b, is a predetermined value DSFREF. It is discriminated whether or not (step 8). When the determination result is NO and DSFZ ≧ DSFREF, the average value TFACTAVE of the actual ignition timing storage values TFACTREGn stored in the step 2 is calculated by the following equation (7) (step 9).
TFACTAVE = {TFACTREG (n-1) + TFACTREG (n-2)
+ TFACTREG (n-3) + TFACTREG (n-4)} / 4 (7)
TFACTREG (n−1), (n−2), and (n−3) are actual ignitions of the other cylinders 3b in which fuel injection was performed one time before, two times before, and three times before the cylinder 3b, respectively. The actual ignition timing memory value TFACTREGn corresponding to the timing TFACT # i. TFACTREG (n-4) is an actual ignition timing storage value TFACTREGn corresponding to the actual ignition timing TFACT # i obtained at the previous fuel injection of the cylinder 3b. As is apparent from this equation (7), the average value TFACTAVE is a total of four actual ignition timings for each of the cylinders 3b obtained from the previous fuel injection of the cylinder 3b to the immediately preceding fuel injection. Corresponds to the simple average of TFACT # i.

  Next, the second feedback correction term CFBO # i is calculated (step 10 in FIG. 3). FIG. 6 shows the subroutine. First, in step 30, the difference (TFCMD−TFACTAVE) between the target ignition timing TFCMD calculated in step 4 of FIG. 2 and the average value TFACTAVE is calculated as a second deviation DSFAVE # i. Next, the map values KP2, KI2, and KD2 are calculated by searching the map of FIG. 7 according to the absolute value | DSFAVE # i | of the calculated second deviation DSFAVE # i, and the proportional term gain KP2 is obtained. Set as #i, integral term gain KI2 # i, and differential term gain KD2 # i (step 31). These map values KP2, KI2, and KD2 are set to larger values in order to increase the convergence to the target ignition timing TFCMD as the absolute value | DSFAVE | of the second deviation increases.

Next, in steps 32 to 35, the proportional term FBOP # i, the integral term FBOI # i, and the derivative term FBOD # i are calculated by the PID control algorithm shown in the following equations (8) to (11), and these values are calculated. By adding together, the second feedback correction term CFBO # i is calculated.
FBOP # i (k) = KP2 # i (k) · DSFAVE # i (k) (8)
FBOI # i (k) = KI2 # i (k) · DSFAVE # i (k)
+ FBOI # i (k-1) (9)
FBOD # i (k) = KD2 # i (k) · {DSFAVE # i (k)
-DSFAVE # i (k-1)}
... (10)
CFBO # i (k) = FBOP # i (k) + FBOI # i (k) + FBOD # i (k)
(11)

  Returning to FIG. 3, in step 11 following step 10, a value obtained by adding the calculated second feedback correction term CFBO # i to the fuel injection timing TI # i is set as the final fuel injection timing TIF # i ( Step 11), the process ends.

  On the other hand, if the determination result in step 8 is YES and DSFZ <DSFREF, correction by the second feedback correction term CFBO # i is prohibited, and the fuel injection timing TI # i is set as the final fuel injection timing TIF # i. (Step 12 in FIG. 3), the process is terminated.

  As described above, according to the present embodiment, the actual ignition timing TFACT # i in the cylinder 3b is detected for each cylinder 3b using the detected in-cylinder pressure PCYL. In addition, the target ignition timing TFCMD and the target fuel injection timing TICMD are set according to the detected engine speed NE and the required torque PMCMD. Then, the fuel injection timing TI # i of any one cylinder 3b is corrected according to the first deviation DSF # i between the actual ignition timing filter value TFACTAF # i and the target ignition timing TFCMD in the other cylinder 3b. Accordingly, the fuel injection timing TI # i of the cylinder 3b is appropriately corrected while reflecting the combustion state of the other cylinder 3b in which the fuel injection is performed at a timing closer to the previous fuel injection of the cylinder 3b. Can do. Therefore, even in a transient operation state in which the combustion state tends to change, the fuel injection timing can be appropriately and accurately controlled in each cylinder 3b without causing a response delay. As a result, combustion noise can be suppressed, and drivability and exhaust gas can be controlled. The characteristics can be improved.

  In addition, by the feedback control, the target fuel injection timing TICMD is corrected so that the actual ignition timing TFACT # i converges to the target ignition timing TFCMD, and the gains KP1 # i, KI1 # i, KD1 # i of this feedback control are set. The larger the first deviation DSF # i between the actual ignition timing filter value TFACTAF # i and the target ignition timing TFCMD is set to a larger value. Thereby, in the transient operation state, the actual ignition timing TFACT can be brought closer to the target ignition timing TFCMD more quickly, and the responsiveness of the feedback control can be improved.

  Further, when the previous value DSFZ of the first deviation DSF, which is the deviation between the actual ignition timing filter value TFACTAF and the target ignition timing TFCMD in the cylinder 3b in which fuel injection has been performed immediately before, is smaller than the predetermined value DSFREF, the fuel injection timing TI correction is prohibited. Thereby, in the steady operation state, by prohibiting the correction of the fuel injection timing TI, it is possible to maintain the stable combustion state in each cylinder 3b by eliminating the influence of the combustion state in the other cylinders 3b.

  On the other hand, when the previous value DSFZ of the first deviation DSF is greater than or equal to the predetermined value DSFREF, a total of four actual ignitions for each of the cylinders 3b obtained from the previous fuel injection to the current fuel injection of the cylinder 3b. An average value TFACTAVE of the timing TFACT # i is calculated, and the fuel injection timing TI # i of the cylinder 3b is corrected according to the second deviation DSFAVE # i between the average value TFACTAVE and the target ignition timing TFCMD. Thus, since the correction of the fuel injection timing TI # i of the cylinder 3b is performed using the average value TFACTAVE of the actual ignition timings TFACT # i of the plurality of other cylinders 3b, the combustion state of the other cylinders 3b is reflected. Thus, it is possible to appropriately correct the fuel injection timing TI # i of the cylinder 3b while removing the influence of temporary noise and better responding to changes in the combustion state. In addition, when calculating the average value TFACTAVE, the actual ignition timing TFACT # i corresponding to the previous fuel injection of the cylinder 3b is also included, so that the influence of temporary noise is reflected while reflecting the combustion state of all the cylinders 3b. It is possible to appropriately correct the fuel injection timing TI # i of the cylinder 3b while removing it and responding better to changes in the combustion state.

  Further, by the feedback control, the fuel injection timing TI # i is corrected so that the average value TFACTAVE converges to the target ignition timing TFCMD, and the gains KP2 # i, KI2 # i, KD2 # i of this feedback control are averaged. The larger the second deviation DSFAVE # i between the value TFACTAVE and the target ignition timing TFCMD, the larger the value is set. Thereby, the average value TFACTAVE can be brought closer to the target ignition timing TFCMD more quickly, and the responsiveness of the feedback control can be improved.

  Further, since the actual ignition timing TFACT having a close correlation with the combustion state in the cylinder 3b is used as the combustion state parameter, it is possible to appropriately correct the fuel injection timing.

  Further, when the target fuel injection timing TICMD is corrected to obtain the fuel injection timing TI # i (step 7 in FIG. 2), the actual ignition timing filter value TFACTAF # i obtained by filtering the actual ignition timing TFACT # i and the target ignition. The first deviation DSF # i from the time TFCMD is used. Thereby, the first deviation DSF can be appropriately obtained while eliminating the influence of noise included in the detected actual ignition timing TFACT. On the other hand, when the fuel injection timing TI # i is further corrected to obtain the final target injection timing TIF # i (step 11 in FIG. 3), the average value TFACTAVE of the actual ignition timing TFACT # i before filtering and the target The second deviation DSFAVE # i from the ignition timing TFCMD is used. Thus, it is possible to appropriately correct the fuel injection timing TI while maintaining the response to the actual ignition timing TFACT.

  8 and 9 show the main flow of the fuel injection timing control process according to the second embodiment of the present invention. This second embodiment differs from the first embodiment described above in the execution condition of the feedback control of the fuel injection timing TI according to the combustion state of the other cylinder 3b.

  First, in steps 40 to 46, the same processing as in steps 1 to 7 in FIG. Next, the average value TFACTAVE of the actual ignition timing TFACT # i is calculated by the above equation (7) (step 47).

  Next, a difference (TFCMD−TFACTAVE) between the target ignition timing TFCMD and the calculated average value TFACTAVE is calculated as a second deviation DSFAVE # i (step 48).

  Next, it is determined whether or not the calculated second deviation DSFAVE # i is smaller than a predetermined value DSFREF (step 49). When the determination result is NO and DSFAVE # i ≧ DSFREF, the second feedback correction term CFBO # i is calculated (step 50 in FIG. 9). This calculation is performed by the subroutine shown in FIG.

  Next, in step 51, a value obtained by adding the fuel injection timing TI # i and the calculated second feedback correction term CFBO # i is set as the final fuel injection timing TIF # i, and this processing is terminated.

  On the other hand, if the determination result in step 49 is YES and DSFAVE # i <DSFREF, the fuel injection timing TI # i is set as the final fuel injection timing TIF # i (step 52 in FIG. 9), and this process is terminated. .

  As described above, in the first embodiment described above, correction of the fuel injection timing TI is prohibited when the first deviation DSF, which is the deviation between the actual ignition timing TFACT and the target ignition timing TFCMD, is smaller than the predetermined value DSFREF. On the other hand, in the present embodiment, the correction of the fuel injection timing TI is prohibited when the second deviation DSFAVE between the average value TFACTAVE of the actual ignition timing TFACT and the target ignition timing TFCMD is smaller than the predetermined value DSFREF. Therefore, as in the first embodiment, in the steady operation state, by prohibiting the correction of the fuel injection timing TI, the influence of the combustion state in the other cylinders 3b is eliminated, thereby achieving a stable combustion state in each cylinder 3b. Can be maintained. Further, since the average value TFACTAVE is compared with the target ignition timing TFCMD, the correction prohibition is appropriately determined while reflecting the combustion state of the other cylinders 3b and eliminating the influence of temporary noise. Can do.

In the first and second embodiments described above, the average value TFACTAVE in step 9 of FIG. 2 and step 47 of FIG. 8 is calculated by simple averaging according to the above equation (7). You may carry out by a weighted average by Formula (12).
TFACTAVE = KWE (n−1) · TFACTREG (n−1)
+ KWE (n-2) ・ TFACTREG (n-2)
+ KWE (n-3) ・ TFACTREG (n-3)
+ KWE (n-4) ・ TFACTREG (n-4)
(12)
Thus, in the equation (12), the average value TFACTAVE is calculated by multiplying the actual ignition timing storage value TFACTREGn by the weighting coefficient KWEn. The weight coefficient KWEn is set to a larger value for the cylinder 3b in which fuel injection is performed at a timing closer to the current fuel injection of the cylinder 3b, and KWE (n-1) to KWE (n -4) is 1.0. Specifically, KWE (n-1) is the largest, for example, 0.5, KWE (n-2) is 0.3, KWE (n-3) is 0.2, KWE (n-4). Is the smallest and is set to 0, for example.

  In this manner, the average value TFACTAVE of the actual ignition timing TFACT # i is calculated as a weighted average value, and the weighting coefficient KWEn used for the weighted average at this time is closer to the current fuel injection of the cylinder 3b. The cylinder 3b in which fuel injection has been performed is set to a larger value. As a result, the cylinder 3b in which the combustion is performed at a closer timing causes a response delay to the change in the combustion state even in the transient operation state in which the combustion state tends to change while reflecting the combustion state more strongly. Therefore, the fuel injection timing TI can be corrected quickly and appropriately.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the actual ignition timing TFACT is used as the combustion state parameter, but any combustion state parameter that represents the combustion state in the cylinder 3b may be used. For example, the ignition delay period from the fuel injection timing to the ignition timing is acceptable. Alternatively, the in-cylinder pressure change rate dPCYL may be used.

  Further, in the embodiment, when the average value TFACTAVE is calculated by the equation (7), the actual ignition timing TFACT (n-4) of the cylinder 3b is included, but this is excluded and corresponds to other cylinders. Only three actual ignition timings TFACT (n-1) to (n-3) may be used. Further, when the average value TFACTAVE is calculated by the above equation (12), the weighting coefficient KWE (n-4) is set to 0, so that the actual ignition timing TFACT ( n-4) is not substantially included, but by setting the weight coefficient KWE (n-4) to a value larger than 0, the actual ignition timing TFACT (n-4) of the cylinder 3b is included. Also good.

  Moreover, although embodiment is an example which applied this invention to the diesel engine mounted in the vehicle, this invention is not restricted to this, You may apply to various engines, such as gasoline engines other than a diesel engine, Further, the present invention can also be applied to engines other than those for vehicles, for example, marine vessel propulsion engines such as outboard motors having a crankshaft arranged vertically. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

1 is a diagram schematically showing an internal combustion engine to which a fuel injection timing control device according to an embodiment is applied. It is a flowchart which shows the main flow of a fuel injection timing control process. 3 is a flowchart showing a continuation of FIG. It is a subroutine which shows the calculation process of 1st feedback correction term CFBS. It is a map for setting the gain of feedback control when calculating the first feedback correction term CFBS. It is a subroutine which shows the calculation process of 2nd feedback correction term CFBO. It is a map for setting the gain of the feedback control when calculating the second feedback correction term CFBO. It is a flowchart which shows the main flow of the fuel-injection control process by 2nd Embodiment. It is a flowchart which shows the continuation of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection timing control apparatus 2 ECU (Operating state detection means, combustion state parameter detection means, target combustion state parameter setting means, fuel injection timing setting means, fuel injection timing correction means, gain setting means, correction prohibition means, average value calculation Means, filtering means, second fuel injection timing correction means)
3 Engine (Internal combustion engine)
3b Cylinder 10 In-cylinder pressure sensor (in-cylinder pressure detection means)
11 Crank angle sensor (operating state detection means)
12 Accelerator opening sensor (operating state detection means)
PCYL In-cylinder pressure
dPCYL In-cylinder pressure change rate (change rate)
TFACT actual ignition timing (ignition timing, combustion state parameters)
TFACTAF actual ignition timing filter value (filtered combustion state parameter)
TFACTAVE average value
TFCMD target ignition timing (target combustion state parameter)
TI fuel injection timing
TIF Final fuel injection timing (fuel injection timing)
DSF first deviation (deviation)
DSFREF predetermined value
DSFAVE 2nd deviation (deviation)
KWE Weight coefficient KP1, KI1, KD1 Map value (gain)
KP2, KI2, KD2 Map value (gain)

Claims (1)

A fuel injection control device for an internal combustion engine that injects fuel into a plurality of cylinders and controls fuel injection timing for each cylinder,
An operating state detecting means for detecting an operating state of the internal combustion engine;
In-cylinder pressure detecting means provided for each cylinder and detecting the pressure in the cylinder as an in-cylinder pressure;
Combustion state parameter detection means for detecting a combustion state parameter representing a combustion state in the cylinder for each cylinder using the detected in-cylinder pressure;
Target combustion state parameter setting means for setting a target combustion state parameter as a target of the combustion state parameter according to the detected operating state of the internal combustion engine;
Fuel injection timing setting means for setting the fuel injection timing according to the operating state of the internal combustion engine;
Average value calculation for calculating an average value of a plurality of combustion state parameters including combustion state parameters in a plurality of other cylinders in which fuel injection has been performed immediately before the current fuel injection in any one of the plurality of cylinders Means,
The fuel injection timing of said one cylinder, the fuel injection timing correction means for correcting in accordance with the deviation of the calculated average value and the set target combustion state parameter,
Second fuel injection timing correction means for correcting the fuel injection timing of the one cylinder according to a deviation between the combustion state parameter detected in the one cylinder and the target combustion state parameter;
Filtering means for filtering the combustion state parameter;
Equipped with a,
When the fuel injection timing is corrected by the second fuel injection timing correction means, the difference between the filtered combustion state parameter and the target combustion state parameter is used, and the fuel injection timing is corrected by the fuel injection timing correction means. When performing, a deviation between the average value of the combustion state parameter before filtering and the target combustion state parameter is used .

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