JP2007032540A - Internal combustion engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve exhaust emissions and driveability by correctly obtaining the property of each cylinder of an internal combustion engine and reflecting it on control. <P>SOLUTION: A detection signal from a rotating speed sensor 18 is input to an ECU 20. The ECU 20 calculates the rotating speed of a crank shaft 17 at a predetermined angle cycle in accordance with the detection signal from the rotating speed sensor 18, and filters the calculated rotating speed with a single frequency set in accordance with the combustion frequency of the engine to calculates an instantaneous torque equivalent value each time. The ECU 20 calculates a by-cylinder work volume in accordance with the instantaneous torque equivalent value calculated by the filtering and controls the property of each cylinder of the engine with the by-cylinder work volume. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a technique for performing appropriate control corresponding to characteristic variations among cylinders in a multi-cylinder internal combustion engine.

  In the internal combustion engine, combustion is performed at a predetermined rotation angle cycle, and a rotational force is applied to the output shaft along with the combustion, so that a desired engine rotation speed is realized. In this case, in a multi-cylinder internal combustion engine, there is a concern that the combustion state and the like are different for each cylinder due to machine differences, changes over time, and the like, thereby deteriorating exhaust emission and drivability.

  As a countermeasure, for example, in Patent Document 1, a rotational speed signal is filtered at different frequencies by at least two filter means, and at least two frequency-specific stable operation actual values and stable operation target values are filtered from the filtered rotational speed signals. The control deviation of the natural frequency is detected. More specifically, band-pass filters (BPF) each having a center frequency of a camshaft frequency, a crankshaft frequency, and a half ignition frequency are used, and a rotation speed signal is input to each band-pass filter. Then, the frequency-specific control deviation is calculated based on the filter output, and the frequency-specific control deviation is added to obtain an added value, and the output of the internal combustion engine is controlled based on the added value. As a result, each cylinder can be controlled equally.

  In the case of the above-mentioned Patent Document 1, if variation in rotational fluctuation occurs between cylinders, the variation between the cylinders is calculated as a control deviation, and the rotational speed tends to be large or small when relatively looking at all the cylinders. You can see if there is. Then, the control is performed so as to eliminate the variation among the cylinders and equalize all the cylinders. For example, the variation is eliminated by increasing or decreasing the fuel injection amount of each cylinder according to the variation between cylinders.

However, in the technique of Patent Document 1, it is unclear how much error has occurred with respect to the ideal value in each cylinder of the internal combustion engine. That is, the absolute characteristic deviation cannot be grasped. Therefore, there is a problem that the combustion state in each cylinder cannot be optimally controlled. For example, when all the cylinders have the same tendency and deviate from the ideal state, optimal control cannot be performed. In recent years, demands for improving exhaust emission and drivability are increasing, and a technology capable of diversifying control is desired to meet the demands.
JP-A-8-218924

  The main object of the present invention is to provide a control device for an internal combustion engine that can appropriately grasp the characteristics of each cylinder of the internal combustion engine and reflect them in the control, thereby improving exhaust emission and drivability. It is.

  According to the first aspect of the present invention, the rotational speed of the crankshaft of the internal combustion engine is sequentially calculated, and the calculated rotational speed is filtered by a filter unit at a single frequency set based on the combustion frequency of the internal combustion engine. The instantaneous torque equivalent value is calculated. The characteristics of each cylinder of the internal combustion engine are controlled based on the instantaneous torque equivalent value calculated by the filter means. Here, the combustion frequency is an angular frequency representing the combustion frequency for each unit angle, and is determined by the reciprocal of the combustion angle cycle corresponding to the number of cylinders of the internal combustion engine.

  In an internal combustion engine, a rotation increase due to combustion and a rotation decrease due to a load are basically repeated, and the instantaneous rotation speed varies according to the rotation angle. At this time, in each cylinder of the internal combustion engine, the combustion state and the like may change due to machine differences between cylinders, changes with time, and the like, which may cause deterioration of exhaust emission and drivability. In such a case, since each rotation speed is considered to be a reflection of the instantaneously generated torque, an instantaneous torque equivalent value can be calculated based on the rotation speed, and if the instantaneous torque equivalent value is monitored for each cylinder, It is possible to grasp the characteristic variation (change in rotational behavior, etc.) for each cylinder. In this respect, in the present invention, the filter means filters the rotational speed at a frequency based on the combustion frequency of the internal combustion engine. Therefore, the component of the combustion frequency is extracted from the rotational speed and the instantaneous torque is set so as to correspond to the combustion cycle. An equivalent value can be calculated. At this time, the instantaneous torque equivalent value can be calculated each time so that the torque balance is completed for each combustion cycle of each cylinder. Then, by performing fuel injection amount control, torque control, and the like based on the instantaneous torque equivalent value, the characteristics of each cylinder in the internal combustion engine can be suitably controlled. As a result, it is possible to appropriately grasp the characteristics of each cylinder and reflect them in the control, thereby improving exhaust emission and drivability.

  In the present invention, since the instantaneous torque equivalent value is calculated by performing the filtering process by the single filtering unit, the filtering process is performed by the plurality of filtering units, and the control deviation is obtained by comparing the rotational speed signals by the respective filtering units. Unlike the prior art (Japanese Patent Laid-Open No. 8-218924) that detects the above, not only the relative characteristic variation among the cylinders but also the absolute characteristic variation (deviation from the ideal value) of each cylinder can be detected. Therefore, it is possible to diversify the control for each cylinder, and it is possible to appropriately cope with various demands for improving exhaust emission and drivability.

  At this time, as described in claim 2, a combustion frequency may be used as a response frequency ω of a transfer function that defines the filter means. Thereby, the filter processing based on the combustion frequency of the internal combustion engine can be realized. When the transfer function is represented by a period T, the period T is 2π / ω.

  Further, as described in claim 3, a bandpass filter (BPF) is preferably used as the filter means. That is, the rotational speed information includes a low-frequency fluctuation component associated with acceleration / deceleration, a high-frequency fluctuation component such as a rotational position error, and noise. It is possible to remove high-frequency fluctuation components and extract only torque fluctuation components. As a result, the instantaneous torque equivalent value can be accurately calculated, and as a result, the characteristics of each cylinder can be grasped more accurately.

  Each time the internal combustion engine is operated (the value equivalent to the instantaneous torque) fluctuates in accordance with the stroke and rotational angle position of each cylinder, and the fluctuation is caused by the combustion torque, inertia torque, and load torque for each cylinder. This is due to the increase / decrease according to the stroke and the rotation angle position. FIG. 10 shows changes in rotational speed, combustion torque, inertia torque, and load torque and their corresponding relationships, taking a four-cylinder engine as an example.

  In FIG. 10, timings A1, A2, and A3 indicate timings at which the rotational speed starts to decrease and increases due to the combustion (explosion) of fuel in any cylinder. The angles between A1 and A2 and between A2 and A3 correspond to the combustion angle period. As shown in (b), the combustion torque increases with the start of combustion and decreases with the end of combustion. In addition, the inertia torque changes according to the rotational inertia force of the flywheel, and as shown in (c), it becomes a negative value when the rotational speed increases (when the piston moves downward), and when the rotational speed decreases (piston) Changes to a positive value during As shown in (d), the load torque is always negative and changes within a relatively small range. The sum of the combustion torque, the inertia torque, and the load torque ((b) + (c) + (d) in FIG. 10) is the instantaneous torque equivalent value.

  Here, if there is no variation in characteristics among cylinders and there is no difference in characteristics between cylinders, the behavior of torque change is the same for each cylinder, and the instantaneous torque equivalent value and other torque values (combustion torque, load torque, etc.) ) Changes with the same waveform in each cylinder. However, if the behavior of the torque change is different due to the characteristic difference between the cylinders, the waveform such as the instantaneous torque equivalent value will be different. In this case, at the same rotation angle position of each cylinder, the instantaneous torque equivalent values differ according to the characteristics of each cylinder. For example, as shown in FIG. 10, when the instantaneous torque equivalent value is obtained at the same rotational angle position “B” of each cylinder, the instantaneous torque equivalent values (C1, C2 in the figure) correspond to the characteristics of each cylinder. Will be. Along with this, a difference between cylinders also occurs in the peak value and bottom value of the instantaneous torque equivalent value.

  Therefore, in the invention according to claim 4, the instantaneous torque equivalent value at a predetermined rotational angle position is obtained for each cylinder, and the characteristic for each cylinder is estimated based on the instantaneous torque equivalent value. According to the fifth aspect of the present invention, the instantaneous torque equivalent value at a predetermined rotational angle position is obtained for each cylinder, and the instantaneous torque equivalent value is compared between the cylinders to estimate the characteristic difference between the cylinders. Note that the rotational angle position for obtaining the instantaneous torque equivalent value may be one or a plurality of the same angular positions or a nearby angular position that can be regarded as substantially the same, and can be evaluated at a predetermined angular position anyway. If it is good.

  In the invention according to claim 6, at least one of the peak value and the bottom value of the instantaneous torque equivalent value is obtained for each cylinder, and the characteristic for each cylinder is estimated based on the obtained value. According to the seventh aspect of the present invention, at least one of the peak value and the bottom value of the instantaneous torque equivalent value is obtained for each cylinder, and the characteristic difference between the cylinders is estimated by comparing the obtained values among the cylinders. . In this case, a method for evaluating the characteristics (or cylinder-to-cylinder difference) of each cylinder only with the peak value of the instantaneous torque equivalent value, a method for evaluating the characteristics (or cylinder-to-cylinder difference) of each cylinder only with the same bottom value, and the same peak value A method for evaluating the characteristics of each cylinder (or the difference between cylinders) based on the difference between the value and the bottom value is conceivable.

  In the combustion state where the combustion is actually performed, the sum of the combustion torque, the inertia torque and the load torque ((b) + (c) + (d) in FIG. 10) becomes the instantaneous torque equivalent value as described above. In a combustion stop state (fuel cut state or the like) in which combustion is not performed, the sum of inertia torque and load torque ((c) + (d) in FIG. 10) is an instantaneous torque equivalent value. That is, a difference corresponding to the combustion torque occurs in the instantaneous torque equivalent value between the combustion state and the combustion pause state. Therefore, as described in claim 8, it is preferable to calculate the combustion torque for each cylinder from the difference between the instantaneous torque equivalent value calculated in the combustion state and the instantaneous torque equivalent value calculated in the combustion stop state in each cylinder. Thereby, the combustion torque for each cylinder can be accurately calculated, and as a result, the fuel injection amount of each cylinder can be grasped for each cylinder. In addition, the characteristics can be controlled for each cylinder so that the actual combustion torque matches the originally ideal value (target value).

  For example, a predetermined angular position is determined within the combustion period in each cylinder, and an instantaneous torque equivalent value in the combustion state and an instantaneous torque equivalent value in the combustion pause state are respectively calculated at the angular position. And it is good to calculate the combustion torque for every cylinder by the difference of these instantaneous torque equivalent values. It is also possible to calculate the difference in combustion torque between cylinders by comparing the combustion torque calculated as described above between cylinders.

  On the other hand, by calculating the instantaneous torque equivalent value in the section corresponding to the combustion angle period, it is possible to obtain the work balance for each cylinder. Also, by integrating and calculating the instantaneous torque equivalent value in the section where the rotation increases with combustion (explosion) and the section where the rotation is lowered due to the load acting on the crankshaft, etc., the respective values due to combustion, inertial force, load, etc. The amount of work can be determined.

  Therefore, as described in claim 9, it is preferable to calculate at least one of the work amount due to combustion, inertial force, load, etc. for each cylinder or the sum thereof by integrating the instantaneous torque equivalent value for each cylinder for a certain interval. If the work amount due to combustion, inertial force, load and the like for each cylinder can be calculated in this way, the fuel injection amount of each cylinder and the torque loss amount due to the load can be grasped for each cylinder. In addition, the characteristics can be controlled for each cylinder so that the work amount due to combustion or the like coincides with an originally ideal value (target value).

  As an assumed process, it is assumed that a hatched portion D1 shown in FIG. 10 (e) corresponds to the work amount due to combustion, and the work amount due to combustion is calculated by integrating the instantaneous torque equivalent value in the section corresponding to the D1 portion. Good. Also, assuming that the shaded portion D2 shown in FIG. 10 (e) corresponds to the work amount due to the load, the work amount due to the load may be calculated by integrating the instantaneous torque equivalent value in the section corresponding to the D2 portion.

  Further, as described in claim 10, the instantaneous torque equivalent value is integrated for a certain interval for each cylinder, and the integrated value is compared between the cylinders to thereby calculate the work amount due to combustion, inertial force, load, etc. or the total sum thereof. It is preferable to calculate the difference between cylinders (variation between cylinders). As a result, the characteristics of the cylinders can be relatively grasped, and the cylinders can be uniformly controlled without any difference between the cylinders.

  In addition, as described in claim 11, the instantaneous torque equivalent value is integrated for each cylinder for a certain period, and at least one of the work amount or the sum of the combustion, inertial force, load, etc. for each cylinder is calculated as the combustion state parameter. In addition, an average value of all the cylinders of the combustion state parameters calculated for each cylinder may be calculated, and a difference between the cylinders may be calculated based on a difference between the average value of all the cylinders of the combustion state parameters and the combustion state parameter for each cylinder. Thereby, the characteristics of each cylinder can be relatively grasped, and it is possible to uniformly control each cylinder without any difference between cylinders.

  As described above, a difference corresponding to the combustion torque is generated in the instantaneous torque equivalent value between the combustion state and the combustion pause state of the internal combustion engine. Therefore, as described in claim 12, in the combustion state and the combustion stop state, the instantaneous torque equivalent value is integrated for each cylinder for a certain period to calculate the work amount for each cylinder, and the work amount and the combustion in the combustion state are calculated. The work amount due to combustion for each cylinder may be calculated from the difference from the work amount in the rest state. Thereby, the work amount by combustion for each cylinder can be accurately calculated.

  In the invention described in claim 13, the work amount or the sum by combustion, inertial force, load, etc. calculated by integrating the instantaneous torque equivalent value for each cylinder for a certain interval or the difference between the cylinders is stored as a learning value. Hold. In other words, the characteristic variation of each cylinder is caused by machine differences and changes over time, and the effects appear constantly. For this reason, it is possible to suitably maintain steady characteristic variations by storing and holding the work amount or the sum of the combustion, inertial force, load, etc. for each cylinder, which represents the characteristic variation of each cylinder, and the difference between the cylinders as a learning value. It can be reflected in the control.

  Here, if the injection start timing, the ignition timing, and the injection end timing by the fuel injection means vary due to the characteristic variation of each cylinder, the behavior of the rotational speed in each cylinder changes accordingly, and the instantaneous torque equivalent value The behavior also changes. In other words, the injection start timing, the ignition timing, and the injection end timing can be estimated from the behavior of the instantaneous torque equivalent value. Therefore, as described in claim 14, when the instantaneous torque equivalent value increases for each cylinder, the injection start timing or the ignition timing by the fuel injection means is estimated by comparing the instantaneous torque equivalent value with a predetermined determination threshold value. Good. Alternatively, as described in claim 15, when the instantaneous torque equivalent value for each cylinder drops, the end timing of injection by the fuel injection means may be estimated by comparing the instantaneous torque equivalent value with a predetermined threshold value.

  In addition, as described in claim 16, when the instantaneous torque equivalent value increases for each cylinder, the injection start timing or the ignition timing by the fuel injection means is estimated by comparing the instantaneous torque equivalent value with a predetermined determination threshold value. In addition, the difference between the cylinders may be calculated by comparing the injection start timing or the ignition timing of each cylinder.

  Further, as described in claim 17, when the instantaneous torque equivalent value for each cylinder drops, the injection end timing by the fuel injection means is estimated by comparing the instantaneous torque equivalent value with a predetermined determination threshold value. The difference between the cylinders may be calculated by comparing the injection end timing of each cylinder.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. The present embodiment embodies the present invention as a common rail fuel injection system for a vehicle diesel engine, and a detailed configuration thereof will be described below.

  FIG. 1 is a configuration diagram showing an outline of a common rail fuel injection system. In FIG. 1, a multi-cylinder diesel engine (hereinafter referred to as an engine) 10 is provided with an electromagnetic injector 11 for each cylinder, and these injectors 11 are connected to a common rail (pressure accumulation pipe) 12 common to each cylinder. A high pressure pump 13 as a fuel supply pump is connected to the common rail 12, and high pressure fuel corresponding to the injection pressure is continuously accumulated in the common rail 12 as the high pressure pump 13 is driven. The high-pressure pump 13 is driven as the engine 10 rotates, and fuel is repeatedly sucked and discharged in synchronization with the engine rotation. The high-pressure pump 13 is provided with an electromagnetically driven suction metering valve (SCV) 13a at its fuel suction portion, and the low-pressure fuel pumped from the fuel tank 15 by the feed pump 14 passes through the suction metering valve 13a. And sucked into the fuel chamber of the pump 13.

  The common rail 12 is provided with a common rail pressure sensor 16, and the fuel pressure (common rail pressure) in the common rail 12 is detected by the common rail pressure sensor 16. Although not shown, the common rail 12 is provided with an electromagnetically driven (or mechanical) pressure reducing valve. When the common rail pressure rises excessively, the pressure reducing valve is opened to perform pressure reduction. It has become.

  A rotation speed sensor 18 for detecting the rotation speed of the crankshaft 17 is provided near the crankshaft 17 of the engine 10. The rotation speed sensor 18 is, for example, an electromagnetic pickup type sensor that detects passage of teeth of a timing rotor provided integrally with the crankshaft 17, and a pulsed rotation speed is obtained by shaping the detection signal of the sensor 18. A signal (NE pulse) is generated. In the present embodiment, the NE pulse angular interval (angle between pulse rising edges) is 30 ° CA, and the rotation speed can be detected at a cycle of 30 ° CA.

  The ECU 20 is an electronic control unit including a known microcomputer including a CPU, ROM, RAM, EEPROM, and the like. The ECU 20 includes an accelerator opening sensor, a detection signal from the common rail pressure sensor 16 and the rotation speed sensor 18, Detection signals are sequentially input from various sensors such as a vehicle speed sensor. Then, the ECU 20 determines an optimal fuel injection amount and injection timing based on engine operation information such as the engine rotation speed and the accelerator opening, and outputs an injection control signal corresponding to the fuel injection amount to the injector 11. Thus, fuel injection from the injector 11 to the combustion chamber is controlled in each cylinder.

  By the way, in the engine 10, a desired engine rotation speed is realized in accordance with each operation state or the like. However, when the rotation speed is viewed in detail, a rotation increase and a rotation decrease are caused according to each stroke in the combustion cycle. Repeated. That is, as shown in FIG. 2A, in the case of a four-cylinder engine, the combustion order of each cylinder is as follows: first cylinder (# 1) → third cylinder (# 3) → fourth cylinder (# 4) → second cylinder Cylinder (# 2), fuel is injected every 180 ° CA, and the fuel is used for combustion. At this time, when viewed in the combustion cycle of each cylinder (180 ° CA cycle), a rotational force is applied to the crankshaft due to combustion and the engine rotational speed increases, and then the engine rotates due to a load acting on the crankshaft and the like. The speed drops. In such a case, it is considered that the work amount for each cylinder can be estimated according to the behavior of the rotational speed.

  Here, at the end of the combustion cycle of each cylinder, it is conceivable to calculate the work amount of the cylinder from the rotational speed at that time. For example, as shown in FIG. 2B, the work amount of the first cylinder is calculated at timing t1, which is the end of the combustion cycle of the first cylinder, and at the end of the combustion cycle of the next third cylinder. The work amount of the third cylinder is calculated at a certain timing t2. However, in this case, the rotational speed calculated by the detection signal (NE pulse) of the rotational speed sensor 18 includes a factor due to noise and detection error. As shown in FIG. The detected value of rotational speed (solid line in the figure) varies with respect to (dotted line in the figure). Therefore, at the timings t1, t2, etc., there is a problem that an accurate work amount cannot be calculated.

  Therefore, in the present embodiment, as shown in FIG. 3, the rotational speed Ne is input to the filter means M1 at a constant angular period as an input signal, and only the rotational fluctuation component at each time point is extracted and instantaneously extracted by the filter means M1. A torque equivalent value Neflt is calculated. At this time, the rotational speed Ne is sampled at an NE pulse output cycle (30 ° CA in the present embodiment). The filter means M1 is composed of, for example, a BPF (band filter), and the high frequency component and the low frequency component included in the rotation speed signal are removed by the BPF. The instantaneous torque equivalent value Neflt (i), which is the output of the filter means M1, is expressed by the following equation (1), for example.

式（１）において、Ｎｅ（ｉ）は回転速度の今回サンプリング値、Ｎｅ（ｉ−２）は回転速度の２回前サンプリング値、Ｎｅｆｌｔ（ｉ−１）は瞬時トルク相当値の前回値、Ｎｅｆｌｔ（ｉ−２）は瞬時トルク相当値の前々回値である。ｋ１〜ｋ４は定数である。上記の式（１）により、回転速度信号がフィルタ手段Ｍ１に入力される都度、瞬時トルク相当値Ｎｅｆｌｔ（ｉ）が算出される。

In equation (1), Ne (i) is the current sampling value of the rotational speed, Ne (i-2) is the sampling value two times before the rotational speed, Neflt (i-1) is the previous value of the instantaneous torque equivalent value, Neflt. (I-2) is the value immediately before the instantaneous torque equivalent value. k1 to k4 are constants. By the above equation (1), the instantaneous torque equivalent value Neflt (i) is calculated every time the rotation speed signal is input to the filter means M1.

  The above equation (1) is a discretization of the transfer function G (s) represented by the following equation (2). Here, ζ is an attenuation coefficient, and ω is a response frequency.

本実施の形態では特に、応答周波数ωをエンジン１０の燃焼周波数としており、上記の式（１）ではω＝燃焼周波数としたことに基づいて定数ｋ１〜ｋ４が設定されている。燃焼周波数は単位角度ごとの燃焼頻度を表した角度周波数であり、４気筒エンジンの場合には燃焼周期（燃焼角度周期）が１８０°ＣＡであり、その燃焼周期の逆数により燃焼周波数が決定される。

Particularly in the present embodiment, the response frequency ω is the combustion frequency of the engine 10, and the constants k1 to k4 are set based on the fact that ω = combustion frequency in the above equation (1). The combustion frequency is an angular frequency representing the combustion frequency for each unit angle. In the case of a four-cylinder engine, the combustion cycle (combustion angle cycle) is 180 ° CA, and the combustion frequency is determined by the reciprocal of the combustion cycle. .

  Further, the integrating means M2 in FIG. 3 takes in the instantaneous torque equivalent value Neflt, and integrates the instantaneous torque equivalent value Neflt for a certain interval for each combustion cycle of each cylinder, so that the work for each cylinder, which is the torque integrated value of each cylinder. The quantities Sneflt # 1 to Sneflt # 4 are calculated. At this time, NE pulses numbered from 0 to 23 are assigned to the NE pulses output at the 30 ° CA cycle. In terms of the combustion order of each cylinder, the NE pulse number = 0-5 are assigned, the pulse number = 6-11 is assigned to the combustion cycle of the third cylinder, the NE pulse number = 12-17 is assigned to the combustion cycle of the fourth cylinder, and the combustion cycle of the second cylinder. Is assigned NE pulse number = 18-23. Then, cylinder-specific work amounts Sneflt # 1 to Sneflt # 4 are calculated for each of the first to fourth cylinders by the following equation (3).

なお以下の記載では、気筒番号を＃ｉと表し、気筒別仕事量Ｓｎｅｆｌｔ＃１〜Ｓｎｅｆｌｔ＃４を気筒別仕事量Ｓｎｅｆｌｔ＃ｉとも表記する。

In the following description, the cylinder number is expressed as #i, and the cylinder work Sneflt # 1 to Sneflt # 4 is also expressed as cylinder work Sneflt # i.

  FIG. 4 is a time chart showing changes in the rotational speed Ne, the instantaneous torque equivalent value Neflt, and the cylinder work Sneft # i. In FIG. 4, the instantaneous torque equivalent value Neflt swings up and down with respect to the reference level Ref, and the instantaneous work torque equivalent value Neflt is integrated within the combustion cycle of each cylinder to calculate the cylinder work Sneft # i. . At this time, the integral value of the instantaneous torque equivalent value Neflt on the positive side of the reference level Ref corresponds to the combustion torque, and the integral value of the instantaneous torque equivalent value Neflt on the negative side of the reference level Ref corresponds to the load torque. The reference level Ref is determined according to the average rotational speed through each cylinder.

  In this case, in the combustion cycle of each cylinder, the balance between the combustion torque and the load torque is originally 0, and the work amount by each cylinder Sneflt # i is 0 (combustion torque−load torque = 0). If the injection characteristics and friction characteristics of the injectors 11 are different between the cylinders due to changes over time or the like, variations in the work amount by cylinder Sneflt # i occur. For example, as shown in the figure, the first cylinder has a variation such as Sneflt # 1> 0 and the second cylinder has a Sneflt # 2 <0.

  By calculating the work amount Sneflt # i for each cylinder as described above, it is possible to grasp how much difference has occurred with respect to the ideal value in each cylinder and how much variation has occurred between the cylinders. Can do.

  Next, various arithmetic processes performed by the ECU 20 will be described. This calculation process includes the filter means M1, the integration means M2, and the like. FIG. 5 is a flowchart showing the calculation processing of the learning value for each cylinder. This processing is executed by the ECU 20 at the rising edge of the NE pulse.

  In FIG. 5, first, in step S101, the NE pulse time interval is calculated from the current NE interrupt time and the previous NE interrupt time, and the current rotational speed Ne (instantaneous rotation) is calculated by reciprocal calculation of the time interval. Speed). In the subsequent step S102, the instantaneous torque equivalent value Neflt (i) is calculated using the above equation (1).

In the subsequent step S103, the current NE pulse number is determined. In steps S104 to S107, the cylinder-specific work amount Sneflt # i is calculated for each of the first to fourth cylinders using the above equation (3). That is,
If NE pulse number = 0 to 5, calculate the cylinder-specific work amount Sneflt # 1 of the first cylinder (step S104),
If NE pulse number = 6 to 11, the cylinder-specific work amount Sneflt # 3 of the third cylinder is calculated (step S105),
If NE pulse number = 12 to 17, the cylinder-specific work amount Sneflt # 4 of the fourth cylinder is calculated (step S106),
If NE pulse number = 18 to 23, the cylinder-specific work amount Sneflt # 2 of the second cylinder is calculated (step S107).

  Thereafter, in step S108, it is determined whether a learning condition for the work amount by cylinder is satisfied. The learning conditions are that the calculation of work for each cylinder is completed for all cylinders, that the power transmission device (drive train) of the vehicle is in a predetermined specified state, and that the environmental conditions are in a predetermined specified state. It is determined that the learning condition is satisfied when all of them are included and all of them are satisfied. For example, in the power transmission device, it is determined that the clutch device of the power transmission system is not in the half clutch state. Specifically, it is determined that the engine water temperature is equal to or higher than a predetermined warm-up completion temperature as the environmental condition.

  If the learning condition is not satisfied, this process is terminated as it is. If the learning condition is satisfied, the process proceeds to step S109. In step S109, the number of integrations nitgr is incremented by 1, and a work amount learning value Qlp # i for each cylinder is calculated using the following equation (4). Also, the cylinder work Sneflt # i of each cylinder is cleared to zero.

その後、ステップＳ１１０では、積分回数ｎｉｔｇｒが所定回数ｋｉｔｇｒに達したか否かを判定する。所定回数ｋｉｔｇｒは、適合値としてあらかじめ定められている。そして、ｎｉｔｇｒ≧ｋｉｔｇｒであることを条件にステップＳ１１１に進む。ステップＳ１１１では、次の式（５）を用いて気筒ごとの仕事量最終学習値Ｑｌｒｎ＃ｉを算出する。また、仕事量学習値Ｑｌｐ＃ｉを０にクリアするとともに、積分回数ｎｉｔｇｒを０にクリアする。

Thereafter, in step S110, it is determined whether or not the integration number nitgr has reached a predetermined number of kitgrs. The predetermined number of kitgrs is determined in advance as a conforming value. Then, the process proceeds to step S111 on condition that nitgr ≧ kitgr. In step S111, the work final learned value Qlrn # i for each cylinder is calculated using the following equation (5). Further, the work learning value Qlp # i is cleared to 0, and the number of integrations nitgr is cleared to 0.

式（５）によれば、所定の積分回数ごとに仕事量学習値Ｑｌｐ＃ｉが平均化され、その平均化した学習値により仕事量最終学習値Ｑｌｒｎ＃ｉが更新される。このとき、仕事量学習値Ｑｌｐ＃ｉの平均化により、仕事量学習値Ｑｌｐ＃ｉの毎回の誤差分が吸収されるようになっている。

According to the equation (5), the work learning value Qlp # i is averaged every predetermined number of integrations, and the work final learning value Qlrn # i is updated with the averaged learning value. At this time, by averaging the work learning value Qlp # i, the error of each time of the work learning value Qlp # i is absorbed.

  Finally, in step S112, the inter-cylinder difference learning value ΔQlrn # i is calculated using the following equation (6).

式（６）によれば、全気筒の仕事量最終学習値Ｑｌｒｎ＃ｉの平均値（ΣＱｌｒｎ＃ｉ／４）に対する気筒ごとの仕事量最終学習値Ｑｌｒｎ＃ｉのばらつきが算出される。

According to the equation (6), the variation of the work final learned value Qlrn # i for each cylinder with respect to the average value (ΣQlrn # i / 4) of the work final learned value Qlrn # i of all cylinders is calculated.

  The work final learned value Qlrn # i and the inter-cylinder difference learned value ΔQlrn # i are written in a backup memory such as an EEPROM or a standby RAM in a timely manner. When each learning value is updated, it is overwritten each time. At this time, a plurality of operation regions are set with the fuel injection amount and the rotation speed (or common rail pressure) as parameters, and the work amount final learning value Qlrn # i and the inter-cylinder difference learning value ΔQlrn # are set for each operation region. i is stored.

  Next, fuel injection control will be described using the flowchart of FIG. The fuel injection control process shown in FIG. 6 is repeatedly executed by the ECU 20 at a predetermined control cycle.

  In FIG. 6, in step S <b> 201, parameters representing the engine operation state such as the engine rotation speed (average rotation speed) and the accelerator opening are read, and in the subsequent step S <b> 202, the basic injection amount is calculated based on the engine rotation speed and the accelerator opening. To do. For the basic injection amount, water temperature correction based on the engine water temperature and fuel pressure correction based on the common rail pressure may be appropriately performed.

  Next, in step S203, the learning value (work amount final learning value Qlrn # i or inter-cylinder difference learning value ΔQlrn # i) corresponding to the current combustion cylinder is read, and in the subsequent step S204, the learning value is read. The basic injection amount is corrected to calculate a command injection amount (target injection amount).

  At this time, the injection quantity is corrected as follows: (1) correction is performed so as to eliminate the absolute characteristic error in each cylinder, and (2) correction is performed so as to eliminate the characteristic variation between the cylinders. It is possible to do it. (1) When correction is performed so as to eliminate an absolute characteristic error in each cylinder, a deviation between a predetermined target work amount and a work final learning value Qlrn # i is calculated for each cylinder. Then, an injection correction amount based on the deviation is calculated. Then, the command injection amount is calculated by correcting the basic injection amount by the injection correction amount. Further, (2) when correction is performed so as to eliminate characteristic variation between cylinders, an injection correction amount is calculated for each cylinder based on the inter-cylinder difference learning value ΔQlrn # i, and the basic correction is performed based on the injection correction amount. The command injection amount is calculated by correcting the injection amount.

  Finally, in step S205, a command injection period is calculated based on the engine speed and the command injection amount. When the command injection period is thus calculated, the command injection start time and the command injection end time are determined according to the command injection period, and the drive of the injector 11 is controlled based on each command time.

  Further, based on the instantaneous torque equivalent value Neflt for each NE pulse, it is possible to estimate the injection start timing by the injector 11, the fuel ignition timing, the injection end timing by the injector 11, and the deviation (variation) between these timings. Yes, the estimation method will be described below.

  FIG. 7 is a time chart showing the transition of the instantaneous torque equivalent value Neflt accompanying the combustion of a certain cylinder. In FIG. 7, timings t11, t12, t13, and t14 are NE pulse output timings, and an instantaneous torque equivalent value Neflt is calculated at each timing. Among them, timings t11 and t12 are pulse output timings during the rotation increase. For example, for the first cylinder, timing t11 is a pulse output timing of pulse number = 23, and timing t12 is a pulse of pulse number = 0. Output timing. Timings t13 and t14 are pulse output timings during rotation descent. Similarly, for the first cylinder, timing t13 is a pulse output timing of pulse number = 5, and timing t14 is a pulse output of pulse number = 6. It is timing.

When the instantaneous torque equivalent value Neflt increases as the rotation increases, the time at the timing t11 (point A in the figure) near the start of injection is Ta, the instantaneous torque equivalent value Neflt is Ya, and the timing t12 (point B in the figure). ) Is Tb, and the instantaneous torque equivalent value Neflt is Yb. Further, the threshold value of the instantaneous torque equivalent value Neflt for determining the injection start timing or the ignition timing is Yc. At this time, the passing time Tc at point C when the instantaneous torque equivalent value Neflt is Yc is
Tc = (Tb−Ta) * (Yc−Ya) / (Yb−Ya) + Ta (7)
Is calculated as

Further, a time Tc0 serving as a reference for the injection start timing or the ignition timing is determined in advance, and the time difference Tc of the injection start timing or the ignition timing is calculated by comparing the time Tc with the reference time Tc0.
ΔTc = K1 * (Tc−Tc0) (8)
Note that the injection start timing and the ignition timing are actually different timings before and after, but it is possible to calculate the injection start timing and the ignition timing by setting the time difference between these timings in advance. Become.

  When calculating the difference between the cylinders of the injection start timing or the ignition timing, the calculated values of the injection start timing or the ignition timing may be appropriately compared for each cylinder. At this time, by calculating the injection start timing or ignition timing of all cylinders and calculating the average value thereof, and further obtaining the difference from the average value for each cylinder, variations in the injection start timing or ignition timing of each cylinder (cylinder It is also possible to calculate the difference.

Further, when the instantaneous torque equivalent value Neflt decreases as the rotation decreases, the time at timing t13 (point D in the figure) near the end of injection is Td, the instantaneous torque equivalent value Neflt is Yd, and timing t14 (point E in the figure). ) Is Te, and the instantaneous torque equivalent value Neflt is Ye. Further, the threshold value of the instantaneous torque equivalent value Neflt for determining the injection end timing is Yf. At this time, the passing time Tf at point F at which the instantaneous torque equivalent value Neflt becomes Yf is
Tf = (Te−Td) * (Yf−Yd) / (Ye−Yd) + Td (9)
Is calculated as

Also, a time Tf0 serving as a reference for the injection end timing is determined in advance, and the time Tf and the reference time Tf0 are compared to calculate the deviation time ΔTf of the injection end timing.
ΔTf = K2 * (Tf−Tf0) (10)
When the inter-cylinder difference in the injection end timing is calculated, the calculated value of the injection end timing may be appropriately compared for each cylinder. At this time, the injection end timing of all the cylinders is calculated, the average value thereof is calculated, and the difference from the average value is calculated for each cylinder, thereby calculating the variation (inter-cylinder difference) in the injection end timing of each cylinder. It is also possible.

  FIG. 8 is a flowchart showing an injection start timing estimation process, and this process is executed by the ECU 20 at a timing synchronized with the rise of the NE pulse.

  In FIG. 8, in step S301, it is determined whether or not the current NE pulse number is a predetermined pulse number n (for example, n = 23 for the first cylinder). If NE pulse number = n, the current time (current time) is stored as Ta in step S302, and the current instantaneous torque equivalent value Neflt is stored as Ya in subsequent step S303.

  On the other hand, in step S304, it is determined whether or not the current NE pulse number is n + 1 (n = 0 in the first cylinder). If NE pulse number = n + 1, the current time (current time) is stored as Tb in step S305, and the current instantaneous torque equivalent value Neflt is stored as Yb in step S306.

  Thereafter, in step S307, using the above equation (7), the time when the instantaneous torque equivalent value Neflt becomes the threshold value Yc (passing time Tc at point C in FIG. 7) is calculated, and injection is performed based on the passing time Tc. Estimate the start time. Finally, in step S308, the deviation of the injection start timing (deviation time from the ideal timing) is estimated using the above equation (8).

  As described above, when the injection start timing and the timing deviation are estimated for each cylinder, the commanded injection period of the injector is corrected based on the estimated value.

  In addition, although description by illustration is abbreviate | omitted for convenience about the estimation process of ignition timing or injection completion time, this should just be the process according to the said FIG. 8, and each said Formula (7)-Formula (10) The parameters may be acquired to estimate the ignition timing, injection end timing, and the like.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  The instantaneous torque equivalent value Neflt was calculated by performing the filter calculation at the combustion frequency of the engine 10 for each rotational speed Ne, and therefore the instantaneous torque equivalent value appropriately reflecting the fuel injection state and the combustion state in each cylinder. Neflt can be determined. Also, the instantaneous torque equivalent value Neflt is integrated for a certain interval for each cylinder to calculate the cylinder work Sneflt # i, and based on the cylinder work Sneflt # i (actually, the work final learning value Qlrn # Since the fuel injection amount is controlled for each cylinder (based on i and the inter-cylinder difference learned value ΔQlrn # i), the characteristics of each cylinder can be controlled as desired. As described above, exhaust emission and drivability can be improved.

  In this case, not only the relative characteristic variation among cylinders but also the absolute characteristic variation of each cylinder can be detected, and the diversification of the control for each cylinder can be achieved. Therefore, it becomes possible to cope with various demands related to improvement of exhaust emission and drivability.

  Since the band filter (BPF) is used as the filter means, it is possible to remove low-frequency fluctuation components due to acceleration / deceleration and high-frequency fluctuation components such as noise from the rotation speed signal and extract only the torque fluctuation components. As a result, the instantaneous torque equivalent value Neflt can be calculated with high accuracy, and as a result, it is possible to properly eliminate the characteristic variation among the cylinders.

  The work amount final learned value Qlrn # i and the inter-cylinder difference learned value ΔQlrn # i are calculated based on the cylinder-specific work amount Sneflt # i, and each learned value is stored and retained in the backup memory. Variations in characteristics due to steady factors such as changes over time and changes over time can be suitably reflected in the control.

  Since the injection start timing, the ignition timing, or the injection end timing is estimated based on the instantaneous torque equivalent value Neflt for each cylinder, it is possible to suitably eliminate variations in the injection start timing, the ignition timing, or the injection end timing for each cylinder. Become.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above embodiment, as means for correcting the characteristics of each cylinder, the basic injection amount is corrected by the learning value for each cylinder (work amount final learning value Qlrn # i or inter-cylinder difference learning value ΔQlrn # i) and commanded. The injection amount (target injection amount) is calculated (see the flow of FIG. 6), but this may be changed. For example, the command injection period (command injection start timing or command injection end timing) may be corrected by the learning value for each cylinder (work amount final learning value Qlrn # i or inter-cylinder difference learning value ΔQlrn # i). .

  In the above embodiment, the instantaneous torque equivalent value Neflt is integrated within the combustion cycle of each cylinder to calculate the cylinder specific work amount Sneflt # i, but this is changed. In other words, the work amount Sneflt # i for each cylinder is the sum of work due to combustion and the work due to load in the combustion cycle of each cylinder (representing the balance of work), but not the sum of the work, The amount of work due to combustion and the amount of work due to load are calculated. More specifically, the instantaneous torque equivalent value Neflt is integrated for each cylinder in a predetermined section corresponding to the rotation increasing section, and the work by combustion (combustion work by cylinder) is calculated. Alternatively, an instantaneous torque equivalent value Neflt is integrated for each cylinder in a predetermined section corresponding to the rotation descent section, and a work due to load (load work for each cylinder) is calculated. Then, it is preferable to control the fuel injection amount for each cylinder based on the load work for each cylinder and the load work for each cylinder.

  From the difference between the cylinder specific work amount Sneflt # i calculated in the combustion state and the cylinder specific work amount Sneflt # i calculated in the combustion stopped state, the work amount by combustion for each cylinder (combustion work amount per cylinder) is calculated. Anyway. The combustion stop state is a fuel cut state in which fuel injection by the injector is not performed. In such a case, the work amount for the combustion torque is not included in the cylinder work amount Sneflt # i. Therefore, the combustion work per cylinder can be accurately calculated. Specifically, based on the flowchart shown in FIG. 9, the ECU 20 executes a process for calculating the combustion work for each cylinder.

  In FIG. 9, in step S401, it is determined whether or not the fuel is currently being cut (F / C). If the fuel is not being cut, the cylinder specific work amount Sneflt # i is calculated in step S402. If the fuel is being cut, the cylinder specific work amount Sneflt # i is calculated in step S403. . In step S404, it is determined whether or not calculation of the work amount Sneflt # i for each cylinder in the combustion state and the fuel cut state (combustion stop state) is completed, and the process proceeds to step S405 on the condition that it is YES. In step S405, the cylinder specific work Sneflt # i at the time of fuel cut is subtracted from the cylinder specific work Sneflt # i at the time of combustion to calculate the cylinder specific work.

  Further, the combustion torque for each cylinder may be calculated based on the difference between the instantaneous torque equivalent value Neflt calculated in the combustion state and the instantaneous torque equivalent value Neflt calculated in the combustion halt state. In this case, specifically, a predetermined angular position is determined within the combustion period of each cylinder, and the instantaneous torque equivalent value Neflt in the combustion state and the instantaneous torque equivalent value Neflt in the combustion stop state at the angular position, respectively. calculate. Then, the combustion torque for each cylinder is calculated from the difference between them. It is also possible to calculate the difference in combustion torque between cylinders by comparing the combustion torque calculated as described above between cylinders.

  Alternatively, the instantaneous torque equivalent value Neflt at the same rotational angle position may be obtained for each cylinder, and the characteristics of each cylinder may be estimated based on the instantaneous torque equivalent value Neflt. Alternatively, the characteristic difference between cylinders may be estimated by comparing the instantaneous torque equivalent value Neflt between the cylinders. In the configuration in which a pulse number is assigned to each NE pulse as described above, the instantaneous torque equivalent value Neflt may be obtained using the same NE pulse number. Here, the rotational angular position for obtaining the instantaneous torque equivalent value Neflt may be a plurality of angular positions in addition to the same angular position. Alternatively, it may be an angular position in the vicinity that can be regarded as almost the same, and in any case, it may be anything that can be evaluated at a predetermined angular position.

  Further, it is preferable to obtain at least one of a peak value and a bottom value of the instantaneous torque equivalent value Neflt for each cylinder, and estimate the characteristics for each cylinder based on the obtained value. Alternatively, the difference between the characteristics of the cylinders may be estimated by comparing at least one of the peak value and the bottom value of the instantaneous torque equivalent value Neflt between the cylinders. In this case, a method for evaluating the characteristics (or cylinder differences) of each cylinder only with the peak value of the instantaneous torque equivalent value Neflt, a method for evaluating the characteristics (or cylinder differences) of each cylinder only with the same bottom value, and the same peak A method for evaluating the characteristics (or cylinder-to-cylinder differences) of each cylinder based on the difference between the value and the bottom value is conceivable.

  In the above embodiment, the band filter (BPF) is used as the filter means, but it can be changed to other filter means. For example, LPF or HPF may be used. At this time, by setting the combustion frequency as the response frequency ω of the transfer function that defines LPF or HPF, a desired instantaneous torque equivalent value can be calculated.

  In the above embodiment, the configuration is such that the rotational speed of the engine is detected at a predetermined rotational angle cycle using the electromagnetic pickup type rotational speed sensor 18, but this may be changed. It is also possible to use a linear detection type rotational speed sensor capable of detecting the rotational position of the crankshaft linearly (that is, continuously). For example, a resolver is known as a linear detection type rotational speed sensor. In this case, the instantaneous torque equivalent value Neflt can be calculated at an arbitrary timing. When estimating the injection start timing, the ignition timing, or the injection end timing, the instantaneous torque equivalent value Neflt is continuously calculated, and the time when the Neflt value reaches a predetermined determination threshold is measured. And it is good to estimate injection start time, ignition time, or injection end time directly from the measurement time.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a time chart which shows transition of the rotational speed of each cylinder. It is a block diagram which shows the control block for calculating the work amount according to cylinder. It is a time chart which shows transition of a rotational speed, an instantaneous torque equivalent value, and the work amount according to cylinder. It is a flowchart which shows the calculation process of the learning value classified by cylinder. It is a flowchart which shows a fuel-injection control process. It is a time chart which shows transition of the instantaneous torque equivalent value accompanying combustion of a certain cylinder. It is a flowchart which shows the estimation process of injection start time. It is a flowchart which shows the calculation process of the combustion work classified by cylinder. It is a time chart which shows transition of a rotational speed, a combustion torque, an inertia torque, and load torque, and those correspondence.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Injector, 17 ... Crankshaft, 20 ... ECU, M1 ... Filter means, M2 ... Integration means.

Claims (17)

Rotational speed calculation means for sequentially calculating the rotational speed of the crankshaft of the internal combustion engine;
Filter means for filtering the rotational speed calculated by the rotational speed calculation means with a single frequency set based on the combustion frequency of the internal combustion engine to calculate an instantaneous torque equivalent value;
Control means for controlling the characteristics of each cylinder of the internal combustion engine based on the instantaneous torque equivalent value calculated by the filter means;
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion frequency is used as a response frequency ω of a transfer function that defines the filter means.   3. The control apparatus for an internal combustion engine according to claim 1, wherein a band filter is used as the filter means.   The internal combustion engine according to any one of claims 1 to 3, wherein the instantaneous torque equivalent value at a predetermined rotational angle position is obtained for each cylinder, and characteristics for each cylinder are estimated based on the instantaneous torque equivalent value. Engine control device.   4. The characteristic difference between cylinders is estimated by obtaining the instantaneous torque equivalent value at a predetermined rotational angle position for each cylinder and comparing the instantaneous torque equivalent value between the cylinders. The control apparatus for internal combustion engines in any one.   4. At least one of a peak value and a bottom value of the instantaneous torque equivalent value is obtained for each cylinder, and characteristics for each cylinder are estimated based on the obtained value. Control device for internal combustion engine.   The characteristic difference between cylinders is estimated by obtaining at least one of a peak value and a bottom value of the instantaneous torque equivalent value for each cylinder, and comparing the obtained value between the cylinders. 4. The control device for an internal combustion engine according to any one of 3 above.   4. The combustion torque for each cylinder is calculated from the difference between the instantaneous torque equivalent value calculated in the combustion state and the instantaneous torque equivalent value calculated in the combustion stop state in each cylinder. The control apparatus for internal combustion engines described in 1.   2. The apparatus according to claim 1, further comprising means for calculating at least one of a work amount or a sum total of combustion, inertial force, load, etc. for each cylinder by integrating the instantaneous torque equivalent value for each cylinder for a certain period. The control apparatus for an internal combustion engine according to any one of 8.   The instantaneous torque equivalent value is integrated for a certain interval for each cylinder, and the integrated value is compared between the cylinders to calculate a work amount due to combustion, inertial force, load, etc. or a sum difference between the cylinders. 9. The control apparatus for an internal combustion engine according to claim 1, wherein the control apparatus is an internal combustion engine. Means for integrating the instantaneous torque equivalent value for each cylinder for a certain interval and calculating at least one of a work amount due to combustion, inertial force, load, etc. for each cylinder or a sum thereof as a combustion state parameter;
Means for calculating an average value of all the cylinders of the combustion state parameter calculated for each cylinder;
Means for calculating a difference between cylinders based on a difference between an average value of all cylinders of the combustion state parameter and a combustion state parameter for each cylinder;
The control apparatus for an internal combustion engine according to any one of claims 1 to 8, further comprising:   Calculate the amount of work for each cylinder by integrating the instantaneous torque equivalent value for each cylinder in the combustion state and the combustion stop state for each cylinder, and by the difference between the work amount in the combustion state and the work amount in the combustion stop state, The control device for an internal combustion engine according to any one of claims 9 to 11, wherein a work amount due to combustion for each cylinder is calculated.   The amount of work or the sum of the combustion torque, inertial force, load, etc. calculated by integrating the instantaneous torque equivalent value for each cylinder for a certain interval, or the difference between the cylinders is stored as a learning value. Item 12. The control device for an internal combustion engine according to any one of Items 9 to 11.   The injection start timing or the ignition timing by the fuel injection means is estimated by comparing the instantaneous torque equivalent value with a predetermined determination threshold when the instantaneous torque equivalent value for each cylinder rises. The control apparatus for an internal combustion engine according to any one of claims 13 to 13.   15. The timing for ending the injection by the fuel injection means is estimated by comparing the instantaneous torque equivalent value with a predetermined threshold value when the instantaneous torque equivalent value for each cylinder is lowered. A control device for an internal combustion engine according to claim 1.   When the instantaneous torque equivalent value for each cylinder rises, the injection start timing or ignition timing by the fuel injection means is estimated by comparing the instantaneous torque equivalent value with a predetermined determination threshold, and the injection start timing or 16. The control device for an internal combustion engine according to claim 1, wherein the difference between the cylinders is calculated by comparing the ignition timings.   When the instantaneous torque equivalent value for each cylinder drops, the injection end timing by the fuel injection means is estimated by comparing the instantaneous torque equivalent value with a predetermined determination threshold, and the comparison is made by comparing the injection end timing of each cylinder. The internal combustion engine control device according to any one of claims 1 to 16, wherein a difference between cylinders is calculated.

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