JP5601232B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  2. Description of the Related Art Conventionally, a control device for an internal combustion engine that performs various controls using measurement data obtained from an in-cylinder pressure sensor is known. For example, as disclosed in Japanese Patent Laid-Open No. 4-81557, in an internal combustion engine equipped with an EGR device, the amount of heat generated in the cylinder is obtained from the measurement data of the in-cylinder pressure sensor, the amount of generated heat is monitored, and EGR A technique for setting the content of control related to an apparatus is known.

JP-A-4-81557

  There are various quantities representing the combustion state of each cylinder of the internal combustion engine (hereinafter also referred to as “combustion state quantity”), and the in-cylinder pressure sensor can measure the various combustion state quantities for each cylinder. it can. Development of a technique for utilizing the measurement data of such an in-cylinder pressure sensor for control of an internal combustion engine is in progress. As one of them, a technique for detecting the amount of heat generated as a combustion state quantity using measurement data of an in-cylinder pressure sensor and using it for calculation of an air-fuel ratio and an EGR rate has been developed. If a highly accurate detection method such as an air-fuel ratio using measurement data of an in-cylinder pressure sensor can be established, information regarding combustion of each cylinder can be grasped individually and accurately in an internal combustion engine provided with the in-cylinder pressure sensor. become.

  In the calculation related to the air-fuel ratio and EGR using the measurement data of the in-cylinder pressure sensor, for example, the amount of generated heat, which is one of the combustion state quantities, is obtained as the measurement data of the in-cylinder pressure sensor, and various effects included in this generated heat amount. A method of detecting the air-fuel ratio while correcting (for example, fuel properties, water temperature, EGR, etc.) is conceivable. In performing the correction, for example, in consideration of the influence of the EGR rate (EGR concentration, EGR gas amount) on the amount of generated heat, the EGR rate is detected using the combustion speed and generated from this EGR rate. A method of finally calculating the air-fuel ratio by correcting the amount of heat can be considered. In order to accurately calculate the calculation target values such as the air-fuel ratio and the EGR rate as in this method, it is preferable to correct various influences included in the combustion state quantity obtained as measurement data of the in-cylinder pressure sensor.

  As described above, there are points to be noted when calculating and correcting the air-fuel ratio and the like using the combustion state quantity obtained from the in-cylinder pressure sensor. That is, for example, the combustion speed listed as one of the combustion state quantities is affected not only by the effect of EGR but also by the air-fuel ratio. Regarding the combustion state quantity other than the combustion speed, the combustion state quantity affected by the air-fuel ratio is affected not only by the air-fuel ratio but also by EGR. Ignoring that these multiple effects affect the combustion state quantity, it is difficult to calculate the air-fuel ratio, EGR rate, etc. with good accuracy. Even if correction is attempted, if a combustion state quantity that is affected by both the air-fuel ratio and EGR is used, the influence of the air-fuel ratio and EGR rate on one combustion state quantity is utilized using the other combustion state quantity. Therefore, there is no correction method to correct. In the conventional technical level, no calculation method has been found in consideration of the above-described circumstances for calculating the air-fuel ratio and the EGR rate using the in-cylinder pressure sensor measurement data.

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine control apparatus capable of accurately calculating an air-fuel ratio or / and an EGR rate using measurement data obtained from an in-cylinder pressure sensor. The purpose is to do.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A control device for an internal combustion engine in which an in-cylinder pressure sensor is attached to at least one cylinder,
At least two types of combustion state quantities having different sensitivities for the air-fuel ratio or EGR rate among the combustion state quantities, which are quantities representing the combustion state of the cylinder to which the in-cylinder pressure sensor is attached, are output to the in-cylinder pressure sensor. A calculation means for calculating based on;
Based on the relationship between the at least two types of combustion state quantities, the air-fuel ratio, and the EGR rate, the air-fuel ratio in the cylinder to which the in-cylinder pressure sensor is attached is calculated from the value of the combustion state quantity calculated by the calculation means. Or / and a calculation means for calculating the EGR rate;
Equipped with a,
The calculating means includes
One of the at least two types of combustion state quantities is defined as a first combustion state quantity, and a combustion state quantity having sensitivity different from the first combustion state quantity for at least one of an air-fuel ratio and an EGR rate is defined as a second combustion state quantity. If
A first relationship that defines the relationship between the first combustion state quantity and the air-fuel ratio and EGR rate, and a second relationship that defines the relationship between the second combustion state quantity and the air-fuel ratio and EGR rate. And storage means for storing
Means for calculating a solution obtained by simultaneously combining the first relation and the second relation as the air-fuel ratio or / and the EGR rate;
It is characterized by including .

The second invention is the first invention, wherein
The at least two types of combustion state quantities include a quantity of heat generated in the at least one cylinder or a parameter correlated with the quantity of heat generated, and a combustion speed in the at least one cylinder. It is characterized by that.

The third invention is the first or second invention, wherein
The fuel cell system further comprises injection amount calculation means for calculating a fuel injection amount of a fuel injection valve provided for the cylinder based on the air-fuel ratio calculated by the calculation means.

According to a fourth invention, in any one of the first to third inventions,
The internal combustion engine includes a plurality of cylinders, and an in-cylinder pressure sensor is attached to at least two of the plurality of cylinders,
The calculation means includes a cylinder-by-cylinder calculation means for calculating the two types of combustion state quantities for each of the at least two cylinders,
The calculating means includes a cylinder-by-cylinder EGR rate calculating means for calculating an EGR rate for each of the at least two cylinders,
Based on the difference of the EGR rate calculated by the EGR rate calculation means for each of the at least two cylinders, the control content of each of the at least two cylinders is calculated or the calculated control content is corrected. Cylinder-by-cylinder control means for performing
It is characterized by providing.

The fifth invention is the fourth invention, wherein
The internal combustion engine includes a plurality of fuel injection valves provided for each of the at least two cylinders and capable of setting different fuel injection amounts.
Setting means for setting the fuel injection amount of the fuel injection valve for each of the at least two cylinders based on the difference of the EGR rate calculated by the EGR rate calculating unit for each cylinder. It is characterized by including.

According to a sixth invention, in any one of the first to fifth inventions,
The internal combustion engine includes a plurality of cylinders, and an in-cylinder pressure sensor is attached to at least two of the plurality of cylinders,
The calculation means includes a cylinder-by-cylinder calculation means for calculating the two types of combustion state quantities for each of the at least two cylinders,
The calculating means includes a cylinder-by-cylinder EGR rate calculating means for calculating an EGR rate for each of the at least two cylinders,
An EGR distribution passage having a plurality of intake side ends connected to an exhaust passage of the internal combustion engine and connected to respective intake passages of the at least two cylinders;
Detecting means for detecting an abnormality in the EGR distribution passage based on the EGR rate calculated by the cylinder-by-cylinder EGR rate calculating means for each of the at least two cylinders;
It is characterized by providing.

According to a seventh invention, in any one of the first to sixth inventions,
The first relationship is represented by a first equation, the second relationship is represented by a second equation;
Said computing means, the solution of the first person equations and the second towards equations of simultaneous equations, the computation to said and Turkey, as the air-fuel ratio and / or the EGR rate.

The inventor of the present application has found that a plurality of types of combustion state quantities have different sensitivities to changes in the air-fuel ratio and EGR rate, and further uses this difference in sensitivity for calculation of the air-fuel ratio and EGR rate. I found. According to the first invention, paying attention to the existence of a plurality of combustion state quantities having different sensitivities regarding the air-fuel ratio and the EGR rate, the relationship between the plurality of combustion state quantities, the air-fuel ratio, and the EGR rate is utilized. As a result, the air-fuel ratio and the EGR rate can be accurately obtained from the output of the in- cylinder pressure sensor as simultaneous solutions .

  According to the second invention, the air-fuel ratio and the EGR rate are accurately determined from the output of the in-cylinder pressure sensor by using two combustion state quantities that are recognized to have a relatively large difference in sensitivity such as a heat generation amount and a combustion speed. You can ask well.

  According to the third invention, the fuel injection amount can be accurately set to an appropriate amount for controlling the internal combustion engine in accordance with the combustion state of the cylinder ascertained from the measurement data of the in-cylinder pressure sensor.

  According to the fourth aspect of the invention, the control content can be optimized for each cylinder by obtaining the EGR rate for each cylinder by the EGR rate calculation means for each cylinder.

  According to the fifth invention, the fuel injection amount can be optimized for each cylinder by obtaining the EGR rate for each cylinder by the EGR rate calculation means for each cylinder.

  According to the sixth invention, the EGR rate for each cylinder is obtained by the EGR rate calculation unit for each cylinder, and the EGR rate for each cylinder is distributed based on how the EGR rate is distributed. Anomaly detection for EGR distribution can be performed.

  According to the seventh aspect of the invention, the correlation identified by grasping the difference in sensitivity is stored in advance in the form of a mathematical expression, and the air-fuel ratio or / and the EGR rate can be obtained by performing the calculation according to the mathematical expression. it can.

It is a figure which shows the structure of the control apparatus of the internal combustion engine concerning Embodiment 1 of this invention with the structure of the internal combustion engine to which this is applied. It is a figure for demonstrating operation | movement of the control apparatus of the internal combustion engine concerning Embodiment 1 of this invention. It is a figure for demonstrating operation | movement of the control apparatus of the internal combustion engine concerning Embodiment 1 of this invention. It is a figure for demonstrating operation | movement of the control apparatus of the internal combustion engine concerning Embodiment 1 of this invention. It is a figure for demonstrating operation | movement of the control apparatus of the internal combustion engine concerning Embodiment 1 of this invention. It is a flowchart of the routine which an arithmetic processing unit performs in the control apparatus of the internal combustion engine concerning Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a control device for an internal combustion engine according to a first embodiment of the present invention, together with a configuration of an internal combustion engine (hereinafter simply referred to as an engine) to which the control device is applied. It can be suitably used for an internal combustion engine mounted on a moving body such as a vehicle. The engine shown in FIG. 1 is a spark ignition type 4-stroke reciprocating engine provided with a spark plug 6. Moreover, it is also a cylinder direct injection engine provided with the fuel direct injection injector 7 which injects a fuel directly in a cylinder. Although only one cylinder is depicted in FIG. 1, a general vehicle engine is composed of a plurality of cylinders. At least one of the cylinders is provided with an in-cylinder pressure sensor 5 for measuring the in-cylinder pressure. In the present embodiment, as a preferred embodiment, the in-cylinder pressure sensor 5 is attached to each of a plurality of cylinders. To do.
The engine is also provided with a crank angle sensor 8 that outputs a signal according to the rotation angle of the crankshaft, and a knock sensor 9 for detecting the occurrence of knock. From the signal CA of the crank angle sensor 8, the in-cylinder volume determined by the engine speed (the number of revolutions per unit time) and the position of the piston can be calculated. An air cleaner 1 is provided at the inlet of the intake passage connected to the cylinder, and a throttle valve 2 is disposed downstream of the air cleaner 1. A surge tank 4 is provided downstream of the throttle valve 2, and an intake pressure sensor 3 for measuring the intake pressure is attached to the surge tank 4.
On the other hand, two catalysts 10 and 11 are arranged in the exhaust passage connected to the cylinder. An EGR cooler 13 and an EGR valve 12 are provided in the EGR passage connecting the exhaust passage and the intake passage of the engine. The EGR cooler 13 is provided with a water temperature sensor 14 for measuring the cooling water temperature. The engine also includes an arithmetic processing unit 20 as a control device. The arithmetic processing unit 20 processes signals from the sensors 3, 5, 8, 9, and 14, and reflects the processing results in the operations of the actuators 2, 6, 7 and 12.

FIG. 2 is a diagram for explaining the operation of the control device for the internal combustion engine according to the first embodiment of the present invention, and shows the sensitivity (Sensitivity) of each combustion state quantity (a quantity representing the combustion state) with respect to the air-fuel ratio. FIG. Fig. 2 shows (i) Pmax (maximum in-cylinder pressure), (ii) Ingition Delay (ignition delay), (iii) Heat Release, (iv) Combustion Speed, (v) Specific Heat The difference in sensitivity for the five combustion state quantities called Ratio (specific heat ratio) is shown.
The upper part of FIG. 2 shows the sensitivity when the air-fuel ratio A / F changes from 14.6 to 13, that is, when it changes from stoichiometric to rich. In this case, for example, (iv) Combustion Speed (combustion speed) shows a relatively high sensitivity to a rich change in the air-fuel ratio in comparison with other combustion state quantities.
The lower part of FIG. 2 shows the sensitivity when the air-fuel ratio A / F changes from 14.6 to 18, that is, when it changes from stoichiometric to lean. In this case, for example, (iii) Ingition Delay (ignition delay) shows a result that the sensitivity to the lean side change of the air-fuel ratio is relatively high in comparison with other combustion state quantities.
When the upper and lower stages in FIG. 2 are observed together, for example, (iii) Heat Release (generated heat amount) and (iv) Combustion Speed (combustion speed) are both relatively high for the rich side change and lean side change of the air-fuel ratio. It can be seen that it shows sensitivity.

FIGS. 3 and 4 are diagrams for explaining the operation of the control device for the internal combustion engine according to the first embodiment of the present invention, and the sensitivity (Sensitivity) of each combustion state quantity (a quantity representing the state of combustion) with respect to EGR. ). FIG. 3 shows the difference in sensitivity for the five combustion state quantities (i) to (v) as in FIG.
According to FIG. 3, (iv) Combustion Speed (combustion speed) shows relatively high sensitivity to EGR, and (ii) Ingition Delay (ignition delay) shows high sensitivity following that. Recognize.
From FIG. 3, as indicated by arrows in FIG. 4, the sensitivity to EGR is different for each combustion state quantity, and in particular, (i) Pmax (maximum in-cylinder pressure) and (ii) Ingition Delay (ignition delay) ) And (iii) Heat Release (generated heat amount) and (iv) Combustion Speed (combustion speed), a difference in sensitivity is noticeable.

  2 to 4, five combustion state quantities are listed. In this embodiment, (i) Pmax (maximum in-cylinder pressure) and (ii) Ingition Delay (ignition delay) are grouped out of them. As (1), (iii) Heat Release (generated heat amount), (iv) Combustion Speed (combustion speed) and (v) Specific Heat Ratio (specific heat ratio) are classified as Group (2).

As described with reference to FIGS. 2 to 4, the present inventor has found that a plurality of types of combustion state quantities have different sensitivities to changes in the air-fuel ratio and EGR rate. The inventor of the present application has further found out a technique of utilizing the difference in sensitivity for calculating the air-fuel ratio and the EGR rate. The EGR rate here means the ratio of EGR gas to in-cylinder gas.
That is, the arithmetic processing unit 20 calculates at least two types of combustion state quantities having different sensitivities with respect to the air-fuel ratio or the EGR rate from the above listed combustion state quantities based on the output of the in-cylinder pressure sensor 5. On the other hand, the relationship between at least two types of combustion state quantities to be calculated, the air-fuel ratio, and the EGR rate is specified in advance through experiments or the like, so that this relationship can be referred to. It is stored in the memory in the processing device 20. Next, the arithmetic processing unit 20 calculates the air-fuel ratio in the cylinder to which the in-cylinder pressure sensor 5 is attached from the value of the combustion state quantity calculated based on the relationship between the combustion state quantity stored in advance and the air-fuel ratio and EGR rate. Or / and calculate the EGR rate.
More specifically, the correlation between at least two types of combustion state quantities to be calculated, the air-fuel ratio, and the EGR rate is organized as a mathematical expression (for example, simultaneous equations) and stored in the arithmetic processing unit 20. May be. The air-fuel ratio or / and the EGR rate may be calculated by substituting the combustion state quantity obtained as measurement data on the basis of the output of the in-cylinder pressure sensor 5 and obtaining the solution thereof.
According to this method, paying attention to the existence of a plurality of combustion state quantities having different sensitivities with respect to the air-fuel ratio and the EGR rate, by utilizing the relationship between the plurality of combustion state quantities, the air-fuel ratio, and the EGR rate. The air-fuel ratio and EGR rate can be obtained with high accuracy from the output of the in-cylinder pressure sensor.

  In the first embodiment, the fuel injection amount of the direct fuel injection injector 7 is determined based on the calculation result of the air-fuel ratio among the above calculation results.

但し、上記の式において、「Ｑ」は熱発生量であり、「ηｃ」は充填効率であり、「ＡＦ」は空燃比であり、「ＥＧＲ」はＥＧＲ率であり、「ＣＳ」は燃焼速度であり、「ＮＥ」はエンジン回転数であり、「Ｐ_{θｃｏｍｐ}」は圧縮圧である。α_１〜α_８は、把握した相関関係に基づいて定めた所定の係数である。
上記の式の連立解として得られる空燃比ＡＦとＥＧＲ率とを、筒内圧センサ５が測定する気筒における空燃比とＥＧＲ率の検出値として取り扱うことができる。 FIG. 5 is a diagram for explaining an example in the control apparatus for an internal combustion engine according to the first embodiment of the present invention. Hereinafter, with reference to FIG. 5, one example of a case where the calculation method in the first embodiment described above is actually applied to a control device for an internal combustion engine will be specifically described. In this embodiment, as the “at least two types of combustion state quantities having different sensitivities to the air-fuel ratio or EGR”, two combustion state quantities such as a generated heat quantity and a combustion speed are selected.
First, the correlation between the air-fuel ratio and EGR is grasped in advance for the heat generation amount and the combustion speed. Specifically, as shown in FIG. 5, the relationship between the heat generation amount and the air-fuel ratio, the relationship between the heat generation amount and the EGR, the relationship between the combustion speed and the air-fuel ratio, and the relationship between the combustion speed and the EGR are measured. Or consider it by calculation. In this embodiment, two conditions of 1200 rpm and 2000 rpm are set for the engine speed NE, and two conditions of 10 g / s and 20 g / s are set for the intake air amount GA. With these combinations, as shown in FIG. 5, three conditions for engine speed and intake air amount are set, and each relationship is examined.
By conducting a study as shown in FIG. 5 and grasping the correlation among the air-fuel ratio, EGR, the amount of heat generation, and the combustion speed and collecting it into a mathematical formula (correlation formula), the inventor of the present application expressed the following formula: Derived.

However, in the above formula, “Q” is the heat generation amount, “ηc” is the charging efficiency, “AF” is the air-fuel ratio, “EGR” is the EGR rate, and “CS” is the combustion rate. “NE” is the engine speed, and “P _θcomp ” is the compression pressure. α _{1 to} α ₈ are predetermined coefficients determined based on the grasped correlation.
The air-fuel ratio AF and EGR rate obtained as simultaneous solutions of the above equations can be handled as detected values of the air-fuel ratio and EGR rate in the cylinder measured by the in-cylinder pressure sensor 5.

According to the above-described example according to the first embodiment described above, the in-cylinder pressure sensor 5 is obtained by using two combustion state quantities that are recognized to have a relatively large difference in sensitivity such as a heat generation amount and a combustion speed. The air-fuel ratio and EGR rate can be obtained from the output with high accuracy.
In particular, according to the first embodiment, since the measurement data of the in-cylinder pressure sensor 5 is used, A / F control in real time is possible based on the combustion state in the cylinder. This is an excellent feature that cannot be obtained by existing A / F control using exhaust (A / F control by detecting the exhaust air-fuel ratio with an air-fuel ratio sensor).

  Further, according to the first embodiment, the fuel injection amount can be accurately set to an appropriate amount for controlling the internal combustion engine according to the combustion state of the cylinder ascertained from the measurement data of the in-cylinder pressure sensor.

In the first embodiment, based on the in-cylinder pressure sensor 5 attached to each of the plurality of cylinders of the engine, the air-fuel ratio or the EGR rate is obtained for each of the plurality of cylinders. Also good. In that case, the arithmetic processing unit 20 calculates two types of combustion state quantities (for example, the amount of generated heat and the combustion speed as in the above embodiment) for each cylinder, and further, the air-fuel ratio and EGR for each cylinder. The rate may be calculated.
Further, based on the difference in the EGR rate calculated for each cylinder, the control content of each cylinder may be calculated, or the control content already calculated may be corrected. As a result, the EGR rate for each cylinder can be obtained and the control content of the internal combustion engine can be optimized.
Specifically, for example, the arithmetic processing unit 20 may set each fuel injection amount of the fuel direct injection injector 7 of each cylinder based on the difference in the EGR rate. According to this, the EGR rate for each cylinder can be obtained and the fuel injection amount can be optimized for each cylinder.

  In the example of the first embodiment described above, two kinds of combustion state quantities such as the amount of generated heat and the combustion speed are used. However, the present invention is not limited to this. It is not limited to the set of generated heat quantity and combustion speed, and at least two kinds of combustion state quantities are selected from “a combustion state quantity having different sensitivity to air-fuel ratio or EGR”. A method similar to that performed, that is, grasping the correlation and collecting the correlation into a mathematical expression or the like may be stored in the arithmetic processing unit 20 and calculated from the output value of the in-cylinder pressure sensor 5. As shown in FIGS. 2 to 4, at least (i) Pmax (maximum in-cylinder pressure), (ii) Ingition Delay (ignition delay), (iii) Heat Release (generated heat amount), (iv) Combustion Speed (combustion speed) Differences in sensitivity to air-fuel ratio or EGR are recognized for the five combustion state quantities (speed) and (v) Specific Heat Ratio. A technique similar to the example of the first embodiment may be applied by appropriately selecting at least two kinds of combustion state quantities from these.

In place of the heat generation amount itself, a parameter correlated with the heat generation amount (generated heat amount related parameter) may be used. As the heat generation amount related parameter, for example, “PV ^κ ” is known. That is, the cylinder pressure detected or estimated by the cylinder pressure sensor 50 at the timing when the crank angle is θ is P (θ), and the timing when the crank angle is θ (when the cylinder pressure P (θ) is detected or The in-cylinder volume at the time of estimation is V (θ), and the specific heat ratio is κ. “PV ^κ ” is the product value P (θ) · the in-cylinder pressure P (θ) and a value V (θ) obtained by raising the in-cylinder volume V (θ) to a specific heat ratio (predetermined index) κ. V ^κ (θ). This PV ^{κ is} also a state quantity that reflects the amount of heat generated in the cylinder.

Note that the EGR detection method established in the current technical level estimates the EGR rate and the like from data obtained in a limited environment such as estimation from intake pressure and EGR valve opening. Remain in technology (estimated model). Such an EGR detection method has a drawback that the detection accuracy is not ensured due to the influence of machine difference variation and deposit accumulation. Further, with such an EGR detection method, it is difficult to detect the EGR rate for each cylinder.
In this regard, according to the calculation method according to the first embodiment, the combustion state determined by the air-fuel ratio and EGR can be directly detected by the in-cylinder pressure sensor. Therefore, it is possible to detect the EGR rate and the air-fuel ratio with high accuracy without being affected by machine difference variations and deposits, as compared with the EGR detection method that has been conventionally constructed. As already described, the EGR rate and air-fuel ratio for each cylinder can also be detected.
Furthermore, the configuration according to the first embodiment has a feature that the air-fuel ratio and the EGR amount can be accurately obtained from only the measurement data of the in-cylinder pressure sensor 5. That is, the air-fuel ratio and the EGR amount can be accurately obtained from only the measurement data of the in-cylinder pressure sensor 5 without using information such as the air-fuel ratio sensor, the intake pressure sensor 3, the air flow meter, and the EGR valve opening degree. However, the EGR rate and the air-fuel ratio may be obtained with higher accuracy by performing correction calculation using such information, and such embodiments are also included in the technical scope of the present invention.

Embodiment 2. FIG.
Hereinafter, a control device for an internal combustion engine according to a second embodiment of the present invention will be described. The hardware configuration of the internal combustion engine control device according to the second embodiment and the internal combustion engine (engine) to which the control device is applied are the same as the hardware configuration of the first embodiment. Hereinafter, in order to avoid duplication, the same or equivalent components as those described in the first embodiment will be described with the same reference numerals, and description thereof will be omitted or simplified as appropriate.

  The control apparatus for an internal combustion engine according to the second embodiment has a function for calculating the air-fuel ratio and the EGR rate for each cylinder mounted in the control apparatus for the internal combustion engine according to the first embodiment described above. This is used for “failure detection related to EGR”.

(Fuel injection amount calculation)
Hereinafter, the control content regarding the fuel injection amount in Embodiment 2 is demonstrated. First, also in the control device for an internal combustion engine according to the second embodiment, the arithmetic processing unit 20 calculates the EGR rate of each cylinder using the air-fuel ratio and EGR rate calculation method according to the first embodiment. In the second embodiment, based on the calculated EGR rate of each cylinder, the variation (distribution characteristics) of EGR introduced into each cylinder is grasped, and “the fresh air amount of each cylinder” is calculated. . The optimum basic fuel injection amount for the fuel direct injection injector 7 is set according to the fresh air amount of each cylinder calculated with high accuracy in this way.
Further, in the control device for an internal combustion engine according to the second embodiment, the arithmetic processing unit 20 calculates the air-fuel ratio of each cylinder using the air-fuel ratio and EGR rate calculation method according to the first embodiment. Then, based on the “deviation between the air-fuel ratio of each cylinder and the target air-fuel ratio” and the “fresh air amount of each cylinder” calculated above, a correction amount is set for each fuel injection amount of each cylinder. Shall.

(Failure detection related to EGR)
In the control apparatus for an internal combustion engine according to the second embodiment, the following two types of failure detection are performed.
As a first failure detection, a distribution abnormality in the EGR distribution passage is detected. That is, in the control apparatus for an internal combustion engine according to the second embodiment, the arithmetic processing unit 20 first obtains “variation in the EGR rate of each cylinder” by comparing the EGR rate for each cylinder. If this variation is more than a preset allowable range, it is determined that a distribution abnormality has occurred in the EGR distribution passage.
As the second failure detection, abnormality detection for the EGR passage is performed. That is, in the control device for an internal combustion engine according to the second embodiment, the arithmetic processing unit 20 is first calculated from the EGR rate for each cylinder calculated by the configuration according to the first embodiment and the compression pressure of each cylinder. From the intake gas amount of each cylinder, the EGR flow rate flowing into each cylinder is calculated. Next, the arithmetic processing unit 20 determines whether or not the correlation between the EGR flow rate of all cylinders (the total value of the EGR amount of each cylinder) and the EGR valve opening is out of a predetermined range. This determination may be made, for example, by diagnosing some predetermined EGR valve opening degrees as to whether or not the values of the EGR flow rates of all cylinders corresponding to the EGR valve opening degrees are within a normal range. . When this correlation is out of the predetermined range set in advance, it is determined that there is an abnormality in the passage portion upstream from the distribution position in the EGR valve 12 or the EGR passage.

  FIG. 6 is a flowchart of a routine executed by the arithmetic processing unit 20 in the control apparatus for an internal combustion engine according to the second embodiment of the present invention. This routine is repeatedly executed every predetermined cycle time.

  In the routine shown in FIG. 6, first, the arithmetic processing unit 20 executes a process of detecting the fresh air amount / EGR amount introduced into the cylinder (step S100). In this step, first, necessary sensor values such as the output value of the intake pressure sensor 3 and the output value of the in-cylinder pressure sensor 5 are acquired, and the air-fuel ratio and EGR rate already explained in the first embodiment are obtained on the arithmetic processing unit 20. The calculation process is executed.

Next, the arithmetic processing unit 20 executes a process for grasping the EGR inflow characteristics for each cylinder (step S102).
Specifically, in this step, the EGR distribution characteristic to each cylinder (the EGR amount tends to be relatively large in each cylinder) from the EGR rate value (detected value) obtained in step S100. Or, conversely, a process for grasping which cylinder has a tendency that the EGR amount tends to be relatively small) is executed. Using the grasped distribution characteristics, the EGR rate of each cylinder in the next cycle is predicted when determining the injection amount of the fuel injection valve (in the present embodiment, the fuel direct injection injector 7). As a specific method in step S102, one or more of the following methods (A1) to (A4) can be applied.
(A1) The arithmetic processing unit 20 executes processing for storing the EGR rate of each cylinder under each operating condition as a learning value in a RAM (storage device).
(A2) The arithmetic processing unit 20 calculates and stores the ratio of the EGR rate between cylinders under all operating conditions, and executes a process of estimating the EGR rate for each operating condition on the assumption that the ratio is similar to this ratio. To do.
(A3) The arithmetic processing unit 20 stores a value obtained by averaging the ratio of the EGR rate predicted under each operating condition and the EGR rate of each cylinder under all operating conditions in the RAM, and the next predicted EGR rate is calculated for each cylinder. Processing for estimating the EGR rate of each cylinder is executed by integrating the RAM stored values of the ratio.
(A4) The arithmetic processing unit 20 calculates the opening area of the EGR distribution passage (distribution piping) from a value obtained by averaging the ratio of the EGR rate predicted for each operating condition and the EGR rate of each cylinder under all operating conditions. A process of saving the obtained value in the RAM is executed.
The “EGR distribution passage” refers to a passage through which EGR gas from the exhaust passage is distributed to each cylinder. “The EGR passage is connected to the exhaust passage and the intake passage of the engine, and this EGR passage is connected to each cylinder. A series of distribution passages to communicate with each cylinder via the intake port ”is included. In other words, the specific configuration of the EGR distribution passage is as follows: “The EGR passage itself is a single passage that communicates with a part of the intake passage (for example, a surge tank, an intake manifold), and downstream of the communication position to each cylinder. Also included is a “distributed configuration”, and “a configuration in which the EGR passage itself has a branched portion and the branched portion communicates with a predetermined intake passage position of each cylinder”.

Next, the arithmetic processing unit 20 executes a process of estimating the fresh air amount for each cylinder from the estimated EGR rate (prefetch value) for each cylinder (step S104).
The purpose of this step is to determine an appropriate amount of fuel injection for each cylinder after estimating the amount of fresh air introduced to each cylinder next time. Specifically, in this step, the fresh air amount for each cylinder is estimated by applying one of the following two methods.
(B1) Obtaining the EGR rate of each cylinder by the calculation processing (estimation calculation processing) of any of (A1) to (A3) above, and multiplying the EGR rate of each cylinder by the predicted inflow total gas amount Thus, the fresh air amount of each cylinder can be obtained. The predicted total inflow gas amount is obtained using measurement data of the intake pressure sensor 3 or an air model.
(B2) From the opening area of each pipe in the EGR distribution pipe obtained by the calculation process (estimation calculation process) of (A4) described above, the EGR inflow amount is calculated at the same time as the fresh air amount. This is an application of the air model technique.

  Next, the arithmetic processing unit 20 executes a process of executing a process of calculating the basic injection amount Qb from the fresh air amount and the target air-fuel ratio for each cylinder (step S106).

  In addition to the processing in step S106, after the processing in step S104, the arithmetic processing unit 20 calculates the injection amount correction value Qd from the detected deviation between the cylinder-by-cylinder air-fuel ratio and the target air-fuel ratio and the fresh air amount. The calculation process is executed (step S108). The air-fuel ratio for each cylinder can be obtained from information such as the EGR rate for each cylinder, the fresh air amount for each cylinder, and the fuel injection amount for each cylinder in steps S102 and S104.

  Next, the arithmetic processing unit 20 executes a process of calculating the sum of the basic injection amount Qb calculated in the process of step S106 and the injection amount correction value Qd calculated in step S108 as a final injection amount (step S110). Thereafter, the process returns.

  The fuel injection amount for each cylinder can be optimized by the series of processes of steps S100, S102, S104, S106, S108, and S110.

  On the other hand, in the routine of FIG. 6, after the process of step S100, the arithmetic processing unit 20 executes a process of calculating the total EGR amount (detected value) of all the cylinders separately from the process of step S102 (step S120).

  Next, the arithmetic processing unit 20 performs a process of calculating an estimated EGR amount from the EGR opening degree and the engine condition (step S122). In this step, for example, the processing unit 20 is caused to perform a process of calculating an estimated value of the EGR amount according to the opening degree of the EGR valve 12 and the engine operating condition (a map reference stored in advance or a calculation according to a mathematical formula). That's fine.

  Next, the arithmetic processing unit 20 executes a process of determining whether or not the difference between the detected value of the total EGR amount in step S120 and the estimated EGR amount in step S122 is larger than a predetermined value (step S124). If the determination result in this step is No, it can be determined that the difference between the EGR total amount detection value and the EGR amount estimation value is within the appropriate range. Therefore, the process returns.

  On the other hand, when the determination result in step S124 is Yes, it can be determined that the difference between the EGR total amount detected value and the EGR amount estimated value exceeds an appropriate range. In this case, the arithmetic processing unit 20 has a configuration of the EGR valve 12 or the EGR passage before distribution (for example, the EGR cooler 13 or an EGR catalyst (not shown) includes this EGR catalyst). A process for determining that an abnormality has occurred is executed (step S126). In this step, for example, various countermeasures may be taken for the contents of engine control processing, or an external notification (for example, a warning lamp may be turned on) may be performed.

  By the series of processes of steps S100, S120, S122, S124, and S126, it is possible to determine whether or not an abnormality has occurred in the EGR distribution passage (that is, failure detection).

Further, in the routine of FIG. 6, after step S100, the arithmetic processing unit 20 executes a process of calculating the variation degree of the EGR rate of each cylinder separately from the processes of steps S102 and S120 (step S130). In this step, for example, the standard deviation is obtained by using the value of the EGR rate of each cylinder, or the degree (size) of the deviation of each EGR rate from the average value is obtained.
Next, the arithmetic processing unit 20 executes processing for determining whether or not the variation degree obtained in step S130 is larger than the predetermined variation degree (step S132). In this step, it is determined whether the standard deviation or the deviation from the average value is within a predetermined range in relation to step S130. Note that a statistical variation evaluation method other than the above may be employed, and for example, it may be determined whether or not the variance is within a predetermined range.

When the determination result in step S132 is No, it can be determined that the variation degree is within the predetermined variation degree. Therefore, in this case, in the routine of FIG. 6, the arithmetic processing unit 20 ends the current routine.
On the other hand, if the determination result in step S132 is Yes, it can be determined that the degree of variation is greater than the predetermined degree of variation. In this case, in the routine of FIG. 6, the arithmetic processing unit 20 executes a process of determining that an abnormality has occurred in the distributed EGR passage (step S134). Thereafter, the current routine is terminated.

  By the series of processes of steps S100, S130, S132, and S134 described above, it is possible to determine whether a distribution variation abnormality has occurred in the EGR distribution path (that is, failure detection).

  In the routine of FIG. 6, “a series of processes of steps S100, S102, S104, S106, S108, and S110”, “a series of processes of steps S100, S120, S122, S124, and S126”, and “step S100 , S130, S132, and S134 "need not all be executed. Of the three series of processes, only one or two may be executed by the arithmetic processing unit 20.

DESCRIPTION OF SYMBOLS 1 Air cleaner 2 Throttle valve 3 Intake pressure sensor 4 Surge tank 5 In-cylinder pressure sensor 6 Spark plug 7 Fuel direct injection injector 8 Crank angle sensor 9 Knock sensor 10, 11 Catalyst 12 EGR valve 13 EGR cooler 14 Water temperature sensor 20 Processing unit

Claims (7)

A control device for an internal combustion engine in which an in-cylinder pressure sensor is attached to at least one cylinder,
At least two types of combustion state quantities having different sensitivities for the air-fuel ratio or EGR rate among the combustion state quantities, which are quantities representing the combustion state of the cylinder to which the in-cylinder pressure sensor is attached, are output to the in-cylinder pressure sensor. A calculation means for calculating based on;
Based on the relationship between the at least two types of combustion state quantities, the air-fuel ratio, and the EGR rate, the air-fuel ratio in the cylinder to which the in-cylinder pressure sensor is attached is calculated from the value of the combustion state quantity calculated by the calculation means. Or / and a calculation means for calculating the EGR rate;
Equipped with a,
The calculating means includes
One of the at least two types of combustion state quantities is defined as a first combustion state quantity, and a combustion state quantity having sensitivity different from the first combustion state quantity for at least one of an air-fuel ratio and an EGR rate is defined as a second combustion state quantity. If
A first relationship that defines the relationship between the first combustion state quantity and the air-fuel ratio and EGR rate, and a second relationship that defines the relationship between the second combustion state quantity and the air-fuel ratio and EGR rate. And storage means for storing
Means for calculating a solution obtained by simultaneously combining the first relation and the second relation as the air-fuel ratio or / and the EGR rate;
Control apparatus for an internal combustion engine, which comprises a.   The at least two types of combustion state quantities include a quantity of heat generated in the at least one cylinder or a parameter correlated with the quantity of heat generated, and a combustion speed in the at least one cylinder. The control apparatus for an internal combustion engine according to claim 1.   3. The internal combustion engine according to claim 1, further comprising an injection amount calculation unit that calculates a fuel injection amount of a fuel injection valve provided for the cylinder based on the air-fuel ratio calculated by the calculation unit. Engine control device. The internal combustion engine includes a plurality of cylinders, and an in-cylinder pressure sensor is attached to at least two of the plurality of cylinders,
The calculation means includes a cylinder-by-cylinder calculation means for calculating the two types of combustion state quantities for each of the at least two cylinders,
The calculating means includes a cylinder-by-cylinder EGR rate calculating means for calculating an EGR rate for each of the at least two cylinders,
Based on the difference of the EGR rate calculated by the EGR rate calculation means for each of the at least two cylinders, the control content of each of the at least two cylinders is calculated or the calculated control content is corrected. Cylinder-by-cylinder control means for performing
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising: The internal combustion engine includes a plurality of fuel injection valves provided for each of the at least two cylinders and capable of setting different fuel injection amounts.
Setting means for setting the fuel injection amount of the fuel injection valve for each of the at least two cylinders based on the difference of the EGR rate calculated by the EGR rate calculating unit for each cylinder. The control apparatus for an internal combustion engine according to claim 4, further comprising: The internal combustion engine includes a plurality of cylinders, and an in-cylinder pressure sensor is attached to at least two of the plurality of cylinders,
The calculation means includes a cylinder-by-cylinder calculation means for calculating the two types of combustion state quantities for each of the at least two cylinders,
The calculating means includes a cylinder-by-cylinder EGR rate calculating means for calculating an EGR rate for each of the at least two cylinders,
An EGR distribution passage having a plurality of intake side ends connected to an exhaust passage of the internal combustion engine and connected to respective intake passages of the at least two cylinders;
Detecting means for detecting an abnormality in the EGR distribution passage based on the EGR rate calculated by the cylinder-by-cylinder EGR rate calculating means for each of the at least two cylinders;
The control apparatus for an internal combustion engine according to any one of claims 1 to 5, further comprising: The first relationship is represented by a first equation, the second relationship is represented by a second equation;
Said computing means, the solution of the first person equations and the second towards equations of simultaneous equations, according to claim 1, wherein the benzalkonium be calculated as the air-fuel ratio and / or the EGR rate The control apparatus for an internal combustion engine according to any one of the preceding claims.

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