JP2019056379A - Control device of internal combustion engine - Google Patents

Abstract

To provide a control device of an internal combustion engine capable of improving merchantability, in which even under the high-humidity environmental condition, it is possible to ensure a stable combustion state of the internal combustion engine.SOLUTION: A control device 1 of an internal combustion engine 3 comprises an ECU2. The ECU2 calculates a basic target EGR amount Gegr_bs in accordance with the operational state of the internal combustion engine 3 (step 12); to obtain a water vapor content in the air Gwtr induced into an intake passage 6 of the internal combustion engine 3 (step 10); by multiplying the water vapor content Gwtr by an EGR conversion factor Rwtr2egr greater than 1, an EGR conversion amount Gegr_wtr converted the amount of steam to the amount of EGR is calculated (step 11); by amending the basic target EGR amount Gegr_bs by the EGR conversion amount Gegr_wtr, a target EGR amount Gegr_cmd is calculated (steps 13 and 15) ; and by using the target EGR amount Gegr_cmd, the operation of the internal combustion engine 3 is controlled (steps 18 to 21).SELECTED DRAWING: Figure 5

Description

  The present invention relates to a control device for an internal combustion engine that controls the operation of the internal combustion engine using a water vapor parameter that represents one of the ratio and amount of water vapor in the air taken into an intake passage.

  Conventionally, the present applicant has already proposed a control device for an internal combustion engine described in Patent Document 1, and in this control device, the EGR rate REGRT is calculated by the calculation process shown in FIG. The In this calculation process, first, the ideal in-cylinder gas amount Gth is calculated by the calculation process shown in FIG. 5 of the same document, and the reference in-cylinder gas temperature Tcylstd is calculated by map search according to the engine speed NE and the like. Thereafter, the in-cylinder gas temperature Tcyl is calculated by the calculation process shown in FIG. 6 of the document (steps 1 to 3). Next, the in-cylinder gas amount Gact is calculated from the equation (9), and the EGR rate REGRT is finally calculated from the equation (12) (steps 4 to 5).

  Further, in the ignition timing control process shown in FIG. 7 of the same document, the optimum ignition timing IGMBT is calculated according to the engine speed NE and the EGR rate REGRT, and the final ignition timing IGLOG is calculated using this. (Steps 31-36). Then, the air-fuel mixture is ignited by the spark plug at a timing corresponding to the ignition timing IGLOG.

International Publication No. 2016/017214

  In general, in the case of an internal combustion engine, since air-fuel mixture is generated using air sucked from the atmosphere (hereinafter referred to as “intake air”), the intake air may become humid during rainy weather. is there. In this case, as will be described later, the water vapor in the intake air lowers the combustion temperature of the air-fuel mixture as well as the reflux gas, and has the characteristics that the ability to lower the combustion temperature is higher than that of the reflux gas. doing.

  On the other hand, according to the control device of Patent Document 1 described above, when calculating the EGR rate, the humidity state of the intake air is not considered. Due to the humidity of the air, the combustion temperature is excessively lowered and the combustion state becomes unstable, which may cause a surge or misfire. Further, for the same reason, there is a risk that the ignition timing is excessively retarded, and in this case, the fuel efficiency is deteriorated.

  The present invention has been made to solve the above-described problems, and can control the internal combustion engine that can ensure a stable combustion state of the internal combustion engine and improve the commerciality even under humid environmental conditions. The purpose is to provide.

  In order to achieve the above object, a control device 1 for an internal combustion engine 3 according to claim 1 sends exhaust gas in the exhaust passage 7 of the internal combustion engine 3 to the intake side of the internal combustion engine 3 according to the operating state of the internal combustion engine 3. Basic target EGR amount calculation means (ECU 2, step 12) for calculating a basic target EGR amount Gegr_bs that is a basis of the target value of the EGR amount that is the amount of recirculation, and air that is sucked into the intake passage 6 of the internal combustion engine 3 The amount of water vapor using a water vapor parameter acquisition means (ECU2, step 10) for obtaining a water vapor parameter (water vapor amount Gwtr) representing one of the proportion and amount of water vapor in a certain intake air and the water vapor parameter (water vapor amount Gwtr) A water vapor amount calculating means (ECU2, step 10) for calculating the water vapor amount Gwtr, and a conversion factor (EGR conversion factor larger than 1) for the water vapor amount Gwtr. EGR conversion amount calculation means (ECU2, step 11) for calculating an EGR conversion amount Gegr_wtr by converting the water vapor amount into an EGR amount by multiplying by Rwtr2egr), and correcting the basic target EGR amount Gegr_bs with the EGR conversion amount Gegr_wtr Thus, the target EGR amount calculating means (ECU 2, steps 13 and 15) for calculating the target EGR amount Gegr_cmd and the control means (ECU 2, steps 18 to 21) for controlling the operation of the internal combustion engine 3 using the target EGR amount Gegr_cmd. And.

  According to the control device for an internal combustion engine, the basic target EGR amount is calculated according to the operating state of the internal combustion engine, and the target EGR amount is calculated by correcting the basic target EGR amount with the correction value. This correction value is obtained by calculating the amount of water vapor using a water vapor parameter representing one of the proportion and amount of water vapor in the intake air, which is the air sucked into the intake passage of the internal combustion engine. By multiplying by a large conversion coefficient, the value is calculated as a value obtained by converting the amount of water vapor into the amount of EGR. Therefore, the value is calculated as a value reflecting the amount of water vapor in the intake air. Since the target EGR amount is calculated by correcting the basic target EGR amount with such a correction value, a value that takes into account the same function as the recirculation gas by the water vapor in the intake air, that is, the function of lowering the combustion temperature. Is calculated as follows. Therefore, by controlling the operation of the internal combustion engine using such a target EGR amount, it is possible to ensure a stable combustion state of the internal combustion engine even under humid environmental conditions, and to improve the merchantability. (In addition, “acquisition” of “acquisition of water vapor parameter” in this specification is not limited to directly detecting this by a sensor or the like, but includes calculating this value using other parameters).

  In addition, as in Patent Document 1, when various control processes are executed using a target EGR amount that does not take into account the function of lowering the combustion temperature due to steam, in order to improve the control accuracy in the various control processes, Various control processes need to be executed by the corresponding correction process and map search method, and as a result, the calculation load and the number of control processes are increased. On the other hand, according to the control device for the internal combustion engine, the target EGR amount can be calculated as a value reflecting the function of reducing the combustion temperature due to the water vapor in the intake air. An increase in the number of control steps can be avoided, and the merchantability can be further improved.

  The invention according to claim 2 is characterized in that, in the control device 1 for the internal combustion engine 3 according to claim 1, the conversion coefficient is set to a value in the vicinity of the value 1.3 including the value 1.3. To do.

  As will be described later, according to the experiment conducted by the present applicant, in the case of water vapor, it was confirmed that the ability to delay the combustion rate of the air-fuel mixture was about 1.3 times larger than that of the reflux gas. Therefore, according to the control device for the internal combustion engine, since the conversion coefficient is set to a value in the vicinity of the value 1.3 including the value 1.3, the ability to delay the combustion speed of the air-fuel mixture in water vapor is appropriately reflected. Thus, the EGR conversion amount can be calculated, and the calculation accuracy can be improved.

It is a figure showing typically composition of a control device concerning one embodiment of the present invention, and an internal-combustion engine to which this is applied. It is a block diagram which shows the electric constitution of a control apparatus. The valve lift curve of the intake valve when the intake cam phase is set to the most advanced value (solid line) and the origin value (broken line) by the variable intake cam phase mechanism, and the exhaust cam phase is the latest by the variable exhaust cam phase mechanism It is a figure which respectively shows the valve lift curve of an exhaust valve when it is set to the angle value (solid line) and the origin value (broken line). It is a flowchart which shows a water vapor | steam ratio calculation process. It is a flowchart which shows an EGR control process. It is the figure which represented the relationship of the influence degree which acts on the combustion sensitivity of water vapor | steam and recirculation | reflux gas by a mutual volume ratio. It is a figure which shows an example of the map used for calculation of the amount of basic target EGR. It is a flowchart which shows a total EGR rate calculation process. It is a figure for demonstrating the derivation | leading-out principle of the calculation algorithm of the various parameters used for calculation of a total EGR rate. It is a flowchart which shows an ignition timing control process. It is a figure which shows the example of a control result when performing the ignition timing control in a humid environmental condition with the control method of this invention, and the conventional control method. It is a figure which shows the instability degree of combustion when ignition timing control under humid environmental conditions is performed with the control method of the present invention and the conventional control method.

  Hereinafter, an internal combustion engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 2, the control device 1 includes an ECU 2. As will be described later, the ECU 2 performs EGR according to the operating state of the internal combustion engine (hereinafter referred to as “engine”) 3 shown in FIG. Various control processes such as a control process are executed.

  The engine 3 is an in-line four-cylinder gasoline engine having four sets of cylinders 3a and pistons 3b (only one set is shown), and is mounted on a vehicle (not shown) as a power source. The engine 3 includes an intake valve 4 (only one is shown) provided for each cylinder 3a, an exhaust valve 5 (only one is shown) provided for each cylinder 3a, and intake air that drives the intake valve 4 to open and close. A valve operating mechanism 40 and an exhaust valve operating mechanism 50 for opening and closing the exhaust valve 5 are provided.

  The intake valve mechanism 40 includes an intake camshaft 41 that drives the intake valve 4 by an intake cam 41a, a variable intake cam phase mechanism 42, and the like. The variable intake cam phase mechanism 42 has a CAIN relative to the intake cam 41a, that is, the intake camshaft 41 relative to the crankshaft 3c (hereinafter referred to as “intake cam phase”) in a stepless manner (that is, continuously) By changing to the retard side, the valve timing of the intake valve 4 is changed and provided at the end of the intake camshaft 41 on the intake sprocket (not shown) side.

  The variable intake cam phase mechanism 42 is of a hydraulic drive type. Specifically, the variable intake cam phase mechanism 42 is configured in the same manner as that proposed by the present applicant in Japanese Patent Application Laid-Open No. 5007-400522, and the like. Although not described, an intake cam phase control valve 42a (see FIG. 2) and a hydraulic circuit (not shown) are provided.

  In this variable intake cam phase mechanism 42, the intake cam phase control valve 42a is controlled by the ECU 2, whereby the hydraulic pressure supplied from the hydraulic circuit to the advance chamber and the retard chamber of the variable intake cam phase mechanism 42 is controlled. . Thereby, the intake cam phase CAIN is changed between a predetermined origin value CAIN_0 and a predetermined maximum advance value CAIN_ADV, whereby the valve timing of the intake valve 4 is changed to the origin timing indicated by a broken line in FIG. It is changed in a stepless manner with respect to the most advanced timing shown by the solid line in FIG.

  In this case, the origin value CAIN_0 is set to the value 0, and the most advanced angle value CAIN_ADV is set to a predetermined positive value. Therefore, as the intake cam phase CAIN increases from the origin value CAIN_0, the valve timing of the intake valve 4 is changed from the origin timing to the advance side, and thereby the valve overlap period of the intake valve 4 and the exhaust valve 5 becomes longer. Become. As a result, the internal EGR amount is changed to the increasing side.

  The exhaust valve mechanism 50 includes an exhaust camshaft 51 that drives the exhaust valve 5 by an exhaust cam 51a, a variable exhaust cam phase mechanism 52, and the like. The variable exhaust cam phase mechanism 52 is configured to step the CAEX relative to the exhaust cam 51a, that is, the exhaust camshaft 51 relative to the crankshaft 3c (hereinafter referred to as “exhaust cam phase”) steplessly (that is, continuously) By changing to the retard side, the valve timing of the exhaust valve 5 is changed and provided at the end of the exhaust camshaft 51 on the exhaust sprocket (not shown) side.

  The variable exhaust cam phase mechanism 52 is a hydraulic drive type configured similarly to the variable intake exhaust cam phase mechanism 42 described above, and includes an exhaust cam phase control valve 52a (see FIG. 2), a hydraulic circuit (not shown), and the like. ing.

  In this variable exhaust cam phase mechanism 52, the exhaust cam phase control valve 52a is controlled by the ECU 2 to control the hydraulic pressure supplied from the hydraulic circuit to the advance chamber and the retard chamber of the variable exhaust cam phase mechanism 52. . Thereby, the exhaust cam phase CAEX is changed between a predetermined origin value CAEX_0 and a predetermined maximum retardation value CAEX_RET, so that the valve timing of the exhaust valve 5 becomes the origin timing indicated by a broken line in FIG. It is changed steplessly with respect to the most retarded angle timing shown by the solid line in FIG.

  In this case, the origin value CAEX_0 is set to the value 0, and the most retarded angle value CAEX_RET is set to a predetermined positive value. Therefore, as the exhaust cam phase CAEX increases from the origin value CAEX_0, the valve timing of the exhaust valve 5 is changed from the origin timing to the retard side, and thereby the valve overlap period becomes longer. As a result, the internal EGR amount is changed to the increasing side.

  The engine 3 is provided with a fuel injection valve 8 and a spark plug 9 shown in FIG. 2 for each cylinder 3a (only one is shown). The fuel injection valve 8 is attached to the cylinder head so as to directly inject fuel into each cylinder 3a, and is electrically connected to the ECU 2, and the ECU 2 uses the fuel injection valve 8 to inject fuel. And the injection timing is controlled.

  Further, the spark plug 9 is attached to the cylinder head of the engine 3 and is electrically connected to the ECU 2, and the ignition timing by the spark plug 9 is controlled by the ECU 2 as will be described later.

  On the other hand, an air cleaner 10 and a throttle valve mechanism 11 are provided in the intake passage 6 in order from the upstream side. The air cleaner 10 is provided at the air suction port of the intake passage 6 and incorporates a filter (not shown). During operation of the engine 3, dust or the like in the air sucked into the intake passage 6 (hereinafter referred to as “intake air”) is removed by the filter of the air cleaner 10.

  The throttle valve mechanism 11 includes a throttle valve 11a and a TH actuator 11b that opens and closes the throttle valve 11a. The throttle valve 11a is rotatably provided in the intake passage 6 and changes the flow rate of the air passing through the throttle valve 11a by the change of the opening degree accompanying the rotation.

  The TH actuator 11b is a combination of a motor connected to the ECU 2 and a gear mechanism (not shown), and is controlled by the ECU 2 to change the opening of the throttle valve 11a.

  The engine 3 is provided with an EGR device 12. The EGR device 12 recirculates a part of the exhaust gas in the exhaust passage 7 to the intake passage 6 and includes an EGR passage 12a, an EGR valve 12b, an EGR actuator 12c (see FIG. 2), and the like. One end of the EGR passage 12 a is connected to a predetermined portion of the intake passage 6 downstream of the throttle valve 11 a, and the other end is connected to a predetermined portion of the exhaust passage 7.

  On the other hand, the EGR valve 12b is of the butterfly valve type and is connected to the EGR actuator 12c. The EGR actuator 12c is composed of a DC motor or the like. In the case of this EGR device 12, the opening of the EGR valve 12b is controlled by supplying a control input signal from the ECU 2 to the EGR actuator 12c, whereby the amount of exhaust gas recirculated from the exhaust passage 7 to the intake passage 6 That is, the external EGR amount is controlled.

  In the following description, the internal EGR and the external EGR are collectively referred to as “EGR”, and the sum of the internal EGR amount and the external EGR amount is referred to as “EGR amount”.

  2, the ECU 2 includes a crank angle sensor 20, a water temperature sensor 21, an air flow sensor 22, an atmospheric pressure sensor 23, an intake air temperature sensor 24, a humidity sensor 25, an intake air pressure sensor 26, an exhaust gas temperature sensor 27, An exhaust pressure sensor 28, an intake cam angle sensor 29, an exhaust cam angle sensor 30, and an EGR valve opening sensor 31 are electrically connected.

  The crank angle sensor 20 outputs a CRK signal and a TDC signal, both of which are pulse signals, to the ECU 2 as the crankshaft 3c rotates. The CRK signal is output at one pulse every predetermined crank angle (for example, 30 °), and the ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b of each cylinder 3a is at a predetermined crank angle position slightly before the TDC position of the intake stroke, and one pulse is output for each predetermined crank angle.

  Further, the water temperature sensor 21 detects the engine water temperature TW, which is the temperature of the cooling water circulating in the cylinder block of the engine 3, and outputs a detection signal representing it to the ECU 2.

  Further, all of the four sensors 22 to 25 described above are provided in the air cleaner 10, and the air flow sensor 22 detects the amount of air flowing into the intake passage 6 via the air cleaner 10 and generates a detection signal representing it. It outputs to ECU2. The ECU 2 calculates an intake air amount Gaircyl (intake air amount parameter) that is the amount of air flowing into one cylinder during one combustion cycle based on the detection signal of the air flow sensor 22.

  The atmospheric pressure sensor 23 detects the atmospheric pressure PA and outputs a detection signal representing the detected pressure to the ECU 2, and the intake air temperature sensor 24 absorbs the temperature of the air flowing into the intake passage 6 via the air cleaner 10. The temperature TA is detected and a detection signal representing it is output to the ECU 2, and the humidity sensor 25 detects the relative humidity RH of the air flowing into the intake passage 6 via the air cleaner 10 and outputs a detection signal representing it. It outputs to ECU2.

  Further, the intake pressure sensor 26 is provided on the downstream side of the joint portion of the intake passage 6 with the EGR passage 12a, and detects the intake pressure PB, which is the gas pressure in the intake passage 6, and represents it. A signal is output to the ECU 2.

  On the other hand, the exhaust temperature sensor 27 detects the exhaust temperature Tex, which is the temperature of the exhaust gas flowing in the exhaust passage 7, and outputs a detection signal representing it to the ECU 2, and the exhaust pressure sensor 28 detects the gas in the exhaust passage 7. The exhaust pressure Pex, which is a pressure, is detected, and a detection signal representing it is output to the ECU 2.

  The intake cam angle sensor 29 is provided at the end of the intake camshaft 41 opposite to the variable intake cam phase mechanism 42, and with the rotation of the intake camshaft 41, an intake CAM signal that is a pulse signal is predetermined. Is output to the ECU 2 at every cam angle (for example, 10 °). The ECU 2 calculates the intake cam phase CAIN based on the intake CAM signal and the above-described CRK signal.

  Further, the exhaust cam angle sensor 30 is provided at the end of the exhaust camshaft 51 opposite to the variable exhaust cam phase mechanism 52, and the exhaust camshaft 51 rotates and the exhaust camshaft 51 receives a predetermined exhaust CAM signal. Is output to the ECU 2 at every cam angle (for example, 10 °). The ECU 2 calculates the exhaust cam phase CAEX based on the exhaust CAM signal and the above-described CRK signal.

  Further, the EGR valve opening sensor 31 detects an EGR valve opening φEGR that is the opening of the EGR valve 12b, and outputs a detection signal representing it to the ECU 2.

  Furthermore, ECU2 is comprised with the microcomputer which consists of CPU, RAM, ROM, and I / O interface (all are not shown) etc., and is based on the detection signal of the above various sensors 20-31, etc. below. As described above, EGR control processing and the like are executed.

  In the present embodiment, the ECU 2 performs the intake air amount parameter acquisition means, the water vapor parameter acquisition means, the dry intake air parameter calculation means, the ignition timing control means, the basic target EGR amount calculation means, the water vapor amount calculation means, and the EGR conversion amount calculation. Means, target EGR amount calculation means and control means.

  Next, the water vapor ratio calculation process will be described with reference to FIG. This calculation process calculates the water vapor ratio Rwtr, which is the ratio of water vapor in the intake air, and is executed by the ECU 2 at a predetermined control period ΔT (for example, 10 msec).

As shown in the figure, first, in step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the water vapor partial pressure Pw is calculated by the following equation (1).

Subsequently, it progresses to step 2, and after calculating water vapor | steam ratio Rwtr by the following Formula (2), this process is complete | finished.

  Next, the EGR control process will be described with reference to FIG. This EGR control process controls the external EGR amount via the EGR device 12, and simultaneously controls the internal EGR amount via the variable intake cam phase mechanism 42 and the variable exhaust cam phase mechanism 52. The ECU 2 described above. It is executed in the control cycle ΔT.

As shown in the figure, first, in step 10, the water vapor amount Gwtr is calculated by the following equation (3). This water vapor amount Gwtr (water vapor parameter) corresponds to the water vapor amount in the intake air.

Next, the process proceeds to step 11, and an EGR conversion amount Gegr_wtr is calculated by the following equation (4). The EGR conversion amount Gegr_wtr is a value obtained by converting the water vapor amount Gwtr into the EGR amount by regarding the water vapor as the reflux gas.

  Rwtr2egr in the equation (4) is an EGR conversion coefficient for converting the water vapor amount Gwtr into an EGR amount. In this embodiment, the EGR conversion coefficient Rwtr2egr is set to a value of 1.3. This is due to the following reason. That is, in the case of water vapor, the specific heat is larger than that of the recirculated gas. As a result, when the degree of influence on both combustion sensitivities is expressed by the volume ratio of each other, as shown in FIG. The relationship of 3% ≒ reflux gas volume ratio 4% is established. That is, in the case of water vapor, the ability to delay the combustion rate of the air-fuel mixture is about 1.3 times larger than that of the reflux gas, so that the EGR conversion coefficient Rwtr2egr is set to the above-mentioned value 1.3 in order to reflect this. ing.

  Next, in step 12, a basic target EGR amount Gegr_bs is calculated by searching a map according to the intake air amount Gaircyl and the engine speed NE. In this case, the calculation map of the basic target EGR amount Gegr_bs is as shown in FIG. 7 when the engine speed NE is the predetermined speed NE1.

In step 13 following step 12, the provisional target EGR amount Gegr_tmp is calculated by the following equation (5).

  Next, the routine proceeds to step 14 where it is determined whether or not the provisional target EGR amount Gegr_tmp is 0 or more. If the determination result is YES and Gegr_tmp ≧ 0 is established, the process proceeds to step 15 where the target EGR amount Gegr_cmd is set to the provisional target EGR amount Gegr_tmp.

  On the other hand, if the determination result in step 14 is NO and Gegr_tmp <0 is established, the process proceeds to step 16 where the target EGR amount Gegr_cmd is set to 0.

  As described above, the provisional target EGR amount Gegr_tmp is calculated by subtracting the water vapor amount Gwtr from the basic target EGR amount Gegr_bs, and the provisional target EGR amount Gegr_tmp is subjected to a lower limit process with a value 0 as a lower limit. The target EGR amount Gegr_cmd is calculated. As a result, the target EGR amount Gegr_cmd is calculated as a value as indicated by a broken line in FIG.

  In step 17 following step 15 or 16, the internal EGR ratio R_in is calculated. This internal EGR ratio R_in defines the ratio of the target internal EGR amount with respect to the target EGR amount Gegr_cmd, and searches for a map (not shown) according to the engine speed NE and the engine load (for example, intake air amount Gaircyl). Is calculated by

Next, the routine proceeds to step 18 where the target internal EGR amount Ginegr_cmd is calculated by the following equation (6). This target internal EGR amount Ginegr_cmd is a target value of the internal EGR amount Ginegr.

Next, in step 19, the target external EGR amount Gexegr_cmd is calculated by the following equation (7). This target external EGR amount Gexegr_cmd is a target value of the external EGR amount Gexegr.

  In step 20 following step 19, internal EGR control processing is executed. Specifically, first, a target intake cam phase CAIN_cmd and a target exhaust cam phase CAEX_cmd are calculated by searching a map (not shown) according to the target internal EGR amount Ginegr_cmd and the engine speed NE.

  Next, control input signals corresponding to the target intake cam phase CAIN_cmd and the target exhaust cam phase CAEX_cmd are supplied to the intake cam phase control valve 42a and the exhaust cam phase control valve 52a, respectively. Thus, the intake cam phase CAIN is controlled to be the target intake cam phase CAIN_cmd, and the exhaust cam phase CAEX is controlled to be the target exhaust cam phase CAEX_cmd. As a result, the internal EGR amount Ginegr is controlled to become the target internal EGR amount Ginegr_cmd.

  In step 20, after the internal EGR control process is executed as described above, the process proceeds to step 21 to execute the external EGR control process. Specifically, a control input signal corresponding to the target external EGR amount Gexegr_cmd is supplied to the EGR actuator 12c. Thereby, the EGR valve opening φEGR is controlled so that the actual external EGR amount Gexegr becomes the target external EGR amount Gexegr_cmd. In step 21, the external EGR control process is executed as described above, and then this process ends.

  Next, the total EGR rate calculation process will be described with reference to FIG. As will be described below, this calculation process calculates the total EGR rate Regr_t, and is executed by the ECU 2 in the control cycle ΔT described above. This total EGR rate Regr_t corresponds to the EGR rate when water vapor is regarded as the recirculation gas in addition to EGR (external EGR and internal EGR), that is, the ratio of EGR in the total gas in the cylinder 3a. The derivation principle of various parameter calculation algorithms described below will be described later.

As shown in the figure, first, in step 30, the ideal in-cylinder gas amount Gth is calculated by the following equation (8).

  Gstdm in the equation (8) is a map value of the reference in-cylinder gas amount, and is calculated by searching a map (not shown) according to the engine speed NE, the intake cam phase CAIN, and the exhaust cam phase CAEX. Further, KTW in Expression (8) is a water temperature correction coefficient, and is calculated by searching a map (not shown) according to the engine water temperature TW. Further, PBwot in the equation (8) is a reference intake pressure, which is a predetermined value corresponding to the intake pressure PB when the throttle valve 11a is fully opened.

  Next, the routine proceeds to step 31 where a reference in-cylinder gas temperature Tic_std is calculated by searching a map (not shown) according to the engine speed NE, the intake cam phase CAIN, and the exhaust cam phase CAEX.

  Next, in step 32, the external EGR amount Gexegr is calculated. Specifically, the external EGR amount Gexegr is calculated based on the EGR valve opening φEGR, the intake pressure PB, and the exhaust pressure Pex, using a nozzle equation (not shown) derived by regarding the EGR valve 12b as a nozzle. The

  In step 33 following step 32, the external EGR temperature Tegr is calculated. Specifically, the external EGR temperature Tegr calculates a reference external EGR temperature Tegr_bs by searching a map (not shown) according to the external EGR amount Gexegr and the engine speed NE, and calculates the reference external EGR temperature Tegr_bs. It is calculated by correcting according to the engine coolant temperature TW.

Next, the routine proceeds to step 34, where the internal EGR amount Ginegr is calculated by the following equation (9).

  Next, in step 35, the water vapor amount Gwtr is calculated by the aforementioned equation (3).

In step 36 following step 35, the dry intake air amount Gair_dry is calculated by the following equation (10). This dry intake air amount Gair_dry (dry intake air parameter) corresponds to the amount of dry air obtained by removing water vapor from the intake air.

Next, the routine proceeds to step 37, where the in-cylinder gas temperature Tic is calculated by the following equation (11).

Next, in step 38, the in-cylinder gas amount Ggas_cyl is calculated by the following equation (12).

  In step 39 following step 38, the EGR conversion amount Gegr_wtr is calculated by the above-described equation (4).

なお、この式（１３）の右辺の分子における括弧内の値が、内部ＥＧＲ量と外部ＥＧＲ量の和に相当する。 Next, the process proceeds to step 40, and after calculating the total EGR rate Regr_t by the following equation (13), the present process is terminated. This total EGR rate Regr_t (total EGR rate) corresponds to an EGR rate calculated by regarding water vapor as EGR.

Note that the value in parentheses in the numerator on the right side of the equation (13) corresponds to the sum of the internal EGR amount and the external EGR amount.

  Next, the derivation principle of the calculation algorithm used in the above total EGR rate calculation process will be described with reference to FIG. This figure shows the relationship between the intake pressure PB and the in-cylinder gas amount when the engine speed NE, the intake cam phase CAIN, and the exhaust cam phase CAEX are at constant predetermined values.

  A reference point Pwot shown in the figure represents an operating point when the throttle valve 11a is in a fully open state (reference state). At this reference point Pwot, since the throttle valve 11a is fully open, the intake pressure PB becomes a reference intake pressure PBwoot substantially equal to the atmospheric pressure PA. For the same reason, there is almost no pressure difference between the exhaust side and the intake side, so even when valve overlap occurs, there is no back flow of exhaust from the exhaust side to the intake side, The amount of internal EGR due to blow-back from the intake side becomes almost zero.

  Further, a line Lth (hereinafter referred to as “ideal line Lth”) connecting the reference point Pwot and the origin O is an ideal state in which it is assumed that the exhaust gas is not recirculated into the cylinder 3a, that is, external EGR is not performed, and internal The relationship between the intake pressure and the in-cylinder gas in an ideal state when it is assumed that there is no EGR is shown. That is, in the reference state and the ideal state, the ideal line Lth is derived as a straight line from the gas state equation because the in-cylinder gas temperature and the gas constant of the in-cylinder gas can be considered to be constant.

  Further, lines L1 to L4 in FIG. 9 represent various gas amounts in the actual in-cylinder gas. That is, the line L1 represents the dry intake air amount Gair_dry in the in-cylinder gas, and the line L2 represents the sum of the dry intake air amount Gair_dry and the water vapor amount Gwtr in the in-cylinder gas, that is, the intake air amount Gaircyl. The line L3 represents the sum of the dry intake air amount Gair_dry, the water vapor amount Gwtr, and the external EGR amount Gexegr, and the line L4 represents the total in-cylinder gas amount Ggas_cyl, that is, the dry intake air amount Gair_dry, the water vapor amount Gwtr, and the external EGR amount. It represents the sum of Gexegr and internal EGR amount Ginegr.

  Here, the relationship between the state of the ideal line Lth and the line L4 when the intake pressure PB is a predetermined intake pressure PB1 that is smaller than the reference intake pressure PBwot at the reference point Pwot will be described.

この式（１４）のＴｉｃ＿ｔｈは、状態Ｐ１における筒内ガス温度（理想筒内ガス温度）である。 First, regarding the relationship between the state P1 in the ideal line Lth and the state P2 in the line L4, the following equation (14) is established from the gas state equation.

Tic_th in the equation (14) is the in-cylinder gas temperature (ideal in-cylinder gas temperature) in the state P1.

Further, in the state P2 on the line L4, the following equation (15) is established from the temperature equilibrium relationship in the cylinder 3a.

When the calculation formula for the internal EGR amount Ginegr is derived based on the above formulas (14) and (15), the following formula (16) is obtained.

  Here, as described above, since the ideal in-cylinder gas temperature is constant on the ideal line Lth, the ideal in-cylinder gas temperature Tic_th in the above equation (16) is used as a reference that is the in-cylinder gas temperature at the reference point Pwot. When the in-cylinder gas temperature Tic_std is substituted, the above-described equation (9) is derived.

  The calculation formulas for the reference in-cylinder gas temperature Tic_std and the reference in-cylinder gas amount Gstd are derived as follows. At the end of the exhaust stroke of the engine 3, when the piston 3b reaches the top dead center, a part of the combustion gas is not discharged from the cylinder 3a but remains in the combustion chamber between the piston 3b and the cylinder head. This residual combustion gas exists in the cylinder 3a together with the amount of intake air filled even in the reference state where the throttle valve 11a is fully open and the internal EGR amount is almost zero.

この式（１７）のＶｄは、ピストン３ｂが上死点にあるときの燃焼室の容積であり、Ｒは気体定数である。 The residual combustion gas amount Gegrd in this case can be expressed by the following equation (17) based on the gas state equation.

Vd in this equation (17) is the volume of the combustion chamber when the piston 3b is at top dead center, and R is a gas constant.

Further, the reference in-cylinder gas temperature Tic_std is calculated by the following equation (18) using the residual combustion gas amount Gegrd calculated by the above equation (17) from the equilibrium relationship of the temperature in the cylinder 3a in the reference state. It will be.

Further, since the reference in-cylinder gas amount Gstd is the sum of the intake air amount Gaircyl and the residual combustion gas amount Gegrd, it can be expressed by the following equation (19).

Therefore, from the relationship between the reference point Pwot and the state P1 on the ideal line Lth, the ideal in-cylinder gas amount Gth in the state P1 is the intake pressure PBhot at the reference point Pwot, the intake pressure PB1 at the state P1, and the reference in-cylinder gas amount Gstd. Is calculated by the following equation (20).

  In this equation (20), if the reference in-cylinder gas amount Gstd is replaced with the product Gstdm · KTW of the map value of the reference in-cylinder gas amount and the water temperature correction coefficient, and the intake pressure PB1 in the state P1 is replaced with the intake pressure PB at that time, As a calculation formula for the ideal in-cylinder gas amount Gth, the above-described formula (8) is derived.

Further, the in-cylinder gas temperature in the state P2 in FIG. 9, that is, the actual in-cylinder gas temperature Tic is calculated by the following equation (21) from the equilibrium relationship among the temperatures in the cylinder 3a by the intake air, the internal EGR, and the external EGR. Will be.

  By substituting Gaircyl = Gair_dry + Gwtr for this equation (21), the aforementioned equation (11) is derived as a calculation equation for the in-cylinder gas temperature Tic.

  Further, when the ideal in-cylinder gas temperature Tic_th in the above-described equation (14) is replaced with the reference in-cylinder gas temperature Tic_std and the in-cylinder gas amount Ggas_cyl is arranged on the left side, the above-described equation is obtained as a calculation equation for the in-cylinder gas amount Ggas_cyl. (12) is derived.

  Next, the ignition timing control process will be described with reference to FIG. This ignition timing control process calculates the ignition timing IGLOG as the ignition timing for each cylinder 3a, and is executed in synchronization with the generation of the TDC signal. The ignition timing IGLOG is calculated such that the crank angle at the TDC position in the compression stroke is 0, and the ignition angle IGLOG becomes a larger positive value as it is more advanced than the TDC position. Further, since the ignition timing control processing methods for the four cylinders 3a are the same as each other, the following description will be given by taking the ignition timing control processing method for one cylinder as an example.

  As shown in the figure, first, at step 50, an optimal ignition timing IGMBT is calculated by searching a map (not shown) according to the engine speed NE and the total EGR rate Regr_t. The optimum ignition timing IGMBT is an ignition timing corresponding to MBT (Minimum advance for Best Torque). In this map, the larger the total EGR rate Regr_t, the larger the value, that is, the more advanced value is set. .

  Next, the routine proceeds to step 51, where the knock limit ignition timing IGKNOCK is calculated. This knock limit ignition timing IGKNOCK is a value that defines the knock generation limit (that is, a value on the advance side that can suppress the occurrence of knocking), and a specific calculation method thereof is not shown here, but is described in Patent Document 1 It is calculated by the same method.

  Next, in step 52, it is determined whether or not the optimal ignition timing IGMBT is equal to or greater than the knock limit ignition timing IGKNOCK. When the determination result is YES, that is, when the optimal ignition timing IGMBT is set to the same value as the knock limit ignition timing IGKNOCK or an advance side thereof, the process proceeds to step 53 in order to avoid the occurrence of knocking. The basic ignition timing IGBASE is set to the knock limit ignition timing IGKNOCK.

  On the other hand, when the determination result of step 52 is NO, the process proceeds to step 54 in order to secure the maximum torque, and the basic ignition timing IGBASE is set to the optimum ignition timing IGMBT.

  In step 55 following the above step 53 or 54, the correction term IGCR is calculated according to the engine water temperature TW and the like.

  Next, the routine proceeds to step 56, where the ignition timing IGLOG is set to the sum IGBASE + IGCR of the basic ignition timing IGBASE and the correction term IGCR, and then this processing is terminated. As described above, when the ignition timing IGLOG is calculated, a control input signal is supplied from the ECU 2 to the ignition plug 9 at a timing corresponding to the ignition timing IGLOG, and the ignition plug 9 is discharged. Thereby, the air-fuel mixture is ignited.

  Next, the effect when the ignition timing control process of the present invention is executed under humid environmental conditions will be described with reference to FIGS. In both figures, the data indicated by shading is based on the control method of the present invention, and the data indicated by hatching is based on the conventional control method described in Patent Document 1.

  As is apparent from FIG. 11, in the case of the conventional control method, the ignition timing is controlled to be greatly retarded from the optimal ignition timing IGMBT by the influence of water vapor contained in a large amount in the intake air. Thus, in the case of the control method of the present invention, it can be seen that the ignition timing can be advanced to the optimum ignition timing IGMBT. As a result, good fuel efficiency can be ensured even under humid environmental conditions.

  In FIG. 12, the value SDM on the vertical axis is a parameter representing the degree of instability of combustion, and the greater the value SDM, the greater the degree of instability of combustion. In other words, the smaller the value SDM is, the higher the stability of combustion is. As is apparent from the figure, in the case of the control method of the present invention, the stability of combustion compared to the conventional control method. It can be seen that is improved. As a result, the occurrence of surges and misfires can be suppressed even under humid environmental conditions.

  As described above, according to the control device 1 of the present embodiment, the basic target EGR amount Gegr_bs is calculated according to the engine speed NE and the intake air amount Gaircyl, and the water vapor amount Gwtr is multiplied by the EGR conversion coefficient Rwtr2egr. Thus, the EGR converted amount Gegr_wtr is calculated, and the target EGR amount Gegr_cmd is calculated by subtracting the EGR converted amount Gegr_wtr from the basic target EGR amount Gegr_bs. In this case, since the water vapor in the intake air has the same function as the recirculation gas, that is, the function of lowering the combustion temperature, the EGR conversion amount Gegr_wtr appropriately converts the water vapor amount Gwtr having such a function into the EGR amount. Therefore, the target EGR amount Gegr_cmd can be calculated as a value that appropriately considers the influence of the same function as the recirculation gas by the water vapor in the intake air.

  Therefore, by controlling the EGR device 12, the variable intake cam phase mechanism 42, and the variable exhaust cam phase mechanism 52 using such a target EGR amount Gegr_cmd, the stability of combustion when the EGR control is executed is improved. be able to. In addition, as in Patent Document 1, the calculation load and the number of control steps can be reduced compared to the case where various control processes are executed using a target EGR amount that does not consider the function of reducing the combustion temperature due to water vapor. The merchantability can be further improved.

  In addition, water vapor in the intake air has a characteristic that the combustion temperature is lowered to a higher degree than the recirculation gas, and the EGR conversion coefficient Rwtr2egr is set to a value 1.3 that appropriately reflects the degree. Therefore, the EGR conversion amount Gegr_wtr can be calculated as a value obtained by appropriately converting the characteristics of such water vapor into the EGR amount, and the calculation accuracy can be improved.

  Further, by subtracting the water vapor amount Gwtr from the intake air amount Gaircyl, the dry intake air amount Gair_dry is calculated, and the total EGR rate Regr_t is calculated using the dry intake air amount Gair_dry, the water vapor amount Gwtr, and the EGR conversion amount Gegr_wtr. Therefore, the total EGR rate Regr_t can be calculated as a ratio of the gas in addition to EGR (external EGR and internal EGR) to which the same function as the water vapor reflux gas is added. Therefore, high control accuracy can be ensured by performing ignition timing control using such total EGR rate Regr_t. As a result, the ignition timing can be prevented from being excessively retarded, and good fuel efficiency can be ensured.

  In addition, the in-cylinder gas temperature Tic is calculated using the dry intake air amount Gair_dry and the water vapor amount Gwtr, and the in-cylinder gas amount Ggas_cyl is calculated using the in-cylinder gas temperature Tic. Since the total EGR rate Regr_t is calculated using the internal gas amount Ggas_cyl, the calculation accuracy of the total EGR rate Regr_t can be further improved. As a result, in the ignition timing control, high control accuracy can be ensured, and fuel consumption performance can be further improved.

  The embodiment is an example in which the water vapor amount Gwtr is used as the water vapor parameter, but the water vapor parameter of the present invention is not limited to this, and one of the proportion and amount of water vapor in the air sucked into the intake passage is used. Anything can be used. For example, the water vapor ratio Rwtr may be used as the water vapor parameter.

  The embodiment is an example in which the control means is configured to control the ignition timing IGLOG of the internal combustion engine 3 using the target EGR amount Gegr_cmd. However, the control means of the present invention is not limited thereto, and the target EGR is not limited thereto. What is necessary is just to control the operation of the internal combustion engine using the quantity. For example, the control means may be configured to execute air-fuel ratio control and fuel injection control of the internal combustion engine 3 using the target EGR amount Gegr_cmd.

  Further, the embodiment is an example in which the intake air amount Gaircyl is used as the intake air amount parameter. However, the intake air amount parameter of the present invention is not limited to this, and the amount of air sucked into the intake passage of the internal combustion engine. As long as it represents. For example, the ratio of the current intake air amount to the intake air amount when the throttle valve 11a is fully open may be used as the intake air amount parameter.

  On the other hand, the embodiment is an example in which the ignition timing control is executed as the ignition timing control in the internal combustion engine provided with the ignition plug. However, the ignition timing control of the present invention is not limited to this, and the ignition timing control is not limited thereto. Good. For example, in a compression ignition type internal combustion engine not provided with a spark plug, the ignition timing of the air-fuel mixture may be controlled.

  The embodiment is an example in which the dry intake air amount Gair_dry is used as the dry intake air parameter. However, the dry intake air parameter of the present invention is not limited to this, and the water vapor component is extracted from the air sucked into the intake passage. It only needs to represent one of the ratio and amount of dry intake air removed. For example, the value 1-Rwtr may be used as the dry intake air parameter.

  Further, the embodiment is an example in which the total EGR rate Regr_t is used as the total EGR rate, but the total EGR rate of the present invention is not limited to this, and may represent the rate of EGR in the total gas in the cylinder. That's fine. For example, the reciprocal of the total EGR rate Regr_t may be used as the total EGR rate.

  On the other hand, the embodiment is an example in which the total EGR rate Regr_t is calculated using the equation (13). Instead, the in-cylinder gas amount Ggas_cyl of the equation (13) is changed to the in-cylinder gas amount ratio ηc_thcl. The total EGR rate Regr_t is calculated using an equation in which the dry intake air amount Gair_dry is replaced with the dry air amount rate ηcair_dry, the water vapor amount Gwtr is replaced with the water vapor amount rate ηc_wtr, and the EGR converted amount Gegr_wtr is replaced with the EGR converted amount rate ηcegr_wtr. Also good. These ratios ηc_thcl, ηcair_dry, ηc_wtr, and ηcegr_wtr correspond to the ratios of the various gas amounts Ggas_cyl, Gair_dry, Gwtr, and Gegr_wtr to the reference in-cylinder gas amount Gstd.

  The embodiment is an example in which the value 1.3 is used as the EGR conversion coefficient Rwtr2egr. However, the EGR conversion coefficient of the present invention is not limited to this, and a predetermined value larger than the value 1 or the vicinity of the value 1.3. May be used (for example, values 1.2 to 1.4).

  Further, in the embodiment, the exhaust gas temperature sensor 27 is used to detect the exhaust gas temperature Tex, but instead, the exhaust gas temperature Tex may be estimated according to the operating state of the engine 3.

  On the other hand, in the embodiment, the exhaust pressure Pex is detected using the exhaust pressure sensor 28, but instead, the exhaust pressure Pex may be estimated according to the operating state of the engine 3.

  In addition, the embodiment is an example in which the control device of the present invention is applied to an internal combustion engine for a vehicle. However, the control device of the present invention is not limited to this, and is used for an internal combustion engine for ships or other industrial equipment. It can also be applied to an internal combustion engine.

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 ECU (water vapor | steam parameter acquisition means, basic target EGR amount calculation means, water vapor amount calculation means, EGR conversion amount calculation means, target EGR amount calculation means, control means)
3 Engine 6 Intake passage 7 Exhaust passage Gwtr Water vapor amount (water vapor parameter)
Rwtr2egr EGR conversion factor (conversion factor)
Gegr_wtr EGR conversion amount Gegr_bs Basic target EGR amount Gegr_cmd Target EGR amount

Claims (2)

A basic target EGR that calculates a basic target EGR amount that is a basis for a target value of an EGR amount that is an amount by which the exhaust gas in the exhaust passage of the internal combustion engine is recirculated to the intake side of the internal combustion engine according to the operating state of the internal combustion engine. A quantity calculating means;
Water vapor parameter acquisition means for acquiring a water vapor parameter representing one of a ratio and an amount of water vapor in the intake air, which is air sucked into the intake passage of the internal combustion engine;
Using the water vapor parameter, a water vapor amount calculating means for calculating a water vapor amount that is the amount of the water vapor,
EGR conversion amount calculation means for calculating an EGR conversion amount obtained by converting the water vapor amount into an EGR amount by multiplying the water vapor amount by a conversion coefficient greater than value 1,
A target EGR amount calculating means for calculating a target EGR amount by correcting the basic target EGR amount with the EGR conversion amount;
Control means for controlling the operation of the internal combustion engine using the target EGR amount;
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the conversion coefficient is set to a value in the vicinity of the value 1.3 including the value 1.3.

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