JP2009085227A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine which determines a target throttle opening based on target suction air quantity and can simply and more surely detect control abnormality. <P>SOLUTION: This invention provides the control device for the internal combustion engine which determines the target throttle opening based on the target suction air quantity mcta and detects control abnormality by comparing the target suction air quantity mcta and suction air quantity mcfm measured by an air flow meter. Control abnormality during processes of determination of the target throttle opening and control throttle opening and control of a throttle valve can be simply and more surely detected by such control device for the internal combustion engine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  An intake air amount (that is, a target intake air amount) is set corresponding to an accelerator depression amount that represents a request of the driver of the vehicle, and a target opening of the throttle valve (that is, a target throttle opening) is set based on the target intake air amount. And a control device for an internal combustion engine that controls the intake amount by controlling the opening of the throttle valve to be the target throttle opening is known (for example, see Patent Document 1).

JP-A-5-65845 JP 2001-41095 A

  In the control apparatus for an internal combustion engine as described above, it is preferable to determine whether or not a control abnormality has occurred in the setting of the target throttle opening based on the target intake air amount and the subsequent throttle valve opening control. As a method for determining the presence or absence of such control abnormality, the required throttle opening that can be determined from the accelerator depression amount and the engine speed is compared with the actual throttle opening measured by the throttle opening sensor. However, there are cases where the two throttle openings do not coincide with each other, and this method may not accurately determine whether or not there is a control abnormality.

  That is, for example, when an electronically controlled transmission is installed, or when a system that controls the engine output to stabilize the vehicle by preventing skidding or the like is installed, the target intake air amount is determined by the driver. Therefore, the required throttle opening and the target throttle opening do not always match, and as a result, the determined throttle opening and the engine speed are determined based on the operating state of the vehicle and the engine. Even if the control is normal, the required throttle opening may not match the actual throttle opening. Further, in the case of controlling the intake air amount by controlling the throttle opening and the valve opening characteristics (for example, lift amount) of the intake valve, the throttle opening that achieves the same target intake air amount by the valve opening characteristics of the intake valve Therefore, there is a case where the required throttle opening and the target throttle opening do not coincide with each other, and there is a case where the requested throttle opening and the actual throttle opening do not coincide with each other.

  The present invention has been made in view of the above points, and an object of the present invention is a control device for an internal combustion engine that determines a target throttle opening based on a target intake air amount. It is an object to provide a control device for an internal combustion engine that can be detected more reliably.

  The present invention provides a control device for an internal combustion engine described in each claim as a means for solving the above-mentioned problems.

  In a control apparatus for an internal combustion engine that determines a target throttle opening based on a target intake air amount, an internal combustion engine that detects a control abnormality by comparing the target intake air amount with an intake air amount measured by an air flow meter. An engine control device is provided.

  In the first aspect of the invention, a control abnormality is detected by comparing the target intake air amount with the intake air amount measured by the air flow meter. By doing so, it becomes possible to easily and more reliably detect the control abnormality in the process of determining the target throttle opening and controlling the throttle valve.

  A second aspect of the invention relates to a control device for an internal combustion engine that determines a target throttle opening based on a target intake air amount, and includes an intake air amount calculation formula that calculates an intake air amount based on an intake pipe pressure downstream of a throttle valve, Provided is a control device for an internal combustion engine that detects a control abnormality by comparing the target intake air amount with an intake air amount obtained from the intake air amount calculation formula using the intake pipe internal pressure measured by an intake pipe internal pressure sensor. .

  In the second aspect of the invention, a control abnormality is detected by comparing the target intake air amount with the intake air amount obtained using the intake pipe internal pressure measured by the intake pipe internal pressure sensor. This also makes it possible to easily and more reliably detect a control abnormality in the process of determining the target throttle opening and controlling the throttle valve.

In the third invention, in the first or second invention, at least one of the target intake air amount and the target throttle opening is based on a driving condition of at least one of the vehicle and the internal combustion engine in addition to a driver's request. To be determined.
The operating state of the internal combustion engine referred to here includes the opening characteristics of the intake valve or exhaust valve at that time.

  The invention described in each claim has a common effect that the control abnormality of the internal combustion engine that determines the target throttle opening degree based on the target intake air amount can detect the control abnormality easily and more reliably.

FIG. 1 is a schematic view showing an example in which the present invention is applied to a direct injection spark ignition type internal combustion engine. FIG. 2 is a diagram showing how the valve lift amount and the operating angle of the intake valve change as the valve lift amount changing device is operated. FIG. 3 is a diagram illustrating a state in which the opening / closing timing of the intake valve is shifted as the opening / closing timing shift device is operated. FIG. 4 is a diagram showing the relationship between the throttle opening and the flow coefficient. FIG. 5 is a diagram illustrating the function Φ (Pm / Pac). FIG. 6 is a diagram showing the basic concept of the throttle model. FIG. 7 is a diagram showing a basic concept of the intake pipe model. FIG. 8 is a diagram showing the basic concept of the intake valve model. FIG. 9 is a diagram relating to definitions of the in-cylinder charged air amount and the in-cylinder intake air flow rate. FIG. 10 is a flowchart showing a control routine of intake air amount control implemented in one embodiment of the present invention. FIG. 11 is a diagram related to step 101 of the control routine of FIG. 10 and shows the target intake air amount mcta. FIG. 12 is a diagram related to step 105 of the control routine of FIG. 10 and shows the target intake pipe pressure Pmta. FIG. 13 is a diagram related to step 107 of the control routine of FIG. FIG. 14 is a flowchart showing a control routine of control abnormality detection control in one embodiment of the present invention. FIG. 15 is a flowchart showing a control routine of control abnormality detection control in another embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or similar components are denoted by common reference numerals.

  FIG. 1 is a schematic view showing an example in which the present invention is applied to a direct injection spark ignition type internal combustion engine. The present invention may be applied to other spark ignition internal combustion engines and compression ignition internal combustion engines.

  In FIG. 1, reference numeral 1 denotes an internal combustion engine body, 2 an intake valve, 3 an intake port, 4 an exhaust valve, 5 an exhaust port, and 6 a combustion chamber formed in a cylinder 7. The intake port 3 of each cylinder is connected to a surge tank 9 via an intake pipe 8 on the downstream side, and the surge tank 9 is connected to an air cleaner 11 via an intake pipe 10 on the upstream side. A throttle valve 12 is disposed in the intake pipe 10. On the other hand, the exhaust port 5 of each cylinder is connected to an exhaust pipe 13.

  Reference numeral 14 denotes a valve lift amount changing device for changing the valve lift amount. That is, in this embodiment, the valve lift amount of the intake valve 2 can be controlled by operating the valve lift amount changing device 14.

  When the valve lift amount of the intake valve 2 is changed by operating the valve lift amount changing device 14, the opening area of the intake valve 2 is changed accordingly. In the intake valve 2 of the present embodiment, the opening area of the intake valve 2 increases as the valve lift amount increases. As will be described later, in this embodiment, when the valve lift amount of the intake valve 2 is changed by the valve lift amount changing device 14, the operating angle of the intake valve 2 is also changed accordingly.

  On the other hand, reference numeral 15 denotes an opening / closing timing shift device for shifting the opening / closing timing without changing the valve lift amount and the operating angle of the intake valve 2. That is, by operating the opening / closing timing shift device 15, the opening / closing timing of the intake valve 2 can be shifted to the advance side or the retard side, thereby adjusting the valve overlap amount, etc. It can be carried out.

  16 is a fuel injection valve, 17 is a spark plug, 18 is a valve opening characteristic sensor for detecting the valve lift amount and operating angle of the intake valve 2 and the opening / closing timing shift amount, and 19 is an engine for detecting the engine speed. It is a rotation speed sensor. 20 is an atmospheric pressure sensor for measuring the pressure of the atmosphere around the internal combustion engine, 21 is a cooling water temperature sensor for measuring the temperature of the cooling water for the internal combustion engine, and 22 is for measuring the temperature of the atmosphere around the internal combustion engine. This is an atmospheric temperature sensor. Reference numeral 23 denotes a throttle opening sensor for measuring the opening of the throttle valve 12, reference numeral 24 denotes an air flow meter, and reference numeral 25 denotes an intake pipe pressure sensor for measuring the pressure in the intake pipe on the downstream side of the throttle valve 12. A load sensor 26 connected to the accelerator pedal 27 generates an output proportional to the amount of depression of the accelerator pedal 27 (that is, the amount of depression of the accelerator). Reference numeral 28 denotes an ECU (electronic control unit). As shown in FIG. 1, the outputs of the above-described sensors are input here.

  In the present embodiment, the fuel injection valve 16 is connected to the ECU 28 and can control the amount of fuel to be injected and the injection timing by a signal from the ECU 28. Similarly, the spark plug 17 is also connected to the ECU 28, and the ignition timing can be controlled by a signal from the ECU 28. Further, the opening degree of the throttle valve 12 can be changed irrespective of the accelerator depression amount, and the pressure in the intake pipe on the downstream side of the throttle valve can be controlled by adjusting the throttle opening degree.

  FIG. 2 is a diagram showing how the valve lift amount of the intake valve 2 changes as the valve lift amount changing device 14 is operated. As shown in FIG. 2, the valve lift amount of the intake valve 2 is continuously changed by the valve lift amount changing device 14. Further, as described above, in the present embodiment, the working angle corresponding to the valve opening period of the intake valve 2 also changes as the valve lift amount changes. Specifically, as the valve lift amount of the intake valve 2 is increased, the operating angle of the intake valve 2 is increased (solid line → broken line → dashed line).

  Further, in the present embodiment, as the valve lift amount changing device 14 is operated, the timing at which the valve lift amount of the intake valve 2 peaks is also changed. More specifically, as shown in FIG. 2, as the valve lift amount of the intake valve 2 is increased, the timing at which the valve lift amount of the intake valve 2 peaks is retarded.

  FIG. 3 is a diagram showing how the opening / closing timing of the intake valve 2 is shifted as the opening / closing timing shift device 15 is operated. As shown in FIG. 3, the opening / closing timing of the intake valve 2 is continuously changed by the opening / closing timing shift device 15. At this time, the operating angle of the intake valve 2 is not changed.

  In the present embodiment, the amount of air sucked into the combustion chamber 6 of each cylinder is determined based on the valve opening characteristics (lift amount, operating angle, valve timing) of the intake valve 2 and the opening of the throttle valve 12 (more specifically, And the intake pipe pressure on the downstream side of the throttle valve). That is, the intake amount of the internal combustion engine can be controlled by cooperatively controlling the valve opening characteristic of the intake valve 2 and the opening degree of the throttle valve 12. In other embodiments, in addition to these, the intake air amount may be controlled by controlling the opening of an idle speed control valve (not shown).

  In recent years, it has been studied to model an intake system of an internal combustion engine based on fluid dynamics and the like and to control the internal combustion engine based on control parameters calculated using the model. That is, for example, for an intake system of an internal combustion engine, a throttle model, an intake pipe model, an intake valve model, etc. are constructed to obtain model expressions representing air passing through the intake system, and various models can be obtained by using these model expressions. Parameters necessary for control are calculated, and the internal combustion engine is controlled based on these parameters.

  Also in the present embodiment, in the configuration as shown in FIG. 1, the intake system is modeled as a throttle model, an intake pipe model, and an intake valve model. It is equipped. Hereinafter, each model and its model formula will be described.

First, the throttle model will be described. The throttle model is a model of a throttle valve. According to this, the throttle valve passing air flow rate mt (g / s) is expressed by the following equation (1). Here, Pac (kPa) is the intake pipe internal pressure upstream of the throttle valve 12 (hereinafter referred to as “upstream intake pipe internal pressure”), and is a value obtained in consideration of at least the pressure loss of the air cleaner 11. . Ta (K) is the atmospheric temperature, Pm (kPa) is the intake pipe pressure downstream of the throttle valve 12 (hereinafter referred to as “downstream intake pipe pressure”), and R is a gas constant. Further, μ is a flow coefficient in the throttle valve 12, which is a function of the throttle opening θt, and is determined from a map as shown in FIG. At (m ² ) represents the opening sectional area of the throttle valve (hereinafter referred to as “throttle opening area”), and is a function of the throttle opening θt. If μ · At, which summarizes the flow coefficient μ and the throttle opening area At, is a function F (θt) in which only the throttle opening θt is a variable, the equation (1) can be rewritten as the equation (2). it can. If the value of this function F (θt) is obtained by experiment or simulation and a map having θt as an argument is prepared in advance, the value of F (θt) is obtained from the throttle opening θt based on the map. be able to.

  Φ (Pm / Pac) is a function shown in the following equation (3), and κ in this equation (3) is a specific heat ratio (κ = Cp (isobaric specific heat) / Cv (isovolume specific heat), a constant value. ). Since this function Φ (Pm / Pac) can be expressed in a graph as shown in FIG. 5, such a graph is stored as a map in the ECU 28 and actually calculated using the equation (3). Instead, the value of Φ (Pm / Pac) may be obtained from the map.

  Equations (1) to (3), which are model equations of these throttle models, are: the gas pressure upstream of the throttle valve 12 is the upstream intake pipe pressure Pac, the gas temperature upstream of the throttle valve 12 is the atmospheric temperature Ta, and the throttle valve 6 is applied to the model of the throttle valve 12 as shown in FIG. 6 with the pressure of the gas passing through the downstream intake pipe pressure Pm, and further, It is obtained by using the equation of state, the specific heat ratio definition equation, and the Meyer relational equation.

  Here, the upstream side intake pipe pressure Pac, not the atmospheric pressure Pa, is used as the gas pressure upstream of the throttle valve 12 because the actual pressure upstream of the throttle valve 12 is upstream of the throttle valve in the engine intake system. This is because the pressure loss on the side is usually lower than the atmospheric pressure Pa during engine operation. In particular, in the configuration shown in FIG. 1, the air cleaner 11 is provided at the most upstream portion of the engine intake system. Therefore, in order to calculate the throttle valve passage air flow rate mt more accurately, at least the pressure loss of the air cleaner 11 is calculated. It is more preferable to use the upstream intake pipe pressure Pac determined in consideration of the above.

  Incidentally, the upstream side intake pipe pressure Pac may be measured by providing a pressure sensor immediately upstream of the throttle valve 12, but can also be calculated without using the pressure sensor. That is, the difference between the atmospheric pressure Pa and the upstream side intake pipe pressure Pac can be expressed by the following equation (4) by Bernoulli's theorem.

  Here, ρ is the atmospheric density, v is the flow velocity of air passing through the air cleaner 11, Ga is the flow rate of air passing through the air cleaner 11, and k is a proportional coefficient of v and Ga. If the standard atmospheric density ρ0 and the pressure correction coefficient ekpa and temperature correction coefficient ektha for converting the standard atmospheric density ρ0 to the current atmospheric density ρ are used, the equation (4) is rewritten as the following equation (5): be able to. Furthermore, the equation (5) can be rewritten as the following equation (6) using a function f (Ga) having only the flow rate Ga as a variable. Then, if the value of the function f (Ga) is obtained by experiment or simulation and a map having Ga as an argument is prepared in advance, the value of f (Ga) is obtained from the flow rate Ga based on the map. Can do.

  The expression (6) can be modified as the following expression (7) representing the upstream side intake pipe pressure Pac. In the equation (7), the flow rate Ga can be measured by the air flow meter 24 on the downstream side of the air cleaner 11. And the value of f (Ga) can be calculated | required from the map of f (Ga) mentioned above using the flow volume Ga. Further, the pressure correction coefficient ekpa can be set by the measured atmospheric pressure Pa, and the temperature correction coefficient ektha can be set by the measured atmospheric temperature Ta.

  In the equation (7), the flow rate Ga of the air passing through the air cleaner 11 can be considered as the throttle valve passing air flow rate mt, and the equation (7) can be modified as the following equation (8).

  Further, since the flow rate Ga is proportional to the engine speed NE and an in-cylinder air filling rate Kl described later, the equation (7) can be modified as the following equation (9) when j is a proportional coefficient. .

Next, the intake pipe model will be described. The intake pipe model is a model of a portion 8 ′ such as an intake pipe 8 (hereinafter referred to as “intake pipe portion”) from the throttle valve 12 to the intake valve 2, and according to this, the downstream side intake pipe pressure Pm Model equations such as the following equations (10) and (11) are obtained for (kPa) and the downstream side intake pipe temperature Tm (K). Here, mc (g / s) is the in-cylinder intake air flow rate, and Vm (m ³ ) is a constant equal to the volume of the intake pipe portion 8 ′.

  Here, the intake pipe model will be described with reference to FIG. When the total gas amount in the intake pipe portion 8 ′ is M, the temporal change in the total gas amount M is the flow rate of the gas flowing into the intake pipe portion 8 ′, that is, the air flow rate mt passing through the throttle valve, and the intake pipe portion 8 ′. Therefore, the following equation (12) is obtained from the law of conservation of mass, and this equation (12) and the equation of state of gas (Pm · Vm = M (10) is obtained from (R · Tm).

  The temporal change amount of the gas energy M · Cv · Tm in the intake pipe portion 8 ′ is the difference between the energy of the gas flowing into the intake pipe portion 8 ′ and the energy of the gas flowing out of the intake pipe portion 8 ′. equal. Therefore, if the temperature of the gas flowing into the intake pipe portion 8 ′ is the atmospheric temperature Ta and the temperature of the gas flowing out of the intake pipe portion 8 ′ is the downstream intake pipe temperature Tm, the following equation (13) is obtained according to the energy conservation law. From this equation (13) and the gas equation of state, equation (11) is obtained.

  Finally, the intake valve model will be described. The intake valve model is a model of the intake valve, and according to this, the in-cylinder intake air flow rate mc is expressed by a model expression such as the following expression (14). A and B in the equation (14) are compatible parameters determined based on at least the engine speed NE. A map is created in advance, and the map is searched for and obtained as necessary. In the present embodiment, as described above, the valve lift amount changing device 14 and the opening / closing timing shift device 15 are provided for the intake valve 2 so that the valve lift amount and the opening / closing timing of the intake valve 2 are opened. Since the characteristics can be changed, the adaptive parameters A and B are determined based on the setting state of the valve opening characteristics of the intake valve 2.

  The above intake valve model will be described with reference to FIG. In general, the cylinder charge air amount Mc, which is the amount of air charged in the combustion chamber 6 when the intake valve 2 is closed, is determined when the intake valve 2 is closed (when the intake valve is closed). It is proportional to the pressure in the combustion chamber 6 when the intake valve is closed. The pressure in the combustion chamber 6 when the intake valve is closed can be regarded as equal to the pressure of the gas upstream of the intake valve, that is, the downstream intake pipe pressure Pm. Therefore, the cylinder charge air amount Mc can be approximated as being proportional to the downstream side intake pipe pressure Pm.

  Here, the average amount of all the air flowing out from the intake pipe portion 8 ′ per unit time, or the amount of air taken into all the combustion chambers 6 from the intake pipe portion 8 ′ per unit time is equalized. If the cylinder intake air flow rate mc (detailed below) is averaged over the intake stroke of one cylinder, the cylinder charge air amount Mc is proportional to the downstream intake pipe pressure Pm. The intake air flow rate mc is also considered to be proportional to the downstream side intake pipe pressure Pm. From this, the above equation (14) is obtained based on the theory and empirical rules. Note that the conforming parameter A in the equation (14) is a proportionality coefficient, and the conforming parameter B is a value related to the amount of burnt gas remaining in the combustion chamber 6 when the exhaust valve is closed.

  Note that the conforming parameters A and B have two different values (for example, A1, B1, and A2, B2) that differ depending on whether the downstream side intake pipe pressure Pm is large or small even if the engine speed is the same. In other words, the in-cylinder intake air flow rate mc is expressed by the two expressions (14) (that is, the primary expression of the downstream intake pipe pressure Pm). It has been found that the intake air flow rate mc can sometimes be determined more accurately. This is considered to be related to the fact that the burned gas flows backward to the intake port 3 particularly when there is a period in which both the intake valve 2 and the exhaust valve 4 are open (that is, valve overlap). That is, when there is a valve overlap and the downstream side intake pipe pressure Pm is equal to or higher than a predetermined pressure, the higher the downstream side intake pipe pressure Pm, the more the backflow of burned gas decreases significantly. Compared to the time when A, the value of A is increased and the value of B is decreased.

  Here, the cylinder intake air flow rate mc will be described with reference to FIG. 9 when the internal combustion engine has four cylinders. In FIG. 9, the horizontal axis represents the rotation angle of the crankshaft, and the vertical axis represents the amount of air actually flowing into the combustion chamber 6 from the intake pipe portion 8 ′ per unit time. As shown in FIG. 9, in a four-cylinder internal combustion engine, the intake valve 2 is opened in the order of, for example, the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder, and the intake valve 2 corresponding to each cylinder is opened. Air flows from the intake pipe portion 8 'into the combustion chamber 6 of each cylinder according to the valve opening amount. The displacement of the flow rate of the air flowing into the combustion chamber 6 of each cylinder from the intake pipe portion 8 ′ is as shown by the broken line in FIG. 9, and the intake pipe portion 8 ′ that combines these changes into the combustion chamber 6 of all cylinders. The flow rate of the inflowing air is as shown by the solid line in FIG. Further, for example, the in-cylinder charged air amount Mc to the first cylinder corresponds to the hatched portion in FIG.

On the other hand, the in-cylinder intake air flow rate mc is obtained by averaging the amount of air flowing into the combustion chambers 6 of all the cylinders from the intake pipe portion 8 'indicated by the solid line, and is indicated by a one-dot chain line in the figure. Has been. In the cylinder intake air flow rate mc indicated by the one-dot chain line, in the case of four cylinders, the crankshaft is 180 ° (that is, the angle 720 ° at which the crankshaft rotates during one cycle in the four-stroke internal combustion engine) Multiplying the time ΔT _{180 °} required for rotation by the angle divided by the number is the in-cylinder charged air amount Mc. Accordingly, the cylinder intake air amount Mc can be calculated by multiplying the cylinder intake air flow rate mc calculated by the intake valve model by ΔT _{180 °} (Mc = mc · ΔT _{180 °} ). Further, the in-cylinder air filling rate Kl can be calculated by dividing the in-cylinder charged air amount Mc by the mass of air that occupies a volume corresponding to the displacement per cylinder in the state of 1 atm and 25 ° C. it can. Thus, the cylinder charge air amount Mc, the cylinder intake air flow rate mc, and the cylinder air charge rate Kl are proportional to each other, and if any one value is obtained, another value can be obtained. That is, these values can be converted into each other.

  In this specification, the intake air amount of the internal combustion engine is the amount of air taken into the combustion chambers of all the cylinders (in operation) of the internal combustion engine, and this is the above-mentioned in-cylinder charged air amount Mc. Any of the in-cylinder intake air flow rate mc and the in-cylinder air filling rate Kl can be used.

  By the way, in this embodiment, as described above, the valve opening characteristics (lift amount, operating angle, valve timing) of the intake valve 2 can be controlled by the valve lift amount changing device 14 and the opening / closing timing shift device 15. The downstream side intake pipe pressure can be controlled by the throttle valve 12. The intake amount is controlled by cooperatively controlling the valve opening characteristic and the opening of the throttle valve 12 (more specifically, the intake pipe pressure downstream of the throttle valve). That is, the throttle valve, the valve lift amount changing device 14 which is the valve opening characteristic control means, and the opening / closing timing shift device 15 cooperate to control the intake air amount. In the present embodiment, the control using each model formula described above is performed in the intake air amount control. The specific method will be described below with reference to the flowchart of FIG.

  FIG. 10 is a flowchart showing a control routine of intake air amount control implemented in the present embodiment. This control routine is executed by an interruption every predetermined time by the ECU 28, that is, every control cycle Ts.

  When the present control routine is started, first, at step 101, a target intake air amount mcta to be realized after elapse of time corresponding to the control cycle Ts is obtained. As described above, the intake air amount can be expressed by using any of the above-mentioned in-cylinder charged air amount Mc, in-cylinder intake air flow rate mc, and in-cylinder air filling rate Kl. This is expressed using the internal intake air flow rate mc. Therefore, the target intake air amount mcta is more specifically the in-cylinder intake air flow rate mc to be realized after the passage of time corresponding to the control cycle Ts.

  For this target intake air amount mcta, a map in which the required torque TQr is associated with the accelerator depression amount L and the engine speed NE representing the driver's request, and a map in which the target intake air amount mcta is associated with the required torque TQr in advance. Although it may be prepared and obtained based on these maps, in the present embodiment, it is obtained as follows.

  That is, in the present embodiment, the throttle opening, that is, the valve opening characteristic when the valve opening characteristic is set to a predetermined reference state from the accelerator depression amount L and the engine speed NE is determined in advance. If the vehicle is set to the reference state, a map for obtaining the throttle opening (requested throttle opening) θtb requested by the vehicle driver by depressing the accelerator is created in advance and stored in the ECU 28. ing. Here, the reference state can be, for example, a standard valve lift amount and working angle in a normal engine that does not have the valve lift amount changing device 14 or the opening / closing timing shift device 15, and an opening / closing timing.

  First, based on the map for obtaining the required throttle opening degree θtb, the required throttle opening degree θtb is obtained from the accelerator depression amount L and the engine speed NE. Based on the required throttle opening θtb, the model equation (Equation (2)) of the throttle model described above is determined (Equation (15) below).

  On the other hand, if the valve opening characteristic is set to a predetermined reference state, the conforming parameters A and B of the above-described intake valve model model equation (Equation (14)) are determined from the engine speed NE and the like. A model formula is defined. If the conforming parameters A and B are determined as Ab and Bb, the following equation (16) is obtained.

  The state where the intake air amount becomes the target intake air amount is a convergence state, and at that time, the throttle valve passing air flow rate mt and the cylinder intake air flow rate mc are equal. Therefore, the throttle valve passing air flow rate mtb obtained from the throttle model model equation (Equation (15)) determined as described above, and the intake valve model model equation (Equation (16)) determined as described above. If the in-cylinder intake air flow rate mcb obtained when the in-cylinder intake air flow rate mcb is equal to the same downstream intake pipe pressure Pm is obtained, it is the target intake air amount mcta.

  Then, the target intake air amount mcta is obtained as described above, as illustrated in FIG. 11, with the curve mtb represented by the model equation (the equation (15)) of the throttle model defined as described above. This is synonymous with obtaining the intersection point EPb with the straight line mcb represented by the model equation (equation (16)) of the intake valve model determined as described above, and obtaining the coordinate of the vertical axis. Here, when obtaining the intersection point EPb, if the equation ((15)) representing the curve mtb is used as it is to obtain the intersection point EPb, the calculation becomes very complicated. Therefore, in order to simplify the calculation, the expression (the expression (15)) representing the curve mtb may be approximated by a linear expression of a plurality of downstream side intake pipe pressures Pm. That is, the curve mtb is approximated by a plurality of straight lines. Specifically, for example, the throttle valve passing air flow rate mtb is calculated based on the equation (Equation (15)) representing the curve mtb at regular intervals of the downstream side intake pipe pressure Pm, and the downstream side intake pipe pressure Pm is constant. A point on the curve mtb for each interval is obtained, and each straight line connecting these two adjacent points is obtained as an approximate straight line of the curve mtb. A linear expression representing each of these approximate straight lines is an approximate primary expression of an expression (formula (15)) representing the curve mtb.

  By the way, the approximation of the equation representing the curve mtb to the linear equation is for easily obtaining the intersection point EPb, and therefore, an approximation linear equation in the vicinity of the intersection point EPb is required. Therefore, only this approximate linear expression may be obtained. In this case, the in-cylinder intake air flow rate mcb is also obtained based on the equation (Equation (16)) representing the straight line mcb at regular intervals of the downstream side intake pipe pressure Pm, and the throttle valve passing air flow rate mtb and the in-cylinder intake are determined. By obtaining a place where the magnitude of the air flow rate mcb is reversed, the position of the intersection point EPb can be specified.

  That is, the approximate linear expression in the vicinity of the intersection point EPb (that is, the portion where the magnitude of the throttle valve passage air flow rate mtb and the in-cylinder intake air flow rate mcb is reversed) is, for example, two points on the curve mtb and passes through the throttle valve. It is a linear expression representing a straight line connecting two points before and after the magnitude of the air flow rate mtb and the in-cylinder intake air flow rate mcb are reversed.

  As can be understood from the above description, the standard state is the standard valve lift amount and operating angle, and opening / closing timing in a normal engine that does not have the valve lift amount changing device 14 or the opening / closing timing shift device 15. As described above, when the target intake air amount mcta is obtained by the above-described method, the same intake air amount as that intended or requested by the driver with the accelerator depression amount Lc and the engine speed NEc in the case of a normal engine is the same in this embodiment. It can be obtained as the target intake air amount mcta with respect to the accelerator depression amount Lc and the engine speed NEc.

  When the target intake air amount mcta is obtained in step 101, in the subsequent step 103, the target valve opening characteristic Cvta of the intake valve 2, that is, the target lift amount Ltta and the target operating angle Sata, and the target opening / closing timing shift amount (that is, the reference Vtta, which is the amount of delay or advance from the opening / closing timing and the displacement angle by the opening / closing timing shift device. As is clear from the above description, in the present embodiment, the lift amount Lt and the operating angle Sa have a certain relationship, and if the operating angle Sa is determined, the lift amount Lt is also determined, so the target lift amount Ltta and the target When determining the operating angle Sata, the target operating angle Sata is actually determined using a map.

  More specifically, in step 103, the target operating angle Sata and the target opening / closing timing shift amount Vtta are combined with conditions such as fuel consumption, emission, torque fluctuation, etc. with respect to the engine speed NE, the target intake air amount mcta, and the like. Is determined on the basis of a map created so as to obtain the optimum working angle Sa and opening / closing timing shift amount Vt. Such a map is obtained in advance by experiments or the like and stored in the ECU 28.

  When the target valve opening characteristic Cvta is determined in step 103, in the subsequent step 105, the target intake pipe pressure Pmta is obtained. This target intake pipe pressure Pmta is the intake pipe pressure Pm on the downstream side of the throttle valve that realizes the target intake air amount mcta when the valve opening characteristic Cv of the intake valve 2 is set to the target valve opening characteristic Cvta.

  In the present embodiment, the target intake pipe pressure Pmta is obtained as follows using the model equation (equation (14)) of the intake valve model described above. That is, first, assuming that the valve opening characteristic Cv is set to the target valve opening characteristic Cvta, the adaptation parameters A and B of the model equation (equation (14)) of the intake valve model described above are determined from the engine speed NE and the like. The model formula is determined. That is, assuming that the adaptation parameters A and B are set to Af and Bf, the following equation (17) is obtained.

  Since the target intake pipe pressure Pmta is the downstream intake pipe pressure Pm that realizes the target intake air amount mcta in the equation (17), it is expressed as the following equation (18) based on the equation (17). Can do.

  When the straight line mcf represented by the model equation (equation (17)) of the intake valve model and the target intake pipe pressure Pmta when the valve opening characteristic Cv is set to the target valve opening characteristic Cvta, for example, As shown in FIG.

  When the target intake pipe pressure Pmta is obtained in step 105, in the following step 107, the target throttle opening θtta is obtained. The target throttle opening degree θtta is a throttle opening degree θt that sets the downstream side intake pipe pressure Pm to the target intake pipe pressure Pmta. In the present embodiment, the target throttle opening degree θtta is obtained as follows using the model equation (equation (2)) of the throttle model described above.

  That is, when the throttle opening θt is set to the target throttle opening θtta, the downstream intake pipe pressure Pm converges to the target intake pipe pressure Pmta, and the throttle valve passing air flow rate mt converges to the target intake air amount mcta. Therefore, the following equation (19) is established.

  The equation (19) can be transformed as the following equation (20).

  Since the left side of the equation (20) is a function of only the throttle opening θt, the target throttle opening θtta is obtained based on the equation (20) by calculating the value on the right side of the equation (20). be able to. That is, for example, by using the map for obtaining the value of F (θt) from the throttle opening θt described above, the target throttle opening θtta is obtained using the value on the right side of the calculated equation (20). it can.

  The above equation (20) can be rewritten as the following equation (21) using the above equations (8) and (18).

  Further, the following equation (22) is obtained by substituting the target throttle opening θtta obtained as described above into the above equation (2). Then, when the curve of the throttle passage air flow rate mtf represented by the equation (22) is illustrated, the curve passes through the point EPf (Pmta, mcta) as shown in FIG.

  When the target throttle opening degree θtta is obtained in step 107, in the subsequent step 109, the valve lift amount changing device 14 and the opening / closing timing shift device 15 are set so that the valve opening characteristic Cv of the intake valve 2 becomes the target valve opening characteristic Cvta. In addition, the throttle valve 12 is controlled so that the throttle opening θt becomes the target throttle opening θtta. Thus, the intake air amount is controlled to become the target intake air amount mcta. When step 109 is completed, the process returns to step 101 and the same control is repeated.

  From the above description, in the present embodiment, the target throttle opening degree θtta is finally determined based on the target intake air amount mcta, and the throttle valve 12 is controlled so that the throttle valve opening degree θt becomes the target throttle opening degree θtta. It can be said that the intake air amount is controlled. In such a case, it is preferable to detect a control abnormality in the process of determining the target throttle opening θtta and controlling the throttle valve.

  As a method for detecting such a control abnormality, generally, a required throttle opening that can be determined from an accelerator depression amount and an engine speed representing a driver's request, and an actual throttle measured by a throttle opening sensor. Although it is conceivable to compare the opening with the opening, in reality, these two throttle openings may not match even if the control is normal. With this method, it is not possible to determine whether there is a control abnormality. That is, there is a case where a control abnormality cannot be accurately detected.

  That is, when the intake air amount is controlled by controlling the throttle opening and the valve opening characteristic of the intake valve as in the present embodiment, the throttle opening that achieves the same target intake air amount by the valve opening characteristic of the intake valve is Therefore, as described above, the required throttle opening θtb and the target throttle opening θtta may not coincide with each other. Even if the control is normal, the required throttle opening θtb and the actual throttle opening Therefore, the above method cannot accurately detect a control abnormality.

  In other cases, for example, an electronically controlled transmission is installed, or a system that controls the engine output to stabilize the vehicle by preventing skidding or the like is considered. . That is, in these cases, since the target intake air amount is determined based on the accelerator depression amount and the engine speed representing the driver's request as well as the operating state of the vehicle and the engine, The target throttle opening does not necessarily match, and as a result, the requested throttle opening and the actual throttle opening may not match even if the control is normal.

  In the present embodiment, in view of the above points, the control abnormality is detected by the method described below. That is, in the present embodiment, in order to detect the control abnormality, the control shown in the control routine of FIG. 14 is performed in parallel with the intake air amount control described above with reference to FIG.

  The control routine of FIG. 14 starts when the target intake air amount mcta is obtained in step 101 of the intake air amount control described with reference to FIG. 10, and in step 201 which is the first step, the target intake air amount mcta is captured. Is done. When the target intake air amount mcta is taken in at step 201, it is determined at step 203 whether or not the control of the opening degree θt of the throttle valve 12 has been performed.

  This determination is to determine whether or not the control in step 109 of the intake air amount control described with reference to FIG. 10 has been performed. For example, whether or not a signal for the current opening degree control is transmitted Or whether or not a predetermined time has elapsed since the signal was transmitted.

  If it is determined in step 203 that the control of the opening degree θt of the throttle valve 12 has been performed, the process proceeds to step 205, and if it is determined that the control of the opening degree θt of the throttle valve 12 has not yet been performed. The control in step 203 is performed again. That is, here, after the opening degree control of the throttle valve 12 is performed, the routine proceeds to step 205.

  In the subsequent step 205, the air flow meter 24 measures the intake air amount (that is, the measured intake air amount) mcfm. When the measured intake air amount mcfm is obtained in step 205, the process proceeds to step 207, where the target intake air amount mcta and the measured intake air amount mcfm are compared. More specifically, in the present embodiment, in step 207, is the magnitude of the difference between the target intake air amount mcta and the measured intake air amount mcfm (| mcta−mcfm |) equal to or smaller than a predetermined tolerance α. (That is, it can be said here that the target intake air amount mcta and the measured intake air amount mcfm are compared and the degree of coincidence thereof is determined).

  If it is determined in step 207 that the magnitude of the intake air amount difference (| mcta-mcfm |) is equal to or smaller than the tolerance α, the routine proceeds to step 209 where normality is determined, and the current control is performed. finish. On the other hand, when it is determined that the magnitude of the intake air amount difference (| mcta-mcfm |) is larger than the tolerance α, the routine proceeds to step 211 where an abnormality is determined and the current control is terminated. .

  As described above, in the present embodiment, a control abnormality is detected by comparing the target intake air amount mcta with the intake air amount mcfm measured by the air flow meter 24. By doing so, it is possible to more reliably detect a control abnormality in the process of determining the target throttle opening θtta and controlling the throttle valve by a simple method.

  Next, another embodiment of the present invention will be described. This embodiment can be implemented with the configuration shown in FIG. 1 and has many parts in common with the above-described embodiment. In principle, description of these common parts is omitted.

  In the present embodiment, in order to detect the control abnormality, the control shown in the control routine of FIG. 15 is performed in parallel with the intake air amount control described with reference to FIG. The control routine of FIG. 15 starts when the target intake air amount mcta is obtained in step 101 of the intake air amount control described with reference to FIG. 10, as in the control routine of FIG. The control in step 301, which is the first step of this control routine, and the control in step 303, which is subsequent thereto, are the same as those in step 201 and step 203 of the control routine of FIG.

  When the control proceeds to step 305, the intake pipe pressure sensor 24 measures the intake pipe pressure (that is, measured intake pipe pressure) Pmth downstream of the throttle valve. When the measured intake pipe pressure Pmth is obtained in step 305, the process proceeds to step 306, and the intake air amount (that is, the calculated intake air amount) mcth based on the model equation of the intake valve model described above using the measured intake pipe internal pressure Pmth. Is calculated.

  In this case, since it is considered that the valve opening characteristic Cv of the intake valve 2 is set to the target valve opening characteristic Cvta, the adaptation parameters A and B are used in the above-described Af and Bf (the above equation (17)). ). That is, here, the calculated intake air amount mcth is calculated by the following equation (23).

  When the calculated intake air amount mcth is obtained in step 306, the process proceeds to step 307, where the target intake air amount mcta and the calculated intake air amount mcth are compared. More specifically, in this embodiment, in step 307, is the magnitude of the difference between the target intake air amount mcta and the calculated intake air amount mcth (| mcta−mcth |) equal to or less than a predetermined tolerance β? Whether the target intake air amount mcta and the calculated intake air amount mcth are compared and the degree of coincidence thereof is determined is determined.

  In step 307, when it is determined that the magnitude of the intake air amount difference (| mcta-mcth |) is equal to or less than the tolerance β, the routine proceeds to step 309, where the normal determination is made, and the current control is performed. finish. On the other hand, if it is determined that the magnitude of the intake air amount difference (| mcta-mcth |) is larger than the tolerance β, the routine proceeds to step 311 where an abnormality is determined and the current control is terminated. .

  As described above, in the present embodiment, a control abnormality is detected by comparing the target intake air amount mcta with the intake air amount mcth calculated using the intake pipe internal pressure Pmth measured by the intake pipe internal pressure sensor 25. It has become. Also in this way, it becomes possible to easily and more reliably detect a control abnormality in the process of determining the target throttle opening degree θtta and controlling the throttle valve.

  In the above description, the case where only the valve opening characteristic of the intake valve 2 is changed by the valve lift amount changing device 14 and the opening / closing timing shift device 15 and the valve opening characteristic of the exhaust valve 4 is not changed has been described as an example. However, the present invention is not limited to this. Even if the present invention is applied to the case where the valve opening characteristic of the exhaust valve 4 can be changed by providing a valve lift amount changing device and an opening / closing timing shift device for the exhaust valve, The control abnormality can be detected in the same manner as in the embodiment.

  In the above, the case where the intake air amount is controlled by cooperative control of the throttle valve 12 and the variable valve mechanism such as the valve lift amount changing device 14 and the opening / closing timing shift device 15 has been described as an example. It is not limited. That is, the present invention is also applicable to the case where the throttle valve and intake variable means other than the variable valve mechanism, such as a cylinder variable mechanism or an exhaust variable mechanism, cooperate to control the intake amount. Even in such a case, the control abnormality can be detected in the same manner as in the above-described embodiment.

  Further, as is clear from the above description, the control for determining the target throttle opening based on the target intake air amount is performed, and the electronically controlled transmission described above is mounted or the skid If the present invention is applied to a case where a system for controlling the output of the engine is installed to prevent the vehicle from becoming unstable, the target throttle opening θtta can be determined as in the case of the above-described embodiment. It is possible to easily and more reliably detect a control abnormality in the process of controlling the throttle valve.

1 Internal combustion engine body 2 Intake valve 3 Intake port 4 Exhaust valve 5 Exhaust port 6 Combustion chamber 7 Cylinder
DESCRIPTION OF SYMBOLS 9 Surge tank 11 Air cleaner 12 Throttle valve 14 Valve lift amount changing device 15 Opening / closing timing shift device 18 Valve opening characteristic sensor 24 Air flow meter 25 Intake pipe pressure sensor 28 ECU (electronic control unit)

Claims (3)

  A control device for an internal combustion engine that detects a control abnormality by comparing the target intake air amount with an intake air amount measured by an air flow meter in a control device for an internal combustion engine that determines a target throttle opening based on a target intake air amount.   In a control apparatus for an internal combustion engine that determines a target throttle opening based on a target intake air amount, an intake air amount calculating expression for obtaining an intake air amount based on an intake pipe pressure on the downstream side of the throttle valve is provided, and the target intake air amount, A control device for an internal combustion engine that detects a control abnormality by comparing the intake air amount obtained from the intake air amount calculation formula using the intake pipe internal pressure measured by an intake pipe internal pressure sensor.   3. The internal combustion engine according to claim 1, wherein at least one of the target intake air amount and the target throttle opening is determined based on an operation state of at least one of the vehicle and the internal combustion engine in addition to a driver's request. Control device.

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