JP2008144641A - Atmospheric pressure estimation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an atmospheric pressure estimation device capable of accurately estimating atmospheric pressure based on pressure in an intake pipe. <P>SOLUTION: This device is provided with a pressure sensor 40 detecting pressure in the intake pipe in a downstream of a throttle valve, and an atmospheric pressure estimation model for estimating atmospheric pressure based on pressure in the intake pipe in the downstream of the throttle valve, and estimates atmospheric pressure by inputting pressure in the intake pipe detected by the pressure sensor into the atmospheric pressure estimation model. Ratio of pressure in the intake pipe to atmospheric pressure is calculated in estimation of atmospheric pressure and atmospheric pressure is estimated only when the ratio of pressure in the intake pipe to atmospheric pressure is predetermined ratio or higher in the atmospheric pressure estimation model. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an atmospheric pressure estimation device.

  In general, the internal combustion engine is controlled so as to be optimal under each operating condition for each operating condition. Specifically, operating parameters such as engine load and engine speed are detected or estimated, and the fuel injection amount, ignition timing, etc. are set using maps and mathematical formulas created in advance based on the values of these operating parameters. Is done.

  One such operating parameter is atmospheric pressure, and some internal combustion engines have an atmospheric pressure sensor for detecting atmospheric pressure, and internal combustion based on the atmospheric pressure detected by the atmospheric pressure sensor for optimal control. The engine is controlled.

  However, if an atmospheric pressure sensor is used to detect atmospheric pressure, the manufacturing cost of the internal combustion engine will increase. Therefore, in Patent Document 1, since many internal combustion engines have an intake pipe pressure sensor that detects an intake pipe pressure downstream of the throttle valve (especially, an intake pressure in a surge tank), the engine is started instead of using an atmospheric pressure sensor. Sometimes the intake pipe pressure detected by the intake pipe pressure sensor is approximated to the atmospheric pressure, and the internal combustion engine is controlled based on the approximated atmospheric pressure.

JP-A-5-1615 JP 2002-161799 A

  However, the atmospheric pressure around the vehicle on which the internal combustion engine is mounted is not constant from the start to the stop of the internal combustion engine, and changes, for example, when the vehicle climbs up or down a slope. For this reason, when the internal combustion engine is controlled using the atmospheric pressure at the time of starting the engine from the start to the stop of the internal combustion engine as in the control device described in Patent Document 1, the actual high pressure around the internal combustion engine is determined. The atmospheric pressure and the atmospheric pressure used for controlling the internal combustion engine may have different values. In this case, the internal combustion engine cannot be appropriately controlled.

  Further, for example, Patent Document 2 discloses a throttle model for calculating a throttle valve passage air flow rate mt based on the atmospheric pressure Pa and the intake pipe pressure Pm downstream of the throttle valve. The model model of this throttle model is modified. The atmospheric pressure Pa can be calculated based on the intake pipe pressure Pm and the throttle valve passage air flow rate mt (for example, detected by an air flow meter).

  However, even if the model formula of the throttle model is modified and used for calculating the atmospheric pressure, when a modeling error occurs in the throttle model, for example, when an error occurs in the flow coefficient μ, etc. May not be able to accurately calculate the atmospheric pressure Pa, and therefore may not be able to properly control the internal combustion engine.

  In view of the above, an object of the present invention is to provide an atmospheric pressure estimation device capable of accurately estimating the atmospheric pressure based on the intake pipe pressure.

In order to solve the above-described problem, the first invention includes a pressure sensor that detects the pressure in the intake pipe downstream of the throttle valve, and an atmospheric pressure estimation model that estimates the atmospheric pressure based on the pressure in the intake pipe downstream of the throttle valve. In the atmospheric pressure estimation device that estimates the atmospheric pressure by inputting the pressure in the intake pipe detected by the pressure sensor into the atmospheric pressure estimation model, the atmospheric pressure estimation model estimates the pressure in the intake pipe relative to the atmospheric pressure when estimating the atmospheric pressure. The ratio is calculated, and the atmospheric pressure is estimated only when the ratio of the pressure in the intake pipe to the atmospheric pressure is equal to or greater than a predetermined ratio.
In estimating the atmospheric pressure, the influence of the modeling error in the atmospheric pressure estimation model is smaller as the ratio of the pressure in the intake pipe to the atmospheric pressure is larger. According to the first aspect, since the atmospheric pressure is estimated only when the ratio of the pressure in the intake pipe to the atmospheric pressure is equal to or higher than the predetermined ratio, the influence of the modeling error is small and accurate in estimating the atmospheric pressure. Atmospheric pressure can be estimated.

  According to a second invention, in the first invention, there is further provided a throttle valve passing air flow rate detecting means for detecting a flow rate of air passing through the throttle valve, and the atmospheric pressure estimation model is configured to adjust the intake pipe pressure downstream of the throttle valve. In addition, the atmospheric pressure is estimated based on the flow rate of air passing through the throttle valve.

  According to a third invention, in the first invention, the atmospheric pressure estimation model includes an air model capable of outputting a ratio of the pressure in the intake pipe to the atmospheric pressure when the atmospheric pressure is inputted, and an arbitrary atmospheric pressure is inputted to the air model. Thus, the ratio of the intake pipe internal pressure to the atmospheric pressure is calculated, and the actual atmospheric pressure is estimated based on the calculated ratio and the intake pipe internal pressure downstream of the throttle valve detected by the pressure sensor.

  According to a fourth aspect, in the third aspect, the air model includes a throttle model that outputs a throttle valve passage air flow rate when a throttle opening, an intake pipe pressure and an atmospheric pressure are input, a throttle valve passage air flow rate, and a cylinder intake. An intake pipe model that outputs the pressure in the intake pipe when the air flow rate is input and an intake valve model that outputs the in-cylinder intake air flow rate when the intake pipe pressure is input, and the atmospheric pressure and the intake pipe model input to the throttle model The ratio of the intake pipe internal pressure to the atmospheric pressure is calculated based on the intake pipe internal pressure output by.

  According to the present invention, the atmospheric pressure can be accurately estimated based on the intake pipe pressure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an internal combustion engine in which the atmospheric pressure estimation device of the present invention is used. Although FIG. 1 shows an in-cylinder injection type spark ignition type internal combustion engine, the atmospheric pressure estimation device of the present invention can be used for another spark ignition type internal combustion engine or a compression self-ignition type internal combustion engine.

  As shown in FIG. 1, the engine body 1 includes a cylinder block 2, a piston 3 that reciprocates within the cylinder block 2, and a cylinder head 4 fixed on the cylinder block 2. A combustion chamber 5 is formed between the piston 3 and the cylinder head 4. In the cylinder head 4, an intake valve 6, an intake port 7, an exhaust valve 8, and an exhaust port 9 are arranged for each cylinder. Further, as shown in FIG. 1, a spark plug 10 is disposed at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is disposed around the inner wall surface of the cylinder head 4. A cavity 12 extending from the lower side of the fuel injection valve 11 to the lower side of the spark plug 10 is formed on the top surface of the piston 3.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a downstream intake pipe 13, and the surge tank 14 is connected to an air cleaner 16 via an upstream intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed in the intake pipe 15. On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected to an exhaust purification catalyst (such as a three-way catalyst) 20. In the following description, the passage defined by the upstream intake pipe 15, the surge tank 14, and the downstream intake pipe 13 between the throttle valve 18 and the intake valve 6 is referred to as an intake passage portion.

  The electronic control unit (ECU) 31 comprises a digital computer, and is connected to each other via a bidirectional bus 32, a RAM (random access memory) 33, a ROM (read only memory) 34, a CPU (microprocessor) 35, an input. A port 36 and an output port 37 are provided. The surge tank 14 is provided with an intake pipe pressure sensor 40 for detecting the pressure of the air in the surge tank 14 (or the air in the intake pipe portion), and the intake pipe pressure sensor 40 is proportional to the intake pipe pressure. The output voltage is generated, and this output voltage is input to the input port 36 via the corresponding AD converter 38. Further, an air flow meter 41 for detecting the flow rate of air flowing in the upstream side intake pipe 15 is provided in the upstream side intake pipe 15 upstream of the throttle valve 18, and similarly, an AD conversion corresponding to the output voltage is provided. It is input to the input port 36 through the device 38.

  In addition, a throttle opening sensor 43 for detecting the opening of the throttle valve 18 and a large temperature for detecting the temperature of the atmosphere around the internal combustion engine or the temperature of the air taken into the intake pipe 15 (intake air temperature). The temperature sensor 44 is provided, and the output voltage of these sensors is input to the input port 36 via the corresponding AD converter 38. A load sensor 46 that generates an output voltage proportional to the amount of depression of the accelerator pedal 45 is connected to the accelerator pedal 45, and the output voltage of the load sensor 46 is input to the input port 36 via the corresponding AD converter 38. The For example, the crank angle sensor 47 generates an output pulse every time the crankshaft rotates 30 degrees, and this output pulse is input to the input port 36. The CPU 35 calculates the engine speed from the output pulse of the crank angle sensor 47. On the other hand, the output port 37 is connected to the spark plug 10, the fuel injection valve 11, and the step motor 17 via a corresponding drive circuit 39.

  By the way, in the internal combustion engine, in order to set the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 5 of the internal combustion engine to the target air-fuel ratio, the amount of air filled in the combustion chamber 5 when the intake valve is closed ( (Hereinafter referred to as “cylinder charged air amount Mc”), and combustion of the internal combustion engine is performed by the fuel injection valve so that the air-fuel ratio of the mixture becomes the target air-fuel ratio based on the estimated cylinder charged air amount Mc. The amount of fuel injected into the chamber 5 (or intake passage) (hereinafter referred to as “fuel injection amount”) is determined. Therefore, in order to accurately set the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber 5 of the internal combustion engine to the target air-fuel ratio, it is necessary to accurately estimate the cylinder charge air amount Mc.

  Therefore, in the internal combustion engine of the present embodiment, the in-cylinder charged air amount Mc is calculated by the air model M10 shown in FIG. Hereinafter, the air model M10 will be described.

  As shown in FIG. 2, the air model M10 includes a throttle model M11, an intake pipe model M12, and an intake valve model M13. In the throttle model M11, the opening (throttle opening) θt of the throttle valve 18 detected by the throttle opening sensor 43 and the atmospheric temperature around the internal combustion engine detected by the atmospheric temperature sensor 44 (or in the intake pipe 15). The pressure of the intake air (Ta), the atmospheric temperature Pa around the internal combustion engine, and the pressure (intake pipe pressure) Pm in the intake passage portion calculated in the intake pipe model M12 described later are input. By substituting the value of each parameter into a model equation of a throttle model M11 described later, the flow rate of air passing through the throttle valve 18 per unit time (hereinafter referred to as “throttle valve passing air flow rate mt”) is calculated. . The throttle valve passage air flow rate mt calculated in the throttle model M11 is input to the intake pipe model M12.

  The intake pipe model M12 includes a throttle valve passage air flow rate mt calculated in the throttle model M11 and a flow rate of air flowing into the combustion chamber 5 per unit time described in detail below (hereinafter referred to as “cylinder intake air flow rate”). The definition of the in-cylinder intake air flow rate mc will be described in detail in the intake valve model M13), and the values of these input parameters are model equations of the intake pipe model M12 described later. By substituting into, the pressure of the air in the intake pipe portion (hereinafter referred to as “intake pipe pressure Pm”) and the temperature of the air in the intake pipe portion (hereinafter referred to as “intake pipe temperature Tm”) are calculated. Is done. The intake pipe internal pressure Pm and the intake pipe internal temperature Tm calculated in the intake pipe model M12 are both input to the intake valve model M13, and the intake pipe internal pressure Pm is also input to the throttle model M11.

  In addition to the intake pipe pressure Pm and the intake pipe temperature Tm calculated in the intake pipe model M12, the atmospheric temperature Ta is input to the intake valve model M13, and the values of these input parameters are set in the intake valve model M13 described later. By substituting into the model equation, the cylinder intake air flow rate mc is calculated. The calculated in-cylinder intake air flow rate mc is converted into the in-cylinder charged air amount Mc, and the fuel injection amount from the fuel injection valve is determined based on the in-cylinder charged air amount Mc. The in-cylinder intake air flow rate mc calculated in the intake pipe model M13 is input to the intake pipe model M12.

  As can be seen from FIG. 2, in the air model M10, the parameter value calculated in one model is used as an input value to another model. Therefore, in the entire air model M10, the actually input value is the throttle opening θt. There are only three parameters, atmospheric pressure Pa and atmospheric temperature Ta, and the cylinder charge air amount Mc is calculated from these three parameters.

Next, the models M11 to M13 of the air model M10 will be described.
In the throttle model M11, the throttle valve passing air flow rate mt is calculated from the atmospheric pressure Pa, the atmospheric temperature Ta, the intake pipe pressure Pm, and the throttle opening θt based on the following equation (1). Here, μt in the equation (1) is a flow coefficient in the throttle valve, which is a function of the throttle opening θt, and is thus determined from a map as shown in FIG. At represents the opening cross-sectional area of the throttle valve, which is a function of the throttle opening θt, and is determined from a map as shown in FIG. Note that μ · At, which is a combination of the flow coefficient μt and the opening cross-sectional area At, may be obtained from one throttle opening θt. R is a constant related to the gas constant, and is actually a value obtained by dividing the gas constant by the mass M _lmol of gas (air) per mol.

Φ (Pm / Pa) is a function shown in the following formula (2), and κ in the formula (2) is a specific heat ratio (a constant value). Since this function Φ (Pm / Pa) can be expressed in a graph as shown in FIG. 5, such a graph is stored as a map in the ROM 34 of the ECU 31 and is actually calculated using the above equation (2). Instead of this, the value of Φ (Pm / Pa) may be obtained from the map.

  The expressions (1) and (2) of the throttle model M11 are such that the gas pressure upstream of the throttle valve 18 is the atmospheric pressure Pa, the gas temperature upstream of the throttle valve 18 is the atmospheric temperature Ta, and the gas downstream of the throttle valve 18 is Applying the law of conservation of mass, the law of conservation of energy and the law of conservation of momentum to the model of the throttle valve 18 as shown in FIG. , And by using the Mayer relation.

In the intake pipe model M12, the intake pipe pressure Pm and the intake pipe temperature Tm are calculated from the throttle valve passage air flow rate mt, the in-cylinder intake air flow rate mc, and the atmospheric temperature Ta based on the following equations (3) and (4). Is done. Note that Vm in the equations (3) and (4) is a constant equal to the volume of the intake pipe portion.

Here, the intake pipe model M12 will be described with reference to FIG. When the total air amount in the intake pipe portion is M, the temporal change in the total air amount M is the flow rate of air flowing into the intake pipe portion, that is, the flow rate mt passing through the throttle valve and the flow rate of air flowing out from the intake pipe portion. That is, since it is equal to the difference from the in-cylinder intake air flow rate mc, the following equation (5) is obtained by the law of conservation of mass. From this equation (5) and the equation of state of gas (Pm · Vm = M · R · Tm) Equation (3) is obtained.

Further, the temporal change amount of the energy M · Cv · Tm of the gas in the intake pipe portion is equal to the difference between the energy of the gas flowing into the intake pipe portion and the energy of the gas flowing out of the intake pipe portion. For this reason, when the temperature of the gas flowing into the intake pipe portion is the atmospheric temperature Ta and the temperature of the gas flowing out from the intake pipe portion is the intake pipe temperature Tm, the following equation (6) is obtained according to the energy conservation law. Equation (4) is obtained from 6) and the gas equation of state.

In the intake valve model M13, the in-cylinder intake air flow rate mc is calculated from the intake pipe pressure Pm, the intake pipe temperature Tm, and the atmospheric temperature Ta based on the following equation (7). In Expression (7), a and b are intake valves in the case of an internal combustion engine having a variable valve mechanism that can change the phase angle (valve timing) and operating angle of the intake valve 6 from the engine speed Ne. 6 is a value determined from the phase angle and the working angle.

  The above-described intake valve model M13 will be described with reference to FIG. In general, the in-cylinder charged air amount Mc, which is the amount of air charged in the combustion chamber 5 when the intake valve 6 is closed, is determined when the intake valve 6 is closed (when the intake valve is closed). This is proportional to the pressure in the combustion chamber 5 when the intake valve is closed. Further, the pressure in the combustion chamber 5 when the intake valve is closed can be regarded as being equal to the pressure of the gas upstream of the intake valve, that is, the intake pipe pressure Pm. Therefore, the cylinder charge air amount Mc can be approximated as being proportional to the intake pipe pressure Pm.

Here, the average amount of all air flowing out from the intake pipe portion per unit time, or the amount of air sucked into all the combustion chambers 5 from the intake pipe portion per unit time is taken as the intake air of one cylinder. If the cylinder intake air flow rate mc (which will be described in detail below) is averaged over the stroke (in this embodiment, the crank angle is 180 ° as will be described later), the cylinder charge air amount Mc is the intake pipe internal pressure. Since it is proportional to Pm, it is considered that the in-cylinder intake air flow rate mc is also proportional to the intake pipe pressure Pm. From this, the above formula (7) is obtained based on the theory and empirical rules. The value a in the equation (7) is a proportional coefficient, and the value b is a value representing the burned gas remaining in the combustion chamber 5 (the amount of burned gas remaining in the combustion chamber 5 when the exhaust valve 8 is closed). Is divided by time ΔT _{180 °} described later). Further, in actual operation, the intake pipe temperature Tm may change greatly during a transition. Therefore, Ta / Tm derived based on theory and empirical rule is multiplied as a correction for this.

  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 flow rate of air actually flowing from the intake pipe portion into the combustion chamber 5 per unit time. As shown in FIG. 9, in a four-cylinder internal combustion engine, the intake valve 6 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 6 corresponding to each cylinder is opened. Air flows from the intake pipe portion into the combustion chamber 5 of each cylinder according to the valve opening amount. For example, the displacement of the flow rate of the air flowing into the combustion chamber 5 of each cylinder from the intake pipe portion is as shown by the broken line in FIG. 9, and these are combined to flow into the combustion chambers of all cylinders from the intake pipe 13. The flow rate of air is as shown by the solid line in FIG. Further, for example, the in-cylinder charged air amount Mc to the first cylinder is as shown by hatching 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 of all the cylinders from the intake pipe shown by the solid line, and is shown by a one-dot chain line in the drawing. 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. Therefore, the cylinder intake air amount Mc is calculated by multiplying the cylinder intake air flow rate mc calculated by the intake valve model M13 by ΔT _{180 °} (Mc = mc · ΔT _{180 °} ). More specifically, in consideration of the fact that the in-cylinder charged air amount Mc is proportional to the pressure when the intake valve is closed, the cylinder intake air flow rate mc when the intake valve is closed is multiplied by ΔT _{180 °.} The inner filling air amount Mc.

Next, a case where the air model M10 is mounted on a control device for an internal combustion engine and the in-cylinder charged air amount Mc is actually calculated will be described. The in-cylinder charged air amount Mc is expressed by solving the above equations (1), (3), (4), and (7) using the air model 10. In this case, in order to be processed by the ECU 31, these equations need to be discretized. When equation (1), equation (3), equation (4), and equation (7) are discretized using time t and calculation interval Δt, the following equations (8), (9), and (10) are obtained. And Equation (11) is obtained. The intake pipe internal temperature Tm (t + Δt) is calculated by Expression (12) from Pm / Tm (t + Δt) and Pm (t + Δt) calculated by Expression (9) and Expression (10), respectively.

In the air model M10 implemented in this way, the throttle valve passing air flow rate mt (t) at time t calculated by the equation (8) of the throttle model M11 and the equation (11) of the intake valve model M13 are calculated. The in-cylinder intake air flow rate mc (t) at time t is substituted into the equations (9) and (10) of the intake pipe model M12, whereby the intake pipe internal pressure Pm (t + Δt) and the intake pipe internal temperature Tm at time t + Δt. (T + Δt) is calculated. Next, the calculated Pm (t + Δt) and Tm (t + Δt) are substituted into the equations (8) and (11) of the throttle model M11 and the intake valve model M13, thereby the throttle valve passing air flow rate mt (t) at the time t + Δt. t + Δt) and in-cylinder intake air flow rate mc (t + Δt) are calculated. By repeating such calculation, the cylinder intake air flow rate mc at an arbitrary time t is calculated from the throttle opening θt, the atmospheric pressure Pa, and the atmospheric temperature Ta, and the calculated cylinder intake air flow rate mc is calculated. Is multiplied by the time ΔT _{180 °} to calculate the in-cylinder charged air amount Mc at an arbitrary time t.

  At the time of starting the internal combustion engine, that is, at time t = 0, the intake pipe pressure Pm is equal to the atmospheric pressure (Pm (0) = Pa), and the intake pipe temperature Tm is equal to the atmospheric temperature (Tm (0)). = Ta), the calculation in each of the models M11 to M13 is started.

  Next, the atmospheric pressure estimation apparatus of the present invention will be described. As described above, it is necessary to input the atmospheric pressure Pa to the throttle model M11. However, if an atmospheric pressure sensor is provided to detect the atmospheric pressure Pa, the manufacturing cost increases. Further, when the intake pipe pressure Pm detected by the intake pipe pressure sensor 40 immediately before or at the start of the internal combustion engine is used as the atmospheric pressure, the atmospheric pressure can be detected almost immediately after the start or at the start. And the actual atmospheric pressure around the vehicle changes, the value of the atmospheric pressure Pa used in the throttle model M11 differs from the actual atmospheric pressure, and as a result, the cylinder calculated by the air model M10 An error occurs in the inner charge air amount Mc. Therefore, there is a need for an atmospheric pressure estimation device that can estimate the actual atmospheric pressure even if the actual atmospheric pressure around the vehicle changes without using the atmospheric pressure sensor.

  By the way, if the throttle valve passage air flow rate mt, the intake pipe pressure Pm, and the throttle opening θt are obtained, the atmospheric pressure Pa is calculated by substituting these values into the equation (1) used in the throttle model M11 described above. be able to. Here, the intake pipe pressure Pm and the throttle opening degree θt (that is, the flow coefficient μt and the throttle valve opening sectional area At) are detected by the intake pipe pressure sensor 40 and the throttle opening degree sensor 43, respectively.

  Further, since the air model M10 described above is the simplest model, the air flow meter 41 for detecting the flow rate of the air flowing in the intake pipe 15 upstream of the throttle valve 18 is not required, but is more than the air model M10. Many complex air models require an air flow meter. Therefore, since this air flow meter is provided immediately upstream of the throttle valve 18, the air flow rate detected by the air flow meter 41 is substantially equal to the throttle valve passing air flow rate mt. The flow rate can be approximated to the throttle valve passing air flow rate mt. In the following description, it is assumed that the air flow meter 41 detects the throttle valve passage air flow rate mt.

  However, in the model equation (1) of the throttle model M11, the flow coefficient μt is obtained in advance by experiment or calculation as a function of the throttle opening θt, but there may be an error in the value of the flow coefficient μt. If there is an error in the value of the flow coefficient μt in this way, the intake pipe pressure Pm, the throttle valve passage air flow rate mt and the throttle opening detected by the intake pipe pressure sensor 40, the air flow meter 41 and the throttle opening sensor 43. Even if θt is substituted into equation (1), the atmospheric pressure Pa cannot be calculated accurately.

  FIG. 10A shows a case where the model equation (1) is created based on the throttle valve passage air flow rate mtact detected by the air flow meter 41 and the intake pipe pressure Pact detected by the intake pipe pressure sensor 40. It is a figure which shows the relationship between the intake pipe internal pressure represented by the model equation (1) and the throttle valve passage air flow rate. Here, when there is no error in the flow coefficient μt of the model formula (1) of the throttle model M11, the relationship between the intake pipe pressure and the throttle valve passing air flow rate expressed by the created formula (1) is shown in FIG. As shown by curve A in (a), the relationship between the actual intake pipe pressure and the throttle valve passing air flow rate is substantially the same. The intake pipe pressure when the flow rate of air passing through the throttle valve is zero, that is, the atmospheric pressure calculated by back-calculating the model equation (1), substantially matches the actual atmospheric pressure Paact.

  On the other hand, when there is an error in the flow coefficient μt of the model equation (1) of the throttle model M11, for example, when the flow coefficient μt is larger than the actual value, the inside of the intake pipe represented by the created model equation (1) The relationship between the pressure and the throttle valve passage air flow rate is as shown by a curve B in FIG. 10A, which is greatly different from the relationship between the actual intake pipe pressure and the throttle valve passage air flow rate. The pressure calculated as the intake pipe pressure when the throttle valve passage air flow rate is zero, that is, the atmospheric pressure Paest calculated by back-calculating the model equation (1) is a value greatly different from the actual atmospheric pressure Paact. (ΔPa in FIG. 10A).

  In this way, if the atmospheric pressure is to be estimated by reversely calculating the model equation (1) of the throttle model M11, if there is an error in the flow coefficient μt, the intake pipe pressure Paest calculated by the reverse calculation and the actual atmospheric pressure Paact are calculated. Becomes a very different value.

  However, the model equation (1) is created based on the throttle valve passage air flow rate mtact and the intake pipe pressure Pmact detected when the intake pipe pressure is close to the atmospheric pressure due to a large throttle opening, etc. In this case, even if there is an error in the flow coefficient μt, the intake pipe pressure can be calculated relatively accurately by calculating back the model equation (1) of the throttle model M11.

  FIG. 10B shows a case where the model equation (1) is created based on the detected throttle valve passage air flow rate mtact and the intake pipe internal pressure Pmact when the intake pipe internal pressure is close to atmospheric pressure. FIG. 6 is a diagram showing the relationship between the intake pipe pressure calculated by the model equation (1) and the throttle valve passing air flow rate. As shown in FIG. 10B, the model formula of the throttle model M11 created based on the throttle valve passage air flow rate mtact detected by the air flow meter 41 and the intake pipe pressure Pmact detected by the intake pipe pressure sensor 40. The relationship between the pressure in the intake pipe expressed by (1) and the flow rate of air passing through the throttle valve is as shown by a curve A ′ in FIG. 10B when there is no error in the flow coefficient μt. The relationship between the pipe pressure and the throttle valve passing air flow rate is almost the same.

  On the other hand, when there is an error in the flow coefficient μt of the model equation (1) of the throttle model M11, the relationship between the intake pipe pressure and the throttle valve passing air flow rate represented by the created model equation (1) is shown in FIG. The curve B ′ is shown in (b), and the actual relationship between the intake pipe pressure and the throttle valve passing air flow rate is different. However, the pressure calculated as the intake pipe pressure when the throttle valve passage air flow rate is zero, that is, the atmospheric pressure Paest calculated by back-calculating the model equation (1) is relatively close to the actual atmospheric pressure Paact. Become.

  That is, when the pressure in the intake pipe is a value close to atmospheric pressure, even if there is an error in the flow coefficient μt of the model equation (1), the atmospheric pressure calculated by back-calculating the model equation (1) Paest has a small error from the actual atmospheric pressure Paact. In other words, when the ratio of the pressure Pm in the intake pipe to the atmospheric pressure Pa (hereinafter referred to as “pressure ratio”) Pm / Pa is close to 1, even if there is an error in the flow coefficient or the like, the model equation (1) is calculated backward. While the calculated atmospheric pressure has a small error from the actual atmospheric pressure, if the pressure ratio Pm / Pa is small, the atmospheric pressure calculated by back-calculating the model equation (1) if there is an error in the flow coefficient, etc. Has a large error from the actual atmospheric pressure.

  Therefore, in the present embodiment, only when the pressure ratio Pm / Pa is close to 1, that is, when the pressure ratio Pm / Pa is equal to or greater than the predetermined ratio α (a value close to 1), the model formula (1) of the throttle model M11. The atmospheric pressure is calculated by calculating back. Here, when the error such as the flow coefficient existing in the model equation is equal to or less than a predetermined value (for example, 20%), the predetermined ratio α is the error of the atmospheric pressure calculated by the model equation (for example, 2). %) Is set to be below. In this way, in the present embodiment, the atmospheric pressure is calculated only when the pressure ratio Pm / Pa is close to 1, so that the atmospheric pressure can be estimated relatively accurately.

Next, the atmospheric pressure estimation device according to the second embodiment of the present invention will be described.
By the way, in the atmospheric pressure estimation device of the above embodiment, the atmospheric pressure is calculated by back-calculating the model equation (1) of the throttle model M11 using the throttle valve passing air flow rate detected by the air flow meter 41. In particular, when the pressure ratio Pm / Pa is a value close to 1, that is, when the intake pipe pressure Pm is high, the atmospheric pressure is calculated.

  However, when the pressure ratio Pm / Pa is a value close to 1, the throttle valve passing air flow rate detected by the air flow meter 41 does not necessarily represent the actual flow rate, and the detection accuracy may be lowered.

  FIG. 11 is a time chart of the flow rate of air flowing in the forward flow direction (from the air cleaner 16 toward the combustion chamber 5) in the intake pipe when the throttle opening is large and the pressure ratio Pm / Pa is close to 1. It is. When the pressure ratio Pm / Pa is in the vicinity of 1, as shown by the solid line C in FIG. 11, the throttle valve passing air flow rate pulsates greatly, and a reverse flow may occur temporarily.

  Here, in general, the air flow meter 41 can detect the flow rate of the air flowing through the intake pipe 15, but cannot detect whether the direction of the air flow is the forward flow direction or the reverse flow direction. For this reason, as shown by the broken line D in FIG. 11, even when the flow rate of air flowing in the forward flow direction in the intake pipe 15 is negative, the air flowing in the forward flow direction detected by the air flow meter 41 is reduced. The flow rate will be positive. Further, since there is a response delay in the air flow meter 41, as shown by a broken line in FIG. 11, there is a delay with respect to the actual flow rate of air passing through the throttle valve.

  Thus, depending on the air flow meter 41 used, the detection accuracy is particularly low when the pressure ratio Pm / Pa is close to 1. Therefore, in the present embodiment, the atmospheric pressure is estimated using the intake pipe model M12 and the intake valve model M13 in addition to the throttle model M11 without using the air flow meter 41.

  Here, in the air model M10, the intake pipe pressure Pm is calculated in the intake pipe model M12. However, if the calculated value of the intake pipe pressure Pm is not accurate, the value of the atmospheric pressure Pa input to the throttle model M11 is not the same. Absolute pressure is not accurate. However, the ratio of the atmospheric pressure Pa input to the throttle model M11 with respect to the intake pipe pressure Pm calculated in this way, that is, the value of the pressure ratio Pm / Pa is calculated relatively accurately regardless of the value of the atmospheric pressure Pa. The

  That is, the value of the pressure ratio Pm / Pa is set to any value if the values of parameters such as the engine speed Ne, the throttle opening θt, and the phase angle VT of the intake valve 6 are the same. Are also equal. That is, if the throttle opening θt is constant, the value of the flow coefficient μt and the like in the throttle model M11 is constant, and if the engine speed Ne and the phase angle VT are constant, the constants a and b in the intake valve model M13 are constant. The value is constant, and as a result, the value of the pressure ratio Pm / Pa calculated using the model formulas of these models is also constant and is a relatively accurate value.

  Therefore, in the present embodiment, an arbitrary value, for example, the standard atmospheric pressure, is input as the atmospheric pressure Pa to the model equation (1) of the throttle model M11, and the values of other parameters are input to the model equations of the air model M10. In-pipe pressure Pm is calculated. Then, the pressure ratio Pm / Pa is calculated by dividing the calculated intake pipe pressure Pm by an arbitrary atmospheric pressure Pa input to the model equation (1). Thereby, the value of the pressure ratio Pm / Pa can be calculated accurately.

  As described above, in the present embodiment, since the intake pipe pressure sensor 40 detects the intake pipe pressure, the actual intake pipe pressure Pmact can be accurately obtained. Therefore, in the present embodiment, the actual atmospheric pressure Pa can be calculated relatively accurately by dividing the actually measured value Pmact of the intake pipe pressure detected in this way by the value of Pm / Pa.

  Also in this embodiment, as described with reference to FIG. 10, when the error such as the flow coefficient μt has an error, the pressure ratio Pm / Pa is closer to 1. An error occurring in the calculated pressure ratio Pm / Pa is small. FIG. 12 shows errors occurring in the value of the pressure ratio Pm / Pa and the value of the pressure ratio Pm / Pa when an error of 20% is added to the flow coefficient μt of the throttle model M11 and the constant a of the intake valve model M13. It is a figure which shows the relationship. FIG. 12B is an enlarged view of FIG.

  From FIG. 12, it can be seen that when the value of the pressure ratio Pm / Pa is low, the value of the error generated in the pressure ratio Pm / Pa is also large and is greatly affected by the modeling error generated in the throttle model M11 and the intake valve model M13. . Conversely, when the value of the pressure ratio Pm / Pa is high, the value of the error generated in the pressure ratio Pm / Pa is small, and it can be seen that it is hardly affected by the modeling error generated in the throttle model M11 and the intake valve model M13. Therefore, if the atmospheric pressure is calculated as described above when the pressure ratio Pm / Pa is equal to or greater than the predetermined ratio α close to 1 (Pm / Pa ≧ α), the atmospheric pressure can be estimated relatively accurately. For example, when there is an error of 20% in each of the flow coefficient μt of the throttle model M11 and the constant a of the intake valve model M13, the pressure ratio Pm / Pa is used when it is desired to suppress the estimation error of the atmospheric pressure to 2% or less. The atmospheric pressure may be estimated when the value of is about 0.965 or more.

  As can be seen from FIG. 12, the error rate of the pressure ratio Pm / Pa hardly changes depending on the engine speed, and thus it can be seen that the value of the predetermined value α does not depend on the engine speed.

  FIG. 13 is a flowchart showing a control routine of the atmospheric pressure estimation apparatus of the present embodiment. The illustrated control routine is executed by interruption at regular time intervals.

  Referring to FIG. 13, first, in step 101, the pressure ratio Pm / Pa is acquired. In the present embodiment, calculation by each model formula is performed by the air model M10 separately from the atmospheric pressure estimation device, and the air model M10 uses the intake pipe pressure detected by the intake pipe pressure sensor 40 at the time of engine start as the atmospheric pressure. Or the calculation is performed using the atmospheric pressure previously calculated by this control routine. Thereby, in the air model M10, the intake pipe pressure Pm is calculated, and the pressure ratio Pm / Pa is calculated. In step 101, the pressure ratio Pm / Pa calculated in this way is acquired.

  Next, in step 102, it is determined whether or not the pressure ratio Pm / Pa acquired in step 101 is equal to or greater than a predetermined value α, that is, whether or not the atmospheric pressure can be estimated with a small error. . Here, the predetermined value α is a value close to 1, and is a value that can suppress an error in the pressure ratio Pm / Pa. If it is determined that the pressure ratio Pm is equal to or greater than the predetermined value α, the process proceeds to step 103. In step 103, the estimation flag flag is set to 1. The estimation flag flag is a flag indicating that the atmospheric pressure is estimated, and is set to 1 when the atmospheric pressure is estimated, and is set to 0 otherwise.

Next, at step 104, the integrated value sum is calculated by the following equation (13). In Expression (13), Pmact is the intake pipe internal pressure detected by the intake pipe internal pressure sensor 40, and Pa and Pm are the atmospheric pressure and the intake pipe internal pressure used in the air model M10, respectively. The integrated value sum is a value obtained by integrating the value of Pmact × Pa / Pm calculated in this control routine over a plurality of times.
sum = sum + Pmact × Pa / Pm (13)

  In step 104, 1 is added to the counter cnt (cnt ← cnt + 1). The counter cnt is a counter that indicates the number of times that Pact × Pa / Pm is added to sum in calculating the integrated value sum.

  Thereafter, steps 101 to 104 are repeated while the value of the pressure ratio Pm / Pa is α or more. Then, when the value of the pressure ratio Pm / Pa becomes smaller than α, the process proceeds from step 102 to step 105. In step 105, it is determined whether or not the estimation flag flag is 1. If Steps 101 to 104 have been repeated until the previous time, the estimation flag flag is set to 1. In this case, the process proceeds to Step 106.

  In step 106, it is determined whether or not the value of the counter cnt is greater than or equal to the counter minimum value cntmin. That is, in order to accurately calculate the atmospheric pressure, it is preferable to calculate the pressure ratio Pm / Pa over a certain number of times and calculate the atmospheric pressure based on the average value. When the number of times of calculation is large, that is, when the value of the counter cnt is greater than or equal to the counter minimum value cntmin, the routine proceeds to step 107, where atmospheric pressure is estimated. When the value of the counter cnt is smaller than the counter minimum value cntmin, the routine proceeds to step 108 where atmospheric pressure is not estimated. In steps 107 and 108, the integrated value sum, the counter cnt, and the estimation flag flag are reset, and the control routine is ended. The atmospheric pressure Pa estimated in this way is input to the model formula (1) of the throttle model M11 of the air model M10.

  In the above embodiment, only the case where the atmospheric pressure is used in the air model M10 has been described. However, in the air model different from the air model M10 and in the fuel injection amount control different from the fuel injection amount control using the air model. In some cases, it is necessary to input atmospheric pressure, and the atmospheric pressure estimation apparatus of the above embodiment can be used even in such a case.

It is a figure which shows the whole internal combustion engine provided with the atmospheric pressure estimation apparatus of this invention. It is a figure which shows the air model applied to an internal combustion engine. It is a figure which shows the relationship between a throttle opening and a flow coefficient. It is a figure which shows the relationship between throttle opening and opening cross-sectional area. It is a figure which shows function (PHI) (Pm / Pa). It is a figure which shows the basic concept of a throttle model. It is a figure which shows the basic concept of an intake pipe model. It is a figure which shows the basic concept of an intake valve model. It is a figure for demonstrating the definition of cylinder filling air amount and cylinder intake air flow volume. It is a figure which shows the relationship between the pressure in an intake pipe, and the throttle valve passage air flow rate when the pressure ratio Pm / Pa is small and large. It is a time chart of a throttle valve passage air flow rate. It is a figure which shows the relationship between the error in pressure ratio Pm / Pa and pressure ratio Pm / Pa. It is a flowchart which shows the control routine of the atmospheric pressure estimation apparatus of 2nd embodiment.

Explanation of symbols

1 Engine Body 5 Combustion Chamber 6 Intake Valve 7 Intake Port 8 Exhaust Valve 11 Fuel Injection Valve 13 Intake Pipe 18 Throttle Valve 31 ECU
40 Pressure sensor 41 Air flow meter

Claims (4)

A pressure sensor for detecting the pressure in the intake pipe downstream of the throttle valve; and an atmospheric pressure estimation model for estimating the atmospheric pressure based on the pressure in the intake pipe downstream of the throttle valve, and increasing the pressure in the intake pipe detected by the pressure sensor. In the atmospheric pressure estimation device that inputs the atmospheric pressure estimation model and estimates the atmospheric pressure,
In the atmospheric pressure estimation model, the ratio of the intake pipe pressure to the atmospheric pressure is calculated in estimating the atmospheric pressure, and the atmospheric pressure is estimated only when the ratio of the intake pipe pressure to the atmospheric pressure is equal to or greater than a predetermined ratio. Barometric pressure estimation device.   Throttle valve passage air flow rate detection means for detecting the flow rate of air passing through the throttle valve is further provided, and the atmospheric pressure estimation model is based on the atmospheric pressure based on the throttle valve passage air flow rate in addition to the pressure in the intake pipe downstream of the throttle valve. The atmospheric pressure estimation device according to claim 1, wherein   The above atmospheric pressure estimation model has an air model that can output the ratio of the intake pipe pressure to the atmospheric pressure when the atmospheric pressure is input, and the ratio of the intake pipe pressure to the atmospheric pressure is calculated by inputting an arbitrary atmospheric pressure to the air model. The atmospheric pressure estimation device according to claim 1, wherein the actual atmospheric pressure is estimated based on the calculated ratio and the intake pipe pressure downstream of the throttle valve detected by the pressure sensor.   The air model includes a throttle model that outputs a throttle valve passage air flow rate when a throttle opening, intake pipe pressure and atmospheric pressure are input, and an intake pipe output of an intake pipe pressure when a throttle valve passage air flow rate and a cylinder intake air flow rate are input. A pipe model and an intake valve model that outputs an in-cylinder intake air flow rate when an intake pipe pressure is input, and is based on the atmospheric pressure input to the throttle model and the intake pipe pressure output by the intake pipe model. The atmospheric pressure estimation device according to claim 3, wherein a ratio of the pressure in the intake pipe to the atmospheric pressure is calculated.

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