JP5169854B2 - Intake air amount estimation device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake air amount estimation device for an internal combustion engine.

  In order to perform the air-fuel ratio control, it is necessary to grasp the amount of intake air supplied into the cylinder. Since the air flow meter has a response delay, it cannot detect the correct intake air amount during engine transients, and the intake pipe pressure at each time must be set to grasp the correct intake air amount during engine transients. It has been proposed to calculate and estimate the intake air amount at each time based on the calculated intake pipe pressure at each time.

  The model formula used for calculating the intake pipe pressure and estimating the intake air amount is preferably completely adapted to the intake system to be estimated, but this requires a huge amount of man-hours, so it is set in advance. A model that is close to the intake system to be estimated may be selected from the model equations that are used. As a matter of course, an error that cannot be ignored occurs between the calculated intake pipe pressure and the actual intake pipe pressure. To reduce this error, an error function is set and calculated. It has been proposed to correct the intake pipe pressure that has been set by a set error function or the like (see, for example, Patent Document 1).

JP-A-4-159439 JP-A-1-271642 JP 63-263238 A International Publication WO2003 / 033897

  However, even if the intake air amount is estimated based on a relatively accurate intake pipe pressure corrected by an error function or the like, the model equation used for estimating the intake air amount is not completely compatible with the intake system to be estimated. Therefore, an error that cannot be ignored occurs between the actual intake air amount. In order to reduce this error, the intake pipe pressure corrected by an error function or the like must be further corrected, and a model equation for calculating the intake pipe pressure before a relatively accurate intake air amount is calculated. Therefore, an error function for absorbing the error generated by the above and a correction amount for absorbing the error generated by the model equation for estimating the intake air amount are set separately, which requires a great amount of man-hours.

  Accordingly, an object of the present invention is to provide a relatively accurate estimation of the intake air amount without requiring a great deal of man-hours in an intake air amount estimation device that estimates the intake air amount based on the calculated intake pipe pressure. It is possible.

An intake air amount estimation device for an internal combustion engine according to claim 1 of the present invention includes an intake pipe pressure calculating means for calculating an intake pipe pressure downstream of the throttle valve, and an intake pipe pressure calculated by the intake pipe pressure calculating means. Intake air amount calculation means for calculating the intake air amount based on the intake pipe pressure, and the intake pipe pressure calculated by the intake pipe pressure calculation means is calculated by a correction function or an error function that absorbs an error from the actual intake pipe pressure. without correction, then, characterized in that it is corrected as a first correction value for simultaneously absorbing and error in calculating the I Ri吸 incoming air amount to the intake air amount calculating means and said error.

  An intake air amount estimation device for an internal combustion engine according to claim 2 according to the present invention is the intake air amount estimation device for an internal combustion engine according to claim 1, wherein the intake pipe pressure calculated by the intake pipe pressure calculation means is used. Is corrected as a second correction value so as to absorb an error from the actual intake pipe pressure separately from the first correction value.

According to the intake air amount estimation device for an internal combustion engine according to claim 1 of the present invention, the intake pipe pressure calculating means for calculating the intake pipe pressure downstream of the throttle valve, and the intake pipe calculated by the intake pipe pressure calculating means An intake air amount calculating means for calculating an intake air amount based on the pressure, and the intake pipe pressure calculated by the intake pipe pressure calculating means is calculated by a correction function or an error function that absorbs an error from the actual intake pipe pressure. without correction, then, in order to be corrected as a first correction value for simultaneously absorbing and error in calculating the I Ri吸 incoming air quantity on the error and the intake air amount calculating means, the current intake pipe The correction using the intake pipe pressure calculated by the pressure calculation means as the first correction value simultaneously absorbs the error generated by the current intake pipe pressure calculation means and the error generated by the current intake air amount calculation means. Is, without the need for much large number of steps, it is possible to estimate the relatively accurate intake air amount.

  According to the intake air amount estimation device for an internal combustion engine according to claim 2 of the present invention, in the intake air amount estimation device for the internal combustion engine according to claim 1, the intake pipe calculated by the intake pipe pressure calculating means is provided. In addition to the first correction value, the pressure is corrected as a second correction value so as to absorb an error from the actual intake pipe pressure, and if necessary, a relatively accurate intake pipe pressure is also obtained. be able to.

1 is a schematic view of an internal combustion engine to which an intake air amount estimation device according to the present invention is attached. It is a map which shows the relationship between throttle-valve opening degree TA and the flow coefficient (micro | micron | mu). It is a map which shows the relationship between the throttle valve opening degree TA and the opening area A of a throttle valve. It is a map which shows the relationship between the ratio of intake pipe pressure Pm and atmospheric pressure Pa, and function (PHI). It is a block diagram which shows the estimation procedure of the intake air amount by the intake air amount estimation apparatus of the internal combustion engine by this invention.

  FIG. 1 is a schematic diagram showing an internal combustion engine to which an intake air amount estimation device according to the present invention is attached. In the figure, 1 is an engine body, and 2 is a surge tank common to each cylinder. An intake branch pipe 3 communicates the surge tank 2 with each cylinder, and 4 is an intake passage upstream of the surge tank 2. A fuel injection valve 5 is disposed in each intake branch pipe 3, and a throttle valve 6 is disposed immediately upstream of the surge tank 2 in the intake passage 4. The throttle valve 6 is not linked to the accelerator pedal, but can be freely set by a drive device such as a step motor. Reference numeral 7 denotes an air flow meter that detects an intake air flow rate upstream of the throttle valve 6 in the intake passage 4. In the engine body 1, 8 is an intake valve, 9 is an exhaust valve, and 10 is a piston.

  In order to set the combustion air-fuel ratio in the internal combustion engine 1 to a desired air-fuel ratio such as a stoichiometric air-fuel ratio, for example, it is necessary to accurately estimate the amount of intake air that has flowed into the cylinder including when the engine is in transition. . The air flow meter 7 can measure the intake air amount relatively accurately when the engine is stationary. However, during engine transition, the output of the air flow meter 7 does not immediately respond to the intake air amount that changes abruptly, making it impossible to accurately measure the intake air amount.

  This intake air amount estimation device estimates the intake air amount by modeling the engine intake system in order to make it possible to accurately grasp the intake air amount even during engine transition.

First, by modeling the throttle valve 6, using the energy conservation law, the momentum conservation law, and the state equation when intake air passes through the throttle valve 6, the current throttle valve passage air amount mt _(i) (G / sec) is expressed by the following equation (1). Including the following expression, the subscript (i) of the variable such as the throttle valve passing air amount indicates the current time, and (i-1) indicates the previous time.

Here, μ _(i) is a flow coefficient of the throttle valve, and A _(i) is an opening area (m ³ ) of the throttle valve 6. Of course, when an idle speed control valve (ISC valve) is provided in the engine intake system, the opening area of the ISC valve is added to A _(i) . Each of the flow coefficient and the opening area of the throttle valve is a function of the throttle valve opening TA _(i) (degree), and FIGS. 2 and 3 show maps for the respective throttle valve openings TA. Yes. R is a gas constant, Ta is an intake air temperature (K) upstream of the throttle valve, Pa is an intake passage pressure (kPa) upstream of the throttle valve, and Pm _(i) is an intake pipe downstream of the throttle valve. Pressure (kPa). The function Φ (Pm _(i) / Pa) is expressed by the following equation (2) using the specific heat ratio κ, and FIG. 4 shows a map for Pm / Pa.

Next, the intake valve is modeled. Since the intake air amount mc _(i) (g / sec) supplied into the cylinder changes substantially linearly based on the intake pipe pressure Pm _(i) , it can be expressed by the following equation (3). .

Here, Tm _(i) is the intake air temperature (K) downstream of the throttle valve, and a and b are constants obtained from empirical rules. However, b is a value corresponding to the amount of residual burned gas in the cylinder, and when there is a valve overlap, burned gas flows backward to the intake pipe, so the value of b increases to a degree that cannot be ignored. Accordingly, it is preferable to map the values of a and b so that an accurate intake air amount mc is calculated based on the presence or absence of valve overlap and the engine speed NE. In addition, when there is a valve overlap, when the intake pipe pressure Pm is equal to or higher than a predetermined pressure, the higher the intake pipe pressure, the more significantly the backflow of burned gas decreases. It is preferable to increase the value of a and decrease the value of b.

By the way, since the throttle valve passing air amount mtTA and the intake air amount coincide with each other when the engine is in a steady state, the throttle pressure in which the intake pipe pressure is the intake pipe pressure PmTA in the steady state of the engine in equation (1). The valve passing air amount mtTA is equal to the intake air amount (a · PmTA−b), so that the equation (1) can be rewritten as the following equation (4).

Here, the intake pipe pressure PmTA when the engine is stationary is the throttle valve opening TA _(i) , the engine speed NE _(i) , and the valve overlap size VT ₍ Based on _i) , it can be mapped in advance.

Next, the intake pipe is modeled. Using the intake mass conservation law, the energy conservation law, and the equation of state existing in the intake pipe, the rate of change over time in the ratio between the intake pipe pressure Pm and the intake air temperature Tm downstream of the throttle valve is expressed by the following equation (5). The time change rate of the intake pipe pressure Pm is expressed by the following equation (6). Here, V is the volume (m ³ ) of the intake pipe, and specifically, the total volume of the surge tank 2 and the intake branch pipe 3.

Equations (5) and (6) are discretized to obtain the following equations (7) and (8), respectively, and if the current intake pipe pressure Pm _(i) is obtained by equation (8), 7), the intake air temperature Tm _(i) in the intake pipe at this time can be obtained. In the equations (7) and (8), the discrete time Δt is the execution interval of the flowchart (FIG. 5) for calculating the current intake air amount mc _(i) , and is 8 ms, for example.

If each model formula is set in this way, the intake pipe pressure Pm _(i) is calculated using the formula (8) when the engine start is completed. Equation (8) is the previous intake pipe pressure Pm _(i-1) , the previous throttle valve passing air amount mt _(i-1) , the previous intake air amount mc _(i-1), and the previous intake air pressure. The current intake pipe pressure Pm _(i) is calculated based on the intake air temperature Tm _{(i-1) in the} pipe. As these initial values, the Pm _(i-1) the atmospheric pressure Pa is, the intake air temperature Ta of the throttle valve upstream side is used is measured each of the Tm _(i-1), the mt _(i-1) Is the value calculated from Equation (1) or (4) using these Pm _(i-1) and Tm _(i-1) , and mc _(i-1) The value calculated by the equation (3) using Pm _(i-1) and Tm _(i-1) is used.

Next, based on the current intake pipe pressure Pm _(i) thus calculated, the intake air temperature Tm _(i) in the current intake pipe is calculated using Equation (7). Next, the current throttle valve passing air amount mt _(i) is calculated using the equation (1) or (4). In calculating the throttle valve passing air amount mt _(i) using this equation (1) or (4), the current throttle valve opening TA takes into account the response delay of the throttle valve drive device (step motor). .

Next, the current intake air amount mc _(i) is calculated using Equation (3). Thereafter, the current intake pipe pressure Pm _(i) is set to the previous intake pipe pressure Pm _(i-1), and the intake temperature Tm _(i) in the current intake pipe is changed to the previous intake temperature Tm _{(i- 1)} , the current throttle valve passage air amount mt _(i) is the previous throttle valve passage air amount mt _(i-1), and the current intake air amount mc _(i) is the previous intake air amount mc _{( i-1)} . Thus, the intake air amount mc is sequentially estimated based on the intake pipe pressure Pm that is sequentially calculated simultaneously with the completion of the engine start.

  Each of the above model equations is preferably set so as to be completely adapted to the internal combustion engine for estimating the intake air amount mc. For this purpose, for example, the flow coefficient μ in the model equation (1) of the throttle valve, An enormous number of test steps for perfectly matching the intake pipe pressure PmTA at the time of engine steady state in the throttle valve model equation (4) and the constants a and b in the intake valve model equation (3) to the internal combustion engine to be estimated Therefore, it is conceivable to select and use one that is close to the estimation target internal combustion engine from the already set model equations.

However, the intake pipe pressure Pm _{(i) at} each time calculated using the model equations of the throttle valve, the intake pipe, and the intake valve is naturally the actual intake pipe pressure at each time. Therefore, an intake pipe pressure Pm _{(i) at} each time must be corrected by an error function or the like so as to absorb the error at the time of calculation.

However, even if the intake air amount mc _(i) is estimated based on the relatively accurate intake pipe pressure Pm _(i) corrected by the error function or the like in this way, the model equation of the intake valve used for estimating the intake air amount is also Since it is not completely compatible with the internal combustion engine to be estimated, an error that cannot be ignored occurs between the actual intake air amount and the estimation. Therefore, the intake pipe pressure Pm _{(i) at} each time corrected by an error function or the like needs to be further corrected by a correction amount ΔPm _(i) for absorbing an error generated when estimating the intake air amount. Therefore, until a relatively accurate estimation of the intake air amount is possible, an error function for absorbing the error in calculating the intake pipe pressure and a correction for absorbing the error in estimating the intake air amount Both the quantity ΔPm _(i) must be set, and a great number of man-hours are required.

In order to enable a relatively accurate estimation of the intake air amount without requiring such a large number of man-hours, the intake air amount estimation device for an internal combustion engine according to the present invention is as shown in the block diagram of FIG. The intake air amount mc is estimated. That is, the current intake pipe pressure Pm _(i) calculated by the current intake pipe model MP (equation (8)) is not corrected so as to absorb an error from the actual intake pipe pressure. Since the correction amount ΔPm _(i) is used as the first correction value so that a relatively accurate intake air amount is calculated by the current intake valve model MV (equation (3)), the first correction is performed. The value absorbs the error generated by the current intake pipe model (calculates the intake pipe pressure based on the current throttle valve model) and the error generated by the current intake valve model at the same time. Without any need, the current intake valve model MV enables a relatively accurate estimation of the intake air amount.

As a result, the first correction value at each time is different from the actual intake pipe pressure at each time. If a relatively accurate intake pipe pressure at each time is required, as shown in FIG. In addition to the first correction value, the current intake pipe pressure Pm _(i) calculated by the current intake pipe model MP (equation (8)) is a second correction value by an error function f (Pm _(i) ). It may be corrected as Pm _(i) ′.

Here, the correction amount ΔPm _{(i) (D1,..., Dn)} for correcting the intake pipe pressure Pm _(i) calculated by the intake pipe model MP is the current throttle valve opening area A _(i). Is set for each operating state (engine speed, ignition timing, and valve overlap amount) (n combinations) with respect to the value of the intake pipe pressure Pm _(i) calculated based on a plurality of time of the current throttle valve opening area a _(i) (e.g., D1, D11, D21, ·· , Dn) approximately equal amount of intake air mc with respective intake air amount measured in the operating state of the _(i) There intake pipe pressure PM of the operating conditions, as estimated by the intake valve model _{MV (i) (D1, D11} , D21, ··, Dn) was calculated back, thus back-calculated intake pipe pressure PM _{(i) ( D1, D11, D21,..., Dn)} and the intake pipe pressure Pm _(i) calculated by the intake pipe model MP in each operating state _{( The difference from D1, D11, D21,..., Dn)} is the correction amount ΔPm _{(i) (D1, D11, D21,..., Dn)} in each operating state.

The first operating state D1 of the combination of the first engine speed, the first ignition timing, and the first valve overlap, and the first operation state of the combination of the eleventh engine speed, the eleventh ignition timing, and the eleventh valve overlap. 11 correction amount .DELTA.Pm of the intake pipe pressure Pm for the operating state between the operating state D11 _{(i) (i),} the correction amount of the intake pipe pressure Pm when the first operating condition _{D11 (i) ΔPm (i)} ( _D1) and the correction amount ΔPm _{(i) (D11)} of the intake pipe pressure Pm _(i) at the time of the eleventh operating state D11, for example, linear with respect to each of the engine speed, ignition timing, and valve overlap, It can be estimated by nonlinear interpolation. Similarly, the correction amount ΔPm _(i) of the intake pipe pressure Pm _(i) for the operation state between the eleventh operation state D11 and the twenty-first operation state D21 is the intake pipe pressure Pm in the eleventh operation state D11. and _(i) of the correction amount .DELTA.Pm _{(i) (D11),} it may be estimated to based on the correction amount of the intake pipe pressure Pm when the first 21 operating condition _{D21 (i) ΔPm (i)} (D21). Thus, the correction amounts ΔPm _{(i) (D1,..., Dn)} for all operating states are set, and similarly, all the operating states are set for the intake pipe pressure Pm for each throttle valve opening area. A correction amount ΔPm is set.

The correction amount ΔPm against calculated by the intake pipe model MP intake pipe pressure Pm _{(i) (i)} has a calculated intake pipe pressure Pm _(i), the current engine speed NE _(i), the current As a function of the ignition timing S _(i) and the current valve overlap VT _(i) , for example, a statistical model such as the following equation (9) may be set and calculated.
ΔPm _(i) = a0 + a1 · Pm _(i) + a2 · NE _(i) + a3 · S _(i) + a4 · VT _(i)
+ A5 ・ Pm _(i)・ NE _(i) + a6 ・ NE _(i)・ S _(i)
+ A7 ・ S _(i)・ VT _(i) + ・ ・ ・ ・ ・ ・
... (9)
Here, a0, a1, a2, a3, a4, a5, a6, a7... Are the opening area of the current throttle valve in which the intake pipe pressure Pm _(i) is calculated in the same estimation target internal combustion engine as described above. A _(i) is a coefficient determined by a test for measuring the amount of intake air in a plurality of operating states.

Further, an error function is used to set the current intake pipe pressure Pm _(i) calculated by the current intake pipe model MP (Equation (8)) to a second correction value Pm _(i) ′ close to the actual intake pipe pressure. f (Pm _(i) ) is the calculated intake pipe pressure Pm _(i) , the current engine speed NE _(i) , the current ignition timing S _(i), and the current valve overlap VT _(i For example, a statistical model such as the following equation (10) can be set and calculated as a function with ₎ .
Pm _(i) '= b0 + b1 · Pm _(i) + b2 · NE _(i) + b3 · S _(i) + b4 · VT _(i)
+ B5 ・ Pm _(i)・ NE _(i) + b6 ・ NE _(i)・ S _(i)
+ B7 · S _(i) · VT _(i) + · · · ·
(10)
Here, b0, b1, b2, b3, b4, b5, b6, b7... Are the throttle valve opening area A _{(i )} in which the intake pipe pressure Pm _(i) is calculated in the internal combustion engine to be estimated. ₎ Is a coefficient determined by a test for measuring the intake pipe pressure in a plurality of operating states.

Of course, in order to set the current intake pipe pressure Pm _(i) calculated by the current intake pipe model MP (Equation (8)) as the second correction value Pm _(i) ′ close to the actual intake pipe pressure, The correction amount ΔPm ′ set for each state may be used.

This correction amount ΔPm _{(i) (D1,..., Dn)} ′ is an operating state (with respect to the value of the intake pipe pressure Pm _(i) calculated based on the current throttle valve opening area A _(i). the engine speed, ignition timing, and are set in the valve overlap amount) for each (combination of n different), for example, a plurality of time of the current throttle valve opening area a _(i) (e.g., D1, D11, Dn, each intake pipe pressure PM _{(i) (D1, D11, D21,..., Dn)} 'measured in the operating state and the intake air calculated by the intake pipe model MP in each operating state A difference from the pipe pressure Pm _{(i) (D1, D11, D21,..., Dn)} is set as a correction amount ΔPm _{(i) (D1, D11, D21,..., Dn)} ′ in each operation state.

The first operating state D1 of the combination of the first engine speed, the first ignition timing, and the first valve overlap, and the first operation state of the combination of the eleventh engine speed, the eleventh ignition timing, and the eleventh valve overlap. 11 correction amount .DELTA.Pm of the intake pipe pressure Pm for the operating state between the operating state D11 _{(i) (i)} ', the correction amount of the intake pipe pressure Pm when the first operating condition D11 _(i) ΔPm _{(i) (D1)} ′ and the correction amount ΔPm _{(i) (D11)} ′ of the intake pipe pressure Pm _(i) at the eleventh operating state D11, for example, each of the engine speed, ignition timing, and valve overlap Can be estimated by linear or non-linear interpolation. Similarly, the correction amount ΔPm _(i) ′ of the intake pipe pressure Pm _(i) for the operation state between the eleventh operation state D11 and the twenty-first operation state D21 is the intake pipe pressure in the eleventh operation state D11. Pm _(i) of the correction amount ΔPm _{(i) (D11)} be estimated to based on the 'a, the correction amount of the intake pipe pressure Pm when the first 21 operating condition _{D21 (i) ΔPm (i)} (D21)' it can. In this way, correction amounts ΔPm _{(i) (D1,..., Dn)} ′ for all operating states are set, and similarly, all operating states are set for the intake pipe pressure Pm for each throttle valve opening area. Correction amount ΔPm ′ can be set.

ここで、μ_(i)’は吸気弁の流量係数であり、Ａ_(i)’は吸気弁の開口面積（ｍ³）である。流量係数及び吸気弁の開口面積は、それぞれが吸気弁のリフト量の関数となっており、スロットル弁に関する図２及び３と同様に、吸気弁のリフト量に対してマップ化することができる。Ｐｃ_(i)は筒内圧力（ｋＰａ）である。 Incidentally, the intake air amount mc (i) may be estimated using an intake valve model represented by the following equation (11) instead of the intake valve model of the equation (3).

Here, μ _(i) ′ is a flow coefficient of the intake valve, and A _(i) ′ is an opening area (m ³ ) of the intake valve. Each of the flow coefficient and the opening area of the intake valve is a function of the lift amount of the intake valve, and can be mapped to the lift amount of the intake valve as in FIGS. Pc _(i) is the in-cylinder pressure (kPa).

ここで、Ｖ_(i)は、現在のクランク角度に基づき定められる筒内容積であり、Ｍｃ_(i)は、吸気弁開弁時から現在までの吸入空気量ｍｃ_(i)を積分することにより得られる筒内吸入空気量であり、Ｔｃ_(i)は、筒内温度である。 The in-cylinder pressure Pc _(i) is calculated by the following equation (12).

Here, V _(i) is the in-cylinder volume determined based on the current crank angle, and Mc _(i) is obtained by integrating the intake air amount mc _(i) from when the intake valve is opened to the present. This is the in-cylinder intake air amount obtained, and Tc _(i) is the in-cylinder temperature.

By using such an intake valve model, for example, intake air at every crank angle (or every several crank angles) based on the throttle valve opening and intake valve lift amount at every crank angle (or every several crank angles). By estimating the amount mc _(i) (intake air flow rate) and accumulating it during the valve opening period of the intake valve, an accurate in-cylinder intake air amount Mc sucked into the cylinder during the intake valve opening is estimated. be able to.

  In such an intake valve model, too much time is required to completely adapt the flow coefficient μ (i) ′ and the like of the intake valve to the internal combustion engine to be estimated. It is preferable to apply.

DESCRIPTION OF SYMBOLS 1 Engine body 2 Surge tank 3 Intake branch pipe 4 Intake passage 6 Throttle valve 7 Air flow meter

Claims (2)

An intake pipe pressure calculating means for calculating an intake pipe pressure downstream of the throttle valve; and an intake air amount calculating means for calculating an intake air amount based on the intake pipe pressure calculated by the intake pipe pressure calculating means, The intake pipe pressure calculated by the intake pipe pressure calculating means is not corrected by a correction function or error function that absorbs an error from the actual intake pipe pressure, and then the error and the intake air amount calculating means are not corrected. intake air quantity estimation apparatus for an internal combustion engine, characterized in that it is corrected as a first correction value for simultaneously absorbing and error in calculating the I Ri吸 inlet air amount.   The intake pipe pressure calculated by the intake pipe pressure calculating means is corrected as a second correction value so as to absorb an error from the actual intake pipe pressure separately from the first correction value. The intake air amount estimation device for an internal combustion engine according to claim 1.

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