JP2006329058A - Fuel injection quantity control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection quantity control device for an internal combustion engine capable of accurately estimating fuel adhesion quantity and accurately making an air fuel ratio of the engine correspond to a target air fuel ratio after completion of a starting period, by accurately determining an initial value of fuel adherence quantity at the time of completion of the starting period. <P>SOLUTION: This device performs asynchronous injection only during the starting period until fuel injection frequency after starting of the engine reaches predetermined frequency, and performs synchronous injection based on a command fuel injection quantity which is determined by considering fuel adhesion quantity to an intake system estimated by a fuel behavioral model after completion of the starting period. The device uses injection pressure Pf (N) at start of each asynchronous injection which is estimated by considering fluctuation of injection pressure Pf generated by asynchronous injection during the starting period, to estimate respective actual fuel injection quantity based on asynchronous injection; and determines the "initial value of fuel adherence quantity" at the time of completion of the starting period which is given to the fuel behavioral model, based on the actual fuel injection quantity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  A part of the fuel injected from the fuel injection valve disposed in the intake passage of the internal combustion engine (hereinafter also simply referred to as “engine”) is an intake system (specifically, the wall surface of the intake pipe, the intake air) It adheres to the umbrella portion of the valve, etc., and is hereinafter collectively referred to as “intake passage component”. Therefore, in order to make the air-fuel ratio of the air-fuel mixture supplied to the engine (hereinafter also referred to as “the air-fuel ratio of the engine”) coincide with the target air-fuel ratio, the adhesion behavior of fuel to the intake passage constituting member It is necessary to determine the amount of fuel to be instructed to inject into the intake passage while taking into account the adhesion of the fuel. Hereinafter, the fuel injection amount instructed to be injected is referred to as “command fuel injection amount”.

For this reason, for example, the fuel injection amount control device for an internal combustion engine described in Patent Document 1 below is a fuel behavior using the adhesion rate of the fuel to the intake passage constituting member and the residual rate of the adhered fuel. The amount of fuel adhering to the intake passage constituent member is estimated using a simulation model (fuel behavior model), and the commanded fuel injection amount is determined in principle based on the estimated amount of fuel adhering. Hereinafter, fuel injection based on an instruction to inject a command fuel injection amount determined so that the air-fuel ratio of the engine matches the target air-fuel ratio will be referred to as “synchronous injection”.
JP-A-9-303173

  By the way, in general, an internal combustion engine has a short period of time (hereinafter referred to as an engine operating speed exceeding a predetermined value, etc.) after the start of fuel injection control by starting to improve startability, etc. In this case, the command fuel injection amount is forcibly determined to be a specific value dedicated to starting regardless of the air-fuel ratio of the engine. Hereinafter, fuel injection based on an instruction to inject a fuel with a commanded fuel injection amount determined independently of the air-fuel ratio of the engine will be referred to as “asynchronous injection”.

  Thus, it is not necessary to match the air / fuel ratio of the engine during the start-up period. Therefore, the fuel injection amount control device actually instructs the fuel injection amount based on the fuel adhesion amount estimated using the fuel behavior model described above from the end of the starting period (that is, the time when the predetermined condition is satisfied). In many cases, the fuel injection amount is determined.

  In this case, in order to accurately estimate the amount of fuel adhering using the fuel behavior model after the start-up period and to accurately match the air-fuel ratio aimed at the air-fuel ratio of the engine, the fuel adhering at the end of the start-up period It is necessary to accurately determine the value of the amount (hereinafter referred to as “initial value of the fuel adhesion amount”) and to give the obtained “initial value of the fuel adhesion amount” to the fuel behavior model. This “initial value of the fuel adhesion amount” is the amount of fuel injected up to the end of the start period, that is, each actual fuel injection corresponding to a plurality of injections (asynchronous injection) executed during the start period. Depends on the amount.

  On the other hand, in general, fuel is injected by an amount equal to the command fuel injection amount by opening the fuel injection valve for an injection period corresponding to the command fuel injection amount in a state where the injection pressure is substantially maintained at an appropriate value. It has become so. In other words, if the fuel is injected in a state where the injection pressure deviates from an appropriate value due to a relatively large variation in the injection pressure, the actual fuel injection amount may deviate from the command fuel injection amount.

  In addition, during the start-up period, due to the fact that the operating speed of the pump (electric pump) that generates the injection pressure has not reached a sufficient speed necessary to maintain the injection pressure at an appropriate value, etc. Due to the execution of fuel injection, relatively large fluctuations are likely to occur in the injection pressure. Therefore, during the start-up period, the actual fuel injection amount may deviate from the command fuel injection amount.

  From the above, under the assumption that the actual fuel injection amount during the start-up period is equal to the command fuel injection amount, the above-mentioned “initial value of the fuel adhesion amount” is performed multiple times (asynchronous). If each commanded fuel injection amount corresponding to (injection) is used, the “initial value of the fuel injection amount” cannot be obtained accurately. In other words, in order to accurately obtain the “initial value of the fuel adhesion amount”, it is necessary to consider the “fluctuation of the injection pressure during the start-up period” described above.

  An object of the present invention is to accurately determine the amount of fuel adhesion at the end of the start-up period (the above “initial value of fuel injection amount”), thereby accurately estimating the amount of fuel adhering after the end of the start-up period. Another object of the present invention is to provide a fuel injection amount control device for an internal combustion engine that can accurately match the air / fuel ratio of the engine.

  A fuel injection amount control device according to the present invention is applied to an internal combustion engine having fuel injection means for injecting fuel into an intake passage upstream of an intake valve of the internal combustion engine, and the intake passage configuration is formed by injection by the fuel injection means. A fuel adhesion amount estimation means for estimating a fuel adhesion amount that is an amount of fuel adhering to the member, and a predetermined condition after the start of fuel injection by the fuel injection means that is started by starting the internal combustion engine. A command fuel injection amount that is a fuel amount that is instructed to be injected from the fuel injection means is determined based on the fuel adhesion amount estimated by the fuel adhesion amount estimation means after the establishment time (that is, at the end of the starting period). Commanded fuel injection amount determining means.

  Here, the fuel adhesion amount estimation means uses, for example, a fuel behavior simulation model (fuel behavior model) using a fuel adhesion rate to the intake passage constituting member and a residual rate of the adhered fuel. Estimate the amount of adhesion. Even if the fuel adhesion amount estimation means starts estimating the fuel adhesion amount from the end of the start period, the fuel adhesion amount estimation means estimates the fuel adhesion amount from the start period before the same point (for example, the start time of fuel injection). May start.

  Examples of the “predetermined condition” include that the operating speed of the engine exceeds a predetermined value as described above, or that the number of fuel injections after starting reaches a predetermined specified number. The command fuel injection amount determining means determines the command fuel injection amount based on the estimated fuel adhesion amount so that the air-fuel ratio of the engine matches the target air-fuel ratio after the end of the start period. Preferably it is comprised. In this case, synchronous injection is executed after the end of the start period. Further, either asynchronous injection or synchronous injection may be executed from the start of the fuel injection to the time when the predetermined condition is satisfied (that is, during the start-up period).

  The fuel injection amount control device according to the present invention is characterized by the value of the fuel adhesion amount (that is, the time when the predetermined condition used by the fuel adhesion amount estimation means is satisfied (that is, when the start period ends) , "The initial value of the fuel adhesion amount") from the start of the fuel injection to the time when the predetermined condition is satisfied (that is, during the starting period), the injection generated by the fuel injection by the fuel injection means It is provided with a fuel adhesion amount initial value determining means for determining at least taking pressure fluctuations into consideration.

  According to this, the above-mentioned “initial value of the fuel adhesion amount” is determined in consideration of at least the “fluctuation of the injection pressure during the starting period”. Therefore, the “initial value of the fuel adhesion amount” can be determined with high accuracy, and as a result, after the start-up period, the fuel adhesion amount is accurately estimated and matched with the target air / fuel ratio. be able to.

  Here, the fuel adhesion amount initial value determining means may be a means for determining the “initial value of the fuel adhesion amount” using the fuel behavior model described above, or without using the fuel behavior model. A means for determining the “initial value of the fuel adhesion amount” using a table (map) or the like may be used.

  Specifically, the fuel adhesion amount initial value determination means generates an injection pressure at each injection start time in a plurality of times of fuel injection by the fuel injection means executed during the start period by the fuel injection. Injection pressure estimating means for estimating in consideration of fluctuations in the injection pressure to be performed, and corresponding actual fuel injection amounts in the plurality of fuel injections are estimated based on the estimated injection pressures at the respective injection start times It is preferable that an actual fuel injection amount estimating means is provided, and an initial value of the fuel adhesion amount is determined based on at least the estimated actual fuel injection amount.

  The injection pressure at each injection start time in a plurality of fuel injections (for example, the asynchronous injection etc.) executed during the start-up period greatly affects the corresponding actual fuel injection amount. Accordingly, as in the above-described configuration, the corresponding actual fuel injection amount is estimated based on the injection pressure at each injection start time that is accurately estimated in consideration of “the fluctuation of the injection pressure during the start period”. For example, each actual fuel injection amount during the start-up period can be accurately estimated. Here, each actual fuel injection amount during the start-up period can be estimated, for example, by correcting the corresponding command fuel injection amount based on the estimated injection pressure at each estimated injection start time.

  In addition, as described above, the “initial value of the fuel adhesion amount” depends on each actual fuel injection amount during the start-up period. From the above, if the “initial value of the fuel adhesion amount” is determined based on each actual fuel injection amount during the start period accurately estimated as in the above configuration, the “initial value of the fuel adhesion amount” Can be accurately determined.

  In this case, the injection pressure estimation means uses the rule that the injection pressure at the current injection start time is determined from the injection pressure at the previous injection start time and a value corresponding to the previous injection period. It is preferable that the injection pressure at each injection start time in each fuel injection is determined. Here, the “value corresponding to the injection period” is, for example, the injection period (that is, the valve opening period of the fuel injection valve) itself, the command fuel injection amount, or the like.

  In general, during the injection period (while the fuel is being injected), the injection pressure decreases due to the injection (release) of the fuel. Therefore, the amount of decrease in the injection pressure during the injection period becomes larger as the injection period becomes longer. In other words, the amount of decrease in the injection pressure at the current injection start time relative to the injection pressure at the previous injection start time can be obtained based on the previous injection period.

  From the above, it is possible to create a rule that determines the injection pressure at the current injection start time from the injection pressure at the previous injection start time and the previous injection period. The above configuration is based on such knowledge. According to this, by sequentially applying the above rules, it is possible to sequentially determine the injection pressure at each injection start time in a plurality of fuel injections during the start-up period.

  Further, the injection pressure estimating means is configured to determine the injection pressure at each of the injection start times further considering the injection start timing in the plurality of fuel injections determined by the operating speed of the internal combustion engine. More preferably.

  In general, during the period from the end of the previous injection to the start of the current injection, the injection pressure that has decreased from the set pressure (the above-mentioned appropriate value) is the same due to the fuel supplied by the pump (electric pump) that generates the injection pressure. It increases (returns) toward the set pressure. Accordingly, the amount of increase in the injection pressure from the end of the previous injection to the start of the current injection becomes larger as the current injection start timing is later, that is, the engine operating speed is lower.

  In other words, the injection pressure at the current injection start time depends greatly on the current injection start time determined by the operating speed of the internal combustion engine. The above configuration is based on such knowledge. According to this, the injection pressure at each of the above injection start times can be determined with higher accuracy in consideration of the corresponding injection start timing determined by the operating speed of the internal combustion engine. As a result, the actual fuel injection amounts during the start-up period can be estimated with higher accuracy, so that the “initial value of the fuel adhesion amount” can be determined with higher accuracy. As a result, after the start-up period, the fuel adhesion amount can be estimated with higher accuracy and matched with the air / fuel ratio aimed at the air / fuel ratio of the engine with higher accuracy.

  Further, the injection pressure estimating means further considers at least one of the temperature supplied to the electric pump for generating the injection pressure and the temperature of the atmosphere, the property of the fuel, and the injection at each injection start time. More preferably, it is configured to determine the pressure.

  The temperature supplied to the electric pump that generates the atmospheric temperature, the fuel properties, and the injection pressure affects the injection pressure at the start of each injection during the start-up period, as with the operating speed of the internal combustion engine described above. Can be a factor that gives Therefore, according to the above configuration, the injection pressure at the start of each injection can be determined with higher accuracy in consideration of these factors. As a result, as described above, the “initial value of the fuel adhesion amount” can be determined with higher accuracy.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a fuel injection amount control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a system applied to a spark ignition type multi-cylinder (4-cylinder) internal combustion engine 10 provided with a fuel injection amount control device according to an embodiment of the present invention.

  The internal combustion engine 10 includes a cylinder block unit 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head unit 30 fixed on the cylinder block unit 20, and a gasoline mixture in the cylinder block unit 20. And an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake camshaft that drives the intake valve 32, and continuously changes the phase angle of the intake camshaft. The variable intake timing device 33, the actuator 33 a of the variable intake timing device 33, the exhaust port 34 communicating with the combustion chamber 25, the exhaust valve 35 that opens and closes the exhaust port 34, the exhaust camshaft 36 that drives the exhaust valve 35, and the spark plug 37 , An igniter 38 including an ignition coil that generates a high voltage to be applied to the spark plug 37, and a fuel injection valve 39 that injects fuel into the intake port 31.

  The fuel injection valve 39 is connected to the discharge side of the electric pump P. The electric pump P sucks fuel in a fuel tank (not shown) and supplies the sucked fuel to the fuel injection valve 39. The discharge pressure of the electric pump P is normally maintained / adjusted at the set pressure P0, whereby the injection pressure Pf of the fuel injected from the fuel injection valve 39 is also maintained / adjusted at the set pressure P0. To be able to be.

  The intake system 40 is provided in an intake pipe 41 including an intake manifold that communicates with the intake port 31 and forms an intake passage together with the intake port 31, an air filter 42 provided at an end of the intake pipe 41, and the intake pipe 41. A throttle valve 43 for changing the opening cross-sectional area of the intake passage and a throttle valve actuator 43a made of a DC motor constituting throttle valve driving means are provided.

  The exhaust system 50 includes an exhaust manifold 51 that communicates with the exhaust port 34, and an exhaust pipe (exhaust pipe) that is connected to the exhaust manifold 51 (actually, a collection portion of the exhaust manifolds 51 that communicate with each exhaust port 34). ) 52, and a three-way catalyst 53 disposed (intervened) in the exhaust pipe 52. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage.

  On the other hand, this system includes a hot-wire air flow meter 61, an intake air temperature sensor 62, a throttle position sensor 63, a cam position sensor 64, a crank position sensor 65, a water temperature sensor 66, and an exhaust passage upstream of the three-way catalyst 53 (in this example, An air-fuel ratio sensor 67 and an intake pipe pressure sensor 68 are provided in a collection portion where the exhaust manifolds 51 are gathered.

  The hot-wire air flow meter 61 outputs a signal representing a mass flow rate (intake air flow rate Ga) per unit time of intake air flowing through the intake pipe 41. The intake air temperature sensor 62 detects the temperature of the intake air and outputs a signal representing the intake air temperature (that is, the atmospheric temperature Ta). The throttle position sensor 63 detects the opening of the throttle valve 43 and outputs a signal representing the throttle valve opening TA.

  The cam position sensor 64 generates a signal (G2 signal) having one pulse every time the intake camshaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °). This signal also represents the opening / closing timing VT of the intake valve 32.

  The crank position sensor 65 outputs a signal having a narrow pulse every time the crankshaft 24 rotates 10 ° and a wide pulse every time the crankshaft 24 rotates 360 °. This signal represents the engine speed NE. The water temperature sensor 66 detects the temperature of the cooling water of the internal combustion engine 10 and outputs a signal representing the cooling water temperature THW.

  The air-fuel ratio sensor 67 outputs a current corresponding to the air-fuel ratio of the exhaust gas, and outputs a signal corresponding to this current. The intake pipe pressure sensor 68 detects the air pressure in the intake pipe 41 and outputs a signal representing the intake pipe pressure Pm.

  The electric control device 70 includes a CPU 71 connected by a bus, a routine (program) executed by the CPU 71, a table (look-up table, map), a ROM 72 in which constants and the like are stored in advance, and the CPU 71 temporarily stores data as necessary. This is a microcomputer comprising a RAM 73 for storing data, a backup RAM 74 for storing data while the power is turned on and holding the stored data while the power is shut off, an interface 75 including an AD converter, and the like. . The interface 75 is connected to the sensors 61 to 68, supplies signals from the sensors 61 to 68 to the CPU 71, and in response to instructions from the CPU 71, the actuator 33a, the igniter 38, and the fuel injection valve 39 of the variable intake timing device 33. A drive signal is sent to the throttle valve actuator 43a and the electric pump P.

(Outline of how to determine the command fuel injection amount)
Next, a method for determining the command fuel injection amount fi that is instructed to be injected into the fuel injection valve 39 by the fuel injection amount control device (hereinafter also referred to as “this device”) configured as described above will be described. To do.

  In order to improve startability and the like, the number of fuel injections started by the start-up is a predetermined number of times Nref (for example, Nref = 8. That is, considering that the internal combustion engine 10 has four cylinders, each cylinder The command fuel injection amount fi is forcibly determined to be a specific value dedicated to starting regardless of the air-fuel ratio of the engine in a short period (hereinafter referred to as “starting period”) until reaching twice. . That is, this apparatus performs asynchronous injection for the specified number of times Nref only in the starting period after starting.

Hereinafter, each command fuel injection amount fi corresponding to the Nref asynchronous injections is also referred to as “command asynchronous injection amount fnsd (N)”. Here, N is the total number of injections, and N = 1, 2,..., Nref. Each command asynchronous injection amount fnsd (N)
(N = 1, 2,..., Nref) is determined based on the coolant temperature THW and the like immediately before the start of the first fuel injection after the start, as will be described later.

  On the other hand, this apparatus starts synchronous injection after the start-up period ends (that is, from the (Nref + 1) th fuel injection after start-up). Specifically, the present apparatus determines the air-fuel ratio of the engine from the amount of air sucked into the combustion chamber 25 (cylinder intake air amount Mc) and the target air-fuel ratio abyfr (in principle, the stoichiometric air-fuel ratio stoich). A required inflow fuel amount Fc, which is the amount of fuel that should flow into the cylinder in order to match the target air-fuel ratio abyfr, is obtained.

  Then, the present apparatus sets the engine air-fuel ratio to the target air-fuel ratio abyfr based on the calculated required inflow fuel amount Fc and the fuel behavior model (inverse model) of the fuel adhering to the intake passage constituent member described later. The command fuel injection amount fi corresponding to the synchronous injection is determined so as to coincide.

  As described above, the present apparatus performs Nref asynchronous injection during the start-up period, and starts and executes synchronous injection using the fuel behavior model after the start-up period ends. The above is the outline of the method for determining the command fuel injection amount fi. Before describing the specific method for determining the command fuel injection amount fi corresponding to the synchronous injection after the start-up period, the fuel used by the present apparatus to determine the command fuel injection amount fi corresponding to the synchronous injection will be described below. The behavior model will be described.

(Fuel behavior model used to determine command fuel injection amount corresponding to synchronous injection)
As conceptually shown in FIG. 2, a part of the fuel injected from the fuel injection valve 39 of the cylinder into which fuel is injected (fuel injection cylinder) is the wall surface of the intake pipe 41 (inside the intake pipe 41). Wall surface) and the umbrella portion of the intake valve 32 (that is, the intake passage constituting member). Hereinafter, the amount of fuel adhering to the intake passage constituting member is referred to as a fuel adhering amount fw.

  More specifically, as shown in FIG. 3 focusing on the fuel injection cylinder, fi is the amount of fuel injected from the fuel injection valve 39 for the current intake stroke (command fuel injection amount), fw ( k-1) is the amount of fuel adhering immediately after the previous intake stroke and immediately before the current intake stroke, and P is the fuel remaining in the above-mentioned fuel adhering amount fw (k-1) while remaining attached to the intake passage components. % (Residual rate) and R is the ratio of the fuel adhering to the intake passage component of the fuel of the command fuel injection amount fi (attachment rate), the intake passage of the fuel adhesion amount fw (k-1) The amount of fuel remaining in the component member is P · fw (k−1), and the amount of fuel newly attached to the intake passage component member of the command fuel injection amount fi is R · fi.

  Therefore, the following equation (1) is established for the fuel adhesion amount fw (k) after the current intake stroke and immediately before the next intake stroke. The following equation (1), which is a recurrence formula, describes a fuel behavior model for the fuel adhering to the intake passage constituting member.

fw (k) ＝ P ・ fw (k-1) ＋ R ・ fi (1)

  Further, the residual rate P and the adhesion rate R used in the above equation (1) strongly depend on the in-cylinder intake air amount Mc, the engine rotational speed NE, the intake pipe pressure Pm, and the cooling water temperature THW. These values are determined in accordance with a predetermined table prepared in advance using these values as arguments.

  In the fuel behavior model described by the above equation (1), the initial value of the fuel adhesion amount fw at the end of the starting period (precisely, immediately before the intake stroke corresponding to the first synchronous injection of each cylinder) is initialized. By giving this value to each cylinder as a value (hereinafter referred to as “initial value fwini of fuel adhesion amount”), the device uses the fuel behavior model to calculate the fuel adhesion amount fw after the start-up period. It is updated every time and every cylinder. A method for obtaining the initial value fwini of the fuel adhesion amount will be described later. The above is the outline of the fuel behavior model used for determining the command fuel injection amount fi corresponding to the synchronous injection.

(Specific determination method of command fuel injection amount fi corresponding to synchronous injection)
Next, a specific method for determining the command injection amount fi corresponding to the synchronous injection will be described. This apparatus determines the command injection amount fi corresponding to the synchronous injection using the inverse model of the fuel behavior model described by the above equation (1). Hereinafter, an inverse model of this fuel behavior model will be described.

  The inverse model of this fuel behavior model is that the amount of fuel injected from the fuel injection valve 39 that flows into the cylinder without adhering to the intake passage constituting member and the amount of fuel adhering to the intake passage constituting member are determined. This is a model for calculating the command fuel injection amount fi required to allow the above-mentioned required inflow fuel amount Fc to flow into the cylinder in consideration of the amount of fuel flowing into the cylinder.

  The fuel deposition amount fwp (k-1) that has already been obtained by the above equation (1) and is immediately after the previous intake stroke of the fuel injection cylinder and immediately before the current intake stroke, as well as the above-described residual rate P and adhesion When the rate R is used, the fuel amount Fin flowing into the cylinder when it is assumed that fuel of the command fuel injection amount fi is injected for the current intake stroke is expressed by the following equation (2) (FIG. 3). See).

Fin = (1−R) ・ fi + (1−P) ・ fw (k−1) (2)

  Accordingly, the command fuel injection amount fi required for the fuel of the required inflow fuel amount Fc to flow into the cylinder in the intake stroke this time is the fuel amount Fin in the above equation (2) is the same as the required inflow fuel amount Fc. The replaced formula can be obtained by solving for the command fuel injection amount fi. The calculation result is as shown in equation (3). This equation (3) describes the inverse model of the fuel behavior model.

fi = (Fc− (1−P) ・ fw (k−1)) / (1−R) (3)

  At the end of the start-up period, the present apparatus obtains the command fuel injection amount fi corresponding to the synchronous injection for each intake stroke and for each cylinder using the above equation (3). As a result, the amount of fuel flowing into the cylinder can coincide with the required inflow fuel amount Fc, and as a result, the air-fuel ratio can be matched with the target air-fuel ratio abyfr. The above is the outline of the specific determination method of the command fuel injection amount fi corresponding to the synchronous injection.

(How to obtain the initial value fwini of the fuel adhesion amount)
Next, a method for obtaining the “initial value fwini of the fuel adhesion amount” given to the fuel behavior model (see the above equation (1)) used for determining the command fuel injection amount fi corresponding to the synchronous injection described above Will be described.

  In order to accurately estimate the fuel adhesion amount fw using the fuel behavior model described in the above equation (1) after the start-up period and to make the engine air-fuel ratio coincide with the target air-fuel ratio abyfr with high accuracy, It is necessary to accurately obtain the initial value fwini of the adhesion amount for each cylinder. The initial value fwini of each fuel adhesion amount depends on each actual fuel injection amount corresponding to asynchronous injection (twice for each cylinder) executed during the start-up period.

  Here, under the assumption that the actual fuel injection amount matches the command fuel injection amount in the Nref asynchronous injection, the asynchronous injection described by the following equation (4) similar to the above equation (1) is supported. A method for obtaining the initial value fwini of the fuel adhesion amount using a fuel behavior model is conceivable. In the following equation (4), fnsd (N) is the command fuel injection amount (command asynchronous injection amount) for the N-th (N = 1,..., Nref) asynchronous injection described above. Pns and Rns are a residual rate and an adhesion rate corresponding to asynchronous injection, respectively, and fwns is an amount of fuel (fuel adhesion amount) adhering to the intake passage constituting member by asynchronous injection.

fwns (k) ＝ Pns ・ fwns (k-1) ＋ Rns ・ fnsd (N) (4)

  Specifically, the fuel adhesion amount at the start of the engine is given as an initial value (hereinafter referred to as “starting fuel adhesion amount initial value fwnsini”) to the fuel behavior model described in the above equation (4), and asynchronously. By updating the fuel adhesion amount fwns (k) for each intake stroke for each injection and for each cylinder using the above equation (4), the end of the starting period (more precisely, the last ( Obtain the fuel deposition amount fwns (k) in the second) (after the asynchronous injection and immediately before the intake stroke corresponding to the first synchronous injection), that is, the above “initial value fwini of the fuel deposition amount” for each cylinder. Can do.

  However, during the start-up period (that is, while the Nref number of asynchronous injections are being performed), as described above, the fuel injection pressure Pf injected from the fuel injection valve 39 may vary greatly. As a result, the actual fuel injection amount can deviate from the command asynchronous injection amount fnsd (N). Hereinafter, the deviation of the actual fuel injection amount from the command asynchronous injection amount fnsd (N) will be described with reference to FIG.

  FIG. 4 is a time chart showing the change in the fuel injection pressure Pf for the first three asynchronous injections among the Nref asynchronous injections executed after the engine is started. In FIG. 4, T (N) (N = 1, 2,..., Nref) is an injection period (period during which fuel is injected) for the Nth asynchronous injection. During the injection period T (N), the fuel injection for injecting an amount of fuel equal to the command asynchronous injection amount fnsd (N) from the fuel injection valve 39 while the injection pressure Pf is substantially maintained at the set pressure P0. This is the valve opening time of the valve 39.

  As shown in FIG. 4, during the injection period corresponding to the asynchronous injection after the engine start (for example, time t1 to t2, time t3 to t4, time t1, which are the first, second and third asynchronous injection periods in FIG. 4) From t5 to t6), the injection pressure Pf decreases greatly due to fuel injection (release). On the other hand, during the period in which asynchronous injection is not performed (for example, time t2 to t3 and time t4 to t5 in FIG. 4), the injection pressure Pf that has decreased from the set pressure P0 is the same due to the supply of fuel by the electric pump P. It increases (returns) toward the set pressure P0. Thus, a relatively large fluctuation occurs in the injection pressure Pf during the start-up period.

  Here, the amount of fuel (injection speed) injected per unit time from the fuel injection valve 39 changes according to the injection pressure Pf. Accordingly, the actual fuel injection amounts corresponding to the first, second, and third asynchronous injections in FIG. 4 correspond to the command asynchronous injection amount fnsd (N) (N = Less than 1,2,3). Thus, due to the “relatively large fluctuation of the injection pressure Pf during the start-up period”, the actual fuel injection amount during the start-up period deviates from (becomes smaller than) the command asynchronous injection amount fnsd (N). ).

  From the above, when the `` initial value fwini of the fuel adhesion amount '' is calculated using the command asynchronous injection amount fnsd (N) as shown in the above equation (4), the value of the `` initial value fwini of the fuel adhesion amount '' Contains a large estimation error. In other words, in order to accurately obtain the “initial value fwini of the fuel adhesion amount”, it is necessary to accurately obtain the respective actual fuel injection amounts corresponding to the Nref specified number of asynchronous injections during the start-up period. is there.

  Here, the injection pressure Pf at each injection start time (for example, times t1, t3, t5 in FIG. 4) in the asynchronous injection greatly affects the corresponding actual fuel injection amount. In other words, if the injection pressure Pf at each injection start time corresponding to asynchronous injection can be estimated with high accuracy, the corresponding actual fuel injection amounts can be obtained with high accuracy.

  The injection pressure Pf at the injection start time corresponding to the N-th (N = 1, 2,..., Nref) asynchronous injection will be described below in order to explain the estimation method of the injection pressure Pf at each injection start time. Is called Pf (N), and the amount of decrease in the injection pressure of Pf (N) with respect to Pf (N-1) is called ΔP (N) (see FIG. 4). Then, the following formula (5) is established.

Pf (N) = Pf (N-1) −ΔP (N) (N = 2,3, ..., Nref) (5)

  As can be understood from this equation (5), if Pf (1) and ΔP (N) (N = 2, 3,..., Nref) can be obtained, the injection at the start of each injection during the start-up period The pressure Pf (N) (N = 1, 2,..., Nref) can be estimated. In this example, as shown in FIG. 4, Pf (1) is treated as being equal to the set pressure P0. Hereinafter, ΔP (N) (N = 2, 3,..., Nref) will be described with reference to FIGS.

  FIG. 5 shows that ΔP (2) in the case shown in FIG. 4 (see solid line) and the first command asynchronous injection amount fnsd (1) are larger than the case shown in FIG. It is a time chart for comparing with ΔP (2) ′ in the case where the period T (1) is long) (see the broken line). As can be understood from FIG. 5, ΔP (2) ′ becomes ΔP (2) because the amount of decrease in the injection pressure Pf during the injection period T (1) increases as the injection period T (1) increases. ) Larger than That is, ΔP (N) (N = 2, 3,..., Nref) depends on the injection period T (N−1), and the longer the injection period T (N−1) (that is, the command asynchronous injection). The larger the quantity fnsd (N−1)), the larger.

  6 shows ΔP (2) in the case shown in FIG. 4 (see the solid line) and ΔP (2 in the case where the engine speed NE is smaller than that shown in FIG. 4 (see the broken line). ) 'Is a time chart for comparison. As can be understood from FIG. 6, the amount of increase in the injection pressure Pf from the end point of the first asynchronous injection (time t2) to the start point of the second asynchronous injection (time t3, t3 ′) is the second injection start timing ( The later the times t3 and t3 ′), that is, the smaller the engine speed NE, the larger the time. Thereby, ΔP (2) ′ becomes smaller than ΔP (2). That is, ΔP (N) (N = 2, 3,..., Nref) depends on the engine speed NE, and decreases as the engine speed NE decreases.

  7 shows ΔP (2) in the case shown in FIG. 4 (see the solid line) and ΔP (2) in the case where the atmospheric temperature Ta is higher than that shown in FIG. 4 (see the broken line). It is a time chart for comparing with '. As can be understood from FIG. 7, ΔP (2) ′ becomes larger than ΔP (2) due to the fact that the higher the atmospheric temperature Ta (that is, the temperature of the fuel at the start), the smaller the viscosity of the fuel. That is, ΔP (N) (N = 2, 3,..., Nref) depends on the atmospheric temperature Ta, and increases as the atmospheric temperature Ta increases.

  From the above, the injection pressure decrease amount ΔP (N) (N = 2, 3,..., Nref) is the command asynchronous injection amount fnsd (N−1) (that is, a value corresponding to the previous injection period). Since it depends on the engine speed NE and the atmospheric temperature Ta, for example, it can be obtained by preparing a table for obtaining the reduction amount ΔP (N) using these as arguments.

  FIG. 8 shows the command asynchronous injection amount fnsd (N−1), the engine speed NE, and the engine rotational speed NE obtained from the table for determining the injection pressure decrease amount ΔP (N) when the atmospheric temperature Ta is fixed to a certain value. 4 is a graph showing an example of a relationship with an injection pressure decrease amount ΔP (N). As can be understood from FIG. 8, the injection pressure decrease amount ΔP (N) increases as the command asynchronous injection amount fnsd (N−1) increases, and decreases as the engine speed NE decreases.

  FIG. 9 shows the command asynchronous injection amount fnsd (N−1) and the atmospheric temperature Ta obtained from the table for determining the injection pressure decrease amount ΔP (N) when the engine speed NE is fixed to a certain value. 4 is a graph showing an example of a relationship with an injection pressure decrease amount ΔP (N). As can be understood from FIG. 9, the injection pressure decrease amount ΔP (N) increases as the command asynchronous injection amount fnsd (N−1) increases, and increases as the atmospheric temperature Ta increases.

  In this way, the injection pressure decrease amount ΔP (N) (N = 2, 3,..., Nref) can be acquired. Thus, the injection pressure Pf (N) (N = 1, 2,..., Nref) at each injection start point during the start period can be estimated using the above equation (5). That is, the injection pressure Pf (N) (N = 1, 2,..., Nref) at each injection start time during the start period is equal to the injection pressure Pf (N−1) at the previous injection start time. Using the rule that the injection pressure Pf (N) at the start of the current injection is determined from the value corresponding to the previous injection period (command asynchronous injection amount fnsd (N−1)) (that is, the “starting period” In view of the “relatively large fluctuation of the injection pressure Pf in the engine”), the asynchronous injection start timing determined by the engine speed NE and the atmospheric temperature Ta can be further taken into consideration.

  With this method, the present apparatus acquires the injection pressures Pf (N) (N = 1, 2,..., Nref) at the respective injection start points during the start-up period. In addition, this device corrects the current command asynchronous injection amount fnsd (N) from the current command asynchronous injection amount fnsd (N) and the current injection pressure ratio Pdratio (= Pf (N) / P0). Correction coefficient K (0 <K <1) is calculated, and the actual fuel injection amount (hereinafter referred to as “actual asynchronous injection amount fnsact”) is calculated by multiplying the current command asynchronous injection amount fnsd (N) by the correction coefficient K. Estimate.)

  FIG. 10 is a graph showing the relationship between the current command asynchronous injection amount fnsd (N), the current injection pressure ratio Pdratio (= Pf (N) / P0), and the correction coefficient K. As can be understood from FIG. 10, the correction coefficient K is determined to be smaller as the current command asynchronous injection amount fnsd (N) is larger and the current injection pressure ratio Pdratio is smaller. This is because the actual fuel injection amount fnsact is more different from the current command asynchronous injection amount fnsd (N) as the current command asynchronous injection amount fnsd (N) is larger and the current injection pressure ratio Pdratio is smaller. This is based on the fact that the degree (the degree to which it becomes smaller) becomes larger.

  Then, this apparatus uses the fuel behavior model described by the following equation (6) obtained by replacing fnsd (N) with fnsact in the above equation (4), and for each intake stroke for asynchronous injection, and cylinder By updating the fuel adhesion amount fwns (k) every time, the fuel adhesion amount fwns (k) at the end of the start-up period, that is, the “initial value fwini of the fuel adhesion amount” is obtained for each cylinder.

fwns (k) ＝ Pns ・ fwns (k-1) ＋ Rns ・ fnsact (6)

  As described above, the present apparatus is based on the injection pressure Pf (N) at each injection start time corresponding to asynchronous injection (specifically, based on the injection pressure ratio Pdratio), and the corresponding command asynchronous injection amount fnsd. Each actual asynchronous injection amount fnsact is estimated by correcting (N), and the above-mentioned “initial value fwini of fuel adhesion amount” is acquired based on each actual asynchronous injection amount fnsact. The above is the outline of the acquisition method of the “initial value fwini of the fuel adhesion amount” by the present apparatus.

(Actual operation)
Next, the actual operation of the electric control device 70 will be described with reference to the flowcharts shown in FIGS.

  The CPU 71 performs a routine for determining the command asynchronous injection amount fnsd (N) and calculating the actual asynchronous injection amount fnsact shown in the flowchart of FIG. 11 after a predetermined cranking period has elapsed after engine startup. It is repeatedly executed every time the crank angle reaches a predetermined crank angle before the intake top dead center (for example, BTDC 90 ° CA).

  Accordingly, after the predetermined cranking period has elapsed, when the crank angle of an arbitrary cylinder (fuel injection cylinder) reaches the predetermined crank angle, the CPU 71 starts processing from step 1100 and proceeds to step 1105, and the total number of injections N (current time) The value of the value indicating the number of injections) is incremented by “1”.

  Here, the value of the total number of injections N is initialized to “0” when an ignition (not shown) is turned on. The total number of injections N = 1 to Nref (in this example, “8”) means that asynchronous injection is executed, and N ≧ Nref + 1 means that synchronous injection is executed. The total number N of injections is incremented every time this routine is executed (that is, every time fuel injection is executed).

  Now, the description will be continued assuming that this routine is executed for the first time after a predetermined cranking period. In this case, the total number of injections N becomes “1” by the processing of step 1105. Next, the CPU 71 proceeds to step 1110, determines whether or not the total number of injections N is equal to or less than the specified number Nref (that is, whether or not asynchronous injection is executed), determines “Yes”, and step 1115. Then, it is determined whether or not the total number N of injections is “1”.

  At this time, the CPU 71 also determines “Yes” in step 1115 and proceeds to step 1120, where the current cooling water temperature THW obtained from the water temperature sensor 66 and the current atmospheric temperature Ta obtained from the intake air temperature sensor 62 are determined. The command asynchronous injection amount fnsd (N) (N = 1, 2,..., Nref) is determined.

  Next, the CPU 71 proceeds to step 1125 and sets the injection pressure Pf (1) at the injection start time corresponding to the first asynchronous injection to a value equal to the set pressure P0. Thus, the actual asynchronous injection amount fnsact corresponding to the first asynchronous injection is set to a value equal to the command asynchronous injection amount fnsd (1). This step 1125 constitutes a part of the injection pressure estimating means, and this step 1130 constitutes a part of the actual fuel injection amount estimating means.

  Then, the CPU 71 proceeds to step 1135 to prepare the initial value of the fuel adhesion amount fwns (k-1) by asynchronous injection for all the cylinders in preparation for starting the processing of the asynchronous injection execution routine of FIG. After setting to a value equal to the initial fuel adhesion amount fwnsini (for example, “0”), the routine proceeds to step 1195 to end the first execution of this routine once.

  Further, the CPU 71 is configured to repeatedly execute a routine for performing asynchronous injection shown in the flowchart of FIG. 12 for each cylinder. The CPU 71 continues to execute the routine shown in FIG. 12 for the current fuel injection cylinder every time the execution of the routine shown in FIG.

  Now, assuming that it is immediately after the first execution of the routine shown in FIG. 11 is completed (that is, the total number of injections N = 1), the CPU 71 performs processing from step 1200 of this routine for the current fuel injection cylinder. The process proceeds to step 1205, where it is determined whether or not the total number N of injections is equal to or less than the specified number Nref (that is, whether or not asynchronous injection is performed). Then, the value of the command fuel injection amount fi is set to the command asynchronous injection amount fnsd (N) (currently fnsd (1)) determined by the execution of the previous step 1120.

  Subsequently, the CPU 71 proceeds to step 1215 to instruct the fuel injection valve 39 for the current fuel injection cylinder to inject the fuel of the set command fuel injection amount fi. Thus, when the crank angle of the fuel injection cylinder reaches a predetermined crank angle before the intake top dead center (for example, BTDC 75 ° CA), the injection period T ((fnsd (N)) corresponding to the command fuel injection amount fi (= fnsd (N)) Only N) fuel is injected into the current fuel injection cylinder. That is, the first asynchronous injection is performed on the current fuel injection cylinder.

  As a result, the latest actual asynchronous injection amount fnsact of fuel acquired in the routine of FIG. 11 is actually injected. This “latest actual asynchronous injection amount fnsact” is the value acquired in the previous step 1130 at the present time (that is, when the first execution of this routine is performed after the engine is started (regardless of the cylinder)). Thus, at the time of execution of this routine after the next time, the value is acquired in step 1170 described later.

  Next, the CPU 71 proceeds to step 1220 and the current cooling water temperature THW, atmospheric temperature Ta, and intake pipe pressure Pm obtained from the water temperature sensor 66, the intake air temperature sensor 62, and the intake pipe pressure sensor 68, and THW, Ta Based on the tables MapRns and MapPns with Pm as arguments, the adhesion rate Rns and the residual rate Pns corresponding to the asynchronous injection are respectively determined.

  Next, the CPU 71 proceeds to step 1225, in which the above determined adhesion rate Rns and residual rate Pns, fuel adhesion amount fwns (k-1), and the above-mentioned "latest actual asynchronous data" acquired in the routine of FIG. Based on the “injection amount fnsact” and the above equation (6), the fuel attachment amount fwns (k) for the current fuel injection cylinder is updated to obtain the fuel attachment amount fwns (k).

  Here, as the fwns (k-1), for example, when the first execution of this routine is performed for the current fuel injection cylinder as in the present time, it is already set in the previous step 1135. If the current value (the above initial value) is used and the second execution of this routine is performed for the current fuel injection cylinder, the value already set and updated in the next step 1230 is used. . That is, when the CPU 71 proceeds to step 1230, the value of the fuel adhesion amount fwns (k-1) is set / updated to the value of the fuel adhesion amount fwns (k) obtained in step 1225.

  Next, the CPU 71 proceeds to step 1235 to determine whether or not the total number of injections N is “specified number Nref−3” or more (that is, “5” or more). Here, considering that the internal combustion engine 10 is a four-cylinder internal combustion engine, the total number of injections N = 1 to 4 means that the first asynchronous injection is made to the current fuel injection cylinder. In addition, the total number of injections N = 5 to 8 means that the second asynchronous injection is performed for the current fuel injection cylinder. That is, in step 1235, it is determined whether or not the injection made this time is the second asynchronous injection for the current fuel injection cylinder.

  At present, the total number of injections N is “1” (that is, the injection made this time is the first asynchronous injection for the current fuel injection cylinder). Therefore, the CPU 71 makes a “No” determination at step 1235 to immediately proceed to step 1295 to temporarily end the first execution of this routine for the current fuel injection cylinder.

  Thereafter, when the crank angle of the next arbitrary cylinder (new fuel injection cylinder) reaches the predetermined crank angle, the CPU 71 starts processing from step 1100 in FIG. 11 and proceeds to step 1105 to set the total number N of injections to “1”. "Is incremented from" 2 ". Subsequently, when the CPU 71 determines “Yes” in step 1110 and proceeds to step 1115, it determines “No” and proceeds to step 1140.

  When the CPU 71 proceeds to step 1140, the injection pressure decrease amount ΔP (N) (currently ΔP (2)), the command asynchronous injection amount fnsd (N−1) (currently fnsd (1)), and the current time Based on the current engine temperature NE, the current atmospheric temperature Ta, and a table MapΔP (see FIGS. 8 and 9) with fnsd (N−1), NE, and Ta as arguments.

  Subsequently, the CPU 71 proceeds to step 1145 to inject the injection pressure Pf (N-1) (currently, Pf (1) already set in step 1125), the obtained injection pressure decrease amount ΔP (N), The injection pressure Pf (N) (currently Pf (2)) is obtained based on the above equation (5). This step 1145 constitutes a part of the injection pressure estimating means.

  Next, the CPU 71 proceeds to step 1150 to determine whether or not the determined injection pressure Pf (N) is greater than the set pressure P0. When determining “Yes”, the CPU 71 proceeds to step 1155 and proceeds to the injection pressure Pf. The value of (N) is reset to the same set pressure P0, and the process proceeds to step 1160. When determining “No”, the CPU 71 proceeds from step 1150 to step 1160 immediately. This prevents the injection pressure Pf (N) (N = 2, 3,..., Nref) from being set to a value exceeding the set pressure P0.

  When the CPU 71 proceeds to step 1160, the injection pressure ratio Pdratio is obtained by dividing the obtained injection pressure Pf (N) (≦ P0) by the set pressure P0, and in step 1165, the injection pressure ratio Pdratio is calculated. The correction coefficient K is obtained based on the command asynchronous injection amount fnsd (N) (currently fnsd (2)) and the table MapK (see FIG. 10) using Pdratio, fnsd (N) as arguments.

  Then, the CPU 71 proceeds to step 1170 to obtain (update) the actual asynchronous injection amount fnsact by multiplying the command asynchronous injection amount fnsd (N) by the obtained correction coefficient K, and proceeds to step 1195 to proceed to step 2 of this routine. End the first execution. This step 1170 constitutes a part of the actual fuel injection amount estimating means.

  Thereafter, the CPU 71 continues the first execution of the routine of FIG. 12 for the current fuel injection cylinder (that is, the new fuel injection cylinder) with the total number of injections N = 2. As a result, the execution of step 1215 causes the first asynchronous injection to the new fuel injection cylinder for the injection period T (2) corresponding to the command fuel injection amount fi (= fnsd (2)). As a result, in reality, the latest actual asynchronous injection amount fnsact (= K · fnsd (N)) of fuel acquired in step 1170 of the routine of FIG. 11 is injected.

  Further, as a result of the execution of step 1225, the fuel adhesion amount fw for the current fuel injection cylinder (that is, a new fuel injection cylinder) uses the above "latest actual asynchronous injection amount fnsact (= K · fnsd (N))". And updated. At this time, since the first execution of this routine is performed for the current fuel injection cylinder (that is, a new fuel injection cylinder), fwns (k-1) is already set in the previous step 1135. The value that has been set (the above initial value) is used. At this time, since N = 2, it is determined as “No” in Step 1235.

  Thereafter, as in the case of N = 2, every time the crank angle of the next arbitrary cylinder (new fuel injection cylinder) becomes the predetermined crank angle, the CPU 71 performs steps 1105 to 1115 and 1140 to 1170 in FIG. The processing of steps 1205 to 1235 in FIG. 12 is executed subsequently (N ≧ 3).

  As a result, at the stage of the total number of injections N ≦ 4, the first asynchronous injection is performed for each new fuel injection cylinder for the injection period T (N) corresponding to the command fuel injection amount fi (= fnsd (N)). Are made in order. As a result, in reality, the latest actual asynchronous injection amount fnsact (= K · fnsd (N)) of fuel acquired in step 1170 of the routine of FIG. 11 is injected.

  Further, as in the case of N = 2, by executing step 1225, the fuel adhesion amount fw for each of the new fuel injection cylinders becomes “the latest actual asynchronous injection amount fnsact (= K · fnsd (N))”. ”In order. Further, when the total number of injections N ≦ 4, “No” is determined in step 1235.

  Further, at the stage where the total number of injections N ≧ 5, the second asynchronous injection is performed for each new fuel injection cylinder for the injection period T (N) corresponding to the command fuel injection amount fi (= fnsd (N)). In order. As a result, in reality, the latest actual asynchronous injection amount fnsact (= K · fnsd (N)) of fuel acquired in step 1170 of the routine of FIG. 11 is injected.

  Further, by executing step 1225, the fuel adhesion amount fw for each of the new fuel injection cylinders is sequentially updated using the “latest actual asynchronous injection amount fnsact (= K · fnsd (N))”. . In this case, as fwns (k−1), the value already set in step 1230 at the previous execution of this routine for the current fuel injection cylinder is used.

  Further, in the stage where the total number of injections N ≧ 5, the CPU 51 determines “Yes” in step 1235 and proceeds to step 1240 to set the value of “initial value fwini of fuel injection amount” for the current fuel injection cylinder. In 1225, the value of the fuel adhesion amount fwns (k) updated is set.

  Subsequently, the CPU 71 proceeds to step 1245, and prepares for the fuel injection amount fw (k-1) by synchronous injection for the current fuel injection cylinder in preparation for starting processing of the synchronous injection execution routine of FIG. After setting the initial value to a value equal to the above-mentioned “initial value fwini of fuel injection amount”, the routine proceeds to step 1295, where the second execution of this routine for the current fuel injection cylinder is temporarily terminated. This step 1245 constitutes a part of the fuel adhering amount initial value determining means.

  Thus, in the total number of injections N = 5 to 8, the initial value of the fuel adhesion amount fw (k-1) by synchronous injection for each cylinder is equal to the corresponding “initial value fwini of fuel injection amount”. The values are set in order.

  When the total number of injections N ≧ Nref + 1 (that is, N ≧ 9), the CPU 51 determines “No” when it proceeds to step 1110 in FIG. 11 and immediately proceeds to step 1195. Thus, only the process of incrementing the total number of injections N is performed thereafter by repeatedly executing the routine of FIG.

  In addition, the CPU 51 makes a “No” determination when it proceeds to step 1205 of FIG. 12, and immediately proceeds to step 1295 to end once. Thereby, the execution of asynchronous injection Nref times (eight times) (two times for each cylinder) by the routine of FIG. 12 is completed.

  Further, the CPU 71 is configured to repeatedly execute a routine for performing the synchronous injection shown by the flowchart in FIG. 13 for each cylinder. The CPU 71 continues to execute the routine shown in FIG. 13 for the current fuel injection cylinder every time the execution of the routine shown in FIG.

  Now, immediately after the execution of the routine shown in FIG. 12 is completed with the total number of times N ≦ Nref (N ≦ 8) (that is, in step 1215, the asynchronous injection instruction for the current fuel injection cylinder is issued) CPU 71 starts processing from step 1300 of this routine for the current fuel injection cylinder and proceeds to step 1305 to determine whether the total number of injections N is greater than the prescribed number Nref (ie, It is determined whether or not the synchronous injection is executed), it is determined as “No”, and the process immediately proceeds to Step 1395 to end the present routine tentatively. As a result, the synchronous injection instruction for the current fuel injection cylinder is not made.

  On the other hand, in a state where the total number of times N ≧ Nref + 1 (N ≧ 9), the state immediately after the execution of the routine shown in FIG. 12 is completed (that is, the state immediately after it is determined “No” in step 1205). Then, the CPU 71 makes a “Yes” determination at step 1305 to proceed to step 1310, where the engine speed NE, the intake air flow rate Ga measured by the air flow meter 61, and the table MapMc using NE and Ga as arguments are obtained. Based on the above, the in-cylinder intake air amount Mc that is the intake air amount of the current fuel injection cylinder is obtained.

  Next, the CPU 71 proceeds to step 1315 and obtains the basic fuel injection amount Fbase by dividing the obtained in-cylinder intake air flow rate Mc by the current target air-fuel ratio abyfr (= stoich). The required inflow fuel amount Fc is obtained by multiplying the basic fuel injection amount Fbase by a coefficient α. The coefficient α is a coefficient that is appropriately changed by air-fuel ratio feedback control or the like based on the output of the air-fuel ratio sensor 67.

  Next, the CPU 71 proceeds to step 1325, in which the cooling water temperature THW, the engine speed NE, the in-cylinder intake air amount Mc, the intake pipe pressure Pm, and the THW, NE, Mc, Pm are used as arguments. The adhesion rate R and the residual rate P are determined based on MapR and MapP, respectively.

  Subsequently, the CPU 71 proceeds to step 1330, in which the calculated required inflow fuel amount Fc, the obtained adhesion rate R, the residual rate P, the fuel adhesion amount fw (k-1), the above equation (3), Based on this, the commanded fuel injection amount fi corresponding to the synchronous injection is obtained. This step 1330 constitutes a part of the command fuel injection amount determining means.

  The fuel adhesion amount fw (k-1) is set in the previous step 1245 when the first execution of step 1330 is performed for the current fuel injection cylinder (that is, N = 9 to 12). If the corresponding value (that is, the corresponding initial value fwini) is used and step 1330 for the current fuel injection cylinder is executed for the second time or later (that is, N ≧ 13), the current fuel injection cylinder The value already updated in step 1345, which will be described later, is used at the time of the previous execution of this routine.

  Subsequently, the CPU 71 proceeds to step 1335 to instruct the fuel injection valve 39 for the current fuel injection cylinder to inject the fuel of the determined command fuel injection amount fi. As a result, when the crank angle of the fuel injection cylinder reaches a predetermined crank angle before the intake top dead center (for example, BTDC 75 ° CA), fuel is supplied to the current fuel injection cylinder only during the injection period corresponding to the command fuel injection amount fi. It is injected against. That is, synchronous injection is performed for the current fuel injection cylinder.

  Subsequently, the CPU 71 proceeds to step 1340, and based on the obtained adhesion rate R and residual rate P, the fuel adhesion amount fw (k-1), and the above equation (1), the fuel adhesion amount fw (k). Update. As the fuel adhesion amount fw (k-1), the same value as that used in step 1330 is used. Then, the CPU 71 proceeds to step 1345, sets the value of the fuel adhesion amount fw (k-1) to the value of the fuel adhesion amount fw (k) updated in step 1340, and then proceeds to step 1395 to temporarily execute this routine. finish. This step 1340 constitutes a part of the fuel adhesion amount estimation means.

  In this way, when the total number of injections N ≧ 9, the fuel deposition amount fw for each cylinder is updated by using the corresponding “initial value fwini of fuel deposition amount” as the initial value according to the routine of FIG. The corresponding command fuel injection amount fi is determined based on the above, and the fuel of the command fuel injection amount fi is injected synchronously into the corresponding cylinder.

  As described above, in the embodiment of the fuel injection amount control device for an internal combustion engine according to the present invention, the number of fuel injections after the engine is started is a predetermined prescribed number Nref (for example, Nref = 8. That is, 2 for each cylinder). Asynchronous injection is performed only during the start-up period until the fuel flow amount is reached, and after the start-up period, the amount of fuel adhering to the intake passage components estimated by the fuel behavior model (see equation (1) above) is taken into account Synchronous injection is performed based on the determined command fuel injection amount fi.

  In this embodiment, the injection pressure Pf (N) (N = 1, 2,... At each asynchronous injection start time estimated in consideration of the fluctuation of the injection pressure Pf generated by the asynchronous injection during the start-up period.・, Nref) is used to estimate each actual fuel injection amount fnsact based on asynchronous injection, and based on these actual fuel injection amounts, the `` fuel at the end of the start-up period used by the fuel behavior model is estimated. The initial value fwini of the adhesion amount fw is determined.

  Accordingly, the “initial value fwini of the fuel adhesion amount” is determined in consideration of “the deviation of the actual fuel injection amount from the command fuel injection amount” caused by “the fluctuation of the injection pressure Pf during the starting period”. Therefore, the “initial value fwini of the fuel adhesion amount” can be accurately determined. As a result, after the start period, the fuel adhesion amount fw corresponding to the synchronous injection is accurately estimated to aim at the engine air-fuel ratio. The air-fuel ratio can be matched with high accuracy.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the injection pressure Pf (N) (N = 1, 2,..., Nref) at each injection start time during the start period is equal to the injection pressure Pf at the previous injection start time. Using the rule that the injection pressure Pf (N) at the start of the current injection is determined from (N−1) and the value corresponding to the previous injection period (command asynchronous injection amount fnsd (N−1)) The asynchronous injection start timing determined by the engine rotational speed NE and the atmospheric temperature Ta are further taken into consideration, but the injection pressure Pf (N) is replaced with the engine rotational speed NE and the atmospheric temperature Ta. Alternatively, in addition to these, the fuel properties (for example, viscosity) may be taken into consideration. This is because the property of the fuel can be a factor that affects the injection pressure decrease amount ΔP (N).

  The injection pressure Pf (N) is acquired in consideration of the voltage (that is, the battery voltage) supplied to the electric pump P at a predetermined time point during the start period (for example, a certain time point during the cranking period). May be. The voltage greatly affects the initial fuel discharge performance of the electric pump P, and the injection pressure Pf (N) (particularly, the injection pressure Pf (1) at the start of the first asynchronous injection) depends on the electric pump P. This is because it largely depends on the initial fuel discharge performance.

  Further, in the above embodiment, the end condition of the asynchronous injection (the end condition of the start period, that is, the “predetermined condition”) is that the number N of fuel injections after the start reaches the predetermined specified number Nref. However, as the “predetermined condition”, it may be adopted that the engine speed NE exceeds a predetermined value (for example, 400 rpm).

  In addition, in the above embodiment, during the start-up period, the fuel adhesion amount fwns is updated for each asynchronous injection by using the fuel model described in the above equation (6), so that “the initial fuel adhesion amount fw Value fwini '' is determined, but the command asynchronous injection amount fnsd (N) (N = 1, 2,..., Nref) during the start-up period can be obtained without using the fuel model. A table for obtaining “initial value fwini of fuel adhesion amount fw” in consideration of “deviation of actual fuel injection amount from command fuel injection amount” due to “fluctuation of injection pressure Pf during start-up period” as at least an argument ( The “initial value fwini of the fuel adhesion amount fw” may be determined using a map) or the like.

1 is a schematic configuration diagram of a system in which a fuel injection amount control device according to an embodiment of the present invention is applied to a spark ignition type multi-cylinder internal combustion engine. It is the figure which showed notionally the mode that the fuel injected from the fuel injection valve adhered to an intake passage structural member. It is a figure for demonstrating the relationship between the fuel amount injected from the fuel injection valve, the fuel adhesion amount to an intake passage structural member, and the fuel amount which flows in in a fuel cylinder. It is the time chart which showed the change of the injection pressure of the fuel about the first three asynchronous injections among the asynchronous injections performed after engine starting. The amount of decrease in the injection pressure in the case shown in FIG. 4 (see the solid line) and the amount of decrease in the injection pressure in the case where the first injection period is longer (see the broken line) than in the case shown in FIG. It is a time chart for comparing. The amount of decrease in the injection pressure in the case shown in FIG. 4 (see the solid line) is compared with the amount of decrease in the injection pressure in the case where the engine speed is lower than that in the case shown in FIG. 4 (see the broken line). It is a time chart for. In order to compare the amount of decrease in the injection pressure in the case shown in FIG. 4 (see the solid line) and the amount of decrease in the injection pressure in the case where the atmospheric temperature is higher (see the broken line) than in the case shown in FIG. It is a time chart. It is the graph which showed an example of the relationship between the instruction | command asynchronous injection amount and engine rotational speed, and injection pressure fall when air temperature is fixed to a certain value. It is the graph which showed an example of the relationship between the command asynchronous injection amount and the atmospheric temperature, and the injection pressure decrease amount when the engine rotation speed is fixed to a certain value. It is the graph which showed the relationship between the command asynchronous injection amount and the injection pressure ratio, and the correction coefficient for correcting the command asynchronous injection amount. 3 is a flowchart showing a program for determining a command asynchronous injection amount and calculating an actual asynchronous injection amount, which is executed by the CPU shown in FIG. 1. It is the flowchart which showed the program for performing asynchronous injection which CPU shown in FIG. 1 performs. It is the flowchart which showed the program for performing the synchronous injection which CPU shown in FIG. 1 performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Spark ignition type multi-cylinder internal combustion engine, 20 ... Cylinder block part (engine main-body part), 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 39 ... Fuel injection valve, 41 ... Intake pipe, 62 ... Intake Temperature sensor 65 ... Crank position sensor 66 ... Water temperature sensor 68 ... Intake pipe pressure sensor 70 ... Electric controller 71 ... CPU

Claims (6)

Applied to an internal combustion engine having fuel injection means for injecting fuel into an intake passage upstream of the intake valve of the internal combustion engine;
Fuel adhesion amount estimation means for estimating a fuel adhesion amount that is an amount of fuel adhering to a member constituting the intake passage by injection by the fuel injection means;
After the start of fuel injection by the fuel injection means that is started by starting the internal combustion engine and after a predetermined condition is satisfied, the fuel based on the fuel adhesion amount estimated by the fuel adhesion amount estimation means Command fuel injection amount determining means for determining a command fuel injection amount that is a fuel amount instructed by the injection means;
A fuel injection amount control device for an internal combustion engine comprising:
The fuel adhering amount estimation means uses the initial value of the fuel adhering amount, which is the value of the fuel adhering amount when the predetermined condition is satisfied, and the predetermined condition is satisfied from the start of the fuel injection. A fuel injection amount control apparatus for an internal combustion engine, comprising: a fuel adhering amount initial value determining means that determines at least a change in injection pressure generated by fuel injection by the fuel injection means until a time point. The fuel injection amount control apparatus for an internal combustion engine according to claim 1,
The fuel adhesion amount initial value determining means includes:
Injection that is generated by the fuel injection, at each injection start time in a plurality of times of fuel injection by the fuel injection means that is executed from the start of the fuel injection to the time when the predetermined condition is satisfied Injection pressure estimating means for estimating in consideration of pressure fluctuations;
An actual fuel injection amount estimating means for estimating a corresponding actual fuel injection amount in the plurality of fuel injections based on the estimated injection pressure at each injection start time;
With
A fuel injection amount control device for an internal combustion engine configured to determine an initial value of the fuel adhesion amount based on at least each estimated actual fuel injection amount. The fuel injection amount control device for an internal combustion engine according to claim 2,
The injection pressure estimating means includes
Each injection start time in the multiple fuel injections using the rule that the injection pressure at the current injection start time is determined from the injection pressure at the previous injection start time and the value corresponding to the previous injection period A fuel injection amount control apparatus for an internal combustion engine configured to determine an injection pressure at the engine. The fuel injection amount control device for an internal combustion engine according to claim 3,
The injection pressure estimating means includes
Fuel injection amount control for an internal combustion engine configured to determine an injection pressure at each of the injection start points in consideration of injection start timings in the plurality of fuel injections determined by the operating speed of the internal combustion engine apparatus. In the fuel injection amount control device for an internal combustion engine according to claim 3 or 4,
The injection pressure estimating means includes
The injection pressure at the start of each injection is determined by further considering at least one of the temperature supplied to the electric pump that generates the injection temperature and the temperature of the atmosphere, the nature of the fuel, and the like. A fuel injection amount control device for an internal combustion engine. The fuel injection amount control device for an internal combustion engine according to any one of claims 2 to 5,
The actual fuel injection amount estimation means includes
The respective actual fuel injection amounts are estimated by correcting the corresponding command fuel injection amounts that are instructed to be injected in the plurality of fuel injections based on the estimated injection pressures at the respective injection start times. A fuel injection amount control device for an internal combustion engine configured as described above.

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