JP2008002330A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine capable of securing a quick response to accelerator operation, while excellently maintaining emission. <P>SOLUTION: A determining part 94 determines the strength of an acceleration request of a driver from an acceleration speed vap. A selecting part 95 sets an opening TAacc to an opening TAt of an arithmetically operated first time when the acceleration request is strong, and to an opening TAt of a second time after a delay time TD from a time when the acceleration request is weak at each arithmetic operation corresponding to an accelerator operation quantity Accp. An actuator 43a controls a throttle valve 43 so as to reach the opening TAt at the first time or the second time. When setting the opening TAt of the first time, a logic A2 determines a fuel injection quantity fi to a fuel injection cylinder from throttle valve opening TA. When setting the opening TAt of the second time, a logic M2 predicts the cylinder inside suction air volume MC of the fuel injection cylinder from an opening TAest corresponding to the opening TAacc, and the logic A2 determines its fuel injection quantity fi on the basis of the air volume MC. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine applied to a multi-cylinder internal combustion engine (hereinafter sometimes simply referred to as “engine”) mounted on a vehicle, and in particular, according to an operation amount of an accelerator pedal. The provisional target throttle valve opening calculated at the first calculation time is set as the target throttle valve opening at a future time when a predetermined delay time has elapsed from the calculation time, and the actual throttle valve opening The present invention relates to a fuel injection control device for an internal combustion engine that drives and controls the throttle valve so that becomes equal to the set target throttle valve opening.

  Conventionally known fuel injection control devices for internal combustion engines of this type use electronically controlled throttle valves. In order to maintain good emissions mainly, throttle valve delay control (referred to as "throttle delay"). .)It is carried out.

  That is, the conventional fuel injection control device, for example, as disclosed in Patent Document 1, delays the temporary target throttle valve opening corresponding to the operation amount of the accelerator pedal by a predetermined delay time, and While setting as the opening, the actual throttle valve opening is driven and controlled so as to match the set target throttle valve opening. That is, the setting of the target throttle valve opening and the drive control of the actual throttle valve opening corresponding thereto are called throttle delay. The conventional device grasps the target throttle valve opening from the present time to the future time by the delay time by this throttle delay, and based on these target throttle valve openings, the above-mentioned delay time from the present time. It is possible to estimate the actual opening of the throttle valve up to a future time point.

  By the way, in a fuel injection cylinder (a cylinder that injects any one of the multiple cylinders), a fuel injection amount required to obtain a predetermined target air-fuel ratio (usually a value around the theoretical air-fuel ratio) is accurately obtained. To this end, when the intake valve is closed at the future end of the intake stroke of the fuel injection cylinder (when the intake valve shifts from the opened state to the closed state), the intake is taken into the fuel injection cylinder. You must predict the amount of air that will be. Here, it is known that there is a close relationship between the intake air amount in the intake stroke of the fuel injection cylinder and the actual opening of the throttle valve when the intake valve is closed. Under this relationship, the intake air amount when the intake valve is closed in the future is predicted based on the actual opening of the throttle valve that can be estimated by the throttle delay.

  Further, in the fuel injection cylinder, at the time immediately before the start of fuel injection corresponding to a predetermined crank angle (the fuel injection amount calculation time when it is necessary to calculate the fuel injection amount), when the intake valve is closed in the future In the conventional apparatus, the delay time is set based on the time from the fuel injection amount calculation time to the intake valve closing time.

  Then, the conventional apparatus obtains the fuel injection amount based on the predicted intake air amount when the intake valve of the fuel injection cylinder is closed and the target air-fuel ratio, and the fuel of this fuel injection amount is determined as the fuel injection amount. The fuel is injected from the injector into the fuel injection cylinder before the intake valve is closed. If the target air-fuel ratio is set appropriately, precise fuel injection with substantially no excess or deficiency in the injection amount is achieved according to the set air-fuel ratio, and thereby the emission is maintained well.

However, in this conventional throttle delay, due to the delay time described above, a delay occurs from when the accelerator pedal is depressed until the actual throttle valve opening increases, so this delay causes For example, a driver who desires rapid acceleration may feel that the response of the engine or the vehicle on which the engine is mounted to the accelerator operation is not good.
JP-A-10-169469

  Therefore, one of the objects of the present invention is to adjust the above-described delay until the actual throttle valve opening increases in the throttle delay according to the strength of the driver's acceleration request. An object of the present invention is to provide a fuel injection control device for an internal combustion engine capable of ensuring a quick response to an accelerator operation while maintaining a good state.

  The fuel injection control device for an internal combustion engine according to the present invention is applied to a multi-cylinder internal combustion engine mounted on a vehicle. The apparatus includes an accelerator operation amount acquisition means, a temporary target throttle valve opening calculation means, an acceleration request acquisition means, an acceleration request determination means, a target throttle valve opening setting means, a throttle valve control means, an intake air An amount prediction unit, a fuel injection amount determination unit, and a fuel injection unit are provided.

The accelerator operation amount acquisition means acquires the operation amount of the accelerator pedal operated by the driver. The temporary target throttle valve opening calculating means calculates the temporary target throttle valve opening according to the acquired accelerator pedal operation amount at a predetermined cycle calculation time.
The acceleration request acquisition means determines whether or not acceleration of the vehicle has started. Specifically, the accelerator pedal opening (according to the accelerator pedal operation amount), the provisional target throttle valve opening (target throttle valve opening provisionally set according to the accelerator pedal operation amount), the target throttle valve opening The time point at which one of the values of the degree (the target opening used for driving and controlling the actual throttle valve) and the actual opening degree of the throttle valve starts to change from 0 is detected. It may be determined that acceleration has started. Further, the acceleration request acquisition means determines whether or not the acceleration of the vehicle has started in this way, and acquires a value corresponding to the strength of the driver's acceleration request when it is determined that the acceleration has started. . The strength of the acceleration request here refers to the degree of acceleration of the vehicle requested by the driver. The acceleration request determination means determines whether the driver's acceleration request is strong or weak based on a comparison between a value corresponding to the acquired acceleration request strength and a predetermined value.

  The target throttle valve opening setting means determines the calculated temporary target when it is determined that the acceleration request is strong every time the temporary target throttle valve opening is calculated at the time of calculation after the determination regarding the acceleration request. The throttle valve opening is set as a target throttle valve opening at a first time after a predetermined first delay time including 0 has elapsed from the calculation time. On the other hand, the target throttle valve opening setting means is calculated when it is determined that the acceleration request is weak every time the provisional target throttle valve opening is calculated at the time of calculation after the determination regarding the acceleration request. The provisional target throttle valve opening is set as a target throttle valve opening at a second time when a second delay time longer than the first delay time elapses from the calculation time.

  When the temporary target throttle valve opening is set as the target throttle valve opening at the first time point, the throttle valve control means is configured to detect the actual throttle valve after the first delay time has elapsed since the calculation of the temporary target throttle valve opening. Is controlled to be equal to the target throttle valve opening at the first time point. On the other hand, when the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, the throttle valve control means sets the actual throttle valve opening after the second delay time from the calculation time point. The throttle valve is driven and controlled so as to be equal to the target throttle valve opening at the two time points.

  When the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, the intake air amount predicting means has a plurality of second time points set for use in future throttle valve drive control. The amount of air sucked in the intake stroke of a specific cylinder (fuel injection cylinder) among the multiple cylinders is predicted by using any one or a plurality of target throttle valve openings. To do.

  For example, the target throttle valve opening used for predicting the amount of air to be sucked is the target throttle valve opening at the second time point when the intake valve of the fuel injection cylinder is closed or in the vicinity thereof. The target throttle valve opening up to the time. More specifically, the target throttle valve opening at the time when the intake valve of the fuel injection cylinder is closed or in the vicinity thereof is sequentially determined based on the amount of operation of the accelerator pedal from the beginning when the accelerator pedal is operated. The actual throttle valve opening is estimated based on the target throttle valve opening. A predetermined physical model (an intake air model using air flow rate, pressure and temperature, actual throttle valve opening degree, etc.) is assumed for intake air in the vicinity of the intake pipe from the throttle valve downstream to the intake valve. be able to.

  Under this physical model, the flow rate, pressure and temperature of the intake air until the future intake valve closing time are sequentially calculated while sequentially using the estimated actual throttle valve opening. The amount of air sucked into the fuel injection cylinder before the intake valve is closed (intake air amount) has a close relationship with the pressure and temperature of the intake air when the intake valve is closed. Based on the pressure and temperature of the intake air calculated as the time, the intake air amount until the intake valve closes can be obtained.

  When the provisional target throttle valve opening is set as the target throttle valve opening at the first time point, the fuel injection amount determining means is one of the multi-cylinders based on a value that changes according to the operation amount of the accelerator pedal. A first injection amount of fuel injected into each cylinder is determined. For example, the value that changes according to the operation amount of the accelerator pedal is the actual opening of the throttle valve (this will be described later). On the other hand, when the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, the fuel injection amount determining means determines the amount of fuel injected into the specific cylinder based on the predicted amount of air. A second injection amount is determined.

  When the provisional target throttle valve opening is set as the target throttle valve opening at the first time point, the fuel injection means injects the determined first injection amount of fuel into any of the cylinders. On the other hand, when the temporary target throttle valve opening is set as the target throttle valve opening at the second time point, the fuel injection means injects the determined second injection amount of fuel into the specific cylinder.

  According to this device, the operation amount of the accelerator pedal operated by the driver is acquired, and the provisional target throttle valve opening is calculated according to the acquired operation amount of the accelerator pedal at the time of calculation of the predetermined period. When it is determined that the acceleration of the vehicle has started, a value corresponding to the strength of the driver's acceleration request is acquired, and it is determined whether the acceleration request is strong or weak.

  After the determination about the acceleration request, every time the provisional target throttle valve opening is calculated at the time of calculation, if it is determined that the acceleration request is strong in the initial acceleration period, the calculated provisional target throttle valve opening Is set as the target throttle valve opening at the first time point after the first delay time (including 0) has elapsed from the calculation time point. On the other hand, if the acceleration request is determined to be weak during the initial acceleration period after the determination of the acceleration request at each calculation time of the temporary target throttle valve opening, the calculated temporary target throttle valve opening is Is set as the target throttle valve opening at the second time point after the second delay time (the second delay time is longer than the first delay time).

  Further, when the temporary target throttle valve opening is set as the target throttle valve opening at the first time point, the actual throttle valve opening is increased after the first delay time has elapsed since the calculation of the temporary target throttle valve opening. The throttle valve is driven and controlled to be equal to the target throttle valve opening at the first time point.

  In this case, along with the drive control of the throttle valve, the first injection amount of fuel injected into any one of the multiple cylinders is determined based on a value that changes according to the operation amount of the accelerator pedal. The determined first injection amount of fuel is injected into one of the cylinders. As described above, the value that changes according to the operation amount of the accelerator pedal is, for example, the actual opening of the throttle valve. That is, a target throttle valve opening is set according to the operation amount of the accelerator pedal, and the throttle valve is driven and controlled according to the target throttle valve opening. Then, the actual opening of the throttle valve is detected, and the first injection amount is determined based on the detected actual opening of the throttle valve and the rotational speed of the engine.

  On the other hand, when the temporary target throttle valve opening is set as the target throttle valve opening at the second time point, the actual throttle valve opening is performed after the second delay time has elapsed since the calculation of the temporary target throttle valve opening. The throttle valve is driven and controlled so that the degree becomes equal to the target throttle valve opening at the second time point.

  In this case, in addition to the drive control of the throttle valve, any one of the target throttle valve openings at a plurality of second time points set for use in the future drive control of the throttle valve is used. Thus, the amount of air sucked in the intake stroke of a specific cylinder among the multiple cylinders is predicted. A second injection amount of fuel injected into the specific cylinder is determined based on the predicted amount of air, and the determined second injection amount of fuel is injected into the specific cylinder.

  The effect of setting the above-described first delay time or second delay time in response to the driver's acceleration request will be described. That is, in this device, after the provisional target throttle valve opening is determined according to the operation of the accelerator pedal, the throttle valve is driven and controlled based on the target throttle valve opening corresponding to the provisional target throttle valve opening. Is shorter when the acceleration request is stronger than when the acceleration request is weak.

  For example, as the second delay time when the acceleration request is weak, the intake valve from the time immediately before the start of fuel injection corresponding to a predetermined crank angle (the fuel injection amount calculation time when the fuel injection amount needs to be calculated) By assuming the time until the valve closing time, the target throttle valve opening at the time of the future intake valve closing time is determined at the time of calculating the fuel injection amount. According to this, since the actual throttle valve opening when the intake valve is closed in the future follows the preset target throttle valve opening, the intake air amount prediction using the physical model is appropriately performed. Will be able to do. More specifically, the second delay time may be variably set according to the engine speed, but may be set to a fixed value in accordance with a representative value of the engine speed.

  When the driver's acceleration request is weak, a separately set target air-fuel ratio is used based on the intake air amount predicted in this way, and the fuel to be injected into the fuel injection cylinder (specific cylinder). The second injection amount is determined, and the determined second injection amount of fuel is injected into the fuel injection cylinder. As a result, fuel injection that is substantially in excess or deficiency in the fuel injection amount with respect to the target air-fuel ratio is achieved, thereby maintaining good emissions.

  On the other hand, when the driver's acceleration request is strong, the first delay time set as the delay time of the target throttle valve opening is shorter than the second delay time. Therefore, after the driver depresses the accelerator pedal, the drive control of the throttle valve according to the operation amount of the accelerator pedal, and the fuel injection of the injection amount corresponding to the amount of air sucked according to the opening degree of the throttle valve And the time interval until the engine torque increases is shorter. As a result, the driver can feel a better response of the engine or the vehicle equipped with the engine than when the acceleration request is weak. In particular, the response of the engine can be remarkably improved by using 0 for the first delay time.

  When the acceleration request is strong, a shorter delay time is set. Therefore, unlike the case where the acceleration request is weak, the target throttle at the time when the intake valve is closed at the time of fuel injection amount calculation. It may not be possible to determine the valve opening (and the actual throttle valve opening following this). At this time, since the intake air amount in the intake stroke of the fuel injection cylinder cannot be accurately predicted during the accelerator operation, it is difficult to determine an accurate fuel injection amount according to the target air-fuel ratio. However, even in such a case, the target throttle valve opening is set according to the amount of operation of the accelerator pedal (in addition, the actual throttle valve opening is estimated based on this, or the actual throttle valve opening is It is possible to estimate the intake air amount in the intake stroke and to determine the second injection amount based on this, under the physical model described above.

  Further, in the fuel injection control device of the present invention, the acceleration request determination means makes the determination regarding the acceleration request described above during the initial acceleration period from the time when it is determined that the acceleration of the vehicle has started to the time when the predetermined time has elapsed. It is preferably configured to do so.

  Specifically, in the initial acceleration period, the ratio of the current accelerator pedal opening to the maximum possible opening of the accelerator pedal is from 0% corresponding to full closure of the accelerator pedal to 10%. It may be a period until reaching. The initial acceleration period is a period until the temporary target throttle valve opening, the target throttle valve opening, and the actual throttle valve opening reach 0 ° to 5 °, after these values start to change from 0. It may be a period until a predetermined time elapses.

  According to this apparatus, the strength of the driver's acceleration request is determined during the initial acceleration period. Usually, the strength of the driver's acceleration request will appear prominently at the beginning of acceleration, so that the strength of the driver's acceleration request can be accurately estimated, particularly during this initial acceleration period. .

  Further, in this fuel injection control device, the target throttle valve opening setting means is configured to set the temporary target throttle valve opening calculated by the temporary target throttle valve opening calculating means during the initial acceleration period regardless of whether the acceleration request is strong or weak. It is preferable that the degree is set as the target throttle valve opening degree at the first time point.

  According to this, in the initial acceleration period, a shorter delay corresponding to the first delay time is always set out of the first delay time, the second delay time, and the two delays. Assuming that the driver's acceleration request is strong now, if a long delay is set during the initial acceleration period, the driver will have to wait until the acceleration request is determined to be strong after the accelerator pedal is depressed. You can feel that the response of the institution is bad. On the other hand, if a short delay is set during the initial acceleration period, the driver is unlikely to feel that the engine response is poor before the acceleration request is determined to be strong after the accelerator pedal is depressed. . That is, the response of the vehicle can be improved during the initial acceleration period.

  In this fuel injection control device, (1) the rate of change of the accelerator pedal operation amount over time, (2) the gear ratio of the transmission, or (3) the vehicle running Speed can be used.

  That is, in the above-described apparatus, as one aspect thereof, (1) the acceleration request acquisition means changes with time in the amount of operation of the accelerator pedal acquired by the accelerator operation amount acquisition means as a value corresponding to the strength of the acceleration request. It is preferable to obtain the rate. At this time, the acceleration request determination means determines that the acceleration request is strong when the temporal change rate of the acquired operation amount is larger than a predetermined change rate threshold, and the temporal change rate of the acquired operation amount is the change rate. When it is smaller than the threshold, it is determined that the acceleration request is weak.

  As the “time change rate of the operation amount of the accelerator pedal” here, the value of the time change rate of the accelerator pedal operation amount between any two time points in the initial acceleration period can be used. For example, using the rate of time change between the accelerator pedal operation amount at the start of the initial acceleration period and the accelerator pedal operation amount at the end of the initial acceleration period (that is, the average depression speed of the accelerator pedal during the initial acceleration period) Good.

  Furthermore, as this “time change rate of the operation amount of the accelerator pedal”, first, a plurality of time change rates of the accelerator pedal operation amount between any two time points in the initial acceleration period are obtained for different time points, An average time change rate value calculated from the plurality of time change rates may be used.

  Here, it is estimated that the acceleration request is strong only when the driver depresses the accelerator pedal in a hurry. Usually, since the driver's acceleration request is directly reflected on the speed at which the accelerator pedal is depressed, it is appropriate to estimate the strength of the acceleration request based on the accelerator pedal depression speed.

  As another aspect, it is desirable that (2) the acceleration request acquisition means acquires a value corresponding to the transmission gear ratio of the vehicle as a value corresponding to the strength of the acceleration request. At this time, the acceleration request determination means detects that the actual gear ratio is at the predetermined low speed stage gear ratio by comparing a value corresponding to the acquired gear ratio with a value indicating the predetermined gear ratio. If it is determined that the acceleration request is strong. On the other hand, the acceleration request determination means compares the value according to the acquired gear ratio with the value indicating the predetermined gear ratio, so that the actual gear ratio is higher than the lower gear ratio. When it is detected that the gear ratio is in the step side gear ratio, it is determined that the acceleration request is weak.

  Here, it is estimated that the driver's acceleration request is strong only when the transmission gear ratio is on the low speed side during the initial acceleration period. Normally, when the transmission is in a low gear stage such as a low gear, when the driver steps on the accelerator pedal, the driver tries to increase the speed of the vehicle traveling at a relatively low speed. It is appropriate to estimate that the demand for acceleration is strong because the transmission is in the low gear during the initial acceleration period when the engine starts operating the accelerator pedal.

  Furthermore, as another aspect, (3) the acceleration request acquisition means may acquire the speed at which the vehicle travels as a value corresponding to the strength of the acceleration request. At this time, the acceleration request determination means determines that the acceleration request is strong when the acquired vehicle speed is smaller than a predetermined speed threshold, and if the acceleration request is weak when the acquired vehicle speed is higher than the speed threshold. It comes to judge.

  Here, it is estimated that the acceleration request is strong only when the traveling speed of the vehicle is low during the initial acceleration period. As described above, it is reasonable to estimate that the acceleration request is strong when the speed of a vehicle traveling at a relatively low speed is increased.

  Any of these aspects can accurately estimate the strength of the driver's acceleration request with a simple configuration. By executing the above-described fuel injection control based on the estimation of the strength of the acceleration request, the above-described effect of maintaining the best possible emission and ensuring a quick response according to the acceleration operation of the accelerator pedal. Can be reached.

  Embodiments of an internal combustion engine fuel injection control apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a system in which the present fuel injection control device is applied to a spark ignition type multi-cylinder (four-cylinder) internal combustion engine 10. FIG. 1 shows only a longitudinal section of one cylinder (cylinder), but the other cylinders have the same configuration. The engine 10 is mounted on a vehicle equipped with a transmission.

  The internal combustion engine 10 supplies a gasoline mixture to the cylinder block unit 20 including a cylinder block, a cylinder block lower case and an oil pan, a cylinder head unit 30 fixed on the cylinder block unit 20, and the cylinder block unit 20. And an exhaust system 50 for releasing the 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 33a 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 spark discharge. An ignition plug 37 that ignites the air-fuel mixture by performing, an igniter 38 that includes an ignition coil that generates a high voltage to be applied to the ignition plug 37, and an injector 39 that injects fuel into the intake port 31 are provided.

  The intake system 40 is provided in an intake passage, an intake pipe (intake manifold) 41 that communicates with the intake port 31 of each cylinder and forms one end of the intake passage, an air filter 42 provided on the other end of the intake passage, and the intake passage. A throttle valve 43 having a variable opening cross-sectional area of the intake passage, a throttle valve actuator 43a composed of a DC motor for driving the throttle valve 43, and a surge tank 44 serving as a collecting portion of the intake pipe 41 branched toward each cylinder. I have.

  When the target throttle valve opening degree TAt is given to the throttle valve actuator 43a by an electronically controlled throttle valve (control) logic A1 (FIG. 4) achieved by an electric control device 70 described later, the actual throttle valve opening degree TA becomes the target throttle valve. The throttle valve 43 is driven and controlled so that the valve opening degree TAt is obtained.

  The exhaust system 50 includes an exhaust manifold 51 that branches and communicates with the exhaust port 34 of each cylinder, and an exhaust pipe 52 that is connected to the exhaust manifold 51 (actually, a collection portion where the branched portions of the exhaust manifold 51 are gathered). In addition, a three-way catalyst 53 provided (intervened) in the exhaust pipe 52 is provided.

  On the other hand, this system includes a hot-wire air flow meter 61, an intake air temperature sensor 62, an atmospheric pressure sensor (a throttle valve upstream pressure sensor) 63, a throttle position sensor 64, a cam position sensor 65, a crank position sensor 66, a water temperature sensor 67, an air-fuel ratio. A sensor 68 and an accelerator opening sensor 69 are provided.

  The air flow meter 61 detects the mass flow rate of the intake air flowing in the intake passage per unit time and outputs a signal representing the mass flow rate Ga. The intake air temperature sensor 62 is provided in the air flow meter 61, detects the intake air temperature (intake air temperature), and outputs a signal representing the intake air temperature Ta. The atmospheric pressure sensor 63 detects the pressure upstream of the throttle valve 43 (ie, atmospheric pressure) and outputs a signal representing the throttle valve upstream pressure Pa. The throttle position sensor 64 detects the opening of the throttle valve 43 and outputs a signal representing the throttle valve opening TA.

  The cam position sensor 65 generates a signal (G2 signal) having one pulse every time the intake camshaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °). The crank position sensor 66 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 67 detects the temperature of the cooling water of the engine 10 and outputs a signal indicating the cooling water temperature. The air-fuel ratio sensor 68 outputs a signal representing the air-fuel ratio by detecting the oxygen concentration in the exhaust gas flowing into the three-way catalyst 53. The accelerator opening sensor 69 detects an operation amount of the accelerator pedal 81 operated by the driver, and outputs a signal representing the accelerator pedal operation amount Accp.

  The electric control device 70 includes a CPU 71 connected to each other by a bus, a routine (program) executed by the CPU 71, a table (look-up table, map), a ROM 72 in which constants are stored in advance, and the CPU 71 temporarily stores data as necessary. The microcomputer includes a RAM 73 to be stored, a backup RAM 74 that stores data while the power is turned on, and retains the stored data while the power is shut off, and an interface 75 including an AD converter. The interface 75 is connected to the sensors 61 to 69, supplies signals from the sensors 61 to 69 to the CPU 71, and in response to instructions from the CPU 71, the actuator 33a, the igniter 38, the injector 39, and the variable intake timing device 33 A drive signal is sent to the throttle valve actuator 43a.

Next, an outline of how the fuel injection control device configured as described above determines the fuel injection amount fi and executes fuel injection after the acceleration operation of the accelerator pedal 81 will be described first. The processing described below is performed by the CPU 71 executing a program.
(Overview of fuel injection control)

  The fuel injection control device performs throttle delay during steady operation. Furthermore, this device stops the throttle delay in a predetermined period (initial acceleration period) from the time when the acceleration operation by the driver is started, and determines whether the driver's acceleration request is strong or weak in the initial acceleration period. To do. When it is determined that the driver's acceleration request is weak, the device starts (restarts) throttle delay. On the other hand, this apparatus stops the throttle delay when it is determined that the driver's acceleration request is strong. Actually, since the throttle delay is stopped in the initial acceleration period, the apparatus continues the throttle delay when it is determined that the driver's acceleration request is strong.

  The throttle delay does not set the provisional target throttle valve opening TAacc, which is determined according to the accelerator pedal operation amount Accp detected at a certain time, to the target throttle valve opening TAt at that time. Is set to the target throttle valve opening TAt at a future time by a predetermined delay time TD, and the actual throttle valve opening TA at a certain time is set to the target throttle valve opening TAt set at that time It is a control to match.

  Therefore, when the throttle delay is performed, the present apparatus grasps the target throttle valve opening degree TAt from the present time to the future time by the delay time TD at the present time. Then, this device can estimate the actual throttle valve opening TA from the current time to the future time by the delay time TD based on the future target throttle valve opening TAt that is currently grasped. Become. This estimated actual throttle valve opening TA is referred to as an estimated throttle valve opening TAest.

By the way, in a fuel injection control apparatus that injects fuel into a cylinder that is about to reach the intake stroke or a cylinder that is in the intake stroke (referred to as “fuel injection cylinder” for convenience), the intake valve of the fuel injection cylinder is closed. The fuel must be injected into the fuel injection cylinder before the time (when the intake valve is closed) before the time (fuel injection amount calculation time t0 described later). In order to perform this fuel injection, the amount of fuel to be injected (fuel injection amount fi) must be determined by the time before the start of the fuel injection. Further, the fuel injection amount fi is set so that the air-fuel ratio of the air-fuel mixture supplied to the engine coincides with the target air-fuel ratio AbyF, which is normally set to a value around the stoichiometric air-fuel ratio, as shown in the following equation (1). In addition, it must be determined based on the amount of air (in-cylinder intake air amount) MC sucked into the fuel injection cylinder. Therefore, the fuel injection control device needs to predict the in-cylinder intake air amount MC when the intake valve of the fuel injection cylinder is closed in advance.

  Therefore, the fuel injection control device first closes the intake valve 32 of the fuel injection cylinder by using the estimated throttle valve opening degree TAest at a future time point that can be estimated by the throttle delay described above. Sometimes, the cylinder intake air amount MC that will be sucked into the fuel injection cylinder is predicted. Then, the present apparatus determines the fuel injection amount fi by applying the predicted in-cylinder intake air amount MC to the above equation (1).

  More specifically, the method of predicting the in-cylinder intake air amount MC will be described in more detail. The in-cylinder intake air amount MC is determined by the pressure of the air in the intake pipe 41 (intake pipe air pressure) Pm and temperature (intake pipe air). (Temperature) Tm is closely related. Further, the intake pipe air pressure Pm and the intake pipe air temperature Tm are estimated for each minute time (calculation cycle) ΔTt under the physical model (the air model M2 described later shown in FIG. 4) of the intake air. Using the throttle valve opening degree TAest, it is possible to sequentially estimate until the intake valve 32 of the fuel injection cylinder is closed. The minute time ΔTt is preferably sufficiently shorter than the time required for the crankshaft to rotate 360 °.

  Therefore, this apparatus uses the physical model described above and the estimated throttle valve opening degree TAest obtained as a result of the throttle delay while performing the throttle delay, and uses the intake pipe air pressure Pm and the intake pipe air temperature. The cylinder intake air amount MC is obtained from the intake pipe air pressure Pm and the intake pipe air temperature Tm that are estimated sequentially, and the fuel injection amount fi is calculated from the cylinder intake air amount MC and the above equation (1). To decide.

  As described above, this apparatus performs throttle delay when it is determined that the acceleration request is weak after the initial acceleration period has elapsed. Therefore, in this case, the present apparatus can inject the fuel of the fuel injection amount fi without excess or deficiency into the fuel injection cylinder so that the air-fuel ratio of the air-fuel mixture supplied to the engine 10 substantially matches the target air-fuel ratio AbyF. This can improve emissions.

  On the other hand, when it is determined that the acceleration request is strong during the initial acceleration period, and the throttle delay is stopped based on the determination result, the device determines the fuel based on the throttle valve opening TA and the engine speed NE. Determine the injection amount fi.

  In addition, instead of determining the fuel injection amount fi based on the throttle valve opening TA and the engine rotational speed NE, the apparatus performs the above-described throttle delay even when the device stops the throttle delay. Similarly to the case, the fuel injection amount fi may be determined based on the estimated in-cylinder intake air amount MC. That is, the in-cylinder intake air amount MC is calculated using the target throttle valve opening degree TAt corresponding to the accelerator pedal operation amount Accp (as will be described later, the estimated throttle valve opening degree TAest corresponding to the target throttle valve opening degree TAt). The fuel injection amount fi can be determined based on the estimated in-cylinder intake air amount MC. The estimated in-cylinder intake air amount MC is a value that varies according to the accelerator pedal operation amount Accp.

However, when the opening degree of the throttle valve 43 is controlled without securing a sufficient delay time for the operation of the accelerator pedal 81, it is difficult to accurately estimate (predict) the in-cylinder intake air amount MC during the accelerator operation. Therefore, it is usually difficult to accurately obtain the fuel injection amount fi in the fuel injection cylinder with respect to the target air-fuel ratio AbyF.
(Overview of target throttle valve opening TAt setting)

  One feature of this apparatus is that a different target throttle valve opening degree TAt is set depending on whether the driver's acceleration request is strong or weak. As described above, this apparatus stops the throttle delay when it is determined that the acceleration request is strong in the initial acceleration period, and performs the throttle delay when it is determined that the acceleration request is weak. A different target throttle valve opening degree TAt is set for the throttle valve 43 according to each case.

  First, the target throttle valve opening degree TAt (FIG. 2C) that is set when the driver's acceleration request is strong during the initial acceleration period will be described. This device performs throttle delay before time ta before acceleration is started.

  If it is determined at time ta that the acceleration of the vehicle has started based on the operation amount Accp of the accelerator pedal 81, this apparatus sets this time ta as the initial acceleration start time. This device sets the time point tb when the value of the accelerator pedal operation amount Accp reaches a predetermined value as the initial acceleration end time point. Here, the period from time ta to time tb is the initial acceleration period. The device stops the throttle delay during this initial acceleration period. That is, this apparatus sets the target throttle valve opening degree TAt (FIG. 2C) without delay with respect to the temporary target throttle valve opening degree TAacc (FIG. 2B) during the initial acceleration period.

  When the initial acceleration period ends at time tb, the apparatus determines whether the driver's acceleration request is strong or weak. In this example, the depression speed vap of the accelerator pedal 81 in the initial acceleration period (time ta to tb) is used as a value corresponding to the strength of the acceleration request. The depression speed vap of the accelerator pedal 81 is a time change rate of the accelerator pedal operation amount Accp during the acceleration operation, and is hereinafter referred to as an accelerator pedal speed vap.

  In the initial acceleration period, the accelerator pedal speed vap is larger than a predetermined accelerator pedal speed threshold vth (that is, the driver has stepped on the accelerator pedal 81), and this apparatus has a strong acceleration request from the driver. If it is determined that, the device continues to stop the throttle delay even after the initial acceleration end time tb. That is, the present apparatus continues to set the target throttle valve opening degree TAt without a delay with respect to the temporary target throttle valve opening degree TAacc even after the initial acceleration period has elapsed.

  On the other hand, the target throttle valve opening degree TAt (FIG. 3C) that is set when the driver's acceleration request is weak during the initial acceleration period will be described. In the initial acceleration period (time ta to time tb), this device stops the throttle delay regardless of whether the driver's acceleration request is strong or weak, in the same way as when the acceleration request described above is strong. That is, this apparatus sets the target throttle valve opening degree TAt (FIG. 3C) without delay with respect to the temporary target throttle valve opening degree TAacc (FIG. 3B) during the initial acceleration period.

  In the initial acceleration period, the accelerator pedal speed vap is smaller than the accelerator pedal speed threshold value vth (that is, the driver gently depresses the accelerator pedal 81), so that this apparatus determines that the driver's acceleration request is weak. In this case, the apparatus starts throttle delay after a switching period of the delay time TD from time tb to time tc. That is, after the time tc, the present apparatus sets the temporary target throttle valve opening degree TAacc as the target throttle valve opening degree TAt at a time point delayed by the delay time TD from the calculated time point.

  This device drives and controls the throttle valve 43 so that the throttle valve opening TA is equal to the target throttle valve opening TAt described above, whether the driver's acceleration request is strong or weak.

As described above, in this apparatus, the target throttle valve opening degree TAt that differs depending on whether the driver's acceleration request during the initial acceleration period is strong or weak is set after the initial acceleration period has elapsed. Then, the throttle valve 43 is driven and controlled so as to follow the set target throttle valve opening degree TAt. In addition to these, in the present apparatus, fuel injections of different fuel injection amounts are executed in accordance with whether the driver's acceleration request during the initial acceleration period is strong or weak.
(Specific configuration and operation of each part)

The configuration and operation of each part of the fuel injection control device will be described more specifically. As shown in the functional block diagram of FIG. 4, the present apparatus mainly uses an electronic control throttle valve logic A1, an electronic control throttle valve model (in order to achieve the above-described fuel injection control and target throttle valve opening degree TAt setting. (Calculation unit) M1, intake air model M2, and injection amount determination logic A2.
<Electronically controlled throttle valve logic A1>

  The electronically controlled throttle valve logic A1 includes a provisional target throttle valve opening calculation unit 91, a first virtual throttle valve opening setting unit 92, a second virtual throttle valve opening setting unit 93, an acceleration request determination unit 94, A target throttle valve opening selector 95.

  The temporary target throttle valve opening calculation unit 91 reads the accelerator pedal operation amount Accp based on the output value of the accelerator opening sensor 69 every time the calculation cycle ΔTt (8 msec in this example) elapses. Then, the temporary target throttle valve opening calculation unit 91 obtains (calculates) the temporary target throttle valve opening TAacc based on the read accelerator pedal operation amount Accp and the table MapTA. This table MapTA is a table that defines the relationship between the accelerator pedal operation amount Accp and the provisional target throttle valve opening degree TAacc as shown in FIG. 5, and is stored in the ROM 72.

  The first virtual throttle valve opening setting unit 92 sets the first virtual throttle valve opening TAt1 based on the provisional target throttle valve opening TAacc (FIGS. 2C and 6). Further, the second virtual throttle valve opening degree setting unit 93 sets the second virtual throttle valve opening degree TAt2 based on the provisional target throttle valve opening degree TAacc (FIGS. 3C and 6). Here, the first virtual throttle valve opening degree TAt1 is a temporary target throttle valve opening degree that has no delay with respect to the temporary target throttle valve opening degree TAacc. That is, in this example, the first virtual throttle valve opening degree TAt1 is the same value as the temporary target throttle valve opening degree TAacc. The second virtual throttle valve opening degree TAt2 is a temporary target throttle valve opening degree obtained by delaying the temporary target throttle valve opening degree TAacc by a delay time TD (32 ms in this example).

  The acceleration request determination unit 94 obtains the accelerator pedal speed vap from the accelerator pedal operation amount Accp during the initial acceleration period, and determines whether or not the accelerator pedal speed vap is greater than the accelerator pedal speed threshold vth. The acceleration request determination unit 94 determines that the driver's acceleration request is strong when the accelerator pedal speed vap is greater than the accelerator pedal speed threshold vth, and the driver when the accelerator pedal speed vap is less than the accelerator pedal speed threshold vth. It is determined that the acceleration request is weak.

  The target throttle valve opening selector 95 selects the value of the first virtual throttle valve opening TAt1 obtained by the first virtual throttle valve opening calculator 92 as the target throttle valve opening TAt during the initial acceleration period. Set. Then, when the acceleration request determination unit 94 determines that the acceleration request is strong during the initial acceleration period, the target throttle valve opening selection unit 95 continues to the first virtual throttle valve opening after the end of the initial acceleration period. The value of TAt1 is set as the target throttle valve opening degree TAt.

  On the other hand, when the acceleration request determination unit 94 determines that the acceleration request is weak during the initial acceleration period, the target throttle valve opening selection unit 95 further performs a switching period (shown in FIG. 3C) after the end of the initial acceleration period. After the elapse of the time tb to the time tc, which is the delay time TD), the value of the second virtual throttle valve opening TAt2 obtained by the second virtual throttle valve opening calculating unit 93 is selected and the target throttle is selected. Set as valve opening TAt.

  When it is determined that the driver's acceleration request is weak, the target throttle valve opening degree TAt based on the first virtual throttle valve opening degree TAt1 in the initial acceleration period is changed to the second virtual period after the initial acceleration period has elapsed. The target throttle valve opening TAt is switched to the throttle valve opening TAt2. During this switching period, the value TAe of the initial acceleration end time tb is maintained as the target throttle valve opening degree TAt.

In this way, the throttle valve actuator 43a controls the drive of the throttle valve 43 based on the target throttle valve opening TAt set at the current time in the target throttle valve opening selector 95.
<Electronically controlled throttle valve model M1>

The electronically controlled throttle valve model M1 obtains an estimated throttle valve opening degree TAest from the temporary target throttle valve opening degree TAacc when the throttle delay is performed. Further, in this case, the intake air model M2 performs calculation using the estimated throttle valve opening degree TAest. In this example, it is assumed that the following formula 2 holds.

  The reason why the estimated throttle valve opening degree TAest may be obtained by the above equation 2 will be described. Assuming that the target throttle valve opening TAt is output from the electronically controlled throttle valve logic A1 to the throttle valve actuator 43a, the actual throttle valve opening TAt is caused by the mechanical delay of the actuator 43a, the inertia of the throttle valve 43, and the like. TA follows the target throttle valve opening degree TAt with a certain delay Δt (FIG. 2D or FIG. 3D).

However, normally, it is assumed that the actual throttle valve opening TA coincides with the target throttle valve opening TAt with almost no delay from the time when the drive signal to the throttle valve actuator 46a is sent, and this delay Δt is ignored. can do. Therefore, the estimated throttle valve opening degree TAest obtained by estimating the actual throttle valve opening degree TA is considered to be equal to the target throttle valve opening degree TAt. That is, it is considered that the following formula 3 holds.

Further, since the target throttle valve opening degree TAt based on the second virtual throttle valve opening degree TAt2 is set by the throttle delay, the target throttle valve output to the throttle valve actuator 46a after the delay time TD from the current calculation time point. The value of the opening degree TAt is equal to the value of the temporary target throttle valve opening degree TAacc at the time of the current calculation (FIG. 6). That is, it is considered that the following number 4 holds.

  Therefore, the electronic control throttle valve model M1 is calculated as the estimated throttle valve opening TAest at substantially the same time as when the estimated throttle valve opening TAest is set. It can be seen that the provisional target throttle valve opening TAacc value may be used.

Unlike the above-described formula 2, the electronically controlled throttle valve model M1 calculates the estimated throttle valve opening degree TAest from the temporary target throttle valve opening degree TAacc, for example, using another mathematical formula shown in the following formula 5. It may be.

  In Equation 5, TAest (k) is the estimated throttle valve opening degree TAest newly estimated at the time of the current calculation. TAest (k-1) is the latest estimated throttle valve opening degree TAest that has already been estimated at the time of this calculation (that is, the estimated throttle valve opening degree TAest estimated at the previous calculation time). TAacc (k) is the provisional target throttle valve opening degree TAacc newly set at the time of this calculation. Furthermore, as shown in FIG. 7, the function f (TAacc, TAest) is a function that takes a larger value (a function that monotonously increases with respect to ΔTA) as the difference ΔTA (= TAacc−TAest) between TAacc and TAest is larger. .

  Here, the estimated throttle valve opening TAest (estimated throttle in FIG. 6) obtained by applying the value of the target throttle valve opening TAt output to the throttle valve actuator 46a after the delay time TD from the current calculation time to the above equation (5). The value of the valve opening TAest2) is the estimated throttle valve opening TAest (estimated throttle valve opening TAest1 in FIG. 6) obtained by applying the provisional target throttle valve opening TAacc value at the time of the current calculation to the same number 5. Is equal to the value of

In the present example, the electronically controlled throttle valve model M1 obtains the estimated throttle valve opening degree TAest from the value of the temporary target throttle valve opening degree TAacc at the present time when the temporary target throttle valve opening degree TAacc is calculated by the above formula 2. In the electronically controlled throttle valve model M1, the provisional target throttle valve opening TAacc and the estimated throttle valve opening TAest from the present time to the time after the future delay time TD are made to correspond to the passage of time from the present time. It is stored in the RAM 73 in the form. Here, the actual throttle valve opening TA after the delay time TD has elapsed from the present time is regarded as a value equal to the estimated throttle valve opening TAest obtained at the current time.
<Intake air model M2>

  The intake air model M2 (FIG. 4) models the behavior of air in the intake system 40, and uses the estimated throttle valve opening degree TAest obtained by the electronically controlled throttle valve model M1 to intake air into the fuel injection cylinder. The cylinder intake air amount MC when the intake valve is closed in the stroke is predicted. In order to predict the in-cylinder intake air amount MC when the intake valve is closed, the intake air model M2 includes a throttle model M21, an intake valve model M22, an intake pipe model M23, and an intake valve model M24. The outline of the structure of each part M21-M24 is as follows.

  The throttle model M21 passes through an estimated throttle valve opening TAest that is sequentially calculated every calculation cycle ΔTt according to the accelerator operation, and a cylinder intake air flow rate estimated by an intake valve model M22 (described later). The flow rate of air passing through the throttle valve 43 in the intake passage is determined using the flow rate of air flowing into the combustion chamber 25) mc and the intake pipe air pressure Pm estimated by an intake pipe model M23 described later. The flow rate of air) mt is estimated. The intake valve model M22 obtains the in-cylinder intake air flow rate mc from the intake pipe air pressure Pm and the intake pipe air temperature Tm estimated by the later-described intake pipe model M23.

  The intake pipe model M23 uses the intake pipe air pressure Pm and the intake air pressure Pm and the intake pipe air pressure Pm and the intake pipe air temperature Tm obtained in the previous calculation using the throttle passage air flow rate mt, the cylinder intake air flow rate mc, and the previous calculation. The pipe air temperature Tm is estimated. The intake valve model M24 obtains the in-cylinder intake air flow rate mc using the intake pipe air pressure Pm and the intake pipe air temperature Tm, and further obtains the in-cylinder intake air amount MC from the obtained in-cylinder intake air flow rate mc. It has become.

  Each of these models M21 to M24 performs each calculation from the start of operation of the engine 10 with k = 1 to the calculation time point for each calculation cycle ΔTt. In the following, each variable with (k-1) represents each physical quantity estimated at the time of the previous (k-1) calculation, and each variable with (k) is the kth calculation this time Represents each physical quantity estimated at the time.

  Further, generalized mathematical expressions (Equations 12 and 13 described later) representing the intake pipe model M23 relate to time differentiation such as the pressure and temperature of air in the intake pipe 41. In the intake pipe model M23, the mathematical expression including this time differential term is discretized so that it can be calculated by a microcomputer (Equation 14 and Equation 15 described later).

  Based on these discretized mathematical formulas and the physical quantity of the intake air in the intake pipe 41 estimated at the current calculation time point, the present apparatus will perform the next time after the calculation cycle ΔTt from the current calculation time point. The physical quantity of the intake air at the time of the calculation is estimated. Specifically, as shown in FIG. 4, after the k-th calculation result in the intake pipe model M23 is updated by adding 1 to k in the throttle model M21 and the intake valve model M22, and then updating k. Is used as the (k-1) th calculation result of the intake pipe model M23 at the time of the kth calculation. Further, the kth calculation result in the intake pipe model M23 is derived from the (k-1) th calculation result of the throttle model M21 and the intake valve model M22.

  Each model M21-M24 repeats each calculation from the calculation time point k = 1. When the calculation time point k = k0 corresponding to the fuel injection amount calculation time point t0 (time t0 in FIG. 6) is reached, the electronically controlled throttle valve model M1 determines the provisional target throttle valve opening degree TAacc at the calculation time point k = k0. Based on (k0), the estimated throttle valve opening degree TAest (k0) after the lapse of the delay time TD from the time t0 is obtained. Accordingly, the in-cylinder inflow air flow rate mc (k0) at this calculation time point k = k0 is in the cylinder in the vicinity of the intake valve closing time (if the delay time TD is an appropriate value for the engine speed NE). This represents the inflow air flow rate mc.

Below, operation | movement of each said model M21-M24 which comprises these intake air models M2 is outlined. Each model M21-M24 is well known. For example, in JP 2001-41095 A, JP 2003-184613 A, and the like, more specific control in each model M21 to M24 for estimating the cylinder intake air amount MC using the estimated throttle valve opening degree TAest. Details of the procedure, the principle on which the models M21 to M24 are based, and the like are disclosed. Please refer to the literature as necessary.
-Throttle model M21-

  The throttle model M21 includes an estimated throttle valve opening degree TAest (k-1), a cylinder intake air flow rate mc (k-1) calculated by an intake valve model M22 described later, and an intake pipe air calculated by an intake pipe model M23 described later. This is a model for estimating the throttle passage air flow rate mt (k-1) by applying the pressure Pm (k-1) or the like to the following equation 6 and the following equation 7. The following formula 6 and the following formula 7 are obtained based on physical laws such as energy conservation law, momentum conservation law, mass conservation law, and equation of state, as described in the above-mentioned references.

Note that the intake pipe model M23 described later uses the calculation result mt (k-1) at the previous calculation time point (k-1) of the throttle model M21, as shown in Expressions 14 and 15, to calculate the current calculation time point. The calculation results Pm (k) and Tm (k) at k are derived. In accordance with the description of the intake pipe model M23, the following equation (6) is a mathematical expression related to the value at the calculation time point (k-1). In Expression 11 in an intake valve model M22 described later, the calculation result mc (k-1) at the calculation time point (k-1) is derived as in Expression 6 below. More precisely, the estimated throttle valve opening TAest (k0) should be used as the estimated throttle valve opening TAest at the fuel injection amount calculation time point t0 (FIG. 6). (k0-1) is used.

  The in-cylinder intake air flow rate mc (k-1) of Equation 6 is obtained by an intake valve model M22 described later. The intake pipe air pressure Pm (k-1) is obtained by an intake pipe model M23 described later. Further, the throttle valve upstream pressure (that is, atmospheric pressure) Pa detected by the atmospheric pressure sensor 63 is used. The throttle valve upstream pressure Pa is substituted for the initial value Pm (0) of the intake pipe air pressure at the operation start time k = 1.

  Φ is a function for (Pm / Pa) as shown in Equation 7 above, and a table MapΦ defining the relationship between the value (Pm / Pa) and the value Φ (Pm / Pa) is stored in the ROM 72. Yes. κ is a specific heat ratio. Hereinafter, κ is treated as a constant value. From the above table MapΦ and the value Pm (k-1) / Pa obtained by dividing the intake pipe air pressure Pm (k-1) by the throttle valve upstream pressure Pa, the value Φ (Pm (k-1) / Pa) (= MapΦ (Pm (k-1) / Pa)) is obtained.

  Similarly, with reference to this table MapΦ, a value Φ (PmTA / Pa) (= MapΦ (PmTA / Pa)) is obtained from a value PmTA / Pa obtained by dividing the intake pipe air pressure PmTA by the throttle valve upstream pressure Pa. . The intake pipe air pressure PmTA here is obtained based on the estimated throttle valve opening degree TAest (k-1) obtained by the electronically controlled throttle valve model M1, the engine speed NE, and the opening / closing timing VT of the intake valve 32. . That is, the ROM 72 stores a table MapPm that defines the relationship among the estimated throttle valve opening degree TAest (k-1), the engine speed NE, the opening / closing timing VT of the intake valve 32, and the intake pipe air pressure PmTA. Yes. The intake pipe air pressure PmTA is obtained as a value MapPm (TAest (k-1), NE, VT) based on this table MapPm.

A more detailed description will be given of the above formula 6. Generally, the throttle passing air mts, the value of Φ (Pm / Pa) and a predetermined coefficient k (a coefficient determined from a flow coefficient, an opening area of the intake passage by the throttle valve 43, an intake air temperature Ta, a throttle valve upstream pressure Pa, etc.) The relationship shown in the following equation 8 holds.

In the above equation 8, when the engine 10 is in a steady state (when the opening degree of the throttle valve 43 remains constant and the intake valve 32 is closed), the throttle-passing air flow rate is mtsTA, and the intake pipe air pressure is PmTA. In this case, using the same coefficient k1 as the coefficient k, the throttle passing air flow rate mtsTA is expressed as the value Φ (PmTA / Pa) multiplied by the coefficient k1, as shown in the following equation 9. Further, the throttle passage air flow rate mt (k−1) is expressed as the value Φ (Pm (k−1) / Pa) multiplied by a predetermined coefficient k2 similar to the coefficient k1 as shown in the following formula 10. Is done. Here, it is assumed that the coefficient k1 is equal to the coefficient k2, and further, the above equation 6 is obtained with the throttle passing air flow rate mtsTA as the cylinder intake air flow rate mc (k-1).

As described above, the throttle model M21 first obtains the value Φ (Pm (k-1) / Pa), and the intake pipe air pressure PmTA obtained using the estimated throttle opening degree TAest (k-1). Based on the above, the value Φ (PmTA / Pa) is obtained. Since the in-cylinder intake air flow rate mc (k-1) is obtained by the following intake valve model M22, each factor on the right side of the above equation 6 is determined. The throttle model M21 obtains the throttle passage air flow rate mt (k-1) as the product of the factors.
-Intake valve model M22-

The intake valve model M22 is a model that estimates the in-cylinder inflow air flow rate mc (k-1) from the intake pipe air pressure Pm (k-1) and the intake pipe air temperature Tm (k-1). The intake pipe air pressure Pm (k-1) and the intake pipe air temperature Tm (k-1) are obtained by an intake pipe model M23 described later. Now, the pressure in the cylinder in the intake stroke (including when the intake valve is closed) can be regarded as the pressure upstream of the intake valve 32, that is, the intake pipe air pressure Pm. It can be considered that it is proportional to the air pressure Pm in the intake pipe when the intake valve is closed. Therefore, the intake valve model M22 obtains the in-cylinder inflow air flow rate mc according to the following formula 11 based on an empirical rule.

  In Equation 11, the value C is a proportional coefficient, and the value D is an amount corresponding to the amount of burned gas remaining in the cylinder. The value C can be obtained from the table MapC that defines the relationship between the engine speed NE and the opening / closing timing VT of the intake valve 32 and the value C, the current engine speed NE, and the current opening / closing timing VT of the intake valve 32. Yes (C = MapC (NE, VT)). Similarly, the value D is obtained from the table MapD that defines the relationship between the engine speed NE and the opening / closing timing VT of the intake valve 32 and the value D, the current engine speed NE, and the current opening / closing timing VT of the intake valve 32. Can be obtained (D = MapD (NE, VT)). The table MapC and the table MapD are stored in the ROM 72. As described above, the throttle upstream pressure Pa is substituted for the initial value Pm (0) of the intake pipe air pressure, and further, the intake air temperature Ta is substituted for the initial value Tm (0) of the intake pipe air temperature. Is substituted.

As described above, the intake valve model M22 includes the intake pipe air pressure Pm (k-1) and the intake pipe air temperature Tm (k-1) estimated by the intake pipe model M23, and the current throttle passage air temperature Ta. Is applied to the above equation 11, the cylinder inflow air flow rate mc (k-1) is estimated.
-Intake pipe model M23-

The intake pipe model M23 has the following expression 14 and expression 15 obtained by discretizing the following expression 12 and expression 13 based on the mass conservation side and the energy conservation law regarding the air in the intake pipe 41 by the difference method, respectively. This is a model for determining the pipe air pressure Pm and the intake pipe air temperature Tm. That is, the throttle passage air flow rate mt, the in-cylinder intake air flow rate (the flow rate of air flowing out from the intake pipe 41) mc, the intake pipe air pressure Pm, and the intake pipe air temperature Tm are discretized, respectively. Thus, Expressions 14 and 15 are obtained.

  Here, R is a gas constant, and Vm is the volume of the intake passage from the throttle valve 43 to the intake valve 32. Further, the throttle passage air flow rate mt (k-1) is obtained by the throttle model M21, and the in-cylinder inflow air flow rate mc (k-1) is obtained by the intake valve model M32. The specific heat ratio κ and the current intake air temperature Ta are also used.

The intake pipe model M23 includes a throttle passage air flow rate mt (k-1), an in-cylinder inflow air flow rate mc (k-1), an intake pipe air pressure Pm (k-1) estimated at the previous calculation, and an intake pipe air temperature. The latest intake pipe air pressure Pm (k) and intake pipe air temperature Tm (k) of this time are calculated by applying Tm (k-1) to the above equations 14 and 15.
-Intake valve model M24-

  The intake valve model M24 includes a model similar to the intake valve model M22. That is, the intake valve model M24 obtains the in-cylinder inflow air flow rate mc (k) by substituting the intake pipe air pressure Pm (k) and the intake pipe air temperature Tm (k) into the above equation (11). The intake pipe air pressure Pm (k) and the intake pipe air temperature Tm (k) are newly obtained by the intake pipe model M23. Furthermore, since the number 2 is adopted in this example, the provisional target throttle valve opening degree TAacc (k0) at the calculation time point k = k0 immediately before the start of fuel injection has elapsed by the delay time TD from the corresponding time t0. Represents the estimated throttle valve opening degree TAest (k0) obtained by estimating the actual opening degree of the throttle valve 43.

  Accordingly, the in-cylinder inflow air flow rate mc (k0) at the calculation time point k = k0 represents the in-cylinder inflow air flow rate near the intake valve closing time. (As described above, in the intake pipe model M23 of the present example, the discretizations of the equations 14 and 15 are performed, and therefore, the intake air model M2 is strictly estimated throttle at the calculation time point k = k0-1. Using the valve opening degree TAest (k0-1), the in-cylinder inflow air flow rate mc (k0) at the calculation time point k = k0 is obtained.)

Further, the intake valve model M24 multiplies in-cylinder intake air when the intake valve is opened by multiplying the in-cylinder inflow air flow rate mc (k0) calculated immediately before the start of fuel injection by the intake valve opening time Tint. Find the amount MC. The intake valve opening time Tint is calculated from the current engine speed NE and the current opening / closing timing VT of the intake valve 32.
<Injection amount determination logic A2>

  The injection amount determination logic A2 determines the fuel injection amount fi based on the in-cylinder intake air amount MC or the throttle valve opening TA. When the target throttle valve opening selector 95 selects the second virtual throttle valve opening TAt2 (FIG. 3C) as the target throttle valve opening TAt (that is, when the acceleration request is weak during the initial acceleration period) In the case where it is determined and after the initial acceleration period has elapsed, the injection amount determination logic A2 applies the in-cylinder intake air amount MC calculated by the intake air model M2 to the above equation 1 to inject fuel. Determine the quantity fi. The injector 39 performs fuel injection according to the fuel injection amount fi.

  On the other hand, when the target throttle valve opening selector 95 selects the first virtual throttle valve opening TAt1 (FIG. 2C) as the target throttle valve opening TAt (that is, in the initial acceleration period, and When it is determined that the acceleration request is strong in the initial acceleration period and after the initial acceleration period elapses), the injection amount determination logic A2 includes the throttle valve opening TA, the engine speed NE, and a predetermined table. The fuel injection amount fi is determined using (a table that defines the relationship between the estimated throttle valve opening degree TAest and the engine speed NE and the fuel injection amount fi). It is assumed that the injection amount determination logic A2 determines the fuel injection amount fi in the same manner even during the switching period. The injector 39 performs fuel injection according to the fuel injection amount fi.

Specifically, the injection amount determination logic A2 is configured to input the target selection data S from the target throttle valve opening selection unit 95. The target selection data S is selected from the first virtual throttle valve opening TAt1 and the second virtual throttle valve opening TAt2 when the target throttle valve opening selector 95 sets the target throttle valve opening TAt. It is data indicating whether or not The injection amount determination logic A2 is determined according to the target selection data S depending on whether the target throttle valve opening TAt is based on the first virtual throttle valve opening TAt1 or the second virtual throttle valve opening TAt2. To obtain the correct fuel injection amount fi.
(Actual operation)

  As described above, one of the features of the present fuel injection control device is the setting of the target throttle valve opening degree TAt and the fuel injection control corresponding to the setting of the target throttle valve opening degree TAt. Hereinafter, an operation related to the setting of the target throttle valve opening degree TAt will be described. First, the outline of the operation will be described. This apparatus calculates a temporary target throttle valve opening degree TAacc according to the accelerator pedal operation amount Accp (refer to FIG. 8 for details), and this temporary target throttle valve. The opening degree TAacc is held for the delay time TD from the calculation time. By executing the routine for calculating the temporary target throttle valve opening TAacc, the function of the temporary target throttle valve opening calculating means is achieved.

  In addition, the device determines the strength of the driver's acceleration request during the initial acceleration period (see FIG. 10 for details). By executing the routine for determining the driver's acceleration request, the functions of the acceleration request acquisition means and the acceleration request determination means are achieved.

Furthermore, the apparatus sets a target throttle valve opening degree TAt based on the first virtual throttle valve opening degree TAt1 during the initial acceleration period. If it is determined that the acceleration request is strong during the initial acceleration period, the apparatus The target throttle valve opening degree TAt based on the first virtual throttle valve opening degree TAt1 is set continuously after the initial acceleration period has elapsed. On the other hand, when it is determined that the acceleration request is weak during the initial acceleration period, the device uses the second virtual throttle valve opening degree TAt2 after the initial acceleration period and further after the switching period of the delay time TD. A target throttle valve opening degree TAt is set (refer to FIG. 11 for details). By executing a routine for setting the target throttle valve opening degree TAt, the function of the target throttle valve opening setting means is achieved.
<Temporary target throttle valve opening calculation>

  The CPU 71 of the electric control device 70 executes the temporary target throttle valve opening calculation routine shown by the flowchart in FIG. 8 every elapse of the calculation cycle ΔTt. Thereby, the CPU 71 calculates the temporary target throttle valve opening degree TAacc from the accelerator pedal operation amount Accp, and further sets the temporary target throttle valve opening degree TAacc as virtual throttle valve opening degrees TAt (0) to TAt (ntdly). Hold only the delay time TD. The delay count ntdly is a value obtained by dividing the delay time TD by the calculation period ΔTt. Here, the virtual throttle valve opening TAt (ntdly) corresponds to the first virtual throttle valve opening TAt1 (FIG. 2C), and the virtual throttle valve opening TAt (0) is the second virtual throttle valve opening TAt2. This corresponds to (FIG. 3C).

  More specifically, when the predetermined timing is reached, the CPU 71 starts processing from step 800, proceeds to step 805, sets "0" to the variable i, proceeds to step 810, and the variable i is the delay count ntdly. It is determined whether or not. Since the variable i is “0” when this loop is executed for the first time, the CPU 71 determines “No” in step 810. In step 815, the CPU 71 stores the value of the virtual throttle valve opening degree TAt (i + 1) in the virtual throttle valve opening degree TAt (i). That is, when the loop by the variable i is first executed, the value of the virtual throttle valve opening degree TAt (1) is stored in the virtual throttle valve opening degree TAt (0).

  Next, the CPU 71 adds “1” to the value of the variable i in step 820 and returns to step 810. If the value of the variable i is smaller than the delay count ntdly, steps 815 and 820 are executed again. That is, Steps 815 and 820 are repeatedly executed until the value of the variable i is increased to be equal to the delay count ntdly. As a result, the value of the virtual throttle valve opening degree TAt (i + 1) is sequentially shifted to the virtual throttle valve opening degree TAt (i).

  For example, when ntdly = 4, as shown in FIG. 9, the new values of the virtual throttle valve openings TAtt5 (0) to TAtt5 (3) at a certain calculation time point t5 are the virtual throttle values at the previous calculation time point t4. It is equal to each value of valve opening TAtt4 (1) to TAtt4 (4). Here, assuming that ta represents time, virtual throttle valve openings TAtta (0) to TAtta (ntdly) represent virtual throttle valve openings TAt (0) to TAt (ntdly) at time ta, respectively. .

  If the value of the variable i becomes equal to the delay number ntdly by repeating the above-described step 820, the CPU 71 determines “Yes” in step 810 and proceeds to step 825. In step 825, the current accelerator pedal operation amount is determined. Get Accp.

Next, in step 830, the CPU 71 obtains a temporary target throttle valve opening degree TAacc based on the accelerator pedal operation amount Accp. In this example, as shown in the following Expression 16, the value MapTA () obtained from the table MapTA in FIG. 5 according to the provisional target throttle valve opening degree TAacc (k-1) at the time of the previous calculation and the accelerator pedal operation amount Accp. Acc) is used to calculate the current temporary target throttle valve opening TAacc (k). Here, the value m and the value n are predetermined values determined by experiments or simulations.

  By the processing in step 830, for example, as shown in FIGS. 2A and 2B, a temporary target throttle valve opening degree TAacc that is delayed with respect to the accelerator pedal operation amount Accp is obtained. Such delay by filtering is performed in order to make the change in the throttle valve opening TA more gradual with respect to the change in the accelerator pedal operation amount Accp.

  In step 835, the CPU 71 sets the value of the provisional target throttle valve opening TAacc to the virtual throttle valve opening TAt (ntdly), and in the subsequent step 895, the routine is temporarily ended. In the example shown in FIG. 9, the virtual throttle valve opening degree TAtt5 (4) is newly set by the processing of step 835 at the calculation time point t5.

In this routine, the temporary target throttle valve opening degree TAacc is set as described above, and this temporary target throttle valve opening degree TAacc is held for the delay time TD.
<Acceleration request determination>

  Next, an acceleration request determination routine executed by the CPU 71 for determining the strength of the driver's acceleration request will be described with reference to FIG. The CPU 71 repeatedly executes this routine every time a predetermined time elapses.

  When the predetermined timing comes, the CPU 71 starts processing from step 1000. In subsequent step 1005, the CPU 71 determines whether or not the current time is the initial acceleration start time. In this example, the time when the value of the accelerator pedal operation amount Accp starts to increase from 0 is set as the initial acceleration start time. If it is now the initial acceleration start time, the CPU 71 determines “Yes” in step 1005 and proceeds to step 1010 to set the current time value as the initial acceleration start time ta (see FIG. 2 or FIG. 3). reference). Next, the CPU 71 proceeds to step 1095 to end the present routine tentatively.

  On the other hand, if it is determined in step 1005 that the current time is not the initial acceleration start time, the CPU 71 determines “No” in step 1005 and further determines whether or not it is the initial acceleration end time in step 1015. . In this example, the time when the value of the accelerator pedal operation amount Accp reaches a predetermined value is set as the initial acceleration end time. If it is now the end point of the initial acceleration, the CPU 71 makes a “Yes” determination at step 1015 and proceeds to step 1020 to set the value of the current time as the initial acceleration end point tb.

  Next, in step 1025, the CPU 71 stores the virtual throttle valve opening degree TAt (ntdly) newly calculated in the temporary target throttle valve opening degree calculation routine of FIG. 8 as a value TAe. This value TAe corresponds to the target throttle valve opening degree TAt in the switching period (time tb to time tc) of FIG. 3C or FIG. 9, and is used in the target throttle valve opening setting routine shown in FIG. .

Then, the CPU 71 proceeds to step 1030, obtains the accelerator pedal speed vap in the initial acceleration period, and determines whether or not the accelerator pedal speed vap is equal to or higher than the accelerator pedal speed threshold vth. The accelerator pedal speed vap is given by the following equation 17, where Accpb is the accelerator pedal operation amount Accp at time tb. Here, the accelerator pedal speed vap is calculated based on the accelerator pedal operation amount “0” at the initial acceleration start time ta and the accelerator pedal operation amount Accpb at the initial acceleration end time tb. Accelerator pedal operation amount Accp at the two time points is detected, and the time change rate between the accelerator pedal operation amount Accp at one time point and the accelerator pedal operation amount Accp at the other time point is defined as the accelerator pedal speed vap. It may be calculated.

  In response to the determination in step 1030, the CPU 71 sets the value of the acceleration request flag X to “1” indicating that the acceleration request is strong or “0” indicating that the acceleration request is weak in steps 1035 and 1040. To do. That is, when the accelerator pedal speed vap is equal to or higher than the accelerator pedal speed threshold vth, the CPU 71 determines “Yes” in step 1030. In this case, in step 1035, the CPU 71 sets the value of the acceleration request flag X to “1”, and stores data indicating that the driver's acceleration request is strong in the initial acceleration period for later processing.

  On the other hand, if the accelerator pedal speed vap is smaller than the accelerator pedal speed threshold vth, the CPU 71 makes a “No” determination at step 1030. In this case, in step 1040, the CPU 71 sets the value of the acceleration request flag X to “0” and stores data indicating that the driver's acceleration request was weak during the initial acceleration period. After these processes, the CPU 71 proceeds to step 1095 to end the present routine tentatively.

  On the other hand, if “No” is determined in both steps 1005 and 1015, that is, if the current time is neither the start time nor the end time of the initial acceleration period, the CPU 71 determines in step 1045 the latest initial acceleration. It is determined whether a predetermined time has elapsed after the period is started. If the predetermined time has not elapsed since the start of the most recent initial acceleration period, the CPU 71 makes a “No” determination at step 1045 to proceed to step 1095 to end the present routine tentatively.

  On the other hand, if the predetermined time has elapsed after the start of the latest initial acceleration period, the CPU 71 determines “Yes” in step 1045. Then, in the subsequent step 1040, the CPU 71 resets the value of the acceleration request flag X to “0”. By resetting the acceleration request flag X, the target throttle valve opening degree TAt for performing throttle delay is set in the target throttle valve opening degree setting routine shown in FIG. That is, the present apparatus performs throttle delay during a period excluding the initial acceleration period during acceleration operation of the accelerator pedal 81, that is, during normal operation (during steady operation, deceleration operation, etc.). After the processing at step 1040, the CPU 71 proceeds to step 1095 to end this routine once.

As described above, in this routine, at the initial acceleration end time tb, it is determined whether the accelerator pedal speed vap in the initial acceleration period is large or small. In response to this, it is estimated whether the driver's acceleration request is strong or weak. If the acceleration request is strong, “1” is set as the value of the acceleration request flag X. On the other hand, if the acceleration request is weak, “0” is set as the value of the acceleration request flag X.
<Target throttle valve opening setting>

  Next, a target throttle valve opening setting routine executed by the CPU 71 for setting the target throttle valve opening TAt will be described with reference to FIG. The CPU 71 repeatedly executes this routine every time a predetermined time elapses. Here, the values of the virtual throttle valve openings TAt (0) and TAt (ntdly) obtained by the provisional target throttle valve opening calculation routine of FIG. 8, and the values of the acceleration request flag X set by the acceleration request judgment routine of FIG. Etc. are used.

  The CPU 71 starts processing from step 1100 when the predetermined timing comes. In the following step 1105, the CPU 71 determines whether or not the current time is in the initial acceleration period. If it is now during the initial acceleration period, the CPU 71 makes a “Yes” determination at step 1105 to proceed to step 1110, where the virtual throttle valve opening degree TAt ( ntdly) is set as the target throttle valve opening degree TAt. That is, in the initial acceleration period, the throttle delay is stopped regardless of whether the acceleration request is strong or weak. Then, the CPU 71 proceeds to step 1195 to end the present routine tentatively.

  On the other hand, if it is determined at step 1105 that the current time is not in the initial acceleration period, the CPU 71 determines “No” at step 1105 and proceeds to step 1115 to check whether the acceleration request flag X is “1”. Determine whether or not. If the acceleration request flag X is set to “1”, and it is determined that the driver's acceleration request is strong in the past initial acceleration period, the CPU 71 determines “Yes” in step 1115. Then, the process proceeds to Step 1110. In step 1110, the CPU 71 stops the throttle delay in the same manner as described above, and in step 1195, the routine is temporarily ended.

  On the other hand, if “No” is determined in both steps 1105 and 1115, that is, the current time is not the initial acceleration period and the acceleration request flag X is set to “0”, the past If it is determined that the driver's acceleration request is weak during the initial acceleration period, the CPU 71 proceeds to step 1120 to determine whether or not the current time is in the switching period (time tb to time tc in FIG. 3C). judge. If it is during the switching period, the CPU 71 determines “Yes” in step 1120, and in the subsequent step 1125, the value TAe stored by the acceleration request determination routine (set at the initial acceleration end time tb). The target throttle valve opening degree TAt) is set as the target throttle valve opening degree TAt. Then, the CPU 71 once ends this routine at step 1195.

  On the other hand, at the time of determination in step 1120, if the current time is not during the switching period but after the lapse of time, the CPU 71 determines “No” in step 1120. In subsequent step 1130, CPU 71 sets the value of virtual throttle valve opening degree TAt (0) obtained by the provisional target throttle valve opening degree setting routine as target throttle valve opening degree TAt. Since this virtual throttle valve opening degree TAt (0) is the target throttle valve opening degree TAt that has been calculated and stored at the previous calculation time point by the delay time TD from the current calculation time point, throttle delay is performed. Then, the CPU 71 once ends this routine at step 1195.

  As described above, in this routine, there is no delay of the delay time TD in the initial acceleration period and when the acceleration request is determined to be strong in the initial acceleration period and after the initial acceleration period has elapsed. The virtual throttle valve opening degree TAt (ntdly) (first virtual throttle valve opening degree TAt1) is set as the target throttle valve opening degree TAt. On the other hand, when it is determined that the acceleration request is weak in the initial acceleration period and the initial acceleration period has elapsed, the virtual throttle valve opening degree TAt (0) (second virtual throttle) having a delay of the delay time TD. The valve opening degree TAt2) is set as the target throttle valve opening degree TAt.

  In this routine, switching from a state where there is no delay by the delay time TD due to the virtual throttle valve opening TA (ntdly) to a state where there is a delay by the delay time TD due to the virtual throttle valve opening TA (0). During the period, the value TAe set as the target throttle valve opening degree TAt at the end of the initial acceleration is continuously set as the target throttle valve opening degree TAt.

  Here, it has been described how the target throttle valve opening degree TAt is set when the throttle valve 43 is driven and controlled. On the other hand, when the provisional target throttle valve opening TAacc is calculated, particularly when the throttle delay is performed after the initial acceleration period has elapsed, the provisional target throttle obtained at the calculation time is calculated. The valve opening degree TAacc is set as the target throttle valve opening degree TAt of the throttle valve 43 at a future time point corresponding to the delay time TD from the calculation time point.

  As described above, according to the fuel injection control device for an internal combustion engine according to the present invention, the accelerator pedal operation amount Accp is acquired, and the provisional target is determined according to the acquired accelerator pedal operation amount Accp at the time of calculation of the calculation cycle ΔTt. The throttle valve opening TAacc is calculated. In the initial acceleration period (time ta to time tb), the accelerator pedal speed vap is acquired, and it is determined whether the driver's acceleration request is strong or weak.

  After the determination regarding the acceleration request, every time the temporary target throttle valve opening degree TAacc is calculated at the time of the above calculation, if it is determined that the acceleration request is strong in the initial acceleration period, the calculated temporary target throttle valve The opening degree TAacc is set as the target throttle valve opening degree TAt (the target throttle valve opening degree TAt based on the first virtual throttle valve opening degree TAt1 shown in FIG. 2C) at the calculation time point (first time point).

  In this case, at the first time point, the throttle valve 43 is driven and controlled so that the actual throttle valve opening degree TA becomes equal to the target throttle valve opening degree TAt at the first time point. Along with the drive control of the throttle valve 43, the fuel injection amount fi to be injected into the fuel injection cylinder is determined based on the throttle valve opening degree TA (and the engine speed NE) that changes according to the accelerator pedal 81. This determined fuel injection amount fi is injected into the fuel injection cylinder.

  According to such fuel injection, after the initial acceleration period has elapsed, the driver can feel a better response of the engine 10 (or the vehicle on which the engine 10 is mounted) than when the acceleration request is weak. That is, when it is determined that the acceleration request is strong, the delay time TD is not set for the target throttle valve opening degree TAt, so that after the driver depresses the accelerator pedal 81, fuel injection corresponding to the depressing is performed. When executed (that is, the target throttle valve opening degree TAt corresponding to the depression is set, the fuel injection amount fi is determined based on the setting, and the fuel of the fuel injection amount fi is injected. The interval until the torque of the engine 10 increases is shorter than when the delay time TD is set. Therefore, it is possible to prevent a driver who wants rapid acceleration from feeling that the response of the vehicle to the accelerator operation is not good.

  On the other hand, after the determination of the acceleration request, if it is determined that the acceleration request is weak in the initial acceleration period at each calculation time of the temporary target throttle valve opening TAacc, the calculated temporary target throttle valve opening TAacc is It is set as the target throttle valve opening degree TAt (the target throttle valve opening degree TAt based on the second virtual throttle valve opening degree TAt2 shown in FIG. 3C) at the second time point when the delay time TD has elapsed from the calculation time point.

  In this case, the throttle valve is set so that the actual throttle valve opening TA becomes equal to the target throttle valve opening TAt at the second time after the lapse of the delay time TD from the time of calculation of the provisional target throttle valve opening TAacc. 43 is driven and controlled. Along with the drive control of the throttle valve 43, the intake valve closing of the fuel injection cylinder among the plurality of target throttle valve openings TAt at the second time point set for use in the future drive control of the throttle valve 43 The one corresponding to the time is used, and the cylinder intake air amount MC in the intake stroke of the fuel injection cylinder is predicted. Based on the predicted in-cylinder intake air amount MC, the fuel injection amount fi of the fuel injected into the fuel injection cylinder is determined. This determined fuel injection amount fi is injected into the fuel injection cylinder.

  According to such fuel injection, when it is determined that the driver's acceleration request is weak during the initial acceleration period (that is, when the driver desires gentle acceleration of the vehicle, further based on the determination result) When the temporary target throttle valve opening degree TAacc is set as the target throttle valve opening degree TAt at the second time point), after the initial acceleration period has elapsed, there is almost no excess or shortage in the fuel injection amount with respect to the target air-fuel ratio AbyF. Fuel injection is achieved, thereby maintaining good emissions.

  The fuel injection control device for an internal combustion engine according to the above embodiment is applied to a “multi-cylinder internal combustion engine mounted on a vehicle”. The accelerator opening sensor 69 in the above embodiment corresponds to “accelerator operation amount acquisition means for acquiring the operation amount of the accelerator pedal operated by the driver”. The provisional target throttle valve opening setting unit 91 corresponds to “a provisional target throttle valve opening calculating means for calculating the provisional target throttle valve opening according to the obtained accelerator pedal operation amount at the time of calculation of a predetermined period”. To do.

  Then, the acceleration request determination unit 94 determines “whether or not acceleration of the vehicle has started, and when it is determined that acceleration of the vehicle has started, the driving is the degree of acceleration of the vehicle requested by the driver. Based on the comparison between the acceleration request acquisition means for acquiring a value corresponding to the strength of the acceleration request of the driver and the predetermined value and the value corresponding to the strength of the acquired acceleration request, This corresponds to “acceleration request determination means” for determining whether it is strong or weak.

  In addition, the first virtual throttle valve opening setting unit 92, the second virtual throttle valve opening setting unit 93, and the target throttle valve opening selection unit 95 indicate that the provisional target throttle valve opening When it is determined that the acceleration request is strong every time the calculation is performed, the calculated temporary target throttle valve opening is set to the predetermined first delay time including 0 from the calculation time. The target throttle valve opening at the first time point that has passed is set. If it is determined that the acceleration request is weak, the provisional target throttle valve opening calculated at the time of this calculation is determined from the time of the calculation. This corresponds to “target throttle valve opening setting means” that sets the target throttle valve opening at the second time point when a second delay time longer than the delay time has elapsed.

  Further, the throttle valve actuator 43a indicates that “if the provisional target throttle valve opening is set as the target throttle valve opening at the first time point, the actual throttle valve opening is not increased after the first delay time has elapsed from the calculation time point. When the target throttle valve opening at the first time is equal and the temporary target throttle valve opening is set as the target throttle valve opening at the second time, the actual throttle valve is opened after the second delay time has elapsed from the calculation time. This corresponds to throttle valve control means for driving and controlling the throttle valve so that the valve opening becomes equal to the target throttle valve opening at the second time point.

  In addition, the electronically controlled throttle valve model M1 and the intake air model M2 are set as “if the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, for use in future throttle valve drive control. The amount of air sucked in the intake stroke of a specific cylinder among the multiple cylinders is predicted using any one of the plurality of target throttle valve openings at the second time point. This corresponds to “intake air amount prediction means”.

  The injection amount determination logic A2 is “if the provisional target throttle valve opening is set as the target throttle valve opening at the first time point, the multi-cylinder is selected based on the value that changes according to the operation amount of the accelerator pedal. When the first injection amount of fuel injected into any one of the cylinders is determined and the temporary target throttle valve opening is set as the target throttle valve opening at the second time point, the predicted amount of air is set. This corresponds to “a fuel injection amount determining means for determining a second injection amount of fuel injected into the specific cylinder”.

  Further, the injector 39 indicates that “if the provisional target throttle valve opening is set as the target throttle valve opening at the first time point, the determined first injection amount of fuel is injected into any of the cylinders. When the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, the fuel injection means for injecting the determined second injection amount of fuel into the specific cylinder ” Equivalent to.

  The present invention is not limited to the above-described embodiment, and various modifications can be employed within the scope of the present invention. In the above-described embodiment, the first virtual throttle valve opening setting unit 92 does not provide a delay time between the temporary target throttle valve opening TAacc and the first virtual throttle valve opening TAt1. Unlike this, the first virtual throttle valve opening setting unit 92 determines that the temporary target throttle valve opening TAacc and the second virtual throttle valve are between the temporary target throttle valve opening TAacc and the first virtual throttle valve opening TAt1. A delay time TD ′ shorter than the delay time TD with respect to the opening degree TAt2 may be set.

  The following modifications can also be adopted. That is, in the above embodiment, (1) the accelerator pedal speed vap is used as an index representing the strength of the driver's acceleration request. Instead of this, as the index, (2) a value corresponding to the gear stage of the engine 10 and the manual transmission (M / T) provided in the vehicle (a value corresponding to the gear ratio) may be used. In this modified example, a predetermined shift position sensor (corresponding to acceleration request acquisition means) detects the position of the shift lever (shift position) operated by the driver, so that it corresponds to the gear position corresponding to the shift position. The detected value is detected (acquired), and a value corresponding to the gear position is output to the acceleration request determination unit 94 (FIG. 2).

  Then, the acceleration request determination unit 94 detects that the actual shift stage is at the predetermined low speed stage shift stage by comparing the value corresponding to the shift stage with a value indicating the predetermined shift stage. In this case, it is determined that the acceleration request is strong. On the other hand, the acceleration request determination unit 94 compares the value corresponding to the shift speed with a value indicating the predetermined shift speed, so that the actual shift speed becomes higher than the low speed shift speed. When it is detected that the gear is in the gear position, it is determined that the acceleration request is weak.

  An automatic transmission (A / T) may be used as the transmission. In this case, the acceleration request acquisition means detects the rotational speed of the A / T input shaft (corresponding to the engine rotational speed NE or the throttle opening TA) and the rotational speed of the A / T output shaft (corresponding to the vehicle speed). Then, the shift speed is detected by, for example, calculating back the shift speed based on the ratio between the detected rotational speed of the input shaft and the detected rotational speed of the output shaft. Further, A / T is not a gear ratio determined in advance, and may be a continuously variable transmission.

  Further, as an index indicating the strength of the driver's acceleration request, (3) the speed at which the vehicle on which the engine 10 is mounted may be used. Here, a predetermined vehicle speed sensor (acceleration request acquisition means) detects the travel speed of the vehicle and outputs a value corresponding to the vehicle speed to the acceleration request determination unit 94. Then, the acceleration request determination unit 94 determines that the acceleration request is strong when the vehicle speed is smaller than a predetermined speed threshold. On the other hand, the acceleration request determination unit 94 determines that the acceleration request is weak when the vehicle speed is higher than the speed threshold.

  Further, in the above embodiment, the second virtual throttle valve opening setting unit 93 sets the second virtual throttle valve opening TAt2 obtained by delaying the temporary target throttle valve opening TAacc by a sufficiently long delay time TD. ing. In other words, for the prediction of the cylinder intake air amount MC, it is assumed that the target throttle valve opening degree TAt when the intake valve of the fuel injection cylinder is closed is set and the corresponding estimated throttle valve opening degree TAest is obtained. .

  In contrast to this, the second virtual throttle valve opening setting unit 93 uses the fixed delay time, while the intake air model M2 is the target throttle valve opening of the throttle valve 43 from the current calculation time point until the delay time has elapsed. One of the estimated throttle valve openings TAest corresponding to TA is selected according to the engine speed NE, and the in-cylinder intake is selected based on the estimated throttle valve opening TAest. The air amount MC may be predicted.

  In place of the above, the second virtual throttle valve opening setting unit 93 sets a delay time shorter than the delay time TD corresponding to the intake valve closing period, and the intake air model M2 has already been set. Based on the change in the target throttle valve opening TAt (or estimated throttle valve opening TAest), the estimated throttle valve opening TAest when the intake valve is closed is calculated. Based on this estimated throttle valve opening TAest, The internal intake air amount MC may be predicted.

  In the above-described embodiment, each part M21 to M24 of the intake air model M2 calculates the in-cylinder intake air amount MC by sequentially calculating based on the estimated throttle valve opening degree TAest. Instead, the intake air model M2 predicts the engine speed NE when the intake valve of the fuel injection cylinder is closed, and calculates the engine speed NE and the actual throttle valve opening TA when the intake valve is closed. Using the estimated throttle valve opening TAest and a predetermined table (a table defining the relationship between the engine speed NE and the estimated throttle valve opening TAest and the cylinder intake air amount MC), the intake valve closing The in-cylinder intake air amount MC at the time may be obtained.

  In the above embodiment, the accelerator opening sensor 69 acquires the accelerator pedal operation amount Accp, and the temporary target throttle valve opening calculator 91 calculates the temporary target throttle valve opening TAacc from the accelerator pedal operation amount Accp. The cycle in which the intake air model M2 calculates the in-cylinder intake air amount MC from the estimated throttle valve opening TAest corresponding to the provisional target throttle valve opening TAacc was the same cycle. Unlike this, the calculation cycle of the intake air model M2 may be longer than the calculation cycle of the provisional target throttle valve opening degree TAacc.

  The injection amount determination logic A2 is performed when the target throttle valve opening selector 95 selects the first virtual throttle valve opening TAt1 as the target throttle valve opening TAt (during the initial acceleration period and during the initial acceleration period). The fuel injection amount fi is determined based on the actual throttle valve opening TA (a value that changes according to the accelerator pedal operation amount Accp). Yes. Instead of this, the injection amount determination logic A <b> 2 may determine the fuel injection amount fi based on the actual intake air mass flow rate Ga detected by the air flow meter 61. That is, here, the injection amount determination logic A2 includes the actual intake air mass flow rate Ga, the engine rotational speed NE, and a predetermined table (intake air mass flow rate Ga and engine rotational speed NE, fuel injection amount fi, The fuel injection amount fi is determined using a table that defines the relationship (1). The mass flow rate Ga of the intake air is a value that changes according to the accelerator pedal operation amount Accp, similarly to the throttle valve opening degree TA.

  Furthermore, in the said embodiment, the accelerator pedal assumed that a driver | operator mainly operated with a foot | leg. The accelerator pedal here includes a lever or the like that is operated by a driver by hand.

  The fuel injection control apparatus according to another aspect of the present invention may stop the throttle delay during steady operation.

  The starting point of the initial acceleration period is not limited to the time when the driver performs an acceleration operation, but when the vehicle starts actual acceleration (when the vehicle speed starts to increase), or the engine speed starts to increase. It may be a point in time. That is, in this specification, the determination of “whether or not the vehicle has started acceleration” that determines the start point of the initial acceleration period is made according to whether the accelerator pedal operation amount Accp (or the provisional target throttle valve opening degree TAacc) is not 0 to 0. The determination is not limited to whether or not the value has been reached. Specifically, this determination of “whether or not vehicle acceleration has started” is made by determining whether or not the time change rate of the vehicle speed is equal to or greater than a predetermined threshold, or the time change rate of the engine rotation speed is predetermined. It may be determined whether or not the threshold is exceeded.

  Further, in the fuel injection control apparatus configured to stop the throttle delay during the above-described steady operation, the target throttle valve opening degree TAt and the actual throttle valve opening degree TA are substantially equal to changes in the accelerator pedal operation amount Accp. Change without delay. Therefore, such a device determines whether the vehicle acceleration has started or not based on the target throttle valve opening degree TAt and the actual throttle valve opening degree TA. Also good.

  In addition, in the fuel injection control device configured to perform throttle delay during steady operation, the determination of whether or not the vehicle acceleration has started is similarly determined based on the target slot valve opening degree TAt and This can be done based on the actual throttle valve opening TA. In this case, the start time of the initial acceleration period is slightly delayed from the start of the actual acceleration operation, but after the start time of the initial acceleration period, the throttle delay is stopped. It is still an improvement over the device.

1 is a schematic configuration diagram of a system in which a fuel injection amount control device according to the present invention is applied to a spark ignition type multi-cylinder internal combustion engine. 5 is a time chart schematically showing a target throttle valve opening set when the driver's acceleration request is strong. 5 is a time chart schematically showing a target throttle valve opening set when a driver's acceleration request is weak. It is a functional block diagram of various logics and various models for controlling the throttle valve opening and determining the fuel injection amount. It is the figure which showed the table which prescribed | regulated the relationship between the accelerator pedal operation amount which the CPU shown in FIG. 1 refers, and provisional target throttle valve opening degree. 6 is a time chart showing changes in a provisional target throttle valve opening and an estimated throttle valve opening. It is the graph which showed an example of the function used when calculating an estimated throttle valve opening. It is the flowchart which showed the program for calculating the temporary target throttle valve opening degree which CPU shown in FIG. 1 performs. It is the time chart which showed the setting of the target throttle valve opening degree in the switching period from the state without a delay to the state with a delay. It is the flowchart which showed the program for determining the driver | operator's acceleration request | requirement which CPU shown in FIG. 1 performs. It is the flowchart which showed the program for setting the target throttle valve opening degree 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 ... Injector, 41 ... Intake pipe, 43 ... Throttle valve, 43a ... throttle valve actuator, 70 ... electric control device, 71 ... CPU, 69 ... accelerator opening sensor, 81 ... accelerator pedal.

Claims (6)

A fuel injection control device for an internal combustion engine applied to a multi-cylinder internal combustion engine mounted on a vehicle,
An accelerator operation amount acquisition means for acquiring an operation amount of an accelerator pedal operated by a driver;
Temporary target throttle valve opening calculating means for calculating a temporary target throttle valve opening according to the acquired accelerator pedal operation amount at the time of calculation of a predetermined cycle;
It is determined whether or not acceleration of the vehicle has started, and if it is determined that acceleration of the vehicle has started, the driver's acceleration request that is the degree of acceleration of the vehicle requested by the driver is strong. Acceleration request acquisition means for acquiring a value according to the length;
Acceleration request determination means for determining whether the driver's acceleration request is strong or weak based on a comparison between a value corresponding to the acquired acceleration request strength and a predetermined value;
After the determination regarding the acceleration request, every time the temporary target throttle valve opening is calculated at the time of the calculation, if it is determined that the acceleration request is strong, the calculated temporary target throttle valve opening is performed. The degree is set as the target throttle valve opening degree at the first time point when the predetermined first delay time including 0 has elapsed from the same calculation time point, and the same calculation is performed when it is determined that the acceleration request is weak. A target throttle valve opening setting means for setting the provisional target throttle valve opening as a target throttle valve opening at a second time when a second delay time longer than the first delay time has elapsed from the same calculation time;
When the temporary target throttle valve opening is set as the target throttle valve opening at the first time point, the actual throttle valve opening at the first time point after the first delay time elapses from the calculation time point. If the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, the actual throttle valve opening after the second delay time elapses from the same calculation time point. Throttle valve control means for driving and controlling the throttle valve so that the valve opening becomes equal to the target throttle valve opening at the second time point;
When the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, a plurality of target throttle valves at the second time point set for use in drive control of the throttle valve in the future An intake air amount predicting means for predicting an amount of air sucked in an intake stroke of a specific cylinder of the multiple cylinders using any one of the target throttle valve openings;
When the provisional target throttle valve opening is set as the target throttle valve opening at the first time point, any one of the multi-cylinders based on a value that changes according to the operation amount of the accelerator pedal A first injection amount of fuel to be injected at a time, and when the provisional target throttle valve opening is set as the target throttle valve opening at the second time point, based on the predicted amount of air Fuel injection amount determination means for determining a second injection amount of fuel injected into a specific cylinder;
When the temporary target throttle valve opening is set as the target throttle valve opening at the first time point, the determined first injection amount of fuel is injected into any of the cylinders, and the temporary target Fuel injection means for injecting the determined second injection amount of fuel into the specific cylinder when the throttle valve opening is set as the target throttle valve opening at the second time point;
A fuel injection control device. The fuel injection control device for an internal combustion engine according to claim 1,
The acceleration request determination means includes
A fuel injection control device configured to make a determination on the acceleration request in an initial acceleration period from a time when it is determined that acceleration of the vehicle has started to a time when a predetermined time elapses. The fuel injection control device for an internal combustion engine according to claim 2,
The target throttle valve opening setting means is
Regardless of whether the acceleration request is strong or weak during the initial acceleration period, the temporary target throttle valve opening calculated by the temporary target throttle valve opening calculating means is set as the target throttle valve opening at the first time point. A fuel injection control device configured to set. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3,
The acceleration request acquisition means includes
As a value corresponding to the strength of the acceleration request, obtain the rate of change over time of the operation amount of the accelerator pedal acquired by the accelerator operation amount acquisition means,
The acceleration request determination means includes
When the temporal change rate of the acquired operation amount is larger than a predetermined change rate threshold, it is determined that the acceleration request is strong, and when the temporal change rate of the acquired operation amount is smaller than the same change rate threshold A fuel injection control device configured to determine that the acceleration request is weak. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3,
The acceleration request acquisition means includes
As a value according to the strength of the acceleration request, obtain a value according to the transmission gear ratio of the vehicle,
The acceleration request determination means includes
When the acceleration request is strong when it is detected that the actual gear ratio is a predetermined low speed gear ratio by comparing a value corresponding to the acquired gear ratio with a value indicating the predetermined gear ratio. By determining and comparing a value corresponding to the acquired gear ratio with a value indicating the gear ratio, the actual gear ratio is changed to a high speed gear ratio that is higher than the low gear ratio. A fuel injection control device configured to determine that the acceleration request is weak when it is detected. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3,
The acceleration request acquisition means includes
As a value according to the strength of the acceleration request, obtain the speed at which the vehicle travels,
The acceleration request determination means includes
The acceleration request is determined to be strong when the acquired vehicle speed is less than a predetermined speed threshold, and the acceleration request is determined to be weak when the acquired vehicle speed is greater than the speed threshold. A configured fuel injection control device.

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