JP2015129454A - Internal combustion engine controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the air-fuel ratio of an air-fuel mixture from becoming inappropriately lean in the fuel injection control over an internal combustion engine with a brake booster.SOLUTION: Provided is an internal combustion engine controller configured so that a fuel injection quantity is corrected in response to the magnitude of the difference between an estimated intake pressure based on an output signal from an air flow meter disposed upstream of a connected part of a brake booster in an intake passage and a measured intake pressure based on an output signal from an intake pressure sensor disposed closer to or downstream of the connected part or disposed in a surge tank, or that the fuel injection quantity is corrected in response to the magnitude of the difference between a measured intake flow rate based on the output signal from the air flow meter disposed upstream of the connected part of the brake booster in the intake passage and an estimated intake flow rate based on the output signal from the intake pressure sensor disposed closer to or downstream of the connected part or disposed in the surge tank.

Description

  The present invention relates to a control device that controls a fuel injection amount of an internal combustion engine mounted on a vehicle.

  Conventionally, in order to reduce the operating force required when braking the vehicle, that is, the pedaling force of the brake pedal, the pedaling force is boosted by using the intake negative pressure generated downstream of the throttle valve in the intake passage of the internal combustion engine. Brake boosters are widely used (see, for example, the following patent document).

  The brake booster has a constant pressure chamber in which intake negative pressure is stored and a variable pressure chamber into which atmospheric pressure is introduced. When the driver is not stepping on the brake pedal, the constant pressure chamber communicates with the variable pressure chamber, and the introduction of atmospheric pressure into the variable pressure chamber is blocked. When the driver depresses the brake pedal, the constant pressure chamber and the variable pressure chamber are shut off, and atmospheric pressure is introduced into the variable pressure chamber, so that a boosting action is performed by the pressure difference between the constant pressure chamber and the variable pressure chamber.

Japanese Patent Laid-Open No. 2005-255072

  The injection amount when fuel is injected into the cylinder of the internal combustion engine is increased or decreased in proportion to the amount of intake air charged in the cylinder. The amount of intake air flowing into the cylinder is measured by installing an air flow meter as a flow sensor on the intake passage, or installing an intake pressure sensor as a pressure sensor on the intake passage and passing through the intake pressure sensor. Is estimated based on the measured intake pressure and the engine speed at that time. The air flow meter is often positioned at the most upstream part of the intake passage, more specifically, directly below the air cleaner.

  The air discharged from the brake booster flows into the intake passage of the internal combustion engine. The connection point of the brake booster to the intake passage is downstream of the throttle valve. Therefore, in the method using the air flow meter, the amount of air flowing from the brake booster into the intake passage cannot be known. For this reason, the intake air amount measured through the air flow meter and the intake air amount actually filled in the cylinder may deviate, and the fuel injection amount may be insufficient, and the air-fuel ratio of the air-fuel mixture may become lean.

  In the fuel injection control of an internal combustion engine, the air-fuel ratio of the gas is measured by an air-fuel ratio sensor installed on the exhaust passage, and feedback control is performed to correct the fuel injection amount so that the air-fuel ratio converges to the target air-fuel ratio. It is customary. However, the air-fuel ratio feedback control cannot prevent the leaning of the air-fuel ratio by the air flowing from the brake booster, that is, the occurrence of the deviation between the actual air-fuel ratio and the target air-fuel ratio. Therefore, an instantaneous decrease in engine torque and a decrease in engine speed due to the lean air-fuel ratio cannot be avoided.

  Moreover, since the inflow of air from the brake booster occurs due to the operation of the brake pedal by the driver, it is difficult to predict this.

  In particular, during idle operation or low load operation close to idle operation, the original fuel injection amount is small, so the air flowing in from the brake booster causes the combustion of the mixture to become unstable or misfire, which causes engine stall. There is a risk of connection.

  Note that the above-described event can also occur in a method of estimating the intake air amount using an intake pressure sensor.

  An object of the present invention is to suppress inappropriate leaning of the air-fuel ratio of an air-fuel mixture in fuel injection control of an internal combustion engine accompanied by a brake booster.

  In the present invention, the fuel injection amount of the internal combustion engine mounted on the vehicle is controlled, and the estimated intake pressure based on the output signal of the air flow meter installed upstream of the connection point of the brake booster in the intake passage and The fuel injection amount is corrected in accordance with the magnitude of the difference from the measured intake pressure based on the output signal of the intake pressure sensor in the vicinity of the connection location or downstream of the connection location or in the surge tank, or the intake passage The actual intake air flow rate based on the output signal of the air flow meter installed upstream from the connection point of the brake booster and the output of the intake pressure sensor in the vicinity of the connection point or downstream from the connection point or in the surge tank A control device for an internal combustion engine that corrects the fuel injection amount in accordance with the magnitude of the difference from the estimated intake flow rate based on the signal is configured.

  In addition, the present invention controls the fuel injection amount of the internal combustion engine mounted on the vehicle, and supplies the hydraulic fluid to the brake device of the vehicle with the brake pedal force amplified by the brake booster. A control device for an internal combustion engine that corrects the fuel injection amount in accordance with the magnitude of the decrease amount of the engine is configured.

  ADVANTAGE OF THE INVENTION According to this invention, in the fuel-injection control of the internal combustion engine which accompanies a brake booster, the improper leaning of the air fuel ratio of an air-fuel mixture can be suppressed.

The figure which shows schematic structure of the internal combustion engine mounted in a vehicle. The figure which shows the structure of the drive system mounted in a vehicle. The figure which shows the relationship between the difference of measured intake pressure and estimated intake pressure, and the minimum value of the instantaneous value of engine speed. The flowchart which shows the example of the procedure of the process which the control apparatus of one Embodiment of this invention performs according to a program. The figure which illustrates transition of change of master cylinder pressure based on a driver's brake operation. The figure which shows the relationship between the integrated value of the fall amount of a master cylinder pressure, and the difference of measured intake pressure and estimated intake pressure. The flowchart which shows the example of the procedure of the process which the control apparatus of one Embodiment of this invention performs according to a program.

  <First Embodiment> An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle. The internal combustion engine is a spark ignition type four-stroke engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The external EGR (Exhaust Gas Recirculation) device 2 realizes a so-called high pressure loop EGR, and an EGR passage 21 communicating the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. The EGR cooler 22 provided on the EGR passage 21 and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are used as elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically to a surge tank 33.

  A brake booster 5 is attached to the vehicle. The brake booster 5 introduces intake negative pressure from the downstream side of the throttle valve 32 in the intake passage 3, specifically a surge tank 33, and boosts the pedal effort of the brake pedal using the negative pressure. It is well known. The brake booster 5 has a constant pressure chamber for storing negative pressure and a variable pressure chamber to which atmospheric pressure is applied, and the constant pressure chamber is connected to the surge tank 33 or its vicinity via a negative pressure line 51. The negative pressure line 51 guides the intake negative pressure downstream of the throttle valve 32 to the constant pressure chamber. A check valve 52 is provided on the negative pressure line 51 to keep the negative pressure in the constant pressure chamber and prevent the positive pressure from being applied to the constant pressure chamber.

  When the brake pedal is not operated by the driver, the constant pressure chamber and the variable pressure chamber communicate with each other, and the variable pressure chamber is isolated from the atmospheric pressure. When the brake pedal is operated, the constant pressure chamber and the variable pressure chamber are interrupted, and the atmosphere is introduced into the variable pressure chamber. As a result, the pressure difference between the constant pressure chamber and the variable pressure chamber becomes a control pressure that boosts the depression force of the brake pedal. The brake pedal force amplified by the brake booster 5 is converted into hydraulic pressure in the master cylinder 6. The hydraulic fluid pressure output from the master cylinder 6 is transmitted to a brake device (not shown) such as a brake caliper or a wheel cylinder via a hydraulic circuit (not shown), and is used for braking the vehicle by the brake device.

  FIG. 2 shows an example of a drive system provided in the vehicle. This drive system includes a torque converter 7 and automatic transmissions 8 and 9. In the present embodiment, a forward / reverse switching device 8 using a planetary gear mechanism and a belt-type CVT (Continuously Variable Transmission) 9 which is a type of continuously variable transmission are adopted as components of the automatic transmissions 8 and 9. Yes.

  The rotational torque output from the internal combustion engine is input from the crankshaft of the internal combustion engine to the pump impeller 71 on the input side of the torque converter 7 and transmitted to the turbine runner 72 on the output side. The rotation of the turbine runner 72 is transmitted to the drive shaft 94 of the CVT 9 via the forward / reverse switching device 8 and rotates the driven shaft 95 through a shift in the CVT 9. The rotation of the driven shaft 95 is transmitted to the output gear 101. The output gear 101 meshes with the ring gear 102 of the differential device, and rotates the axle 103 and the drive wheels (not shown) via the differential device.

  In the forward / reverse switching device 8, the sun gear 81 communicates with the turbine runner 72, and the ring gear 82 communicates with the drive shaft 94. Between the planetary carrier 83 that supports the planetary gear 831 and the transmission case, a forward brake 84 that is a hydraulic clutch that can be connected and disconnected is interposed. Further, a reverse clutch 85, which is a hydraulic clutch capable of switching connection / disconnection, is also interposed between the planetary carrier 83 and the sun gear 81 (or the output side of the torque converter 7).

  In the D range of the traveling range, the forward brake 84 is engaged and the reverse clutch 85 is disconnected. As a result, the rotation of the output shaft of the torque converter 7 is reversed and decelerated and transmitted to the drive shaft 94 for forward travel. In turn, in the R range, the reverse clutch 85 is engaged and the forward brake 84 is disconnected. As a result, the sun gear 81 and the planetary carrier 83 rotate integrally, and the output shaft of the torque converter 7 and the drive shaft 94 are directly connected to perform reverse travel. A solenoid valve (not shown) that controls the hydraulic pressure for driving the forward brake 84 or the reverse clutch 85 to connect / disconnect is a flow rate control valve that receives a control signal m and changes its opening.

  In the N range and P range, which are non-traveling ranges, both the forward brake 84 and the reverse clutch 85 are disconnected, and the connection between the torque converter 7 and the CVT 9 is disconnected. Also in the D range, the mechanical brake (that is, the load of the torque converter 7) acting on the internal combustion engine is reduced by disconnecting the forward brake 84 and the reverse clutch 85 during idling while the vehicle is stopped. “Neutral control” may be executed.

  The CVT 9 includes a driving pulley 91 and a driven pulley 92, and a belt 93 wound around the pulleys 91 and 92 as elements. The drive pulley 91 is disposed behind the movable sheave 912, a fixed sheave 911 fixed to the drive shaft 94, a movable sheave 912 supported on the drive shaft 91 via a roller spline so as to be displaceable in the axial direction. A hydraulic servo 913. The driven pulley 92 is disposed on the back of the movable sheave 922, a fixed sheave 921 fixed to the driven shaft 95, a movable sheave 922 supported on the driven shaft 95 via a roller spline so as to be axially displaceable. And a hydraulic servo 923 provided.

  A generator (alternator), which is a power supply source for various electric loads mounted on a vehicle, receives rotational torque from an internal combustion engine crankshaft and is rotationally driven to generate power. The magnitude of the voltage generated and output by this generator can be controlled via a regulator. The regulator is an IC type attached to the generator, and performs a switching operation for switching ON / OFF the energization to the field coil of the generator.

  The output voltage of the generator, that is, the voltage induced in the stator coil of the generator increases in proportion to fDUTY, which is the DUTY ratio of the field current flowing through the field coil. The regulator receives a signal o for instructing an output voltage of a generator from an ECU (Electronic Control Unit) 0, and performs PWM control for adjusting fDUTY so as to realize the instructed output voltage. The amount of power generated by the generator, in other words, the amount of power supplied to the electric load and / or the amount of charge to the on-vehicle battery increases as fDUTY increases and decreases as fDUTY decreases.

  The generator is a mechanical load when viewed from the internal combustion engine. When a high output voltage is commanded to the regulator, the mechanical load of the generator with respect to engine rotation increases, and when a low output voltage is commanded, the mechanical load of the generator with respect to engine rotation decreases.

  The ECU 0 serving as a control device for the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), and an intake air flow rate in the intake passage 3 (particularly immediately below the air cleaner 31). The intake air flow signal d output from the air flow meter 35, the intake air temperature / intake pressure signal e output from the intake air temperature / intake pressure sensor 36 for detecting the intake air temperature and intake pressure in the intake passage 3 (particularly, the surge tank 33). The coolant temperature signal f output from the coolant temperature sensor for detecting the coolant temperature indicating the temperature of the internal combustion engine flows through the exhaust passage 4 Liquid detects the master cylinder pressure which is the pressure of the hydraulic fluid the air-fuel ratio signal g outputted from the air-fuel ratio sensor for detecting an air-fuel ratio of the exhaust gas (O ₂ sensor or linear A / F sensor), the master cylinder 6 is discharged A master cylinder pressure signal h and the like output from the pressure sensor are input.

  From the output interface, an ignition signal i for the igniter 13 of the spark plug 12, a fuel injection signal j for the injector 11, an opening control signal k for the throttle valve 32, and an opening control signal for the EGR valve 23. l, the opening control signal m for the solenoid valve for switching the connection of the forward brake 84 or the reverse clutch 85, the transmission ratio control signal n for the CVT 9, and the voltage for the voltage regulator for controlling the output voltage of the generator. Command signal o etc. are output.

  The processor of the ECU 0 interprets and executes a program stored in the memory, calculates an operation parameter, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for operation control of the internal combustion engine via the input interface, and requests the required fuel injection amount, fuel injection timing (once (Including the number of times of fuel injection for combustion), fuel injection pressure, ignition timing, required EGR rate, gear ratio, power generation amount of the generator, and the like. The ECU 0 applies various control signals i, j, k, l, m, n, and o corresponding to the operation parameters via the output interface.

In determining the fuel injection amount, the ECU 0 determines a basic injection amount TP corresponding to the intake air amount (fresh air amount and EGR gas amount) charged in the cylinder 1. Next, the basic injection amount TP is corrected with a feedback correction coefficient FAF corresponding to the deviation between the actual air-fuel ratio of the current gas and the target air-fuel ratio obtained via the air-fuel ratio sensor. Further, the final fuel injection time (injector) is determined by taking into account the correction coefficient K determined according to various environmental conditions and the like, the correction coefficient X resulting from the operation of the brake booster 5 described later, and the invalid injection time TAUV of the injector 11. 11 is calculated. The fuel injection time T is
T = TP × FAF × K × X + TAUV
It becomes. Then, the signal j is input to the injector 11 for the fuel injection time T, and the injector 11 is opened to inject fuel.

  In addition, the ECU 0 performs a fuel cut that temporarily stops the fuel supply to the cylinder 1 when a predetermined fuel cut condition is satisfied. At this time, the ECU 0 determines that the fuel cut condition is satisfied, at least when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed.

  When the predetermined fuel cut end condition is satisfied after the fuel cut condition is satisfied, the fuel cut is ended, and the fuel supply to the cylinder 1 is resumed. At this time, the ECU 0 determines that the fuel cut end condition is satisfied, for example, when the amount of depression of the accelerator pedal exceeds a threshold value, or when the engine speed decreases to the fuel cut return speed.

  As already described, in this embodiment, the intake air amount that is the basis for the basic injection amount TP is measured via the air flow meter 35. The air flow meter 35 is installed upstream of the connection location of the brake booster 5 in the intake passage 3. From this, the intake air amount obtained by referring to the output signal d of the air flow meter 35, and hence the basic injection amount TP, is the amount of air that flows into the intake passage 3 from the brake booster 5 and is sucked into the cylinder 1. Not taken into account.

  That is, there is a possibility that the intake air amount actually filled in the cylinder 1 is larger than the intake air amount obtained through the air flow meter 35. In this case, the amount of fuel injected from the injector 11 of the cylinder 1 is small in proportion to the intake air amount filled in the cylinder 1, and the air-fuel ratio of the air-fuel mixture in the combustion chamber of the cylinder 1 becomes the target air. It becomes leaner than the fuel ratio. If this is the case, the engine torque may decrease, leading to a decrease in engine speed.

  The air flows into the intake passage 3 from the brake booster 5 when the driver depresses the brake pedal, or releases his foot from the brake pedal. The driver cannot predict that the brake pedal will be depressed, and the amount of air flowing from the brake booster 5 into the intake passage 3 at that time cannot be directly measured.

  Therefore, the ECU 0 of the present embodiment estimates the intake pressure in the surge tank 33 (or the intake manifold 34) close to the cylinder 1 based on the output signal d of the air flow meter 35. Then, a difference between the estimated intake pressure and the actually measured intake pressure in the surge tank 33 (intake manifold 34) measured via the intake pressure sensor 36 is obtained, and the fuel injection amount is corrected according to the magnitude of the difference. The coefficient X is determined.

  There is a correlation between the intake air flow rate measured via the air flow meter 35, the engine speed and the intake pressure in the surge tank 33. In other words, the intake pressure in the surge tank 33 can be estimated from the intake flow rate and the engine speed. However, in detail, it is necessary to consider the influence of the temperature of the intake air flowing through the intake passage 3 and the atmospheric pressure.

  In the memory of the ECU 0, map data defining the relationship between the intake pressure in the surge tank 33, the intake flow rate, the engine speed, the intake air temperature, the atmospheric pressure, and the like is stored in advance. The ECU 0 obtains the current estimated intake pressure by searching the map using the intake air flow rate measured via the air flow meter 35, the current engine speed, the intake air temperature, the atmospheric pressure, and the like as keys.

  Then, the ECU 0 subtracts the estimated intake pressure from the measured intake pressure based on the output signal e of the intake pressure sensor 36 located near or downstream of the connection location of the brake booster 5 in the intake passage 3. Find the difference between This difference suggests the amount of air flowing from the brake booster 5 into the intake passage 3. That is, it is considered that the larger the difference between the two, the more air is discharged from the brake booster 5 and flows into the intake passage 3. When no air is discharged from the brake booster 5, the difference between the two should be zero or almost zero.

  The ECU 0 increases and corrects the fuel injection amount T by increasing the correction coefficient X of the fuel injection amount as the difference becomes larger, that is, as the amount of air flowing into the intake passage 3 from the brake booster 5 increases. If the difference is 0 or almost 0, the correction coefficient X is set to the minimum value (usually 1). Thereby, the deviation of the air-fuel ratio of the air-fuel mixture from the target air-fuel ratio due to the operation of the brake booster 5 can be prevented.

  However, it is not necessary to always perform the increase correction of the fuel injection amount multiplied by the correction coefficient X. The reason why the lean air-fuel ratio due to the air flowing in from the brake booster 5 becomes a problem is during idling of the internal combustion engine or during operation in a low load region close to idling. Under such circumstances, the throttle valve 32 opening is originally small, and the intake air amount and fuel injection amount charged into the cylinder 1 are small. At this time, if air flows into the intake passage 3 from the brake booster 5, the amount of increase in intake air with respect to the fuel injection amount becomes relatively large, the air-fuel ratio of the air-fuel mixture becomes lean, and combustion becomes unstable. Sometimes misfires. Misfires during idling or low load operation can lead to engine stall. Therefore, it is desirable that the increase correction of the fuel injection amount multiplied by the correction coefficient X is performed under a situation where engine stall is a concern.

  FIG. 3 shows the difference between the measured intake pressure and the estimated intake pressure and the lowest instantaneous value of the engine speed when the internal combustion engine is idling without an increase correction of the fuel injection amount multiplied by the correction coefficient X. Is a plot of the results obtained by measuring a number of times. In FIG. 3, the horizontal line drawn with a solid line represents the allowable lower limit α of the engine speed at which engine stall does not occur. The cluster of plot points of the measurement results shows a downward trend. That is, it can be said that the larger the difference between the actually measured intake pressure and the estimated intake pressure, the more easily the combustion of the air-fuel mixture becomes unstable or misfires, and the engine speed tends to decrease greatly.

  In FIG. 3, the vertical line drawn by a broken line represents a threshold value β of the difference in intake pressure that distinguishes whether there is a risk that the lowest instantaneous value of the engine speed falls below the allowable lower limit α. If the difference between the actually measured intake pressure and the estimated intake pressure is larger than β, there is a risk that the lowest instantaneous value of the engine speed falls below the allowable lower limit α. The risk is assumed to be higher as the difference between the measured intake pressure and the estimated intake pressure is larger. Therefore, when the difference is larger than β, the fuel injection amount increase correction by multiplying the correction coefficient X should be executed. Further, it is preferable to increase the fuel injection amount in the increase correction as the difference is larger.

In FIG. 4, the example of a procedure of the process which ECU0 of this embodiment performs is shown. The ECU 0 performs an increase correction of the fuel injection amount in a situation where there is a concern of causing an engine stall due to the lean air-fuel ratio due to the air flowing into the intake passage 3 from the brake booster 5 (steps S1 and S2). More specifically, the difference obtained by subtracting the estimated intake pressure obtained by referring to the output signal d of the air flow meter 35 from the actually measured intake pressure obtained by referring to the output signal e of the intake pressure sensor 36 is greater than or equal to the threshold value β. (Step S1), and at least one of the following conditions (i) to (iv) is satisfied (step S2), the fuel injection amount increase correction is performed.
(I) The amount of depression of the accelerator pedal or the opening of the throttle valve 32 is not more than a predetermined value, and the engine speed is not more than a predetermined value (low load / low rotation range or idling).
(Ii) The amount of power generated by the generator is small (the basic amount of the throttle valve 32 opening (intake amount) is small by the amount that power is not generated)
(Iii) During “neutral control” in which the shift position is the travel range but both the forward brake 84 and the reverse clutch 85 of the forward / reverse switching device 8 are disconnected (the throttle valve is reduced by the amount of load applied to the internal combustion engine) The basic amount of 32 opening (intake amount) is small)
(Iv) The air-fuel ratio detected via the air-fuel ratio sensor is greater than or equal to a predetermined value. However, even if both steps S1 and S2 are true, the fuel injection amount increase correction based on a specific situation has already been performed for a certain amount or more. (Step S3), the above fuel injection amount increase correction is not performed. For example, the fuel increase correction that enriches the air-fuel ratio is often executed immediately after the end of the fuel cut. This is a measure for promoting the consumption of oxygen stored in the catalyst 41 during the fuel cut. Even if excess air flows into the intake passage 3 from the brake booster 5 during execution of the correction, misfire may occur. It is unlikely that an engine stall will occur. Therefore, if the correction is being executed, no further increase correction of the fuel injection amount (after step S4 with step S3 being true) is not performed.

  In the fuel injection amount increase correction for the purpose of avoiding engine stall (step S4), an increase correction coefficient X corresponding to the magnitude of the difference between the measured intake pressure and the estimated intake pressure is determined and multiplied to obtain the fuel injection. The quantity T is calculated. As a result of step S4, the fuel injection amount T is obtained by adding the increment of the air amount flowing from the brake booster 5 and sucked into the cylinder 1 to the basic injection amount TP. The correction coefficient X is set so that the air-fuel ratio of the air-fuel mixture charged in the cylinder 1 is close to the target air-fuel ratio.

  In the increase correction of the fuel injection amount described above, the difference between the actually measured intake pressure and the estimated intake pressure falls below the threshold (step S5), and none of the above conditions (i) to (iv) is satisfied (step S5). S6) The process ends. The threshold used in step S5 may be the same value as the threshold β used in step S2, but is preferably set to a value smaller than β. This is because when the difference between the measured intake pressure and the estimated intake pressure increases or decreases in the vicinity of β, the fuel injection amount increase correction is not performed or is not performed repeatedly, causing the engine speed to pulsate. Is intended to avoid.

  In this embodiment, the fuel injection amount of the internal combustion engine mounted on the vehicle is controlled, and the output signal d of the air flow meter 35 installed upstream of the connection location of the brake booster 5 in the intake passage 3 is used. The fuel injection amount is determined in accordance with the magnitude of the difference between the estimated intake pressure based on and the measured intake pressure in the vicinity of the connection location or downstream thereof or the output signal e of the intake pressure sensor 36 installed in the surge tank 33. A control device 0 for the internal combustion engine to be corrected is configured.

  According to the present embodiment, in the fuel injection control of the internal combustion engine accompanied by the brake booster 5, inappropriate leaning of the air-fuel ratio of the air-fuel mixture is suppressed, the engine torque is unduly reduced, and the engine speed is reduced. It is possible to prevent an unreasonable decline. In addition, as the difference between the actually measured intake pressure and the estimated intake pressure is larger, the amount of increase in the fuel injection amount is increased, and the execution opportunity of the fuel injection amount increase correction is limited as shown in steps S1 to S3. Therefore, it is not necessary to increase the amount of unnecessary fuel, and the fuel efficiency is not deteriorated.

  Further, it is not necessary to separately install a sensor (such as a brake booster pressure sensor) for detecting the amount of air flowing into the intake passage 3 from the brake booster 5, so that the cost is not increased.

  In the above embodiment, the difference between the intake pressure measured through the intake pressure sensor 36 and the intake pressure estimated from the intake flow rate measured through the air flow meter 35 is taken, and the difference is compared with the threshold value β. In addition, it was used to determine the fuel injection amount increase correction amount. Instead, the difference between the intake flow rate estimated from the intake pressure measured via the intake pressure sensor 36 and the intake flow rate measured via the air flow meter 35 is taken, and the difference is compared with a threshold value, It may be used to determine the amount of increase correction for the injection amount.

  The intake pressure sensor 36 installed in the surge tank 33 measures the intake pressure in which the presence of air that flows into the intake passage 3 from the brake booster 5 and is sucked into the cylinder 1 is added. In turn, the air flow meter 35 installed in the vicinity of the air cleaner 31 does not sense the presence of air flowing into the intake passage 3 from the brake booster 5. The difference between the output signal e of the intake pressure sensor 36 and the output signal d of the air flow meter 35 suggests the amount of air flowing from the brake booster 5 into the intake passage 3. In the above embodiment, the output signal d of the air flow meter 35 is converted into the intake pressure and compared with the output signal e of the intake pressure sensor 36 in order to clarify the difference. Is converted into an intake air flow rate and compared with the output signal d of the air flow meter 35 has the same meaning.

  There is a correlation between the intake pressure measured via the intake pressure sensor 36, the engine speed and the flow rate of the intake air sucked into the cylinder 1, and the surge tank 33 or the intake air is determined from the intake pressure and the engine speed. The intake air flow rate in the manifold 34 can be estimated. However, in detail, it is necessary to consider the influence of the temperature of the intake air flowing through the intake passage 3 and the atmospheric pressure.

  When obtaining the difference between the actually measured intake flow rate and the estimated intake flow rate, the map data defining the relationship between the intake flow rate, the intake pressure in the surge tank 33, the engine speed, the intake air temperature, the atmospheric pressure, etc., in the memory of the ECU0. Is stored in advance. Then, the ECU 0 searches the map using the intake pressure in the surge tank 33 measured via the intake pressure sensor 36, the current engine speed, the intake air temperature, the atmospheric pressure, etc. as keys, so that the current estimated intake flow rate is obtained. Know. Then, a difference is obtained by subtracting the actually measured intake flow rate based on the output signal d of the air flow meter 35 from the estimated intake flow rate. By comparing this difference with a threshold value, it is possible to determine whether or not the fuel injection amount increase correction is necessary. In addition, even when the fuel injection amount increase correction is performed, the fuel injection amount increase in the increase correction is increased as the difference is larger.

  <Second Embodiment> In the second embodiment described below, the amount of operation of the brake pedal of the driver is grasped based on the master cylinder pressure that is the hydraulic fluid pressure discharged from the master cylinder 6, and the brake booster is based on this. 5, the amount of air flowing into the intake passage 3 is estimated to determine whether or not the fuel injection amount increase correction is necessary and to determine the increase correction amount. Hereinafter, it demonstrates centering on difference with 1st embodiment. Matters not particularly mentioned can be the same as those in the first embodiment.

  In the present embodiment as well, as in the first embodiment, the intake air amount that is the basis for the basic injection amount TP is measured via the air flow meter 35. The air flow meter 35 is installed upstream of the connection location of the brake booster 5 in the intake passage 3. From this, the intake air amount obtained by referring to the output signal d of the air flow meter 35, and hence the basic injection amount TP, is the amount of air that flows into the intake passage 3 from the brake booster 5 and is sucked into the cylinder 1. Not taken into account.

  Therefore, the ECU 0 of the present embodiment determines the fuel injection amount correction coefficient X in accordance with the amount of decrease in the master cylinder pressure. Decreasing the master cylinder pressure is synonymous with the driver releasing the brake pedal. It is considered that a larger amount of air flows from the brake booster 5 into the intake passage 3 as the amount of decrease in the master cylinder pressure increases.

  FIG. 5 shows an example of changes in the master cylinder pressure. FIG. 5 is an example of the fluctuation of the master cylinder pressure when the driver performs the operation of loosening the depression of the brake pedal five times within a certain period. Assuming that the amount of decrease in the master cylinder pressure from the maximum value to the minimum value is the decrease amount, the master cylinder pressure has decreased five times within a certain period. The first decrease amount is | Δp1 |, and the second decrease amount is | Δp2. |, The third reduction amount is | Δp3 |, the fourth reduction amount is | Δp4 |, and the fifth reduction amount is | Δp5 |.

  FIG. 6 shows the integrated value of the decrease amount of the master cylinder pressure within a certain period, the actually measured intake pressure, and the estimated intake pressure when the internal combustion engine is idling without the increase correction of the fuel injection amount multiplied by the correction coefficient X. The result of having measured the difference between and a number of times is plotted. In the example shown in FIG. 5, the integrated value of the decrease amount of the master cylinder pressure is a value obtained by adding the decrease amounts | Δp1 |, | Δp2 |, | Δp3 |, | Δp4 |, and | Δp5 |. The difference between the measured intake pressure and the estimated intake pressure is referred to the output signal d of the air flow meter 35 from the measured intake pressure obtained by referring to the output signal e of the intake pressure sensor 36 as described in the first embodiment. This is a value obtained by subtracting the estimated intake pressure obtained.

  The cluster of the plot points of the measurement result shows a tendency to rise to the right. That is, as the amount of decrease in the master cylinder pressure (the integrated value thereof) increases, the difference between the measured intake pressure and the estimated intake pressure increases, and the combustion of the air-fuel mixture tends to become unstable or misfire, and the engine speed greatly decreases. It can be said that it is easy to do. In FIG. 6, a horizontal line drawn with a solid line represents the threshold value β described in the first embodiment.

  In FIG. 6, the vertical line drawn with a chain line represents the threshold value γ of the integrated value of the decrease amount of the master cylinder pressure, which distinguishes whether or not the difference in intake pressure is equal to or greater than the threshold value β. Risk that the difference between the measured intake pressure and the estimated intake pressure is greater than β if the accumulated value of the master cylinder pressure drop is greater than the threshold value γ, and the minimum instantaneous value of the engine speed is below the allowable lower limit α There is. The risk is assumed to increase as the integrated value of the amount of decrease in the master cylinder pressure increases. Therefore, when the integrated value is larger than γ, the fuel injection amount increase correction by multiplying the correction coefficient X should be executed. Further, it is preferable to increase the fuel injection amount in the increase correction as the integrated value is larger.

  In FIG. 7, the example of a procedure of the process which ECU0 of this embodiment performs is shown. The ECU 0 performs an increase correction of the fuel injection amount in a situation where there is a concern of causing an engine stall due to the lean air-fuel ratio due to the air flowing into the intake passage 3 from the brake booster 5 (steps S7 and S8). More specifically, the integrated value of the amount of decrease in the master cylinder pressure within a certain period obtained by referring to the output signal h of the master cylinder pressure sensor is γ or more (step S7), and the first embodiment When at least one of the conditions (i) to (iv) described in (4) is satisfied (step S8), the fuel injection amount increase correction is performed.

  However, even if steps S7 and S8 are both true, if the fuel injection amount increase correction based on the specific circumstances has already been performed (step S9), the above fuel injection amount increase correction is not performed. For example, the fuel increase correction that enriches the air-fuel ratio is often executed immediately after the end of the fuel cut. Even if surplus air flows from the brake booster 5 into the intake passage 3 during execution of the correction, the possibility that a misfire occurs and an engine stalls is small. Therefore, if the correction is being executed, no further increase correction of the fuel injection amount (after step S10, with step S9 being true) is not performed.

  In the fuel injection amount increase correction for the purpose of avoiding engine stall (step S10), an increase correction coefficient X corresponding to the integrated value of the decrease amount of the master cylinder pressure within a certain period is determined, and this is calculated. Multiply to calculate the fuel injection amount T. As a result of step S <b> 10, the fuel injection amount T is obtained by adding the increment of the air amount that flows into the cylinder 1 and flows from the brake booster 5 to the basic injection amount TP. The correction coefficient X is set so that the air-fuel ratio of the air-fuel mixture charged in the cylinder 1 is close to the target air-fuel ratio.

  In the increase correction of the fuel injection amount described above, the difference between the actually measured intake pressure and the estimated intake pressure falls below the threshold (step S11), or none of the above conditions (i) to (iv) is satisfied (step S11). S12) The process ends. The threshold used in step S11 may be the same value as the threshold γ used in step S8, but may be set to a value smaller than γ.

  In the present embodiment, the amount of fuel injected by the internal combustion engine mounted on the vehicle is controlled, and the hydraulic fluid of the master cylinder 6 that supplies the hydraulic fluid to the brake device of the vehicle with the brake pedal force amplified by the brake booster 5. The control device 0 for the internal combustion engine that corrects the fuel injection amount in accordance with the amount of decrease in the pressure (master cylinder pressure) is configured.

  According to the present embodiment, in the fuel injection control of the internal combustion engine accompanied by the brake booster 5, inappropriate leaning of the air-fuel ratio of the air-fuel mixture is suppressed, the engine torque is unduly reduced, and the engine speed is reduced. It is possible to prevent an unreasonable decline. In addition, as the difference between the actually measured intake pressure and the estimated intake pressure is larger, the increase in the fuel injection amount is increased, and the execution opportunity of the fuel injection amount increase correction is limited as shown in steps S7 and S8. Therefore, it is not necessary to increase the amount of unnecessary fuel, and the fuel efficiency is not deteriorated.

  Further, it is not necessary to separately install a sensor for detecting the amount of air flowing from the brake booster 5 into the intake passage 3, so that the cost is not increased.

  In this embodiment, since the intake pressure sensor 36 that measures the intake pressure in the surge tank 33 (or the intake manifold 34) is not used, the intake pressure sensor 36 can be eliminated.

  The present invention is not limited to the embodiment described in detail above. The specific configuration of each part and the specific processing procedure can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 3 ... Intake passage 35 ... Air flow meter 36 ... Intake pressure sensor 5 ... Brake booster 6 ... Master cylinder d ... Output signal of air flow meter e ... Output signal of intake pressure sensor h ... Output signal of master cylinder pressure sensor

Claims (2)

Controlling the fuel injection amount of an internal combustion engine mounted on a vehicle,
The estimated intake pressure based on the output signal of the air flow meter installed upstream of the connection point of the brake booster in the intake passage, and the intake pressure sensor installed in the vicinity of the connection point or downstream of the connection point or in the surge tank Correct the fuel injection amount according to the difference between the measured intake air pressure based on the output signal,
Alternatively, the measured intake air flow rate based on the output signal of the air flow meter installed upstream of the connection point of the brake booster in the intake passage, and the suction gas installed near or downstream of the connection point or in the surge tank. A control device for an internal combustion engine that corrects a fuel injection amount in accordance with a magnitude of a difference from an estimated intake flow rate based on an output signal of an atmospheric pressure sensor. Controlling the fuel injection amount of an internal combustion engine mounted on a vehicle,
A control device for an internal combustion engine that corrects a fuel injection amount in accordance with a reduction amount of a hydraulic fluid pressure of a master cylinder that supplies hydraulic fluid to a brake device of a vehicle with a brake pedal force amplified by a brake booster.

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