JPH0719086A - Fuel injection quantity controller for internal combustion engine for vehicle - Google Patents

Abstract

PURPOSE:To prevent any remarkable deviation of an air-fuel ratio from a specified air-fuel ratio like a theoretical air-fuel ratio, etc., and prevent stall of an internal combustion engine and/or deterioration of exhaust gas purifying characteristic before it happens, when a brake pedal is returned. CONSTITUTION:A negative pressure sensor 21 for detecting pressure in a transformer chamber is provided for comprehending an air quantity flown to the transformer chamber 31 of a brake booster 27 at the time of stepping-in of a brake pedal 25. The pressure in the transformer chamber by a negative pressure sensor 21 is read out by an electric control unit(ECU) 37, when an output signal of a stop lamp switch 17 is switched to 'OFF'. A correction injection quantity corresponding to the pressure in the transformer chamber is calculated by the ECU 37 by utilizing a pre-regulated map assuming that air inside the transformer chamber 31 is sucked to an engine 1 at one time. The correction injection quantity is added to a standard injection quantity by the ECU 37 when the final fuel injection quantity calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle provided with a brake booster for amplifying the depression force of the brake pedal by utilizing the intake pipe pressure (negative pressure) of an internal combustion engine. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for a vehicle internal combustion engine, in which fuel injection is performed in consideration of excess air sucked from a brake booster into the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in a vehicle, as a device for amplifying a pedaling force of a brake pedal and transmitting it to a master cylinder (a cylinder for converting the force applied to the brake pedal into a hydraulic pressure), a vacuum type Force devices (brake boosters) are commonly used. The casing of the brake booster is partitioned into a constant pressure chamber and a variable pressure chamber by a power piston. The intake pipe pressure (negative pressure) of the internal combustion engine mounted on the vehicle acts on the constant pressure chamber. The power piston is provided with a communication passage that communicates between the constant pressure chamber and the variable pressure chamber. Atmosphere can be introduced into the transformer room. Then, in accordance with the depression operation of the brake pedal, the communication state between the constant pressure chamber and the variable pressure chamber or the communication state between the inside and outside of the variable pressure chamber is switched as follows.

When the brake pedal is not depressed, communication between the constant pressure chamber and the variable pressure chamber is allowed, and the introduction of air into the variable pressure chamber is cut off. When the brake pedal is depressed from this state, communication between the constant pressure chamber and the variable pressure chamber is cut off and the introduction of the atmosphere into the variable pressure chamber is permitted. As a result, a pressure difference is generated on both sides of the power piston, and the force based on this pressure difference is added to the depression force applied to the brake pedal and transmitted to the master cylinder. After that, when the brake pedal is returned, the introduction of the atmosphere into the variable pressure chamber is interrupted again and the communication between the constant pressure chamber and the variable pressure chamber is allowed.

As described above, according to the brake booster, the depression force of the brake pedal can be reduced. However, on the other hand, the brake booster exerts the following adverse effects on the fuel injection of the internal combustion engine, especially the fuel injection during low load operation including idling.

In the brake booster, when the brake pedal is returned, the air accumulated in the variable pressure chamber is connected to the communication passage,
It flows into the combustion chamber of the internal combustion engine through the constant pressure chamber and the intake passage. This air is not measured by a sensor that detects the amount of intake air, such as an air flow meter. Therefore, the air-fuel ratio of the air-fuel mixture that has been adjusted to an appropriate value (theoretical air-fuel ratio) in the internal combustion engine is temporarily leaner (lean) than the theoretical air-fuel ratio due to the addition of air from the brake booster. )become. Here, the air-fuel ratio is the ratio of air and fuel in the air-fuel mixture. Further, the stoichiometric air-fuel ratio is the air-fuel ratio value of the air-fuel mixture that contains just enough oxygen to completely oxidize the fuel.

Originally, during low load operation in which the absolute amounts of the fuel injection amount and the intake air amount are small, the influence of the air from the brake booster is great. The lean air-fuel ratio that accompanies an increase in the intake air amount causes a temporary decrease in the engine speed, resulting in a stall of the engine and a decrease in exhaust gas purification performance.

Therefore, various techniques have been proposed for solving such a problem. For example, the actual Kaihei 3-45
In Japanese Patent No. 445, when the brake pedal is returned and excess air flows from the brake booster to the internal combustion engine, the fuel injection amount is increased and corrected for a predetermined time that is uniquely determined. More specifically, the coefficient for correcting the fuel injection amount when the brake pedal is released is changed to a value larger than that in normal times.

[0008]

The amount of air actually sucked from the brake booster into the internal combustion engine is largely controlled by the volume of the variable pressure chamber immediately before the brake pedal is returned. This volume differs depending on how the brake pedal is depressed (for example, when the brake pedal is depressed and immediately returned, or when the brake pedal is returned after a predetermined time elapses).

However, in the prior art, the correction coefficient is determined on the basis of the ON / OFF signal of the stop lamp switch and the engine speed that are activated when the brake pedal is depressed, without considering the volume of the variable pressure chamber. Moreover, the correction of the fuel injection amount using the correction coefficient is always performed for a fixed time. Therefore, in the conventional technique, the amount of fuel injection amount is increased and correction is performed while the volume of the variable pressure chamber, which is different each time the brake pedal is depressed, remains unknown. As a result, the air-fuel ratio greatly exceeds the theoretical air-fuel ratio ( (Ovalen) or a phenomenon that falls significantly below (overrich)
Could cause

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a brake pedal in a vehicle provided with a brake booster for amplifying the depression force of the brake pedal by utilizing the intake pipe pressure. When the engine is returned, the fuel of the internal combustion engine for vehicles can be reliably prevented from largely deviating from the predetermined air-fuel ratio such as the theoretical air-fuel ratio, and the stall of the internal combustion engine and the deterioration of the exhaust gas purification performance can be prevented in advance. An object is to provide an injection amount control device.

[0011]

To achieve the above object, the first invention is, as shown in FIG. 1, an internal combustion engine M for a vehicle.
1, a fuel injection valve M2 for injecting fuel into the air flowing through the intake passage M3 to generate a mixture, and an intake air amount detecting means M4 for detecting the amount of air flowing through the intake passage M3. An operating state detecting means M5 for detecting the operating state of the internal combustion engine M1 and the intake air amount detecting means M
4 based on the intake air amount according to No. 4 and the operating state according to the operating state detecting unit M5, the basic injection amount calculating unit M6 for calculating the basic injection amount of the fuel injection valve M2 and the intake air amount detecting unit M4 for the intake passage M3. A constant pressure chamber M7a on which the intake pipe pressure on the downstream side acts, and a variable pressure chamber M7b capable of introducing the atmosphere.
When the brake pedal M8 is not depressed, the constant pressure chamber M
7a and the variable pressure chamber M7b are allowed to communicate with each other, the introduction of air to the variable pressure chamber M7b is blocked, and when the brake pedal M8 is depressed, the communication between the constant pressure chamber M7a and the variable pressure chamber M7b is blocked and the atmosphere to the variable pressure chamber M7b is blocked. A brake booster M7 that has a communication state switching mechanism M7c that allows introduction, and that amplifies the pedaling force by utilizing the pressure difference between the constant pressure chamber M7a and the variable pressure chamber M7b by the communication state switching mechanism M7c when the brake pedal M8 is depressed. An excess air amount estimating means M10 for estimating the amount of excess air sucked from the brake booster M7 to the internal combustion engine M1 by the intake pipe pressure when the brake pedal M8 is switched from the depressed state to the non-depressed state; Brake switching detection that detects the switching of the pedal M8 from the depressed state to the non-depressed state When the step M11 and the brake switching detecting means M11 detect the switching of the brake pedal M8 to the non-depressed state, the basic injection amount calculating means M6 operates in accordance with the excess air amount in the excess air amount estimating means M10. An injection amount correction means M12 for increasing and correcting the basic injection amount, and an injection control means M13 for driving and controlling the fuel injection valve M2 according to the injection amount corrected by the injection amount correction means M12 are provided.

In a second aspect of the invention, in addition to the configuration of the first aspect of the invention, the excess air amount estimating means M10 changes with the passage of time when the brake pedal M8 is switched from a depressed state to a non-depressed state. The amount of excess air flowing into the internal combustion engine M1 from the brake booster M7 is estimated.

As shown in FIG. 2, a third aspect of the present invention includes a fuel injection valve M22 provided in a vehicle internal combustion engine M21 for injecting fuel into air flowing through an intake passage M23 to generate a mixture. An intake air amount detection means M24 for detecting the amount of air flowing through the intake passage M23, and the internal combustion engine M
An operating state detecting means M25 for detecting the operating state of 21;
A basic injection amount calculating means M26 for calculating a basic injection amount of the fuel injection valve M22 based on the intake air amount by the intake air amount detecting means M24 and an operating state by the operating state detecting means M25, and an exhaust passage of the internal combustion engine M21. An air-fuel ratio sensor M28 provided in M27 for detecting the air-fuel ratio of the air-fuel mixture by detecting the concentration of a specific component in the exhaust gas, and the air-fuel ratio of the air-fuel mixture to a predetermined air-fuel ratio. When the air-fuel ratio by the air-fuel ratio sensor M28 is less than or equal to a predetermined air-fuel ratio, the basic injection amount by the basic injection amount calculation means M26 is reduced and corrected, and when the air-fuel ratio is higher than the predetermined air-fuel ratio, the basic injection amount is increased and corrected. When the predetermined operating state is detected by the first injection amount correcting means M29 and the operating state detecting means M25, the basic injection amount calculating means M26 is used as the basis. A second injection amount correcting means M30 for increasing and correcting the injection amount, a constant pressure chamber M31a on which the intake pipe pressure on the downstream side of the intake air amount detecting means M24 of the intake passage M23 acts, and a variable pressure chamber capable of introducing the atmosphere. When M31b and the brake pedal M32 are not depressed, the constant pressure chamber M31
a and the variable pressure chamber M31b are allowed to communicate with each other, and the introduction of air into the variable pressure chamber M31b is cut off, and the brake pedal M3
When stepping on 2, the constant pressure chamber M31a and the variable pressure chamber M31
and a communication state switching mechanism M31c that cuts off the communication between b and allows the introduction of the atmosphere into the variable pressure chamber M31b.
The brake booster M31 that amplifies the depression force by utilizing the pressure difference between the constant pressure chamber M31a and the variable pressure chamber M31b by the communication state switching mechanism M31c when the brake pedal M32 is depressed, and the depression state of the brake pedal M32 to the non-depression state. Brake switching detecting means M33 for detecting switching and the brake switching detecting means M
When the switching of the brake pedal M32 to the non-depressed state is detected by 33, the first injection amount correction means M29 and the second injection amount correction means until the air-fuel ratio by the air-fuel ratio sensor M28 becomes equal to or lower than the predetermined air-fuel ratio. A correction amount changing means M34 forcibly increasing at least one of the increase correction amounts by M30, and an injection control means M35 for driving and controlling the fuel injection valve M22 according to the correction injection amount changed by the correction amount changing means M34. It has and.

[0014]

In the first aspect of the invention, as shown in FIG. 1, while the internal combustion engine M1 for a vehicle is operating, the amount of air taken into the internal combustion engine M1 through the intake passage M3 is the intake air amount detecting means. Detected by M4. Further, the operating state of the internal combustion engine M1 is detected by the operating state detecting means M5. The basic injection amount calculation means M6 calculates the basic injection amount of the fuel injection valve M2 based on the intake air amount and the operating state detected as described above.

When the brake pedal M8 is depressed or released while the internal combustion engine M1 is operating, the brake booster M7 operates as follows. Brake pedal M8
When the pedal is not depressed, the communication state switching mechanism M7c allows the constant pressure chamber M7a and the variable pressure chamber M7b to communicate with each other and shuts off the introduction of air into the variable pressure chamber M7b. Therefore, at this time, the intake pipe pressure (negative pressure) of the internal combustion engine M1 acts in the constant pressure chamber M7a and the variable pressure chamber M7b, and both chambers M7a, M7
The respective pressures in 7b are almost the same. Brake pedal M8
When stepping on, the communication state switching mechanism M7c
The communication between the constant pressure chamber M7a and the variable pressure chamber M7b is blocked, and the introduction of the atmosphere into the variable pressure chamber M7b is permitted. Then, the pressure difference between the constant pressure chamber M7a and the variable pressure chamber M7b is used to amplify the depression force of the brake pedal M8.

In the operation of the brake booster M7, when the brake pedal M8 is switched from the depressed state to the non-depressed state, the variable pressure chamber M7b is in the depressed state.
The air accumulated therein flows into the internal combustion engine M1 via the constant pressure chamber M7a and the intake passage M3 as excess air that is not detected by the intake air amount detecting means M4. For this reason, unless fuel injection that considers excess air is performed, the intake air amount becomes unsuitable for the fuel amount, and the air-fuel ratio greatly deviates from a predetermined air-fuel ratio such as the theoretical air-fuel ratio.

On the other hand, in the first invention, the excess air amount estimating means M10 sucks the brake booster M7 from the brake booster M7 to the internal combustion engine M1 when the brake pedal M8 is switched from the depressed state to the non-depressed state. Estimate the amount of excess air that will be consumed.

When the brake switching detecting means M11 detects the switching of the brake pedal M8 to the non-depressed state, the injection amount correcting means M12 determines the basic injection amount according to the excess air amount by the excess air amount estimating means M10. The basic injection amount by the calculating means M6 is increased and corrected. The injection control means M13 drives and controls the fuel injection valve M2 according to the injection amount corrected as described above.

As described above, according to the first aspect of the invention, when the brake pedal M8 is switched to the non-depressed state, the internal combustion engine M
The excess air quantity sucked into 1 is estimated. Then, by reflecting the fuel completely burned by the estimated excess air in the fuel injection amount, it is possible to suppress the disturbance of the air-fuel ratio with respect to a predetermined air-fuel ratio such as the theoretical air-fuel ratio.

Particularly, in the second invention, the brake pedal M
When switching from the stepped state of 8 to the non-depressed state,
The excess air amount estimating means M10 estimates the amount of excess air flowing into the internal combustion engine M1 from the brake booster M7 while changing over time. Therefore, it is possible to perform the fuel increase correction based on the change in the amount of excess air actually sucked into the internal combustion engine M1 from the brake booster M7, and further suppress the disturbance of the air-fuel ratio.

In the third aspect of the present invention, as shown in FIG. 2, when the internal combustion engine M21 for a vehicle is operated, fuel is injected from the fuel injection valve M22 into the air flowing through the intake passage M23 to generate a mixture. To be done. During this operation, the amount of air taken into the internal combustion engine M21 via the intake passage M23 is detected by the intake air amount detecting means M24. Further, the operating state of the internal combustion engine M21 is the operating state detecting means M2.
Detected by 5. The basic injection amount calculation means M26
The basic injection amount of the fuel injection valve M22 is calculated based on the intake air amount and the operating state detected as described above.

This basic injection amount is corrected by the first injection amount correction means M29 and the second injection amount correction means M30. That is, during operation of the internal combustion engine M21, the concentration of the specific component in the exhaust gas flowing through the exhaust passage M27 is detected by the air-fuel ratio sensor M28, and the air-fuel ratio of the air-fuel mixture is detected. The first injection amount correction means M29 is arranged to change the air-fuel ratio of the air-fuel mixture to a predetermined air-fuel ratio by the air-fuel ratio sensor M.
When the air-fuel ratio by 28 is less than or equal to the predetermined air-fuel ratio, the basic injection amount is corrected to decrease, and when the air-fuel ratio is greater than the predetermined air-fuel ratio, the basic injection amount is corrected to increase. In addition, the second injection amount correction means M30 is the operation state detection means M25.
When a predetermined operating state is detected by, the basic injection amount is increased and corrected.

When the brake pedal M32 is depressed or released while the internal combustion engine M21 is operating, the brake booster M31 operates as follows. When the brake pedal M32 is not depressed, the communication state switching mechanism M3
The constant pressure chamber M31a and the variable pressure chamber M31b communicate with each other by 1c, and the introduction of the atmosphere into the variable pressure chamber M31b is blocked. Therefore, at this time, the intake pipe pressure (negative pressure) of the internal combustion engine M21 acts in the constant pressure chamber M31a and the variable pressure chamber M31b, and the respective pressures in both chambers M31a and M31b become substantially the same. When the brake pedal M32 is depressed, the communication between the constant pressure chamber M31a and the variable pressure chamber M31b is cut off by the communication state switching mechanism M31c, and the variable pressure chamber M31
Atmosphere introduction into 31b is permitted. And the constant pressure chamber M3
The pressure difference between 1a and the variable pressure chamber M31b is used to amplify the depression force of the brake pedal M32.

When the brake booster M31 is operated, when the brake pedal M32 is switched from the depressed state to the non-depressed state, the variable pressure chamber M is depressed in the depressed state.
The air accumulated in 31b is the intake air amount detecting means M24.
As excess air not detected by the constant pressure chamber M31a
And flows into the internal combustion engine M21 via the intake passage M23.
For this reason, unless fuel injection that takes into consideration excess air is performed, the intake air amount becomes unsuitable for the fuel amount, and the air-fuel ratio deviates from a predetermined air-fuel ratio such as the theoretical air-fuel ratio.

On the other hand, in the third aspect of the invention, when the brake switch detecting means M33 detects the switching of the brake pedal M32 from the depressed state to the non-depressed state, the correction amount changing means M34 is caused by the air-fuel ratio sensor M28. Until the air-fuel ratio becomes equal to or lower than the predetermined air-fuel ratio, at least one of the increase correction amounts by the first injection amount correction means M29 and the second injection amount correction means M30 is forcibly increased. Then, the injection control unit M35 is responsive to the corrected injection amount changed by the correction amount changing unit M34, and the fuel injection valve M22.
Drive control.

Thus, when the brake pedal M32 is switched to the non-depressed state, the brake booster M31 is
Although excess air is sucked into the internal combustion engine M21 from the above, the increase correction amount is changed to a large value during the period until the air-fuel ratio measured by the air-fuel ratio sensor M28 becomes equal to or lower than the predetermined air-fuel ratio. Therefore, even if the excess air amount to the internal combustion engine M21 varies depending on how the brake pedal M32 is depressed, the injection fuel amount is increased and corrected over an appropriate period, and the disturbance of the air-fuel ratio with respect to a predetermined air-fuel ratio such as the theoretical air-fuel ratio is corrected. It is possible to suppress.

[0027]

【Example】

(First Embodiment) A first embodiment of the first invention will be described below with reference to FIGS.

As shown in FIG. 3, a vehicle is equipped with a multi-cylinder (four cylinders in FIG. 3) gasoline engine (hereinafter simply referred to as engine) 1 as an internal combustion engine. The engine body 1a, which constitutes a main part of the engine 1, includes combustion chambers (not shown) for each cylinder, and the intake passage 2 and the exhaust passage 3 communicate with these combustion chambers.

In the intake passage 2, from the upstream side toward the engine body 1a, an air cleaner 4, a throttle valve 5,
A surge tank 6 and an intake manifold 7 are arranged in this order. The outside air is taken into the combustion chamber via these members 4 to 7. The throttle valve 5 is driven in conjunction with the depression operation of an accelerator pedal (not shown), and the amount of intake air flowing through the intake passage 2 is adjusted by the drive. Further, the surge tank 6 smoothes the pulsation of the intake air.

The intake manifold 7 has fuel injection valves 8A, 8B, 8C, 8 for injecting fuel into the combustion chamber of each cylinder.
D is attached. And each fuel injection valve 8A-8
A mixture of the fuel injected from D and the outside air introduced into the intake passage 2 is introduced into each combustion chamber. A spark plug 9 is provided to ignite the mixture introduced into each combustion chamber.
A, 9B, 9C and 9D are attached to the engine body 1a. The spark plugs 9A to 9D are the distributor 1
It is driven based on the ignition signal distributed at 0. The distributor 10 distributes the high voltage output from the igniter 11 to the ignition plugs 9A to 9D in synchronization with the rotation angle of the crankshaft of the engine body 1a. Then, the air-fuel mixture introduced into the combustion chamber is burned by ignition of the spark plugs 9A to 9D. The driving force of the engine 1 is generated by this combustion. The combustion gas thus generated in the combustion chamber is discharged to the outside through the exhaust passage 3.

In the exhaust passage 3, an exhaust manifold 12 and a catalytic converter 13 are arranged in this order from the engine body 1a toward the downstream side. The catalytic converter 13 purifies hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) in the exhaust gas by the action of a catalyst.

The engine 1 has an air flow meter 15,
A fully closed switch 16, a throttle sensor 18, a rotation speed sensor 19, an oxygen sensor 20 and the like are provided. The air flow meter 15 constitutes an intake air amount detecting means, and the rotation speed sensor 19 constitutes a part of the operating state detecting means. The air flow meter 15 is provided downstream of the air cleaner 4 and detects the amount of air flowing through the intake passage 2 (intake air amount Q). As the air flow meter 15, for example, a vane type, a heat wire type, or a Kalman type can be used.

The throttle sensor 18 is provided near the throttle valve 5 and its opening (throttle opening TA)
To detect. The fully-closed switch 16 is also provided in the vicinity of the throttle valve 5 and outputs an ON signal when the throttle valve 5 is at the fully-closed position. At other times, that is, when the throttle valve 5 is slightly opened. The off signal is output to.

The rotation speed sensor 19 detects the rotation speed (engine speed NE) of the crankshaft of the engine body 1a based on the rotation of a rotor (not shown) incorporated in the distributor 10. The oxygen sensor 20 as an air-fuel ratio sensor includes an exhaust manifold 12 and a catalytic converter 13
It is provided between and. The oxygen sensor 20 detects the residual oxygen concentration as the concentration of the specific component in the exhaust gas to detect the air-fuel ratio of the air-fuel mixture taken into the engine body 1a, and outputs an electric signal (output voltage Ox) corresponding to the concentration. Output. The air-fuel ratio is the weight ratio of air and fuel in the air-fuel mixture.

On the other hand, the vehicle is provided with a hydraulic foot brake (not shown) in order to stop or decelerate the running vehicle or prevent the stopped vehicle from running. It is provided. This brake is
In response to the driver's depression of the brake pedal 25, pressure is applied to the brake fluid in the master cylinder 26,
A brake force is generated by operating a brake shoe or the like. In the vicinity of the brake pedal 25, a push-type stop lamp switch 17 as a brake switching detecting means is provided. The stop lamp switch 17 is normally off and outputs an on signal only when the driver depresses the brake pedal 25 by a predetermined amount or more.

A brake booster 27 is arranged between the master cylinder 26 and the brake pedal 25 in order to reduce the operation force when the brake pedal 25 is depressed. The casing 28 of the brake booster 27 is partitioned by a power piston 29 into a constant pressure chamber 30 and a variable pressure chamber 31. The constant pressure chamber 30 and the surge tank 6 are connected by a negative pressure passage 32, and the intake pipe pressure (negative pressure) in the surge tank 6 generated by the operation of the engine 1 passes through the negative pressure passage 32. It operates within 30. Also, from the transformer room 31 to the atmosphere passage 3
3 is extended, and the extended end is open to the atmosphere. Then, the atmosphere can be introduced into the variable pressure chamber 31 through the atmosphere passage 33. Furthermore, the power piston 29
A communication passage 34 that connects the constant pressure chamber 30 and the variable pressure chamber 31 to each other is provided in the.

The brake booster 27 has a constant pressure chamber 30 and a variable pressure chamber 3 in response to the depression operation of the brake pedal 25.
1 and a communication state switching mechanism 35 for switching the communication state between the inside and outside of the variable pressure chamber 31. This communication state switching mechanism 35
Is the constant pressure chamber 3 when the brake pedal 25 is not depressed.
0 and the transformer room 31 are allowed to communicate with each other, and the transformer room 3
Cut off the introduction of air into 1. In this state, the pressure of the intake pipe in the surge tank 6 acts on the constant pressure chamber 30 and the variable pressure chamber 31, so that the insides of both chambers 30 and 31 have the same negative pressure.

Further, the communication state switching mechanism 35 cuts off the communication between the constant pressure chamber 30 and the variable pressure chamber 31 and allows the introduction of the atmosphere into the variable pressure chamber 31 when the brake pedal 25 is depressed. In this state, negative pressure acts on the constant pressure chamber 30 and atmospheric pressure acts on the variable pressure chamber 31. As a result, a pressure difference occurs on both sides of the power piston 29, and a force based on this pressure difference is added to the depression force applied to the brake pedal 25 and transmitted to the master cylinder 26. By this addition, the depression force of the brake pedal 25 is reduced.

In the brake booster 27 having the above-described structure, the air flowing into the variable pressure chamber 31 when the brake pedal 25 is stepped on, the constant pressure chamber 30, the negative pressure passage 32, when the brake pedal 25 is returned, It is sucked into the combustion chamber of the engine body 1a via the surge tank 6 and the intake manifold 7. The amount of air at this time is almost the same as the amount of air that has flowed into the variable pressure chamber 31 (or the volume of the variable pressure chamber 31) when the brake pedal 25 is depressed. Therefore, if the amount of this inflowing air is obtained, when the brake pedal 25 is returned, the brake booster 27 causes the engine body 1a to move.
It should be possible to indirectly detect the amount of air drawn into the.

Various methods are conceivable for obtaining the amount of air flowing into the variable pressure chamber 31. In the first embodiment, the negative pressure sensor 21 for detecting the pressure in the pressure changing chamber 31 (pressure changing chamber pressure P).
Is attached to the brake booster 27 as a part of the excess air amount estimating means, and the inflow air amount is calculated based on the output signal thereof. The basis is shown below. The amount of air flowing into the variable pressure chamber 31 when the brake pedal 25 is depressed is proportional to the amount of depression of the brake pedal 25. At this time, if the brake pedal 25 is depressed a lot, the amount of air flowing into the variable pressure chamber 31 increases, and
Increases the volume of. Along with this, the pressure in the variable pressure chamber 31 approaches the atmospheric pressure. Therefore, if the pressure in the variable pressure chamber 31 is known, the volume of the variable pressure chamber 31 at that time, that is, the amount of air flowing into the variable pressure chamber 31 can be calculated.

A check valve 36 is provided in the middle of the negative pressure passage 32. This check valve 3
Reference numeral 6 is for restricting the direction of the air flow in the negative pressure passage 32, and allows only the air flow from the constant pressure chamber 30 side to the surge tank 6 side.

The engine system of this embodiment is provided with an electronic control unit (ECU) 37 for comprehensively controlling the engine 1 and its related equipment. As shown in FIG.
The ECU 37 includes a central processing unit (CPU) 38, a read only memory (ROM) 39, a random access memory (RAM) 40, a backup RAM 41, an external input circuit 42 and an external output circuit 43, and these units are connected to each other by a bus 44. Has been done. The CPU 38 constitutes a basic injection amount calculation means, an injection amount correction means, and an injection control means. Further, the CPU 38 uses the negative pressure sensor 2
1 constitutes an excess air amount estimating means. CPU
Numeral 38 executes various arithmetic processes according to a preset control program. The ROM 39 stores in advance control programs and initial data necessary for the CPU 38 to execute arithmetic processing. The RAM 40 temporarily stores the calculation result of the CPU 38. The backup RAM 41 is backed up by a battery (not shown) so as to retain various data even after the power is turned off.

The external input circuit 42 is connected to the air flow meter 15, the fully closed switch 16, the stop lamp switch 17, the throttle sensor 18, the rotation speed sensor 19, the oxygen sensor 20 and the negative pressure sensor 21 described above. Further, the external output circuit 43 includes the fuel injection valves 8A to 8 described above.
D and the igniter 11 are connected. And CP
U38 is the air flow meter 1 via the external input circuit 42.
5, the output signals of the switches 16 and 17 and the sensors 18 to 21 are read as input values. Further, the CPU 38 drives and controls the fuel injection valves 8A to 8D and the igniter 11 via the external output circuit 43 based on these input values.

More specifically, the CPU 38 detects the air-fuel ratio A / F of the air-fuel mixture from the output signal of the oxygen sensor 20, and the fuel injection amount from the fuel injection valves 8A-8D so that the value becomes the stoichiometric air-fuel ratio. Adjust. Here, the theoretical air-fuel ratio is
It is the air-fuel ratio value of the air-fuel mixture containing the oxygen amount necessary for completely oxidizing the fuel, which is "1" in this embodiment.
4.5 ”. In order to adjust the fuel injection amount, the CPU 38 calculates the final injection amount TAU, which is the target value, based on the following equation (1).

TAU = TAUP × FAF × α + β (1) Here, TAUP is a basic injection amount set to obtain a stoichiometric air-fuel ratio, and is a product of the intake air amount per one engine revolution and a constant (K -(Q / NE)). FAF is a feedback correction coefficient that changes with a change in the output signal of the oxygen sensor 20. The feedback correction coefficient FAF is a correction coefficient for correcting the basic injection amount TAUP so that the air-fuel ratio A / F becomes the stoichiometric air-fuel ratio. α and β are correction amounts determined based on other operating state parameters such as the throttle opening TA and the battery voltage. In particular, the correction amount β includes a correction injection amount β1 described later. This corrected injection amount β
1 is the air-fuel ratio A / when excess air is sucked into the engine body 1a from the brake booster 27 by the intake pipe pressure.
This is for preventing F from being disturbed.

The CPU 38 obtains the feedback correction coefficient FAF based on the output signal of the oxygen sensor 20 as follows. As shown in FIG. 5, the CPU 38 controls the output voltage Ox of the oxygen sensor 20 and a preset reference voltage Vx.
r (eg 0.45V). The CPU 38
If the output voltage Ox is higher than the reference voltage Vr, it is determined to be rich, and if it is low, it is determined to be lean. In the case of rich, the CPU 38 compares it with the previous detection result, and determines whether or not it has been reversed from lean to rich. When lean is reversed to rich (timing ta), the CPU 38 causes FAF-RSL.
(RSL is a skip amount) is set as a new feedback correction coefficient FAF, and if there is no inversion from lean to rich (a period from timing ta to tb), FAF-KiL.
(KiL is an integration amount, RSL >> KiL) is set as a new feedback correction coefficient FAF.

When the air-fuel ratio A / F based on the signal from the oxygen sensor 20 is lean, the CPU 38 compares it with the previous detection result and determines whether or not the rich-to-lean reversal is performed. Invert from rich to lean (timing tb)
Then, the CPU 38 sets FAF + RSR (RSR is a skip amount) as a new feedback correction coefficient FAF, and there is no inversion from rich to lean (timing ta.
Period before, a period after timing tb),
FAF + KiR (KiR is an integration amount, RSR >> KiR) is set as a new feedback correction coefficient FAF.

Therefore, when there is an inversion between rich and lean (timing ta, tb), the CPU 38 changes (skips) the feedback correction coefficient FAF stepwise to increase or decrease the fuel injection amount, and at the same time, rich or lean. At this time (the period excluding the timings ta and tb), the feedback correction coefficient FAF is gradually increased or decreased.

When the air-fuel ratio A / F is controlled to the stoichiometric air-fuel ratio, the feedback correction coefficient FAF is "1.
It fluctuates around "0". The CPU 38 uses the equation (1) described above.
When the final injection amount TAU is calculated based on, the drive signal corresponding to it is output to the fuel injection valves 8A to 8D via the external output circuit 43, as shown in FIG. The opening time of the fuel injection valves 8A to 8D is controlled by the output of this signal, and the amount of fuel corresponding to the final injection amount is injected. In this way, feedback control of the air-fuel ratio A / F is performed so that the air-fuel ratio A / F becomes the stoichiometric air-fuel ratio.

The CPU 38 also controls the igniter 11 via the external output circuit 43. Therefore, the optimum ignition timing corresponding to the operating state of the engine 1 is previously set in the ROM 39.
The CPU 38 detects the operating state of the engine 1 from the signals from the various sensors including the rotation speed sensor 19 and calculates the optimum ignition timing. And CP
U38 outputs an ignition instruction signal to the igniter 11 via the external output circuit 43 to control the ignition timing.

Next, the operation and effect of this embodiment configured as described above will be described with reference to the flowchart of FIG. 6 and the timing chart of FIG. FIG. 6 shows the CPU 38
The routine for calculating the corrected injection amount β1 is shown among the respective processes executed by, and is executed at a predetermined timing. Further, FIG. 8 shows a case where the brake pedal 25 is depressed at the timing t3 and returned at the timing t5.

First, the case where the correction injection amount calculation routine of FIG. 6 is started at the timing t0 of FIG. 8 will be described. At this timing, the accelerator pedal is depressed, the throttle valve 5 is opened (the fully closed switch 1
The output signal of 6 is "OFF"), and the intake pipe pressure has a relatively high value. In the brake booster 27, the brake pedal 25 is not depressed (the stop lamp switch 17 is “off”), and the communication state switching mechanism 35 allows the constant pressure chamber 30 and the variable pressure chamber 31 to communicate with each other, and the atmosphere. The passage 33 is closed to block the introduction of air into the variable pressure chamber 31. Therefore, the intake pipe pressure reaches the variable pressure chamber 31, and the variable pressure P becomes a value P1 lower than the atmospheric pressure. However, at this time, it is assumed that the non-depressed state of the brake pedal 25 has continued from before and air is not sucked from the brake booster 27 into the combustion chamber of the engine 1.

When the correction injection amount calculation routine is started,
In step 101, the CPU 38 determines whether or not the output signal of the stop lamp switch 17 is switched from "ON" to "OFF". As described above, since the non-depressed state of the brake pedal 25 continues here, the CPU 38 determines that the determination condition is not satisfied, and ends this routine as it is.

Therefore, when the final injection amount TAU is calculated using the above equation (1), the increase correction of the injection amount when the brake pedal is returned is not performed. And this final injection amount T
A drive signal corresponding to AU controls the operation of the fuel injection valves 8A to 8D to inject a predetermined amount of fuel, and the air-fuel ratio A /
F converges near the stoichiometric air-fuel ratio (14.5).

This state is maintained until the brake pedal 25 is depressed and then returned again. Subsequently, at timing t1 in FIG. 8, when the accelerator pedal is returned and the throttle valve 5 is closed, the intake pipe pressure starts to decrease, and the output signal of the fully closed switch 16 is switched from “OFF” to “ON”. Replace Brake pedal 25
Is still not depressed, stop lamp switch 1
The output signal of 7 remains "off".

After the timing t2 when the intake pipe pressure drops to some extent, a small amount of air is sucked from the variable pressure chamber 31 into the engine body 1a. With this suction, the pressure in the transformer chamber P
Is lower than the value P1. Further, the suction pipe pressure slightly increases due to the suction.

When the brake pedal 25 is depressed at the timing t3, the communication state switching mechanism 35 shuts off the communication between the constant pressure chamber 30 and the variable pressure chamber 31. Further, the atmosphere passage 33 is opened to allow the atmosphere to be introduced into the variable pressure chamber 31. Due to the inflow of air into the variable pressure chamber 31 at this time, the pressure P in the variable pressure chamber starts to increase with the passage of time. At this time, since the intake pipe pressure acts on the constant pressure chamber 30, a pressure difference is generated on both sides of the power piston 29, and the force based on this pressure difference is added to the depression force applied to the brake pedal 25 to be added to the master cylinder 26. Be transmitted to.

Then, at a timing t4 when a predetermined time has elapsed from the timing t3, the variable pressure chamber pressure P becomes atmospheric pressure. Next, when the brake pedal 25 is returned at timing t5, that is, when the brake pedal 25 is switched from the depressed state to the non-depressed state, the brake booster 27 operates as follows. Communication state switching mechanism 35
As a result, the communication between the constant pressure chamber 30 and the variable pressure chamber 31 is allowed, and the atmosphere passage 33 is closed to interrupt the atmosphere introduction into the variable pressure chamber 31. Therefore, the intake pipe pressure in the surge tank 6 acts on the constant pressure chamber 30 and the variable pressure chamber 31. Therefore, before the timing t5, the brake pedal 25
When the brake pedal 25 is returned, the air that has flown into the variable pressure chamber 31 by being depressed is sucked into the engine body 1a via the constant pressure chamber 30, the negative pressure passage 32, the surge tank 6, and the intake manifold 7.

At the timing t5, the output signal of the stop lamp switch 17 is switched from "ON" to "OFF" by returning the brake pedal 25. Therefore, C
The PU 38 determines that the determination condition of step 101 of FIG. 6 is satisfied and moves to step 102. Step 1
In 02, the CPU 38 reads the pressure in the variable chamber from the negative pressure sensor 21. At timing t5, the variable chamber pressure P is atmospheric pressure as shown in FIG.

Subsequently, in step 103, the CPU 38 obtains the corrected injection amount β1 corresponding to the variable pressure chamber pressure P using the map shown in FIG. Here, the amount of air sucked from the brake booster 27 to the engine body 1a is determined by the amount of air that has flowed into the variable pressure chamber 31 when the brake pedal 25 is depressed. The air volume of the latter is
The volume is the same as the volume of the variable pressure chamber 31 immediately before the brake pedal 25 is returned, and this volume becomes larger as the variable pressure chamber pressure P approaches the atmospheric pressure. Considering this point, in the map, the pressure P in the variable chamber is 0 mmHg, and the value P is slightly higher than that.
When it is in the range up to 2 (> P1), the corrected injection amount β1 is set to “0”. When the variable pressure chamber pressure P is in the range from the value P2 to the atmospheric pressure, the correction injection amount β1 increases in proportion to the increase in the variable pressure chamber pressure P.

When the CPU 38 calculates the corrected injection amount β1 according to the variable pressure chamber pressure P at that time in step 103, this routine is ended. Therefore, at the timing t5, when the final injection amount TAU is calculated using the equation (1), the corrected injection amount β1 is added to the basic injection amount TUP. Then, by the drive signal corresponding to the final injection amount TAU including the corrected injection amount β1, the fuel injection valves 8A to
The operation of 8D is controlled to inject a predetermined amount of fuel.

As described above, in the first embodiment, when the output signal of the stop lamp switch 17 switches from "ON" to "OFF", the pressure in the variable chamber P by the negative pressure sensor 21 is changed.
Is read (steps 101 and 102), and the volume of the variable pressure chamber 31 is grasped based on the value. This volume corresponds to the amount of air flowing into the variable pressure chamber 31 when the brake pedal 25 is depressed. Further, the amount of excess air is estimated as an amount of air corresponding to the pressure in the variable pressure chamber P that is sucked into the engine body 1a at a time by the intake pipe pressure after the brake pedal 25 is returned. Then, the correction injection amount β1 corresponding to the excess air amount is obtained from the map of FIG. 7 (step 103), and the basic injection amount TAUP is calculated with this correction injection amount β1.
Is increased.

Therefore, unlike the prior art in which the volume of the variable pressure chamber is not taken into consideration and the amount of injected fuel is simply increased and corrected for a fixed time when the brake pedal is returned, in the first embodiment, the variable pressure chamber 31 of the variable pressure chamber 31 is changed. The volume, that is, the amount of excess air sucked from the brake booster 27 into the engine body 1a can be reliably grasped, and the amount of injected fuel that is completely burned by the air can be increased almost without excess or deficiency.

Further, even if the volume of the variable pressure chamber 31 varies depending on how the brake pedal 25 is depressed, the volume can be accurately known by detecting the variable pressure chamber pressure P, so that an appropriate increase correction of the injected fuel amount can be made. it can. For this reason,
When the brake pedal 25 is returned, the brake booster 2
Although excess air is sucked into the engine body 1a from 7, the air-fuel ratio A / F can be reliably converged to near the stoichiometric air-fuel ratio by performing the above-described increase correction. In other words, it is possible to prevent the phenomenon that the air-fuel ratio A / F greatly exceeds the theoretical air-fuel ratio (over lean) as shown by the two-dot chain line in FIG. As a result, it is possible to prevent the stall of the engine 1 and the deterioration of the exhaust gas purification performance (increase of nitrogen oxides, deterioration of catalyst function, etc.). (Second Embodiment) Next, a second embodiment of the first and second inventions will be described with reference to FIGS.

In the first embodiment described above, the basic injection amount is increased and corrected only at the first fuel injection after the brake pedal 25 is returned, whereas in the second embodiment, the brake pedal 25 is released. The fuel injection amount is gradually decreased over a period of several fuel injections after the injection. Strictly speaking, the suction of air from the brake booster 27 to the engine body 1a is not performed only in an extremely short time immediately after the brake pedal 25 is returned, but as shown in FIG. This is because it is performed over a certain period of time, and the suctioned amount changes with the passage of time. Therefore, in the second embodiment, the increase correction amount is changed according to the amount of air actually sucked from the brake booster 27 into the engine body 1a.

FIG. 9 is a flowchart corresponding to FIG. 6, and shows a routine for calculating the correction coefficient α1 instead of the correction injection amount β1. This correction coefficient calculation routine is executed in synchronization with the timing of calculating the basic injection amount TAUP (for example, every time the crankshaft of the engine body 1a rotates by 720 °). The correction coefficient α1 constitutes a part of the correction amount α in the equation (1), and is multiplied by the basic injection amount TAUP when the final injection amount TAU is calculated.

FIG. 11 is a timing chart corresponding to FIG. In FIG. 11, timing t
Since the correspondence relationship of the variable chamber pressure P and the like before 5 is the same as that in FIG. 8, the corresponding numbers are given to the corresponding timings, and the description will be simplified.

When the correction coefficient calculation routine is started at the timing t0 when the non-depressed state of the brake pedal 25 continues, the CPU 38 determines in step 201 whether the output signal of the stop lamp switch 17 is "OFF". To judge. As mentioned above, the brake pedal 25
Is returned for a certain period, the CPU 38
Determines that the determination condition of step 201 is satisfied,
Control goes to step 202. In step 202,
After the output signal of the stop lamp switch 17 is switched to "OFF", the CPU 38 sets a predetermined time Δt1.
Is determined. This predetermined time Δt1 is
This is the approximate time required for the air in the variable pressure chamber 31 of the brake booster 27 to be sucked into the intake passage 2.

As described above, at the timing t0, the brake pedal 25 has been returned to the previous state, so that the CPU 38 determines that the determination condition of step 202 is satisfied, and the negative pressure is determined in step 203. The pressure P in the variable chamber is read by the sensor 21. As shown in FIG. 11, at the timing t0, the variable chamber pressure P is a value P1 close to 0 mmHg.

Subsequently, in step 204, the CPU 38 obtains the correction coefficient α1 corresponding to the pressure P in the variable pressure chamber using the map shown in FIG. This map is set from the same viewpoint as the map of FIG. 7 in the first embodiment. More specifically, in the map shown in FIG. 10, the pressure P in the variable pressure chamber is 0 mmHg and is slightly higher than the value P2 (>
In the range up to P1), the correction coefficient α1 is "1.
It is 0 ". When the transformer chamber pressure P is in the range from the value P2 to the atmospheric pressure, the correction coefficient α1 increases in proportion to the rise of the transformer chamber pressure P. The correction coefficient α1 when the transformer chamber pressure P is atmospheric pressure is the maximum value α1max.

Further, in the second embodiment, as described above, the increase correction is performed over several times of fuel injection after the brake pedal 25 is returned. From this,
The change rate (slope) θ2 of the correction coefficient α1 with respect to the variable pressure chamber pressure P in FIG. 10 is set to be gentler than the change rate (slope) θ1 of the injection correction amount β1 with respect to the variable pressure chamber pressure P in FIG. 7.

In FIG. 10, the correction coefficient α1 corresponding to the pressure in the variable pressure chamber P = P1 is "1.0". For this reason,
In step 204, the CPU 38 corrects the correction coefficient α1 (= 1.
When 0) is calculated, this routine ends. Therefore,
When calculating the final injection amount TAU using the above equation (1), the basic injection amount TAUP is multiplied by the correction coefficient α1, but since α1 = 1.0, the injection fuel amount is increased when the brake pedal is returned. There is virtually no correction. Then, the drive signal corresponding to the final injection amount TAU controls the operation of the fuel injection valves 8A to 8D to inject a predetermined amount of fuel, and the air-fuel ratio A / F is converged to near the stoichiometric air-fuel ratio.

Next, when the correction coefficient calculation routine is started at timing t3 in FIG. 11, the output signal of the stop lamp switch 17 is switched from "OFF" to "ON" by depressing the brake pedal 25. When it is determined that the determination condition of step 201 is not satisfied, the process proceeds to step 205. In step 205, C
The PU 38 sets the correction coefficient α1 to “1.0” and ends this routine. Therefore, in this case as well, the final injection amount T
When calculating the AU, the increase correction of the injected fuel amount when the brake pedal is returned is substantially not performed.

Subsequently, when the correction coefficient calculation routine is started at timing t5 in FIG. 11, the output signal of the stop lamp switch 17 is switched from "ON" to "OFF" by returning the brake pedal 25, so that the CPU 38 It is determined that the determination condition of step 201 is satisfied, and the process proceeds to step 202. However, it is immediately after switching to "OFF", and the predetermined time Δt1 has not elapsed. Therefore, the CPU 38 determines that the determination condition of step 202 is not satisfied, sets the correction coefficient α1 to “1.0” in step 205, and ends this routine. Therefore, also in this case, when the final injection amount TAU is calculated, the increase correction of the injected fuel amount when the brake pedal is returned is not substantially performed.

After the timing t5 when the brake pedal 25 is returned, in the brake booster 27, the air flowing into the variable pressure chamber 31 by the depression of the brake pedal 25 before the timing t5 causes the engine main body to act due to the action of the intake pipe pressure. 1a is sucked. Due to this suction, the pressure P in the variable pressure chamber gradually decreases from the atmospheric pressure.

At a timing t6 when a predetermined time Δt1 has elapsed from the timing t5, the brake pedal 25 is not depressed, and the pressure P in the variable pressure chamber is slightly lower than the atmospheric pressure. When the correction coefficient calculation routine is started at this timing t6, the CPU 38 proceeds to step 201,
It is determined that both the determination conditions of 202 are satisfied, the pressure P of the variable chamber is read in step 203, and step 204
Then, a correction coefficient α1 corresponding to the pressure P in the variable pressure chamber is calculated. The correction coefficient α1 at this time is a value slightly smaller than the maximum value α1max. After calculating the correction coefficient α1, the CPU 38 ends this routine.

Therefore, when calculating the final injection amount TAU using the above equation (1), the basic injection amount TAUP is multiplied by a relatively large correction coefficient α1 to increase the amount of injected fuel when the brake pedal is returned. Done.

Timing t after timing t6
At 7, t8 and t9, every time the correction coefficient calculation routine is executed, the correction coefficient α1 obtained in step 204 gradually decreases as the pressure P in the variable pressure chamber decreases. Therefore, as shown in FIG. 11, the correction injection amount at the time of returning the brake pedal gradually decreases as time passes.

As described above, in the second embodiment, when the predetermined time Δt1 elapses after the output signal of the stop lamp switch 17 is switched to "OFF", the pressure P in the variable chamber is read by the negative pressure sensor 21 ( Steps 201 and 20
2, 203), and the volume of the variable pressure chamber 31 is grasped based on the value. This volume corresponds to the amount of air flowing into the variable pressure chamber 31 when the brake pedal 25 is depressed. Further, an amount of air corresponding to the pressure change chamber pressure P is sucked into the engine body 1a by the intake pipe pressure after the brake pedal 25 is returned, but it is assumed that the amount changes with the passage of time. Estimate the quantity. Then, the correction coefficient α1 corresponding to the excess air amount is obtained from the map of FIG. 10 (step 204), and the basic injection amount TAUP is increased and corrected by this correction coefficient α1.

Therefore, according to the second embodiment, the first
The same operation and effect as those of the embodiment are achieved. In addition to that, after the brake pedal 25 is returned, the brake booster 2
In consideration of a minute change in the amount of air sucked into the engine body 1a from 7, the correction amount of the injected fuel amount is gradually reduced with the passage of time. Therefore, it is possible to further reduce the turbulence of the air-fuel ratio A / F due to the inflow of the excess air and to converge it near the theoretical air-fuel ratio. (Third Embodiment) Next, a third embodiment of the first and second inventions will be described with reference to FIGS. 12
3 corresponds to FIG. 3 and shows a schematic configuration of the engine 1 and its related equipment.

In the third embodiment, in order to detect the amount of air flowing into the variable pressure chamber 31 of the brake booster 27 when the brake pedal 25 is depressed, an inflow air amount detecting mechanism 46 is provided instead of the negative pressure sensor 21. ing. The inflow air amount detection mechanism 46 constitutes an excess air amount estimation means together with the CPU 38. Other configurations are the same as those of the first and second embodiments. Therefore, the same members as those in the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted.

The inflow air amount detection mechanism 46 is provided in the atmosphere passage 33.
And a free piston 48 slidably inserted into the cylinder 47. A pressure chamber 49 is formed between the inner bottom portion of the cylinder 47 and the free piston 48, and the free piston 48 moves up and down according to the magnitude of the pressure here. Here, the area of the surface of the free piston 48 on which the pressure in the pressure chamber 49 acts is S. In addition to the cylinder 47 and the free piston 48 described above, the inflow air amount detection mechanism 46 shows the lift sensor 22 for detecting the movement amount L of the free piston 48, and the raised free piston 48 by a chain double-dashed line in the figure. A return actuator 50 for returning to the reference position is provided.

In the atmosphere passage 33, a vacuum switching valve (VS) is provided on the upstream side of the inflow air amount detecting mechanism 46.
V) 51 is provided. The VSV 51 is a control valve that opens and closes the atmosphere passage 33 by an electric signal, and is opened when the raised free piston 48 is returned to the reference position by the return actuator 50. At other times, the VSV 51 is closed.

The engine system of this embodiment is provided with an electronic control unit (ECU) 37 for comprehensively controlling the engine 1 and its related equipment. FIG. 13 corresponds to FIG. 4 and shows the configuration of the ECU 37 and the like. ECU3
Reference numeral 7 denotes a CPU 38, a ROM 39, a RAM 40, a backup RAM 41, an external input circuit 42 and an external output circuit 4.
3 and these parts are connected to each other by a bus 44.

The external input circuit 42 is the air flow meter 1
5, fully closed switch 16, stop lamp switch 17,
The throttle sensor 18, the rotation speed sensor 19, the oxygen sensor 20, and the lift sensor 22 are connected. Further, the external output circuit 43 is connected to the fuel injection valves 8A to 8D, the igniter 11, the return actuator 50, and the VSV 51.

Then, the CPU 38 reads the output signals from the air flow meter 15, the switches 16 and 17, and the sensors 18 to 20 and 22 as input values via the external input circuit 42. Further, the CPU 38, based on these input values, through the external output circuit 43, the fuel injection valves 8A to 8D,
Igniter 11, return actuator 50 and VSV
Drive control of each 51 is carried out.

For example, when controlling the fuel injection amount, the CPU 38 calculates the final injection amount TAU corresponding to the fuel injection amount according to the above equation (1), and based on this value, the fuel injection valve 8A
8D is opened to perform fuel injection.

Further, the following equation (2) is preset in order to estimate the excess air amount (excess air amount ΔQ) flowing from the brake booster 27 to the engine body 1a when the brake pedal 25 is returned. .

[0089]

[Equation 1]

However, ω = {(k / m)-
μ ² } ^1/2 , μ = (γ / 2m). Also, equation (2)
Where m is mass, X is displacement, k is spring constant, γ is coefficient,
t is time and A is an arbitrary number.

This expression (2) is an approximate expression set from the following circumstances. First, after returning the brake pedal 25 and switching the output signal of the stop lamp switch 17 from “ON” to “OFF”, the change over time in the amount of air flowing from the brake booster 27 to the surge tank 6 was measured. The results shown in 15 were obtained. As is clear from this figure, it is understood that the air amount changes with the passage of time.

Therefore, if the fuel injection suitable for the characteristics of the air amount is performed, the adverse effect of the excess air flowing from the brake booster 27 to the engine body 1a on the control of the fuel injection amount can be offset. That is, an equation (2) that digitizes the characteristics of FIG. 15 is prepared in advance, and the excess air amount ΔQ at that time is obtained based on this equation (2), and this is reflected in the calculation of the fuel injection amount. Thus, it should be possible to prevent the air-fuel ratio A / F from becoming lean.

The theoretical basis of equation (2) is shown below. FIG.
As shown in, brake booster 27 and surge tank 6
It is assumed that there is a point Y having a mass m in the middle of the negative pressure passage 32 connecting the and. When the brake pedal 25 is returned, the surge tank 6 has a negative pressure and the brake booster 27 has a positive pressure (atmospheric pressure). And the point Y
The force received by the brake booster 2 and the surge tank 6
Since it is proportional to the pressure difference with the inside of 7, the Hooke's law can be applied. That is, ignoring the resistance when the point Y flows through the negative pressure passage 32, the point Y continues to vibrate in the negative pressure passage 32 in the direction indicated by the arrow with the same amplitude. However, in actuality, the effect of the resistance on the vibration at the point Y is large. This resistance is considered to be proportional to the flow velocity, and the action greatly reduces the vibration.

From these facts, the equation of motion expressed by the following equation (3) is established. m · (d ² X / dt ² ) = − kX−γ (dX / dt) (3) In equation (3), m · (d ² X / dt ² ) = − kX corresponds to Hooke's law. However, γ (dX / dt) corresponds to the resistance of the fluid.

When the above equation of motion is solved and the initial condition is taken into consideration, the above-mentioned equation (2) is obtained. Ω and μ in the equation (2) are appropriately set according to the engine 1, the brake booster 27, and the like.

Judging from the actual air flow,
The damping vibration at the point Y seems to be close to the critical braking as shown in FIG. Here, the critical braking means γ (d in Expression (3).
X / dt) is always larger than -kX.

Then, by changing the size of "A" in the above equation (2) according to the inflow air amount q detected by the inflow air amount detecting mechanism 46, the excess air flowing into the surge tank 6 can be obtained. The amount (excess air amount ΔQ) can be estimated.

Next, the operation and effect of the third embodiment constructed as described above will be explained. The flowchart of FIG. 14 shows the intake air amount Q used in the calculation of the final injection amount TAU among the processes executed by the CPU 38.
Shows a routine for correcting the above according to the depression operation of the brake pedal 25. This routine is executed at a predetermined timing.

First, in step 301, the CPU 38 turns off the output signal of the stop lamp switch 17.
From "ON", that is, whether or not the brake pedal 25 is depressed for the first time in this control cycle. When the output signal of the stop lamp switch 17 is "OFF", or when both the previous control cycle and the current control cycle are "ON", the CPU 38 once ends this routine. On the other hand, if the control cycle was "off" in the previous control cycle and was switched to "on" in the control cycle this time, the CPU
38 shifts to step 302.

In step 302, the CPU 38 reads the moving amount L of the free piston 48 by the lift sensor 22. That is, when the brake pedal 25 is depressed, in the brake booster 27, the atmosphere is introduced into the variable pressure chamber 31 by the operation of the communication state switching mechanism 35. At this time, the VSV 51 is closed, so that the free piston 48 is introduced as the atmosphere is introduced into the variable pressure chamber 31.
Rises. The CPU 38 reads the movement amount L at the time of this ascent.

Next, in step 303, the CPU 38 multiplies the moving amount L and the area S of the free piston 48, and the multiplication result is used for the pressure change chamber 3 of the brake booster 27.
It is obtained as the inflowing air amount q to 1.

Subsequently, in step 304, the CPU 38 determines whether or not the output signal of the stop lamp switch 17 is switched from "ON" to "OFF", that is, whether the brake pedal 25 is returned. When the output signal is “ON”, the CPU 38 causes the air to still flow from the atmosphere passage 33 into the variable pressure chamber 31,
It is determined that the air in the variable pressure chamber 31 has not yet flowed to the engine body 1a and it is not necessary to correct the intake air amount Q when calculating the fuel injection amount, the timer is reset in step 305, and this routine is once ended. To do.

On the other hand, when the output signal of the stop lamp switch 17 is switched from "ON" to "OFF" in step 304, the CPU 38 causes the brake pedal 25 to operate.
Since the air that has flowed into the variable pressure chamber 31 at the time of stepping on flows into the engine body 1a as excess air, it is determined that it is necessary to correct the intake air amount Q when calculating the fuel injection amount, and the timer is activated in step 306. Then, the time t elapsed after the brake pedal 25 is returned is measured.

Next, in step 307, the CPU 3
8 uses the time t in step 306 to determine the size of “A” in the above equation (2) according to the inflowing air amount q in step 303, and based on this equation (2), surge The amount of air (excess air amount ΔQ) flowing into the tank 6 is calculated. Then, in step 308, the calculated value is added to the actual intake air amount Q by the air flow meter 15, and the intake air amount Q used to calculate the final injection amount TAU is increased and corrected.

After the correction of the intake air amount Q, the CPU 38 determines in step 309 whether or not the time t by the timer has exceeded a preset predetermined time.
If the predetermined time has not been reached, the CPU 38 repeats the processes of steps 306 to 308 described above. Step 309
If the determination condition of No. 3 is satisfied, the CPU 38 prepares for step 3 in preparation for the next depression of the brake pedal 25.
Processing for returning the free piston 48 to the reference position is performed at 10 to 312.

First, in step 310, the CPU 38 sets VS
A signal for opening V51 is output. When the VSV 51 opens in response to this signal, the inflow air amount detection mechanism 4
6, the pressure chamber 49 is opened to the atmosphere, and the free piston 48
Is easy to move. Then, the CPU 38 proceeds to step 3
At 11, a signal for driving the return actuator 50 is output. In response to this signal, the return actuator 5
0 is activated, and the free piston 48 is returned to the reference position shown by the chain double-dashed line in FIG. Then, the CPU 38 outputs a signal for closing the VSV 51 in step 312. When VSV51 closes according to this signal,
The atmosphere passage 33 upstream of the inflow air amount detection mechanism 46 is closed, and the preparation for the next movement amount measurement of the free piston 48 is completed.

After executing step 312, the CPU 38 ends this routine. Thus, in the third embodiment,
When the brake pedal 25 is depressed, the brake booster 2
Amount of air flowing into the variable pressure chamber 31 of No. 7 (inflow air amount q)
Is detected by the inflow air amount detection mechanism 46 (steps 302 and 303). This inflowing air amount q is the same as the volume of the variable pressure chamber 31 immediately before the brake pedal 25 is returned. When the stop lamp switch 17 detects the switching of the brake pedal 25 to the non-depressed state,
Based on the inflow air amount q into the variable pressure chamber 31 by the inflow air amount detection mechanism 46 and the equation (2), the amount (ΔQ) of the excess air flowing from the brake booster 27 to the engine body 1a while changing with the passage of time is calculated. Yes (Step 30)
4, 306, 307). That is, the excess air amount is estimated on the assumption that the inflow air amount changes with the lapse of time after the brake pedal 25 is returned. When the stop lamp switch 17 detects that the brake pedal 25 is in the non-depressed state, the air flow meter is used to calculate the final injection amount TAU so as to increase the fuel injection amount from the fuel injection valves 8A to 8D. The excess air amount ΔQ is added to the actual intake air amount Q of 15 (step 308).

Therefore, according to the third embodiment, the second
The same operation and effect as those of the embodiment are achieved. Besides, the excess air amount that changes with the passage of time is experimentally obtained and expressed by the equation (2), and the correction amount of the injected fuel amount is changed using the excess air amount obtained from the equation (2). I am letting you. Therefore, the increase correction can be performed according to the actual flow (flow rate) of excess air, and the turbulence of the air-fuel ratio A / F due to the inflow of excess air can be further reduced as compared with the second embodiment. (Fourth Embodiment) Next, a fourth embodiment of the third invention will be described with reference to FIGS.

In the first to third embodiments described above, the brake pedal 25 is released (returned) based on the amount of air flowing into the variable pressure chamber 31 when the brake pedal 25 is depressed.
At some time, the amount of excess air sucked from the brake booster 27 into the engine body 1a is estimated, and this is used as the final injection amount TAU.
Is reflected in. On the other hand, in the fourth embodiment, when the brake pedal 25 is returned, the integral amount KiR at the time of calculating the feedback correction coefficient FAF is changed to a value larger than that at the normal time until the air-fuel ratio A / F becomes rich. However, this is reflected in the final injection amount TAU. Further, in the fourth embodiment, the CPU 38 constitutes a basic injection amount calculation means, a first injection amount correction means, a second injection amount correction means, a correction amount changing means and an injection control means. The configuration of the engine 1 and its related equipment is the same as that of the first embodiment except that the negative pressure sensor 21 is omitted, and therefore the description thereof is omitted here.

FIG. 18 is a flowchart corresponding to FIG. 6 and shows a routine for calculating the integrated amount KiR instead of the corrected injection amount β1. Further, FIG. 19 is a timing chart corresponding to FIG.

The integrated amount calculation routine of FIG.
It is executed based on OXRICH. Flag XOXRI
CH indicates that the output of the oxygen sensor 20 is richly inverted. More specifically, flag XOX
The RICH is set to "0" when the output signal of the stop lamp switch 17 is "on". Also, flag XO
XRICH has the output signal "off", and
It is set to "0" when the output of the oxygen sensor 20 is not switched from lean to rich. Furthermore, flag XO
XRICH is set to "1" when the output signal of the stop lamp switch 17 is "OFF" and the output of the oxygen sensor 20 is switched from lean to rich.

The operation and effect of the fourth embodiment will be described below. FIG. 19 shows the brake pedal 25 at timing t11.
Is returned, and the brake pedal 25 is again returned at timing t15.
It shows the case where is stepped on.

First, when the integral amount calculation routine of FIG. 18 is started at timing t10, the CPU 38 makes a step 4
At 01, it is determined whether or not the output signal of the stop lamp switch 17 is “OFF”. As described above, at the timing t10, the brake pedal 25 is depressed,
The output signal of the stop lamp switch 17 is "on". Therefore, the CPU 38 determines that the determination condition of step 401 is not satisfied, and sets the flag XOXRICH to “0” in step 402.

Next, in step 403, the CPU 38 sets the integration amount KiR to a predetermined value a and ends this routine. Therefore, at the timing t10, the integration amount K
The value a is used as iR, and the feedback correction coefficient FAF is obtained based on this value. Then, when the final injection amount TAU is calculated using the equation (1), the basic injection amount TAUP is multiplied by the feedback correction coefficient FAF. The drive signal corresponding to the calculated final injection amount TAU controls the operation of the fuel injection valves 8A to 8D to inject a predetermined amount of fuel, and the air-fuel ratio A / F converges near the stoichiometric air-fuel ratio.

When the brake pedal 25 is returned at the timing t11, the air that has flowed into the variable pressure chamber 31 of the brake booster 27 before that is fixed to the constant pressure chamber 30 and the negative pressure passage 3.
2, the surge tank 6, and the intake manifold 7 to be sucked into the engine body 1a.

Since the air-fuel ratio A / F becomes lean due to this suction, when calculating the feedback correction coefficient FAF,
If the value a is continuously used as the integration amount KiR, the period in which the output voltage Ox of the oxygen sensor 20 is lower than the reference voltage Vr becomes long as shown by the chain double-dashed line in FIG. Along with this, the feedback correction coefficient FA
Also in F, the period for performing the increase correction becomes long as indicated by the chain double-dashed line. As a result, the time during which the air-fuel ratio A / F greatly deviates from the stoichiometric air-fuel ratio becomes long.

On the other hand, in the third embodiment, the brake pedal 25 is returned at the timing t11 so that the output signal of the stop lamp switch 17 is turned "on".
Is switched to "OFF", the CPU 38 determines that the determination condition of step 401 in FIG. 18 is satisfied, and proceeds to step 404.

In step 404, the CPU 38 determines whether or not a predetermined time Δt2 has elapsed since the output signal of the stop lamp switch 17 was switched to "OFF". The predetermined time Δt2 is an approximate time required for the air in the variable pressure chamber 31 to be sucked into the engine body 1a, burned, and reach the oxygen sensor 20.

Here, since the output signal of the stop lamp switch 17 has just been switched to "OFF", CP
U38 determines that the determination condition of step 404 is not satisfied, and proceeds to step 405.

In step 405, the CPU 38 switches the integral amount KiR to a value b larger than the value a, and ends this routine. Therefore, after the timing t11, the value b is used as the integration amount KiR, and the feedback correction coefficient FAF is obtained based on this value. That is, at the timing t12, the output voltage Ox of the oxygen sensor 20
Is below the reference voltage Vr. Then, CPU38
Determines that the air-fuel ratio A / F is reversed from rich to lean, and the feedback correction coefficient FAF is set to the skip amount RSR.
Is added. Then, at a timing after the timing t12, the CPU 38 updates the feedback correction coefficient FAF by using the value b as the integration amount KiR.

Next, from the timing t11, a predetermined time Δt
A case where the integral amount calculation routine is started at timing t13 when 2 has elapsed will be described. At this time, the output voltage Ox of the oxygen sensor 20 is the reference voltage Vr (= 0.45V).
If it is lower than the threshold, the CPU 38 determines that both the determination conditions of steps 401 and 404 are satisfied, and step 40
At 6, it is determined whether the flag XOXRICH is "1".

At timing t13, the flag XOXRIC is set.
H is still "0". Therefore, the CPU
38 determines that the determination condition of step 406 is not satisfied, and in step 407, it is determined whether the output voltage Ox of the oxygen sensor 20 is higher than the reference voltage Vr.
At the timing t13, Ox <Vr as described above. Therefore, the CPU 38 determines that the determination condition of step 407 is not satisfied, and the flag X is determined in step 408.
Set OXRICH to "0". Then, the CPU 38 holds the integral amount KiR at the value b in step 405, and ends this routine. Therefore, at the timing t13,
The value b is used as the integration amount KiR, and the feedback correction coefficient FAF is obtained based on this value.

When the integral amount calculation routine is started at timing t14 when the output voltage Ox of the oxygen sensor 20 exceeds the reference voltage Vr, the CPU 38 makes a positive determination in steps 401 and 404, and makes a negative determination in step 406. And
The CPU 38 determines that the determination condition of step 407 is satisfied, and switches the flag XOXRICH from "0" to "1" in step 409. Subsequently, the CPU 38 switches the integration amount KiR from the value b to the value a in step 403,
This routine ends.

When the integral amount calculation routine is started after timing t14, the CPU 38 executes steps 401 and 40.
It is determined that all the determination conditions of 4 and 406 are satisfied, the integration amount KiR is set to the value a in step 403, and this routine is finished. Therefore, after the timing t14, the value a is used as the integration amount KiR, and the feedback correction coefficient FAF is obtained based on this value.

After that, when the brake pedal 25 is depressed at the timing t15 and the output signal of the stop lamp switch 17 is switched from "OFF" to "ON", CP
U38 determines that the determination condition of step 401 is not satisfied, switches the flag XOXRICH from "1" to "0" in step 402, and the integration amount K in step 403.
iR is held at the value a, and this routine ends.

At a timing after the timing t15, the CPU 38 performs the same processing as the timing t10 and thereafter. As described above, in the fourth embodiment, when the output signal of the stop lamp switch 17 is switched to "OFF", the integral amount KiR at the time of calculating the feedback correction coefficient FAF is changed to a value b larger than that in the normal time (step 401). ，
404, 405, 407). Then, when the predetermined time Δt2 has elapsed and the air-fuel ratio A / F becomes rich, the integrated amount K
iR is returned to the normal value a (steps 401, 40).
4, 407, 403). Therefore, if the value a is used as the integrated amount KiR regardless of the depression / return operation of the brake pedal 25, the timing at which the air-fuel ratio A / F reverses from lean to rich is, for example, t14a in FIG.
On the other hand, in the fourth embodiment, the timing is advanced to the timing t14. Along with this, the time during which the air-fuel ratio A / F deviates from the stoichiometric air-fuel ratio becomes shorter.

Further, unlike the prior art in which the amount of injected fuel is increased and corrected for a fixed time which is uniquely determined when the brake pedal is released, in the fourth embodiment, the period for changing the integrated amount KiR to the value b is set. , Stop lamp switch 1
For a predetermined time Δt2 after the output signal of No. 7 is turned off
And the air-fuel ratio A / F by the oxygen sensor 20 becomes rich. Therefore, even if the amount of excess air to the engine body 1a varies depending on how the brake pedal 25 is depressed, the amount of injected fuel can be increased and corrected over an appropriate period. Therefore, by changing the integration amount KiR, it is possible to prevent the air-fuel ratio A / F from largely deviating from the stoichiometric air-fuel ratio after a predetermined time Δt2 has passed (after the air in the variable pressure chamber 31 reaches the oxygen sensor 20). Therefore, the stall of the engine 1 and the deterioration of the exhaust gas purification performance can be prevented in advance. (Fifth Embodiment) Next, a fifth embodiment of the third invention will be described with reference to FIGS.

In the fifth embodiment, when the brake pedal 25 is returned, the acceleration increase coefficient α2 at the time of calculating the final injection amount TAU is changed to a value larger than that at the normal time until the air-fuel ratio A / F becomes rich. This is different from the fourth embodiment in that the throttle sensor 18 constitutes a part of the driving state detecting means.

The acceleration increase coefficient α2 is used when the final injection amount TAU is calculated based on the equation (1), and constitutes a part of the correction amount α in the equation (1). The reason why the basic injection amount TAUP is increased and corrected by using the acceleration increase coefficient α2 is to prevent the air-fuel ratio A / F from becoming lean during the transition in which the vehicle accelerates. More specifically,
Generally, most of the fuel injected from the fuel injection valves 8A to 8D adheres to the intake valve and its vicinity. The amount of fuel adhered at this time increases especially during acceleration, that is, when the throttle valve 5 is opened. It takes a predetermined time for the attached fuel to vaporize. Therefore, the air-fuel ratio A / F becomes lean corresponding to the increase in the amount of adhered fuel during acceleration. Therefore, at the time of acceleration, the basic injection amount T
The AUP is increased and corrected.

FIG. 20 is a flowchart corresponding to FIG. 18, in which the acceleration injection amount coefficient α is replaced by the correction injection amount β1.
2 shows a routine for calculating 2. Also, FIG.
1 is a timing chart corresponding to FIG.
The acceleration boosting coefficient calculation routine of FIG. 20 is executed based on the flag XOXRICH, which is the same as the integral quantity calculation routine.

The operation and effect of the fifth embodiment will be described below. In FIG. 21, the brake pedal 25 is at the timing t2.
It is returned at 1, treaded at timing t26, and returned again at timing t27. Further, the accelerator pedal depression is started at timings t22 and t30 for the vehicle to accelerate.

First, when the acceleration boosting coefficient calculation routine is started at timing t20, the CPU 38 proceeds to step 50.
At 1, it is determined whether or not the output signal of the stop lamp switch 17 is "OFF". As described above, the brake pedal 25 is depressed at the timing t20, and the output signal of the stop lamp switch 17 is "on". Therefore, the CPU 38 determines that the determination condition of step 501 is not satisfied, and in step 502,
Set the flag XOXRICH to "0".

Next, in step 503, the CPU 38 sets the acceleration amount increase coefficient α2 to "1.0" and terminates this routine. Therefore, when calculating the final injection amount TAU using the above equation (1), the basic injection amount TAU is multiplied by the acceleration increase coefficient α2, but since α2 = 1.0, the acceleration increase coefficient at timing t20. Substantially no increase correction using α2 is performed. Calculated final injection amount T
A drive signal corresponding to AU controls the operation of the fuel injection valves 8A to 8D to inject a predetermined amount of fuel, and the air-fuel ratio A /
F converges near the stoichiometric air-fuel ratio.

When the brake pedal 25 is returned at the timing t21, the air flowing into the variable pressure chamber 31 of the brake booster 27 is sucked into the engine body 1a before that.

Since the air-fuel ratio A / F becomes lean due to this suction, if some increase correction is not performed to compensate for this, the period in which the output voltage Ox of the oxygen sensor 20 is lower than the reference voltage Vr is long. Become. Along with this, the increase correction time for making the air-fuel ratio rich becomes longer. As a result, it takes a long time for the air-fuel ratio A / F to deviate from the stoichiometric air-fuel ratio.

On the other hand, in the fifth embodiment, the brake pedal 25 is returned at the timing t21 so that the output signal of the stop lamp switch 17 is turned "on".
Is switched from "OFF" to "OFF", the CPU 38 executes step 5
It is determined that the determination condition of 01 is satisfied, and step 50
Go to 4.

In step 504, the CPU 38 determines whether or not a predetermined time Δt2 has elapsed since the stop lamp switch 17 was switched off. This predetermined time Δt2 is the same as that in the fourth embodiment, and the air in the variable pressure chamber 31 is sucked into the engine body 1a and burns,
It is an approximate time required to reach the oxygen sensor 20.

Here, since the output signal of the stop lamp switch 17 has just been turned off, the CPU 3
In step 8, it is determined that the determination condition of step 504 is not satisfied, and the process proceeds to step 505.

In step 505, the CPU 38 determines whether the vehicle is accelerating. The content of the determination here is, for example, whether or not the amount of change (increase) in the throttle opening TA per unit time is larger than a predetermined value. Timing t21 is immediately after the brake pedal 25 is returned, and the acceleration operation is not yet performed. Therefore, the CPU 38 determines that the determination condition of step 505 is not satisfied, and executes the processes of steps 502 and 503. Execute and end this routine. Therefore, at timing t21, the increase correction using the acceleration increase coefficient α2 is not substantially performed.

When the vehicle accelerates at the timing t22 before the predetermined time Δt2 elapses after the brake pedal 25 is released, the CPU 38 causes the step 381,
After the determination processing of 504, it is determined that the determination condition of step 505 is satisfied, and the flag XOXRI is determined in step 506.
Set CH to "0". Then, as the acceleration increase coefficient α2, a value d (1.0 <
c <d) is set, and this routine ends. Therefore,
After the timing t22, when calculating the final injection amount TAU, the value d is set as the acceleration increase coefficient α2 to the basic injection amount TAUP.
Is multiplied, and the amount of fuel is increased and corrected more than in the normal case.

Next, from the timing t21, a predetermined time Δt
A case will be described in which the acceleration increase coefficient calculation routine is started at timing t23 when 2 has elapsed. At this time, the output voltage Ox of the oxygen sensor 20 is equal to the reference voltage Vr (= 0.4).
It is lower than 5 V) and the vehicle continues to be accelerated. Then, the CPU 38 executes steps 501 and 50.
It is determined that all the determination conditions of 4 are satisfied, and in step 508, it is determined whether the flag XOXRICH is “1”.

At timing t23, the flag XOXRIC is set.
H is still "0". Therefore, the CPU 38 determines that the determination condition of step 508 is not satisfied,
In step 509, the output voltage O of the oxygen sensor 20
It is determined whether x is higher than the reference voltage Vr. At timing t23, Ox <Vr. Therefore, CPU3
In step 8, it is determined that the determination condition of step 509 is not satisfied, the processes of steps 505, 506 and 507 are executed, and this routine ends. Therefore, the timing t2
Also in 3, the value d is used as the acceleration increase coefficient α2, and based on this value, the basic injection amount TAUP is increased and corrected more than in the normal case.

When the acceleration increasing coefficient calculation routine is started at the timing t24 when the output voltage Ox of the oxygen sensor 20 exceeds the reference voltage Vr, the CPU 38 proceeds to step 501 → 5.
After performing each determination process of 04 → 508, step 509
It is determined that the determination condition of is satisfied, and the flag XOXRICH is switched from "0" to "1" in step 510.
Subsequently, in step 511, the CPU 38 determines whether or not the vehicle is accelerating, as in step 505. At timing t24, since the vehicle is still accelerating, the CPU 38 determines that the determination condition of step 511 is satisfied, and at step 512, the acceleration increase coefficient α2 is switched from the value d to the normal value c, and this routine is executed. finish. Therefore, after the timing t24, when calculating the final injection amount TAU, the basic injection amount TAU is calculated.
P is multiplied by the value c as the acceleration increase coefficient α2, and the normal fuel increase correction is performed.

At timing t25, when the accelerator pedal begins to be released and the throttle opening TA changes from increasing to decreasing, that is, when the acceleration running ends, the CPU 38 satisfies all the determination conditions of steps 501, 504 and 508. Therefore, the process proceeds to step 511. C
The PU 38 determines that the determination condition of step 511 is not satisfied, and ends this routine.

When the brake pedal 25 is depressed at the timing t26 and the output signal of the stop lamp switch 17 is switched from "OFF" to "ON", CP
U38 determines that the determination condition of step 501 is not satisfied, and switches the flag XOXRICH from "1" to "0" in step 502. CPU38 is step 5
At 03, the acceleration increase coefficient α2 is switched from the value c to “1.0”, and this routine is ended.

At a timing after timing t26, the fuel injection amount control using the normal value c as the acceleration increase coefficient α2 is performed. That is, although the brake pedal 25 is released at the timing t27, the acceleration is not performed before the timing t28 when the predetermined time Δt2 elapses. Therefore, at timing t28, CP
U38 has steps 501 → 504 → 508 → 509 →
After each processing of 505 → 502 → 503, this routine is ended. Therefore, the fuel amount increase correction using the acceleration amount increase coefficient α2 is not substantially performed.

At timing t29 when the output voltage Ox of the oxygen sensor 20 exceeds the reference voltage Vr, the CPU 3
8 is steps 501 → 504 → 508 → 509 → 510
→ After performing each processing of 511, this routine is ended. By the processing of step 510, the flag XOXRIC
H switches from "0" to "1". Therefore, the fuel amount increase correction using the acceleration amount increase coefficient α2 is not performed even at the timing t29.

When acceleration is started at timing t30,
The CPU 38 executes steps 501 → 504 → 508 → 511.
→ After performing each processing of 512, this routine is ended. By the processing of step 512, the acceleration increase coefficient α2 is switched from “1.0” to a value c larger than that.

As described above, in the fifth embodiment, when the output signal of the stop lamp switch 17 is switched to "OFF",
If the vehicle is accelerating, the acceleration increase coefficient α2 is changed to a value d larger than the normal value c (step 504).
505, 507). Then, the predetermined time Δt2 has elapsed,
In addition, when the air-fuel ratio A / F becomes rich and the vehicle is accelerating, the acceleration increase coefficient α2 is returned to the normal value c (steps 504, 509, 511 and 512).
Therefore, in the third embodiment, the timing at which the air-fuel ratio A / F reverses from lean to rich is compared to the case where the value c in the normal state is used as the acceleration increase coefficient α2 regardless of the depression / return operation of the brake pedal 25. Will speed up. Along with this, the time during which the air-fuel ratio A / F deviates from the stoichiometric air-fuel ratio becomes shorter.

Also, unlike the prior art in which the amount of injected fuel is increased and corrected for a fixed time that is uniquely determined when the brake pedal is released, in the fifth embodiment, the acceleration increase coefficient α
The period during which 2 is changed from the value c to the value d is set from when the output signal of the stop lamp switch 17 is “OFF” until the air-fuel ratio A / F by the oxygen sensor 20 becomes rich. Therefore, even if the amount of excess air to the engine body 1a varies depending on how the brake pedal 25 is depressed, the amount of injected fuel can be increased and corrected for an appropriate period. Therefore, by changing the acceleration increase coefficient α2, the air-fuel ratio A
It is possible to prevent / F from deviating greatly from the stoichiometric air-fuel ratio, and to prevent the stall of the engine 1 and the deterioration of the exhaust gas purification performance.

The first to third inventions are not limited to the configurations of the above-described embodiments, and may be arbitrarily modified within the scope not departing from the spirit of each invention, for example, as follows. (1) In the first to fifth embodiments, the brake booster 27
The intake pipe pressure of the surge tank 6 was used as the negative pressure introduced into the constant pressure chamber 30 of the intake manifold 7 instead.
The intake pipe pressure may be used.

(2) In the first to third embodiments, as the sensor for detecting the amount of air flowing into the variable pressure chamber 31 of the brake booster 27, various flow rate sensors other than the above embodiment are used. be able to. For example, there is a vane type, hot wire type, Kalman type flow sensor, or an air amount detecting means using a constant capacity pump such as a roots blower.

(3) The processing content of step 309 of the flowchart of FIG. 14 is changed from that of the above embodiment to "whether or not the integrated value of the excess air amount ΔQ exceeds a predetermined value" or "excessive value". Whether or not the air amount ΔQ exceeds a predetermined value and the time t measured by the timer has passed a predetermined time ”.

(4) In the first and second embodiments, the negative air pressure sensor 21 may be replaced with the inflow air amount detecting mechanism 46 of the third embodiment. (5) In the fourth and fifth embodiments, when the brake pedal 25 is returned, the integrated amount KiR or the acceleration increase coefficient α2 is set until the air-fuel ratio A / F measured by the oxygen sensor 20 exceeds the stoichiometric air-fuel ratio.
Is changed to a value b or d larger than the normal time, but both the integrated amount KiR and the acceleration increase coefficient α2 may be changed to values b and d, respectively.

[0155]

As described in detail above, in the first invention,
In a vehicle provided with a brake booster for amplifying the depression force of the brake pedal by using the intake pipe pressure, when the brake pedal is switched from the depressed state to the non-depressed state, the internal pressure of the internal combustion engine is changed from the brake booster by the intake pipe pressure. Estimate the amount of excess air drawn into the. Then, when the brake pedal is switched from the depressed state to the non-depressed state, the basic injection amount is increased and corrected according to the excess air amount. Therefore, when the brake pedal is switched to the non-depressed state, the air-fuel ratio is reliably prevented from largely deviating from the predetermined air-fuel ratio such as the theoretical air-fuel ratio, and the stall of the internal combustion engine and the deterioration of the exhaust gas purification performance are prevented. Can be prevented.

In particular, in the second aspect of the invention, in estimating the excess air amount, excess air flowing from the brake booster into the internal combustion engine while changing with the passage of time when the brake pedal is switched from the depressed state to the non-depressed state. I try to estimate the amount of. Therefore, in addition to the effect of the first aspect of the invention, the fuel amount increase correction is performed in accordance with the actual change of the excess air sucked from the brake booster to the internal combustion engine, and the disturbance of the air-fuel ratio with respect to the predetermined air-fuel ratio can be further reduced.

In the third aspect of the invention, when the switch to the non-depressed state of the brake pedal is detected, the increase correction amount is forcibly increased until the air-fuel ratio by the air-fuel ratio sensor becomes equal to or lower than the predetermined air-fuel ratio. ing. Therefore, even if excess air is sucked into the internal combustion engine when the brake pedal is switched to the non-depressed state, the injection fuel can be increased and corrected for an appropriate period, and the air-fuel ratio can be adjusted to a predetermined air-fuel ratio or the like. A large deviation from the fuel ratio can be reliably prevented, and a stall of the internal combustion engine and deterioration of the exhaust gas purification performance can be prevented in advance.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram of first and second inventions.

FIG. 2 is a conceptual configuration diagram of a third invention.

FIG. 3 is a schematic configuration diagram of a fuel injection amount control device in a first embodiment embodying the first and second inventions.

FIG. 4 is a block diagram showing an electrical configuration of an ECU in the first embodiment.

FIG. 5 is a timing chart showing the correspondence relationship between the output voltage of the oxygen sensor and the feedback correction coefficient in the first embodiment.

FIG. 6 is a flowchart for explaining a correction injection amount calculation routine executed by the CPU in the first embodiment.

FIG. 7 is a characteristic diagram showing a map in which the correction injection amount with respect to the pressure in the variable pressure chamber is defined in advance in the first embodiment.

FIG. 8 is a timing chart showing the correspondence relationship between the pressure in the variable pressure chamber, the pressure in the intake pipe, and the like in the first embodiment.

FIG. 9 is a flowchart for explaining a correction coefficient calculation routine executed by the CPU, showing a second embodiment of the first and second inventions.

FIG. 10 is a characteristic diagram showing a map in which the correction coefficient for the pressure in the variable pressure chamber is defined in advance in the second embodiment.

FIG. 11 is a timing chart showing the correspondence relationship between the pressure in the variable pressure chamber and the pressure in the intake pipe in the second embodiment.

FIG. 12 is a schematic configuration diagram of a fuel injection amount control device in a third embodiment in which the first and second inventions are embodied.

FIG. 13 is a block diagram showing an electrical configuration of an ECU in the third embodiment.

FIG. 14 is a flowchart for explaining an intake air amount correction routine executed by a CPU in the third embodiment.

FIG. 15 is a characteristic diagram showing a correspondence relationship between the output signal of the stop lamp switch and the amount of air sucked from the brake booster to the surge tank in the third embodiment.

FIG. 16 is an operation explanatory view for explaining the flow of air between the surge tank and the brake booster when the brake pedal is returned in the third embodiment.

FIG. 17 is a characteristic diagram showing damping vibration of air near critical braking in the third embodiment.

FIG. 18 is a flow chart for explaining an integrated amount calculation routine executed by the CPU in the fourth embodiment which embodies the third invention.

FIG. 19 is a timing chart showing the correspondence relationship between the output signal of the stop lamp switch and the output voltage of the oxygen sensor in the fourth embodiment.

FIG. 20 is a flowchart for explaining an acceleration increase coefficient calculation routine executed by the CPU in the fifth embodiment of the third invention.

FIG. 21 is a timing chart showing the correspondence relationship between the output signal of the stop lamp switch and the output voltage of the oxygen sensor in the fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gasoline engine as an internal combustion engine, 2 ... Intake passage, 3 ... Exhaust passage, 8A, 8B, 8C, 8D ... Fuel injection valve, 15 ... Air flow meter as intake air amount detecting means, 17 ... As brake switching detecting means Stop lamp switch, 18 ... Throttle sensor forming part of operating condition detecting means, 19 ... Rotation speed sensor forming part of operating condition detecting means, 20 ... Oxygen sensor as air-fuel ratio sensor, 21 ... First , A negative pressure sensor constituting a part of the excess air amount estimating means in the second embodiment, 25 ... Brake pedal, 27 ... Brake booster, 30 ... Constant pressure chamber, 31
... a variable pressure chamber, 35 ... a communication state switching mechanism, 38 ... In the first to third embodiments, the basic injection amount calculation means, a part of the excess air amount estimation means, the injection amount correction means and the injection control means are configured, In the fourth and fifth embodiments, the CP that constitutes the basic injection amount calculation means, the first injection amount correction means, the second injection amount correction means, the correction amount change means, and the injection control means.
U, 46 ... In the third embodiment, an inflow air amount detection mechanism forming a part of excess air amount estimation means

Claims (3)

[Claims] 1. A fuel injection valve provided in an internal combustion engine for a vehicle, for injecting fuel into air flowing through an intake passage to generate a mixture, and an intake for detecting an amount of air flowing through the intake passage. An air amount detecting means, an operating state detecting means for detecting an operating state of the internal combustion engine, and a basic injection amount of the fuel injection valve based on an intake air amount by the intake air amount detecting means and an operating state by the operating state detecting means. A basic injection amount calculating means for calculating, a constant pressure chamber on which the intake pipe pressure on the downstream side of the intake air amount detecting means of the intake passage acts, a variable pressure chamber capable of introducing the atmosphere, and a non-depressing state of the brake pedal, Allows communication between the constant pressure chamber and the variable pressure chamber, shuts off the introduction of air to the variable pressure chamber, and cuts off the communication between the constant pressure chamber and the variable pressure chamber when the brake pedal is depressed, and at the same time introduces air into the variable pressure chamber. A brake booster for amplifying the stepping force by utilizing the pressure difference between the constant pressure chamber and the variable pressure chamber by the communication state switching mechanism when the brake pedal is stepped on, and the stepped state of the brake pedal. From the brake pedal to the non-depressed state, the excess air amount estimating means for estimating the amount of excess air sucked from the brake booster to the internal combustion engine by the intake pipe pressure, and switching the brake pedal from the depressed state to the non-depressed state. When the brake switching detection means detects the switching of the brake pedal to the non-depressed state, the basic injection amount calculation means is generated according to the excess air amount by the excess air amount estimation means. Injection amount correction means for increasing and correcting the basic injection amount by Injection quantity of fuel injection control apparatus for an engine for a vehicle, characterized in that a injection control means for driving and controlling the fuel injection valve in accordance with the. 2. The excess air amount estimating means estimates the amount of excess air flowing from the brake booster into the internal combustion engine while changing over time when the brake pedal is switched from a depressed state to a non-depressed state. The fuel injection amount control device for an internal combustion engine for a vehicle according to claim 1, wherein 3. A fuel injection valve provided in an internal combustion engine for a vehicle, for injecting fuel into air flowing through an intake passage to generate a mixture, and an intake for detecting an amount of air flowing through the intake passage. An air amount detecting means, an operating state detecting means for detecting an operating state of the internal combustion engine, and a basic injection amount of the fuel injection valve based on an intake air amount by the intake air amount detecting means and an operating state by the operating state detecting means. A basic injection amount calculating means for calculating, an air-fuel ratio sensor for detecting the air-fuel ratio of the air-fuel mixture, which is provided in the exhaust passage of the internal combustion engine, and detects the concentration of a specific component in the exhaust gas, In order to make the air-fuel ratio of the air-fuel mixture a predetermined air-fuel ratio, when the air-fuel ratio by the air-fuel ratio sensor is less than or equal to a predetermined air-fuel ratio, the basic injection amount by the basic injection amount calculation means is reduced and corrected so that the air-fuel ratio is the predetermined air-fuel ratio When the predetermined operating state is detected by the operating state detecting means, the basic injection amount is increased by the first injection amount correcting means for increasing the basic injection amount. Second injection amount correcting means for correcting, a constant pressure chamber on which an intake pipe pressure on the downstream side of the intake air amount detecting means of the intake passage acts, a variable pressure chamber capable of introducing the atmosphere, and a non-depressing state of the brake pedal , Allow the communication between the constant pressure chamber and the variable pressure chamber, and cut off the introduction of air into the variable pressure chamber, and when the brake pedal is depressed, cut off the communication between the constant pressure chamber and the variable pressure chamber and allow the introduction of air into the variable pressure chamber. A brake booster that has a communication state switching mechanism and that amplifies the stepping force by utilizing the pressure difference between the constant pressure chamber and the variable pressure chamber by the communication state switching mechanism when the brake pedal is depressed. , A brake switching detection means for detecting switching of the brake pedal from a depressed state to a non-depressed state, and an air-fuel ratio detected by an air-fuel ratio sensor when the brake switching detection means detects a switching of the brake pedal to a non-depressed state. Until it becomes equal to or less than the predetermined air-fuel ratio, the correction amount changing unit forcibly increasing at least one of the increase correction amounts by the first injection amount correcting unit and the second injection amount correcting unit, and the correction amount changing unit A fuel injection amount control device for an internal combustion engine for a vehicle, comprising: an injection control unit that drives and controls the fuel injection valve according to the corrected injection amount.