JP2002089331A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of restraining deterioration of fuel cinsumption to the minimum while restraining degradation of a catalyst. SOLUTION: The control device for the internal combustion engine to control an air-fuel ratio stoical or rich by supplying fuel at the time of deceleration in a catalyst high temperature state while stopping fuel supply at the time of deceleration not in the catalyst high temperature state constitutes its characteristic feature of providing a sudden decelerating state detection means to detect a sudden decelerating state large in deceleration and a fuel supply prohibition means to prohibit fuel supply at the time when the sudden decelerating state is detected by the sudden decelerating state detection means even at the time of deceleration in the catalyst high temperature state. The sudden decelerating state detection means is to detect the sudden decelerating state having possibility to cause fuel supply stoppage to be carried out in the case when injection time of less than the minimum injection time free to inject by an injector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly, to a control for stopping supply of fuel to the internal combustion engine during deceleration for the purpose of improving a fuel consumption rate (hereinafter referred to as fuel). Cut or F / C).

[0002]

2. Description of the Related Art Conventionally, in an electronically controlled fuel injection control device for an internal combustion engine, when the throttle valve is fully closed and the engine speed is equal to or higher than a predetermined value, it is determined that the fuel supply is in an unnecessary deceleration state. In order to improve the fuel consumption rate, a fuel cut for temporarily stopping the fuel injection is performed.

On the other hand, a catalyst in a catalytic converter for purifying exhaust gas provided in an exhaust system of an internal combustion engine is in a high temperature state (80 ° C.).
(0 ° C. to 900 ° C. or more), the degree of progress of the catalyst deterioration rapidly increases only by slightly increasing the catalyst temperature. Therefore, for example, in Japanese Patent Application Laid-Open No. 8-144814, the fuel cut during deceleration is prohibited when the temperature of the catalyst is high, thereby preventing the catalyst from being exposed to a high-temperature lean atmosphere and preventing the catalyst from deteriorating. It has been proposed to. In addition to prohibiting fuel cut, feedback control of the air-fuel ratio to stoichiometry (stoichiometric air-fuel ratio) is also performed to suppress catalyst deterioration and improve fuel efficiency.

[0004]

During rapid deceleration (especially at high speeds), even if the throttle is suddenly closed at the time of deceleration, the engine speed does not decrease and the fuel injection amount per cylinder becomes extremely small. . And when the injection time shorter than the minimum injection time that can be injected by the injector is calculated,
When the injection is performed, the air-fuel ratio is shifted, so that the fuel injection is not performed, that is, a fuel cut (referred to as a fuel cut at the time of the minimum injection amount) is momentarily performed.

[0005] Immediately after the deceleration, the negative pressure changes in a direction to increase, so that the fuel adhering to the intake wall surface is peeled off and flows into the catalyst as it is. In addition, oxygen is supplied to the catalyst by the fuel cut at the time of the minimum injection amount.
Therefore, combustion occurs on the catalyst, and the catalyst temperature is 20 ° C
Above, it increases rapidly. As a result, even if the stoichiometric control of the air-fuel ratio is performed, the increase in the catalyst temperature cannot be suppressed.
It simply leads to poor fuel economy.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a control device for an internal combustion engine capable of minimizing deterioration of fuel economy while suppressing deterioration of a catalyst. It is in.

[0007]

According to the present invention, the fuel supply is stopped during deceleration when the catalyst is not in the high temperature state, and the fuel is supplied during the deceleration in the high catalyst state to provide the air-fuel ratio. In a control device for an internal combustion engine that controls stoichiometrically or richly, a rapid deceleration state detecting means for detecting a rapid deceleration state with a large deceleration, and a sudden deceleration state detection means even when decelerating in a high temperature state of the catalyst. Fuel supply prohibition means for prohibiting fuel supply when the state is detected,
A control device for an internal combustion engine is provided.

Further, according to the present invention, the sudden deceleration state detecting means may cause a fuel supply stop which is executed when an injection time shorter than a minimum injection time that can be injected by the injector is calculated. Detects sudden deceleration.

As described above, even during deceleration in the high-temperature state of the catalyst, in the case of rapid deceleration, the increase in the catalyst temperature cannot be suppressed by executing the stoichiometric control of the air-fuel ratio. In the thus configured control device for an internal combustion engine according to the present invention, the fuel supply is stopped (fuel cut) in such a case, so that the fuel efficiency can be improved.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall schematic diagram of an internal combustion engine provided with a control device according to one embodiment of the present invention. Internal combustion engine 1
Is an in-line multi-cylinder 4-stroke cycle reciprocating gasoline engine mounted on a vehicle. The engine 1 includes a cylinder block 2 and a cylinder head 3. A plurality of cylinders 4 extending in the vertical direction are arranged in the cylinder block 2 in parallel in the thickness direction of the drawing, and a piston 5 is housed in each cylinder 4 so as to be able to reciprocate. Each piston 5 is connected via a connecting rod 6 to a common crankshaft 7
It is connected to. The reciprocating motion of each piston 5 is converted into a rotational motion of a crankshaft 7 via a connecting rod 6.

A combustion chamber 8 is provided between the cylinder block 2 and the cylinder head 3 above each piston 5. The cylinder head 3 is provided with an intake port 9 and an exhaust port 10 for communicating both outer surfaces thereof with the respective combustion chambers 8. In order to open and close these ports 9 and 10, an intake valve 11 and an exhaust valve 12 are supported on the cylinder head 3 so as to be able to reciprocate substantially vertically. In the cylinder head 3,
Above the valves 11 and 12, an intake camshaft 13 and an exhaust camshaft 14 are rotatably provided, respectively. Cams 15 and 16 for driving the valves 11 and 12 are attached to the camshafts 13 and 14, respectively. Timing pulleys 17 and 1 provided at ends of camshafts 13 and 14, respectively.
8 is connected to a timing pulley 19 provided at an end of the crankshaft 7 by a timing belt 20. The rotation speed of the camshafts 13 and 14 is
The rotation speed is reduced to half of the rotation speed of the crankshaft 7.

The intake port 9 is connected to an intake passage 30 having an air cleaner 31, a throttle valve 32, a surge tank 33, an intake manifold 34 and the like. Air (outside air) outside the engine 1 is supplied to the intake passage 3 toward the combustion chamber 8.
0 sequentially passes through the respective parts 31, 32, 33 and 34. An idle adjustment passage 35 that bypasses the throttle valve 32 is provided with an idle speed control valve (ISCV) 36 for adjusting the air flow during idling. An injector 40 that injects fuel toward each intake port 9 is attached to the intake manifold 34. The fuel is stored in a fuel tank 41, from which the fuel is pumped by a fuel pump 42 and a fuel pipe 43
Is supplied to the injector 40 via the Then, a mixture of fuel injected from the injector 40 and air flowing in the intake passage 30 is introduced into the combustion chamber 8 via the intake valve 11.

A spark plug 50 is attached to the cylinder head 3 in order to ignite the mixture. At the time of ignition, the igniter 51 that has received the ignition signal controls the supply and cutoff of the primary current of the ignition coil 52, and the secondary current is supplied to the spark plug 50 via the ignition distributor 53.

The burned air-fuel mixture is guided to an exhaust port 10 via an exhaust valve 12 as exhaust gas. The exhaust port 10 has an exhaust manifold 61 and a catalytic converter 62.
The exhaust passage 60 provided with the above is connected. HC (hydrocarbon), which is an incomplete combustion component, is supplied to the catalytic converter 62.
And a three-way catalyst that simultaneously promotes the oxidation of CO (carbon monoxide) and the reduction of NO _x (nitrogen oxide) generated by the reaction of nitrogen in the air with unburned oxygen. . The exhaust gas thus purified in the catalytic converter 62 is discharged into the atmosphere. The catalyst to which the present invention is applied may be any of a three-way catalyst (platinum-based, palladium-based), an oxidation catalyst, and the like, and is not particularly limited.

The following various sensors are attached to the engine 1. An air flow meter 70 for detecting an intake air amount (flow rate QA) is attached to the intake passage 30. In the intake passage 30, near the throttle valve 32, a throttle opening sensor 72 for detecting a rotation angle of the shaft 32a is provided. When the throttle valve 32 is in the fully closed state, the idle switch 82 is turned on, and the throttle fully closed signal output from the idle switch 82 becomes active. An accelerator opening sensor 77 for detecting an accelerator depression amount (accelerator opening) is provided near the accelerator pedal of the vehicle. In addition, a brake sensor 78 for detecting a brake depression amount is provided near the brake pedal of the vehicle.
Further, an O ₂ sensor 75 for detecting the concentration of residual oxygen in the exhaust gas is provided in the middle of the exhaust passage 60.

The distributor 53 has a built-in rotor that rotates in synchronization with the rotation of the crankshaft 7, and converts the crank angle (CA) based on the rotation of the rotor to detect the reference position of the crankshaft 7. A crank reference position sensor 80 for generating a reference position detection pulse every 720 ° CA is provided. In addition, the crank reference position sensor 80 detects the rotation speed of the crankshaft 7 (engine speed NE) based on the rotation of the rotor. A crank angle sensor 81 for generating a rotation speed detection pulse for each ° CA is provided.

Engine electronic control unit (engine ECU) 90
Is a microcomputer system that executes fuel injection control, ignition timing control, idle speed control, and the like. The fuel injection control includes a fuel cut control at the time of deceleration.
By the way, as described above, when the fuel cut is performed when the temperature of the catalyst (catalyst bed temperature) is high, lean exhaust gas generated accompanying the fuel cut flows into the catalyst, but the catalyst deteriorates under such a high-temperature lean atmosphere. It is known to

FIG. 2 is a time chart in which behaviors of the vehicle speed, the air-fuel ratio and the catalyst bed temperature are experimentally obtained, and is a diagram for explaining an increase in the catalyst bed temperature at the time of fuel cut. According to this figure, the execution of the fuel cut (F / C) at the time of deceleration causes the air-fuel ratio (A / F) to become a large value, that is, lean, but at the same time, the catalyst bed temperature starts to rise to about 20 °.
It can be seen that C rises. Under such circumstances, the degree of progress of the deterioration of the catalyst rapidly increases, and as described above, when the temperature of the catalyst is high, the fuel cut at the time of deceleration is prohibited, and the air-fuel ratio is stoichiometric (stoichiometric air-fuel ratio). Feedback control is performed.

On the other hand, in general, in a control device of an internal combustion engine, when an injection time shorter than a minimum injection time that can be injected by an injector is calculated (that is, when there is no linearity in the flow rate characteristic of the injector, or when a small combustion that cannot clearly burn) is performed. In the case of the injection time range), the fuel injection is not performed because the air-fuel ratio is shifted when the injection is performed. Here, the fuel cut in this case is referred to as a fuel cut at the time of the minimum injection amount. FIG. 3 is a flowchart showing a control procedure for executing the fuel cut at the time of the minimum injection amount executed by the ECU 90. In the example of FIG. 3, as shown in steps 102, 104 and 106, the execution condition of the fuel cut at the time of the minimum injection amount is such that the fuel injection time TAU is 700 μs or less and the engine speed NE is 2400 rpm or more. Further, as shown in steps 102, 108 and 110, the condition for returning from the execution state of the fuel cut at the time of the minimum injection amount to the normal state is that the fuel injection time TAU is 900 μs or more and the engine speed NE is 2300 rpm or less. is there.

Therefore, even if the fuel cut during deceleration is prohibited to prevent catalyst deterioration and air-fuel ratio feedback control is performed, the engine speed after the throttle is suddenly closed due to rapid deceleration cannot be reduced, and the number of cylinders per cylinder can be reduced. When the fuel injection amount is extremely small, the above-described fuel cut at the time of the minimum injection amount is executed, and oxygen is supplied to the catalyst. Immediately after deceleration, the negative pressure changes in a direction to increase, so that the fuel adhering to the intake wall surface is stripped off and flows into the catalyst as it is.
As a result, combustion occurs on the catalyst. As described above, at the time of rapid deceleration, even if the fuel cut during deceleration is prohibited and the stoichiometric control of the air-fuel ratio is performed, the increase in the catalyst temperature cannot be suppressed, and the fuel efficiency is merely deteriorated.

FIG. 4 is a time chart exemplifying the behavior of the vehicle speed, the engine speed and the air-fuel ratio, and shows how the fuel cut at the time of deceleration and the fuel cut at the time of the minimum injection amount occur. In the example shown in this figure, at the time of the first deceleration, the fuel cut at the time of deceleration is performed, and the air-fuel ratio becomes lean for about 5 seconds. The cut is executed and the air-fuel ratio becomes lean for a moment. It has been experimentally found that even in the case of the fuel cut at the time of the minimum injection amount which occurs only for a moment, the catalyst temperature rise is almost the same as in the case of the fuel cut at the time of deceleration.

Accordingly, the present invention is designed to provide a rapid fuel cut-off at the time of the minimum injection amount during the execution of the air-fuel ratio feedback control even when the catalyst is decelerated in the high-temperature state of the catalyst, so that a rise in the catalyst temperature cannot be suppressed. In the case of deceleration, a fuel cut during deceleration is executed to ensure an improvement in fuel efficiency. Hereinafter, a specific processing procedure will be described.

FIG. 5 shows the ECU 90 for estimating the catalyst bed temperature.
Is a flowchart showing a processing procedure of a catalyst bed temperature estimation routine executed by the CPU. This routine is executed at a predetermined cycle. The catalyst bed temperature can be estimated from the intake air flow rate QA. However, the catalyst bed temperature gradually changes with a certain delay time with respect to the change in the intake air flow rate. Therefore, the delayed intake air flow rate DQA that reflects a change in the intake air flow rate
(Delay QA) is used as the catalyst bed temperature.

First, at step 202, the current intake air flow rate QA is detected based on the output of the air flow meter 70. Next, at step 204, it is determined whether or not the current intake air flow rate QA is greater than the previously calculated intake air flow rate QAO. If it is, the process proceeds to step 206, where the delayed intake air flow rate QA is delayed by a predetermined amount QAC. The flow rate DQA is increased, and if not, the routine proceeds to step 208, where the delayed intake air flow rate DQA is decreased by a predetermined amount QAD. Finally, in step 210, the Q calculated this time is
A is stored as QAO for the next use. The delayed intake air flow rate DQA thus obtained follows the intake air flow rate QA at a gentle speed, and can be used as an amount reflecting the catalyst bed temperature. As a method for detecting the catalyst bed temperature, a temperature sensor such as a thermocouple may be provided on the catalyst to directly detect the catalyst bed temperature.

FIG. 6 is a flowchart showing a processing procedure of a deceleration fuel cut execution control routine executed by the ECU 90. The deceleration-time fuel cut execution control routine determines whether or not to execute the deceleration-time fuel cut at the next fuel injection timing. In this routine, the fuel cut during deceleration is prohibited in principle when the catalyst bed temperature is high, but even when the catalyst is decelerated in the high temperature state of the catalyst, the fuel supply is prohibited when the rapid deceleration state is detected. That is, a fuel cut is to be executed.

First, in step 302, as a precondition for executing fuel cut during deceleration, the idle switch 82 is turned on, that is, the throttle valve 32 is fully closed, and the engine speed NE is equal to or higher than a predetermined value. Is determined. When the result of the determination in step 302 is NO, that is, when the precondition is not satisfied, this routine ends. On the other hand, when the result of the determination in step 302 is YES, that is, when the precondition is satisfied, the routine proceeds to step 304.

In step 304, the catalyst bed temperature equivalent amount DQA obtained by the aforementioned catalyst bed temperature estimation routine
Is compared with a predetermined determination reference value to determine whether or not the temperature of the catalyst is high (800 ° C. to 900 ° C. or higher). When the catalyst bed temperature is directly detected by the temperature sensor, the determination is made based on the output of the temperature sensor. When the catalyst bed temperature is lower than the reference value, there is no possibility of catalyst deterioration due to the high-temperature lean atmosphere, so the routine proceeds to step 310, where the deceleration F / C is executed.

On the other hand, when the catalyst bed temperature is higher than the reference value, there is a possibility that the catalyst is deteriorated.
Under conditions that prohibit the execution of However, in the present embodiment, the process proceeds to step 306 to determine whether or not the vehicle is in a rapid deceleration state with a large deceleration. The determination as to whether or not the vehicle is in the rapid deceleration state is made based on the brake depression force detected by the brake sensor 78, or based on the return amount and return speed of the accelerator opening detected by the accelerator opening sensor 77. For this determination, a reference value for detecting a sudden deceleration state in which the above-described fuel cut at the time of the minimum injection amount is likely to occur is experimentally obtained in advance. Note that, as the engine speed is higher, the fuel cut at the time of the minimum injection amount is more likely to be performed. Therefore, the determination that the engine speed is equal to or more than a certain value may be added to the condition of rapid deceleration.

In the rapid deceleration state, even if the air-fuel ratio feedback control is performed to prevent a high-temperature lean atmosphere of the catalyst, a fuel cut at the time of the minimum injection amount occurs during the execution, and the catalyst temperature rise is reduced. Since it is determined that it cannot be suppressed, the process proceeds to step 310, and the fuel efficiency is improved by setting the deceleration F / C execution state.

On the other hand, when the vehicle is not in the rapid deceleration state, the routine proceeds to step 308 to execute the idle self-sustaining control in order to prevent the high-temperature lean atmosphere of the catalyst. That is, the air-fuel ratio is feedback-controlled so that the exhaust air-fuel ratio becomes stoichiometric. Note that as another embodiment, the supply of oxygen to the catalyst may be completely eliminated by controlling the stoichiometry to be slightly richer. In addition, the idle self-sustaining control may be performed only for a predetermined period from the start of deceleration, and thereafter, may be switched to deceleration-time fuel cut to improve fuel efficiency. Alternatively, the catalyst bed temperature becomes 7 from the start of deceleration.
Even if the idle self-sustained control is performed only for a period of 80 ° C. or more, the fuel consumption can be improved by switching to the fuel cut during deceleration thereafter.

[0032]

As described above, according to the present invention,
Even during deceleration in a high-temperature catalyst state in which catalyst deterioration is promoted by the inflow of lean exhaust, in the case of rapid deceleration in which suppression of catalyst temperature rise by air-fuel ratio stoichiometric control is not successful due to fuel cut at the minimum injection amount, Since the fuel cut at the time of deceleration is executed without being prohibited, the fuel efficiency is improved.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an internal combustion engine including a control device according to an embodiment of the present invention.

FIG. 2 is a time chart illustrating behaviors of a vehicle speed, an air-fuel ratio, and a catalyst bed temperature, and is a diagram illustrating an increase in a catalyst bed temperature during a fuel cut.

FIG. 3 is a flowchart showing a processing procedure of a fuel cut execution control routine at the time of a minimum injection amount executed by an ECU.

FIG. 4 is a time chart illustrating behaviors of a vehicle speed, an engine speed, and an air-fuel ratio, and is a diagram illustrating a state of occurrence of a fuel cut during deceleration and a fuel cut during minimal injection amount.

FIG. 5 is a flowchart showing a processing procedure of a catalyst bed temperature estimation routine executed by the ECU.

FIG. 6 is a flowchart showing a processing procedure of a deceleration fuel cut execution control routine executed by the ECU.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... In-line 4-cylinder 4-stroke cycle reciprocating gasoline engine 2 ... Cylinder block 3 ... Cylinder head 4 ... Cylinder 5 ... Piston 6 ... Connecting rod 7 ... Crank shaft 8 ... Combustion chamber 9 ... Intake port 10 ... Exhaust port 11 ... Intake valve 12 ... Exhaust valve 13 ... Intake side camshaft 14 ... Exhaust side camshaft 15 ... Intake side cam 16 ... Exhaust side cam 17,18,19 ... Timing pulley 20 ... Timing belt 30 ... Intake passage 31 ... Air cleaner 32 ... Throttle valve 32a ... Throttle valve shaft 33 Surge tank 34 Intake manifold 35 Idle adjust passage 36 Idle speed control valve (ISCV) 40 Injector 41 Fuel tank 42 Fuel pump 43 Fuel pipe 50 Spark plug 51 A Gunaita 52 ... ignition coil 53 ... ignition distributor 60 ... exhaust passage 61 ... exhaust manifold 62 ... catalytic converter 70 ... air flow meter 72 ... Throttle opening sensor 75 ... O ₂ sensor 77 ... accelerator opening sensor 78 ... brake sensor 80 ... crank reference Position sensor 81 ... Crank angle sensor 82 ... Idle switch 90 ... Engine electronic control unit (engine ECU)

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 3G084 BA06 BA09 BA13 CA03 CA06 DA02 DA19 DA25 EA04 EA07 EA11 EB11 EC01 FA06 FA07 FA10 FA27 FA29 FA33 FA38 3G091 AA02 AA17 AA23 AA28 AB02 AB03 BA07 CA13 CB02 CB07 EA00 EA18 EA26 EA30 EA31 EA34 EA39 FA05 FA19 FB10 FB11 FB12 FC08 GA06 GB06W GB07W HA36 HA39 3G301 JA02 JA33 KA07 KA17 KA26 KA27 LA04 LC01 MA01 MA11 MA24 MA25 NA08 NB02 NB11 NB15 ND01 NE11 NE01 NE13 NE01 NE13 NE03 NE11 PF05Z

Claims (2)

[Claims] 1. A control device for an internal combustion engine that stops fuel supply during deceleration when the catalyst is not in a high temperature state and supplies fuel during deceleration in a high catalyst state to control the air-fuel ratio to stoichiometric or rich. A rapid deceleration state detecting means for detecting a rapid deceleration state; and even when decelerating in a catalyst high temperature state, when the rapid deceleration state detection means detects the rapid deceleration state,
A control device for an internal combustion engine, comprising: fuel supply prohibition means for prohibiting fuel supply. 2. The rapid deceleration state detecting means detects a rapid deceleration state in which a fuel supply stop which may be executed when an injection time shorter than a minimum injection time that can be injected by an injector is calculated is generated. The control device for an internal combustion engine according to claim 1, wherein