JPH08200166A - Air-fuel ratio control device - Google Patents

Abstract

PURPOSE: To improve drivability through improvement of high temperature restartability of an internal combustion engine by executing optimum evaporation purge, taking it into consideration whether air bubbles are generated or not during high temperature restarting. CONSTITUTION: A water temperature THW detected by a water temperature sensor 44 and an intake air temperature THA detected by an intake air temperature sensor 43 are inputted to an RAM in an ECU 70 to detect a high temperature state and further it is detected that an engine is under starting. During high temperature starting, a present starting time (an elapse time starting from the starting of cranking by a starter) T is inputted. Based on the starting time T, an vaporization purge amount E1 is determined by referring to a given map and vaporization purge is executed. The map is determined in such a manner that an amount of fuel steam fed from a fuel steam chamber 15 is gradually increased to a specified amount responding to the operation state of an engine 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine (engine).
In regard to the air-fuel ratio control device for controlling the air-fuel mixture ratio (air-fuel ratio A / F) by supplying an appropriate amount of fuel according to the intake air amount, more specifically, in more detail, at the time of high temperature restart The present invention relates to an air-fuel ratio control device that improves air-fuel ratio control accuracy.

[0002]

2. Description of the Related Art Generally, when an engine is restarted at a high temperature (that is, when the engine is restarted before the temperature of the engine is lowered), bubbles are generated in an injector (fuel injection valve) and a fuel pipe. The fuel injection amount decreases, and as a result, the A / F becomes lean, and startability may become a problem. In such a case, even if the injection time of the injector is extended to increase the amount of fuel, the amount of fuel actually injected may differ depending on the bubble generation state, such as when bubbles are generated at the tip of the injector. It may not be possible to prevent such A / F lean without increasing.

Therefore, there has been proposed a technique for improving such high temperature restartability by utilizing evaporative purge (canister purge) control instead of increasing the fuel injection amount by the injector. The evaporative purge control is to temporarily store the fuel vapor (vapor) evaporated from the fuel tank in a canister (a container containing an adsorbent such as activated carbon) for the purpose of preventing air pollution and fuel loss. The processing is to release the air to the intake system according to the operating state. The reason why the evaporative purge is used is that at the time of high temperature restart, it can be determined that the canister has adsorbed the vapor because it has been traveling at a high temperature until then. For example, the technology disclosed in Japanese Patent Laid-Open No. Sho 61-98956 is a fuel vapor adsorbed by a canister when the fuel temperature is restarted at a high temperature above a set value and the air-fuel ratio is lean. Is supplied to the downstream side of the throttle valve to replenish the fuel that is insufficient due to evaporation at the time of high temperature restart and improve the high temperature restartability. In addition, the technology disclosed in Japanese Patent Publication No. 6-74773 is also
Further, it is detected that the engine is restarting at a high temperature based on the intake air temperature and the engine cooling water temperature, and at the time of a high temperature restart, the evaporation purge is performed as in the above-mentioned publication.

[0004]

However, the above-mentioned conventional techniques do not accurately predict the occurrence of bubbles and perform the purge control. That is, just by considering the fuel temperature and the engine water temperature, even when the engine is restarted at high temperature, it is not always the case that bubbles are generated in the fuel. Is detected, the purge control is performed assuming the occurrence of bubbles. Originally,
In order to fully predict the bubble formation in the injector,
It is necessary to accurately detect the fuel property, the temperature at the tip of the injector, and the like. Therefore, in the conventional example, there is a possibility that the evaporative purge is executed at the time of high temperature restart where no bubbles actually occur, and in such a case, a sudden fuel rich state may be induced.

In view of such circumstances, an object of the present invention is to improve the air-fuel ratio control accuracy at the time of high temperature restart by executing the optimum evaporative purge in consideration of the presence or absence of bubbles at the time of high temperature restart. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine to improve the high temperature restartability of the internal combustion engine and further improve drivability.

[0006]

The present invention adopts a technical configuration as described below based on the basic idea of gradually increasing the evaporation purge amount at the time of high temperature restart according to the starting time. By doing so, the above object is achieved.

That is, the air-fuel ratio control apparatus for an internal combustion engine according to the first invention of the present application has a canister for adsorbing fuel vapor, and during normal operation, the fuel vapor adsorbed by the canister according to the engine operating state. In an air-fuel ratio control device for an internal combustion engine configured to supply to the intake system, a high temperature restart time detection means for detecting a high temperature restart time,
When the high temperature restart detection means detects that the high temperature restart is in progress, the fuel vapor adsorbed in the canister is gradually increased to a specified amount according to the engine operating state, and the fuel supplied to the intake system is gradually increased. And a vapor supply means.

According to a second aspect of the present invention, as an aspect of the air-fuel ratio control device according to the first aspect, the fuel vapor supply start timing of the fuel vapor supply means from the start to the engine operating state. Supply delay means for delaying by a predetermined period according to the above.

[0009]

In the air-fuel ratio control device configured as described above, at the time of high temperature restart, the fuel vapor is gradually increased to the specified amount according to the operating state of the engine and supplied to the intake system. Therefore, even when restarting at high temperature, no bubbles are generated in the injector, and when the normal fuel injection amount is supplied, a small amount of fuel vapor is initially supplied to prevent fuel richness. Will be done. Also,
When air bubbles are generated in the injector and the fuel injection amount is insufficient, the fuel lean is prevented by gradually increasing the fuel vapor to a prescribed amount according to the engine operating state. In this way, the air-fuel ratio at high temperature restart is optimally controlled by simple means.

According to the second aspect of the invention, it can be judged that the start has not been completed and the bubbles are surely generated at the time when a predetermined period corresponding to the engine operating state has passed since the start. The start of the supply of fuel vapor will be delayed until such time as possible. That is, the fuel correction by supplying the fuel vapor is more accurately performed.

[0011]

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

FIG. 1 is an overall schematic view of an electronically controlled internal combustion engine equipped with an air-fuel ratio control device according to an embodiment of the present invention. Air required for combustion in the engine 20 is filtered by the air cleaner 2, passes through the throttle body 4, and is distributed to the intake pipe 7 of each cylinder at the surge tank (intake manifold) 6. The intake air flow rate is adjusted by the throttle valve 5 provided on the throttle body 4 and measured by the air flow meter 40. Also,
The intake air temperature is detected by the intake air temperature sensor 43.
Further, the intake pipe pressure is detected by the vacuum sensor 41.

The opening of the throttle valve 5 is detected by the throttle opening sensor 42. When the throttle valve 5 is fully closed, the idle switch 52 is turned on, and the output of the throttle fully closed signal is active. In addition, an idle speed control valve (I) for adjusting the air flow rate during idling is provided in the idle adjust passage 8 that bypasses the throttle valve 5.
SCV) 66 is provided.

On the other hand, the fuel stored in the fuel tank 10 is pumped up by the fuel pump 11, and the fuel pipe 12
Then, the fuel is injected into the intake pipe 7 by the fuel injection valve 60. Such air and fuel are mixed in the intake pipe 7, and the mixture is sucked into the engine body, that is, the cylinder (cylinder) 20 via the intake valve 24. In the cylinder 20, the air-fuel mixture is compressed by the piston and then ignited to explode and burn to generate power. In such ignition, the igniter 62 receiving the ignition signal controls the energization and interruption of the primary current of the ignition coil 63, and the secondary current is supplied to the spark plug 65 via the ignition distributor 64. Made by.

The ignition distributor 64 includes
Its axis is, for example, 720 ° converted to crank angle (CA)
A reference position detection sensor 50 that generates a reference position detection pulse for each CA and a crank angle sensor 51 that generates a position detection pulse for each 30 ° CA are provided. The engine 20 is cooled by the cooling water guided to the cooling water passage 22, and the temperature of the cooling water is detected by the water temperature sensor 44.

The burned air-fuel mixture is discharged as exhaust gas to the exhaust manifold 30 via the exhaust valve 26, and is then guided to the exhaust pipe 34. The exhaust pipe 34 is provided with an O ₂ sensor 45 for detecting the oxygen concentration in the exhaust gas. Further, a catalytic converter 38 is provided in the exhaust system downstream thereof, and the catalytic converter 38 has
A three-way catalyst that simultaneously promotes the oxidation of unburned components (HC, CO) and the reduction of nitrogen oxides (NO _x ) in the exhaust gas is housed. The exhaust gas thus purified by the catalytic converter 38 is discharged into the atmosphere.

The vehicle speed sensor 53 is a sensor for detecting the vehicle speed. The starter switch 54 is a switch that is closed when driving a starter motor (not shown).

This internal combustion engine also uses activated carbon (adsorbent).
A canister 13 having a built-in 14 is provided. The canisters 13 are provided on both sides of the activated carbon 14 in the fuel vapor chamber 1 respectively.
5 and the atmosphere chamber 16. The fuel vapor chamber 15 is connected to the fuel tank 10 via the vapor collecting pipe 17 on the one hand, and is connected to the intake passage on the downstream side of the throttle valve 5, that is, the surge tank 6 via the purge passage 18 on the other hand. An electromagnetic valve 68 for controlling the purge gas amount is installed in the purge passage 18. In such a configuration,
The fuel vapor or vapor generated in the fuel tank 10 is
It is guided to the canister 13 through the vapor collection pipe 17 and is temporarily stored by being adsorbed by the activated carbon (adsorbent) 14 in the canister 13. When the solenoid valve 68 is opened, the intake pipe pressure is negative, so that air is sent from the atmosphere chamber 16 into the purge passage 18 through the activated carbon 14. When the air passes through the activated carbon 14, the fuel vapor adsorbed by the activated carbon 14 is separated from the activated carbon 14. Thus, the air containing the fuel vapor, that is, vapor, is introduced into the surge tank 6 through the purge passage 18, and the fuel injection valve 6
It is used as fuel in the cylinder 20 together with fuel injected from zero.

Engine electronic control unit (engine EC
U) 70 is a microcomputer system that executes fuel injection control, ignition timing control, idle speed control, etc., and its hardware configuration is shown in the block diagram of FIG. According to the programs and various maps stored in the ROM 73, the central processing unit (CPU) 71
A / D conversion circuit 7 for signals from various sensors and switches
5 or via the input interface circuit 76, performs arithmetic processing based on the input signal, and outputs various actuator control signals via the output interface circuit 77 based on the arithmetic result. The RAM 74 is used as a temporary data storage location in the calculation / control processing process. Further, each constituent element in these ECUs is connected by a system bus (including an address bus, a data bus and a control bus) 72.

The engine control processing of the ECU 70 executed in the internal combustion engine (engine) having the above hardware structure will be described. Ignition timing control is
Based on the engine speed obtained from the crank angle sensor 51 and signals from other sensors, the state of the engine is comprehensively determined, the optimum ignition timing is determined, and the ignition signal is sent to the igniter 62 via the output interface circuit 77. It is something to send. In addition, the idle rotation speed control detects an idle state by a throttle fully closed signal from the idle switch 52 and a vehicle speed signal from the vehicle speed sensor 53, and a target rotation speed determined by the engine cooling water temperature from the water temperature sensor 44 and the like. By comparing the actual engine speed with the actual engine speed, determining the control amount so that the target speed is reached according to the difference, and controlling the ISCV 66 via the output interface circuit 77 to adjust the air amount, It keeps the idle speed.

The fuel injection control is basically based on the intake air amount per engine revolution calculated from the intake air flow rate measured by the air flow meter 40 and the engine rotation speed obtained from the crank angle sensor 51. , The fuel injection amount that achieves a predetermined air-fuel ratio, that is, the fuel injection valve 6
The output interface circuit 77 calculates the injection time by 0, and injects the fuel when the predetermined crank angle is reached.
The fuel injection valve 60 is controlled via the. In addition,
The intake air amount per one revolution of the engine may be estimated from the intake pipe pressure obtained from the vacuum sensor 41 and the engine rotation speed. When the fuel injection amount is calculated, the throttle opening sensor 42 and the intake air temperature sensor 4
3. Basic correction based on signals from respective sensors such as the water temperature sensor 44, air-fuel ratio feedback correction based on signals from the O ₂ sensor 45, air with which the median of the feedback correction values becomes the theoretical air-fuel ratio Fuel ratio learning correction, correction based on evaporative purge (canister purge), and the like are added.

The air-fuel ratio control according to the present invention will be described in detail below. The air-fuel ratio control is achieved by the fuel injection control and the evaporative purge control, but as described above, the present invention provides a novel air-fuel ratio control system particularly at the time of starting. That is, the present invention considers the presence or absence of bubbles at the time of high temperature restart, and gradually increases the evaporation purge amount at the time of high temperature restart in accordance with the start time, thereby achieving optimum air-fuel ratio control at the time of high temperature restart. This is achieved by a simple means to improve the high temperature restartability.

The processing procedure of the first embodiment for embodying such a start-up evaporative purge control is shown in the flow chart of FIG. It should be noted that this routine is configured to be activated at a predetermined cycle. First, the A / D conversion circuit 7
By inputting the output signal from the water temperature sensor 44 via 5, the water temperature THW is taken into the RAM 74 (step 102). Next, similarly, the intake air temperature THA is taken in based on the output signal from the intake air temperature sensor 43 (step 104). Then, in the next step 106, it is determined whether or not the taken-in water temperature THW is higher than a predetermined value (here, 100 ° C). When THW> 100 ° C, the process proceeds to step 108, where THW ≦ 100 ° C. At times, the processing of this routine ends. In step 108, it is determined whether or not the intake air temperature THA is higher than a predetermined value (here, 60 ° C.), and if THA> 60 ° C., step 11
The routine proceeds to 0, and when THA ≦ 60 ° C., the processing of this routine is ended.

As described above, in step 110 executed when it is determined that the temperature is high, it is determined whether or not the engine is currently being started. This start determination is, for example, when the starter is on (determined based on the signal from the starter switch 54) or when the engine rotation speed is equal to or lower than a predetermined value (400 rpm, for example). It is a judgment. When it is determined that the engine is being started, the routine proceeds to step 112, and when it is determined that the engine is not being started, that is, when the startup is completed, the processing of this routine is ended.

In step 112, which is first executed when it is determined that the engine is restarting at a high temperature as described above, the current starting time (time elapsed since the start of cranking by the starter) T is fetched. In addition, in order to measure such a starting time T, a predetermined counter is provided in the RAM 74.
Is provided in a predetermined area of and is updated at a predetermined cycle.
In the next step 114, the evaporative purge amount E1 is obtained by referring to the map as shown in FIG. 4 based on the starting time T, and the evaporative purge is executed. Note that such a map for determining the evaporation purge amount E1 according to the starting time T is set so that the fuel vapor is gradually increased to a specified amount according to the engine operating state, and is previously stored in the ROM 73. It is stored in. Further, the execution of the evaporation purge is performed by determining the duty ratio (ratio of ON time of the pulse signal) of the pulse signal for controlling the opening degree of the purge control valve 68 based on the evaporation purge amount E1, and the drive control signal of the purge control valve 68. Done by creating.

By executing the control of the first embodiment in a predetermined cycle, the fuel vapor is supplied to the intake system while the fuel vapor is gradually increased to a prescribed amount according to the engine operating state at the time of high temperature restart. . Therefore, while restarting at high temperature,
When air bubbles are not generated in the injector and the normal fuel injection amount is supplied, the fuel rich is prevented because the fuel vapor is initially supplied in a small amount. When air bubbles are generated in the injector and the fuel injection amount is insufficient, the fuel lean is prevented by gradually increasing the fuel vapor to a specified amount according to the engine operating state. . In this way, the air-fuel ratio at high temperature restart is optimally controlled by simple means. If purging is executed by normal on / off control, it is necessary to limit it to the area where it can be determined that bubbles are definitely generated, and control in the gray area (uncertain area) cannot be executed. Becomes

Next, the second embodiment will be described. In the second embodiment, the delay (delay) time according to the engine operating state is provided at the start time of the above-described evaporative purge at the time of starting, so that the necessity of the evaporative purge at the time of high temperature restart is determined more accurately. It is a thing. The specific processing procedure is shown in the flowchart of FIG. In the first steps 202 to 210, steps 102 to 210 in FIG.
Similar to 110, it is determined whether or not it is a high temperature restart.

At the time of high temperature restart, first, at step 212, the start purge start delay time Kw corresponding to the water temperature THW is obtained by referring to the map shown in FIG. Note that in such a map showing the relationship between THW and Kw, considering that the higher the THW is, the more likely it is that the engine becomes leaner in restart, FIG.
As shown in, the higher the THW, the smaller the delay time is set.

In the next step 214, the coefficient Ka for correcting the starting purge start delay time Kw determined according to the water temperature THW according to the intake air temperature THA is referred to the map shown in FIG. Ask by. In such a map showing the relationship between the intake air temperature THA and the correction coefficient Ka, in consideration of the fact that the higher the temperature of THA, the more likely it is to become leaner to restart, as shown in FIG. The smaller the correction coefficient, the smaller the correction coefficient.

Then, in step 216, the arithmetic expression K ←
The final start-up purge start delay time K is obtained from Kw * Ka. Next, the starting time T is fetched (step 218), and the starting time T is compared with the starting purge start delay time K (step 220). When T ≦ K, this routine is ended. However, when T> K, that is, when the start purge start delay time K has elapsed after the start of the start, the routine proceeds to step 222, similarly to step 114 of FIG. , The evaporation purge amount E1 corresponding to the starting time T is obtained with reference to the map shown in FIG. 8, and the evaporation purge is executed. Instead of the map of T and E1 as shown in FIG. 8, a map showing the relationship between (TK) and E1 as shown in FIG. 9 may be used to obtain the evaporation purge amount.

As described above, according to the second embodiment, it is determined that the start has not been completed and the bubbles are surely generated at the time when a predetermined period corresponding to the engine operating state has passed from the start. The start of the supply of the fuel vapor is delayed until the time when it is possible to perform the fuel correction by the supply of the fuel vapor more accurately.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, of course.
It will be easy for those skilled in the art to devise various embodiments.

[0033]

As described above, according to the present invention,
By performing the optimum evaporative purge in consideration of the presence or absence of bubbles at the time of high temperature restart, the air-fuel ratio control device is provided in which the accuracy of the air-fuel ratio control at the time of high temperature restart is improved. Therefore, there is an effect that the high temperature restartability of the internal combustion engine is improved and the drivability is further improved.

That is, in the air-fuel ratio control device according to the first aspect of the present invention, at the time of high temperature restart, the fuel vapor is supplied to the intake system while being gradually increased to the specified amount according to the operating state of the engine. Therefore, even when restarting at high temperature, no bubbles are generated in the injector, and when the normal fuel injection amount is supplied, a small amount of fuel vapor is initially supplied to prevent fuel richness. To be done. Also,
When air bubbles are generated in the injector and the fuel injection amount is insufficient, the fuel lean is prevented by gradually increasing the fuel vapor to a prescribed amount according to the engine operating state. Thus, there is an effect that the air-fuel ratio at the time of high temperature restart is optimally controlled by a simple means.

Further, in the air-fuel ratio control device according to the second aspect of the present invention, the start is not completed at the time when a predetermined period corresponding to the engine operating state has elapsed since the start, and bubbles are surely generated. The start of fuel vapor supply is delayed until it can be determined that As described above, there is an effect that the fuel correction by the supply of the fuel vapor is more accurately performed and the controllability of the air-fuel ratio is further improved.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an electronically controlled internal combustion engine equipped with an air-fuel ratio control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a hardware configuration of an engine ECU according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a processing procedure of a startup evaporative purge control routine according to the first embodiment.

FIG. 4 is a diagram showing a map for determining an evaporation purge amount E1 according to a starting time T.

FIG. 5 is a flowchart showing a processing procedure of a startup evaporative purge control routine according to the second embodiment.

FIG. 6 is a diagram showing a map in which a startup purge start delay time Kw is set according to a water temperature THW.

FIG. 7 is a diagram showing a map in which a startup purge start delay time correction coefficient Ka according to the intake air temperature THA is determined.

FIG. 8 is a diagram showing a map for determining an evaporation purge amount E1 according to a starting time T.

FIG. 9 is a diagram showing a map for determining an evaporation purge amount E1 according to time (TK).

[Explanation of symbols]

2 ... Air cleaner 4 ... Throttle body 5 ... Throttle valve 6 ... Surge tank (intake manifold) 7 ... Intake pipe 8 ... Idle adjust passage 10 ... Fuel tank 11 ... Fuel pump 12 ... Fuel piping 13 ... Canister 14 ... Activated carbon 15 ... Fuel vapor Chamber 16 ... Atmosphere chamber 17 ... Vapor collection pipe 18 ... Purge passage 20 ... Engine body (cylinder) 22 ... Cooling water passage 24 ... Intake valve 26 ... Exhaust valve 30 ... Exhaust manifold 34 ... Exhaust pipe 38 ... Catalytic converter 40 ... Air flow meter 41 ... vacuum sensor 42 ... throttle opening sensor 43 ... intake air temperature sensor 44 ... water temperature sensor 45 ... O ₂ sensor 50 ... reference position sensor 51 ... crank angle sensor 52 ... idle switch 53 ... vehicle speed sensor 54 ... starter switch 60 ... Fuel injection valve 62 ... Igniter 63 Ignition coil 64 Ignition distributor 65 Spark plug 66 Idle speed control valve (ISC
V) 68 ... Purge control valve 70 ... Engine ECU 71 ... CPU 72 ... System bus 73 ... ROM 74 ... RAM 75 ... A / D conversion circuit 76 ... Input interface circuit 77 ... Output interface circuit

Claims (2)

[Claims] 1. A canister for adsorbing fuel vapor,
During normal operation, in an air-fuel ratio control device for an internal combustion engine configured to supply the fuel vapor adsorbed by the canister to the intake system according to the engine operating state, a high temperature re-detection that detects a high temperature restart is performed. When the high temperature restart detecting means and the high temperature restart detecting means detect the high temperature restart, the fuel vapor adsorbed in the canister is gradually increased to a specified amount according to the engine operating state. An air-fuel ratio control device, comprising: a fuel vapor supply means for supplying the intake system. 2. A supply delay means for delaying a supply start timing of the fuel vapor by the fuel vapor supply means from a start time by a predetermined period according to an engine operating state, further comprising: The air-fuel ratio control device described in.