JP2001329919A - Evaporated fuel processing device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively process evaporated fuel adsorbed to an adsorbing means even during an idle operation under lean combustion. SOLUTION: When the evaporated fuel is purged under a designated condition during an idle operation under lean combustion, a purge concentration is detected based on the quantity of the control change of intake air quantity by an idle rotational speed control means, and the target opening of a purge control valve is set based on the purge concentration. Thereby, maximum possible evaporated fuel is processed while suppressing influence on the combustion of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing apparatus for an internal combustion engine, and more particularly, to an evaporative fuel processing at idle operation during lean combustion.

[0002]

2. Description of the Related Art Conventionally, an internal combustion engine has an evaporative fuel processing device, in which evaporative fuel generated in a fuel tank is temporarily adsorbed by a canister (adsorbing means), and the adsorbed evaporative fuel is removed. Is purged under predetermined engine operating conditions, and a purged air-fuel mixture mixed with the purge air is sucked into the intake system of the engine while controlling the flow rate (purge amount) by the purge control valve, thereby evaporating the fuel. Is prevented from dispersing into the atmosphere (see Japanese Patent Application Laid-Open No. 5-215020).

[0003] In an internal combustion engine equipped with such an evaporative fuel processing device, when purging during the feedback control to the stoichiometric air-fuel ratio, the stoichiometric air-fuel ratio is maintained while correcting the fuel injection amount according to the purge concentration. be able to. In some cases, the purge concentration is grasped while monitoring the feedback correction amount at this time, and the purge amount is adjusted.

On the other hand, when the air-fuel ratio is controlled by feed forward, the fuel injection amount cannot be corrected in accordance with the purge concentration, so that the purge amount must be fixed and the purge rate fixed.

Particularly, in the case of lean combustion (stratified combustion, etc.) during idling operation, the output fluctuation caused by the purge is large, so that even if the purge concentration is the highest, the rotation is increased so that the influence of flammability is not minimized. It was necessary to limit the amount of purge to a minimum or abandon the purge.

[0006]

However, even during lean combustion, sufficient purging cannot be ensured unless the purging is performed efficiently during a frequent idling operation, causing overflow from the canister. The fuel vapor evaporates into the atmosphere, and the fuel is lost. On the other hand, it is conceivable to cope with the problem by increasing the capacity of the canister, but there is a problem in that the layout is limited and the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and purifies as much evaporated fuel as possible during idle operation during lean combustion without increasing the canister capacity. It is an object of the present invention to provide an evaporative fuel processing apparatus for an internal combustion engine that can reliably adsorb fuel vapor from a fuel tank to a canister and process the fuel in the engine.

[0008]

Therefore, according to the first aspect of the present invention, as shown in FIG. 1, feedback control is performed such that the engine rotation speed is set to a target rotation speed by controlling the intake air amount during idling operation. Evaporated fuel from the fuel tank B of the internal combustion engine provided with the idle rotation speed control means A is temporarily adsorbed to the adsorption means D via the vapor passage C, and purge control is performed from the adsorption means under predetermined engine operating conditions. An evaporative fuel processing apparatus for an internal combustion engine, which is supplied to an intake system G of the engine via a purge passage E in which a valve F is interposed and burns, includes the following components.

The purge concentration detecting means H detects the purge concentration based on the control change amount of the intake air amount by the idle speed control means. The target opening setting means I sets the opening of the purge control valve based on the purge concentration detected by the purge concentration detecting means.

According to a second aspect of the present invention, the idle rotation speed control means controls an opening of an air auxiliary valve provided in an auxiliary air passage which bypasses a throttle valve of the internal combustion engine, thereby controlling an intake air amount. Is controlled.

The invention according to claim 3 is characterized in that the idle speed control means controls the intake air amount by controlling the opening of an electronically controlled throttle valve of the internal combustion engine.

The invention according to a fourth aspect is characterized in that the purge concentration detecting means detects and updates the purge concentration at a predetermined cycle.

The invention according to claim 5 is characterized in that the target opening setting means sets the target opening to be smaller as the purge concentration is higher and to be larger as the purge concentration is lower.

[0014]

According to the first aspect of the present invention, even during the idle operation during the lean combustion, the idling speed control means (ISC) when the fuel vapor is purged under predetermined conditions.
Control), the purge concentration is detected on the basis of the control change amount of the intake air amount, and the valve opening of the purge control is set based on the purge concentration. It is possible to process as much as possible while suppressing the influence, and the fuel efficiency is also improved.

According to the second aspect of the present invention, the idle speed control means controls the opening degree of the auxiliary air valve provided in the auxiliary air passage bypassing the throttle valve, thereby controlling the intake air amount. The above I
By detecting the purge concentration based on the control amount change amount of the auxiliary air valve opening degree by the SC control, the purge concentration can be easily detected even during the idle operation during the lean combustion by using the existing control and the like. it can.

According to the third aspect of the present invention, the idle speed control means controls the intake air amount by controlling the opening of an electrically controlled throttle valve. By detecting the purge concentration by detecting the amount of change in the valve opening with a throttle sensor, the existing control and the like can be used to easily detect the purge concentration even during the idle operation during lean combustion.

According to the fourth aspect of the present invention, the purge concentration is detected and updated at predetermined intervals, so that the fuel vapor can be efficiently processed according to the situation.

According to the fifth aspect of the present invention, the target opening is set to be smaller as the purge concentration is higher, and the target opening is set to be larger as the purge concentration is lower. The fuel vapor can be purged without increasing the speed or deteriorating the combustion.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a system configuration according to an embodiment of the present invention.
Is provided with an air flow meter 3 for detecting an intake air flow rate Q, and the intake air amount Q is controlled by a throttle valve 4. The throttle valve 4 is provided with a throttle sensor 5 for detecting the opening TVO by a potentiometer.
An idle switch that is N is built in.

An auxiliary air valve 7 is interposed in an auxiliary air passage 6 provided by-passing the throttle valve 4, and assists the engine speed at the target speed during idling when the idle switch is turned on. Feedback control (ISC control) is performed so as to adjust the intake air amount by increasing or decreasing the opening of the air valve 7.

A cylinder portion of the engine 1 is provided with a fuel injection valve 9 for injecting fuel into the combustion chamber 8 and a spark plug 10 for performing spark ignition in the combustion chamber 8. The exhaust passage 11 of the engine 1 is provided with an air-fuel ratio sensor 12 that detects the air-fuel ratio of the air-fuel mixture based on the oxygen concentration in the exhaust gas. In addition, a crank angle detection sensor 13 for detecting an engine crank angle position and an engine rotation speed Ne, a water temperature sensor (not shown) for detecting an engine cooling water temperature, and the like are provided.

Further, a vapor passage 15 for guiding the fuel evaporated from the fuel tank 14, a canister 16 for temporarily adsorbing the evaporated fuel introduced via the vapor passage 15, and the canister 16 from the intake passage 2 upstream of the throttle valve 4 to the canister 16. A purge air introduction passage 17 for introducing air for purging evaporated fuel, a purge passage 18 for leading purged evaporated fuel to the intake passage 2 downstream of the throttle valve 4, and a purge control valve 19 for controlling a purge amount of the evaporated fuel are provided. Configure the fuel processing system.

Signals from various sensors for detecting the engine operating state are input to a control unit (ECU) 20. The control unit 20 responds to these signals by the auxiliary air valve 7, fuel injection valve 9, Spark plug 1
0, a drive signal is output to actuators such as the purge control valve 19 to perform various controls of the engine.

In this configuration, the evaporative fuel processing by the control unit 20 during the idling operation during lean combustion according to the present invention will be described with reference to the flowchart of FIG.

In step 1 (referred to as S1 in the figure, the same applies hereinafter), it is determined whether or not the engine is idling. If the idle switch is ON, it is determined that the vehicle is idling, and the process proceeds to step S2. If the idling operation is not being performed, the routine proceeds to step 21, where a purge process is performed in normal air-fuel ratio feedback control.

In step 2, it is determined whether lean combustion is being performed. If lean combustion is being performed, the process proceeds to step 3, and if combustion is performed at the stoichiometric air-fuel ratio, the process proceeds to step 21.
In step 3, it is determined whether or not purging is being performed. If the purging is being performed, the process proceeds to step 11, and if the purging is not being performed, that is, if the purging is to be started, the process proceeds to step 4.

In step 4, the fuel vapor is purged under predetermined conditions to detect the purge concentration. This purge increases the amount of fuel supplied to the engine and increases the engine rotational speed. Therefore, the intake air amount is reduced by the ISC control so as to reach the target rotational speed. Here, in the ISC control, as shown in FIG. 4, the intake air amount is controlled by correcting the opening control value of the auxiliary air valve.

In FIG. 4, in step 41, an idle switch ON signal is read. In step 42, the engine rotation speed N is calculated based on the signal from the crank angle sensor 13, and is compared with the target rotation speed N0. When the engine rotation speed N is lower than the target rotation speed N0, the routine proceeds to step 43, where a predetermined amount △ ISC is added to the feedback correction amount ISCf of the opening control value ISC of the auxiliary air valve, and IS
Cf + △ ISC, and when the engine speed N is higher than the target speed N0, the routine proceeds to step 44, where the IS
△ ISC is subtracted from Cf to obtain ISCf- △ ISC as the target rotation speed. This ΔISC or −ΔISC is the control change amount of the auxiliary air valve opening.

Returning to FIG. 3, in step 5, the control change amount of the auxiliary air valve opening degree by the ISC control is read. This corresponds to the control change amount of the intake air amount. Actually, if the vaporized fuel is adsorbed in the canister, the vaporized fuel is supplied to the engine by the purge, and the engine rotational speed is increased. Therefore, the control value correction amount may be considered as -ΔISC.

In step 6, the purge concentration is detected from a preset map or the like based on the control change amount (−ΔISC) of the opening degree of the auxiliary air valve in the ISC control. Steps 4 to 6 correspond to the purge concentration detecting means.

In step 7, the target opening of the purge control valve is set from a preset map based on the detected purge concentration. When the detected purge concentration is high, the target opening is set low so as not to affect the engine combustion, etc., and when the purge concentration is low, the target opening is set high, and output is made according to the situation. It is set to purge as much evaporated fuel as possible.

Subsequently, when this routine is restarted, steps 1 and 2 are the same as described above, but in step 3, since the fuel vapor has been purged under the predetermined conditions in step 4, the purging is in progress. Proceed to step 11.

In step 11, it is determined whether the purge control valve set in step 7 is purging at the target opening. When the purge is not performed at the target opening, the process proceeds to step 12, and the predetermined value purge control valve opening is increased within the target opening so as to approach the target opening. The predetermined value may be simply fixed, but is preferably set smaller as the purge concentration is higher, and set higher as the purge concentration is lower, in order to prevent the mixture ratio from rapidly becoming rich.

The above steps 1, 2, 3, 11, 12
Are repeated until the purge control valve opening reaches the target opening. When the purge control valve reaches the target opening, the process proceeds from step 11 to step 4, where the purge concentration is detected again as described above, and the target opening of the purge control valve is updated, so that the evaporated fuel can be efficiently discharged. To process.

As described above, even during the idling operation during lean combustion, the purge concentration is detected based on the control change amount of the intake air amount by the ISC control, and the target opening of the purge control valve is set based on the purge concentration. To purge
It is possible to treat as much evaporated fuel as possible depending on the situation without affecting the combustion of the engine.

In this embodiment, by controlling the opening degree of the auxiliary air valve 7 interposed in the auxiliary air passage 6 provided to bypass the throttle valve 4, the idle time I
Although the internal combustion engine which performs the SC control is shown, in the internal combustion engine having the electronic control throttle valve, the one which performs the ISC control by directly controlling the (electronic control) throttle valve may be used.
In that case, the same effect can be obtained by configuring the detection of the purge concentration in the step 15 based on the change amount of the throttle valve opening (electronic control) detected by the throttle sensor 5.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a system configuration diagram according to an embodiment of the present invention.

FIG. 3 is a flowchart showing control according to an embodiment of the present invention.

FIG. 4 is a flowchart showing idle rotation speed control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake passage 6 ... Auxiliary air passage 7 ... Auxiliary air valve 14 ... Fuel tank 18 ... Purge passage 19 ... Purge control valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F02D 41/14 310 F02D 41/14 310C 41/16 41/16 P 43/00 301 43/00 301E 301K 301L 301M F-term (reference) 3G044 AA05 BA20 BA40 CA06 CA11 DA02 DA09 EA03 EA19 EA23 EA27 EA50 FA28 FA29 GA02 3G065 AA00 CA23 DA04 EA03 FA11 FA13 GA05 GA43 KA36 3G084 AA04 BA05 BA06 BA24 CA03 DA13 FA30 FA33 FA30 FA33 LA04 NA08 NC02 ND01 ND21 PA11A PA11Z PA14Z PE01A PE01Z PE03Z PE08Z

Claims (5)

[Claims] 1. An evaporative fuel from a fuel tank of an internal combustion engine provided with idle speed control means for performing feedback control so that an engine speed becomes a target speed by controlling an intake air amount during idle operation. The internal combustion engine is adapted to temporarily adsorb to the adsorbing means through the purge means and supply the fuel to the intake system of the engine through a purge passage provided with a purge control valve from the adsorbing means under predetermined engine operating conditions to burn the engine. A purge concentration detecting means for detecting a purge concentration based on a control change amount of an intake air amount by the idle rotation control means when the evaporative fuel is purged under predetermined conditions during an idle operation during lean combustion; A target opening setting means for setting a target opening of the purge control valve based on the purge concentration detected by the purge concentration detecting means; If, fuel vapor treatment system for an internal combustion engine, characterized in that it is configured to include. 2. The method according to claim 1, wherein the idle speed control means controls an intake air amount by controlling an opening of an auxiliary air valve interposed in an auxiliary air passage that bypasses a throttle valve of the internal combustion engine. The fuel vapor treatment device for an internal combustion engine according to claim 1. 3. An evaporative fuel for an internal combustion engine according to claim 1, wherein said idle speed control means controls an intake air amount by controlling an opening degree of an electronic control slot valve of the internal combustion engine. Processing equipment. 4. The apparatus according to claim 1, wherein said purge concentration detecting means detects and updates the purge concentration at a predetermined cycle.
The fuel vapor treatment device according to any one of claims 1 to 3. 5. The apparatus according to claim 1, wherein the target opening degree setting means sets the target opening degree to be smaller as the purge concentration is higher, and to be larger as the purge concentration is lower. 5. The evaporative fuel processing apparatus for an internal combustion engine according to any one of 4.