Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Patent
1995-06-15
1997-06-03
Miller, Carl S.
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
123516, F02M 3704
Patent
active
056344511
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus and method for treating fuel vapor of an engine. In particular, the invention relates to technology for supplying fuel vapor produced inside a fuel tank, to the engine intake system to thereby prevent diffusion into the atmosphere.
BACKGROUND ART
Apparatus for treating fuel vapor to prevent fuel vapor inside a fuel tank from diffusing into the atmosphere (referring to Japanese Unexamined Patent Publication No. 62-7962), have involved temporarily absorbing the fuel vapor produced inside the fuel tank into a canister, and then purging the absorbed fuel vapor and supplying the purge air through a purge passage to the engine intake system.
With such an apparatus the purge air from a canister is supplied to the engine intake system, with the normal supply mixture. As a fixed quantity of purge air is supplied irrespective of the engine operating conditions, there is the likelihood of a large discrepancy in the air-fuel ratio.
To compensate, the quantity of purge air is changed in accordance with engine operating conditions such as engine load. To achieve this, the purge air quantity is adjusted by duty controlling the ON/OFF switching of a purge control solenoid valve that drives a valve for opening and closing the purge passage, according to a duty ratio corresponding to the purge flow quantity required for the operating conditions.
However, with the duty control of the purge control solenoid valve, when the frequency of the duty control is low, purge air pulsations occur with the opening/closing of the purge passage. As a result, variations occur in the purge air quantity drawn into the respective cylinders causing variations in the air-fuel ratio between the cylinders.
So that the purge air is drawn in uniformly into the respective cylinders, the frequency of the duty control should be as high as possible. However, if a high frequency is used, then the power supply time becomes shorter so that the flow quantity region, where there is a drop in control accuracy due to the valve opening delay time, is enlarged compared to when a low frequency is used. As a result, high accuracy flow quantity adjustment cannot be made in the low flow quantity region.
More specifically, while the solenoid valve has a constant valve opening delay time, when duty control is carried out at a high frequency, the power supply time (valve opening time) is shortened compared to that for control at a low frequency, so that the proportion of the power supply time control region occupied by the valve opening delay time is increased. Therefore, when adjusting a low flow quantity at a high frequency, the power supply time within the valve opening delay time during which the air quantity is unstable is given, making it difficult to adjust a low flow quantity to a high accuracy.
Moreover, with a construction wherein a high frequency that can reliably avoid purge air pulsations is used indiscriminately, since the ON/OFF switching per unit time is increased significantly, then there is the likelihood of deterioration in the life of the valve seat components.
DISCLOSURE OF THE INVENTION
In view of the above situation, it is an object of the present invention, with a construction wherein the purge air quantity is adjusted by a duty control, to suppress variations in purge air intake quantity between cylinders, so as to avoid a deterioration in flow quantity control accuracy, and a deterioration in the life of components.
Accordingly, with the apparatus and method according to the present invention for treating the fuel vapor of an engine incorporating a canister for absorbing the fuel vapor in a fuel tank, purging the absorbed fuel vapor, and supplying the purge air to the engine intake system by way of a purge passage. The purge air quantity supplied to the engine intake system is set based on engine operating conditions, while the control frequency at the time of duty controlling the opening/closing of the purge passage is set in accordance with the set purge air quantity. The
REFERENCES:
patent: 4641623 (1987-02-01), Hamburg
patent: 4677956 (1987-07-01), Hamburg
patent: 5048492 (1991-09-01), Davenport
patent: 5150686 (1992-09-01), Okawa
patent: 5216997 (1993-06-01), Osanai
patent: 5263460 (1993-11-01), Baxter
patent: 5329909 (1994-07-01), Hosoda
patent: 5363832 (1994-11-01), Sozumura
patent: 5368002 (1994-11-01), Hoshino
patent: 5465703 (1995-11-01), Abe
patent: 5474049 (1995-12-01), Nagaishi
Miller Carl S.
Unisia Jecs Corporation
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