Measuring and testing – Instrument proving or calibrating – Gas or liquid analyzer
Reexamination Certificate
2000-01-11
2003-05-27
Raevis, Robert (Department: 2856)
Measuring and testing
Instrument proving or calibrating
Gas or liquid analyzer
Reexamination Certificate
active
06568240
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for controlling an air fuel ratio by using a gas concentration sensor in a fuel supply system for an internal combustion engine, particularly to a method and apparatus for measuring a gas concentration of a combustible gas such as a gasoline vapor gas purged from a canister and mixed with an intake air that is supplied to an intake manifold of an internal combustion engine cylinder by opening a throttle valve, the sensor being placed between the engine cylinder and an inlet for the vapor gas that is purged from the canister and introduced downstream of the throttle valve.
2. Related Art
Conventionally, a fuel supply system for supplying fuel from a fuel tank to the internal combustion engine includes a first supply system which functions in a manner that a fuel liquid such as gasoline is pumped from the fuel tank through a fuel pipe to a fuel injector fixed to an internal combustion engine cylinder by means of a fuel pump.
The fuel supply system further includes a second supply system which functions in a manner that a fuel vapor generated in the fuel tank is temporarily adsorbed or stored by a canister and then the fuel vapor is purged by the canister and sent as a purge gas to the intake manifold so as to be mixed with an intake air entering from the throttle valve.
In other words, in addition to the fuel liquid injected from the injector to the engine cylinder, the fuel vapor vaporized from the fuel tank is purged and mixed with the intake air to form a mixture gas that injects the fuel liquid to be atomized in the engine cylinder. Such fuel vapor vaporized in the fuel tank may be hereinafter referred to as ‘purge gas’.
3. Problems to be Solved by the Invention
As a result of supply to the engine of the purge gas in addition to the injected fuel, an air-fuel ratio maintained or determined by a throttle valve, which ratio is controlled based on an injection amount of the fuel is affected or rather deviated from a target value such as a theoretical one, lowering a purification capability of a three-way catalytic exhaust gas purification system for reducing harmful gasses such as CO, HC and NOx.
Further, when the purge gas is used as a main portion of fuel for combustion at the time of starting up the engine and/or when a three-way catalytic converter of the exhaust gas purification system is in an inactive state due to a cold weather, a misfire or incomplete combustion occurs, unless the purge gas concentration is measured with high accuracy and the supply amount of the purge gas is controlled optimally.
Various sensors using surface-characteristics such as an ultrasonic sensor and an oxide semiconductor sensor having electrodes on its surface have been proposed for measuring concentration of such a purge gas contained in the mixture gas before the mixture gas atomizes the liquid fuel by the fuel injector. However, a satisfactory sensor for accurate measurement of the purge gas amount or concentration have not been developed yet, because in addition to variation in output of such a sensor over time, output errors due to adhesion of foreign substances to a surface of the ultrasonic sensor and/or due to moisture and miscellaneous gases contained in the air taken in have always hindered accurate measurement of the purge gas concentration.
Therefore, it has been difficult that a precise or accurate measurement of the purge gas concentration of the gas mixture made of the purge gas and the intake air flowing in the intake manifold or an intake pipe before the liquid fuel is atomized with the gas mixture by fuel injector or before being injected into the engine cylinder.
SUMMARY OF THE INVENTION
The present invention has been accomplished in order to solve the above-described problems.
An object of the present invention is to provide a method and apparatus using a gas concentration sensor for measuring concentration a fuel vapor (or rather purge gas) mixed in an intake air, by which method and apparatus an accurate measurement of concentration of such a fuel-vaporized purge gas entering an intake manifold of an internal combustion engine is attained.
Another object of the present invention is to provide a fuel supply system using a gas concentration sensor for accurately controlling an air fuel ratio for an internal combustion engine, the sensor being disposed in an intake manifold (or an air-intake pipe) which is located between a throttle valve and a fuel injector of the internal combustion engine.
A feature of a method and apparatus using a gas concentration sensor for accurately measuring the vapor gas according to the invention is that before the fuel-vaporized gas purged from the canister enters into the intake manifold whereat the sensor detects the gas concentration of the purged gas, the sensor is adjusted so as to read a zero point (or zero output level) of the sensor output. In other words, when the purge gas stops its flow from the canister, namely when the intake pipe or manifold evacuates the purge gas so that an ambient air enters the intake pipe or manifold, the sensor output is offset reading a zero output of the sensor for measuring the concentration of the specific fuel vaporized gas purged.
Specifically, the present invention provides a method and apparatus using a gas concentration sensor for measuring concentration of a purge gas (i.e. vapor gas vaporized from a liquid fuel) purged and contained in a mixture gas comprised of the purge gas and an ambient air before the mixture gas atomizes the liquid fuel by a fuel injector: wherein the gas concentration sensor is disposed in an intake manifold of an internal combustion engine or a pipe connected to the intake manifold so as to measure concentration of the purge gas; and wherein the concentration of the purge gas is determined by comparing two output values of the gas concentration sensor, the one output value being measured before the purge gas is supplied into the intake manifold or pipe while the other output value being measured after the purge gas is supplied into the intake manifold or pipe. In one aspect of the invention, a degree of degradation or rather deterioration of the gas concentration sensor is pre-checked when the sensor outputs the concentration of the purge gas for computing the concentration. In other words, a zero-point correction of the gas concentration sensor is renewed every time when the purge gas is evacuated from the intake manifold wherein the sensor is placed.
In the present invention, during that the specific purge gas is not supplied from the canister and therefore the concentration of the purge gas to be mixed with the intake air that enters into the fuel injector for atomization of the liquid fuel is supposed to be zero, the output of the gas concentration sensor is preset or offset to be a zero level output(V
0
) corresponding to a relative gas concentration of 0%.
In actual use, the gas concentration sensor is affected not only by its variation over time but also miscellaneous gases and/or foreign substances including moisture of the air taken in or evaporating from the liquid fuel so that the sensor output often deviates from the preset value (V
0
) even when the purge gas concentration is 0%. When the sensor output shows a deviation from V
0
that corresponds to the specific purge gas concentration of 0%, a certain shift amount (&Dgr;V) namely a subtraction V
0
from the sensor output V
1
(V
1
−V
0
=&Dgr;V) represents either a true value of concentration of the purge gas in the mixture gas or a degraded or deteriorated performance of the sensor due to such variation or influence.
Therefore, the method and apparatus using a gas concentration sensor for measuring the purge gas according to the invention is characterized in that zero-point correction of the sensor output is performed before the sensor output is subjected to computing the purge gas concentration, regardless that the gas concentration sensor has undergone deterioration or deterioration or
Ishida Noboru
Ishikawa Hideki
Oshima Takafumi
Sato Yasushi
Sato Yoshikuni
NGK Spark Plug Co. Ltd.
Raevis Robert
Sughrue & Mion, PLLC
LandOfFree
Method and apparatus using a gas concentration sensor for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus using a gas concentration sensor for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus using a gas concentration sensor for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3054983