Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2001-02-02
2002-05-28
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S274000, C060S277000, C060S290000, C060S293000
Reexamination Certificate
active
06393833
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality determination apparatus and method for a secondary air supply system, and more specifically, to an abnormality determination apparatus for a secondary air supply system using an air injection method.
It is known that CO, HC and NOx, which are toxic gas components in the exhaust gas discharged from vehicle internal-combustion engines, are converted by the use of a catalytic converter. By the use of a catalytic converter, CO and HC are oxidized, and NOx is reduced to clean the exhaust gas. The components are converted to CO
2
, H
2
O and N
2
, respectively.
However, in this catalytic converter, the cleanliness of the exhaust gas is reduced during low-temperature operation of the engine. Thus, to increase the temperature of the exhaust gases supplied to the catalytic converter during low temperature operation, a secondary air supply system, which supplies air (secondary air) to the exhaust system, has been employed. That is, the air supplied to the exhaust system increases the temperature of the exhaust gases supplied to the catalytic converter by a reaction with CO and HC in the exhaust gases, and this improves the cleaning rate of the catalyst.
The secondary air supply systems mainly include an air suction type system, which supplies air by the use of pressure pulse of the exhaust system, and an injection type, which supplies air by the use of an air pump.
In the air suction system, an exhaust pressure pulse is employed, and when a sufficient pulse does not occur in the exhaust system, the necessary amount of secondary air may not be supplied. Therefore, the air injection system, which can pump a precise and sufficient supply of secondary air, is preferred.
On the other hand, an apparatus that can determine the presence or absence of a malfunction in the above-mentioned secondary air supply system has been proposed. For example, the apparatus described in Japanese Patent No. 2570287 determines that when an air-fuel ratio sensor provided upstream in a catalytic converter produces lean signals over a predetermined period of time after the secondary air has been supplied, the secondary air supply system is in an abnormal condition.
By the above-described abnormality determination apparatus, the presence or absence of an abnormality in the secondary air supply system can be positively determined. However, in the air injection system, the following disadvantages cannot be avoided.
Since the air injection type secondary air supply system usually includes an air pump, which supplies air, and a valve, which connects an exhaust system to a secondary air supply passage when air is supplied by the air pump, if the system is determined to be as abnormal, it is impossible to judge whether the abnormality is due to the air pump or the valve.
Incidentally, in the air-injection type secondary air supply system, an abnormality such as the air pump failing to stop is particularly serious. The reason is that, when the air pump continues operating in spite of an instruction to stop the air pump, the temperature of the air pump will become too high and the vehicle battery, which is the power supply for the pump, will be drained unnecessarily, or excessive current will flow in a relay between the pump and the battery.
Thus, an abnormality determination apparatus for an air-injection type secondary air supply system must be capable of precisely detecting a failure of the air pump to stop. However, no such apparatus exists. It is considered that methods for detecting abnormalities of the operation of the pump include measuring the current flowing in the air pump or placing a flowmeter downstream of the air pump. However, such methods require new parts and, in view of the cost and weight considerations, such methods have not been employed.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide an abnormality detections apparatus and method for a secondary air supply system that are capable of detecting operational abnormalities of the air pump in an air-injection type secondary air supply system with a simple structure.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a secondary air supply apparatus for a vehicle is provided. The apparatus includes an air pump for pumping secondary air through an air supply passage to an exhaust passage of the vehicle, a valve for opening and closing the air supply passage, an air-fuel ratio sensor and an electronic control unit. The air-fuel ratio sensor senses characteristics of gas in the exhaust passage. Information sensed by the sensor is used to determine the air-fuel ratio of a mixture being burned by an engine that powers the vehicle. The electronic control unit controls the pump and the valve. The electronic control unit is constructed and arranged to judge whether the pump has failed to stop by instructing the pump to stop, instructing the valve to open, and determining whether the air-fuel mixture has been relatively lean based on information from the air-fuel ratio sensor.
The present invention may be applied to a method for determining abnormality in a secondary air supply apparatus for a vehicle. The method includes sending an instruction to a secondary air supply pump for pumping secondary air into an exhaust passage of an engine powering the vehicle, sending an instruction to a valve for regulating a flow of secondary air from the pump, monitoring the air-fuel ratio of a mixture being burned by the engine, and judging whether the pump has failed to stop by instructing the pump to stop, instructing the valve to open, and determining whether the air-fuel mixture has been relatively lean.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
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patent: 5542292 (1996-08-01), Schneider et al.
patent: 5615552 (1997-04-01), Shimasaki et al.
patent: 5706653 (1998-01-01), Shoji et al.
patent: 5735121 (1998-04-01), Kato et al.
patent: 5782086 (1998-07-01), Kato et al.
patent: 6185931 (2001-02-01), Shimasaki et al.
patent: 63-111256 (1988-05-01), None
patent: 63-143362 (1988-06-01), None
patent: 63-248908 (1988-10-01), None
patent: 8-246851 (1996-09-01), None
patent: 9-21313 (1997-01-01), None
Denion Thomas
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
Tran Binh
LandOfFree
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