Internal-combustion engines – Charge forming device – Supercharger
Reexamination Certificate
1999-08-23
2001-05-08
Denion, Thomas (Department: 3748)
Internal-combustion engines
Charge forming device
Supercharger
C060S295000, C060S280000, C060S307000, C060S278000
Reexamination Certificate
active
06227180
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a supercharged gasoline internal combustion engine including a charger arranged in the engine intake air supply duct, which includes a throttle member upstream of the charger, and a secondary air duct branching off the intake air duct between the charger and the throttle member and leading to an exhaust duct of the internal combustion engine upstream of a catalytic converter. The secondary air duct includes a control valve, which can be controlled, together with the throttle member, by an electronic control unit to which engine operating parameters are supplied for controlling the throttle member and control valve.
The power output of an internal combustion engine is proportional to the airflow through the engine and the air density. Consequently, the engine power output can be increased by compression of the air before it enters the cylinders, that is, by a supercharger. The supercharger is arranged in the intake air duct for compressing the engine intake air. The air mass flow is controlled by the throttle member depending on the instant engine operating point. Before they are discharged to the environment, the exhaust gases of the internal combustion engine are conducted through a catalytic converter, wherein poisonous compounds contained in the exhaust gases are converted.
In order to heat the catalytic converter during the startup phase of the engine rapidly to the operating temperature needed for the conversion, part of the intake air is diverted and admixed to the exhaust gas as it is known from DE 44 41 164 A1. The oxygen added to the exhaust gas with the intake air causes in the catalytic converter an after-combustion, whereby the catalytic converter is heated. In this known arrangement, a secondary air conduct extends from an area of the intake air duct between the supercharger and the throttle to the exhaust duct upstream of the catalytic converter. The secondary air flow conduit is controlled by a flow control valve. The flow control valve and the throttle are connected, by control lines, to an electronic control unit. The control unit receives operating parameters of the internal combustion engine indicative of the engine operating state and the respective air mass flow (for example, the throttling cross-section of the throttle and the position of the control valve) from which it generates the control signals.
In addition to controlling the air mass flow the throttle also enhances the airflow through the secondary air pipe. During operation with secondary air flow when the control valve is open, the throttle may be adjusted beyond the point corresponding to the respective engine load, that is, the throttling cross-section may be reduced to such an extent that the back up pressure ahead of the throttle valve is increased and an increased amount of air is forced through the secondary air duct. Although part of the air is flowing through the secondary air duct, the charge air pressure can be maintained sufficiently high for the respective engine operating conditions by the closing of the throttle valve.
It is the object of this known arrangement to reduce costs and weight. It eliminates the need for air pumps and other components for supplying air to the catalytic converter to cause heating of the catalytic converter during the engine warm-up phase. However, the control arrangement requires an air circulation line by-passing the charger which is connected to the air supply duct downstream of the charger and which leads to the intake side of the charger. The air circulation line includes a control valve, which is controlled by the control unit. The control valve operating mechanism therefore includes an arrangement for a long-term adaptation and the control unit must include a complete performance graph for the angular position of the control valve depending on engine load and engine speed which is deposited in the control unit.
It is the object of the present invention to provide a control arrangement for a supercharged internal combustion engine, which permits air injection into the exhaust gas flow with little constructional expenses and which provides for optimal engine operating conditions.
SUMMARY OF THE INVENTION
In an arrangement and method for controlling a super-charged internal combustion engine having a charger arranged in the air intake duct and a catalytic converter arranged in the exhaust duct, with a secondary air duct including a control valve extending from a point of the intake duct downstream of the charger and upstream of a first throttle member to a point of the exhaust duct upstream of the catalytic converter, a second throttle member is arranged in the intake duct upstream of the charger and the throttle members and control valve are controlled by a control unit in such a way that sufficient air is supplied to the exhaust duct upstream of the catalytic converter such that, during engine warm-up, combustion takes place in the catalytic converter causing rapid heat-up of the catalytic converter.
With the second throttle member arranged in the intake duct upstream of the supercharger, the overall efficiency of the internal combustion engine during partial load operation can be increased by providing a reduced air mass flow. The second throttle member is connected with the control unit—like the throttle member arranged in the intake duct downstream of the charger—so as to receive control signals from the control unit. It is used during which operation for controlling the engine load when the control valve in the secondary air duct is closed. The throttle member arranged in the intake duct downstream of the charger controls the engine load when the control valve in the secondary air duct is open. The control unit decides, depending on the engine operation parameters, whether the air mass flow should be throttled by throttling of the air flow upstream of the charger (by actuating the throttle member upstream of the charger) or whether the throttle member arranged downstream of the charger should be used for controlling the engine air mass flow when the secondary air duct control valve is open that is when secondary air is injected into the exhaust gas flow. During vehicle operation, the charger noise is reduced by the air mass flow control upstream of the charger particularly during operation of the engine under partial load. In addition, a direct charge air pressure build-up and, as a result, improved operating behavior of the internal combustion engine upon activation of the charger, that is during the transition from suction operation to charged air operation of the internal combustion engine, is achieved.
The control arrangement according to the invention requires less constructional expenses than the arrangements that have become known so far since the necessary air ducts of the whole arrangement are short and there is no need for a bypass duct around the charger. The ambient air flap valve used in prior art arrangements also may be eliminated whereby, on one hand, the load control during vehicle operation is improved and, on the other hand, the control chain maintained by the control unit is simplified by inclusion of the ambient air flap valve if such valve is still used. During operation of the engine with secondary air injection the throttle member arranged in the air intake duct downstream of the charger is used for controlling engine load. In this case, the charge air mass flow is throttled downstream of the charger. As a result, the control unit reduces the flow cross-section of the intake air duct to such a degree that the pressure generated upstream of the throttle member provides in the secondary air line the air flow necessary for the injection of air into the exhaust duct. Depending on the engine operating conditions, that is the necessary pressure and flow conditions, the control unit determines the optimum setting of the throttle member for achieving the air injection into the exhaust gas flow.
The control unit synchronizes the control movements of the two throttle members takin
Hoffmann Hanns
Widmann Wolfgang
Bach Klaus J.
Daimler Chrysler AG
Denion Thomas
Trieu Thai-Ba
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