Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-07-19
2001-08-14
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
Reexamination Certificate
active
06272860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and an apparatus for checking the functioning of a pressure-operated actuating element in an internal combustion engine.
2. Related Art
DE 33 06 484 A1 discloses an internal combustion engine with an exhaust turbocharger, the turbine of which, which is located in the exhaust line of the internal combustion engine, drives a compressor arranged in the intake duct for the purpose of increasing the intake pressure. To heat an exhaust catalyst mounted in the exhaust line downstream of the turbine to its operating temperature as quickly as possible, the turbine can be bypassed by means of a bypass passage which can be opened and closed by a pressure-dependent actuator. When the bypass passage is open, some of the hot exhaust gasses flow directly to the catalyst, bypassing the turbine, and heat it quickly to its operating temperature, thereby reducing pollutant emissions after a cold start.
The actuator that opens and closes the bypass passage comprises a spring-loaded diaphragm in a housing with a pressure chamber supplied via a pressure line. If the pressure chamber is subjected to the reduced pressure that prevails, for example, in the intake manifold at idle when the internal combustion engine is started, the diaphragm and an actuating rod connected to the diaphragm are displaced, the bypass passage thereby being opened and the exhaust gas passed directly to the catalyst.
In the event of a leak in the pressure line that supplies the pressure chamber of the actuator, the pressure chamber is not supplied with the reduced pressure required to open the bypass passage but, instead, is subjected to ambient pressure, with the result that the bypass passage remains closed and the useful exergy of the exhaust gas is used to drive the turbine but not to heat the catalyst directly. If the catalyst is below its operating temperature, larger quantities of unpurified exhaust gas are then emitted.
SUMMARY OF THE INVENTION
The object on which the invention is based is to diagnose malfunctions of emission-improving measures at an early stage.
According to the method of the invention, it is possible to perform a check on the ability to function of the actuating element and the lines supplying the actuating element and branching off from it. In the diagnostic test, the actuating element is supplied with a diagnosis pressure that results in a particular setting of the actuating element which affects the cross section of the bypass passage, with the result that a particular quantity of exhaust gas flows through the bypass passage and the remainder of the exhaust-gas flow serves to drive the turbine. The flow of exhaust gas through the turbine can be assigned an intake-pressure target value or a known target-value curve; if the measured actual intake-pressure value deviates from the target value, a fault signal is generated, indicating that the actuating element or a component associated with the actuating element is malfunctioning.
This method has the advantage that it is suitable for diagnosing many different actuating elements that can be set by means of pressure. The method can be carried out at regular intervals in different or identical engine operating conditions. Depending on the type of actuating element and the operating condition, supplying diagnosis pressure when the system is functioning correctly can lead to a change in the pressure in the intake duct or an approximately constant pressure curve for the intake pressure. If the actual intake pressure deviates from the target value, a fault signal is generated.
According to an expedient development, the actuating element is moved in the direction of the open position if the actuating pressure within the pressure chamber drops and in the direction of the closed position if the pressure rises. In a first preferred embodiment, the actuating element is supplied in boost mode with increased intake pressure as the diagnosis pressure, and this leads to the closure of the actuating element and consequently to an increase in the mass flow of exhaust gas through the turbine as the intake pressure rises. If the increasing intake pressure reaches a particular pressure value, the actuating element is functioning correctly. If the pressure value is not reached, there is a fault, and a fault signal is generated.
In a second preferred embodiment, the actuating element is designed in such a way that, at a given standard pressure—generally ambient pressure—the bypass passage is closed and, at an actuating pressure above or below the standard pressure, the bypass passage is opened. If the system is functioning correctly, the actuating element is supplied with the intake pressure at idle, particularly just after the internal combustion engine has started, and at this pressure the actuating element remains in the open position due to the vacuum at idle, with the result that a constant flow of exhaust gas flows through the turbine and the pressure profile in the intake duct remains essentially the same. In the event of a fault—a leaking line—on the other hand, the actuating element is supplied with the higher ambient pressure, which moves the actuating element into the closed position, with the result that the turbine is supplied with a higher mass flow of exhaust gas and the intake pressure rises owing to the higher compressor output. The rise is diagnosed and leads to a fault signal.
In the second embodiment, diagnostic testing can also be carried out when the internal combustion engine is in boost mode by supplying the actuating element with the intake pressure p
2S
as the diagnosis pressure, this pressure lying above the standard pressure but below p
2
, with the result that the actuating element is for a brief period moved further into the open position than by the boost-pressure control system. The quantity of exhaust gas flowing through the turbine decreases slightly and, accordingly, the boost pressure falls slightly. In the event of a fault, the actuating element is subjected to ambient pressure and is thus displaced into the closed position, as a result of which the output of the turbocharger and hence also the boost pressure is increased, this being used to generate a fault signal.
There is another diagnosis option with the use of a secondary air pump that can be used to introduce secondary air directly downstream of the engine exhaust valves in order to initiate an exothermic secondary reaction involving the exhaust pollutants. A switching valve supplied with the intake pressure as the switching pressure is provided for controlling the secondary air. In normal operation, the switching valve opens if there is a vacuum in the intake manifold, whereupon secondary air is injected. In the case of diagnosis, the oxygen concentration in the exhaust line is measured and compared with a target value. If there is a leak, the pressure in the switching valve rises and the valve is then moved into the closed position, reducing or shutting off the supply of secondary air. In the event of a fault, the actual oxygen concentration is below the target value, whereupon a fault signal is generated.
The apparatus according to the invention has an actuating element in an internal combustion engine with an exhaust turbocharger, the turbine of which can be bypassed in the exhaust line by a bypass passage. The bypass passage is opened or shut off by the actuating element, the actuating element being in the open position when a reduced pressure is applied and in the closed position when the standard pressure is applied. The actuating element is connected to the intake duct by a pressure line. Arranged in the pressure line is a nonreturn valve which opens towards the intake duct and via which reduced pressure can be transmitted from the intake duct to the actuating element. The reduced pressure moves the actuating element into the open position in the normal operating mode.
Arranged in parallel with the nonreturn valve is a diagnosis valve which can be activated by means of an actuating s
Brosecke Harald
Klein Rudolf
Calcaterra Mark P.
Daimler-Chrysler AG
Denion Thomas
Trieu Thai-Ba
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