Device for preventing an exhaust gas recirculation valve from sticking after switching off an internal combustion engine

ABSTRACT

The invention relates to an exhaust gas recirculation device for an internal combustion engine, especially for a motor vehicle, comprising an exhaust gas recirculation line for recirculating exhaust gas, the line branching off from the exhaust line and running into an unburned gas line. The exhaust gas recirculation line includes a valve having a closing element which can be displaced between a closing position and an opening position by means of an actuator. One aim of the invention is to especially reliably prevent the closing element of the valve from sticking to the valve seat after the operation of the internal combustion engine. To this end, the closing element of the valve is placed in an idle position by means of the actuator, when the internal combustion engine is not in operation.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DETAILED DESCRIPTION OF THE INVENTION

Parts which correspond to one another are provided with the same reference numbers in all of the figures.

The motor vehicle according to FIG. 1 comprises an internal combustion engine . The internal combustion engine comprises a multiplicity of components, for example injection nozzles for fuel, a fuel pump, pistons and cylinders, this not being illustrated specifically in the drawing. A fresh gas line having a pipe Interior which is connected on the input side to the surroundings of the motor vehicle leads into the internal combustion engine . Fresh gas is fed via the pipe interior of the fresh gas line to the internal combustion engine for the combustion of fuel. The fuel may be diesel or petrol. This exemplary embodiment illustrates an internal combustion engine which is provided for diesel. In the internal combustion engine , fresh gas is mixed with fuel in a manner not illustrated specifically and is burned.

The exhaust gas which arises during the combustion is carried away into the surroundings of the motor vehicle via an exhaust line . To recirculate exhaust gas into the internal combustion engine of the motor vehicle , the motor vehicle has an exhaust gas recirculation device . The exhaust gas recirculation device comprises an exhaust gas recirculation line which branches off from the exhaust line and leads into the fresh gas line . The opening of the exhaust gas recirculation line into the fresh gas line is provided directly after a swing-valve mechanism . The amount of fresh gas which can be fed to the internal combustion engine can be adjusted via the swing-valve mechanism . For this purpose, the swing-valve mechanism has a butterfly valve which is arranged in a rotatable manner on a shaft .

The exhaust gas recirculation device furthermore comprises a valve with a closing element . Further elements of the valve , such as, for example, the housing, seals and flanges for screwing it down are not illustrated specifically in the drawing. The closing element is arranged in the pipe interior of the fresh gas line . The valve uses its closing element to close, from the interior of the fresh gas line , a valve seat which is formed as an edge region of a cutout in the pipe wall of the fresh gas line . As an alternative, however, the valve seat which is formed as an edge region of the cutout in the pipe wall of the fresh gas line can also be closable from the outside by the closing element of the valve .

In addition, the exhaust gas recirculation device comprises a gear mechanism to which the closing element of the valve is connected. The gear mechanism can be activated by a control unit via a control line by means of an actuator which is designed as an electric motor. FIGS. 2 to show the approximately oval-shaped cutout which is indicated by a dashed line in FIG. . FIGS. 2 to each show different positions of the closing element of the valve .

FIG. 2 shows the section of the fresh gas line with its pipe interior in which the valve is arranged. Fresh gas flows through the fresh gas line in accordance with the direction of the arrow . The closing element of the valve comprises an approximately disk-shaped closure element and a retaining element which is arranged on the approximately disk-shaped closure element . The approximately disk-shaped closure element closes the valve seat . The retaining element is connected rigidly at its first end to the approximately disk-shaped closure element . As an alternative to this, the retaining element can also be connected at its first end in a flexible manner, for example via a spring, to the approximately disk-shaped closure element . With its second end , the retaining element is passed with a seal through the pipe wall of the fresh gas line on that side of the pipe wall of the fresh gas line which lies opposite the valve seat . The valve comprises further elements, such as, for example, a housing, seals and connecting flanges, which are not illustrated specifically in the drawing.

The retaining element of the closing element of the valve is connected to the gear mechanism . For this purpose, the gear mechanism comprises a pivoting arm which is connected at its first end in a rotatable manner to the second end of the retaining element . The pivoting arm and the retaining element of the closing element can be rotated about the connecting point. The second end of the pivoting arm is, in turn, connected in a rotatable manner to a first corner region of an approximately triangular toothed segment , both the toothed segment and the pivoting arm being rotatable about the connecting point.

The toothed segment of the gear mechanism can be acted upon on one of its three sides by the actuator designed as an electric motor. For this purpose, the actuator which is designed as an electric motor has a drivable toothed wheel which engages in a corresponding toothing of the toothed segment . The toothing of the toothed segment is arranged on one of the sides of the approximately triangular toothed segment , the side having the toothing being designed approximately in the shape of a circular arc so that the toothing can engage, upon rotation of the toothed segment , into the toothed wheel of the actuator designed as an electric motor. The toothed segment is fixed in a pivotable manner at a fixing point in a second corner region .

The pivoting arm is connected in its second end region not only to the approximately triangular toothed segment , but in addition also to a resetting spring . The resetting spring is designed in such a manner that it always pushes the pivoting arm back into the position according to FIG. 2 that corresponds to the closing position of the valve .

A sensor which is connected via a sensor line to the control unit according to FIG. 1 is connected to the closing element of the valve . During operation of the valve , the sensor detects the current position of the closing element . As a function of the current position of the closing element of the valve in each case, the control unit activates the actuator , which is designed as an electric motor, via the control line in such a manner that the desired position of the closing element of the valve always corresponds to the actual position.

FIG. 3 shows the valve in the “opening position”. The toothed segment has been moved from the position according to FIG. 2 into the position according to FIG. 3 by the toothed wheel of the actuator designed as an electric motor. The resetting spring So is in a state of maximum stress. The resetting force of the resetting spring is limited by the supply of current to the actuator which is designed as an electric motor.

FIG. 4 shows the closing element of the valve in a second opening position which corresponds to the maximum opening position in the control range of the valve .

Finally, FIG. 5 shows the valve in the idle position. The toothed segment bears with its one side against a stop . The closing element of the valve has been brought into this position via a movement of the actuator that drives the pivoting arm .

In the process, the resetting spring fixes the closing element in its idle position. The stop can change its current position, this not being illustrated specifically in the drawing.

During operation of the motor vehicle , fresh gas is fed to the internal combustion engine via the fresh gas line . Combustion of fuel takes place in the internal combustion engine with the addition of fresh gas , which is not illustrated specifically in the drawing. The exhaust gas is carried out of the internal combustion engine via the exhaust line .

During operation of the motor vehicle the exhaust gas recirculation device is also operated. For this purpose, exhaust gas is fed out of the exhaust line into the exhaust gas recirculation line . This takes place without additional auxiliary means by the exhaust gas recirculation line branching off from the exhaust line . As an alternative, it is also possible, however, for exhaust gas to be actively removed from the exhaust line for feeding into the exhaust gas recirculation line .

The amount of exhaust gas which is added to the fresh gas is controlled via the control unit by means of a movement of the closing element . For this purpose, the control unit is connected in a manner not illustrated specifically to further components of the internal combustion engine , which are likewise not illustrated specifically. As a function of parameters which the control unit obtains from further elements of the internal combustion engine , the control unit controls the amount of exhaust gas to be added to the fresh gas by means of a movement of the closing element . The first movement range of the gear mechanism lies between the closing position according to FIG. and the opening position according to FIG. . The position of the closing element of the valve determines here how much exhaust gas is fed into the fresh gas of the fresh gas line .

When the motor vehicle is not in operation, the cooling and cold impurities from the exhaust gas form a film in the flow region of the fuel/air mixture, as a result of which there is the risk of the closing element adhering to the valve seat because of the cooling film. In order now to reliably prevent the closing element from adhering to the valve seat after operation of the motor vehicle when the internal combustion engine is not in operation, the closing element of the valve is moved by means of the actuator , which is designed as an electric motor, and the gear mechanism into the idle position according to FIG. 5 after the internal combustion engine. is switched off. In this case, the idle position of the closing element of the valve is defined by the stop . A movement of the closing element of the valve into its idle position takes place via current which is still available after the internal combustion engine is switched off. This phase is also referred to as the trailing effect of the control apparatus. This second movement range of the gear mechanism therefore lies between the closing position according to FIG. and the idle position according to FIG. . The arrangement of the closing element of the valve in the idle position instead of in the closing position reliably prevents the closing element from adhering to the valve seat of the fresh gas line .

When the internal combustion engine of the motor vehicle is re-started, a movement of the closing element of the valve into the closing position according to FIG. 2 takes place by means of the control unit . Further operation of the exhaust gas recirculation device takes place from the closing position.

In order to ensure correct operation of the internal combustion engine even if the actuator which is designed as an electric motor should fail, the closing element is designed in such a manner that it can be moved in the de-energized state by the resetting spring . If, during operation of the exhaust gas recirculation device , the actuator which is designed as an electric motor fails, the resetting spring pushes back the toothed segment from an opening position in the movement range of the gear mechanism between the opening position according to FIG. and the closing position according to FIG. 2 into the closing position according to FIG. . Further operation of the exhaust gas recirculation device is not possible without operation of the actuator designed as an electric motor. However, operation of the internal combustion engine is reliably ensured even without operation of the exhaust gas recirculation device , as a result of which the driver of the motor vehicle can at least travel as far as the next repair garage.

In the exhaust gas recirculation device , reliable operation of the exhaust gas recirculation device is ensured by the movement range of the gear mechanism between the closing position according to FIG. and the maximum opening position according to FIG. . Even if the internal combustion engine is not in operation, the closing element is reliably prevented from adhering to the valve seat by the fact that the closing element of the valve is moved into a state with a small opening position when the internal combustion engine is switched off. Should the actuator which is designed as an electric motor fail in this position, then a constant amount of exhaust gas is continuously added to the fresh gas . The idle position of the closing element of the valve is dimensioned in such a manner that correct operation of the internal combustion engine is ensured and, at the same time, the closing element is prevented from adhering to the valve seat .

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

An exemplary embodiment will be explained in greater detail with reference to a drawing, in which, in the figures:

FIG. 1 shows, schematically, an internal combustion engine with an exhaust gas recirculation device,

FIG. 2 shows, schematically, the closing mechanism according to FIG. 1 in the closed state,

FIG. 3 shows the closing mechanism according to FIG. 1 in the state of maximum opening,

FIG. 4 shows the closing mechanism in the state of the open position according to FIG. 1, and

FIG. 5 shows the closing mechanism in the idle position according to FIG. .

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International Application PCT/DE02/01779, which designated the United States and was filed on May 17, 2002, and further claims priority to German reference DE10125094.0, filed on May 23, 2001, the both of which are herein incorporated by reference.

CLAIMS

1. A device for preventing an internal combustion engine exhaust gas recirculation valve from sticking after the engine is switched off, comprising: an exhaust gas recirculation line branching off from an exhaust line and leading into a fresh gas line, the recirculation line being used for recirculating exhaust gas and having a valve with an actuator driven closing element such that when the engine is not in operation the closing element is in an idle position, the closing element being activated by the actuator via a gear mechanism such that a rotational movement of the actuator is converted into a linear movement of the closing element by means of the gear mechanism, and wherein the gear mechanism has a first movement range and a second movement range, the first movement range being limited by an opening and a closing position of the closing element, and the second movement range being limited by the closing and idle position of the closing element.

2. The device according to claim 1, wherein the idle position of the closing element is predetermined by a stop for the gear mechanism.

3. The device according to claim 2, wherein the stop is adjustable.

4. The device according to claim 1, wherein the gear mechanism further comprises a resetting spring arranged to facilitate resetting the closing element both into the idle position and into the closing position.

5. The device according to claim 1, further comprising a sensor and a control unit connected to one another and arranged to detect a current position of the closing element.

6. The device according to claim 1, wherein the valve is a disk valve.

7. The device according to claim 1, further comprising an activatable spring-valve mechanism arranged such that the valve leads downstream of the activatable spring-valve mechanism and into the fresh gas line, and an amount of fresh gas to be supplied to the engine can be set via an activatable spring-valve mechanism.

8. The device according to claim 1, wherein the swing-valve mechanism comprises a butterfly valve.

9. The device according to claim 1, wherein the engine comprises one of a direct injection spark ignition engine or a direct injection diesel engine.

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