Device for controlling an exhaust gas stream

The invention relates to a device for controlling an exhaust gas stream. Said device comprises a housing (1, 101) with at least a first, second and third connection (2, 3, 4, 102, 103, 104) that form links to a first, second and third exhaust gas conduit for conducting the exhaust gases of an internal combustion engine, a first sliding element (6, 106) with a displaceable first sliding rod (6a, 106a) and a first sealing member (6c, 106c) that is located on said rod, a second sliding element (7, 107) with a displaceable second sliding rod (7, 107a) and a second sealing member (7c, 107c) that is located on said rod and an actuator for a force-assisted actuation of the device. According to the invention, a link (4c, 104b) can be established between the first and the second connection and can be adjusted by means of the first sealing member (6, 106) and a link (3c, 103b) can be established and adjusted between the first and the third connection by means of the second sealing member (7c, 107c). The device is equipped with a control mechanism (8, 108) that is connected to the actuator, said mechanism (8, 108) permitting the first sliding element (6, 106) and the second sliding element (7, 107) to be displaced.

The present invention relates to a device for controlling an exhaust gas stream as per the preamble of claim1.

Present demands on pollutant emissions, in particular of diesel engines, have led to the development of exhaust gas recirculation systems for internal combustion engines. Here, the recirculated exhaust gas is generally to be cooled by means of an exhaust gas cooler, with a bypass line often being arranged parallel to the exhaust gas cooler in order to ensure functionality. There is fundamentally the problem of regulating the hot and chemically aggressive exhaust gas stream both in the dosing and also in the branching to the exhaust gas cooler or bypass. For this purpose, control valves are known in which a first actuating flap carries out the dosing and a second actuating flap carries out the distribution between the cooler and bypass. For this purpose, two separate drive units are generally required for the actuating flaps.

It is an object of the invention to specify a device for controlling an exhaust gas stream which can be produced in a cost-effective manner by means of a small number of required components.

Said object is achieved according to the invention, for a device as specified in the introduction, by means of the characterizing features of claim1.

As a result of the provision of the control mechanism with the actuator, it is made possible according to the invention for both the first slide element and also the second slide element to be adjusted, which often makes only a single actuator necessary. Here, it is preferable for in each case one of the at least three ports to be connected to an exhaust line, to an exhaust gas cooler and to an exhaust gas line of the exhaust gas cooler. The two slide elements can thus be arranged for example downstream of the exhaust gas line and distribute the exhaust gas supplied in the exhaust gas line in a dosable manner to the exhaust gas cooler and to the bypass line by means of only one actuator. Alternatively, the exhaust gas line can be arranged downstream of the bypass line and the exhaust gas cooler, which results in a relatively low exhaust gas temperature in the region of the slide elements at least in normal operation when the exhaust gas is conducted via the exhaust gas cooler.

In one preferred embodiment, at least the first slide element can be acted on with force in the closing direction by means of a spring, resulting in particularly tight closure of the closure element in the closed position.

It is also preferable for the exhaust gas stream to exert a pressure in the opening direction on at least the first closure element. In this way, the actuator and also the control mechanism can be of small construction, since only low opening forces are necessary. Alternatively, the exhaust gas stream can also act in the closing direction on the closure element.

In one particularly preferred embodiment, a further closure element which is movable with respect to the first closure element is provided on at least the first slide element, with the closure elements, during the course of an opening movement of the slide element, releasing in succession openings which are assigned to said closure elements. In this way, it is possible to obtain substantially a two-stage opening of the path of the first slide element, as a result of which particularly flexible adjustability of the exhaust gas stream is provided using simple means. It is also possible, in particular by means of suitable, for example conical shaping of the closure element, to realize good continuously variable adjustability in addition to the two-stage property. When one of the closure elements is acted on with pressure in the closing direction, it is possible by means of the two-stage opening for the required opening force to be kept low, since not the entire cross sectional area of the opening is to be released at once.

In one preferred embodiment, the control mechanism comprises at least one rotatably mounted lever in order to deflect the force of the actuator in a suitable way to the slide elements. Alternatively or in addition, the control mechanism can also comprise a rotatable shaft with an eccentric element or slotted guide disk. Said mechanical elements of the control mechanism are in each case suitable, individually or else in combination, for assigning an opening of the first slide element to a first position of the actuator and an opening of the second slide element to a second position of the actuator. Here, depending on the design of the control mechanism, there is a high degree of flexibility with regard to the selection of a suitable actuator. The actuator can thus preferably comprise a linear, in particular hydraulic drive unit, or alternatively a rotary, in particular electromotive drive unit. Fundamentally any actuator is suitable for combination with a device according to the invention. With suitable design of the control mechanism, it is possible for the actuator to be spatially arranged in such a way that the actuator is heated only to a small extent by the recirculated exhaust gas.

In one preferred embodiment of the device according to the invention, at least the first closure element is of plate-shaped design. Valve plates which provide sealing closure require only little installation space and can be produced cost effectively.

In an alternative embodiment, at least the first closure element is of conical design, as a result of which, with suitable shaping, particularly good adjustability of the opening between the relevant ports is made possible.

It is also alternatively possible for at least the first closure element to comprise a rotatable actuating flap. In general, however, it is possible to provide any design of valve closure which is suitable with regard to the temperature demands.

Further advantages and features of a device according to the invention can be gathered from the exemplary embodiments described below and from the dependent claims.

The device according to the first exemplary embodiment as perFIG. 1comprises a housing1with a first port2, a second port3and a third port4. The first port2is, according to the drawing, duly of two-part design, but is connected by means of a suitable branch (not illustrated) to the same exhaust gas duct for the supply of exhaust gas of an internal combustion engine. The two chambers2a,2bwhich, as per the schematic sectioned illustration, are separate, of the housing1are therefore acted on substantially with the same exhaust gas pressure.

Provided between the chambers2a,2bis a chamber3awhich is connected to the port3and a chamber4awhich is connected to the port4, with a wall5separating the chambers3a,4afrom one another. The chamber3ahas a connection3bto the chamber2aof the port2and a connection3cto the chamber2bof the port2. The chamber4ahas a connection4bto the chamber2aof the port2and a connection4cto the chamber2bof the port2. The connections4b,4cand the connections3b,3clie in each case in pairs on a common axis.

A first slide element6is arranged along the connection axis of the connections4b,4c. Said slide element6comprises a slide rod6awhich is movable in a translatory fashion in its longitudinal direction and which is slidingly guided in a substantially sealing fashion at an outer aperture6bof the housing1. Situated at one end of the slide rod6ais a closure element which is connected to the valve rod6aand which is embodied as a valve plate6cwhich can bear sealingly against the connection4c. A second valve plate6dis slidingly mounted on the slide rod6aand is supported against the first valve plate6cby means of a spring element6g. At the other end of the slide rod6a, the latter has a sliding piece6e, with a spring6fbeing supported between the wall of the chamber2aand the sliding piece6e.

The spring6facts, according to the illustration as perFIG. 1, on the first slide element6with a force directed to the left. In the illustrated closed position of the first slide element6, the second valve plate6dis pressed by the spring6gsealingly against the connection4b, so that the spring6gexerts a force which, with respect to the support against the housing1, acts counter to the spring6f. The spring6fis stronger than the spring6g, so that the summed spring forces hold the two valve plates6c,6din the closed position.

Arranged parallel to the first slide element6is a second slide element7which is of identical construction to the first slide element6, so that the components of said second slide element7have corresponding reference symbols7ato7g. The second slide element7is arranged on the axis of the connections3b,3c, so that its valve plates7c,7dare arranged for the closure of the connections3c,3b. In contrast to the first slide element6, the second slide element7is illustrated in a fully-open position, which can be seen from the position of the slide rod7amoved to the right. Here, as can be seen, the first valve plate7cof the second slide element7has a greater spacing from the opening3cassigned to it than the second valve plate7dhas from the opening3bassigned to it. This results in a two-stage property of the opening process, wherein when the respective slide element6,7is pressed in counter to the force of the spring6f,7f, an opening of the end-side, fixed valve plate6c,7cis firstly brought about. During the course of said first opening section, the spring6g,7gbetween the valve plates is gradually relaxed until the second valve plate6d,7dis likewise positively moved in the opening direction by means of a driver (not illustrated) of the valve rod6a. It is possible by means of said two-stage property of the opening to bring about particularly well-defined dosing of the recirculated exhaust gas stream.

A control mechanism8comprises a rotatably mounted lever8a, with the center of rotation being positionally fixed with respect to the housing1.

The rotatably mounted lever8ais shaped such that, during its movement in one direction, a sliding face8bof the lever8ainteracts with the sliding cam6eof the first slide element and, during a deflection in the opposite direction, with the sliding cam7eof the second slide element7. Here, the in each case non-actuated slide element passes out of engagement with the sliding face8bof the lever8a, so that said slide element is closed on account of the above-described spring forces.

An actuator (not illustrated) is embodied in the form of a linear hydraulic force introduction unit. By means of the actuator, it is possible for the lever8ato be moved in a driving fashion in the one or the other direction, as a result of which either the first slide element6or the second slide element7is actuated in the opening direction. When the first slide element6is actuated in the opening direction, the chambers2a,2bwhich supply the exhaust gas are connected via the connections4b,4cin each case to the chamber4a. Here, the port4leads to an exhaust gas cooler of the recirculated exhaust gas. With a correspondingly oppositely directed actuation of the lever8a, the second slide element7is actuated in the opening direction, with the ducts2a,2bbeing connected to the duct3aby means of the connections3b,3c. The duct3ais connected by means of the port3to a bypass line which bypasses the exhaust gas cooler in parallel.

Overall, therefore, it is possible by means of a one-dimensional adjustment of a single actuator both to make a selection as to whether an exhaust gas stream is connected to the exhaust gas cooler or the bypass line, and also to ensure the dosing of the recirculated exhaust gas. Here, the valve plates4b,4c,3b,3ccan be at least partially conical in shape and if appropriate held in corresponding cup-shaped valve seats in order to permit yet more precise dosing of the recirculated exhaust gas stream.

The second exemplary embodiment as perFIG. 2, in contrast to the first exemplary embodiment, has only a single supplying chamber102awith one port102. The supplying chamber102ais connected by means of a first connecting opening103bto a chamber103aof a second port103, and by means of a connecting opening104bto a chamber104aof a third port104. Similarly to the first exemplary embodiment, a first slide element106and a second slide element107are provided. On account of the simplified design of the housing101with only in each case one connection103b,104bbetween the inlet line102aand the two outlet lines103a,104a, each of the slide elements106,107has only one valve plate106c,107cwhich is fixed in each case to the end of a corresponding slide rod106a,107a. As in the first exemplary embodiment, the two slide rods106a,107aare guided in openings106b,107bof the housing101and are acted on with force in the closing direction by means of springs106f,107f. Situated at the end sides of the slide rods106a,107aare sliding faces106e,107e. The control mechanism108of the second exemplary embodiment comprises a rotatable shaft108awhich runs perpendicularly to the slide rods106aand107aand has cam-like eccentric elements108b,108cin each case at the level of the sliding faces106e,107e. The eccentric elements108b,108care substantially identical in shape but are fixed to the shaft108so as to be offset with respect to one another by a rotational angle of 180°.

In the rotational position of the shaft108aas perFIG. 2, the one eccentric108bengages on the sliding face107esituated opposite it in such a way that the slide rod107ais pressed in to a maximum extent in the opening direction counter to the spring force and the slide element107is open. The other eccentric108b, in contrast, does not engage on the sliding face106eof the first slide element106, so that the first slide element106is closed on account of the spring force. As can be seen, the cams108b,108care shaped to be so steep that there is a position of the rotary shaft108ain which neither of the slide elements106,107is open. On account of the shaping of the flanks of the cams, an only partial opening of a slide element106,107is also possible depending on the rotational position, with the in each case other slide element being closed.

An actuator (not illustrated) is embodied in the manner of an electric motor and is if appropriate connected by means of a step-up transmission to the rotary shaft108a. Said actuator can however also be a linear hydraulic cylinder which transmits a linear movement into the rotational movement of the rotary shaft108afor example by means of a toothed rack and a pinion.

It is self-evident that the components, in particular the control mechanisms8,108of the first and second exemplary embodiments are interchangeable. It is thus for example possible for only one of the slide elements to be of two-stage design. It is likewise possible for the arrangement of the closure elements to be acted on by the exhaust gas pressure in the closing direction or in the opening direction depending on the arrangement.