Abstract:
A valve device for controlling an exhaust gas flow of an internal combustion engine includes a housing comprising a channel which has the exhaust gas flow therethrough. A shaft is disposed in the housing. The shaft is rotatably mounted about a shaft axis. A flap is connected to the shaft. The flap controls a flow cross section of the channel. The flap comprises two flexurally rigid support plates. The support plates each comprise an outer periphery. An elastic flap body is arranged between the support plates. The elastic flap body comprises an outer periphery which is larger on all sides than the outer periphery of the support plates. A distance between the outer periphery of the elastic flap body and the outer periphery of the support plates is largest in an area of the shaft axis, and smallest at an angle of 90° relative to the shaft axis.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2012/059854, filed on May 25, 2012 and which claims benefit to German Patent Application No. 10 2011 106 744.6, filed on Jun. 28, 2011. The International Application was published in German on Jan. 3, 2013 as WO 2013/000643 A1 under PCT Article 21(2). 
     
    
     FIELD 
       [0002]    The present invention relates to a valve device for controlling an exhaust gas flow of an internal combustion engine. The valve device includes a shaft that is rotatably mounted about a shaft axis in a housing containing a channel for a flow. The valve device also includes a flap that is connected to the shaft with which the flow cross section of the channel can be controlled. The flap includes two flexurally rigid support plates with a first periphery and an elastic flap body with a larger periphery on all sides that is arranged between the support plates. 
       BACKGROUND 
       [0003]    Valve devices of the above type can be used, for example, as exhaust gas return flaps or exhaust gas flaps. Such flaps can also be used as throttle flaps in air-conducting conduits. When using such valve devices as an exhaust gas return flap, the tightest possible closure of the channel in the closed state of the flap is required on the one hand, and, on the other hand, a good controllability of the volume flow is needed. Care must further be taken to obtain a sufficient thermal endurance in the hot exhaust gas tract. 
         [0004]    There are various designs of such multi-part flaps which are intended to improve the sealing tightness in the closed state. 
         [0005]    EP 1 455 124 A1, for example, describes a flap valve for a gas- or liquid-conducting conduit which is eccentrically supported and consists of a flexurally rigid element arranged on the outflow side and an elastic spring sheet arranged on the inflow side. In the housing, an abutment edge is formed which is abutted by the spring sheet in the closed state. In this arrangement, one half of the spring sheet has the same size as the flexurally rigid element, wherein this half is biased in a direction leading away from the flexurally rigid element so that the spring sheet, when laid onto the abutment edge, is pressed with tension against the abutment portion. The other half of the spring sheet is larger than the flexurally rigid element so that this side can also abut on the abutment portion formed in the opposite direction within the channel. A possible distortion of the spring sheet is restricted by the abutment of the flexurally rigid element. 
         [0006]    EP 1 489 285 A2 describes a flap valve which can be used as a throttle flap and is made of two support plates and an elastomeric plate arranged between the support plates, the elastomeric plate extending on all sides beyond the periphery of the support plates and, in the closed state of the flap, abutting by its outer periphery on the inner wall of the channel. This flap, however, is not suited for use in the exhaust gas area because the elastomer does not have the required thermal endurance. 
         [0007]    The disadvantages of the previous designs are that relatively high actuating forces are necessitated to safeguard a sufficient sealing tightness of the valve device in the closed state. 
       SUMMARY 
       [0008]    An aspect of the present invention is to provide a valve device having a minimum leakage corresponding to the smallest possible actuating forces. A further aspect of the present invention is to provide a valve device which can be produced in an inexpensive manner with good control characteristics. 
         [0009]    In an embodiment, the present invention provides a valve device for controlling an exhaust gas flow of an internal combustion engine which includes a housing comprising a channel configured to have the exhaust gas flow therethrough. A shaft is disposed in the housing. The shaft is mounted about a shaft axis so as to be rotatable. A flap is connected to the shaft. The flap is configured to control a flow cross section of the channel. The flap comprises two support plates configured to be flexurally rigid. The two support plates each comprise an outer periphery. An elastic flap body is arranged between the two support plates. The elastic flap body comprises an outer periphery configured to be larger on all sides than the outer periphery of the two support plates. A distance between the outer periphery of the elastic flap body and the outer periphery of the two support plates is largest in an area of the shaft axis, and smallest at an angle of 90° relative to the shaft axis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
           [0011]      FIG. 1  shows a plan view of a valve device of the present invention; and 
           [0012]      FIG. 2  shows a lateral sectional view of the valve device of the present invention according to  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    In an embodiment of the present invention, because the distance between the outer periphery of the elastic flap body and the outer periphery of the support plates is largest in the area of the shaft axis and smallest at an angle of 90° relative to the shaft axis, the elasticity is largest in the area close to the shaft where, due to the small lever arm, the largest torques must be applied for pressing the flap bodies against a housing wall. As a result, a tight closure is accomplished by a press-on force which is to be applied, while relatively small actuating forces of the actor will be required. 
         [0014]    In an embodiment of the present invention, the distance between the outer periphery of the elastic flap body and the outer periphery of the support plates can, for example, decrease with an increasing angle relative to the point of intersection of the shaft axis and the channel axis, so that, with an increasing distance from the shaft axis, a continuous reduction of the elasticity is effected. A continuous press-on force can thus be applied over the entire periphery. 
         [0015]    In an embodiment of the present invention, the channel and the flap body are circular in cross section, and the support plates are substantially elliptic or shaped as a circle expanded in one direction. These shapes can be produced and mounted in an easy manner. 
         [0016]    The flap body can, for example, be made of spring steel. Spring steel has a high thermal endurance, thus allowing its use in the exhaust gas channel. 
         [0017]    In an embodiment of the present invention, a ledge can, for example, be formed in the housing on which an outer edge of the flap body is supported in the closed state of the flap. A reliable sealing is thus achieved even in case of a reduced tolerance sensitivity in the production and assembly process of the individual component parts. 
         [0018]    In an embodiment of the present invention, a section of the channel located downstream relative to the flap and an upstream section of the channel can be arranged at a radial offset relative to each other at the level of the shaft axis, whereby identical flow cross sections are also achieved in regard to the use of the ledge within the channel, so that, in the opened state, no change of the flow characteristic upstream and downstream of the valve will occur. 
         [0019]    In an embodiment of the present invention, the shaft axis can, for example, divide the flap body into a first flap half and a second flap half, wherein the first flap half is supported on a surface of the ledge that faces in the flow direction, and the second flap half is supported on a surface of the ledge that faces in a direction opposite to the flow direction. While using a centrically supported flap which can be produced at low cost, there can thus be effected a circumferential support on a surface for sealing purposes. 
         [0020]    In an embodiment of the present invention, the axial distance of the two surfaces of the ledge can, for example, be smaller than the thickness of the flap body so that, in the vertical position of the flap body in the channel, an additional press-on force is exerted on the surface by means of the flap body, resulting in an improved sealing in the closed state. Primarily in connection with the higher elasticity in the area close to the shaft, it is possible to thereby achieve a largely leak-free closure while merely applying low actuating forces. A clattering of the flap in the channel is further prevented. 
         [0021]    In the closed state of the flap, the flap body further has a slight distance to the radially adjacent inner wall of the channel. This makes it possible to produce the component parts with the tolerances required for the different temperature-induced expansions and will thus providing for inexpensive production and assembly. Depending on the distance, one can also achieve a changed flow characteristic while using small opening angles. 
         [0022]    The support plates are arranged fully within the inner periphery of the ledge in order to make possible that the press-on force applied onto the surface of the ledge can be completely exerted via the edge of the flap body. The applied press-on force is thus not limited. 
         [0023]    In an embodiment of the present invention, a valve device is provided by which a tight abutment of the flap is achieved along the full periphery of the flap while only small torques have to be exerted. The flap can be produced and mounted in an inexpensive manner because no narrow tolerances need be observed. This valve device will tend neither to become wedged nor to become clogged. 
         [0024]    The valve device in accordance with the present invention comprises a housing  2  in which a channel  4  is formed for throughflow of exhaust gas, for example. Internally of channel  4 , a flap  6  is arranged for controlling the flow cross section, the flap being controlled by an actuator (not shown). For this purpose, the actuator is connected to a shaft  8  supported at support sites  14  in housing  2 . 
         [0025]    On both sides of channel  4 , the shaft  8  extends into the support sites  14  through shaft passages  10  formed in a wall  12  of housing  2  on opposite sides of channel  4 , with channel  4  being divided into two halves by a shaft axis  16  about which the flap  6  can be rotated. 
         [0026]    The flap  6  arranged in the interior of channel  4  comprises two flexurally rigid support plates  18 ,  20  and an elastic flap body  22  of spring steel arranged between the support plates  18 ,  20 . The two support plates  18 ,  20  and the flap body  22  are disposed immediately above each other and are arranged in a slot  24  in shaft  8 , and they are fastened by screws  26 . 
         [0027]    In the closed state of flap  6 , an outer edge  28  of flap body  22  is supported on a ledge  30  formed in housing  2 . The flap  6  is divided by the shaft axis  16  into a first half  32  and a second half  34 , the first half  32  being supported by its edge on a first surface  36  of ledge  30  that is facing toward a downstream section  38  of channel  4 , and the second half  34  being supported by its edge on a second surface  40  of ledge  30  that is facing toward an upstream section  42  of channel  4 . From this, the downstream section  38  relative to the upstream section  42  also has a radial offset at the level of the shaft axis  16  so as to obtain identical flow cross sections of the two channel sections  38 ,  42 . Between the radially adjacent inner wall  12  of channel  4  and the edge  28  of flap body  22 , a slight distance remains because a reliable and leakage-free sealing is already provided by the abutment of flap body  22  on ledge  30 . On the other hand, the two support plates  18 ,  20  are only large enough to the effect that, in the closed state, their entire surface is arranged within the flow cross section of the downstream section  38  and of the upstream section  42  of channel  4  so that, in radial direction, the support plates  18 ,  20  terminate before the surfaces  36 ,  40  of ledge  30 . 
         [0028]    In the shown embodiment, the distance of the surfaces  36 ,  40  of ledge  30  is smaller than the thickness of flap body  22 , and the axial distance from these two surfaces  36 ,  40  to the shaft axis  16  is identical, so that, with the flap  6  arranged orthogonally to the shaft axis  16 , the flap body  22  is, by means of spring force, pressed by its edge  28  against the surfaces  36 ,  40 , thus providing a further improvement of the sealing tightness in the closed state. 
         [0029]    In an embodiment, channel  4  (just as flap body  22 ) is of a circular cross section. The support plates  18 ,  20 , however, as evident from  FIG. 1 , are shaped substantially as a circle expanded in one direction, wherein the largest extension of the ellipse is formed orthogonally to the shaft axis  16  and the smallest extension exists at the level of the shaft axis  16 . From this, the distance between the outer periphery of the elastic flap body  22  and the outer periphery of the support plates  18 ,  20  is largest in the area of the shaft axis  16  and is smallest at an angle of 90° relative to the shaft axis  16 . The portion of the non-covered surface of the flap body  22  relative to the total surface of flap body  22  further becomes smaller with increasing distance from the shaft axis  16  to the end of the support plates  18 ,  20 . In other words, according to the present invention, the distance between the outer periphery of the elastic flap body  22  and the outer periphery of the support plates  18 ,  20  decreases with increasing angle relative to the point of intersection between the shaft axis  16  and the channel axis, whereby the elasticity of the flap  6  decreases with increasing angle. 
         [0030]    Based on all of the above, the flap  6  has a higher elasticity in the area of the shaft axis  16  than in the area remote from shaft axis  16 . Due to the short lever arm in the area close to the axis, the flap body  22  can thus be deformed by means of relatively small torsional moments when abutting on the surfaces  36 ,  40  of ledge  30 , thus effecting a high sealing tightness while merely requiring low actuating forces. In this situation, the valve body is brought into abutment on the surfaces  36 ,  40  over the whole periphery whereby the leakage of the valve device is minimized. At the same time, this clamping effect will prevent a clattering of the flap  6  in channel  4  caused by occurrence of pressure pulsations. By well-aimed selection of the distance of the flap body  22  from the adjacent inner wall  12  of channel  4 , it is also possible to adapt the flow characteristic in the range of small angles of attack. In comparison to known designs, the tolerance sensitivity is distinctly lower so that the valve device can be produced at low cost. 
         [0031]    It should be understood that the scope of protection of the present application is not restricted to the described exemplary embodiment. With respect to the precise design, various constructional modifications are possible within the protective scope, for example, concerning the mutual distance of the surfaces or the specific shape of the support plates. It can also be contemplated to design such flap in a corresponding manner for use in non-round channels. Reference should be had to the appended claims.