Abstract:
A flap device for an internal combustion engine includes a flow housing comprising a flow channel, an actuating shaft, a flap body arranged on the actuating shaft in the flow channel, a housing bore arranged in the flow housing, a lever fixed on the actuating shaft, a bearing bush arranged in the housing bore, and a sealing disk comprising a surface which is at least partially spherically shaped. The housing bore has the actuating shaft protrude outwards therethrough. The lever comprises a rear wall. The bearing bush has the actuating shaft mounted therein. The surface rests under tension against the rear wall of the lever.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2013/076068, filed on Dec. 10, 2013 and which claims benefit to German Patent Application No. 10 2013 101 983.8, filed on Feb. 28, 2013. The International Application was published in German on Sep. 4, 2014 as WO 2014/131478 A1 under PCT Article 21(2). 
     FIELD 
     The present invention relates to a flap device for an internal combustion engine, having a flow housing in which a flow channel is formed, an actuating shaft, a flap body arranged on the actuating shaft in the flow channel, a housing bore in the flow housing through which housing bore the actuating shaft protrudes outward, a lever fastened to the actuating shaft, a bearing bush which is fastened to the actuating shaft and in which the actuating shaft is supported, and a sealing disc with an at least partly spherically shaped surface. 
     BACKGROUND 
     Such flap devices serve, for example, as exhaust gas retention flaps or exhaust gas recirculation flaps in the exhaust system of an internal combustion engine. Exhaust gas contains pollutants that must be prevented from escaping to the outside so that a reliable sealing must be ensured along the shaft which extends outward towards an actuator. This sealing must function perfectly at all times under varying thermal loads. A very precise controllability must also be observed with the flaps in order to meet pollution emission standards for modern internal combustion engines. It has been found, however, that damage at the bearing site is caused even more often by ingress from outside. This leads to corrosion in the area of the bearing, caused by the introduction of dirt or by the introduction of salt and humidity. 
     Various flap devices have previously been described which have attempted to ensure a sufficient sealing. WO 2006/003017 A1, for example, describes a flap valve for an exhaust system of a motor vehicle, wherein a bearing bush, as well as a spring element, a sealing disc, and a bearing ring, are arranged in a bearing housing fastened to the flow housing. The shaft protrudes out from the bearing housing which has a conical restriction at its end facing away from the flow housing and surrounding the opening through which the shaft protrudes, the spring force pressing the correspondingly conical surface of the bearing ring against the restriction with interposition of the sealing disc. The contact area of the conical surfaces serves as a sliding and sealing surface between the bearing housing and the bearing ring. An escape from the bearing region along the shaft is intended to be achieved by placing the sealing disc in a manner free of play. 
     An exhaust gas flap is also described in U.S. Pat. No. 5,630,571, the exhaust gas flap comprising a bearing housing in which a bearing bush and a spherical sealing disc are arranged, which disc is in contact with a negative spherically shaped ceramic disc. The end of the shaft protruding from the bearing housing is provided with a lever against the rear side of which a wave spring rests, the opposite side thereof being in contact with a bush which is, in turn, in contact with the ceramic disc. The sealing disc pressed on the shaft is urged against the stationary ceramic disc by the wave spring. The outer bush is, however, thereby subjected to exposure to spray water in the internal combustion engine. 
     The components in each of these two above-described exhaust gas flap sealing systems must be manufactured with an extremely high precision in order to provide sufficient sealing since the correspondingly shaped surfaces would otherwise have no sealing effect. An ingress of corrosive substances into the bearing region from outside cannot therefore be prevented in a reliable manner. A great number of components is moreover required, which results in an increased assembly effort. 
     SUMMARY 
     An aspect of the present invention is to provide a flap device for an internal combustion engine, wherein a safe sealing to the outside is obtained independent of the the thermal load and thermal expansion resulting therefrom, and where an ingress of corrosive substances from outside is prevented. A further aspect of the present invention is that the sealing be manufactured as economically as possible so that narrow manufacturing tolerances can be omitted and a simple assembly provided. 
     In an embodiment, the present invention provides a flap device for an internal combustion engine which includes a flow housing comprising a flow channel, an actuating shaft, a flap body arranged on the actuating shaft in the flow channel, a housing bore arranged in the flow housing, a lever fixed on the actuating shaft, a bearing bush arranged in the housing bore, and a sealing disk comprising a surface which is configured to be at least partially spherically shaped. The housing bore is configured to have the actuating shaft protrude outwards therethrough. The lever comprises a rear wall. The bearing bush is configured to have the actuating shaft be mounted therein. The surface is configured to rest under tension against the rear wall of the lever. Due to the at least partly spherically shaped surface which rests under tension against a rear wall of the lever, the number of components is reduced and assembly is thereby facilitated. The lever is for the first time also used as a part of the sealing by preventing a flow along the shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
         FIG. 1  shows a side elevational view of a flap device of the present invention in section. 
     
    
    
     DETAILED DESCRIPTION 
     In an embodiment of the present invention, the surface of the sealing disc can, for example, be formed with a positive spherical shape and the rear wall of the lever can, for example, be formed at least partly with a negative spherical or conical shape, the radius of curvature of the surface being smaller than the radius of curvature of the lever rear wall. In an alternative embodiment of the present invention, the lever rear wall can, for example, be formed at least partly with a positive spherical shape and the surface of the sealing disc can, for example, be formed with a negative spherical shape, the radius of curvature of the surface being greater than the radius of curvature of the lever rear wall. Both embodiments provide a linear contact between the lever and the sealing disc which is obtained even when errors in parallelism exist. An ingress of gases or liquids into the bearing region through the gap between the lever and the sealing disc is thereby reliably prevented. 
     It should be pointed out that throughout the present application, a positive spherical shape of a body refers to a body with a partly spherical surface whose radius of curvature extends through the body, and that a negative spherical shape of a body refers to a body with a partly hollow-spherical shape whose radius of curvature is directed to the side opposite the body. 
     The sealing disc may advantageously be arranged to be movable with respect to the actuating shaft and to surround the actuating shaft radially so that a tilting of the sealing disc relative to the shaft is possible. This leads to a secure sealing and a simultaneous insensitivity in the event of occurring thermal expansions. 
     In an embodiment of the present invention, a spring can, for example, load the lever with the actuating shaft towards the channel. The required tension for generating the pressing force between the lever and the sealing disc is thus generated in a simple manner. 
     In an embodiment of the present invention, the plane surface of the sealing disc axially opposite the spherically curved surface can, for example, rest on the bearing bush in a planar and tensioned manner. A sealing between the bearing bush and the sealing disc is thus also formed without having to use additional components. 
     In an embodiment of the present invention, the bearing bush can, for example, be a carbon bearing bush that is insensitive to thermal and corrosive loads caused by the exhaust gas. 
     In order to provide the tensioning of the entire bearing and sealing unit, the axial end of the bearing bush opposite the sealing disc rests on a stop of the housing bore. The entire unit is thus pressed against this stop by the spring and is tensioned thereby. 
     In an embodiment of the present invention, the actuating shaft can, for example, be formed in a convex shape in the region situated radially inward with respect to the bearing bush. A secure bearing without the occurrence of inner tensions is thus also provided if misalignments exist between the bearing bush and the actuating shaft. 
     In an embodiment of the present invention, the actuating shaft and the housing bore can, for example, each comprise at least one shoulder between the channel and the bearing bush. These shoulders act as a labyrinth seal and increase the flow resistance along the shaft so that an ingress of exhaust gas into the bearing becomes significantly more difficult. 
     In order to prevent an ingress of liquid or salt along the shaft from outside, the lever is connected with the actuating shaft in a material circumferential or a form-fitting tight manner. This connection is tight and has a long useful life. 
     It can further be advantageous if the lever has a sleeve arranged thereon which extends in the direction of the flow channel. The region of the housing that accommodates the bearing is thus additionally shielded from the outside so that a direct contact, for example, with spray water, is avoided. 
     A flap device for an internal combustion engine is thus provided which is sufficiently tight both to the outside and to the inside even under varying thermal conditions because component and assembly tolerances, as well as thermal expansions, and errors in alignment and parallelism, are compensated for in the present structure by the flexibility of the sealing disc position without limiting the sealing effect. The assembly of this sealing and bearing as well as the manufacture of the components is simple so that costs are significantly reduced. This bearing and sealing still have a long useful life. 
     An embodiment of a flap device of the present invention is illustrated in the drawing and will be described hereunder. 
     The flap device of the present invention comprises a flow housing  10  in which a flow channel  12  is formed through which, for example, exhaust gas flows. 
     The flow channel  12  is divided in cross section into two halves by an actuating shaft  14  on which a flap body  16  is fastened by means of a screw  18 , with a material connection also being possible. The actuating shaft  14  is supported in the flow housing  10  by two bearing bushes  20 ,  22 , wherein the first bearing bush  20  is arranged in a continuous housing bore  24  through which the actuating shaft  14  extends outward from the flow housing  10 , and the second bearing bush  22  is arranged on the side opposite the continuous housing bore  24  in a blind hole  26  formed in the flow housing  10 . The actuating shaft  14  is correspondingly supported on two sides of the flow housing  14  opposite to each other with respect to the center axis. 
     On the end of the actuating shaft  14  protruding outward, a disc serving as a lever  28  is fastened by a material connection in the form of a circumferential weld joint  30  at the radial end portion of which a pin  32  is fastened via which the actuating shaft  14  can be connected with an actuator through a linkage (not illustrated herein), which actuator may be designed in particular as an electric motor. By virtue of the circumferential weld joint  30 , no gas or liquid can flow between the actuating shaft  14  and the lever  28 . 
     The continuous housing bore  24  is of a step-shaped design and accordingly has three sections  34 ,  36 ,  38  with diameters becoming larger towards the outer side. The first section  34  with the smallest diameter defines the flow channel  12  and is slightly larger than the diameter of the actuating shaft  14 . Behind the first section  34 , as seen from the flow channel  12 , not only the continuous housing bore  24  has a shoulder  35 , but also the actuating shaft  14  has shoulder  40 , so that the actuating shaft  14  extends further outward with a larger diameter. This portion of the actuating shaft  14  is arranged radially in the second section  36  of the continuous housing bore  24 . The first shoulder  35  and the second shoulder  40  together form a labyrinth seal that hinders the ingress of exhaust gas in the direction of the first bearing bush  20 . 
     A shoulder of the continuous housing bore  24  is formed between the second section  36  and the third section  38  that serves as a stop  42 . The first bearing bush  20  designed as a carbon bearing rests on this stop  42  in the axial direction. The first bearing bush  20  is fastened by press-fitting in the third section  38  of the continuous housing bore  24  and surrounds and supports the actuating shaft  14  which is of a convex shape in the portion  44  situated radially inward with respect to the first bearing bush  20 . The opposite axial end of the first bearing bush  20  extends slightly beyond this bearing portion of the flow housing  10  in the axial direction and rests on a sealing disc  46  radially surrounding the actuating shaft  14  with a slight distance therebetween, wherein the face  48  of the sealing disc  46  that faces the first bearing bush  20  is of a planar design. 
     According to the present invention, an axially opposite surface of the sealing disc  46  has a spherically curved surface  50  in its radially outer region. This spherically shaped surface  50  rests directly on a rear wall  52  of the lever  28 . To provide a reliable sealing between the rear wall  52  of the lever  28  and the sealing disc  46 , the rear wall  52  also has a curvature, although a negative spherical curvature, which in the present application always means that the center of the radius of the sphere is arranged on a side of the curved surface opposite to the lever  28 . The radius of curvature of this spherically shaped region of the rear wall  52  should be chosen to be larger than the radius of curvature of the sealing disc  42  in the corresponding region. An annular linear contact thereby always exists between the rear wall  52  of the lever  28  and the sealing disc  46 . 
     At its outer circumference, the lever  28  has a sleeve  54  extending toward the flow housing  10  that at least partly surrounds the first bearing portion  20  of the flow housing  10  in the radial direction. 
       FIG. 1  further shows a schematically illustrated spring  56  which exerts a spring force on the lever  28  in the direction towards the flow channel  12 . The illustration of the spring  56  is schematical since the force application point of the spring  56  and the design and arrangement of the spring  56  are variable to a large extent. It is, for example, conceivable that spring  56  can be designed as a compression spring or as a tension spring. It may at the same time also serve as a return spring and act on the lever  28 , for example, via sleeve  54 . 
     It is essential to the present invention that a force be generated on the actuating shaft  14  or the lever  28  firmly connected therewith, the force acting in the direction of the second bearing bush  22  or in the direction of the flow channel  12 . By this force, which in the shown embodiment is exerted by the spring  56 , the rear wall  52  of the lever  28  with its negative spherical surface is pressed against the spherically shaped surface  50  of the sealing disc. The sealing disc  46  is at the same time pressed with its face  48  against the first axial end of the first bearing bush  20  and at the same is in turn pressed against stop  42 . Since the actuating shaft  14  can be tilted slightly in the first bearing bus  20 , and thereby the lever  28  can also be tilted slightly with respect to the axis, and since the sealing disc  46  is arranged to be movable relative to the actuating shaft  14  and to surround the actuating shaft  14 , the face  48  of the sealing disc  46  always rests on the first bearing bush  20  in a planar manner and is in linear circumferential contact with the rear wall  52  of the lever  28  even if slight errors of alignment and parallelism exist. It is thereby achieved that no dirty water, salt, or other contaminants can reach the bearing surface of the first bearing bush  20  from the outside since no gaps are present, be it along the actuating shaft  14  or on the radial outer side. No exhaust gas can further escape to the outside from the flow channel  12  since the circumferential weld joint  30  provides for a sealing along the actuating shaft  14  to the lever  28  and a radial escape of exhaust gas is avoided by the two sealing surfaces, face  48  and spherically shaped surface  50 , of the sealing disc  46 . When the actuating shaft  14  is rotated with the lever  28  via the actuator, a relative movement between the first bearing bush  20  and the sealing disc  26  is obtained, which, due to the large planar contact surface, can, however, slide thereon without much wear and with the sealing effect remaining unchanged. 
     If component and assembly tolerances not taken into account occur during operation or if, for example, due to varying thermal loads, thermal expansion or wear caused by use occur, an ever sufficient sealing is thereby provided in both directions since the position of the sealing disc  46  and the position of the actuating shaft  14  will adapt in a corresponding manner. The ingress of dirt from the outside is hindered by the sleeve which prevents a direct contact with dirty water. The flap device and its sealing have a long service life due to low wear and are simple to mount because of the low number of components. 
     It should be clear that the scope of protection is not restricted to the flap device described, but that various modifications and structural changes are conceivable. The press force can in particular be applied in different ways. The connection between the shaft and the lever can also be realized in different ways. The two spherical surfaces of the lever and the sealing disc may also each be curved in the opposite direction. Reference should be had to the appended claims.