Abstract:
A sealing arrangement for a control device of an internal combustion engine includes a housing. A channel is formed in the housing. The channel has a gas flow therethrough. A control member controls a flow of the gas in the channel. The control member is arranged on a shaft. A bearing supports the shaft in a bearing bore of the housing. A vent bore extends in the housing from an inner wall of the channel on an inlet side of the control member to a rear side, facing outward from the channel, of the bearing arranged in the housing, and into the bearing bore. A first groove is formed in the shaft behind the bearing. The first groove is configured so as to be circumferential when seen from the channel. The first groove is surrounded radially by a sealing device which is configured to cooperate with the first groove.

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/EP2010/070056, filed on Dec. 17, 2010 and which claims benefit to German Patent Application No. 10 2010 006 023.2, filed on Jan. 27, 2010. The International Application was published in German on Aug. 4, 2011 as WO 2011/091909 A1 under PCT Article 21(2). 
     FIELD 
     The present invention relates to a sealing arrangement for a control device of an internal combustion engine, comprising a housing, a channel arranged in the housing and through which gas flows, a control member by which a gas flow in the channel can be controlled, a shaft on which the control member is arranged, bearings by means of which the shaft is supported in bearing bores in the housing, and a vent bore extending in the housing from an inner wall of the channel on an inlet side of the control member to a rear side, facing out from the channel, of the bearings arranged in the housing, and into the bearing bore. 
     BACKGROUND 
     Such sealing arrangements are used, for example, in control devices, such as exhaust gas recirculation flap valves, for controlling a recirculated exhaust gas flow in commercial vehicles, where large quantities of exhaust gas must be supplied to the engine in a precisely controlled manner. It is necessary here to prevent the intrusion of exhaust gas into the bearings and, further, to prevent the gas from flowing through the bearing bore out into the atmosphere. 
     DE 10 2006 054 041 B3 discloses an exhaust gas control device comprising a housing in which an exhaust gas recirculation channel is formed that is controlled by a flap. This flap is driven by an electric motor via a transmission unit and is arranged for rotation on a shaft that is supported in bearing bores formed in the housing defining the channel. In order to prevent the intrusion of exhaust gas, and thus soot, into the bearings, and to simultaneously prevent a leakage gas flow to the outside, the housing is provided with a bore leading from the front side of the flap out from the channel to the rear side of the bearing and into the bearing bore. A sealing flow thus prevails on the rear side of the bearing that leads to a pressure balance with the inside of the channel so that the exhaust gas flow is not drawn into the bearing. To the outside, sealing is provided by means of a sealing disc abutting against a step of the bearing bore. This sealing disc is pressed against the step of the bearing bore by means of a spring via a collar bush and a sliding bush arranged between the collar bush and the sealing disc. The sliding bush serves to reduce friction, whereas a radially directed escape of a leakage flow is supposed to be prevented by the sealing disc and an escape is intended to be realized in the axial direction along the shaft via the axial extension of the collar bush which therefore forms a very narrow and long gap with the shaft. 
     It has, however, been found that such a design is insufficient with respect to the leakage values. The necessity of precise manufacturing furthermore results in high production costs. 
     SUMMARY 
     An aspect of the present invention is to provide a sealing arrangement for a control device with which the leakage values can be further minimized or with which it is possible at least to obtain cost advantages and assembly facilitations, while the leakage values remain the same. 
     In an embodiment, the present invention provides a sealing arrangement for a control device of an internal combustion engine which includes a housing. A channel is formed in the housing. The channel is configured to have a gas flow therethrough. A control member is configured to control a flow of the gas in the channel. The control member is arranged on a shaft. A bearing is configured to support the shaft in a bearing bore of the housing. A vent bore extends in the housing from an inner wall of the channel on an inlet side of the control member to a rear side, facing outward from the channel, of the bearing arranged in the housing, and into the bearing bore. A first groove is formed in the shaft behind the bearing. The first groove is configured so as to be circumferential when seen from the channel. The first groove is surrounded radially by a sealing device which is configured to cooperate with the first groove. 
    
    
     
       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 sealing arrangement according to the present invention, illustrated in section; 
         FIG. 2  shows a side elevational view of a slightly modified form of the sealing arrangement of the present invention shown in  FIG. 1 , illustrated in section; 
         FIG. 3  shows a side elevational view of an alternative sealing arrangement of the present invention, illustrated in section; and 
         FIG. 4  shows a side elevational view of a slightly modified form of the sealing arrangement of the present invention shown in  FIG. 3 , illustrated in section. 
     
    
    
     DETAILED DESCRIPTION 
     By forming a circumferential groove on the shaft behind the bearing, seen from the channel, which grove is radially surrounded by a sealing means cooperating with the groove, the forming of turbulences in the groove or an improved sealing by the groove is achieved, the groove serving as a labyrinth. 
     In an embodiment of the present invention, the groove of the shaft can, for example, be arranged radially within a collar bush serving as a further sealing means and being arranged on the shaft. This results in the forming of turbulences in the groove, whereby the resistance against a further flow through the gap between the shaft and the collar bush is increased significantly. 
     In an embodiment of the present invention, the inner circumference of the collar bushing is provided with a groove. A second opposite turbulence is thereby obtained that again increases the resistance against a flow through the gap and thereby improves the sealing effect. 
     In an embodiment of the present invention, the groove closer to the bearing has a larger volume than the farther groove. Additional pressure reduction is thereby achieved so that the driving pressure gradient is minimized. 
     In an embodiment of the present invention, the groove in the collar bush can, for example, be closer to the bearing than the groove in the shaft. The same groove lengths and groove depths can thus be used. 
     In an embodiment of the present invention, the collar bush can, for example, be biased by a spring against a sliding disc arranged on the shaft, which abuts against the housing from outside. The friction occurring can thus be minimized. At the same time, the sliding disc serves as a sealing against a radially outward directed leakage flow. 
     In an embodiment of the present invention, a slit metal sealing ring is arranged in the shaft groove which serves as an additional sealing means. This sealing ring, known as a piston ring, can be manufactured at low cost and is simple to assemble. The sealing effect of such a slit metal sealing ring in a groove is very high. 
     In an embodiment of the present invention, the slit metal sealing ring can, for example, be biased against an inner circumferential wall of the bearing bore, whereby a sealing at the radially outer circumference of the slit metal sealing ring is provided in addition to the sealing of the radially inner portion that is sealed by the cooperation of the sealing ring and the groove. 
     In an embodiment of the present invention, the slit metal sealing ring is biased to axially abut against a shoulder serving as a stop formed in the bearing bore. This additionally prevents a flow around the outer circumference of the sealing ring since the radially outer portion of the sealing ring abuts against the housing in the axial and the radial direction. 
     In an embodiment of the present invention, the two ends of the slit metal sealing ring can, for example, abut in the axial direction. A leakage flow through the separating gap of the sealing ring is thereby reliably prevented. 
     The present sealing arrangement for a control device is characterized by a high degree of tightness. Leakage flows along the shaft are reliably avoided. This leads to a longer lifetime of the bearings and to a reduced soiling of the outer portion. At the same time, such an arrangement can be manufactured and assembled in a cost-effective manner. 
     Two embodiments of a sealing ring arrangement according to the present invention are illustrated in the Figures and will be described hereunder. 
     The sealing arrangement for a control device illustrated in  FIG. 1  comprises a housing  2  defining a channel  4  in which a flap is arranged for rotation therein, the flap serving as a control member  6  for controlling the mass flow in the channel  4  and being mounted on a shaft  8 . The shaft  8  extends from one wall of the housing  2 , in which a first bearing bore is arranged, to an opposite wall in which a further bearing bore  10  is arranged, the Figures respectively illustrating only the bearing bore  10  through which the shaft extends outward to a non-illustrated actuator unit. 
     A bearing  12  is arranged in the bearing bore  10 , which bearing surrounds the shaft  8  and by which the shaft  8  is supported in the bearing bore  10 . Upstream of the shaft  8 , seen in the flow direction, a vent bore  14  is formed that extends from an inner wall  16  of the channel  4  through the housing  2  up to a rear side  18  of the bearing  12  and into the bearing bore  10 . The gas present at the rear side  18  acts as a sealing gas. A pressure drop across the bearing  12 , i.e., a pressure difference between the channel  4  and the outer portion, is thereby prevented so that the entraining of dirt from the channel  4  into the bearing  12  is reduced, whereby the lifetime of the bearing  12  is extended. 
     In order to also prevent the sealing gas from escaping to the outside, a sliding disc  20  arranged on the shaft  8  abuts against the housing  2 . The sliding disc  20  has an inner diameter that substantially corresponds to the outer diameter of the shaft and an outer diameter that is larger than the diameter of the bearing bore  10  so that the abutment of the sliding disc  20  across the entire diameter of the bearing bore  10  is provided. 
     On the side of the sliding disc  20  axially opposite the housing  2  and the bearing bore  10 , a collar bush  22  is arranged on the shaft  8 . This collar bush  22  is pressed by a spring  24  against the sliding disc  20  and thus against the housing  2 . For this purpose, the spring  24  is supported on a plate  26  fastened on the shaft  8  and at the end thereof, the plate serving as a lever for adjusting the shaft  8 . Correspondingly biased, the spring  24  abuts against the plate  26  by its first end, and its second end abuts against a shoulder  28  formed on the outer diameter of the collar bush  22 . 
     In order to additionally prevent a leakage flow along the shaft  8  between the shaft  8  and the collar bush  22 , the inner diameter of the collar bush  22  and the outer diameter of the shaft  8  are formed with a respective groove  30 ,  32 . In  FIG. 1 , the groove  30  formed in the shaft  8  is closer to the bearing  12  than the groove  32  of the collar bush  22 . The collar bush  22  here serves as a sealing means cooperating with the groove  30  since it closes the groove  30  in the radial direction and thereby allows the forming of turbulences in the groove  30 . In addition, the volume of the groove  30  is smaller than that of the groove  32 . A further pressure reduction is thus achieved. 
     When a gas flows through the channel  4 , there is a risk that this gas escapes outward along the shaft  8  between the bearing  12  and the shaft  8 . If high pressure prevails in the channel  4 , an outward directed driving pressure gradient exists. Due to the vent bore  14 , the same pressure prevails behind the bearing  12  as in the channel so that a flow along the bearing can be reduced significantly. 
     In addition, however, care should be taken that no gas can escape outward through the vent bore  14  due to the pressure difference prevailing there. Gas flowing along the shaft  8  and into the gap between the collar bush  22  and the shaft  8  will first reach the groove  32 . Due to the additional space existing there, a turbulence forms in the groove, whereby a flow resistance is created. The same occurs in the groove  30  disposed therebehind. Due to the fact, however, that this groove  30  has a smaller volume, the pressure is reduced relative to the groove  32  so that the driving pressure gradient is reduced. Because of these measures, the leakage values can be reduced significantly. 
     The embodiment in  FIG. 2  differs from that in  FIG. 1  only in that the groove  32  of the collar bush  22  is closer to the bearing  12  than the groove  30  in the shaft  8 . The functioning is, however, substantially identical to that described with reference to  FIG. 1 , while it is again possible to make the groove  32  smaller than the groove  30  in the shaft  8  in order to intensify the sealing effect. 
     In the embodiment of the present invention illustrated in  FIG. 3 , a slit metal sealing ring  34  is provided in the groove  30  as a sealing means cooperating with the same, the ring being arranged in the groove  30 . Seen from the channel  4 , the groove is again arranged behind an opening of the vent bore  14  into the bearing bore  10 . Contrary to the previously described embodiments illustrated in  FIGS. 1 and 2 , the groove  30  and the slit metal sealing ring  34  are situated radially inside the bearing bore  10 . The outer circumference of the sealing ring  34  is biased to abut against an inner circumferential wall  38  of the bearing bore  10 . In the context of the present application, a slit metal sealing ring is a kind of piston ring that has an axial separation plane so that its diameter is slightly variable. The separation plane can, for example, not be strictly axial, but extend obliquely, i.e., under an angle to the center axis, or extend in a step-like manner so that an axially continuous gap is avoided that could serve as a flow gap with little flow resistance. The two ends of the sealing ring  34  accordingly at least abut against each other in the axial direction. 
     A sealing effect in the groove  30 , i.e., at the inner circumference of the sealing ring  34 , is produced by the existing pressure difference by which the sealing ring  34  is pressed against the wall  40  axially delimiting the groove  30 . In this embodiment, the collar bush can therefore be omitted. 
     In  FIG. 4 , another modification of the embodiment illustrated in  FIG. 1  is shown. Here, the sealing ring  34  abuts against a shoulder  42  formed, seen from the channel  4 , immediately behind the opening  36  of the vent bore  14  into the bearing bore  10 . For a better sealing effect, the sealing ring  34  is pressed against the shoulder  42  by the spring  24  so that a gas flow in the radial direction is prevented by means of the abutment surface of the sealing ring  34 . The gas will accordingly not reach the outer circumference of the sealing ring  34 . 
     Sealing arrangements for control devices are thus provided that achieve a good sealing effect both along the shaft and across the circumference of the sealing elements. Clearly better leakage values can thus be achieved, while the control devices remain cost-effective to produce and simple to assemble. 
     It should be understood that the scope of protection is not limited to the embodiments described herein, but that various structural modifications are conceivable, in particular with respect to the structure of the control device, depending on the application.