Abstract:
A sealing system for an exhaust gas recirculation valve, the exhaust gas recirculation valve including a housing and a valve stem disposed in the housing, the sealing system being disposed between the housing and the valve stem in order to prevent exhaust gas from entering a valve body interior. The sealing system includes at least two sealing assemblies. An exhaust gas recirculation valve includes the sealing system, and the sealing system effectively prevents exhaust gas from leaking into the valve body interior, and effectively prevents carbon deposits from sticking to the valve stem or entering the valve body interior, so as to increase the lifespan and reliability of the exhaust gas recirculation valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of PCT Application PCT/EP2015/076102, filed Nov. 9, 2015, which claims priority to Chinese Application 201420666603.0, filed Nov. 10, 2014. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a sealing system, in particular to a sealing system for an exhaust gas recirculation valve. The present invention also relates to an exhaust gas recirculation valve which includes the sealing system. 
       BACKGROUND OF THE INVENTION 
       [0003]    During the operation of an engine, in order to reduce NOx emissions, a portion of exhaust gas is led into the air intake pipe, and mixed with fresh air or atomized gas mixture before entering the engine cylinders to undergo combustion—this is known as exhaust gas recirculation. However, if too much exhaust gas takes part in recirculation, the engine&#39;s performance will be affected. Therefore the rate of exhaust gas recirculation should be controlled, so as to lower the content of pollutants emitted by the vehicle without lowering the engine&#39;s performance. 
         [0004]    An exhaust gas recirculation valve is generally used to regulate the exhaust gas recirculation rate. Specifically, the degree of opening of the exhaust gas recirculation valve is controlled according to the operating conditions of the engine, in order to regulate the exhaust gas recirculation rate. For example, when the engine is idling or under full load, the exhaust gas recirculation valve is closed; when the engine is under a partial load, the exhaust gas recirculation valve is opened. 
         [0005]    The exhaust gas recirculation valve generally includes a sealing system, to prevent exhaust gas and carbon deposits from entering the valve body interior. Ingress of exhaust gas into the valve body interior will cause corrosion of internal valve members, thereby shortening the life of the exhaust gas recirculation valve. Accumulation of carbon deposits on the valve stem will cause increased resistance to movement of the valve stem or even seizure thereof. 
         [0006]    Existing exhaust gas recirculation valve sealing systems generally only include one set of sealing elements, but this is unlikely to completely prevent exhaust gas leakage. Moreover, carbon deposits are likely to stick to the valve stem or even enter the valve body interior; as a result, valve life is reduced and valve reliability cannot be guaranteed. 
       SUMMARY OF THE INVENTION 
       [0007]    One of the technical problems to be solved by the present invention is to provide a sealing system capable of effectively preventing exhaust gas from leaking into the valve body interior and effectively preventing carbon deposits from sticking to the valve stem or even entering the valve body interior, so as to increase the lifespan and reliability of the exhaust gas recirculation valve. 
         [0008]    To this end, the present invention provides a sealing system for an exhaust gas recirculation valve, the exhaust gas recirculation valve includes a housing and a valve stem disposed in the housing, the sealing system being disposed between the housing and the valve stem in order to prevent exhaust gas from entering a valve body interior, where the sealing system includes at least two sealing assemblies. 
         [0009]    Preferably, the sealing system includes two sealing assemblies, i.e. an upper sealing assembly and a lower sealing assembly. 
         [0010]    Advantageously, a vent hole may be disposed on the housing between the upper sealing assembly and the lower sealing assembly, in order to discharge exhaust gas which enters a region between the upper sealing assembly and the lower sealing assembly. As components age, it is possible that a very small amount of exhaust gas will leak through the lower sealing assembly into a space between the upper sealing assembly and the lower sealing assembly. Through the provision of the vent hole, the shock caused to the upper sealing assembly by pressurized exhaust gas is reduced, thereby helping to ensure the sealing effect. 
         [0011]    Preferably, the vent hole is disposed below and immediately adjacent to the upper sealing assembly. 
         [0012]    Since the lower sealing assembly is closer than the upper sealing assembly to the end at which exhaust gas enters and is therefore subject to higher pressure, the lower sealing assembly may advantageously be set to have a higher compressibility than the upper sealing assembly. 
         [0013]    Advantageously, the sealing assembly may be formed of a support ring and an O-ring fitted tightly round an outer surface of the support ring, the support ring may be made of polytetrafluoroethylene material, and the O-ring may be flexible. Due to the lubricating properties of polytetrafluoroethylene material, when the support ring is fitted closely and rigidly on the valve stem to prevent exhaust gas and carbon deposits from passing between the support ring and valve stem to enter the valve body interior, the support ring may also allow the valve stem to move up and down freely. The flexible O-ring allows a close fit between itself and an inner wall of the housing, to prevent exhaust gas and carbon deposits from passing between the O-ring and the housing to enter the valve body interior. 
         [0014]    Advantageously, the exhaust gas recirculation valve may also include a bushing disposed around the valve stem, for guiding the valve stem during movement of the valve stem up and down; the upper sealing assembly is disposed at an upper end of the bushing and kept fixed by an upper spacer, while the lower sealing assembly is disposed at a lower end of the bushing and kept fixed by a lower spacer. 
         [0015]    Advantageously, the sealing system may also include a carbon scraper disposed below the sealing assemblies and press-fitted in the housing. 
         [0016]    According to an embodiment of the present invention, the carbon scraper includes a vertical cylindrical part, the vertical cylindrical part includes an upper cylindrical part and a lower cylindrical part, and the diameter of the lower cylindrical part being slightly smaller than the diameter of the upper cylindrical part, to facilitate press-fitting into the housing and scrape carbon deposits away more effectively. 
         [0017]    Alternatively, the carbon scraper includes a vertical cylindrical part, the vertical cylindrical part having at a lower end thereof a part with reduced internal diameter. Similarly, the part with reduced internal diameter may likewise serve the functions of facilitating press-fitting into the housing and scraping carbon deposits away more effectively. 
         [0018]    Alternatively, the carbon scraper includes a vertical cylindrical part, the vertical cylindrical part having an inverted cone shape. Similarly, the vertical cylindrical part having an inverted cone shape may likewise serve the functions of facilitating press-fitting into the housing and scraping carbon deposits away more effectively. 
         [0019]    Preferably, the carbon scraper may also include an increased-diameter part above the vertical cylindrical part, for causing back-flow of exhaust gas entering the carbon scraper. 
         [0020]    The present invention also relates to an exhaust gas recirculation valve, including a housing and a valve stem disposed in the housing. The exhaust gas recirculation valve also includes a sealing system as described above, disposed between the housing and the valve stem. 
         [0021]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0023]      FIG. 1  is a partial section view of an exhaust gas recirculation valve, with the sealing system exposed, according to embodiments of the present invention; 
           [0024]      FIG. 2  is a partial perspective view of an exhaust gas recirculation valve, showing the flow path of exhaust gas according to embodiments of the present invention; 
           [0025]      FIG. 3  is an enlarged sectional view of a sealing system, according to embodiments of the present invention; 
           [0026]      FIG. 4  is a side view of a sealing assembly used as part of a sealing system, according to embodiments of the present invention; 
           [0027]      FIG. 5  is a perspective view of a sealing assembly used as part of a sealing system, according to embodiments of the present invention; 
           [0028]      FIG. 6  is a sectional view of a carbon scraper used in an exhaust gas recirculation valve, according to embodiments of the present invention; 
           [0029]      FIG. 7  is a perspective view of a carbon scraper used in an exhaust gas recirculation valve, according to embodiments of the present invention; 
           [0030]      FIG. 8  is a sectional view of an alternate embodiment of a carbon scraper for an exhaust gas recirculation valve, according to embodiments of the present invention; and 
           [0031]      FIG. 9  is a perspective view of an alternate embodiment of a carbon scraper for an exhaust gas recirculation valve, according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0033]    A sealing system according to embodiments of the present invention and an exhaust gas recirculation valve including the sealing system are described below with reference to the accompanying drawings. In the description below, many specific details are expounded in order to give those skilled in the art a more comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the implementation of the present invention may omit some of these specific details. Furthermore, it should be understood that the present invention is not limited to the specific embodiments presented. On the contrary, consideration may be given to using any combination of the features and key elements below to implement the present invention, regardless of whether they relate to different embodiments. Therefore the aspects, features, embodiments and advantages below serve merely an illustrative purpose, and should not be regarded as key elements or limitations of the claims, unless explicitly set out in the claims. 
         [0034]    The structure and function of the sealing system are described in detail below with reference to particular embodiments of the exhaust gas recirculation valve. 
         [0035]    As  FIG. 1  shows, an exhaust gas recirculation valve  1  includes a housing  2  and a valve stem  3  disposed in the housing  2 . The exhaust gas recirculation valve  1  also includes a bushing  4  disposed around the valve stem  3 , for guiding the valve stem  3  during movement of the valve stem  3  up and down. A valve head  5  is disposed at a bottom end of the valve stem  3 . When the valve stem  3  causes the valve head  5  to leave a valve seat  6  under the action of a drive means (not shown), exhaust gas enters a space V enclosed by the housing  2  through a gap between the valve head  5  and the valve seat  6 , and then enters an air intake manifold of an engine through an opening  21  on the housing  2  (as shown by arrow A in  FIG. 2 ), to realize exhaust gas recirculation. 
         [0036]    During this process, a small amount of exhaust gas will enter a gap between a carbon scraper  7  and a valve stem  3 , as shown by arrow B in  FIG. 2 . In order to prevent exhaust gas from then entering the valve body interior, a sealing system  8  is disposed between the housing  2  and the valve stem  3 , as shown in  FIGS. 1 and 3 . The sealing system  8  includes an upper sealing assembly  81  and a lower sealing assembly  82 . The upper sealing assembly  81  is disposed at an upper end of the bushing  4  and kept fixed by an upper spacer  9 . The lower sealing assembly  82  is disposed at a lower end of the bushing  4  and kept fixed by a lower spacer  10 . Optionally, a greater number of sealing assemblies may be provided. 
         [0037]    As  FIGS. 4 and 5  show, the upper sealing assembly  81  and the lower sealing assembly  82  are each formed of a support ring  810  and an O-ring  811  fitted tightly round an outer surface of the support ring  810 . The support ring  810  is fitted closely and rigidly on the valve stem  3 , and therefore effectively prevents exhaust gas and carbon deposits from passing between the support ring  810  and valve stem  3  to enter the valve body interior. The support ring  810  is made of polytetrafluoroethylene material. Due to the lubricating properties of polytetrafluoroethylene material, the support ring  810  allows the valve stem  3  to move up and down freely. The O-ring  811  is flexible, e.g. a rubber O-ring commonly seen on the market. The O-ring  811  is fitted closely to an inner wall of the housing  2 , thereby effectively preventing exhaust gas and carbon deposits from passing between the O-ring  811  and housing  2  to enter the valve body interior. 
         [0038]    Advantageously, as  FIG. 3  shows, a vent hole  11  may also be disposed on the housing  2  between the upper sealing assembly  81  and lower sealing assembly  82 , to discharge any exhaust gas which might leak in from the lower sealing assembly  82 . Preferably, the vent hole  11  is disposed below and immediately adjacent to the upper sealing assembly  81 . 
         [0039]    Preferably, as  FIGS. 1 and 3  show, a carbon scraper  7  may be disposed below the lower sealing assembly  82 , in order to scrape away, during movement of the valve stem  3  up and down, any carbon deposits which might stick to the valve stem  3 , thereby preventing excessive resistance to the movement of the valve stem  3  or even seizure thereof. In order to serve the function of scraping away carbon deposits effectively, an inner wall of the carbon scraper  7  should be disposed as close as possible to the valve stem  3 , but should not obstruct free movement of the valve stem  3 . 
         [0040]      FIGS. 6 and 7  show a carbon scraper  7  according to an embodiment of the present invention, the carbon scraper  7  including a vertical cylindrical part. The vertical cylindrical part includes an upper cylindrical part  712  and a lower cylindrical part  713 . The diameter of the lower cylindrical part  713  is slightly smaller than the diameter of the upper cylindrical part  712 , to facilitate press-fitting into the housing  2  and scrape carbon deposits away more effectively. Advantageously, the carbon scraper  7  also includes an upper flange  711 . The carbon scraper  7  is press-fitted in the housing  2  by means of the upper flange  711  and the upper cylindrical part  712 , as  FIG. 3  shows. Optionally, the vertical cylindrical part of the carbon scraper  7  may have an inverted cone shape, so as to likewise serve the functions of facilitating press-fitting into the housing  2  and scraping carbon deposits away more effectively. 
         [0041]      FIGS. 8 and 9  show a carbon scraper  7 ′ according to another embodiment of the present invention. The carbon scraper  7 ′ includes a vertical cylindrical part, the vertical cylindrical part having at a lower end thereof a part with reduced internal diameter  713 ′, for scraping away any carbon deposits which might stick to the valve stem  3 . Advantageously, the carbon scraper  7 ′ is provided with an increased-diameter part  711 ′ above the vertical cylindrical part, thereby forming a cavity relative to the valve stem  3 ; this enables back-flow of exhaust gas entering the carbon scraper  7 ′, thereby reducing the pressure shock caused to the sealing assemblies by the gas flow, reducing the loss in performance of the sealing assemblies, and improving the sealing effect. Clearly, in the case of the previous embodiment of the carbon scraper, an increased-diameter part could also be disposed above the vertical cylindrical part, to enable back-flow of exhaust gas entering the carbon scraper. 
         [0042]    As  FIGS. 1 and 2  show, when the exhaust gas recirculation valve  1  is opened to allow recirculation of exhaust gas, the valve head  5  leaves the valve seat  6 , and exhaust gas enters the space V enclosed by the housing  2  through the gap between the valve head  5  and valve seat  6 . At this time, a small amount of exhaust gas will enter a space between the housing  2  and the lower sealing assembly  82  through the gap between the carbon scraper  7  and the valve stem  3 . Due to the sealing effect of the lower sealing assembly  82 , exhaust gas cannot then enter the valve body interior. However, as components age, it is possible that a very small amount of exhaust gas will leak into the space between the upper sealing assembly  81  and the lower sealing assembly  82 . This very small amount of exhaust gas will be discharged from the sealing system  8  through the vent hole  11 ; this may reduce the shock caused to the upper sealing assembly  81  by pressurized exhaust gas. The upper sealing assembly  81  further ensures that exhaust gas is prevented from entering the valve body interior, e.g. from entering a valve drive means. According to the present invention, due to the double sealing effect of the upper sealing assembly  81  and lower sealing assembly  82 , it is ensured that exhaust gas is prevented from entering the valve body interior. 
         [0043]    Since the lower sealing assembly  82  is closer than the upper sealing assembly  81  to the end at which exhaust gas enters and is therefore subject to higher pressure, the lower sealing assembly  82  may be set to have a higher compressibility than the upper sealing assembly  81 . 
         [0044]    Although the present invention has been disclosed above by way of preferred embodiments, it is by no means limited to these. Changes and amendments of all kinds made by any person skilled in the art without departing from the spirit and scope of the present invention shall be included in the scope of protection thereof. Therefore the scope of protection of the present invention should be regarded as the scope defined by the claims. 
         [0045]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.