Sealing system and exhaust gas recirculation valve comprising same

Technical field

The present device relates to a sealing system, in particular to a sealing system for an exhaust gas recirculation valve. The present device also relates to an exhaust gas recirculation valve comprising the sealing system.

Background art 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'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' s performance . 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 re ^¬ circulation valve is closed; when the engine is under a partial load, the exhaust gas recirculation valve is opened.

The exhaust gas recirculation valve generally comprises 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.

Existing exhaust gas recirculation valve sealing systems generally only comprise 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.

Content of the utility model The technical problem to be solved by the present device 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 .

To this end, the present device provides a sealing system for an exhaust gas recirculation valve, the exhaust gas recirculation valve comprising 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, characterized in that the sealing system comprises at least two sealing assemblies.

Preferably, the sealing system comprises two sealing assemblies, i.e. an upper sealing assembly and a lower sealing assembly.

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 as ^¬ sembly. Through the provision of the vent hole, the shock caused to the upper sealing assembly by pressurized exhaust gas can be reduced, thereby helping to ensure the sealing effect.

Preferably, the vent hole is disposed below and immediately adjacent to the upper sealing assembly.

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.

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 can 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.

Advantageously, the exhaust gas recirculation valve may also comprise a bush 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 bush and kept fixed by an upper spacer, while the lower sealing assembly is disposed at a lower end of the bush and kept fixed by a lower spacer .

Advantageously, the sealing system may also comprise a carbon scraper disposed below the sealing assemblies and press-fitted in the housing.

According to an embodiment of the present utility model, the carbon scraper comprises a vertical cylindrical part, the vertical cylindrical part comprising 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.

Alternatively, the carbon scraper comprises a vertical cy ^¬ lindrical part, the vertical cylindrical part having at a lower end thereof a part with reduced internal diameter. Similarly, the part with reduced internal diameter can likewise serve the functions of facilitating press-fitting into the housing and scraping carbon deposits away more effectively.

Alternatively, the carbon scraper comprises a vertical cy ^¬ lindrical part, the vertical cylindrical part having an inverted cone shape. Similarly, the vertical cylindrical part having an inverted cone shape can likewise serve the functions of fa ^¬ cilitating press-fitting into the housing and scraping carbon deposits away more effectively. Preferably, the carbon scraper may also comprise an in- creased-diameter part above the vertical cylindrical part, for causing back-flow of exhaust gas entering the carbon scraper.

The present device also relates to an exhaust gas recirculation valve, comprising a housing and a valve stem disposed in the housing, characterized in that the exhaust gas recirculation valve also comprises a sealing system as described above, disposed between the housing and the valve stem.

Description of the accompanying drawings

The present device is described in detail below by way of non-limiting examples with reference to the accompanying drawings, wherein: Fig. 1 is a main view of an exhaust gas recirculation valve according to the present utility model, wherein part has been cut open to show the sealing system according to the present utility model ; Fig. 2 is a partial perspective drawing of an exhaust gas recirculation valve according to the present utility model, showing the flow path of exhaust gas;

Fig. 3 is a longitudinal sectional view of a sealing system according to the present utility model;

Fig. 4 and Fig. 5 are a main view and a perspective drawing, respectively, of a sealing assembly of a sealing system according to the present utility model;

Fig. 6 and Fig. 7 are a longitudinal sectional view and a perspective drawing, respectively, of an embodiment of a carbon scraper for an exhaust gas recirculation valve according to the present utility model.

Fig. 8 and Fig. 9 are a longitudinal sectional view and a perspective drawing, respectively, of another embodiment of a carbon scraper for an exhaust gas recirculation valve according to the present utility model.

Particular embodiments A sealing system according to embodiments of the present device and an exhaust gas recirculation valve comprising 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 utility model. However, it is obvious to those skilled in the art that the implementation of the present device may omit some of these specific details. Furthermore, it should be understood that the present device 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 utility model, regardless of whether they relate to different embodiments. Therefore the aspects, fea- tures, embodiments and advantages below serve merely an il ^¬ lustrative purpose, and should not be regarded as key elements or limitations of the claims, unless explicitly set out in the claims . The structure and function of the sealing system are described in detail below with reference to particular embodiments of the exhaust gas recirculation valve.

As Fig. 1 shows, an exhaust gas recirculation valve 1 comprises a housing 2 and a valve stem 3 disposed in the housing 2. The exhaust gas recirculation valve 1 also comprises a bush 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. ^

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 comprises an upper sealing assembly 81 and a lower sealing assembly 82. The upper sealing assembly 81 is disposed at an upper end of the bush 4 and kept fixed by an upper spacer 9. The lower sealing assembly 82 is disposed at a lower end of the bush 4 and kept fixed by a lower spacer 10. Optionally, a greater number of sealing assemblies may be provided .

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 can therefore effectively prevent 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 can allow 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. 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. _n

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.

Figs. 6 and 7 show a carbon scraper 7 according to an embodiment of the present utility model, the carbon scraper 7 comprising a vertical cylindrical part. The vertical cylindrical part comprises 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 comprises 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.

Figs. 8 and 9 show a carbon scraper 7' according to another embodiment of the present utility model. The carbon scraper 7' comprises 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.

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 can 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 utility model, due to the double sealing effect of the upper sealing assembly 81 and lower sealing assembly 82, it can be ensured that exhaust gas is prevented from entering the valve body interior . 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.

Although the present device 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 device shall be included in the scope of protection thereof. Therefore the scope of protection of the present device should be regarded as the scope defined by the claims.