Abstract:
A gas valve  1,  in particular a dosing valve for a gaseous medium, having a valve seat body  3,  which is arranged on a valve housing  2,  and a closing body  7,  which can perform a stroke motion relative to the valve seat body  3  and to an opening stroke stop  17  interacting with the valve housing  2.  According to the invention, a gas valve  1  is provided which is improved as regards its durability. This is achieved by virtue of the fact that the gas valve  1  has an impact body which reduces the impact speed and/or impact energy of the closing body  7  on the valve seat body  3  and/or on the opening stroke stop  17.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a gas valve, in particular a dosing valve for a gaseous medium, having a valve seat body, which is arranged on a valve housing, and a closing body, which can perform a stroke motion relative to the valve seat body and to an opening stroke stop interacting with the valve housing. 
         [0002]    A gas valve of this kind is known from DE 10 2009 002 836 A1. This gas valve is a dosing valve for a gaseous medium, which has a valve chamber arranged in a valve housing and having at least two chamber openings, of which a first chamber opening is surrounded in an annular manner by a valve seat, and a closing body, which is arranged in the valve chamber and on which a sealing seat that can be placed on the valve seat and raised from the valve seat is formed. The sealing seat is in the form of a knife edge and thereby ensures leaktight seating upon initial commissioning of the gas valve by means of a sealing impact into the closing body. However, the disadvantage is that the sealing seat in the form of a knife edge can wear relatively quickly owing to the knife-edge design and, as a result, malfunctions in the gas valve thus formed can occur. 
         [0003]    Moreover, the prior art includes gas valves, the sealing seat of which is designed as a flat seat. In the case of a flat seat, the sealing effect is achieved by means of the very flat surface. However, this flat contact surface is also worn through the action of impacts during operation. 
       SUMMARY OF THE INVENTION 
       [0004]    It is the underlying object of the invention to provide a gas valve which is improved as regards its durability. 
         [0005]    This object is achieved by virtue of the fact that the gas valve has a damping impact body which reduces the impact speed and/or impact energy of the closing body on the valve seat body and/or on the opening stroke stop. This embodiment is based on the realization that, at the sensitive sealing surface of the valve seat body, the closing body in current gas valves impacts directly on the seat thus formed, without being braked. Complex measures, e.g. special pairs of materials, coatings or a reduction in the mass of the closing body, are necessary to control any possible wear on this sealing surface. During the opening process, the closing body strikes the opening stroke stop in the same way. To maintain a constant stroke and hence a constant opening cross section in relation to the valve seat body over the service life of the gas valve, wear likewise needs to be avoided at this point as well. By virtue of the fact that, according to the invention, an impact body which reduces both the closing speed and the opening speed of the closing body, for example, is provided, any wear that occurs over the service life of the gas valve is prevented or at least significantly reduced in these sensitive regions, thus increasing the durability of the correspondingly designed gas valve. 
         [0006]    As a development of the invention, the impact body is an annular body surrounding the valve seat body and/or the opening stroke stop. However, it is also possible for the impact body to be formed by a plurality of blocks arranged on the circumference of the valve seat body. On the one hand, an impact body of this kind designed as an annular body or as blocks, for example, can be manufactured without problems and can furthermore be integrated without problems into an existing gas valve. At the same time, it is furthermore possible for the material of the impact body to be chosen in such a way in relation to the closing body that the impact body can undergo a calculable wear over the service life of the gas valve, without this wear impairing the operation of the gas valve designed in this way, however. Consequently, the impact body functions as a “sacrificial mass” over the service life of the gas valve, while the sealing surface between the closing body and the valve seat body and between the closing body and the opening stroke stop is not prejudiced during this time. This ensures that the operating behavior of the gas valve designed in this way is more or less unchanged over its entire service life. 
         [0007]    In another embodiment of the invention, the impact body is a cylinder or, alternatively, a block arranged centrally in the valve seat body. This embodiment is suitable as a replacement for a corresponding impact body, in the form of an annular body or block for example, arranged on the valve body side but can also be present in addition to such an annular body. If both the annular body, for example, and the central cylinder are present, it is possible to significantly increase the impact area of the closing body and hence to further increase durability. As an alternative, however, the damping rate or the kinetic energy remaining in the closing body after the impact processes can be influenced thereby. 
         [0008]    In another embodiment of the invention, the impact body can be moved during interaction with the closing body, in particular in relation to the valve housing. The travel is dimensioned in such a way that the impact of the closing body, especially on the valve seat body, takes place in such a way that no wear can occur between these components. Fundamentally, quasi-static spring forces of the impact body (bodies) or the storage thereof in the form of potential energy do not play a role. They merely serve to return the impact body (bodies). The effect achieved according to the invention is based on the dynamic impact process and the resulting transfer of at least part of the kinetic energy of the closing body to the impact body. In the case of closure, this furthermore takes place on an area outside the sealing region between the closing body and the valve seat body, this area being insignificant for the sealing function of the gas valve. 
         [0009]    In a development of the invention, the closing body can be moved against the force of at least one spring device. The spring device can consist of a number of individual springs, for example, or can be a single spring. In particular, the spring device brings about return of the impact body to its initial position after the closing body has been moved away from the impact body again during a subsequent switching operation. 
         [0010]    As a development of the invention, the impact body itself is elastically deformable. This elastic deformability of the impact body can be provided by an appropriate choice of material. By means of this embodiment too, the speed of impact of the closing body on the valve seat body, in particular, is reduced. 
         [0011]    In a development of the invention, the maximum opening stroke of the closing body relative to the valve seat body is greater than the maximum stroke of the closing body relative to the impact body. This embodiment ensures that the closing movement of the closing body is braked only shortly before or immediately before impact on the valve seat body. This ensures that the closing time of the gas valve designed in this way is not changed or not substantially changed, in particular lengthened, as compared with a gas valve without an impact body according to the invention. At the same time, it is possible under some circumstances for a possible lengthening of the closing time to be balanced out by a higher initial closing speed of the closing body. The same applies in reverse to the opening stroke of the closing body. 
         [0012]    In another embodiment of the invention, the impact body includes an alignment function for the closing body relative to the valve seat body. It is thereby possible to compensate for a slight slope in the position of the closing body before impact of the closing body on the valve seat body and thus to ensure more accurate closure of the gas valve. 
         [0013]    As a development of the invention, the gas valve is a gas inlet valve of an internal combustion engine, the gas inlet valve being used to allow a combustion gas into an intake device, an intake port or directly into a combustion chamber of the internal combustion engine. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Further advantageous embodiments of the invention can be found in the description of the drawing, in which illustrative embodiments shown in the figures are described in detail. 
           [0015]    In the drawing: 
           [0016]      FIG. 1  shows a longitudinal section through a gas valve designed in accordance with the invention, 
           [0017]      FIG. 2  shows a partial longitudinal section through a variant of a gas valve, 
           [0018]      FIG. 3  shows an illustration of the reduction in speed of a closing body of the gas valve designed in accordance with the invention, 
           [0019]      FIG. 4  shows a schematic representation of an alignment function for a closing body performed by an impact body of the gas valve, 
           [0020]      FIGS. 5   a,    5   b  show a schematic representation of a wearing function of an impact body according to the invention, and 
           [0021]      FIG. 6  shows an illustration in diagrammatic form of a transfer of momentum to an impact body during a closing process of a closing body. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The gas valve  1  shown in  FIG. 1  is designed as a gas inlet valve, by means of which a gaseous fuel is fed directly or indirectly to a combustion chamber of an internal combustion engine. In this case, the gas valve can be installed on an intake section of the internal combustion engine and can inject the gaseous fuel centrally into the intake section. However, it is also possible for the gas valve  1  to be installed in an intake branch of the intake section, wherein the intake branch is the intake duct leading to an inlet valve directly adjoining a combustion chamber of the internal combustion engine. In the context of the invention, it is furthermore also possible for the gas valve  1  to be installed in a cylinder head of the internal combustion engine and to be in direct contact on the outlet side with the combustion chamber, bypassing the intake section and the intake duct. By means of the gas valve  1 , gaseous fuel is introduced into the combustion chamber, is burnt there with combustion air supplied and performs work on a crankshaft of the internal combustion engine. 
         [0023]    The gas valve has a valve housing  2 , in which a valve seat body  3 , which is in the form of a circular ring for example, is arranged and fastened in a suitable manner. In the case of an annular embodiment, the valve seat body  3  is inserted into a corresponding annular aperture in the valve housing  2 , for example. The valve seat body  3  has a number of outlet passages  4   a,    4   b  of fundamentally arbitrary design, being in the form of circular rings in the illustrative embodiment. To reinforce the valve seat body  3 , radially arranged valve seat body ribs  5  are arranged on the circumference of the valve seat body  3 . A closing body  7  is arranged in a recess  6  in the valve housing  2 , said recess being designed as a guide if appropriate, in a manner which allows axial movement relative to the valve seat body  3 . Like the valve seat body  3 , the closing body  7  is provided with passages  8   a,    8   b,  which are arranged offset relative to the outlet passages  4   a,    4   b  and are, for example, likewise annular, wherein the closing body  7  likewise has radially arranged closing body ribs  9 . In the illustrated open position of the closing body  7  relative to the valve seat body  3 , a gas fed to a valve chamber  10  flows through the passages  8   a,    8   b  and the outlet passages  4   a,    4   b  - as illustrated on the right-hand side of the figure—out of the gas valve  1  and onward directly or indirectly into the combustion chamber of the internal combustion engine. 
         [0024]    The closing body is connected to an armature  12  of an electromagnet  13  by means of a fastening bolt  11 . The electromagnet  13  is fastened firmly in the valve housing  2  and has a magnet body  14 , in which a coil  15  and a compression spring  16  are arranged. When the coil  15  is energized, a magnetic field is built up, moving the armature  12  together with the closing body  7  into one open position. In the drawing, a central position of the closing body  7  between the open position and a closed position is shown. If the energization of the coil  15  is discontinued, the compression spring  16  pushes the armature  12  and thus the closing body  7  downward until the closing body  7  makes contact with the valve seat body  3 . Owing to the offset between passages  8   a,    8   b  and the outlet passages  4   a,    4   b,  the gas flow through the gas valve  1  is ended. 
         [0025]    In order to reduce the impact speed and/or impact energy of the closing body  7  on the valve seat body  3  and, during an opening movement, on an opening stroke stop  17  formed in the valve housing  2 , two impact bodies are provided in the illustrative embodiment shown, these being designed as annular bodies  18   a,    18   b  and being arranged in annular-body recesses  19   a,    19   b  in the valve housing  2 . In the illustrated position of the closing body  7 , the annular bodies  18   a,    18   b  are pushed against stops  21   a,    21   b  in the annular-body recesses by annular-body springs  20   a,    20   b,  said stops projecting relative to the opening stroke stop  17  and the valve seat body  3  to such an extent that the closing body  7  strikes annular body  18   a  first during an opening movement and strikes annular body  18   b  first during a closing movement. If there is a further opening movement or closing movement, the closing body  7  comes into contact with the opening stroke stop  17 , displacing annular body  18   a  in annular-body recess  19   a,  or comes into contact with the valve seat body  3 , displacing annular body  18   b  in annular-body recess  19   b  Annular-body springs  20   a,    20   b  interacting with the annular bodies  18   a,    18   b  serve only to return the two impact bodies to the respective initial position after an impact has occurred. The spring force is as low as possible in order to avoid generating an increase in the necessary magnetic force in the open valve state or to avoid generating an increase in the spring force of the compression spring  16  required to keep the valve closed. The reduction in the impact speed is accomplished through the dynamic transfer of momentum to the impact body but not through the spring forces of the annular-body springs  20   a,    20   b.  Wear on the gas valve  1  caused by a conventional impact of the closing body  7  on the valve seat body  3  or opening stroke stop  17  is thereby avoided. 
         [0026]    In an alternative embodiment to annular body  18   b,  which reduces the closing speed of the closing body  7  relative to the valve seat body  3 , the gas valve  1  according to  FIG. 2  has an impact body which is arranged in the valve seat body  3 , is designed as a cylinder  22  and can be moved against the force of one or more cylinder springs  23 . To provide the intended function, h 1 &lt;h 2 . The impact body designed as a cylinder  22  can be installed instead of annular body  18   b  or in addition to annular body  18   b  and can be combined with annular body  18   a.    
         [0027]    The schematic diagram according to  FIG. 3  shows a relationship between an actuating speed v S  of the closing body  7  and a speed of movement v P  of the impact body, whatever the design thereof, up to the point of impact on the valve seat body  3 . Initially, the closing body  7  is moved at a high actuating speed v S  by the force of the compression spring  16  until the closing body  7  strikes the impact body, in this case annular body  18   b,  at time t 1 . At time t 1 , some of the momentum is transferred from the closing body  7  to annular body  18   b  through the impact process, depending on the ratio of masses and the coefficient of restitution. The closing body  7  then moves at the reduced actuating speed v′ S  toward the valve seat body  3  until, at time t 2 , it comes to rest on the valve seat body  3  and then has the speed  0 . 
         [0028]      FIG. 4  shows a closing body  7  sloping relative to the valve seat body  3 . This slope by an angle a, which can be caused by the compression spring  16 , for example, is absorbed when the closing body  7  strikes annular body  18   b,  and the closing body  7  is aligned parallel to the valve seat body  3  shortly before it strikes the latter, as indicated in broken lines. 
         [0029]      FIGS. 5   a,    5   b  show annular body  18   b  in the new state ( FIG. 5   a ) and in a worn state ( FIG. 5   b ). The worn state is reached at the end of the predetermined service life of the gas valve  1  and ensures wear-free movement of the closing body  7  relative to the valve seat body  3  or the opening stroke stop  17  up to this time. When the worn position is reached, annular body  18   b  has been worn down on both sides in relation to stop  21   b  in the annular-body recess and relative to the closing body  7  to such an extent that offsets  24   a,    24   b  caused by wear result. These offsets  24   a,    24   b  caused by wear can arise from abrasion of the material of annular body  18   b,  which is manufactured from a less resistant material, in relation to the valve housing  2  and the closing body  7 . Owing to the fact that the offsets  24   a,    24   b  caused by wear have the same extent, i.e. the same depth, as the height of the closing body  7  in the new state, the extent of projection V M  remains virtually the same from the new state to the worn state. 
         [0030]    A time/displacement diagram for the closing body  7  is given in the upper diagram in  FIG. 6 . After initiation of a closing movement x S  by discontinuation of the energization of the coil  15 , the closing body  7  is moved ultimately from its open position a into the closed position b, wherein it strikes annular body  18   b  at time t 1  (see lower diagram). The further closing movement takes place at a slower speed, this being indicated by a reduction in the gradient. At time t 1 , there is a transfer of momentum to the impact body mass—this being illustrated in the lower diagram—said transfer undergoing a maximum backswing x P  up to time t max . At time t 2  of the return of the impact body mass, the closing body  7  is already back in the open position and is not affected by the impact body mass springing back.