Abstract:
A bistable electromagnetic valve is proposed, which is to be used in refrigerant circuits. The valve can be produced at particularly low outlay and at the same time is reliably leaktight. This is achieved, according to the invention, in that the valve chamber ( 7 ) is formed within a control coil ( 3 ) by a cylindrical tubular body ( 2 ) which extends at least beyond the pole pieces ( 5, 6 ) inserted into the cylindrical tubular body ( 2 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a bistable electromagnetic valve characterized by a valve chamber ( 7 ) arranged within a control coil ( 3 ) and the outer wall of the valve chamber ( 7 ) that is formed within the control coil ( 3 ) by a cylindrical tubular body ( 2 ) which extends at least beyond the pole pieces ( 5 ,  6 ) inserted into the cylindrical tubular body ( 2 ). 
   2. Description of the Related Art Including Information Disclosed Under 37 C.F.R. 1.97 And 1.98 
   Prior art valves of this type are used, for example, in refrigerant circuits, such as are described in the publications DE 37 18 490 or BP 10 54 200. 
   In such valves, a bistable situation is achieved by permanent magnets being arranged outside the valve housing, next to the valve chamber or next to the pole pieces, so that the valve body has, at the pole pieces, two end positions in which it is held by these permanent magnets. 
   High requirements in terms of leaktightness and long-term stability are placed on such valves. Furthermore, as is customary, there is the requirement to produce such a valve as cost-effectively as possible. 
   BRIEF SUMMARY OF THE INVENTION 
   The object of the invention is, therefore, to propose a valve which can be produced at little outlay and is reliably leaktight. 
   This object is achieved, starting from a valve for a refrigerant circuit of the type mentioned in the field of the invention characterized by a valve chamber ( 7 ) arranged within a coil ( 3 ) and the outer wall of the valve chamber ( 7 ) that is formed within the coil ( 3 ) by a cylindrical tubular body ( 2 ) which extends at least beyond the pole pieces ( 5 , 6 ) inserted into the cylindrical tubular body ( 2 ). 
   Advantageous designs and developments of the invention are possible as a result of the features described in the following description of the invention including drawings and dependent claims. 
   Accordingly, a valve according to the invention is distinguished in that the valve chamber is arranged within the control coil and the outer wall of the valve chamber within the control coil is formed by a cylindrical tubular body. The tubular body in this case extends at least beyond the pole pieces inserted into the cylindrical tubular body. 
   This means that, in contrast to conventional valves, the pole pieces do not have the connections, but, instead, the latter are simply introduced into the tubular body. Leaktightness problems between the tubular body and the pole pieces are consequently prevented completely at the lowest possible outlay. 
   In a development of the invention, the tubular body is designed to be of a length such that it extends at least as far as the end faces of the control coil. Thus, even with the control coil put in place, the tubular body is easily accessible. Moreover, the tubular body can be adapted to the inside diameter of the coil, without connection points having to be taken into account. 
   Furthermore, in this case, fluid connections of the valve can be attached in a particularly simple way to the cylindrical tubular body accessible outside the control coil. 
   A particularly simple design of such a fluid connection arises in that at least one end of the tubular body is used as a tubular connection for the fluid. In addition to a minimal number of sealing points, this, in turn, affords the advantage of extremely favorable manufacture, since the tubular connection is formed in the simplest instance by one end of the cylindrical tubular body which is already present in any case. 
   Preferably, further valve components are inserted into the tubular body. Those which come under consideration in this case are, for example, the permanent magnets necessary for bistable functioning or else filter elements in order to filter dirt particles or, in general, impurities out of the fluid. In principle, however, further valve components may also be integrated readily into the cylindrical tubular body. 
   Dirt filters, which may be designed, for example, as a sieve tube or else as a magnetic filter element for the separation of magnetic or magnetizable particles, keep impurities away from the valve body and the valve seat, so that the wear of these components is effectively reduced. This results, in turn, in a high long-term stability of the valve. It is pointed out particularly, at the same time, that such valves are used conventionally in closed fluid circuits, so that the filter capacity has to be sufficient merely for once-only purification of the fluid volume located in the circuit. 
   Moreover, it is advantageous to fix at least one of the said valve components to the inside of the tubular body at least in the axial direction. The valve thereby forms a unit capable of being handled in the unconnected state, without the possibility of any valve components falling out of the cylindrical tubular body on the end face. 
   Axial fixing can be achieved, for example, by the corresponding valve component being pressed together with the tubular body inside the latter. Such pressing can be implemented at little outlay, for example, by pressure on the tubular body from outside, and, in particular, even a plurality of valve components can be fixed in one operation. Furthermore, by pressing, a valve component can also be fixed reliably in the radial direction. 
   In a simple embodiment, even a peripheral bead or a nose pressed in on the outside may be sufficient for axial fixing. Thus, for example, all the valve components may be designed in such a way that they have in each case an abutment against one another, so that, by a bead or a nose being applied on both sides, the complete valve unit pushed into the tubular body is both fixed in the tubular body and secured against relative displacement by the mutual abutments. 
   In a further advantageous embodiment, an additional inner tube is pushed into the tubular body at least on one side of the valve chamber. What is known as a 3/2-way valve can also be produced in this way. The space between the inner tube and the cylindrical tubular body accordingly serves as an inflow line, in which case a duct to the inner valve chamber must be formed on or in the corresponding pole piece. In the simplest instance, such a duct may be formed by a circumferential recess on the pole piece. The inner tube itself then forms an outflow for the fluid in one switching position of the valve body. In the other switching position, the opposite end of the tubular body can be used as an outflow. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An exemplary embodiment of the invention is illustrated in the drawing and is explained in more detail below with reference to the figures of which, in particular, 
       FIG. 1  shows a cross section through a 2/2-way valve according to the invention; 
       FIG. 2  shows a cross section through a 3/2-way valve according to the invention; and 
       FIG. 3  shows a cross section of a 2/2-way valve schematically connected to a refrigerated appliance having refrigerated spaces a cold generating circuit including a compressor, condenser and evaporators. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The valve  1  according to  FIG. 1  comprises a cylindrical tubular body  2  according to the invention as a valve housing which passes completely through a control coil  3 . Adapter pieces  4  in this case ensure a good fit in the valve housing  2  and are designed at the same time as flux guide elements for an increased magnetic flux through pole pieces  5 ,  6  and through a valve chamber  7 . Inside the valve chamber  7  is located a spherical valve body  8  which, in the position illustrated, lies on the spherical seat  9  of the pole piece  6  and at the same time closes a passage bore  10 . The passage bore  10  issues into the outflow line  11  of the valve  1 . 
   The tubular body  2  extends into the space outside the coil  3  and therefore also beyond the pole pieces  5 ,  6 . 
   Annular magnets  12 ,  13  lying outside the tubular body  2  ensure the bistable behavior of the valve and are fixed by means of a spacer ring  14  between the adapter pieces  4 . 
   The pole piece  5  has in its outer circumference recesses or flattenings which produce fluid ducts  15  between the pole piece  5  and the tubular body  2  into the inside of the valve chamber  7 . The fluid ducts could also be implemented by bores in the pole piece  5 , the inflow-side orifices of said bores lying in the annular region between a tubular sieve  18  and the inner wall of the tubular body  2 . The pole piece  5  has, furthermore, a spherical seat  16 , in order to bring about a defined end position of the valve body  8  in the second end position, not illustrated. 
   The pole piece  5  comprises a step  17 , onto which the tubular sieve  18  is pushed. At the opposite end, the tubular sieve  18  is fixed in a magnetic filter  19  designed as an annular magnet. The tubular region of the tubular body  2  in which the tubular sieve  18  and the magnetic filter  19  are located serves as an inflow line  20  for the corresponding fluid, that is to say, in particular, for refrigerant. 
   Inflowing fluid (see arrow P) passes first into the region of the magnetic filter  19 , which is designed as an annular magnet, and comes directly into contact with the fluid. As a result, magnetic or magnetizable dirt particles are already fixed permanently to the magnetic filter  19  at a considerable distance from the valve chamber  7 . 
   The fluid subsequently passes into the inside of the tubular sieve  18  which is closed on the end face, at the opposite end, by the pole piece  5  or its step  17 . The fluid flow accordingly has to take place radially outward in the tubular sieve  18 , dirt particles larger than the sieve orifices  21  of the tubular sieve  18  being retained in the interior of the tubular sieve  18 . Thus, only purified fluid passes into the exterior  22  between the tubular sieve  18  and the tubular body  2 . The fluid passes from there, via the fluid ducts  15 , into the inside of the valve chamber  7 . 
   The flow, of course, takes place only with the valve open, that is to say in the switching position in which the valve body  8  lies on the spherical seat  16  and the passage bore  10  is released. 
   A valve  1  according to the invention can easily be built into a fluid circuit, for example a refrigerant circuit, which, as a consequence of manufacture, contains dirt particles which are not compatible with conventional refrigerant valves and cause malfunctions. 
   The use of the valve  1  is aimed at closed fluid circuits which remain closed after manufacture over the useful life of the valve  1 . The filter capacity of the filter system consisting of the tubular filter  18  and of the magnetic filter  19  must in this case be designed in such a way that once-only complete purification of the fluid located in the circuit, without clogging, can follow. 
   In this way, that is to say by the use of a filter  18 ,  19  in the inflow line  20  of the tubular body  2  and, in particular, by the direct arrangement next to the valve chamber  7 , an introduction of dirt into the valve chamber  7  is reliably ruled out to an extent such that permanently leaktight and low-wear functioning of the valve  1  can be ensured. 
     FIG. 2  corresponds essentially to the abovementioned exemplary embodiment, in this case, by contrast, a second tubular outflow line  23  leading into the inside of the tubular body  2  as far as the pole piece  5  and being fixed there in a leaktight manner in a corresponding bore  24 . The tubular body  2  and the outflow line  23  are closed off relative to one another, for example pressed or soldered, in a leaktight manner at a sealing point  25 . 
   An interspace  26 , to which an inflow line  27  is connected, is thus obtained between the outflow line  23  and the tubular body  2 . The inflow line  27  may, for example, be soldered in a corresponding orifice of the tubular body  2 . 
   In this embodiment, the pole piece  5  also comprises a passage bore  28  connecting the valve chamber  7  to the interspace  26  via the fluid ducts  15 . 
   The fluid or refrigerant can pass in the direction of the arrow P into the interspace  26  and from there through the magnetic filter  19  into the in this case annular interior between the tubular sieve  18  and the outflow line  23 . The fluid subsequently flows radially outward into the exterior  22  between the tubular sieve  18  and the tubular body  2 , from where it passes via the fluid ducts  15  into the valve chamber  7 . 
   The fluid then flows out either via the outflow line  23  or via the outflow line  11 , depending on the switching position of the valve body  8 . In the switching position illustrated, the passage bore  28  of the pole piece  5  is open, that is to say outflow takes place via the outflow line  23 . 
   By means of a control pulse from the control coil  3 , the valve body  8  can be brought onto the opposite spherical seat  16 , with the result that the passage bore  28  is closed and the passage bore  10  is opened. In this switching position described, but not illustrated, the fluid flows out via the outflow line  11 . 
   Instead of the adapter pieces  4  which have a conical outflow surface inside the control coil  3 , in the present case sleeve-shaped flux guide plates  29 , which completely fill the interspace between the tubular body  2  and the control coil  3 , are provided for guiding the magnetic flux inside the control coil  3 . The flux guide plates  29  are in each case connected to a closing plate  30  which itself is connected to what are known as yoke plates, not illustrated in any more detail, or merges into these. The flux guide plates  29  may be punched, bent or wound together with the closing plate  30  and the entire yoke plate arrangement, not illustrated in any more detail, out of a flat material. 
   LIST OF REFERENCE SYMBOLS 
   
       
         1  Valve 
         2  Tubular body 
         3  Control coil 
         4  Adapter pieces 
         5  Pole piece 
         6  Pole piece 
         7  Valve chamber 
         8  Valve body 
         9  Spherical seat 
         10  Passage bore 
         11  Outflow line 
         12  Annular magnet 
         13  Annular magnet 
         14  Spacer ring 
         15  Fluid duct 
         16  Spherical seat 
         17  Step 
         18  Tubular sieve 
         19  Magnetic filter 
         20  Inflow line 
         21  Sieve orifice 
         22  Exterior 
         23  Outflow line 
         24  Bore 
         25  Sealing point 
         26  Interspace 
         27  Inflow line 
         28  Passage bore 
         29  Flux guide plate 
         30  Closing plate