Abstract:
A multi-way valve, particularly for a refrigerant circuit, includes a housing having a number of inlets and outlets and a chamber with a number of seats respectively associated with an inlet or outlet. The multi-way valve also includes a closing element that can move between the seats and at least one actuator, which is provided in the form of an element made of a shape-memory alloy and capable of being displaced from one of the seats when the closing element is heated. The direction of displacement is transversal to the normal direction of the seat.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation, under 35 U.S.C. § 120, of copending international application No. PCT/EP02/13808, filed Dec. 5, 2002, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. 101 62 502.2, filed Dec. 19, 2001; the prior applications are herewith incorporated by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The present invention relates to a multi-way valve and to a refrigerating machine having a circuit in which the multi-way valve is inserted. 
   Such multi-way valves or refrigerating machines are used, for example, in refrigerators that have a plurality of cooling compartments capable of being regulated in each case by a specific evaporator to temperatures that can be set independently of one another; they serve, there, for apportioning the refrigerant stream to one or more evaporators. The multi-way valves used at the present time in refrigerating machines are, generally, solenoid valves. These valves have a housing with a plurality of valve seats and with a closing member movable between stable positions, in each case on one of the valve seats, by magnetic force. 
   A solenoid valve, not actuated magnetically, having a housing with a plurality of inlets and outlets and a chamber with a plurality of valve seats associated, in each case, with an inlet or outlet is disclosed in German Published, Non-Prosecuted Patent Application DE 198 22 735 A1. The housing of this known multi-way valve includes three chambers: a middle chamber, in which a closing member is movable between two seats on opposite side walls; and two lateral chambers, into which the orifices of the valve seats issue and in each of which a spring of a form memory alloy is accommodated. The two springs press onto the closing member in the middle chamber in each case through a piston and a rod extending through the orifice of the respective valve seat. By heating a first of the two lateral chambers, the spring located therein is lengthened and presses the closing member against the valve seat leading to the second lateral chamber, the spring, at the same time, compressing the spring in the second lateral chamber. 
   To displace the closing body from one seat to the other, a spring not only has to apply the force necessary for deforming the other spring in each case, but, furthermore, a force that corresponds to the product of the pressure difference between the central and the lateral chamber and the cross-sectional area of the valve seat orifice. There is, therefore, the risk that, if the pressure difference is too high, the multi-way valve does not change over reliably. 
   SUMMARY OF THE INVENTION 
   It is accordingly an object of the invention to provide a multi-way valve and refrigerating machine with multi-way valve that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that can be changed over with the aid of a form memory alloy element and has a function capacity that is not impaired even by a high pressure difference at a closed valve seat. 
   With the foregoing and other objects in view, there is provided, in accordance with the invention, a multi-way valve, including a housing having a plurality of inlets and outlets and valve seats associated with a respective one of the inlets and outlets, the housing defining a chamber fluidically connected to the valve seats, a closing member movable between the valve seats, and at least one actuator of a form memory alloy that, under heating, displaces the closing member from one of the valve seats to another of the valve seats in a displacement direction transverse to a normal direction of at least one of the valve seats. 
   With the objects of the invention in view, in a refrigerating machine having a refrigerant circuit with a plurality of evaporators, there is also provided a switching device including a multi-way valve of the invention disposed in the refrigerant circuit and fluidically connected to at least one of the evaporators. 
   Because the direction in which the closing member is displaced from the seat is placed substantially transversely to the normal direction of the seat, the force acting in the normal direction and resulting from the pressure difference does not need or at most needs to a slight extent to be overcome to displace the closing member from its seat. 
   In accordance with another feature of the invention, the closing member is spherical. When the closing member is spherical, it can be displaced from its seat in a rolling movement so that no appreciable frictional resistance has to be overcome for displacement. Furthermore, the ball shape makes leak-tight closing-off of a circular valve seat easier. 
   In accordance with a further feature of the invention, to ensure that the closing member cannot escape from the surroundings of the valve seat and always closes one of these in a state of rest, the closing member is, preferably, held in a slide that can be displaced by the actuator to displace the closing structure. 
   In accordance with an added feature of the invention, the slide defines a receptacle therewithin and the closing member is held within the receptacle. 
   In accordance with an additional feature of the invention, the valve seats are two valve seats, the closing member moves in the slide in the displacement direction, and a freedom of movement of the closing member in the slide is less than a distance between the two valve seats. 
   Preferably, furthermore, the closing member is movable in the displacement direction in the slide itself, the freedom of movement of the closing member in the slide being lower than the distance between two seats. This, on one hand, ensures that, in each position of rest of the slide, the closing member can close in each case only one valve seat corresponding to this position, and, on the other hand, a movement of the slide between adjacent positions of rest, which is smaller than the distance between two adjacent seats, is sufficient to displace the closing member so far from one of the two seats that it no longer closes this and, unobstructed by the slide, can assume a closing position at a second valve seat. 
   In accordance with yet another feature of the invention, the multi-way valve, preferably, includes a spring-elastic valve for exerting on the closing member a counterforce that counteracts the displacement of the closing member from each seat. Such a spring element keeps the closing member firmly against the seat, even when no fluid is flowing through the valve, and, consequently, the pressure difference between the middle chamber and the secondary chamber shut off by the closing member disappears, even when the pressure in the secondary chamber becomes slightly higher than in the central chamber. 
   In accordance with yet a further feature of the invention, the chamber has a first side wall, the valve seats are disposed on the first side wall, and the spring-elastic element acts on the closing member in a direction of the first side wall. This spring-elastic element may, expediently, be a leaf spring. 
   In accordance with yet an added feature of the invention, the seats are, preferably, located on the same side wall of the chamber so that a single spring-elastic element preferably disposed on an opposite side wall of the housing is sufficient to act upon the closing member in each case in the direction of these seats. 
   To change over the multi-way valve between its different switching positions, each spring-elastic element serving as an actuator and being of form memory alloy is, preferably, assigned an electrical heating device for the selective heating of the element. 
   In accordance with yet an additional feature of the invention, the heating device may be a heating resistor wound around the housing of the multi-way valve in the vicinity of the associated actuator or a heating resistor wound around the element itself. The first alternative is especially simple and cost-effective because, for the electrical supply of the heating device, there is no need for wires to be led through the housing; the second alternative has the advantage that it allows faster reaction times of the multi-way valve, particularly when the heating device can be cooled by direct contact with fluid flowing through the valve. 
   In accordance with again another feature of the invention, the heating devices are to be cooled in direct contact by fluid flowing through the valve. 
   In accordance with again a further feature of the invention, fluid flows through the inlets to the chamber and out the outlets, the heating devices are disposed in the housing, and the heating device are to be cooled in direct contact by fluid flowing through the housing. 
   In accordance with again an added feature of the invention, at least part of the heating device is disposed outside the housing. 
   In accordance with again an additional feature of the invention, the heating devices are disposed outside the housing. 
   In accordance with a concomitant feature of the invention, the housing and the actuator are integral and the housing and the actuator are of a one-piece form memory alloy. 
   Other features that are considered as characteristic for the invention are set forth in the appended claims. 
   Although the invention is illustrated and described herein as embodied in a multi-way valve and refrigerating machine with multi-way valve, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
   The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary perspective view of a first embodiment of a multi-way valve according to the invention; 
       FIG. 2  is a cross-sectional view through the multi-way valve of  FIG. 1  along a plane defined by lines A and B in  FIG. 1 ; 
       FIG. 3  is a cross-sectional view through the multi-way valve of  FIG. 1  along a plane defined by lines A and C in  FIG. 1 ; 
       FIG. 4  is a fragmentary, perspective view of a second embodiment of a multi-way valve according to the invention; and 
       FIG. 5  is a fragmentary, cross-sectional view, similar to that of  FIG. 2 , through a third embodiment of a multi-way valve according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown a multi-way valve according to the invention, with a housing  1  of metal, which has, on one housing side (here, the top side facing away from the viewer), an inlet connection  2  and, on the opposite housing underside  3 , two outlet connections  4   a ,  4   b  for a fluid. Two current leadthroughs  18  are, likewise, led on the underside  3  into the interior of the housing  1  so as to be insulated relative to the latter. A ground connection is connected directly to the housing at any desired point and is not illustrated in  FIG. 1 . 
     FIG. 2  shows a “horizontal” section through the multi-way valve of  FIG. 1  in the plane defined by the lines A and B of  FIG. 1 . A slide  6  of an electrically nonconductive material, for example, a plastic, is mounted displaceably in the direction of the line A in a chamber  5  inside the housing  1 . The slide  6  includes a base plate  8  guided displaceably along a side wall  7  of the housing  1  and two legs  9   a ,  9   b  that, starting from the base plate  8 , extend as far as a short distance from the opposite side wall  10  of the housing  1 . The legs  9   a ,  9   b  subdivide the chamber  5  into a central chamber  11  between the two legs  9   a ,  9   b  and two lateral chambers  12   a ,  12   b  in each case on the far side of the legs  9   a ,  9   b.    
   A ball  13  functioning as a closing member is accommodated in the central chamber  11 . In the configuration of the multi-way valve, as shown in  FIG. 2 , the ball  13  lies centrally on a left valve seat  14   a  formed on the bottom of the chamber  5  and, thus, shuts off the outlet connection  4   a  associated with this valve seat  14   a  (see also  FIG. 3 ). A second right valve seat  14   b , which belongs to the right outlet connection  4   b , is open. The distance between the legs  9   a ,  9   b  is selected such that, in the illustrated position of the slide  6 , in which the distance from the center point of the valve seat  14   a  to the nearest leg  9   a  is slightly greater than the radius of the ball  13 , the corresponding distance of the right valve seat  14   b  from the leg  9   b  nearest to it is smaller than this radius. In this position of the slide  6 , therefore, the ball  13 , even if it were to lose its place on the seat  14   a  because of vibration or the like, cannot shut off the seat  14   b.    
   The two lateral chambers  12   a ,  12   b  accommodate elements of a form memory alloy, here in the form of curved bars  15   a ,  15   b , which are connected in each case at one end to the housing  1  and at another end to the slide  6 . In the illustrated configuration of the multi-way valve, the slide  6  is in the vicinity of its left stop, and the bar  15   a  in the left lateral chamber  12   a  is curved to a greater extent than the bar  15   b  in the right lateral chamber  12   b . A wire  16 , which forms a heating resistor, is wound around each bar  15   a ,  15   b . A first end of each resistance wire  16 , the first end facing the electrically nonconductive slide  6 , is connected to the conductor  17  of the electrical leadthrough  18 ; the other end of the resistance wire  16 , in each case, is connected to ground through the housing  1 . 
     FIG. 3  shows a section through the multi-way valve of  FIG. 1  in the plane defined by the lines A and C of  FIG. 1 . The height of the slide  6  is smaller than the diameter of the ball  13 , and a leaf spring clamped above the slide  6  between the ball  13  and the top side of the housing  1  exerts on the ball a downwardly directed force that keeps the ball  13  firmly pressed against the seat occupied by it in each case, here seat  14   a.    
   By acting upon one of the two resistance wires  16  selectively with current, the bar  15   a  or  15   b  wound around with the wire  16  is heated and changes into its respective memory form corresponding to the heated state. As a result, the slide  6  is displaced and, at the same time, in each case, the other non-heated bar  15   b  or  15   a  is deformed. As such, the deformation caused by heating may be both a stretching and a curving of the heated bar. The following description of the operation of the valve assumes that the deformation is a stretching; however, the operation of the valve in the case of a curving is exactly analogous and does not need to be explained specifically. 
   When the bar  15   a  is heated with the aid of its resistance wire  16  and is, at the same time, stretched, the slide  6  is displaced in the direction of its right stop. At the same time, the left leg  9   a  displaces the ball  13  from its place on the left valve seat  14   a . The force that has to be exerted on the ball  13  for this purpose is low because the direction of displacement of the ball is virtually perpendicular to the normal direction of the orifice of the valve seat  14   a  that is parallel to the line C. As may be appreciated, the angle between the normal direction and the displacement direction of the ball is the nearer to 90°, the smaller the diameter of the valve seat  14   a  is in comparison with the diameter of the ball  13 . The diameter of the valve seat should, if possible, be no larger than half the diameter of the ball  13 . 
   The displacement of the slide  6  leading to the displacement of the ball  13  from the valve seat  14   a  has the effect, at the same time, that the leg  9   b  moves away from the right valve seat  14   b , so that sufficient space becomes available at this valve seat  14   b  so that the ball  13  can descend onto it and close it. As soon as the leg  9   a  has pushed the ball  13  over somewhat more than half its excursion between the two valve seats  14   a ,  14   b , the ball  13  is acted upon by the force of the leaf spring  19  and, if present, by a flow of the fluid from the inlet connection to the outlet connections in the direction of the right valve seat  14   b  and descends on the latter. Excursion of the ball  13  is, in this case, almost twice as great as the excursion over which the bar  15   a  has to drive the ball  13 . 
   Because the lateral chambers  12   a ,  12   b  communicate with the central chamber  11  through gaps between the housing wall and the legs  9   a ,  9   b , the fluid pressure in the lateral chambers  12   a ,  12   b  is always the same as in the central chamber  11 . Consequently, during the displacement of the ball  13 , the bars  15   a ,  15   b  do not have to work counter to a pressure difference between the chambers. 
   Because the lateral chambers  12   a ,  12   b  communicate with the central chamber  11 , the resistance wires  16  of the bars  15   a ,  15   b  are surrounded normally by the fluid flowing through the valve and are cooled by the fluid. When the fluid is a liquid, however, it may be evaporated when the resistance wires are in operation and may, thus, form a thermally insulating bubble around the bar  15   a  or  15   b  to be heated. After the resistance wires  16  have been switched off, the bar  15   a ,  15   b  can be cooled rapidly again, in that evaporated fluid surrounding it is flushed away by the flow running through the valve and is replaced by liquid fluid. 
     FIG. 4  shows a second embodiment of the multi-way valve according to the invention in a perspective view similar to that of  FIG. 1 . In this embodiment, there are no electrical leadthroughs; instead, the walls of the housing  1  are closed with the exception of the inlet and outlet connections  2 ,  4   a ,  4   b . Resistance wire windings  20   a ,  20   b  are disposed respectively around the lateral chambers  12   a ,  12   b  on the housing  1 . Thus, in the second embodiment, a bar  15   a ,  15   b  of form memory alloy is heated indirectly by the diffusion of heat from a resistance wire winding through the housing  1  and through the fluid contained in the respective lateral chamber  12   a ,  12   b . The heating of a form memory alloy element, therefore, obviously takes up more time than in the embodiment of  FIGS. 1 to 3 , but this is not necessarily an impediment for a use of the solenoid valve in a refrigerant circuit, for example, for a household refrigerator  100 , ( FIG. 1 ), because there, as a rule, markedly fewer than one switching operation of the multi-way valve per minute is necessary and, also, switching delays in the region of a few tens of seconds are acceptable. The lengthening of the reaction time has against it the advantage of markedly more cost-effective manufacture and a longer expected service life of the multi-way valve because the electrical leadthrough is never dispensed with. 
   To accelerate the heating of the bars  15   a ,  15   b  functioning as actuators, it is conceivable to produce these, together with the entire housing  1 , in one piece from form memory alloy. 
     FIG. 5  shows a third embodiment of the multi-way valve according to the invention by a section similar to that of  FIG. 2 . The slide  6  here is in the form of a frame that surrounds the ball  13  on four sides. In each case, first ends of bars  15   a ,  15   b  of a form memory alloy are fastened to lateral extensions  21  of the slide  6 . Two resistance wires wound around the bars  15   a ,  15   b  and supplied with current in each case through a conductor guided through the housing are not illustrated in  FIG. 5  for the sake of simplicity. The bars  15   a ,  15   b  extend in each case laterally past the slide  6  as far as that end of the housing  1  that faces away from the first end of the respective bar  15   a ,  15   b . The second ends of the bars  15   a ,  15   b  are fastened to the extensions  21  in each case. Thus, in comparison with the length of the housing  1 , the length of the bars  15   a ,  15   b  is substantially larger than in the embodiment of  FIGS. 1 to 3 , and a stroke of the slide  6  that is greater in relation to the length of the housing  1  can, therefore, also be driven. To guide the movement of the slide  6  linearly, a channel  22  is recessed into the bottom of the housing  1 , and two plates  23  integrally formed onto the extensions  21   a ,  21   b  lie displaceably with slight play in the channel  22 .