Abstract:
A housing of a multiway valve contains several inlets and outlets and a chamber containing several valve seats, each of which is allocated to one of the outlets. A closing device can be displaced between the valve seats. A cylinder contains a cylinder chamber having a fluid. A heating device is provided for heating the fluid and a plunger is provided that can be displaced in the cylinder by the pressure of the fluid. By its displacement, the plunger is able to dislodge the closing device from one of the valve seats.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation, under 35 U.S.C. § 120, of copending international application No. PCT/EP02/13879, filed Dec. 6, 2002, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. 101 62 504.9, filed Dec. 19, 2001; the prior applications are herewith incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a multiway valve and to a fluid circuit and a refrigerator in which such a multiway valve can be used.  
         [0004]     Multiway valves are used in refrigerators having more than one cooling space and mutually independent temperature regulations of the plurality of cooling spaces, in order to supply a refrigerant stream selectively in each case to the evaporator of that cooling space where it is required. Conventionally, multiway valves of this type are configured as solenoid valves, in which a closing member formed of a ferromagnetic material is changed over, as a result of the action of the magnetic field of an electromagnet, between two different rest positions, in which it blocks in each case one of two possible paths of the refrigerant through the valve. In order to achieve a good leaktightness of the solenoid valve in its various switching positions, the closing member, at rest, must not be pressed with too low a force against its seat; this force has to be overcome during the changeover of the valve, in order to bring the closing member into a new position. The higher the closing force is, the larger, the more powerful and correspondingly the more costly is the electromagnet required for this purpose.  
       SUMMARY OF THE INVENTION  
       [0005]     It is accordingly an object of the invention to provide a multiway valve which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which the closing member can be changed over without the use of a magnetic force. A further object is to specify a multiway valve which can be manufactured cost-effectively in large quantities.  
         [0006]     With the foregoing and other objects in view there is provided, in accordance with the invention, a multiway valve. The valve contains a housing having a plurality of inlets and outlets and a chamber. A plurality of valve seats is provided and each is associated with one of the inlets or outlets. A closing member is disposed in the housing and is movable between the valve seats. At least one cylinder having a fluid-containing cylinder chamber is provided and disposed in the housing. A heating device is provided for heating the cylinder. A plunger is movable in the cylinder under pressure of a fluid. The plunger, by virtue of its movement, is capable of displacing the closing member from one of the valve seats to another of the valve seats.  
         [0007]     Instead of magnetic force, the solenoid valve utilizes the expansion of a heated fluid in the chamber, in order to drive a changeover movement of the closing member from one switching position of the valve to another.  
         [0008]     Preferably, the cylinder chamber communicates temporarily with one of the inlets and outlets of the valve during the movement of the plunger. This makes it possible for the fluid switched by the multiway valve to be used as a working fluid in the cylinder chamber. It is therefore easy to ensure that there is always sufficient working fluid for driving the cylinder movement. An absolute leaktightness of the cylinder chamber for long periods of time, that is to say over a multiplicity of switching cycles, is not necessary for the operation of the valve, thus allowing the valve to be produced cost-effectively.  
         [0009]     Preferably, each seat of the valve is assigned in each case to an outlet in the valve, so that the pressure of the fluid flowing through the valve can be utilized in order to press the closing member against its seat.  
         [0010]     In order to allow a reliable changeover of the valve, even in the state where the fluid does not flow through the latter, there is expediently a spring-elastic element that exerts on the closing member a counter force that counteracts the displacement of the closing member from each seat. The spring-elastic element can ensure, furthermore, that, when the closing member has been displaced from one seat, it assumes a new closing position on another seat.  
         [0011]     The closing member is movable in a housing chamber which is designated here as a seat chamber. The valve seats are preferably disposed on the first wall of the seat chamber, and the spring-elastic element acts upon the closing member in the direction of the first sidewall, so that the closing member assumes there a position on one of the seats. The spring-elastic element used for this purpose is preferably a leaf spring.  
         [0012]     The cylinder is preferably in each case provided with a pressure compensation orifice that, in the extended state of the plunger, allows pressure compensation between the seat chamber and a cylinder chamber of the cylinder. When this pressure compensation takes place, the movement of the plunger ends.  
         [0013]     The cylinder preferably has a rear wall which is displaceable under spring load which makes it possible to displace the plunger of one cylinder, which is driven in a movement by another cylinder, at least in an initial phase of the movement, solely counter to the spring force and without the compression of the fluid contained in the cylinder chamber.  
         [0014]     A spring chamber on the outside of the movable rear wall, the spring chamber receiving the spring loading the rear wall, can communicate with the surroundings of the multiway valve, but preferably with the seat chamber itself, so that the volume of the spring chamber can be varied, as required.  
         [0015]     Preferably, the valve configuration according to the invention is used in a multiway valve which has two seats and two cylinders located diametrically opposite one another; the invention may, however, also be applied to valves with a larger number of seats and cylinders.  
         [0016]     A heating device for heating the fluid in the cylinder chamber is preferably disposed in the heating chamber that communicates with the cylinder chamber, but is offset from the latter, in order to protect the heating device from the movements of the cylinder.  
         [0017]     The multiway valve according to the invention can be used for gaseous, liquid or partly gaseous and partly liquid fluid streams. When the fluid entering the multiway valve is a liquid or a gas/liquid mixture, a supply circuit for supplying the electrical heating device with heating energy is expediently configured with high enough power such that it is capable of at least partially evaporating the fluid used in the cylinder chamber.  
         [0018]     Other features which are considered as characteristic for the invention are set forth in the appended claims.  
         [0019]     Although the invention is illustrated and described herein as embodied in a multiway valve, it is nevertheless not intended to be limited to the details shown, since 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.  
         [0020]     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  
       [0021]     FIGS.  1  to  4  are diagrammatic, longitudinal sectional views through a multiway valve according to a first embodiment of the invention in four different phases of operation; and  
         [0022]      FIG. 5  is a diagrammatic, horizontal sectional view through the multiway valve according to a second embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a longitudinal sectional view of a multiway valve according to a first embodiment of the invention in a stable rest state. The valve has a housing  1  in the form of a tubular piece  2  which is closed in a leaktight manner at its two ends by small inserted, for example, soldered plates  3 .  
         [0024]     The tubular piece  2  has three bores that issue in each case into a central chamber, designated as a seat chamber  5 , of the housing  1 . An inlet line  4  for a fluid is inserted into a first bore on a plane of symmetry, illustrated as a dash-and-dot line, of the housing  1 , and an outlet line  6   a  and  6   b  with a hollow-conical valve seat  7   a  and  7   b  is inserted in each case into two bores on a diametrically opposite side of the housing  1 . The outlet lines  6   a ,  6   b  run toward one another in the direction of the housing  1 , so that the valve seats  7   a ,  7   b  are virtually contiguous to one another inside the housing  1 . A closing member in the form of a ball  8  on the right-hand seat  7   b  shuts off the right-hand outlet line  6   b.  Opposite to two valve seats  7   a ,  7   b , on the same side as the inlet line  4 , is a leaf spring  9  which is symmetrical with respect to the mid-plane and, in the state shown in  FIG. 1 , presses the ball  8  against the valve seat  7   b  and thus keeps the right-hand outlet line  6   b  closed.  
         [0025]     Two cylinders  10   a ,  10   b  are accommodated in the housing  1  on the right and on the left of the seat chamber  5 . In a bore of each of the cylinders  10   a ,  10   b , a plunger  11   a  and  11   b  and a displaceable rear wall  12   a  and  12   b  delimit a cylinder chamber  13   a ,  13   b.  The cylinder bodies in each case have formed in them, in each case outside the displaceable rear walls,  12   a ,  12   b , a spring chamber  14   a ,  14   b  which accommodates a helical spring  15   a  and  15   b  which in each case presses the displaceable wall  12   a  and  12   b  away from the small plate  3  of the housing and toward the middle of the valve. The plungers  11   a ,  11   b  in each case carry, on their side directed outward toward the cylinder chamber  13   a  and  13   b , a bar  21  which, in the state shown in  FIG. 1 , touches the displaceable rear wall  12   a  and  12   b.  The spring force exerted by the helical springs  15   a ,  15   b  is thus transmitted to the ball  8  via the displaceable rear walls  12   a ,  12   b  and the plungers  11   a ,  11   b.  The forces of the springs  15   a ,  15   b  are oriented opposite to one another and largely compensate one another. None of the springs  15   a ,  15   b  is capable of overcoming the force exerted on the ball  8  by the leaf spring  9 , which keeps the ball pressed against its seat, and of displacing the ball  8  from its seat  6   b.    
         [0026]     A heating chamber  16   a ,  16   b  in which an ohmic resistor  17   a ,  17   b  is located as a heating element, is provided next to the cylinder chamber  13   a ,  13   b  and, communicating with the latter, on both sides of the housing  1 . Current leadthroughs  18  for a selective supply of current to the resistor  17   a  or  17   b  are led through the tubular piece  2 .  FIG. 1  shows two current leadthroughs  18  for each heating resistor  17   a  and  17   b . It is also possible to provide in each case, for each heating resistor, only one leadthrough  18  which is insulated relative to the housing  1  and which is connected to one end of its resistance wire. The other end of both resistance wires can be grounded via the metallic tubular piece  2 .  
         [0027]     In the state shown in  FIG. 1 , the right-hand cylinder chamber  13   b , which is filled with the same fluid that flows through the valve, is sealed off relative to the seat chamber  5  and its inlets and outlets. The piston  11   b  shuts off pressure compensation orifices  23   b.  When, in this state, the resistor  17   b  is supplied with energy from a current supply  100 , the fluid in the heating chamber  16   b  heats up and the cylinder chamber  13   b  connected to it begins to expand. This leads in the first place, as shown in  FIG. 2 , to the displaceable rear wall  12   b  of the cylinder  10   b  moving back outward under the simultaneous compression of the helical spring  15   b.  The stroke of the backward movement may be substantially smaller than that illustrated in  FIG. 2  and be virtually zero.  
         [0028]     The fluid in this case displaced out of the spring chamber  14   b  reaches the seat chamber  5  via a duct  19  and is thus mixed with the fluid stream flowing through the valve.  
         [0029]     A shoulder  20   b  projecting from the wall of the spring chamber  14   b  on the inside forms a stop that immediately terminates the outward movement of the rear wall  12   b.  Finally, in the event of further heating and evaporation of the fluid in the cylinder chamber  13   b , a state is reached where the internal pressure in the cylinder chamber  13   b  is sufficiently high to ensure that the plunger  11   b  displaces the ball  8  from the seat  7   b  counter to the force of the leaf spring  9 . The ball  8  thus begins to move to the left, as shown in  FIG. 3 . In this case, it also displaces the plunger  11   a  and, via the latter, the displaceable rear wall  12   a  of the left-hand cylinder  10   a  and at the same time compresses its helical spring  15   a . Finally, in this way, the unstable position of equilibrium shown in  FIG. 3  is reached, in which the ball  8  is pressed centrally by the leaf spring  9  against a fin  22  between the two valve seats  7   a ,  7   b.  As soon as the fin  22  is overcome as a result of the further expansion of the heated fluid in the cylinder chamber  13   b , the leaf spring  9  assists the further displacement of the ball  8  to the left and downward in the  FIG. 4  onto the valve seat  7   a . While this is taking place, the rear side of the plunger  12   b  passes the pressure compensation orifice  23   b  that connects the cylinder chamber  13   b  to the duct  19 . The heated fluid escapes from the cylinder chamber  13   b , and the inward movement of the plunger  11   b  driven by the fluid comes to a stop. At the same time, the compressed helical spring  15   b  can stretch again and push the displaceable rear wall  12   b  inward until the latter butts against the tip of the bar  21 .  
         [0030]     The configuration shown in  FIG. 4  is thus established, which is a mirror image of the configuration of  FIG. 1 . The supply current to the resistor  17   b  is then interrupted, so that the heating chamber  16   b  and the cylinder chamber  13   b  can cool and the fluid density there again assumes the same value as in the other chambers  5 ,  13   a ,  16   a  of the valve.  
         [0031]     When, at a later time, the resistor  17   a  is supplied with heating energy, the process proceeds mirror-symmetrically to that described above, and the ball  8  returns into the position of  FIG. 1 . The changeover operation functions, irrespective of whether fluid actually flows through the housing or whether this fluid stands in the latter. Only the force required for changing over the ball  8  can be higher in the case of a valve through which fluid flows than in the case without a flow, since the pressure of the fluid streams presses the ball  8  against its respective seat.  
         [0032]     The invention can also be applied to multiway valves having more than two outlets.  FIG. 5  shows a diagrammatic sectional view through a seat chamber  5  where the sidewall of the seat chamber in which the valve seats, three seats  7   a ,  7   b ,  7   c  here, are disposed are shown in a top view. One of the valve seats, which is illustrated as a dashed circle  7   b , is closed by the ball  8 . Three plungers  11   a ,  11   b ,  11   c , the cylinder chambers of which are constructed in the same way as shown in FIGS.  1  to  4  and are not illustrated in the  FIG. 5 , are disposed symmetrically in each case at an angular spacing of 120°. Each plunger  11   a ,  11   b ,  11   c  is symmetrically opposite two valve seats  7   b ,  7   c ;  7   c ,  7   a  and  7   a ,  7   b.  The width of each plunger, for example  11   a , is sufficiently large to ensure that it can touch tangentially the ball  8 , when the latter lies on one of the two seats  7   b ,  7   c  located in front of the plunger, and can push the ball in front of it, and, on the other hand, is sufficiently small to ensure that the plunger can be pushed forward inside the seat chamber  5  to an extent such that it overcomes the fin  22  between adjacent valve seats and, assisted by the leaf spring (not illustrated here), reaches the valve seat  7   a  located opposite the plunger  11   a , without either plunger  11   a  touching the other two plungers  11   b ,  11   c.    
         [0033]     A multiway valve, as described above, can be used particularly in the refrigerant circuit of a refrigerator. In this case, the refrigerant that circulates in the circuit, for example isobutane, can be utilized as the working substance in the cylinder chambers  13   a ,  13   b.  The performance of the heating resistor  17   a  and  17   b  and of the heating current supply circuit assigned to them are sufficiently dimensioned, as a function of the other dimensioning of the refrigerant circuit, to ensure that the refrigerant can evaporate in the cylinder chambers  13   a ,  13   b.