Abstract:
In a valve arrangement for closing off a working line in a refrigeration system, the working line includes a high and a low-pressure section. An expansion valve is coupled to the working line and has a working pressure chamber forming part of the valve. A control line system that includes a control device is coupled to the expansion valve and defines a connection that is in full communication with the high and low pressure sections of the working line. A closure element forming part of the control device is positioned in the connection line and arranged in the pressure equalizing configuration that couples the working pressure chamber of the expansion valve to the low-pressure section of the working line.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in German Patent Application No. 101 25 789.9 filed on May 26, 2001. 
     FIELD OF THE INVENTION 
     The invention relates to a valve arrangement for shutting off a working line in a refrigeration system with an expansion valve, which is arranged in the working line, and a control line system connecting the expansion valve with a low-pressure side and a high-pressure side of the working line, the expansion valve being controllable by the control line system, and the control line system being able to provide a closing pressure in the expansion valve by means of a control device. 
     BACKGROUND OF THE INVENTION 
     An arrangement of this kind is known from “Sporlan Bulletin 30-10” of January 1993, pages 17 and 18 wherein a valve arrangement is shown, in which the working line of a refrigeration circuit can be closed by means of a solenoid valve. The actual closing and opening of the working line takes place via the expansion valve, which is controlled by the solenoid valve. The solenoid valve is a 3-way valve, which has a connection line for the expansion valve, as well as a high-pressure connection and a pressure-equalising connection for the working line. During normal operation of the expansion valve, the connection line is connected with the pressure-equalising line via the solenoid valve. In order to close the expansion valve, the connection between the connection line and the pressure-equalising connection is closed via the solenoid valve, and at the same time a connection is created between the connection line and the high-pressure connection. The high pressure, which now is controlling in the expansion valve, ensures that the expansion valve closes the working line. 
     U.S. Pat. No. 6,053,417 shows a valve arrangement with a solenoid valve working directly in the working line within the expansion valve. When closing the solenoid valve, a high pressure propagates inside the expansion valve and ensures that a valve element, which is also arranged in the working line, comes to rest against a valve seat. This arrangement of both valves in the working line should reduce the disturbing noises when opening and closing the expansion valve. When, however, this is to be used with large refrigeration systems, the solenoid valve must also be large, which causes an increase in the cost of such refrigeration systems. 
     Thus, the prior art arrangements have either employ small, relatively expensive control devices, which are arranged outside the working line, or relatively large control devices, which work within the working line. In both cases, the manufacturing cost is high for the valve arrangement. 
     Based on the foregoing it is the general object of the present invention to improve upon or overcome the problem and drawbacks associated with the prior art. 
     SUMMARY OF THE INVENTION 
     The invention is based on the task of simplifying the closing of a working line in a refrigeration system. 
     According to the invention, this task is accomplished by means of a valve arrangement, in which the control device has a closure element in a connection path, via which the control line system connects a high-pressure side with a low-pressure side and the closing pressure can build up in the expansion valve. 
     In this way, it is possible to build up the closing pressure for the expansion valve by shutting off the connection path in the control line system. The size of the closing element merely has to be adapted to the connection path, which can be relatively small compared with the working line. “Working line” here means the line, in which the actual flow of a refrigerant in the refrigeration system occurs. On the other hand, the control line system comprises lines like those of the connection path, which merely ensure a gradual pressure equalising or propagation of control pressures. 
     It is favourable that the closing element is arranged in a pressure-equalising connection, which connects a working pressure chamber of the expansion valve with the low-pressure side. With such an arrangement, a high pressure, which acts upon the working pressure chamber of the expansion valve from the high pressure side via the control line system, is removed again via the pressure-equalising connection. In the closed state of the closing element, however, the high pressure builds up before the closing element and acts back upon the working pressure chamber. Thus, in a simple way, the high pressure available in the refrigeration system can be utilised for closing the expansion valve. In this way, a fast and reliable closing of the expansion valve can be ensured. 
     It is advantageous that the smallest cross-section of the pressure-equalising connection is larger than that of a high-pressure control line, which connects the working pressure chamber with the high-pressure side. Thus, it is achieved that the high pressure, which acts upon the connection path from the high-pressure side, is removed again via the pressure-equalising connection in the open state of the closing element, and cannot build up in the working pressure chamber at all. In this way, an unwanted closing of the expansion valve can be prevented. In this case, the expansion valve works as an expansion valve without a high-pressure control line. The pressure-equalising connection, the high-pressure control line and the working pressure chamber form the connection path. 
     Further, it is advantageous that the relationship between the smallest cross-section of the high-pressure control line and the smallest cross-section of the pressure-equalising line is approximately 1:20. In the open state of the closing element, this means that the pressure in the high-pressure control line is removed reliably via the pressure-equalising line. In this way, a high operation reliability of the arrangement can be achieved. 
     Further, it is favourable that the area of the pressure-equalising connection acted upon by the closing element is arranged outside a valve housing of the expansion valve. With this method, it is possible also to use commercially available expansion valves. Such valves can be modified or expanded in a simple way, which reduces the costs. 
     In a further embodiment, the area of the pressure-equalising connection, upon which the closing element acts, is arranged inside the valve housing of the expansion valve. In this way, a relatively compact design of the valve arrangement can be achieved. 
     Further, it is advantageous that the closing element is made on the valve housing of the expansion valve. In this way, an optimum matching between the control device and its closing element can be achieved during manufacture of the expansion valve. Thus, the mode of operation of the valve arrangement can be optimised. Further, this ensures a compact design of the expansion valve and the closing element. 
     It is also favourable that the high-pressure control line is arranged outside the valve housing of the expansion valve. Such a high-pressure control line can also be fitted on a commercially available expansion valve in a simple manner. Thus, the manufacturing cost of the valve arrangement can be further reduced. 
     In an alternative embodiment, the high-pressure control line is arranged inside the valve housing of the expansion valve. 
     Further, it is favourable that the high-pressure control line is formed by a predetermined leakage path in the expansion valve. Such predetermined leakage paths are very easily made in a traditional expansion valve, for example, by removing seals. Thus, separate bores for creating the high-pressure control line can be avoided. The leakage paths can, for example, be in the shape of bores, in which movable parts of the expansion valve are guided and which connect the working line with the working pressure chamber. 
     It is also advantageous that the connection path through the closing element can be hermetically closed. The term “hermetical” means that with the conditions occurring during normal operation, an at least substantially tight closing of the connection path is achieved. In this way, it is possible to build up a particularly high closing pressure for the expansion valve. Further, the closing pressure is available relatively fast. 
     Further, it is favourable that the closing element is in the form of a solenoid valve. Thus, it is possible to select a proven control device, which ensures a reliable operation of the valve arrangement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention is described in detail on the basis of a preferred embodiment in connection with the drawings, showing: 
     FIG. 1 schematically illustrates a refrigeration system with a known valve arrangement 
     FIG. 2 schematically illustrates a refrigeration system with a valve arrangement according to the invention 
     FIG. 3 schematically illustrates a refrigeration system with a further embodiment of the valve arrangement according to the invention 
     FIG. 4 is a cross-sectional side view through a valve arrangement according to FIG. 2 
     FIG. 5 is a cross-sectional side view through a further embodiment of the expansion valve arrangement according to FIG. 2 with an integrated high-pressure control line 
     FIG. 6 is a cross-sectional side view through a further embodiment of the expansion valve arrangement according to FIG. 2 without a separate high-pressure control line 
     FIG. 7 is a cross-sectional side view through a valve arrangement according to FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a traditional refrigeration system  1 , in which a compressor  2 , a condenser  3 , a closing element  4 , an expansion valve  5  and an evaporator  6  are arranged in series in a circuit via a working line  7 . The closing element is in the form of a solenoid valve. In a flow direction, indicated by the arrow labelled  8 , of a refrigerant of the refrigeration system  1 , a low-pressure side  9  of the working line  7  is connected downstream, between the expansion valve  5  and the compressor  2 , and a high-pressure side  10  of the working line  7  is connected upstream of the expansion valve  5 . 
     Further, the refrigeration system  1  has a control line system  11  with a pressure-equalizing connection  12 , which connects the expansion valve  5  with the low-pressure side of the working line  7 . Further, the refrigeration system  1  has a thermal connection  13 , which connects a bulb  14 , which is arranged in an area of the low-pressure side  9  on the working line  7  downstream of the evaporator  6 , with the expansion valve  5 . The expansion valve  5 , the closing element  4 , the control line system  11  as well as the thermal connection  13  and the bulb  14  form a valve arrangement  15 . 
     The operation of such a refrigeration system  1  is commonly known. The refrigerant of the refrigeration system  1  leaves the compressor  2  as a gas under high pressure and is subsequently condensed under heat emission in the condenser  3 . Subsequently, the liquid refrigerant passes the solenoid valve  4  and reaches the expansion valve  5 . Here, the refrigerant is expanded and passed on to the evaporator as a mixture of gas and fluid, which now has a relatively low pressure. In the evaporator  6 , the refrigerant is evaporated under heat absorption and returns to the condenser  2  as superheated gas. 
     During normal operation, such a refrigeration system  1  is turned on as soon as an area to be cooled exceeds a predetermined turn-on temperature. The refrigeration system  1  stays on, until the temperature in the refrigerated area drops below a predetermined turn-off value. Then, the refrigeration system  1  is turned off and stays off until the temperature once again exceeds the predetermined turn-on temperature. 
     With the solenoid valve  4  liquid refrigerant is prevented from being trapped in the compressor  2  or between the compressor  2  and the evaporator  6  when the refrigeration system  1  is turned on. Otherwise, the compressor  2  would attempt to compress the liquid refrigerant, which could cause damage to the compressor. For this reason, the solenoid valve  4  of the valve arrangement  15  is located directly in the working line  7 , and must be relatively large, which in turn causes relatively high costs on the refrigeration system  1 . 
     FIG. 2 shows the refrigeration system  101  with an embodiment of the valve arrangement  115  in accordance with the present invention. The refrigeration system shown in FIG. 2 is somewhat similar to that of FIG. 1 with like elements bearing the same reference numbers preceded by the number  1 . 
     The closing element  104  is arranged in the pressure-equalizing connection  112  of the control line system  111  (dashed lines). The control line system  111  has a high-pressure control line  116 , which extends from the expansion valve  105  to the high-pressure side  110 . 
     FIG. 3 shows the refrigeration system with a further embodiment of the valve arrangement  215 . The refrigeration system  201  shown in FIG. 3 is somewhat similar to the refrigeration system shown in FIGS. 1 and 2. Accordingly, like elements will be indicated by like reference numbers preceded by the number  2 . In this embodiment, the closing element  204  is arranged in a pressure-equalizing connection  212 , which connects the expansion valve  205  with an area of the low-pressure side  209 , which is arranged between the expansion valve  205  and the evaporator  206 . 
     Further, this embodiment comprises a bulb  214  arranged between the expansion valve  205  and the evaporator  206  on the working line  207 . The bulb  214  is provided with a heating element, which is controlled by a control unit RE. The control of the heating occurs via data, which is obtained from a temperature sensor  217  and a pressure sensor  218 . The temperature sensor  217  and the pressure sensor  218  arranged at the outlet of the evaporator  206  on the working line  207 . 
     FIG. 4 shows a cross-section through a valve arrangement  115  according to the invention in accordance with FIG.  2 . It has an expansion valve  105 , comprising a valve housing  119 , a diaphragm capsule  120 , an inlet  121  on the high-pressure side  110  and an outlet  122  on the low-pressure side  109 . The inlet  121  and the outlet  122  are connected with each other via a connection channel  123 . In this connection channel  123  a valve seat  124  is formed, which cooperates with a valve element  125 . The valve element  125  is biased in the direction of the valve seat  124  by means of a spring  126 . 
     The diaphragm capsule  120  is fixedly connected with the valve housing  119  of the expansion valve  105 . The inside of the diaphragm capsule is divided by a diaphragm  127 . Over the diaphragm  127  a thermal pressure chamber  128  is formed, in which a capillary tube  129  ends, which is connected with the bulb  114 . Under the diaphragm  127 , the diaphragm capsule  120  has a working pressure chamber  130 . In the following, the terms “over” and “under” merely refer to the views in FIGS. 4 to  7 . Of course, also any other orientation of the valve arrangement  115  is possible. 
     The pressure in the thermal pressure chamber  128  depends on the temperature at the location of the bulb  114 . The high-pressure control line  116  from the high-pressure side  110  as well as the pressure-equalizing connection  112  from the low-pressure side  109  of the working line  107  open into the working pressure chamber  130 , under the diaphragm  127 . In this way, the high-pressure control line  116 , the working pressure chamber  130  and the pressure-equalizing connection  112  form a connection path that is part of the control line system  111 . Both the high-pressure control line  116  and the pressure-equalizing connection  112  are substantially arranged outside the valve housing  119 . Inside the valve housing  119 , the high-pressure control line  116  has a restriction  131  and the pressure-equalizing connection  112  has a bore  132 . Further, the closing element  104 , in the form of a solenoid valve (schematic view), is arranged in the pressure-equalizing connection  112 . 
     At the bottom side of the diaphragm  127  is arranged a diaphragm plate  133 , which is connected with a pressure pin  134 . The pressure pin  134  is guided in a pin bore  135  of the valve housing  119  and connects the diaphragm plate  133  via the connection channel  123  with the valve element  125 . Under the diaphragm plate  133 , a seal  136  comprising several seal parts is provided in the valve housing  119 , the seal  136  seals the working pressure chamber  130  from the connection channel  123 . 
     In the open state of the solenoid valve  104 , the valve arrangement  115  works like a traditional arrangement. The working pressure chamber  130  is connected with the high-pressure side  110  via the high-pressure control line  116  and with the low-pressure side  109  of the working line  107  via the pressure-equalizing connection  112 . As the restriction  131  of the high-pressure control line  116  has a substantially smaller cross-section than the bore  132  of the pressure-equalizing connection  112 , the pressure from the high-pressure side  110  in the working pressure chamber  130  is removed again via the pressure-equalizing connection  112 . The pressure in the working pressure chamber  130  is thus substantially determined by the pressure of the low-pressure side  109 , which is typically approximately 5 bars. 
     A relation of 1:20 between a minimum cross-section of the high-pressure control line  116  to the minimum cross-section of the pressure-equalizing connection  112  has proved to be favorable. In this case, the forces, which act upon the diaphragm  127  from the spring  126  and the pressure in the working pressure chamber  130 , are approximately as large as the force, which acts upon the diaphragm  127  from the pressure in the thermal pressure chamber  128 . Via these generally oppositely directed forces acting upon the diaphragm  127 , the position of the valve element  125  in relation to the valve seat  124 , and thus the opening and closing of the connection channel  123  in the expansion valve  105 , is determined. The forces occurring in the connection channel  123  because of the flow of the refrigerant are thus substantially balanced. 
     When the solenoid valve  104  is closed, the pressure from the high-pressure side  110  is built up in front of the solenoid valve  104  via the high-pressure control line  116 , the working pressure chamber  130  and the beginning of the pressure-equalizing connection  112  and acts backward upon the working pressure chamber  130 . Typically, this causes the pressure in the working chamber  130  to increase to approximately 15 bars, however, the invention is not limited in this regard. This causes the diaphragm  127  to be pressed upwards, which again causes the valve element  125  to be pressed against the valve seat  124  via the diaphragm plate  133  and the pressure pin  134 . In this way, the closing of the solenoid valve  104  also causes the expansion valve  105  to close. 
     FIG. 5 shows an alternative embodiment of the valve arrangement according to FIG. 4 in which the complete high-pressure line  316  is formed inside the valve housing  319 . Also this high-pressure control line  16  has the restriction  331 , which is now formed direct at the inlet  321  of the expansion valve  305 . 
     A further alternative embodiment of the valve arrangement  415  is shown in FIG.  6 . It shows a traditional expansion valve  405 , which has no specifically designed signal line from the high-pressure side  410  to the working chamber  430 . The function of the high-pressure control line  116 , 316  according to FIGS. 4 and 5 is taken over by a leakage path  437 , which is formed between the bore  435  and the pressure pin  434 . In order that the pressure from the high-pressure side  410  can be passed on to the working pressure chamber  430  via the inlet  421  and the leakage path  437 , the seal  136 , 336  under the diaphragm plate  133 , 333  must be removed. 
     FIG. 7 shows an additional embodiment of the valve arrangement in accordance with the refrigeration system shown schematically in FIG.  3 . It shows an expansion valve  205 , in which the pressure-equalizing connection  212  is made inside the valve housing  219 . The pressure-equalizing connection  212  connects the working pressure chamber  230  via the closing element  204  with the outlet  222  of the expansion valve. The closing element  204  is also made directly on the valve housing  219 . In this way, the expansion valve  205  and the closing element  204  can be optimally matched to each other during manufacture. Also in this embodiment, the function of the high-pressure control line  116 , 316  is taken over by the leakage path  237 . As shown already in FIG. 3, the bulb  214  of this valve arrangement  215  is arranged immediately next to the outlet  222  of the expansion valve  205 . The bulb  214  is provided with a heating element, with which the bulb temperature can be controlled. 
     It is also possible to combine the embodiments of the individual elements of FIGS. 4 to  7  in any other possible way. Further, the diaphragm  127 - 427  in the expansion valve  105 - 405  can be replaced by a bellows or any other suited and known deformation element. 
     Additionally, the solenoid valve  104 , 404  can be replaced by any other known and suited valve type, by means of which a sufficiently tight closing of the connection path can be achieved. 
     Additionally to the refrigeration systems  101 , 201  shown schematically in FIGS. 2 and 3, the valve arrangement  115 , 215  can also be used in any other suited refrigeration system  1 . For example, such a use would also be appropriate in a system, in which a manual stop valve is normally arranged in series with a solenoid valve  4  and an expansion valve  5  in the working line  7 . When such a system leaves the factory, refrigerant is often trapped in the working line  7  between the manual stop valve and the solenoid valve  4 . During transport, the pressure in this section of the working line  7  between the two valves can become so high, that the working line is damaged. To avoid this, the solenoid valve  4  is usually equipped with a check valve, which opens in the direction of the expansion valve at a pressure of, for example, 25 bars. When using one of the valve arrangements  115 , 415  described above, in accordance with the FIGS. 2 to  7 , however, such a check valve can be avoided. In such an arrangement, the damaging pressure between the manual stop valve and the expansion valve cannot occur, as the expansion valve  105 - 405  is not completely tight.