Abstract:
A four-way reversing valve includes a valve casing having a plurality of ports through which fluid flows, a valve main body fixedly installed to the valve casing and having a valve chamber in which a plurality of main port connection holes for selectively connecting the ports are formed, a main spool rotatably installed at the valve chamber of the valve main body, for selectively connecting the ports according to a rotation position, and a spool driving unit for reversibly rotating the main spool by using part of fluid supplied through one of the ports in the valve casing. Thus, the number of welding points is minimized by incorporating the overall pilot valves and excluding additional capillary connection for the pilot valves. Also, manufacturing thereof is made easy and, during the manufacturing and use thereof, the rate of breakdown due to defective welding can be remarkably reduced.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a four-way reversing valve which is one of direction control valves to control the direction of flow of liquid in a hydraulic or pneumatic circuit and is used, for example, to change the flow of coolant when a cooling or heating operation is selected in a heat pump air conditioning system for a double use of cooling and heating, and particularly, is configured as a solenoid hydraulic operating type using an inner pilot method by incorporating a solenoid-controlled pilot-operated valve and a vane type spool valve which is operated by pilot hydraulic pressure of the solenoid-controlled pilot-operated valve. 
     2. Description of the Related Art 
     A heat pump air conditioning system for a double use of cooling and heating uses a heat transfer mechanism performed during a cycle formed of compression, condensation, expansion, and evaporation of coolant and generates cold or hot air flow needed for cooling or heating through heat exchange between the condensation and evaporation steps. Theoretically, the cooling operation or heating operation in such a system could be selected by switching the position of heat exchangers (a condenser and an evaporator) used in the condensation and evaporation steps, respectively. However, switching the positions of the condenser and the evaporator is practically impossible. Thus, the flow of coolant with respect to the condenser and evaporator is changed by using a four-way reversing valve that is one of direction control valves. 
     A conventional four-way reversing valve used for the cooling/heating operation of a heat pump air conditioning system for a double use of cooling and heating, as shown in FIG. 1, is an inner pilot type four-port two-position solenoid-hydraulic operated direction control valve combined with a main valve  10  and a pilot valve  20 . The main valve  10  has four ports and two pilot connection holes located at both left and right ends of the main valve  10 . Four coolant connection pipes  11 ,  12 ,  13 , and  14  connected to an outlet and an inlet of a compressor and coolant pipes of indoor and outdoor heat exchangers of an air conditioning system are welded at the main valve  10 . Also, the pilot valve  20  is combined with the main valve  10  into an inner pilot type through four capillary pipes  21 ,  22 ,  23 , and  24 . Reference numeral  27  denotes a solenoid coil for controlling the pilot valve  20 . 
     FIGS. 2A and 2B show the conventional four-way reversing valve together with an air conditioning system circuit. Referring to the drawings, the pilot valve  20  combined with the main valve  10  is a four-port two-position spring offset solenoid operated type. A pilot spool  25  is moved to a normal position by a spring  26  and a converting position by an electromagnetic force obtained by exciting the solenoid coil  27  so that one of load ports A and B of the pilot valve  20  is connected to a supply port P while the remaining load port is connected to a drain port R. The exciting current of the solenoid coil  27  is blocked when a cooling operation of an air conditioning system is selected. After a heating operation is selected, the exciting current of the solenoid coil  27  is continuously applied during the operation. 
     That is, when the cooling operation is selected, the pilot spool  25  is positioned at the normal position as shown in FIG.  2 A. Here, pilot pressure in a chamber  15  at one side of the main valve  10  is higher than the other side of the main valve  10 . Then, a main spool  17  of the main valve  10  is moved to the left and a supply port P of the main valve  10  is connected to a load port A thereof. A load port B of the main valve  10  is connected to a drain port R thereof. Thus, in the air conditioning system, coolant exhausted from an outlet of a compressor  1  is transferred to an outdoor heat exchanger  2  through the ports P and A of the main valve  10  so that the outdoor heat exchanger  2  works as a condenser. The coolant depressurized by an expansion mechanism  3  is transferred to the indoor heat exchanger  4  so that the indoor heat exchanger  4  works as an evaporator. The coolant is transferred from the indoor heat exchanger  4  to an inlet of the compressor  1  through the port B and R of the main valve  10 , thus a cooling cycle is carried out. 
     Next, when a heating operation is selected, the pilot spool  25  is moved to a converting position by the solenoid coil  27 , as shown in FIG.  2 B. Here, pilot pressure in a chamber  16  at the other side of the main valve  10  is higher than the chamber  15 . Then, the main spool  17  of the main valve  10  is moved to the right and the supply port P is connected to the load port B. The load port A at the other side of the load is connected to the drain port R. Thus, in the air conditioning system, the coolant exhausted from the outlet of the compressor  1  is transferred to the indoor heat exchanger  4  through the ports P and B of the main valve  10  so that the indoor heat exchanger  4  works as a condenser. The coolant depressurized by the expansion mechanism  3  is transferred to the outdoor heat exchanger  2  so that the outdoor heat exchanger  2  works as an evaporator. The coolant is transferred from the outdoor heat exchanger  2  to the inlet of the compressor  1  through the port A and R of the main valve  10 , thus a heating cycle is carried out. 
     In the meantime, Korean Registration Utility Model Publication Nos. 0127597, 0130152, and 20-0213450 and Korean Patent Publication No. 2001-0007231 disclose various types of main valve operating means in which a slide type spool of the main valve is directly converted by using a thermodynamic piston mechanism, instead of the above-descried pilot valve, or a rotary spool driven by an electric motor is provided at the main valve. 
     However, the thermodynamic piston mechanism or electric motor for directly driving the main spool is hardly used because converting time is slow and converting operation is inaccurate, and thus the use of such devices results in malfunctions in the operating system. 
     As a valve used in a hydraulic or pneumatic circuit, a solenoid operated type valve such as the above-described pilot valve is widely used due to its merits of easy control of automatic operation or remote operation and fast and accurate converting time. However, since the solenoid operated type valve utilizes electrical thrust of a solenoid, it is not appropriate for a case of controlling a huge amount of fluid and is usually used for conversion at a pressure of 210 kg/cm 2  and the maximum fluid amount of 80 l/min. Accordingly, the conventional four-way reversing valve as described above is generally configured such that the main valve is a hydraulic operating type and the pilot valve operating the main valve is a solenoid operated type. 
     To manufacture a four-way reversing valve formed by combining the main valve and the pilot valve, capillary pipes whose diameters are small are further provided, in addition to the coolant connection pipes welded at the main valve. Thus, the number of welding points increases so that manufacturing of a four-way reversing valve becomes complicated and breakdown during manufacture and use thereof is frequent due to welding defects. 
     SUMMARY OF THE INVENTION 
     To solve the above-described problems, it is an object of the present invention to a four-way reversing valve which is a solenoid operated type exhibiting an easy control and fast and accurate converting time, in which pilot pressure is converted and a vane type main spool is rotated by using the converted pilot pressure, so that the number of welding points are minimized. 
     To achieve the above object, there is provided a four-way reversing valve which comprises a valve casing having a plurality of ports through which fluid flows, a valve main body fixedly installed to the valve casing and having a valve chamber in which a plurality of main port connection holes for selectively connecting the ports are formed, a main spool rotatably installed at the valve chamber of the valve main body, for selectively connecting the ports according to a rotation position, and a spool driving unit for reversibly rotating the main spool by using part of fluid supplied through one of the ports in the valve casing. 
     It is preferred in the present invention that the ports of the valve casing comprise a supply port for connecting to a fluid supply source, two load ports for connecting to an external load, and a drain port for draining, the main spool comprises a spool portion for selecting one of the two load ports and a groove passing through the spool portion and connected to the drain port, and the four way reversing valve operates by forming a first main flow path for moving fluid from the supply port to one of the two load ports via the valve chamber, and a second main flow path for moving fluid from the other one of the two load ports to the drain port via the groove. 
     It is preferred in the present invention that the valve main body further comprises a pilot hydraulic chamber which is formed by extending one side of the valve chamber and has two pilot input and output ports penetrating the pilot hydraulic chamber to alternately input and output the part of fluid in two opposite directions inside the valve casing and a pilot drain port for obtaining a pilot hydraulic pressure, that the main spool further comprises a vane portion formed by extending one side of the main spool to be rotatable between the two pilot input and output ports in the pilot hydraulic chamber, and that the spool driving unit can select one of the two pilot input and output ports. 
     It is preferred in the present invention that the spool driving unit comprises a solenoid for generating an electrical thrust by being excited by an electric signal, a plunger moved by the electrical thrust of the solenoid, a spring developing an elastic force to return the plunger in an opposite direction to the electrical thrust, and a pilot spool coupled to the plunger, and moving and returning together with the plunger and having a cavity for connecting one of the two pilot input and output ports and the drain port. 
     According to the present invention, since the main spool is directly rotated by applying pilot hydraulic pressure in the valve main body, the additional capillary pipe needs not be welded unlike the conventional technology. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above object and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
     FIG. 1 is a perspective view of a conventional inner pilot type solenoid hydraulic pressure operated four-way reversing valve; 
     FIGS. 2A and 2B are coolant circuit views for cooling operation and heating operation of a heat pump air conditioning system for a double use of cooling and heating adopting the conventional four-way reversing valve; 
     FIG. 3 is a perspective view of a four-way reversing valve according to the present invention; 
     FIG. 4 is an exploded perspective view of the four-way reversing valve according to the present invention; 
     FIG. 5 is a vertical sectional view of the four-way reversing valve according to the present invention; 
     FIGS. 6A and 6B are sectional views taken along line VI—VI of FIG. 5, showing a pilot spool converting state of the four-way reversing valve according to the present invention; and 
     FIGS. 7A and 7B are sectional views taken along line VII—VII of FIG. 5, showing a main spool converting state of the four-way reversing valve according to the present invention 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 3, a four-way reversing valve according to the present invention includes a cylindrical valve casing  30 . The valve casing  30  has a supply port P formed at one side of the upper surface thereof, two load ports A and B formed with a slight gap between them and placed at the same height on the outer circumferential surface thereof, and a drain port R formed at the center of the lower surface thereof. Coolant connection pipes  31 ,  32 ,  33 , and  34 , connected to the respective portions of an air conditioning system, for example, the outlet and inlet of the compressor and respective coolant pipes of the heat exchangers, are welded at the respective ports and bent properly. Reference numeral  70  denotes a solenoid installed at the upper surface of the valve casing  30 . The solenoid is operated to convert the valve by being excited by an electric signal. The electric signal is applied only when the heating operation of an air conditioning system is selected, but not applied when cooling operation is selected. 
     Referring to FIG. 4, the valve casing  30  is formed into a cup shape by processing metal such as brass. A cap  36  having a disc shape is capped on a hooking step  35  formed at the upper portion of the valve casing  30  and the edge of the cap  36  is welded to seal the cap  36 . It is possible to screw together the valve casing  30  and the cap  36  with a separate sealing member so that they can be easily assembled and disassembled. 
     A valve main body  40  fixedly installed in the valve casing  30  is a mold formed by injecting resin, for example. The valve main body  40  includes a cylindrical body portion  41 , a flange portion  42  at the upper portion of the body portion  41 , and a block support portion  43  at the upper portion of the flange portion  42 . The body portion  41  has a diameter slightly less than the inner circumferential surface of the valve casing  30 , so that it can be easily inserted during assembly. The flange portion  42  has such a diameter as to tightly fit to the inner circumferential surface of the valve casing  30 , so that it can be placed on a hooking step  37  formed on the inner circumferential surface of the valve casing  30  and fixed thereon. A cut-away portion  44  is formed at one side of the flange portion  42  and the block support portion  43  and accommodates an end portion  31   a  of a coolant connection pipe  31  penetrating the supply port P formed at the cap  36 . 
     The valve main body  40  has a valve chamber  50   a  formed in the body portion  41  and a pilot hydraulic chamber  50   b  formed by extending the side of the valve chamber  50   a . The valve chamber  50   a  is connected to the coolant connection pipe  31  at the support port P through a main port connection hole  51  at the supply&#39;s side penetrating the cut-away portion  44  of the flange portion  42  above the valve chamber  50   a . Also, the valve chamber  50   a  can be connected to each of the coolant connection pipes  32  and  33  at the side of load ports A and B through main port connection holes  52  and  53  at the load&#39;s side penetrating a wall surface of the body portion  41 . The pilot hydraulic chamber  50   b  is formed by cutting the wall surface and bottom surface of the body portion  41  to secure a sufficient space and thus encompassed by the wall surface and bottom surface of the inner circumference of the valve casing  30  exposed thereto and fixed vanes  57  and  58  at both ends of the cut portion. Two pilot input ports  54  and  55  respectively formed along the wall surface at the side of the fixed vanes  57  and  58  and above the flange portion  42  penetrate the pilot hydraulic chamber  50   b . A pilot drain port  56  of the pilot hydraulic chamber  50   b  penetrates the center of the flange portion  42  to be always connected to a second flow path of the main spool  60  which is described later. 
     The body portion  41  of the valve main body  40  is cut in a diametric direction between the valve chamber  50   a  and the pilot hydraulic chamber  50   b  and seal blocks  45  and  46  are inserted in the cut portion. The seal blocks  45  and  46  maintain sealing with respect to a boss portion  61  of the main spool  60  which is described later by the inner end portions thereof and the inner circumferential surface of the valve casing  30  by the outer end portions thereof, so that the valve chamber  50   a  and the pilot hydraulic chamber  50   b  are separated into sealed spaces. Seal rings  47  and  48  installed around the main port connection holes  52  and  53  at the load&#39;s side on the outer circumferential surface of the body portion  41  in a half-embedded state closely contact the load ports A and B penetrating the inner circumferential surface of the valve casing  30  to maintain a sealing state. The seal blocks  45  and  46  and the seal rings  47  and  48  are formed of a material exhibiting a high mechanical and sealing feature, for example, Teflon based resin. 
     The main spool  60  is formed of a cylindrical boss portion  61 , a spool portion  62  extending from one side of the boss portion  61  and accommodated in the valve chamber  50   a , a vane portion  63  extending from the other side of the boss portion  61  and accommodated in the pilot hydraulic chamber  50   b , and a groove  64  formed from the end of the spool portion  62  to the lower end portion of the boss portion  61 . The groove  64  at the end of the spool portion  62  is connected to the load port A or B through one of the main port connection holes  52  and  53  at the load&#39;s side of the valve main body  40  and always connected to the drain port R of the bottom of the valve casing  30  at the lower end portion of the boss portion  61 , thus forming the second main flow path. Also, a drain connection hole  65  for connecting the pilot drain port  56  of the valve main body  40  to the groove  64  is formed by penetrating the upper end portion of the boss portion  61  of the main spool  60 . 
     Sealing rings  66  and  67  formed of Teflon-based resin are coupled to the upper and lower end portions of the boss portion  61  of the main spool  60  to seal around the drain connection hole  65  penetrating the flange portion  42  of the valve main body  40  and around the drain portion R at the bottom of the valve casing  30 . Seal members  68  and  69  formed of Teflon-based resin are coupled to the end portion of the spool portion  62  to maintain sealing with the inner circumferential wall surface at the side of the valve chamber  50   a  and to the edge of the vane portion  63  to maintain sealing with the ceiling of the pilot hydraulic chamber  50   b  and the inner circumferential wall surface and the bottom surface of the valve casing  30 . 
     Next, the solenoid  70 , a stem  71 , a plunger  72 , a pilot spool  75 , and a spool seat block  80  are provided as a pilot hydraulic converting means. The solenoid  70  is inserted around the stem  71  and fixed by a screw  77 . An end portion of the stem  71  penetrates the cap  36  so that the stem  71  is fixedly welded on the cap  36  to erect thereon. The plunger  72  is inserted in the stem  71  together with a spring  74  and always protrudes toward a normal position (refer to FIG. 6A) in a spring offset manner. When the solenoid  70  is excited, the plunger  72  is pulled to a converting position (refer to FIG. 6B) by an electrical thrust. The pilot spool  75  has a concave cavity  76  and is inserted into a groove  73  formed in an end portion of the plunger  72 . the pilot spool  75  closely contacts a seat surface  81  of the spool seat block  80  and slides thereon and moves together with the plunger  72 . 
     The spool seat block  80  accommodated on the block support portion  43  of the valve main body  40  is manufactured by processing metal such as brass and has three pilot port connection holes  82 ,  83 , and  84  formed in the seat surface  81  which are open with an interval in a vertical direction, that is, in a direction in which the plunger  72  moves. The interval between two neighboring ones of the three pilot port connection holes  82 ,  83 , and  84  is less than the diameter of the cavity  76  of the pilot spool  75  and the length between the uppermost pilot port connection hole  82  and the lowermost pilot port connection hole  83  is greater than the diameter of the cavity  76 . That is, when the pilot spool  75  is in a normal position, the lower two neighboring pilot port connection holes  83  and  84  are connected by the cavity  76  of the pilot spool  75  and the uppermost pilot port connection hole  82  is exposed outside the cavity  76  (referring to FIG.  6 A). At the converting position, the upper two neighboring pilot port connection holes  82  and  84  are connected by the cavity  77  of the pilot spool  75  and the lowermost pilot port connection hole  83  is exposed. 
     The two uppermost and lowermost pilot port connection holes  82  and  83  of the pilot port connection holes  82 ,  83 , and  84  of the spool seat block  80  are connected to the two pilot input ports  54  and  55  formed in the valve main body  40  and the other pilot port connection hole  84  is connected to the pilot drain port  56 . 
     In FIG. 5, reference numerals  38  and  49  denote a concave groove and a protrusion correspondingly formed to guide an assembly position when the valve main body  40  is assembled to the valve casing  30 . 
     In the operation of the four-way reversing valve according to the present invention, referring to FIG. 5, most of fluid (coolant) supplied through the coolant connection pipe  31  at the side of supply port P flows into the valve chamber  50   a  through the port connection hole  51  at the supply&#39;s side. Part of the fluid flows into a space at the upper side of the flange portion  42  of the valve main body  40  along a gap provided at the inner circumferential surface of the valve casing  30  and further enters in the one side of the pilot hydraulic chamber  50   b  through one of the two pilot port connection holes  82  and  83  of the spool seat block  80  exposed to the space. 
     When the solenoid  70  is not in an excited state, the plunger  72  protrudes downward by the spring  74 , that is, at the normal position on the seat surface  81  of the spool seat block  80 . When the pilot spool  75  is positioned at the normal position, as shown in FIG. 6A, the lower two pilot port connection holes  83  and  84  of the three pilot port connection holes  82 ,  83 , and  84  formed in the spool seat block  80  are connected by the cavity  76  of the pilot spool  75  and the uppermost pilot port connection hole  82  is exposed. Thus, part of the fluid supplied from the supply port P flows in the exposed uppermost pilot port connection hole  82  and moves toward the pilot hydraulic chamber  50   b  through the pilot input port  54  at one side connected thereto. 
     The fluid input to the pilot hydraulic chamber  50   b  through the pilot input port  54  at one side applies pressure to the vane portion  63  of the main spool  60  from the fixed vane  57  at one side toward the fixed vane  58  at the other side, so that the entire main spool  60  rotates clockwise. 
     When the main spool  60  is rotated clockwise, as shown FIG. 7A, the load port A at one side of the two load ports A and B is connected to the valve chamber  50   a , forming a first main flow path. Also, the load port B at the other side is connected to the drain port R through the groove  64  of the main spool  60 , forming a second main flow path. Thus, the air conditioning system is set to perform a cooling operation. 
     In the meantime, during the clockwise rotation of the main spool  60 , the fluid remaining in the clockwise direction of the vane portion  63  in the pilot hydraulic chamber  50   b  is exhausted through the pilot input port  55  at the other side formed in the main spool  60 . As shown in FIG. 6A, the remaining fluid proceeds via the pilot port connection hole  83  connected to the pilot input port  55 , the cavity  76  of the pilot spool  75 , and the pilot port connection hole  84 . Then, as shown in FIG. 5, the fluid sequentially passes the pilot drain port  56  of the valve main body  40  and the drain connection hole  65  of the main spool  60 , and is guided toward the groove  64  of the main spool  60  forming the second main flow path. The fluid joins the main stream of the fluid flowing along the second main flow path of the groove  64  and then is drained. 
     Next, when the solenoid  70  is excited, the plunger  72  is pulled upward by an electrical thrust according to the excitation of the solenoid  70 . Here, as shown in FIG. 6B, the pilot spool  75  is located at the converting position on the seat surface  81  of the spool seat block  80 . When the pilot spool  75  is positioned at the converting position, the upper two pilot port connection holes  82  and  84  of the three pilot port connection holes  82 ,  83 , and  84  formed in the spool seat block  80  are connected by the cavity  76  of the pilot spool  75  and the lowermost pilot port connection hole  83  is exposed. Thus, part of the fluid supplied from the supply port P flows in the exposed lowermost pilot port connection hole  83  and moves toward the other side of the pilot hydraulic chamber  50   b  through the pilot input port  55  connected thereto. 
     The fluid input to the pilot hydraulic chamber  50   b  through the pilot input port  55  at the other side applies pressure to the vane portion  63  of the main spool  60  from the fixed vane  57  at the other side toward the fixed vane  58  at one side, so that the entire main spool  60  rotates counterclockwise. 
     When the main spool  60  is rotated counterclockwise, as shown FIG. 7B, the load port B at the other side of the two load ports A and B is connected to the valve chamber  50   a , forming a first main flow path. Also, the load port A at one side is connected to the drain port R through the groove  64  of the main spool  60 , forming a second main flow path. Thus, the air conditioning system is set to perform a heating operation. 
     In the meantime, during the counterclockwise rotation of the main spool  60 , the fluid remaining in the counterclockwise direction of the vane portion  63  in the pilot hydraulic chamber  50   b  is exhausted through the pilot input port  54  at one side formed therein. As shown in FIG. 6A, the remaining fluid proceeds via the pilot port connection hole  82  connected to the pilot input port  54 , the cavity  76  of the pilot spool  75 , and the pilot port connection hole  84 . Then, as shown in FIG. 5, the fluid sequentially passes the pilot drain port  56  of the valve main body  40  and the drain connection hole  65  of the main spool  60 , and is guided toward the groove  64  of the main spool  60  forming the second main flow path. The fluid joins the main stream of the fluid flowing along the second main flow path of the groove  64  and then is drained. 
     As described above, the four-way reversing valve according to the present invention includes a vane type main spool as a solenoid-hydraulic-rotation operating type. Since a solenoid operated type pilot valve of an inner pilot type to operate the vane type main spool is incorporated into the valve main body in a casing, only the connection pipes corresponding to the main port need to be welded at the valve casing. Therefore, the number of welding points can be minimized and manufacturing thereof is made easy. Further, during the manufacturing and use thereof, the rate of breakdown due to defective welding can be remarkably reduced. 
     Although the present invention is described as being used for a heat pump air conditioning system for a double use of cooling and heating in the above preferred description, it is not limited to the use thereof and the accompanying drawings. That is, the number of ports can be changed according to products to which the present invention is applied. Also, the solenoid operated type pilot valve for the operation of the vane type main spool or the structure of the vane can be realized in various ways.