Abstract:
A reversible valve for reversible refrigeration cycle. The valve means used therein is a hollow cylindrical body longitudinally extending within the valve body. It has a pair of inclined annular walls projecting from around the hollow cylindrical body to define an annular chamber therearound in cooperation with the valve body such that the annular chamber communicates the suction tube selectively with either one of said pair of tubes.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an improvement in a four-way valve for a reversible refrigeration cycle which has a comparatively small pressure receiving side constantly subjected to a high fluid pressure and a comparatively large pressure receiving side selectively subjected to a high fluid pressure and a low fluid pressure by switching action of a solenoid operated pilot valve, and constructed such that its piston or plunger moves due to the difference in effective cross sectional area between the two pressure receiving sides when a high fluid pressure is communicated to the larger pressure receiving side and due to the pressure differential when a low fluid pressure is communicated to the larger pressure receiving side. 
     A prior art four-way valve of the type described and actuated by a three-way solenoid operated pilot valve will be briefly described. 
     Referring to FIG. 1 of the drawings, the prior art four-way valve has a generally cylindrical valve body 1 which is made up of a first section 1a and a second section 1b larger in diameter than the first section 1a. Plugs 2, 3 are securely fitted by welding to the open ends of the valve body 1, respectively. 
     A delivery tube 5 is connected with the plug 2 to provide fluid communication between a compressor 4 and the valve body 1. A suction tube 6 is connected with the peripheral wall of the valve body 1 and leads therefrom to the compressor 4. 
     A tube 9 is connected with the peripheral wall of the valve body 1 to extend therefrom to a heat exchanger 7 which selectively serves as a condenser and an evaporator. Likewise, but on the opposite side to the tube 9 with respect to the tube 6, a tube 10 is connected with the peripheral wall of the casing 1 to extend therefrom to a second heat exchanger 8 which functions in the same manner as the first heat exchanger 7. 
     A valve member 11 is located inside the valve body 1. The valve member 11 is formed with a recess 11b in its sliding surface 11a which is calibrated such that the suction tube 6 is communicatable selectively with the tubes 9, 10 depending on the position of the valve member 11. 
     Valve member 11 is rigidly carried on a plunger 12 as by a rivet 13 or by brazing. The plunger 12 has a pressure receiving portion or piston A which slides within the small diameter casing section 1a and a second pressure receiving portion or piston B which is larger in diameter than the portion A and slides in the larger diameter casing section 1b. As shown, the rigid connection of the valve member 11 with the plunger 12 is located adjacent to the smaller diameter pressure receiving portion A. 
     The piston A of the plunger 12 defines a chamber R 1  in cooperation with the casing 1 while the piston B defines chambers R 2 , R 3  on opposite sides thereof in cooperation with the casing 1. 
     A solenoid operated pilot valve 14 includes a switching mechanism having a body 15. The body 15 is formed with a high pressure induction passageway 15a, a low pressure discharge passageway 15b and a common passageway 15c. A valve seat 16 having a passageway 16a therethrough is threaded into the body 15 to define a chamber R in cooperation with the body 15. Thus, the chamber R has fluid communication with the high pressure induction passageway 15a, low pressure discharge passageway 15b via the passageway 16a and the common passageway 15c. The passageway 15a leads to the delivery tube 5 through a bleed tube 17, the passageway 15b to the suction tube 6 via a low pressure discharge tube 18, and the passageway 15c to the chamber R 2  in the casing 1 via a pilot tube 19. 
     The chamber R 3  between the larger diameter casing section 1b and the larger diameter piston B of the plunger 12 is communicated with the suction tube 6 by a low pressure induction tube 20. 
     The pilot valve 14 has a plunger 14a from which a rod 14b extends throughout the passageway 16a of the valve seat 16. A valve member in the form of a ball 21 is received in the chamber R and actuated by the rod 14b to selectively communicate the passageways 15a, 15b with the passageway 15c as will be described. 
     The four-way valve constructed as above will be operated as follows. Let it be assumed that the heat exchanger 7 is located outside a desired enclosure such as a room and the heat exchanger 8 inside the enclosure. 
     In a cooler mode, all the components of the four-way valve and its associated pilot valve are positioned as shown in FIG. 1. The solenoid coil of the pilot valve 14 remains deenergized so that the plunger 14a is held by a coil spring 14c in a rightward position as viewed in FIG. 1. The rod 14b urges the ball 21 against the body 15 to block the passageway 15a overcoming the high pressure communicated to the passageway 15a. The passageway 16a in the valve seat 16 is communicated to the chamber R 2  in the casing 1 via the common passageway 15c and pilot tube 19. 
     Under this condition, a low fluid pressure is admitted in both the chambers R 2 , R 3  and acts equally on the opposite sides of the larger diameter piston B. On the other hand, a high fluid pressure is admitted in the chamber R 1  defined by the smaller diameter piston A. Due to this pressure differential, the plunger 12 is maintained in its rightward position as viewed in the drawing. 
     Moved rightwardly together with the plunger 12, the valve member 11 causes the delivery tube 5 into communication with the outdoor heat exchanger 7 via the tube 9 while causing the indoor heat exchanger 8 into communication with the suction tube 6 via the tube 10. In this situation, fluid, i.e., refrigerant is allowed to circulate as indicated by arrows in FIG. 1 so that the outdoor heat exchanger 7 functions as a condenser and the indoor heat exchanger 8 as an evaporator. 
     When the coil of the pilot valve 14 is energized to switch the operation mode of the system from the cooler mode to a heater mode, the plunger 14a is attracted to the left accompanied by the rod 14b as illustrated in FIG. 2. Then, the ball 21 is urged clear of the body 15 into contact with the seat 16 by the high pressure in the passageway 15a, whereby the passageway 15a is opened and the passageway 16a closed. The high pressure is therefore admitted in the chamber R 2  of the casing 1 via the pilot tube 19 so as to act on the larger diameter piston B of the plunger 12. 
     The pressure acting on the piston B is as high as the pressure acting on the other piston A. However, due to the difference in effective cross sectional area between the pistons A and B, the plunger 12 is moved to the left from the position shown in FIG. 1. The valve member 11 moving together with the plunger 12 reaches a position where it communicates the delivery tube 5 to the indoor heat exchanger 8 via the tube 10 and the outdoor heat exchanger 7 to the suction tube 6 via the tube 9. This sets up a fluid flow path as indicated by arrows in FIG. 2 and causes the heat exchangers 8, 7 to operate as a condenser and an evaporator, respectively. 
     As described above, the prior art valve causes a high pressure to constantly act on the smaller diameter piston and thereby prevents damage which would otherwise result from repeated variation in the pressure. Another advantage is that the valve member connected to the plunger can be placed in the casing simultaneously with the insertion of the plunger. However, since the plunger and valve member are formed separately from each other and then rivetted or soldered to each other, not only the assembly needs a disproportionate period of time but fixing the valve member requires a great deal of skill from the viewpoint of refrigerant flow path switching accuracy. 
     Because the volume of the recess formed in the valve member is smaller than that of the casing and, therefore, the resistance to the flow of a refrigerant is substantial, the casing cannot be reduced in size beyond a certain limit. To regulate the orientation of the recess in the valve member, the plunger has to be furnished with a mechanism for preventing it from being rotated about its axis. 
     Furthermore, where both the valve member and the plunger are made of metal, a relatively large clearance is indispensable between them and the casing to ensure a good sliding relation against any change in the temperature of the refrigerant. This frequently results leakage of the refrigerant which is detrimental to accurate switching of the refrigerant flow direction. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a four-way valve which simplifies the construction of the plunger and valve member, makes it unnecessary to regulate the rotation of the plunger and valve member, eliminates the leakage of the refrigerant, and thereby ensures smooth and accurate switching of the refrigerant flow direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are vertical sections showing a prior art four-way valve for a reversible refrigeration cycle in a cooler mode and in a heater mode, respectively; 
     FIGS. 3 and 4 are vertical sections showing a four-way valve for a reversible refrigeration cycle embodying the present invention in a cooler mode and in a heater mode, respectively; 
     FIGS. 5 and 6 are vertical sections of another embodiment of the present invention in a cooler mode and a heater mode, respectively; 
     FIGS. 7 and 8 are vertical sections of a farther embodiment of the present invention also in a cooler mode and heater mode, respectively. 
     FIG. 9 is a section of a four-way valve embodying the present invention in which a solenoid operated valve for actuating the four-way valve is deenergized; 
     FIG. 10 is a view similar to FIG. 9 but showing a valve spool of the four-way valve which is stroking in response to energization of a solenoid operated valve; 
     FIG. 11 is a view also similar to FIG. 9 but showing the valve spool at the end of the stroke; 
     FIGS. 12A, 12B and 12C are sections of pressure receiving portions formed around the valve spool; 
     FIG. 12D is a plan view of FIG. 12C; 
     FIG. 13 is a section of the valve spool; and 
     FIGS. 14 and 15 are sections of further modifications of the present invention, respectively. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     A four-way valve embodying the present invention will be described with reference to FIGS. 3 and 4. 
     In FIGS. 3 and 4, the four-way valve is actuated by a three-way solenoid operated pilot valve as in the prior art. The parts and elements common to those of the prior art will be designated by the same reference numerals. 
     A characteristic feature of the present invention resides in that a plunger and a valve member comprise an integral moulding of resin. Considering the other aspects, the illustrated arrangement and construction is the same as the that of the prior art. 
     As shown, a plunger 22 has a smaller diameter pressure receiving portion 22A and a larger diameter pressure receiving portion 22B at its axially opposite ends. The smaller diameter pressure receiving portion 22A is formed with an annular inclined wall or tongue 22a therearound slidably engaged with a smaller diameter section 1a of a casing 1. Likewise, the larger diameter pressure receiving portion 22B is formed with an annular inclined wall or tongue 22b therearound which is slidably engaged with a larger diameter section 1b of the casing 1. The plunger 22 has a hollow cylindrical extension 23 which is formed coaxially with the plunger 22 and open at its end remote from the piston 22. Annular inclined walls or tongues 23a, 23b extend generally radially outward from the cylindrical extension 23 into slidable contact with the smaller diameter casing section 1a. Thus, the combined plunger 22 and annular tongues 22a, 22b,23a, 23b constitute a unitary valve spool. 
     The cylindrical extension 23 is slotted as at 23d adjacent to the plunger 22 so that a high fluid pressure is constantly applied to the smaller diameter pressure receiving portion 22A of the plunger 22. 
     With the above structure, it will be seen that the annular tongues 23a, 23b are equivalent in function to the sliding surface 11a of the valve member 11 of the prior art valve while the space 23c defined by the annular tongues 23a, 23b and the smaller diameter casing section 1a corresponds to the recess 11b of the valve member 11 in the prior art. 
     FIG. 3 represents the valve of the invention in a cooler mode and FIG. 4 in a heater mode. Details of the operation in each mode are substantially the same as those of the prior art and, therefore, will not be described for simplicity. 
     While the illustrated embodiment employs a three-way valve as the solenoid operated pilot valve, a two-way or four-way pilot valve may be employed as the case may be without any substantial modification to the unique integral design of the valve spool. FIGS. 5 and 6 illustrate an example using a two-way pilot valve while FIGS. 7 and 8 an example using a four-way pilot valve. All these examples will be operated generally in the same way as the three-way valve shown in FIGS. 3 and 4 and, therefore, their description and designation will be omitted for simplicity. 
     Further, in order to minimize the leakage of pressurized fluid through the respective pressure receiving portions of the valve spool and promote smooth movement of the valve spool for switching the fluid circulation path, the following modification to the pressure receiving portions may be resorted to. 
     Referring to FIGS. 9-11, a four-way valve embodying the present invention has a generally cylindrical casing of metal which is generally designated by the reference numeral 1. The casing 1 comprises a first section 1a and a second section 1b which is larger in diameter than the first 1a. Plugs 2, 3 are securely fitted by welding in the opposite open ends of the casing 1, respectively. A delivery tube 5 is connected with the plug 2 to extend therefrom to the delivery side of a compressor 4. A suction tube 6 is connected with the peripheral wall of the casing 1 and leads therefrom to the suction side of the compressor 4. A tube 9 leads from the casing 1 to a heat exchanger 7 which selectively serves as a condenser and an evaporator. Likewise, but on the opposite side to the tube 9 with respect to the suction tube 6, a tube 10 leads from the casing 1 to a second heat exchanger 8 which functions in the same way as the first heat exchanger 7. A valve spool 23 formed of resin is slidably received in the casing 1. The valve spool 23 includes a pressure receiving portion 23A located at one end of the valve spool and formed with an annular tongue 22c therearound which is slidably engaged with the inner wall of the smaller diameter casing section 1a. The valve spool 23 also includes a second pressure receiving portion 22B located at an axially intermediate position of the valve spool and formed with an annular tongue 22b therearound which is slidably engaged with the inner wall of the larger diameter casing section 1b. Further included in the valve spool 23 is a third pressure receiving portion 22C located at the other end of the valve spool 23 and formed with an annular tongue therearound 22c which is slidably engaged with the larger diameter casing section 1b as the second pressure receiving portion 22B. Examples of the tongues 23a, 22b, 22c on the valve spool 23 are illustrated in FIGS. 12A and 12B. As shown in FIGS. 12A to 12D, each tongue is formed with an annular recess or groove 24 which is open at the high pressure receiving side of the tongue, so that a flap 25 formed around the groove 24 is pressed against the inner wall of the casing 1 by a pressurized fluid. If necessary, a wire ring 26 may be fitted in the groove 24 for reinforcement as shown in FIG. 12A, or a leaf spring ring 26&#39; which is bent into a substantially U-shaped configuration to fit in the groove as shown in FIGS. 12c and 12D which is a plan view thereof may be employed for the same purpose. Each pressure receiving portion 22A-22C of the valve spool 23 is recessed as at 27 on its other or low pressure receiving surface to form a flap 25&#39; whose outside diameter is equal to or slightly smaller than the inside diameter of the casing 1. When subjected to a fluid pressure, the annular flap 25&#39; will intimately engage with the inner wall of the casing 1 to minimize mutual communication of high pressure and low pressure fluids in the course of a switching movement of the valve spool 23. 
     The valve spool 23 is a hollow cylindrical member which is open at the end of the smaller pressure receiving portion 23A. An opening 23d is formed through the peripheral wall of the valve spool 23 between the neighboring larger diameter pressure receiving portions 22B and 22C. 
     The annular tongues 23a, 22b, and 22c on the valve spool 23 are located so that they will communicate the tubes 6, 10 to each other in a first position of the valve spool 11 shown in FIG. 9, but communicate the tubes 6, 9 to each other in a second position shown in FIG. 11 in which the valve spool 23 has moved downward from the position of FIG. 1. 
     By opening the annular recesses or grooves in the high and low pressure receiving surfaces of the two large diameter pressure receiving portions and the one small diameter pressure receiving position and further providing, if necessary reinforcement rings within the recesses on the high pressure side such that the annular tongues are pressed against the inner wall of the valve body, excellent sealing effect is obtained even if the spool valve axially rotates during the switching operation. 
     Referring to FIG. 14, a valve 23 is formed of metal and provided with successive pressure receiving portions 40A, 40B, 40C. Annular pieces 40a, 40b, and 40c formed of fluoric resin such as Teflon are attached to the respective pressure receiving portions 40A, 40B, and 40C as illustrated to constitute annular valve tongues. 
     The annular tongue 40a in the pressure receiving portion 40A slides smoothly on the inner wall of a larger diameter casing section (not shown) due to a very small coefficient of friction of Teflon (about 0.05). The other annular tongues, 40c not only slide smoothly on the casing wall but attain a mechanical strength large enough for them to be prevented from being turned over during movement. 
     Referring to FIG. 15, a valve body 23 according to an alternative embodiment of the invention has successive pressure receiving portions 50A, 50B and 50C formed of polyamide resin such as Nylon and annular tongues 50B, 50C in the pressure receiving portions 50B, 50C also formed of polyamide resin. An annular tongue 50a in the pressure receiving portion 50A at the end of the valve body 50 is formed of fluoric resin such as Teflon. 
     The annular tongue 50a slides smoothly on and intimately engages with the casing inner wall due to the very small coefficient of friction of Teflon (which softens more easily than Nylon whose coefficient of friction is about 0.2, for a common high temperature). The annular tongues 50b, 50c on the other hand has a sufficient mechanical strength against turning-over as well as smooth sliding contact with the casing inner wall, which results from significant wear resistance and tensile strength of Nylon. Incidentally, Nylon has a tensile strength of about 530-780 kg/cm 2  while Teflon is about 140-210 kg/cm 2  in tensile strength. 
     For reinforcement purpose, a ring, again, may be fitted in the annular recess in the high pressure receiving surface of the annular tongue in the larger pressure receiving portion at the end of the valve body in any one of the embodiments described. In such a case, Teflon will prove effective as a material of said annular tongue in ensuring smooth sliding contact thereof with the casing inner wall against a force which would tend to urge the flap radially outwardly. 
     Apart from the advantages of the prior art valve, the following additional advantages are achievable with the present invention due to unitary moulding of a valve spool with multiple valving members from resin. The valve can be produced accurately with ease and by a minimum of steps. Despite any change in the temperature of a refrigerant, the valving members remain seated liquid-tight on the inner wall of the casing to avoid leakage of the refrigerant, because of the combined effect of the pressure with which the valving members whose hardness varies in proportion to the temperature change are engaged with the casing and the fluid pressure acting on the valving members inside the casing. 
     The passage for selective communication of the suction tube with the other tubes is defined by the annular space between a pair of annular valving tongues and the casing. Compared to the conventional recess for such selective communication, the annular space is large enough to reduce the resistance to the flow of a refrigerant and, therefore, to make the casing small in size. Also, any angular movement of the valve spool about its axis does not affect the selective communication among the tubes, unnecessitating an anti-rotation mechanism heretofore employed. As a whole, the valve of the invention is durable and economical.