Patent Publication Number: US-6712281-B2

Title: Expansion valve

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention relates to an expansion valve, and more particularly to a block-type expansion valve which is employed as an expansion device in a rear-side part of the system of a so-called dual air conditioner for an automotive vehicle, which uses an orifice tube in a front-side part thereof. 
     (2) Description of the Related Art 
     Conventionally, as the system of the automotive dual air conditioner, there are known one which uses an orifice tube as a front-side expansion device, and one which uses an expansion valve as the same. Both of the systems use an expansion valve as a rear-side expansion device. 
     In the system which uses an orifice tube as the front-side expansion device, refrigerant compressed by a compressor is condensed by a condenser, and liquid refrigerant formed by complete condensation by the condenser is expanded in the orifice tube, evaporated by an evaporator, and caused to undergo gas/liquid separation by an accumulator. Gaseous refrigerant obtained by the separation is returned to the compressor. 
     On the other hand, in the system which uses an expansion valve as the front-side expansion device, refrigerant compressed by a compressor is condensed by a condenser, the condensed refrigerant is caused to undergo gas/liquid separation by a receiver/dryer, and liquid refrigerant obtained by the gas/liquid separation is expanded by the expansion valve, and completely evaporated by an evaporator, followed by returning to the compressor. 
     In general, the receiver/dryer not only separates gaseous refrigerant from liquid refrigerant and removes moisture but also clears foreign matter from the refrigerant circulating through the system with a strainer incorporated therein. Therefore, the refrigerant having passed through the receiver/dryer is sent into the front-side expansion valve in a state cleared of foreign matter. At this time, liquid refrigerant cleared of foreign matter by the receiver/dryer is also supplied to the rear-side expansion valve. 
     On the other hand, in the system which uses the orifice tube as the front-side expansion device, the liquid refrigerant delivered from the condenser is directly supplied to the front-side orifice tube and the rear-side expansion valve. Since the orifice tube is configured to incorporate the strainer as an integral part thereof, foreign matter in the refrigerant is removed on the inlet side of the orifice tube. However, for the rear-side expansion valve, since the refrigerant containing foreign matter is directly supplied thereto, a strainer is usually arranged in a pipe on the upstream side of the valve. 
     To incorporate the strainer in the pipe, the pipe needs being formed into a specific shape and increased man-hours are necessary for the assembly work, resulting in an increase in manufacturing costs. On the other hand, some of the conventional expansion valves contain a strainer and make it unnecessary to incorporate the strainer in the pipe. 
     The above strainer-containing expansion valve is called a joint connection-type or angle-type expansion valve, which includes connecting portions for connecting thereto a pipe extending from a condenser and a pipe leading to an evaporator. According to this type of valve, only the connecting portions can be lengthened with ease, and therefore the strainer can be inserted into an inlet-side connecting portion, by lengthening the same. 
     However, when the so-called box-type or block-type expansion valve is used as the rear-side expansion valve, it is necessary to incorporate a strainer in a pipe on the upstream side of the valve. More specifically, in the block-type expansion valve, the pipe is inserted to an intermediate portion of an inlet-side port, and there is no space for mounting the strainer in the port. Therefore, if the strainer is desired to be attached to the inlet-side port, it is necessary to extend an end of the body on a high-pressure refrigerant inlet side to make a hole of the port deep enough to mount the strainer at an inner portion of the hole. This increase in length and size of the body only for arranging the strainer therein results in an increase in the material cost and working cost of the body besides an additional cost of the strainer, which further increase the manufacturing costs of the expansion valve. To avoid such an disadvantage, it is necessary to incorporate the strainer in the pipe separately from the valve. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above circumstances, and an object thereof is to provide a low-cost block-type expansion valve containing a strainer. 
     To solve the above problem, the present invention provides an expansion valve of a block type including a power element for sensing a temperature and pressure of refrigerant delivered from an evaporator, and a valve portion containing a valve element in a block-shaped body thereof, characterized by comprising a hollow cylindrical strainer which is mounted in a fluid passage having said valve element arranged therein, in a manner surrounding said valve element. 
     According to this expansion valve, the strainer is configured to be mounted in a space of a refrigerant passage having the valve element arranged therein. Since the refrigerant passage is an existing one, it is possible to maintain the present costs of parts except for the cost of the strainer. 
     The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a system diagram showing a dual air conditioner to which is applied an expansion valve according to the invention. 
     FIG. 2 is a longitudinal sectional view showing the construction of the expansion valve according to the invention. 
     FIG. 3 is a diagrams showing an example of a strainer, in which: 
     (A) is a plan view of the strainer; 
     (B) is a cross-sectional view of the strainer taken on line a—a of (A); and 
     (C) is a cross-sectional view of the strainer taken on line b—b of (B). 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the embodiment, an expansion valve according to the invention is applied to a rear-side expansion device for an automotive dual air conditioner, by way of example. 
     FIG. 1 is a system diagram of a dual air conditioner to which is applied the expansion valve according to the invention. 
     The automotive dual air conditioner to which is applied the expansion valve according to the invention includes a compressor  1 , a condenser  2 , an orifice tube  3 , a front-side evaporator  4 , and an accumulator  5 , which form a refrigeration cycle for a front-side air conditioner, as well as a temperature-type expansion valve  6  and a rear-side evaporator  7  which are connected in parallel with a circuit of the orifice tube  3 , the front-side evaporator  4 , and the accumulator  5 , and form part of a refrigeration cycle for a rear-side air conditioner. 
     Refrigerant compressed by the compressor  1  is condensed by the condenser  2 . Part of the liquid refrigerant formed by the condensation is guided into the orifice tube  3 , and the remainder of the same is guided to the expansion valve  6 . 
     The refrigerant guided into the orifice tube  3  is subjected to throttle expansion therein to be changed into low-temperature and low-pressure refrigerant which is then caused to exchange heat with front-side cabin air by the front-side evaporator  4 . The refrigerant evaporated through the heat exchange by the front-side evaporator  4  is caused to undergo gas/liquid separation by the accumulator  5  and gaseous refrigerant obtained by the separation is returned to the compressor  1 . 
     On the rear side, the refrigerant guided into the expansion valve  6  is subjected to throttle expansion according to the temperature and pressure of the refrigerant delivered from the rear-side evaporator  7 , to be changed into low-temperature and low-pressure refrigerant, which is then guided into the rear-side evaporator  7  to exchange heat with rear-side cabin air. In the rear-side evaporator  7 , the refrigerant is completely evaporated through the heat exchange, followed by returning to the compressor  1 . 
     Next, the expansion valve  6  according to the present invention, which is used as the rear-side air conditioner expansion device, will be described in detail. 
     FIG. 2 is a longitudinal sectional view showing the construction of the expansion valve according to the invention. FIG. 3 provides diagrams showing an example of the strainer, in which (A) is a plan view of the strainer, (B) is a cross-sectional view of the same taken on line a—a of (A), and (C) is a cross-sectional view of the same taken on line b—b of (B). 
     In the expansion valve  6 , a refrigerant pipe-connecting hole  12  formed through a side portion of a body  11  of the expansion valve  6  is connected to a refrigerant pipe through which high-temperature and high-pressure refrigerant is supplied from the condenser  2 , a refrigerant pipe-connecting hole  13  is connected to a refrigerant pipe for supplying low-temperature and low-pressure refrigerant obtained by adiabatically expanding the high-temperature and high-pressure refrigerant by the expansion valve  6  to the rear-side evaporator  7 , a refrigerant pipe-connecting hole  14  is connected to a refrigerant pipe extending from an outlet port of the evaporator, and a refrigerant pipe-connecting hole  15  is connected to a refrigerant pipe leading to the compressor  1 . Arrows shown in FIG. 2 indicate flows of refrigerant, respectively. 
     In a fluid passage communicating between the refrigerant pipe-connecting hole  12  and the refrigerant pipe-connecting hole  13 , a valve seat  16  is integrally formed with the body  11 , and on the upstream side of the valve seat  16  is arranged a ball valve element  17 . In a fluid passage on the side of the refrigerant pipe-connecting hole  12  is arranged a compression coil spring  18  for urging the valve element  17  in a direction of seating the valve element  17  on the valve seat  16 . The compression coil spring  18  is received by an adjusting screw  19 . The adjusting screw  19  is screwed into a lower end of the body  11  and has a function of adjusting a preset value of pressure at which the valve element  17  starts to be opened, by having the amount of screwing thereof adjusted to change the load on the compression coil spring  18 . In the fluid passage accommodating the valve element  17  and the compression coil spring  18 , the strainer  20  having a hollow cylindrical shape is arranged in a manner surrounding the valve element  17  and the compression coil spring  18 . 
     As shown in FIG. 3, the strainer  20  is comprised of a hollow cylindrical net  21 , annular frames  22 ,  23  for reinforcing both open ends of the net  21 , and longitudinal frames  24  for connecting the frames  22 ,  23  thereby at respective three locations. The net  21  is held by the frames  24  in a state buried thereunder. The frames  22 ,  23 ,  24  are integrally formed with each other by molding using a resin. Each of the annular frames  22 ,  23  is formed such that it has an outer diameter approximately equal to the inner diameter of the fluid passage in which the strainer  20  is mounted, and hence the frames  22 ,  23  are arranged in contact with the body  11  when the strainer  20  is mounted in the fluid passage. On the other hand, the net  21  has an outer diameter smaller than the inner diameter of the fluid passage so as to form a gap between the same and the inner wall of the fluid passage. This permits the refrigerant flowing from the refrigerant pipe-connecting hole  12  to flow into a space accommodating the valve element  17  through the net  21  from a whole periphery thereof. 
     The expansion valve  6  further includes a power element arranged on an upper end of the body  11 , which is comprised of an upper housing  25 , a lower housing  26 , a diaphragm  27  for dividing a space enclosed by the upper and lower housings, and a disc  28  arranged on an underside of the diaphragm  27 . 
     Arranged at a location below the disc  28  is a shaft  29  for transmitting displacement of the diaphragm  27  to the valve element  17 . The shaft  29  has an upper portion thereof held by a holder  30  which is arranged in a manner crossing a fluid passage communicating between the refrigerant pipe-connecting holes  14 ,  15 . The holder  30  has a compression coil spring  31  arranged therein for giving a lateral load to an upper end of the shaft  29 , such that the compression coil spring  31  controls longitudinal vibration of the shaft  29  which occurs in response to pressure fluctuation of the refrigerant. 
     Further, in the vicinity of the valve seat  16 , a bleed hole  32  is formed in the body  11  in a manner bypassing the valve. The bleed hole  32  is arranged such that a very small amount of refrigerant is permitted to flow even when the valve is fully closed, thereby making it possible to always supply lubricating oil contained in the refrigerant to the compressor  1 . 
     In the expansion valve  6  constructed as above, the power element senses the pressure and temperature of the refrigerant returned from the rear-side evaporator  7  into the refrigerant pipe-connecting hole  14 . When the temperature of the refrigerant is high, or when the pressure thereof is low, the power element pushes the valve element  17  in the valve-opening direction, whereas when the temperature of the refrigerant is low, or when the pressure thereof is high, the power element allows the valve element  17  to move in the valve-closing direction, whereby the valve travel is controlled. 
     The refrigerant supplied from the condenser  2  enters the refrigerant pipe-connecting hole  12 , and flows into the space accommodating the valve element  17  through the net  21  of the strainer  20 . At this time, foreign matter contained in the refrigerant is removed. The refrigerant cleared of the foreign matter is subjected to throttle expansion by passing through the valve whose valve travel is controlled as described above, thereby being changed into low-temperature and low-pressure refrigerant. The low-temperature and low-pressure refrigerant is discharged from the refrigerant pipe-connecting hole  13 , and supplied to the rear-side evaporator  7 , where the refrigerant is caused to exchanges heat with rear-side cabin air, followed by returning to the refrigerant pipe-connecting hole  14  of the expansion valve  6 . 
     As described hereinabove, according to the present invention, the block-type expansion valve is configured such that the strainer having a hollow cylindrical shape is arranged in a space for introducing high-pressure liquid refrigerant, in a manner surrounding the valve element. Therefore, it is possible to incorporate the strainer within the expansion valve without substantially changing the shape of the body, thereby making it possible to suppress an increase in the manufacturing costs of the expansion valve only to the cost of the strainer. 
     Since there is no need to attach the strainer to a pipe, it is possible to dispense with a special pipe for mounting the strainer therein, which makes it possible to reduce the manufacturing costs of the system. 
     The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.