Abstract:
In an expansion valve the pressure vessel of which is constituted by a reduced number of parts and which does not require seal members a valve unit is surrounded by first and second half shells which in turn are surrounded by a pressure vessel formed as a one-piece body by molding resin by an insert molding process. Since the resin constituting the resin molded one-piece pressure vessel simultaneously form internal sealing member structures no additional seal members are required to be positioned and mounted. The first and second half shells are shaped such that the necessary refrigerant passages for the valve unit are defined in communication with connection holes of the pressure vessel.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an expansion valve and to a method for manufacturing the expansion valve conventionally used in a refrigerating cycle of an automobile air-conditioner or the like for adiabatically expanding a high temperature, high-pressure liquid refrigerant to turn the refrigerant into a low temperature low-pressure gas liquid mixture of refrigerant and also for controlling the flow rate of the refrigerant such that the refrigerant has a predetermined degree of overheat at the outlet of an evaporator. The expansion valve according to the invention includes a in-built valve unit, said valve unit having the function of a temperature sensing section detecting the degree of refrigerant overheat at an outlet of an evaporator and the function of a valve element controlling a passing amount of high-pressure refrigerant to be adiabatically expanded in accordance with changes of the degree of refrigerant overheat as detected by said temperature sensing section. 
     In known refrigerant cycles of car air-conditioners the expansion valve arranged in an evaporator casing is connected to refrigerant inlet and outlet pipes of the evaporator which is arranged in the vehicle compartment. Said expansion valve is also connected to pipes leading to a compressor and a condenser, respectively, both of which are arranged in the engine compartment. 
     The mounting of a conventional expansion valve is illustrated in FIG.  19 . The expansion valve  111  is fixed to a partition wall  112  separating the vehicle compartment from the engine compartment. Due to the irregular external shape of expansion valve  111  a connector  113  is needed as an adapter matching to the external shape of the expansion valve. Connector  113  is joined to that side of the expansion valve to which the pipes are connected leading to the compressor and the condenser. Around connector  113  an insulator  114  is provided sealing the gap between the connector  113  and the partition wall  112  and between the connector  113  and an evaporator casing  115 . Pipes  116  and  117  to compressor and the condenser are connected to connector  113  and fixed thereto by a mounting bolt  119  with a plate  118  interposed therebetween. Pipes  120  and  121  leading to an evaporator are fixed to en evaporator side of the expansion valve  111  by a mounting bolt  123  with a blade plate  122  interposed therebetween. Expansion valve  111  includes a valve unit  124  comprising a temperature sensing section measuring the refrigerant temperature at the outlet of the evaporator and a valve element the degree of opening of which is determined by the refrigerant temperature at the outlet of the evaporator. In FIG. 19 valve  124  has its temperature sensing section arranged outside of the refrigerant pipe. There are other types of expansion valve units where the temperature sensing section is arranged inside the refrigerant pipe. In either type, the expansion valve unit used has a low-pressure passage for the refrigerant exiting the evaporator and a high-pressure passage with the valve element inserted therein for restricting the flow of liquid refrigerant and expanding the refrigerant prior to the refrigerant reaching the evaporator. The temperature sensing section is arranged in the low-pressure passage. The valve element is actuated in accordance with the measured temperature. 
     Among expansion valves having the temperature sensing section received inside its casing, there is a type known in which the valve unit (temperature sensing section and valve element integrally combined) is completely received in a pressure vessel. The pressure vessel used is formed from extruded aluminium material. A chamber or cavity is cut out for receiving the valve unit. Also the high-pressure and low-pressure passages are formed into said pressure vessel. However, seal members are needed in said pressure vessel, and a lid closing the pressure vessel after the valve unit is inserted, such that any gaps between the valve unit and the refrigerant passages and the surrounding are sealed in order to completely seal the pressure vessel. The plurality of seals needs corresponding manufacturing machining or preparation. Due to the complexity of the seals and their number the likelihood of refrigerant leaking to the outside is high. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to create an expansion valve included into a pressure vessel which expansion valve is constituted by a reduced number of parts and does not require seal members to be inserted or manufacturing preparation for the insertion of seal members. 
     In the expansion valve according to the invention, the pressure vessel completely enclosing the valve unit is formed solely by resin moulding. By said moulding process it is unnecessary to use seal members such as O-rings, which normally constitute a primary cause of refrigerant leakages to the outside. Forming the pressure vessel solely by resin moulding also allows to reduce the number of parts necessary to constitute the expansion valve, because the pressure vessel is constituted by a single resin-moulded article. The expansion valve is completed for operation as soon as the pressure vessel is formed with the valve unit contained therein. Any further assembling steps can be avoided. 
     The valve unit is surrounded by two half shells which in turn are surrounded by a body block formed by insert moulding and defining said pressure vessel. Since the pressure vessel is formed solely by resin moulding, any further step of assembling the expansion valve can be omitted. Since neither a lid nor any O-rings are required for sealing purposes, the number of parts of the expansion valve can be reduced, thus reducing the manufacturing and assembling costs. Furthermore, no O-rings are used for sealing purposes, so that the refrigerant is prevented from leaking to the outside. 
     Both half shells are shaped to define therein a gap at a boundary between the high-pressure region and the low-pressure region. By injecting resin into the gap when the body block or pressure vessel is formed by insert moulding a wall sealing structure is formed by injected resin. It is, therefore, unnecessary to provide any separate seal member at the boundary between the high and low pressure regions. 
     The expansion valve defines by its pressure vessel an elliptic outer form and as such can serve as a connector so that no separate connector is needed when mounting the expansion valve. A flange is formed on the expansion valve adjacent to its surface to which pipes leading to the evaporator are to be mounted. Thus, satisfactory sealing performance can be ensured with ease by simply interposing an insulator between said flange and the partition separating the vehicle compartment from the engine compartment. 
     Metal collars are fitted in the respective holes through which the mounting bolts are inserted. In this case any stress induced by tightening the mounting bolts is taken up by the metal collars so that the pressure vessel or body block of the expansion valve made of resin is prevented from being fractured by excessively large stress applied thereto. 
     Particularly serial production of a large number of identical expansion valves of this type can be carried out with reduced costs. The half shells and the valve units are prefabricated components. The half shells do not need precise machining for positioning sealing members. Sub-units thus can be prefabricated by solely inserting the valve between the interconnected half shells. The sub-units can be comfortably stored and transported to the injection or insertion moulding site and can be placed one by one or in series in the respective mould cavities. By injecting the resin the pressure vessel surrounding each sub-unit and simultaneously the internal sealing member structures necessary between the regions of the expansion valve having different pressures are formed. With the termination of the insertion mould process the expansion valves are readily assembled for use. The degree of freedom to design the outer contour of the pressure vessel in view to easy and comfortable mounting of the expansion valve in an evaporator casing and at the separation wall between the engine compartment and the vehicle compartment and finally the mounting of the expansion are simplified to a considerable extent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention as well as a prior art expansion valve will be hereinafter described with reference to the drawings. In the drawings is: 
     FIGS. 1A,  1 B and  1 C a front view, a side view and a rear of a first embodiment of an expansion valve, 
     FIG. 2 a vertical sectional view of the expansion valve, 
     FIG. 3 a further detailed longitudinal sectional view of the expansion valve, 
     FIGS. 4A,  4 B,  4 C,  4 D a first half shell of the expansion valve in a rear view, a side view, a front view and a sectional view, 
     FIGS. 5A,  5 B,  5 C,  5 D a second half shell of the expansion valve in a front view, a side view, a rear view and a sectional view, 
     FIG. 6 a front view of a sub-unit constituted by first and second half shells confining a valve unit, 
     FIG. 7 a longitudinal sectional view of the sub-unit of FIG. 6, in detail, 
     FIG. 8 another longitudinal sectional view of the first embodiment of the expansion valve illustrating an integrated seal member structure, 
     FIGS. 9 and 10 horizontal sectional views in sectional plane a—a and b—b in FIG. 8, 
     FIG. 11 a vertical sectional view illustrating the first embodiment of the expansion valve in mounted condition, 
     FIG. 12 a vertical sectional view of a second embodiment of the expansion valve, 
     FIGS. 13A,  13 B, and  13 C a third embodiment of the expansion valve in a front view, a side view and a rear view, 
     FIGS. 14A,  14 B,  14 C and  14 D a example of a mounting bolt for the expansion valve, in a front view, a side view, a rear view and a sectional view (sectional plane a—a in FIG.  14 A), 
     FIGS. 15A,  15 B,  15 C and  15 D another example of a mounting bolt for the expansion valve, in a front view, a side view, a rear view and a view in viewing direction b—b of FIG. 15A, 
     FIG. 16 a horizontal sectional view of a modified expansion valve containing method collars, 
     FIG. 17 a vertical sectional view of an expansion valve in mounted condition, 
     FIG. 18 a vertical sectional view of another mounting structure of a flanged expansion valve, and 
     FIG. 19 a vertical sectional view of a mounted conventional expansion valve according to prior art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIGS. 1A to  1 C a first embodiment of an expansion  1 , as an example for an expansion valve useful for a refrigerating cycle of a car air-conditioner, has the shape of a elliptic cylinder with front and rear pipe mounting surfaces and refrigerant pipe connection holes  2 ,  3 ,  4  and  5 . Hole  2  is an opening to which a refrigerant pipe extending from the outlet of a not shown evaporator is connected. To hole  3  a refrigerant pipe extending to the inlet of said evaporator is to be connected. To hole  4  a refrigerant pipe extending to a not shown compressor is to be connected. To hole  5  a refrigerant pipe extending from a not shown condenser is to be connected. 
     Refrigerant pipes connected to holes  4  and  5  can be fixed by means of an embedded bolt  6 . Holes  7  and  8  permit to insert bolts, not shown, provided on the evaporator side, to secure the expansion valve  1  in position. The compressor and the condenser of the refrigerating cycle are arranged in the engine compartment, while the evaporator is arranged in the vehicle compartment. Expansion valve  1  is intended to be arranged at a partition wall separating the engine compartment from the vehicle compartment. In FIG. 2 a valve unit  10  is arranged in a central portion of the expansion valve  1 . Valve unit  10  is surrounded by first and second half shells  11 ,  12  which, in turn, are surrounded by a body block or pressure vessel  13 . 
     Valve unit  10  has a temperature sensing section and a valve member integrally combined with each other. The first and second half shells  11 ,  12  have the function to define refrigerant passages between the valve unit  10  and the pressure vessel  13  in communication with refrigerant pipe connection holes  2 ,  3 ,  4  and  5  provided in said pressure vessel. Said pressure vessel or body block  13  forming the outermost part of said expansion valve  1  is formed by moulding a resin into a one-piece body by insert moulding. 
     In FIG. 3 a diaphragm  23  is arranged in valve unit  10  a space surrounded by upper and lower housing parts  21 ,  22 . A retainer  25  is provided above diaphragm  23  for retaining activated charcoal  24  adjusting the response speed of the temperature sensing section. A capillary tube  26  protrudes from the upper housing  21  used to fill gas into upper housing part  21 . After filling the gas tube  26  is crushed flat and is cut and it brazed using a brazing filler metal  27  to prevent leakage of the gas. In lower housing part  22  a pressure equalising hole  28  is cut leaving space beneath diaphragm  23  open. 
     Below diaphragm  23  a disk  29  and below disk  29  a stopper  31  are provided. Stopper  31  is slidably received in a cylinder chamber formed in an upper portion of valve body  30  for controlling and regulating the stroke of the diaphragm  23 . A shaft  32  transmits displacement of the diaphragm  23  to a valve ball  33 . O-ring  34  prevents high-pressure refrigerant acting upon valve ball  33  from leaking to the low-pressure, equalised pressure region. 
     Shaft  32  and valve ball  33  are welded together. Valve ball  33  is urged in closing direction towards a valve seat by a spring  36  and via a valve holder  35 . Spring  36  is seated against an adjusting screw  37  allowing to adjust the force of spring  36 . By spring  36  a set value for the static overheat degree of the expansion valve can be adjusted. 
     Valve body  30  has a high-pressure refrigerant inlet port  38  at an upstream side of valve ball  33 , and a low-pressure refrigerant outlet port  39  downstream of valve ball  33 . 
     When upper housing part  21  is exposed to the refrigerant at the outlet of the evaporator, the refrigerant temperature is converted into a pressure depending on the adsorptivity of activated charcoal provided. As said pressure changes valve body  33  is displaced by the diaphragm  23 , disk  29  and shaft  32 . In this way the opening degree of said valve ball in relation to its associated valve seat is controlled. 
     The valve unit  10  surrounded by said first and second half shells  11  and  12  (FIGS. 4 and 5) forms a sub-unit as shown in FIG. 6. A body  41  of the first half shell  11  in FIGS. 4A to  4 D has a hole  42  defining an opening for communication with refrigerant pipe connection hole  4  of pressure vessel  13 , and a hole  43  defining an opening for communication with refrigerant pipe connection hole  5 . In an end face of body  41  along the outer circumference or continuous edge region an engaging groove  44  is cut fitting to an engaging rib  54  of the other second half shell of FIG. 5A to FIG.  5 D. This is the edge region in which the first half shell  11  is to be joined to the second half shell  12 . At the periphery of body  41  hooks  45  are formed serving to securely join the second half shell  12  to the first half shell  11 . 
     Inside body  41  a refrigerant passage  46  is formed for guiding refrigerant from hole  43  to high-pressure refrigerant inlet port  38  of valve unit  10 . Into body  41  resin injection holes  47  are cut so as to open from the outside into a seal-forming groove  48  formed inside body  41 . Resin injection holes  47  and seal-forming groove  48  are used to form a seal member structure integrally with pressure vessel or body block  13  when said pressure vessel  13  is formed from resin by an insert moulding process. During said process resin is injected through said resin injection holes  47  into the space defined between the seal-forming groove  48  and valve unit  10  resulting in the integral seal member structure. 
     A body  51  of the second half shell  12  in FIGS. 5A to  5 D has holes  52 ,  53  defining openings for communication with refrigerant pipe connection holes  2  and  3 . On an end face of body  51  along the outer circumference or edge region an engaging ridge  45  is formed fitting into groove  44  of first half shell  11 . Said engaging ridge  54  extends along the edge region of said second half shell  12  along which both half shells  11 ,  12  are to be joined to each other. At the outer periphery of body  51  engaging portions  55  are formed in alignment with hooks  45  of the first half shell  11 . When joining both half shells  11 ,  12  engaging portions  55  are brought into engagement with hooks  45  for a positive joint of both half shells. 
     Inside body  51  of second half shell  12  a refrigerant passage  56  is formed for guiding refrigerant from low-pressure refrigerant pressure outlet port  39  of valve unit  10  to hole  53 . Resin injection holes  53  are cut into body  51  so as to open from outside into a seal forming groove  58  formed inside body  51 . Also through resin injection holes  57  resin is to be injected into the space defined between the seal forming groove  58  and the valve unit  10  to form a seal member structure integrally with pressure vessel or body block  13  at the same time when pressure vessel  13  is formed from resin by insert moulding. 
     FIG. 6 illustrates the sub-unit in which valve unit  10  is surrounded by the interconnected first and second half shells prior to moulding the pressure vessel. Portion  55  are engaging with hooks  45 . In the sectional view of FIG. 7 the engaging ridge  54  of the second half shell  12  is fitted into engaging groove  44  of the first half shell  11  to assemble the valve unit  10  and both shells  11 ,  12  in said sub-unit. In said sub-unit port  38  of valve unit  10  is aligned with refrigerant passage  46  of first half shell  11  and also with outlet port  39  of valve unit  10  aligned with refrigerant passage  56  of the second half shell  12 . The assembling of said sub-unit is completed as soon as engaging portions  55  of the second half shell are brought into engagement with hooks  45  of first half shell  11 . 
     At this stage of the manufacturing of the expansion valve, in FIG. 7, seal-forming passages  61  are defined by portions of the surface of valve unit  10  near inlet port  38  and outlet port  39  and by said seal-forming grooves  48  an  58  inside first and second half shells  11 ,  12 . Said seal-forming passages  61  communicate with each other inside the half shells and open to the outside through said resin injection holes  47 ,  57  of both half shells  11 ,  12 . 
     The assembled sub-unit thus obtained is positioned in a form cavity in an injection moulding machine. Then said body block or pressure vessel  13  is formed by insert moulding from resin. During insert moulding said pressure vessel  13  is formed from resin around the first and second half shells  11 ,  12 . At the same time the seal-forming passages  61  are filled with resin injected through resin injection holes  47 ,  57 , so that a seal member structure and the body block or pressure vessel  13  are formed as a one-piece body. 
     In FIGS. 8,  9  and  10  resin injected through resin injection holes  47 ,  57  of both shells  11 ,  12  flows along the outer surface of valve body  30  and surrounds the outer peripheral surface of same, except inlet port  38  and outlet port  39  of valve unit. Seal forming passages  61  then are consequently filled by the injected resin thus forming a seal member structure  62 . Said seal member structure  62  serves to seal in a boundary between a high-pressure region close to connection hole  5  and low-pressure region close to connection hole  3 . Seal member structure  62  further seals at a boundary at which the refrigerant passage connecting connection holes  2 ,  4  is bounded by the high-pressure region close to connection hole  5  and the low-pressure region close to connection hole  3 . As seal member structure  62  and body block or pressure vessel  13  are formed as a one-piece body, no seal members such as O-rings are needed as in conventional arrangements. 
     In FIG. 11 expansion valve  1  is fitted through an elliptic hole cut in a partition wall  71  separating the vehicle compartment from the engine compartment in a car. An insulator  73  winds around expansion valve  1  to seal a gap between the outer contour of expansion valve  1  and the hole in partition wall  71  as well between partition walls  71 , an evaporator casing  72  and said expansion valve  1 . Said insulator  73  interrupts communication between the vehicle compartment and the engine compartment. Furthermore, the portion of the expansion valve  1  at which the valve is mounted to the evaporator casing  72  is sealed. Due to the elliptic outer form of expansion valve  1  it is unnecessary to use a connector as necessary for conventional expansion valves. 
     Pipes  74 ,  75  leading to the evaporator are connected to connection holes  2 ,  3 , respectively, and fixed to the expansion valve  1  by mounting bolts  76  inserted from the engine compartment side through holes  7 ,  8  additionally, a plate  77  is used for the fixation. Pipes  78 ,  79  leading to the compressor and the condenser, respectively, are connected to connection holes  4 ,  5  and are fixed to the expansion valve  1  by embedded bolt  6  and a plate  80 . 
     For the second embodiment of the expansion valve according to the present invention in FIG. 12 identical reference numerals are used to denote elements identical to those of the expansion valve of the first embodiment. Different from the first embodiment the valve unit  10   a  in FIG. 12 includes a valve poppet  83  instead of a valve ball. Valve unit  10   a  includes a piston  81  movably received in the cylinder of valve body  30  for reciprocating motion, a shaft  82 , valve poppet body  83  and a spring seat  84  unified in a one-piece body. The upper end of piston  81  is fixed to disk  29 . Spring seat  84  bears the load of spring  36 . Disk  29  also functions as a stopper and regulates the stroke of diaphragm  23 . 
     FIGS. 13A to  13 C illustrate the external appearance of a third embodiment of an expansion valve  1  according to the invention. Identical reference numerals are used to denote elements identical with those of the first embodiment of FIG.  1 . Flush with the end face in which connection holes  2 ,  3  are formed a flanged  91  is formed on the expansion valve  1 . The flange  91  is formed integrally with the body block or pressure vessel when the body block is formed using resin and by an insert moulding process. In the other end face of expansion valve  1  where pipe connection holes  4 ,  5  are formed a recess  92  for receiving a separate mounting bolt  93  or  98  is formed. 
     FIGS. 14A to  14 D illustrate said mounting bolt  93  comprising a bolt  94  and a plate  95  joined together by welding. Plate  95  has holes  96 ,  97  at locations corresponding to holes  7 ,  8 , respectively, of the expansion valve  1 . Mounting bolt  93  is attached to recess  92  when the pipes are to be connected to the expansion valve  1 . 
     FIGS. 15A to  15 D illustrate said other mounting bolt  98  comprising a plate  100  and a bolt  99  formed as a one-piece body. Plate  100  has holes  101 ,  102  at locations corresponding to the respective holes  7 ,  8  in the expansion valve  1 . Mounting bolt  98  is attached in recess  92  and is used when the pipes are to be connected to the expansion valve  1 . 
     Holes  7 ,  8  of expansion valve  1  are fitted with pipe mounting bolts. Those mounting bolts, when inserted, are tightened to securely fix the pipes. As soon as said mounting bolts are tightened there tightening forces are applied directly to pressure vessel  13 . Since pressure vessel  13  is made of resin there is a possibility that the pressure vessel will fracture when applied with excessively large stress. According to FIG. 16 a structure is employed for preventing such fracture. 
     In FIG. 16 the expansion valve  1  is shown in a section along a plane passing through holes  7 ,  8 . In holes  7 ,  8  metal collars  103 ,  104  are fitted. Collars  103 ,  104  are of a length slightly greater than the length of holes  7 ,  8 . As soon as the pipes are mounted at the evaporator side with the mounting bolts inserted into holes  7 ,  8 , the pipe fixing plate abuts against the evaporator side end faces of metal collars  103 ,  104 , while plate  95  of mounting bolt  93  abuts against the opposite end faces of said collars, so that the plates attached to the opposite end faces of the expansion valve  1  do not directly contact portions of the resin body block or pressure vessel  13  where mounting bolts are tightened. Any stress induced by the tightening of said mounting bolts is borne by the metal collars  103 ,  104  to prevent the application of excessive stress to the pressure vessel  13  made of resin eliminating the danger of fractures of expansion valve  1  at the time of mounting the pipes. 
     In FIG. 17 identical reference numerals are used to denote identical elements as appearing in FIG.  11 . An insulator  73   a  having an L-shaped cross-section is fitted around expansion valve  1  and is interposed between the elliptic opening of the partition wall  71  and the outer peripheral surface of expansion valve  1  and in close contact with flange  91  and evaporator casing  72 . Consequently, the gap between partition wall  72  and expansion valve  1  is sealed, blocking air communication between the vehicle compartment and the engine compartment. Simultaneously the gap between partition wall  71  and evaporator casing  72  is sealed. By thus forming the flange  91  with the shown configuration and its shown location on the expansion valve  1  it is possible to provide with ease a sealing structure for the partition wall  71  separating the vehicle compartment from the engine compartment. 
     In FIG. 18 identical reference numerals are used to denote elements identical with those appearing in FIG.  11 . In FIG. 18 those end faces of flange  91  and evaporator casing  72  facing partition wall  71  are positioned flush with each other. Between said end faces and partition  71  a ring-shaped insulator  73   b  is simply interposed to provide the necessary sealing. The insulator  73   b  as used is simple in shape. Also the sealing structure for the partition wall  71  separating the vehicle compartment from the engine compartment can be simplified.