RELATED APPLICATIONS 
       [0001]    This application claims benefit of Chinese Patent Application No. CN201420306097.4, filed Jun. 10, 2014. The above application is incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present utility model relates generally to the field of mechanical engineering, to a type of expansion valve, and more particularly to a type of automatic two-way expansion valve. 
         [0004]    2. Related Art 
         [0005]    The expansion valve is an important component in refrigeration systems, generally installed between the condenser and the evaporator. It enables that the gas evaporated from the evaporator pass through the compressor and get pressurized and liquefied to liquid refrigerant at high temperature and high pressure, pass through its throttle orifice and get throttled into atomized liquid refrigerant at low temperature and low pressure, and the refrigerant absorbs the heat in the evaporator to realize the cooling effect. The expansion valve controls the flow rate according to changes in the superheat at the rear end of the evaporator, so as to prevent the under utilization of the evaporator surface due to over restricted flow, as well as liquid slugging caused by under evaporated refrigerant inhaled into the compressor due to insufficient evaporator surface and excessive flow rate. 
         [0006]    In one prior art expansion valve, the first valve core and second valve core are sealed by a sealing cone in between. Specifically, there is a front throttle cone on first valve core, and there is a front throttle cone bore which matches the front throttle cone. Although this structure can realize the seal, it requires a relatively high precision process for machining the front throttle cone and the front throttle cone bore. In actual production, it requires high precision fabrication equipment, yet, still the parts passing rate is low. This results in an issue of high manufacturing cost on parts and thus a weak marketing competitiveness. A test shows that the expansion valves above also has an issue of low precision in its flow control. 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, it is an object of the invention to avoid the issues of the prior art stated above. 
         [0008]    It is further object of the invention to provide an automatic two-way expansion valve that reduces the manufacturing costs of the first and second valve cores. 
         [0009]    It is further object of the invention to provide a simple, efficient, durable, and cost effective automatic two-way expansion valve. 
         [0010]    The above objects of the present invention can be achieved by the following: 
         [0011]    This automatic two-way expansion valve comprises a valve body and the first and second valve cores inside the valve body. It is characterized in that: 
         [0012]    There is a small bore concatenate with a big bore inside second valve core. One end of first valve core passes through the big bore and plugs into the small bore. There is a flow clearance between the end of first valve core and the sidewall of the small bore. There is a sealing cone on first valve core, which can press against the chamfer rim between the small bore and the big bore. 
         [0013]    For this automatic two-way expansion valve, both the small bore and the big bore on second valve core are cylindrical and concentric. Specifications for manufacturing equipments for the small bore, the big bore and the sealing cone are less stringent, and for a good seal to form between the sealing cone and the rim requires less strict manufacturing precision; therefore, this can effectively improve the parts passing rate and reduce the production cost. Preferably, the sharp rim between the small bore and the big bore is rounded into an arc chamfer. The arc chamfer not only removes the burrs on the chamfer rim, but also improves fit between the chamfer rim and the sealing cone, which further ensures the sealing performance between first and second valve cores. 
         [0014]    In the present automatic two-way expansion valve, on the end of the first valve core, from the sealing cone to the end face of the end, there is a big cylinder followed by a small cylinder. When the first valve core or the second valve core moves, and the sealing cone detaches from the chamfer rim between the small bore and the big bore, the flow rate of the expansion valve is controlled by the flow clearance between the big cylinder and the sidewall of the small bore, entering the domain of small flow rate control. After the big cylinder completely enters into the big bore, the flow rate is controlled by the flow clearance between the small cylinder and the sidewall of the small bore, entering the domain of large flow rate control. 
         [0015]    In the present automatic two-way expansion valve, from the sealing cone to the end face of the end, there is a big cylinder, followed by a flow transition section and a small cylinder on the end of the first valve core. When the first valve core or the second valve core moves, and the sealing cone detaches from the chamfer rim between the small bore and the big bore, the flow rate of the expansion valve is controlled by the flow clearance between the big cylinder and the sidewall of the small bore, entering the domain of small flow rate control. After the big cylinder completely enters into the big bore, the flow rate is controlled by the flow clearance between the flow transition section and the sidewall of the small bore, entering the domain of variable flow rate control. After the flow transition section completely enters into the big bore, the flow rate is controlled by the flow clearance between the small cylinder and the sidewall of the small bore, entering the domain of large flow rate control. 
         [0016]    In the present automatic two-way expansion valve, the first valve core is clasped by a guide valve seat, which is fastened to the valve body. There is the first vent on the other end face of first valve core, and there are several second vents on the sidewall of first valve core, connecting to the first vent. The small bore passes through second valve core. This structure enables that the fluid flows through the second vents and the first vent, in a circumferential direction along the valve body, and avoids a complex structure necessary for the fluid flowing through the space between the outer shell and the valve body to the inlet and outlet on the valve body. In other words, the outer shell can be omitted with this structure. 
         [0017]    In the present automatic two-way expansion valve, the first gasket is installed between the end face of the guide valve seat and the end face of second valve core. Through the first gasket, second valve core presses against the guide valve seat, preventing fluid leakage or recirculation through the clearances between second valve core and the guide valve seat, between the guide valve seat and the valve body, and between second valve core and the valve body. That further improves the precision in flow control. 
         [0018]    In the present automatic two-way expansion valve, the first valve core comprises a seal abutment surface, and the second gasket is installed between the other end face of the guide valve seat and the seal abutment surface of first valve core. Through the second gasket, first valve core presses the guide valve seat. This prevents the fluid from leaking or returning through the clearances between the sealing surface of first valve core and the guide valve seat, between the guide valve seat and the valve body, and between first valve core and the valve body, which further improves the precision in flow control. 
         [0019]    In order to protect the valve body better, in the present automatic two-way expansion valve, the valve body is fitted with a protective sleeve. Both ends of the valve body are tube fittings, located outside of the protective sleeve. The protective sleeve is fixed to the valve body. 
         [0020]    In the present automatic two-way expansion valve, there are at least two seal grooves on the outer surfaces of first and second valve cores. A second ring seal is installed in each seal groove. Multiple ring seals improve not only the sealing performance, but also the smoothness of the valve core movement, and in particular, avoid the oscillation of the valve cores. 
         [0021]    In the present automatic two-way expansion valve, bumping posts are fixed to both ends of the valve body. There are slots along the side surfaces of the posts, and there are auxiliary slots throughout in radial directions on inner end faces of the posts. When a valve core abuts the inner end face of a bumping post, the auxiliary slots ensure free fluid flow. This prevents the valve core jamming due to a vacuum between the end face of a valve core and the inner end face of a bumping post. 
         [0022]    Compared to the prior art, by modifying the sealing structure between first and second valve cores, the present automatic two-way expansion valve not only reduces the production cost, but also improves the sealing performance between first and second valve cores. It effectively improves the precision in flow control, by modifying the shape of the end of first valve core and adding the first and the second gaskets. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a cutaway view of a first preferred embodiment of the invention. 
           [0024]      FIG. 2  is the detailed view of Section A of  FIG. 1 . 
           [0025]      FIG. 3  is the detailed view of Section B of  FIG. 1 . 
           [0026]      FIG. 4  is the detailed view of the inner end of the bumping posts in the first preferred embodiment of the invention. 
           [0027]      FIG. 5  is a cutaway view of a second preferred embodiment of the invention. 
           [0028]      FIG. 6  is a cutaway view of a third preferred embodiment of the invention. 
           [0029]      FIG. 7  is the detailed view of Section C of  FIG. 1 . 
           [0030]      FIG. 8  is the detailed view of Section D of  FIG. 5 . 
           [0031]      FIG. 9  is a cutaway view of a fourth preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    The embodiments of this utility model will be described below and the technical solutions of the invention will be further illustrated in connection with the accompanying figures. However, the present invention shall not be limited to these embodiments. 
       First Embodiment 
       [0033]    As shown in  FIG. 1 , An automatic two-way expansion valve comprises the valve body ( 1 ), the outer shell ( 2 ), the first valve core ( 3 ), the second valve core ( 4 ), the bumping post ( 5 ) and the guide valve seat ( 6 ). 
         [0034]    Valve body ( 1 ) is tubular in shape. First valve core ( 3 ), second valve core ( 4 ), bumping posts ( 5 ), springs and guide valve seat ( 6 ) are all situated inside the valve body ( 1 ). Outer shell ( 2 ) is fitted outside of the valve body ( 1 ). Both ends of the outer shell ( 2 ) have tube fittings. 
         [0035]    There are two bumping posts ( 5 ). The two bumping posts ( 5 ) are fixed to the two end ports of the valve body ( 1 ), respectively. There are slots ( 5   a ) on the side walls of the bumping posts ( 5 ). Both first valve core ( 3 ) and second valve core ( 4 ) are located in between the two bumping posts ( 5 ). There are two seal grooves each on the outer surfaces of first valve core ( 3 ) and second valve core ( 4 ), with one second ring seal ( 7 ) each pressing against the inner wall of the valve body ( 1 ) and embedded into each of the grooves. Hence, both first valve core ( 3 ) and second valve core ( 4 ) can slide along the inner wall of the valve body ( 1 ), and each of first valve core ( 3 ) and second valve core ( 4 ) forms a seal with the inner wall of valve body ( 1 ). 
         [0036]    There is a small bore ( 4   a ) concatenate with a big bore ( 4   b ) inside second valve core ( 4 ). Both the small bore ( 4   a ) and big bore ( 4   b ) are concentric with second valve core ( 4 ), and the small bore ( 4   a ) passes throughout in the axial direction. 
         [0037]    One end of first valve core ( 3 ) passes through the big bore ( 4   b ) and plug into the small bore ( 4   a ). There are flow clearances between the end of first valve core ( 3 ) and the side walls of both small bore ( 4   a ) and big bore ( 4   b ). On the end portion of first valve core ( 3 ), there is a sealing cone ( 3   a ) which can press against the chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ). When the sealing cone ( 3   a ) detaches from the chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ), the fluid can flow through the space between the small bore ( 4   a ) and the big bore ( 4   b ). The chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ) has an arc chamfer ( 4   c ). 
         [0038]    The guide valve seat ( 6 ) is installed outside of first valve core ( 3 ), and fixed to the valve body ( 1 ). The first spring ( 8 ) is installed between first valve core ( 3 ) and one bumping post ( 5 ), and the second spring ( 9 ) is installed between second valve core ( 4 ) and the other bumping post ( 5 ). As shown in  FIG. 3 , the first gasket ( 10 ) is installed between one end face of the guide valve seat ( 6 ) and the end face of second valve core ( 4 ). The first gasket ( 10 ) has a press fit with the valve body ( 1 ), and presses against the end face of the guide valve seat ( 6 ). As shown in  FIG. 2 , first valve core ( 3 ) comprises a seal abutment surface ( 3   b ). In between the other end face of the guide valve seat ( 6 ) and the seal abutment surface ( 3   b ) of first valve core ( 3 ), the second gasket ( 11 ) is installed. The second gasket ( 11 ) has a press fit with the valve body ( 1 ), and presses against the other end of the guide valve seat ( 6 ). As shown in  FIG. 1 , when the sealing cone ( 3   a ) presses against the chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ), second valve core ( 4 ) presses against the guide valve seat ( 6 ) through the first gasket ( 10 ), and the seal abutment surface ( 3   b ) of first valve core ( 3 ) is detached from the second gasket ( 11 ). 
         [0039]    In accordance with the actual spring forces of the first spring ( 8 ) and the second spring ( 9 ), the seal abutment surface ( 3   b ) of first valve core ( 3 ) presses against the guide valve seat ( 6 ) through the second gasket ( 11 ), and second valve core ( 4 ) detaches with the first gasket ( 10 ). 
         [0040]    As shown in  FIG. 7 , on one end of first valve core ( 3 ), from the sealing cone ( 3   a ) to the end face of the end, there is a big cylinder ( 3   c ) followed by a small cylinder ( 3   d ). 
         [0041]    As shown in  FIG. 1  and  FIG. 4 , there are throughout auxiliary slots ( 5   b ), in radial directions, at the inner end face of the bumping post ( 5 ). The auxiliary slots ( 5   b ) are located opposite the small bore ( 4   a ). 
         [0042]    As shown in  FIG. 1 , there is a spacer sleeve ( 12 ) between the outer shell ( 2 ) and the valve body ( 1 ). The spacer sleeve ( 12 ) is welded firm onto the valve body ( 1 ), and fastened to the outer shell ( 2 ). On the spacer sleeve ( 12 ) there is the third ring seal ( 13 ) which presses against the inner wall of the outer shell ( 2 ). The third ring seal ( 13 ) prevents the fluid from leaking through the space between the spacer sleeve ( 12 ) and the inner wall of the outer shell ( 2 ), so as to affect the precision in flow control. There are flow ports (la) on the valve body ( 1 ) and the guide valve seat ( 6 ), as shown in  FIG. 1 . When the pressure at the bottom port of the outer shell ( 2 ) is higher than that at the top port, first valve core ( 3 ) is forced to move under the fluid pressure, and the sealing cone ( 3   a ) detaches from the chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ). Hence, the fluid passes through the small bore ( 4   a ), the big bore ( 4   b ), the flow port (la), and the passage between the outer shell ( 2 ) and the valve body ( 1 ), in sequence. 
         [0043]    When the pressure at the bottom port of the outer shell ( 2 ) is lower than that at the top port, second valve core ( 4 ) is forced to move under the fluid pressure, and the sealing cone ( 3   a ) detaches from the chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ). Hence, the fluid passes through the passage between the outer shell ( 2 ) and the valve body ( 1 ), the flow port (la), the big bore ( 4   b ), the small bore ( 4   a ), in sequence. 
       Second Embodiment 
       [0044]    The principle and structure of this embodiment are basically similar to that of the first preferred embodiment. The difference is that, as shown in  FIG. 5 , on one end of first valve core ( 3 ), from the sealing cone ( 3   a ) to the end face of the end, there is a big cylinder ( 3   c ), followed by a flow transition section ( 3   e ) and a small cylinder ( 3   d ). 
         [0045]    On the other end face of first valve core ( 3 ), there is the first vent ( 3   f ). On the side wall of first valve core ( 3 ), there are second vents ( 3   g ) connecting to the first vent ( 3   f ). 
         [0046]    When the pressure at the bottom port of the outer shell ( 2 ) is higher than that at the top port, first valve core ( 3 ) is forced to move under the fluid pressure, and the sealing cone ( 3   a ) detaches from the chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ). Hence, the fluid passes through the small bore ( 4   a ), the big bore ( 4   b ), the second vent ( 3   g ), and the first vent ( 3   f ), in sequence. 
         [0047]    When the pressure at the bottom port of the outer shell ( 2 ) is lower than that at the top port, second valve core ( 4 ) is forced to move under the fluid pressure, and the sealing cone ( 3   a ) detaches from the chamfer rim between the small bore ( 4   a ) and the big bore ( 4   b ). Hence, the fluid passes through the first vent ( 3   f ), the second vent ( 3   g ), the big bore ( 4   b ), and the small bore ( 4   a ), in sequence. 
       Third Embodiment 
       [0048]    The principle and structure of this embodiment are basically similar to that of the second preferred embodiment. The difference is that, as shown in  FIG. 6 , the valve body ( 1 ) doesn&#39;t have the outer shell ( 2 ) and the spacer sleeve ( 12 ), on its outside, and both ends of the outer shell ( 2 ) are extended to become tube fittings. 
       Fourth Embodiment 
       [0049]    The principle and structure of this embodiment are basically similar to that of the third preferred embodiment. The difference is that, as shown in  FIG. 9 , a protective sleeve ( 14 ) encases the valve body ( 1 ). The tube fittings are located outside of the protective sleeve ( 14 ), and both ends of the protective sleeve ( 14 ) are fastened to the valve body ( 1 ). 
         [0050]    There is the third vent ( 5   c ) passing throughout the axis of the bumping post ( 5 ), through which the fluid will pass. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
         
           
               1  Valve Body 
               1   a  Flow Port 
               2  Outer Shell 
               3  First Valve Core 
               3   a  Sealing Cone 
               3   b  Seal Abutment Surface 
               3   c  Big Cylinder 
               3   d  Small Cylinder 
               3   e  Flow Transition Section 
               3   f  First Vent 
               3   g  Second Vent 
               4  Second Valve Core 
               4   a  Small Bore 
               4   b  Big Bore 
               4   c  Arc Chamfer 
               5  Bumping Post 
               5   a  Slot 
               5   b  Auxiliary Slot 
               5   c  Third Vent 
               6  Guide Valve Seat 
               7  Second Ring Seal 
               8  First Spring 
               9  Second Spring 
               10  First Gasket 
               11  Second Gasket 
               12  Spacer Sleeve 
               13  Third Ring Seal 
               14  Protective Sleeve 
               15  First Ring Seal
An automatic two-way expansion valve that resolves the issue where the precision in flow control of existing expansion valves is low. This automatic two-way expansion valve comprises a valve body and the first and second valve cores inside the valve body. There is a small bore concatenate with a big bore inside second valve core. One end of first valve core passes through the big bore and plug into the small bore. There is a flow clearance between the end of first valve core and the sidewall of the small bore. There is a sealing cone on first valve core, which can press against the chamfer rim between the small bore and the big bore. It effectively improves the precision in flow control, by modifying the shape of the end of first valve core and adding the first and the second gaskets.