Abstract:
A flow-adjusting valve including a valve base and a valve rod. The valve base has arranged within a valve cavity thereof a valve opening. The valve rod opens or shuts the valve opening. The valve rod is tube-shaped, and the lower part thereof is a cylinder. The valve base has arranged at circumferential positions around the valve opening a sealing stepped surface. A lower end face of the valve rod is sealedly in contact with or disengaged from the sealing stepped surface. Furthermore, the valve opening has protruding upwards along the axial direction thereof a sleeve protrusion part. The sealing stepped surface is arranged within the sleeve protrusion part. The structure of flow-adjusting valve on the one hand balances a refrigerant pressure exerted along the axial direction of the valve rod while on the other hand improves the service life and sealing performance of the valve rod.

Description:
[0001]    The present application claims the benefit of priority to Chinese Patent Application No. 201110175317.5, entitled “FLOW-ADJUSTING VALVE” and filed with the Chinese State Intellectual Property Office on Jun. 27, 2011, the entire disclosure of which is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present application relates to the technical field of the fluid control component, and particularly to a flow-adjusting valve. 
       BACKGROUND OF THE INVENTION 
       [0003]    The flow-adjusting valve is an important component of the refrigeration system, and is another one of four fundamental components of the refrigeration system besides the evaporator, the compressor and the condenser. Operation process of the flow-adjusting valve is generally as follows: with the energizing or de-energizing of the coil device, the valve needle is driven to adjust the opening degree of the valve port, so as to adjust the flow of the refrigerant. 
         [0004]    In the prior art, U.S. Pat. No. 6,568,656B1 discloses a flow-adjusting valve. Referring to  FIG. 1  and  FIG. 2 ,  FIG. 1  is a structural schematic view of a flow-adjusting valve in the prior art, and  FIG. 2  is a pressure distribution schematic view of a refrigerant at the valve port of the flow-adjusting valve in  FIG. 1 . 
         [0005]    As shown in  FIG. 1 , the flow-adjusting valve in the prior art includes a valve seat  1 ′ and a valve rod  2 ′. The valve seat  1 ′ is provided with a valve port  1 ′ 1  which is located in the valve cavity of the valve seat, and the valve rod  2 ′ is moved up and down along the axial direction, thereby adjusting the flow of the valve port  1 ′ 1 . As shown in  FIG. 1 , the valve rod  2 ′ has a split structure and includes a conical tube segment  2 ′ 1 , a cylindrical tube segment  2 ′ 2 , and a sealing member  2 ′ 3  provided between the conical tube segment and the cylindrical tube segment. As the valve rod  2 ′ is moved up and down, the valve port  1 ′ 1  is opened or closed by the sealing member  2 ′ 3 . Furthermore, the valve rod  2 ′ is provided with a balancing flow passage  2 ′ 4  for communicating an upper end and a lower end of the valve rod  2 ′, thereby balancing the effect of the pressure exerted by the refrigerant on the valve rod  2 ′. However, the flow-adjusting valve has disadvantages as follows. 
         [0006]    Firstly, as shown in  FIG. 2 , since the lower end portion of the valve rod  2 ′ is provided with a conical tube segment  2 ′ 1 , pressures from the refrigerant at the valve port  1 ′ 1  are substantially divided into three grades, that is, pressure grade A which has the maximum pressure (at the densest position of the transverse schematic line), pressure grade B which has the moderate pressure (at the denser position of the transverse schematic line), and pressure grade C which has the minimum pressure (at the sparsest position of the transverse schematic line). Therefore different positions of the conical tube segment  2 ′ 1  are subject to the above three different pressures, respectively. As shown in  FIG. 2 , the lower end opening of the balancing flow passage  2 ′ 4  is extended in the area of the pressure grade A, thus the upper end of the valve rod  2 ′ suffers a pressure of pressure grade A. It can be seen that, under the precondition that the force bearing areas of the upper end and lower end of the valve rod  2 ′ are the same, the force suffered by the upper end of the valve rod  2 ′ is different from the force suffered by the lower end (i.e., the conical tube segment  2 ′ 1 ) of the valve rod  2 ′. That is, pressures exerted by the refrigerant on the valve rod  2 ′ are uneven. Therefore the stability of the axial movement of the valve rod  2 ′ is affected. 
         [0007]    Secondly, as shown in  FIG. 1 , during the closing of the valve port  1 ′ 1  by the sealing member  2 ′ 3 , the sealing member  2 ′ 3  may collide with the valve port  1 ′ 1 . Since the impact force is large, after performing the opening and closing operations time and again, the sealing member  2 ′ 3  is easy to be deformed, resulting in the leakage of the refrigerant and a short service life of the sealing member. 
         [0008]    Thirdly, as shown in  FIG. 1 , the valve rod  2 ′ has a split structure and includes a conical tube segment  2 ′ 1 , a sealing member  2 ′ 3 , and a cylindrical tube segment  2 ′ 2 , and the three components are connected in a threaded manner or in other connection manners. The valve rod  2 ′ has a risk of being loosen and disconnected due to the bump and vibration in transportation or the vibration of the compressor in operation. 
         [0009]    Furthermore, it should be noted that, in the prior art, a flow-adjusting valve disclosed in Chinese patent application No. 200580023202.7 also has the above three disadvantages, reference may be made to the specification of the application, which will not be described in detail herein. 
         [0010]    Therefore, it becomes an urgent problem to be solved by the person skilled in the art to improve the flow-adjusting valve in the prior art, such that, on the one hand, pressures exerted by the refrigerant on the valve rod along the axial direction thereof can be balanced, and on the other hand, the service life and sealing performance of the valve rod can be improved. 
       SUMMARY OF THE INVENTION 
       [0011]    The technical problem to be solved by the preset application is to provide a flow-adjusting valve. With the structural arrangement of the flow-adjusting valve, on the one hand, pressures exerted by the refrigerant on the valve rod along the axial direction thereof can be balanced; and on the other hand, the service life and sealing performance of the valve rod can be improved. 
         [0012]    For solving the above technical problem, the present application provides a flow-adjusting valve. The flow-adjusting valve includes a valve seat and a valve rod. The valve seat is provided, in a valve cavity thereof, with a valve port, and the valve port is opened or closed by the valve rod. The valve rod has a tubular shape, the valve seat is provided, at a circumferential position of the valve port, with a sealing stepped surface, and a lower end face of the valve rod is hermetically contacted with the sealing stepped surface or is disengaged from the sealing stepped surface. 
         [0013]    Preferably, the valve port is provided with a sleeve protrusion portion protruded upwards along an axial direction of the valve port, the sealing stepped surface is provided inside of the sleeve protrusion portion, and a lower end portion of the valve rod is protruded into the sleeve protrusion portion or is moved out of the sleeve protrusion portion. 
         [0014]    Preferably, a chamfered surface is provided between a circumferential lateral wall of the valve rod and the lower end face of the valve rod, and the sealing stepped surface is an inclined surface cooperated with the chamfered surface. 
         [0015]    Preferably, an opening groove is provided on a circumferential lateral wall of the sleeve protrusion portion for adjusting a flow amount. 
         [0016]    Preferably, cross-sections of the valve rod that are perpendicular to an axis of the valve rod have the same outer diameter, the valve seat is provided with a guiding portion, and the valve rod is extended into an inner cavity of the valve seat through the guiding portion. 
         [0017]    Preferably, the valve seat is provided, at a position above the guiding portion, with an annular groove, and a sealing member is provided in the annular groove and is sleeved on the valve rod. 
         [0018]    Preferably, the valve seat has a split structure and includes an upper valve seat and a lower valve seat, the valve port and the sleeve protrusion portion are provided on the lower valve seat, and the sleeve protrusion portion is protruded into a cavity of the upper valve seat. 
         [0019]    Preferably, the valve rod is an integral component. 
         [0020]    Preferably, a tubular inner cavity of the valve rod is axially run through the valve rod so as to form a balancing flow passage for balancing forces applied to an upper end and a lower end of the valve rod. 
         [0021]    Preferably, a filter screen is provided in the tubular inner cavity. 
         [0022]    Based on the prior art, the valve rod of the flow-adjusting valve according to the present application has a tubular shape, and the lower end portion of the valve rod is a cylinder. The valve seat is provided with a sealing stepped surface at a circumferential position of the valve port, and the lower end face of the valve rod is hermetically contacted with or is disengaged from the sealing stepped surface. Since the lower end portion of the valve rod is a cylinder, but not a cone, pressures exerted by the refrigerant on the lower end of the valve rod are uniform. Meanwhile, since the valve rod has a tubular shape, and is run through along the axial direction, the pressure exerted by the refrigerant on the upper end of the valve rod is equal to that on the lower end thereof. Under the precondition that the force bearing areas of the upper end and lower end of the valve rod are the same, pressures exerted by the refrigerant on the valve rod along the axial direction of the valve rod are balanced. 
         [0023]    Furthermore, unlike the prior art, in the present application, the lower end face of the valve rod is hermetically contacted with the sealing stepped surface at the circumferential position of the valve port. The lower end face of the valve rod is not easy to be deformed because of its strong rigidity, therefore the sealing performance and service life of the valve rod is significantly improved. 
         [0024]    In summary, with the flow-adjusting valve according to the present application, on the one hand, pressures exerted by the refrigerant on the valve rod along the axial direction thereof can be balanced; and on the other hand, the service life and sealing performance of the valve rod can be improved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a structural schematic view of a flow-adjusting valve in the prior art; 
           [0026]      FIG. 2  is a pressure distribution schematic view of a refrigerant at the valve port of the flow-adjusting valve in  FIG. 1 ; 
           [0027]      FIG. 3  is a structural schematic view of a flow-adjusting valve according to an embodiment of the present application; 
           [0028]      FIG. 4  is a structural schematic view of a valve rod of the flow-adjusting valve in  FIG. 3 ; 
           [0029]      FIG. 5  is a structural schematic view of a lower valve seat cooperated with the valve rod in  FIG. 4 ; 
           [0030]      FIG. 6  is a structural schematic view of a lower valve seat which is improved on the basis of the lower valve seat in  FIG. 5 ; 
           [0031]      FIG. 7  is a sectional view of the lower valve seat in  FIG. 6 ; 
           [0032]      FIG. 8-1  is a structural schematic view of a valve rod according to another embodiment of the present application; 
           [0033]      FIG. 8-2  is a structural schematic view of a lower valve seat cooperated with the valve rod in  FIG. 8-1 ; 
           [0034]      FIG. 8-3  is a sectional view of the valve rod in  FIG. 8-1 ; 
           [0035]      FIG. 8-4  is a structural schematic view showing the cooperation between a valve rod and a lower valve seat according to another embodiment of the present application; 
           [0036]      FIG. 9-1  is a schematic view showing an assembling relationship among a valve seat, a sleeve and a connecting pipe of the flow-adjusting valve in  FIG. 3 ; 
           [0037]      FIG. 9-2  is an exploded schematic view of various components in  FIG. 9-1 ; 
           [0038]      FIG. 9-3  is a schematic view showing an assembly relationship among a valve seat, a sleeve and a connecting pipe improved on those in  FIG. 9-1 ; and 
           [0039]      FIG. 9-4  is a schematic view showing an assembly relationship among a valve seat, a sleeve and a connecting pipe improved in another way on those in  FIG. 9-1 . 
       
    
    
       [0040]    Relationships between the reference numerals and components in  FIG. 1  and  FIG. 2  are as follows:
         1 ′ valve seat;  1 ′ 1  valve port;  2 ′ valve rod;  2 ′ 1  conical tube segment;     2 ′ 2  cylindrical tube segment;  2 ′ 3  sealing member;  2 ′ 4  balancing flow passage.       
 
         [0043]    Relationships between the reference numerals and components in  FIG. 3  to  FIG. 9-4  are as follows:
         1  valve seat;  11  upper valve seat;  111  guiding portion;  112  annular groove;     113  sealing member;  12  lower valve seat;  121  valve port;  122  sleeve protrusion portion;     123  sealing stepped surface;  124  base;     2  valve rod;  21  filter screen;  22  stepped surface;  23  clamping ring;     3  opening groove;  41  first connecting pipe;  42  second connecting pipe;     43  connecting orifice;     5  motor;  51  output shaft;  52  motor shell;     61  screw rod;  62  gear seat;  63  sleeve.       
 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0052]    A spirit of the present application is to provide a flow-adjusting valve, the structure of which is configured that, on the one hand, pressures exerted by the refrigerant on the valve rod of the flow-adjusting valve in the axial direction can be balanced, and on the other hand, the service life and sealing performance of the valve rod can be improved. 
         [0053]    In order that those skilled in the art can better understand technical solutions of the present application, the present application is described in detail hereinafter in conjunction with the accompanying drawings and the embodiments. 
         [0054]    Referring to  FIG. 3  and  FIG. 4 ,  FIG. 3  is a structural schematic view of a flow-adjusting valve according to an embodiment of the present application; and  FIG. 4  is a structural schematic view of a valve rod of the flow-adjusting valve in  FIG. 3 . 
         [0055]    In the present application, the flow-adjusting valve is configured to adjust the flow of the refrigerant. As shown in  FIG. 3 , the flow-adjusting valve includes a motor shell  52  in which a motor  5  is provided. The output shaft  51  of the motor  5  is in transmission connection with the screw rod  61  via a gear system, therefore the screw rod  61  is rotated with the output shaft  51 . As shown in  FIG. 3 , the gear system is supported on the gear seat  62 , a sleeve  63  is provided outside of the gear seat  62 , and the screw rod  611  is passed through the gear seat  62  and is connected to the valve rod  2 . With the rotation of the screw rod  61 , the valve rod  2  is moved up and down axially, thereby achieving the adjusting of the flow of the refrigerant. 
         [0056]    As shown in  FIG. 3 , the valve seat  1  is provided, in the valve cavity thereof, with a valve port  121  which is closed or opened by the valve rod  2 . Based on this arrangement, as shown in  FIG. 3  and  FIG. 4 , the valve rod  2  has a tubular shape, and the lower end portion of the valve rod is a cylinder. The valve seat  2  is provided, at a circumferential position of the valve port  121 , with a sealing stepped surface  123 . The lower end face of the valve rod  2  is hermetically contacted with the sealing stepped surface  123  or is disengaged from the sealing stepped surface  123 . 
         [0057]    Since the lower end portion of the valve rod  2  is a cylinder, but not a cone, pressures exerted by the refrigerant on the lower end of the valve rod are uniform. Meanwhile, since the valve rod  2  has a tubular shape and is run through along the axial direction, the pressure exerted by the refrigerant on the upper end of the valve rod  2  is equal to that exerted on the lower end thereof. Under the precondition that the force bearing areas of the upper and lower ends of the valve rod  2  are equal, pressures exerted by the refrigerant on the valve rod  2  along the axial direction thereof are balanced. 
         [0058]    Furthermore, unlike the prior art, in the present application, the sealing stepped surface  123  at the circumferential position of the valve port  121  is sealed by the lower end face of the valve rod  2 , the lower end face of the valve rod  2  will not be easily deformed because of its strong rigidity. Therefore the sealing performance and service life of the valve rod are significantly improved. 
         [0059]    In summary, with the flow-adjusting valve according to the present application, on the one hand, pressures exerted by the refrigerant on the valve rod  2  along the axial direction thereof can be balanced; and on the other hand, the service life and sealing performance of the valve rod  2  can be improved. 
         [0060]    Referring to  FIGS. 5 ,  6  and  7 ,  FIG. 5  is a structural schematic view of a lower valve seat cooperated with the valve rod in  FIG. 4 ;  FIG. 6  is a structural schematic view of a lower valve seat which is improved on the basis of the lower valve seat in  FIG. 5 ; and  FIG. 7  is a sectional view of the lower valve seat in  FIG. 6 . 
         [0061]    Further improvements may be made based on the above technical solutions. As shown in  FIG. 5  to  FIG. 7 , the valve port  121  is provided with a sleeve protrusion portion  122  protruded upwards along the axial direction of the valve port. The sealing stepped surface  123  is provided inside of the sleeve protrusion portion  122 , and the lower end portion of the valve rod  2  is protruded into the sleeve protrusion portion  122  or is moved out of the sleeve protrusion portion  122 , such that the lower end face of the valve rod  2  is hermetically contacted with the sealing stepped surface  123  or is disengaged from the sealing stepped surface  123 . The sleeve protrusion portion  122  can guide the movement of the valve rod  2 , thereby avoiding the shaking of the valve rod  2 . Therefore, the axial movement stability and reliability of the valve rod is improved. 
         [0062]    Furthermore, as shown in  FIG. 7 , the sealing stepped surface  123  inside of the sleeve protrusion portion  122  is an inclined surface, in view of this, a chamfered surface cooperated with the inclined surface is provided between the circumferential lateral wall and the lower end face of the valve rod  2 , which structure arrangement further improves the reliability of the sealing. 
         [0063]    Meanwhile, as shown in  FIG. 5  to  FIG. 7 , an opening groove  3  corresponding to a flow curve is provided on the circumferential lateral wall of the sleeve protrusion portion  122 . The shape of the opening groove  3  is corresponded to the required flow curve, for example, a V-shaped groove, Y-shaped groove or other shapes. An opening groove  3  having a shape corresponded to that of the flow curve required by a refrigeration system may be provided on the circumferential lateral wall of the sleeve protrusion portion  122 . In operation, as the valve rod  2  is disengaged from the sleeve protrusion portion  122 , the opening groove  3  is initially in communication with the valve port  121  in a way allowing a small flow passing through, and as the valve rod  2  is further moved out from the sleeve protrusion portion  122 , the circulation area of the opening groove  3  is gradually increased, and the flow of the refrigerant is gradually increased. When the opening groove  3  is fully opened, the maximum flow between the opening groove and the valve port  121  is achieved. Thus it can be seen that, the flow-adjusting valve according to the present application can obtain the required flow curve. 
         [0064]    Referring to  FIG. 9-1  to  FIG. 9-4 ,  FIG. 9-1  is a schematic view showing an assembly relationship among a valve seat, a sleeve and a connecting pipe of the flow-adjusting valve in  FIG. 3 ;  FIG. 9-2  is an exploded schematic view of various components in  FIG. 9-1 ;  FIG. 9-3  is a schematic view an assembly relationship among a valve seat, a sleeve and a connecting pipe improved on those in  FIG. 9-1 ; and  FIG. 9-4  is a schematic view showing an assembly relationship among a valve seat, a sleeve and a connecting pipe improved in another way on those in  FIG. 9-1 . 
         [0065]    Further improvements may be made to the above technical solutions. For example, as shown in  FIG. 9-1  and  FIG. 9-2 , the valve seat  1  has a split structure which includes an upper valve seat  11  and a lower valve seat  12 . The valve port  121  and the sleeve protrusion portion  122  are provided on the lower valve seat  12 , and the sleeve protrusion portion  122  is protruded into the cavity of the upper valve seat  11 . In machining, the valve port  121  and the sleeve protrusion portion  122  are firstly machined on the lower valve seat  12 , then the upper valve seat  11  is machined, and finally the machined lower valve seat  12  and upper valve seat  11  are assembled. It can be seen that, since the valve seat  1  has a split structure, the machining of the sleeve protrusion portion  122  can be easily realized. Therefore the machining process is simplified. 
         [0066]    In addition, as shown in  FIG. 9-1  to  FIG. 9-2 , the flow-adjusting valve further includes a first connecting pipe  41  and a second connecting pipe  42 . The first connecting pipe  41  is connected to the upper valve seat  11 , and the second connecting pipe  42  is connected to the lower valve seat  12 . As shown in  FIG. 9-1 , the first connecting pipe  41  and the second connecting pipe  42  are arranged in parallel and are located at two sides of the valve seat  1 , respectively. As shown in  FIG. 9-2 , the first connecting pipe  41  and the second connecting pipe  42  are arranged in parallel and are located at the same side of the valve seat  1 . As shown in  FIG. 9-3 , the first connecting pipe  41  and the second connecting pipe  42  are arranged at different planes and are arranged substantially at an angle of  90  degree, of course, it is not limited to the  90  degree angle. It can be seen that, with the above structure arrangement, the positions of the first connecting pipe  41  and the second connecting pipe  42  can be arranged based on different application environments of the refrigeration system. Therefore, the present application has a good adaptability. 
         [0067]    As shown in  FIG. 9-2 , the lower valve seat  12  includes a base  124 . The sleeve protrusion portion  122  is provided at the upper end of the base  124 , and the lower end face of the base  124  is closed. A connecting orifice  43  is provided on the circumferential lateral wall of the base  124 , and the second connecting pipe  42  may be connected to the connecting orifice  43 . The connecting orifice  43  may be provided at any positions of the circumferential lateral wall of the base  124  as required so as to achieve the structural arrangements of  FIGS. 9-1 ,  9 - 3  and  9 - 4 . 
         [0068]    In addition, further improvements may be made to the above technical solutions. As shown in  FIG. 3  and  FIG. 4 , cross-sections of the valve rod  2  which are perpendicular to the axis of the valve rod have the same outer diameter, i.e. contour dimensions of the upper portion and the lower portion of the valve rod  2  are uniform. As shown in  FIG. 3 , the valve seat  1  is provided with a guiding portion  111 , and the valve rod  2  is extended into an inner cavity of the valve seat  1  after passing through the guiding portion  111 . In particular, as shown in  FIG. 3 , the guiding portion  111  is provided on the upper valve seat  11 , and the valve rod  2  is extended into the inner cavity of the upper valve seat  11  after passing through the guiding portion  111 . 
         [0069]    In the flow-adjusting valve disclosed in Chinese patent application No. 200580023202.7, as is shown in  FIG. 2  thereof, the valve unit  40  has a structure in which the lower portion of the structure is larger while the upper portion thereof is smaller, i.e. the lower portion has a larger outer diameter while the upper portion has a smaller outer diameter. Therefore the assembling of the flow-adjusting valve is complicated, and the assembling cost is high. However, in the present application, cross-sections of the valve rod  2  which are perpendicular to the axis of the valve rod have the same outer diameter, and the valve rod  2  is extended into the valve cavity after passing through the guiding portion  111  of the upper valve seat  11 . Thus the flow-adjusting valve according to the present application has a simpler assembling process and is easier to be assembled. 
         [0070]    Furthermore, further improvement may be made to the above technical solutions. As shown in  FIG. 3 , the valve seat  1  is provided with an annular groove  112  at a position above the guiding portion  111 . In particular, the upper valve seat  11  is provided with the annular groove  112  at a position above the guiding portion  111 , and a sealing member  113  is provided in the annular groove  112  and is sleeved on the valve rod  2 . 
         [0071]    In the flow-adjusting valve disclosed in Chinese patent No. 200580023202.7, as is shown in  FIG. 2  thereof, the sealing ring  102  is provided on the valve unit  40 . In particular, the sealing ring is provided on the annular groove at the circumferential lateral wall of the valve unit. Since it requires that the valve unit  40  be slid axially, in order to maintain the sealing performance of the sealing ring  102 , the external threaded guide handle  46  should have a large axial length, resulting in that the valve body has a large axial dimension. 
         [0072]    While in the present application, as shown in  FIG. 3 , the upper valve seat  11  is provided with an annular groove  112  at a position above the guiding portion  111 , and a sealing member  113  is provided in the annular groove  112  and is sleeved outside of the valve rod  2 . That is, the seal member  113  is provided on the upper valve seat  11 , rather than on the valve rod  2 , at this time, in order to maintain the sealing performance of the sealing member  113 , there is no requirement on the axial length of the guiding portion  111 , the guiding portion  111  may have a small axial length, thereby the axial dimension of the valve body is reduced. 
         [0073]    Furthermore, as shown in  FIG. 3  and  FIG. 4 , the present application avoids the structural arrangement of the sealing member in the prior art, the valve rod  2  may have an integrated structure along the axial direction thereof. Therefore, the risk of being disengaged due to bump and vibration in transportation or vibration of the compressor in operation can be avoided. 
         [0074]    There may be another structure form of valve rod, referring to  FIGS. 8-1 ,  8 - 2  and  FIG. 8-3 ,  FIG. 8-1  is a structural schematic view of a valve rod according to another embodiment of the present application;  FIG. 8-2  is a structural schematic view of a lower valve seat cooperated with the valve rod in  FIG. 8-1 ; and  FIG. 8-3  is a sectional view of the valve rod in  FIG. 8-1 . 
         [0075]    As shown in  FIG. 8-1 , the valve rod  2  is provided with an opening groove  3  on the circumferential lateral wall of the lower end portion thereof. Based on this arrangement, as shown in  FIG. 9-2 , the lower end portion of the valve rod  2  is provided with a stepped surface  22  which is located at a position higher than that of the opening groove  3 , and further, the stepped surface  22  may be provided inside of the lower end portion of the valve rod  2 . Based on this, reference is also made to  FIG. 9-1  to  FIG. 9-3 , the sleeve protrusion portion  122  may be further extended into the lower end portion of the valve rod  2  or be moved out of the valve rod  2 , such that the upper end face of the sleeve protrusion portion  122  is hermetically contacted with the stepped surface  22  or is disengaged from the stepped surface  122 . This kind of structure arrangement has the same technical effect as that of the structure arrangement in which the opening groove  3  is provided on the sleeve protrusion portion  122  (as shown in  FIG. 4  and  FIG. 5 ), which will not be described in detail. 
         [0076]    Moreover, in this kind of structure arrangement, the upper end face of the sleeve protrusion portion  122  is connected with the stepped face  22  in a sealed manner, and the stepped face  22  is not easy to be deformed because of its strong rigidity. Therefore, compared with the structural arrangement of the sealing member in the prior art, the sealing performance and service life of the present application are significantly improved. 
         [0077]    As shown in  FIG. 8-3 , the tubular inner cavity of the valve rod  2  is axially run through the valve rod  2  so as to form a balancing flow passage for balancing forces exerted on the upper end and the lower end of the valve rod  2 , such that pressures exerted by the refrigerant on the upper end and the lower end of the valve rod  2  respectively are equal to each other. 
         [0078]    Further, as shown in  FIG. 8-3 , a filter screen  21  is provided in the tubular inner cavity, and the filter screen  21  may be fixed in the tubular inner cavity of the valve rod  2  via a clamping ring  23 . The filter screen  21  can filter the refrigerant to prevent impurities in the refrigerant from entering into the gap between the screw rod  61  and a nut. Thereby the movement of the screw rod  61  will not be influenced. 
         [0079]    Moreover, the stepped surface  22  may be provided outside of the lower end portion of the valve rod  2 . Reference may be made to  FIG. 8-4  which is a structural schematic view showing the cooperation between a valve rod and a lower valve seat according to another embodiment of the present application. 
         [0080]    As shown in  FIG. 8-4 , the lower end portion of the valve rod  2  is provided with an opening groove  3 , a stepped surface  22  is provided outside of the lower end portion of the valve rod  2 , the lower end portion of the valve rod  2  is extended into the sleeve protrusion portion  122  or is moved out of the sleeve protrusion portion  122 , such that the stepped surface  22  is hermetically contacted with the upper end face of the sleeve protrusion portion  122  or is disengaged therefrom. Apparently, this kind of technical solution can solve the technical problem and achieve the object of the present application. Also, this kind of structure arrangement can form the stepped surface  22  more easily, and has a low cost. 
         [0081]    The flow-adjusting valve according to the present application is introduced in detail through the above description. Specific examples are employed to describe the principle and embodiments of the present application. The description of the above embodiments is only provided for the understanding of the method of the present application and the core idea thereof. It should be noted that, those skilled in the art may made many modifications and improvements to the present application without departing from the principle of the present application, and all these modifications and improvements should fall within the protection scope of the claims of the present application.