Abstract:
Disclosed in the present invention is a flow regulating valve comprises a valve seat ( 1 ) and a casing ( 2 ). A motor ( 21 ) provided inside the casing ( 2 ) is connected to a screw rod ( 3 ) through the output shaft of the motor. The screw rod is connected to a screw nut ( 4 ) connecting with a valve rod ( 5 ) and the inner part of the valve rod ( 5 ) is provided with a mounting groove ( 51 ). The screw nut ( 4 ) is in clearance fit with the mounting groove ( 51 ) along the radical direction, and the inner wall of the mounting groove ( 51 ) is provided with an annular limiting groove ( 52 ). A limiting element ( 53 ) provided in the annular limiting groove ( 52 ) limits the position along the axial direction of the screw nut ( 4 ) and is in clearance fit with the outside of the screw nut. On one hand, the configuration design of the flow regulating valve is able to eliminate the coaxial degree error between the screw rod and the screw nut generated during the processing and assembling of components and parts, on the other hand, it is able to improve the reliability of the axial limitation of the screw nut.

Description:
[0001]    The present application claims the benefit of priority to Chinese patent application No. 201110176275.7, titled “FLOW REGULATING 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, in particular, to a flow regulating 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. Furthermore, the flow regulating valve is widely used in other fluid control fields such as the hydraulic system and the oil transportation fields. 
         [0004]    In the prior art, a flow regulating valve is disclosed in Chinese patent application No. 200580023202.7. Referring to  FIG. 1  and  FIG. 2 ,  FIG. 1  is a structural schematic view of a flow regulating valve in the prior art, and  FIG. 2  is a partial enlarged view of the flow regulating valve in  FIG. 1 . 
         [0005]    As shown in  FIG. 1 , a motor  70  is provided in the motor shell  62 , and the lower shell  60  of the motor shell  62  is connected in the head portion  48  in a thread cooperation manner. As shown in  FIG. 2 , the valve unit  40  includes a discharge piston  130  (equivalent to a nut), and the discharge piston  130  has an internal thread and is configured for housing a driving shaft  78  (equivalent to a screw rod) which has an external thread. The discharge piston  130  is extended a longe length in the axial direction, and is slidably mounted in the sleeve  146  which is mounted in the lower shell  60 . The discharge piston  130  is limited by the sleeve  146  and cannot rotate circumferentially. When the motor  70  drives the driving shaft  78  having an external thread to rotate via a gear system, since the discharge piston  130  cannot rotate circumferentially, it can only move axially to thereby drive the valve unit  40  to regulate the opening degree of the valve port on the valve seat  22 . However, the flow regulating valve in the prior art has the following drawbacks: 
         [0006]    Firstly, the valve unit  40  includes a rear component  94  which is connected in a middle component  96  in a thread cooperation manner. Thereby the axial position of the discharge piston  130  is limited. As shown in  FIG. 2 , since the discharge piston  130  needs to close or open a small valve port  120   b , the discharge piston  130  should not wobble in the radial direction. That is, not gap is formed between the discharge piston  130  and the rear component  94  or the middle component  96  in the radial direction. Otherwise the sealing performance in sealing the small valve port  120   b  will be affected. The machining and assembling of the components and parts of the valve body may cause a large coaxial error, resulting in a large coaxial error between the driving shaft  78  and the discharge piston  130 . Since the discharge piston  130  cannot wobble in the radial direction, the driving shaft is likely to get stuck. 
         [0007]    Secondly, the rear component  94  is connected with the middle component  96  through threads, as the discharge piston  130  and the valve unit  40  are moved in the axial direction, the thread cooperation may become loosened, resulting in a low reliability in axially limiting the discharge piston  130 . 
         [0008]    Thirdly, the discharge piston  130  needs to be fixed in the sleeve  146  of the lower shell  60 , such that it is circumferentially limited by the sleeve  146  and thus cannot be rotated. In view of this, the length of the portion of the discharge piston  130  that is protruded out of the valve unit  40  should be sufficient such that it can be extended into the sleeve  146 . In this structure configuration, the driving shaft  78  cooperated with the discharge piston  130  also has a large length, therefore the driving shaft  78  has a large deflection, and it is difficult to ensure the coaxial degree between the discharge piston  130  and the driving shaft  78  when assembling the same, and if they are not assembled in proper, the resistance moment will be increased, and moreover, the driving shaft  78  will get stuck. 
         [0009]    Fourthly, as is described above, it requires that the discharge piston  130  be protruded out of the valve unit  40  at a sufficient length such that it can be extended into the sleeve  146 . Accordingly, the driving shaft  78  and the lower shell  60  have large lengths in the axial direction. Thereby the material cost is increased. 
         [0010]    In view of this, there is an urgent demand for the person skilled in the art to make an improvement to the flow regulating valve in the prior art, such that, on the one hand, the coaxial error between the screw rod and the nut, resulting from the machining and assembling of the components and parts, can be eliminated, and on the other hand, the axial position of the nut can be limited more reliably. 
       SUMMARY OF THE INVENTION 
       [0011]    A problem to be solved by the present application is to provide a flow regulating valve, with the structure configuration of the flow regulating valve, on the one hand, the coaxial error between the screw rod and the nut, resulting from the machining and assembling of the components and parts, can be eliminated, and on the other hand, the axial position of the nut can be limited more reliably. 
         [0012]    In view of the above, it is provided according to the present application a flow regulating valve which includes a valve seat and a shell connected to the valve seat, among which, a motor is provided in the shell, and the motor is connected to a screw rod via an output shaft of the motor; the screw rod is connected with a nut in a thread cooperation manner; and the nut is connected with a valve rod, and the valve rod is movable in an axial direction to regulate an opening degree of a valve port on the valve seat; and wherein the valve rod is provided therein with an mounting groove, and the whole of the nut or a lower portion of the nut is in clearance fit with the mounting groove in a radial direction; and an internal wall of the mounting groove is provided with an annular position limiting groove, and a position limiting component that limits an axial position of the nut and in clearance fit with an exterior portion of the nut is provided in the annular position limiting groove. 
         [0013]    Preferably, the position limiting component includes a snap ring, and a circumferential side wall of the nut is provided with a position limiting step surface. The snap ring is mounted in the annular position limiting groove and is supported on the position limiting step surface, and there is a gap between the internal wall of the snap ring and a corresponding side wall of the nut. 
         [0014]    Preferably, the position limiting component further includes a check ring which is sleeved and supported on the position limiting step surface in a circumferential direction, and there is a gap between an internal wall of the check ring and a corresponding side wall of the nut; and the snap ring is supported on the position limiting step surface via the check ring. 
         [0015]    Preferably, a top surface of the check ring is provided with a check ring step surface, the snap ring is supported on the check ring step surface, and there is a gap between an internal wall of the snap ring and a corresponding side wall of the check ring. 
         [0016]    Preferably, the position limiting step surface is a first tapered surface, a bottom surface of the check ring is a second tapered surface, and an inclined angle of the first tapered surface is less than that of the second tapered surface. 
         [0017]    Preferably, one of a bottom wall of the mounting groove and a bottom wall of the nut is provided with a circumferential position limiting groove, the other one is provided with a position limiting projection, and the position limiting projection is provided in the circumferential position limiting groove. 
         [0018]    Preferably, the valve rod includes an injection molded body and a metal housing wrapping the injection molded body, an inner cavity of an upper portion of the injection molded body forms the mounting groove, and the annular position limiting groove is provided on an internal wall of the injection molded body. 
         [0019]    Preferably, the valve rod includes an injection molded body and a metal housing wrapping the injection molded body. An inner side of a top end portion of the metal housing is provided with a metal projection, an inner cavity of an upper portion of the injection molded body and an inner cavity of the metal projection form the mounting groove, and the annular position limiting groove is provided on an inner wall of the metal projection. 
         [0020]    Preferably, the whole of the nut is provided in the mounting groove; the output shaft of the motor is connected with the screw rod via a gear system, the gear system is supported on the gear seat which is located in a valve cavity of the valve seat, and the screw rod is passed through the gear seat and is in thread cooperation with the nut; and a lower portion of the gear seat is provided with a first position limiting portion, and an upper portion of the valve rod is provided with a second position limiting portion which is cooperated with the first position limiting portion such that the position of the valve rod relative to the gear seat is circumferentially limited and the valve rod is slidable in the axial direction. 
         [0021]    Preferably, the first position limiting portion is a noncircular special-shaped cavity, and the second position limiting portion is a noncircular special-shaped portion which is slidable in the axial direction and is provided in the noncircular special-shaped cavity. 
         [0022]    Preferably, the gear seat is provided with a plurality of first locating rod members extended in an axial direction, and the first position limiting portion is the first locating rod member; among the first locating rod members, at least one group of adjacent first locating rod members form a position limiting gap; and the second position limiting portion is a second locating rod member provided on a side wall of the valve rod, an upper portion of the valve rod is extended into a space surrounded by the first locating rod members in the circumferential direction, and the second locating rod member is inserted in the position limiting gap. 
         [0023]    On the basis of the prior art, the valve rod of the flow regulating valve according to the present application is provided therein with an mounting groove, and the whole of the nut or the lower portion of the nut is in clearance fit with the mounting groove in the radial gap. The inner wall of the mounting groove is provided with an annular position limiting groove, and a position limiting component that limits the axial position of the nut and in clearance fit with the exterior portion of the nut is provided in the annular position limiting groove. In the present application, since the whole of the nut or the lower portion of the nut is in clearance fit with the mounting groove in the radial direction, and the position limiting component is in clearance fit with the nut in the radial direction, after being assembled, the nut may be driven under the action of the screw rod to wobble radially in a small gap in the valve rod. Thus the coaxial error between the screw rod and the nut, resulting from the machining and assembling of the components and parts, can be eliminated, and the phenomenon in which the screw rod gets stuck can further be avoided. 
         [0024]    Furthermore, in the present application, since the internal wall of the mounting groove is provided with an annular position limiting groove, a position limiting component is mounted in the annular position limiting groove, and the nut is axially limited through the position limiting component, this kind of position limiting structure can avoid the loosening problem of the thread cooperation connection manner, and thus the reliability of the structure in limiting the axial position of the nut is improved. 
         [0025]    Above all, with the flow regulating valve according to the present application, on the one hand, the coaxial error between the screw rod and the nut, resulting from the machining and assembling of the components and parts, can be eliminated, and on the other hand, the axial position of the nut can be limited more reliably. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a structural schematic view of a flow regulating valve in the prior art; 
           [0027]      FIG. 2  is a partial enlarged view of the flow regulating valve in  FIG. 1 ; 
           [0028]      FIG. 3  is a structural schematic view of a flow regulating valve in a first embodiment of the present application; 
           [0029]      FIG. 4  is a structural schematic view of a valve rod of the flow regulating valve in  FIG. 3 ; 
           [0030]      FIG. 4-1  is a sectional view of the valve rod in  FIG. 4 ; 
           [0031]      FIG. 4-2  is an exploded view of the valve rod in  FIG. 4-1 ; 
           [0032]      FIG. 4-3  is a partial enlarged view of part A of the valve rod in  FIG. 4-1 ; 
           [0033]      FIG. 4-4  is an assembling schematic view of a check ring and a nut of the valve rod in  FIG. 4-1 ; 
           [0034]      FIG. 5  is a structural schematic view of a valve rod in a second embodiment of the present application; 
           [0035]      FIG. 5-1  is a sectional view of the valve rod in  FIG. 5 ; 
           [0036]      FIG. 5-2  is an exploded view of the valve rod in  FIG. 5 ; 
           [0037]      FIG. 5-3  is a partial enlarged view of part B of the valve rod in  FIG. 5-1 ; 
           [0038]      FIG. 6  is a structural schematic view of a gear seat cooperated with the valve rod in  FIG. 4 ; and 
           [0039]      FIG. 7  is a structural schematic view of a gear seat cooperated with the valve rod in  FIG. 5 . 
       
    
    
       [0040]    Corresponding relationships among the reference numbers and the component in FIG.  1  and  FIG. 2  are as follows:
         62  motor shell;  70  motor;  48  head portion;  40  valve unit;  130  discharge piston;  78  driving shaft;  146  sleeve;  60  lower shell;  22  valve seat;  94  rear component;  96  middle component;  120   b  small valve port.       
 
         [0042]    Corresponding relationships among the reference numbers and the component in  FIG. 3  to  FIG. 7  are as follows:
         1  valve seat;  11  upper valve seat;  12  lower valve seat;  13  sleeve;     2  shell;  21  motor;  22  gear system;     3  screw rod;     4  nut;  41  position limiting step surface;  42  position limiting projection;     5  valve rod;  51  mounting groove;  52  annular position limiting groove;  53  position limiting component;  531  snap ring;  532  check ring;  532   a  check ring step surface;  532   b  second tapered surface;  54  circumferential position limiting groove;  55  injection molded body;  56  metal housing;  56   a  metal projection;  57  noncircular special-shaped portion;  58  second locating rod member;     6  gear seat;  61  noncircular special-shaped cavity;  62  first locating rod member;  63  position limiting gap.       
 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    A spirit of the present application is to provide a flow regulating valve, with the structure configuration of the flow regulating valve, on the one hand, the coaxial error between the screw rod and the nut, resulting from the machining and assembling of the components and parts, can be eliminated, and on the other hand, the axial position of the nut can be limited more reliably. 
         [0050]    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. 
         [0051]    Preferring to  FIG. 3  to  FIG. 4-4 ,  FIG. 3  is a structural schematic view of a flow regulating valve according to a first embodiment of the present application;  FIG. 4  is a structural schematic view of a valve rod of the flow regulating valve in  FIG. 3 ;  FIG. 4-1  is a sectional view of the valve rod in  FIG. 4 ;  FIG. 4-2  is an exploded view of the valve rod in  FIG. 4-1 ;  FIG. 4-3  is a partial enlarged view of part A of the valve rod in  FIG. 4-1 ; and  FIG. 4-4  is an assembling schematic view of a check ring and a nut of the valve rod in  FIG. 4-1 . 
         [0052]    In the basic technical solution, the flow regulating valve according to the present application includes a valve seat  1  and a shell  2  connected to the valve seat  1 . A motor  21  is provided in the shell  2 , and an output shaft of the motor  21  is in transmission connection with the screw rod  3  via the gear system  22  supported on the gear seat  6 , thus the screw rod  3  is rotated with the output shaft of the motor  21 . The screw rod  3  is connected with the nut  4  in a thread cooperation manner, and the nut  4  is connected to the valve rod  5 . As the output shaft of the motor  21  is rotated, the screw rod  3  is rotated, and then the screw rod  3  drives the valve rod  5  to move in the axial direction. Thereby the valve rod regulates the opening degree of the valve port on the valve seat  1 . 
         [0053]    On basis of the above structure, referring to  FIG. 4-1  to  FIG. 4-2 , the valve rod  5  is provided therein with a mounting groove  51 , and the whole of the nut  4  or a lower portion of the nut  4  is in clearance fit with the mounting groove  51  in a radial direction. The internal wall of the mounting groove  51  is provided with an annular position limiting groove  52 , and a position limiting component  53  that limits the axial position of the nut  4  and in clearance fit with the exterior portion of the nut  4  is provided in the annular position limiting groove  52 . 
         [0054]    In the present application, since the whole of the nut  4  or the lower portion of the nut  4  is in clearance fit with the mounting groove  51  in the radial direction, and the position limiting component  53  is in clearance fit with the nut  4  in the radial direction, after being assembled, the nut  4  may be driven under the action of the screw rod  3  to wobble radially in a small gap in the valve rod  5 . Thus the coaxial error between the screw rod  3  and the nut  4 , resulting from the machining and assembling of the components and parts, can be eliminated, and the phenomenon in which the screw rod gets stuck can further be avoided. 
         [0055]    Furthermore, in the present application, since the internal wall of the mounting groove  51  is provided with an annular position limiting groove  52 , and a position limiting component  53  is mounted in the annular position limiting groove  52 , the nut  4  is axially limited through the position limiting component  53 , therefore this kind of position limiting structure can avoid the loosening problem of the thread cooperation connection manner, and thus the reliability of the structure in limiting the axial position of the nut  4  is improved. 
         [0056]    It is to be noted that, the emphasis of the above basic technical solution lies in how to connect the nut  4  to the valve rod  5 , but not in whether the nut  4  is integrally provided in the valve rod  5 . Thus, as long as the connection structure between the nut  4  and the valve rod  5  in the present application is employed, regardless of whether the nut  4  is integrally provided in the mounting groove  51  of the valve rod  5  as shown in  FIG. 4-1 , or only the lower portion of the discharge piston  130  (corresponding to the nut  4  in the present application) is provided in the valve unit  40  (corresponding to the valve rod  5  in the present application), it should fall within the protection scope of the present application. 
         [0057]    Furthermore, it is to be noted that, as shown in  FIG. 3 , the valve seat  1  may have a split structure, including an upper valve seat  11 , a lower valve seat  12  and a sleeve  13 . However, in the present application, the structure of the valve seat  1  is not limited, the valve seat  1  may be an integral member, that is, the upper valve seat  11 , the lower valve seat  12  and the sleeve  13  may be made into one piece. Alternatively, the upper valve seat  11  and the lower valve seat  12  may be made into one piece, and then forms together with the sleeve  13  into the valve seat  1 , which is not limited in the present application. 
         [0058]    In the above basic technical solution, the structure of the position limiting component  53  may be configured in detail. For example, as shown in  FIG. 4-1 ,  FIG. 4-2  and  FIG. 4-3 , the position limiting component  53  includes a snap ring  531 , the circumferential side wall of the nut  4  is provided with a position limiting step surface  41 , and the snap ring  531  is mounted in the annular position limiting groove  52  and is supported on the position limiting step surface  41 . There is a gap between the internal wall of the snap ring  531  and the corresponding side wall of the nut  4 . As shown in  FIG. 4-2 , the snap ring  531  is opened such that it can become contracted when suffering a force, and thus it can be conveniently mounted in the annular position limiting groove  52 , and after being mounted in the annular position limiting groove  52 , the snap ring  531  can restore to its original shape, to thereby be further mounted and supported on the position limiting step surface  41 , which structure configuration can limit the axial position of the nut  4  conveniently, and has a simple structure and a low cost. 
         [0059]    Further, as shown in  FIG. 4-1 ,  FIG. 4-2  and  FIG. 4-3 , the position limiting component  53  may further include a check ring  532 . The check ring  532  is mounted and supported on the position limiting step surface  41  in the circumferential direction, and there is a gap between the internal wall of the check ring and the corresponding side wall of the nut  4 ; and the snap ring  531  is supported on the position limiting step surface  41  via the check ring  532 . With the cooperative actions of the snap ring  531  and the check ring  532 , the reliability of the structure configuration in limiting the axial position of the nut  4  can be further improved. 
         [0060]    Furthermore, as shown in  FIG. 4-3 , there is a gap between the internal wall of the check ring  532  and the corresponding side wall of the nut  4 , meanwhile there is a gap b between the internal wall of the mounting groove  51  and the corresponding side wall of the nut  4 , the concurrence of the two gaps can make the nut  4  radially wobble in the mounting groove  51  in a small gap. Furthermore, as shown in  FIG. 4-3 , there is a gap c between the internal wall of the snap ring  531  and the side wall of the corresponding check ring  532 , and with the gap c, the snap ring  531  can be conveniently mounted in the annular position limiting groove  52 . 
         [0061]    Above all, with the structure configuration of the snap ring  531  and the check ring  532 , on the one hand, the nut  4  can be conveniently wobbled in the radial direction in a small gap, and on the other hand, the reliability of limiting the axial position of the nut  4  can be further improved. 
         [0062]    Furthermore, as shown in  FIG. 4-4 , the position limiting step surface  41  is a first tapered surface, and the bottom surface of the check ring  532  is a second tapered surface  532   b ; and, as shown in  FIG. 4-4 , the inclined angle β of the first tapered surface is less than the inclined angle α of the second tapered surface  532   b . Since the inclined angle β of the first tapered surface is less than the inclined angle α of the second tapered surface  532   b , when the first tapered surface is contacted with the second tapered surface  532   b , the contact between them is a line contact, rather than a surface contact, therefore the contact area is small and the friction force between the first tapered surface and the second tapered surface  532   b  is small. Thereby the resistance restraining the nut  4  from wobbling radially can be greatly decreased. 
         [0063]    Furthermore, further improvements may be made in the above basic technical solution. Specifically, as shown in  FIG. 4-2 , the bottom wall of the mounting groove  51  is provided with a circumferential position limiting groove  54 , and the bottom wall of the nut  4  is provided with a position limiting projection  42 . As shown in  FIG. 4-1 , the position limiting projection  42  is provided in the circumferential position limiting groove  54 , with which structure configuration, the circumferential rotation of the nut  4  relative to the valve rod  5  can be limited, and the structure is simple and the processing is low-cost. Alternatively, the bottom wall of the mounting groove  51  may be provided with a position limiting projection  42 , and the bottom wall of the nut  4  may be provided with a circumferential position limiting groove  54 , and it is apparent that this kind of structure can also achieve the above technical effect. 
         [0064]    Further improvements may be made on the basis of the above basic technical solution to thereby obtain the first embodiment according to the present application. Specifically, in the first embodiment, as shown in  FIG. 4-1  and  FIG. 4-2 , the valve rod  5  includes an injection molded body  55  and a metal housing  56  wrapping the injection molded body  55 . The inner cavity of the upper portion of the injection molded body  55  forms the mounting groove  51 , and the annular position limiting groove  52  is provided on the internal wall of the injection molded body  55 . The formation manner and machining process of the annular position limiting groove  52  are simple, and the processing cost is low. 
         [0065]    Furthermore, further improvements may be made on the basis of the above basic technical solution to thereby obtain the second embodiment according to the present application. Specifically, referring to  FIG. 5  to  FIG. 5-3 ,  FIG. 5  is a structural schematic view of a valve rod in the second embodiment of the present application;  FIG. 5-1  is a sectional view of the valve rod in  FIG. 5 ;  FIG. 5-2  is an exploded view of the valve rod in  FIG. 5 ; and  FIG. 5-3  is a partial enlarged view of part B of the valve rod in  FIG. 5-1 . 
         [0066]    It is to be noted that, the structure configuration of the valve rod  5  in the second embodiment according to the present application is substantially the same as that in the first embodiment according to the present application, and the differences are that: in the second embodiment, as shown in  FIG. 5-1  to  FIG. 5-3 , the inner side of the top end portion of the metal housing  56  is provided with a metal projection  56   a ; the inner cavity of the upper portion of the injection molded body  55  and the inner cavity of the metal projection  56   a  form the mounting grooves  51 , and the annular position limiting groove  52  is provided on the inner wall of the metal projection  56   a.    
         [0067]    In the first embodiment described above, since the annular position limiting groove  52  is provided on the injection molded body  55 , the injection molded body  55  is formed in the metal housing  56 , and then the valve rod  5  is clamped to machine the annular position limiting groove  52 . If the valve rod  5  is clamped during the machining operation, the sealing surface formed by the portion of the injection molded body  55  at the lower end of the valve rod  5  will be affected, which thereby will influence the sealing performance of the valve rod  5 . 
         [0068]    While in the second embodiment, since the metal housing  56  is machine-shaped before the injection molding, that is, the metal projection  56   a  is provided with the annular position limiting groove  52  before the injection molded body  55  being formed in the metal housing  56 , after the injection molded body  55  is formed, there is no need to clamp the valve rod  5  to machine the annular position limiting groove  52 , thus the influence of the clamping on the sealing surface formed by the portion of the injection molded body  55  at the lower end of the valve rod  5  can be avoided, which thus can ensure that the sealing performance of the valve rod  5  will not be influenced. 
         [0069]    Further improvements may be made on the basis of any of the above basic technical solutions. For example, referring to  FIG. 4 ,  FIG. 5 ,  FIG. 6  and  FIG. 7 ,  FIG. 6  is a structural schematic view of a gear seat cooperated with the valve rod in  FIG. 4 ; and  FIG. 7  is a structural schematic view of a gear seat cooperated with the valve rod in  FIG. 5 . 
         [0070]    A lower portion of the gear seat  6  may be provided with a first position limiting portion, and an upper portion of the valve rod  5  may be provided with a second position limiting portion which is cooperated with the first position limiting portion, such that the position of the valve rod  5  relative to the gear seat  6  is limited in the circumferential direction and the valve rod  5  is slidable in the axial direction. Based on this arrangement, the nut  4  can be wholly provided in the mounting groove  51  of the valve rod  5 , and the nut  4  is limited both in the axial and circumferential directions and is connected in the mounting groove  51 . 
         [0071]    Since the whole of the valve rod  5  is circumferentially limited relative to the gear seat  6  and is slidable in the axial direction, and the nut  4  is limited both in the axial and circumferential directions and is connected in the mounting groove  51  of the valve rod  1 , as the screw rod  3  is rotated, the nut  4  drives the valve rod  5  to slide in the axial direction, thereby the opening degree of the valve port is adjusted by the valve rod  5 . 
         [0072]    As shown in  FIG. 1  and  FIG. 2 , the discharge piston  130  needs to be fixed in the sleeve  146  of the lower shell  60 , since the discharge piston is limited by the sleeve  146  and thus cannot rotate circumferentially, it requires that the discharge piston  130  be protruded out of the valve unit  40  at a sufficient length such that it can be extended into the sleeve  146 . In this structure configuration, the driving shaft  78  cooperated with the discharge piston  130  also has a large length, therefore the driving shaft  78  has a large deflection, and it is difficult to ensure the coaxial degree between the discharge piston  130  and the driving shaft  78  when assembling the same, and if they are assembled slantingly, the resistance moment will be increased, and moreover, the driving shaft  78  will get stuck. 
         [0073]    While in the present application, instead of limiting the circumferential position of the nut  4  directly, the circumferential position of the whole valve rod  5  is directly limited by the gear seat  6 , and the nut  4  is limited both in the axial and circumferential directions and is connected in the mounting groove  51  of the valve rod  1 , therefore the nut  4  needs not to be protruded out of the valve rod  5 , and the nut  4  can be provided within the valve rod  5 . Thus the axial length of the nut  5  can be greatly decreased, and thus the length of the screw rod  3  can be greatly decreased and the deflection thereof can be decreased. Thereby it is easy to ensure the coaxial degree error when assembling the screw rod  3  and the nut  4 , which in turn can prevent the screw rod  3  from getting stuck. 
         [0074]    In the above basic technical solutions, structures of the first position limiting portion and the second position limiting portion may be configured in detail. For example, as shown in  FIG. 6 , the first position limiting portion is a noncircular special-shaped cavity  61 ; and as shown in  FIG. 4 , the second position limiting portion is a noncircular special-shaped portion  57  which is slidable in the axial direction and is provided in the noncircular special-shaped cavity  61 . The above structure conveniently achieves the object that the valve rod  5  is limited and fixed in the circumferential direction relative to the gear seat  6  and is slidable in axial direction. 
         [0075]    It is to be noted that, as shown in  FIG. 4  and  FIG. 6 , each of the noncircular special-shaped cavity  61  and the noncircular special-shaped portion  57  has a hexagonal shape, but their shapes are not limited herein, any noncircular shape that can limit the valve rod  5  such that it cannot be rotated relative to the gear seat  6  should fall within the protection scope of the present application. 
         [0076]    As shown in  FIG. 7 , the gear seat  6  is provided with a plurality of first locating rod members  62  extended in the axial direction, and the first position limiting portion is the first locating rod member  62 . In the first locating rod members  62 , the gap between at least one group of adjacent first locating rod members  62  form a position limiting gap  63 . Specifically, as shown in  FIG. 7 , the gear seat  6  may be provided with four first locating rod members, and two position limiting gaps  63  are formed by the four first locating rod members. As shown in  FIG. 5 , the second position limiting portion is the second locating rod member  58  provided on the side wall of the valve rod  5 , and on the basis of this arrangement, the upper portion of the valve rod  5  is extended into the space surrounded by the first locating rod members  62  in the circumferential direction, and the second locating rod member  58  is inserted into the position limiting gap  63 . Apparently, with this structure configuration, the valve rod  5  can also be limited and fixed in the circumferential direction relative to the gear seat  6  and is also slidable in the axial direction. Meanwhile the gear seat  6  is merely provided with several first locating rod members  62 , and thus the material cost of the gear seat  6  can be greatly decreased. 
         [0077]    The flow regulating 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 make 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.