Patent Publication Number: US-2020284373-A1

Title: Electrically operated valve

Description:
CROSS-REFERENCED APPLICATIONS 
     The present application is the national phase of International Application No. PCT/CN2018/108293, entitled “ELECTRICALLY OPERATED VALVE,” filed on Sep. 28, 2018, which claims the priority to Chinese patent application No. 201711025591.8, titled “ELECTRIC VALVE”, filed with the China National Intellectual Property Administration on Oct. 27, 2017, which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present application relates to the technical field of fluid control, and in particular to an electric valve. 
     2. Discussion of the Background Art 
     In commercial air-conditioning systems, such as the variable refrigerant flow system, one outdoor unit is required to be connected with multiple indoor units; therefore, a flow control valve is required to be mounted in a refrigerant loop of each indoor unit for cutting off the refrigerant or regulating the flow. The flow control valve is required to be capable of regulating the flow to any degree by the regulation of the opening and operating stably. Further, since the flow control valve is required to be mounted in the refrigerant loop of each indoor unit, the flow control valve is further required to meet the requirements of minimization. 
     SUMMARY 
     An object of the present application is to provide an electric valve. The electric valve has a compact structure which is beneficial to reducing the size of the electric valve. 
     The electric valve disclosed by the present application includes a valve body component, wherein, the valve body component includes a valve body and a valve cover, and the valve cover is fixedly connected with an outer margin portion of the valve body; a valve seat component, which is fixedly connected with the valve body; a valve core component, which is arranged inside an inner chamber of the valve body; a transmission component, wherein the transmission component includes a magnetic rotor, a screw rod, and a screw nut, the magnetic rotor is arranged inside an inner chamber of the valve cover, the screw nut is screwed to the screw rod, and the screw rod is static with respect to the valve body in an axial direction; and a screw nut kit, wherein the screw nut kit includes a first limiting portion for limiting circumferential rotation of the screw nut, and a cross-section of the first limiting portion is non-circular. 
     The electric valve provided according to the present application has a compact structure which helps to reduce the size of the electric valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic structural view of an electric valve according to an embodiment of the present application in a fully open state; 
         FIG. 2  is schematic structural view of the electric valve shown in  FIG. 1  in a closed state; 
         FIG. 3  is a schematic structural view of a valve body component of the electric valve shown in  FIG. 1 ; 
         FIG. 4  is a schematic structural view of a valve seat component of the electric valve shown in  FIG. 1 ; 
         FIG. 5  is a schematic structural view of a transmission component of the electric valve shown in  FIG. 1 ; 
         FIG. 6  is a schematic structural view of a valve core component of the electric valve shown in  FIG. 1 ; 
         FIG. 7  is a schematic structural view of a valve core guiding component of the electric valve shown in  FIG. 1 ; 
         FIG. 8  is a schematic structural view of a screw nut kit of the electric valve shown in  FIG. 1 ; 
         FIG. 9  is a schematic structural view of a valve seat of the valve seat component shown in  FIG. 4 ; 
         FIG. 10  is a schematic structural view of a valve port jacket of the valve seat component shown in  FIG. 4 ; 
         FIGS. 11 a  and 11 b    are a front view and a top view of another specific embodiment of the valve port jacket; 
         FIG. 12  is a schematic structural view of another embodiment of the valve seat component according to the present application; 
         FIG. 13  is a schematic structural view of another embodiment of the screw nut kit according to the present application; 
         FIG. 14  is a schematic structural view of a third embodiment of the screw nut kit according to the present application; 
         FIG. 15  is a schematic structural view of another embodiment of the electric valve according to the present application; 
         FIG. 16  is a schematic structural view of a third embodiment of the electric valve according to the present application; and 
         FIG. 17  is a schematic structural view of a third embodiment of the valve seat component according to the present application. 
     
    
    
     Reference numerals in  FIGS. 1 to 17 : 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 10/10A valve core component 
                 11 valve core body, 
                 12 valve core sleeve, 
               
               
                 13 filter member, 
                 14 balance passage, 
                 15 valve core head, 
               
               
                 20/20A/20B valve seat component 
                   
                 21/21A/21B valve seat body 
               
               
                 211 upper stepped portion, 
                   
                 212 lower stepped portion, 
               
               
                 213 outer stepped portion, 
                   
                 214 protrusion portion, 
               
               
                 215 conical surface, 
                   
                 22/22A/22B valve seat core, 
               
               
                 221 groove, 
                   
                 23 axial connecting pipe, 
               
               
                 24/24A/24B/24C valve port jacket 
                   
                 241 balance aperture/passage, 
               
               
                 243 cylinder portion, 
                   
                 244 flange portion, 
               
               
                 25 valve port pressing ring, 
                   
                 30 transmission component, 
               
               
                 31 screw rod, 
                 32 screw nut, 
                 33 bearing, 
               
               
                 34 magnetic rotor, 
                   
                 40 valve body component, 
               
               
                 41 valve body, 
                   
                 411 first mating portion, 
               
               
                 412 second mating portion, 
                   
                 413 third mating portion, 
               
               
                 414 fourth mating portion, 
                   
                 415 fifth mating portion, 
               
               
                 416 inner chamber of the valve body, 
                   
                 417 communication aperture, 
               
               
                 418 valve chamber, 
                   
                 41a upper cylinder portion, 
               
               
                 41b middle cylinder portion, 
                   
                 41c lower cylinder portion, 
               
               
                 42 valve cover, 
                   
                 421 inner chamber of the valve cover, 
               
               
                 43 radial connecting pipe, 
                   
                 44 bracket, 
               
               
                 50/50A/50B screw nut kit, 
                   
                 51 first limiting portion, 
               
               
                 52 second limiting portion, 
                   
                 53 bearing accommodating portion, 
               
               
                 54 outer circumferential portion, 
                   
                 55 tubular portion, 
               
               
                 56 flat plate portion, 
                   
                 57 radial ribbed plate, 
               
               
                 58 plane section, 
                   
                 60 valve core guiding component, 
               
               
                 61 guide sleeve, 
                   
                 611 stepped portion, 
               
               
                 62 elastic member, 
                   
                 63 sealing member, 
               
               
                 64 gasket, 
                   
                 65 guide surface, 
               
               
                 70 electromagnetic coil. 
               
               
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In order to provide those skilled in the art with a better understanding of the solutions of the present application, the present application will be described hereinafter in further detail in conjunction with the drawings and specific embodiments. 
     It should be noted that, the orientation terms, such as upper and lower, involved in this application are defined with reference to the positions of the components in the figures and the relative positions of the components as shown in  FIGS. 1 to 17 , which are only for clarity and ease of describing the technical solutions. It will be appreciated that, those orientations terms used herein do not limit the protection scope of the present application. 
       FIG. 1  is a schematic structural view of the electric valve according to the present application in an open state;  FIG. 2  is a schematic structural view of the electric valve according to the present application in a closed state;  FIG. 3  is a schematic structural view of a valve body component of the electric valve;  FIG. 4  is a schematic structural view of a valve seat component of the electric valve;  FIG. 5  is a schematic structural view of a transmission component of the electric valve;  FIG. 6  is a schematic structural view of a valve core component of the electric valve;  FIG. 7  is a schematic structural view of a valve core guiding component of the electric valve; and  FIG. 8  is a schematic structural view of a screw nut kit of the electric valve. 
     As shown in  FIGS. 1 to 8 , the electric valve includes a valve core component  10 , a valve seat component  20 , a transmission component  30 , a valve body component  40 , a screw nut kit  50 , a valve core guiding component  60  and an electromagnetic coil  70 . 
     The valve body component  40  includes a valve body  41  and a valve cover  42 . The valve body  41  is a substantially cylindrical structure, which is easy to manufacture in a specific processing process by methods such as pressing, punching, rolling, extrusion shaping or the like. The valve body  41  includes an upper cylinder portion  41   a , a middle cylinder portion  41   b  and a lower cylinder portion  41   c.    
     In the embodiment according to  FIGS. 1 and 2 , a diameter of an outer margin of the upper cylinder portion  41   a  is the smallest in the three cylinder portion structures, and the diameter of outer margin of the lower cylinder portion  41   c  is the largest. Such an arrangement facilitates internal installation of functional parts and external welding of assembly parts, which makes the structure more compact.  FIG. 15  is a schematic structural view of another embodiment of the electric valve according to the present application. In the technical solution disclosed by  FIG. 15 , the diameter of the outer margin of the middle cylinder portion  41   b  is the same as that of the lower cylinder portion  41   c.    
     A radial connecting pipe  43  is fixed to the lower cylinder portion  41   c  of the valve body  41  by welding, and the radial connecting pipe  43  is in communication with an inner chamber  416  of the valve body  41 . The valve cover  42  is fixed to the middle cylinder portion  41   b  of the valve body  41  by welding, an inner chamber  421  of the valve cover  42  is formed between the valve body  41  and the valve cover  42 , and the upper cylinder portion  41   a  of the valve body  41  is extended into the inner chamber  421  of the valve cover  42 . A communication aperture  417  is provided in a wall portion of the upper cylinder portion  41   a  of the valve body  41 , and the communication aperture  417  is configured to communicate the inner chamber  421  of the valve cover  42  with the inner chamber  416  of the valve body  41 . It will be appreciated that, the valve cover  42  may be indirectly fixed to the valve body  41  by a welding joint. The welding of other components below may also be replaced by other indirect fixing means, which will not be repeated herein. 
     The valve seat component  20  includes a valve seat body  21 , a valve seat core  22  and a valve port jacket  24 .  FIG. 9  is a schematic structural view of the valve seat of the valve seat component. As shown in  FIG. 9 , the valve seat body  21  is substantially an annular structure, an upper stepped portion  211  is provided on an inner wall of the valve seat body  21  with a stepped surface facing an upper end portion of the valve seat body  21 , the valve seat core  22  is arranged on the upper stepped portion  211 , and an inner wall surface of the valve seat core  22  is nested with the valve port jacket  24 . 
     The valve seat core  22  may be made of a non-metallic soft material to improve the sealing performance of a valve port. A stepped portion is provided on an outer wall of the valve seat core  22 , a valve port pressing sheet  25  is arranged on the stepped portion, and a protrusion portion  214  is provided on the upper end portion of the valve seat body  21 . The valve port pressing sheet  25  is pressed against the stepped portion of the valve seat core  22  by crimping the protrusion portion  214 , thereby realizing the installation of the valve seat core  22 . 
       FIG. 17  is a schematic structural view of a third embodiment of the valve seat component according to the present application. In the present embodiment, an inner margin surface of the upper stepped portion of a valve seat body  21 B of a valve seat component  20 B is a conical surface  215  which tapers upwardly, a valve seat core  22 A is made of a plastic or rubber soft material, and an outer margin of the valve seat core abuts against the conical surface  215  (the inner margin surface), also realizing fixation. 
     A lower stepped portion  212  with a stepped surface facing a lower end portion of the valve seat body  21  is provided on the inner wall of the valve seat body  21 . In the present embodiment, the valve port jacket  24  is an annular thin-walled cylinder, which includes a cylinder portion  243  and a flange portion  244  formed by flanging. The flange portion  244  abuts against the stepped surface of the lower stepped portion  212 , and an end portion of an axial connecting pipe  23  abuts against the flange portion  244 . The axial connecting pipe  23  is fixed with the valve seat body  21  by welding. 
     As another technical solution, the valve port jacket  24  may be a two-body structure, that is, the cylinder portion  243  is fixedly connected with the flange portion  244  by welding or other means. 
     An outer stepped portion  213  with a stepped surface facing the lower end portion of the valve seat body  21  is provided on the outer wall of the valve seat body  21 . As a preferred solution, a lower end portion of the valve body  41  abuts against the stepped surface of the outer stepped portion  213  and is fixed by welding. 
     In the above structures, the installation and cooperation of the parts are compact, the mutual position accuracy can be guaranteed, the process is simple, and the product is highly reliable. Since a magnetic rotor of the transmission component is arranged in the inner chamber of the valve cover, a screw rod is extended from an end portion of the upper cylinder portion of the valve body into the inner chamber of the valve body. During the axial movement of the valve core component with respect to the valve seat component, axial positions of the magnetic rotor and the screw rod are fixed with respect to the valve body  41 , so that the relative position between the magnetic rotor and a coil component sleeved outside the electric valve is fixed, and the driving force is increased and relatively stable during the operation. 
       FIG. 10  is a schematic structural view of the valve port jacket of the valve seat component. As shown in  FIG. 10 , in the present embodiment, a balance aperture in communication with an inner chamber of the valve port jacket  24  is arranged at a position of the cylinder portion of the valve port jacket  24  corresponding to the stepped surface of the upper stepped portion  211 , and is used as a balance passage  241 . Such an arrangement is advantageous in that, during the operation of the electric valve, part of the medium enters and remains between a bottom of the valve seat core  22  and the stepped surface of the upper stepped portion  211  of the valve seat body  21 , and while the electric valve is being opened or closed, abnormal fluctuations such as instantaneous vaporization of the medium due to the instantaneous pressure change may cause the valve seat core  22  to detach from the valve seat body  21 , resulting in product failure, while an object of providing the balance aperture  241  is to keep the medium at the bottom of the valve seat core  22  in communication with an inner chamber (that is, the valve chamber  418 ) of the axial connecting pipe  23  to avoid the above situation. 
       FIG. 11 a    and  FIG. 11 b    respectively are a front view and a top view of another specific embodiment of the valve port jacket. 
     As shown in  FIGS. 11 a  and 11 b   , different from the above embodiment, a valve port jacket  24 A is an annular thin-walled member formed by crimping a thin metal sheet. An opening groove  242  which is through in an axial direction is formed at a butt portion of the crimping of the thin metal sheet, and is used as the balance passage, to keep the medium at the bottom of the valve seat core  22  in communication with the inner chamber of the axial connecting pipe  23 . Such a structure is simpler and will not be repeated herein. 
     In the above embodiments, the valve port jacket is a cylindrical structure formed by crimping the thin-walled metal material. The technical solution may be further developed with reference to  FIG. 12 , wherein the valve port jacket  24 C is a one-piece structure directly processed by the inner wall of the valve seat body  21 A. In the present embodiment, the upper stepped portion of the valve seat body  21 A forms an annular groove together with the valve port jacket  24 C with the one-piece structure, and the valve seat core  22 A is arranged in the annular groove. In the present embodiment, an axial balance groove is arranged between the valve seat core  22 A and the stepped side wall of the valve seat body  21 A, and the balance groove can also keep the medium at the bottom of the valve seat core  22 A in communication with an upper portion, which will not be repeated herein. 
     Referring to  FIG. 17 , in the structure of a third embodiment of the valve seat component  20 B, a vertical groove  221  is arranged on an inner margin portion of the valve seat core  22 B, the vertical groove  221  is in communication with the stepped surface of the upper stepped portion, and can also function as the balance aperture, which will not be repeated herein. 
     The transmission component  30  includes a screw rod  31 , a screw nut  32  and a magnetic rotor  34 . The magnetic rotor  34  is arranged inside the inner chamber of the valve cover  42 , and the screw rod  31  is extended from the upper end portion of the valve body  41  into the inner chamber of the valve body  41  and mates with the screw nut  32 . 
     The screw nut kit  50  is fixedly connected to an inner margin (distinguished from the present embodiment, in  FIGS. 15 and 16 , the screw nut kit is fixedly connected to an inner margin of the middle cylinder portion of the valve body by welding of a flat plate portion) of the upper cylinder portion  41   a  of the valve body  41  by welding of a pipe wall portion. 
     Referring to  FIG. 8 , in the present embodiment, the screw nut kit  50  is a thin-walled metal cylinder, which may be formed by sheet punching and crimping. In the present embodiment, the screw nut kit has four ribbed plates  51  axially extending and formed by punching and bending the side wall of the thin-walled cylinder inwardly. The ribbed plate  51  serves as a first limiting portion, and a cross-section of the first limiting portion is non-circular, wherein an inner wall thereof cooperates with an outer margin portion of the screw nut  32 , and can limit the rotation of the screw nut  32  in a circumferential direction (it will be appreciated that, if only two ribbed plates are provided, the limiting function still works). A bearing accommodating portion  53  is formed between an upper end surface of the ribbed plate  51  and an inner wall surface of the screw nut kit, which can be used as an accommodating portion of a bearing  33  cooperating with the screw rod  31 . The bearing  33  abuts against an upper end portion of the ribbed plate  51 , realizing axial positioning of the bearing  33 . The bearing  33  is fixed by crimping the upper end portion of the valve body  41 . 
     In the above embodiments, the screw nut kit  50  is a cylindrical kit formed by metal sheet punching and crimping. The technical solution may be further developed with reference to  FIG. 13 , wherein, a screw nut kit  50 A is a cylindrical kit formed by metal sheet punching and crimping, and when a lower section of the pipe wall portion is punched and bent inwardly to form the ribbed plate  51  extending axially, an upper section of the pipe wall portion is punched and bent inwardly to form a radial ribbed plate  57 , a region between the radial ribbed plate  57  and the inner wall surface of the screw nut kit  50  is used as the accommodating portion of the bearing  33 , the radial ribbed plate  57  is used as an axial positioning portion of the bearing  33 , and a lower end portion  52  of the screw nut kit  50  is used as a second limiting portion to limit an axial movement stroke of the valve core component  10 . 
     Similarly, the technical solution may be further developed with reference to  FIG. 14 , wherein, a screw nut kit  50 B is formed by metal sheet punching and crimping, which includes a tubular portion  55  and a flat plate portion  56  formed by bending an end portion of the tubular portion  55 ; and the tubular portion includes at least one axial plane section  58 . Due to the existence of the plane section  58 , the inner wall portion of the tubular portion cooperates with the outer margin portion of the screw nut  32  to limit the circumferential rotation of the screw nut  32 . The flat plate portion  56  is used as the second limiting portion. In the present technical solution, the flat plate portion  56  may be formed by punching and flanging, or may be formed by welding another ring member. 
     In the present embodiment, the whole structure is simple by welding the flat plate portion  56  of the screw nut kit  50 B to the inner margin of the middle cylinder portion of the valve body  41 . 
     In the present embodiment, the valve core guiding component  60  includes a guide sleeve  61  and a sealing assembly. The guide sleeve  61  is fixed to the inner margin of the middle cylinder portion  41   b  of the valve body  41  by welding. A stepped portion  611  is provided on an inner wall of the guide sleeve  61 , and the sealing assembly is fixed to the stepped portion  611  by crimping via a gasket  64 . The sealing assembly includes a sealing member  63  made of abrasion-resistant material and an elastic member  62  made of rubber material. 
     Similarly, the technical solution may be further developed with reference to  FIG. 14 , wherein the screw nut kit  50 B may be formed by material injection molding. The screw nut kit includes the tubular portion and the flat plate portion, the tubular portion includes at least one axial plane section, the plane section serves as the first limiting portion, the flat plate portion serves as the second limiting portion, and the tubular portion and the flat plate portion are integrally formed by material injection molding, such as precision casting of metal materials or injection molding of non-metal materials, so that the tubular portion and the flat plate portion are an integrally formed structure. 
       FIG. 16  is a schematic structural view of a third embodiment of the electric valve according to the present application. Compared with the preceding solutions, the sealing assembly in the present embodiment is fixed on the valve core component  10 A, which has the same function and will not be repeated herein. 
     The valve core component  10  is arranged inside the inner chamber  416  of the valve body  41 . The valve core component  10  includes a valve core body  11  and a valve core sleeve  12  (the valve core body and the valve core sleeve may be a one-piece material molding structure). The screw nut  32  is connected with the valve core sleeve  12  to drive the valve core body  11  to move relative to the valve seat core  22 , and to realize the opening/closing of the electric valve and regulation of the flow. 
     The lower end portion  52  of the screw nut kit  50  is used as the second limiting portion for the valve core component  10 . While the screw nut  32  drives the valve core sleeve  12  to move upward, the valve core sleeve  12  may abut against the lower end portion  52  of the screw nut kit. In a large-flow electric valve, the screw rod is connected with the screw nut by a non-self-locking thread, which is advantageous in that, hidden danger such as stuck is avoided after the valve core component  10  is limited. 
     The inner wall  65  of the guide sleeve  61  serves as a guide surface and is in a clearance-fit with the valve core sleeve  12 . The sealing member  62  abuts against the valve core sleeve  12  and the guide sleeve  61 , and is arranged therebetween. The inner wall  65  of the guide sleeve  61  is in a clearance-fit with an outer wall of the valve core sleeve  12 . 
     The valve core body  11  is substantially a cylindrical structure, a lower end thereof is an annular valve core head  15 , and the valve core head  15  cooperates with the valve seat core  22 . The annular-valve-port sealing cooperation can make an abutting area between the valve core head  15  and the valve seat core  22  relatively small and improve the flexibility of the valve core component  10 , while increasing the flow of the valve port, which is especially suitable for commercial refrigeration systems. 
     The valve core body  11  is further provided with a though hole  14  which is through in the axial direction as the balance passage, and a filter member  13  is further arranged in the middle of the through hole  14 . The communication aperture  417  is provided in the wall portion of the upper cylinder portion  41   a  of the valve body  41 . The through hole  14  is combined with the communication aperture  417  to form a passage. The passage communicates the inner chamber of the valve cover  42  with the valve chamber  418  (a space of the valve port in communication with the connecting pipe). 
     In conjunction with the above specific embodiments, a method for manufacturing an electric valve with the above structure is described as follows. 
     Step A 10 : processing a metal sheet or metal tube into the cylindrical valve body  41 . 
     The valve body  41  may be formed by drawing the metal sheet or punching/rolling/pressing the metal tube (it should be noted that, the metal sheet is processed into the cylindrical structure mainly by the drawing process, and the metal tube is processed into the cylindrical structure mainly by the punching/rolling processing. In the specific processing process, the procedures such as pressing/punching/rolling/extrusion molding and the like are combined for processing. Compared with the cutting processing of the metal, this process can reduce processing costs and material costs). 
     By the metal cutting method, a positioning stepped surface in cooperation with the valve seat component  20  and a positioning surface in cooperation with the valve cover  42  are machined on the outer margin of the valve body  41 , respectively. 
     The above operations may preferably be performed by one-time clamping and positioning, so that the relative position and the positioning accuracy of each positioning stepped surface are guaranteed. After the subsequent installation by welding, the fit precision of each component can be ensured, so that the operation stability of the valve core component is good, and the reliability of the product is improved, which will not be repeated herein. 
     Step A 20 : fixedly connecting the screw nut kit  50  to the inner margin of the valve body  41  by welding; fixing the guide sleeve  61  of the valve core guiding component  60  to the inner margin of the middle cylinder portion  41   b  of the valve body  41  by welding, and mounting the sealing assembly to the guide sleeve  61 . 
     Since the screw nut kit  50  and the guide sleeve  61  are welded to the valve body  41 , the relative position accuracy can be guaranteed. Therefore, the relative position accuracy among the screw nut kit  50 , the guide sleeve  61  and the valve body  41  is further improved. Preferably, the screw nut kit  50  and the guide sleeve  61  may be welded to the valve body  41  at a time, to avoid affecting the accuracy due to secondary heat. 
     Step A 30 : extending the screw rod  31  of the transmission component  30  from the end portion of the upper cylinder portion  41   a  of the valve body  41  into the inner chamber of the valve body  41 ; assembling the screw nut  32  of the transmission component  30  with the valve core component  10 , mounting the assembled assembly into the inner chamber of the valve body  41  from the lower cylinder portion of the valve body  41 , and screwing the screw nut  32  to the screw rod  31 , so that the screw nut  32  cooperates with the first limiting portion  51  of the screw nut kit  50 , the guide sleeve  61  is in a clearance-fit with the valve core component  10 , and the sealing assembly elastically abuts against the outer margin of the valve core component  10 . 
     It will be appreciated that, since the screw nut kit  50  and the guide sleeve  61  are welded to the valve body  41 , the relative position accuracy can be guaranteed. The mounting accuracy of the transmission component  30  and the valve core component  10  is relatively high, so that the valve core is driven stably. 
     Step A 40 : mounting the valve seat core  22  to the valve seat body  21 , and nesting the valve port jacket  24  on the inner margin surface of the valve seat core  22 , wherein the flange portion  244  of the valve port jacket  24  abuts against the lower stepped portion  212  of the valve seat body  21 , the end portion of the axial connecting pipe  23  abuts against the flange portion  244 , the axial connecting pipe  23  is fixed to the valve seat body  21  by welding, and the lower end portion of the valve body  41  abuts against the outer stepped portion  213  of the valve seat body  21  and is fixed to the outer stepped portion by welding. 
     Preferably, the above parts may be fixed by welding multiple parts at a time, the process is simple, and the product is highly reliable. 
     Step A 50 : fixing the valve cover  42  to the valve body  41  by welding, wherein the magnetic rotor of the transmission component  30  is arranged in the inner chamber of the valve cover  42  after welding. 
     Since the valve cover  42  and the screw nut kit are respectively welded to the valve body  41 , the position accuracy thereof is relatively high, a gap between the magnetic rotor and the inner wall surface of the valve cover can be controlled to be smaller, and the structure is thereby compact. 
     Step A 60 : fixing the radial connecting pipe  43  to the lower cylinder portion  41   c  of the valve body  41  by welding. 
     Step A 70 : sleeving the electromagnetic coil  70  outside the outer margin of the valve cover  42 , and fixing the electromagnetic coil  70  to a fixing bracket  44 . 
     It will be appreciated by those skilled in the art that, based on the technical idea of the present application, a variety of assembly sequences and assembly changes may be obtained on the basis of the above technical solutions. For example, step A 60  can be placed in the previous process without affecting the technical effect of the present application; and the sequence of step A 50  and step A 40  can be interchanged. These changes shall fall within the protection scope of the present application and will not be repeated herein. 
     The electric valve according to the present application is described in detail hereinbefore in conjunction with specific embodiments. As for the electric valve provided according to the present application, the valve cover is fixedly connected with the outer margin portion of the valve body, the transmission component includes the magnetic rotor, the screw rod and the screw nut, the magnetic rotor is arranged in the inner chamber of the valve cover, the screw nut is screwed to the screw rod, the screw rod is static with respect to the valve body in the axial direction, the screw nut kit includes the first limiting portion for limiting circumferential rotation of the screw nut, and the cross-section of the first limiting portion is non-circular, so that the electric valve has a compact structure, which helps to reduce the size of the electric valve. 
     The principle and the embodiments of the present application are illustrated herein by specific examples. The above description of examples is only intended to facilitate the understanding of the concept of the present application. It should be noted that, for the person skilled in the art, a few of improvements and modifications may be made to the present application without departing from the principle of the present application, and these modifications and improvements are also deemed to fall into the protection scope of the present application defined by the claims.