Abstract:
To provide a small motor-operated valve which can control a high flow, there is provided a motor-operated valve of which a body has an orifice, seat and a valve element provided opposite to the seat. The valve element is operated by a driver which is driven to rotate by an output gear to which the rotation of a rotor having been reduced by means of a mechanical paradox planetary gear mechanism is transmitted. To force the valve element in the direction in which the valve is opened, a coil spring is disposed in a bore formed in the upper portion of the body oppositely to a bush.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a motor-operated valve destined to control the flow rate of fluids, for example, a refrigerant used in air conditioners. 
         [0003]    2. Description of the Conventional Art 
         [0004]    The structure of a motor-operated valve invented by the Applicant of the present invention is disclosed in detail in the Japanese Published Unexamined Application No. 101765 of 2008. As disclosed in this patent document, the motor-operated valve uses a mechanical paradox planetary gear mechanism to considerably reduce the speed of rotation of a stepping motor provided to let the valve disc ascend and descend, thereby providing micro-flow control of a refrigerant or the like. 
         [0005]      FIG. 4  shows the structure of a motor-operated valve similar to that disclosed in the Japanese Published Unexamined Application No. 101765 of 2008. In  FIG. 4 , the essential parts of the motor-operated valve are shown hatched. 
         [0006]    This motor-operated valve is designed to be larger in bore diameter of the valve element than disclosed in the cited patent document and accordingly the front end of the valve element is enlarged correspondingly to the increase in bore diameter of the valve seat. 
         [0007]    As shown, the motor-operated valve includes a body  10  having formed therein a valve chamber  14  and an orifice  16  communicating with the chamber  14 . 
         [0008]    The body  10  has connected thereto a pipe  12   a  at the side of the orifice  16  and a pipe  12   b  at the side of an opening formed in the side wall of the chamber  14 . Also the body  10  has inserted and fixed in the upper portion of the chamber  14  thereof a bush  20 . 
         [0009]    The bush  20  has an internal thread  22  formed on the inner wall of the central bore thereof. A base plate  28  is firmly fixed to the top of the body  10 . A bottomed cylindrical can  30  is installed on the base plate  28 . 
         [0010]    On the outer circumference of the can  30  there is fitted a stator member generally indicated with a reference sign  40 . The stator member  40  includes a yoke  44  and a coil  46  wound on a bobbin provided inside the yoke  44 . These elements of the stator member  40  are wholly covered with a plastic member  42 . The coil  46  is supplied with a power through a lead wire  48 . The stator member  40  and a rotor member  50  pivotally supported inside the can  30  form together a stepping motor. 
         [0011]    The rotor member  50  made of a magnetic material is connected integrally with a sun gear member  51  made of a plastic material, and a shaft  62  is inserted in the central portion of the sun gear member  51 . The shaft  62  is inserted and supported at the upper portion thereof in a hole formed in a support member  60  provided inside the upper portion of the can  30 , and at the lower portion thereof in a hole formed in the upper portion of a shank  70   a  which will be further described later. 
         [0012]    The sun gear member  51  includes a sun gear  52  which is in mesh with a plurality of planetary gears  55  supported pivotably on a plurality of shafts  54 , respectively, provided upright on a carrier  53 . Each of the planetary gears  55  is axially long and in mesh at the upper half thereof with a ring gear  58  mounted on the top of a cylindrical member  24  installed on the top of the bush  20 . 
         [0013]    The planetary gear  55  is in mesh at the lower half thereof with an internal gear  71  of an annular output gear  70 . 
         [0014]    The above-mentioned gears form together a so-called “mechanical paradox planetary gear mechanism”. With the ring gear  58  and the internal gear  71  of the output gear  70  being designed a little different in number of teeth from each other, it is possible to reduce the rotation of the sun gear  52  at a large ratio for transmission to the output gear  70 . 
         [0015]    The output gear  70  has a downward extending shank  70   a  firmly fixed to the center of the lower surface thereof. A slit  73   a  is formed in the lower portion of the shank  70   a.  Also a driver  72  is provided. The driver  72  has formed at the top thereof a flat convexity (flat plate-shaped portion)  73   b  which is to be inserted in the slit  73   a  in the shank  70   a.  The slit  73   a  and flat plate-shaped portion  73   b  form together a coupling which connects the output gear  70  and driver  72 . 
         [0016]    The driver  72  has an external thread  74  formed thereon. The external thread  74  is in mesh with the internal thread  22  formed inside the bush  20 . Thus, the driver  72  moves axially while rotating. This axial movement of the driver  72  is transmitted to a shaft-shaped valve element  80  through a ball-shaped pressing member  76 . The ball-shaped pressing member  76  prevents the rotation of the driver  72  from being transmitted to the valve element  80 . 
         [0017]    The body  10  has fixed therein a tubular spring case  90  having a small-diameter portion  90   c.  Guided by the lower small-diameter portion  90   c  of the tubular spring case  90 , the valve element  80  is moved axially. In this motor-operated valve cited herein by way of example, a flange  90   a  is provided at the top of the spring case  90 . It is held between the upper end face of a small-diameter portion formed at the top of the body  10  and the lower surface of the bush  20 , and thus the spring case  90  is fixed inside the body  10 . 
         [0018]    A spring shoe member  84  is firmly fixed at the top of the valve element  80 , and a coil spring  92  is provided compressed between the lower surface of a large-diameter portion  84   d  formed at the top of the spring shoe member  84  and a stepped portion  90   b  of the spring case  90 . The coil spring  92  normally forces the valve element  80  in a direction in which the valve is opened. 
       SUMMARY OF THE INVENTION 
       [0019]    In the motor-operated motor having been described in the above, the spring case  90  which guides the valve element  80  is disposed to project in the chamber  14  with the flange  90   a  provided at the upper end of the spring case  90  being supported on the upper end face of the small-diameter portion formed at the upper portion of the body  10 . Therefore, in case it is intended to change the design of the motor-operated valve for an increased diameter D 1  of the orifice  16  for the purpose of controlling a higher flow, the spring case  90  (especially, a portion thereof in which the coil spring  92  is accommodated) should be relocated to above the chamber  14  in order to secure a space  14   a  for passage of a fluid inside the chamber  14 . For this design change, the body  10  has to be extended axially as shown in  FIG. 4 , which however will lead to an increased size of the entire motor-operated valve. 
         [0020]    Also, since the valve element  80  is guided by the spring case  90  which is a separate member from the body  10 , it is difficult to assure a high coaxiality between a valve seat  18  formed at the body  10  and the valve element  80  and inclined surface  82  formed at the free end of the latter. 
         [0021]    It is therefore desirable to overcome the above-mentioned drawbacks of the conventional art by providing a novel and improved motor-operated valve. 
         [0022]    According to the present invention, there is provided a motor-operated valve including as basic elements: 
         [0023]    a body having a seat formed therein; 
         [0024]    a bush fixed to the body and having an internal thread formed inside; 
         [0025]    a driver having an external thread which is in mesh with the internal thread of the bush; 
         [0026]    a valve element arranged to abut on or come close to the seat when pressed by the driver; 
         [0027]    a can firmly fixed to the body; 
         [0028]    a rotor disposed pivotably inside the can and of which the rotation is transmitted to the valve element via the driver; 
         [0029]    a stator disposed on the outer circumference of the can; and 
         [0030]    a coil spring means for forcing the valve element toward the rotor, 
         [0031]    at least a part of the coil spring means being disposed at the side of the bush. 
         [0032]    According to the present invention, there may be provided a spring case disposed on the outer circumference of the bush and having an outer flange overhanged outwardly at the side of the rotor and engaged on or firmly fixed to the top of the valve element, and the coil spring means may be disposed between the outer flange and a stepped portion of the inner circumference of the body inside a space defined by the body and spring case. 
         [0033]    According to the present invention, the body may include a guide portion to guide the valve element. 
         [0034]    According to the present invention, the bore diameter of the seat may be nearly equal to the diameter of the guide portion and the valve element may have a pressure equalization path which provides communication between an end of the valve element which is at the side of the seat and a back pressure chamber located at an end of the valve element which is opposite to the seat-side end. 
         [0035]    As mentioned above, with at least a part of the coil spring means being disposed at the side of the bush or with the coil spring means being disposed between the outer flange of the spring case and the stepped portion of the inner circumference of the body in the space defined by the body and spring case, it is possible to manufacture the motor-operated valve with no increase of its total height. 
         [0036]    Also, with the guide portion being provided on the body to guide the valve element, it is possible to slide the valve element more smoothly. 
         [0037]    Further, with the bore diameter of the seat being set nearly equal to the diameter of the guide portion and with the pressure equalization path being formed in the valve element to provide communication between the back pressure chamber located at the end of the valve element which is at the side of the seat and the back pressure chamber located at the end of the valve element which is opposite to the seat-side end, it is possible to keep the pressures before and after the valve element in balance with each other and thus provide a smaller actuator for the motor-operated valve, and hence it is possible to provide a more smaller motor-operated valve. 
         [0038]    The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention when taken in conjunction with the accompanying drawings. It should be noted that the present invention is not limited to the embodiments but can freely be modified without departing from the scope and spirit thereof defined in the claims given later. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]      FIG. 1  is a longitudinal sectional view of the motor-operated valve according to one embodiment of the present invention. 
           [0040]      FIG. 2  is a longitudinal sectional view of the motor-operated valve according to another embodiment of the present invention. 
           [0041]      FIG. 3  is a longitudinal sectional view of the motor-operated valve according to a further embodiment of the present invention. 
           [0042]      FIG. 4  is a longitudinal sectional view of an example of the conventional motor-operated valves. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0043]    The present invention will be described in detail below concerning the embodiments thereof with reference to the accompanying drawings. 
         [0044]      FIG. 1  is a longitudinal sectional view of the motor-operated valve according to one embodiment of the present invention. In  FIG. 1 , the same or similar elements as or to those shown in  FIG. 4  are indicated with the same or similar reference signs as or to those used in  FIG. 4 . So, such elements will not further be explained hereunder. 
         [0045]    The motor-operated valve according to this embodiment includes a body  110 . The body  110  has a seat  18  formed at the opening of an orifice  16  which is at the side of the chamber  14 . The seat  18  faces an inclined surface  82  formed at the free end of a valve element  180 . A bush  120  is firmly fixed to the top of the body  110 , and a shank  70   a  firmly fixed to an output gear  70  is inserted in the upper portion of the bush  120 . The shank  70   a  of the output gear  70  has formed therein a slit  73   a  in which a flat plate-shaped portion  73   b  of a driver  72  is inserted to be slidable axially. The driver  72  has formed thereon an external thread  74  which is in mesh with an internal thread  22  formed on the lower inner wall of the bush  120  to thereby transform the rotation of the output gear  70  into an axial linear motion for transmission to a locking member  184  fixed to the top of the valve element  180  via a pressing member  76 . Thus, the valve element  180  is moved toward or away from the seat  18 . The locking member  184  locks an inner flange  190   b  of a spring case  190  which will be further explained later. 
         [0046]    The inner wall of a bore formed at the opening of the chamber  14  serving as a guide portion  110   d  guides the valve element  180  to slide at the outer circumference thereof which is at the side of the locking member  184 . The inside diameter of the guide portion  110   d  is set nearly equal to the inside diameter D 1  of the seat  18  (inside diameter of the orifice  16 ). 
         [0047]    The spring case  190  is formed cylindrical to have formed at the lower end thereof an inner flange  190   b  which projects inwardly. The inner flange  190   b  is installed to the valve element  80  between a large-diameter portion  184   a  formed at the upper portion of the locking member  184  and the valve element  80 . A coil spring  92  is disposed between the outer surface of the spring case  190  and the inner wall of a bore  110   e  in the body  110  and set compressed between an outer flange  190   a  formed at the upper end of the spring case  190  to project outwardly and the upper surface of the guide portion  110   d.  Thus, the valve element  180  is normally forced along with the spring case  190  in the direction in which it is pushed up (the valve is opened). 
         [0048]    In this embodiment, the bush  120  has formed at the lower portion thereof a small-diameter portion  120   a  which is inserted in the spring case  190 . Thus, the upper half of the coil spring  92  is disposed in a position where it overlaps the bush  120  in the axial direction, and the coil spring  92  (and the spring case  190 ) is wholly disposed above the chamber  14  (at the side of the actuator). 
         [0049]      FIG. 1  shows the valve element  180  resting on the seat  18 . When the driver  72  ascends from this position as the rotor member  50  rotates in a predetermined direction, the spring case  190  is moved up under the elasticity of the coil spring  92  within a space defined by the outer circumference of the small-diameter portion  120   a  and the inner wall of the bore  110   e,  and the valve element  80  is also guided to ascend by the guide portion  110   d.    
         [0050]    Similarly, when the rotor member  50  rotates in the reverse direction, the driver  72  descends, and also the spring case  190  and valve element  180  are moved down against the elasticity of the coil spring  82 . 
         [0051]    Owing to the above-mentioned design, the space  14   a  of the chamber  14  opposite to the pipe  12   b  inserted in the side wall of the body  110  can be formed large enough to control a high flow without the necessity of increasing the axial size of the motor-operated valve. 
         [0052]      FIG. 2  is a longitudinal sectional view of a motor-operated valve according to another embodiment of the present invention. In  FIG. 2 , the same or similar elements as or to those shown in  FIGS. 1 and 4  are indicated with the same or similar reference signs as or to those used in  FIGS. 1 and 4 . So, such elements will not further be explained hereunder. 
         [0053]    In this embodiment of the motor-operated valve, a pressure equalization path  280   a  is provided in the center of a valve element  280 . Also there are provided in a locking member  284  a pressure equalization path  284   a  communicating with the pressure equalization path  280   a  in the valve element  280  and a pressure equalization path  284   b  which provides communication between the pressure equalization path  284   a  a and a back pressure chamber  285 . Thus, a fluid pressure in a pipe  12   a  is introduced into the back pressure chamber  285 . These pressure equalization paths  280   a,    284   a  and  284   b  and back pressure chamber  285  thus provided permit to eliminate the difference between pressures applied to the upper and lower portions, respectively, of the valve element  280 . A sealing member  230  is fitted between the valve element  280  and a guide portion  210   d  of a body  210  and fixed with a holding member  270  around the locking member  284 . 
         [0054]    In this embodiment, there is provided a cylindrical spring case  290  having an inner flange  290   b  provided at the lower portion thereof. The inner flange  290   b  is engaged on the bottom of a large-diameter portion  284   c.    
         [0055]    The coil spring  92  is disposed between the outer surface of the spring case  290  and the inner wall of a bore  210   e  in the body  210 , and compressed between an outer flange  290   a  provided at the upper end of the spring case  290  to project outwardly and the upper surface of the guide portion  210   d.  Thus, the valve element  280  is normally forced along with the spring case  290  in the direction in which it is pushed up (the valve is opened). 
         [0056]    Also in this embodiment, there is provided a bush  220  having provided at the lower portion thereof a small-diameter portion  220   a  which is inserted in the spring case  290 . Thus, the upper half of the coil spring  92  is disposed in a position where it overlaps the bush  220  in the axial direction, and the coil spring  92  (and a spring case  290 ) is wholly disposed above the chamber  14  (at the side of the actuator). 
         [0057]      FIG. 2  shows the valve element  280  resting on the seat  18  as in  FIG. 1 . When the driver  72  ascends from this position as the rotor member  50  rotates in a predetermined direction, the spring case  290  is moved up under the elasticity of the coil spring  92  within a space defined by the outer circumference of the small-diameter portion  220   a  and the inner wall of the bore  210   e,  and the valve element  280  is also guided to ascend by the guide portion  210   d.    
         [0058]    Also, when the rotor member  50  rotates in the reverse direction, the driver  72  descends, and also the spring case  290  and valve element  280  are moved down against the elasticity of the coil spring  92 . 
         [0059]    Owing to the above-mentioned design, the inner space  14   a  of the chamber  14  opposite to the pipe  12   b  inserted in the side wall of the body  210  can be designed large enough to control a high flow without the necessity of increasing the axial size of the motor-operated valve. 
         [0060]    In this embodiment, the inside diameter of the guide portion  210   d  is set nearly equal to the inside diameter D 1  of the seat  18  and the fluid at the pipe  12   a  is introduced into a back pressure chamber  285 , whereby the axial forces applied to the back and front of the valve element  280  are balanced with each other. 
         [0061]    Owing to this design, the valve element  80  can be operated with a small thrust. 
         [0062]      FIG. 3  is a motor-operated valve according to still another embodiment of the present invention. In  FIG. 3 , the same or similar elements as or to those shown in  FIGS. 1 ,  2  and  4  are indicated with the same or similar reference signs as or to those used in  FIGS. 1 ,  2  and  4 . So, such elements will not further be explained hereunder. 
         [0063]    The motor-operated valve according to this embodiment is applied for control of a higher flow. In this embodiment, the valve body includes a barrel  310  and lid  350 . 
         [0064]    In an opening at the top of the chamber  14  of the barrel  310 , the lid  350  serving as a guide portion for a valve element  380  is firmly fixed with a bolt  360 . A clearance between the lid  350  and barrel  310  is sealed with a sealing member  354 . The lid  350  includes a cylindrical portion  352  which is inserted in the chamber  14 . The valve element  380  is inserted and slides in a guide portion  352   a  which is a bore formed in the cylindrical portion  352 . The locking member  284  firmly fixed to the valve element  380  is supported slidably on a small-diameter portion  350   d  of the lid  350 . 
         [0065]    It should be noted that since the valve element  380  is supported slidably in the guide portion  352   a,  it is not necessary to slide the locking member  284  and small-diameter portion  350   d  but a clearance may be provided between these members. 
         [0066]    A sealing member  320  is fitted between the valve element  380  and guide portion  352   a  and fixed with the holding member  270  around the locking member  284 . 
         [0067]    In this embodiment, there is provided a cylindrical spring case  390  having an inner flange  390   b  provided at the lower portion thereof. The inner flange  390   b  is engaged on the bottom of the large-diameter portion  284   c  provided at the upper portion of the locking member  284 . 
         [0068]    The coil spring  92  is disposed between the outer surface of the spring case  390  and the inner wall of a bore  350   a  in the lid  350 , and compressed between an outer flange  390   a  provided at the upper end of the spring case  390  to project outwardly and the upper surface of the small-diameter portion  350   d.  Thus, the valve element  380  is normally forced along with the spring case  390  in the direction in which it is pushed up (the valve is opened). 
         [0069]    Also in this embodiment, the small-diameter portion  220   a  provided at the lower portion of the bush  220  is adapted to be inserted inside the spring case  390 . Thus, the upper half of the coil spring  92  is disposed in a position where it overlaps the bush  220  in the axial direction, and the coil spring  92  (and a spring case  390 ) is wholly disposed above (at the side of the actuator) the chamber  14 . 
         [0070]    According to this embodiment, the motor-operated valve is designed for the valve element  380  to slide long in the guide portion  352   a.  Therefore, even a larger valve element  380  can be guided positively with a high concentricity with the seat  18 . 
         [0071]    Also, the inside diameter of the guide portion  352   a  in which the valve element  380  is housed is set nearly equal to the inside diameter D 1  of the seat  18 . 
         [0072]    Further, the pressure equalization path  280   a  is provided in the center of the valve element  380 . In the locking member  284  there are provided the pressure equalization path  284   a  communicating with the pressure equalization path  280   a  and also the pressure equalization path  284   b  which provides communication between the pressure equalization path  284   a  and back pressure chamber  285 . These pressure equalization paths  280   a,    284   a  and  284   b  and back pressure chamber  285  thus provided permit to introduce a fluid pressure in the pipe  12   a  into the back pressure chamber  285 , whereby the difference between pressures applied to the upper and lower portions, respectively, of the valve element  380  can be eliminated. 
         [0073]    Owing to this design, the valve element  380  can be operated with a small thrust. 
         [0074]    As having been described in the foregoing, the valve element  180  ( 280  and  380 ) has the inclined surface  82  formed at the front end thereof to abut on the seat and a smaller-diameter portion  180   s  ( 280   s  and  380   s ) as shown in  FIGS. 1 to 3  and hence the motor-operated valve of this design is suitable for high-flow control among others. However, it should be noted that the present invention is not limited to the high-flow control motor-operated valve alone but is applicable to a low-flow control motor-operated valve including a valve element having no smaller-diameter portion. 
         [0075]    The entire disclosure of Japanese Patent Application No. 2011-078702 filed Mar. 31, 2011, is expressly incorporated by reference herein.