Abstract:
A motor-operated valve includes a valve body having a valve chamber and a valve seat; a valve element; a valve rod for operating the valve element; a cylindrical can fixed to the valve body; a motor energizing device mounted in the outer peripheral portion of the can; a permanent magnet type rotor assembly which is supported rotatably on the inner peripheral portion of the can and is rotationally driven by the motor energizing device; a reduction gear apparatus for reducing the rotational speed of the rotor assembly; and a screw mechanism for advancing and retreating the valve element with respect to the valve seat via the reduction gear apparatus by means of the rotational movement of the rotor assembly. The rotor assembly and the reduction gear apparatus are arranged in a space defined by the valve body and the can.

Description:
[0001]     The present application is based on and claims priority of Japanese patent applications No. 2005-208399 filed on Jul. 19, 2005, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a motor-operated valve for controlling the flow rate of a refrigerant for an air conditioner and, more particularly, to a canned gear motor-operated valve provided with a gear reduction mechanism in a can, which is a gastight vessel.  
         [0004]     2. Description of the Related Art  
         [0005]     It is known that motor-operated valves, which are opened and closed via an electric motor, are broadly divided into two types. A first type is a type in which the valve is opened and closed by directly transmitting the rotation of a rotor to a screw mechanism, and is disclosed, for example, in Patent Reference 1. A second type is a type in which the valve has a reduction gear apparatus for transmitting the rotation of the rotor to the screw mechanism while reducing the speed, and is disclosed, for example, in Patent References 2 and 3.  
         [0006]     [Patent Reference 1] Japanese Patent Laid-Open No. 2000-356278  
         [0007]     [Patent Reference 2] Japanese Patent Laid-Open No. 2002-84732  
         [0008]     [Patent Reference 3] Japanese Patent Laid-Open No. 2003-232465  
         [0009]     The motor-operated valve of the first type has a relatively compact configuration, but has a disadvantage that the application thereof is limited to a case where the load is low, and it is difficult to increase the resolution of valve opening per one drive pulse.  
         [0010]     The motor-operated valve of the second type can be used even in a case where the load is high and can be configured so that the resolution of valve opening per one drive pulse is increased, but has a problem in that the size of the whole of the motor-operated valve is increased because a gearbox for a reduction gear apparatus is provided separately from a motor section.  
         [0011]     An object of the present invention is to provide a motor-operated valve suitable for accommodating a reduction gear apparatus in a small space in a rotor in a compact manner.  
       SUMMARY OF THE INVENTION  
       [0012]     A motor-operated valve in accordance with the present invention includes, as basic means, a valve body having a valve chamber and a valve seat; a valve element disposed so as to be capable of opening and closing an opening of the valve seat in the valve chamber; a valve rod for operating the valve element; a cylindrical can fixed to the valve body; a motor energizing device mounted in an outer peripheral portion of the can; a permanent magnet type rotor assembly which is supported rotatably on an inner peripheral portion of the can and is rotationally driven by the motor energizing device; a reduction gear apparatus for reducing the rotational speed of the rotor assembly; and a screw mechanism for advancing and retreating the valve element with respect to the valve seat via the reduction gear apparatus by means of the rotational movement of the rotor assembly. The rotor assembly and the reduction gear apparatus are arranged in a space defined by the valve body and the can. In this motor-operated valve, the reduction gear apparatus includes a sun gear integral with the rotor assembly; a fixed gear having a ring gear, which is fixed on the valve body side; a planetary gear which is supported on a carrier and meshes with the sun gear and the fixed gear at the same time; and an output gear having a ring gear meshing with the planetary gear, a cylindrical gear case which supports the fixed gear by an upper end portion is fixed to a holder fixedly arranged in a space in the can, and the output gear located in a space in the gear case below the fixed gear is directly or indirectly supported by the holder so as to be rotatable.  
         [0013]     By providing the above-described means, a construction can be obtained in which a strong valve operating force is achieved, high resolution is provided, and the gear case for the reduction gear apparatus is fixed rationally in a limited space.  
         [0014]     Further, a construction for keeping a uniform pressure in the can at the time of the expansion and contraction of bellows can be secured. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a sectional view showing a general construction of a canned gear motor-operated valve in accordance with the present invention.  
         [0016]      FIG. 2  is an explanatory view showing the details of a valve body, supporting member, valve rod, and the like.  
         [0017]      FIG. 3  is a sectional view a can fixed to a supporting member.  
         [0018]      FIG. 4  is an explanatory view showing the details of a bearing, shaft, and rotor assembly.  
         [0019]      FIG. 5  is an explanatory view showing the details of a holder, screw bearing, screw shaft, and ball.  
         [0020]      FIG. 6  is an explanatory view showing the details of a gear case constituting a reduction gear apparatus.  
         [0021]      FIG. 7  is an explanatory view showing the details of a fixed gear  120 .  
         [0022]      FIG. 8  is an explanatory view showing the details of a belleville spring for preventing the float of a fixed gear.  
         [0023]      FIG. 9  is an explanatory view showing the details of a carrier and a planetary gear which constitute a reduction gear apparatus.  
         [0024]      FIG. 10  is an explanatory view showing the details of an output gear and an output shaft which constitute a reduction gear apparatus.  
         [0025]      FIG. 11  is a perspective view showing a state in which principal elements are assembled. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]      FIG. 1  is a sectional view showing a general construction of a canned gear motor-operated valve in accordance with the present invention.  
         [0027]     A canned gear motor-operated valve the whole of which is denoted by reference numeral  1  has a rotor assembly  50  provided rotatably in a can  30 , which is a gastight vessel. On the outside of the can  30 , a motor energizing device  2  in which a coil  3  constituting a motor stator is molded integrally with a resin is provided, and is detachably fitted to the can  30  with a installation member  5  formed by a plate spring. The coil  3  is connected to a power source on the outside via an electrical circuit  4 .  
         [0028]     The can  30  is fixed to a valve body  10  via a supporting member  20 . The valve body  10  has a valve chamber  12  and an orifice  14 , and refrigerant pipes  18   a  and  18   b  are fixed to the valve body  10 . A chamber  16  into which a refrigerant is introduced is provided so as to communicate with the valve chamber  12  of the valve body  10 .  
         [0029]     The rotor assembly  50  mounted in the can  30  is rotated by a drive signal supplied to the coil  3  of the motor energizing device fitted on the outside of the can  30 .  
         [0030]     The rotation of the rotor assembly  50  is transmitted to an output shaft  200  of an output gear  160  while the rotational speed thereof is reduced by a reduction gear apparatus  100  provided with a planetary gear. The output shaft  200  drives a screw shaft  210 . The screw shaft  210  is threadedly engaged with a bearing  230 , and the bearing  230  is supported on a holder  220  fixed to the supporting member  20 .  
         [0031]     The bearing  230  is sometimes formed integrally with the holder  220 . At this time, the output gear  160  (output shaft  200 ) is directly supported on the holder  220 .  
         [0032]     The travel of the screw shaft  210  is transmitted to a valve rod  250  via a ball  240  and a ball receiving member  242 , and a valve element  260  mounted at the tip end of the valve rod  250  is moved up and down. The flow path area between the valve element and the orifice is controlled, so that the flow rate of refrigerant is regulated.  
         [0033]     On the outside of the valve rod  250  is installed a bellows  270 , so that the refrigerant introduced into the chamber  16  communicating with the valve chamber  12  is prevented from intruding into the can  30 .  
         [0034]     The details of component members of the canned gear motor-operated valve in accordance with the present invention will be explained with reference to FIGS.  2  to  11 .  
         [0035]      FIG. 2  shows the details of the valve body  10 , the supporting member  20 , the valve rod  250 , and the like.  
         [0036]     The valve body  10  has the valve chamber  12  and the orifice  14 , and the pipes  18   a  and  18   b  are fixed to the valve body  10 . The supporting member  20  fixed to the upper part of the valve body  10  has a cylindrical portion  22  and a flange portion  24  expanding horizontally from the cylindrical portion  22 . The flange portion  24  receives the opening end portion of the can. The upper end of the cylindrical portion  22  is formed into four concave portions  28  and a convex portion  26 , and is engaged with the holder  220 .  
         [0037]     The convex portion  26  of the supporting member  20  supports the holder  220 , and a gap G is provided between the supporting member  20  and the holder  220  so that air is allowed to flow. Therefore, even if the bellows, described later, expands or contracts, the pressure on the inside and outside of the supporting member  20  can be uniformed, so that an influence on operation is not exerted.  
         [0038]     The upper end of the bellows  270  installed on the outside of the valve rod  250  supporting the valve element  260  is fixed to the valve body  10  by a staking portion K 1  via a ring member  272 . A lower end  274  of the bellows  270  is fixed to the valve rod  250 . The bellows  270  prevents the refrigerant introduced into the chamber  16  of the valve body  10  from intruding to the can side.  
         [0039]      FIG. 3  is a sectional view of the can  30  fixed to the supporting member  20 .  
         [0040]     The can  30 , which is a cylindrical pressure vessel, has a flange portion  32  lapped on the flange portion  24  of the supporting member  20 , and is formed with a protruding portion  34 , which accommodates a bearing, in the top portion thereof.  
         [0041]      FIG. 4  shows the details of a bearing  40 , a shaft  42 , and the rotor assembly  50 .  
         [0042]     The bearing  40  is pressed into the protruding portion  34  in the top portion of the can  30  under pressure. In a hole  41  in the bearing  40  is inserted the shaft  42 .  
         [0043]     The rotor assembly  50  is formed of a plastic material containing a magnetic material, and is molded integrally with a sun gear member  54  disposed in the center thereof.  
         [0044]     In the center of the sun gear member  54 , a boss  55  having a through hole, through which the shaft  42  passes is provided. On the outside of the boss  55 , a sun gear  56  constituting a planetary gear speed reduction mechanism is formed.  
         [0045]      FIG. 5  shows the details of the holder  220 , the bearing  230 , the screw shaft  210  and the ball  240 .  
         [0046]     The holder  220  has an inside diameter portion  221  in which an outside diameter  231  of the bearing  230  is inserted and a step portion  222 , and a step portion  232  on the outside diameter of the bearing  230  abuts on the step portion  222 . The bearing  230  and the holder  220  are integrated with each other by a pressing portion P 1  or the like after the bearing  230  has been fitted in the holder  220 .  
         [0047]     An outside diameter portion  223  on the upper side of the holder  220  is fitted with a gear case, described later, and the gear case is supported on a step portion  224 . An outside diameter portion  225  on the lower side of the holder  220  is inserted in the upper end portion of the supporting member  20  fixed to the valve body  10 , and the upper end portion of the supporting member  20  is fixed by a step portion  226 . The convex portion  26  of the supporting member  20  holds the holder  220  by welding etc.  
         [0048]     The bearing  230  has an internal thread portion  234  so that an external thread portion  214  of the screw shaft  210  is threadedly engaged with the internal thread portion  234 . The screw shaft  210  has a slit  212 , in which a driver of the output shaft of the reduction gear apparatus  100 , described later, is inserted, at an upper part, and the ball  240  is fixed to a lower concave portion  216 .  
         [0049]      FIG. 6  shows the details of the gear case  110  constituting the reduction gear apparatus  100 .  
         [0050]     The gear case  110  is a cylindrical member, and the lower part thereof is fitted on the upper part of the holder  220 . The upper end of the gear case  110  is formed with four extending elements  112 . The extending element  112  is formed in an inversely tapered shape such that a tip end  112   a  thereof has a greater width than a root  112   b  thereof, and has undercut portions at both-side edges.  
         [0051]     The extending elements  112  of the gear case  110  is inserted in concave portions  124  of a fixed gear  120  and is heated, by which plastic of the raw material for the fixed gear  120  is melted, so that the fixed gear  120  is fixed surely to the gear case  110 .  
         [0052]      FIG. 7  shows the details of the fixed gear  120 .  
         [0053]     The fixed gear  120  is manufactured by molding, for example, plastic, and is formed with a flange  123  in the outer peripheral portion thereof, concave portions  124  fixed to the upper part of the gear case, and convex portions  122 . On the inner periphery side of the fixed gear, a ring gear  126  constituting the planetary gear speed reduction mechanism is formed.  
         [0054]      FIG. 8  shows the details of a belleville spring  130  for restraining the float of the fixed gear and the noise caused by vibrations at the time of the rotor rotation.  
         [0055]     As also shown in  FIG. 1 , the fixed gear  120  fitted in the upper part of the gear case  110  is prevented from floating by the belleville spring  130  disposed between the fixed gear  120  and the rotor assembly  50 .  
         [0056]     Also, vibrations occurring at the time of rotor rotation are reduced by the spring property of the belleville spring, and noise caused by the vibrations is restrained. The belleville spring  130  has a hole  132  through which the sun gear  56  of the rotor assembly  50  passes and spring portions  134  extending to three directions.  
         [0057]      FIG. 9  shows the details of a carrier  140  and the planetary gear  150 , which constitute the reduction gear apparatus having the planetary gear.  
         [0058]     The carrier  140  is manufactured by molding, for example, plastic, and has a hole  142 , through which the shaft  42  passes, in the center thereof. The carrier  140  has three masts  144  and three partition walls  146 . The planetary gear  150  has a hole  152  fitted on the mast  144  and a gear portion  154 . On the upper surface of the carrier  140  in which the three planetary gears  150  are fitted on the masts  144 , a plate is put, and the masts  144  and convex portions at the tops of the partition walls  146  are pressed into the holes in the plate under pressure, by which the carrier  140  is fixed to the plate.  
         [0059]      FIG. 10  shows the details of the output gear  160  and the output shaft  200  integral with the output gear  160 , which constitute the reduction gear apparatus.  
         [0060]     The output gear  160  has a hole  162  into which a columnar portion of the output shaft  200  is pressed under pressure. On the inside of the output gear  160  is formed a ring gear  164 .  
         [0061]     The output shaft  200  has a bottomed hole  204  for accommodating the shaft  42  and a flat driver portion  206 . The flat driver portion  206  is engaged with the slit  212  of the screw shaft  210 .  
         [0062]     The reduction gear apparatus  100  is configured so that the sun gear  56  of the rotor assembly  50  serves as an input gear, and the planetary gear  150  supported on the carrier  140  meshes with the sun gear  56  and the ring gear  126  of the fixed gear  120  at the same time.  
         [0063]     The planetary gear  150  of this carrier also meshes with the ring gear  164  of the output gear  160 , so that the input of the sun gear  56  is outputted to the output gear  160  while the speed thereof is reduced.  
         [0064]     The reduction gear apparatus  100  has a high speed reducing ratio, and can reduce the speed greatly, for example, at a ratio of about 50 to 1.  
         [0065]     Thus, the rotational speed of the rotor assembly  50  is reduced to, for example, one-fiftieth and is transmitted to the screw shaft  210 .  
         [0066]     The screw shaft  210  can rotate at a low speed, so that valve opening control with high resolution is achieved.  
         [0067]      FIG. 11  is a perspective view showing a state in which principal elements are assembled.  
         [0068]     The two pipes  18   a  and  18   b  are fixed to the valve body  10 . The supporting member  20  is welded to the upper portion of the valve body  10 , and the holder  220  is supported by welding of the four convex portions of the supporting member  20 .  
         [0069]     The gear case  110  is fitted in the upper part of the holder  220 . The four extending elements  112  and concave portions  114  are formed in the upper part of the gear case  110 .  
         [0070]     The tip end  112   a  of the extending element  112  is formed so as to have a greater width than the root  112   b . The fixed gear  120  made of a resin etc. is formed with the ring gear  126  on the inner peripheral surface thereof, and is formed with four concave portions  124  in the outer peripheral portion thereof.  
         [0071]     The fixed gear  120  is fixed firmly by engaging the concave portions  124  with the extending elements  112  of the gear case  110  and by heating this portion to melt the plastic-made fixed gear.  
         [0072]     This motor-operated valve has a construction such that the gear case is fixed surely, and the pressure in the can corresponding to the expansion and contraction of bellows is kept uniform.