Abstract:
A traditional compressor unit of the sealed type suffers in that a failure of either the motor or the compressor require both to be discarded Provided is a compressor ( 1 ) having a rotor assembly ( 3 ) within which a rotor ( 24 ) is rotated on an eccentric shaft ( 28 ) in a sealed chamber ( 23 ) Two or more intake ports ( 32, 33 ) are provided that open into the sealed chamber ( 23 ) and two or more exhaust ports ( 34, 35 ) are provided with one way valves ( 38 ), to permit compressed gas to exit the sealed chamber ( 23 ) The geometry of the rotor ( 24 ) and sealed chamber ( 23 ) and eccentric drive ( 28 ) are such that apices of the rotor ( 24 ) remain in contact with a peripheral wall ( 22 ) of the sealed chamber ( 23 ) as the rotor ( 24 ) rotates and apex seals ( 36 ) are provided on the apices of the rotor ( 24 ) to prevent leakage of the gas around the apices of the rotor ( 24 ) In a preferred embodiment the rotor ( 24 ) is a multi-lobed rotor orbiting within a trochoidal chamber ( 23 ).

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to rotor assemblies for rotary compressor units especially but not exclusively units for small refrigeration units such are suitable for use in small refrigerators and automotive air conditioners. Such units must be compact, quiet, reliable and economical to manufacture and operate. 
       BACKGROUND OF THE INVENTION 
       [0002]    Compressor units for domestic refrigerators are commonly of the sealed unit type in which both the compressor and a motor permanently coupled to the compressor is located within an enclosure that is completely and permanently sealed except for refrigerant connections to the remainder of the refrigeration unit. Such a unit has the disadvantages that failure of either the motor or the compressor requires both to be discarded, different sealed units are required for electrical supplies requiring different motors, even though the compressor is identical, and two devices, both of which generate unwanted heat, are thermally coupled within the same enclosure. 
         [0003]    It is known in compressor units for automotive air conditioning systems, which are engine driven, and thus require a clutch mechanism, to utilize an electromagnetic clutch between a belt driven pulley and the compressor. 
         [0004]    In the interests of smoother and more silent compressors, there has been some adoption of scroll type compressors in compression type refrigeration units, available for example from Lennox, Copeland and EDPAC International. 
         [0005]    An alternative form of piston compressor which has been proposed, is the rotary piston compressor using a lobed rotor in a trochoidal chamber and having some resemblance to rotary piston engines such as the Wankel engine although the operating cycle is substantially different and the shaft is driven by an external power source rather than being driven by the rotary piston. Such compressors are exemplified in U.S. Pat. Nos. 3,656,875 (Luck); 4,018,548 (Berkowitz); and 4,487,561 (Eiermann). 
         [0006]    U.S. Pat. No. 5,310,325 (Gulyash) discloses a rotary engine using a symmetrical lobed piston moving in a trochoidal chamber on an eccentric mounted on a rotary shaft and driven through a ring gear by a similarly eccentric planet gear rotated at the same rate as the eccentric, the gear ratio of the ring gear to the planet gear being equal to the number of lobes on the rotor, typically three. The apices of the lobes trace trochoidal paths tangent to the trochoidal chamber wall thus simplifying sealing. 
         [0007]    U.S. Pat. No. 6,520,754 (Randolphi) discloses a compressor for a refrigeration unit having a three lobed rotor orbiting in a chamber defined within a sealed casing and using a magnetic coupling outside of the casing to rotate the rotor. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention relates to a compressor having a rotor assembly within which a rotor is rotated on an eccentric shaft in a sealed chamber. Two or more intake ports are provided that open into the sealed chamber and two or more exhaust ports are provided with one way valves, to permit compressed gas to exit the sealed chamber. The geometry of the rotor and sealed chamber and eccentric drive are such that apices of the rotor remain in contact with a peripheral wall of the sealed chamber as the rotor rotates and apex seals are provided on the apices of the rotor to prevent leakage of the gas around the apices of the rotor. In a preferred embodiment the rotor is a multi-lobed rotor orbiting within a trochoidal chamber. 
         [0009]    The features of the present invention will be apparent from the following description of a presently preferred embodiment thereof. 
     
    
     
       SHORT DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a front schematic perspective view of a compressor having a rotor assembly in accordance with the present invention and magnetic drive assembly within a sealed outer casing; 
           [0011]      FIG. 2  is a cross sectional schematic view of the compressor of  FIG. 1  through line  2 - 2  with an outer magnetic drive; 
           [0012]      FIG. 3  is a perspective view of the rotor assembly for the compressor of  FIG. 1 ; 
           [0013]      FIGS. 4 and 5  are cross-sections of the rotor assembly of  FIG. 3  on the line  4 - 4  showing different phases of its operation; 
           [0014]      FIG. 6 . is a cross sectional schematic view of the rotor assembly of  FIG. 4  on the line  6 - 6 ; 
           [0015]      FIG. 7 . is a cross sectional schematic view of the rotor assembly of  FIG. 4  on the line  7 - 7 ; 
           [0016]      FIG. 8 . is a cross sectional schematic view of the rotor assembly of  FIG. 4  on the line  8 - 8 ; 
           [0017]      FIG. 9  is a schematic view of a flapper valve assembly contained within the rotor housing of  FIG. 3 ; 
           [0018]      FIG. 10  is a cross section of the flapper valve assembly on the line  9 - 9  in  FIG. 9 . 
           [0019]      FIG. 11  is a top plan view of another embodiment of a compressor having a rotor assembly in accordance with the present invention without the magnetic drive assembly and sealed outer casing as shown in  FIG. 1  and showing major internal components in dotted lines; 
           [0020]      FIG. 12  is a cross sectional schematic view of the compressor of  FIG. 9  through the line  12 - 12 ; 
           [0021]      FIG. 13  is a cross sectional schematic view of the compressor of  FIG. 9  through the line  13 - 13 . 
           [0022]      FIG. 14  is a perspective view of another embodiment of a compressor having a rotor assembly in accordance with the present invention; 
           [0023]      FIG. 15  is a top schematic view of the compressor of  FIG. 14  showing the assembly transparently; 
           [0024]      FIG. 16  is a rear perspective view of the compressor of  FIG. 14  showing the assembly transparently. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Referring to the  FIGS. 1-8 , a compressor, generally indicated at  1  in  FIGS. 1 &amp; 2 , comprises a sealed outer casing generally indicated at  2  retains a rotor assembly in accordance with one embodiment of the present invention, generally indicated at  3  and an inner magnetic drive assembly generally indicated at  5 . The compressor  1  in one application may be connected (as shown in  FIG. 2 ) by an intake  90  and outlet  91  such as to an evaporator and a condenser of a refrigeration unit. In the embodiment illustrated the sealed outer casing  2  has a canister section  6  which holds the rotor assembly  3  and inner magnetic drive assembly  5  and a lid section  7  which fits over the inner magnetic drive assembly  5  and onto the canister section  6  with a pair of O-rings  8 , 9  to seal the outer casing. In the embodiment illustrated the canister section  6  has a cylindrical outer wall  10  closed at one end by plate section  11 . A peripheral flange  12  extends outwardly from the top  13  of the cylindrical outer wall  10 . The thickness of cylindrical outer wall  10  in a first section  14  adjacent the plate section  11  is greater than the thickness of a second section  15  which in turn is thicker than a third section extending  16  from the top  13  of the cylindrical outer wall  10 . The reduction in thickness in the outer cylindrical wall  10  forms a pair of lips  17 ,  18  on its inner surface  4 . 
         [0026]    The rotor assembly  3 , in the embodiment illustrated in  FIGS. 2-8 , is comprised of a back plate  19 , rotor housing  20  and front plate  21 . The inner peripheral wall  22  of the rotor housing  20  together with the inner surfaces  25 ,  26  of back plate  19  and front plate  21  define a sealed chamber  23  within which a rotor  24  is rotated. One end  27  of an eccentric shaft  28  on which the rotor  24  is mounted, is journal led in bearings  29  housed within the back plate  19 . A timing pinion  30  is attached to the inner surface  25  of back disk  19  and mates with a ring gear  31  attached to rotor  24 . In the embodiment illustrated the timing pinion  30  is % the diameter of the ring gear  31 . A pair of intake ports  32 ,  33  (see  FIGS. 4 ,  5  &amp;  7 ) are provided in back plate  19  that open into the sealed chamber  23 . A pair of exhaust ports  34 ,  35  are provided in the rotor housing  20  (see  FIG. 6 ). One way valves generally indicated at  38  (see  FIG. 9 ), shown as flapper valves in the drawings, permit compressed gas to exit the sealed chamber  23  but do not allow any return flow back through the exhaust ports  34 , 35  into the chamber  23 . 
         [0027]    In the embodiment illustrated, the rotor  24  is mounted on an eccentric shaft  28  for orbital movement along a path within chamber  23 . The profile of chamber  23  is an outline of the path that the tips of the lobes A, B, C of the rotor  24  follows. The ratio of the ring gear  31  to the eccentric gear  30  (or timing pinion) is equal to the number of lobes, in this case three, of the rotor  24 . In the embodiment illustrated in  FIGS. 1 to 8 , the end  32  of the eccentric shaft  28  remote from the rotor  24  is attached to an inner magnetic drive assembly generally indicated at  5 . The inner magnetic drive assembly  5  has an inner magnetic drive element  33  attached to the eccentric shaft  28  where the shaft  28  extends from the front plate  21  of the rotor assembly  3 . A cap portion  37  of lid section  7  of the sealed outer casing  2  encloses the inner magnetic drive assembly  5 . An outer magnetic drive  38  is attached to a source of rotation (not shown) and rotates about the cap portion  37  of lid section  7  providing a mating magnetic force to turn the inner magnetic drive element  33 . 
         [0028]      FIG. 4  shows the position of the rotor  24  when the eccentric shaft  28 , timing pinion  30  and ring gear  31  are as seen in the drawing. The direction of rotation in this example is clockwise, and the apices of the lobes of the rotor are labeled A, B and C for convenient reference. The geometry of the rotor  24  and chamber  23  and of the drive are such that the apices remain in contact with the inner wall  25  of the sealed chamber  23 . Apices A, B and C of rotor  24  divide the sealed chamber  23  into three parts labeled D, E and F. Gas is introduced into the sealed chamber  23  through intake ports  32 , 32 A. As the rotor  24  rotates the gas in the parts D, E and F of the chamber  23  is compressed as the rotation of the rotor  24  reduces the size of part D, E and F of the chamber.  FIG. 5  shows the position of the rotor  24  rotated from the position in  FIG. 4  with the eccentric shaft  28 , timing pinion  30  and ring gear  31  positioned as seen in the drawing. The part F of the sealed chamber  23  has been reduced, compressing the gas in that section. The compressed gas is exhausted through exhaust port  34 . As the rotor moves clockwise, gas is drawn through the intake port  32 , 32 A into the parts D, E and F of chamber  23 , the gas is compressed and forced out of the chamber  23  through exhaust ports  34 ,  35  past flapper valves  38 . 
         [0029]    In order to prevent compressed gas leaking from part D, E or F of chamber  23  into one of the other parts D, E or F of chamber  23  as the rotor  24  is rotated, apex seals  36  are provided in a slot  36 A in the apex A, B and C of rotor  24 . In the embodiment illustrated in  FIGS. 1-8 , the back side of the rotor  24  fits tight against the inner surface  25  of back plate  19  and together with a lubricant provides a seal. Similarly the front side of the rotor  24  fits tight against the inner surface  26  of front plate  21  and together with a lubricant provides a seal. As an alternative to relying on the tight fit and lubricant to form a seal, side seals may be inserted to prevent gas from leaking around the front and back sides of the rotor. 
         [0030]      FIG. 6  illustrates a cross section of the rotor assembly  3  of  FIG. 4  on line  6 - 6 . The exhaust ports  34 ,  35  are shown in the rotor housing  20 .  FIG. 7  illustrates a cross section of the rotor assembly  3  of  FIG. 4  on line  7 - 7 . In this view the intake ports  32 ,  32 A are shown in the back plate  19  although they could be located in the front plate  21  if desired.  FIG. 8  illustrates a cross section of the rotor assembly  3  of  FIG. 4  on line  8 - 8 . In this view the apex seals  36  on apex B of rotor  24  are shown. The apex seals  36  are preferably compression seals retained within slots  37  on rotor  24 . The apex seals  36  run on the peripheral wall  22  of the chamber  23  defined by rotor housing  20  and as noted previously prevent leakage across the tips of the rotor  24 . An apex seal spring (not shown) provides the force to keep the apex seals  36  in contact with the profile of the chamber  23 . In the embodiment illustrated the apex seal springs are coil springs but a leaf spring or other suitable design can be used. 
         [0031]      FIGS. 9 and 10  illustrate schematically the one way flapper valves  38  in the exhaust ports  34 , 35  which allow the compressed gas to exit the compressor yet allow no return flow back. The flapper valves  38  have a disk  39  connected to one end of a spring  40  attached to a plug  42 . The spring  40  keeps disk  39  in sealing engagement with the inlet  43  of exhaust port  34  or  35  until the pressure of the compressed gas is sufficient to push the disk  39  to open the inlet  43  and permit the compressed gas to exit through outlet  44 . Alternatively the flapper valve design can be different. For example the valve may be secured on one end and flexes to allow gas to exit the compressor. 
         [0032]      FIGS. 11-13  illustrate another embodiment of a compressor (suitable for use as in refrigerators although many other applications are possible) having a rotor assembly in accordance with the present invention with a direct shaft drive. The compressor, generally indicated at  51  in  FIGS. 11-13 , comprises a rotor assembly, generally indicated at  53  and a vector plate assembly generally indicated at  55 . In the embodiment illustrated the vector plate assembly  55  comprises a rear vector plate  56  and a seal retention plate  57  which are attached to the rotor assembly  53 . Pressure and suction lines are attached to the rear vector plate  56  which is in turned bolted to the back plate  59  of the rotor assembly  53 . A refrigerant gas coming into the compressor by the suction line is collected in the internal cavity  58  formed by the mating of the rear vector plate  56  and back plate  59  of the rotor assembly  53 . 
         [0033]    The rotor assembly  53  is similar to the rotor assembly  3  shown in  FIGS. 3 ,  4  and  5 . It comprises a back plate  59 , rotor housing  60  and front plate  61 . The inner peripheral wall  62  of the rotor housing  60  together with the inner surfaces  65 ,  66  of back plate  59  and front plate  61  define a sealed chamber  63  within which a rotor  64  is rotated. One end  67  of an eccentric shaft  68  on which the rotor  64  is mounted, is journalled in bearings  69  housed within the back plate  59 . A timing pinion is attached to the inner surface  65  of back plate  59  and mates with a ring gear  71  attached to rotor  64 . In the embodiment illustrated the timing pinion is % the diameter of the ring gear  71 . Intake ports are provided in back plate  59  from cavity  58  and open into the sealed chamber  63 . In large models the refrigerant may also pass from cavity  58  through internal passages to the front of the compressor and then through intake ports in the front plate  61  into chamber  63 . In situations where intake ports are provided in the front plate  61  the seal retention plate  57  is replaced with a front vector plate. A pair of exhaust ports  74 , 75  are provided in the rotor housing  60  (see  FIG. 13 ). One way valves generally indicated at  78  (see  FIG. 13 ), shown as flapper valves in the drawings, permit compressed gas to exit the sealed chamber  63  but do not allow any return flow back through the exhaust ports  74 , 75  into the chamber  63 . 
         [0034]    In the embodiment illustrated, the rotor  64  is mounted on an eccentric shaft  68  for orbital movement along a path within chamber  63 . The profile of chamber  63  is an outline of the path that the tips of the lobes of the rotor  64  follows. The ratio of the ring gear  71  to the eccentric gear or timing pinion is equal to the number of lobes, in this case three, of the rotor  64 . In the embodiment illustrated in  FIGS. 11 to 13 ; the end  82  of the eccentric shaft  68  remote from the rotor  64  may be attached to direct drive assembly (not shown). The seal retention plate  57  retains a shaft seal  81  around the shaft  68  as it passes through the seal retention plate  57 . 
         [0035]    The operation of the rotor  64  in  FIGS. 11-13  is the same as in  FIGS. 3-5 . With the eccentric shaft  68 , timing pinion and ring gear  71  as described, rotation of the rotor  64  is such that the apices of the rotor  64  remain in contact with the inner wall  62  of the sealed chamber  63 . The apices of rotor  64  divide the sealed chamber  63  into three parts. Gas is introduced into the sealed chamber  63  through the intake ports. As the rotor  64  rotates the volume of each part of chamber  63  between the lobes of the rotor is continuously varied. As the volume of the chambers increases refrigerant is drawn into the compressor, inversely as the volume decreases the now compressed gas is exhausted out of the compressor. The three parts of chamber  63  are never compressing at once, each is in a different phase of what could be considered a 2 phase cycle—intake and exhaust. As the size of a part of the sealed chamber  63  is reduced, the gas in that section is compressed. The compressed gas is exhausted through exhaust port  74 . As the rotor moves clockwise, the part of the chamber from which the compressed gas has been exhausted, increases in size and gas is drawn through the intake port into that part of chamber  63 . As the rotor  64  continues to rotate, the gas is again compressed and forced out of the chamber  63  through the other exhaust port  75  past flapper valves. 
         [0036]    In order to prevent compressed gas leaking from one part of chamber  63  into another one of the other parts of chamber  63  as the rotor  24  is rotated, apex seals  76  are provided on the apices of rotor  64  as shown in  FIG. 12 . 
         [0037]      FIG. 12  illustrates a cross section of the compressor  51  of  FIG. 11  on line  12 - 12 . 
         [0038]      FIG. 13  illustrates a cross section of the compressor  51  of  FIG. 11  on line  13 - 13 . In this view the exhaust ports  74 ,  75  are shown in the rotor housing  60 . 
         [0039]      FIGS. 14-16  illustrate another embodiment of a compressor (suitable for use as in automotive air conditioners although many other applications are possible) having a rotor assembly in accordance with the present invention with a direct shaft drive. The compressor, generally indicated at  101  in  FIGS. 14-16 , comprises a rotor assembly and a vector plate assembly. In the embodiment illustrated the vector plate assembly comprises a rear vector plate  106  and a front vector plate  107  which are attached to the rotor assembly  103 . Pressure and suction lines are attached to the rear vector plate  106  at suction inlet  104 A and pressure outlet  104 B respectively which is in turned bolted to the back plate  109  of the rotor assembly  103 . A refrigerant gas coming into the compressor by the suction line is collected in the internal cavity  108  formed by the mating of the rear vector plate  106  and back plate  109  of the rotor assembly  103 . In this embodiment one or more internal passages  108 A connects the internal cavity  108  formed by the mating of the rear vector plate  106  and back plate  109 , with a similar internal cavity  108 B formed by the mating of the front vector plate  107  and front plate  111  of the rotor assembly  103 . 
         [0040]    The rotor assembly  103  is similar to the rotor assembly  3  shown in  FIGS. 3 ,  4  and  5 . It comprises a back plate, rotor housing and front plate similar to the embodiments shown in the other figures although relative dimensions are different. The inner peripheral wall of the rotor housing together with the inner surfaces of back plate  109  and front plate  111  define a sealed chamber within which a rotor is rotated. One end of an eccentric shaft  118  on which the rotor is mounted, is journalled in bearings housed within the back plate  109 . A timing pinion is attached to the inner surface of back plate  109  and mates with a ring gear attached to rotor. In the embodiment illustrated the timing pinion is ⅔ the diameter of the ring gear. Intake ports are provided in back plate  109  from cavity  108  and front plate  111  from cavity  108 B and open into the sealed chamber. A pair of exhaust ports are provided in the rotor housing. One way valves preferably flapper valves, permit compressed gas to exit the sealed chamber at pressure outlets  104 B but do not allow any return flow back through the exhaust ports into the chamber. 
         [0041]    In the embodiment illustrated, the rotor is mounted on an eccentric shaft  118  for orbital movement along a path within chamber. The profile of the chamber is an outline of the path that the tips of the lobes of the rotor follow. The ratio of the ring gear to the eccentric gear or timing pinion is equal to the number of lobes, in this case three, of the rotor. In the embodiment illustrated in  FIGS. 14 to 16 ; the end  132  of the eccentric shaft  118  remote from the rotor may be attached to direct drive assembly (not shown). The front vector plate  107  retains a shaft seal around the shaft  118  as it passes through the front vector plate  107 . 
         [0042]    The operation of the rotor in  FIGS. 14-16  is the same as in  FIGS. 3-5 . Rotation of the rotor is such that the apices of the rotor remain in contact with the inner wall of the sealed chamber. The apices of rotor divide the sealed chamber into three parts. Gas is introduced into the sealed chamber through the intake ports. In the embodiment illustrated there are intake ports provided in the back plate  109  and additional intake ports in the front plate  111 . As the rotor rotates the volume of each part of the chamber between the lobes of the rotor is continuously varied. As the volume of a part of the chamber increases refrigerant is drawn into the compressor, inversely as the volume decreases the now compressed gas is exhausted out of the compressor. The three parts of chamber are never all compressing at the same time, each is in a different phase of what could be considered a  2  phase cycle—intake and exhaust. As the size of a part of the sealed chamber is reduced, the gas in that section is compressed. The compressed gas is exhausted through exhaust port which is connected to pressure outlet  104 B. As the rotor moves clockwise, the part of the chamber from which the compressed gas has been exhausted, increases in size and gas is drawn through the intake port into that part of chamber. As the rotor continues to rotate, the gas is again compressed and forced out of the chamber through the other exhaust port past flapper valves to pressure outlet  104 B. 
         [0043]    In order to prevent compressed gas leaking from one part of chamber into another one of the other parts of chamber as the rotor is rotated, apex seals are provided on the apices of rotor. 
         [0044]    The rotor assembly of the present invention is particularly useful in compressors in various applications including (but not limited to) consumer household, automotive air conditioners, industrial, portable, transportable, commercial, scientific, medical, environmental and military disciplines. If required, multiple rotors or multiple rotor assemblies can be provided in a compressor in accordance with present invention. A number of the advantages of the present invention over conventional compressor designs are as follows: 
         [0000]    (a) only two major moving parts in the compressor
 
(b) light weight
 
(c) shaft driven rotor in combination with a simplified gear reduction drive
 
(d) apex seals on the rotor prevent loss of compression
 
(e) can utilize a variable speed drive
 
(f) can obtain variable output
 
         [0045]    It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended to limit the broader aspects of the present invention. 
         [0046]    Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, which variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.