Patent Application
20050031465
1. Field of the Invention
The present invention relates to a rotary compressor having a compact design wherein the compression chamber is defined by the rotor of the motor driving the compressor.
2. Description of the Related Art
Rotary compressors typically include a housing in which a motor and a compression mechanism are mounted being operably connected by a drive shaft. Rotary type compression mechanisms typically include a roller disposed about an eccentric portion of a shaft. The roller is located in a cylinder block that defines a cylindrical compression space. At least one vane extends between the roller and the outer wall of the compression chamber to divide the compression chamber into a plurality of compression pockets. The roller is eccentrically located within the compression chamber and, as the shaft rotates, the compression pockets become progressively smaller thereby compressing a refrigerant or other fluid disposed therein. Oftentimes, the vane is biased into contact with either the wall of the compression chamber or the roller by a spring. Other configurations of rotary compressors are also known.
The present invention provides a compact rotary compressor in which the rotor of the motor includes a single integral part that also defines an internal compression chamber and includes an integrally formed vane extending radially inwardly into the compression chamber.
The present invention comprises, in one form thereof, a rotary compressor for compressing a fluid that includes a motor having a stator and a rotor. The rotor includes an integrally formed part defining an internal compression chamber and an integrally formed vane extending radially inwardly within the compression chamber. A roller is rotatably mounted and eccentrically disposed within the compression chamber. The vane is engaged with the roller wherein rotation of the rotor rotates the roller and thereby compresses the fluid within the compression chamber.
The integrally formed rotor part may also include a radially outer surface having a plurality of permanent magnets mounted thereon. Further, the roller may define a recess having a bushing mounted therein, wherein the bushing defines a radially extending slot with the vane being slidably disposed within the slot. The roller may be mounted on a stationary shaft wherein the shaft defines an internal passageway in fluid communication with the compression chamber.
The compressor may also include first and second end plates disposed at opposite axial ends of the compression chamber. At least one of the end plates may define a fluid passageway providing fluid communication between the internal passageway of the shaft and the compression chamber. The shaft extends through one of the end plates. In some embodiments, the shaft may extend through only one of the end plates and with the other end plate being rotatably mounted on a stationary support structure. The stator circumscribes the rotor, the compression chamber disposed therein and the first and second end plates.
One of the end plates disposed at an end of the compression chamber may define a discharge fluid line having a discharge valve cavity in fluid communication with the compression chamber and a discharge valve member disposed within the discharge valve cavity and controlling fluid flow from the compression chamber through the discharge valve cavity. The end plate may also further define a noise attenuation chamber in fluid communication with the discharge fluid line.
The present invention comprises, in another form thereof, a rotary compressor for compressing a fluid that includes a housing and a motor mounted in the housing. The motor has a stator and a rotor with the stator circumscribing the rotor. The rotor defines a rotational axis and includes an integrally formed part defining an internal compression chamber and an integrally formed vane extending radially inwardly within said compression chamber. Opposite axial ends of the rotor define first and second rotor faces respectively. A first end plate is secured to the first rotor face and a second end plate is secured to the second rotor face. A stationary shaft is mounted in the housing and extends through at least one of the end plates and is at least partially disposed within the compression chamber. A roller is rotatably mounted on the shaft eccentric wherein the roller is rotatable about an axis spaced from the rotational axis of the rotor. The vane is engaged with the roller wherein rotation of the rotor rotates the roller on the shaft and thereby compresses the fluid within the compression chamber.
An advantage of the present invention is that it provides a compact rotary compressor having relatively high reliability with reduced vibrations and noise.
The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, in one form, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed.
Referring now to the drawings and particularly to
Compressor 10 includes electric motor 24 having stator 26 and rotor 28 which defines a portion of compression mechanism 30 provided for compressing refrigerant from a low pressure to a higher pressure for use in a refrigeration system, for example. Stator 26, having coil assembly 32, is rigidly mounted and circumscribes rotor 28. Extending through rotor 28 is stationary shaft 34 which is fixedly mounted at end 36 in aperture 38 centrally formed in body portion 16 of housing 12 by welding, brazing, or the like (
Referring to
Stationary shaft 34 is formed from any suitable metal material including steel, powder metal, ductile iron, or the like by any conventional method including machining, for example. Referring to
Referring to
Guide bushing 60 is made from a material with suitable antifriction properties. In the illustrated embodiment, bushing 60 is formed using Vespel SP-21, a material commercially available from E.I. du Pont de Nemours and Company, and which facililtates the reduction of frictional losses caused by sliding movement of vane 54 in slot 62 and relative oscillating movement of bushing 60 within aperture 58 of roller 50. The use of a guide bushing 60 from a material with good antifriction properties facilitates the reduction of wear of the surfaces of roller 50, vane 54, and guide bushing 60 that are in moving contact to thereby improve the longevity and reliability of the compressor.
As discussed above, vane 54 is integrally formed with the cylinder block portion 46 of rotor 28 and the use of bushing 60 together with such an integrally formed vane, eliminates the need for a vane spring to press the vane against the roller. The use of bushing 60 to slidably receive vane 54 instead of a spring biased vane, may also reduce the frictional resistance to created by the vane during operation of the compressor. The relatively minimal frictional losses caused by vane 54 facilitates the minimization of power losses due to friction. The use of an integral vane that is slidably received within bushing 60 also facilitates the reduction of refrigerant vapor leakage across the barrier formed by vane 54 between a relatively high pressure compression pocket to a relatively low pressure compression pocket during operation of the compressor. The reduced frictional losses and refrigerant leakage facilitate the efficient and reliable operation of the compressor. The use of an integral vane 54 also facilitates the reduction of parts needed to manufacture compressor 10 thereby simplifying and facilitating the cost efficient manufacture of compressor 10.
Referring to
Compression assembly 30 is rotatably mounted on shaft 34 by a plurality of bearings 82, 84, and 86 which are press-fit into the apertures defined by outer plate 70 and inner plate 64, and the inner diameter of roller 50, respectively. Bearing 88 is press-fit onto protrusion 78 to rotatably support second end plate 74 by rotatably mounting protrusion 78 in upstanding member 80. When the compressor is operating and rotor 28 is rotated, bearings 82, 84, 86, and 88 rotatably support compression assembly 30 as it is rotatably driven about stationary shaft 34. As best seen in
Bearings 82, 84, 86, 88 and 89 may be formed from a polyamide material having relatively low coefficients of static and kinetic friction such as Vespel SP-21. Another beneficial characteristic associated with polyamide is that it demonstrates thermal stability over a relatively broad temperature range. For example, polyamide bushings may be capable of withstanding a bearing pressure of approximately 300,000 lb ft/in2 and a contact temperature of 740° F. For the optimum performance of the bushings and to avoid overheating, bushings 82, 84, 86 and 88 advantageously have a length to inside diameter ratio of no more than 3:2.
Compressor 10 as described above utilizes a bushing 60 and bearings 82, 84, 86 and 88 that do not require lubrication. While the above-described embodiment is equipped with self-lubricating bushings and bearings, alternative embodiments may utilize alternative bushings and bearings, e.g., needle or ball-type bearings and a conventional oil sump and pump for supplying lubricating oil to the bearings.
Assembly of compressor 10 may advantageously include first assembling compression assembly 30. Initially, roller 50, having guide bushing 60 press fit therein is located in compression space 52 such that vane 54 engages slot 62 and rotor 28 is positioned in abutting contact with second end plate 74. Bushing 86 is press fit within cylindrical aperture 58 of roller 50 and shaft 34 is inserted within bushing 86 to thereby rotationally engage roller 50 and shaft 34. Inner plate 64 and outer plate 70, having the respective bearings 82 and 84 assembled therewith, are then positioned on shaft 34 and fasteners are used to secure the compression chamber components together. Also mounted to shaft 34 is compression kit 89 (
The compact arrangement provided by the present invention allows the axial length of the compressor to be reduced to approximately the same axial length of the stator 26.
During compressor operation, electrical current supplied to stator 26 via terminal assembly 104 creates a magnetic flux which in turn causes rotation of rotor 28. The rotation of rotor 28 drives the rotation of roller 50 about drive shaft 34 through vane 54 which is integrally formed with rotor 28 and engaged with roller 50. Referring to
The refrigerant flows through a pathway best seen in
In the illustrated embodiment, the refrigerant passes through a suction port (not shown) in inner plate 64 and is introduced into a relatively large compression pocket 56 defined within compression chamber 52. The suction port is located in inner plate 64 such that discharge valve 106 and the suction port are in communication with separate compression pockets 56 throughout an entire 360 degree rotation of rotor 28 and roller 50 about shaft 34. After refrigerant is drawn into a compression pocket 56, rotation of rotor 28 and roller 50 about shaft 34 causes the progressive reduction in size of the compression pocket and the compression of the refrigerant vapor disposed therein, when the compression pocket is in fluid communication with discharge valve assembly 106 and the pressure within the compression pocket is sufficient to open the discharge valve assembly 106, compressed refrigerant is discharged from compression chamber 52 through discharge port 140 and the discharge valve assembly 106 disposed within discharge valve cavity 12 formed in plate 64 as best seen with reference to
The discharge valve assembly includes a valve seat body 142 defining discharge port 140 in fluid communication with compression chamber 52 and a spherical valve member 144 biased into engagement with a valve seat defined by body 142 by spring 146 to thereby seal the discharge port. A retaining ring 148 secures spring 146 within valve seat body 142. When the fluid pressure within the discharge pocket 56 that is in fluid communication with the discharge port 140 exceeds the pressure necessary to overcome the biasing force of spring 146, the valve will be forced open and refrigerant will be discharged from compression chamber 52 through discharge port 140. The discharged refrigerant is then communicated through discharge cavity 112 to fluid channel 110. Fluid channel 110 defines a passageway to the circular channel forming discharge muffler 108. Discharge muffler 108, and passages 110 and 120, are defined by recesses in inner plate 64 and the sealing engagement of outer plate 70 with inner plate 64 as best seen in
The configuration of discharge muffler passage 108 helps to control noise and reduces the flow velocity. By providing a greater cross sectional area than the discharge port and channel 110, passage 108 reduces the flow velocity of the discharged fluid which facilitates the reduction of noise. Additionally, during operation of the illustrated compressor, compressed refrigerant vapors are discharged through valve 106 on a periodic basis as the individual compression pockets 56 reach the necessary pressure to open valve 106. The periodic discharge of vapors through valve 106 may create a pressure wave within the discharged vapors. By splitting the discharge flow into two separate channels, i.e., branches 116 and 118, which then meet before the compressed fluid enters radial channel 120, the pressure waves present in the two separate channels meet and, if they are out of phase, at least partially destructively interfere with each other, thereby reducing the amplitude of the pressure wave and the vibrations and resulting noise that may be created thereby. By altering the respective lengths of branches 116 and 118 the wavelength of the pressure waves subject to the most destructive interference can also be altered. In the illustrated embodiment, channel 120 is located diametrically opposite channel 110 and branches 116 and 118 have similar lengths, however, in alternative embodiments, it may be advantageous to locate channel 120 such that branches 116 and 118 have unequal lengths to enhance the destructive interference of pressure waves having a selected wavelength. Dashed lines in
Referring to
To inhibit the loss of efficiency and reverse flow as a result of the interaction of vane 54 and slot 62, bushing 60 engages opposite sides of vane 54 and a communication passage 134 (
While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.
