WO2012041259A1

WO2012041259A1 - Variable capacity compressor with line-start btushles permanent magnet motor

Info

Publication number: WO2012041259A1
Application number: PCT/CN2011/080488
Authority: WO
Inventors: Vincent Fargo; Pingshan Cao; Xin Li; Qiang Liu
Original assignee: Emerson Electric Co.
Priority date: 2010-09-30
Filing date: 2011-09-30
Publication date: 2012-04-05
Also published as: EP2622224A1; CN102444580B; EP2622224A4; WO2012041259A8; CN102444580A; US20140147294A1

Abstract

A variable capacity compressor assembly (20) configured for variable capacity modulation includes a housing (30), with a compressing mechanism (22) and a driving mechanism (24) disposed within the housing. The compressing mechanism includes compressing members (54, 56) that are shiftable relative to one another between loaded and unloaded states. The driving mechanism includes a line-start brushless permanent magnet motor (26). The line-start brushless permanent magnet motor includes a plurality of permanent magnets (102) that are mounted on, and extend generally axially along, a rotor core body (90) of the motor. Using the motor may reduce manufacture cost, maintain conveniently, and increase reliability.

Description

VARIABLE CAPACITY COMPRESSOR WITH

LINE-START BRUSHLESS PERMANENT MAGNET MOTOR

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001 ] This application claims the benefit and priority of Chinese Patent Application for Invention No. 201010537890.1 , filed on September 30, 2010. The entire disclosure of the above application is incorporated herein by reference.

FIELD

[0002] The present disclosure relates generally to a variable capacity compressor assembly configured to provide variable capacity modulation. More specifically, the present disclosure relates to a variable capacity compressor including a compressing mechanism with mechanical elements shiftable between loaded and unloaded states, wherein the compressing mechanism is driven by a driving mechanism including a line-start brushless permanent magnet motor.

BACKGROUND

[0003] Compressors are commonly used in a variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system to provide a desired heating or cooling effect. For example, some traditional air conditioning systems often use a compressor that is either working at maximum capacity, or is switched off, in order to regulate the temperature of the room. A thermostat can be used to measure the ambient air temperature and switch the compressor on when the ambient air temperature is too far from the desired temperature.

[0004] One way to meet the varying cooling demand is to vary (or modulate) the capacity of the compressor. A particular type of compressor that has been generally effective in this area is the scroll compressor, in which a pair of scroll members cooperate to compress a working fluid (e.g., coolant in liquid or gas phase). A scroll compressor typically includes two main groups of components: a mechanical compressing device including the scrolls, and an electrical motor driving device to move at least one of the scrolls. Either of these components, the compressing device or the driving device, may be manipulated to modulate the capacity of the compressor.

[0005] Conventionally, the electrical motor driving device has been manipulated to modulate the capacity of the compressor. For example, inverter technology operates on the principle of variable compressor motor speed, wherein an electrical signal is given to the compressor motor to make it rotate faster or slower, depending on the load. If the load is high, the compressor motor rotates at a faster speed and delivers higher capacity; conversely, if the load is low, the compressor motor rotates at a lower speed to deliver lower output.

[0006] Traditional variation of compressor motor speed, therefore, has incorporated within the compressor assembly either a two-speed motor, or a full variable speed motor. Both of these known motors have been satisfactory in some respects, but also present drawbacks. For example, the two-speed motor is very complicated to manufacture and often produces merely adequate performance results. The full variable speed motor often achieves increased system performance over a two-speed motor, but requires a complex and expensive drive unit to continuously vary the motor speed. The complexity of these prior art systems to vary compressor motor speed not only require additional manufacturing costs, but can also lead to maintenance and/or reliability issues.

SUMMARY

[0007] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0008] A variable capacity compressor assembly is configured to provide variable capacity modulation. The compressor assembly includes a housing, a compressing mechanism disposed within the housing and including first and second mechanical elements. The mechanical elements are shiftable relative to one another between a loaded state and an unloaded state. The driving mechanism is disposed within the housing and drivingly engages at least one of the mechanical elements for causing the mechanical elements to move relative to one another. The driving mechanism includes a line-start brushless permanent magnet motor. The motor including a stator and a rotor rotatable about an axis and spaced away from the stator. The rotor includes a rotor core body and a plurality of permanent magnets mounted on the rotor core body. The permanent magnets extend generally axially along the rotor core body.

[0009] A variable capacity compressor assembly is configured to provide variable capacity modulation including a compressing mechanism disposed within a housing with first and second mechanical elements shiftable relative to one another between a loaded state and an unloaded state, and a driving mechanism disposed within the housing for drivingly engaging one of the mechanical elements to cause the mechanical elements to move relative to one another. The improvement comprises combining the shiftable mechanical elements with a single-speed, line-start brushless permanent magnet motor operable to drive the one of the mechanical elements. The motor includes a stator and a rotor rotatable about an axis and spaced away from the stator. The rotor includes a rotor core body and a plurality of permanent magnets mounted on the rotor core body. The permanent magnets extend generally axially along the rotor core body.

[0010] A method of delivering increased compressor efficiency at lower incremental cost within a variable capacity compressor assembly configured to provide variable capacity modulation, wherein the compressor includes first and second scroll members generally axially shiftable relative to one another between a loaded state and an unloaded state, said method includes driving one of the scroll members with a single-speed, line-start brushless permanent magnet motor, such that the driven scroll member moves in a generally orbital relationship relative to the other scroll member to thereby compress a working fluid when the scrolls are in the loaded state, and shifting the scroll members into the unloaded state during continuous operation of the single-speed motor to thereby efficiently modulate capacity of the compressor without the expense of a complex drive unit to vary motor speed.

[001 1 ] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. DRAWINGS

[001 2] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[001 3] FIG. 1 is an isometric view of a variable capacity compressor assembly configured to provide variable capacity modulation constructed, with a compressing mechanism and a driving mechanism including a line-start brushless permanent magnet motor assembly disposed therein, in accordance with the present disclosure;

[0014] FIG. 2 is a sectional view of the variable capacity compressor assembly, taken approximately through the middle of the compressor assembly of FIG. 1 , depicting internal details of construction of the compressing mechanism including first and second mechanical elements, and of the driving mechanism including rotor and stator assemblies of the line-start brushless permanent magnet motor, in accordance with the present disclosure;

[001 5] FIG. 3 is an isometric view of the line-start brushless permanent magnet motor assembly included in the driving mechanism of the variable capacity compressor assembly shown in FIGS. 1 -2, illustrating the rotor and stator assemblies, in accordance with the present disclosure;

[001 6] FIG. 4 is a sectional view of the line-start brushless permanent magnet motor assembly, taken approximately through the middle of the motor assembly of FIG. 2, depicting internal details of construction of the rotor assembly, including a plurality of permanent magnets disposed therein, in accordance with the present disclosure;

[001 7] FIG. 5 is a sectional view of another variable capacity compressor assembly, in accordance with the present disclosure;

[001 8] FIG. 6 is a sectional view of another variable capacity compressor assembly, in accordance with the present disclosure;

[001 9] FIG. 7 is a sectional view of another variable capacity compressor assembly, in accordance with the present disclosure; and

[0020] FIG. 8 is a sectional view of another variable capacity compressor assembly, in accordance with the present disclosure.

[0021 ] The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiments.

[0022] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRI PTION

[0023] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0024] The present disclosure is susceptible of embodiment in many different forms. While the drawings illustrate, and the specification describes, certain preferred embodiments of the disclosure, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present disclosure to the particular disclosed embodiments. [0025] The present disclosure provides a variable capacity compressor assembly configured for variable capacity modulation, wherein a mechanical compressing device is manipulated to modulate the capacity of the compressor. For example, in a variable capacity, pulse width modulated (loaded and unloaded) scroll compressor, the mechanical scrolls of the compressing mechanism are moved relative to one another to modulate the capacity of the compressor, while the electrical motor driving the compressing device is run at a generally constant speed.

[0026] Variable capacity, pulse width modulated scroll compressor technology operates on the principle of loading and unloading of the scrolls. While the motor runs at a generally constant speed, the scrolls are engaged and disengaged periodically in order to provide durations of "full capacity" and "no capacity" of the compressing device. Time averaging of the loading and unloading states results in an effectively infinitely variable capacity output. Other mechanical compressor capacity modulation technologies may also be used to vary the capacity of the compressor while the electric motor driving the compressing device is operated at a generally constant speed. Additional examples of mechanical compressor capacity modulation technology, as described in further detail below, include: delayed suction devices, blocked suction devices, pulse width modulation of delayed suction devices, and pulse width modulation of blocked suction devices. Further, these compressor capacity modulation technologies may be utilized with scroll compressors, reciprocating compressors, rotary vane compressors, and the like.

[0027] Eliminating some of the complexity of prior art modulating systems that rely upon traditional variation of compressor motor speed, such as via a two-speed motor, or a full variable speed motor, may reduce manufacturing and/or maintenance costs and provide enhanced reliability. Furthermore, manipulation of the mechanical compressing device can lead to quicker and more efficient transitions between capacity loading states. Embodiments of the present disclosure improve overall system efficiency by driving the mechanical compressing device at a generally constant speed with a line-start brushless permanent magnet motor.

[0028] Improving the efficiency of the electric motor driving the mechanical compressing device, often one of the highest power-consuming components of a compressor assembly, can improve overall compressor system efficiency. It is believed that a refrigeration system incorporating the variable capacity compressor assembly with the line-start brushless permanent magnet motor of the present disclosure provides improved overall system performance to meet high efficiency standards (e.g., seasonal efficiency energy rating). Moreover, it is believed that the variable capacity compressor incorporating the line-start brushless permanent magnet motor of the present disclosure can achieve new Chinese Level 1 efficiencies.

[0029] Some embodiments of the present disclosure may even offset a considerable portion of material cost incurred by incorporating permanent magnets in a rotor assembly of the line-start brushless permanent magnet motor by using a stator assembly with a winding formed of aluminum. It has been unexpectedly determined that such a construction of a line-start brushless permanent magnet motor with windings formed of aluminum (a material not ordinarily used in windings for high-performance motors) exhibited only a slight performance difference compared to a line-start brushless permanent magnet motor with traditional copper windings. [0030] According to one aspect of the present disclosure, a variable capacity compressor assembly is provided that is configured to provide variable capacity modulation. The compressor assembly includes a housing and a compressing mechanism disposed within the housing that includes first and second mechanical elements. The mechanical elements are shiftable relative to one another between a loaded state and an unloaded state. The compressor assembly further includes a driving mechanism disposed within the housing that drivingly engages at least one of the mechanical elements for causing the mechanical elements to move relative to one another. The driving mechanism includes a line-start brushless permanent magnet motor. The motor includes a stator and a rotor rotatable about an axis and spaced away from the stator. The rotor includes a rotor core body and a plurality of permanent magnets mounted on the rotor core body. The permanent magnets extend generally axially along the rotor core body.

[0031 ] According to another aspect of the present disclosure, in a variable capacity compressor assembly configured to provide variable capacity modulation, which includes a compressing mechanism disposed within a housing with first and second mechanical elements shiftable relative to one another between a loaded state and an unloaded state, and a driving mechanism disposed within the housing for drivingly engaging one of the mechanical elements to cause the mechanical elements to move relative to one another, the improvement includes combining the shiftable mechanical elements with a single-speed, line-start brushless permanent magnet motor operable to drive the one of the mechanical elements. The motor includes a stator and a rotor rotatable about an axis and spaced away from the stator. The rotor includes a rotor core body and a plurality of permanent magnets mounted on the rotor core body. The permanent magnets extend generally axially along the rotor core body.

[0032] Another aspect of the present disclosure concerns a method of delivering increased compressor efficiency at lower incremental cost within a variable capacity compressor assembly configured to provide variable capacity modulation, wherein the compressor includes first and second scroll members generally axially shiftable relative to one another between a loaded state and an unloaded state. The method includes the step of driving one of the scroll members with a single-speed, line-start brushless permanent magnet motor, such that the driven scroll member moves in a generally orbital relationship relative to the other scroll member to thereby compress a working fluid when the scrolls are in the loaded state. The method also includes the step of shifting the scroll members into the unloaded state during continuous operation of the single-speed motor to thereby efficiently modulate capacity of the compressor without the expense of a complex drive unit to vary motor speed.

[0033] Various other aspects and advantages of the present disclosure will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures.

[0034] With reference to FIGS. 1 -2, a variable capacity compressor assembly 20 constructed in accordance with the principles of an embodiment of the present disclosure is depicted for use in various applications. The compressor assembly 20 is configured to provide variable capacity modulation. The compressor assembly 20 may be used in a variety of industrial and residential applications including, for example, an HVAC, refrigeration, heat pump, or chiller system. [0035] With reference to FIG. 2, the compressor assembly 20 broadly includes a compressing mechanism 22 configured to provide variable capacity modulation, and a driving mechanism 24 including a line-start brushless permanent magnet motor assembly 26, described in further detail below with reference to FIGS. 3-4.

[0036] Some conventional structural aspects of the compressor assembly 20 are described herein only relatively briefly. Nevertheless, it will be appreciated that various structural details of the compressor assembly 20 will be readily understood by one of ordinary skill in the art.

[0037] With reference to FIGS. 1 and 2, components of the compressor assembly 20 are contained within an internal chamber 28 that is broadly defined by a case in the form of a housing 30. As shown, the housing 30 is substantially sealed such that the internal chamber 28 is hermetically sealed from an outside environment. The housing 30 is generally cylindrical and presents opposite top and bottom axial margins 32, 34. The housing 30 comprises a shell element 36, a base 38 disposed generally adjacent the bottom margin 34, and a cap 40 disposed generally adjacent the top margin 32.

[0038] While the internal chamber 28 is hermetically sealed from an outside environment, some elements (e.g., electrical power and a working fluid to be compressed) must pass through the housing 30 through specific sealed passageways. In this regard, the compressor assembly 20 includes a compressor power connector 42 disposed on the shell element 36. The compressor power connector 42 is in electrical communication with an appropriate element of the line-start brushless permanent magnet motor assembly 26 described below. [0039] Furthermore, the compressor assembly 20 includes an inlet 44 disposed on the shell element 36, and an outlet 46 disposed on the cap 40 to transport compressible working fluid (e.g., coolant in liquid or gas phase) into and out of the internal chamber 28 of the compressor assembly 20. The specific dispositions of the inlet 44 and the outlet 46 could be altered without departing from the teachings of the present disclosure.

[0040] With reference to FIG. 2, the compressor assembly 20 includes the compressing mechanism 22 and the driving mechanism 24 including the motor assembly 26, described in detail below, disposed within the housing 30. The compressor assembly 20 further includes an upper bearing assembly 48 and a lower bearing assembly 50 for rotatably supporting a shaft 52 of the driving mechanism 24 and components of the compressing mechanism 22.

[0041 ] The compressing mechanism 22 includes first and second mechanical elements, depicted in the form of scroll members 54, 56 that cooperate to compress a working fluid. In the illustrated embodiment, the first scroll member 54 is rotatably fixed relative to the second scroll member 56. The first scroll member 54 is also axially shiftably secured relative to the second scroll member 56 within the internal chamber 28 in a manner generally known in the art. The second scroll member 56 is operably coupled with the driving mechanism 24 to be drivingly connected to the shaft 52 of the motor assembly 26 via a crankpin 58 and a drive bushing 60, such that the second scroll member 56 is orbitally moveable relative to the first scroll member 54, as described in detail below. [0042] The non-orbiting scroll member 54 and the orbiting scroll member 56 are positioned in meshing engagement with one another, and a suitable conventional coupling 57 permits generally eccentric orbital motion (along an annular path) therebetween, but prevents relative spinning motion therebetween.

[0043] A partition plate 62 is provided generally adjacent the top margin 32 of the housing 30 and serves to divide the internal chamber 28 into a discharge chamber 64 at the upper end thereof and a suction chamber 66 at the lower end thereof.

[0044] When the first non-orbiting scroll member 54 and the second orbiting scroll member 56 are shifted axially relative to one another into a first position corresponding with a loaded state, the compressing mechanism 22 is configured to compress a working fluid and run at full (100%) capacity during rotation of the motor assembly 26 of the driving mechanism 24. Alternatively, when the first non-orbiting scroll member 54 and the second orbiting scroll member 56 are shifted axially relative to one another into a second position corresponding with an unloaded state, the compressing mechanism 22 is configured such that it does not compress the working fluid and runs at no (0%) capacity, even during continued rotation of the motor assembly 26 of the driving mechanism 24. In this way, the capacity of the variable capacity scroll compressor assembly 20 can be changed quickly and efficiently without necessarily altering the speed of the motor assembly 26 of the driving mechanism 24.

[0045] The relative axial disposition between the first non-orbiting scroll member 54 and the second orbiting scroll member 56 may be operably shifted via a control, such as a solenoid valve, as is generally known in the art. Therefore, by appropriately varying the loaded state time and the unloaded state time during any given cycle time, the variable capacity scroll compressor assembly 20 can deliver any capacity desired for a given system. In this way, pulse width modulation can be used, with an appropriate cycle time, to vary the capacity of the compressor assembly 20 to any capacity between 100% capacity and 0% capacity.

[0046] During operation at full (100%) capacity, as the second orbiting scroll member 56 orbits with respect to the first non-orbiting scroll member 54, working fluid to be compressed is drawn into the suction chamber 66 of the internal chamber 28 of the compressor assembly 20 via the inlet 44. From the suction chamber 66, the working fluid moves into a volume-decreasing compression chamber 68 cooperatively defined by portions of the scroll members 54, 56. The intermeshing scroll wraps of the scroll members 54, 56 define moving pockets of working fluid within the compression chamber 68 that progressively decrease in size as they move radially inwardly as a result of the orbiting motion of the second orbiting scroll member 56, thus compressing the working fluid entering via inlet 44. The compressed working fluid is then discharged into the discharge chamber 64 and out of the variable capacity compressor assembly 20 via the outlet 46.

[0047] During operation at no (0%) capacity, even if the second orbiting scroll member 56 orbits with respect to the first non-orbiting scroll member 54, the scroll members 54, 56 are shifted axially away from one another into the unloaded state, such that no suction is generated by the compression chamber 68 and there is no mass flow of the working fluid through the variable capacity compressor assembly 20. Because the variable capacity compressor assembly 20 can run at no (0%) capacity even as the second orbiting scroll member 56 is moving with respect to the first non-orbiting scroll member 54, the compressing mechanism 22 can effectively and efficiently be driven by the driving mechanism 24 including the line-start brushless permanent magnet motor assembly 26 configured as a single-speed motor, as described in detail below.

[0048] As also described in detail below, one embodiment of the line-start brushless permanent magnet motor assembly 26 incorporated within the capacity compressor assembly 20 demonstrated a motor efficiency of approximately 95%. Since a motor assembly of a driving mechanism is often one of the highest power-consuming components of a compressor assembly (or even of an entire system incorporating the compressor assembly, such as an air conditioning system), the efficiency improvements provided by incorporation of the line-start brushless permanent magnet motor assembly 26 in the present disclosure provides significant performance enhancements in the compressor assembly 20. In one embodiment, the compressor assembly 20 including the line-start brushless permanent magnet motor assembly 26, as described below, demonstrated a higher seasonal efficiency energy rating than has been achieved by prior compressor assemblies.

[0049] Many of the components of the compressor assembly 20 are substantially conventional in nature, and various aspects of such components may take alternative forms and/or otherwise vary significantly from the illustrated embodiment without departing from the teachings of the present disclosure. Any such modifications to generally conventional components of the variable capacity compressor assembly 20 are not intended to impact the scope of the present disclosure.

[0050] With continued reference to FIGS. 1 -2 and additional reference to FIGS. 3-4, the line-start brushless permanent magnet motor assembly 26 will be described in further detail. The motor assembly 26 includes a rotor assembly 70, which is rotatable about an axis 72 (FIG. 4) and a stator assembly 74. The rotor assembly 70 includes the axially disposed shaft 52 that is configured for rotation with the rotor assembly 70 and that projects axially outwardly from both ends of the stator assembly 74. While only one exemplary embodiment is depicted here, of course alternative arrangements of suitable rotor and stator assemblies are contemplated and are clearly within the ambit of the present disclosure.

[0051 ] Turning to construction details of the stator assembly 74, the stator assembly 74 depicted in FIGS. 3-4 broadly includes a stator core body 76 and a generally axially concentric winding 78. The illustrated stator core body 76 is comprised of a plurality of axially stacked stator laminations 80 (FIG. 4), as is generally known in the art. It is noted that the winding 78 depicted in FIG. 3 is shown in a conventional schematic form, but that additional details regarding the winding 78 are described below. The particular configuration of the winding 78 may directly impact the power, torque, voltage, operational speed, number of poles, etc. of the motor assembly 26.

[0052] Each individual stator lamination 80 includes a substantially annular steel body, such that the plurality of axially stacked stator laminations 80 forming the stator core body 76 cooperatively presents a generally central axial bore 82 for receiving the rotor assembly 70. An air gap 84 extends radially between the stator core body 76 of the stator assembly 74 and the rotor assembly 70, such that the rotor assembly 70 is able to rotate freely within the stator assembly 74.

[0053] The plurality of axially stacked stator laminations 80 forming the stator core body 76 also cooperatively presents a plurality of generally arcuate slots 86 extending axially therethrough, with each depicted slot 86 being in communication with the air gap 84. Electrically conductive wires make up the winding 78, which passes through the slots 86 for receipt therein. It is noted that in the illustrated embodiment, the stator core body 76 of the stator assembly 74 includes twenty-four slots 86, although various numbers of slots may be alternatively provided without departing from the teachings of the present disclosure.

[0054] The motor assembly 26 of the depicted embodiment is configured as a three-phase motor. Shifting briefly now to operation considerations of three-phase motors, and to details of the windings used therein, a three-phase motor is often more compact and can be less costly than a single-phase motor of the same voltage class and duty rating. In addition, many three-phase motors often exhibit less vibration and may therefore last longer than corresponding single-phase motors of the same power used under the same conditions. The principles of the present disclosure, however, are not limited to a three-phase motor, but also apply with equal force to a single-phase motor. Further, the motor assembly 26 of the depicted embodiment is configured as a single-speed motor.

[0055] The winding 78 comprises a phase winding for each of the three power phases. Winding configurations for three-phase motors are generally known and are not described in detail herein. With reference to FIG. 3, in the depicted embodiment of the present disclosure, the stator assembly 74 includes a power connector 88 that includes three leads to be connected to a power source, with one of each of the leads corresponding to each of the three power phases. As will be readily understood, and with brief reference to FIG. 2, the stator power connector 88 is in electrical communication with the compressor power connector 42 described above.

[0056] It is contemplated that the winding 78 of the line-start brushless permanent magnet motor assembly 26 may comprise copper, or may comprise aluminum as described further below. While it is noted that the winding 78 comprising aluminum may also include other materials (e.g., aluminum alloys or copper-cladded aluminum), the winding 78 of the illustrated embodiment consists essentially of aluminum wire. Additional details and unforeseen advantages of this atypical winding material within the line-start brushless permanent magnet motor assembly 26 will be described in further detail below.

[0057] Turning next to construction details of the rotor assembly 70, and with specific reference to FIG. 4, the rotor assembly 70 broadly includes a rotor core body 90 comprising a plurality of axially stacked rotor laminations 92 integrally formed (such as by die casting) with a plurality of aluminum bars 94. The bars 94 extend axially along the plurality of rotor laminations 92 and may include aluminum rings disposed along respective axial margins thereof. The particular configuration of the bars 94 may directly impact startup operation of the motor assembly 26. Other configurations of bars may be used and are within the ambit of the present disclosure, including, but not limited to, bars that skew helically around the rotor core body 90 or bars that have no skew at all.

[0058] With continued reference to FIG. 4, each individual rotor lamination 92 includes a substantially annular steel body, such that the plurality of axially stacked rotor laminations 92 forming the rotor core body 90 cooperatively presents a radially outer periphery 96 and an axially aligned shaft hole 98 extending axially therethrough to receive the shaft 52. Additionally, the plurality of axially stacked rotor laminations 92 forming the rotor core body 90 further cooperatively presents a plurality of a generally arcuate slots 100 extending axially therethrough, with each slot 100 being disposed at least adjacent (if not in communication with) the radially outer periphery 96. The aluminum bars 94 are formed to pass through the slots 100 to be disposed at least adjacent the radially outer periphery 96 of the rotor core body 90 to cooperatively define at least a portion thereof (if not cooperatively forming an exposed bar a rotor body). It is noted that in the illustrated embodiment, each rotor lamination 92 includes thirty-four slots 100, although various numbers of slots may be similarly provided without departing from the teachings of the present disclosure.

[0059] The rotor assembly 70 further includes a plurality of permanent magnets 102 mounted on the rotor core body 90, with the permanent magnets 102 extending generally axially along the rotor core body 90. In the illustrated embodiment, the permanent magnets 102 are received within generally elongated openings 104 cooperatively defined within the plurality of rotor laminations 92 of the rotor core body 90. At least one of the rotor laminations 92 is disposed in contact with each of the plurality of permanent magnets 1 02 to retain the permanent magnets 102 in place within the rotor core body 90.

[0060] In more detail, and with continued reference to FIG. 4, each of the plurality of permanent magnets 102 is disposed generally parallel to the axis 72. Furthermore, each of the plurality of permanent magnets 102 is disposed substantially adjacent the radially outer periphery 96 of the rotor core body 90. While the permanent magnets 102 mounted on the rotor core body 90 may be present in various numbers and configurations, one advantageous configuration is depicted in the drawings.

[0061 ] In the illustrated configuration, the rotor assembly 70 includes four permanent magnets 102, with each of the permanent magnets 1 02 being of substantially equal size. As can be seen in the sectional view of FIG. 4, the four permanent magnets 1 02 are arranged across a section of the rotor core body 90 in two pairs, with each of the pairs of permanent magnets 102 being generally symmetrical to the other of the pairs of permanent magnets 102 with respect to the axis 72. In the depicted embodiment, each of the permanent magnets 102 of the line-start brushless permanent magnet motor assembly 26 comprises neodymium.

[0062] Turning briefly now to electric motor efficiency, an energy cost associated with the operation of an electric motor over the lifetime of the motor can amount to a significant financial burden for an end user. Thus, an improvement in overall motor efficiency, even if such an improvement is only a relatively small percentage, can result in significant savings in energy costs over the lifetime of the motor. An improvement to motor design or construction resulting in an efficiency gain, therefore, may provide significant competitive advantage, not only for the motor itself, but also for a device (such as the compressor assembly 20) into which the improved motor is incorporated.

[0063] Against the efficiency backdrop above, it is noted that in some embodiments of the present disclosure, the combination within the line-start brushless permanent magnet motor assembly 26 of the rotor assembly 70 including the plurality of permanent magnets 1 02, and the stator assembly 74 including the winding 78 formed of aluminum, yields significant motor performance enhancements at considerably lower incremental cost than has been realized by prior line-start brushless permanent magnet motors. These performance enhancements were unexpected.

[0064] More specifically, a winding formed of aluminum (which is a less expensive material than copper from which to construct a winding) has historically corresponded with a relatively significant loss in overall motor efficiency compared with a winding formed of copper. For example, from previous testing it was observed that in a prior embodiment of an induction motor, a transition from a winding formed of copper to a winding formed of aluminum resulted in a relatively significant loss in overall motor efficiency of approximately 2% (efficiency dropped from approximately 91 % to approximately 89%).

[0065] The correspondence between high efficiency and high cost has made traditional line-start brushless permanent magnet motors a premium category of motors, designed with maximum performance in mind. Further, permanent magnets add significant material cost to an otherwise typical induction motor. Conventional design, therefore, of prior line-start brushless permanent magnet motors has consistently taught that the high-cost, high-grade permanent magnets of the rotor be paired with correspondingly high-cost, high-grade copper windings of the stator.

[0066] In the case of some embodiments of the present disclosure, however, it has been unexpectedly determined that the line-start brushless permanent magnet motor assembly 26 with the winding 78 formed of aluminum exhibited only a slight performance difference compared to a prior line-start brushless permanent magnet motor with copper windings. For example, it was observed that, as opposed to an efficiency drop relatively consistent with that exhibited in the induction motor testing above, the counterintuitive combination of the present disclosure results in a relatively small loss in overall motor efficiency of approximately only one-half of the loss observed in the induction motor testing described above. More specifically, the line-start brushless permanent magnet motor assembly 26 with the winding 78 formed of aluminum exhibited a loss in overall motor efficiency of only approximately 1 % (efficiency dropped from approximately 95% to approximately 94%).

[0067] Moreover, the aluminum material used for the winding 78 of some embodiments of the line-start brushless permanent magnet motor assembly 26 can offset a considerable portion of the material cost of the permanent magnets 102. In one embodiment, as referenced above, the line-start brushless permanent magnet motor assembly 26 with the winding 78 formed of aluminum was constructed for a lower incremental cost than would have been the case had the winding been formed of copper, and the lower-cost motor assembly 26 demonstrated a motor efficiency of approximately 94%.

[0068] It is again emphasized, however, that not all embodiments of the line-start brushless permanent magnet motor assembly 26 include the winding 78 being formed of aluminum. Rather, it is specifically noted that some embodiments of the line-start brushless permanent magnet motor assembly 26 include the winding 78 being formed of copper. Such embodiments of the line-start brushless permanent magnet motor assembly 26 including a copper winding may result in an efficiency of approximately 95%, which may result in even higher overall system performance of the variable capacity compressor assembly 20. [0069] As discussed above, the line-start brushless permanent magnet motor assembly 26 described above may be used in conjunction with other mechanical compressor capacity modulation technologies that vary the capacity of the compressor. For example, the line-start brushless permanent magnet motor assembly 26 described above may be used as the electric motor in compressors that include delayed suction devices, blocked suction devices, pulse width modulation of delayed suction devices, and pulse width modulation of blocked suction devices. Further, the line-start brushless permanent magnet motor assembly 26 described above may be used in scroll compressors, reciprocating compressors, rotary vane compressors, and the like.

[0070] For example, with reference to FIG. 5, a scroll compressor is shown with a delayed suction device and the line-start brushless permanent magnet motor assembly described above. A similar compressor is described in detail in U.S. Pat. No. 7,988,433, issued August 2, 201 1 , titled "Compressor Having Capacity Modulation Assembly," which is incorporated herein by reference in its entirety. In FIG. 5, a compressor 51 0 may include a hermetic shell assembly 512, a compression mechanism 518, a seal assembly 520, a refrigerant discharge fitting 522, a suction gas inlet fitting 526, and a capacity modulation assembly 528. The compressor 510 includes a line-start brushless permanent magnet motor assembly 51 6 in accordance with the above described line-start brushless permanent magnet motor assembly 26, described with reference to FIGS. 2-4. Shell assembly 512 houses the line-start brushless permanent magnet motor assembly 516, compression mechanism 518, and capacity modulation assembly 528. [0071 ] Shell assembly 512 may include a transversely extending partition 534 that defines a discharge chamber 538. Partition 534 may include a discharge passage 544 therethrough providing communication between compression mechanism 51 8 and discharge chamber 538.

[0072] As described above, the motor assembly 516 includes a rotor assembly 560, which is rotatable about an axis 72 (FIG. 4) and a stator assembly 558. The rotor assembly 560 includes an axially disposed shaft 562 that is configured for rotation with the rotor assembly 560 and that projects axially outwardly from both ends of the stator assembly 558.

[0073] Compression mechanism 518 may generally include an orbiting scroll 568 and a non-orbiting scroll 570. The orbiting scroll 568 and non-orbiting scroll 570 may be meshingly engaged with one another defining compression pockets 594, 596, 598, 500, 502, and 504. It is understood that the pockets 594, 596, 598, 500, 502, and 504 change throughout compressor operation.

[0074] A first pocket, pocket 594, may define a suction pocket in communication with a suction pressure region 506 operating at a suction pressure and a second pocket, pocket 504, may define a discharge pocket in communication with a discharge pressure region 508 operating at a discharge pressure via discharge passage 92. Pockets intermediate the first and second pockets, pockets 596, 598, 500, and 502, may form intermediate compression pockets operating at intermediate pressures between the suction pressure and the discharge pressure. [0075] The non-orbiting scroll 570 may include first and second modulation ports 513 and 514, each in fluid communication with one of the intermediate compression pockets.

[0076] Capacity modulation assembly 528 may include a modulation valve ring 526, a modulation lift ring 529. During operation, capacity modulation assembly 528 may operate modulation valve ring 526 and modulation lift ring 529 to open and close the first and second modulation ports 513 and 514. When open (as shown in FIG. 5), the first and second modulation ports 513 vent the corresponding intermediate compression pockets back to suction pressure region 506. With the vented intermediate compression pockets being at suction pressure, compression within the compression mechanism 518 commences with the intermediate compression pockets inward of the first and second modulation ports 51 3 and 514.

[0077] In this way, by delaying the start of compression within the compression mechanism 518, the capacity modulation assembly 528 is able to modulate capacity of the compressor 510 between two capacities, including full capacity (loaded state) and an intermediate capacity (partially unloaded state). Additional modulation ports may also be used such that additional intermediate capacities may be provided.

[0078] Additionally, the capacity modulation assembly 528 may use pulse width modulation. Therefore, by appropriately varying the loaded state time and the partially unloaded state time during any given cycle time, the capacity modulation assembly 528 can deliver any capacity desired for a given system between full capacity and the intermediate capacity. In this way, pulse width modulation can be used, with an appropriate cycle time, to vary the capacity of the compressor 51 0 to any capacity between full capacity and the intermediate capacity.

[0079] In this way, pulse width modulation can be used, with an appropriate cycle time, to vary the capacity of the compressor 510 to any capacity between full capacity and the intermediate capacity.

[0080] With reference to FIG. 6, a reciprocating compressor 600 is shown with a blocked suction device. A similar compressor is described in detail in U.S. Pub. No. 2009/0028723, published January 29, 2009, titled "Capacity Modulation System for Compressor and Method," which is incorporated herein by reference in its entirety. The reciprocating compressor 600 includes a line-start brushless permanent magnet motor assembly in accordance with the above described line-start brushless permanent magnet motor assembly 26, described with reference to FIGS. 2-4. In FIG. 6, the reciprocating compressor 600 includes a manifold 612, a compression mechanism 614, and a discharge assembly. The manifold 61 2 may be disposed in close proximity to a valve plate 607 and may include at least one suction chamber 618. The compression mechanism 614 may similarly be disposed within the manifold 61 2 and may include at least one piston 622 received generally within a cylinder 624 formed in the manifold 612. The discharge assembly may be disposed at an outlet of the cylinder 624 and may include a discharge-valve that controls a flow of discharge-pressure gas from the cylinder 624.

[0081 ] The reciprocating compressor 600 includes a plurality of pistons 610 (shown raised and lowered for illustration purposes only), each having a reed or valve ring 640 slidably disposed within the lower end of the piston 610. Operation of the valve ring 640 is such that discharge-pressure gas on top of the valve ring 640 holds the valve ring 640 against the valve seat 608 when the piston 610 is moved to the "down" position. Discharge-pressure gas above seal 690 is confined by the outside and inside diameter of the seal 690. The valve ring 640 is loaded against the valve seat 608 by the pressure in the piston 61 0 acting against seal 690, which has a high pressure above the seal 690 and a lower pressure (system suction and/or a vacuum) under the seal 690. When the piston 610 is in the unloaded (downward) position and the valve ring 640 is against the valve seat 608, suction gas may have the potential to leak between the upper surface of the valve ring 640 and the bottom surface of seal 690.

[0082] The use of a porting plate 680 provides a means for routing suction or discharge-pressure gas from a solenoid valve 630 to the chambers 620 on top of single or multiple pistons 61 0. The port on the solenoid valve 630 that controls the flow of gas to load or unload the pistons is a "common" port 670, which communicate via control pressure passage 624 to chambers 620. The solenoid valve 630 in this application may be a three-port valve in communication with suction and discharge-pressure gas and a common port 670 that is charged with suction or discharge-pressure gas depending on the desired state of the piston 610.

[0083] Capacity may be regulated by opening and closing one or more of the plurality of pistons 61 0 to control flow capacity. A predetermined number of pistons 61 0 may be used, for example, to block the flow of suction gas to the cylinder 624. The percentage of capacity reduction is approximately equal to the ratio of the number of "blocked" cylinders to the total number of cylinders. Capacity reduction may be achieved by the various disclosed valve mechanism features and methods of controlling the valve mechanism. The valve's control of discharge-pressure gas and suction-pressure gas may also be used in either a blocked suction application or in a manner where capacity is modulated by activating and de-activating the blocking pistons 61 0 using pulse width modulation and an appropriate duty cycle and cycle time. In this way, pulse width modulation can be used, with an appropriate cycle time, to vary the capacity of the compressor 600 to any capacity between full capacity and either no capacity or one or more intermediate capacities, depending on the number of blocking pistons available.

[0084] With reference to FIGS. 7 and 8, a rotary compressor 754 is shown with a capacity modulation device. A similar compressor is described in detail in U.S. Pat. No. RE40,830, issued July 7, 2009, titled "Compressor Capacity Modulation," which is incorporated herein by reference in its entirety. The rotary compressor 754 includes a line-start brushless permanent magnet motor assembly 758 in accordance with the above described line-start brushless permanent magnet motor assembly 26, described with reference to FIGS. 2-4.

[0085] The rotary compressor 754 includes an outer shell 756 within which is disposed a compressor assembly and the motor assembly 758 with the stator 760 and rotor 762 that turns a shaft 766. A compression rotor 772 is eccentrically mounted on and adapted to be driven by the shaft 766. Compression rotor 772 is disposed within cylinder 774 provided in housing 776 and cooperates with a vane 778 (shown in FIG. 8) to compress fluid drawn into cylinder 774 through inlet passage 780. Inlet passage 780 is connected to suction fitting 782 provided in shell 756 to provide a supply of suction gas to compressor 754. [0086] A three-way valve 790 operates to alternately connect between suction gas and discharge gas to control the vane 778. When the three-way valve applies discharge gas to the vane 778, the vane is biased against the compression rotor 772 to load the rotary compressor 754. When the three-way valve applies suction gas to the vane 778, the vane is biased away from the compression rotor 772 (as shown in FIG. 8) to unload the rotary compressor 754.

[0087] Additionally, the three-way valve 790 may be controlled with pulse width modulation to appropriately vary the loaded state time and the unloaded state time during any given cycle time. In this way, pulse width modulation can be used, with an appropriate cycle time, to vary the capacity of the rotary compressor 754 to any capacity between full capacity and the intermediate capacity.

[0088] The preferred forms of the disclosure described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present disclosure. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present disclosure.

Claims

CLAIMS What is claimed is

1 . A variable capacity compressor assembly configured to provide variable capacity modulation, said compressor assembly comprising:

a housing;

a compressing mechanism disposed within the housing and including first and second mechanical elements,

said mechanical elements being shiftable relative to one another between a loaded state and an unloaded state; and

a driving mechanism disposed within the housing and drivingly engaging at least one of the mechanical elements for causing the mechanical elements to move relative to one another, said driving mechanism including a line-start brushless permanent magnet motor,

said motor including a stator and a rotor rotatable about an axis and spaced away from the stator,

said rotor including a rotor core body and a plurality of permanent magnets mounted on the rotor core body,

said permanent magnets extending generally axially along the rotor core body.

2. The variable capacity compressor assembly as claimed in claim 1 , said mechanical elements comprising scroll members.

3. The variable capacity compressor assembly as claimed in claim 2, said driving mechanism further including a drive shaft configured to rotate with the rotor,

said drive shaft being operably coupled with one of the scroll members for causing the one of the scroll members to move in a generally orbital relationship relative to the other of the scroll members.

4. The variable capacity compressor assembly as claimed in claim 3, said scroll members being shiftable generally axially relative to one another between the loaded and unloaded states.

5. The variable capacity compressor assembly as claimed in claim 4, said housing comprising a hermetic shell defining a substantially enclosed space.

6. The variable capacity compressor assembly as claimed in claim 1 ,

said permanent magnets being received within the rotor core body,

said rotor core body comprising a plurality of axially stacked rotor laminations, at least one of said rotor laminations being disposed in contact with the plurality of permanent magnets to retain the same in place.

7. The variable capacity compressor assembly as claimed in claim 6,

said permanent magnets being disposed generally parallel to the axis, said permanent magnets being disposed substantially adjacent a radially outer periphery of the rotor core body.

8. The variable capacity compressor assembly as claimed in claim 7,

said rotor assembly further including a plurality of circumferentially spaced axial bars disposed adjacent the radially outer periphery of the rotor core body to cooperatively define at least a portion thereof.

9. The variable capacity compressor assembly as claimed in claim 8,

said rotor assembly including four substantially equally-sized permanent magnets,

said permanent magnets being arranged in two pairs, with each of the pairs of magnets being symmetrical to the other of the pairs of magnets with respect to the axis.

10. The variable capacity compressor assembly as claimed in claim 9,

said mechanical elements comprising scroll members shiftable generally axially relative to one another between the loaded and unloaded states, said motor assembly defining a single-speed, three-phase motor.

1 1 . The variable capacity compressor assembly as claimed in claim 1 ,

said motor assembly defining a single-speed motor.

12. The variable capacity compressor assembly as claimed in claim 1 1 , said motor assembly defining a three-phase motor.

13. The variable capacity compressor assembly as claimed in claim 1 ,

said stator including a stator core body presenting a plurality of circumferentially spaced axial slots and defining a central bore for receiving the rotor, said stator further including electrically conductive winding coils received within and distributed generally across multiple ones of the axial slots of the stator core body, said winding coils comprising aluminum.

14. The variable capacity compressor assembly as claimed in claim 1 , said permanent magnets comprising neodymium.

15. The variable capacity compressor assembly as claimed in claim 1 , said compressing mechanism comprising a piston and cylinder assembly, and said mechanical elements including a valve to block suction gas to said piston and cylinder assembly.

16. The variable capacity compressor assembly as claimed in claim 1 , said compressing mechanism comprising scroll members and said mechanical elements including a valve to release gas from an intermediate chamber of said scroll members to a suction chamber within said housing.

17. The variable capacity compressor assembly as claimed in claim 1 , said compressing mechanism comprising a rotary vane and a compression rotor and said mechanical elements including a three-way valve to alternately apply suction gas and discharge gas to said rotary vane to bias said rotary vane against and away from said compression rotor.

18. In a variable capacity compressor assembly configured to provide variable capacity modulation including a compressing mechanism disposed within a housing with first and second mechanical elements shiftable relative to one another between a loaded state and an unloaded state, and a driving mechanism disposed within the housing for drivingly engaging one of the mechanical elements to cause the mechanical elements to move relative to one another, wherein the improvement comprises combining the shiftable mechanical elements with a single-speed, line-start brushless permanent magnet motor operable to drive the one of the mechanical elements,

said permanent magnets extending generally axially along the rotor core body.

19. In the variable capacity compressor assembly configured to provide variable capacity modulation as claimed in claim 18,

said mechanical elements comprising scroll members, said driving mechanism further including a drive shaft configured to rotate with the rotor,

20. In the variable capacity compressor assembly configured to provide variable capacity modulation as claimed in claim 19,

said permanent magnets being received within the rotor core body,

21 . In the variable capacity compressor assembly as claimed in claim 18, said compressing mechanism comprising a piston and cylinder assembly, and said mechanical elements including a valve to block suction gas to said piston and cylinder assembly.

22. The variable capacity compressor assembly as claimed in claim 18, said compressing mechanism comprising scroll members and said mechanical elements including a valve to release gas from an intermediate chamber of said scroll members to a suction chamber within said housing.

23. The variable capacity compressor assembly as claimed in claim 18, said compressing mechanism comprising a rotary vane and a compression rotor and said mechanical elements including a three-way valve to alternately apply suction gas and discharge gas to said rotary vane to bias said rotary vane against and away from said compression rotor.

24. A method of delivering increased compressor efficiency at lower incremental cost within a variable capacity compressor assembly configured to provide variable capacity modulation, wherein the compressor includes first and second scroll members generally axially shiftable relative to one another between a loaded state and an unloaded state, said method comprising:

driving one of the scroll members with a single-speed, line-start brushless permanent magnet motor, such that the driven scroll member moves in a generally orbital relationship relative to the other scroll member to thereby compress a working fluid when the scrolls are in the loaded state; and shifting the scroll members into the unloaded state during continuous operation of the single-speed motor to thereby efficiently modulate capacity of the compressor without the expense of a complex drive unit to vary motor speed.

The increased compressor efficiency delivering method of claim 24,

said motor including a stator and a rotor rotatable about an axis and spaced away from the stator, said rotor including a rotor core body and a plurality of permanent magnets mounted on the rotor core body,

said permanent magnets extending generally axially along the rotor core body. 26. The increased compressor efficiency delivering method of claim 25, said scroll members and said single-speed motor being disposed within a hermetic shell defining a substantially enclosed space.