permanent magnet motors

Abstract

A rotor assembly for a permanent magnet electric machine includes a rotor stack having laminated ferromagnetic layers and partial end plates located at opposite axial ends of the rotor stack, wherein each axial end of the rotor carries two partial end plates, each of the partial end plates covering a partial circle and not axially overlapping another partial end plate at the same axial end. The two partial end plates at each axial end are formed from a first axial end plate formed as a first partial annular disk and a second partial end plate formed as a second partial annular disk, the first and second partial end plates being made of stamped metals of different masses.

Description

Technical Field

[0001] The present disclosure relates to a permanent magnet motor. In particular, the present disclosure relates to a brushless permanent magnet motor for a scroll machine, such as a compressor for an automotive HVAC system. Background Art

[0002] The rotor of a compressor with a rigid rotor—that is, one that operates at a speed well below its specific natural frequency—is often equipped with counterweights to balance the moving parts of the compressor mechanism. This is a measure to reduce vibration and stress caused by imbalance. The counterweights can be attached to the rotor itself or to a shaft driven by the rotor. An example of a brushless permanent magnet motor with a counterweight-balanced rotor is a scroll compressor in the HVAC system of an electric or hybrid vehicle.

[0003] The rotor of a brushless motor can be composed of a stack of ferromagnetic sheets alternating with insulating layers. Permanent magnets can be inserted into slots formed in the stack. Typically, the stack is held together by non-ferrous end plates secured by fastening pins that extend axially through the end plates and stack from end to end. The imbalance of the compressor mechanism depends on the overall geometry of the rotor assembly, which includes all components that rotate with the shaft, such as the orbiting scroll.

[0004] While counterweights are therefore necessary to balance the moving parts of the compressor mechanism, they also take up valuable packaging space, especially in motor vehicles where packaging space is very limited. Summary of the Invention

[0005] It would therefore be desirable to produce a rotor for a brushless motor that allows for proper balancing of the compressor mechanism while occupying little volume.

[0006] This is achieved by separate end plates at the axial ends of the rotor, wherein each axial end of the rotor carries two complementary partial end plates, each of which covers a part circle of the end surface and does not axially overlap with the other partial end plate.

[0007] These end plates can be made of non-ferrous materials of different densities, so that even if they are made of the same shape and volume, they will still have different masses. Therefore, the end plates themselves constitute the counterweight without requiring additional space. For example, the first end plate can be made of aluminum or a lightweight aluminum alloy, and the second end plate can be made of brass or another high-density non-ferrous metal (including another non-ferrous alloy).

[0008] Alternatively or additionally, the first and second partial end plates may have different axial thicknesses, such that a thicker one of the partial end plates has a greater mass than a thinner one of the complementary partial end plates.

[0009] The two complementary partial end plates can cover the same angular range around the shaft, such that the gap between the two partial end plates is located on opposite sides of the shaft, offset by 180 degrees from each other. Alternatively, however, the angular range of the first partial end plate can differ from the angular range covered by the second partial end plate, such that the gap between the end plates is offset by an angle beyond 180 degrees, for example, dividing a 360-degree circle into a portion of approximately 180 degrees plus / minus 5 degrees for the first partial end plate and a portion of approximately 160 degrees for the second partial end plate (wherein the gap between the end plates may be approximately 10 degrees in each case). Within these angular ranges, the width of the gap between the partial end plates reduces the angular range of one or both of the partial end plates, such that the total combined angular range of the two partial end plates is less than 360 degrees. Furthermore, extending the larger-mass partial end plates significantly beyond 180 degrees (e.g., beyond 10 degrees) would cause the mass in one end of the partial end plate to cancel the mass in the opposite end of the partial end plate, while unnecessarily increasing the rotor's moment of inertia. Therefore, it is preferred to limit the larger-mass partial end plates to a range of at most 180 degrees.

[0010] Additionally or alternatively, portions of one or both of the end plates on one or both axial sides of the rotor may be machined for fine-tuning the balance of the rotor assembly.

[0011] Using part of the end plate as a counterweight not only provides a space saving alternative to adding counterweights to an assembled rotor or shaft, but also allows for a cost effective stamping of part of the end plate, including any shaft pin holes.

[0012] Further details and advantages will become apparent from the following description of the examples illustrated in the accompanying drawings. The drawings provided herein are for illustration purposes only and are not intended to limit the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In the accompanying drawings,

[0014] Figure 1 shows a schematic cross-sectional view of a scroll compressor embodying a rotor with a counterweight according to the present disclosure;

[0015] Figure 2 The invention discloses a Figure 1 A detailed view of a portion of the rotor;

[0016] Figure 3 Shown Figure 1 and Figure 2 a first perspective view of a rotor; and

[0017] Figure 4 A second perspective view of the rotor of the previous figure is shown. DETAILED DESCRIPTION

[0018] Figure 1 A scroll compressor 10 is shown, which includes a generally cylindrical housing 12 and a cover 14 that seals the housing 12. Since scroll compressors are well known in the art, only those elements relevant to the present disclosure are shown, and any ports, connectors, conduits, and bearings are omitted. The housing 12 of the scroll compressor 10 houses an electric motor 16 and a scroll assembly 18, which consists of a fixed scroll member 20 that remains stationary relative to the housing 12 and an orbiting scroll member 22 that is driven by an eccentric shaft end of a shaft 24. As is well known, each of the fixed scroll member and the orbiting scroll member carries a wrap that forms an involute spiral with a constant spacing between the threads, wherein the spacing defines an eccentric circle of the shaft 24. The wrap of the orbiting scroll member meshes with the wrap of the fixed scroll member 20 and forms two cavities between them. The shaft 24 is fixedly coupled to and rotated by a rotor 26 of the electric motor 16. The rotor 26 is driven by a stator 28 that surrounds the rotor 26 and is fixed to the housing.

[0019] The rotor 26 includes a rotor stack 30 formed of a plurality of rotor laminations 32 and a plurality of permanent magnets (outside the plane of the image). The rotor 26 also includes an upper counterweight arrangement 34 and a lower counterweight arrangement 36 attached to opposite axial ends of the rotor 26 for static balancing of the rotor. The upper counterweight arrangement 34 and the lower counterweight arrangement 36 are initially composed of components similar to each of the counterweight arrangements 34 and 36, including a lightweight section end plate 38 and a heavy section end plate 40 that is heavier than the lightweight section end plate 38. The lightweight section end plates 38 are offset from each other by 180 degrees about the axis of rotation A, while the heavy section end plates 40 may be offset from each other by several degrees to provide for both static and dynamic balancing of the rotating components. Further details are as follows Figure 3 and Figure 4 This is shown and will be discussed below.

[0020] The rotor laminations 32 define a central shaft bore 42, a plurality of magnet slots (outside the plane of the image), and a plurality of pin holes 44. The upper and lower counterweight arrangements 34 and 36 have fastening holes 46 that align with the pin holes 44. A respective fastening pin 48 extends through each of the pin holes 44 and the fastening holes 46 of the upper and lower counterweight arrangements 34 and 36 that align with the respective pin holes 44.

[0021] Although Figure 2 Only a schematic cross section of the upper portion of the rotor 26 including only the upper counterweight arrangement 34 is shown, but Figure 3 and 4 The rotor 26 is shown from the opposite side. Figure 3 An upper counterweight arrangement 34 is shown, Figure 4 A lower counterweight arrangement 36 is shown.

[0022] although Figure 2 and Figure 3 The counterweight arrangement 34 shown is only the upper counterweight arrangement 34, but referring to Figure 2 and Figure 3 The description also applies to Figure 4 A lower counterweight arrangement 36 is shown.

[0023] The counterweight arrangement 34 consists of two partial annular discs 50 and 52. The first partial annular disc 50 is smaller in both its axial thickness and radial width than the second partial annular disc 52. The first partial annular disc 50 forms the light-weight portion end plate 38, while the second partial annular disc 52 forms the heavy-weight portion end plate 40.

[0024] In the example shown, the first partial annular disk 50 is made of aluminum or a light aluminum alloy. In contrast, the second partial annular disk 52 is made of brass or another heavy metal or alloy. As a general rule, the materials of the partial annular disks do not have any ferromagnetic properties.

[0025] In an example such as this, where the partial end plates 38 and 40 are constructed of materials of different densities, the rotary compressor mechanism can be balanced using partial end plates of the same size, shape, and volume by selecting the appropriate materials. However, for mass production, it is more practical to consistently use a first predetermined material for the lightweight partial end plate 38 and another predetermined material for the heavy partial end plate 40. Since the geometry of the rotor assembly is known, the heavy partial end plate 40 can be pre-manufactured with a predetermined thickness, which increases the required counterweight over the angular range covered by the heavy partial end plate 40.

[0026] like Figure 3 and Figure 4 As shown, the angular range covered by the light section end plates 38 is smaller than the angular range covered by the heavy section end plates 40. Each of the heavy section end plates 40 covers up to half a circle, i.e. up to 180 degrees, while the light section end plates 38 each cover an angular range of 125 to 140 degrees. In the example shown, the gaps 58 and 60 between the section end plates 38 and 40 do not extend in a strictly radial direction, but are arranged to be aligned with each other along a straight line. The direction of the gap has little effect on the mass distribution and inertia of the rotor and can be taken into account in the calculations at the design stage. Figure 4 As shown, the gaps 58 and 60 have different widths on at least one axial end of the rotor 26 for dynamic balancing so that the centers of gravity of the heavy end plates 40 on opposing axial ends are offset from each other about the rotation axis A by an angle slightly different than 180 degrees, such as 175 to 179 degrees.

[0027] The rotor is held together by six fastening pins 48 which extend through pin holes 44 in the rotor stack and aligned fastening holes 46 in the partial end plates 38 and 40. The number of fastening pins 48 may vary depending on the number of magnet slots in the rotor for space reasons.

[0028] The two complementary partial end plates 38 and 40 can cover the same angular range around the shaft, such that the gap between the two partial end plates is located on opposite sides of the shaft, offset by 180 degrees from each other. Alternatively, however, the angular range of the lightweight partial end plates 38 can be different from the angular range covered by the heavy partial end plates 40, such that the gap between the complementary partial end plates at one of the axial ends of the rotor stack 30 is offset by an angle other than 180 degrees from each other, for example, dividing a 360-degree circle into a portion of approximately 180 degrees for the angular range covered by the heavy partial end plates and a portion of approximately 160 degrees for the angular range covered by the lightweight partial end plates (wherein the gap between the partial end plates can be up to approximately 10 degrees in each case). Within these angular ranges, the width of the gap between the partial end plates 38 and 40 is reduced by the angular range of one or both of the partial end plates 38 and 40, such that the total combined angular range of the two partial end plates is less than 360 degrees.

[0029] Extending the heavy-mass partial end plate 40 significantly beyond 180 degrees would cause the mass of one end of the partial end plate 40 to offset the mass of the other end of the partial end plate 40, while unnecessarily increasing the moment of inertia of the rotor 26. Therefore, it is preferred to limit the heavy-mass partial end plate 40 to occupy an angular range of approximately 180 degrees or less. The variation in gap width, thickness of the partial end plates, and the angular range covered by each of the partial end plates is determined by the overall geometry of the rotary compressor mechanism, taking into account inertia, space requirements, and overall mass.

[0030] If you can from Figure 4 As can be seen in FIG, each of the fastening pins 48 has an enlarged head 54 that abuts an axial end surface of the partial end plates 38 and 40. Each of the fastening pins 48 extends through one of the partial end plates 38 and 40, through the rotor stack, and through the other of the partial end plates 38 and 40. Typically, each of the fastening pins extends through the lightweight partial end plate 38 on one side and through the heavy partial end plate 40 on the opposite side. At an end 56 opposite the enlarged head 54, each of the fastening pins 48 is riveted to secure the partial end plates 38 and 40 to the rotor stack 30, as shown. Figure 3 shown.

[0031] In a variation of the illustrated construction, the heavy partial end plates 40 on each axial end of the rotor 26 may be composed of two or more stacked stamped sheet layers, thereby allowing a modular approach. The stack of partial end plates constructed in this manner may be made of different or the same materials.

[0032] While the above description constitutes preferred embodiments of the invention, the invention is susceptible to modification, variation, and change.

Claims

1. A rotor for a permanent magnet motor, comprising: a rotor stack of laminated ferromagnetic layers, and end plates at opposite axial ends of the rotor stack, wherein each axial end of the rotor carries two partial end plates, each of said partial end plates covering a part of a circle and not axially overlapping another of said partial end plates at the same axial end, The two end plates at each axial end have different masses. wherein the two partial end plates at the same end of the two axial ends are made of different materials, so that the material of one of the two partial end plates has a higher density than the material of the other partial end plate, and / or Each of the two partial end plates at the same end of the two axial ends covers a corresponding angular range, wherein the two corresponding angular ranges are different from each other.

2. The rotor according to claim 1, wherein The two partial end plates at each axial end are formed by a first axial end plate shaped as a first partial annular disk and a second partial end plate shaped as a second partial annular disk.

3. The rotor according to claim 2, wherein: The first partial annular disk and the second partial annular disk are made of stamped metal.

4. The rotor according to claim 1, wherein: The material of one of the two partial end plates includes copper, and the material of the other partial end plate includes aluminum.

5. The rotor according to claim 1, wherein The two partial end plates at the same end of the two axial ends have different axial thicknesses.

6. The rotor according to claim 1, wherein A partial end plate having a greater mass than another partial end plate extends over a greater angular range than said other partial end plate having a smaller mass.

7. The rotor according to claim 6, wherein: The larger angular range is at most 180 degrees.

8. The rotor of claim 1, further comprising a plurality of fastening pins, each of the fastening pins extending through the rotor stack in an axial direction and passing through exactly one of the two partial end plates at each axial end.

9. The rotor of claim 1, further comprising a plurality of fastening pins, each of the fastening pins extending through the rotor stack in the axial direction and passing through a partial end plate at each axial end that is less than the entire partial end plate located at the axial end.

10. A permanent magnet motor comprising the rotor according to claim 1.

11. The permanent magnet motor according to claim 10, further comprising a motor stator, wherein: The permanent magnet motor is a brushless induction motor.

12. An electrically driven scroll compressor comprising the permanent magnet motor according to claim 10.

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