EP3215737B1

EP3215737B1 - Improved rotor for use in an electric motor of a hermetic compressor

Info

Publication number: EP3215737B1
Application number: EP14793100.0A
Authority: EP
Inventors: Bilgin Hacioglu
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2014-11-03
Filing date: 2014-11-03
Publication date: 2021-01-06
Anticipated expiration: 2034-11-03
Also published as: WO2016070898A1; EP3215737A1; PL3215737T3

Description

The present invention relates to a hermetically sealed compressor of a refrigeration appliance such as a domestic refrigerator. The present invention particularly relates to the electric motor of the hermetically sealed compressor. The present invention more particularly relates to the rotor of the electric motor.
Hermetically sealed compressors which are used in refrigeration appliances are commonly known. In general, the refrigeration appliances come with different refrigeration capacities. The refrigeration capacity of the refrigeration appliance generally depends on the refrigeration capacity of the compressor used therein. For facilitating the production and reducing the overall costs, the hermetically sealed compressors having different refrigeration capacities are generally produced as a family of compressors in which the individual compressors differ from each other mainly through a small number of components such as the electric motor, and a small number of modifications made to the size of the cylinder bores, the pistons and the like. Other differences are generally kept minor such that the same or similar components can be used in the assembly of the individual compressors. However, the electric motors with different electric powers have respectively different dimensions, and thus require a corresponding installation space inside the casing, in particular below the cylinder housing.
Prior art document BR9201761 describes a hermetic compressor including a bearing for supporting a vertical eccentric shaft that is fixed to the rotor of an electric motor. WO 1995/27138 A1 discloses a compressor with a pump rotor of an inverted frustoconical shape having a lower nozzle immersed in the oil sump.
The document DE 10 2007 038443 discloses a hermetic compressor which motor rotor comprises a ring element into which the bearing enters and to which the crankshaft is attached. The lower portion providing a tapered shape. To the outer circumferential surface being attached the permanent magnets of the electric motor.
Fig. 1 shows a hermetically sealed compressor (3') which is known from the prior art. This prior art compressor (3') comprises a cylinder housing (4') which has a main bearing (5'), a crankshaft (6') which is journalled into the main bearing (5'), a sump (7') which contains lubricant, and a lubricant pick-up tube (7a') which is partly immersed into the lubricant sump (7'). The prior art compressor (3') further comprises an electric motor (2') which is arranged below the cylinder housing (4'). The prior art electric motor (2') comprises a rotor (1') and a matching stator (10') which respectively have the heights H1'. The rotor (1') comprises a core (8') which has a central through hole (9') for concentrically receiving the crankshaft (6'). The stator (10') comprises a core (11'), a winding (12'), and a central opening (13') for concentrically receiving the rotor core (8'). The rotor core (8') comprises an outer diameter portion (14) with a height H1' which is concentrically arranged into the opening (13') of the stator core (11'), and an inner diameter portion (15') with a height H2' which is press-fitted onto the crankshaft (6).
A problem with the prior art compressor (3') is that the stable operation of the crankshaft (6') is jeopardized with increasing size and power of the electric motor (2'). Therefore, in the hermetically sealed compressor (3') it is generally desired to increase the height B' of the main bearing (5') so as to safeguard the stable operation of the crankshaft (6'). If the height B' of the main bearing (5') is increased in the upward direction, the overall height of the compressor (3') must also be increased. This would impede the lubrication performance. Moreover, this is not desired in view of the increasing transportation costs and the drop in the utilizable volume of the refrigeration appliance. On the other hand if the height B' of the main bearing (5') is increased in the downward direction, the height H2' of the inner diameter portion (15') must be reduced. Then, the clamping force between the inner diameter portion (15') and the crankshaft (6') also decreases. Thus, a secure operation of the crankshaft (6') cannot be maintained.
An objective of the present invention is to provide a rotor for use in an electric motor of a hermetically sealed compressor, and a refrigeration appliance having the same which overcomes the aforementioned drawbacks of the prior art in a cost effective way and which enables a reliable assembly of the rotor and a reliable operation of the crankshaft.
This objective has been achieved by the rotor as defined in claim 1, the electric motor as defined in claim 11, the hermetically sealed compressor as defined in claim 12, and the refrigeration appliance as defined in claim 15. Further achievements have been attained by the subject-matters respectively defined in the dependent claims.
The rotor of the present invention comprises an extending portion which extends downwardly from the lower surface of the outer diameter portion. The extending portion has a tapered shape. At least a part of the through hole within the extending portion is defined by the inner diameter portion which is to be press fitted onto the crankshaft.
With the present invention, particularly by virtue of the downwardly extending portion of the rotor core, the fixation of the rotor to the crankshaft has been improved. Thereby, an electric motor with a comparatively smaller or a comparatively larger size can be reliably installed into the compressor. With the electric motor of the present invention, a power-to-size ratio of the hermetically sealed compressor has also been improved. With the rotor of the present invention, it becomes also possible to utilize a comparatively longer main bearing without the need of increasing the overall height of the compressor. With the present invention, a hermetically sealed compressor has been provided which can be reliably operated even at comparatively high refrigeration capacities involving comparatively large sized electric motors and high rotational speeds. Thereby, a consumer satisfaction can be increased.
In an embodiment, the rotor core comprises an inner tubular portion for picking up lubricant from the lubricant sump. At least a part of the through hole within the extending portion is defined by the inner tubular portion. With the present invention, particularly by virtue of the inner tubular portion, the rotor core also serves as a lubricating device. Thereby, the need for installing a separate lubricant pick-up tube has been obviated.
In another embodiment, the rotor core has a divider. The divider improves the lubrication performance of the extending portion.
In another embodiment, the rotor has a laminated core.
In an alternative embodiment, the rotor has a solid core.
Additional advantages of the rotor, the electric motor and the hermetically sealed compressor of the present invention will become apparent with the detailed description of the embodiments with reference to the accompanying drawings in which:

Figure 1 - is a schematic sectional view of a hermetically sealed compressor according to the prior art;
Figure 2 - is a schematic sectional view of a hermetically sealed compressor which has a rotor according to an embodiment of the present invention;
Figure 3 - is a schematic side view of a rotor according to another embodiment of the present invention;
Figure 4 - is a schematic sectional view of the rotor according to an embodiment of the present invention, taken along the line A-A of Fig. 3;
Figure 5 - is a schematic sectional view of a hermetically sealed compressor which has a rotor according to another embodiment of the present invention;
Figure 6 - is a schematic side view of a rotor according to another embodiment of the present invention;
Figure 7 - is a schematic sectional view of the rotor according to an embodiment of the present invention, taken along the line B-B of Fig. 6;
Figure 8 - is a schematic perspective view of the rotor according to an embodiment of the present invention;
Figure 9 - is a schematic perspective view of the rotor according to another embodiment of the present invention.

The reference signs appearing on the drawings relate to the following technical features.

1. Rotor
2. Motor
3. Compressor
4. Cylinder housing
5. Main bearing
6. Crankshaft
7. Sump
7a Tube
8. Core
9. Hole
10. Stator
11. Core
12. Winding
13. Opening
14. Portion
15. Portion
16. Portion
17. Portion
18. Portion
19. Abutment
20. Divider
21. Gap
22. Piston
23. Cylinder chamber
24. Rod
25. Pin
26. Cylinder head
27. Exhaust chamber
28. Exhaust port
29. Valve
30. Silencer
31. Intake port
B: Height of the main bearing (5)
H1: Height of the stator core (11)
H1: Height of the outer diameter portion (14)
H2: Height of the inner diameter portion (15)

The rotor (1) is suitable for use in an electric motor (2) of a hermetically sealed compressor (3) (Fig. 2 to 9).
The compressor (3) comprises a cylinder housing (4) which has a main bearing (5), a crankshaft (6) which is journalled into the main bearing (5), and a lubricant sump (7).
The rotor (1) comprises a core (8) which has a central through hole (9) for concentrically receiving the crankshaft (6).
The electric motor (2) comprises a stator (10) which has a core (11), a winding (12), and a central opening (13) for concentrically receiving the rotor core (8).
The rotor core (8) further comprises an outer diameter portion (14) and an inner diameter portion (15). The outer diameter portion (14) has a substantially constant outer diameter that is slightly smaller than the inner diameter of the central opening (13). The outer diameter portion (14) has a height H1 which is equal to the height H1 of the stator core (11). The inner diameter portion (15) has a substantially constant inner diameter for receiving the crankshaft (6) by press fitting. The inner diameter portion (15) has a height H2.
In the rotor (1) of the present invention, the rotor core (8) further comprises an extending portion (16) which extends downwards from the lower surface of the outer diameter portion (14). The extending portion (16) has a tapered shape. At least a part of the through hole (9) within the extending portion (16) is defined by the inner diameter portion (15). Thereby, the rotor core (8) can be press fitted onto the corresponding segment of the crankshaft (6) via the extending portion (16).
In an embodiment, the rotor core (8) further comprises an enlarged inner diameter portion (17) for receiving the main bearing (5). The enlarged inner diameter portion (17) has a substantially constant and relatively larger inner diameter in comparison to the inner diameter of the inner diameter portion (15). The enlarged inner diameter portion (17) is positioned above the inner diameter portion (15). At least a part of the through hole (9) within the outer diameter portion (14) is defined by the enlarged inner diameter portion (17) (Fig. 2 to 9).
In another embodiment, the through hole (9) within the outer diameter portion (14) is entirely defined by the enlarged inner diameter portion (17). In this embodiment, the outer diameter portion (14) and the enlarged inner diameter portion (17) have the same height (H1) so that the tip of main bearing (5) is adjacent to the lower surface of the of the outer diameter portion (14) (Fig. 2 and 5).
In another embodiment, at least a part of the through hole (9) within the outer diameter portion (14) is also defined by the inner diameter portion (15). In this embodiment, the inner diameter portion (15) is positioned both in the extending portion (16) and the outer diameter portion (14) (Fig. 3 to 4, and 6 to 9).
In another embodiment, the rotor core (8) comprises an inner tubular portion (18) for picking up lubricant from the lubricant sump (7). At least a part of the through hole (9) within the extending portion (16) is defined by the inner tubular portion (18). The inner tubular portion (18) is positioned below the inner diameter portion (15). In the mounted state, the extending portion (16), in particular the inner tubular portion (18) is partly immersed into the lubricant sump (7) (Fig. 5 to 9).
In another embodiment, the inner tubular portion (18) has a substantially constant and relatively smaller inner diameter in comparison to the inner diameter of the inner diameter portion (15) (Fig. 5 to 9).
In another embodiment, the rotor (1) comprises an abutment (19) for contacting the tip of the crankshaft (6). The abutment (19) is defined by the step between the inner diameter portion (15) and the inner tubular portion (18) (Fig. 5 to 9).
In another embodiment, the rotor core (1) comprises a divider (20) (Fig. 9).
In another embodiment, the divider (20) is diametrically disposed into the inner tubular portion (18).
In another embodiment, the rotor core (8) comprises a plurality of stacked laminations (not shown). In this embodiment, the entire rotor core (8), including the outer diameter portion (14) and the extending portion (16) are produced by stacking a plurality of laminations.
In an alternative embodiment, the rotor core (8) is a single piece. In this embodiment, the entire rotor core (8), including the outer diameter portion (14) and the extending portion (16) are produced as a solid core (8).
The present invention also provides an electric motor (2) for use in the hermetically sealed compressor (3) of a refrigeration appliance. The electric motor (2) of the present invention comprises the rotor (1) and the stator (10). In the electric motor (2), a gap (21) is provided between the rotor (1) and the stator (10).
The present invention also provides a hermetically sealed compressor (3) which comprises the electric motor (2).
In another embodiment, the electric motor (2) is arranged under the cylinder housing (4) (Fig. 2 to 9).
In another embodiment, the tip of the extending portion (16) is partly immersed into the lubricant sump (7) (Fig. 5 to 9). In this embodiment, the inner tubular portion (18) pumps lubricant from the sump (7) to the crankshaft (6) under the action of the centrifugal forces (Fig. 5 to 9).
In the subsequent description, the operation of the hermetically sealed compressor (3) will be briefly explained by way of example. The compressor (3) is hermetically sealed by the upper casing and the lower casing. The lower casing serves as the lubricant sump (7). The extending portion (16) of the rotor (1) is partly immersed into the lubricant sump (7). The lubricant enters the inner tubular portion (18) via the through hole (9). When the crankshaft (6) is rotated by the motor (2), the extending portion (16) sets the lubricant therein into whirling motion, and the lubricant starts ascending along the inner surface of the inner tubular portion (18) into the lubricant passageway (not shown) of the crankshaft (6), and therefrom to the bearing regions of the piston (22) and the crankshaft (6). The piston (22) is reciprocatingly disposed into the cylinder chamber (23) for compressing the refrigerant therein. The piston (22) is coupled via the rod (24) and the pin (25) to the crankshaft (6). The cylinder chamber (23) is covered by the cylinder head (26). As the piston (22) moves forwards, the compressed refrigerant enters the exhaust chamber (27) of the cylinder head (26) via the exhaust port (28) of the valve (29) which is arranged between the cylinder head (26) and the cylinder chamber (23). As the piston (22) moves rearwards, the refrigerant is sucked through the silencer (30) and the intake port (31) of the valve (29) into the cylinder chamber (23) (Fig. 5 to 9).
In the present invention, the rotor (1) can be alternatively utilized in combination with an auxiliary lubricant pick up tube (7a) which is mounted into the tip of the crankshaft (6) (Fig. 2 to 4).
The present invention also provides a refrigeration appliance (not shown), in particular a domestic refrigerator which comprises the hermetically sealed compressor (3) (Fig. 2 to 9).
With the rotor (1) of the present invention, the assembly of the electric motor (2) with the hermetically sealed compressor (3) has been improved. With the electric motor (2) of the present invention, a power-to-size ratio of the hermetically sealed compressor (3) has also been improved. Thereby, a consumer satisfaction can be increased.

Claims

A hermetically sealed compressor (3) comprising
- a cylinder housing (4) which has a main bearing (5),

- a crankshaft (6) which is journalled into the main bearing (5),

- a lubricant sump (7), and

- an electric motor (2) with a rotor (1) comprising a core (8) which has a central through hole (9) for concentrically receiving the crankshaft (6), the electric motor (2) further comprising a stator (10) which has a core (11), a winding (12), and a central opening (13) for concentrically receiving the rotor core (8),
wherein the rotor core (8) comprises

- an outer diameter portion (14) which has a substantially constant outer diameter that is slightly smaller than the inner diameter of the central opening (13), and a height H1 which is equal to the height H1 of the stator core (11) and

- an inner diameter portion (15) which has a substantially constant inner diameter for receiving the crankshaft (6) by press fitting, and a height H2,

- an extending portion (16) which extends downwards from the lower surface of the outer diameter portion (14) and has a tapered shape, wherein at least a part of the through hole (9) within the extending portion (16) is defined by the inner diameter portion (15),

- an inner tubular portion (18) for picking up lubricant from the lubricant sump (7), wherein at least a part of the through hole (9) within the extending portion (16) is defined by the inner tubular portion (18), and wherein the inner tubular portion (18) is positioned below the inner diameter portion (15).
The hermetically sealed compressor (3) according to claim 1, characterized in that the rotor core (8) further comprises an enlarged inner diameter portion (17) which has a substantially constant and relatively larger inner diameter for receiving the main bearing (5), wherein at least a part of the through hole (9) within the outer diameter portion (14) is defined by the enlarged inner diameter portion (17), and wherein the enlarged inner diameter portion (17) is positioned above the inner diameter portion (15).
The hermetically sealed compressor (3) according to claim 1 or 2, characterized in that at least a part of the through hole (9) within the outer diameter portion (14) is defined by the inner diameter portion (15).
The hermetically sealed compressor (3) according to any of claims 1 to 4, characterized in that the inner tubular portion (18) has a substantially constant and relatively smaller inner diameter.
The hermetically sealed compressor (3) according to claim 4, characterized by an abutment (19) for contacting the tip of the crankshaft (6), wherein the abutment (19) is defined by the interface between the inner diameter portion (15) and the inner tubular portion (18).
The hermetically sealed compressor (3) according to any one of claims 4 or 5, characterized in that the rotor core (1) comprises a divider (20).
The hermetically sealed compressor (3) according to claim 6, characterized in that divider (20) is diametrically disposed into the inner tubular portion (18).
The hermetically sealed compressor (3) according to any one of claims 1 to 7, characterized in that the rotor core (8) comprises a plurality of stacked laminations.
The hermetically sealed compressor (3) according to any one of claims 1 to 7, characterized in that the rotor core (8) is a single piece.
The hermetically sealed compressor (3) according to claim 9, characterized in that the electric motor (2) is disposed under the cylinder housing (4).
The hermetically sealed compressor (3) according to claim 10, characterized in that the tip of the extending portion (16) is immersed into the lubricant sump (7).
A refrigeration appliance, in particular a domestic refrigerator characterized by a hermetically sealed compressor (3) as defined in any one of claims 1 to 11.