EP2126357A1

EP2126357A1 - A compressor

Info

Publication number: EP2126357A1
Application number: EP08717669A
Authority: EP
Inventors: Husnu Kerpicci; Gunsu Albas Cirpanli; Tolga Kurtulus
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2007-03-28
Filing date: 2008-03-12
Publication date: 2009-12-02
Also published as: CN101652568B; WO2008116752A1; BRPI0809327A2; CN101652568A

Abstract

The present invention relates to a compressor (1) comprising a casing (2) that holds the elements inside, an electric motor having a rotor (3) and a stator (4), and a cylinder block (6) that provides bearing of the crankshaft (5) axially by an axial sliding bearing (7), wherein the weight effect of the rotor (3) and the crankshaft (5) and the vertical components of forces created during operation are reduced, thus decreasing the frictional forces at the bearing (7).

Description

A COMPRESSOR

[0001] The present invention relates to a reciprocating hermetic compressor wherein the mechanical losses due to friction of the movable components thereof are reduced.

[0002] In reciprocating hermetic compressors utilized in cooling devices, the weights of the rotor and the crankshaft and the forces that are created in the vertical direction during operation are carried by the axial bearing. The axial bearing generally is located between the crankshaft and the cylinder block, and the oil in the compressor casing is conveyed to the axial bearing to decrease the mechanical losses due to friction. Dry friction is created in the axial bearing particularly at the initial start-up of the compressor since there is an insufficient oil film, and the compressor performance decreases due to the increase in torque that the electric motor has to counterbalance. Metal to metal abrasion in the axial bearing increases due to the dry friction created at the initial start-up of the compressor, and the compressor that is supposed to serve for a long period of time is out of service before expected. In this case, particularly in regions wherein there are oscillations in the power network, the compressor cannot start-up and the desired cooling cannot be provided in the cooling device.

[0003] In the United States of America Patent No US4632644, the weights of the rotor and the crankshaft are carried by a roller bearing instead of an axial sliding bearing.

[0004] In the European Patent Application No EP1740833, a magnetic axial bearing arrangement in a reciprocating hermetic compressor is explained. The magnetic axial bearing is formed of two ring shaped magnets positioned oppositely with the like poles of each facing the other. One of magnets forming the magnetic axial bearing is connected to the cylinder block or an external bearing connected to the cylinder block. The other magnet opposite thereof is connected to the crankshaft or the rotor. In this implementation, stop surfaces had to be formed on both opposite surfaces of the axial bearing in addition to the magnets for averting metal to metal friction. The stop surfaces ensure that the opposite sides do not contact in the event that the magnets cannot function due to reasons of shaking, expansion in high temperature and heavy work conditions. Furthermore, the said axial bearings carrying the vertical loads have to be processed with fine tolerances suitable for the magnets.

[0005] The object of the present invention is to design a compressor wherein the mechanical losses due to friction of the movable components are reduced with a simple and low cost arrangement.

[0006] The compressor designed to fulfill the objective of the present invention, explicated in the first claim and the respective claims thereof, comprises an electric motor having a rotor and a stator, operating in a casing, a crankshaft connected to the rotor core that transmits the rotational movement of the rotor, a cylinder block situated at the upper side of the motor and an axial sliding bearing that provides the crankshaft to be beared to the cylinder block in the axial direction and a rotor weight reducing arrangement assembled underside the rotor while remaining inside the casing.

[0007] The rotor weight reducing arrangement is formed of two magnets positioned oppositely such that the like poles face each other on separate, opposite surfaces, being spaced apart under normal conditions, not connected to the cylinder block above the rotor and between casing and the underside of the rotor and the crankshaft, not contacting each other as per the design of the compressor. As long as heavy load and impact conditions are absent, under normal work conditions the distance between the casing and the rotor and crankshaft group stays virtually constant. The first magnet is immobilized to a point supported by the casing, for example to an element immobilized to the casing or to the stator connected to the casing, and the second magnet is immobilized under the rotor and the crankshaft group, the rotor and the crankshaft are supported from bottom upwards by the second magnet that is pushed by the first magnet.

[0008] The weights of the rotor and the crankshaft are reduced, being supported by the rotor weight reducing arrangement from bottom upwards and consequently the forces applied by the crankshaft to the axial bearing on the cylinder block are reduced. «

[0009] In an embodiment of the present invention, the magnets are selected such that the repelling force therebetween is less that the weight of the rotor and the crankshaft and thus the friction force between the cylinder block and the crankshaft is reduced without losing the contact of the two opposite surfaces on the bearing. In this embodiment, the rotor and the crankshaft are pushed from bottom upwards as a result of the repelling force between the magnets arranged on separate elements. Since the opposite surfaces of the cylinder block and the crankshaft in the axial bearing do not lose contact, the crankshaft making right to left tilting movements and balance disorders due to this bending movement and increase of noise are prevented.

[0010] In another embodiment of the present invention, the first magnet forming the rotor weight reducing arrangement which is located at the lower side is situated on the upper surface of the bracket that is immobilized to the casing and bearing the oil suction tube while the second magnet located at the upper side is attached to the oil suction tube immobilized to the lower end of the crankshaft.

[0011] In another embodiment of the present invention, the first magnet forming the rotor weight reducing arrangement and located at the lower side is attached to a magnet retaining element that is immobilized to the stator while the second magnet located at the upper side is attached to the lower surface of the rotor.

[0012] In yet another embodiment of the present invention, a washer made of a non-magnetic material, e.g. plastic, is placed between the magnets in the rotor weight reducing arrangement to prevent the magnets from contacting each other and be out of order by abrasion while the electric motor operates or during transportation etc.

[0013] The compressor designed to fulfill the objective of the present invention is illustrated in the attached figures, where:

[0014] Figure 1 - is the schematic view of a compressor.

[0015] Figure 2 - is the schematic view of a compressor motor in another embodiment of the present invention. [0016]

[0017] The elements illustrated in the figures are numbered as follows:

1. Compressor

2. Casing

3. Rotor

4. Stator

5. Crankshaft

6. Cylinder block

7. Bearing

8. , 108 Magnet

9. Rotor weight reducing arrangement

10. Oil suction tube

11. Bracket

12. Magnet retaining element

13. Washer

[0018] The compressor (1) comprises a casing (2) that holds the elements inside, an electric motor having a rotor (3) and a stator (4), a crankshaft (5) connected to the rotor (3) core, providing to transmit the rotational movement of the rotor (3), a cylinder block (6) situated at the upper side of the rotor (3) having a cylinder hole (D) wherein the piston functions and an axial sliding bearing (7) situated on the cylinder block (6) that provides bearing of the crankshaft (5) to the cylinder block (6) in the axial direction and thus maintaining the cylinder block (6) to sustain the weight of the crankshaft (5) together with the rotor (3) to which the crankshaft (5) is connected and the vertical components of the forces created during operation.

[0019] The compressor (1) of the present invention comprises a rotor weight reducing arrangement (9) having:

[0020] - two magnets (8, 108) between the casing (2) and the underside of the rotor (3) - crankshaft (5) group, positioned oppositely such that the like poles face each other on separate surfaces, not contacting each other, and having a certain distance therebetween under normal conditions,

[0021] - the first magnet (8) being immobilized to the casing (2) or to a point supported by the casing (2),

[0022] - the second magnet immobilized below the rotor (3) and the crankshaft (5) group,

[0023] - providing the rotor (3) and the crankshaft (5) to be supported from bottom upwards by means of the second magnet (108) that is pushed by the first magnet (8).

[0024] The rotor weight reducing arrangement (9) reduces or altogether eliminates the friction forces of the sliding bearing (7) on which the crankshaft (5) is seated by decreasing the weight effect of the rotor (3) and the crankshaft (5) and the vertical components of the forces created during operation.

[0025] The rotor weight reducing arrangement (9) is positioned at a point farther than the interrelated surfaces of the cylinder block (6) forming the axial sliding bearing (7) and the crankshaft (5) and reduces the frictional forces on the bearing (7) indirectly from outside the bearing (7).

[0026] By the embodiment of the present invention, without making any structural alterations of the axial sliding bearing (7) that supports the weight of the rotor (3) and the crankshaft (5) on the cylinder block (6), the forces that affect the bearing (7) are reduced or eliminated altogether. The rotor (3) and the crankshaft (5) are pushed from below by placing the magnets (8, 108) that form the rotor weight reducing arrangement (9) below the rotor (3), thus reducing the forces acting on the bearing (7) that is above the rotor (3) and the bearing (7) surfaces are not required to be processed for placing the magnets (8, 108). The rotor weight reducing arrangement (9) is easily mounted outside the electric motor and the cylinder block (6) group and does not require a detailed workmanship.

[0027] In an embodiment of the present invention, in the rotor weight reducing arrangement (9) the magnets (8, 108) are selected such that the repelling force therebetween is less than the weight of the rotor (3) and the crankshaft (5) thus in the bearing (7) the contact between the two opposite surfaces of the cylinder block (6) and the crankshaft is (5) is not lost and the effect of the friction force is reduced.

[0028] The opposite surfaces, on which the magnets (8, 108) are placed, one connected to the casing (2) and the other under the rotor (3) and crankshaft (5) group, do not contact due to the design of the compressor (1) and there is a certain distance therebetween. By taking advantage of the distance between the separate elements, the magnets (8, 108) are arranged on the two opposite surfaces and due to the repelling force therebetween, the rotor (3) and the crankshaft (5) are pushed from bottom upwards. Since the opposite surfaces of the cylinder block (6) and the crankshaft (5) in the axial bearing (7) do not lose contact, the crankshaft (5) making right to left tilting movements and balance disorders due to this tilting movement and increase of noise are prevented.

[0029] In another embodiment of the present invention, the compressor (1) comprises an oil suction tube (10) that is situated at the lower end of the crankshaft (5) for aspirating the oil in the casing (2) to deliver into the crankshaft (5), a bracket (11) immobilized inside the casing (2) at the lower side, that houses the oil suction tube (10), preventing bumping and deformation during transport, the first magnet (8) is immobilized to the bracket (11), the second magnet (108) is immobilized to the oil suction tube (10) (Figure 1). Since the bracket (11) is directly connected to the casing (2), the first magnet (8) thereon is stationary and pushes the second magnet (108) in the upwards direction. A pushing force in the upward direction is applied by the second magnet (108) on the oil suction tube (10) and the crankshaft (5) and rotor (3) to which the oil suction tube (10) is snap-fitted. Thus the load of the axial bearing (7) at the upper side of the rotor (3), between the crankshaft (5) and the cylinder block (6) is reduced or eliminated altogether.

[0030] In another embodiment of the present invention, the rotor weight reducing arrangement (9) comprises a magnet retaining element (12) immobilized to the stator (4) and the first magnet (8) is attached to the magnet retaining element (12) while the second magnet (108) is attached to the lower surface of the rotor (3) (Figure 2). While the first magnet (8) is virtually stationary, pushes the second magnet (108) in the upward direction and applies an upwards pushing force on the rotor (3) and the crankshaft (5). Consequently, as in the previous embodiment, the load of the axial bearing (7) at the upper side of the rotor (3), between the crankshaft (5) and the cylinder block (6), is reduced or eliminated altogether.

[0031] In the embodiment, since the stator (4) is connected to the casing (2) by springs having a high spring force that attenuates the vibrational movements, a good anchor is formed for the first magnet (8) that has to stay virtually steady.

[0032] In another embodiment of the present invention, the rotor weight reducing arrangement (9) comprises a washer (13) placed between the magnets (8, 108) to prevent the magnets (8, 108) from contacting each other and being abraded while the electric motor operates (Figure 1). The washer (13) is produced of a non-magnetic material and only forms a protective layer between the two magnets (8, 108) in the possibility that they may contact each other, without affecting the repelling force of the magnets (8, 108).

[0033] By means of the rotor weight reducing arrangement (9) in the compressor (1) of the present invention, the forces acting on the axial bearing (7) are reduced or eliminated altogether thus reducing the mechanical losses and an increase of the compressor (1) performance (COP) is maintained. Since mechanical losses are reduced, particularly the problem of the compressor (1) not being able to make the initial start-up is solved. The magnets (8, 108) forming the rotor weight reducing arrangement (9) are placed elsewhere than the axial bearing (7), thus eliminating the need for special processing on the opposite surfaces of the cylinder block (6) and the crankshaft (5) forming the axial bearing (7), a simple and low cost solution is provided.

Claims

1. A compressor (1) comprising a casing (2) that holds the elements inside, an electric motor having a rotor (3) and a stator (4), a crankshaft (5) connected to the rotor (3) core, providing to transmit the rotational movement of the rotor (3), a cylinder block (6) situated at the upper side of the rotor (3) having a cylinder hole (D) and an axial sliding bearing (7) situated on the cylinder block (6) that provides bearing of the crankshaft (5) to the cylinder block (6) in the axial direction, and characterized by a rotor weight reducing arrangement (9) - having two magnets (8, 108) between casing (2) and the underside of the rotor (3) - crankshaft (5) group, positioned oppositely such that the like poles face each other on separate surfaces, not contacting each other, having a certain distance therebetween under normal conditions, - the first magnet (8) being immobilized to the casing (2) or to a point supported by the casing (2), - the second magnet immobilized below the rotor (3) and the crankshaft (5) group, - providing the rotor (3) and the crankshaft (5) to be supported from bottom upwards by means of the second magnet (108) that is pushed by the first magnet (8).

2. A compressor (1) as in Claim 1 , characterized by the magnets (8, 108) being selected such that the repelling force therebetween is less than the weight of the rotor (3) and the crankshaft (5).

3. A compressor (1) as in Claim 1 or 2, characterized by an oil suction tube (10) for aspirating the oil in the casing (2) to deliver into the crankshaft (5), a bracket (11) immobilized inside the casing (2) at the lower side, that houses the oil suction tube (10), a first magnet (8) immobilized to the bracket (11) and a second magnet (108) attached (fitted) to the oil suction tube (10).

4. A compressor (1) as in Claim 1 or 2, characterized by a rotor weight reducing arrangement (9) comprising a magnet retaining element (12) immobilized to the stator (4), a first magnet (8) attached to the magnet retaining element (12) and a second magnet (108) attached to the lower surface of the rotor (3).

5. A compressor (1) as in any one of the above claims, characterized by a rotor weight reducing arrangement (9) comprising a washer (13) situated between the magnets (8, 108).