US20090068035A1

US20090068035A1 - Refrigerant compressor arrangement

Info

Publication number: US20090068035A1
Application number: US12/185,982
Authority: US
Inventors: Jesper Valbjoern; Kristoffer Riemann Hansen; Anders Jakob Madsen
Original assignee: Danfoss Compressors GmbH
Current assignee: Secop GmbH
Priority date: 2007-08-16
Filing date: 2008-08-05
Publication date: 2009-03-12
Also published as: DE102007038432A1; CN101368556B; ITTO20080621A1; IT1391039B1; CN101368556A

Abstract

The invention concerns a refrigerant compressor arrangement (1) with a compressor block (21) comprising a compressor unit (9) with a cylinder formed in the compressor block, and with a motor (8) having a stator (12) and a rotor (13), the rotor being unrotatably connected to a drive shaft (31) driving the compressor unit (9), the drive shaft (31) being supported in a bearing section (32) of the compressor block (21). It is endeavoured to make the refrigerant compressor arrangement with a smaller total height. For this purpose, the bearing section (32) penetrates an active area of the stator (12) and that the rotor (13) and the drive shaft (31) are connected to each other outside the active area on the side of the rotor (13) facing away from the compressor unit (9).

Description

REFERENCE TO RELATED APPLICATIONS

Applicant hereby claims foreign priority benefits under U.S.C. § 119 from German Patent Application No. 10 2007 038 432.9 filed on Aug. 16, 2007, the contents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention concerns a refrigerant compressor arrangement with a compressor block comprising a compressor unit with a cylinder formed in the compressor block, and with a motor having a stator and a rotor, the rotor being unrotatably connected to a drive shaft driving the compressor unit, the drive shaft being supported in a bearing section of the compressor block.

BACKGROUND OF THE INVENTION

Such a refrigerant compressor arrangement is, for example, known from DE 195 16 811 C2. The compressor is formed as a piston compressor, in which a piston, which is connected to a crank pin of the drive shaft via a connecting rod, reciprocates in a cylinder, thus sucking in and compressing refrigerant. The bearing section has a radial bearing and an axial bearing for the drive shaft. The bearing section ends above the rotor.
A similar refrigerant compressor arrangement is known from DE 35 21 742 A1. Also here, a cylinder is formed on the upper side of the compressor block, a piston, driven by the drive shaft via a connecting rod, reciprocating in the cylinder. The bearing section, in which the drive shaft is supported, is offset somewhat into the rotor.
In both cases, the refrigerant compressor arrangement requires a certain total height. When the refrigerant compressor arrangement is built into a refrigeration appliance, whose outer dimensions are predetermined, the space required by the refrigerant compressor arrangement will not be available as refrigeration space. Particularly in connection with refrigeration appliances used in domestic applications, however, it is desired to maintain the largest possible refrigeration space, in spite of predetermined outer dimensions.

SUMMARY OF THE INVENTION

The invention is based on the task of providing refrigerant compressor arrangements with a small total height.
With a refrigerant compressor arrangement as mentioned in the introduction, this task is solved in that the bearing section penetrates an active area of the stator and that the rotor and the drive shaft are connected to each other outside the active area on the side of the rotor facing away from the compressor unit.
With this embodiment a smaller total height of the refrigerant compressor arrangement is achieved, as, in a manner of speaking, the complete height of the active area of the stator can be utilised to form the bearing section. The active area of the stator is the area, in which the real driving forces are generated. In the simplest case, this is the core lamination forming the stator. The stator also has windings and end windings, which extend over the stator core lamination. However, here practically no forces or torques are generated, which are used to drive the rotor. If the bearing section is permitted to penetrate the active area of the stator, the drive shaft can be supported over a relatively large axial length. Therefore, otherwise the bearing section can be dimensioned to be somewhat weaker than with a shorter length. The stator can then be moved closer to the compressor block, which further saves total height. The fact that the rotor is unrotatable connected to the end of the drive shaft, which faces away from the compressor unit, causes that the total bearing of the drive shaft and thus also of the rotor can be located in the compressor block. This ensures a very accurate bearing, which is substantially more accurate than a bearing formed by two or more parts. Also, a bearing made in one piece will not be exposed to displacements between two or more parts. With a usual mounting position of the refrigerant compressor arrangement, the compressor unit is upwards, that is, located at the upper side of the compressor block, whereas the motor is located under the compressor block. Thus, the connection between the rotor and the drive shaft occurs at the lower end of the drive shaft. Preferably, the motor is a permanent magnet energized synchronous motor with inner rotor. The stator comprises a stator lamination core formed by identically shaped and punched metal sheets, the stator lamination core having a central opening for adopting the rotor. The inner surface of this central opening is formed by a number of pole teeth, which are connected to the radial outer metal sheet body by means of radial supports. Between the pole teeth groves are provided for adopting coil windings, which are wound around the supports to form so-called salient poles. The use of such a motor substantially reduces the axial extension of the upper and lower winding heads in comparison with normally used asynchronous motors. In general, the stator can be moved closer to the compressor block, which further reduces the total height of the refrigerant compressor arrangement.
Preferably, the rotor has a support part, on which several permanent magnets are located. The fixing of the permanent magnets to the support part occurs by means of appropriate means, for example adhesives or special holders. As by means of the drive shaft and the bearing section the rotor is supported very stably in the compressor block, which also provides a fixing for the stator, relatively small air gaps can be realised, so that the electric motor has a good efficiency.
Preferably, the rotor is connected to the drive shaft via the support part. Thus, the support part assumes a further task. It transmits a torque from the permanent magnets to the drive shaft.
Preferably, the support part is adjacent to the bottom of the bearing section. This does not necessarily mean that the bearing section and the support part must touch each other. A small axial distance between the support part and the bearing section is even desirable, to prevent an additional friction. If, however, the support part is located relatively close to the bearing section, only a relatively small total height is required for fixing the rotor to the drive shaft.
Preferably, a fixing section, with which the support part is fixed on the drive shaft, is shorter in the axial direction than a magnet section, on which the permanent magnets are located. Also this is a measure for keeping the axial total height of the refrigerant compressor arrangement small. The fixing section merely has to be able to transmit the torque to the drive shaft. Often, the total height required for this is smaller than the total height of the permanent magnets.
Preferably, an oil pump opening at the lower end of the drive shaft is in connection with a bore in the drive shaft, said bore being inclined in relation to the rotation axis of the drive shaft. Thus, the oil pump opening serves as inlet for the oil pump. It is immersed in an oil sump formed at the bottom of an enclosure, in which the refrigerant compressor arrangement is located. As the total height of the drive shaft is kept relatively small, a diagonal or inclined bore will be sufficient to transport oil from the oil sump to the spots, where the oil is needed. An oil pump as such is thus no longer needed, even though such an oil pump can still be used. As the bore is inclined, a certain centrifugal force will transport the oil upwards. This transport occurs already with relatively small speeds, that is, already during the start, so that an earlier lubrication of the moving parts of the refrigerant compressor arrangement can be ensured. Due to the small total height, an operation with sufficient lubrication is also possible, if the refrigerant compressor arrangement is operated at low or variable speeds. This provides energetic advantages in relation to a pure on/off operation.
Preferably, the oil pump opening is located in an attachment, which is adjacent to the lower end of the drive shaft. Thus, the oil pump opening is not provided directly in the drive shaft, but in an additional attachment. This simplifies the manufacturing of the drive shaft.
It is preferred that the attachment forms part of the support part. This means that the attachment with the oil pump opening is handled together with the support part.
It is particularly preferred that the attachment is made in one piece with the support element. In this case, the attachment can additionally be used as stop when connecting the support part to the drive shaft.
It is preferred that the support element and the attachment are made as a common sintered part. If the support part and the attachment are made as one sintered piece almost no additional costs will occur in connection with the integration of the attachment in the support part.
Preferably, the bore is connected to a helical groove on the outside of the drive shaft via a radial channel, which is covered by the bearing section at the area of the lower end of the bearing section. Oil from the bore can then reach the helical groove that is covered by the bearing section through the radial channel. The oil that is available in the helical groove is then transported further upwards by the rotation of the drive shaft in the bearing section, so that the oil can reach all parts, which have to be lubricated.
Preferably, a crank pin is located at the upper end of the drive shaft, eccentrically to the drive shaft, said crank pin surrounding an upwardly open hollow, which is connected to the bore. This hollow serves as an oil reservoir, which is filled through the bore. During a rotation movement of the drive shaft, oil that is available in the oil reservoir will be slung out through the opening and sprayed inside an enclosure that surrounds the refrigerant compressor arrangement. Thus, practically all required parts are lubricated. The crank pin can also have an opening in its wall, through which opening the oil reaches an intermediate space between the crank pin and the crank eye of the connecting rod.
Preferably, the lower part of the bearing section has a reduced outer diameter. Directional details, like “lower” refer to the normal mounting direction of the refrigerant compressor arrangement. In the lower area the bearing section has its largest distance to the crank pin, so that the forces generated by the crank pin when acted upon by the connecting rod are no longer too large. Thus, a reduction of the wall thickness of the bearing section will cause no problems. The reduction of the bearing section will leave more space for the rotor or the support part of the rotor, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is described on the basis of preferred embodiments in connection with the drawings, showing:

FIG. 1 a longitudinal section through a refrigerant compressor arrangement

FIG. 2 a section of FIG. 1 with the rotor in a different rotation angle position

FIG. 3 a modified embodiment of the arrangement according to FIG. 2

FIG. 4 a third embodiment in the view according to FIG. 2.

DETAILED DESCRIPTION

FIG. 1 shows a longitudinal section through a refrigerant compressor arrangement 1. The refrigerant compressor arrangement 1 comprises an enclosure 2 with an upper part 3 and a lower part 4. The upper part 3 comprises a flange 5 and the lower part 4 comprises a flange 6. The flanges 5, 6 are connected to each other by welding, so that the enclosure 2 is hermetically closed.
In the enclosure is located a unit 7 with a motor 8 and a compressor unit 9. The unit 7 is supported on the lower part 4 of the enclosure 2 by means of springs 10, 11.
The motor 8 has a stator 12 and a rotor 13. The stator 12 comprises a stator core lamination 14, which is stacked of identically formed and punched metal sheets. On the radial inside, the stator core lamination 14 has several pole teeth 15, which again are formed by webs and salient poles on the inside of a central stator opening. In the grooves formed between the pole teeth 15, windings 16 are located, each surrounding a web. Between the stator core lamination 14 and the windings 16, isolating layers in the form of an upper end plate 17 and a lower end plate 18 are located. The end plates 17, 18 completely cover the axial end faces of the stator core lamination 14 as well the surfaces of the pole teeth 15, except for the radial inner pole faces, which surround the central stator opening. In other words, the end plates 17, 18 form a complete coating and electrical isolation of the groove surfaces.
The rotor 13 has several permanent magnets 19, which are located on a metal support part 20. The permanent magnets 19 are fixed to the support part 20 by suitable means, for example adhesives or special holders.
This means that the motor 8 is a permanent magnet energized synchronous motor with inner rotor. The use of such a motor 8 ensures that, compared to previously used asynchronous motors, the axial extension of the parts of the windings 16 extending upwards and downwards from the stator core lamination 14 is substantially smaller. Thus, in the axial direction the motor 8 has a relatively small total height.
The motor 8 is located under a compressor block 21. In this connection, the directional terms “up” and “down” refer to a usual mounting direction of the refrigerant compressor arrangement 1.
The compressor unit 9 is located on the upper side of the compressor block 21. It comprises a cylinder 22, in which a piston 23 can reciprocate to increase or reduce a pressure chamber 24. During an increase of the pressure chamber 24, refrigerant gas is sucked in through a suction connection 25, and during a reduction of the pressure chamber 24 the refrigerant gas is ejected through an outlet pipe 26. For the control of the refrigerant flow, a valve plate 27 is provided, which is fitted on the front side of the cylinder 22. The valve plate 27 again is covered by a cylinder head cover 28.
The driving of the piston 23 occurs via a crank shaft 29, which engages a crank pin 30, which is located at the upper side of a drive shaft 31 and eccentrically to the axis of the drive shaft 31.
The drive shaft 31 is supported in the compressor block 21. For this purpose, the compressor block 21 has a bearing section 32 forming a radial bearing 33 and an axial bearing 34.
The bearing section 32 penetrates the stator core lamination 14 of the stator 12, that is, the active area of the stator 12. Forces, which make the rotor 13 rotate, are practically only generated in this area.
The drive shaft 31 penetrates the bearing section 32, that is, projects from the lower end of the bearing section 32. Here, the drive shaft 31 is unrotatably connected to the rotor 13. The connection occurs via the support part 20, which also carries the permanent magnets 19. The fixing of the support part 20 on the drive shaft 31 in the fixing section 36 can, for example, occur in that the support part 20 is shrunk or pressed onto the drive shaft. With a small gap, this support part 20 is adjacent to the lower end of the bearing section 32. Together with the drive shaft 31, the support part 20 forms a fixing section 36, whose axial extension is smaller than the axial extension of the permanent magnets 19. Also this makes it possible to keep the axial extension of the motor 8, and thus also the total height of the refrigerant compressor arrangement 1, small.
The lower end of the drive shaft 31 projects into an oil sump 37 (for reasons of clarity, the oil is not shown here). Here, the drive shaft 31 has an oil pump opening 38, which is, as can be seen from FIG. 2, connected to a bore 39 in the drive shaft 31, which is inclined in relation to a rotation axis 40, that is, encloses an angle together with the rotation axis 40.
From the bore 39 a radial channel 41 branches off, whose outside is covered by the bearing section 32, and which ends in a helical groove 42, which is provided at the circumferential wall of the drive shaft 31 and is covered in its full length by the bearing section 32. The helical groove supplies oil to the axial bearing 34, so that all surfaces, at which the drive shaft 31 performs a movement in the compressor block 21, are lubricated with oil.
The crank pin 30 has a hollow 43 with an upward opening 44, the hollow being connected to the bore 39 via a channel 45 (partly seen in FIG. 2). Thus, during operation the hollow 43 in the crank pin 30 is filled with oil. Through an opening 46, a share of the oil can reach an area between the connecting rod 29 and the crank pin 30 in order to lubricate this area. During a rotation movement of the drive shaft 31, a further share of the oil is slung through the opening 44 onto the inside of the upper part 3 of the enclosure 2, from where it drops off to lubricate other parts of the unit 7.
As can be seen, for example, from FIG. 2, the lower end of the bearing section 32 has an area 47 with a reduced outer diameter. In this area, the support part 20 may have a larger wall thickness. The bearing section 32 no longer has to adopt large forces here.
Compared to FIG. 2, FIG. 3 shows a modified embodiment, in which same and functionally same elements have the same reference numbers.
The oil pump opening 38 is now located in an attachment 48, which is fitted at the lower end of the drive shaft 31 and at the support part 20. Such an embodiment facilitates the manufacturing of the drive shaft 31. When manufacturing the drive shaft 31, the suction function of the oil pump must no longer be considered. In many cases, it will be sufficient only to connect the attachment 48 to the support part 20, so that here no special measures have to be taken with regard to a connection to the drive shaft 31. When the support part 20 is connected to the drive shaft 31, and the attachment is connected to the support part 20, the attachment with the oil pump opening 38 is turned together with the drive shaft 31.
A further modification appears from the embodiment according to FIG. 4. Here, the attachment 48 is made in one piece with the support part 20. This is also possible without problems, if the support part is made of metal. For example, the combination of support part 20 and attachment 48 can be made as a sintered part.
While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention.

Claims

1. A refrigerant compressor arrangement with a compressor block comprising a compressor unit with a cylinder formed in the compressor block, and with a motor having a stator and a rotor, the rotor being unrotatably connected to a drive shaft driving the compressor unit, the drive shaft being supported in a bearing section of the compressor block, wherein the bearing section penetrates an active area of the stator and that the rotor and the drive shaft are connected to each other outside the active area on the side of the rotor facing away from the compressor unit.

2. The arrangement according to claim 1, wherein the motor is a permanent magnet energized synchronous motor with inner rotor.

3. The arrangement according to claim 2, wherein the rotor has a support part, on which several permanent magnets are located.

4. The arrangement according to claim 3, wherein the rotor is connected to the drive shaft via the support part.

5. The arrangement according to claim 3, wherein the support part is adjacent to the bottom of the bearing section.

6. The arrangement according to claim 3, wherein a fixing section, with which the support part is fixed on the drive shaft, is shorter in the axial direction than a magnet section, on which the permanent magnets are located.

7. The arrangement according to claim 1, wherein an oil pump opening at the lower end of the drive shaft is in connection with a bore in the drive shaft, said bore being inclined in relation to the rotation axis of the drive shaft.

8. The arrangement according to claim 7, wherein the oil pump opening is located in an attachment, which is adjacent to the lower end of the drive shaft.

9. The arrangement according to claim 8, wherein the attachment forms part of the support part.

10. The according to claim 8, wherein the attachment is made in one piece with the support element.

11. The arrangement according to claim 10, wherein the support element and the attachment are made as a common sintered part.

12. The arrangement according to claim 7, wherein the bore is connected to a helical groove on the outside of the drive shaft via a radial channel, which is covered by the bearing section at the area of the lower end of the bearing section.

13. The arrangement according to claim 7, wherein a crank pin is located at the upper end of the drive shaft, eccentrically to the drive shaft, said crank pin surrounding an upwardly open hollow, which is connected to the bore.

14. The arrangement according to claim 1, wherein the lower part of the bearing section has a reduced outer diameter.