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Refrigerant compressor arrangement

Refrigerant compressor arrangement description/claims

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.

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.

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.

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.

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