Pumps – Motor driven – Electric or magnetic motor
Patent
1998-12-28
2000-08-01
Walberg, Teresa
Pumps
Motor driven
Electric or magnetic motor
417372, 417569, F04B 3504
Patent
active
060957689
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a hermetic motor-driven compressor for refrigerators according to the preamble of claim 1.
The preamble of claim 1 describes a conventional compressor which is very common and has been known for very many decades.
One examples of such compressor is known from the document EP-A-0 524 552.
This known compressor comprises a single bearing constituted by a bush-like element which is fixed to the block and extends inside the rotor of the electric motor and in which the shaft of the compressor is mounted for rotation with a spheroidal coupling.
Since the rotor of the electric motor is fixed to a projecting portion of the shaft, the bush-like element and the portion of the shaft which co-operates therewith have to be of fairly generous dimensions with regard both to their diameters and to their lengths.
Amongst further countless examples of this arrangement, the documents DE-A-2 030 047, EP-A-0 507 091, EP-A-0 530 480, GB-A-771 194, GB-A-2 103 759, U.S. Pat. No. 3,295,753 and U.S. Pat. No. 4,386,856 may be cited.
The motor-driven compressor industry is tending to produce ever more efficient machines in order to reduce electrical-energy consumption for a given capacity.
One way of reducing energy consumption, in addition to that of increasing the thermodynamic efficiency of a compressor, is to reduce mechanical friction.
In the prior art, the coupling between the shaft and the single bearing constituted by the bush-like element of the block represents a source of considerable friction which it would be desirable to reduce.
The main object of the invention is precisely to provide a motor-driven compressor for refrigerators according to the preamble of claim 1 in which the friction of rotation of the crankshaft is reduced in comparison with the prior art.
According to the invention, this object is achieved by means of a motor-driven compressor having the characteristics defined in the characterizing part of claim 1.
In a motor-driven compressor according to the invention, the main self-aligning bearing, which is situated in the vicinity of the axis of the cylinder, withstands most of the forces developed between the piston and the crank pin of the shaft in operation; the secondary self-aligning bearing which is situated on the opposite side of the electric motor to the main bearing, however, is subject to very little stress, given that it is in a position remote from the axis of the cylinder.
This arrangement according to the invention enables a motor-driven compressor unit to be constructed with a crankshaft which, for a given power, has a smaller diameter than the shafts of similar units according to the most widespread prior art. This translates into a smaller circumference and axial length of the frictional surfaces of the bearings.
The mounting of the crankshaft by means of self-aligning bearings also offers the advantage that it enables the rotating parts (the crank-shaft and the rotor) to be centred easily relative to the fixed parts (the block, the casing and the stator). This results in a reduction in manufacturing costs.
Hermetic motor-driven compressors for refrigerators in which a block comprising two cylindrical bearings situated on either side of the crank pin of a crankshaft in an arrangement similar to that of small two-stroke reciprocating engines are also known, for example, from the documents GA-A-1 067 395 and EP-A-0 325 694.
In these less commonly-known motor-driven compressors, the rotor of the electric motor is again mounted on a projecting portion of the crankshaft, as in the more common motor-driven compressors according to the preamble of claim 1, and the two cylindrical bearings in practice have a function similar to that of the single long bush-like bearing, with corresponding relatively high friction.
Further characteristics and advantages of the invention will become clear from a reading of the following detailed description with reference to the appended drawings, provided by way of non-limiting example, in which:
FIG. 1 is a diametral section of a herm
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Embraco Europe S.r.l.
Fastovsky Leonid
Walberg Teresa
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