Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D25/00—Pumping installations or systems
  • F04D25/02—Units comprising pumps and their driving means
  • F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
  • F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
  • F04D29/668—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps damping or preventing mechanical vibrations

Definitions

• the invention concerns a compressor driveable by an electric motor according to the precharacterizing portion of Claim 1.
• This type of compressor is driven by an electric motor, which can be constructed for example as an asynchronous or induction motor. It is comprised essentially of a rotor with a rotor shaft, which works in cooperation with a corresponding stator provided in the motor housing.
• the rotor shaft is supported in the motor housing via two journals or bearings, and exhibits an axial mounting or receiving segment, onto which a compressor wheel is provided fixed against rotation. Energizing the motor causes the rotor shaft to rotate, which in turn directly drives the compressor wheel.
• the axial segments which receive the mounting rings as well as in many cases the necessary shaft seal rings are designed to be as small as possible with regard to their diameter. This applies in like manner to the shoulder segments immediately adjacent to the mounting points, on which the mounts, for example the inner mount rings, are brought to bear.
• the diameters are so dimensioned, that they are capable of standing up to the demands occurring during the projected product life.
• Modern design processes, which utilize intelligent or cascade simulation programs, make possible a relatively reliable prediction of the component behavior, so that the diameter of the axial segment of interest for a given rotor shaft can be constructed or designed to be relatively small . Beyond this, small diameters are considered desirable for rotating construction components, since this makes possible a reduction of the rotation inertia. This results in an optimal responsiveness during charges in rotational speed, in particular during accelerating or decelerating the compressor.
• the present invention is thus concerned with the problem of improving the compressor of the above-described type in such a manner that the mentioned disadvantages no longer occur.
• the running quietness and noise emissions should be improved and the life expectancy should be increased.
• the invention is based upon recognition of the fact that in the application of design criteria until now the rotating group of components, comprised essentially of the rotor with the rotor shaft and the compressor wheel, have a first critical bending fundamental frequency or resonance frequency, which lies within the operational rotational speed spectrum. During acceleration of the compressor this fundamental frequency must be passed through, at which time the vibrations and noise emissions are triggered.
• Measures are known from other technical fields, for example, the driving of hard disks for a computer, which are directed to a targeted dampening of oscillations which are emitted by components rotating at a high rotational speed.
• a complex governing process is described for dampening vibrations in a rotating system.
• An application to the present case of electric motor driven compressors might appear possible, but requires however a complex supplemental design and control means.
• the present invention makes it possible to avoid the vibrations occurring in the conventionally designed, electric motor driven compressors, in simple manner thereby, that the first critical bending harmonic frequency is raised to a value which lies above the maximal rotational speed occurring during operation.
• substantial improvements in the operational behavior in particular with respect to running quietness, noise emissions and operational life, can be achieved.
• This is achieved without the usual conventional supplemental measures, such as for example active or passive dampening, so that these advantages can be achieved practically without supplemental construction complexity or investment .
• the raising in the harmonic frequency is achieved by modification of the rotor shaft.
• a raising of the fundamental frequency is also produced as a consequence of increasing the dimensions of the shoulder segments adjacent to the mounting segments.
• the shoulder segments respectively serve for the abutment of the inner ring of the roller bearing, so that any enlargement of the diameter of the bearing segment necessarily also produces a corresponding enlargement of the diameter of the adjacent shoulder segment.
• the fundamental frequency can be increased by enlargement of the axial segments which receive the seal disks. It is understood that the diameter of this bearing segment may at most be equal to the diameter of the adjacent bearing segments, since otherwise an introduction of the inner bearing rings is no longer possible.
• a further, additional option for raising the fundamental frequency is comprised in designing the bearings arrangement of the rotor shaft to be particularly stiff.
• FIG. 1 compressor in axial view
• FIG. 4 deformation condition for a second rotor geometry.
• the basic construction of a compressor can be seen from Fig. 1.
• the compressor 1 includes a compressor wheel 10 which is driveable via rotor shaft 20.
• the rotor shaft 20 exhibits a receiving segment 30, upon which the compressor wheel 10 is seated and is secured on the rotor shaft against rotation via a securing nut 12, which is screwed onto a threaded segment 32 of the rotor shaft 20.
• Air channels 16, 18 are formed by an appropriate design of the compressor housing segment 14.
• the rotor shaft 20 includes a central segment 22.
• a corresponding stator part 50 is provided.
• Interstitial spaces 54 serve as coolant water channels.
• an asynchronous motor is constructed, which serves for driving the compressor wheel 10.
• a motor control is provided in housing part 60, which closes the end side of the compressor 1.
• the rotor shaft 20 For mounting the rotor shaft 20, two roller bearings 46 are provided.
• the rotor shaft 20 includes bearing segments 26, which are designed as bearing seats with close tolerances.
• the housing parts 56, 58 in the area of the roller bearings 46 are manufactured with close tolerances, whereby a defined fit results.
• shoulder segments 24 Adjacent to the bearing segments 26 shoulder segments 24 are provided which transition to the central segment 22, and against which the roller bearings 46 respectively are supported axially.
• the rotor shaft 20 exhibits a seal segment 28 between the receiving segment 30 and the bearing segment 26, which seal segment carries a seal disk 46 with a piston ring 44. Thereby a seal is formed between the air channel and the area of the asynchronous motor.
• the invention is manifested therein, that the rotating construction components, comprised essentially of the rotor shaft 20 and compressor wheel 10, are so designed, that its first critical bending fundamental frequency wi lies above the maximal operating rotational speed n ma ⁇ .
• the design of the rotor shaft 20, as is also shown in Fig. 2 has significant meaning.
• the maximal diameter in the area of the central segment 22 in general is predetermined, since it is dependent upon the geometry of the stator, in particular the stator part 50. These values are determined by the electrical power data of the asynchronous motor, and with respect to the required drive requirements are not variable.
• a first possibility for influencing the first critical bending fundamental frequency thus lies in the enlargement of the diameter in the area of the shoulder segment 24.
• the diameter enlargement is essentially subject to a limit with respect to the housing contour running in this area.
• an increase in the first critical bending fundamental frequency wi is possible by an enlargement of the diameter in the area of the mounting or bearing segment 26.
• the maximal possible diameter is influenced by the design of the bearing and limited by the maximal possible internal diameter of the lower bearing 46. It must be observed, that the diameter of a mounting or bearing segment 26 and the shoulder segment 24 must, at least in the transition area, be coordinated or adapted with respect to each other, so that the axial supporting of the roller bearing 46 can satisfy design requirements .
• a further possibility for raising of the first critical bending fundamental frequency wi can finally also occur by a corresponding enlarging of the diameter in the area of the seal segment 28.
• the diameter may however maximally reach the value of the diameter in the area of the adjacent bearing segment 26, since during the assembly of the motor the roller bearing 46 must be slid axially over the seal segment 28 and onto the bearing segment 26.
• Fig. 3 shows a first construction component group, comprised of compressor wheel 10 and rotor shaft 20, which is symbolized by a network.
• the representation shows a so-called “screenshot” of a numeric simulation, in which the deformation corresponding to the first critical bending characteristic of the network is represented exaggerated.
• the repeated parameters show a frequency of 1210.71 hertz.
• the rotating construction component shown in Fig. 4 is, with respect to the compressor wheel 10, provided with the same design. The differences are concerned with the modified axial segment of the rotor shaft 20 in the above described mode and manner.
• the screenshot according to Fig. 4 shows that as a result of the comparatively small modification to the rotor shaft 20 the first critical bending fundamental frequency can be displaced to 2124.67 hertz.
• the simulation shows that it is possible, with comparatively small expense and complexity, to raise the first critical bending fundamental frequency wi by a factor of 2 and therewith to displace it to an area which, in the present case, lies above the maximal operational rotational speed n max .

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
• Compressor (AREA)
• Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
• Applications Or Details Of Rotary Compressors (AREA)

Applications Claiming Priority (1)

Publications (2)

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ID=8164492

Family Applications (1)

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Cited By (1)

Families Citing this family (4)

Family Cites Families (8)

• 2001
  • 2001-07-06 EP EP01954021A patent/EP1404974B1/de not_active Expired - Lifetime
  • 2001-07-06 WO PCT/EP2001/007790 patent/WO2003004878A1/en active Application Filing
  • 2001-07-06 JP JP2003510618A patent/JP2004521267A/ja active Pending
  • 2001-07-06 DE DE60136492T patent/DE60136492D1/de not_active Expired - Fee Related
  • 2001-07-06 US US10/483,019 patent/US20040241018A1/en not_active Abandoned

Non-Patent Citations (1)

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