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
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
  • F04D29/30—Vanes
  • F04D29/305—Flexible vanes
• • 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
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
  • F04D29/287—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps with adjusting means
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K9/00—Arrangements for cooling or ventilating
  • H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
  • H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
  • H02K9/06—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium with fans or impellers driven by the machine shaft
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K2213/00—Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
  • H02K2213/09—Machines characterised by the presence of elements which are subject to variation, e.g. adjustable bearings, reconfigurable windings, variable pitch ventilators

Definitions

• the present invention relates to a radial type cooling fan for an electric motor and with an impeller, driven by the motor, with a plurality of stiff fan blades arranged on the impeller .
• the torque of the motor is approximately constant at all speeds. It is previously known in such a motor drive to equip the electric motor with a cooling fan with fixed blades. In order for the fan to give the necessary substantial cooling also at low speeds, it must be very amply dimensioned. This makes the fan bulky and results in very high losses as well as a high sound level at high speeds.
• the invention aims to provide a cooling air fan of the kind mentioned in the introductory part of the description, which may be adapted to give an approximately constant cooling air flow at varying speeds and which has low losses and high reliability.
• the fan blades are rotatable in their entirety and influenced by spring members which give a torque on the blades which counteracts the torque generated by the centrifugal force on the blade .
• the fan may be adapted in a simple manner to give a desired speed-dependence of the cooling air flow, for example a constant cooling air flow, within the speed range current for a certain motor drive. Since the angle of incidence of the entire blades will decrease at increasing speed, the blades may be adapted to work with an approximately optimum angle of incidence within the entire speed range, thus obtaining a high efficiency and low losses of the fan and hence of the drive equipment as a whole .
• the fan blades are stiff, the problems with fatigue and vibrations, which arise in fans with flexible blades, are eliminated.
• the blades may be provided in a simple manner with mechanical link members which ensure that all the blades of the impeller always operate with the same angle of incidence. In this way, thus, any risk of unsymmetry and unbalance of the fan can be avoided in a simple manner. Since the blades are so arranged that the radially inner edge of each blade is positioned before the outer edge of the same blade in the direction of rotation, at a certain air flow the outlet speed of the air, and hence the losses dependent on the outlet speed, will be low (the losses are proportional to the square of the outlet speedj .
• the air flow through the fan will be as free from disturbances as possible, and loss-generating slow separation and eddy formation are avoided. Furthermore, when the blades of the fan according to the invention are moved outwards to an increasing extent, both the pressure generated by the fan and the air flow through the fan are reduced. Since the loss power is proportional to the product of the pressure and the air flow, the desired reduction of the flow is obtained with optimally low power losses .
• Figure 1 shows an embodiment of the invention in which Figure la shows the motor with a cooling fan in a section through the axis of rotation of the motor, Figure lb shows the motor and the cooling fan in a plane perpendicular to the motor axis, and Figure lc shows in more detail the embodiment of one of the fan blades with its spring member.
• Figures 2a and 2b show another embodiment in which the fan is provided with a mechanical link system for ensuring mutually identical angles of incidence of the different fan blades.
• Figure 2a shows a section through the rotary axis of the motor and Figure 2b shows a plane perpendicular to the same rotary axis.
• Figure 2c shows an example of how one single common spring member may be arranged for all the blades of the impeller.
• Figure 3 shows an alternative embodiment in which the shaft of a fan blade is utilized as spring member.
• Figure 4 shows an additional alternative embodiment in which the shaft of a fan blade is fixed to the blade and rotatably journalled in the impeller.
• Figure 1 shows an electric motor 1 with a motor shaft 2 projecting from one end of the motor.
• the motor is assumed to be arranged for operation with variable speed and may consist of, for example, a d.c. motor or of a frequency convertor-supplied a.c. motor.
• the rotary axis of the motor is designated A-A in the figures.
• the motor has an outer casing 3 and a cooling fan 4 mounted on the motor shaft.
• the direction of rotation for the motor and the fan is the one shown by the arrow E in Figure lb, that is, clockwise in the figure.
• the cooling fan which is of radial type, sucks air into its central part and drives the cooling air past the motor through a space 5 between the motor 1 itself and the outer casing 3.
• the path of the cooling air flow is schematically shown by the lines designated D in the figure.
• the cooling air fan has an impeller 4 with a hub 40 applied on the motor shaft 2.
• Six fan blades 41-46 are arranged on the impeller 4.
• Each fan blade is rotatably journalled around a shaft fixedly mounted in the impeller, which shaft is substantially parallel to the rotary axis of the motor.
• the fan blade 41 shown in Figure la has the shaft 411, around which the blade is rotatable around a turning axis B-B.
• the fan blade 45 has the shaft 451 and the turning axis C-C.
• the other blades are designed in the same way.
• each blade is rotatable between two end positions.
• a blade 41 is provided with a spring member in the form of a helical spring 412.
• One end 413 of the spring makes contact with the blade and strives to press this in a direction inwards towards the centre of the fan.
• the other end (not shown) of the spring is fixed to the shaft 411 of the blade.
• the other blades are provided with corresponding spring members .
• each blade When the motor does not rotate or rotates at a low speed, the blades are pressed inwards by their spring members towards the centre of the impeller and adopt the positions indicated by unbroken lines in Figure lb.
• each blade At increasing motor speed, each blade will be influenced by an increasing outwardly-directed centrifugal force. At a certain rotary speed, the centrifugal force on the blades will overcome the spring force and the blades are turned in a direction outwards from the centre of the impeller.
• the rotation of the blades increases continuously with increasing motor speed, and at maximum motor speed the blades adopt, for example, the positions indicated by broken lines in Figure lb.
• the angle of incidence of the blades will thus continuously decrease with increasing motor speed, which counteracts the approximately linear increase of the cooling air flow with the speed which would have occurred if the angle of incidence had been constant.
• the angle of incidence and hence the cooling air flow are made suitable functions of the motor speed.
• the speed dependence of the angle of incidence of the blades may be adjusted in a simple manner such that the cooling air flow becomes approximately constant and independent of the speed of the motor.. In this way, the cooling air flow at all speeds will be sufficient but not greater than what is required for cooling of the motor.
• the ventilating losses of the motor are therefore kept at the lowest possible level at all speeds.
• the disc is parallel to the impeller 4 itself but rotatable in relation thereto.
• the disc 6 has a number of approximately radially directed slots 61-66.
• Each blade has its above- mentioned pin, for 414, 454, arranged in the corresponding slot, 61 and 65, respectively, of the disc 6.
• the disc 6 will be actuated by the pins of the blades and be rotated clockwise in Figure 2b from the position shown in unbroken lines to the position shown in broken lines.
• Figure 2c shows an alternative embodiment of the fan shown in Figures 2a and 2b.
• the blades are here not provided with separate spring members but a spring member, common to all blades, in the form of a helical spring 7 is arranged around the hub 40 of the impeller.
• One end 71 of the helical spring makes contact with a boss 72 on the disc 6 and its other end 73 makes contact with a boss on the hub 40.
• the spring strives to turn the disc 6 in a counterclockwise direction in Figure 2b, that is, to turn the blades inwards towards the centre of the fan, that is, towards an increasing angle of incidence.
• FIG 3 shows an embodiment of an impeller according to the invention, in which the shafts of the blades are utilized as torsion springs to impart to the blades the torque which counteracts the centrifugal force.
• a blade 41 has a shaft 411 fixed to the impeller. At the outer end of the shaft, the blade is fixed to the shaft, for example by a weld 415, but is otherwise freely rotatable around the shaft .
• the shaft will therefore act as a torsion spring and serve the same purpose as the spring members 412 and 7, respectively, shown in Figures lc and 2c.
• Figure 4 shows how a blade 41 according to a further alternative embodiment may be fixed to its shaft, which may consist of a shaft stub 411 projecting from the blade.
• the shaft stub is rotatably journalled in a hole 416 in the impeller 4.
• the spring member consists of a helical spring 412 which is applied around the shaft 411.
• One end 413 of the spring is fixed to the shaft, for example by being passed through a hole in the shaft .
• the other end 417 of the spring makes contact with a boss 418 on the impeller 4.
• the cooling fan is mounted on the motor shaft.
• a cooling fan according to the invention may be used also in those cases where the fan is not mounted on the motor shaft but is driven from this through a toothed gearing or another power transmission.
• the spring members described above are also only examples of suitable embodiments and may, within the scope of the invention, be formed in a large number .of other ways.
• each blade is mounted in such a way that its turning axis, for example B-B, is located near one of the edges of the blade, that is, spaced from the centre of gravity of the blade.
• the blades may be mounted in other ways than those shown above, for example such that the turning axis of the blade passes through the centre of gravity of the blade.
• the centrifugal force on the blade itself does not produce any torque on the blade itself.
• the desired torque, increasing with the centrifugal force may be obtained, for example, by suitably fixing an arm with a weight applied thereon on the blade or on the blade shaft .
• the desired torque on the blades may alternatively be obtained by one single device, for example in the form of a suitably arranged weight which influences the link system (the disc 6 of Fig. 2) and, via this, also influences the blades.
• the link system shown in Figure 2 is only one of many feasible examples of link means for ensuring mutually equal angles of incidence of the blades.
• oscillation-damping members may be individual for each blade, or a common damping member may be arranged for the blades if these are mechanically linked to each other, as in the embodiment shown in Figure 2.
• the damping may be made, for example, by friction members or with the aid of viscous damping in air, gas or liquid dampers, and the damping members may be wholly or partially integrated with the spring members .
• the latter may possibly be made of material with a high internal friction to provide the desired damping.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Motor Or Generator Cooling System (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20376986

Family Applications (1)

Country Status (3)

Cited By (8)

Citations (5)

• 1989
  • 1989-09-27 SE SE8903174A patent/SE464550B/sv not_active IP Right Cessation
• 1990
  • 1990-09-27 WO PCT/SE1990/000620 patent/WO1991005397A1/en unknown
  • 1990-09-27 AU AU65053/90A patent/AU6505390A/en not_active Abandoned

Patent Citations (5)

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