Abstract:
The invention relates to a fan motor in a ventilator for an interior ventilation system of a motor vehicle, comprising a first part having a plurality of radially aligned coils and a second part rotatably supported relative to the first part and having a plurality of radially aligned permanent magnets, wherein a concentric ring gap is formed between coils of the first part and permanent magnets of the second part, and the coils are air-core coils.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Mechanically or electrically commutated electric motors are normally used, corresponding to the desired blower power, for electrically driving fan impellors in HVAC (“heating, ventilating and air conditioning”) installations (referred to in the following text as ventilation installations). In this case, one part of the electric motor, for example the stator, is fitted with a number of coils, and the other part, for example the rotor, is fitted with a number of permanent magnets. The two parts are borne such that they can rotate with respect to one another, and the coils and the permanent magnets are arranged on different sides of a concentric annular gap. The coils are wound around cores, which are integrated with an annular magnetic flux element which guides the magnetic flux between the coils. In practice, a hollow-cylindrical flux element, for example in the form of a stack of stamped laminate parts, is used for this purpose. The flux element has radial slots, with the turns of a coil passing through adjacent slots, such that the area which is surrounded by the turns is filled by a section of the flux element, which acts as a ferromagnetic coil core. The coil is manufactured from a non-ferromagnetic material, for example copper wire. 
         [0002]    When the rotor rotates with respect to the stator, a ferromagnetic section (the coil core) and a non-ferromagnetic section (the coil) of the stator are alternately opposite a permanent magnet on the rotor. This results in permanently alternating forces acting between the rotor and the stator during rotation, thus allowing the rotor to be accelerated or braked with respect to the stator, and this adversely affects smooth running of the rotor. The frequency of the smooth-running fluctuation resulting from this is dependent on the rotation speed of the rotor and the number of coils along the circumference of the stator. This means that narrow bandwidth noise can occur during operation of the described fan motor, and can be perceived as howling or whistling. This noise can propagate through the ventilation installation in the motor vehicle, and occupants can find it to be unpleasant. The noise can also interact with further oscillations, which, for example, can also provoke harmonics, superimposed noises and beat frequencies, which are audible in the interior of the motor vehicle and lead to increased noise stress. 
         [0003]    In the past, attempts have been made to counteract such noise development by damping the excitation or by reducing the electromagnetic forces. However, this has led to fan motors which had a large mass with respect to their performance class. This is undesirable for reasons relating to handling, production and consumption of resources during production. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention is therefore based on the object of specifying a fan motor which provides good smooth running with a low mass, as a result of which the fan motor produces little noise. 
         [0005]    According to a first aspect of the invention, a fan for an interior ventilation installation for a motor vehicle comprises a fan motor which comprises a first part having a multiplicity of radially aligned coils and a second part, which is borne such that it can rotate with respect to the first part and has a multiplicity of radially aligned permanent magnets, with a concentric annular gap being formed between coils on the first part and permanent magnets on the second part, and the coils being air-cored coils. 
         [0006]    The use of air-cored coils avoids a ferromagnetic element of a part of the fan motor cyclically entering a magnetic field of the other part of the fan motor during operation, and leaving it again. Smooth-running fluctuations caused by an interaction such as this in a conventional fan motor therefore do not occur, and for the first time there is no noise at all caused by such smooth-running fluctuations. Furthermore, the coreless air-cored coils have considerably less hysteresis than coils wound around a ferromagnetic core. 
         [0007]    The fan motor of the fan may comprise a first magnetic flux element for magnetic coupling of the coils on their side facing away from the annular gap. The first magnetic flux element closes the magnetic lines of force of adjacent coils which are being operated, and thus increases an effective magnetic force and, in consequence, an efficiency of the fan motor. 
         [0008]    The turns of the coils may rest on the first magnetic flux element in the axial direction. Although this limits the maximum number of turns for each of the coils, because sections of all the turns have to be located alongside one another and only a restricted external circumference of the flux element is available for making contact with the turns, each of the turns is, however, at the same time at the shortest possible distance from the annular gap which separates the turns from the permanent magnets on the other part of the fan motor. This embodiment can therefore further increase the efficiency of the fan motor. 
         [0009]    The fan motor of the fan may furthermore comprise a second magnetic flux element for magnetic coupling of the permanent magnets on the side facing away from the annular gap. Like the first magnetic flux element, the second magnetic flux element is used to guide magnetic lines of force, and therefore in the end to increase the efficiency of the fan motor. 
         [0010]    The first part of the fan motor of the fan may be a stator, and the second part may be a rotor, which surrounds the stator. A fan motor such as this is known as an external rotor. The permanent magnets are fitted radially on the outside on the rotor, in order to maximize a rotating mass of the external rotor. There is no need for a mechanical commutator because the coils which are arranged on the stator cannot move with respect to an attachment element of the fan motor, to which the electrical connections of the fan motor are fitted. 
         [0011]    In addition to the fan motor, the fan may comprise a fan impellor which is connected to the rotor of the fan motor. By way of example, it may be a radial or axial fan impellor. In one refinement, the fan impellor is half-axial and comprises both suction blades for sucking air in axially, and outlet-flow blades for the air which has been sucked in to flow out radially. A deflection element guides the air which has been sucked in to the outlet-flow blades, and at the same time restricts the flow area of the air in an axial direction. The deflection element may be designed to be radially-symmetrically concave. The fan motor with an external rotor may be arranged on the concave side of the deflection element, facing away from the blades of the fan, thus resulting in particularly good utilization of the available installation space. This makes it possible to produce a compact fan in particular with a short length in the axial direction. 
         [0012]    Furthermore, the fan motor of the fan may comprise a winding former for fixing the first magnetic flux element. The winding carrier may furthermore be fitted with the windings of coils of the fan motor, thus resulting in a stator assembly which can be handled separately and can be produced at low cost. 
         [0013]    The winding former may comprise two axially arranged parts. By way of example, the two parts may be shaped such that they bear the first magnetic flux element axially and radially after being joined together axially. After being joined together, the winding on the coils can be fitted to the winding former. The two parts of the winding former may be congruent, thus making it possible to save further production costs during mass production. 
         [0014]    Each part of the winding former may comprise a projection for fixing one turn of one of the coils. Projections which are opposite one another in the axial direction may be used to bear a plurality of turns of one coil. The two parts of the winding former are connected to one another by the turns, holding the first magnetic flux element in place such that it cannot move. 
         [0015]    Finally, the fan motor of the fan may comprise a control circuit, which is connected to the coils, for rotation-speed control without a sensor, based on excitation of the coil through which no current is flowing. 
         [0016]    According to a second aspect, a motor vehicle comprises an interior ventilation installation having a fan as above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention will be described in more detail in the following text with reference to the attached drawings, in which: 
           [0018]      FIG. 1  shows a schematic illustration of a ventilation installation in a motor vehicle; 
           [0019]      FIG. 2  shows a detail of the fan motor from  FIG. 1 , in the form of an axial perspective; 
           [0020]      FIG. 3  shows the detail from  FIG. 2 , in the form of a radial perspective; and 
           [0021]      FIG. 4  shows a side section view through a fan motor from  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Unless stated to the contrary, axial and radial details relate to a rotation axis of the fan motor. Identical or mutually corresponding elements have identical reference symbols in all the figures. 
         [0023]      FIG. 1  shows a schematic illustration of an interior ventilation installation  100 . A motor vehicle  110  comprises an induction section  120 , a fan  130  and a distribution section  140 . The fan  130  comprises a fan impellor  150  and a fan motor  160 . The illustration in  FIG. 1  does not include optional elements of the interior ventilation installation  100 , such as filters, flaps, valves, heat exchangers, condensers and the like, which have no further relevance in the present context. The fan motor  160  causes the fan impellor  150  to rotate, thus resulting in air being sucked into the fan impellor  150  through the induction section  120  from outside the motor vehicle  110 , and then being fed through the distribution section  140  into an interior of the motor vehicle  140 . The induction section  120  and the distribution section  140  are frequently integrated in one section. 
         [0024]      FIG. 2  shows a detail  200  of the fan motor  160  from  FIG. 1  with air-cored coils, in the form of an axial perspective. A coil  210  is wound around a projection  220  and comprises three turns, whose axial sections are located, parallel to one another, on a circumference about the rotation axis of the fan motor  160 . The visible ends of each turn are shown, not connected, in order to indicate that the turns can be connected in any desired manner to one another, to other turns or to electrical connections of the control circuit  410 . A first concentric magnetic flux element  230 , one section of which is illustrated, extends on a side of the coil  210  facing the rotation axis of the fan motor  160 . The first magnetic flux element  230  is in the form of a hollow cylinder, overall. The first magnetic flux element  230  may, for example, be a stator core of any desired shape. For example, this may comprise a solid hollow-cylindrical element, a stack of laminates or a spirally wound flat wire. Elements or sections of the first magnetic flux element may be connected to one another in order to further reduce noise, for example by adhesive bonding, welding, riveting, clamping or screwing. In the center of the coil  210 , the projection  220  covers the first magnetic flux element  230 . There is no core between the turns of the coil  210  along the external circumference of the first magnetic flux element  230 ; the interior of the coil  210  is filled with air (“air-cored coil”). 
         [0025]    A permanent magnet  250  extends in the radial direction, separated from the coil  210  by an annular gap  240 . The ratio of the sizes of the permanent magnets  250  with respect to the coil  210  is not to scale. The number of coils  210  in the fan motor  160  may differ from the number of permanent magnets  250 , for example  12  coils  210  and  11  or  13  permanent magnets  250 . The permanent magnet  250  is magnetically radially aligned, in which case, as illustrated, the magnetic north pole may be on the inside or else on the outside. On its side facing away from the annular gap  240 , the permanent magnet  250  rests on a second magnetic flux element  260 , one section of which is illustrated. Overall, the second magnetic flux element  260  has a hollow-cylindrical shape. Like the first magnetic flux element  230 , it may consist of a plurality of elements or of solid material and, for example, may be rolled, thermoformed, deep-drawn or turned from a tube (pushed off). 
         [0026]    The figure does not show further coils  210  on both sides of the coil  210  that is illustrated, nor further permanent magnets  250  on both sides of the permanent magnet  250  that is illustrated. Adjacent elements may rest on one another, and adjacent permanent magnets may have mutually opposite magnetic alignments. 
         [0027]      FIG. 3  shows a further detail view  300  of two coils  210  from  FIG. 2  of the fan motor  160  from  FIG. 1 , in the form of a radial view. The permanent magnet  250  illustrated in  FIG. 2  and the second magnetic flux element  260  are not illustrated in  FIG. 3 . The coils  210  are each wound around mutually opposite projections  220 . Each of the coils  210  comprises three turns, with adjacent coils  210  being connected directly to one another. The axial sections of the turns of the coils  210  are arranged parallel to one another along the outer surface of the first magnetic flux element  230 . The area in the interior of each coil  210 , which is surrounded by the respective innermost turns, is filled with air; in other refinements, it is also possible to use a different magnetically neutral material, for example a synthetic resin such as polyester or epoxy. 
         [0028]      FIG. 4  shows a side section view through the fan  130  from  FIG. 1 . The fan  130  comprises the fan impellor  150 , the fan motor  160 , and an attachment flange  470  which holds the control circuit  410 . The control circuit  410  is designed to activate and deactivate the coils  210  in a specific sequence during operation, in order to achieve a predetermined rotation speed for the fan motor  160 . The actual rotation speed of the fan motor  160  can be determined by detecting an induced voltage, which is induced in unactivated coils  210  by the permanent magnets moving past them. Since no such voltage is induced when the fan motor  160  is stationary, there is no need to detect the actual rotation speed initially during a starting phase of the fan motor  160 , and a predetermined activation sequence of the coils  210  can be used until the fan motor  160  has reached a sufficiently high rotation speed in order to carry out rotation-speed regulation. 
         [0029]    The fan impellor  150  comprises suction blades  420  for sucking air in axially, outlet-flow blades  430  for the air which has been sucked in to flow out radially, and a deflection element  440  for deflection of the air which has been sucked in to the outlet-flow blades  430 . 
         [0030]    The deflection element  440  is connected in a rotationally stable manner to the suction blades  420  and to the outlet-flow blades  430 . Furthermore, the deflection element  440  is fitted with a rotor  490  of the fan motor  160  in the form of the permanent magnets  250  and the second magnetic flux element  260 . A stator  480  of the fan motor  160  comprises a winding former, which is formed from a first part  450  and a second part  460  and is fitted with the first magnetic flux element  230  and the coils  210 . Each of the parts  450 ,  460  of the winding former has projections  220  for fixing the coils  210 . The annular gap  240  extends between the coils  210  and the permanent magnets  250 . The attachment flange  470  bears the stator  480  of the fan motor  160 . 
         [0031]    On an upper section, the attachment flange  470  is designed such that it can bear the fan  130  for example in an appropriate cutout in one wall of a ventilation section. The fan  130  may be removable from the cutout as a complete unit in the axial direction. 
         [0032]    The described fan motor  160  is able to cover a broad rotation-speed range with a low to medium torque, and is therefore particularly suitable for use in the fan  130 . Its low mass and its low tendency to produce noise qualify the fan motor  160  in a particular manner for use in the interior ventilation installation  100  of a motor vehicle  110 . 
         [0033]    In comparison to a conventional fan motor with the same drive power, a considerable weight saving can additionally be achieved, since there is no need to increase the rotation mass of the fan motor  160  for smooth-running stabilization purposes, or to operate the fan motor  160  permanently below its design performance, in order to avoid noise. In the case of a test example of a described fan motor  160 , a weight of 400 g could be achieved, while a conventional fan motor with a comparable output power would have a weight of 880 g.