Abstract:
The invention relates to a fan wheel ( 6 ) for a blower module ( 2 ), comprising a hub ( 5 ) and a radial fan ring ( 8 ) composed of a plurality of fan blades ( 12 ) and further comprising means for resolving imbalances in the fan wheel ( 6 ). According to the invention, balancing weights ( 18 ) can be fastened to the radial ends of the fan blades ( 12 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention proceeds from a fan wheel for a blower module. 
         [0002]    Such blower modules are known from a wide variety of different industrial applications, for example they are used for ventilating various technical appliances or for channeling the air stream when used in air-conditioning systems of motor vehicles. 
         [0003]    In many applications, for example when used in air-conditioning systems of motor vehicles, the fans of the blower modules are balanced following installation. Usually, added or positive balancing is carried out here with balancing weights, e.g. in the form of (balancing) clips, being fitted on the fan wheel. The balancing weights here are fixed in the selected position by resilience and frictional fitting. The balancing weights are usually fastened exclusively on the (axial) inside of the fan blades, this side being directed toward the fan center point, and they are secured here by form fitting against the radially acting centrifugal forces. 
         [0004]    The disadvantage here, inter alia, is that the fan has to be configured such that an edge, on which the balancing weights can be fastened, is provided on the inside of the fan blades. Furthermore, this fastening edge also has to be freely accessible once the fan has been installed on the motor. In many cases, these requirements are not met. A further disadvantage is that, in the case of such fastening, with balancing of moments and/or dynamic balancing, the quality of balancing is dependent on whether the measuring plane and the balancing plane are positioned correctly in relation to one another. The operator or installer, however, can install the balancing weights axially at any desired height or in any desired plane, as a result of which the balancing quality realized is dependent on the skill of the installer. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the invention to design a fan wheel and/or the balancing weights so as to ensure permanent and externally easily accessible fastening of the balancing weights and, at the same time, good balancing quality. 
         [0006]    According to the invention, it is proposed to arrange the balancing weights at the end of the radially oriented fan blades. The balancing weight or weights is/are thus positioned at the maximum fan diameter, and therefore the balancing weight is relatively distant from the axis of rotation, or center axis, of the fan wheel. It is thus possible to select a lower weight for the balancing elements. This positioning also makes it possible for the region in which the balancing weights have to be fitted for balancing purposes still to be very easily accessible even once the fan has been installed. Handling for the operator is more straightforward and the risk of the balancing weight accidentally passing into the blower module during installation, and causing malfunctioning as a result, is lower. 
         [0007]    The balancing weights are advantageously designed as (balancing) clips and are fastened in a form-fitting and/or force-fitting manner at the ends of the fan blades. The (balancing) clips here usually consist of steel. However, it is basically also possible to use, for this balancing method, other resilient materials, which should have the highest density possible in order that the volume can be kept appropriately small. 
         [0008]    The (balancing) clips differ in size, in order for it to be possible to provide the operator with a selection of different balancing masses. It is also possible to use different shapes. On the one hand, the (balancing) clip is adapted to the shape of the fan blade and, on the other hand, the attempt is made, by configuring the (balancing) clips in a suitable manner, to improve the form fitting or frictional fitting. 
         [0009]    The inside and outside of the radially oriented fan blades contain grooves, in which the (balancing) clips engage in a form-fitting manner by way of their clamping edges. As a result of these grooves, it is advantageously the case that the (balancing) clips are secured against being slung off axially not only by frictional fitting, but also by corresponding form fitting. Furthermore, the grooves ensure always the same axial positioning of the (balancing) clips, which helps to achieve a uniform quality for the balancing of moments, since the balancing plane is clearly defined. 
         [0010]    The radially oriented fan blades form a fan ring, which is made up alternately of short and long fan blades, wherein the (balancing) clips and the grooves for the (balancing) clips are provided at the radial end of the fan blades. The balancing clips are arranged preferably on the long fan blades, since these are designed to be stiffer than the short fan blades and are thus less likely to vibrate. 
         [0011]    The fan wheel is produced preferably by injection molding, wherein the grooves can advantageously be demolded from the mold without any additional outlay. 
         [0012]    The fan wheel is a constituent part of a blower module, which is connected to a drive unit comprising an electric motor. The fan wheel here is connected in a rotationally fixed manner to the drive shaft of the electric motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    An exemplary embodiment of the invention will be explained in more detail in the following description and in the drawing, in which: 
           [0014]      FIG. 1  shows a first perspective view of a blower module, 
           [0015]      FIG. 2  shows a second view (of part) of the blower module, 
           [0016]      FIG. 3  shows a first perspective view of a fan wheel, 
           [0017]      FIG. 4  shows a second perspective view of the fan wheel, 
           [0018]      FIG. 5  shows an enlarged detail of the fan wheel with a balancing element fastened on a fan blade, and 
           [0019]      FIG. 6  shows an enlarged illustration of the balancing weight fastened on a fan blade. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The blower module  2  illustrated in  FIG. 1  comprises a basic housing  4 , on which a fan wheel  6  is mounted such that it can be rotated on a drive shaft  7 . The fan wheel  6 , in turn, is fastened on the drive shaft  7  by way of its hub  5 . The (radial) fan wheel  6  has, on its outer end side, an axial fan ring  8 , which is made up of curved fan blades  9 . The (radial) fan wheel  6  also has a radial fan ring  10 , which is likewise made up of curved fan blades, referred to hereinbelow as radial fan blades  12 . As can be seen from  FIG. 4 , the radial fan ring  10  has two different types of fan blade  12 . A first group comprises long fan blades which extend as far as the hub  5 , and will be referred to hereinbelow as long fan blades  14 , whereas a second group comprises short fan blades  16  which, as seen from the external diameter of the radial fan ring  10 , extend only some way in the direction of the axis of rotation. The two groups of fan blades  14 ,  16  are formed alternately on the (radial) fan wheel  6 . The functioning of such a radial blower is known and will therefore not be explained in any more detail. The essential factor is that the air is taken in via the axial fan ring  8 , deflected through 90°, compressed and then blown out via the radial fan ring  10 . 
         [0021]    For the purpose of balancing dynamic imbalances in the (radial) fan wheel  6 , a clip element, which serves as a balancing weight and will be referred to hereinbelow as a balancing clip  18 , is plugged and fastened if required, following installation of the blower module  2 , on an outer radial end of a long fan blade  14 . 
         [0022]    In order to ensure permanent fastening, the inside and outside of the long fan blades  14  contain grooves  20  and  22 , which run parallel to the axis of rotation of the fan wheel  6  and in which—as can be seen, for example, from FIG.  6 —the clamping edges of the balancing clip  18  can engage in a form-fitting manner. This ensures that, despite high blower speeds, the balancing clip  18  is fastened securely on the fan blade  14 . The length of grooves  20 ,  22  here corresponds substantially with the width of the balancing clips  18 , and therefore the balancing clips  18  are prevented from slipping laterally. 
         [0023]    Balancing takes place as follows. The blower module  2  is mounted, in the ready-installed state, in a measuring apparatus. The rotor, i.e. the armature of the motor and the fan wheel  6 , is set in rotation by virtue of the motor being switched on. Suitable measuring sensors pick up the dynamic forces in the predetermined measuring planes and the respective imbalance is displayed to the operator in terms of magnitude and angle. The measuring apparatus uses this to calculate the necessary balancing mass and the balancing angle, and indicates this correspondingly to the operator. The operator uses the display information (and his experience) to fit the balancing clips  18  on the corresponding fan blade  14 , and then starts a monitoring-measurement operation. The blower module  2  here is balanced in two planes which are positioned as far apart from one another as possible. It is only this which ensures that both the static equilibrium and the balancing of moments are improved, wherein the second plane in this fan is located in the region which is designated  9  in  FIG. 1 . 
         [0024]    The number of balancing clips  18  which are necessary depends on the magnitude and angular position of the imbalance measured. Balancing is ideally achieved with a maximum of two balancing clips, i.e. one balancing clip for each plane. In practice, it is quite possible for two or three balancing clips to be placed in different positions along each plane, in order for an adequate result to be achieved. 
         [0025]    However, a maximum of just one balancing clip  18  should be fastened on each fan blade  14 . Therefore—as is illustrated in FIG.  6 —the length of the groove  20 ,  22  is coordinated with the width of the balancing clip  18 . 
         [0026]    The abovedescribed practice of fastening the balancing weights is not restricted either to the number or to the shape of the fan blades. It is thus the case that the practice according to the invention of fastening the balancing weights can also be used for other types of fan wheel, for example for those which have just one group of fan blades.