Abstract:
A fan has a sensor ( 86; 186 ) for sensing at least one value of the air that flows through the fan ( 20; 120 ). The fan has a fan housing ( 22, 24; 122, 124 ); an electronically commutated external-rotor motor, arranged in that housing, having an internal stator ( 30; 130 ) and an external rotor ( 46; 146 ); a fan wheel ( 56; 156 ) coupled to the external rotor ( 46; 146 ); an air inlet opening ( 58; 90; 158 ) for the inflow of air that is to be moved by the fan wheel ( 56; 156 ); a circuit board ( 68; 185 ) having a portion ( 66; 188 ) that extends adjacent the air passage opening ( 58; 158 ); and conductors ( 82, 84; 182′, 182″ ) arranged on that portion ( 66; 188 ), to which conductors the sensor ( 86; 186 ) is connected, preferably by a Surface Mounted Device (SMD) method. Premounting the sensor on the circuit board facilitates automated manufacture and reduces cost.

Description:
FIELD OF THE INVENTION:  
       [0001]     Sensor fans are used, for example, for air measurement for air-conditioning systems in motor vehicles. They have a diameter of, for example, 30 mm, i.e. these are what is referred to in technical language as “mini-fans.” 
       BACKGROUND  
       [0002]     Mini-fans of this kind contain an electronically commutated motor whose rotor drives a fan wheel. The latter takes in air through an air inlet opening, and that air is then blown out through one or more outlet openings, e.g. radial openings.  
         [0003]     Arranged in the region of the air passage opening are one or more sensors, e.g. a Negative Temperature Coefficient (NTC) resistor at which the present air temperature is measured, or a sensor for the moisture content, quality, radioactivity, stuffiness, dustiness, etc. of the air. For example, air quality in a workplace could be maintained by keeping a particular gas or pollutant, such as carbon dioxide or methane or flammable fumes, below a predetermined threshold level. An air conditioning system, for example, can be controlled in accordance with data from such a sensor or sensors. Since the fan is so small, installation of such a sensor, e.g. an NTC resistor, as a discrete device, is difficult and also entails considerable cost. In addition, an electrical connection must be made from the sensor installation location to a connector of the fan, which results in additional labor and material costs.  
       SUMMARY OF THE INVENTION  
       [0004]     It is therefore an object of the invention to provide a new fan structure which is compact and cost-effective to manufacture.  
         [0005]     According to the invention, this object is achieved by providing a sensor on a circuit board which is mounted directly on the housing of the fan. The use of a circuit board substantially simplifies manufacture, since a sensor can be mounted on the circuit board using automatic production methods, e.g. as a Surface Mounted Device (SMD) component. This also makes it possible to miniaturize the fan further, since a sensor that is installed on a circuit board has only a very low overall height. The present invention thus enables the overall size of such a fan to be further reduced.  
         [0006]     An advantageous embodiment of the invention is to make the circuit board bifurcated, with a hinge or bend between a sensor portion of the board and a commutation control portion of the board. The circuit board advantageously has a reduced thickness in the region of its bend, to increase its flexibility. That thickness can be reduced, for example, by at least 50%, preferably by 70 to 85%, compared to a remaining portion of the board.  
         [0007]     It has proven very advantageous in this context to brace the circuit board, in particular in positively engaged fashion, in the region of its bend against a rounded or “bending” edge of the fan housing. This bending edge has important advantages:  
         [0008]     It supports the circuit board during a bending operation and thereby prevents the circuit board from breaking during installation or mounting of the board onto the housing.  
         [0009]     It supports and protects the circuit board during the entire service life of the fan, so that the thin portion of the circuit board, because it rests on the bending edge, is very well braced and thereby protected from mechanical damage. 
     
    
     BRIEF FIGURE DESCRIPTION  
       [0010]     Further details and advantageous refinements of the invention are evident from the exemplary embodiment, in no way to be understood as a limitation of the invention, that is described below and shown in the drawings.  
         [0011]      FIG. 1  is a very greatly enlarged longitudinal section through a preferred embodiment of a fan according to the present invention, viewed along line I-I of  FIG. 2 ;  
         [0012]      FIG. 2  is a plan view of the intake opening of the fan, viewed in the direction of arrow II of  FIG. 1 ;  
         [0013]      FIG. 3  is a three-dimensional depiction of a circuit board used in the context of  FIGS. 1 and 2 , in the state before it is bent;  
         [0014]      FIG. 4  shows the same circuit board in the bent state;  
         [0015]      FIG. 5  is a greatly enlarged exploded view of the fan according to  FIGS. 1 and 2 ;  
         [0016]      FIG. 6  is a variant of  FIGS. 1 through 5  showing, in perspective, a fan in which an NTC resistor  186  is mounted on a separate circuit board  185 ; and  
         [0017]      FIG. 7  is an exploded view of the fan of  FIG. 6 . 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 1  shows a mini-fan  20 . The latter has, for example, an outside diameter of 30 mm and a height of 20 mm, and is shown greatly enlarged, so that details can be depicted with sufficiently accuracy.  FIG. 1  shows, by way of example, an indication of scale, in order to illustrate size relationships.  
         [0019]     Fan  20  has a lower housing part  22  and an upper housing part  24  joined mechanically thereto. Lower housing part  22  has in the center a bearing support tube  26 , into which a sintered bearing  28  is pressed and on whose outer side is mounted an internal stator  30  that here, as shown in  FIG. 5 , comprises claw poles  32 ,  34  including two annular coils  36 ,  38  (indicated only schematically) that are preinstalled on a carrier  40 . Annular coil  36  serves to drive the motor, and annular coil  38  as a so-called sensor coil for sensing the rotor position for electronic commutation. Carrier  40  has four pegs  42 , with which it is pressed into corresponding holes  44  of lower housing part  22 , as shown in  FIG. 5 .  
         [0020]     Also provided is an external rotor  46  that has a rotor cup  48  within which is arranged an annular permanent magnet  50 , which here is magnetized with four poles, since the claw-pole stator shown also has four poles.  
         [0021]     Mounted in rotor cup  48  is a shaft  52  that, as shown, is supported in sintered bearing  28  and is in contact with its free end against lower housing part  22 . Since rotor magnet  50  in  FIG. 1  is offset axially upward with respect to claw poles  32 ,  34 , a force K acts on rotor  46  in the direction toward lower housing part  22 , and presses shaft  52  against the latter (axial plain bearing with axial preload).  
         [0022]     Fan blades  56  of a radial fan are arranged on rotor cup  48 . These blades draw air through an axial air passage inlet opening  58  in upper housing part  24 , and blow that air back out radially through lateral openings  60 .  FIG. 5  shows one of the two lateral openings  60 .  
         [0023]     Upper housing part  24  has a flat upper side  64 , and mounted thereon is a first portion  66  of a circuit board  68  whose shape is clearly evident from  FIGS. 1 through 5 . This circuit board  68  has in general a thickness d of approximately  1  mm, which is reduced to approximately 0.22 mm by a milled recess  72  in a bending region  70 , in order to facilitate easier bending there. It has been shown that this makes possible a bend whose bending angle can be between 0° and approximately 180°. Circuit board  68  has, below bending region  70 , a second portion  54  on which are arranged other electronic components of fan  20 , e.g. those which control commutation. According to  FIG. 1 , a plug connector  76  of arbitrary design is mounted at the bottom of second portion  74 , in order to allow easy installation.  
         [0024]     Serving to mount circuit board  68  are pegs  78  made of plastic, which are provided on housing parts  22 ,  24 . The pegs project through openings  80  in circuit board  68 , and are permanently secured there e.g. by heating or other types of positively engaged connection. Also located on circuit board  68  are printed conductors  82  that lead to contact surfaces  84  on which a sensor (here an NTC resistor  86 ) is soldered in place using a Surface Mounted Device (SMD) method. Such NTC resistors are well known in the art. A resistor  86  of this kind has a very low overall height while functioning normally.  
         [0025]     Contact surfaces  84  are located on a thin strut  88  that extends in portion  66  approximately diametrically with respect to an opening  90  in board  68  whose shape matches that of air inlet passage  58  formed in housing part  24 .  
         [0026]     A rounded support surface  92 , whose shape is best evident from  FIG. 1 , is provided in the region of bend  70  on housing part  24 . When circuit board  68  is bent, support surface  92  fits (preferably in positively engaged fashion) into milled recess  72 , therefore optimally braces circuit board  68  in the region of its bend  70 , and at the same time forms bend  70  so that conductors  82  do not become cracked there. The thickness of the copper layer that forms conductors  82  is advantageously selected to be sufficient, especially in the region of bend  70 , to exploit the ductility of copper.  
         [0027]     Provided in lower housing part  22  are two diametrically opposite pockets  94  ( FIG. 5 ) in which are arranged positioning magnets (not shown) which, when the motor is currentless, rotate rotor  46  into a predetermined rotational position, from which starting in the correct rotation direction can occur without difficulty.  
         [0028]     The connectors of coils  36 ,  38  are connected to corresponding conductors (not shown) of circuit board  68 . Lower housing part  22  has four slots  96  (see  FIG. 5 ) for that purpose.  
         [0029]      FIGS. 6 and 7  show a second exemplary embodiment of the sensor fan  120  of the present invention. It has a fan wheel  156  that is driven by an electronically commutated motor. It furthermore has a lower housing part  122  and an upper housing part  124  connected thereto. The latter is formed on its upper (in  FIG. 6 ) side with an air passage opening  158 , which is defined by a cylindrical collar  159  and into which air flows from above during operation. Collar  159  has two lateral gaps or orifices  161 ′ and  161 ″.  
         [0030]     The motor has an internal stator  130  that here has claw poles  132 ,  134  and two annular coils  136 ,  138 . An external rotor  146  has a rotor cup  148  (not clearly shown, but similar to rotor cup  48  of the first embodiment) within which an annular magnet is arranged. Mounted in rotor cup  148  is a shaft that is supported in a sintered bearing  129  that is arranged in a bearing support tube  128 .  
         [0031]     Located laterally on housing parts  122 ,  124  is a contact array comprising six contacts K 1  through K 6  that transition at the bottom into solder lugs  176  which serve, for example, for connection to conductors (not depicted) of a circuit board. Housing  120 ,  124  is provided with resilient mounting pegs  178 .  
         [0032]     Contact array K 1  through K 6  is immovably joined to housing parts  122 ,  124  e.g. by plastic welding. Its contacts K 2  through K 5  serve for connection to four connecting pins  137  of the two stator coils  136 ,  138 . Its contacts K 1  and K 6  serve for connection to two connecting leads of an NTC sensor  186  that is located approximately at the center of inlet opening  158  in order to measure the temperature of the inflowing air there.  
         [0033]     Rotor  146  is coupled directly to the blades of fan wheel  156 . NTC sensor  186  is mounted on a transverse strut  188  of a generally annular circuit board  185  using SMD technology, and electrically connected there to two conductors  182 ′,  182 ″ that lead to contact holes  183 ′ and  183 ″, respectively. These contact holes are soldered directly to contacts K 6  and K 1 , respectively, of the contact array. NTC sensor  186  is thereby electrically connected, and the annular circuit board  185 , a component of which is strut  188  that runs diagonally with respect to that annular circuit board  185 , is mechanically mounted on sensor fan  120  by the soldering operation.  
         [0034]     The advantage resulting from this is that circuit board  185  can easily be replaced or swapped out, in the event that it becomes damaged. It is also possible to use the same sensor fan  120  for NTC resistors  186  having different resistance values, only circuit board  185  being different. Because annular circuit board  185  is located outside collar  159 , it does not impede the inward flow of air through opening  158 , and strut  188  likewise does not constitute a substantial obstacle to that air flow.  
         [0035]     The air outlet openings are labeled  160  in  FIGS. 6 and 7 .  
         [0036]     Many variants and modifications are, of course, possible within the scope of the present invention. Therefore, the invention is not limited to the specific embodiments shown and described, but rather is defined by the following claims.