Abstract:
A cooling fan module for a motor vehicle. has a first fan motor which is used to drive a first cooling fan and a second fan motor which is used to drive a second cooling fan. A control unit ( 6, 13 ) is associated with the first fan motor ( 2, 11 ), which operates the first fan motor ( 2, 11 ) and the second fan motor ( 4, 12, 23 ) simultaneously, in order to provide an economical and compact technical solution for the cooling fan.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. national stage application of International Application No. PCT/EP2006/066021 filed Sep. 5, 2006, which designates the United States of America, and claims priority to German application number 10 2005 048 887.0 filed Oct. 12, 2005, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a cooling fan module for a motor vehicle. In particular the invention relates to a cooling fan module with a first fan motor for driving a first cooling fan and with a second fan motor for driving a second cooling fan. 
       BACKGROUND 
       [0003]    Frequently two or more cooling fans are used in cooling fan modules for motor vehicles. When two cooling fans are used the module is also referred to as a double module. There are a number of reasons for using more than one cooling fan: 
         [0004]    One is that the space available in the motor vehicle is often restricted. Another is that the fan output required is often an argument for using a number of cooling fans. Since for higher outputs the fan motors employed are of greater length, it often makes sense, as regards the length of module needed, to divide the module up into two smaller, shorter fan motors. If high cooling power is required, a separation into two (or more) cooling fans is often sensible and/or necessary, since, because of its inadequate heat removal, a single fan motor cannot provide the power needed. 
         [0005]    In addition it can be necessary, because of the design of a motor vehicle or for other reasons, to use heat exchangers which have a more rectangular shape. By contrast with a cube shape, a double-fan configuration makes more sense for a more rectangular shape, since a greater coverage of the heat exchanger can be achieved with this shape and the air flow from the corners of the heat exchanger is improved. 
         [0006]    Finally two or more cooling fan modules can be used if—for example for reasons of availability—a redundancy is to be achieved. 
         [0007]    Previously such double modules have featured two direct current motors with brushgear which have been operated either in series or in parallel, in order to obtain specific speeds and thereby power output stages. In newer applications the direct current motors with brushgear have been operated with internal, external PWM actuating units or units integrated into one of the two motors. 
         [0008]    Increased demands in respect of module length, power and costs have also demanded new approaches to solutions for double modules. 
       SUMMARY 
       [0009]    According to an embodiment, a cost-effective and compact fan cooling can be provided by a cooling fan module for a motor vehicle, comprising a brushless first fan motor for driving a first cooling fan and a second fan motor for driving a second cooling fan, a control unit being assigned to the first fan motor, which, at the same time as operating the first fan motor, also operates the second fan motor. 
         [0010]    According to a further embodiment, the first fan motor and the second fan motor may be connected in parallel. According to a further embodiment, the second fan motor may be a dc motor with brushgear which on the one hand is connected via a phase-dependent number of rectifiers to connection elements of the first fan motor and on the other hand to the power supply line or the ground line of the control unit. According to a further embodiment, the second fan motor may be an asynchronous motor or a synchronous motor which is connected directly to the connection elements of the first motor. 
         [0011]    According to another embodiment, a method for operating a cooling fan module for a motor vehicle, wherein the cooling fan module has a brushless first fan motor for driving a first cooling fan and a second fan motor for driving a second cooling fan, may comprise the steps of: assigning a control unit to the first fan motor, which, as well as operating the first fan motor also operates the second fan motor at the same time, and controlling the first fan motor via the control unit with speed regulation and the speed of the second fan motor being set as a function of the speed of the first fan motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]    The invention will be described below with reference to exemplary embodiments which are explained in greater detail with the aid of drawings. The drawings show the following simplified diagrams: 
           [0013]      FIG. 1  a schematic block diagram of a parallel double module, 
           [0014]      FIG. 2  a switching diagram of a parallel double module with a second motor with brushgear in a version with a plus-side connection, 
           [0015]      FIG. 3  a switching diagram of a parallel double module with a second motor with brushgear in a version with ground-side connection and 
           [0016]      FIG. 4  a switching diagram of a parallel double module with an asynchronous motor. 
       
    
    
     DETAILED DESCRIPTION  
       [0017]    The cooling fan module according to various embodiments has a brushless first fan motor for driving a first cooling fan and a second fan motor for driving of a second cooling fan, with the first fan motor being assigned a control unit which operates the first fan motor at the same time as it operates the second fan motor. 
         [0018]    Such a cooling fan module allows a method to be implemented with which the first fan motor is activated via the control unit with its speed regulated and the speed of the second fan motor is set as a function of the speed of the first fan motor. 
         [0019]    According to an embodiment, a hybrid arrangement of a brushless fan motor with a second fan motor is provided. In this arrangement only one electronics unit is used for the brushless fan motor and this is used for the second fan motor as well. In other words the second fan motor (which does not have a control unit of its own) is operated automatically and inevitably as soon as the first fan motor is operated. Only a single control unit is employed in this case. 
         [0020]    The various embodiments are thus in complete contrast with previously known approaches in which a single control unit can only be used to operate two fan motors because the control unit has two separate actuation units, namely one for each fan motor. Strictly speaking, such known control units consist of two individual control units which are accommodated in one and the same housing. 
         [0021]    Because a brushless fan motor is used, considerably higher reliability and service life of the cooling fan can be achieved compared to solutions known from the prior art. 
         [0022]    The use of a brushless fan motor also makes it possible to implement a double or multiple fan configuration with a very short physical length. Despite a restricted length it is possible with this design to integrate the control unit into the brushless cooling fan. With dc motors with brushgear, as are used in the prior art, this approach is not possible without increasing the length. 
         [0023]    A higher system efficiency overall can be achieved since the brushless fan motor as a rule has an approximately 10-15% higher efficiency. 
         [0024]    According to an embodiment the first fan motor and the second fan motor are connected in parallel, so that a “parallel double module” is produced. 
         [0025]    According to a further embodiment, the control unit is connected to a power supply line and a ground line and has a number of connection elements for connecting the first fan motor. The control unit in such cases can be arranged on the one hand in the housing of the first fan motor. On the other hand however it can also be provided outside the housing of the first fan motor as an external control unit. 
         [0026]    The first fan motor may be preferably a brushless motor with any number of phases, for example with three or five phases, which is operated in bipolar or unipolar mode. The second fan motor may be preferably a dc motor with brushgear, which on the one hand is connected via a phase-dependent number of rectifiers to the connection elements of the first fan motor and on the other hand is linked to the power supply line or the ground line of the control unit. The use of a direct current motor with brushgear enables the cooling fan module to be produced in a more cost-effective manner than comparable solutions with two brushless fan motors. Since no separate control unit has to be provided for the dc motor with brushgear, none of the components listed below are needed either: Voltage regulator, microcontroller, resonators or similar, power components such as MOSFETs or diodes, driver stages, interface switching elements, etc. This reduces the manufacturing costs. 
         [0027]    Alternatively, instead of a dc motor with brushgear, an asynchronous motor or a synchronous motor can also be used. This can then be connected directly to the connection elements of the first motor. The use of an asynchronous motor or synchronous motor enables the number of components needed to be further reduced. In addition asynchronous motors are not only extremely robust, but are also comparatively cheap to manufacture. 
         [0028]    The speed of the first motor is regulated in accordance with a further embodiment in the control unit, which receives setpoint speed information as an input signal. 
         [0029]    According to an embodiment, a cooling fan module for a motor vehicle features a first fan motor  2  for driving a first cooling fan  3  and a second fan motor  4  for driving a second cooling fan  5 .  FIG. 1  shows such a double configuration in a greatly simplified illustration, in which the power supply line  9  as well as the further connecting lines are only shown schematically. The integrated control unit  6  of the first fan motor  2  serves as the sole control unit for simultaneous operation of the second fan motor which is connected in parallel with the first fan motor  2 . The integrated control unit  6  in this case is arranged in the housing  7  of the first fan motor  2 , while the housing  8  of the second fan motor remains free and can accordingly be designed smaller. 
         [0030]    In a first exemplary embodiment (cf.  FIG. 2 ) a cooling fan motor for a motor vehicle has a brushless motor  11  as its first fan motor and a dc motor with brushgear  12  as its second fan motor. The cooling fans  3 ,  5  themselves are not shown in order to improve the clarity of  FIG. 2 . Fan motors  11 ,  12  are connected in parallel. The brushless motor  11  features an integrated control unit  13 , while no separate control unit is required according to various embodiments for the dc motor with brushgear  12 . In the exemplary embodiment shown the brushless motor  11  is a three-phase, bipolar-operated motor (ac motor). 
         [0031]    The control unit  13  has control electronics  14 , which for supplying the fan motors  11 ,  12  with a supply voltage, is connected to a standard vehicle main power supply line  15  (“terminal 30”) of the motor vehicle and a corresponding ground line  16  (“terminal 31”). To control the brushless ac motor  11  with a three-phase ac system the control unit  13  is equipped in its power section with the functionality of a converter. An arrangement of electronic switching transistors  17 ,  17 ′ (power transistors, MOSFETs) is used for this, as is required for control of the brushless ac motor  11 . Since the control unit  13  of the brushless ac motor  11  is also used for the operation of the dc motor with brushgear  12 , it must be designed for both motor currents, i.e. in the design of the control unit  13  a corresponding power dissipation must be taken into account in the dimensioning. 
         [0032]    The control electronics  14  is connected via an access line  22  to an external signal generator (not shown) which provides setpoint speed information. 
         [0033]    To connect the brushless ac motor  11  the control unit  13  has three phase connections  19  which are connected accordingly to the electronic switching transistors  17 ,  17 ′. The dc motor with brushgear  12  is on the one hand connected via three rectifiers  21  (power diodes) to these phase connections  19 . A direct current is created again from the three-phase ac system by the rectifiers  21 . On the other hand the dc motor with brushgear  12  is connected to the dc power supply line  15 . The dc power supply line  15  also serves as common reference point for the two fan motors  11 ,  12 . 
         [0034]    For connecting dc motors with brushgear  12  as second fan motors according to an embodiment only the said three-phase connections  19  must additionally be provided. In such cases any types of terminal contacts can be used, for example screw or clamp contacts. The rectifiers  21  are also preferably arranged, because of the cooling facilities already provided there (as illustrated in  FIG. 2 ), in the housing  7  of the brushless ac motor  11  or alternatively in the housing  8  of the dc motor with brushgear  12 . Accordingly just a single connection or also three connections must be brought out of the housing  7  of the brushless ac motor  11 . 
         [0035]    In a second exemplary embodiment (cf.  FIG. 3 ) a three-phase brushless ac motor  11  is again used as the first fan motor and a dc motor with brushgear  12  as the second fan motor. The layout of the cooling fan module and the wiring in this case corresponds to the exemplary embodiment shown in  FIG. 2 , with the difference that the dc motor with brushgear  12  is not connected to the dc power supply line  15  but to the ground line  16 . In other words the ground line  16  serves as a common reference point for the two fan motors  11 ,  12 . The three rectifiers  21  (diodes) are accordingly connected in the reverse direction. 
         [0036]    The parallel connection of the two fan motors  11 ,  12  has the following effects: 
         [0037]    By limiting the current in the brushless ac motor  11  with integrated control unit  13  the current is also limited in the dc motor with brushgear  12  without additional electronic components or other measures being necessary. This enables both a blocking protection function and also a short-circuit protection function to be achieved in a simple manner for the dc motor with brushgear  12 . The prerequisite for an effective protection function is that both motor currents are recorded for current measurement in the control unit  13 . The easiest way to achieve this is for the two currents to be directed via the same current measurement device (not shown), e.g. a shunt. Any overcurrent switch-off or similar protection functions in the integrated control unit  13  of the brushless ac motor  11  also protects the dc motor with brushgear  12 . 
         [0038]    A further advantage of the arrangement according to various embodiments is that, no further electronic components are required in addition to the rectifiers  21  for the dc motor with brushgear  12 . Since the dc motor with brushgear  12  does not have a separate control unit, no power dissipation occurs through electronic components. This also reduces the cooling effort required. 
         [0039]    The parallel connection according to various embodiments of the two fan motors  11 ,  12  also has effects on the operating behavior of the two cooling fans  3 ,  5 . The brushless ac motor  11  is operated via the control unit  13  with speed regulation. The speed of a motor always depends directly on the equivalent voltage at the motor. A voltage is also predetermined via the rectifiers  21  for the dc motor with brushgear  12  corresponding to the speed of the brushless ac motor  11  and the speed of the dc motor with brushgear  12 . This corresponds to a speed setting similar to that undertaken with a PWM controller. The speed of the dc motor with brushgear  12  is not controlled in this case. 
         [0040]    Alternatively, instead of a dc motor with brushgear  12 , an asynchronous motor  23  can also be provided as the second fan motor, cf.  FIG. 4 . The asynchronous motor  23  is connected in this case directly to the phase terminals  19  of the brushless ac motor  11 . In such cases three connections are brought out from housing  7  of the first fan motor  11 . The asynchronous motor  23  in this configuration follows the three-phase power predetermined by the integrated control unit  13  of the brushless ac motor  11 . This embodiment, in addition to the characteristics already described, has the further advantage of not requiring any rectifiers. 
         [0041]    In a further exemplary embodiment (not illustrated) there is provision for using identical motors as first and second fan motors, preferably brushless ac motors  11 .