Abstract:
A radiator blower, in particular for motor vehicles, is indicated that comprises a plurality of individual fans ( 11, 12 ), each having an electrical drive motor ( 13, 14 ), and a plurality of switches (S 1,  S 2,  S 3 ), each capable of being switched over into two positions, by means of which the drive motors ( 13, 14 ) are capable of being turned on and back off individually or in a series or parallel connection. To prevent disturbing noises from developing when the individual fan ( 11, 12 ) comes to rest after being turned off, when the operating drive motor or motors ( 13, 14 ) is/are turned off, an electronic control unit ( 20 ) forces the switches (S 1,  S 2,  S 3 )—at least temporarily—over into switch positions that bring about a short-circuiting of the turned-off drive motor or motors (FIG.  1 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention is based on a radiator blower, in particular for motor vehicles, according to the preamble of claim 1.  
           [0002]    Radiator blowers are used in motor vehicles that comprise at least two separate individual fans to cover a large demand for cooling, which said fans are operated either to ventilate the radiator of the internal combustion engine evenly, or to ventilate the radiator of the internal combustion engine and an air conditioner separately within a common circuit configuration that makes it possible to turn on either just one of the individual fans or both individual fans in series or in parallel.  
           [0003]    When such radiator blowers come to rest after being turned off, they generate noise that is not inconsiderable, because the individual fans pass through various resonant frequencies that, depending on excitation, can result in disturbing tonal magnifications in the noise spectrum. The tonal magnifications are perceived as being very unpleasant in particular when an internal combustion engine is running at idle and producing little noise, or when the internal combustion engine is switched off.  
         ADVANTAGES OF THE INVENTION  
         [0004]    The radiator blower according to the invention having the features of claim 1 has the advantage that, when the individual fans are switched off, their drive motors are operated at least temporarily in short circuit immediately after they are switched off, so that the short-circuited drive motor operates in the generating mode and comes to a stop after less than 20-30% of its usual slow-down time. The only switches and electric lines used to short circuit the drive motors are those that are provided in the circuit configuration anyway to perform on/off switching functions and establish series and parallel connections. No additional components are required, therefore, to short circuit the drive motors after they are turned off, and noise abatement is achieved at practically no additional cost. The only modification that is required is the triggering of the switches-which is carried out as programmed by the electronic control unit-when the individual fans are shut off, which can be achieved by making a cost-negligible software change.  
           [0005]    Advantageous further developments and improvements of the radiator blower indicated in claim 1 are made possible by the measures listed in the further claims.  
           [0006]    According to a preferred exemplary embodiment of the invention, n available drive motors are situated in n parallel sub-circuits, whereby n is a whole number greater than one. The network formed by the n parallel sub-circuits is connected via a switch—designed as a NO contact having one active switch contact—to a voltage source. Additionally, to operate n drive motors individually in n−1 parallel sub-circuits, one switch—designed as a NC contact having one active switch contact-is connected in series with each respective drive motor. These circuitry features make it possible to turn selected drive motors on and off by closing and opening the NO contact, while the drive motors to be put into operation are selected by actuating the NC contact. If a NC contact in a parallel branch is opened, the associated drive motor is no longer affected by the common control by the NO contact.  
           [0007]    To connect the n drive motors in series, according to an advantageous exemplary embodiment of the invention, a switch designed as a changeover switch having two active switch contacts is located in each of n−1 parallel sub-circuits. In each case, the changeover contact is located on the connection side of the drive motor opposite the NC contact, whereby the first switch contact of the changeover contact is located in the sub-circuit, and the second switch contact is connected to the connection between the NC contact and the drive motor in the adjacent sub-circuit. Only one changeover contact is located in the first of n parallel sub-circuits, and only one NC contact is located in the last of the parallel sub-circuits, whereby one is located on the high-potential side, and the other is located on the low-potential side of the respective associated drive motor. This circuit configuration provides advantages in terms of regulating the speed of the individual fans and adjusting the cooling output.  
           [0008]    Since it is usually sufficient to operate two individual fans in series, a switch—designed as a changeover contact having two active switch contacts—is located, according to an advantageous exemplary embodiment of the invention, on the connection side of the drive motor opposite the NC contact in each uneven-numbered, parallel sub-circuit as counted from the NO contact, in order to connect two of the n drive motors in series, with the possibility of operating the series connections of two drive motors in parallel. The first switch contact of said switch is located in the sub-circuit, and the second switch contact of said switch is connected to the connection between the NC contact and the drive motor in the subsequent, even-numbered, parallel sub-circuit. A cost advantage can be obtained with this circuit configuration by the fact that a changeover contact can be eliminated from every second sub-circuit.  
           [0009]    The changeover contacts serving to establish either a series or parallel connection of the drive motors are also used, according to an advantageous exemplary embodiment of the invention, to temporarily short circuit the drive motor that is located in the same parallel sub-circuit by establishing a short-circuit connection in the adjacent, parallel sub-circuit by changing over to the second switch contact via the changeover contact and the NC contact situated in the closed position. When the NO contact is opened in order to turn the drive motors off, the drive motor located in the last parallel sub-circuit and connected only in series with the NC contact is short-circuited—after at least one of the changeover contacts is switched back to its first switch contact—via the drive motor connected in series with this changeover contact and the closed NC contact connected in series with said changeover contact in the sub-circuit.  
           [0010]    According to an advantageous exemplary embodiment of the invention, an electronic control unit is provided that triggers the switches—according to a specified program—to change over in order to turn the drive motors on and off and establish the series and parallel connection. When the drive motors are turned off, the switches are triggered in such a fashion that the NO contact assumes its opened position, the NC contacts assume their closed position, and the changeover contacts are switched over to their first switch contacts. To turn off the drive motors that are operating, the switches are triggered in such a fashion that the NO contact opens, the NC contacts are moved to their closed position, and the changeover contacts are temporarily switched over to their second switch contact. 
       
    
    
     SUMMARY OF THE DRAWINGS  
       [0011]    The invention is described in greater detail in the description hereinbelow with reference to the exemplary embodiments presented in the drawings.  
         [0012]    [0012]FIG. 1 is a diagram of a radiator blower having two individual fans operated in one circuit configuration,  
         [0013]    [0013]FIG. 2 is a representation of the control program for triggering the switches in the circuit configuration according to FIG. 1,  
         [0014]    [0014]FIG. 3 is a modified diagram of a radiator blower having two individual fans,  
         [0015]    [0015]FIG. 4 is a diagram of a radiator blower having three individual fans,  
         [0016]    [0016]FIG. 5 is a diagram of a radiator blower having four individual fans.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    The radiator blower shown in diagram form in FIGS. 1 and 3 comprises two individual fans  11 ,  12 , each of which has a fan wheel  15  and  16  driven by an electric drive motor  13  and  14 . The drive motors  13 ,  14 —designed as DC motors—are integrated in a circuit configuration  10  comprising a plurality of switches in such a fashion that they are capable of being connected to and disconnected from a voltage source  17  by actuating the switches accordingly, whereby the two drive motors  13 ,  14  can be operated individually or together in a series or parallel connection. The switches are switched by an electronic control unit  20  that sends appropriate control signals to the switches, according to a specified program, to reverse them.  
         [0018]    In FIG. 1, the circuit configuration  10  for the two drive motors  13 ,  14  comprises a total of three switches, one of which is designed as a NO contact S 1  having one active switch contact, another one of which is designed as a NC contact S 3  having one active switch contact, and the further one of which is designed as a changeover contact S 2  having two active switch contacts. Each switch has two switch positions, 0 and 1, whereby the three switches S 1 -S 3  are designed so that, in the non-triggered state, they assume their “0” switch position in which the NO contact S 1  is open, the NC contact S 3  is closed, and the changeover contact S 2  is switched to the first of two active switch contacts.  
         [0019]    The two drive motors  13 ,  14  are located in two parallel sub-circuits  18  and  19  that are both connected to the voltage source  17  via NO contact S 1 . In sub-circuit  19 , NC contact S 3  is connected in series with drive motor  14 , while, in sub-circuit  18 , changeover switch S 2  is connected in series with drive motor  13 . The first switch contact of changeover contact S 2  is located in sub-circuit  18 , so that, when changeover switch S 2  is switched to the first switch contact (switch position 0), sub-circuit  18  is closed. The second active switch contact of changeover contact S 2  is connected to the connection between NC contact S 3  and drive motor  14  in sub-circuit  19 . Changeover contact S 2  is located in sub-circuit  18  on the low-potential side of drive motor  13 , i.e., on the ground side, while NC contact S 3  in sub-circuit  19  is located on the high-potential side of drive motor  13 . When NO contact S 1  is closed, therefore, said drive motor is connected with the DC voltage potential UBat of voltage source  17 .  
         [0020]    It is possible to flip-flop the arrangement of the switches S 2  and S 3  with regard for the drive motors  13  and  14  in the parallel sub-circuits  18 , 19 , so that—as shown in the modified circuit configuration in FIG. 3—changeover switch S 2  is located on the high-potential side of drive motor  13 , and NC contact S 3  is located on the low-potential side of drive motor  14 .  
         [0021]    Switches S 1 , S 2  and S 3  are triggered by means of the electronic control unit  20  according to the control program shown in FIG. 2 in table form. Using a control logic integrated in the electronic control unit  20  and based on operating data, a decision is made whether to put just drive motor  13  or just drive motor  14  into operation, or to put both drive motors  13 , 14  in operation in a parallel or series connection.  
         [0022]    When the radiator blower is turned off, all switches S 1 , S 2  and S 3  assume their “0” switch position, as illustrated in FIG. 1. Basically, NO contact S 1  serves to establish the electrical connection with the voltage source  17 . NC contact S 3  and changeover contact S 2  determine whether individual fan  11  or individual fan  12  is put into operation, or whether both fans  11  and  12  are put into operation in a series or a parallel connection.  
         [0023]    If the intention is to turn on only individual fan  11  with drive motor  13 , then the electronic control unit  20  closes NO contact S 1  and opens NC contact S 3 , as indicated in the first program line in FIG. 2. To turn it off, NO contact S 1  is reopened, and NC contact S 3  is closed again, and changeover contact S 2  is switched over to its second switch contact (switch position 1) for a time interval t 1 . As a result, drive motor  13  is short-circuited via changeover contact S 2  and NC contact S 3 , so that it comes to a standstill quickly. When the time interval t 1  is over, the changeover contact S 2  is switched back to its first switch contact. All switches S 1 , S 2  and S 3  assume their home positions, which is described in FIG. 2 as “Final State”.  
         [0024]    If the intention is to turn on only individual fan  12 , the electronic control unit  20  triggers NO contact S 1  and changeover contact S 2  in such a fashion that NO contact S 1  closes and changeover contact S 2  switches to its second switch contact, as shown in the second program line in FIG. 2. As a result, only drive motor  14  is connected to the voltage source  17 . To turn drive motor  14  back off, the two switches S 1  and S 2  are returned to their home positions. As a result, the turned-off drive motor  14  is short-circuited via closed NC contact S 3 , drive motor  13 , and changeover contact S 2  located in switch position 0, and it is braked to a halt very quickly.  
         [0025]    If the intention is to put both individual fans  11 ,  12  into operation simultaneously and run their electric drive motors  13 ,  14  in a parallel connection, then only NO contact S 1  is closed, as shown in the third program line in FIG. 2. The two drive motors  13 ,  14  are therefore connected in parallel with the voltage source  17 . To turn off the two operating drive motors  13 ,  14 , NO contact S 1  is opened, and changeover contact S 2  is switched to its second switch contact (switch position 1) for the duration t 2 . As a result, drive motor  13  is short-circuited via changeover contact S 2  and NC contact S 3  located in its closed position, and it is braked to a halt quickly. After the time interval t 2 , changeover contact S 2  is switched over to its “0” switch position, and its first switch contact is contacted. The slowing-down drive motor  14  is therefore short-circuited via NC contact S 3 , drive motor  13 , and changeover contact S 2 , and it is braked to a halt as well.  
         [0026]    If the intention is to put both individual fans  11 ,  12  into operation, but drive motors  13 ,  14  must be operated in a series connection, the electronic control unit  20  triggers all switches S 1 , S 2  and S 3  to switch over, as shown in the fourth program line in FIG. 2. NO contact S 1  closes, changeover contact S 2  is switched over to its second switch contact, and NC contact S 3  opens. With NO contact S 1  closed, drive motors  13 ,  14  are now connected in series with the voltage source  17  via the changeover contact S 2 . If the operating individual fans  11 , 12  must be turned back off, NO contact S 1  and NC contact S 3  are triggered first of all in such a way that NO contact S 1  opens, and NC contact S 3  closes. Drive motor  13  is therefore short-circuited via changeover contact S 2  and NC contact S 3 , and it quickly comes to a standstill. After a time interval t 3 , changeover contact S 2  is triggered by the control electronics  20  once more and returned to its “0” switch position in which it contacts its first switch contact. Drive motor  14  is now short-circuited via NC contact S 3 , drive motor  13 , and changeover contact S 2 .  
         [0027]    In the exemplary embodiment of the radiator blower according to FIG. 4, the radiator blower is equipped with a third individual fan  21 , the electric drive motor  22  of which is connected, in a further parallel sub-circuit  23 , in series with a further NC contact S 3 ′ and a further changeover contact S 2 ′. The connection between the second switch contact of changeover contact S 2  to sub-circuit  19  is broken. Instead, the second switch contact of the further changeover contact S 2 ′ is connected to the connection between NC contact S 3  and drive motor  14  in sub-circuit  19 . The second switch contact of changeover contact S 2  is connected to the connection between the further NC contact S 3 ′ and drive motor  22  in sub-circuit  23 .  
         [0028]    Of course, even more parallel sub-circuits, each having a drive motor, can be located between sub-circuits  18  and  19  in the circuit configuration  10  according to FIG. 4 in the same fashion as sub-circuit  23 . Every additional sub-circuit is designed identical to sub-circuit  23 . With this circuit configuration  10 , all n drive motors can then be operated individually or together in a parallel or series connection, whereby n is a whole number greater than one. When each of the operating drive motors is turned off, the drive motors are short-circuited temporarily and braked to a halt by opening NO contact S 1 —which is common to all drive motors—and correspondingly switching over NC contacts S 3 , S 3 ′ and changeover contacts S 2 , S 2 ′, so that the critical resonant frequencies of individual fans  11 ,  12 ,  21  are passed through very quickly.  
         [0029]    In the exemplary embodiment of the radiator blower according to FIG. 5, the radiator blower is equipped with a total of four individual fans  11 ,  12 , and  11 ′ and  12 ′. The two individual fans  11 ′,  12 ′—that are additional as compared with FIG. 122—are located, with their drive motors  13 ′ and  14 ′, in parallel sub-circuits  18 ′ and  19 ′ of the circuit configuration  10 , whereby drive motor  14 ′ is connected in series with a NC contact S 3 ″ in the same fashion as drive motor  14 , and drive motor  13 ′ is connected in series with a changeover contact S 2 ′ in the same fashion as drive motor  13 . The second active switch contact “1” of said changeover contact S 2 ′ is connected to the connection between NC contact S 3 ″ and drive motor  14 ′ in sub-circuit  19 ′. Additionally, a NC contact S 3 ′ is installed upstream from drive motor  13 ′ in sub-circuit  19 ′. The three new additional switches S 3 ′, S 3 ″ and S 2 ′ are triggered by the electronic control unit  20 .  
         [0030]    In the circuit configuration shown in FIG. 5, all four drive motors  13 ,  14 ,  13 ′,  14 ′ can be operated in parallel or individually. Moreover, drive motors  13  and  14  and drive motors  13 ′ and  14 ′ can be operated in a series connection. Additionally, the two series connections of two drive motors— 13  and  14 , or  13 ′ and  14 ′—can be operated in parallel. Depending on the operating mode, the electronic control unit  20  triggers the remaining switches in the necessary manner with NO contact S 1  closed. When the operating drive motors are turned off, the drive motors are short-circuited temporarily and, therefore, braked to a halt, by opening NO contact S 1 -which is common to all drive motors-and correspondingly switching over NC contacts S 3 , S 3 ′, S 3 ″ and changeover contacts S 2 , S 2 ′, so that the critical resonant frequencies of the individual fans are passed through very quickly. To short-circuit the individual motors, switches S 2  and S 3  must be actuated as described for FIG. 1, and switches S 3 ′, S 3 ″ and S 2 ′ must be actuated in analogous fashion.  
         [0031]    Additional parallel sub-circuits, each having a drive motor, can be provided in the circuit configuration  10  according to FIG. 5 as well, whereby drive motors, NC contacts and changeover contacts are incorporated in identical fashion with parallel sub-circuits  18 ′ and  19 ′. With n drive motors in n parallel sub-circuits, one changeover contact and one NC contact are connected in series with the respective drive motor in the uneven-numbered sub-circuits as counted from the NO contact S 1 , and only one NC contact is connected in series with the respective drive motor in each even-numbered sub-circuit. The number n of possible drive motors is an even number.