Abstract:
An automotive fluidic pump includes a driving device, a pump wheel, a hydraulic coupling configured as a magneto-rheological coupling comprising a rotatable driving clutch element which is permanently connected to the driving device. A rotatable driven clutch element is permanently connected to the pump wheel. A magneto-rheological liquid filling a working gap is arranged between the rotatable driven clutch element and the rotatable driving clutch element. A magnetic unit comprises a permanent magnet and an electromagnet. The permanent magnet and the electromagnet are each configured to magnetically affect the working gap. Each of the driving device and the pump wheel are connectable by the hydraulic coupling. The electromagnet is arranged to compensate a magnetic field created by the permanent magnet in the working gap when the electromagnet is activated.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2012/050675, filed on Jan. 18, 2012 and which claims benefit to European Patent Application No. 11425010.3, filed on Jan. 18, 2011. The International Application was published in English on Jul. 26, 2012 as WO 2012/098137 Al under PCT Article 21(2). 
     
    
     FIELD 
       [0002]    The present invention relates to a mechanical automotive fluidic pump which is directly mechanically driven by an internal combustion engine. The fluidic pump can be a pneumatic pump or a liquid pump. 
       BACKGROUND 
       [0003]    A mechanical automotive fluidic pump is directly driven by the combustion engine so that the rotational frequency of the pump is proportional to the rotational frequency of the engine. For an improved adaptation of the pumping performance to the pumping performance demand, the pump is provided with a coupling. The pumping performance of the pump is adapted by engaging and disengaging the coupling, thereby connecting and disconnecting the pump wheel with/from an actuated driving means which can be a belt pulley driven by the engine. 
         [0004]    U.S. 2005/0188690 A1 and U.S. Pat. No. 7,422,093 B2 describe a coupling for an automotive hydraulic power steering pump which is realized in the form of a magneto-rheological coupling. The coupling is provided with a driven clutch element being permanently connected to the pump wheel, with a driving clutch element being permanently connected to the pulley wheel, and with a magneto-rheological liquid filling a working gap between the two clutch elements. The coupling is engaged or connected by activating an electromagnet so that the magnetic field generated by the electromagnet penetrates the working gap so that the magnetic field immediately causes an increased viscosity of the magneto-rheological liquid. If the electromagnet fails, the coupling cannot be engaged or connected. This arrangement is not failsafe, so that it is not suitable for pumps with essential functions. 
       SUMMARY 
       [0005]    An object of the present invention is to provide a failsafe mechanical automotive fluidic pump. 
         [0006]    In an embodiment, the present invention provides an automotive fluidic pump which includes a driving device, a pump wheel, a hydraulic coupling configured as a magneto-rheological coupling comprising a rotatable driving clutch element which is permanently connected to the driving device. A rotatable driven clutch element is permanently connected to the pump wheel. A magneto-rheological liquid filling a working gap is arranged between the rotatable driven clutch element and the rotatable driving clutch element. A magnetic unit comprises a permanent magnet and an electromagnet. The permanent magnet and the electromagnet are each configured to magnetically affect the working gap. Each of the driving device and the pump wheel are connectable by the hydraulic coupling. The electromagnet is arranged to compensate a magnetic field created by the permanent magnet in the working gap when the electromagnet is activated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
           [0008]      FIG. 1  shows the longitudinal section of a mechanical pneumatic pump; and 
           [0009]      FIG. 2  shows a longitudinal section of a mechanical automotive coolant pump. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The mechanical automotive fluidic pump according to the present invention is provided with a magneto-rheological coupling which is provided with a permanent magnet magnetically affecting the working gap and also with an electromagnet magnetically affecting the working gap. When the electromagnet is not activated, only the permanent magnet affects the magneto-rheological liquid in the working gap so that the viscosity of the liquid is high and the coupling is engaged or connected. When the electromagnet is activated, i.e., electrically energized, the magnetic field generated by the permanent magnet affecting the working gap is significantly compensated so that the resulting magnetic field is decreased significantly. This decreased magnetic field in the working gap has the effect that the viscosity of the magneto-rheological liquid is significantly decreased, so that the coupling is more or less disconnected. 
         [0011]    If the electromagnet fails, the coupling will always be engaged or connected so that the coupling of the pump and the pump itself are failsafe. This failsafe arrangement of a magneto-rheological coupling is generally applicable for many other applications of a magneto-rheological coupling and is principally not limited to a pump. 
         [0012]    In an embodiment of the present invention, the fluidic pump can, for example, be a coolant pump and the driving means can, for example, be a pulley wheel driven by an internal combustion engine via a transmission belt. The functionality of a coolant pump pumping a coolant for cooling an internal combustion engine is significant for the life of the internal combustion engine so that the coolant pump must not fail, even if electric or electronic problems occur. The fail safe pump is therefore suitable for an application as a coolant pump. 
         [0013]    In an embodiment of the present invention, a pump control means can, for example, be provided which activates the electromagnet as long as the engine&#39;s temperature is below a limiting value. When the engine is cold, the pumping performance of the coolant pump is reduced to a minimum by activating the electromagnet. When the coolant temperature is increasing and is higher than the limiting value, the electromagnet is switched off so that the magneto-rheological liquid&#39;s viscosity is increased and the clutch is engaged. 
         [0014]    In an embodiment of the present invention, the magnetic arrangement with the electromagnet and/or the permanent magnet can, for example, be arranged so as to be non-rotating and to be a stationary part of the pump. The electromagnet and the permanent magnet can be fixedly connected to the pump frame. The static arrangement of the electromagnet makes it easier to electrically connect the electromagnet with a non-rotating control means. 
         [0015]    In an embodiment of the present invention, the permanent magnet can, for example, be a magnet ring and the electromagnet can, for example, be a ring coil which is surrounded by a toroidal or, in cross-section, a U-shaped back iron with the opening radially outwardly. The magnetizing of the permanent ring magnet is in-line with the back iron so that the magnetic field of the permanent magnet is parallel with and overlaps the magnetic field of the activated electromagnet. The permanent magnet is magnetized in-line with the orientation of the activated electromagnet&#39;s magnetic field penetrating the permanent magnet. 
         [0016]    The permanent magnet can be arranged radially adjacent to the electromagnet ring coil. In this case, the permanent magnet is magnetized axially. 
         [0017]    Two embodiments of the present invention are described with reference to the drawings. 
         [0018]      FIG. 1  shows a mechanical automotive pneumatic pump  10  and  FIG. 2  shows a mechanical automotive fluidic pump  10 ′ in the form of a coolant pump. Both pumps  10 ; 10 ′ are fluid pumps. The pneumatic pump  10  provides a gas, for example air, under pressure, or provides vacuum to other engine&#39;s components. The coolant pump  10 ′ provides a liquid coolant to an internal combustion engine. The pumps  10 ; 10 ′ are directly driven by the engine via a transmission belt  12 . 
         [0019]    Both pumps  10  comprise a pump frame  14 ; 14 ′ which can be mounted to an engine block of the engine (not shown). The pump frame  14 ; 14 ′ supports a rotor shaft  16  of a pump rotor  18  by means of two roller bearings  20 . The pump rotor  18  consists of a pump wheel  88 /an impeller pump wheel  22 , the rotor shaft  16 , and a rotatable clutch part  24  which is permanently connected to the pump wheel  22  by the rotor shaft  16 . 
         [0020]    The pneumatic pump  10  is provided with a pump section  82  which comprises the pump housing  83 , a pump inlet  84 , a pump outlet  86 , and a pump wheel  88  inside the pump housing  83 . The coolant pump  10 ′ is provided with impeller pump wheel  22 . The housing enclosing of the impeller pump wheel  22  is defined by a respective opening in an engine block (not shown). 
         [0021]    The pump rotor  18 , and in particular the rotatable clutch part  24  is provided with a cylindrical clutch portion  28  which is connected to the rotor shaft  16  by a substantially radial rotor ring portion  26 . The cylindrical clutch portion  28  defines a driven clutch element  29 . 
         [0022]    The pump  10 ; 10 ′ comprises a rotatable driving means  30  which is rotatably supported by the rotor shaft  16  by means of two roller bearings  32 , 33 . The rotatable driving means  30  is S-shaped in cross-section, whereby the end of the inner axial leg  34  is supported by one roller bearing  32  at the rotor shaft  16 . The inner half of the S-shaped driving means  30  encloses a ringlike magnetic unit  36 . The outer half of the S-shaped driving means  30  encloses the cylindrical rotor clutch portion  28  defining the driven clutch element  29 . 
         [0023]    The two cylindrical portions  38 ,  40  of the outer half of the S-shaped driving means  30  form two rotatable driving clutch elements  39 ,  41  which define two cylindrical working gaps  42 ,  44  between them and the driven clutch element  29 , respectfully. The radial outside cylindrical portion  40  of the driving means  30  serves as a pulley wheel  46  which is driven by the transmission belt  12 . The radial outside cylindrical portion  40  of the driving means  30  is directly rotatably supported by the second roller bearing  33  at the rotor shaft  16  by means of a radial support ring  65 . 
         [0024]    The magnetic unit  36  consists of a ringlike electromagnet  50  which is surrounded by a (in cross section) U-shaped ringlike back iron  52  which is open to the radial outside. The cylindrical part of the back iron  52  is formed by a ringlike cylindrical permanent magnet  54  which is axially magnetized so that it is magnetized in parallel and in-line with the toroidal magnetic field  72  generated by the activated electromagnet  50 . The back iron  52  and the radial outside cylindrical portion  40  of the driving means  30  are made of ferromagnetic material and define a toroidal path for the magnetic fields  70 ,  72 . 
         [0025]    The permanent magnet  54  generates a toroidal magnetic field  70  which penetrates the working gaps  42 ,  44  radially. When the electromagnet  50  is active, i.e., energized with electric energy, it generates a toroidal magnetic field  72  as well which is parallel to the toroidal magnetic field  70  of the permanent magnet  54  but has an opposite polarity. 
         [0026]    The magnetic unit  36  and the clutch elements  29 , 39 , 41  define a magneto-rheological coupling  60  whereby the working gaps  42 ,  44  are filled with a magneto-rheological liquid  62 . 
         [0027]    When the electromagnet  50  is not active, only the permanent magnet  52  generates a toroidal magnetic field  70  which penetrates the working gaps  42 ,  44 . The viscosity of the magneto-rheological liquid is therefore high, so that the coupling is engaged or connected. When the electromagnet  50  is activated by an external pump control means  80 , the toroidal magnetic field  72  of the electromagnet  50  substantially compensates the toroidal magnetic field  70  of the permanent magnet  52  so that the resulting magnetic field in the working gaps  42 ,  44  is reduced to a minimum. As a consequence, the viscosity of the magneto-rheological liquid significantly increases so that the coupling is more or less disconnected or disengaged. 
         [0028]    The pump control means  80  of the coolant pump  10 ′ activates the electromagnet  50  as long as the engine&#39;s temperature is below a limiting value of 70° C., for example. 
         [0029]    If the pump control means  80  and/or the electromagnet  50  should fail, the coupling  60  is always automatically in the engaged or connected state. The fluidic pump  10 ; 10 ′ is consequently failsafe. 
         [0030]    The present invention is not limited to embodiments described herein; reference should be had to the appended claims.