Abstract:
The invention relates to a coolant pump having an impeller which is arranged on a pump impeller shaft and having a drive device for the impeller, which drive device has a mechanical drive and an electric-motor drive. The impeller shaft is divided into a driving section and a driven section, and an openable and closable clutch is arranged between the driving section and the driven section. Operation of the coolant pump by either the mechanical drive or the electric-motor drive can be dependent upon a predetermined speed of threshold of rotation of the impeller, and/or upon a predetermined power usage threshold.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation-in-part of U.S. patent application Ser. No. 12/937,746, filed on Feb. 6, 2011, and entitled “Coolant Pump.” 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to coolant pumps which have both a mechanical mode of operation and an electric mode of operation. 
       BACKGROUND OF THE INVENTION 
       [0003]    A coolant pump is known from DE 102 14 637 A1. To be able to realize different driving operation states of a vehicle with such a coolant pump, which has both an electric-motor drive and also a mechanical drive, a planetary drive is provided which can be driven by the electric motor and/or by the mechanical drive. However, such a design is complex with regard to its mechanical construction and is susceptible to operation inconsistencies. 
         [0004]    It is therefore an object of the present invention to create a coolant pump with a simpler and more reliable design in relation to the prior art and whose operation is efficient and fail-safe. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with a preferred embodiment, the pump wheel shaft is divided into a driving section and a driven section which is separate from said driving section. A clutch is arranged between the driving section and the driven section and can be opened in order to separate said two sections and which can be closed in order to connect the two sections. With this embodiment, the pump wheel can be driven both by an electric-motor drive and also by a mechanical drive, in each case independently. 
         [0006]    With the present invention, pumps are provided, such that the mechanical pump takes over the function of the electric pump in order to boost the pump power for operating conditions for which the electric pump would be inefficient or inadequate. It is also possible to obtain a fail-safe function for the electric pump, since it can be coupled to the mechanical pump if an interruption occurs in the electrical energy supply. 
         [0007]    One of the features of the invention is that the operation of a heavy truck engine using a fully variable coolant pump showed that there is a need for two different flow volumes of coolant fluid. A smaller volume or amount of coolant flow (i.e. “base flow”) is needed to, for example, avoid hot spots in the engine. A higher volume or amount of coolant flow (i.e. “peak flow”) is needed to, for example, cool the vehicle in full load conditions. 
         [0008]    In principle, the following implementations of the invention are possible: 
         [0009]    (A) Although it is possible to operate both pump types in parallel, it is particularly preferably provided according to the invention that the electric pump and the mechanical pump be connected in series, with a regulated clutch performing the function of coupling in the mechanical pump, for example, on the basis of pressure measurements or monitoring of the electrical energy supply. 
         [0010]    (B) In the case of a sequential arrangement of the mechanically operated pump and the electrically operated pump, it is preferable, for both pumps to use a single pump wheel. 
         [0011]    (C) It is also possible according to the invention, as a result of a downsizing of the coolant pump, for said coolant pump to be adapted both for the utility vehicle field and also for the passenger vehicle field. In the case of the passenger vehicle field, the warm-up behaviour of the engine can be improved by precise adjustment of the basic coolant flow. 
         [0012]    (D) In hybrid vehicles, the invention may also provide a coolant flow when the engine is stopped. The coolant flow is required for the functioning of the alternator/generator and for the battery. The coolant flow which is required may accordingly be provided by the combination according to the present invention of the electric pump and of the mechanically driven pump, without an auxiliary pump being required, as in the prior art. 
         [0013]    The invention has numerous benefits and advantages: 
         [0014]    (1) A fail-safe design of the entire system, since it is possible, when the electric-motor drive is deactivated, for the pump wheel to be actuated solely by the mechanical drive. The decoupling from the mechanical drive takes place by means of an actuation of the clutch. In the rest position of the clutch, the pump wheel shaft is driven by the mechanical drive. In this situation, the clutch could be held in a deactivated state by an electrical mechanism. In the event of an electrical failure, the clutch will automatically connect the mechanical drive to the pump wheel. 
         [0015]    (2) Two operating principles for actuating a driving side, wherein the two driving sides can be decoupled entirely from the driven side, or the two driving sides can be decoupled only individually from the driven side. 
         [0016]    (3) In-line concept for coupling/decoupling with electric-motor drive. The electric-motor drive, which is preferably designed as a brushless direct-current (“DC”) motor, is arranged on the driven side of the pump wheel shaft. The mechanical drive and also the electric-motor drive may, connected by the clutch, be arranged in alignment on the same axis of the coolant pump, and drive only a single pump wheel. This is a preferred embodiment. 
         [0017]    (4) The concept of the coolant pump according to the invention is compatible with different coolant pump designs. 
         [0018]    (5) If the coolant pump is for an internal combustion engine of a passenger vehicle, the coolant pump according to the invention can provide hydraulic energy when the internal combustion engine is at a standstill. Post-operation cooling can take place by the main pump wheel by operation of the electric motor. 
         [0019]    (6) Sequential operating logic can be obtained with the coolant pump according to the invention, since the pump wheel can be driven either by the electric motor or by the mechanical drive. 
         [0020]    (7) The bearings on the driving side and on the driven side can be arranged in alignment on the same axle. 
         [0021]    (8) It is possible to recover electrical energy from the electric-motor drive (generator operation) when the pump wheel is being driven exclusively by the mechanical drive. From an energy aspect, this is particularly possible in the overrun mode of the internal combustion engine. 
         [0022]    (9) The provision of sufficient cooling power for most operating states by decoupling the mechanical drive and operation by means of the electric motor. 
         [0023]    (10) As a result of the cubic power characteristic curve of a coolant pump, the electric motor provides a basic volume flow. The maximum delivery power for maximum cooling power takes place by coupling the mechanical drive (without electric-motor pump). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Further details, advantages and features of the present invention can be gathered from the following description of an exemplary embodiment on the basis of the drawing, in which: 
           [0025]      FIG. 1  shows a sectioned illustration through an embodiment of a coolant pump according to the invention; 
           [0026]      FIG. 2  shows a schematic construction of a cooling circuit of an internal combustion engine having the coolant pump according to the invention; 
           [0027]      FIGS. 3 and 4  show two statistical distribution plots of the pump wheel rotational speed in relation to the engine speed for two transient driving cycles; 
           [0028]      FIG. 5  depicts the power consumption for an embodiment of a coolant pump according to the invention; 
           [0029]      FIGS. 6 and 7  show a coolant flow scenario and power consumption, respectfully, for an embodiment of a coolant pump according to the invention; 
           [0030]      FIG. 8  is a cross-sectional view of an embodiment of a coolant pump according to the invention; and 
           [0031]      FIG. 9  is a schematic illustration of a cooling circuit of an internal combustion engine utilizing an embodiment of the coolant pump according to the invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]      FIG. 1  shows a sectioned illustration through a coolant pump  15  according to one embodiment of the invention. The coolant pump  15  has a pump wheel (also called an “impeller”) which is arranged on a pump wheel shaft (also called an “impeller shaft”). The pump wheel shaft is divided into a driving section  3  and a driven section  11 . In the illustrated embodiment, the driving section  3  is formed as a flange-shape structure to which a mechanical drive  1 , in the form of a belt pulley in this example, is rotationally fixedly connected. In the illustrated embodiment, the arrangement composed of a flange-shape structure  3  and a belt pulley  1  is mounted in a housing  7  by means of a bearing  6 . 
         [0033]    The mechanical drive  1  may be connected to an internal combustion engine of a motor vehicle, wherein in the illustrated embodiment, it is possible to use a belt drive. Only the belt pulley  1  is shown in order to simplify the illustration. 
         [0034]    The driven section  11  of the pump wheel (impeller) shaft is mounted in the housing  7  by means of two bearings  6  and  10 , and at its free end  16 , supports the pump wheel  13 . Here, the free end  16  of the driven section  11  is sealed off with respect to the housing  7  by means of a seal  12  which is arranged between the pump wheel  13  and the bearing  10 . 
         [0035]    As is also shown in  FIG. 1 , the driven section  11  and the driving section  3  of the pump wheel shaft can be connected by means of a clutch  4  which is arranged between the two sections  3  and  11 . The clutch  4  may for example be embodied as an electromagnetic clutch with a coil  5 . 
         [0036]    An electric-motor drive is positioned in the driven section  11  of the pump wheel shaft, which electric-motor drive is arranged, with its rotor  9  and a stator  8  which surrounds said rotor  9 , in axial alignment with the mechanical drive  3  on the driven section  11 . Here, as shown in  FIG. 1 , the rotor  9  and the stator  8  are positioned in the housing  7 . 
         [0037]    An optional Hall effect device  14  can be arranged between the rotor  9  and the bearing  6 . 
         [0038]    With this design of the coolant pump  15  according to the invention, it is possible for the pump wheel  13  to be completely separated from the mechanical drive  1  by opening the clutch  4 . Here, the electric-motor drive, which is preferably embodied as a brushless DC motor, is arranged on the side of the driven section  11  of the pump wheel shaft. This allows the electric motor drive to provide a regulable coolant flow in a predeterminable power range, which is independent of the rotational speed of the motor to which the coolant pump  15  is connected, when the driven section  11  is separated from the driving section  3  by the opened clutch  4 . 
         [0039]    For this purpose, the rotor  9  of the electric-motor drive is arranged directly on the driven section  11  of the pump wheel shaft, as can be seen from  FIG. 1 . The stator  8  is integrated, around the same axis of the housing  7 , in the housing  7  around the rotor  9 , as can likewise be seen from  FIG. 1 . 
         [0040]    The electric-motor drive  8 ,  9  can be regulated by means of a commutated signal from an electronic regulating device (not illustrated in any more detail in  FIG. 1 ). If the driven side  11  is separated from the driving side  3 , the pump wheel  13  can be driven solely by the electric-motor drive. Here, it is provided that sufficient hydraulic output power is provided in order to provide the required coolant flow or all normal operating conditions of the engine which is connected to the coolant pump  15 . To obtain a maximum available coolant flow, the driven section  11  can be connected to the driving section  3  of the pump wheel shaft by means of the clutch  4 . In this case, the pump wheel  13  is driven solely by the mechanical drive  1  when the electric motor is deactivated. 
         [0041]      FIG. 2  illustrates a schematic construction of a possible cooling circuit of an internal combustion engine  17  which uses the coolant pump  15  according to the invention. In this schematically highly simplified illustration, the pump which is driven by an electric motor is denoted by the reference symbol  20  and the mechanically driven pump is denoted by the reference symbol  21 . The two pumps, which are arranged in series, may be connected via the clutch  4  to a belt drive  2  and via the belt pulley  1  to the engine  17  for the provision of the required mechanical drive energy. In the illustrated embodiment, the coolant circuit also has a thermostat  18  and a cooler member  19 , such as a radiator, the interaction of which is shown by the arrows. 
         [0042]    The coolant pump can be arranged in a sequential or parallel manner, wherein the electrical pump can be arranged in series or in parallel to the mechanical driven member. This includes serial/parallel operation in both mechanical and hydraulic manner (drive side or pump side). 
         [0043]      FIGS. 3 and 4  show data of two transient driving cycles evaluated with a fully variable pump, with the curves and entries plotted therein. The graphs  50  and  60  show two occurrence plots, which show the flow requirement for two typical drive cycles. The two major occurrences of base flow  52  and  62 , and peak flow  54  and  64  are depicted. 
         [0044]    In the occurrence plot  50 , the base flow  52  could be provided by the electrical pump drive at less than one kW power. The peak flow  54  could be provided by the mechanical pump drive at more than one kW power in the illustrated example. 
         [0045]      FIG. 5  illustrates the power considerations of the two major modes for a variable coolant pump. The top graph  70  plots the power consumption of the coolant pump, showing the volume flow in liters per minute (1/min) versus the power (in kW). The area  72  is the preferred area for use of an electrical pump, and the area  74  is the preferred area for use of a mechanically driven pump. The borderline for determining the choice of pump and drive type is shown at  76 . The borderline is one kW in the illustrated example. 
         [0046]    The bottom graph  80  is the same as occurrence plot  60  in  FIG. 4 , and is the basis for the graph  70  and preferred areas  72  and  74 , as well as borderline  76 . On the basis of graph  80 , the borderline for determining whether to use mechanical drive or electric drive in this example is at about  1500  rpm of the impeller. 
         [0047]    The power considerations shown in  FIGS. 3-5  depict the two major modes for a variable coolant pump. The base flow provided by the pump can be delivered by a pump driven by an electric motor, since the power consumption is below one kW. The power consumption above one kW is difficult to be achieved by an electric motor, mainly due to the lack of electrical power in common vehicles today. Here, a mechanically driven system is preferred. The mechanical drive provides a “boost” when more cooling is needed. 
         [0048]    The discussed embodiment above also provides a “failsafe” coolant pump. If the electrical system or power in the vehicle were to fail or stop in some manner, the mechanical drive would take over and the coolant pump would be driven by the pulley and mechanical drive. This would allow the operator of the vehicle to continue to operate the vehicle until the electrical system failure could be repaired and reactivated. 
         [0049]    In addition, the discussed embodiment can continue to deliver coolant through the system even when the engine is switched or turned off. The electrical drive powered by the battery of the vehicle can continue to operate the coolant pump and circulate the cooling fluid until the engine and other components are sufficiently cooled. Some vehicles today require use of an auxiliary pump to accomplish this. 
         [0050]    Significant benefits and advantages of the invention include the following: 
         [0051]    (i) Hydraulically parallel or sequential running electric and mechanical pumps with a controlled clutch on the mechanical member driven by the backpressure or electrical power of the electric pump system (the clutch is controlled by the electrical power supply of the electric pump system or by the back pressure of the coolant circuit); 
         [0052]    (ii) Mechanically sequential running mechanical and electrical drive sharing one hydraulic member (i.e. impeller). 
         [0053]    Beside these features, the inventive coolant pump can be downsized to the needs for the automotive market segment, where it could improve the warm-up behavior of the vehicle and engine by exactly applying the needed base flow with the speed of the electric motor. 
         [0054]    In accordance with embodiments of the invention, the coolant pump drive can be completely decoupled from the FEAD drive side by the clutch, such as an electromagnetic clutch. The DC motor is integrated in the driven shaft axle to provide a controllable coolant flow in a defined performance range completely independent from the engine speed when the driven axle is decoupled from the drive shaft. For this, the rotor of the DC motor is directly mounted on the driven shaft, and is positioned between two bearings above and beneath the rotor. The stator is mounted in the coolant pump housing on the same axis. 
         [0055]    The DC motor, which preferably is brushless, is controlled by a commutated signal from an electronic control device. If the driven side is decoupled from the drive side, the impeller can be driven by the DC motor. This will provide sufficient hydraulic power to meet the required coolant flow for most of the operating conditions of a vehicle. To achieve the maximum available coolant flow, the driven side is coupled with the drive side, for example, with an electromagnetic clutch. The impeller will then be driven by the FEAD. 
         [0056]    As indicated, benefits and features of the embodiments of the invention include:
       Failsafe function of the system, due to jointly supplied voltage. The clutch will engage to drive the impeller by the pulley, if the brushless DC motor is powered off   Inline concept of On/Off clutch with electronic motor. The DC motor is mounted on the driven side. Both devices, clutch and DC motor, are aligned on the same axis and are driving just one impeller.   Hydraulic power can be provided at engine stop conditions.   Sequential operational logic where the impeller can be driven simply by one device (electronic motor or by pulley).   Bearing of drive side and driven side are aligned on the same axis.   Possible electric energy recovery from the brushless DC motor, if the impeller is driven by the pulley.       
 
         [0063]      FIGS. 6 and 7  are two additional graphs which illustrate the operations and benefits of embodiments of the present invention.  FIG. 6  depicts the coolant flow verses engine speed, while  FIG. 7  depicts the power consumption verses engine speed. 
         [0064]    In  FIG. 6 , which is designated generally by the reference numeral  100 , the line  102  depicts the engagement of the electromagnetic clutch. Line  104  depicts the amount of 20% of the coolant flow. This amount is controlled by the electric DC motor, particularly a brushless DC motor, and also is the maximum amount of flow that the electric motor can produce. Disengagement of the clutch is represented by the line  106 . 
         [0065]    With an electric DC motor, only about 5% of the total power is needed to provide about 20% of the coolant flow. 
         [0066]    In  FIG. 7 , which is designated by the reference numeral  120 , the line  122  depicts the power consumption when the electromagnetic clutch is engaged. Line  124  depicts the maximum power consumption by the DC motor, which is preferably brushless. 
         [0067]      FIG. 8  depicts an embodiment  150  of a dual mode coolant pump in accordance with the invention. The pump includes a first body member  152  which is fixedly connected to a pulley member  154 . The body member  152  is rotated at input speed by a belt member (not shown) attached to the vehicle engine. This provides the mechanical drive member for rotation of the coolant impeller  156 . 
         [0068]    Bearing member  158  allows the mechanical drive body member  152  to rotate freely when it is not needed to drive (rotate) the impeller member  156  and provide additional coolant flow to assist in cooling the engine. 
         [0069]    The mechanical drive body member is situated inside a housing member  160 . When the coolant pump  150  is in use, the housing member  160  is attached to the vehicle engine or another component or housing which in turn is attached to the engine and in fluid communication with the engine coolant system. 
         [0070]    Impeller shaft member  162  is positioned centrally inside the housing  160 . The shaft member  162  is fixedly secured at one end  162 -A to the impeller member  156 . The other end of the shaft member  162 -B is secured to an openable and closeable clutch mechanism  170 . The clutch mechanism  170  is preferably an electromagnetic clutch mechanism and is operated by electric coil  180 . 
         [0071]    The impeller shaft member  162  is rotatably positioned inside the housing  160  by a pair of bearing members  172  and  174 . An electric motor  190 , which preferably is a brushless DC motor, is positioned in the housing and situated between the two bearing members  172 ,  174 . The motor  190  includes a stator member  192  and a rotor member  194 . The rotor member  194  is fixedly secured to the impeller shaft member  162  and rotates with it. 
         [0072]    A sealing member  196  is used to isolate the coolant fluid (in which the impeller  156  is positioned) from the components of the coolant pump  150 . In addition, an optional Hall Effect Device (HED)  198  is positioned in the housing adjacent the rotor member in order to monitor the speed of rotation of the impeller shaft and provide data to a computer control system, such as, for example, an electronic control unit (ECU). The data generated and supplied by the HED as well as other possible data supplied by other sensors, generally controls the operation of the coolant pump. 
         [0073]    The cooling pump  150  is a dual mode coolant pump for operating and controlling the operation of the rotation of the impeller and thus the flow of coolant in the engine and/or vehicle cooling system. Under normal conditions, the impeller is operated by the electric motor  190 . Under these conditions, the electromagnetic clutch mechanism  170  is held in an open condition by power from the coil member  180 . When more cooling is needed, or in a failsafe situation where electric power is lost to the coolant pump, the clutch mechanism  170  closes and the shaft member  162  is rotated by the mechanical drive member  152 . 
         [0074]    As indicated in the description of  FIG. 8 , the first body member  152  comprises the mechanical drive mechanism for the coolant pump, while the electric motor  190  comprises the driven drive mechanism for the coolant pump. 
         [0075]      FIG. 9  schematically depicts a cooling system  200  for a vehicle engine, as well as a control system  230  for the cooling system. The cooling system includes a vehicle engine  202 , a thermostat  204 , a heat exchanger  206 , such a as a radiator, and a dual mode coolant pump  208 . The coolant pump  208  includes a pulley member  210 , a mechanical drive mechanism  212 , a clutch mechanism  214 , and a DC electric motor  216 . 
         [0076]    The coolant pump  208  could be, for example, the coolant pump  150  discussed above and shown in  FIG. 8 . 
         [0077]    The pulley member  210  is driven by a belt  220  from a pulley member  222  attached to and rotated by the vehicle engine  202 . Engine coolant flows from the engine  202  through the radiator  206  and then through the coolant pump  208  before being directed back to the engine. 
         [0078]    The control system  230  includes an electronic control unit (ECU)  232  which controls the operation of the coolant pump  208 . The ECU receives data from various sensors, such as one or more temperature sensors  234 , which assist in directing the operation of the cooling system. Also, control logic  240  in the coolant pump  208  can be supplied to operate the various coolant pump components and mechanisms. The ECU  232  can also be in communication and receive data from one or more other ECUs in the engine and vehicle. 
         [0079]    With the present invention, the coolant pump drive can be completely decoupled from the FEAD drive side by, for example, an electromagnetic clutch. A brushless DC motor integrated with the driven shaft member to provide a controllable coolant flow in a defined performance range independent from the engine speed. For this, the rotor of the brushless DC motor is directly mounted on the driven shaft member with roller bearings positioned above and beneath the rotor. The stator is mounted in the coolant pump housing on the same axis. 
         [0080]    The brushless DC motor is controlled by a commutated signal from an electronic control unit. If the driven side is decoupled from the drive side, the impeller is driven by the brushless DC motor. It is designed to provide sufficient hydraulic power to meet the required coolant flow for the most of the operating conditions of a vehicle. To achieve the maximum available coolant flow, the driven side is coupled with the drive side, by, for example, an electromagnetic clutch. The impeller will then be driven by the FEAD. 
         [0081]    The present invention provides at least the following:
       A failsafe system, due to jointly supply voltage. The clutch will engage to drive the impeller by the pulley, if the brushless DC motor will be powered off   Inline Concept of On/Off clutch with electronic motor. The brushless DC motor is mounted on the driven side. Both devices, clutch and brushless DC motor, are aligned on the same axis and are both positioned operably to drive the same impeller.   Hydraulic power can be provided at engine stop condition.   Sequential operation logic in which the impeller can be driven just by one device (electronic motor or by pulley).   Bearings on the drive side and the driven side are aligned on the same axis.       
 
         [0087]    Electric energy recovery from the brushless DC motor when the impeller is driven by the pulley. 
         [0088]    While preferred embodiments of the present invention have been shown and described herein, numerous variations and alternative embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention is not limited to the preferred embodiments described herein but instead limited to the terms of the appended claims.