Patent Publication Number: US-2022213833-A1

Title: Hybrid pump apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present disclosure is based on and claims priority to GB Application No. 2100078.1, filed Jan. 5, 2021, the entire disclosure of which is incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The present invention is concerned with a hybrid pump apparatus. More specifically, the present invention is concerned with a vehicle hybrid pump apparatus, for example a vehicle hybrid pump apparatus for a coolant fluid. 
     BACKGROUND 
     Internal combustion (IC) engines have many uses—for example they may be used to power on- and off-highway vehicles, or for power generation. Many IC engines have a fluid-based cooling system in order to keep the engine at the optimum temperature. Such cooling systems typically employ a liquid medium to transfer heat energy from parts of the engine that are prone to overheating to other parts of the engine or vehicle (e.g. a radiator for heat dissipation). This is particularly important for heavy commercial vehicles such as goods vehicles, and heavy goods vehicles (HGVs) in particular. 
     IC engines are provided with a cooling circuit containing the coolant. The circuit extends from a heat source (such as the engine block) to an appropriate heat sink (such as the vehicle radiator). Pumping fluid around the circuit ensures transmission and dissipation of heat energy. A coolant pump is provided, the pump comprising an impeller driven by a shaft. A pump pulley is mounted to the shaft. The engine crankshaft also has a pulley mounted thereto, and a belt drive drivingly engages the crankshaft and pump pulleys such that the impeller is driven by the crankshaft. 
     Although a gear ratio may be provided by appropriately sizing the pulleys, in such systems the speed of the input shaft (and hence the impeller) is proportional to the speed of the engine. As such the size of the pulleys must be selected to provide sufficient cooling for the most demanding situation. 
     In certain circumstances it is desirable to reduce the effect of the cooling circuit. For example, upon startup it is desirable for the IC engine to heat up to its optimum operating temperature quickly. Therefore, conduction and convection of thermal energy away from the engine block is not desirable. Once the engine is up to temperature, and perhaps undergoing a heavy duty cycle, it is important that the coolant system can work at maximum effectiveness to avoid overheating. It is always desirable to reduce unnecessary coolant flow because this creates a parasitic power loss. Reduction in unnecessary flow of coolant can therefore provide a fuel saving. 
     In order to address this need, hybrid pumps including an electric motor as well as a mechanical drive have been developed. By connecting or disconnecting the electric motor or the mechanical drive, the output of the pump can be adjusted. Such hybrid pumps tend to be complex, including arrangements of gears and solenoid assemblies. 
     What is required is a less complex solution that is compact to fit into the typically crowded environments in which IC engines are found. 
     What is also required is a system which allows for a failsafe condition which will ensure pumping operation during an electrical failure event so as to prevent the engine from becoming too hot. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is a hybrid pump apparatus comprising:
         a pump subassembly having an inlet and an outlet;   an electrical drive arranged to selectively drive the pump subassembly;   a mechanical drive comprising a driven member configured to receive a drive torque; and   a clutch in a load path between the driven member and the pump subassembly, the clutch being movable between a first condition in which the driven member drives the pump subassembly and a second condition in which the driven member can rotate freely relative to the pump sub assembly;   in which the clutch is a dog clutch.       

     Advantageously, the use of a dog clutch removes the need to include a complex gear arrangement within the pump apparatus. The hybrid pump apparatus also has a compact and light arrangement. 
     The dog clutch may be configured to move to the first condition upon interruption of electrical power to the electrical drive. 
     The dog clutch may comprise a first dog clutch component which is configured for operable connection to the driven member and a second dog clutch component. The second dog clutch component may be resiliently biased by a spring. Additionally or alternatively, the second dog clutch component may be at least partially constructed from a ferromagnetic material. 
     The electrical drive may include a rotor and a stator. The stator may be an axial stator and/or the stator may be yokeless. 
     An electromagnetic field produced by the stator may cause the clutch to move to the second condition. 
     Preferably
         the dog clutch defines a clutch axis;   the dog clutch comprises a plurality of cooperating teeth for transferring torque;   the plurality of teeth each define a mating surface provided at a tooth angle; and,   the tooth angle is at a non-zero angle to the clutch axis.       

     The tooth angle is preferably between 5 and 20 degrees. The tooth angle is preferably selected to reduce the axial force required to disengage the dog clutch to a separation force above zero. In this way, less energy is required by the disengagement mechanism (e.g. solenoid) than if the tooth angle was 0 (i.e. parallel to the clutch axis). 
     The hybrid pump apparatus may be a vehicle hybrid pump apparatus, for example an internal combustion engine hybrid pump apparatus. The hybrid pump apparatus may be a vehicle hybrid pump apparatus for a coolant fluid. 
     Preferably the electrical drive is configured to generate electricity when driven by the mechanical drive in a ‘regen’ mode. 
     Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description or drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An example hybrid pump apparatus will now be described with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic representation of part of a coolant circuit and a hybrid pump apparatus in accordance with the present invention; 
         FIG. 2  is an exploded diagram showing a hybrid pump apparatus according to the present invention; 
         FIG. 3  is a section view of the hybrid pump apparatus of  FIG. 2  in a first configuration; 
         FIG. 4  is a section view of the hybrid pump apparatus of  FIG. 2  in a second configuration; 
         FIG. 5  is a side view of a part of the apparatus of  FIG. 2 ; and, 
         FIG. 6  is a detail view of region VI in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT 
     Referring to  FIG. 1 , an IC engine coolant circuit  10  is arranged to convey a liquid coolant  12  from a heat source in the form of engine component  14  to a radiator  16 . The liquid coolant  12  is recirculated in the circuit  10 . The engine  14  is controlled by an electronic engine control unit (ECU)  18 , as known in the art. 
     A hybrid pump apparatus  100  comprises a shaft  102  which is connected to a mechanical drive having a driven member in the form of a pulley  104  at one end and an impeller  106  at a second, opposite, end. The shaft  102  extends through a pump housing  108  in which an electrical drive in the form of electric motor  110  is provided. The impeller  106  is arranged to pump the coolant  12  around the circuit  10 . 
     The ECU  18  is configured to provide command signals to the gearbox via data line  112 . 
     The hybrid pump apparatus  100  is shown in  FIGS. 2, 3 and 4 . 
     Referring to  FIG. 2 , the hybrid pump apparatus  100  is shown in more detail. 
     The shaft  102  is a solid cylindrical component having a first end  120 . Proximate the first end  120 , there is provided an annular collar  122  having a shoulder  124  facing the first end  120 . At a second end  126  of the shaft  102  there is provided a shoulder  128  leading to a smaller diameter section  130  which comprises a central bore  132 . 
     The pulley  104  is an open, cylindrical body with one closed end wall  114  having a central shaft engagement formation  116 . The pulley  104  defines a cylindrical outer surface  118  which is contacted and driven by a belt (not shown) in use. 
     The impeller  106  is positioned at a second end  126  of the shaft  102 . 
     The hybrid pump apparatus  100  comprises a pump subassembly in the form of a housing  108  having a first housing part  142  and a second housing part  144 . The first housing part  142  is hollow and generally cylindrical, having an end wall  146  at one end and a collar  147  at an opposite end. The end wall  146  defines a central bore  148 . The second housing part  144  defines an annular wall  150  having a central bore  152 . A first cylindrical portion  154  extends from the central bore  152 . A second cylindrical portion  155  extends from an inner surface of the second housing part  144  such that a lip  157  is formed between the annular wall  150  and the first cylindrical portion  154 . The outer diameter of the second cylindrical portion  155  fits within the first housing part  142 . The outer diameter of the annular wall  150  is sized for a press fit with the inner diameter of the first housing part  142 . In this way, the housing parts can be assembled to form a closed chamber containing the electric motor  110 . 
     The electric motor  110  includes a rotor  158  and a stator  159 . In embodiments of the invention, the stator  159  is a yokeless, axial stator. 
     The hybrid pump apparatus  100  also includes a clutch  160  in the form of a dog clutch having a first dog clutch component  162  which is operably connected to the pulley  104  and a second dog clutch component or plate  164  which is at least partially constructed from a ferromagnetic material. The dog clutch  160  relies on a mechanical interlocking between the two components (rather than e.g. friction) such that the clutch cannot slip when engaged. Each of the components  162 ,  164  defines a respective axial, annular face  167 ,  169  having a plurality of interlocking teeth  163 ,  165  respectively. The teeth each define faces that are flat and planar, and face in a generally circumferential direction. The teeth  163  of the clutch component  162  face in a direction D 1  (the drive direction) whereas the teeth  165  of the clutch component  164  face in the opposite direction such that rotation of the clutch component  162  indirection D 1  drives rotation of the clutch component  164 . Rather than being parallel to the axis of rotation of the clutch (when viewed from a radial direction), the teeth are at a non-zero angle TA. The angle TA is such that the surface of each tooth  163  on each clutch component forms an opening angle OA above 90 degrees (i.e. OA=TA+90) with the adjacent part of the face  167 ,  169 . Specifically, in this embodiment the angle TA is 8 degrees (although values less than 10 degrees are selected based on e.g. the coefficient of friction between the materials as will be described below). This reduces the amount of axial force required to disengage the teeth. 
     The hybrid pump apparatus is assembled as follows. 
     An electronic control board  166 , a pump housing bearing  168 , and the rotor  158  and stator  159  of the motor  110  are mounted within the hollow first housing part  142  of the pump housing  108 . 
     The shaft  102  is mounted through the central apertures in each of the components such that the annular collar  122  of the shaft  102  abuts the stator  159  and the smaller diameter section  130  of the shaft  102  extends through the central bore  148  of the first housing part  142 . 
     The impeller  106  is then mounted on the smaller diameter section  130  of the shaft  102 . 
     A resilient biasing element in the form of a spring  170  is placed on the shoulder  124  of the shaft  102 . The second housing part or cover  144  is then bolted to the first housing part  142  to secure the motor  110  within the pump housing  108 . 
     The second dog clutch component  164  is mounted on the shoulder  124  of the shaft  102  and the dog clutch bearings  174 ,  176  are positioned at the first end  120  of the shaft  102 . 
     The first dog clutch component  162  is positioned within the open cylindrical body of the pulley  104 , which is then mounted on the second housing part or cover  144 . 
     The spring  170  is configured such that the second dog clutch component  164  is resiliently biased in an axial direction towards the first dog clutch component  162 . The second dog clutch component  164  is able to slide along the shoulder  124  of the shaft  102 . 
     The hybrid pump assembly is operated as follows. 
     With the motor  110  switched off, the second dog clutch component  164  is resiliently biased towards the first dog clutch component  162 . If the IC engine of the vehicle is running, the pulley  104  will be running. In this first, ‘high flow’ condition, the shaft  102  is driven by the pulley  104  and the impeller  106  is caused to rotate. 
     An air gap, supported by the spring  170 , will be formed between the second dog clutch component  164  and the pump housing  108 . The components of the motor  110  and the impeller  106  will rotate by virtue of their connection to the shaft  102 . 
     The first mode is for a high cooling demand at high engine speed. The pump is driven by the engine at higher speeds not achievable by electric drive. This is also the default mode for the failsafe mechanism (i.e. electrical failure). 
     In a second condition (‘reduced flow’) when the motor  110  is switched on, an electromagnetic field will be produced by the stator  159 . The electromagnetic field will attract the second dog clutch component  164  (which includes a ferromagnetic material). The magnetic attraction between the stator  159  and the second dog clutch component  164  is sufficient to overcome the resilience of the spring  170  and thus the second dog clutch component  164  will be moved away from the first dog clutch component  162  towards the stator  159 . 
     The angle of the engaged teeth on the dog facilitate disengagement of the clutch. Referring to  FIGS. 5 and 6 , forces are shown as if the teeth were engaged. The force F torque  driving the clutch members in rotation in direction D 1  comprises a component normal to the surface  163  (F perpendicular ) and a component parallel to the surface (F parallel ). The perpendicular component results in a frictional force between the two surfaces F friction =μs·F perpendicular . The parallel component F parallel  acts to separate the two clutch components against F friction . It will be noted that as TA grows, F parallel  increases (because F parallel =F torque ·sin(TA)), and at a certain value of TA (depending on the coefficient of static friction between the materials μ s ), F parallel  will increase beyond F friction  and the plates will separate. 
     In the present invention, TA is selected that a separation force SF=F friction −F parallel , where SF&gt;0 and TA&gt;0. This means that an increase in TA can reduce the amount of separation force (SF) required of the solenoid compared to TA=0, thus reducing power consumption. 
     The spring  170  is compressed between the stator  159  and the second dog clutch component  164 . With the electric motor  110  on, the shaft  102  is rotated by the electric motor  110  and thus the impeller  106  is rotated. In this, second, condition, the pulley  104  is able to rotate independently of the pump subassembly. The second mode is used for low cooling demand at high engine speed. The pump can be driven by the electric motor at a reduced speed by disengaging the clutch. This benefits fuel economy and CO2 emissions. 
     A third mode, ‘over flow’ is provided when the motor is run faster than the impeller can otherwise provide. It is for high cooling demand at low engine speed. The pump can be driven by electric motor at a higher speed than that which can be achieved by the engine. This benefits engine cooling and durability. 
     In a fourth mode, ‘engine off’, the pulley is not rotating at all, and all flow can be provided by the electric motor. This is for high cooling demand due to heat soak after the engine is shut down. The pump can be driven to circulate coolant even when the engine is off. This helps to avoid damage to engine. 
     In a fifth mode, ‘regen’, the motor is driven by the pulley with the clutch engaged, and used as a generator to provide an electrical output to the vehicle. The electric motor works as a generator to harvest wasted mechanical energy and feed it back into vehicle battery for storage. This aids fuel economy and CO2 emissions. 
     In the instance that the motor  110  is switched off, or there is a failure resulting in the interruption of electrical power to the electrical drive, the electromagnetic field is lost, and the spring  170  bias the second dog clutch component  164  towards the first dog clutch component  162  (i.e. into a ‘failsafe’ mode). 
     The following table provides a summary of the running modes of the hybrid pump apparatus  100 . 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                   
                 Impeller 
               
               
                   
                   
                 Pulley 
                 Clutch 
                 Motor 
                 Impeller 
                 speed 
               
               
                 Mode 
                 Description 
                 state 
                 State 
                 rotor state 
                 state 
                 ratio 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 High flow 
                 Running 
                 Engaged 
                 Driven 
                 Running 
                 1 
               
               
                 2 
                 Reduced flow 
                 Running 
                 Disengaged 
                 Driver 
                 Running 
                 &lt;1 
               
               
                 3 
                 Over flow 
                 Running 
                 Disengaged 
                 Driver 
                 Running 
                 &gt;1 
               
               
                 4 
                 Engine off 
                 Not running 
                 Disengaged 
                 Driver 
                 Running 
                 ∞ 
               
               
                 5 
                 Regen 
                 Running 
                 Engaged 
                 Driven 
                 Running 
                 1 
               
               
                 6 
                 Failsafe 
                 Running 
                 Engaged 
                 Driven 
                 Running 
                 1 
               
               
                   
               
            
           
         
       
     
     Although the invention has been described above with reference to preferred embodiments, it will be appreciated that various changes or modification may be made without departing from the scope of the invention as defined in the appended claims.