Patent Publication Number: US-2022228591-A1

Title: Coolant pump for a vehicle

Description:
The present invention relates to a pump for recirculating a cooling fluid for a vehicle, in particular the cooling fluid for vehicle combustion engines, with a control system comprising an electromagnetic friction coupling and an independent electric motor. 
     It is known in the sector for the production of vehicles, in particular engines, for example combustion engines, that there exists the need to cool said engines by means of recirculation of a cooling fluid which is driven by means of a corresponding recirculating pump, the impeller of which is rotated by a shaft driven by means for taking up a rotational movement, generally comprising a pulley, and by a belt connected to a movement source such as in particular a drive shaft. 
     It is also known that the recirculation of the cooling fluid must be performed with a flowrate depending on the actual cooling requirement determined by the real conditions of use of the engine and by the external temperature, in order to avoid the constant and unnecessary operation at full speed of devices which draw useful power, thereby increasing the wear of the various component parts and the fuel consumption of the vehicle. 
     It is also known that, in order to solve this problem, devices have been proposed for controlling operation of the pump impeller, rotation of which depends on the engagement of a friction coupling for transmission of a rotational movement depending on the revolutions of the drive shaft, and on an electric motor which instead is activated when the friction coupling is disengaged, so as to ensure a controlled speed rotation independent of the drive shaft. 
     Examples of these devices are for example known from WO 2012/142065 and WO 2018/229669 on which the claimed invention is based. 
     Although fulfilling their function, these devices nevertheless have drawbacks which limit their applications, in particular since they envisage the positioning of the friction coupling in a position axially on the outside of the pulley for taking up the movement from the drive shaft, thereby resulting in an increase in the axial dimensions of the assembly which is incompatible with the small dimensions of the seats for housing the assembly inside the engine compartment. Similar problems arise in the case of secondary or auxiliary cooling circuits, which are not directly designed to cool the engine, but which require in any case recirculation of the cooling fluid. 
     The technical problem which is posed therefore is that of providing a pump for recirculating cooling fluid, in particular a cooling fluid for vehicle engines and the like, able to produce a variation in the speed of rotation of the impeller depending on the actual requirements. 
     In connection with this problem it is also required that this device should have small dimensions—in particular axial, but also radial dimensions—but at the same time should be able to produce high torques also at a slow speed of rotation of the engine, so as to be applicable also to high performance pumps of heavy vehicles with an engine operating at a low number of rpm, or rotation of the impeller at a slow speed in conditions where the combustion engine is operating at a high number of rpm. 
     It is also required the device should be easy and inexpensive to produce and assemble and be able to be easily installed on the pump body without the need for special adaptation. 
     These results are obtained according to the present invention by a pump for recirculating cooling fluids for engines of vehicles and the like according to the present disclosure. 
     Owing to the pump configuration of the present invention, in which the movement take-up means, in particular in the form of a pulley, are formed on an outer circumferential edge of a shaped circular ring which forms part of the rotor of an electromagnetic friction coupling, are mounted on a bearing on the outside of the pump body and are arranged in a position radially more outer lying than the electromagnet and/or the armature of the friction coupling, it is possible to obtain a pump, the impeller of which may be rotationally driven according to the actual requirements and which is axially very compact, while allowing a great degree of flexibility with regard to design of the dimensions of the movement take-up means and/or the bell member and/or the electromagnetic coupling and the outer bearing. 
     In fact, the pump according to the invention provides the designer with a great degree of freedom as regards the design of the dimensions of the movement take-up means, for example in the form of a pulley with a suitable axial length to be coupled with a belt, but also of the bearing supporting the same and the transmittable torque of the electromagnetic coupling, without an increase in the axial dimensions. Moreover, the rotor and the bell member for operation by means of the electric motor may be more freely designed in terms of their dimensions. Therefore, it is possible to adapt the pump to the actual cooling requirements of the vehicle, while keeping at the same time the overall axial dimensions thereof compact. 
     In particular, in preferred embodiments, the movement take-up means may be arranged in a position which is radially more outer lying than the bell member, thus resulting in the maximum degree of freedom with regard to the design of the axial dimensions thereof and/or in a gain in volume between the movement take-up means and a part of the pump body which houses the impeller. 
     According to preferred configurations, the movement take-up means may be at least partially arranged axially above the electromagnet and preferably arranged concentrically therewith. The electric motor and/or the bell member may be arranged in an axially outer position with respect to the movement take-up means (not arranged above them). 
     According to further preferred configurations, the movement take-up means are at least partially arranged axially above the armature and optionally the bell member. In particular, the circular ring on the outer circumferential edge of which the movement take-up means are formed may project axially from a body of the rotor which is mounted on the outer bearing, towards the end of the driven shaft fastened to the bell member, optionally also until it is arranged axially above the bell member itself. 
     Further preferred embodiments are described in the dependent claims. 
    
    
     
       Further details may be obtained from the following description of non-limiting examples of embodiment of the subject of the present invention provided with reference to the attached drawings in which: 
         FIG. 1 : shows a partially sectioned view of an example of embodiment of the device according to the present invention, in conditions where the friction coupling is closed and the motor is energized; 
         FIG. 2 : shows a view similar to that of  FIG. 1  in conditions where the friction coupling is open and the motor is not energized; and 
         FIG. 3 : shows a view, similar to that of  FIG. 1 , of a further of embodiment of the pump according to the invention. 
         FIG. 4 : shows a third embodiment of a pump according to the invention; and 
         FIG. 5 : shows a fourth embodiment of a pump according to the invention. 
     
    
    
     As shown in  FIG. 1 , the impeller  1  of a pump for recirculating a cooling fluid for vehicles and the like is mounted on a first end of a shaft  2  supported by a fixed group  10  comprising a pump body  11  which in turn is fixed to the base  11   a  of the engine of the vehicle. 
     Sealing means, in particular a sealing gasket  12 , coaxial with the shaft  2 , are arranged inside the pump body  11 . 
     The shaft  2  of the impeller is designed to rotate with respect to the pump body  11 , in particular by means of internal bearings  13 , on the inner ring of which the said shaft  2  is keyed. 
     On the outside of the pump body  11  there is keyed an outer bearing  40 , the outer ring  40   a  of which is integral with a suitably shaped circular ring  21   a , the outer circumferential edge of which has, formed thereon, movement take-up means, in the example in the form of a pulley  21   c , suitable for coupling with a belt  3  for taking up the movement from the shaft of the combustion engine and transmission to the ring  21   a  itself, generating the rotational movement for the shaft  2  of the pump. 
     Since the pulling force of the belt  3  is transmitted onto the outer bearing  40  it is possible to limit the size of the inner bearings  13  which are not subject to dynamic loads, thus increasing the working life and limiting the overall dimensions. 
     The circular ring  21   a  forms part of the rotor  21  of an electromagnetic coupling  20  which comprises a fixed electromagnet  22  housed inside a corresponding seat  21   b  of the rotor  21  itself, and an armature  23  arranged facing the electromagnet  22  on the opposite side thereto relative to the impeller  1 . 
     The armature  23  is connected to a resilient recall lamina  24  in turn fixed to a bell member  14  to be rotated (described more fully below) and designed to allow an axial displacement of the armature, but prevent it from performing relative rotational movements with respect to the said bell member. 
     The rotor  21  may be provided with through-openings in the axial direction for defining the path of the magnetic flow able to determine the force of attraction of the armature  23 . 
     With this coupled arrangement, the armature  23  is able to perform movements in the axial direction towards/from the rotor  21 , being prevented from performing a relative rotation with respect to the bell member  14  when the electromagnet  22  is energized or de-energized. 
     As shown in  FIG. 1 , it is also envisaged that in the an electric motor  50  is provided in a position axially on the outside of the pulley  21   c  and the friction coupling  20 , the stator  51  thereof being supported by the pump body  11  and the rotor  53  thereof being connected to the bell member  14  which is in turn axially connected to the end of the pump shaft  2  opposite to the impeller  1 . 
     The connection between bell member and shaft is performed using conventional means  14   a  (not described in detail). 
     As shown, the electric motor  50 , which is preferably of the brushless or asynchronous type, is arranged in a position axially on the outside of the electromagnet  22 . The electromagnetic coupling  20  is preferably arranged axially between the pump impeller and the electric motor. 
     As shown, the pulley  21   c  which forms the movement take-up means is formed on the outer edge of a circular ring of the rotor  21 , radially on the outside of the seat  21   b  of the electromagnet  22 . In this embodiment, the pulley  21   c  is also situated radially more outer lying than both the armature  23  and the bell member  14 . 
     Preferably, the movement take-up means, in particular the pulley  21   c  and the electromagnetic coupling, in particular at least the electromagnet  22 , are arranged concentrically. With such a configuration it is possible to ensure the maximum freedom for design of the dimensions (including the radial dimensions) of the bell member  14  and the electric motor  50 , in particular when the movement take-up means are arranged in an axially outer position with respect to the said bell member  14  and optionally the armature  23  (and not arranged above them). 
     The electric power supply for the motor may be provided for example by means of a cable  52  connected to an energy source, such as an electric power supply for the engine. 
     Independently of the power supply for the motor  50 , a second power supply for energizing the electromagnet via wires  52   a  is provided. 
     With this configuration the operating principle of the pump is as follows: 
     A) when the electromagnet  22  is energized ( FIG. 2 ), the magnetic field induced overcomes the recall action of the resilient lamina  24 , axially recalling the armature  23  against the rotor  23  which causes rotation of the bell member  14  and therefore the shaft of the pump which is connected to the latter and which in turn causes rotation of the impeller  1  at the same number of revolutions as the pulley  21   c  and the ring  21   a;    
     B) when the electromagnetic  22  is de-energized ( FIG. 1 ), the armature  23  is axially recalled by the resilient lamina  24  away from the rotor  21  and against the bell member  14  which is then disengaged from the driving movement supplied by the belt  3  connected to the combustion engine; the driven shaft  2  is in the idle condition and the impeller is at a standstill; 
     C) if, in the idle condition of the shaft  2 , a rotation of the impeller  1  with an independent number of revolutions, for example less than that determined by the rotor  21   b  of the electromagnetic coupling  20 , is required, the electric motor  50  is powered so that the movement of the electric rotor  53  causes rotation of the bell member  14  and therefore the shaft  2  at the desired speed of rotation suitable for determining recirculation of the fluid which is actually required. 
     In a first embodiment, the electric motor is designed with a single winding on the poles of the stator, said form being advantageous if the amount of material used and the costs are to be kept to a minimum. 
     According to a further embodiment it is envisaged that the electric motor  50  comprises at least one pair of windings on the poles of the stator which are connected in cascade to a drive  70  which controls the motor which may for example a brushless or asynchronous motor. 
     The drive  70  may comprise in turn a twin-section configuration with a CPU  71  which controls a first driver  72   a  and a second driver  72   b  for driving a respective first bridge  73   a  and second bridge  73   b ; in this way it is possible to provide a configuration known by the term “fail-safe” such that, in the event of malfunctioning or breakage of one of the windings and/or one of the sections of the drive  70 , the other winding nevertheless becomes operative, ensuring the movement of the impeller  1  and therefore recirculation of the cooling fluid for the combustion engine. 
     As shown, the drive may be provided on the outside of the motor ( FIG. 1 ) or arranged on-board the pump, preferably within the axial dimensions or inside the volume of the bell member  14 , as schematically shown in  FIG. 3 . 
     It is also envisaged that the two windings may comprises a different number of polarities for providing different driving torques: for example a high torque for normal operation and low torque for emergency fail-safe operation. 
     In any case a fail-safe function may be always ensured by an independent drive via an electric motor or electromagnetic coupling connected to different movement take-up means. 
     In preferred embodiments, a preferred example of which is shown in  FIG. 4 , the movement take-up means, in particular a pulley  121   c , are arranged in a position radially more outer lying than the bell member  14  and are arranged at least partially axially above the armature  23 . 
     In these embodiments, the movement take-up means  121   c  may be extended so as to be arranged at least partially above the bell member  14  and optionally also the electric motor  50 . 
     In greater detail, the shaped circular ring  121   a , on the outer circumferential circular edge of which the movement take-up pulley  121   c  is formed, is composed at least partly by a projecting coaxial extension of the rotor  121  of the coupling; namely, the rotor comprises a body  121  which is keyed onto the outer bearing  40  (and includes the seat  122  for the electromagnet) and from which at least a part of the circular ring  121   a  projects axially in the direction of the end of the driven shaft  2  fastened to the bell member  14 . 
     With this configuration, the movement take-up means may be arranged axially at least partly above the armature  23  and optionally also the bell member  14 , this allowing a great freedom to increase the axial dimensions of the movement take-up means and therefore increase the pulling force of the belt  3  without increasing the overall axial dimensions of the pump; in this way a space between the belt edge  3  and the end of the driven shaft  2  fastened to the bell member  14  is reduced. 
     As shown in  FIG. 4  it is also possible to displace the entire ring part  121   a  with pulley  121   c  towards the bell member end of the driven shaft, preferably so that it is axially on the outside of the electromagnet  22 , so as to gain volume between the movement take-up means and the part of the body  11  of the pump which houses the impeller  1 , for the same overall axial size. 
     Such a greater volume allows greater freedom to design the dimensions of the outer bearing  40  and/or the electromagnetic coupling, allowing optimum definition of the transmittable torque value of the coupling and/or preventing any constructional complications (e.g. due to welded eyelets). It will be clear to the person skilled in the art that in this configuration the movement take-up means  121   c  could also be arranged radially more inner lying than the electromagnet  22  of the friction coupling. 
       FIG. 5  shows a further embodiment of the pump according to the invention, which differs from that shown in  FIG. 4  in that the electric rotor  153  forms part of single body made of plastomagnetic material which also forms the bell member fastened to the driven shaft  2  and connected to the armature  23  of the electromagnetic coupling. 
     In particular, the rotor/bell member  153  has a body formed as a single pressed part, comprising a hollow cylinder coaxial with the driven shaft  2  and a circular rear closing plate fastened to the said shaft; said body is made, in particular by means of injection-moulding, of a plastomagnetic material consisting essentially of a plastic binder and at least 50%, preferably at least 80%, more preferably at least 90%, 93%, 95% or 99% by weight of a ferromagnetic metal which can be magnetized in a permanent manner, such as ferrite, neodymium or samarium cobalt. The body formed as one piece is magnetized with Halbach magnetization so as to reproduce inside the hollow cylinder, which forms part of an electric rotor, a permanent magnetic field with at least two magnetic poles and on the outside of the hollow cylinder a substantially zero magnetic field. 
     The plastic binder may be a polyamide, preferably PA6, PA12, PA66 or PPS. The single-piece body is for example injection-moulded from a preform of the plastomagnetic material. The magnetic field inside the hollow cylinder may for example have at least 2, at least 4 or at least 8 magnetic poles arranged angularly equidistant on the circumferential extension of the internal volume of the cylinder. The magnetic poles of the field of the rotor may be inclined at a predefined skew angle, for example of 20°. 
     As shown in  FIG. 5 , the bell member/rotor  153  has a central through-hole passing through the plate, configured to house stably an element for connection to the pump shaft, in particular a metal bush and/or a fixing screw. Advantageously, the hole and optionally the bush may be formed during the injection-moulding step. 
     As shown, the single body made of plastomagnetic material may also comprise a circumferential radial base, to which the armature of the electromagnetic coupling is connected, in a manner similar to the bell member  14  described above. 
     An example of a method for forming an external rotor  153  made of plastomagnetic material may for example comprise the following steps:
         preparation of a preform, for example a ball, made of a plastomagnetic material consisting essentially of at least 50%, preferably at least 80%, more preferably 90%, even more preferably at least 93%, 95% or 99% by weight of a permanently magnetizable metal, in particular ferrite or neodymium or samarium cobalt, and, for the remaining part, of a plastic binder, in particular a polyamide, preferably PA6, PA12, PA66 or PPS;   moulding, preferably by means of injection, the preform inside a mould so as to form a rotor body comprising a hollow cylinder extending around a longitudinal axis and closed by a circular plate at one of its two bases;   magnetization of at least the hollow cylinder of the body so as to provide a Halbach array which produces a permanent magnetic field of the rotor which has at least two magnetic poles in the internal volume of the hollow cylinder and is substantially zero on the outside thereof.       

     It is therefore clear how with the pump according to the invention it is possible to obtain effective recirculation of the cooling fluid for vehicles which may be varied depending on the actual requirement by means of the alternative operation by an external movement source, such as the combustion engine, or an auxiliary electric motor, while keeping the overall axial dimensions small owing to the particular arrangement of the rotational movement take-up means which are designed for connection to the combustion engine itself and are arranged between the impeller and the bell member and radially more outer lying than the electromagnet, the armature and optionally the bell member and the electric motor, so that the definition of the dimensions during the design stage of each drive may also be adapted to the actual cooling requirement of the vehicle while keeping the overall axial dimensions compact. 
     In addition to the above, the small radial size of the pulley, which incorporates also the rotor function of the electromagnetic coupling, makes the device, and therefore the pump, suitable also for vehicles with engines which run at a low number rpm, but require a high rotational speed of the cooling pump. Since the pulley extends in the axial direction from the rotor body it is also advantageously possible to increase the pulling force of the belt and/or gain volume for other components of the pump, without increasing the overall axial dimensions. 
     In addition, the pump according to the invention ensures the rotation of the impeller  1  also in the case of electrical failure of either one of the two independent power supply circuits, i.e. of the motor or the electromagnetic coupling, ensuring the recirculation of the cooling fluid (“fail-safe mode). 
     It is also envisaged that, when the electromagnet  122  is de-energized, the pump may be operated by the electric motor  50 :
         at a slow speed when the combustion engine has a high number of revolutions; and   with a suitable speed also when the combustion engine is not running, so as to ensure recirculation and therefore cooling of the combustion engine also in the case of temporary stoppages such as stop-and-go conditions in the vicinity of traffic lights.       

     A further advantageous effect of the structure according to the invention consists in the absence of radial loads, due to the pulling force of the belt  3 , acting on the bearings supporting the impeller shaft, said absence helping increase the working life of the bearings and reducing the risks of malfunctioning. 
     Although described with reference to a circuit for cooling a vehicle combustion engine, it is envisaged that the pump according to the invention may perform the recirculation of a fluid for cooling also other secondary or auxiliary circuits of the vehicle, by deriving the movement where possible also from sources other than the drive shaft.