WO2017195056A1

WO2017195056A1 - Pump group with electric drive and mechanical drive in the impeller shaft

Info

Publication number: WO2017195056A1
Application number: PCT/IB2017/052332
Authority: WO
Inventors: Alfonso SURACE; Marco Pedersoli
Original assignee: Industrie Saleri Italo S.P.A.
Priority date: 2016-05-10
Filing date: 2017-04-24
Publication date: 2017-11-16
Also published as: EP3455476A1; CN109196199A

Abstract

A pump group (1) for a cooling system of a motor of a vehicle, comprising an impeller (2), rotatable around an axis (X-X) and an impeller shaft (4). The pump group (1) comprises a mechanical drive (3) and a mechanical shaft (300) rotatable by the mechanical drive (3) and an electric drive (5) and an electric shaft (500) rotatable by the electric drive (5). Said mechanical shaft (4) houses a mechanical shaft impeller end (302) of the mechanical shaft (300) and an electric shaft impeller end (502) of the electric shaft (500), respectively operatively connected to the impeller shaft (4) respectively by a first one-way coupling (61) and a second one-way coupling (62).

Description

DESCRIPTION

"PUMP GROUP WITH ELECTRIC DRIVE AND MECHANICAL DRIVE IN

THE IMPELLER SHAFT"

[0001] The present invention relates to a pump group for a cooling system of a vehicle, preferably for cooling a motor, such as an internal combustion motor.

[0002] As is known, during normal use of a motor, it is appropriate to vary the intensity of the cooling action.

[0003] For example, an intense cooling is appropriate when the motor is working at full capacity or in towing conditions or on an uphill road or with high ambient temperatures .

[0004] In other conditions of use instead, it is appropriate for the cooling not to be accentuated, for example when starting the motor or after use.

[0005] The prior art discloses cooling pumps in which this need has been addressed.

[0006] Cooling pumps with electric drive are in fact known of, in which the speed of rotation of the impeller is regulated by means of an electric drive and thus the amount of coolant liquid moved by it in circulation in the cooling system.

[0007] Unfortunately, such pumps, although extremely versatile in their application and in the possibilities of rotation management thanks to the dedicated electronic control, typically have low delivery power, limited by the electric power provided by the vehicle's electrical system.

[0008] Furthermore, these pumps do not have the "fail-safe" feature in case of failure, i.e. the possibility to function in an emergency configuration when the electric motor has suffered a breakage.

[0009] Cooling pumps with mechanical drive are also known of wherein the rotation of the impeller is related to the number of revolutions of the internal combustion engine; in these solutions, the adjustment of the quantity of coolant liquid is entrusted to special adjustment elements, placed upstream or downstream of the impeller, suitable to change the through cross-section of the circuit thus varying the flow of coolant liquid.

[0010] Unfortunately, such solutions although suitable for delivering high power and proving conspicuously reliable, have less versatile cooling management, related to the motor speed and the characteristics of the adjustment element, and are typically too large. Also, in a "post- run" configuration, i.e. with the motor off, no cooling is performed .

[0011] Lastly, dual driven pumps are also known of, i.e. comprising both an electric drive and a mechanical drive.

[0012] Unfortunately, these pumps have particularly complex management of the two drives, as well as an articulated and bulky structure.

[0013] The purpose of the present invention is to provide a pump group for a cooling system of a vehicle, for example for an internal combustion motor, which meets the requirements mentioned, overcoming the drawbacks spoken of. In other words, the aim is to provide a dual action pump group, with simplified management of the two drives, and with a simple and compact structure.

[0014] Such purpose is achieved by a pump group made according to claim 1. The dependent claims refer to preferred embodiment variants having further advantageous aspects .

[0015] The object of the present invention will be described in detail below, with the help of the appended drawings, wherein :

- figures la and lb shows two perspective views of the pump group according to the present invention, according to a possible embodiment;

- figure 2 shows a longitudinal cross-section view of the pump group referred to in figures la and lb, according to a first embodiment variant;

- figure 3 shows a longitudinal cross-section view of the pump group in figures la and lb, according to a second embodiment variant; - figure 4 shows a longitudinal cross-section view of the pump group referred to in figures la and lb, according to a third embodiment variant;

- figure 5 shows an enlarged cross-section view of a detail of the pump group shown in figure 3;

-figure 6 shows an enlarged cross-section view of a detail of the pump group shown in figure 4.

[0016] With reference to the aforesaid drawings, reference numeral 1 globally denotes a pump group for a cooling system of a motor, preferably an internal combustion motor.

[0017] The pump group 1 of the present invention comprises an impeller 2 rotatable around an axis X-X so that the rotation of the impeller 2 corresponds to the movement of a predetermined quantity of coolant liquid in the circuit.

[0018] Preferably, the impeller 2 is of the radial type, i.e. provides that the incoming flow of liquid has an overall substantially axial direction and the flow of liquid in output has a radial direction.

[0019] The pump group 1 comprises an impeller shaft 4 which extends along the axis X-X integrally connected to the impeller 2 to move it in rotation; that is to say that a rotation of the impeller shaft 4 corresponds to an induced rotation of the impeller 2 itself.

[0020] The pump group 1 provides a dual drive, i.e. is operable both mechanically and electrically. To such purpose, the pump group 1 comprises a mechanical drive 3 and an electric drive 5.

[0021] In particular, the pump group 1 comprises a mechanical shaft 300 rotatable by the mechanical drive 3 and operationally connected to the impeller shaft 4.

[0022] In a preferred embodiment, the mechanical drive 3 comprises a pulley 33 for a drive belt connected, for example by using a kinematic chain, to the drive shaft.

[0023] Preferably, the pulley 33 is an electromagnetic pulley. In the embodiment with the electromagnetic pulley, this is normally engaged and only when it is actuated (i.e. the coil in it is electrically excited) does the release mechanism disengage the pulley from the mechanical shaft 300.

[0024] In fact, preferably, the electromagnetic pulley comprises an outer ring on which the drive belt is mounted, an inner ring and an intermediate release mechanism which comprises an intermediate coil. The inner ring is in this embodiment the drive ring operatively connected to the mechanical shaft 300, which by means of a first one-way coupling 61 (described below) is operatively connected to the impeller shaft 4.

[0025] Normally, when the electromagnetic pulley is not electrically energized, the outer ring is integral in rotation with the inner ring. In this configuration of electromagnetic pulley disabled, the inner ring has a rotation speed equal to that of the driven ring and the mechanical shaft 300 is dragged in rotation mechanically. Instead, when the electromagnetic pulley is activated (i.e. the coil is electrically energised) the release mechanism releases the outer ring from the inner ring, so that the outer ring, while driven in rotation by the belt, does not transmit any rotation to the inner ring and thus to the mechanical shaft 300.

[0026] In addition, the pump group 1 comprises an electric shaft 500 rotatable by the electric drive 5 and operatively connected to the impeller shaft 4.

[0027] Preferably, the electric drive 5 comprises an electric motor 50 comprising an impeller 51 mounted on an impeller portion 501 of the electric shaft 500 and a stator 52 fixed coaxial to the rotor 51.

[0028] In a preferred embodiment, the rotor 51 is not of the wet rotor type.

[0029] The pump group 1 further comprises an electronic control unit 55 to control the electric drive 5 and/or the electromagnetic pulley 33.

[0030] As mentioned, the mechanical shaft 300 and electric shaft 500 are both operatively connected to the impeller 2 via the impeller shaft 4, to move it in rotation.

[0031] Preferably, the mechanical shaft 300 and electric shaft 500 extend in turn along the axis X-X.

[0032] In a preferred embodiment, the mechanical shaft 300 and electric shaft 500 extend in two opposite directions, at the two sides of the impeller 2.

[0033] Preferably, the mechanical drive 3 is placed behind the impeller 2 while the electric drive 5 is placed in front of the impeller 2.

[0034] The mechanical shaft 300 and the electric shaft 500 comprise a mechanical shaft impeller end 302 and an electric shaft impeller end 502 operatively connected to the impeller shaft 4 respectively via a first one-way coupling 61 and a second one-way coupling 62.

[0035] In other words, between the mechanical shaft 300 and the impeller shaft 4 a one-way coupling 61 is interposed, while between the electric drive 500 and the impeller shaft 4 a second one-way coupling 62 is placed.

[0036] According to a preferred embodiment, the first one^¬ way coupling 61 comprises a rolling bearing for the support in rotation of the mechanical shaft impeller end 302. For example, the rolling bearing is of the type with rollers or needle rollers, having rolling elements placed between the driven ring and the drive ring.

[0037] According to a preferred embodiment, the second one^¬ way coupling 62 comprises a rolling bearing for the support in rotation of the electric shaft impeller end 502. For example, the rolling bearing is of the type with rollers or needle rollers, having rolling elements placed between the driven ring and the drive ring.

[0038] According to a preferred embodiment, the impeller shaft 4 houses the mechanical shaft impeller end 302 and the electric shaft impeller end 502.

[0039] In a preferred embodiment, the impeller shaft 4 is axially hollow identifying a housing cavity 40 housing the mechanical shaft impeller end 302 and the electrical shaft impeller end 502. In other words, the shaft 4 is axially hollow identifying the mechanical shaft housing cavity 43 and electric shaft housing cavity 45 respectively suitable to house the mechanical shaft impeller end 302 and the electrical shaft impeller end 502. Preferably, in a preferred embodiment, the shaft 4 has an axial cavity which extends along the axis X-X for its entire length.

[0040] In one embodiment variation, the impeller shaft 4 is axially hollow at its ends identifying the mechanical shaft housing cavity 43 and electric shaft housing cavity 45 respectively suitable to house the mechanical shaft impeller end 302 and the electrical shaft impeller end 502. Preferably, in a preferred embodiment, the shaft 4 is axially hollow, presenting two axial cavity extending along the axis X-X starting from the two axial ends. For example, the shaft 4 is solid and is machined by removing material at both ends.

[0041] Preferably, the shaft 4 comprises a central portion 41, preferably solid, at the axial ends of which the mechanical shaft housing cavity 43 and the electric shaft housing cavity 45 are located. Preferably, the mechanical shaft impeller end 302 and the electric shaft impeller end 502 are operatively connected with said central portion 41. In another preferred embodiment, the central portion 41 is inserted inside the cavity 40 of the shaft.

[0042] In other words, the impeller shaft 4 houses inside it a respective portion of the mechanical shaft 302 and the electrical shaft 502.

[0043] Preferably, the first one-way coupling 61 and the second one-way coupling 62 are co-moulded with the impeller shaft 4.

[0044] According to a preferred embodiment, the impeller shaft 4 and the impeller 2 are in one piece.

[0045] According to a preferred embodiment, the electric shaft impeller end 502 comprises a pin 502' which extends along the axis X-X, while the mechanical shaft impeller end 302 comprises a housing 302' suitable to house and rotationally support the pin 502'.

[0046] In another preferred embodiment, not shown, the mechanical shaft impeller end 302 comprises a pin which extends along the axis X-X, while the electric shaft impeller end 502 comprises a housing suitable to house and rotationally support the pin.

[0047] Preferably, by means of such mutual coupling the mechanical shaft 300 and electric shaft 500 are kept mutually aligned and centred on the axis X-X.

[0048] In some preferred embodiments, said pins are engaged directly to the shaft 4 for example to its central portion 41.

[0049] Preferably, the impeller shaft 4 and the impeller 2 are rotationally supported and kept centred on the axis X- X by the electrical shaft 300 and the mechanical shaft 500.

[0050] According to a preferred embodiment, the pump group 1 comprises a pump body 10 defining an impeller chamber 120 housing the impeller 2 and containing the coolant liquid in transit; in other words the impeller chamber 120 impeller has an inlet mouth 121 through which the coolant liquid enters, aspirated, and an outlet mouth 122 through which the coolant liquid comes out, impelled.

[0051] According to a preferred embodiment, the impeller shaft 4 is housed in said impeller chamber 120 and the housing cavity 40 (either in the embodiment in which it is in one piece, or in the embodiment in which it is has two distinct portions at either end) is isolated from the coolant liquid. In other words, the first and second one- way couplings are dry, not bathed by the coolant liquid.

[0052] Preferably, the pump group 1 comprises a pair of sealing elements 91, 92 operatively connected to the ends of the impeller shaft 4 suitable to separate the housing cavity 40 from the impeller chamber 120.

[0053] For example, the sealing elements 91, 92 are dynamic type seals and extend radially from the impeller shaft 40 to the pump body 10 to sealingly delimit the impeller chamber 120 and delimit inside it the coolant liquid.

[0054] In a preferred embodiment, the impeller 2 comprises a paddle portion 21 and a support portion 22 comprising a support surface 220; preferably, the paddle portion 21 comprises a plurality of radial paddles suitable to perform a thrust action on the coolant liquid; preferably, the support portion 22 is suitable to allow the support of the impeller 2.

[0055] Indeed, the pump group 1 comprises a support and centering bearing 20 operatively connected to the support surface 220 suitable to support and keep centred on the axis X-X the impeller 2 and the impeller shaft 4 absorbing the fluid dynamic action of the coolant liquid.

[0056] Preferably, the support and centering bearing 20 is a ball bearing.

[0057] In a preferred embodiment, the support and centering bearing 20 is positioned behind the paddle portion 21 of the impeller 2. In other words, the impeller 2 has its support portion 22 at the rear.

[0058] For example the support surface 220 has an annular shape so as to house within it the support and centering bearing 20.

[0059] Further preferred embodiments of the pump group 1 exist, including a preferred embodiment in which the pump group 1 comprises a throttle valve (not shown) , fitted in the pump body so as to be placed along the outlet duct 122 from the impeller chamber 120. The valve is controllable using an actuator (not shown) , for example electric, hydraulic or vacuum, preferably controllable by the control device. The characteristics of such valve are disclosed in the documents EP2534381, EP13188771, EP13801735, W02015/ 059586 and BS2014A000171 on behalf of the Applicant.

[0060] In addition, according to yet another embodiment, the pump group 1 comprises, upstream of the impeller 2 in the inlet duct 121, an adjustment cartridge (not shown) suitable to adjust the amount of coolant liquid towards the impeller. The characteristics of said obturator cartridge are illustrated for example in the document WO2015/004548 on behalf of the Applicant.

[0061] According to the embodiments described above, the electric drive 5 and/or any electromagnetic pulley 33 are controlled electronically depending on the occurrence of certain conditions during use of the vehicle.

[0062] In a normal configuration, the electromagnetic pulley is not energised and the electric drive 5 is off, so that the impeller shaft 4 is moved only by the electromagnetic pulley 33, i.e. by the rotation of the mechanical shaft 300.

[0063] For example, when starting the vehicle, if the engine is still cold (so-called "warm-up" configuration), the electromagnetic pulley 33 is activated, in order to disengage the action on the mechanical shaft 300 while the electric drive 5 is left off. As a result the impeller shaft 4 and consequently the impeller 2 remain stationary and the liquid does not circulate in the circuit and the motor warms up faster.

[0064] According to another example, under heavy load conditions, such as when the vehicle is towing a trailer or going uphill struggle, typically at low speed (for example at low engine revs), the electric drive 5 is activated in order to place the electric shaft 500 in rotation at a speed greater than that induced by the mechanical drive 3 and by the mechanical shaft 300, thus inducing the impeller shaft 4 and thus the impeller 2 to rotate at the speed induced by the electric shaft 500.

[0065] Advantageously, in this configuration, the first one- way coupling 61 disengages in rotation the impeller shaft 4 from the mechanical shaft 300 reducing the masses dragged in rotation by the electric drive 5.

[0066] According to a further example, after use of the vehicle, if the coolant liquid is still very hot, the electric drive 5 is activated so as to keep the impeller shaft 4 and thus the impeller 2 in rotation (this stage is called "post run") . This way, the impeller 2 rotates at a predetermined rotation speed, while the mechanical drive 3 is completely inactive, since the vehicle engine is off. Specifically, for example, the electromagnetic pulley 33 is not energized, it not being necessary for the movement of the rotation shaft. In this case too, the first one-way coupling 61 disengages in rotation the impeller shaft 4 from the mechanical shaft 300 reducing the masses dragged in rotation by the electric drive 5.

[0067] In general, therefore, the electric drive 4 is activated whenever it is necessary to increase the cooling capacity, regardless of the mechanical drive 3, related to the engine speed.

[0068] For example, in an embodiment in which the pump group 1 comprises a mechanical drive 3 which has a "classic pulley", of the mechanical type, therefore not controlled electronically, and the above described throttle valve, in the above-described " warm-up ", phase in which the engine is still cold and heating as fast as possible is desired, the quantity of coolant in circulation is regulated by controlling the positioning of the throttle valve.

[0069] Innovatively, the pump group according to the present invention satisfies the cooling requirements of the engine and overcomes the drawbacks referred to above.

[0070] In the first place, advantageously, the pump group according to the invention is very flexible, as it responds to the cooling needs of the vehicle depending on the actual demand and not on the engine speed or availability of electric power of the system. That is to say that, advantageously, the pump group proves particularly suitable for entirely managing the quantity of coolant liquid in the cooling system, for example by managing the cooling of further vehicle components besides the engine, such as the turbo group, obviating the need to have specific electrical pumps to move the predetermined quantities of coolant liquid in such components. This gives additional space in the engine compartment.

[0071] Moreover, advantageously, the pump group is particularly compact and small in dimensions, making it particularly suitable to be housed in the engine compartment of a motor vehicle.

[0072] For example, advantageously, the impeller (and the impeller chamber with the volute) is more compact and not oversized, and always operating under optimum performance conditions compared to the known pump groups, where the impeller is often oversized to compensate for the poor flexibility of the mechanical pumps and limited power of the electric pumps.

[0073] A further advantageous aspect lies in the fact that the engagement of an electric drive and a mechanical drive housed directly in the impeller shaft simplifies the structure of the pump group, which proves more compact in size compared to solutions of the prior art.

[0074] A further advantageous aspect is that the one-way couplings are sealingly housed inside the shaft, thus preventing contamination and any wear and tear caused by the coolant liquid.

[0075] Advantageously, the pump group requires a limited number of dynamic seals: specifically only the two dynamic seals placed at the ends of the impeller shaft sealingly isolating the two drives are needed.

[0076] Advantageously, the design of the mechanical drive and the electric drive is extremely simplified and can be optimised by the engineer. For example, the electromagnetic pulley, if provided, does not require special design updates. In addition, the rotor of the electric motor is mounted directly on the respective shaft without the need for special screening bearings, thus limiting the axial dimensions of the rotor.

[0077] Moreover, advantageously, the transition from the electric drive to the mechanical drive and vice versa is operated mechanically by the one-way couplings. Therefore, advantageously, the electronic management of the pump group is very simple.

[0078] Advantageously, the pump group is able to avoid the cooling action, even though the engine is in gear, when, for example, in conditions of "warm-up", it is appropriate to heat the motor.

[0079] In a further advantageous aspect, the pump group has the "fail-safe "characteristic; in fact, in the event of a failure of the electric drive the pump group, thanks to the mechanical drive and the second one-way coupling, it continues to ensure the movement of the impeller.

[0080] According to a further advantageous aspect, the pump group is operative in "post-run" conditions, i.e. with the engine off. In such conditions it is possible to avoid electrically powering the electromagnetic pulley saving electricity.

[0081] A further advantageous aspect consists in the fact that the pump group has a more limited power absorption compared to standard mechanical pumps.

[0082] Moreover, the kinematic chain between the mechanical drive, electric drive and impeller is extremely simplified.

[0083] In addition, advantageously, the second one-way coupling, in a configuration in which the impeller is made to rotate by the mechanical drive, prevents the rotor from being dragged in rotation by the shaft; magnetic friction is thus not produced (or nor does the rotor-stator group work as an electric generator) .

[0084] Moreover, advantageously, the first one-way coupling and the second one-way coupling are selectable with different characteristics in function of the different actions required of the electric drive and the mechanical drive .

[0085] Advantageously, the electric drive is totally disconnected from the dynamic seal and the bearing supporting the drive shaft, thus presenting greater electrical efficiency and a wider range of electrical operation .

[0086] A further advantageous aspect is that the impeller is supported and centred by the mechanical shaft and the electric shaft.

[0087] A further advantageous aspect is that in the embodiment with the impeller supported by a support and centering bearing, the pump group does not require special support elements for the impeller shaft or mechanical or electric shafts which are in turn supported by the support and centering bearing. Advantageously the one-way couplings must also be suitable to support less stress and can be provided of smaller and more compact dimensions.

[0088] Advantageously, the pump group of the present invention finds effective application even coupled to next-generation motor groups, typically with engine boosting. These motor groups are suitable to deliver high power even at low revs, therefore having a mechanical drive of limited efficiency with consequent limited hydraulic performance of the impeller, recovered by the pump group of the present invention by the electric drive.

[0089] It is clear that a person skilled in the art may make modifications to the pump group described above so as to satisfy contingent requirements, all contained within the scope of protection as defined by the following claims.

[0090] In addition, each variant described as belonging to a possible embodiment may be realised independently of the other embodiments described.

Claims

1. Pump group (1) for a cooling system of an engine of a vehicle, comprising:

- an impeller (2) rotatable around an axis (X-X) ;

-an impeller shaft (4) extending along the axis (X-X) integrally connected to the impeller (2) to move it in rotation;

- a mechanical drive (3) and a mechanical shaft (300) rotatable by the mechanical drive (3) ;

- an electric drive (5) and an electric shaft (500) rotatable by the electric drive (5), wherein the electric drive (5) comprises an electric motor (50) ;

wherein the impeller shaft (4) houses a mechanical shaft impeller end (302) of the mechanical shaft (300) and an electrical shaft impeller end (502) of the electrical shaft (500) ;

wherein the mechanical shaft impeller end (302) and the electrical shaft impeller end (502) are operatively connected to the impeller shaft (4) respectively by a first one-way coupling (61) and a second one-way coupling (62) .

2. Pump group (1) according to claim 1, wherein the impeller shaft (4) comprises a housing cavity (40) housing a mechanical shaft impeller end (302) of the mechanical shaft (300) and an electrical shaft impeller end (502) of the electrical shaft (500) .

3. Pump group (1) according to any of the previous claims, wherein the impeller shaft (4) comprises a mechanical shaft housing cavity (43) and a electric shaft housing (45) respectively suitable to house the mechanical shaft impeller end (302) and the electrical shaft impeller end(502) .

4. Pump group (1) according to claim 3, wherein the shaft (4) comprises a central portion (41), preferably solid, at the axial ends of which the mechanical shaft housing cavity (43) and the electric shaft housing cavity (45) are located.

5. Pump group (1) according to any of the preceding claims, wherein the impeller shaft (4) and the impeller (2) are in one piece.

6. Pump group (1) according to any of the preceding claims, wherein the electrical shaft (300) and the mechanical shaft

(500) extend at opposite sides of the impeller (2) .

7. Pump group (1) according to claim 6 wherein the electrical shaft impeller end (502) comprises a pin (502') which extends along the axis (X-X) , while the mechanical shaft impeller end (302) comprises a housing (302') suitable to house and rotationally support the pin (502') or the central portion (41) comprises a housing suitable to house and rotationally support the pin (502') .

8. Pump group (1) according to claim 6 wherein the mechanical shaft impeller end (302) comprises a pin which extends along the axis (X-X) , while the electrical shaft impeller end (502) comprises a housing suitable to house and rotationally support the pin or the central portion (41) comprises a housing suitable to house and rotationally support the pin (502') .

9. Pump group (1) according to any one of the preceding claims, wherein the mechanical drive (3) is positioned rearwards of the impeller (2) while the electric drive (5) is placed in front of the impeller (2) .

10. Pump group (1) according to any of the preceding claims, comprising a pump body (10) delimiting an impeller chamber (120) housing the impeller (2) and containing the coolant liquid in transit, wherein said impeller shaft (4) is housed in said impeller chamber (120) and the housing cavity (40) is isolated from the coolant liquid.

11. Pump group (1) according to claim 10, comprising a pair of sealing elements (91, 92) operatively connected to the ends of the impeller shaft (4) suitable to separate the housing cavity (40) from the impeller chamber (120) .

12. Pump group (1) according to any of the preceding claims, wherein the first one-way coupling (61) comprises a rolling bearing for the support in rotation of the mechanical shaft impeller end (302) .

13. Pump group (1) according to any of the preceding claims, wherein the second one-way coupling (62) comprises a rolling bearing for the support in rotation of the electrical shaft impeller end (502) .

14. Pump group (1) according to any of the preceding claims, wherein the mechanical drive (3) comprises an electromagnetic pulley (33) operatively connected to the mechanical shaft (300) .

15. Pump group (1) according to any of the preceding claims, wherein the impeller shaft (4) and the impeller (2) are rotationally supported and kept centred on the axis (X-X) by the electrical shaft (300) and the mechanical shaft (500) .

16. Pump group (1) according to any of the claims from 1 to 14, wherein the impeller (2) comprises a paddle portion (21) and a support portion (22) comprising a support surface (220), wherein the pump group (1) comprises a support and centering bearing (20) operatively connected to the support surface (220) suitable to support and keep the impeller (2) and the impeller shaft (4) centred on the axis (X-X) absorbing the fluid-dynamic action of the coolant liquid.

17. Pump group (1) according to claim 16, wherein said support and centering bearing (20) is positioned behind the paddle portion (21) of the impeller (2) .

18. Pump group (1) according to the claims 16 or 17, wherein the support and centering bearing (20) is a ball bearing .