WO2014096494A1

WO2014096494A1 - Sealed and compact gear pump

Info

Publication number: WO2014096494A1
Application number: PCT/ES2013/070891
Authority: WO
Inventors: Pedro Javier Gamez Montero; Esteve CODINA MACIA
Original assignee: Universitat Politècnica De Catalunya
Priority date: 2012-12-21
Filing date: 2013-12-18
Publication date: 2014-06-26
Also published as: ES2482869A1; ES2482869B1

Abstract

The invention relates to a gear pump having a sealed casing (100, 200) including a pump body (126) and a cover (156), comprising: a cavity in fluid communication with a suction area (140) and a discharge area (152); an inner gear wheel (102) provided with a number Z-1 of outer teeth and housed in the aforementioned cavity such that it can rotate about a first axis of rotation (Ei); an outer gear wheel (104) provided with a number Z of inner teeth, housed in the cavity such that it can rotate about a second axis of rotation (Ee) parallel to the first axis of rotation (Ei), and meshed with the inner gear wheel (102); and first and second inner electromagnetic assemblies that actuate the rotation of the inner and outer gear wheels (102, 104) respectively, in which said first and second inner electro-magnetic assemblies can be controlled independently by control means.

Description

COMPACT AND SEALED GEAR PUMP

Technical field

The present invention concerns a gear pump for fluids provided with a dobie electro-magnetic assembly that allows a compact and tight design, without transmission shafts externally coupled to the pump, and where said double electro-magnetic assembly provides a torque independent motor for each gear, resulting in a gear with a minimum contact voltage, or with a controlled contact voltage, in order to minimize the wear of the gears.

Gear pumps have application in numerous industrial sectors, among which are the automotive sector and the aeronautics sector.

Background of the invention

In essence, a conventional gear pump consists of a pair of cogwheels: a pinion with external teeth called an internal cogwheel and a crown with internal teeth called an external cogwheel, housed in a cavity of a housing generally formed by a body of pump and a cover connected to each other. The mentioned cavity is in fluid communication with a suction area (fluid inlet) and a discharge area (fluid outlet). The two sprockets rotate around respective parallel axes and are conjugated so that each tooth of the inner sprocket is in permanent sliding contact with the outer sprocket forming what are known as "contact points".

The outer sprocket has a Z number of teeth, while the inner sprocket has a Z-1 number of teeth. In this way, between the inner sprocket and the outer sprocket there are permanently Z points of contact between the corresponding sealed chambers Z defined by surfaces of the teeth of both sprockets and by surfaces of the housing.

The pumping action is produced by a variation in the volume of said watertight chambers as a result of the complete rotation of the inner and outer sprockets, creating the circulation of successive watertight chambers with increasing fluid volume from said suction area to said suction area impulsion. In general, the Rotational movement is generally imparted by a drive shaft driven by an external motor that rotates the inner gearwheel and the inner gearwheel transmits the rotation motion to the outer gearwheel, although alternative drive means are known.

For example, patent application US 20060039815 A1 discloses a gear pump comprising a concentric magnetic ring with the axis of rotation of the outer sprocket and fixed to an outer periphery of the outer sprocket, and a ring with windings concentric with the axis of rotation of the outer sprocket and fixed to the housing so that this ring with windings is radially adjacent around said magnetic ring. When the windings are excited by supply of electric current, a magnetic field is generated in the magnetic ring that causes the rotation of the outer sprocket, and this transmits the rotational movement to the inner cogwheel by the force exerted by the internal teeth of the outer sprocket on the outer teeth of the inner sprocket at the contact points.

US Patent 7500837 B2 describes a gear pump that includes an internal electromagnetic assembly arranged to drive the rotation of the inner gearwheel, and this transmits the rotational movement to the outer gearwheel by the force exerted by the outer teeth of the wheel. internal toothed on the inner teeth of the outer gearwheel at the contact points.

US 8182235 B2 discloses a gear pump that includes a drive shaft driven by a first external mechanical actuator and operatively connected through a first clutch to drive the rotation of the inner gearwheel, a driven drive gearwheel. by a second external mechanical actuator and operatively connected through a second clutch to drive the rotation of the outer gearwheel, and an additional internal electromagnetic assembly arranged to drive the rotation of the outer gearwheel. The three drives are alternative and are not intended to act simultaneously to drive the rotation of both inner and outer sprockets, whereby the rotational movement to the inner sprocket is transmitted to the outer sprocket by the force exerted by the teeth external of the internal gearwheel on the internal teeth of the external gearwheel at the contact points or alternatively the rotation movement to the external gearwheel is transmitted to the internal gearwheel by the force exerted by the internal teeth of the outer sprocket on the outer teeth of the inner sprocket at the contact points.

Gear pumps have a significant number of advantages, such as a low noise level and a small number of components, which is why they apply in a wide range of industrial sectors, including the automotive sector and the automotive sector. aeronautics. However, some of the advantages of its design have disadvantages in some aspects of its behavior.

The fact that in the gear pumps of the prior art the rotational movement of one of the sprockets is transmitted to the other of the sprockets by the force exerted by one of them on the other at the contact points generates a tension called "contact tension" in the material of both sprockets, which causes wear on the profile of the teeth.

In addition, from a fluid dynamics point of view, this gap between the teeth allows a fluid flow from one of the sealed chambers to others, favored by a pressure gradient between the sealed chambers and by a relative movement of the sprockets. Consequently, pump performance is negatively influenced. Since gear pumps produce a fluctuation of flow that overlaps the average flow, this fluctuation of flow is negatively influenced, producing pressure pulsations, which are the major source of vibration and fatigue failures in gear pumps. prior art

A major disadvantage of gear pumps is the absence of parts that can be adjusted to compensate for the clearance caused by wear on the profile of the teeth of the sprockets, which results in a progressive reduction in the efficiency of the pump gears, which can be remarkable. Consequently, when the loss of performance due to this wear on the gear profiles exceeds a preset threshold, the only possible alternative is the replacement of both sprockets, with a significant associated economic cost.

It should be borne in mind that although a correct selection of the design parameters of the sprockets was obtained that would allow to reach an optimum contact tension from the mechanical point of view, it cannot be ignored that these same geometric parameters also determine the volumetric characteristics of the pump, and that a gain in the mechanical aspect could lead to an impairment in such volumetric characteristics.

Exhibition of the invention

Taking into consideration the disadvantages of the operation of prior art gear pumps, an objective of the present invention is to eliminate the need for transmission of the torque from one of the cogwheels to the other by a force exerted on the contact points. of the gear of the sprockets, and consequently eliminate or drastically reduce the mechanical tension known as contact tension in the material of the sprockets.

The present invention contributes to achieving this and other objectives by providing a compact and sealed gear pump comprising a sealed housing that includes a pump body and a cover connected to each other defining between them a cavity in fluid communication with a suction area and a driving area, an inner sprocket, provided with a number Z-1 of external teeth, housed in said cavity capable of rotating around a first axis of rotation, an outer cogwheel, provided with a number Z of internal teeth, housed in the cavity with the ability to rotate about a second axis of rotation parallel to said first axis of rotation and engaged with said inner gear wheel, and drive means configured and arranged to rotate at least one of said inner gear wheels and Exterior.

The gear pump of the present invention is characterized in that said drive means comprise a first internal electro-magnetic assembly that drives the rotation of the inner gearwheel and a second internal electromagnetic assembly that drives the rotation of the outer gearwheel, where said first and second internal electro-magnetic assemblies are independently controllable by control means.

Consequently, both inner and outer sprockets are independently driven, which allows controlling the torque ratio between the two, including the possibility of minimizing torque transmission between the inner and outer sprockets. Since there is no transmission of torque between the inner and outer wheels by forces exerted by the teeth at the contact points, there are also no contact voltages on the gearwheel material and consequently the wear of the wheels is canceled or drastically reduced. same. Alternatively, the independent drive of the inner and outer gearwheels allows the contact voltage to be controlled at a desired value.

In one embodiment, said first internal electro-magnetic assembly comprises a first winding ring, coaxial with said first axis of rotation, fixed to said pump body and a first magnetic ring, also coaxial with said first axis of rotation, arranged radially adjacent to said first winding ring and fixed to the inner gearwheel, so that when windings of the first winding ring are excited by means of electric current supply, a magnetic field is generated in the first magnetic ring that transmits a first motor torque and a first rotation speed to the inner sprocket.

Similarly, said second internal electro-magnetic assembly comprises a second coaxial magnetic ring with said second axis of rotation and fixed to the outer toothed wheel and a second ring with coaxial winding with said second axis of rotation, arranged around said second magnetic and fixed ring with respect to said pump body to transmit a second motor torque and a second rotation speed to the outer sprocket.

In addition, and as an additional result of the research carried out by the inventors to achieve the objective indicated above, the gear pump of the present invention provides an innovative, more compact and watertight design, since it does not have any primary transmission shaft that goes out through the pump body or cover, no axis being seen from the outside of the sealed housing of the pump.

In one embodiment, one or both inner and outer gearwheels include on the surfaces of mutual contact a coating of a thermoplastic material, such as for example polyoxymethylene or polyacetal, an elastomeric, polymer, plastic or synthetic coating, which aids in the The tightness of the sealed chambers although the contact voltage is very low. In this way a benefit is obtained in the volumetric yield.

Effects of the Invention

The compact and sealed gear pump of the present invention allows the contact voltages of the contact points between the inner and outer sprockets to be controlled by means of the two internal electro-magnetic assemblies independent that drive the rotation of the inner sprocket and the rotation of the outer sprocket, respectively.

As a result of the research carried out by the inventors, in the compact and sealed gear pump of the present invention, the magnitude of the contact tension can be controlled if torque transmission by gear between the inner gear wheel and the outer gear wheel is desired. , the torque of each wheel being controllable independently. Thus, it can be controlled whether the inner sprocket is the one that transmits torque to the outer sprocket, or if the outer sprocket is the one that transmits torque to the inner sprocket, or if both sprockets and transmit torque between they at different magnitudes, as well as if there is no torque transmission by gear between both sprockets.

Likewise, the compact and sealed gear pump of the present invention makes it possible to control the wear of the surfaces of the tooth profiles of the inner gear wheel and the outer gear wheel, said wear being zero or minimum, which consequently improves the Volumetric efficiency and performance of the gear pump.

Fig. 4 shows a comparative graph of the volumetric characteristics and the maximum contact voltage as a function of the number of teeth in a gear pump according to the design of the present invention, where:

- Q _s is the specific flow rate;

- 5Q is the irregularity of the flow;

- Cv is the volumetric capacity;

- Oyy is the maximum contact voltage; Y

- Z is the number of teeth.

Fig. 5 shows a comparative graph of the maximum contact voltage for different angular positions of the gear in a gear pump according to a conventional design and the range of variation of the maximum contact voltage as a function of the angular position of the gear in a gear pump according to the design of the present invention.

The compact and sealed gear pump of the present invention minimizes internal fluid leaks, from one another of the sealed chambers thanks to the absence of wear, and prevents external leaks, from inside to outside the housing waterproof thanks to the absence of shafts that cross the walls of the waterproof housing.

The compact and sealed gear pump of the present invention allows to control the synchronization and the relative speed of both gearwheels independently, allowing rotation in both directions of rotation to produce a pumping action of lower flow rate pulsation, reducing pressure pulsations , which are the major source of vibrations and fatigue failure.

The compact and sealed gear pump of the present invention improves the environmental relationship of this type of fluid pumps thanks to its tightness in relation to the surrounding environment.

Brief Description of the Drawings

The foregoing and other features and advantages will become more apparent from the following detailed description of some embodiments with reference to the attached drawings, in which: Fig. 1 is a sectioned plan view of a compact gear pump and waterproof according to an embodiment of the present invention; Fig. 2 is a cross-sectional view taken by the piano l l-ll of Fig. 1; Fig. 3 is a sectional elevational view of a compact and sealed gear pump according to another embodiment of the present invention;

Fig. 4 is a comparative graph of the volumetric characteristics and the maximum contact voltage as a function of the number of teeth in a gear pump according to the present invention; Y

Fig. 5 is a comparative graph of the maximum contact voltage in a gear pump according to a conventional design and the maximum contact voltage in a gear pump according to the present invention as a function of the angular position of the gear.

Detailed description of some embodiments

Referring firstly to Figs. 1 and 2, there is shown a compact and sealed gear pump according to an embodiment of the present invention, which comprises a sealed housing 100 formed by a pump body 126 and a cover 156 fixed to each other by means of screws or any other fastening element 162. Between said pump body 126 and said cover 156 a cavity is defined in fluid communication with a suction area 140 and a discharge area 152.

Within said cavity there are arranged an inner gearwheel 102 provided with a number Z-1 of external teeth and an external gearwheel 104 provided with a number Z of internal teeth. Said inner sprocket 102 is rotatable about a first axis of rotation Ei and said outer sprocket 104 is rotatable about a second axis of rotation Ee parallel to said first axis of rotation Ei and is engaged with the inner sprocket 102. External teeth of the inner gearwheel 102 have Z contact points 172 with the outer gearwheel 104, and between these Z contact points are defined Z sealed chambers of variable volume 110 delimited by surfaces of the outer teeth of the inner gearwheel 102 , surfaces of the internal teeth of the outer gearwheel 104, and surfaces of the chamber body 126 and the cover 156. The pump body cavity is cylindrical and coaxial with said second axis of rotation Ee.

The gear pump comprises drive means that include a first internal electro-magnetic assembly that drives the rotation of the inner gearwheel 102 and a second internal electro-magnetic assembly that drives the rotation of the outer gearwheel 104, with the particularity that said first and second internal electro-magnetic assemblies are independently controllable by control means. In the embodiment shown in Figs. 1 and 2, said first internal electro-magnetic assembly comprises a first ring with winding 1 14 fixed to said pump body 126 and a first magnetic ring 1 18 arranged around said first ring with winding 1 12 and fixed to the inner toothed wheel 102, to transmit a first torque and a first rotation speed to the inner gearwheel 102. Both said first ring with winding 114 and said first magnetic ring 118 are coaxial with said first axis of rotation Ei.

Similarly, said second internal electro-magnetic assembly comprises a second magnetic ring 120 fixed to the outer gearwheel 104 and a second winding ring 122 disposed around said second ring magnetic 120 and fixed to said pump body 126 to transmit a second motor torque and a second rotation speed to the outer gearwheel 104. Both said second magnetic ring 120 and said second winding ring 122 are coaxial with said second axis of rotation USA

The pump body 126 has an outer surface 154 and an inner surface 148 and the cover 156 has an outer surface 158 and an inner surface 160, so that when the cover 156 is attached to the pump body 126, the inner surface 148 of the pump body 126 and the inner surface 160 of the covers are located directly adjacent to the sealed chambers of variable volume 10 cooperating with the surfaces of the teeth of the inner and outer sprockets 102, 104 in the definition of the variable volumes of the waterproof cameras of variable volume 110.

The inner surface 148 of the pump body 126 has machining that forms non-variable empty volumes that act as a suction port 106 and a discharge port 108 of opposite semicircular elongated shapes (Fig. 1).

The pump body 126 also has a suction duct 142 of optimum fluid-dynamic geometry that connects the suction area 140 with said suction port 108 and consequently with those of the sealed chambers of variable volume 1 10 which are coincident with the suction port 108, and a discharge conduit 150 of optimum fluid-dynamic geometry connecting the discharge port 106, and consequently those of the sealed chambers of variable volume 110 which are coincident with the discharge port 106, with the drive area 152.

Thus, the gear pump sucks a fluid that is conducted from a corresponding reservoir or fluid source (not shown) to the suction area 140, and through the suction conduit 142, suction port 108, sealed chambers of variable volume 110, discharge port 106 and discharge conduit 150 to the discharge area 152 to be driven to a corresponding component or system (not shown).

Optionally, the cover 156 can also have machining that defines non-variable empty volumes that act as a suction port 168 and a discharge port 170 of opposite semicircular elongated shapes (Fig. 2). The suction port 168 of the cover 156 is opposite and aligned with the suction port 106 of the pump body 126 and is exposed to those of the sealed chambers of variable volume 1 10 which are coincident with the suction port 168, while the discharge port 170 of the cover 156 is opposite and aligned with the discharge port 108 of the pump body 126 and is exposed to those of the sealed chambers of variable volume 1 0 which are coincident with the discharge port 170.

The inner gearwheel 102 and the outer gearwheel 104 are conjugated so that each tooth of the inner gearwheel 102 is in permanent non-sliding contact with the outer gearwheel 104 forming those known as contact points 172. The outer gearwheel 104 Z has teeth (Z being an integer), one more than the internal gearwheel 102. In this way, Z contact points 172 are formed. The pumping action is produced by the variation of the volume of the variable volume sealed chambers 110 with the complete rotation of the inner gearwheel assembly 102 and the outer gearwheel 104, creating the circulation of successive sealed chambers of variable volume 1 10 with increasing fluid volume from the suction area 140 (inlet) to the area of drive 152 (output).

The contact voltages of the contact points 172 are controlled by means of the first and second independent internal electro-magnetic assemblies for the inner gearwheel 102 and the outer gearwheel 104. Accordingly, the magnitude of the tension of the tension of contact if a transmission of torque by gear is desired between the inner sprocket 102 and the outer sprocket 104, the torque of each wheel being independently controlled. Thus, it can be contracted if the inner sprocket 102 is the one that transmits torque to the outer sprocket 104, or it can be contracted if the outer sprocket 102 is the one that transmits the torque to the inner sprocket 102, or if both Inner and outer wheels 102 and 104 transmit torque between them at different torque magnitudes, or if there is a minimum torque transmission per gear between both inner and outer sprockets 102 and 104.

The first magnetic ring 1 18 of the first electromagnetic assembly is located circumferentially and connected to the inner sprocket 102. The first magnetic ring 1 18 is formed by a plurality of permanent magnets located in the radial direction and whose orientation, location and polarity can be exchanged at convenience. In an alternative embodiment (not shown) the inner gearwheel 02 does not incorporate a magnetic ring formed by a plurality of permanent magnets but is formed and constructed entirely or partially by magnetic material forming the corresponding first magnetic ring. The first magnetic ring 1 18 is operated by said first ring with winding 1 14, which, in the embodiment shown in Figs. 1 and 2 comprises two first concentric rings connected to each other by first radial ribs in which first windings 1 18 are interconnected by means of wire or appropriate material, and connected to a corresponding power supply (not shown), for example through a central cylindrical conduit 112 and through the cover 158 and / or the pump body 126. When the first windings 1 16 are properly excited by the power supply of the power supply, a magnetic field is generated in the magnets permanent of the magnetic ring 1 18 causing the rotation of the inner gearwheel 102. Between the power supply and the ring with winding 1 14 a controller, a programmable automaton or a logic card (not shown) can be placed to control, between others, the speed of rotation and the torque of the inner sprocket 102 that allow cooperating in the control of the tension of contact and relative speed. In the pump body 126 two hydrodynamic bearings 144 and 146 are located to position, support and facilitate the rotation of the inner gearwheel 102 by hydrodynamic lubrication, with grooves (not shown). Likewise, on the cover 156, two other hydrodynamic bearings 144 and 146 are located to position, support and facilitate the rotation of the inner gear wheel 102 by hydrodynamic lubrication, with grooves (not shown).

As shown in Fig. 2, the first two concentric rings connected by first radial ribs of the winding ring 14 are fixed and centered with the pump body 126 and with the cover 156 by means of the rings 114 embedded in machined circumferential grooves in the inside the inner surface 148 of the pump body 126 and inside the inner surface 160 of the cover 156. This configuration forms the radial seal towards the center of the pump body 126 through the faces of the inner toothed wheel 102 in contact adjacent to the inner surface 148 of the pump body 126 and the inner surface 160 of the cover 156, and consequently, the tightness of the sealed chambers of variable volume 1 10 in contact adjacent to the inner surface 148 of the pump body 126 and the inner surface 160 of the cover 156.

The outer gearwheel 104 carries the second magnetic ring 120, which is located circumferentially and joined to the outer gearwheel 104, The second magnetic ring 120 is formed by a plurality of permanent magnets located in the radial direction and whose orientation, location and Polarity can be exchanged at convenience. Alternatively, the outer gearwheel 104 instead of incorporating a second magnetic ring formed by a plurality of permanent magnets may be formed and constructed entirely or partially by a magnetic material (not shown) forming the second magnetic ring.

The second magnetic ring 120 is operated by said second ring with winding 122 concentric to the second magnetic ring 120, which, in the embodiment shown in Figs. 1 and 2, it comprises two second concentric rings connected to each other by a few radial ribs in which are arranged a few second windings 124 interconnected by means of wire or appropriate material, and connected to the corresponding power supply (not shown) through the cover 158 and / or the pump body 126. When the second windings 124 are properly excited by the power supply of the power supply, a magnetic field is generated in the permanent magnets of the magnetic ring 120 causing the wheel to rotate. external toothed 104. Between the power supply and the winding ring 122 a controller, a programmable automaton or a logic card (not shown) can be placed that allows to control, among others, the rotation speed and the wheel motor torque external toothed 104 allowing control of the contact voltage and relative speed. In the pump body 126 two hydrodynamic bearings 164 and 166 are located to position, support and facilitate the rotation of the outer gearwheel 104 by hydrodynamic lubrication, with grooves (not shown). Similarly, on the cover 156 two hydrodynamic bearings 164 and 166 are located to position, support and facilitate the rotation of the outer gearwheel 104 by hydrodynamic lubrication, with grooves (not shown).

As shown in Fig. 2, the two second concentric rings connected by second radial ribs of the winding ring 122 are fixed and centered with the pump body 126 and the cover 156 by means of the rings 122 embedded in a circumferential grooves machined inside of the inner surface 148 of the body of pump 126 and inside the inner surface 160 of the cover 156. This configuration forms the radial seal to the outside of the pump body 126 through the faces of the outer sprocket 104 in contact adjacent to the inner surface 148 of the pump body 126 and the inner surface 160 of the cover 156, and consequently, the tightness of the sealed chambers of variable volume 110 in contact adjacent to the inner surface 148 of the pump body 126 and the intended surface 160 of the cover 156 ,

Fig. 3 shows a compact and sealed gear pump according to another alternative embodiment of the present invention, which comprises, in a manner analogous to that described above in relation to Figs. 1 and 2, a sealed housing 200 that includes a pump body 126 and a cover 156 connected to each other defining between them a cavity in fluid communication with a suction area 140 and a driving area 152, an intentional gearwheel 102 provided with a number Z-1 of external teeth housed in said cavity capable of rotating around a first axis of rotation Ei, an external gearwheel 104 provided with a number Z of internal teeth housed in the cavity capable of rotating about a second rotation axis Ee parallel to said first rotation axis Ei and engaged with said inner gearwheel 102, and drive means including a first internal electro-magnetic assembly that drives the rotation of the internal gearwheel 102 and a second electro- internal magnetic that drives the rotation of the outer gearwheel 104, said first and second internal electromagnetic assemblies being independently controllable entirely by means of control.

In the embodiment shown in Fig. 3, the waterproof housing 200 comprises a first sealed motor housing 206 connected tightly to the pump body 126 and a second sealed motor housing 208 connected tightly to the cover 156. The first Internal electro-magnetic assembly comprises a first magnetic ring 18 fixed to a first concentric shaft 210 with the first axis of rotation Ei housed inside said first sealed motor housing 206 and a first winding ring 1 14 housed within the first housing of sealed engine 206 and fixed thereto surrounding the first magnetic ring 1 18. This first shaft 210 is directly connected to the inner gear wheel 102.

The second internal electro-magnetic assembly comprises a second magnetic ring 120 fixed to a second concentric shaft 212 with the second axis of rotation Ee housed within said second sealed motor housing 208 and a second winding ring 122 housed within the second housing motor airtight 208 and fixed thereto surrounding the second magnetic ring 120. This second shaft 212 is connected to a rigid transmission member 204 which is in turn connected to the outer sprocket 104 by means of drive pins 202 or elements Similar.

Note that the first and second watertight motor housings 208, 208 do not have openings through which the first and second shafts 210, 212 exit to the outside, which ensures perfect sealing of the watertight housing 200.

In a variant (not shown) of any of the possible embodiments of the present invention, in which the gear pump operates with a very low or minimal torque transmission from one of the inner and outer sprockets 102, 104 through the contact points 172, one of the inner and outer sprockets 102, 104 or both inner and outer sprockets 102, 104 have a synthetic material coating in those areas that make mutual contact, that is, in those areas of the teeth of the inner and outer sprockets 102, 104 which include the contact points 172.

Said synthetic material may be a thermoplastic, such as for example polyoxymethylene or polyacetal, or an elastomer. This coating helps the tightness of the sealed chambers of variable volume 1 10 without any contact voltage or with a very low contact voltage. In this way a benefit in volumetric yield is obtained.

One skilled in the art will be able to introduce modifications and variations in the exemplary embodiments shown and described without departing from the scope of the present invention as defined in the appended claims.

Claims

1.- Compact and sealed gear pump, comprising a sealed housing (100, 200) that includes a pump body (126) and a cover (158) connected to each other defining a cavity in fluid communication with a suction area between them (140) and a driving area (152), an inner gear wheel (102) provided with a number Z-1 of outer teeth housed in said cavity capable of rotating around a first axis of rotation (Ei), a wheel external toothed (104) provided with a number Z of internal teeth housed in the cavity capable of rotating around a second axis of rotation (Ee) parallel to said first axis of rotation (Ei) and engaged with said internal gearwheel (102 ), and drive means for rotating at least one of said inner and outer gear wheels (102, 104), characterized in that said drive means comprise a first internal electro-magnetic assembly that drives the rotation of the wheel internal gear (102) and a second internal electro-magnetic assembly that drives the rotation of the external gearwheel (104), wherein said first and second internal electro-magnetic assemblies are independently controllable by control means.

2 - Compact and sealed gear pump according to claim 1, characterized in that said first internal electro-magnetic assembly comprises a first ring with coaxial winding (114) with said first rotation axis (Ei) fixed with respect to said pump body (126) and a first magnetic ring (118) coaxial with said first axis of rotation (Ei), arranged radially adjacent to said first ring with winding (112) and fixed relative to the inner toothed wheel (102), to transmit a first torque and a first rotation speed to the inner gearwheel (102). 3. A compact and sealed gear pump according to claim 2, characterized in that said first ring with winding (1 14) comprises two first concentric rings connected to each other by first radial ribs in which first windings are arranged (16 ).

4. - Compact and sealed gear pump according to claim 2 or 3, characterized in that said first two concentric rings are fitted in first circumferential grooves formed in an inner surface (148) of the pump body (126) and in a inner surface (160) of the cover (156).

5. - Compact and sealed gear pump according to claim 2, 3 or 4, characterized in that said first magnetic ring (118) comprises a plurality of permanent magnets fixed along an inner perimeter of the inner sprocket (102) around the winding ring (114).

6. - Compact and sealed gear pump according to claim 2, 3 or 4, characterized in that at least one circumferential region of the inner gear wheel (102) is formed by a magnetic material, wherein said circumferential region includes an inner perimeter forming said first magnetic ring (1 18) located around the winding ring (114).

7. - Compact and sealed gear pump according to any one of claims 1 to 6, characterized in that the inner gear wheel (102) is guided and supported with respect to the pump body (126) and with respect to the cover (56) by first hydrodynamic bearings (144, 146).

8. - Compact and sealed gear pump according to claim 2, characterized in that said first magnetic ring (118) is fixed to a first shaft (210) concentric with the first axis of rotation (Ei), connected to the sprocket inside (102) and housed inside a first sealed motor housing (206) connected tightly to the pump body (126), and said first winding ring (1 14) is housed within said first sealed motor housing ( 206) and fixed thereto around the first magnetic ring (118).

9. - Compact and sealed gear pump according to claim 1, characterized in that said second internal electro-magnetic assembly comprises a second magnetic ring (120) coaxial with said second axis of rotation (Ee) and fixed to the outer sprocket (104) and a second winding ring (122) coaxial with said second axis of rotation (Ee), arranged around said second magnetic ring (120) and fixed relative to said pump body (126) to transmit a second motor torque and a second rotation speed to the outer gearwheel (104).

10. - Compact and sealed gear pump according to claim 9, characterized in that said second winding ring (122) comprises two second concentric rings connected to each other by a few radial ribs in ios which are arranged a few winding seconds (124) . 1 1. Compact and sealed gear pump according to claim 9 or 10, characterized in that said two second concentric rings are fitted in second circumferential grooves formed in an inner surface (148) of the pump body (126) and in an inner surface (160) of the cover (156).

12. - Compact and sealed gear pump according to claim 9, 10 or 11, characterized in that said second magnetic ring (120) comprises a plurality of permanent magnets fixed along an outer perimeter of the outer gearwheel (104 ).

13. - Compact and sealed gear pump according to claim 9, 10 or 11, characterized in that at least one circumferential region of the outer gear wheel (104) is formed by a magnetic material, wherein said circumferential region includes an outer perimeter forming said second magnetic ring (120).

14. - Compact and sealed gear pump according to any one of claims 9 to 13, characterized in that the outer gear wheel (104) is guided and supported with respect to the pump body (126) and with respect to the cover (158) for a few seconds hydrodynamic bearings (184, 168).

15. - Compact and sealed gear pump according to claim 9, characterized in that said second magnetic ring (120) is fixed to a second shaft (212) concentric with the second axis of rotation (Ee), connected to the sprocket exterior (104) and housed within a second sealed motor housing (208) connected tightly to the cover (156), and said second winding ring (122) is housed within said second sealed motor housing (208) and fixed thereto around the second magnetic ring (120).

18. Compact and sealed gear pump according to claim 15, characterized in that said second shaft (212) is connected to the outer gearwheel (104) by means of a transmission member (204).

17. - Compact and sealed gear pump according to any one of the preceding claims, characterized in that at least one of the inner and outer gear wheels (102, 104) has a synthetic material coating in those areas that make contact with the other of the inner and outer sprockets (102, 104).

18, - Compact and sealed gear pump according to claim 17, characterized in that said synthetic material is selected from a group comprising a thermoplastic and an elastomer.

19. Compact and sealed gear pump according to claim 18, characterized in that said thermoplastic is selected from a group comprising polyoxymethiene and polyamide !.