EP4350145A1

EP4350145A1 - Gear pump for oil

Info

Publication number: EP4350145A1
Application number: EP23201234.4A
Authority: EP
Inventors: Otto Varini
Original assignee: PIUSI SpA
Current assignee: PIUSI SpA
Priority date: 2022-10-06
Filing date: 2023-10-02
Publication date: 2024-04-10

Abstract

A gear pump (1) for oil comprising a hydraulic part (2), which is provided with a pump body (4) which defines internally an oil pumping chamber (5) accommodating at least one movable gear (6) for pumping the oil, and a driving part (3), provided with an electric motor (7) housed in a compartment (8) defined inside a containment casing (9), and provided with a shaft (10) which is functionally connected to the movable gear (6); at least one dividing wall (12) is provided between the pumping chamber (5) and the compartment (8) which is passed through by the shaft (10) of the electric motor (7) without the interposition of gasket seals. Means for circulating oil between the pumping chamber (5) and the compartment (8) are further provided.

Description

The present invention relates to a gear pump for oil.
As is known, for transferring cooling oils or lubricating oils, gear pumps are widely used which have, in general, a hydraulic part, constituted by a pump body, inside which a pumping chamber is defined which accommodates at least one pumping element constituted by a gear system, and a driving part, which is joined to the hydraulic part and is constituted by an electric motor.
The driving part can be connected to the hydraulic part by means of an external entrainment coupling or, alternatively, the shaft of the motor is inserted in the hydraulic part and the pumping element is keyed directly to it.
Such construction solutions imply the use of a rotating gasket to seal the oil under pressure at the external coupling or at the shaft of the motor.
The wear to which the rotating gasket is subjected means it is not possible to guarantee a high number of hours of operation of the pump.
The aim of the present invention is to provide a gear pump for oil which is capable of improving the known art in one or more of the above-mentioned aspects.
Within this aim, an object of the invention is to provide a gear pump for oil that is capable of guaranteeing a high number of hours of operation.
Another object of the invention is to provide a gear pump that is extremely compact.
Another object of the present invention is to provide a gear pump that can ensure an optimal cooling and performance of the motor.
Another object of the invention is to provide a gear pump for oil that is capable of offering the widest guarantees of reliability and safety in its operation.
A further object of the present invention is to overcome the drawbacks of the known art in an alternative manner to any existing solutions.
Another object of the invention is to provide a gear pump for oil that is simple in terms of construction so as to be competitive from a purely economic viewpoint as well.
This aim and these and other objects which will become more apparent hereinafter are achieved by a gear pump for oil according to claim 1, optionally provided with one or more of the characteristics of the dependent claims.
Further characteristics and advantages of the invention will become more apparent from the description of preferred, but not exclusive, embodiments of the gear pump for oil according to the invention, which are illustrated for the purposes of non-limiting example in the accompanying drawings wherein:

Figure 1 is a cross-sectional side view of the pump according to the invention;
Figure 2 shows a detail of Figure 1;
Figure 3 is a cross-sectional side view of another embodiment of the pump according to the invention;
Figure 4 is an enlarged-scale view of a detail of Figure 3.

With reference to the figures, a gear pump for oil according to the invention, generally designated by the reference numeral 1, comprises a hydraulic part 2 and a driving part 3, connected directly to each other, without the interposition of entrainment couplings.
In particular, the hydraulic part 2 has a pump body 4, which defines internally an oil pumping chamber 5, in which at least one movable gear 6 for pumping the oil is accommodated.
In particular, the pumping chamber 5 is connected to an intake connector 5a, which is connected to an oil intake line, and with an outflow connector, not shown, which in turn is adapted to be connected to an oil outflow line.
The driving part 3 of the pump has, in turn, an electric motor 7, accommodated in a compartment 8 defined inside a containment casing 9, which is advantageously fixed to the pump body 4.
The electric motor 7 is provided with a shaft 10, protruding from the electric motor 7, which is functionally connected to the movable gear 6, in order to actuate it in rotation inside the pumping chamber 5.
The movable gear 6 actuated by the electric motor 7 conveniently has an external set of teeth that meshes with the external set of teeth of a driven gear, not shown, which is mounted so that it can rotate idle inside the pumping chamber 5, about an axis that is substantially parallel to the axis of the movable gear 6.
Alternatively, the movable gear 6 can be arranged inside an external gear, not shown, which is also accommodated in the pumping chamber 5, and have an external set of teeth that meshes with an internal set of teeth defined by the external gear, according to a configuration of the type known as a "gerotor".
The shaft 10 of the electric motor 7 is, conveniently, supported by bearings 11a, 11b connected to the casing 9.
The rotation of the movable gear 6 by the electric motor 7 consequently creates, inside the pumping chamber 5, an oil intake region, connected to the intake connector 5a, and an oil outflow region, connected to the outflow connector.
According to the invention, between the pumping chamber 5 and the compartment 8 in which the electric motor 7 is accommodated, at least one dividing wall 12 is interposed which is passed through, at a through hole 12a, by the shaft 10 of the electric motor 7, without the interposition of gasket seals that separate the hydraulic part 2 from the driving part 3 of the pump, thus allowing the passage of oil between the pumping chamber 5 and the compartment 8 but avoiding the problems of the known art associated with the wear of gaskets fitted on the shaft 10 of the electric motor 7.
Also according to the invention, there are means for circulating oil between the pumping chamber 5 and the compartment 8, which make it possible to obtain an optimal cooling of the driving part 3 and the correct lubrication of the bearings 11a, 11b, which can be of the unshielded type.
In particular, conveniently, at least one inlet opening 13 for the passage of the oil from the pumping chamber 5 to the compartment 8 and at least one outlet opening 14 for the passage of the oil from the compartment 8 to the pumping chamber 5 are defined in the dividing wall 12.
Conveniently, such inlet opening 13 is located substantially at the oil outflow region of the pumping chamber 5, while the outlet opening 14 is arranged substantially at the oil intake region of the pumping chamber 5.
Advantageously, the electric motor 7 is a brushless direct current (BLDC) motor or a single-phase or three-phase induction alternating current (AC) motor.
In particular, the electric motor 7 comprises, conveniently, a stator 15 which is anchored to the casing 9 and a rotor 16 which is accommodated axially inside the stator 15 and is rigidly fixed to the shaft 10.
More specifically, the stator 15 is constituted, advantageously, by a magnetic metallic lamination pack with copper wire winding, while the rotor 16 can be constituted by at least one magnet made of ferrite or rare earth elements, if the electric motor 7 is a brushless direct current (BLDC) motor, or by a metallic lamination pack, with a die-cast aluminum cage, if, instead, the electric motor 7 is a single-phase or three-phase induction alternating current (AC) motor.
Conveniently, a power supply connector 17 is defined in the casing 9 and is provided with an oil sealing gasket, for the electrical connection to the stator 15 of the electric motor 7.
Conveniently, the parts of the electric motor 7 are structured to be chemically compatible with various types of oil, by way of plastic insulating elements, suitable coating of electric wires and the like.
It should be noted that the electric motor 7 is, furthermore, conveniently configured to limit to the minimum the effect of viscous coupling i.e. the loss of torque owing to the friction created by the veil of oil present between the stator 15 and the rotor 16.
In particular, between the stator 15 and the rotor 16 there is an air gap 18, i.e. an interspace with a thickness comprised between 0.3 and 0.9 mm.
With this configuration of the electric motor 7, it is possible to avoid braking phenomena on the movable parts of the electric motor 7, caused by the presence of oil in the air gap 18, and obtain an adequate performance of the electric motor 7.
With reference, in particular, to the embodiment of Figures 1 and 2, the casing 9 can be made as a single piece of thermosetting material, conveniently molded at low temperature on the stator 15, with or without an electronic control board 7a of the electric motor 7.
In practice, the casing 9 in this case is provided by inserting the stator 15 in a mold and then embedding the stator in a thermosetting epoxy resin which is injected into the mold.
Also with reference to this embodiment, it should be noted that the dividing wall 12 can be provided by a covering element 20, made preferably of the same material as the pump body 4 and interposed between the casing 9 and the pump body 4.
In particular, the covering element 20 is coupled to the pump body 4, so as to close the side of the pumping chamber 5 that is directed toward the driving part 3 of the pump.
More specifically, the covering element 20 is provided with a flanged edge 21, for fixing it to a flanged portion 22 of the pump body 4.
In turn, the casing 9 is provided, on its side directed toward the pump body 4, with a flange 23 for fixing it to the flanged edge 21 of the covering element 20.
Respective accommodation seats 24 are defined for the bearings 11a and 11b on the side directed toward the compartment 8 both of the covering element 20 and of the end wall 8a of the casing 8 located at the other end with respect to the covering element 20.
With reference to the embodiment of Figures 3 and 4, the casing 9 can also be made, alternatively, from a pair of die-cast aluminum half- shells 25 and 26, which are axially coupled together with the interposition of at least one gasket 27 which makes it possible to prevent the seepage of oil from the compartment 8 through the two half- shells 25, 26.
In this case, the stator 15 of the electric motor 7 is anchored by interference fit to at least one of the half- shells 25, 26.
In particular, according to this embodiment, a first half-shell 25 is provided which is coupled, at an axial end thereof, to the pump body 4, by way of a flanged region 28 thereof, and which defines, with an end portion thereof, the dividing wall 12, and at least one second half-shell 26, which is also provided, at its axial end opposite to the end coupled to the first half-shell 25, with a respective end portion, on the outward-facing side of which, for example, the power supply connector 17 is mounted.
On the side directed toward the compartment 8 of the end portions of the two half- shells 25 and 26, respective accommodation seats 24 are defined for the bearings 11a, 11b.
The first half-shell 25, at its end opposite to the end coupled to the pump body 4, is conveniently provided with a flanged portion 30 for fixing it to a corresponding flanged portion 31 defined on the second half-shell 26 using axial bolts 32.
The operation of the pump, according to the invention, is the following.
Following the activation of the electric motor 7, the shaft 10 pulls the movable gear 6 in rotation, so as to cause the pumping of the oil by the pump through the pumping chamber 5.
During the pumping of the oil, besides the passage of oil from the pumping chamber 5 to the compartment 8 in which the electric motor 7 is accommodated by virtue of the seepage of oil, due to the absence of gasket seals, through the through hole 12a present in the dividing wall 12, there is circulation of the oil between the pumping chamber 5 and the compartment 8, through the inlet opening 13 and the outlet opening 14 which are also defined in the dividing wall 12, so as to ensure an optimal cooling of the electric motor 7 and an optimal lubrication of the moving parts of the pump.
In practice it has been found that the invention fully achieves the intended aim and objects.
The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.
In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.
The disclosures in Italian Patent Application No. 102022000020532 from which this application claims priority are incorporated herein by reference.
Where technical features mentioned in any claim are followed by reference signs, such reference signs have been inserted for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

A gear pump (1) for oil, comprising a hydraulic part (2), provided with a pump body (4) which defines internally an oil pumping chamber (5) accommodating at least one movable gear (6) for pumping the oil, and a driving part (3), which is provided with an electric motor (7) housed in a compartment (8) defined inside a containment casing (9), and provided with a shaft (10) which is functionally connected to said movable gear (6), characterized in that it comprises at least one dividing wall (12) between said pumping chamber (5) and said compartment (8), which is passed through by the shaft (10) of said electric motor (7) without the interposition of gasket seals, means for circulating oil between said pumping chamber (5) and said compartment (8) being provided.
The pump according to claim 1, characterized in that at least one inlet opening (13) for the passage of the oil from the pumping chamber (5) to said compartment (8) and at least one outlet opening (14) for the passage of the oil from said compartment (8) to said pumping chamber (5) are defined in said dividing wall (12).
The pump according to claim 2, characterized in that said inlet opening (13) is substantially located at an outflow region of said pumping chamber (5) and in that said outlet opening (14) is arranged substantially at an oil intake region of said pumping chamber (5).
The pump according to claim 1, characterized in that said electric motor (7) is a brushless direct current (BLDC) motor or a single-phase or three-phase induction alternating current (AC) motor.
The pump according to one or more of the preceding claims, characterized in that said electric motor (7) comprises a stator (15) anchored to said casing (9) and a rotor (16) accommodated axially inside said stator (15) and rigidly fixed to said shaft (10), an air gap (18) with a thickness of dimensions comprised between 0.3 and 0.9 mm being interposed between said stator (15) and said rotor (16).
The pump according to one or more of the preceding claims, characterized in that said casing (9) is made in a single piece of thermosetting material molded at low temperature on said stator (15).
The pump according to one or more of the preceding claims, characterized in that said casing (9) is molded on said stator (15) with an electronic control board (7a) for said electric motor (7).
The pump according to one or more of the preceding claims, characterized in that said casing (9) comprises a pair of die-cast aluminum half-shells (25, 26), which are axially coupled together with the interposition of at least one gasket (27), said stator (15) being anchored by interference fit to at least one of said half-shells (25).