Centrifugal pump with radial air gap whose efficiency is improved by positioning the rotor in the secondary leakage circuit.

Abstract

The invention relates to a centrifugal pump (1) adapted to circulate a heat transfer fluid, and comprising a casing (11) with a suction port (112) and a discharge port (113) of the fluid, an impeller (12) installed in the casing, an electric motor (14), a main fluid circulation circuit (2) arranged between the suction port and the discharge port and passing through an annular flow chamber (1212), a secondary leakage circuit (3) separate from the main circuit (2) and arranged between an inlet port (31) located at the discharge port and an outlet port (32) located at the suction port, the electric motor being a radial or axial air gap motor whose stator (142) is installed at the casing and whose rotor (141) is carried by the rotation shaft and installed in the secondary circuit. Figure from the summary: Figure 2

Description

Title of the invention: Centrifugal pump with radial air gap whose efficiency is improved by positioning the rotor in the secondary leak circuit. Technical field.

[0001] The present invention relates to a centrifugal pump driven by an electric motor. The invention also relates to a vehicle cooling device comprising said pump, and an electric or hybrid vehicle comprising said cooling device.

[0002] The invention relates to the technical field of centrifugal pumps, and more particularly to centrifugal pumps whose electric motor is a radial or axial air gap motor. This type of pump is particularly suitable for vehicles, and more preferably hybrid or electric vehicles. State of the art.

[0003] Currently, more and more vehicles are electric or hybrid vehicles, with batteries that are no longer used solely for starting or powering certain components, but also for propulsion. Consequently, these vehicles require a greater number of batteries for their proper operation.

[0004] Each battery consists of individual cells, each cell producing both energy and heat. It is important, however, that the heat emitted by these cells be well dissipated, as excessive heat can cause irreversible damage to the cells, leading to a reduction or even a loss of their functionality. Therefore, efficient battery cooling must be provided. This cooling is generally achieved by a heat transfer fluid circulating in a cooling circuit around and within the battery.

[0005] The heat transfer fluid is used to regulate the temperature of the batteries and can be circulated by a centrifugal pump. The pump comprises at least one impeller installed in a housing, said impeller being driven by an electric motor so as to move the fluid.

[0006] Centrifugal pumps with an axial air gap are known, such as those described in published patent document US 8,303,268 B2, and of which Figure 7 is reproduced in [Fig. 1] of this application. This pump 1 comprises an impeller 5 mounted in a casing 2, and an electric motor driving said impeller and enabling the circulation of the fluid. The motor consists of a stator positioned in the pump casing and a rotor 33 mounted in the impeller blades of said impeller 5. The casing 2 comprises also a suction port 52 and a discharge port 51 for the fluid, the main circuit of the fluid being arranged between said suction ports 52 and discharge ports 51 of the pump. Thus, the fluid circulates around a tubular rotation shaft 3 of the impeller and around said blades, before entering the shaft through an end opposite the suction port, forming a circular circulation of the fluid. The main circuit comprises a first section between the suction and discharge ports and a second section for returning the fluid to the suction port, this second section serving for cooling and degassing the pump. This second section passes in particular through the air gap 49 of the electric motor. A secondary leakage circuit 53 is also described, and extends between the casing 2 of the pump and the impeller 5. This secondary circuit is separate from the main circuit and is positioned on the periphery of the pump.However, the main circuit is complex, designed to maximize the removal of heat emitted by the pump. This complexity is costly to implement and reduces the pump's efficiency.

[0007] Published patent document US 2021 / 0003147 Al discloses a radial air-gap centrifugal pump in which the fluid suction and discharge ports are positioned on the same side at the impeller blades. The blades are also positioned outside the pump housing. In this document, the fluid path is deliberately complex, notably by circulating around the pump's electric motor. This complexity allows for maximum contact between the heat transfer fluid and the pump components, thus enabling optimal pump cooling. However, the presence of the blades may impede fluid inlet, reducing the pump's efficiency.

[0008] The invention aims to overcome at least one of the drawbacks of the aforementioned prior art. More specifically, the invention aims to improve the efficiency of the pump by reducing fluid recirculation in the secondary leakage circuit. The invention also makes it possible to reduce the energy consumption required for the pump's operation, and therefore to improve the vehicle's operating time.

[0009] The invention also aims to reduce the leakage flow in the secondary leakage circuit, so as to improve the torque of the pump at equivalent delivery flow. Presentation of the invention.

[0010] The solution proposed by the invention is a centrifugal pump driven by an electric motor and adapted to circulate a heat transfer fluid, said pump comprising: a casing comprising a suction port and a discharge port for the fluid, an impeller installed in the casing and comprising a shaft tubular rotation, which shaft is housed in a complementary cavity of the casing and extends along the axis of the suction port, from said suction port, a fixed shaft which extends in the rotation shaft and on which the impeller is mounted to rotate freely, the electric motor whose rotor is carried by the impeller and whose stator is carried by the casing, a main fluid circulation circuit arranged between the suction port and the discharge port, which main circuit passes through an annular flow chamber formed in the rotation shaft, between the fixed shaft and an internal wall of said rotation shaft, a secondary leak circuit separate from the main circuit and arranged to return a portion of the fluid from the discharge port to the suction port, which circuit includes an inlet port located at the discharge port and an outlet port located at the suction port,which secondary circuit is formed by a space located between an outer wall of the impeller and an inner wall of the complementary cavity of the casing, such that the fluid circulates around the periphery of said impeller; the electric motor is a radial or axial air gap motor whose stator is installed at the level of the complementary cavity of the casing and whose rotor is carried by the rotating shaft and is installed in the secondary leakage circuit, so that the air gap forms part of said secondary circuit.

[0011] The heat transfer fluid can be any fluid configured to allow thermal regulation, for example, of a vehicle engine or, more specifically, of a battery. This fluid can be any fluid capable of absorbing and transferring heat; it can also be a gas such as air, water, or a glycol compound.

[0012] The casing forms a sealed enclosure around the impeller so as to retain the heat transfer fluid within the pump and prevent leaks. The casing and the fixed shaft also keep the impeller in position within the pump and allow for efficient fluid movement within said pump.

[0013] The suction port allows the fluid to enter the pump, and the discharge port allows it to be evacuated.

[0014] The presence of the rotor in the secondary leakage circuit partially blocks said circuit. The rotor therefore limits the recirculation of fluid in the secondary circuit. Thus, the leakage rate of fluid in the secondary leakage circuit is limited, and the fluid pressure losses are also increased due to the increased circuit length. As a result, the pump's efficiency is improved, while its energy consumption is reduced. The reduced energy consumption of the pump allows the batteries to operate for longer periods. This additional energy can be used by the vehicle, notably to increase its operating time.

[0015] Other advantageous features of the pump of the invention are listed below. Each of these features may be considered alone or in combination with the notable features defined above. Each of these features contributes, where applicable, to solving specific technical problems defined further in the description and in which the notable features defined above do not necessarily participate. The latter may, where applicable, be the subject of one or more divisional patent applications.

[0016] According to one embodiment of the invention, the secondary leak circuit is constituted by a first channel located between the inlet orifice and the air gap, a second channel in fluid continuity with the first channel and corresponding to the air gap, and a third channel in fluid continuity with the second channel and located between the air gap and the outlet orifice, the second channel and the third channel forming at least one baffle.

[0017] The presence of the various channels demonstrates the complexity of the secondary leakage circuit, and in particular the reduction of the leakage flow rate in the circuit. This makes fluid circulation more difficult.

[0018] According to one embodiment of the invention, the second channel and the third channel form at least two baffles.

[0019] According to one embodiment of the invention, the first channel, the second channel and the third channel form at least three baffles.

[0020] The formation of baffles also reduces the leakage rate and decreases fluid recirculation in the secondary circuit by making fluid circulation more difficult. Thus, the more baffles there are, the more complicated fluid circulation becomes in the secondary leakage circuit. Fluid recirculation is even more difficult with two baffles, and even more so with three. Increasing the number of baffles therefore improves the pump's efficiency.

[0021] Advantageously, the sections of the second channel and the third channel of the secondary circuit have a width between 0.2 mm and 1.5 mm.

[0022] The smaller the cross-sectional area of ​​the secondary circuit, particularly in the second and third channels, the more difficult the recirculation of fluid in the leaky secondary circuit becomes, and the more the pump efficiency is improved. Thus, the overall energy consumption of the pump is reduced.

[0023] Advantageously, the ratio L / l is between 5 and 50, where L is the cumulative length of the second and third channels, and 1 is the average width of the sections of the second and third channels.

[0024] When this ratio is between 5 and 50, it allows the fluid pressure losses to be optimized.

[0025] According to one embodiment of the invention, blades are installed in the orifice suction so as to impart a rotation of the fluid in the flow chamber, in the direction of rotation of the impeller.

[0026] According to one embodiment of the invention, a propeller is installed in the suction orifice so as to impart a rotation of the fluid in the flow chamber, in the direction of rotation of the impeller.

[0027] The presence of blades or propellers at the fluid suction port allows the fluid to begin rotating upstream of the main fluid circulation in the impeller, and thus facilitates the rotation of the fluid within said pump and improves its efficiency.

[0028] According to one embodiment of the invention, the pump includes a printed circuit board for the operation of the electric motor, which board is mounted on a plate made of a heat-conducting material, all or part of said plate being installed in the secondary leakage circuit.

[0029] Positioning the board in the secondary leakage circuit makes the recirculation of the fluid in said circuit more complex, thus improving its efficiency. The board is thus positioned in the heat transfer fluid, which improves the release of the heat produced by the board directly into the fluid, and, more specifically, the release of heat emitted by the electrical and / or electronic components of said board. The cooling of the board is therefore improved, reducing the detrimental effects of heat on the electronic components of the board.

[0030] According to one embodiment of the invention, the printed circuit board is made of a metallic material, preferably aluminum.

[0031] Making the plate from metallic material improves heat diffusion in the heat transfer fluid. This material is also easy to manufacture and handle, and it is inexpensive.

[0032] The invention also relates to a vehicle cooling device comprising a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump configured to move said fluid in said circuit, the pump being in accordance with the invention.

[0033] The vehicle is, for example, a motor vehicle, and may be a hybrid or electric vehicle. The cooling circuit of said vehicle serves to regulate the temperature of at least one vehicle battery, but may, alternatively, also serve to cool the engine, or to cool any system that can benefit from such cooling.

[0034] The improvements to the pump also make the circulation of the fluid within the circuit more efficient and reduce the energy consumption required for the operation of said pump.

[0035] The invention also relates to an electric or hybrid vehicle comprising at least one battery pack and a device for cooling said battery pack, which device comprises a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump configured to set said fluid in motion in said circuit, the pump being in accordance with the invention.

[0036] The electric or hybrid vehicle comprising a pump according to the invention has the capacity to consume less thanks to the increased efficiency of the pump. The operating time of said vehicle is therefore also increased. Brief description of the figures.

[0037] Other advantages and characteristics of the invention will appear better on reading the description of a preferred embodiment which follows, with reference to the appended drawings, produced as indicative and non-limiting examples and in which: - [Fig.l] represents a pump as found in the prior art. - [Fig.2] is a diagram representing a cross-sectional view of a centrifugal pump according to the invention, configured to be installed in a cooling device. Description of the embodiments.

[0038] As used herein, and unless otherwise indicated, the use of the ordinal adjectives "first", "second", etc., to describe an object simply indicates that different occurrences of similar objects are referred to and does not imply that the objects so described must be in any given sequence, whether in time, space, ordering, etc. "X and / or Y" means: X alone or Y alone or X+Y. Generally speaking, it will be appreciated that in the various accompanying drawings, the objects are arbitrarily drawn to facilitate their reading.

[0039] Generally speaking, a vehicle, such as a motor vehicle, may include a cooling system. This cooling system includes a cooling circuit in which a heat transfer fluid circulates, set in motion by a centrifugal pump.

[0040] The vehicle also includes at least one battery pack. In the case of hybrid and electric vehicles, several battery packs are necessary not only to enable the operation of the vehicle's components, but also to enable its movement. Each battery pack is composed of individual cells, each cell being capable of producing the energy required for the vehicle's operation. However, energy production is coupled with heat production, which can lead to a decrease in cell efficiency and / or deformation of the cells.

[0041] Therefore, the cooling system provided in the vehicle can be designed for at least the battery pack(s), so as to regulate their temperature. The cooling device comprises the cooling circuit in which the heat transfer fluid circulates, and configured to regulate the temperature of the cells of the battery pack around which the fluid circulates. This heat transfer fluid is known to those skilled in the art, and may be, for example, air, water, or a dielectric fluid. The movement of such a fluid in the cooling circuit is carried out by a centrifugal pump. This pump is described in more detail in [Fig.2].

[0042] Fig. 2 shows a cross-sectional view of the centrifugal pump according to the invention.

[0043] The centrifugal pump 1 according to the invention comprises a casing 11 forming a complementary cavity 111 in which the heat transfer fluid circulates. This housing 11 further comprises a fluid suction port 112 and a fluid discharge port 113, the fluid flowing from the suction port 112 to the discharge port 113. Preferably, the suction port 112 is positioned on one side of the housing, and the discharge port 113 is positioned on a second side of the pump 1, at 90°, with a margin of error of plus or minus 5°, from the suction port 112. The additional cavity 111 further comprises an internal wall 1111 oriented towards the interior of the housing 11, so as to be opposite an impeller 12 installed in said housing. Thus, the impeller 12 is housed in the additional cavity 111 of the housing.

[0044] The impeller 12 comprises a tubular rotation shaft 121 also housed in the complementary cavity 111 of the casing 11. This shaft 121 comprises a first end extending close to the suction orifice 112, the shaft 121 extending in the axis of the suction orifice 112 of the casing 11. At a second opposite end of the shaft 121 are the blades 122 of the impeller 12, these blades extending close to the discharge orifice 113. The tubular rotation shaft 121 further comprises an internal wall 1211 delimiting an annular flow chamber 1212 of the fluid, and an external wall 1213 facing the internal wall 1111 of the casing 11.

[0045] The impeller 12 is mounted to rotate freely on a fixed axis 13 so as to allow the impeller 12 to be held in position and rotated in the housing 11 of the pump 1. The fixed axis 13 is configured to extend into the rotation shaft 121 of said impeller, and into opposite walls of the housing 11.

[0046] The centrifugal pump 1 is driven by an electric motor 14. This motor comprises a rotor 141 carried by the impeller 12 and a stator 142 carried by the casing 11. More specifically, the electric motor 14 is a radial air gap motor, the stator 142 being installed in the complementary cavity 111 of the casing 11 and the rotor 141 being more specifically mounted on the rotation shaft 121 of the impeller 12.

[0047] The pump 1 further comprises a printed circuit board 15 which enables the operation of said pump. This board 15 is mounted on a preferred plate principally made of a heat-conducting material. Such a material is preferably a metallic material, such as aluminum. Thus, the card 15 is advantageously mounted, at least partially, in the casing 11 of the pump 1. This card 15 comprises electrical and / or electronic components necessary for the operation of said pump, in particular the mosfets components.

[0048] The centrifugal pump 1 according to the invention is particularly suitable for circulating the heat transfer fluid of the cooling device via a main fluid circulation circuit 2. This main circuit 2 is arranged between the suction orifice 112 and the discharge orifice 113 of the casing 11, and passes in particular through the annular flow chamber 1212 located between the internal wall 1211 of the rotation shaft 121 and the fixed axis 13 of the pump 1. The main circuit 2 is represented in [Fig.2] by arrows in thick lines.

[0049] However, the design of this type of pump 1 also involves the formation of a secondary leakage circuit 3, separate from the main circuit 2. This secondary circuit 3 returns a portion of the heat transfer fluid from an inlet orifice 31 located at the discharge orifice 113, to an outlet orifice 32 positioned at the suction orifice 112 of the casing 11. The secondary circuit 3 is thus formed by a space located between the external wall 1213 of the impeller 12 and the internal wall 1111 of the complementary cavity 111 of the casing 11. Thus, the heat transfer fluid circulates around the periphery of the impeller 12. The secondary circuit 3 is represented by dotted arrows in [Fig.2].

[0050] In order to limit fluid circulation in this secondary circuit 3, the rotor 141, carried by the rotating shaft 121, is installed in the secondary leakage circuit 3. The stator 142 is then positioned opposite the rotor 141 and carried by the housing 11, the air gap thus forming at least a part of said secondary circuit. The secondary circuit 3 comprises a first channel 33 located between the inlet port 31 and the air gap, a second channel 34 in fluidic continuity with the first channel 33 and corresponding to the air gap, and a third channel 35 in fluidic continuity with the second channel 34 and located between the air gap and the outlet port 32. The second channel 34 and the third channel 35 form at least one baffle, and preferably, form at least two baffles. In a particularly preferred manner, the first, second and third channels (33, 34, 35) form at least three baffles.Increasing the number of baffles increases pressure losses, thus improving the efficiency of pump 1. Preferably, the printed circuit board 15 is positioned at least partially within the secondary leakage circuit 3 so that it can be cooled by contact with the fluid. The board's presence within the circuit also increases the fluid pressure losses.

[0051] Advantageously, the sections of the second and third channels (34, 35) of the circuit secondary 3 have a width between 0.2mm and 1.5mm. A small section improves the efficiency of the pump 1. Advantageously, the ratio L / l is between 5 and 50, where L is the cumulative length of the second channel 34 and the third channel 35, and 1 is the average width of the sections of the second channel 34 and the third channel 35.

[0052] More preferably, blades 16 or a propeller 16 are installed in the suction orifice 112, so as to drive the rotation of the fluid in the flow chamber 1212, thus reducing the energy required to move the fluid.

[0053] The arrangement of the various elements and / or means and / or steps of the invention, in the embodiments described above, should not be understood as requiring such an arrangement in all implementations. In any event, it will be understood that various modifications may be made to these elements and / or means and / or steps, without departing from the spirit and scope of the invention.

[0054] Furthermore, one or more features described only in one embodiment can be combined with one or more other features described only in another embodiment. Similarly, one or more features described only in one embodiment can be generalized to other embodiments, even if this or these features are described only in combination with other features.

[0055] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

Claims

Claims

1. Centrifugal pump (1) driven by an electric motor (14) and adapted to circulate a heat transfer fluid, said pump comprising: - a casing (11) comprising a suction port (112) and a discharge port (113) for the fluid, - an impeller (12) installed in the casing (11) and comprising a tubular rotation shaft (121), which shaft is housed in a complementary cavity (111) of the casing (11) and extends in the axis of the suction orifice (112), from said suction orifice, - a fixed axis (13) which extends into the rotation shaft (121) and on which the impeller (12) is mounted so as to be rotatable, - the electric motor (14) whose rotor (141) is carried by the impeller (12) and whose stator (142) is carried by the casing (11), - a main circuit (2) for circulating the fluid arranged between the suction orifice (112) and the discharge orifice (113), which main circuit (2) passes through an annular flow chamber (1212) formed in the rotation shaft (121), between the fixed axis (13) and an internal wall (1211) of said rotation shaft, - a secondary leakage circuit (3) separate from the main circuit (2) and arranged to return a portion of the fluid from the discharge orifice (113) to the suction orifice (112), which circuit comprises an inlet orifice (31) located at the discharge orifice (113) and an outlet orifice (32) located at the suction orifice (112), which secondary circuit (3) is formed by a space located between an external wall (1213) of the impeller (12) and an internal wall (1111) of the complementary cavity (111) of the casing (11), so that the fluid circulates around the periphery of said impeller, characterized in that the electric motor (14) is a radial or axial air gap motor whose stator (142) is installed at the complementary cavity (111) of the casing (11) and whose rotor (141) is carried by the rotation shaft (121) and is installed in the secondary leakage circuit (3),so that the air gap forms part of said secondary circuit.,

2. Centrifugal pump (1) according to claim 1, characterized in that the secondary leakage circuit (3) is constituted by a first channel (33) located between the inlet orifice (31) and the air gap, a second channel (34) in fluidic continuity of the first channel (33) and corresponding to the air gap, and a third channel (35) in fluidic continuity of the second channel (34) and located between the air gap and the outlet orifice (32), the second channel (34) and the third channel (35) forming at least one baffle.

3. Centrifugal pump (1) according to claim 2, characterized in that the second channel (34) and the third channel (35) form at least two baffles.

4. Centrifugal pump (1) according to one of claims 2 or 3, characterized in that the first channel (33), the second channel (34) and the third channel (35) form at least three baffles.

5. Centrifugal pump (1) according to one of the preceding claims, characterized in that blades (16) are installed in the suction port (112) so as to cause rotation of the fluid in the flow chamber (1212), in the direction of rotation of the impeller (12).

6. Centrifugal pump (1) according to one of claims 1 to 4, characterized in that a propeller (16) is installed in the suction port (112) so as to cause rotation of the fluid in the flow chamber (1212), in the direction of rotation of the impeller (12).

7. Centrifugal pump (1) according to one of the preceding claims, characterized in that said pump comprises a printed circuit board (15) for the operation of the electric motor (14), which board is mounted on a plate made of a heat-conducting material, all or part of said plate being installed in the secondary leakage circuit (3).

8. Centrifugal pump (1) according to claim 7, characterized in that the printed circuit board (15) is made of a metallic material, preferably aluminum.

9. A device for cooling a vehicle comprising a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump (1) configured to set said fluid in motion in said circuit, characterized in that the pump (1) conforms to one of the preceding claims.

10. Electric or hybrid vehicle comprising at least one battery pack and a device for cooling said battery pack, which device comprises a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump (1) configured to set said fluid in motion in said circuit, characterized in that the pump (1) is in accordance with one of claims 1 to 8.

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