DE102021111677B4 - Centrifugal pump with wet-running electric motor - Google Patents

Abstract

Centrifugal pump (2) with a wet-running electric motor (14) for conveying a pumping medium, comprising: a pump housing (4) with a motor compartment (4a) and a pump compartment (4b), a control unit (22), a shaft (8) with which a Pump impeller (6) is connected in a rotationally fixed manner and the shaft (8) is rotatably supported by a plain bearing (8c), and an electric motor (14), which drives the pump impeller (6) via the shaft (8), with a rotor (16) and a stator (18), wherein a gap is arranged between the rotor (16) and the stator (18), and the rotor (16) is in a rotationally fixed connection with the shaft (8) and the conveying medium at least partially flows around it, the plain bearing (8c) consists of a sintered material, and the conveying medium penetrates the plain bearing (8c), characterized in that the rotor (16) has a larger diameter on a side facing away from the plain bearing (8c) than on a side facing the plain bearing (8c) and, that the ratio between a volume flow through the sintered bearing and a volume flow in the engine compartment (4a) is less than 1 to 1000, which means that the pump can be operated even if no funding is pumped for a certain time.

Description

The invention relates to a centrifugal pump with a wet-running electric motor, a method for cooling an electric motor and a use of the centrifugal pump with a wet-running electric motor.

Centrifugal pumps with wet-running electric motors are known from the prior art. In these pumps, shafts that connect the rotor of the electric motor and the pump impeller are generally supported by plain bearings. These plain bearings are conventionally made of carbon, ceramic or plastic. In order to make plain bearings made from the above materials permeable to a pumped medium, so that elements in the engine compartment can be cooled by the pumped medium, holes are provided in the plain bearings.

The underlying state of the art is: DE 35 11 464 A1 and the DE 10 2018 104 015 A1 to call.

This results in the problem that foreign substances that are in the pumped medium end up in the engine compartment. These foreign substances can accumulate on components in the engine compartment and thus these components can be restricted in their functionality. In particular, it can happen that moving components in the engine compartment become blocked. The pump's function is then severely limited or out of operation.

Furthermore, the aforementioned plain bearings have a lot of play in relation to the shaft. The wave is therefore not very restricted in its movement. Vibrations and other undesirable effects can occur in the shaft, which is why the volume of a pump with such a bearing is increased and efficiency is reduced due to losses.

This results in the task of creating a pump with a wet-running electric motor in which, while the components in the engine compartment are well cooled, there is little play between bearings and shafts and also to reduce blocking of moving components.

This task is solved by the centrifugal pump according to the invention. The centrifugal pump according to the invention with a wet-running electric motor for conveying a pumped medium has: a pump housing with a motor compartment and a pump compartment, a control unit, a shaft to which a pump impeller is connected in a rotationally fixed manner and the shaft is rotatably supported by a plain bearing, and an electric motor, which drives the pump impeller via the shaft, with a rotor and stator, with a gap being arranged between the rotor and the stator, and the rotor is in a rotationally fixed connection with the shaft and is at least partially flowed around by the pumped medium.

The centrifugal pump according to the invention shows for the first time that the plain bearing consists of a sintered material and that the plain bearing is continuous for the pumped medium.

The design of the plain bearing from a sintered material results in several advantages. On the one hand, the structure of a sintered material is designed in such a way that the smallest flows of funding can pass through the sintered material. This ensures sufficient cooling for the components in the engine compartment.

On the other hand, a bearing gap between the plain bearing and the shaft is small. This means that only a small part of the fluid in the engine compartment penetrates into the pump compartment. The amount of fluid in the engine compartment remains essentially constant, which is why cooling and lubrication of the moving components and other components in the engine compartment is ensured.

Overall, the centrifugal pump according to the invention offers the advantage that, with sufficient cooling and lubrication in the engine compartment, blocking of moving components can be avoided.

According to the invention, the rotor has a larger diameter on a side facing away from the plain bearing than on a side facing the plain bearing.

An advantage of this design of the rotor is that the pumped medium is moved efficiently in the engine compartment. Additional mechanisms to move the fluid in the engine compartment are not required. In particular, no additional pump or wheel is required to move the pumped medium in the engine compartment.

In one embodiment of the invention, the sintered material filters the penetrating conveying medium. The sintered material is designed with such a pore structure that the conveying medium is filtered as it passes through the sintered material. Based on this filtering, there are no longer any foreign substances in the pumped medium, so that the pumped medium in the engine compartment does not contaminate the engine compartment. The service life of the motor, the bearing and the entire pump are improved.

The foreign substances that are filtered out of the pumped medium by the plain bearing initially remain as a residue in the plain bearing. Subsequently, at least some of the foreign substances that are filtered out of the pumped medium through the plain bearing can be removed tert, is picked up by pumped medium that flows from the pump chamber directly to the pump outlet and flows along the plain bearing and discharged through the pump outlet. Saturation of the plain bearing with foreign substances is avoided.

In one embodiment, the conveying medium penetrates a bearing gap at the contact point of the plain bearing and the shaft.

The pumped medium is sucked from the pump room into the engine compartment via a pressure gradient. At the same time, from a certain pressure in the engine compartment, a certain amount of the pumped medium flows back into the pump compartment. This flow of fluid flows through the bearing gap between the plain bearing and the shaft. The flow of the pumped medium from the engine compartment into the pump compartment is promoted by the rotation of the shaft in the plain bearing.

With this flow of fluid from the engine compartment through the bearing gap to the pump compartment, the bearing is also lubricated by the plain bearing, so that abrasion and friction losses are reduced.

In one embodiment, the control unit is fixed to an aluminum cover, the aluminum cover being arranged on the side of the rotor facing away from the pump impeller.

The centrifugal pump according to the invention shows for the first time a cover that seals the engine compartment, the cover being arranged on the side of the rotor facing away from the pump impeller, and the control unit being arranged on the cover outside the engine compartment.

In one embodiment, the control unit transfers heat to the aluminum cover and the aluminum cover transfers heat to the pumped medium located in the engine compartment.

By arranging a cover on the side of the rotor facing away from the pump impeller and the control unit arranged on it, the heat transfer from the control unit via the cover to the pumped medium is both shortened and more effective. The heat loss from the control unit can be efficiently dissipated.

By efficiently dissipating the heat loss or cooling the control unit, overheating of the control unit is avoided, so that the centrifugal pump can be operated properly. This extends the lifespan of the pump.

In one embodiment, the pump housing is made of aluminum or an aluminum alloy.

Aluminum with its alloys is a light metal. The weight of the centrifugal pump is therefore lower than with a pump housing made of iron or steel. Fastening devices, such as flanges, can therefore be made smaller. If the centrifugal pump is installed in a machine, for example, this design saves installation space, material and weight.

In one embodiment, the plain bearing is sintered from sintered bronze, sintered iron, graphite bronze or ferrobronze.

The aforementioned materials are ideal for both a sintering process and as plain bearings. They therefore offer properties that are advantageous for the plain bearing according to the invention.

According to the invention, the ratio between a volume flow through the sintered bearing and a volume flow in the engine compartment is less than 1 to 1000.

This shows the extent to which the pumped medium flows into the engine compartment. The volume flow through the sintered bearing is at least a thousand times smaller than the volume flow that is moved in the engine compartment by rotation of the rotor. The volume flow through the sintered bearing is therefore significantly smaller than the volume flow that is moved in the engine compartment by the rotation of the rotor.

This ratio is advantageous because the pump can be operated even if no fluid is pumped for a certain period of time. The engine compartment is only slowly emptied by a flow of the conveying medium through the bearing gap. Components in the engine compartment continue to be cooled and moving connections between components are lubricated.

1. a) einmaliges Befüllen des Motorraums mit gefiltertem Fördermedium,
2. b) Betreiben des Elektromotors, und
3. c) Drehen des Rotors , wodurch das Fördermedium im Motorraum zirkuliert,

wobei
ein Teil des Fördermediums durch den Lagerspalt aus dem Motorraum austritt und Fördermedium durch das Gleitlager in den Motorraum strömt.One aspect of the invention is a method for cooling an electric motor and simultaneously filtering coolant in a centrifugal pump according to one of the above embodiments, comprising the steps:

1. a) filling the engine compartment once with filtered fluid,
2. b) operating the electric motor, and
3. c) turning the rotor, whereby the pumped medium circulates in the engine compartment,

where
part of the pumped medium exits the engine compartment through the bearing gap and the pumped medium flows through the plain bearing into the engine compartment.

This aspect describes how filtering of the conveying medium and a flow are designed. The engine compartment is first filled with an already filtered pumping medium. In this way, there is a volume of the pumped medium in the engine compartment that cools and lubricates sufficiently for the pump to operate. In the next step, the electric motor is operated. This can be a conventional wet-running electric motor. In the usual way, a current is passed through an electrical conductor. This creates an electromagnetic field that sets a rotor in motion in the effective area of the electromagnetic field.

When the rotor is rotating, a pressure gradient forms in the engine compartment, with a higher pressure on the side of the rotor facing away from the plain bearing than on the side of the rotor facing the plain bearing. In the radially outer region of the rotor, the pressure is also lower than in the radially inner region of the rotor. This means that the lowest pressure is on the radial outside between the rotor and the plain bearing.

Because of this, the pumped medium can penetrate into the engine compartment along the pressure gradient through the plain bearing, which is made of a porous sintered material. The pores of the sintered material are so large that the pumped medium can penetrate through, but foreign substances and bodies remain in the sintered material. The pumped medium is therefore filtered.

Due to the higher pressure in the radially inner area of the rotor between the rotor and the plain bearing, a small amount of fluid flows from the engine compartment through the bearing gap, between the plain bearing and the shaft into the pump chamber.

One aspect of the invention discloses the use of the centrifugal pump according to the invention as a coolant pump. The centrifugal pump according to the invention is particularly suitable as a coolant pump. Coolants often exhibit lubricating properties and have good thermal properties. This means that heat from components in the engine compartment can be easily transferred to the coolant, while lubrication of the plain bearing is ensured.

The materials and designs mentioned are examples. Other materials or designs of parts can be used as long as the functionality of the centrifugal pump is not affected.

Additional rooms, for example for the control unit, can be provided in the pump housing. In addition, the rotor can be designed in such a way that the transport of conveyed medium in the engine compartment and thus circulation of the conveyed medium is promoted.

The shaft can be non-rotatably connected to the pump impeller in any possible way. Likewise, the rotor can be connected to the shaft in a rotationally fixed manner, for example via a press fit, a positive or non-positive shaft-hub connection.

When fixing the control unit to the aluminum cover, it makes sense to provide the greatest possible surface contact between the control unit and the cover. Furthermore, a heat transfer layer can be present between the two components. This heat transfer layer can promote heat transfer from the control unit to the aluminum lid.

The materials for the sinter bearing are exemplary. The sintered bearing can be made of any material, as long as the material is suitable for sintering and a pore size can be defined.

• 1 zeigt einen Schnitt einer erfindungsgemäßen Kreiselpumpe.

The invention is explained in detail below with reference to the figures.

• 1 shows a section of a centrifugal pump according to the invention.

In 1 a part of a centrifugal pump 2 is shown in section. In 1 On one side, a part of the pump housing 4 is shown, in which a pump impeller 6 is housed. This pump impeller 6 is connected in a rotationally fixed manner to a shaft 8, so that the pump impeller 6 rotates when the shaft 8 rotates. When the pump impeller 6 rotates, a pumped medium is conveyed from a pump inlet 10 to a pump outlet 12.

The shaft 8 runs from an end 8a on the pump impeller side through a bearing 8c to an end 8b on the engine side in an engine compartment 4a. In this case, the bearing 8c is realized by a plain bearing 8c. In the engine compartment 4a, a rotor 16 of a wet-running electric motor 14 is connected to the shaft 8 in a rotationally fixed manner. In addition, the wet-running electric motor 14 has a stator 18.

The stator 18 is wrapped with an electrical conductor, thereby having one or more turns. This electrical conductor is both electrically insulated and sealed against moisture.

During pump operation, electrical current flows through the coil formed in this way, consisting of the stator 18 and the electrical conductor. A magnetic field is formed. The magnetic field causes the rotor 16 to rotate. This rotation is transmitted to the pump impeller 6 via the non-rotatable connection. As a result of the rotation, the pump impeller 6 conveys the pumped medium.

The plain bearing 8c according to the invention is made of a sintered material. In other words, the plain bearing 8c was manufactured using a sintering process. The plain bearing 8c according to the invention is designed in such a way that pores or cavities are present between the individual sinter particles.

If the rotor 16 is rotating, a pressure gradient is formed in the engine compartment 4a, with a higher pressure prevailing on the side of the rotor 16 facing away from the sliding bearing 8c than on the side of the rotor 16 facing the sliding bearing 8c. In the radially outer region of the rotor 16, the pressure is also lower than in the radially inner region of the rotor 16. This means that the lowest pressure is radially outside between the rotor 16 and the plain bearing 8c. Due to this, the conveying medium can penetrate to a small extent into the engine compartment 4a along the pressure gradient through the plain bearing 8c, consisting of a porous sintered material.

The pores of the sintered material are so large that the pumped medium can penetrate to a small extent, but foreign substances and bodies remain in the sintered material. The pumped medium is therefore filtered. Due to the higher pressure in the radially inner region of the rotor 16 between the rotor 16 and the plain bearing 8c, the pumped medium also flows from the motor chamber 4a through the bearing gap, between the plain bearing 8c and the shaft 8 into the pump chamber.

The motor compartment 4a is sealed with a cover 20 at one end on the side of the rotor 16 facing away from the pump impeller 6. A control unit 22 is arranged on the cover 20 outside the engine compartment 4a. This control unit 22 is in heat-transferring contact with the cover 20.

During operation of the centrifugal pump 2, heat loss that occurs in the control unit 22 during operation of the centrifugal pump 2 is transferred to the cover 20. At the same time, heat is continuously transferred to the pumped medium, which is in heat-transferring contact with the cover 20 in the engine compartment 4a.

The conveying medium, which is in heat-transferring contact with the cover 20 in the engine compartment 4a, can permanently absorb heat from the cover 20 during operation, since the rotation of the rotor 16 generates a continuous flow of the conveying medium in the engine compartment 4a. The conveying medium, which is in heat-transferring contact with the cover 20 in the engine compartment 4a, is therefore continuously circulated and exchanged. The cooling of the control unit 22 via the cover 20 is therefore ensured.

Reference symbol list

2

centrifugal pump

4

Pump housing

4a

Engine compartment

4b

Pump room

6

Pump impeller

8th

Wave

8a

End on the pump impeller side

8b

Engine end

8c

bearings

10

Pump inlet

12

Pump outlet

14

Wet running electric motor

16

rotor

18

stator

20

Aluminum lid

22

Control unit

Claims (9)

Centrifugal pump (2) with a wet-running electric motor (14) for conveying a pumping medium, comprising: a pump housing (4) with a motor compartment (4a) and a pump compartment (4b), a control unit (22), a shaft (8) with which a Pump impeller (6) is connected in a rotationally fixed manner and the shaft (8) is rotatably supported by a plain bearing (8c), and an electric motor (14), which drives the pump impeller (6) via the shaft (8), with a rotor (16) and a stator (18), wherein a gap is arranged between the rotor (16) and the stator (18), and the rotor (16) is in a rotationally fixed connection with the shaft (8) and is at least partially flowed around by the conveying medium, wherein the plain bearing (8c) consists of a sintered material, and the conveying medium penetrates the plain bearing (8c), characterized in that the rotor (16) is on a plane extending from the plain bearing (8c). facing side has a larger diameter than on a side facing the plain bearing (8c) and that the ratio between a volume flow through the sintered bearing and a volume flow in the engine compartment (4a) is less than 1 to 1000, which means that the pump can also be operated is when no funding is received for a certain period of time. Centrifugal pump (2). Claim 1 , whereby the sintered material filters the pumped medium. Centrifugal pump (2) according to one of the preceding claims, wherein the pumped medium penetrates a bearing gap at the contact point of the plain bearing (8c) and the shaft (8). Centrifugal pump (2) according to one of the preceding claims, wherein the control unit (22) is fixed to an aluminum cover (20), the aluminum cover (20) being arranged on the side of the rotor (16) facing away from the pump impeller (6). Centrifugal pump (2). Claim 4 , wherein the control unit (22) transfers heat to the aluminum cover (20) and the aluminum cover (20) transfers heat to the pumped medium located in the engine compartment (4a). Centrifugal pump (2) according to one of the preceding claims, wherein the pump housing (4) consists of aluminum or an aluminum alloy. Centrifugal pump (2) according to one of the preceding claims, wherein the plain bearing (8c) is sintered from sintered bronze, sintered iron, graphite bronze or ferrobronze. Method for cooling a wet-running electric motor (14) and simultaneously filtering coolant in a centrifugal pump (2) according to one of the preceding claims, which has the steps: a) filling the engine compartment (4a) once with filtered pumping medium, b) operating the electric motor (14), and c) rotating the rotor (16), whereby the pumped medium circulates in the engine compartment (4a), with part of the pumped medium exiting the engine compartment (4a) through the bearing gap and the pumped medium flowing through the plain bearing (8c) into the engine compartment (4a). Use the centrifugal pump (2) according to one of the Claims 1 until 7 as a coolant pump.

Images