ELECTRIC MOTOR WITH COOLING ARRANGEMENT

Description

[0001] The invention relates to an electric motor for driving a centrifugal pump with a cooling arrangement comprising a fan wheel and a hood, wherein the hood encloses a space around the fan wheel.

[0002] A centrifugal pump assembly typically comprises one or more centrifugal pumps, one or more electric motors, and power electronic devices for speed control via frequency conversion. The electric motors and their associated motor electronics, in particular, require adequate cooling during operation.

[0003] Such typical electric motors are well-known and are mainly manufactured in large series. An electric motor consists of a rotor fixed to the motor shaft, a stator with a wound stator core, a stator housing with cooling fins on the outside, bearing shields on both sides with rolling or sliding bearings, and a fan wheel fixed to the shaft end opposite the drive end, enclosed by a fan shroud fixed to the stator housing.

[0004] A box, often called an electronics housing, is frequently attached to the stator housing. This housing contains the components of the motor electronics. The motor electronics typically include a frequency converter and a power controller and / or a speed controller. These electronics housings are often mounted on a base to prevent the heat generated by the electric motor from affecting the motor electronics and to allow the cooling airflow from the motor fan to also be used for cooling the motor electronics.

[0005] The fan shroud directs the cooling air exiting radially from the fan wheel in an axial direction to the cooling fins of the stator housing and, on the other hand, prevents the ingress of foreign bodies by means of a grid arranged on the upstream side of the fan wheel.

[0006] DE 10 2008 051 650 A1 discloses an invention with combined cooling of the motor and the motor electronics, in which the airflow is drawn in through the inlet grille of the fan housing before the fan wheel drives the airflow to cool the motor and the electronics housing. The focus here is on cooling a very large motor electronics unit that is arranged both axially and radially around the motor.

[0007] US patent 2021 / 006128 A1 reveals an engine fan with a protective device for directing cooling air.

[0008] US 2019 / 186500 A1 discloses an assembly consisting of a housing, a motor and a cooling fan, wherein a cover has a rear surface and a periphery and the periphery defines at least one inlet for air which is drawn radially into the cover by the operation of the cooling fan.

[0009] DE 10 2011 109 535 A1 describes a fan arrangement with a housing and an air guide, wherein the air guide is detachably connected to the housing.

[0010] JP H11 275812 A discloses a cooling fin structure of a motor, wherein the cooling fins are arranged on the motor.

[0011] Mass-produced electric motors are typically equipped with non-directional fans. This allows the motors, including their fans, to be used in both clockwise and counter-clockwise directions. The fan blades are radially oriented to achieve consistent cooling performance regardless of the direction of rotation. This results in a highly turbulent flow of cooling air. This turbulent flow leads to turbulence and airflow separation, reducing the effectiveness and efficiency of the cooling process. Furthermore, the turbulence of the cooling air generates noise that can be disturbing to people in the vicinity and, at higher intensities, even harmful to their health.

[0012] Furthermore, in electric motors operated at low speeds, the cooling airflow may no longer be sufficient to simultaneously dissipate the waste heat from the stator and the motor electronics.

[0013] The covers or fan shrouds of the fan wheel are poorly optimized with regard to the flow of cooling air. Besides simply redirecting the cooling airflow, their main function is to protect against accidental contact with the rotating parts of the fan assembly. Therefore, the design of the fan shroud contributes significantly to the noise level.

[0014] The object of the invention is to design an electric motor with a cooling device in such a way that sufficient cooling capacity can be achieved even at low speeds. The electric motor and the cooling device should operate with minimal noise. Furthermore, the cooling device should provide protection against unintentional access. The design of the electric motor with a cooling device should facilitate the replacement of spare parts. The device should be simple and inexpensive to manufacture.

[0015] This problem is solved according to the invention by an electric motor with a cooling arrangement according to claim 1. Preferred embodiments are described in the dependent claims.

[0016] According to the invention, guide elements are arranged in the space enclosed by the hood of an electric motor for driving a centrifugal pump with a cooling arrangement comprising a fan wheel and a hood.

[0017] Ideally, the guide elements are blade-shaped and have a radial leading edge and an axial trailing edge. They are stationary within the fan housing. Their function is to redirect the swirling air exiting the fan wheel into a swirl-free flow with minimal loss for cooling the electric motor and motor electronics. Advantageously, this cooling method is highly effective even at low motor speeds, as the airflow is directed precisely to the heat dissipation point.

[0018] The blade-like guide elements are designed similarly to the guide vanes of guide wheels, which are primarily used downstream of the centrifugal impellers in multi-stage pumps. They surround the fan wheel in a radial space around it. The cooling airflow encounters a radial leading edge of the blade-like guide elements. Due to their curvature opposite to the direction of rotation of the fan wheel and the rounded fan shroud, the radially oriented cooling airflow is deflected into an axial flow without flow separation or turbulence. The particularly effective and virtually loss-free deflected cooling airflow exits the blade-like guide elements by entering the annular channel for cooling the stator housing at the axial trailing edge of the blade-like guide elements.

[0019] According to the invention, the guide elements extend radially from the inner wall of the housing towards the centrally arranged rotor shaft. According to the invention, the guide elements have an increasing radius of curvature opposite to the direction of rotation of the fan wheel as they extend. This preferably achieves flow deflection without shocks, flow separation, or turbulence. Ideally, this intensifies the cooling performance of the cooling arrangement. At the same time, the noise level during operation is significantly reduced compared to cooling arrangements that are independent of the direction of rotation.

[0020] According to the invention, the hood of the cooling arrangement is formed integrally with the guide elements. This allows the hood to be manufactured economically, for example, as an injection-molded plastic part. In an alternative embodiment of the invention, a hood with a metallic base is also conceivable.

[0021] The electronics housing sits on the stator housing of the electric motor and is spaced apart by the height of the heat dissipation elements, particularly the cooling fins. The electronics housing is shaped to form a heat dissipation channel between the stator housing and the electronics housing. Advantageously, the housing features an extension with elongated guide elements that efficiently direct the flow of cooling air into this cooling channel, thus dissipating the waste heat from the electric motor and the motor electronics particularly effectively.

[0022] According to the invention, a space formed by the hood with guide elements completely surrounds the fan wheel of the cooling arrangement radially. This design solution is particularly ideal for the directed deflection of the cooling flow in order to avoid flow separation and turbulence. This results in particularly quiet operation of the cooling arrangement.

[0023] For efficient cooling at full cooling capacity, a directed cooling airflow is crucial. Ideally, the hood forms an annular channel between the inner wall surface of the cylindrical part of the hood and an outer wall surface of the electric motor housing, particularly the stator housing with integrated cooling fins. The cooling airflow drawn in and generated by the fan wheel is initially deflected from a radial to an axial direction by the hood's guide elements and the hood's shape itself. Thanks to the inventive design of the blade-like guide elements, this deflection occurs without turbulence, flow separation, or disruptive noise emissions. Advantageously, the cylindrical part of the hood connects to the stator housing in such a way that an annular channel is formed into which the cooling airflow is injected.This makes the cooling performance of the cooling arrangement particularly powerful, especially at low speeds of the electric motor.

[0024] In a particularly advantageous embodiment of the invention, the hood has a rounded shape that promotes the turbulence-free deflection of the cooling airflow. This rounded transition is located between the axially arranged intake grille and the cylindrical part of the hood that connects radially to the stator housing. The rounded transition also influences the shape of the guide elements, which, due to their integral construction with the hood, seamlessly connect to the inner wall of the hood and its rounded shape. This allows the cooling airflow to be deflected without flow separation or disruptive noise generation onto the axial flow over the stator housing and the cooling channel between the stator housing and the electronics housing.Since the cooling airflow should not only be directed evenly onto the motor's cooling fins, but also cool the electronics housing for the power electronics, an asymmetrical distribution of the cooling airflow is required in the area of ​​the electronics housing. Therefore, in this design, the fan shroud has an asymmetrical, non-circular shape that allows for a larger airflow in this area.

[0025] The fan wheel is mounted on the rotor shaft of the electric motor directly behind the bearing shield, outside the stator housing on the side facing away from the pump. Thus, the rotor shaft drives the fan wheel at the respective speed of the electric motor. The cooling assembly is positioned minimally away from the electric motor to avoid negatively impacting the installation dimensions with excessively bulky components.

[0026] According to the invention, the fan wheel has blades that are curved backwards in the direction of rotation. The fan wheel's support disc has a hub projection formed on the intake side of the cooling airflow, to which the blades engage offset from the center. The blades project from the support disc in the intake direction and preferably have a curvature opposite to the direction of rotation. In particular, all blades can have the same curvature.

[0027] In a particularly advantageous embodiment of the invention, the fan wheel and blades are formed in one piece. It proves advantageous if the impeller and / or the blades are made of a metallic material or injection-molded plastic.

[0028] Ideally, the fan wheel's support disc is shaped like a trumpet, tapering towards the intake, particularly towards the intake grille. A cross-section of this trumpet shape reveals a series of one or more arcs and straight lines. This curve can be represented mathematically by the form of a hyperbola. This special design of the support disc deflects the cooling airflow very gently, thus preventing flow separation, which would otherwise cause turbulence and noise emissions.

[0029] The optimized flow of cooling air by the fan is achieved primarily through the blade arrangement. The fan blades are radially curved in the opposite direction to the direction of rotation. They are mounted on the trumpet-shaped support disc off-center, thus in an offset arrangement. The mounting point originates from an imaginary ring on the trumpet-shaped support disc, which corresponds to approximately one-third of the diameter of the support disc.

[0030] The path of the blade's centerline between the blade inlet and outlet is called the skeleton line. It is often described by a circular arc, but also by parabolic arcs, S-curves, and other analytical curves.

[0031] The fan blades according to the invention have a rounded section at their point of attachment to the support disc. The blade's skeletal line extends from this rounded section and terminates precisely at the outer edge of the support disc. This advantageous design is part of the flow-optimized configuration of the fan wheel, which enables a cooling airflow generated by the cooling arrangement without flow separation or turbulence. This allows the waste heat from the electric motor and motor electronics to be dissipated particularly effectively without disruptive noise generation.

[0032] In a particularly advantageous embodiment of the invention, the blades of the fan wheel are arranged at an angle in the circumferential direction. This allows for a particularly quiet generation of the cooling airflow. The angle of inclination to the rotor shaft of the electric motor is preferably more than 5°, more particularly more than 10°, more preferably more than 15°, and / or preferably less than 45°, more particularly less than 40°, more preferably less than 35°. Since the fan wheel is preferably to be manufactured as an easily molded injection-molded part, the blade surface is designed as a helical surface, which is created by distorting the blade's skeleton line with a suitable pitch around the axis of rotation of the fan wheel.

[0033] The design of the cooling assembly, particularly the hood and the fan wheel, is characterized by its ease of maintenance. The components are especially easy to disassemble, thus enabling time-saving maintenance.

[0034] Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the drawings and from the drawings themselves.

[0035] This shows: Fig. 1 a section of an electric motor with a cooling arrangement for driving a centrifugal pump, Fig. 2 a front view of the electric motor, Fig. 3 a perspective view of the electric motor with cooling arrangement and removed cover, Fig. 4 a section of the cooling arrangement, Fig. 5 a perspective view of a fan wheel according to the invention.

[0036] In Fig. 1 Figure 1 shows a cross-section of an electric motor 1 designed to drive a centrifugal pump. The rotor shaft 12 is supported and rotatably mounted by integrated rolling bearings 16 on the pump side and on a bearing shield formed integrally with the stator housing 13. The rotor shaft 12 has a rotor 14. According to the electromechanical principle, the rotating magnetic field of the stator 15 drives the rotor 14.

[0037] The electronics housing 8 sits on the stator housing 13 and is formed from the electronics housing base 9 and the electronics housing cover 10. The motor electronics, consisting of a frequency converter, power control, and / or speed control, are arranged in the electronics housing 8. Heat dissipation elements 7 are positioned in the electronics housing base 9. In this embodiment, the heat dissipation elements 7 are designed as cooling fins. The heat from the electric motor 1 is transferred to the heat dissipation elements 7 via the stator housing 13, and the heat from the motor electronics is transferred to the heat dissipation elements 7 via the electronics housing base 9.

[0038] The cooling arrangement 2 is mounted on the side of the electric motor 1 facing away from the pump. This arrangement consists of the fan wheel 5 and the housing 4 with integrated openings 6. The housing 4 encloses a radial space 17 around the fan wheel 5, within which guide elements 3 are arranged. The blade-like guide elements 3 have a radial leading edge 31 and an axial trailing edge 30. The fan wheel 5 draws in an airflow axially through the openings 6 of the housing 4 and deflects it radially into the space 17. The guide elements 3, which according to the invention are blade-like and integrally formed with the housing 4, deflect the airflow axially by means of their curvature opposite to that of the fan wheel 5, so that it sweeps over the heat dissipation elements 7 and 20, which are arranged radially over the entire stator housing 13, for efficient cooling of the motor and the motor electronics.

[0039] The Fig. 2 Figure 1 shows a side view of the electric motor 1 from the perspective of the connection to the centrifugal pump. The electronics housing 8 is mounted on the stator housing 13. The electronics housing comprises the lower electronics housing part 9 and the cover 10. Heat dissipation elements 7 are attached to the lower electronics housing part 9, and heat dissipation elements 20 are attached to the stator housing 13. In this embodiment, both heat dissipation elements 7 and 20 are designed as cooling fins. The cover 4 extends over the stator housing 13 with the heat dissipation elements 7 and 20 in such a way that an annular channel 19 is formed which just encloses the heat dissipation elements 7 and 20. Advantageously, the cooling airflow can thus be ideally introduced into the channels formed by the heat dissipation elements 7 and 20 with the stator housing 13 and flow through them for cooling.

[0040] The Fig. 3 Figure 1 shows an electric motor 1 with the cooling arrangement 2, in which the cover 4 is shown detached. The cover 4 has openings for the intake grille 6, which in this embodiment are formed as a grille within the cover 4. Furthermore, the cover 4 has an asymmetrical projection 21 designed to direct a sufficiently large cooling airflow into the channel formed by the heat dissipation elements 7, the stator housing 13, and the lower electronics housing 9. Advantageously, this allows the heat generated by the electric motor 1 and the heat generated by the motor electronics, which are arranged in the electronics housing 8, to be dissipated. The cover 4 has a rounded transition 22 from the openings 6 to the cylindrical part 25. This advantageously deflects the radial cooling airflow axially so that it flows through the channels formed by the heat dissipation elements 20 and the stator housing 13.This cooling airflow is generated by the fan wheel 5, which has backward-curved blades 23 arranged on the funnel-shaped support disc 26. The blades 23 have a rounded section 27 on their skeletal line at their attachment point.

[0041] The Fig. 4 Figure 1 shows a cross-section of the cooling arrangement 2. Inside the cooling arrangement 2, the fan wheel 5, with its blades 23 curved backwards in the direction of rotation, is positioned on the rotor shaft 12 (not shown) by means of the opening 24. The fan wheel 5 has a trumpet-shaped support disk 26, which tapers towards the opening 24 in the top view. The blades 23 extend from the support disk 26 with a curve 27. The point of attachment of the blades 23 lies on an imaginary line that corresponds to approximately one-third of the diameter of the fan wheel 5. The point of attachment of the blades 23 is therefore off-center, which is marked by the opening 24. The cover 4 encloses the space 17, which completely surrounds the fan wheel 5 radially. The guide elements 3 are arranged in this space 17 and are integrally formed with the cover 4. The guide elements 3 have a radial curvature opposite to the fan wheel curvature and a radial leading edge 31.Furthermore, the hood 4 has an asymmetrical shaping 21, in which the guide elements 3 are also extended and adapted to the asymmetrical shape.

[0042] The Fig. 5 Figure 1 shows a perspective view of the fan wheel 5, which has a trumpet-shaped support disk 26 tapering towards the opening 24. The blades 23 are curved backwards in the direction of rotation and are additionally inclined in the circumferential direction. The angle of inclination relative to the rotor shaft 12 (not shown), which projects through the opening 24 to position the fan wheel 5, is greater than 5°, preferably greater than 10°, particularly greater than 15°, and / or less than 45°, preferably less than 40°, particularly less than 35°. The blades 23 have a rounded section 27 at their point of attachment to the support disk 26. Advantageously, this allows the cooling airflow to be generated in a particularly quiet manner.

Claims

1. Electric motor (1) for driving a centrifugal pump, having a cooling arrangement (2) which comprises a fan impeller (5) and a shroud (4), the shroud (4) enclosing a space (17) around the fan impeller (5), guide elements (3) being arranged in the space (17), the guide elements (3) being formed as a single piece with the shroud (4), the guide elements (3) extending radially from the shroud (4) in the direction of a rotor shaft (13), characterized in that the guide elements (3) have, with increasing extent, an increasing radius of curvature counter to the direction of rotation of the fan impeller (5).

2. Electric motor according to Claim 1, characterized in that the guide elements (3) have a radial leading edge (31) and an axial trailing edge (30).

3. Electric motor according to Claim 1 or 2, characterized in that the shroud (4) has a protuberance (21) for forming a channel to heat dissipation elements (7) of an electronics housing (8).

4. Electric motor according to any one of Claims 1 to 3, characterized in that the space (17) radially fully encloses the fan impeller (5).

5. Electric motor according to any one of Claims 1 to 4, characterized in that an annular channel (19) is formed between an inner wall surface of the shroud (4) and an outer wall surface of a housing of the electric motor (1).

6. Electric motor according to any one of Claims 1 to 5, characterized in that the shroud (4) has a rounded transition (22) from an intake grille (6) to a cylindrical part (25).

7. Electric motor according to any one of Claims 1 to 6, characterized in that the fan impeller (5) has blades (23) that are curved backwards in a direction of rotation.

8. Electric motor according to Claim 7, characterized in that all of the blades (23) of the fan impeller (5) have the same curvature.

9. Electric motor according to any one of Claims 1 to 8, characterized in that a carrying disc (26) of the fan impeller (5) is configured in the shape of a trumpet bell, the carrying disc (26) tapering in the direction of an opening (24).

10. Electric motor according to Claim 9, characterized in that the blades (23) of the fan impeller (5) are attached, outside the central point of the carrying disc (26), to a ring of the bell shape.

11. Electric motor according to Claim 10, characterized in that the blades (23) have a rounded portion (27) at their point of attachment on the carrying disc (26).

12. Electric motor according to any one of Claims 7 to 11, characterized in that the blades (23) of the fan impeller (5) are arranged so as to be oblique in a circumferential direction, the angle of the obliquity with respect to the rotor shaft (12) being preferably more than 5°, in particular more than 10°, preferably more than 15°, and / or preferably less than 45°, in particular less than 40°, preferably less than 35°.