Electric axial fan for a vehicle front-end cooling module

Abstract

The invention relates to an electric axial fan (1) for a vehicle front-end cooling module, comprising an electric motor (2) with a stationary stator (3) and a rotatable rotor (4), a rotor housing (5) coupled to the rotor (4) which has an end face with several axial openings (13), a fan hub (6) attached to the rotor housing (5) which has radially outwardly extending fan blades (8) to convey air from a suction side (11) to a pressure side (12), and a cover (7) covering the end face of the rotor housing (5) on which several projections (14) are formed which correspond to the several axial openings (13) such that air from the pressure side (12) passes through the rotor housing (5) and the cover (7) to the suction side (11), each projection (14) of the several projections (14) having a first section (14.1) and a second section (14.2) has, wherein the first section (14.1) covers a corresponding axial opening (13) at axial distances, and the second section (14.2) forms a channel open to the end face on an end face of the cover (7) facing the suction side (11), which leads to a radial outer circumference of the cover (7) and has a curved course.

Description

The invention relates to an electric axial fan for use on a vehicle front-end cooling module. In vehicles, fans are used to distribute air and improve heat transfer to heat exchangers, with the air being actively moved through the heat exchanger by a fan. These heat exchangers, known as front-end cooling modules, are located at the front of a vehicle as part of a cooling system. The fan helps to ensure that air flows over the surface of the heat exchanger, thus promoting heat transfer. External rotor motors are used for these fans, in which a rotor with the fan impeller rotates around a stator. Typically, DC motors, especially brushless DC motors (BLDC motors), are used, in which the hub is designed as a rotor housing.The rotor housing is an integral part of the rotor, serving to hold the permanent magnets of the electric motor. The rotor housing has a bell- or cylindrical shape that surrounds the stator of the electric motor. The permanent magnets are mounted on the inside of the rotor housing and, together with the electromagnetic fields of the stators, generate the rotational movement of the electric motor. Airflow is generated by fan blades that extend radially outwards from an impeller hub. The impeller hub is typically attached to the rotor housing, so that the impeller hub rotates with the rotor housing. However, designs are also possible in which the impeller hub is formed by the rotor housing and the fan blades are attached directly to a surface of the rotor housing. In some designs, the rotor bell is mounted directly on an electric motor shaft and rotates with it. In other designs, the rotor bell can be connected to the electric motor shaft via a separate bracket or bearing. The rotor bell, with the magnets attached to it, rotates around the stationary stator, which contains the coils. The advantage of a rotor bell design is that it allows for a uniform distribution of the magnetic fields and a compact construction, which contributes to improved performance of the electric motor. On the other hand, the rotor housing of fans can negatively impact the cooling of an electric motor. The housing can cover parts of the rotor and stator, obstructing airflow and hindering heat dissipation from the motor's interior. In motor cooling mechanisms that rely on air circulation, the rotor housing can thus impede airflow, especially if it has a closed structure. Restricted airflow can reduce cooling efficiency and cause certain parts of the electric motor to overheat. To address this problem, rotor housings with ventilation slots or openings are used. The fan's rotation creates circulating airflow through these openings on the front of the rotor housing, allowing heat generated inside to be dissipated. An example of a motorized fan device can be found in US 2021 / 0 218315 A1. The fan device described therein has an impeller rotating about an axis, a cup-shaped body on which blades are arranged, and an electric motor whose motor housing is partially located inside the cup-shaped body. A centrifugal device is provided between the cup-shaped body and the motor housing to guide and accelerate an airflow. The cup-shaped body has at least one opening for the passage of an airflow, while the motor housing has at least one corresponding opening so that an airflow can be directed through the motor to cool it. EP 4 198 318 A1 relates to an electric fan for vehicle applications with an axial impeller and an electric motor. The impeller has a hub with a cup-shaped structure, the base of which has several openings. On the side opposite the base, a disc-shaped element is arranged, forming an annular gap with the hub. The openings in the base provide a first flow path between the interior of the hub and the annular gap, while a further passage is formed between the annular gap and the environment. This generates a cooling airflow during operation, which is directed through the motor and contributes to cooling the motor components. Further motorized fan assemblies are known from the documents DE 698 24 126 T2 and US 2012 / 0 207 631 A1. It has been shown that the probability of extreme weather conditions with prolonged heat waves and significant temperature fluctuations is increasing, leading to greater stress on air conditioning systems. The fans used to handle the necessary airflow in such systems are therefore subjected to frequent continuous operation and, particularly in vehicles used for short trips, to frequent short bursts of full load. Under extreme stress during full load and / or continuous operation, simple axial openings in the rotor bell face may not be sufficient to completely dissipate the heat generated within the electric motor assembly by the stator windings and the integrated power electronics. This can lead to overheating of the drive electronics, especially during full load or continuous operation, impairing efficiency and increasing wear on the electric motor. The invention is therefore based on the objective of proposing an axial fan operated by an electric motor for a vehicle front-end cooling module, which enables improved cooling of the electric motor and the integrated electric motor electronics. The problem is solved by an electric axial fan with the features according to claim 1, wherein advantageous embodiments or further developments are specified in the subordinate claims. According to the invention, an electric axial fan for use on a vehicle front-end cooling module is proposed. The electric axial fan comprises an electric motor with a stationary stator and a rotatable rotor, a rotor housing coupled to the rotor which has an end face with several axial openings, and a cover covering the end face of the rotor housing, on which several projections are formed that correspond to the several axial openings such that air passes from the pressure side through the rotor housing and the cover to the suction side.According to the invention, each of the multiple forms has a first section and a second section, wherein the first section covers a corresponding axially spaced opening and the second section forms a channel open to the end face of the cover on an end face facing the suction side, which leads to a radial outer circumference of the cover and has a curved course. In accordance with the invention, the axial direction always refers to the axis of rotation of the electric motor or the rotor of the electric motor. The suction and pressure sides are defined by the arrangement of the fan blades. Air is drawn in on the suction side as a result of the fan's rotation and conveyed to the pressure side. The electric axial fan is always configured so that the rotor housing faces the suction side with its closed end. According to the invention, the axial openings on the axial end face of the rotor bell, together with the recesses of the cover, form multiple flow paths to guide air through the rotor bell from the pressure side to the suction side. The axial openings are located in the rotor bell base, which forms the end face facing the suction side on its opposite side. Each axial opening corresponds to one recess of the multiple recesses of the cover, such that each axial opening is associated with a recess comprising a first section and a second section. The recesses are designed with the first and second sections such that the air flowing through the axial openings is deflected in a radial direction.To ensure airflow into the first section, this section features an axial opening that corresponds to the axial perforation in the rotor bell. The axial opening of the first section and the axial perforation in the rotor bell are aligned to guarantee unimpeded airflow. These features thus form multiple cooling air channels for channeling airflow exiting axially from the perforations. According to an advantageous embodiment, the cover with its features can be formed as an integral part of the fan hub. In this embodiment, the fan hub is thus attached to the radial circumference of the cover, so that the cover merges seamlessly into the fan hub. Consequently, the fan hub incorporates the cover with the features according to the invention, so that the fan hub and the cover form a single component. However, the cover does not necessarily have to be connected to the fan hub. The cover with the features according to the invention can also be designed as a separate component, which can be attached to the front face of the rotor bell independently of the fan hub. The cover, with its various shapes, forms an integrated radial fan on the fan hub, both as a separately attached element and as an integral part of the fan hub. The function of the radial fan is to utilize the pressure difference between the suction and pressure sides of the fan to further increase the airflow through the electric motor and to cool the motor windings and power electronics more efficiently. The axial openings formed on the rotor bell face or in the rotor bell base are arranged at uniform intervals. Attached to the rotor bell, the recessed covers, together with the corresponding axial openings in the rotor bell, form multiple airflow paths, allowing air to flow from the pressure side through the rotor bell to the suction side. The first section of each recess is preferably designed such that an axial airflow exiting a corresponding axial opening can be deflected in a radially outward direction. This deflection is achieved by shaping the first section such that the surface upon which the axial cooling airflow impinges has a curvature in the direction of the second section. The first section of the recess, which overlaps the axial opening at an axial distance, can thus have a curvature that deflects the air flowing axially outward from the corresponding axial opening.From the first section, the air is thus deflected into the second section of the shape, so that the deflected air enters the semi-open channel formed on the front of the cover and can follow the curvature of the semi-open channel in the direction of flow. Advantageously, the inventive design creates the function of an additional radial fan in the hub area, thereby increasing the airflow and improving the cooling capacity of the electric motor. Increased airflow through the electric motor advantageously results in lower temperatures at the stator windings and the integrated electronics. The multiple axially open channels formed by the several projections in the second sections of the projections can have radially outward-terminating openings through which the cooling air can escape on the suction side. These openings are formed as recesses in the outer surface of the cover on a radial outer circumference and can extend into the outer surface of the fan hub. Advantageously, the radially outward-terminating openings can have rounded edges. The rounded edges prevent flow separation and thus turbulence, contributing to reduced noise and improved flow characteristics. According to a particularly preferred embodiment, the cross-section of the axially open channels can increase along their length towards the radial outer circumference of the cover. That is, the flow cross-section becomes larger from the inside out. Along the resulting flow paths, the cross-section through which cooling air can flow is small at the axial opening and increases in the flow direction due to the cover's projections. This accelerates the airflow through the projections, contributing to improved cooling. According to the invention, the paths of the axially open channels of the molded sections in the second section are curved backwards. This means that the paths of the multiple axially open channels are curved in the opposite direction to the rotation of the fan. This measure allows for further acceleration of the airflow in the molded sections on the suction side, thereby further improving the cooling performance. In one embodiment of the electric axial fan, the rotor housing can completely cover the stator axially. In this embodiment, the stator and the integrated motor electronics are located within the rotor housing and thus within the influence of a generated cooling airflow or circulation, further improving cooling. According to a further embodiment, the first sections can form depressions on the end face of the cover facing the suction side. The cover can be screwed to the rotor bell. Preferably, the cover, or the fan hub attached to it, is screwed to the end face of the rotor bell, with the rotor bell being radially and axially covered by the cover and fan hub. The cover is preferably dimensioned so that it extends radially beyond the rotor bell. The electric motor is preferably mounted on a grid structure so that the rotor can rotate freely. The grid structure can be part of the front-end cooling module. The electric axial fan is designed for mounting on a front-end cooling module of a vehicle. Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1: a schematic sectional view of an exemplary embodiment of an electric axial fan; Fig. 2a / b: schematic representations of an exemplary embodiment of a fan impeller of an electric axial fan as a top view a) and as a side view in section b); Fig. 3a / b: a detail a) of Fig. 2a and a detailed side view in section b); Fig. 4: a detail of the representation of the fan impeller shown in Fig. 2a; Fig. 5: a schematic representation of a detail of an exemplary embodiment of an electric axial fan; and Fig. 6: another schematic representation of a detail of an exemplary embodiment of an electric axial fan. Fig. 1 shows a schematic sectional view of an embodiment of an electric axial fan 1 according to the invention, which comprises an electric motor 2 with a stator 3 and a rotor 4 to which a rotor housing 5 is attached. The term "axial" used below refers to the orientation of the rotor 4 of the electric motor 2. The electric axial fan 1 further comprises a fan hub 6 attached to the rotor housing 5, on which fan blades 8 of a fan wheel 9 extend radially outwards. The fan blades 8 are oriented such that air is conveyed in the direction of the arrows 10 from a suction side 11 to a pressure side 12 when the fan hub 6 rotates in the direction of the arrows (see Fig. 2a).The rotor bell 5 has an axially flat end face with several axial openings 13 on one side facing the suction side 11 in order to allow an airflow from the pressure side 12 through the rotor bell 5 to the suction side 11. A cover 7, which is formed as an integral part of the fan hub 6, has several projections 14. The cover 7 is arranged such that it partially covers the axial end face of the rotor bell 5, with each projection 14 of the several projections 14 corresponding to an axial opening 13 of the several axial openings 13. Each axial opening 13 corresponds to each projection 14 such that a separate flow path 15 (arrow) is formed. Each projection 14 of the several projections 14 has a first section 14.1 and a second section 14.2, wherein the first section 14.1 has an axial opening which is aligned with the axial opening 13 and covers the corresponding axial opening 13 at a distance. The second section 14.2 forms an axially open channel on the end face of the cover 7 facing the suction side 11. This channel leads to a radial outer circumference of the cover and has a curved path. The first section 14.1, which axially covers a corresponding axial opening 13 at a distance, has a curvature 14.1.1 that deflects an airflow exiting the corresponding axial opening 13 towards the second section 14.2. The axial openings 13 and their respective associated features 14, with their first sections 14.1 and second sections 14.2, thus form several flow paths 15, which, as cooling channels, allow airflow from the pressure side 12 through the rotor housing 5 to the suction side 11. This contributes to improved cooling of the electric motor 2. Figures 2a and 2b show schematic representations of an embodiment of a fan wheel 9 of an electric axial fan according to the invention, with Figure 2a showing a top view of the fan wheel 9 and Figure 2b showing a side view of the fan wheel 9 in section. The fan wheel 9 comprises the fan hub 6 with the cover 7, in which nine recesses 14 are formed. Nine fan blades 8 extend radially outwards along the radial circumference of the fan hub 6 to a ring 16. The nine recesses 14 each comprise a first section 14.1 and a second section 14.2. The first section 14.1 of each recess 14 is designed such that it covers a corresponding axial opening 13 (see Figure 1) at an axial distance. The first sections 14.1 of the features 14 each have a curvature 14.1.1 (see Fig. 1). In the top view of the cover 7 of Fig. 2a, the first sections 14.1 are therefore partially visible as depressions. The first section 14.1 of each molding 14 is followed by a second section 14.2, which is designed as an axially open channel. This semi-open channel leads to a radial outer circumference of the cover 7 and has a curved profile, the cross-section of which increases in the direction of the radial outer circumference of the cover 7. Every second section 14.2 of the moldings 14 thus forms a channel with a bottom enclosed by two side walls, the top being open towards the suction side 11 (see Fig. 1). The direction of rotation of the fan wheel 9 is indicated by the direction-of-rotation arrows 17. The contours of the projections 14 are therefore curved backwards in the respective second sections 14.2. The cover 7 has three holes 18, which are provided for attaching the fan hub 6 or the fan wheel 9 to the end face of the rotor bell 5 by means of screws. Fig. 2b shows the fan wheel 9 in a side view along the section line AA shown in Fig. 2a. In contrast to Fig. 1, the electric motor 2 with the rotor bell 5 is missing in this view. Thus, only the fan hub 6 with the cover 7, the fan blades 8, the ring 16, and a second section 14.2 of one of the nine sections 14 are shown. Fig. 3a shows a detail of Fig. 2a, while Fig. 3b shows a detailed side view of a section along the section line CC shown in Fig. 3a. The top view of the cover 7 in Fig. 3a shows several of the projections 14, the first section 14.1 of each projection 14 being recognizable as the contour of a recess. The second section 14.2 of each projection 14 forms an axially open, i.e., semi-open, channel, which is open at the radial end and has a curved profile. The second sections 14.2, which form the axially open channel, are curved backwards with respect to the direction of rotation 17 of the fan wheel 9. Fig. 3b shows a section CC which passes through the cover 7 along one of the projections 14. As can be seen in Fig. 3b, the first section 14.1 has a curvature 14.1.1, so that an airflow striking the first section 14.1 is deflected into the second section 14.2. Fig. 4 shows a section of the representation of the fan wheel 9 shown in Fig. 2a. A top view of the fan wheel 9 is shown, with the cover 7 partially exposed, so that in this area the axially overlapping part of the first section 14.1 of the projections 14 is omitted. Thus, in the exposed area, the part of the first section 14.1 is visible which forms the corresponding connection with an axial opening 13 in the rotor bell 5. The first section 14.1 transitions into the second section 14.2. It is clear from this that each projection 14 of the multiple projections 14 has an axial opening which is aligned with an axial opening 13 (see Fig. 1) to allow the flow of air from the pressure side 12 through the rotor bell 5 (see Fig. 1, arrow 15) to the suction side 11. The flow paths 15 for the air currents are each marked by the arrows. Fig. 5 shows a schematic representation of a detail of an embodiment of a fan wheel 9. The illustration provides a view of the projections 14 formed on the cover 7. Each projection 14 of the multiple projections 14 has a first section 14.1 and a second section 14.2, wherein the first section 14.1 corresponds to an axial opening 13 in the rotor bell 5 (see Fig. 1 or Fig. 6) and covers it at an axial distance. The second section 14.2 of the projections 14 forms a channel open towards the end face, which leads to a radial outer circumference of the cover 7 and has a curved profile. Fig. 6 shows a further schematic representation of a detail of an embodiment of an electric axial fan 1. The illustration allows a view through one of the projections 14, through the corresponding axial opening 13 of the rotor bell 5 (obscured), to the stator windings 19 of the stator 3 (see Fig. 1). The first section 14.1 of the projection 14 corresponds to the axial opening 13 of the rotor bell 5 (obscured) and covers it axially spaced apart, so that the opening 13 is also axially spaced and covered. The second section 14.2 of the projections 14 forms a channel open at the end face, which leads to a radial outer circumference of the cover 7 and has a curved profile. The arrow 20 indicates the flow path for flowing air from the Sator windings 19 through the opening 13, the first section 14.1 and the second section 14.2. Reference symbol list 1 Electric axial fan 2 Electric motor 3 Stator 4 Rotor 5 Rotor housing 6 Fan hub 7 Cover 8 Fan blade 9 Fan wheel 10 Arrow 11 Suction side 12 Pressure side 13 Axial opening 14 Shape 14.1 First section 14.1.1 Curve 14.2 Second section 15 Flow path 16 Ring 17 Direction of rotation arrow 18 Holes 19 Stator windings 20 Arrow

Claims

An electric axial fan (1) for a vehicle front-end cooling module, comprising an electric motor (2) with a stationary stator (3) and a rotatable rotor (4), a rotor bell (5) coupled to the rotor (4) which has an end face with several axial openings (13), a fan hub (6) attached to the rotor bell (5) which has radially outwardly extending fan blades (8) to convey air from a suction side (11) to a pressure side (12), and a cover (7) covering the end face of the rotor bell (5) on which several projections (14) are formed which correspond to the several axial openings (13) such that air from the pressure side (12) passes through the rotor bell (5) and the cover (7) to the suction side (11), characterized in that each projection (14) of the several projections (14) has a first section (14.1) and a second section (14.2) has, wherein the first section (14.1) covers a corresponding axially spaced axial opening (13) and the second section (14.2) forms a channel open to the end face on an end face of the cover (7) facing the suction side (11), which leads to a radial outer circumference of the cover (7) and has a curved course, and that the courses of the axially open channels of the projections (14) in the second section (14.2) are curved backwards with respect to a direction of rotation (17) of the rotor (4). Electric axial fan (1) according to claim 1, characterized in that the cover (7) is designed as an integral part of the fan hub (6). Electric axial fan (1) according to claim 1 or 2, characterized in that the first section (14.1) is designed such that an axial airflow exiting from an axial opening (13) can be deflected in a radially outward direction. Electric axial fan (1) according to one of the preceding claims, characterized in that the axially open channels have openings ending radially outwards. Electric axial fan (1) according to one of the preceding claims, characterized in that the radially outwardly ending openings have rounded edges. Electric axial fan (1) according to one of the preceding claims, characterized in that a cross-section along the axially open channels increases along their course towards the radial outer circumference of the cover (7). Electric axial fan (1) according to one of the preceding claims, characterized in that the rotor bell (5) axially covers the stator (3). Electric axial fan (1) according to one of the preceding claims, characterized in that the first sections (14.1) form recesses on the end face of the cover (7) facing the suction side (11). Electric axial fan (1) according to one of the preceding claims, characterized in that the cover (7) is screwed to the rotor bell (5). Electric axial fan (1) according to one of the preceding claims, characterized in that the electric motor (2) is attached to a grid structure.

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