Fan with a circuit board as impeller suspension and with coil units incorporated in the circuit board of an axial flux motor

Abstract

A fan with an axial flux motor comprises a circuit board as impeller support / suspension with a bearing LP which defines a central rotation axis extending in an axial direction x, an impeller W which is rotatably drivable with respect thereto, and an electric motor, a rotor of which has a set of several juxtaposed permanent magnets MS provided around the central rotation axis which are connected to the impeller and which are axially directed with alternating polarity and which are each situated in a plane at right angles to the rotation shaft at a clear distance Tr from and parallel to the coil units, wherein the circuit board is situated in a plane at right angles to the rotation shaft, wherein juxtaposed coil units provided around the rotation shaft are provided on the circuit board as guide tracks, and wherein the guide track of each coil unit forms at least one coil winding track running helically around its own axis, which extends parallel to the rotation shaft of the bearing, on a surface of the circuit board.

Description

[0001] Title: Fan with a circuit board as impeller suspension and with coil units incorporated in the circuit board of an axial flux motor.

[0002] FIELD

[0003] The invention relates to a fan of the type with an axial flux motor, comprising a suspension, an impeller which is rotatably drivable with respect to the suspension about a central rotation axis extending in an axial direction, and an electric motor for rotatably driving the impeller. In this case, the axial flux motor of the fan has a set of several juxtaposed coil units provided around the central rotation axis as a stator which are connected to the suspension and which are configured to induce magnetic flux in alternating axial directions. In addition, the axial flux motor of the fan in this case has a set of several juxtaposed permanent magnets provided around the central rotation axis as a rotor which are connected to the impeller and which are axially directed with alternating polarity.

[0004] STATE OF THE ART

[0005] Current fans, such as for example microfans of computers, but also slightly larger fans of sanitary facilities, kitchens, or the like, are often equipped with electric motors of the radial flux motor type. In this case, the motor comprises a stator with coils composed of windings wound around an armature. In addition, the motor comprises a rotor which is connected to a plastic impeller. This impeller comprises a circular core and impeller blades which extend outwards in a radial direction. In the core of the impeller, a central bearing pin is installed and, at a distance around the latter, a metal cup-shaped screen arranged in a circle at a distance around it containing a magnetic flexible strip with several magnetic poles thereon. In the fitted position, the impeller with the magnetic strip attached therein is arranged so as to be rotatable in a circle around the coils. The position and actuation of the coils with respect to the permanent magnets causes the rotor and thus also the impeller to rotate.

[0006] With this type of fan, the armature of the coils is formed directly by a plastic part which is extruded in one piece, which also has provisions for accommodating a bearing and a locking device, so that the impeller can be fitted therein by means of its bearing pin, mounted and locked in an axial direction. In the centre of the armature, a provision is made to this end, such as a recess for accommodating a bearing bush therein, usually made of bronze, and a locking ring or clip, to limit movement of the bearing pin of the impeller both in an axial and in a radial direction. Often, the plastic part not only forms the armature, but also a part of an external fan frame. This external fan frame often has a square outer shape and serves, on the one hand, for fitting purposes and, on the other hand, for protecting the blades of the impeller.

[0007] In this case, electrical control means of these known fans are situated on a circuit board which is fitted between the stator and the fan frame, so that it does not project beyond the circular core of the impeller. From the circuit board, wires are passed to the outside in order to supply power to the latter and to control it by means of signals.

[0008] In this case, it is a drawback that, due to the labour-intensive production of such fans, these are virtually only being manufactured in low-cost countries, such as in the Far East, and in particular in China. This results in long journey times by boat together with the associated environmental footprint. Due to pandemics and wars, the delivery times of these fans fluctuate greatly and can rapidly escalate from a few months to more than a year, which then quickly becomes irreconcilable, from an economic point of view, with a great increase in demand for a certain product. In particular if it is difficult to predict this demand over time.

[0009] Another drawback is the fact that the impeller of every fan has to be balanced during assembly. This serves to prevent vibrations from occurring due to imbalance which would lead to annoying noise during use and result in a reduction in the service life. In this case, each individual impeller is tested and, depending on the deviations which are found with respect to the balance, mass is added or removed at certain locations, such as by local addition of a small amount of liquid adhesive. This is a labour-intensive process.

[0010] Finally, it is a drawback that such fans of the type with a radial flux motor require a relatively large installation space.

[0011] In order to reduce the installation space, US-2021 / 0083551 discloses a fan of a type with an axial flux motor. Here, a microfan is disclosed which comprises a rotor and a stator. The stator comprises two separate coil units. In this case, each coil unit comprises a large number of wire windings which are wound into a bundle on top of a guide frame in as compact a way as possible. The bundle and a part of the guide frame are then covered by a block-like insulating material. Thereafter, the guide frame is cut off and two coil units which have been formed in this way are fitted at diametrically opposite positions with respect to a central axis on top of a circuit board. In addition, a microcontroller is fitted on top of the circuit board.

[0012] The circuit board containing the coil units and the microcontroller is then secured in a bottom part of a rectangular plastic fan frame. This plastic bottom part also forms the suspension for a rotatably drivable impeller and to this end comprises an upright cylindrical bearing part in the centre, in which a bearing bush is arranged. In this case, a central recess of the circuit board comes to lie over the upright cylindrical bearing part. In a recess on the bottom side of the impeller, a ring magnet with a magnetic guide shield on top thereof is attached. The guide shield is also provided with a downwardly projecting bearing pin which, in the fitted position of the impeller, extends into the bearing bush. In order to prevent the bearing pin, during use, from touching the bottom part of the housing frame when rotating, a small wear-resistant pad is provided on the bottom of the upright cylindrical bearing part before the bearing bush is arranged therein. Once the impeller has thus been fitted with its bearing pin into the bearing bush, a plastic top part is click-fitted onto the plastic bottom part of the housing frame.

[0013] This has the drawback that this fan of the axial flux motor type leaves to be desired with regard to a number of usage aspects, such as noise, efficiency and power consumption. In addition, despite the fact that an axial flux motor is used, the construction of this fan is still relatively thick. In addition, the fan comprises components, such as the coil units, which are not only relatively expensive but also laborious in terms of production and composition.

[0014] It is another drawback that the impeller is designed to remain in situ in the bearing part on account of the force of gravity. This means that this fan can substantially only be fitted and used in one position. In order to prevent the impeller from accidentally coming loose when the fan or the device in which it is provided is held upside down for a short period of time, the top part of the plastic housing frame has to be provided with a limiting edge which extends inwards in a radial direction up to a point above the impeller blades. However, this edge also means that the impeller can only be removed after the housing frame has been opened up.

[0015] Finally, it is a drawback that this fan is also susceptible to the impeller being out of balance and to wear of the bearing, as a result of which it thus requires individual balancing of the impellers while it might then still start to produce an annoying noise rather quickly.

[0016] BRIEF DESCRIPTION OF THE INVENTION

[0017] It is an object of the present invention to overcome the abovementioned drawbacks at least partly or to provide a usable alternative. In particular, it is an object of the invention to provide a fan which can be produced efficiently and simply and which makes it possible to quickly satisfy the fluctuating demand of the market, and which satisfies the wishes and desires of users even better, both with regard to comfort and noise, as well as cleanability.

[0018] This object is achieved by a fan of the type having an axial flux motor according to claim 1. In this case, the fan comprises:

[0019] • an impeller support / suspension with a bearing which defines a central rotation axis extending in an axial direction;

[0020] • an impeller which is rotatably drivable around the central rotation axis with respect to the impeller support / suspension; and • an electric motor for rotatably driving the impeller, wherein the electric motor is an axial flux motor, with a set of several juxtaposed coil units provided around the central rotation axis as a stator which are connected to the impeller support / suspension, and with a set of several juxtaposed permanent magnets provided around the central rotation axis as a rotor which are connected to the impeller and which are directed axially with alternating polarity and which are each situated in a plane at right angles to the central axis at a clear distance spaced apart from and parallel to the coil units.

[0021] According to the inventive main idea of the invention, the impeller support / suspension is formed by a circuit board which is situated in a plane at right angles to the central rotation axis, wherein the juxtaposed coil units provided around the central rotation axis are provided as guide tracks on the circuit board, and wherein the guide track of each coil unit forms at least one coil winding track running helically around its own axis, which extends parallel to the central rotation axis of the bearing, on a surface of the circuit board.

[0022] Now, the invention very advantageously makes it possible to produce fans in a very efficient and economical way close to the market while making it possible to adjust the production capacity quickly and simply if desired. The circuit board which in many devices is often already intended to be the carrier of all kinds of electronic control components can now also be used directly in a multifunctional way as impeller support / suspension for the fan and as direct carrier of coil winding tracks of an axial flux motor. The coil winding tracks may be provided on one or more surfaces of the circuit board at the same time as other guide tracks which have to be present on the circuit board are being provided. This process may take place in a completely automated manner. The circuit board may then also be directly provided with other desired electronic components, such as control resistors and microprocessors. As a result of extensive automation and robotisation, the degree of human labour required during production can be greatly reduced.

[0023] Due to the simultaneous use of the circuit board itself as an impeller support / suspension, the fan as a whole only requires a very small installation space. According to the inventive idea, this installation space may very advantageously be limited to only a few millimetres, i.e. a thickness of the circuit board which may be less than a millimetre, plus a thickness of the impeller or of the set of permanent magnets connected thereto, which may also be less than a millimetre, respectively, plus a thickness of an axial air gap between the circuit board and the impeller of the set of permanent magnets connected thereto, respectively, which may also be less than a millimetre. A dedicated individual fan housing frame is no longer strictly necessary. Thus, the present invention makes it advantageously possible for the manufacturer to assemble the fans locally in very little time. This makes it possible to react quickly to the market’s fluctuating demand.

[0024] The fact that no separate coil units with bundles of copper wire windings have to be provided, and the thinness of the coil winding tracks on the one or more surfaces of the circuit board has the additional advantage that considerable savings in weight and space can be achieved compared to the fans with their own rectangular fan frames which were hitherto often used customarily. With the invention, the impeller which is situated directly above the circuit board additionally advantageously ensures that the circuit board is automatically cooled. Due to the fact that the circuit board can be kept substantially flat on the side of the impeller, and for example no components projecting in the direction of the impeller have to be provided on the circuit board on the side of the impeller, the air flow which is produced by the impeller is not disturbed there and the impeller is easily able to find and maintain its balance during rotation. Partly as a result thereof, the fan according to the invention has highly advantageously been found to be extremely quiet and efficient. This makes the fan perfectly suitable to satisfy practically all wishes and requirements of users.

[0025] The north and south poles of the permanent magnets are placed in an axial direction in turns. Preferably, all of the permanent magnets are of equal size and strength and are placed in a circle with the polarity alternating.

[0026] In a preferred embodiment, the permanent magnets may be made of neodymium. The strong permanent magnetic forces which the neodymium material can produce have been found to complement the relatively thin coil winding tracks which are provided in a helical manner on the one or more surfaces of the circuit board and the magnetic fluxes to be generated thereby.

[0027] The permanent magnets may highly advantageously be provided on a magnetic disc as local magnetic alternatingly polarised segments. In this case, non-magnetised spaces may be present between the segments, in particular of less than 1 mm, more particularly of approximately 0.5 mm.

[0028] It has been found that if such a magnetic disc is made of neodymium, a thickness of less than 1.5 mm, in particular a thickness of less than 1 mm, for example 0.8 mm, is already sufficient, in combination with the relatively thin coil winding tracks provided on the one or more surfaces of the circuit board in a helical manner, to actuate the impeller so that it reaches high rotary speeds in a silent way and using relatively little energy. In addition, such a relatively thin magnetic disc advantageously makes it possible to keep the impeller lightweight and thin. The small dimensions and limited weight of the magnetic disc then advantageously contribute to maintaining the important balance of the impeller and preventing it from being rapidly disturbed.

[0029] The magnetic disc may, for example during assembly, be click-fitted to the impeller easily and quickly by means of a complementary click-fit recess.

[0030] If the impeller is made of plastic, it is advantageously also possible to injection-mould the plastic material for the impeller directly around the magnetic disc. In one embodiment, the impeller blades of the impeller are then directly moulded onto an outer peripheral edge of the magnetic disc, while a central bearing part of the impeller is directly moulded onto an inner peripheral edge of the magnetic disc. The thickness of the impeller blades and of the central bearing part can then advantageously be kept smaller than or equal to the thickness of the magnetic disc, so that the total installation space of the impeller and the associated set of permanent magnets is limited to the thickness of the magnetic disc.

[0031] A significant advantage of the magnetic disc made in one piece is that it is able to provide stiffness to the impeller and can be a structurally supporting part, instead of the impeller forming the structural part.

[0032] One of the further preferred embodiments relates to the provision of a so-called back iron as a magnetic flux conductor on the rear side of the multipolar magnetic disc, i.e. on the side of the magnetic disc facing away from the circuit board. During excitation of the axial flux motor, it is then advantageously possible for an efficient flow of magnetic flux to occur from the coils to the opposite alternating polarised permanent magnet segments in the impeller. This generated magnetic flux then flows through the polarised permanent magnet segments to the rear side of the magnetic disc, where it can easily and virtually without loss deflect via the back iron to the adjacent alternating polarised permanent magnet segments, and from there deflect back to the rear side of the circuit board via the coil units opposite to the former. The back iron is configured to conduct the magnetic flux well on the rear side of the multipolar magnetic disc. As a result thereof, resistance of the deflection of the magnetic flux to the adjacent alternating polarised permanent magnet segments on this rear side of the magnetic disc is reduced, thus making the axial flux motor more efficient.

[0033] In a further preferred embodiment, a magnet-amplifying / attracting element may be provided around the central rotation axis on an outer surface of the circuit board, which is configured to pull the set of permanent magnets connected to the impeller towards the circuit board in an axial direction. The attractive force of the permanent magnets in the direction of the magnet-amplifying / attracting element achieves the advantage that the impeller will hardly vibrate, if at all, in an axial direction, which benefits efficiency and is also positive with regard to noise reduction.

[0034] Another advantage is the fact that when the constant attractive force of the permanent magnets on the magnet-amplifying / attracting element exceeds the force of gravity of the complete impeller, including the set of permanent magnets connected thereto, the impeller can also be kept in position without having to be physically axially blocked and may, for example, be fitted upside down without falling down while still being able to rotate. The advantage of freely suspending the impeller and the set of permanent magnets connected thereto upside down due to the action of the magnetic attractive force under the circuit board is that the impeller will then hardly vibrate, if at all, during operation. It has furthermore been found that the fan can then be even more efficient than when the impeller is placed above the circuit board and the force of gravity on the impeller is directed in the direction of the circuit board.

[0035] As a result of the fact that, due to the provision of the magnet-amplifying / attracting element, an axial retaining force is continuously exerted in the direction of the circuit board by the set of permanent magnets connected to the impeller, a physical locking of the impeller by means of, for example, spring rings or clips is no longer strictly necessary. This saves an assembly operation and a component which would otherwise have been required. In addition, the impeller can then advantageously be configured so as to be freely releasable from the bearing. Thus, a situation is created where the impeller can easily be removed from the circuit board by anyone, for example in order to quickly clean off dust. As a result thereof, maintenance and replacement can also easily be effected, which is a significant improvement from the point of view of durability. If desired, the impeller may obviously still be additionally secured, for example in order to ensure that the impeller does not become detached in case of large shocks and axial accelerations. For this purpose, an easily removable securing cap may already suffice.

[0036] The magnet-amplifying / attracting element may be provided on, for example, a rear side of the circuit board which faces away from the impeller. In this case, it has advantageously been found that the presence of the circuit board does not prevent a sufficient degree of magnetic attractive force of the set of permanent magnets in the direction of the magnet-amplifying / attracting element.

[0037] One of the preferred embodiments relates to the arrangement of a so-called back iron as a magnet-amplifying / attracting element to the rear side of the multilayered circuit board at the location of the multilayered coil winding track coils printed thereon, i.e. on the other side of the multilayered circuit board to that on which the magnetic disc connected to the impeller is situated. During the excitation of the axial flux motor, a magnetic flux occurs from the coils to the opposite magnet poles of the impeller. This flux flows through the magnetic disc to the other side of the set of magnets and this flux is subsequently deflected by the magnetic disc to the adjacent magnet poles and from there back to the rear side of the board via the coils which are opposite the former. By arranging the back iron on this rear side of the board, resistance to the deflection of the magnetic flux towards the adjacent coils on this rear side of the board is reduced, thus making the axial flux motor more efficient.

[0038] The magnet-amplifying / attracting element may also be provided on a front side of the circuit board which faces towards the impeller. In this case, it has advantageously been found that this has a similar effect with regard to keeping the impeller in place as it would have to attach the magnet-amplifying / attracting element on the rear side, but the added advantage that was found was that the axial air gap between the set of permanent magnets and the circuit board can then be increased slightly, compared to installation on the rear side - certainly up to 2 millimetres - instead of approximately 1-1.5 millimetres otherwise. This has the significant advantage that, in particular with relatively large fans having larger / heavier sets of permanent magnets, a small deviation in the parallel positioning between the circuit board (with the coil winding tracks provided on the one or more surfaces thereof) and the impeller (with the set of permanent magnets connected thereto) will not lead to the latter running out of true.

[0039] In addition, the provision of the magnet-amplifying / attracting element may in addition contribute advantageously to the magnetic fluxes which are generated during excitation of the coil units on or incorporated in the circuit board being amplified, since less dispersion of the induced magnetic fields has to take place. Due to this amplification of the magnetic fields, in combination with the axially directed magnetic attractive forces which are distributed symmetrically around the central rotation axis, the fan will run virtually vibration-free and very smoothly. In addition, due to this amplification of the magnetic fields, the axial flux motor of the fan will start easily and quickly.

[0040] Also, the fan can now rotate across a larger range of lower and higher revolutions. A feedback to a control unit, such as a control microprocessor, will also be stronger, so that the control unit is able to determine the position of the set of permanent rotor magnets installed in the impeller with respect to the stator coils on or incorporated in the circuit board more accurately and more quickly. This makes it possible for the actuation to be efficient.

[0041] In addition, empirical tests have shown that a clear space between the circuit board and the permanent magnets in the impeller can be less critical. Where in the past, for example, 0.5 millimetres + / - 0.2 were necessary to allow the impeller to rotate, now a clear space of more than 1.0 millimetre is sufficient. This renders the assembly and production process less critical.

[0042] In a preferred embodiment, the magnet-amplifying / attracting element is at least partly made of ferrite. Due to the high electrical resistance of ferrite, so-called eddy current losses can advantageously be kept small as a result, meaning that the provision of the magnet- amplifying / attracting element does not have to be to the detriment of the efficiency of the fan. In a further preferred embodiment, the magnet-amplifying / attracting element is at least partly made of soft ferrite. Such soft ferrite is characterized by a low coercivity. As a result thereof, the magnet-amplifying / attracting element is always able to easily and very quickly change its magnetisation during operation of the fan and serve as a conductor for the generated magnetic fields during operation which will be produced at an alternating speed by the respective coil winding tracks on the one or more surfaces of the circuit board. In this case, the soft ferrite preferably contains nickel, zinc and / or manganese compounds. The soft ferrite is advantageously not suitable to render the magnet-amplifying / attracting element permanently magnetic. It has a high magnetic permeability, as a result of which it can readily conduct the magnetic fields generated by the coil winding tracks during operation and as a result of which it is reliably attracted by the set of permanent magnets both when operating and when stationary in order thus to keep the impeller in place. As soon as the supply of electricity to the coil winding tracks stops, remanent magnetism in the magnet- amplifying / attracting element will hardly occur, if at all, due to the low coercivity. As soon as the coil winding tracks are supplied with electricity again, the magnetisation of the magnet- amplifying / attracting element will easily and very quickly be able to change direction due to the low coercivity, without a large degree of energy loss resulting from hysteresis.

[0043] In a variant, the magnet-amplifying / attracting element may also at least partly be made of permanently magnetic ferrite materials.

[0044] The magnet-amplifying / attracting element may advantageously be formed by a flexible film comprising the ferrite material thereon or therein, which film may be attached to the circuit board in particular by means of a self-adhesive layer. This flexible film may then, for example, have a thickness of less than a few tenths of a millimetre, and in particular only be approximately 0.08 millimetres thick. The flexible film may then have a ring shape, with the centre of this ring corresponding to the central rotation axis.

[0045] In a further preferred embodiment, the circuit board may comprise a central discshaped stator portion on which the juxtaposed coil units provided around the central rotation axis are provided as guide tracks on the one or more surfaces of the circuit board, and wherein the circuit board may comprise bearing arms extending from the central disc-shaped stator portion outwards in a lateral direction between which ventilation openings have been left clear. Advantageously, contact tracks may then be provided as guide tracks on one or more surfaces of these bearing arms which connect to the coil winding tracks for power and control and which extend in a lateral direction beyond the outer diameter of the impeller. The circuit board has thus been given a weight-saving and material-saving design which advantageously makes it possible to achieve an optimum axial air flow brought about by the impeller. In a further preferred embodiment, the bearing may comprise a bearing pin which is fixedly connected to the circuit board and extends from the latter in an axial direction towards the impeller. The impeller can then rotate freely about the fixedly arranged bearing pin. To this end, the impeller preferably comprises a central bearing recess which extends in an axial direction and is configured to be mounted rotatably over the bearing pin. The impeller is then preferably made of a plastic having friction-reducing sliding properties, such as polyacetal (POM) and / or PTFE-containing plastic. As a result thereof, no separate bearing has to be installed.

[0046] The bearing recess in the impeller may be blind and / or may be designed with a very low tolerance, in particular a tolerance of a hundredth of a millimetre, fitting around the bearing pin so as to be able to rotate freely, with a lubricant being enclosed in the bearing recess by positioning the impeller with its bearing recess over the bearing pin. This lubricant then not only helps to make the impeller run more smoothly, but can also ensure that the impeller is held in place on the bearing pin in an axial direction by an additional force. If the fit between the bearing recess and the bearing pin is made sufficiently small, for example with a tolerance in the order of a few hundredths of millimetres, the lubricant will then be able to ensure that the bearing recess automatically creates a vacuum over the bearing pin if the impeller is moved in an axial direction away from the circuit board. The embodiment with the blind bearing recess also makes it possible to use the bearing pin as a spacer to define a clear distance between the circuit board on the one hand and the impeller containing the set of permanent magnets on the other hand. This can then easily be achieved by making the part of the bearing pin protruding on the side of the impeller of the circuit board just slightly longer than the depth of the bearing recess in the impeller.

[0047] The bearing pin may, for example, be made of metal, in particular brass, bronze or stainless steel. In this case, brass and bronze offer the possibility of being soldered to the circuit board, so that the bearing pin can reliably be secured on the circuit board in a position at right angles to the circuit board.

[0048] The circuit board may be provided with a central installation through-hole at the location of the central rotation axis, with the bearing pin having a proximal end which is configured to extend through the installation hole. The proximal end may then be attached in the installation hole in the circuit board, for example, by means of pressing.

[0049] Preferably, the bearing pin may then comprise a laterally protruding positioning flange which is configured to bear against the circuit board. This positioning flange may then help the bearing pin to position itself correctly at right angles to the plane of the circuit board, and may additionally offer a larger surface area for additional ways of attachment, for example gluing or soldering. In this case, the positioning flange may be configured in particular to bear against the front side of the circuit board facing towards the impeller. This then ensures that the positioning flange can also serve as a spacer in order to define a minimum clear distance between the circuit board on the one hand and the impeller containing the set of permanent magnets on the other hand.

[0050] The circuit board, for example comprising a resin-impregnated woven glass cloth as supporting dielectric, can be used as a single-sided PCB (printed-circuit-board) and then has a single conductive layer on top thereof, for example formed by copper tracks as guide tracks, which is situated on top of the supporting dielectric. However, the circuit board may also be used as a double-sided PCB and then has two conductive layers separated by an insulating supporting dielectric. Such a double-sided PCB is additionally provided with connectors, for example so-called Plated Through Holes (PTH), i.e. copper-plated holes which are used in circuit boards to transmit signals to other layers and thus to establish connections between the top and bottom side and vice versa.

[0051] In a preferred embodiment of the invention, the circuit board is configured to have several layers, with the guide track of each coil unit comprising several of the coil winding tracks running helically around its own axis, and wherein the several coil winding tracks of each coil unit are provided one above the other on the respective layers of the circuit board. Such a multilayered PCB then has three or more conductive layers which are separated from each other by insulating support layers. In this case, connectors which extend through the layers of the circuit board may again be provided, such as the PTHs, in order to bring about connections from layer to layer.

[0052] Preferred embodiments with at least six, eight or ten, but also twenty layers of coil winding tracks are possible. This greatly increases the magnetic force in order to cause the impeller to rotate via the axial flux motor for use as a powerful radiator-fan unit and renders the axial flux motor in this application significantly more efficient, so that it will use less electricity.

[0053] The guide tracks, for example copper tracks, may be provided on the one or more layers of the circuit board by means of known techniques, such as printing and / or milling or etching techniques. In this case, the guide tracks of the stator coils can be provided very accurately and thus be kept well insulated from each other and from other components or tracks on the circuit board. The thickness of the copper tracks may be, for example, approximately 70pm. This makes relatively high current strengths possible and allows for a good heat dissipation. Preferably, multiples of three coil units, in particular six or nine coil units, are provided as guide tracks on the one or more surfaces of the circuit board. This makes it possible to measure the rotation of the impeller without an external sensor, and to actuate the coil units in such a way that the electrical energy can be converted in an optimum manner into usable torque by the coil units. In addition, this makes a 3-phase system possible.

[0054] As an alternative or in addition hereto, it is also possible to provide a Hall sensor which is configured to detect the strength of the generated magnetic veld and can help to optimize the actuation of the coils by means thereof. On the other hand, a sensor which is configured to determine the position of the permanent magnetic poles may contribute to an efficient actuation of the coils, in particular also across a larger rotational speed ranges.

[0055] Many combinations of numbers of coil units and permanent magnets are possible. In one preferred embodiment, the set of permanent magnets may comprise eight or twelve, and the set of coil units may comprise six or nine. In this way, an optimum is achieved between available space, vibration-free and quiet operation and efficiency.

[0056] The coil units which are provided as guide tracks on the one or more layers of the circuit board may preferably have the shape of a triangle with rounded transitions. This is then preferably combined with permanent magnets which also have the shape of a triangle. By matching the shapes, it will be possible to transmit torque efficiently and to generate as little torque as possible in other (non-useful) directions. This reduces vibrations and losses. In addition, with this pattern, the space is used in an optimum manner and the number of guide tracks is maximized. This increases the conductive surface and helps to improve cooling.

[0057] Further preferred embodiments of the invention are defined in the dependent subclaims.

[0058] DESCRIPTION OF THE DRAWINGS

[0059] The invention will be explained below by means of a non-limiting example with reference to the attached drawings, in which:

[0060] - Fig. 1 shows a perspective of a preferred embodiment of the fan according to the invention;

[0061] - Fig. 2a shows a cross section of Fig. 1;

[0062] - Fig. 2b shows a partial magnification of Fig. 2;

[0063] - Fig. 3 shows the bearing pin in Fig. 2;

[0064] - Figs. 4a-b show a top view and a cross section of the magnetic disc in Fig. 2;

[0065] - Fig. 5 shows an example of the layered structure of the circuit board from Figs. 1-2; - Figs. 6a-f show six layers of the circuit board in Figs. 1 and 2 with coil winding tracks of six coil units provided thereon;

[0066] - Fig. 7 shows a variant with a circuit board comprising nine flat coil units;

[0067] - Fig. 8 shows a variant comprising a 12-pole magnetic disc;

[0068] - Fig. 9 shows a variant comprising a bearing pin which also serves as a spacer;

[0069] - Fig. 10 shows a variant comprising a vibration damper;

[0070] - Figs. 11a-f show variants of very thin impellers with magnet discs secured therein for axial flux motors;

[0071] - Fig. 12a-b show two variants of a thin impeller with a magnetic disc secured therein and fitted to a circuit board with a magnet-amplifying / attracting element provided either on a front side or provided on a rear side of the circuit board; and

[0072] - Fig. 13 shows an embodiment with a double impeller on either side of a circuit board.

[0073] Figs. 1 and 2 show a circuit board P. The multilayered circuit board P here comprises five supporting so-called prepreg layers PI1-PI5 of an insulating dielectric material. See Fig. 4. Six layers 11-16 of flat copper tracks are printed onto the bottom and / or top sides of the supporting layers PI1-PI5 of the circuit board P as guide tracks. A surface-finishing layer la, a soldering layer Is and a protective coating layer Ic are furthermore provided on the top and bottom sides of the circuit board P. In addition, it can be seen that the copper tracks of the various layers 11-16 are connected to each other via electrically conductive connectors PTH which extend in a transverse direction through the circuit board P. The circuit board P comprises a central disc-shaped stator portion Ps and four bearing arms Pd. The bearing arms Pd extend outwards in a substantially radial direction. Between each pair of bearing arms Pd, there is a ventilation opening VO.

[0074] In the centre of the central disc-shaped stator portion Ps of the circuit board P, an installation through-hole is provided, through which a shaft part LPa of a bearing pin LP extends straight in a downward direction. The bearing pin LP forms a central rotation axis and extends in an axial direction x which is at right angles to the plane of the circuit board P. On its proximal end, the bearing pin Lp is provided with a laterally protruding positioning flange LPf. See also Fig. 3. The positioning flange LPf bears against a top side of the circuit board P. The bearing pin LP is made of copper or bronze, and is fixedly soldered to the circuit board P by means of the positioning flange LPf. On the bottom side of the circuit board P, the shaft part LPa of the bearing pin Lp protrudes along a length L1.

[0075] A plastic impeller W is provided which comprises a central impeller shaft Ws in which a bearing recess LU extending in an axial direction is left open. The bearing recess LU has a length L2 and is configured to be pushed rotatably over the bearing pin LP with a small tolerance of approximately + 1 / 100thmillimetre. From the central impeller shaft Ws, the impeller W furthermore comprises a cap-shaped impeller part Wk. The cap-shaped impeller part Wk comprises a peripheral wall from which impeller blades Wb extend outwards in a substantially radial direction.

[0076] On the side of the circuit board P, a magnetic disc MS is attached in the cap-shaped impeller part Wk. See also Fig. 4. By means of a click-fit connection, the magnetic disc MS is in this case secured behind a click-fit edge SR of the impeller W projecting inwards in a radial direction. The magnetic disc MS consists of a 1 millimetre thin neodymium magnetic disc with twelve permanent magnet segments N-S thereon. The magnet segments N-S are alternately polarized north-south, viewed in an axial direction. The magnetic disc MS is parallel with the circuit board P. Between the bottom side of the circuit board P and the top side of the magnetic disc MS, an air gap Tr has been kept clear.

[0077] Flat copper tracks are printed onto the five supporting layers PI1-PI5 of the circuit board P as guide tracks. On the central disc-shaped stator portion Ps, the guide tracks form six stator coil units SPe1-SPe6. See Figs. 6a-f. Guide tracks may also be provided on the bearing arms Pd which may then function as contact paths which are joined to the stator coil units SPe.

[0078] Viewed from above, the six stator coil units SPe1-SPe6 are all triangular in shape and arranged so as to be juxtaposed around the central rotation axis x. See Figs. 6a-f. Here, each stator coil unit SPe1-SPe6 comprises six layers 11-16 positioned one above the other. Each layer 11-16 of every coil unit SPe1-SPe6 comprises a coil winding track running helically around its own stator coil unit axis. The various layers 11-16 in Figs. 6a-f are shown juxtaposed one by one. The axes of the stator coil units SPe1-SPe6 all run parallel to the central rotation axis, that is to say at right angles to the plane of the circuit board and in an axial direction x.

[0079] The stator coil units SPe1-SPe6 form part of an axial flux motor and are excited according to a specific pattern during operation.

[0080] In one of the preferred embodiments, the coil units are electrically excited in three groups according to a pattern of a sinus curve over 360 degrees, and each group of coil units is in each case 120 degrees offset with respect to the other coil units, evenly distributed around the central rotation axis.

[0081] This has the advantage that generated magnetic fluxes are always able to cancel each other out due to the coil units SPe being supplied with electricity.

[0082] The actuation according to the sinus curve has the additional advantage that less vibration occurs with respect to square-wave voltage actuated coil units.

[0083] One of the preferred embodiments is a 3-phase H-bridge in which the sinus curve is generated by quickly switching electronic transistor switches.

[0084] Preferred embodiments then consist of, for example, the six coil units SPe1-SPe6 as illustrated in Figs. 6a-f, consisting of three groups of two coil units each, wherein the six coil units are offset in diametrically opposite pairs SPe1+SPe4, SPe2+SPe5 and SPe3+SPe6 in each case by 120 degrees with respect to the other coil unit pairs. In this embodiment, the magnetic disc MS is then preferably configured as having eight poles as permanent magnet segments N-S, as is illustrated in Fig. 4.

[0085] In another preferred embodiment, as is illustrated in Fig. 7, nine coil units SPe may also be provided, with each of the three groups then being configured as having three coil units SPe, with each coil unit SPe within a group being offset by 120 degrees with respect to the other coil unit SPe, and with all coil units SPe being evenly distributed around the central rotation axis. In this case, nine copper guide tracks are printed onto the circuit board P as coil units SPe and run in a helical manner. Furthermore, it can be seen that the shape which has been chosen for each individual coil unit SPe now resembles more that of a square with unequal sides.

[0086] In this other preferred embodiment, the rotor-magnetic disc MS can then preferably be configured as having twelve poles as permanent magnet segments N-S, as is illustrated in Fig. 8.

[0087] On the top side of the circuit board P, around the central rotation axis, a soft ferrite- containing film is affixed as magnet-amplifying / attracting element FS. This can be seen in both Figs. 1 and 2 and serves to pull the magnetic disc MS with the impeller W attached thereto in an axial direction x towards it, and to help amplify the magnetic fields generated by coil units SPe1-SPe6. The axial tensile forces also ensure that the impeller W will not fall down without a further physical locking device, but remains securely in place. The lack of a physical locking device then has the further advantage that the impeller can freely be removed at any desired point in time.

[0088] Fig. 9 shows a variant which differs in particular in that the shaft part LPa and the positioning flange LPf of the bearing pin LP are situated on the side of the impeller W. In this case, the positioning flange LPf bears against a bottom side of the circuit board P and can consequently also serves as a spacer, since the central impeller shaft Ws is now consequently delimited upwards in an axial direction x by the circuit board P. It can thus be ensured that a sufficiently large clear distance Tr remains clear between the impeller W and the magnetic disc MS connected thereto, respectively, on the one hand, and the circuit board P on the other hand. Now, the positioning flange LPf of the bearing pin LP not only bears against the bottom side of the circuit board P, but now also has an upwardly projecting fitting part LPm, by means of which it is securely click-fitted in the installation hole provided in the circuit board P.

[0089] It can furthermore be seen in Fig. 6 that the shaft part LPa of the bearing pin Lp projects from the impeller W on the bottom side and that a securing cap BD is fastened thereon as an additional locking device for the impeller W so that the latter does not fall from the circuit board P even under extreme loads.

[0090] Fig. 10 shows that a vibration damper TD is fitted to the rear side, here the bottom side, of the circuit board P. In this case, the vibration damper TD is configured as a rubber disc provided with ring-shaped ridges. In a fitted position, the vibration damper may come to lie against a housing part which accommodates the fan.

[0091] Fig. 11a shows a very thin variant of the impeller W. Plastic material of an impeller W for an axial flux motor is now directly moulded onto and surrounds neodymium material of a magnetic disc MS. A cap-shaped impeller part Wk is now completely moulded onto the magnetic disc MS. The impeller W now has approximately twice the thickness of the magnetic disc MS secured therein, due to the fact that the thickness of the bottom of the cap-shaped impeller part Wk approximately corresponds to that of the magnetic disc MS, and due to the fact that the impeller blades Wb are smaller or equal to the thickness of the magnetic disc MS plus the thickness of the bottom of the cap-shaped impeller part Wk.

[0092] Fig. 11b shows how a saving in weight has been achieved by replacing the bottom of the cap-shaped impeller part Wk by moulded-on spokes. These spokes between the impeller blades Wb and the central impeller shaft WS provide sufficient strength to the impeller W and still offer a degree of protection to the magnetic disc MS. As a result thereof, the impeller W is still approximately twice as thick as the magnetic disc MS mounted therein.

[0093] Fig. 11c shows the variant from Figs. 11a and 11b, but entirely without a bottom or spokes. As a result thereof, the impeller blades Wb and the central impeller shaft WS are completely separate from one another. This makes the impeller even more lightweight.

[0094] Fig. 11 d also shows a very thin variant of the impeller W. Here, the magnetic disc MS is provided with internal and external click-fit fingers which are designed for click-fitting the magnetic disc MS in between. The impeller W is again approximately twice as thick as the magnetic disc MS mounted therein, due to the fact that the thickness of the click-fit fingers approximately corresponds to that of the magnetic disc MS.

[0095] Fig. 11e shows a variant in which the impeller blades Wb are connected to each other by a connecting ring at their free ends.

[0096] Finally, Fig. 11f shows a variant for a very thin impeller W for an axial flux motor, the surfaces of the impeller blades of which are parallel to the central rotation axis. As a result thereof, the impeller is configured to distribute air in the plane over a circuit board, which may be advantageous, for example, with applications comprising circuit boards which are not or cannot be provided with ventilation openings. Fig. 12a shows a variant of a slightly differently configured circuit board P which is provided with ventilation openings VO. In this case as well, a bearing pin LP is fixedly connected at a central position to a central disc-shaped stator portion Ps of the circuit board P which is supported by bearing arms Pd of the circuit board P. The bearing pin LP extends downwards freely. A very thin impeller W with a magnetic disc MS secured therein is pushed over the bearing pin P. The impeller W in this case comprises a central impeller shaft Ws which forms an integral part of impeller blades Wb via an impeller socket Wk. In the impeller shaft, a blind hole is provided as a bearing recess which can be pushed over the bearing pin LP with a very tight fit. Just before it is pushed over the latter, an amount of lubricant is provided in the blind hole. As is the case with the embodiment from Fig. 1, on the side of the circuit board P facing away from the impeller W, in this case the top side, a soft ferrite- containing thin disc is provided as magnet-amplifying / attracting element FS.

[0097] Fig. 12b shows a variant in which the bearing pin LP in this case extends freely upwards. The very thin impeller W with the magnetic disc MS fitted therein is now pushed over the bearing pin LP from above. In contrast with the embodiment from Figs. 1 and 11a, this time the soft ferrite-containing thin disc as magnet-amplifying / attracting element FS is provided on that side of the stator portion Ps of the circuit board P which faces the impeller W.

[0098] Fig. 13 shows a variant according to the invention wherein advantageously a double set of impellers W1 , W2 is used. In this case, a common bearing pin LP is used which protrudes on either side by means of a shaft part of a circuit board P, so that an impeller W can be pushed over both shaft parts which is provided with a magnetic disc MS. The juxtaposed coil units provided in or on one or more surfaces of the circuit board P around the position of the bearing pin LP as flat guide tracks can then advantageously serve a double function for simultaneously causing both impellers W1, W2 to rotate. Then, a magnet- amplifying / attracting element FS no longer has to be provided, the magnet discs on either side of the circuit board P are perfectly able to attract each other and keep each other balanced.

[0099] The embodiment of the impellers W1 , W2 illustrated in Fig. 13 is particular because here, viewed in an axial direction, the height of the impeller blades Wb1, Wb2 and the height of the central bearing parts Ws1 , Ws2 are advantageously equal to the thickness of the magnetic disc MS. As a result thereof, the total installation space of each impeller and the magnetic disc MS connected thereto can remain very thin.

[0100] Many variants are possible in addition to the illustrated and described embodiments. Thus, for example, other materials and / or dimensions and / or proportions may be used. Instead of a neodymium magnetic disc, it is also possible to use a ferrite magnetic disc. By making these of a slightly thicker design, for example approximately 3 mm, it is possible to produce sufficiently strong permanent magnetic forces to be able to cooperate well and reliably with the coil units incorporated in the circuit board. It should furthermore be noted that for some applications, a single-layer circuit board with helical flat guide tracks as coil units provided on the front and / or rear side thereof may also suffice.

[0101] The fan according to the invention can be used in all kinds of locations and for all kinds of uses, for example as micro-fan for a laptop, PC or other type of computer, in which case the axial flux motor can then advantageously be incorporated with the circuit board which is already present in the computer anyway. A significant additional advantage is then that after the computer has been opened, the impeller can simply be removed from the circuit board in order to quickly be cleaned. Such microfans are known for gathering a lot of dust over the course of time and they then have to increase the rotary speed in order to be able to still provide a sufficient degree of cooling to the computer. However, the invention can also be used very successfully as a fan in sanitary facilities. Nowadays, such toilet and bathroom fans are often known for producing a large amount of noise. For this application, the circuit board with impeller may then, for example, be placed in a suitable housing which facilitates fitting in or connection to a ventilation duct. For wet applications, the circuit board may, in addition, be provided with a suitable waterproof coating which is able to ensure the coil winding tracks printed thereon are not adversely affected or short-circuit. It is noted that for such wet applications, the neodymium magnetic disc is already eminently suitable as it is not susceptible to corrosion. Other possible applications are heat pumps, air-conditioning units, heat-recovery fans and all kinds of other applications in and around houses and buildings where compactness, efficiency and silent operation are of great importance.

[0102] It will be clear that these various adjustments and modifications of the present preferred embodiments are possible without departing from the scope of protection of the invention, and that such adjustments and modifications are covered by the attached claims.

Claims

CLAIMS1. Fan of the type having an axial flux motor, comprising:• an impeller support / suspension with a bearing which defines a central rotation axis extending in an axial direction (x);• an impeller (W) which is rotatably drivable around the central rotation axis with respect to the impeller support / suspension; and• an electric motor for rotatably driving the impeller (W), wherein the electric motor is an axial flux motor, with a set of several juxtaposed coil units (SPe) provided around the central rotation axis as a stator which are connected to the impeller support / suspension, and with a set of several juxtaposed permanent magnets (N-S) provided around the central rotation axis as a rotor which are connected to the impeller (W) and which are directed axially with alternating polarity and which are each situated in a plane at right angles to the central axis at a clear distance (Tr) from and parallel to the coil units (SPe), characterized in that the impeller support / suspension is formed by a circuit board (P) which is situated in a plane at right angles to the central rotation axis, wherein the juxtaposed coil units (SPe) provided around the central rotation axis are provided as guide tracks on the circuit board (P), and wherein the guide track of each coil unit (SPe) forms at least one coil winding track running helically around its own axis, which extends parallel to the central rotation axis of the bearing, on a surface of the circuit board (P).

2. Fan according to one of the preceding claims, wherein the permanent magnets (N-S) are made of neodymium.

3. Fan according to claim 1 or 2, wherein the permanent magnets (N-S) are provided on a magnetic disc (MS) as local magnetic alternating polarised segments, in particular a magnetic disc having a thickness of less than 1.5 mm, more particularly of less than 1 mm.

4. Fan according to claim 2 or 3, wherein a maximum height of the impeller (W) in an axial direction is smaller than or equal to a thickness of the magnetic disc (MS), in particular wherein impeller blades (Wb) of the impeller (W) are attached to a peripheral edge of the magnetic disc (MS) while a central impeller shaft (Ws) of the impeller (W) is attached to an inner peripheral edge of the magnetic disc (MS).

5. Fan according to one of the preceding claims, wherein a magnet-amplifying / attracting element (FS) is provided around the central rotation axis on an outer surface of the circuit board (P) and is configured to pull the set of permanent magnets (N-S) connected to the impeller (W) towards the circuit board (P) in an axial direction (x).

6. Fan according to claim 5, wherein the magnet-amplifying / attracting element (FS) is at least partly made of ferrite material, in particular soft ferrite material.

7. Fan according to claim 6, wherein the magnet-amplifying / attracting element (FS) is formed by a flexible film comprising the ferrite material thereon or therein, which film is attached to the circuit board (P) in particular by means of a self-adhesive layer.

8. Fan according to one of the preceding claims, wherein the circuit board (P) comprises a central disc-shaped stator portion (Ps) on which the juxtaposed coil units (SPe) provided around the central rotation axis are provided as guide tracks, and wherein the circuit board (P) comprises bearing arms (Pd) extending from the central disc-shaped stator portion (Ps) outwards in a lateral direction between which ventilation openings (VO) have been left clear and on which bearing arms (Pd) contact tracks are provided as guide tracks which connect to the coil winding tracks for power and control and which extend in a lateral direction beyond an outer diameter of the impeller (W).

9. Fan according to one of the preceding claims, wherein the bearing comprises a bearing pin (LP) which is fixedly connected to the circuit board (P) and extends from the latter in an axial direction towards the impeller (W), wherein the bearing pin (LP) in particular is made of a non-ferrite material, such as copper, stainless steel or bronze, and wherein the bearing pin (LP) is more particularly also configured as a spacer to define a clear distance between the circuit board (P) on the one hand and the impeller (W) containing the set of permanent magnets (N-S) connected thereto on the other hand.

10. Fan according to claim 9, wherein the impeller (W) delimits a central bearing recess (LU) which extends in an axial direction (x) and is configured to be mounted rotatably over the bearing pin (LP), in particular wherein the impeller (W) is made of a plastic with friction-reducing properties, such as polyacetal (POM) and / or PTFE-containing plastic.

11. Fan according to claim 10, wherein the bearing recess (LU) in the impeller (W) is blind and / or designed with a very small tolerance, in particular a tolerance of less than a fewhundredths of a millimetre, fitting around the bearing pin (LP) so as to be able to rotate freely, with a lubricant being enclosed in the bearing recess (LU) by positioning the impeller (W) with its bearing recess (LU) over the bearing pin (LP).

12. Fan according to one of the preceding claims 9-11 , wherein the circuit board (P) is provided with a central installation through-hole at the location of the central rotation axis, wherein the bearing pin (LP) has a proximal end (LPm) which is configured to extend through the installation hole.

13. Fan according to one of the preceding claims 9-12, wherein the bearing pin (LP) comprises a laterally protruding positioning flange (LPf) which is configured to bear against the circuit board (P), wherein the positioning flange (LPf) is in particular configured to bear against the side of the circuit board (P) facing towards the impeller in order to also serve as a spacer in order to define a minimum clear distance (Tr) between the circuit board (P) on the one hand and the impeller (W) containing the set of permanent magnets (N-S) on the other hand.

14. Fan according to one of the preceding claims, wherein the circuit board (P) comprises several layers, and wherein the guide track of each coil unit (SPe) comprises several of the coil winding tracks running helically around their own axis, and wherein the several coil winding tracks of each coil unit (SPe1-SPe6) are provided one above the other on the respective layers of the circuit board (P).

15. Fan according to one of the preceding claims, wherein the set of several juxtaposed permanent magnets (N-S) provided around the central rotation axis comprises eight or twelve permanent magnets (N-S), and wherein the set of several juxtaposed coil units (SPe) provided around the central rotation axis comprises six or nine coil units (SPe).

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