TITLE OF THE INVENTION

A BLDC motor driven ceiling fan

FIELD OF INVENTION

This invention relates to a BLDC motor driven celing fan.

This invention also relates to a control unit for a BLDC motor.

BACKGROUND OF INVENTION

Ceiling fans are generally induction motor driven or BLDC (Brush Less Direct Current) motor driven. BLDC motor driven ceiling fans are preferred as they have advantages like reduced power consumption, higher performance and controllability and increased life. A BLDC motor driven ceiling fan includes a control unit to sense the rotor polarity and energise corresponding set of coils in the stator windings. The control unit comprises a passive power factor correction (PFC) circuit based electronic controller incorporated in a printed circuit board (PCB), a sensor magnet and hall sensors. The PCB comprising the electronic controller of the BLDC driven ceiling fan is potted in a protective casing and disposed within the upper canopy of the fan. The electronic controller is mounted at the upper end of the down rod (hanger rod) of the fan using hardware fasteners like nuts and bolts. The sensor magnet is disposed within the motor housing around the lower end of the fan shaft protruding down into the motor housing and fixed to the upper inner surface of the upper end shield of the motor housing. The hall sensors are disposed within the motor housing below the sensor magnet and fixed to the lower end of the fan shaft . The electronic controller is supplied with the fan as a separate part and the customer has to fix it to the down rod of the fan during installation of the fan. The customer also has to connect the hall sensors to the electronic controller using lead wires. All this is inconvenient and troublesome and increases the installation time. Long lead wires are required for the connection of the hall sensors to the

electronic controller. The motor housing and fan shaft and down rod are required to be large enough to accommodate the sensor magnet and large number of lead wires, respectively. AU this increases the cost of the fan and also makes it bulky and heavy. The sensor magnet and hardware fasteners and the protective casing of the electronic controller also increase the cost of the fan. Use of hardware fasteners to fit the electronic controller to the down rod increases the installation time of the fan and can also cause fitment errors and reduce the reliability of the fan. The upper end of the down rod of the fan is heavy because of the electronic controller fixed to it. Unless the electronic controller is carefully mounted and the fasteners are properly tightened, the electronic controller will experience excessive vibrations which can reduce the life of the electronic controller and render the operation of the fans noisy. During assembly of the motor alignment of the sensor magnet and rotor magnet also increases the manufacturing time of the motor. Fitment of the electronic controller using hardware components and connection of the hall sensors to the electronic controller by the customer render the fan non-user friendly.

OBJECTS OF INVENTION

An object of the invention is to provide a BLDC motor driven ceiling fan which is simple in construction and which comprises a control unit without the sensor magnet and which is fully located within the motor housing and which, besides possessing the various advantages of a BLDC motor driven ceiling fan, also has further advantages.

Another object of the invention is to provide a BLDC motor driven ceiling fan which comprises reduced number of components, which reduces assembly and installation time, which is compact, free from fitment errors, reliable and user friendly, which is noise free in operation and which reduces the cost considerably.

Another object of the invention is to provide a control unit for a BLDC motor, which is simple in construction and which is without the sensor magnet and is fully located within the motor housing.

Another object of the invention is to provide a control unit which is compact and reduces the cost considerably.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention there is provided a BLDC motor driven ceiling fan comprising a control unit comprising an electronic controller comprising a printed circuit board (PCB) incorporating a passive power factor correction (PFC) circuit, the PCB being disposed within the motor housing and fixed to the lower end of the fan shaft protruding into the motor housing, the control unit further comprising hall sensors located in adjacent stator slots, the stator windings and hall sensors being connected to the PFC circuit which in turn is connected to a power supply.

According to the invention there is also provided a control unit for a BLDC motor, the control unit comprising an electronic controller comprising a printed circuit board (PCB) incorporating a passive power factor correction (PFC) circuit, the PCB being disposed within the motor housing and fixed to the lower end of the fan shaft protruding into the motor housing, the control circuit further comprising hall sensors located in adjacent stator slots, the stator windings and hall sensors being connected to the PFC circuit which in turn is connected to a power supply.

The following is detailed description of the invention with reference to the accompanying drawings, in which :

Fig 1 is a crosssectional view of a ceiling fan according to an embodiment of the invention;

Fig 2 is an enlarged view of the lower end of the fan shaft with the electronic controller fixed to it;

Fig 3 is plan view of the mounting bracket;

Fig 4 is plan view of the electronic controller; and

Fig 5 is plan view of the stator of the BLDC motor of the fan.

The ceiling fan 1 as illustrated in Figs 1 to 5 of the accompanying drawings is driven by BLDC motor 2. The motor housing comprises upper and bottom end shields 3 and 4 rotatably held onto the lower end of the fan shaft 5 using bearings 6 and 7, respectively. Fan blades 8 (only one fan blade is shown in Fig 1) are fixed to the upper end shield using screws 9 and washers 10. The stator and the rotor of the motor are marked 11 and 12, respectively. The stator windings are marked 13. The upper end of the fan shaft is fixed to the lower end of the down rod 14 of the fan by bolt 15 and nut 16. The upper end of the down rod is fixed to the shackle 17 of the fan by bolt 18 and nut 19. The lower and upper canopies of the fan are marked 20 and 21, respectively. 22 is a flat circular mounting bracket provided with a centre slot 23 corresponding to the lower end of the fan shaft and a plurality of spaced first upright support members 24 and a plurality of spaced second upright support members 25 at the upper surface thereof. Each of the first support members is provided with an upwardly tapered lateral extension 26 at the upper end thereof. Each of the second upright support members is shorter than each of the first upright support members. The mounting bracket is disposed around the lower end of the fan shaft through the centre slot therein and is fixed in position by a grub screw (not shown) secured through a lateral hole 27 provided in the

mounting bracket and a corresponding hole (not shown) at the lower end of the fan shaft.

The mounting bracket can also be of other shapes like rectangular or square. 28 is an electronic controller provided with a centre slot 29 corresponding to the lower end of the fan shaft and a plurality of spaced through openings 30 as equally spaced as the first upright support members. The electronic controller comprises a PCB incorporating a PFC circuit and is disposed around the lower end of the fan shaft through the centre slot therein and supported at the upper ends of the second upright support members by snap fitting the electronic controller over the upper ends of the first upright support members through the openings in the electronic controller. The tapered lateral extensions at the upper ends of the first support members are compressible and get compressed and pass through the openings in the electronic controller. After passing through the openings in the electronic controller, the tapered lateral extensions at the upper ends of the first upright support members expand to their original position. The distance between the upper ends of the second upright support members and the lower surface of the tapered lateral extensions at the upper ends of the first upright support members corresponds to the thickness of the electronic controller. The electronic controller remains supported against the second upright support members with the lower surface of the tapered lateral extensions at the upper ends of the first support members abutting against the upper surface of the electronic controller. The electronic controller is thus well supported on the mounting bracket at the lower end of the fan shaft. The electronic controller as illustrated is square shaped with chamfered corners. It can also be of other shapes like circular or rectangular. Fitment of the electronic controller at the lower end of the fan shaft is very simple, effortless and convenient in that the mounting bracket is fitted with only one grub screw and the electronic controller is simply snap fitted on the bracket. Three hall sensors located in the stator slots are marked 31. The stator windings are connected to the electronic controller with lead wires collectively marked 32. The hall sensors are connected to the electronic controller with lead wires collectively marked 33. The two lead wires for connecting the electronic controller to the AC mains (not shown) are collectively

marked 34. The lead wires 34 are taken up through the hollow fan shaft and hollow down rod via a port 35 at the lower end of the fan shaft. During operation of the fan, depending upon the polarity of the rotor as sensed by the hall sensors, the electronic controller energizers the corresponding set of coils in the stator windings to control the rotation of the ceiling fan.

According to the invention, the sensor magnet has been eliminated, the hall sensors are directly located in the stator slots and the control unit is fully located in the motor housing. As the electronic controller is located within the motor housing it does not require any protective casing. The length of lead wires required to connect the hall sensors and stator windings to the electronic controller has been considerably reduced. The size of the motor, motor shaft and down rod are reduced and the fan is rendered compact. The fan is supplied to the customer with the controller unit fully assembled and the hall sensors and stator windings connected to the electronic controller. The customer has to simply fix the shackle of the fan to the hook or similar clamp in the ceiling and connect the two lead wires from the electronic controller to the power supply. Hardware fasteners for fitment of the electronic controller have been eliminated and the electronic controller is simply snap fitted at the lower end of the fan shaft. Only one screw is used for fitment of the mounting bracket. Therefore, fitment errors in the fitting of the electronic controller and resultant noise and vibrations during the running of the fan have been eliminated. Life of the electronic controller is increased. As the sensor magnet has been eliminated there is no need for alignment of the rotor magnets with the sensor magnets. Because of the constructional changes and functional benefits as explained above, the number of parts of the fan is reduced, cost of the fan is reduced, reliability of the fan is improved, installation time and assembly time of the fan are reduced, assembly and installation are rendered easy and convenient and the fan is also rendered customer friendly. Additionally the fan also has all the other advantages associated

with a BLDC motor driven fan like reduced power consumption, higher performance and controllability and increased life.

The configuration and construction of the mounting bracket can vary. The mounting bracket can be fixed to the lower end of the fan shaft in a different manner. The electronic controller can be directly fixed to the lower end of the fan shaft without the mounting bracket. There can be two hall sensors fixed in adjacent stator slots instead of three. Such variations in the configuration and construction of the invention are obvious to those skilled in the art and the scope of the invention is to be construed and understood to be accordingly. The control unit of the invention is essentially for sensing the rotor polarity and switching the respective coils in the windings of a BLDC motor which can have applicability in other areas besides ceiling fan. The scope of the invention is also to be construed and understood accordingly.