FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
HALL SENSOR HOLDER FOR A BLDC MOTOR
APPLICANTS
Name : Crompton Greaves Limited
Address : CG House, Dr Annie Besant Road, Worli, Mumbai 400 025, Maharashtra,
INDIA
Nationality : an Indian Company
INVENTORS
1. Name : Chandrashekar Munirathnamreddy
Address : Crompton Greaves Ltd, Industrial Design Centre, Corporate R&D and
Quality, Kanjur Marg(E), Mumbai 400042, Maharashtra, India Nationality : Indian
2. Name : Rao Guruprasad Kuppu
Address : Crompton Greaves Ltd, Industrial Design Centre, Corporate R&D and
Quality, Kanjur Marg(E), Mumbai 400042, Maharashtra, India Nationality : Indian
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed :

Field of invention
This invention relates to a Hall sensor holder for BLDC motors.
Background of the invention
Different types of motors find a wide variety of applications in many industries such as Appliances, Automotive, Aerospace, Consumer, Medical, Industrial Automation Equipment and Instrumentation. In the recent times Brushless Direct Current (BLDC) motors have become more popular due to their better efficiency and better conversion of electrical power into mechanical power as compared with brushed motors. BLDC Motors are used in devices such as computer hard drives, CD/DVD players, PC cooling fans, direct-drive turntables, electric vehicles, industrial machinery and the like.
Like other motors a BLDC motor comprises components such as a rotor, a stator, a shaft and the like. The stator of a BLDC motor consists of stacked steel laminations with slots that are axially cut along the outer periphery of the stator. In a BLDC motor, the brush assembly is replaced by an electronic controller. The controller must monitor the speed and position of the rotor. Hall Effect sensors are typically used for sensing the relative position of the rotor. Once the rotor position is determined the controller then energizes and de-energizes the coils required to drive the BLDC motor. BLDC motors usually have three Hall sensors fixed into the stator on the outer periphery of the stator. Whenever the rotor magnetic poles pass near the Hall sensors, they give a high or low signal, indicating the N or S pole is passing near the sensors, thus sensing the position of the rotor.
Prior Art
Conventionally the method used to fix the Hall sensor into the stator winding of a BLDC motor is as follows:
The Hall sensor is fitted in a slot provided in the stator. An adhesive such as glue or silicon gel is used to hold the sensor in position. However this method of placement of the Hall sensor is disadvantageous. Since the sensor is glue fixed, replacement of the sensor is very inconvenient and the stator slot where the sensor was placed has to be
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cleaned before replacement. This method of replacement of sensor is labourious and time consuming. Further care has to be taken that the Hall sensor has to be accurately aligned in the stator slot, if not aligned properly it would result in an erroneous sensing of the position of the rotor.
Other methods known in the prior art are evident from the following patent documents. PCT publication number WO02089304 discloses a rotor position sensor mounting assembly which includes a housing, Hall Effect devices, a PCB, plurality of leads and a cable tie. The housing further includes two pairs of guides that fixedly attach the housing to a stator end cap and a plurality of stator laminations. The mounting assembly disclosed is very complex and expensive. In this case the stator laminations need to be specifically designed to accommodate the mounting assembly.
US Patent application number 20060169061 discloses a Hall Effect sensor assembly which comprises a thin, removable annular substrate with the Hall Effect sensors and the associated connection wiring mounted on the thin annular substrate. The thin annular substrate slips underneath the wound stator end turn of the stator. Further the assembly discloses that the Hall sensors are held in position by clips or a high temperature epoxy.
The assembly disclosed is very complex and while replacing the Hall Effect sensors the entire motor has to be dismantled. Another disadvantage is that in the event of vibrations occurring in the motor there is a possibility that the clips may be dislodged thus displacing the Hall sensor from their position which reduces the accuracy of sensing the position of the rotor.
This invention seeks to overcome the limitations of the prior art.
An object of this invention is to provide a simple and inexpensive Hall sensor holder.
Another object of this invention is to provide a Hall sensor holder wherein the Hall sensor is tightly held in position in the Hall sensor holder.
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Another object of this invention is to provide a Hall sensor holder which can be easily removed replaced and fitted.
Summary of the invention
In accordance with this invention there is provided a Hall sensor holder for a BLDC motor, said holder comprising a flexible body made of an electric and thermal insulating material, and having a recess formed therein corresponding to the outer profile of the Hall sensor to be housed therein, said holder being tightly held in a holder slot provided at the mouth of a stator slot co-axially therewith.
Typically, the body is provided with a slit along the length therein to render it flexible. Typically, the holder slot provided at the mouth of the stator slot is dovetail profiled and the outer surface of said holder is correspondingly dovetail profiled to ensure proper fitment of the holder in the holder slot.
Brief description of the accompanying drawings
The preferred embodiment of this invention is represented in the accompanying drawings. However the represented embodiment is only illustrative and does not limit the scope of the invention.
In the drawings:
Figure la illustrates the Hall sensor holder with the Hall sensor fitted in the Hall sensor
holder in accordance with this invention;
Figure lb illustrates a disassembled view of the Hall sensor holder and Hall sensor;
Figure 2a illustrates a plan view of the Hall sensor holder;
Figure 2b illustrates a sectional view of the Hall sensor holder taken along the line K-K;
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Figure 3a illustrates a plan view of the stator in accordance with this invention;
Figure 3b illustrates an enlarged scrap view of the stator as seen in circle H of the figure 3a;
Figure 4a illustrates a plan view of the stator with the Hall sensor holder fitted in the stator slot in accordance with this invention; and
Figure 4b illustrates an enlarged scrap view of the stator as seen in circle A provided in figure 4a.
Detailed description of the accompanying drawings
The invention will now be described in detail with reference to figure la to 4b of the accompanying drawings:
In accordance with Figure la and Figure lb, the Hall sensor holder (10) is made of an electric and thermal insulating material such as nylon. The Hall sensor holder (10) is provided with a slit (12) along its length. The slit provides flexibility to the Hall sensor holder (10). The Hall sensor holder (10) has a recess (14) which is adapted to accommodate the Hall sensor (16), the recess is particularly seen in figure 2a and 2b of the accompanying drawing. The profile of the recess (14) is such that it matches the profile of the Hall sensor (16). The Hall sensor holder (10) has a dovetail profile.
As seen in Figure 3a and figure 3b, a holder slot (22) having a dovetail profile is provided at the mouth of the stator slot (20), which holds the Hall sensor holder (10) in position. The Hall sensor holder (10) is held in the holder slot (22) in a manner such that it is coaxial with the stator slot (20).
As seen in Figure 4a and Figure 4b, the Hall sensor holder (10) is made such that on introduction of the Hall sensor (16) in the recess (14) the leads of the Hall sensor are
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always perpendicular to the stator winding (24). The side walls of the sensor holder (10) abuts the laminations of the stator winding (24) thus prevents the sensor holder (10) from being displaced and also holds the Hall sensor (16) tightly in the Hall sensor holder (10), in the running condition of the motor. While fitting the Hall sensor holder (10) in the holder slot (22) of the stator (24) the flexible holder (10) is slightly pressed and introduced in the holder slot (22) after releasing the holder (10) expands and is tightly held in position. The flexibility of the holder (10) helps easy removal and replacement of the sensor (16) from the holder (10) and also easy removal and replacement of the holder (10) from the holder slot (22) of the stator.
Even though emphasis is laid herein on the components and component parts of the preferred embodiment. It should be understood that the disclosure herein is only illustrative and does not limit the scope of this invention. Further many modifications and alterations can be made in the preferred embodiment without departing from the principles of this invention. Other modifications that may be made in the sensor holder is that the body may be made without providing a slit. A further modification may be that the profile of the holder need not be limited to dovetail.
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We Claim:
1. A Hall sensor holder for a BLDC motor, said holder comprising a flexible body
made of an electric and thermal insulating material, and having a recess formed
therein corresponding to the outer profile of the Hall sensor to be housed therein, said holder being tightly held in a holder slot provided at the mouth of a stator slot co-axially therewith.
2. A Hall sensor holder as claimed in claim 1, wherein said body is provided with a slit along the length therein to render it flexible.
3. A Hall sensor holder as claimed in claim 1, wherein said holder slot provided at the mouth of the stator slot is dovetail profiled and the outer surface of said holder is correspondingly dovetail profiled to ensure proper fitment of said holder in the holder slot.
Dated this 8th day of January 2007

of Khaitan & Co
Agent for the Applicants
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ABSTRACT
A Hall sensor holder (10) for a BLDC motor is disclosed. The holder comprises a flexible body made of an electric and thermal insulating material, and having a recess (14) formed therein corresponding to the outer profile of the Hall sensor (16) to be housed therein. The holder is tightly held in a holder slot (22) provided at the mouth of a stator slot (20) co-axially therewith (Fig 4b).