0001] The present disclosure relates to the field of starter motors for Internal Combustion engines. In particular, the present disclosure relates to water sealing of permanent magnet starter motors to prevent ingress of water.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Starter motors, also known in the art as self-starters or cranking motors, are now an essential part of all IC engines, and are required for initial cranking so as to initiate the engine's operation under its own power. Specifically, the starter motors help to start the engines without human efforts replacing other devices such aswind-up springs, gunpowder cylinders etc. that had been in use earlier as an alternative to human human-powered techniques such as a removable crank handle which engaged the front of the crankshaft, pulling on an airplane propeller, or pulling a cord that was wound around an open-face pulley.
[0004] A Starter Motor primarily comprises a hollow,cylinder shaped yoke that is open at ends; a static magnetic field system provided on an inner periphery of the yoke; an armature surrounded by a rotating magnetic field system with a predetermined gap between the two magnetic field systems, an electromagnetic switch with actuator, the armature having an armature shaftcoupled to a driving pinion that engages with a ring gear of the engine to transfers torque, and coupled to the shaft through a one way clutch that allows transfer of torque only in one direction, i.e. from the pinion to the ring gear, and a shift lever having one end connected to the plunger of the electromagnetic switch and other end connected to a shifting ring that provides axial travel to the driving pinion assembly for engagement/disengagement with the ring gear.
[0005] Earlier, the static magnetic field system provided on theinner periphery of the yoke used to be a set of stator field windings, which may be connected in series with field

windingsof the rotating magnetic field system. Starter motors with static magnetic field system having permanent magnet were introduced on IC engines of vehicles in the late 1980s. The principle of operation of these starters known in the art as permanent magnet starter motors, is almost similar to the conventional starter motors, in which the field windings and pole shoes are replaced with high quality permanent magnets. This provides a reduction in weight up to 15 percent. Less weight and small size of these motors, compared to conventional types makes the permanent magnet starter to be more popular as space in » modern carswhere most IC engines are used, is at premium. The reduction in weight also contributes towards reduction in fuel consumption.
[0006] In order to meet higher torque requirements, the permanent magnet starter motors may also include intermediate transmission of generally epicyclic type between the shaft and the pinion, that reduces rotational speed of the pinion, thus enabling the armatures to rotate at a higher and more efficient speed while delivering the torque. Such motors are known in the art as permanent magnet gear reduction starter motors.
[0007] Permanent magnet starter motors, though offering above stated advantages, provide a difficulty in sealing to prevent water ingress from ends of yoke of the motor. This is because, yoke in the permanent magnet starter motors is a thin walled cylinder preventing fitment of a sealing ring or like sealing element at annular end face of the Yoke. [0008] In view of above, conventionally such starter motors are not water sealed due to complications involved in achieving complete protection against water ingress. This restricts use of permanent magnet gear reduction starter motors in certain applications, for example, tractor engines engaged at work at high water level fields etc. Water ingress leads to corrosion of internal metallic parts of the motor housing and electromagnetic switch and short circuiting of field coils resulting in premature failure of the units.
[0009] Efforts have been made in the art to provide a sealing at ends of the yoke. For example, United States Patent number US7888828 discloses a starter generator incorporating a rotor having a cuplike-shaped rotor yoke and magnets attached to an inner periphery of the rotor yoke, a stator being arranged inside of the rotor and mounted on a stator bracket, and a protecting cover covering said rotor and stator, in which a hermetically sealed casing is constituted by said protecting cover and stator bracket in particular, the protecting cover is formed into a cup-like shape having an end wall facing the bottom wall portion of the rotor yoke and a cylindrical side wall portion surrounding the peripheral wall portion of the rotor

yoke. The document discloses a protective cover cup like shape to provide sealing on ends of the yoke which is not a very efficient solution to the sealing problem.
[0010] There is therefore a need in the art of an efficient and cost effective sealing methodology in permanent magnet starter motors.
[0011] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. [0012] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term "about." Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0013] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
[0014] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the

invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0015] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
OBJECTS OF THE INVENTION
[0016] A general object of the present disclosure is to provide an efficient and longer
lasting permanent magnet starter motor.
[0017] An object of the present disclosure is to providea permanent magnet starter motor
that is designed to prevent ingress of water to make the motor efficient and longer lasting.
[0018] Another object of the present disclosure is to provide a methodology to efficiently
seal the starter motor at two ends of yoke of the starter motor.
[0019] Another object of the present disclosure is to provide a cost effective solution for
sealing the starter motor at two ends of yoke of the starter motor.
[0020] Yet another object of the present disclosure is to provide a solution for sealing the
starter motor at two ends of yoke of the starter motor that does not result in appreciable
increase in weight of the starter motor.
SUMMARY
[0021] Aspects of the present disclosure relate toa permanent magnet starter motor. In particular, the present disclosure provides a cost effective and efficient solution to problem of water sealing of permanent magnet starter motors at junctions of yoke of the motor and end brackets.
[0022] In an aspect, the disclosed permanent magnet starter motor comprises a yoke of substantially hollow cylindrical shape having thin wall cross section and two open ends;at least one end bracket to close at least one of the two open ends of the yoke; and at least one sealing ring adapted for fitment between the at least one end bracket and the at least one

open end of the yoke to prevent water ingress through joint between the at least one end
bracket and the yoke. In an aspect, the at least one open end of the yoke is flanged to provide
a larger flat surface perpendicular to a longitudinal axis of the yoke for the at least one end
bracket to rest on. The flat surface can be large enough to accommodate a grove for the
sealing ring.
[0023] In an aspect, the thin wall cross section of the yoke has a thickness less than
2.5mm.
[0024] In an aspect, the at least one sealing ring has a first side and a second side opposite
the first side, the first side being adapted to take seat against the yoke and the second side
adapted to take seat against the at least one end bracket.
[0025] In an aspect, the at least one sealing ring has substantially rectangular cross
section incorporating a raised rib of substantially semi-circular shape on the first side.
[0026] In an aspect, the raised rib of semi-circular shape on the first side of the at least
one sealing ring is accommodated in the grove and rest of the first side of the at least one
sealing ring rests against remaining of the flat surface of the flanged yoke.
[0027] In an aspect, the yoke further incorporates a spigot extending beyond the at least
one flanged open end to guide and locate the at least one end bracket.
[0028] In an aspect, the at least one end bracket incorporates an inner diameter that
locates on the spigot extending beyond the at least one flanged open end of the yoke.
[0029] In an aspect, the present disclosure also provides a method for water sealing at
least one joint between an at least one open end of a yoke and at least one end bracket of a
permanent magnet starter motor, the method comprising the steps of: (a) providing a flange
on the at least one open end of the yoketo provide a larger flat surface perpendicular to a
longitudinal axis of the yoke; (b) providing a grove on the flat surface; (c) positioning at least
one sealing ring on the flat surface such that a raised rib on a first surface of the sealing ring
gets located in the grove on the flat surface; and (d) fitting the at least one end bracket on the
flange. In an aspect, the at least one sealing ring prevents ingress of water through the joint
between the at least one open end of the yoke and the at least one end bracket.
[0030] In an aspect, a second side of the sealing ring opposite the first side is
substantially flat and takes seat against the at least one end bracket.
[0031] In an aspect, the method further comprises the step of providing a spigotextending
beyond the flange on the at least one open end of the yoke to guide and locate the at least one

end bracket; wherein the at least one end bracket incorporates an inner diameter that locates on the spigot.
[0032] Various objects, features, aspects and advantages of the inventive subject matter
will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The accompanying drawings are included to provide a further understanding of
the present disclosure, and are incorporated in and constitute a part of this specification. The
drawings illustrate exemplary embodiments of the present disclosure and, together with the
description, serve to explain the principles of the present disclosure.
[0034] FIG. 1 illustrates an exemplary sectional view of the disclosed permanent magnet
starter motor, in accordance with embodiments of the present disclosure.
[0035] FIGs. 2A and 2B illustrate exemplary sectional and perspective views respectively
of yoke and sealing ring of the disclosed the permanent magnet starter motor, in accordance
with embodiments of the present disclosure.
[0036] FIG. 3 illustrates an exemplary flow diagram for the proposed method for water
sealing a joint between an open end of a yoke and an end bracket of a permanent magnet
starter motor, in accordance with embodiments of the present disclosure.
DETAILED DESCRIPTION
[0037] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0038] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be

recognized that references to the "invention" will refer to subject matter recited in one or
more, but not necessarily all, of the claims.
[0039] Various terms are used herein. To the extent a term used in a claim is not defined,
it should be given the broadest definition persons in the pertinent art have given that term as
reflected in printed publications and issued patents at the time of filing.
[0040] Embodiments explained herein relate to permanent motor starter motors.In
particular, they pertain to sealing to prevent ingress of water through joints between yoke and
end brackets of the motor.
[0041] Permanent motor starter motors, by virtue of having permanent magnets as static
magnetic field system,have very thin yoke. The thickness of the yoke may be as low as 2 mm,
which does not provide enough surface at end of the yoke that could be used for proper
sealing between the yoke and the end brackets. Specifically, it does not allow incorporation
of a sealing element such as a gasket or an O ring that could effectively prevent ingress of
water through the joint between the yoke and the end bracket. Therefore, sealing is typically
done by providing cup shaped protective covers or other similar arrangements which are not
cost efficient.
[0042] In an embodiment, the present disclosure proposes to incorporate a section of
larger thickness, known in the related art as flange, near the open ends of the yoke. Such
flanges can provide larger surface area (also referred to as sealing surface) at end faces of the
yoke to enable effective sealing between the yoke and the end brackets.
[0043] In another embodiment, end face of the yoke that has larger surface on account of
flanges provided at ends, can incorporate a grove to locate a sealing ring.
[0044] In another embodiment, sealing ring can incorporate a raised rib on its side that
rest against the end face of the yoke, the rib can be of semi-circular cross section and can
engage with the grove on the end face to prevent dislocation of the sealing ring.
[0045] In yet another embodiment, yoke can incorporate spigots at the open ends that
extend beyond the sealing surface toguide and locate the end brackets; Each of the end
brackets can incorporate an inner diameter that locates on the spigot thus ensuring proper
alignment between the yoke and the end brackets.
[0046] It is to be appreciated that while embodiments explained herein illustrate use of
the proposed methodology on both ends of the yoke, it is possible to implement the disclosed
concept on any one of the two ends and sealing the other end based on any other concept

suited to the application, and application of the concept just on one of the two sides is well within the scope of the present disclosure.
[0047] It is to be further appreciated that there are many potential water ingress points in a starter motor, each of which may require different methodology for water sealing that may be related or unrelated to sealing of the joint between yoke and end brackets. As would be appreciated by those skilled in the art all such potential water ingress points need to be attended to make the starter motor completely sealed against water ingress, and the present disclosure is related to just the joints between the yoke of the permanent magnet starter motor and its end brackets.
[0048] Referring now to FIG. 1 where an exemplary sectional view of the permanent magnet starter motor incorporating sealing of joint between yoke and end brackets in accordance with embodiments of the present disclosureis illustrated. As shown thepermanent magnet starter motor 100 (also referred to as starter motor 100 or simply as motor 100 hereinafter) can comprise a yoke 102 and two end brackets such as rear end bracket 104-1 and front end bracket 104-2 (collectively referred to as end bracket 104). As shown, yoke 102 is a thin walled hollow cylinder having a thickness as low as 2mm, and is open on its front and rear ends, which are covered by the end brackets 104-1 and 104-2. The yoke 102 and the two end brackets 104 enclose all the internal moving and stationary parts of the starter motor 100, such as rotary armature, static field system, electromagnetic switch with actuator, epicyclic gear set, output shaft and pinion driven by the motor linked through the over¬running clutch that transfers torque in one direction only.
[0049] In an aspect of the present disclosure, sealing rings such as 106-1 and 106-2 are incorporated between the yoke 102 and the end brackets 104-1 and 104-2 respectively to prevent water ingress through the joint between the yoke 102 and the end brackets 104, wherein the sealing ring 106 is accommodated on end face of the thin wall yoke 102 by increasing end surface, referred to as sealing surface, by flanging the ends of the yoke 102. [0050] In an embodiment, flanging of ends of the yoke 102 can be done by any of different suitable processes or combination thereof known in the art, such as but not limited to machining a higher thickness hollow cylinder, upsetting the ends of the yoke, welding of flanges, such as by any or a combination of electric resistance welding, arc welding, gas welding or friction welding, to name a few.

[0051] As would be appreciated, flanging results in increasing the thickness of the yoke at end portions, and therefore any other suitable term as prevalent in the related art, can also be used for the disclosed feature/operation.
[0052] FIGs. 2A and 2B illustrate exemplary sectional and perspective views respectively of yoke 102 and sealing rings106 of the disclosed permanent magnet starter motor 100, in accordance with embodiments of the present disclosure.As shown therein, open ends of the yoke 102 incorporate flanges such as flange 202-1 on the rear end and flange 202-2 at front end of the yoke 102 (collectively flange 202) providing a larger cross sectional area than normal thickness of the yoke 102 such as in between the two flanges 202. The larger cross section results in a larger seating/sealing surface at the ends of the yoke 102. In an embodiment, the sealing surface at ends of the yoke 102 can incorporate groves such as grove 204 for accommodating the sealing ring 106. The grove 204 can have a semi-circular cross section.
[0053] In an embodiment, the sealing ring 106 can incorporate a raised rib 206 of semi¬circular cross section on the side that is to rest against the yoke 102 (referred to as first side). Specifically the rib 206 can have a shape that matches shape of the grove 204 on the sealing face of the yoke 102 so that the sealing ring 106 is securely held on the open end of the yoke 102.
[0054] In an embodiment, side of the sealing ring 106 opposite the first side (referred to as second side) is flat 208 and adapted to take seat against the at least one end bracket. Thus, cross section of the sealing ring 106 is substantially rectangular having a first side and a second side that is opposite the first side, with the first side incorporating a raised rib 206 of semi-circular shape and the second side being flat 208; and as stated above, the raised rib 206 of semi-circular shape on the first side of the sealing ring 106 is accommodated in grove 204, and rest of the first side of the sealing ring 106 rests against remaining of the flat surface of the flanged yoke 102.
[0055] In an embodiment, open ends of the yoke 102 further incorporates spigotssuch as 210-1 and 210-2(collectively 210) extending beyond the flanged open end. The spigots 210 to guide and locate the at least one end bracket. The end brackets 104 can incorporate an inner diameter that locates on the respective spigots210.
[0056] In an aspect, the present disclosure also provides a method for water sealing of joints between open ends of the yoke and respective end brackets of a permanent magnet starter motor as illustrated by an exemplary flow diagram in FIG. 3.
10

[0057] As shown in FIG. 3, the disclosed method 300 comprises the steps ofproviding flanges on the open ends of the yoketo provide a larger flat surface perpendicular to a longitudinal axis of the yoke, as shown in block 302. In an embodiment, the flanging of ends of the yoke can be done by any of different suitable processes or combination thereof known in the art, such as but not limited to machining a higher thickness hollow cylinder, upsetting the ends of the yoke, welding of flanges, such as by any or a combination of electric resistance welding, arc welding, gas welding or friction welding, to name a few. The block 304 can be providing a grove on the flat surface. The grove can be of semi-circular cross section. Block 306 can bepositioning sealing rings on the flat surfaces such that a raised rib on a first surface of the sealing rings gets located in the grove on the flat surfaces. The raised rib can be of semi-circular cross section matching the grove in the yoke.Method 300 at block 308 involvefitting end brackets on the flange. In an aspect, the sealing rings prevent ingress of water through the joint between the open ends of the yoke and the end brackets. [0058] In an embodiment, second sides of the sealing rings opposite the respective first sidescan be substantially flat and can take seat against the respective end brackets. [0059] In an embodiment, the method 300 further comprises step of providing spigotsextending beyond the respective flanges on the open ends of the yoke to guide and locate the end brackets; wherein the end brackets incorporate an inner diameter that locates on the spigot.
[0060] Thus the present disclosure provides a simple and cost effective concept for water sealing of joints between thin walled yoke and end brackets of a permanent magnet starter motors enhancing life of the motors by preventing corrosion of internal metallic parts of the motor housing and electromagnetic switch and short circuiting of field coils that results in premature failure of the units.
[0061] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
11

ADVANTAGES OF THE INVENTION
[0062] The present disclosure provides an efficient and longer lasting permanent magnet
starter motor.
[0063] The present disclosure provides a permanent magnet starter motor that is designed
to prevent ingress of water to make the motor efficient and longer lasting.
[0064] The present disclosure provides a methodology to efficiently seal the starter motor
at two ends of yoke of the starter motor.
[0065] The present disclosure provides a cost effective solution for sealing the starter
motor at two ends of yoke of the starter motor.
[0066] The present disclosure provides a solution for sealing the starter motor at two ends
of yoke of the starter motor that does not result in appreciable increase in weight of the starter
motor.

We Claim:
A permanent magnet starter motor comprising:
a yoke of substantially hollow cylindrical shape having thin wall cross section and two open ends;
at least one end bracket to close at least one of the two open ends of the yoke; and
at least one sealing ring adapted for fitment between the at least one end bracket and the at least one open end of the yoke to prevent water ingress through joint between the at least one end bracket and the yoke; wherein:
the at least one open end of the yoke is flanged to provide a larger flat surface perpendicular to a longitudinal axis of the yoke for the at least one end bracket to rest on; the flat surface being large enough to accommodate a grove for the sealing ring.
The starter motor as claimed in claim 1, wherein the thin wall cross section of the yoke has a thickness less than 2.5mm.
The starter motor as claimed in claim 1, wherein the at least one sealing ring has a first side and a second side opposite the first side, the first side being adapted to take seat against the yoke and the second side adapted to take seat against the at least one end bracket.
The starter motor as claimed in claim 3, wherein the at least one sealing ring has substantially rectangular cross section incorporating a raised rib of substantially semi-circular shape on the first side.
The starter motor as claimed in claim 4, wherein the raised rib of semi-circular shape on the first side of the at least one sealing ring is accommodated in grove and rest of the first side of the at least one sealing ring rests against remaining of the flat surface of the flanged yoke.

The starter motor as claimed in claim 1, wherein the yoke further incorporates a spigot extending beyond the at least one flanged open end to guide and locate the at least one end bracket.
The starter motor as claimed in claim 1, wherein the at least one end bracket incorporates an inner diameter that locates on the spigot extending beyond the at least one flanged open end of the yoke.
A method for water sealing at least one joint between an at least one open end of a yoke and at least one end bracket of a permanent magnet starter motor, the method comprising the steps of:
providing a flange on the at least one open end of the yoketo provide a larger flat surface perpendicular to a longitudinal axis of the yoke;
providing a grove on the flat surface;
positioning at least one sealing ring on the flat surface such that a raised rib on a first surface of the sealing ring gets located in the grove on the flat surface; and
fitting the at least one end bracket on the flange; wherein the at least one sealing ring prevents ingress of water through the joint between the at least one open end of the yoke and the at least one end bracket.
The method as claimed in claim 8, wherein a second side of the sealing ring opposite the first side is substantially flat and takes seat against the at least one end bracket.
The method as claimed in claim 8, wherein the method further comprises the step of providing a spigotextending beyond the flange on the at least one open end of the yoke to guide and locate the at least one end bracket; wherein the at least one end bracket incorporates an inner diameter that locates on the spigot.