FIELD OF THE INVENTION:

The present invention relates to an improved DC motor arrangement more particularly the invention is robust fixation in the system, occupy less space, flexible for a wide variation of systems and offer superior performance in that range of products.

BACKGROUND OF THE INVENTION:

Various types of DC motors are known in the state of art, the motor assembly is held together by various fastening methods. The fastening method used to hold the motors together generally subject to loosening by vibration during operation. Any loosening of internal elements may cause further vibrations of the fixing process device and lead to an increase in friction and heat dissipation.

In addition, the numerous fasteners which are required to hold the various elements together result in a difficult assembly operation thus further adding to overall cost.

The present invention was considered to provide a unique DC motor assembly in which the improved internal elements thereof are easily assembled and reliably held together as long as required.

OBJECTS OF THE INVENTION:

The main object of the invention is to provide high degree of robustness to motor and fixation of motor in the system.

The another object of the invention is to protect the internal components of motor from vibration
With a view to accomplish the above objects, the following solutions will be provided in the present invention.

SUMMARY OF THE INVENTION:

The present invention relates to a unique DC motor construction arranged with rotor, stator, armature(ll), armature shaft(5), commutator(8), pinion(3), magnets(13), brushes(lO), housing/casing(14) with bumps(39), tabs(34), flared fingers(28), terminal(4), top shield cap(l) with upper ball bearing(16) and slinger(7), bottom shield cap(17) with lower ball bearing(15) and end cap assemblies(2) with portion for placing capacitor(20), resistor(21), choke coil(6), H bridge, control module thereof can be easily assembled and held together with a high degree of accuracy. The special construction to provide high degree of robustness and high efficiency to motor.

DESCRIPTION OF THE DRAWINGS:

Fig 1 illustrates the exploded view of the motor assembly.

Fig 2 illustrates the cross section view of the magnet with retainer assembly.

Fig 3 illustrates the cross section of the motor assembly.

Fig 4 illustrates the top view of the end cap assembly.

Fig 5 illustrates the elevation view of the motor assembly.

Fig 6 illustrates the interior of the end cap assembly.

Fig 7 illustrates the interior of the end cap assembly with control module.

Fig 8 illustrates the top shield cap assembly with bumps.

Fig 9 illustrates the armature assembly.

Fig 10 illustrates the casing, magnet and magnet retainer of the motor assembly.

Fig 11 illustrates the top shield cap assembly with upper ball bearing.

Fig 12 illustrates the end cap assembly.

Fig 13 illustrates the bottom shield cap assembly with lower ball bearing.

Fig 14 illustrates the end cap assembly with wire holes in the side wall.

DESCRIPTION OF THE INVENTION:

Like in any DC motor this motor herein described in the invention has also all the six basic parts, i.e., rotor, stator, armature shaft(5), commutator(8), field magnets(13), brushes(lO) and a frame/casing(14) having a cylindrical portion. As in many small motors, due to constraint in size and space the casing is generally cylindrical in shape to match the conventional rotor shape. The armature assembly includes all of the rotating parts referred as armature or rotor in the specification. The casing(14) assembly houses within itself the stationery permanent magnets(13) referred as stator. The two ends of the armature shafts(5) are supported by bearings(15&16) pressed in two top and bottom shields(l&17). armature shaft(5) is made to protrude through the top shield cap (1) to hold a pinion(3) used to actuate the system.

The two essential components of DC motor, the armature and rotor play a vital role. The armature(ll) is the part of DC motor that rotates and provides energy at the end of the armature shaft(5). It is basically an electro magnet, since it is a coil of wire that has to be specifically designed to fit around the core material on the armature shaft(5). The core of armature(ll) is generally made of laminated steel(32) pressed on to the armature shaft(5) and provides slots for the coils of the wire. Refer Fig. 9.

One end of the armature(ll) has commutator(8) segments. There is one commutator(8) segment for each end of each coil. Refer fig. 9. The commutator(8) segments are used as a contact point between the stationery brushes(lO) and the rotating armature(ll).

When each coil of wire is wound onto the armature(ll), the end of the coil is soldered to a specific commutator(8) segment. This makes an electrical terminal point for the current that will flow from the brushes onto the commutator(8) segment and finally through the coil of wire.

Conventionally the motors with two ball bearings are designed in following ways.

1. the lower ball bearing(15) is pressed on to the armature shaft(5) and made to slide on the bottom shield cap(17) with a preload.

2. the lower ball bearing(15) pressed into the bottom shield cap(17) have a higher inner diameter compared to upper one/top shield cap(l).

The above options do not holds good for vibration application and standardization of bearings

In the present invention, the upper(16) and lower ball(15) bearings are press fitted to the top and bottom shield cap (1&17) armature shaft(5) is press fitted to the upper ball bearing(16) and the armature shaft(5) is turned as an armature to provide sliding fit with the lower ball bearing(15).

The shape of the bottom shield cap (17) is closely fitted to the magnet, coils and bearing, resulting in the most optimized shape, and providing a locating surface/area for a wavy washer(18) that is away from the case retention features. The carbon content of the shield controlled to greater than 0.05% carbon so that the steel will impart a spring holding of the bearing.

As such the armature(ll) is essentially made of coils of wire wrapped around the core, and the core has an extended armature shaft(5) that rotates on bearings(15&16). Also the ends of each coil of wire on the armature are terminated at one end of the armature which termination points are called commutator(8) and this is where the brushes(lO) make electrical contact to bring electrical current from stationary part to the rotating part of the machine. This is illustrated in Fig. 9.

Since the armature(ll) is a coil of wires, it will need DC current flowing through it to become magnetized. Since armature(ll) is rotating DC voltage wires cannot directly be connected to the armature coil(ll). A stationery set of carbon brushes(lO) is used to make contact to the rotating armature(ll). The brushes ride on the commutator(8) segments to make contact so that the current will flow through the armature coil(ll).

The DC voltage that is used to energise the armature(ll) will pass through the brushes(lO) to the commutator(8) segments and into the armature coils(ll). Each brush(lO) has a wire connected to it. The wires will be connected to either positive or negative terminal of the DC power supply.

There are two brush sets which is equal to number of field poles. The voltage polarity will remain constant on each brush i.e., one brush will be connected to positive terminal and the other will be connected permanently to negative terminal(4).

The brushes(lO) will cause the polarity of each armature segment to alternate from positive to negative. When the armature(ll) is spinning, each commutator(8) segment will come in contact with the positive brush for an instant and will be positive during that time. As the armature(ll) rotates slightly, that commutator(8) segment will next come in contact with a brush that is connected to the negative voltage supply and it will become negative during that time. As the armature(ll) continues to spin each commutator (8) segment will be alternatively powered by positive and then negative voltage.

The brushes(lO) are made of carbon composite materials to facilitate continuous cleaning operation of commutator(8) and to expose of copper surface to brush. The end of the brush(lO) that rides on the commutator(8) is contoured to fit the commutator(8) exactly so that current will transfer easily.

The stator being the stationery part of the motor includes the carbon brushes(lO) and also includes the motor casing(14), as well as two more permanent magnet(13) pole pieces. (Fig. 2)

The field magnet in the motor is formed by the frame casing(14) itself plus two curved permanent magnets(13). The magnet(13) generally having a circumferential surface on an inside thereof and having a conformable contact with the motor frame casing on the outside thereof. The magnet(13) has two sides and a curved body with two surfaces, the inner and outer. The outer surface conforming to the motor casing(14) and the inner surface forming a semi-circular opening. Each curved magnet(13) is contoured to fit exactly into the casing(14), and along the inner curved surface of the casing(14) excepting at its two ends where the ends are spaced away from the casing(14) surface. Magnetic retainers(12) are disposed in the two spaced gaps. The magnetic retainer is holded by a holder(41) which is placed inside the casing (14). The air gap between the magnet(13) and the rotor has a constant distance excepting having a distance less than this constant distance at the two ends of the magnet(13). This is illustrated in Fig. 2. The cross section of the motor assembly is illustrated on Fig. 3.

The casing(14) is illustrated in Fig. 10, wherein it generally has a top and bottom end and defining a closed interior chamber and a central axis. The top end and bottom end are open. Two shield caps(l & 17) are fastened to longitudinal ends of the casing(14).

Conventional design of DC motors have the magnet outer radius exactly matching with the inner radius of the case. In this invention due to tolerances of case and magnets(13) and variation in cylindricity of the case, the magnets(13) usually rocks about the center point which is detrimental to vibration application and the magnets are supported by a pair of magnetic stoppers(19) formed on the bottom shield cap(17). In the present design the magnet(13) outer surface is so designed to have combination of circular surfaces which helps the motor to work under severe vibration

1. The magnet(13) outer surface have a two point line contact with the case(14) inner surface over the full tolerance range of magnet(13) and case(14) avoiding magnet(13) from rocking under vibration or during magnetization

2. The end of the magnet(13) is shaped to accommodate the magnet retainer lip(12) which avoids the retainer from popping out due to vibration

The armature(ll) is placed inside the frame casing(14) of the motor where the magnets(13) are mounted when the armature(ll) coils become energized, the armature(ll) will begin to rotate.

The frame casing(14) is such that it is having two ends top end and bottom end and a side wall. The casing(14) is circular in cross section. The casing(14) has a predetermined length and continuous side wall. The magnets(13) are mounted around the inner surface of the side wall and within the casing(14), and providing sufficient space for the armature(ll) to be mounted within the casing(14). The two shield caps (1&17) of the motor are mounted on the two ends of the motor frame casing(14). Both shield caps (1&17) are held in place by plurality of flared fingers(28) which are integral part of the casing(14). By bending the fingers(28&38) and away from each other each shield cap (1&17) is fixed onto the casing(14) and by bending back the fingers straight(28&38), the shield cap is released and can be removed. The flared finger(28&38) is similar to configuration as a extended tab. The top shield cap(l) has a provision for two terminals (4) connected to the brushes(lO) where DC voltage can be connected. (Fig. 4 & fig. 5). The terminals(4) are mounted on one side of the axis of the motor to provide more space for the mating gear and other features of the system. To facilitate larger diameter of the pinion(3) that is mounted on the armature shaft(5) of motor, the terminals(4) are shifted inline with the wall of the case(14). The terminals so provided being over the casing(14) and molded within locaters, permits larger gear on the armature shaft(5).

The two shield caps (1&17) are mounted, one mounted at the top end of the casing(14) and another at the bottom end of the casing(14) and together they enclose the internal chamber of the casing(14).

The motor assembly including a casing(14) defining an interior chamber, an armature(ll) disposed within this interior chamber and having the armature shaft(5) mounted for rotational movement by bearings(15&16) and stator of magnet means for inducing rotational movement of the armature shaft(5), comprises in the invention a arrangement of the end caps(2). Each shield cap including a central hub portion defining a central axis and an outer portion concentrically arranged about the central axis. The shield caps(l&17) defining a specific stamped pattern and further each shield cap has a raised cylindrical neck(36&37) formed with raised portion, to accommodate the bearings(15&16) are concentrically arranged about the central axis.

The top shield cap (1) and the end cap(2) having a matching set of four protrusion (25) on the top shield cap(l) and a set of four dents(33) on the end cap(2) for fitting the two together concentrically to the motor axis. (fig. 8 & fig. 10). The four protrusions in the top shield cap (1) serves two purposes.

1. It positions the end cap(2) concentric to the motor axis.

2. It positions the top shield cap (1) concentric to motor axis to facilitate good alignment of the upper ball bearings (16) and to maintain uniform air gap.

At the top of the casing(14) is mounted the end cap(2) along with a top shield cap(l). The end cap(2) is positioned on the casing(14) and covered with the top shield cap (1). The top shield cap (1) assembly and the casing(14) have a matching set of corresponding six holes(26) and six flared pair of fingers(28) for fixing together. (Fig. 8 and Fig. 10)

Further the end cap(2) and the top shield cap (1) are together adapted to bring out the two power terminals(4) formed on end cap( 2 ) through a pair of terminal holes(27) formed on top shield cap assembly(l) (fig. 11 & fig. 12).

A pair of stationery carbon brushes(lO) is disposed in the central gap of the end cap assembly( 2 ) (fig. 12).

To meet these EMI / EMC international norms, a pair of choke coils(6) and capacitors(20) are added to the motor circuit to filter out the unwanted noise signals. The choke coils(6) are connected between brushes(lO) and terminals(4) by welding process(fig 14). Capacitors(20) are connected in parallel to terminals(4). One end of the capacitor(20) is welded to terminal(4) and other end is grounded to the case(14).

The electronic throttle body in which our DC Motor is assembled is used to control the air
Intake to the engine based on the driving requirements of the Driver.

This is done by moving a flap (Butterfly Valve). Upon doing so, due to principle of Electrostatics, high voltage (in the range of Kilovolts) is developed in the throttle body. This high voltage will damage the Motors if applied on the Motor Terminals(4).

The Purpose of providing the resistors(21) is to prevent the potential damage to the Motors due to this High Voltage.

Capacitors(20), choke coils(6) and resistors(21) forms the electronic circuit of the motor. The routing of leads(24) and packaging of these components is unique to the size of the motor.

Conventionally the leads go over the walls of the end cap to get grounded to case. In this design grounding is done through wire holes(30) in the side wall(29) of brush card making it easy for both mechanical and electrical connection of leads to case(14).

One of the two bearings is disposed on the top shield cap assembly (1) (fig. 11). Another bearing is disposed on the bottom shield cap (17).

Inside the end caps(2) are motor's brushes(lO) (fig. 12). These brushes(lO) transfer power from battery to commutator(8) as motor spins.

The top shield cap (1) also houses a bearing(16) with a slinger(7) for the armature shaft(5), wherein the bearing(16) is pressed to the top shield cap(l) and the armature shaft(5). It traps the bearing(16) on one side of the armature shaft(5). A pinion(3) is mounted on armature shaft(5) above the top shield cap(l) which also traps the armature shaft(5) on the other side of the bearing(16) (fig.l & fig. 5).

Conventionally the slinger(7) is a turned metal part or a plastic part pressed on to the armature shaft(5). The slinger(7) is made from sheet steel(32) with a carbon content of >0.05% carbon so the slinger(7) has the holding power to trap the armature shaft(5) to the upper ball bearing(16) with the pressed gear on the other side this avoids the required press to the upper ball bearing(16) that would otherwise distort and bind the ball bearing, In this design the slinger(7) serves two purposes

1. protects the commutator^) from oil particles from ball bearing(16)

2. Avoid movement of armature shaft(5) in the ball bearing(16).

The armature shaft protrudes from the top shield cap (1) is press fitted to the ball bearing(16) which is in turn press fitted to top shield cap (1).

To avoid reduction of radial clearance in the ball bearing due to this press fit, the armature shaft(5) is not too heavily forced into the ball bearing. Instead the armature shaft(5) is supported by a stepped pinion(3) on one side of the upper ball bearing(16) and the other side is supported by the slinger(7). The slinger(7) is so formed that it contacts the inner ring of the upper ball bearing(16). The stepped pinion(3), bearing(16) and the slinger(7) forms a robust connection on the top shield cap (1).

The top shield cap(l) also has two mounting ears (31) with mounting holes(35) (fig.ll & fig. 8)for position the motor to intended surface.

The end cap (2) also has a cylindrical short neck(36) formed along the referred central hole on its surface which is facing away from the top shield cap(l) (fig. 8). Inside the end cap (2) portion of the interior is adapted for mounting the choke coil(6) (fig. 7 & fig. 6).

Inside the end cap(2) portion(23) of the interior is further adapted to mount on control module (fig. 7).

The brushes riding on the commutator(8) are mounted on the end cap (2)such that the brushes(lO) will be accessible by removing the end cap (2) (fig. 12).

The details are illustrated in fig. 5, 6, 7, 8,10,11, 12 and 14.

At the bottom end of casing(14) is the bottom shield cap (17) (fig. 13).

The bottom shield cap(17) also similarly houses the bearing(15) for the armature shaft(5). The lower ball bearing(15) is press fit into the bottom shield cap (17) as done in the top shield cap(l). The bottom shield cap assembly(17) and corresponding end of casing(14) having a matching set of four tabs(34) and holes(40) for positioning and fixing together (fig. 13). The central portion of the top shield cap(l) and bottom shield cap(17) surface have a short neck(36&37) described before in the preceding paras.

The motor is mounted with two mounting holes(35) of the mounting ears (31) on the top shield cap(l) and at the bottom side it is supported in the system housing with four bumps(39) formed on the case(14) outer surface, (fig. 8). The bumps(25) are either sliding or press fitted to the housing to form a perfect protection for motor under vibration.

Further to the bumps(39), the bottom shield cap(17) of the motor is so formed to accommodate a wavy washer (fig. 13). The wavy washer is secured to the bottom end(18) by pressing it on the hub of the bottom shield cap (17). The wavy washer acts as a compression spring to damp the vibrations to motor, (fig. 3).

The exploded view of the invention is illustrated in fig. 1.

The size of the casing(14) has been a substantial limiting factor in the construction of small but powerful DC motor. The object of the invention is to design the casing(14), the top and bottom shield caps(l&17) and the stator in a manner to achieve a small compact DC motor assembly which can function efficiently like conventional DC motor assembly.

Therefore in one aspect, the application relates to selective shape and positioning of magnets(13) and including selective mounting means of magnets(13) within the casing(14).

The application in second aspect further relates to novel mounting means for positioning the two top and bottom shiedl caps(l&17) on the casing(14).

The application in third aspect further relates to novel arrangement of the mounting choke coils(6) and control module in the top end cap( 2 ).

The application in fourth aspect also provides a novel arrangement of using a slinger(7) with a upper ball bearing(16) to support the armature shaft(5) at the top end of the motor assembly.

The application in sixth aspect has a top shield cap assembly(l) and the bottom shield cap assembly (17) which are distinctively shaped and configured with stamping and interior designed for achieving the objects of the invention.

All of above components so designed to matingly align together to form a compact small motor assembly.

DETAILED DESCRIPTION OF THE INVENTION:

The present invention relates to a DC motor assembly comprising of a top shield cap (1), end cap (2), pinion (3), terminal (4), armature shaft (5), choke coil (6), slinger (7), commutator (8), brush spring (9), carbon brush (10), core pack/armature (11), magnet retainer (12), magnet (13), casing / housing (14), lower ball bearing(15), upper ball bearing (16), bottom shield cap (17), area for placing wavy washer (18), magnet stopper (19), capacitor (20), resistor (21), portion for placing capacitors, resistors and choke coil (22), portion for control module/area for placing sensor, H bridge& controller (23), protrusion (25), slots /holes (26), terminal space(27) on top shield cap, flared fingers(28&38) on top and bottom shield cap , side wall (29), holes for wire (30), mounting ears(31),dents(33), tabs(34), mounting holes (35), cylindrical neck (36&37).

The casing (14) defining an interior chamber formed with a cylindrical side wall and the wall terminate at its two extreme ends forming a top end and a bottom end along its cylindrical axis wherein the stamped top shield cap(l) mounted on the top end of the casing(14) and the stamped bottom shield cap(17) mounted on the bottom end of the casing(14) and also six flared fingers(28) projecting along the edge of the top end of the casing(14) adapted to fit into a set of corresponding holes(26) formed on the top shield cap(l), The bottom end of the casing (14) has a plurality of tabs(34) with flared fingers(38) projecting along the edge adapted to fit into a set of corresponding holes(40&43) formed on the bottom shield cap(17). The casing(14) also has four bumps(39) formed on its outer surface at its lower end for fitment into a desired surface.

The DC motor assembly has the upper ball bearing(16) which is accommodated with press fit arrangement for fitting into a cylindrical neck(36) formed on the top shield cap(l) and the lower ball bearing(15) accommodated with press fit arrangement for fitting into a cylindrical neck(37) formed on the bottom shield cap(17). The armature shaft(5) of the DC motor assembly disposed within the casing(14) and supported by the bearings(15&16) and extending beyond the top shield cap(l) to hold a pinion(3),

The top end cap(2) has a brush card positioned between the casing(14) and the top shield cap(l), a stator with a pair of contoured permanent magnets(13) mounted along the inside surface of the cylindrical casing(14) and supported on a set of magnetic stoppers! 19), and the two ends of each magnet(13) being spaced away from the cylindrical casing(14) such that the air gap between the magnet(13) and the armature shaft(5) has a constant distance over the substantial portion of the magnet(13) and having distance lesser than this constant around the two ends and a magnetic retainers(12) disposed in the spaced gap between the permanent magnet(13) and casing(14), The magnetic retainer(12) is holded by the retainer holder (41).

The top shield cap(l) is adapted to receive two terminals(4) there onto which terminals(4) are connected to the brushes(lO) onto which DC voltage is connected. The end cap(2) has the terminals(4) closely and adjacently disposed around the pinion(3) thereby allowing a large gear engagement at the opposite side of the terminal(4). The terminals(4) are mounted on one side of the axis and along the wall of the casing(14). The top shield cap(l) and top end cap(2) having corresponding matching set of four protrusions(25) on top shield cap(l) and four dents(33) on the end cap(2) for corresponding matching and mating fittingly together and concentrically around the axis. Similarly the casing (14) and top end cap(2) having corresponding matching set of three dents(44) on the top shield cap(l) and three tabs(42) on the circumference of the end cap(2) for corresponding matching and mating fittingly together and concentrically around the axis. The pair of stationery carbon brushes(lO) is disposed in the central gap of the end cap(2). The choke coil(6), capacitors(20), resistors(21) and control module or some of them may be mounted on the end cap(2). The choke coils(6) are connected between the brushes(lO) and the terminals(4) on the top end cap(2). one end of the capacitor(20) is welded to the terminal(4) mounted on the end cap(2) and the other end is grounded to the casing(14).

The pair of mounting ears(31) with two mounting holes(35) is formed in the top shield cap(l) to bolt the motor onto any desired surface. The top shield cap(l) houses the upper ball bearing(16) with a slinger(7) for the armature shaft(5) wherein the upper ball bearing(16) is pressed onto top shield cap(l) thereby trapping the armature shaft(5) on one side of the bearing(16) and the pinion(3) mounted on the armature shaft(5) protruding above the top shield cap(l) also traps the armature shaft(5) on the other side of the bearing(16) such that the armature shaft(5) is supported by a stepped pinion(3) on one side of the bearing(16) and supported by the slinger(7) on the other side. The slinger(7) is a sheet steel with a carbon content of greater than 0.05 % carbon. The slinger(7) contacts a inner ring of the upper ball bearing(16). The end cap (2) also has a cylindrical neck along a central axis and formed on the side which is facing away from the top shield cap(l). The end cap(2) also has a side wall(29) along a portion of circumference of the end cap(2) to insolate the choke oil(6) from the contact. The side wall(29) has holes(30) to allow supply cables. The bottom shield cap(17) has a portion (18) accommodates a wavy washer acting as a compression spring.

WE CLAIM :

1. A DC motor assembly comprising of :
a. a casing (14) defining an interior chamber formed with a cylindrical side wall and the wall terminating at its two extreme ends forming a top end and a bottom end along its cylindrical axis,

b. a stamped top shield cap(l) mounted on the top end of the casing(14),

c. a stamped bottom shield cap(17) mounted on the bottom end of the casing(14),

d. a plurality of flared fingers(28) projecting along the edge of the top end of the casing(14) adapted to fit into a set of corresponding holes(26) formed on the top shield cap(l),

e. a plurality of tabs(34) and flared fingers(38) projecting along the edge of the bottom end of the casing(14) adapted to fit into a set of corresponding holes(40 & 43) formed on the bottom shield cap(17),

f. a upper ball bearing(16) accommodated with press fit arrangement for fitting into a cylindrical neck(36) formed on the top shield cap(l),

g. a lower ball bearing(15) accommodated with press fit arrangement for fitting into a cylindrical neck(37) formed on the bottom shield cap(17),

h. an armature shaft(5) disposed within the casing(14) and supported by the bearings(15&16) and extending beyond the top shield cap(l) to hold a pinion(3),

i. a top end cap(2) which is essentially a brush card positioned between the casing(14) and the top shield cap(l),

j. a plurality of tabs(42) projecting along the circumference of the end cap(2) adapted to fit into a set of corresponding dents(44) formed on the top end of the casing (14),

k. a stator with a pair of contoured permanent magnets(13) mounted along the inside surface of the cylindrical casing(14) and supported on a set of magnetic stoppers(19), and the two ends of each magnet(13) being spaced away from the cylindrical casing(14) such that the air gap between the magnet(13) and the armature shaft(5) has a constant distance over the substantial portion of the magnet(13) and having distance lesser than this constant around the two ends, I. magnetic retainers(12) disposed in the spaced gap between the permanent magnet(13) and casing(14).

2. The DC motor assembly as claimed in claim 1, wherein the top shield cap(l) is adapted to receive two terminals(4) there onto which terminals(4) are connected to the brushes(lO) onto which DC voltage is connected.

3. The DC motor assembly as claimed in claim 1, wherein the end cap(2) has terminals(4) closely and adjacently disposed around the pinion(3) thereby allowing a large gear engagement at the opposite side of the terminal(4).

4. The DC motor assembly as claimed in claim 1, wherein the terminals(4) are mounted on one side of the axis and along the wall of the casing(14).

5. The DC motor assembly as claimed in claim 1, wherein the top end shield cap(l) and top end cap(2) having corresponding matching set of four protrusions(25) on top shield cap(l) and four dents(33) on the end cap(2) for corresponding matching and mating fittingly together and concentrically around the axis.

6. The DC motor assembly as claimed in claim 1, wherein the preferred numbers of the flared fingers(28) is six are spaced evenly along the top surface of the casing(14).

7. The DC motor assembly as claimed in claim 1, wherein a pair of stationery carbon brushes(lO) is disposed in the central gap of the top end cap(2).

8. The DC motor assembly as claimed in claim 1, wherein a pair of choke coils(6), capacitors(20) and resistors(21) or some of them may be mounted on the end cap(2).

9. The DC motor assembly as claimed in claim 1, wherein the choke coils(6) are connected between the brushes(lO) and the terminals(4) on the top end cap(2).

10. The DC motor assembly as claimed in claim 1, wherein the control module is mounted on the top end cap(2).

11. The DC motor assembly as claimed in claim 1, wherein one end of the capacitor(20) is welded to the terminal(4) mounted on the top end cap(2) and the other end is grounded to the casing(14).

12. The DC motor assembly as claimed in claim 1, wherein a pair of mounting ears(31) with two mounting holes(35) is formed in the top shield cap(l) to bolt the motor onto any desired surface.

13. The DC motor assembly as claimed in claim 1, wherein the top shield cap(l) houses the upper ball bearing(16) with a slinger(7) for the armature shaft(5) wherein the upper ball bearing(16) is pressed onto top shield cap(l) thereby trapping the armature shaft(5) on one side of the upper ball bearing(16) and the pinion(3) mounted on the armature shaft(5) protruding above the top shield cap(l) also traps the armature shaft(5) on the other side of the upper ball bearing(16) such that the armature shaft(5) is supported by a stepped pinion(3) on one side of the upper ball bearing(16) and supported by the slinger(7) on the other side.

14. The DC motor assembly as claimed in claim 1, wherein the slinger(7) is a sheet steel with a carbon content of greater than 0.05 % carbon.

15. The DC motor assembly as claimed in claim 1, wherein the slinger(7) contacts a inner ring of the upper ball bearing(16).

16. The DC motor assembly as claimed in claim 1, wherein the end cap (2) also has a cylindrical neck along a central axis and formed on the side which is facing away from the top end shield cap(l).

17. The DC motor assembly as claimed in claim 1, wherein the bottom shield cap(17) accommodates a wavy washer acting as a compression spring.

18. The DC motor assembly as claimed in claim 1, wherein the casing(14) has four bumps(39) formed on its outer surface at its lower end for fitment into a housing.

19. The DC motor assembly as claimed in claim 1, wherein the end cap(2) has a side wall(29) along a portion of circumference of the end cap(2) to insolate the choke oil(6) from the contact.

20. The DC motor assembly as claimed in claim 1, wherein the sidewall(29) of claim 19 has holes(30) to allow supply cables.