FIELD OF THE INVENTION

The invention pertains to starter motor of automobiles. Particularly the Invention pertains to making smaller starter motor with higher torque. The invention also pertains to use of plastic and insert moulding and improved design of the assembly. The invention comprises lessening the number of parts and also making the process of assembly simpler. The invention also comprises use of the starter motor having planetary gears and of smaller size in two wheelers. BACKGROUND OF THE INVENTION

When the starter button available in a two wheeler automobile, a motor-bike, on the handle bar is pressed, current is passed in to the starter motor from battery. By energising the starter motor, the starter motor cranks the engine through gear train. In prior art starter motors currently used in two wheeler automobiles, the gear train comprises a reduction gear system (See Figure 1 A).

In two wheeler automobiles there has been a long standing need for making the size of the parts smaller and smaller, higher in performance efficiency, lesser and lesser in cost of production and more and more convenient for making an assembly during production process. Such a starter motor, can also be equally relevant also for even three- or four- or multi-wheeler automobiles. SUMMARY OF THE INVENTION

This invention discloses a starter motor for an automobile having planetary gear construction for achieving reduction in gear ratio higher than 5:1 and with concurrent reduction in length and overall width of the starter motor. The above starter comprises means to achieve transmission of required torque for achieving high reduction ratio in a planetary construction. The said means comprises a small module planetary gear (8) with high bending strength, the required torque is about 7Nm (Newton Meter) or more and the high reduction ratio comprises a reduction ratio that is higher man 5:1 reduction; preferably in the range of ratio 20:1 to 30:1.

In one aspect of this invention, the small module planetary gear (8) is made in a plastic material.

In another aspect, the starter motor of this invention, has, in comparison with the prior art starter motor having a gear train comprising a reduction gear system and providing same reduction: its length is lesser, excluding the shaft protruding out from the body (48) of the starter motor, up to about 30%, the overall width is lesser up to about 50%, has lesser number of parts, occupies smaller space in the engine layout, does not create an excentric over hanging of motor and noise level is lower, The number of parts of starter motor of this invention is lesser than 46, preferably 33 or lesser, and the noise level is lower than level of around 72 dB-A (decibel scale).

in a further aspect of this invention, the starter motor comprises internal gear integrated and combined with brush holder and terminals by insert moulding in plastic/polymer material. The starter motor comprises at least all gears and body of the starter motor made in plastic. In the illustrative example, the starter motor of this invention has torque of the starter motor is 7Nm and a diameter of 61.0 mm and Length of 90.5mm, excluding the shaft protruding out from the body (48) of the starter motor. Depending on what was the initial property of the starter motor of prior art with reduction gear construction, the starter motor of this invention may have the torque of the motor ranges from 3Nm to 14Nm, diameter ranging from about 40 mm to 68 mm, and length, excluding the shaft protruding out of the body(48), ranges from about 70 mm to 150 mm..

In a further embodiment of this invention, the starter motor of this invention as described above has (a) the output shaft of Gear termination which connects with mating gear train or ring gear of the engine, or (b) the motor of this invention is connected with One way clutch build in construction; a pinion moves forward while starting and return after switching off the motor electricity connection like bendix drive. The starter motor of this invention may be for a two wheeler automobile. The starter motor of this invention may also be for more than two wheeler automobiles.

BRIEF DESCRIPTION OF FIGURES AND LEGENDS

Legends and their description:

Parts of prior at Starter motor: 29.Washer, 30.Circlip, 31.Sprocket, 32.Fixtng brocket assembly, 33. O Ring, 34.Positive brush assembly, 35.gasket, 36.lnter bracket assembly, 37. O Ring, 38.Brush box, 39.Armature assembly, 40. Yoke assembly, 41. Negative brush assembly, 42,Washer, 43.Ball bearing, 44.Reduction gear, 45.Spacer bush, Parts of starter motor of this invention: LCirclip, 2.Sprocket, 3. Fixing bracket, 4.Bush, 5. O ring, 6.Washer, 7.Drive piate, 8. Smaii Module Planetary gear, 9,Bush, lO.Screw, 11.Bali, 12.Pin, 13. Yoke seal, 14. Ring gear, 15.Spring, 16.Brush box, 17.Carbon brush, 18.Brush box cover, 19. Positive terminal, 20.Armature assembly, 21. Magnet, 22 Yoke, 23.Bush, 24.Negative terminal. 25.Yoke assembly, 26.Fixing bracket assembly, 27.Ring gear assembly, 28,Sun gear (Armature shaft), 46 Drive plate with gear, 47 One-way clutch, 48 Shaft protruding out of the body

Figure 1: Relative shape and size of starter motor of prior art and of this invention wherein the length of the starter motor of this invention is up to 30% less than the starter motor of prior art.

A - Starter motor of prior art:

B - Compact starter motor of this invention.

Figure 2: [Exploded view of the assembly of the compact starter motor

Figure 3: Dimensions of one illustration of a starter motor of this invention made for two wheeler automobiles

Figure 4: Gears, shaft, brush holders and terminals integrated as a single insert moulded unit made in a plastic/polymer with brush holders being the only metal part

Figure 5: Rear View of Ring gear assembly).

A - Left side section view - CC ; B - Front view of ring gear assembly

Figure 6: Drawing/design of the prior art motor and its parts.

A - Left side section view - BB ; B - Motor front view

Figure 7: Drawing/design of motor of this invention with sprocket drive output and its parts. A - left side section view - AA; B - Motor front view

Figure 8: Drawing/design of Gear drive motor of this invention with gear drive output and its parts.

A - left side section view - AA; B - Motor front view

Figure 9: Drawing/design of motor of this invention with one-way clutch drive output and its parts.

This invention embodies a two wheeler automobile wherein its starter motor comprises a gear train comprising a planetary gear and a planetary gear system.

A planetary gear system comprises a sun gear around the centre of which revolves an outer bigger gear, ring gear, providing reduction and the movement of sun gear is transmitted to the outer ring gear through smaller gears, the planetary gears, which are meshed with the sun gear on one end and to the outermost gear of the gear train on the other end. The net effect is that better transmission of the torque is effected along an axis that is common to the armature of the starter motor as well as the output shaft that transmits the torque to the engine; and in the process, length as well as breadth of the transmitting system is also reduced to a significant extent. Reduction gear system has long been replaced in starter motors used in four wheelers, however, this has not been introduced for two wheelers for the reason that generally in two wheelers low torque high speed motors are used with high reduction range by using gear train inside the engine. This is followed traditionally, as this system is considered to be cost effective. As two wheelers require high reduction ratio, typically in the range of 20:1 to 30:1 , it is difficult to bring high reduction in gear ratio in a planetary construction i.e. higher than 5:1 unless the size of the planetary gear construction is made bigger than the current size of most of the starter motors of two wheeler automotive applications. Planetary construction can be usually used wherever low reduction is required. However, the instant invention comprises means that are capable of transmission of required torque for achieving high reduction ratio in a planetary construction with concurrent reduction in the size of the planetary gear construction. One of the means illustrated in the examples comprises a small module planetary gear (8} with high bending strength. The illustrative gear is made in a plastic material. Also using planetary system in automobile electric motors is the latest technology started in 4 wheelers since at least about 10 years but the same has not been adapted so far for two wheeler segment on account of need to overcome the technical difficulties in providing required torque, typically about 7Nm (Newton Meter) or more, to bring high reduction, typically more than 5:1 reduction, in planetary construction. This invention overcomes mis limitation. Thus, this invention embodies a starter motor for two wheeler automobiles comprising a planetary gear system with concurrent reduction in size of the starter motors that were being used prior to this invention. The advantage of smaller size of the starter motor of this invention comprises (a) less number of parts, typically from about 46 for prior art motor to 33 in the starter motor of this invention, (b) occupies sma!ller space in the engine layout, typically up to 30% of the prior art starter motor space (c) unlike prior art motor does not create an excentric over hanging of motor, (d) noise level is lower than the typical noise levels of around 72 dB-A (decibel scale) of prior art starter motors, and (e) starter motor length of this invention is shorter by about 30%. This invention also comprises a starter motor in which Internal gear and Planetary gear designed are in plastic material with less number of components. In illustrated embodiment, these parts are made in glass filled Delrin (Polyoxymethylene; also called as POM) in the beginning of this work and later shifted to use of glass filed Nylon 66 material. Any other plastic having properties at least same as glass filled Nylon 66 may be used in place of glass filled Nylon.

This invention also comprises a starter motor comprising internal gear integrated and combined with brush holder and terminals by insert moulding in plastic/polymer material .(figure 4).

This invention comprises a starter motor that is compact and comprising combination of internal gear with brush holder.

This invention comprises a starter motor that is compact and comprises planetary gear and combination of internal gear with brush holder and terminals.

This invention comprises a starter motor that is compact and comprises at least all gears and body of the starter motor made in plastic. The diameter and length of starter motors of prior art two wheeler automobiles is highly variable, and depends on the model used. However, for each of these models, this invention provides a starter motor for two wheeler automobiles comprising up to 30% lesser length than currently used length in the prior art model. The illustrative embodiment of the starter motor of mis invention has a high torque motor with torque of 7Nm and has a smaller frame size i.e. with a diameter of 61.0mm and Length of 90.5mm, excluding the shaft protruding out from the body (48) of the starter motor. The illustrative motor is concentrically arranged and has an overall width of 81mm. Its prior art version has torque of 7Nm, frame size with a diameter of 52mm and Length of 110mm, excluding the shaft protruding out from the body (48) of the starter motor, and the starter motor is aligned in an eccentric way on account of the reduction gear. Hence, not only the length but even overall width of the prior art starter motor is more i.e. 112.5mm. Thus the illustrative starter motor of this invention has length lesser than 18% of the length of the prior art starter motor; and the overall width of the starter motor of this invention is lesser than 28% of the overall width of the prior art starter motor. Depending on the model of the two wheeler automobile the torque, diameter and length of the starter motor shall vary, however, in each case, the torque may range from 3Nm to 14Nm, the diameter may range from about 40 mm to 68 mm, the overall width may range between 45 and 72 mm, and length (excluding the shaft protruding out of the body(48)) shall be up to 30% lesser than the corresponding prior art started motors and shall range from about 70 mm to 150 mm.

Figure 6 provides a drawing/design of prior art starter motor and figure 7 provides the drawing/design of the motor of this invention.

The illustrative starter motor (Figure 2) of this invention has following specifications:

In general, Prior art starter motor of figure 6 comprising reduction gear mechanism and having reduction gear and having no integration of interna! gear with brush holder has (a) more number of parts, (b) occupies Large Space in the Engine layout, (c) has eccentric output shaft, which creates over hanging of motor, (d) noise level is high, and (e) starter motor length high.

The starter motor of this invention comprises unique terminal design for insert moulding to get compactness. Starter motor of this invention has less number of parts on account of steps comprising (a) integration of brush box and terminals in internal gear by insert molding in a plastic/polymer, and (b) use of planetary gear instead of Reduction gear. The starter motor of this invention occupies less space in the engine layout. The concentric output shaft of the starter motor of this invention makes mounting of the motor compact and rigid. Noise level of the starter motor of this invention is also low. The length of the starter motor of this invention is lesser than the length of the starter motor of prior art.

The Same starter motor can be made with output shaft of Gear termination to connect with mating gear train or ring gear of the engine as shown in Figure 8.

The another option is that the motor of this invention can be connected with One way clutch build in construction. The pinion shown in the figure 9 will move forward while starting and return after switching off the motor electricity connection like bendix drive as shown in Figure 9. For four wheelers, the gear reduction required is not more than 5:1, planetary construction has already been introduced without any difficulty, However, it is an embodiment of this invention that if all the features described above, which have enabled for planetary construction in two wheeler starter motors too with concurrent 18% reduction in length, are applied to the starter motors of two wheelers also that have planetary construction, they shall enable improvement in them from the point of view of smaller number of parts, more efficient assembly and reduction in cost. Hence, the inventive features of this invention adapted for the starter motors of four wheelers with planetary construction shall provide far improved starter motors.