A Starter motor Assembly for an Internal Combustion Engine

Field of the Invention:

The present invention relates to "A starter motor assembly for cranking an Internal Combustion Engine " and more particularly for a two wheeler.

Background of the Invention:

A Starter motor is used In an Internal Combustion Engine to rotate the crankshaft assembly to a minimum angular speed required for reliable starting of the engine. Starter motors for Internal Combustion Engine starting are generally DC motors with either permanent magnets or series field coils providing the stationery magnetic field.

A rotor with armature coils wound around a laminated core is located under the stator poles, separated by an air gap. Commutator segments are connected with one end of the rotor shaft and the other end of the rotor shaft has toothed pinion for meshing with gears. The armature coils are connected to commutator segments that are generally made of copper. Carbon brushes are always in sliding contact with the commutator segments and are connected with a yoke by means of a brush holder assembly. The yoke holds the stator poles and completes the magnetic circuit. When a power supply is connected across the brushes, a current flows in the armature coil and the stator field causes a torque to be developed, thereby rotating the rotor shaft.

The rotor shaft is supported by bearings at both ends to reduce friction. The toothed pinion end of the shaft has a drive end bracket connected with the yoke. The drive end bracket has an oil seal to prevent the engine oil from entering into the starter motor through the clearance between the shaft and the drive end bracket. The drive end bracket also has a bearing to support the shaft-at the pinion end. For connecting the starter motor to the engine, the yoke is connected to a crankcase of the engine by means of fasteners. There is an opening for the starter motor shaft in the crankcase. The crankcase has a boss for supporting the drive end bracket of the starter motor. The drive end bracket has an 0-Ring forming a tight seal with the crankcase opening boss and thereby preventing the engine oil from escaping through the clearance between the crankcase opening and the drive end bracket. There is also an 0 - Ring between the drive end bracket and the yoke preventing water or other fluids from entering into the starter motor through the clearance between the yoke and drive end bracket.

The problem associated with this kind of arrangement is that it requires much number of processes thereby increasing the assembling time. Even the cost associated with this is enormously high.

Hence the objective of the invention is to provide a starter motor assembly which overcomes the above mentioned problems.

Summary of the Invention:

The principle object of the invention is to provide a starter motor assembly for an internal combustion engine without a drive end bracket for connecting to the engine crankcase.

Another object, of the invention is to reduce an O - Ring that is-used for sealing the clearance between the crankcase opening for starter motor shaft entry and drive end bracket.

It is a further object of the invention to reduce the number of processes performed on the starter motor assembly.

Yet another object of the present invention is to provide a starter motor assembly with reduced number of part counts.

Further object of the present invention is to provide a starter motor assembly which is cost effective.

Another object of the present invention is to provide a starter motor assembly that reduces assembly time drastically.

Brief Description of the Drawings:

The present invention ( become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein

Figure 1 showing a perspective view of an internal combustion engine comprising a starter motor.

Figure 2 is a pictorial view of the starter motor.

Figure 3 showing left hand side crankcase with cover magneto removed.

Figure 4 showing the starter motor assembly for an internal combustion engine with an oil seal.

Figure 5 showing the starter motor assembly for an internal combustion engine with a bearing.

Detail Description of the Invention:

For the purpose of illustration only it will be illustratecl with the help of a two wheeler motorcycle. First the whole structure of the vehicle will be roughly described. With reference to, a motorcycle comprises of a frame, front fork attached to a pivot tube of the vehicle frame, a front wheel attached to these front forks, a handle bar connected to the front forks, a fuel tank attached so as to straddle an upper part of the vehicle frame, a seat attached to the upper rear portion of the vehicle frame, an engine unit attached to the lower front section of the vehicle frame, a swing arm attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown in the drawing) from the vehicle frame and a rear wheel attached to a rear end of swing arm. The intake system of the engine comprises of a carburettor, intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front-fender for covering an upper part of the front wheel, and a rear fender for covering an upper part of the rear wheel. The drive from the engine is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

Now referring to Figure 1 showing a internal combustion engine (101), wherein a starter motor (102) is provided. The said starter motor is mounted to the crankcase of the internal combustion engine with fasteners (103). A cover magneto (104) is provided on the left of the crankcase.

Figure 2 showing a starter motor having a yoke (201) that is removably-connected with a crankcase of the. engine. The said yoke (201) carries the stationery field poles (202), either permanent magnets or field coils wound around laminated poles. A rotor shaft (203) has armature coils wound around the slots in a laminated rotor core and is located concentrically within the stator poles, separated by an air gap. One end of the rotor shaft has commutator segments connected concenthcally along the circumference of the shaft, this side is provided with a rear end bracket (204). The other end of the rotor shaft has toothed pinion (205) for meshing with gears. Carbon brushes are in sliding contact with the commutator segments and are connected with the said yoke (201) by means of a brush holder assembly.

The said yoke (201) is removably connected to a crankcase of the engine such that the motor shaft enters into a crankcase opening (402) for meshing with gears (it can be seen in figure 4). An O - Ring prevents water or other fluids from entering through the clearance between the crankcase and yoke. Figure 4 shows the crankcase opening (402) with an oil seal (401) for preventing oil ingress into the starter motor through the clearance between the crankcase opening and rotating shaft. Figure 5 shows the crankcase opening (402) with a bearing (501) for supporting the rotating shaft and reducing friction.

The said yoke (201) through its rear end bracket (204) is fastened to the crankcase. -Since there is no drive end bracket, there is one 0 - Ring less required and the processes done on the drive end bracket are not required. For assembly of starter motor with the engine, the yoke is connected to the crankcase and thereby the pinion in the rotor shaft engages with the gear inside the crankcase.

Oil seal and bearing are fitted to the crankcase opening during manufacturing of the crankcase. Thus the number of processes performed for the starter motor assembly is reduced. Assembly time is reduced and hence productivity can be improved during mass production.

Since the starter motor is manufactured for assembly with the Internal Combustion Engine, the function of the drive end bracket can be transferred to the opening in the crankcase meant for rotor shaft entry.

The elimination of the drive end bracket from the starter motor assembly results in cost reduction, process reduction and part count reduction.

Although this invention has been described in terms of a certain preferred embodiment, other embodiments apparent to those of ordinary skill in the art are also within the scope of this invention. Accordingly, the scope of the invention is intended to be defined only by the claims that follow.

We claim:

1. A starter motor assembly for an internal combustion engine mounted to the crankcase of the said engine comprises:
a starter motor comprising a rotor shaft output pinion and a rear end bracket connected to a yoke;
a crankcase opening to accommodate the said starter motor;
an oil seal fitted to the said crankcase opening to prevent oil and dust ingress to the starter motor; and
a bearing fitted to the said crankcase opening to reduce friction.

2. A starter motor assembly for an internal combustion engine as claimed in claim 1 wherein the said yoke rear end bracket is mounted to the crankcase by means of fasteners.

3. A starter motor assembly for an internal combustion engine as claimed in claim 1 wherein the said yoke holds the stator poles.

4. A starter motor assembly for an internal combustion engine as claimed in claim 1 wherein the said rotor shaft is provided with toothed pinion on one end to mesh with engine gear inside the crankcase.

5. A starter motor assembly for an internal combustion engine as claimed in claim 1 wherein the said rotor is located concentrically with the stator poles separated by an air gap.

6. A starter motor assembly for an internal combustion engine as claimed in claim 1 wherein the said crankcase opening is provided to accommodate both the yoke and rotor shaft entry.

7. A starter motor assembly for an internal combustion engine as claimed in claim 1 wherein the said yoke is removably connected to the crankcase.