Starter motor

A starter motor for an engine which does not readily admit water into a casing thereof and which allows water to be discharged promptly from the housing. The starter motor comprises a seal member for closing a gap between an outer periphery of a pinion moving member on an output rotary shaft or of an overrunning clutch and the casing, and the casing has two communicating holes formed therein for the communication with the atmospheric air outside the casing. One of the communicating holes is formed at a lower portion of the casing so that water may be discharged outwardly from within the casing therethrough. The other communicating hole is formed at a higher location of the casing and may be a communicating groove formed in an end face of a front bracket of the casing along which the front bracket is coupled to a yoke of an electric motor which is mounted in the casing and operatively coupled to the pinion moving member by way of the overrunning clutch.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a starter motor, and more particularly to a 
starter motor for driving a pinion for engagement with a ring gear of an 
engine to start the engine. 
2. Description of the Prior Art 
Starter motors of the so-called overhang type are conventionally well 
known. An exemplary one of such starter motors is disclosed, for example, 
in Japanese Utility Model Laid-Open No. 6679/1986. The exemplary starter 
motor is shown in FIGS. 10 and 11. 
Referring to FIGS. 10 and 11, the conventional starter motor of the 
overhand type shown includes a front bracket 1 of an outer casing or motor 
frame in which an opening 2 is formed. An extension or output rotary shaft 
3 of an armature rotary shaft of a dc motor (not shown) disposed in the 
inside of the motor frame extends outwardly through the opening 2 of the 
front bracket 1. A pinion moving member 4 is fitted for sliding movement 
on and for rotation relative to the output rotary shaft 3 with a pair of 
bearings 5 interposed therebetween. The pinion moving member 4 is 
supported also for rotation and for axial sliding movement by means of a 
bearing 6 mounted on an inner face of the front bracket 1 adjacent the 
opening 2 to thus support the output rotary shaft 3 on the motor frame. 
The pinion moving member 4 has a pinion 4a formed on an outer periphery of 
a front end portion (right-hand end portion in FIG. 10) thereof while a 
rear end thereof terminates in a clutch inner member 7a which is a 
component of an overrunning clutch device 7. Meanwhile, an outer periphery 
of the pinion moving member 4 between the pinion 4a and the clutch inner 
member 7a serves as a sliding supporting face 4b at which the pinion 
moving member 4 is supported for axial sliding movement by the bearing 6. 
The overrunning clutch device 7 further includes a clutch outer member 7b 
and a plurality of rollers 7c for transmitting turning force from the 
clutch outer member 7b to the clutch inner member 7a. An oil seal 8 is 
fitted around the outer periphery of the pinion moving member 4 forwardly 
of the bearing 6. A dust protective cap 9 is removably mounted at a front 
end of the pinion moving member 4. A stopper 10 is mounted at an end of 
the output rotary shaft 3 and prevents the pinion moving member 4 from 
coming off from the output rotary shaft 3. A ring gear 11 of an engine, 
not shown, is positioned in an opposing relationship to an outer periphery 
of a front end portion of the output rotary shaft 3. 
In operation, the overrunning clutch device 7 will be shifted forwardly in 
the direction of an arrow mark 12 in FIG. 10 by way of a shift lever (not 
shown) of a vehicle in which the engine is installed. Upon such shifting 
movement of the overrunning clutch device 7, also the pinion moving member 
4 is slidably mounted in an integral relationship with the overrunning 
clutch device 7 on the output rotary shaft 3 so that the pinion 4a thereof 
extending outwardly through the opening 2 of the front bracket 1 is 
brought into meshing engagement with the ring gear 11 of the engine as 
shown in FIG. 11. The dc motor is energized just before the pinion 4a is 
brought into meshing engagement with the ring gear 11, and rotation of the 
armature rotary shaft thereof is transmitted from the clutch outer member 
7b to the clutch inner member 7a by way of the rollers 7c of the 
overrunning clutch device 7 to rotate the pinion moving member 4 to start 
the engine by way of the pinion 4a and the ring gear 11. 
When the pinion moving member 4 is rotated at a high speed by the engine 
after starting of the engine but before returning of the pinion moving 
member 4 in the direction opposite to the direction of the arrow mark 12 
to its home position by a spring means, not shown, the clutch inner member 
7a of the overrunning clutch device 7 is rotated at a higher speed than 
the clutch outer member 7b. Consequently, the rollers 7c are brought out 
of meshing engagement with the clutch inner member 7a and the clutch outer 
member 7b to allow the clutch inner member 7a to rotate idly with respect 
to the clutch outer member 7b. Thus, the overrunning clutch device 7 
serves as a one-way clutch which has a function to transmit turning force 
only in one of the two opposite directions, and high speed rotation of the 
pinion moving member 4 is not transmitted to the dc motor. 
While the oil seal 8 serving as a waterproof and dust tight structure of 
the starter motor is not described in detail in Japanese Utility Model 
Laid-Open No. 6679/1986 mentioned hereinabove, such a conventional oil 
seal as shown in FIG. 12 may be employed as the oil seal 8. Referring to 
FIG. 12, the conventional oil seal 8 shown includes a mounting ring 8a 
made of iron and having a substantially L-shaped cross section, and a 
rubber seal element 8b having a V-shaped cross section and securely 
mounted on an inner periphery of the mounting ring 8a. As apparently seen 
in FIG. 12, the oil seal 8 having such construction as described just 
above is mounted by force fitting on an inner periphery of the opening 2 
of the front bracket 1 which is formed axially outwardly of and has a 
smaller diameter than another inner periphery of the opening 2 of the 
front bracket 1 in which the bearing 6 is fitted. The oil seal 8 is spaced 
forwardly from the bearing 6, and the opening side of the V-shaped seal 
element 8b is directed outwardly of the opening 2 while a radially inward 
lip portion 8c thereof is held in contact with the outer periphery of the 
pinion moving member 4. 
A conventional starter motor of the overhand type which includes such a 
waterproof and dust tight structure as described above has a drawback that 
water is likely to gather in the V-shaped seal element 8b of the oil seal 
8. Particularly where the starter motor is mounted in a vertical 
orientation on an engine such that the pinion 4a is located upwardly while 
the dc motor is located downwardly, water may be received in the V-shaped 
seal element 8b. Once water gathers in the seal element 8b of the oil seal 
8 in this manner, it will readily advance into the inside of the front 
bracket 1 due to a breathing action by heat or due to vibrations and will 
thus cause rust on the bearing 6 which may be in the form of a ball 
bearing. Such rust will deteriorate sliding movement of the pinion moving 
member 4 with respect to the output rotary shaft 3 coupled to the dc 
motor. Or worse, water may advance into the inside of the dc motor and 
cause a failure in operation of the dc motor. 
A starter motor is also conventionally known which is constructed such that 
water which eventually gathers in the motor is removed from within the 
motor by way of a water drain hole. The starter motor of the type just 
mentioned is shown in FIG. 13. Referring to FIG. 13, the starter motor 
shown includes a motor body 51 composed of an armature 52, an armature 
rotary shaft 53, a plurality of field coils 54, a plurality of armature 
coils 55, a plurality of magnetic poles 56, a yoke 57 and so forth. A 
pinion 58 for engaging with a ring gear (not shown) of an engine (not 
shown) is mounted on an output rotary shaft 59 which may be in the form of 
a forward extension of or may be coupled to the armature rotary shaft 53. 
The pinion 58 is operatively coupled to the output rotary shaft 59 by way 
of an overrunning clutch device 60 which includes a clutch outer member 61 
and a clutch inner member 62 formed in an integral relationship with the 
pinion 58. A rear end portion of the armature rotary shaft 53 is supported 
for rotation on a rear bracket 63 by way of a bearing 65 while a front end 
portion of the output rotary shaft 59 is supported for rotation on a front 
bracket 64 by way of another bearing 66. A sleeve bearing 67 is interposed 
between the pinion 58 and the output rotary shaft 59. An electromagnetic 
switch 68 is disposed in parallel to the armature rotary shaft 54 and 
actuates, upon closing of a starter switch not shown, a shift lever 69 to 
push the pinion 58 axially outwardly of the motor body 51 and close 
contacts, not shown, to supply electric power to the motor body 51. 
The rear bracket 63 and the front bracket 64 cooperate to form an outer 
casing which surrounds the motor body 51 together with the yoke 57, and an 
oil seal 70 for waterproofing is interposed between the front bracket 64 
and the overrunning clutch device 60 while a radial water discharging hole 
71 is formed in the front bracket 64 forwardly of the oil seal 70. 
With this starter motor, even if water comes to a location around the 
pinion 58 from the engine side, it is prevented from advancing into the 
inside of the starter motor by the oil seal 70 on the outer periphery of 
the overrunning clutch device 60 or pinion 58 and is discharged by way of 
the water discharging hole 71. 
However, if water comes to a location around the pinion 58 from a 
transmission side of the engine when the motor body 51 is in a high 
temperature condition, water is sometimes admitted into the outer casing 
of the starter motor due to a capillary phenomenon along the overrunning 
clutch device 60. Consequently, water gathers around the motor body 51 and 
causes rust on the motor body 51, which will deteriorate operation of the 
starter motor. 
In order to discharge water which may possibly gather in the inside of the 
outer casing of the starter motor, a water drain hole 72 is formed at a 
lower or bottom portion of a side wall of the outer casing, that is, the 
rear bracket 63. Actually, however, such water drain hole 72 is not very 
effective to discharge water gathering in the inside of the starter motor. 
Or rather, splashed water may be admitted into the inside of the starter 
motor by way of the water drain hole 72, resulting in deterioration in 
operation of the starter motor. 
In the case of the starter motor which is mounted on the engine in a 
horizontal orientation wherein the axis of the armature rotary shaft 53 
extends in a horizontal direction, the water drain hole 72 is formed at a 
bottom portion of the side wall of the rear bracket 63 as described above. 
However, where the starter motor is mounted in a vertical orientation 
wherein the axis of the armature rotary shaft 53 extends in a vertical 
direction as shown in FIG. 14, the water drain hole 72 is conventionally 
formed at a different bottom portion, that is, at an axial end wall of the 
rear bracket 63 as shown in FIG. 14. Also the arrangement is not effective 
to prevent the motor body from being wet with water admitted into the 
inside of the starter motor from the transmission side. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a starter 
motor which can effectively prevent water from being admitted into the 
inside thereof whether a pinion moving member is in a rest position or in 
an operative position irrespective of an orientation of the starter motor 
mounted on an engine. 
It is another object of the present invention to provide a starter motor 
which does not readily admit water into the inside of an outer casing 
thereof even if the temperature of a motor body rises and which can 
discharge water promptly from the inside of the outer housing. 
It is a further object of the present invention to provide a starter motor 
which is simple in construction and easy to produce and can effectively 
prevent a motor body from being wet with water admitted into the inside of 
the starter motor from a transmission side of an engine on which the 
starter motor is mounted. 
In order to attain the objects, according to one aspect of the present 
invention, there is provided a starter motor for starting an engine, which 
comprises a casing including a front bracket and a rear bracket, an output 
rotary shaft mounted for rotation in the casing, an electric motor 
accommodated in the casing for rotating the output rotary shaft, a bearing 
mounted on the front bracket, the front bracket having an opening formed 
therein, a pinion moving member mounted for rotation and for axial sliding 
movement on the output rotary shaft and supported at an outer periphery 
thereof for axial sliding movement on the bearing and also for rotation on 
the front bracket by way of the bearing, the pinion moving member 
extending outwardly through the opening of the front bracket, an 
overrunning clutch for coupling the output rotary shaft to the pinion 
moving member, the pinion moving member having a pinion formed at a front 
end portion thereof such that, when the pinion moving member is moved 
outwardly in an axial direction from its rest position, the pinion is 
operatively coupled to the engine to start the engine, an annular seal 
member mounted in the opening of the front bracket and extending radially 
inwardly and generally axially outwardly from the front bracket to form a 
lip portion, and a flange member securely mounted on the outer periphery 
of the pinion moving member such that, when the pinion moving member is at 
its rest position, the lip portion of the annular seal member contacts 
with the flange member to close the opening of the front bracket, the rear 
bracket having a water drain hole formed at a location thereof opposite to 
the opening of the front bracket for discharging water from the inside of 
the casing, the casing having an atmosphere communicating hole formed at a 
suitable location thereof for preventing admission of water into the 
inside of the casing but permitting passage only of air therethrough. 
With the starter motor, when the pinion moving member is at its rest 
position, the lip portion of the annular seal member mounted in the 
opening of the front bracket of the casing contacts with the flange member 
to close the opening of the front bracket. Consequently, even where the 
starter motor is mounted in a vertical orientation wherein the output 
rotary shaft extends in a vertical direction and the pinion is positioned 
upwardly, water coming from above to the starter motor is prevented from 
advancing into the inside of the casing along the outer periphery of the 
pinion moving member. Besides, even if water is admitted into the inside 
of the casing of the starter motor, such water is promptly discharged 
outwardly by way of the water drain hole due to presence of the atmosphere 
communicating hole. 
According to another aspect of the present invention, there is provided a 
starter motor for starting an engine, which comprises a casing including a 
front bracket and a rear bracket, an output rotary shaft mounted for 
rotation in the casing, an electric motor accommodated in the casing for 
rotation the output rotary shaft, a bearing mounted on the front bracket, 
the front bracket having an opening formed therein, a pinion moving member 
mounted for rotation and for axial sliding movement on the output rotary 
shaft and supported at an outer periphery thereof for axial sliding 
movement on the bearing and also for rotation on the front bracket by way 
of the bearing, the pinion moving member extending outwardly through the 
opening of the front bracket, an overrunning clutch for coupling the 
output rotary shaft to the pinion moving member, the pinion moving member 
having a pinion formed at a front end portion thereof such that, when the 
pinion moving member is moved outwardly in an axial direction from its 
rest position, the pinion is operatively coupled to the engine to start 
the engine, and an annular seal member mounted in the opening of the front 
bracket and extending radially inwardly to form a lip portion which is 
held in normal contact with the outer periphery of the pinion moving 
member, the rear bracket having a water drain hole formed at a location 
thereof opposite to the opening of the front bracket for discharging water 
from the inside of the casing, the casing having an atmosphere 
communicating hole formed at a suitable location thereof for preventing 
admission of water into the inside of the casing but permitting passage 
only of air therethrough. 
With the starter motor, the lip portion of the annular seal member mounted 
in the opening of the front bracket of the casing remains in normal 
contact with the flange member to close the opening of the front bracket. 
Consequently, even where the starter motor is mounted in a vertical 
orientation wherein the output rotary shaft extends in a vertical 
direction and the pinion is positioned upwardly, water coming from above 
to the starter motor is prevented from advancing into the inside of the 
casing along the outer periphery of the pinion moving member. Besides, 
even if water is admitted into the inside of the casing of the starter 
motor, such water is promptly discharged outwardly by way of the water 
drain hole due to presence of the atmosphere communicating hole. 
According to a further aspect of the present invention, there is provided a 
starter motor for starting an engine, which comprises a casing including a 
front bracket and a rear bracket, an output rotary shaft mounted for 
rotation in the casing, the starter motor being mounted on the engine in a 
vertical orientation wherein the output rotary shaft extends in a vertical 
direction and the front and rear brackets are positioned upwardly and 
downwardly, respectively, an electric motor accommodated in the casing for 
rotating the output rotary shaft and having a yoke which serves as part of 
the casing, a pinion moving member mounted for rotation and for axial 
sliding movement on the output rotary shaft and also in the front bracket 
and having a pinion formed at an outer end portion thereof, an overrunning 
clutch for coupling the output rotary shaft to the pinion moving member, a 
shift lever mounted at a supporting portion of the front bracket in the 
casing for moving the pinion moving member in the opposite axial 
directions, an electromagnetic switch located in a juxtaposed relationship 
with the electric motor in the casing for controlling energization of the 
electric motor and operating the shift lever to move the pinion moving 
member axially to and from a position in which the pinion thereof is 
operatively coupled to the engine to start the engine, and a seal member 
for closing a gap between an outer periphery of the overrunning clutch and 
the front bracket, the rear bracket having a water drain hole formed at a 
lower portion thereof such that water may be discharged downwardly through 
the water drain hole, the front bracket having a communicating groove 
formed in an end face thereof adjacent the supporting portion such that 
the inside and the outside of the yoke of the electric motor are 
communication with each other by way of the communicating groove. 
With the starter motor, the communicating groove which communicates the 
inside and the outside of the yoke with each other prevents the inside of 
the yoke from being put into a negative pressure condition. Consequently, 
admission of water into the inside of the casing due to a capillary 
phenomenon along the seal member is prevented. Further, even if water is 
admitted into the casing, such water is promptly discharged outwardly by 
way of the water drain hole. Besides, the structure for minimizing a 
possible bad influence of water which may be admitted into the inside of 
the casing from the engine side can be produced readily, for example, by 
forming directly in a front bracket by die-casting a communicating hole or 
groove which communicates the inside and the outside of the casing. 
According to a still further aspect of the present invention, there is 
provided a starter motor for starting an engine, which comprises a casing, 
an output rotary shaft mounted for rotation in the casing, an electric 
motor accommodated in the casing for rotating the output rotary shaft, a 
pinion moving member mounted for rotation and for axial sliding movement 
on the output rotary shaft and also in the front bracket and having a 
pinion formed at an outer end portion thereof, an overrunning clutch 
accommodated in the casing for coupling the output rotary shaft to the 
pinion moving member, an electromagnetic switch for controlling 
energization of the electric motor and moving the pinion moving member 
axially to and from a position in which the pinion of the pinion moving 
member is operatively coupled to the engine to start the engine, and a 
seal member for closing a gap between an outer periphery of the 
overrunning clutch and the casing, the casing having at least two 
communicating holes formed therein for the communication with the 
atmospheric air outside the casing, one of the communicating holes being 
formed at a lower portion of the casing in such a manner as to be directed 
downwardly. 
With the starter motor, even if the temperature of the electric motor rises 
or lowers, admission of water into the casing is prevented or minimized 
since air in the casing communicates with the atmospheric air outside the 
casing. Further, even if water is admitted into the casing, it is promptly 
discharged outwardly by way of the downwardly directed communicating hole 
due to presence of another one of the communicating holes which 
communicates with the atmospheric air outside the casing. Also splashed 
water which may be admitted into the casing is also discharged promptly. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following description and the 
appended claims, taken in conjunction with the accompanying drawings in 
which like parts are denoted by like reference characters all through the 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, there is shown a starter motor to which the 
present invention is applied. The starter motor has somewhat similar 
construction to that of the conventional starter motor described 
hereinabove with reference to FIGS. 10 to 12, and detailed description of 
such common construction is omitted herein to avoid redundancy. 
The starter motor is generally denoted at 20 and is mounted in a vertical 
orientation on an engine, not shown. The starter motor 20 includes a front 
bracket 1 having an opening 2 formed at an upper wall thereof through 
which a pinion moving member 4 can pass. A radially inwardly extending 
flange 2a is formed over an entire circumference on an inner periphery of 
the opening 2 of the front bracket 1. An annular oil seal 21 is interposed 
between the flange 2a of the front bracket 1 and a bearing 6 force fitted 
in the opening 2. The annular oil seal 21 is fixedly held along an outer 
periphery thereof between the bearing 6 and a lower face of the flange 2a 
of the front bracket 1. The annular oil seal 21 extends radially inwardly 
and is intermediately bent axially outwardly, that is, axially upwardly, 
to provide a lip portion 21a as seen in FIG. 1. The annular oil seal 21 is 
cut out at a circumferential portion thereof together with an axial or 
upper end face of the front bracket 1, along which the opening 2 is 
defined, to form a water discharging groove 2b. 
A flange member 22 having a channel-shaped cross section is mounted over an 
entire circumference on a sliding supporting face 4b of the pinion moving 
member 4. The flange member 22 is secured by suitable means such as force 
fitting at a location of the pinion moving member 4 such that, when the 
pinion moving member 4 is at its normal rest or inoperative position shown 
in FIG. 1, the lip portion 21a of the oil seal 21 extends into the inside 
of the channel-shape of the flange member 22 and contacts with an inner 
bottom face of the channel-shape member 22 as shown in FIG. 1. 
A water drain hole 24 is formed in a bottom wall or axially lower wall of a 
rear bracket 23 which constitutes an outer casing together with the front 
bracket 1, and a grommet 25 for draining water from within the outer 
casing but preventing admission of water from the outside of the outer 
casing of the starter motor is fitted in the water drain hole 24. 
In order to allow water to be discharged from the inside of the outer 
casing of the starter motor by way of the water drain hole 24 of the rear 
bracket 23, it is necessary to keep the inside of the outer casing in 
communication with the atmospheric air outside the outer casing at some 
other location of the outer casing. To this end, an atmosphere 
communicating hole 26 is formed in a side wall of the front bracket 1. 
Since the starter motor 20 is mounted and used in a vertical orientation 
wherein the front bracket 1 is located upwardly while the rear bracket 23 
is located downwardly as shown in FIG. 1, an outer opening 26a of the 
atmosphere communicating hole 26 is directed downwardly so that water may 
not be admitted into the inside of the outer casing by way of the 
atmosphere communicating hole 26. 
It is to be noted that reference numeral 13 in FIG. 1 denotes a motor body 
of a dc motor, 14 an electromagnetic switch device, and 17 an armature 
rotary shaft of the dc motor. The output rotary shaft 3 is either an 
extension of the armature rotary shaft 17 of the dc motor or coupled to 
the armature rotary shaft 17. 
When the starter motor 20 is mounted in position on the engine, not shown, 
the opening 2 of the front bracket 1 through which the pinion moving 
member 4 can be axially advanced and retracted in vertical directions is 
closed completely by the flange member 22 and the oil seal 21. 
Accordingly, when the starter motor 20 is in a rest condition, admission 
of water or dust into the inside of the outer casing of the starter motor 
can be prevented effectively. On the other hand, when the starter motor 20 
is moved axially outwardly to an operative condition so that the pinion 
moving member 4 is projected axially upwardly into meshing engagement with 
a ring gear (not shown) of the engine, the flange member 22 is spaced 
upwardly from the lip portion 21a of the oil seal 21. According, water may 
be admitted into the inside of the outer casing by way of a gap between 
the flange member 22 and the oil seal 21. Such water thus admitted in will 
pass through the opening 2 of the front bracket 1 and then along the 
sliding supporting face 4b of the pinion moving member 4 and then through 
between the bearing 6 and the pinion moving member 4 into the inside of 
the outer casing. However, water admitted into the inside of the starter 
motor 20 in this manner will be discharged promptly to the outside by way 
of the water drain hole 24. 
Thus, it is apparent that, if water comes to the starter motor 20, only 
while the pinion moving member 4 is in its normal rest position when a 
vehicle on which the engine is carried is operating, admission of water 
into the inside of the starter motor 20 can be prevented perfectly. 
Referring now to FIG. 2, there is shown a modification to the starter motor 
shown in FIG. 1. The modified starter motor is generally denoted at 30 and 
is only different in construction from the starter motor 20 described 
hereinabove with reference to FIG. 1 in that the flange member 22 is 
omitted and the lip portion 21a of the oil seal 21 is normally held in 
direct contact with the sliding support face 4b of the pinion moving 
member 4. 
With the modified starter motor, whether the pinion moving member 4 is in 
its normal inoperative position or in its operative position in which it 
projects axially outwardly from the front bracket 1 and the pinion 4a 
thereof meshes with the ring gear (Not shown) of the engine on which the 
starter motor is mounted, the lip portion 21a of the oil seal 21 is always 
held in contact with the sliding supporting face 4b of the pinion moving 
member 4. Consequently, the opening 2 of the front bracket 1 is closed 
perfectly, and accordingly, admission of water or dust can be prevented 
perfectly. Even if water should be admitted into the inside of the outer 
casing of the starter motor 30, it can be discharged promptly from the 
inside of the starter motor 30 by way of the water drain hole 24 formed in 
the rear bracket 23 as described hereinabove. 
Referring now to FIGS. 3 and 4, there is shown a modification to the 
modified starter motor shown in FIG. 2. The further modified starter motor 
is generally denoted at 40 and is different in construction from the 
starter motor of FIG. 2 in that an additional oil seal 41 is interposed 
between the front bracket 1 and the overrunning clutch device 7 and a 
communicating groove 42 is formed in place of the atmosphere communicating 
hole 26 formed in the front bracket 1 as described below. 
In particular, the motor body 13 includes a yoke 15 which cooperates with 
the front bracket 1 and the rear bracket 23 to constitute the outer casing 
or motor frame. The yoke 15 of the motor 13 is mounted on the front 
bracket 1 such that an upper end face thereof presses against and 
compresses a packing 16 which cooperates with the front bracket 1 to 
support a shift lever 19 for pivotal motion around a fixed point in the 
starter motor and protects a pivotally supported portion of the shift 
lever 19 against water. Also the electromagnetic switch device 14 is 
mounted on the front bracket 1 such that a casing 14a thereof presses, at 
an upper end face thereof, against and compresses the packing 16. 
Referring particularly to FIG. 4, there is shown a relationship between the 
packing 16 and the front bracket 1. The front bracket 1 is shown in a 
bottom end view and has an annular portion 44 at which it contacts with 
and is connected to the upper end of the yoke 15 of the motor body 13. The 
front bracket 1 further has another annular portion 45 at which it 
contacts with and is connected to the upper end of the casing 14a of the 
electromagnetic switch device 14. Accordingly, portions 46 of the front 
bracket 1 indicated by meshes are exposed to the external air outside the 
outer casing of the starter motor 40. The communicating groove 42 is 
formed on the lower end face of the front bracket 1 and extends between 
inner peripheries of the annular portions 44 and 45 through one of the 
externally exposed portions 46 so that the inside and the outside of the 
yoke 15 and the inside and the outside of the casing 14a of the 
electromagnetic switch device 14 may be communicated with each other by 
way of the communicating groove 42. 
With the modified starter motor 40, the structure for minimizing a possible 
bad influence of water which may be admitted into the inside of the outer 
casing from the transmission side of the engine can be produced readily, 
for example, by forming directly in a front bracket by die-casting a 
communicating hole or groove which communicates the inside and the outside 
of the outer casing. 
It is to be noted that, while the oil seal 21 in the starter motors 20, 30 
and 40 of the embodiment and modifications described above may be of any 
type including an oil seal having a spring accommodated therein, the oil 
seal in the present invention is not limited to such oil seals but may be 
any seal member other than such oil seals. 
Referring now to FIG. 5, there is shown a starter motor according to a 
second preferred embodiment of the present invention. The starter motor 
has somewhat similar construction to that of the conventional starter 
motor described hereinabove with reference to FIG. 13, and detailed 
description of such common construction is omitted herein to avoid 
redundancy. 
The starter motor shown is mounted on an engine, not shown, in a horizontal 
orientation wherein an armature rotary shaft 53 and an output rotary shaft 
59 extend in a substantially horizontal direction. A front bracket 64 
which cooperates with a rear bracket 63 to form an outer casing has a 
communicating hole 73 formed at an upper portion thereof for communicating 
the inside of the outer casing with the outside atmospheric air. 
Meanwhile, a water drain hole 72 is formed at a bottom portion of the rear 
bracket 63 by means of a tube or grommet 72a and extends downwardly toward 
the ground. 
With the starter motor, even if the temperature of a motor body 51 rises or 
lowers, water will not be sucked into the inside of the outer casing along 
a pinion 58 or an overrunning clutch device 60 because the inside of the 
outer casing communicates with the outside atmospheric air by way of the 
communicating hole 73 in the front bracket 64 and the water drain hole 72 
formed in the rear bracket 63. 
On the other hand, even if water should be admitted into the inside of the 
outer casing, since the inside of the outer casing communicates with the 
outside atmospheric air by way of upper and lower holes, that is, by way 
of the communicating hole 73 and the water drain hole 72, such water will 
be discharged outside promptly by way of the water drain hole 72 without 
remaining in the inside of the outer casing. Even if splashed water is 
admitted in by way of the water drain hole 72, it will be discharged 
similarly by way of the water drain hole 72. 
It is to be noted that the tube 72a in which the water drain hole 72 is 
defined is preferably in the form of a labyrinth type tube 72a as shown in 
FIG. 6. This is because the labyrinth type tube 72a will effectively 
prevent admission of splash water or water from below. 
Referring now to FIG. 7, there is shown a modification to the starter motor 
of the embodiment shown in FIG. 5. The modified starter motor is different 
in construction from the starter motor of the embodiment shown in FIG. 5 
in that it is mounted in a vertical orientation wherein the armature 
rotary shaft 53 extends in a vertical direction relative to the ground, as 
indicated by an arrow mark A, and the pinion 58 is located upwardly. 
Accordingly, the water drain hole 72 is formed in an axial end wall of the 
rear bracket 63 which now serves as a bottom wall. 
Also with the modified starter motor, similar effects can be attained to 
those of the starter motor of the embodiment shown in FIG. 5. 
Referring now to FIG. 8, there is shown another modification to the starter 
motor of the embodiment shown in FIG. 5. The modified starter motor is 
different in construction from the starter motor of the second embodiment 
in that an oil seal 74 for sealing the output rotary shaft 59 is 
additionally provided on an inner periphery of the pinion 58. 
Thus, the modified starter motor exhibits, in addition to the effects of 
the starter motor of the second embodiment shown in FIG. 5, an effect that 
the effect of preventing admission of water into the inside of the outer 
casing is further improved by the oil seal 74. 
Referring now to FIG. 9, there is shown a further modification to the 
starter motor of the embodiment shown in FIG. 5. The modified starter 
motor is different from the starter motor of the second embodiment in that 
the oil seal 70 is mounted in normal contact with an outer periphery of 
the clutch outer member 61 of the overrunning clutch device 60. The 
starter motor thus exhibits similar effects to those of the starter motor 
of the second embodiment described hereinabove. 
In summary, the starter motor of the second embodiment and the modified 
starter motors include an oil seal for closing a gap between an outer 
periphery of an overrunning clutch and an outer casing which has at least 
two communicating holes formed therein for the communication with the 
atmospheric air outside the outer casing, one of the communicating holes 
being formed at a lower portion of the outer casing in such a manner as to 
be directed downwardly. 
It is to be noted that preferably the communicating hole 73 for the 
communication with the outside atmospheric air is formed above the water 
drain hole 72 and at a location as high as possible with respect to the 
motor body 51 of the dc motor. Further, the communicating hole 73 need not 
be formed in the front bracket 64 but may be formed otherwise in the yoke 
57 or the rear bracket 63. 
Further, preferably the water drain hole 72 has a greater sectional area 
than the communicating hole 73 for the communication with the outside 
atmospheric air so that a ratio of water which is discharged from within 
the inside of the starter motor may be greater than that of water which 
may be admitted into the inside of the starter motor. 
Having now fully described the invention, it will be apparent to one of 
ordinary skill in the art that many changes and modifications can be made 
thereto without departing from the spirit and scope of the invention as 
set forth herein.