Engine starter

An engine starter is equipped with a motor having a cylindrical armature rotating shaft (3), a clutch mechanism (15) which transmits the rotational force of the motor, an output rotating shaft (17) which is disposed so as to be movable in the axial direction so as to mesh with the clutch mechanism (15), and a solenoid switch (25) which has a moving member (35) which pushes the output rotating shaft (17) in the axial direction by electromagnetic force and which causes a movable contact (39) to contact a stationary contact (40) and supply current to the motor. The rear portion of the output rotating shaft (17) and the front portion of the moving body (35) are both inserted into the cylindrical bore of the armature rotating shaft (3) from opposite ends. The rear bracket (7) of the motor is made from molded plastic. The front portion of the rear bracket (7) is equipped with a bearing recess (7d) in which fits a bearing (8) which journals the rear end of the armature rotating shaft (3), and the stationary contact (40) is disposed on the bracket (7).

TECHNICAL FIELD 
This invention relates to improvements in an engine starter for use in 
automobile engines and the like, and more particularly, it relates to an 
engine starter which houses a planetary reduction gear. 
BACKGROUND ART 
In the past, as one example of a starter of this type which housed a 
planetary reduction gear, there was the device shown in FIG. 1. In this 
figure, 100 is the armature of a direct current motor which is constituted 
by the following components. 101 is an armature core and 102 is an 
armature rotating shaft on the middle of which the armature core 101 is 
mounted. A commutator 103 fits on the rear portion of the armature 100. An 
armature coil 104 which is wound on the armature core 101 is connected to 
the commutator 103. 
105 indicates brushes which are in contact with the commutator 103 and a 
holder which is connected to a rear bracket 107 by a bolt 106. 108 is a 
bearing which journals the rear end portion of the armature rotating shaft 
102 and which fits into a recess in the rear bracket 107. 109 is a yoke of 
the direct current motor. A plurality of permanent magnets 109a which 
generate a magnetic field in the armature 100 are secured to its inner 
peripheral surface. A front bracket 111 into which is fit an internal gear 
110 which constitutes a planetary reduction gear is mounted on the end 
surface of the yoke 109 as shown in the figure. A spur gear 112 is formed 
on the front end of the armature rotating shaft 102. Both it and the 
internal gear 110 mesh with a plurality of planetary gears 113. 114 
indicates bearings which are mounted on the inner peripheral surfaces of 
the planetary gears 113 and which are journalled on supports pins 115. 116 
is a flange to which the support pins 115 are secured. It constitutes an 
arm of the planetary reduction gear and it is secured to an output 
rotating shaft 117. 118 is a sleeve bearing which fits into the inner 
periphery of a protrusion of the internal gear 110 and which journals the 
output rotating shaft 117. 119 is a sleeve bearing which fits into a 
recess in the rear portion of the output rotating shaft 117 and which 
journals the front end of the armature rotating shaft 102. 120 is a steel 
ball which is disposed between the armature rotating shaft 102 and the 
output rotating shaft 117 and which has the function of bearing thrusts. 
121 indicates helical splines which are formed on the outside of the 
midportion of the output rotating shaft 117. An overrunning clutch 122 
engages therewith so as to be able to slide back and forth. 123 is a 
stopper which is disposed on the front end of the output rotating shaft 
117 and which restricts the axial movement of a pinion 124 which is 
connected to the overrunning clutch 122. 125 is a sleeve bearing which is 
mounted on the inner surface of the front end of the front bracket 111 and 
which journals the front end of the output rotating shaft 117. 126 is a 
molded resin-based plastic lever which has a rotating shaft 126a at its 
midportion. As shown in the drawing, one end is connected to a plunger 128 
of a solenoid switch 127 and the other end fits around the outside of the 
overrunning clutch 122. 129 is a movable contact which is mounted on a rod 
131 through an electrically insulating member 130, the rod 131 being 
inserted into a core 132 and being slidable back and forth therein. 133 is 
a stationary contact which is secured to an electrically insulating member 
in the form of a cap 135 by a nut 134. 136 is an exciting coil which 
activates the plunger 128. It is wound around a molded resin-based plastic 
bobbin 137 and is housed inside a case 138. 139 is a lead wire which is 
connected to the stationary contact 133 and to the brushes of the brushes 
and holder 105. 
Next, the operation will be explained. When an unillustrated starter switch 
is closed to cause current to flow through the exciting coil 136 of the 
solenoid switch 127, the plunger 128 is activated and moves backwards, 
pushing the rod 131 backwards and making the movable contact 129 and the 
stationary contact 133 come into contact with one another. As a result, 
current is supplied from the stationary contact 133 to the armature 100 by 
the brushes and holder 105 via the lead wire 139, and the armature 100 
generates a rotational force. The rotation of the armature 100 is 
transmitted from the spur gear 112 to the planetary gears 113, and the 
rotation is transmitted to the overrunning clutch 122 while being reduced 
in speed by the planetary reduction gear. At this time, the pinion 124 
which engages with the overrunning clutch 122 is made to rotate. 
On the other hand, the force of the plunger 128 which is activated in the 
above manner causes the lever 126 to rotate in the counterclockwise 
direction about the rotating shaft 126a and slide the overrunning clutch 
122 and the pinion 124 forward in the axial direction. As a result, the 
pinion 124 is brought into engagement with a ring gear which is secured to 
a flywheel which is mounted on the crankshaft of an unillustrated engine, 
for example. 
After the engine is started, the overrunning clutch 122 separates from the 
pinion 124 due to the rotation of the engine with respect to the pinion 
124, and the pinion 124 alone performs idle rotation. 
As a conventional engine starter is constructed in the above-described 
manner, the solenoid switch and the direct current motor have their shafts 
arranged in parallel, so when the starter is mounted on an engine, it is 
necessary to ensure space for the solenoid switch in either the engine or 
in the portion of the side of the vehicle into which the engine fits. This 
creates problems such as restrictions on the engine layout in the vehicle. 
In addition, there was the problem that in order to avoid interference 
between the front end of the front bracket and a member such as a flywheel 
within the engine transmission housing, the shape of the flywheel was 
limited. 
This invention was made in order to solve the above-described problems, and 
its object is to provide an engine starter in which a solenoid switch and 
a motor can be coaxially disposed in a compact manner, in which the 
bearing for the output rotating shaft can be cantilevered as seen from the 
pinion, and which is easy to mount on an engine. 
DISCLOSURE OF THE INVENTION 
An engine starter in accordance with this invention is of the type having 
an electric motor having a cylindrical armature rotating shaft, a clutch 
mechanism which transmits the rotational force of the motor, an output 
rotating shaft which is disposed so as to be able to move axially into 
engagement with the clutch mechanism, and a solenoid switch which has a 
moving member which pushes the output rotating shaft in the axial 
direction by electromagnetic force and which also causes a movable contact 
and a stationary contact to contact one another so as to supply current to 
the motor, characterized in that the end portion of the output rotating 
shaft and the front portion of the moving body are both inserted into the 
cylindrical bore of the armature rotating shaft from opposite directions, 
the rear bracket of the motor is made of a molded plastic, a recess is 
provided in the front portion of the rear bracket into which fits a 
bearing which journals the rear portion of the armature rotating shaft, 
and a stationary contact is disposed on the rear bracket. As a result, the 
extension of the overall length due to aligning the axes of the armature 
rotating shaft of the motor, the output rotating shaft, and the solenoid 
switch is decreased, and the structure becomes more compact and lighter. 
Furthermore, in this invention, a radial commutator is used as a commutator 
for supplying current to the motor, as a result of which the overall 
length is made shorter. 
In addition, in this invention, the holder which holds the brushes which 
contact the radial commutator is disposed on the rear bracket, and a 
recess for the stationary contact is provided in a location which is 
removed from the holder and the bearing recess. 
In addition, notches which extend to the recess of the rear bracket are 
formed in the rear portion of the rear bracket with a shape which 
corresponds to that of a core which fits into the inner peripheral surface 
of the front end of the case of the solenoid switch which forms an 
opening, and the rear end of the bracket is made so as to be able to fit 
into the inner peripheral surface of the case. As a result, the overall 
length is decreased. In addition, with the above arrangement, the 
dimensions of the recesses can be made large, the contact surfaces of the 
stationary contact and the movable contact can be made large, and the 
capacity can be increased.

BEST MODE FOR CARRYING OUT THE INVENTION 
In order to explain the present invention in greater detail, it will 
hereinbelow be explained based on the drawings. 
With respect to FIG. 2, "front" refers to the right side of the relevant 
components, and "rear" indicates the left side. 1 is the armature of a 
direct current motor which is composed of the following elements. 2 is an 
armature core, 3 is a cylindrical armature rotating shaft on the 
midportion of which the armature core 2 is mounted, the shaft having a 
cylindrical bore 3a. A radial commutator 4 fits onto the rear portion 
thereof, the commutator having a flat brush contact surface 4a which has 
an extending surface which is disposed at a prescribed angle, such as 
perpendicularly, with respect to the axis. An armature coil 5 which is 
wrapped around the armature core 2 is connected to the radial commutator 4 
by suitable means. 
6 is a brush which is urged forwards by a spring 6a disposed to the rear 
thereof. The end of the brush is pressed against the brush contact surface 
4a. 7 is a plastic-molded rear bracket for the direct current motor. It 
has a plurality of holder holes 7a for housing members while allowing them 
to move back and forth which are disposed around the central axis and 
parallel to the axis. It also has a recess 7b which extends forwards from 
the rear end and is formed closer to the axis than the holder holes 7a. 
The rear bracket 7 has a shaft through hole 7c which is formed at the 
center of the bottom surface of the recess 7b and which extends frontwards 
and backwards in the axial direction and a bearing recess 7d which is 
formed in the front portion of the rear bracket 7, which is the front end 
of the shaft through hole 7c. Furthermore, the rear bracket 7 has holes 7e 
for reces 7b which extend between the inner peripheral surface of the 
recess 7b and the holder holes 7a, recesses 7f in recess 7b which are 
formed in the inner peripheral surface of recess 7b, and through holes 7g 
for screws which extend from recesses 7f to a portion of the rear bracket 
7 not having a holder hole 7a and which are perpendicular, for example, 
with respect to the holder holes 7a. 8 is a bearing which journals the 
extreme rear end of the armature rotating shaft 3 and which fits into the 
bearing recess 7d. 
9 is the yoke of the direct current motor whose rear end surface is joined 
to the front end surface of the rear bracket 7. A plurality of permanent 
magnets 9a which form a magnetic field in the armature 1 are secured to 
its inner peripheral surface. The step-shaped rear rim of a front bracket 
10 which has an internal gear 10a which constitutes a portion of a 
planetary gear train formed thereon is mounted on the step-shaped outer 
rim on the front end surface of the yoke 9 as shown in the figure. 
The front bracket 10 has a plurality of recesses formed therein whose inner 
diameters decrease in a step-wise manner from the rear towards the front. 
It has an internal gear 10a formed on the inner surface of its rear 
portion, bearing recesses 10b formed on the inside of its midportion, a 
small-diameter hole 10c formed in its front portion, and a screw hole 10d 
which extends forwards from its rear end surface. 11 is a spur gear which 
is formed on the outside of the front end of the armature rotating shaft 3 
and which serves as a sun gear, and 12 indicates planetary gears which are 
disposed between and mesh with the spur gear 11 and the internal gear 10a. 
13 indicates bearings which fit inside the planetary gears 12, 14 
indicates support pins which support the bearings 13, and 15 is an 
overrunning clutch having a conventional overrunning clutch mechanism. It 
comprises an overrunning clutch inner member 15A having helical splines 
15a which are formed on its inner surface near the axis and an inward 
protrusion 15b which is forward of the splines and has an inner diameter 
which is smaller than the inner diameter of the splines, an overrunning 
clutch outer member 15B which can engage with and disengage from the inner 
member 15A and which has the support pins 14 secured to its rear portion, 
and rollers 15C which are disposed between the overrunning clutch inner 
member 15A and the overrunning clutch outer member 15B. 
16 is a bearing which fits over the overrunning clutch inner member 15A and 
carries radial loads and fits into the recess 10b in the front bracket 10. 
17 is an output rotating shaft which has a recess 17a in its rear end 
surface. Teeth 18 for engaging with the splines 15a and which have a 
larger diameter than the inner diameter of the opening at the front end of 
the armature rotating shaft 3 are formed on the midportion of the output 
rotating shaft 17. These teeth engage with the helical splines 15a so as 
to be able to slide backwards and forwards. 19 is a spring which is 
disposed closer to the rotational axis than the roots of the teeth 18 
between front surfaces thereof and the rear end of the inwards protrusion 
15b. The spling 19 always biases the output rotating shaft 17 backwards. 
20 is a pinion which engages with straight splines 21 which are formed on 
the front end of the output rotating shaft 17. 22 is a stopper which is 
disposed on the front end of the output rotating shaft 17 and which causes 
the pinion 20, which is biased in the forward direction by a spring which 
is disposed between a recess at the rear of the pinion 20 and a step in 
the output rotating shaft 17, to engage with the output rotating shaft 17. 
23 is a sleeve bearing which fits into the cylindrical bore 3a of the 
armature rotating shaft 3. It journals the rear portion of the output 
rotating shaft 17 which is inserted into the cylindrical bore 3a from its 
front end and makes it possible for the output rotating shaft 17 to 
perform both linear and rotational movement. 24 is a bearing which fits 
into a bearing hole in the midportion of the front end of the yoke 9 and 
which journals the armature rotating shaft 3 between the installation 
portion for the armature core 2 and the spur gear 11. 
25 is a solenoid switch which is directly connected to the rear portion of 
the direct current motor which has the armature 1. It has a switch 
mechanism for supplying current to the armature 1 when it is to be 
excited, and a mechanism for applying thrust to the output rotating shaft 
17 at the same time. It comprises the following elements. 26 is a case 
which has an opening in its front end and which is rigidly held in place 
with its front end abutting against the rear end of the rear bracket 7. 27 
is a lug which is formed on the front of the case 26 and protrudes 
outwards from the rear bracket 7 and has a bolt hole which extends 
forwards and backwards. 28 is a bolt which passes through the hole in the 
lug 27 and screws into the screw hole 10d of the front bracket 10 and 
secures the case 26 to the direct current motor and connects it to the 
rear bracket 7. 29 is a bobbin around which an exciting coil 30 is wound 
and which is housed in the case such that a recess for a coil extends 
forwards and backwards. 31 is a plunger which is made from a strongly 
magnetic member, which has a hollow portion 31a in a rear portion, and 
which loosely fits into the case 26 so as to be able to move within the 
coil recess of the bobbin 29. The front portion is a plunger tube 31b 
which has a hole which extends forwards and backwards and connects to the 
hollow portion 31a. 32 is a core which fits into an inner peripheral 
surface of the opening of the case 26, which has a step to which the 
bobbin 29 is secured, and which has a bearing hole 32a at its center. 33 
is a spring which is disposed between the rear end surface of the core 32 
and the front side of a step in the rear portion of the plunger 31 and 
which urges the plunger 31 backwards. 34 is a bearing which fits into the 
bearing hole 32a in the core 32 and which supports the plunger tube 31b so 
that it move forwards and backwards. 
35 is a plunger rod having a T-shaped longitudinal cross section. Its rear 
end is disposed inside the hollow portion 31a and its rear surface is 
urged forwards by a spring 36A which is disposed to its rear within the 
hollow portion 31a. The portion to the front of the rear end is shaped 
like a rod. This portion passes through the plunger tube 31b, passes 
through the shaft through the hole 7c, is inserted into the rear opening 
of the armature rotating shaft 3, and is journalled by a bearing 36B which 
fits into the cylindrical hole 3a in the rear of the armature rotating 
shaft 3. The front end surface of the plunger rod 35 always abuts against 
a steel ball 37 which contacts the recess 17a. 
38 is an electrically insulating member which is mounted on the outer 
surface of the front end of the plunger tube 31b in the cavity between the 
recess 7b and the core 32. It has a step formed in its front edge. 39 is a 
movable contact which has a hole formed therein and which fits into the 
step of the electrically insulating member 38. 
40 indicates L-shaped stationary contacts. A first section of each, which 
is housed within recess 7b, confronts the movable contact 39. 41 is a 
screw which is connected to a back side of a second section of each 
stationary contact 40. The screw 41 passes through the screw through hole 
7g and protrudes to the outside of the rear bracket 7 and a nut 42 is 
screwed onto the protruding portion. In this manner, an external terminal 
is formed, and at the same time the stationary contacts 40 are secured to 
the rear bracket 7. 
One of the stationary contacts 40 is connected to an unillustrated direct 
current power supply. Another of the stationary contacts 40 is connected 
to (+) brushes 6 by unillustrated lead wires. The (-) brushes 6 are 
grounded by unillustrated lead wires. The (+) terminal of the direct 
current power supply is connected to the stationary contact 40 which is 
not connected in the above manner by an unillustrated lead wire the nut 
42. Furthermore, the direct current power supply is connected to the 
exciting coil 30 through an unillustrated starter switch. 
FIGS. 3(A) and 3(B) show the bracket 7, the stationary contacts 40, and the 
like of FIG. 2 in greater detail. FIG. 3(A) is a rear view as seen from 
the rear, and FIG. 3(B) is a cross-sectional view of FIG. 3(A). In these 
views, 40a and 40b are the stationary contacts 40, 42a and 42b are the 
nuts 42, 43a is a B terminal which is constituted by a screw 41a which is 
connected to stationary contact 40a and a nut 42b, and 43b is an M 
terminal which is constituted by a screw which is connected to stationary 
contact 40b and a nut 42b. The B terminal 43a is connected to the (+) 
terminal of a direct current power supply by an unillustrated lead wire, 
and the M terminal 43b is connected by unillustrated lead wires to (+) 
brushes 6 which are inside the holder holes 7a. Recess 7b has a two-level 
cylindrical recess and rectangular recesses in the shape of legs on either 
side of the central axis. The stationary contacts 40 are positioned in the 
rectangular recesses. The direct current power supply is connected to the 
exciting coils 30 of FIG. 1 through an unillustrated starter switch. 
FIG. 4 is a disassembled view which shows the relationship between the rear 
bracket 7, the case 26, and the core 32 which are shown in cross section 
in FIG. 2. The inner peripheral surface of the case 26 which forms an 
opening at the front end of the case 26 has a step 26a formed therein with 
respect to the axial direction. The diameter of the core 32 and the outer 
diameter of the rear end of the rear bracket 7 are roughly the same as the 
diameter of the opening of the case 26 so as to fit onto the step 26a. 7h 
is a pair of notches which are formed in the rear end of the rear bracket 
7 and which connect to the recess 7b of FIG. 2. Their locations and size 
correspond to the core 32 and they are provided in locations which are 
removed from the holder holes 7a. With this structure, the core 32 can be 
fit onto the step 26a of the case 26, and by positioning the core 32 and 
the notches 7h so as to correspond with one another, the rear end of the 
rear bracket 7 can be fit onto the same step 26a. 
Next, the operation of this embodiment of the present invention will be 
explained. 
When the unillustrated starter switch is in an open state, the exciting 
coil 30 is in a nonconducting state in which it is unexcited, so the only 
force acting on the plunger 31 is the force of the spring 33. The plunger 
31 and the plunger rod 35 are urged rearwards by this spring 33 to the 
rearmost position to which they can move. As a result, the output rotating 
shaft 17 does not receive a thrust from the solenoid switch 25, it is 
biased backwards the spring 19, and it is positioned backwards until the 
front end surface of the armature rotating shaft 3 and the rear surface of 
the teeth 18 abut, as shown in the drawing. At this time, as the movable 
contact 39 is separated from the stationary contacts 40, the stationary 
contacts 40 are in a floating state, current is not supplied from the 
direct current power supply to the armature 1, and the armature 1 is 
stopped. 
If the above-mentioned starter switch is then closed, current is passed 
through the exciting coil 30 and it is energized. The electromagnetic 
force resulting from this energizing activates the plunger 31 and moves it 
forwards. As a result of this movement, the movable contact 39 also moves 
forwards and the movable contact 39 comes into contact with the stationary 
contacts 40. This contact shorts the stationary contacts 40 through the 
movable contact 39, and current from the direct current power supply flows 
through the stationary contacts 40, from the brushes which are 
electrically connected to the stationary contacts 40 to the radial 
commutator 4, and through the armature coil 5 to ground. The rotational 
force which is generated by the current flowing through the armature 1 in 
this manner is transmitted from the spur gear 11 to the planetary gears 
12. The planetary gears 12 generate a revolving force, and this force is 
transmitted to the overrunning clutch 15. Due to the action of the rollers 
15c, the overrunning clutch 15 is engaged, so the revolving force which is 
transmitted to the overrunning clutch 15 is transmitted from the helical 
splines 15a to the teeth 18 with which they are engaged. As a result, the 
output rotating shaft 17 rotates integrally with the pinion 20 at a slower 
rate than the armature 1. 
On the other hand, the force of the plunger 31 which is urged forwards 
pushes the plunger rod 35 through the spring 36A and moves it forwards. 
Therefore, the output rotating shaft 17 receives a forward thrust from the 
plunger rod 35 through the steel ball 37, and this thrust moves it 
forwards together with the pinion 20 against the force of spring 19. At 
this time, the teeth 18 move forwards while engaging with the helical 
splines 15a and their position of engagement changes. Due to the forwards 
movement of the output rotating shaft 17, the pinion 20 which protrudes 
forwards through the small-diameter hole 10c meshes with a ring gear on 
the outer periphery of a flywheel which is mounted on the engine. 
Therefore, the rotational force of the armature 1 is transmitted to the 
ring gear by the pinion mechanism at a reduced speed, and the engine is 
started. 
Immediately after the engine has started, the rotational force of the 
engine is transmitted to the pinion 20 through the ring gear. Therefore, 
the rotational speed of the pinion 20 and the output rotating shaft 17 
increases. Due to the action of the rollers 15c caused by this rotation, 
the overrunning clutch 15 disengages, and the pinion 20 rotates idly 
together with the output rotating shaft 17 and the like. 
Furthermore, after the starting of the engine, when the starter switch is 
opened, the starter returns to its initial state (the illustrated state). 
In the above-described embodiment, the case was explained in which a radial 
commutator was employed, but a conventional commutator can be used 
instead. 
In addition, in the above-described embodiment, the case was explained in 
which a planetary reduction gear was provided between the armature 
rotating shaft and the output rotating shaft, but when it is not necessary 
to reduce the rotational speed of the output rotating shaft, a planetary 
reduction gear may be omitted. 
In addition, in the above-described embodiment, the case was explained in 
which the magnetic field of the direct current motor was generated by 
permanent magnets, but the same effects as with the above-described 
embodiment can be obtained if a coil is wound around a magnetic pole core. 
Furthermore, in the above-described embodiment, the stationary contact 40 
and the (+) brushes 6 were connected by lead wires, but it is possible to 
omit lead wires and have them directly contact one another through hole 
7e.