Information
-
Patent Grant
-
6169333
-
Patent Number
6,169,333
-
Date Filed
Monday, October 6, 199726 years ago
-
Date Issued
Tuesday, January 2, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 290 1 C
- 290 38 R
- 290 38 B
- 290 38 C
- 074 6
- 074 7 A
- 074 7 C
- 074 7 R
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International Classifications
-
Abstract
In one embodiment of the present invention, a method for forming a starter motor drive stop includes the steps of forming a splined portion in a starter motor output shaft and forming at least one stop surface. Preferably, the stop surfaces are located in the splined portion and are formed as an integral part of the spline forming step.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to starter motor assemblies, and more particularly to drive stops for starter motors.
2. Description of the Related Art
In typical designs for starter motor assemblies for motor vehicle engines, an output shaft is coupled to be driven by the armature of the starter motor. This output shaft typically has external splines which interact with internal splines on a starter motor “drive” assembly. A pinion gear is affixed to the drive assembly for rotation therewith. The splines on the output shaft and on the drive assembly cooperate to transmit rotational power from the starter motor to the pinion gear. The splines also act to facilitate translation of the pinion gear into mesh with a ring gear of the engine being cranked by the starter motor.
Overtranslation of the drive assembly, and therefore of the pinion gear, must be avoided. In some designs, an outboard pinion stop surface is provided, against which the pinion gear abuts to prevent overtranslation. In other designs, a stop is provided on the output shaft, slightly outboard of the splines. The stop is located so that the splines of the spline tube abut against the stop once the maximum intended translation of the drive assembly (and therefore the pinion gear) has been reached. U.S. Pat. No. 5,370,009, issued to Isozumi, discloses such a drive stop, designated therein as reference numeral
10
.
Locating the stop on the output shaft has the distinct advantage of reducing the axial length of the starter motor assembly when compared to designs with an outboard stop against which the pinion gear abuts. However, as presently practiced in the art, designs with a stop on the output shaft have some disadvantages of their own. First, such a stop adds length to the output shaft beyond that necessary for the splines. This added length translates into added overall length for the starter motor assembly. Reduced package size is an ever-present requirement in the design of motor vehicle components; added length for a starter motor assembly is therefore disadvantageous. Second, as presently practiced in the art, a drive stop on the output shaft outboard of the splines requires one or more added manufacturing steps beyond the process of rolling the splines. The added manufacturing steps add cost to the manufacture of the output shaft.
Therefore, a drive stop design for a starter motor assembly which can reduce the added length and added cost required for prior-art drive stops will provided advantages over the prior art.
SUMMARY OF THE INVENTION
The present invention provides a method for forming a starter motor drive stop. The method includes forming a splined portion on a starter motor output shaft, the splined portion comprising alternating grooves and ridges. The method also comprises forming at least one stop surface as an integral part of the spline forming step.
The present invention also provides a second method for forming a starter motor drive stop. The method comprises forming a splined portion in a starter motor output shaft, the splined portion comprising alternating grooves and ridges and having a first axial end and a second axial end. Additionally, the method includes forming at least one stop surface between the first axial end and the second axial end of the splined portion.
Further, the present invention provides a starter motor output shaft. The output shaft includes a splined portion comprising a plurality of alternating ridges and grooves disposed about a circumference of the output shaft, the splined portion having a first axial end and a second axial end. In addition, the output shaft comprises a plurality of stop surfaces, each stop surface disposed between the first axial end and the second axial end of the splined portion.
Designs and manufacturing processes according to the present invention can result in reduced cost and reduced length of starter motor assemblies. In doing so, the present invention provides considerable advantage over the prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a cross-sectional view of a starter motor assembly
10
according to one embodiment of the present invention.
FIG. 2
illustrates output shaft
16
of starter motor assembly
10
.
FIG. 3
illustrates a rolling process preferably used to form splined portion
20
of output shaft
16
.
FIG. 4
shows a portion of the rolling surface of rolling wheels
60
and
62
of FIG.
3
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Refer first to FIG.
1
. Illustrated there is a starter motor assembly
10
for a motor vehicle. Starter motor assembly
10
includes a motor having an armature
12
mounted about a motor shaft
14
. Coupled through appropriate gearing to motor shaft
14
for rotation therewith is an output shaft
16
. Mounted on output shaft
16
is a drive assembly
17
. Drive assembly
17
includes a pinion extension tube
18
and a barrel
19
. An overrunning clutch assembly
30
is formed by clutch inner portion
22
(a portion of pinion extension tube
18
) and clutch outer portion
23
(a portion of barrel
19
), with suitable rollers disposed therebetween. Barrel
19
also includes an interior-splined portion
25
. An exterior-splined portion
20
on output shaft
16
interacts with interior-splined portion
25
of barrel
19
to allow axial translation of drive assembly
17
(and therefore pinion gear
28
) with respect to output shaft
16
. Such translation occurs under the influence of lever
24
, which is coupled to solenoid
26
. Pinion gear
28
is coupled to pinion extension tube
18
for rotation therewith, to transmit rotation from armature
12
to a ring gear (not shown) on a motor vehicle engine.
Refer additionally now to FIG.
2
. Those skilled in the art recognize that means must be provided for preventing overtranslation of pinion gear
28
to the right as viewed in FIG.
1
. Splined portion
20
of output shaft
16
includes alternating channels, such as channel
40
, which proceed unobstructed through splined portion
20
. Such channels alternate with channels, such as channels
42
, which are interrupted by a stop portion
44
. Stop portions
44
each have a stop surface
46
which, once drive assembly
17
is assembled onto output shaft
16
, prevents overtranslation of spline tube
18
to the right as viewed in FIG.
1
. As can be seen in
FIG. 2
, stop portions
44
are preferably located totally entirely within the axial extent of splined portion
20
.
Unobstructed channels
40
and channels
42
containing stop portions
44
alternate to facilitate the process of assembling starter motor assembly
10
. Drive assembly
17
is inserted from the right as seen in
FIG. 1
over output shaft
16
. Splines
25
of drive assembly
17
are aligned with unobstructed channels
40
to allow drive assembly
17
to slide over output shaft
16
. Once the splines of drive assembly
17
are to the left of the splines of output shaft
16
, drive assembly
17
is rotated so that the splines of drive assembly
17
are now aligned with channels
42
. Stop surfaces
46
will now prevent drive assembly
17
(and therefore pinion gear
28
) from overtranslating to the right. A snap ring is placed in groove
48
of output shaft
16
to prevent drive assembly
17
from moving far enough to the left to allow the splines of drive assembly
17
to become disengaged from the splines of output shaft
16
.
Preferably, splined portion
20
, including stop portions
44
, are formed by a rolling process. Refer additionally to FIG.
3
. There, output shaft
16
is shown positioned between two rolling wheels
60
and
62
which, when rotated, form splined portion
20
.
Refer additionally to FIG.
4
. There, a portion of the rolling surface of rolling wheels
60
and
62
is illustrated. Teeth
64
form through channels
40
in splined portion
20
. Teeth
66
form channels
42
, with depressed portions
68
forming stop portions
44
. At the portions of wheels
60
and
62
where they first begin forming splined portion
20
, teeth
64
and
66
are preferably relatively short to make shallow impressions in output shaft
16
. As wheels
60
and
62
proceed to rotate in forming splined portion
20
, teeth
64
and
66
are taller to make deeper impressions. One can see that in this embodiment of the present invention, stop portions
44
are integral parts of output shaft
16
, due to stop portions
44
being formed from the material of which output shaft
16
is comprised. That is, stop portions
44
are not formed separately and subsequently attached to output shaft
16
.
A distinct advantage of forming stop portions
46
within the axial extent of splined portion
20
is that the rolling process herein described holds output shaft
16
in place without axial fixturing. This occurs because in the formation of stop portions
44
by depressions
68
, balanced axial forces are applied to the two axial ends of stop portions
44
. Output shaft
20
thus remains in place through the rolling process, with no axial fixturing required.
Another substantial advantage provided by the process and design described herein accrues from forming stop portions
44
and stop surfaces
46
by rolling, and particularly by rolling in an integral process with the rolling of the splines in splined portion
20
. Secondary operations required to complete the pinion stop in other designs having splines and stops located in proximity therewith is thus avoided. Yet another advantage provided by locating the stop surfaces
48
within the axial extent of splined portion
20
is a reduction in length of output shaft
16
, and therefore also the length of starter motor assembly
10
, over the other designs.
Various other modifications and variations will no doubt occur to those skilled in the arts to which this invention pertains. Such variations which generally rely on the teachings through which this disclosure has advanced the art are properly considered within the scope of this invention. This disclosure should thus be considered illustrative, not limiting; the scope of the invention is instead defined by the following claims.
Claims
- 1. A method for forming a starter motor drive stop, said method comprising the steps of:forming a splined portion on a starter motor output shaft, said splined portion comprising alternating grooves and ridges and having a first axial end and a second axial end, said axial ends defining an axial extent of said splined portion; and forming at least one stop surface having an axial thickness at one of said first and second axial ends of each of said alternating grooves and connecting with the one of the first and second axial ends of adjacent ridges within said axial extent of said splined portion as an integral part of said spline forming step.
- 2. A method as recited in claim 1, wherein said spline forming step is performed by rolling.
- 3. A method as recited in claim 1, wherein said spline forming step and said stop surface forming step are performed simultaneously.
- 4. A starter motor output shaft defining an axis of rotation, said output shaft comprising:a splined portion comprising a plurality of alternating ridges and grooves disposed about a circumference of said output shaft, said splined portion having a first axial end and a second axial end, said axial ends defining an axial extent of said splined portion; a plurality of stop portions each having a surface having an axial thickness and disposed at one of the first and second said axial ends of each of said alternating grooves and connecting with the one of the first and second axial ends of adjacent ridges, wherein each said axial thickness of said stop surface is disposed entirely within said axial extent of said splined portion.
- 5. A starter motor output shaft as recited in claim 4, wherein said stop surfaces are integral parts of said output shaft.
- 6. A starter motor output shaft as recited in claim 5 further comprising:a member having a splined portion engaged with said splined portion of said output shaft; an output gear coupled for rotation with said member.
- 7. A starter motor output shaft as recited in claim 6, further comprising:a motor armature; wherein said starter motor output shaft is coupled for rotation with said motor armature.
US Referenced Citations (10)
Foreign Referenced Citations (5)
Number |
Date |
Country |
0494681A1 |
Jul 1992 |
EP |
0 562 475 A1 |
Sep 1993 |
EP |
0 732 498 A1 |
Mar 1996 |
EP |
2 270 954 |
Nov 1993 |
GB |
55-96362 |
Jul 1980 |
JP |