# US 5,706,700 A · Overrunning clutch for starters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,700 A - Document ID: US5706700A - Status: Granted - Kind: A - Application number: 08/705,041 - Filed: 1996-08-30 - Granted: 1998-01-13 - Earliest claimed: 1994-09-07 - Assignees: Nippondenso Co., Ltd. - Inventors: Yoshito Takagi; Tsutomu Shiga; Yasuhiro Nagao - Web page: https://patentgrep.com/patent/US5706700A ## CPC - F02N 15/023: {of the overrunning type} - F16D 41/064: the intermediate members wedging by rolling and having a circular cross-section, e.g. balls (F16D41/061 takes precedence) - Y10T 74/134: Clutch connection - F02N: STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR - F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract An overrunning clutch that can absorb the impact torque, and accurately and easily conveys the maximum torque. A clutch outer tubular portion and inner tubular portion are separately fixed on an internal gear and a center case of an epicycle gear reduction mechanism. A wedge-shaped groove is formed on one of an inner circumference of the outer tubular portion and an outer circumference of the inner tubular portion to accomodate a rolling element. A fitting concave portion to fit the rolling element is formed on the other one of the inner circumference of the outer tubular portion and the outer circumference of the inner tubular portion. With this, the torque value generated when the rolling element leaves the fitting concave portion can be accurately set just by setting the depth of the fitting concave portion. The radial force that acts on the opposite direction of the tubular portions holding the rolling element can be reduced. This allows the strength of the tubular portions to be reduced, and the weight to be lightened. As the torque is not conveyed with frictional force, the wear is also reduced. ## Claims ### Claim 1 A starter structure having an overrunning clutch, comprising: a starter motor; a drive shaft constructed and arranged to be driven by said starter motor; a pinion axially movably mounted on said drive shaft and constructed and arranged to be selectively engageable with an engine ring gear; the overrunning clutch being disposed to regulate transmission of torque between said starter motor and said pinion, said overunning clutch including: an outer tubular portion and an inner tubular portion placed with a clearance therebetween in the radial direction and facing so as to rotate freely relative to one another, one of said outer tubular portion and said inner tubular portion being fixed; at least one rolling element; at least one wedge-shaped groove which accommodates said rolling element, each said groove being formed concavely on one of an inner circumference of said outer tubular portion and an outer circumference of said inner tubular portion; and at least two concave portions each of which selectively fittingly engages said rolling element, said at least two concave portions being formed concavely on an other one of said inner circumference of said outer tubular portion and said outer circumference of said inner tubular portion, a depth of each said concave portion being determined to keep said rolling element received therein while said rolling element is kept pressed to an end wall of said wedge-shaped groove when a predetermined starter drive torque usually required for starting an engine is applied between said outer tubular portion and said inner tubular portion, said depth of each said concave portion further being a value such that said rolling element can move from one concave portion to an other concave portion while said rolling element is kept pressed to the end wall of said wedge-shaped groove when an excessive impact torque, exceeding the predetermined starter drive torque usually required for starting an engine, is applied between said outer tubular portion and said inner tubular portion in a direction to move said rolling element toward a short depth side of said wedge-shaped groove, thereby reducing said excessive impact torque. ### Claim 2 (depends on 1) The starter structure having an overrunning clutch according to claim 1, wherein said concave portions are formed circumferentially and are more in number than said wedge-shaped groove. ### Claim 3 (depends on 1) The starter structure having an overrunning clutch according to claim 1, in combination with: a starter motor having an armature shaft; a speed reduction mechanism including a sun gear formed on said armature shaft an epicycle gear engaging said sun gear; and an internal gear engaging said epicycle gear, wherein one of said outer tubular portion and said inner tubular portion extends axially from a disc-shaped base section formed radially from one end of said internal gear and has a smaller diameter than said internal gear. ### Claim 4 (depends on 3) The starter structure having an overrunning clutch according to claim 3, wherein one of said tubular portions is formed from resin as a base material integrally with said internal gear. ### Claim 5 (depends on 4) The starter structure having an overrunning clutch according to claim 4, wherein said clearance is filled with a lubricant with a friction coefficient of 0.3 or less. ### Claim 6 (depends on 5) The starter structure having an overrunning clutch according to claim 5, wherein the friction coefficient of said lubricant is less than 0.18. ### Claim 7 (depends on 3) The starter structure having an overrunning clutch according to claim 3, wherein said outer tubular portion is formed with said at least one wedge-shaped groove and is fixed to said internal gear. ### Claim 8 (depends on 3) The starter structure having an overrunning clutch according to claim 3, further comprising: a biasing member laid on said outer circumference of said inner tubular portion fixed to said internal gear and biasing said rolling element in a centrifugal direction by a centrifugal force thereof. ### Claim 9 (depends on 8) The overrunning clutch according to claim 8, wherein said biasing member includes a ring-shaped elastic member which is accomodated in a ring-shaped groove concavely formed on said outer circumference of said inner tubular portion and which expands with said centrifugal force. ### Claim 10 A starter with an overrunning clutch comprising: an armature shaft rotated by a starter motor; a drive shaft coaxially disposed with said armature shaft and operatively coupled with said armature shaft; and a clutch mechanism operatively coupling said shafts and having a cylindrical clutch outer member, a cylindrical clutch inner member coaxially disposed in said clutch outer member, and a plurality of rollers disposed between said clutch outer member and said clutch inner member, wherein one of said clutch outer member and said clutch inner member is fixed; wherein one of said clutch outer member and said clutch inner member is formed with a plurality of wedge-shaped spaces for accommodating said rollers therein and an other of said clutch outer member is formed with a plurality of indentations for each of said wedge-shaped spaces, wherein a depth of each of said indentations is determined to keep said rolling element received therein while said rolling element is kept pressed to an end wall of said wedge-shaped space upon application of a predetermined starter drive torque usually required for starting an engine, said depth of each of said indentations further being determined to be a value whereby each of said rollers is enabled to move from one indentation to another while said rolling element is kept pressed to an end wall of said wedge-shaped space upon application of excessive torque, exceeding a torque usually required for starting an engine, in a direction from said armature shaft to said drive shaft under a condition that said clutch outer member and said clutch inner member are locked to each other through said rollers. ### Claim 11 (depends on 10) The starter according to claim 10, wherein: each of said wedge-shaped spaces has a radial depth increasing gradually from one circumferential end wall toward an other circumferential end wall thereof, whereby said rollers are moved toward said other circumferential end wall thereby releasing a lock condition between said clutch outer member and said clutch inner member upon overrunning of said drive shaft. ### Claim 12 (depends on 11) The starter according to claim 11, further comprising: a plurality of springs disposed in said wedge-shaped spaces, respectively, for biasing said rollers toward said one circumferential end wall thereby to lock said clutch outer member and said clutch inner member upon application of a torque in said direction from said armature shaft to said drive shaft. ### Claim 13 (depends on 12) The starter according to claim 12, wherein said depth of said indentations is determined to enable a movement of said rollers upon application of said excessive torque while keeping said rollers in contact with said one circumferential wall. ### Claim 14 (depends on 13) The starter according to claim 13, wherein: at least one of said clutch inner member and said clutch outer member is made of resin. ### Claim 15 (depends on 12) The starter according to claim 12, wherein: each of said indentations has a smoothly curved bottom ending at a shoulder portion which contacts said rollers when said clutch outer member and said clutch inner member are locked; said curved bottom having a gradually increasing depth toward said shoulder and having at said shoulder a largest depth as said depth of said indentations, whereby upon said overrunning of said drive shaft said rollers disengage from said shoulders and move along said curved bottom to a shortest depth. ### Claim 16 (depends on 10) The starter according to claim 10, wherein: said determined depth of each of said indentations is equal to a largest depth of each of said indentations.