Source: http://www.google.com/patents/US5905309?ie=ISO-8859-1
Timestamp: 2015-05-28 23:36:32
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Matched Legal Cases: ['art 20', 'art 20', 'art 22', 'art 20', 'art 20', 'art 20', 'art 20', 'art 22', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20']

Patent US5905309 - Starter with shock absorbing device - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsIn a starter having a planetary gear reduction mechanism and a shock absorbing device, a first friction plate of the shock absorbing device is engaged with an internal gear of the reduction mechanism to restrict the internal gear from rotating. A space is provided radially between the internal gear and...http://www.google.com/patents/US5905309?utm_source=gb-gplus-sharePatent US5905309 - Starter with shock absorbing deviceAdvanced Patent SearchPublication numberUS5905309 APublication typeGrantApplication numberUS 08/863,002Publication dateMay 18, 1999Filing dateMay 23, 1997Priority dateFeb 15, 1996Fee statusPaidPublication number08863002, 863002, US 5905309 A, US 5905309A, US-A-5905309, US5905309 A, US5905309AInventorsMasanori Ohmi, Keiichi Matsushima, Tsutomu Shiga, Yasuhiro NagaoOriginal AssigneeDenso CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (10), Referenced by (19), Classifications (12), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetStarter with shock absorbing device
US 5905309 AAbstract
In a starter having a planetary gear reduction mechanism and a shock absorbing device, a first friction plate of the shock absorbing device is engaged with an internal gear of the reduction mechanism to restrict the internal gear from rotating. A space is provided radially between the internal gear and a housing to allow rotation of the internal gear upon application of an impact shock. A cylindrical member which is harder than the housing is disposed between the space relatively movably against the housing and the internal gear so that the internal gear is restricted from directly contacting the housing.
1. A starter comprising:a starting motor having an armature rotatable by electric power supplied thereto and an armature shaft supporting the armature thereon; a planetary gear reduction mechanism for reducing rotational speed of the armature and having a sun gear formed on the armature shaft, planetary gears engaged with the sun gear and an internal gear engaged with the planetary gears; an output shaft disposed to be driven by the starting motor through the reduction mechanism; a pinion disposed on the output shaft so as to be movable through a helical spline and so as to be engageable with an engine ring gear to transmit rotation of the output shaft to the ring gear; a shock absorbing device operatively coupled with the reduction mechanism to turn the internal gear when an impact torque is applied to the reduction mechanism at the time of engagement of the pinion with the ring gear, thus absorbing the impact torque; a housing surrounding the reduction mechanism and being disposed to have a space between an inner periphery thereof and an outer periphery of the internal gear; and a cylindrical member movably disposed in the space and relatively rotatable against at least one of the housing and the internal gear. 2. The start according to claim 1, further comprising:a partition plate disposed between the reduction mechanism and the armature; and a center casing disposed adjacent the shock absorbing device at a side of the pinion and fixedly against the housing, the center casing rotatably supporting the output shaft; wherein the cylindrical member is disposed axially between the center casing and the partition plate and has an axial length substantially equal to an axial distance between the center casing and the partition plate. 3. The starter according to claim 1, further comprising:a center casing disposed adjacent to the shock absorbing device at a side of the pinion; wherein the shock absorbing device includes a friction plate engaged with the internal gear for integral rotation therewith, and a spring biasing the friction plate against the center casing so that the friction plate slidingly rotates on the center casing only when the impact torque exceeds a predetermined value. 4. The starter according to claim 1, further comprising:a center casing disposed adjacent to the shock absorbing device at a side of the pinion; wherein the shock absorbing device includes a friction plate disposed in sliding contact with the center casing, a spring biasing the friction plate against the center casing, and an elastic member disposed to engage the internal gear with the friction plate so that the elastic member deforms to restrict the friction plate from rotating upon application of an impact torque lower than a predetermined value and to allow the friction plate to rotate upon application of the impact torque higher than the predetermined value. 5. The starter according to claim 1, wherein:the cylindrical member has a hardness higher than that of the housing. 6. A starter comprising:a starting motor having an armature rotatable by electric power supplied thereto and an armature shaft supporting the armature thereon; a planetary gear reduction mechanism for reducing rotational speed of the armature and having a sun gear formed on the armature shaft, planetary gears engaged with the sun gear and an internal gear engaged with the planetary gears; an output shaft disposed to be driven by the starting motor through the reduction mechanism; a pinion disposed on the output shaft so as to be movable through a helical spline and so as to be engageable with an engine ring gear to transmit rotation of the output shaft to the ring gear; a shock absorbing device operatively coupled with the reduction mechanism to turn the internal gear when an impact torque is applied to the reduction mechanism at the time of engagement of the pinion with the ring gear, thus absorbing the impact torque; a housing surrounding the reduction mechanism and being disposed to have a space between an inner periphery thereof and an outer periphery of the internal gear; and a member disposed in the space to contact the internal gear only when the internal gear moves eccentrically and to restrict the internal gear from directly contacting the housing. Description
This application is a continuation-in-part of Nagao U.S. patent application Ser. No. 08/798,133 filed on Feb. 12, 1997 which claims priorities of Japanese patent applications No. 8-27462 and No. 8-326365.
In another conventional starter having a planetary gear reduction mechanism and a shock absorbing device, an internal gear turns against a housing to absorb a shock applied to the reduction mechanism. When the internal gear turns in an eccentric condition because of backlash between gears, the outer peripheral surface of the internal gear slides frictionally on the inner peripheral surface of the housing. The housing generally made of an aluminum alloy or the like wears more than the internal gear made of resin reinforced by impregnation of glass fibers. Thus, aluminum wear powder is produced by the sliding of the outer periphery of the internal gear along the inner periphery of the housing, thereby causing the housing to become thinned and weakened. Further, the wear powder from the housing will enter bearings and gear engagement portion of the reduction mechanism, causing abnormal noise.
To counter this drawback, it is proposed in Japanese Unexamined Patent Publication No. 63-266166 to dispose wavy ring springs between the inner periphery of the hosing and the outer periphery of the internal gear as well as between the inner peripheries of the planetary gears and the outer periphery of support pins for the planetary gears. Thus, even when the internal gear turns eccentrically, the internal gear and the planetary gears are enabled by the resilient force of the springs to swing against respective radial centers and engage properly.
According to this starter, however, a relative movement occurs between the ring spring and the internal gear at the time of turning of the internal gear, because the ring spring is disposed stationary to the housing by the respective resiliency. Thus, friction occurs unavoidably between the contacting portions, i.e., between the ring spring and the internal gear.
It is therefore an object of the present invention to provide a starter having a planetary gear reduction mechanism, in which frictional wear caused between contacting surfaces at the time of turning of an internal gear is reduced by a shock absorbing device.
According to the present invention, in addition to a shock absorbing device, a generally cylindrical member is disposed in a space provided between the inner periphery of a housing and the outer periphery of an internal gear to be relatively rotatable against the housing and the internal gear. The cylindrical member rotates relatively against the housing and the internal gear at the time of turning of the internal gear. The relative rotation speed differences between the housing and the cylindrical member and between the cylindrical member and the internal gear become smaller than that between the internal gear and the housing. As a result, even when the eccentric turning of the internal gear causes contacting between the outer periphery of the cylindrical member and the inner periphery of the housing and contacting between the inner periphery of the cylindrical member and the outer periphery of the internal gear thus causing the wear at the contacting portions, the degree of wear is reduced compared to the case of conventional direct contact between the outer periphery of the internal gear and the inner periphery of the housing.
Preferably, the cylindrical member has the axial length which is substantially equal to the axial distance between a partition wall and a center casing. Thus, the cylindrical member operates also as a spacer which defines the axial spacing between the partition plate and the center casing. In addition, the cylindrical member restricts the center casing from moving toward the partition plate even when the center casing is pressed toward the motor side through an output shaft by a helical spline at the time of engagement of a pinion with an engine ring gear.
FIGS. 5A and 5B are respectively side and front views of a connecting member in the first embodiment;
FIGS. 6A and 6B are respectively side sectional view and front view of a shock absorbing device in a second embodiment of the present invention;
FIG. 7 is a partial sectional view of a starter according to a third embodiment of the present invention;
FIG. 8 is an enlarged sectional view of a shock absorbing device and a planetary gear reduction mechanism in the third embodiment;
FIGS. 9A through 9C are perspective views of a cylindrical member in the third embodiment; and
FIG. 10 is an enlarged sectional view of a shock absorbing device and a planetary gear reduction mechanism in a fourth embodiment.
Next, a starter of the present invention will be described with reference to preferred embodiments shown in the accompanying drawings throughout which the same or similar parts are designated by the same reference numerals to omit repeated description.
The reduction mechanism comprises a sun gear 11 formed on the outer periphery of the armature shaft 6a, a plurality of planetary gears 12 engaged with the sun gear 11, and an internal gear 13 engaged with each of the planetary gears 12. The reduction mechanism is of such a design that with the rotation of the sun gear 11 on the armature shaft 6a, each planetary gear 12 rotates while revolving around the outer periphery of the sun gear 11. The force of rotation is transmitted to the output shaft 3 through the one-way clutch.
The connecting member 34 serves to connect the internal gear 13 with the rotary disk 30 through the elastic member 33, and forms an annular member as shown in FIGS. 5A and 5B. On the outer peripheral side of the connecting member 34, engaging projections 34a and 34c are provided in connecting recesses 13a and 13c of the internal gear 13. The engaging projection 34a is provided to receive the torque from the peripheral wall section 13d of the connecting recess 13a through the elastic member 33. The engaging projection 34c is arranged off the peripheral wall section 13a so that when the internal gear 13 turns a predetermined angle of rotation (α) in relation to the connecting member 34, the torque of the internal gear 13 will directly be transmitted to the connecting member 34.
Therefore, the internal gear 13 connected to the rotary disk 30 via the connecting member 34 and the elastic member 33 is rotatable (rotation is restricted during ordinary torque transmission) with respect to the center casing 22, and is also radially displaceable.
In a starter 1 according to the present embodiment shown in FIG. 7, a one-way clutch 60 is disposed near a pinion 4 and is comprised of an inner member 61, an outer member 62, rollers 63, a clutch cover 64 and a restricting plate 67. The inner member 61 is formed integrally with the pinion 4 and is movably fitted on an output shaft 3, while the outer member 62 is formed integrally with a spline tube 66 spline-fitted on the output shaft 3 and engaged with a lever 28 driven by a magnet switch 5. The rollers 63 are disposed radially between the inner member 61 and the outer member 62. The clutch cover 64 surrounds the outer member 62 and the restricting plate 67 which restricts axial movement of the rollers 63, and fixes the outer member 62 and the restricting plate 67 in position.
A center casing 22 has its outer periphery fitted with a step part 20b of a housing 20 and is restricted from turning or rotating by a cylindrical part 20a of the housing 20. The output shaft 3 disposed coaxially with an armature shaft 6a is supported rotatably radially inside an inner cylindrical part 22a of the center casing 22 via a bearing 21.
As shown in detail in FIG. 8, a partition plate 50 is disposed between an armature 6 and a planetary gear reduction mechanism which is comprised of a sun gear 11, planetary gears 12 and an internal gear 13 and disposed radially inside the cylindrical part 20a of the housing 20. The planetary gears 12 are supported rotatably around respective pins 18 fitted into a flange 3b formed at one end of the output shaft 3 so that the planetary gears 12 revolve around the sun gear 11 while rotating around the pins 18. The internal gear 13 is made of resin impregnated with glass fibers, while the housing 20 is made of aluminum alloy.
A shock absorbing device 40 is disposed adjacently to the planetary gear reduction mechanism. In shock absorbing device 40, a first friction plate 41 engages the internal gear 13 to restrict turning of the internal gear 13 while allowing turning of the internal gear 13 to a certain extent. For allowing the internal gear 13 to turn to the certain extent, a space is provided between the outer periphery of the internal gear 13 and the inner periphery of the cylindrical part 20a of the housing 20.
In this clearance, a cylindrical member 44 made of a hard metal such as tool steel or high carbon steel is disposed relatively movably against the cylindrical part 20a and the internal gear 13. That is, small clearances are maintained between the cylindrical member 44 and the cylindrical part 20a and between the internal gear 13 and the cylindrical member 44. The cylindrical member 44 may be any form which is a simple cylinder form as shown in FIG. 9A, which has an axially extending slit 44a as shown in FIG. 9B, or which is divided into a plurality of parts circumferentially or axially as shown respectively in FIG. 9C or 9D. The axial length of the cylindrical member 44 is set to be longer than that of the internal gear 13 and substantially equal to the axial distance between the partition plate 50 and the center casing 22.
The shock absorbing device 40 is comprised of, in addition to the first friction plate 41, a second friction plate 42, an adjusting screw 48 and a disk spring 49. The first friction plate 41, receiving a biasing force of the disk spring 49 through the second friction plate 42, is maintained in frictional engagement with both the center casing 22 and the second friction plate 42. The adjusting screw 48 is in thread engagement with the male thread formed on the outer periphery of the cylindrical part 22a of the center casing 22 thereby to adjust the biasing force. The rotation of the first friction plate 41 is restricted normally by the frictional engagement against the center casing 22 and the second friction plate 42. When an excessive torque exceeding the stationary torque provided by the frictional engagement is applied, the first friction plate 41 turns together with the internal gear 13 to absorb the excessive torque.
In operation, the starter according to this embodiment operates in substantially the same way as in the foregoing embodiments. When the teeth of the pinion 4 come into contact with the teeth of the ring gear 36 at high speeds in the process of engagement of the pinion 4 with the ring gear 36, a large impact shock occurs between the pinion 4 and the ring gear 36. With an excessive torque which is caused by this engagement and exerts in turn on a pinion driving structure in the starter 1, the first friction plate 41 engaged with the internal gear 13 slides against the center casing 22 and the second friction plate 42 and causes the internal gear 13 to turn together. When the internal gear 13 turns eccentrically because of backlash between the gears in the planetary gear reduction mechanism, the internal gear 13 rotates relatively against the cylindrical member 44 in sliding contact with the inner periphery of the cylindrical member 44 disposed between the cylindrical part 20a of the housing 20 and the internal gear 13. Because the cylindrical member 44 is maintained relatively movably against the cylindrical part 20a, the cylindrical member 44 will also turn together with the internal gear 13.
In this operation, even when the internal gear 13 rotates relatively to the cylindrical member 44 in sliding contact therewith, wear between the internal gear 13 and the cylindrical member 44 will be reduced to a minimum because of the high hardness of the cylindrical member 44. Further, because the cylindrical member 44 restricts the direct contact between the internal gear 13 and the cylindrical part 20a, the eccentric rotation of the internal gear 13 never slides on the cylindrical part and hence the wear of the cylindrical part can be reduced. It may occur that the contacting portions between the cylindrical part 20a and the cylindrical member 44 wear during the turning of the cylindrical member 44 together with the internal gear 13. However, the wear of the cylindrical part 20a of the housing 20 will be minimal, because the cylindrical member 44 rotates only intermittently and more slowly than the internal gear 13 does.
Due to the wear of the cylindrical member 44 and the internal gear 13, which are relatively movable, the clearance between the inner periphery of the cylindrical member 44 and the outer periphery of the internal gear 13 may be reduced to a minimum so that the outer diameter of the cylindrical part 20a may be reduced accordingly.
Still further, with the axial length of the cylindrical member 44 being substantially equal to the axial distance between the partition plate 50 and the center casing 22, the cylindrical member 44 functions as a spacer as well for assuring an axial spacing between the partition plate 50 and the center casing 22. With the cylindrical member 44 being disposed between the center casing 22 and the partition plate 50, the center casing 22 can be restricted from moving toward the partition plate 50, even when the center casing 22 is pushed toward the starting motor side through the helical spline 25 at the time of engagement of the pinion 4 with the ring gear 36.
In the present embodiment, a shock absorbing device 40 is modified from that in the third embodiment while maintaining the same or similar construction of the third embodiment for the other construction of a starter. More specifically, an elastic member 45 made of rubber or the like is disposed between an internal gear 13 and a first friction plate 41 as in the first embodiment. According to this embodiment, when an excessively large impact torque is applied to a driving structure in a starter, the first friction plate 41 slidingly turns against frictional engagement forces between a center casing 22 and a second friction plate 42 to absorb the large torque. Provided that the impact torque is relatively small, the first friction plate 41 does not slidingly turn but the elastic member 45 deforms or twists to absorb such impact torque.
In this embodiment as well, a cylindrical member 44 is disposed in a space provided between the internal gear 13 and a housing cylindrical part 20a. The axial length of the cylindrical member 44 is set to be substantially equal to the axial distance between the center casing 22 and the partition plate 50.
The present invention should not be limited to the disclosed embodiments but may be modified in various ways without departing from the scope and spirit of the invention. One such modification may be that a cylindrical member used in the third and the fourth embodiment is used also in the first and the second embodiment.
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