Patent Application
20090320644
This application relates to the field of engine starters, and more particularly to torque absorbing or limiting components in an engine starter.
Many engine starters include a planetary gear system that transmits power from an electric starter motor to a pinion configured to engage an engine ring gear. The planetary gear system typically includes a sun gear connected to the output shaft of the electric motor. A plurality of planet gears revolve around the ring gear. The planet gears also engage teeth provided on an outer ring gear in the planetary gear system.
Engine starters may encounter excessive torque in the radial direction of the output shaft of the starter. For example, the torque associated with initial rotation of the electric motor, a slow turning pinion, or a jammed pinion may all result in excessive torque to the planetary gear system. When the planetary gear system encounters excessive torque, the planet gears may grind against the teeth of the outer ring gear. After time, the teeth of the planet gears grinding against the teeth of the ring gear may result in excessive wear or even failure of the planetary gear system.
In view of the foregoing, it would be advantageous to provide an engine starter having torque absorbing features provided in association with the planetary gear system of the starter. It would also be advantageous if such torque absorbing features could be easily incorporated into the engine starter.
An engine starter comprises a housing with a planetary gear arrangement provided within the housing. The planetary gear arrangement includes a ring gear configured to pivot about an axis. The ring gear includes a face oriented substantially perpendicular to the axis, the face including a plurality of detents provided as a plurality of ribs and a plurality of depressions on the face. An output shaft is connected to the planetary gear arrangement such that the planetary gear arrangement is configured to drive the output shaft. A pinion provided on the output shaft.
A torque limiter is positioned adjacent to the face of the ring gear within the housing of the engine starter. The torque limiter includes a plurality of projecting members engaging the plurality of detents on the ring gear when the ring gear pivots about the axis. The torque limiter is provided as a plate including a central hole, a body portion, and a perimeter portion. The plurality of projecting members comprise a plurality of spring fingers extending from the body portion at an angle. The plurality of spring fingers are provided as cut out portions of the body portion such that an opening is provided in the body portion in association with each of the plurality of spring fingers. The plurality of spring fingers each include a end tip portion that is bent away from the rest of the spring finger such that the end tip portion is generally parallel to the main body portion.
The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. Furthermore, while it would be desirable to provide an engine starter that includes one or more of the foregoing or other advantageous features as may be apparent to those reviewing this disclosure, the teachings disclosed herein extend to those embodiments which fall within the scope of the appended claims, regardless of whether they include the above-mentioned features accomplish or provide one or more of the above-mentioned advantages.
With reference to
The electric motor provided within the housing 12 is a direct current motor. The direct current motor includes an armature and an armature shaft. The motor further has a means for developing field flux (also not illustrated) which may take the form of a plurality of permanent magnets.
The armature shaft of the direct current motor is connected to the sun gear (not shown) of the planetary gear mechanism 14. The sun gear is provided at the center of the planetary gear mechanism 14 along the same axis 21 as the pinion drive shaft 20. A plurality of planet gears (not shown) are positioned about and engage the sun gear. Each of the planet gears is provided on a post 22. The posts 22 holding the planet gears are connected to a rotatable platform 24 which, in turn, is connected to the pinion drive shaft 20. The planet gears rotate about the sun gear within a ring gear 30.
With reference now to
A torque limiter 60 is provided adjacent to the ring gear 30 on the pinion-side of the ring gear 30. Accordingly, the forward face 36 of the ring gear 30 abuts the torque limiter 60. As explained in further detail below, the torque limiter 60 is provided as a plate comprising a plurality of spring fingers. The spring fingers engage detents 42 on the forward face 36, allowing the ring gear to rotate slightly in the radial direction about the axis 21 (i.e., in a circular direction about the axis 21). As best seen in
The interior portion of the ring gear 30 includes a planetary gear track 38 including a plurality of teeth 40 provided on the interior surface of the circular sidewall 34. The teeth of the planet gears engage the teeth 40 of the planetary gear track 38 and the planet gears circle the planetary gear track 38 as they rotate about the sun gear.
The rotatable platform 24 is rotatably positioned within the ring gear 30. In particular, as the planet gears rotate, the posts 22 holding the planet gears also rotate. Because the posts 22 are connected to the platform 24, the platform 24 also rotates with the planet gears. As shown in
The shaft 20 drives a starter drive that is comprised of the overrunning clutch 16 and a pinion gear 18. The pinion gear 18 is adapted to be moved into mesh with the ring gear of an engine. The shell 26 of the overrunning clutch has a helical splined connection to the shaft 20, which is not illustrated. During operation of the starter motor, after the engine fires and the pinion begins to rotate at excessive speeds, the overrunning clutch prevents translation of this excessive speed back to the planetary gear mechanism 14 and the electric motor.
The housing 12 includes an end nose portion 50. The nose portion 50 has an access opening (not shown) which allows the pinion gear 18 to be moved into mesh with a ring gear of an engine.
The housing 12 also includes a solenoid chamber or compartment 52. A solenoid (not shown) is held within the solenoid chamber 52. The plunger of the solenoid engages a shift lever 44 which extends between the solenoid chamber 52 and the drive housing 54. The shift lever 44 includes arms 46 that extend from an end portion and engage the overrunning clutch 16. It can be appreciated that when shift lever 44 is pivoted in the counter-clockwise direction by action of the solenoid in the solenoid chamber, the arms 46 will engage surface of the clutch 16 to push the overrunning clutch 16 and pinion 18 to the right, in
With reference now to
The body portion 62 of the torque limiter includes a generally flat surface 63 provided within a body plane. A plurality of projecting members 68 extend from the body portion 66 and engage the plurality of detents 42 on the ring gear. In the embodiment of
Each of the spring fingers 68 includes an elongated portion 72 and an integral end tip portion 74. The end tip portion 74 is provided on the end of the spring finger 68 that is most distant from the flat surface 63. The end tip portion 74 angles away from the elongated portion 72 of the spring finger such that the end tip portion 74 is generally parallel to the flat surface 63 of the body portion 62. This angled relationship between the end tip portion 74 and the elongated portion 72 may be provided by bending the end tip portion 74 on the elongated portion 76 when the spring finger 68 is bent away from the flat surface 63 of the body portion 62. As shown in
Returning to
The perimeter portion 66 of the torque limiter 60 includes an outer lip 78 that extends around the perimeter of the torque limiter 60. A plurality of tabs 80 are provided on the outer lip 78 in the form of rounded knobs. These knobs 80 are configured to engage slots or recesses formed in the housing 12. The slots in the housing are also rounded and complimentary in shape to the knobs 80. Accordingly, when the knobs 80 are fitted into the slots in the housing 12, the knobs secure the torque limiter 60 in place within the housing 12, preventing the torque limiter 60 from rotating about the axis 21.
In operation of the engine starter 10, when the ring gear 30 is exposed to excessive torque, the torque limiter 60 provides a dampening feature for the ring gear, limiting wear to the teeth 40 of the ring gear 30. In particular, when the ring gear experiences excessive torque, the forces of the planet gears against the ring gear encourage the ring gear 30 to pivot about the axis 11. The degree of ring gear 30 pivot within the housing is dependent upon the amount of torque encountered by the ring gear. In particular, when the ring gear 30 begins to rotate about the axis 21, the ribs 56 on the face 36 of the ring gear 30 are forced against the spring fingers 68 of the torque limiter 60. As the spring fingers 68 ride up the contoured surface of the ribs 56, the spring fingers 68 flex back toward the flat surface 63 of the torque limiter body portion 62. This force provided by the spring fingers 68 against the ribs 56 of the ring gear 30 increases as the spring fingers flex. When the ring gear 30 is exposed to sufficient torque, the ring gear 30 rotates such that the spring fingers 68 slide completely past the ribs and into the next subsequent depression 58 on the ring gear This rotation action by the ring gear 30 provides a torque dampening feature for the engine starter, allowing the planetary gear system to minimize wear caused by excessive torque events. When the excessive torque is removed, the ring gear 30 remains in the last incremental orientation encountered during the excessive torque event, with the spring fingers 68 sliding down into the closest depressions 58 on the ling gear.
Although the present invention has been described with respect to certain preferred embodiments, it will be appreciated by those of skill in the art that other implementations and adaptations are possible. Moreover, there are advantages to individual advancements described herein that may be obtained without incorporating other aspects described above. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.
