Starter return mechanism
A permanently engaged starter assembly includes a ring gear, a return gear, and a starter gear. The return gear is fixed to a shaft of a starter return mechanism. The starter gear is arranged for fixing to a shaft of a starter motor and arranged in a torque path between the ring gear and the return gear. In an example embodiment, the ring gear has a central axis and the return gear is radially outside of the starter gear when measured from the ring gear central axis. In an example embodiment, the ring gear includes a first gear tooth, the return gear includes a second gear tooth, and the starter gear includes third and fourth gear teeth engaged with the first and second gear teeth, respectively.
1. A starter gear assembly comprising:
a ring gear;
a return mechanism comprising:
a slip tube;
a return mechanism shaft, and,
a torsion spring rotationally engaged with the return mechanism shaft and the slip tube:
a return gear fixed to the return mechanism shaft; and,
a starter gear arranged for fixing to a shaft of a starter motor and arranged in a torque path between the ring gear and the return gear.
2. The starter gear assembly of claim 1 wherein:
the ring gear has a central axis; and,
the return gear is radially outside of the starter gear when measured from the ring gear central axis.
3. The starter gear assembly of claim 1 wherein:
the ring gear includes a first gear tooth;
the return gear includes a second gear tooth; and,
the starter gear includes third and fourth gear teeth engaged with the first and second gear teeth, respectively.
4. The starter gear assembly of claim 1 wherein the starter return mechanism shaft extends predominantly from the return gear in a first axial direction and the shaft of the starter motor extends predominantly from the starter gear in a second axial direction, opposite the first axial direction.
5. The starter gear assembly of claim 1 further comprising:
a starter housing for fixing the starter motor and the return mechanism to an engine.
6. The starter gear assembly of claim 5 wherein the starter return mechanism shaft includes a portion supported by the starter housing.
7. The starter gear assembly of claim 1 wherein the torsion spring is disposed radially between the return mechanism shaft and the slip tube.
8. The starter gear assembly of claim 1 wherein each of the slip tube and the return mechanism shaft include respective helical cuts for rotationally engaging respective end coils of the torsion spring.
9. The starter gear assembly of claim 1 further comprising:
a shaft plate fixed to the return mechanism shaft and including a radial tab arranged for lash engagement with a slip tube radial tab.
10. The starter gear assembly of claim 9 wherein the radial tabs are arranged to maintain preload of the torsion spring and limit rotational displacement of the return mechanism shaft relative to the slip tube.
11. The starter gear assembly of claim 1 wherein the return mechanism further comprises:
a housing;
a first friction plate drivingly engaged with one of the housing or the slip tube; and
a resilient element for preloading the first friction plate for frictional engagement with the other of the housing or the slip tube.
12. The starter gear assembly of claim 11 wherein the resilient element is a wave spring, belleville washer, or diaphragm spring.
13. The starter gear assembly of claim 11 wherein the return mechanism further comprises a first clutch plate drivingly engaged with the other of the housing or the slip tube and contacting the friction plate.
14. The starter gear assembly of claim 13 wherein the return mechanism further comprises a second friction plate and a second clutch plate.
15. A return mechanism for a starter comprising:
a shaft including a first helical cut;
a slip tube including a second helical cut and a first radial tab;
a torsion spring disposed radially between the shaft and the slip tube and including respective end coils rotationally engaged with the first and second helical cuts; and,
a shaft plate fixed to the shaft and including a second radial tab, wherein the first and second radial tabs are arranged to maintain preload of the torsion spring and limit rotational displacement of the shaft relative to the slip tube.
16. The return mechanism of claim 15 further comprising:
a housing;
a first friction plate drivingly engaged with one of the housing or the slip tube; and
a resilient element for preloading the first friction plate for frictional engagement with the other of the housing or the slip tube.
17. The return mechanism of claim 16 wherein the return mechanism further comprises a first clutch plate drivingly engaged with the other of the housing or the slip tube and frictionally engaged with the friction plate.
18. The return mechanism of claim 17 wherein the return mechanism further comprises a second friction plate and a second clutch plate.