Armature with torque limiter for engine starter

1. An engine starter comprising:

a gear assembly including a pinion gear configured to engage an engine ring gear; and

an electric motor coupled to the gear assembly and configured to drive the gear assembly and the pinion gear, the electric motor including an armature configured to rotate

within a stator, the armature including:

a core member defining a central cavity extending in an axial direction;

an armature shaft positioned within the core member; and

a clutch arrangement positioned between the core member and the armature shaft, wherein the armature shaft and the clutch arrangement are positioned within the central cavity.

2. The engine starter of claim 1 , wherein the clutch arrangement is a multi-plate clutch.

3. The engine starter of claim 2 , the armature shaft including a first axial portion and a second axial portion, the first axial portion including an output gear positioned outside the core member, the second axial portion extending through a central cavity in the core member.

4. The engine starter of claim 3 , the multi-plate clutch arrangement including a first plurality of clutch discs and a second plurality of clutch discs, the first plurality of clutch discs including teeth in meshed engagement with splines on the second axial portion of the armature shaft, and the second plurality of clutch discs including teeth in meshed engagement with splines on a core bushing positioned within the central cavity of the core member and fixed to the core member.

5. The engine starter of claim 4 further comprising at least one spring configured to bias the first plurality of clutch discs into engagement with the second plurality of clutch discs.

6. The engine starter of claim 5 wherein the core member is a lamination stack, the armature further comprising conductors extending through slots in the lamination stack.

7. The engine starter of claim 6 , the armature further comprising a commutator connected to the conductors on an opposite side of the core member from the output gear, the commutator coaxial with a shaft coupler, the shaft coupler fixedly connected to the core bushing and rotatably connected to the armature shaft via a shaft bushing.

8. The engine starter of claim 4 wherein the first plurality of clutch discs include at least five clutch discs with inner perimeter teeth and the second plurality of clutch discs include at least five clutch discs with outer perimeter teeth.

9. The engine starter of claim 1 wherein the clutch arrangement is configured to release the armature shaft from the core member such that the core member rotates relative to the armature shaft when a torque on the armature shaft is greater than a threshold torque.

10. An engine starter comprising:

a gear assembly including a pinion gear; and

an electric motor including an armature coupled to the gear assembly and configured to drive the gear assembly and the pinion gear, the armature including:

a core member defining a central cavity extending in an axial direction within the core member;

an armature shaft extending from the central cavity; and

a clutch arrangement positioned in the central cavity, the clutch arrangement configured to releasably couple the core member and the armature shaft.

11. The engine starter of claim 10 wherein the clutch arrangement includes a plurality of first discs, a plurality of second discs, and at least one biasing member configured to urge the first discs into engagement with the second discs.

12. The engine starter of claim 11 further comprising a core bushing positioned in the central cavity between the core member and the armature shaft, the core bushing and the armature shaft each including axial splines, wherein the first discs include teeth that engage the axial splines on the armature shaft and the second discs include teeth that engage the axial splines on the core bushing.

13. The engine starter of claim 10 wherein the core member is an armature lamination stack and a plurality of conductors extend through slots in the armature lamination stack.

14. The engine starter of claim 10 wherein the clutch arrangement is configured to release the armature shaft from the core member such that the core member rotates relative to the armature shaft when a torque on the armature shaft is greater than a threshold torque.

15. An engine starter comprising:

a gear assembly including a pinion gear; and

an electric motor including an armature coupled to the gear assembly and configured to drive the gear assembly and the pinion gear, the armature including:

a core member defining a central cavity;

an armature shaft positioned within the core member;

a clutch arrangement positioned within the central cavity and configured to couple the core member to the armature shaft when a torque on the armature shaft is less than a threshold torque and configured to de-couple the core member from the armature shaft when the torque on the armature shaft is greater than the threshold torque.

16. The engine starter of claim 15 wherein the clutch arrangement is a multi-plate clutch including a plurality of discs.

17. The engine starter of claim 15 wherein the electric motor is configured to rotate the pinion gear via the drive assembly, the engine starter further including a solenoid configured to drive the pinion in an axial direction.

18. The engine starter of claim 15 wherein the armature further includes a plurality of conductors and a commutator, the plurality of conductors forming U-turn portions on a first end of the core member and the commutator is positioned axially past a second end of the core member that is opposite the first end, wherein the clutch arrangement is positioned entirely between the first end of the core member and the commutator.