Starter machine performance improvement

1. A method of improving the performance of a rotary electric machine, operable in a low speed region and in a comparatively higher-speed high speed region, for machine operation in the high speed region, comprising:

between a first steel material having a first flux density at a given magnetizing force level, and a second steel material having a second flux density at the given magnetizing force level that is at least about 20% less than the first flux density, selecting the second steel material for use as a magnetically active portion of the machine;

whereby machine operation at a given speed in the low speed region causes the machine comprising the magnetically active portion using the second steel material to generate a back EMF that is substantially similar to the back EMF that would be generated by the machine were the first steel material used instead of the second steel material for the magnetically active machine portion, and machine operation at a given speed in the high speed region causes the machine comprising the magnetically active portion using the second steel material to generate a back EMF that is substantially less than the back EMF that would be generated by the machine were the first steel material used instead of the second steel material for the magnetically active machine portion.

2. The method of claim 1 , wherein the given magnetizing force level is less than approximately 100 ampere-turns/inch.

3. The method of claim 1 , wherein the low speed region and the high speed region are adjacent regions along a range of machine operational speeds.

4. The method of claim 1 , wherein the machine comprises an electric motor and, at the given speed of machine operation in the high speed region, the comparatively lesser back EMF generated by the machine comprising the magnetically active portion using the selected second steel material, relative to the back EMF that would be generated by the machine were the first steel material used instead of the selected second steel material for the magnetically active machine portion, is manifested by a comparatively higher motor output torque level.

5. The method of claim 1 , wherein said method is also a method of improving the performance of an electric machine, operable in a high torque region and in a comparatively lower-torque low torque region, for machine operation in the low torque region,

whereby, relative to machine operation at a given torque level in the high torque region, the back EMF generated by the machine comprising the magnetically active portion using the selected second steel material is substantially similar to the back EMF that would be generated by the machine were the first steel material used instead of the selected second steel material for the magnetically active machine portion, and, relative to machine operation at a given torque in the low torque region, the back EMF generated by the machine comprising the magnetically active portion using the selected second steel material is substantially less than the back EMF that would be generated by the machine were the first steel material used instead of the selected second steel material for the magnetically active machine portion.

6. The method of claim 5 , wherein the machine comprises an electric motor and, at the given torque level in the low torque region, the comparatively lesser back EMF produced by the machine comprising the magnetically active portion using the selected second steel material, relative to the back EMF that would be generated by the machine were the first steel material used instead of the selected second steel material for the magnetically active machine portion, is manifested by a comparatively higher motor output speed.

7. The method of claim 6 , wherein the machine is a starter machine in which the motor is connected to a pinion that is engageable with an engine ring gear that is rotatable at varying speeds, and the engine is capable of being cranked by the starter machine under cold start conditions during machine operation in the low speed or high torque region, and under warm start conditions during machine operation in the high speed or low torque region;

whereby the engine is capable of being cranked under warm start conditions at comparatively higher speed and/or higher torque by the starter machine including the magnetically active machine portion using the selected second steel material, relative to the speed and/or torque at which the engine would be cranked by the starter machine were the first steel material used instead of the selected second steel material for the magnetically active machine portion.

8. The machine of claim 6 , wherein the motor comprises the magnetically active machine portion for which the selected second steel material is used.

9. The method of claim 1 , wherein the first steel material is a low carbon steel.

10. The method of claim 9 , wherein the first steel material is selected from the group consisting of AISI 1008 steel and AISI 1010 steel.

11. In combination with a rotary electric starter machine operable in a low speed region and a comparatively higher-speed high speed region for cranking an engine under cold start and warm start conditions, respectively, and which includes an electric motor, a housing surrounding the motor, and a pinion connected to the motor and engageable with an engine ring gear, wherein at least one of the motor and the housing includes a magnetically active portion of the machine, the improvement which comprises:

using for the magnetically active machine portion an enhanced performance steel material having a flux density at a given magnetizing force level that is at least about 20% less than the flux density at the given magnetic force level of a conventional low carbon steel material chosen from the group consisting of AISI 1008 and AISI 1010 steel;

whereby operation of the machine at a given speed in the low speed region causes the machine to generate a back EMF that is substantially similar to the back EMF that would be generated by the machine were the conventional low carbon steel material used instead of the enhanced performance steel material for the magnetically active machine portion, and whereby operation of the machine at a given speed in the high speed region causes the machine to generate a back EMF that is substantially less than the back EMF than would be generated by the machine were the conventional low carbon steel material used instead of the enhanced performance steel material for the magnetically active machine portion.

12. The combination of claim 11 , wherein the given magnetizing force level is less than approximately 100 ampere-turns/inch.

13. The combination of claim 11 , wherein the low speed region and the high speed region are adjacent regions along a range of machine operational speeds.

14. The combination of claim 11 , wherein at the given speed of machine operation in the high speed region, the comparatively lesser back EMF generated by the machine comprising the magnetically active portion using the enhanced performance steel material, relative to the back EMF that would be generated by the machine were the conventional low carbon steel material used instead of the enhanced performance steel material for the magnetically active machine portion, is manifested by a comparatively higher motor output torque level.

15. The combination of claim 11 , wherein the machine is operable in a high torque region and a comparatively lower-torque low torque region, which respectively correspond to the low speed and high speed regions;

whereby, relative to machine operation at a given torque level in the high torque region, the back EMF generated by the machine comprising the magnetically active portion using the enhanced performance steel material is substantially similar to the back EMF that would be generated by the machine were the conventional low carbon steel material used instead of the enhanced performance steel material for the magnetically active machine portion; and

whereby, relative to machine operation at a given torque in the low torque region, the back EMF generated by the machine comprising the magnetically active portion using the enhanced performance steel material is substantially less than the back EMF that would be generated by the machine were the conventional low carbon steel material used instead of the enhanced performance steel material for the magnetically active machine portion.

16. The combination of claim 15 , wherein the comparatively lesser back EMF produced by the machine comprising the magnetically active portion using the enhanced performance steel material at the given torque level in the low torque region, relative to the back EMF that would be generated by the machine were the conventional low carbon steel material used instead of the enhanced performance steel material for the magnetically active machine portion, is manifested by a comparatively higher motor output speed.

17. The combination of claim 16 , wherein the engine is capable of being cranked under warm start conditions at comparatively higher speed and/or higher torque by the machine including the magnetically active machine portion using the enhanced performance steel material, relative to the speed and/or torque at which the engine would be cranked by the machine were the conventional low carbon steel material used instead of the enhanced performance steel material for the magnetically active machine portion.

18. The combination of claim 16 , wherein the motor comprises the magnetically active machine portion for which the enhanced performance steel material is used.

19. A rotary electric starter machine comprising an electric motor, a housing surrounding the motor, and a pinion connected to the motor, at least one of the motor and the housing comprising a magnetically active portion of the machine; and

wherein the magnetically active motor portion is made of an enhanced performance steel material having a flux density at a given magnetizing force level that is at least about 20% less than the flux density at the given magnetic force level of a conventional low carbon steel material chosen from the group consisting of AISI 1008 and AISI 1010 steel.

20. The starter machine of claim 19 , wherein the given magnetizing force level is less than approximately 100 ampere-turns/inch.