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A device and method for matching the rates of speed at which an electric motor that is drivingly connected to a worm gear raises and lowers a window in an automobile power window assembly. By axially displacing the motor's armature, and/or by varying the thread and tooth profiles of the worm and the

A device and method for matching the rates of speed at which an electric motor that is drivingly connected to a worm gear raises and lowers a window in an automobile power window assembly. By axially displacing the motor's armature, and/or by varying the thread and tooth profiles of the worm and the gear, the amount of torque produced by the motor and transmitted through the worm gear can be altered. In order to compensate for the effect of gravity on the motor load and on the window's speed of ascent and descent, more torque is provided when the window is being raised and less torque is provided when the window is being lowered.

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1. An improved power window assembly for an automobile having an electric motor drivingly connected to a window, the electric motor having an armature rotatably driven about an axis by a magnetic field, the improvement comprising means for axially displacing the armature to change an alignment with

1. An improved power window assembly for an automobile having an electric motor drivingly connected to a window, the electric motor having an armature rotatably driven about an axis by a magnetic field, the improvement comprising means for axially displacing the armature to change an alignment with the magnetic field wherein the armature and the electric field are arranged such that displacing the armature to change the alignment with the magnetic field alters torque produced by the motor, and wherein the armature is configured to be axially displaced to a first position in which at least part of the armature is outside of the magnetic field when the window is being lowered, and wherein the armature is configured to be axially displaced to a second position in which more of the armature is within the magnetic field when the window is being raised. 2. An improved power window assembly for an automobile having a window driven by a rotary motor, the motor containing an armature rotatably driven by a magnetic field, the armature driving a worm gear having a plurality of gear teeth, the improvement comprising asymmetrical gear teeth for transferring torque from the worm gear more efficiently when rotating the worm gear in one direction and less efficiently when rotating the worm gear in an opposite direction. 3. An improved power window assembly for an automobile having a window driven by a rotary motor, the motor containing an armature rotatably driven by a magnetic field, the armature driving a worm gear with a worm having a plurality of threads, the improvement comprising asymmetrical worm threads for driving a cooperating gear more efficiently when rotating the worm in one direction and less efficiently when rotating the worm in an opposite direction. 4. A method for matching the rates of ascent and descent of a window in a power window assembly of an automobile, the method comprising: providing the assembly having an electric motor drivingly connected to the window, the electric motor having an armature at least partially aligned with, and rotatably driven by, a magnetic field;displacing the armature axially to change its alignment with the magnetic field; andaltering torque production by the motor when the armature is displaced axially for matching the rates of ascent and descent of the window. 5. The method of claim 4, further comprising a step of displacing the armature axially to a first position when the window is being lowered in which at least part of the armature is outside of the magnetic field. 6. The method of claim 5, wherein the step of displacing the armature further comprises generating an axial thrust force on the armature by a gearing relationship between the armature and at least one output gear, and wherein the axial direction of said thrust force is determined by a rotational direction of the armature. 7. The method of claim 5, further comprising a step of displacing the armature axially to a second position when the window is being raised in which more of the armature is within the magnetic field than when the armature is in the first position. 8. A method for matching the rates of ascent and descent of a window in a power window assembly of an automobile, the assembly having an electric motor drivingly connected to the window, the electric motor having an armature at least partially aligned with, and rotatably driven by, a magnetic field, the armature driving a worm gear which in turn drives a cooperating gear, the cooperating gear having a plurality of teeth, the method comprising: (a) displacing the armature axially to decrease alignment with the magnetic field when the gear rotates to lower the window, and wherein decreasing alignment with the magnetic field alters a torque produced by the motor; and(b) disposing asymmetric teeth on the cooperating gear to more efficiently drive the cooperating gear with the worm gear when the worm gear rotates to raise the window and less efficiently drive the gear with the worm gear when the worm gear rotates to lower the window. 9. The method of claim 8, further comprising a step of displacing the armature axially to increase alignment with the magnetic field when the worm gear rotates to raise the window. 10. The method of claim 8, wherein axial displacement of the armature is driven by an axial thrust force on the armature generated by a gearing relationship between the armature and the cooperating gear, and wherein the axial direction of said thrust force is determined by a rotational direction of the armature. 11. A method for matching the rates of ascent and descent of a window in a power window assembly of an automobile, the assembly having an electric motor drivingly connected to the window, the electric motor having an armature at least partially aligned with, and rotatably driven by, a magnetic field, the armature driving a worm gear, a worm of the worm gear having a plurality of threads, the method comprising: (a) displacing the armature axially to decrease alignment with the magnetic field when the worm rotates to lower the window, and wherein decreasing alignment with the magnetic field reduces torque supplied by the motor; and(b) disposing asymmetric threads on the worm to more efficiently drive the gear when the gear rotates to raise the window and less efficiently when the gear rotates to lower the window. 12. The method of claim 11, further comprising a step of displacing the armature axially to increase alignment with the magnetic field when the worm rotates to raise the window. 13. The method of claim 11, wherein axial displacement of the armature is driven by an axial thrust force on the armature generated by a gearing relationship between the armature and at least one output gear, and wherein the axial direction of said thrust force is determined by a rotational direction of the armature. 14. An improved power window assembly for an automobile having an electric motor drivingly connected to a window, the electric motor having an armature rotatably driven about an axis by a magnetic field, the improvement comprising means for axially displacing the armature to change an alignment with the magnetic field wherein the armature and the electric field are arranged such that displacing the armature to change the alignment with the magnetic field alters torque produced by the motor, wherein the means for axially displacing the armature to change the alignment with the magnetic field includes provision of a gap at an axial end of the armature that allows axial displacement of the armature due to an axial thrust force generated between a worm gear driven by the armature and a cooperating gear. 15. A power window assembly for a vehicle, comprising: an electric motor drivingly connected to a window, the electric motor having an armature rotatably driven about an axis by a magnetic field;a worm gear driven by the armature, the worm gear having a worm thread; anda cooperating gear having gear teeth meshingly engaged with the worm thread such that driving of the worm gear drives the cooperating gear, wherein at least one of the armature, the magnetic field, the worm gear and the cooperating gear are configured to provide a first torque to the cooperating gear when the armature is rotated in a first direction and to provide a second torque to the cooperating gear when the armature is rotated in a second, opposite direction, the second torque mechanically reduced relative to the first torque. 16. The power window assembly of claim 15, wherein the armature and the magnetic field are arranged such that the armature is axially shifted in a first direction when driven in the first rotatable direction and axially shifted in a second direction when driven in the second rotatable direction, axially shifting of the armature moves the armature relative to the magnetic field such that the magnetic field provides an increased or decreased magnetic force on the armature depending on the axial position of the armature. 17. The power window assembly of claim 16, wherein at least one of the worm thread of the worm gear and the gear teeth of the cooperating gear are asymmetrically configured to more efficiently transfer torque to the cooperating gear when the armature is driven in the first rotatable direction and less efficiently transfer torque to the cooperating gear when the armature is driven in the second rotatable direction. 18. The power window assembly of claim 15, wherein at least one of the worm thread of the worm gear and the gear teeth of the cooperating gear are asymmetrically configured to more efficiently transfer torque to the cooperating gear when the armature is driven in the first rotatable direction and less efficiently transfer torque to the cooperating gear when the armature is driven in the second rotatable direction. 19. The power window assembly of claim 18, wherein asymmetrically configured includes having a first pitch side and a second pitch side, wherein the first pitch side has a different pitch than the second pitch side.