Brushless DC motor system with optically scannable member for commutation
First Claim
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1. A brushless DC motor system, comprising:
- a DC motor which includes a plurality of stator coils to receive commutation current, a rotatable member having an optically scannable code, and a plurality of permanent magnets, fixedly positioned with respect to the scannable code, mounted along a circular path in the rotatable member opposite the coils so that the coils and magnets are spaced apart by gaps;
fixed scanner means with respect to the stator coils for scanning the code to generate scanner signals having phase positions; and
control means for evaluating the scanner signals with respect to their phase positions to determine the moment of commutation, and for supplying the commutation current to the coils,wherein the motor requires n commutation steps during each revolution, n being an integer greater than 1,wherein the rotatable member is composed of a rotationally symmetrical light-transmitting plastic element which includes a ring with an edge bearing the scannable code, the scannable code including a plurality of light-impermeable equidistant zones on the ring, the light-impermeable zones being distributed around the circumference of the ring, each light-impermeable zone corresponding to respective commutation step, andwherein there are n-1 first light-impermeable zones and one second light-impermeable zone, the second light-impermeable zone being shaped differently than the first light-impermeable zones.
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Abstract
A brushless DC motor system includes a multi-pole DC motor having coils and permanent magnets. Optically scannable markers are applied on the circumference of a rotating member of the motor in fixed association with the magnets. By means of a scanner, these markers are converted to signals. These signals are evaluated with respect to their phase position and moment of commutation, and as a result commutation current is supplied to the coils.
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Citations
11 Claims
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1. A brushless DC motor system, comprising:
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a DC motor which includes a plurality of stator coils to receive commutation current, a rotatable member having an optically scannable code, and a plurality of permanent magnets, fixedly positioned with respect to the scannable code, mounted along a circular path in the rotatable member opposite the coils so that the coils and magnets are spaced apart by gaps; fixed scanner means with respect to the stator coils for scanning the code to generate scanner signals having phase positions; and control means for evaluating the scanner signals with respect to their phase positions to determine the moment of commutation, and for supplying the commutation current to the coils, wherein the motor requires n commutation steps during each revolution, n being an integer greater than 1, wherein the rotatable member is composed of a rotationally symmetrical light-transmitting plastic element which includes a ring with an edge bearing the scannable code, the scannable code including a plurality of light-impermeable equidistant zones on the ring, the light-impermeable zones being distributed around the circumference of the ring, each light-impermeable zone corresponding to respective commutation step, and wherein there are n-1 first light-impermeable zones and one second light-impermeable zone, the second light-impermeable zone being shaped differently than the first light-impermeable zones. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A brushless DC motor system, comprising:
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a DC motor which requires a plurality of commutation steps during each revolution and which includes a rotatably mounted shaft, a unitary light-transmitting plastic element having a cylindrical sleeve portion which mounts the element on the shaft, having an intermediate portion which extends radially outward from the sleeve portion, and having a cylindrical outer portion which is connected to the intermediate portion at a position that is spaced apart from the sleeve portion, the outer portion being coaxially disposed with respect to the sleeve portion and bearing an optically scannable code, the optically scannable code including a plurality of light-impermeable equidistant zones on the outer portion of the plastic element, the light-impermeable zones being distributed around the circumference of the outer portion, each light-impermeable zone corresponding to a respective commutation step, a plurality of fixedly mounted stator coils to receive commutation current, the stator coils being disposed between the shaft and the outer portion of the plastic element, a plurality of permanent magnets, and means for mounting the permanent magnets on the plastic element, the permanent magnets being disposed along a circular path adjacent the stator coils so that the coils and magnets are spaced apart by gaps; fixed scanner means with respect to the stator coils for scanning the code to generate scanner signals having phase positions; and control means for evaluating the scanner signals with respect to their phase positions to determine the moment of commutation, and for supplying the commutation current to the coils, wherein there are n commutation steps, n being an integer, and wherein there are n-1 first light-impermeable zones and one second light-impermeable zone, the second light-impermeable zone being shaped differently than the first light-impermeable zones. - View Dependent Claims (8, 9, 10)
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11. A brushless DC motor system, comprising:
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a DC motor which includes a rotatably mounted shaft, a unitary light-transmitting plastic element having a cylindrical sleeve portion which mounts the element on the shaft, having an intermediate portion which extends radially outward from the sleeve portion, and having a cylindrical outer portion which is connected to the intermediate portion at a position that is spaced apart from the sleeve portion, the outer portion being coaxially disposed with respect to the sleeve portion and bearing an optically scannable code, a plurality of fixedly mounted stator coils to receive commutation current, the stator coils being disposed between the shaft and the outer portion of the plastic element, a plurality of permanent magnets, and means for mounting the permanent magnets on the plastic element, the permanent magnets being disposed along a circular path adjacent the stator coils so that the coils and magnets are spaced apart by gaps; fixed scanner means with respect to the stator coils for scanning the code to generate scanner signals having phase positions; and control means for evaluating the scanner signals with respect to their phase positions to determine the moment of commutation, and for supplying the commutation current to the coils, wherein the optically scannable code includes a plurality of spaced-apart, elongated markers borne by the outer portion of the plastic element, the markers being disposed parallel to the shaft, one of the markers having a thickness that is substantially greater than the rest.
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Specification