Auxiliary drive circuit for an electric assist steering system
First Claim
1. An auxiliary drive circuit for use in an electric power assist steering system having an electric assist motor and a main drive circuit connectable to the electric assist motor through a mechanically actuatable reversing switch assembly for applying electrical power to energize the electric assist motor in response to an output signal from a torsion sensing device by controlling the amount of current through the electric assist motor from a source of electrical energy, a value of the output signal from the torque sensing device varying as a function of applied steering torque, said auxiliary drive circuit comprising:
- means for, when actuated, providing an auxiliary electrical path between the source of electrical energy and the mechanically actuatable reversing switch assembly through the electric assist motor;
fault detection means for sensing a fault condition in the main drive circuit, said fault detection means including first sensing means for sensing an electrical output signal from the torsion sensing device and for outputting one electrical signal when steering torque is not being applied and a second electrical signal when steering torque is being applied, second sensing means for sensing operation of the main drive circuit and for outputting an electrical signal indicative of the main drive circuit applying electrical power to the electric assist motor; and
means for actuating said auxiliary electrical path means in response to (i) said first sensing means indicating application of steering torque, and (ii) said second sensing means indicating the main drive circuit is not applying electrical power to the electric assist motor.
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Accused Products
Abstract
An auxiliary drive circuit is disclosed for an electric, power assist steering system including an actuatable switching device which, when actuated, provides an auxiliary electrical path between a source of electrical energy and a mechanically actuatable reversing switch assembly for applying electrical power to energize an electric assist motor. The actuatable switching device in the auxiliary drive circuit is electrically connected in parallel to an actuatable switching device in a main drive circuit. A detector circuit monitors the operation of the main drive circuit and the output signal from a torque sensor. Upon detection of applied steering torque greater than a predetermined value and that the main drive circuit is not operating, the detector circuit outputs an electrical signal indicative thereof. A latching element latches the output of the detector circuit to actuate the actuatable switching device in the auxiliary drive circuit. Actuating the actuatable switching device in the auxiliary drive circuit provides an auxiliary connection of the electric assist motor to the source of electrical energy. In one embodiment, the auxiliary drive circuit, when actuated, permits maximum, continuous current flow through the power assist motor. In another embodiment, the auxiliary drive circuit provides a controllable amount of power assist in response to applied steering torque.
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Citations
14 Claims
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1. An auxiliary drive circuit for use in an electric power assist steering system having an electric assist motor and a main drive circuit connectable to the electric assist motor through a mechanically actuatable reversing switch assembly for applying electrical power to energize the electric assist motor in response to an output signal from a torsion sensing device by controlling the amount of current through the electric assist motor from a source of electrical energy, a value of the output signal from the torque sensing device varying as a function of applied steering torque, said auxiliary drive circuit comprising:
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means for, when actuated, providing an auxiliary electrical path between the source of electrical energy and the mechanically actuatable reversing switch assembly through the electric assist motor; fault detection means for sensing a fault condition in the main drive circuit, said fault detection means including first sensing means for sensing an electrical output signal from the torsion sensing device and for outputting one electrical signal when steering torque is not being applied and a second electrical signal when steering torque is being applied, second sensing means for sensing operation of the main drive circuit and for outputting an electrical signal indicative of the main drive circuit applying electrical power to the electric assist motor; and means for actuating said auxiliary electrical path means in response to (i) said first sensing means indicating application of steering torque, and (ii) said second sensing means indicating the main drive circuit is not applying electrical power to the electric assist motor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An auxiliary drive circuit for use in an electric power assist steering system having an electric assist motor and a main drive circuit connectable to the electric assist motor through a mechanically actuatable reversing switch assembly for applying electrical power to energize the electric assist motor in response to an output signal from a torsion sensing device by controlling the amount of current through the electric assist motor from a source of electrical energy, a value of the output signal from the torque sensing device varying as a function of applied steering torque, said auxiliary drive circuit comprising:
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means for, when actuated, providing an auxiliary electrical path between the source of electrical energy and the mechanically actuatable reversing switch assembly through the electric assist motor; fault detection means for sensing a fault condition in the main drive circuit, said fault detection means including first sensing means for sensing an electrical output signal from the torsion sensing device and for outputting an electrical signal when steering torque greater than a predetermined value is being applied, second sensing means for sensing operation of the main drive circuit and for outputting an electrical signal when the main drive circuit applies electrical power to the electric assist motor; and means for actuating said auxiliary electrical path means in response to (i) said first sensing means indicating application of steering torque greater than said predetermined value, and (ii) said second sensing means indicating the main drive circuit is not applying electrical power to the electric assist motor. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification