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US 9,174,668 B2Granted
Electric power steering system
AssigneeJtekt Corporation
InventorHiroshi Kichise
Life of this patent
Estimating the term…
Abstract
In an electric power steering system, an ECU calculates a steering angle of a steering wheel based on an output of a rotation angle sensor and an EPS gear ratio. The ECU calculates a correction amount for canceling a steering deviation caused due to a temperature change, based on a temperature of a rack shaft detected by a temperature sensor and a map stored in a memory, and corrects the correction amount by adding the correction amount to the calculated steering angle.
Claims2
An electric power steering system comprising:
- a housing;
- a rack shaft accommodated in the housing, the rack shaft reciprocating in an axial direction in accordance with rotation of a steering shaft, and the rack shaft being formed of a material different from a material of which the housing is formed;
- an electric motor fixed to the housing and applying an assist force to the rack shaft;
- a rotation angle sensor configured to detect a rotation angle of the electric motor for a single rotation of the steering shaft;
- an estimator configured to estimate a temperature of the rack shaft or a characteristic value that depends on the temperature;
- and
- an electronic control unit configured to control driving of the electric motor by:
- (i) calculating a steering angle of a steering wheel for the single rotation of the steering shaft based on an output of the rotation angle sensor and an EPS gear ratio of the electric power steering system, (ii) determining a deviation amount between the calculated steering angle and an actual steering angle of the steering wheel caused by a change in an ambient temperature around the rack shaft, (iii) determining a correction amount for canceling the deviation of the calculated steering angle or the output of the rotation angle sensor based on the estimated temperature or the estimated characteristic value obtained by the estimator, and (iv) correcting the calculated steering angle or the output of the rotation angle sensor by applying the correction amount.
5 more elements
Dependencies are inferred from the claim text.