Electric power steering system
First Claim
1. An electric power steering system comprising:
- an electric motor that generates power for assisting in steering of a vehicle;
a motor drive circuit that includes a switching component for controlling current flowing through the electric motor;
a power supply circuit that includes a step-up circuit for stepping up a power source voltage and applies the stepped up power source voltage to the electric motor via the switching component;
a control unit that controls step-up operation of the power source voltage in the step-up circuit and drive of the switching component;
possible ground fault detecting means that detects a possible ground fault in a line electrically connected with electric motor; and
actual ground fault determining means that determines an actual ground fault, which is a ground fault actually present in the line, wherein the control unit includes application voltage control means that controls a voltage applied to the switching component by the power supply circuit.
1 Assignment
0 Petitions
Accused Products
Abstract
An electronic control unit (ECU) stops driving a first switching transistor in a step-up circuit until an actual ground fault is determined after a possible ground fault is detected in a line that is electrically connected with an electric motor. As a result, a voltage stepped-up by the step-up circuit is controlled. Since current flowing through the electric motor does not sharply decrease immediately after the possible ground fault is detected in the line, unusual power steering movement is less likely to be produced. Moreover, switching transistors in an H bridge circuit, which is a motor drive circuit, are protected from damage because no excess voltage is applied to the switching transistors.
17 Citations
13 Claims
-
1. An electric power steering system comprising:
-
an electric motor that generates power for assisting in steering of a vehicle;
a motor drive circuit that includes a switching component for controlling current flowing through the electric motor;
a power supply circuit that includes a step-up circuit for stepping up a power source voltage and applies the stepped up power source voltage to the electric motor via the switching component;
a control unit that controls step-up operation of the power source voltage in the step-up circuit and drive of the switching component;
possible ground fault detecting means that detects a possible ground fault in a line electrically connected with electric motor; and
actual ground fault determining means that determines an actual ground fault, which is a ground fault actually present in the line, wherein the control unit includes application voltage control means that controls a voltage applied to the switching component by the power supply circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
Specification