Patent ID: 7360848
Filing Date: 2008-04-22
Classification: B60T

Abstract:
1. A parallel relay circuit in a braking device in which a fluid pressure accumulated in an accumulating unit is detected by a pressure detection unit, and when the fluid pressure detected by the pressure detection unit becomes lower than a first predetermined value, a motor is driven to activate a pump for increasing the fluid pressure accumulated in the accumulating unit such that a boosting function of a servo unit is maintained based on the fluid pressure, the parallel relay circuit comprising: a plurality of relays each provided in a power supply line to the motor and connected in parallel with one another; a parallel relay drive unit that controls an operation state of each of the plurality of relays; and a disconnection abnormality detection unit that detects a disconnection abnormality in the plurality of relays based on whether a voltage is supplied to the motor, wherein: the parallel relay drive unit drives only one of the plurality of relays sequentially in a predetermined order for driving the motor while turning rest of the relays off, the disconnection abnormality detection unit detects the disconnection abnormality of each of the plurality of relays individually by determining whether the voltage is applied to the motor when the one of the relays is driven, the disconnection abnormality detection unit detects the disconnection abnormality of the currently-driven relay by determining whether the voltage is applied to the motor through the currently-driven relay, when the motor is driven upon decrease in the fluid pressure accumulated in the accumulating unit, which is detected by the pressure detection unit to be lower than the first predetermined value, the parallel relay drive unit stops applying the voltage to the motor by turning the plurality of relays off at a timing at which the fluid pressure accumulated in the accumulating unit becomes equal to or higher than a second predetermined value that is higher than the first predetermined value, and drives only one of the plurality of relays sequentially in a predetermined order until the fluid pressure accumulated in the accumulating unit becomes equal to or higher than the second predetermined value, and the parallel relay drive unit only drives the rest of the relays in which the disconnection abnormality is not detected when the disconnection abnormality is detected in one of the plurality of relays.