A pressure source for a pressure device includes a pump for pumping fluid from fluid tank, an accumulator connected to the pump and a pressure device, a device for detecting the pressure in the accumulator, and a controller for controlling the operation of the pump in an ON-OFF manner on the basis of a result of detection by the pressure detecting device. In this pressure source, the controller includes first and second drive signal generating circuits each capable of independently generating a drive signal for determining the on-off operation of the pump, and a judging circuit which has a calculating function therein and to which at least the pressure detecting device is connected. The judging circuit is connected to the first drive signal generating circuit, and the pressure detecting device is connected to the second drive signal generating circuit. This ensures that the control of the first drive signal generating circuit can be carried out at any time by a calculation in the judging circuit, leading to an increased function. When the judging circuit is in trouble, the on-off control of the pump can be carried out by the second drive signal generating circuit.
An electric pump is turned ON and OFF by a main drive circuit including a negative pressure sensor for detecting a negative pressure in an accumulator, a first relay and a control device, and also turned ON and OFF by a back-up drive circuit including a negative pressure switch for detecting a negative pressure in an accumulator, and a second relay. For a period from the starting of the electric pump by the back-up drive circuit to the stopping of the electric pump by the main drive circuit, there is a period during which the electric pump is being driven only by the back-up drive circuit and a period during which the electric pump is being driven only by the main drive circuit. For each of these periods, a trouble of the main drive circuit and/or the back-up drive circuit can be determined by reference to a check signal indicative of the operational state of the electric pump. Thus, it is possible to reliably detect a trouble with the driving of the electric pump connected to the accumulator.
A process and system for attaining a desired braking value is disclosed. The actual braking value is adjusted until the desired braking value is attained. Conventionally the braking hysteresis worsens the response of a brake and, thereby, worsens the quality of the regulation of a braking system with regulated braking value. Known processes reduce the brake application energy in steps if the actual braking value is too great until the braking hysteresis has been overcome and the desired braking value has been attained. Whereas, the present invention decreases the brake application energy ZS by a value (HyS+W) consisting of the braking hysteresis HyS associated with the desired braking value and a effect drop-off W. This decrease occurs in the case of excessive actual braking value BI. The process accelerates the attainment of the desired braking value BS. The preferred area of application for the invention are braking systems in the automotive industry.
A pressure control apparatus is operated to connect a wheel cylinder to a reservoir via a return fluid passage so that brake fluid will be stored in the reservoir to reduce the pressure. In accordance with the operation of a fluid pressure pump, the brake fluid is discharged from the reservoir into the return fluid passage to supply the brake fluid to the wheel cylinder, so that the wheel cylinder pressure is gradually increased. Based on detection of a sharp decrease of the motor load, it is estimated that the reservoir has become empty. Then, brake fluid is taken from a fluid pressure generating apparatus into the wheel cylinder.
