Brake-pressure control device having rear-axle brake circuit self-priming recirculation pump

Claim 1

A brake-pressure control device for a vehicle with hydraulic brake system having two brake circuits and equipped with an anti-lock brake system (ABS) which operates according to a recirculation principle, and with a device for dynamic movement control (FDR) mode operating according to a principle of keeping longitudinal slip and lateral slip of vehicle wheels within limits which are compatible overall with dynamic stability of the vehicle by electronically controlled, automatic activation of at least one wheel brake, comprising (a) a brake-pressure control device including a brake circuit distribution with a front-axle brake circuit and a rear-axle brake circuit, and a static main cylinder with pressure outputs individually assigned to the brake circuits; (b) ABS recirculation pumps configured to operate as at least one pressure source from which the at least one wheel brake utilized for the dynamic movement control is suppliable with brake pressure, with a recirculation pump assigned to the brake circuit of the front axle requiring minimum input pressure level for feed mode; (c) a low pressure input of the recirculation pump of the front-axle brake circuit configured for connection by a precharging control valve to an output pressure space of a precharging cylinder configured as a single-circuit main cylinder which has a piston forming an axially movable boundary of the drive pressure space and being arranged to be displaceable by applying pressure to a drive pressure space to increase pressure in the output pressure space, and has axially spaced flanges between which an overrun space is defined and kept in constant communication with a front-axle pressure output of the main cylinder, the piston being provided with a valve arranged to be activated mechanically to function as a non-return valve which blocks a through-flow channel of the piston connecting the overrun space to the output pressure space when pressure in the output pressure space of the precharging cylinder is larger than a pressure in the overrun space and opens the through-flow channel when the output pressure of the main cylinder is larger than a pressure in the output pressure space of the precharging cylinder; (d) change-over valves individually assigned to each of the brake circuits and operatively connected between the main cylinder pressure outputs and main brake lines of the brake circuits, the change-over valves having an open, basic position assigned to a normal braking mode and a blocking, switched position assigned to the dynamic movement control (FDR) mode; (e) an inflow control valve operatively arranged to have a basic, blocking position in which a supply path from the rear-axle pressure output of the main cylinder to the low pressure side of the recirculation pump of the brake circuit of the rear axle is blocked and a switched position assigned to the dynamic movement control (FDR) mode in which a through-flow position opens the supply path; and (f) low pressure inputs of the two recirculation pumps operatively connected to a return line of the respective brake circuit via a non-return valve arranged to be acted on in an opening direction by relatively higher pressure in the return line than at the respective low pressure input and is otherwise in a blocking state; wherein (g) the recirculation pump of the rear-axle brake circuit is configured as a self-priming pump; and (h) the precharging cylinder is configured selectively to increase pressure in the output pressure space by one of (i) valve-controlled application to a drive pressure space of the precharging cylinder of output pressure of a built-in vehicle hydraulic pressure source, wherein the output pressure is generated by one of a hydraulic power steering system and a permanently driven hydraulic ride leveller pump and (ii) valve-controlled venting of a drive chamber constituting the drive pressure space previously connected to a built-in vacuum source of a pneumatic driving cylinder and output pressure of a built-in, pneumatic pressure source to the pneumatic driving cylinder.