Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1992-08-27
1994-12-13
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303 8, 303 227, B60T 834, B60T 1326
Patent
active
053724135
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a vehicle braking system, particularly, but not exclusively, to a trailer braking system for use with a trailer adapted to be towed by a tractor vehicle.
More particularly, the invention relates to a vehicle braking system hereinafter referred to as being "of the kind specified", comprising a controller responsive to wheel speed signals for sensing skid conditions of the wheels and for generating skid control instructions, a primary fluid pressure supply including a fluid pressure source and a fluid pressure reservoir, a plurality of wheel brakes responsive to fluid pressure, hereinafter referred to as brake pressure, supplied thereto, a supply means, comprising a supply valve, for supplying brake pressure to said brakes from said primary supply in accordance with a brake operating signal, and a skid control means, controlled by said skid control instructions, comprising a skid control unit for controlling the brake pressure.
EP-A-0307579 discloses an example of a vehicle braking system of the kind specified.
The vehicle braking system of EP-A-0307579 is a "single channel" system where wheel speed sensors are provided only for one wheel on each side of the vehicle, generally the wheels of a single axle, and only a single supply valve, which is of the relay valve type, and a single skid control unit, which modulates a control signal for the relay valve, are combined together into one unit.
However, in a "multi-channel" system where wheel speed sensors are provided for a plurality of wheels on each side of the vehicle with associated respective supply valves and skid control units there have been hitherto a large number of discrete components which must be fitted separately to the vehicle with appropriate separate electrical and fluid connections both where the supply valves are relay valves or in-line valves. Such fitting is relatively complex and time consuming.
An object of the present invention is to provide a vehicle braking system of the kind specified and which provides a multi-channel facility and which is simple to fit.
According to one aspect of the present invention we provide a vehicle braking system of the kind specified wherein said supply means comprises a plurality of supply valves, each of which is adapted to supply fluid pressure to a different wheel brake or brakes, the skid control means comprises a plurality of fluid pressure skid control units, each of which is adapted to control the fluid pressure of a different wheel brake or brakes, there are provided first signal generating means to generate, independently of said skid control means, a plurality of brake operating signals as a function of a brake command signal and to supply a brake operating signal for each of said supply valves, and all said means are connected together so as to be mountable on the vehicle as a discrete unit.
The fluid pressure source may comprise a fluid pressure inlet for connection to an external source of fluid pressure and which is connected by a non-return valve means to the fluid pressure reservoir and said supply valves may supply brake pressure to said brakes from said reservoir in accordance with said brake operating signals.
The operating signals generated by said first signal generating means may be derived from said fluid pressure supplied from said primary fluid pressure supply.
The first signal generating means may comprise a relay valve to modulate said fluid pressure supplied from said primary supply as said function of the brake command signal.
The first signal generating means may comprise a load sensing valve to modulate said command signal as a function of a load carded by the vehicle.
Second signal generating means may be provided to generate a plurality of brake operating signals as a function of the fluid pressure in said fluid pressure source falling below a predetermined pressure and to supply said brake operating signal to each of said supply valves, and all said means connected together so as to be mountable on the vehicle as a discrete unit.
The operating sign
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Grau Girling, Skidchek MGX, Section M/T 3, p. 9 (from Maintenance Manual), FIG. 11 Valve-At Rest Schematic, Jan. 1984.
Graubremse, Hauszeitschrift IAA-Ausgabe 1987, "GRAU Girling ABS System DGX 4S/4K".
Broome William S.
Ross Colin F.
Ballato Jose A.
Grau Limited
Oberleitner Robert J.
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