Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1998-05-12
2000-04-11
Schwartz, Christopher P.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303127, B60T 836
Patent
active
060480408
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF INVENTION
This invention relates to an anti-lock vehicle braking system for a vehicle having a pair of drive wheels, the wheels of said pair being disposed on opposite sides of the vehicle, comprising a wheel speed sensor for each wheel, a controller responsive to wheel speed signals from said two wheel speed sensors, for sensing skid conditions at said wheels and for generating skid control instructions, a wheel brake for each wheel, responsive to fluid pressure, hereinafter referred to as brake pressure, supplied thereto, a common supply line, for supplying a common brake pressure for both of said brakes from a fluid pressure supply in accordance with a brake demand signal and a skid control means controlled by said skid control instructions for modulating the common brake pressure. Such a braking system will be referred to hereinafter as being of the kind specified.
A braking system of the kind specified provides an effective anti-lock braking system without the need for a separate skid control means for each wheel brake to provide independent brake pressure. This can be achieved by utilising adaptive logic in the controller to switch between a "select low" or a "select high" mode in which the controller is responsive to the speed of the wheel which is in engagement with the lower friction surface or the wheel which is in engagement with the higher friction surface respectively.
However, hitherto it has not been possible for such an anti-lock brake system having two wheel speed sensors and a single skid control means, to provide wheel slip control (ASR). It is a requirement of ASR control to be able to apply the brakes of one wheel which is spinning on a low friction surface to enable the higher friction surface on the opposite side of the vehicle to be utilised, thereby improving acceleration. With the anti-lock system as described above where only one skid control means controls both wheels, in the case of one wheel spinning it is only possible to apply or release the brakes on both sides of the vehicle, which is of no value for ASR control.
Accordingly, it is an object of the present invention to provide an anti-lock vehicle braking system of the kind specified with an ASR facility.
According to the present invention we provide a braking system of the kind specified, having a brake apply valve to supply fluid under pressure to the common supply valve, in response to the controller detecting a wheel spin condition of one of said wheels, to provide a common brake pressure for both of said brakes and isolating means to isolate the brake associated with the other of said wheel brakes from the brake pressure.
In one more specific aspect said brake pressure is a pneumatic brake pressure comprising air or other gas, hereinafter referred to as air.
The air may be supplied from a supply such as a reservoir for air under pressure.
Said common supply valve may comprise an in-line valve.
In this case the air to provide said pneumatic brake pressure may be fed from the air supply to the common supply valve under the control of a brake pressure demand valve which may be manually operable or said brake apply valve and which provides said brake demand signal.
Alternatively, said common supply valve may comprise a relay valve.
In this case the air to provide said pneumatic brake pressure may be fed from the air supply to the common supply valve and a brake demand signal may be supplied to the common supply valve under the control of a brake pressure demand valve which may be manually operable or said brake apply valve.
In another more specific aspect the said brake pressure is a hydraulic brake pressure comprising a liquid such as oil, hereinafter referred to as hydraulic fluid.
The system may comprise a fluid pressure converter responsive to a pneumatic signal to provide a hydraulic brake pressure which is supplied to the vehicle brakes.
The air providing said pneumatic signal may be fed to said converter by said common supply valve.
Said common supply valve may comprise an in-line valve.
In this cas
REFERENCES:
patent: 4156547 (1979-05-01), Marsh
patent: 4260199 (1981-04-01), Reinecke
patent: 4616881 (1986-10-01), Muller et al.
patent: 4819998 (1989-04-01), Goebels et al.
patent: 4852953 (1989-08-01), Brearley et al.
Haldex Brake Products Limited
Schwartz Christopher P.
Talavera Melanie
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