Brakes – Vehicle – Hub or disk
Reexamination Certificate
1999-06-17
2001-06-12
Schwartz, Christopher P. (Department: 3613)
Brakes
Vehicle
Hub or disk
C188S071500, C188S141000
Reexamination Certificate
active
06244391
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ABS braking system for motor vehicles.
BACKGROUND OF THE INVENTION
Typically, production vehicles, such as automobiles having a Automatic Braking System (ABS) employ a single brake disc fixed to the wheel hub and a sliding brake caliper mounted on a suspension member of the vehicle. Operation of a brake foot pedal by the operator with excessive force is sensed by a sensor, and a deceleration of the wheel is sensed by a wheel position or speed sensor mounted adjacent the wheel. The wheel speed sensor particularly monitors for front wheel locking up while in the braking condition with its loss of steerability and its longer stopping distance. The stopping distance of the vehicle may be made shorter if the wheels are operated iteratively at a low slip rather than a longer, fully locked or skid condition. The brake caliper is preferably operated at a high brake torque “apply” rate to increase brake torque for quick response. Additionally, caliper preferably is operated at a “high release” rate to decrease brake torque for quick response when the condition of lock-up is sensed as about to begin to allow the wheel to accelerate to a velocity approaching the vehicle velocity.
In conventional production vehicles having this fixed brake disc and slidable brake caliper, a hydraulic piston in a hydraulic cylinder on the caliper is operated to shift an inner movable brake pad into braking engagement with one side of the brake disc fixed to a rotating wheel hub mounted on the vehicle suspension. A reaction force from the hydraulic fluid moving the piston shifts the slidable caliper to slide the caliper and a second brake pad on the distal end of a caliper into engagement with the other side of the fixed brake disc. Typically, the braking system operates with hydraulic fluid at a pressure of about 70 BAR or more to provide the clamping pressure to opposite sides of the brake disc.
From the foregoing, it will be understood that when high excessive force is applied to a brake pedal by a vehicle operator causing rapidly deceleration of the wheel towards the lock-up condition, the ABS sensors and control system senses the rotational position of the wheel relative to the vehicle's speed; and if these conditions are within preset stored parameters, the ABS hydraulic system is activated to operate the brakes. The ABS hydraulic system isolates the pedal-operated hydraulics, and the braking operation is taken over by the ABS system, which causes the braking effort to drop and allows the wheel rotation to accelerate or spin up. When the wheel spin-up approaches the vehicle speed, as sensed by the wheel sensor, but does not equal the vehicle speed, the ABS hydraulics apply increased hydraulic pressure to the sliding caliper to decrease or spin down the braked wheel's rotational velocity. When the vehicle wheel spins down to approach vehicle lock as sensed by the wheel sensor and within the preset parameters, the ABS hydraulic pressure at the slidable caliper is increased to allow wheel spin up. This process is iterated to provide modulation of the ABS hydraulic pressure and a deceleration of the vehicle's velocity to provide a stopping of the vehicle within a predetermined distance depending on the kind of surface on which the wheels are engaging. Manifestly, the stopping distance on ice or other low coefficient of friction surfaces is greater than the sloping distance for higher coefficient of friction surfaces. Governmental regulations in many countries require the ABS braking system to stop the vehicle within a set stopping distance for a given coefficient of friction surface.
The ABS system senses the initial apply rate and release rates and scales or calibrates the resolution of subsequent “apply” and “release” rates to stop the vehicle. For example, the amplitude of the initial apply and release rates is quite high when the wheel is on a dry concrete surface and the frequency of the brake applications and releases is quite large in amplitude and at a low frequency. The ABS system then compares the frequency and amplitude of brake apply and brake release rates relative to the preset stored parameters in a controller and then operates the braking system according to this algorithm that is used to decelerate the vehicle's speed to stop the vehicle with the governmental stopping distance. This deceleration is usually a constant deceleration and is linear with respect to time and vehicle velocity or distance traveled. Hereinafter, this will be called a vehicle deceleration curve, which need not be linear, but which is usually a linear curve. A graphical representation of vehicle wheel speed and of hydraulic pressure shows that they are modulated along this theoretical vehicle deceleration curve until the vehicle is slowed down to a very low speed, e.g., under 10 mph when the brakes are allowed to lock up to complete the stopping of the vehicle. If the same vehicle traveling at the same speed and braked with the same brake pedal pressure was traveling on polished ice, having a very low coefficient of friction, relative to the coefficient of friction for the concrete surface, the initial braking by the ABS system recognizes this and sets the scale or calibration to generate a finer resolution with a more frequent application and release of the brakes and with a smaller amplitude of wheel acceleration and deceleration. Thus, with a smaller coefficient of friction surface, the average pressure variation and wheel acceleration is less over the stopping distance.
Current ABS braking systems suffer from being relatively heavy in weight, in being relatively costly, and from operational deficiencies such as operating at high pressures, high residual torque drag, and large hystersis losses. The present invention is directed to providing a significant weight reduction, for example, with respect to one commercial automobile, to reduce the weight of the braking system from about 18 kilograms to 15 kilograms of unsprung weight at the wheel. A cost saving of thirty (30%) percent or more can be achieved relative to the braking system currently used on a commercial vehicle. As will be explained in detail hereinafter, better operation is achieved with a reduction in residual torque drag, which occurs when the brake pads rub against the brake disc when the brake pedal has not been operated. A reduction in residual torque drag results in a significant increase in brake pad life, lower operating temperatures, and faster wheel acceleration as will be described in more detail hereinafter.
To facilitate acceptance and adoption of the braking system of this invention by original equipment manufacturers, the preferred braking system of this invention may be used with the same installed ABS controller and operating system on vehicles now in use. The preferred braking system without the ABS control system is more fully described in the aforesaid co-pending United States patent application and to a lesser extent hereinafter in this application. This braking system includes twin slidable brake discs and four brake pads for rubbing or clamping engagement with the four sides on the twin brake discs and a fixed caliper mounted on a suspension stub axle or knuckle. Preferably, the hydraulic cylinder for operating the brake discs is formed integrally with the suspension knuckle; and an outer, distal brake pad is fixedly mounted on a stationary bridge of the caliper. This is unlike the current slidable caliper on the typical conventional disc brake that has only two rubbing surfaces engaging opposite sides of a cast iron or cast aluminum, heavy brake rotor.
The present invention is, as stated above, directed to providing a better ABS system from an operational standpoint. Current ABS systems suffer from a number of shortcomings. One of these shortcomings is that they operate at relatively high hydraulic pressures, for example, 70 BAR on high friction surfaces. With only two braking surfaces for a wheel, a large amount of energy must be dissipated at each rubbing s
Federal-Mogul Technology Limited
Fitch Even Tabin & Flannery
Schwartz Christopher P.
LandOfFree
Disc brake system with ABS does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disc brake system with ABS, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disc brake system with ABS will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452966