Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-05-16
2000-07-18
Schwartz, Chris
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303 10, 3031131, 3031141, 3031161, 3031162, 303DIG2, 303DIG4, B60T 834
Patent
active
060896787
DESCRIPTION:
BRIEF SUMMARY
This invention relates to hydraulic braking systems for vehicles of the kind in which an electrical signal from a pedal-responsive transducer is utilised in an electric control circuit to operate a solenoid-operated actuator for normal service braking, and upon failure of the electric control circuit a master cylinder can be operated by the pedal in a mode known as "push through" to apply an operating pressure to the brake.
BACKGROUND OF THE INVENTION
A braking system of the kind set forth is disclosed in WO-A-93/00236. In this system the pedal-operated master cylinder communicates with a brake through a pilot pressure operated isolation valve which is spring urged into an open position, and the output from an hydraulic pump is communicated to the isolation valve. When the pressure generated by the pump in response to an electric signal from an electrical sensor associated with the pedal is greater than the force needed to overcome the spring force of the isolation valve, the valve switches to communicate the pump directly to the brake, and isolates the master cylinder from the brake. After the isolation valve changes state the master cylinder is not used to pressurise the brake. However, in the event of malfunction of the electro-hydraulic portion of the system the brake can be applied directly from the master cylinder through the isolation valve in the "push through" mode with the valve switching to its original state.
SUMMARY OF THE INVENTION
We are also aware of GB-A2-0 357 922. This application discloses a procedure for operation of an electrical pressure medium service brake system. The procedure proposed involves performing integrity checks in order to determine the correct operation of various sensors in the system by comparing various outputs from the sensors. If the outputs from the sensors do not correspond to each other in an expected manner it is assumed that a sensor must be at fault. However, a problem with this procedure is that if a fault occurs in the integrity of a brake line, an incorrect diagnosis that it was a sensor fault may occur.
According to our invention in an hydraulic braking system of the kind set forth for vehicles, an electrical signal from the pedal responsive transducer is adapted to be compared with an electrical signal from a pressure sensor responsive to output pressure from the master cylinder in order to check the integrity of a direct flow path through which the brake can be applied from the master cylinder by movement of the pedal in the "push through" mode.
This has the advantage that malfunctions such as blockages or leaks in at least the direct flow path may be detected. On detection of the leak or blockage the driver may be alerted and a repair effected. This may aid in the prevention of problems associated with faults in the brake circuit.
Preferably the pedal responsive transducer is adapted to monitor the displacement of the brake pedal and the pressure sensor is adapted to monitor the pressure in the direct flow path.
Preferably the output from the master cylinder is disabled and the brake is applied from a high pressure hydraulic source under the control of electrical control means including a solenoid operated actuator responsive to electric signals from the transducer associated with the pedal, and upon failure of the electrical control means the brake can be applied through the direct flow path.
This has the advantage that pressure fluid from the master cylinder is utilised in the application of the brake upon failure of the electrical control means. For normal service braking the operating fluid is supplied from the hydraulic source to the brake.
During a first part of the travel of the pedal fluid from the master cylinder may fill the brakes in the manner of a conventional "quick-fill" master cylinder to provided "pedal feel" and during a second continuous part of the travel the fluid may be pressurised to apply the brakes. However, such a "quick fill" master cylinder is an optional feature of the invention.
Since the hydraulic actuator is norma
REFERENCES:
patent: 4662687 (1987-05-01), Leiber
patent: 4812777 (1989-03-01), Shirai
patent: 4919493 (1990-04-01), Leiber
patent: 5567021 (1996-10-01), Gaillard
patent: 5709438 (1998-01-01), Isakson et al.
patent: 5921640 (1999-07-01), Mortimer et al.
Lucas Industries Public Limited Company
Schwartz Chris
Whitesel J. Warren
LandOfFree
Hydraulic braking systems for vehicles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic braking systems for vehicles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic braking systems for vehicles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2029073