Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1998-09-29
2000-11-07
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031221, B60T 834
Patent
active
061425826
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic vehicle brake system, comprising a pump-fed hydraulic pressure accumulator unit for selective feeding of a hydraulic pressure medium to at least one brake circuit via an operable brake valve unit and a first pressure sensor which is arranged, when the pressure in a pressure accumulator unit is below a predetermined pressure level, to activate a warning unit for sending an alarm.
DESCRIPTION OF THE RELATED ART
In a known hydraulic vehicle brake system of the above mentioned type for construction machinery (see FIG. 1 in the accompanying drawings) a pressure sensor 1 for an accumulator unit provides a signal to a warning unit 3 as long as the sensor senses that the pressure is too low in the pressure accumulator unit 2, when the starter switch is turned on. If there should be a leak in the brake circuit 5 downstream of the foot-operated brake valve 6, the pressure in the accumulator 2 will again be built up to a level exceeding that at which the alarm is kept activated, when the brake valve closes after the pressure on the brake pedal is removed. i.e. the alarm will be deactivated despite the fact that there is still a defect in the brake circuit 5. In such a system, the alarm is reset (deactivated) automatically when there is once again sufficient pressure in the accumulator unit, and therefore there is a risk that an alarm which has been indicated will be forgotten without remedying the fault.
SUMMARY OF THE INVENTION
A main purpose of the present invention is to achieve a hydraulic vehicle brake system which improves the functioning and security of a fault monitoring arrangement for such a brake system, in which an alarm once triggered will be maintained and where the maintained alarm can normally first be reset after the pressure in the brake circuit even downstream of the brake valve is above a predetermined minimum level.
For this purpose, the brake system described by way of introduction according to the invention is characterized in that with the warning unit there is coordinated means for maintaining a triggered alarm, and that there is coordinated with the brake circuit downstream of the brake valve unit a second pressure sensor, which is arranged to be activated to reset the warning unit first when a minimum pressure level has been exceeded in the brake circuit downstream, of the brake valve unit. A triggered alarm is thereby maintained until the second sensor indicates that there is sufficiently high pressure in the brake circuit downstream of the brake valve unit, the second sensor being adapted to reset the warning unit. Temporary shut-off of the warning unit can, if so desired, normally be done by breaking the voltage to the starter switch of the vehicle.
It is suitable to apply the principle according to the invention to a brake system with two brake circuits, of which at least with one of the brake circuits, but preferably with both, there is coordinated a second pressure sensor in the brake circuit portion downstream of the brake valve unit for resetting the warning unit when a predetermined minimum pressure level has been exceeded.
The second alarm-resetting pressure sensors can be coupled in series or in parallel with each other. In the latter case, it is possible to determine which of the brake circuit portions located downstream of the brake valve unit is defective.
The means for maintaining a triggered alarm can comprise a relay or be integrated into a control computer which in turn controls the warning unit, which can comprise a visual and/or acoustic alarm and possibly provide text information on a driver display.
The alarm-resetting pressure sensor can be a pressure monitor which is disposed to break or close an electric circuit at a predetermined pressure in a the brake circuit downstream of the brake valve unit. If the alarm-resetting pressure sensors are analog pressure sensors, they are disposed to continuously feed a signal corresponding to the current brake circuit pressure value to the control com
REFERENCES:
patent: 4726629 (1988-02-01), Resch
patent: 5054860 (1991-10-01), Nomura et al.
patent: 5221125 (1993-06-01), Okochi et al.
patent: 5547264 (1996-08-01), Tozu et al.
patent: 5695260 (1997-12-01), Tanaka et al.
patent: 5733017 (1998-03-01), Nakashima et al.
Oberleitner Robert J.
Talavera Melanie
Volvo Wheel Loaders AB
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