Fluid-pressure and analogous brake systems – Speed-controlled – Brake force or pressure determined from speed sensors
Patent
1997-12-18
1999-12-21
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Brake force or pressure determined from speed sensors
303166, 303DIG3, 303DIG4, B60T 836
Patent
active
060039604
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic brake system Such systems are, among others, anti-lock systems (ABS), traction slip control systems (TCS) and driving stability control systems (DSC, ASMS).
In prior art and customary brake systems with electronic braking pressure control, the pilot pressure, i.e. the pressure in the braking pressure generator or in the master cylinder which is responsive to pedal application, and the braking pressure prevailing in the individual wheel brakes is not measured, although the control could be considerably improved in some situations by taking into account the actual pressure. Monitoring of the systems could also be simplified or improved by measuring the pressure. Pressure measurement in brake systems with ABS or TCS is not performed mainly for cost reasons. In other control systems, pressure measurement is imperative.
An object of the present invention is to develop a brake system of the previously mentioned type which takes into account the pressure actually prevailing in the braking pressure generator and/or in the individual wheel brakes for the control. Nevertheless, the brake system should require only comparatively limited expenditure in manufacture.
SUMMARY OF THE INVENTION
It has been found that this object can be achieved by the brake system of the present invention. The special features of the brake system of the present invention include that the change-over behavior of the hydraulic valves during control operations is sensed by sensors and is evaluated for the approximate determination of the braking pressure prevailing in the braking pressure generator and/or in the individual wheel brakes.
In a preferred aspect of the present invention, wherein the hydraulic valves include valve tappets arranged in a valve housing which are moved to a final position when the hydraulic valves are actuated, the sensors, are configured as acoustic sensors or vibration or acceleration pickups to determine the change-over behavior of the valves. The sensors sense the sound vibrations caused when the valve tappet moves to sit on a valve stop or on the valve seat.
The present invention is based on the knowledge that the pressure in the master cylinder and in the wheel brakes can be derived with a sufficient degree of accuracy from the change-over behavior of the hydraulic valves. This task does not require pressure sensors, but only one single bone-conduction sensor (or, in special cases, also a plurality of acoustic sensors). The sensors which can be semiconductor sensors permit being mounted on the valve housing, i.e. outside the actual hydraulic system, and hence do not involve a safety risk.
Further features, advantages and possible applications of the present invention can be seen in the following description of embodiments, making reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 is a schematic view of the most important hydraulic and electronic components of a brake system with anti-lock control (ABS).
FIG. 2 is a cross-sectional view of an inlet valve of the type used in the present invention.
FIGS. 3(A) and 3(B) are diagrams showing the dependence of the delay in switching (FIG. 3A) and the sound amplitude (3B) on the master cylinder pressure.
FIGS. 4(A) and 4(B) show, in the same representation as FIG. 3, a diagram plotting the dependence of the delay in switching (4A) and the sound amplitude (4B) on the pressure in the wheel brake.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows in an anti-lock brake system a tandem master cylinder 1, preceded by a pedal-operated vacuum booster 2, and a hydraulic brake circuit I to which the wheels of a diagonal or an axle are connected. The second brake circuit II has the same components as the brake circuit I and, therefore, is not illustrated.
An inlet valve 5, 6 is respectively inserted into the pressure fluid lines leading from the master cylinder to the wheel brakes 3, 4 of the wheels VR, HL. Further, the wheel brakes 3, 4 are connected t
REFERENCES:
patent: 5551770 (1996-09-01), Hrovat et al.
Search Report of the German Patent Office Relating to Parent German Patent Application No. 195 14 171.7.
Buschmann Gunther
Gronau Ralph
Butler Douglas C.
ITT Manufacturing Enterprises Inc.
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