Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-02-07
2000-10-24
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031141, B60T 840
Patent
active
061355755
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to automotive brake systems and more particularly relates to an electronically controllable, antilock brake actuating system for motor vehicles.
BACKGROUND OF THE INVENTION
A brake actuation system of this kind is known, for example, from DE 4,102,497 C1. In this brake actuation system, the buffer memories that can be used for pedal path simulation, which are positioned separately from the master cylinder, are located relatively far from the brake pedal, so that in a control event, no optimum pedal feel can be obtained. Considered to be less favorable is the space requirement associated with the installation of the buffer memory and also the relatively poor ventilation of the buffer memories.
In addition, from DE-OS 4,229,041 A1 an electronically controllable, fail-safe brake actuating system is known in which both the master cylinder and also the electrically controllable brake pressure transducer equipped with a separate hydraulic fluid supply tank can be connected by means of an electromagnetically actuated 3/2-way valve with the wheel brakes. In a first switch setting of the 3/2-way valve, a hydraulic linkage exists between the master cylinder and/or the pressure transducer and the wheel brake, whereas the connection between the pressure transducer and/or the master cylinder and the wheel brake is blocked. In a second switch setting, the 3/2-way valve establishes a hydraulic connection between the pressure transducer and/or the master cylinder and the wheel brake, whereas the connection between the master cylinder and/or the pressure transducer and the wheel brake is blocked. Due to the stated measures, in intact systems the driver is separated from the wheel brake and feels a hard pedal. Since the brake pressure transducers are equipped with separate hydraulic fluid supply tanks, they must be separated from the wheel brake in case of a power failure, so that complicated valves have to be used.
DE-OS 3,424,915 discloses blocking of the hydraulic linkages between the brake pressure transducers and the master cylinder by means of holes (blow holes) drilled in the hydraulic cylinders of the brake pressure transducers, the holes being passed therefor over by sealing sleeves located on their piston upon actuation of the brake pressure transducers.
However, the known brake actuating systems are less well suited for use in antilock brake systems. For example, the locking, hydraulic linkages do not permit the relief of the hydraulic pressure prevailing in the wheel brake down to near zero, in an ABS control event since during the necessary complete restoring motion of the brake pressure transducer piston, the drill hole mentioned above would be released to which the relatively high pressure created by the driver is applied.
Also less advantageous for an ABS control are the chambers formed in the hydraulic cylinders of the brake pressure transducers; the volume of hydraulic fluid displaced by the driver of the vehicle is introduced into said chambers in order to maintain the usual pedal feel for the driver upon actuation. The drive units of the brake pressure transducers must in every case actively ensure the restoring motion of the pressure transducer pistons, so that large costs are required for a four-quadrant control electronics system and also a design for maximum actuating force is necessary. In addition, an undamped pedal restoration takes place against the driver's foot.
Finally, the direct actuation of the valve device formed by the combination of drill hole (blow hole) and sealing sleeve takes place in actuality by means of the electric drive due to the non-negligible mass inertia at a time delay, which, for its part, results in an inflow of a considerable volume of hydraulic fluid, so that a pressure relief to values near zero bar is not possible. This adversely affects particular control processes at lower values.
Therefore it is the purpose of the present invention to improve an electronically controllable brake actuating system of the kind described above
REFERENCES:
patent: 4708404 (1987-11-01), Seibert et al.
patent: 4730877 (1988-03-01), Seibert et al.
patent: 4730878 (1988-03-01), Reinartz et al.
patent: 5234263 (1993-08-01), Haerr et al.
patent: 5312172 (1994-05-01), Takeuchi
Feigel Hans Jorg
Klein Andreas
Neumann Ulrich
Schiel Lothar
Graham Matthew C.
ITT Automotive Europe GmbH
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