Fluid-pressure and analogous brake systems – Speed-controlled – Pressure reapply control
Reexamination Certificate
1999-03-01
2001-05-29
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Pressure reapply control
Reexamination Certificate
active
06238020
ABSTRACT:
The present invention relates to a method which is intended for use in an automotive vehicle brake system with electronic braking pressure control and for controlling the braking pressure increase or braking pressure reincrease during a control operation, wherein the rotational behavior of the individual vehicle wheels is measured and evaluated to determine braking pressure control signals, and wherein during a braking pressure control operation the braking pressure reduction in the previous cycle is taken into account for the control of the braking pressure reincrease. Brake systems for implementing the above method are also comprised in the present invention. Braking pressure control operations of this type occur especially during anti-lock control operations, but also in the event of driving stability control operations, and like control operations.
Brake systems with electronic anti-lock control (ABS) are known in the art and on the market in various designs. In customary systems, the rotational behavior of the individual vehicle wheels is known to be measured by means of wheel rotational speed sensors, wheel sensors in short, and evaluated as the only or the most important input quantity of the braking pressure control system. In order to achieve a satisfactory control which ensures maintaining steerability and driving stability despite very different road conditions and driving situations, the vehicle requiring only a short stopping distance due to the control, a very sophisticated control philosophy is necessary which can only be achieved by complex calculating algorithms.
The braking pressure increase or reincrease after a previous braking pressure reduction which was initiated by the control presents a special rating problem to the control philosophy. A basic objective is that the braking pressure approaches the locking pressure level very quickly and with great precision so that the wheel runs stable and is effectively braked simultaneously. The control frequency, i.e., the decrease and reincrease of the pressure during an anti-lock control operation, is desired to be as low as possible for physical and comfort reasons.
German patent application No. 39 03 180 A1 (P 6632) discloses a circuit arrangement for a brake system with anti-lock control wherein for pressure reincrease after pressure reduction which was triggered by the control, the braking pressure is introduced in to the wheel brake with a steep and subsequently with a flatter gradient. This pressure introduction is achieved by a variable pulse and short invariable pulses which are successive at long intervals. The proportioning of the pressure reincrease depends on the duration of the pressure increase during the steep rise phase in the previous cycle, the duration of the entire pressure increase in the previous cycle, and the duration of the previous pressure reduction.
An object of the present invention is to develop a method which permits adjusting a precisely controlled pressure reincrease conformed to the respective situation, after a preceding pressure reduction which was triggered by the control. The pressure level of the controlled wheel, which run s stable again and is underbraked after the previous pressure reduction, s hall be raised to the locking pressure level as quickly as possible. Also, in order to keep the control frequency low, the introduction of an excessively high braking pressure shall be avoided, and the locking pressure level shall not be exceeded again instantaneously. An additional requirement is an adaption to the constant variations of the control quantities or influencing variables as quickly and precisely as possible.
It has been found that this object can be achieved by the method described in claim
1
. The special features of the method of the type initially referred to involve that a braking pressure rise gradient is calculated on the basis of the braking pressure increase in the previous braking pressure increase phase, that the braking pressure increase and variation of the braking pressure increase is calculated and predetermined on the basis of this braking pressure rise gradient and the wheel cylinder pressure at the commencement of the current braking pressure increase phase and on the basis of the current locking pressure level.
Some particularly advantageous embodiments of the method of the present invention and brake systems for implementing the method are described in the subclaims.
Thus, according to the present invention, the braking pressure rise gradient in the previous increase phase is made the basis for determining or dimensioning the braking pressure reincrease during a control operation. The starting point of the braking pressure reincrease is the current wheel cylinder pressure which is determined from the directly preceding braking pressure reduction phase. The braking pressure increase is continued until the locking pressure level is reached again. A variation of the locking pressure level which has meanwhile occurred is immediately taken into account for the proportioning of the braking pressure increase.
The braking pressure rise gradient in a braking pressure increase phase depends on the pilot pressure or master cylinder pressure and, thus, on the force by which the driver applies the brake. According to the present invention, the data about the pilot pressure is taken into account for the calculation of the braking pressure reincrease.
This way, the pilot pressure which respectively prevailed in the cycle that directly preceded or the directly preceding braking pressure increase phase is made the basis for the calculation of the current braking pressure increase.
Further details of the present invention can be taken from the following description of an embodiment making reference to the accompanying drawings.
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Buschmann Gunther
Ehmer Norbert
Gronau Ralph
Lambert Utz
Butler Douglas C.
Continental Teves AG & Co. oHG
Rader & Fishman & Grauer, PLLC
Siconolfi Robert A.
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