Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1999-07-07
2001-04-24
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S070000, C701S083000, C701S091000, C303S186000, C303S189000, C303S901000
Reexamination Certificate
active
06223115
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method for improving the control behavior of an anti-lock control system and more particularly for improving the steerability of the vehicle and the driving stability during cornering, wherein a vehicle reference speed is derived and criteria for identifying a cornering situation and the direction of cornering are obtained from the rotational behavior of the vehicle wheels wherein, instead of the standard control mode, a special control mode or rather a corner control mode starts operating or is put into operation, respectively, when a cornering situation is identified, said special control mode or cornering control mode producing a reduction of the braking pressure on the front wheel on the inside of the corner and/or on the rear wheel on the inside of the corner already in the partial braking range.
In a cornering identification system, with a method of control of the type presently mentioned, the pressure relief of the wheels on the inside of a corner generates a yawing moment around the vertical axis of the vehicle which balances and stabilizes the cornering situation. With control coming on during a partial braking operation, the braking pressure on the wheels on the outside of the corner will be kept constant or will automatically increase due to the cut-off of any further build-up of braking pressure on the wheel or wheels on the inside of the corner.
From DE 34 13 738 C2 (P 5547) there is already known an anti-lock control system (ABS) with a cornering identification circuit likewise based on wheel slip measurement. For the purpose of identifying a cornering situation the slip values of the wheels of one vehicle side are added up and compared with the slip sum of the wheels of the other vehicle side and a cornering identification signal will be generated as soon as the difference between the slip sums exceeds a predetermined limit value. Selection criteria such as “select low” or “select high” criteria, according to which the pressure variation is controlled in the individual braking pressure control channels of this brake system, and limit values for the coming-on of these selection criteria will be varied when a cornering situation is identified. In this way, control is to be adapted to the varying conditions during straight-onwards driving and during cornering.
It is known from older DE 21 19 590 A1 to obtain a cornering identification signal by means of a transverse acceleration measuring device such as a mercury switch.
It is further already known to expand the functions of an ABS control system in that the system is used for improving the driving and braking stabilities in corners. This is done in that a stabilizing moment is generated around the vertical axis of the vehicle by means of a calculated deceleration of the build-up of the braking pressure on the wheels on the inside of the corner as compared with the braking pressure on the wheels on the outside of the corner during cornering and a partial braking operation, i.e. during a braking operation, where ABS response threshold values are not reached (“Bremsanlage und Schlupf-Regelsystem der neuen 7er-Reihe von BMW”, ATZ 97 (1995), pages 8-15; and “Bremsanlage und Schlupf-Regelungssysteme der neuen Baureihe 5 von BMW”, ATZ 98 (1996), pages 188-194 [“Brake system and slip control system of BMW's new no. 7 line of models {ATZ auto journal, 97 (1995), pages 8-15}; and “Brake system and slip control systems of BMW's new no. 5 line of models” {ATZ auto journal, 98 (1996), pages 188-194}]). With no steering angle sensor being used, the information on the current steering angle is derived from the transverse acceleration which, on its part, is calculated from the wheel sensor signals.
It is thus an object of the present invention to develop a method of the type referred to above which will provide a marked contribution to improving the driving behavior and stabilization, respectively, of the vehicle by means of reliable cornering identification and reaction to this situation.
SUMMARY OF THE INVENTION
It has been found out that this object is achieved by a method the particular features of which consist in that the gradient of the braking pressure build-up on the front wheel and/or on the rear wheel on the inside of the corner is reduced in the partial braking range when a threshold value of a wheel speed difference is exceeded, which difference is the difference between the wheel speed sums per side formed from the speeds of the two wheels of one side of the vehicle, the reduction taking place in dependence on the extent by which the threshold value is exceeded.
In practice, pressure management of the front wheels is of particular importance in the special control mode or rather in the corner control mode. As a rule, while reducing the braking pressure on the wheel on the inside of the corner it is beneficial to simultaneously increase the braking pressure on the wheel on the outside of the corner.
Thus, according to this invention, a wheel speed difference threshold value is used for identifying a cornering situation and for calculating and reducing, respectively, the further pressure build-up on the wheel on the inside of the corner the amount of which value, according to a preferred example of an embodiment of this invention, is varied in dependence on the vehicle speed. Below the threshold value, there applies the maximum value of the braking pressure build-up gradient. The extent by which the threshold value is exceeded determines the reduction of the gradient which may fall from the original maximum value down to a very low value or, practically, may sink down to the value of zero.
According to another example of an embodiment of this invention, the reduction of the braking pressure gradient is adjusted by going over to a pulse-shaped introduction of braking pressure and by varying the pulse-and-pulse-pause ratio by means of which an inlet valve will be actuated.
Thus, this invention relates to the braking pressure correction on the wheel on the inside of the corner, more particularly on the front wheel, in order to enhance the steerability and driving stability during cornering for the purpose of increasing the stability of the vehicle and improving the braking stability under transverse-dynamic influences in the partial braking range. There will be generated a stabilizing moment around the vertical axis of the automotive vehicle.
Any further details and applications of this invention will become evident from the following description of examples of embodiments, reference being made to the accompanying Figures.
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Arthur Gertrude
Continental Teves AG & Co. oHG
Cuchlinski Jr. William A.
Rader & Fishman & Grauer, PLLC
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