Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2000-02-23
2001-12-11
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S070000, C180S197000
Reexamination Certificate
active
06330505
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and a device for controlling the wheel performance of a vehicle.
BACKGROUND INFORMATION
Modern motor vehicles employ a plurality of feedback control and control systems to control wheel performance. An anti-lock control system, a traction control system having brake intervention and/or engine intervention, an operating dynamics controller having brake intervention and/or engine intervention, and an electrically controlled braking system (brake-by-wire) are some examples.
German Patent Application No. 196 51 154 describes a system in which the temperature of the hydraulic fluid and, thus, the temperature of the hydraulic unit of the braking system are estimated based on the after-run behavior of a pump supplying the hydraulic fluid. The valve opening times, especially in reference to the pressure build-up, are then changed as a function of the estimated temperature, so that the pressure change dynamics in the wheel brakes do not deteriorate considerably at low temperatures. However, determining the temperature of the hydraulic fluid or the hydraulic unit on the basis of the pump's after-run behavior is a relatively inaccurate method, so that this information cannot be used satisfactorily for exact control of a braking system.
European Patent No. 166 178 describes a traction control system which actuates the brakes and/or influences the engine torque when a slip threshold is exceeded due to the slip of at least one drive wheel. The manner in which the threshold values and/or the extent of the torque intervention are established results from a compromise between traction and stability, which is maintained over the entire temperature range.
SUMMARY
An object of the present invention is to provide a method and device which satisfactorily take into account the temperature conditions at the vehicle when controlling the wheel performance.
In accordance with the present invention, by taking into account the coolant temperature, oil temperature, outside air temperature, and/or intake air temperature when controlling wheel performance, this control is improved because the control can be adjusted to the temperature conditions prevailing at any one time.
Especially advantageous is the guarantee of a satisfactory estimation of the hydraulic unit temperature and, consequently, of the hydraulic fluid temperature, which is evaluated during the control of the braking system. Depending on at least one of the mentioned temperature variables, not only are the valve opening times increased advantageously in this context, but also, additionally or alternatively, the circuit is pre-pressurized by operating the return pump, and/or the inlet pressure of the return pump is increased by operating a pre-charging pump. This ensures that in response to a change in pressure, above all, a build-up of pressure, improved dynamics are attained even at low temperatures, meaning that larger gradients with a varying coefficient of friction can be overcome even in the case of a cold vehicle at low temperatures.
Especially advantageous is that due to the improvement in the pressure build-up dynamics based on the temperature estimation, there is only a limited need to use the pre-charging pump, and in extreme cases, the need is even eliminated. As a result, noise is substantially reduced and driving comfort is thereby improved. In addition, the vehicle's traction is improved at low temperatures.
Another advantage of the present invention is that in order to determine the temperature of the hydraulic unit or the hydraulic fluid, a model is used which simulates the temperature curve on the basis of existing measured temperature variables. This model is easily transferable to other vehicle types.
A further advantage of the present invention is that the model estimates the warming and cooling of the hydraulic unit on the basis of recurrence formulas, which are adjusted to the actual temperature curve. This also allows the influences on the temperature of the hydraulic unit to be considered which are, at best, difficult to describe in a physical context. Another exemplary embodiment, which can be used with or without the above-mentioned measures, has the advantage that the operating conditions and the extent of the intervention by a traction control system are varied as a function of at least one of the given temperatures. In this way, the previous compromise between better traction and vehicle stability shifts more towards higher stability in response to low outside temperatures and shifts more towards higher traction in response to high outside temperatures. This is done by altering the slip thresholds, above which the traction control system sets in (increasing them at higher temperatures) and/or by altering the magnitude of the torque change (intensifying torque changes are increased in response to higher temperatures, reductive torque changes are decreased. As a result, one attains a satisfactory controller design, since the conflict between targeting traction and stability is analyzed in a different way, i.e., as a function of temperature, so that one comes closer to resolving this conflict.
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patent: 196 51 154 (1997-06-01), None
patent: 0 166 178 (1986-01-01), None
Braun Michael
Brueggemann Rainer
Hessmert Ulrich
Isella Thomas
Schmitt Johannes
Chin Gary
Kenyon & Kenyon
Robert & Bosch GmbH
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