초록 ▼

A braking system may include a brake booster, the piston-cylinder system of which is driven by an electric motor, wherein at least one working chamber of the piston-cylinder system is connected by hydraulic lines to at least two wheel brakes, a wheel brake being allocated a 2/2-way switching valve i

A braking system may include a brake booster, the piston-cylinder system of which is driven by an electric motor, wherein at least one working chamber of the piston-cylinder system is connected by hydraulic lines to at least two wheel brakes, a wheel brake being allocated a 2/2-way switching valve in each case and the hydraulic connection lines between the wheel brakes and the piston-cylinder system being closable, optionally separately or jointly, by means of the 2/2-way switching valves, so that a pressure can be adjusted in the wheel brakes one after the other in terms of a multiplex method and/or simultaneously. The electric motor and switching valves may be activated by a control device configured to adjust or control the piston movement and piston speed during the pressure generation and pressure reduction as a function of the pressure-volume characteristic of the wheel brakes.

대표청구항 ▼

1. A braking system including: a brake booster comprising a piston-cylinder system driven, by transmission means, mechanically or hydraulically, by an electric motor, the piston-cylinder system including at least one working chamber;hydraulic lines arranged to couple the at least one working chamber

1. A braking system including: a brake booster comprising a piston-cylinder system driven, by transmission means, mechanically or hydraulically, by an electric motor, the piston-cylinder system including at least one working chamber;hydraulic lines arranged to couple the at least one working chamber of the piston-cylinder system to at least two wheel brakes;respective 2/2-way switching valves allocated to the respective at least two wheel brakes and arranged to separately or jointly close the hydraulic connection so that a pressure can be adjusted in the wheel brakes one after the other using a multiplex method and/or simultaneously;a control device configured to control the electric motor and the switching valves,wherein a hydraulic connection line from a working chamber of the piston-cylinder system to a respective magnetic valve has a dimensioned flow resistance RLi, and each switching valve has a dimensioned flow resistance RVi, and the hydraulic line to a respective wheel cylinder has a flow resistance RVRi, wherein the flow resistances RLi and RVi are sufficiently small enough to enable piston speed to determine a pressure reduction gradient and pressure generation gradient in each wheel brake, the flow resistance RLi being smaller than the flow resistance RVi and wherein the control device is configured to adjust or control the piston movement and piston speed during the pressure generation and pressure reduction as a function of a pressure-volume characteristic of the wheel brakes,wherein the control device continuously calculates the pressure levels of the wheel brakes using a pressure model, wherein the pressure model uses, as a model parameter, an equivalent flow resistance, which corresponds to the hydraulic resistance of the path from the piston-cylinder system via the switching valve up to the wheel cylinder of the wheel brake. 2. The braking system according to claim 1, wherein the flow resistance RVi is greater than the flow resistance RLi by a factor of 1.3 to 2.5. 3. The braking system according to claim 1, wherein the maximum achievable pressure gradient of the piston-cylinder system when the switching valves are closed is greater by at least a factor of 2 than the maximum achievable pressure gradient in the wheel brakes when at least one switching valve is open. 4. The braking system according to claim 1, wherein a sum of the flow resistances RLi and RVi associated with a respective wheel brake is configured such that, with a maximum dynamic of the piston-cylinder system and the drive thereof, and with at least one opened switching valve, because of the simultaneous volume intake or volume output of the wheel brakes in the time during which the switching valves are open, no pressure equalisation takes place between the wheel brakes. 5. The braking system according to claim 1, wherein the control device is configured to control a respective switching valve by means of a pulse width modulation (PWM). 6. The braking system according to claim 1, wherein the hydraulic connection line from the working chamber of the piston-cylinder system to the respective magnetic valve is shorter than 30 cm. 7. The braking system according to claim 1, wherein the pressure in each wheel brake is adjusted on the basis of the pressure-volume characteristic of the respective wheel by means of a stroke control of the piston of the piston-cylinder system. 8. The braking system according to claim 1, wherein a superordinate controller predetermines a desired pressure for the piston-cylinder system. 9. The braking system according to claim 1, wherein a pressure gradient to be calculated in the piston-cylinder system is a function of an amount of required pressure change in a wheel brake. 10. The braking system according to claim 1, wherein an input variable of the pressure model is an actual pressure in the piston-cylinder system or the piston stroke. 11. The braking system according to claim 1, wherein the pressure model within the hydraulic path from the piston-cylinder system via the switching valve-up to the wheel cylinder of the wheel brake takes into account a weighting of the flow conditions laminar and turbulent. 12. The braking system according to claim 1, wherein the pressure model calculates a closing instant of a respective switching valve as a function of calculated actual pressure and current pressure, as well as switching times of the magnetic valves determined in an end test by measurement, and a respective pressure gradient. 13. The braking system according to claim 1, wherein the pressure model takes into account, as a model parameter, a hydraulic equivalent inductance, which reflects mass and/or inertia of the brake fluid. 14. The braking system according to claim 1, wherein the pressure model contains, as a model parameter, the pressure-volume characteristic of each individual wheel brake, which represents the capacity or volume intake of the wheel brake. 15. The braking system according to claim 1, wherein one or more model parameters of the pressure model are a function of ambient temperature of the switching valves or are adapted by means of the temperature. 16. The braking system according to claim 1, wherein the control device corrects or adjusts the pressure model when at least one predetermined slip is not achieved. 17. The braking system according to claim 1, wherein the control device checks the pressure model and/or equalises values and parameters thereof, wherein the control device determines the actual pressure in the piston-cylinder system when the switching valve is open after waiting for a pressure settling time. 18. The braking system according to claim 1, wherein hysteresis contained in the hydraulic system is also accounted in the pressure model. 19. The braking system according to claim 18, wherein the control device carries out checking and adjustment of the pressure model several times, one after the other or at short time intervals, when the pressure model differs from actually measured values. 20. The braking system according to claim 1, wherein a time difference between the beginning of the piston movement and the switchover of a switching valve is variable in such a way that it can be controlled by means of the piston speed. 21. The braking system according to claim 1, wherein the control device calculates the respective pressure in the wheel brakes by means of the pressure model and transmits the calculated pressure values at least to an ABS/ESP controller and a pressure control device the pressure control device at least activating the 2/2-way switching valves and the electric motor, and wherein a prioritisation device carries out a wheel selection, at least with the aid of data transmitted by the ABS/ESP controller, and transmits it to the pressure control device. 22. The braking system according to claim 1, wherein the control device adapts pressure model parameters with the aid of at least one temperature determined in the braking system or at specific points in the braking system. 23. The braking system according to claim 21, wherein the prioritisation device carries out the prioritisation of the wheel selection based at least in part on at least one criterion selected from the group consisting of: “optimal braking path” and “stability of the control”. 24. The braking system according to claim 21, wherein the prioritisation device does not simultaneously permit a pressure generation in one or more wheel brakes during a pressure reduction currently taking place in one or more wheel brakes, and vice versa. 25. The braking system according to claim 21, wherein the prioritisation device switches to simultaneous or partially simultaneous pressure generation or pressure reduction during a wheel slip greater than a slip limit value and/or during a wheel acceleration or deceleration of greater than 5 g or −5 g. 26. The braking system according to claim 1, wherein a second arithmetic unit carries out a plausibility test of the input and output signals of the entire control loop. 27. A method for adjusting a brake pressure in at least one wheel brake using a braking system according to claim 1, comprising generating or reducing, by the braking system according to claim 1, the pressure in at least two wheel brakes consecutively, simultaneously, or overlapping with respect to time. 28. A method for adjusting a brake pressure in at least one wheel brake using a braking system according to claim 1, comprising selecting, by the braking system according to claim 1, during simultaneous pressure generation or pressure reduction in at least two wheel brakes, the pressure difference between the working chamber of the piston-cylinder system and the respective wheel brakes to be so great that no pressure equalisation takes place between the respective wheel brakes. 29. The method according to claim 28, further comprising readjusting the piston of the piston-cylinder system by the control device to maintain the pressure difference when the switching valves are open. 30. The method according to claim 29, further comprising: calculating, by the control device, the necessary pressure difference and therefore the required volume change of the working chamber of the piston-cylinder system, at which no volume equalisation takes place between the wheel brakes, the associated switching valve of which is open or the opening of which is immediately immanent; and readjusting or activating, by the control device, the piston of the piston-cylinder system for pressure control to adjust the required differential pressure. 31. A method for adjusting a brake pressure in at least one wheel brake using a braking system according to claim 1, comprising generating and/or reducing, by the braking system according to claim 1, pressure in at least two wheel brakes simultaneously and/or overlapping with respect to time, the starting level of the respective wheel brakes being different from one another. 32. A method for adjusting a brake pressure in at least one wheel brake using a braking system according to claim 1, comprising equalizing, by the braking system according to claim 1, the pressure-volume characteristic of each wheel brake by static comparison of the piston stroke with the pressure in the working chamber of the piston-cylinder system before the start of travelling. 33. A method for adjusting a brake pressure in at least one wheel brake using a braking system according to claim 1, comprising adjusting or controlling, by the braking system according to claim 1, the pressure in the working chamber of the piston-cylinder system, before the beginning of the pressure reduction, to the pressure in the respective wheel brake or a lower pressure; and opening thereafter the switching valve associated with the respective wheel brake by the control device. 34. A method for adjusting a brake pressure in at least one wheel brake using a braking system according to claim 1, comprising adjusting or controlling, by the braking system according to claim 1, the pressure in the working chamber of the piston-cylinder system, before the beginning of the pressure generation, to a pressure in the respective wheel brake or a higher pressure; and opening thereafter the associated switching valve by the control device.