Brake system with noise-optimized valve control
A brake system for a motor vehicle comprises a hydraulic line system with at least one normally closed hydraulic valve, wherein a final stage is provided for electrically actuating the at least one hydraulic valve. To minimize noise emissions, the final stage is a final stage with analog control and a computing unit is provided which is configured to determine a valve current based on a pressure difference across the hydraulic valve and to actuate the final stage to make the valve current available at the hydraulic valve.
1. A brake system for a motor vehicle comprising:
a hydraulic line system with at least one hydraulic valve which is normally closed;
an electric coil which is supplied with current by a final stage having analog control is provided for electrically actuating the at least one hydraulic valve; and
a computing unit is-provided-which is configured to:
determine a counterforce at least from a spring force of the hydraulic valve and the pressure difference across the hydraulic valve;
determine from the counterforce an opening force which is greater than the counterforce by a predetermined amount:
determine an associated valve opening current from the opening force; and
actuate the final stage when the hydraulic valve is switched on to provide the associated valve opening current.
2. The brake system as claimed in claim 1 , wherein the computing unit to close the hydraulic valve:
determines a closing force which is smaller than the counterforce by a predetermined amount;
determines an associated valve closing current from the closing force; and
actuates the final stage when the hydraulic valve is switched off to provide the associated valve closing current.
3. The brake system as claimed in claim 1 , wherein the final stage is configured to provide current pulses at the hydraulic valve in order to open the hydraulic valve for a predetermined time, wherein the current pulses have a length of 10 ms to 1000 ms.
4. The brake system as claimed in claim 3 , wherein the length of the current pulses is adjusted based on the valve current, so that a flow rate through the hydraulic valve corresponds to the flow rate at a maximum valve current.
5. The brake system as claimed in claim 1 , wherein the hydraulic valve is an outlet valve on a wheel brake of the brake system.
6. The brake system as claimed in claim 1 , wherein the predetermined amount is based at least on valve and/or coil tolerances.
7. The brake system as claimed in claim 1 , wherein the hydraulic valve has a residual air gap in an energized state.
8. The brake system as claimed in claim 1 , wherein the hydraulic valve is arranged in a housing with a brake master cylinder.
9. A method for controlling a hydraulic valve, which is normally closed, in a brake system comprising:
determining a pressure difference across a hydraulic valve:
calculating a counterforce from at least a spring force of the hydraulic valve and the pressure difference across the hydraulic valve;
calculating from the counterforce a switching force, wherein the counterforce is one of greater and less than the counterforce by a predetermined amount; and
calculating a valve current from the switching force; and
providing the valve current with a final stage that has analog control.