# US 12,759,410 B2 · Method for operating a hydraulic braking system, control unit and braking system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,759,410 B2 - Document ID: US12759410B2 - Status: Granted - Kind: B2 - Application number: 17/828,100 - Filed: 2022-05-31 - Published: 2022-12-01 - Granted: 2026-10-13 - Earliest claimed: 2021-05-31 - Assignees: ZF Active Safety GmbH - Applicants: ZF Active Safety GmbH - Inventors: Markus Necknig; Andreas Dahm; Michael Olscher - Web page: https://patentgrep.com/patent/US12759410B2 ## CPC - B60L 7/26: Controlling the braking effect - B60T 13/586: {the retarders being of the electric type} - B60T 13/686: {in hydraulic systems or parts thereof} - B60T 13/745: {acting on a hydraulic system, e.g. a master cylinder} - B60T 2270/604: Merging friction therewith; Adjusting their repartition - B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES - B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES ## Abstract The disclosure relates to a method for operating a hydraulic braking system for a motor vehicle with an electrified drive train. The braking system comprises a brake booster. First, a braking request is registered and it is determined that the braking request is to be met by pure recuperative braking. In addition, an input member of the brake booster is shifted in the direction of a pressure generation unit so that it assumes an actuation position corresponding to the braking request. From here, the input member is then shifted back from the actuation position in a direction away from the pressure generation unit for hydraulic pressure relief. A control unit designed to carry out such a method is also disclosed. A braking system comprising such a control unit is also presented. ## Claims ### Claim 1 A method for operating a hydraulic braking system for a motor vehicle with an electrified drive train which has at least one electric drive machine that can be operated as a generator, wherein the braking system comprises a brake booster which has a first input member which is coupled to a brake pedal, a second input member which is coupled to a drive unit of the brake booster, and an output member which is coupled to a hydraulic pressure generation unit, the method comprising the following steps: a) registering a braking request by detecting a brake pedal movement that causes the first input member to be shifted in a direction of the pressure generation unit, b) determining, based on sensor feedback from brake pedal sensor configured to detect pedal displacement, pedal speed, or pedal acceleration, whether the braking request is to be met by pure recuperative braking, in which the drive machine is operated as a generator, c) shifting the second input member of the brake booster in the direction of the pressure generation unit to support the braking request, so that the second input member assumes an actuation position corresponding to the braking request, and d) shifting the second input member back from the actuation position in a direction away from the pressure generation unit for hydraulic pressure relief, wherein the control unit determines when to initiate and terminate the backward shift of the second input member based on whether the pedal movement has reached a substantially static condition. ### Claim 2 (depends on 1) The method according to claim 1, wherein a backward shift distance by which the second input member is shifted back from the actuation position is smaller than an actuation distance which the second input member travels from a non-actuated starting position into the actuation position. ### Claim 3 (depends on 2) The method according to claim 2, wherein a backward shift speed at which the second input member is shifted back from the actuation position is less than a standard backward shift speed at which the second input member is shifted from the actuation position into a non-actuated starting position when the brake pedal is released. ### Claim 4 (depends on 2) The method according to claim 2, wherein the second input member reaches the actuation position when the brake pedal does not perform a brake pedal movement or performs a brake pedal movement at a speed below a predetermined limit speed. ### Claim 5 (depends on 1) The method according to claim 1, wherein a backward shift speed at which the second input member is shifted back from the actuation position is less than a standard backward shift speed at which the second input member is shifted from the actuation position into a non-actuated starting position when the brake pedal is released. ### Claim 6 (depends on 5) The method according to claim 5, wherein the second input member is shifted back from the actuation position at a speed below a predetermined minimal threshold, such that the movement is substantially static. ### Claim 7 (depends on 5) The method according to claim 5 wherein the second input member is held in a backwardly shifted position until a changed braking request is registered or a braking request is no longer registered. ### Claim 8 (depends on 1) The method according to claim 1, wherein the second input member reaches the actuation position when sensor feedback indicates that the brake pedal is either not actuated or is actuated at a speed below a predetermined threshold, wherein the threshold corresponds to a predefined limit speed associated with pedal-speed detection logic of the control unit. ### Claim 9 (depends on 8) The method according to claim 8 wherein the second input member is held in a backwardly shifted position until a changed braking request is registered or a braking request is no longer registered. ### Claim 10 (depends on 9) The method according to claim 9, wherein, after it has been determined that the braking request is to be met by pure recuperative braking, a hydraulic fluid reservoir is hydraulically connected to the pressure generation unit. ### Claim 11 (depends on 1) The method according to claim 1 wherein the second input member is held in a backwardly shifted position until a changed braking request is registered or a braking request is no longer registered. ### Claim 12 (depends on 1) The method according to claim 1, wherein, after it has been determined that the braking request is to be met by pure recuperative braking, a hydraulic fluid reservoir is hydraulically connected to the pressure generation unit. ### Claim 13 (depends on 12) The method according to claim 12, wherein the hydraulic fluid reservoir is hydraulically connected to the pressure generation unit by opening a pressure relief valve, associated with a hydraulic brake actuator. ### Claim 14 (depends on 12) The method according to either claim 12 wherein, before the second input member is shifted back, in its actuation position, the hydraulic fluid reservoir is shut off from the pressure generation unit. ### Claim 15 (depends on 13) The method according to claim 13, wherein the hydraulic fluid reservoir is shut off from the pressure generation unit by closing the pressure relief valve. ### Claim 16 (depends on 13) The method according to claim 13, wherein the pressure relief valve is an ABS outlet valve. ### Claim 17 (depends on 13) The method according to claim 13 wherein, before the second input member is shifted back in its actuation position, the hydraulic fluid reservoir is shut off from the pressure generation unit. ### Claim 18 (depends on 14) The method according to claim 14, wherein the hydraulic fluid reservoir is shut off from the pressure generation unit by closing the pressure relief valve. ### Claim 19 (depends on 1) A control unit for a hydraulic braking system, wherein the control unit is designed to carry out a method according to claim 1. ### Claim 20 (depends on 19) A motor vehicle comprising a control unit according to claim 19.