Patent Publication Number: US-2023141579-A1

Title: Vehicle launch mode pressure removal in hydraulic braking system

Description:
FIELD 
     The invention relates to a system for controlling launch of a vehicle and, in particular, to a system that employs a vehicle electronic braking system to quickly release brake pressure in a launch mode. 
     BACKGROUND 
     1. Field 
     Launch control is an advanced driving assistance system (ADAS) currently employed in sport cars and other performance-oriented vehicles that helps facilitate quick acceleration from a standing start and thus reduce 0 to 60 mph times and or drag racing times. In a drag race, getting off the line faster than your competition is as important as the power of the engine. Wheel spin may delay the time to get off the line since the vehicle may not be gripping the road during such wheel spin. Launch control minimizes wheel spin (and hop) and also helps avoid over-revving the engine and overheating the transmission. 
     2. Description of Related Art 
     Conventional launch control is typically associated with electronic braking systems that use hydraulic brakes. Current launch control systems actuate one or more solenoid valves to release hydraulic fluid pressure at the vehicle wheel brakes to initiate the launch. 
     There is a need in a system for controlling launch of a vehicle to reduce the time to remove pressure at the wheel brakes during the launch mode. 
     SUMMARY 
     An objective of one or more embodiments is to fulfill the need referred to above. In accordance with the principles of a present embodiment, this objective is obtained by providing a system for controlling launch of a vehicle that includes a pressure-providing device constructed and arranged to deliver a pressure medium to wheel brakes of the vehicle. A pressure chamber is fluidly connected with the pressure-providing device and is configured for containing the pressure medium. An electronic control unit has a processor circuit that is constructed and arranged, during a launch mode of the vehicle, to control the pressure-providing device to cause fluid from the wheel brakes to be directed to the pressure chamber so as to release the pressure medium from the wheel brakes, permitting launch of the vehicle. 
     In accordance with another aspect of a disclosed embodiment, a method for controlling wheel brakes during a launch of a vehicle includes, upon initiation of a launch mode of a vehicle, causing fluid pressure to be held at wheel brakes of the vehicle, and after determining that a vehicle operating parameter threshold is reached, controlling, via a processor circuit, a brake pressure-providing device to release the fluid pressure held at the wheel brakes to permit launch of the vehicle. 
     Other objectives, features and characteristics of the embodiments, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which: 
         FIG.  1    is a schematic view of a system for controlling launch of a vehicle in accordance with an embodiment. 
         FIG.  2    is a flowchart of method steps of controlling wheel brakes of the embodiments. 
         FIG.  3    is a schematic view of a system for controlling launch of a vehicle in accordance with a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the apparatus may be practiced. These embodiments, which are also referred to herein as “examples” or “options,” are described in enough detail to enable those skilled in the art to practice the present embodiments. The embodiments may be combined, other embodiments may be utilized, or structural or logical changes may be made without departing from the scope of the disclosure. The following detailed description is, therefore, not to be taken in a limiting sense but defined by the appended claims and their legal equivalents. 
     Referring to  FIG.  1   , a system for controlling launch of a vehicle is shown generally indicated at  1  in accordance with an embodiment. The system  1  includes an electronic braking system shown generally indicated at  2  and a launch control system  250  associated there-with. The braking system  2  can be of the type disclosed in Patent Application Publication US 2020/0001846 A1, the contents of which is hereby incorporated by reference. The braking system  2  comprises a master brake cylinder  10  actuated by means of an actuation pedal or brake pedal  6 , a simulation device  14  cooperating with the master brake cylinder  10 , a fluid pressure reservoir  18  assigned to the master brake cylinder  10  and standing under atmospheric pressure, an electrically controllable pressure-providing device  20  formed by a cylinder-piston arrangement with a hydraulic pressure chamber  26 , the piston  32  of which can be displaced by an electromechanical actuator, an electrically controllable pressure-modulation device for setting wheel-individual brake pressures, and an electronic control unit (ECU)  40  for controlling the electrically operated components. 
     The pressure-modulation device comprises, for example, hydraulically actuatable wheel brakes  42 ,  44 ,  46 ,  48 , and for each actuatable wheel brake  42  to  48  a respective inlet valve  50 ,  52 ,  54 ,  56  and an outlet valve  60 ,  62 ,  64 ,  66  connected together hydraulically in pairs via central connections and connected to the wheel brakes  42  to  48 . The input connections of the inlet valves  50  to  56  are supplied with pressures by means of brake circuit supply lines  70 ,  72 ; in a “brake-by-wire” operating mode, these pressures are derived from a system pressure present in a system pressure line  80  connected to the pressure chamber  26  of the pressure-providing device  20 , and corresponds to the pressure provided by the pressure-providing device. Here, the brakes  42 ,  44  are hydraulically connected to a first brake circuit  84 , and the brakes  46 ,  48  are hydraulically connected to a second brake circuit  88 . 
     A respective check valve  90 ,  92 ,  94 ,  96  which opens towards the brake circuit supply lines  70 ,  72  is connected in parallel to each inlet valve  50  to  56 . In fallback operating mode, the brake circuit supply lines  70 ,  72  are loaded with the pressures of the brake medium from pressure chambers  120 ,  122  of the master brake cylinder  10  via hydraulic lines  100 ,  102 . The output connections of the outlet valves  60  to  66  are connected to the fluid pressure reservoir  18  via a return line  130 . 
     The master brake cylinder  10  has, in a housing  136 , two pistons  140 ,  142  arranged in series and which delimit the hydraulic pressure chambers  120 ,  122 . The pressure chambers  120 ,  122  are connected on one side to the pressure medium reservoir  18  via radial bores formed in the pistons  140 ,  42  and via corresponding pressure-balancing lines  150 ,  152 , wherein the connections can be shut off by a relative movement of the pistons  140 ,  142  in the housing  136 . On the other side, the pressure chambers  120 ,  122  are connected to the above-mentioned brake circuit supply lines  70 ,  72  by means of hydraulic lines  100 ,  102 . 
     A normally open valve  160  is situated in the pressure-balancing line  150 . The pressure chambers  120 ,  122  contain restoring springs, which position the pistons  140 ,  142  in a starting position when the master brake cylinder  10  is not actuated. A piston rod  166  couples the pivot movement of the brake pedal  6  due to pedal actuation to the translation movement of the first master brake cylinder piston  140  or primary piston, the actuation travel of which is detected by a travel sensor  170 , configured in redundant fashion. In this way, the corresponding piston travel signal is a measure of the brake pedal actuation angle. It represents a braking request by the vehicle driver. 
     A separating valve  180 ,  182  configured as an electrically actuatable, normally open, 2/2-way directional control valve is arranged in each line portion  100 ,  102  connected to the pressure chambers  120 ,  122 . The separating valves  180 ,  182  can shut off the hydraulic connection between the pressure chambers  120 ,  122  of the master brake cylinder  10  and the brake circuit supply lines  70 ,  72 . A pressure sensor  188  connected to the line portion  102  detects the pressure built up in the pressure chamber  122  by movement of the second piston  142 . 
     The simulation device  14  can be hydraulically coupled to the master brake cylinder  10  and substantially comprises for example a simulator chamber  190 , a simulator spring chamber  194 , and a simulator piston  198  separating the two chambers  190 ,  194  from each other. This simulator piston  198  is supported on the housing  136  by an elastic element (e.g. a spring) arranged in the simulator spring chamber  194  and advantageously preloaded. The simulator chamber  190  is connectable to the first pressure chamber  120  of the master brake cylinder  10  by means of an electrically actuatable simulator valve  200 . When a pedal force is input and simulator valve  200  is open, pressure medium flows from the master brake cylinder pressure chamber  120  into the simulator chamber  190 . A check valve  210  arranged hydraulically antiparallel to the simulator valve  200  allows the pressure medium to flow back from the simulator chamber  190  to the master brake cylinder pressure chamber  120  largely unhindered, irrespective of the switching state of the simulator valve  200 . Other embodiments and connections of the simulation device to the master brake cylinder  10  are conceivable. 
     The electrically controllable brake pressure-providing device  20 , providing brake system pressure, is configured as a hydraulic cylinder-piston arrangement or a single circuit electrohydraulic actuator, in which the pressure piston  32  delimiting the pressure chamber  26  can be actuated by an electrically controlled motor  220  with the interposition of a rotation-translation gear mechanism (also indicated diagrammatically) configured as a ball screw drive (KGT). A rotor position sensor  226  serves to detect the rotor position of the electric motor  220 . In addition, a temperature sensor  228  may be used for sensing the temperature of the motor  220  winding. 
     The actuator pressure generated by the effect of the force of the piston  32 , moving in direction A, on the pressure medium enclosed in the pressure chamber  26  is fed into the system pressure line  80  and detected by means of a pressure sensor  230 , which is of redundant design. When the pressure switching valves  240 ,  242  are opened, the pressure medium actuates the wheel brakes  42  to  48 . A wheel brake pressure is built up and dissipated for all wheel brakes  42  to  48  by the forward and return movement of the piston  32 , when the pressure actuation valves  240 ,  242  are opened, in normal braking in brake-by-wire operating mode. 
     When the pressure dissipates, the pressure medium (fluid) previously displaced from the pressure chamber  26  into the wheel brakes  42  to  48  returns to the pressure chamber  26  on the same route. In contrast, when braking with different wheel brake pressures for each individual wheel which are regulated using the inlet and outlet valves  50  to  56 ,  60  to  66  (e.g. on ABS braking), the part of the pressure medium discharged via the outlet valves  60  to  66  flows into the pressure medium reservoir  18  and is therefore no longer available initially to the pressure-providing device  20  for actuating the wheel brakes  42  to  48 . 
     In the embodiment, the electronic braking system  2  is co-operable with a conventional vehicle launch control system  250 . The launch control system  250  includes an actuator  252 , such as an actuatable push-button in the vehicle cockpit, to initiate a launch mode of the vehicle. The launch control system  250  has a control unit  254  that is electrically connected with sensors such as a sensor associated with the brake pedal  6 , with an accelerator pedal  258 , with the transmission to control the transmission, and with a speed sensor to measure speed of the vehicle&#39;s output shaft. In the embodiment, after actuation of the actuator  252 , the control unit  254  is configured to send an electrical signal  256  to the braking system  2  and thus to the ECU  40  indicating that the present condition requires that the rate of pressure decrease at the wheel brakes be greater than achievable by the braking system  2  in normal operation (e.g., when fluid normally returns to the reservoir  18  as described above). 
     As noted above in the Background section, in conventional launch control and braking systems, the electric signal sent from the launch control system to the braking system instructs the ECU of the braking system to actuate at least one solenoid valve, such as valves  240  and  242  in  FIG.  1   , to unlock the wheel brakes and permit vehicle launch. However, actuating valve  240  and  242  may not be sufficient to quickly remove brake pressure from the braking system  10  and thus may hinder the launch. Thus, in accordance with an embodiment of  FIG.  1   , in the launch mode when the brake pedal  6  is first depressed and then released and while the accelerator pedal  258  is depressed, the signal  256  is received at the ECU  40  and a processor circuit  41  thereof signals the motor  220  to move the piston or movable member  32  in a direction opposite of direction A to quickly cause the hydraulic fluid at, at least certain of the wheel brakes  42 ,  44 ,  46  and  48 , to be directed into the pressure chamber  26 . When the motor  220  is controlled to move the piston  32 , valve  240  and  242  can also be actuated to aid in fluid at certain of the wheel brakes to return to the pressure chamber  26 . Thus, the time required for pressure to decrease at the wheel brakes is greatly reduced by use of the motor  220  and piston  32 . 
     With reference to  FIG.  2   , a method for controlling wheel brakes during a launch of a vehicle includes in step  410 , upon initiation of a launch mode of a vehicle, causing fluid pressure to be held at certain of the wheel brakes  42 ,  44 ,  46 ,  48 . In step  420 , after determining that a vehicle operating parameter threshold is reached (explained further below), the processor circuit  41  controls the brake pressure-providing device  20  to release the fluid pressure held at the wheel brakes to permit launch of the vehicle. 
     A detailed description of controlling a launch mode of a vehicle with the system  1  includes the following steps:
         a) Initiate launch mode by engaging actuator  252  in vehicle,   b) Press on the brake pedal  6  and hold, causing at least certain of the wheel brakes  42 ,  44 ,  46 ,  48  to receive and hold fluid pressure at wheel brakes,   c) Release the brake pedal  6  while braking system continues to hold fluid pressure at wheel brakes,   d) Press on accelerator pedal  258  until kick down and hold,   e) Controller  254  regulates the rpm and starting speed, and once desired engine rpm (e.g., vehicle operating parameter threshold) is reached, the processor circuit  41  automatically controls the pressure-providing device in the form of the motor  220  and piston  32 , with the motor moving the piston  32  to cause release of the fluid pressure from the engaged wheel brakes,   f) Controller  254  causes the clutch/gear to engage, thereby causing launch of the vehicle.       

     With reference to  FIG.  3   , a system for controlling launch of a vehicle is show generally indicated at  1 ′ in accordance with a second embodiment. The system  1 ′ includes an electronic braking system  2 ′ and the launch control system  250 . The braking system  2 ′ can be of the type disclosed in Patent Application Publication US 2015/0298670 A1, the contents of which is hereby incorporated by reference. The brake pedal  6  actuated by the driver acts on a (tandem) master brake cylinder  320 , via a pressure rod with superimposition of an auxiliary force built up by an underpressure brake booster  300 , which (tandem) master brake cylinder  320  is connected in the inactivated state to a pressureless brake fluid reservoir container  310 . The absolute pressure in the underpressure chamber or the differential pressure with respect to the surroundings can be measured by means of a vacuum sensor or pressure sensor  330 . It is therefore possible to check whether sufficient underpressure is present or whether hydraulic assistance is necessary. The brake system has two brake circuits I, II, to each of which two wheel brakes are assigned (in the case of a four-wheeled motor vehicle). In the text which follows, only the brake circuit I is described. The other brake circuit II is of identical design. The division of the brake circuits, that is to say whether for example in each case a front wheel brake and a rear wheel brake are combined in a brake circuit, is in principle insignificant for the system and method according to the embodiment. 
     The master brake cylinder  320  is fluidly connected via brake lines to the wheel brakes  370   a,    370   b,  wherein the first wheel brake  370   a  can be disconnected from the master brake cylinder  320  by closing a first inlet valve  350   a,  and the second wheel brake  370   b  can be disconnected from the master brake cylinder  320  by means of a second inlet valve  350   b.  The pressure in the first and second wheel brakes can be reduced by opening an outlet valve  360   a  or  360   b  in that brake fluid is diverted into a low pressure chamber or accumulator  380 . A hydraulic pump  390 , driven by an electrically controlled motor M, permits the low pressure accumulator  380  to be emptied. In addition, the brake system has a solenoid valve  340 , designated as an isolating valve, that can be actuated in an analogous fashion. Valve  340  is open in a currentless state and is arranged between the outlet side of the hydraulic pump  390  and the master brake cylinder  320 . The suction side of the hydraulic pump  390  is connected to the low pressure accumulator  380  and can be connected to the master brake cylinder  320  via a solenoid valve  400  as an electronic switching valve and is closed in a currentless state. The motor and pump  390  can be considered as a brake pressure-providing device since the motor M can be activated in such a way that the pump  390  can build up a brake pressure on the high-pressure side by drawing in brake fluid on the intake side. 
     Wheel speed sensors, which are connected to an electronic control unit (ECU)  40 ′ with processor circuit  41 ′, are expediently arranged on each wheel of the motor vehicle. The ECU  40 ′ is configured to control the electrically controlled components of the system  2 , including motor M. If the wheel speed of a wheel during braking decreases strongly, a brake slip control process or antilock brake control process can take place in that the corresponding inlet valve is closed and the pressure in the wheel brake, and therefore the braking force, are reduced by opening the corresponding outlet valve. The brake slip control process can be carried out by means of methods which are known per se and in which pressure buildup phases, pressure holding phases and pressure reduction phases repeat cyclically. 
     The ECU  40 ′ and thus the electronic braking system  2 ′ is co-operable with a conventional vehicle launch control system  250 . As noted above, the launch control system  250  includes an actuator  252 , such as a push-button in the vehicle cockpit, to initiate a launch mode of the vehicle. The launch control system  250  has a control unit  254  configured to send an electrical signal  256  to the ECU  40 ′ indicating that the present condition requires that the rate of pressure decrease be greater than achievable by the braking system  2  in normal operation (e.g., when fluid normally returns to the reservoir  310 ). 
     In accordance with the second embodiment, in the launch mode when the brake pedal  6  is first depressed and then released while the accelerator pedal  258  is depressed, the signal  256  is received at the ECU  40 ′ and a processor circuit  41 ′ thereof instructs the motor M to operate the pump or movable member  390  in a suction mode to quickly cause the hydraulic fluid at the wheel brakes  370   a,    370   b,  to be directed into the pressure chamber or accumulator  380 . The processor circuit  41 ′ of the ECU can also open valve  360   a,    360   b  to cause brake fluid from the wheel brakes to return to the accumulator  380 . Thus, the time required for pressure to decrease at the wheel brakes is greatly reduced due to use of the motor M and suction pump  390 . 
     As noted above,  FIG.  2    shows a flowchart of a method for controlling wheel brakes during a launch of a vehicle. The method is applicable to the system  1 ′ as well. Thus, in step  410 , upon initiation of a launch mode of a vehicle, fluid pressure is caused to be held at certain of the wheel brakes  370   a,    370   b.  In step  420 , after determining that a vehicle operating parameter threshold is reached, the processor circuit  41 ′ controls the brake pressure-providing device (motor M, pump  390 ) to release the fluid pressure held at the wheel brakes to permit launch of the vehicle. 
     A more detailed description of controlling a launch mode of a vehicle with the system  1 ′ ( FIG.  3   ) includes the following steps:
         a) Initiate launch mode by engaging actuator  252  in vehicle,   b) Press on the brake pedal  6  and hold, causing at least certain of the wheel brakes  370   a,    370   b  to receive and hold fluid pressure at wheel brakes,   c) Release the brake pedal  6  while braking system continues to hold fluid pressure at wheel brakes,   d) Press on accelerator pedal  258  until kick down and hold,   e) Controller  254  regulates the rpm and starting speed, and once desired engine rpm (e.g., vehicle operating parameter threshold) is reached, the processor circuit  41 ′ automatically controls pressure-providing device in the form of the motor M and piston pump  390 , with the motor M moving the piston pump  390  to cause release of the fluid pressure from the engaged wheel brakes,   f) Controller  254  causes the clutch/gear to engage, thereby causing launch of the vehicle.       

     Thus, with the launch control systems  1  and  1 ′, the time required to release brake pressure from the wheel brakes during a launch mode is greatly decreased when compared to conventional systems. Also, the embodiments allow for a calibrated release speed for application specific settings. 
     The operations and algorithms described herein can be implemented as executable code within the processor circuits  41 ,  41 ′ as described, or stored on a standalone computer or machine readable non-transitory tangible storage medium that are completed based on execution of the code by a processor circuit implemented using one or more integrated circuits. Example implementations of the disclosed circuits include hardware logic that is implemented in a logic array such as a programmable logic array (PLA), a field programmable gate array (FPGA), or by mask programming of integrated circuits such as an application-specific integrated circuit (ASIC). Any of these circuits also can be implemented using a software-based executable resource that is executed by a corresponding internal processor circuit such as a microprocessor circuit and implemented using one or more integrated circuits, where execution of executable code stored in an internal memory circuit causes the integrated circuit(s) implementing the processor circuits  41 ,  41 ′ to store application state variables in processor memory, creating an executable application resource (e.g., an application instance) that performs the operations of the circuit as described herein. Hence, use of the term “circuit” in this specification refers to both a hardware-based circuit implemented using one or more integrated circuits and that includes logic for performing the described operations, or a software-based circuit that includes a processor circuit (implemented using one or more integrated circuits), the processor circuit including a reserved portion of processor memory for storage of application state data and application variables that are modified by execution of the executable code by a processor circuit. A memory circuit can be implemented, for example, using a non-volatile memory such as a programmable read only memory (PROM) or an EPROM, and/or a volatile memory such as a DRAM, etc. 
     The operations described with respect to any of the Figures can be implemented as executable code stored on a computer or machine readable non-transitory tangible storage medium (i.e., one or more physical storage media such as a floppy disk, hard disk, ROM, EEPROM, nonvolatile RAM, CD-ROM, etc.) that are completed based on execution of the code by a processor circuit implemented using one or more integrated circuits; the operations described herein also can be implemented as executable logic that is encoded in one or more non-transitory tangible media for execution (e.g., programmable logic arrays or devices, field programmable gate arrays, programmable array logic, application specific integrated circuits, etc.). Hence, one or more non-transitory tangible media can be encoded with logic for execution by a machine, and when executed by the machine operable for the operations described herein 
     The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.