Patent Publication Number: US-2023148031-A1

Title: Control method for electronic hydraulic brake

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on, and claims priority from, Korean Patent Application Number 10-2021-0152022, filed on Nov. 8, 2021, the disclosure of which is incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a control method for an electric hydraulic brake. 
     BACKGROUND 
     Description of this section only provides the background information of the present disclosure without configuring the related art. 
     An autonomous driving vehicle secures a redundancy function using an auxiliary braking system disposed between a main braking system and a plurality of wheel brake apparatus when the main braking system malfunctions. 
     An auxiliary braking system of the related art performs 2-channel pressurization/decompression control and 2-channel decompression control. An auxiliary braking system of the related art performs a function of pressurizing/decompressing front wheels and decompressing rear wheels. For this purpose, four input pipelines and four output pipelines, that is, a total of eight pipelines should be connected to the auxiliary braking system. Accordingly, there is a problem in that the manufacturing cost of a brake system increases and assembly is complicated. 
     When a driver intervenes in braking in a situation in which redundancy is applied, disconnection may occur in braking of a vehicle because it is difficult to adjust a stroke, and as a result, there is a problem in that a braking force is not transmitted well to the vehicle and an accident may occur. 
     SUMMARY 
     According to at least one embodiment, the present disclosure provides a control method of an electric hydraulic brake including an auxiliary braking system generating a braking force in a vehicle when a main brake system fails, the control method comprising: determining whether the main brake system fails; opening a rear-wheel High pressure Switching Valve (HSV) connecting a rear wheel of the main brake system and a Low Pressure Accumulator (LPA) of the auxiliary braking system when the main brake system is determined to have failed; determining whether a driver intervenes in braking; and controlling the auxiliary brake system to generate a braking force in the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a hydraulic circuit diagram of an electric hydraulic brake according to an embodiment of the present disclosure. 
         FIG.  2    is a flowchart of a method of controlling an auxiliary braking system of an electric hydraulic brake according to an embodiment of the present disclosure. 
         FIG.  3    is a flowchart of a method of controlling an auxiliary braking system of an electric hydraulic brake according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     A control method for an electric hydraulic brake according to an embodiment can generate a braking force in a vehicle by controlling an auxiliary braking system that can perform 2-channel pressurization/decompression control and 1-channel decompression control. 
     A control method for an electric hydraulic brake according to an embodiment can use a front wheel-auxiliary braking system and a rear wheel-electric parking brake when a driver intervenes in braking in a redundancy situation. 
     The objects of the present disclosure are not limited to the objects described above and other objects will be clearly understood by those skilled in the art from the following description. 
     Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, like reference numerals preferably designate like elements, although the elements are shown in different drawings. Further, in the following description of some embodiments, a detailed description of related known components and functions when considered to obscure the subject of the present disclosure will be omitted for the purpose of clarity and for brevity. 
     Additionally, alphanumeric codes such as first, second, i), ii), (a), (b), etc., in numbering components are used solely for the purpose of differentiating one component from the other but not to imply or suggest the substances, the order, or sequence of the components. Throughout this specification, when parts “include” or “comprise” a component, they are meant to further include other components, not excluding thereof unless there is a particular description contrary thereto. The terms such as ‘unit,’ ‘module,’ and the like refer to one or more units for processing at least one function or operation, which may be implemented by hardware, software, or a combination thereof. 
     As for the terms “forward” or “backward” related to the relative positions of lines in the present disclosure, when brake oil flows, the parts disposed closer to a reservoir  10  is described by “forward” and the parts disposed farther are described by “backward”. However, this means not only directly continuous forward or backward lines, but lines relatively farther even they are spaced. 
       FIG.  1    is a hydraulic circuit diagram of an electric hydraulic brake according to an embodiment of the present disclosure. 
     The hydraulic circuit diagram shown in  FIG.  1    only conceptually shows configurations for the convenience of description, and the actual positions of a hydraulic pressure block and lines formed in the hydraulic pressure block may be different. In  FIG.  1   , an inlet line is indicated by a bold line, an outlet line is indicated by a medium line, and a circulation line is indicated by a thin line. 
     Referring to  FIG.  1   , an electric hydraulic brake  1  may include some or all of a reservoir  10 , a brake pedal  11 , a main brake system  20 , and auxiliary braking system  100 . 
     The reservoir  10  is configured to store brake oil therein. The brake pedal  11  can translate a piston disposed in a master cylinder or the main brake system  20  by a stroke of a driver. 
     A plurality of wheel brakes FR, FL, and RL can generate a braking force at a plurality of wheels using pressure of brake oil discharged from the reservoir  10 . When a driver strokes the brake pedal  11 , a control unit can sense a braking request of the driver using a Pedal Stroke Sensor (PSS). The control unit sensing a braking request of a drive can generate a brake signal. In this case, the brake signal is an electrical signal that is transmitted to make each of the braking systems  20  and  100  generate a braking force corresponding to a stroke of the brake pedal  11  by a driver in accordance with the stroke. 
     The main brake system  20  is disposed between the reservoir  10  and the plurality of wheel brakes FR, FL, and RL and may be configured to transmit brake oil discharged from the reservoir  10  to the plurality of wheel brakes FR, FL, and RL and control the hydraulic pressure of the brake oil. When at least some of the components of the main brake system  20  fail, the control unit can transmit an auxiliary braking signal to the auxiliary braking system  100 . When an auxiliary braking signal is transmitted to the auxiliary braking system  100  by the control unit, all or some of the components of the auxiliary braking system  100  may be driven. Accordingly, the electric hydraulic brake according to the present disclosure can perform a fail-safe function. 
     The auxiliary braking system  100  is disposed between the main brake system  20  and the plurality of wheel brakes FR, FL, and RL. When the main brake system  20  fails during autonomous driving or when the main brake system  20  fails in a situation in which a driver intervenes in braking in person, the auxiliary braking system  100  can operate. 
     The auxiliary braking system  100  may include some or all of hydraulic pressure input units  101 ,  102 , and  103 , hydraulic pressure output units  104 ,  105 , and  106 , inlet lines  111 ,  112 , and  113 , an actuator  150 , traction control valves TCV 1  and TCV 2 , inlet valves FRIV and FLIV, outlet lines  121 ,  122 , and  123 , outlet valves FROV and FLOV, accumulators A 1  and A 2 , oil chambers  131  and  132 , circulation lines  141  and  142 , and high pressure switching valves HSV 1 , HSV 2 , and HSV 3 . 
     One or more hydraulic pressure input units  101 ,  102 , and  103  are disposed on a line through which brake oil discharged from the main brake system  20  flows into the auxiliary braking system  100 . The inlet lines  111 ,  112 , and  113  may be fluid-communicated with the main brake system  20  by the hydraulic pressure input units  101 ,  102 , and  103 . 
     One or more hydraulic pressure output units  104 ,  105 , and  106  are disposed on a line through which brake oil discharged from the main brake system  20  flows to the plurality of wheel brakes FR, FL, and RL. The inlet lines  111 ,  112 , and  113  can be fluid-communicated with the plurality of wheel brakes FR, FL, and RL by the hydraulic pressure output units  104 ,  105 , and  106 . 
     The inlet lines  111 ,  112 , and  113  are formed between the hydraulic pressure input units  101 ,  102 , and  103  and the hydraulic pressure output units  104 ,  105 , and  106  and can transmit brake oil discharged from the main brake system  20  to the plurality of wheel brakes FR, FL, and RL. 
     A first inlet line  111  is configured to transmit some or entire of brake oil discharged from the main brake system  20  to a first wheel brake FR. A second inlet line  112  is configured to transmit a portion or the entire of the brake oil discharged from the main brake system  20  to a second wheel brake FL. 
     The actuator  150  can increase the pressure of the fluid flowing through the first inlet line  111  and the second inlet line  112 . The actuator  150  may include some or all of a first pump SP 1 , a second pump SP 2 , a motor formed to drive the pumps SP 1  and SP 2 . An outlet of the first pump SP 1  is connected to a point on the first inlet line  111  and an outlet of the second pump SP 2  is connected to a point on the second inlet line  112 . When one or more of the first pump SP 1  and the second pump SP 2  is driven, the internal hydraulic pressure of one or more of the inlet lines  111  and  112  connected to the pumps SP 1  and SP 2 , respectively, can be increased. 
     A first traction control valve TCV 1  is disposed at a point on the first inlet line  111  and can adjust opening/closing of the first inlet line  111 . The first traction control valve TCV 1  may be disposed ahead of a point at which the first inlet line  111  and the outlet of the first pump SP 1  are connected. The first traction control valve TCV 1  may be formed in a normal open type. Accordingly, in a non-powered mode in which an auxiliary braking signal is not applied, the first traction control valve TCV 1  is open. When the first traction control valve TCV 1  is closed, a portion of a brake oil pressurized by the first pump SP 1  cannot flow backward to the main brake system  20 . 
     A first inlet valve FRIV is disposed at another point on the first inlet line  111  and can adjust opening/closing of the first inlet line  111 . The first inlet valve FRIV may be disposed behind a point at which the first inlet line  111  and the outlet of the first pump SP 1  are connected. The first inlet valve FRIV may be formed in a normal open type. Accordingly, the first inlet valve FRIV is open in a non-powered mode in which an auxiliary braking signal is not applied. When the first inlet valve FRIV is closed, a portion of brake oil pressurized by the first pump SP 1  is not transmitted to the wheel brake FR. 
     Description of a second inlet line  112 , a second traction control valve TCV 2 , and a second inlet valve FLIV refers to the description of the first inlet line  111 , the first traction control valves TCV 1 , and the first inlet valve FRIV, respectively. 
     The third inlet line  113  is not pressurized by the actuator  150 , and only the first inlet line  111  and the second inlet line  112  are pressurized by the actuator  150 . Accordingly, the control method of the auxiliary braking system  100  according to the present disclosure can perform 2-channel pressurization control. 
     The outlet lines  121 ,  122 , and  123  may be connected to points on the inlet lines  111 ,  112 , and  113  such that at least a portion of the brake oil in the inlet lines  111 ,  112 , and  113  diverges. The outlet lines  121 ,  122 , and  123  may include a first outlet line  121 , a second outlet line  122 , and a third outlet line  123 . 
     An end of the first outlet line  121  may be connected to a bifurcation on the first inlet line  111  formed behind the first inlet valve FRIV and another end may be connected to an inlet of the first pump SP 1 . 
     A first outlet valve FROV is disposed at a point on the first outlet line  121  and the first outlet valve FROV can adjust opening/closing of the first outlet line  121 . The first outlet valve FROV may be formed in a normal close type. Accordingly, the first outlet valve RFOV is closed in a non-powered mode in which an auxiliary braking signal is not applied. When the first outlet valve FROV is opened, at least a portion of the brake oil pressurized and flowing through the first inlet line  111  can be discharged to the first outlet line  121 . That is, hydraulic pressure that is transmitted to the first wheel brake FR can be decreased. 
     A first accumulator A 1  may be further disposed at another point on the first outlet line  121  formed behind the first outlet valve FROV. The first accumulator A 1  can temporarily accommodate a portion or the entire of the brake oil transmitted from the first outlet line  121 . Accordingly, it is possible to minimize damage that occurs in the first outlet line  121  due to fluctuation of a brake oil. In this case, the damage that occurs in the first outlet line  121  may include fatigue, transformation, abrasion, or the like that occurs in at least a portion of the line when the line is exposed to continuous fluctuation for a long period of time. 
     The description of a second outlet line  122 , a second outlet valve FLOV, and a second accumulator A 2  refers to the description the description of the first outlet line  121 , the second outlet valve FLOV, and the first accumulator A 1 , respectively. 
     An end of a third outlet line  123  may be connected to a point on the third inlet line  113  and another end may be connected to the first outlet line  121 . The point at which the third outlet line  123  and the first outlet line  121  may be formed behind the first outlet valve FROV. Accordingly, the brake oil transmitted by the third outlet line  123  may join the brake oil flowing through the first outlet line  121 . 
     The third outlet line  123  may be connected to one or more of the first outlet line  121  and the second outlet line  122 . The brake oil transmitted by the third outlet line  123  may be accumulated in at least one of the first accumulator A 1  and the second accumulator A 2 . 
     The auxiliary braking system  100  according to the present disclosure can generate a maximum braking force of a vehicle by controlling a rear-wheel high pressure switching valve HSV 3  connecting the third wheel brake RL and the accumulators A 1  and A 2  when there is intervention of a driver. 
     The rear-wheel high pressure switching valve HSV 3  is disposed at a point on the third outlet line  123  and can adjust opening/closing of the third outlet line  123 . The rear-wheel high pressure switching valve HSV 3  is formed in a normal open type. Accordingly, in a non-powered mode, the rear-wheel high pressure switching valve HSV 3  is closed. 
     When the rear-wheel high pressure switching valve HSV 3  is opened, at least a portion of the brake oil flowing through the third inlet line  113  diverges to the third outlet line  123 . Accordingly, hydraulic pressure that is transmitted to the third wheel brake RL can be decreased. 
     When there is no intervention of a driver, hydraulic pressure that is supplied from the reservoir  10  to the auxiliary braking system  100  is blocked. Accordingly, the auxiliary braking system  100  according to the present disclosure can replace the braking force of the third wheel brake RL with an electronic parking brake and can transmit the brake oil that is transmitted to the third wheel brake RL to the first wheel brake FR and the second wheel brake FL. 
     When the rear-wheel high pressure switching valve HSV 3  is opened, at least a portion of the brake oil flowing through the third inlet line  113  may diverge to the third outlet line  123  and join the brake oil flowing through the first outlet line  121  and the second outlet line  122 . The first accumulator A 1  and the second accumulator A 2  can temporarily accommodate a portion or the entire of the brake oil transmitted from the first outlet line  121  and the second outlet line  122 . Accordingly, the actuator  150  can increase the pressure of a brake oil that is transmitted to the first wheel brake FR and the second wheel brake FL by receiving a brake oil that is transmitted to the third wheel brake RL. 
     A first oil chamber  131  may be further disposed on the first inlet line  111 . In this case, the first oil chamber  131  is disposed ahead of the first traction control valve TCV 1 . The first oil chamber  131  can temporarily accommodate at least a portion of the brake oil discharged from the main brake system  20  therein. Since hydraulic pressure that is supplied from the reservoir  10  to the auxiliary braking system  100  is blocked when there is no intervention in braking of a driver, at least a portion of the brake oil accommodated in the oil chambers  131  and  132  can be supplied to the actuator  150 . 
     Ends of the circulation lines  141  and  142  are connected to the oil chambers  131  and  132  and the other ends are connected to the outlet lines  121  and  122  adjacent to the inlets of the pumps SP 1  and SP 2 . In this case, a point at which the other ends of the circulation lines  141  and  142  are connected to the outlet lines  121  and  122  may be, preferably, formed behind the accumulators A 1  and A 2 . Accordingly, the brake oil discharged from the accumulators A 1  and A 2  and the oil chambers  131  and  132  is supplied to the actuator  150 , so a sufficient amount of brake oil for driving the actuator  150  can be provided. 
     A first high pressure switching valve HSV 1  is disposed at a point on the first circulation line  141  and can adjust opening/closing of the first circulation line  141 . The first high pressure switching valve HSV 1  may be formed in a normal close type. Accordingly, in a non-powered mode, the first high pressure switching valve HSV 1  is closed. When the first high pressure switching valve HSV 1  is opened, at least a portion of the brake oil accommodated in the first oil chamber  131  can be provided to the actuator  150 . 
     The description of a second circulation line  142  and a second high pressure switching valve HSV 2  refers to the description of the first circulation line  141  and the first high pressure switching valve HSV 1 . 
       FIG.  2    is a flowchart of a method of controlling an auxiliary braking system of an electric hydraulic brake according to an embodiment of the present disclosure. 
     Referring to  FIG.  2   , when the main brake system  20  fails during autonomous driving or when the main brake system  20  fails in a situation in which a driver intervenes in braking in person, the auxiliary braking system  100  can operate. 
     The control unit can determine whether at least some of the components of the main brake system  20  failed (S 201 ). When the control unit determines that the main brake system failed, the control unit can transmit an auxiliary braking signal to the auxiliary braking system  100 . 
     The auxiliary braking system  100  can control the rear-wheel high pressure switching valve HSV 3  to open (S 203 ). By opening the rear-wheel high pressure switching valve HSV 3 , it is possible to improve a braking force of a vehicle removing the hydraulic pressure of the third wheel brake RL and taking the brake oil to the front wheels. 
     In relation to the point in time when the rear-wheel high pressure switching valve HSV 3  is opened, the rear-wheel high pressure switching valve HSV 3  can be controlled to be always open when the auxiliary braking system  100  is driven. In this case, pressure is not generated at the third wheel brake RL even though a drive does not intervene in braking. When a driver intervenes in braking, reactivity of the auxiliary braking system  100  can be improved because the accumulators A 1  and A 2  are immediately charged. However, since the rear-wheel high pressure switching valve HSV 3  is always controlled, a current consumption amount may be increased. 
     In relation to the point in time when the rear-wheel high pressure switching valve HSV 3  is opened, the rear-wheel high pressure switching valve HSV 3  can be controlled to be selectively opened only when a driver intervenes in braking. It is possible to determine intervention of a driver using a pedal stroke or a pressure sensor of the main brake system  20 . In this case, since the rear-wheel high pressure switching valve HSV 3  is opened after a driver intervenes in braking, reactivity of removing the pressure generated at the third wheel brake RL may be deteriorated. However, since the rear-wheel high pressure switching valve HSV 3  is controlled, when necessary, a current consumption amount can be reduced. 
     The auxiliary braking system  100  can determine whether there is intervention of a driver in a rapid braking situation (S 205 ). When there is intervention of a driver, the auxiliary braking system  100  can control the first traction control valve TCV 1  and the second traction control valve TCV 2  to close and can drive the actuator  150  (S 207 ). 
     The auxiliary braking system  100  can control the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  to open. That is, the auxiliary braking system  100  of the present disclosure can generate a maximum braking force in a vehicle by opening all of the plurality of high pressure switching valves HSV 1 , HSV 2 , and HSV 3  and closing all of the plurality of traction control valves TCV 1  and TCV 2 . 
     When the plurality of high pressure switching valves HSV 1 , HSV 2 , and HSV 3  are all maintained in an open state in a rapid braking situation, a phenomenon in which the accumulators A 1  and A 2  are not empted may occur, depending on a pressure value of the master cylinder. Since the inlets of the pumps SP 1  and SP 2  are connected with the circulation lines  141  and  142 , the hydraulic pressure at the inlets of the pumps SP 1  and SP 2  may be increased when the brake pedal is being stroked. Accordingly, it is impossible to take a brake oil from the accumulators A 1  and A 2 , so a phenomenon in which the accumulators A 1  and A 2  are not empted may occur. 
     The process in which it is possible to improve a braking force of a vehicle removing the hydraulic pressure of the third wheel brake RL and taking the brake oil to the front wheels by opening the rear-wheel high pressure switching valve HSV 3  may usually occur in the early stage of intervention in braking of a driver. 
     The auxiliary braking system  100  of the present disclosure can control the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  using the pressure of the master cylinder and the intervention time in braking of a driver so as to effectively generate a braking force in a vehicle. The auxiliary braking system  100  can determine a first condition defined as a case in which the pressure of the master cylinder is larger than a preset pressure and a second condition defined as a case in which the intervention time in braking of a driver is less than a preset time (S 209 ). For example, when the pressure of the master cylinder exceeds 2˜5 bar, it may be set the first condition is satisfied, and when the intervention time in braking of a driver is less than 100˜300 ms, it may be set that the second condition is satisfied. Here, the intervention time is the duration of braking intervention from the driver. 
     When one or more conditions of the first condition and the second condition are satisfied, the auxiliary braking system  100  can perform pattern control or sequence control on the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  (S 211 ). It is possible to solve the phenomenon in which the accumulators A 1  and A 2  are not empted, solve instability of the rear wheels due to residual pressure of the accumulators A 1  and A 2 , and effectively generate a braking force in a vehicle. 
     The pattern control is control of opening and closing the high pressure switching valves HSV 1 , HSV 2 , and HSV 3  in a predetermined cycle. For example, it is possible to repeatedly open and close the high pressure switching valves HSV 1 , HSV 2 , and HSV 3  by applying duty of 50% thereto. The sequence control is control of sequentially opening and closing the high pressure switching valves HSV 1 , HSV 2 , and HSV 3 . 
     When both of the first condition and the second condition are not satisfied, the auxiliary braking system  100  can open the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  (S 213 ). 
       FIG.  3    is a flowchart of a method of controlling an auxiliary braking system of an electric hydraulic brake according to another embodiment of the present disclosure. 
       FIG.  3    is a control method of the auxiliary braking system  100  according to a case in which a driver intervenes in braking in a slow braking situation rather than a rapid braking situation. 
     The description of a process of determining failure of the main brake system  20  (S 301 ), a process of controlling the rear-wheel high pressure switching valve HSV 3  to open (S 303 ), a process of determining whether there is intervention of a driver in a braking situation (S 305 ), and a process of controlling the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  to close and driving the actuator  150  (S 307 ) refer to the corresponding processes S 201  to S 207  of  FIG.  2   . 
     When the auxiliary braking system  100  controls the high pressure switching valves HSV 1 , HSV 2 , and HSV 3 , disconnection may be generated in pedal feel due to opening of the high pressure switching valves HSV 1 , HSV 2 , and HSV 3  and movement of a brake oil. 
     In order to solve this problem, the auxiliary braking system  100  may control the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  to close. That is, by closing the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2 , opening the rear-wheel high pressure switching valve HSV 3 , and closing all of the plurality of traction control valves TCV 1  and TCV 2 , the auxiliary braking system  100  can smoothen the stroke of a driver in slow braking. Thereafter, it is possible to adjust the pedal feel by opening or performing pattern control on the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2 , depending on a pressure variation of the master cylinder. 
     The auxiliary braking system  100  of the present disclosure can control the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  using a pressure variation of the master cylinder and an intervention time in braking of a driver so as to smoothen a braking stroke. The auxiliary braking system  100  can determine a third condition defined as a case in which a pressure increase variation of the master cylinder is smaller than a preset value and a fourth condition defined as a case in which the intervention time in braking of a driver is less than a preset time (S 309 ). 
     When one or more conditions of the third condition and the fourth condition are satisfied, the auxiliary braking system  100  can close the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  (S 311 ). 
     When both of the third condition and the fourth condition are not satisfied, the auxiliary braking system  100  can open or perform pattern control on the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2  (S 313 ). That is, when a pressure increase value of the master cylinder is large, it is possible to generate a braking force in a vehicle by controlling the first high pressure switching valve HSV 1  and the second high pressure switching valve HSV 2 . 
     According to the present disclosure, a control method of an electric hydraulic brake has an effect of being able to reduce the manufacturing cost and increasing convenience of assembly by controlling an auxiliary braking system that can perform 2-channel pressurization control and 1-channel decompression control. 
     According to an embodiment of the present disclosure, the control method for an electric hydraulic brake can generate a braking force in a vehicle by using a front wheel-auxiliary braking system and a rear wheel-electric parking brake when a driver intervenes in braking in a redundancy situation. 
     Although exemplary embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the idea and scope of the claimed invention. Therefore, exemplary embodiments of the present disclosure have been described for the sake of brevity and clarity. The scope of the technical idea of the present embodiments is not limited by the illustrations. Accordingly, one of ordinary skill would understand that the scope of the claimed invention is not to be limited by the above explicitly described embodiments but by the claims and equivalents thereof