Patent Publication Number: US-2023146934-A1

Title: Hydraulic brake for vehicle and control method therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2021-0152599, filed on Nov. 8, 2021, the entire contents of which is incorporated herein for all purposes by this reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a hydraulic brake for a vehicle and a control method therefor. 
     BACKGROUND 
     Description of this section only provides the background information of the present disclosure without configuring the related art. 
     An assistant brake device configured to generate breaking pressure in order to assist a main brake device in a vehicle when the main brake device fails. An assistant controller that controls the assistant brake device to assist the main controller that controls the main brake device may be mounted with the assistant brake device. An assistant brake system is configured to start cooperative control when the output of the main brake device does not satisfy preset conditions. The case in which the output of the main brake device does not satisfy preset conditions may be understood as a case in which the main brake device fails. 
     Meanwhile, the main brake device may not be normally operated although the main brake device does not satisfy preset conditions. Further, it may take time for the hydraulic pressure of a wheel brake reaches target hydraulic pressure due to communication time between the main controller and the assistant controller and channel resistance at the time point at which cooperated control is started because the main brake device does not satisfy preset conditions. There is a problem in that, in these situations, even though a brake system of a vehicle is equipped with the assistant brake device, the assistant controller, and a cooperative control means between the assistant brake device and the assistant controller, a braking force required to safely drive the vehicle cannot be generated. 
     SUMMARY 
     According to at least one aspect, the present disclosure provides a control method of a hydraulic brake apparatus for a vehicle including a first brake device and a second brake device configured to supply hydraulic pressure to wheel brakes, and a control unit including a first controller controlling the first brake device and a second controller controlling the second brake device, the control method comprising: receiving information for determining a status of the first brake device by means of the control unit; determining whether the first brake device is normally operated using the information for determining a status of the first brake by means of the control unit; and a controlling at least one of the first brake device and the second brake device to decrease a hydraulic pressure loss amount in the wheel brakes when the control unit determines that the first brake is not normally operated. 
     According to another aspect, the present disclosure provides a hydraulic brake apparatus for a vehicle comprising a first control unit configured for controlling a first brake device configured to supply first hydraulic pressure to a plurality of wheel brakes, and a second control unit configured for controlling a second brake device connected in series between at least some of the plurality of wheel brakes and the first brake device, wherein the first control unit includes: a first receiver receiving a status signal of components of the first brake device from a signal generator of the first brake device; a first determining unit determining whether the first brake device is normally operated; and a first controller controlling the first brake device to block flow of fluid to a fluid reservoir from the wheel brakes when the first brake device is not normally operated, and the second control unit includes: a second receiver receiving required braking force information from a required braking force calculator of the vehicle and receiving information about pressure from a middle flow path pressure sensor mounted in a channel at the first brake device; a second determining unit determining whether the first brake device is normally operated; and a second controller controlling the second brake device to block flow of fluid from the fluid reservoir from the wheel brakes when the first brake device is not normally operated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a flowchart showing a control method according to an embodiment of the present disclosure. 
         FIG.  2    is a block diagram schematically showing the configuration of a hydraulic brake for a vehicle of the control method according to an embodiment of the present disclosure. 
         FIG.  3    is a hydraulic circuit diagram showing a hydraulic brake for a vehicle of a control method according to an embodiment of the present disclosure. 
         FIG.  4    is a flowchart showing an information collection process according to an embodiment of the present disclosure. 
         FIG.  5    is a flowchart showing a status determination process of a first brake device according to an embodiment of the present disclosure. 
         FIG.  6    is a flowchart showing a process in which a control unit of the present disclosure controls a first brake device or a second brake device. 
         FIG.  7    is a block diagram showing the configuration of a hydraulic brake for a vehicle and a control method therefor according to an embodiment of the present disclosure. 
         FIG.  8    is a hydraulic circuit diagram showing a hydraulic brake for a vehicle and a control device therefor according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     A hydraulic brake for a vehicle and a control method therefor can stably generate a braking force required for the vehicle by controlling a main brake device or an assistant brake device to prevent a loss of hydraulic pressure of a wheel brake during a transition phase in which a normal control steps enters a cooperative brake step. 
     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 exemplary 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 known functions and configurations incorporated therein will be omitted for the purpose of clarity and for brevity. 
     Additionally, various terms such as first, second, A, B, (a), (b), etc., are used solely to differentiate one component from the other but not to imply or suggest the substances, order, or sequence of the components. Throughout this specification, when a part ‘includes’ or ‘comprises’ a component, the part is meant to further include other components, not to exclude thereof unless specifically stated to the contrary. 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. 
     When components are connected, it means that the components communicate with each other such that fluid can flow. 
       FIG.  1    is a flowchart showing a control method according to an embodiment of the present disclosure. 
     Referring to  FIG.  1   , in a control method  100  for a hydraulic brake for a vehicle according to an embodiment of the present disclosure, a control unit  290  receives information for determining the status of a first brake device  210  (S 110 ). The control unit  290  determines whether the first brake device  210  is normally operated using the received information (S 120 ). When the first brake device  210  is not normally operated, the control unit  290  controls the first brake device  210  and/or the second brake device  220  to decrease a hydraulic pressure loss amount in wheel brakes w 1  to w 4 . Control is ended when the first brake device  210  is normally operated. 
     In detail, when the first brake device  210  is not normally operated, the control unit  290  determines whether all components in the first brake device  210  are abnormally operated through first controllers  291  in the wheel brakes w 1  to w 4 . In the present disclosure, a non-normal operation case is referred to an ‘abnormal operation case’. Although it is shown in  FIG.  1    that a process S 130  is performed after a process S 120 , the present disclosure is not limited thereto. Determination processes of the process S 120  and the process S 130  may be simultaneously or collectively performed. For example, when the first controller  291  determines that only some components of the first brake device  210  fail by receiving a status signal showing that only some components fail from a signal generator  215 , the process S 120  and the process S 130  are collectively performed. Unlikely, the first controller  291  may control the first brake device  210  or the second controller  292  may control the second brake device  220  to suppress a loss of hydraulic pressure of the wheel brakes w 1  to w 4  not via the process S 130  after the process S 120 . 
     When only some components of the first controller  291  are abnormally operated, the control unit  20  controls the first brake device  210  and/or the second brake device  220  to decrease a hydraulic pressure loss amount in the wheel brakes w 1  to w 4  (S 140 ). The control unit  290  determines whether the first brake device  210  is being abnormally operated over a preset period after the process S 140  (S 160 ). When it is determined that the preset period is not exceeded in a process S 160 , the control unit  290  keeps performing the control of the process S 140  (S 181 ). 
     Unlikely, when all of the components of the first controller  292  are abnormally operated, the control unit  20  controls the second brake device  220  to decrease a hydraulic pressure loss amount in the wheel brakes w 1  to w 4  (S 150 ). After the step S 150 , whether the second controller  292  needs back-up control is determined (S 170 ). When it is determined that back-up control is not needed, the second controller  292  determines whether required braking power was increased after the time point at which the process S 130  is performed (S 182 ). When it is determined that the required braking power was not increased, the second controller  292  stops the control of S 150  (S 183 ). When it is determined that the required braking power was increased, the second controller  292  keeps performing the control of the process S 150 . When the second controller  292  determines that a lapse time of abnormal operation of the first brake device  210  exceeded a preset period in a process S 160  or that back-up control is needed in a process S 170 , the second controller performs back-up control (S 190 ). The back-up control may be understood as a process in which the second controller  292  controls the second brake device  220  such that the second brake device  220  forms a braking force by assisting the first brake device  210  when the output of the first brake device  210  reaches a status in which the first brake device  210  cannot satisfy preset conditions. Further, the first brake device  210  undergoes a ‘non-operating status’ of the present disclosure, that is, a transition phase before reaching the status in which the first brake device  210  cannot satisfy preset conditions. 
     According to the control method  100  according to an embodiment of the present disclosure, the control unit  290  determines whether it is a transition phase, and correspondingly controls the first and second brake devices  210  and  220 . Accordingly, there is an effect that the hydraulic brake for a vehicle can stably generate required braking force. 
       FIG.  2    is a block diagram showing the configuration of a hydraulic brake for a vehicle of the control method according to an embodiment of the present disclosure. 
       FIG.  3    is a hydraulic circuit diagram showing a hydraulic brake for a vehicle of a control method according to an embodiment of the present disclosure. 
     The configuration of a hydraulic brake for a vehicle of the control method  100  according to an embodiment of the present disclosure is briefly described. The hydraulic brake for a vehicle includes all or some of wheel brakes w 1  to w 4 , a fluid reservoir  240 , a first brake device  210 , a second brake device  220 , a required braking force calculator  250 , an electronic parking brake  260 , and a control unit  290 . 
     The wheel brakes w 1  to w 4  are configured to brake a vehicle using hydraulic pressure. The hydraulic brake for a vehicle may include a plurality of wheel brakes w 1  to w 4 . The fluid reservoir  240  is configured to receive fluid from the wheel brakes w 1  to w 4  when fluid that is supplied to a first and/or a second pressurizing device  211  and/or  222  is stored or the hydraulic pressure of the wheel brakes w 1  to w 4  is decreased. Referring to  FIG.  3   , the fluid reservoir  240  is directly connected between the master cylinder  111   a  of the first brake device  210  and the wheel brakes w 1  to w 4 . 
     The first brake device  210  is configured to supply first hydraulic pressure to the wheel brakes w 1  to w 4 . The first brake device  210  may include a first pressurizing device  211  that pressurizes fluid, a signal generator  215 , and a plurality of first valves  212  configured to adjust a flow path of fluid. The first pressurizing device  211  may include all or some of a master cylinder  111   a  and a motor piston  111   b.  The first brake device  210  may include a signal generator  215  that generates a status signal showing whether components of the first brake device  210  fail. The signal generator  215  includes sensors that sense hydraulic pressure, temperature, current, or the like in the channel of the first brake device  210  and the status signal may be a hydraulic pressure value measured by the sensors. 
     Some of the plurality of first valves  212  may be first block valves WSV, LPSV, and MCV, LSV, and LPMCV configured to control flow of fluid from the wheel brakes w 1  to w 4  to the fluid reservoir  240 . The first block valves WSV, LPSV, and MCV, LSV, and LPMCV are not necessarily mounted for the purpose of blocking flow of fluid from the wheel brakes w 1  to w 4  to the fluid reservoir  240 . The first block valves WSV, LPSV, and MCV, LSV, and LPMCV, for example, may be valves that are mounted so that the motor piston  111   b  can supply hydraulic pressure to the wheel brakes w 1  to w 4  and that are configured to serve to block decompression of the wheel brakes w 1  to w 4 . 
     Referring to  FIG.  3   , in the hydraulic brake for a vehicle of the first control method  100 , the first block valves WSV, LPSV, and MCV, LSV, and LPMCV may be combinations of valves LPWSV and WSV connected in series between the master cylinder  111   a  and the wheel brakes w 1  to w 4  and valves MCV, LSV, and LPMCV connected in series between the motor piston  111   b  and the wheel brakes w 1  to w 4 . The first valve  212  may be configured such that not only whether the first valve  212  is opened, but the degree of opening are controlled. The first block valves WSV, LPSV, and MCV, LSV, and LPMCV may be normal open type solenoid valves of which the channels therein are open when a current is not applied. 
     The second brake device  220  is configured to supply second hydraulic pressure to at least some of the wheel brakes w 1  to w 4 . The second brake device  220  may include a second pressurizing device  221  that pressurizes fluid, and a plurality of second valves  222  configured to adjust a flow path of fluid. The second pressurizing device  221  is configured to pressurize fluid. The second pressurizing device  221 , for example, may be a motor pump. Some of the second valves  222  may be second block valves TCV 1  and TCV 2  configured to control flow of fluid from the wheel brakes w 1  to w 4  to the fluid reservoir  240 . The second block valves TCV 1  and TCV 2  are not necessarily mounted for the purpose of blocking flow of fluid from the wheel brakes w 1  to w 4  to the fluid reservoir  240 . The second block valves TCV 1  and TCV 2  , for example, may be valves that are mounted so that the motor piston can supply hydraulic pressure to the wheel brakes w 1  to w 4  and that are configured to serve to block decompression of the wheel brakes w 1  to w 4 . Referring to  FIG.  3   , the second block valves TCV 1  and TCV 2  may be connected in series between the first brake device  210  and the wheel brakes w 1  to w 4 . The first valve  212  may be configured such that not only whether the first valve  212  is opened, but the degree of opening are controlled. The control unit  290  includes first and second controller  291  and  292 . The first controller  291  controls the first brake device  210  and the second controller  292  controls the second brake device  220 . 
       FIG.  4    is a flowchart showing an information collection process according to an embodiment of the present disclosure. 
     The control unit  290  receives information for determining the status of the first brake device  210 . In the process S 110 , the first controller  291  can receive a component status signal of the first brake device  210  from the signal generator  215  of the first brake device  210 . 
     In the process S 110 , the control unit  290  can receive required braking force information from the required braking force calculator  250  and can receive hydraulic pressure information, which is supplied to the wheel brakes w 1  to w 4  from the first brake device  210 , from the second brake device  220 . The required braking force calculator  250  is configured to calculate required braking force on the basis of a deceleration signal generated by an autonomous driving system for a vehicle (not shown) or a pedal effort by a driver. In the present disclosure, the hydraulic pressure supplied to the wheel brakes w 1  to w 4  by the first brake device  210  is referred to as first hydraulic pressure and the hydraulic pressure supplied to the wheel brakes w 1  to w 4  by the second brake device  220  is referred to as second hydraulic pressure. When the second brake device  220  does not generate hydraulic pressure, it is possible to measure the first hydraulic pressure using wheel-side hydraulic pressure sensors mounted on the wheel brakes w 1  to w 4 . When the second brake device  220  is connected in series between the first brake device  210  and the wheel brakes w 1  to w 4 , a middle flow path pressure sensor MPS mounted in the channel of the second brake device  220  at the first brake device  210  can measure the first hydraulic pressure. By using the middle flow path pressure sensor MPS, there is an advantage in that the middle flow path pressure sensor MPS can measure the first hydraulic pressure when the channel connecting the second pressurizing device  221  and the middle flow path pressure sensor MPS is closed even though the second pressurizing device  221  generates second hydraulic pressure. 
     In the process S 110 , the second controller  292  can receive required braking force information from the required braking force calculator  250  and the second controller  292  can receive first hydraulic pressure information from the second brake device  220  (S 112 ). In the process S 110  to the process S 130 , a process in which the first controller  291  and the second controller  292  exchange information for determining the status of the first brake device  210  may be performed. For example, the first controller  292  may transmit a status signal received from the first brake device  210  to the second controller  292 . According to the process S 112 , since the second controller  292  can receive required braking force information even not via the first controller  291 , so the communication time decreases, and accordingly, the control unit  290  can easily respond to a situation in which the first brake device  210  is abnormally operated. 
     Although it is shown in  FIG.  4    that the process S 112  is performed after the process S 111 , the present disclosure is not limited thereto. The control method  100  according to an embodiment of the present disclosure includes a control method  100  that simultaneously performs the process S 111  and the process S 112  or performs only one of the process S 111  and the process S 112 . For example, since the signal generator  215  of the first brake device  210  is also a component included in the first brake device  210 , when the first brake device  210  is entirely abnormally operated due to a case which power is not supplied to the first brake device  210 , or the like, the process S 111  cannot be performed. In this case, the second controller  292  can determine whether the first brake device  210  is normally operated using the required braking force and the first hydraulic pressure (S 112 ). 
       FIG.  5    is a flowchart showing a status determination process of the first brake device  210  according to an embodiment of the present disclosure. 
     Referring to  FIG.  5   , the control unit  290  determines whether the first brake device  210  is normally operated using received information (S 120 ). In the process S 120 , the first controller  291  can determine whether the first brake device  210  is normally operated using information for determining the status of the first brake device  210 . The information for determining the status of the first brake device  210  may be a status signal transmitted from the signal generator  215  (S 121 ). 
     The control unit  290  can determine whether the first brake device  210  is normally operated on the basis of required braking force information and information about pressure. When the required braking force is larger than the hydraulic pressure of the wheel brakes w 1  to w 4  and the hydraulic pressure measured by the middle flow path pressure sensor MPS was not increased for a predetermined time, the control unit  290  can determine that the first brake device  210  is not normally operated. The predetermined time, which is time that the wheel brakes w 1  to w 4  take to generate the required braking force after the time point at which the first controller  291  receives a required braking signal, may be a value that is obtained by the transmission/reception speed of a signal, channel resistance, etc. The predetermined time may be experimentally obtained and stored in the form of a look up table (LUT) in a memory. The second controller  292  can determine whether the first brake device  210  is normally operated on the basis of required braking force information and information about pressure (S 122 ). The process S 122  may be performed even through the first controller  291  is not normally operated. 
     In the process of S 120 , when it is determined that the first brake device  210  is not normally operated, the control unit  290  controls the first brake device  210  and/or the second brake device  220  to decrease a hydraulic pressure loss amount in the wheel brakes w 1  to w 4  (S 130  to S 190 ). The first controller  291  can control the open or closed status of the first valves. The first controller  291  can control the open or closed status of the first block valves (WSV, LPSV, and MCV, LSV and LPMCV). Referring to  FIG.  3   , when the second brake device  220  is connected in series between the first control device and at least one of the wheel brakes w 1  to w 4 , the second controller  292  can control the second brake device  220  to decrease the amount of fluid that is transmitted to a low-pressure fluid reservoir from the second brake device  220 . The second controller  292  controls the open or closed status of the second block valves TCV 1  and TCV 2 , so it is possible to suppress a loss of hydraulic pressure of the wheel brakes w 1  to w 4 . Controlling the open/close status means that the first controller  291  adjusts a current that is supplied to the first block valves WSV, LPSV, and MCV, LSV, and LPMCV. The first block valves WSV, LPSV, and MCV, LSV, and LPMCV and the second block valves TCV 1  and TCV 2  may be configured such that the open or closed status thereof changes in accordance with the magnitude of a current that is supplied thereto. 
     The control unit  290  according to an embodiment of the present disclosure can determine whether all of the components of the first brake device  210  are abnormally operated. Referring to  FIG.  1   , the first controller  291  can determine whether all of the components of the first brake device  210  are abnormally operated. The components of the first brake device  210  may be the first pressurizing device  211  and the first valves  212 . A status signal may include failure information of each of the components of the first brake device  210 . The first controller  291  can perform the process S 130  on the basis of the status signal. 
     When all of the components of the first controller  292  are abnormally operated in the process S 130 , the second controller  292  controls the second brake device  220  to decrease a hydraulic pressure loss amount in the wheel brakes w 1  to w 4  (S 150 ). Referring to  FIG.  3   , when the second brake device  220  is connected in series between the first brake device  210  and at least one of the wheel brakes w 1  to w 4 , the second controller  292  can control the open or closed status of the second block valves TCV 1  and TCV 2  that control flow of fluid to the first brake device  210 . Hereafter, controlling the open or closed status of a valve means that whether the valve is opened or closed or the degree of opening thereof is controlled. When the second block valves TCV 1  and TCV 2  are closed, fluid is not transmitted to the low-pressure fluid reservoir  240  from the wheel brakes w 1  to w 4  to which the second brake device  220  is connected. It is possible to prevent a loss of the braking pressure of the wheel brakes w 1  to w 4  to which the second brake device  220  is connected. The process S 150  is a process in which the second controller  292  controls the second brake device  220 , so the process S 150  may be performed when all of the components of the first brake device  210  are abnormally operated. Thereafter, the second controller  292  can determine whether the back-up control of the second controller  292  is needed (S 170 ). When back-up control is not needed, the second controller  292  determines whether the required braking force was increased (S 182 ). When the required braking force was not increased in S 182 , the second controller  292  stops the control of S 150  (S 183 ), and when the required braking force was increased, the second controller  292  keeps performing the control of S 150  (S 184 ). 
       FIG.  6    is a flowchart showing a process in which a control unit of the present disclosure controls a first brake device or a second brake device. 
     Referring to  FIG.  6   , in the process of S 130 , when it is determined that some components of the first brake device  210  are normally operated, the control unit  290  controls the first brake device  210  and/or the second brake device  220  to decrease a hydraulic pressure loss amount in the wheel brakes w 1  to w 4  (S 140 ). 
     In the process S 140  according to an embodiment of the present disclosure, the first controller  291  can determine whether the first block valves WSV, LPSV, and MCV, LSV, and LPMCV are normally operated (S 141 ). When it is determined that at least some of the first block valves WSV, LPSV, and MCV, LSV, and LPMCV are normally operated, the first block valves WSV, LPSV, and MCV, LSV, and LPMCV that are normally operated are closed, and the first controller  291  initializes the operation status of the components of the first brake device  210  that are abnormally operated. When the first block valves WSV, LPSV, and MCV, LSV, and LPMCV are closed, fluid is not transmitted from the wheel brakes w 1  to w 4  to the fluid reservoir  240 . Accordingly, it is possible to suppress a loss of hydraulic pressure of the wheel brakes w 1  to w 4 . 
     When it is determined that all of the first block valves WSV, LPSV, and MCV, LSV, and LPMCV are abnormally operated in the process S 141 , the first controller  291  initializes the operation status of the components, which are abnormally operated, of the components of the first brake device  210 . For example, the first controller  291  can temporarily stop a current from being supplied to some of the first valves  212  that are abnormally operated. Further, the second controller  292  can control the second brake device  220  to decrease a hydraulic pressure loss amount in the wheel brakes w 1  to w 4  (S 144 ). Referring to  FIG.  3   , when the second brake device  220  is connected in series between the first brake device  210  and at least one of the wheel brakes w 1  to w 4 , the second controller  292  can control the open or closed status of the second block valves TCV 1  and TCV 2  that control flow of fluid to the first brake device  210  in the process S 144 . In detail, the second controller  292  can control the second block valves TCV 1  and TCV 2  to be closed. 
     In the process S 140 , cooperative control in which the first controller  291  controls some components of the first brake device  210  that are normally operated and the second controller  292  controls the second brake device  220 . In a common redundancy brake system, an auxiliary controller suppresses a loss of hydraulic pressure of the wheel brakes w 1  to w 4  by controlling an auxiliary brake device. In order for the auxiliary controller to control the auxiliary brake device, the auxiliary controller should undergo a process of receiving a status signal from a main controller. On the contrary, the control method  100  according to an embodiment of the present disclosure receives a status signal (S 111 ) and suppresses a loss of hydraulic pressure of the wheel brakes w 1  to w 4  and controlling the first brake device  210 . Accordingly, it is possible to quickly suppress a loss of hydraulic pressure of the wheel brakes w 1  to w 4  without undergoing the process in which an auxiliary controller receives a status signal from a main controller. 
     After a preset period is exceeded from the process  5140 , the control unit  290  determines whether the first brake device  210  is abnormally operated (S 160 ). If it is determined that it is not so, the control unit  290  keeps performing the control of the process s 140  (S 181 ). For example, the first controller  291  maintains the closed status of the first block valves WSV, LPSV, and MCV, LSV, and LPMCV that are normally operated. Unlikely, when it is determined that the first brake device  210  is being abnormally operated after a preset period is exceeded, the second controller  292  performs back-up control (S 190 ). Even though it is determined that back-up control is needed in the process S 170 , the second controller  292  may perform back-up control (S 190 ). That is, the second controller  292  controls the second pressurizing device  221  of the second brake device  220  and controls the open or closed status of the second valves  222  on the basis of a required braking force, the hydraulic pressure information of the wheel brakes w 1  to w 4 , etc. 
     According to the control method  100  according to an embodiment of the present disclosure, by determining whether the status of the first brake device is a transition phase and correspondingly controlling the first and second brake devices  210  and  220 , it is possible to prevent a loss of pressure of the wheel brakes w 1  to w 4  due to a communication time between the first and second controllers  291  and  292 , channel resistance, etc. The control method  100  according to an embodiment of the present disclosure may be performed using a hydraulic brake for a vehicle of the control method  100  according to an embodiment. 
       FIG.  7    is a block diagram showing the configuration of a hydraulic brake for a vehicle according to an embodiment of the present disclosure. 
       FIG.  8    is a hydraulic circuit diagram showing a hydraulic brake apparatus for a vehicle according to an embodiment of the present disclosure. 
     Referring to  FIGS.  7  and  8   , a hydraulic brake  600  for a vehicle according to an embodiment of the present disclosure includes all or some of a first brake device  610 , a second brake device  620 , a required braking force calculator  650 , a first control unit  670 , a second control unit  680 , and an electronic parking brake  660 . 
     The first control unit  670  controls the first brake device  610  configured to supply first hydraulic pressure a plurality of wheel brakes w 1  to w 4 . The first brake device  610  may include all or some of a signal generator  615 , a first pressurizing device  611 , and a first valve  612  configured to selectively transmit hydraulic pressure generated by a pressurizing device to the plurality of wheel brakes w 1  to w 4 . The signal generator  615  includes sensors that sense hydraulic pressure, temperature, current, or the like in the channel of the first brake device  610  and the status signal may be a hydraulic pressure value measured by the sensors. The first control unit  670  may include all or some of a first receiver  671 , a first determining unit  672 , and a first controller  673 . The first receiver  671  receives a status signal of the components of the first brake device  610  from the signal generator  615  of the first brake device  610 . The first determining unit  672  determines whether the first brake device  610  is normally operated. The first determining unit  672  can determine whether the first brake device  610  is normally operated on the basis of a status signal. When the first brake device  610  is not normally operated, the first controller  673  controls the first brake device  610  to block flow of fluid from the wheel brakes w 1  to w 4  to the fluid reservoir  640 . For example, the first controller  673  can close first block valves WSV, LPSV, and MCV, LSV, and LPMCV connected in series between the wheel brakes w 1  to w 4  and the fluid reservoir  640  when the first brake device  610  is not normally operated. 
     The second control unit  680  controls the second brake device  620  configured to supply second hydraulic pressure to at least one of the wheel brakes w 1  to w 4 . The second brake device  620  is connected in series between at least some of the wheel brakes w 1  to w 4  and the first brake device  610 . The second brake device  620  may include all or some of a middle flow path pressure sensor MPS, a second pressurizing device  621 , and a second valve  622  configured to selectively transmit hydraulic pressure generated by a pressurizing device to the plurality of wheel brakes w 1  to w 4 . Referring to  FIG.  8   , the middle flow path pressure sensor MPS is mounted in a channel at the first brake device  610 . In the present disclosure, the hydraulic pressure supplied to the wheel brakes w 1  to w 4  by the first brake device  610  is referred to as first hydraulic pressure and the hydraulic pressure supplied to the wheel brakes w 1  to w 4  by the second brake device  620  is referred to as second hydraulic pressure. When the second brake device does not generate hydraulic pressure, it is possible to measure the first hydraulic pressure using wheel-side hydraulic pressure sensors mounted on the wheel brakes w 1  to w 4 . 
     The second control unit  680  may include all or some of a second receiver  681 , a second determining unit  682 , and a second controller  683 . The second receiver  681  receives required braking force information from the required braking force calculator  650  for a vehicle and receives information about pressure from the middle flow path pressure sensor MPS. The second receiver  681  can receive information about whether the first brake device  610  is normally operated which was determined by the first determining unit  672 . The second determining unit  682  determines whether the first brake device  610  is normally operated. When the required braking force is larger than the hydraulic pressure of the wheel brakes w 1  to w 4  and the hydraulic pressure measured by the middle flow path pressure sensor MPS was not increased for a predetermined time, the second control unit  682  can determine that the first brake device  610  is not normally operated. When the first control unit  670  is not normally operated, the second controller  683  controls the second brake device  620  to block flow of fluid from the wheel brakes w 1  to w 4  to the fluid reservoir  640 . For example, when the first brake device  610  is not normally operated, the second controller  683  can close second block valves TCV 1  and TCV 2  connected in series between the first brake device  610  and the wheel brakes w 1  to w 4 . 
     According to the hydraulic brake for a vehicle  600  according to an embodiment of the present disclosure, by determining whether it is a transition phase and correspondingly controlling the first and second brake devices  610  and  620 , it is possible to prevent a loss of pressure of the wheel brakes w 1  to w 4  due to a communication time between the first and second controllers  673  and  683 , channel resistance, etc. Further, even if not only the first brake device  610 , but the first controller  673  is not normally operated, the second controller  683  can prevent a loss of hydraulic pressure of the wheel brakes w 1  to w 4  through the reception, determination, and control processes. Further, since the first controller  673  controls some components of the first brake device  610  that can be normally operated, it is possible to prevent a loss of hydraulic pressure of the wheel brakes w 1  to w 4  in the transition phase using only the first brake device  610 . When only the first brake device  610  is used, it is not required to undergo the process in which the first controller  673  and the second controller  683  transmit and receive signals, so the hydraulic brake for a vehicle  600  according to an embodiment of the present disclosure can quickly cope with a loss of hydraulic pressure due to failure of the first brake device  610 . 
     A pair of electronic parking brakes  660  may be mounted on each of the left rear wheel and the right rear wheel of a vehicle. The electronic parking brakes  660  brake the corresponding wheels using a motor. The second brake device  620  is connected in series between wheel brakes w 1  to w 4  mounted on the front wheel of a vehicle of the wheel brakes and the first brake device  610 . The second brake device  620  can provide braking pressure to the front wheels of a vehicle by assisting the first brake device  610  and the electronic parking brake  660  can provide braking pressure to the rear wheel of the vehicle by assisting the first brake device  610 . 
     According to an embodiment, there is an effect in that the control method of a hydraulic brake for a vehicle and the hydraulic brake stably generate a braking force required for the vehicle by controlling a main brake device or an assistant brake device to prevent a loss of hydraulic pressure of a wheel brake during a transition phase I which a normal control steps enters a cooperative brake step. 
     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 the scope of the claimed invention is not to be limited by the above explicitly described embodiments but by the claims and equivalents thereof.