Patent Publication Number: US-2017361823-A1

Title: Electric brake apparatus and control method thereof

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention is related to an electric brake system of a vehicle and a control method using the same, and more particularly, to an electric brake apparatus capable of reflecting driver&#39;s braking intent even when braking power is generated by electronic stability control (ESC) and a control method using the same. 
     2. Discussion of Related Art 
     Recently, vehicle technologies have been advancing according to increasing customer demand for eco-friendly technologies. In addition, various electric devices are included in the vehicle. 
     Particularly, to further improve driver safety, electronic stability control (ESC) systems are widely included in recent vehicles. The ESC system is an apparatus that electronically controls a brake included in each wheel to stably control a vehicle stance. 
     However, in a vehicle, there is a problem in that using a conventional brake system utilizing a vacuum booster is difficult since the use of an engine is limited. Accordingly, an integrated electric booster is used, however, individually controlling two hydraulic circuits therein is theoretically impossible using one fluid pressure source included therein. 
     Accordingly, there is a problem in that a driver feels a strange sensation. 
     Thus, a method to resolve the above-describe problems are being demanded. 
     Patent Document 
     Korean Patent Registration No. 10-0844670 
     SUMMARY OF THE INVENTION 
     The present invention is directed to providing a brake control system of a vehicle and a control method using the same for reflecting a driver&#39;s intension during a simultaneous occurrence of braking intended by a driver and braking under an electronic stability control (ESC) in an integrated electric booster in which an electric booster is integrated with an ESC system. 
     The present invention is also directed to minimizing a strange sensation during driver&#39;s driving. 
     The scope of the present invention is not limited to the above-described objects, and other unmentioned objects may be clearly understood by those skilled in the art from the following descriptions. 
     According to an aspect of the present invention, there is provided an electric brake apparatus that includes a pump unit driven based on driving of a motor and a plurality of wheel cylinders, each of which receives a fluid pressure generated by the pump unit. The electric brake apparatus includes: a hydraulic circuit disposed between the pump unit and the wheel cylinders; a plurality of wheel valves that regulate a fluid flow between the hydraulic circuit and the wheel cylinders; and an electronic control unit that controls the wheel valves and the motor, wherein the electronic control unit controls the wheel valves and the motor on the basis of an input of a driver stepping on a brake pedal and a need for ESC. 
     The electronic control unit may include: a braking determination device that determines a driver&#39;s braking intent on the basis of an output value of a stroke sensor that detects the driver&#39;s pedal operation; an ESC device that determines a need for the electric stability control of a vehicle on the basis of an output of at least one sensor installed in the vehicle; a motor controller that controls the motor on the basis of an output of at least one of the braking determination device and the ESC device; and a wheel valve controller that controls the wheel valves on the basis of an output of at least one of the braking determination device and the ESC device. 
     The hydraulic circuit may include a first hydraulic circuit that connects the pump unit to some of the wheel cylinders and the second hydraulic circuit that connects the pump unit to the other wheel cylinders, and the electronic control unit may control to open the wheel valves of the wheel cylinders connected to the second hydraulic circuit when an input of a driver stepping on a brake pedal is detected while supplying a fluid to the wheel cylinders connected to the first hydraulic circuit for the ESC of the vehicle. 
     The hydraulic circuit may include a first hydraulic circuit that connects the pump unit to some of the wheel cylinders and the second hydraulic circuit that connects the pump unit to the other wheel cylinders, and the electronic control unit may control to open the wheel valves of the wheel cylinders connected to the second hydraulic circuit when electronic stability control is needed while supplying a fluid to the wheel cylinders connected to the first hydraulic circuit to brake a vehicle when an input of a driver stepping on a brake pedal is detected. 
     According to another aspect of the present invention, there is provided a control method of an electric brake apparatus that includes a pump unit driven based on driving of a motor and a plurality of wheel cylinders each of which receives a fluid pressure generated by the pump unit. The control method includes: detecting one of an input of a user braking and a need for ESC of a vehicle; driving the motor and discharging a fluid into a hydraulic circuit disposed between the pump unit and the wheel cylinders by an electronic control unit; controlling a plurality of wheel valves disposed between the hydraulic circuit and the wheel cylinders by the electronic control unit; and generating braking power for one of the plurality of wheels on the basis of the controlling of the plurality of wheel valves. 
     The hydraulic circuit may include a first hydraulic circuit that connects the pump unit to some of the wheel cylinders and the second hydraulic circuit that connects the pump unit to the other wheel cylinders, and the electronic control unit may control to open the wheel valves of the wheel cylinders connected to the second hydraulic circuit when an input of a driver stepping on a brake pedal is detected while supplying a fluid to the wheel cylinders connected to the first hydraulic circuit for the ESC of the vehicle. 
     The hydraulic circuit may include a first hydraulic circuit that connects between the pump unit and some of the wheel cylinders and the second hydraulic circuit that connects between the pump unit and the other wheel cylinders, and the electronic control unit may control to open the wheel valves of the wheel cylinders connected to the second hydraulic circuit when electronic stability control is needed while supplying a fluid is supplied to the wheel cylinders connected to the first hydraulic circuit to brake a vehicle when an input of a driver stepping on a brake pedal is detected. 
     The detecting of the input of braking may include detecting a driver&#39;s braking intent by a stroke sensor that detects a driver&#39;s pedal operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a view illustrating each component of an electric bake apparatus according to one embodiment of the present invention; 
         FIG. 2  is a graph that shows a wheel pressure while a vehicle is moving under an electronic stability control (ESC) and a wheel pressure reflecting driver&#39;s braking; 
         FIG. 3  is a view specifically illustrating an electronic control unit (ECU) in the electric brake apparatus according to one embodiment of the present invention; 
         FIG. 4  is a flowchart illustrating each operation of the control method of the electric brake apparatus according to one embodiment of the present invention; 
         FIG. 5  is a flowchart illustrating an algorithm of the control method of a brake of a vehicle according to one embodiment of the present invention; and 
         FIG. 6  is a flowchart illustrating another algorithm of a control method of the brake of the vehicle according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the embodiments, the same names and reference numerals refer to the same components, and repeated descriptions thereof will be omitted accordingly. 
       FIG. 1  is a view illustrating each component of an electric bake apparatus according to one embodiment of the present invention,  FIG. 2  is a graph that shows a wheel pressure while a vehicle is moving under an electronic stability control (ESC) and a wheel pressure reflecting driver&#39;s braking, and  FIG. 3  is a view specifically illustrating an electronic control unit (ECU) in the electric brake apparatus according to one embodiment of the present invention. 
     As illustrated in  FIG. 1 , an electric brake apparatus includes a master cylinder  20 , a reservoir  30 , wheel cylinders  40 , a pedal simulator  50 , a motor  60 , a gear unit  70 , and a pump unit  80 . 
     The master cylinder  20  is pressurized by an input rod  12  when a driver operates a brake pedal  10  and performs a function of generating a fluid pressure, the generated fluid pressure is transmitted to the pedal simulator  50 , the pedal simulator  50  transmits a reaction force via the master cylinder  20  corresponding to the fluid pressure to the brake pedal  10 , and thus the driver feels a pedaling sensation. In addition, in an emergency situation such as when no power is supplied to the entire system, the vehicle may also be braked due to a direct transmission of the fluid pressure of the master cylinder  20  to the wheel cylinders  40 . 
     Meanwhile, in a normal situation, the pump unit  80  transmits a fluid to the wheel cylinders  40 . Specifically, when a driver presses the brake pedal  10  to cause a stroke sensor  11  to detect a displacement of the brake pedal  10  and transmit the displacement to the ECU, the ECU drives the motor  60  on the basis of the displacement of the brake pedal  10 . When a rotary motion generated by the motor  60  is converted into a straight-line reciprocating motion by the gear unit  70  to press a piston in the pump unit  80 , a fluid accommodated in a chamber of the pump unit  80  is moved to the wheel cylinders  40 . 
     The reservoir  30  is a unit for storing a fluid and is configured to communicate with the master cylinder  20 , the pedal simulator  50 , and the pump unit  80  through the fluid. In addition, a hydraulic circuit  90  includes a flow path for transferring a fluid between the pump unit  80  and the wheel cylinders  40  and valves for regulating a fluid flow in the flow path. 
     Such a hydraulic circuit  90  may be divided into a first hydraulic circuit  91  and a second hydraulic circuit  92 . Specifically, the first hydraulic circuit  91  is a circuit that connects the pump unit  80  to a part of the wheel cylinders  40 , and the second hydraulic circuit  92  is a hydraulic circuit that connects the remaining pump unit  80  to the remaining part of the wheel cylinders  40 . For example, as illustrated in  FIG. 1 , a wheel cylinder  40  of rear right (RR) and front left (FL) wheels and the pump unit  80  are connected by the first hydraulic circuit  91 , and a wheel cylinder  40  of front right (FR) and rear left (RL) wheels are connected by the second hydraulic circuit  92 . 
     Meanwhile, a plurality of wheel valves  93 ,  94 ,  95 , and  96  that regulate fluid flowing between the hydraulic circuit  90  and the wheel cylinders  40  are disposed between the hydraulic circuit  90  and the wheel cylinders  40 . As illustrated in  FIG. 1 , the first wheel valve  93  may be disposed between the first hydraulic circuit  91  and the wheel cylinder of the RR wheel, the second wheel valve  94  may be disposed between the first hydraulic circuit  91  and the wheel cylinder of the FL wheel, the third wheel valve  95  may be disposed between the second hydraulic circuit  92  and the wheel cylinder of the FR wheel, and the fourth wheel valve  96  may be disposed between the second hydraulic circuit  92  and the wheel cylinder of the RL wheel. 
     An ECU  100  is a unit that performs a function of controlling driving of the motor  60  or opening and closing of the wheel valves. The ECU  100  in the electric brake apparatus according to one embodiment of the present invention controls the wheel valves and motor  60  on the basis of an input of a driver stepping on a brake pedal and a need for an ESC. 
     For example, as illustrated in  FIG. 2 , when the ECU  100  determines that the ESC is needed while a vehicle is moving, the ECU  100  first drives the motor  60  to fill the hydraulic circuit  90  with a fluid, and a pressure in the hydraulic circuit  90  is thus increased. 
     Since a current state is a state in which the ESC is being performed, a power piston generates a high pressure in the hydraulic circuit as indicated by d 1  in the graph shown in  FIG. 2 , and the target wheel is controlled. 
     When driver braking is input in such a state, the ECU  100  determines driver&#39;s intent to brake and calculates braking power of the driver braking as indicated by d 2  in the graph. Then the ECU  100  opens the wheel valves that were closed by the ESC to generate a fluid pressure as indicated by d 3  in the graph, and accordingly controls the wheels according to the calculated driver braking power. 
     Accordingly, according to one embodiment of the present invention, when braking intended by a driver and control of an ESC apparatus simultaneously occur, there are advantages in that the driver&#39;s braking intent and turning intent may be reflected and a driver&#39;s sense of strangeness may be minimized. 
     To realize the above-described technological effects, as illustrated in  FIG. 3 , the ECU  100  may specifically include a braking determination device  110 , an ESC device  120 , a motor controller  130 , and a wheel valve controller  140 . 
     The braking determination device  110  performs a function for determining the driver&#39;s intent on the basis of an output value of the stroke sensor  11  that detects a driver&#39;s pedal operation. 
     The ESC device  120  performs a function for determining a need for the ESC of the vehicle on the basis of an output from at least one sensor, for example, a lateral acceleration sensor, an acceleration sensor, a yaw rate sensor, etc., installed in the vehicle. 
     The motor controller  130  performs a function for controlling the motor  60  on the basis of one output of at least one of the braking determination device  110  and the ESC device  120 . 
     The wheel valve controller  140  controls the wheel valves on the basis of an output of at least one of the braking determination device  110  and the ESC device  120 . 
     Hereinafter, a control method of the electric brake apparatus according to one embodiment of the present invention will be described with reference to  FIGS. 4 to 6 . However, detail descriptions that are overlapped with the descriptions already described for the electric brake apparatus according to one embodiment of the present invention will be omitted.  FIG. 4  is a flowchart illustrating each operation of the control method of the electric brake apparatus according to one embodiment of the present invention,  FIG. 5  is a flowchart illustrating an algorithm of the control method of a brake of a vehicle according to one embodiment of the present invention, and  FIG. 6  is a flow chart illustrating another algorithm of a control method of the brake of the vehicle according to one embodiment of the present invention. 
     A control method of the electric brake apparatus according to one embodiment of the present invention is related to controlling the pump unit driven based on driving of the motor and a plurality of wheel cylinders that receives a fluid pressure generated by the pump unit. 
     The control method of the electric brake apparatus according to one embodiment of the present invention is mainly divided into four operations as illustrated in  FIG. 4 . 
     First, a detection for at least one of an input of a user braking and a need for an ESC of a vehicle is performed (S 100 ). 
     After operation S 100  is performed, discharging a fluid to the hydraulic circuit disposed between the pump unit and the wheel cylinder by driving the motor is performed by the ECU (S 200 ). 
     Then, controlling the plurality of wheel valves disposed between the hydraulic circuit and the wheel cylinder is performed by the ECU (S 300 ), and generating braking power for at least one of the plurality of wheels on the basis of the control of the wheel valves (S 400 ) is performed. 
     Meanwhile, a case in which the ESC is performed while a user is braking or, conversely, driver&#39;s braking intent is detected while the ESC is being performed will be specifically described with reference to  FIGS. 5 and 6 . 
     First, as illustrated in  FIG. 5 , when the ESC is needed while a driver is braking, target braking power is measured by the stroke sensor, and required braking power may be independently applied to each wheel by a non-ESC hydraulic circuit or by the control of the wheel valve based on the target braking power. 
     In addition, as illustrated in  FIG. 6 , when an input of a driver stepping on a brake pedal is detected under ESC, target braking power is measured by the stroke sensor, and required braking power may be independently applied to each wheel by a non-ESC hydraulic circuit or by the control of the wheel valve based on the target braking power. 
     As described above, a brake control system of a vehicle and a control method using the same according to one embodiment of the present invention have effects as follows. 
     First, there is an advantage of being able to reflect a driver&#39;s braking and turning intent when braking intended by a driver and ESC simultaneously occur. 
     Second, there is also an advantage of minimizing a strange feeling sensed by a driver while a driver drives a vehicle. 
     Effects of the present invention is not limited to the above-described effects, and other unmentioned effects may be clearly understood by those skilled in the art from the above descriptions. 
     The embodiments and drawings described in the specification are only examples for describing a part of a technological concept included in the present invention. Accordingly, since the embodiments disclosed in this specification are not for limiting the concept of the present invention but are for describing the concept, it is clear that the scope of the concept of the invention is not limited by the embodiments. All modifications and specific embodiments that may be easily made by those skilled in the art within the technical concept included in the specification and the drawings in the present invention fall within the scope of the appended claims.