Patent Publication Number: US-2023160486-A1

Title: Check valve and brake system including same

Description:
TECHNICAL FIELD 
     The present invention relates to a check valve and a brake system, and more particularly, to a check valve used in a brake system of a vehicle and a brake system including the same. 
     BACKGROUND ART 
     A brake system is generally intended to efficiently prevent a slip phenomenon of a wheel which may occur during braking, sudden starting or sudden acceleration of a vehicle. 
     A brake system includes a plurality of solenoid valves for controlling a braking hydraulic pressure transmitted from a master cylinder to a wheel cylinder side, and a number of check valves for preventing a reverse flow of oil, which are installed in a modulator block in which a flow path of a hydraulic circuit is formed and which operate in accordance with a braking hydraulic pressure. 
     Conventional brake systems supply a required brake pressure to a wheel cylinder by means of a vacuum booster when a driver depresses a brake pedal. However, in recent years, an electronic brake system has been used, in which a driver&#39;s braking intention is transmitted as an electrical signal from a pedal displacement sensor that senses a displacement of a brake pedal when the driver depresses the brake pedal, and a hydraulic pressure supply device that supplies a brake pressure to a wheel cylinder based on the received signal is provided. 
     An example of an electronic brake system includes Korean Patent Publication No. 10-2013-0092045. According to the disclosed document, an electronic brake system provided with a hydraulic pressure supply device operates a motor in accordance with a tread force of a brake pedal to generate a brake pressure. At this time, the braking pressure is generated by converting the rotational force of the motor into a linear motion and pressing a piston. 
     In a brake system, in order to control the flow of oil in one direction, a plurality of check valves are provided at various positions in a flow path formed in a modulator block. For example, the check valves may be provided in a flow path connecting a hydraulic pressure supply device and a reservoir, a distribution flow path of a wheel cylinder, a simulator connection flow path, or the like. 
     As is well known, a check valve is assembled in the shape of a single component while including a valve housing, a ball provided in the valve housing to open and close a flow path, an elastic member that elastically supports the ball, a retainer or a plug member that prevents the elastic member from being detached, and the like. The check valve is then installed on a brake system so that oil flows only in one direction. 
     A conventional check valve is not easy to manufacture because each component has to be manufactured through a process forming and a press scheme, and thus the manufacturing cost is high. 
     Since a plurality of check valves provided in a modulator block of a vehicle are each provided in the shape of a single component, it is necessary not only to secure holes in the modulator block by the number of check valves when applied to a brake system, but also to independently connect peripheral flow paths. 
     Accordingly, a brake system requires as much space for assembly as the number of check valves installed, which in turn increases the size of the product and adversely affects automotive parts where size and weight are important. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem 
     According to an embodiment of the present invention, a check valve which is in a simplified structure and in which a plurality of valve parts are integrally formed and a brake system including the check valve are provided. 
     Technical Solution 
     According to an aspect of the present invention, there may be provided a check valve including a plurality of valve parts in which an internal flow path is selectively open/closed by an opening/closing member, the plurality of valve parts being stacked in a line. 
     In addition, the valve housing may further include a cylinder-shaped valve housing open on one side, wherein each opening/closing member of the plurality of valve parts is received from the open one side of the valve housing. 
     In addition, the valve housing may include a housing body that is stepped along a longitudinal direction and sequentially receives the opening/closing members, and a housing cap that is engaged with the housing body. 
     In addition, the housing body may include a first body and a second body longitudinally engaged with the first body, the first and second bodies each including at least one valve part. 
     In addition, the first body and the second body may each include a body hole in which the opening/closing members selectively contact by a pressure of fluid. 
     in addition, the valve housing may include a plurality of body holes communicating between the inside and the outside, and each opening/closing member of the plurality of valve parts is provided between two adjacent body holes. 
     In addition, each valve part of the plurality of valve parts may further include a valve seat including an orifice through which fluid passes, an elastic member elastically supporting one side of the opening/closing members which is selectively in contact with the orifice, and a filter cap engaged with the valve seat to receive the opening/closing members and supporting the other side of the elastic member. 
     In addition, a valve seat of another adjacent valve part may be engaged with a filter cap of any one of the plurality of valve parts. 
     In addition, each opening/closing member of the plurality of valve parts may be arranged in the valve housing so as to pass fluid in one direction. 
     In addition, the valve housing may include a first body hole communicating between the inside and the outside, a second body hole, a third body hole, and a fourth body hole, and the plurality of valve parts may include a first valve part provided between the first and second body holes of the valve housing, a second valve part disposed between the second and third body holes, and a third valve part formed between the third and fourth body holes. 
     In addition, the first valve part, the second valve part, and the third valve part may be arranged in the valve housing so as to pass fluid in one direction. 
     in addition, the first valve part to the third valve part may each further include a valve seat having an orifice through which fluid passes, an elastic member for elastically supporting one side of the opening/closing members in selective contact with the orifice, and a filter cap for receiving the opening/closing members by being engaged with the valve seat and supporting the other side of the elastic member, and a valve seat of the adjacent second valve part may be engaged with the filter cap of the first valve part. 
     In addition, the valve housing may include a housing body provided in a cylindrical shape with one side open, and a housing cap engaged with the housing body with the first to third valve parts received in the open one side, the housing member may include a first body and a second body separated in a longitudinal direction, one of the first and second bodies may include the first valve part, and the other may include the second valve part and the third valve part. 
     In addition, the first body may include a first body hole as an orifice with which an opening/closing member of the first valve part selectively comes into contact, the second body may include a second body hole as an orifice with which an opening/closing member of the second valve part selectively comes into contact, and the third valve may include a valve seat provided with an orifice with which an opening/closing member selectively comes into contact. 
     In addition, the opening/closing members provided in at least one of the plurality of valve parts may be provided in the shape of a lip seal. 
     in addition, at least one valve part of the plurality of valve parts may include a valve seat comprising a small diameter head, a large diameter flange, and a small diameter valve body; and a filter cap engaged with the valve body, wherein the opening/closing members in the form of a lip seal are fitted into the valve member of the valve seat and are positioned between the flange and the filter cap. 
     In addition, the opening/closing members provided in at least one of the plurality of valve parts may be provided in a ball shape. 
     According to another aspect of the present invention, there may be provided a brake system including: a check valve which is provided according to claim  1 ; a reservoir which a pressurizing medium is stored; a master cylinder which is connected to the reservoir, the master cylinder having a master chamber and a master piston for discharging the pressurizing medium in response to a tread force of a brake pedal; a hydraulic pressure supply device which operates by an electrical signal to generate a hydraulic pressure; and a hydraulic control unit which has a first hydraulic circuit and a second hydraulic circuit to transmit the hydraulic pressure discharged from the hydraulic pressure supply device to wheel cylinders provided on two wheels, respectively, wherein the check valve is installed in a flow path connecting the hydraulic pressure supply device and the hydraulic control unit, and selectively transmits the hydraulic pressure of the hydraulic pressure supply device to the first hydraulic circuit or the second hydraulic circuit. 
     Advantageous Effects 
     A check valve and a brake system including the check valve according to an embodiment of the present invention may greatly improve the mass productivity of products because a plurality of valve parts are assembled in a single valve housing, thereby reducing the manufacturing cost due to a reduction in the number of parts and facilitating the assembly operation. 
     In addition, since a cheek valve and a brake system including the same according to an embodiment of the present invention simplify the structure of a valve part, the same may be manufactured by forging, which is a low cost method, and may reduce the component cost, and when applied to a vehicle, it is possible to solve the installation space constraints of the check valve and a flow path in a modular block, thereby improving the design freedom. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a view exemplifying a brake system of a vehicle in which a check valve according to a first embodiment of the present invention is used. 
         FIG.  2    is a schematic enlarged cross-sectional view showing a part of a flow path of a brake system of a vehicle in which a check valve according to a first embodiment of the present invention is used. 
         FIG.  3    is a sectional view showing a check valve according to a first embodiment of the present invention. 
         FIG.  4    is combined perspective view showing a check valve according to a first embodiment of the present invention. 
         FIG.  5    is an exploded perspective view showing a check valve according to a first embodiment of the present invention. 
         FIG.  6    is a combined sectional view showing a check valve according to a (2-1)th embodiment of the present invention. 
         FIG.  7    is a combined sectional view showing a check valve according to a (2-2)th embodiment of the present invention. 
         FIG.  8    is a combined sectional view showing a check valve according to a (2-3)th embodiment of the present invention. 
         FIG.  9    is a combined perspective view showing a check valve according to a third embodiment of the present invention. 
         FIG.  10    is a combined sectional view showing a check valve according to a third embodiment of the present invention. 
         FIG.  11    is a combined perspective view showing a check valve according to a fourth embodiment of the present invention. 
         FIG.  12    is a combined sectional view showing a check valve according to a fourth embodiment of the present invention. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Before this, the terms and words used in the specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be interpreted as meaning and concept consistent with the technical concept of the present invention based on the principle that the inventors may appropriately define the concept of terms to describe their own invention in the best manner. Therefore, it should be understood that the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the invention, and various equivalents and modifications may be made thereto at the time of filing the present application. 
       FIG.  1    is a hydraulic circuit diagram showing an electronic brake system  1000  in which a check valve according to a first embodiment of the present invention is used. 
     Referring to  FIG.  1   , an electronic brake system  1000  according to an embodiment of the present invention includes: a reservoir  1100  in which a pressurizing medium is stored; an integrated master cylinder  1200  that provides a reaction force according to the pedal effort of a brake pedal  10  to ad river and pressurizes and discharges a pressurizing medium such as brake oil received inside; a hydraulic pressure supply device  1300  that receives the driver&#39;s braking intention as an electrical signal by a pedal displacement sensor that detects the displacement of the brake pedal  10  and generates hydraulic pressure of the pressurizing medium through a mechanical operation; a hydraulic control unit  1400  for controlling the hydraulic pressure provided from a hydraulic pressure supply device  1300 ; hydraulic circuits  1510 ,  1520  having a wheel cylinder  20  for braking each wheel (RR, RL, FR, and FL) by transferring the hydraulic pressure of the pressurizing medium; a dump control unit  1800  provided between the hydraulic pressure supply device  1300  and the reservoir  1100  to control the flow of the pressurizing medium; backup flow paths  1610 ,  1620  hydraulically connecting the integrated master cylinder  1200  and the hydraulic circuits  1510 ,  1520 ; a reservoir flow path  1700  hydraulically connecting the reservoir  1100  and the integrated master cylinder  1200 , and an inspection flow path  1900  connected to the master chamber of the integrated master cylinder  1200 ; an electronic control unit (ECU, not shown) that controls the hydraulic pressure supply device  1300  and various valves based on the hydraulic pressure information and the pedal displacement information. 
     The integrated master cylinder  1200  is provided so that, when the driver applies a tread force to the brake pedal  10  for braking operation, the driver provides a reaction force thereto to provide a stable pedal feel, and at the same time, the brake pedal  10  is actuated to pressurize and discharge the pressurizing medium contained therein. 
     The highly integrated master cylinder  1200  may be arranged coaxially in one cylinder body  1210  with a simulation unit for supplying the driver with a pedal feel and a master cylinder unit for pressurizing and discharging the pressurizing medium received inside by the pedal depression force. 
     Specifically, an integrated master cylinder  1200  may include a cylinder body  1210  that has a chamber formed at the inside, a first master chamber  1220   a  that is formed on the inlet side of the cylinder body  1210  to which a brake pedal  10  is connected, a first master piston  1220  that is provided in the first master chambers  1220   a  and is displaceably provided by actuation of the brake pedal  10 , a second master piston  1230  that is disposed on a second master chamber  1230   a  on the inner side or on the front side (left side with reference to  FIG.  1   ) of the first master pistons  1220 , and a pedal simulator  1240  that provides a pedal sensation through an elastic restoring force that occurs during compression and is disposed between the first master piston  1220  and the second master piston  1230 . 
     A first master chamber  1220   a  and a second master chamber  1230   a  may be formed sequentially from the brake pedal  10  side (right side with reference to  FIG.  1   ) to the inner side (left side with reference to  FIG.  1   ), on a cylinder body  1210  of an integrated master cylinder  1200 . In addition, the first master piston  1220  and the second master piston  1230  are provided in each of the first and second master chambers  1220   a,    1230   a,  and may form a hydraulic pressure or a negative pressure in the pressurizing medium received in each chamber according to the forward and backward movements. 
     The cylinder body  1210  may include a large-diameter portion  1211  in which the first master chamber  1220   a  is formed, and the inner diameter thereof is relatively large, and a small-diameter portion  1212  in which the second master chamber  1230   a  is formed, The large-diameter portion  1211  and the small-diameter portion  1212  of the cylinder body  1210  may be integrally formed. 
     The actuation first master chamber  1220   a  may be formed inside a large diameter portion  1211 , which is an inlet side or a rear side (right side with reference to  FIG.  1   ) of the cylinder body  1410 , and a first master piston  1220  connected to the brake pedal  10  through an input rod  12  may be reciprocally received in the first master chambers  1220   a.    
     In the first master chamber  1220   a,  a pressurizing medium may be introduced and discharged through the first hydraulic pressure port  1280   a  and the second hydraulic pressure ports  1280   b,  the third hydraulic pressure port  1280   c  and the fourth hydraulic pressure port  1280   d.  The first hydraulic pressure port  1280   a  may be connected to a first reservoir flow path  1710 , hick will be described later, so that pressurizing medium flows from the reservoir  1100  into the first master chamber  1220   a,  or pressurizing medium received in the first master chamber  1220   a  may be discharged to the reservoir, and the second hydraulic pressure port is connected to the first backup flow path  1610 , so as to discharge pressurizing medium to the side of the first backup flow path. 
     In addition, the first master chamber  1220   a  is connected to the first and second branch flow paths  1910 ,  1920  of the inspection flow path  1900  described later through the third hydraulic pressure port  1280   c  and the fourth hydraulic pressure port  1280   d,  respectively, so that the pressurizing medium contained in the first master chamber  1220   a  may be discharged toward the inspection fluid path  1900  or may flow from inspection flow path  1900  into the first master chamber  1220   a.    
     The first master piston  1220  is received in the first a  1220   a,  and may be advanced (left direction with reference to  FIG.  1   ) to form a hydraulic pressure by pressurizing a pressurizing medium received in a first master chamber  1220   a,  or may be moved backward (right direction with reference to  FIG.  1   ) to create a negative pressure in the interior of the first master chamber  1220   a.  The first master piston  1220  may include a first body  1121  formed in a cylindrical shape so as to be in close contact with an inner circumferential surface of the first master chamber  1220   a,  and a first flange  1222  formed to extend in a radial direction at a rear end (a right end with reference to  FIG.  1   ), to which the input rod  14  is connected. The first master piston  1220  may be elastically supported by a first piston spring  1120   b,  which may be provided with one end supported on the front surface (left side with reference to  FIG.  1   ) of the first flange  1022  and the other end supported by the outer surface of the cylinder body. 
     The first master piston  1220  is provided with a first cut-off hole  1220   d  that communicates with the first master chamber  1220   a  and communicates with a fourth hydraulic pressure port  1280   d  and a second branch flow path  1920  in a non-operation state, that is, a preparation state before displacement occurs. Further, a first sealing member  1290   a  may be provided between the outer peripheral surface of the first master piston  1220  and the cylinder body  1210  to seal the first master chamber  1220   a  from the outside. The first sealing member  1290   a  may be provided so as to be in contact with the outer circumferential surface of the first master piston  1220  by being seated in a receiving groove formed in a recess on the inner circumferential surface thereof, thereby preventing the pressurizing medium contained in the first master chamber  1220   a  from leaking to the outside and preventing external foreign matters from flowing into the first master chamber  1220   a.  The first sealing member  1290   a  may be provided on the outermost side of the inner circumferential surface of the cylinder body  110 , that is, on the rear side (right side with reference to  FIG.  1   ) of the fourth hydraulic pressure port  1280   d  to which the later-described second branch flow path  1920  is connected. 
     A third sealing member  1290   c  may be provided between the outer peripheral surface of the first master piston  1220  and the cylinder body  1210  to block the flow of the pressurizing medium flowing into the first master chamber  1220   a  from the first branch flow path  1910  connected to the third hydraulic pressure port  1280   c.  The third sealing members  1290   c  may be respectively seated in a pair of receiving grooves which are respectively recessed in front and rear of the third hydraulic pressure port  1280   c  on the inner circumferential surface of the cylinder body  1210  and contact the outer circumferential surface of the first master piston  1220 . The pair of third sealing members  1290   c  may be provided in front of the first sealing member  1290   a  (left side with reference to  FIG.  1   ), and may allow the flow of the pressurizing medium contained in the first master chamber  1220   a  to be transmitted to the first branch flow path  1910  through the third hydraulic pressure port  1280   c,  but may block the flow of the pressurizing medium from the first branch flow path  1910  into the first master chamber  1220   a.    
     The second master chamber  1230   a  may be formed at the inside of the small diameter portion  1212 , which is the inside or the front side (left side with reference to  FIG.  1   ) on the cylinder body  1210 , and the second master piston  1230  may be reciprocally received in the second master chamber  1230   a.    
     The pressurizing medium may be introduced into and discharged from the second master chamber  1230   a  through the fifth hydraulic pressure port  1280   e  and the sixth hydraulic pressure port  1280   f.  The fifth hydraulic pressure port  1280   e  is connected to a second reservoir flow path  1720 , which will be described later, so that the pressurizing medium contained in the reservoir  1100  may flow into the second master chamber  1230   a.  In addition, the sixth hydraulic pressure port  1280   d  is connected to the second backup flow path  1620  to be described later, so that the pressurizing medium contained in the second master chamber  1230   a  may be discharged to the side of the second backup flow path  1620 , and conversely, the pressurizing medium may flow from the second backup flow path  1620  toward the side of the second master chamber  1230   a.    
     The second master piston  1230  is received in the second master chamber  1230   a,  and may form the hydraulic pressure of the pressurizing medium received in the second master chamber  1230   a  by advancing and form the negative pressure in the second master chamber  1230   a.  The second master piston  1230  may include a second body  1231  formed in a cylindrical shape so as to closely contact the inner circumferential surface of the second master chamber  1430   a,  and a second flange  1232  formed radially at a rear end portion (right end portion with reference to  FIG.  1   ) of the first body  231  and disposed inside the first master chamber. The diameter of the second flange  1232  may be larger than the inner circumferential surface diameter of a second master chamber  1230   a.  The second master piston  1230  may be elastically supported by a second piston spring  1230   b,  and the second piston spring  1230   b  may be provided so that one end thereof is supported on a front surface (a left side surface with reference to  FIG.  1   ) of the second body  1231  and the other end thereof on an inner surface of the cylindrical body  210 . 
     A second sealing member  1290   b  may be provided between the outer circumferential surface of the second master piston  1230  and the cylinder body  1210  to seal the first master chamber  1220   a  with respect to the second master chamber  1230   a.  The second sealing member  1290   b  may be provided so as to be seated in a receiving groove recessed on the inner peripheral surface of the cylinder body  1210  and to be in contact with the outer periphery of the second master piston  1230 , and may prevent the pressurizing medium contained in the first master chamber  1220   a  from leaking out to the second master chamber  1230   a  by the second sealing member  1290   b.    
     The second master piston  1230  is provided with a second cut-off hole  1230   d  that communicates with the second master chamber  1230   a  and communicates with a fifth hydraulic pressure port  280   e  and a second reservoir flow path  1720  in a non-operation state, that is, a preparation state before displacement occurs. In addition, a fourth sealing member  1290   d  may be provided between the outer peripheral surface of the second master piston  1230  and the cylinder body  1210  to block the flow of the pressurizing medium discharged from the second master chamber  1230   a  to the second reservoir flow path  1720  connected to the fifth hydraulic pressure port  1280   e.  The fourth sealing member  1290   d  may be seated in a receiving groove recessed in front of the fifth hydraulic pressure port  1280   e  (left side with reference to FIG,  1 ) on the inner circumferential surface of the cylinder body  1210 , and contact the outer circumferential surface of the second master piston  1230 . The fourth sealing member  1290   d  may be provided in front of (left side with reference to  FIG.  1   ) the second sealing member, and may allow the flow of the pressurizing medium transferred from the second reservoir flow path  172 . 0  connected to the fifth hydraulic pressure port  1380   e  to the second master chamber  1430   a,  while blocking the flow thereof transferred from a second master space  1120   a  to the first and second hydraulic pressure ports  1620   e.    
     The reciprocating-integrated master cylinder  1200  has the first master chamber  120   a  and the second master chamber  1230   a  independently of each other, so that safety in the event of failure of component elements may be ensured. For example, the first master chamber  1220   a  may be connected to one of the two wheel cylinders  21 ,  22  through a first backup flow path  1610 , described below, and the second master chamber  1230   a  may be connected to the other two wheel cylinders  23 ,  24  through a second backup flow path  1620 , described below, and thus, braking of the vehicle may be possible in the event of a problem such as a leak in any one chamber. 
     The pedal simulator  1240  may be provided between the first piston  1220  and the second master piston  1230 , and may provide a driver with a pedal feel of the brake pedal  10  by the elastic restoring force thereof. Specifically, the pedal simulator  1240  may be interposed between the front surface of the first master piston  1220  and the rear surface of second master piston  1230 , and may be made of an elastic material such as compressible and expandable rubber. The pedal simulator  1240  may include a cylindrical-shaped body that is at least partially inserted and supported on the front surface of the first master piston  1120  and a tapered portion that is inserted or supported at least partly on the rear surface of a second master piston, the tapered portion gradually decreasing in diameter toward the front (left side with reference to  FIG.  1   ). At least part of both ends of the pedal simulator  1240  may be stably supported by being inserted into the first master piston  1220 , respectively. Furthermore, it is also possible to provide a stable and familiar pedal feel to a driver by changing the elastic restoring force according to the degree of the tread force of the brake pedal  10  by the tapered portion. 
     A simulator valve  1711  is provided in the first reservoir flow path  1710  described later so that the flow of the pressurizing medium between the reservoir  1100  and the first master chamber  1220   a  may be controlled. The simulator valve  1711  may be provided as a normal closed-type solenoid valve which is normally closed and which, upon receiving an electrical signal from the electronic control unit, operates to open the valve and may be open in a normal operating mode of the electronic brake system  1000 . 
     To explain the pedal simulation operation by the integrated master cylinder  1200 , in the normal operation mode, the driver operates the brake pedal  10 , and the first cut valve  1611  and the second cut valve  1621  provided in each of the first backup flow path  1610  and the second backup flow path  1620 , which will be described later, are closed, while the simulator valve  1711  in the first reservoir flow path  1710  is open. As the operation of the brake pedal  10  proceeds, the first master piston  1220  advances, but as the second cut valve  1621  closes, the second master chamber  1230   a  closes, so that no displacement occurs in the second master piston  1230 . At this time, the pressurizing medium contained in the first master chamber  1220   a  flows along the first reservoir flow path  1710  by the closing operation of the first cut valve  1611  and the opening operation of a simulator valve  2711 . While the second master piston  1230  does not move forward, the first master piston  1220  continues to move forward and thus compresses the pedal simulator  1340 , and the elastic restoring force of the pedal simulation  1440  may be provided to the driver as a pedal feel. Then, when the driver releases the braking force of the brake pedal  10 , the first and second piston springs  1220   b,    1230   b  and the elastic restoring force of a pedal simulator  1240  cause the first, second master piston  1120 ,  230  and the pedal simulator to return to the original shape and position, and the first master chamber  1220   a  may be filled with pressurizing medium supplied from the reservoir  1710  through the first reservoir flow path  1610 . 
     Since the interior of the first master chamber  1220   a  and the second master chamber  1230   a  is always filled with pressurizing medium, as in the case of a pedal simulation, the friction between the first and second master pistons  1220  and  1230  is minimized, so that the durability of the integrated master cylinder  1200  is improved, as well as the entry of foreign substances from the outside may be blocked. 
     The homogenizer  1100  may house and store a pressurizing medium therein. The reservoir  1100  may he connected to the integrated master cylinder  1200 , the hydraulic pressure supply device  1300  described below, and each component such as a hydraulic circuit described below to supply or receive pressurizing medium. Although several reservoirs  1100  are shown with the same reference numerals in the drawings, as an example to facilitate understanding of the invention, the reservoir  1100  may be provided as a single part or as a plurality of separate and independent parts. 
     The shock absorber flow path  1700  is provided to connect the integrated master cylinder  1200  and the reservoir  1100 . 
     The reservoir flow path  1700  may include a first reservoir flow path  1710  that connects the first master chamber  1220   a  and the reservoir  1100 , and a second reservoir flow path  1720  that connects the second master chamber  1230   a  and the reservoir  1100 . To this end, one end of the first reservoir flow path  1710  may be in communication with the first master chamber  1220   a  by the first hydraulic pressure port  1280   a  of the integrated master cylinder  1200 , the other end may be communicating with the reservoir  1100 , and one end of the second reservoir flow path  1720  may be communicating with the second master chamber  1230   a  by the fifth hydraulic pressure port  1280   e  of the integrated master cylinder  1200 , and the other end may be communicating with the reservoir  1100 . In addition, as described above, the first reservoir flow path  1710  is provided with the simulator valve  1711  that opens in the normal operation mode, so that the flow of the pressurizing medium between the reservoir  1100  and the first master chamber  1220   a  through the first reservoir flow path  1710  may be controlled. 
     The brake hydraulic pressure supply device  1300  is arranged to receive an electric signal from a pedal displacement sensor that senses the displacement of the brake pedal  10  to generate the hydraulic pressure of the pressurizing medium through mechanical actuation. 
     The hydraulic pressure supply device  1300  may include a hydraulic pressure supply unit for supplying a pressure medium pressure to be transmitted to the wheel cylinder  20 , a motor (not shown) for generating a rotational force by an electric signal of a pedal displacement sensor, and a power converting unit (not shown) for converting a rotational motion of the motor into a linear motion and transmitting the linear motion to the hydraulic pressure supply unit. 
     The hydraulic pressure supply unit includes a cylinder block  1310  in which a pressurizing medium is provided so as to be able to be received, a hydraulic piston  1320  housed in the cylinder block, a sealing member  1350  provided between the hydraulic piston  1320  and the cylinder block  1350  for sealing the pressure chambers  1330 ,  1340 , and a drive shaft  1390  for transmitting the power output from the power conversion unit to the hydraulic pistons  1320 . 
     The pressure chambers  1330 ,  1340  may include a first pressure chamber  1330  located in front of the hydraulic piston  1320  (left direction of the hydraulic piston  1320  with reference to  FIG.  1   ) and a second pressure chamber  1340  located in the rear of the hydraulic piston  1320  (right direction of the hydraulic piston  1320  with reference to  FIG.  1   ). That is, the first pressure chamber  1330  is defined by the front surface of the cylinder block  1210  and the hydraulic piston  1420  so as to vary in volume according to the movement of the hydraulic pistons  1520 , and the second pressure chamber  1340  is defined by rear surfaces of the cylinder block  1310  and the hydraulic piston  1320 . 
     The first pressure chamber  1330  is connected to a first hydraulic flow path  1401 , which will be described later, through a first communication hole  1360   a  formed in the cylinder block  1310 , and the second pressure chamber  1340  is connected through a second communication hole  1360   b  formed in a cylinder block. 
     The sealing member includes a piston sealing member  1350   a  provided between the hydraulic piston  1320  and the cylinder block  1410  to seal between the first pressure chamber  1330 , and the second pressure chamber  1340 , and a drive shaft sealing member  1450   b  provided between a chive shaft  1690  of the cylinder  1710 , to seal an opening of the second and cylinder blocks  1840 . The hydraulic pressure or the negative pressure in the first pressure chamber  1330  and the second pressure chamber  1340  caused by the forward or backward movement of the hydraulic piston  1320  is sealed by the piston sealing member  1150   a  and the drive shaft sealing member  1250   b  so as not to leak, and may be transmitted to the first hydraulic flow path  1401  and second hydraulic flow paths  1502  described later. In addition, a chamber sealing member  1350   c  may be provided between the second pressure chamber  1340  and the drive shaft sealing member  1350   b,  and the chamber sealing members  155   c  may allow the flow of the pressurizing medium flowing into the first pressure chamber  1330  through the auxiliary inflow path  1850 , which will be described later, but may block the flowing of the pressurizing medium leaking out of the second pressure chamber  1340  and into the auxiliary inflow path  1850 . 
     A motor (not shown) is provided to generate a driving force of the hydraulic piston  1330  by an electric signal output from the electronic control unit (ECU). The motor may include a stator and a rotor, thereby supplying power for generating displacement of the hydraulic piston  1320  by rotating in a forward or reverse direction. The rotational angular velocity and the rotational angle of the motor may be precisely controlled by a motor control sensor. Since the motor is a well-known technique, a detailed description thereof will be omitted. 
     A power conversion unit (not shown) is provided to convert the rotational force of the motor into linear motion. As an example, the power converter may be provided with a structure including a worm shaft (not shown), a worm wheel (not shown and a drive shaft  1390 . 
     The worm shaft may be integrally formed with a rotational shaft of the motor, and a worm may be formed on an outer peripheral surface thereof to engage with the worm wheel to rotate the worm wheel. The worm wheel may be engaged with engage the drive shaft  1390  to linearly move the drive shaft  1390 , which in turn is engaged with and integrally operates with the hydraulic piston  1320 , thereby allowing the hydraulic piston  1320  to slide within the cylinder block  1310 . 
     In other words, when the displacement of the brake pedal  10  is sensed by the pedal displacement sensor, the sensed signal is transmitted to the electronic control unit, which drives the motor to rotate the worm shaft in one direction. The rotational force of the worm shaft is transmitted to the drive shaft  1390  through the worm wheel, so that the hydraulic piston  1320  connected to the driving shaft may generate a hydraulic pressure in the first pressure chamber  1330  while advancing in the cylinder block  1310 . 
     On the contrary, when the tread force of the brake pedal  10  is released, the electronic control unit drives the motor to rotate the worm shaft in the opposite direction. Thus, the worm wheel may also rotate in the opposite direction and the hydraulic piston  1320  connected to the drive shaft  1390  may generate a negative pressure in the first pressure chamber  1330  while reversing in the cylinder block  1310 . 
     The generation of the hydraulic pressure and the negative pressure in the economizer second pressure chamber  1340  may be realized by operating in the opposite direction. That is, when the displacement of the brake pedal  10  is sensed by the pedal displacement sensor, the sensed signal is transmitted to the electronic control unit, which drives the motor to rotate the worm shaft in the opposite direction. The rotational force of the worm shaft is transmitted to the drive shaft  1390  through the worm wheel, so that the hydraulic piston  1320  connected to the driving shaft may generate a hydraulic pressure in the second pressure chamber  1340  while moving backward in the cylinder block  1310 . 
     On the contrary, when the tread force of the brake pedal  10  is released, the electronic control unit drives the motor n one direction to rotate the worm shaft in one direction. Thus, the worm wheel also rotates in the opposite direction and the hydraulic piston  1320  connected to the drive shaft  1390  may generate a negative pressure in the second pressure chamber  1340  while advancing in the cylinder block  1310 . 
     As described above, the hydraulic pressure supply device  1300  may generate a hydraulic pressure or a negative pressure in each of the first pressure chamber  1330  and the second pressure chamber  1340  depending on the rotational direction of the worm shaft by driving the motor, and may determine whether to transmit the liquid pressure to implement braking or to release braking by using the negative pressure by controlling the valves. 
     For the sake of brevity, the power conversion unit according to the present embodiment is not limited to any structure as long as the power conversion unit is possible to convert the rotational movement of the motor into the linear motion of the hydraulic piston  1320 , and the same should be understood in the case of devices of various structures and types. 
     The foaming liquid pressure supply device  1300  may be hydraulically connected to the reservoir  1100  by a dump controller  1800 . The dump controller  1800  may include a first dump controller that controls a flow of pressurizing medium between the first pressure chamber  1330  and the reservoir  1100 , and a second dump processor that controls the flow of the pressurizing medium among the second pressure chamber  1340  and the reservoirs  1100 . The first dump control unit may include a first dump flow path  1810  that connects the first pressure chamber  1330  and the reservoir  1100 , a first bypass flow path  1830  that branches and then re-merges on the first dump path  2010 , and the second dump controller may include the second dump flow path  1820  that links the second pressure chamber and the reservoirs  1200  and a second bypass flow path  1840  that branch and subsequently re-joins on a second dump flow path. 
     A first dump check valve  1811  and a first dump valve  1831  that control the flow of the pressurizing medium may be provided in the first dump flow path  1810  and the first bypass flow path  1830 , respectively. The first dump check valve  1811  may be provided to allow only the flow of the pressurizing medium from the reservoir  1100  to the first pressure chamber  1330  and block the flow of the pressurizing medium in the opposite direction A first bypass flow path  1830  may be connected in parallel to the first dump check valve  1811  in the first dump flow path  1810 , and a first dump valve  1831  for controlling the flow of the pressurizing medium between the first pressure chamber  1330  and the reservoir  1100  in the first bypass flow path  1830  may be provided. In other words, the first bypass flow path  1830  may bypass and connect the front end and the rear end of the first dump check valve  1811  on the first dump flow path  1810 , and the first dump valve  1831  may be provided as a two-way solenoid valve that controls the flow of pressurizing medium between the first pressure chamber  1330  and the reservoir  1100 . The first dump valve  1831  may be provided as a normal closed-type solenoid valve that is normally in a closed state and operates to open the valve upon receiving an electrical signal from the electronic control unit. 
     A second dump check valve  1821  and a second dump valve  2841  that control the flow of the pressurizing medium may be provided in the economizer second dump flow path  220  and the second bypass flow path  1840 , respectively. The second dump check valve  1821  may be provided to allow only the flow of the pressurizing medium from the reservoir  1100  to the second pressure chamber  1330  and block the flow of the pressurizing medium in the opposite direction A second bypass flow path  1840  may be connected in parallel to the second dump check valve  1821  in the second dump flow path  1820 , and a second dump valve  1841  for controlling the flow of the pressurizing medium between the second pressure chamber  1330  and the reservoir  1100  are connected to the second bypass flow path  1840 . In other words, the second bypass flow path  1840  may bypass and connect the front end and the rear end of the second dump check valve  1821  on the second dump flow path  1820 , and the second dump valve  1841  may be provided as a two-way solenoid valve that controls the flow of pressurizing medium between the second pressure chamber  1330  and the reservoir  1100 . The second dump valve  1841  may be provided as a normal open-type solenoid valve that is normally open and operates to close the valve upon receiving an electrical signal from the electronic control unit. 
     In addition, the dump control unit  1800  may include an auxiliary inflow path  1850  that connects the reservoir  1100  and the second pressure chamber  1340  so that the pressure medium may be filled into the second temperature chamber  240 . The auxiliary inflow path  1850  may be connected to the rear (right side with reference to  FIG.  1   ) of the chamber sealing member  1350   c  on the cylinder body  1310 . As a result, the pressurizing medium flows from the reservoir  1100  into the second pressure chamber  1340  through the auxiliary inflow path  1850 , and the flow of pressurizing medium that leaks from the first pressure chamber  1330  into the additional inflow path  1840  by the chamber sealing member  1250   c  may be blocked. 
     The hydraulic control unit  1400  may be arranged to control the hydraulic pressure delivered to each wheel cylinder  20 , and the electronic control unit (ECU) is provided to control a hydraulic pressure supply device  1300  and various valves based on hydraulic pressure information and pedal displacement information. 
     The hydraulic control unit  1400  may include a first hydraulic circuit  1510  for controlling a flow of hydraulic pressure delivered to the first and second wheel cylinders  21 ,  22 , and a second hydraulic circuit for controlling the flow of the hydraulic pressure transferred to the third and fourth wheel cylinders  23 ,  24 , among the four wheel cylinders  20 , and includes a plurality of flow paths and valves for controlling hydraulic pressure transmitted from the hydraulic pressure supply device  1300  to the wheel cylinder. 
     The first hydraulic flow path  1401  may be provided to communicate with the first pressure chamber  1330 , and the second hydraulic flow path  2402  may be arranged to communicate therewith. After merging into the third hydraulic flow path  1403 , the first and second hydraulic flow paths  1201  and  1302  may be provided so as to be branched again into a fourth hydraulic flow path  2404  connected to the first hydraulic circuit  1510  and a fifth hydraulic flow paths  2505  connected to a second hydraulic circuit. 
     The sixth hydraulic flow path  1406  is provided so as to communicate with the first hydraulic circuit  1510 , and the seventh hydraulic flow path  2407  is provided to communicate therewith. After merging into the eighth hydraulic flow path  1408 , the sixth and seventh hydraulic flow paths  1206  and  1307  may be provided so as to be branched again into the ninth hydraulic flow path  2409  communicating with the first pressure chamber  1330  and the tenth hydraulic flow paths  210  communicating with a second pressure chamber  1340 . 
     A first valve  1431  for controlling the flow of the pressurizing medium may be provided in the first hydraulic flow path  1401 . The first valve  1431  may be provided as a check valve to allow flow of pressurizing medium from the first pressure chamber  1330 , but to shut off flow of the pressurizing medium in the opposite direction. The second hydraulic fluid path  1402  may also be provided with a second valve  1432  for controlling the flow of pressurizing medium, which may be provided as a non-return valve for allowing flow of the pressurizing medium out of the second pressure chamber  1340 , but for blocking flow of pressurizing medium in the opposite direction. 
     The fourth hydraulic flow path  1404  is provided so as to be branched again from the third hydraulic flow paths  1403  where the first and second hydraulic flow paths  1402 ,  1403  merge and connected to the first hydraulic circuit  1510 . A third valve  1433  for controlling the flow of the pressurizing medium may be provided in the fourth hydraulic flow path  1404 . The third valve  1433  may be provided as a check valve that allows only the flow of pressurizing medium from the third hydraulic flow path  1403  to the first hydraulic circuit  1510 , and blocks the reverse pressurizing medium flow. 
     The fifth hydraulic flow path  1405  is provided so as to be branched again from thee third hydraulic flow paths  1503  where the first and second hydraulic flow paths  1401 ,  1402  join to each other and connected to the second hydraulic circuit  1520 . A fourth valve  1434  for controlling the flow of the pressurizing medium may be provided in the fifth hydraulic flow path  1505 . The fourth valve  1434  may be provided as a check valve that allows only the flow of pressurizing medium from the third hydraulic flow path  1303  to the second hydraulic circuit  1520 , and blocks the reverse pressurizing medium flow. 
     The sixth hydraulic flow path  1406  is provided to communicate with the first hydraulic circuit  1510 , and the seventh hydraulic flow paths  1407  are provided to connect with the second hydraulic circuit  1520  and to join with the eighth hydraulic flow path  2408 . A fifth valve  1435  for controlling the flow of the pressurizing medium may be provided in the sixth hydraulic flow path  1406 . The fifth valve  1435  may be provided as a check valve that allows only the flow of pressurizing medium discharged from the first hydraulic circuit  1510 , and blocks the reverse pressurizing medium flow. Further, the seventh hydraulic flow path  1407  may be provided with a sixth valve  1436  for controlling the flow of the pressurizing medium. The sixth valve  1436  may be provided as a check valve that allows only the flow of pressurizing medium discharged from the second hydraulic circuit  1520 , and blocks the reverse pressurizing medium flow. 
     The ninth hydraulic flow path  1409  is provided so as to be branched off from the eighth hydraulic flow paths  1408  in which the sixth and seventh hydraulic flow paths  1406 ,  1407  merge and connected to the first pressure chamber  1330 . A seventh valve  1437  for controlling the flow of the pressurizing medium may be provided in the ninth hydraulic flow path  1209 . The seventh valve  1437  may be provided as a bi-directional control valve that controls the flow of the pressurizing medium delivered along the ninth hydraulic fluid path  1409 . The seventh valve  1437  may be provided as a normal closed-type solenoid valve that is normally in a closed state and that operates to open the valve upon receiving an electrical signal from the electronic control unit. 
     The tenth hydraulic flow path  1410  is provided so as to be branched off from the eighth hydraulic flow paths  1408  in which the sixth and seventh hydraulic flow paths  1406 ,  1407  merge and connected to the second pressure chamber  1340 . An eighth valve  1438  for controlling the flow of the pressurizing medium may be provided in the tenth hydraulic flow path  1510 . The eighth valve  1438  may be provided as a bi-directional control valve that controls the flow of pressurizing medium delivered along the tenth hydraulic fluid path  1410 . The eighth valve  1438  may be provided as a normal closed-type solenoid valve that is normally in a closed state and operates to open the valve upon receiving an electrical signal from the electronic control unit, similarly to the seventh valve  1437 . 
     The hydraulic control unit  400  may transmit the hydraulic pressure formed in the first pressure chamber  1330  according to the forward movement of the hydraulic piston  1320  to the first hydraulic circuit  1510  through the first, third, and fourth hydraulic lines  1401 ,  1403 , and  1404 , sequentially, and transmit the same to the second hydraulic circuit  1520  through the first and fifth hydraulic lines  1401 ,  1405 . In addition, the hydraulic pressure formed in the second pressure chamber  1340  in response to the backward movement of the hydraulic piston  1320  may be transmitted to the first hydraulic circuit  1510  through the second hydraulic flow path  1402  and the fourth hydraulic flow paths  1404  in sequence, and may be transferred to the second fluid circuit  1520  through the first, third, and fifth hydraulic flow paths  1402 ,  1403 ,  1405  in sequence. 
     As shown in  FIG.  1   , the negative pressure formed in the first pressure chamber  1330  due to the backward movement of the hydraulic piston  1320  may sequentially recover the pressurizing medium provided to the first hydraulic circuit  1510  to the second pressure chamber  1340  through the sixth hydraulic flow path  11406 , the eighth hydraulic flow paths  1208 , and the ninth hydraulic flow path  1520 . In addition, as the hydraulic piston  1320  advances, the negative pressure formed in the second pressure chamber  1340  may recover the pressurizing medium provided to the first hydraulic circuit  1510  into the first pressure chamber  1330  in sequence through the sixth hydraulic flow path  1406 , the eighth hydraulic flow paths  1608 , and the tenth hydraulic flow path  1410 , and recover the pressurizing medium provided by the second hydraulic circuit  1520  through the seventh hydraulic flow path  1407 , the eighth hydraulic flow path  1408 , and the tenth hydraulic flow path  1410 . 
     The first hydraulic circuit  1510  of the hydraulic control unit  1400  may control the hydraulic pressures of the first and second wheel cylinders  21 , which are two wheel cylinders  20  among the four wheels (RR, RL, FR, FL), and the second hydraulic circuit  1520  may control the hydraulic pressure of the third and fourth wheel cylinders  23 ,  24 , which are the other two wheel cylinders. 
     The first hydraulic circuit  1510  may receive the hydraulic pressure through the fourth hydraulic flow path  1404 , and may discharge the hydraulic fluid through the sixth hydraulic flow path  1406 . For this purpose, as shown in  FIG.  1   , the fourth hydraulic flow path  1404  and the sixth hydraulic flow paths  1406  may be provided so as to be branched into two flow paths that are connected to the first wheel cylinder  21  and the second wheel cylinders  22  after merging. In addition, the second hydraulic circuit  1520  is provided with the hydraulic pressure through the fifth hydraulic flow path  1405 , and is capable of discharging the hydraulic fluid through the seventh hydraulic flow paths  1207 , and thus, as shown in  FIG.  1   , may be provided so as to be branched into two flow paths connected to the third wheel cylinder  23  and the fourth wheel cylinders  24  after joining the fifth and seventh hydraulic flow paths  1205  and  1217 . However, the connection to the hydraulic fluid shown in  FIG.  1    is not limited to this structure as an example to facilitate understanding of the present invention, and the same should be understood when the fourth hydraulic fluid  1404  and the sixth hydraulic fluid are connected to the first hydraulic circuit  1510  side, the first wheel cylinder  21  and the second wheel cylinders  22  are independently branched and connected, and similarly, the fifth and seventh hydraulic fluids  1405 ,  1407  are connected to the second hydraulic circuit  1520  side, and the third and fourth wheel cylinders  23 ,  24  are independently branched and connected. 
     The first and second hydraulic circuits  1510 ,  1520  may each include first to fourth inlet valves  1511   a,    1511   b,    1521   a  and  15212   b  to control the flow and hydraulic pressure of the pressurizing medium delivered to the first to the fourth wheel cylinders  24 . The first to fourth inlet valves  1511   a,    1511   b,    1521   a  and  1521   b  may each be provided as a normal open-solenoid valve which is arranged on the upstream side of the first to the fourth wheel cylinder  20  and which is normally open and which operates to close the valve upon receiving an electrical signal from the electronic control unit. 
     The first and second hydraulic circuits  1510 ,  1520  may include first to fourth check valves  1513   a,    1513   b,    1523   a  and  1523   b  that are provided in parallel with respect to the first to the fourth inlet valves  1511   a,    1511   b,    1521   a,    1521   b.  The check valves  1513   a,    1513   b,    1523   a,    1523   b  may be provided in a bypass flow path connecting the front and rear sides of the first to fourth inlet valves  1511   a,    1511   b,    1521   a,    1521   b  on the first and second hydraulic circuits  1510 ,  1520 , allowing only the flow of the pressurizing medium from each wheel cylinder  20  to the hydraulic supply device  1300 , and blocking the flow thereof to the hydraulic pressure supply device  1300  from the wheel cylinder  20 . The hydraulic pressure of the pressurizing medium applied to each of the wheel cylinders  20  may be quickly extracted by the first to fourth check valves  1513   a,    1513   b,    1523   a,    1523   b  and, even when the first through fourth inlet valves  1511   a,    1511   b,    1521   a,    1521   b  do not operate normally, the hydraulic pressure in the pressurizing medium applied to the wheel cylinder  20  may be smoothly returned to the hydraulic pressure supply unit. 
     The economizer second hydraulic circuit  1520  may have first and second outlet valves  1522   a,    1522   b,  which control the flow of pressurizing medium discharged from the third and fourth wheel cylinders  23 ,  24  for improved performance upon release of the braking of the third and fourth wheel cylinders  23 ,  24 . The first and second outlet valves  152   1522   b  are provided on the discharge sides of the third and fourth wheel cylinders  23 ,  24 , respectively, to control the flow of the pressurizing medium delivered from the third or fourth wheel cylinder  23 ,  24  to the reservoir  100 . The first and second outlet valves  1522   a,    1622   b  may be provided as normal closed-type solenoid valves that operate to open when the outlet valves are normally closed and receive electrical signals from the electronic control unit. In the ABS braking mode of the vehicle, the first and second outlet valves  1522   a,    1622   b  may selectively release the hydraulic pressure of the pressurizing medium applied to the third wheel cylinder  23  and the fourth wheel cylinder  24 , and transmit the same to the reservoir  1100  side. 
     The first and second wheel cylinders  21 ,  22  of the first hydraulic circuit  1510  may be branched and connected to a first backup flow path  1610 , which will be described later, and at least one first cut valve  1611  may be provided in the first backup flow path  1610  to control the flow of pressurizing medium between the first and second wheel cylinders  21 ,  22  and the integrated master cylinder  1200 . 
     The electronic brake system  1000  according to an embodiment of the present invention may include first and second backup flow paths  1610 ,  1620  to directly supply pressurizing medium discharged from the integrated master cylinder  1200  to the wheel cylinder  20  and implement braking when normal operation is not possible due to a failure of the device or the like. The mode in which the hydraulic pressure of the integrated master cylinder  1200  is transmitted directly to the wheel cylinder  20  is referred to as an abnormal operating mode, that is, a fallback mode. 
     The first backup flow path  1610  may be provided to connect the first master chamber  1220   a  and the first hydraulic circuit  1510  of the integrated master cylinder  1200 , and the second backup flow path  1620  may also be provided for connecting the second master chamber  1230   a  and second hydraulic circuit  1520  of the combined master cylinder  1200 . 
     The first backup flow path  1610  may have one end connected to the first master chamber  1220   a  and the other end branched and connected on the first hydraulic circuit  1510  to the downstream side of the first and second inlet valves  1511   a,    1511   b,  and the second backup flow path  1620  may be connected on one end to the second master chamber  1230   a  and the opposite end connected on a second hydraulic circuit  1520  between the third inlet valve  1521   a  and first outlet valve  1522   a.  Although the second backup flow path  1620  is shown in  FIG.  1    as being connected between the third inlet valve  15211   a  and the first outlet valve  1522   a,  it should be understood that the same should be true if the second backup flow path is branched and connected to at least one of the upstream sides of the first and second outlet valves  1522   a,    1522   b.    
     The first backup flow path  1610  may be provided with at least one first cut valve  1611  for controlling the flow of the pressurizing medium in both directions, and the second backup flow path  1620  may be provided with a second cut valve  1621  for controlling flow of a pressurizing medium in both directions. The first cut valve  1611  and the second cut valve  1621  may be provided as a normal open-type solenoid valve which is normally open and which operates to close the valve when the electronic control unit receives a closing signal. 
     As shown in  FIG.  1   , a pair of the first cut valves  1611  may be provided on the first and second wheel cylinders  21 ,  22 , respectively, and may selectively release the hydraulic pressure of the pressurizing medium applied to the first wheel cylinder  21  and the second wheel cylinder  22  in the ABS braking mode of the vehicle and discharge the same to the reservoir  1100  side through the first backup flow path  1610 , the first master chamber  1220   a,  the second branch flow path  1920  described later, and the dump controller  1800 . Details thereof will be described later 
     When closing the first and second cut valves  1611 ,  1621 , it is possible to prevent the pressurizing medium of the integrated master cylinder  1200  from being directly transferred to the wheel cylinder  20  and also prevent the hydraulic pressure provided by the hydraulic pressure supply device  1300  from leaking to the integrated master cylinder  1200 . Furthermore, when the first and second cut valves  1611 ,  1621  are open, the pressurizing medium pressurized in the integrated master cylinder  1200  may be supplied directly to the side of the first hydraulic circuit  1510 ,  1520  through the first and second backup flow paths  1610 ,  1620  to implement braking. 
     The inspection flow path  1900  is provided to connect the integrated master cylinder  1200  and the hydraulic pressure supply device  1300 , and is provided so as to inspect whether or not the simulator valve  1711  leaks from various component elements attached to the integrated master cylinder  1200 . 
     The inspection flow path  1900  may have one end connected to the second pressure chamber  1340 , and the other end branched to the first branch flow path  1910  and the second branch flow path  1920 , and may be connected to each of the first master chambers  1220   a  through the third hydraulic pressure port  1280   c  and fourth hydraulic pressure port  1280   d.  One end of the inspection flow path  1900  may be directly connected to the second pressure chamber  1340  or, as shown in  FIG.  1   , may be connected through a second dump flow path,  1820 , to the first pressure chamber. 
     The first branch flow path  1910  may be provided with an inspection valve  1911  for controlling the flow of the pressurizing medium in both directions between the first master chamber  1220   a  and the second pressure chamber  1340 , and the second branch flow path  1920  may include an inspection check valve  1921  for allowing only a flow of a pressurizing medium from the first master chamber  1220  to the second pressure chamber  1340  and blocking the flow thereof in the opposite direction. The inspection valve  1911  may be provided as a normal open-type solenoid valve which is normally open and which operates to close the valve upon receiving an electrical signal from the electronic control unit. The inspection valve  1911  may be controlled in a closed state in a first inspection mode of the electronic brake system  1000  and in an open state in the second inspection mode. 
     The electronic brake system  1000  may include a circuit pressure sensor PS 1  for sensing a hydraulic pressure of a pressurizing medium provided by the hydraulic pressure supply device  1300 , and a cylinder pressure sensors PS 2  for sensing hydraulic pressure in the second master chamber  1230   a.  The circuit pressure sensor PS 1  is provided on the side of the first hydraulic circuit  1510 , so as to sense the hydraulic pressure of the pressurizing medium generated and provided from the hydraulic supply device  1300  in the inspection mode and transmitted thereto, and the cylinder pressure sensors PS 2  are provided between the second master chamber  1230   a  and the second cut valve  1621  on the second backup flow path  1620  and sense the hydraulic pressure of a pressurizing medium received in the first master chamber. In the first inspection mode described later, the pressure value information of the pressurizing medium sensed by the circuit pressure sensor PS 1  and the cylinder pressure sensor PS 2  may be sent to the electronic control unit, which compares the hydraulic pressure value sensed by a circuit pressure sensors PS 1  with the hydraulic water value sensed in the cylinder pressures sensor PS 2  to determine whether the integrated master cylinder  200  or the simulator valve  1711  leaks. The electronic brake system  1000  may also include a stroke sensor (not shown) that measures a displacement amount of the hydraulic piston  1320  of the hydraulic pressure supply device  1300 , and the stroke sensor may inspect a leak in the integrated master cylinder  1200  based on the displacement amount information of the hydraulic piston  1320  in a second inspection mode described below. 
     The electronic brake system  1000  according to an embodiment of the present invention provided as described above may include an inspection mode for inspecting whether the integrated master cylinder  1200  and the simulator valve  1711  leak, a normal operation mode for performing braking by operating normally without failure or abnormality of various component elements, and an abnormal operation mode (fallback mode) for performing vehicle braking urgently in a state where failure or failure of the brake system occurs. 
     Hereinafter, a normal operation mode of the electronic brake system  1000  according to an embodiment of the present invention will be described. 
     The normal operation mode of the electronic brake system  1000  according to an embodiment of the present invention may operate in a different manner from the first braking mode to the third braking mode as the hydraulic pressure transmitted from the hydraulic supply device  1300  to the wheel cylinder  20  increases. Specifically, the first braking mode may provide the hydraulic pressure by the hydraulic power supply  1300  to the wheel cylinder  20  primarily, the second braking mode provides the hydraulic fluid by the hydraulic pressure supply device  1300  secondarily to the wheels cylinder  20  to transmit the brake pressure higher than that in the first brake mode, and the third braking mode thirdly provides the liquid pressure by means of the fluid-pressure supply device  1300  to be transmitted the brake pressures higher than those in the second brake mode. 
     The first braking mode to the third braking mode may be changed by changing the operations of the hydraulic pressure supply device  1300  and the hydraulic control unit  1400 . By utilizing the first to third braking modes, the hydraulic pressure supply device  1300  may provide a sufficiently high hydraulic pressure of the pressurizing medium without a high-specification motor, and may further prevent unnecessary load applied to the motor. As a result, a stable braking force may be ensured while reducing the cost and weight of the brake system, and durability and operation reliability of the device may be improved. 
       FIG.  2    is a hydraulic circuit diagram schematically showing a part of the hydraulic control unit of  FIG.  1    in which the check valve according to the first embodiment of the present invention is installed. For ease of description, each of the flow paths (e.g.,  1401 ,  1403 ,  1405 , and  1407 ) and the valves  1431 ,  1434 ,  1436  may be hereinafter referred to as flow paths  101 - 104  and valves  120 ,  130 , or  140 .  FIG.  3    is a cross-sectional view showing a specific state in which the check valve of  FIGS.  2 A and  2 B  is provided in the valve mounting hole of the modulator block. 
     Since the check valve according to the present embodiment is formed by stacking a plurality of valve parts in a line as illustrated, the check valve may be easily installed in one valve mounting hole provided in a modulator block by replacing the conventional three one-way check valves provided independently on the plurality of flow paths  101 - 104  provided in the modulator block  1 . As a result, it is possible to eliminate the shortage of installation space and to reduce the number of parts due to a simple structure, thereby reducing manufacturing costs and assembly processes. 
       FIG.  4    is a combined perspective view showing the check valve according to the first embodiment of the present invention, and  FIG.  5    is an exploded perspective view showing a check valve according to a first embodiment of the present invention. 
     As shown in  FIGS.  3  to  5   , the check valve  100  according to the first embodiment may include a valve housing  110  having therein a flow path passing through the inside and the outside, and a plurality of valve parts  120 ,  130 , and  140  provided on the flow paths of the valve housing. Hereinafter, for convenience of description, in the present embodiment, the plurality of valve parts are illustrated as three valve parts including the first valve part  120 , the second valve parts  130 , and the third valve  140 , but the present invention is not limited thereto and may include at least two or more valve parts. 
     The valve housing  110  may include a housing body  111  that is provided in a cylindrical shape with one side open, and a housing cap  116  that is engaged with the opening of the housing body  111 . 
     The housing body  111  is made of a metal material, and the outer and inner shapes of the body may be machined in a forging or other manner to facilitate machining. According to the present embodiment, the housing body  111  may include a first body  111   a  and a second body  111   b.    
     The first body  111   a  is provided in a cup shape with an opening on one side, and the second body  111   b  is provided with openings on both sides, so that one side of the open sides of the second body  111   b  is assembled on the open one side of the first body  111   a.  A housing cap  116  is assembled on the other side of the second body  111 B. Thus, the housing body  111  may have a generally cylindrical shape. The ends of the first body  111   a  and the second body  111   b  that are assembled together in the longitudinal direction may be firmly joined in such a way as to be press-fitted or cocked. 
     Further, the side wall of the cup-shaped housing body  111  may be stepped along the longitudinal direction. This is to allow the plurality of valve parts  120 ,  130 ,  140  described above to be seated in the correct position when assembled in the valve housing  110 , while allowing the plurality of valve parts  120 ,  130 ,  140  to be easily assembled sequentially in the housing body  111 . For example, the plurality of valve parts  120 ,  130 ,  140  may be arranged to sequentially increase in size along the direction of the open end from the closed bottom of the housing body  111  for ease of assembly as shown. 
     The housing body  111  has, on a bottom surface of one end thereof, a first body hole  112  for communicating the inside and the outside of the valve housing  110 , and may have, at a predetermined interval along a longitudinal direction of a side wall, a second body hole, a third body hole and a fourth body hole that communicate the inside with the outside thereof. Here, the first body hole  112  is provided in the longitudinal direction of the housing body  1  and the second, third, and fourth body holes  113 ,  114 , and  115  are provided in a circumferential direction of a housing body  111 , but the present invention is not limited thereto. A plurality of second, third, and fourth body holes  113 ,  114 , and  115  may be provided at predetermined intervals along the circumferential direction of the housing body  111 . 
     The valve housing  110  provided as described above is firmly and closely engaged with a flow path (valve mounting hole) in the shape of a bore formed in the modulator block. In other words, as shown in  FIG.  3   , the first body hole  112  of the housing body  111  communicates with the first flow path  101  of the modulator block  1 , the second body hole  113  communicate with the second flow path  102 , the third body hole  114  communicates with the third flow path  103 , and the fourth body hole  115  is communicated with the fourth flow path  104 . 
     According to the present embodiment, the plurality of valve parts  120 ,  130 ,  140  may include the first valve part  120 , the second valve part  130 , and the third valve part  140 . 
     The first valve part  120  may be provided between the first flow path  101  and the second flow path  102 . Specifically, an opening/closing member (e.g., a ball) for selectively opening/closing the flow path in the valve part may be provided in a valve housing  111  so as to be located between at least two adjacent body holes, for example, a first body hole  112  communicating with the first flow path  101  and a second body hole  113  communicating with. the second flow path. 
     The first valve part  120  may include a first valve seat  121  in which an orifice through which fluid passes is formed, a first ball  122  as an opening/closing member which is selectively in contact with the orifice, a coil spring-like first elastic member  123  which is elastically supported on one side by pressure on the first ball  122 , and a first filter cap  124  which is engaged with the first valve seat  121  to receive the first ball  122  and is elastically supported on the other side of the first elastic member  123 . 
     The first ball  122  is provided so as to be able to selectively contact the inclined first valve surface  121   a  of the first valve seat  121 , the first elastic member  123  is provided to be capable of pressing the first ball  122  to the side of the second valve surface  141   a,  and the first filter cap  104  elastically presses and supports the first elastic member  123 . The first filter cap  124  may support the first elastic member  123 , and may also function as a spacer for filtering incoming foreign matter and maintaining a distance from other adjacent valve parts. Here, in the present embodiment, the ball is exemplified as an opening/closing member for selectively opening/closing the orifice, but the present invention is not limited thereto, and may be provided in various other forms such as a semicircle and an arc. When a ball is adopted, the first valve part  120  may be referred to as a first ball valve part. 
     The first valve part  120  forms one independent valve part together with the valve housing  111  by having the first valve seat  121  seated on the bottom surface and the stepped inner wall of the valve housing  111  and the first filter cap  124  engaged with the first valve seat  121  through the first ball  122  and first elastic member  123 . 
     The first valve part  120  provided as described above allows the fluid to move from the outside to the inside of the housing body  111  (or from the first body hole  112  to the second body hole  113 ) of the valve housing  10  when the hydraulic pressure of the fluid is greater than the elastic force of the first elastic member  123 , but prevents the fluid from moving. Therefore, in the first embodiment, when only the first flow path  101  is used as the inlet flow path of the fluid, the second flow path  102 , the third flow path  103 , and the fourth flow path [ 104 ] may be used as outlet flow paths of the fluids, respectively. In addition, when the first, second, and third valve parts  120 ,  130 ,  140  having a one-way flow are provided in the housing body  111  so as to pass the fluid in the same direction as in the present embodiment, if the first to third flow paths  101 - 103  are each used as an independent inlet flow path, the fourth flow path may be used as a common outlet flow path. 
     Meanwhile, the second valve part  130  may be provided between the second flow path  102  and the third flow path  103 , and may be specifically provided in the valve housing  111  between a second body hole  113  communicating with a second flow path  120  and a third bod hole  114  communicating with a third flow path  103 . 
     The second valve part  130  may include a second valve seat  131  having an orifice formed therein, a second ball  132  as an opening/closing member that selectively contacts the orifice, a third elastic member  133  in the shape of a coil spring that is elastically supported on one side by the second ball  132 , and a second filter cap  134  that is engaged with the second valve seat  131  and is elastically supported on the other side of the second elastic member  132 . 
     The second ball  132  is provided so as to be able to selectively contact the inclined second valve surface  131   a  of the second valve seat  113 , the second elastic member  132  may be provided so as to press the second ball  132  toward the first valve surface  131   a,  and the second filter cap  154  elastically presses and supports the second elastic member  132 . The second filter cap  134  may support the second elastic member  132 , and may also function as a spacer for filtering incoming foreign matter and maintaining a distance from other adjacent valve parts. Here, in the present embodiment, the ball is exemplified as a member for selectively opening/closing the orifice, but the present invention is not limited thereto and may be provided in various other forms such as a semi-circle and an arc. When a ball is adopted, the second valve part  130  may be referred to as a second ball valve part. 
     The second valve part  130  forms one independent valve part together with the valve housing  111  by the second valve seat  131  being seated on a stepped surface formed in the middle of the valve housing  111  and the second filter cap  134  being engaged with the second valve seat  131  through the second ball  132  and second elastic member  133 . At this time, the second valve seat  131  of the first valve part  120  may be supported in contact with the first filter cap  124  thereof. 
     The second valve part  130  provided as described above allows the fluid inside the valve housing  110  to move from the second body hole  113  to the third body hole  114  when the hydraulic pressure of the fluid is greater than the elastic force of the second elastic member  132 , but prevents the fluid from moving. Therefore, in the first embodiment, when the second flow path  102  is used as the inlet flow path of the fluid together with the first flow path  101 , the third flow path and the fourth flow path may be used respectively or together as the outlet flow path for the fluid. When the first, second, and third valve parts  120 ,  130 ,  140  having one-way flow are disposed in the housing body  111  in the same direction as in the present embodiment, the fourth flow path  104  may be used as a common outlet flow path if the first flow path to the third flow path are used as independent inlet flow paths. In other words, when the hydraulic pressure of the fluid flowing through the first flow path  101  is greater than the elastic force of the elastic members  123 ,  133 , and  143  of the valve part, the fluid that has passed the first valve part  120  may be transmitted to the second valve part  130  and the third valve parts  140 . 
     In short, the third valve part  140  may be provided between the third flow path  103  and the fourth flow path  104 , and specifically, is provided in the valve housing  111 , specifically, the second body  111   b,  between a third body hole  114  communicating with the third fluid path  103  and a fourth body hole  115  communicating therewith. 
     The third valve part  140  may include a third valve seat  41  having an orifice formed therein, a third ball  142  as an opening/closing member selectively in contact with the orifice, a fourth elastic member  143  in the shape of a coil spring which is elastically supported on one side by the third ball  142 , and a third filter cap  144  which is engaged with the third valve seat  141  and is elastically supported on the other side of the third Mastic member  144 . 
     The third ball  142  is provided so as to be selectively in contact with the inclined third valve surface  121   a  of the third valve seat  131 , the third elastic member  143  is configured to be able to press the third ball  142  toward the third valves surface  141   a,  and the third filter cap  144  elastically presses and supports the third elastic member  143 . The third filter cap  144  may support the third elastic member  143 , and may also function as a spacer for filtering incoming foreign matter and maintaining a distance from other adjacent valve parts. Here, in the present embodiment, the ball is exemplified as a member for selectively opening/closing the orifice, but e present invention is not limited thereto and may be provided in various other forms such as a semi-circle and an arc. When a ball is adopted, the third valve part  140  may be referred to as a third ball valve part. 
     The third valve part forms one independent valve part together with the valve housing  111  by the third valve seat  141  being seated on a stepped surface formed on the bottom side of the second body  111   b  of the valve housing  111  and the third filter cap  144  being engaged with the third valve seat  141  through the third ball  142  and the third elastic member  143  that are interposed. At this time, the third valve seat  141  of the second valve part  130  may he supported on one side by being in contact with the second filter cap  134  and on the other side by contacting the housing cap  116 . 
     The third valve part  140 , which is provided as described above, allows the fluid passing through the orifice of the third valve part  140  to move from the third body hole  114  to the fourth body hole  115 , but prevents the fluid from moving, when the hydraulic pressure of the fluid flowing in is greater than the elastic force of the second elastic member  132 . Therefore, in the present first embodiment, when the third flow path  103  is used as an inlet flow path for fluid together with flow path and the second flow path, the fourth flow path may be used as the outlet flow path of the fluid. That is, when the first, second, and third valve parts  120 ,  130 ,  140  having a one-way flow are disposed in the housing body  111  in the same direction as in the present embodiment, the fourth flow path  104  may he used as a common outlet flow path if the first flow path to the third flow path are used as independent inlet flow paths. In other words, when the hydraulic pressure of the fluid flowing through the first flow path  101  is greater than the elastic force of the first elastic member  123  of the first valve part  120  and when the hydraulic pressure of fluid that flows through the second flow path  102  is greater than the spring force of the second elastic member  132  of the second valve part  130 , the fluid that has passed the first valve part  120  is transmitted to the second valves  140 . 
     Accordingly, in the check valve  100  according to the first embodiment, when fluid flows into the interior of the modulator block through the first flow path  101  to which the first valve part  120  is connected, the second flow path  102  to each of which the second valve part  130  is connected and the third flow path  103  to which the third valve part  140  is connected among the plurality of flow paths  101 - 104  of the hydraulic control unit provided in the modulator block, it is possible to discharge the fluid to the exterior of the modulator block through the fourth flow path  104 . In addition, when only one first valve part  120  is provided in the modulator block, the first flow path  101  may be used as an inlet flow path and the second flow path  102  may be use as an outlet flow path, and when only two valve parts (the first valve part  120  and the second valve part  130 ) are provided in a modulator block, the first and second flow paths  101 ,  102  may also be used for common outlet flow paths. 
       FIG.  6    is a combined sectional view showing a check valve according to (2-1)th embodiment of the present invention. The check valve  200 A according to the (2-1)th embodiment will be described mainly in terms of differences from the check valves  100  of the above-described first embodiment, and the same reference numerals as in the first embodiment perform the same functions, and detailed description thereof will be omitted. 
     In the check valve  200 A according to the (2-1)th embodiment, unlike the first embodiment, the cylinder-shaped housing body  211  open on one side is provided integrally without being separated into two, and it is the same that a stepped portion is formed on the side wall along the longitudinal direction and the open end is engaged with the housing cap  216 . in addition, the sizes of the plurality of valve parts  120 ,  130 ,  140  sequentially increase along an end direction open from the bottom of the housing body  211 . 
     Accordingly, the housing body  211  is an integrated check valve  200 A in which the first valve part  120 , the second valve part  130 , and the third valve part  140  are sequentially seated inside, and then the first, second, and third valve parts  120 ,  130 ,  140  are stacked in a line on one housing body  211  while being hermetically assembled with the housing cap  216 . 
       FIG.  7    is a combined sectional view showing a check valve according to (2-2)th embodiment of the present invention. The check valve  20013  according to the (2-2)th embodiment will be described mainly in terms of differences from the check valve of the first embodiment, and the same reference numerals as those in the  1 st embodiment perform the same functions, and detailed description thereof will be omitted. 
     In the check valve  200 B according to the (2-2)th embodiment, the housing body  211  in the shape of a cylinder open on one side is separated into the first body  11  la and the second body  311   b  in the same manner as in the first embodiment, and at least one valve part is provided in each of the bodies  101   a,    101   b.  Specifically, one valve part  120  is provided in the first body  211   a  on the lower side in the longitudinal direction, and two valve parts  130 ,  140  are provided in a second body  211   b  on the upper side. In addition, a step is formed in the side wall of the housing body  211  along the longitudinal direction, and the housing cap  216  is engaged with the end of the open housing body  211 . In addition, the sizes of the plurality of valve parts  120 ,  130 ,  140  sequentially increase along an end direction open from the bottom of the housing body  211 . 
     Accordingly, the housing body  211  is an integrated check valve  200 B in which the first, second, and third valve parts  120 ,  130 ,  140  are sequentially seated and then hermetically assembled with the housing cap  116 , with the first, second, and third valves  120 ,  130 ,  140  disposed in a line on one housing body  211 . 
     The check valve  200 B provided as described above is relatively excellent in product stability because the check valve  200 B is less deformed against the pressure applied when the modulator block is assembled, as compared with the check valve  100  of the first embodiment. 
       FIG.  8    is a combined sectional view showing a check valve according to a (2-3)th embodiment of the present invention. The check valve  2000  according to the present (2-3)th embodiment will be described focusing on the difference from the above-described check valve  200 B in a (2-2)th embodiment, and the same reference numerals as those of the second to second embodiment perform the same functions, and detailed description thereof will be omitted. 
     In the check valve  200 C according to the (2-3)th embodiment, the housing body  211  in the shape of a cylinder open on one side is separately provided as the first body  211   a  and the second body  211   b,  and at least one valve part is provided in each of the bodies  121   a,    211   b.  Specifically, one valve part  120 ′ is provided in the lower first body  211   a  in the longitudinal direction, and two valve parts  130 ′,  140  are provided in an upper second body  211   b.  In addition, a step is formed in the side wall of the housing body  211  along the longitudinal direction, and the housing cap  216  is engaged with the end of the open housing body  211 . In addition, the sizes of the plurality of valve parts  120 ′,  130 ′,  140  sequentially increase along an end direction open from the bottom of the housing body  211 . 
     Accordingly, the housing body  211  is an integral check valve  200 C in which the first, second, and third valve parts  120 ′,  130 ′,  140  are sequentially seated and then hermetically assembled by the housing cap  116 , with the first, second, and third valve parts  120 ′,  130 ′,  140  stacked in a line on one housing body. 
     Here, in the check valve  200 C according to the (2-3)th embodiment, the first valve part  120 ′ and the second valve parts  130 ′ are each free of a valve seat, and only the third valve part  140  has the valve seat  141 . That is, the first valve part  120 ′ and the second valve parts  130 ′ function as orifices for selectively opening/closing the first and second body holes  212   a  and  212   b,  respectively, provided in the first body  211   a  and the second body  211   b  of the housing body  211 , in direct contact with the first ball  122  and the second ball  132 , which are opening/closing members. 
     Accordingly, the check valve  200 C provided as described above may further simplify the structure by reducing the number of components as compared with the check valves  200 B of the (2-2)th embodiment. 
       FIGS.  9  and  10    are an engagement perspective view of a check valve according to a third embodiment of the present invention and a sectional view showing a modulator block with which the check valve is engaged. The check valve  300  according to the third embodiment will be described mainly in terms of differences from the check valves  100 ,  200 A- 200 C of the above-described first and second embodiments, and the same reference numerals as in the first and the second embodiments perform the same functions, and detailed description thereof will be omitted. 
     The check valve  300  according to the present embodiment may be integrated by stacking the first valve part  320 , the second valve part  330 , and the third valve unit  340  and the housing cap  316  in a. line without a valve housing, and thus the check valve in which a plurality of valve units are integrated may be simply engaged with the bore (valve mounting groove) provided in the modulator block  1 . 
     For example, as shown in  FIGS.  9  and  10   , in the check valve  300  of this embodiment, a second valve seat  331  of the second valve part  330  adjacent to the first filter cap  324  of the first valve part  320  may be fastened by an engaging method such as forced press-fitting or rotation jamming, the third valve seat  341  of the third valve part  340  adjacent to the second filter cap  334  of the second valve part  330  may be fastened by an engaging method such as forced press-fitting or rotation jamming, the housing cap  316  may be finally fastened to the third filter cap  344  of the third valve unit  340  by an engaging method such as forced press-fitting or rotational engagement. 
     In addition, in the third embodiment, the first valve part  320  may employ a ball-seat type using balls as the flow path opening/closing member as described above, but the second and third valve parts  330  and  340  may adopt type using a lip seal as well as a ball seat type as the opening/closing member of the flow path. 
     Specifically, as shown in  FIG.  10   , a second lip seal  332  serving as an opening/closing member provided in the second valve part  330  may be provided between the second valve seat  331  and the second filter cap  334 . 
     The second valve seat  331  is provided in a cylindrical shape and may include a small-diameter head  321   a,  a large-diameter flange  321   b,  and a smaller-diameter valve body  321   c.  The hollow second lip seal  332  is engaged with the valve body  331   c  of the second valve seat  331 . 
     As a result, the second lip seal  332 . is fixed in position in the front-rear direction of the fluid flow while being supported on both sides by the flange  331   b  of the second valve seat  331  and the second filter cap  334 . 
     In addition, the second lip seal  332  may have a second lip sealing surface  332   a  in the shape of an inclined surface with an outer diameter extending from the upstream side to the downstream side in the fluid flow direction to allow movement of fluid while being selectively contacted by hydraulic pressure with the inner surface of the bore  2  provided in the modulator block  1 . For reference, an undescribed reference numeral  331   d  denotes a valve flow path provided in the shape of a groove between the head  331   a  and the flange  331   b  of the second valve seat  331 . 
     Similarly to the second valve part  330 , the third valve part  340  is also provided with a third valve seat  341  having a head, a flange, a valve body and a valve flow path, a third lip seal  342 , and a third filter cap  344 , and each member operates in the same manner as the second valve part  330  except for the diameter thereof, and thus a detailed description thereof is omitted. 
     Accordingly, the check valve  300  according to the third embodiment is inserted and fixed in the bore  2  of the modulator block  1 , as shown in  FIG.  10   , so that the plurality of flow paths  101  to  104 , the first valve part  320 , the second valve part  330 , and the third valve part  340  selectively communicate with each other. As a result, fluid that has flowed into the modulator block  1  independently through at least one inlet flow path of the plurality of flow paths  101 - 104  may be discharged to the outside of the modulator block  1  through another outlet flow path. 
       FIGS.  11  and  12    are a combined perspective view of a check valve according to a fourth embodiment of he present invention and a sectional view showing a modulator block with which the check valve is engaged. The check valve  400  according to the fourth embodiment will be described focusing on the difference from the check valve  300  of the third embodiment, and the same reference numerals as in the first, second, and third embodiments perform the same functions, and detailed description thereof will be omitted. 
     The check valve  400  according to the fourth embodiment has a simpler form than the check valve  300  of the third embodiment, and the second valve part  430  and the third valve part  440  include the valve blocks  435 ,  445  and the lip seals  432 ,  442 , and no filter cap is provided. 
     In addition, in the check valve  400  of the present embodiment, as shown in  FIGS.  11  and  12   , the first valve part  420  has a ball-seat structure, and the second valve part  430  and the third valve part  440  have a lip-seal structure. 
     The first valve part  420  includes the first valve seat  421 , the first ball  422 , and the first elastic member  423  as described above. However, the first ball  422  and the first elastic member  423  are supported by the first valve block  425  which is engaged with the second valve seat  421 . In other words, the first valve block  425  has a front end engaged with the second valve seat  421  and a rear end engaged with the second valve block  435  through the first block protrusion  426 . In the present embodiment, the first filter member  424  is provided in front of the fluid flow of the first valve seat  421 , and the undescribed reference numeral s denotes a seal member provided in the first valve seat  421 . 
     The second valve part  430  includes a second lip seal  432  and a second valve block  435 . The second valve block  435  includes a second block head groove  437  with which the first block protrusion  426  of the first valve part  420  is engaged in front of the fluid flow, and the second lip seal  432  is engaged with the second block protrusion  436  provided behind the fluid flow of the second valve body  435 . The second lip seal  432  may be supported on both sides by a flange of the second valve body  435  and a third valve block  445  of the third valve part  440 . The second valve block  435  according to the fourth embodiment is formed integrally with the valve seat of the third embodiment and the filter cap, and may be in the shape of one single member. 
     The third valve part  440  includes a third lip seal  442  and a third valve block  445 . The third valve block  445  includes a third block head groove  447  with which the second block protrusion  436  of the second valve part  410  is engaged in front of the fluid flow, and the third lip seal  442  is engaged with the third block protrusion  446  provided in the rear of the fluid flow of the third valve block  445 . The third lip seal  442  may be stably supported on both sides by the flange of the third valve block  445  and the housing cap  416 . 
     Accordingly, the check valve  400  according to the fourth embodiment is inserted into and fixed to the bore  2  of the modulator block  1  as shown in  FIG.  12   , so that the plurality of flow paths  101 - 104 , the first valve part  420  and the second and third valve parts  430  and  440  may selectively communicate with each other. As a result, fluid that has flowed into the modulator block  1  independently through at least one inlet flow path of the plurality of flow paths  101 - 104  may be discharged to the outside of the modulator block  1  through another outlet flow path. 
     Although the embodiments above illustrate a non-return valve configuration in which three integrally formed valve parts, e.g., a first valve part, a second valve part and a third valve part are provided in the same direction of fluid flow in one valve housing or in a bore of a modulator block, the present invention is not limited thereto and may be provided in more various forms through suitable variations and modifications. 
     In addition, although not shown in detail, the internal flow path of the valve housing and the flow path provided in the bore of the modulator block are parallel to each other as well as may be changed and modified in any suitable form such as “L”, “T” or “+”.