Patent Publication Number: US-2023141694-A1

Title: Brake apparatus for vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Korean Patent Application Number 10-2021-0151791, filed on Nov. 5, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a brake system for a vehicle. 
     BACKGROUND 
     The contents described in this section simply provide background information related to the present disclosure and do not constitute the prior art. 
     A hydraulic brake system of a vehicle selectively transfers working fluid to a plurality of wheel brake mechanisms by adjusting the opening/closing state of a plurality of solenoid valves. 
       FIG.  11    is a block diagram schematically illustrating a hydraulic circuit of a conventional brake system for a vehicle. Referring to  FIG.  11   , in the case that an inlet valve  1  is opened and an outlet valve  2  is closed, a fluid in a fluid storage unit  5  may be pressurized by a master cylinder  8  and transferred to a wheel brake  7 . This increases braking pressure of the wheel brake  7 . In the case that the inlet valve  1  is closed and the outlet valve  2  is opened, the fluid inside the wheel brake  7  is transferred to the fluid storage unit  5  and the braking pressure of the wheel brake  7  decreases. The conventional brake system for the vehicle includes both the inlet valve  1  and the outlet valve to adjust the braking pressure applied to the vehicle. 
     Meanwhile, in the case that a traction control valve  3  is opened, the fluid pressurized by the master cylinder  8  may be transferred to the wheel brake  7 . In the case that a high-pressure switch valve  4  is opened, fluid may be supplied from the fluid storage unit  5  to a pump. The pump assists the master cylinder  8  to generate hydraulic pressure corresponding to the required braking force. The brake system for the vehicle may include both the traction control valve  3  and the master cylinder  8  to control the flow of fluid flowing out from or flowing in the master cylinder  8  or the pump. 
     Such a vehicle brake system includes a plurality of solenoid valves, which results in the high manufacturing cost and the large volume. 
     SUMMARY 
     According to at least one embodiment, the present disclosure provides a brake system for a vehicle, comprising: a fluid storage unit; a fluid pressing unit; a plurality of wheel brakes configured to apply braking force to the vehicle using internal hydraulic pressure; and at least one 3-way solenoid valve configured to selectively connect the fluid storage unit, the fluid pressing unit, and the wheel brakes, wherein the 3-way solenoid valves comprises: first to third ports; an armature to which electromagnetic force is applied; a first body having one side disposed to face the armature and having a hollow therein; a second body having one side disposed to face the first body and having a hollow therein; a plunger configured such that at least a portion thereof penetrates the hollow in the first body and the second body, and one end thereof is pressed and moved by the armature; a first opening/closing flow passage configured to fluid-communicate with or block the first port and the second port; and a second opening/closing flow passage configured to fluid-communicate with or block the second port and the third port. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a hydraulic circuit diagram illustrating a brake system for a vehicle according to a first embodiment of the present disclosure. 
         FIG.  2    is a hydraulic circuit diagram illustrating a brake system for a vehicle according to a second embodiment of the present disclosure. 
         FIG.  3    is a cross-sectional view of a 3-way solenoid valve of the brake system according to the first embodiment of the present disclosure. 
         FIG.  4    is a cross-sectional view illustrating an integrated valve on a wheel side of the brake system according to the second embodiment of the present disclosure. 
         FIG.  5    is a cross-sectional view illustrating an integrated valve on a pressing unit side of the brake system according to the second embodiment of the present disclosure. 
         FIG.  6    is a hydraulic circuit diagram illustrating a flow path of a fluid in the case that braking pressure of the brake system according to the first embodiment of the present disclosure is increased. 
         FIG.  7    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that braking pressure of the brake system according to the first embodiment of the present disclosure is decreased. 
         FIG.  8    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that hydraulic pressure is selectively supplied to some of wheel brakes according to the first embodiment of the present disclosure. 
         FIG.  9    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that a second pump of the brake system according to the first embodiment of the present disclosure is driven. 
         FIG.  10    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that a pump of the brake system according to the second embodiment of the present disclosure is driven. 
         FIG.  11    is a block diagram schematically illustrating a hydraulic circuit of a conventional brake system for a vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     In view of the above, the present disclosure provides a brake system for a vehicle which includes a 3-way solenoid valve to reduce the number of solenoid valves mounted to the brake system. 
     The objects to be achieved by the present disclosure are not limited to the above-mentioned objects, and other objects not mentioned may be clearly understood by those skilled in the art from the following description. 
     Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, like reference numerals preferably designate like elements, although the elements are shown in different drawings. Further, in the following description of some embodiments, a detailed description of related known components and functions when considered to obscure the subject of the present disclosure will be omitted for the purpose of clarity and for brevity. 
     Additionally, alphanumeric codes such as first, second, i), ii), (a), (b), etc., in numbering components are used solely for the purpose of differentiating one component from the other but not to imply or suggest the substances, the order, or sequence of the components. Throughout this specification, when parts “include” or “comprise” a component, they are meant to further include other components, not excluding thereof unless there is a particular description contrary thereto. The terms such as ‘unit,’ ‘module,’ and the like refer to one or more units for processing at least one function or operation, which may be implemented by hardware, software, or a combination thereof. 
     In the present disclosure, the connection of the components means that the components are fluidly connected. 
       FIG.  1    is a hydraulic circuit diagram illustrating a brake system for a vehicle according to a first embodiment of the present disclosure. 
       FIG.  2    is a hydraulic circuit diagram illustrating a brake system for a vehicle according to a second embodiment of the present disclosure. 
     Referring to  FIGS.  1  and  2   , a brake system for a vehicle  100  or  200  according to the first or second embodiment of the present disclosure includes all or part of fluid storage units  120  and  130 , or  220  and  230 , fluid pressing units  150  and  160 , or  250  and  260 , wheel brakes w 1  or w 2 , 3-way solenoid valves  170 , or  270  and  280 , traction control valves TCV 1  and TCV 2 , high pressure switch valves HSV 1  and HSV 2  and electronic parking brakes EPB 1   a  and EPB 1   b , or EPB 2   a  and EPB 2   b.    
     The wheel brakes w 1  and w 2  are configured to apply a braking force to the vehicle using an internal hydraulic pressure. The wheel brakes w 1  and w 2  may be caliper brakes or drum brakes. The wheel brakes w 1  or w 2  of the brake system  100  or  200  may include a front left wheel brake FL 1  or FL 2 , a front right wheel brake FR 1  or FR 2 , a rear left wheel brake RL 1  or RL 2 , and a rear right wheel brake RR 1  or RR 2 . Each of the wheel brakes w 1  or w 2  may be connected to the fluid storages units  120  and  130  or  220  and  230 , and the fluid pressing units  150  and  160  or  250  and  260  with the 3-way solenoid valves  170  or  270  and  280  interposed therebetween. In the case that the fluid pressurized by the fluid pressing units  150  and  160  or  250  and  260  is transferred to the wheel brakes w 1  or w 2 , the hydraulic pressure inside the wheel brakes w 1  or w 2 ) increases. Accordingly, the braking pressure applied to the wheels by the wheel brakes w 1  or w 2  increases. In the case that the fluid inside the wheel brakes w 1  or w 2  is transferred to the fluid storages units  120  and  130  or  220  and  230 , the hydraulic pressure inside the wheel brakes w 1  or w 2  decreases. As a result, the braking pressure applied to the wheels by the wheel brakes w 1  or w 2  is reduced. In the case that the hydraulic pressure inside the wheel brakes w 1  or w 2  is maintained, the braking pressure is maintained. 
     The fluid storage units  120  and  130  or  220  and  230  are configured to store fluid. Fluid on the sides of the fluid storage units  120  and  130  or  220  and  230  may be supplied to the fluid pressing units  150  and  160  or  250  and  260 . The fluid storage units  120  and  130  or  220  and  230  may include an oil reservoir  120  or  220  and/or accumulator  130  or  230 . 
     The fluid inside the oil reservoir  120  or  220  may be transferred to the wheel brakes w 1  or w 2  through the fluid pressing units  150  and  160  or  250  and  260 . The inlets of pumps  160  or  260  and the wheel brakes w 1  or w 2  may be connected in parallel to the oil reservoir  120  or  220 . A master cylinder  150  or  250  may be connected in series between the oil reservoir  120  or  220  and the wheel brakes w 1  or w 2 . The oil reservoir  120  or  220  may include a first reservoir chamber  121  or  221  and a second reservoir chamber  122  or  222 . A first hydraulic chamber  151  or  251  may be connected in series between the first reservoir chamber  121  or  221  and the wheel brakes (w 1  or w 2 ), and a second hydraulic chamber  152  or  252  may be connected in series between the second reservoir chamber  122  or  222  and the wheel brakes w 1  or w 2 . Fluid on the side of the first reservoir chamber  121  or  221  may be supplied to a first pump  161  or  261  through the first hydraulic chamber  151  or  251 . The fluid on the side of the second reservoir chamber  122  or  222  may be supplied to a second pump  162  or  262  through the second hydraulic chamber  152  or  252 . 
     The accumulators  130  or  230  are configured to receive fluid from the wheel brakes w 1  or w 2 ) in the case that the braking pressure is reduced. The brake system  100  or  200  may include a first accumulator  131  or  231  and a second accumulator  132  or  232 . The first accumulator  131  or  231  may be connected to the first pump  161  or  261 , the front left wheel brakes FL 1  or FL 2 , and the rear right wheel brakes RR 1  or RR 2 , and the second accumulator  132  or  232  may be connected to the second pump  162  or  262 , the right front wheel brakes RR 1  or RRL 2  and the rear left wheel brake RL 1  or RL 2 . The accumulators  130  or  230  are connected to the inlets of the pumps  160  or  260 , and the fluid transferred from the accumulators  130  or  230  to the pumps  160  or  260  may be pressurized in the pumps  160  or  260 . 
     The fluid pressing units  150  and  160  or  250  and  260  are configured to press the fluid. The fluid pressing units  150  and  160  or  250  and  260  are configured to form hydraulic pressure corresponding to a braking signal. Here, the braking signal may be a signal corresponding to an input amount of pedals  153  or  253  by a driver or a deceleration signal provided by an autonomous driving system. The fluid pressing units  150  and  160  or  250  and  260  may include all or part of a master cylinder  150  or  250  and pumps  160  or  260 . The master cylinder  150  or  250  may include a pedal  153  or  253 , a first hydraulic chamber  151  or  251 , and a second hydraulic chamber  152  or  252 . The front left wheel brake FL 1  or FL 2  and the rear right wheel brake RR 1  or RR 2  are connected in parallel to the first hydraulic chamber  151  or  251 , and fluid pressurized by the first hydraulic chamber  151  or  251  may be transferred to the front left wheel brake FL 1  or FL 2  and the rear right wheel brake RR 1  or RR 2 . The front right wheel brake FR 1  or FR 2  and the rear left wheel brake RL 1  or RL 2  are connected in parallel to the second hydraulic chamber  152  or  252 , and fluid pressurized by the second hydraulic chamber  152  or  252  may be transferred to the front right wheel brake FR 1  or FR 2  and the rear left wheel brake RL 1  or RL 2 . However, the present disclosure is not limited to such a connection relationship. For example, the brake systems  100  or  200  according to one embodiment of the present disclosure may be configured such that each of the wheel brakes w 1  or w 2  receives all of the fluid pressurized by the first hydraulic chamber  151  or  251  and the second hydraulic chamber  152  or  252 . 
     The pumps  160  or  260  may be configured to assist the master cylinder  150  or  250  and to generate braking hydraulic pressure in the case that the braking hydraulic pressure formed in the master cylinder  150  or  250  is not sufficient to form the required braking force. In the brake system  100  or  200  of an autonomous vehicle, the master cylinder  150  or  250  that receives pedal pressure of a driver is not mounted, and only the pumps  160  or  260  may be mounted. The pumps  160  or  260  may generate hydraulic pressure corresponding to a deceleration signal provided by the autonomous driving system. The brake systems  100  or  200  may include the first pump  161  or  261  and the second pump  162  or  262 . The front left wheel brake FL 1  or FL 2  and the rear right wheel brake RR 1  or RR 2  are connected in parallel to the first pump  161  or  261 , and fluid pressurized by the first pump  161  or  261  may be transferred to the front left wheel brake FL 1  or FL 2  and the rear right wheel brake RR 1  or RR 2 . The front right wheel brake FR 1  or FR 2  and the rear left wheel brake RL 1  or RL 2  are connected in parallel to the second pump  162  or  262 , and fluid pressurized by the second pump  162  or  262  may be transferred to the front right wheel brake FR 1  or FR 2  and the rear left wheel brake RL 1  or RL 2 . However, the present disclosure is not limited to such a connection relationship. For example, the brake system  100  or  200  according to one embodiment of the present disclosure may be configured such that each of the wheel brakes w 1  or w 2  receives all of the fluid pressurized from the first pump  161  or  261  and the second pump  162  or  262 . The pumps  160  or  260  of the present disclosure may be a motor pump configured to be pressed in a radial direction by an eccentric shaft (not shown) of a motor  163  or  263 , or may be a gear pump including a driving gear (not shown) that rotates in combination with a rotation shaft of the motor  163  or  263  and a driven gear (not shown) that rotates in engagement with the driving gear. 
     The brake system  100  or  200  includes all or part of three-way solenoid valves  170  or  270  and  280 , traction control valves TCV 1  and TCV 2 ), and a high-pressure switch valves HSV 1  and HSV 2 . The 3-way solenoid valves  170  or  270  and  280 , the traction control valves TCV 1  and TCV 2 , and the high-pressure switch valves HSV 1  and HSV 2  are configured to change a path through which fluid flows and/or the amount of fluid flowing in the flow path in the brake system  100  or  200  in response to a valve control signal. The 3-way solenoid valves  170  or  270  and  280 , the traction control valves TCV 1  and TCV 2 , and the high-pressure switch valves HSV 1  and HSV 2  may be configured to change their opening and closing states depending on the magnitude of current applied thereto. 
     Referring to  FIG.  1   , in the brake system for a vehicle according to the first embodiment of the present disclosure, traction the control valves TCV 1  and TCV 2  are installed on flow paths connecting the master cylinder  150  and the wheel brakes w 1 . The first traction control valve TCV 1  may be connected to the first hydraulic chamber  151 , the front left wheel brake FL 1  and the rear right wheel brake RR 1 , and the second traction control valve TCV 2  may be connected to the second hydraulic chamber  152 , the front right wheel brake FR 1 , and the rear left wheel brake RL 1 . The traction control valves TCV 1  and TCV 2  regulate the flow of fluid transmitted from the master cylinder  150  to the wheel brakes w 1 . The traction control valves TCV 1  and TCV 2  may be a normal open type valve which opens the flow path when no current is applied to a coil (not illustrated). High pressure switch valves HSV 1  and HSV 2  are installed in flow paths connecting the fluid storage units  120  and  130  and the inlets of the pumps  160 , respectively. The high-pressure switch valves HSV 1  and HSV 2  may be installed in the flow paths connecting the inlets of the pumps  160  and the oil reservoir  120 , respectively. A first high pressure switch valve HSV 1  may be connected to the first hydraulic chamber  151  and the first pump  161 , and a second high pressure switch valve HSV 2  may be connected to the second hydraulic chamber  152  and the second pump  162 . The high-pressure switch valves HSV 1  and HSV 2  regulate the flow of fluid transferred from the fluid storage units  120  and  130  to the inlets of the pumps  160 . The high-pressure switch valves HSV 1  and HSV 2  may be a normal close type valve that closes the flow path when no current is applied to a coil. 
     Referring to  FIG.  1  or  2   , the electronic parking brakes EPB 1   a  and EPB 1   b  or EPB 2   a  and EPB 2   b  may be mounted on the rear wheels. The electronic parking brakes are configured to generate a braking force to assist the wheel brakes of the present disclosure. 
       FIG.  3    is a cross-sectional view of the 3-way solenoid valve of the brake system for a vehicle according to the first embodiment of the present disclosure. In the present disclosure, a longitudinal direction of the 3-way solenoid valve  170  is referred to as a Y-axis direction. Among the directions illustrated in the drawings, an upward direction is referred to as a ‘positive Y direction’ and a downward direction is referred to as a ‘negative Y direction’. 
     Referring to  FIG.  3   , the 3-way solenoid valve  170  according to the first embodiment of the present disclosure includes all or part of first to third ports  175 _ a  to  175 _ c , first and second opening/closing flow passages  179 _ a  and  179 _ b , first and second bodies  173  and  174 , a coil (not shown), an armature  171 , a plunger  172 , a sealing member  176 , first and second fluid control units  177 _ a  and  177 _ b , an elastic member  177 _ e , and a check valve  178 . 
     The armature  171  is configured to form an electromagnetic force corresponding to the magnitude of a current applied to the coil. The coil may be disposed to surround an outer peripheral surface of the armature  171 . The electromagnetic force formed by the armature  171  acts on the armature  171  to move the armature  171  toward the first body  173 . As the electromagnetic force formed on the armature  171  increases, the armature  171  and the first body  173 _ b  ecome closer to each other. Hereinafter, the electromagnetic force formed by the armature  171  is simply referred to as an ‘electromagnetic force. 
     The first body  173  is disposed such that one side thereof faces the armature  171  and has a hollow (i.e., first hollow) therein. The second body  174  is disposed such that one side thereof faces the other side of the first body  173  and has a hollow (i.e., second hollow) therein. The plunger  172  slides in the hollows of the first and second bodies  173  and  174  and may linearly move in the Y-axis direction. A groove disposed or formed at a lower end of the first body  173  and an upper surface of the second body  174  may form an outer peripheral surface of the flow path configured to connect the first port  175 _ a , the second port  175 _ b , or the third port  175 _ c  to the hollow inside the second body  174 . On the other hand, a groove disposed or formed at an upper end of the second body  174  and a lower surface of the second body  174  may be configured to connect the first port  175 _ a , the second port  175 _ b , or the third port  175 _ c  to the hollow inside the second body  174 . A concave groove portion  173 _ a  is formed on the lower surface of the first body  173 , and at least a portion of the second body  174  is accommodated in the groove portion  173 _ a . The 3-way solenoid valve  170  configured in this way has a shorter length and a simpler shape than a conventional 3-way solenoid valve, so that the volume of the brake system can be reduced and the manufacturing cost thereof can be lowered. A flange portion  173 _ b  is formed at the lower end of the first body  173 . 
     At least a portion of the plunger  172  is configured to penetrate the hollow inside the first body  173  and the hollow inside the second body  174 . One end surface of the plunger  172  faces the armature  171 . The plunger  172  and the armature  171  have cylindrical shapes having the same center line, and the plunger  172  may be disposed to contact a lower end surface of the armature  171 . The other end surface of the plunger  172  faces a flow path control assembly  177 . The flow path control assembly  177  may include the first fluid control unit  177 _ a  that opens and closes the first opening/closing flow passage  179 _ a , and may be disposed such that the lower end surface of the plunger  172  faces the first fluid control unit  177 _ a . The plunger  172  is configured to move by the armature  171  pressing one end of the plunger  172 . The armature  171  moves toward the first body  173 _ b  y electromagnetic force to press the plunger  172  in the negative Y direction. In the case that the plunger  172  is pressed in the negative Y direction, the first fluid control unit  177 _ a  is pressed in the negative Y direction. Hereinafter, a force of the plunger  172  pressing the first fluid control unit  177 _ a  is referred to as a pressing force. 
     The lower end of the plunger  172  may be disposed to penetrate a portion of the flow path control assembly  177 . The elastic member  177 _ e  is disposed inside the flow path control assembly  177 . Due to this arrangement, when the armature  171  presses the plunger  172 , the plunger  172  may press the elastic member  177 _ e . The plunger  172  applies a pressing force corresponding to the electromagnetic force formed by the armature  171  to the elastic member  177 _ e . A cross-sectional area of a lower portion of the plunger  172  may be smaller than a cross-sectional area of an upper portion of the plunger  172  to penetrate a portion of the flow path control assembly  177 . Here, the cross-sectional area refers to a cross-sectional area in a plane perpendicular to the Y-axis. 
     The sealing member  176  is disposed between the flow path control assembly  177  and the second body  174 . The sealing member  176  is in close contact with an outer peripheral surface of an upper housing  177 _ c  and an inner peripheral surface of the second body  174  to prevent the fluid from flowing between the flow path control assembly  177  and the second body  174 . The fluid may move only through a space within the flow path control assembly  177 . 
     The flow path control assembly  177  is disposed inside the second body  174 . The flow path control assembly  177  includes all or part of a first fluid control unit  177 _ a , housings  177 _ c  and  177 _ d , an elastic member  177 _ e , and a second fluid control unit  177 _ b.    
     The first fluid control unit  177 _ a  is configured to open or close the first opening/closing flow passage  179 _ a  depending on the magnitude of the pressing force. The first fluid control unit  177 _ a  is disposed in contact with the lower end of the plunger  172  and the upper end of the elastic member  177 _ e  in the flow path control assembly  177 . When the plunger  172  is pressed by the armature  171 , the first fluid control unit  177 _ a  in contact with the lower end of the plunger  172  is pressed in the negative Y direction by the plunger  172 . When the plunger  172  presses the first fluid control unit  177 _ a  with a sufficient force, the first fluid control unit  177 _ a  moves toward the elastic member  177 _ e  to open the first opening/closing flow passage  179 _ a . As shown in  FIG.  3   , the first fluid control unit  177 _ a  may be formed in a sphere shape, but is not limited thereto and may be formed in any shape which is able to be disposed in the housings  177 _ c  and  177 _ d  and close the first opening/closing flow passage  179 _ a.    
     The housings  177 _ c  and  177 _ d  are configured to move linearly in the Y-axis direction in the first and second bodies  173  and  174 . Fluid outside the housings  177 _ c  and  177 _ d  may be introduced into the housings  177 _ c  and  177 _ d  through orifices formed in the housings  177 _ c  and  177 _ d . An opening is formed in an upper portion of the housings  177 _ c  and  177 _ d  such that a portion of the plunger  172  may penetrate therethrough. The housings  177 _ c  and  177 _ d  may include an upper housing  177 _ c  and a lower housing  177 _ d  as illustrated in  FIG.  3   , but may be integrally formed. 
     The elastic member  177 _ e  may be disposed inside the housings  177 _ c  and  177 _ d , and may be disposed such that one end thereof contacts the first fluid control unit  177 _ a  and the other end thereof contacts a lower surface of the housings  177 _ c  and  177 _ d . The elastic member  177 _ e  may provide an elastic force to the first fluid control unit  177 _ a  and the lower housing  177 _ d . The magnitude of the elastic force of the elastic portion  177 _ e  corresponds to the magnitude of the pressing force. When the elastic member  177 _ e  is pressed in the negative Y direction by the first fluid control unit  177 _ a , the housings  177 _ c  and  177 _ d  are pressed in the negative Y direction. 
     The second fluid control unit  177 _ b  may be disposed at an outer lower end of the housings  177 _ c  and  177 _ d . The second opening/closing flow passage  179 _ b  is opened or closed as the second fluid control unit  177 _ b  moves in the Y-axis direction from an upper end of the second opening/closing flow passage  179 _ b.    
     The 3-way solenoid valve  170  may include a check valve  178  that allows fluid to flow only in one direction. Specifically, the check valve  178  allows the fluid to flow from the second port  175 _ b  to the third port  175 _ c  only. The check valve  178  may be disposed below the 3-way solenoid valve  170 . The check valve  178  is formed such that the fluid flows only in the direction from the second port  175 _ b  to the third port  175 _ c , which replaces the role of a check valve disposed in a conventional inlet valve. 
     The first port  175 _ a  and the second port  175 _ b  may be formed on a side surface of the 3-way solenoid valve  170 . The third port  175 _ c  may be formed in a lower portion of the 3-way solenoid valve  170 . However, the first to third ports  175 _ a  to  175 _ c  of the present disclosure are not limited to the above-described configuration and connection relationship. A fluid introduced into a portion of the first to third ports  175 _ a  to  175 _ c  may flow through the valve chamber D to another portion of the first to third ports  175 _ a  to  175 _ c.    
     In at least a part of the 3-way solenoid valves  170  according to the first embodiment of the present disclosure, the first port  175 _ a  is connected to the fluid storage units  120  and  130 , the second port  175 _ b  is connected to the wheel brakes w 1 , and the third port  175 _ c  is connected to the outlets of the fluid pressing units  150  and  160 . Referring to  FIG.  1   , in at least a part of the 3-way solenoid valves  170  according to the first embodiment, the first port  175 _ a  may be connected to the accumulator  130 , the second port  175 _ b  may be connected to the wheel brakes w 1 , and the third port  175 _ c  may be connected to the outlets of the pumps  160 . In the present disclosure, the 3-way solenoid valve  170  connected in this way is referred to as a wheel-side integrated valve  170 . The brake system  100  may include a front left wheel-side integrated valve  170 _ a , a front right wheel-side integrated valve  170 _ b , a rear left wheel-side integrated valve  170 _ c , and a rear right wheel-side integrated valve  170 _ d . The front left and rear right wheel-side integrated valves  170 _ a  and  170 _ d  may be connected to the first accumulator  131 , the first pump  161 , and the first hydraulic chamber  151 , and the front right and rear left wheel-side integrated valves  170 _ b  and  170 _ c  may be connected to the second accumulator  132 , the second pump  162 , and the second hydraulic chamber  152 . Each wheel-side integrated valve  170  functions as both an inlet valve and an outlet valve. 
     The magnitude of the electromagnetic force may be adjusted by adjusting the magnitude of a current applied to the 3-way solenoid valve  170 . By adjusting the magnitude of the electromagnetic force, opening and closing of the first opening/closing flow passage  179 _ a  and the second opening/closing flow passage  179 _ b  may be adjusted. Here, the first to third electromagnetic forces are preset values, which may be experimentally obtained and stored in a memory of a controller in the form of a look-up table (LUT). Each of the first to third electromagnetic forces may be a value determined within a predetermined range. The second electromagnetic force is greater than the first electromagnetic force, and the third electromagnetic force is greater than the second electromagnetic force. 
     In the case that no current is applied to the 3-way solenoid valve  170 , no electromagnetic force is applied to the armature  171 . When no electromagnetic force is applied to the armature  171 , the armature  171  does not press the plunger  172 . The second opening/closing flow passage  179 _ b  can be opened and closed due to a pressure difference between the second and third ports  175 _ b  and  175 _ c  and the first port  175 _ a . Specifically, when no electromagnetic force is applied to the armature  171 , the armature  171  does not move toward the first body  173 . Accordingly, the plunger  172  does not press the flow path control assembly  177 . In this case, the first fluid control unit  177 _ a  is pressed upward by the elastic force of the elastic member  177 _ e  to close the first opening/closing flow passage  179 _ a.    
     The fluid introduced into the second port  175 _ b  and the third port  175 _ c  presses a first area X 1  in the positive Y direction, and the second opening/closing flow passage  179 _ b  is opened. The fluid pressurized in the fluid pressing units  150  and  160  sequentially passes through the second opening/closing flow passage  179 _ b  and the second port  175 _ b  to be transferred to the wheel brakes w 1 . When the pressure of the fluid pressing units  150  and  160  is released, the second opening/closing flow passage  179 _ b  is opened to allow the fluid to flow from the second port  175 _ b  to the third port  175 _ c  so that the pressure of the wheel brakes w 1  is decreased. When the fluid flows from the second port  175 _ b  toward the third port  175 _ c , the fluid may also flow through the check valve  178 . As a result, in the case that no current is applied to the coil, the 3-way solenoid valve  170  opens the second opening/closing flow passage  179 _ b  between the second port  175 _ b  and the third port  175 _ c , and closes the first opening/closing flow passage  179 _ a  between the first port  175 _ a  and the second port  175 _ b.    
     When the first opening/closing flow passage  179 _ a  of the wheel-side integrated valve  170  is closed and the second opening/closing flow passage  179 _ b  is opened, hydraulic pressure formed in the fluid pressing units  150  and  160  is transmitted to the wheel brakes w 1 , and the fluid in the wheel brakes w 1  is not transferred to the accumulator  130 . Such a fluid flow path corresponds to a fluid flow path in the case that the inlet valve is opened and the outlet valve is closed in the conventional brake system for a vehicle. 
     When a second current corresponding to the second electromagnetic force is applied to the 3-way solenoid valve  170 , the second electromagnetic force is applied to the armature  171 . The second electromagnetic force is greater than the sum of the force applied by the fluid introduced through the third port  175 _ c  to the flow path control assembly  177  and the force applied by the fluid introduced through the second port  175 _ b  to the flow path control assembly  177 . Here, the force applied by the fluid introduced through the third port  175 _ c  to the flow path control assembly  177  is caused by the pressure applied by the fluid introduced through the third port  175 _ c  to a third area. The force applied by the fluid introduced through the second port  175 _ b  to the flow path control assembly  177  is caused by the pressure applied by the fluid introduced through the second port  175 _ b  to the first area X 1  and the pressure applied to the third area X 3 . In addition, the second electromagnetic force is smaller than the sum of the force applied by the fluid introduced through the second port  175 _ b  to a second area X 2  and the elastic force of the elastic member  177 _ e.    
     The armature  171  to which the second electromagnetic force is applied indirectly presses the second fluid control unit  177 _ b  to close the second opening/closing flow passage  179 _ b . The force of the armature  171  with the second electromagnetic force pressing the elastic member  177 _ e  is not large enough to deform the elastic member  177 _ e , and thus the first opening/closing flow passage  179 _ a  is also closed. Here, the indirect pressing of the armature  171  means that the plunger  172  moves in the negative Y direction due to the electromagnetic force of the armature  171 , and the plunger  172  presses the flow path control assembly  177 . When the second electromagnetic force is applied to the armature  171 , a gap between the armature  171  and the first body  173  decreases. In the case that the second electromagnetic force is formed in the armature  171 , all of the first and second opening/closing flow passages  179 _ a  and  179 _ b  are closed. 
     When all of the first and second opening/closing flow passages  179 _ a  and  179 _ b  of the wheel-side integrated valve  170  are closed, the hydraulic pressure formed in the fluid pressing units  150  and  160  is not transmitted to the wheel brakes w 1 . The fluid of the wheel brakes w 1  is not transferred to the accumulator  130 . As a result, the hydraulic pressure in the wheel brakes w 1  is maintained. Such a fluid flow path corresponds to a fluid flow path in the case that both the inlet valve and the outlet valve are closed in the conventional brake system for a vehicle. 
     When a third current corresponding to the third electromagnetic force is applied to the 3-way solenoid valve  170 , the third electromagnetic force corresponding to the third current is applied to the armature  171 , and the armature  171  presses the plunger  172 . The third electromagnetic force is set to be greater than the sum of the force applied by the fluid introduced through the second port  175 _ b  to the second part X 2  and the elastic force of the elastic member  177 _ e . The armature  171  to which the third electromagnetic force is applied indirectly presses the second fluid control unit  177 _ b  to close the second opening/closing flow passage  179 _ b . In addition, the armature  171  indirectly presses the elastic member  177 _ e  to be compressed. As the elastic member  177 _ e  is compressed, the first opening/closing flow passage  179 _ a  is opened. As a result, in the case that the third electromagnetic force is applied to the armature  171 , the first opening/closing flow passage  179 _ a  is opened and the second opening/closing flow passage  179 _ b  is closed. 
     When the first opening/closing flow passage  179 _ a  of the wheel-side integrated valve  170  is opened and the second opening/closing flow passage  179 _ b  is closed, hydraulic pressure formed in the fluid pressing units  150  and  160  is not transmitted to the wheel brakes w 1 , and the fluid in the wheel brakes w 1  sequentially passes through the second port  175 _ b  and the second port  175 _ a  to be transferred to the accumulator  130 . As a result, the hydraulic pressure in the wheel brakes w 1  is decreased. Such a fluid flow path corresponds to a fluid flow path in the case that the inlet valve is closed and the outlet valve is opened in the conventional brake system for a vehicle. 
     When a first current corresponding to the first electromagnetic force is applied to the 3-way solenoid valve  170 , the first electromagnetic force is applied to the armature  171 , and the armature  171  presses the plunger  172  to close the first opening/closing flow passage  179 _ a . The force of the armature  171  indirectly pressing the second fluid control unit  177 _ b  is smaller than the force applied by the fluid introduced through the third port  175 _ c  to the second fluid control unit  177 _ b . When the first electromagnetic force is applied to the armature  171 , the second opening/closing flow passage  179 _ b  is partially opened. 
     When the first opening/closing flow passage  179 _ a  of the wheel-side integrated valve  170  is closed and the second opening/closing flow passage  179 _ b  is completely opened, the pressure of the wheel brakes w 1  may increase sharply to cause wheel-slip or wheel-lock. In order to prevent wheel slip or wheel lock, the first electromagnetic force corresponding to a force immediately before the first opening/closing flow passage  179 _ a  is opened is formed in the armature  171 , and then the first electromagnetic force is linearly reduced to partially open the second opening/closing flow passage  179 _ b.    
     When the first opening/closing flow passage  179 _ a  of the wheel-side integrated valve  170  is closed and the second opening/closing flow passage  179 _ b  is partially opened, the fluid pressurized by the fluid pressing units  150  and  160  passes sequentially through the third port  175 _ c  and the second port  175 _ b  to be transferred to the wheel brakes w 1 . Since the first opening/closing flow passage  179 _ a  is closed, hydraulic pressure inside the wheel brakes w 1  is not transmitted to the accumulator  130 . As a result, the hydraulic pressure inside the wheel brakes w 1  increases. Such a fluid flow path corresponds to a fluid flow path in the case that the inlet valve is partially opened and the outlet valve is closed in the conventional brake system for a vehicle. 
     The 3-way solenoid valve  170  may be configured to change the amount of fluid flowing between the first to third ports  175 _ a  to  175 _ c  as the current applied to the coil continuously changed. The opening and closing states of the plurality of solenoid valves included in the brake system  100  may be controlled independently of each other. 
       FIG.  4    is a cross-sectional view illustrating an integrated valve on the wheel side of the brake system for a vehicle according to a second embodiment of the present disclosure. 
     Referring to  FIG.  4   , a first port  275 _ a  of some of the 3-way solenoid valves according to the second embodiment of the present disclosure is connected to the fluid storage units, a second port  275 _ b  is connected to the wheel brakes w 2 , and a third port  275 _ c  is connected to the outlets of the fluid pressing units  250  and  260 . Referring to  FIGS.  2  and  4   , the first port  275 _ a  of some of the 3-way solenoid valves according to the second embodiment may be connected to the accumulator, the second port  275 _ b  may be connected to the wheel brakes w 2 , and the third port  275 _ c  may be connected to the outlet of the pump  260 . In the present disclosure, the three-way solenoid valve  270  connected in this way is referred to as a wheel-side integrated valve  270 . The brake system  200  may include a front left wheel-side integrated valve  270   a , a front right wheel-side integrated valve  270   b , a rear left wheel-side integrated valve  270   c , and a rear right wheel-side integrated valve  270   d . The wheel-side integrated valve  270  functions as both the inlet valve and the outlet valve. Since the structure, operation mechanism, and function of the wheel-side integrated valve  270  according to the second embodiment are substantially the same as those of the 3-way solenoid valve  170  according to the first embodiment of the present disclosure, the redundant descriptions thereof will be omitted. 
       FIG.  5    is a cross-sectional view illustrating an integrated valve on the pressing unit side of the brake system  200  according to the second embodiment of the present disclosure. 
     Referring to  FIG.  5   , in at least a part of the 3-way solenoid valves according to the second embodiment of the present disclosure, a first port  285 _ a  is connected to the inlet of the pump  260 , a second port  285 _ b  is connected to the master cylinder  250 , and a third port  285 _ c  is connected to the wheel brakes w 2 . Referring to  FIGS.  2  and  5   , in at least a part of the 3-way solenoid valves according to the second embodiment, the first port  285 _ a  may be connected to the inlet of the pump  260 , the second port  285 _ b  may be connected to the master cylinder  250 , and the third port  285 _ c  may be connected to the wheel brakes w 2 . In the present disclosure, the three-way solenoid valve connected in the way is referred to as a pressing unit-side integrated valve  280 . The brake system  200  may include a first pressing unit-side integrated valve  280  and a second pressing unit-side integrated valve  280 . Referring to  FIGS.  2  and  5   , the master cylinder  250  is connected in series between the oil reservoir and the pressing unit-side integrated valve  280 , and the pressing unit-side integrated valve  280  is connected to the master cylinder  250 , the inlet of the pump  260 , and the wheel brakes w 2 . The pressing unit-side integrated valve  280  functions as both a normal open type traction control valve and a normal close type high-pressure switch valve. The first pressing unit-side integrated valve  280  is connected to the first pump  260 , the first hydraulic chamber, the front left wheel brake w 2 , and the rear right wheel brake w 2  through the first to third ports  285 _ c . The second pressing unit-side integrated valve  280  is connected to the second pump  260 , the second hydraulic chamber, the front right wheel brake w 2 , and the rear left wheel brake w 2  through the first to third ports  285 _ c . A first opening/closing flow passage  289 _ a  of the pressing unit-side integrated valve  280  is configured to fluid-communicate with or block the first port  285 _ a  and the second port  285 _ b . The second opening/closing flow passage  289 _ b  is configured to fluid-communicate with or block the second port  285 _ b  and the third port  285 _ c . When the first opening/closing flow passage  289 _ a  of the pressing unit-side integrated valve  280  is closed and the second opening/closing flow passage  289 _ b  is opened, the fluid pressurized in the master cylinder  250  may be transferred to the wheel brakes w 2 , and the fluid on the oil reservoir side is not transferred to the inlet of the pump  260 . Such a fluid flow path corresponds to a fluid flow path in the case that a traction control valve is opened and a high-pressure switch valve is closed in the conventional brake system for a vehicle. In addition to the difference in components connected to each port and the difference in functions, the structure and operation mechanism of the pressing unit-side integrated valve  280  are substantially the same as those of the 3-way solenoid valve  170  according to the first embodiment, and thus the redundant description thereof will be omitted. The brake system of the present disclosure is not limited to the configuration and arrangement of the brake systems  100  and  200  according to the first and second embodiments. For example, the brake system of the present disclosure may include at least one 3-way solenoid valve, the inlet valve, and the outlet valve. 
       FIG.  6    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that braking pressure of the brake system for a vehicle according to the first embodiment of the present disclosure is increased. 
     Referring to  FIG.  6   , a driver presses the pedal  153 . In the case that a required braking force corresponding to an input amount of the pedal  153  of the driver may be formed using the hydraulic pressure of the master cylinder  150 , the pump  160  may not be driven. The high-pressure switch valves HSV 1  and HSV 2  are closed such that fluid is not transferred from the oil reservoir  120  to the inlet of the pump  160 . The traction control valves TCV 1  and TCV 2  are opened such that the hydraulic pressure by the master cylinder  150  is transferred to the wheel brakes w 1 . The 3-way solenoid valve  170  closes the flow path connected from the wheel brakes w 1  to the accumulator  130  and opens the flow path connected from the master cylinder  150  to the wheel brake w 1 . When the first electromagnetic force is applied to the 3-way solenoid valve  170  according to one embodiment of the present disclosure, the first opening/closing flow passage  179 _ a  is closed and the second opening/closing flow passage  179 _ b  is opened to guide the fluid through the route as shown in  FIG.  6   . As the hydraulic pressure formed in the master cylinder  150  is transferred to the wheel brakes w 1 , the hydraulic pressure in the wheel brakes w 1  increases, which increases the braking force. 
       FIG.  7    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that braking pressure of the brake system for a vehicle according to the first embodiment of the present disclosure is reduced. 
     Referring to  FIG.  7   , a driver presses the pedal  153 . In the case that ABS function is operated to prevent a wheel lock phenomenon or a system of an autonomous vehicle determines that the braking force of the brake system  100  is to be reduced, the brake system  100  may need to reduce the braking force even though the driver presses the pedal  153 . In this case, the high-pressure switch valves HSV 1  and HSV 2  are closed such that the fluid is not transferred from the oil reservoir  120  to the inlet of the pump  160 . The 3-way solenoid valve  170  closes the flow path connected from the fluid pressing units  150  and  160  to the wheel brakes w 1 , and opens the flow path connected from the wheel brakes w 1  to the accumulator  130 . In this way, the fluid in the wheel brakes w 1  is transferred to the accumulator  130  and the braking force is reduced. When the third electromagnetic force is applied to the 3-way solenoid valve  170  according to one embodiment of the present disclosure, the first opening/closing flow passage  179 _ a  is opened and the second opening/closing flow passage  179 _ b  is closed, thereby guiding the fluid through the route as shown in  FIG.  7   . 
       FIG.  8    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that hydraulic pressure is selectively supplied to a part of the wheel brakes according to the first embodiment of the present disclosure. 
     Referring to  FIG.  8   , a driver presses the pedal  153 . Since the traction control valves TCV 1  and TCV 2  are opened, the fluid pressurized by the master cylinder  150  may be transferred to the front right wheel brake FR 1 . In order to increase only the braking force applied by the brake system  100  to the front right wheel, the first opening/closing flow passage  179 _ a  of the front right wheel-side integrated valve  170   b  is closed and the second opening/closing flow passage  179 _ b  is opened. In order to reduce the braking force applied by the brake system  100  to the front left wheel, the rear left wheel, and the rear right wheel, the first opening/closing flow passage  179 _ a  of the front left, rear left and rear right wheel-side integrated valves  170 _ a ,  170 _ b  and  170 _ d  is opened and the second opening/closing flow passage  179 _ b  is closed. In the brake system  100  according to one embodiment of the present disclosure, the first current is applied to the front right wheel-side integrated valve  170 _ b , and the third current is applied to the front left, rear left, and rear right wheel-side integrated valves  170 _ a ,  170 _ b , and  170 _ d , thereby guiding the fluid through the route as shown in  FIG.  8   . 
       FIG.  9    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that the second pump of the brake system according to the first embodiment of the present disclosure is driven. 
     When a required braking force calculated using a braking signal is smaller than the braking force currently formed by the brake system  100 , the pump  160  may pressurize the fluid. Referring to  FIG.  9   , the pedal  153  is not pressed. Since the first pump  161  is not driven, braking pressure applied to the front left wheel and the rear right wheel is maintained. The second high pressure switch valve HSV 2  is opened. The fluid is transferred to the inlet of the second pump  161  through the second reservoir chamber  122 , the second hydraulic chamber  152 , and the second high pressure switch valve HSV 2  sequentially. The first opening/closing flow passage  179 _ a  of the front right wheel-side integrated valve  170   b  is closed, and the second opening/closing flow passage  179 _ b  is opened. The fluid pressurized by the second pump  162  sequentially passes through the third port and the second port of the front right wheel-side integrated valve  170 _ b  to be transferred to the front right wheel brake FR 1 . This increases the braking pressure applied to the front right wheel. The first opening/closing flow passage  179 _ a  of the rear left wheel-side integrated valve  170 _ c  is opened, and the second opening/closing flow passage  179 _ b  is closed. Accordingly, the hydraulic pressure in the rear left wheel brake RL 1  is reduced. 
       FIG.  10    is a hydraulic circuit diagram illustrating a flow path of the fluid in the case that the pump of the brake system according to the second embodiment of the present disclosure is driven. 
     Referring to  FIG.  10   , a driver does not press the pedal  253 . The first and second pumps  261  and  262  are driven to increase the braking pressure applied to the front left wheel and the rear left wheel. The fluid on the side of the oil reservoir  220  sequentially passes through the master cylinder  250 , the second port  285 _ b  of the fluid pressing unit-side integrated valve  280 , and the first port  285 _ a  to be transferred to the inlet of the pump  260 . The first opening/closing flow passage  279 _ a  of the rear left and rear right wheel-side integrated valves  270 _ c  and  270 _ d  is opened, and the second opening/closing flow passage  279 _ b  is closed. Accordingly, the fluid in the rear left wheel brake RL 2  is transferred to the second accumulator  232  to reduce the braking pressure applied to the rear left wheel. The fluid in the rear right wheel brake RR 2  is transferred to the first accumulator  231  to reduce the braking pressure applied to the rear right wheel. The first opening/closing flow passage  279 _ a  of the front left and front right wheel-side integrated valves  270 _ a  and  270 _ b  is closed, and the second opening/closing flow passage  279 _ b  is opened. Accordingly, the fluid pressurized by the first pump  261  is supplied to the front left wheel brake FL 2 , and the fluid pressurized by the second pump  262  is supplied to the front right wheel brake FR 2 , thereby increasing the braking pressure applied to the front wheels. Braking force may be applied to the rear wheels by using the electronic parking brake EPB 2  mounted on each rear wheel. 
     According to one embodiment of the present disclosure, the brake system for the vehicle includes the 3-way solenoid valve so that the number of solenoid valves mounted to the brake system is reduced. 
     Although exemplary embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the idea and scope of the claimed invention. Therefore, exemplary embodiments of the present disclosure have been described for the sake of brevity and clarity. The scope of the technical idea of the present embodiments is not limited by the illustrations. Accordingly, one of ordinary skill would understand that the scope of the claimed invention is not to be limited by the above explicitly described embodiments but by the claims and equivalents thereof.