Patent Publication Number: US-2011074208-A1

Title: Pump unit for electronic control brake system

Description:
This application claims the benefit of Korean Patent Application Nos. 10-2009-0092328, 10-2009-0092329, and 10-2009-0092330 filed on Sep. 29, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The discloser relates to a pump unit for an electronic control brake system, capable of rapidly forming a brake oil pressure while reducing hydraulic pressure pulsation generated in pump operation by improving the arrangement structure of pumps. 
     2. Description of the Related Art 
     In general, electronic control brake systems are used to obtain strong and stable braking force by effectively preventing a vehicle from slipping. The electronic control brake systems have been developed as an ABS (Anti-Lock Brake System) to prevent a wheel from slipping during a braking operation, a BTCS (Brake Traction Control System) to prevent a driving wheel from slipping upon sudden start or sudden acceleration of a vehicle, and a VDC (Vehicle Dynamic Control System) to stably maintain the driving state of the vehicle by controlling a brake oil pressure in the combination of the ABS and the BTCS. 
     Each of the electronic control brake systems includes a plurality of solenoid valves to control a brake oil pressure transferred to a hydraulic brake mounted on wheels of a vehicle, low and high pressure accumulators to temporarily store oil flowing out of the hydraulic brake, a motor and pumps to forcibly pump the oil of the low pressure accumulators, and an ECU (Electronic Control Unit) to control the driving of the motor and the solenoid valves. These components are compactly embedded in a modulator block made of aluminum. 
     Therefore, the electronic control brake system performs the electronic control for the wheels by compressing and pumping the oil of the low pressure to the high pressure accumulators through the operation of the pumps, and transferring the oil to the hydraulic brake or a master cylinder assembly. 
     However, the electronic control brake system according to the related art has a dual pump-type structure in which two pumps are coupled with one motor. In other words, each pump performs one suction stroke and one exhaust stroke as a rotational shaft of the motor rotates one time to supply the compressed oil to each hydraulic circuit. Accordingly, the great hydraulic pressure pulsation occurs at the side of a master cylinder in the exhaust stroke of the pump, and the brake pressure of the hydraulic brake may not be rapidly formed when the pumps operate to control the wheels. 
     SUMMARY 
     Accordingly, it is an aspect of the disclosure to provide a pump unit for an electronic control brake system, capable of rapidly forming a brake oil pressure while reducing hydraulic pressure pulsation generated in pump operation by improving the arrangement structure of pumps. 
     Additional aspects and/or advantages of the disclosure will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure. 
     The foregoing and/or other aspects of the disclosure are achieved by providing a pump unit for an electronic control brake system having a shaft of a motor part for driving the pump unit, the pump unit including first to sixth pumps installed in first and second hydraulic circuits linking a master cylinder assembly with a plurality of brake cylinders to form a closed circuit. The first to third pumps of the pump unit are arranged on a first plane vertically intersecting a third plane including a rotational axis of the shaft, the first pump is arranged about an axis of the intersection between the first plane and the third plane, the second pump is arranged counterclockwise away from the first pump at an angle of about 120 degrees, and the third pump is arranged clockwise away from the first pump at an angle of about 60 degrees. 
     According to the disclosure, the fourth to sixth pumps are arranged on a second plane parallel to the first plane in a direction of the rotational axis, the fourth pump is arranged about an axis of intersection between the second and third planes while facing the first pump, the fifth pump is arranged about an axis counterclockwise away from the fourth pump at an angle of about 60 degrees, and the sixth pump is arranged about an axis clockwise away from the fourth pump at an angle of about 120 degrees. 
     According to the disclosure, the shaft includes a first eccentric part corresponding to the first plane and a second eccentric part corresponding to the second plane. 
     According to the disclosure, the first and second eccentric parts have an eccentric phase difference of about 180 degrees. 
     According to the disclosure, the first, second, and fifth pumps are connected to the first hydraulic circuit, and remaining three pumps are connected to the second hydraulic circuit. 
     According to another embodiment of the disclosure, there is provided a pump unit for an electronic control brake system having a shaft of a motor part for driving the pump unit. The pump unit includes first to sixth pumps installed in first and second hydraulic circuits linking a master cylinder assembly with a plurality of brake cylinders to form a closed circuit. The first to third pumps of the pump unit are arranged on a first plane vertically intersecting a third plane including a rotational axis of the shaft, the first pump is arranged about an axis of the intersection between the first plane and the third plane, the second pump is arranged counterclockwise away from the first pump at an angle of about 60 degrees, and the third pump is arranged counterclockwise away from the first pump at an angle of about 120 degrees. The fourth to sixth pumps are arranged on a second plane parallel to the first plane in a direction of the rotational axis, the fourth pump is arranged about an axis of intersection between the second and third planes while facing the first pump, the fifth pump is arranged about an axis clockwise away from the fourth pump at an angle of about 60 degrees, and the sixth pump is arranged about an axis counterclockwise away from the fourth pump at an angle of about 120 degrees. 
     According to the disclosure, the shaft includes a first eccentric part corresponding to the first plane and a second eccentric part corresponding to the second plane. 
     According to the disclosure, the first and second eccentric parts have an eccentric phase difference of about 60 degrees. 
     According to the disclosure, the first, third, and sixth pumps are connected to the first hydraulic circuit, and remaining three pumps are connected to the second hydraulic circuit. 
     According to still another embodiment of the present invention, there is provided a pump unit for an electronic control brake system having a shaft of a motor part for driving the pump unit. The pump unit includes first to sixth pumps installed in first and second hydraulic circuits linking a master cylinder assembly with a plurality of brake cylinders to form a closed circuit. The first to third pumps of the pump unit are arranged on a first plane vertically intersecting a third plane including a rotational axis of the shaft, the first pump is arranged clockwise away from the third plane at an angle of about 30 degrees, the second pump is arranged counterclockwise away from the first pump at an angle of about 120 degrees, and the third pump is arranged counterclockwise away from the first pump at an angle of about 90 degrees. The fourth to sixth pumps are arranged on a second plane parallel to the first plane in a direction of the rotational axis, the fourth pump is arranged counterclockwise away from the third plane at an angle of about 30 degrees, the fifth pump is arranged about an axis counterclockwise away from the fourth pump at an angle of about 90 degrees, and the sixth pump is arranged about an axis clockwise away from the fourth pump at an angle of about 120 degrees. 
     According to the disclosure, the shaft includes a first eccentric part corresponding to the first plane and a second eccentric part corresponding to the second plane. 
     According to the disclosure, the first and second eccentric parts have an eccentric phase difference of about 90 degrees. 
     According to the disclosure, the first pump, the second pump, and the fifth pump are connected to the first hydraulic circuit, and remaining three pumps are connected to the second hydraulic circuit. 
     As described above, in the electronic control brake system according to one embodiment of the disclosure, rapid response performance can be ensured upon the operation of a motor and a pump. In addition, durability of the electronic control brake system can be improved and the hydraulic pressure pulsation can be reduced by reducing the load and the number of operations of the elements so that a user can comfortably steps on a brake pedal and the operating noise of the system can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a hydraulic system diagram of an electronic control brake system according to one embodiment of the disclosure; 
         FIG. 2  is a perspective view schematically showing the arrangement structure of a motor and a pump unit according to one embodiment of the disclosure; 
         FIG. 3  is a view showing a pump unit arranged on a first plane according to one embodiment of the disclosure; 
         FIG. 4  is a view showing a pump unit arranged on a second plane according to one embodiment of the disclosure; 
         FIG. 5  is a perspective view schematically showing the connection structure of a pump unit and a hydraulic circuit according to one embodiment of the disclosure; 
         FIG. 6  is a hydraulic system diagram of an electronic control brake system according to another embodiment of the disclosure; 
         FIG. 7  is a perspective view schematically showing the arrangement structure of a motor and a pump unit according to another embodiment of the disclosure; 
         FIG. 8  is a view showing a pump unit arranged on a first plane according to another embodiment of the disclosure; 
         FIG. 9  is a view showing a pump unit arranged on a second plane according to another embodiment of the disclosure; 
         FIG. 10  is a perspective view schematically showing the connection structure of a pump unit and a hydraulic circuit according to another embodiment of the disclosure; 
         FIG. 11  is a hydraulic system diagram of an electronic control brake system according to still another embodiment of the disclosure; 
         FIG. 12  is a perspective view schematically showing the arrangement structure of a motor and a pump unit according to still another embodiment of the disclosure; 
         FIG. 13  is a view showing a pump unit arranged on a first plane according to still another embodiment of the disclosure; 
         FIG. 14  is a view showing a pump unit arranged on a second plane according to still another embodiment of the disclosure; and 
         FIG. 15  is a perspective view schematically showing the connection structure of a pump unit and a hydraulic circuit according to still another embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements. The embodiments are described below to explain the disclosure by referring to the figures. 
       FIG. 1  is a hydraulic system diagram of an electronic control brake system according to one embodiment of the disclosure. 
     As shown in  FIG. 1 , an electronic control brake system according to one embodiment of the disclosure includes a master cylinder assembly  10  to provide braking force, a plurality of brake cylinders  20  to achieve a braking operation, and first and second hydraulic circuits A and B connecting the master cylinder assembly  10  and the brake cylinders  20  to form a closed circuit. In this case, since the first and second hydraulic circuits A and B have the same arrangement structure, only the first hydraulic circuit A will be representatively described below except for a specific case related to the structure of the second hydraulic circuit B. 
     The first and second hydraulic circuits A and B include a plurality of solenoid valves  30  and  31  to intermittently control the transmission of a braking oil pressure formed in the master cylinder assembly  10  to each brake cylinder  20 , and low pressure accumulators  40  to temporarily store oil returning from the brake cylinders  20 . 
     In addition, the electronic control brake system according to the disclosure further includes a pump unit  50  to re-circulate oil stored in the low accumulator  40  by compressing the oil, a motor part  51  to drive the pump unit  50 , and a high pressure accumulator  60  to damp hydraulic pressure pulsation of oil discharged from the pump unit  50 . 
     The pump unit  50  includes a first pump  50   a , a second pump  50   b , a third pump  50   c , a fourth pump  50   d , a fifth pump  50   e , and a sixth pump  50   f . Among them, the first pump  50   a , the second pump  50   b , and the fifth pump  50   e  are connected to the first hydraulic circuit A, and the third pump  50   c , the fourth pump  50   c , and the sixth pump  50   f  are connected to the second hydraulic circuit B. A check valve  52  is provided at suction and exhaust sides of the first to sixth pumps  50   a  to  50   f  to prevent the oil from flowing back. 
     The above devices are compactly embedded in a modulator block  100  having a rectangular parallelepiped shape and made of aluminum Al. The modulator block  100  is provided therein with a plurality of fluid passages connecting the devices to each other. 
     The solenoid valves  30  and  31  are classified into a normal-open solenoid valve  30  (hereinafter, referred to as “NO-type solenoid valve”) provided at an upstream fluid passage of the brake cylinder  20  to maintain an open state in a normal time, and a normal-close solenoid valve  31  (hereinafter, “NC-type solenoid valve”) provided at a downstream fluid passage of the brake cylinder  20  to maintain a close state in a normal time. 
     The low pressure accumulator  40  is provided at a passage linking the downstream side of the NC-type solenoid valve  31  to the pump unit  50  to temporarily store oil returning from the brake cylinder  20  due to the opening of the NC-type solenoid valve  31  in the pressure reducing brake operation of the brake cylinder  20 . The high pressure accumulator  60  serves as a damping chamber provided at the passage linking the outlet side of the pump unit  50  to the upstream side of the NO-type solenoid valve  30  to damp the hydraulic pressure pulsation of oil discharged from the pump unit  50 . Reference number  70  represents an orifice allowing a fluid to stably flow. 
       FIG. 2  is a schematic perspective view showing the arrangement structure of a motor and the pump unit  50  according to one embodiment of the disclosure.  FIG. 3  is a view showing the pump unit  50  arranged on a first plane according to one embodiment of the disclosure.  FIG. 4  is a view showing the pump unit  50  arranged on a second plane according to one embodiment of the disclosure.  FIG. 5  is a perspective view showing the connection structure of the pump unit  50  and the hydraulic circuits A and B according to one embodiment of the disclosure. 
     As shown in  FIG. 2 , the motor part  51  driving the pump unit  50  includes one motor including a shaft  53  rotating about a rotational axis X. Two eccentric parts  54  and  55  are provided at different positions of the shaft  53  in the direction of the rotational axis X. 
     The eccentric parts  54  and  55  may be integrated with the shaft  53  or coupled with an eccentric bearing. The eccentric parts  54  and  55  include the first eccentric part  54  adjacent to the motor part  51  and the second eccentric part  55  spaced apart from the first eccentric part  54  at a predetermined interval. 
     The first and second eccentric parts  54  and  55  are provided corresponding to a piston (not shown) of the pump unit  50  to be described below such that the first and second eccentric parts  54  and  55  are connected to the piston. The first and second eccentric parts  54  and  55  have a predetermined eccentric phase difference therebetween. 
     According to the present embodiment, the first and second eccentric parts  54  and  55  may have an eccentric phase difference of about 180 degrees. 
     Accordingly, the pump unit  50  including six pumps to be described below sequentially receives loads. Therefore, the shaft  53  of the motor part  51  is not excessively loaded, so that the durability of the pump unit  50  can be improved. 
     Hereinafter, the arrangement structure of the pump unit  50  operated by the eccentric parts  54  and  55  provided on the shaft  53  of the motor part  51  will be described. 
     The shaft  53  is provided thereon with a third plane  56   c  including the rotational axis X, and first and second planes  56   a  and  56   b  which vertically intersect the third plane  56   c  and are provided at different positions in the direction of the rotational axis X while being parallel to each other. 
     The first plane  56   a  is positioned corresponding to the first eccentric part  54  provided on the shaft  53 , and the second plane  56   b  is positioned corresponding to the second eccentric part  55  provided on the shaft  53 . 
     The first to third pumps  50   a ,  50   b , and  50   c  are provided on the first plane  56   a.    
     The first pump  50   a  is arranged about an axis of the intersection between the first and third planes  56   a  and  56   c . As shown in  FIG. 3 , the second pump  50   b  is arranged about an axis counterclockwise away from the axis of the first pump  50   a  at an angle of about 120 degrees on the basis of the rotational axis X, and the third pump  50   c  is arranged about an axis clockwise away from the axis of the first pump  50   a  at an angle of about 60 degrees on the basis of the rotational axis X. 
     In other words, the first pump  50   a  is arranged away from the second pump  50   b  at an angle of about 120 degrees, and away from the third pump  50   c  at an angle of about 60 degrees. The second pump  50   b  is arranged away from the second pump  50   b  at an angle of about 180 degrees. 
     The fourth pump  50   d , the fifth pump  50   e , and the sixth pump  50   f  are arranged on the second plane  56   b.    
     The fourth pump  50   d  is arranged about an axis of the intersection between the second plane  56   b  and the third plane  56   c  while facing the first pump  50   a . As shown in  FIG. 4 , the fifth pump  50   e  is arranged about an axis counterclockwise away from the axis of the fourth pump  50   d  at an angle of about 60 degrees on the basis of the rotational axis X, and the sixth pump  50   f  is arranged about an axis clockwise away from the axis of the fourth pump  50   d  at an angle of about 120 degrees on the basis of the rotational axis X. 
     In other words, the fourth pump  50   d  is arranged away from the fifth pump  50   e  at an angle of about 60 degrees, and away from the sixth pump  50   f  at an angle of about 120 degrees. The fifth pump  50   e  is arranged away from the fifth pump  50   f  at an angle of about 180 degrees. 
     In the above structure, since the pumps of the pump unit  50  are bilaterally symmetrical to each other about the third plane  56   c  including the rotational axis X, the arrangement of pistons of the pump unit  50  may be concentrated at one side of the hydraulic circuits A and B. 
     In other words, as shown in  FIG. 1 , the first and second pumps  50   a  and  50   b  arranged on the first plane  56   a  and the fifth pump  50   e  arranged on the second plane  56   b  may be connected to the first hydraulic circuit A, and the third pump  50   c  arranged on the first plane  56   a  and the fourth and sixth pumps  50   d  and  50   f  arranged on the second plane  56   b  may be connected to the second hydraulic circuit B. 
     Accordingly, in the electronic control brake system according to the embodiment of the disclosure, as the rotational axis X rotates one time, pressures are formed three times in each of the first and second hydraulic circuits A and B, so that the period of a pressure pulse is shorted, and the width of the pressure pulse is narrowed. Accordingly, the vibration and the operating noise of the electronic control brake system are reduced. 
     Further, in the electronic control brake system according to the disclosure, suction and exhaust passages of the pump unit  50  are directed toward the same surface, so that the spatial arrangement of the pumps and a compact passage design are achieved. 
     In other words, suction passages  80   a ,  80   b ,  80   c ,  80   d ,  80   e , and  80   f  and exhaust passages  90   a ,  90   b ,  90   c ,  90   d ,  90   e , and  90   f  are provided in one direction, so that the share of the low and high pressure accumulators  40  and  60  is easily achieved. In other words, as shown in  FIG. 5 , the three pumps  50   a ,  50   b , and  50   e  connected to the first hydraulic circuit A is connected to one low pressure accumulator  40  at the suction side, and connected to one high pressure accumulator  60  at the exhaust side. The three pumps  50   c ,  50   d , and  50   f  connected to the second hydraulic circuit B are connected one low pressure accumulator  40  at the suction side, and connected to the high pressure accumulator  60  at the exhaust side. Accordingly, the compact brake system is easily designed. 
     For the purpose of explanation, the first pump  50   a , the second pump  50   b , and the fifth pumps  50   e  are connected to the first hydraulic circuit A, and the third pump  50   c , the fourth pump  50   d , and the sixth pump  50   f  are connected to the second hydraulic circuit B according to the present embodiment. However, the three pumps connected to the first hydraulic circuit A and the second hydraulic circuit B may vary according to the structure of the hydraulic circuits A and B. 
     In addition, the above hydraulic circuits according to the disclosure are provided for the purpose of explanation, and the pump units according to the disclosure may be applicable to different hydraulic circuits. 
     The arrangement structure of the pump unit according to another embodiment of the disclosure will be described below. Hereinafter, the same reference numbers will be designated to the same components, and details thereof will be omitted in order to avoid redundancy. 
       FIG. 6  is a hydraulic system diagram of an electronic control brake system according to another embodiment of the disclosure, and  FIG. 7  is a perspective view schematically showing the arrangement structure of the motor and the pump unit according to another embodiment of the disclosure.  FIG. 8  is a view showing the pump unit arranged on the first plane according to another embodiment of the disclosure, and  FIG. 9  is a view showing the pump unit arranged on the second plane according to another embodiment of the disclosure.  FIG. 10  is a perspective view showing the connection structure of the pump unit and the hydraulic circuit according to another embodiment of the disclosure. 
     Referring to  FIGS. 6 and 10 , according to the present embodiment, first and second eccentric parts  154  and  155  may have an eccentric phase difference of about 60 degrees. 
     In addition, first to third pumps  150   a ,  150   b , and  150   c  are arranged on the first plane  56   a.    
     The first pump  150   a  is arranged about an axis of the intersection between the first plane  56   a  and the third plane  56   c . As shown in  FIG. 8 , the second pump  150   b  is arranged about an axis counterclockwise away from the axis of the first pump  150   a  at an angle of about 60 degrees on the basis of the rotational axis X. The third pump  150   c  is arranged about an axis counterclockwise away from the axis of the first pump  150   a  at an angle of about 120 degrees on the basis of the rotational axis X. 
     A fourth pump  150   d , a fifth pump  150   e , and a sixth pump  150   f  are arranged on the second plane  56   b.    
     The fourth pump  150   d  is arranged about an axis of the intersection between the second plane  56   b  and the third plane  56   c . As shown in  FIG. 9 , the fifth pump  150   e  is arranged about an axis clockwise away from the axis of the fourth pump  150   d  at an angle of about 120 degrees on the basis of the rotational axis X. The sixth pump  150   f  is arranged about an axis clockwise away from the axis of the fourth pump  150   d  at an angle of about 60 degrees on the basis of the rotational axis X. 
     In other words, the fourth pump  150   d  is arranged away from the fifth pump  150   e  at an angle of about 240 degrees, and away from the sixth pump  150   f  at an angle of about 60 degrees. The fifth pump  150   e  is arranged away from the fifth pump  150   f  at an angle of about 60 degrees. 
     In the above structure, since the pumps of the pump unit  50  are bilaterally symmetrical to each other about the third plane  56   c  including the rotational axis X, arrangement of pistons of the pump unit  50  may be concentrated at one side of the hydraulic circuits A and B. 
     According to the present embodiment, as shown in  FIG. 6 , the first and third pumps  150   a  and  150   c  arranged on the first plane  56   a  and the sixth pump  150   f  arranged on the second plane  56   b  may be connected to the first hydraulic circuit A, and the second pump  150   b  arranged on the first plane  56   a  and the fourth and fifth pumps  150   d  and  150   e  arranged on the second plane  56   b  may be connected to the second hydraulic circuit B. 
     Accordingly, in the electronic control brake system according to the embodiment of the disclosure, as the rotational axis X rotates one time, pressures are formed three times in each of the first and second hydraulic circuits A and B, so that the period of a pressure pulse is shorted, and the width of the pressure pulse is narrowed. Accordingly, the vibration and the operating noise of the electronic control brake system are reduced. 
     Further, in the electronic control brake system according to the disclosure, suction and exhaust passages of the pump unit  51  are directed toward the same surface, so that the spatial arrangement of the pumps and a compact passage design are achieved. 
     In other words, the suction passages  80   a ,  80   b ,  80   c ,  80   d ,  80   e , and  80   f  and the exhaust passages  90   a ,  90   b ,  90   c ,  90   d ,  90   e , and  90   f  are provided in one direction, so that the share of the low and high pressure accumulators  40  and  60  is easily achieved. In other words, as shown in  FIG. 10 , the three pumps  150   a ,  150   c , and  150   f  connected to the first hydraulic circuit A is connected to one low pressure accumulator  40  at the suction side, and connected to one high pressure accumulator  60  at the exhaust side. The three pumps  150   b ,  150   d , and  150   e  connected to the second hydraulic circuit B are connected one low pressure accumulator  40  at the suction side, and connected to the high pressure accumulator  60  at the exhaust side. Accordingly, the compact brake system is easily designed. 
     The arrangement structure of a pump unit according to still another embodiment of the disclosure will be described below. Hereinafter, the same reference numbers will be designated to the same components, and the details thereof will be omitted in order to avoid redundancy. 
       FIG. 11  is a hydraulic system diagram of an electronic control brake system according to still another embodiment of the disclosure, and  FIG. 12  is a perspective view schematically showing the arrangement structure of a motor and the pump unit according to still another embodiment of the disclosure.  FIG. 13  is a view showing the pump unit arranged on the first plane according to still another embodiment of the disclosure, and  FIG. 14  is a view showing the pump unit arranged on the second plane according to still another embodiment of the disclosure.  FIG. 15  is a perspective view showing the connection structure of the pump unit and the hydraulic circuit according to still another embodiment of the disclosure. 
     Referring to  FIGS. 11 to 15 , first and second eccentric parts  254  and  255  according to the present embodiment have an eccentric phase difference of about 90 degrees. 
     First, second, and third pumps  250   a ,  250   b , and  250   c  are arranged on the first plane  56   a.    
     As shown in  FIG. 13 , the first pump  250   a  is arranged about an axis clockwise away from the third plane  56   c  at an angle of about 30 degrees, and the second pump  250   b  is arranged about an axis counterclockwise away from the axis of the first pump  250   a  at an angle of about 120 degrees on the basis of the rotational axis X. The third pump  250   c  is arranged about an axis clockwise away from the axis of the first pump  250   a  at an angle of about 90 degrees on the basis of the rotational axis X. 
     In other words, the first pump  250   a  is arranged away from the second pump  250   b  at an angle of about 120 degrees, and the second pump  250   b  is arranged away from the third pump  250   c  at an angle of bout 150 degrees. The first pump  250   a  is arranged away from the third pump  250   c  at an angle of about 90 degrees. 
     Four, fifth, and sixth pumps  250   d ,  250   e , and  250   f  are arranged on the second plane  56   b.    
     As shown in  FIG. 14 , the fourth pump  250   d  is arranged about an axis counterclockwise away from the third plane  56   c  at an angle of about 30 degrees, and the fifth pump  250   e  is arranged about an axis counterclockwise away from the axis of the fourth pump  250   d  at an angle of about 90 degrees on the basis of the rotational axis X. The sixth pump  250   f  is arranged about an axis clockwise away from the axis of the fourth pump  250   d  at an angle of about 120 degrees on the basis of the rotational axis X. 
     In other words, the fourth pump  250   d  is arranged away from the fifth pump  250   e  at an angle of about 90 degrees, and the fifth pump  250   e  is arranged away from the sixth pump  250   f  at an angle of bout 150 degrees. The fourth pump  250   d  is arranged away from the sixth pump  250   f  at an angle of about 120 degrees. 
     In the above structure, since the pumps of the pump unit are bilaterally symmetrical to each other about the third plane  56   c  including the rotational axis X, the arrangement of the pistons of the pump unit may be concentrated at one side of the hydraulic circuits A and B. 
     According to the present embodiment, as shown in  FIG. 15 , the first and second pumps  250   a  and  250   b  arranged on the first plane  56   a  and the fifth pump  250   e  arranged on the second plane  54   b  may be connected to the first hydraulic circuit A, and the third pump  250   c  arranged on the first plane  56   a  and the fourth and sixth pumps  250   d  and  250   f  arranged on the second plane  56   b  may be connected to the second hydraulic circuit B. 
     Accordingly, in the electronic control brake system according to the embodiment of the disclosure, as the rotational axis X rotates one time, pressures are formed three times in each of the first and second hydraulic circuits A and B, so that the period of a pressure pulse is shorted, and the width of the pressure pulse is narrowed. Accordingly, the vibration and the operating noise of the electronic control brake system are reduced. 
     Further, in the electronic control brake system according to the disclosure, suction and exhaust passages of the pump unit  50  are directed toward the same surface, so that the spatial arrangement of the pumps and a compact passage design are achieved. 
     In other words, the suction passages  80   a ,  80   b ,  80   c ,  80   d ,  80   e , and  80   f  and the exhaust passages  90   a ,  90   b ,  90   c ,  90   d ,  90   e , and  90   f  are provided in one direction, so that the share of the low and high pressure accumulators  40  and  60  is easily achieved. In other words, as shown in  FIG. 15 , the three pumps  250   a ,  250   b , and  250   e  connected to the first hydraulic circuit A is connected to one low pressure accumulator  40  at the suction side, and connected to one high pressure accumulator  60  at the exhaust side. The three pumps  250   c ,  250   d , and  250   f  connected to the second hydraulic circuit B are connected one low pressure accumulator  40  at the suction side, and connected to the high pressure accumulator  60  at the exhaust side. Accordingly, the compact brake system is easily designed. 
     Although few embodiments of the disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.