Patent Publication Number: US-2011074205-A1

Title: Pump unit for electronically controlled brake system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 2009-0091179, filed on Sep. 25, 2009 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments of the present invention relate to a pump unit for an electronically controlled brake system, which has an improved pump arrangement, thereby reducing hydraulic pulsation during operation of a pump and enabling rapid generation of hydraulic pressure. 
     2. Description of the Related Art 
     Generally, electronically controlled brake systems are devised to achieve strong and stabilized brake force by effectively preventing vehicle slip. A variety of electronically controlled brake systems have been developed. Examples of the electronically controlled brake systems include an Anti-Lock Brake System (ABS) to prevent wheel slip upon braking, a Brake Traction Control System (BTCS) to prevent wheel slip upon sudden acceleration of a vehicle, and a Vehicle Dynamic Control system (VDC) that is a combination of the ABS and BTCS to stably maintain traveling of a vehicle by controlling hydraulic brake pressure. 
     A conventional electronically controlled brake system includes a plurality of solenoid valves to control hydraulic brake pressure transmitted to hydraulic brakes provided at wheels, low-pressure and high-pressure accumulators in which oil discharged from the hydraulic brakes is temporarily stored, a motor and pumps to forcibly pump the oil in the low-pressure accumulator, and an Electronic Control Unit (ECU) to control operations of the solenoid valves and motor. All the above mentioned elements are received in a compact aluminum modulator block. 
     In operation, the oil in the low-pressure accumulator is pressurized and pumped to the high-pressure accumulator via operation of the pumps. As the pressurized oil is transmitted to the hydraulic brakes or a master cylinder assembly, electronic control of wheels is carried out. 
     The above described conventional electronically controlled brake system, however, is of a dual pump type in which a single motor is connected to two pumps. That is, whenever a rotating shaft of the motor rotates once, the pumps respectively perform a suction stroke and discharge stroke once to supply the pressurized oil to each hydraulic circuit. This may cause an excessive hydraulic pulsation amplitude at a master cylinder during the discharge stroke of the respective pumps and also, the pumps may have difficulty in rapid generation of hydraulic brake pressure required to control wheels. 
     SUMMARY 
     Therefore, it is an aspect of the present invention to provide an electronically controlled brake system, which has an improved pump arrangement, thereby reducing hydraulic pulsation during operation of a pump and achieving rapid generation of hydraulic pressure. 
     Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     In accordance with an aspect of the present invention, a pump unit for an electronically controlled brake system is connected to first and second hydraulic circuits that connect a master cylinder assembly and a plurality of brake cylinders to each other to define closed circuits, and is operated by a motor having a shaft to be rotated about a rotating axis, wherein the shaft includes a concentric shaft portion and an eccentric portion integrally formed with each other, an eccentric bearing coupled to the concentric shaft portion, and a concentric bearing coupled to the eccentric portion. 
     The concentric bearing and the eccentric bearing may be press-fitted respectively. 
     The pump unit may include first to third pumps arranged on a first plane, which intersects at a right angle with the rotating axis at a position corresponding to the concentric bearing, so as to be connected to the concentric bearing, and fourth to sixth pumps arranged on a second plane, which intersects at a right angle with the rotating axis at a position corresponding to the eccentric bearing, so as to be connected to the eccentric bearing. 
     Three pumps of the first to sixth pumps may be connected to the first hydraulic circuit, and the remaining three pumps may be connected to the second hydraulic circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the invention 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 electronically controlled brake system in accordance with an embodiment of the present invention; 
         FIG. 2  is an exploded perspective view illustrating a motor in accordance with an embodiment of the present invention; 
         FIG. 3  is a perspective view schematically illustrating the arrangement of a motor and pump unit in accordance with an embodiment of the present invention; and 
         FIG. 4  is a perspective view schematically illustrating the connection of a pump unit and hydraulic circuits in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
       FIG. 1  is a hydraulic system diagram of an electronically controlled brake system in accordance with the embodiment of the present invention. 
     As illustrated in  FIG. 1 , the electronically controlled brake system in accordance with the embodiment of the present invention includes a master cylinder assembly  10  to provide brake force, a plurality of brake cylinders  20  to execute a braking operation, and a first hydraulic circuit A and second hydraulic circuit B to connect the master cylinder assembly  10  and the plurality of brake cylinders  20  to each other so as to form closed circuits. The first hydraulic circuit A and second hydraulic circuit B have the same arrangement and thus, a description of the second hydraulic circuit B will be omitted hereinafter except for specially mentioned cases. 
     The hydraulic circuits A and B respectively include a plurality of solenoid valves  30  and  31  to control intermittent transmission of hydraulic brake pressure from the master cylinder assembly  10  to the respective brake cylinders  20 , and a low-pressure accumulator  40  in which oil returned from the brake cylinders  20  is temporarily stored. 
     The electronically controlled brake system of the present embodiment further includes a pump unit  50  to pressurize and recirculate the oil stored in the low-pressure accumulator  40 , a motor  51  to drive the pump unit  50 , and high-pressure accumulators  60  to alleviate pressure pulsation of the 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 . The first pump  50   a , second pump  50   b  and fifth pump  50   e  are connected to the first hydraulic circuit A, and the third pump  50   c , fourth pump  50   d  and sixth pump  50   f  are connected to the second hydraulic circuit B. The respective pumps  50   a ,  50   b ,  50   c ,  50   d ,  50   e  and  50   f  are provided at suction and discharge sides thereof with check valves  52  to prevent backflow. 
     All the above mentioned constituent elements are received in a compact state in a cuboidal aluminum modulator block  100 . The modulator block  100  contains a plurality of paths to connect these constituent elements to each other. 
     The solenoid valves  30  and  31  are divided into normal open type solenoid valves  30  (hereinafter, referred to as “NO type solenoid valves”), which are located at upstream paths of the brake cylinders  20  and are normally kept in an open state, and normal close type solenoid valves  31  (hereinafter, referred to as “NC type solenoid valves”) which are located at downstream paths of the brake cylinders  20  and are normally kept in a closed state. 
     The low-pressure accumulators  40  are arranged at paths connected between downstream sides of the NC type solenoid valves  31  and the pump unit  50 . When the brake cylinders  20  generate reduced brake pressure, the low-pressure accumulators  40  temporarily store the oil returned from the brake cylinders  20  through the opened NC type solenoid valves  31 . The high-pressure accumulators  60  are arranged at paths connected between upstream sides of the NO type solenoid valves  30  and the pump unit  50  and serve as damping chambers to alleviate pressure pulsation of the oil discharged from the pump unit  50 . Reference numeral  70  represents an orifice to stabilize fluid flow. 
       FIG. 2  is an exploded perspective view illustrating the configuration of a shaft of the motor in accordance with the embodiment of the present invention,  FIG. 3  is a perspective view schematically illustrating the arrangement of the motor and pump unit in accordance with the embodiment of the present invention, and  FIG. 4  is a perspective view schematically illustrating the connection of the pump unit and hydraulic circuits in accordance with the embodiment of the present invention. 
     As illustrated in  FIG. 2 , a single motor  51  is used to drive the pump unit  50 . The motor  51  has a shaft  53  to be rotated about a rotating axis X. 
     An eccentric portion  53   a  is integrally provided on a lower portion of the shaft  53  so as to be eccentric in a given direction from the rotating axis X. A concentric bearing  54  is press-fitted around the eccentric portion  53   a . The concentric bearing  54  includes concentric inner and outer rings. 
     An eccentric bearing  55  is concentrically press-fitted on the shaft  53  at a position above the eccentric portion  53   a . The eccentric bearing  55  includes inner and outer rings, center points of which are spaced apart from each other by a predetermined distance. 
     Specifically, the shaft  53  includes the two bearings  54  and  55  arranged at different positions spaced apart from each other in a direction of the rotating axis X, to allow the concentric bearing  54  operatively assembled to the eccentric portion  53   a  of the shaft  53  and the eccentric bearing  55  operatively assembled to the shaft  53  at a position spaced apart upward from the concentric bearing  54  to be rotated with a predetermined phase difference. 
     The concentric bearing  54  and eccentric bearing  55  are connected to corresponding positions of the pump unit  50  that will be described hereinafter, to operate the pump unit  50 . 
     In this way, as load is sequentially applied to the pump unit  50  including the six pumps that will be described hereinafter, it may be possible to prevent excessive load from being applied to the bearings  54  and  55  and shaft  53  of the motor  51 , resulting in enhanced durability and lifespan. 
     Hereinafter, the arrangement of the pump unit  50  with respect to the bearings  54  and  55  press-fitted to the shaft  53  of the motor  51  will be described. 
     Referring to  FIG. 3 , there are illustrated a first plane  56   a , a second plane  56   b  and a third plane  56   c . The third plane  56   c  contains the rotating axis X of the motor shaft  53 . The first pump  50   a  is arranged on the third plane  56   c  and has a center axis intersecting at a right angle with the rotating axis X of the shaft  53 . The first plane  56   a  intersects at a right angle with the rotating axis X of the shaft  53  and is located to correspond to the concentric bearing  54  to contain the center axis of the first pump  50   a . The second plane  56   b  is parallel to the first plane  56   a  and is spaced apart from the first plane  56   a  by a predetermined distance to correspond to the eccentric bearing  55 . 
     The first pump  50   a , second pump  50   b  and third pump  50   c  are arranged on the first plane  56   a . The second pump  50   b  has a center axis, which intersects at a right angle with the rotating axis X of the shaft  53  and is rotated counterclockwise about the rotating axis X by 120 degrees from the center axis of the first pump  50   a . The third pump  50   c  has a center axis, which intersects at a right angle with the rotating axis X of the shaft  53  and is rotated counterclockwise about the rotating axis X by 270 degrees from the center axis of the first pump  50   a.    
     The fourth pump  50   d , fifth pump  50   e  and sixth pump  50   f  are arranged on the second plane  56   b . The fourth pump  50   d  has a center axis, which intersects at a right angle with the rotating axis X and is rotated counterclockwise about the rotating axis X by 30 degrees from the center axis of the first pump  50   a . The fifth pump  50   e  has a center axis, which intersects at a right angle with the rotating axis X of the shaft  53  and is rotated counterclockwise about the rotating axis X by 90 degrees from the center axis of the fourth pump  50   d . The sixth pump  50   f  has a center axis, which intersects at a right angle with the rotating axis X of the shaft  53  and is rotated counterclockwise about the rotating axis X by 240 degrees from the center axis of the fourth pump  50   d.    
     In the present embodiment, as illustrated in  FIG. 4 , the first pump  50   a  and second pump  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 pump  50   d  and sixth pump  50   f  arranged on the second plane  56   b  may be connected to the second hydraulic circuit B. 
     With the above described arrangement, in the electronically controlled brake system in accordance with the embodiment of the present invention, whenever the shaft  53  rotates once about the rotating axis X, the first and second hydraulic circuits A and B each performs generation of pressure three times. This reduces a pressure pulse period and pressure pulse width, resulting in alleviated system shaking and operation noise. 
     In the electronically controlled brake system of the present embodiment, suction and discharge paths of the pump unit  50  may be oriented in the same direction. This enables compact spatial arrangement of the pumps and compact path design. 
     Specifically, suction paths  80   a ,  80   b ,  80   c ,  80   d ,  80   e  and  80   f  and discharge paths  90   a ,  90   b ,  90   c ,  90   d ,  90   e  and  90   f  are formed in a single direction, and thus, may easily hold the low-pressure and high-pressure accumulators  40  and  60  in common. More specifically, as illustrated in  FIG. 3 , the three pumps  50   a ,  50   b  and  50   e  connected to the first hydraulic circuit A are connected at their suction sides to the single low-pressure accumulator  40  and at their discharge sides to the single high-pressure accumulator  60 . The three pumps  50   c ,  50   d  and  50   f  connected to the second hydraulic circuit B are connected at their suction sides to the single low-pressure accumulator  40  and at their discharge sides to the single high-pressure accumulator  60 . In this way, more compact design of the brake system may be possible. 
     Although the present embodiment illustrates the first, second and fifth pumps  50   a ,  50   b  and  50   e  as being connected to the first hydraulic circuit A and the third, fourth and sixth pumps  50   c ,  50   d  and  50   f  as being connected to the second hydraulic circuit B, this is only given by way of example, and three pumps connected to each of the first and second hydraulic circuits may be adjustable according to the configuration of the hydraulic circuits. For example, the second, fourth and fifth pumps  50   b ,  50   d  and  50   e  may be connected to the first hydraulic circuit A, and the first, third and sixth pumps  50   a ,  50   c  and  50   f  may be connected to the second hydraulic circuit B. 
     The hydraulic circuits in accordance with the embodiment of the present invention are given by way of example, and of course, the pump unit of the present embodiment may also be applied to other hydraulic circuits. 
     As is apparent from the above description, an electronically controlled brake system in accordance with an embodiment of the present invention may have the effects of assuring rapid response ability during operation of a motor and pump, enhanced durability owing to a reduction in load and operations of respective components, and comfortable pedaling and reduced operation noise owing to a reduction in hydraulic pulsation. 
     Although a few embodiments of the present invention 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 invention, the scope of which is defined in the claims and their equivalents.