Patent Publication Number: US-2009223752-A1

Title: Disk break apparatus for electromechanical brake system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is based on, and claims priority from, Korean Application Serial Number 10-2008-0020909, filed on Mar. 6, 2008, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a disk brake apparatus, and more particularly disk brake apparatus for an electromechanical brake system. 
     BACKGROUND OF THE INVENTION 
     In general, an electromechanical brake system (hereafter, referred to as EMB system), the next generation brake system, is a system that senses the driver&#39;s intention of braking a vehicle using a pedal simulator, and then controls the brake pressure of the front wheels and rear wheels, using a motor. 
     In addition to a general braking function, an ABS (Anti-Lock Brake System) function, and a VDC (Vehicle Dynamic Control) function, the EMB system allows all intelligent braking functions, including an automatic braking function that is required for an intelligent cruise control system that will be used in the close future. 
     Technologies considering safety of a vehicle have been considerably developed and development of an active safe system has been carried out, by integrating technologies of electronics and control engineering. 
     In particular, it can be said that a brake system is given much weight in a vehicle accident and the safety system and the present braking technology is used to control the position of a vehicle when it is accelerated or is in normal travel. 
     Since the brake system is given much weight in the safety of a vehicle as described above, requirement of the active safe system has been increased, and particularly, necessity of the intelligent brake system for an ITS vehicle equipped with an intelligent cruise control system, which will come into the market, is on an increasing trend. 
     As a variety of functions has been required for such a brake system, pumps or valves needed for an existing hydraulic circuit for braking have been added or modified, but the specification should be changed again to be used for a vehicle with the intelligent cruise control system. 
     Therefore, efforts for providing simple and various function to an existing brake system that has been used in an ABS and VDC in the related art have been made, and typically, an electro-hydraulic brake system (EHB system) and an EMB system that estimates appropriate pressure using a controller according to pedal effort applied by a driver and other signals generated by sensors and controls the brake pressure according to the signal has been known in the related art. 
     It is considered that the EMB system gradually replace the ABS and VDC hydraulic systems and it is estimated that the EMB system sufficiently satisfies demand as an actuator in an electric vehicle or a brake actuator in an intelligent vehicle, such as the intelligent cruise control system. 
       FIG. 1  schematically shows the entire configuration of a common EMB system. 
     When a driver operates a brake pedal  1 , singles are inputted to a main control unit  4  from a brake pedal switch  2  and a brake pedal operation force detecting sensor  3 . 
     Main control unit  4  estimates appropriate pressure according to the operation pressure of brake pedal  1  and signals of a barking force sensor  5  and a wheel speed sensor  6 , and then transmits signals corresponding to the estimated value to a first sub-control unit  7  and second sub-control unit  8 . 
     As a first driving unit  11  and a second driving unit  12  are driven in response to signals of first sub-control unit  7  and second sub-control unit  8  respectively and a disk brake apparatus  20  equipped to front wheels  13  and rear wheels  14  are actuated by the operation of first driving unit  11  and second driving unit  12 , an appropriate braking force is applied. 
     Meanwhile, reference numerals  15 ,  16 ,  17 ,  18 , and  19  indicate an engine, an automatic transmission, a main battery, a first sub-battery, and a second sub-battery, respectively. Further, reference numerals &#39; 21 ,  26 , and  27  indicate a disk, a first motor, and a second motor that are included in disk brake apparatus  20 . 
       FIG. 2  illustrates the configuration of disk brake apparatus  20  in the related art. 
     The disk brake apparatus shown in  FIG. 2  includes two motors and a planetary gear set  25 , and disk brake apparatus  20  in the related art further includes disk  21  that rotates with the wheel and a friction pad  22  that is selectively pressed against a friction surface  21   a  of disk  21  to prevent rotation of disk  21 . A cylindrical inner screw member  23  with threads on the outer circumference is fastened to friction pad  22  and is engaged with a cylindrical outer screw member  24  with threads on the inner circumference thereof. 
     That is, as outer screw member  24  rotates, inner screw member  23  reciprocates. 
     Outer screw member  24  is connected with a planetary gear set  25  for power transmission and planetary gear set  25  is connected with first motor  26  and second motor  27  for power transmission. 
     As disclosed in the related art, planetary gear set  25  is composed of a sun gear  25   a,  planetary gears  25   b,  a carrier  25   c,  and a ring gear  25   d,  in which sun gear  25   a  is directly connected with first motor  26 , planetary gears  25   b  are engaged with the outer circumference of sun gear  25   a  and connected to carrier  25   c  to revolve around sun gear  25   a.    
     Carrier  25   c  makes an output and is connected to outer screw member  24  for power transmission, and ring gear  25   d  that is an internal gear with teeth on the inner circumference is engaged with planetary gears  25   b  and connected with second motor  27  for power transmission. 
     Therefore, as first and second motors  26 ,  27  equipped to front wheel  13  and rear wheel  14  are activated by the operation of first and second driving units  11 ,  12  and carrier  25   c  of planetary gear set  25  correspondingly rotates, outer screw member  24  rotates and inner screw member  23  reciprocates. As a result, friction pad  22  is selectively pressed against friction surface  21   a  of disk  21  that is rotating and a barking force applied. 
     However, according to disk brake apparatus  20  having the above configuration in the related art, because first and second motors  26 ,  27  are coaxially connected in a series in the left-right direction, i.e. the width direction of the car body, planetary gear set  25  is large in length L 1  from the left to the right, i.e. width, and accordingly, a large space is needed in the left-right direction, i.e. the width direction of the car body and it is difficult to secure high freedom in the layout. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide a disk brake apparatus for an electromechanical brake system including two motors and a planetary gear set, in which the planetary gear set is considerably reduced in length in the left-right direction, i.e. the width direction of the car body by disposing a second motor outside from a first motor, such that it is possible to secure high freedom in the layout and effectively dispose the disk brake apparatus in a small space. 
     A disk brake apparatus for an electromechanical brake system according to an exemplary embodiment of the present invention includes a first motor and a second motor. The first motor is provided for front wheels and rear wheels for power transmission with a sun gear of a planetary gear set. The second motor is provided for the front wheels and second wheels for power transmission with a ring gear of the planetary gear set. Further, the second motor connected with the ring gear is disposed outside from the first motor connected with the sun gear. 
     In another exemplary embodiment of the present invention, a disk brake apparatus for an electromechanical brake system, may comprise a first motor connected with a sun gear of a planetary gear set for power transmission; and a second motor connected with a ring gear of the planetary gear set for power transmission, wherein the first motor and the second motor are disposed co-axially and in series each other, and the second motor substantially surrounds an outer circumference of the ring gear. The second motor may include: a stator that has a metal core supporting a wire and a frame supporting the metal core; and a rotator that is formed of a hollow shaft and rotatably disposed inside the stator. The ring gear of the planetary gear set may be fitted in the rotator. 
     According to the disk brake apparatus of the invention, since the length of planetary gear set, which is included in the disk brake apparatus, in the width direction, i.e. in the left-right direction of the car body, is significantly reduced and the high freedom for disk brake apparatus in the layout can be secured, it is possible to dispose disk brake apparatus in a small space in the left-right direction, i.e. the width direction of the car body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which: 
         FIG. 1  is a schematic view illustrating the entire configuration of a conventional EMB system; 
         FIG. 2  is a view illustrating a disk brake apparatus according to the related art, in the EMB system shown in  FIG. 1 ; 
         FIG. 3  is a schematic view illustrating the entire configuration of an EMB system equipped with a disk brake system according to an exemplary embodiment of the present invention; 
         FIG. 4  is a view illustrating a disk brake apparatus according to an exemplary embodiment of the present invention, equipped in an EMB system; and 
         FIG. 5  is a view illustrating a second motor of a disk brake apparatus according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the invention are described hereafter in detail with reference to the accompanying drawings. 
     An EMB system according to an exemplary embodiment of the present invention, as shown in  FIG. 3 , includes a brake pedal  1  that is operated by a driver, a brake pedal switch  2  that detects the operation of brake pedal  1 , and a brake operation force detecting sensor  3  that detects the operation force of brake pedal  1 . 
     A main control unit  4 , receiving signals from brake pedal switch  2  and brake operation force detecting sensor  3 , also receives signals from a braking force sensor  5  and a wheel speed sensor  6 . 
     Main control unit  4  estimates appropriate pressure according to the operation pressure of brake pedal  1  and the signals of braking force sensor  5  and wheel speed sensor  6  and then transmits signals corresponding to the estimated value to a first sub-control unit  7  and a second sub-control unit  8 . 
     Main control unit  4  can transmit/receive signals to/from an engine  15  and an automatic transmission  16  and is supplied with power from a main battery  17 . 
     First sub-control unit  7  and second sub-control unit  8  can control a first driving unit  11  and a second driving unit  12  respectively by generating control signals, and first driving unit  11  and second driving unit  12  are supplied with power from a first sub-battery  18  and a second sub-battery  19  respectively. 
     First driving unit  11  and second driving unit  12  are designed to actuate disk brake apparatus  30  according to an exemplary embodiment of the present invention, which are each equipped to a front wheel  13  and a rear wheel  14 , and disk brake apparatus  30  receives driving forces from first driving unit  11  and second driving unit  12  and generate braking forces. 
     Meanwhile, reference numerals  31 ,  36 , and  37 , which are shown in  FIG. 3 , indicate a disk, a first motor, and a second motor that are included in disk brake apparatus  30  according to an exemplary embodiment of the present invention. 
     Further, disk brake apparatus  30  according to an exemplary embodiment of the present invention, as shown in  FIG. 4 , includes disk  31  and a friction pad  32  that is selectively pressed against a friction surface  31  a of disk  31  to prevent rotation of disk  31 . 
     Friction pad  32  is connected with a cylindrical inner screw member  33  with threads on the outer circumference thereof, the inner screw member  33  is engaged with a cylindrical outer screw member  34  with threads on the inner circumference thereof such that as the cylindrical outer screw member  34  rotates, inner screw member  33  reciprocates. 
     Outer screw member  34  is connected with a planetary gear set  35  for power transmission and planetary gear set  35  is connected with first motor  36  and second motor  37  for power transmission. 
     Planetary gear set  35  is composed of a sun gear  35   a,  planetary gears  35   b,  a carrier  35   c,  and a ring gear  35   d,  in which sun gear  35   a  is directly connected with first motor  36 , planetary gears  35   b  are engaged with the outer circumference of sun gear  35   a  and connected to carrier  35   c  to revolve around sun gear  35   a.    
     Carrier  35   c  makes an output and is connected to cylindrical outer screw member  34  for power transmission, and ring gear  35   d  is engaged with planetary gears  35   b  and connected with second motor  37  for power transmission. 
     That is, second motor  37  is disposed outside from first motor  36  in disk brake apparatus  30  according to an exemplary embodiment of the present invention. 
     When second motor  37  is disposed outside from first motor  36  as described above, the length L 2  of planetary gear set  35  in the width direction (the left-right direction, i.e. the width direction of the car body) is considerably reduced as compared with that in the related art, described above with reference to  FIG. 2 . 
     Therefore, it is possible to secure high freedom in the layout for disk brake apparatus  30  according to an exemplary embodiment of the present invention and to effectively dispose disk brake apparatus  30  in a small space in the left-right direction, i.e. the width direction of the car body. 
     On the other hand, second motor  37 , as shown in  FIG. 5 , includes a stator  37   a  having a metal core supporting a wire and a frame supporting the metal core and a rotator  37   b  formed of a hollow shaft and rotatably disposed inside stator  37   a.    
     Further, ring gear  35   d  of planetary gear set  35  is fitted in rotator  37   d.    
     Accordingly, according to disk brake apparatus  30  of the invention, since the length L 2  of planetary gear set  35  in the width direction, i.e. in the left-right direction of the car body, is significantly reduced and the high freedom for disk brake apparatus in the layout can be secured, it is possible to dispose disk brake apparatus  30  in a small space in the left-right direction, i.e. the width direction of the car body. 
     The forgoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiment were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof It is intended that technical spirit and scope of the present invention be defined by the Claims appended hereto and their equivalents.