Abstract:
Disclosed is a disc brake for a vehicle, such as an electronic wedge brake, capable of preventing a disc from being subject to the moment due to misalignment of inner and outer friction members with respect to a disc. The disc brake includes a disc rotating together with a vehicle wheel, inner and outer friction pads disposed at both sides of the disc, respectively, a wedge unit installed at rear sides of the inner and outer friction pads to press the inner and outer friction pads against the disc, a driving device that operates the wedge unit for a braking operation, and a sync member for synchronizing braking positions of the inner and outer friction pads with respect to the disc. Since the disc is prevented from being subject to the moment, uneven wear does not occur in the friction member and/or the disc and deformation of the disc is prevented.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. 10-2008-0124004 filed on Dec. 8, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a disc brake for a vehicle. More particularly, the present invention relates to a disc brake for a vehicle, which presses a friction pad against a disc through a wedge action. 
         [0004]    2. Description of the Related Art 
         [0005]    A disc brake is a device for obtaining braking force by pressing a friction pad against an outer surface of a disc rotating together with a wheel. The disc brake includes an electronic wedge brake (EWB) that presses a friction pad against a disc by using a sliding type wedge member. For instance, the wedge member presses the friction pad against the disc while being moved along an oblique side thereof by a driving device. 
         [0006]    The EWB includes a driving motor for driving the wedge member, a screw shaft coupled with a rotating shaft of the driving motor, and a pressing member coupled to the screw shaft such that the pressing member can move back and forth according to the operation of the driving motor to press the wedge member against the disc. 
         [0007]    According to the EWB, as the driving motor operates, the pressing member presses the wedge member against the disc, so that the friction pad makes contact with the disc. At the same time, the wedge member further presses the friction pad against the disc while being moved along an oblique side thereof, so that the braking action is achieved. 
         [0008]    However, according to the disc brake for the vehicle of the related art, a first friction member, which is provided at one side of the disc brake where the driving motor is installed, makes contact with the disc according to the operation of the wedge member while moving toward the disc along the oblique side of the wedge member. In contrast, a second friction member, which is provided at the other side of the disc brake, linearly moves perpendicularly to the disc, so that the first and second friction members may not be aligned in the same position at the braking time. As a result, the moment is applied to the disc, so that uneven wear may occur in the friction members or the disc. In extreme case, the disc may be deformed. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, it is an aspect of the present invention to provide a disc brake for a vehicle, capable of preventing a disc from being subject to the moment by aligning inner and outer friction members in the same position with respect to the disc. 
         [0010]    Additional aspects and/or advantages of the invention 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 invention. 
         [0011]    The foregoing and/or other aspects of the present invention are achieved by providing a disc brake for a vehicle, the disc brake including a disc rotating together with a vehicle wheel, inner and outer friction pads disposed at both sides of the disc, respectively, a wedge unit installed at rear sides of the inner and outer friction pads to press the inner and outer friction pads against the disc, a driving device that operates the wedge unit for a braking operation, and a sync member for synchronizing braking positions of the inner and outer friction pads with respect to the disc. 
         [0012]    According to the present invention, the wedge unit includes sliding wedge parts installed at the rear sides of the inner and outer friction pads and formed at rear sides thereof with oblique surfaces, respectively, and inner and outer wedge parts formed with oblique surfaces corresponding to the oblique surfaces of the sliding wedge parts and supported by a caliper housing of the vehicle. 
         [0013]    According to the present invention, the sync member includes first and second rods, which are provided at the sliding wedge parts installed at the rear sides of the inner and outer friction pads, and the first and second rods are assembled with each other in such a manner that a length of the sync member is adjustable. 
         [0014]    According to the present invention, the sync member has an anti-rotation structure. 
         [0015]    According to the disc brake for the vehicle of the present invention, the sliding wedge members are installed corresponding to the inner and outer friction pads provided at both sides of the disc, and the movement of the sliding wedge parts is synchronized by the sync bar, so that the inner and outer friction pads can be aligned in the same position with respect to the disc, thereby preventing the disc position with respect to the disc, thereby preventing the disc from being subject to the moment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and/or other aspects and advantages 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: 
           [0017]      FIG. 1  is an exploded perspective view schematically showing a disc brake for a vehicle according to one embodiment of the present invention; 
           [0018]      FIG. 2  is a plan view of a disc brake for a vehicle according to one embodiment of the present invention; 
           [0019]      FIG. 3  is a sectional view showing sync bars of a disc brake for a vehicle according to one embodiment of the present invention; and 
           [0020]      FIG. 4  is a view for explaining an operation of a disc brake for a vehicle according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    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 the like elements. The embodiments are described below to explain the present invention by referring to the figures. 
         [0022]      FIG. 1  is an exploded perspective view of a disc brake for a vehicle according to the present invention, and  FIG. 2  is an assembled view of  FIG. 1 . 
         [0023]    As shown in  FIGS. 1 and 2 , the disc brake for the vehicle according to the present invention includes a disc  10  rotating together with a vehicle wheel (not shown), and inner and outer friction pads  11  and  12  installed at both sides of the disc  10  for the purpose of friction braking of the disc  10 . In addition, the disc brake for the vehicle further includes a caliper housing  20  and a wedge unit  30  for pressing the inner and outer friction pads  11  and  12  against the disc  10 , and a driving device  50  that operates the wedge unit  30  to press the inner and outer friction pads  11  and  12 . 
         [0024]    The inner and outer friction pads  11  and  12  are supported by a carrier  40  fixed to a knuckle part (not shown) of the vehicle in such a manner that the inner and outer friction pads  11  and  12  can move back and forth to press both sides of the disc  10 . The caliper housing  20  is coupled to both sides of the carrier  40  through a guide rod  21  coupled to both sides of the caliper housing  20  in such a manner that the caliper housing  20  can move back and forth. The guide rod  21  is coupled to both sides of a rod coupling part  23  of the caliper housing  20  by a fixing screw  22  in a state in which an elastic member (not shown) is interposed between the guide rod  21  and the fixing screw  22 . The caliper housing  20  moves back and forth to press an outer surface of the outer friction pad  12 . 
         [0025]    The wedge unit  30  includes sliding wedge parts  31  provided at rear sides of the inner and outer friction pads  11  and  12 , respectively, an inner wedge part  24  provided at one inner sidewall of the caliper housing  20  while facing one of the sliding wedge parts  31 , and an outer wedge part  25  provided at the other inner sidewall of the caliper housing  20  while facing the other of the sliding wedge parts  31 . That is, the sliding wedge parts  31  are positioned between the inner friction pad wedge parts  31  are positioned between the inner friction pad  11  and the inner wedge part  24  and between the outer friction pad  12  and the outer wedge part  25 , respectively. 
         [0026]    The sliding wedge parts  31  are formed on rear surfaces thereof with oblique surfaces  32  and  33  which are symmetrically arranged in the form of a V shape. In addition, the inner and outer wedge parts  24  and  25  are formed on front surfaces thereof with oblique surfaces  26  and  27 , which are symmetrically arranged in the form of an inverse-V shape corresponding to the oblique surfaces  32  and  33  of the sliding wedge parts  31 . In the following description, the sliding wedge part  31  arranged between the inner wedge part  24  and the inner friction pad  11  will be referred to as a first sliding wedge part  31   a  and the sliding edge part  31  arranged between the outer wedge part  25  and the outer friction pad  12  will be referred to as a second sliding wedge part  31   b.    
         [0027]    The first sliding wedge part  31   a  is coupled with the second sliding wedge part  31   b  by a sync bar  34  such that the first and second sliding wedge parts  31   a  and  31   b  can move simultaneously. The sync bar  34  transversely extends while crossing over the disc  10  and includes a first rod  34   a  provided in the first sliding wedge part  31   a  and a second rod  34   b  provided in the second sliding wedge part  31   b.  The first and second rods  34   a  and  34   b  are assembled with each other such that the length of the sync bar  34  can be variously adjusted. In addition, as shown in  FIG. 3 , the first and second rods  34   a  and  34   b  must have angular sectional shapes or concave-convex sectional shapes such that the first and second rods  34   a  and  34   b  can be arranged in the same position with respect to the disc  10  without rotating relative to each other. 
         [0028]    The driving device  50 , which operates the first and second sliding wedge parts  31   a  and  31   b  for the purpose of braking operation, is installed at one side of the  31   a  and  31   b  for the purpose of braking operation, is installed at one side of the inner wedge part  24  of the caliper housing  20 . For instance, the driving device  50  may include a driving motor  51  positioned at an outer surface of the inner wedge part  24  and having a rotating shaft extending by passing through the inner wedge part  24  in parallel to the pressing direction for the inner friction pad  11 , a screw shaft  52  arranged in parallel to the disc  10  and in perpendicular to the rotating shaft of the driving motor  51 , a worm  54  provided at the rotating shaft of the driving motor  51 , a worm gear including a worm wheel  54  mounted on the center of the screw shaft  52  to engage with the worm  53 , and bolt walls  55  screw-coupled with the screw shaft  52  and moved according to rotation of the screw shaft  52  in order to move the first sliding wedge part  31   a  toward the disc  10 . 
         [0029]    In addition, the screw shaft  52  is rotatably installed in the first sliding wedge part  31   a  and the bolt walls  55  are fixed to the first sliding wedge part  31   a  while being screw-coupled with the screw shaft  52 . Thus, if the driving motor  51  is driven for the purpose of the braking operation, the first sliding wedge part  31   a  moves closely to the disc  10  along the oblique surfaces  26  and  27  of the inner wedge part  24 , thereby pressing the inner friction pad  11 . 
         [0030]    Since the second sliding wedge part  31   b  also moves together with the first sliding wedge part  31   a  due to the sync bar  34 , if pressing force for the second friction pad  12  is applied through the caliper housing  20 , the second sliding wedge part  31   b  presses the outer friction pad  12  against the disc  10  at the position the same as that of the first sliding wedge part  31   a.    
         [0031]    Hereinafter, the operation of the disc brake for the vehicle according to the present invention will be described. 
         [0032]      FIG. 2  shows the disc brake when the braking operation is not performed. In this state, if the braking operation starts, as shown in  FIG. 4 , the driving motor  51  is driven so that the first sliding wedge part  31   a  approaches the disc  10  due to the rotation of the worm  53 . As the worm  53  rotates, the worm wheel  54  is also rotated at a low speed according to the reduction gear ratio between the worm  53  and the worm wheel  54 , so that the worm wheel  54  can rotate the screw shaft  52  with higher torque. Upon the rotation of the screw shaft  52 , the bolt walls  55  of the first sliding wedge part  31  a moves lengthwise along the screw shaft  52  so that the first sliding wedge part  31   a  is moved toward the disc  10 . That is, the oblique surface  32  formed on the rear side of the first sliding wedge part  31   a  is moved along the oblique surface  26  of the inner wedge part  24 , so that the first sliding wedge part  31   a  presses the inner friction pad  11  against the disc  10 , thereby achieving the braking action. As the inner friction pad  11  makes contact with the disc  10 , the inner friction pad  11  is urged to rotate in the rotational direction of the disc  10 , so the first sliding wedge part  31   a  tends to move in the rotational direction of the disc  10 . Thus, the self-reinforcement effect is generated so that the greater braking force can be obtained. 
         [0033]    As the inner friction pad  11  presses the disc  10 , the caliper housing  20  is subject to repulsive force, so the caliper housing  20  moves reversely to the pressing direction of the inner friction pad  11 , thereby pressing the outer friction pad  12  against the disc  10 . Thus, the same friction occurs at both sides of the disc  10 . 
         [0034]    In detail, when the first sliding wedge part  31   a  moves along the oblique surface of the inner wedge part  24 , the second sliding wedge part  31   b  moves to the the inner wedge part  24 , the second sliding wedge part  31   b  moves to the position identical to the position of the first sliding wedge part  31   a  with respect to the disc  10  by means of the sync bar  34  before the caliper housing  20  is moved. Then, the caliper housing  20  moves inversely to the pressing direction for the inner friction pad  11 , so that the outer wedge part  25  approaches the second sliding wedge part  31   b.  In this state, the outer friction pad  12  is pressed against the disc  10 , thereby stopping the rotation of the disc  10 . 
         [0035]    When the braking operation is released, the driving motor  51  is inversely driven, so that the screw shaft  52  is inversely rotated. Thus, the first and second sliding wedges  31   a  and  31   b  may move back, so that the wedge unit  30  is released from the inner and outer friction pads  11  and  12 . 
         [0036]    Although 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.