Patent Publication Number: US-9896112-B2

Title: Brake apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a brake apparatus. 
     BACKGROUND ART 
     Conventionally, a brake apparatus has been used which brakes the rotation of a wheel by causing a force by an actuator to act on points of force of a pair of link arms rotatable about fulcrums and causing brake linings supported on points of action of the link arms to slide in contact with brake discs. 
     JP10-505038A discloses a brake caliper unit in which one end parts of caliper levers are coupled to each other, the other end parts are respectively rotationally mounted on brake pads and an eccentric body transmission device provided on a fulcrum between the both end parts of the caliper lever rotates the caliper levers. The eccentric body transmission device includes an eccentric pin configured to rotate by receiving a force by a braking force generator and rotates the caliper lever about the one end part by the rotation of this eccentric pin. 
     However, in the caliper brake unit of JP10-505038A, a circumferential tangential force acting on the brake pad from the brake disc during braking in which the brake pad slides in contact with the brake disc acts on the eccentric pin of the eccentric body transmission device. Thus, a large force is necessary to rotate the eccentric pin during braking and it has been difficult to improve machine efficiency. 
     The present invention aims to improve the machine efficiency of a brake apparatus. 
     According to one aspect of the present invention, a brake apparatus for braking by sandwiching a brake disc rotating together with a wheel, includes a brake main body supported on a vehicle body or a truck; an actuator provided on the brake main body and configured to advance and retract an output member; a pair of link arms having supporting portions between one and other end parts rotatably supported on the brake main body, the pair of link arms being respectively provided to face both surfaces of the brake discs, the pair of link arms having the one end parts coupled by a coupling rod and configured such that the other end parts respectively support brake linings for giving a frictional force by sliding in contact with the brake discs; a lever rotatably coupled to the output member of the actuator and configured to rotate by advancing and retracting movements of the output member; and a booster unit provided on at least one of the one end parts of the pair of link arms and configured to rotate the link arms with the supporting portions as fulcrums by boosting a force transmitted by the rotation of the lever. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of a brake apparatus according to an embodiment of the present invention, and 
         FIG. 2  is a front view of the brake apparatus according to the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, an embodiment of the present invention is described with reference to the drawings. 
     First, the configuration of a brake apparatus  100  according to the embodiment of the present invention is described with reference to  FIGS. 1  and  2 . 
     The brake apparatus  100  is mainly applied to railway vehicles. The brake apparatus  100  brakes a wheel  1  by sandwiching brake discs  1   a  rotating together with the wheel  1 . Specifically, the brake apparatus  100  brakes the rotation of the wheel  1  by frictional forces between the brake discs  1   a  and brake linings  2  by sandwiching the brake discs  1   a  from opposite sides by a pair of brake linings  2 . 
     The brake discs  1   a  are formed on both sides of the wheel  1  and integrally rotate with the wheel  1 . Instead of a configuration in which the brake discs  1   a  are integrally formed with the wheel  1 , separate brake discs  1   a  configured to rotate together with the wheel  1  may be provided. 
     The brake lining  2  faces the brake disc  1   a  with a predetermined interval set in advance therebetween (state shown in  FIG. 1 ). The brake lining  2  moves toward the brake disc  1   a  and is pressed into contact with the brake disc  1   a  in parallel during braking. 
     The brake lining  2  includes a back plate portion  2   a  supported on a lining holding portion  3  of the brake apparatus  100  and a friction member  2   b  configured to come into contact with the brake disc  1   a  during braking. The friction member  2   b  is composed of a plurality of segments and fixed to a surface of the back plate portion  2   a . The brake lining  2  brakes the rotation of the wheel  1  by a frictional force generated by the contact of the friction member  2   b  and the brake disc  1   a.    
     The lining holding portion  3  includes dovetail grooves (not shown) into which the back plate portions  2   a  of the brake linings  2  are to be inserted. Anchor blocks  4  fixed to the lining holding portion  3  are respectively provided on upper and lower end parts of the lining holding portion  3  by a pair of anchor bolts  5 . The anchor blocks  4  fix end parts of the back plate portions  2   a  of the brake linings  2  in a longitudinal direction (vertical direction in  FIG. 2 ). This causes the brake linings  2  inserted into the dovetail grooves to be held on the lining holding portion  3 . 
     The brake apparatus  100  includes a brake main body  10 , an actuator  20  provided on the brake main body  10  and configured to advance and retract a rod  21  as an output member, a pair of link arms  30  having supporting portions  32  between one end parts  31  and other end parts  33  rotatably supported on the brake main body  10 , levers  40  rotatably coupled to the rod  21  of the actuator  20  and configured to rotate by advancing and retracting movements of the rod  21  and a booster unit  50  provided on at least one of the one end parts  31  of the pair of link arms  30  and configured to rotate the link arms  30  with the supporting portions  32  as fulcrums by boosting a force transmitted by the rotation of the lever  40 . 
     The brake main body  10  is supported on a truck (not shown) when the brake apparatus  100  is applied to a railway vehicle. The brake main body  10  is supported on a vehicle body (not shown) when the brake apparatus  100  is applied to a vehicle other than railway vehicles. 
     The actuator  20  is a fluid pressure actuator configured to be operated by a liquid pressure such as a hydraulic pressure or a pressure of working fluid such as a pneumatic pressure. Without limitation to this, the actuator  20  may be of another type such as a mechanical actuator configured to be operated by the rotation of an electric motor. The actuator  20  operates based on a braking operation of a driver and advances and retracts the rod  21  relative to the brake main body  10 . 
     The rod  21  includes a coupling shaft  22 , to which the levers  40  are respectively rotatably coupled, on both end parts. The coupling shaft  22  is so arranged that a center axis thereof is parallel to the brake linings  2 . Centers of the brake discs  1   a  are located on an extension of a center axis along which the rod  21  reciprocates. The rod  21  can be advanced and retracted relative to the brake main body  10  and swing in a movable direction of the brake linings  2  (vertical direction in  FIG. 1 ). 
     As shown in  FIG. 1 , the link arms  30  are respectively provided to face both surfaces of the brake discs  1   a . The one end parts  31  of the pair of link arms  30  are coupled by a coupling rod  35 . The other end parts  33  of the link arms  30  swingably support the brake linings  2  configured to give frictional forces by sliding in contact with the brake discs  1   a . As shown in  FIG. 2 , the link arm  30  is formed into a substantially U shape having a pair of arm portions  30   a  provided on upper and lower sides. 
     As shown in  FIG. 1 , a coupling shaft  31   a  coupling the coupling rod  35  and the link arm  30  by penetrating therethrough is provided on the one end part  31  of one link arm  30 . The booster unit  50  coupling the coupling rod  35 , the link arm  30  and the pair of levers  40  by penetrating therethrough and configured to rotate the link arms  30  by boosting a force given by advancing and retracting movements of the rod  21  of the actuator  20  is provided on the one end part  31  of the other link arm  30 . 
     Instead of this configuration, the booster units  50  may be provided on both the one end part  31  of the one link arm  30  and the one end part  31  of the other link arm  30 . In that case, each booster unit  50  can rotate each of the one and other link arms  30 . The booster unit  50  is described in detail later. 
     An arm shaft  32   a  coupling the link arm  30  and the brake main body  10  by penetrating therethrough is provided on the supporting portion  32  of the link arm  30 . The link arm  30  is rotatably supported on the brake main body  10  by the arm shaft  32   a . A circumferential tangential force acting on the brake lining  2  from the brake disc  1   a  during the braking of the brake apparatus  100  acts on the brake main body  10  via the arm shaft  32   a  from the supporting portion  32 . 
     A lining shaft  33   a  coupling the link arm  30  and the lining holding portion  3  by penetrating therethrough is provided on the other end part  33  of the link arm  30 . The lining holding portion  3  is rotatably supported on the link arm  30  by the lining shaft  33   a . In this way, the brake lining  2  is made swingable relative to the link arm  30  and can constantly come into contact with the brake disc  1   a  in parallel during braking. 
     The levers  40  transmit the force by advancing and retracting movements of the rod  21  of the actuator  20  to the booster unit  50 . One end part  41  of the lever  40  is rotatably coupled to the coupling shaft  22  of the rod  21 . Another end part  42  of the lever  40  is unrotatably coupled to a later-described eccentric portion  53  of the booster unit  50 . 
     The lever  40  rotates between the coupling shaft  22  and the eccentric portion  53  when the rod  21  is advanced and retracted relative to the brake main body  10 . The lever  40  rotates to a position where it is parallel to the coupling rod  35  in a state where the rod  21  is most retracted from the brake main body  10 . 
     As shown in  FIG. 2 , the booster unit  50  includes an eccentric cam  51  configured to rotate about an axis of rotation A 1  by the rotation of the levers  40 . The axis of rotation A 1  of the eccentric cam  51  is provided at the same position as a center axis of the coupling shaft  31   a  relative to the link arm  30 . 
     The eccentric cam  51  includes a large-diameter portion  52  rotatably coupled to the coupling rod  35 , the eccentric portions  53  having a center axis A 2  at a position offset from the axis of rotation A 1  of the eccentric cam  51  and configured to rotate along an arcuate path centered on the axis of rotation A 1  by the rotation of the levers  40  and a pair of arm coupling portions  54  formed coaxially with the eccentric portions  53  and rotatably supported on the link arm  30 . 
     The large-diameter portion  52  is formed to have the same outer diameter as the coupling shaft  31   a . A center axis of the large-diameter portion  52  is the axis of rotation A 1  of the eccentric cam  51 . 
     The eccentric portions  53  are formed to have a smaller diameter than the large-diameter portion  52 . The eccentric portions  53  are respectively provided at opposite axial sides of the large-diameter portion  52 . The levers  40  are relatively unrotatably coupled to the eccentric portions  53 . Thus, when the rod  21  is advanced and retracted relative to the brake main body  10  and the levers  40  rotate, the eccentric portions  53  rotate along the arcuate paths centered on the axis of rotation A 1 . 
     The arm coupling portions  54  are formed to have the same diameter as the eccentric portions  53 . The arm coupling portions  54  are provided at opposite sides of the large-diameter portion  52  with the eccentric portions  53  located between the arm coupling portions  54  and the large-diameter portion  52 . Instead of this, the arm coupling portions  54  may be formed to have a smaller diameter than the eccentric portions  53 . Further, the arm coupling portions  54  may be respectively provided between the eccentric portions  53  and the large-diameter portion  52 . 
     As just described, the eccentric cam  51  includes the large-diameter portion  52  in a center, the eccentric portions  53  having a smaller diameter than the large-diameter portions  52  at opposite ends thereof and the arm coupling portions  54  having a diameter equal to or smaller than the eccentric portions  53  at further opposite ends thereof. Thus, the eccentric cam  51  is narrowed in diameter in a stepwise manner from the center toward the opposite end parts, wherefore processing is easy. Further, since the coupling rod  35 , the levers  40  and the link arm  30  can be successively assembled with the eccentric cam  51 , assemblability is good. 
     Next, functions of the brake apparatus  100  are described. 
     The brake apparatus  100  enters a braking state from a non-braking state (state shown in  FIGS. 1 and 2 ) when the actuator  20  operates based on a braking operation of the driver. 
     When the actuator  20  operates and the rod  21  is retracted from the brake main body  10 , the levers  40  rotate by being pushed by the coupling shaft  22 . A force of the actuator  20  for retracting the rod  21  is transmitted to the eccentric portions  53  of the eccentric cam  51  via the levers  40 . 
     The eccentric cam  51  rotates in one direction (counterclockwise direction in  FIG. 1 ) by the rotation of the eccentric portions  53  along the arcuate paths centered on the axis of rotation A 1  due to the force transmitted via the levers  40 . Since this causes the arm coupling portions  54  to integrally rotate with the eccentric portions  53  in a direction away from the rod  21 , the one end parts  31  of the pair of link arms  30  move in directions to separate from each other. 
     Since the link arms  30  are rotatably supported on the brake main body  10  by the supporting portions  32 , if the one end parts  31  move in the directions to separate from each other, the other end parts  33  move in directions to approach each other. Thus, the brake linings  2  move toward the brake discs  1   a  and are pressed into contact with the brake discs  1   a  in parallel to brake the rotation of the wheel  1 . 
     At this time, a force transmitted from the rod  21  via the levers  40  is boosted by a factor of L 1 /L 2  and transmitted to the link arms  30  by a lever ratio of a distance L 1  between an axis of rotation A 3  of the coupling shaft  22  and the axis of rotation A 1  and a distance L 2  between the axis of rotation A 1  and the center axis A 2  of the eccentric portions  53 . Thus, a large braking force can be obtained without providing a large-size actuator. Therefore, a size and weight reduction of the brake apparatus  100  is possible. 
     Further, the supporting portion  32  of the link arm  30  between the one and other end parts  31 ,  33  is rotatably supported on the brake main body  10 . The eccentric cam  51  configured to rotate the link arms  30  by boosting the force transmitted to the rod  21  by the rotation of the levers  40  is provided on the one end part  31  of the link arm  30 . Thus, the circumferential tangential forces acting on the brake linings  2  from the brake discs  1   a  during the braking of the brake apparatus  100  act on the arm shafts  32   a  of the supporting portions  32  and do not act on the eccentric cam  51 . Thus, frictional resistance when the eccentric cam  51  rotates does not become large, wherefore machine efficiency during the braking of the brake apparatus  100  can be improved. 
     The force transmitted to the one end part  31  of the link arm  30  from the eccentric cam  51  is boosted by a factor of L 3 /L 4  by a lever ratio of a distance L 3  between the one end part  31  and the supporting portion  32  and a distance L 4  between the supporting portion  32  and the other end part  33 . Since the distance L 4  is longer than the distance L 3  in the brake apparatus  100 , a force for pressing the brake lining  2  against the brake disc  1   a  is smaller than the force transmitted to the one end part  31  of the link arm  30  from the eccentric cam  51 . 
     However, in the brake apparatus  100 , the force transmitted from the rod  21  of the actuator  20  via the levers  40  by the eccentric cam  51  is boosted by a large factor. Thus, a sufficiently large braking force can be obtained even if the link arms  30  are shortened to reduce the distance L 3  for a size and weight reduction of the brake apparatus  100 . 
     It should be noted that, in the brake apparatus  100 , a degree of design freedom of the positions of the arm shafts  32   a  of the supporting portions  32  is increased by providing the eccentric cam  51  on the one end part  31  of the link arm  30 . Thus, it is also possible to arrange the arm shafts  32   a  at positions facing a side surface of the wheel  1 . Therefore, the distance L 3  can be made longer than the distance L 4  and the brake linings  2  can be pressed against the brake discs  1   a  by further boosting the force boosted by the eccentric cam  51 . 
     The brake apparatus  100  enters the non-braking state (state shown in  FIGS. 1 and 2 ) from the braking state when the actuator  20  operates in a direction opposite to that during braking based on a brake releasing operation of the driver. 
     When the actuator  20  operates and the rod  21  enters the brake main body  10 , the levers  40  rotate by being pulled by the coupling shaft  22 . A force of the actuator  20  for causing the rod  21  to enter is transmitted to the eccentric portions  53  of the eccentric cam  51  via the levers  40 . 
     The eccentric cam  51  rotates in the other direction (clockwise direction in  FIG. 1 ) by the rotation of the eccentric portions  53  along the arcuate paths centered on the axis of rotation A 1  due to the force transmitted via the levers  40 . This causes the one end parts  31  of the pair of link arms  30  to move in directions to approach each other. Thus, the other end parts  33  of the pair of link arms  30  move in directions to separate from each other. In this way, the brake linings  2  are separated from the brake discs  1   a  to release the braking of the wheel  1 . 
     According to the above embodiment, the following effects are exhibited. 
     The supporting portions  32  of the link arms  30  between the one and other end parts  31 ,  33  are rotatably supported on the brake main body  10 . The eccentric cam  51  configured to rotate the link arms  30  by boosting the force transmitted to the rod  21  by the rotation of the levers  40  is provided on the one end part  31  of the link arm  30 . Thus, circumferential tangential forces acting on the brake linings  2  from the brake discs  1   a  during the braking of the brake apparatus  100  act on the arm shafts  32   a  of the supporting portions  32 , but do not act on the eccentric cam  51 . Accordingly, frictional resistance when the eccentric cam  51  rotates does not become large, wherefore machine efficiency during the braking of the brake apparatus  100  can be improved. 
     Embodiments of this invention were described above, but the above embodiments are merely examples of applications of this invention, and the technical scope of this invention is not limited to the specific constitutions of the above embodiments. 
     This application claims priority based on Japanese Patent Application No. 2014-108761 filed with the Japan Patent Office on May 27, 2014, the entire contents of which are incorporated into this specification.