Patent Publication Number: US-2016230826-A1

Title: Disc brake device

Description:
TECHNICAL FIELD 
     The present invention relates to a disc brake device equipped in an automobile and the like. 
     TECHNICAL BACKGROUND 
     As such a disc brake device, there has been known a floating brake device that is configured with a disc rotor that rotates along with a wheel of an automobile or the like, a pair of brake pads that are disposed to face each other with the disc rotor therebetween, and a caliper that is provided in such a manner as to stride over the outer circumference of the disc rotor and to be movable in the direction perpendicular to the rotor surfaces of the disc rotor (see Patent Documents 1 and 2, for example). This disc brake device has a brake actuator only on one of the brake pads, wherein this brake pad is pressed against the rotor surface by the actuation of the brake actuator and the resultant reaction force pulls the other brake pad toward the opposite rotor surface through the caliper, causing the pair of brake pads to sandwich the disc rotor therebetween and use the frictional force thereof to brake the rotation of the disc rotor and the wheel. 
     This type of disc brake device has a pad pressing device for pressing the brake pads against the rotor surfaces of the disc rotor by the actuation of the brake actuator. The pad pressing device has a brake shaft disposed substantially parallel to the rotor surfaces, wherein this brake shaft is turned in the brake actuation direction by the actuation of the brake actuator, to press the brake pads against the rotor surfaces. Also, by releasing the braking operation, the brake shaft is turned in the brake release direction by the biasing force of a spring, separating the brake pads from the rotor surfaces. 
     PRIOR ARTS LIST 
     Patent Document 
     Patent Document 1: Japanese Patent No. 3881710 
     Patent Document 2: Japanese Patent No. 3960396 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the disc brake device described above, the brake shaft is supported turnably on the inside of the brake housing the caliper). Various configurations have conventionally been devised as a method for turnably supporting the brake shaft. Because most brake shafts are supported by bearings, the inside of the brake housing has a depression or a projection. Such a depression or projection has a machine finish in order to have a smooth surface. However, the section where the depression or projection is to be formed is located at the back of the brake housing, making it difficult to machine the depression or projection and consequently increasing the manufacturing cost. Machining is even more difficult especially in a caliper with an integral bridge because a tool and the like cannot be inserted from the front. 
     The present invention was contrived in view of these problems, and an object thereof is to provide a disc brake device that is designed to reduce the number of machining steps on the interior of the brake housing and to easily create a structure for turnably supporting the brake shaft. 
     Means to Solve the Problems 
     In order to achieve the foregoing object, a disc brake device according to the present invention has: a disc rotor that rotates along with a wheel; a brake pad that is disposed to face a rotor surface of the disc rotor; a pad pressing device that presses the brake pad against the rotor surface; and a brake housing that houses the pad pressing device therein (e.g., a caliper  6  according to an embodiment), the disc brake device being configured to apply a brake to the disc rotor and the wheel by using frictional force generated between the brake pad and the rotor surface when the pad pressing device presses the brake pad against the rotor surface. In this configuration the pad pressing device has a brake actuator that is actuated when a braking operation is performed, a brake shaft that is disposed substantially parallel to the rotor surface and turned in a brake actuation direction by the actuation of the brake actuator (e.g., an operating shaft  20  according to the embodiment), a pad pushing mechanism that moves the brake pad toward the rotor surface by means of the turning motion of the brake shaft, and a brake release spring that moves the pad pushing mechanism away from the rotor surface and turns the brake shaft in a brake release direction when the braking operation is released (e.g., a return spring  15  according to the embodiment). The brake shaft is supported on an inner surface of the brake housing by a cylindrical shaft support member extending substantially parallel to the rotor surface, and is turned in the brake actuation direction and the brake release direction along a surface of the shaft support member. The shaft support member is provided in such a manner that a portion of the surface thereof is inserted into a support concavity that is formed on the inner surface of the brake housing. The coefficient of friction of a surface of the support concavity is greater than the coefficient of friction of the surface of the shaft support member. 
     In the disc brake device with the foregoing configuration, it is preferred that the shaft support member be finished to have a smooth surface, that the support concavity be formed by casting at the same time as when the brake housing is formed by casting, and that the surface of the support concavity remain rough without being finished. In other words, it is preferred that the support concavity be merely formed by casting or that the support concavity be only subjected to rough machining after casting. In addition, it is preferred that when incorporating the brake shaft in the support concavity, the radius of an arc of the support concavity be slightly smaller than the radius of the brake shaft in order to improve the stability of the brake shaft, and that the support concavity conic into contact with the brake shaft at both ends of the arc of the support concavity. It is also preferred that the support concavity have a shape such that the support concavity comes into contact with the brake shaft at both ends thereof also in the shaft axial direction, it is preferred that a middle portion of the support concavity be slightly depressed. 
     Advantageous Effects of the Invention 
     According to the disc brake device of the present invention, the support concavity with a rough surface is formed on the inner surface of the brake housing. By inserting the cylindrical shaft support member into the support concavity, the brake shaft can be supported turnably by the shaft support member. Specifically, the support structure of the brake shaft can be created without finishing the surface of the support concavity. Therefore, the number of complicated machining steps performed on the interior of the brake housing can be reduced, achieving a reduction in manufacturing cost. 
     A further reduction in manufacturing cost can be accomplished by casting the support concavity, which is to be formed on the inner surface of the brake housing, together with the brake housing so that it is no longer necessary to insert a tool and the like into the brake housing to form the support concavity. In addition, a caliper with an integral bridge can be produced easily at low cost. Moreover, casting fluctuation can be avoided by setting the support concavity as a reference position for machining (finishing) the brake housing. In so doing, a position where a jig of the same shape as the brake shaft is combined with the support concavity is taken as the reference position, so that a position where the casted surface (surface) of the support concavity actually conies into contact with the brake shaft can be recreated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical cross-sectional diagram of a substantially middle portion of a disc brake device according to the present invention; 
         FIG. 2  is a horizontal cross-sectional diagram taken along arrow II-II shown in  FIG. 1 ; and 
         FIG. 3  is a vertical cross-sectional diagram showing a modification of a support concavity to be formed in a caliper. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present invention is described hereinafter with reference to the drawings.  FIGS. 1 and 2  each show a disc brake device according to an embodiment of the present invention. Hereinafter, the directions of the arrows shown in the diagrams that indicate top, down, left, right, front, and back are described as a vertical direction, a horizontal direction, and a front-back direction, for convenience of explanation. 
     The disc brake device  1  is a floating disc brake device that is configured with, as shown in  FIGS. 1 and 2 , a disc-shaped disc rotor  2  that rotates along with a wheel of an automobile or the like, a carrier  3  fixed to an axle (an axle bearing case), a pair of brake pads  4 .  5  that are disposed to face each other in the carrier  3 , with the disc rotor  2  therebetween, a caliper  6  that is provided in such a manner as to be movable in the horizontal direction with respect to the disc rotor  2  in the carrier  3 , a brake actuator (not shown) that is actuated by air or oil pressure, and a pad pressing device  10  for pressing the left and right brake pads  4  and  5  against left and right side surfaces  2 L and  2 R of the disc rotor  2  (referred to as “rotor surfaces  2 L,  2 R,” hereinafter) by the actuation of the brake actuator. 
     A guide sleeve (not shown) that extends in the direction substantially perpendicular to the rotor surfaces  2 L,  2 R of the disc rotor  2  (the surfaces against which the brake pads are pressed) is attached to the carrier  3  by a bolt. The caliper  6  is provided in such a manner as to be movable in the direction substantially perpendicular to the rotor surfaces  2 L,  2 R (the horizontal direction) by being guided by the guide sleeve. The caliper  6  is configured with a pressing mechanism housing portion  6   a  that is connected to the guide sleeve and houses the pad pressing device  10 , a pad support portion  6   b  for supporting the right brake pad  5 , and a coupling portion  6   c  for coupling the housing portion  6   a  and the support portion  6   b  to each other. 
     The left and right brake pads  4  and  5  are configured, respectively, with pad members  4   a,    5   a  that are brought into contact with the rotor surfaces  2 L,  2 R of the disc rotor  2 , and metal plate members  4   b,    5   b  that are attached to the rear surfaces of the pad members  4   a,    5   a  (the surfaces that are not in contact with the disc rotor  2 ). 
     The pad pressing device  10  is configured with a brake actuator (not shown) that is activated when a braking operation is performed, an operating shaft  20 , a slide block  30 , a return spring  15 , a pad pushing mechanism  40 , and an adjuster mechanism  50 . The operating shaft  20  is configured with a shaft main body  21  that extends substantially parallel to the rotor surfaces of the disc rotor  2  and in the front-back direction, and a lever portion  22  that extends upward front substantially the middle of the shaft main body  21 . A concavity  22   a  that is connected to a tip of an actuating portion of the brake actuator is formed at an upper end portion of the lever portion  22 . 
     A side surface of the shaft main body  21  that faces the disc rotor  2  has a substantially semicircular convex surface  23 , and a surface of the same on the side opposite to the disc rotor  2  (the side surface facing the inner surface to the left of the caliper  6 ) has a substantially semicircular concavity  24  that extends in the front-back direction. A cylindrical shaft support member  25  extending in the front-back direction is fitted in the concavity  24 , with a bearing  26  therebetween. The shaft support member  25  is machined to have a smooth surface. The position of the center of curvature of the convex surface  23  and the position of the central axis of the shaft support member  25  are off in the vertical direction. As shown in  FIG. 2 , the convex surface  23  is provided at the front and back, with the lever portion  22  therebetween. 
     The inner surface to the left of the caliper  6  (the pressing mechanism housing portion  6   a ) is provided with a flat portion  18  that is substantially parallel to the rotor surfaces of the disc rotor  2 . This flat portion  18  has a substantially semicircular support concavity  19  that extends in the front-back direction and is in the shape corresponding to the shape of a surface of the shaft support member  25 . This support concavity  19  is formed by casting together with the caliper  6  but is not followed by a finishing work for creating a smooth surface. Specifically, the support concavity  19  is merely formed by casting. Alternatively, the support concavity  19  is only subjected to rough machining after casting. Therefore, the coefficient of friction of a surface of the support concavity  19  is greater than the coefficient of friction of the surface of the shaft support member  25 . The operating shaft  20  is supported on an inner surface of the caliper  6  by the shaft support member  25 , a portion of which is inserted into the surface of the support concavity  19 , and is turned along the surface of the shaft support member  25 . 
     The slide block  30  is provided closer to the disc rotor  2  than to the operating shaft  20  and adjacent to the operating shaft  20 . The slide block  30  is provided in such a manner as to be movable in the direction substantially perpendicular to the rotor surfaces of the disc rotor  2  (the horizontal direction) by being guided by a bearing (not shown) provided inside the caliper  6  (the pressing mechanism housing portion  6   a ). The surface of the slide block  30  that faces the convex surface  23  of the shaft main body  21  has as a substantially semicircular concave surface  31  corresponding to the convex surface  23 . This concave surface  31  is provided with a bearing  32  (e.g., a needle bearing). Front and rear end portions of the slide block  30  are provided respectively with shaft support portions  33  for regulating the back-and-forth movement of the shaft main body  21  by supporting the front and rear end portions of the shaft main body  21  (see  FIG. 2 ). 
     The return spring  15  is provided in a compressed manner between a wall portion  17  located at the right end portion of the inside of the caliper  6  (the pressing mechanism housing portion  6   a ) and a spring support concavity  34  formed at the right end portion of the slide block  30 . The slide block  30  is biased toward the operating shaft  20  by the elastic force of the return spring  15 . The concave surface  31  of the slide block  30  is in abutment with the convex surface  23  of the shaft main body  21 , with the bearing  32  therebetween. Furthermore, the shaft support member  25  is inserted into the concavity  24  of the shaft main body  21 , with the bearing  26  therebetween. Then, this shaft support member  25  is inserted into the support concavity  19  formed inside the caliper  6 . 
     In this manner, the return spring  15  presses the operating shaft  20  against the shaft support member  19 , which is inserted into the support concavity  19  provided on the inside of the caliper  6 , through the slide block  30 , regulating the horizontal movement of the operating shaft  20 . In addition, the operating shaft  20  is supported while having the back-and-forth movement thereof regulated by the shaft support portions  33  of the slide block  30 . The operating shaft  20  is also supported white having the vertical movement thereof regulated by the abutment between the concave surface  31  of the slide block  30  and the convex surface  23  and the fitting between the shaft support member  25  and the concavity  24 . The operating shaft  20  is supported in such a manner that the convex surface  23  can be rotated and moved along the concave surface  31  of the slide block  30  by the bearing  32  provided on the concave surface  31 . In addition, the operating shaft  20  is supported by the bearing  26  provided in the concavity  24 , in such a manner as to be turnable along the surface of the shaft support member  25 . 
     As shown in  FIG. 2 , the pad pushing mechanism  40  is configured with a pair of front and back nut members  41 ,  42  coupled to the slide block  30 , screw members  43 ,  44  attached to the front and back nut members  41 ,  42  respectively, and a head member  45  attached to the tips (right end portions) of the screw members  43 ,  44 . The nut members  41 ,  42 , in a substantially cylindrical shape, are coupled to the slide block  30  so as to be movable together with the slide block  30  in the direction substantially perpendicular to the rotor surfaces of the disc rotor  2  (the horizontal direction). Inner circumferential surfaces of the nut members  41 ,  42  are threaded. 
     The screw members  43 ,  44  are in a substantially cylindrical shape, and outer circumferential surfaces of the screw members  43 ,  44  are threaded. The screw members  43 ,  44  are attached by screwing to the nut members  41 ,  42  respectively. The head member  45  is attached to the tips of the screw members  43 ,  44 . The head member  45  is in the shape of a substantially flat board, and the left brake pad  4  (the plate member  4   b ) is in contact with the right side surface of the head member  45 . 
     As shown in  FIG. 2 , the adjuster mechanism  50  is configured with an adjuster pin (not shown), a first wheel  52 , a second wheel  53 , a wrap spring  54 , a cone member  55 , a dutch spring  56 , and an interlocking gear train  57 . The adjuster pin, although not shown, is fixed to a rear end surface of the operating shaft  20  (the shaft main body  21 ) and moves in the vertical direction as the operating shaft  20  turns. 
     The first wheel  52  is a cylindrical member that is provided in an outer circumferential portion of the nut member  42  so as to be rotatable relative to the nut member  42 . An insertion hole (not shown) into which a tip of the adjuster pin is inserted is formed in the first wheel  52 . The inner diameter of this insertion hole is greater than the outer shape of the adjuster pin, and a predetermined gap (space) is provided between an inner surface of the insertion hole and the adjuster pin. The first wheel  52  rotates relative to the nut member  42  when the adjuster pin moves vertically as the operating shaft  20  turns and presses the inner surface of the insertion hole. 
     The second wheel  53 , too, is a cylindrical member that is provided in the outer circumferential portion of the nut member  42  (at a position to the left of the first wheel  52 ) so as to be rotatable relative to the nut member  42 . A first tapered surface  53   a  tapering to the right is formed on an inner surface of the left end portion of the second wheel  53 . A second tapered surface  53   b  expanding to the right is formed at a position on an inner surface of the second wheel  53  that is located to the right of the first tapered surface  53   a.    
     The wrap spring  54  has one end portion thereof attached to the first wheel  52  and the other end portion to the second wheel  53  and is provided in such a manner as to surround outer circumferential portions of the first and second wheels  52  and  53 . The wrap spring  54  is configured to transmit, to the second wheel  53 , a rotary movement of the first wheel  52  in only one direction, based on the direction of rotation of the first wheel  52  and the winding direction of the wrap spring  54 . More specifically, when the first wheel  52  is rotated in the winding direction of the wrap spring  54 , the first and second wheels  52  and  53  are held by the wrap spring  54  as the inner diameter of the wrap spring  54  becomes small, thereby transmitting the rotary movement of the first wheel  52  to the second wheel  53 . On the other hand, when the first wheel  52  is rotated in the direction opposite to the winding direction of the wrap spring  54 , the wrap spring  54  does not hold the first and second wheels  52  and  53  because the inner diameter of the wrap spring  54  increases, so the rotary movement of the first wheel  52  is not transmitted to the second wheel  53 . The relationship between the direction of rotation of the first wheel  52  and the winding direction of the wrap spring  54  is described hereinafter. 
     The cone member  55  is configured with a disc-shaped main body  55   a  disposed outside the nut member  42 , and an insertion portion  55   h  that extends from a middle portion of the main body  55   a  to the left and is inserted into the nut member  42  through a mounting hole formed in the nut member  42 . An outer circumferential portion of the insertion portion  55   b  and the mounting hole are each shaped into a hexagon; thus, the cone member  55  is provided in the nut member  42  so as to be movable relative to the nut member  42  in the horizontal direction and rotatable integrally with the nut member  42 . A washer  58  is attached to the right end portion of the insertion portion  55   b  by a bolt. The clutch spring  56  is provided in a compressed manner between an inner surface of the left end of the nut member  42  and the washer  58 . The cone member  55  is biased to the right by the elastic force of this clutch spring  56 , and an outer circumferential end portion of the main body  55   a  is held by the first tapered surface  53   a  of the second wheel  53 . In this state, the second tapered surface  53   b  of the second wheel  53  is in abutment with an outer circumferential end portion of the nut member  42 . 
     The interlocking gear train  57  is configured with a first gear  57   a  that is fixed to the right end portion of the nut member  42  and rotates integrally with the nut member  42 , a second gear  57   b  that is provided rotatably at a position on the right end side of the slide block  30  and meshes with the first gear  57   a,  and a third gear  57   c  that is fixed to the right end portion of the nut member  41  at the front, rotates integrally with the nut member  41 , and meshes with the second gear  57   b.    
     In the disc brake device  1  according to the foregoing configuration, the execution of a braking operation causes the brake actuator to press and swing the tip of the lever portion  22  of the operating shaft  20  in the brake actuation direction in accordance with the operation amount (the direction of arrow A shown in  FIG. 1 ). As a result of swinging the lever portion  22  in this manner, the shaft main body  21  is turned clockwise in  FIG. 1  by leverage. At this moment, the shaft main body  21  is turned clockwise along the surface of the shaft support member  25 . The shaft main body  21  is disposed in such a manner that the position of the center of curvature of the convex surface  23  and the position of the central axis of the shaft support member  25  are off (offset) in the vertical direction. For this reason, when the shaft main body  21  is turned clockwise, the convex surface  23  moves the slide block  30  in the direction of pressing the slide block  30 , with the bearing  32  therebetween (in the direction against the biasing force of the return spring  15 ) while turning clockwise along the concave surface  31  of the slide block  30 . 
     When the convex surface  23  moves the slide block  30  in the direction of pressing the slide block  30  as the shaft main body  21  turns, the slide block  30  is moved toward the left rotor surface  2 L of the disc rotor  2  integrally with the pad pushing mechanism  40  (the nut members  41 .  42 , the screw members  43 ,  44 , and the bed member  45 ) against the biasing force of the return spring  15 . Consequently, the left brake pad  4  that is in contact with the head member  45  is pressed against the left rotor surface  2 L. Using the reaction force resulting from pressing the left brake pad  4  against the left rotor surface  2 L, the caliper  6  is moved to the left in  FIG. 1 . As a result, the right brake pad  5  supported by the pad support portion  6   b  of the caliper  6  is pressed against the right rotor surface  2 R of the disc rotor  2 . In this manner, with the left and right sides of the disc rotor  2  being held between the left and right brake pads  4  and  5 , the frictional force that is generated therebetween applies a brake to the disc rotor  2  and the wheel. 
     Moreover, turning the shaft main body  21  clockwise in  FIG. 1  as a result of the braking operation moves downward the adjuster pin of the adjuster mechanism  50  fixed to the shaft main body  21 . When the adjuster pin is moved downward past the gap between the adjuster pin and the inner surface of the insertion hole of the first wheel  52 , it causes the adjuster pin to press the inner surface of the insertion hole and the first wheel  52  to rotate relative to the nut member  42 . The winding direction of the wrap spring  54  is the same as this direction of rotation of the first wheel  52 . Therefore, when the first wheel  52  is rotated, the inner diameter of the wrap spring  54  becomes small. Consequently, the first and second wheels  52  and  53  are held by the wrap spring  54 , and the rotary movement of the first wheel  52  is transmitted to the second wheel  53 , rotating the second wheel  53  counterclockwise. 
     As a result of rotating the second wheel  53  in this manner, the rotational force thereof is transmitted to the nut member  42  that is in abutment with the cone member  55  (the main body  55   a ) and the second tapered surface  53   b,  the cone member  55  being held by the first tapered surface  53   a  of the second wheel  53 , thereby rotating the cone member  55  integrally with the nut member  42 . The threads formed on the inner circumferential surface of the nut member  42  and the outer circumferential surface of the screw member  44  are configured in such a manner that the screw member  44  is moved relative to the nut member  42  in the direction toward the left rotor surface  2 L of the disc rotor  2  as a result of the rotation of the nut member  42 . Therefore, when the nut member  42  is rotated, the screw member  44  moves relative to the nut member  42  in the direction toward the left rotor surface  2 L. 
     Also, such rotary movement of the nut member  42  is transmitted to the nut member  41  at the front via the interlocking gear train  57  (the first to third gears  57   a  to  57   c ), rotating the nut member  41  in the same direction. The threads that are formed in the nut member  41  and the screw member  43  at the front, too, are configured in the same manner as the nut member  42  and the screw member  44 . Therefore, the screw member  41 , too, is moved relative to the nut member  41  in the direction toward the left rotor surface  2 L by the same distance as the screw member  44 . Consequently, the left brake pad  4  is moved toward the Left rotor surface  2 L via the head member  45  attached to the screw member  43 ,  44 . Once the left brake pad  4  comes into abutment with the left rotor surface  2 L, the resistance to the relative movements of the screw members  43 ,  44  increases. As a result, a slide occurs in the portion held between the first tapered surface  53   a  of the second wheel  53  and the cone member  55  and the abutment portion between the second tapered surface  53   b  and the nut member  42 , preventing the left brake pad  4  from further moving toward the left rotor surface  2 L. Therefore, even when the distance between the Left brake pad  4  and the left rotor surface  2 L increases due to wear of the left brake pad  4 , the distance can be adjusted to an appropriate distance at the time of brake actuation. 
     Releasing the braking operation leads to release of the pressing force applied by the brake actuator to the lever portion  22 , and thereby the slide block  30  is moved away from the left rotor surface  2 L of the disc rotor  2  integrally with the pad pushing mechanism  40  by the elastic force of the return spring  15 , releasing the brake application to the wheel. 
     When the slide block  30  is moved away from the left rotor surface  2 L, the convex surface  23  of the shaft main body  21  is moved away from the left rotor surface  2 L (to the left) while turning counterclockwise in  FIG. 1  along the concave surface  31  of the slide block  30  with the bearing  32  therebetween. At this moment, the shaft main body  21  is turned counterclockwise along the surface of the shaft support member  25 . 
     As a result of releasing the braking operation and turning the shaft main body  21  clockwise in  FIG. 1 , the adjuster pin of the adjuster mechanism  50  fixed to the shaft main body  21  is moved upward. Moving the adjuster pin upward past the gap between the adjuster pin and the inner surface of the insertion hole of the first wheel  52 , the adjuster pin presses the inner surface of the insertion hole, moving the first wheel  52  relative to the nut member  42 . Because the winding direction of the wrap spring  54  is set as described above, the inner diameter of the wrap spring  54  becomes large when the first wheel  52  is rotated. As a result, the binding force of the wrap spring  54  applied to the first and second wheels  52  and  53  weakens, and consequently the rotary movement of the first wheel  52  cannot be transmitted to the second wheel  53 . Therefore, the nut member  42  is not rotated clockwise, and the screw member  44  is not moved relative to the nut member  42  in the direction away from the left rotor surface  2 L. The appropriate distance between the left brake pad  4  and the left rotor surface  2 L that is adjusted at the time of brake actuation is kept as it is. 
     According to this disc brake device  1  the support concavity  19  with a rough surface is formed on the inner surface of the caliper  6 . By inserting the cylindrical shaft support member  25  into the support concavity  6 , the operating shaft  20  can be supported turnably by the shaft support member  25 . In other words, the support structure of the operating shaft  20  can be created without finishing the surface of the support concavity  19 . This means that the number of complicated machining steps performed on the interior of the caliper  6  can be reduced, achieving a reduction in manufacturing cost. 
     According to the disc brake device  1 , the support concavity  19  to be formed on the inner surface of the caliper  6  is casted together with the caliper  6  but is not subjected to surface finishing or the like thereafter. This eliminates the need to perform a process for inserting a tool and the like into the caliper  6  to form the support concavity, achieving a further reduction in manufacturing cost. This also enables easy and inexpensive production of a caliper with an integral bridge. In addition, casting fluctuation can be avoided by setting the support concavity  19  as a reference position for machining the caliper  6 . In so doing, a position where a jig of the same shape as the operating shaft  20  is combined with the support concavity  19  is taken as the reference position, so that a position where the casted surface (surface) of the support concavity  19  actually conies into contact with the operating shaft  20  can be recreated. 
     The embodiment according to the present invention has been described, however, the scope of the present invention is not limited to the foregoing embodiment. For instance, in the foregoing embodiment, the substantially semicircular support concavity  19  corresponding to the shape of the surface of the shaft support member  25  is formed on the inner surface of the caliper  6 . However, the shape of the support concavity is not limited to a substantially circular shape; thus, a support concavity  19 ′ that has a substantially triangular shape when viewed in a vertical section may be formed, as shown in  FIG. 3 . Furthermore, in the foregoing embodiment, the radius of the arc of the support concavity  19  may be made slightly smaller than the radius of the operating shaft  20 , and the support concavity  19  may be brought into contact with the operating shaft  20  at both ends of the arc of the support concavity  19 . In addition, the support concavity  19  may have a shape such that the support concavity  19  comes into contact with the operating shaft  20  at both ends thereof also in the shaft axial direction, i.e., the middle portion of the support concavity  19  may be slightly depressed. Accordingly, the stability of the operating shaft  20  can be improved when incorporating the operating shaft  20  in the support concavity  19 . 
     EXPLANATION OF NUMERALS AND CHARACTERS 
       1  Disc brake device 
       2  Disc rotor 
       4 ,  5  Brake pad 
       6  Caliper (brake housing) 
       10  Pad pressing device 
       15  Return spring (brake release spring) 
       19  Support concavity 
       20  Operating shaft (brake shaft) 
       25  Shaft support member 
       30  Slide block 
       40  Pad pushing mechanism