Disc brake

Provided is a disc brake capable of preventing large positional shift of a position of abutment of a return spring against a mounting member, which occurs with wear of a friction pad and the like. The return spring for biasing the friction pad in a direction away from a disc includes a fixed portion on one side, which is fixedly mounted to the friction pad, an extending portion extending from the fixed portion in an axial direction of the disc and in a direction away from the friction pad, a turned-back portion formed by turning back a distal end side of the extending portion toward the mounting member, and an abutting portion provided on a distal end side of the turned-back portion so as to be elastically brought into abutment against a side of the mounting member. A portion (bent portion) of the turned-back portion, which is formed by bending the turned-back portion at the middle thereof, is located at a position separated farther away from the fixed portion than the abutting portion in a disc rotating direction.

TECHNICAL FIELD

The present invention relates to a disc brake which applies a braking force to, for example, a vehicle such as an automobile.

BACKGROUND ART

In general, a disc brake provided to a vehicle such as an automobile slides and displaces a piston provided to a caliper toward a disc by supplying a hydraulic pressure from exterior to press friction pads against the disc when a driver of the vehicle or the like performs a braking operation. Then, the caliper slides and displaces relative to a carrier by a counterforce generated at this time to press the friction pads against both surfaces of the disc between a claw portion and the piston, thereby applying a braking force to the rotating disc.

Further, there is known a disc brake which includes return springs for biasing the friction pads in a direction in which the friction pads move away from both surfaces of the disc when the braking operation of the vehicle is released. The return springs are provided between the carrier and the friction pads and bias the frictions pads in a return, direction in which the friction pads move away from the disc (for example, see Patent Literature 1).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The return spring used in the aforementioned related art has a configuration in which a middle portion between a fixed portion on one side, which is fixedly mounted to a back metal of the friction pad, and an abutting portion on the other side, which is brought into abutment against (elastic contact with) an arm portion side of a mounting member is formed to be bent in an inverted V shape or inverted U shape.

Therefore, when the friction pads are worn away through repetition of the braking operation, the amount of deformation of the return springs used in the related art becomes large with the wear. As a result, the position of abutment of each of the return springs with respect to the side of the mounting member is shifted in a direction away from the friction pads. An area of abutment of the return spring is required to be set large in view of the positional shift. Thus, there is a problem in that the size of the carrier is disadvantageously increased, which in turn results in increased size of the disc brake.

Solution to Problem

In order to solve the above-mentioned problem, according to an exemplary embodiment of the present invention, a return spring includes: a fixed portion fixed to a friction pad; an abutting portion to be brought into abutment against a side of a mounting member; an extending portion extending from the fixed portion in a disc axial direction and a direction away from the friction pad; and a turned-back portion turned back from the extending portion toward the abutting portion. The turned-back portion includes one extension portion extending, from a position separated farther away from the fixed portion than the abutting portion in a disc rotating direction, in the disc axial direction and a direction closer to the mounting member so as to be connected to the abutting portion.

Further, in order to solve the above-mentioned problem, according to another exemplary embodiment of the present invention, a return spring includes: a fixed portion provided on one end side, fixed onto a plane of a friction pad on a side opposite to a disc abutting surface; an abutting portion provided on another end side, to be brought into elastic abutment against a side of a mounting member; an extending portion extending from the fixed portion in a disc axial direction and in a direction away from the friction pad; and a turned-back portion formed between a distal end side of the extending portion and the abutting portion, and turned back toward the mounting member. The turned-back portion includes: a first extension portion extending from a distal end side of the extending portion in a direction along the plane of the friction pad and in a direction away from the fixed portion to a position beyond the abutting portion; and a second extension portion obliquely turned back from a distal end side of the first extension portion toward the mounting member in the disc axial direction so as to be connected to the abutting portion.

Further, in order to solve the above-mentioned problem, according to still another exemplary embodiment of the present invention, a disc brake includes a return spring for biasing a friction pad in a return direction in which the friction pad moves away from a disc, the return spring including: a fixed portion fixed to the friction pad; an abutting portion to be brought into abutment against a side of a mounting member; an extending portion extending from the fixed portion in a disc axial direction and in a direction away from the friction pad; and a turned-back portion turned back from the extending portion toward the abutting portion. The turned-back portion of the return spring includes at least two bent portions formed in a direction along a disc abutting surface of the friction pad. A bending stiffness of one bent portion of the at least two bent portions, which is on a side of the friction pad, is set lower than a bending stiffness of another bent portion thereof on the side of the mounting member.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a disc brake according to embodiments of the present invention is described in detail with reference to the accompanying drawings.

First Embodiment

FIGS. 1 to 8illustrate a first embodiment of the present invention. InFIGS. 1 to 3, a disc1rotates with a wheel (not shown) in a direction A indicated by an arrow inFIG. 1when, for example, a vehicle runs forward. In the following description, a side of a carrier2from which the disc1enters while rotating (right side inFIG. 1) is referred to as a rotating entrance side, whereas a side of the carrier2from which the disc1exits while rotating (left side inFIG. 1) is referred to as a rotating exit side.

The carrier2is mounted to a non-rotating portion of the vehicle as a mounting member. As illustrated inFIGS. 1 to 3, the carrier2includes a pair of arm portions2A,2A provided so as to be separated from each other in a rotating direction (circumferential direction) of the disc1, the pair of arm portions2A,2A extending in an axial direction of the disc1so as to extend over an outer circumference of the disc1, and a bearing portion2B having a large thickness, which is provided so as to connect base end sides of the arm portions2A into one and is fixed to the non-rotating portion of the vehicle at a position on an inner side of the disc1.

A reinforcing beam2C for connecting distal end sides of the arm portions2A,2A at positions on an outer side of the disc1is formed integrally with the carrier2as illustrated inFIGS. 1 and 2.

In a middle portion of each of the arm portions2A in the axial direction of the disc1, a disc path portion3extending in an arc-like shape along an outer circumference (locus of rotation) of the disc1is formed as illustrated inFIG. 3. On both sides of the disc path portion3in the axial direction of the disc1, pad guides4on the inner side and the outer side are respectively formed. A pin hole (not shown) is provided to each of the arm portions2A along the axial direction of the disc1. A sliding pin6described below is slidably fitted into each of the pin holes.

The pad guides4,4, . . . are provided to each of the arm portions2A of the carrier2on the base end side (inner side) and the distal end side (outer side) of each of the arm portions2A so as to be located on both sides of the disc path portion3in the axial direction to interpose the disc path portion3therebetween. Each of the pad guides4is formed as a concave groove extending in the axial direction of the disc1to form a squared C-like cross section as illustrated inFIGS. 1,4, and5. Moreover, the pad guides4also serve as torque-receiving portions for receiving a braking torque applied to friction pads9described below from the disc1when a braking operation is performed.

A caliper5is slidably provided to the carrier2. As illustrated inFIGS. 1 to 3, the caliper5includes an inner leg portion5A provided on one side (inner side) of the disc1, a bridge portion5B provided so as to extend from the inner leg portion5A to the other side (outer side) of the disc1between the arm portions2A of the carrier2so as to extend over the outer circumferential side of the disc1, and an outer leg portion5C having a plurality of claw portions on the distal end side, which extends inward in a radial direction of the disc1from the distal end side (outer side) of the bridge portion5B.

A cylinder into which a piston is slidably fitted (both not shown) is provided to the inner leg portion5A of the caliper5. A pair of mounting portions5D,5D respectively projecting in right and left directions inFIGS. 1 and 2are provided to the inner leg portion5A. The mounting portions5D constitute support arms for allowing the arm portions2A of the carrier2to slidably support the caliper5through an intermediation of the sliding pins6. A protective boot8for covering the periphery of a base end side of the sliding pin6to prevent rain water or the like from entering between the sliding pin6and the pin hole of the arm portion2A is mounted between the sliding pin6and each of the arm portions2A.

Friction pads9,9on the inner side and the outer side are provided so as to be respectively opposed to both surfaces of the disc1. As illustrated inFIGS. 1,2,4, and6, each of the friction pads9includes a flat-plate like back metal10extending in the circumferential direction (rotating direction) of the disc1, a lining11(seeFIG. 6) serving as a friction member which is fixedly provided on a surface side of the back metal10and comes into frictional contact with the surface of the disc1, and the like.

Each of the back metals10of the friction pads9is formed from a flat plate material having a fan-like shape as a whole. On both end sides thereof in a length direction (circumferential direction of the disc1), ear portions10A,10A serving as fitting portions are provided so that each ear portion10A forms a convex shape. The ear portions10A of the back metal10are respectively slidably fitted into the pad guides4of the carrier2through an intermediation of guide plate portions18of pad springs14described below. The friction pads9on the inner side and the outer side are pressed against both surfaces of the disc1by the caliper5when the braking operation is performed. At this time, the ear portions10A of the back metals10slide and displace in the axial direction of the disc1along the pad guides4.

A radial-direction biasing portion19of the pad spring14described below elastically abuts against each of the ear portions10A of the friction pads9(back metals10). As a result, the friction pads9are constantly biased outward in the radial direction of the disc1. Right and left caulking portions10B,10B are provided to the back metal10of the friction pad9so as to be positioned close to the base end (bottom) sides of the ear portions10A.

Meanwhile, the ear portion10A of the ear portions10A of the friction pads9(back metals10), which is located on the rotating exit side of the disc1, continues to abut against the arm portion2A (bottom portion of the pad guide4) on the rotating exit side of the carrier2through an intermediation of the guide plate portion18of the pad spring14by a braking torque (rotation torque in the direction A indicated by the arrow inFIG. 1) received from the disc1by the friction pads9at the time of, for example, the braking operation of the vehicle. Between the abutting surfaces of the ear portion and the arm portion, the braking torque generated at the time of the braking operation is received by the carrier2.

A shim plate12for preventing squeal is removably provided to the friction pad9on the outer side, illustrated inFIGS. 1 and 4, on a rear surface side of the back metal10. A shim plate (not shown) for preventing squeal is removably provided to the friction pad9on the inner side, illustrated inFIG. 2, on the rear surface side of the back metal10.

The pad springs14,14are respectively provided between the arm portions2A of the carrier2and the friction pads9, and are respectively mounted to the arm portions2A of the carrier2. The pad springs14,14elastically support the fiction pads9on the inner side and the outer side therebetween and smooth the sliding displacement of the friction pads9. As illustrated inFIGS. 1,2,4, and5, each of the pad springs14is integrally formed by punching out a stainless steel plate having a spring property and then bending the punched-out stainless steel plate by using means such as press working. By the processes described above, a connection plate portion15, the guide plate portions18,18, the radial-direction biasing portions19,19, and seating-surface plate portions20,20are provided to the pad spring14.

The connection plate portion15connects the guide plate portions18of the pad spring14or the like to each other. The connection plate portion15is formed so as to extend in the axial direction so as to extend over the outer circumferential side of the disc1. On the both end sides in the length direction thereof, a pair of flat plate portions16,16are integrally formed so as to extend inward in the radial direction of the disc1. An engagement plate portion17is located between the pair of flat plate portions16,16and is integrally formed with the connection plate portion15. The engagement plate portion17is mounted to the carrier2so as to be brought into engagement with the disc path portion3of the arm portion2A from the radially inner side. In this manner, the pad spring14is positioned in the axial direction of the disc1with respect to the arm portion2A of the carrier2.

The guide plate portions18,18are provided on both end sides of the connection plate portion15through an intermediation of the flat plate portions16. Each of the guide plate portions18is formed by bending from the distal end side of the flat plate portion16into an approximate squared C shape. One guide plate portion18of the guide plate portions18,18is mounted by being fitted into the pad guide4on the outer side, as illustrated inFIG. 4, whereas another guide plate portion18is mounted by being fitted into the pad guide4on the inner side. The guide plate portion18includes an upper surface plate18A and a lower surface plate18B respectively opposed to upper and lower wall surfaces of the pad guide4, and a guide bottom plate18C which connects the upper surface plate18A and the lower surface plate18B in the radial direction of the disc1and forms a flat surface shape to extend in the axial direction of the disc1so as to be brought into abutment against a rear-side wall surface (bottom portion) of the pad guide4.

The radial-direction biasing portions19,19bias the friction pads9,9outward in the radial direction of the disc1. Each of the radial-direction biasing portions19is formed by being bent outward in the radial direction of the disc1in an approximate U shape or an approximate C shape at a position at which the radial-direction biasing portion extends from the lower surface plate18B of the guide plate portion18outward in the axial direction of the disc1. The radial-direction biasing portion19elastically biases the ear portion10A of the friction pad9outward in the radial direction of the disc1so as to prevent the friction pad9from clattering.

The seating-surface plate portions20,20are integrally formed by bending the base end sides thereof into an L shape so as to be vertical to the guide bottom plates18C of the guide plate portions18as illustrated inFIGS. 4 and 5. The distal end sides of the seating-surface plate portions20are free ends extending outward in the circumferential direction of the disc1(outward in the right and left directions) so as to be slightly separated away from the arm portions2A of the carrier2as illustrated inFIGS. 1,2, and8. The free end side of the seating-surface plate portion20is formed into a flat-plate shape having a larger width than that of a return spring21described below, as illustrated inFIG. 4, and provides a receiving seating surface when the return spring21is brought into abutment in an elastically deformed state. On the distal end side of the seating-surface plate portion20, a bent piece portion20A bent outward in the axial direction of the disc1in an L shape is provided as exemplarily illustrated inFIG. 2.

The return springs21,21are provided between the arm portion2A located on the rotating entrance side (on the entrance side in the rotating direction, that is, the rotating entrance side) of the disc1which rotates in the direction A indicated by the arrow and the friction pads9so as to bias the friction pads9on the inner side and the outer side in a return direction in which the friction pads move away from the disc1as illustrated inFIGS. 1,2, and4. As illustrated inFIG. 8, one side of each of the return springs21in the length direction is mounted to the back plate10of each of the friction pads9, whereas the other side in the length direction is brought into abutment against the carrier2side (the seating-surface plate portion20of the pad spring14) in an elastically deformed state. The return spring21includes a fixed portion21A, an extending portion21B, a turned-back portion21C, and an abutting portion21D, as illustrated inFIGS. 4, and6to8.

The fixed portion21A is located on one side of the return spring21in the length direction, formed into a flat plate shape, and fixed to the friction pad9(back metal10) on the ear portion10A side by the caulking portion10B. The extending portion21B is provided so as to be bent from the fixed portion21A into an L shape as illustrated inFIGS. 6 to 8so that a distal end side extends in the axial direction of the disc1, corresponding to a direction in which the distal end side vertically moves away from the surface of the disc1. The extending portion21B is not necessarily required to be bent into the L shape so that the distal end side extends in the axial direction of the disc1, corresponding to the direction in which the distal end side vertically moves away from the surface of the disc1, and can be extended with an angle with respect to the axial direction of the disc1as needed.

The turned-back portion21C is formed by bending a distal end side of the extending portion21B toward the carrier2, that is, toward the seating-surface plate portion20of the pad spring14. The abutting portion21D is located on the other side of the return spring21in the length direction in continuity with the turned-back portion21C and is formed by being bent into an approximate U shape. The turned-back area of the abutting portion21D, that is, the area bent into the U shape so as to be rounded off, elastically abuts against the seating-surface plate portion20of the pad spring14. The return spring21biases the friction pad9in a direction away from the disc1, based on the abutting area as a base point.

The turned-back portion21C of the return spring21includes a first extension portion21C1extending from the distal end side of the extending portion21B in a direction along a plane of the friction pad9(back metal10) (disc rotating direction) away from the fixed portion21A, and a second extension portion21C2bent from the distal end side of the first extension portion21C1toward the carrier2(toward the seating-surface plate portion20of the pad spring14) so as to be smoothly connected to the abutting portion21D.

The turned-back portion21C includes a first bent portion21C3which is formed into a curved approximate L shape between the extending portion21B and the first extension portion21C1of the turned-back portion21C and a second bent portion21C4between the first extension portion21C1and the second extension portion21C2, which corresponds to a middle portion of the turned-back portion21C. The second bent portion21C4is located at a position which is separated farther away from the fixed portion21A than the abutting portion21D in the direction along the plane of the friction pad9(back metal10), that is, the disc rotating direction. The second extension portion21C2of the turned-back portion21C is formed so as to be turned back from the distal end side of the first extension portion21C1(at the position of the second bent portion21C4) to extend in the direction along the plane of the back metal10, that is, the disc rotating direction and in a direction closer to the fixed portion21A. Specifically, an angle formed between the first extension portion21C1and the second extension portion21C2(hereinafter, referred to as “angle of the second bent portion21C4” for convenience) is an acute angle and is smaller than an acute angle formed between the extending portion21B and the first extension portion21C1(hereinafter, referred to as “angle of the first bent portion21C3” for convenience). As described above, the turned-back portion21C of the return spring21extends in a direction in which the turned-back portion passes over the pad guide4, the seating-surface plate portions20of the pad spring14, which are located on the rotating entrance side of the disc1, and the like, as illustrated inFIG. 4(outward in the horizontal direction inFIG. 4).

The first extension portion21C1is configured as another extension portion, whereas the second extension portion21C2is configured as one extension portion. The first bent portion21C3is configured as one bent portion, whereas the second bent portion21C4is configured as another bent portion. When the extending portion21B extends vertically from the surface of the disc1, the angle of the first bent portion21C3and the angle of the second bent portion21C4are not required to be both acute as described above as long as the second extension portion21C2extends in the disc rotating direction and in the direction closer to the fixed portion21A. For example, when the angle of the first bent portion21C3is acute, the angle of the second bent portion21C4can be set to be right or obtuse. When the angle of the first bent portion21C3is right or obtuse, the angle of the second bent portion21C4can be set to be acute. In any of the cases, the angles are set so as to satisfy the following Formula 1.
(90°−angle of first bent portion 21C3)>(angle of second bent portion) 21C4−90°  [Formula 1]

The return spring21constantly biases the friction pad9(back metal10) by the abutment or sliding contact of the abutting portion21D located on the distal end side thereof (on the other side in the length direction) against/with the surface of the seating-surface plate portion20in the elastically deformed state so as to stably return the friction pad9to a standby position which is separated away from the disc1when, for example, the braking operation of the vehicle is released.

The disc brake according to this embodiment has the configuration described above. Next, an operation thereof is described.

First, when the braking operation of the vehicle is performed, a brake fluid pressure is supplied to the inner leg portion5A (cylinder) of the caliper5to slide and displace the piston toward the disc1. In this manner, the friction pad9on the inner side is pressed against one side surface of the disc1. At this time, the caliper5is subjected to a counterforce from the disc1, which is generated by pressing. Therefore, the entire caliper5slides and displaces toward the inner side with respect to the arm portion2A of the carrier2. Then, the outer leg portion5C presses the friction pad9on the outer side against the other side surface of the disc1(see a stroke S illustrated inFIG. 8).

As a result, the friction pads9on the inner side and the outer side can interpose the disc1rotating in the direction A indicated by the arrow inFIGS. 1 to 4therebetween from both sides in the axial direction so as to apply a braking force to the disc1. Then, when the braking operation is released, the supply of the hydraulic pressure to the piston is stopped to separate the friction pads9on the inner side and the outer side away from the disc1so that the friction pads return to a non-braking state.

When the braking operation is performed and released (the braking operation is not performed) as described above, the right and left ear portions10A of the back metal10of the friction pad9are biased outward in the radial direction of the disc1by the radial-direction biasing portions19of the respective pad springs14. Therefore, each of the ear portions10A of the back metal10is pressed so as to be brought into sliding contact with the upper side wall surface of the pad guide4of each of the arm portions2A of the carrier2through the guide plate portion18of the pad spring14(upper surface plate18A). As a result, the clattering of the friction pads9in the radial direction and the rotating direction or the circumferential direction of the disc1due to vibrations or the like generated while the vehicle is running can be restrained by an elastic force (biasing force) of the radial-direction biasing portions19provided to the pad spring14. When the braking operation is performed, the friction pads9are subjected to the braking torque (rotation torque in the direction A indicated by the arrow) from the disc1. At this time, the ear portion10A on the rotating exit side is continuously held in abutment against the pad guides4(torque-receiving portions) of the carrier2through an intermediation of the guide bottom plates18C of the guide plate portions18of the pad spring14. Thus, the braking torque generated during the braking operation can be received by the arm portion2A (torque-receiving portion) on the rotating exit side.

When the braking operation is performed, each of the ear portions10A of the friction pad9can be held in sliding contact with the upper side wall surfaces of the pad guides4through an intermediation of the upper surface plates18A of the guide plate portions18of the pad spring14by the radial-direction biasing portions19of each of the pad springs14. Besides, the friction pads9on the inner side and the outer side can be smoothly guided in the axial direction of the disc1along the guide plate portions18.

In this embodiment, the return spring21on the inner side is formed as an integral member including the fixed portion21A, the extending portion21B, the turned-back portion21C, and the abutting portion21D by bending the metal plate having the spring property. The second bent portion21C4corresponding to the middle portion of the turned-back portion21C is configured so as to be located at the position separated farther away from the fixed portion21A than the abutting portion21D in the direction along the plane of the back metal10of the friction pad9, that is, in the disc rotating direction.

With the aforementioned configuration, even when the lining11of the friction pad9is worn away and the return spring21is deformed with the wear as exemplarily illustrated inFIG. 8through repetition of the braking operation, a shift of the position of abutment of the abutting portion21D of the return spring21against the carrier2side, that is, against the seating-surface plate portion20side of the pad spring14can be reduced as indicated by dimension a inFIG. 8. In addition, a direction of the shift can be set to a direction in which the position moves closer to the fixed portion21A of the return spring21, that is, moves closer to the back metal10. Therefore, the moving distance of the abutting portion21D of the return spring21with respect to the seating-surface plate portion20of the pad spring14becomes small. Therefore, the seating-surface plate portion20can be shortened. Correspondingly, a corresponding portion of the seating-surface plate portion20of the carrier2is not required to be provided. Thus, the carrier2and in turn, the disc brake can be reduced in size.

Moreover, the amount of projection (dimension γ illustrated inFIG. 8) of the extending portion21B and the turned-back portion21C of the return spring21in the axial direction of the disc1can be relatively reduced by the turned-back portion21C. Therefore, a space for mounting the return spring21can be easily ensured between the carrier2and the friction pad9, thereby enhancing the degree of freedom in layout design.

On the other hand, in the case of a comparative example illustrated inFIG. 9, a return spring22includes a fixed portion22A on one side, which is fixedly mounted to the back metal10of the friction pad9, an extending portion22B extending from the fixed portion22A in the axial direction of the disc and in the direction away from the friction pad9, a turned-back portion22C formed by turning back the distal end side of the extending portion22B toward the carrier2, and an abutting portion22D provided on the distal end side of the turned-back portion22C so as to be elastically brought into abutment against the carrier2side (seating-surface plate portion20of the pad spring14). The turned-back portion22C includes a first extension portion22C1extending from the distal end side of the extending portion22B in the direction along the plane of the friction pad9′ (back metal10′) and in the direction away from the fixed portion22A, and a second extension portion22C2bent from the distal end side of the first extension portion22C1toward the carrier2′ side (seating-surface plate portion20′ side of a pad spring14′) so as to be smoothly connected to the abutting portion22D. The turned-back portion22C includes a first bent portion22C3formed between the extending portion22B and the first extension portion22C1of the turned-back portion22C, and a second bent portion22C4formed between the first extension portion22C1and the second extension portion22C2, corresponding to a middle portion of the turned-back portion22C. The second bent portion22C4is located at a position closer to the fixed portion22A than the abutting portion22D in the direction along the plane of the friction pad9(back metal10). Specifically, an angle formed between the first extension portion22C1and the second extension portion22C2(hereinafter, referred to as “angle of the second bent portion22C4” for convenience) is obtuse and is larger than a right angle corresponding to an angle formed between the extending portion22B and the first extension portion22C1(hereinafter, referred to as “angle of the first bent portion22C3” for convenience).

Specifically, the return spring22of the comparative example is configured by bending the middle portion (for example, the turned-back portion22C) between the fixed portion22A on one side in the length direction and the abutting portion22D on the other side, which is brought into abutment against (elastic contact with) the seating-surface plate portion20on the arm portion2A side of the carrier2, into an inverted V-shape or inverted U-shape. Therefore, in the case of the return spring22according to the comparative example, when the lining11of the friction pad9is gradually worn away through repetition of the braking operation, the deformation of the return spring22becomes large with the wear. As a result, the position of abutment of the return spring22(abutting portion22D) against the seating-surface plate portion20of the pad spring14is greatly shifted in a direction away from the fixed portion22A, that is, in a direction away from the friction pad9as indicated by dimension β (β>α) illustrated inFIG. 9.

In addition, in the case of the comparative example illustrated inFIG. 9, a length dimension for ensuring a spring constant of the return spring22is required. Therefore, the amount of projection of the extending portion22B and the turned-back portion22C from the position of the fixed portion22A in the axial direction of the disc (dimension γ′ illustrated inFIG. 9) is inevitably required to be increased. As a result, layout design becomes difficult for ensuring the space for mounting the return spring22.

Operations of the return spring21according to this embodiment and the return spring22according to the comparative example are described in detail referring toFIGS. 10 and 11. The fixed portion21A of the return spring21and the fixed portion22A of the return spring22move in the disc axial direction. InFIGS. 10 and 11, however, the abutting portions21D and22D are described as moving in the disc axial direction to exert a force, for convenience of the description.

In the case of the return spring21of this embodiment, when the movement of the abutting portion21D as illustrated inFIG. 10(A)is a length S1in an initial state in which the return spring21is subjected to a force, a force F1vertical to the seating-surface plate portion20corresponding to an abutting surface acts on the abutting portion21D of the return spring21. The force F1is divided into a component force F1L parallel to the second extension portion21C2and a component force F1S vertical to the second extension portion21C2, which are then transmitted to the second extension portion21C2. Then, the second extension portion21C2is formed by turning back a distal end side of the first extension portion21C1(at the position of the turned-back portion21C4) in a direction along the plane of the back metal10, that is, the disc rotating direction in a direction closer to the fixed portion21A. Therefore, the component force F1S acting on the second extension portion21C2is going to deflect the second extension portion21C2in a direction along the plane of the back metal10and a direction closer to the fixed portion21A. At this time, the fixed portion21A is immobile. Therefore, the component force F1S deflects the extending portion21B in a direction closer to the fixed portion21A, that is, toward the side opposite to the abutting portion21D in the disc rotating direction. By the deflection of the extending portion21B, the abutting portion21D does not move. The second bent portion21C4reaches a second bent portion21C4′ with a smaller amount of movement than the length S1by the deflection of the second extension portion21C2and the extending portion21B.

Further, when the lining11of the friction pad9is abnormally worn away to exert a force on the return spring21to move the abutting portion21D over a longer length S2as illustrated inFIG. 10(B), the deflection of the extending portion21B reaches an upper limit. Therefore, a component force F2L of a force F2acting on the second extension portion21C2, which is parallel to a second extension portion21C2′, deflects the second extension portion21C2in a direction away from the first extension portion21C1(in which the angle of the second bent portion21C4increases). As a result, the abutting portion21D moves by α′ in the direction along the plane of the back metal10and in the direction away from the fixed portion21A.

On the other hand, in the case of the return spring22of the comparative example, when the movement of the abutting portion22D is the length S1as illustrated inFIG. 11(A)in an initial stage in which the return spring22is subjected to the force, a force F1′ vertical to the seating-surface plate portion20′ corresponding to the abutting surface acts on the abutting portion22D of the return spring22. The force F1′ is divided into a component force F1L′ parallel to the second extension portion22C2and a component force F1S′ vertical to the second extension portion22C2, which are then transmitted to the second extension portion22C2. The second extension portion22C2is formed so as to be bent from the distal end side of the first extension portion22C1(at the position of the second bent portion22C4) in the direction along the plane of the back metal10, that is, the disc rotating direction and in the direction away from the fixed portion22A. Therefore, the component force F1S′ acts on the second extension portion22C2in the direction away from the fixed portion22A to deflect the second extension portion22C2in the direction along the plane of the back metal10, that is, the disc rotating direction and in the direction away from the fixed portion22A. By the deflection of the second extension portion22C2, the abutting portion22D slides on the seating-surface plate portion20′ to move in the direction along the plane of the back metal10and in the direction away from the fixed portion22A by a length β1. At this time, the deflection of the second extension portion22C2allows the second bent portion22C4to reach a second bent portion22C4′ with the amount of movement smaller than the length S1.

Further, when the return spring22is subjected to the force so that the abutting portion22D moves farther by a length S2as illustrated inFIG. 11(B), because the deflection of the second extension portion22C2has reached the upper limit, at this time, the extending portion22B is deflected in a direction closer to the fixed portion22A by a component force F2L′. By the deflection of the extending portion22B, the position of the abutting portion22D does not change. As described above, the abutting portion22D moves in the direction along the plane of the back metal10and the direction away from the fixed portion22A by β.

As described above, in comparison between the return spring21according to this embodiment and the return spring22according to the comparative example, the amount of movement of the abutting portion21D in the disc rotating direction, caused by the movement of the fixed portion21A, and the amount of movement of the abutting portion22D in the disc rotating direction, caused by the movement of the fixed portion22A, differ from each other, that is, the amount of movement of the abutting portion21D is smaller than the amount of movement of the abutting portion22D due to a difference in extending direction between the second extension portions21C2and22C2.

The operations of the return spring21according to this embodiment and the return spring22according to the comparative example described above are now described from a different point of view. In the case of the return spring21according to this embodiment, the angle of the second bent portion21C4is acute and is smaller than the acute angle of the first bent portion21C3. Therefore, when the fixed portion21A moves with respect to the abutting portion21D in the direction closer to the disc1, the angle of the first bent portion21C3is more likely to be enlarged than that of the second bent portion21C4. In other words, a bending stiffness of the first bent portion21C3is lower than that of the second bent portion21C4. Specifically, when the friction pad9moves in the direction closer to the disc1to bend the second bent portion21C4so as to enlarge the angle thereof, the first bent portion21C3is subjected to the force to be bent so as to enlarge the angle thereof earlier than the second bent portion21C4. As a result, the distal end of the extending portion21B is deflected to the side opposite to the abutting portion21D in the disc rotating direction. Therefore, for the return spring21, the abutting portion21D is scarcely moved in the disc rotating direction by the movement of the fixed portion21A.

On the other hand, in the case of the return spring22of the comparative example, the angle of the second bent portion22C4is obtuse and is larger than the right angle corresponding to the angle of the first bent portion22C3. Therefore, when the fixed portion22A moves with respect to the abutting portion22D in the direction closer to the disc1, the angle of the second bent portion22C4is more likely to be enlarged than that of the first bent portion22C3. In other words, a bending stiffness of the first bent portion22C3is higher than that of the second bent portion22C4. Specifically, when the friction pad9moves in the direction closer to the disc1so that the second bent portion22C4is bent so as to enlarge the angle thereof, the second bent portion22C4is directly bent so as to increase the angle. As a result, the extending portion22B cannot be deflected in the direction closer to the fixed portion22A, that is, toward the side opposite to the abutting portion22D in the disc rotating direction. Ultimately, the abutting portion22D moves in the disc rotating direction and in the direction away from the fixed portion22A.

As described above, the lower bending stiffness of the first bent portion21C3of the return spring21than that of the second bent portion21C4can suppress the amount of movement of the abutting portion21D in the disc rotating direction, caused by the movement of the fixed portion21A.

As described above, the return spring21used in this embodiment adopts the configuration as described above. As a result, even when the lining11of the friction pad9is worn away by the repeated braking operations, the positional shift of the position of abutment of the return spring21(abutting portion21D) against the seating-surface plate portion20of the pad spring14can be reduced as indicated by the dimension a illustrated inFIG. 8.

As a result, the length dimension of the seating-surface plate portion20of the pad spring14can be shortened. Therefore, a corresponding portion of the seating-surface plate portion20of the carrier2is not required to be provided correspondingly. Thus, the carrier2, and in turn, the disc brake can be reduced in size. Moreover, a stock layout of the pad spring14can be efficiently determined. Further, even when a layout of the pad guide4and the pin hole (not shown) on the arm portion2A side of the carrier2is strict, the layout can be relatively easily performed.

Further, the amount of projection (dimension γ illustrated inFIG. 8) of the return spring21can be relatively made small by the turned-back portion21C having the middle portion (second bent portion21C4) located at the position separated farther away from the fixed portion21A than the abutting portion21D in the direction along the plane of the back metal10(disc rotating direction). Therefore, a space for mounting the return spring21can be easily ensured to enhance the degree of freedom in layout design.

Further, the turned-back portion21C of the return spring21includes the second bent portion21C4between the first extension portion21C1and the second extension portion21C2, which is located at the position separated farther away from the fixed portion21A than the abutting portion21D in the direction along the plane of the back metal10, that is, in the disc rotating direction, or the first extension portion21C1extends from the distal end side of the extending portion21B in the direction along the plane of the friction pad9, that is, in the disc rotating direction and the direction away from the fixed portion21A to the position beyond the abutting portion21D. Therefore, a length of extension (total length dimension) of the first extension portion21C1and the second extension portion21C2can be formed longer than that of a conventional product (comparative example illustrated inFIG. 9). In this case, the spring constant can be easily ensured.

Specifically, for the return spring21, by appropriately selecting the length of extension of the first extension portion21C1and the second extension portion21C1, the spring constant can be easily adjusted to increase the degree of freedom in design. Moreover, a yield rate in fabrication of the return spring21can be improved to easily ensure a necessary strength.

Moreover, in the case of the return spring21including the extending portion21B and the turned-back portion21C, the biasing force of the return spring21can be applied on the friction pad9at an appropriate position when, for example, the braking operation of the vehicle is released or the like. Therefore, the friction pad9can be stably returned while keeping a posture parallel to the surface of the disc1.

Therefore, according to this embodiment, the disc brake can be reduced in size. In addition, the degree of freedom in layout design can be enhanced. Moreover, the friction pad9can be smoothly returned to the standby position by the biasing force of the return spring21when the braking operation is released. Therefore, the return operation of the friction pad9can be stabilized. As a result, uneven wear of the friction pad9or the like can be reduced. As a result, a drag of the pad and a brake squeal can be prevented.

Second Embodiment

Next,FIG. 12illustrates a second embodiment of the present invention. This embodiment is characterized in a configuration in which a turned-back portion of a return spring is formed so as to be curved from a distal end side of the extending portion in an arc-like shape and a middle portion thereof is located at a position separated farther away from a fixed portion than an abutting portion in the direction along the plane of the friction pad. The same components as those of the first embodiment described above are denoted by the same reference numerals in the second embodiment, and the description thereof is omitted.

In the drawing, the reference numeral31denotes a return spring for biasing the friction pad9in a return direction in which the friction pad9is moved away from the disc1. The return spring31is configured approximately in the same manner as the return spring21described in the first embodiment, and includes a flat-plate like fixed portion31A located on one side in a length direction thereof, an extending portion31B formed by bending into an L shape from the fixed portion31A so that a distal end side extends in the axial direction of the disc, a turned-back portion31C formed by bending a distal end side of the extending portion31B so as to be turned back in a C shape toward the carrier2, and an abutting portion31D formed by bending the other side of the return spring31in the length direction in an approximate U shape.

However, the return spring31in this case differs from that of the first embodiment in that the extending portion31B is bent from the fixed portion31A into the L shape to extend parallel to the disc axial direction and then is slightly bent toward the side opposite to the abutting portion31D to extend in the disc axial direction (extend to a position X illustrated inFIG. 12at which an alternate long and short dash line crosses) and in that the turned-back portion31C is formed so as to be curved from the distal end side of the extending portion31B in an arc-like shape to form a C shape. A base end side of the turned-back portion31C is formed as an arc continuous from the distal end of the extending portion31B. The turned-back portion31C forms, for example, an approximate C-like whole shape. The turned-back portion31C forming the arc-like shape has a configuration in which a middle portion31C1is located at a position farther away from the fixed portion31A than the abutting portion31D in the direction along the plane of the friction pad9.

As described above, even in the second embodiment configured as described above, substantially the same functions and effects as those of the first embodiment described above can be obtained. In particular, the return spring31in this case is formed in an approximate shape as a whole and has a configuration in which the turned-back portion31C is formed to be curved into the C shape (arc-like shape) as the arc continuous from the distal end side of the extending portion31B.

Therefore, for the return spring31, the spring constant can be easily adjusted to enhance the degree of freedom in design by appropriately selecting a radius of the arc (curvature) or a length of extension of the turned-back portion31C. Moreover, a yield rate in fabrication of the return spring31can be improved to easily ensure a necessary strength.

The turned-back portion31C is formed as a continuous arc as compared with the straight first extension portion21C1and second extension portion21C2described with the first embodiment. If the turned-back portion is to be forcibly divided into a first extension portion31C1and a second extension portion31C2, the extension portions are separated at a position Y crossing an alternate long and short dash line illustrated inFIG. 12. In the second embodiment described above, the whole shape of the return spring31is the arc-like approximate Ω shape. However, a part thereof, for example, the extending portion31B may be extended to form an approximate P shape.

Third Embodiment

Next,FIG. 13illustrates a third embodiment of the present invention. Even in the third embodiment, the same components as those of the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted. This embodiment is characterized in a configuration in which an abutting portion41D described below is oriented in an inward direction of an arc formed by a turned-back portion41C.

In the drawing, the reference numeral41denotes a return spring for biasing the friction pad9in a return direction away from the disc1. The return spring41includes a fixed portion41A, an extending portion41B, a turned-back portion41C, and an abutting portion41D. The turned-back portion41C is configured to be curved into an arc-like shape from a distal end side of the extending portion41B extending in an axial direction of the disc2along a tangent direction.

However, the return spring41in this case differs from those of the first and second embodiments in that the abutting portion41D located on the other side of the return spring41in the length direction is bent in an inward direction of the arc formed by the turned-back portion41C into an approximate U shape so as to be curved into the arc-like shape. The turned-back portion41C forming the arc-like shape has a configuration in which a middle portion41C1thereof is located at a position farther away from the fixed portion41A than the abutting portion41D in the direction along the plane of the friction pad9. If the turned-back portion41C is to be forcibly divided into a first extension portion41C1and a second extension portion41C2, the extension portions are separated at a position Y illustrated inFIG. 13, at which an alternate long and short dash line crosses.

As described above, even in the third embodiment configured as described above, substantially the same functions and effects as those of the first and second embodiments described above can be obtained. In this case, the abutting portion41D is bent into the approximate U shape in the inward direction of the arc formed by the turned-back portion41C. As a result, the distal end of the abutting portion41D does not come into contact with another component or the like during the fabrication of the disc brake, thereby improving fabrication efficiency.

Fourth Embodiment

Next,FIG. 14illustrates a fourth embodiment of the present invention. This embodiment is characterized in a configuration in which a turned-back portion of a return spring is formed by first to fourth extension portions described below and a middle portion thereof is located at a position farther away from a fixed portion than an abutting portion in the direction along the plane of the friction pad. The same components as those of the first embodiment described above are denoted by the same reference numerals in the fourth embodiment, and the description thereof is omitted.

In the drawing, the reference numeral51denotes a return spring for biasing the friction pad9in a return direction in which the friction pad9is moved away from the disc1. The return spring51is configured approximately in the same manner as the return spring21described in the first embodiment, and includes a flat-plate like fixed portion51A located on one side in a length direction thereof, an extending portion51B formed by bending into an L shape from the fixed portion51A so that a distal end side extends in the axial direction of the disc, a turned-back portion51C formed by bending a distal end side of the extending portion51B a plurality of times toward the carrier2, and an abutting portion51D formed by bending the other side of the return spring51in the length direction in an approximate U shape or an arc-like shape.

However, the turned-back portion51C of the return spring51includes a first extension portion51C1extending from the distal end side of the extending portion51B in the direction along the plane of the friction pad9(back metal10) and in the direction away from the fixed portion51A, a second extension portion51C2-1turned back from a distal end side of the first extension portion51C1toward the carrier2(seating-surface plate portion20side of the pad spring14) in an approximate L shape to extend approximately parallel to the extending portion51B, a third extension portion51C2-2turned back from a distal end side of the second extension portion51C2-1in an approximate L shape to extend approximately parallel to the first extension portion51C1, and a fourth extension portion51C2-3turned back from a distal end side of the third extension portion51C2-2in an approximate L shape to extend approximately parallel to the extending portion51B.

The abutting portion51D of the return spring51is formed by bending a distal end side of the fourth extension portion51C2-3in an approximate U shape or an arc-like shape. A first bent portion51C3is provided between the extending portion51B and the first extension portion51C1. In a middle portion of the turned-back portion51C, a second bent portion51C4-1is provided so as to be located between the first extension portion51C1and the second extension portion51C2-1. A third bent portion51C4-2is provided between the second extension portion51C2-1and the third extension portion51C2-2. Further, a fourth bent portion51C4-3is provided between the third extension portion51C2-2and the fourth extension portion51C2-3. The second extension portion51C2-1, the third extension portion51C2-2, and the fourth extension portion51C2-3correspond to the second extension portion21C2in the first embodiment.

The second bent portion51C4-1corresponding to the middle portion of the turned-back portion51C, the second extension portion51C2-1, the third bent portion51C4-2and the like are located at the positions separated farther away from the fixed portion51A than the abutting portion51D in the direction along the plane of the friction pad9(back metal10) (disc rotating direction).

As described above, even in the fourth embodiment configured as described above, substantially the same functions and effects as those of the first embodiment described above can be obtained. Even in this case, because the turned-back portion51C of the return spring51is composed of the first extension portion51C1, the second extension portion51C2-1, the third extension portion51C2-2, the fourth extension portion51C2-3, and the like, the spring constant can be easily adjusted to enhance the degree of freedom in design.

Fifth Embodiment

Next,FIG. 15illustrates a fifth embodiment of the present invention. This embodiment is characterized in a configuration in which a turned-back portion of a return spring is formed by first to third extension portions described below and a middle portion thereof is located at a position separated farther away from a fixed portion than an abutting portion in the direction along the plane of the friction pad (disc rotating direction). The same components as those of the first embodiment described above are denoted by the same reference numerals in the fifth embodiment, and the description thereof is omitted.

In the drawing, the reference numeral61denotes a return spring for biasing the friction pad9in a return direction in which the friction pad9is moved away from the disc1. The return spring61is configured approximately in the same manner as the return spring21described in the first embodiment, and includes a fixed portion61A, an extending portion61B, a turned-back portion61C formed by bending a distal end side of the extending portion61B a plurality of times toward the carrier2, and an abutting portion61D formed by bending the other side of the return spring61in the length direction.

However, the turned-back portion61C of the return spring61includes a first extension portion61C1-1and a second extension portion61C1-2extending from the distal end side of the extending portion61B in the direction along the plane of the friction pad9(back metal10) (disc rotating direction) and in the direction away from the fixed portion61A, and a third extension portion61C1-2turned back from a distal end side of the second extension portion61C1-2toward the carrier2(seating-surface plate portion20side of the pad spring14) to connect to the abutting portion61D. The first extension portion61C1-1and the second extension portion61C1-2correspond to the first extension portion21C1in the first embodiment.

The turned-back portion61C of the return spring61includes a first bent portion61C3provided between the extending portion61B and the first extension portion61C1-1, a second bent portion61C4provided between the second extension portion61C1-2and the third extension portion61C2so as to be bent in an approximate L shape, and a third bent portion61C1-3provided between the first extension portion61C1-1and the second extension portion61C1-2so as to be bent to form an obtuse angle. The second bent portion61C4corresponding to the middle portion of the turned-back portion61C is located at the position separated farther away from the fixed portion61A than the abutting portion61D in the direction along the plane of the friction pad9(back metal10).

As described above, even in the fifth embodiment configured as described above, substantially the same functions and effects as those of the first embodiment described above can be obtained. Even in this case, because the turned-back portion61C of the return spring61is composed of the first extension portion61C1-1, the second extension portion61C1-2, the third extension portion61C2, and the like, the spring constant can be easily adjusted to enhance the degree of freedom in design.

Sixth Embodiment

Next,FIGS. 16 to 18illustrate a sixth embodiment of the present invention. This embodiment is characterized in that a rib72is provided so as to increase a bending stiffness of a second bent portion71C4. In the embodiments described above, in particular, in the first embodiment, the angle of the second bent portion21C4is set smaller than that of the first bent portion21C3so as to set the bending stiffness of the first bent portion21C3lower than that of the second bent portion21C4. On the other hand, in this sixth embodiment, the bending stiffnesses of the bent portion21C3and the second bent portion21C4are set different from each other by thicknesses, width dimensions, shapes, and the like of the bent portion21C3and the second bent portion21C4other than by an angle formed thereby. In the sixth embodiment, the components other than the springs are the same as those in the first embodiment described above, and the detailed description thereof is omitted.

The return spring71includes a fixed portion71A on one side, which is fixedly mounted to the back metal10of the friction pad9, an extending portion71B extending from the fixed portion71A in the disc axial direction and in the direction away from the friction pad9, a turned-back portion71C formed by turning back a distal end side of the extending portion71B toward the carrier2, and an abutting portion71D provided on the distal end side of the turned-back portion71C to be elastically brought into abutment against on the carrier2side (seating-surface plate portion20side of the pad spring14).

The turned-back portion71C includes a first extension portion71C1extending from a distal end side of the extending portion71B in the direction along the plane of the friction pad9(back metal10) (disc rotating direction) and in the direction away from the fixed portion71A, and a second extension portion71C2bent from a distal end side of the first extension portion71C1toward the carrier2(the seating-surface plate portion20side of the pad spring14) so as to be smoothly connected to the abutting portion71D.

The turned-back portion71C includes a first bent portion71C3formed between the extending portion71B and the first extension portion71C1of the turned-back portion71C, and a second bent portion71C4formed between the first extension portion71C1and the second extension portion71C2, which corresponds to a middle portion of the turned-back portion71C. The second bent portion71C4is located at a position closer to the fixed portion71A than the abutting portion71D in the direction along the plane of the friction pad9(back metal10), that is, in the disc rotating direction. Specifically, an angle formed by the first extension portion71C1and the second extension portion71C2(hereinafter, referred to as “angle of the second bent portion71C4” for convenience) is obtuse and is larger than a right angle corresponding to an angle formed by the extending portion71B and the first extension portion71C1(hereinafter, referred to as “angle of the first bent portion71C3” for convenience). Hence, the return spring71has the same whole shape as that of the return spring22illustrated inFIG. 9, corresponding to the comparative example described in the first embodiment.

The rib72, which projects in a direction to form convexity by bending, is provided to the second bent portion71C4. By the rib72, a bending stiffness of the second bent portion71C4becomes higher than that of the first bent portion71C3. Therefore, when the fixed portion71A moves with respect to the abutting portion71D in the direction closer to the disc1, the angle of the first bent portion71C3is enlarged earlier than the angle of the second bent portion71C4.

As a result, a positional shift of the position of abutment of the abutting portion71D of the return spring71against the seating-surface plate portion20of the pad spring14can be reduced to be small. Moreover, the length dimension of the seating-surface plate portion20of the pad spring14can be reduced. Therefore, a corresponding portion of the seating-surface plate portion20of the carrier2is not required to be provided correspondingly. Thus, the carrier2, and in turn, the disc brake can be reduced in size. Further, a stock layout of the pad spring14can be efficiently determined. Further, even in the case where a layout of the pad guide4and the pin hole (not shown) on the arm portion2A side of the carrier2is strict, the layout can be relatively easily performed.

In the first embodiment described above, the case where the abutting portion21D of the return spring21is elastically brought into abutment against the seating-surface plate portion20of the pad spring14has been described as an example. However, the present invention is not limited thereto. For example, there may be used a configuration in which a seating-surface plate portion formed from a member different from the pad spring is fixedly provided to the mounting member (carrier) so that the abutting portion21D of the return spring21is brought into abutment against the seating-surface plate portion. Moreover, there may be used a configuration in which, without using the seating-surface plate portion20or the like, the abutting portion of the return spring is directly brought into abutment against an end surface of the mounting member (or a seating-surface portion for the return spring, which is provided to the mounting member) or the like. This point can be similarly applied to the second to sixth embodiments.

Further, in the first embodiment described above, there has been described as an example the case where the pad guide4forming the concave shape is provided to the arm-portion2A of the carrier2and each of the ear portions10A of the back metal10, corresponding to the fitting portions into the pad guides4, is formed to have the convex shape. However, the present invention is not limited thereto. For example, there may be used a configuration in which a fitting portion having a concave shape is provided to the back metal of the friction pad and a pad guide having a convex shape is provided to the arm portion of the mounting member.

In the first embodiment described above, there has been described as an example the case where the base end side of the return spring21is caulked to the ear portion10A side, which is located on the rotating entrance side of the disc1, among the right and left ear portions10A of the back metal10. However, the present invention is not limited thereto. For example, there may be used a configuration in which the return springs are similarly provided on the rotating exit side of the disc1.

In the first embodiment described above, there has been described as an example the case where the so-called integral type pad spring14including the flat plate portions16, the guide plate portions18, and the radial-direction biasing portions19respectively on the inner side and the outer side of the disc1is used. However, the present invention is not limited thereto. For example, there may be used a configuration in which two pad springs having shapes obtained by splitting the pad spring14into one on the inner side and the other one on the outer side of the disc1are respectively provided on the inner side and the outer side of the disc1. This point can be similarly applied to the pad spring14located on the rotating exit side of the disc1.

In the invention encompassed in the embodiments described above, the turned-back portion of the return spring includes the first extension portion extending from the distal end side of the extending portion in the direction along the plane of the friction pad and in the direction away from the fixed portion, and the second extension portion turned back from the distal end side of the first extension portion toward the mounting member so as to be connected to the abutting portion. The second extension portion is formed by being turned back from the distal end side of the first extension portion in the direction along the plane of the friction pad and in the direction closer to the fixed portion.

In this manner, the turned-back portion between the first extension portion and the second extension portion can be located at the position farther away from the fixed portion than the abutting portion in the direction along the plane of the friction pad. Thus, the length of extension (total length dimension) of the first extension portion and the second extension portion can be formed longer than that of a conventional product. Therefore, for the return spring, the spring constant can be easily adjusted to enhance the degree of freedom in design. Moreover, the yield rate in fabrication of the return spring can be improved to easily ensure the necessary strength.

In the invention encompassed in the one embodiment described above, the turned-back portion of the return spring is formed so as to be curved from the distal end side of the extending portion into the arc-like shape and to have the middle portion extending in the direction along the plane of the friction pad (disc rotating direction) to the position farther away from the fixed portion than the abutting portion.

As described above, the middle portion of the turned-back portion which is formed so as to be curved from the distal end side of the extending portion of the return spring into the arc-like shape is extended to the position farther away from the fixed portion than the abutting portion in the direction along the plane of the friction pad. As a result, the positional shift of the position of abutment of the return spring against the mounting member side can be reduced to be small even when the friction pads are worn away. Thus, the friction pads can be returned in a stable posture, while the space for mounting the return springs can be easily ensured.

According to the embodiments of the present invention described above, the disc brake can be reduced in size.

Although some exemplary embodiments of the invention of this application have been described above in detail, those skilled in the art can easily understand that various modifications can be made to the exemplary embodiments described above without substantially departing from the novel teachings and advantages of the invention of this application. Therefore, all the modifications are intended to be encompassed in the scope of the invention of this application.

The present application claims priority under the Paris convention on the basis of Japanese Patent Application No. 2009-222773 filed on Sep. 28, 2009 and Japanese Patent Application No. 2010-207292 filed on Sep. 15, 2010. The entire disclosure of Japanese Patent Application No. 2009-222773 filed on Sep. 28, 2009 and Japanese Patent Application No. 2010-207292 filed on Sep. 15, 2010 including specification, claims, drawings and summary is incorporated herein by reference.

REFERENCE SIGNS LIST