JPS6015956Y2 - Disc brake friction pad wear limit warning device - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a wear limit warning device for a disc brake that warns that the friction material of a friction pad has been worn to the wear limit.

Background of the invention A disc brake for a vehicle consists of a disc rotor that rotates integrally with the wheel, a friction pad that includes a friction material that faces the friction surface of the disc rotor, and a back plate that is fixed to the back surface of the friction material. , an actuator that presses the friction pad against the friction surface of the disc rotor, and a torque receiving member that is fixed to a non-rotating member near the disc rotor and supports the friction pad so as to be movable in a direction perpendicular to the friction surface of the disc rotor. It is usually configured to include

As a result of repeated use of such disc brakes, if the friction material of the friction pad wears down to the wear limit, it is necessary to notify the driver that it should be replaced. A type of telegraph device,
Attach the information member made of thin plate material to the friction pad,
When the friction material wears down to the wear limit, the contact portion of the warning member comes into contact with the rotating disc rotor, and an alarm is emitted.

In order to obtain a warning sound that can be clearly distinguished from surrounding noise with this type of wear limit 2' telegraph device, it is necessary to vibrate the contact part at a high frequency. It is necessary to prevent the friction surface of the disc rotor from being damaged by this.

In this regard, in the wear limit gate informing device described in Japanese Utility Model Application Publication No. 51-77484, the informing member is equipped with a pair of arms that sandwich the sides of the back plate of the friction pad from the front and back sides. The screws pass from the rear of the back plate between the mounting leg, which is fitted into the back plate from the side, and the side of the back plate and the surface of the torque receiving member facing it, to the friction surface of the disc rotor. The contact portion extends toward the friction material, and has a contact portion whose tip reaches the wear limit surface of the friction material, and a spring portion that elastically connects the contact portion and the mounting leg portion,
In addition, when the vehicle moves forward, the contact portion is not strongly pinched by the back plate and the torque receiving member (although there is no description to that effect, it is assumed that this is done due to the structure). Therefore, the contact portion is prevented from hitting the friction surface of the disc rotor too strongly due to the elastic deformation of the spring portion, and there is less risk of damaging the friction surface of the disc rotor or damaging itself.

However, in this wear limit warning device, the contact portion is strongly pinched between the back plate and the torque receiving member (although there is no description to that effect, it is understood as such in the drawing) when the vehicle moves backward. There is a risk that the friction surface of the disc rotor may be hit too hard and the friction surface may be damaged, or the disc rotor itself may be damaged.

In addition, since this alarm member also serves as an anti-ladle spring that prevents ruddling of the friction pad, the direction in which the spring part biases the contact part is opposite to the rotation direction of the disc rotor when the vehicle moves forward. When the friction material wears to its wear limit and the tip of the contact part contacts the friction surface of the disc rotor, the contact part is bent away from the torque receiving member by the frictional force with the disc rotor, resulting in a relatively long contact part. The whole body vibrates in a mode in which it rotates around the spring part.

Therefore, the natural frequency is low and it is difficult to obtain a high frequency warning sound.

Therefore, the present applicants have proposed a wear limit alarm including an alarm member having a mounting leg portion, a contact portion, and a spring portion as described above in accordance with Japanese Patent Application No. 56-24484 (Japanese Unexamined Patent Publication No. 57-140934). The device is characterized in that the direction in which the spring part biases the contact part is the same direction as the rotational direction of the disc rotor when the vehicle moves forward, and the contact part is opposite to that of the side surface of the friction pad back plate and the torque receiving member. We proposed a system that extends toward the disc rotor through a gap that does not disappear even during braking between the disc and the disc rotor.

There is often a gap between the side of the friction pad back plate and the torque receiving member that does not disappear even during braking, so if such a gap exists, an alarm member is placed in that area. However, if such a gap does not exist, a gap is intentionally created and the alarm member is disposed there.

In this way, the contact portion will be pressed against the side surface of the back plate of the friction pad or the surface of the torque receiving member opposite to that side surface, and the friction material will be worn to the wear limit and the contact portion will be pressed against the friction surface of the disc rotor. Even if the friction pad comes into contact with the friction pad, it will not be deflected away from the back plate or the torque receiving member due to the frictional force with the disc rotor, and the contact portion will be strongly pinched between the friction pad back plate and the torque receiving member. Therefore, the contact parts vibrate using the points of contact with them as nodes, and the natural frequency becomes high, producing an alarm sound that can be clearly distinguished from other noises. There is no risk of damaging the friction surface or damaging the friction surface itself by hitting the friction surface too strongly.

However, when the direction in which the spring part biases the contact part is the same as the rotational direction of the disc rotor when the vehicle moves forward, and the contact part is pressed against the torque receiving member, the reaction force causes the friction parad of the disc rotor. This causes a problem in that when the friction pad is pressed against the disc rotor, it moves against the urging force and generates collision noise on the torque receiving member.

Furthermore, when assembling the friction pad to the torque receiving member, it is necessary to bend the contact portion toward the friction pad against the biasing force of the spring portion, which causes the problem of poor assembly workability. .

Therefore, it is desirable that the contact portion be pressed against the back plate of the friction pad.

Problems to be Solved by the Invention However, in this case, the reaction force of the pressing force of the contact part against the back plate acts in the direction of detaching the mounting leg from the back plate, and furthermore, even when a wear alarm occurs, the contact part In order to obtain stable frequency vibration, it is desirable to prevent the mounting legs from separating from the back plate as much as possible, so the reaction force will be quite large, so measures must be taken to reliably prevent the mounting legs from separating from the back plate. It is necessary to carry out

Although detachment can be prevented by fixing the mounting legs to the back plate using rivets, screw members, welding, etc., the assembly work becomes troublesome and costs inevitably increase.

With the above-mentioned circumstances as a background, the present invention includes an alarm member including a mounting leg portion, a contact portion, and a spring portion as described above, and the spring portion elastically presses the contact portion against the back plate of the friction pad. Moreover, the mounting leg part can be easily attached to the back plate of the friction pad, and the elastic force of the spring part is increased to strongly press the contact part against the back plate to ensure stability at a sufficiently high frequency. This was done in order to provide a wear limit warning device in which there is no fear that the mounting legs will separate from the back plate even if the device is made to vibrate.

Means for Solving the Problems The gist of the present invention is to attach the spring portion of the information member so that the longitudinal intermediate portion of the contact portion is oriented in the same direction as the rotational direction of the disc rotor when the vehicle moves forward. In addition, at least one of the pair of arms of the U-shaped mounting leg shall be pressed against the side surface of the back plate by a protruding amount from the opening side of the U-shape toward the back side. An engaging claw with a shape that gradually increases is provided on the back plate, and when the mounting leg is attached to the back plate, the mounting leg engages with the most protruding tip of the engaging claw, and the mounting leg becomes a spring part. The reason is that an engaging recess is formed to prevent the back plate from being laterally separated from the back plate due to the elastic force of the cover plate.

In addition, since the U-shaped mounting legs are attached to the side of the back plate of the friction pad from the side, the part corresponding to the bottom of the U-shape is rotated to the side of the back plate. In such a case, the contact part, which is urged toward the back plate by the spring part, may be obstructed by the bottom of the mounting leg and cannot come into direct contact with the side surface of the back plate. An opening for exposing the side surface of the back plate may be provided in a portion corresponding to the bottom of the U-shape of the mounting leg, so that the contact portion and the side surface of the back plate can come into contact through this opening. .

In the present invention, the contact portion is prevented from being pressed against the mounting leg because if the contact portion is pressed against the bottom of the mounting leg, contact may occur even before the alarm member is attached to the back plate. The contact part needs to be elastically pressed against the mounting leg, and it is not easy to manufacture such an alarm member with a sufficiently large pressing force of the contact part against the mounting leg. On the other hand, the contact part is pressed against the side of the back plate, and in the process of engaging the mounting legs with the side of the back plate, the contact part comes into contact with the side of the back plate, and from that state, the mounting legs are pressed against the side of the back plate. This is because it is relatively easy to make the pressing force of the contact part sufficiently large by elastically deforming the spring part as the part is deeply engaged with the side part of the back plate. .

In addition, in order for the contact part to vibrate stably, it is desirable that the contact part and the side surface of the back plate make point-like contact at least in the longitudinal direction of the contact part. It is desirable to form a protrusion that protrudes more toward the side surface of the back plate than other parts.

Functions and Effects In this invention, as mentioned above, the middle part of the contact part in the longitudinal direction is pressed against the back plate by the elastic force of the spring part, so that the length from the part of the contact part supported by the back plate to the tip is The sound becomes shorter and vibrates at a higher frequency, producing an alarm sound that can be clearly distinguished from surrounding noise.

In addition, the contact part passes through a gap between the friction pad back plate and the torque receiving member that does not disappear when the vehicle moves forward or backward, so the contact part passes between the back plate and the torque receiving member. There is no possibility of contacting the disc rotor in a state where the disc rotor is strongly sandwiched between the receiving member and its movement is restricted, and there is no risk of damaging the friction surface of the disc rotor or damaging the contact portion.

Furthermore, the U-shaped mounting leg is provided with an engagement claw whose protrusion amount gradually increases from the opening side of the U-shape toward the back, and this is engaged with the engagement recess on the back plate. By simply fitting the alarm member into the side of the back plate from the side, the engaging claw can engage with the engaging recess with its own elastic deformation or the elastic deformation of the mounting leg, making it easy to attach the alarm member to the back plate. It can be attached to the side of the

Moreover, in the process of attaching the mounting leg to the side of the back plate, the contact portion comes into contact with the side of the back plate, and when the mounting leg is brought into deeper engagement with the side of the back plate from that state, the spring portion is elastically deformed to generate an urging force for pressing the contact portion against the side surface of the back plate, which is convenient.

In addition, the spring portion elastically deformed in this way applies a force to the mounting leg in the direction of separating from the side of the back plate, but this separation occurs between the most protruding tip of the engagement claw and the engagement recess. This ensures that the alarm member remains in place.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, 10 is a disk-shaped disc rotor,
It is rotated along with the vehicle's wheels.

The disc rotor 10 has friction surfaces 12°14 on both sides of the outer circumference.
A pair of friction pads, that is, an inner pad 16 and an outer pad 18, are arranged opposite these friction surfaces.

Each pad 16.18 is separated from a friction material 20.21 and a steel backing plate 22.24 secured to its rear surface.

These pads 16, 18 are torque receivers consisting of pad supports 26, 28 disposed on both sides of the disc rotor 10, and a connecting part 30 that extends beyond the outer periphery of the disc rotor 10 and connects them, as shown in FIG. It is supported by a member 32 so as to be slidable in a direction parallel to the axis of the disc rotor 10 .

This point will be explained in detail later. The pads 16 and 18 are connected to the disk by the caliper 33 as an actuator.
It is pressed by the rotor 10.

That is, the caliper 33 connects a hydraulic cylinder 34 provided opposite to the back surface of the inner pad 16 and the outer pad 1.
A reaction section 36 provided opposite to the back surface of 8;
It is equipped with a connecting part 38 that connects these parts beyond the outer periphery of the disc rotor 10, and is moved in a direction parallel to the axis of the disc rotor 10 by two slant pins (not shown) provided upright on the torque receiving member 32. Possibly supported.

Therefore, when brake fluid pressure is supplied to the cylinder bore 40 of the hydraulic cylinder 34, the piston 42
is pressed against the friction surface 12 of the disc rotor 10, and the reaction section 36 pushes the outer pad 18 against the friction surface 12 by the reaction force.
It forces it to 4.

Next, the manner in which the pads 16 and 18 are supported by the torque receiving member 32 will be explained in detail, but since this is almost the same for both pads, only the outer pad 18 will be explained, and the explanation about the inner pad 16 will be omitted.

As shown in FIG. 2, the pad support portion 28 of the torque receiving member 32 is formed with a substantially rectangular pad accommodating notch 44, and small rectangular notches 46 are formed near the bottom on both sides of this notch 44. .48 is formed.

The back plate 24 of the outer pad 18 is provided with ears 50, 52 that project laterally from the lower ends of both sides, and when these ears 50, 52 are engaged with the small notches 46, 48. The pad is accommodated in the pad accommodation notch 44.

During braking, the back plate 24 is adapted to transmit torque by abutting the surface of the torque receiving member 32 facing this, that is, the inner surface of the notch 44, at the upper side of the side surface.
A gap is formed between the tip surfaces of the ears 50 and 52, which are the lower portions of the side surfaces of the back plate 24, and the surfaces of the small notches 46 and 48 that face them, which do not disappear even during the torque transmission. There is.

A stainless steel anti-rust member 54 is inserted between the contact surface between the back plate 24 and the pad support portion 28, and is integrated with the anti-rust member 54 to prevent the outer pad 18 from ruddling. A ladle spring 56 is formed.

Note that the shape of the anti-ladle spring on the inner pad 16 side is different from that on the outer pad 18 side.

A wear limit warning device 60 is provided on one ear of the back plate 24, that is, on the ear 52 on the disk rotor entry side (leading side) when the vehicle is moving forward.

This wear limit warning device is shown in enlarged form in FIGS. 3 to 8.

The wear limit alarm device 60 is provided with an ear portion 52 that is a part of the back plate 24.
It consists of a protrusion 62 projecting laterally from the side surface (front end surface) of the sensor, and an alarm member 64 made of a thin stainless steel plate for a spring.

Alarm member 64 is separated from mounting leg 66, spring portion 68 and contact portion 70 as best shown in FIG.

The mounting leg portion 66 is approximately U-shaped, and has a shape in which the ear portion 52 is sandwiched between the front and rear sides by a pair of arms. As shown, it is manufactured so that the U-shaped opening becomes narrow, and when it is attached, it is expanded by elastic deformation as shown by the two-dot chain line and is attached to the ear portion 52.

As is clear from FIGS. 6 and 7, two mounting legs 66 are provided parallel to each other, and the pair of mounting legs 66 are attached to sandwich the protrusion 62 from both upper and lower sides. Therefore, the mounting leg portion 66 is prevented from moving in the vertical direction along the ear portion 52.

These gripping legs 66 are combined into one at one end and are connected to the spring part 68, and an engaging pawl 71 is provided in this combined part.

As is clear from FIGS. 3 and 7, the engaging pawl 71 has a part of the information member 64 bent inside the U-shape, and extends from the opening side of the U-shape toward the back side. The ear part 52 is engaged with an engagement recess 72 formed on the back surface of the ear part 52.

The engagement recess 72 is formed in a shape that becomes deeper from the proximal end side to the distal end side of the ear part 52, and has a surface on the distal end side that is approximately perpendicular to the rear surface of the ear part 52, and the engagement claw is formed on this surface. The ear portion 52 engages with the tip of the ear portion 71 to prevent the alarm member 64 from slipping out from the proximal end side of the ear portion 52 toward the distal end side, and contacts the inner surface of the pair of mounting legs 66. In cooperation with the distal end surface of the alarm member 64, it functions to prevent the alarm member 64 from rotating in a plane parallel to the back plate 24.

Moreover, since the engaging claw 71 is formed so that the amount of inward protrusion gradually increases from the opening side of the U-shaped mounting leg portion 66 toward the back side, the mounting leg portion 66 is attached to the ear portion 52. When installed, the ears 52 themselves are elastically deformed to a state substantially parallel to the pair of arms of the mounting legs 66, and the installation does not interfere with the work.

As is clear from FIG.
A U-shape is formed so as to open laterally from the center of the pad, and the second bent portion is formed such that a U-shape opens toward the back surface of the back plate 24 .

As clearly shown in FIGS. 4 and 5, an elongated hole 73 is formed in the center of the spring portion 68 in the axial direction, spanning the first bent portion and the second bent portion. hole 73
The spring constant of each bending portion is adjusted by forming .

A contact portion 70 extends from one end of the spring portion 68.

The contact portion 70 has a flat plate shape, and connects the ear portion 5 from the rear side of the back plate 24.
2 and the surface facing this of the torque receiving member 32, and extends to the front side of the back plate 24, and the tip thereof meets the wear limit surface shown by the two-dot chain line in FIG. It has reached 74.

The contact portion 70 has a protrusion 76 that bulges toward the ear portion 52 at the center position in the axial direction. The elastic force of the spring portion 68 presses against the tip of the protrusion 62 that protrudes toward the direction.

That is, in the standalone state before installation, the contact portion 70 is
As shown by the solid line in FIG. 8, it is formed close to the mounting leg 66, but in the mounted state,
The contact portion 70 is pushed away by the projection 62 to the position shown by the two-dot chain line against the elastic force of the spring portion 68, and the direction in which the contact portion 70 is biased by the spring portion 68 is The direction of rotation of the disc rotor 10 coincides with the direction of rotation of the disc rotor 10 during forward movement.

Wear limit warning device 6 provided on the outer pad 18
0, it is also possible to provide the inner pad 16 with a similar wear limit information device, and since the inner pad and the outer pad are usually replaced at the same time, the sooner of the two pads 16 and 18 is replaced. It is also possible to provide the wear limit warning device 60 only on one side that is predicted to wear out.

In the disc brake equipped with the wear limit warning device 60 configured as described above, when the friction material 20 of the outer pad 18 is worn down to the wear limit, an alarm is issued in the following manner.

When the friction material 20 reaches its wear limit, the tip of the contact portion 70 of the alarm member 64 comes into contact with the friction surface 14 of the disc rotor 10, as shown in FIG.

Since the disc rotor 10 is rotating in the direction shown by arrow A in FIG. 9 when the vehicle is moving forward, the friction surface 14
The contact portion 70 in contact with the warning member 64 is pulled in the rotational direction of the disc rotor 10 by the frictional force and deformed as shown by the solid line, and then returns to its original position by the elastic force of the alarm member 64 itself.

Thereafter, by repeating this operation, the contact portion 70 is connected to the ear portion 52.
While in contact with the protrusion 62, it vibrates violently and emits an alarm sound.

At this time, the contact portion 70 contacts the protruding end surface of the protrusion 62 as the side surface of the back plate 24 at the protrusion 76, and does not contact at other portions, so that the contact point of the contact portion 70 with respect to the back plate 24 is clearly determined, and the alarm member vibrates stably in the scheduled vibration mode and natural frequency to emit the scheduled alarm sound.

Furthermore, if the protrusion 76 separates from the protrusion 62 when the alarm sound is generated, the vibration of the contact portion 70 will become unstable and a clear alarm sound with the expected frequency will not be obtained. , in this embodiment, as mentioned above, the protrusion 76
is pressed against the projection 62 with a sufficiently strong force, a stable and clear alarm sound is emitted.

Moreover, in this embodiment, in order to press the protrusion 76 against the protrusion 62 with sufficient force, the alarm member 64 is sometimes attached so that the contact portion 70 is pushed away from the mounting leg portion 66 by the protrusion 62 itself. Therefore, in the standalone state before being attached to the back plate 24, the contact portion 70 only needs to be brought close to the mounting leg portion 66 as shown in FIG. 8, and does not need to be brought into contact with the mounting leg portion 66. Therefore, when bending the alarm member 64, it is possible to allow the contact portion 70 to be separated from the mounting leg portion 66 by the amount indicated by α in FIG. 8 due to springback, and the production of the alarm member 64 is extremely easy. .

Further, in this embodiment, the spring portion 68 of the alarm member 64
has a first bent portion that effectively allows movement of the contact portion 70 in a direction perpendicular to the friction surface 14, so that the contact portion 70 comes into contact with the disc rotor 10 and is partially pulled in the rotational direction of the disc rotor 10. -) It promotes the occurrence of a kind of stick-slip phenomenon in which it returns to its original position after being stretched, so that the alarm sound is emitted stably.

When this alarm sound is generated, not only the contact portion 70 but the entire alarm member vibrates violently, and moreover, a biasing force is applied to the mounting leg portion 66 by the spring portion 68 in the direction of pulling it out from the ear portion 52. However, due to the engagement between the most protruding tip of the engagement claw 71 and the engagement recess 72, and the engagement between the mounting leg 66 and the protrusion 62, the alarm member 64 can be prevented from falling off or being displaced from its normal position. Definitely prevented.

It should be noted that in the above embodiment, the alarm member 64
was attached to the ear portion 52 of the back plate 24, however, the alarm member 64 may be attached to the side edge of the back plate of the friction pad, and is not necessarily limited to the ear portion.

In short, it suffices to mount the U-shaped mounting legs with their pair of arms sandwiching the back plate from both front and rear sides.

Moreover, if the protrusion 62 that protrudes laterally from the mounting leg portion 66 is provided on the side surface of the back plate, the back plate 24 of the contact portion 70 can be
Although it is easy to increase the pressing force against
Providing the protrusion 62 is not necessarily essential; in short, in the process of fitting the mounting leg to the back plate, the contact portion comes into contact with the side surface of the back plate, and from that state the mounting leg is engaged more deeply with the back plate. At this time, the spring portion may be elastically deformed to elastically press the contact portion against the side surface of the back plate.

Further, the spring part of the alarm member does not necessarily have to have two bent parts as in the above embodiment, but rather connects the mounting leg part and the contact part and keeps the contact part fixed on the side surface of the back plate. Any material that can generate a spring force for pressing with a force of .

Moreover, various types of means for preventing the attachment legs from coming off the back plate may be used instead of the combination of the engagement claws 71 and the engagement recesses 72.

For example, as the engaging claw, the tongue-shaped engaging claw as in the above embodiment is most suitable, but instead of this, the 10th
An engaging pawl 80 having a shape as shown in the drawings and FIG. 11 can also be adopted.

This engaging claw 80 is formed by bending a part of the arm portion of the mounting leg portion 66 to form two approximately right triangular protrusions. By engaging the shaped engagement recess 72, the mounting portion 6
6 can be prevented from coming off from the ear portion 52.

Note that since the engaging claw 80 of this embodiment is not elastically deformable, the engaging claw 80 is allowed to engage with the engaging recess 72 by elastic deformation of the mounting leg portion 66.

Furthermore, it is also possible to employ mounting legs 82 and engagement claws 84 as shown in FIG.

This engaging pawl 82 is formed by bending the tip of one arm portion of the mounting leg portion 84 at an acute angle.

The action and effect of the engaging claw 82 are almost the same as those of the tongue-shaped engaging claw 71.

Furthermore, is it possible to form the engaging claw on the arm on the side closer to the contact part of the pair of arms of the U-shaped mounting leg? ″
: Desirable in order to stably hold the information member on the back plate, but
Is it possible to form an engaging pawl on the portion farthest from the contact portion as in this embodiment? 'The effect of preventing the telegraph member from falling off can be obtained, and the most stable attachment can be achieved by providing engaging claws on both arms.

Although other examples will not be given, it goes without saying that the present invention can be implemented in various modifications without departing from the scope of the claims of the utility model registration.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a disc brake equipped with a wear limit warning device according to an embodiment of the present invention, and FIG. 2 is a front sectional view of the same. FIG. 3 is an enlarged plan sectional view showing a wear limit warning device which is an embodiment of the present invention, FIG. 4 is a view taken along IV-IV in FIG. 3, and FIG. − ■View,
Fig. 6 is a VI-VI view in Fig. 3, and Fig. 7 is a VI-VI view in Fig. 3.
FIG. 8 is a plan sectional view showing a comparison between the shape of the four-signal member used in the wear limit warning device before and after installation. FIG. 9 is a plan sectional view showing a state in which the wear limit warning device emits a warning sound. FIG. 10 shows another embodiment of the present invention? FIG. 11 is a plan sectional view of the main part of the information member, and FIG.
It is an M view. FIG. 12 is a plan view of a main part of an alarm member in still another embodiment of the present invention. 10: Disc rotor, 16: Inner pad, 18: Outer pad, 20.21: Friction material, 22.24: Back plate,
32: Torque receiving member, 33: Caliper, 50.52: Ear portion, 60: Wear limit 7 warning device, 62: Protrusion, 64: Visual notification member, 66.82: Mounting leg portion, 68: Spring portion, 70 :
Contact portion, 71.80, 84: Engagement claw, 72: Engagement recess,
74: Wear limit surface 76: Protrusion.

Claims (1)

[Claims for Utility Model Registration] A friction pad comprising a disc rotor that rotates integrally with a vehicle wheel, a friction material facing the friction surface of the disc rotor, and a back plate fixed to the back surface of the friction material. an actuator that presses the friction pad against the friction surface of the disc rotor; and an actuator that is fixed to a non-rotating member in the vicinity of the disc rotor and supports the friction pad so as to be movable in a direction perpendicular to the friction surface of the disc rotor. With,
The side surface receives the rotational torque of the friction pad when the brake is applied while the vehicle is moving backwards by contacting a part of the side surface of the back plate of the friction pad, and creates a gap that does not disappear even during the contact. A device that generates an alarm sound when the friction material is worn to a wear limit in a disc brake including a torque receiving member formed between the back plate and other parts of the disc rotor when the vehicle moves forward. It is equipped with a pair of arms that sandwich the side part of the rotation side from the front and back sides to create a U-shape, and the bottom part of the U-shape is positioned on the side of the back plate. The fitted mounting leg extends from the back of the back plate through the gap toward the friction surface of the disc rotor, and the tip reaches the wear limit surface of the friction material, causing the friction material to wear to the wear limit. A wear limit alarm device including an alarm member having a contact portion that contacts the friction surface of the disc rotor when the disc rotor is pressed, and a spring portion that elastically connects the contact portion and the mounting leg portion, wherein the spring portion is The longitudinal intermediate portion of the contact portion is always pressed against the side surface of the back plate by being biased in the same direction as the rotational direction of the disc rotor when the vehicle moves forward, and the pair of the U-shaped mounting legs. An engaging pawl is provided on the inner side of at least one of the arms of the U-shape, and the engagement claw has a shape in which the amount of protrusion gradually increases from the opening side of the U-shape toward the back side. A lock that engages with the most protruding tip of the engaging claw when attached to the back plate to prevent the mounting leg from being laterally separated from the back plate due to the elastic force of the spring portion. A friction pad wear limit warning device for a disc brake, characterized in that a mating recess is formed.