FR3118428A1 - PROCEDURE FOR CONNECTING A PORTION OF SHEET METAL TO A BRAKE PAD BY RIVETING WITH A PUNCH - Google Patents

Abstract

The invention relates to a method of connecting a portion of sheet metal to a support plate (70) of a brake shoe. The connection process comprises riveting the portion of sheet metal to the support plate (70), by means of a rivet whose head is shaped by a punch (10). The riveting being carried out with a punching force on the rivet head which is between 5 kN and 9 kN. Figure 6b

Description

PROCEDURE FOR CONNECTING A SHEET METAL PORTION TO A BRAKE PAD BY RIVETING WITH A PUNCH

The invention relates to the general technical field of brakes for motorized vehicles. More specifically, the invention relates to the connection of a return spring of a brake pad to a support plate of a brake pad.

PRIOR ART

A floating caliper disc brake has a brake disc, fixed cage and sliding caliper body that straddle the disc. The disc brake comprises two brake pads which are located on either side of the disc and which are designed to grip the disc in order to exert a braking torque. These brake pads each include a backing plate and a brake lining which is attached to the backing plate. They are each movable axially relative to the disc between an inactive position of absence of braking and an active position of braking.

The disc brake also comprises two return springs for each pad which are each configured to return the pad to its inactive position in order to limit the residual braking, called drag, which could remain after the release of the brake. As is known, these return springs can also deform plastically by modifying the inactive position of the brake pad to compensate for the wear of the brake lining of the brake pad.

The shoe return springs are fixed in known manner at a first of their longitudinal ends by stamping to the support plate of the brake shoe. The expansion force of the pin which is secured to the support plate is high, which can damage the pin or deform the support plate. The attachment of the return spring to the brake shoe may then not be sufficiently durable.

There is therefore a need to connect, in a limited time, in a reliable and durable manner, a sheet portion of a shoe return spring to a support plate of a brake shoe.

The invention aims to at least partially solve the problems encountered in the solutions of the prior art.

In this respect, the subject of the invention is a method for connecting a portion of sheet metal to a support plate of a brake pad. The connection process includes the riveting of the portion of sheet metal to the support plate, by means of a rivet whose head is shaped by a punch. The riveting is carried out with a punching force on the rivet head which is between 5 kN and 9 kN.

Thanks to the connection method according to the invention, the connection of a portion of sheet metal to a brake pad is improved, by quickly and securely fixing the portion of sheet metal to the brake pad. The sheet metal portion is in particular a portion for fixing a return spring to a brake pad support plate.

In particular, the connection process is carried out in a limited time, which allows its industrial implementation on an assembly line for a disc brake or a brake pad. The connection process is for example much faster than a connection process by rotary riveting or riveting.

The connection process according to the invention allows better crushing of the rivet head by the punch than a stamping process or a connection process by rotary riveting or riveting. The connection process is also carried out with a punching force which does not damage the portion of sheet metal, the rivet and/or the pad support plate. This results in a stronger and more durable attachment of the sheet metal portion to the brake pad.

The invention may optionally include one or more of the following characteristics, combined or not.

According to a particular embodiment, the punching speed during the crushing of the rivet head is between 5 mm/s and 15 mm/s, preferably between 5 mm/s and 8 mm/s.

According to another particular embodiment, the punch comprises a tip and at least one first face which extends from the tip.

According to a particular embodiment, the first face is curved.

Alternatively, the first face is steep.

According to a particular embodiment, the first face is curved while being concave towards the outside from the tip.

According to another particular embodiment, the punch comprises at least two curved faces which each extend from the tip.

Alternatively, the punch comprises at least two sloping faces.

According to a particular embodiment, the curved faces are regularly distributed around a longitudinal axis of the punch.

Alternatively, the sloping faces of the punch are regularly distributed around a longitudinal axis of the punch.

According to another particular embodiment, the imprint of the punch on the rivet head is symmetrical with respect to at least one plane of symmetry comprising the longitudinal axis of the punch, when the punch crushes the rivet head.

According to a particular embodiment, a ratio between a punching force on a maximum punching depth of the rivet head is substantially constant, when the rivet head is crushed with a punching force which is between 4 and 10 kN.

The ratio between the punching force on the maximum punching depth is in particular between 5.5 and 6.1 kN/mm.

The present invention will be better understood on reading the description of exemplary embodiments, given purely for information and in no way limiting, with reference to the appended drawings in which:

is a schematic representation in exploded view of a disc brake for a motor vehicle;

is a schematic representation in perspective of a shoe return spring which is fixed to a clevis and to a brake shoe of a disc brake;

is a partial schematic representation in perspective of a brake shoe, two shoe springs and two shoe return springs;

is a partial schematic representation in perspective of a punch for implementing a connection method according to a first embodiment of the invention;

is a partial schematic representation in top view of a fixing tab of a shoe return spring which has been connected by riveting to a brake shoe support plate by the connection method according to the first embodiment;

illustrates the approach of a punch to a brake pad support plate, during the implementation of the connection method according to the first embodiment;

illustrates the crushing of a pin to rivet a shoe return spring to a brake shoe support plate, during the implementation of the connection method according to the first embodiment.

Identical, similar or equivalent parts of the different figures bear the same reference numerals so as to facilitate passage from one figure to another.

There represents a floating caliper disc brake 1 of known structure, for braking a wheel of a motorized vehicle. Disc brake 1 comprises a caliper 2, a yoke 3, a piston 11, an actuator 12, a disc 9 and two pads 7.

Disc 9 is fixed in rotation to the wheel of the motorized vehicle. It rotates around an axis of rotation B-B which is oriented axially. It comprises a first front face 9a and a second rear face 9b which are spaced axially from each other.

In the document and in the rest of the presentation, an axial direction A is a direction parallel to the axis of rotation B-B of the disc 9. This is a general direction of movement of the pads 7 relative to the disc 9 and movement of the caliper 2 relative to the yoke 3. A transverse direction T is a lateral direction of the brake, which is orthogonal to the axial direction A. A vertical direction V is a direction which is orthogonal to the axial direction A and to the transverse direction T. The vertical direction V typically corresponds to a direction of the height of the brake.

The clevis 3 is fixed to the chassis of the vehicle. It overlaps a peripheral edge of the disc. It comprises two lateral arms 30 which are spaced from each other in the transverse direction T of the brake.

The side arms 30 of the yoke 3 each define a housing 31 for a guide pin 22 of the yoke 2 relative to the yoke 3. The side arms 30 each comprise two slides 32 which are spaced axially from each other and which each guide one of the pads 7. The side arms 30 also comprise two ribs 34 for fixing return springs, which are visible at the .

The caliper 2 comprises a caliper body 20 which forms an arch which overlaps the disc 9. The caliper 2 houses the piston 11 and it is mechanically connected to the actuator 12. The caliper 2 is movable relative to the yoke 3 in the axial direction A between an active braking position and an inactive position of no braking.

The caliper body 20 is connected in a sliding manner to the yoke 3 by two guide pins 22 which each extend axially at least partially in one of the housings 31 of the yoke. The guide pins 22 and the housings 31 of the pins are means for guiding the stirrup 2 relative to the yoke 3.

The piston 11 is axially movable in translation relative to the caliper body 20, under the effect of the actuator 12. The displacement of the piston 11 in the axial direction A makes it possible to bring the pads 7 closer to each other. to brake the wheel.

The actuator 12 is configured to move the piston in translation in the axial direction. The actuator 12 is hydraulic and/or electromechanical. It is used for service braking and/or parking braking of the motorized vehicle.

The pads 7 each comprise a support plate 70 and a brake lining 71 which is fixed to the support plate 70. They are in particular of identical structure. The pads 7 are located inside the yoke 3 axially on either side of the disc 9. They are each axially movable between an inactive position of absence of braking in which the brake 1 does not brake the wheel and a active braking position in which they grip the disc 9 to brake the wheel.

Each support plate 70 has a first face 70a to which the brake lining 71 is fixed and a second face 70b which is opposite the first face 70a. Each of the opposite transverse ends of the support plate 70 has lateral lugs 72 to connect the pad 7 to the yoke 3.

The brake lining 71 comprises a material which is configured to brake the rotation of the disc 9 by friction when it is in contact with one of the first face 9a and the second face 9b of the disc.

The brake 1 also comprises means 4 for guiding each pad. These guide means 4 for the pads comprise a pad spring 40 and a guide rail 44.

With joint reference to FIGS. 1 and 3, each shoe spring 40 comprises a lower sliding branch 42 and an intermediate pinching branch 41. It is also known by the name of “snail spring” in reference to its general shape. The pad spring 40 is configured to mount and to guide the pad 7 in the slide 32 of the yoke via a possible guide rail 44.

The lower sliding branch 42 cooperates with a lower horizontal face of the associated slide 32 by pressing an upper edge of the lug 72 of the skate against the upper horizontal face of the slide 32. It is also configured to cause the lug 72 to slide axially in the slide 32 via the guide rail 44.

The pinching branch 41 is configured to elastically pinch the lug 72 of the pad to ensure the securing of the pad spring 40 and the lug 72 of the pad. It serves as a clip for lug 72 of the skate.

Each guide rail 44 has the general shape of a C in cross-section of the brake. It comprises a leaf spring which hugs the walls of the slide 32 associated. It is located transversely between the slider 32 and the slider spring 40. It serves to axially guide the slider spring 40 and the corresponding slider 7 relative to the slider 32.

With joint reference to Figures 1 to 3, the brake 1 also comprises two return springs 5 for each pad 7 brake. Each return spring 5 is configured to return the corresponding shoe 7 to its inactive position to avoid residual braking, called drag, which could remain after the release of brake 1.

Each return spring 5 comprises a first attachment portion 50, a second attachment portion 52 and a deformable portion 6 which connects the first attachment portion 50 to the second attachment portion 52. The return spring 5 is manufactured in a portion of spring steel sheet, for example of constant thickness. The return spring 5 is manufactured by cutting, stamping and/or bending the sheet metal portion.

The first attachment portion 50 comprises a base 50a, a first arm 50b and a second arm 50c which are interconnected by the base 50a. It is configured to be assembled to the yoke 3 by elastic pinching of the first arm 50b and the second arm 50c around a fixing rib 34 which is part of the yoke 3.

The deformable portion 6 comprises a first rigid branch 62, a second rigid branch 64 and a third rigid branch 66 which are each formed by a rigid metal strip. The deformable portion 6 comprises a first deformable ply 61, a second deformable ply 63 and a third deformable ply 65. It has a general V shape.

The first rigid branch 62 is connected to the second fixing portion 52 by the first deformable fold 61. The first rigid branch 62 and the second rigid branch 64 are oblique and oriented towards each other. They are interconnected by the second deformable ply 63. The second rigid branch 64 and the third rigid branch 66 are interconnected by the third deformable ply 65.

Each of the deformable plies 61, 63, 65 includes a through slot which gives the return spring 5 the ability to plastically deform over the life of the slider 7.

The deformable portion 6 is configured to deform plastically at the level of the deformable folds 61, 63, 65, by modifying the inactive position of the brake pad 7 to compensate for the wear of the brake pad 71 of the pad. The return spring 5 thus serves as a return means for the pad 7 and for compensating for the wear of the brake lining 71.

The method of connecting 200 each shoe return spring 5 to the support plate 70 is now described with joint reference to FIGS. 3 to 6b. The connection method 200 comprises the riveting of a rivet 8 which comprises a stem and a rivet head 80, to fix each of the return springs 5 to one of the two brake pads 7. The connection method 200 according to the first embodiment is implemented by means of a punch 10 which is shown in .

The punch 10 comprises a rod 102 and a punching head 100. The rod 102 is substantially cylindrical of circular section around a longitudinal axis X-X of the punch. The punching head 100 is located at one longitudinal end of the rod 102. The punch 10 is a tool for riveting each return spring 5 to a shoe 7 of the brake. It makes it possible to make an imprint 82 in a head 80 of rivet 8 during the riveting of the second fixing portion 52 to the support plate 70 of pad 7. It is for example made of steel.

The punch head 100 comprises a tip 101, a first curved face S1, a second curved face S3, a third curved face S5 and a fourth curved face S7 which are connected by straight edges 104a, 104b, 104c, 104d. The punching head 100 is symmetrical with respect to a first longitudinal plane P1 and with respect to a second longitudinal plane P3 which are perpendicular and which each include the longitudinal axis X-X of the punch 10. More generally, the curved faces S1, S3, S5, S7 are regularly distributed around the longitudinal axis X-X of the punch.

Each of the curved faces S1, S3, S5, S7 extends from the tip 101 to the shaft 102. Each of the curved faces S1, S3, S5, S7 is curved by being concave outward from the tip 101. It delimits in particular a frustoconical surface which has the tip 101 as its apex, being for example manufactured by conical milling. More generally, each of the curved faces S1, S3, S5, S7 is in particular produced with a radius of curvature which is substantially constant.

The imprint 82 which is left by the punching head 100 in a head 80 of rivet 8 during the riveting of a return spring 5 to a shoe 7 has a hollow shape which is substantially complementary to that of the punching head 100.

The cavity 82 comprises four petals 84 which are each delimited by a surface S2, S4, S6, S8 which matches that of one of the curved surfaces S1, S3, S5, S7 of the punching head 100. Each of the petals 84 s extends from a center 83 of the footprint 82 to an outer contour of the footprint 82. The center 83 of the footprint 82 is the location of maximum depth Hp of the footprint 82. The footprint 82 is substantially symmetrical with respect to a first longitudinal plane of the rivet P2 and with respect to a second longitudinal plane P4 which are perpendicular to each other and which include the longitudinal axis of the stem of the rivet 8.

With more specific reference to the and at the , the connection method 200 includes the temporary attachment 204 of the fastening tongue 52a of the return spring 5 to the second face 70b of the support plate 70 of the pad. During this temporary fastening 204, a pin 74 is inserted into the through hole 52b of the fastening tongue 52a by detachably connecting the second fastening portion 52 to the second face 70b of the support plate 70.

This pin 74 is in particular cylindrical with a circular section. It is rigidly secured to the second face 70b of the support plate, being for example fixed by welding to the second face 70b. It forms the rivet 8 when it is punched by the punch 10 to fix the return spring 5 to the support plate 70. In particular, the stem of the rivet 8 is cylindrical with a circular section of the same diameter as the pin 74.

With reference to the , the connection method 200 also comprises the axial displacement 205 of the punch 10 towards the pin 74 in a crushing direction B1-B1 which is substantially coincident with the longitudinal axis of the pin 74 and which is parallel to the axis of rotation BB of disk 9. The longitudinal axis XX of the punch is then substantially aligned with the longitudinal axis of pin 74. Punching head 100 is oriented towards pin 74 which releasably connects return spring 5 to shoe 7.

With reference to the , the connection method 200 comprises the crushing 206 of the pin 74 so that it forms a rivet 8 for fixing the second fixing portion 52 of the return spring 5 to the support plate 70. The punching head 100 punches the pin 74 to form the rivet head 80 which comprises the recess 82 of the punching head 100 as shown in .

During the crushing 206 of the pin 74 and the formation of the imprint 82, the punching force Fp of the punching head 100 on the pin is between 5 kN and 9 kN with the materials used. The punching force Fp is typically of the order of 3 to 12 kN, preferably between 4 and 10 kN and very preferably between 6 and 8 kN.

During the crushing 206 of the pin 74 and the formation of the indentation 82, the punching speed Vp is between 5 mm/s and 15 mm/s, preferably between 5 mm/s and 8 mm/s.

A ratio Rp between a punching force Fp during the crushing 206 of the pin on a maximum punching depth Hp of the rivet head 80 after riveting is between 5.5 and 6.1 kN/mm. More generally, the ratio Rp between the punching force Fp on the maximum punching depth Hp is substantially constant during the crushing 206 of the pin.

Thanks to the connection method 200 according to the invention, the connection of a return spring 5 to a support plate 70 of pad 7 is improved, by quickly and solidly fixing the second fixing portion 52 of the return spring 5 to the pad 7 brake.

In particular, the connection process 200 is carried out in a limited time, which allows its industrial implementation on an assembly line for a disc brake 1 or a brake shoe 7. The connection process 200 is notably much faster than a connection process 200 by rotary riveting or riveting.

The connection process 200 according to the invention allows better crushing of the rivet head 80 by the punch 10 than a stamping process or a connection process by rotary riveting or riveting. The connection process 200 is also carried out with a punching force Fp which does not damage the second fastening portion 52, the rivet 8 outside the footprint 82 and/or the pad support plate 70. This results in a stronger and more durable fixing of the return spring 5 to the pad 7 of the brake.

Of course, various modifications can be made by those skilled in the art to the invention which has just been described without departing from the scope of the description of the invention.

Alternatively, the disc brake 1 is a fixed caliper disc brake. The return spring 5 returns the brake shoe 7 to its inactive position of no braking from its active braking position.

In addition or alternatively, the connection method 200 is implemented to connect a metallic element, such as a spring and in particular a shoe spring 40, to the support plate 70.

The structure of the brake shoe 7 return spring may vary.

In particular, the structure of the deformable portion 6 of the return spring 5 can vary. The number of rigid branches 62, 64, 66 and of deformable folds 61, 63, 65 can vary. The angles between the rigid branches 62, 64, 66 in a new inactivated state of the return spring 5 can vary.

The structure of the second fixing portion 52 of the return spring 5 can vary. In particular, the second fixing portion 52 can comprise an axial stop which mechanically engages the clevis 3 and/or the guide slide 44, to fix the second fixing portion 52 to the clevis 3 and/or to the guide slide 44.

The second fixing portion 52 can also have the shape of a hairpin to fix it to the yoke 3, in particular at the level of the guide rail 44.

The structure of the punch 10 can vary, in particular that of the punching head 100. The number and the shape of the faces S1, S3, S5, S7 of the punching head 100 can vary.

The punching head 100 has for example a first face S1, which is steep. As a variant, the punch 10 comprises at least two sloping faces S1, S3, S5, S7 which each extend from the tip 101. These sloping faces S1, S3, S5, S7 are in particular regularly distributed around the longitudinal axis X-X of the punch.

The shape of the rivet can also vary, in particular that of the imprint 82 which is of complementary shape to that of the punching head 100.

The punching speed Vp, the punching force Fp and/or the maximum punching depth Hp may vary, in particular depending on the nature of the material of the rivet 8, that of the material of the support plate 70 and/or that of the material of the second fastening portion 52. The punching speed Vp, the punching force Fp and/or the maximum punching depth Hp can also vary according to the thickness of the rivet head 80, that of the of the fixing tongue 52a and/or that of the support plate 70.

NOMENCLATURE WITH REFERENCE TO THE FIGURES

1: disc brake
2: stirrup
3: clevis
4: pad guiding means
5: shoe return spring
6: deformable portion of the return spring
7: pad
8: rivet
9: disk
9a: first side of the disc
9b: second side of the disc
10: punch
11: plunger
12: actuator
20: caliper body
22: guide pin
30: yoke side arm
32: slide
34: fixing rib
31: housing of a guide pin
40: pad spring
41: intermediate pinch branch
42: lower sliding branch
44: guide rail
50: first fixing portion
50a: base of the first fixing portion
50b: first arm
50c: second arm
52: second fixing portion
52a: fixing tab
52b: through hole
61: deformable first ply
62: first rigid branch
63: deformable second ply
64: rigid second branch
65: deformable third ply
66: rigid third branch
70: support plate
70a: first face of the support plate
70b: second face of the support plate
71: brake lining
72: side ear
74: pawn
80: rivet head
82: footprint
83: center
84: petal
100: punching head
101: tip
102: punch rod
104a, 104b, 104c, 104d: straight edge
S1, S3, S5, S7: curved punch surface
S2, S4, S6, S8: curved surface of the cavity
P1, P3: longitudinal plane of symmetry of the punching head
P2, P4: longitudinal plane of symmetry of the indentation
Hp: maximum punching depth
Vp: punching speed
Fp: punching force
Rp: report
200: connection method
204: temporary connection
205: axial movement of the punch
206: crushing of the pawn
A: axial direction
T: transverse direction
V: vertical direction
BB: axis of rotation of the disc
B1-B1: crush direction
XX: longitudinal axis of the punch

Claims (8)

Method of connecting a portion of sheet metal to a support plate (70) of a brake pad (7), comprising:
the riveting of the portion of sheet metal to the support plate (70), by means of a rivet (8) whose head (80) is shaped by a punch (10),
the riveting being performed with a punching force on the rivet head (80) which is between 5 kN and 9 kN. Connection method according to the preceding claim, in which the punching speed (Vp) during the crushing of the rivet head (80) is between 5 mm/s and 15 mm/s, preferably between 5 mm/s and 8mm/s. A joining method according to any preceding claim, wherein the punch (10) comprises a tip (101) and at least one first face (S1, S3, S5, S7) extending from the tip (101) , the first face (S1, S3, S5, S7) being curved or the first face (S1, S3, S5, S7) being steep. Connection method according to the preceding claim, in which the first face (S1, S3, S5, S7) is curved while being concave towards the outside from the tip (101). A joining method according to any of claims 3 to 4, wherein the punch (10) comprises at least two curved faces (S1, S3, S5, S7) each extending from the tip (101). Connection method according to the preceding claim, in which the curved faces (S1, S3, S5, S7) are regularly distributed around a longitudinal axis (X-X) of the punch. Connection method according to any one of the preceding claims, in which the recess (82) of the punch (10) on the rivet head (80) is symmetrical with respect to at least one plane of symmetry (P2, P4) comprising the longitudinal axis (X-X) of the punch, when the punch (10) crushes the rivet head (80). Joining method according to any one of the preceding claims, in which a ratio (Rp) between a punching force (Fp) on a maximum punching depth (Hp) of the rivet head (80) is substantially constant, during the crushing of the rivet head (80) with a punching force which is between 4 and 10 kN, the ratio (Rp) between the punching force on the maximum punching depth being between 5.5 and 6 .1kN/mm.