DESCRIPTION

[0001] The present invention relates to a spring for elastically retaining and positioning the pads in a disc brake caliper, as well as to a disc brake equipped with such a spring.

[0002] Cross-shaped expansion springs for fixed caliper disc brakes provided with a longitudinal piece, the ends of which abut e.g. against two support pins which support the pads, and a cross piece, the ends of which abut against the upper edges of the pads in order to retain the pads elastically in a“lowered” position, are known. By virtue of an inclined configuration of the lower surface of the cross piece, the expansion springs bias the pads away from one another to ensure a separation of the pads from the brake disc after each braking.

[0003] The ends of the longitudinal piece of the known expansion springs usually engage both support pins from underneath and the cross piece of the expansion springs presses from above in springing manner on the support plates of the pads.

[0004] The known expansion springs are thus used to obtain a three-fold action:

[0005] - to reduce the vibrations of the pads,

[0006] - to distance the brake pads from the brake disc in order to reduce or eliminate a residual braking torque due to undesired contacts between the brake pads and the brake disc with the brake deactivated,

[0007] - to obtain a uniform wear of the friction linings of the pads.

[0008] The expansion springs of the prior art abut on the pads with an application angle of the elastic force of less than 15° with respect to the plane of the pad and consequently transmit a high radial elastic force and a much lower elastic axial force to the pad. The axial elastic force moves the pads away from each other and from the brake disc along a planned axial sliding direction. In contrast with this, the radial elastic force generates a frictional resistance which opposes the axial thrust of the spring and thus the mutual distancing of the pads in the resting interfaces between the pads and the caliper, e.g. in resting interfaces between a support pin and a corresponding pad hole.

[0009] With the expansion springs of the prior art, the axial elastic force is insufficient to overcome the frictional resistance generated by the elastic radial elastic force in every operating condition of the brake in complete and reliable manner.

[0010] An incomplete detachment between brake pads and disc thus often occurs with the brake deactivated, resulting in:

[0011] - undesired residual braking moments, [0012] - unplanned pad positioning and orientation,

[0013] - non-uniform pad wear.

[0014] Furthermore, the axial elastic force applied by the expansion springs of the prior art varies according to the wear state (and therefore according to the axial position) of the friction pad.

[0015] Consequently, the application conditions of the elastic forces and thus the constraint conditions of the pads are uncertain, difficult to predict with precision and variable over time. The balance of the moments acting on the friction pad is undesirably sensitive to (and influenced by) frictions and by geometric variability.

[0016] It follows that the distancing function of the pads from the brake disc is not ensured during the entire life cycle of the pad which gradually wears.

[0017] It is therefore the object of the present invention to provide an improved spring for pads and disc brake having such features as to reduce the residual braking torque with the brake deactivated and to improve and make more uniform the distancing function of the pads from the brake disc also in the presence of pad wear and during their entire life cycle.

[0018] In the scope of the general object of the invention, further objects relate to a reduction of the sensitivity (or in other words: an improvement of the robustness) of the elastic constraint system of the friction pads and in the balance of the moments acting on the friction pads, to geometric tolerances, friction effects and variations of the supporting conditions between the pads and the caliper and between the expansion spring and the pad.

[0019] These and other objects are achieved by a spring for pads according to claim 1 and by a disc brake according to claim 8. The dependent claims relate to advantageous and preferred embodiments.

[0020] In order to better understand the invention and appreciate its advantages, some non-limiting examples of embodiments will be described below with reference to the accompanying figures, in which:

[0021] figure 1 is a radial section view (with respect to a rotation axis of a disc brake) of a disc brake according to an embodiment, in deactivated configuration,

[0022] figure 2 shows the disc brake in figure 1 (with the brake disc removed for greater clarity) in an activated configuration,

[0023] figure 3 is a bottom view of the disc brake in figure 1 ,

[0024] figure 4 is a side view of the disc brake in figure 1 ,

[0025] figures 5 and 6 are perspective views of a disc brake pad according to an embodiment,

[0026] figure 7 is a rear view of the friction pad in figure 5,

[0027] figure 8 is a side view of the friction pad in figure 5,

[0028] figures 9, 10, 1 1 are views of a spring for friction pad according to an embodiment,

[0029] figure 12 is a perspective view of a disc brake (with brake disc removed for clarity) according to a further embodiment,

[0030] figure 13 is a radial section view (with respect to a rotation axis of a disc brake) of the disc brake in figure 12,

[0031] figure 14 is a radial section view of the disc brake in figure 12, in a deactivated brake configuration,

[0032] figure 15 is a radial section view of the disc brake in figure 12, in an activated brake configuration,

[0033] figure 16 is a side view of the disc brake in figure 12,

[0034] figure 17 is a top view of the disc brake in figure 12,

[0035] figure 18 is a rear view of the disc brake in figure 12,

[0036] figure 19 is a longitudinal section view of the disc brake in figure 12,

[0037] figures 20-23 are views of a spring for friction pad according to an embodiment.

[0038] With reference to the figures, a disc brake, in particular for use on motor vehicles, is globally indicated by reference numeral 1. In the specific case, it is a disc brake of the fixed caliper type. However, the invention also applies to so-called floating calipers and to brakes with floating caliper.

[0039] The disc brake 1 comprises a caliper 2 and a brake disc 3. The caliper 2 can be fixed, e.g. by means of fixing screws, to a vehicle suspension, while the brake disc 3, provided with an annular braking band 4, can be connected to the wheel hub of the vehicle (not shown).

[0040] The caliper 2 comprises two side walls 5 which are arranged on both sides of the brake disc 3 and connected to each other by means of connecting elements which extend straddling the braking band 4 of the brake disc 3. Advantageously, the caliper 2 comprises two end bridges 6 delimiting a central opening 7, as well as at least or exactly one linkage 8 arranged in the central opening 7 and which structurally connects the two side walls 5 so as to limit the deformation of the caliper 2 during braking. Preferably, the linkage 8 is arranged approximately at the center of the central opening 7 so as to divide it into two half-openings 9, 10 of substantially equal circumferential extension (with reference to the brake disc 3).

[0041] At least two pads 1 1 having a support plate 12, e.g. made of steel, and a friction material lining 13, are each arranged on one side of the brake disc 3 at the braking band 4 and housed in dedicated seats 14 of the caliper 2 and supported by at least one, preferably two support pins 15. The size and mechanical strength of the support pins 15 is sufficient to allow the pads 1 1 to hang from or rest on such support pins 15, e.g. by means of a support hole or slot 16 formed in the support plate 12, preferably in a side end portion 17 or in two opposite side end portions 17 of the support plate 12, preferably in a radially inner half (with respect to a rotation axis 18 of the brake disc 3) and/or at or near a lower (i.e. radially inner) edge 19 of the support plate 12, in order to prevent radial displacements (related to the rotation axis 18 of the brake disc 3) of the friction pads 1 1 . It is worth noting that the support pins 15 for the friction pads 1 1 generally do not contribute to the overall rigidity of the caliper 2.

[0042] The friction pads 1 1 are movable in direction perpendicular to the plane 55 of the brake disc 3 along the support pins 15 and are biased by thrust means, e.g. such as one or more hydraulic cylinder-piston units 20, 21 arranged in the caliper 2, so as to clamp, via the friction lining 13, a sector of the braking band 4, the surface and shape of which corresponds to those of the friction linings 13.

[0043] The disc brake 1 further comprises at least one pad spring 22 which applies an elastic preload onto the pads 1 1 to keep the friction pads 1 1 distanced from the brake disc 3 with the brake deactivated. The same one or more springs 22 or one or more additional springs 23 for pad can perform the further function of stopping the friction pads 1 1 elastically in the seats 14 and thus reducing the onset of vibrations and brake noise due to movements of the pads with respect to the caliper 2.

[0044] Generally, the disc brake 1 may comprise four springs 22, respectively two associated with each friction pad 1 1.

[0045] The spring 22 comprises an elongated plate 27 bent so as to form a descending fixing stretch 24, an ascending resting stretch 25, opposite to the fixing stretch 24, and an arch-shaped return stretch 26 formed between the fixing stretch 24 and the resting stretch 25, wherein the return stretch 26 extends from a narrowing region 29, in which the fixing stretch 24 and the resting stretch 25 locally approach each other, in form of a widened loop with respect to the narrowing region 29 to a lower apical region 28 of the spring 22.

[0046] The fixing stretch 24 forms a fixing seat 30 for interlocking the spring 22 to a corresponding fixing portion 31 formed by the caliper 2 or by the support plate 12 of the friction pad 1 1.

[0047] The resting stretch 25 forms a plate-shaped contact portion 32, preferably flat, for freely resting (with slipping possibility) the spring 22 against a corresponding contact surface 33 formed by the support plate 12 of the friction pad 1 1 or by the caliper 2.

[0048] With the spring 22 undeformed, the plate-shaped contact portion 32 extends, starting from the narrowing region 29, in diverging manner with respect to the fixing stretch 24 and is inclined with respect to the fixing portion 31 with an inclination angle 34 of less than 90°, preferably less than 60°.

[0049] The particular configuration of the spring 22 allows a fixing thereof by interlocking by means of the fixing seat 30 and a free support thereof (with possibility of sliding and orientation) by means of the plate-shaped contact portion 32, as well as an elastic widening of the distance between the fixing stretch 24 and the resting portion 25, against the elastic resistance generated by the elastic deformation of the large loop formed by the return portion 26. By virtue of the widening of the loop of the return stretch 26 with respect to the narrowing region 29, the return stretch 26 makes available a sufficiently intense elastic force towards the fixing stretch 24 and resting stretch 25 so as to effectively push the friction pads 1 1 away from the brake disc 3.

[0050] According to an aspect of the invention, the spring 22 is fixed in the disc brake 1 with the return segment 26 facing towards a lower (or radially inner) side 46 of the caliper 2, i.e. towards the rotation axis 18 of the brake disc 3 and extending at least partially, possibly completely, under the friction pad 1 1 (or in other words, radially more inwards with respect to the friction pad 1 1 ) and with the resting stretch 25 and the fixing stretch 24 both extending towards an upper side 47 of the caliper 2, i.e. radially outwards.

[0051] This low positioning of the springs 22 allows more space for the elastic loop of the return stretch 26 of the spring 22 and for an optimized choice of connection/resting regions between the springs 22 and the friction pads 1 1 regardless of the possible presence of the aforesaid additional springs 23 (anti-vibration springs) which are usually placed on a radially outer side of the friction pads 1 1.

[0052] According to an embodiment (figures 1 -1 1 ), the fixing portion 31 is formed on the support plate 12 of the friction pad 1 1 and the contact surface 33 is formed on the caliper 2.

[0053] Advantageously, the fixing seat 30 of the spring 22 is locked onto the support plate 12 of the friction pad 1 1 on an outer side of the friction pad 1 1 facing away from the brake disc 3 and the contact portion 32 of the spring 22 abuts from below (i.e. from a radially inner side in a radially outer direction) against a wall portion 45 formed by the inner wall 5 and also protruding towards the lower (radially inner side) 46 of the caliper 2 (figures 1 , 2).

[0054] More precisely, the contact portion 32 of the spring 1 1 extends in inclined manner from under the side portion 45 axially outwards (away from the brake disc 3) and radially upwards or towards the upper (radially outer) side 47 of the caliper 2 and rests in free contact and with the possibility of sliding on an axially outer edge 48 of a lower edge of the wall portion 45.

[0055] The contact portion 32 applies an axial elastic force towards the brake disc 3 and a radial elastic force towards the upper (radially outer) side 47 of the caliper 2 on the wall portion 45. The fixing stretch 24 of the spring 22 applies an axial elastic force away from the brake disc 3 and a radial elastic force towards the lower (radially inner) side 46 onto the friction pad 1 1.

[0056] According to a further embodiment (figure 5 and 7), the fixing portions 31 are formed in the support plate 12 at the same height (radial with respect to rotation axis 18 of the brake disc 3) of the support holes 16. Advantageously, the fixing portions 31 are each positioned laterally next to a support hole 16 and, preferably, on one side of the support hole 16 directed towards a circumferentially central area 49 of the friction pad 1 1.

[0057] Advantageously, both the support holes 16 and the fixing portions 31 are positioned at lower, i.e. radially inner, end zones and/or in side end zones 17, i.e. circumferentially more outward, of the support plate 12 of the friction pad 1 1.

[0058] In the embodiment shown in figure 5, the lower end zone has a radial extension either equal to or less than 1/3 of the total radial extension (height) of the pad 1 1. Similarly, the side end zones 17 have a circumferential extension either equal to or smaller than 1/3, preferably equal to or smaller than 1/4, of the total circumferential extension (width) of the pad 1 1.

[0059] According to a further embodiment (figures 5, 6, 7), the support plate 12 and possibly also the friction lining 13 of the friction pad 1 1 may form a central upper cavity 50 formed in a radially outer edge 51 of the pad 1 1 and positioned centrally between the fixing portions 31 , to allow the passage of a central upper pin 52 fixed to both of the side walls 5 of the caliper 2 and forming a further positioning reference for the friction pads 1 1 and/or for the aforesaid further spring 23. Alternatively, the upper central cavity 50 can serve to allow the fixing of one or more sensors for signaling wear of the friction material.

[0060] The additional spring 23 can be supported by the caliper 2 and positioned on the radially outer side 47 of the caliper 2 and elastically push against the radially outer edge 51 of the support plate 12 of the friction pad 1 1 , to bias the friction pad 1 1 towards the radially inner side 46 against the support pins 15.

[0061] According to an embodiment (figure 9), the fixing seat 30 may comprise a through hole 35 formed in an end portion 40 of the fixing stretch 24 and adapted to accommodate a corresponding protrusion 36 formed(e. g. riveted or drawn) in or by the fixing portion 31. The through hole 35 may have a substantially circular shape with one or more external recesses 37 which perform, for example, an anti-rotation locking function of the spring, being the outer recess 37 then filled by the protuberances 31 and 36 which are plastically deformed to constrain the springs to the pad.

[0062] According to a further embodiment (figures 9, 5), a step 41 is formed between the end portion 40 of the fixing stretch 24 and a further adjacent portion of the fixing stretch 24, which makes an offset, between a fixing plane 38 defined by the end portion 40 and an extension plane 39 on which the portion adjacent to the fixing stretch 24 extends.

[0063] By virtue of the offset of the end portion 40, preferably away from resting stretch 25, the entire end portion 40 or at least one part of the fixing stretch adjacent to the end portion 40 can be accommodated (with shape coupling) in a dedicated recess 42 formed by the fixing portion 31 (figure 5). In this manner, it is possible to interlock the spring 22 against rotations about an axis parallel to the rotation axis of the brake disc 3.

[0064] According to a further embodiment, a free end portion 43 of the resting stretch 25 bent with respect to the contact portion 32 (adjacent thereto) in a direction facing away from the fixing stretch 24, so that:

[0065] - the free end portion 43 protrudes away from the fixing portion 24 and, preferably, downwards (i.e. radially towards the rotation axis 18) and/or

[0066] - a convex bending edge 44 is formed (preferably without sharp edges) facing in the direction opposite to the lower apical region 28 of the spring 22, i.e. upwards or radially outwards, between the contact portion 32 and the free end portion 43.

[0067] In this manner, the free end portion 43 forms a guided and snapping positioning of the contact portion 32 onto the contact surface 33, during the axial insertion (with respect to the rotation axis 18 of the brake disc 3) of the friction pad 1 1 on the support pins 15 and the seat 14 formed in the caliper 2 (figures 1 ,2).

[0068] Advantageously, the spring 22 is formed in one piece, preferably of plate-shaped or strip-shaped metallic material contoured so as to display only curvatures about axes substantially parallel to one another and substantially parallel to the plane 55 of the brake disc 3, with the spring 22 mounted in the caliper 2.

[0069] In accordance with a further embodiment (figures 12-23), the fixing portion 31 is formed at the caliper 2, preferably at the support pin 15, and the contact surface 33 is formed at the support plate 12 of the friction pad 1 1 . [0070] Advantageously, the fixing seat 30 of the spring 22 is locked to the support pin 15 on a rear side of the friction pad 1 1 facing away from the brake disc 3 and the contact portion 32 of the spring 22 abuts brom below (i.e. on a radially inner side in radially outer direction) against a lower (i.e. radially inner) edge 19 of the support plate 12 of the friction pad 1 1 (figure 12, 14, 15).

[0071] More precisely, the contact portion 32 of the spring 1 1 extends in inclined manner from below the support plate 12 axially inwards (towards the brake disc 3) and radially upwards or towards the upper (radially outer) side 47 of the caliper 2 and rests in free contact and with possibility of sliding against an axially inner edge 54 of the inner edge 19.

[0072] The contact portion 32 applies an axial elastic force away from the brake disc 3 and a (nearly negligible) radial elastic force towards the upper (radially outer) side 47 of the caliper 2 on the friction pad 1 1. Indeed, the inclination angle 65 (figure 15) of the contact portion 32 with respect to the plane 55 the brake disc 3 is lower than 45°, preferably less than or equal to 30°, so as to transmit a force component prevalent in axial direction. The fixing stretch 24 of the spring 22 applies on the support pin 15 an axial elastic force in approaching direction toward the brake disc 3 and a (nearly negligible) radial elastic force towards the lower (radially inner) side 46 (figures 14, 15).

[0073] According to an embodiment (figures 15, 19, 23), the fixing portions 31 for the springs 22 are formed in the support pins 15 in a centered manner with respect to the support holes 16 of the friction pads 1 1.

[0074] Advantageously, both the support holes 16 and the fixing portions 31 (formed not at the friction pad 1 1 but at the support pins 15) are positioned at lower, i.e. radially inner, end zones and/or in side end zones 17, i.e. circumferentially more outward, of the support plate 12 inserted on the support pins 15 (figures 15, 19).

[0075] In the embodiment shown in figure 19, the lower end zone has a radial extension either equal to or smaller than 2/5, preferably equal to or smaller than 1/3 of the total radial extension (height) of the pad 1 1 . Similarly, the side end zones 17 have a circumferential extension either equal to or smaller than 1/5, preferably equal to or smaller than 1/6, of the total circumferential extension (width) of the pad 1 1.

[0076] According to a further embodiment (figure 19), the support plate 12 and possibly also the friction lining 13 of the friction pad 1 1 can form one or more upper cavities 56 formed in a radially outer edge 51 of the pad 1 1 and positioned symmetrically with respect to a radial median plane 58 of the pad 1 1 to allow fixing of one or more sensors for signaling the friction material wear. [0077] The additional spring 23 can be supported by the caliper 2 and positioned on the radially outer side 47 of the caliper 2 and elastically push against the radially outer edge 51 of the support plate 12 of the friction pad 1 1 , to bias the friction pad 1 1 towards the radially inner side 46 against the support pins 15.

[0078] Advantageously, with reference to both described embodiments, the shape of the friction pad 1 1 , seen from the side facing towards the disc brake 3, can be symmetrical with respect to the median radial plane 58 of the friction pad 1 1 . With further advantage, also the position of the springs 22 is symmetrical with respect to the median radial plane 58 of the friction pad 1 1 (figures 6, 19).

[0079] According to an embodiment (figures 22, 23), the fixing seat 30 may include a recess 57 formed in an end portion 40 of the fixing stretch 24 and adapted to embrace the corresponding support pin 15 and possibly to be inserted in a groove 59, preferably annular, possibly formed in the support pin 15. The recess 57 forms a converging inlet portion 60 and a inner portion 61 wider with respect to the input portion 60 and, preferably, two or more projections 66 which protrude into the inside of the recess 57, so as to form a lead-in for a centered insertion of a recess 57 of the spring 22 into the circumferential groove 59 of the supporting pin 15 and to allow a temporary widening of the recess 57 with the purpose of snap-engaging with the support pin 15.

[0080] According to an embodiment (figures 15, 22), the fixing stretch 24 of the spring 22 forms a tongue 62 bent out from a plane of the fixing stretch 24 preferably towards a side facing away from the brake disc 3, and adapted to be used as thrust plane for fitting the spring 22 in the support pin 15. In this manner, it is possible to fix the springs 22 to the support pins 15 by means of a simple insertion by snapping from below, during which insertion the end portions 40 are inserted or elastically snap into the corresponding groove 59 (if provided) and blocks the spring 22 to the support pin 15.

[0081] In this regard, the fixing portion 31 , in particular, the annular groove 59, is advantageously formed on a plane immediately adjacent to an inner surface of the side wall 5 of the caliper 2.

[0082] According to a further embodiment (figures 20-22), the fixing stretch 24 of the spring 22 forms a reinforcing rib 64, preferably a local deformation produced by pressing, e.g. a indent or a drawing, which stiffens the fixing stretch 24 so as to concentrate the elastic deformation of the spring 22 mainly in its return stretch 26 and to increase the total rigidity of the spring 22, the elastic material, e.g. steel for springs, used being equal.

[0083] Advantageously, the spring 22 is formed in one piece, preferably of plate-shaped or strip-shaped metallic material contoured so as to display only curvatures about axes substantially parallel to one another and substantially parallel to the plane of the brake disc 3, with the spring 22 mounted in the caliper 2 (with the exception of the anti-rotation tongue 62 and of the reinforcing rib 64).

[0084] From the description provided, the person skilled in the art will appreciate that the spring 22 for friction pad 1 1 and the disc brake 1 according to the invention keeps the pads detached from the brake disc when the brake is deactivated, thereby reducing the residual braking torque with the brake deactivated.

[0085] Furthermore, the disc brake 1 and the spring 22 according to the invention are less sensitive to geometric tolerances, to the effects of friction and to variations in the support conditions between the pads 1 1 and the caliper 2 and between the spring 22 and the pad 1 1 . As a result, the springs 22 provide a more intense axial elastic bias, which is more uniform even in the presence of a progressive wear of the friction lining 13 of the pads 1 1.

[0086] Furthermore, the spring 22 according to the invention can be easily fitted onto the caliper and onto the friction pad and its position does not violate the space of other functional components of the brake, whereby allowing an optimized placement and sizing targeted for each of the functional components.

[0087] Obviously, a person skilled in art may make further changes and variants to the spring 22 for pads 1 1 and to the disc brake 1 according to the present invention all without departing from the scope of protection of the invention, as defined in the following claims.