JP2011247420A - Protective boot of piston-cylinder unit of disk brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible boot for protecting a piston-cylinder unit usable for a disk brake.SOLUTION: The flexible boot 100 includes a piston acting on a brake pad by sliding in a cylinder and protects a piston-cylinder unit of a disk brake. The flexible boot includes a surface 103 including a part which can face a wall of a pad. The flexible boot 100 includes at least one spacer member 105 related to the surface and intended to keep the part of the surface in a state separated from the wall of the pad by contacting the wall of the pad.

Description

  The present invention relates to a flexible boot, also known as a dust guard for protecting a piston-cylinder unit that can be used in a disc brake.

  In general, in a disc brake, the braking force is formed in a suitable caliper, each having a cylinder, in which the piston slides so that it can act on the opposing surface of the rotating disc by means of a pad. Can be generated by a piston-cylinder unit.

  This piston-cylinder unit typically removes the cylinder and piston (especially their sliding surfaces) against the ingress of flying materials such as dust, dirt, water vapor and / or corrosives. A flexible boot for protection so that the piston slides precisely inside the cylinder during the braking operation and / or the sliding surface of the piston and the sliding of the cylinder Protect the surface from corrosion.

  These flexible boots that are normally used are bellows-like and such boots are secured by fixing one of their ends around the piston and the other end around the cylinder. Fit to the piston-cylinder unit to form a protective barrier surrounding and extending the piston-cylinder unit in the region of the opening of the cylinder.

  When the flexible protective boot is at rest, i.e. when it is fitted in the disc brake and the piston is completely placed in the cylinder, the boot will occur on the unworn pad , One part of the boot is turned around each other to form one or more curved or pleated portions. Note that when the flexible boot is fitted to the disc brake surface, these pleats have a protruding part facing the pad side, in particular a protruding part facing the support plate side of the friction lining of the pad. Should. As a result of the wear of the friction lining of the pad, the piston extends toward the disc and the flexible boot is extended to accommodate the new position occupied by the piston.

  During assembly of the disc brake, in particular during assembly of the piston-cylinder unit and its flexible protective boot, a certain amount of air remains trapped in the gap between the boot and the piston-cylinder unit. It has been known.

  During operation of the brake, due to overheating of the disk on which the pad acts, heat is released and transferred to the trapped air by the piston, increasing the pressure that the air exerts on the flexible boot. This pressure causes the flexible boot to swell, and the pleats and other parts of the boot are in direct contact with the pad, particularly the support plate. This contact has a new or non-abrasive friction lining, the piston is substantially completely housed in the cylinder, and the pleat protrusion of the flexible boot is close to the support plate There is a particular tendency to occur.

  As a result of the braking action, especially as a result of this prolonged action, the pad can reach a high temperature and burn out, and in any case can damage the flexible boot with which the pad contacts, It has been pointed out that boots must be replaced as soon as problems are found.

  Furthermore, the problem of contact between the flexible boot and the pad is particularly noticeable in disc brakes using floating calipers that require a substantial amount of flexible boot with several pleats where the boot approaches the pad. Attention has been paid.

  One method proposed by the prior art to prevent this damage provides the use of a flexible boot with one suitable hole that provides an outlet for trapped air. According to this technique, the release of air prevents the boot from expanding and therefore also prevents contact with the pad.

  As known from US Pat. No. 4,809,821, another method provides for the formation of a suitable annular channel in the vicinity of the cylinder, in which case the pleats forming the flexible boot are The pleat portion remains appropriately spaced from the pad because it can be fully contained within the channel.

  However, it has been found that the previously proposed methods are unable to prevent contact between the flexible protective boot and the pad that flares and damages the boot.

  In fact, due to the high temperatures reached during braking, the use of air outlet holes is not sufficient to completely prevent the air and the boot from trapping air.

  It has been noted that the contact between the boot and the pad is not only caused by the air expansion described above, but also occurs due to the incorrect placement of the pleats forming the boot. For example, inaccurate placement of the boot pleats may occur during assembly by the manufacturer, and is more likely to occur as a result of flexible boot refolding following replacement of the pad by the maintenance worker. Likely to happen. In fact, changing the pad requires the piston to be moved back into the cylinder, so that in the state in which the work is performed, the space freed by the removed pad is limited, so that the exact refolding of the boot is possible. Is not necessarily guaranteed.

  As well as complicating and weakening the caliper structure within which the cylinder is formed, the presence of a suitable channel to fully accommodate the flexible boot is improperly mounted or trapped in the boot. It must also be kept in mind that it does not solve the problems created by blisters caused by overheating of the air.

U.S. Pat. No. 4,809,821

  The problem solution on which the present invention relies is to provide a flexible boot for protecting a piston-cylinder unit that can be used in a disc brake, which does not have the above-mentioned drawbacks associated with the prior art.

  This problem is solved by a flexible boot for protecting the piston-cylinder unit of the disc brake, which includes a piston that slides in the cylinder and acts on the brake pad, said flexible boot facing the pad wall. And at least one spacer member in contact with the pad wall with the aim of maintaining said portion of the surface spaced apart from the pad wall in relation to the surface. It is characterized by the provision.

  Other features and advantages of the present invention will become apparent from the following description of preferred embodiments, given through non-limiting illustrations taken in conjunction with the accompanying drawings.

The top view by which a part of disc brake of this invention was drawn by the cross section. A part of the disc brake of FIG. 1 is shown on an enlarged scale. Part of the disc brake of FIG. 1 with fully worn pads shown on an enlarged scale. The 1st example of the flexible boot of this invention is shown. The 2nd specific example of the flexible boot of this invention is shown. The 3rd example of the flexible boot of this invention is shown.

  1 and 2 generally show a disc brake 1 which acts on a braking band of a vehicle disc 2 (not shown).

  In the specific embodiment shown in FIG. 1, the disc brake 1 is a floating caliper type, but the invention can also be applied to different types of disc brakes, such as, for example, a fixed caliper type disc brake.

  The disc brake 1 has a disc 2 associated with a vehicle wheel and a caliper 3 including a bracket 4 and a floating body 5 mechanically coupled to the bracket 4.

  A bracket 4 fixed to a stub axle of an automobile suspension is substantially U-shaped, and a first bridge member 6 provided straddling the disc 2 on the right and left sides of the axis II of the disc brake 1. And a second bridge member 7. The first and second bridge members 6, 7 are formed by a first cross member 8 and a second cross member 8 ′ that extend at substantially right angles to the axis II on opposite sides of the disk 2. Are firmly connected to each other.

  Further, two seats 11 and 12 are formed in the bracket 4 to accommodate the respective pads 13 and 14. These pads 13, 14 have respective plates 25, 26 for supporting corresponding friction linings 35, 36.

  The floating body 5 is provided across the disk 2 and the pads 13, 14, and has a side 40 extending near the plate 25 and a side 41 extending near the plate 26, and acts on the plate 26. The protrusion part 42 provided with the flat surface is provided.

  The side 40 of the floating body 5 has respective cylindrical seats 43 in the regions at opposite ends of the axis II, and each is fixed to the bracket 4 so as to slide in a guided manner. The cylinder-shaped guide member 44 is engaged. Only the cylindrical seat 43 and the guide member 44 located on the left side of the corresponding axis II can be seen in FIG. Furthermore, a conventional protective boot 17 is fitted between each cylindrical seat 43 and the corresponding guide member 44.

  In the embodiment described, the side 40 of the floating body 5 includes two piston-cylinder units 19, only one of which can be seen in FIG. Each piston-cylinder unit 19 has a part 45 of a side 40, said one part 45 defining a hydraulic cylinder 9 with an axis aa inside, said cylinder 9 being in the direction of the seat 12 And a piston 10 provided with a head 29 and capable of sliding on the cylinder 9 in the axial direction and acting on the pad 14.

  A duct exists in the floating body 5 in a conventional manner, and brake oil is supplied to the cylinder 9. This cylinder 9 is provided with an annular groove 18 for the sealing part 28 as in the conventional case.

  The piston-cylinder unit 19 also has a flexible boot 100 to protect the cylinder 9 and the piston 10 (especially their sliding surfaces) from the ingress of flying materials and / or corrosives.

  The flexible boot 100 is in the form of bellows, which is produced when the bellows is at rest or when the piston 10 to which the bellows is connected is inside the cylinder 9. It takes the form of a rolled up with a pleat or bend. Further, the flexible boot 100 can have a substantially cylindrical or truncated conical shape with the piston 10 extending from the cylinder 9 toward the disk 10.

  In particular, when the pads 13, 14 are in a new state, i.e., the friction linings 35, 36 are not worn (as illustrated in FIG. 2), the flexible boot 100 is in a raised configuration. However, when the piston 10 extends as a result of wear of the friction linings 35, 36, it is in an extended state. FIG. 3 shows a portion of the disc of the brake of FIG. 1 with the piston extended forward as a result of the friction linings 35, 36 being almost completely worn out. In the viewpoint of FIG. 3, the flexible boot 100 is in close contact with the outer surface of the piston 10, but when the piston 10 extends forward, the flexible boot 100 is still on the surface. For example, it has a corrugated shape although it is almost in close contact.

  FIG. 4 is a cross-sectional view of a portion of the flexible boot 100 when in the rolled up configuration.

  The flexible boot 100 has at its one end a first annular region or first engagement ring 101 intended to be fixed to a part 45 defining the cylinder 9 and on the opposite side. At the end is a second annular region or second engagement ring 102 intended to be fixed to the piston 10.

  The portion 45 has a groove 20 for accommodating the first ring 101 in the vicinity of the opening 27 so that the flexible boot 100 can be fixed. A groove 29 for accommodating the second ring 102 is provided in the vicinity. For example, the thickness and shape of the engagement rings 101, 102 allows both of these rings to engage in grooves 20, 21 that are shaped to ensure the fixation of the flexible boot 100. Is formed. In any case, any other suitable means can be used to secure the flexible boot 100 to the piston-cylinder unit 19.

  Further, the portion 45 is formed with an optional annular housing 22 in the region of the opening 27 to at least partially accommodate the flexible boot 100 when it is in a raised configuration.

  The flexible boot 100 has an outer surface 103 and an inner surface 104 and includes a plurality of concentric annular band portions connected to each other and having different diameters.

  More specifically, the flexible boot 100 is accommodated in the first engagement ring 101 and the seat 22 in a state where the flexible boot 100 is rolled up and raised, and is provided in the second direction. A first connecting band 106 which is adapted to lie in a plane substantially perpendicular to the axis aa of the cylinder 9 when the flexible boot 100 is fitted to the piston-cylinder unit 19. Is provided.

  The second band 107 is connected to the third band 108 so as to define a cylinder of axis aa when the flexible boot 100 is fitted to the piston-cylinder unit 19. The third band 108 is connected to the first pleat portion 109.

  The first pleat portion 109 is connected to the second engagement ring 102 by the fourth band 111 and provided in the radial direction. That is, the flexible boot 100 is fitted to the piston-cylinder unit 19. Is connected to the fifth band 112 so as to be substantially perpendicular to the axis aa of the cylinder 9.

  The first and second pleat portions 109, 110 have respective annular protrusions 113, 114 connected to each other by an annular depression 115.

  One or more parts of the outer surface 103 can face the pad 14 (see FIG. 2), ie these parts face the pad, in particular the flexible boot 100 is the piston-cylinder unit 19. It is pointed out that it can face the wall 30 of the plate 25 when fitted. In particular, as shown in FIG. 2, the annular protrusions 113 and 114 can face the pad 14.

  The flexible boot 100 advantageously comprises at least one spacer member 105, with at least a part of the outer surface 103 being spaced from the pad 14, in particular from the wall 30 of the plate 25. Can be maintained appropriately.

  In the illustrated example, the spacer member 105 is disposed on the surfaces of the annular protrusions 113 and 114.

  These spacer members 105 are interposed between the outer surface 103 and the plate 25 and are advantageously designed to contact the wall 30 and are capable of being connected to the plate and, for example, annular projections 113, 114. Preventing direct contact with portions of the flexible boot 100, thus reducing the exchange of heat resulting from the braking action between the pad 14 and the flexible boot 100.

  According to one specific example, the spacer member 105 is a raised portion formed in the boot 100 and can take various shapes. In this context, according to one embodiment, a shape that ideally reduces the contact area between the ridge and the wall 30 of the plate 25 to one point is particularly suitable for this purpose. In FIG. 4, the spacer member 105 is a spherical cap-shaped raised portion.

  FIG. 5 shows, as another example, a flexible boot having a spacer member formed with a ridge 105 ′ having a generally frustoconical shape, and FIG. 6 shows a ridge 105 ″ with a truncated elliptical cone shape. The flexible boot 100 which has the spacer member formed in FIG.

  However, it is also possible to use other shapes other than those shown, such as truncated pyramids or irregular cross-sectional shapes (further protruding in one or more directions).

  Further, the spacer member 105 can be provided on the surface 103 of the flexible boot 100 with various possible surface densities. For example, the spacer members 105 can be distributed substantially uniformly over a portion of the surface of the flexible boot (eg, the surface of the ridges 113, 114), or two or more of these spacer members The above groups can be formed, and these groups can be provided so as to be appropriately dispersed in the flexible boot 100. In this regard, in FIGS. 4 and 5, the ridges 105 and 105 ′ are arranged in two groups, whereas the ridges 105 ″ shown in FIG. 6 are distributed almost uniformly. Note that there is.

  The flexible boot 100 provided with the spacer member 105 can be manufactured in a conventional manner. For example, it is manufactured by injecting a fluid material into a mold with a cavity that can reproduce a raised structure boot in a passive configuration. Typically, the material used to manufacture the flexible boot 100 is a material that is resistant to brake oil and resistant to the temperatures experienced by the boot. Preferably, the following materials are used to manufacture the flexible boot 100 as the temperature reached during braking increases. : SBR (styrene butadiene rubber), EPDM (ethylene-propylene-diene rubber) or silicon rubber, NBR (acrylonitrile butadiene rubber) used in an environment where mineral oil is present.

  As already explained, the flexible boot 100, in its resting state, has the same roll it has when it is fitted to the piston-cylinder unit 19 with the new pads 13,14. It is formed in a mode that takes a natural form.

  Furthermore, in order not to noticeably change this form naturally taken by the flexible boot 100, the spacer member 105 is advantageously suitably dimensioned.

  For example, the spherical cap-type spacer member 105 has a radius between 0.3 mm and 0.9 mm, preferably between 0.5 mm and 0.7 mm, specifically about 0.6 mm.

  It is pointed out that in the extended state, the flexible boot 100 takes a considerable length (depending on the thickness of the pad used). For example, if a fixed caliper is used, this length of the flexible boot 100 is between 8 mm and 20 mm, and if a floating caliper is used, the length is between 25 mm and 40 mm, but it can reach 50 mm. .

  In addition, the flexible boot typically has two or three pleats.

  The flexible boot 100 preferably comprises an opening and a valve (not shown) of a type known to take advantage of the derivation of the air present between the boot and the piston-cylinder unit 19.

  During attachment of the flexible boot 100 to the piston-cylinder unit 19 in the conventional manner, the flexible boot 100 and the spacer member 105, when they are rolled up, are separated from the wall 30 of the plate 25. It is possible to arrange so that it does not contact.

  When the braking action occurs, the piston 10 pressurizes the plate 25 under the pressure of the brake oil, so that the pad 14 acts on the disk 2 by the friction lining 35 to exert pressure on the brake band. As a result of the pad 14 being pressurized and coming into contact with the disk 2, a reaction force acts on the floating body 5 guided by the guide member 44 and exerts a force in the opposite direction on the force of the piston 10.

  Due to the reaction of the floating body 5, the protrusions 42 react to the pad 13 and thus to the disk 2, so that the brake band of the disk is equal in magnitude and opposite in direction to the force exerted by the pad 14. Under the influence of a certain force.

  As explained above, during braking, the disk 2 is overheated and releases heat, which is transferred to the pads 13, 14 and thus also to the piston 10. Furthermore, the released heat is transferred by the piston 10 to the trapped air between the flexible boot 100 and the piston-cylinder unit 19 to increase the pressure exerted on the boot by the air.

  In known flexible boots, this pressure causes the flexible boot to expand so that the boot contacts the pad 14, in particular the plate 25. Because this contact tends to occur as new friction linings, i.e., they are not worn, the flexible boot has a raised configuration with a pleated portion that extends toward the pad 14. ing.

  As already explained, the pad 14 will reach high temperatures and burn out or damage the boot if it is assumed to be in direct contact with the flexible boot.

  In contrast to what can occur in a conventional disc brake, in the disc brake of FIG. 1, the flexible boot 100 does not contact the pad 14 except by a spacer member 105. In particular, the spacer member 105 maintains the flexible boot 100 spaced from the pad 14 even if the boot is inflated by air trapped therein.

  The presence of the spacer member 105 greatly reduces the contact area between the flexible boot 100 and the pad 14 and creates a space between them to heat or exchange the flexible boot. prevent.

  The presence of the spacer member 105 is not in a state where the boot is accurately raised as occurs during the process of attaching the boot to the piston-cylinder unit 19 or during the operation of replacing the pads 13,14. Even in such a case, the flexible boot advantageously prevents direct contact with the pad 14.

  Further, thanks to the teachings of the present invention, the integrity of the flexible boot may cause design changes to the body defining the cylinder, complexity to form a suitable channel for receiving the boot, and Or it can be maintained without weakening this structure.

  It will be appreciated that many modifications may be made to the flexible boots and disc brakes described above by those skilled in the art to satisfy the particular requirements involved, All of these fall within the scope of protection of the present invention as defined by the appended claims.

Claims (15)

A flexible boot (100) for protecting a piston-cylinder unit (19) of a disc brake (1), comprising a piston (10) that slides in a cylinder (9) and acts on a brake pad (14). ,
The flexible boot has a surface (103) with a portion that can face the wall (30) of the pad;
Flexible, characterized in that it comprises at least one spacer member (105) associated with said surface and intended to maintain a portion of said surface spaced from the pad wall in contact with the pad wall. Sex boots (100).   The flexible boot (100) of claim 1, wherein the at least one spacer member (105) is a raised portion of the flexible boot (100) extending toward the wall (30) of the pad (13).   The flexible boot (100) of claim 1, wherein the ridge (105) comprises a spherical cap shape.   The flexible boot (100) of claim 3, wherein the spherical cap comprises a radius between about 0.3 mm and 0.9 mm.   The flexible boot (100) of claim 2, wherein the raised portion (105 ') is frustoconical.   The flexible boot (100) according to claim 2, wherein the raised portion (105 '') has a truncated elliptical cone shape.   Multiple connections so that when the piston (10) is substantially inside the cylinder (9), it takes a swollen configuration and when the piston extends from the cylinder, it takes an extended configuration. The flexible boot (100) according to claim 1, comprising an annular band (106, 107, 108, 111, 112) and at least one pleat portion (109; 110).   At least one pleat portion (109; 110) has a protrusion (113, 114) that can face the wall (30), and at least one spacer member (105) is disposed on the protrusion. The flexible boot (100) of claim 7, wherein:   The flexible according to claim 1, comprising a first annular end (101) for engaging the cylinder (9) and a second annular end (102) for engaging the piston (10). Sex boots (100).   The flexible boot (100) according to claim 1, manufactured from one of the materials belonging to the group of SBR, EPDM, silicone rubber, NBR rubber. A portion (45) defining a cylinder (9) for sliding a piston (10) for applying a brake to the brake pad (14);
A flexible boot (100) formed according to at least one of claims 1 to 10 for protecting a piston-cylinder unit;
Piston-cylinder unit (19) for disc brakes having   The part (45) has a first seat (20) in the cylinder (9) to accommodate the first annular end (101), and the piston (10) has a second annular shape. 12. A piston cylinder unit (19) according to claim 11, comprising a second seat (21) for receiving the end (102).   The first and second seats have a first annular groove (20) and a second annular groove for engaging the first annular end (101) and the second annular end (102), respectively. The piston-cylinder unit (19) according to claim 12, each having (21).   12. Piston-cylinder unit (19) according to claim 11, wherein the portion (45) has one annular housing (22) for at least partially receiving the flexible boot (100). A brake pad (14) for applying a braking force to the disc (2) in relation to the disc brake;
At least one piston-cylinder unit (19) comprising a cylinder (9) and a piston (10) capable of sliding in the cylinder to act on the brake pads;
Disc brake (1), wherein at least one piston-cylinder unit is formed by at least one of claims 11-14.

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