PISTON FOR A DISC BRAKE, DISC BRAKE WITH AT LEAST ONE PISTON AND SERIES OF PISTONS

Description

[0001] The invention relates to pistons for disc brakes with a contact surface for a brake pad, with an outer part forming a piston skirt and an inner part inserted into the outer part, wherein the inner part has an opening on its side facing away from the contact surface and a receptacle in its interior, via which the piston can be acted upon with a hydraulic fluid and / or with adjusting means of a parking brake drive.

[0002] The document US 2011 / 0315007 A1 discloses a piston for a brake caliper of a disc brake, which is produced from a metallic material by forming and is designed as a pot that is open on one side, comprising: a longitudinal axis, a wall and a piston head, wherein the piston is designed to bear against a brake pad with an axial contact surface in a region of the piston head, wherein a projection with a conical surface for attaching a drive nut for mechanical actuation is provided on an inner surface of the piston head, wherein a recess is provided in an outer surface of the piston head, which recess is at substantially the same distance from the longitudinal axis as the projection.

[0003] The document WO 2015 074 905 A1 discloses a piston arrangement for a disc brake, comprising a piston which is essentially designed as a pot-like hollow cylinder open on one side from flat steel sheet, deep-drawn using a cold forming process, and comprises a piston head and, integrally therewith, a wall with a groove, wherein the piston head can be hydraulically subjected to braking pressure from the interior of the pot, so that an outwardly directed contact surface of the piston head is pressed against a friction lining, and wherein the piston has a clutch cone for the purpose of cooperation with a drive nut of a parking brake actuating device, characterized in that the clutch cone is provided as a work hardening on a free end side of the open end of the wall, so that the parking brake forces are introduced from the open end via the wall into the piston head by the piston.

[0004] The document US 2011 / 132188 A1 discloses a multi-part piston for a brake caliper of a hydraulically and / or mechanically and / or electromechanically actuated disc brake, which is essentially designed as a pot-like hollow cylinder open on one side with a base and a wall formed thereon, wherein the base is designed to be subjected to a brake pressure coming from the interior of the pot, so that an outwardly directed contact surface of the base is designed to be pressed against a brake pad, and wherein the interior of the pot accommodates at least one pressure piece, wherein the pressure piece and the base have conical surfaces which are aligned with one another for force transmission.

[0005] The document DE 10 2009 017 167 A1 discloses a multi-part piston for a brake caliper of a hydraulically and / or mechanically and / or electromechanically actuated disc brake, which is designed essentially as a pot-like hollow cylinder open on one side, and comprises a base and a wall integrally formed thereon, wherein the base can be subjected to braking pressure from the interior of the pot, so that an outwardly directed contact surface of the base can be pressed against a brake pad, and wherein the interior of the pot accommodates at least one pressure piece, which is in particular integrated into a force flow from a parking brake mechanism, characterized in that the pressure piece and the base have conical surfaces facing one another for force transmission.

[0006] Such pistons are known from US 2011 / 0315007 A1, WO 2015 074 905 A1, US 2011 / 132188 A1, and DE 10 2009 017 167 A1 and are used to press a brake pad of a disc brake against a brake disc of the disc brake. This can be achieved either by applying hydraulic fluid to the piston or by applying an actuating means of a parking brake drive to the piston.

[0007] The invention further relates to a disc brake with at least one such piston and to a series comprising at least two types of such pistons.

[0008] The design of the pistons can influence the performance characteristics of the disc brakes equipped with them and can also be crucial for the economical production of the pistons.

[0009] The design of the pistons can influence the responsiveness of the disc brakes equipped with them. A piston that is as light as possible can be beneficial for the responsiveness of the disc brake. However, it is important to ensure that the pistons are strong enough to withstand the potentially high pressures and associated loads over time.

[0010] The design of the pistons, for example, can also be crucial for easy bleeding of disc brakes. A disc brake that is as well vented as possible is desirable in order to achieve a defined pressure point that the user can feel when using the disc brake.

[0011] The object of the invention is therefore to provide a piston of the type mentioned at the outset with improved performance characteristics which can also be manufactured economically.

[0012] To achieve this object, a piston having the features of the first independent claim directed to such a piston is initially proposed. In particular, to achieve this object, a piston for a disc brake is proposed, having a contact surface for a brake pad, an outer part forming a piston skirt, and an inner part inserted into the outer part. The inner part has an opening on its side facing away from the contact surface and a receptacle in its interior, via which the piston can be acted upon by a hydraulic fluid and / or by an actuating means of a parking brake drive. A cavity is formed between the outer part and the inner part, which cavity is sealed in a fluid-tight manner by at least one fluid-tight connection between the inner part and the outer part to prevent hydraulic fluid from entering the cavity from the receptacle of the inner part.

[0013] In this way, a piston with a comparatively large effective outer diameter, determined by its outer part, can be provided, whereby the piston can be operated with a comparatively small quantity of hydraulic fluid due to its inner part having an outer dimension compared to the outer diameter of the outer part. The fluid-tight connection between the inner part and the outer part effectively prevents hydraulic fluid from escaping from the receptacle of the inner part into the cavity between the inner part and the outer part. The reduced quantity of hydraulic fluid can simplify the venting of the disc brake equipped with the piston. In addition, the use of an outer part and an inner part arranged in the outer part enables a lightweight design of the piston. This can improve the dynamics of the piston during operation of the disc brake.Reducing the amount of hydraulic fluid in a disc brake equipped with the piston according to the invention can have a positive effect on the braking function and responsiveness of the disc brake. The greater the amount of hydraulic fluid in the braking system, the softer the disc brake can feel to the user when braking. In addition to weight savings through reducing the amount of hydraulic fluid in the braking system, parts of the disc brake upstream of the piston, such as a brake caliper, can be made less rigid and therefore less expensive. Using less material in the manufacture of the parts upstream of the piston can also result in further weight savings. The piston according to the invention thus enables the provision of disc brakes with improved braking function that are also lighter and can be offered at a lower price than previous disc brakes.

[0014] The piston's at least two-part construction, comprising the inner and outer parts, reduces the material required for piston production, even if the piston has a comparatively large external dimension. This results in a relatively inexpensive and also lightweight piston.

[0015] In one embodiment of the piston, it is provided that the cavity is sealed in a liquid-tight manner by two liquid-tight connections between the inner part and the outer part, which are axially spaced apart from one another with respect to a longitudinal axis of the piston, against the entry of hydraulic fluid from the receptacle of the inner part into the cavity.

[0016] Such a piston can have a particularly simple design. The outer part can be in the form of a sleeve that surrounds the inner part. By means of two liquid-tight connections between the inner part and the outer part, the inner part and the outer part can be connected to one another and, in addition, the cavity formed between the inner part and the outer part can be closed, in particular sealed, in a liquid-tight manner. The two liquid-tight connections between the inner part and the outer part can be applied or produced from different axial sides of the piston. This enables simple production of the piston and, in particular, the liquid-tight connections. Furthermore, the use of two liquid-tight connections can also facilitate the provision of a series of pistons, which will be explained in more detail below and which comprises at least two different types of piston.

[0017] To achieve this object, a piston having the features of the second independent claim directed to such a piston is also proposed. Thus, in particular to achieve this object with a piston of the type mentioned at the outset, it is proposed that the outer part has a retaining opening for the inner part, axially spaced from an insertion opening for the inner part with respect to a longitudinal axis of the piston, in which retaining opening the inner part is arranged for support on the outer part. Due to the retaining opening of the outer part for the inner part, which is provided axially spaced from the insertion opening, it is possible to transmit a compressive force from the inner part particularly reliably and effectively to the outer part and / or to a bearing surface of the piston for a brake pad of a disc brake equipped with the piston. The retaining opening can penetrate a base of the outer part.

[0018] This type of support of the inner part on the outer part offers advantages, particularly in light of the increasing demands for lightweight construction to which such pistons are also subject. Supporting the inner part on the outer part via the retaining opening in the outer part enables a rigid piston design, even with comparatively low material usage. This enhances the performance characteristics of the piston according to the invention.

[0019] In one embodiment of the piston, it is provided that it has the features of the two independent claims, each directed to a piston for a disc brake, combined with one another.

[0020] In one embodiment of the invention, the at least one liquid-tight connection is a material-to-material connection, for example, a welded connection. It is particularly preferred, because it can be produced quickly and efficiently, if the at least one liquid-tight connection is a laser-welded connection.

[0021] The at least one liquid-tight connection can surround the longitudinal axis of the piston in a closed ring, particularly a circular ring. This ensures that the connection is liquid-tight.

[0022] In one embodiment of the piston, it is provided that the insertion opening of the outer part for the inner part is closed in a liquid-tight manner by a, in particular first, liquid-tight connection.

[0023] According to the invention, the first, particularly liquid-tight connection is formed between an edge of the outer part, which defines the insertion opening of the outer part for the inner part, and the inner part. In one embodiment of the piston, this connection can be formed between a rim of the inner part and the outer part. The rim can surround the opening of the inner part and / or form a largest diameter of the inner part.

[0024] The inner part is preferably designed as a liquid-tight pot. Such a liquid-tight pot can have a liquid-tight inner wall. This effectively prevents fluid from leaking through the inner wall of the inner part into the cavity formed between the inner and outer parts. The inner part's receptacle can be designed without an undercut. Designing the receptacle without an undercut prevents air bubbles from becoming trapped within the receptacle and complicating the bleeding of the disc brake equipped with the piston.

[0025] The outer part can have a support section on which the retaining opening for the inner part is formed and via which the inner part is supported on the outer part in the feed direction of the piston. The support section can be arranged or formed, in particular, on a base of the outer part. The support section can be formed by deforming the outer part, in particular by deforming its base section.

[0026] In one embodiment, the support section, starting from the contact surface of the piston, forms an acute angle with the longitudinal axis of the piston and / or with the contact surface of the piston. The acute angle can be an angle between 30° and 60° inclusive, and preferably an angle of 45°. In particular, when the support section is aligned at an angle of 45° to the longitudinal axis and / or to the contact surface of the piston, particularly efficient force transmission between the inner part and the outer part is possible. The support section allows force to be redirected in stages from the inner part to the outer part, which in turn promotes force transmission between the inner and outer parts.

[0027] A, in particular a second, liquid-tight connection can close the aforementioned holding opening in a liquid-tight manner and / or be formed between the support section of the outer part and the inner part.

[0028] The retaining opening of the outer part can be arranged axially between the contact surface of the piston and the insertion opening of the outer part with respect to a longitudinal axis of the piston. The retaining opening can be formed in a base of the outer part.

[0029] The insertion opening of the outer part can have a larger diameter than its holding opening for the inner part.

[0030] The inner part can have a conically tapered section with which the inner part is supported on the outer part. The inner part can be arranged with the conical section in the holding opening of the outer part and supported on the outer part. The conically tapered section of the inner part can be an end section of the inner part, which is formed at an end of the inner part facing away from the opening of the inner part. The conical section can be truncated cone-shaped and have an axial surface of the inner part at its end, which can form at least part of the contact surface of the piston. The holding opening of the outer part can have an inner diameter that is smaller than an outer dimension of the inner part in a section upstream of the conical section. The conical section makes it particularly easy to position the inner part centered in the preferably circular holding opening of the outer part.Because the inner part has a larger diameter in the section upstream of the conical section, the inner part can be brought into its correct position relative to the outer part particularly easily and accurately. This promotes the economical production of the piston.

[0031] The piston's contact surface can be formed at least partially on the outer part and / or at least partially on the inner part. Overall, the piston's contact surface for a brake pad can thus be distributed between the outer part and the inner part. In this context, it is advantageous if an axial end face of the outer part and an axial end face of the inner part lie in a common plane and / or together form the piston's contact surface.

[0032] The inner part can have a guide section for an actuating means of a parking brake drive in its receptacle. The inner part can have an anti-twist device, for example in the form of a non-circular inner cross-section of the guide section, for an actuating means of a parking brake drive.

[0033] The inner part can have a hydraulically effective pressure surface in its receptacle. The hydraulically effective pressure surface can be arranged axially, relative to a longitudinal axis of the piston, between the piston's stop surface for a brake pad and the aforementioned retaining opening of the outer part for the inner part.

[0034] The inner part can have a stop surface for an actuating means of a parking brake drive. The stop surface can be arranged, with respect to a longitudinal axis of the piston, between the piston's contact surface for a brake pad and the insertion opening of the outer part and / or the opening of the inner part.

[0035] The aforementioned hydraulically effective application surface can be arranged axially with respect to a longitudinal axis of the piston between the aforementioned stop surface for an actuating means of a parking brake drive and the contact surface of the piston for a brake pad.

[0036] In one embodiment of the piston, at least one liquid-tight connection between the inner part and the outer part is a liquid-tight connection formed on an end face of the piston. In a preferred embodiment of the piston, the piston has a liquid-tight connection between the inner part and the outer part on two opposite end faces. Liquid-tight connections on the end face are advantageous from a manufacturing perspective. The arrangement of the connections on the end face can simplify the formation of the liquid-tight connections, in particular by a welding process, for example, laser welding.

[0037] In one embodiment of the piston, the outer part has a closed collar that extends around a longitudinal axis of the piston. The collar can define the insertion opening of the outer part for the inner part and / or be oriented radially inward in the direction of the longitudinal axis of the piston or the outer part. A fluid-tight connection between the inner part and the outer part can be arranged or formed between the collar and the inner part. Even in a piston whose outer part has such a collar, it is possible to create the fluid-tight connection between the collar and the inner part at the end face.

[0038] In one embodiment of the piston whose outer part has a collar, the collar can further have a step. The inner part can rest against the step, in particular with a rim that the inner part has and that can surround the previously mentioned opening of the inner part. Such a step on a collar of the outer part can simplify the positioning of the inner part in or on the outer part and ultimately also promote the formation of a fluid-tight connection between the outer part and the inner part at the end face.

[0039] In one embodiment of the piston, the outer part can have a base. The base can be the part of the outer part that is aligned transversely or at right angles to the longitudinal axis of the outer part and / or transversely or at right angles to the longitudinal axis of the piston and / or is arranged at an end of the outer part facing away from the insertion opening of the outer part. In one embodiment of the piston, the base can be closed. The inner part of the piston can then be arranged on or at this base. In particular, in this context, the inner part can be sleeve-shaped and not have its own base.

[0040] In one embodiment of the piston, a recess, for example a groove, preferably a closed, circumferential annular groove, is formed in the preferably closed base of the outer part. The inner part can then be arranged in this recess, in particular in this groove or annular groove. In this context, in particular, it is possible for the inner part to be sleeve-shaped and not have a base itself. The recess formed in the base of the outer part, in particular the groove or annular groove, can be helpful for reliably and easily positioning the inner part in the outer part and for forming a liquid-tight connection between the outer part and the inner part.

[0041] In a preferred embodiment of the piston, a liquid-tight connection between the outer part and the inner part is a welded joint created by a, in particular, closed, base of the outer part. The welded joint can be a laser-welded joint, for example. Such a welded joint between the outer part and the inner part created by the base of the outer part can be easily produced in a particularly efficient manner, even in series production, and is therefore advantageous for the economical production of the piston.

[0042] In one embodiment of the piston, the outer part can have an end opening on its end face facing away from the insertion opening. The end opening can be formed in the base of the outer part and / or have an edge spaced apart from the inner part. In this way, the inner part sits within the end opening of the outer part without contacting the outer part. The end opening, which can be formed in addition to the insertion opening on the outer part, allows the outer part to be particularly lightweight.

[0043] In one embodiment of the piston, the inner part can have a shoulder on its outer side. Particularly preferably, the shoulder can be designed as a holding shoulder. The inner part can contact the outer part with the shoulder. For example, it is possible for the inner part to be arranged with its shoulder in a holding opening, for example in the previously mentioned one, in particular in the base of the outer part. In this way, the inner part can be positioned and centered in the outer part relatively easily and precisely thanks to the shoulder. This can promote the creation of a liquid-tight connection, particularly at the end, between the outer part and the inner part in the region of the holding opening of the outer part.

[0044] In one embodiment of the piston, the inner part has a section facing away from the opening into the receptacle of the inner part, the diameter of which, in particular its outer diameter, is smaller than a diameter, in particular an outer diameter, of a section of the inner part adjacent to the opening of the inner part. In this way, the inner part can have a stepped cross-section. The stepped cross-section can form the aforementioned shoulder on the outer side of the inner part.

[0045] It is a further object of the invention to provide a series of such pistons which enables a rational production of such pistons.

[0046] Finally, the invention also relates to a series of pistons for disc brakes with at least two types of pistons according to one of the claims directed to a piston, wherein the at least two types of pistons have identical inner parts, in particular inner parts which are identical to one another with regard to their receptacles, and different outer parts, in particular outer parts with different outer diameters. In this way, it is possible to vary only the outer parts in order to produce pistons with different outer parts, in particular to produce pistons with different outer diameters, and to use inner parts which are identical at least with regard to the volume of their receptacles. The inner parts can be designed to be identical to one another, in particular with regard to the inner contour of their respective receptacles.All piston types can then have only one type of inner part, at least with regard to the inner part. This can simplify the production of the entire piston series by reducing the variety of parts.

[0047] In addition, the mounting of the inner part can determine the volume of hydraulic fluid in the brake system that is equipped with the piston. In order to optimize the braking behavior of the brake system, the smallest possible amount of hydraulic fluid in the brake system is desirable. The fact that the inner parts of at least two types of pistons have the same mountings and that there is at least one fluid-tight connection between the outer part and inner part in the pistons of this series ensures that the amount of hydraulic fluid in the piston is independent of the outer diameter of the outer part of the piston, which defines the outer diameter of the piston. The amount of hydraulic fluid in the different pistons of the series is then determined by the mounting of the inner parts and their volume.Since the receptacles of the internal parts of the different types of pistons in the series are preferably identical at least in terms of their volume, the pistons in the series then contain the same amount of hydraulic fluid regardless of their piston diameters.

[0048] In one embodiment of the piston series, the outer parts of the different types of pistons have retaining openings with identical inner diameters for the inner parts, even if they differ in their outer diameters. In this way, the outer parts of the different types of pistons are designed identically with regard to their retaining openings, so that they are suitable for accommodating the inner parts that are identical for all types of pistons.

[0049] The invention is described in more detail below using exemplary embodiments, but is not limited to these exemplary embodiments. Further exemplary embodiments result from the combination of the features of individual or multiple claims with one another and / or from the combination of individual or multiple features of the exemplary embodiments. They show: Fig. 1 a sectional side view of a piston with an inner part inserted into an outer part, wherein the outer part and the inner part are connected to each other by two liquid-tight connections spaced apart from each other with respect to a longitudinal axis of the piston such that a cavity arranged between the inner part and the outer part is closed in a liquid-tight manner, Fig. 2 a bottom view of the in Fig. 1 shown piston, Fig. 3 a plan view of the Fig. 1 and 2shown piston, Fig. 4 a sectional view of a further piston before producing two liquid-tight connections axially spaced from each other with respect to a longitudinal axis of the piston, the outer part of which has a closed bottom with a recess, namely with a closed circumferential groove, in which the sleeve-shaped inner part of the piston, which has no bottom or an open bottom, is arranged, wherein the outer part further has an inwardly directed collar which delimits the insertion opening of the outer part for the inner part, Fig. 5 a sectional view of the in Figure 4shown piston after creation of the two liquid-tight connections between outer part and inner part, wherein the lower of the two connections is a frontal laser-welded connection created by a closed bottom of the outer part, Fig. 6 a sectional view of a further piston, the outer part of which has a holding opening for the inner part in its bottom, which is flat, wherein between the outer part and inner part two liquid-tight, with respect to a longitudinal axis of the piston spaced apart, frontal laser-welded connections are formed, by which the cavity between the outer part and inner part is sealed in a liquid-tight manner, Fig. 7 a sectional view of a further piston, which in terms of construction is similar to the piston of Fig.1similar, wherein in this piston the outer part has an angled bottom through which a holding opening for the inner part is penetrated, and a first liquid-tight connection between a rim of the inner part and an inwardly directed collar of the outer part and a second liquid-tight connection in the holding opening of the outer part for the inner part are formed between the outer part and the inner part, Fig. 8 is a sectional view of a further piston having an outer part open at the end without a bottom and a stepped inner part arranged therein and a single liquid-tight laser-welded connection arranged at the end between a collar of the outer part and a rim of the inner part, Fig. 9 is a sectional view of a further piston, the structure of which is similar to the structure of the piston shown in Figure 8shown piston, this piston having on its outer part a collar with a step against which the inner part rests with its rim, Fig. 10 is a sectional view of a further piston with an inner part which has a holding section containing the opening of the inner part and which is widened compared to a downstream section of the inner part, and with an outer part which has a holding opening for the inner part, wherein two liquid-tight connections are formed between the inner part and outer part, by means of which the cavity between the outer part and inner part is closed off in a liquid-tight manner, and Fig. 11 is a sectional view of a further piston which has an inner part with a holding shoulder on its outer side, via which the inner part is supported on the outer part in a holding opening of the outer part.

[0050] All figures show a piston for a disc brake, designated as a whole with 1.

[0051] In the following description of different embodiments of the pistons 1, parts of the pistons that correspond in terms of their function are given the same reference numerals, even if they have different designs. Unless otherwise stated, the following explanations refer to all embodiments shown in the figures.

[0052] Each of the pistons 1 has a contact surface 2 which is axially aligned with respect to its longitudinal axis 11 and with which a brake pad can be pressed against a brake disc of a disc brake.

[0053] Each of the pistons 1 comprises an outer part 4 forming a piston skirt 3 and an inner part 5 inserted into the outer part 4.

[0054] The inner part 5 has an opening 6 on its side facing away from the contact surface 2 of the piston 1 and a receptacle 7 in its interior, via which the piston 1 can be acted upon with a hydraulic fluid and / or with an actuating means of a parking brake drive in order to advance the piston 1 in a feed direction 16.

[0055] A cavity 8 is formed between the outer part 4 and the inner part 5. The cavity 8, in particular the piston 1 according to the Figures 1 to 3 , 5 to 7 as well as 10 and 11 is sealed in a liquid-tight manner by two liquid-tight connections 9 and 10 between the inner part 5 and the outer part 4, preventing the ingress of hydraulic fluid from the receptacle 7 of the inner part 5 into the cavity 8. The two liquid-tight connections 9 and 10 are axially spaced from one another with respect to the longitudinal axis 11 of the piston 1. The cavity 8 is formed between the two connections 9 and 10.

[0056] For pistons 1 of the Figures 1 to 3 , 6 and 7 as well as 10 and 11 The outer part 4 has a holding opening 13 for the inner part 5, which is axially spaced from an insertion opening 12 for the inner part 5 with respect to the longitudinal axis 11 of the piston 1. The inner part 5 is arranged in the holding opening 13 for support on the outer part 4. In all pistons 1 shown in the figures that have a holding opening 13, the holding opening 13 penetrates a bottom 17 of the respective outer part 4.

[0057] The two liquid-tight connections 9 and 10 are each material-locking connections, namely laser-welded connections. The two connections 9 and 10 surround the longitudinal axis 11 of the respective piston 1 in a ring-shaped manner, namely in a circular ring, like the Figures 2 and 3 illustrate.

[0058] The insertion opening 12 of the outer part 4 for the inner part 5 is sealed in a liquid-tight manner by a first liquid-tight connection 9 of the two liquid-tight connections 9 and 10 between the outer part 4 and the inner part 5.

[0059] The first liquid-tight connection 9 is formed between an edge 14 of the outer part 4, which borders the insertion opening 12 of the outer part 4, and the inner part 5. The pistons 1 according to the Figures 8 and 9 have only a single liquid-tight connection 9 between the outer part 4 and the inner part 5.

[0060] The inner part 5 is designed as a liquid-tight pot, as can be seen in particular from the sectional view of the piston 1 from Figure 1 Also with piston 1 of the Figures 6 to 11The inner part 5 is designed as a liquid-tight pot. Furthermore, the receptacle 7 of the inner part 5 of all pistons 1 is designed without undercuts. This prevents air bubbles from becoming trapped within the receptacle 7 and complicating the bleeding of the disc brake equipped with the piston 1.

[0061] The outer part 4 of the piston 1 of the Figures 1 to 3 , 6 and 7 as well as 10 and 11 has a support section 15 on which the holding opening 13 for the inner part 5 is formed and via which the inner part 15 is supported on the outer part 4 in the feed direction 16 of the piston 1.

[0062] According to the sectional views from the Figure 1 , 7 and 10The support section 15 of the outer part 4 forms an acute angle with the longitudinal axis 11 and also with the contact surface 2 of the piston 1 on the other hand. The support section 15 forms an angle of 45° with the contact surface 2 and the longitudinal axis 11 of the piston 1. According to the sectional views from the Figures 6 and 11 the support section 15 of the outer part 4 forms a right angle with the longitudinal axis 11 of the piston 1.

[0063] The second liquid-tight connection 10 of the two liquid-tight connections 9 and 10, which is provided for individual pistons 1, seals the retaining opening 13 of the outer part 4 in a liquid-tight manner. The second liquid-tight connection 10 is formed between the support section 15 of the outer part 4 and the inner part 5.

[0064] The holding opening 13 of the outer part 4 is formed axially between the contact surface 2 of the piston 1 and the insertion opening 12 of the outer part 4 in a bottom 17 of the outer part 4 with respect to the longitudinal axis 11 of the piston 1.

[0065] For all pistons 1 that have a retaining opening 13, the insertion opening 12 of the outer part 4 has a larger diameter than the retaining opening 13 of the outer part 4 for the inner part 5. The inner part 5 has a section 18 that tapers conically toward its closed end. The inner part 5 is supported on the outer part 4 by the conical section 18. The inner part 5 is positioned with its conical section 18 in the retaining opening 13 of the outer part 4.

[0066] The contact surface 2 of the piston 1 is formed partly on the outer part 4 and partly on the inner part 5. For this purpose, an axial end face 19 of the outer part 4 and an axial end face 20 of the inner part 5 are arranged in a common plane, namely in a common axial plane of the piston 1, and together form the contact surface 2 of the piston 1.

[0067] The inner part 5, in particular the Figures 1 to 10 The piston 1 shown has a rim 24 which surrounds the opening 6 on the outside and between which and the outer part 4 the first liquid-tight connection 9 is formed.

[0068] The inner part 5 has according to Figure 1In its receptacle 7, it has a guide section 21 for an actuating means of a parking brake drive. The guide section 21 has a non-circular inner cross-section to prevent the actuating means from rotating. The inner parts 4 of the remaining pistons 1 also have a guide section 21 in their receptacles 7 for an actuating means of a parking brake drive.

[0069] In its housing 7, the inner part 5 of the piston 1 of the Figures 1 to 3 and 6 to 11 further comprise a hydraulically effective application surface 22 and a stop surface 23 for an actuating means of a parking brake drive. The stop surface 23 for the actuating means of a parking brake drive is in the Figures 1 to 3The piston 1 shown is arranged in continuation of the support section 15 of the outer part 4. The stop surface 23 is formed on an inner side of the conical section 18 of the inner part 5. This promotes a direct transmission of force from the actuating means of a parking brake drive via the inner part to the support section 15 of the outer part 4. In the position of use, the piston 1 shown in the figures is part of a disc brake (not shown).

[0070] In the Figures 4 and 5 In the embodiment of the piston 1 shown, the outer part 4 has a circumferential collar 25 which surrounds the insertion opening 12 of the outer part 4 for the inner part 5.

[0071] The inner part 5 of the Figure 4 The piston 1 shown is sleeve-shaped and has no bottom and has a rim 24 at its end adjacent to the collar 25 of the outer part 4. Between the rim 24 and the collar 25, according to Figure 5A liquid-tight connection 9 is formed on the end face between the outer part 4 and the inner part 5 in the form of a laser-welded joint. This liquid-tight connection 9 seals the cavity 8 between the outer part 4 and the inner part 5 in a liquid-tight manner with respect to a hydraulically loaded side of the piston 1.

[0072] The outer part 4 of the Figure 4 The piston 1 shown has a closed bottom 17. A recess 26 in the form of a groove 27, namely an annular groove, is formed in the closed bottom 17. The inner part 5 is arranged in this groove 27.

[0073] Figure 5 shows piston 1 from Figure 4with a second liquid-tight connection 10 created in addition to the first liquid-tight connection 9 on the end face between the outer part 4 and the inner part 5. This second liquid-tight connection 10 is formed between the outer part 4 and the inner part 5 at a distance axially from the first liquid-tight connection 9 with respect to a longitudinal axis 11 of the piston 1. Figure 5shows that this wide, liquid-tight connection 10 is formed as a welded connection, namely a laser-welded connection, created by the closed base 17 of the outer part 4. This variant of the piston 1 is characterized by its particularly simple manufacturability, even in series production. The recess 26 in the form of the groove 27 in the base 17 of the outer part 4 of this piston 1 facilitates the precise positioning of the inner part 5 in the outer part 4 and thus also the formation of the second liquid-tight connection 10 created on the end face by the closed base 17 of the outer part 4.

[0074] Figure 6 shows an embodiment of the piston 1, in which the outer part 4 has a collar 25 and a holding opening 13 at its end facing away from the collar 25. The holding opening 13 is according to Figure 6formed in a flat, non-angled base 17 of the outer part 4. The inner part 25, which has a stepped cross-section, has a rim 24 that surrounds the opening 6 of the inner part 5. Furthermore, the inner part 5 is arranged with the end facing away from the rim 24 in the holding opening 13 of the outer part 4 and is supported on the outer part 4 via this opening.

[0075] A first liquid-tight connection 9 in the form of a laser-welded connection is formed on the front side between the collar 25 of the outer part 4 and the rim 24 of the inner part 5. A second liquid-tight connection 10 between the outer part 4 and the inner part 5 is formed within the holding opening 13 in the base 17 of the outer part 4 on the front side between the outer part 4 and the inner part 5.

[0076] Figure 7 shows a further embodiment of a piston 1, the structure of which corresponds to that shown in Figure 1shown construction of the piston 1. In this piston 1, too, the outer part 4 has a bottom 17 which is angled and is penetrated by a holding opening 13 for the inner part 5. However, the inner part 5 in the Figure 7 The piston 1 shown has a rim 24 and the outer part 4 has a collar 25. In this piston 1, too, one of the two liquid-tight connections 9 and 10 is formed between the rim 24 on the inner part 5 and the collar 25 on the outer part 4.

[0077] The Figures 1 to 3 , 4 to 7 and 10 and 11 The pistons 1 shown each have a liquid-tight connection 9 or 10 between the outer part 4 and the inner part 5 on two opposite end faces 31 and 32 of the respective piston 1.

[0078] The two in the Figures 8 and 9The pistons 1 shown each have an outer part 4 which has an end opening 28 on its end face 32 facing away from the insertion opening 12 for the inner part 5. The Figures 8 and 9 show that the respective edge 29 of the front opening 28 is spaced apart from the inner part 5 of the respective piston 1. At the end of the outer part 4 facing away from the insertion opening 12, there is therefore no connection between the outer part 4 and the inner part 5. At this point, it should be mentioned that the inner part 5 of the Figures 8 and 9 The piston 1 shown can, if required, also be inserted through the end openings 28 into the respective outer part 4.

[0079] The outer part 4 of the Figure 9 The piston 1 shown further has a step 33 on its collar 25, against which the inner part 5 rests with its rim 24.

[0080] The Figures 1 , 7 , 10 and 11show that the inner parts 5 of the pistons 1 shown in these figures each have a shoulder 30 on their outer side. The respective shoulder 30 acts as a holding shoulder with which the inner part 5 contacts the outer part 4 and here in particular a bottom 17 of the respective outer part 4. In the Figures 1 , 7 , 10 and 11 In each embodiment of the piston 1 shown, it can be clearly seen that the inner parts 5 are centered via their shoulders 30 in the holding openings 13 of the respective outer part 4. This promotes the formation of the respective second liquid-tight welded connection, in particular a laser welded connection, created on the end face between the inner part 4 and the support 5.

[0081] The structure of the Figures 1-11The piston 1 shown allows the provision of a series comprising at least two different types of such pistons 1. The two types of pistons 1 have identical inner parts 5 and differ from one another in their outer parts 4. The outer parts 4 have different outer diameters. Thus, it is possible to provide a series of several types of pistons 1 that have different outer diameters, without, however, having to use different inner parts 5.

[0082] The outer parts 4 of the different types of pistons 1 have holding openings 13 with identical inner diameters for the inner parts 5.

[0083] The invention relates to improvements in the technical field of disc brakes. For this purpose, a piston 1 for a disc brake is proposed, comprising an outer part 4 and an inner part 5 inserted into the outer part 4. A cavity 8 is formed between the outer part 4 and the inner part 5, which cavity is sealed in a fluid-tight manner against the ingress of hydraulic fluid by at least one fluid-tight connection 9, 10 between the inner part 5 and the outer part 4. List of reference symbols

[0084] 1Piston 2Contact surface 3Piston skirt 4Outer part 5Inner part 6Opening 7Receptacle in 5 8Cavity between 4 and 5 9First liquid-tight connection 10Second liquid-tight connection 11Longitudinal axis of 1 12Insertion opening 13Retaining opening 14Edge around 12 15Support section 16Feed direction 17Bottom of 4 18Conical section of 5 19Axial end face of 4 20Axial end face of 5 21Guide section of 5 22Pressure surface of 5 23Stop surface of 5 24Rim on 5 25Collar on 4 26Recess in 17 27Groove in 17 28End opening of 4 29Edge of 28 30Step on 5 31Front side of 1 - hydraulic side 32Front side of 1 33Step on 25

Claims

1. Piston (1) for a disc brake having a contact surface (2) for a brake lining, having an outer part (4) forming a piston jacket (3) and an inner part (5) inserted into the outer part (4), wherein the inner part (5) has an opening (6) on its side facing away from the contact surface (2) and a receptacle (7) in its interior, via which the piston (1) can be acted upon by a hydraulic fluid and / or by an actuating means of a parking brake drive, characterized in that a cavity (8) is formed between the outer part (4) and the inner part (5), which cavity is sealed in a liquid-tight manner against the entry of hydraulic fluid from the receptacle (7) of the inner part (5) into the cavity (8) by at least one liquid-tight connection (9, 10) between the inner part (5) and the outer part (4), wherein the liquid-tight connection (9, 10) is formed between an edge (14) of the outer part (4) delimiting an insertion opening (12) of the outer part (4) and the inner part (5).

2. Piston (1) according to the preceding claim, wherein the cavity (8) is closed in a liquid-tight manner against the entry of hydraulic fluid from the receptacle (7) of the inner part (5) into the cavity (8) by two liquid-tight connections (9, 10) between the inner part (5) and the outer part (4), which connections are axially spaced apart from one another with respect to a longitudinal axis (11) of the piston (1).

3. Piston (1) according to claim 1 or 2, characterized in that the outer part (4) has a retaining opening (13) for the inner part (5) at an axial distance from one or the insertion opening (12) for the inner part (5) with respect to a longitudinal axis (11) of the piston (1), in which retaining opening the inner part (5) is arranged for support on the outer part (4), in particular the retaining opening (13) passing through a base (17) of the outer part (4).

4. Piston (1) according to one of the preceding claims, wherein the at least one liquid-tight connection (9, 10) is a materially bonded connection, in particular a welded connection, preferably a laser-welded connection, and / or surrounds the longitudinal axis (11) of the piston (1) in an annular, in particular circular, closed manner.

5. Piston (1) according to one of the preceding claims, wherein the insertion opening (12) of the outer part (4) for the inner part (5) is closed in a liquid-tight manner by a, in particular first, liquid-tight connection (9, 10) between the outer part (4) and the inner part (5).

6. Piston (1) according to one of claims 3 to 5, wherein the outer part (4) has a support section (15) on which the retaining opening (13) for the inner part (5) is formed and via which the inner part (5) is supported on the outer part (4) in the feed direction (16) of the piston (1).

7. Piston (1) according to the preceding claim, wherein the support section (15), starting from the contact surface (2) of the piston (1), forms an acute angle, in particular an angle of between 30° and 60°, preferably an angle of 45°, with the longitudinal axis (11) and / or the contact surface (2) of the piston (1).

8. Piston (1) according to one of the preceding claims, wherein a, in particular second, liquid-tight connection (9, 10) closes the retaining opening (13) in a liquid-tight manner and / or is formed between the support section (15) of the outer part (4) and the inner part (5).

9. Piston (1) according to one of claims 3 to 8, wherein the retaining opening (13) of the outer part (4) is formed axially with respect to a longitudinal axis (11) of the piston (1) between the contact surface (2) of the piston (1) and the insertion opening (12) of the outer part (4), in particular in a base (17) of the outer part (4), and / or wherein the insertion opening (12) of the outer part (4) has a larger diameter than the retaining opening (13) for the inner part (5).

10. Piston (1) according to one of claims 3 to 9, wherein the inner part (5) has a section (18) tapering conically in the direction of the contact surface (2), with which the inner part (5) is supported on the outer part (4), in particular wherein the inner part (5) is arranged with its conical section (18) in the retaining opening (13) of the outer part (4).

11. Piston (1) according to one of the preceding claims, wherein the contact surface (2) of the piston (1) is formed at least in part on the outer part (4) and / or at least in part on the inner part (5), in particular wherein an axial end face (19) of the outer part (4) and an axial end face (20) of the inner part (5) lie in a common plane and / or together form the contact surface (2) of the piston (1).

12. Piston (1) according to one of the preceding claims, wherein the inner part (5) has in its receptacle (7) a guide section (21), in particular with a non-circular inner cross-section for preventing rotation, for an actuating means of a parking brake drive, and / or wherein the inner part (5) has in its receptacle (7) a hydraulically effective impact surface (22) and / or a stop surface (23) for an actuating means of a parking brake drive.

13. Piston (1) according to one of the preceding claims, wherein at least one liquid-tight connection (9, 10) between the inner part (5) and the outer part (4) is a liquid-tight connection (9, 10) formed on an end face (31, 32) of the piston (1), preferably wherein the piston (1) has a respective liquid-tight connection (9, 10) between the outer part (4) and the inner part (5) on two end faces (31, 32) facing away from each other.

14. Piston (1) according to one of the preceding claims, wherein the outer part (4) has a collar (25) which extends in a closed manner around a longitudinal axis (11) of the piston (1) and which delimits the insertion opening (12) for the inner part (5), in particular wherein a liquid-tight connection (9, 10) between the inner part (5) and the outer part (4) is arranged between the collar (25) and the inner part (5).

15. Piston (1) according to one of the preceding claims, wherein the outer part (4) comprises a, preferably closed, base (17) at or on which the inner part (5) is arranged, in particular wherein a depression (26), for example a groove (27), is formed in the base (17), in which the inner part (5) is arranged.

16. Piston (1) according to one of the preceding claims, wherein a liquid-tight connection (9, 10) between outer part (4) and inner part (5) is a welded connection, preferably a laser welded connection, produced by a, in particular closed, base (17) of the outer part (4).

17. Piston (1) according to one of the preceding claims, wherein the outer part (4) has an end opening (28) on its end face (32) facing away from the insertion opening (12), the edge (29) of which has a distance from the inner part (5).

18. Piston (1) according to one of the preceding claims, wherein the inner part (5) has a shoulder (30) on its outer side, in particular with which the inner part (5) contacts the outer part (4).

19. Disc brake having at least one piston (1) according to one of the preceding claims.

20. Series comprising at least two types of pistons (1) according to one of claims 1-18, wherein the at least two types of pistons (1) have identical inner parts (5), in particular identical inner parts (5) at least with respect to the volume of their receptacles (7), and outer parts (4) with different outer diameters.

21. Series according to the preceding claim, wherein the outer parts (4) of the different types of pistons (1) have retaining openings (13) with identical inner diameters for inner parts (5) and / or identical inner parts (5).