Reduction of the residual drag torque in a disc brake

Abstract

Piston guide device for a disc brake (1), comprising: a housing (80) having a cavity (88) for guiding a guide piston (70) parallel to a designated direction (z); a guide piston (70) which is displaceably mounted in the cavity (88) parallel to the marked direction (z) along its piston longitudinal axis (A) between a first position and a second position, the first position being in front of the second position when viewed in the marked direction (z); a first coil spring (60) whose coils are formed around an axis parallel to the designated direction (z); wherein, viewed along the designated direction (z), one end of the first coil spring (60) is connected to the inner wall of the housing (80) or is supported on the inner wall of the housing (80) in the direction of the designated direction (z), and the other end of the first coil spring (60) viewed along the designated direction (z) is connected to the guide piston (70) or is supported on the guide piston (70) opposite to the designated direction (z); wherein the coil spring (60) is unloaded when the guide piston (70) is in the first position and is subjected to a load when the piston (70) is in the second position, or the coil spring (60) is subjected to a first load when the guide piston (70) is in the first position and the coil spring (60) is subjected to a second load when the guide piston (70) is in the second position, the second load being greater than the first load; characterized in that the housing (80) of the piston guide device is firmly connected to a brake calliper carrier of the disc brake (1) or is integrated into the brake calliper carrier; a brake calliper (20) of the disc brake (1) is connected to the end (72b) of the guide piston (70) pointing in the marked direction (z); at least one of the coil springs (60) has two or more coil spring elements (61, 62, 63) which are arranged one behind the other along the marked direction (z), and wherein the coil spring elements (61, 62, 63) are each themselves designed as coil springs.

Description

Technical area

[0001] The present invention relates to a piston guide device for a disc brake, in particular for a disc brake for a motor vehicle, which allows for improved management of the residual drag torque. The invention further relates to a disc brake with improved properties with respect to the residual drag torque. Furthermore, the invention relates to a floating caliper brake with improved properties with respect to the residual drag torque. Technical background

[0002] Disc brakes are used in vehicles, particularly motor vehicles, as a braking device. Braking is achieved by bringing one or more brake pads into contact with a brake disc and pressing them against it during braking. The brake disc is coupled to the wheel to be braked, so that it rotates together with the wheel around a common axis of rotation. A change in the rotational movement of the brake disc (especially a deceleration) results in a corresponding change in the rotational movement of the coupled wheel.

[0003] Such disc brakes are known from the prior art. At least one of the brake pads is moved toward the brake disc by a brake piston. The movement of the brake piston can be achieved, for example, hydraulically (usually during normal service braking) or by mechanical actuators (e.g., when parking). One of the problems, particularly with hydraulic braking systems, is restoring a certain clearance or gap (air clearance) between the brake disc and the friction material (brake pad) after braking and maintaining this clearance while driving.On the one hand, this gap must be sufficiently large (to avoid contact between the brake disc and the friction materials while driving or at least to keep it as small as possible), but on the other hand it must also be very small (on the one hand, to keep the brake piston stroke low during braking and thus to be able to quickly establish contact between the brake disc and the friction materials and on the other hand, to keep the pedal travel for the driver as short as possible).

[0004] However, even after braking has ended – i.e. while driving – contact between the brake disc and the friction materials can continue to occur due to, for example, unevenness or roughness caused by material deposits, or due to lateral runout of the brake disc. This can happen while the vehicle is in motion, particularly if the brake pad is not fully returned to its original position (i.e., its position relative to the brake disc before the braking operation, particularly the first braking operation performed with the brake in question). Such contact between the brake disc and the friction materials that remains after braking has ended creates a residual drag torque, i.e., an undesirable frictional resistance phenomenon occurs that has adverse effects such as increased brake pad wear, increased fuel consumption, annoying noise, and the like.In the literature, the terms "drag torque" or "residual braking torque" are also used. In English, the term "drag torque" is used.

[0005] To address this problem, design, CAE and test engineers have already developed a variety of approaches with regard to different elements of a disc brake, such as the piston / housing seal or the guide pin bushing.

[0006] Document DE 42 22 044 A1 discloses a hydraulic disc brake for bicycles, consisting of a brake caliper, a brake piston, and a guide cylinder, with which the braking system can be roughly pre-adjusted relative to the bicycle frame. The total play of the brake pads is pre-adjustable, and the center position of the brake caliper can be adjusted using an adjusting screw. The brake is designed for constant play in the unloaded state by springing the brake piston relative to the brake caliper. Furthermore, it features an adjustment feature that guarantees the center position of the brake disc relative to the brake pads in the brake caliper.

[0007] Furthermore, document DE 10 2017 202 813 A1 describes a braking system for a motor vehicle and a method for operating this braking system, wherein the braking system has a braking pressure source and at least one wheel brake which can be acted upon by a braking pressure acting on a brake piston and provided by means of the braking pressure source.

[0008] While many state-of-the-art solutions offer some improvements, they also have negative side effects, such as long pedal travel (poor pedal feel). Bushing solutions that rely on the lubricity of the rubber material can also be critical due to their dependence on temperature and surface treatment. The use of various chamfers (bevels) on the seal groove offers effective solutions, but due to the hyperplastic, homogeneous behavior of the seal material, the seal is compressed after braking, pushing the piston back toward the disc.

[0009] A special type of disc brake is a floating caliper brake. Here, the brake caliper (floating caliper) is movably mounted on at least one - usually two - sliding pins, which in turn are guided in a brake caliper carrier. An actuating device is attached to the brake caliper, which can act on a brake pad and bring it into contact with the brake disc. The counterforce moves the brake caliper in the opposite direction relative to the brake caliper carrier. After the brake caliper has finished applying the brake, the brake caliper carrier should be fully returned to its original position to prevent residual drag torque between the brake pad(s) and the brake disc. This, in turn, creates the problem that the brake caliper may not be fully returned to its original position.

[0010] There is therefore a need for a disc brake with improved properties with regard to the residual drag torque, in particular a disc brake with which the occurrence of a residual drag torque can be prevented or at least reduced, and which at the same time avoids the further disadvantages or negative side effects described above with regard to the prior art.

[0011] The object of the present invention is therefore to provide a solution with which the properties of a disc brake with regard to residual drag torque can be improved, i.e., the occurrence of residual drag torque can be prevented or reduced, and which simultaneously avoids the further disadvantages or negative side effects described above with reference to the prior art. This can be achieved by implementing a piston guide device according to one of claims 1 to 13 in a disc brake and by providing a floating caliper brake according to claim 14. Disclosure of the invention

[0012] The invention is defined by the appended claims. The following description of the invention is subject to the limitations defined by these claims. Any disclosure outside the scope of the claims is for illustrative or comparative purposes only.

[0013] One aspect of the invention relates to a piston guide device for a disc brake, comprising: a housing having a cavity for guiding a piston parallel to a designated direction; a piston which is displaceably mounted in the cavity parallel to the designated direction along its piston longitudinal axis between a first position and a second position, wherein the first position - viewed in the designated direction - is located in front of the second position; a first coil spring whose coils are formed around an axis parallel to the designated direction.One end of the first coil spring, viewed along the designated direction, is connected to the inner wall of the housing or supported on the inner wall of the housing in the direction of the designated direction, and the other end of the first coil spring, viewed along the designated direction, is connected to the piston or supported on the piston opposite to the designated direction. The coil spring is either unloaded when the piston is in the first position and loaded with a load when the piston is in the second position. Alternatively, the coil spring is loaded with a first load when the piston is in the first position and loaded with a second load when the piston is in the second position, the second load being greater than the first load.The housing of the piston guide device is firmly connected to a brake caliper carrier of the disc brake or integrated into the brake caliper carrier. Furthermore, a brake caliper of the disc brake is connected to the end of the piston pointing in the designated direction. At least one of the coil springs has two or more coil spring elements arranged one behind the other along the designated direction, with the coil spring elements themselves each being designed as coil springs.

[0014] Also disclosed is a disc brake for a motor vehicle, comprising: a brake caliper with an actuating device; a brake disc with a radius, wherein the brake disc is arranged to be rotatable relative to the brake caliper about a virtual axis of rotation, wherein the axis of rotation runs through the center of the brake disc and perpendicular to the brake disc; a brake pad which is mounted displaceably relative to the brake disc parallel to the axis of rotation, wherein the brake pad is located at least partially within a virtual cylinder which has the radius and whose cylinder axis coincides with the axis of rotation. The actuating device has a piston guide device according to the first aspect of the invention. The axis of rotation runs parallel to the designated direction. The end of the piston pointing in the designated direction is mechanically firmly connected to the brake pad.Viewed in the designated direction, the piston is located in front of the brake pad, and the brake pad is located in front of the brake disc. A clearance exists between the brake pad and the brake disc when the piston is in the first position relative to the housing. The brake pad is in contact with the brake disc when the piston is in the second position relative to the housing. The actuating device is configured to cause the piston to move relative to the housing from the first position to the second position in the designated direction.

[0015] A second aspect of the invention relates to a floating caliper brake for a motor vehicle, comprising: a brake caliper with an actuating device; a brake disc with a radius, wherein the brake disc is arranged to be rotatable relative to the brake caliper about a virtual axis of rotation, wherein the axis of rotation runs through the center of the brake disc and perpendicular to the brake disc; a brake pad which is mounted displaceably relative to the brake disc parallel to the axis of rotation, wherein the brake pad is located at least partially within a virtual cylinder which has the radius and whose cylinder axis coincides with the axis of rotation; a brake caliper carrier; and at least one piston guide device. The housing of the piston guide device is firmly connected to the brake caliper carrier or integrated into the brake caliper carrier. The axis of rotation runs parallel to the designated direction.The brake caliper is mounted for displacement along the designated direction by means of the piston of the piston guide device and is located—as viewed in the designated direction—behind the brake pad. The brake caliper is connected to the end of the piston pointing in the designated direction. The brake caliper has an actuating device designed to move the brake pad counter to the designated direction and bring it into contact with the brake disc.The piston guide device for a disc brake comprises: the housing with a cavity for guiding a piston parallel to a specific direction; the piston, which is displaceably mounted in the cavity parallel to the specific direction along its piston longitudinal axis between a first position and a second position, wherein the first position - viewed in the specific direction - is located in front of the second position; a first coil spring, the coils of which are formed about an axis parallel to the specific direction. Viewed along the specific direction, one end of the first coil spring is connected to the inner wall of the housing or is supported on the inner wall of the housing in the direction of the specific direction, and the other end of the first coil spring, viewed along the specific direction, is connected to the piston or is supported on the piston opposite to the specific direction.The coil spring is unloaded when the piston is in the first position and subjected to a load when the piston is in the second position, or the coil spring is subjected to a first load when the piston is in the first position and the coil spring is subjected to a second load when the piston is in the second position, wherein the second load is greater than the first load. According to the invention, at least one of the coil springs has two or more coil spring elements arranged one behind the other along the designated direction, wherein the coil spring elements are each themselves designed as coil springs.

[0016] Further aspects of the present disclosure emerge from the dependent claims or can be taken from the following description. Short description of the characters

[0017] The features will become clear to those skilled in the art from the detailed description of exemplary embodiments with reference to the accompanying drawings. Fig. 1 a typical disc brake 1 from the state of the art; Fig. 2 an excerpt from Fig. 1; Fig. 3 a first embodiment of the piston guide system according to the invention; Fig. 4 a second embodiment of the piston guide system according to the invention; Fig. 5 a third embodiment of the piston guide system according to the invention; Fig. 6 a fourth embodiment of the piston guide system according to the invention; Fig. 7 a fifth embodiment of the piston guide system according to the invention; Fig. 8 shows a sixth embodiment of the piston guide system according to the invention; Fig. 9 a seventh embodiment of the piston guide system according to the invention; Fig. 10 an eighth embodiment of the piston guide system according to the invention. Detailed description of the invention

[0018] Hereinafter, preferred embodiments and features of the present invention will be described in more detail with reference to the accompanying drawings, which show exemplary embodiments of the invention. Throughout the drawings, like reference numerals refer to like elements. Conversely, however, like corresponding elements in different drawings may be provided with different reference numerals if a portion of the description is intended to refer to a particular drawing. Redundant descriptions will be omitted. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed elements. Furthermore, the use of "may" when describing embodiments of the present invention refers to "one or more embodiments of the present invention."

[0019] It should be understood that terms such as "first" and "second" are used to describe various elements, but these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of the present invention.

[0020] In the following description of embodiments of the present invention, the use of the singular may also include the plural, unless the context clearly indicates otherwise.

[0021] Relative terms describing spatial relationships such as “beneath,” “below,” “above,” “above,” “above,” “spaced apart,” and the like may be used hereinafter to simplify the description, whereby the spatial relationship of one element or feature to another element or feature is then to be understood as shown in the figures. If one or more coordinate systems are included in a figure, relative terms may also refer to a coordinate system; this is generally expressly indicated in the relevant passage of the description. It is to be understood that the spatially relative terms are intended to include various orientations of the device used in addition to the orientation shown in the figures. For example, if a device shown in the drawings (and possibly also each of the included coordinate systems) is with respect toIf the horizontal plane of the figure in question is flipped / mirrored, elements described as "below" other elements or features would consequently be positioned "above" the other elements or features. The device may be oriented differently (e.g., rotated by 90° or in other orientations); in this case, the prepositions used here to describe spatial relations should be reinterpreted accordingly.

[0022] It is also understood that when a first element or layer is described as being "attached to" a second element or layer, the first layer or element may be attached directly to the second element or layer, or it may be attached to the second element or layer by means of one or more intervening other elements or layers. Furthermore, it is also understood that when an element or layer is described as being "between" two other elements or layers, it may be the only element or layer between the two other elements or layers, or there may be one or more intervening other elements or layers.

[0023] Unless expressly defined otherwise, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It is further understood that terms as defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning in the context of the relevant prior art and / or the present specification, i.e., they should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. General concept of the invention

[0024] One aspect of the invention relates to a piston guide device for a disc brake, comprising: a housing having a cavity for guiding a piston parallel to a designated direction; a piston which is displaceably mounted in the cavity parallel to the designated direction along its piston longitudinal axis between a first position and a second position, wherein the first position - viewed in the designated direction - is located in front of the second position; a first coil spring whose coils are formed around an axis parallel to the designated direction.One end of the first coil spring, viewed along the designated direction, is connected to the inner wall of the housing or supported on the inner wall of the housing in the direction of the designated direction, and the other end of the first coil spring, viewed along the designated direction, is connected to the piston or supported on the piston opposite to the designated direction. The coil spring is either unloaded when the piston is in the first position and loaded with a load when the piston is in the second position. Alternatively, the coil spring is loaded with a first load when the piston is in the first position and loaded with a second load when the piston is in the second position, the second load being greater than the first load.The housing of the piston guide device is firmly connected to a brake caliper carrier of the disc brake or integrated into the brake caliper carrier. Furthermore, a brake caliper of the disc brake is connected to the end of the piston pointing in the designated direction. At least one of the coil springs has two or more coil spring elements arranged one behind the other along the designated direction, with the coil spring elements themselves each being designed as coil springs.

[0025] The phrase "supported in the direction of the specified direction" in connection with the helical spring is intended to mean that an extension of the helical spring (and thus in particular its end pointing in the specified direction) in the specified direction beyond the position of the corresponding support is not possible (i.e., is blocked by the support). Accordingly, the phrase "supported against the specified direction" in connection with the helical spring is intended to mean that an extension of the helical spring (and thus in particular its end pointing against the specified direction) in the opposite direction beyond the position of the corresponding support is not possible.However, the position of a support may be shiftable, meaning the coil spring may extend beyond the original position of the support in question if the support moves away from the coil spring. The displacement may be caused by the coil spring itself.

[0026] Coil springs consist of a spring wire that revolves around a (virtual) axis (spring axis), similar to the shape of a screw thread. In this way, a coil spring (sometimes abbreviated to "spring" below) has one or usually several coils, i.e., revolutions of the coil wire by 360° around the spring axis of the coil spring, with the beginning and end of each coil offset in relation to the axis. The number of coils does not have to be an integer; for example, the last (or first) coil can be only half a coil, a third of a coil, or a quarter of a coil. The radius of the coils (i.e., the distance of the spring wire from the axis) can vary along the axis. In such cases, a variation in the radius is typically even present within a single coil. If the radius decreases or increases monotonically along the axis, the spring is also referred to as "conical springs."Instead of a spring wire, a coil spring can also be realized using a spring band.

[0027] The addition of “virtual” to a geometric term (e.g. an axis or circle, cylinder, etc.) is intended above and below to clarify that the geometric term is used purely to describe the arrangement, without, however, there necessarily having to be a component that is designed in the corresponding geometric shape.

[0028] The spring wire or spring strip is made of an elastic material, preferably an elastic metal (e.g. steel or a steel alloy, copper or a copper alloy, or the like). After deformation (i.e., under load), the coil spring attempts to return to its original shape. When subjected to a load, the spring absorbs mechanical energy (in the form of torsional stress in the spring wire). The load can compress the spring along its spring axis (compression load) or stretch it (tension load). Due to the elasticity of its material, in the first case, a compression load, the spring attempts to expand again along the spring axis; in the second case, a tension load, the spring attempts to contract again along the spring axis. In both cases, a corresponding counterforce (restoring force) is exerted on the load.

[0029] When reference is made to "the coil spring" or "the spring" in the following, the corresponding description refers to the first coil spring, unless expressly stated otherwise. However, in embodiments with more than one coil spring (see below), the same may apply to additional coil springs.

[0030] The above structure implies that there is a member on the piston for connecting the spring to the piston or for supporting the spring to the piston in the direction of the designated direction, and that there is a member on the inner wall of the cavity for connecting the spring to the inner wall or for supporting the spring to the inner wall opposite to the designated direction.

[0031] The piston is mounted in the cavity, but can protrude from the cavity at least in the designated direction. This allows it to be attached directly to a brake pad of a conventional disc brake or to the brake caliper of a floating-caliper brake. Otherwise, the connection between the piston and the brake pad or caliper must be established indirectly.

[0032] When the piston is displaced in the designated direction relative to the housing, the coil spring is loaded (i.e., the spring is deformed and thus tensioned by compression or extension along the designated direction, i.e., its spring axis, depending on the design). Since the spring is attached at one end to the inner wall of the cavity or is supported on the inner wall of the cavity in the designated direction (i.e., this end cannot be displaced in the designated direction), the spring creates a reaction force (restoring force) that attempts to drive the piston coupled to the other end of the spring against the designated direction.

[0033] The arrangement described above further implies that the coil spring is located between the connection of the coil spring to the piston or the support of the coil spring on the piston and the connection of the coil spring to the inner wall of the cavity or the support of the coil spring on the inner wall of the cavity.

[0034] Preferably, the coil spring is located entirely within the cavity. This allows for a simple design of the device and also protects the spring from contamination (e.g., particles worn off from brake pads).

[0035] In embodiments of the piston guide device, the end of the piston facing in the designated direction can be mechanically and firmly connected to a brake pad. The brake pad itself is therefore not part of the piston guide device, but can be connected to it in a suitable manner, namely by firmly attaching the brake pad to the end of the piston facing in the designated direction.

[0036] In alternative embodiments of the piston guide device, the end of the piston pointing in the designated direction can be mechanically and firmly connected to the brake caliper of a floating-caliper brake. The brake caliper of the floating-caliper brake is therefore not itself part of the piston guide device, but can be connected to it in a suitable manner, namely by firmly attaching the brake caliper to the end of the piston pointing in the designated direction.

[0037] In one embodiment of the piston guide device, the spring is not subjected to a load (relaxed) when the piston is in the first position (or the first load is zero when the piston is in the first position).

[0038] In an alternative embodiment, the spring is loaded (preloaded) when the piston is in the first position.

[0039] The connection between the spring and the piston or the inner wall of the cavity can be achieved by means of an annular groove, or alternatively by welding, one or more projections, edges, etc. The connection can be permanent. The connection can be detachable. The latter has the advantage that the spring or the components coupled to it (piston, housing) are replaceable.

[0040] The cavity can be a drilled hole. Other shapes are possible, although less advantageous in manufacturing.

[0041] In one embodiment of the piston guide device, at least some of the turns of the first coil spring are arranged so as to surround the piston.

[0042] In other words, at least a portion of the piston is pushed along or opposite to the designated direction through at least a portion of the coils of the helical spring or is arranged within at least a portion of the coils. In preferred embodiments, all coils of the helical spring encircle the piston.

[0043] Such an arrangement of piston and coil spring has the advantage that, viewed along the designated direction, no additional space, or at least less additional space, is required for the coil spring besides the space occupied by the piston. This arrangement has the further advantage that the coil spring is stabilized by the piston, as the center of the coils is held in a position on the piston axis by the piston rod. Compression of the spring cannot displace it (or at least not arbitrarily far) in the radial direction from its position on the piston axis.

[0044] In one embodiment of the piston guide device, the connection of the first coil spring to the piston or the support of the coil spring on the piston is arranged in the direction of the marked direction before the connection of the first coil spring to the inner wall of the cavity or the support of the first coil spring on the inner wall of the cavity.

[0045] In this case, the spring is compressed (along the designated direction) (i.e., the coils move closer together, the elastic material of the spring is deformed, and thus the spring absorbs stress energy) when the piston is moved from its initial position in the designated direction relative to the housing. The spring is thus loaded "in compression."

[0046] In an alternative embodiment, the connection of the coil spring to the piston or the support of the coil spring on the piston is arranged behind the connection of the coil spring to the inner wall of the cavity or the support of the coil spring on the inner wall of the cavity, as seen in the direction of the marked direction.

[0047] In this case, the spring is stretched (along the designated direction) (i.e., the coils move away from each other, the elastic material of the spring is deformed, and thus the spring absorbs stress energy) when the piston is moved from its initial position in the designated direction relative to the housing. In this case, the spring is loaded "in tension."

[0048] Precise control of the spring tension of the coil spring under load, i.e., as a function of the piston's deflection parallel to the specified direction from the initial position, can be achieved using various methods, some of which can also be combined with one another. The spring tension of the coil spring can be controlled by the spring's elasticity, which must therefore be selected according to the specific requirements. For example, the elasticity of the coil spring can be adjusted by the elasticity of the materials used in the coil spring and / or by the thickness of the spring wire or spring strip used.

[0049] In particular, a linear behavior of the spring tension can be achieved over the entire required displacement range of the piston, e.g. over a distance of 12 mm.

[0050] In one embodiment, the piston guide device comprises at least one further coil spring, wherein for each of the further coil springs, one end of the respective coil spring is connected to the inner wall of the housing or is supported on the inner wall of the housing in the direction of the designated direction, and the other end of the respective coil spring is connected to the piston or is supported on the piston opposite to the designated direction, as viewed along the designated direction.

[0051] In such a structure, the coils of the different springs are typically “twisted” together, i.e., viewed along the designated direction, the coils of different springs alternate and / or cross each other.

[0052] In embodiments, for example, exactly two or exactly three or exactly four coil springs can be used.

[0053] The support on the piston and / or the inner wall of the housing can be indirect, i.e., for example, the first turn of one of the additional springs, viewed in the designated direction, can be supported on the first turn of the first spring, with the first turn of the first spring in turn being connected to the piston or being supported on the piston opposite to the designated direction. However, with three or more springs, for example, the first turn of one of the additional springs, viewed in the designated direction, can also be supported on the first turn of one of the other additional springs, and so on. The same applies to the last turns of the respective springs.

[0054] In one embodiment of the piston guide device, at least one of the coil springs is made of a material or has a material that is different from the material(s) from which at least one of the other coil springs is made or which is contained in at least one of the other coil springs.

[0055] For example, in embodiments, all springs may be made of a different material than the material of each of the other springs. In other words, in any pair of two springs of the piston guide device, the two springs are made of different materials.

[0056] In one embodiment of the piston guide device, at least one of the coil springs has an elasticity that is different from the elasticity of at least one of the other coil springs.

[0057] For example, in embodiments, all springs may have an elasticity that is different from the elasticity of each of the other springs. In other words, in any pair of two springs of the piston guide device, the two springs have different elasticity.

[0058] In one embodiment of the piston guide device, the radius of the coils varies along the designated direction for at least one of the coil springs. For example, in some embodiments, the first spring can be designed as a conical spring.

[0059] In one embodiment of the piston guide device, the thickness of the spring wire of the coil spring varies along the specified direction for at least one of the coil springs. The thickness of a spring wire is understood here and below to be the diameter of the spring wire (at a specific point along the spring wire).

[0060] In embodiments, the thickness of the spring wire may increase or decrease monotonically along the designated direction. In general, both the (average) radius of a coil and the (average) thickness of the spring wire of a coil influence the elasticity of the corresponding coil.

[0061] In one embodiment of the piston guide device, one or more of the coil springs are made of plastic. As is clear from the foregoing, the plastic must be elastic. In some embodiments, all of the coil springs can also be made of plastic.

[0062] In one embodiment of the piston guide device, one or more of the coil springs (60, 60') are each made of metal. Preferably, the metal is steel or copper. In some embodiments, all coil springs can also be made of metal.

[0063] In one embodiment of the piston guide device, at least one of the coil springs is manufactured using an injection molding process. In other embodiments, all coil springs can also be manufactured using an injection molding process.

[0064] In one embodiment of the piston guide device, at least one of the coil springs is manufactured using a 3D printing process. In some embodiments, all coil springs can also be manufactured using 3D printing.

[0065] In one embodiment of the piston guide device, at least one of the coil springs is designed symmetrically with respect to its respective inlet and outlet sides. In some embodiments, all coil springs can also be designed symmetrically with respect to their respective inlet and outlet sides.

[0066] In one embodiment of the piston guide device, at least one of the coil springs is designed asymmetrically with respect to its respective inlet and outlet sides. In some embodiments, all coil springs can also be designed asymmetrically with respect to their respective inlet and outlet sides.

[0067] The springs can therefore be symmetrical or asymmetrical with respect to their inlet and outlet sides. This depends, for example, on the CAE simulation results for the desired pad rebound and / or on the design and configuration, as some brake calipers may not be symmetrical. Thus, for example, the same spring types can be used in certain embodiments, but with different characteristics, or alternatively, two (or more) different spring designs can be used.

[0068] Due to the complexity of the spring and depending on the stiffness calculation, two or more small springs can be inserted one after the other in the switching system instead of one spring.

[0069] For example, in embodiments, a first coil spring element may be connected to the piston at a first end or supported thereon and connected to the second coil spring element at the other end (ends in each case relative to the designated direction) or supported against the latter, while the second coil spring element is connected to the housing inner wall at one end or supported thereon and connected to the first coil spring element at the other end or supported against the latter.

[0070] Two adjacent coil spring elements can be firmly connected to each other or designed so that they can support each other.

[0071] In embodiments, at least one of the coil spring elements may be made of a material or comprise a material that is different from the material(s) from which at least one of the other coil spring elements is made or that is included in at least one of the other coil spring elements.

[0072] In embodiments, at least one of the coil spring elements may have an elasticity that is different from the elasticity of at least one of the other coil spring elements.

[0073] In embodiments, the radius of the coils may vary along the marked direction for at least one of the coil spring elements.

[0074] In embodiments, at least for one of the coil spring elements, the coils may have a radius that is different from the radius of the coils of at least one of the other coil spring elements.

[0075] In embodiments, the thickness of the spring wire or spring band of the coil spring may vary along the designated direction for at least one of the coil spring elements.

[0076] In embodiments, at least for one of the coil spring elements, the spring wire may have a thickness that is different from the thickness of the spring wire of at least one of the other coil spring elements.

[0077] In one embodiment of the piston guide device, at least one coil spring element is made of plastic. In other embodiments, all coil spring elements can also be made of plastic.

[0078] In one embodiment of the piston guide device, at least one coil spring element is made of metal. In other embodiments, all coil spring elements can also be made of metal.

[0079] In one embodiment of the piston guide device, at least one coil spring element is manufactured using the injection molding process. In some embodiments, all coil spring elements can also be manufactured using the injection molding process.

[0080] In one embodiment of the piston guide device, at least one coil spring element is manufactured using 3D printing methods (particularly additive manufacturing or regenerative processes). In other embodiments, all coil spring elements can also be manufactured using 3D printing methods.

[0081] In one embodiment of the piston guide device, at least one coil spring element is designed symmetrically with respect to its respective inlet and outlet sides. In other embodiments, all coil spring elements can also be designed symmetrically with respect to their respective inlet and outlet sides.

[0082] In one embodiment of the piston guide device, at least one coil spring element is designed asymmetrically with respect to its respective inlet and outlet sides. In other embodiments, all coil spring elements can also be designed asymmetrically with respect to their respective inlet and outlet sides.

[0083] The selection of which spring (or combination of springs and / or combination of coil spring elements) is suitable for a specific application is preferably made on the basis of CAE studies and validation with test results.

[0084] Furthermore, the respective shape of each of the coil springs and / or each of the coil spring elements is preferably designed such that each of the coil springs and / or each of the coil spring elements has a (at least almost) constant characteristic curve.

[0085] The following also describes a disc brake for a motor vehicle, comprising: a brake caliper with an actuating device; a brake disc with a radius, wherein the brake disc is arranged to be rotatable relative to the brake caliper about a virtual axis of rotation, wherein the axis of rotation runs through the center of the brake disc and perpendicular to the brake disc; a brake pad which is mounted displaceably relative to the brake disc parallel to the axis of rotation, wherein the brake pad is located at least partially within a virtual cylinder which has the radius and whose cylinder axis coincides with the axis of rotation. The actuating device has a piston guide device according to the first aspect of the invention. The axis of rotation runs parallel to the designated direction. The end of the piston pointing in the designated direction is mechanically firmly connected to the brake pad.Viewed in the designated direction, the piston is located in front of the brake pad, and the brake pad is located in front of the brake disc. A clearance exists between the brake pad and the brake disc when the piston is in the first position relative to the housing. The brake pad is in contact with the brake disc when the piston is in the second position relative to the housing. The actuating device is configured to cause the piston to move relative to the housing from the first position to the second position in the designated direction.

[0086] The piston of the piston guide device therefore acts as a brake piston.

[0087] Since, as already explained in connection with the brake pad guide according to the invention, the load (spring tension) applied to the spring is greater in the second position of the piston than the load when the piston is in the first position, the spring (due to its elasticity) attempts to return to the less loaded state, thereby exerting a restoring force on the piston, which drives it to the first position. This restoring force is in turn transferred from the piston to the brake pad, which then releases from the brake disc, creating a clearance between the brake pad and the brake disc.

[0088] The piston can be mechanically connected directly or indirectly to one of the brake pads. However, the brake pad can be detachably attached to the piston to allow for replacement if necessary.

[0089] In embodiments, the disc brake according to the invention can have an additional brake pad. This can be arranged opposite the first brake pad with respect to the brake disc.

[0090] In embodiments, the actuating device of the disc brake can be hydraulically operated.

[0091] A second aspect of the invention relates to a floating caliper brake for a motor vehicle, comprising: a brake caliper with an actuating device; a brake disc with a radius, wherein the brake disc is arranged to be rotatable relative to the brake caliper about a virtual axis of rotation, wherein the axis of rotation runs through the center of the brake disc and perpendicular to the brake disc; a brake pad which is mounted displaceably relative to the brake disc parallel to the axis of rotation, wherein the brake pad is located at least partially within a virtual cylinder which has the radius and whose cylinder axis coincides with the axis of rotation; a brake caliper carrier; and at least one piston guide device. The housing of the piston guide device is firmly connected to the brake caliper carrier or integrated into the brake caliper carrier. The axis of rotation runs parallel to the designated direction.The brake caliper is mounted for displacement along the designated direction by means of the piston of the piston guide device and is located—as viewed in the designated direction—behind the brake pad. The brake caliper is connected to the end of the piston pointing in the designated direction. The brake caliper has an actuating device designed to move the brake pad counter to the designated direction and bring it into contact with the brake disc.The piston guide device for a disc brake comprises: the housing with a cavity for guiding a piston parallel to a specific direction; the piston, which is displaceably mounted in the cavity parallel to the specific direction along its piston longitudinal axis between a first position and a second position, wherein the first position - viewed in the specific direction - is located in front of the second position; a first coil spring, the coils of which are formed about an axis parallel to the specific direction. Viewed along the specific direction, one end of the first coil spring is connected to the inner wall of the housing or is supported on the inner wall of the housing in the direction of the specific direction, and the other end of the first coil spring, viewed along the specific direction, is connected to the piston or is supported on the piston opposite to the specific direction.The coil spring is unloaded when the piston is in the first position and subjected to a load when the piston is in the second position, or the coil spring is subjected to a first load when the piston is in the first position and the coil spring is subjected to a second load when the piston is in the second position, wherein the second load is greater than the first load. According to the invention, at least one of the coil springs has two or more coil spring elements arranged one behind the other along the designated direction, wherein the coil spring elements are each themselves designed as coil springs.

[0092] In the floating caliper brake according to the invention, the piston of the piston guide device therefore functions as a sliding bolt for the brake caliper, on which the brake caliper is “floatingly” mounted.

[0093] In embodiments, the floating caliper brake according to the invention can have an additional brake pad. This can be arranged opposite the first brake pad with respect to the brake disc.

[0094] In embodiments, the actuating device of the floating caliper brake can be hydraulically operated. Special embodiments

[0095] Specific embodiments of the invention are discussed in more detail below. For illustrative purposes or for comparison purposes, reference is also made to the prior art, which is briefly explained or outlined in one or more figures.

[0096] Fig. Figure 1 shows a typical prior art disc brake 1. To simplify the description, a coordinate system with a longitudinal axis z and a radial axis r is included. The illustrated 2-dimensional coordinate system can be understood as a planar section through a cylindrical coordinate system, wherein the section plane contains the longitudinal axis z and corresponds to the drawing plane of the figure. The disc brake 1 has a substantially rotationally symmetrical brake disc 50 with a radius R, which is mounted for rotation about an axis of rotation D running through the center of the brake disc 50. In the figure, the axis of rotation D coincides with the longitudinal axis z of the coordinate system.When implementing the disc brake 1 in a vehicle, the central region 50a of the brake disc 50 is firmly coupled to the wheel axle of the wheel (not shown) that is to be braked by the disc brake 1, wherein the wheel axle is in turn aligned along the rotational axis D or the longitudinal axis z of the coordinate system.

[0097] Two brake pads, a first brake pad 40a and a second brake pad 40b, are arranged spaced apart in the radial direction r from the rotational axis D. These pads are arranged one behind the other and spaced apart from one another, as viewed in the longitudinal direction z, such that a radially outer region 50b of the brake disc 50 can rotate between the two brake pads 40a, 40b. The brake pads 40a, 40b are held by a brake caliper 20, which surrounds the brake disc 50 in a radially outer region. At least one of the two brake pads 40a, 40b (the first brake pad 40a on the left in the figure) is mounted so as to be displaceable along the z-direction (i.e., parallel to the z-axis or rotational axis D). This is made possible by a brake piston 30, the piston longitudinal axis A of which is aligned along the z-direction and which is guided in a corresponding borehole (not shown) which is displaceable along the z-direction.The end of the brake piston 30 facing the brake disc 50 is firmly connected to the side of the first brake pad 40a facing away from the brake disc 50. A movement of the brake piston 30 along the z-direction is thus transmitted directly to the first brake pad 40a.

[0098] If no braking is to be carried out, i.e., during normal driving of the motor vehicle, the brake disc 50 should be able to rotate freely between the two brake pads 40a, 40b. For this purpose, the brake pads 40a, 40b must each be positioned at a distance from the brake disc 50, i.e., a first clearance L1 must be present between the first brake pad 40a and the brake disc 50, and a second clearance L2 must be formed between the second brake pad 40b and the brake disc 50. This relative position of the brake pads 40a, 40b and the brake disc 50 to one another is referred to below as the "initial position". The initial position is Fig. 2, which shows a section of Fig. 1, which includes the two brake pads 40a, 40b and the upper area of ​​the brake disc 50. Typical values ​​for the spacing between a brake pad and brake disc in the initial position are approximately between 0.1 and 0.3 mm.

[0099] In order to initiate a braking action, the brake pads 40a, 40b must each be brought into contact with the brake disc 50. To do this, the brake piston 30 must be moved in the z-direction so that the first brake pad 40a connected to the brake piston 30 is pressed against the brake disc 50, thus creating friction between the friction material of the first brake pad 40a and the left side of the brake disc 50. The force thus acting on the brake disc 50 in the z-direction also moves the outer region 50b of the brake disc 50 in the z-direction - in the area between the brake pads 40a, 40b - and thus brings it into contact with the second brake pad 40b. This now also creates friction between the friction material of the second brake pad 40b and the left side of the brake disc 50.The described friction phenomena now cause a deceleration of the rotational movement of the brake disc 50 relative to the brake caliper 20 (which is permanently installed in the vehicle), wherein the deceleration is transferred to the rotational movement of the wheel through the coupling of the brake disc 50 with the wheel.

[0100] As already mentioned in the introduction, various methods have been developed in the prior art to return the relative position of the brake pads 40a, 40b and the brake disc 50 to one another back to the initial position described above. In hydraulic brake systems (i.e., when the displacement of the brake piston 30 in the direction of the brake disc 50 is effected hydraulically during braking), the elasticity of a sealing ring (not shown) attached to the brake piston 30, which is deformed by the displacement of the brake piston 30, can be utilized, for example. The elastic deformation of the sealing ring then causes a restoring force acting on the brake piston 30, which, after the end of the braking process (i.e., after the hydraulic pressure acting on the brake piston 30 has been released), moves the brake piston 30 against the z-direction towards its initial position (i.e., into its position relative to the brake caliper 20 when the brake pads 40a, 40b are in the initial position). However, as already described above, such braking systems have a number of disadvantages.

[0101] According to the invention, a piston guide device is therefore provided which, after completion of a braking operation, allows a reliable return of a guide piston 70 to its initial position. An embodiment of such a piston guide device is shown schematically in longitudinal section in Fig. 3. The guide piston 70 is arranged displaceably along its longitudinal axis A (which in turn is aligned parallel to the z-axis of the coordinate system described above) in a longitudinal cavity 88 of a housing 80.

[0102] Guide piston 70 and housing 80 are designed to be rotationally symmetrical with respect to the piston's longitudinal axis A, i.e., guide piston 70 and housing 80 have a rotationally symmetrical cross-section. In this case, the cavity 88 can be designed as a borehole. In alternative embodiments, however, guide piston 70 and housing 80 can also have other cross-sections. In particular, guide piston 70 can function as a brake piston in that a brake pad (not shown in the figure) can be attached to its second end 72b pointing in the z-direction. The opposite first end 72a can be connected to a suitable actuating device (not shown), by means of which guide piston 70 can be moved in the z-direction within the housing.

[0103] The guide piston 70 has two sections with different radii (relative to the piston's longitudinal axis A), which are arranged one behind the other in the z-direction. The first guide piston section 70a has a larger radius R1 than the second guide piston section 70b, which has a radius R2 and is arranged behind the first guide piston section 70a in the z-direction, i.e., R1 > R2. The two guide piston sections 70a, 70b are each cylindrical. Therefore, an edge 74—which is naturally also rotationally symmetrical—is formed at the transition between the first guide piston section 70a and the second piston section 70b.

[0104] In the area of ​​the second guide piston section 70b, there is also a helical spring 60 with a plurality of turns (schematically shown in the figure by five turns 601, 602, 603, 604, 605), each winding around the second guide piston section 70b. The first turn 601, viewed in the z-direction, is supported by the edge 74 opposite to the z-direction or is fastened to the guide piston 70 in the position shown. In addition, an annular groove 90 (annular groove) is formed on the inner wall of the housing 80, i.e., on the wall of the cavity 88, in which the last turn 605, viewed in the z-direction, of the helical spring 60 can be fastened. The fastening can be achieved, for example, by snapping the last turn 605 into place, i.e., the last turn 605 is supported in the z-direction by an edge 94 created by the groove 90, so that the last turn 605 is fixed in the z-direction at the position of the groove 90 or at least cannot move beyond the position of the groove 90.

[0105] In Fig. In Figure 3, the coils of the helical spring 60 are schematically illustrated as vertical bars for the sake of simplicity. It is understood that the coils (with the possible exception of the first coil 601 and / or the last coil 605) in reality each have a certain inclination (more precisely: with respect to a plane perpendicular to the plane of the drawing, the tangent to the course of the spring wire has a slight inclination angle not equal to 0 at any position between the edge 74 and the groove 90), so that the coils in the view of the figure actually have a sinusoidal course and should be drawn approximately as bars slightly inclined with respect to the radial axis r. This also applies accordingly to the following figures. It is further understood that coil springs with more or fewer than five coils can also be used in embodiments of the piston guide device.

[0106] Fig. 3A shows a state of the piston guide device in which the guide piston 70 is in an initial position, ie, in a certain predefined position relative to the housing 80. In this state of the piston guide device, the coil spring 60 is unloaded, ie, it is not elastically deformed by a force, in particular in or against the z-direction.

[0107] In contrast, Fig. 3B shows a state of the piston guide device in which - for example driven by a hydraulic actuating device (not shown) - the guide piston 70 is moved relative to the initial position ( Fig. 3A) has been displaced by a distance Δz in the z-direction. Since the coil spring 60, as described above, is fixed or supported by its two outer coils 601, 605 on the edge 74 of the guide piston 70 or by the groove 90, it follows that the coil spring 60 has been compressed and thus elastically deformed during the displacement of the guide piston 70 along the z-direction. In other words, the coil spring 60 is subjected to a load in the state shown and has absorbed deformation energy (spring tension).This deformation energy causes both a force to act in the z-direction on the right-hand side edge 94 of the groove 90 and a force to act counter to the z-direction on the edge 74 of the guide piston 70, so that a relative movement of the guide piston 70 counter to the z-direction is caused with respect to the housing 80 as soon as the force acting on the guide piston 70 in the z-direction by the actuating device decreases or disappears after the braking process. In the latter case, the coil spring 60 can return to its shape in the unloaded state, thereby pushing the guide piston 70 counter to the z-direction into the position shown in . Fig. Return to the starting position shown in Figure 3A.

[0108] In the above-described embodiment, the coil spring 60 is unloaded when the guide piston 70 is in the starting position. In alternative embodiments, however, the coil spring 60 can also be preloaded when the guide piston 70 is in the starting position, ie, the coil spring 60 is then already loaded in the starting position. As a result, an overall higher spring tension and thus spring force can be achieved compared to the above-described embodiment, so that the guide piston 70 can be returned with a higher restoring force from the Fig. 3B shown position to the starting position of Fig. 3A can be moved back. In such an embodiment, it is of course important to ensure that the guide piston 70 - despite the preload of the spring 60 in the initial position - does not move against the z-direction beyond the Fig. 3A. This can be achieved, for example, by a blocking at a suitable position on the inner wall of the housing 80 (for example by a - preferably annular - projection directly to the left of the position of the first guide piston end 72a in Fig. 3A).

[0109] In the example of Fig. 3, the helical spring 60 is designed as a so-called "conical spring," i.e., the radius of its coils relative to the shown axis A changes monotonically in the z-direction, for example, in a linear manner. Here, the radius of the coils 601, 602, 603, 604, 605 increases. The last coil 605 has a radius that is larger than the radius of the inner wall of the cavity 88, so that the last coil 605 can be engaged with the annular groove 90 located in the inner wall of the cavity 88 and thus firmly fixed to the housing 80. Conversely, the first winding 601 has a smaller radius than the first guide piston section 70a, so that it is supported counter to the z-direction against the edge 74 formed perpendicular to the axis A (i.e. in the radial direction) between the first guide piston section 70a and the second guide piston section 70b.

[0110] If the space between the edge 74 of the guide piston 70 and the groove 90 is dimensioned such that it is no longer along the z-direction than the dimension of the spring 60 between its outer ends (i.e., the respective outer sides of the first and last coils 601, 605), the outer coils 601, 605 do not necessarily have to be fixed to the guide piston 70 or to the inner wall of the housing 80. Rather, it is sufficient that the first coil 601 is supported by the edge 74 opposite to the z-direction and, correspondingly, the last coil 605 is supported in the z-direction on the inner wall of the housing 80. In embodiments, the groove 90 can therefore also be replaced by an annular, inwardly directed projection 80a (relative to the axis A), which is formed on the inner wall of the housing 80 such that an inner wall edge 84 is created. This is shown in Fig. 4 shown schematically. Instead of fixing the last turn 605 in the annular groove 90 ( Fig. 3) In such embodiments, a support of the last winding 605 in the z-direction occurs (ie, a movement of the last winding 605 in the z-direction beyond the position of the inner wall edge 84 is blocked by the inner wall edge 84). Otherwise, the structure and design of the piston guide device essentially correspond to that described in the context of Fig. 3. Furthermore, in embodiments, instead of a continuous annular projection 80a, a plurality of projections can alternatively be used that are located at the same position in the z-direction but are not connected to one another. Preferably, three or more projections are then used, which are arranged symmetrically with respect to the axis A.

[0111] The elastic properties of the coil spring 60 can be suitably selected using a variety of parameters. For example, the material of the coil spring 60 (e.g., a steel or copper alloy) or the thickness of the spring wire or spring band can be suitably selected. Such and similar properties can be easily combined in embodiments of the piston guide device by using multiple coil springs instead of a single coil spring. Such an embodiment is shown schematically in Fig. 5. The structure and design of guide piston 70 and housing 80 essentially correspond to that described in the context of Fig. 4. In addition to a first coil spring 60, which here has three coils 601, 602, 603, a second coil spring 60' is implemented, which also has three coils 601', 602', 603'. The first coil 601 of the first screwdriver 60, as viewed in the z-direction, is supported on the edge 74 of the guide piston 70, while the first coil 601' of the second spring 60', as viewed in the z-direction, is in turn supported on the first coil 601 of the first spring 60. On the opposite side, the last turn 603' of the second coil spring 60', seen in the z-direction, is supported on the inner wall edge 84 of the cavity 88, while the last turn 603 of the first spring 60 is supported in the z-direction against the last turn 603' of the second coil spring 60'.

[0112] In the exemplary embodiment shown, coil springs 60, 60' are designed as conical springs and furthermore have the same number of coils, so that the coils can be guided essentially parallel and therefore do not cross over. In alternative embodiments, however, coil springs with a different number of coils can also be used; in this case, the two spring wires cross over at least at one point. Care must first be taken to ensure that the radii of the corresponding coils at which a crossover occurs are selected such that, on the one hand, the springs do not hook into each other and, on the other hand, there is sufficient space in the radial direction for the crossover(s). Furthermore, in alternative embodiments, more than two coil springs can also be used in a corresponding manner.

[0113] The elastic properties of the first spring 60 and the second spring 60' can be in the embodiment of Fig. 5 can be selected differently from each other, for example, by using different materials and / or different thicknesses for the corresponding spring wires. This allows the elasticity of the overall structure consisting of both springs 60, 60' to be very precisely adapted to the required properties.

[0114] Fig. 6 schematically illustrates a further embodiment of the piston guide device according to the invention, which essentially corresponds to the embodiment of Fig. 5, in which, however, the thickness of the spring wires varies along the z-direction for both springs 60, 60'. In particular, the respective middle coils 602, 602' of the two springs 60 and 60' have a smaller thickness than the respective outer coils 601, 603 and 601', 603'. This can, for example, reinforce the spring wires at the respective support positions in order to counteract excessive wear of the springs at these locations.

[0115] Fig. Figure 7 shows schematically another embodiment of the piston guide device according to the invention, which is similar to that of Fig. 5, if the two coil springs 60, 60' were used in reverse with respect to the z-direction. The structure shown here differs from that shown in Fig. 5, however, is further distinguished by the fact that not two coil springs are used here, but rather a single coil spring 60 composed of three interconnected coil spring elements 61, 62, 63 (coil spring system), each of the coil spring elements 61, 62, 63 in the example shown having two coils (the first coil spring element 61, viewed in the z-direction, has two coils 611, 612, the middle coil spring element 62 comprises the two coils 621 and 622, and the last coil spring element 63 comprises the two coils 631 and 632). The first coil 611, viewed in the z-direction, of the first coil spring element 61 rests on the edge 74 of the guide piston 70, and the last coil 632 of the third coil spring element 63 rests on the inner wall edge 84 of the housing 80.Furthermore, the second turn 612 of the first coil spring element 61 is connected to the first turn 621 of the middle coil spring element 62, and the second turn 622 of the middle coil spring element 62 is connected to the first turn 631 of the last coil spring element 63.

[0116] The elastic properties of the three coil spring elements 61, 62, 63 can be in the embodiment of Fig. 7 can be selected differently from one another, for example, by using different materials and / or different thicknesses for the corresponding spring wires. This allows the elasticity of the entire coil spring 60 to be very precisely adapted to the required properties.

[0117] It is understood that in alternative embodiments, only two or even more than three coil spring elements can be used instead of three. Furthermore, it is not absolutely necessary for the various coil spring elements to be firmly connected to one another; rather, it is usually sufficient for adjacent coil spring elements to support one another. In corresponding embodiments, a fixed connection between the various coil spring elements can therefore be dispensed with.

[0118] The radii of the windings 611, 612, 621, 622, 631, 632 are in the embodiment of Fig. 7 is selected such that for each pair of adjacent turns, the left turn - in each case based on the representation in the figure - has a larger radius than the respective right turn. In this way, the entire coil spring 60 takes the shape of a conical spring tapering in the z-direction. It is therefore necessary to allow the annular and inwardly directed projection 80a on the inner wall of the cavity 88 to extend correspondingly far up to the axis A, i.e., the radius of the cavity 88 in this embodiment must be smaller in the region of the projection 80a than the radius of the last turn 632 of the third coil spring element 63. The radius of the second guide piston section 70b must be adapted accordingly to these conditions.

[0119] The projection 80a can be selected lower (relative to the inner wall of the cavity 88) if the spring elements are arranged as shown schematically in Fig. 8. In particular, the last turn 632 seen in the z-direction (ie, the second turn of the third coil spring element 63) has a different winding direction compared to the corresponding turn of the embodiment of Fig. 7, so that the height of the inner wall edge 84 (relative to the inner wall of the housing 80) can be selected accordingly lower. This allows a larger piston radius to be selected for the second guide piston section 70b than in the embodiment of Fig. 7; such a dimensioning of the second guide piston section 70b has an advantageous effect with regard to the maximum permissible force that can be transmitted by the guide piston 70 (e.g., to a brake pad attached to the second guide piston end 72b). Similar to the Fig. 6 also have the embodiment of Fig. 8 the middle coils (here realized by the coils 621, 622 of the middle coil spring element 62) have a spring wire thickness which is small compared to the spring wire thickness of the outer coils (here realized by the coils 611, 612 and 631, 632 of the first and third coil spring elements 61, 63).

[0120] In this embodiment, too, the elastic properties of the three helical spring elements 61, 62, 63 can be adapted differently from one another, for example, by using different materials for the corresponding spring wires in addition to the different thicknesses.

[0121] A further embodiment is shown schematically in Fig. 9. The spring 60 here has two helical spring elements 61, 62 arranged one behind the other along the axis A. The first helical spring element 61 has four coils 611, 612, 613, 614 and is supported with its first coil 611, viewed in the z-direction, opposite to the z-direction, on the edge of the guide piston 70. The second helical spring element 62 has three coils 621, 622, 623 and is supported with its last coil 623, viewed in the z-direction, in the z-direction on the inner wall edge 84 of the cavity 88. The helical spring elements 61, 62 are each designed as helical springs whose coils have a constant radius (in other words, both helical spring elements 61, 62 are designed as normal helical springs). The windings 611, 612, 613, 614 of the first coil spring element 61 have a smaller radius than the windings 621, 622, 623 of the second coil spring element 62.In addition, the spring wire thickness of the first coil spring element 61 is selected to be smaller than that of the second coil spring element 62. Here, too, the elastic properties of the overall spring 60 can be further adjusted by a corresponding selection of the materials of the spring wires, which can be selected differently for the two coil spring elements 61, 62.

[0122] Finally, Fig. 10 schematically shows an embodiment with a first helical spring element 61 (with five turns 611, 612, 613, 614, 615) and a second helical spring element 62 (also with five turns 621, 622, 623, 624, 625), both of which are implemented as conical springs, wherein the turn radius of the first helical spring element 61 increases in the z-direction, while the turn radius of the second helical spring element 62 decreases in the z-direction. Thus, the two middle turns (ie, the last turn 615 of the first coil spring element 61, seen in the z-direction, and the first turn 621 of the second coil spring element 62) have a maximum radius, while the two outer turns of the overall spring 60 (ie, the first turn 611 of the first coil spring element 61, seen in the z-direction, and the last turn 625 of the second coil spring element 62) have a minimum radius.

[0123] It is understood that with regard to the functioning (in particular the movement of the guide piston 70 and the provision of a restoring force acting on the guide piston 70) of the piston guide device with reference to the Fig. 3A and Fig. 3B What has been said in connection with the Fig. 4 to 10, insofar as there are any deviations of the respective embodiment from that of the Fig. 3 unless expressly stated otherwise.

[0124] The piston guide device according to the invention or embodiments of the piston guide device according to the invention can now be implemented in various types of disc brakes and can improve the properties with regard to the residual drag torque. For example, the piston guide device can be integrated into the Fig. 1 and Fig.2 by replacing the brake piston 30 (and its piston guide (not shown) with a suitable embodiment of the piston guide device according to the invention. The housing 80 of the piston guide device according to the invention can be installed in the brake caliper 20 or even formed integrally with the brake caliper 20. The guide piston 70 then functions as a brake piston acting on the first brake pad 40a.

[0125] A special type of disc brake is the floating caliper brake, whose design and operation were outlined above. The piston guide device according to the invention can also be used in floating caliper brakes. In this case, the guide piston 70 acts as a sliding pin for guiding the brake caliper. Reference list 1 disc brake 20 brake caliper 30 brake pistons 40a, 40b brake pads 50 brake disc 50a middle area of ​​the brake disc 50b outer area of ​​the brake disc 60, 60' coil springs 61, 62, 63 Coil spring elements 601, 602, 603, 604, 605 turns of the first coil spring 601', 602', 603' turns of the second coil spring 611, 612, 613, 614 turns of the first coil spring element 621, 622, 623 Turns of the second coil spring element 631, 632 turns of the third coil spring element 70 guide pistons 70a, 70b first and second guide piston sections 72a, 72b first and second guide piston ends 74 Edge on the guide piston surface 80 housings 80a inward-facing projection 84 inner wall edge 88 cavity 90 groove (annular groove) 94 Side wall of the groove A Piston longitudinal axis D axis of rotation L1, L2 clearance between brake disc and first or second brake pad R Radius of the brake disc R1, R2 radius of the first and second piston sections r, z axes of a coordinate system Δz displacement of the piston

Claims

[1] Piston guide device for a disc brake (1), comprising: a housing (80) having a cavity (88) for guiding a guide piston (70) parallel to a designated direction (z); a guide piston (70) which is displaceably mounted in the cavity (88) parallel to the marked direction (z) along its piston longitudinal axis (A) between a first position and a second position, the first position being in front of the second position when viewed in the marked direction (z); a first coil spring (60) whose coils are formed around an axis parallel to the designated direction (z); wherein, viewed along the designated direction (z), one end of the first coil spring (60) is connected to the inner wall of the housing (80) or is supported on the inner wall of the housing (80) in the direction of the designated direction (z), and the other end of the first coil spring (60) viewed along the designated direction (z) is connected to the guide piston (70) or is supported on the guide piston (70) opposite to the designated direction (z); wherein the coil spring (60) is unloaded when the guide piston (70) is in the first position and is subjected to a load when the piston (70) is in the second position, or the coil spring (60) is subjected to a first load when the guide piston (70) is in the first position and the coil spring (60) is subjected to a second load when the guide piston (70) is in the second position, the second load being greater than the first load; characterized by that the housing (80) of the piston guide device is firmly connected to a brake calliper carrier of the disc brake (1) or is integrated into the brake calliper carrier; a brake calliper (20) of the disc brake (1) is connected to the end (72b) of the guide piston (70) pointing in the marked direction (z); at least one of the coil springs (60) has two or more coil spring elements (61, 62, 63) which are arranged one behind the other along the marked direction (z), and wherein the coil spring elements (61, 62, 63) are each themselves designed as coil springs. [2] Piston guide device according to claim 1, wherein at least some of the turns (601, 602, 603, 604, 605) of the first coil spring (60) are each arranged circumferentially around the guide piston (70). [3] Piston guide device according to claim 1 or 2, wherein the connection of the first coil spring (60) to the guide piston (70) or the support of the coil spring (60) on the guide piston (70) is arranged in the direction of the marked direction (z) before the connection of the first coil spring (60) to the inner wall of the cavity (88) or the support of the first coil spring (60) on the inner wall of the cavity (88). [4] Piston guide device according to one of claims 1 to 3, comprising at least one further helical spring (60'), wherein for each of the further helical springs (60') one end of the respective further helical spring (60') is connected to the inner wall of the housing (80) or is supported on the inner wall of the housing (80) in the direction of the designated direction (z), as seen along the designated direction (z), and the other end of the respective further helical spring (60') is connected to the guide piston (70) or is supported on the guide piston (70) opposite to the designated direction (z). [5] Piston guide device according to claim 4, wherein at least one of the coil springs (60, 60') is made of a material or comprises a material which is different from the material(s) from which at least one of the other coil springs is made or which is included in at least one of the other coil springs. [6] Piston guide device according to claim 4 or 5, wherein at least one of the coil springs (60, 60') has an elasticity which is different from the elasticity of at least one of the other coil springs. [7] Piston guide device according to one of claims 1 to 6, wherein at least for one of the coil springs (60, 60') along the marked direction the radius of the turns varies and / or the thickness of the spring wire of the coil spring varies. [8] Piston guide device according to one of claims 1 to 7, wherein one or more of the coil springs (60, 60') is / are each made of plastic or metal. [9] Piston guide device according to one of claims 1 to 8, wherein at least one of the coil springs (60, 60') is manufactured by injection molding or by 3D printing. [10] Piston guide device according to one of claims 1 to 9, wherein at least one of the coil springs (60, 60') is designed symmetrically with respect to its respective inlet and outlet sides. [11] Piston guide device according to one of claims 1 to 10, wherein at least one of the coil springs (60, 60') is designed asymmetrically with respect to its respective inlet and outlet sides. [12] Piston guide device according to claim 1, wherein at least one coil spring element: is made of plastic or metal; and / or is manufactured by injection molding or 3D printing; and / or is designed symmetrically with respect to its respective inlet and outlet sides; and / or is designed asymmetrically with respect to its respective inlet and outlet sides. [13] Piston guide device according to one of claims 1 to 11, wherein each of the coil springs and / or each of the coil spring elements has a substantially constant characteristic curve. [14] Floating caliper brake for a motor vehicle, comprising: a brake calliper (20) with an actuating device; a brake disc (50) with a radius (R), wherein the brake disc (50) is arranged to be rotatable relative to the brake caliper (20) about a virtual axis of rotation, wherein the axis of rotation (D) runs through the center of the brake disc (50) and perpendicular to the brake disc (50); a brake pad (40a) which is mounted displaceably relative to the brake disc (50) parallel to the axis of rotation (D), wherein the brake pad (40a) is located at least partially within a virtual cylinder which has the radius (R) and whose cylinder axis coincides with the axis of rotation (D); a brake caliper carrier; at least one piston guide device; wherein the housing (80) of the piston guide device is fixedly connected to the brake caliper carrier or integrated into the brake caliper carrier; wherein the axis of rotation (D) runs parallel to the designated direction (z); wherein the brake calliper (20) is mounted displaceably along the designated direction (z) by means of a guide piston (70) of the piston guide device and is located behind the brake pad (40a) as seen in the designated direction (z); wherein the brake calliper (20) is connected to the end (72b) of the guide piston (70) pointing in the distinguished direction (z); wherein the brake calliper (20) has an actuating device which is designed to move the brake pad (40a) against the marked direction (z) and to bring it into abutment with the brake disc (50), wherein the piston guide device for a disc brake (1) comprises: the housing (80) having a cavity (88) for guiding a guide piston (70) parallel to a designated direction (z); the guide piston (70) which is mounted in the cavity (88) parallel to the marked direction (z) along its piston longitudinal axis (A) so as to be displaceable between a first position and a second position, the first position being located in front of the second position when viewed in the marked direction (z); a first coil spring (60) whose coils are formed around an axis parallel to the designated direction (z); wherein, viewed along the designated direction (z), one end of the first coil spring (60) is connected to the inner wall of the housing (80) or is supported on the inner wall of the housing (80) in the direction of the designated direction (z), and the other end of the first coil spring (60) viewed along the designated direction (z) is connected to the guide piston (70) or is supported on the guide piston (70) opposite to the designated direction (z); wherein the coil spring (60) is unloaded when the guide piston (70) is in the first position and is subjected to a load when the piston (70) is in the second position, or the coil spring (60) is subjected to a first load when the guide piston (70) is in the first position and the coil spring (60) is subjected to a second load when the guide piston (70) is in the second position, the second load being greater than the first load; characterized by that at least one of the coil springs (60) has two or more coil spring elements (61, 62, 63) which are arranged one behind the other along the marked direction (z), and wherein the coil spring elements (61, 62, 63) are each themselves designed as coil springs.

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