METHOD FOR STRUCTURALLY OPTIMIZING A BRAKE CALIPER

Abstract

The invention concerns a method for the structural optimization of a brake caliper (10), the brake caliper (10) having a first face (24) and a second face (26) that are spaced apart from one another along a piston movement axis (A), wherein the first and second face (24, 26) are connected by a bridge section (22) of the caliper (10), wherein the method is performed based on a computer-implemented model (30) of the brake caliper (10), caliper model, the method comprising: prescribing a boundary condition according to which an orientation of the first face (24) and the second face (26) relative to one another and/or to the piston movement axis (A) remains constant even under load; performing a structural optimization of the caliper model (30) taking into account said boundary condition.

Also disclosed is a brake caliper (10).

Claims

1. A method for structurally optimizing a brake caliper (10), the brake caliper (10) having a first face (24) and a second face (26) that are spaced apart from one another along a piston movement axis (A), wherein the first and second face (24, 26) are connected by a bridge section (22) of the caliper (10), wherein the method is performed based on a computer-implemented model (30) of the brake caliper (10), caliper model, the method comprising: prescribing a boundary condition according to which an orientation of the first face (24) and the second face (26) relative to one another and/or to the piston movement axis (A) remains constant under load; performing a structural optimization of the caliper model (30) taking into account said boundary condition.

2. The method of claim 1, further comprising: manufacturing the brake caliper (10) based on the structurally optimized caliper model (30) and by means of a generative manufacturing process.

3. The method of claim 1, wherein prescribing the boundary condition includes: selecting a plurality of nodes (51-53) or other model elements comprised by the first face (24) and a plurality of nodes (51-53) or other model elements comprised by the second face (26); and prescribing for each of the first and second face (24, 26) a uniform axial displacement of their respective nodes (51-53) or other model elements.

4. The method of claim 3, wherein the uniform axial displacement of the first face (24) is different from the uniform axial deflection of the second face (26).

5. The method of claim 1, wherein no or at least less restrictive boundary conditions are prescribed for deformations of the first and second face (24, 26) in directions extending at an angle and in particular orthogonally to the piston movement axis (A).

6. The method of claim 1, further comprising: wherein the structural optimization is performed with respect to at least one of the following targets: weight; deformation behavior and/or stiffness; natural frequency; mass distribution; additional brake fluid intake during brake activation; thermal distribution within the caliper (10).

7. The method of claim 1, wherein the method further includes: defining locally admissible degrees of stiffness within the caliper (10); wherein the structural optimization takes said locally admissible degrees of stiffness into account.

8. The method of claim 1, wherein the structural optimization includes varying at least one of the following with respect to at least one form feature or at least one section of the caliper (10), the form feature or section being preferably comprised by the bridge section (22): a positioning of said form feature or section; an orientation of said form feature or section; a dimensioning of said form feature or section; a density of said form feature or section; a stiffness of said form feature or section.

9. The method according to claim 8, wherein the form feature is one of a recess or cut-out (25), a rib (27) or web, a thinned portion, a thickened portion.

10. The method of claim 1, wherein as a further boundary condition for the structural optimization an admissible deformation of the bridge section (22) is prescribed, in particular a permissible axial deformation.

11. Brake caliper (10), having a first face (24) and a second face (26) that are spaced apart from one another along a piston movement axis (A), wherein the first and second face (24, 26) are connected by a bridge section (22), wherein an orientation of the first face (24) and the second face (26) relative to one another and/or to the piston movement axis (A) remains constant under load.

Description

[0096] FIG. 1 is a view of a prior art brake caliper that is to be structurally optimized;

[0097] FIG. 2 is a view of a system for implementing a method according to an embodiment of the invention;

[0098] FIG. 3 is a flow diagram indicating the steps of a method according to an embodiment of this invention;

[0099] FIG. 4 is a view of a brake caliper used in the method of FIG. 3 and with locally varying of degrees of an admissible stiffness.

[0100] FIG. 5 is an illustration of the caliper model for which an additional or alternative boundary condition is defined.

[0101] FIG. 6-8 show a comparison between a non-optimized brake caliper and structurally optimized brake calipers according to an embodiment of the invention.

[0102] In FIG. 1, a brake caliper 10 of a wheel brake assembly 11 is shown. The brake caliper 10 is generally configured according to known prior-art examples, i.e. its structure not having been optimized according to this disclosure. The view of FIG. 1 is a cross-sectional view with the cross-sectional plane extending vertically and including a rotational axis R. A non-depicted vehicle wheel rotates about said rotational axis R. The non-depicted vehicle wheel is disposed (in FIG. 1) to the left of a brake disc 12 that equally rotates about the rotational axis R.

[0103] The brake caliper 10 axially spans across the brake disc 12 and receives at least a radially outer portion thereof. Specifically, the brake caliper 10 has a gap of space 14 receiving at least a radially outer edge section of the brake disc 12. The gap or space 14 has two inner sides 16 extending substantially orthogonally with respect to the rotational axis R and each facing an outer side face 13 of the brake disc 12. Specifically, in FIG. 1 a left inner side 16 faces a left outer side face 13 and a right inner side 16 faces a right outer side face 13. The brake caliper 10 is thus arranged to face opposite sides of the brake disc 12.

[0104] The brake caliper 10 has a cylindrical receiving section 18 for receiving a brake piston 20 and for delimiting a hydraulic chamber 21. A side or portion of the brake caliper 10 comprising said receiving section 18 may be referred to as a piston side. The piston 20 is movable along a piston movement axis A which extends in parallel to the rotational axis R.

[0105] The brake caliper 10 has a bridge section 22. It extends substantially axially and connects the piston side 19 with a region or portion of the brake caliper 10 located at the opposite of the brake disc 12. This region or portion may be referred to as finger side 17. Non-depicted guide pins on which the brake caliper 10 is axially slidingly guided preferably extend from the piston side 19 up to the finger side 17.

[0106] The finger side 17 and piston side 19 each delimit the space 14 for receiving the brake disc 12. Specifically, the each comprise one of the inner sides 16 (or, put differently, inner faces). Further, said inner sides 16 are comprised by a first and second face 24, 26 of the brake caliper 10, respectively.

[0107] FIG. 1 further shows brake pads 28. One brake pad 28 is arranged at each of the first and second face 24, 26. The brake pads 28 thus face opposite side faces 13 of the brake disc 12. In a generally known manner, the piston 20 can be moved along the piston movement axis A to press the (in FIG. 1 right) brake pad 28 at the second face 26 against the opposite side faces 13 of the brake disc 12. When further increasing the hydraulic pressure at the piston 20, the brake caliper 10 slides to the right of FIG. 1 along the non-depicted guide pins until the brake disc 12 is clamped between both brake pads 28.

[0108] Existing brake systems suffer from inhomogeneous brake pad wear, excessive brake noise generation and excessive additional brake fluid intake by the hydraulic chamber 21 during braking at e.g. high hydraulic pressures. It has presently been determined that this typically results from non-uniform axial widening of the space or gap 14. Specifically, the inner sides 14 and thus first and second face 24, 26 may change their initially typically upright orientation. They may thus become slanted. An axial distance between their radially inner or lower edges 27 often increases to larger extent than between their radially outer or upper edges 29. In other words, the first and second face 24, 26 may change from an initially parallel orientation to extending obliquely to one another.

[0109] Referring to FIG. 4 and as discussed in further detail below, this may result in the axial distances L1-L3 becoming different from one another and/or in these distances L1-L3 changing by different degrees under load. In particular, the radially lower distance L3 may increase to a larger extent than the radially outer distances L1, L2.

[0110] In order to compensate for this non-uniform axial widening along each of the first and second face 24, 26, a standard approach would include iteratively increasing the mass e.g. near said lower edges 27 or within the bridge section 22. This, however, would increase the overall weight.

[0111] Instead, according to a method disclosed herein, a suitable boundary condition has been determined that can be directly implemented into a CAE workflow for preventing the above-discussed undesired deformation. At the same time, however, it allows for an optimization with respect to other targets, such as weight.

[0112] FIG. 2 shows a system 100 for implementing the method. The system 100 comprises a user interface arrangement 102 (e.g. comprising any of a mouse, microphone, keyboard, display, touch panel or combinations thereof). The system 100 also comprises a computer device 104, such as a personal computer. Further, the system 100 comprises a generative manufacturing device 106, e.g. a laser sintering device.

[0113] The computer device 104 has a processor (e.g. a CPU) 108 and a storage unit 110. The storage unit 110 stores a computer program and/or computer program instructions. These are executed by the processor 108 to implement steps of the method disclosed herein.

[0114] Specifically, a computer implemented model of a brake caliper that is to be structurally optimised is stored in the storage unit 110. By way of the user interface arrangement 102, a user can provide any inputs, provide any settings or definitions disclosed herein and e.g. for preparing a structural optimisation of said model. Such inputs, settings and definitions may equally be stored in the storage unit 110. They may include any of the boundary conditions disclosed herein.

[0115] Further, by way of the user interface arrangement 102, a structural optimisation algorithm whose computer program instructions are stored in the storage unit 110, can be activated. Said algorithm is applied to the brake caliper model in order to determine an optimised structure of the brake caliper model while further taking the user input, settings and definitions and/or any of the boundary conditions disclosed herein into account. This may also include taking specifics and in particular manufacturing restrictions of the manufacturing device 106 into account.

[0116] The structurally optimised model may be transmitted to the generative manufacturing device 106 which may determine suitable control actions to manufacture a real product corresponding to said digital/virtual optimised model. Alternatively, these control actions may be determined by the computer device 104 and then be transmitted to the generative manufacturing device 106.

[0117] A sequence of a respectively implemented method is depicted in the flow diagram of FIG. 3. In step S1 the computer implemented model of the brake caliper is generated or provided, said brake caliper having a non-optimised structure. In step S2 any boundary conditions that should be considered during structural optimisation are defined, preferably by being directly inputted by a user. In step S3, the structural optimisation algorithm is executed to structurally optimised be brake caliper model while taking any of the boundary conditions of step S2 into account. In step S4, the structurally optimised model is received and stored, preferably in order to determine control actions for manufacturing a brake caliper according to said model. Of course, in case the result of step S4 is non-satisfying, steps S2 and S3 can iteratively be repeated and/or the initial brake caliper model of step S1 may be adjusted.

[0118] With respect to FIGS. 4 and 5, two examples of boundary conditions are discussed that can be set in the context of step S2 of the presently disclosed method. FIG. 4 shows a representation of the computer implemented caliper model 30. Because said caliper model 30 is a virtual representation of the actual brake caliper 10 depicted in FIG. 1, same reference signs will be used with respect to said model. Accordingly, the first and second face 24, 26 can again be seen.

[0119] As a boundary condition, it is defined that under load changes of the axial distance L1, L2, L3 along the piston movement axis A for at least three points, e.g. defined as nodes of the model 30, should be similar. This means that the first and second face 24, 26 remain their relative orientation to one another but also to the piston movement axis A.

[0120] For example, the position of three exemplary nodes 51-53 comprised by the first face 24 is indicated in FIG. 4. The boundary condition may prescribe that an axial displacement along the piston movement axis A must be identical for each of said nodes 51-53. Similar requirements may be prescribed by the boundary condition for (non-specifically marked) nodes of the second face 26. As a result, for each node 51-53 the change in the axial distance to a directly opposite node at the opposite face 24, 26 is identical.

[0121] A user may define said boundary condition by selecting the respective nodes 51-53 out of a plurality of nodes comprised by the first face 24 (and a respective plurality of nodes comprised by the second face 26) for which any of the above conditions shall apply. Afterwards, he may activate the structural optimisation algorithm and e.g. verify or adjust its results.

[0122] FIG. 5 is an illustration of the caliper model 30 for which an additional or alternative boundary condition is defined. According to this boundary condition admissible degrees of stiffness are set for selected regions of the caliper model 30. These regions art marked in FIG. 5 by different outlines.

[0123] For example, a dashed outline 31 with an increased line width marks regions with a first admissible stiffness. The dashed outlines 33 having a reduced line width mark regions having a second admissible stiffness. The first admissible stiffness in the regions of the outlines 31 may be larger than the second admissible stiffness in the regions of the outlines 33.

[0124] The positioning of said stiffness-regions may be done based on experience and/or according to predetermined rules. For example, a number and/or size of regions 33 having a lower admissible stiffness can be higher in the bridge section 22 compared to the finger side 17 and piston side 19. With respect to the number and/or size of regions 31 having a higher admissible stiffness, the opposite may apply, i.e. they may be predominantly concentrated in and/or may be larger outside of the bridge section 22 than e.g. near at first and second face 24, 26 or generally within the finger side 17 and piston side 19.

[0125] As an optional measure, at least some regions 33.1 may be defined having a lowered admissible stiffness and being positioned in a transition region (or edge portion) between the bridge section 22 and one of the piston side 19 or finger side 17. Furthermore, at least one further respective region 33 having a lowered admissible stiffness is optionally placed axially between the edge portions or transition regions at both axial ends or edges of the bridge section 22. This way, the bridge section 22 can as such have a defined axial deformability that helps to fulfil the boundary condition of FIG. 4. For example, this may help to limit the risk of the first and second face 24, 26 tilting with respect to one another, e.g. due to having an excessively stiff connection to the bridge section 22.

[0126] Optionally, regions 35 can be defined that are not to be structurally optimized. These include in the depicted example the first and second face 24, 26.

[0127] FIGS. 6-C depict a brake caliper model 30 in various stages of the structural optimisation and from different viewing angles. In FIG. 6, the initial model 30 of a brake caliper 10 is provided that has not yet undergone the presently disclosed structural optimisation. The bridge section 22 is marked by at least two comparatively massive axial sections 23 as well as comparatively small a central cut-out 25.

[0128] In FIG. 7, the structural optimisation has been carried out for achieving a first (comparatively low) weight reduction target while observing the boundary condition of FIG. 4. As a result, a thickness of the bridge section 22 is at least somewhat reduced and a size of the centre opening 25 is increased.

[0129] In FIG. 8, the structural optimisation has been carried out for achieving a second (comparatively large) weight reduction target while again observing the boundary condition of FIG. 4. In this case, the mass of the bridge section 22 is significantly reduced e.g. because its axial sections 23 no longer merge with one another on the finger side 17 and are partially hollow. The latter is in particular made possible by using a generative manufacturing method, such as selective laser melting. The axial sections 23 of the bridge section 22 are now connected by a thin rib 27. Also, the volume of the brake caliper 10 at the finger side 17 is significantly reduced.

[0130] However, due to an optimised positioning and dimensioning of the rib 27 and of the the axial sections 23, it is ensured that the boundary condition of FIG. 4 is still met.

LIST OF REFERENCE SIGNS

[0131] 10 brake caliper [0132] 11 wheel brake assembly [0133] 12 brake disc [0134] 13 side face of the brake disc [0135] 14 space or gap [0136] 16 inner side (of caliper) [0137] 17 finger side [0138] 18 receiving section [0139] 19 piston side [0140] 20 piston [0141] 21 hydraulic chamber [0142] 22 bridge section [0143] 23 axial section of bridge section [0144] 24 first face [0145] 25 cut out [0146] 26 second face [0147] 27 lower edge [0148] 28 brake pad [0149] 29 upper edge [0150] 30 caliper model [0151] 31, 33, 33.1 regions of defined admissible stiffness [0152] 35 non-optimization region [0153] 51-53 node [0154] 100 system [0155] 102 interface arrangement [0156] 104 computer [0157] 106 generative manufacturing device [0158] 108 processor [0159] 110 storage unit [0160] A piston movement axis [0161] R rotational axis