Electromechanical brake actuator, drive assembly for an electromechanical brake actuator and method for assembling an electromechanical brake actuator

Abstract

The invention relates to a drive assembly (100) for an electromechanical brake actuator (300) comprising: a housing (1) having at least one guide groove (11) extending along a longitudinal axis (L1) and an end opening (13) which is positioned coaxially relative to the longitudinal axis and is formed on an end surface (1a) of the housing extending transverse to the longitudinal axis; a transmission (2) accommodated in the housing, having a guide part (20) which is moveably guided in the guide groove; at least one retaining element (3) which is fixed in the guide groove, protrudes over the end surface of the housing relative to the longitudinal axis, and projects into the end opening in relation to a radial direction (R1) extending perpendicular to the longitudinal axis; and a restoring spring (4) which is supported on the retaining element and the transmission in order to exert a pretensioning force, directed along the longitudinal axis and away from the opening, on the transmission.

Description

[0001] Description

[0002] title

[0003] Electromechanical brake actuator, drive assembly for an electromechanical brake actuator and method for assembling an electromechanical brake actuator

[0004] Technical area

[0005] The present invention relates to an electromechanical brake actuator, a drive assembly for an electromechanical brake actuator and a method for assembling an electromechanical brake actuator.

[0006] State of the art

[0007] Electromechanical brake boosters are typically used to amplify the manually applied force on a brake pedal by actuating a master cylinder using an electric motor. So-called "brake-by-wire" systems, in which a control signal is generated by actuating the brake pedal or by other means, and an electrohydraulic actuator is actuated based on the control signal to generate brake pressure, also use actuators constructed in a similar way to electrohydraulic brake boosters.

[0008] DE 10 2013 213 888 B3 discloses a hydraulic actuator for a braking system with a master brake cylinder, an electric motor, and a transmission that couples the electric motor to the master brake cylinder to convert a movement of the motor into an actuation of the master brake cylinder. The transmission is accommodated in a housing, with the master brake cylinder positioned in an opening of the housing. Typically, the transmission that couples the electric motor to the master brake cylinder is subjected to a restoring force via a return spring in order to assist in moving the transmission to its initial position upon removal of a force generated by the electric motor. This is described, for example, in DE 10 2008 038320 A1 or DE 10 2008 054 852 A1.

[0009] Since the return spring is usually supported directly on a flange via which the master brake cylinder is coupled to the housing in which the gearbox is housed, the return spring is usually secured to the housing before the master brake cylinder is mounted.

[0010] Disclosure of the invention

[0011] According to the invention, a drive assembly for an electromechanical brake actuator having the features of claim 1, an electromechanical brake actuator having the features of claim 9 and a method for assembling an electromechanical brake actuator having the features of claim 10 are provided.

[0012] According to a first aspect of the invention, a drive assembly for an electromechanical brake actuator comprises a housing with at least one guide groove extending along a longitudinal axis and an end opening which is positioned coaxially to the longitudinal axis and formed on an end face of the housing extending transversely to the longitudinal axis, a gear accommodated in the housing with a guide part which is slidably guided in the guide groove, at least one holding element which is fixed in the guide groove, protrudes beyond the end face of the housing with respect to the longitudinal axis and projects into the end opening with respect to a radial direction extending perpendicular to the longitudinal axis, and a return spring which is supported on the holding element and the gear in order to exert a pretensioning force on the gear directed away from the opening along the longitudinal axis.According to a second aspect of the invention, an electromechanical brake actuator comprises a drive assembly according to the first aspect of the invention and a master brake cylinder with a cylinder housing which has a flange with a support surface, and a piston which can be displaced in the cylinder housing, wherein the cylinder housing is fastened to the housing of the drive assembly by means of the flange and the support surface faces the end face of the housing, wherein each holding element projects into a respective receiving recess of the flange and the return spring is supported on the support surface of the flange, and wherein the piston is coupled to the transmission.

[0013] According to a third aspect of the invention, a method for assembling a brake actuator according to the second aspect of the invention is provided. The method comprises coupling the piston of the master cylinder to the gear box of the drive assembly, positioning the master cylinder relative to the drive assembly such that each retaining element is inserted into the respective receiving recess of the flange and the return spring is brought into contact with the support surface of the flange and disengaged from the retaining element with respect to the longitudinal axis, and securing the flange to the housing of the drive assembly.

[0014] One idea underlying the invention is to secure the return spring of the drive assembly against falling out during assembly by means of a retaining element that is fixed in the guide groove provided for guiding the guide part of the transmission and that only supports a discrete area of ​​the circumference of the return spring. The retaining element is thus fixed in the guide groove provided anyway and projects from the guide groove beyond a front end of the housing and in a radial direction into the front opening of the housing. The return spring thus also projects with one end out of the front opening. For assembly, the spring can thus be compressed by a support surface on the flange of the housing of the master brake cylinder, while the retaining element engages a respective recess in the flange or the support surface.Fixing the retaining element in the guide groove provided anyway offers the advantage of increasing functional integration. In particular, a more compact design of the drive assembly with respect to the longitudinal axis can be achieved. A further advantage is that the housing is not mechanically weakened by additional fixing structures for holding retaining elements.

[0015] Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures of the drawing.

[0016] According to some embodiments, the housing may have a first guide groove and a second guide groove, each extending in the longitudinal direction, and wherein a first retaining element is fixed in the first guide groove and a second retaining element is fixed in the second guide groove, and wherein the return spring is supported on the retaining elements. The return spring is thus held by the retaining elements at spaced-apart locations on its circumference. The guide grooves may, in particular, be arranged opposite one another, e.g., offset by 180 degrees in a tubular interior of the housing.

[0017] The features disclosed herein for one or the retaining element are disclosed for all retaining elements if more than one retaining element is provided. In this case, the retaining elements are preferably constructed identically.

[0018] According to some embodiments, it can be provided that the holding element has a base web and two side webs extending transversely to the base web and elastically deformable relative to the base web, wherein the base web projects into the end opening in the radial direction, and wherein the holding element is elastically deformed such that the side webs rest against side walls of the guide groove. The holding element is thus designed as a substantially U-shaped clamp, wherein the side webs can be bent towards or away from one another by elastic deformation. In this way, the holding element can advantageously spread into the guide groove and be fixed there, e.g. in a form-fitting, force-fitting or material-fitting manner.The elastic deformability and the fact that the side webs are pre-tensioned by the side walls of the guide groove ensures reliable, defined positioning of the holding element regardless of the type of fixation and thus reduces the risk of noise generation.

[0019] According to some embodiments, it can be provided that the holding element has a foot web on each side web, which protrudes transversely from the respective side web, wherein the foot webs are received in a slot which is formed in the housing and extends transversely to the guide groove. The foot webs protrude away from one another or each protrude from an outer side of the respective side web. The slot can in particular be arranged in an end region of the respective guide groove facing the end opening. The slot forms a pocket or recess in the opposite side walls of the guide groove, into which pocket the foot webs protrude. This easily achieves a positive fixing of the holding element in the guide groove.

[0020] According to some embodiments, a bevel can be formed between each side web and the base web, which projects increasingly radially into the front opening in the direction of the base web. The bevel forms a type of spacer, which ensures that the base webs do not come into contact with moving sections of the return spring when the holding element is displaced in the radial direction, e.g., when the drive assembly is mounted with the master brake cylinder. This effectively prevents noise generation. In particular, the spring can be moved closer to the peripheral wall of the housing in which the guide groove is formed, thus resulting in a more compact design.

[0021] According to some embodiments, the guide groove can open into the end opening. The guide groove can thus end at the end face of the housing. This allows the retaining element to protrude easily from the guide groove, further facilitating the installation of the retaining element in the guide groove. According to some embodiments, the return spring can be designed as a spiral spring, with only a last turn of the spiral spring in contact with the retaining element. In particular, the last turn of the spiral spring can be in contact with the optionally provided bevel of the retaining element when the drive assembly is mounted with the master brake cylinder. Since the last turn is immobile or stationary relative to the housing, no noise is generated during operation due to the bevel contacting the last turn of the spiral spring.

[0022] According to some embodiments, it can be provided that the gear has a threaded spindle which is connected in a rotationally fixed manner to the guide part, and wherein the return spring applies a return force to the threaded spindle

[0023] According to some embodiments, the drive assembly may include an electric motor kinematically coupled to the transmission. This electric motor may be arranged or attached to the housing or accommodated in the housing.

[0024] The invention is explained below with reference to the figures of the drawings. The figures show:

[0025] Fig. 1 is a partial view of a brake actuator according to an embodiment of the invention in a sectional view;

[0026] Fig. 2 is a perspective view of a holding element of a brake actuator according to an embodiment of the invention;

[0027] Fig. 3 is a plan view of an end face of a housing of the brake actuator from Fig. 1;

[0028] Fig. 4 is a partial sectional view of the brake actuator of Fig. 1, taken along the longitudinal axis; Fig. 5 is a perspective view of a master brake cylinder of a

[0029] Brake actuator according to an embodiment of the invention; and

[0030] Fig. 6 is a schematic representation of the sequence of a method according to an embodiment of the invention.

[0031] In the figures, the same reference symbols denote identical or functionally identical components, unless otherwise stated.

[0032] Fig. 1 shows, by way of example, a fragmentary sectional view of an electromechanical brake actuator 300, which can be used, for example, as a brake booster or as a pressure-generating device independent of a brake pedal in a vehicle's braking system. The brake actuator 300 has a drive assembly 100 and a master brake cylinder 200. Fig. 3 shows a plan view of an end face of the drive assembly 100. Fig. 4 shows another sectional view of the drive assembly 100, with some components omitted. Fig. 5 shows a perspective view of the master brake cylinder 200.

[0033] As can be seen in Fig. 1, the drive assembly 100 comprises a housing 1, a gear 2 (only partially shown in Fig. 1), a first and a second retaining element 3A, 3B, and a return spring 4. Furthermore, an electric drive motor (not shown) can be part of the drive device 100.

[0034] The housing 1 defines an interior space 10. In particular, the interior space 10 can be defined at least in sections by a cylindrical peripheral wall. In general, the housing 1 extends along a longitudinal axis L1, which can be defined, for example, by a cylinder axis of the interior space 10. The housing 1 has an end opening 13 on an end face 1a, which connects the end face 1a to the interior space 10. A central axis of the end opening 13 is arranged coaxially to the longitudinal axis L1. As shown in Fig. 3, the end opening 13 can, for example, have a circular circumference. As shown in Figs. 1, 3 and 4, the housing 1 has a first guide groove 11 and a second guide groove 12, which extend along or parallel to the longitudinal axis L1 and preferably open into the end opening 13 or end at the end face 1a. The guide grooves 11, 12 are formed in particular on the peripheral wall of the housing 1, as shown in Figs.3 and 4 as examples. As further shown in Fig. 3, it can optionally be provided that in an end region of the respective guide groove 11, 12 facing the end opening 13, a slot 14 is formed in the housing 1, in particular the peripheral wall, which runs transversely to the respective guide groove 11, 12 and crosses the guide groove 11, 12.

[0035] As further shown in Fig. 3, the end face 1a can optionally have mounting holes 16 via which the master brake cylinder 200 can be fastened to the housing 1, as will be explained below.

[0036] The transmission 2 is only partially shown in Fig. 1 and comprises a guide part 20 and a threaded spindle 21 which is fastened to the guide part 20 in a rotationally fixed manner. Furthermore, the transmission 2 can have a coupling assembly 22 which is kinematically coupled to the threaded spindle 21 and can be displaced thereby along the longitudinal axis L1. The guide part 20 can, for example, be designed as a plate and is guided displaceably in the guide grooves 11, 12 along the longitudinal axis L1. For example, the guide part 20 can have guide projections 20A which protrude into the grooves 11, 12. The threaded spindle 21 is designed for coupling to the electric drive motor (not shown) or is coupled to it and can be displaced along the longitudinal axis L1 in order to actuate the master brake cylinder 200.

[0037] As shown in Figs. 1 and 3, the gear 2 is accommodated in the interior 10 of the housing 1.

[0038] In the drive assembly 100 shown by way of example in Figs. 1, 3 and 4, a first and a second guide groove 11, 12 and a first and a second guide element 3A, 3B are provided. In particular, one holding element 3 can be provided for each guide groove 11, 12. However, it is also conceivable that more guide grooves 11, 12 are provided than holding elements 3. Alternatively, only one guide groove 11 and only one holding element 3 can be provided. The features disclosed herein for a holding element 3 thus apply to all holding elements 3, in particular to the first and second holding elements 3A, 3B.

[0039] Fig. 2 shows a retaining element 3 purely by way of example. As shown in Fig. 2, the retaining element 3 can be designed as a substantially U-shaped clamp. The retaining element 3 can, in particular, have a base web 30 and two side webs 31. Optionally, a foot web 32 can also be provided for each side web 31.

[0040] The base web 30 is implemented as a rectangular web. The side webs 31 extend from the base web 30 transversely thereto. In particular, the side webs 31 protrude from the base web 30 with respect to a first direction X1, which runs perpendicular or transversely to the base web 30. As shown in Fig. 2, the side webs 31 can in particular run at an angle to one another or towards one another, so that a distance d31 between them increases with increasing distance from the base web 30. The side webs 31 are dimensioned such that they are elastically deformable relative to the base web 30, in particular such that they can be aligned parallel to one another. The base web 30 extends in particular in a plane which is defined by a second and a third direction X2, X3, which each run perpendicular to the first direction X1. As shown in Fig.2, the base web 30 has a width b30 with respect to the second direction X2, which is greater than a width b31 of the longitudinal webs 31 in the second direction X2. As can be seen in Fig. 2, it can optionally be provided that a bevel 33 is formed between each side web 31 and the base web 30. As shown in Fig. 2, the bevel 33 is defined by a width b31 of the side webs 31 with respect to the second direction X2, which width increases towards the base web 30.

[0041] As further shown by way of example in Fig. 2, the optional foot webs 32 each protrude outwardly, or in relation to the third direction X3, from the respective side web 31. In particular, the foot webs 32 can each be arranged at an end of the respective side web 31 facing away from the base web 30. Optionally, the foot webs 32 extend perpendicular to the side webs 31.

[0042] The holding element 3 can, in particular, be formed from a metal material. For example, a semi-finished product can be milled from a sheet metal, and the base web 30 and the side webs 31, as well as optionally the foot webs 32, can be produced by bending the milled semi-finished product.

[0043] As shown in Figs. 1, 3 and 4, the holding elements 3A, 3B can be inserted into the guide grooves 11, 12 of the housing 1 and fixed there in such a way that the holding elements 3A, 3B each protrude beyond the end face 1a of the housing 1 with respect to the longitudinal axis L1 and protrude into the end opening 13 with respect to a radial direction R1 extending perpendicular to the longitudinal axis L1.

[0044] As can be seen in particular in Fig. 4, in which the first holding element 3A and the first guide groove 11 are shown purely by way of example, the side webs 31 can be elastically deformed such that they run parallel or substantially parallel to one another and are prestressed against side walls 15 of the guide groove 11, so that they bear against them. The optional foot webs 32 are optionally received in the slot 14. As a result, the holding element 3 is fixed in the guide groove 11 with a form-fitting connection with respect to the longitudinal axis L1 and with a frictional connection with respect to the radial direction R1. However, the invention is not limited to this, but other types of fixing of the holding element 3 in the respective guide groove 11, 12 are also conceivable. The holding element 3 further projects with the side webs 31 beyond the end face 1a of the housing 1. As can be seen in particular in Figs. 1 and 3, the base web 30 projects radially into the front opening 13.

[0045] The return spring 4 can in particular be designed as a spiral spring and is accommodated in the interior 10 of the housing, as shown in Fig. 1. In particular, the return spring 4 can be arranged coaxially to the longitudinal axis L1. As shown in Fig. 1, the spring 4 is supported with a first end on the gear 2, e.g. on a centering sleeve 23 connected to the coupling assembly 22. In an unassembled state, in which the drive assembly 100 is not mounted with the master brake cylinder 200, the spring 4 is supported with a second end, e.g. with a last turn 40 of the spiral spring, on the holding element 3. As a result, the return spring 4 exerts a preload force on the gear 2, in particular on the threaded spindle 21, directed along the longitudinal axis L1 away from the opening 13.

[0046] In the unassembled state of the drive assembly 100, the at least one holding element 3 thus secures the return spring 4 against falling out of the front opening 13 and holds the return spring 4 in the desired position.

[0047] The master brake cylinder 200 comprises, as shown schematically and purely by way of example in Figs. 1 and 5, a cylinder housing 210 and a piston 220, which is axially displaceably guided in the cylinder housing 210. The piston 220 serves to displace hydraulic fluid in order to generate a pressure build-up and a pressure reduction in a wheel brake (not shown) connected or connectable to the master brake cylinder 200.

[0048] The cylinder housing 210 has, as shown in particular in Fig. 5, a flange 212. The flange 212 can, for example, have mounting holes 216, via which the cylinder housing 210 can be fastened to the housing 1 of the drive assembly 100, e.g., by means of screws (not shown). The flange 212 has an end face or support surface 212a, in which a number of the holding elements

[0049] 3 of the drive assembly 100. The support surface 212a is preferably realized as a flat surface. As shown in Fig. 5, the support surface 212a can further comprise a through-opening 214 through which the piston 220 is guided. Further optionally, a centering structure for centering the return spring can be provided on the flange 212 on the support surface 212a.

[0050] 4. The centering structure can, for example, be designed in the form of an annular projection protruding from the end face 212a and surrounding the through-hole 214, as shown purely by way of example in Fig. 5.

[0051] In Fig. 1, the master brake cylinder 200 and the drive assembly 100 are fastened to one another as one, e.g. by means of screws (not shown) that are passed through the mounting holes 16, 216 of the housing 1 and the cylinder housing 210. As shown in Fig. 1, the support surface 212a of the flange 212 of the master brake cylinder 200 faces the end face 1a of the housing 1 of the drive assembly 100. Furthermore, it can be seen in Fig. 1 that each holding element 3A, 3B projects into a respective receiving recess 213 of the flange 212 and the return spring 4 is supported on the support surface 212a of the flange 212. This means that the holding elements 3A, 3B are relieved of load in the axial direction or along the longitudinal axis L1. In particular, the base web 30 is no longer in contact with the spring 4. As shown in Fig.1, the optionally provided bevel 33 can be in contact with the last coil 40 of the preload spring 4, which rests against the support surface 212a and remains stationary with respect to the longitudinal axis L1 even when the preload spring 40 is compressed or stretched. The bevel 33 thus prevents the respective retaining element 3A, 3B from slipping radially inward in the axially unloaded state and coming into contact with movable coils of the spring 4, e.g., with the side webs 31.

[0052] The piston 220 is coupled to the transmission 2, e.g., an actuating rod 24 of the coupling assembly 22 can be coupled to the piston 220, as shown by way of example in Fig. 1.

[0053] Fig. 6 shows schematically the sequence of a method M for assembling a brake actuator 300, which is described below by way of example with reference to the brake actuator described above.

[0054] In step M1, the piston 220 of the master brake cylinder 200 is coupled to the gear 2 of the drive assembly 100, e.g. by inserting the actuating rod 24 into the corresponding interface of the piston 220 or generally coupling it thereto.

[0055] In step M2, the master brake cylinder 200 is positioned relative to the drive assembly 100 such that each retaining element 3A, 3B is inserted into the respective receiving recess 213 of the flange 212 and the return spring 4 is brought into contact with the support surface 212a of the flange 212 and disengaged from the retaining elements 3A, 3B with respect to the longitudinal axis L1. For example, the drive assembly 100 and the master brake cylinder 200 can be moved towards each other along the longitudinal axis L1, so that the holding elements 3A, 3B are inserted into the receiving recess 213 of the flange 212 and the return spring 4 comes into contact with the support surface 212a of the flange 212. By applying a force acting along the longitudinal axis L1, the return spring 4 is compressed and thereby brought out of engagement with the holding elements 3A, 3B with respect to the longitudinal axis L1.

[0056] Finally, in step M3, the flange 212 is fastened to the housing 1 of the drive assembly 100. For example, screws (not shown) can be passed through the mounting holes 16, 216 of the housing 1 and the cylinder housing 210 and secured with nuts (not shown).

[0057] Although the present invention has been explained above using exemplary embodiments, it is not limited thereto but can be modified in a variety of ways. In particular, combinations of the above embodiments are also conceivable.

Claims

Claims 1. Drive assembly (100) for an electromechanical brake actuator (300), comprising: a housing (1) with at least one guide groove (11, 12) extending along a longitudinal axis (L1) and an end opening (13) which is positioned coaxially to the longitudinal axis (L1) and is formed on an end face (1a) of the housing (1) extending transversely to the longitudinal axis (L1); a gearbox (2) received in the housing (1) with a guide element (20) which is slidably guided in the guide groove (11, 12); at least one retaining element (3) which is fixed in the guide groove (11, 12), projects beyond the end face (1a) of the housing (1) with respect to the longitudinal axis (L1) and projects into the end opening (13) with respect to a radial direction (R1) extending perpendicular to the longitudinal axis (L1);and a return spring (4) which is supported on the retaining element (3) and the transmission (2) in order to exert a preload force on the transmission (2) directed along the longitudinal axis (L1) away from the opening (13).

2. Drive assembly (100) according to claim 1, wherein the housing (1) has a first guide groove (11) and a second guide groove (12), each extending in the longitudinal direction (L1), and wherein a first retaining element (3A) is fixed in the first guide groove (11) and a second retaining element (3B) is fixed in the second guide groove (12), and wherein the return spring (4) is supported on the retaining elements (3A, 3B).

3. Drive assembly (100) according to claim 1 or 2, wherein the retaining element (3) has a base web (30) and two extending transversely to the base web (30) and elastically relative to the base web (30). The drive assembly (100) has deformable side webs (31), wherein the base web (30) projects into the end opening (13) in the radial direction (R1), and wherein the retaining element (3) is elastically deformed such that the side webs (31) bear against side walls (15) of the guide groove (11, 12). The drive assembly (100) according to claim 3, wherein the retaining element (3) has a foot web (32) on each side web (31) which projects transversely from the respective side web (31), and wherein the foot webs (32) are received in a slot (14) which is formed in the housing (1) and extends transversely to the guide groove (11, 12). Drive assembly (100) according to claim 3 or 4, wherein a slope (33) is formed between each side web (31) and the base web (30), which projects increasingly in a radial direction (R1) into the end opening (13) towards the base web (30). Drive assembly (100) according to any one of the preceding claims, wherein the guide groove (11, 12) opens into the end opening (13).Drive assembly (100) according to any one of the preceding claims, wherein the return spring (4) is designed as a coil spring, and wherein only a last turn (40) of the coil spring is in contact with the retaining element (3). Drive assembly (100) according to any one of the preceding claims, wherein the gearbox (2) has a threaded spindle (21) which is rotationally fixed to the guide part (20), and wherein the return spring (3) applies a return force to the threaded spindle (21). Electromechanical brake actuator (300), comprising: a drive assembly (100) according to any one of the preceding claims; and. a master brake cylinder (200) with a cylinder housing (210) having a flange (212) with a support surface (212a), and a piston (220) slidable in the cylinder housing (210); wherein the cylinder housing (210) is attached to the housing (1) of the drive assembly (100) by means of the flange (212) and the support surface (212a) faces the end face (1a) of the housing (1); wherein each retaining element (3) projects into a respective receiving recess (213) of the flange (212) and the return spring (4) is supported on the support surface (212a) of the flange (212); and wherein the piston (220) is coupled to the transmission (2). Method (M) for assembling a brake actuator (300) according to claim 9, comprising: Coupling (M1) of the piston (220) of the master brake cylinder (200) to the gearbox (2) of the drive assembly (100); Positioning (M2) of the master brake cylinder (200) relative to the drive assembly (100) such that each retaining element (3) is inserted into the respective receiving recess (213) of the flange (212) and the return spring (4) is in contact with the support surface (212a) of the flange (212) and is disengaged from the retaining element (3) with respect to the longitudinal axis (L1); and Attaching (M3) the flange (212) to the housing (1) of the drive assembly (100).

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