Method for joining housing parts and electromechanical actuator

Abstract

A method for joining housing parts (3, 4), wherein two end faces (5, 6) of the housing parts (3, 4) are to be joined together, comprises the following steps: - Creating a circumferential elevation (7) in the end face (5) of one of the two housing parts (3), wherein the elevation (7) forms a cutting edge (8) and inside and outside the circumferential elevation (7) a circumferential depression (9, 10) is formed, - The two housing parts (3, 4) are placed against each other so that the cutting edge (8) is pressed into the end face (6) of the second housing part (4) and at the same time material of the second housing part (4) is displaced into the circumferential recesses (9, 10), - Welding the first housing part (3) to the second housing part (4), producing a weld seam (15) that reaches a maximum of the area in which the circumferential protrusion (7), the recesses (9, 10) and the displaced material are located.

Description

[0001] The invention relates to a method for joining two housing parts. Furthermore, the invention relates to an electromechanical actuator, in particular in the form of a steering actuator for a motor vehicle, with a multi-part housing.

[0002] German patent application DE 10 2014 213 137 A1 relates to a roll stabilizer, i.e., a chassis actuator, with a flange. The flange has a base body that is connected to at least one sheet metal part by a joining process to increase torsional stiffness. Welding, friction welding, riveting, and flanging are listed as joining processes in DE 10 2014 213 137 A1.

[0003] From DE 10 2021 104 646 A1, a steering actuator for a rear axle steering system and a method for mounting a steering actuator are known. The known steering actuator has a multi-part housing and a rotary-linear transmission arranged in the housing. A compensating element, press-fitted into the housing, is interposed between a bearing, in particular an angular contact bearing, which supports a rotating transmission component against the housing, and one of two housing components.

[0004] The invention is based on the objective of further developing the assembly of housing parts, in particular chassis actuators, compared to the aforementioned prior art, whereby a particularly favorable ratio between rational assembly and process reliability is sought.

[0005] This problem is solved according to the invention by a method for joining housing parts as designed according to claim 1. According to claim 6, the housing parts can in particular be parts of an electromechanical actuator, for example, a steering actuator of a motor vehicle.

[0006] The joining method according to the application serves to connect end faces of two housing parts and comprises the following steps: - Creating a circumferential elevation in the end face of one of the two housing parts, wherein the elevation forms a cutting edge and a circumferential depression is formed both inside and outside the circumferential elevation, whereas the end face of the second housing part initially remains flat, - Applying force to the two housing parts so that the cutting edge of the first housing part is pressed into the end face of the second housing part and at the same time material of the second housing part is displaced into the circumferential recesses, whereby outside the area in which the circumferential protrusion, the recesses and the displaced material are located, a flat contact of the second housing part with the first housing part is achieved, - Welding the first housing part to the second housing part, creating a weld seam that reaches a maximum of the area in which the circumferential protrusion, the depressions and the displaced material are located.

[0007] The circumferential raised section, which provides a cutting edge, and the material displaced into the recesses create a barrier that serves a protective function during welding. In particular, this ensures that no material, such as contaminants, enters the interior of the housing during welding. The circumferential recesses, which, like the raised section, describe a ring shape when viewed from the front, are also referred to as expansion basins.

[0008] In contrast to conventional joining methods, for example in the form of pressing, the joining method according to the application offers the possibility to determine the alignment of the two housing parts - within a given tolerance range - immediately before joining and to correct it if necessary.

[0009] The end face of the first housing part can be machined, for example by turning. Grinding the end face of the first housing part is also an option. This also applies to the initially completely flat end face of the second housing part. Optionally, the end face of the first housing part can be heat-treated to optimize the suitability of the circumferential protrusion as a cutting edge. Rounding the cutting edge during joining is unproblematic, provided the cutting edge penetrates the second housing part and creates a material spur that originates from the second housing part and partially fills the recesses in the first housing part.

[0010] The two housing parts can be made of the same metallic material, in particular an iron-based alloy, or of different materials, for example, steel in one case and a light metal or non-ferrous metal alloy in the other, whereby the welding process must be adapted to the choice of material. Nesting of several ring-shaped protrusions and corresponding recesses on the end face of one or both housing parts is also possible. In no case do the protrusions and recesses on the end face of at least one housing part require a significant amount of installation space.

[0011] In particular, the two housing parts can be joined together by laser welding. The laser beam can lie in a plane to which the common central axis of both housing parts forms a surface normal. Especially in this configuration, the combination of penetrated and extruded material prevents unwanted heat input that could affect components located inside the housing.

[0012] Regardless of the welding parameters chosen in each individual case, it is possible to join the two housing parts without inserting a separate gasket, whether metallic or non-metallic. Rather, the overlap area, where the material of the housing parts is deformed during assembly, constitutes a sealing area.

[0013] Likewise, no adhesive bonding between the housing parts is required. The formed areas at the joint between the housing parts are not designed to absorb axial forces that would separate the housing parts and therefore make no or at most a minimal contribution to the permanent connection of the housing parts. Disassembly of the housing parts is generally not intended. The wall thickness of the housing parts can be significantly less than the wall thickness of conceivable housing elements that are to be joined by an interference fit.

[0014] The electromechanical actuator, whose housing comprises two housing parts permanently joined according to the patent application, is, for example, a steering actuator for steering the rear wheels of a vehicle or for steering the front wheels in the case of a steer-by-wire system. The actuator could also be configured as an electromechanical actuator for a roll stabilizer.

[0015] In all cases, the overlap area, in which the protrusion of the first housing part, which at least partially penetrates the second housing part, is located, and in addition, material of the second housing part is displaced into the recesses of the first housing part, provides a surface structuring at the joint of two components, namely housing parts, which serves as protection against penetration welding, especially in laser welding.

[0016] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows: Fig. 1. Sectional view of a steering actuator housing composed of two housing parts, Fig. 2 a detail of one of the two housing parts in a cutaway perspective view, Fig. 3 to 5 several steps to connect the two housing parts, Fig. 6. Schematic representation of the steering actuator.

[0017] An actuator, designated by reference numeral 1 and shown in the figures only partially and in a partially schematic manner, is designed as an electromechanical steering actuator for the rear axle steering system of a motor vehicle. The steering actuator 1 has a central axis MA oriented in the transverse direction of the motor vehicle. For the basic design and function of rear axle steering systems with electromechanical actuation, reference is made to the prior art cited at the beginning.

[0018] The housing 2 of the actuator 1 has a cylindrical shape and comprises two housing parts 3, 4. The two housing parts 3, 4 have end faces 5, 6 at which they are to be connected. An electric motor 17 is integrated into the actuator, the central axis of which is identical to the central axis MA of the entire actuator 1.

[0019] A rotor of the electric motor 17 is designated 18, and an associated stator is designated 19. The rotor 18 is connected to a shaft 21, which is driven, among other things, by a Fig. 6 recognizable bearing 20, in the present case a rolling bearing, namely a ball bearing, is mounted in housing 2. A bearing also in Fig. The control unit 16 shown in the diagram comprises a printed circuit board 13, which is not visible in this representation and lies in a plane to which the central axis MA is a plane normal, as well as a number of components 14 which are located on the printed circuit board 13.

[0020] To prepare the connection between the two housing parts 3, 4, which in this case are made of steel, the end face 5 of the first housing part 3 is machined. Without loss of generality, it is assumed in the following that the interior of the housing 2, designated IR, has a circular cylindrical shape, which is equivalent to the end faces 5, 6 being annular disk-shaped surfaces. The central axis of each housing part 3, 4 coincides with the central axis MA of the entire actuator 1. The space outside the housing 2 is designated as the external space AR.

[0021] By machining the end face 5, in this case by turning, a ring-shaped circumferential protrusion 7 is produced, which provides a cutting edge 8. The term "cutting edge" is used in this case although no object is to be cut, i.e., divided into several pieces, by this edge.

[0022] Radially inside and radially outside – each with reference to the central axis MA of the housing parts 3, 4 – the projection 7 including the cutting edge 8 creates an inner circumferential recess 9 and an outer circumferential recess 10, respectively, during machining. The overall ring-shaped recesses 9, 10, i.e., expansion spaces, border the projection 7.

[0023] As long as the housing parts 3 and 4 are separated from each other, as shown in Fig. As shown in Figure 3, the alignment between housing parts 3 and 4 can be adjusted as needed. A joining area is generally designated FB. The interior area IR, enclosed by the first housing part 3, contains the [missing information]. Fig. 6 electric motor 17 shown, for example in the form of a permanent magnet excited or separately excited synchronous motor, optionally together with a gearbox, while in the second housing part 4 the control unit 16 required for controlling the electric motor 17 is placed.

[0024] Once the final assembly position is determined, the second housing part 4 is installed as shown in Fig. Figure 4 illustrates that the actuator 1 is pressed against the first housing part 3 by means of a mounting force F acting in the axial direction. The final mounting position is determined, for example, by the position of busbars in the interior IR.

[0025] The assembly force F ensures that the cutting edge 8 penetrates the initially completely flat end face 6 of the second housing part 4. As the protrusion 7 penetrates the second housing part 4, material 11, 12 of the second housing part 4 is raised, which then finds space in the inner recess 9 and the outer recess 10, respectively.

[0026] In the constellation according to Fig. 5 is the relative positioning between the housing parts 3, 4 compared to the arrangement according to Fig. 4 unchanged. In both figures, one of the components 14 is indicated, which is located in the interior IR on the circuit board 13. Component 14 is a heat-sensitive part that must not be damaged by the subsequent welding process. In addition, the introduction of contamination, for example in the form of particles or soot, into the interior IR must be avoided.

[0027] As in Fig.As illustrated in Figure 5, a laser beam LS is used to create a weld 15 at the joint between the two housing parts 3 and 4. At worst, the laser beam LF reaches the joining area FB, where there is an overlap between the housing parts 3 and 4. Should the laser beam LS reach the joining area FB at all, it will be stopped at the latest at an impact point AP within the joining area FB. Overall, especially outside the joining area FB, a gap-free contact between the housing parts 3 and 4 is already present before the weld 15 is formed.

[0028] Theoretically, stopping the laser beam LS could also be achieved by means of circumferential steps formed on the end faces 5, 6. However, this would eliminate the possibility of aligning the housing parts 3, 4 in the intended manner before joining. The simple geometric design of the housing parts 3, 4, in particular the end face 6 of the second housing part 4, is also worth mentioning. Reference symbol list 1 actuator 2 cases 3 first housing part 4 second housing part 5. End face of the first housing part 6. Front surface of the second housing part 7. Circulating survey 8 cutting edge 9 inner circumferential depression 10 outer circumferential recesses 11 materials raised, within the survey 12 materials raised, outside the survey 13 Circuit board 14 Component 15 weld seam 16 Control unit 17 Electric motor 18 Rotor 19 Stator 20 bearings, rolling bearings 21st wave AP impact point AR Outdoor space F Assembly force FB joining area IR interior LS Laser radiation MA Central Axis QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2014 213 137 A1

[0002] DE 10 2021 104 646 A1

[0003]

Claims

[1] Method for joining housing parts (3, 4) wherein two end faces (5, 6) of the housing parts (3, 4) are to be joined together, comprising the following steps: - Creating a circumferential elevation (7) in the end face (5) of one of the two housing parts (3), wherein the elevation (7) forms a cutting edge (8) and inside and outside the circumferential elevation (7) a circumferential depression (9, 10) is formed, whereas the end face (6) of the second housing part (4) initially remains flat, - The two housing parts (3, 4) are brought together under force, so that the cutting edge (8) is pressed into the end face (6) of the second housing part (4) and at the same time material of the second housing part (4) is displaced into the circumferential recesses (9, 10), whereby outside the area in which the circumferential protrusion (7), the recesses (9, 10) and the displaced material are located, a flat contact of the second housing part (4) with the first housing part (3) is achieved, - Welding the first housing part (3) to the second housing part (4), producing a weld seam (15) that reaches a maximum of the area in which the circumferential protrusion (7), the recesses (9, 10) and the displaced material are located. [2] Method according to claim 1, characterized by that the two housing parts (3, 4) are aligned within a given tolerance range before being attached. [3] Method according to claim 1 or 2, characterized by , that the end face (5) of the first housing part (3) is machined by machining, in particular by turning. [4] Method according to any one of claims 1 to 3, characterized by , that the two housing parts (3, 4) are joined together by laser welding. [5] Method according to any one of claims 1 to 4, characterized by , that during welding at least one heat-sensitive component (14) is located in the interior (IR) enclosed by the housing parts (3, 4). [6] Electromechanical actuator (1) comprising two housing parts (3, 4) joined according to the method of claim 1. [7] Actuator (1) according to claim 6, characterized by , that the two housing parts (3, 4) are joined without seals. [8] Actuator (1) according to claim 6 or 7, characterized by that it is designed as a steering actuator, in particular as an actuator for rear axle steering.

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