Spindle drive unit

Abstract

Spindle drive device (10), comprising a spindle (12) provided with an external thread, a thread engagement element (16) that engages with the external thread of the spindle (12), a drive assembly (20) with a drive unit (22) which is configured to drive the spindle (12) or the thread engagement element (16), wherein the spindle (12) or the thread engagement element (16) is connected to at least one connecting unit (14, 18) for connecting the spindle drive device (10) to a superior assembly, i.e., not belonging to the spindle drive device (10), characterized in that the spindle (12) is a trapezoidal thread spindle made of carbon steel and is heat-treated by means of at least one thermochemical process.

Description

[0001] The invention relates to a spindle drive device comprising a spindle provided with an external thread, a thread engagement element engaged with the external thread of the spindle, a drive assembly with a drive unit which is configured to drive the spindle or the thread engagement element, wherein the spindle or the thread engagement element is connected to at least one connecting unit for connecting the spindle drive device to a superior assembly, i.e., not belonging to the spindle drive device.

[0002] Spindle drives are well-known in the automotive sector and are used, for example, to open and close doors and / or tailgates of motor vehicles. The requirements regarding wear and corrosion are particularly high in the automotive industry, so it is common practice to use stainless steels to meet these requirements. At the same time, however, it is desirable to provide cost-effective components. The totality of these conflicting requirements cannot be met with currently known spindle drives.

[0003] It is therefore an object of the present invention to provide an improved spindle drive device which can meet all the requirements.

[0004] This problem is solved according to the invention by a spindle drive device comprising a spindle provided with an external thread, a thread engagement element engaged with the external thread of the spindle, a drive assembly with a drive unit which is configured to drive the spindle or the thread engagement element, wherein the spindle or the thread engagement element is connected to at least one connecting unit for connecting the spindle drive device to a superior assembly, i.e., not belonging to the spindle drive device, wherein the spindle is a trapezoidal threaded spindle made of carbon steel and is heat-treated by means of at least one thermochemical process.

[0005] Trapezoidal lead screws, capable of transmitting high axial forces, are used to convert rotary motion into linear motion. In contrast to the prior art, the spindle drive device according to the invention features a trapezoidal lead screw made of carbon steel. This significantly reduces raw material costs. The heat treatment of the spindle ensures compliance with requirements regarding corrosion and wear.

[0006] Thermochemical heat treatments that can improve the wear and corrosion properties of the spindle include processes such as carburizing, boronizing, carbonitriding, nitriding, nitrocarburizing, oxidizing, silicifying or vanadizing.

[0007] In an advantageous further development of the invention, the spindle is heat-treated using several thermochemical processes. This allows the properties of the spindle to be further improved.

[0008] Preferably, the spindle is heat-treated at least by means of a nitriding process, so that the spindle has a wear-resistant surface layer. The nitriding process is a method for surface hardening. The core of the component remains unchanged and retains its strength, so that the wear and corrosion behavior of the spindle can be improved without affecting the core properties.

[0009] Nitriding processes such as nitrocarburizing in gas or in a salt bath have proven to be particularly advantageous, especially with regard to costs.

[0010] Preferably, the spindle is provided with an oxidized surface, giving it a dark appearance. Advantageously, the oxidation process can follow a nitrocarburizing process in a gas or salt bath.

[0011] In general, within the scope of the invention, the thermochemical treatments carbonitriding, nitriding and oxidizing can be part of the heat treatment.

[0012] However, other thermochemical processes are also possible to ensure compliance with corrosion requirements and wear-resistant surface layer properties.

[0013] Post-oxidation can apply an additional thin oxide layer to the compound layer formed during nitriding, which further improves corrosion resistance.

[0014] According to an advantageous embodiment of the spindle drive device, the spindle can be connected to a first connecting unit for connecting the spindle drive device to a superior assembly, i.e., not belonging to the spindle drive device, and the thread engagement element can be connected to a second connecting unit for connecting the spindle drive device to a superior assembly, i.e., not belonging to the spindle drive device.

[0015] Alternatively, an actuating element or connecting element directly or indirectly connected to the threaded engagement element can be provided as a connecting unit.

[0016] According to advantageous embodiments of the invention, the thread engagement element can be designed as a spindle nut or worm gear.

[0017] Preferably, the spindle drive device is designed as an electric spindle drive for opening and / or closing a movable vehicle part. The movable vehicle part can be, for example, a vehicle door, a tailgate, a hood, a cargo door, or a luggage compartment lid.

[0018] The present invention is described below with reference to an exemplary embodiment.

[0019] It represents: Fig. 1 a side cross-sectional view of a spindle drive device according to the invention.

[0020] In Fig. Figure 1 shows a spindle drive device 10 according to the invention, which is described as an example of an electric spindle drive as used in the automotive sector. Such spindle drives are provided for opening and / or closing a movable vehicle part such as a vehicle door or tailgate.

[0021] As can be seen, the spindle drive device 10 comprises a spindle 12 provided with an external thread, which is connected to a first connecting unit 14 for connecting the spindle drive device 10 to a superior assembly, i.e., not belonging to the spindle drive device 10, such as a tailgate of a vehicle, and a thread engagement element 16 which engages with the external thread of the spindle 12 and is connected here as a spindle nut to a second connecting unit 18 for connecting the spindle drive device 10 to a superior assembly, i.e., not belonging to the spindle drive device, such as a vehicle body.

[0022] The spindle drive device 10 further comprises a drive assembly 20, which has an electric motor as a drive unit and is designed to drive the spindle 12.

[0023] According to the illustrated embodiment, an output shaft of the drive unit, which is not visible, carries a worm shaft which in turn meshes with a drive wheel 22 designed as a worm gear. The drive wheel 22 is non-rotatably connected to the spindle 12 via a splined shaft 24.

[0024] The drive assembly 20 is housed in a drive assembly housing 26, which is made of plastic.

[0025] The drive wheel 22 and the spindle 12 are mounted via a bearing 28 relative to a cylindrical coupling element 30 and relative to the drive assembly housing 26.

[0026] The coupling element 36 connects the first connecting unit 14 to the spindle 12 in such a way that a displacement of these two elements away from each other in an axial direction of the spindle 12 is prevented.

[0027] A steel tube 32 connected to the threaded engagement element 16 is connected to the second connecting unit 18.

[0028] In the cutaway side view of Fig. Figure 1 shows how the spindle nut 16 engages with the spindle 12 in threaded engagement. Upon rotation of the spindle 12, the thread engagement element 16 is engaged according to the direction of rotation and the type of thread of the spindle 12. Fig. 1 shifted to the left or right, so that the second connecting unit 18 is shifted towards or away from the first connecting unit 14 via the steel tube 32.

[0029] The in Fig. 1 The right end of the spindle 12 is supported in the steel tube 32 via a guide ring 34, which is supported and received in a guide tube 38 via a guide bushing 36.

[0030] Furthermore, in Fig. 1 to recognize that the first connecting unit 14 is connected to a first sheathing tube 40 and the second connecting unit 18 is connected to a second sheathing tube 42, wherein the second sheathing tube 42 can be inserted into the first sheathing tube 40 in a telescopic manner.

[0031] The use of trapezoidal lead screws is particularly advantageous in electric spindle drives, as they can transmit high axial forces. In contrast to the prior art, the spindle drive device according to the invention features a trapezoidal lead screw made of carbon steel. This significantly reduces raw material costs. Heat treatment of the lead screw 12 ensures compliance with requirements regarding corrosion and wear.

[0032] Suitable cost-effective spindle raw materials include, for example, carbon steels such as C15 from the group of unalloyed case-hardening steels [DIN EN 10084], C25 from the group of unalloyed heat-treatable steels [DIN EN 10083-2] or other carbon steels from the general structural steels (including carbon steels with additional symbols, such as C45U or C15R).

[0033] The spindle 12 is heat-treated, at least by means of a nitriding process, so that it has a wear-resistant surface layer. Nitriding processes such as nitrocarburizing in gas or salt baths, which are particularly advantageous in terms of cost, enable surface hardening while leaving the core of the component unchanged and retaining its strength. This improves the wear and corrosion behavior of the spindle 12 without affecting its core properties. A further thin oxide layer can be applied to the compound layer formed during nitriding by post-oxidation, which further improves corrosion resistance. The resulting dark or black surface is sometimes an additional requirement in the automotive industry.

[0034] As already mentioned, the in Fig.The spindle drive device 10 shown and described in section 1 is not to be considered limiting to the invention. Alternatively, for example, a connecting element or actuating element directly or indirectly connected to the threaded engagement element 16, which can be designed as a spindle nut or worm gear within the scope of the invention, can be provided as a connecting unit, and which serves as a connection to a vehicle part (body, door, tailgate, etc.) according to the respective application.

[0035] According to one exemplary embodiment, the actuating element can also be a safety strap connected to a vehicle door. Furthermore, it is possible that the threaded engagement element 16 is connected to the vehicle body by means of a connecting element or a bracket.

[0036] The drive assembly can also be arranged parallel or essentially perpendicular to a spindle 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 non-patent literature

[0000] DIN EN 10084

[0032] DIN EN 10083-2

[0032]

Claims

[1] Spindle drive device (10) comprising a spindle (12) provided with an external thread, a thread engagement element (16) that engages with the external thread of the spindle (12), a drive assembly (20) with a drive unit (22) which is configured to drive the spindle (12) or the thread engagement element (16), wherein the spindle (12) or the thread engagement element (16) is connected to at least one connecting unit (14, 18) for connecting the spindle drive device (10) to a superior assembly, i.e., not belonging to the spindle drive device (10), characterized by , that the spindle (12) is a trapezoidal threaded spindle made of carbon steel and is heat-treated by means of at least one thermochemical process. [2] Spindle drive device (10) according to claim 1, characterized by, that the spindle (12) is heat-treated by several thermochemical processes. [3] Spindle drive device (10) according to claim 1 or 2, characterized by , that the spindle (12) is heat-treated at least by means of a nitriding process, so that the spindle (12) has a wear-resistant surface layer. [4] Spindle drive device (10) according to one of the preceding claims, characterized by , that the spindle (12) is provided to be oxidized, so that it has a dark surface. [5] Spindle drive device (10) according to one of the preceding claims, characterized by, that the spindle (12) is connected to a first connecting unit (14) for connecting the spindle drive device (10) to a superior assembly, i.e., not belonging to the spindle drive device (10), and the thread engagement element (16) is connected to a second connecting unit (18) for connecting the spindle drive device (10) to a superior assembly, i.e., not belonging to the spindle drive device (10). [6] Spindle drive device (10) according to any one of the preceding claims 1 to 4, characterized by , that a connecting element or connecting element directly or indirectly connected to the threaded engagement element (16) is provided as a connecting unit. [7] Spindle drive device (10) according to one of the preceding claims, characterized by , that the thread engagement element (16) is designed as a spindle nut or worm gear. [8] Spindle drive device (10) according to one of the preceding claims, characterized by , that the spindle drive device (10) is intended as an electric spindle drive for opening and / or closing a movable part of the vehicle.

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