METHOD FOR CONNECTING A SPINDLE HOLDING ELEMENT TO A GUIDE RAIL, AND LONGITUDINAL ADJUSTMENT DEVICE FOR A VEHICLE SEAT

Description

[0001] The invention relates to methods for connecting a spindle holding element with a guide rail for manufacturing a longitudinal adjustment device for a vehicle seat and a longitudinal adjustment device for a vehicle seat, see claims 1, 3 and 11.

[0002] In such a process, the spindle retaining element for attaching a spindle is materially bonded to a wall section of the guide rail.

[0003] A longitudinal adjustment device is used to adjust the longitudinal position of a vehicle seat within a vehicle. In a longitudinal adjustment device, a vehicle seat is, for example, mounted on two pairs of guide rails on either side of the seat and thus slidable to the vehicle floor, such that the longitudinal position of the vehicle seat can be adjusted by sliding the upper rails of the guide rail pairs to the lower rails of the guide rail pairs.

[0004] Such longitudinal adjustment devices typically use a spindle drive in which, in one embodiment, a spindle is fixed to an associated guide rail and engages in threaded contact with a spindle nut of an adjustment mechanism connected to the other guide rail. When the spindle nut is driven, it rotates relative to the spindle and, by the action of the threaded engagement, is moved longitudinally along the spindle, thus displacing the guide rails relative to each other.

[0005] When connecting the spindle to the associated guide rail, it must be ensured that the spindle remains securely attached to the guide rail even under high loads, especially in a crash, and cannot detach from the guide rail. Therefore, the connection between the spindle and the guide rail is subject to stringent strength requirements.

[0006] Furthermore, the spindle must assume a defined position relative to the associated guide rail and, in particular, be held at a defined height (in the Z direction), but also in a defined longitudinal and transverse position (in the X and Y directions) relative to the guide rail to ensure quiet and smooth adjustment operation. For this to be possible, the spindle must maintain a defined position relative to the associated guide rail despite any existing tolerances.

[0007] In a longitudinal adjustment device known from DE 10 2004 001 593 B3, a spindle is welded at both ends to an associated fastening element in the form of a retaining bracket and is thereby fixed to the fastening elements.

[0008] In a longitudinal adjustment device known from WO 2016 / 150791 A1, a spindle is connected at its ends to an associated guide rail via spindle holders. The spindle holders each have two flanges between which the spindle is mounted and which are connected to the spindle by welded joints.

[0009] From DE 10 2018 212 288 A1 (disclosing the preamble of claims 1, 3 and 11) a method for connecting a spindle to a spindle holding element for manufacturing a longitudinal adjustment device for a vehicle seat is known, in which the spindle is joined to the spindle holding element by means of a material bond using a resistance welding process.

[0010] JP 2015-067146 A discloses a longitudinal adjustment device for a vehicle seat, comprising an upper guide rail and a lower guide rail. A spindle is arranged on the lower guide rail via a spindle retaining element. A spindle nut is arranged on the spindle and is rotatably mounted on the upper guide rail, so that by rotating the spindle nut the upper guide rail can be moved relative to the lower guide rail.

[0011] Another longitudinal adjustment device using a spindle drive for longitudinal adjustment of a vehicle seat is known from JP S62227831 A.

[0012] The object of the present invention is to provide a method for connecting a spindle holding element with a guide rail for manufacturing a longitudinal adjustment device for a vehicle seat and a longitudinal adjustment device for a vehicle seat that enables a fixed connection of a spindle via one or more spindle holding elements with a guide rail, with a manufacturing process that is easy to handle and monitor.

[0013] This problem is solved by an object having the features of claim 1 and claim 3.

[0014] Accordingly, the spindle retaining element is connected to the wall section of the guide rail using a resistance welding process.

[0015] The spindle retaining element is intended to secure a spindle to an associated guide rail of a longitudinal adjustment device in such a way that the spindle is reliably and securely connected to the guide rail. The connection of the spindle to the guide rail is achieved by bonding the spindle retaining element to a section of the guide rail wall, in particular the base of a guide rail with a generally U-shaped cross-section, thus ensuring that the spindle retaining element is securely attached to this section of the guide rail wall.

[0016] To create the material-bonded connection, a resistance welding process is used, in which a welding current is passed between the spindle holding element and the guide rail in order to create a welded connection at the transition between the spindle holding element and the guide rail via a current density acting there.

[0017] In principle, various resistance welding processes can be used. For example, resistance spot welding can be employed, in which a current density is set via approximately spot-shaped welding electrodes. Alternatively, a resistance projection welding process can be used, in which the current density required for welding is generated by the geometric shape of the components to be joined. In each case, the spindle holding element and the guide rail are advantageously held against each other under force during the joining process and welded together using a welding current.

[0018] Resistance welding is advantageously performed without the addition of filler material. In resistance welding, the spindle retaining element and the guide rail are melted on their facing sides, thus creating a metallurgical bond between the spindle retaining element and the guide rail. This process causes the spindle retaining element to conform to the guide rail, enabling simple and advantageous tolerance compensation for a defined position of the spindle retaining element and, consequently, of the spindle mounted on the spindle retaining element relative to the guide rail.

[0019] The position of the spindle relative to the guide rail along a vertical direction (Z-direction) can be adjusted via the settling behavior of the spindle retaining element during resistance welding. In contrast, the position of the spindle retaining element relative to the guide rail in the longitudinal direction (X-direction) and transverse direction (Y-direction) can be set by predefining the position of the spindle retaining element relative to the guide rail within the welding tool.

[0020] In the resistance welding process according to the invention, a first welding electrode is attached to the spindle holding element and a second welding electrode to the guide rail. An electric welding current is passed between the first and second welding electrodes through the spindle holding element and the guide rail, resulting in a high current density at the interface between the spindle holding element and the guide rail. This welding current then creates a weld joint at the interface between the spindle holding element and the guide rail.

[0021] The first welding electrode and the second welding electrode are used, for example, to press the spindle holding element and the guide rail against each other with a predetermined contact force, so that the weld joint is produced under force between the spindle holding element and the guide rail.

[0022] The first welding electrode can, for example, be placed on a side of the spindle holder facing away from the guide rail wall section. The first welding electrode can have a flat contact surface to rest against an edge of the spindle holder facing away from the guide rail wall section. However, it is also conceivable and possible that the first welding electrode is curved or otherwise shaped differently from a linear form in the area of ​​its contact surface, in order to adapt the welding electrode to a shape of the spindle holder and thus enable a flat contact of the first welding electrode against the spindle holder.

[0023] The first welding electrode has (according to a first aspect of the invention; see claim 1) a receiving opening in which the spindle holding element for introducing the welding current is received. The receiving opening can, for example, be shaped like a slot formed in the first welding electrode and shaped such that the spindle holding element can be received in the receiving opening and brought into surface contact with the first welding electrode. The first welding electrode can be configured for one-sided or two-sided surface contact with the spindle holding element. In particular, in an advantageous embodiment, the welding electrode can be brought into surface contact with a surface section of the spindle holding element that extends transversely to a longitudinal axis of the spindle to be held by the spindle holding element. The contact can be on one side of the surface section.However, it can be advantageous to position the welding electrode against the surface section on both sides in order to introduce a welding current into the spindle holding element from both sides. In particular, by positioning the welding electrode against the spindle holding element on both sides, a high-strength connection between the spindle holding element and the guide rail can be achieved.

[0024] According to a further aspect of the invention (see claim 3), the spindle retaining element is connected to the wall section of the guide rail using a resistance welding process, wherein, in the resistance welding process, a first welding electrode is applied to the spindle retaining element and a second welding electrode is applied to the guide rail in order to conduct an electric welding current between the first and second welding electrodes. The first welding electrode has a first electrode section and a second electrode section, between which the spindle retaining element is arranged for introducing the welding current. The first electrode section can be brought into contact with a first side of the spindle retaining element, while the second electrode section is brought into contact with a second side of the spindle retaining element opposite the first side.The electrode sections thus enable contact on both sides of the spindle holding element, in particular on opposite sides of a surface section of the spindle holding element extending transversely to the longitudinal axis of the spindle, so that a welding current can be introduced into the spindle holding element on both sides.

[0025] In one embodiment, the electrode sections can be clamped relative to each other using a clamping device, so that the electrode sections can be brought into contact with the spindle holding element located between them in a clamping manner. The clamping device can, for example, have a clamping bolt whose shaft end engages an opening in the spindle holding element, which itself serves to receive the spindle, thus positioning the spindle holding element relative to the first welding electrode. The electrode sections can be clamped relative to each other via a clamping bolt, so that the electrode sections are brought into contact with opposite sides of the spindle holding element in a clamped manner to initiate the welding current.

[0026] In one embodiment of the method, the second welding electrode can, for example, be attached to a side of the guide rail wall section facing away from the spindle holding element. It is conceivable to attach the second welding electrode at a location on the rear side of the wall section, i.e., on the side of the wall section facing away from the spindle holding element, that corresponds to the axial location where the spindle holding element attaches to the wall section, so that the second welding electrode is opposite the spindle holding element. This results in a comparatively short current path through the wall section. Alternatively, it is also conceivable that the second welding electrode is attached to the guide rail axially offset from the spindle holding element.

[0027] In one embodiment, the spindle retaining element has a surface section with a formed end edge. To connect the spindle retaining element to the guide rail, its end edge is butted against the wall section of the guide rail, and the end edge is then welded to the wall section of the guide rail using resistance welding.

[0028] The spindle retaining element can, for example, be formed as a stamped part and has a plate shape, so that the spindle retaining element and its surface section extend essentially along a flat plane. The connection to the wall section of the guide rail is achieved by butting the end edge formed on the surface section against the wall section of the guide rail.

[0029] In one embodiment, the spindle retaining element extends transversely to a longitudinal axis along which the spindle is longitudinally extended, and is attached to the wall section of the guide rail in such a way that, when the spindle is connected to the spindle retaining element, the spindle nut extends longitudinally along the guide rail, and the longitudinal axis of the spindle is thus aligned parallel to the guide rail.

[0030] In one embodiment, particularly when using a resistance projection welding process, the spindle retaining element has at least one projection section on its end face. This projection is brought into contact with the wall section when the spindle retaining element is positioned, in order to create a weld joint in the area of ​​the projection section. During resistance projection welding, the spindle retaining element is melted, particularly in the area of ​​the projection section, so that a metal bond is created across the projection section.

[0031] Advantageously, the spindle holding element has several projection sections, each separated in pairs by an intervening recessed section and arranged, for example, along a transverse direction perpendicular to the longitudinal axis. The projection sections extend from the surface section towards the wall section and serve to abut the wall section. During resistance welding, a metallurgical bond is created in the area of ​​the projection sections.

[0032] By using one or more protruding sections formed on the front edge of the surface section of the spindle retaining element, the advantage of favorable settling behavior during resistance welding is achieved. Thus, by melting in the area of ​​the protruding sections, the spindle retaining element can settle relative to the wall section in such a way that a defined height of the spindle retaining element can be set for connecting the spindle to the guide rail.

[0033] In one embodiment, when connecting the spindle retaining element to the guide rail, a nominal height of an opening in the spindle retaining element, designed for securing the spindle to the spindle retaining element, is set relative to the wall section of the guide rail. This nominal height can be adjusted relative to the wall section of the guide rail when the spindle retaining element is positioned, thus compensating for tolerances in the shape of the spindle retaining element and the wall section, particularly in the area of ​​the bump sections, and ensuring that these tolerances do not affect the position of the spindle retaining element relative to the guide rail.

[0034] To adjust the nominal height of the opening, one embodiment, for example, can monitor the distance between the welding electrodes during welding as a shut-off criterion. The distance between the welding electrodes is related to the height of the spindle holding element relative to the guide rail. By monitoring the distance between the first and second welding electrodes, the spindle holding element can be positioned at a defined height relative to the guide rail, ensuring that the spindle, once attached to the spindle holding element, assumes a defined height position relative to the guide rail.

[0035] As part of the process control, for example, the distance between the welding electrodes during resistance welding can be compared to a predetermined distance value in order to switch off the welding current as soon as the distance between the welding electrodes corresponds to the predetermined distance value. Once the predetermined distance value is reached, the welding process is thus terminated. Such control of the welding process enables precise tolerance compensation, particularly for the height position of the spindle holding element relative to the associated guide rail.

[0036] It is conceivable and possible to use such a control system when connecting each spindle holder to its corresponding guide rail during series production, thus controlling the welding process during the connection process. It is also conceivable and possible to use such a control system during initial calibration to define a welding duration that is then used in subsequent series production. The subsequent series production, in which spindle holders are connected to their corresponding guide rails, can then proceed without process monitoring, i.e., without monitoring the distance between the welding electrodes.

[0037] Various parameters can be set for resistance welding to influence the quality of the weld, particularly its strength. For example, the welding current can be set to a value between 5 kA and 25 kA, such as between 10 kA and 20 kA. The clamping force with which the spindle holder and the guide rail are pressed against each other via the welding electrodes can be set, for example, between 100 daN (decanewtons) and 1000 daN, preferably between 400 daN and 900 daN. The current duration for which the welding current is applied during the resistance welding process can be set, for example, to a value between 10 ms and 200 ms, preferably between 30 ms and 100 ms, such as 50 ms. All values ​​can be preset, for example, based on initial calibration and material testing.It is also conceivable and possible to vary the process parameters in the welding process in a controlled manner, for example the contact force and / or the current time depending on a control system based on the distance between the welding electrodes.

[0038] By using a short current duration, particularly one of 50 ms or less, it is possible to create durable bonds between different materials. For example, it allows for the metallurgical bonding of very hard materials, such as the hard steel used for the spindle retaining element, with softer materials, such as the softer material of the guide rail.

[0039] The problem is also solved by a longitudinal adjustment device with a guide rail according to claim 11, with a spindle connected to the guide rail and extending along a longitudinal axis, and a spindle retaining element by means of which the spindle is connected to the guide rail. It is provided that the spindle retaining element is connected to a wall section of the guide rail using a resistance welding process, wherein the spindle retaining element has a surface section with an end edge arranged thereon, and wherein the end edge of the spindle retaining element is butt-jointed to the wall section of the guide rail.

[0040] The advantages and beneficial designs described above for the method also apply analogously to the longitudinal adjustment device, so reference should be made to what has been stated above in this regard.

[0041] The underlying concept of the invention will be explained in more detail below with reference to the exemplary embodiments shown in the figures. The figures show: Fig. 1 a schematic view of a longitudinal adjustment device for a vehicle seat; Fig. 2 a view of a spindle retaining element for attaching a spindle to an associated guide rail; Fig. 3 a view of the spindle retaining element on a wall section of the associated guide rail; Fig. 4 an end view of the arrangement according to Fig. 3 Fig. 5 shows a partially cut-out side view of the arrangement according to Fig. 3 , showing the spindle retaining element on a wall section of the guide rail; Fig. 6 a partially enlarged view of the view according to Fig. 5 ; Fig. 7 an enlarged view of a section of the view according to Fig. 6Fig. 8 shows a view of a welding device for connecting the spindle holding element to the guide rail; Fig. 9 shows a view of the welding device according to Fig. 8 , without a second welding electrode and with the guide rail in a transparent view; Fig. 10 a view of a clamping device of the welding device; Fig. 11 a separate view of a first welding electrode with a spindle holding element mounted on it; Fig. 12 a view of a clamping bolt of the clamping device; and Fig. 13 an enlarged view of a shaft end of the clamping bolt with a spindle holding element arranged on it.

[0042] Fig. 1 shows an embodiment of a longitudinal adjustment device 1, which is used for longitudinal adjustment of a (in Fig. 1 (only schematically represented) vehicle seat 16 along a longitudinal direction X in a vehicle.

[0043] The longitudinal adjustment direction 1 typically has two pairs of guide rails, each formed by guide rails 10 and 11, of which an upper guide rail 11 is associated with the vehicle seat 16 and a lower guide rail 10 with the vehicle floor. By longitudinally adjusting the guide rails 10 and 11 relative to each other, the longitudinal position of the vehicle seat 16 in the vehicle can be adjusted.

[0044] The adjustment of the guide rails 10, 11 relative to each other is carried out by an electric motor via a spindle drive, which in the illustrated embodiment has a spindle 12 fixed to the lower guide rail 10 and an adjustment gear 15 attached to the upper guide rail 11 for each pair of guide rails.The spindle 12 is fixedly held on the lower guide rail 10 by means of spindle retaining elements 13, 14 and is thus rotationally fixed. It has an external thread 120, through which the spindle 12 engages with a spindle nut of the adjustment gear 15 in such a way that the spindle nut can be set into a rotational movement relative to the spindle 12 by means of an electric motor drive and thereby rolls along the spindle 12 over the thread engagement, so that the adjustment gear 15 is adjusted longitudinally along a longitudinal axis L, along which the spindle 12 extends, relative to the spindle 12 and thus the upper guide rail 11 is moved relative to the lower guide rail 10 along the longitudinal axis L.

[0045] In the illustrated embodiment, the spindle 12 is firmly connected to the lower guide rail 10 via spindle retaining elements 13, 14 and is fixed to a base 100 of the lower guide rail 10 via the spindle retaining elements 13, 14.

[0046] While the spindle 12 is screwed into the spindle retaining element 13, for example, and thus connected to the spindle retaining element 13, the spindle 12 is welded to the other spindle retaining element 14, for example, so that the spindle 12 is fixed to the guide rail 10 in a rotationally fixed manner.

[0047] Fig. 2 Figure 1 shows an embodiment of a spindle holding element 14, which is plate-shaped, for example as a stamped part, and made of, for example, a steel material. The spindle holding element 14 has a surface section 140 which—with the longitudinal adjustment device 1 mounted—extends transversely to the longitudinal axis L of the spindle 12 and—as shown in Figure 1— Figs. 3 to 7 shown - with a wall section in the form of a base 100 of the guide rail 10 such that the spindle retaining element 14 protrudes from the base 100 and is thereby load-bearingly connected to the base 100.

[0048] The surface section 140 forms an opening 141 into which the spindle 12 is inserted for attachment to the spindle retaining element 14. The spindle 12 can be secured in the opening 141, for example, by welding, so that in the assembled position the spindle 12 is rotationally fixed to the spindle retaining element 14. Alternatively, a screw connection between the spindle 12 and the spindle retaining element 14 can also be made via the opening 141.

[0049] The surface section 140 is bounded by an end edge 142, with which the spindle retaining element 14 is attached to the base 100 for connection with the guide rail 10, in order to create a welded connection 2 between the spindle retaining element 14 and the base 100 of the guide rail 10. The connection of the spindle retaining element 14 to the base 100 is carried out using a resistance welding process, in particular resistance projection welding, in the course of which the welded connection 12 is created and thus a butt joint of the spindle retaining element 14 with the guide rail 10 is formed.

[0050] On the end face 142 of the spindle retaining element 14, bossed sections 143 are formed, which are regularly spaced apart from each other along a transverse direction Y extending perpendicular to the longitudinal axis L and are separated from each other in pairs by an intervening recessed section 144. The bossed sections 143 project towards the base 100 relative to the recessed sections 144, so that when the spindle retaining element 14 is placed against the base 100 to establish the connection between the spindle retaining element 14 and the guide rail 10, the bossed sections 143 come into contact with the base 100.

[0051] The weld connection 2 between the spindle retaining element 14 and the base 100 of the guide rail 10 is made using a Figs. 8 to 13The welding device 3 shown is manufactured by a resistance welding process, in which a welding current is passed through the spindle holding element 14 and the base 100 via welding electrodes 30, 31, as shown in Fig. 8 As shown, a first welding electrode 30 is located on the spindle holding element 14, while a second welding electrode 31 is located on the back side of the base 100 of the guide rail 10 in order to conduct a welding current between the welding electrodes 30, 31 and thus between the spindle holding element 14 and the base 100 to produce the weld joint 2.

[0052] If a welding current is passed through the welding electrodes 30, 31 via the spindle holding element 14 and the base 100 to produce the welded joint 2, a current density of such a high magnitude is established at the transition between the spindle holding element 14 and the base 100 in the area of ​​the projection section 143, with which the spindle holding element 14 rests on the base 100, that the projection sections 143 of the spindle holding element 14 and the base 100 are melted in the area of ​​the transition and thus a metallurgical connection is established between the spindle holding element 14 and the base 100.

[0053] The welding electrodes 30, 31 apply a clamping force to the spindle retaining element 14 and the base 100, pressing the spindle retaining element 14 against the base 100. This causes the spindle retaining element 14 and the base 100 to align with each other during welding. This allows for the compensation of tolerances and the precise adjustment of the height of the spindle retaining element 14 relative to the base 100 and thus to the associated guide rail 10.

[0054] The welding electrodes 30, 31 are part of a welding device 3, which includes a control unit 32 for controlling the welding process. The control unit 32 is used in particular to control the welding current through the welding electrodes 30, 31 and also to adjust the contact force F exerted by the welding electrodes 30, 31 on the spindle holding element 14 and the base 100.

[0055] The welding current can be set via the control unit 32, in particular to a value in the range between 5 kA and 25 kA, preferably between 10 kA and 20 kA, for example between 13 kA and 18 kA. The contact force can be set, for example, to a value between 100 daN and 1000 daN, preferably between 400 daN and 900 daN, for example between 500 daN and 800 daN. The holding time for the contact force and the current duration for the welding current I can also be set and controlled via the control unit 32.

[0056] The welding current is supplied via the welding electrodes 30, 31 such that it flows through the spindle retaining element 14 and the base 100, and a current density is established at the interface between the spindle retaining element 14 and the base 100 such that the spindle retaining element 14 and the base 100 are partially melted. To ensure optimal current supply, the first welding electrode 30 is adapted to maintain a flat contact surface on both sides between the first welding electrode 30 and the surface section 140 of the spindle retaining element 14. In contrast, the second welding electrode 31 can, for example, be flat, to ensure a flat contact surface on the base 100 behind the spindle retaining element 14.

[0057] At the in Figs. 8 to 13In the welding device 3 shown, the first welding electrode 30 has a slot-like receiving opening 300 in which the spindle holding element 14 is received for producing the weld joint 2. The receiving opening 300 is bounded on both sides by electrode sections 301, 302, which extend parallel to each other and are spaced axially apart from each other along the longitudinal axis L (relative to the spindle 12 to be connected to the spindle holding element 14) such that the spindle holding element 14 can be received between the electrode sections 301, 302.

[0058] To produce the weld joint 2, the spindle holding element 14 is positioned in the receiving opening 300 of the first welding electrode 30 and fixed to the first welding electrode 30 by means of a clamping device 33. This is achieved by engaging a clamping bolt 331, guided in a bearing block 330, with a shaft end 334 in the opening 341 of the spindle holding element 14, so that the spindle holding element 14 is fixed at its height relative to the welding electrode 30 and supported on the welding electrode 30 by the clamping bolt 331. The shaft end 334 extends through an opening 303 in the electrode section 302 and engages with the spindle holding element 14 within the receiving opening 300, as can be seen from a view of Figs. 12 and 13 with Figs. 10 and 11 as is evident.

[0059] The clamping bolt 331 can be clamped by means of a clamping handle 332 such that the electrode sections 301, 302 are brought close together and the spindle holding element 14 is thus clamped between the electrode sections 301, 302. At the transition between the shaft end 334 and a shaft 333 axially adjoining the shaft end 334, a contact section 335 is formed in the form of a circumferential step, with which the clamping bolt 331 acts on the electrode section 302 and clamps it relative to the electrode section 301.

[0060] The electrode sections 301, 302 thus enable the first welding electrode 30 to be positioned on opposite sides of the surface section 140 of the spindle holding element 14, so that a welding current can be introduced into the surface section 140 and thus into the spindle holding element 14 from both sides. In this way, a high-strength weld joint can be produced between the spindle holding element 14 and the base 100 of the guide rail 10, which is particularly resistant to the tensile forces F acting axially along the spindle 12 (see Fig. 7 ) can withstand the longitudinal adjustment direction 1 during operation. The spindle 12 can thus be firmly and securely connected to the guide rail 10 via the spindle retaining element 14.

[0061] The clamping device 33 is arranged on a table 336, as can be seen from Fig. 10The guide rail 10 can be mounted on a support element 337, the first welding electrode 30 and the bearing block 330 for connection with the spindle holding element 14, as shown in Fig. 9 It is evident that by attaching the second welding electrodes 31 to the back of the base 100 of the guide rail 10, the welding connection 2 can be made.

[0062] During the welding process, the projection sections 143 of the spindle retaining element 14 and the base 100 are melted where a connection exists, causing the spindle retaining element 14 and the base 100 to join together. After the weld is completed, a metallurgical bond is formed between the projection sections 143 of the spindle retaining element 14 and the base 100.

[0063] During the welding process, the spindle holding element 14 and the base 100 are pressed together with a clamping force by the welding electrodes 30, 31, and a welding current is applied. The holding time for the clamping force and the duration of the welding current are not usually the same; for example, the clamping force can be applied for a longer period than the welding current. After the welding current is switched off, the spindle holding element 14 and the base 100 are thus pressed against each other with force for a certain period of time until the weld joint 2 has hardened.

[0064] The welding process can be controlled, for example, depending on the distance between the welding electrodes 30, 31, in order to set a nominal height H nom of the spindle holding element 14 relative to the base 100, relative, for example, to the longitudinal axis L extending centrally through the opening 141, along which the spindle 12 extends when the longitudinal adjustment device 1 is fully assembled. For example, the distance between the welding electrodes 30, 31, which correlates with the height of the spindle holding element 14 relative to the base 100, can be used as a shutdown criterion. If, during welding, it is determined that the distance between the welding electrodes 30, 31 has reached a predetermined value and thus the spindle holding element 14 and the base 100 have moved to the desired height relative to each other, the welding current can be switched off and the welding process terminated.

[0065] Such control can be implemented during series production. However, it is also conceivable and possible to use such a control system to set process parameters during an initial calibration procedure, and then to carry out subsequent series production based on these set process parameters without further control, using the distance between the welding electrodes 30 and 31.

[0066] The nominal height H nom of the spindle retaining element 14 can be, as shown from Fig. 4 This can be seen, for example, from measuring points MP1, MP2, MP3. The nominal height H nom is relative to the center of the opening 141, which has a diameter D, where this center is spaced a height distance D1 from measuring point MP1 above the opening 141 and a height distance D2 from measuring points MP2, MP3 below the opening 141, as can be seen from Fig. 4 as is evident.

[0067] In particular, one or more spindle retaining elements can be connected to the associated guide rail by means of resistance welding of the type described above.

[0068] The spindle retaining elements can also be designed differently than shown and can, for example, have a block shape or the like. Reference symbol list

[0069] 1 Longitudinal adjustment device 10 Guide rail (lower rail) 100 Base 11 Guide rail (upper rail) 12 Spindle 120 Thread 13 Spindle holding element 14 Spindle holding element 140 Surface section 141 Opening 142 End edge 143 Hump section 144 Recessed section 15 Adjustment gear 16 Vehicle seat 2 Welded joint 3 Welding device 30, 31 Welding electrode 300 Receiving opening 301, 302 Electrode section 303 Opening 32 Control device 33 Clamping device 330 Bearing block 331 Clamping bolt 332 Clamping handle 333 Shank 334 Shank end 335 Mounting section 336 Table 337 Support element Diameter D1, D2 Distance F Force H Nominal height L Longitudinal axis MP1-MP3 measurement point

Claims

1. A method of connecting a spindle holding element (14) to a guide rail (10) for producing a longitudinal adjustment device (1) for a vehicle seat (16), wherein in the method the spindle holding element (14) is cohesively connected to a wall portion of the guide rail (10) for fastening a spindle (12), characterized in that the spindle holding element (14) is connected to the wall portion of the guide rail (10) by using a resistance welding method, wherein in the resistance welding method a first welding electrode (30) is attached to the spindle holding element (14) and a second welding electrode (31) is attached to the guide rail (10) in order to conduct an electric welding current between the first welding electrode (30) and the second welding electrode (31), wherein the first welding electrode (30) includes a receiving opening (300) in which the spindle holding element (14) is received for introducing the welding current.

2. The method according to claim 1, characterized in that the first welding electrode (30) is attached to a side of the spindle holding element (14) facing away from the wall portion of the guide rail (10).

3. A method of connecting a spindle holding element (14) to a guide rail (10) for producing a longitudinal adjustment device (1) for a vehicle seat (16), wherein in the method the spindle holding element (14) is cohesively connected to a wall portion of the guide rail (10) for fastening a spindle (12), characterized in that the spindle holding element (14) is connected to the wall portion of the guide rail (10) by using a resistance welding method, wherein in the resistance welding method a first welding electrode (30) is attached to the spindle holding element (14) and a second welding electrode (31) is attached to the guide rail (10) in order to conduct an electric welding current between the first welding electrode (30) and the second welding electrode (31), wherein the first welding electrode (30) includes a first electrode portion (301) and a second electrode portion (302), between which the spindle holding element (14) is arranged for introducing the welding current such that the first electrode portion (301) is in abutment with a first side of the spindle holding element (14) and the second electrode portion (302) is in abutment with a second side of the spindle holding element (14) facing away from the first side.

4. The method according to claim 3, characterized in that the first electrode portion (301) and the second electrode portion (302) are tensioned with each other relative to each other via a tensioning device (33) for abutment against the spindle holding element (14).

5. The method according to any of preceding claims, characterized in that the second welding electrode (31) is attached to a side of the wall portion of the guide rail (10) facing away from the spindle holding element (14).

6. The method according to any of the preceding claims, characterized in that the spindle holding element (14) includes a surface portion (140) with a front edge (142) arranged thereon, wherein for connecting purposes the spindle holding element (14) is bluntly attached to the wall portion of the guide rail (10) with the front edge (142).

7. The method according to claim 6, characterized in that the spindle holding element (14) includes at least one hump portion (143) which is formed at the front edge (142) and via which a welding connection (2) between the spindle holding element (14) and the wall portion of the guide rail (10) is produced.

8. The method according to claim 7, characterized in that the spindle holding element (14) includes a plurality of hump portions (143) which are formed at the front edge (142) and via which the welding connection (2) between the spindle holding element (14) and the wall portion of the guide rail (10) is produced.

9. The method according to any of the preceding claims, characterized in that on connection a nominal height (Hnom) of an opening (141) of the spindle holding element (14), which is configured for fastening the spindle (12) to the spindle holding element (14), is set relative to the wall portion of the guide rail (10).

10. The method according to any of the preceding claims, characterized in that a current time for the resistance welding method is set to a value in a range between 10 ms and 200 ms, preferably between 30 ms and 100 ms.

11. A longitudinal adjustment device (1) for a vehicle seat (16), comprising a guide rail (10), a spindle (12) which is connected to the guide rail (10) and extends along a longitudinal axis (L), and a spindle holding element (14) via which the spindle (12) is connected to the guide rail (10), characterized in that the spindle holding element (14) is connected to a wall portion of the guide rail (10) by using a resistance welding method, wherein the spindle holding element (14) includes a surface portion (140) with a front edge (142) arranged thereon, wherein the spindle holding element (14) is bluntly attached to the wall portion of the guide rail (10) with the front edge (142).

12. The longitudinal adjustment device (1) according to claim 11, characterized in that the spindle holding element (14) includes a plurality of hump portions (143) which are formed at the front edge (142) and via which a welding connection (2) between the spindle holding element (14) and the wall portion of the guide rail (10) is produced.