Method and apparatus for resistance welding a first component to a second component

Abstract

Method for resistance welding a first component (12) to a second component (14), wherein the second component (14) is inserted into an opening (12a) of the first component (12) at least with a connection area (38) by an insertion path (36) and is welded in place, wherein an inner dimension (12b) of the opening (12a) and an outer dimension (14b) of the connection area (38) are designed similarly to an interference fit, wherein the insertion path (36) is limited by a preferably adjustable external displacement limiter (32), wherein during insertion the first component (12) is held by a first holding device (28) and the second component (14) is held by a second holding device (30), characterized in that the displacement limiter (32) is rigidly connected to one of the two holding devices (28, 30).

Description

State of the art

[0001] The invention relates to a method and a device according to the preamble of the independent claims.

[0002] Various welding processes are known on the market for joining two metallic components. For example, in automotive manufacturing, some parts of internal combustion engine components can be joined using laser welding. An alternative welding process is resistance welding, in which the respective welding partners are heated using an electric current.

[0003] From US patent 2009 / 0 110 575 A1, a method for joining and welding two metallic parts on a pipe section in a high-pressure fuel pump is known, wherein an electric current is applied to one of the connecting surfaces between different components of the pump while the two parts are pressed against each other to generate a plastic flow.

[0004] From JP 2011 - 177 715 A, a resistance welding connection structure and a resistance welding process are known, wherein at least one connection part to be butt welded is provided with a protruding shaped part that projects towards the connection surface of the counterpart, and the connection structure is configured such that it is in pressure contact with the other connection part in the protruding shaped part.

[0005] From JP H05 - 77 053 A a resistance welding machine is known which is provided with two oppositely arranged electrodes that can be opened and closed, a stop attached to one electrode and a micrometer attached to the other electrode, which faces the stop, wherein the elastic force of the weld metal is applied as a pressure force.

[0006] From JP 2006 - 297 448 A, a pressure welding process and a pressure welding device are known in which a first component with a perforated part in which an inner wall surface part for pressing in is formed, and a shaft-shaped second component with a connecting surface part in which a predetermined press-in clearance between the perforated part and itself is provided, are joined together.

[0007] From JP 2007 - 170 672 A, a method for manufacturing a shaft with a flange and a shaft insertion device is known, in which a shaft is inserted and fastened into a hole of a flange with a chamfered hole by means of a shrink fit and a surface of the flange is orthogonal to the axis, wherein a holding device is provided for holding the shaft in a vertical direction. Disclosure of the invention

[0008] The problem underlying the invention is solved by a method according to claim 1 and by a device according to claim 5. Advantageous embodiments are specified in the dependent claims.

[0009] The invention relates to a method for resistance welding a first component to a second component, wherein the second component is inserted into an opening of the first component and welded, at least with a connection area, by means of an insertion path, and wherein an inner dimension of the opening and an outer dimension of the connection area are configured similarly to an interference fit, for example, an inner dimension of the opening being smaller than an outer dimension of the connection area. Because the inner and outer dimensions are configured similarly to an interference fit, welding is possible without the addition of a metallic fastener or the like. According to the invention, the insertion path is limited by a preferably adjustable external displacement limiter. This displacement limiter is therefore not arranged on one or both of the components to be welded and is thus effective independently of any component tolerances.This allows a defined position of the components relative to each other to be specified during the welding process, which significantly improves dimensional accuracy even after the welding process has finished.

[0010] The defined position is achieved by measuring the relative distance between the components before the actual welding process, as will be explained further below. Furthermore, component tolerances, such as those affecting so-called "external dimensions," can be compensated for by this method. Even with comparatively large "external" tolerances of the components to be welded, relatively tight tolerances for "functional dimensions" can still be achieved. For example, the first component is an inlet valve for a high-pressure fuel pump for an internal combustion engine, and the second component is an associated electromagnetic actuator. This allows for improved (final) positional accuracy.In particular, this positional accuracy concerns "internal" distances between functionally relevant sections of the first and second components, which distances are generally not determinable on the outside of the components during the welding process.

[0011] According to the invention, during insertion the first component is held by a first holding device and the second component is held by a second holding device, wherein the travel limiter is rigidly connected to one of the two holding devices.

[0012] Preferably, each holding device comprises an electrode that supplies the welding current, which is designed, for example, as a clamping device. The holding devices enable particularly precise positioning of the components. The travel limiter can, for example, be permanently connected to one of the two holding devices or to a device that secures the holding device. Alternatively, the travel limiter can be detachably connected to it.

[0013] Furthermore, the insertion path can be predetermined depending on an actual distance, defined in the insertion direction, between a section of the first component and a section of the second component, and depending on a target distance, defined in the insertion direction, between the section of the first component and the section of the second component. For example, the insertion path can be determined by simply calculating the difference between the actual distance (determined before the start of a feed) and the target distance required for the operation of the welded components. This simplifies and reduces the cost of the method according to the invention. The insertion path is equal to or greater than a dimension of the connection area defined in the insertion direction.

[0014] Preferably, the insertion path is determined before the insertion process begins. This makes the determination of the insertion path particularly accurate, and final tolerances of the welded components can be kept small. In one embodiment, the insertion path is determined depending on the joining partners. In another embodiment, the insertion path is defined by a predefinable stop.

[0015] The process works particularly well when resistance welding is a capacitor discharge press-fit welding process. In this process, a high current flowing through the components melts a joint area, while simultaneously pressing the components together along this joint area. This allows for particularly durable joints and comparatively high precision.

[0016] The invention further relates to a device for resistance welding the first component to the second component, wherein the second component can be inserted into an opening of the first component at least with the connection area around the insertion path and welded in place, and wherein an inner dimension of the opening and an outer dimension of the connection area are designed similarly to an interference fit, for example an inner dimension of the opening is smaller than an outer dimension of the connection area, and wherein the device has a preferably adjustable path limiter that limits the insertion path.

[0017] According to the invention, the device comprises a first and a second holding device for holding the first and second components, wherein the travel limiter is rigidly connected to one of the two holding devices.

[0018] Additionally, the device may be provided with means for determining an actual distance, defined in the insertion direction, between a section of the first component and a section of the second component. The device according to the invention thus has comparable advantages to those already described above for the method according to the invention.

[0019] In a further embodiment of the device, the travel limiter is a stop that can be adjusted mechanically or manually. This allows for a particularly simple and cost-effective, yet precise, design of the travel limiter. The mechanically adjustable stop is, for example, a mechanically adjustable stop on a press used for resistance welding.

[0020] In one embodiment, the path limiter comprises at least two wedges that are movable relative to each other and / or at least two pivotable stops positioned differently in the insertion direction. By moving the wedges relative to each other, a defined dimension of the wedges in the insertion direction can be continuously adjusted. This improves positioning accuracy. The pivotable stops, positioned differently in the insertion direction, can, for example, be arranged on a rotating disc in a manner similar to steps, enabling a stepped, yet equally precise, path limitation.

[0021] The invention further relates to a high-pressure fuel pump for a fuel system for an internal combustion engine, wherein at least one element of the high-pressure fuel pump is welded using the method described above. The accuracy of the welding process achievable according to the invention is particularly advantageous for the high-pressure fuel pump, for example, to enable precise fuel quantity control.

[0022] Exemplary embodiments of the invention are explained below with reference to the drawing. The drawing shows: Fig. 1 a first schematic sectional view of a device for resistance welding a first component to a second component in a first state; Fig. 2 the device of Fig. 1 in a second state; Fig. 3 the device of Fig. 1 in a third state; Fig. 4 a simplified second schematic sectional view of the device of Fig. 1 with a first alternative embodiment of a path limiter; Fig. 5 a representation similar to Fig. 4 with a second alternative embodiment of the path limiter; Fig. 6 a representation similar to Fig. 4 with a third alternative embodiment of the path limiter; and Fig. 7 a flowchart for a process for resistance welding the first component to the second component.

[0023] The same reference symbols are used for functionally equivalent elements and sizes in all figures, even in different embodiments.

[0024] Fig. Figure 1 shows a schematic sectional view of a device 10 for resistance welding a first component 12 to a second component 14. The Fig. The components shown in Figure 1 are arranged on a base 16, which is located in a lower area of ​​the Fig. Figure 1 is shown. The base 16 is designed as a flat plate and is preferably an element of the device 10.

[0025] Components 12 and 14 are made of metal and are electrically conductive. The first component 12 has an opening 12a, which has an inner dimension 12b perpendicular to an insertion direction 24 described below. The second component 14 has an outer dimension 14b, which is also defined perpendicular to the insertion direction 24 and, similar to an interference fit, is larger than the inner dimension 12b by, for example, 0.1 mm to 1 mm (millimeters). For example, the opening 12a in the first component 12 is characterized by a cavity that is at least partially circular cylindrical. Correspondingly, the second component 14 is also designed as a circular cylinder, at least partially. Alternatively, the first component 12 and the second component 14 ("joining partners") can also have a different geometry, for example, a truncated cone that deviates from a circular cylindrical shape by a few degrees.

[0026] The device 10 further comprises a lower electrode 18 arranged on the base 16, which is, for example, cuboid in shape. The first component 12 is electrically contacted on the lower electrode 18, as shown in the illustration. Fig. 1 rests on the lower electrode 18 and is connected via a current supply (not shown) to a capacitor storage device (also not shown). A horizontal dashed line 19 at a contact surface between the first component 12 and the lower electrode 18 marks a virtual zero point. The virtual zero point can optionally be used additionally in the method described below. In an outer left and outer right area of ​​the Fig. Figure 1 shows a linear guide 20 belonging to the device 10 and explained in more detail below, which is mechanically fixed in relation to the base 16.

[0027] In an upper area of ​​the Fig. Figure 1 shows a bridge 22, which is defined in the drawing as being arranged on the linear guides 20 on the left and right sides and is vertically movable relative to the linear guides 20 in the insertion direction 24 indicated by an arrow in the drawing. The necessary drive means are not shown in the drawing. Fig. Below bridge 22, an upper electrode 26 is arranged, to which the second component 14 is electrically connected. The second component 14 is also connected to the aforementioned capacitor storage device via a further current supply (not shown) through the upper electrode 26.

[0028] It is understood that the electrical contact via the lower electrode 18 on the first component 12 or via the upper electrode 26 on the second component 14 can alternatively or additionally be made on a respective side surface or lateral surface or on any other suitable surface of the first component 12 or the second component 14. The lower electrode 18 and upper electrode 26 shown in the drawing therefore represent only one of several possible embodiments.

[0029] The base 16, together with the lower electrode 18, forms a first holding device 28 for holding the first component 12 before and during the welding process. Similarly, the bridge 22, together with the upper electrode 26, forms a second holding device 30 for holding the second component 14. Any clamping devices or similar components required to fix the first component 12 to the lower electrode 18 or the second component 14 to the upper electrode 26 are not shown for clarity.

[0030] Furthermore, the device 10 comprises two identically acting adjustable external mechanical travel limiters 32, which define an insertion path 36 (see Fig. 3) limit and in exemplary embodiments in the Fig. 4, Fig. 5 to Fig. 6 will be explained in more detail. The path limiters 32 have an upper stop 50 and are located in a Fig. The lower section is defined in relation to the base 16 and is therefore also firmly connected to the first holding device 28. The bridge 22 can be attached to the one in the Fig. 1. Strike the upper stop 50 of the travel limiter 32, as described in Fig. 3 will be shown.

[0031] Using the described elements, a [something] can be created in the Fig. 1. The actual (vertical) distance between a (virtually arbitrarily selectable) section of the first component 12 and a (virtually arbitrarily selectable) section of the second component 14 is defined and determined in the insertion direction 24. A linkage can, for example, be as follows: From the section of the first component 12 via the first holding device 28 or via the lower electrode 18 to the base 16, then from the base 16 via the guide(s) 20 to the bridge 22, then from the bridge 22 via the second holding device 30 or via the upper electrode 26 to the section of the second component 14.

[0032] For example, the first component 12 is an inlet valve of a high-pressure fuel pump, and the second component 14 is an actuator for operating the inlet valve. Then, the aforementioned sections on the first component 12 could be a valve element of the inlet valve, and on the second component 14, an end section of a mechanical coupling element of the actuator.

[0033] The Fig. Figure 1 shows the device 10 and the two components 12 and 14 in a first state. Fig. 2 and Fig. Figure 3 each show a subsequent second and third state. By means of the Fig. 1, Fig. 2 to Fig. 3 A method for resistance welding the first component 12 to the second component 14 is described in more detail below.

[0034] In the state of the device 10 of Fig. Bridge 22 has a (vertical) distance 35 to line 19. The path limiters 32 are arranged in a basic position. As described above, the actual distance between the section of the first component 12 and the section of the second component 14, defined in the insertion direction 24, is determined.

[0035] In the initial state of Fig. In Figure 1, components 12 and 14 are shown almost without any distance between them. However, this is not strictly necessary; components 12 and 14 can be positioned differently in the initial state. Fig. 1. They can also be arranged (vertically) spaced apart to carry out the procedure. In the latter case, the insertion path 36 would be larger than a dimension 38 defined in the insertion direction 24 (see Fig. 3) of a connection area (without reference numeral) between the first component 12 and the second component 14.

[0036] In the state of Fig. 1. The desired vertical insertion path 36 is determined in the drawing. This is preferably done before the insertion process begins. The means required for this are not shown and include, for example, devices for mechanical or optical distance measurement between predetermined sections on components 12 and 14. The insertion path 36 is determined based on the actual distance between the section of the first component 12 and the section of the second component 14, as defined in the insertion direction 24, and based on a target distance between the section of the first component 12 and the section of the second component 14, also defined in the insertion direction 24. The insertion path 36 essentially represents the difference between the actual distance and the target distance.

[0037] Based on the determined insertion path 36 and a known distance (without reference numerals) between the bridge 22 and the base 16, the travel limiters 32 and the respective stops 50 attached to them can now be adjusted mechanically or manually. This is done such that a distance (without reference numerals) between an upper section in the drawing (the upper stop 50) of the travel limiters 32 and a lower section in the drawing of the bridge 22 (the underside of the bridge 22) corresponds to the determined insertion path 36, see the Fig. 2.

[0038] The first component 12 is then welded to the second component 14 by resistance welding, whereby the second component 14 is inserted into the opening 12a of the first component 12 by at least the joining area (corresponding to dimension 38) by the insertion path 36 and is welded in place. As described above, the inner dimension 12b of the opening 12a is smaller than the outer dimension 14b of the joining area on the second component 14.

[0039] The in the Fig. 1, Fig. 2 to Fig. The method shown in Figure 3 is therefore also referred to as "capacitor discharge press-fit welding," wherein the bridge 22 or the second component 14 is moved towards the base 16 or the first component 12 by means of a compressive force. Before and during insertion, the first component 12 is held by the first holding device 28 and the second component 14 by the second holding device 30. During the welding process, a radially inner section of the first component 12 and a radially outer section of the second component 14 melt, thereby forming the aforementioned connection area. In particular, during this process, the insertion path 36 is limited according to the invention by the adjustable external travel limiters 32.This creates a particularly precise connection between the first component 12 and the second component 14; that is, the target distance between the aforementioned sections of the first component 12 and the second component 14 is achieved with exceptional accuracy. Instead of a distance between the sections, one could also say that a desired relative position of components 12 and 14 to each other can be established with exceptionally high precision.

[0040] The Fig. 3 points to the Fig. 2. The following state of the device 10, or of the components 12 and 14, or of the process, after the welding process has ended. The bridge 22 rests against the upper stops 50 of the travel limiters 32, so that the bridge 22 has a distance 40 from the line 19. Current no longer flows through the first component 12 and the second component 14. The components 12 and 14 can cool down, and the resistance welding is complete.

[0041] It is understood that the positions of the first component 12 and the second component 14 with respect to the device 10 can also be reversed. Furthermore, a single travel limiter 32 may also be sufficient.

[0042] Fig. Figure 4 shows a simplified representation of device 10. Fig. 1 with a first alternative embodiment of the travel limiter 32. In the present case, the travel limiter 32 has, for example, a substantially cylindrical shape and can be clamped or locked in a defined position along the insertion direction 24 by means of a clamping device 42 and / or by means of a latch 44.

[0043] Fig. Figure 5 shows a further alternative embodiment of the travel limiter 32. In this embodiment, the travel limiter 32 comprises a support 46 of fixed length and a rotatable disk 48 arranged on the support 46. The disk 48 includes a plurality of stops 50, each of which has a different length in the insertion direction 24 and is preferably arranged on the disk 48 in a "staircase" manner. By rotating the disk 48, the travel limiter 32 can thus be adjusted vertically.

[0044] Fig. Figure 6 shows another alternative embodiment of the travel limiter 32. In this embodiment, the travel limiter 32 comprises the support 46 and two wedges 52 and 54, which are arranged to be horizontally displaceable relative to each other in the drawing, thus enabling continuous vertical adjustment of the travel limiter 32. For the sake of clarity, a clamping device for fixing the wedges 52 and 54 is not shown.

[0045] In an embodiment not shown, the travel limiter 32 is not a mechanical element but a numerical value which can be preset as a limit value for a (not shown) feed device ("press") in a device controlling the apparatus 10. While the feed device advances the second component 12 by the insertion path 36, the stop 50 can be formed "virtually," so to speak, and the insertion path 36 can thereby be limited in a comparable manner.

[0046] Furthermore, it is understood that in the embodiments according to the Fig. 4, Fig. 5 to Fig. 6 the path limiter 32 can also be present on both sides, similar to this in the Fig. 1, Fig. 2 to Fig. 3 is the case.

[0047] Fig.Figure 7 shows a flowchart for carrying out the method in one embodiment. For example, components of a high-pressure fuel pump for a fuel system of an internal combustion engine can be welded together using this method. It is understood that the process steps described below can also be carried out in a different order than described, where possible and practical.

[0048] In a first step 60, the first component 12 is fixed using the first holding device 28, and the second component 14 is fixed using the second holding device 30. In a second step 62, the actual distance between a section of the first component 12 and a section of the second component 14 is determined. In a third step 64, the insertion path 36 is determined from the actual distance and the target distance. In a fourth step 66, the path limiter(s) 32 are adjusted. In a fifth step 68, the first and second holding devices 28 and 30 are moved towards each other by sliding the bridge 22, whereby the components 12 and 14 touch and a very high (discharge) current flows briefly. During this process, the second component 14, with its connection area (dimension 38) extending around the insertion path 36, is inserted into the opening 12a of the first component 12 and simultaneously welded.In a sixth step 70, the insertion path 36 is limited by the effect of the path limiters 32 and the welding of the first component 12 with the second component 14 is thus completed.

Claims

[1] Method for resistance welding a first component (12) to a second component (14), wherein the second component (14) is inserted into an opening (12a) of the first component (12) and welded together with at least a joining area (38) by an insertion path (36), wherein an inner dimension (12b) of the opening (12a) and an outer dimension (14b) of the joining area (38) are designed similarly to an interference fit, wherein the insertion path (36) is limited by a preferably adjustable external displacement limiter (32), wherein during insertion the first component (12) is held by a first holding device (28) and the second component (14) is held by a second holding device (30), characterized by , that the path limiter (32) is firmly connected to one of the two holding devices (28, 30). [2] Method according to claim 1, characterized by, that the insertion path (36) is specified depending on an actual distance defined in the insertion direction (24) between a section of the first component (12) and a section of the second component (14) and depending on a target distance defined in the insertion direction (24) between the section of the first component (12) and the section of the second component (14). [3] Method according to at least one of the preceding claims, characterized by , that the insertion path (36) is determined before the insertion begins. [4] Method according to at least one of the preceding claims, wherein the resistance welding is a capacitor discharge press-fit welding. [5] Device (10) for resistance welding a first component (12) to a second component (14), wherein the second component (14) can be inserted into an opening (12a) of the first component (12) and welded at least with a connection area (38) about an insertion path (36), wherein an inner dimension (12b) of the opening (12a) and an outer dimension (14b) of the connection area (38) are designed similarly to an interference fit, wherein the device (10) has a preferably adjustable displacement limiter (32) that limits the insertion path (36), wherein the device (10) comprises a first and a second holding device (28, 30) for holding the first and the second component (12, 14), characterized by , that the path limiter (32) is firmly connected to one of the two holding devices (28, 30). [6] Device (10) according to claim 5, characterized by, that it has means to determine an actual distance defined in the insertion direction (24) between a section of the first component (12) and a section of the second component (14). [7] Device (10) according to one of claims 5 or 6, characterized by , that the travel limiter (32) is a stop (50) that can be adjusted mechanically or manually. [8] Device (10) according to one of claims 5 or 6, characterized by , that the path limiter (32) comprises at least two wedges (52, 54) that can be moved relative to each other and / or at least two pivotable stops (50) that are positioned differently in the insertion direction (24).

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