Pump-flange assembly process

Abstract

A pump-flange assembly process comprising the steps of: providing a pump (10) with a pump nose (10.1) defining a pump axis; providing a flange (12) comprising a first surface (12.1) and an opposite second surface (12.2) connected via a through-hole (14) defining a hole axis (X), the hole axis (X) defining a first direction (X1) and a second direction (X2) such that the first surface (12.1) faces towards the first direction (X1) and the second surface (12.2) faces towards the second direction (X2), wherein the flange (12) is pre-deformed along the hole axis (X), such that the first and second surfaces (12.1, 12.2) of the flange (12) diverge towards the first direction (X1) as their distance from the hole axis (X) increases; inserting the pump nose (10.1) through the flange hole (14) from the first direction (X1) towards the second direction (X2); welding the flange (12) onto the pump (10) from the second direction (X2), whereby the surfaces (12.1, 12.2) of the flange (12) diverge towards the second direction (X2) as their distance from the hole axis (X) increases.

Description

[0001] PUMP-FLANGE ASSEMBLY PROCESS

[0002] Technical field

[0003] The present invention generally relates to a method of assembling a pump with a flange, in particular for mounting a fuel pump onto an engine.

[0004] Background Art

[0005] In the automotive industry, fuel pumps are typically mounted onto an engine by the intermediary of a flange which defines the interface between the pump and the engine. Such a flange is generally flat and comprises a through-hole at its center and a plurality of bores around it. The flange may further comprise a welding hub extending radially inwards from an inner surface of the through-hole.

[0006] A usual process for mounting a fuel pump onto an engine involves the steps of:

[0007] - Inserting a nose of the fuel pump in the through-hole of the flange, thereby forming a pump-flange assembly.

[0008] - Welding the outer surface of the nose with the welding hub (if present) or with the inner surface of the through-hole (if no welding hub is present), thereby securing the pump onto the flange.

[0009] - Mounting the assembly on the engine by placing the nose in a cavity of the engine.

[0010] - Inserting attachment means through the bores of the flange and fastening them onto the engine, thereby securing the flange onto the engine.

[0011] However, when welding the nose with the flange in the second step of the above process, the flange may be subject to welding distortion. More specifically, surfaces of the flange may curve towards the side of the weld.. Excessive curvatures are to be avoided as they may generate stress onto the weld or the fastening means once the flange is secured to the engine. In fact, a flange having a flatness greater than a predetermined value may be considered as faulty and discarded. If a curvature for the flange is inevitable, it is preferable that the flange curves towards the side of the pump nose and the engine rather than towards the body of the pump. Traditionally, the power of the welding operation is reduced to prevent the flange from curving excessively. Unfortunately, decreasing the welding power increases the duration of the weld, which decreases productivity.

[0012] Technical problem

[0013] It is an object of the present invention to provide an improved pump-flange assembly process allowing for an enhanced robustness of the assembly.

[0014] This object is achieved by a pump-flange assembly process as claimed in claim 1 .

[0015] General Description of the Invention

[0016] The present inventors have found that an improved assembly can be obtained by controlling the curvature / flatness of the flange during the process. The invention namely derives from the observation that, when welding the pump nose to its mounting flange, the flange may be subject to welding distortion. More specifically, surfaces of the flange may curve towards the side of the weld. The welding distortion leads to a certain curvature of the flange, which may generate stress onto the weld and / or on the fastening means once the flange is secured to the engine. In fact, a flange having a flatness greater than a predetermined value may be considered as faulty and discarded.

[0017] In this context, if a curvature for the flange is inevitable, it is preferable that the flange curves towards the side of the pump nose and the engine rather than towards the body of the pump.

[0018] According to the present invention, pump-flange assembly process comprising the steps of:

[0019] - providing a pump with a pump nose defining a pump axis;

[0020] - providing a flange comprising a first surface and an opposite second surface connected via a through-hole defining a hole axis, the hole axis defining a first direction and a second direction such that the first surface faces towards the first direction and the second surface faces towards the second direction, wherein the flange is pre-deformed along the hole axis, such that the first and second surfaces of the flange diverge towards the first direction as their distance from the hole axis increases; inserting the pump nose through the flange hole from the first direction towards the second direction;

[0021] - welding the flange onto the pump from the second direction, whereby the surfaces of the flange diverge towards the second direction as their distance from the hole axis increases.

[0022] The present invention uses a flange that is pre-deformed, i.e. formed as flat flange with a predetermined curvature, here with a concavity on the first surface. That is, the flange has a controlled curvature via a predetermined flatness and orientation (during the assembly process).

[0023] Furthermore, during the welding operation, the curvature of the flange is inverted, as a result of the welding operation that is carried out from the second side of the flange. In doing so, the flange is thus curved away from the pump body, toward the pump holder, which is more favorable having regard to the mechanical constraints applied to the weld during operation of the pump. Any appropriate type of welding technology may be used, e.g. fiber laser welding, in particular Yterrbium laser welding.

[0024] Preferably, the flange comprises a welding hub protruding inwardly from a surface of the through-hole. In embodiments, a central plane for the welding hub is offset along the hole axis from a central plane for the flange. Ideally, the central plane for the welding hub is offset along the hole axis towards the second direction. Such a welding hub defines an area for the weld and drastically improves control over the welding distortion.

[0025] The welding hub may have a thickness comprised between 1.5 and 2.5 mm, preferably around 2 mm.

[0026] The distance between the welding hub and the second surface of the flange may be between 0.5 and 1.5 mm, preferably around 1 mm.

[0027] The flange may have a length of up to 100mm, e.g. between 85 and 100 mm. . The flange may have a thickness comprised between 4 and 8 mm. The flatness of the flange after welding may be at most 0.15 mm.

[0028] Preferably, the flatness of the flange after welding is lower than 0.15% of its length. The welding hub may have a diameter comprised between 36 mm and 46 mm, preferably around 41 mm.

[0029] The pump nose may be inserted through the flange hole such that the pump axis and the hole axis coincide, and such that the pump axis is significantly perpendicular to the first and second surface. By further controlling the squareness, i.e. perpendicularity between the pump axis and the first and second surface, the durability of the assembly is increased.

[0030] The flange may be obtained by stamping from a metal sheet and pre-deformed by plastically deforming the stamped flange. Alternatively, the flange may be directly obtained pre-deformed by stamping from a metal sheet (i.e. the bending is included in the stamping tool).

[0031] The assembly process may comprise the additional steps of :

[0032] - providing a pump holder with a pump socket,

[0033] - inserting the pump nose into the pump socket and attaching the flange to the pump holder.

[0034] Preferably, the flange comprises fixation bores and the step of attaching the flange to the pump holder comprises inserting attachment means through the fixation bores and fastening to the engine.

[0035] The pump holder may be a part of an engine. That is, the assembly process may generally provide for the assembly of a pump (in particular a fuel pump) to an internal combustion engine.

[0036] According to an other aspect of the invention, a flange and pump assembly obtained by any of the process detailed above is provided.

[0037] Brief Description of the Drawings

[0038] A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

[0039] Fig. 1 is a top view of a pre-deformed flange for assembling a fuel pump to an engine; Fig. 2 is a longitudinal cross-section view of the flange before being plastically deformed;

[0040] Figs. 3 is a longitudinal cross-section view of the flange of Fig.1 ;

[0041] Fig. 4 is a longitudinal cross-section view illustrating the configuration of the flange following welding of the pump and the flange;

[0042] Fig. 5 shows a fuel pump mounted on an engine by the intermediary of a flange.

[0043] Description of Preferred Embodiments

[0044] An embodiment of the present invention will now be explained in the context of internal combustion engines, wherein a fuel pump is fixed to an engine by means of a flange. Such assembly is shown in Fig.5, wherein the fuel pump 10 is only shown in part, reference sign 10.1 designating a nose portion thereof. The nose portion 10.1 here forms a guide portion for the pump plunger (not shown), which can thus be externally driven along a pump axis. The pump 10 is assembled to the engine by means of mounting flange 12 (or simply flange), which comprises a through-hole 14 for the pump nose 10.1.

[0045] According to the invention, the flange 12 is a pre-deformed flange, for the purpose of the assembly process, as will be explained in the following.

[0046] Figure 1 and 3 respectively are top and cross-sectional views (along plane A) of the pre-deformed flange 12, ready for assembly, respectively welding. By contrast, Fig.2 shows the flange 12 before being plastically deformed to obtain the configuration of Fig.3.

[0047] As it can be seen in Fig.2, the flange 12 comprises a first and a second surface 12.1 , 12.2, opposite one another. The surfaces 12.1 , 12.2 are parallel to one another, the constant distance between them defining the thickness of the flange 12. A central plane F of the flange 12 passing through the middle of thickness of the flange 12 (i.e. equidistant to surfaces 12.1 , 12.2) is represented.

[0048] A central through-hole 14 and a plurality of fixation bores 18 are arranged in the flange 12, traversing the first and the second surfaces 12.1 , 12.2. The through-hole 14 defines a hole axis X normal to the central plane F for the flange 12. The hole axis X itself defines a first direction X1 and a second direction X2, such that the first surface 12.1 faces towards the first direction X1 and the second surface 12.2 faces towards the second direction X2.

[0049] As can be seen, the flange 12 has a generally oval shape, the two bores 18 being located opposite one another relative to the through-hole 14. Axis X further represents a central axis of symmetry of the flange 12.

[0050] An annular welding hub 16 extends radially inwards from an inner surface 14’ of the through hole 14. The welding hub 16 has a thickness inferior to the thickness of the flange 12. A central plane W of the welding hub 16 passing through the middle of thickness of the welding hub 16 is represented.

[0051] As it can be seen on figure 2, central planes F and W are parallel and spaced apart. In fact, the central plane W of the welding hub 16 is offset from the central plane F of the flange 12 towards the second surface 12.2 and the second direction X2.

[0052] In practice, the flange 12 may be initially stamped from sheet metal, obtaining the shape of Fig.2, the latter being then subjected to a plastic deformation step performed with a calibration tool to obtain the pre-deformed configuration shown in Fig.3. Alternatively, the stamping tool may directly include means for plasticly deforming the flange, such that no additional step is required, i.e. the flange is stamped directily with the shape shown in Fig.3.

[0053] The shape shown in Figure 3 corresponds to the desired curvature before assembly.

[0054] As it can be seen, the flange 12 curves towards to first direction X1 such that surfaces 12.1 , 12.2 diverge towards the first direction X1 as their distance from the hole axis X increases.

[0055] The curvature of the flange 12 is thus controlled such that the first side is concave before assembly and welding, the second side being convex since the flange is a metal sheet.

[0056] The curvature may be characterized by its flatness defined as the distance between point 12.2b and the projection of point 12.2a onto the hole axis X. In Fig.3, point 12.2a is the radially outermost point on second surface 12.2; point 12.2b represents the center of the second surface 12.2, i.e. the theoretical intersection between the second surface 12.2 and the hole axis X. Figure 4 shows a cross-sectional view of the pre-deformed flange 12 following welding to the fuel pump 10.

[0057] The welding operation was performed from the second direction X2 (i.e. with the welding head pointing towards the first direction X1 ) with faying surfaces corresponding to the welding hub 16 and a portion of the fuel pump (pump nose 10.1 is illustrated by dashed lines). In this embodiment, fiber laser welding was used.

[0058] As alluded before, the welding operation will cause distortion of the flange 12 in direction of the weld. As it will be clear to those skilled in the art, distortion tends to increase with welding power.

[0059] In the present embodiment, the welding hub 16 is offset from the central plane F for the flange 12 towards the second direction X2, i.e. the welding area is offset from the middle of the thickness of the flange 12. This will enhance the welding distortion resulting from the welding operation when compared to a welding hub 16 centred on the central plane F.

[0060] Figure 5 shows the resulting pump-flange assembly. After welding of the flange 12 to the pump 10, the pump nose 10.1 is engaged in a cavity 24 in the engine. In the shown configuration the pump axis coincides with axis X. Attachment means 20, here screws, are inserted through the bores 18 and fastened onto the engine 22 so as to pin the flange 12 to a surface of the engine 22. In embodiments, the nose 10.1 may have an annular protrusion (not shown) arranged such that the annular protrusion and the welding hub 16 are in contact, thereby forming the faying surfaces of the pump-flange weld. The dashed lines 12.T and 12.2’ illustrate the curvature of the flange before fastening to the engine 22 (as in Fig.4).

[0061] The present invention hence provides an assembly process where the curvature of the flange is controlled, which allows limiting the elastic deformation and constraints. In prior art approaches, a flat flange was used, without particular attention to the flatness and orientation of the flange during assembly.

[0062] Thanks to the approach proposed by the present invention, welding distortions are anticipated by using of a pre-deformed flange, the curvature of which is initially in the opposite direction (Fig.3) compared to the curvature and flatness desired after the welding operation (Fig.4). It may be noted that whereas the pre-deformed flange has a certain curvature, it may still be referred to as flat or planar flange since the desired degree of flatness may generally represent less than 5% of its thickness.

[0063] The pre-bending may generally be adapted in function of the flange length (maximum distance in a plane parallel to the first or second surface 12.1 , 12.2). For a flange of length 100 mm, the flatness of the pre-deformed flange 12, before assembly (Fig.3), may be of about 0.05 to 0.15 mm.

[0064] The flatness the pre-deformed flange 12 after welding is preferably below 0.15 mm.

[0065] In exemplary embodiments, the flange 12 has a thickness greater than 4 mm, e.g. between 4 and 8 mm) the welding hub 16 has a thickness of 2 mm, and central plane W for the welding hub 16 is offset from the central plane F for the flange 12 such that the distance between the central plane W for the welding hub 16 and the second surface 12.2 is of 2 mm.

[0066] After the plastic deformation step, the flange curves towards direction X1 with a flatness of 0.1 mm. In other words, the outermost point 12.2a of the second surface 12.2 has moved 0.1 mm towards the X1 direction, relative to the position of the center of the second surface 12.2b. After being welded to the fuel pump, the flange curves towards direction X2 with a flatness of 0.1 mm. In other words, the outermost point 12.2a of the second surface has moved 0.2 mm towards the X2 direction, relative to the position of the center of the second surface 12.2b. Such a curvature has been observed to be compatible with the mechanical constraint present when the fuel pump is mounted on the engine, and is therefore considered acceptable.

Claims

Claims1 . A pump-flange assembly process comprising the steps of:- providing a pump (10) with a pump nose (10.1 ) defining a pump axis;- providing a flange (12) comprising a first surface (12.1 ) and an opposite second surface (12.2) connected via a through-hole (14) defining a hole axis (X), the hole axis (X) defining a first direction (X1 ) and a second direction (X2) such that the first surface (12.1 ) faces towards the first direction (X1 ) and the second surface (12.2) faces towards the second direction (X2), wherein the flange (12) is pre-deformed along the hole axis (X), such that the first and second surfaces (12.1 , 12.2) of the flange (12) diverge towards the first direction (X1 ) as their distance from the hole axis (X) increases;- inserting the pump nose (10.1 ) through the flange hole (14) from the first direction (X1 ) towards the second direction (X2);- welding the flange (12) onto the pump (10) from the second direction (X2), whereby the surfaces (12.1 , 12.2) of the flange (12) diverge towards the second direction (X2 )as their distance from the hole axis (X) increases.

2. The assembly process according to claim 1 , wherein the flange (12) comprises a welding hub (16) protruding inwardly from a surface of the through-hole (14’).

3. The assembly process according to claim 2, wherein a central plane (W) for the welding hub (16) is offset along the hole axis (X) from a central plane (F) for the flange (12).

4. The assembly process according to claim 3, wherein the central plane (W) for the welding hub (16) is offset along the hole axis (X) towards the second direction (X2).

5. The assembly process according to an of claims 2 to 4, wherein the welding hub (16) has a thickness comprised between 1.5 and 2.5 mm, preferably around 2 mm.

6. The assembly process according to any of the preceding claims, wherein the distance between the welding hub (16) and the second surface of the flange (12.2) is between 0.5 and 1.5 mm, preferably around 1 mm.

7. The assembly process according to any of the preceding claims, wherein the flange (12) has a length of up to 100 mm, and / or wherein the flange (12) has a thickness comprised between 4 and 8 mm and / or wherein after welding, the flatness of the flange (12) is no more than 0.15 mm.

8. The assembly process according to any of the preceding claims, wherein after welding, the flatness of the flange (12) is lower than 0.15% of its length.

9. The assembly process according to any of the preceding claims, wherein the welding hub (16) has a diameter comprised between 36 mm and 46 mm, preferably around 41 mm.

10. The assembly process according to any of the preceding claims, wherein the pump nose (10.1 ) is inserted through the flange hole (14) such that the pump axis and the hole axis (X) coincide, and such that the pump axis is significantly perpendicular to the first and second surface (12.1 , 12.2).11 . The assembly process according to any one of the preceding claims, wherein the flange (12) is obtained by stamping from a metal sheet and pre-deformed by plastically deforming the stamped flange, or wherein the flange (12) is directly obtained pre-deformed by stamping from a metal sheet.

12. The assembly process according to any of the preceding claims, further comprising the steps of:- providing a pump holder (22) with a pump socket (24),- inserting the pump nose (10.1 ) into the pump socket (24) and attaching the flange (12) to the pump holder (22).

13. The assembly process according to claim 12, wherein the flange (12) comprises fixation bores (18) and the step of attaching the flange (12) to the pump holder(22) comprises inserting attachment means (20) through the fixation bores (18) and fastening to the engine.

14. The assembly process according to claim 12 or 13, wherein the pump holder (22) is a part of an engine.

15. A flange and pump assembly obtained by the process according to one of claims11 to 14.

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