WO2022048967A1

WO2022048967A1 - Device and method for welding a pot-shaped housing lid onto a housing body of a high-pressure fuel pump

Info

Publication number: WO2022048967A1
Application number: PCT/EP2021/073504
Authority: WO
Inventors: Christoph Lehmeier; Daniel Beckmann; Matthias Hartweg
Original assignee: Robert Bosch Gmbh
Priority date: 2020-09-03
Filing date: 2021-08-25
Publication date: 2022-03-10
Also published as: DE102020211105A1

Abstract

The invention relates to a device (40) used to weld a pot-shaped housing lid (16) to a housing body (14) of a high-pressure fuel pump (10) by means of a capacitor discharge press-fit welding process (CDPF welding process), with a force application device (42) for pressing the housing lid (16) onto the housing body (14) and an upper electrode (44) for electrically contacting the housing lid (16). According to the invention, the upper electrode (44) is separate from the force application device (42), and the upper electrode (44), at least in a contact region (64) to the housing lid (16), comprises a softer material than the force application device (42) in a contact region (50, 54) to the housing lid (16).

Description

description

title

Device and method for welding a pot-shaped housing cover to a housing body of a high-pressure fuel pump

State of the art

The invention relates to a device and a method for welding a pot-shaped housing cover to a housing body of a high-pressure fuel pump according to the preambles of the independent claims.

DE 102016 212 469 A1 describes a fuel system in which fuel is pumped from a fuel tank into a high-pressure reservoir ("rail") under high pressure by means of a pre-supply pump and a mechanically driven high-pressure fuel pump. A pressure damper device is usually arranged on or in a pump housing of such a high-pressure fuel pump. Such a pressure damper device usually comprises a pot-shaped housing cover and a membrane damper which is arranged between the housing cover and a housing body and is usually designed as a gas-filled membrane can. The pressure damper device is fluidically connected to a low-pressure area. It serves to dampen pressure pulsations in the low-pressure area of the fuel system, which are caused, for example, by the opening and closing processes of valves, for example an inlet valve, in the high-pressure fuel pump. A material connection between the housing body and the housing cover is produced using a capacitor discharge press-fit welding process (KEEP welding process).

Disclosure of Invention

The problem on which the invention is based is solved by a device and a method having the features of the independent claims. Developments of the invention are specified in the dependent claims. In the device according to the invention and the method according to the invention, the function “pressing the housing cover onto the housing body” is separated from the function “electrical contacting of the housing cover”.

This reduces the wear on the collet to a minimum, since a softer material can be used for the upper electrode, at least in that contact area with which the upper electrode makes direct contact with the housing cover, which can produce good electrical contact with the housing cover, but which at the same time cannot cause any deformation or damage to the housing cover.

On the other hand, a comparatively hard material can be used for the loading device, at least in that contact area which directly contacts the housing cover, which is therefore only subject to little wear and can therefore be used for welding a large number of housing covers. The device therefore has an increased service life, which reduces the tool costs. The maintenance costs are also reduced since the tool, in particular the application device, has to be replaced less frequently. After all, the manufacturing process as a whole is a more stable process than before, since there are fewer fluctuations in manufacturing quality and thus greater independence from batches.

Specifically, this is achieved by a device for welding a pot-shaped housing cover to a housing body of a high-pressure fuel pump using a capacitor discharge press-in welding process (KEEP welding process). Such a pot-shaped housing cover usually has a curved base on which a peripheral cover jacket is formed. The weld seam produced creates a circumferential, materially bonded and fluid-tight connection between the housing cover and the housing body.

On the one hand, a pressurizing device is used to produce the weld seam, with which the housing cover is pressed onto the housing body. A first electrode is used to introduce the electric current required for the welding process into the housing cover is called "upper electrode" in the present case and which makes electrical contact with the housing cover. A special feature of the device according to the invention is that the upper electrode and the application device are functionally separate devices from one another. This makes it possible to produce the direct contact area of the upper electrode to the housing cover from a comparatively soft material, whereas the direct contact area of the application device to the housing cover is made from a comparatively hard material.

It goes without saying that the device also has a carrier on which the housing body is held during the production of the welded connection and which serves as a counter-holder during the loading of the housing body by the loading device. Furthermore, the device also has a second electrode, which is referred to here as the "lower electrode" and which makes electrical contact with the housing body. It is conceivable that the carrier and the lower electrode are one and the same component, or that the lower electrode is integrated into the carrier.

Specifically, the advantages according to the invention are also achieved by a method for welding a pot-shaped housing cover to a housing body of a high-pressure fuel pump using a capacitor discharge press-in welding process (KEEP welding process), comprising the following steps: pressing the pot-shaped housing cover onto the housing body using an application device and electrically contacting the housing cover with a top electrode. The housing cover is electrically contacted by means of an upper electrode separate from the application device, and a softer material is used for at least one contact area of the upper electrode to the housing cover than for a contact area of the application device to the housing cover.

In a further development of the device, it is proposed that the contact area of the top electrode includes copper and the contact area of the application device includes steel. These two materials perform the desired functions very well. Copper is a very good conductor of electricity and also comparatively soft. Steel is hard and therefore wear-resistant.

In a further development of the device, it is proposed that the loading device comprises at least one axial loading device and at least one radial loading device, with the axial loading device loading a cover base in a substantially axial direction and the radial loading device including a cover casing and/or a cover section projecting radially outwards acted upon in a substantially radial direction. Thus, not only is there a functional separation between the introduction of the current into the housing cover and the pressing of the housing cover onto the housing body, but there is also a functional separation between the loading of the housing cover in the axial direction and the loading of the housing cover in the radial direction . Above all, the radial loading device prevents or counteracts a radially outwardly directed deflection of the housing jacket.

It goes without saying that the existence of an axial direction and a radial direction does not necessarily require a rotationally symmetrical configuration of the high-pressure fuel pump with a longitudinal axis. The axial direction merely defines that direction along which the housing cover is pressed onto the housing body for resistance welding, and the radial direction is then an at least substantially orthogonal direction thereto.

In a further development, it is proposed that the top electrode makes contact with the cover jacket in a substantially radial direction. The current is thus introduced relatively close to the area where the weld seam is usually also produced. This increases the efficiency in making the welded joint.

In a further development, it is proposed that the application device and the upper electrode are parts of a pot-shaped collet which, for welding the housing cover to the housing body, is slipped over the housing cover at least in regions can be. Such a device is comparatively simple in construction and can be handled easily and also automatically.

In one development, it is proposed that the collet chuck has at least one first actuator, which acts on the top electrode radially inward against the cover jacket. This ensures reliable electrical contact and prevents the upper electrode from damaging, for example scratching, the surface of the cover jacket when the collet chuck is placed on the pot-shaped housing cover and/or the upper electrode itself being damaged or at least exposed to considerable wear when being placed on.

In a development of this, it is proposed that the collet has at least one second actuator, which acts on the radial loading device radially inward against the cover jacket and/or against a cover section projecting radially outward. This also prevents the radial loading device from damaging, for example scratching, the surface of the housing cover when the collet chuck is placed on the pot-shaped housing cover. This applies in particular when the housing cover has a cover section which protrudes radially outwards and is also referred to as a “cutting balcony”.

In a development of the method, it is proposed that a harder material than the material from which the pot-shaped housing cover is made be used at least for the contact area of the loading device.

The invention is explained in more detail below with reference to the accompanying drawing. Show in the drawing:

FIG. 1 shows a longitudinal section through a high-pressure fuel pump with a housing cover and a housing body; FIG. 2 shows a highly schematized longitudinal section through a region of a device for welding the housing cover to the housing body of FIG. 1; and

Figure 3 shows a flow chart of a method for welding the housing cover to the housing body of Figure 1.

In the following, functionally equivalent elements and areas in different figures bear the same reference symbols.

A high-pressure fuel pump bears the reference numeral 10 overall in FIG. 1. It is used in a fuel system of an internal combustion engine. There it can draw in fuel from a fuel tank and convey it to a fuel collection line. From there, the fuel can get into the combustion chambers of the internal combustion engine via injectors under high pressure.

The high-pressure fuel pump 10 comprises a pump housing 12 that is essentially rotationally symmetrical overall, for example, with a housing body 14 and a housing cover 16. In the housing body 14, a pump piston 18 is accommodated in a longitudinally displaceable manner. It delimits a pumping chamber 20 into which the fuel can get via an inlet valve 22 . The fuel can be ejected from the pumping chamber 20 via an outlet valve 24 .

Due to the discontinuous delivery of the fuel, as is typical in the case of piston pumps, undesired pressure pulsations in the fuel can occur, in particular upstream of the inlet valve 22 . A pressure damper device in the form of a membrane damper 28 is therefore arranged in a receiving space 26 formed between the housing body 14 and the housing cover 16, by means of which such pressure pulsations are damped.

The receiving space 26 is delimited in FIG. The housing cover 16 has a curved or outwardly curved cover base 32 on which a peripheral and essentially cylindrical cover jacket 34 is formed. Thus, the housing cover 16 has an overall pot-like shape. On the bottom edge of the cover jacket 34 in FIG. 1, a cover section 36 that extends all the way around and protrudes radially outwards is formed, which is also referred to as the “cutting balcony”. In the transition area between the cover casing 34 and the protruding cover section 36 , the housing cover 16 is welded to an edge of the end face 30 of the housing body 14 by means of a circumferential weld seam 38 in a materially bonded and fluid-tight manner.

FIG. 2 shows a highly schematic drawing of a device 40 which serves to weld the housing cover 16 to the housing body 14 . The weld seam 38 is thus produced with the device 40 . In the present case, this is done using a special resistance welding process, namely the so-called "capacitor discharge press-fit welding process". This is also referred to as the KEEP welding process. Basically, resistance welding is a welding process for electrically conductive materials based on the Joule current heat of a through the connection point of the to The components to be connected are heated at the connection point until the welding temperature is reached and welded at the connection point under the effect of a force by solidification of melt, by diffusion or in the solid phase.

The device 40 comprises a welding tongs 41 which itself also has an approximately pot-shaped shape overall. The welding tongs 41 have an application device 42 and an upper electrode 44 . The loading device 42 in turn comprises an axial loading device 46 and a radial loading device 48.

In the present case, the axial loading device 46 can have, for example, a substantially flat plate 50 which can be pressed against the cover base 32 by an actuator (not shown), for example a pneumatic, hydraulic or electric actuator, which acts parallel to the longitudinal axis 17 and in this respect has a contact area with the Housing cover 16 forms towards. The force acting through the actuator is shown in Figure 2 indicated by an arrow with the reference number 52 . The axial loading device 46 thus acts in the axial direction of the longitudinal axis 17 and presses the housing cover 16 in the axial direction against the housing body 14.

The welding tongs 41 also include the aforementioned radial loading device 48, which in the present example has a plurality of contact regions 54 that are movable in the radial direction (ie orthogonal to the longitudinal axis 17) and are arranged uniformly distributed in the circumferential direction. These are arranged relative to the flat plate 50 in such a way that when the flat plate 50 rests against the cover base 32 , the contact areas 54 are at the axial height of the protruding cover section 36 .

The contact areas 54 are pressed radially outward into a rest position by a spring device (not shown), in which they are spaced apart from the protruding edge of the protruding cover section 36 . A plunger 58, which can be actuated parallel to the longitudinal axis 17 by means of an actuator 56, can act on the contact areas 54 radially inwards against the edge of the protruding cover section 36 against the force of the spring device via an inclined surface 60, which interacts with a complementary inclined surface 62 on the contact area 54. This prevents the lower edge of the cover casing 34 with the protruding cover section 36 from deflecting radially outwards in FIG. This is indicated by an arrow 63 in FIG.

Just above the contact areas 54, the welding gun 40 comprises a plurality of contact areas 64 of the upper electrode 44, which are also distributed uniformly in the circumferential direction are spaced. A plunger 68, which can be actuated parallel to the longitudinal axis 17 by means of an actuator 66, can act on the contact areas 64 radially inwards against the force of the spring device against the outer surface of the cover jacket 34 via an inclined surface 70, which interacts with a complementary inclined surface 72 on the contact areas 64. this is in Figure 2 drawn by an arrow 74. In this way, electrical contact is established between the contact areas 64 and the housing cover 16 . It can be seen that the top electrode 44 contacts the cover jacket 34 in a substantially radial direction, that is to say orthogonally to the longitudinal axis 17 .

It can be seen from FIG. 2 that on the one hand the application device 42 with the axial application device 46 and the radial application device 48 and on the other hand the upper electrode 44 are both functionally and spatially separate devices or elements. This makes it possible to produce these devices or elements from different materials. The contact areas 64 of the top electrode 44 are made of a copper material. On the other hand, the contact portions 54 of the radial biasing device 48 and the flat plate 50 of the axial biasing device 46 are made of a steel material. The housing cover 16 of the high-pressure fuel pump 10 is also made of a steel material. Thus, the contact areas 64 of the upper electrode 44 are made of a softer material than both the application device 42 or its contact areas 50 and 64 contacting the housing cover 16 and the housing cover 16 itself.

It goes without saying that the device 40 also has a carrier, not shown, on which the housing body 14 is held during the production of the welded connection 38 and which serves as a counter-holder while the housing cover 16 is pressed onto the housing body 14 . Furthermore, the device 40 also has a lower electrode, also not shown, which makes electrical contact with the housing body 14 .

A method for welding the pot-shaped housing cover 16 to the housing body 14 will now be explained with reference to FIG. After a starting block 76 , the housing cover 16 is placed loosely on the housing body 14 in a function block 78 . The welding tongs 41 of the device 40 are then slipped over the housing cover 16 in a function block 80 . In this case, the contact areas 54 and 64 are in their retracted rest positions. In a block 82, the flat plate 50 of the axial loading device 46 is now pressed against the curved cover base 32. according to the arrow 52, and the actuators 56 and 66 are actuated, as a result of which the contact areas 54 and 64 are acted upon radially inwards against the protruding cover section 36 or the outer surface of the cover casing 34. In a function block 84, a voltage is now applied to the upper electrode 44 and the lower electrode (not shown), as a result of which a current flows through the linear contact area between the housing body 14 and the housing cover 16 and the weld seam 38 is produced. Then, in a function block 86, the actuators 56 and 66 are switched off again, so that the housing cover 16 is released from the welding tongs and the latter can be removed from the high-pressure fuel pump 10. The method ends in a function block 88.

Claims

Expectations

1. Device (40) for welding a pot-shaped housing cover (16) to a housing body (14) of a high-pressure fuel pump (10) by means of a capacitor discharge press-in welding process (KEEP welding process), with an application device (42) for pressing on the housing cover (16) on the housing body (14) and an upper electrode (44) for making electrical contact with the housing cover (16), characterized in that the upper electrode (44) is separate from the application device (42), and in that the upper electrode (44) is at least in a contact area (64) to the housing cover (16) comprises a softer material than the loading device (42) in a contact area (50, 54) to the housing cover (16).

2. Device (40) according to claim 1, characterized in that the contact area (64) of the upper electrode (44) comprises copper and the contact area (50, 54) of the application device (42) comprises steel.

3. Device (40) according to at least one of the preceding claims, characterized in that the loading device (42) comprises at least one axial loading device (46) and at least one radial loading device (48), the axial loading device (46) having a cover base (32 ) is acted upon in a substantially axial direction and the radial urging device (48) acts on a cover casing (34) and/or a cover section (36) protruding radially outwards in a substantially radial direction.

4. Device (40) according to at least one of the preceding claims, characterized in that the upper electrode (44) contacts the cover jacket (34) in a substantially radial direction.

5. Device (40) according to at least one of the preceding claims, characterized in that the application device (42) and the upper electrode (44) are parts of a generally pot-shaped collet (41) which is used to weld the housing cover (16) to the Housing body (14) can be slipped over the housing cover (16) at least in certain areas.

6. Device (40) according to claim 5, characterized in that the collet (41) has at least one first actuator (66) which acts on a contact region (64) of the upper electrode (44) radially inwards against the cover jacket (34).

7. Device (40) according to at least one of claims 5-6, characterized in that the collet (41) has at least one second actuator (56) which has a contact area (54) of the radial loading device (48) radially inward against the Cover jacket (34) and/or a cover section (36) projecting radially outwards.

8. A method for welding a pot-shaped housing cover (16) to a housing body (14) of a high-pressure fuel pump (10) by means of a capacitor discharge press-in welding process (KEEP welding process), comprising the following steps: pressing on the pot-shaped housing cover (16). the housing body (14) by means of an application device (42) and electrical contacting of the housing cover (16) with an upper electrode (44), characterized in that the housing cover (16) is electrically contacted by means of an upper electrode (44) separate from the application device (42). and that a softer material is used for at least one contact area (64) of the upper electrode (44) to the housing cover (16) than for a contact area (50, 54) of the application device (42) to the housing cover (16).

9. The method according to claim 8, characterized in that at least for the contact area (50, 54) of the loading device (42). harder material is used than the material from which the pot-shaped housing cover (16) is made.