EP3298263B1 - High-pressure fuel pump - Google Patents

Description

State of the art

The invention relates to a fuel pump, in particular a high-pressure fuel pump, with a piston, on the end section of which faces a drive, a sealing device radially enclosing the piston is arranged.
The invention further relates to a method for producing a fuel pump, in particular a high-pressure fuel pump.

In fuel systems of internal combustion engines, fuel pumps are used to transport fuel. In systems with direct petrol injection, the fuel pumps are supplemented by high-pressure fuel pumps, which compress the fuel supplied, for example, by an electric fuel pump with a pre-pressure in sufficient quantity to the level required for high-pressure gasoline injection.

Such fuel pumps usually have at least one piston which can be moved axially by means of a drive formed by a cam or an eccentric disk. A required restoring force of the piston is generated by means of a compression spring. For example, a spring plate acted upon by a compression spring is pressed onto an end section of the piston. In this case, a piston seal arranged radially on the outside of the piston can separate a first fuel-side section of the piston from a second oil-side section of the piston, as a result of which mixing of fuel and oil is at least kept to a minimum. Such a piston seal, also referred to as a low-pressure seal, is usually held by a holding device, which is also referred to as a seal carrier. The Seal carrier is connected to the housing of the high-pressure fuel pump in such a way that here too the oil-side section of the fuel pump is reliably sealed from a fuel-side section, the seal carrier representing a static seal against the low-pressure seal and against the housing.

Seal carriers are realized, for example, as deep-drawn elements which form a material connection with the housing of the high-pressure fuel pump via a laser weld seam and thereby statically seal between the oil and fuel side. Out DE 10 2013 205909 A1 a fuel piston pump with a sealing device radially enclosing the piston is known. Out DE 10 2013 206930 A1 the use of the capacitor discharge welding method in fuel pumps is also known.

Disclosure of the invention

The object of the invention is to provide a fuel pump, the manufacture of which enables improved cycle times when joining or welding the seal carrier and which enables improved error detection in the manufacturing process.

The object is achieved by a high-pressure fuel pump with a piston, on the end section of which faces a drive, a sealing device radially enclosing the piston is arranged, the sealing device being held by at least one seal carrier, and the seal carrier being connected at least in sections to a housing of the fuel pump solved that the seal carrier has at least one radially circumferential section, at which the seal carrier is integrally connected to the housing by means of capacitor discharge welding.

The integral connection of the seal carrier to the fuel pump housing by means of capacitor discharge welding reduces the cycle time in the manufacture of the fuel pump, since a faster and more precise integral connection between the seal carrier and the housing can be produced by means of the capacitor discharge welding. In particular, in the case of capacitor discharge welding, in comparison to the laser welding process, there are almost no splashes and no smoke. This eliminates also the need for regular cleaning of the protective glass, for example to ensure the quality of the weld.

Any leakage that may occur in a weld seam, which arises in the welding processes used up to now, in particular laser welding, can only be determined during the so-called band end test during the leak test. By using capacitor discharge welding, the welding process can be monitored in production. Preferably, a so-called sink path or follow-up path and / or the current profile during the capacitor discharge welding are monitored here. This makes it possible to identify the rejects much earlier, which makes it easier to adapt the manufacturing process and reduce error costs.

According to the invention, the seal carrier comprises a substantially axially extending first section, which radially surrounds the sealing device, a second section adjoining the first section and extending essentially radially outwards, and a radially outer connecting section adjoining the second section, the is integrally connected to the housing of the fuel pump by means of capacitor discharge welding. The connecting section of the seal carrier has an angle with respect to the axis of the piston of approximately 30 ° to 60 °, preferably approximately 40 ° to 50 °. The radial extent of this connecting section is approximately 2 to 4 mm, preferably approximately 3 mm. With these embodiments, a connection length of at least approx. 1 mm can be achieved in the capacitor discharge welding, as a result of which a robust and securely sealing weld seam is produced.

According to a preferred embodiment, there is a gap of at least about 0.1 mm between the second section of the seal carrier and the housing. This ensures that no undesired or undefined shunt occurs when the capacitor discharge welding is carried out.

According to another possible embodiment, the second section of the seal carrier is connected to the housing of the fuel pump by means of a pressure. In this embodiment, a particularly stable connection between the seal carrier and the housing can be achieved.

The connection section of the seal carrier is preferably integrally connected to the housing on a radially circumferential shoulder of the housing by means of capacitor discharge welding. The provision of the radially circumferential shoulder on the housing enables improved production of the fuel pump and increases the stability of the integral connection.

• Anordnen des Gehäuses an einer ersten Elektrode einer Schweißeinrichtung für ein Kondensator-Entladungsschweißen;
• Anordnen des Dichtungsträgers an einem radial inneren Abschnitt des Gehäuses;
• Anordnen einer im Wesentlichen ringförmigen zweiten Elektrode an einem radial umlaufenden Verbindungsabschnitt des Dichtungsträgers, wobei die zweite Elektrode den Dichtungsträger mit einer vorgebbaren Kraft federnd und/oder schwimmend beaufschlagt;
• Justieren und/oder Zentrieren des Dichtungsträgers in dem Gehäuse;
• Durchführen eines Kondensators-Entladungsschweißens zwischen dem Verbindungsabschnitt des Dichtungsträgers und dem Gehäuse.

The object is also achieved by a method for producing a fuel pump, the method comprising the following steps:

• Arranging the housing on a first electrode of a welding device for capacitor discharge welding;
• Arranging the seal carrier on a radially inner portion of the housing;
• Arranging an essentially annular second electrode on a radially circumferential connecting section of the seal carrier, the second electrode acting on the seal carrier with a predeterminable force in a resilient and / or floating manner;
• Adjusting and / or centering the seal carrier in the housing;
• Performing capacitor discharge welding between the connection portion of the seal carrier and the housing.

A cohesive connection between the seal carrier and the housing of the high-pressure fuel pump can be achieved by means of this method, as a result of which the above-mentioned advantages are realized.

According to a possible embodiment, the second section of the seal carrier is pressed into a radially inner section of the Pressed housing and then the capacitor discharge welding is performed on a connecting portion of the seal carrier.

A force and / or a relative movement of the seal carrier to the housing and / or a current profile of the capacitor discharge welding are preferably determined during the capacitor discharge welding. The values determined in this way can be used to determine the quality of the welded joint. The ascertained values are preferably compared with stored values for the force, the relative movement and / or the current profile.

Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments of the invention, which are explained with reference to the drawings.

Figur 1

eine vereinfachte schematisierte Darstellung eines Kraftstoffsystems für eine Brennkraftmaschine;

Figur 2

einen Ausschnitt eines Längsschnitts durch eine Kraftstoffhochdruckpu mpe;

Figur 3

eine axiale Schnittansicht des radial äußeren Randbereichs des Dichtungsträgers sowie eines Abschnitts des Gehäuses der Kraftstoffhochdruckpumpe gemäß einer möglichen Ausführungsform;

Figur 4

eine axiale Schnittansicht eines radial äußeren Randbereichs einer Dichteinrichtung sowie eines Abschnitts des Gehäuses einer Hochdruckpumpe gemäß einer anderen möglichen Ausführungsform;

Figur 5

eine axiale Schnittansicht eines radial äußeren Randbereichs eines Dichtungsträgers sowie eines Abschnitts eines Gehäuses gemäß einer weiteren möglichen Ausführungsform;

Figur 6

eine axiale Schnittansicht eines Dichtungsträgers sowie eines Gehäuses gemäß einer möglichen Ausführungsform;

Figur 7

eine schematisierte Darstellung einer Schnittansicht eines Teils der Kraftstoffhochdruckpumpe während der Durchführung des KE-Schweißprozesses; und

Figur 8

ein vereinfachtes Flussdiagramm mit bei der Herstellung der Kraftstoffhochdruckpumpe möglichen Verfahrensschritten.

Show it:

Figure 1

a simplified schematic representation of a fuel system for an internal combustion engine;

Figure 2

a section of a longitudinal section through a high pressure fuel pump;

Figure 3

an axial sectional view of the radially outer edge region of the seal carrier and a portion of the housing of the high-pressure fuel pump according to a possible embodiment;

Figure 4

an axial sectional view of a radially outer edge region of a sealing device and a portion of the housing of a high pressure pump according to another possible embodiment;

Figure 5

an axial sectional view of a radially outer edge region of a seal carrier and a portion of a housing according to another possible embodiment;

Figure 6

an axial sectional view of a seal carrier and a housing according to a possible embodiment;

Figure 7

a schematic representation of a sectional view of a part of the high-pressure fuel pump during the implementation of the KE welding process; and

Figure 8

a simplified flow chart with possible process steps in the manufacture of the high-pressure fuel pump.

Figure 1 shows a fuel system 10 for an internal combustion engine, not shown, in a simplified schematic representation. Fuel is supplied from a fuel tank 12 via a suction line 14, by means of a prefeed pump 16 and a low pressure line 18 via an inlet 20 of a quantity control valve 24 which can be actuated by an electromagnetic actuating device 22 to a delivery chamber 26 of a high pressure fuel pump 28. For example, the quantity control valve 24 can be an inlet valve of the high-pressure fuel pump 28 that can be positively opened.

In the present case, the high-pressure fuel pump 28 is designed as a piston pump, a piston 30 being able to be moved vertically in the drawing by means of a cam disk 32 (“drive”). Hydraulically between the delivery chamber 26 and an outlet 36 of the high-pressure fuel pump 28 is in the Figure 1 arranged as a spring-loaded check valve outlet valve 40 which can open towards the outlet 36. The outlet 36 is connected to a high-pressure line 44 and via this to a high-pressure accumulator 46 (“common rail”). Furthermore, a pressure relief valve 42, which is also drawn as a spring-loaded check valve and which can open toward the delivery chamber 26, is arranged hydraulically between the outlet 36 and the delivery chamber 26.

During operation of the fuel system 10, the prefeed pump 16 delivers fuel from the fuel tank 12 into the low-pressure line 18. The quantity control valve 24 can be closed and opened depending on a particular fuel requirement. As a result, the pumped to the high pressure accumulator 46 Fuel quantity affected. The electromagnetic actuating device 22 is controlled by a control and / or regulating device 48.

In Figure 2 A section of a high-pressure pump 28 is shown, which comprises an approximately cup-shaped seal carrier 68 and a piston spring 70, which is arranged radially on the outside around a section of the seal carrier 68 and is designed as a helical spring and is supported with an end section on the seal carrier 68. A spring plate 72, on which an end section of the piston spring 70 is received, is pressed onto an end section of the piston 30 which is lower in the drawing and faces the drive.

Arranged radially inside the seal carrier 68 is a piston seal (also referred to as “low-pressure seal”), which is referred to as a sealing device 74 and radially surrounds the lower second section (which faces the drive) of the piston 30 and one that is present between the housing 50 and the seal carrier 68 Seals fluid space ("step room") to the outside to the engine block 53. The piston 30 is displaceable along the longitudinal axis 64 relative to the sealing device 74. In a rough approximation, the sealing device 74 has an overall annular structure.

In the present case, the sealing device 74 is shown in FIG Figure 2 axially supported upwards by a holding section 76 arranged inside the seal carrier 68 and also approximately hat-shaped. In the drawing, a space area above the sealing device 74 characterizes a "fuel side" and a space area below the sealing device 74 a "oil side".

The sealing device 74 is also shown in FIG Figure 2 supported axially downward by a radially inward curved peripheral portion of the seal carrier 68. It goes without saying that the sealing device 74 can optionally have a small axial play within a region determined by the holding section 76 and the said edge section.

The sealing device 74 is arranged on the piston 30 radially on the outside along the longitudinal axis 64 and is essentially rotationally symmetrical. Figure 3 shows part of the substantially radially outwardly extending and also in Figure 2 shown second section 92 and a radially outer edge region 93 which adjoins the second section 90 and has a connecting section 94. According to the in Figure 3 In the embodiment shown, the connecting section 94 has an angle 96 with respect to the axis of the piston, which, according to a possible embodiment, is approximately 45 °. The angle 96 is preferably in ranges between approximately 30 ° to 60 °. It is advantageous if the angle 96 is in a range between 40 ° to 50 ° and very particularly advantageous if the angle 96 is as in FIG Figure 3 shown is approximately 45 °.

In order to achieve a connection length 97 of approximately 1 mm when carrying out the capacitor discharge welding process, it is advantageous if a radius 98 of at least approximately 0.3 mm of the housing 50 meets a surface of the seal carrier 68 or a connecting section 94 which is inclined by the angle 96. The more solid component preferably has the radius 98. This reduces the line cross section, so that the solid component, in this case the housing 50 of the high-pressure fuel pump 28, melts similarly early as the thinner-walled component, in this case the seal carrier 68, and a robust weld seam arises. In order to avoid an undesired or undefined shunt in the welding process, according to the in Figure 3 In the embodiment shown, a minimum gap 99 of approximately 0.1 mm is maintained between the housing 50 and the edge region 93 of the seal carrier 68.

Figure 4 shows the same section of the housing 50 of the high pressure fuel pump 28 and the seal carrier 68 as in FIG Figure 3 , but according to another possible embodiment, in which the weld seam is formed by means of a ring boss 100. The ring boss 100 is formed on the housing 50 of the high-pressure pump 28 before the welding process. The connecting section 94 is here inclined at an angle 101 of approximately 90 ° about the longitudinal axis 64 of the piston 30. This enables a particularly stable weld, but other angles of the connecting section 94 are also possible.

According to another possible embodiment, as in Figure 5 can be provided to provide on the housing 50 of the high-pressure fuel pump 28 a shoulder 102, on which the capacitor discharge welding takes place, whereby a shortening of the lever arm and a reduction in the load is possible.

In Figure 6 Another possible exemplary embodiment is shown, in which the radially outer edge region 93 is additionally pressed onto the housing 50 of the high-pressure fuel pump 28, as a result of which an even more stable connection is possible. Of course, the increased contact area must be taken into account when carrying out the capacitor discharge welding process.

Figure 7 shows an arrangement with which the capacitor discharge welding process according to the invention can be carried out. For this purpose, the housing 50 of the high-pressure fuel pump 28 is arranged on a first electrode 110. A substantially annular second electrode 112 is arranged on the connecting section 94 of the seal carrier 68. The connecting portion 94 is, for example, as in FIG Figure 3 shown trained. The second electrode 112 is preferably designed such that it applies a predeterminable force to the seal carrier 68 or the connecting section 94 in a resilient and / or floating manner. After the seal carrier 68 has been adjusted and / or centered in the housing 50, the capacitor discharge welding is carried out, so that a weld seam is formed between the connecting section 94 and the part of the housing 50 adjacent there.

Figure 8 shows in a flow chart method steps that are carried out according to a possible embodiment of the method according to the invention in the manufacture of the high-pressure fuel pump 28.

The method begins in a step 200, in which the housing 50 of the high-pressure fuel pump 28 is positioned on the first electrode 110. In a step 201, the seal carrier 68 is inserted and prepositioned. In a step 202, the second electrode 112 is put on and floating stored. Their own weight is preferably selected such that the force required for the welding process to be carried out later is generated.

The arrangement is centered in a step 203 and in a step 204 the process parameters, in particular the sinking path, the force and / or the current profile, are monitored when the welding process is carried out.

In a step 205, the capacitor discharge welding takes place, so that the seal carrier 68 in the connecting section 94 is connected to the housing 50 of the high-pressure fuel pump 28 in a cohesive manner.

In a step 206, the process parameters monitored in step 204 are evaluated. The sinking path of the second electrode 112, which is also referred to as the repositioning path, and the current profile when carrying out the capacitor discharge welding are particularly meaningful here. These output variables of the production are compared with predetermined values in a step 207. If deviations are ascertainable that go beyond a definable tolerance threshold, the manufacturing process of this high-pressure fuel pump 28 is interrupted in a step 209 and it is declared as a reject. If necessary, some parameters are adjusted for the welding process. If the monitored process parameters were within the predefinable tolerance ranges, the method ends in a step 208.

The fact that the output parameters can be examined directly for errors means that the rejects are recognized much earlier, which makes corrective action considerably easier and saves error costs.

The use of the capacitor discharge welding process shortens the cycle time in the production of the high-pressure fuel pump 28, in particular when the seal carrier 68 is connected to the housing 50 of the high-pressure fuel pump 28. Furthermore, the use of capacitor discharge welding eliminates the need for regular cleaning of the protective glass, which is required, for example, in the laser welding process in order to ensure faultless welding.

With the method according to the invention, a leaky laser weld seam is not only determined during the end-of-band test during the tightness test carried out there, but rather by evaluating the process parameters, it can be recognized in production whether the welding process was successful.

Claims (8)

1. Fuel pump, in particular a high-pressure fuel pump (28) having at least one piston (30) on which a sealing device (74) is arranged radially surrounding the piston (30), wherein the sealing device (74) comprises a seal carrier (68) and wherein the seal carrier (68) is connected, at least in portions, to a housing (50) of the fuel pump, wherein the seal carrier (68) has at least one radially peripheral portion (92, 94) at which the seal carrier (68) is substance-bonded to the housing (50); wherein the seal carrier (68) comprises:

   - a first portion (90) extending substantially axially and surrounding the sealing device (74) radially,

   - a second portion (92) adjacent to the first portion (90) and extending substantially radially outward,

   - and a radially outer edge region (93) adjacent to the second portion (92) and substance-bonded to the housing (50) of the fuel pump;

   wherein the edge region (93) of the seal carrier (68) has a connecting portion (94), and the connecting portion (94) has an angle of approximately 30° to 60°, preferably approximately 40° to 50° relative to the axis (64) of the piston (30), and a radial extension of approximately 2 millimetres to 4 millimetres, and wherein the connecting portion (94) is substance-bonded to the housing (50) of the fuel pump by means of capacitor discharge welding.
2. Fuel pump, in particular a high-pressure fuel pump (28) having at least one piston (30) on which a sealing device (74) is arranged radially surrounding the piston (30), wherein the sealing device (74) comprises a seal carrier (68) and wherein the seal carrier (68) is connected, at least in portions, to a housing (50) of the fuel pump, wherein the seal carrier (68) has at least one radially peripheral portion (92, 94) at which the seal carrier (68) is substance-bonded to the housing (50); wherein the seal carrier (68) comprises:

   - a first portion (90) extending substantially axially and surrounding the sealing device (74) radially,

   - a second portion (92) adjacent to the first portion (90) and extending substantially radially outward,

   - and a radially outer edge region (93) adjacent to the second portion (92) and substance-bonded to the housing (50) of the fuel pump;

   wherein the edge region (93) of the seal carrier (68) has a connecting portion (94), and the connecting portion (94) has an angle of approximately 100° to 80°, preferably approximately 90°, relative to the axis (64) of the piston (30), and wherein a ring bulge (100) is formed on the housing (50), and the connecting portion (94) via the ring bulge (100) is substance-bonded to the housing (50) of the fuel pump by means of capacitor discharge welding.
3. Fuel pump according to either of Claims 1 and 2, wherein a radial gap (99) of at least approximately 0.1 millimetre is formed between the edge region (93) of the seal carrier (68) and the housing (50).
4. Fuel pump according to any of Claims 1 to 3, wherein the seal carrier (68) at the edge region (93) is connected to the housing (50) of the fuel pump by means of a press fit.
5. Fuel pump according to any of the preceding Claims 1 to 4, wherein the connecting portion (94) of the seal carrier (68) is substance-bonded to the housing (50) at a radially peripheral shoulder (102) of the housing (50).
6. Method for production of a high-pressure fuel pump (28) according to any of the preceding claims, characterized by the following steps:

   - arranging the housing (50) at a first electrode (110) of a welding device for capacitor discharge welding;

   - arranging the seal carrier (68) on a radially inner portion of the housing (50);

   - arranging a substantially annular second electrode (112) on a radially peripheral connecting portion (94) of the seal carrier (68), wherein the second electrode applies a predefinable force to the seal carrier (68) in a springing and/or floating manner;

   - adjusting and/or centring the seal carrier (68) in the housing (50);

   - performing a capacitor discharge welding between the radially peripheral connecting portion (94) of the seal carrier (68) and the housing (50).
7. Method according to Claim 6, wherein the edge region (93) of the seal carrier (68) has a press fit at a radially inner portion of the housing (50), and the capacitor discharge welding is carried out at a connecting portion (94) of the seal carrier (68) adjacent to the edge region (93).
8. Method according to either of Claims 6 and 7, wherein during the capacitor discharge welding, a force and/or a movement of the seal carrier (68) relative to the housing (50) and/or a current development of the capacitor discharge welding is determined, and wherein the determined force and/or the determined relative movement and/or the determined current development are compared with stored values for the force and/or relative movement and/or current development, and wherein a quality of the weld connection is determined depending on the comparison.

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