DE102020208849A1 - Fuel pump, in particular high-pressure fuel pump - Google Patents

Abstract

Fuel pump (10) comprises a pump housing (12), a pump piston (18), a sealing device (32) arranged around the pump piston (18) and a seal carrier (34) by which the sealing device (32) is supported and the one alignment section (42), by means of which the seal carrier (34) is aligned in the radial direction on a counter-section (60) of the pump housing (12). It is proposed that a spacer device (56) made of an electrically insulating material is arranged at least in regions between the alignment section (42) and the counter-section (60).

Description

State of the art

The invention relates to a fuel pump, in particular a high-pressure fuel pump, according to the preamble of claim 1.

the DE 10 2015 209 539 A1 describes a high-pressure fuel pump, for example for direct fuel injection. Such a high-pressure fuel pump compresses the fuel to a comparatively high pressure and conveys it to a high-pressure area or a fuel collection line ("rail") to which several injectors are connected, which inject the fuel directly into the combustion chambers of an internal combustion engine assigned to them. To separate a low-pressure fuel area of the high-pressure fuel pump from a drive area, an annular sealing device is provided, which encloses a pump piston and is held by a seal carrier. The seal carrier is attached to a pump housing of the high-pressure fuel pump.

Disclosure of Invention

The problem on which the invention is based is solved by a fuel pump having the features of claim 1 . Advantageous developments are specified in the dependent claims.

In certain configurations of fuel pumps, the pump piston is not necessarily aligned completely axially with respect to the pump housing when the individual parts are assembled. Rather, it may be that the pump piston is (initially) slightly inclined compared to the ideal line. When assembling the seal carrier, such a pump piston cannot be used for the centered alignment of the seal carrier. Therefore, in such a configuration, the seal carrier is aligned in the radial direction with an alignment section on a counter-section of the pump housing and is guided during assembly of the seal carrier on the pump housing.

However, the seal carrier should preferably be attached to the pump housing by resistance welding. This normally excludes a surface contact between the aligning section and the counter-section, since otherwise a bypass for the current flow occurs during resistance welding, making this difficult or impossible. By providing a spacer device made of an electrically insulating material between the fastening section and the mating section, the seal carrier can be connected to the pump housing by resistance welding along a linear weld seam, and at the same time an alignment or centering of the seal carrier on the mating section of the pump housing can be ensured.

The invention thus makes it possible, even in those configurations of fuel pumps which initially do not have precise guidance or alignment of the pump piston in the housing, on the one hand to align the seal carrier precisely with respect to the pump housing in the radial direction, and on the other hand to weld the seal carrier to the pump housing by means of resistance welding associate. This greatly simplifies assembly as the alignment function is built into the individual parts of the fuel pump during assembly. A complex centering tool is therefore no longer required.

Basically, the fuel pump according to the invention can be assembled on the same production line as previous fuel pumps, which have, for example, a piston bushing for more or less precise centering or alignment of the pump piston. In the fuel pump according to the invention, the electrical insulation between the pump housing and the seal carrier is ensured where no electrical contact is desired. This makes it possible for there to be a direct metallic contact only where a connection is desired by means of resistance welding. Overall, the fuel pump according to the invention can be manufactured inexpensively, and due to the precise alignment of the seal carrier relative to the pump housing, high efficiency in the operation of the fuel pump and a long service life are nevertheless achieved.

This is achieved specifically by a fuel pump, in particular a high-pressure fuel pump, such as is used in fuel systems of internal combustion engines with direct fuel injection. It comprises a pump housing and a pump piston which is at least partially accommodated in the pump housing, for example by means of a piston bushing. The fuel pump according to the invention is therefore a piston pump. For example, it can be a single-cylinder piston pump that is driven by a camshaft of the internal combustion engine.

To separate a fuel area of the fuel pump from a drive area of the internal combustion engine, a sealing device is arranged around the pump piston, which can be designed, for example, as a sealing ring made of a plastic material, for example a PTFE material. The sealing means is stationary and is a sliding fit on an outer one Lateral surface of the pump piston. The sealing device is held by a seal carrier in its at least essentially stationary operating position relative to the pump piston. For this purpose, the seal carrier has an alignment section, which can be designed, for example, as a cylindrical, circumferential ring section.

The seal carrier is aligned in the radial direction on a counter-section of the pump housing by means of the alignment section. This counter-section can be, for example, a recess in the pump housing that is complementary to the alignment section. According to the invention, it is proposed that a spacer device made of an electrically insulating material is arranged at least in regions between the fastening section and the counter-section. In this way, the alignment section is at least partially spaced apart from the counter-section, so that no electrical contact is possible there. To create the fixed connection between the seal carrier and the pump housing by means of resistance welding, there can be a corresponding welding section on the seal carrier and/or on the pump housing, for example in the form of a circumferential projection, which is required for the more or less linear contact between the seal carrier and the pump housing for resistance welding Pump housing ensures. The "alignment" function and the "connection" function are therefore implemented by different sections on the seal carrier and/or on the pump housing, and these functions are therefore decoupled from one another.

In a further development it is provided that the spacer device comprises at least one ring-shaped spacer element. Such a system ensures that the desired distance is reliably maintained over the entire circumferential extension of the fastening section of the seal carrier. In addition, it can be manufactured comparatively easily.

In a development of this, it is provided that the ring-shaped spacer element is formed by a shrink tube. Such is known from electrical engineering applications as a reliable means of electrically insulating electrical conductors. It comprises a material which usually shrinks under the influence of heat.

In a further development of this, it is provided that the spacer device comprises at least two annular spacer elements spaced axially from one another. As a result, the use of material can be reduced, and at the same time reliable spacing is made possible over a desired axial extent.

In a further development it is provided that the spacer device comprises at least two spacer elements which are spaced apart from one another in the circumferential direction. This also reduces the amount of material used to implement the spacer device. In order to ensure a reliable spacer function, it is advantageous if a spacer element is present at least at 0°, 120° and 240°, viewed in the circumferential direction. It is conceivable that at least one spacer element is designed, for example, as a pad, which can have a circular, elliptical, or polygonal outer contour when viewed from above. However, it is also conceivable that a spacer element extends, for example, over a circumferential sector of approximately 120°, and that a spacer element in the form of a pad is arranged opposite this spacer element.

In a further development it is provided that the spacer device comprises a lacquer layer. This is particularly easy to implement and very inexpensive. It should be noted that the spacer function of the spacer element only has to be ensured during assembly of the seal carrier on the pump housing, ie until the seal carrier is firmly connected to the pump housing, for example by resistance welding. On the other hand, durability of the spacer element is not absolutely necessary.

In a further development it is provided that the spacer device comprises a plastic coating. This is also very inexpensive and easy to implement.

In a further development it is provided that the spacer device is attached to the fastening section and/or to the counter-section. Attachment to the seal carrier is probably the easiest way to implement, but attachment to the opposite section is also functionally possible.

• 1 einen teilweisen Schnitt durch eine Kraftstoff-Hochdruckpumpe;
• 2 einen vergrößerten Bereich der Kraftstoff-Hochdruckpumpe von 1 zur Darstellung eines Befestigungsabschnitts eines Dichtungsträgers, eines Gegenabschnitt eines Pumpengehäuses und einer dazwischen angeordneten Abstandshalteeinrichtung;
• 3 eine Seitenansicht des Dichtungsträgers und der Abstandshalteeinrichtung von 2;
• 4 eine perspektivische Darstellung des Dichtungsträgers und der Abstandshalteeinrichtung von 3;
• 5 eine Darstellung ähnlich zu 3 eines Dichtungsträgers mit einer abgewandelten Ausführungsform einer Abstandshalteeinrichtung;
• 6 eine Darstellung ähnlich zu 4 des Dichtungsträgers von 5;
• 7 eine Darstellung ähnlich zu 3 eines Dichtungsträgers mit einer nochmals abgewandelten Ausführungsform einer Abstandshalteeinrichtung;
• 8 eine Darstellung ähnlich zu 4 des Dichtungsträgers von 7; und
• 9 ein Flussdiagramm eines Verfahrens zur Herstellung der Kraftstoffpumpe von 1.

Embodiments of the invention are explained below with reference to the drawings. Show in the drawing:

• 1 a partial section through a high-pressure fuel pump;
• 2 an enlarged area of the high-pressure fuel pump from 1 to show a fastening section of a seal carrier, a counter section of a pump pen housing and spacer means disposed therebetween;
• 3 a side view of the seal carrier and the spacer device of FIG 2 ;
• 4 a perspective view of the seal carrier and the spacer device of 3 ;
• 5 a representation similar to 3 a seal carrier with a modified embodiment of a spacer device;
• 6 a representation similar to 4 of the seal carrier 5 ;
• 7 a representation similar to 3 a seal carrier with a further modified embodiment of a spacer device;
• 8th a representation similar to 4 of the seal carrier 7 ; and
• 9 a flow chart of a method for manufacturing the fuel pump of FIG 1 .

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

In 1 carries a high-pressure fuel pump for an internal combustion engine, not shown, overall reference numeral 10. The high-pressure fuel pump 10 has an overall substantially cylindrical pump housing 12, in or on which the essential components of the high-pressure fuel pump 10 are arranged. Thus, the high-pressure fuel pump 10 has an inlet/quantity control valve 14 , a pump piston 18 which is arranged in a pumping chamber 16 and can be moved back and forth by a drive shaft (not shown), an outlet valve 20 and a pressure-limiting valve 22 .

In operation, the pump piston 18, which reciprocates parallel to a longitudinal axis 24, in a suction stroke fuel -. B. gasoline or diesel fuel - sucked via the inlet / quantity control valve 14 in the pumping chamber 16. During a delivery stroke, the fuel in the delivery chamber 16 is compressed by the pump piston 18 and ejected via the outlet valve 20, for example, into a high-pressure area 26, for example to a fuel collection line (“rail”), where the fuel is stored under high pressure. The amount of fuel that is ejected during a delivery stroke is adjusted by the electromagnetically actuated inlet/quantity control valve 14 . In the event of an impermissible excess pressure in the high-pressure area 26, the pressure-limiting valve 22 opens, as a result of which fuel can flow from the high-pressure area 26 into the pumping chamber 16.

The pump piston 18 is guided in the pump housing 12 by means of a piston bushing 28, with a certain small play being present between the piston bushing 28 and the pump piston 18 in order to facilitate the insertion of the pump piston 18 into the piston bushing 28 when the high-pressure fuel pump 10 is being assembled. in the in 1 In the lower region of the pump housing 12 there is a socket-like peripheral collar 30 which has a receiving groove for an O-ring seal 32 extending in the peripheral direction on its outside.

The high-pressure fuel pump 10 also includes a sealing device 32 in the form of a sealing ring, which can preferably be made of a plastic material, for example a PTFE material. The sealing device 32 rests with a radial inner side on a lateral surface of the pump piston 18 in a sliding fit. During operation of the high-pressure fuel pump 10, it is at least essentially stationary and relative to the pump piston 18, and it is held in this stationary position by a seal carrier 34. This is produced, for example, as a shaped sheet metal part by a deep-drawing process and is attached even closer to the pump housing 12 descriptive manner.

The seal carrier 34 has at its in 1 lower end has a first portion 36 extending radially inward and terminating at a distance from the pump piston 18. Section 36 is integrally formed with a second section 38 which extends substantially in the axial direction and in 1 from the first section 36 extends upwards. At its in 1 A third section 40 is formed at the upper end and extends outwards in a substantially radial direction. At its radially outer end, a fourth section 42 is formed, which extends substantially in the axial direction 1 extends downward. A comparatively short fifth section 44 is formed on its lower axial end and extends outward at an angle of approximately 40° relative to the longitudinal axis 24 .

The inclined fifth section 44 of the seal carrier 34 is firmly connected to the lower end of the collar 30 by means of a circumferential weld line 46 by means of resistance welding. The sealing device 32 is fixed downwards in the axial direction by the first section 36 of the seal carrier 34 . The sealing device 32 is fixed in the radial direction by the second section 38 of the seal carrier 34 . To fix the sealing device 32 in the axial direction upwards is a fixing sleeve 48 in the second Section 38 of the seal carrier 34 is pressed.

at one in 1 lower end of the pump piston 18, a spring plate 50 is attached to this. A piston spring 52 is clamped between this section and the third section 40 of the seal carrier 34 . The high-pressure fuel pump 10 can, for example, be inserted with the collar 30 into an opening in an engine block of an internal combustion engine and fastened to the engine block by means of a fastening flange 54 . This in 1 The lower end of the pump piston 18 and the spring plate 50 can interact with a camshaft of the internal combustion engine, which causes the pump piston 18 to move back and forth during operation. The sealing device 32 ensures a fluidic separation between a fuel area of the high-pressure fuel pump 10 and a drive area, for example of the internal combustion engine.

How from the 2-4 As can be seen, the fourth section 42 of the seal carrier 34 has on its radial outside a comparatively thin and to this extent layer-like spacer device 56 made of an electrically insulating material. In the present example, this is designed as an annular spacer element 58 . This ring-shaped spacer element 58 can also be produced by way of example in that a shrink tube, as is known, for example, for the electrical insulation of electrical conductors, is pushed onto the fourth section 42 and then heated. In this way, the heat-shrinkable tube reduces its diameter, whereby it comes into contact with the outside of the fourth section 42 under tension. However, it is also conceivable that the spacer element 58 is applied to the outside of the fourth section 42 as a liquid paint, where it then hardens. It is also conceivable that the spacer element 58 is formed by a plastic sleeve that is pushed onto the fourth section 42 of the seal carrier 34 .

One recognizes readily in particular from the representation of 2 that due to the spacer device 56, the fourth section 42 of the seal carrier 34 forms an alignment section, whereas the radial inner side of the collar 30 forms a counter-section 60 which interacts with the alignment section 42 of the seal carrier 34 via the spacer device 56 and thus with the seal carrier 34 and with it aligns the sealing device 32 relative to the pump housing 12 or centers it in the radial direction relative to the longitudinal axis 24 . The spacer device 56 ensures that direct electrical contact between the seal carrier 34 and the collar 30 or the pump housing 12 is only possible in a circumferential linear area at the lower end of the collar 30, so that the weld line 46 is produced there by resistance welding can. In the other areas, on the other hand, there is a distance D between the alignment section 42 and the counter-section 60 .

The alternative embodiment of the spacer device 56 of 5-6 differs from that of 2-4 in that there are two axially spaced annular spacer elements 58a and 58b. The alternative embodiment of the spacer device 56 of 7-8 differs from those of 2-6 in that the spacer device 56 has a total of four spacer elements 58a-d spaced apart from one another in the circumferential direction in the manner of pads, which in the present case have a rectangular outer contour in the top view. In principle, however, other outer contours would also be conceivable, for example circular or elliptical, as well as other numbers of spacer elements, with a minimum number of three being preferred.

The fuel pump 10 is manufactured as follows (cf 9 ): First, the pump housing 12, the pump piston 18, the sealing device 32 and the seal carrier 34 for the sealing device 32 are provided in a function block 62. Then, in a functional block 64 , the spacer device 56 is applied to the alignment section 42 of the seal carrier 34 . In a subsequent function block 66, the alignment section 42 of the seal carrier 34 is inserted with the spacer device 56 into the mating section 60 of the pump housing 12, so that the alignment section 42 is at least partially spaced from the mating section 60 (distance D in 2 ). Finally, in a functional block 68, the weld line 46 between the seal carrier 34 and the pump housing 12 is produced by means of resistance welding.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102015209539 A1 [0002]

Claims (9)

Fuel pump (10), in particular a high-pressure fuel pump, with a pump housing (12), a pump piston (18), a sealing device (32) arranged around the pump piston (18) and a sealing carrier (34) through which the sealing device (32) and which has a preferably peripheral alignment section (42) by means of which the seal carrier (34) is aligned in the radial direction on a preferably peripheral counter-section (60) of the pump housing (12), characterized in that between the alignment section (42) and a spacer device (56) made of an electrically insulating material is arranged at least in regions on the counter-section (60). Fuel pump (10) according to at least one of the preceding claims, characterized in that the spacer device (56) comprises at least one annular spacer element (58). Fuel pump (10) after claim 2 , characterized in that the annular spacer element (58) is formed by a shrink tube. Fuel pump (10) according to at least one of claims 2 or 3 that the spacer device (56) comprises at least two axially spaced annular spacer elements (58a, 58b). Fuel pump (10) according to at least one of the preceding claims, characterized in that the spacer device (56) comprises at least two spacer elements (58a-d) spaced apart from one another in the circumferential direction. Fuel pump (10) according to at least one of the preceding claims, characterized in that the spacer device (56) comprises a layer of lacquer. Fuel pump (10) according to at least one of the preceding claims, characterized in that the spacer device (56) comprises a plastic coating. Fuel pump (10) according to at least one of the preceding claims, characterized in that the spacer device (56) is attached to the alignment section (42) and/or to the counter-section (60). Method for manufacturing a fuel pump (10), which has the following steps: a. providing a pump housing (12), a pump piston (18), a sealing device (32) and a seal carrier (34) for the sealing device (32); b. applying a spacer device (56) to an alignment section (42) of the seal carrier (34) and/or a mating section (60) of the pump housing (12); c. Inserting the alignment section (42) of the seal carrier (34) into the mating section (60) of the pump housing (12), or placing the alignment section (42) of the seal carrier (34) on the mating section (60) of the pump housing (12) so that the Alignment section (42) is at least partially spaced apart from the counter-section (60); i.e. Establishing a welded connection (46) between the seal carrier (34) and the pump housing (12) by means of resistance welding.

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