DE102020208202A1 - High pressure fuel pump - Google Patents

Abstract

A high-pressure fuel pump (10) comprises a pump housing (12) and a pump piston (18). It is proposed that it further comprises a sleeve element (64) which is arranged around the pump piston (18) and a guide section (66) which extends in the longitudinal direction (24) of the pump piston (18) and protrudes from the pump housing (12). the pump piston (18) and a support section (70) which protrudes radially outwards from the guide section (66) and via which the sleeve element (64) is supported in the radial direction on the pump housing (12).

Description

State of the art

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

High-pressure fuel pumps for fuel systems of internal combustion engines are known from the market. These high-pressure fuel pumps compress the fuel to a high pressure and pass it on to a fuel collecting line (“rail”), from where the fuel is injected directly into the combustion chambers of the internal combustion engine. A pump piston provided with a step is guided in the pump housing, and the pump piston is acted upon by a piston spring towards a drive, that is to say out of the pump housing. In order to prevent the pump piston from falling out of the pump housing in a preassembled state of the high-pressure fuel pump, a sleeve element is provided which has a stop section for the pump piston so that movement of the pump piston in the direction of the drive and away from the housing is limited and it cannot fall out of the pump piston from the pump housing is prevented. An example of such a high-pressure fuel pump is shown in DE 10 2015 209 539 A1 .

Disclosure of the invention

The problem on which the present invention is based is solved by a high-pressure fuel pump having the features of claim 1. Advantageous further developments are given in the subclaims.

The invention makes it possible for the pump piston to be already guided through the sleeve element when installing, for example, a low-pressure seal. This has the advantage that the pump piston hits the low-pressure seal centrally, thus avoiding damage to the low-pressure seal. The sleeve element provided according to the invention also takes into account important strength-critical aspects in that the guide of the pump piston can be arranged outside a seal carrier of the low-pressure seal or independently of this seal carrier. The function “guiding the pump piston” is thus decoupled from the function “holding the low pressure seal”. This has the decisive advantage that the radial bearing forces occurring, for example, due to coaxial tolerances of the pump piston, are absorbed by the sleeve element and transferred directly into the housing. It goes without saying that here and below the terms “axial” and “radial” are defined by the longitudinal axis of the pump piston. “Axial” is in the direction of the longitudinal axis of the pump piston, “radial” is orthogonal to it. The radial bearing forces are thus kept away from the seal carrier. The load on the seal carrier is thus reduced, which prevents failure of the seal carrier during operation. Another advantage is that a seal carrier can be used, as is customary in previous high-pressure fuel pumps.

This is achieved specifically by a fuel pump, in particular a high-pressure fuel pump, such as is used, for example, in fuel systems of internal combustion engines with direct fuel injection. It comprises a pump housing and a pump piston at least partially received 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.

The high-pressure fuel pump according to the invention has a sleeve element arranged radially around the pump piston. This sleeve element has a guide section, the primary purpose and function of which is to guide the pump piston in a sliding fit and to center it in the radial direction relative to the pump housing. The guide section extends in the longitudinal direction of the pump piston and protrudes from the pump housing. It can thus be designed, for example, in the manner of a tube which is free radially outward at least in some areas, that is, not supported by the pump housing, for example pressed into it.

The sleeve element further comprises a support section that is integral with the guide section. This protrudes radially outward from the guide section, and the sleeve element is supported in the radial direction on the pump housing via the support section. Forces acting transversely relative to the longitudinal axis of the pump piston and the sleeve element (transverse forces) are thus directed from the pump piston via the sleeve element and the support section directly into the pump housing. The support section can be designed, for example, in the form of an annular collar. The support section is preferably supported on the pump housing in that the support section is pressed into a corresponding opening in the pump housing. In principle, however, other types of fastening are also conceivable.

In a further development it is provided that the pump piston has a first section facing a delivery chamber and having a first diameter ser and a second portion facing a drive with a second diameter, wherein the first diameter is larger than the second diameter and wherein a shoulder is formed between the first portion and the second portion, and that the sleeve element viewed in the longitudinal direction of the pump piston approximately Height of the paragraph is arranged. The pump piston is thus designed as a so-called “stepped piston”. By arranging the sleeve element in the area of the shoulder or the "step" of the pump piston, the guide function of the sleeve element is implemented in an axial area of the pump piston that is already relatively far away from a delivery chamber of the high-pressure fuel pump and a guide usually present in its area is, whereby the effect of the coaxial centering is improved by the sleeve element.

In a further development of this, it is provided that the sleeve element has a stop section which can interact with the shoulder in order to limit a movement of the pump piston in the direction of the drive. The sleeve element thus fulfills a double function, namely on the one hand it provides the (additional) guidance of the pump piston, and on the other hand it serves as a safeguard against loss for the pump piston when the high-pressure fuel pump is installed, for example during transport and storage from the manufacturer of the high-pressure fuel pump to the manufacturer of the Internal combustion engine.

In a further development of this, it is provided that the stop section has a collar which projects radially inward from the guide section and which is arranged at the end of the guide section opposite the support section. This is very inexpensive and easy to implement.

In a further development of this, it is provided that there is a distance between the edge of the collar and the lateral surface of the pump piston. The gap created in this way enables pressure equalization and a passage for a certain (small) amount of fuel, which can be used, for example, for the lubrication of a subsequently arranged low-pressure seal.

In a further development, it is provided that the sleeve element has a fluid path running overall in its longitudinal direction. The function of this fluid path is the same as that of the gap described above.

In a further development of this, it is provided that the fluid path has at least one groove running overall in the longitudinal direction in a guide surface of the sleeve element. This can be done very easily.

In a further development it is provided that an axial edge of a guide opening of the sleeve element, by means of which the pump piston is guided, has an insertion bevel for the pump piston. This simplifies the sliding of the sleeve element onto the pump piston, in particular when the pump piston is in a certain inclined position.

In a further development, it is provided that the high-pressure fuel pump has a seal carrier for a low-pressure seal, which is a component that is separate from the sleeve element. The function “holding the low-pressure seal” is thus decoupled from the function “guiding the pump piston”, which improves the service life of the seal carrier.

The invention also includes a method for producing a high-pressure fuel pump of the type just mentioned, which comprises the following steps: a. Inserting the pump piston into the pump housing; b. Sliding the sleeve element onto the pump piston; c. Fastening the sleeve element by means of the support section on the pump housing, for example by pressing into an opening in the pump housing; d. Sliding the preassembled unit consisting of the low-pressure seal and seal carrier onto the pump piston; e. Attach the seal carrier to the pump housing, for example by resistance welding.

• 1 einen teilweisen und schematischen Schnitt durch eine Kraftstoff-Hochdruckpumpe mit einem Pumpengehäuse, einem Pumpenkolben, einem Hülsenelement, einem Dichtungsträger und einer Niederdruckdichtung;
• 2 ein vergrößertes Detail aus 1, welches vor allem das Hülsenelement zeigt;
• 3 eine perspektivische Darstellung des Hülsenelements der 1 und 2; und
• 4 ein Flussdiagramm zur Erläuterung eines Verfahrens zum Herstellen der Kraftstoff-Hochdruckpumpe.

Embodiments of the invention are explained below with reference to the accompanying drawings. In the drawing show:

• 1 a partial and schematic section through a high-pressure fuel pump with a pump housing, a pump piston, a sleeve element, a seal carrier and a low-pressure seal;
• 2 an enlarged detail 1 , which mainly shows the sleeve element;
• 3 a perspective view of the sleeve element of 1 and 2 ; and
• 4th a flowchart for explaining a method for producing the high-pressure fuel pump.

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 in detail Machine as a whole has the reference numeral 10. The high-pressure fuel pump 10 has a generally essentially cylindrical pump housing 12 in or on which the essential components of the high-pressure fuel pump 10 are arranged. The high-pressure fuel pump 10 has an inlet / quantity control valve 14, a pump piston 18 which is arranged in a delivery chamber 16 and can be set in a reciprocating motion by a drive shaft (not shown), an outlet valve 20 and a pressure limiting valve 22.

In operation, the pump piston 18, which moves back and forth parallel to a longitudinal axis 24, is fueled during a suction stroke - z. B. gasoline or diesel fuel - sucked into the pumping chamber 16 via the inlet / quantity control valve 14. During a delivery stroke, the fuel in delivery chamber 16 is compressed by pump piston 18 and ejected via outlet valve 20, for example into a high pressure area 26, for example to a fuel collecting line (“rail”), where the fuel is stored under high pressure. The amount of fuel that is expelled during a delivery stroke is set by the electromagnetically actuated inlet / quantity control valve 14. In the event of an impermissible overpressure 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 delivery chamber 16.

The pump piston 18 has a first section 28 which faces the delivery chamber 16 and which has a first diameter. Furthermore, the pump piston 18 has a second section 30 which faces a drive and has a second diameter. The first diameter is larger than the second diameter, so that a shoulder 32 is formed between the first section 28 and the second section 30. The pump piston 18 is therefore a stepped piston.

In the present example, the pump housing 12 has a blind hole-like opening 34 in which the pump piston 18 is received. In the opening 34 three annular elements are arranged one after the other in the direction of the longitudinal axis 24 (longitudinal direction). Adjacent to the delivery chamber 16, a guide ring 36 is first pressed into the opening 34, which works in a sliding fit with the first section 28 of the pump piston 18 and which guides it in the radial direction and centers it relative to the pump housing 12. A high-pressure seal 38 adjoins the guide ring 36, by means of which the very high fluid pressure occurring in the delivery chamber 16 is sealed off from a low-pressure area (without reference number) of the high-pressure fuel pump 10 during a delivery stroke of the pump piston 18. During a delivery stroke of the pump piston 18, the high pressure seal 38 is pressed against the outer jacket surface of the pump piston 18 by the high pressure prevailing on its outside. The high-pressure seal 38 is followed by a retaining ring 40 which is pressed into the opening 34 and which axially secures the high-pressure seal 38. In principle, however, it would also be conceivable for an elongated piston bushing to be provided instead of the three elements mentioned.

The high-pressure fuel pump 10 also includes a low-pressure seal 42, which can preferably be made from a plastic material, for example a PTFE material. The low-pressure seal 42 rests with a radial inside on a lateral surface of the second section 30 of the pump piston 18 in a sliding fit. During operation of the high-pressure fuel pump 10, it is at least essentially stationary relative to the pump piston 18, and it is held in this stationary position by a seal carrier 44 kept in a descriptive manner.

The seal carrier 44 has at its in in the 1 and 2 the lower end has a first section 46 which extends radially inward and ends at a distance from the pump piston 18. The section 46 is integrally formed on a second section 48 which extends essentially in the axial direction and in 1 extends upward from the first section 46. At its in 1 A third section 50 is integrally formed on the upper end and extends essentially in the radial direction outward. At its radially outer end, a fourth section 52 is formed, which extends essentially in the axial direction in 1 extends downwards. At its lower axial end, a comparatively short fifth section 54 is formed, which extends outward at an angle of approximately 40 ° relative to the longitudinal axis 24.

The inclined fifth section 54 of the seal carrier 44 is firmly connected to the lower end of a collar 58 of the pump housing 12 by means of a circumferential weld line 56 by means of resistance welding. The low-pressure seal 42 is fixed in the axial direction downwards by the first section 46 of the seal carrier 44. The low-pressure seal 42 is fixed in the radial direction by the second section 48 of the seal carrier 44. A narrowing (without reference number) in the inner width of the second section 48 serves to fix the low-pressure seal 42 upwards.

At an in 1 A spring plate 60 is located on the lower end of the pump piston 18 attached. A piston spring 62 is tensioned between this and the third section 50 of the seal carrier 44. The high-pressure fuel pump 10 can, for example, be inserted with the collar 58 into an opening of an engine block of an internal combustion engine and fastened to the engine block by means of a fastening flange (without reference symbols). This in 1 The lower end of the pump piston 18 and the spring plate 60 can interact with a camshaft of the internal combustion engine, by means of which the pump piston 18 is set in a reciprocating motion during operation. The low-pressure seal 42 ensures a fluidic separation between a low-pressure area of the high-pressure fuel pump 10 and a drive area, for example of the internal combustion engine.

The high-pressure fuel pump 10 also includes a sleeve element 64, the design of which in particular also consists of 3 can be seen. The sleeve element 64 is arranged around the pump piston 18 in the region of the shoulder 32 of the pump piston 18. It has a guide section 66 which extends in the direction of the longitudinal axis 24 of the pump piston 18 and is designed in the manner of a sleeve or a tube. The guide section 66 is free from the pump housing 12, that is to say is not held radially by the latter, as would be the case, for example, if the guide section 66 were pressed into the pump housing 12. An inner jacket surface 68 of the guide section 66 delimits a guide opening (without reference number), rests in a sliding fit on the pump piston 18 and serves to guide and center the pump piston 18 in the radial direction. To this extent, it forms a guide surface.

At the upper end of the guide section 66 in the figures, an annular disk-shaped support section 70 in the manner of an annular collar is formed thereon.

This extends radially outward from the guide section 66, that is to say protrudes from the guide section 66. The sleeve element 64 is supported in the radial direction directly on the pump housing 12 via the support section 70. In the present example, the support section 70 is pressed into the opening (without reference number) formed in the interior of the collar 58 for this purpose. In principle, however, other types of fastening are also conceivable. In the transition between the support section 70 and the guide section 66, the inner jacket surface 68 has an insertion bevel 72.

At the end of the guide section 66 opposite the support section 70, the sleeve element 64 has a collar 74 which protrudes radially inward from the guide section 66 and which forms a stop section which can interact with the shoulder 32 of the pump piston 18 in order to move the pump piston 18 in the direction of To limit the drive (ie away from the delivery chamber 16). In this case, there is a distance between the radially inner edge (without reference number) of the collar 74 and the outer surface of the second section 30 of the pump piston 18, through which an annular gap 76 is formed.

In the inner jacket surface 68 of the guide section 66 there are four grooves 78 which are evenly distributed over the circumference and run in the direction of the longitudinal axis 24 and through which a fluid path is formed through the sleeve element 64 in its longitudinal direction. Correspondingly, an annular groove 80 is present in the stop section 74 in its upper end face in the figures, which also belongs to the fluid path.

A method of manufacturing the high pressure fuel pump 10 will now be described with reference to FIG 4th explained. In a function block 82, the pump piston 18 is first inserted into the pump housing 12 or the three ring-shaped elements preassembled there, guide ring 36, high pressure seal 38 and retaining ring 40. Then, in accordance with a function block 84, the sleeve element 64 with the support section 70 first is pushed onto the second section 30 and then onto the first section 28 of the pump piston 18. This is facilitated by the insertion bevel 72 in the transition area between guide section 66 and support section 70.

In a function block 86, the sleeve element 64 is fastened to the pump housing 12 by means of the support section 70 by pressing in. Then, in a function block 88, the preassembled unit consisting of the low-pressure seal 42 and seal carrier 44 is pushed onto the pump piston 18 and onto the sleeve element 64 until the fifth section 54 comes into contact with the edge of the collar 58. Finally, the seal carrier 44 is attached to the edge of the collar 58 of the pump housing 12 by resistance welding (function block 90).

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed 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 (10)

High-pressure fuel pump (10) with a pump housing (12) and a pump piston (18), characterized in that it further comprises a sleeve element (64) which is arranged around the pump piston (18) and which extends in the longitudinal direction (24) of the pump piston (18) extending and protruding from the pump housing (12) guide section (66) for the pump piston (18) and a support section (70) protruding radially outward from the guide section (66), over which the sleeve element (64) extends in a radial direction Direction on the pump housing (12). High pressure fuel pump (10) Claim 1 , characterized in that the pump piston (18) has a first section (28) facing a delivery chamber (16) and having a first diameter and a second section (30) facing a drive and having a second diameter, the first diameter being greater than that second diameter and wherein a shoulder (32) is formed between the first section (28) and the second section (30), and that the sleeve element (64) viewed in the longitudinal direction (24) of the pump piston (18) approximately at the level of the shoulder ( 32) is arranged. High pressure fuel pump (10) Claim 2 , characterized in that the sleeve element (64) has a stop section (74) which can interact with the shoulder (32) in order to limit a movement of the pump piston (18) away from the delivery chamber (16). High pressure fuel pump (10) Claim 3 , characterized in that the stop section (74) has a collar which projects radially inward from the guide section (66) and which is arranged at the end of the guide section (66) opposite the support section (70). High pressure fuel pump (10) Claim 4 , characterized in that there is a distance (76) between the edge of the collar (74) and the lateral surface of the pump piston (18). High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the sleeve element (64) has a fluid path (78) extending overall in its longitudinal direction (24). High pressure fuel pump (10) Claim 6 , characterized in that the fluid path has at least one groove (78) running overall in the longitudinal direction (24) in a guide surface (68) of the sleeve element (64). High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that an axial edge of a guide opening of the sleeve element (64), by means of which the pump piston (18) is guided, has an insertion bevel (72) for the pump piston (18) . High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that it has a seal carrier (44) for a low-pressure seal (42), which is a component separate from the sleeve element (64). Method for producing a high-pressure fuel pump (10) according to Claim 9 , characterized in that it comprises the following steps: a. Inserting the pump piston (18) into the pump housing (12); b. Sliding the sleeve element (64) onto the pump piston (18); c. Fastening the sleeve element (64) to the pump housing (12) by means of the support section (70); d. Sliding the preassembled unit comprising the low-pressure seal (42) and seal carrier (44) onto the pump piston (18); e. Attach the seal carrier (44) to the pump housing (12).

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