EP4010581A1

EP4010581A1 - High-pressure fuel pump

Info

Publication number: EP4010581A1
Application number: EP20745158.4A
Authority: EP
Inventors: Stefan Kolb; Daniel Beckmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-08-09
Filing date: 2020-07-22
Publication date: 2022-06-15
Also published as: DE102019212005A1; KR20220043928A; JP2022543692A; CN114555932A; WO2021028169A1; US20220333568A1

Abstract

The invention relates to a high-pressure fuel pump (28) comprises a pump housing (46), a receiving space (52) in the pump housing (46), a pressure pulsation damper (44) in the form of a diaphragm cell (56) having two diaphragms (58a, 58b), which pressure pulsation damper is arranged in the receiving space (52), and a holding device (62) for holding the diaphragm cell (56) in the receiving space (52). According to the invention, the holding device (62) comprises a connection portion (66), which is connected to the pump housing (46) rigidly both in the axial direction (70) and in the radial direction (72), in particular is fastened, both in the axial direction (70) and in the radial direction (72), to an inner lateral surface (92) that delimits the receiving space (52).

Description

description

title

High pressure fuel pump

State of the art

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

DE 102015219 537 A1 describes a high-pressure fuel pump that is used in a fuel system of an internal combustion engine. With it, the fuel is compressed to a very high pressure in order to then be injected directly into the combustion chambers of the internal combustion engine by means of injectors. The known high-pressure fuel pump is a piston pump, the delivery rate of which can be influenced by a quantity control valve on the inlet side. This results in pressure pulsations in a low-pressure area on the inlet side, which are reduced by a pressure pulsation damper arranged there. This comprises a diaphragm box with, for example, two diaphragms which are essentially arranged approximately parallel to one another and which are welded to one another at the edges. The diaphragm box is clamped between a retaining ring and a spring in a receiving space of a pump housing.

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 of the invention are specified in the subclaims.

The high-pressure fuel pump according to the invention comprises a low-pressure area and a pressure pulsation damper arranged in the low-pressure area. The term “low pressure area” refers to an inlet-side area before the fuel is compressed. The pressure pulsation damper comprises at least one diaphragm box and is in a receiving space is arranged, which is limited, for example, by a housing cover of the high-pressure fuel pump.

The diaphragm can preferably has two membranes, which can be arranged in mirror image to one another, for example, and between which an interior space of the pressure pulsation damper is formed, which is delimited by these membranes. The interior can be filled, for example, with a compressible gaseous fluid (for example air or nitrogen), so that under certain external conditions a certain pressure prevails in the interior.

A holding device is provided for holding the diaphragm can in the receiving space. According to the invention, this comprises a connecting section which is firmly connected to the pump housing both in the axial and in the radial direction, in particular on an inner circumferential surface that delimits the receiving space, in both the axial and the radial direction. In the high-pressure fuel pump according to the invention, the previously existing retaining ring and the previously existing spring are thus dispensed with. Instead, the diaphragm box is fastened to the pump housing both in the axial and in the radial direction via the holding device and its connecting section. In the present case, one can speak of an axial and a radial direction, since the diaphragm box is usually a part that is at least partially and at least essentially rotationally symmetrical.

Due to the invention, the previous components of the retaining ring and spring can be dispensed with, which saves costs and reduces the necessary axial extension (overall height). The spring variance is also eliminated, and the costs are further reduced by the possible omission of further interface components. Since a spring no longer has to be supported, for example, on a housing cover delimiting the receiving space, the relevant specification is omitted, so that the cover can also be of a simpler design and thus less expensive. The same applies to the design of a housing surface on which the retaining ring previously had to be supported.

In a further development, it is proposed that the connecting section be fixed on the inner lateral surface in a press fit and / or with the inner one Shell surface is welded. These are particularly simple, reliable and durable types of connection. In the case of the inner jacket surface of a housing cover, the diaphragm box can be preassembled in a simple manner in the housing cover, which further saves costs.

In a further development, it is proposed that the two membranes are welded to one another in the area of a radially outer edge by means of a weld line extending in the circumferential direction, and that the holding device has at least two clamping sections between which the two membranes are clamped in an area radially inward from the weld line are. This relieves the welding line and improves the fatigue strength of the diaphragm can. The relief is based on the fact that the movements of the membranes are kept away from the weld line or at least reduced, so that the bending stress on the welded connection is reduced.

In a further development, it is proposed that at least one of the clamping sections is designed in one piece with the connecting section. This reduces the number of parts to be handled, which simplifies assembly and ultimately saves costs again.

In a further development, it is proposed that the clamping sections are welded to one another. In this way, a very stable unit is created.

In a further development it is proposed that the clamping sections are clipped together. This can be implemented inexpensively.

In a further development, it is proposed that the connecting section is integrally formed on the diaphragm box. In this way, a particularly stable and easy-to-assemble unit is created.

In a further development, it is proposed that the two membranes are welded to one another in the area of an edge of at least one of the two membranes by means of a weld line extending in the circumferential direction, with an area being present between the weld line and an interior space formed between the two membranes in which the both membranes rest against one another at least in sections with frictional engagement. The discharge The welding line with regard to the movements of the membranes is not achieved here by a radially inward clamping, but by a "radially" inward frictional connection between the two membranes from the welding line. In this way, the relative movements of the two membranes are at least substantially kept away from the welding line during operation.

In a further development, it is proposed that a fold be present between the weld line and the interior space formed between the two membranes. Such a “bend” is understood to mean that the two membranes are bent, that is to say that a type of common collar-like section extending in the axial direction is formed. The fold is preferably approximately 90 ° and takes place with a radius, the radius of the inner membrane in the area of the fold being smaller than the radius of the outer membrane in the area of the fold. Such a fold also reduces the bending loads acting on the welding line during operation.

In a further development, it is proposed that, in the area of the fold, a radially inner section of one membrane is received in a press fit in a radially outer section of the other membrane. An additional cylindrical interference fit is thus created between the two membranes, by means of which a strong frictional connection is achieved between the two membranes, which reliably keeps the relative movements of the two membranes away from the weld line.

An embodiment of the invention is explained below with reference to the drawing. In the drawing show:

FIG. 1 shows a schematic representation of a fuel system of an internal combustion engine with a high-pressure fuel pump;

FIG. 2 shows a partial longitudinal section through a region of the high-pressure fuel pump from FIG. 1 in a first embodiment;

FIG. 3 shows a detail III from FIG. 2; FIG. 4 shows a representation similar to FIG. 3 for a high-pressure fuel pump in a second embodiment;

FIG. 5 shows a region of the high-pressure fuel pump from FIG. 4 in a modified embodiment; and

FIG. 6 shows a representation similar to FIG. 5 for a further modified embodiment.

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

In FIG. 1, a fuel system bears the overall reference number 10. It is used to provide fuel for an internal combustion engine, not shown further, in a very simplified schematic representation.

From a fuel tank 12, fuel is fed via a suction line 14, a mostly electric pre-feed pump 16, a low-pressure line 18 to an inlet 20 of a quantity control valve 24, which can be actuated by an electromagnetic actuator 22, to a working chamber 26 of a high-pressure fuel pump 28, for example with one provided by the pre-feed pump 16 Pre-pressure of 4-8 bar, especially about 6 bar. For example, the quantity control valve 24 can be a positively openable inlet valve of the high-pressure fuel pump 28.

A piston 30 of the high-pressure fuel pump 28 can be moved vertically by means of a cam disk 32 in the drawing. An outlet valve 36, shown as a spring-loaded check valve, and a pressure-limiting valve 38, also shown as a spring-loaded check valve, are arranged hydraulically between the working chamber 26 and an outlet 34 of the high-pressure fuel pump 28. The outlet 34 is connected to a high pressure accumulator 42 (“common rail”) via a high pressure line 40.

When the fuel system 10 is in operation, 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 as a function of a particular fuel requirement. As a result, the amount conveyed to the high-pressure accumulator 42 is conveyed Fuel amount influenced. Due to the discontinuous mode of operation of the high-pressure fuel pump 28, so-called pressure pulsations occur in several sections of the fuel system 10, in particular also upstream of the working chamber 26, that is to say in a low-pressure region 43 of the high-pressure fuel pump 28 or of the fuel system 10. In order to dampen these, a pressure pulsation damper 44 is arranged there.

As can be seen from FIG. 2, the high-pressure fuel pump 28 comprises a pump housing 46 which is essentially cylindrical or rotationally symmetrical in shape. In the upper area of the pump housing 46 in FIG. 2, it has an end face 48 on which a hood-like housing cover 50 is placed, which is connected to the pump housing 46 in a fluid-tight manner, for example welded. A fluid space 52 is formed between the end face 48 and the housing cover 50 and is connected to the low-pressure region 43 via a channel 54. The above-mentioned pressure pulsation damper 44, which in the present case comprises a diaphragm box 56, is arranged in the fluid space 52. In this respect, the fluid space 52 can also be referred to as a receiving space.

The diaphragm box 56 in turn comprises in the present case two diaphragms 58a and 58b which are essentially identical to one another in a central area and are arranged in mirror image, which have an essentially circular contour in plan view and are designed to be rotationally symmetrical. As can be seen from FIG. 3, the two membranes 58a and 58b are welded to one another in a fluid-tight manner at their radially outer edge by a weld line 60. The diaphragm box 56 is held in the fluid space 52 by a holding device 62. The holding device 62 will be discussed in greater detail below. An interior space 64 is formed between the two membranes 58a and 58b. This is therefore limited by the two membranes 58a and 58b. This interior space 64 is filled with a gas, for example nitrogen or air, specifically at a specific pressure.

The holding device 62 comprises a connecting section 66, which in the present case is integrally formed on the upper membrane 58a and thus on the membrane box 56. For this purpose, the upper diaphragm 58a is designed as follows (see also FIG. 3): a working area of the diaphragm 58a is formed by a central area 68 already mentioned above, in which there are bead-like formations (without reference numerals) that run around the circumference Allow movement of diaphragm 58a in an axial direction 70. Since the membranes 58a and 58b, as mentioned above, have an essentially circular contour and are designed to be rotationally symmetrical, said axial direction 70 can be defined. To this end, a corresponding radial direction 72 results orthogonally. The above-mentioned function of damping pressure pulsations is achieved by the aforementioned movement of the central area 68 of the diaphragm 58a and the corresponding central area (without reference symbols) of the diaphragm 58b.

Radially outside of the central region 68, the membrane 58a has a flat first section 74 extending radially outward in the circumferential direction. A bend 76 is provided on its radially outer edge, by means of which the membrane 58a is bent downward by 90 ° in the present example. The bend 76 has a radius R. From the bend 76 extends downward in the axial direction in the circumferential direction, a second section 78 in the manner of a cylindrical collar. A third section 80 running around in the circumferential direction is integrally formed thereon, specifically at an angle of, for example, approximately 45 ° to the outside obliquely. In the third section 80 there is a plurality of openings 82, evenly distributed in the circumferential direction, through which fuel can flow during operation. On the third section 80 a fourth section 84 is formed, for example in the circumferential direction, which extends straight in the axial direction 70 and downwards in FIG. 3 and is in this respect also designed in the manner of a cylindrical collar.

The diaphragm 58b has, radially outside of its central region 68, a flat first section 86 which likewise extends radially outward and runs in the circumferential direction. At its radially outer edge there is a bend 88 by means of which the membrane 58b is bent downward by 90 ° in the present example. The fold 88 has a radius r. A second section 90 extending in the circumferential direction in the manner of a cylindrical collar extends axially downward from the fold 88. In this way, the second section 90 of the diaphragm 58b forms a radially inner section and the second section 78 of the diaphragm 58a forms a radially outer section. However, the second section 90 of the membrane 58b extends less far in the axial direction 70 than the second section 78 of the membrane 58a. At the protruding free edge of the second section 90 of the membrane 58b, the latter is welded to the second section 78 of the membrane 58a by the welding line 60 already mentioned above. The second and radially inner section 90 of the diaphragm 58b is received in a press fit in the second and radially outer section 78 of the diaphragm 58a. In addition, the fold 76 and the fold 88 as well as the first section 74 and the first section 86 are joined together in such a way that they rest against one another in a frictionally engaged manner. In this way it is achieved that the movement of the central regions 68 of the two membranes 58a and 58b is at least substantially kept away from the weld line 60.

The fourth section 84 of the membrane 58a is fixed on an inner lateral surface 92 of the housing cover 50 in a press fit. In an embodiment not shown, it is additionally or alternatively welded to the inner jacket surface. In this way, the connecting section 66 of the holding device 62, formed in the present case in particular by the bend 76, the second section 78, the third section 80 and the fourth section 84, is connected to the housing cover 50 and to that extent to the pump housing 46 both in the axial direction 70 and also firmly connected in the radial direction 72. The diaphragm can 56 is thus held immovably and cannot be lost in the housing cover 50.

An alternative embodiment of a holding device 62 will now be explained with reference to FIG. 4: in this embodiment, the two membranes 58a and 58b are identical to one another, and the weld line 60 is on the protruding edge of the first section 74 of the membrane 58a and of the second section 86 of the Membrane 58b is present. The holding device 62 has two resilient clamping sections 94 and 96 which are prestressed towards one another, between which the first section 74 of the membrane 58a and the first section 86 of the membrane 58b are clamped. The two diaphragms 58a and 58b are clamped in a region radially inward from the weld line 60. The upper clamping section 94 in FIG. 4 is formed on the upper edge of the second section 78 of the holding device 62 in FIG. 4 and is thus one-piece with the connecting section 66 formed primarily by the second section 78, the third section 80 and the fourth section 84 educated. The lower clamping section 96 in FIG. 4 is fastened to the second section 78 in a manner not shown in detail in FIG. The fastening of the lower clamping section 96 to the second section 78 can, as can be seen from FIG. 5, be achieved via a snap-in clip connection. For this purpose, openings 98 are provided in the second section 78, into which resilient latching lugs 100 of the lower clamping section 96 can engage.

Alternatively, as can be seen from FIG. 6, the lower clamping section 96 can also simply be welded to the second section 78 (weld line 102). In both cases it must be ensured that the two clamping sections 94 and 96 are axially pretensioned relative to one another, so that a sufficiently strong clamping force is exerted on the first sections 74 and 86 of the membranes 58a and 58b.

Claims

Expectations

1. High-pressure fuel pump (28) with a pump housing (46), a receiving space (52) present in the pump housing (46), a pressure pulsation damper (44) arranged in the receiving space (52) in the form of a diaphragm box (56) with two diaphragms (58a, 58b), and a holding device (62) for holding the diaphragm box (56) in the receiving space (52), characterized in that the holding device (62) comprises a connecting section (66) which both with the pump housing (46) is firmly connected in the axial direction (70) and in the radial direction (72), in particular on an inner jacket surface (92) which delimits the receiving space (52), both in the axial direction (70) and in the radial direction (72) is attached.

2. High-pressure fuel pump (28) according to claim 1, characterized in that the connecting section (66) is fixed on the inner lateral surface (92) in a press fit and / or is welded to the inner lateral surface (92).

3. High-pressure fuel pump (28) according to at least one of the preceding claims, characterized in that the two membranes (58a, 58b) are welded to one another in the region of a radially outer edge by means of a weld line (60) extending in the circumferential direction, and that the Holding device (62) has at least two clamping sections (9496), between which the two membranes (58a, 58b) are clamped in an area radially inward from the weld line (60).

4. High-pressure fuel pump (28) according to claim 3, characterized in that at least one of the clamping sections (94, 96) is formed in one piece with the connecting section (66).

5. High pressure fuel pump (28) according to at least one of claims 3 or 4, characterized in that the clamping sections (94, 96) are welded to one another (102).

6. High-pressure fuel pump (28) according to at least one of claims 3-5, characterized in that the clamping sections (94, 96) are clipped together (98, 100).

7. High-pressure fuel pump (28) according to at least one of claims 1-2, characterized in that the connecting portion (66) is integrally formed on the diaphragm box (56).

8. High-pressure fuel pump (28) according to at least one of the preceding claims, characterized in that the two membranes (58a, 58b) in the region of an edge of at least one of the two membranes (58a, 58b) by means of a weld line (60) extending in the circumferential direction ) are welded to one another, with an area between the weld line (60) and an interior space (64) formed between the two membranes (58a, 58b) in which the two membranes (58a, 58b) abut against one another at least in sections with frictional engagement.

9. High-pressure fuel pump (28) according to claim 8, characterized in that a fold (76, 88) is present between the weld line and the interior space formed between the two membranes (58a, 58b).

10. High-pressure fuel pump (28) according to claim 9, characterized in that in the region of the fold (76, 88) a radially inner section (90) of one membrane (58b) in a radially outer section (78) of the other membrane ( 58a) is received in a press fit.