DE102021209837A1 - Cyclically operating pump, in particular high-pressure fuel piston pump - Google Patents

Abstract

A cyclically operating pump comprises a pump housing (12) and an outlet connection (32) which is welded on by means of a circumferential welding area (30) and which has a first hydraulically effective surface (40) in its interior immediately adjacent to the welding area (30) with a first hydraulic force resultant , which acts in a first direction (73). It is proposed that the outlet socket (32) has a second hydraulically effective surface (52) in its interior with a second hydraulic force resultant which acts in a second direction (75) which is at least essentially opposite to the first direction (73). and is coaxial.

Description

State of the art

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

For example from the DE 10 2019 217 207 A1 a cyclically operating pump in the form of a high-pressure fuel piston pump for a fuel system of an internal combustion engine is known. Such a high-pressure fuel piston pump compresses the fuel to a high pressure and forwards it to a fuel collection line (“rail”), from where the fuel is injected directly into the combustion chambers of the internal combustion engine. A pump piston is guided in the pump housing, and the pump piston is acted upon by a piston spring in the direction of a drive. During each delivery stroke, the pump piston delivers fuel via an outlet valve to an outlet connection, which is welded to the pump housing. In this respect, the pump works "cyclically".

Disclosure of Invention

The problem on which the present invention is based is solved by a cyclically operating pump, for example a piston pump, in particular a high-pressure fuel piston pump. Advantageous developments are specified in the dependent claims.

The high-pressure fuel pump according to the invention has the advantage that the strength and thus the service life of the pump is improved even at very high pressure peaks in the outlet connection without, for example, the welded connection between the outlet connection and the pump housing having to be reinforced by an additional screw connection. Thus, such a pump can be manufactured on existing production facilities. Such a pump is also smaller and more compact than a pump with an additional screw connection. The individual components are also comparatively inexpensive. Since the connection between the outlet socket and the pump housing is still exclusively non-detachable (namely welded), no additional effort is required to secure it against detachment. Finally, the connection between the outlet nozzle and the pump housing remains completely fluid-tight and diffusion-tight, so that no additional fluid-tightness measures are required.

Specifically, this is achieved by a cyclically operating pump, in particular a high-pressure fuel piston pump. Such a pump comprises a pump housing and an outlet connection welded to the pump housing by means of a circumferential weld area. The pump housing can be essentially rotationally symmetrical, for example polygonal, and the outlet connection can be arranged on a radial outside of the pump housing. The outlet connector, in turn, can be designed as a tubular element and have an inclined contact surface toward the pump housing. For connection to the pump housing, this is pressed against an annular edge of an outlet opening in the pump housing.

The contact pressure with which the outlet connector is pressed against the pump housing while the connection is being made can be very high. The connection is preferably made by resistance welding, in particular by capacitor discharge welding (KE welding). In this way, the annular edge of the pump housing is fused to the sloping contact surface in a weld area. In order to prevent the outlet connector from deforming in the radial direction during the connection process due to the high contact pressure, the outlet connector has a stiffening area acting in the radial direction immediately adjacent to the welding area, on which there is a first hydraulically effective surface. This has a first resultant hydraulic force acting in a first direction. The first direction typically points away from the pump housing.

When the outlet connection is connected to the pump housing, a circumferential, groove-like indentation ("inner notch") is formed on the radially inner edge of the welding area. Due to the cyclic operation of the pump according to the invention, the first resultant hydraulic force has a pulsating strength, through which—without countermeasures—the welding area in the area of the inner notch would be subject to a pulsating load. According to the invention, however, the outlet socket has a second hydraulically effective surface in its interior. This has a second hydraulic force resultant acting in a second direction at least substantially opposite and coaxial with the first direction of the first force resultant. In this way, the aforementioned pulsating load acting on the inner notch is largely eliminated, which leads to the initially mentioned improvement in the fatigue strength of the welded connection, even at high pressure peaks.

In a further development it is provided that the two resultant forces act parallel to a longitudinal axis of the outlet connector and are at least approximately at the same height in the radial direction. Thus, the two run hydraulically effective surfaces at least substantially orthogonal to a longitudinal axis of the outlet, which has manufacturing advantages.

In a further development it is provided that the two hydraulically effective surfaces are at least approximately the same size. Accordingly, the two resultant forces are approximately the same in terms of magnitude, so that the load acting on the inner notch is eliminated particularly well.

In a further development it is provided that the second hydraulically effective surface is provided at least also by an undercut in an inner peripheral wall of the outlet connector. This is easy to implement in terms of manufacturing technology, since the outlet connection is usually machined anyway.

A further development of this is characterized in that the undercut is produced by a puncture. Corresponding turning tools are inexpensive.

In a further development it is provided that the second hydraulically effective surface is provided at least also by a support element arranged inside the outlet connector. Such a support element can provide a stiffening area acting in the radial direction, in which very high radial forces can also be absorbed and thus a radial deformation of the outlet connection piece when the welded connection is produced is reliably prevented.

In a further development of this, it is provided that the support element is ring-shaped. Such a support element is easy to produce and offers uniform radial stiffening with, at the same time, a sufficiently free passage inside the outlet connector for the fluid delivered by the pump.

In a further development it is provided that the support element is pressed into a socket body. This has manufacturing advantages and is inexpensive.

In a further development it is provided that the support element is made of high-strength steel. In this way, the supporting effect according to the invention can be realized with little material and thus with little installation space, as a result of which more dead volume is provided, which helps to dampen pressure pulsations, and as a result more space is provided for internal components.

In a further development it is provided that the support element has projections distributed over its circumference and protruding in the axial direction. Such projections can additionally support an emerging torque.

Where, in the context of this invention, the range of features relating to geometric relationships is defined by explanations such as “essentially coaxial”, “essentially perpendicular”, “about the same size”, etc., the feature may include the geometric relationship as such concern, i.e. in the examples "caxial", "perpendicular", "equal size" etc.

However, areas can also be included or defined as they usually arise in practice due to industrial manufacturability, for example with regard to angles 1° or with regard to areas 1%.

In addition, however, areas can also be included or defined within which the advantageous effects of the invention and its developments result, for example with regard to angles 10° or with regard to surfaces 10%.

• 1 einen teilweisen Längsschnitt durch eine Kraftstoff-Hochdruckpumpe mit einem Pumpengehäuse und einer ersten Ausführungsform eines Auslassstutzens mit einem durch einen Einstich gebildeten Hinterschnitt;
• 2 einen detaillierten Schnitt durch den Auslassstutzen von 1;
• 3 eine vergrößerte Darstellung eines Schweißbereichs zwischen Auslassstutzen und Pumpengehäuse von 1;
• 4 eine Darstellung ähnlich zu 3 einer alternativen Ausführungsform eines Auslassstutzens mit einem ringförmigen Stützelement;
• 5 eine geschnittene perspektivische Darstellung der Ausführungsform von 4 und eines Bereichs des Pumpengehäuses in einem Zustand unmittelbar vor der Verschweißung; und
• 6 eine Draufsicht und einen Schnitt durch ein alternatives ringförmiges Stützelement.

The invention is explained below with reference to the attached drawing. In this show:

• 1 a partial longitudinal section through a high-pressure fuel pump with a pump housing and a first embodiment of an outlet with an undercut formed by a recess;
• 2 a detailed section through the outlet nozzle of 1 ;
• 3 an enlarged view of a welding area between the outlet nozzle and the pump housing 1 ;
• 4 a representation similar to 3 an alternative embodiment of an outlet nozzle with an annular support element;
• 5 a sectional perspective view of the embodiment of FIG 4 and a portion of the pump casing in a state just before welding; and
• 6 a plan view and a section through an alternative annular support member.

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

In the figures, a cyclically operating pump in the form of a high-pressure fuel piston pump for a fuel system of an internal combustion engine The machine has the overall reference number 10. It comprises a pump housing 12, which in the present example has an approximately polygonal shape with a longitudinal axis 14. in which a pump piston 18 is accommodated. This limits with its in 1 upper end together with the pump housing 12 a pumping chamber 20. With its in 1 In the lower end region, the pump piston 18 cooperates with a drive (not shown), for example a camshaft or an eccentric shaft, which can set the pump piston 18 in a reciprocating motion.

The pump 10 also includes an inlet valve 22 which is designed as a non-return valve, but which can be held in an open position by an electromagnetic actuating device 24 . The high-pressure fuel pump 10 also includes an outlet valve 26 embodied as a non-return valve and a pressure-limiting valve 28 . The outlet port 32 will be discussed in greater detail further below. In 1 a membrane damper 34 for damping low-pressure pulsations is also present in the area of an upper end face (without reference number) of the pump housing 12 .

As mentioned above, the pump piston 18 reciprocates parallel to its longitudinal axis 14 during operation of the pump 10 . If the pump piston moves 18 in 1 down (intake stroke), fuel is sucked into the pumping chamber 20 via the inlet valve 22 . If the pump piston moves 18 in 1 upwards (delivery stroke), the fuel in the delivery chamber 20 is first compressed to a high pressure until the outlet valve 26 opens and the fuel is ejected via the outlet connection 32 to a fuel collection line (“rail”). From there, the fuel reaches the associated combustion chambers via injectors.

Now the outlet port 32 of 1 referring in particular to 2 explained in more detail: the outlet connector 32 has a longitudinal axis 36 which is orthogonal to the longitudinal axis 14 of the pump housing 12 and to which it is rotationally symmetrical. On an installed condition ( 1 ) The end 37 facing away from the pump housing 12 has an external thread 38 to which a high-pressure line (not shown) can be screwed, which connects the outlet socket 32 to the above-mentioned fuel collection line.

On one in the installed condition of 1 The end 39 pointing toward the pump housing 12 has an end face 40 that runs orthogonally to the longitudinal axis 36 and is arranged radially on the inside. This is adjoined radially outward by a sloping contact surface 42 running in the circumferential direction, for example running at an angle of 45°, which in turn is adjoined by an outer lateral surface 44 extending coaxially to the longitudinal axis 36 . From this, a circumferential radial constriction 46 finally leads to the external thread 38.

Inside the outlet connector 32, a first inner lateral surface 48 coaxial with the longitudinal axis 36 extends from the end face 40 in the direction of the end 37. This opens into an undercut 50 in the form of an inner groove running around in the circumferential direction. In the present example, the undercut 50 is produced by turning in the form of a recess. The cross-sectional shape of the undercut is of particular interest in the present case: a lateral surface 52, which runs orthogonally to the longitudinal axis 36 and extends radially outwards, first extends from the first inner lateral surface 48. This flows into a base surface 54, which is evenly curved in the direction of the end 39 and extends approximately over extends an angle of 135° in the present example. The base surface 54 in turn opens into a side surface 56 running at an angle of 45° to the longitudinal axis 36, for example. From this, an inner end surface 58 running orthogonally to the longitudinal axis 36 branches off radially inwards, from which finally a side surface extends coaxially to the longitudinal axis 36 in the direction towards the end 39 extending outlet channel 60 branches off.

A support section 62 is formed by the material region formed between the end face 40 and the side face 52 . To connect the outlet connector 32 to the pump housing 12, the outlet connector 32 is acted upon in the direction of its longitudinal axis 36 with high force towards the pump housing 12, where it is pressed with its inclined contact surface 42 against an edge of an outlet opening 64 ( 1 and 3 ) is present. The connection is ultimately made by resistance welding, in the present example by capacitor discharge welding. In this way, the initially present annular edge of the outlet opening 64 of the pump housing 12 is fused with the inclined contact surface 42, as a result of which the weld region 30 is formed. Notches are formed on the radially inner and radially outer edges of the welding area 30, namely a circumferential inner notch 66 and a Circumferential outer notch 68 ( 3 ). During the connection process, the support section 62 stabilizes the end 39 of the outlet connector 32 pointing toward the pump housing 12 radially inwards, as a result of which an impermissible deformation is prevented there. To this extent, the support section 62 forms a stiffening area acting radially inward.

During operation of the pump 10, the cyclic ejection of the fuel leads to cyclically recurring pressure peaks in the fuel pressure inside the outlet connection 32. The hydraulic pressure acts both on the end face 40 (arrows 70 in 3 ) as well as on the side surface 52 (arrows 72 in 3 ). In this respect, the end face 40 forms a first hydraulically effective surface with a first hydraulic force resultant, which acts in a first direction 73, namely the direction of the arrows 70, i.e. in a direction parallel to the longitudinal axis of the outlet connector 36 to the end 37 facing away from the pump housing 12 of the outlet port 32 out.

The side surface 52 forms a second hydraulically effective surface with a second hydraulic force resultant that acts in a second direction 75, namely the direction of the arrows 72, i.e. again in a direction parallel to the longitudinal axis of the outlet connector 36, but to the end pointing to the pump housing 12 39 of the outlet port 32 out. Since the end face 40 and the side face 52 are at least approximately the same size, the corresponding hydraulic forces acting on the end face 40 and the side face 52 are also approximately the same in magnitude.

It can be seen that the two resultant forces are thus opposite and coaxial to one another. This prevents the hydraulic pressure cyclically acting on the end face 40 from leading to a cyclic bending stress in the area of the inner notch 66 and thereby impairing the strength of the welded area 30 . Instead, the hydraulic force acting on the end face 40 is at least largely eliminated by the hydraulic force acting in the opposite direction on the side face 52 with regard to the loading of the support section 62 .

An alternative embodiment show the 4 and 5 . In this case, the outlet connector 32 is produced essentially without the end face that bears the reference number 40 above. Instead, the sloping contact surface 42 merges directly into the first inner lateral surface 48 , which in turn merges directly into the inner end face 58 via a sloping intermediate surface 74 . In this embodiment, the support section 62 is formed by a support element 76 in the form of an inner ring made of high-strength steel, which is pressed into a connector body 78 of the outlet connector 32 . 5 shows the outlet nozzle 32 immediately before the start of the welding process. At this point in time, the edge at the edge of the outlet opening 64 is still relatively pronounced. In 5 Also shown is an electrode 80 used to make the weld.

In the embodiment of 4 and 5 the front surface 40 and the side surface 52 are flat. In yet another embodiment according to FIG 6 For example, the inner ring 76 on the end face 40 can have a plurality of projections 82 in the form of nubs, which are arranged evenly distributed over the circumference and, in the installed position, point towards the end 39 of the outlet connector 32 pointing toward the pump housing 12 . In the present example, the in 6 drawn inner ring 76 three such projections 80.

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 102019217207 A1 [0002]

Claims (10)

Cyclically operating pump (10), in particular a high-pressure fuel piston pump, with a pump housing (12) and an outlet connection (32) which is welded to the pump housing (12) by means of a circumferential welding area (30) and which in its interior is directly adjacent to the welding area (30) has a first hydraulically effective surface (40) with a first hydraulic force resulting in a first direction (73), characterized in that the outlet connector (32) has a second hydraulically effective surface (52) in its interior with a second hydraulic Force resultant acting in a second direction (75) at least substantially opposite and coaxial with the first direction (73). Cyclic pump (10) after claim 1 , characterized in that the two resultant forces act parallel to a longitudinal axis (36) of the outlet connector and are at least approximately at the same height in the radial direction. Cyclically operating pump (10) according to at least one of the preceding claims, characterized in that the two hydraulically active surfaces (40, 52) are at least approximately the same size. Cyclic pump (10) according to at least one of the preceding claims, characterized in that the second hydraulically effective surface (52) is provided at least also by an undercut (50) in an inner peripheral wall of the outlet socket (32). Cyclic pump (10) after claim 4 , characterized in that the undercut (50) is produced by a puncture. Cyclically operating pump (10) according to at least one of the preceding claims, characterized in that the second hydraulically effective surface (52) is provided at least also by a support element (76) arranged inside the outlet connector (32). Cyclic pump (10) after claim 6 , characterized in that the support element (76) is annular. Cyclic pump (10) according to at least one of Claims 6 - 7 , characterized in that the support element (76) is pressed into a socket body (78). Cyclic pump (10) according to at least one of Claims 6 - 8th , characterized in that the support element (76) is made of a high-strength steel. Cyclic pump (10) according to at least one of Claims 6 - 9 , characterized in that the supporting element (76) has projections (82) distributed over its circumference and projecting in the axial direction.

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