EP2273115B1 - Fluid pump, particularly high-pressure fuel pump, having pressure damper - Google Patents

Description

State of the art

The invention relates to a fluid pump, in particular a high-pressure fuel pump, having a housing and having at least one inlet-side low-pressure connection, an inlet valve, and a delivery chamber, which is delimited by a delivery element.

A fluid pump of the type mentioned is from the DE 195 39 885 A1 known and used for example in internal combustion engines with direct fuel injection. In such internal combustion engines, the fuel from the fluid pump is compressed to a high pressure and conveyed into a fuel rail. From this, the fuel passes under high pressure via fuel injectors directly into the combustion chambers of the internal combustion engine. The fluid pump sucks the fuel via a low pressure port and an inlet valve into a delivery chamber. This is limited by the delivery piston. To compensate for pressure fluctuations in a fuel line, which is connected to the low pressure port, a pressure damper is arranged there. This includes a spring loaded piston defining a damping chamber connected to the fuel line via a bag port.

The EP 1 342 911 A2 shows a fuel pump with a pump housing, a reciprocating pump piston, a low pressure port, a high pressure port and a compression chamber. In the pump housing, a pressure damper is provided between the low pressure port and the compression space. The subject of claim 1 is delimited in two-part form against this document.

Object of the present invention is to provide a fluid pump of the type mentioned in such a way that on the one hand compact builds and that on the other hand, the upstream of the low-pressure connection arranged components, such as a low-pressure fuel line, are as little as possible.

This object is achieved in a fluid pump of the type mentioned above in that it comprises a pressure damper which damps inlet-side pressure fluctuations and which comprises at least one compressible volume, which is arranged directly in the flow path between low-pressure port and inlet valve.

Advantages of the invention

Characterized in that the pressure damper has a damper housing with two axial end faces, wherein the damper housing is clamped between the housing body of the fluid pump and the housing cover, the installation is particularly simple and the reliability is significantly improved. Clamping the damper housing effectively prevents material fatigue in the damper and damper housing of the damper.

The arrangement of the compressible volume directly in the flow path between low pressure port and inlet valve has the advantage that Pump internal coupling vibrations are prevented, which then load the low pressure port and a low pressure line connected to this. The reason for this is that the usual pressure fluctuations on the inlet valve itself arise when it is forcibly opened, for example, to control the flow rate of the fluid pump during a delivery stroke of the delivery piston. The inventive arrangement of the compressible volume, the pressure fluctuations are attenuated immediately at the place of their emergence. Thus, cheaper components can be used for the low pressure port and the low pressure line, which reduces their cost. In addition, otherwise required holes in the pump housing can be omitted. The use of a compressible volume instead of the usual spring-loaded piston also has the advantage that it is easy to build and therefore the fluid pump is overall comparatively inexpensive.

Advantageous developments of the invention are specified in subclaims.

In a first development, it is proposed that the compressible volume is a gas volume which is delimited by at least one membrane. The compressibility of gas allows a very simple construction of the corresponding pressure damper, which reduces the manufacturing cost of the fluid pump. In addition, such a gas volume can be formed almost arbitrarily, so that it can be easily integrated into the area between the inlet valve and the low-pressure port of the fluid pump. In principle, it is also conceivable to form the gas volume by a plurality of individual small gas-filled capsules.

It is particularly advantageous if the compressible volume is received in an extension of the flow path, which by a Housing cover is covered. This facilitates the assembly of the fluid pump. The housing cover can be deep-drawn, for example, and screwed or welded to a corresponding counterpart of the pump housing.

The radial dimensions of the fluid pump are reduced when the housing cover is arranged on an axial end face of the pump housing.

A further reduction of the radial dimensions of the fluid pump is achieved in that the low-pressure connection is arranged on the housing cover. Usually, a connection piece is used for the low pressure connection, which is welded to the housing cover or screwed to it. The nozzle can be straight or angular, so that the same fluid pump can be easily adapted to different installation situations. In principle, any exit direction is possible.

A particularly advantageous embodiment of the fluid pump according to the invention provides that the pressure damper has a substantially rotationally symmetrical damper housing with two axial end faces, towards which, starting from an axial center plane, in the region of which it has its maximum diameter, it tapers, that in each End face has at least one opening, and / or that in the housing walls between the two end faces and the center plane in each case at least one opening is present. Such a damper housing thus has approximately discus-like shape. In it, the compressible volume can be easily absorbed and thereby have such large boundary surfaces that an effective damping of pressure pulsations is possible. At the same time it builds in the axial direction short, what the dimensions of the Fluid pump benefits. On the one hand, it is ensured through the openings in the wall of the damper housing that the fluid can pass from the low-pressure connection to the inlet valve without being throttled, and, on the other hand, that the fluid flows directly around the compressible volume. The so designed pressure damper is therefore particularly effective.

The installation of the pressure damper is simplified when the damper housing is jammed with its two end faces between a pump body and the housing cover. It is understood that to achieve reproducible balance of power damper housing should at least partially (for example, at least one housing half in a two-part housing) and in the clamping direction should have a certain spring elasticity.

In the same direction aims that repeated development of the fluid pump according to the invention, in which the damper housing distributed over the circumference arranged and a total radially projecting centering sections which radially center the damper housing relative to the extension of the flow path. In this way, the pressure damper can be used in the extension of the flow path and is then, after installation of the housing cover, automatically set in the installed position. This facilitates the assembly of the fluid pump.

In a further development, it is proposed that at least some of the centering sections each have an end section extending approximately axially and somewhat beyond the median plane of the damper housing, on which the compressible volume is radially centered relative to the damper housing. In this case, the centering sections are assigned a double function: they do not serve only the Centering of the damper housing relative to the extension of the flow path, but also for the radial centering of the compressible volume, which is accommodated in the damper housing. As a result, the assembly of the pressure damper itself is simplified.

It is also possible that a radially outer edge of the compressible volume at least partially rests against the wall of the extension of the flow path and is thus centered with respect to this. For this purpose, the wall of the extension of the flow path, for example, distributed over the circumference arranged impressions.

In a similar direction aims that development of the fluid pump according to the invention, in which the damper housing comprises two housing halves and the compressible volume is clamped between the two housing halves. Again, this allows for easy assembly of the compressible volume within the damper housing without the need for additional fixtures. It is understood that the compressible volume is preferably clamped at its edge. Otherwise, the damper housing itself should at least partially (in a two-part housing, for example, a housing half) and in the axial direction have resilient properties, so as not to hinder the change in volume of the compressible volume.

A further advantageous embodiment of the fluid pump according to the invention is characterized in that the housing cover has a protuberance on which the low pressure port is arranged. By such a protuberance, the connection of a connecting piece of the low-pressure connection is facilitated. Likewise, a direct connection of the low pressure line is conceivable.

drawing

Figur 1

eine schematische Darstellung eines Kraftstoffsystems mit einer Fluidpumpe mit einem integrierten Druckdämpfer;

Figur 2

einen Teilschnitt durch die Fluidpumpe von Figur 1;

Figur 3

einen Schnitt durch einen Bereich einer alternativen Ausführungsform einer Fluidpumpe;

Figur 4

einen Schnitt durch einen Bereich einer etwas abgewandelten Ausführungsform der Fluidpumpe von Figur 3;

Figur 5

einen Schnitt durch einen Bereich einer nochmals alternativen Ausführungsform einer Fluidpumpe; und

Figur 6

einen Schnitt durch einen Bereich einer nochmals alternativen Ausführungsform einer Fluidpumpe.

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

FIG. 1

a schematic representation of a fuel system with a fluid pump with an integrated pressure damper;

FIG. 2

a partial section through the fluid pump of FIG. 1 ;

FIG. 3

a section through a portion of an alternative embodiment of a fluid pump;

FIG. 4

a section through an area of a slightly modified embodiment of the fluid pump of FIG. 3 ;

FIG. 5

a section through a portion of yet another alternative embodiment of a fluid pump; and

FIG. 6

a section through a portion of yet another alternative embodiment of a fluid pump.

Description of the embodiments

In FIG. 1 a fuel system carries the overall reference numeral 10. It comprises a fuel tank 12, from which a prefeed pump 14 conveys the fuel into a low-pressure line 16. This leads to a Low pressure port 18 of a high-pressure piston pump designed as a fluid pump 20, the FIG. 1 is indicated by a dashed line.

A high pressure port 22 of the high pressure piston pump 20 is connected to a fuel rail 24. This is also called "Rail". In it, the compressed by the high-pressure piston pump 20 fuel is stored under high pressure. To the fuel manifold 24 a plurality of fuel injectors 26 are connected, which inject the fuel directly into each associated combustion chamber 28. The fuel system 10 thus belongs to an internal combustion engine with direct fuel injection.

• Hierzu gehört ein Förderkolben 30, der beispielsweise von einer nicht gezeigten Antriebswelle in eine Hin- und Herbewegung versetzt werden kann. Er begrenzt einen Förderraum 32. Dieser ist mit einer Einlassventileinrichtung 34 und einem als federbelastetes Rückschlagventil ausgebildeten Auslassventil 36 fluidisch verbunden. Durch ein Druckregelventil 38 kann der Druck stromabwärts vom Auslassventil 36 eingestellt werden.

This in FIG. 1 shown hydraulic circuit diagram of the high-pressure piston pump 20 shows some of its essential components:

• This includes a delivery piston 30, which can be offset, for example, by a drive shaft, not shown in a reciprocating motion. It defines a delivery chamber 32. It is fluidically connected to an inlet valve device 34 and an outlet valve 36 designed as a spring-loaded check valve. By a pressure control valve 38, the pressure downstream of the outlet valve 36 can be adjusted.

The inlet valve device 34 comprises on the one hand a spring-loaded check valve 40, which represents the actual inlet valve. Via an electromagnetic actuator 42, the inlet valve 40 can be forcibly brought into its open position. This is represented by the switching symbol 44. Between the low-pressure connection 18 and the inlet valve device 34, a pressure damper 48 is arranged in a flow path 46. Although this is from the hydraulic diagram of the FIG. 1 not apparent, the pressure damper 48 is not in a bag circuit, but as compressible volume disposed directly in the flow path 46 between the low pressure port 18 and inlet valve means 34. This will be further detailed below with reference to FIG. 2 be explained.

By means of the inlet valve device 34, the delivery rate of the high pressure piston pump 20 can be adjusted. For this purpose, the inlet valve 40 is brought into its forced open position 44 during a delivery stroke of the delivery piston 30. In this case, during the delivery stroke of the delivery piston 30, the fuel is not discharged to the fuel rail 24 but back into the low-pressure passage 16 via the flow path 46. The pressure pulsations that occur, inter alia, in the flow path 46 and in the low-pressure line 16 are smoothed by the pressure damper 48.

How out FIG. 2 As can be seen, the high-pressure piston pump 20 comprises a housing 50, which comprises a housing body 52, a piston bushing 53, and a housing cover 54. The housing cover 54 has a cylindrical shape with a peripheral wall 56 and a base 58. The free edge of the peripheral wall 56 is welded to the housing body 52.

The housing cover 54 forms in FIG. 2 the upper cover of the housing 50 and is so far as seen in the longitudinal direction of the delivery piston 30 disposed on an axial end face of the pump housing 50. The low-pressure connection 18 is formed by an inlet connection, which is welded centrally to the base 58 of the housing cover 54. Through the housing body 52 and the housing cover 54, a space 62 is limited, which, as will be shown below, represents an expanded portion of the flow path 46 from the inlet port 18 to the inlet valve 40 back. For this purpose leads from the extension 62 in an axial direction extending channel 63 to the in FIG. 2 The high-pressure port 22 is formed by an outlet, which is welded to the housing body 52.

The pressure damper 48 is inserted into the extension 62. It comprises a rotationally symmetrical damper housing 66. This extends from an axial center plane 68, in whose area it has its maximum diameter, to two end faces with a smaller diameter, in each of which an opening 70 is present (it should be noted that the pressure damper 48th is formed identically on both sides of the median plane 68, so for reasons of illustration, the reference numerals are entered only for one side). Also in one of the region of the median plane 68 to the end face conically tapered wall 72 of the damper housing 66 distributed over the circumference arranged openings 74 are present.

Enclosed in the damper housing 66 is a compressible gas volume 76 between two substantially and generally parallel diaphragms 78a and 78b. The damper housing 66 is in two parts with a top 66a and a bottom 66b. The edges of the two membranes 78a and 78b are clamped in the region of the median plane 68 between the two parts 66a and 66b of the damper housing 66. In a developed initial state, the axial longitudinal extension of the damper housing 66 is slightly larger than the height of the extension 62. This leads to that in the in FIG. 2 shown installation position, the damper housing 66 is clamped between the housing cover 54 and the housing body 52. It lies in the FIG. 2 Upper opening 70 of the damper housing 66 exactly in the region of the inlet nozzle 18th

By a rigid configuration of the support on the housing 66 is achieved that an axial compressive force occurring during assembly does not lead to a radial change in diameter. The diaphragms 78a and 78b are therefore securely centered with respect to the housing 66.

• Währens eines Saugtaktes bewegt sich der Förderkolben 30 in Figur 2 nach unten. Hierdurch wird Kraftstoff über den Einlassstutzen 18, die Erweiterung 62, den Kanal 63, und das Einlassventil 40 in den Förderraum 32 angesaugt. Da das Dämpfergehäuse 66 zwischen dem Gehäusedeckel 54 und dem Gehäusekörper 52 verspannt ist und hierdurch zwischen den Rändern der Öffnungen 70 und dem Gehäusedeckel 54 beziehungsweise dem Gehäusekörper 52 ein weitgehend fluiddichter Kontakt hergestellt ist, strömt der Kraftstoff vom Einlassstutzen 18 durch die in Figur 2 obere Öffnung 70 in das Innere des Dämpfergehäuses 66, umspült dort die Membran 78a, tritt aus den Öffnungen 74 aus dem Dämpfergehäuse 66 in die Erweiterung 62 aus, wo er auch die Membran 78b beaufschlagt, um dann weiter in den Kanal 63 zu strömen.

In the FIG. 2 shown high-pressure piston pump 20 operates as follows:

• During a suction cycle, the delivery piston 30 moves in FIG. 2 downward. As a result, fuel via the inlet port 18, the extension 62, the channel 63, and the inlet valve 40 is sucked into the delivery chamber 32. Since the damper housing 66 is clamped between the housing cover 54 and the housing body 52 and thus a largely fluid-tight contact is made between the edges of the openings 70 and the housing cover 54 and the housing body 52, the fuel flows from the inlet port 18 through the in FIG. 2 Upper opening 70 into the interior of the damper housing 66, there flows around the membrane 78 a, exits from the openings 74 from the damper housing 66 in the extension 62, where he also acts on the membrane 78 b, and then further into the channel 63 to flow.

It can be seen that the gas volume 76 enclosed between the two diaphragms 78a and 78b, which has the actual pressure damping task, lies directly in the flow path 46 of the fuel and is flowed around directly by it. If it comes, starting from the inlet valve 40, to a pressure surge, this can be smoothed by the pressure damper 48 before he can propagate through the inlet port 18 into the low pressure line 16.

In FIG. 3 For example, that portion of an alternative embodiment of a high pressure piston pump 20 is shown in which the pressure damper 48 is disposed is. In this case, bear such elements and areas which have equivalent functions to elements and areas of the figures described above, the same reference numerals. They are not explained again in detail. Incidentally, this also applies to all subsequent figures.

It can be seen that the inlet port 18 in contrast to FIG. 2 not straight, but angled by 90 ° is formed. In addition, it can be seen that in the region of its center plane 68, the damper housing 66 has a plurality of centering sections 80 distributed over the circumference and projecting radially in total. The centering sections 80 are formed by a radially outwardly extending extension of the conical wall 72. They each have an end section 82 extending approximately axially relative to the respective other housing half.

The radially outer side of the end portions 82 abuts against the inside of the peripheral wall 56 of the housing cover 54. As a result, the damper housing 66 is centered relative to the extension 62 or relative to the housing cover 54. The end portions 82 extend slightly beyond the median plane 68. The radially outer edges of the membranes 78a and 78b abut the radially inner side of the end portion 82. By means of the end section 82, the membranes 78a and 78b or the gas volume 76 are thus radially centered relative to the damper housing 66.

How out FIG. 4 can be seen, in addition to the housing cover 54 distributed over the circumference several impressions 86 may be present. On the inside, the radially outer edges of the membranes 78a and 78b can center directly opposite the housing cover 54.

Basically, it should be noted that by centering the damper housing 66 with radial bias creates a pre-assembled assembly, which is particularly easy to install. Such a bias further minimizes the radial tolerances so that the diameter and thus the action of the pressure damper 48 itself can be maximized.

The area of the inlet nozzle 18 and the housing cover 54 of yet another embodiment of a high-pressure piston pump 20 is in FIG. 5 shown. It can be seen that in the housing cover 54, a protuberance 84 is present, with which the inlet port 18 is welded.

A further modified variant shows this FIG. 6 In this, a thread 88 is rolled into the inside of the protuberance 84, into which the inlet port 18 is screwed.

Claims (11)

1. Fluid pump (20), in particular high-pressure fuel pump, with a casing (50) and with at least one inlet-side low-pressure connection (18), an inlet valve (40) and a conveying space (32) which is delimited by a conveying element (30), end with a pressure damper (48) which damps inlet-side pressure fluctuations and comprises at least one compressible volume (76) which is arranged directly in the flow path (46) between the low-pressure connection (18) and the inlet valve (40), characterized in that the pressure damper (48) has a damper casing (66) having two axial end faces, and the damper casing (66) is clamped with its two end faces between a casing body (52) and a casing cover (54).
2. Fluid pump (20) according to Claim 1, characterized in that the compressible volume is a gas volume (76) which is delimited by at least one diaphragm (78).
3. Fluid pump (20) according to either one of Claims 1 and 2, characterized in that the compressible volume (76) is received in a widening (62) of the flow path (46), which widening is covered by the casing cover (54).
4. Fluid pump (20) according to one of the preceding claims, characterized in that the casing cover (54) is arranged on an axial end face of the casing body (52).
5. Fluid pump (20) according to one of the preceding claims, characterized in that the low-pressure connection (18) is arranged on the casing cover (54).
6. Fluid pump (20) according to one of the preceding claims, characterized in that the damper casing (66) is essentially rotationally symmetrical and tapers proceeding from an axial mid-plane (68), in the region of which said damper casing has its maximum diameter, in that said damper casing has at least one orifice (70) in each end face, and/or in that at least one orifice (74) is present in each case in the casing walls (72) between the two end faces and the mid-plane (68).
7. Fluid pump (20) according to one of the preceding claims, characterized in that the damper casing (66) has centring portions (80) which are arranged so as to be distributed over the circumference and, overall, project radially and which centre the damper casing (66) radially with respect to the widening (62) of the flow path (46).
8. Fluid pump (20) according to Claim 7, characterized in that at least some of the centring portions (80) have in each case an end portion (82) which extends approximately axially and somewhat beyond the mid-plane (68) of the damper casing (66) and at which the compressible volume (76) is centred radially with respect to the damper casing (66).
9. Fluid pump (20) according to one of Claims 3 to 8, characterized in that a radially outer margin of the compressible volume (76) bears at least in regions against a wall of the widening (62) of the flow path (46) and is thus centred with respect to the said widening.
10. Fluid pump (20) according to one of the preceding claims, characterized in that the damper casing (66) comprises two casing halves (66a, 66b), and the compressible volume (76) is clamped between the two casing halves (66a, 66b).
11. Fluid pump (20) according to one of the preceding claims, characterized in that the casing cover (54) has a protuberance (84) on which the low-pressure connection (18) is arranged.

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