DE10345725B4 - High-pressure fuel pump - Google Patents

Abstract

High-pressure fuel pump with a housing (50) and with at least one inlet-side low pressure port (18), an inlet valve (40), and a delivery chamber (32) bounded by a delivery element (30) comprising a pressure damper (48), the pressure on the inlet side is damped and includes at least one compressible volume (76) located directly in the flow path (46) between the low pressure port (18) and the inlet valve (40), the compressible volume being a gas volume (76) extending from at least one Diaphragm (78) is limited, wherein the compressible volume (76) in an extension (62) of the flow path (46) is covered by a housing cover (54), wherein the housing cover (54) at an axial end face of the pump housing (50) is arranged, characterized in that the low pressure port (18) on the housing cover (54) is arranged.

Description

State of the art

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

A high pressure fuel 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.

From the US 2003/0164161 A1 a high-pressure fuel pump is known, whose low-pressure connection is arranged on the pump body of the high-pressure pump and which comprises a pressure damper, which is arranged in a blind circuit.

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

The arrangement of the compressible volume directly in the flow path between low-pressure port and inlet valve has the advantage, in contrast to the hitherto customary bag circuit, 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 occur at the inlet valve itself 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.

According to the invention, the compressible volume is a gas volume which is bounded 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.

According to the invention, the compressible volume is received in an extension of the flow path, which is covered by a housing cover. 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.

According to the invention, the housing cover is arranged on an axial end side of the pump housing. The radial dimensions of the fluid pump are reduced.

A further reduction of the radial dimensions of the fluid pump is inventively achieved in that the low-pressure connection is arranged on the housing cover.

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 may be straight or angular, so that the same fluid pump also on different installation situations can be easily adjusted. In principle, any departure 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 is tapered 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 have so large boundary surfaces that an effective damping of pressure pulsations is possible. At the same time it builds short in the axial direction, which benefits the dimensions of the fluid pump. On the one hand, it is ensured by the openings in the wall of the steamer housing that the fluid can pass from the low-pressure connection to the inlet valve without being throttled, and, on the other hand, the fluid immediately circulates the compressible volume. The pressure steamer designed in this way 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 in order to achieve reproducible ratios of forces the steamer housing should at least partially (in a two-part housing, for example, at least one Gehausehälfte) 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 steamer can be used in the extension of the Stromungswegs and is then, after installation of the housing cover, automatically set in installation 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 which extends approximately axially and somewhat beyond the median plane of the damper housing, at which point the compressible volume is radially centered relative to the damper housing. In this case, the centering sections are assigned a dual function: they not only serve to center the damper housing in relation 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 steamer 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 Einpragungen have.

In a similar direction aims that development of the fluid pump according to the invention, in which the steamer 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 steamer housing itself should at least partially (in a two-part housing, for example, a Gehausehalfte) 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 inventive fluid pump is characterized in that the housing cover has a Ausstulpung on which the low pressure port is arranged. By such a bulge 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

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

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

2 a partial section through the fluid pump of 1 ;

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

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

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

6 a section through a region of yet another alternative embodiment of a fluid pump.

Description of the embodiments

In 1 a fuel system carries the reference numeral 10 , It includes a fuel tank 12 , from which a Vorforderpumpe 14 the fuel into a low pressure line 16 calls. This leads to a low pressure connection 18 a designed as a high-pressure piston pump fluid pump 20 , in the 1 is indicated by a dashed line.

A high pressure connection 22 the high-pressure piston pump 20 is with a fuel rail 24 connected. This is also called "Rail". In it is the one of the high pressure piston pump 20 compressed fuel stored under high pressure. To the fuel manifold 24 are several fuel injectors 26 connected to the fuel in their respective associated combustion chamber 28 inject directly. The fuel system 10 So belongs to an internal combustion engine with direct fuel injection.

This in 1 shown hydraulic diagram of the high-pressure piston pump 20 shows some of its essential components:
This includes a Forderkolben 30 , which can be offset, for example, by a drive shaft, not shown, in a reciprocating motion. He limits a Forderraum 32 , This is with an inlet valve device 34 and a discharge valve designed as a spring-loaded check valve 36 fluidly connected. By a pressure control valve 38 the pressure can be downstream from the exhaust valve 36 be set.

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

By means of the inlet valve device 34 can be the Fordermenge the high-pressure piston pump 20 be set. For this purpose, during a Forderhubs the delivery piston 30 the inlet valve 40 into his compulsorily opened position 44 brought. In this case, during the delivery stroke of the Forderkolbens 30 the fuel does not go to the fuel rail 24 but back over the Stromungsweg 46 in the low pressure line 16 pushed out. Among other things, this in Stromungsweg 46 and in the low pressure line 16 occurring pressure pulsations are from the pressure steamer 48 smoothed.

How out 2 As can be seen, the high pressure piston pump includes 20 a housing 50 , which a Gehäusekorper 52 , a piston sleeve 53 , and a housing cover 54 includes. 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 with the Gehausekorper 52 welded.

The housing cover 54 forms in 2 the top cover of the housing 50 and is so far in the longitudinal direction of the delivery piston 30 seen on an axial end face of the pump housing 50 arranged. The low pressure connection 18 is formed by an inlet nozzle, which is centric at the base 58 of the housing cover 54 is welded. Through the Gehäusekorper 52 and the housing cover 54 becomes a space 62 which, as will be discussed below, extends an extended portion of the flowpath 46 from the inlet nozzle 18 to the inlet valve 40 represents. To this end leads from the extension 62 an axially extending channel 63 to the in 2 out of the picture plane and therefore not visible inlet valve 40 , The high pressure connection 22 is formed by an outlet connecting with the Gehausekorper 52 is welded.

The pressure damper 48 is in the extension 62 used. It includes a rotationally symmetrical steamer housing 66 , This extends from an axial center plane 68 , in whose area it has its maximum diameter, to two end faces of smaller diameter, in each of which an opening 70 is present (it should be noted that the pressure damper 48 on both sides of the median plane 68 is identical; For reasons of representation, the reference numbers are therefore only entered for one page). Also in one of the area of the median plane 68 to the front, conically tapered wall 72 the damper housing 66 are openings distributed over the circumference 74 available.

In the damper housing 66 is a compressible gas volume 76 enclosed, between two substantially and generally parallel membranes 78a and 78b , The steamer housing 66 is two-piece with a top 66a and a lower part 66b , The edges of the two membranes 78a and 78b are in the midplane area 68 between the two parts 66a and 66b the damper house 66 jammed. In a developed initial state is the axial elongation of the steamer housing 66 slightly larger than the height of the extension 62 , This leads to that in the in 2 installation position shown the steamer housing 66 between the housing cover 54 and the Gehausekorper 52 is stuck. It lies in the 2 upper opening 70 the steamer house 66 exactly in the area of the inlet nozzle 18 ,

By a rigid design of the support on the housing 66 is achieved that an axial compressive force occurring during assembly does not lead to a radial diameter change. The membranes 78a and 78b are therefore safe against the case 66 centered.

In the 2 shown high-pressure piston pump 20 works as follows:
During a suction cycle, the delivery piston moves 30 in 2 downward. This will fuel through the inlet port 18 , the extension 62 , the channel 63 , and the inlet valve 40 in the pump room 32 sucked. Because the steamer house 66 between the housing cover 54 and the Gehausekorper 52 is strained and thereby between the edges of the openings 70 and the housing cover 54 or the housing body 52 a largely fluid-tight contact is made, the fuel flows from the inlet port 18 through the in 2 upper opening 70 into the interior of the steamer housing 66 , there rewinds the membrane 78a , steps out of the openings 74 from the steamer house 66 in the extension 62 from where he also has the membrane 78b charged, then further into the channel 63 to stream.

You can see that between the two membranes 78a and 78b enclosed gas volume 76 , which has the actual Druckdampfungsaufgabe, immediately in Stromungsweg 46 the fuel is located and is directly circulated by this. Does it come, starting from the inlet valve 40 , to a pressure surge, this can from the pressure steamer 48 be smoothed before turning over the inlet nozzle 18 in the low pressure line 16 can reproduce.

In 3 is that area of an alternative embodiment of a high-pressure piston pump 20 shown in which the pressure steamer 48 is arranged. 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 in detail again. Incidentally, this also applies to all subsequent figures.

It can be seen that the inlet nozzle 18 in contrast to 2 not straight, but angled by 90 ° is formed. In addition, one recognizes that the steamer housing 66 in the area of its middle plane 68 a plurality of distributed over the circumference arranged and a total radially projecting centering 80 having. The centering sections 80 are by a radially outwardly extending extension of the conical wall 72 educated. They each have an end section extending approximately axially relative to the respective other housing half 82 on.

The radially outer side of the end sections 82 lies on the inside of the peripheral wall 56 of the housing cover 54 at. This will be the damper housing 66 towards the extension 62 or opposite the housing cover 54 centered. The end sections 82 extend slightly over the median plane 68 time. The radially outer edges of the membranes 78a and 78b lie on the radially inner side of the end portion 82 at. Through the end section 82 thus become the membranes 78a and 78b or the gas volume 76 opposite the steamer house 66 radially centered.

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

Basically, it should be noted that by centering the steamer housing 66 with radial prestressing a pre-assembled assembly is created, which is particularly easy to install. By such a bias further the radial tolerances are minimized, so that the diameter and thus the effect of the pressure damper 48 themselves can be maximized.

The area of the inlet nozzle 18 and the housing cover 54 Yet another embodiment of a high-pressure piston pump 20 is in 5 shown. One recognizes that in the housing cover 54 an outpouring 84 is present, with the inlet nozzle 18 is welded.

A modified version shows this 6 : This one is in the inside of the bulge 84 a thread 86 rolled up, in which the inlet nozzle 18 is screwed.

Claims (8)

High-pressure fuel pump with a housing ( 50 ) and with at least one inlet-side low-pressure connection ( 18 ), an inlet valve ( 40 ), and a delivery room ( 32 ), of a conveying element ( 30 ), which is a pressure damper ( 48 ) attenuating the inlet side pressure fluctuations and the at least one compressible volume ( 76 ), which is directly in the flow path ( 46 ) between low-pressure connection ( 18 ) and inlet valve ( 40 ), wherein the compressible volume is a gas volume ( 76 ), which of at least one membrane ( 78 ), the compressible volume ( 76 ) in an extension ( 62 ) of the flow path ( 46 ) received by a housing cover ( 54 ) is covered, wherein the housing cover ( 54 ) on an axial end face of the pump housing ( 50 ), characterized in that the low-pressure connection ( 18 ) on the housing cover ( 54 ) is arranged. Fuel high pressure pump ( 20 ) according to claim 1, characterized in that the pressure damper ( 48 ) a substantially rotationally symmetrical damper housing ( 66 ) having two axial end faces to which it is starting from an axial center plane ( 68 ), in the area of which it has its maximum diameter, tapers so that it has at least one opening ( 70 ), and / or that in the housing walls ( 72 ) between the two end faces and the median plane ( 68 ) at least one opening ( 74 ) is available. Fuel high pressure pump ( 20 ) according to claim 2, characterized in that the damper housing ( 66 ) arranged distributed over the circumference and a total of radially projecting centering ( 80 ), which the damper housing ( 66 ) against the enlargement ( 62 ) of the flow path ( 46 ) center radially. Fuel high pressure pump ( 20 ) according to claim 3, characterized in that at least some of the centering sections ( 80 ) one each approximately axially and slightly above the median plane ( 68 ) of the damper housing ( 66 ) extending end portion ( 82 ), where the compressible volume ( 76 ) opposite the damper housing ( 66 ) is radially centered. High-pressure fuel pump according to one of claims 3 or 4, characterized in that at least some of the centering sections ( 80 ) one each approximately axially and slightly above the median plane ( 68 ) of the damper housing ( 66 ) extending end portion ( 82 ), where the compressible volume ( 76 ) opposite the damper housing ( 66 ) is radially centered. Fuel high pressure pump ( 20 ) according to one of claims 1 to 5, characterized in that the housing cover ( 54 ) a protuberance ( 84 ), at which the low pressure port ( 18 ) is arranged. Fuel high pressure pump ( 20 ) according to one of claims 1 to 6, characterized in that the extension ( 62 ) through a housing body ( 52 ) and through the housing cover ( 54 ) is limited. Fuel high pressure pump ( 20 ) according to claim 7, characterized in that the low-pressure connection ( 18 ) is a straight connecting piece, which points in an axial direction, and that in the same axial direction through the housing body ( 52 ) a channel ( 63 ) of the extension ( 62 ) to the inlet valve ( 60 ) leads.

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