EP1411236B1 - Device for damping of pressure pulsations in a fluid system, especially in a fuel system of an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a device for damping pressure pulsations in a fluid system, in particular in a fuel system of an internal combustion engine, with a housing and with at least one working space, which communicates at least partially with the fluid system.

Such a device is from the DE 195 39 885 A1 known. There is shown a fuel system of an internal combustion engine with direct fuel injection. From a prefeed pump, the fuel is conveyed to a high-pressure piston pump, which compresses the fuel to a very high pressure. From the high-pressure piston pump, the fuel enters a fuel rail ("rail"). The high-pressure piston pump is driven by a camshaft of the internal combustion engine. In order to adjust the delivery rate of the high pressure piston pump independently of the speed of the camshaft, a quantity control valve is provided. Through this, the Delivery chamber of the high-pressure piston pump during a delivery stroke are briefly connected to the located between the electric feed pump and the high-pressure fuel pump portion of the fuel system.

As a result, however, significant pressure pulsations are initiated in this area of the fuel system. To dampen this, a pressure damper is provided there. This consists of a housing and a piston which is biased by a spring.

Also known from the market is a pressure damper, which works with a spring-biased rubber membrane. In order for non-pressurized systems (that is, for example, when the internal combustion engine is switched off), the rubber membrane is not stretched inadmissible over time, a stopper is present, against which the membrane is supported at low pressure.

In the from the DE 195 39 885 A1 known fuel system, the pressure between the prefeed pump and the high-pressure piston pump is approximately constant. However, in modern fuel systems, this pressure can be variable. Typically, it is between 0.5 and 8 bar, with an overload safety must be present to about 10 to 12 bar. If the known pressure damper, which has a rubber membrane, used in such a fuel system, there is a risk that at a low system pressure, for example. Of 0.5 bar and the superimposed pressure pulsations, the rubber membrane abuts against the stop. As a result, the damping effect of the pressure damper is weakened and it can damage the rubber membrane occur. The from the DE 195 39 885 A1 known pressure damper with a piston and a spring in turn would have to build very large when used in such a variable-pressure fuel system.

The NL-C2-1 016 384 describes a damping device which comprises a arranged in a working space and sealed by a membrane gas volume. The state of the art is still on the US 6,079,450 , the EP 1 342 911 A2 , the EP 0 950 809 A2 , the US 3,366,144 , the US 3,948,288 , the JP 167299 A and the US 6,062,830 directed.

The present invention therefore has the object, a device of the type mentioned in such a way that it can be used in a fuel system with variable form, but it builds small and has a long life.

This object is achieved by a device having the features of claim 1.

Advantages of the invention

By using a sealed volume of gas, the compressibility of gases can be exploited to ensure the elastic movement of the membrane required to dampen pressure pulsations. The membrane is not affected by any mechanical elements, which significantly increases their service life and reduces the risk of damage. In addition, such a gas volume can be realized in almost any geometric shape. It can therefore be accommodated very space-saving in the fluid system. Another advantage of the device according to the invention is that it can be dispensed with a leakage line, which simplifies the construction of the fuel system again.

According to the gas volume is limited by at least two membranes which are clamped in the region of their edges. Such a pressure damper builds comparatively flat. All the more so, when the membranes are substantially parallel. In principle, it is of course conceivable that the gas volume is introduced into the space lying between the two membranes during their assembly, so that a filling opening can be dispensed with.

By limiting the maximum deflection of the membrane, this can be chosen so that damage to the membrane, such as a plastic deformation, are just avoided. Therefore, this device is at least in a certain area "overload-proof", that is, it still shows an overload function even with overloads, without being damaged.

The one membrane has at least one stop section and the other membrane at least one counter surface, which come into contact with each other at a maximum deflection of the two membranes. This makes use of the fact that in the case of a high pressure, the two membrane surfaces move towards each other. When they come into contact with each other, they support each other. A separate stop is not required.

Advantageous developments of the invention are specified in subclaims.

In a first development, it is proposed that the membrane is made of metal. Such a membrane has several advantages: First, such a membrane compared to conventional gases and also to fluids very dense. In particular, the high density of metal membranes in comparison to HC emissions plays a positive role here. On the other hand occurs in a metal diaphragm even at low pressures, for example. With the engine OFF, no overstretching over time, so that a damper device can be used with a metal diaphragm in a fluid system, which has a variable fluid pressure in a wide range.

It is also advantageous if the gas volume is formed by a thin-walled and at its ends gas-tight sealed metal tube. This is very easy and inexpensive to realize.

If at least one outer wall of the working space is likewise designed as a membrane, an additional hydraulically effective area is obtained in a minimum space. The effectiveness of the device according to the invention is thereby significantly increased again, while requiring little space.

It is particularly advantageous if the enclosed gas volume has a defined pressure at a standard external pressure (for example 1013 hPa), preferably an overpressure. With such a defined pressure, the "spring stiffness" can be adjusted. Usually, an overpressure in the trapped gas volume in comparison to the external pressure will be chosen, because in this way the entire possible voltage range (tension and pressure) of the membrane material can be utilized.

It is also conceivable, however, a negative pressure or standard pressure. Preferably, such an internal overpressure is selected, which is approximately half of the maximum Operating pressure minus the pressure increase caused by the compression of the component.

It can also be optimized by minimizing the trapped gas volume, the effectiveness of the gas volume. By such minimization namely a higher spring stiffness is realized. This can make the membrane thinner and the stresses in the membrane material can be minimized. In addition, a stop-free operation of the device is made possible throughout the work area. Furthermore, the load over the entire operating range is reduced because the pressure difference across the membrane wall is reduced by the enclosed internal pressure. Thus, the membrane geometry can be designed for higher strokes and lower pressure load or small installation volume.

In this case, the gas volume may have a closable opening, via which the pressure can be adjusted. This facilitates the production of the gas volume. Otherwise, the production would have to be done even at a certain pressure.

Particularly advantageous is that embodiment of the device according to the invention, in which the membrane has at least one bead. By such a bead, the spring properties of the membrane itself and also their strength properties can be significantly influenced. With a bead, the membrane can thus be optimally adapted to the individual requirements of the fluid system. Above all, the damper with comparable volume can have even more damping volume, or alternatively be built smaller. The beads may have different height and / or a different course and / or a different cross-section.

In this way one can achieve an asymmetrical spring stiffness of the membrane depending on the load direction.

As a result, for example, in the main working range of the pressure damper device a targeted, for example, a largely constant and rather soft spring constant of the diaphragm can be achieved. In rarely used operating areas, on the other hand, higher rigidity can be achieved. In this way you can achieve a non-linear or only piecewise linear spring characteristic. Ultimately, this achieves an optimal damping effect in the entire operating range of the fluid system with at the same time low installation space.

The beads can also be shaped so that the maximum stress does not occur at the edge of the membrane, and the mechanical stresses are distributed as evenly as possible over the surface of the membrane. Furthermore, the entire material bandwidth in the tensile and compressive stress range can be used by a corresponding membrane design.

It can also be provided that the membrane has at least one stop area which comes into contact with a maximum deflection of the membrane with a counter surface. The maximum deflection is chosen so that damage to the membrane, such as a plastic deformation, are just avoided. Therefore, this device is at least in a certain area "overload-proof", that is, it still shows an overload function even with overloads, without being damaged.

In a further development, it is proposed that the counter surface on the housing, on a separate which the gas volume between the two membrane is formed and the two membranes each have at least one stop surface or a mating surface, which touch at a maximum deflection of the two membrane. This makes use of the fact that in the case of a high pressure, the two membrane surfaces move towards each other. When they come into contact with each other, they support each other with the stop surfaces. These abutment surfaces can be designed plan to get a clean system of the membranes together. An overload of the membranes at too high pressure is thereby reliably excluded, without a separate stop is required.

It is also possible that the edges of the two membrane are sealed together and clamped radially inwardly of the sealing line. In particular, when the connection is made by a weld, is prevented by this embodiment of the device according to the invention that the welds must withstand additional mechanical forces. The sealing connection thus serves only for sealing and does not have to take on other tasks and can thus fulfill particularly high tightness requirements safely. For the evaluation of the durability of the pressure damper according to the invention so only the membranes themselves must be considered.

It is particularly advantageous if the clamping has a structural elasticity. This is understood to mean such an elasticity that is "constructively intended". For example, a retaining ring made of a rubber-elastic material may be used, or a metal support may be used which has a spring portion. Thus, on the one hand a secure fixation of the membranes is achieved, and on the other hand can Manufacturing tolerances are compensated. Basically, the clamping can attack at any location of the membrane, but particularly favorable is an approach in the region of a median plane of the two membranes.

The costs for the device according to the invention are reduced if the two membranes are identical.

The installation space of the device according to the invention is particularly small if the working space of the two membranes is subdivided into two fluid areas which communicate with one another by a fluid connection.

An annular spacer between the two membranes simply defines or increases the trapped volume of gas. In this case, it is inexpensive possible to form the fluid connection, which connects the two fluid areas of the working space with each other, in the spacer.

It is particularly advantageous if the device is integrated in a housing of a fuel pump. There, the benefits of the invention are particularly noticeable, since such a fuel pump is usually to build very small.

In fuel pumps, there are often circumferential areas in which shafts or pistons are arranged. In these cases, the damping device according to the invention can be accommodated in a particularly space-saving manner when the working space comprises an annular space and the gas volume is likewise annular. It is particularly advantageous if the working space and the gas volume are arranged on a cylinder of a fuel pump at least approximately coaxially with the cylinder axis. The pressure damper surrounds so to speak the cylinder and the existing in this piston, which additionally causes a noise attenuation.

It is also proposed that the gas volume be arranged in the manner of a spiral in the annular space, wherein the spiral and the annular space are at least approximately coaxial. Such a spiral results in a large deformation surface, which contributes to a particularly effective pulsation damping.

If the spiral gas volume is biased against the outer wall of the working space, results without additional parts a fixation of the gas volume in the working space.

The effective area of the gas volume can be further increased if the spiral gas volume extends helically in the axial direction of the working space.

Again, the fixation of the gas volume is made possible without additional parts when the spiral and helical gas volume is biased in the axial direction against the front ends of the working space.

A further preferred embodiment of the device according to the invention is characterized in that the gas volume is filled with helium. This facilitates the detection of leakage.

In addition, the membrane and / or the housing may be magnetic. By appropriate manufacturing processes (for example, mechanical rolling and embossing) arises in the material martensitic structure ("Umformmartensit"), which has magnetic properties. When this magnetic property targeted in the corresponding Component is left, the device can trap in the fluid existing magnetic dirt particles and prevent their further distribution. This increases the reliability of the components present in the fluid system, for example a pump. In addition, costs are saved, since the complex demagnetization of the component is eliminated. Since no directly abutting and relatively movable parts are present in the device, the trapped dirt particles cause no functional damage to the device.

Furthermore, it is possible that the membrane is made of a strip material which has residual stresses. Such residual stresses lead during the forming process to a flat distortion, so that the material is discarded in the formed state. This can now be used specifically for the simplification of the production of the membrane can, especially if it has at least one bellows section: Due to the delay namely a targeted separation of the non-pressurized state flat contiguous areas of the membrane is no longer required. The safe evacuation of the membrane and filling of the gas volume, for example with helium is therefore easy and reliable possible.

The order of assembly can be as follows: First, the individual sections ("segments") of the membrane are stacked and "stacked" in a welding device. After closing the welding device whose interior is evacuated and filled with filling gas, such as helium, with a desired pressure. In this phase, the distorted membrane sections ensure that the filling gas flows safely into all cavities. Then the individual sections pressed together and welded together.

In another advantageous embodiment of the device according to the invention, the membrane comprises at least one bead section and at least one bellows section. This allows the combination of the advantages of both versions.

It is further preferred if the membrane has at its radially outer edge a fastening portion which extends approximately parallel to the central axis and is secured to the housing. In this way, the entire inner diameter of the housing can be used hydraulically effective, which minimizes the required space and reduces costs.

It is possible that the device comprises a clamping device which acts on the mounting portion radially against the housing. The clamping device may be formed, for example, as a clamping ring. It relieves the attachment of the membrane to the housing.

drawing

Figur 1

eine schematische Darstellung eines Kraftstoffsystems einer Brennkraftmaschine mit einer Kraftstoffpumpe und einer dort vorhandenen Vorrichtung zum Dämpfen von Druckpulsationen;

Figur 2

einen Schnitt durch ein erstes Ausführungsbeispiel der Vorrichtung zum Dämpfen von Druckpulsationen von Figur 1;

Figur 3

ein Detail III der Vorrichtung zum Dämpfen von Druckpulsationen von Figur 2;

Figur 4

einen Schnitt durch ein zweites Ausführungsbeispiel der Vorrichtung zum Dämpfen von Druckpulsationen von Figur 1;

Figur 5

ein Detail V der Vorrichtung zum Dämpfen von Druckpulsationen von Figur 4;

Figur 6

einen schematischen Schnitt durch eine Membran der Vorrichtung zum Dämpfen von Druckpulsationen von Figur 4;

Figur 7

einen Schnitt durch eine Kraftstoffpumpe mit einem dritten Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen;

Figur 8

einen Schnitt durch einen Bereich der Kraftstoffpumpe von Figur 7 mit einem vierten Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen;

Figur 9

einen Schnitt durch ein fünftes und ein sechstes Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen;

Figur 10

einen Schnitt durch ein siebtes Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen;

Figur 11

einen Schnitt durch ein achtes Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen;

Figur 12

einen Schnitt durch ein neuntes Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen;

Figur 13

einen Schnitt durch ein zehntes Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen; und

Figur 14

einen Teilschnitt durch ein elftes und ein zwölftes Ausführungsbeispiel einer Vorrichtung zum Dämpfen von Druckpulsationen.

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

FIG. 1

a schematic representation of a fuel system of an internal combustion engine having a fuel pump and a device there for damping pressure pulsations;

FIG. 2

a section through a first embodiment of the device for damping of pressure pulsations of FIG. 1 ;

FIG. 3

a detail III of the device for damping of pressure pulsations of FIG. 2 ;

FIG. 4

a section through a second embodiment of the device for damping of pressure pulsations of FIG. 1 ;

FIG. 5

a detail V of the device for damping pressure pulsations of FIG. 4 ;

FIG. 6

a schematic section through a membrane of the device for damping of pressure pulsations of FIG. 4 ;

FIG. 7

a section through a fuel pump with a third embodiment of a device for damping pressure pulsations;

FIG. 8

a section through a portion of the fuel pump of FIG. 7 with a fourth embodiment of a device for damping pressure pulsations;

FIG. 9

a section through a fifth and a sixth embodiment of a device for damping pressure pulsations;

FIG. 10

a section through a seventh embodiment of an apparatus for damping pressure pulsations;

FIG. 11

a section through an eighth embodiment of a device for damping pressure pulsations;

FIG. 12

a section through a ninth embodiment of a device for damping pressure pulsations;

FIG. 13

a section through a tenth embodiment of a device for damping pressure pulsations; and

FIG. 14

a partial section through an eleventh and a twelfth embodiment of a device for damping pressure pulsations.

Description of the embodiments

In FIG. 1 carries a fuel system of an internal combustion engine overall the reference numeral 10. The internal combustion engine itself is not shown in detail.

The fuel system 10 includes a fuel tank 12 from which an electric fuel pump 14 delivers fuel to a low pressure fuel line 16. The low-pressure fuel line 16 leads to a high-pressure fuel pump 18, which is shown symbolically dash-dotted lines.

The high-pressure fuel pump 18 comprises a delivery chamber 20, which from a in FIG. 1 Piston not shown is limited. The piston is displaced by a drive shaft, also not shown, in a reciprocating motion. The drive shaft, in turn, is driven by the camshaft, again not shown, of the internal combustion engine driven. The high-pressure fuel pump 18 further comprises an inlet valve 22, which is designed as a check valve. Further, an outlet valve 24 is provided, which is also formed by a check valve.

The high pressure fuel pump 18 compresses the fuel to a very high pressure and delivers into a fuel rail 26 ("rail"). In this the fuel is stored under high pressure. To the fuel manifold 26 a plurality of fuel injectors 28 are connected. These inject the fuel directly into each associated combustion chambers 30 a.

In order to adjust the delivery rate of the high-pressure fuel pump 18 independently of the rotational speed of the drive shaft, a quantity control valve 32 is provided. This is actuated by a magnetic actuator 33, which in turn is driven by a control and device, not shown. The quantity control valve 32 is designed such that during a delivery stroke of the high-pressure fuel pump 18, the inlet valve 22 can be forcibly opened. As a result, the fuel under pressure in the delivery chamber 20 is not conveyed into the fuel collecting line 26, but back into the low-pressure fuel line 16. The corresponding switching position of the quantity control valve 32 bears the reference numeral 34.

The thus introduced into the low-pressure fuel line 16 pressure pulsations are attenuated by a device for damping pressure pulsations. This wears in FIG. 1 the reference numeral 36 and is hereinafter referred to briefly as "pressure damper". The pressure damper 36 is constructed as follows (see. FIG. 2 and 3 ):

The pressure damper 36 comprises a housing with a lower part 38 and a top 40. The lower part 38 has in the in FIG. 2 It comprises an installation section 42 with an inlet channel 43 introduced centrally therefrom and a bottom plate section 44 which is generally plate-shaped and circular in plan view, the plane of which extends approximately at a right angle to the central axis 41 stands. The upper part 40 of the housing is also plate-shaped and circular in plan view.

Between the bottom portion 44 of the lower part 38 of the housing and the upper part 40 of the housing, an annular spacer 46 is arranged. It is welded on welds 48a and 48b firmly on the one hand with the bottom portion 44 of the lower part 38 of the housing and on the other hand with the upper part 40 of the housing. At an annular holding portion 52 extending radially inwards on the spacer 46, two circular membranes 54a and 54b are provided which are generally circular in plan view. The attachment is made by circumferential welds 57a and 57b at the outermost edge of the membranes 54a and 54b (see. FIG. 3 ). The two membranes 54a and 54b are thin-walled and made of metal, preferably of stainless steel.

Between the upper membrane 54a and the lower membrane 54b and the spacer 46, a gas volume 58 is enclosed. The gas is introduced through a channel 60 provided in the annular spacer 46 (see FIG. FIG. 2 ). After the introduction of the gas into the volume 58 between the two membranes 54a and 54b, the channel 60 is closed by a ball 62. The entire area between the bottom portion 44, the Upper part 40 of the housing, and the spacer 46 forms a working space 66. The gas volume 58 is thus arranged within the working space 66.

Between the bottom portion 44 of the lower part 38 of the housing and the lower diaphragm 54 b, a first fluid region 64 of the working space 66 is formed. Between the upper part 40 of the housing and the upper diaphragm 54a, a second fluid region 68 of the working space 66 is formed. Both fluid regions 64 and 68 may communicate with each other through a channel 70 in the annular spacer 46.

The two membranes 54a and 54b are of identical construction (for reasons of clarity, in FIG. 3 all the reference numerals for the upper diaphragm 54a only): At their radially outer edge they have a radially extending holding portion 72 with which they are welded to the annular spacer 54b. From the holding portion 72 of the diaphragm, a spring portion 74 bends at an angle of about 80 °. The spring portion 74 thus extends approximately in the axial direction. On the spring portion 74, in turn, a radially extending bead portion 76 is integrally formed. This is characterized by a plurality of extending beads 78. The beads 78 extend concentrically around the central axis 41 of the pressure damper 36. A central region of the two membranes 54a and 54b is flat. The corresponding region in the membrane 54a is referred to as a stopper portion 80a, the corresponding area on the membrane 54b as a counter-surface 80b (see. FIG. 2 ).

The pressure damper 36 operates as follows:

About the inlet channel 43 in the installation section 42 communicates in the Figures 2 and 3 lower fluid area 64 (the terms "bottom" and "top" are below always referring to the figures, the pressure damper can be basically arranged arbitrarily in space) of the working space 66 with the low pressure fuel line 16. Via the channel 70 communicates the upper fluid portion 68 of the working space 66 in turn with the lower fluid portion 64. Within the working space 66 of the two membranes 54a and 54b and the annular spacer 46 limited gas volume 58 is present. This is in the idle state of the fuel system 10 under a slight overpressure against the outside atmosphere. Due to this overpressure, the bead portion 76 and the abutment portion 80a and the counter surface 80b of the two diaphragms 54a and 54b, respectively, bulge slightly outward.

However, the distance between the two diaphragms 54a and 54b and the sections 54a or 40 of the housing adjacent to them is so great that, even in the idle state, that is to say with a pressureless fuel system, a contact of the two diaphragms 54a and 54b with the corresponding sections 40 and 44 of the housing is excluded. Such a limitation of the "stroke" of the membranes is possible by the use of metal as a membrane material.

The distance of the membranes 54 a and 54 b from the housing 40 and 44 is selected so that at a system pressure, for example, less than 100 kPa in case of pressure undershoot the membranes 54 a and 54 b, the housing 40 and 44 do not touch. Thus, the damping function of the pressure damper 36 is guaranteed even in this Betriebsbeziehungsweise pressure range.

When the fuel system 10 is in operation, that is, delivering the electric fuel pump 14 at a certain pressure, the two diaphragms 54a and 54b become moved towards each other. The pressure in the gas volume 58 on the one hand and the stiffness of the two diaphragms 54a and 54b are selected so that at normal operating pressure in the low-pressure fuel line 16, that is approximately between 0.5 and 8 bar, a contact of the two membranes 54a and 54b does not take place with each other. Pressure fluctuations can thus be easily absorbed in this normal operating range of the fuel system 10 by a corresponding movement of the two membranes 54a and 54b and a compression of the gas volume 58 and thereby damped.

In the event of an overload in the low-pressure fuel line 16, when the pressure rises, for example, to more than 10 bar, the abutment portion 80a of the diaphragm 54a and the counter-surface 80b engage the diaphragm 54b. The two membranes 54a and 54b can thus no longer move, so that an overload of the two membranes 54a and 54b can be excluded. In order to ensure a clean contact of the two diaphragms 54a and 54b in the event of an overload in the low-pressure fuel line 16, the stopper portion 80a and the mating surface 80b are machined flat or crowned.

In addition to the pressure of the gas volume 58, which is enclosed between the two membranes 54a and 54b, the characteristic of the pressure damper 36 can also be influenced by the height of the annular spacer 46. This height in particular has an influence on the pressure at which the two diaphragms 54a and 54b come into contact with each other.

Furthermore, by a suitable design of the internal geometry of the holding portion 52 (for example, at the position 53 in FIG FIG. 3 ) the internal volume also targeted be downsized. Thereby, the effectiveness of the air spring formed by the enclosed gas volume 58 can be further increased.

The shape of the beads 78 and their number plays an essential role in the properties of the pressure damper 36. In a membrane with a diameter of 30 - 60 mm and a wall thickness of 0.2 - 1.0 mm, a number of three to six beads with different bead height proved to be advantageous. The bead height can vary between +/- 0.15 and 2 mm. The bead may be circular, sinusoidal or spline-shaped.

In this way, an asymmetrical spring stiffness under load of the two membranes 54a and 54b in the Figures 2 and 3 be reached from below or from above. This makes it possible to achieve a comparatively low rigidity with constant spring constant in the usual operating pressure range of the fuel system or the low-pressure fuel line 16, whereas at very low operating ranges, for example. At very low pressure in the low-pressure fuel line 16 or at a prevailing there very high pressure, a higher rigidity of the membranes 54a and 54b is realized.

The shape of the beads 78 and the design of the spring portion 74 ensures that the maximum stresses do not occur at the outermost edge of the two membranes 54a and 54b, but are largely evenly distributed over the diameter of the two membranes 54a and 54b.

Now on the FIGS. 4 and 5 and 6 are referred to. In these, a second embodiment of a pressure damper 36 is shown. In doing so, carry such areas and elements which have equivalent functions to regions and elements of the Figures 2 and 3 illustrated embodiment, the same reference numerals. They are not explained again in detail.

An essential difference between the two embodiments is that when in the FIGS. 4 and 5 represented pressure damper no spacer is no longer available. Instead, the top 40 and the bottom portion 44 of the housing are directly welded together. The corresponding weld bears the reference numeral 48. Accordingly, the two holding portions 72a and 72b of the two membranes 54a and 54b are welded directly together (weld seam 57).

They are also, at a position slightly radially inwardly of the weld 57, with which the two membranes 54a and 54b are gas-tight welded together, of an upper clamping ring 82 and a lower clamping ring 84, the upper part 40 and the bottom portion 44th of the housing are formed, clamped against each other. As a result, the weld, which connects the two membranes 54a and 54b with each other, relieved of mechanical loads.

An in FIG. 5 only shown in dashed lines fluid connection 70, which is formed by regional breakthroughs in the clamping rings 82 and 84, the two fluid portions 64 and 68 of the working space 66 are fluidly connected to each other. The openings 70 must be chosen so that the two membranes 54a and 54b are charged approximately equally.

FIG. 6 shows the lower membrane 54b schematically detail. A is the depth of the diaphragm 54b, it corresponds to the maximum possible stroke. B denotes a transition region, and C the height of the sinking of the membrane 54b.

In FIG. 7 is a partial section through a fuel pump shown as high-pressure fuel pump 18, for example, in the in FIG. 1 shown fuel system 10 is used. It can be seen a cylinder housing 92 with a piston 88 which limits the delivery chamber 20. The quantity control valve 32 can be seen in the upper region of the fuel pump 18. The outlet valve 24 is located in the left area. The inlet valve 22 is formed as a spring-loaded plate valve, which can be forced by a plunger (not numbered) of the quantity control valve 32 during a delivery stroke of the piston 88 forcibly in an open position.

Coaxial with a cylinder central axis 90, a circumferential step 94 is incorporated in the outer boundary surface of the cylinder housing 92. About this a housing sleeve 96 is pushed. Due to the circumferential step 94 and the housing sleeve 96, a circumferential around the cylinder central axis 90 annular space 66 is provided. This communicates on the one hand via a channel 100 with a low-pressure inlet 102 of the fuel pump 18. On the other hand, it communicates via a channel 104 with a pressure relief groove 106, which in a cylinder bore 108 in which the piston 88 is guided, is present.

In the annular space 66, two annular peripheral membranes 54a and 54b are arranged. Their outer edges are via welds 57a to 57d on the one hand with the cylinder housing 92 and the other with the housing sleeve 96th welded. This creates two separate gas volumes 58a and 58b. Between these there is a fluid region 64 of the working space 66, which in particular communicates via the channel 100 with the low-pressure inlet 102. The annular space 66 and the gas volumes 58a and 58b in this way form a pressure damper 36, which is arranged coaxially with the cylinder central axis 90 of the high-pressure fuel pump 18.

In FIG. 8 a modified embodiment of such an annular pressure damper 36 is shown. In this case, carry such elements and areas, which equivalent functions to elements and areas of the in the FIGS. 7 have shown pressure damper 36, the same reference numerals. They are not explained again in detail.

The pressure damper 36, which in FIG. 8 is shown, comprises a flattened metal tube 54, which is sealed gas-tight at the ends. Its interior forms a gas volume 58. The metal tube 54a is wound in the working space 66 in a spiral and helical manner coaxially with the central cylinder axis 90. As a result, it stands on the one hand with respect to the housing sleeve 96 and the other with respect to the in FIG. 8 upper and lower end surfaces of the working space 66 under a bias and is thereby fixed.

In FIG. 9 a further variant of a pressure damper 36 is shown. Here and in all subsequent figures, it applies that such elements and regions which have equivalent functions to elements and regions which have already been explained in connection with the preceding figures bear the same reference numerals. Normally they will not be explained again in detail.

The pressure damper 36 shown is in the left half of FIG. 9 differently designed than on the right half. Both devices 36 have in common that they have only a single membrane 54. This is welded in the region of its holding portion 72 in 57 with the upper part 40 of the housing. Unlike the example in the Figures 2 and 3 Membrane has the in FIG. 9 illustrated diaphragm 54 a bellows portion 110 which is disposed between the bead portion 76 and the holding portion 72 and is composed of individual segments 110a to 110d. This bellows portion 110 allows a comparatively large volume change of the gas volume 58 enclosed by the diaphragm 54 and the housing 40.

The gas volume 58 is thereby reduced overall in that between the membrane 54 and the upper part 40 of the housing, a packing 112 is attached to the upper part 40 of the housing. In the left half of the FIG. 9 a stopper portion 80a extends from the bead portion 76 of the diaphragm 54 to the lower portion 38 of the housing, whereas in the right half of the FIG. 9 the stopper portion 80a extends toward the packing 112. Depending on either the filler body 112 or the lower part 38 of the housing acts as a counter surface 80b for the stopper portion 80a.

The gas volume 58 trapped by the membrane 54 is filled with helium. This is under an overpressure, which corresponds to approximately half of the maximum operating pressure, minus the pressure increase caused by the compression of the diaphragm 54. In this case, a magnetic metal material is used for the membrane 54. As a result, the pressure damper 36 acts like a "dust catcher", because through them magnetic dirt particles from the fluid intercepted and prevented their distribution in the fluid system 10.

Furthermore, for the production of the bellows portion 110 of the membrane 54 in particular, a strip material is used in which residual stresses are present which lead to a flat distortion of the individual segments 110a, 110b, 110c, and 110d. As a result, during the production of the bellows portion 110, the individual segments 110a to 110d are never so close to each other that evacuation of the air and filling with helium is not reliably possible. A conceivable procedure in the manufacture of the bellows section 110 is as follows:

First, the individual segments 110a to 110d of the bellows portion 110 are stacked in a welding apparatus (not shown). Then the welding device is closed and the interior evacuated. Then, the interior of the welding device is filled with helium to a desired internal pressure. By having a delay portions 110a to 110d of the bellows 110 ensures that helium can flow reliably into the corresponding cavities. The individual segments 110a to 110d are then pressed together and welded together in FIG. 114 (for reasons of clarity, this reference symbol is only located at one point on the left side of FIG FIG. 9 entered).

An alternative to this is in FIG. 10 shown. The in FIG. 10 shown pressure damper 36 differs from that in FIG. 9 shown by the fact that instead of a separate packing 112 in the upper part 40 of the housing, a deep-drawn section 112 is present, which on the one hand the trapped gas volume 58th reduced and on the other hand has the counter surface 80b, which cooperates with the stopper portion 80a of the diaphragm 54.

FIG. 11 again shows an embodiment in which a separate filler body 112 is present, which is not hollow, but solid and, moreover, in a the stopper portion 80a of the diaphragm 54 facing portion 116 has a smaller diameter. Thus, the contour of the filling body 112 of FIG. 11 something adapted to the contour of the membrane 54, so that the corresponding gas volume 58 is particularly low.

In FIG. 12 an embodiment is shown in which two membranes 54a and 54b are present, corresponding to, for example, the in FIG. 4 shown embodiment of a pressure damper 36. In contrast to FIG. 4 is at the in FIG. 12 In the embodiment shown, in each membrane 54a and 54b, there is a bellows portion 110 which, however, is simpler than that of FIGS FIGS. 9 to 11 , The in FIG. 12 shown pressure damper has - analogous to that in the FIGS. 4 and 5 shown - upper and lower clamping rings 82 and 84, which, however, in FIG. 12 are shown only schematically. By this, the hydraulically effective area of the membranes 54a and 54b is maximized, which can be used to reduce the overall size of the pressure damper 36. However, the clamping rings 82 and 84 are supported by spring portions 118 and 120 on the upper part 40 and on the lower part 38 of the housing. In this way, manufacturing tolerances of the membranes 54a and 54b can be compensated.

Between the two membranes 54a and 54b, a disc-shaped retaining ring 122 is clamped, which has a central opening 124. In this is a two-piece Packing 112 inserted, and the retaining ring 122 is clamped between the two halves 112a and 112b of the filling body 112. Alternatively, it is also possible that in the filling body 112, a circumferential groove is present, into which the edge of the opening 124 of the retaining ring 122 engages. Also, a one-piece design of the retaining ring 122 with the packing 112 is conceivable.

Yet another variant of a pressure damper 36 is in FIG. 13 shown. In this pressure damper 36, no filler is present, so that this device is constructed similar to those in the FIGS. 4 and 5 is shown. The differences relate in particular to the clamping rings 82 and 84, with which the membranes 54a and 54b are held on the housing 40 and 38: The clamping rings 82 and 84 have cantilevered spring portions, wherein a spring portion 118a and 120a, the membranes 54a and 54b in FIG. 13 positioned in the vertical direction, whereas a spring portion 118b and 120b, the two membranes 54 and 56 in FIG. 13 positioned or centered in the horizontal direction.

The spring sections 118a and 120a are formed by individual radially inwardly facing brackets of the two clamping rings 82 and 84, which in the in FIG. 13 shown mounting position against the upper part 40 and the lower part 38 of the housing are biased. The spring sections 118b and 120b, in turn, are formed by individual radially outwardly acting brackets which abut against the inner circumferential surface of the upper part 40 of the housing 40 and are biased against it.

In FIG. 14 a further modified embodiment of a pressure damper 36 is shown. This is at the radially outer edge of the bead portion 76th a tubular attachment portion 122 is provided which extends approximately parallel to the central axis 41 of the pressure damper 36 and is welded in its edge to the housing 40 in FIG. 57. Ultimately, therefore, the membrane 54 is attached directly to the housing 40, which saves otherwise required additional designs. In addition, the pressure damper 36 in FIG. 14 a clamping ring 124, which presses the mounting portion 122 from radially inwardly against the housing 40. As a result, the weld 57 is mechanically relieved. The radially maximum outer weld 57 allows the use of the entire inner diameter of the housing 40 as a hydraulically effective diameter. This lowers the manufacturing costs.

The gas volume 58 can be established either during the production of the weld seam 57 (welding in a pressure chamber). Or the working space 66 is subsequently filled via the opening 60, which is then closed by the element 62. The latter can be welded to the housing 40, for example. As in the embodiments of the FIGS. 9 to 11 is also at the in FIG. 14 shown pressure damper 36, the gas volume 58 between the diaphragm 54 and the housing 40 is formed. This leads to a minimization of the required installation space.

Claims (30)

1. Device (36) for damping pressure pulsations in a fluid system (16), in particular in a fuel system of an internal combustion engine, having a housing (38, 40) and having at least one working chamber (66) which communicates at least in regions with the fluid system (16), wherein within the working chamber (66) there is provided at least one gas volume (58) which is sealingly closed off by a diaphragm (54), characterized in that the gas volume (58) is delimited by at least two diaphragms (54a, 54b) which are clamped (82, 84) in the region of their edges, and one diaphragm (54a) has at least one abutment portion (80a) which, when the diaphragm (54) is at a maximum deflection, comes into contact with a counterpart surface (80b) formed on the other diaphragm (54b).
2. Device (36) according to one of the preceding claims, characterized in that the diaphragm (54) is composed of metal.
3. Device (36) according to Claim 2, characterized in that the diaphragm is delimited by a thin-walled metal tube (54) which is closed off in a gas-tight fashion at its ends.
4. Device (36) according to one of the preceding claims, characterized in that at least one outer wall of the working chamber is likewise in the form of a diaphragm.
5. Device (36) according to one of the preceding claims, characterized in that the enclosed gas volume (58) has a defined pressure, preferably a positive pressure, when a standard outside pressure prevails.
6. Device (36) according to Claim 5, characterized in that the gas volume (58) has a closable opening (60) by means of which the pressure can be adjusted.
7. Device (36) according to one of the preceding claims, characterized in that the diaphragm (54) has at least one bead (78).
8. Device (36) according to Claim 7, characterized in that the diaphragm (54) has a plurality of beads (78) which have different heights and/or different profiles and/or different cross sections.
9. Device (36) according to one of the preceding claims, characterized in that the enclosed gas volume (58) is reduced by a filled region (112).
10. Device (36) according to one of the preceding claims, characterized in that the diaphragms (54a, 54b) are, on the whole, substantially parallel.
11. Device (36) according to Claim 10 in conjunction with Claim 10, characterized in that the gas volume (58) is formed between the two diaphragms (54a, 54b) and the two diaphragms (54a, 54b) have in each case at least one abutment surface (80a) and a counterpart surface (80b) respectively which make contact when the two diaphragms (54a, 54b) are at a maximum deflection.
12. Device (36) according to one of the preceding claims, characterized in that the edges of the two diaphragms (54a, 54b) are sealingly connected to one another and are clamped (82, 84) radially inward of the sealing line (57).
13. Device (36) according to Claim 12, characterized in that the clamping (82, 84) has structural elasticity (118, 120).
14. Device (36) according to one of the preceding claims, characterized in that the two diaphragms (54a, 54b) are identical.
15. Device (36) according to one of the preceding claims, characterized in that the working chamber (66) is divided by the two diaphragms (54a, 54b) into two regions (64, 68) which communicate with one another by means of a fluid connection (70).
16. Device (36) according to one of the preceding claims, characterized in that an annular spacer (46) is provided between the two diaphragms (54a, 54b).
17. Device (36) according to Claims 15 and 16, characterized in that the fluid connection (70) is formed in the spacer.
18. Device (36) according to one of the preceding claims, characterized in that it is integrated into a housing (92) of a fuel pump (18).
19. Device (36) according to one of the preceding claims, characterized in that the working chamber comprises an annular chamber (66), and the gas volume (58) is annular.
20. Device (36) according to Claims 18 and 19, characterized in that the working chamber (66) and the gas volume (58) are arranged in or on a cylinder (92) of a fuel pump (18), at least approximately coaxially with respect to the cylinder axis (90).
21. Device (36) according to either of Claims 19 and 20, characterized in that the gas volume (58) is arranged in the manner of a spiral within the annular chamber (66), wherein the spiral (58) and the annular chamber (66) are at least approximately coaxial.
22. Device (36) according to Claim 21, characterized in that the spiral-shaped gas volume (58) is preloaded against the outer wall of the working chamber (66).
23. Device (36) according to either of Claims 21 and 22, characterized in that the spiral-shaped gas volume (58) runs in helical form in the axial direction of the working chamber (66).
24. Device (36) according to Claim 23, characterized in that the spiral-shaped and helical gas volume (58) is preloaded in the axial direction against the face ends of the working chamber (66).
25. Device (36) according to one of the preceding claims, characterized in that the gas volume (58) is filled with helium.
26. Device (36) according to one of the preceding claims, characterized in that the diaphragm (54) and/or the housing are magnetic at least in regions.
27. Device (36) according to one of the preceding claims, characterized in that the diaphragm (54) is produced at least partially from a material strip which has internal stresses.
28. Device (36) according to one of the preceding claims, characterized in that the diaphragm (54) comprises at least one bead portion (76) and at least one bellows portion (110).
29. Device (36) according to one of the preceding claims, characterized in that the diaphragm (54) has, at its radially outer edge, a fastening portion (122) which extends approximately parallel to the central axis (41) and which is fixed to the housing (40).
30. Device (36) according to Claim 29, characterized in that it comprises a clamping device (124) which loads the fastening portion (122) radially against the housing (40).

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