ES2393308T3 - Device for damping pressure pulsations in a fluid system, especially in a fuel system of an internal combustion machine - Google Patents

Abstract

Device (36) for damping pressure pulsations in a fluid system (16), especially in a fuel system in an internal combustion machine, with a housing (38, 40) and with at least one working area (66 ), which at least in certain areas communicates with the fluid system (16), where within the work area (66) there is at least one volume of gas (58) sealed tightly by a membrane (54) , characterized in that the volume of gas (58) is limited by at least two membranes (54a, 54b), which are held in the area of its edges (82, 84) and a membrane (54a) has at least one section of stop (80a), which in case of a maximum deviation of the membrane (54) joins a contact surface (80b) that is in the other membrane (54b).

Description

Device for damping pressure pulsations in a fluid system, especially in a fuel system of an internal combustion machine

Current state of the art

The present invention refers to a device for damping pressure pulsations in a fluid system, especially in a fuel system in an internal combustion machine, with a housing and with at least one work area, which by at least in certain areas it contacts the fluid system.

A device of this type is known from the application DE DE 195 39 885 A1. It shows a fuel system of an internal combustion machine with direct fuel injection. The fuel is driven from a pre-supply pump to a high pressure plunger pump, which compresses the fuel at a very high pressure. From the high pressure plunger pump, the fuel reaches the fuel manifold ("rail"). The high pressure plunger pump is driven by a camshaft of the internal combustion machine. In order to adjust the flow rate of the high-pressure piston pump independently of the revolutions per minute of the cam shaft, a flow regulation valve is provided. With this, during a pumping run, the pumping chamber of the high-pressure plunger pump can be momentarily connected to the area of the fuel system that is between the electric preset pump and the high-pressure fuel supply pump .

In that way, however, considerable pressure pulsations occur in that area of the fuel system. To dampen them, a pressure damper is provided. This is composed of a housing and a piston, which is prestressed by a spring.

A pressure absorber that works with a rubber membrane prestressed by a spring is known in the market. So that in systems without pressure (for example in an internal combustion machine turned off), the rubber membrane does not expand over time, there is a stop on which the membrane rests when low pressure is present.

In the fuel system known from application DE 195 39 885 A1, the pressure between the presupply pump and the high pressure plunger pump is more or less constant. But in modern fuel systems this pressure can be variable. Typically, the pressure is between 0.5 and 8 bar, where there must also be an overload safety of approx. 10 to 12 bar If the known pressure damper, which has a rubber membrane, is used in such a fuel system, there is a danger that in the case of a low system pressure, for example 0.5 bar, and with pressure pulsations superimposed, the membrane collides with the stop. In this way the attenuating effect of the pressure damper is weakened and damage to the rubber membrane can occur. The pressure damper known by the application DE 195 39 885 A1 with a piston and a spring, on the other hand, in use in a fuel system like that, with a very variable initial pressure, should be very large.

Application NLC21 016 384 describes a damping device that contains a volume of gas tightly insulated in a work area by means of a membrane. The current state of the art also refers to applications US 6 079 450, EP 1 342 911 A2, EP 0 950 809 A2, US 3 366 144, US 3 948 288, JP 167299 A and US 6,062,830

The present invention therefore has as its object, to develop a device like the one mentioned at the beginning, so that it can be used in a fuel system with variable initial pressure, which, however, is smaller and has a long durability.

This object is achieved by a device with the characteristics of claim 1.

Advantages of the invention

With the use of an isolated gas volume, the compressibility of the gases can be used to ensure the elastic movement of the membrane, necessary to dampen the pulsations of pressure. Thus, the membrane does not apply any type of mechanical element that can reduce its durability and increase the risk of damage. In addition, such a volume of gas can be made in almost any geometric shape. Therefore, to save space, it can be housed in the fluid system. Another advantage of a device according to the invention is that a spill line can be dispensed with, which further simplifies the design of the fuel system.

According to the invention, at least two membranes, fastened in the area of their edges, limit the volume of gas. A pressure damper of this type is constructed comparatively flat. And even more, when the membranes are essentially parallel. It is also entirely possible that the volume of gas is introduced into the area between the two membranes during their coupling, so that a filling opening can be dispensed with.

By limiting the maximum deviation of the membrane, damage to the membrane can be avoided in time, for example a plastic deformation. Therefore, this device is, at least in a certain area, "safe against overloads", that is to say that also with overloads it has a damping function, without being damaged.

One membrane has at least one stop section and the other at least one contact surface, which meet in case of a maximum deviation of the two membranes. In this way, it is taken advantage of the fact that, in the case of a high pressure, the two surfaces of the membranes move successively. When they come into contact, they support each other. This does not require a separate stop.

Advantageous developments of the invention are presented in the secondary claims.

In a first development it is proposed that the membrane be made of metal. Such a membrane has different advantages: On the one hand, such a membrane is very tight compared to conventional gases and fluids. The high tightness of metal membranes against hydrocarbon emissions plays a particularly positive role here. On the other hand, overdilation does not occur over time in a metal membrane, nor with low pressures, for example when the internal combustion machine is turned off; so that a damping device with a metal membrane can be used in a fluid system that has variable fluid pressure over a large area.

It is also advantageous that the volume of gas is formed by a thin-walled metal tube and that at its ends it is sealed tightly to the gas. This is very easy to perform and economical.

If at least one outer wall of the work area is also designed as a membrane, an additional surface area of good hydraulic performance is obtained in a minimum construction space. The effectiveness of the device according to the invention is again considerably increased, with the same or less need for space.

It is especially advantageous if the volume of gas enclosed has a defined pressure, preferably an overpressure, with a normalized external pressure (eg 1013 hPa). With a defined pressure like that, the "spring stiffness" can be adjusted. Normally, in the volume of gas enclosed, an overpressure is selected with respect to the external pressure, since in this way the entire possible range of tension (stretching and pressure) of the membrane material can be used.

You can also think of a negative pressure or a normal pressure. Preferably an internal overpressure is chosen, which is approximately half of the maximum operating overpressure, subtracting the increase in pressure that arises from the compression of the part.

The efficiency of the gas volume can be optimized by minimizing the volume of gas enclosed. With such a minimalization, greater rigidity of the spring is achieved. In this way, the membrane can be thinner and tensions in the membrane material can be minimized. In addition, throughout the work area, the device works without impact. On the other hand, the load on the entire work area is reduced, since the pressure difference on the membrane wall is reduced by means of the enclosed internal pressure. With this, the geometry of the membrane can be designed for greater career paths and lower pressure load or lower mounting volume.

The volume of gas can have an opening with a lock, by means of which the pressure can be regulated. This facilitates the manufacture of the gas volume. Otherwise, the manufacturing should be done for a given pressure.

The design of the device according to the invention in which the membrane has at least one molding is especially advantageous. Such a molding can decisively influence the spring characteristics of the membrane itself and also its spring stiffness characteristics. With such a molding the membrane can be optimally adapted to the individual needs of the fluid system. The shock absorber with a similar constructive volume may have more damping volume or be constructed in a smaller size. Thus, the moldings can have different height and / or a different path and / or a different cross section.

In this way, a stiffness of the membrane spring that is asymmetric can be achieved, according to the load direction.

In this way, a certain flexibility of the membrane spring, for example constant or more elastic, can be achieved in the main working area of the pressure damping device. In less used areas of operation, on the contrary, the rigidity may be greater. Thus a characteristic curve of non-linear or partially linear elasticity can be achieved. Finally, in this way an optimum damping effect can be achieved in the entire fluid system operating area with a smaller construction space.

The moldings can be formed in such a way that the maximum tension does not reach the edge of the membrane and the mechanical stresses are distributed on the surface of the membrane in the most homogeneous way possible. Furthermore, by means of a corresponding membrane design, the entire bandwidth of the material in the area of tension and compression tension can be used.

It can also be provided that the membrane has at least one abutment area, which in case of a maximum deviation of the membrane joins a contact surface. The maximum deviation is chosen in such a way that damage to the membrane is avoided in time, such as plastic deformation. Therefore, this device is, at least in a certain area, "safe against overload", that is to say that also with overloads it has a damping function, without being damaged.

In a further development it is recommended that the contact surface in the housing be located in a space separated from the volume of gas between both membranes and that the two membranes have at least one stop or contact surface, which are touched in case of a maximum deviation of the membranes. In this way, it is taken advantage of the fact that, in the case of a high pressure, the two surfaces of the membranes move successively. When they come into contact, they support each other with the stop surfaces. The stop surfaces may be designed flat, to maintain an orderly arrangement between the membranes. In this way, an overload of the membranes is safely ruled out in case of high pressure, without the need for a separate stop.

Also the edges of the two membranes can be tightly connected to each other and radially held inwards by the sealing line. Especially when the joint is made by welding, this design of the device according to the invention prevents welded joints from having to withstand additional mechanical forces. The hermetic joint is only for the tight seal and must not perform other tasks, so it can meet especially high tightness requirements. To assess the firmness of the shock absorber according to the invention, it is only necessary to observe the membranes.

It is especially advantageous when the fastener has a consecutive elasticity. In this context, such elasticity is what is "constructively planned." For example, an elastic rubber support ring can be used, or a metal support can be used, which has a spring section. This ensures a secure fixation of the membranes on the one hand and, on the other, manufacturing tolerances can be equated. Basically, the fastener can be attached to any part of the membrane, however a joint in the mid-plane of the two membranes is more suitable.

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

The construction space of the device according to the invention is especially small, if the working area of the two membranes is divided into two fluid areas, which communicate with each other by means of a fluid union.

A ring-shaped separator between the two membranes simply defines or increases the volume of gas enclosed. In this case, to improve the price, it is possible to design the fluid union that joins the two fluid areas of the work area directly in the spacer.

It is especially advantageous when the device is integrated in a housing of a fuel pump. In this way the advantages according to the invention become especially evident, since such a fuel pump generally must be very small.

In fuel pumps you can often find circular areas in which axes or plungers are located. In these cases, the damping device according to the invention can be placed so that it occupies very little space, when the work area covers an annular space and the volume of gas is also ring-shaped. Especially advantageous is that the work area and the volume of gas are located in a cylinder of a fuel pump at least more or less coaxially with respect to the axis of the cylinder. The pressure damper thus surrounds the cylinder and the piston in it, which generates additional sound insulation.

It is also recommended that the volume of gas be spirally located in the annular space, where the spiral and the annular space are more or less coaxial. Through a spiral like that, a large deformation surface is produced that contributes to a particularly efficient attenuation of pulsations.

When the spiral-shaped gas volume is prestressed against the outer wall of the work area, a fixation of the gas volume in the work area is generated without additional parts.

The effective surface of the gas volume can be raised again if the spiral-shaped gas volume extends helically in the axial direction of the work area.

This makes it possible to fix the gas volume without additional parts when the spiral and helical gas volume is prestressed axially against the front ends of the work area.

Another preferred design of the device according to the invention is characterized in that the gas volume is filled with helium. This facilitates the detection of an escape.

In addition, the membrane and / or the housing can be magnetic. By means of corresponding manufacturing procedures (for example laminate and mechanical stamping) in the material a martensitic texture (martensite of avenue) is achieved, which has magnetic characteristics. If this magnetic characteristic is intentionally maintained in the corresponding part, the device can trap magnetic dirt particles that are in the fluid and keep them from dispersing. This increases the reliability of the components included in the fluid system, for example of a pump. In addition, costs are saved, since the costly demagnetization of the piece is avoided. Since there are no moving parts in the device that are next to each other and juxtaposed, the trapped dirt particles do not cause any damage to the device's operation.

In addition, the membrane can be manufactured from a web material that has its own tensions. The tensions themselves generate a flat distortion during the transformation process, so that the material in the distorted state is rejected. This can be used intentionally to simplify the fabrication of the membrane capsule, especially when it has at least one section of bellows. Due to the distortion it is no longer necessary to intentionally separate the areas of the membrane that are next to each other flat when there is no pressure. The safe evacuation of the membrane and the filling of the gas volume, for example with helium, can be carried out simply and reliably.

The assembly sequence can be performed as described below: First, each of the sections ("segments") of the membrane are placed successively and "stacked" in a welding device. After welding, the internal space is evacuated and filled with filling gas, for example helium, with the desired pressure. In this phase it is ensured by the twisted sections of the membrane that the filling gas enters all the cavities. Then the sections are compressed and welded together.

In another advantageous design of the device according to the invention, the membrane has at least one section of moldings and one section of bellows. This allows the combination of the advantages of the two designs.

Furthermore, it is preferred that the membrane has a clamping section on its outer radial edge, which extends more or less parallel to the central axis and is fixed to the housing. In this way, the entire inner diameter of the housing can be used effectively for hydraulics, which minimizes the necessary construction space and reduces costs.

The device may also have a tensioner that pressurizes the radial clamping section against the housing. The tension device may be designed, for example, as a tension ring. This tensioner relieves the membrane fixation to the housing.

Drawings

Preferred embodiments of the present invention are explained below with reference to the corresponding detailed drawing. The drawing shows:

Figure 1: A systematic representation of a fuel system of an internal combustion machine with a fuel pump and a device that is in the system and serves to dampen pressure pulsations.

Figure 2: A cross-section of a first embodiment of the device for damping pressure pulsations of Figure 1.

Figure 3: A detail III of the device for damping pressure pulsations of Figure 2.

Figure 4: A cross section of a second embodiment of the device for damping pressure pulsations of Figure 1.

Figure 5: A detail V of the device for damping pressure pulsations of Figure 4.

Figure 6: A schematic section of a membrane of the device for damping pressure pulsations of Figure 4.

Figure 7: A cross section of a fuel pump with a third embodiment of a device for damping the pulsations of pressure.

Figure 8: A cross-section of an area of the fuel pump of Figure 7 with a fourth embodiment of a device for damping pressure pulsations.

Figure 9: A cross section of a fifth and a sixth embodiment of a device to dampen pressure pulsations.

Figure 10: A cross section of a seventh exemplary embodiment of a device for damping pressure pulsations.

Figure 11: A cross-section of an eighth embodiment of a device for damping pressure pulsations.

Figure 12: A cross-section of a ninth example of embodiment of a device for damping pressure pulsations.

Figure 13: A cross-section of a tenth embodiment of a device for damping pressure pulsations.

Figure 14: A cross section of an eleventh and twelfth example of a device for damping pressure pulsations.

Description of the embodiments

In Figure 1 the fuel system of an internal combustion machine has together the reference sign 10. The internal combustion machine is not shown in detail.

The fuel system 10 comprises a fuel container 12, from which an electric fuel pump 14 pumps the fuel into a low pressure fuel line. The low pressure fuel line 16 leads to a high pressure fuel pump 18, which is symbolically represented by lines and points.

The high-pressure fuel pump 18 comprises a pumping chamber 20, which is limited by a piston that is not shown in Figure 1. The piston is put in a round-trip movement by a transmission shaft that is also not represented. The drive shaft, in turn, is driven by the camshaft of the internal combustion machine, which is also not represented. The high pressure fuel pump 18 also includes an intake valve 22, which is designed as a check valve. In addition, an evacuation valve is provided, which is also comprised of a check valve.

The high pressure fuel pump 18 compresses the fuel at a very high pressure and conducts it to a fuel collection line 26 ("rail"). The fuel is introduced into it under high pressure. Several fuel injection devices 28 are connected to the fuel collection line 26. They inject the fuel directly into their combustion chambers 30.

In order to be able to adjust the flow rate of the high pressure fuel pump 18 independently at the revolutions per minute of the drive shaft, a flow regulating valve 32 is provided. This is actuated by a magnetic actor 33, which is driven by a control and a device that are not represented. The flow regulating valve 32 is designed such that during a pumping stroke of the high pressure fuel pump 18 the intake valve 22 can be forced open. For this, the fuel under pressure in the pumping chamber 20 is not taken to the fuel collection line 26, but back to the low pressure fuel line 16. The commissioning position of the regulating valve of the flow 32 bears the reference sign 34.

The pressure pulsations that occur in the low pressure fuel line 16 are attenuated by a device to dampen the pressure pulsations. This bears the reference sign 36 in Figure 1 and will then be briefly referred to as a "pressure damper." Pressure damper 36 is constructed as follows (see Figures 2 and 3):

The pressure damper 36 comprises a housing with a lower part 38 and an upper part 40. In the section shown in Figure 2, the lower part is shaped like a fungus, that is to say it is basically rotationally symmetrical with a central axis 41. an installation section 42 with a feed channel 43 located in the center thereof and a base section 44, generally in the form of a plate, and in the view from above in the form of a circle, whose surface is at a right angle with the central axis 41. The upper part 40 of the housing also has a plate shape and in the view from above it has a circle shape.

Between the base section 44 of the lower part 38 of the housing and the upper part 40 of the housing is a ring-shaped spacer 46. This is fixed by means of welds 48a and 48b on one side with the base section 44 of the lower part 38 of the housing and, on the other hand, is welded with the upper part 40 of the housing. In a ring-shaped retention section 52, which extends radially inwardly next to the spacer 46, two membranes 54a and 54b are fixed, which in the top view are circular in shape. Fixing is done by means of rotary welds 57a and 57b on the outer edge of membranes 54a and 54b (see fig. 3). Both membranes 54a and 54b are thin-walled and metal, preferably stainless steel.

Between the upper membrane 54a and the lower membrane 54b and the spacer 46 is an enclosed gas volume 58. The gas is introduced through a channel 60, which is located in the ring-shaped spacer 46 (see Figure 2). After introducing the gas in volume 58 between the two membranes 54a and 54b, the channel 60 is closed with a sphere 62. The entire area between the base section 44, the upper part 40 of the housing and the spacer 46, forms a work area 66. The volume of gas 58 is then located in the work area 66.

Between the base section 44 of the lower part 38 of the housing and the lower membrane 54b is a first fluid chamber 64 of the working area 66. Between the upper part 40 of the housing and the upper membrane 54a is a second fluid chamber 68 of the work area. Both fluid chambers 64 and 68 can communicate with each other via a channel 70 in the ring-shaped separator 46.

The two membranes 54a and 54b are constructed identically (for reasons of clarity, only reference signs for the upper membrane 54a are included in Figure 3). On their outer radial edge they have a retention section 72 that runs radially, with which they are welded to the ring-shaped spacer 54b. From the retention section 72 of the membranes a spring section 74 rotates at an angle of approximately 80 °. The spring section 74 then runs in a relatively axial direction. Next to the spring section 74 is a section of moldings 76. This is highlighted by several deviated moldings 78. The moldings 78 run concentrically around the central axis 41 of the pressure absorber 36. A central area of the two membranes 54a and 54b is designed flat. The corresponding area in the membrane 54a is called the stop section 80a, the corresponding area in the membrane 54b is called the contact surface 80b (see Figure 2). The pressure damper 36 works as follows:

Through the feed channel 43 in the installation section 42, the fluid chamber 64 in the lower part of Figures 2 and 3 (the concepts "lower" and "upper" refer to the figures below always; the shock absorber pressure can be located in the space arbitrarily) of the work area 66 communicates with the low pressure fuel line 16. Through the channel 70, the upper fluid chamber 68 of the work area 66 is communicated to its once with the lower fluid chamber 64. Within the work area 66 is the volume of gas 58 limited by the two membranes 54a and 54b and the ring-shaped separator 46. This, when the fuel system 10 is at rest, It is under a slight lower pressure than the outside atmosphere. Through this lower pressure, the molding section 76 and the stop section 80a or the contact surface 80b of the two membranes 54a and 54b is somewhat arched outwards.

However, the distance between both membranes 54a and 54b and the sections of the housing that are next to them 44 or 40 is so great that also in the resting state, that is in the fuel system without pressure, the contact is discarded. of the two membranes 54a and 54b with the corresponding sections 40 and 44 of the housing. Such a limitation of the "lifting" of the membranes is possible thanks to the use of metal as a material for the membranes.

The distance of the membranes 54a and 54b of the housing 40 or 44 is selected such that at a system pressure less than 100 kPa, in case of a lower pressure pulse, the membranes 54a and 54b do not touch the housing 40 or 44. This ensures the damping function of the pressure absorber 36 also in this operation or pressure range.

When the fuel system 10 is in operation and the electric fuel pump 14 pumps with a certain pressure, the two membranes 54a and 54b move successively. The pressure in the gas volume 58, on the one hand, and the stiffness of the two membranes 54a and 54b, on the other, are selected such that at a normal operating pressure in the low pressure fuel line 16, that is, between 0.5 and 8 bar, there is no contact between the two membranes 54a and 54b with each other. Thus, in this normal operation of the fuel system 10, the pressure fluctuations can be absorbed and damped without problems by a corresponding movement of the two membranes 54a and 54b and a compression of the gas volume 58.

In case of an overpressure in the low pressure fuel line 16, when the pressure for example rises to more than 10 bar, the stop section 80a of the membrane 54a and the contact surface 80b of the membrane 54b come into contact. The two membranes 54a and 54b cannot continue moving, so that an overload of the two membranes 54a and 54b can be ruled out. So that a neat arrangement of the two membranes 54a and 54b can be ensured in the event of an overload in the low pressure fuel line 16, the stop section 80a and the contact surface 80 are designed flat or bulged.

Next to the gas volume pressure 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 ring-shaped separator 46. This height has an influence especially on the pressure with which the membranes 54a and 54b are touched.

Furthermore, by means of a suitable design of the internal geometry of the retention section 52 (for example at position 53 in Figure 3) the internal volume can be reduced if desired. In that way, the efficiency of the pneumatic springs formed by the volume of gas 58 enclosed can be further increased.

Also the shape of the moldings 78 and their quantity have an important role in the characteristics of the pressure absorber 36. In a membrane with a diameter of 30 to 60 mm and a wall thickness of 0.2 to 1.0 mm, the quantity of three to six moldings with different thicknesses has proved advantageous. The height of the molding can vary between +/- 0.15 and 2 mm. The molding can be circular, sinuous or spline shaped.

In this way an asymmetric spring rigidity can also be achieved in a load of the membranes 54a and 54b in Figures 2 and 3 from below and from above. In this way, in the most common operating pressure areas of the fuel system or the low pressure fuel line 16, it is possible to achieve low rigidity while maintaining a constant spring flexibility, while in the less used operating areas, for example, with a very low pressure in the low pressure fuel line or even with a very high pressure, a greater rigidity of the membranes 54a and 54b occurs.

By means of the shape of the moldings 78 and the design of the spring section 74 it is achieved that the maximum tensions do not occur at the outer edge of the two membranes 54a and 54b, but are distributed homogeneously over the diameter of the two membranes 54a and 54b.

From now on, reference will be made to Figures 4, 5 and 6. Here, a second embodiment of a pressure damper 36 is shown. The areas and elements having functions equivalent to the areas and elements of the embodiment shown in Figures 2 and 3 have the same reference signs. They will not be explained again in detail.

A fundamental difference between the two embodiments is that there is no separator in the pressure absorber shown in Figures 4 and 5. Instead, the upper part 40 and the base section 44 of the housing are welded directly together. The corresponding weld bears the reference sign 48. Accordingly, the two retention sections 72a and 72b of the two membranes 54a and 54b are also welded directly to each other (weld 57).

Furthermore, they are held against each other, in a radial position retracted from the weld 57, with which the two membranes 54a and 54b are welded together in a gas tight manner, by means of an upper fixing ring 82 and a fixing ring lower 84, which are located in the upper part 40 or in the base section 44 of the housing. In this way, the welding with which the two membranes 54a and 54b are joined is released from the mechanical loads.

By means of a fluid joint 70, shown in Figure 5 only with broken lines, which is formed by perforations in the fixing rings 82 and 84, the two fluid chambers 64 and 68 of the work area are joined . The perforations 70 should be chosen in such a way that both membranes 54a and 54b receive as much as possible the same load.

Figure 6 shows the lower membrane 54b in schematic representation. The depth of the membrane 54b is signaled with A, which corresponds to the highest possible elevation. B indicates a transition area and C the height of the membrane depression 54b.

A partial cut through a fuel pump is shown in Figure 7, such as that used for example as a high pressure fuel pump 18 in the fuel system 10 represented in Figure 1. A housing of the cylinder 92 with a plunger 88, which limits the pumping chamber 20. The flow regulating valve 32 is recognized in the upper area of the fuel pump 18. The drain valve 24 is located in the left area. The intake valve 22 is designed as a spring-loaded saucer valve, which can be brought to an open position by a pusher (without reference sign) of the flow regulating valve 32 during a piston pumping stroke 88.

Coaxially with respect to a central axis of the cylinder 90, a rotary step 94 is incorporated in the outer limitation surface of the cylinder housing. A casing shell 96 is pushed thereon. By means of the rotary step 94 and the sleeve a rotating annular space 66 about a central axis of the cylinder 90 is achieved from the housing 96. This communicates by means of a channel 100 with a low pressure inlet 102 of the fuel pump 18. On the other hand, it communicates by means of a channel 104 with a depressurization groove 106, which is in the bore of the cylinder 108, in which the plunger 88 is located.

In the annular space 66 there are two ring-shaped rotating membranes 54a and 54b. Its outer edges are welded by means of welds 57a to 57d with the cylinder housing 92, on the one hand, and with the housing sleeve 96, on the other. In this way two volumes of gas 58a and 58b separated from each other are achieved. Among these is the fluid area 64 of the work area 66, which communicates primarily through the channel 100 with the low pressure inlet 102. The annular space 66 and the gas volumes 58a and 58b thus form a pressure damper 36, which is located coaxially towards the central axis of the cylinder 90 of the high pressure fuel pump 18.

A modified embodiment of a ring-shaped pressure damper 36 is shown in Figure 8. The elements and areas having functions equivalent to the elements and areas of the pressure damper 36 represented in Figure 7 have the Same reference signs. They will not be explained again in detail.

The pressure damper 36 shown in Figure 8 comprises a flattened metal tube 54, which at its ends is welded tightly to the gas. Its interior forms a volume of gas 58. The metal tube 54a is wound in the working area 66 in the form of a spiral spiral towards the central axis of the cylinder. In this way, this is under an initial tension, on the one hand with respect to the housing bushing 96 and, on the other, with respect to the upper and lower front surfaces of the work area 66, shown in Figure 8; which is fixed.

In Figure 9 another variant of a pressure damper 36 is shown. Here and in all the following figures, the elements and areas having functions equivalent to the elements and the areas of which were already mentioned in relation to the previous figures, They have the same reference signs. They will not be explained again in detail in normal cases.

The pressure damper 36 shown is designed differently in the left half of Figure 9, than in the right half. Both devices 36 have in common the fact that they have a single membrane 54. This is welded in the area of its abutment section 72 and 57 with the upper part 40 of the housing. Unlike the membrane of Figures 2 and 3, the membrane shown in Figure 9 54 has a bellows section 110, which is located between the molding section 76 and the stop section 72 and is constructed from individual segments 110a to 110d. This bellows section 110 allows a relatively large modification of the volume of gas 54 enclosed by the membrane 54 and the housing 40.

The volume of gas 58 is generally reduced because between the membrane 54 and the upper part 40 of the housing a filling body 112 is fixed next to the upper part of the housing 40. In the left half of Figure 9 extends a stop section 80a of the molding section 76 of the membrane 54 in the direction of the lower part of the housing 38, while in the right half of figure 9 the stop section 80a extends towards the filling body 112. Depending on the case, the filling body 112 or the lower part of the housing 38 acts as a contact surface 80b for the stop section 80a.

The volume of gas 58 enclosed by membrane 54 is filled with helium. This is under a negative pressure, which corresponds approximately to half of the maximum negative pressure that occurs in operation, minus the increase in pressure that is produced by compression of the membrane 54. For membrane 54, it is used a magnetic metal material. In this way, the pressure damper 36 acts as if it were a "vacuum cleaner", since it traps the magnetic dirt particles of the fluid and prevents its distribution in the fluid system 10.

In addition, for the production, especially of the bellows section 110 of the membrane 54, a web material is used that has its own tensions, which lead to a flat distortion of the individual segments 110a, 110b, 110c and 110d. This means that, during the manufacture of the bellows section 110, the individual segments 110a, 110b, 110c and 110d are never so close together that an evacuation of the air and a filling with helium cannot be reliably possible. One admissible way of proceeding in the manufacture of the bellows section 110 is as follows:

First, the individual elements 110a to 110d of the bellows section 110 are stacked in a welding device (not shown). Then the welding device is closed and its internal space is evacuated. The internal space of the welding device is then filled with helium to a desired internal pressure. Thanks to sections 110a to 110d of the bellows section 110 that present a distortion, it is ensured that helium also enters reliably into the corresponding cavities. The individual elements 110a to 110d are then compressed and welded at 114 (for reasons of clarity this reference sign is included only in a position on the left side of Figure 9).

An alternative to this is shown in Figure 10. The pressure damper 36 shown in Figure 10 differs from that in Figure 9 because instead of having a separate filling body 112 in the upper part of the housing 40, there is a section 112 formed by deep drawing, which reduces the volume of gas enclosed 58, on the one hand, and also has the contact surface 80b, which acts in conjunction with the stop section 80a of the membrane.

Figure 11 shows an embodiment in which there is a separate filling body 112, which however is not hollow but solidly designed and also has a smaller diameter in an area oriented towards the stop section 80a of the membrane 54. Thus, the contour of the filling body 112 of Figure 11 is adapted to the contour of the membrane 54, so that the corresponding volume of gas 58 is especially low.

An embodiment is shown in Figure 12 in which two membranes 54a and 54b are found, according to the embodiment of a pressure damper 36 indicated in Figure 4. Unlike that shown in Figure 4, in the embodiment of figure 12, in each membrane 54a and 54b there is a bellows section 110, which is nevertheless designed more simply than that of figures 9 to 11. The pressure damper shown in figure 12 presents, in a manner analogous to that of Figures 4 and 5, fixing rings 82 and 84, which in Figure 12 are shown only schematically. Through these, the effective hydraulic surface of the membranes 54a and 54b is maximized, which can be used to reduce the overall construction size of the pressure absorber 36. The clamping rings 82 and 84 are supported by spring sections 118 and 120 in the upper part 40 or lower 38 of the housing. In this way, the manufacturing tolerances of membranes 54a and 54 b can be equated.

Between both membranes 54a and 54b there is fixed a disk-shaped support ring 122, which has an opening 124 in the center. In the opening a two-piece filling body 112 is placed and the support ring 122 is fixed between the two halves 112a and 112b of the filling body 112. Alternatively, it is also possible that the filling body is located a rotating groove, in which the opening edge 124 of the support ring 122 meshes. An embodiment of a support ring 122 with the filling body 112 is also possible.

Another variant of a pressure absorber 36 is shown in Figure 13. In this pressure absorber 36 there is no filling body, so that this device is designed similarly to that shown in Figures 4 and 5. The differences they are found mainly in the fixing rings 82 and 84 with which the membranes 54a and 54b are attached to the housing 40 and 38: The fixing rings 82 and 84 have protruding spring sections, where a spring section 118a or 120a position the membranes 54a and 54b in Figure 13 in the vertical direction, while a spring section 118b or 120b positions or centers the membranes 54 and 56 in Figure 13 in the horizontal direction.

The spring sections 118a and 120 are formed by the individual arcs of the two clamping rings, radially inwardly extending, which are prestressed in the mounting position indicated in Figure 13 against the upper part 40 or the part lower 38 of the housing. The spring sections 118b and 120b are also formed by the individual arches extending outwards, which are located on the inner side surface of the upper part 40 of the housing or are pressed against it.

In Figure 14 another modified variant of a pressure damper 36 is shown. In this damper, a tube-shaped fixing section 122 is located on the outer radial edge of the molding section 76, which extends further or less parallel to the central axis 41 of the pressure absorber 36 and at its edge it is welded at 57 with the housing 40. Finally, the membrane is fixed directly to the housing 40, which saves additional constructions that in other cases are necessary . In addition, the pressure damper 36 in Figure 14 has a tensioning ring 124, which presses the fixing section 122 from the radial interior into the housing 40. This relieves the mechanical load of the weld 57. Weld 57 which is located in the outer radial maximum allows the use of the entire inner diameter of the housing 40 as a more efficient hydraulic diameter. This decreases manufacturing costs.

The volume of gas 58 can be created during the manufacture of welding 57 (welded in a pressure chamber). Or the work area 66 is subsequently filled by means of an opening 60, which is then closed by the element 62. Finally, the volume of gas can be welded together with the housing, for example. As in the embodiments of Figures 9 to 11, also in Figure 14 the pressure absorber 36 the volume of gas 58 is designed between the membrane 54 and the housing 40. This minimizes the necessary construction space.

Claims (30)

one.

 Device (36) for damping pressure pulsations in a fluid system (16), especially in a fuel system in an internal combustion machine, with a housing (38, 40) and with at least one work area (66), the one that at least in certain areas communicates with the fluid system (16), where within the work area (66) there is at least one volume of gas (58) sealed tightly by a membrane (54), characterized in that the volume of gas (58) is limited by at least two membranes (54a, 54b), which are held in the area of its edges (82, 84) and a membrane (54a) has at least one stop section (80a), which in case of a maximum deviation of the membrane (54) joins a contact surface (80b) that is in the other membrane (54b).

2.

 Device (36) according to one of the preceding claims, characterized in that the membrane (54) is made of metal.

3.

 Device (36) according to claim 2, characterized in that the membrane is limited by a metal tube (54) with a thin wall and closed at its ends in a gas tight manner.

Four.

Device (36) according to one of the preceding claims, characterized in that at least one outer wall of the work area is also designed as a membrane.

5.

 Device (36) according to one of the preceding claims, characterized in that the volume of enclosed gas (58) has a defined pressure, preferably an overload, there is a normalized external pressure.

6.

 Device (36) according to claim 5, characterized in that the volume of gas (58) has an opening with closure (60) by means of which the pressure can be adjusted.

7.

 Device (36) according to one of the preceding claims, characterized in that the membrane (54) has at least one molding (78).

8.

 Device (36) according to claim 7, characterized in that the membrane (54) has several moldings (78), which have different heights and / or a different path and / or a different cross-section.

9.

 Device (36) according to one of the preceding claims, characterized in that the volume of enclosed gas (58) is reduced by a filling area (112).

10.

 Device (36) according to one of the preceding claims, characterized in that the membranes (54a 54b) are basically parallel.

eleven.

 Device (36) according to claim 10 in relation to claim 10, characterized in that the volume of gas (58) is located between the two membranes (54a 54b) and the two membranes (54a 54b) each have at least a stop surface (80a) or a contact surface (80b) that is touched in case of a maximum deviation of the two membranes (54a 54b).

12.

 Device (36) according to one of the preceding claims, characterized in that the edges of the two membranes (54a, 54b) are tightly connected to each other and are radially held inwardly by the sealing line (57).

13.

 Device (36) according to claim 12, characterized in that the fastener (82, 84) has a consecutive elasticity (118, 120).

14.

 Device (36) according to one of the preceding claims, characterized in that the membranes (54a 54b) are identical.

fifteen.

 Device (36) according to one of the preceding claims, characterized in that the work area

(66) between the two membranes (54a, 54b) is divided into two areas (64, 68), which communicate through a fluid junction (70).

16.

 Device (36) according to one of the preceding claims, characterized in that a ring-shaped spacer (46) is located between the two membranes (54a 54b).

17.

 Device (36) according to claims 15 and 16, characterized in that the fluid union (70) is in the spacer.

18.

 Device (36) according to one of the preceding claims, characterized in that it is integrated in a housing (92) of a fuel pump (18).

19.

 Device (36) according to one of the preceding claims, characterized in that the work area comprises an annular space (66) and the volume of gas (58) is ring-shaped.

twenty.

 Device (36) according to claims 18 and 19, characterized in that the work area (66) and the volume of gas (58) are located in a cylinder (92) of a fuel pump (18) in a more or more less coaxial with respect to the axis of the cylinder (90).

twenty-one.

 Device (36) according to one of claims 19 or 20, characterized in that the volume of gas (58) is spirally located in the annular space (66), where the spiral (58) and the annular space (66 ) are more or less coaxial.

22

 Device (36) according to claim 21, characterized in that the volume of spiral-shaped gas (58) is prestressed against the outer wall of the work area (66).

2. 3.

 Device (36) according to one of claims 21 or 22, characterized in that the spiral-shaped volume of gas (58) extends helically in the axial direction of the work area (66).

24.

 Device (36) according to claim 23, characterized in that the spiral and helical gas volume (58) is prestressed in an axial direction against the front end of the work area (66).

25.

 Device (36) according to one of the preceding claims, characterized in that the volume of gas

(58) is filled with helium.

26.

 Device (36) according to one of the preceding claims, characterized in that the membrane (54) and / or the housing can be magnetic in at least some areas.

27.

 Device (36) according to one of the preceding claims, characterized in that the membrane (36) is manufactured from a web material having its own tensions.

28.

 Device (36) according to one of the preceding claims, characterized in that the membrane (54) has at least one section of moldings (76) and at least one section of bellows (110).

29.

 Device (36) according to one of the preceding claims, characterized in that the membrane (54) has on its outer radial edge a clamping section (122), which extends more or less parallel to the central axis (41) and is fixed to the housing (40).

30

 Device according to claim 30, characterized in that it has a tension ring (124), which presses the fixing section (122) from the radial inside towards the housing (40).