Method for producing a sealing element in the form of a corrugated or bellows, sealing element

Abstract

The invention relates to a method for producing a sealing element (1) in the form of a corrugated or bellows, in which at least one more highly loaded area is determined depending on an expected load on the sealing element (1) and the stiffness of the sealing element (1) is locally increased in this area by at least one geometric adjustment, preferably by changing the corrugation or fold height (h), the corrugation or fold width (b) and / or the wall thickness (s) of the corrugated or bellows. The invention further relates to a sealing element (1) in the form of a corrugated or bellows.

Description

The invention relates to a method for producing a sealing element in the form of a corrugated or bellows. Such a sealing element can be used in particular in valves, injectors and / or pumps for media separation. The invention further relates to a sealing element in the form of a corrugated or bellows.Preferred application areas of the invention are valves, injectors and / or pumps that require media separation.Prior ArtThe published patent application DE 10 2010 042 476 A1 describes, by way of example, a device for injecting fuel, which device has a corrugated bellows for sealing a region filled with fuel from a region free of fuel. The corrugated bellows is made of a single-layer metal material and is fastened at one end to a valve needle that can move in a stroke, and at the other end to a bushing that is held in a fixed position in a holding body.A seal in the form of a corrugated or bellows has the advantage that it can be fastened to components which can be moved in the stroke, such as, for example, to a valve needle or to a pump piston, without the stroke movements of the component being restricted as a result. The seal is dynamically stressed, which can lead to very high stress amplitudes in particularly loaded regions, in particular in the end regions of the corrugated or bellows. In these regions, therefore, component failure can occur as a result of continuous oscillation failure. Whether one or both end regions of the corrugated or bellows are highly loaded depends on the specific load. The load, in turn, depends on the stroke, on the speed, on the acceleration and / or on the ambient pressures. If the strength objective is not achieved by a corrugated or bellows, changes must be made to the bellows. For example, the bellows length, the corrugation or fold number and / or the corrugation or fold height can be adapted. However, these changes do not remain without any effects on the installation space requirement, the rigidity and the dynamic behavior and are therefore not always possible or advantageous.The invention is concerned with the problem of remedying this. In particular, an increase in robustness of a sealing element in the form of a corrugated or bellows is to be achieved without relevant influencing of the installation space.To achieve the object, the method having the features of claim 1 is proposed. Advantageous further developments of the invention can be found in the dependent claims. Furthermore, a sealing element in the form of a corrugated or bellows is proposed.Disclosure of the InventionIn the proposed method for producing a sealing element in the form of a corrugated or bellows, at least one more highly loaded region is determined as a function of an expected load on the sealing element, and the rigidity of the sealing element is locally increased in this region by at least one geometry adaptation, preferably by a change in the corrugation or fold height, the corrugation or fold width and / or the wall thickness of the corrugated or bellows.In the proposed method, the geometry adaptation to increase the stiffness of the sealing element is locally limited, specifically limited to the region or regions which are to be regarded as particularly critical on account of an increased load. The increased rigidity in this region or in these regions increases the robustness of the sealing element. At the same time, the geometry adaptations, since they are locally limited, have little or no effect on the installation space.The geometry adaptation for increasing the stiffness can be carried out in different ways. The geometry adaptation is particularly simple to implement and very effective by changing the corrugation height or fold height. If the corrugated or bellows is produced in an injection molding process, the geometry adaptation can be carried out in particular by changing the wall thickness. Depending on the load to be expected on the sealing element, several measures for adaptation of the geometry can also be carried out.If the corrugation or fold height is changed for the geometry adaptation, the change preferably consists in the corrugation or fold height being reduced in the at least one more highly loaded region, because the rigidity of the sealing element in this region is thereby increased. The increased rigidity in turn leads under load to a reduction in the stress amplitudes in this region. Depending on how large the region with increased stiffness is, the overall stiffness of the bellows is only slightly influenced.The at least one geometry adaptation is carried out circumferentially, that is to say the geometry of an individual corrugation or fold is identical circumferentially. However, the geometries of two adjacent corrugations or folds may differ.The increased robustness of a sealing element produced according to the proposed method has the effect that it fails only after a higher load cycle number and / or from a higher load. If a fracture occurs, this does not necessarily occur in the at least one modified / stiffer region, but can occur everywhere. This is because the locally increased rigidity at the same time leads to a more uniform distribution of the load of the sealing element.The at least one more highly loaded region of the sealing element is preferably determined by tests and / or by means of FE simulation. Compared to experiments, the FE simulation yields more accurate results, so that this is preferably used. This reduces the risk that an excessively large change in the geometry is carried out for the respective application / loading or that the potential is not fully utilized. In addition, the FE simulation is less time-consuming and thus expensive.Furthermore, it is preferred to determine stress amplitude maxima by means of FE simulation and to assign these to the individual corrugations or folds of the corrugated or bellows. For example, operating loads, pressures, lifting, speed and / or acceleration profiles to be expected by means of FE simulation can be applied to the sealing element in order to determine the corrugations or folds at which stress amplitude maxima occur. The at least one geometry adaptation can then be carried out in a targeted manner on this shaft or folds in order to increase its stiffness. This leads to a reduction of the voltage amplitude maxima and to a homogenization of the load.In order to achieve the most uniform possible distribution of the load over the entire length of the corrugated or bellows, adjacent corrugations or folds can be incorporated into the geometry adaptation. That is, the geometry of corrugations or pleats disposed adjacent to the corrugations or pleats of a higher load area is also changed to make the transition smooth. For this purpose, the geometry adaptation is carried out in the adjacent corrugations or folds in attenuated form, preferably in a form which weakens stepwise or continuously.In a further development of the invention, it is therefore proposed that the corrugation or fold height, the corrugation or fold width and / or the wall thickness of the corrugation or bellows is or are changed stepwise or continuously in regions, in particular in a transition region from a higher-load region to a lower-load region.Since a more highly loaded region can be, in particular, an end region of the corrugated or bellows, the corrugation or fold height in this end region is preferably reduced until a comparable tension state, for example comparable tension oscillation widths, has been established compared to the centrally arranged corrugations or folds. In order to create a transition that is as uniform as possible, the corrugation or fold height of the corrugations or folds adjoining the end region is likewise changed, but less strongly, preferably stepwise or continuously less strongly, so that these provide between the different corrugation or fold heights. It is possible here to mimiculate until an optimum is reached.To achieve the object mentioned at the beginning, a sealing element in the form of a corrugated or bellows is furthermore proposed. The corrugated or bellows has locally increased stiffness in at least one region, preferably in an end region, by geometrically modified corrugations or folds.In the proposed sealing element, the stiffness accordingly varies over the length of the sealing element. This is advantageous since, as a rule, the load on the sealing element also varies over its length. By means of the locally increased rigidity, a more uniform loading of the sealing element during use can thus be achieved. Accordingly, the robustness of the sealing element increases.However, this presupposes that the rigidity is locally increased in a region which is actually loaded to a higher degree during the use of the sealing element. These can also be a plurality of regions, usually these are the end regions or at least one end region. In order to determine the at least one more heavily loaded region, an FE simulation can be used-as described above in connection with the method according to the invention. The proposed sealing element can therefore have been produced in particular by a method according to the invention.The corrugated or bellows is preferably designed as a rotationally symmetrical body. This means that the geometrically modified corrugations or folds have a constant geometry all around, or the change in geometry has been carried out all around. The change in geometry in this case follows the load profile of a corrugated or bellows which is primarily stretched and compressed in the axial direction.Furthermore, the geometrically modified corrugations or folds preferably have a different corrugation or fold height, a different corrugation or fold width and / or a different wall thickness. By means of these parameters, the stiffness of the corrugated or bellows can be increased locally in a particularly effective manner. The parameters can be changed individually or in different combinations. For example, the geometrically modified corrugations or folds can have only a different, namely reduced corrugation or fold height for locally increasing the stiffness.Furthermore, it is proposed that the corrugation or fold height, the corrugation or fold width and / or the wall thickness change or change stepwise or continuously at least in regions. This applies in particular in a transition region which connects a region with a higher load to a region with a lower load, so that the most uniform possible load distribution over the entire length of the corrugated or bellows is achieved when the sealing element is in use.As already mentioned at the outset, the proposed sealing element can be used in particular in valves, injectors and / or pumps. In a further development of the invention, therefore, a valve, an injector and / or a pump are each provided with a sealing element according to the invention.The invention and its advantages are explained in more detail below with reference to the attached drawings. These show: FIG. 1 shows a longitudinal section through a conventional sealing element in the form of a corrugated bellows, and FIG. 2 shows a diagram for the graphical representation of a possible distribution of the stress amplitude maxima of a sealing element designed as a corrugated bellows.DETAILED DESCRIPTION OF THE DRAWINGSFIG. 1 shows a conventional sealing element 1 in the form of a corrugated bellows. The sealing element 1 has an overall length I 1 and a bellows length I 2 since shaft-free end sections 1.1, 1.2 connect to the corrugated bellows on both sides. The corrugated bellows itself forms corrugations 2 which allow the corrugated bellows to be stretched and compressed in the axial direction. In the region of the shafts 2, the corrugated bellows has an inner diameter ID and an outer diameter AD, wherein (AD-ID) / 2 gives the shaft height h. The wave width b is measured from the wave center to the wave center. Further parameters which influence the geometry of the shafts 2 are the radii R 1 and R 2 and the wall thickness s.The sealing element 1 of FIG. 1 is designed rotationally symmetrically and all shafts 2 have the same geometry over the entire length I 2. In use, however, the sealing element 1 is not uniformly loaded, so that there is an increased risk of breakage in a region with a higher load.Two curves A and B are shown by way of example in FIG. 2. Curve A shows the course of the stress amplitude maxima over the length I 2 of a conventional sealing element 1 designed as a corrugated bellows under load. The determination was made on each shaft 2, namely on the inner diameter ID. It can be clearly seen that voltage amplitude maxima occur in each of the end regions, that is to say in the region of the first three and the last three shafts 2. The end regions are thus the more heavily loaded regions. Curve B, on the other hand, has a much flatter course. These stress amplitudes were determined on a sealing element 1 according to the invention, which is designed as a corrugated bellows and whose corrugations 2 have been geometrically changed in the regions under higher load. The geometric change relates to the shaft height h of individual shafts 2, which has been reduced in order to locally increase the rigidity of the sealing element 1. The reduction was performed stepwise to adapt to the course of the voltage amplitude. Starting from the normal shaft height h, the shaft height of the first shaft is 0.9*h, that of the second shaft is 0.92*h, that of the third shaft is 0.94*h, that of the fourth shaft is 0.96*h and that of the fifth shaft is 0.98*h. The shaft heights of the fourth and fifth shafts 2 have also been changed to create a flowing transition.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2010 042 476 A1

[0003]

Claims

Method for producing a sealing element (1) in the form of a corrugated or bellows, in which at least one more highly loaded region of the sealing element (1) is determined as a function of an expected load on the sealing element (1), and the rigidity of the sealing element (1) is locally increased in this region by at least one geometry adaptation, preferably by a change in the corrugation or fold height (h), the corrugation or fold width (b) and / or the wall thickness (s) of the corrugated or bellows.Method according to Claim 1, characterized in that the at least one more heavily stressed region is determined by experiments and / or by means of FE simulation.Method according to Claim 2, characterized in that stress amplitude maxima are determined by means of FE simulation and are assigned to individual corrugations (2) or folds of the corrugated or bellows.Method according to one of the preceding claims, characterized in that the corrugation or fold height (h), the corrugation or fold width (b) and / or the wall thickness (s) of the corrugation or bellows is or are changed stepwise or continuously in regions.Sealing element (1) in the form of a corrugated or bellows, which has locally increased stiffness in at least one region, preferably in an end region, by geometrically modified corrugations (2) or folds.Sealing element (1) according to claim 5, characterised in that the corrugated or bellows is designed as a rotationally symmetrical body.Sealing element (1) according to claim 5 or 6, characterised in that the geometrically modified corrugations (2) or folds have a different corrugation or fold height (h), a different corrugation or fold width (b) and / or a different wall thickness (s).Sealing element (1) according to claim 7, characterised in that the corrugation or fold height (h), the corrugation or fold width (b) and / or the wall thickness (s) changes or change stepwise or continuously at least in regions.Valve having a sealing element (1) according to one of Claims 5 to 8.Injector having a sealing element (1) according to one of Claims 5 to 8.Pump having a sealing element (1) according to one of Claims 5 to 8.

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