Method for detecting a defect in a sealing element designed as a corrugated or bellows, sealing element

Abstract

The invention relates to a method for detecting a defect in a sealing element (1) designed as a corrugated or bellows, in which - the sealing element (1) is electrically contacted in the region of an electrical conductor (2) which extends in the longitudinal direction from a first end region (1.1) at least to a second end region (1.2) of the sealing element (1) and is formed by the sealing element (1) or is integrated into the sealing element (1), - the electrical resistance in the longitudinal direction of the sealing element (1) is measured via the electrical contact and - the measured resistance is compared with a stored reference value which was measured with the sealing element (1) intact. 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 detecting a defect on a sealing element, wherein the sealing element is designed as a corrugated or bellows. The invention furthermore relates to a sealing element in the form of a corrugated or bellows, which is suitable for carrying out the method.Preferred application areas of the invention are valves, injectors and / or pumps in which the sealing element, which is designed as corrugated or bellows, can be used for media separation despite a stroke movement.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 mechanically stressed in this case, which can lead to a defect, for example a fracture or a crack, of the sealing element. The media separation is then no longer ensured and media entrainment and consequent damage resulting therefrom can occur. In order to prevent subsequent damage, the fastest possible detection of a defect of the sealing element is advantageous.This object is addressed by the present invention. To achieve the object, the method having the features of claim 1 and the sealing element having the features of claim 3 are proposed. Advantageous further developments of the invention can be found in the respective dependent claims.Disclosure of the InventionA method for detecting a defect on a sealing element designed as a corrugated or bellows is proposed, in whichthe sealing element is electrically contacted in the region of an electrical conductor which extends in the longitudinal direction from a first end region at least as far as a second end region of the sealing element and is formed by the sealing element or is integrated into the sealing element,measuring the electrical resistance in the longitudinal direction of the sealing element via the electrical contacting; andcomparing the measured resistance with a stored reference value which has been measured with the sealing element intact.If the comparison with the reference value produces a deviation, a defect can generally be deduced, since with the sealing element intact, a substantially constant electrical resistance is to be expected, which is not influenced by the lifting movements of the sealing element. Unless, on account of too high a stroke or too high a dynamic, the corrugated or bellows partially blocks, so that at least two corrugations or folds contact one another, or a marked plastic deformation of the corrugated or bellows and thus changed conditions or measurement values occur. In most cases, however, the deviation between the measured value and the reference value will be due to a defect in the form of a fracture or crack of the sealing element, in which case the measured resistance is greater than the reference value. The resistance is measured in the longitudinal direction, i.e. in the direction of movement of the sealing element. A defect in the form of a fracture or crack usually runs transversely thereto.As the crack formation progresses, the sealing element is ultimately torn off, and depending on the surrounding medium and / or contact of the sealing element with other components, a changed electrical resistance can occur.If alternating resistance measurement values occur, this can likewise be attributed to a defect. For example, the defect can be a crack which is temporarily pulled apart by the lifting movements of the sealing element and then closed again.The resistance measurement requires a sealing element which forms or has an electrical conductor. Furthermore, the electrical conductor must be electrically contacted. Preferably, the electrical conductor is electrically contacted (a) directly via contact elements or contact regions formed on the sealing element or (b) indirectly via contact elements or contact regions of an adjoining component.Depending on the configuration of the sealing element or of the electrical conductor, the electrical contacting takes place in the two end regions of the sealing element, so that the measurement section extends-at least approximately-over the entire length of the sealing element. In order to carry out the electrical contacting in a single end region of the sealing element, the electrical conductor must extend from this one end region to the respective other end region and back again. The electrical contacting in an end region of the sealing element can provide construction space advantages.For the measurement of the resistance, a voltage can be applied and the current intensity that is established can be measured as a measure of the electrical resistance. Alternatively, an electric current can be passed through the electric conductor and the voltage drop which is produced can be measured, which is then taken as a measure of the electrical resistance.To achieve the object mentioned at the beginning, a sealing element in the form of a corrugated or bellows is furthermore proposed, wherein the sealing element forms or has an electrical conductor which extends in the longitudinal direction from a first end region at least as far as a second end region of the sealing element. The electrical conductor has a contact element or a contact region for electrical contacting at each of its two ends.The proposed sealing element is suitable in particular for carrying out the method described above, so that the same advantages can be achieved. In particular, a defect of the sealing element, for example a fracture or crack, can be detected very quickly by means of electrical resistance measurement.According to a first preferred embodiment of the invention, the sealing element is embodied in one or more layers and has at least one layer made of an electrically conductive, for example a metallic, material for forming the electrical conductor. In the single-layer embodiment, the sealing element can be embodied, for example, as a single-layer metal bellows. In the multi-layer embodiment, at least one layer is made of an electrically conductive, preferably metallic, material. The at least one layer can be arranged both on the inside and on the outside. The external arrangement facilitates the electrical contacting.If the sealing element is embodied in multiple layers, at least one layer of the multiple-layer sealing element is preferably manufactured from an electrically insulating material, for example a polymer. Via this layer, the electrical conductor can then be electrically insulated from an electrically conductive medium or an adjoining component which is electrically conductive. Depending on the position of the space to which the electrically conductive medium is applied or depending on the position of the component which is electrically conductive, the electrically insulating layer is arranged lying on the inside or on the outside.According to a second preferred embodiment of the invention, the sealing element has, at least in regions, a coating with an electrically conductive material for forming the electrical conductor. The coating can be applied subsequently to the sealing element, so that in this way a conventional sealing element can be made available as a sealing element according to the invention. The coating can also be applied only in regions, so that it extends only over a partial circumferential region of the sealing element. In the longitudinal direction, it extends from one end region to the other end region of the sealing element.According to a third preferred embodiment of the invention, the sealing element is manufactured from an electrically insulating material, on or in which a strip or wire made from an electrically conductive material is arranged for forming the electrical conductor. The strip or the wire can rest on top or can be embedded at least in regions in the electrically insulating material. With the aid of such a band or wire, a conventional sealing element to form a sealing element according to the invention can likewise be developed. This applies in particular if the strip or the wire is placed only on the sealing element.If the electrical conductor extends only over a partial circumferential region of the sealing element, as is the case with a coating, a strip or a wire made of electrically conductive material only in regions, a crack forming outside this region can only be detected by means of the proposed resistance measurement if it has enlarged as far as into the region of the electrical conductor. The detection of the defect can thereby be delayed.In a development of the invention, it is proposed that the band or the wire has a first section which is guided from the first end region to the second end region of the sealing element, and a second section which is guided at a distance from the first section from the second end region back to the first end region. The two sections are electrically conductively connected in one of the two end regions via a third section. All sections together form the electrical conductor. The greater the distance between the first and the second section is selected, the more likely the detection of a defect if it arises outside the electrical conductor is. The two sections can therefore be arranged in particular at an angular distance of 180° from one another, so that they are situated opposite one another on the sealing element.Furthermore, it is proposed that the first and the second section each have a contact element or a contact region for electrical contacting at their free end. This means that both ends of the electrical conductor can be electrically contacted in the same end region of the sealing element, for example in the end region which is fixed on the housing side. The electrical contacting is thereby simplified.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, a valve, an injector and / or a pump each with a sealing element according to the invention are therefore also proposed.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 the wall of a first sealing element according to the invention, FIG. 2 shows a cross section through a second sealing element according to the invention, FIG. 3 shows a longitudinal section through the wall of a third sealing element according to the invention, and FIG. 4 shows a longitudinal section through the wall of a fourth sealing element according to the invention.DETAILED DESCRIPTION OF THE DRAWINGSFIG. 1 shows a sealing element 1 according to the invention embodied as a corrugated bellows. This is made of an electrically conductive material, for example metal, so that the sealing element 1 simultaneously forms an electrical conductor 2. The electrical conductor 2 has two ends 2.1, 2.2 which coincide with end regions 1.1, 1.2 of the sealing element 1. At the same time, the end regions 1.1, 1.2 form contact regions 4 for the electrical contacting of the electrical conductor 2.An electric voltage for measuring the resistance in the longitudinal direction of the sealing element 1 can be applied via the contact regions 4. If the measured value deviates from a reference value which was measured with the sealing element 1 intact, this indicates a defect in the sealing element 1.FIG. 2 shows a further sealing element 1 according to the invention. This is likewise designed as a corrugated bellows. In contrast to the sealing element 1 of FIG. 1, the sealing element 1 is here not made of an electrically conductive material, but of an electrically insulating material, for example of a polymer. The electrical conductor 2 required for measuring the resistance is formed by a wire 8 which extends from one end region 1.1 to the other end region 1.2 of the sealing element 1. At its ends 2.1, 2.2, the wire 8 forms contact elements 3 in the form of contact lugs, via which the electrical conductor 2 can be contacted. In this way, a resistance measurement in the longitudinal direction of the sealing element 1 can also be carried out with this sealing element 1 in order to detect a defect.FIG. 3 shows a further sealing element 1 according to the invention, which is designed as a corrugated bellows. The electrical conductor 2 is formed by a coating 6 of the sealing element 1 with an electrically conductive material. The coating 6 likewise extends from the first end region 1.1 to the second end region 1.2 of the sealing element 1, so that it enables resistance measurement in the longitudinal direction. The electrical contacting takes place in the present case via contact regions 4 arranged on both sides.With reference to FIG. 3, further embodiments of a sealing element 1 according to the invention can be explained. This is because instead of the coating 6, the electrical conductor 2 shown could also be an electrically conductive layer 5 (see reference numerals in brackets) of a sealing element 1 embodied in multiple layers. The at least one further layer can then be manufactured from an electrically insulating material in order to separate the electrical conductor 2 in the form of the electrically conductive layer 5 from a specific medium and / or an adjoining component, which is optionally electrically conductive. Furthermore, the electrical conductor 2 shown in FIG. 3 could also be a strip 7 (see reference numerals in brackets) made of an electrically conductive material, which extends from end region 1.1 to end region 1.2 in a similar manner to the wire 8 shown in FIG. 2. Furthermore, a plurality of bands 7 or wires 8 can be arranged distributed around the circumference of the sealing element 1.FIG. 4 shows a further embodiment of a sealing element 1 according to the invention, which is designed as a corrugated bellows and is manufactured from an electrically insulating material and has an electrical conductor 2, which extends on the one side from the first end region 1.1 to the second end region 1.2 and on the other side from the second end region 1.2 back again to the first end region 1.1 of the sealing element 1. The electrical conductor 2 is in the present case a coating 6 made of an electrically conductive material applied on both sides to the sealing element 1. The coating 6 is electrically conductively connected in the second end region 1.2 of the sealing element 1. The electrical conductor 2 thus has two sections running in the longitudinal direction and a third section for connecting the two first sections. This is identified in FIG. 4 by the reference numeral 9. Instead of a coating 6, the electrical conductor 2 could also be a strip 7 or a wire 8 (see reference numerals in brackets) made of an electrically conductive material. In this case, the band 7 or the wire 8 can be guided around the second end region 1.2 of the sealing element 1. In the region of the first end region 1.1, the electrical conductor 2 forms a contact region 4 for electrical contacting at each of its two ends 2.1, 2.2.In a further modification, the sealing element 1 of FIG. 4 could also be formed in multiple layers, wherein two outer layers 5 made of an electrically conductive material surround at least one layer made of an electrically insulating material. The two outer layers 5 are then to be connected in an electrically conductive manner in an end region 1.1, 1.2 of the sealing element 1. In the respective other end region 1.2, 1.1, each layer 5 forms a contact region 4 for electrical contacting.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 detecting a defect on a sealing element (1) designed as a corrugated or bellows, in which - the sealing element (1) is electrically contacted in the region of an electrical conductor (2) which extends in the longitudinal direction from a first end region (1.1) at least as far as a second end region (1.2) of the sealing element (1) and is formed by the sealing element (1) or is integrated into the sealing element (1), - the electrical resistance is measured in the longitudinal direction of the sealing element (1) via the electrical contacting, and - the measured resistance is compared with a stored reference value which has been measured when the sealing element (1) is intact.Method according to Claim 1, characterized in that the electrical conductor (2) is electrically contacted (a) directly via contact elements (3) or contact regions (4) formed on the sealing element (1) or (b) indirectly via contact elements or contact regions of an adjoining component.Sealing element (1) in the form of a corrugated or bellows, wherein the sealing element (1) forms or has an electrical conductor (2) which extends in the longitudinal direction from a first end region (1.1) at least as far as a second end region (1.2) of the sealing element (1), wherein the electrical conductor (2) has at each of its two ends (2.1, 2.2) a contact element (3) or a contact region (4) for electrical contacting.Sealing element (1) according to Claim 3, characterized in that the sealing element (1) is embodied in one or more layers and has at least one layer (5) made of an electrically conductive, for example a metallic, material for forming the electrical conductor (2).Sealing element (1) according to Claim 3, characterized in that the sealing element (1) has, at least in regions, a coating (6) with an electrically conductive material for forming the electrical conductor (2).Sealing element (1) according to Claim 3, characterized in that the sealing element (1) is produced from an electrically insulating material on or in which a strip (7) or wire (8) made from an electrically conductive material for forming the electrical conductor (2) is arranged.Sealing element (1) according to claim 6, characterised in that the strip (7) or the wire (8) has a first section which is guided from the first end region (1.1) to the second end region (1.2) of the sealing element (1) and a second section which is guided at a distance from the first section from the second end region (1.2) back to the first end region (1.1), wherein the two sections are electrically conductively connected in one of the two end regions (1.1, 1.2) via a third section.Sealing element (1) according to claim 7, characterised in that the first and the second section each have a contact element (3) or a contact region (4) for electrical contacting at their free end.Valve having a sealing element (1) according to one of Claims 3 to 8.Injector having a sealing element (1) according to one of Claims 3 to 8.Pump having a sealing element (1) according to one of Claims 3 to 8

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