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

Abstract

The invention relates to a method for detecting a defect in a sealing element (1) designed as a corrugated or folded bellows, in which method - the sealing element (1) is electrically contacted in the region of an electrical conductor (2) that 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 that was measured for an intact sealing element (1). The invention also relates to a sealing element (1) in the form of a corrugated or folded bellows.

Description

[0001] Description

[0002] Method for detecting a defect in a sealing element designed as a corrugated or bellows, sealing element

[0003] The invention relates to a method for detecting a defect in a sealing element, wherein the sealing element is designed as a corrugated or bellows. Furthermore, the invention relates to a sealing element in the form of a corrugated or bellows, which is suitable for carrying out the method.

[0004] The preferred field of application of the invention is valves, injectors and / or pumps in which the sealing element designed as a corrugated or bellows can be used for media separation despite the lifting movement.

[0005] State of the art

[0006] German Patent Application DE 10 2010 042 476 A1 discloses, by way of example, a fuel injection device comprising a corrugated bellows for sealing a fuel-filled area from a fuel-free area. The corrugated bellows is made of a single-layer metal material and is attached at one end to a valve needle that can be lifted and at the other end to a bushing that is fixedly housed in a holding body.

[0007] A seal in the form of a corrugated or bellows-type seal has the advantage that it can be attached to components with a movable stroke, such as a valve needle or a pump piston, without restricting the component's stroke movement. This places mechanical stress on the seal, which can lead to a defect, such as a break or crack, in the sealing element. Media separation is then no longer guaranteed, and media entrainment and resulting consequential damage can occur. To prevent consequential damage, the fastest possible detection of a defect in the sealing element is advantageous.

[0008] The present invention addresses this problem. To achieve this problem, 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 subclaims.

[0009] Disclosure of the invention

[0010] A method is proposed for detecting a defect in a sealing element designed as a corrugated or bellows, in which the 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 to a second end region of the sealing element and is formed by the sealing element or is integrated into the sealing element, the electrical resistance in the longitudinal direction of the sealing element is measured via the electrical contact and the measured resistance is compared with a stored reference value which was measured when the sealing element was intact.

[0011] If a comparison with the reference value reveals a deviation, it can usually be assumed that there is a defect. This is because, with an intact sealing element, an essentially constant electrical resistance can be expected that is not influenced by the lifting movements of the sealing element. This does not apply unless, due to an excessively high stroke or excessive dynamics, the corrugated or bellows seal blocks in some areas, so that at least two corrugations or folds come into contact with each other, or there is significant plastic deformation of the corrugated or bellows, thus leading to changed conditions or measured values. In most cases, however, the deviation between the measured value and the reference value is due to a defect in the form of a break or crack in the sealing element. In this 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 perpendicular to it.

[0012] As the crack develops, the sealing element ultimately breaks off and, depending on the ambient medium and / or contact of the sealing element with other components, the electrical resistance may change.

[0013] If resistance readings fluctuate, this could also be due to a defect. For example, the defect could be a crack that is temporarily stretched and then closed again by the lifting movements of the sealing element.

[0014] Resistance measurement requires a sealing element that forms or has an electrical conductor. Furthermore, the electrical conductor must be electrically contacted. The electrical conductor is preferred.

[0015] (a) directly via contact elements or contact areas formed on the sealing element or

[0016] (b) indirectly electrically contacted via contact elements or contact areas of an adjacent component.

[0017] Depending on the design of the sealing element or the electrical conductor, the electrical contact is made in both end areas of the sealing element, so that the measuring section extends – at least approximately – over the entire length of the sealing element. To establish electrical contact in a single end area of ​​the sealing element, the electrical conductor must extend from this one end area to the other end area and back again. Electrical contact in one end area of ​​the sealing element can provide space advantages.

[0018] To measure the resistance, a voltage can be applied and the resulting current strength can be measured as a measure of the electrical resistance. Alternatively, an electrical current can be passed through the electrical conductor and the resulting voltage drop can be measured, which is then taken as a measure of the electrical resistance. To achieve the object mentioned above, a sealing element in the form of a corrugated or bellows is further proposed, wherein the sealing element forms or has an electrical conductor which extends longitudinally 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 contact at each of its two ends.

[0019] The proposed sealing element is particularly suitable for implementing the previously described method, so that the same advantages can be achieved. In particular, a defect in the sealing element, such as a break or crack, can be detected very quickly using electrical resistance measurement.

[0020] According to a first preferred embodiment of the invention, the sealing element is designed in one or more layers and has at least one layer made of an electrically conductive, for example, a metallic, material to form the electrical conductor. In the single-layer design, the sealing element can be designed, for example, as a single-layer metal bellows. In the multi-layer design, at least one layer is made of an electrically conductive, preferably metallic, material. The at least one layer can be arranged either internally or externally. The external arrangement facilitates electrical contact.

[0021] If the sealing element is designed in multiple layers, preferably at least one layer of the multi-layer sealing element is made of an electrically insulating material, such as a polymer. This layer can then be used to electrically insulate the electrical conductor from an electrically conductive medium or an adjacent electrically conductive component. Depending on the position of the space exposed to the electrically conductive medium or the position of the electrically conductive component, the electrically insulating layer is arranged internally or externally.

[0022] According to a second preferred embodiment of the invention, the sealing element has, at least in some regions, a coating with an electrically conductive material to form the electrical conductor. The coating can be subsequently applied to the sealing element, thus converting a conventional sealing element into a sealing element according to the invention. The coating can also be applied only in certain regions, so that it extends only over a partial circumferential area of ​​the sealing element. In the longitudinal direction, it extends from one end area to the other end area of ​​the sealing element.

[0023] According to a third preferred embodiment of the invention, the sealing element is made of an electrically insulating material, on or in which a strip or wire made of an electrically conductive material is arranged to form the electrical conductor. The strip or wire can rest on top or be embedded in the electrically insulating material, at least in some areas. Using such a strip or wire, a conventional sealing element can also be upgraded to a sealing element according to the invention. This applies in particular if the strip or wire is only placed on the sealing element.

[0024] If the electrical conductor extends only over a partial circumferential area of ​​the sealing element, as is the case with a coating, tape, or wire made of electrically conductive material that is only partially coated, a crack forming outside this area can only be detected using the proposed resistance measurement once it has expanded into the area of ​​the electrical conductor. This can delay the detection of the defect.

[0025] In a further development of the invention, it is proposed that the strip or wire has a first section which runs from the first end region to the second end region of the sealing element, and a second section which runs from the second end region back to the first end region at a distance from the first section. The two sections are electrically connected in one of the two end regions via a third section. All sections together form the electrical conductor. The greater the distance selected between the first and second sections, the more likely it is that a defect will be detected if it arises outside the electrical conductor. The two sections can therefore be arranged in particular at an angular distance of 180° from one another, so that they lie opposite one another on the sealing element.Furthermore, it is proposed that the first and second sections each have a contact element or contact area for electrical contacting at their free end. This means that both ends of the electrical conductor can be electrically contacted in the same end area of ​​the sealing element, for example, in the end area defined by the housing. This simplifies electrical contacting.

[0026] As already mentioned at the beginning, 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, is therefore further proposed.

[0027] The invention and its advantages are explained in more detail below with reference to the accompanying drawings. These show:

[0028] Fig. 1 is a longitudinal section through the wall of a first sealing element according to the invention,

[0029] Fig. 2 shows a cross section through a second sealing element according to the invention,

[0030] Fig. 3 a longitudinal section through the wall of a third sealing element according to the invention and

[0031] Fig. 4 shows a longitudinal section through the wall of a fourth sealing element according to the invention.

[0032] Detailed description of the drawings

[0033] Figure 1 shows a sealing element 1 according to the invention designed 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 electrically contacting the electrical conductor 2. An electrical voltage can be applied across the contact regions 4 to measure the resistance in the longitudinal direction of the sealing element 1. If the measured value deviates from a reference value that was measured with an intact sealing element 1, this indicates a defect in the sealing element 1.

[0034] Figure 2 shows a further sealing element 1 according to the invention. This is also designed as a corrugated bellows. In contrast to the sealing element 1 in Figure 1, the sealing element 1 here is not made of an electrically conductive material, but of an electrically insulating material, for example a polymer. The electrical conductor 2 required for resistance measurement 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.

[0035] Figure 3 shows another sealing element 1 according to the invention, designed as a corrugated bellows. The sealing element 1 itself is again made of an electrically insulating material. The electrical conductor 2 is formed by a coating 6 of the sealing element 1 with an electrically conductive material. The coating 6 also extends from the first end region 1.1 to the second end region 1.2 of the sealing element 1, thus enabling a resistance measurement in the longitudinal direction. In this case, the electrical contact is established via contact regions 4 arranged on both sides.

[0036] Further embodiments of a sealing element 1 according to the invention can be explained with reference to Figure 3. Instead of the coating 6, the electrical conductor 2 shown could also be an electrically conductive layer 5 (see reference numeral in parentheses) of a multi-layer sealing element 1. The at least one further layer can then be made of 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 adjacent component that is possibly electrically conductive. Furthermore, the electrical conductor 2 shown in Figure 3 could also be a strip 7 (see reference numeral in parentheses) made of an electrically conductive material that extends from end region 1.1 to end region 1.2, analogous to the wire 8 shown in Figure 2.Furthermore, several bands 7 or wires 8 can be arranged distributed around the circumference of the sealing element 1.

[0037] Figure 4 shows a further embodiment of a sealing element 1 according to the invention designed as a corrugated bellows. This is made of an electrically insulating material and has an electrical conductor 2 which extends on 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 to the first end region 1.1 of the sealing element 1. In this case, the electrical conductor 2 is a coating 6 made of an electrically conductive material applied to both sides of 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 first two sections. This is identified by the reference numeral 9 in Figure 4.Instead of a coating 6, the electrical conductor 2 could also be a strip 7 or a wire 8 (see reference numerals in parentheses) made of an electrically conductive material. In this case, the strip 7 or the wire 8 can be guided around the second end region 1.2 of the sealing element 1. In the area of ​​the first end region 1.1, the electrical conductor 2 forms a contact region 4 for electrical contact at each of its two ends 2.1, 2.2.

[0038] In a further modification, the sealing element 1 of Figure 4 could also be designed in multiple layers, with two outer layers 5 made of an electrically conductive material surrounding at least one layer made of an electrically insulating material. The two outer layers 5 are then electrically connected in an end region 1.1, 1.2 of the sealing element 1. In the other end region 1.2, 1.1, each layer 5 forms a contact region 4 for electrical contact.

Claims

Claims 1 . 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 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 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 when the sealing element (1) was intact.

2. Method according to claim 1, characterized in that the electrical conductor (2) (a) directly via contact elements (3) or contact areas (4) formed on the sealing element (1) or (b) is electrically contacted indirectly via contact elements or contact areas of an adjacent component.

3. 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 to 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.

4. Sealing element (1) according to claim 3, characterized in that the sealing element (1) is designed 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).

5. Sealing element (1) according to claim 3, characterized in that the sealing element (1) has at least in some regions a coating (6) with an electrically conductive material for forming the electrical conductor (2).

6. Sealing element (1) according to claim 3, characterized in that the sealing element (1) is made of an electrically insulating material on which or in which a band (7) or wire (8) made of an electrically conductive material is arranged to form the electrical conductor (2).

7. Sealing element (1) according to claim 6, characterized in that the band (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), the two sections being electrically conductively connected in one of the two end regions (1.1, 1.2) via a third section.

8. Sealing element (1) according to claim 7, characterized in that the first and the second section each have a contact element (3) or a contact area (4) for electrical contacting at their free end.

9. Valve with a sealing element (1) according to one of claims 3 to 8.

10. Injector with a sealing element (1) according to one of claims 3 to 8.

11. Pump with a sealing element (1) according to one of claims 3 to 8

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