Sliding ring of a sliding ring seal, and method for producing same
Patent Information
- Application Number
- EP2023808700
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-11-24
- Filing Date
- 2023-11-13
- Publication Date
- 2025-10-01
AI Technical Summary
The challenge lies in securely and cost-effectively making electrical contact with sensors on the sliding surface of ceramic mechanical seal rings without risking damage or cracking, especially when high-temperature coatings are involved, as traditional methods are either costly or lead to high scrap rates due to thermal issues and coating detachment.
A sintered ceramic ring with an electrically conductive contact body, comprising a harder ceramic region for the sliding surface and a composite metallic silicon and SiC region for the rear, allows for simple and secure electrical contact through a recess, preventing cracking and enabling uniform thermal expansion, while allowing for a diamond coating post-manufacturing.
This solution enables reliable, cost-effective, and crack-free electrical contacting of sensors on ceramic mechanical seal rings, maintaining excellent seal properties and extending the service life by preventing thermal-induced damage and ensuring uniform temperature-related volume changes.
Smart Images
Figure 1.1
Abstract
Description
[0001] Mechanical seal ring and method for its manufacture
[0002] Description
[0003] The present invention relates to a sliding ring of a mechanical seal, a mechanical seal arrangement and a method for producing the sliding ring.
[0004] Mechanical seal rings are known in various designs from the prior art. Recently, sensors have increasingly been arranged on a sliding surface of the seal ring to monitor, for example, its wear. This gives rise to a problem in that the sensors located on the sliding surface must be electrically contacted. Since the sensors are located on the sliding surface, it is necessary to have an electrical through-hole connection through the seal ring. Since a very brittle ceramic is often used as the material for the seal ring, holes or similar holes that have to be drilled into the seal ring to enable electrical contact are particularly dangerous in that they pose the risk of invisible damage and cracks in the seal ring.Furthermore, seal rings are often coated on their sliding surfaces, for example with a diamond coating. However, bores in the seal ring that extend to the sliding surface, even if filled with material, are very disadvantageous in this case, as the coating often detaches at the edges of the bores. Since a coating is usually applied as the last step in the manufacture of the seal ring, very high process temperatures of up to 900°C occur with a diamond coating, for example. This creates thermal problems for any low-melting metals present in the seal ring for electrical contact, as the melting points of such metals are significantly lower than the coating temperatures.
[0005] Furthermore, it must be ensured that the electrical contact hole, which extends to the sliding surface, does not cause increased cracking either at the edges of the hole or in any material located within the hole. Furthermore, it is also necessary to ensure simple and reliable electrical contact with the material filling the hole.
[0006] It is therefore an object of the present invention to provide a sliding ring, a mechanical seal arrangement and a method for producing a sliding ring, which enable a reliable electrical contacting of sensors on a sliding surface of the sliding ring with a simple structure and simple, cost-effective manufacture and implementation.
[0007] This object is achieved by a sliding ring having the features of claim 1, a mechanical seal arrangement having the features of claim 14, and a method having the features of claim 15. The subclaims each show preferred developments of the invention.
[0008] The sliding ring of a mechanical seal arrangement according to the invention with the features of claim 1 has the advantage that simplified and reliable electrical contact is possible through a sliding ring up to the sliding surface. This makes it possible, in particular, to electrically contact sensors that are arranged on or near a sliding surface of the sliding ring or in the sliding ring. However, it is also possible, for example, for an electrical circuit to be passed through the sliding ring, which can be used, for example, to measure wear if the electrical circuit is arranged in such a way that, in the event of wear on the sliding surface of the sliding ring, the electrical circuit is interrupted when wear is sufficiently advanced. The sliding ring can be made from an electrically non-conductive, ceramic material, which is advantageous with regard to its suitability as a sliding ring material.This is achieved according to the invention in that the sliding ring has a sintered, ceramic ring with a sliding surface, wherein the ceramic ring is made of an electrically non-conductive ceramic material. Furthermore, an electrically conductive contact body is provided which is arranged in the ring for electrical contact. The electrically conductive contact body is arranged in a recess in the ring, e.g. a bore-like recess, and completely fills the recess. The electrically conductive contact body comprises a first and a second region, wherein the first region is arranged in the recess at an end of the recess directed towards the sliding surface and the second region fills the remaining recess. The second region is thus arranged in the recess on a side of the sliding ring directed towards the rear.The first and second regions are each made of an electrically conductive material, with a first electrically conductive material of the first region having a greater hardness than a second electrically conductive material of the second region. Thus, the first electrically conductive material with greater hardness lies on the side facing the sliding surface. This prevents cracking on the sliding surface, which in the prior art frequently occurs at the edge of the recess or in the electrically conductive material of the contact body. The first region is made of an electrically conductive, ceramic material.The second region of the electrically conductive contact body, which faces away from the sliding surface, is made of an electrically conductive material and can therefore be optimized on its exit side from the sliding ring for excellent electrical contact with a wire or the like for connection to a power source and / or an evaluation unit or the like.
[0009] Since the first area is made of a ceramic material, which preferably has a similar thermal expansion behavior as the material of the ceramic ring, the sliding ring produced in this way still has excellent sliding ring properties and enables a wide range of applications with regard to maximum pressures and maximum temperatures.
[0010] Thus, a ceramic seal ring can be provided that, due to the introduction of the electrically conductive contact body, is electrically conductive only in the region of the electrically conductive contact body. Since both the ring and the first region of the contact body are made of a ceramic material, significant operational advantages result, for example, compared to a seal ring in which only a metallic material is arranged as an electrical conductor. This is because the heat generated on the seal surface during operation of the mechanical seal assembly leads to a very uniform, temperature-dependent volume change on the seal surface in the seal ring according to the invention.
[0011] Particularly preferably, the first region of the electrically conductive contact body is made of electrically conductive SiSiC. This is a reaction-bonded, silicon-infiltrated SiC, which material has a very high hardness. The sintered ceramic ring is preferably made of SiC and thus has almost identical thermal expansion behavior to the SiSiC material. The second region is preferably a composite material comprising silicon and SiC. In this case, the metallic silicon, in particular, provides the electrical conductivity of the second region of the electrically conductive contact body. This allows for easy electrical contact to be made by means of a wire or the like to an exposed end in the recess of the material of the second region of the electrically conductive contact body.The electrical contact is preferably established by a welded or soldered connection or electrical bonding. Alternatively, a metallic pin or a metallic sleeve or the like can be provided for electrical contact in or on the second region. The second region is thus preferably metallic silicon reinforced with an admixed SiC portion. Preferably, the volume fraction of the metallic silicon is greater than the volume fraction of the SiC. Preferably, the volume fraction of the metallic silicon is 63 vol% - 72 vol% and the volume fraction of the SiC is 18 vol% - 27 vol%. More preferably, the second region has gas-filled pores, wherein the volume fraction of the gas-filled pores is preferably between 5 vol% - 15 vol%.
[0012] The SiC added to the second region ensures that atomic bonds are formed between the second region and the ceramic ring. This results in a uniform volume change in the ring with the electrically conductive contact body during temperature-induced volume changes. The second region is therefore preferably made of a mixture of metallic silicon and SiC, possibly with a small volume fraction of gas-filled pores.
[0013] More preferably, the first region has a first length L1 in the axial direction of the recess, which is smaller than a second length L2 of the second region in the axial direction of the recess. The first length L1 is preferably much smaller than the second length L2. The first length L1 is preferably in a range from 1 mm to 2 mm. Particularly preferably, the second length L2 is at least 10 times greater than the first length L1.
[0014] Further preferably, the first region of the electrically conductive contact body is connected to a sensor arranged on the sliding surface. The sensor preferably comprises an electrically conductive sensor layer made of the same material as the first region of the electrically conductive contact body. This allows the sensor and the first region to be manufactured in a single step. Particularly preferably, the sensor layer is arranged in a recess in the sliding surface of the sliding ring.
[0015] Alternatively, the sensor is an electrically conductive sensor layer which is arranged on the entire sliding surface of the sliding ring.
[0016] The sensor is further preferably covered with a protective coating. The coating is preferably an electrically non-conductive layer, for example, undoped DLC. Coated seal rings are preferred because the coating on the sliding surface of the seal ring can extend the service life of the seal ring by reducing wear. However, one problem with coating the sliding surface of a seal ring is that this typically requires very high process temperatures, for example, up to 900°C for a diamond coating. However, metals intended for electrical contact in a seal ring melt at such high temperatures of approximately 900°C.However, this has not yet made it possible to equip coated seal rings with a sensor, especially a wear sensor, because electrical contacting of the sensor is not possible using conventional contacting methods. However, subsequently introducing an electrical connection, for example, by drilling a hole in the ceramic ring after the coating has been applied, is very difficult and costly, and there is always the risk of cracks in the ceramic seal ring or damage to the coating. As a result, the reject rate in the production of such coated ceramic seal rings with electrical leads is very high and generally uneconomical.
[0017] Particularly preferably, a plurality of chemical bonds produced by sintering are formed between the electrically conductive contact body and the ring. This ensures, on the one hand, secure fixation of the contact body in the ring, and, on the other hand, thermally induced volume changes of the ring and the contact body are carried out particularly uniformly. It should be noted that at least partial regions of the contact body and the ring can be sintered together in one step, or alternatively, the ring can be pre-sintered, and subsequently the materials for the first and second regions of the contact body are introduced into the recess. Then, in a second sintering step, the pre-sintered ring and the materials for the first and / or second regions of the contact body are post-sintered.
[0018] The recess in the ring is preferably a through-hole. The through-hole can run from a rear side to the sliding surface, in particular in a straight line, or alternatively from an inner circumferential side or an outer circumferential side to the sliding surface. This allows electrical contact of the sliding ring on the circumferential sides, which is advantageous in some designs of mechanical seal arrangements.
[0019] Particularly preferably, the second region of the electrically conductive contact body on the outlet side of the contact body forms an electrical connection for the electrically conductive contact body, to which an electrical line can be attached in a simple manner, e.g. by soldering or welding.
[0020] Preferably, the sliding ring is a stationary sliding ring of the mechanical seal assembly and comprises two electrically conductive contact bodies in the ring of the sliding ring to enable electrical contact with the sensor via a closed circuit. The first contact body is an electrical supply line, and the second contact body is an electrical return line. The ceramic ring of the sliding ring is preferably made of SiC, which is an electrically non-conductive material, i.e., has an electrical conductivity of < 10' 8 S / m at 20°C.
[0021] Furthermore, the present invention relates to a mechanical seal assembly comprising a sliding ring according to the invention. The sliding ring according to the invention is preferably used as the stationary sliding ring of the mechanical seal assembly. The mechanical seal assembly particularly preferably comprises a sensor on the stationary sliding ring, which is electrically connected to a measuring device via the electrically conductive contact body. The sensor is, in particular, a wear sensor.
[0022] Furthermore, the present invention relates to a method with the features of claim 15 for producing a sliding ring, in particular a stationary sliding ring, of a mechanical seal assembly. The method comprises the following steps:
[0023] - Producing a ring-shaped green compact from an electrically non-conductive ceramic material,
[0024] - Making a through-hole in the green body,
[0025] - Pre-sintering of the green body
[0026] - filling a first partial area of the recess in the pre-sintered green body with a first, electrically conductive, ceramic material, in particular SiSiC,
[0027] - introducing a second electrically conductive material, in particular a composite material comprising metallic silicon and SiC, into the remaining second partial area of the recess and
[0028] - re-sintering the sliding ring with the first and second electrically conductive material in order to form a first region and a second region of an electrically conductive contact body in the recess, so that a ceramic sliding ring with an electrically non-conductive ceramic ring and the electrically conductive contact body is produced, wherein a hardness of the first region is greater than a hardness of the second region.
[0029] The method according to the invention thus makes it possible to produce a ceramic sliding ring of a mechanical seal assembly that is electrically non-conductive, yet has an electrically conductive contact body due to the sintered first and second electrically conductive materials, i.e., those located in the recess here. Thus, the sliding ring can be obtained by sintering in two steps. Preferably, a sensor material of a sensor, in particular a wear sensor, is also sintered simultaneously during the re-sintering process. This achieves the advantages described above for the sliding ring.
[0030] Preferably, after the double sintering of the sliding ring, a coating, in particular a diamond coating, is applied to a sliding surface of the sliding ring.
[0031] Preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings. In the drawing:
[0032] Fig. 1 is a schematic sectional view of a mechanical seal arrangement with a sliding ring according to the invention according to a first embodiment of the invention,
[0033] Fig. 2 is a schematic sectional view of the sliding ring according to the invention of Fig. 1,
[0034] Fig. 3 is an enlarged view of Fig. 2,
[0035] Fig. 4 is a schematic sectional view of a sliding ring according to a second
[0036] Embodiment of the invention, and
[0037] Fig. 5 is a schematic sectional view of a sliding ring according to a third
[0038] Embodiment of the invention.
[0039] In the following, with reference to Figures 1 to 3, a mechanical seal arrangement
[0040] 1 according to a first preferred embodiment of the invention is described in detail.
[0041] As can be seen from Fig. 1, the mechanical seal arrangement 1 comprises a mechanical seal
[0042] 2 with a rotating seal ring 3 and a stationary seal ring 4. The rotating seal ring
[0043] 3 has a first sliding surface 3a and the stationary sliding ring 4 has a second sliding surface 4a.
[0044] A sealing gap 5 is defined between the two sliding surfaces 3a, 4a of the seal rings 3, 4. The mechanical seal assembly 1 seals an area 18, in which a product to be sealed is present, from an atmospheric area 19 on a shaft 14. The rotating seal ring 3 is connected to the shaft 14 in a rotationally fixed manner by means of a seal ring carrier 16 and a screw 17.
[0045] Furthermore, a preloading element 15 is provided, which preloads the rotating slide ring 3 in an axial direction of a central axis XX against the stationary slide ring 4.
[0046] The stationary seal ring 4 is sealed to a stationary housing component 20 by means of a first O-ring 21. The rotating seal ring 3 is sealed to the shaft 14 by means of a second O-ring 22 on its inner circumference. The mechanical seal assembly 1 further comprises a measuring device 6, which is particularly designed to measure wear of the stationary seal ring 4 on its sliding surface 4a. The measuring device 6 is connected to a sensor 7. The sensor 7 is arranged on the sliding surface 4a of the stationary seal ring 4.
[0047] The sensor 7 is arranged in a recess 43 in the sliding surface and is preferably a wear sensor.
[0048] For this purpose, an electrical contact of the sensor 7 must be provided on the sliding surface 4a, which is shown in detail in Fig. 2. As can be seen from Fig. 2, the stationary sliding ring 4 has a sintered, ceramic ring 41, which is made of an electrically non-conductive ceramic material, in particular SiC. Furthermore, two identically constructed electrically conductive contact bodies 42 for contacting the sensor are arranged in the ring 41.
[0049] 7 arranged.
[0050] As can be seen from Figs. 2 and 3, the electrically conductive contact bodies 42 extend from a rear side 4b to the sliding surface 4a. The electrically conductive contact bodies 42 are arranged in recesses 40 formed in the ring 41 and extend straight and parallel through the sliding ring 4.
[0051] The electrically conductive contact body 42 comprises a first region 42a and a second region 42b.
[0052] The electrically conductive contact bodies 42 each have an electrical connection area 13 for an electrical line 8 on an outlet side on the rear side 4b of the sliding ring 4. The electrical connection area 13 is formed such that the electrical line
[0053] 8 can be connected directly to the second area 42b.
[0054] The first region 42a is arranged in the recess 40 at an end of the recess 40 directed towards the sliding surface 4a and contacts the sensor 7. The second region 42b fills the remaining recess 40 and extends to the rear side 4b of the stationary sliding ring 4.
[0055] The first region 42a is made of a first electrically conductive ceramic material, and in this embodiment, is made of SiSiC. The second region is made of a different, second electrically conductive material, and in this embodiment, is made of a mixture of metallic silicon and SiC to form a composite material. The composite material can have a maximum of 15 vol% gas-filled pores.
[0056] The hardness of the first electrically conductive ceramic material is greater than the hardness of the second electrically conductive material. The hardness of the first and second electrically conductive materials can be determined using known methods, such as the Vickers method.
[0057] The harder first region 42a, which is formed in the recess 40 on the side facing the sliding surface 4a, can prevent cracks from forming on the sliding surface. This applies both to cracks that can enter the ceramic ring 41 due to the recess 40, i.e., at the edge of the recess 40, and to cracks in the electrically conductive contact body 42 itself, which can propagate further into the ceramic ring 41 even after they have formed. The second region 42b of the electrically conductive contact body 42, which comprises metallic silicon and extends to the rear side 4b of the stationary sliding ring 4, enables direct and uncomplicated electrical contact with the electrical line 8. In particular, no metal pin or the like needs to be provided in the electrically conductive contact body 42 for electrical contact. The electrical line 8 can be fixed directly, e.g., by welding.
[0058] Thus, the electrically conductive contact body 42 with the two different areas 42a and 42b on the sliding surface prevents crack formation and enables simple, fast and cost-effective electrical contact with the electrical line 8 on the back of the stationary sliding ring 4.
[0059] As can be further seen from Fig. 2, in this exemplary embodiment, the sensor 7 is made of the same material as the first region 42a, namely SiSiC. This allows for a simple connection between the sensor 7 and the electrically conductive contact bodies 42 during production. In particular, the sensor 7 is manufactured simultaneously with the first region 42a.
[0060] As can be seen in particular from Fig. 3, the first region 42a has a first length L1 in the axial direction of the contact body 42, which is smaller than a second length L2 of the contact body 42 in the axial direction. The first length L1 is preferably in a range of 1 mm to 2 mm.
[0061] A thickness of the layer of the sensor 7 is further smaller than the first length L1.
[0062] As shown in Fig. 1, the two electrically conductive contact bodies 42 are electrically connected to the measuring device 6 by the electrical lines 8 and thus the sensor 7 is also electrically connected to the measuring device 6.
[0063] The stationary sliding ring 4 made of ceramic material can be manufactured in such a way that, in a first step, an annular green compact is provided corresponding to the desired geometric shape of the stationary sliding ring 4 made of an electrically non-conductive ceramic material, e.g., SiC. Simultaneously or subsequently, the recesses 40 for the electrically conductive contact bodies 42 are introduced into the green compact. The green compact is then pre-sintered. Subsequently, the depression 43 is also introduced. In a next step, the depression 43 for the sensor 7 is filled, as well as the recesses 40 are partially filled, using the same material, e.g., SiSiC. The recesses 40 are only partially filled until the first length L1 in the recess 40 is filled, in order to form the first region 42a.Subsequently, the second electrically conductive material, which forms the second region 42b, is introduced into the still free region in the recess 40. A mixture of metallic silicon and a ceramic material, in particular SiC, can be introduced for the second region 42b. Subsequently, the sliding ring is re-sintered so that the first and second regions 42a, 42b are also sintered with the sensor 7. In the second region 42b, no SiSiC is formed, but rather a mixture of metallic silicon and SiC.
[0064] In addition to the formation of SiSiC in the first region 42a, the re-sintering also results in chemical bonds between the material of the ring and the material of the second region 42b of the contact body 42.
[0065] Since the thermal expansion of the ceramic of the ring 41 and the two regions 42a, 42b of the electrically conductive contact body 42 is essentially the same, there is no component weakening due to thermal expansion, as would be the case when using a metallic material for electrical contact. This also eliminates temperature-dependent restrictions on the choice of coating 9. In particular, a diamond coating, which must be applied at temperatures of approximately 900°C, can be provided, which can be applied after the sliding ring has been manufactured.
[0066] Furthermore, the atomic bonds during the post-sintering step between the material of the ring 41 and the material of the first region 42a of the electrically conductive contact body 42 result in flush terminations, in particular at the sliding surface, so that the sliding ring has excellent flatness and, in particular, there is also an edgeless transition between the ring material and the material of the electrical contact region.
[0067] This also results in significantly improved emergency running properties, particularly with regard to the possible duration of emergency running, since, for example, after wear of the sensor 7, a flat surface remains on the sliding surface 4a, particularly at the transition between the two materials, which can be used as a sliding surface for emergency running. Thus, a stationary sliding ring 4 can be provided, which, for example, has a sensor 7 for measuring wear on the sliding surface. If the sensor 7 is worn away due to wear, an electrical circuit is interrupted via the contact bodies 42, which serves as a wear indicator. The sensor contact is integrated into the ring and ensured by the lubricious, ceramic material. The second area 42b also allows for particularly simple thermal electrical contact by welding or soldering directly on the sliding ring, without damaging the sliding ring.
[0068] Fig. 4 shows a sliding ring 4 of a mechanical seal assembly according to a second embodiment of the invention. Identical or functionally identical parts are designated by the same reference numerals as in the first embodiment.
[0069] In contrast to the first embodiment, the sliding ring of the second embodiment has a coating 9. The coating is applied over the entire sliding surface of the sliding ring and, in this embodiment, is an electrically conductive DLC coating. This can be achieved, for example, using a doped DLG coating. The electrically conductive coating 9 forms the sensor 7 and closes the electrical circuit between the two contact bodies 42 in the ring 41. If the coating 9 becomes worn, the electrical circuit at the sliding surface is interrupted, so that wear on the measuring device 6 is indicated by the interrupted circuit. Otherwise, the embodiment corresponds to the previous embodiment, so that reference can be made to the description given there.
[0070] Fig. 5 shows a sliding ring 4 according to a third embodiment of the invention. Identical or functionally identical parts are designated by the sliding reference numerals as in the previous embodiments.
[0071] As can be seen from Fig. 5, the third embodiment essentially corresponds to the first embodiment. However, in the third embodiment, no recess is provided on the sliding surface of the ring 41. The sensor 7 is provided as an electrically conductive coating on a partial area of the sliding surface of the ring 41. The sensor 7 electrically connects the two electrically conductive contact bodies 42 to one another and closes the electrical circuit. An electrically non-conductive coating 9' is formed above the sensor 7. The electrically non-conductive coating 9' covers the entire sliding surface of the sliding ring 4. The structure of the contact body 42 with the first area 42a and the second area 42b again corresponds to the previous embodiments.
[0072] If the electrically non-conductive coating 9' and the sensor 7 wear, the electrical circuit is again electrically disconnected, so that the measuring device 6 can output a corresponding wear signal. Otherwise, this embodiment corresponds to the previous embodiments, so reference can be made to the description given there.
[0073] In addition to the above written description of the invention, reference is hereby explicitly made to the graphic representation of the invention in Figs. 1 to 5 for its supplementary disclosure.
[0074] List of reference symbols
[0075] 1 mechanical seal arrangement
[0076] 2 mechanical seals
[0077] 3 rotating slide ring
[0078] 3a first sliding surface
[0079] 4 stationary sliding ring
[0080] 4a second sliding surface
[0081] 4b back
[0082] 5 Sealing gap
[0083] 6 Measuring device
[0084] 7 Sensor
[0085] 8 electrical cable
[0086] 9 electrically conductive coating
[0087] 9' electrically non-conductive coating
[0088] 13 electrical connection
[0089] 14 Wave
[0090] 15 Preload element
[0091] 16 sliding ring carriers
[0092] 17 Screw
[0093] 18 Area where the product to be sealed is present
[0094] 19 Atmosphere area
[0095] 20 Housing component
[0096] 21 first O-ring
[0097] 22 second O-ring
[0098] 40 recess
[0099] 41 electrically non-conductive ceramic ring
[0100] 42 electrically conductive contact body
[0101] 42a first area
[0102] 42b second area
[0103] 43 Recess in the sliding surface
[0104] L1 first length
[0105] L2 second length
[0106] XX Central axis
Claims
Claims 1 . A sliding ring of a mechanical seal arrangement, comprising a sintered, ceramic ring (41) with a sliding surface (4a), which is made of an electrically non-conductive ceramic material, and an electrically conductive contact body (42) which is designed for electrical contact and is arranged in a recess (40) in the ring (41), wherein the electrically conductive contact body (42) has a first region (42a) and a second region (42b), wherein the first region (42a) is arranged in the recess (40) at an end of the recess (40) directed towards the sliding surface (4a) and fills a part of the recess (40), and wherein the second region (42b) fills the remaining recess (40), wherein the first region (42a) is made of a first, electrically conductive, ceramic material with a first hardness, and wherein the second region (42b) is made of a second,electrically conductive material having a second hardness, and wherein the first hardness of the first region (42a) is greater than the second hardness of the second region (42b)., 2. Slide ring according to claim 1, wherein the first region (42a) is made of electrically conductive SiSiC.
3. A sliding ring according to any one of the preceding claims, wherein the second region (42b) is made of a composite material of metallic silicon and SiC.
4. A sliding ring according to any one of the preceding claims, wherein the first region (42a) has a first length (L1) in the axial direction of the recess (40) which is smaller than a second length (L2) of the second region (42b) in the axial direction of the recess (40).
5. Sliding ring according to one of the preceding claims, wherein the first region (42a) is connected to a sensor (7) arranged on the sliding surface (4a).
6. Slide ring according to claim 5, wherein the sensor (7) is an electrically conductive sensor layer and is made of the same material as the first region (42a).
7. A sliding ring according to claim 6, wherein the sensor layer is arranged in a recess (43) in the sliding surface (4a) of the sliding ring.
8. Sliding ring according to claim 5 or 6, wherein the sensor (7) is an electrically conductive coating arranged on the entire sliding surface.
9. Sliding ring according to one of claims 5 to 7, wherein the sensor (7) is covered by an electrically non-conductive coating (9) which forms the sliding surface of the sliding ring.
10. Sliding ring according to one of the preceding claims, wherein chemical connections produced by sintering are formed between the electrically conductive contact body (42) and the ring (41).
11. A sliding ring according to any one of the preceding claims, wherein the recess (40) is a through-recess which extends from a rear side (4b) to the sliding surface (4a) or which extends from an inner peripheral side (4c) or an outer peripheral side (4d) to the sliding surface (4a).
12. Slide ring according to one of the preceding claims, wherein an electrical line (8) is electrically connected to the electrically conductive contact body (42) directly at the second region (42b).
13. Sliding ring according to one of the preceding claims, wherein the sliding ring is a stationary sliding ring (4) of the mechanical seal arrangement and two contact bodies (42) are present in the ring (41) for electrically contacting the sensor (7) in order to form an electrically closed circuit.
14. Mechanical seal arrangement comprising a stationary sliding ring (4) according to one of the preceding claims and a measuring device (6) which is electrically connected to the contact body (42) of the sliding ring (4).
15. A method for producing a sliding ring, comprising the steps: Producing a ring-shaped green body from an electrically non-conductive ceramic material, Making a through-hole (40) in the green body, pre-sintering the green body Filling a portion of the recess (40) with a first electrically conductive ceramic material, introducing a second electrically conductive material into the not yet filled portion of the recess (40), and Re-sintering the sliding ring with the first and second electrically conductive materials to form a first region (42a) and a second region (42b) of an electrically conductive contact body (42) in the recess (40), thereby producing a ceramic sliding ring with an electrically non-conductive ceramic ring (41) and the electrically conductive contact body (42), wherein a hardness of the first region is greater than a hardness of the second region. The method according to claim 15, wherein a coating (9) is applied to the sliding surface (4a) of the sliding ring after re-sintering and / or wherein a sensor material is also sintered during re-sintering.