Monitoring Device and Measurement Method for Wear State of Sealing Ring

Abstract

The present invention provides a monitoring device and a measuring method for the wear state of a sealing ring, which relate to the field of sealing. The monitoring device is used to monitor the wear state of the sealing ring. The sealing ring is arranged in a sealing cavity and seals the sealing cavity. Wherein, the monitoring device includes: a rangefinder arranged in the sealing cavity and measuring the height of the sealing cavity; a pressure gauge arranged outside the sealing ring and measuring the pressure at the outer wall surface of the sealing ring; a calculation unit electrically connected to the rangefinder and the pressure gauge respectively. The calculation unit calculates the wear amount of the sealing ring according to the height and the pressure. The monitoring device and method for the sealing wear state provided by the present invention have simple wiring and do not affect the sealing performance.

Description

Technical Field

[0001] The present invention relates to the field of sealing, and particularly to a monitoring device and a measuring method for the wear state of a sealing ring. Background Art

[0002] The main drive sealing system of a shield machine is the safety guarantee of the main drive. The quality of the main drive seal directly determines the safety and reliability of the shield machine. The main function of the main drive sealing system is to prevent impurities such as sand, soil, and water in the excavation chamber from invading the main bearing and to prevent the lubricating gear oil of the main bearing from leaking. The main drive seal of a shield machine generally adopts a rotary contact sealing structure, and the sealing element is installed on the sealing track with a certain compression amount. During the operation of the shield machine, the sealing element and the track make a relative rotary motion and there is friction in the contact area between the two. The existence of the friction force in the contact area causes wear of the sealing element, resulting in insufficient sealing compression amount and decreased sealing performance. Furthermore, it leads to the sealing element being unable to effectively block the invasion of impurities such as sand, soil, and water into the main bearing, ultimately causing risks such as damage to the main drive system, extended construction period, and increased construction costs.

[0003] In recent research on seal condition monitoring, a monitoring device is mostly placed on the seal or a monitoring micro-structure is buried in the seal body. For example, in the sealing component and the method for monitoring the dynamic performance of the sealing component with the application number CN107110221A, a vibration sensor is fixed on the sealing element to monitor the signal during the working state. As time goes by, when the sealing element wears, a vector change can be measured and a warning signal is sent. In patent CN106523710A, a magnet is fixed at the seal opening and a magnetic field sensor is fixed at the seal body part. As the seal wears, the wear amount of the seal is calculated by measuring the distance from the magnet fixed at the lip opening with the magnetic field sensor. In patent CN107504188A, a metal wire is buried in the lip, and the alarm is connected to the metal wire and the shaft. When the wear amount reaches a certain level, the circuit is connected and an alarm is sent.

[0004] However, for the above patents, the installation of sensors and micro-monitoring structures on the seal body is difficult for wiring. At the same time, installing a monitoring structure on the seal body requires damaging the seal's own structure, which affects its compression permanent deformation, aging and other indicators, and thus affects its service life.

[0005] In view of this, based on the production design experience in this field and related fields for many years, the inventor has designed a monitoring device and a measuring method for the wear state of a sealing ring through repeated tests, in order to solve the problems existing in the prior art. Summary of the Invention

[0006] The purpose of the present invention is to provide a monitoring device and a measuring method for the wear state of a sealing ring, which are simple in wiring and do not affect the sealing performance.

[0007] To achieve the above object, the present invention provides a monitoring device for the wear state of a sealing ring. The main drive seal of the shield machine has a sealing cavity and at least one sealing ring disposed in the sealing cavity. Among them, the monitoring device includes:

[0008] A rangefinder disposed in the sealing cavity and measuring the height of the sealing cavity;

[0009] A pressure gauge disposed outside the sealing ring and measuring the pressure at the outer wall surface of the sealing ring;

[0010] A calculation unit electrically connected to the rangefinder and the pressure gauge respectively. The calculation unit calculates the wear amount of the sealing ring according to the height and the pressure.

[0011] The monitoring device for the wear state of the sealing ring as described above, wherein the sealing cavity is disposed in the main drive of the shield machine. The sealing cavity is an annular cavity surrounded by a sealing runway and a grease ring. The sealing runway is connected to the inner ring of the main bearing of the shield machine, and the grease ring is connected to the outer ring of the main bearing of the shield machine. The sealing rings are respectively in sealing cooperation with the sealing runway and the grease ring.

[0012] The monitoring device for the wear state of the sealing ring as described above, wherein a plurality of the sealing rings are disposed in the sealing cavity, and a spacer ring is disposed between every two adjacent sealing rings. The pressure gauge is disposed at the position of the outer wall surface of one of the sealing rings.

[0013] The monitoring device for the wear state of the sealing ring as described above, wherein a first mounting hole is formed in the inner wall of the grease ring corresponding to the position of the sealing ring. The pressure gauge is disposed in the first mounting hole, and the measuring end face of the pressure gauge is in close contact with the outer wall of the sealing ring.

[0014] The monitoring device for the wear state of the sealing ring as described above, wherein the pressure gauge is a pressure sensor, a strain gauge or a dynamometer.

[0015] The monitoring device for the wear state of the sealing ring as described above, wherein a compression ring is disposed at one end of the sealing cavity. The compression ring is fixedly disposed on the grease ring, and a second mounting hole is formed in the compression ring. The rangefinder is disposed in the second mounting hole.

[0016] The monitoring device for the wear state of the sealing ring as described above, wherein the rangefinder is an eddy current sensor, a displacement sensor or a laser rangefinder.

[0017] The monitoring device for the wear state of the sealing ring as described above, wherein the calculation unit internally stores a theoretical difference curve of seal wear, and the calculation unit calculates the wear amount of the sealing ring according to the theoretical difference curve of seal wear.

[0018] The present invention also provides a method for measuring the wear state of a sealing ring, which is used to monitor the wear state of the sealing ring. Wherein, the sealing ring is arranged in a sealing cavity and seals the sealing cavity, the height of the sealing cavity and the pressure at the outer wall surface of the sealing ring are measured, and the wear amount of the sealing ring is calculated according to the height and the pressure.

[0019] The method for measuring the wear state of the sealing ring as described above, wherein the wear amount is calculated based on the theoretical interpolation curve of the seal wear amount.

[0020] The method for measuring the wear state of the sealing ring as described above, wherein the steps for drawing the theoretical interpolation curve of the seal wear amount include:

[0021] Step 1, draw the theoretical interpolation curve of the seal wear amount with δ = 0. Compress the wear amount of the sealing ring that has not undergone wear so that the sealing ring has a sealing height H1. Theoretically calculate the pressure F1 at the outer wall surface of the sealing ring corresponding to the sealing height H1. Continue to compress the sealing ring so that the sealing height is Hi, and use the same method to obtain the pressure Fi. Set up a coordinate system with the height Hi as the abscissa and the pressure Fi as the ordinate, and connect each coordinate point to obtain the theoretical interpolation curve of the seal wear amount when δ = 0.

[0022] Step 2, by analogy, draw the theoretical interpolation curve of the seal wear amount under different wear amounts δ = i.

[0023] The method for measuring the wear state of the sealing ring as described above, wherein the steps for calculating the wear amount include:

[0024] Take the measured height Ha as the abscissa and the measured pressure Fa as the ordinate, and then set the coordinate point A. Determine the theoretical interpolation curve of the seal wear amount that is closest to the coordinate point A, and the wear amount δ = a corresponding to the theoretical interpolation curve of the seal wear amount is the wear amount of the seal.

[0025] Compared with the prior art, the present invention has the following characteristics and advantages:

[0026] The present invention provides a monitoring device and a measuring method for the wear state of a sealing ring, which do not need to change the processing technology of the sealing structure, ensure the integrity and service performance of the sealing structure, and the equipment installation is simple and the wiring is convenient.

[0027] The present invention provides a monitoring device and a measuring method for the wear state of a sealing ring, which simply and quickly determine the seal wear amount by combining the monitoring data with the theoretical calculation results, and predict the seal wear state. Description of the Drawings

[0028] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Additionally, the shapes, proportional dimensions, etc. of the components in the drawings are only schematic and are used to assist in understanding the present invention, rather than specifically defining the shapes and proportional dimensions of the components of the present invention. Those skilled in the art can, under the teachings of the present invention, select various possible shapes and proportional dimensions according to specific circumstances to implement the present invention.

[0029] Figure 1 Schematic diagram of the monitoring device for the wear state of the sealing ring proposed by the present invention;

[0030] Figure 2 Theoretical interpolation curve graph of the sealing wear amount;

[0031] Figure 3 Schematic diagram of the height measurement of the sealing ring in three states;

[0032] Figure 4 Sealing wear monitoring flowchart.

[0033] Description of reference numerals:

[0034] 100, monitoring device; 110, rangefinder;

[0035] 120, pressure gauge; 10, sealing cavity;

[0036] 20, sealing ring; 30, sealing runway;

[0037] 40, grease ring; 41, first mounting hole;

[0038] 50, spacer ring; 51, grease pipeline

[0039] 60, pressure ring; 61, second mounting hole. Detailed implementation manners

[0040] Combined with the accompanying drawings and the description of the specific implementation manners of the present invention, the details of the present invention can be more clearly understood. However, the specific implementation manners of the present invention described herein are only for the purpose of explaining the present invention and cannot be understood in any way as a limitation of the present invention. Under the teachings of the present invention, those skilled in the art can conceive any possible variations based on the present invention, and these should all be regarded as belonging to the scope of the present invention.

[0041] The present invention proposes a monitoring device 100 for the wear state of a sealing ring, which is used to monitor the wear state of the sealing ring 20, such as Figure 1As shown, the sealing ring 20 is disposed within the sealing cavity 10 and seals the sealing cavity 10. The monitoring device 100 includes a rangefinder 110, a pressure gauge 120, and a calculation unit (not shown in the figure). Among them, the rangefinder 110 is disposed within the sealing cavity 10 and measures the height H of the sealing cavity 10. The pressure gauge is disposed within the sealing cavity 10 and measures the pressure F at the outer wall surface of the sealing ring 20 (i.e., Figure 1 the pressure at the top of the sealing ring 20 in Figure 1 ). The calculation unit is electrically connected to the rangefinder 110 and the pressure gauge 120 respectively. The calculation unit calculates the wear amount of the sealing ring 20 based on the height H and the pressure F.

[0042] The present invention also relates to a method for measuring the wear state of a sealing ring, which is used to monitor the wear state of the sealing ring 20. The sealing ring 20 is disposed within the sealing cavity 10 and seals the sealing cavity 10. The height H of the sealing cavity 10 and the pressure F at the outer wall surface of the sealing ring 20 are measured. The wear amount δ of the sealing ring 20 is calculated based on the height H and the pressure F.

[0043] In the present invention, the pressure F at the outer wall surface of the sealing ring 20 (i.e., the top of the sealing ring 20) is directly related to the wear amount δ of the sealing ring 20, and is also affected by the compression amount of the sealing ring 20. Different heights H of the sealing cavity 10 correspond to different compression amounts of the sealing ring 20. Therefore, the wear amount δ of the sealing ring 20 can be calculated through the height of the sealing cavity 10 and the pressure F at the outer wall surface of the sealing ring 20.

[0044] The measuring device and measuring method for the wear state of the sealing ring proposed by the present invention integrate two monitoring indicators, namely the height H of the sealing cavity 10 and the pressure F at the outer wall surface of the sealing ring 20, and can accurately monitor the wear amount of the sealing ring to judge the state of the sealing system, improve the sealing safety performance, and reduce the risk of seal failure.

[0045] In the present invention, the rangefinder 110 and the pressure gauge 120 are disposed in the sealing cavity 10, without damaging the sealing structure, and without changing the sealing processing technology, ensuring the integrity and sealing performance of the sealing structure.

[0046] For the monitoring device 100 for the wear state of the sealing ring proposed by the present invention, the rangefinder 110 and the pressure gauge 120 are simply installed and the wiring is convenient, facilitating installation and maintenance.

[0047] For the monitoring device 100 for the wear state of the sealing ring proposed by the present invention, the wear state of the sealing ring is monitored in real time by using the rangefinder 110 and the pressure gauge 120. Furthermore, the wear amount of the sealing ring can be monitored quickly and efficiently, and the wear condition of the sealing system can be grasped in real time, the wear state of the seal can be predicted, seal failure can be detected in time, and the sealing ring can be ensured to be in a safe working state.

[0048] In an alternative example of the present invention, the calculation unit internally stores a theoretical interpolation curve for seal wear, and the calculation unit determines whether the seal is worn and the wear amount δi in the theoretical interpolation curve of seal wear through the relationship of "seal cavity height Hi - seal top pressure Fi".

[0049] In an alternative example of the present invention, the seal cavity 10 is provided in the main drive of the shield machine. Specifically, the seal cavity 10 is an annular cavity surrounded by a seal runway 30 and a grease ring 40. The seal runway 30 is connected to the inner ring of the main bearing of the shield machine, and the grease ring 40 is connected to the outer ring of the main bearing of the shield machine. The inner wall surface and the outer wall surface of the sealing ring 20 are respectively in sealing cooperation with the seal runway 30 and the grease ring 40.

[0050] With the above structure, the sealing ring 20 is used to seal the space between the outer ring and the inner ring of the main bearing of the shield machine, preventing external impurities from entering the main drive bearing of the shield machine. Through the monitoring device 100, the wear amount of the sealing ring 20 can be quickly and efficiently monitored, so as to master the wear condition of the sealing system in real time, predict the wear state of the seal, discover seal failure in time, and ensure that the main drive sealing system is in a safe working state. The shield machine effectively avoids damage to the main drive bearing and reduces the operation risk of the equipment.

[0051] In an alternative example of the present invention, a plurality of sealing rings 20 are provided in the seal cavity 10, and a spacer ring 50 is provided between every two adjacent sealing rings 20. The monitoring device 100 includes a pressure gauge 120, and the pressure gauge 120 is installed at the position of one of the sealing rings 20 and measures the pressure at the outer wall surface of the corresponding sealing ring 20.

[0052] In another alternative example of the present invention, a plurality of sealing rings 20 are provided in the seal cavity 10, and a spacer ring 50 is provided between every two adjacent sealing rings 20. The monitoring device 100 includes a plurality of pressure gauges 120, and the plurality of pressure gauges 120 are arranged in one-to-one correspondence with the plurality of sealing rings 20, and each pressure gauge 120 measures the pressure at the outer wall surface of the corresponding sealing ring 20.

[0053] In an alternative example of the present invention, the sealing ring 20 is a rubber sealing ring to enhance the sealing performance of the sealing ring 20 for the seal cavity 10. When the sealing ring 20 is a rubber elastomer, it is more sensitive to changes in displacement load. Under different compression amounts, the sealing ring 20 shows different stress-strain distributions as a whole. By installing a pressure gauge 120 on the top of the sealing ring 20 (i.e., the outer wall surface of the sealing ring 20), the magnitude of the pressure at the top of the sealing ring 20 can be measured. Under different compression amounts, the sealing rings 20 in the worn state and the unworn state show different pressure magnitudes at the top.

[0054] Such as Figure 3As described above, it gives a schematic diagram of the measurement of the height of the sealing ring cavity in three states of sealing, namely, the free and uncompressed state of the sealing ring 20; the initial installation state of the sealing ring 20 (when the seal has not worn); and the worn state of the sealing ring 20.

[0055] In an alternative example of the invention, a first mounting hole 41 is provided at a position on the inner wall of the grease ring 40 corresponding to the sealing ring 20, and a pressure gauge 120 is disposed in the first mounting hole 41. The measuring end face of the pressure gauge 120 is in close contact with the outer wall of the sealing ring 20 (i.e., the top of the sealing ring 20). Because the first mounting hole 41 is provided on the grease ring 40, when wiring, the circuit of the pressure gauge 120 can be led out through the outer wall of the grease ring 40, completely avoiding the sealing ring 20 and not affecting the sealing effect; and since the sealing ring 20 can seal the first mounting hole 41, the first mounting hole 41 also does not affect the sealing effect. The measuring end face of the pressure gauge 120 is in close fit with the outer wall surface of the sealing ring 20 to more accurately measure the magnitude of the force F on the top of the sealing ring 20.

[0056] In an alternative example, the first mounting hole 41 is a threaded hole, and the outer wall of the pressure gauge 120 is in threaded fit with the inner wall of the threaded hole.

[0057] In an alternative example of the present invention, the pressure gauge 120 is a pressure sensor, a strain gauge or a dynamometer. Of course, the pressure gauge 120 can also be other measuring instruments as long as it can measure the magnitude of the pressure (force) F on the top of the sealing ring 20.

[0058] In an alternative example of the present invention, a pressure ring 60 is provided in the sealing cavity 10. The pressure ring is disposed close to the sealing ring 20 and fixedly connected to the grease ring 40. A second mounting hole 61 is provided in the pressure ring 60, and a distance measuring instrument 110 is disposed in the second mounting hole 61.

[0059] In an alternative example, the second mounting hole 61 is a threaded hole, and the outer wall of the distance measuring instrument 110 is in threaded fit with the inner wall of the threaded hole.

[0060] In an alternative example of the present invention, the distance measuring instrument 110 is an eddy current sensor, a displacement sensor or a laser rangefinder. The distance measuring instrument 110 can also be other measuring instruments as long as it can measure the height H of the sealing cavity 10.

[0061] In an alternative example, the distance measuring instrument 110 directly measures the vertical distance H between the lower surface of the pressure ring 60 and the sealing track 30 j , so as to obtain the real-time height H of the sealing cavity 10 during the operation of the main drive of the shield machine i , specifically, H i =H j +H2, where H2 is the thickness of the pressure ring 60, which is known and fixed.

[0062] It should be noted that, as Figure 2 shown, the theoretical interpolation curve of the seal wear amount is obtained by theoretically calculating the pressure at the top of the seal ring for a series of seal rings with different wear degrees under different compression amounts, and each curve represents a wear amount.

[0063] In an alternative example of the present invention, the steps for drawing the theoretical interpolation curve of the seal wear amount include:

[0064] Step 1, draw the theoretical interpolation curve of the seal wear amount with δ = 0. Compress the wear amount of the unsealed seal ring so that the seal ring has a sealing height H1, theoretically calculate the pressure F1 on the outer wall surface of the seal ring corresponding to the sealing height H1, and continue to compress the seal ring so that the sealing height is H i , and use the same method to obtain the pressure F i , set up a coordinate system so that the height H i is the abscissa and the pressure F i is the ordinate, and connect each coordinate point to obtain the theoretical interpolation curve of the seal wear amount when δ = 0;

[0065] Step 2, by analogy, draw the theoretical interpolation curve of the seal wear amount under different wear amounts δ = i.

[0066] Furthermore, the steps for drawing the theoretical interpolation curve of the seal wear amount further include Step 3, refining the theoretical interpolation curve of the seal wear amount by reducing the seal height increment (Hi - Hi-1) and the wear amount increment (δi - δi-1). Theoretically, the greater the density of the curve, the more accurate the seal wear amount δ calculated based on it.

[0067] In an alternative example, the steps for calculating the wear amount include: taking the measured height Ha as the abscissa and the measured pressure Fa as the ordinate to set the coordinate point A, and judging the theoretical interpolation curve of the seal wear amount closest to the coordinate point A, then the wear amount δ = a corresponding to the theoretical interpolation curve of the seal wear amount is the wear amount of the seal.

[0068] Now, in combination with an embodiment, the working principle and specific implementation process of the monitoring device 100 for the wear state of the seal ring proposed by the present invention will be described in detail:

[0069] As Figure 1As shown in the figure, the sealing device has a sealing cavity 10 and at least one sealing ring 20 disposed within the sealing cavity 10. The sealing cavity 10 is an annular cavity formed by enclosing a sealing track 30 and a grease ring 40. The sealing track 30 is connected to the inner ring of the main bearing of the shield machine, and the grease ring 40 is connected to the outer ring of the main bearing of the shield machine. The inner wall surface and the outer wall surface of the sealing ring 20 are respectively in sealing fit with the sealing track 30 and the grease ring 40. The installation state of the initial sealing ring 20 without wear is as shown in Figure 1 the figure. Adjacent sealing rings 20 are separated by a spacer ring 50. The spacer ring 50 has a through grease pipeline 51 for delivering grease into the sealing cavity 10.

[0070] Considering the height change of the sealing cavity 10 caused by vibration, eccentricity, etc. during the operation of the main drive of the shield machine, a distance measuring instrument 110 (eddy current sensor) is fixed on the pressure ring 60 to measure the vertical distance Hj between the lower surface of the pressure ring 60 and the upper surface of the sealing track 30, so as to obtain the height Hi of the sealing cavity during the operation of the equipment (Hi = Hj + H2, where H2 is the thickness of the pressure ring, which is known and fixed). At the same time, a pressure measuring instrument 120 (pressure sensor) is fixed on the grease ring 40, and the pressure measuring end face of the pressure measuring instrument 120 is in close contact with the top of the sealing ring 20 to accurately measure the magnitude of the top pressure (force) F of the sealing ring 20. The above-mentioned pressure measuring instrument 120 (pressure sensor) and distance measuring instrument 110 (eddy current sensor) can be fastened on the grease ring 40 and the pressure ring 60 respectively by means of threaded holes. The calculation unit is disposed outside the main drive of the shield machine. The calculation unit is electrically connected to the pressure measuring instrument 120 (pressure sensor) and the distance measuring instrument 110 (eddy current sensor) respectively. It can be connected by wires, and the wiring method is led out from the upper end of the grease ring 40, completely avoiding the sealing ring 20 without affecting the sealing structure; it can also be connected by wireless communication technology without wiring.

[0071] During the operation of the main drive of the shield machine, due to equipment vibration, eccentricity, etc., the height H of the sealing cavity 10 changes. At the same time, the pressure measuring instrument 120 (pressure sensor) and the distance measuring instrument 110 (eddy current sensor) are used to measure the top pressure Fi of the seal and the height Hi of the sealing cavity in real time. Then, based on the relationship between "the height Hi of the sealing cavity - the top pressure Fi of the seal", it is judged whether the seal is worn and the wear amount δi in the theoretical interpolation curve of the seal wear amount.

[0072] The theoretical interpolation curve of the seal wear amount can be built into the calculation unit. By processing the monitoring data of the two sensors and interpolating in the theoretical interpolation curve of the seal wear amount, the seal wear amount range is finally obtained and output to the user, so as to judge the use state of the shield machine seal. When the seal wears to the specified range, stop the machine to replace the seal to avoid more serious damage to the equipment caused by continued use of the worn seal.

[0073] The theoretical interpolation curve of the seal wear amount is obtained by the following method:

[0074] (1) Compress the non-worn sealing ring 20 (wear amount δ0 = 0) to make the sealing ring 20 have different sealing heights, and theoretically calculate (such as the finite element simulation method) to obtain the sealing top pressure, and then make the sealing height be H i , and use the same method to obtain the sealing top pressure F i , and then connect this series of (H i , F i ) to obtain the curve when the sealing wear amount δ0 = 0;

[0075] (2) By analogy, use the same method to obtain the curve when the wear amount of the sealing ring 20 is δi.

[0076] (3) The theoretical interpolation curve of the sealing wear amount can be refined by reducing the sealing cavity height increment (H i - H i-1 ) and the wear amount increment (δ i - δ i-1 ).

[0077] As Figure 2 , Figure 4 shown, at time t, the distance measuring instrument 110 (eddy current sensor) on the pressure ring 60 shows H j , and the height H i of the sealing cavity 10 is obtained, H j = H i + H2. At this time, the pressure measuring instrument 120 (pressure sensor) measures the top pressure Fi of the sealing ring 20. In the theoretical interpolation curve graph of the sealing wear amount ( Figure 2 shown), draw a straight line parallel to the coordinate axes through the coordinate points of H i , F i . If the point A is on the δ0 curve, it indicates that the seal is not worn. If the point A is between the δ0 and δ1 curves, it indicates that the seal is worn, and the wear amount is between δ0 and δ1. Theoretically, more theoretical interpolation curves of the sealing wear amount can be added between δ0 and δ1 to more accurately evaluate the size of the sealing wear amount.

[0078] Regarding the detailed explanations of the above embodiments, their purposes are only to explain the present invention so that it can be better understood. However, these descriptions cannot be construed as limitations on the present invention for any reason. In particular, the various features described in different embodiments can also be arbitrarily combined with each other to form other embodiments. Unless there are explicit contrary descriptions, these features should be understood to be applicable to any one of the embodiments and not limited only to the described embodiments.

Claims

1. A monitoring device for the wear state of a sealing ring, which is used to monitor the wear state of the sealing ring. The sealing ring is arranged in a sealing cavity and seals the sealing cavity, and is characterized in that, The monitoring device includes: A rangefinder, which is arranged in the sealing cavity and measures the height of the sealing cavity; A pressure gauge, which is arranged outside the sealing ring and measures the pressure at the outer wall surface of the sealing ring; A calculation unit, which is electrically connected to the rangefinder and the pressure gauge respectively. The calculation unit calculates the wear amount of the sealing ring according to the height and the pressure; The calculation unit internally stores multiple theoretical interpolation curves of seal wear, and the calculation unit calculates the wear amount of the sealing ring based on the multiple theoretical interpolation curves of seal wear amount; The multiple theoretical interpolation curves of seal wear amount are set in the same coordinate system. The abscissa of the coordinate system is the height Hi, and the ordinate of the coordinate system is the pressure Fi; The drawing steps of the theoretical interpolation curve of seal wear amount include: Step 1, draw the theoretical interpolation curve of seal wear amount with wear amount δ = 0. Compress the wear amount of the sealing ring that has not undergone wear so that the sealing ring has a sealing height H1. Theoretically calculate the pressure F1 on the outer wall surface of the sealing ring corresponding to the sealing height H1. Continue to compress the sealing ring so that the sealing height is Hi, and use the same method to obtain the pressure Fi. Set up a coordinate system with the height Hi as the abscissa and the pressure Fi as the ordinate, and connect each coordinate point to obtain the theoretical interpolation curve of seal wear amount when δ = 0; Step 2, and so on, draw the theoretical interpolation curve of seal wear amount under different wear amounts δ = i; Using the measured height Ha as the abscissa and the measured pressure Fa as the ordinate, in the graph of the theoretical interpolation curve of seal wear amount, draw straight lines parallel to the coordinate axes through the coordinate points Hi and Fi. Let the intersection point of the two straight lines be the coordinate point A. Judge the theoretical interpolation curve of seal wear amount closest to the coordinate point A, and the wear amount δ = a corresponding to the theoretical interpolation curve of seal wear amount is the wear amount of the seal; 2. The monitoring device for the wear state of the sealing ring according to claim 1, characterized in that The sealing cavity is arranged in the main drive of the shield machine. The sealing cavity is an annular cavity surrounded by a sealing runway and a grease ring. The sealing runway is connected to the inner ring of the main bearing of the shield machine, and the grease ring is connected to the outer ring of the main bearing of the shield machine. The sealing ring is hermetically matched with the sealing runway and the grease ring respectively; 3. The monitoring device for the wear state of the sealing ring according to claim 2, characterized in that A plurality of the sealing rings are arranged in the sealing cavity. A spacer ring is arranged between every two adjacent sealing rings. The pressure gauge is arranged at the position of the outer wall surface of one of the sealing rings; 4. The monitoring device for the wear state of the sealing ring according to claim 2, wherein, A first installation hole is opened at the inner wall of the grease ring corresponding to the position of the sealing ring. The pressure gauge is arranged in the first installation hole, and the measuring end face of the pressure gauge is in close contact with the outer wall of the sealing ring; 5. The monitoring device for the wear state of the sealing ring according to claim 1 or 2, characterized in that The pressure gauge is a pressure sensor, a strain gauge or a dynamometer; 6. The monitoring device for the wear state of the sealing ring according to claim 2, wherein, One end of the sealing cavity is provided with a pressing ring, the pressing ring is fixed on the grease ring, and a second installation hole is opened in the pressing ring. The rangefinder is arranged in the second installation hole; 7. The monitoring device for the wear state of the sealing ring according to claim 1 or 6, characterized in that, The rangefinder is an eddy current sensor, a displacement sensor or a laser rangefinder; 8. A method for measuring the wear state of a sealing ring, characterized in that, For monitoring the wear state of a sealing ring, the sealing ring is arranged in a sealing cavity and seals the sealing cavity, measure the height of the sealing cavity and the pressure at the outer wall surface of the sealing ring, and calculate the wear amount of the sealing ring according to the height and the pressure; Calculate the wear amount according to the theoretical interpolation curve of the seal wear amount; The steps for drawing the theoretical interpolation curve of the seal wear amount include: Step 1, draw the theoretical interpolation curve of the seal wear amount with the wear amount δ = 0. Compress the wear amount of the sealing ring that has not undergone wear so that the sealing ring has a sealing height H1. Theoretically calculate the pressure F1 on the outer wall surface of the sealing ring corresponding to the sealing height H1. Continue to compress the sealing ring so that the sealing height is Hi, and use the same method to obtain the pressure Fi. Set up a coordinate system with the height Hi as the abscissa and the pressure Fi as the ordinate, and connect each coordinate point to obtain the theoretical interpolation curve of the seal wear amount when δ = 0; Step 2, and so on, draw the theoretical interpolation curve of the seal wear amount under different wear amounts δ = i; Using the measured height Ha as the abscissa and the measured pressure Fa as the ordinate, in the graph of the theoretical interpolation curve of the seal wear amount, draw straight lines parallel to the coordinate axes through the coordinate points Hi and Fi. Let the intersection point of the two straight lines be the coordinate point A. Judge the theoretical interpolation curve of the seal wear amount closest to the coordinate point A, and the wear amount δ = a corresponding to the theoretical interpolation curve of the seal wear amount is the wear amount of the seal.

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