Method for predicting a failure of at least one component of an x-ray tube

Abstract

The invention relates to a method for predicting a failure of at least one component of an X-ray tube (11), in which at least one reference value of the X-ray tube (11) is stored in an evaluation device of a controller for the X-ray tube (11), wherein the X-ray tube (11) comprises a cathode (16) with a filament (18), and at least one filament current of the cathode (16), an anode current of an anode (14) of the X-ray tube (11), and / or an anode voltage are stored as a reference value, in which, during operation of the X-ray tube (11), actual values of at least the filament current, the anode current and / or the anode voltage are detected and fed to the evaluation device, in which at least one prediction for a filament failure and one prediction for a vacuum leakage at a housing (12) of the X-ray tube (11) is determined in the evaluation device at least on the basis of a comparison of the reference values and the values actually detected during operation of the X-ray tube (11) and, based thereon, at least one of the predictions for the failure of the filament (18) and the leakage of the housing (12) of the X-ray tube (11) is output.

Description

[0001] Predicting the failure of at least one component of an X-ray tube

[0002] The invention relates to a method for predicting the failure of at least one component in an X-ray tube.

[0003] US Patent 10,753,969 B2 discloses a method and system for predicting the lifespan of X-ray tubes. This method involves training an X-ray tube model with data. This data can include both the X-ray tube voltage and current. Based on this predetermined data, an algorithm can predict a failure or determine the remaining service life. The X-ray tube model is designed to characterize the X-ray tube current as a function of the filament current and the X-ray tube voltage. From this, the failure of a cathode filament can be predicted. Other potential sources of X-ray tube failure, such as a leak in the tube housing that could compromise the vacuum and lead to premature failure, are not predicted.

[0004] German patent DE 10 2009 036 940 A1 discloses a method for determining the aging state of an X-ray tube cathode. This method involves determining reference values ​​of an electric current flowing through the cathode at a given voltage applied to the cathode. Based on these values, the aging state is then calculated as a function of the actual measured cathode current and the applied voltage. If a deviation exceeds a permissible tolerance, an alarm is triggered indicating that the end of the X-ray tube's service life is approaching. Additionally, the method detects electrical discharges occurring within the X-ray tube.

[0005] These electrical discharges occur particularly when the vacuum in the X-ray tube decreases and also contribute to aging. These discharges are measured indirectly via the internal pressure of the X-ray tube by measuring the pump current of a vacuum ion pump. Direct detection of a leak in the X-ray tube is not possible.

[0006] From DE 103 38 693 B3, a method for estimating the remaining service life of an X-ray tube is known. Under defined test conditions, a measurement suitable for the remaining service life of the operating X-ray tube is determined at time intervals and stored in a storage device. From the current measurement and the past measurements stored in the storage device, determined under the same test conditions, a predicted trend of future measurements is then estimated. Based on this predicted trend and a limit value assigned to the individual X-ray tube and stored in the storage device, the predicted remaining service life of the X-ray tube is determined.

[0007] From DE 103 14 538 Al a method for measuring the pressure prevailing in an X-ray tube is known.

[0008] A method for predicting the lifetime of an X-ray generator is known from DE 10 2012 204 138 A1. For this purpose, data from at least one physical quantity influencing the generator's lifetime are regularly stored. The stored data are evaluated using a stored statistical formula to determine the expected remaining lifetime of the X-ray generator.

[0009] The invention is based on the objective of proposing a method for predicting the failure of an X-ray tube, in which several components of the X-ray tube are monitored simultaneously and at least one prediction of failure is determined for each monitored component of the X-ray tube. This objective is achieved by a method according to the features of claim 1. It is provided that reference values ​​from the X-ray tube, preferably new or newly commissioned, are stored in a memory of a control unit for the X-ray tube, wherein at least a filament current of the cathode, an anode current of an anode of the X-ray tube, and / or a predetermined acceleration voltage or anode voltage of the X-ray tube are stored.During operation of the X-ray tube, particularly in an X-ray fluorescence analyzer, current values ​​from the X-ray tube are recorded, including at least the filament current, the anode voltage, and / or the anode current, which are then transmitted to the evaluation unit. The evaluation unit generates at least one prediction for a filament failure and one prediction for a vacuum leak in the X-ray tube housing based on a comparison of reference values ​​and the recorded values. At least one of the failures—filament failure and vacuum leak—is then evaluated, and preferably at least one result for the next failure is output.

[0010] This method offers the advantage of predicting potential failures of multiple X-ray tube components and differentiating between filament failure and vacuum leakage from the tube housing. This enables improved quality assurance for the device or system powered by the X-ray tube. Furthermore, it facilitates predictive maintenance to prevent unexpected X-ray tube downtime.

[0011] Preferably, the prediction of at least one filament failure and a vacuum leakage of the housing is based on an evaluation of the filament current profile and, more preferably, the ratio between the filament current and the anode voltage. A filament failure is indicated when a decrease in the current filament current is detected, and a leakage failure is indicated when an increase in the current filament current is detected. This change in the filament current, particularly under otherwise constant operating conditions, can be used to differentiate between filament failure and vacuum leakage failure of the housing.

[0012] To improve the prediction of failure, at least for the filament and vacuum leakage, it is preferably provided that a filament resistance is additionally measured and fed to the evaluation unit. The filament resistance increases monotonically over time during operation of the X-ray tube. By including the filament resistance and its changes in the prediction of failure, and preferably in determining which failure will occur first, a tendency for failure can be identified very early, or a decision can be made as to which component of the X-ray tube will be affected by the failure.

[0013] In particular, it is provided that the values ​​recorded for predicting failure during the operation of the X-ray tube are normalized in the evaluation unit before comparison with the stored reference values. This has the advantage that the evaluation of the recorded values ​​for predicting failure is independent of the operating conditions set by the user for the X-ray tube.

[0014] According to an advantageous embodiment of the method, filament failure is detected at a constant anode current in the X-ray tube if a reduction in filament current and an increase in filament resistance are observed. Surprisingly, it was found that the reduction in filament current and the increase in filament resistance are closely related to the prediction of filament failure.

[0015] Furthermore, it is preferably provided that a vacuum leakage of the X-ray tube is detected at a constant anode current, provided that an increase in the filament current and a constant or unchanging electrical resistance of the filament are detected. Surprisingly, it was again found that, with a constant electrical resistance of the filament and an increase in the filament current, a prediction of an impending failure due to a vacuum leakage of the X-ray tube is possible.

[0016] To predict failure, the filament current is preferably stored in the evaluation unit as a function of the anode current and the anode voltage in a preparatory step. Preferably, several values ​​of the filament current are stored as a function of the user-adjustable anode voltage and anode current. This allows baseline values ​​from an unused or soon-to-be-commissioned X-ray tube to be used as a basis for determining changes during use and predicting failure.

[0017] As a first step in determining the X-ray tube failure, a divergence calculation is preferably performed. The actual operating data of the X-ray tube are recorded and compared with the stored reference values, with the evaluation unit calculating a divergence value. Based on this divergence value, a subsequent step can then be taken to select which failure is most likely to occur first. Preferably, the divergence value is calculated from the filament current, and a mean value curve is determined from the current values ​​for the filament current and / or from the filament resistance calculated from the current values ​​of the filament current and filament voltage, independent of the user-set anode operating parameters. This allows for a more precise prediction of the respective failure.

[0018] Furthermore, it is preferably intended that a conditional random field or an auto-encoder neural network be used as the evaluation algorithm to determine the divergence value and to use it as a basis for further prediction of the failure.

[0019] In a second step to predict X-ray tube failure, a selection process is preferably performed. This selection is based on the difference values ​​determined in the previous step through divergence calculation. This allows for a preliminary selection of the fault that will most likely lead to failure. At a minimum, the predictions for filament failure and vacuum leakage are evaluated and initiated.

[0020] In predicting filament failure, the recorded values ​​are preferably compared with the reference data and an expected time of failure is determined, preferably using a logarithmic inverse curve of a divergence value together with a regression technique to calculate the time of failure, where a 1st order, 2nd order, etc. regression is dynamically selected in the regression technique.

[0021] When predicting vacuum leakage, the actually measured filament flow values ​​are preferably used and compared with a threshold value to determine the point of failure. Advantageously, the point of filament failure can be determined by fitting a curve generated based on the recorded filament flow values.

[0022] In a subsequent step, an output multiplexer is used to select data, particularly from the second step, for output. The amount of information to be displayed can be determined. For example, only the first predicted failure can be displayed. Alternatively, a weighting of the predicted failures can be displayed, revealing a sequence of successive failures and, in particular, their respective expected times.

[0023] The steps described above for predicting the failure of the X-ray tube make it possible not only to differentiate between the type of failure or between at least two components of the X-ray tube, but also to determine the time of the expected failure for each component of the X-ray tube.

[0024] This allows for timely ordering of replacement parts, enabling the necessary replacement of the affected component shortly before or during the failure of the X-ray tube. This prevents uncontrolled operational downtime.

[0025] The invention, as well as further advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the examples shown in the drawings. The features that can be derived from the description and the drawings can be applied individually or in any combination according to the invention. The drawings show:

[0026] Figure 1 shows a schematic view of an X-ray tube.

[0027] Figure 2 shows a schematic diagram with individual steps for predicting an X-ray tube failure.

[0028] Figure 3 shows a schematic diagram for the detection of a filament failure in an X-ray tube, and

[0029] Figure 4 shows a schematic diagram for detecting a vacuum leak in the X-ray tube.

[0030] Figure 1 shows a schematic view of an X-ray tube 11. This X-ray tube 11 comprises a housing 12, within which a vacuum is maintained. An anode 14 and, opposite it, a cathode 16 are arranged in the housing 12. The anode 14 advantageously includes a cooling element 17. The cathode 16 is advantageously designed as a heated cathode and comprises a filament 18. A filament voltage, also referred to as the heating voltage, is applied to the cathode 16. An anode voltage is applied between the cathode 16 and the anode 14. This is also referred to as the accelerating voltage, as it is responsible for accelerating electrons from the cathode 16 to the anode 14. The electrons emitted from the cathode 14, or the filament 18, are emitted in the form of an electron beam 19 and strike the anode 14.The material of the anode 14 emits fluorescence radiation 21 and bremsstrahlung, also known as X-rays. This X-ray radiation can be used in the medical field. It can also be used to analyze materials of an object and / or of at least one layer on an object and / or of the at least one layer and the object on which the layer is applied.

[0031] During operation of cathode 16, the cathode voltage (or filament voltage) and the filament current are measured. Simultaneously, during operation of the X-ray tube 11, both the anode voltage and the anode current are measured. The anode current is set by the user to operate the X-ray tube 11. As a result of the user setting the anode current, the filament voltage is automatically adjusted so that the filament current resulting from the filament resistance, under the influence of the set anode voltage, can generate the correct anode current.

[0032] During operation of the X-ray tube 11, the emitted electrons can cause changes in the filament 18. Furthermore, leakage can occur in the housing 12 of the X-ray tube 11, which may prevent or severely compromise the vacuum from being maintained. At least these two components 16 and 18 of the X-ray tube 11 will be considered for predicting a failure, as will be described below. Other components, such as the anode 14, can also be taken into account when predicting a potential failure.

[0033] Figure 2 shows a schematic diagram with individual steps for predicting at least one failure of the X-ray tube component.

[0034] In the method for predicting a failure of at least one component 16, 18 of the X-ray tube 11, reference data from an evaluation unit, in particular in a memory of a controller (not shown in detail), are stored before or during the commissioning of the X-ray tube 11. This data preferably consists of reference data for the respective filament current and, more preferably, the filament voltage of the filament 18 of the cathode 16, which depend on the adjustable anode voltage and anode current. To predict a failure of at least one component 16, 18 of the X-ray tube, a divergence calculation is performed in a first step 31. In this divergence calculation, the values ​​actually recorded by the X-ray tube 11 during operation are compared with the reference values ​​in the evaluation unit.The filament current depends on the anode current and the anode voltage, whereby the anode voltage can be adjusted by the user.

[0035] For divergence calculation, the filament current is first calculated as a function of the anode current and the cathode voltage and then normalized. This allows for a smooth, continuously differentiable curve for the filament current. Preferably, this step also includes determining the filament resistance from the measured filament current and the filament voltage. These calculated data are compared with the reference data to determine any deviation. A conditional random number generator or an auto-encoder neural network, for example, can be used to combine the normalization and the deviation calculation. This first step of the divergence calculation outputs divergence values, at least for the filament current.

[0036] In a subsequent, or second, step 34, the divergence values ​​form the basis of a selection process. This selection process determines which failure is more relevant, i.e., which is more likely to occur first. If it is determined that the divergence value has increased, the selection is made that a leakage failure is likely to occur. If it is determined that the divergence value has decreased, a filament failure is expected.

[0037] Based on the failure selection described above in step 34, the time of the expected failure is calculated in a third step 36. This step 36 can be subdivided into several individual steps. A first individual step 37 is intended to determine the service life of the filament 18 until its failure. A second individual step 38 is intended to determine the service life of the housing 12 until vacuum leakage failure. In a third individual step 39 or further individual steps, other failures of components of the X-ray tube 11 that may occur can be determined individually.

[0038] Figure 3 shows a schematic diagram illustrating the filament current IF as a function of the lifetime t of the filament 18. The filament current remains constant for an extended period and only decreases after a longer time with an exponentially similar curve. This curve is used to determine the remaining lifetime. In addition to the filament current, the filament resistance, based on the measured values ​​of the X-ray tube 11, is also taken into account. The time, or remaining lifetime, is predicted using a value from a logarithmic inverse curve of a divergence value, combined with a first-order, second-order, etc., regression technique. Step 37 outputs the determined time.

[0039] Figure 4 shows a schematic diagram depicting the filament current IF and the anode current IA over a predetermined duration t. Based on the curves for the filament current IF and the anode current IA, the remaining service life of the housing 12 can be predicted with respect to the leakage failure. Towards the end of the housing 12's service life, the filament current IF increases while the anode current IA remains constant until its threshold value is reached. From that point on, due to the onset of the leakage failure, both the filament current IF and the anode current IA immediately drop. To determine the leakage failure, a fit of the normalized filament current IF or the divergence value calculated from the normalized filament current IF is performed to capture its increase relative to a nearly constant value at which the failure will occur. This determined time is output by step 38.

[0040] In a fourth step 42 of the monitored component according to Figure 2, the result of the remaining service life, which was determined in the third step 36, is output. This can be done on a display of the evaluation unit. In this step 42, according to a first embodiment, it can be provided that the failure selected in the second step 34 by the selection process is calculated in the third step 36 and then output in the fourth step 42. No further calculations are performed. Alternatively, it can be provided that at least one further failure, not selected by the selection process, is also calculated in the third step 36 and additionally output in the fourth step 42.This allows the user to get an overview of the expected failures and their timing, and additionally to decide whether maintenance should only fix the initially predicted failure or, for example, fix other predicted failures at the same time.

Claims

Claims 1. Method for predicting the failure of at least one component of an X-ray tube (11), in which at least one reference value from the X-ray tube (11) is stored in an evaluation unit of a control unit for the X-ray tube (11), wherein the X-ray tube (11) comprises a cathode (16) with a filament (18) and at least one filament current of the cathode (16), one anode current of an anode (14) of the X-ray tube (11) and / or one anode voltage is each stored as a reference value, in which, during the operation of the X-ray tube (11), actual values ​​of at least the filament current, the anode current and / or the anode voltage are recorded and supplied to the evaluation unit, in which at least one prediction for a filament failure and a prediction for a vacuum leak at a housing (12) of the X-ray tube (11) is determined in the evaluation unit at least on the basis of a comparison of the reference values ​​and the values ​​actually recorded during the operation of the X-ray tube (11) and based on this at least one of the predictions for the failure of the filament (18) and the leakage of the housing (12) of the X-ray tube (11) is output.

2. Method according to claim 1, characterized in that, for predicting filament failure (18) and vacuum leakage of the housing (12), the course of the filament current and preferably the ratio between the filament current, the anode voltage and / or the anode current is evaluated, and in the event of a detected reduction in the filament current, a filament failure and A leakage failure is reported when an increase in filament flow is detected.

3. Method according to claim 1 or 2, characterized in that at least for one of the predictions of filament failure and leakage failure, a filament resistance is additionally detected and supplied to the evaluation device.

4. Method according to one of the preceding claims, characterized in that the values ​​recorded for prediction during the operation of the X-ray tube (11) are normalized in the evaluation device before comparison with the reference values.

5. Method according to claim 3 or 4, characterized in that, at a constant anode current and / or a constant anode voltage, a filament failure is predicted if a reduction in the filament current and an increase in the filament resistance are detected.

6. Method according to claim 3 or 4, characterized in that, at a constant anode current and / or a constant anode voltage, a vacuum leakage of the housing (12) is predicted if an increase in the filament current and a constant filament resistance are detected.

7. Method according to one of the preceding claims, characterized in that in a prepared step for determining the prediction of the failure of at least one component of the X-ray tube (11) in the evaluation device the filament current, preferably as a function of the anode current and the anode voltage, is stored, wherein several values ​​of the filament current are stored as a function of the anode voltage and / or anode currents adjustable by the user.

8. Method according to one of the preceding claims, characterized in that in a first step a divergence calculation is performed for at least one of the predictions of failure, wherein for this first step the current values ​​of the X-ray tube (11) are recorded, which include at least the anode current, the anode voltage and / or the filament voltage, and a divergence value is calculated with the reference values ​​by an evaluation algorithm.

9. Method according to claim 8, characterized in that an average value curve is determined from the current values ​​for the filament current and / or for the filament resistance determined from the current values ​​of the filament current and the filament voltage, independently of the set operating voltages and operating currents of the anode.

10. Method according to claim 8 or 9, characterized in that a conditional random number generator or an auto-encoder neural network is used as the evaluation algorithm to determine and output the difference value.

11. Method according to one of claims 8 or 9, characterized in that in a second step (34) a failure selection is carried out for at least one of the predictions of failure based on the difference values ​​determined in the first step and it is determined whether at least the filament failure or the vacuum leakage will occur as the next failure.

12. Method according to claim 11, characterized in that in the subsequent step (36) for predicting filament failure the actually determined data are compared with the reference data and a probable time for failure is determined, and preferably the calculation of the probable- At the time of the failure, a logarithmic inversion curve of a divergence value is performed together with a regression technique with a first order, second order, etc.

13. Method according to claim 11, characterized in that in the subsequent step (36) the actually determined data of the filament flow are used for the prediction of the vacuum leakage, which are compared with a threshold value for determining the expected time of failure and preferably a fitting of a curve formed on the basis of the recorded data of the filament flow is carried out.

14. Method according to one of the preceding claims, characterized in that in a fourth step (42) the prediction for the first occurring failure is output, or that a weighting of the prediction is carried out at least for the filament failure and the vacuum leakage and the sequence of the expected failures and / or the corresponding time is output.

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