Shaft condition monitoring system, internal combustion engine, electric generator and method for monitoring a condition of a shaft

Abstract

Shaft condition monitoring system (100) for a shaft designed to transmit a torque, wherein the shaft condition monitoring system (100) comprises a shaft (14), a measured value acquisition system (118, 508) for acquiring a shaft parameter, and an evaluation unit (108, 208, 308), wherein the measured value acquisition system (118, 508) has: - at least one first rotation angle sensor (110) which is designed to detect a first rotational position (φ) of the shaft (14) with respect to a reference rotational position (φr) in order to determine a rotational position deviation (Δσ) between the first rotational position (φ) and the reference rotational position (φr), wherein the rotational position deviation (Δσ) is assigned to a stress of a torsional state of the shaft (14) under load, - at least one first torque sensor (116) which is designed to detect a first torque (M) of the shaft (14) with respect to a reference torque (Mr) in order to determine a torque deviation between the first torque (M) and the reference torque (Mr), wherein the torque deviation (Δε) is assigned to an extension of the torsional state of the shaft (14) under load, - wherein the evaluation unit (108, 208, 308) is designed - to determine a modulus of elasticity (Δσ / Δε) as a relationship between stress and strain of a torsional state of the shaft (14) under load using a number of rotational position deviations and a number of torque deviations (Δε), characterized in that - the evaluation unit (108, 208, 308) is further developed, - to compare the modulus of elasticity (Δσ / Δε) with at least one reference curve (602) having a region (B_lin) associated with an elastic behavior of the shaft (14), and - to determine whether the determined elastic modulus (Δα / Δε) corresponds to a region (B_lin) assigned to the elastic behavior, wherein the region (B_lin) of the reference curve (602) assigned to the elastic behavior corresponds to an at least approximately linear relationship between stress and strain of the shaft (14), or whether the determined modulus of elasticity (Δσ / Δε) lies outside a range (606) assigned to the elastic behavior, wherein the reference curve (602) has, outside the range (606) assigned to the elastic behavior, a range assigned to a plastic behavior which corresponds to a non-linear relationship between stress and strain of the shaft (14).

Description

[0001] The invention relates to a shaft condition monitoring system according to the preamble of claim 1, comprising a shaft, preferably an engine shaft of an internal combustion engine, in particular a crankshaft and / or a camshaft, or a generator shaft of an electric generator, a measured value acquisition system for acquiring a shaft parameter, and an evaluation unit, in particular for damage condition detection. The invention also relates to a method for monitoring the condition of a shaft, in particular with damage condition detection.

[0002] CN 104 964 820 A describes a measurement method based on a shaft sensor for predicting shaft failure. CN 105 157 961 A describes a measurement method for predicting shaft failure based on a torque sensor.

[0003] DE 10 2009 025 989 A1 shows a measuring device for a torque and for a vibration of a turbomachinery system.

[0004] For a motor shaft of an engine in an internal combustion engine, it is generally known to provide a measured value acquisition system that has: - at least one first rotation angle sensor which is designed to detect a first rotational position of the motor shaft with respect to a reference rotational position in order to determine a rotational position deviation between the first rotational position and the reference rotational position, and - at least one first torque sensor configured to detect a first torque of the motor shaft with respect to a reference torque to determine a torque deviation between the first torque and a reference torque.

[0005] In principle, it can be assumed that the rotational position deviation is caused by tension in the torsional state of the motor shaft under load, and that the torque deviation is caused by expansion in the torsional state of the motor shaft under load. An engine shaft, particularly a crankshaft or camshaft, of an internal combustion engine is generally exposed to large mechanical forces during operation, which can lead to deformations or similar torsions of the engine shaft, as mentioned above.

[0006] US 4,347,748 A describes a device for determining a torque of a shaft and shows in Fig. 1 shows the course of a Young's modulus under torsional loading of the shaft.

[0007] To prevent engine shaft breakage, engine shafts are typically inspected for cracks as part of preventive maintenance. For such an inspection, an engine shaft is typically removed from an internal combustion engine and examined separately. One method for visualizing plastic deformation in an engine shaft involves taking an X-ray of the engine shaft. X-ray images can then be used to look for signs of plastic deformation, such as cracks.

[0008] Another common method is the so-called dye penetrant test, in which electrically magnetized powder or a liquid is applied to the motor shaft and penetrates any cracks present in the motor shaft. However, fine hairline cracks, in particular, are often difficult to detect with these methods and cannot always be reliably detected. It is desirable to either minimize or completely avoid regularly scheduled inspections of the engine shaft, thus avoiding the downtime caused by maintenance and inspection. To detect damage to the engine shaft that may occur, for example, between maintenance visits, it would also be desirable to implement continuous monitoring of the engine shaft. This allows for immediate response to potential damage and thus prevent major damage to the internal combustion engine. Therefore, maintenance work should only be performed when it is actually necessary due to damage.

[0009] The invention is based on the object of providing a shaft condition monitoring system that, in particular, enables improved damage condition detection. Furthermore, the invention is based on the object of providing a method for monitoring the condition of a shaft, in particular with improved damage condition detection.

[0010] With regard to the shaft condition monitoring system, this object is achieved by a shaft condition monitoring system according to claim 1.

[0011] The invention is based on a shaft condition monitoring system comprising a shaft, a measured value acquisition system for detecting a shaft parameter and an evaluation unit, wherein the measured value acquisition system comprises: - at least one first rotation angle sensor configured to detect a first rotation position of the shaft relative to a reference rotation position to determine a rotation position deviation between the first rotation position and the reference rotation position, wherein the rotation position deviation is associated with a stress of a torsional state of the shaft under load, - at least one first torque sensor configured to detect a first torque of the shaft with respect to a reference torque to determine a torque deviation between the first torque and a reference torque, wherein the torque deviation is associated with an extension of the torsional state of the shaft under load.

[0012] The shaft can be, for example, an engine shaft of an internal combustion engine, in particular a crankshaft and / or a camshaft, or also a shaft of an electric generator, e.g. of a wind turbine.

[0013] According to the invention, it is provided that - the evaluation unit is designed, - to determine a modulus of elasticity as a relationship between stress and strain of a torsional state of the shaft under load, given a number of rotational position deviations and a number of torque deviations, - to compare the modulus of elasticity with at least one reference curve having a region associated with an elastic behaviour of the shaft and to determine - especially for damage condition detection, whether the determined modulus of elasticity corresponds to a range assigned to the elastic behavior, or whether the determined modulus of elasticity lies outside a range associated with elastic behavior.

[0014] The invention is based on the consideration that the occurrence of damage caused, for example, by torsion, results in plastic and thus irreversible deformation, which in the worst case can lead to shaft fracture. Before a shaft breaks, cracks typically form in the shaft. Such plastic deformations are an indication of a possible shaft fracture. The invention is further based on the consideration that a condition of, for example, an engine shaft of an internal combustion engine can also be detected during operation of the internal combustion engine, making routine inspection of an engine shaft obsolete. The invention includes the discovery that the modulus of elasticity of a shaft is a material characteristic value which can be used to determine the condition of a shaft, particularly with regard to its plastic deformation, during operation, i.e. when torque is applied. In the case of linear elastic behavior, the modulus of elasticity describes the proportional relationship between stress and strain during the deformation of a solid body. As long as the deformation of a shaft is elastic, the relationship between stress and strain in the motor shaft is essentially linear. If the deformation of a shaft is no longer exclusively elastic but the shaft also deforms plastically, this linear relationship no longer applies. A non-linear relationship between stress and strain therefore indicates crack formation in a shaft and is an indication of a possible impending shaft fracture.

[0015] According to the concept of the invention, it is provided that the shaft condition monitoring system has at least one first rotation angle sensor and at least one first torque sensor, which are designed to detect a first rotational position with respect to a reference rotational position and a first torque with respect to a reference torque. A rotational position deviation can be determined from the rotational position and the reference rotational position, and a torque deviation can be determined from the torque and the reference torque. The rotational position deviation indicates a measure of torsion, i.e., stress, of the shaft. The torque deviation indicates a measure of a change in length, i.e., strain, of the shaft. A modulus of elasticity of the shaft can be determined from the rotational position deviation and the torque deviation, which corresponds to the slope of a curve in a stress-strain diagram.

[0016] The evaluation unit of the shaft condition monitoring system is designed to determine a modulus of elasticity as a relationship between stress and strain of a torsional state of the shaft under load using a number of rotational position deviations and a number of torque deviations, and to compare the modulus of elasticity with at least one reference curve that has a range associated with an elastic behavior of the shaft. Through the comparison, it can be determined whether the modulus of elasticity determined by the evaluation unit corresponds to this range associated with the elastic behavior of the shaft. Based on the comparison, it can therefore be determined whether stress and strain of the shaft follow an elastic relationship during a torque application to the shaft. According to the invention, for this purpose, in particular for damage state detection, whether the determined modulus of elasticity corresponds to a range assigned to the elastic behavior, or whether the determined modulus of elasticity lies outside a range associated with elastic behavior.

[0017] Advantageously, the shaft condition monitoring system according to the invention enables a reliable and timely analysis of the condition of a shaft with regard to plastic deformation of the shaft. This allows cracks in a shaft to be detected in a timely manner, and shaft breakage can be reliably prevented. This advantageously eliminates the need for purely preventative or routine inspections of a shaft, e.g., an internal combustion engine. The shaft condition monitoring system advantageously requires only a few components.

[0018] With regard to the method, the object mentioned at the outset is achieved by a method according to claim 18.

[0019] According to the invention, a method for monitoring a shaft of a shaft condition monitoring system is provided, wherein the shaft condition monitoring system comprises a shaft, a measured value acquisition system for detecting a shaft parameter and an evaluation unit, and the measured value acquisition system is designed to detect a shaft parameter.

[0020] The procedure includes the following steps: - Determining a first rotational position of a shaft with respect to a reference rotational position to determine a rotational position deviation between the first rotational position and the reference rotational position, wherein the rotational position deviation is assigned to a stress of a torsional state of the shaft under load, - Determining a first torque of the shaft with respect to a reference torque to determine a torque deviation between the first torque and a reference torque, wherein the torque deviation is assigned to an extension of the torsional state of the shaft under load, - Determining a modulus of elasticity with a number of rotational position deviations and a number of torque deviations as a relationship between stress and strain of a torsional state of the shaft under load, - comparing the modulus of elasticity with at least one reference curve having a region associated with an elastic behavior of the shaft, - Determine, in particular for damage detection, whether the determined modulus of elasticity corresponds to a range assigned to the elastic behavior, or whether the determined modulus of elasticity lies outside a range associated with elastic behavior.

[0021] If the comparison step shows that the determined elastic modulus does not correspond to the range assigned to the elastic behavior of the shaft, a warning signal is preferably output to a user interface, which represents information about the current state of the shaft.

[0022] Advantageous further developments of the shaft condition monitoring system according to the invention can be found in the dependent claims and specify in detail advantageous possibilities for realizing the concept explained above within the scope of the task and with regard to further advantages.

[0023] If the shaft condition monitoring system is implemented as part of an internal combustion engine, the evaluation unit can be an engine control unit (ECU) of the internal combustion engine or part of an engine control unit (ECU).

[0024] The evaluation unit can be configured such that, after determining during a torque application that the determined elastic modulus corresponds to the range assigned to the elastic behavior of the shaft, it determines a new elastic modulus after a predefined period of time and compares it again with at least one reference curve to determine whether this newly determined elastic modulus corresponds to the range assigned to the elastic behavior of this reference curve used for comparison. This allows continuous monitoring of the shaft condition of the shaft condition monitoring system to be implemented at predefined intervals.

[0025] The evaluation unit is preferably designed to provide a warning signal if it is determined that the determined modulus of elasticity does not correspond to the range assigned to the elastic behavior. If the comparison shows that the determined modulus of elasticity does not correspond to the range assigned to the elastic behavior, this is an indication that the shaft is plastically deformed and must be replaced or repaired to prevent the shaft from breaking. Such a warning signal can represent visual information about the current state of the shaft, which is displayed to a user on a monitor. A provided warning signal can also cause a lamp to light up, which signals the state of the shaft to a user. It is also conceivable that an acoustic warning signal is provided to draw the user's attention to the state of the shaft.

[0026] The evaluation unit can be configured to computationally determine the reference torque based on the detected torque and a shaft speed. The speed can be determined, for example, by using the angle sensor to measure two rotational positions of the shaft consecutively at two different times. The reference torque can be computationally determined based on the detected first torque and the determined speed.

[0027] Alternatively or additionally, the evaluation unit can be designed to determine a total torque of the shaft from a characteristic map of an internal combustion engine or an electric generator and to derive the reference torque from the total torque.

[0028] If a torque is to be measured at the shaft during operation with a power take-off, the torque can also be measured at the power take-off before the actual operation of an internal combustion engine or electric generator. Based on this torque measured in advance at the power take-off and the load applied during operation, the evaluation unit can determine the reference torque during operation of the internal combustion engine or electric generator and use it to determine the modulus of elasticity.

[0029] At least one rotation angle sensor of the measured value acquisition system is preferably a resolver or a perforated wheel sensor. Sensors designed to magnetically scan the shaft can also be used to detect a rotational position of the shaft.

[0030] The measured value acquisition system can have at least one additional angle of rotation sensor, which is arranged on the shaft at a distance from the first angle of rotation sensor and is designed to detect the reference rotational position. Preferably, the first angle of rotation sensor is then arranged on the force side of the shaft, and at least one additional angle of rotation sensor is arranged on the opposite force side of the shaft. The two angle of rotation sensors are then spaced apart from one another at a distance suitable for reliably detecting torsion of the shaft during a torque application to the shaft. Furthermore, it is advantageous if the area at risk of crack formation lies between the two angle of rotation sensors.

[0031] The measured value acquisition system can also comprise at least one additional torque sensor, which is arranged on the shaft at a distance from the first torque sensor and is configured to detect the reference torque. Preferably, the first torque sensor is arranged together with the first angle of rotation sensor on the force side of the shaft, and at least one additional torque sensor is arranged on the opposite force side of the shaft. The two torque sensors are then generally spaced sufficiently apart to reliably detect an extension, in particular a change in length along the longitudinal direction of the shaft, during a torque application to the shaft.

[0032] In particular, if a torque is picked up on the shaft by a drive on the power side and by a secondary drive on the opposite power side, it can be advantageous to arrange an angle of rotation sensor and a torque sensor on both the power side and the opposite power side in order to reliably record the stress and strain of the shaft and thus to be able to determine the modulus of elasticity of the shaft and its temporal progression during operation.

[0033] The reference curve preferably represents a time course of the modulus of elasticity or a course of the modulus of elasticity as a function of the load applied to the shaft or a course of the modulus of elasticity with increasing torsion of the shaft.

[0034] The area of the reference curve associated with the elastic behavior of the shaft corresponds, in particular, to an at least approximately linear relationship between stress and strain in the shaft. In this area, the deformations of the shaft under load are reversible.

[0035] The reference curve can also include a region associated with the shaft's plastic behavior, which corresponds to a nonlinear relationship between stress and strain in the shaft. A shaft that undergoes plastic deformation typically exhibits cracks. A shaft with plastic deformation is therefore irreversibly altered in its structure. If the shaft's modulus of elasticity determined by the evaluation unit is compared with a reference curve and this comparison shows that the determined modulus of elasticity corresponds to a region associated with the shaft's plastic behavior, the shaft, e.g., of an internal combustion engine or an electric generator, should be replaced to prevent the shaft from breaking during further operation.

[0036] At least one reference curve with which the determined modulus of elasticity can be compared during operation, i.e., during torque application, is preferably a curve of a stress-strain diagram of the shaft. A stress-strain diagram shows a relationship between stress and strain in a solid body. For small stresses and strains, the relationship between stress and strain is linear or at least approximately linear. The strain is then proportional to the stress, and the modulus of elasticity is the proportionality constant. The modulus of elasticity then corresponds to the slope of the reference curve in the linear range.

[0037] Preferably, such a stress-strain diagram used as a reference curve was created by measurements on a reference shaft and then made available for use as a reference curve for the shaft.

[0038] At least one reference curve with which the determined modulus of elasticity of the shaft during operation can be compared can also represent the temporal progression of the modulus of elasticity during operation. Such a reference curve is therefore generated during operation and continuously expanded by newly determined modulus of elasticity values. In such a curve, in particular the area of the reference curve assigned to the elastic behavior of the shaft corresponds to the area of the curve that was determined during a start-up, e.g. of an internal combustion engine or an electric generator. Since a shaft typically has a low torque during a start-up, the relationship between stress and strain in the shaft is linear or at least approximately linear, particularly during the start-up, meaning the deformation of the shaft is essentially elastic.In particular, a currently determined modulus of elasticity can be compared during operation with the reference curve generated up to that point.

[0039] To compare a modulus of elasticity during operation, depending on availability, either a reference curve of a stress-strain diagram or a reference curve representing the temporal progression of a continuously determined modulus of elasticity of the shaft during operation or - to increase the reliability of monitoring the condition of the shaft - both reference curves can be used.

[0040] The shaft condition monitoring system can also include a synchronization unit, which is preferably configured such that at least the first rotational position and the first torque are detected synchronously. For example, the synchronization unit can include a clock line and be configured to simultaneously control the sensors of the measured value detection system via the clock line with a clock signal. The clock signal allows the sensors of the measured value detection system to be controlled simultaneously during operation and thus simultaneously detect a corresponding shaft parameter.

[0041] The synchronization unit can also have at least one A / D (analog / digital) converter, which is connected via lines at least to the first rotation angle sensor and the first torque sensor for transmitting a first rotational position signal representing the first rotational position and a first torque signal representing the first torque, and is designed to sample the signals fed to the A / D converter in a time-synchronized manner and subsequently transmit them to the evaluation unit. The A / D converter is then preferably connected between the sensors of the measured value acquisition system and the evaluation unit. Due to the time-synchronous sampling, only those rotational position signals and torque signals are transmitted to the evaluation unit that represent rotational positions and torques detected in a time-synchronized manner.

[0042] The invention also includes an internal combustion engine of claim 15. The internal combustion engine comprises a motor with a motor shaft and a shaft condition monitoring system, wherein the shaft condition monitoring system comprises the motor shaft and is designed according to one of the embodiments described here.

[0043] The invention further includes an electric generator according to claim 17. The electric generator has a generator shaft, wherein the electric generator has a shaft condition monitoring system. The shaft condition monitoring system comprises the generator shaft, and the shaft condition monitoring system is designed according to one of the embodiments described here.

[0044] Embodiments of the invention will now be described below with reference to the drawings in comparison to the prior art, some of which are also shown. These are not necessarily intended to represent the embodiments to scale; rather, where useful for explanation, the drawings are presented in a schematic and / or slightly distorted form. For supplements to the teachings immediately apparent from the drawings, reference is made to the relevant prior art.

[0045] It should be noted that various modifications and changes to the form and detail of an embodiment can be made without departing from the general idea of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiment shown and described below, or to an object that would be more limited than the object claimed in the claims. Where dimensioning ranges are stated, values within the stated limits are also intended to be disclosed as limiting values and can be used and claimed as desired.

[0046] Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawing, which shows: Fig. 1 a schematically illustrated shaft condition monitoring system with a shaft, an evaluation unit and a measured value acquisition system, Fig. 2 a schematically illustrated internal combustion engine with an engine, an evaluation unit and a measured value acquisition system, which additionally has a synchronization unit, Fig. 3 a schematically illustrated internal combustion engine with an engine, an evaluation unit and a measured value acquisition system, which additionally has a synchronization unit, Fig. 4 is a schematically illustrated flowchart of a method for monitoring a state of a shaft according to a concept of the invention, Fig. 5 a schematic representation of a wind turbine with an electric generator, Fig. 6 a schematic stress-strain diagram with a linear-elastic region and a region lying outside the linear-elastic region.

[0047] Fig. 1 shows a schematically illustrated shaft condition monitoring system 100 with a shaft 14. For example only, the shaft 14 is configured as an engine shaft 104 of an internal combustion engine connected to a number of cylinders 106. The shaft condition monitoring system 100 also includes an evaluation unit 108 and a measured value acquisition system 118 for acquiring a shaft parameter. The measured value acquisition system 118 includes a first rotation angle sensor 110, a second rotation angle sensor 112, a first torque sensor 114, and a second torque sensor 116.

[0048] The first angle of rotation sensor 110 and the first torque sensor 114 are arranged on the force side KS of the motor shaft, and the second angle of rotation sensor 112 and the second torque sensor 116 are arranged on the opposite force side KGS of the motor shaft 104. In particular, when the shaft 104 is subjected to a torque, a first rotational position can be measured with the first angle of rotation sensor 110 and a reference rotational position with the second angle of rotation sensor 112. During operation, a first torque and a reference torque of the motor shaft 104 can be detected accordingly with the first torque sensor 114 and the second torque sensor 116.The use of such a measured value acquisition system (118) with a first rotation angle sensor 110 and a first torque sensor 114 on the power side KS of the motor shaft 104 and a second rotation angle sensor 112 and a second torque sensor 116 on the opposite force side KGS of the shaft 104 is particularly advantageous when a torque is tapped both on the power side KS of a drive and on the opposite force side KGS of a power take-off. If a torque is only tapped on the power side KS of the motor shaft 104, the second torque sensor 116 can be dispensed with, and the reference torque can be determined mathematically. Under certain circumstances, the second rotation angle sensor 112 can also be dispensed with, and the reference rotational position can be determined during operation using a model of the motor shaft 104.

[0049] The shaft parameters detected by the sensors of the measured value acquisition system (118) can then be represented by corresponding rotational position signals or torque signals and transmitted via lines or wirelessly to the evaluation unit 108.

[0050] Using the evaluation unit 108, a rotational position deviation can be determined from the first rotational position and the reference rotational position, which is a measure of the torsion of the motor shaft 104, and a torque deviation can be calculated from the first torque and the reference torque, which is a measure of the elongation of the motor shaft 104. A modulus of elasticity of the motor shaft 104 can then be determined from the rotational position deviation and the torque deviation.

[0051] The evaluation unit 108 is further configured to compare the determined modulus of elasticity with one or more reference curves.

[0052] Such a reference curve can be a curve of a stress-strain diagram of the motor shaft 104 or a reference shaft. Particularly for small stresses and strains, the relationship between stress and strain is essentially linear, and the slope of the curve corresponds to the modulus of elasticity of the motor shaft 104 under elastic deformation. At greater stress and / or strain, the relationship between stress and strain of the motor shaft 104 becomes nonlinear, meaning the motor shaft deforms plastically. By comparing the determined modulus of elasticity with the stress-strain diagram of the motor shaft 104, it can be determined whether the determined modulus of elasticity corresponds to the region of the reference curve assigned to the elastic behavior of the motor shaft 104.

[0053] Such a reference curve can also be a curve that represents the temporal progression of the elastic modulus of the motor shaft 104 during operation. To generate such a reference curve, for example, elastic modulus values of the motor shaft 104 can be determined at predefined time intervals using the evaluation unit 108 and added to the reference curve. The reference curve is then dynamically expanded during operation of the motor shaft. A currently determined elastic modulus can then be compared with the dynamically generated reference curve, and a possible deviation from the previous progression can be determined. In particular, during the start-up of an internal combustion engine, the relationship between stress and strain of the motor shaft 104 is linear or at least approximately linear, so that this range can be assigned to an elastic behavior of the motor shaft 104.Thus, if in operation a determined elastic modulus represents a slope that differs from the slope of the as in relation to . Fig. 6, this may be an indication of crack formation in the motor shaft 104.

[0054] It may be advantageous if the evaluation unit 108 is configured to compare a determined elastic modulus with both a stress-strain diagram of the motor shaft 104 and a dynamically generated reference curve representing the course of the elastic modulus. By comparing a determined elastic modulus with multiple reference curves, the reliability of detecting a crack in the motor shaft 104 can advantageously be further increased.

[0055] Preferably, the evaluation unit 108 is configured to provide a warning signal if it is determined that the determined modulus of elasticity does not correspond to the range assigned to the elastic behavior of the motor shaft 104. A determined modulus of elasticity that does not correspond to the range assigned to the elastic behavior may then represent a condition of the motor shaft 104 in which the motor shaft 104 exhibits plastic deformations, as described, for example, with reference to FIG. 6, and should be replaced.

[0056] Fig. 2 shows an internal combustion engine 200 with a motor 202 having a motor shaft 204. The motor shaft 204 is connected to a number of cylinders 206 and has a power side KS and a counter-power side KGS. The internal combustion engine 200 has a shaft condition monitoring system 201, which includes the motor shaft 204, a measured value acquisition system for acquiring a motor shaft parameter of the motor shaft 204, and an evaluation unit 208. The measured value acquisition system has a first rotation angle sensor 210, a second rotation angle sensor 212, a first torque sensor 214, and a second torque sensor 216, which—as described with reference to Fig. 1. If, during operation, a torque is only sensed on the force side KS of the motor shaft 204, the second angle of rotation sensor 212 and the second torque sensor 216 can be omitted, and the reference rotational position and the reference torque can be determined mathematically, e.g., based on a model of the motor shaft 204.

[0057] The evaluation unit 208 is connected via lines 209 to one of the sensors 210, 212, 214, 216 of the measured value acquisition system for transmitting rotational position signals and torque signals. The rotational position signals and torque signals respectively represent a detected rotational position or a detected torque. During operation of the internal combustion engine 200, a modulus of elasticity of the motor shaft can then be determined using at least the detected first rotational position and the reference rotational position and the detected first torque and the reference torque and compared with at least one reference curve. Based on the comparison, it can be determined whether the determined modulus of elasticity corresponds to a region of the reference curve assigned to the elastic behavior of the motor shaft 204.

[0058] In addition to the information provided in relation to Fig. 1, the shaft condition monitoring system of the internal combustion engine 200 shown here has a synchronization unit comprising a clock line 218. The clock line 218 connects the evaluation unit 208 to the sensors 210, 212, 214, 216 of the measured value acquisition system. The evaluation unit 208 is designed to provide a clock signal, which can then be transmitted during operation via the clock lines 218 to the sensors 210, 212, 214, 216 in order to control them synchronously. When the sensors 210, 212, 214, 216 receive a clock signal during operation, they simultaneously detect a corresponding motor shaft parameter, so that a modulus of elasticity can be determined based on the synchronously detected motor shaft parameters.

[0059] Fig. 3 shows an internal combustion engine 300 with a motor 302 having a motor shaft 304. The motor shaft 304 is connected to a number of cylinders 306. The internal combustion engine 300 has a shaft condition monitoring system 301 that includes the motor shaft 304, an evaluation unit 308, and a measured value acquisition system with a first rotation angle sensor 310, a second rotation angle sensor 312, a first torque sensor 314, and a second torque sensor 316. The first rotation angle sensor 310 and the first torque sensor 314 are arranged on the power side KS of the motor shaft 304 and are designed to detect a first rotational position or a first torque, respectively. The second rotation angle sensor 312 and the second torque sensor 316 are arranged on the opposite power side KGS of the motor shaft 304 and are designed to detect a reference rotational position or a reference torque, respectively. As also described with reference to Fig. 1, in particular the reference rotational position and the reference torque can be determined mathematically and accordingly the second rotation angle sensor 312 and the second torque sensor 316 can be dispensed with.

[0060] The shaft condition monitoring system of the internal combustion engine 300 has a synchronization unit comprising an A / D converter 318. The A / D converter 318 is connected to the sensors 310, 312, 314, 316 via a line 309, so that rotational position signals or torque signals provided by the sensors 310, 312, 314, 316 can be transmitted to the A / D converter 318 in a time-synchronous manner. The A / D converter 318, in turn, provides discrete rotational position signals and torque signals that represent the rotational positions and torques detected synchronously. The A / D converter 318 is further connected to the evaluation unit 308 and is designed to transmit to the evaluation unit 308 only those rotational position signals and torque signals that represent rotational positions and torques detected synchronously.As a result, the evaluation unit 308 can determine a modulus of elasticity of the motor shaft 304 during operation of the internal combustion engine 300 on the basis of time-synchronously recorded motor shaft parameters.

[0061] In Fig. 4 is a schematic flowchart of a method for monitoring a condition of a shaft of a shaft condition monitoring system.

[0062] The shaft condition monitoring system comprises a shaft, which may in particular be a crankshaft or a camshaft of an internal combustion engine. Furthermore, the shaft condition monitoring system comprises an evaluation unit and a measured value acquisition system for detecting a shaft parameter.

[0063] In the method, in a first step S1, a first rotational position φ of a shaft 14 is determined with respect to a reference rotational position φr. Furthermore, in a second step S2, a first torque M of the shaft 14 is determined with respect to a reference torque Mr. By means of at least the first rotational position φ and the reference rotational position φr and the first torque M and the reference torque Mr, a modulus of elasticity Δσ / Δε of the shaft 14 is determined in a third step S3. The modulus of elasticity Δσ / Δε determined in this way is then compared in a fourth step S4 with at least one reference curve 602, which has a range B_lin assigned to an elastic behavior of the shaft 14. Based on the comparison between the modulus of elasticity Δσ / Δε and at least one reference curve 602, it is then determined in a fifth step S5 whether the modulus of elasticity Δσ / Δε corresponds to the area B_lin of the reference curve 602 assigned to the elastic behavior of the shaft 14.If the comparison shows that the determined modulus of elasticity does not correspond to the range B_lin assigned to the elastic behavior, a warning signal S is output in a sixth step S6.

[0064] In Fig. 5 shows a wind turbine 500 with a rotor blade 502 of an unspecified aerodynamic rotor and an electric generator 504. The electric generator 504 includes a shaft condition monitoring system with a generator shaft 14, 506, a measured value acquisition system 508, and an evaluation unit (not shown). The measured value acquisition system 508 includes two rotation angle sensors 510, 512, with a first rotation angle sensor 510 being arranged on the generator shaft 14, 506 between the rotor blade 502 and the electric generator 504, and a second rotation angle sensor 512 being arranged on the generator shaft 14, 506 on the side of the electric generator 504 opposite the rotor blade 502. The electric generator 504 itself is used as a torque sensor during operation, so that the stress and strain of the generator shaft 14, 506 can be determined during operation based on detected rotation angle positions and torques.Using the evaluation unit, a modulus of elasticity can then be determined, particularly during operation, as the relationship between stress and strain in a torsional state of the generator shaft 14,506, and the modulus of elasticity can be compared with a reference curve. Based on the comparison, the evaluation unit can determine whether the determined modulus of elasticity corresponds to a range assigned to the elastic behavior or lies outside this range.

[0065] In Fig. 6 shows an example of a schematic stress-strain diagram 600. The measurement curve 602 represents the mechanical stress and strain behavior of a solid body under the action of force. In the stress-strain diagram 600, the stress σ is plotted against the strain ε. The measurement curve 602 has a linear-elastic region B_lin and a region 606 lying outside the linear-elastic region. The region 606 lying outside the linear-elastic region comprises a non-linear elastic region that extends up to the yield point 608 and an elastic-plastic region adjoining this in the direction of greater strains ε. If the strain ε is increased beyond the elastic-plastic region, fracture 610 of the solid body occurs.

[0066] With a e.g. as in relation to Fig.In the shaft condition monitoring system described in Section 1, stress and strain of a shaft under load can be measured using the shaft condition monitoring system's measured value acquisition system. For this purpose, angle sensors and torque sensors are arranged on the shaft to measure a rotational position deviation Δσ and a torque deviation Δε, respectively.

[0067] With an evaluation unit of the shaft condition monitoring system, a modulus of elasticity can be determined as a relationship between stress and strain of a torsional state of a shaft under load using a number of rotational position deviations and a number of torque deviations.

[0068] The evaluation unit can compare the elastic modulus determined in this way with at least one reference curve, e.g., a measurement curve 602 of a stress-strain diagram 600. Through this comparison, the evaluation unit can determine whether the determined elastic modulus corresponds to a range B_lin associated with the elastic behavior, or whether the determined elastic modulus lies outside a range 606 associated with the elastic behavior. LIST OF REFERENCE SYMBOLS 14 Wave 100 Shaft condition monitoring system 104 Wave 106 cylinders 108 Evaluation unit 110 first angle sensor 112 second angle sensor 114 first torque sensor 116 second torque sensor 118 Measurement data acquisition system 200 internal combustion engine 201 Shaft condition monitoring system 202 engine 204 Motor shaft 206 cylinders 208 Evaluation unit 209 lines 210 first angle sensor 212 second angle sensor 214 first torque sensor 216 second torque sensor 218 Clock line 300 internal combustion engine 301 Shaft condition monitoring system 302 engine 304 Motor shaft 306 cylinders 308 Evaluation unit 309 lines 310 first angle sensor 312 second angle sensor 314 first torque sensor 316 second torque sensor 318 A / D converters 500 wind turbines 502 rotor blade 504 Electric generator 506 Generator shaft 508 measured value acquisition system 510 rotation angle sensor 512 angle sensor 600 Stress-strain diagram 602 measurement curve 606 area outside the linear elastic range 608 Yield limit 610 fraction KS power side of the motor shaft KGS power side of the motor shaft S1 Determining a first rotational position of a shaft S2 Determining a first torque of a shaft S3 Determine the elastic modulus of the shaft S4 Compare the elastic modulus with at least one reference curve S5 Determine whether the modulus of elasticity corresponds to the area of the reference curve assigned to the elastic behavior of the shaft S6 Emitting a warning signal M torque Mr Reference torque φ, rotational position φr reference rotation position Δσ / Δε elastic modulus B_lin linear-elastic region S warning signal

Claims

[1] Shaft condition monitoring system (100) for a shaft designed to transmit a torque, wherein the shaft condition monitoring system (100) comprises a shaft (14), a measured value acquisition system (118, 508) for acquiring a shaft parameter and an evaluation unit (108, 208, 308), wherein the measured value acquisition system (118, 508) has: - at least one first rotation angle sensor (110) which is designed to detect a first rotational position (φ) of the shaft (14) with respect to a reference rotational position (φr) in order to determine a rotational position deviation (Δσ) between the first rotational position (φ) and the reference rotational position (φr), wherein the rotational position deviation (Δσ) is assigned to a stress of a torsional state of the shaft (14) under load, - at least one first torque sensor (116) which is designed to detect a first torque (M) of the shaft (14) with respect to a reference torque (Mr) in order to determine a torque deviation between the first torque (M) and the reference torque (Mr), wherein the torque deviation (Δε) is assigned to an extension of the torsional state of the shaft (14) under load, - wherein the evaluation unit (108, 208, 308) is designed - to determine a modulus of elasticity (Δσ / Δε) as a relationship between stress and strain of a torsional state of the shaft (14) under load using a number of rotational position deviations and a number of torque deviations (Δε), characterized by , that - the evaluation unit (108, 208, 308) is further developed, - to compare the modulus of elasticity (Δσ / Δε) with at least one reference curve (602) having a region (B_lin) associated with an elastic behavior of the shaft (14), and - to determine whether the determined elastic modulus (Δα / Δε) corresponds to a region (B_lin) assigned to the elastic behavior, wherein the region (B_lin) of the reference curve (602) assigned to the elastic behavior corresponds to an at least approximately linear relationship between stress and strain of the shaft (14), or whether the determined modulus of elasticity (Δσ / Δε) lies outside a range (606) assigned to the elastic behavior, wherein the reference curve (602) has, outside the range (606) assigned to the elastic behavior, a range assigned to a plastic behavior which corresponds to a non-linear relationship between stress and strain of the shaft (14). [2] Shaft condition monitoring system (100) according to claim 1, characterized bythat the shaft (14) is a motor shaft (104, 204) of an internal combustion engine (200), namely a crankshaft and / or a camshaft, or a generator shaft (506) of an electric generator (504). [3] Shaft condition monitoring system (100) according to claim 1 or 2, characterized by that the evaluation unit (108, 208, 308) is designed to determine, for damage state detection, whether the determined elastic modulus (Δσ / Δε) corresponds to a range (B_lin) assigned to the elastic behavior, or whether the determined elastic modulus (Δσ / Δε) lies outside a range (606) assigned to the elastic behavior. [4] Shaft condition monitoring system (100) according to one of claims 1 to 3, characterized bythat the evaluation unit (108, 208, 308) is designed, after it has determined during operation that the determined modulus of elasticity (Δσ / Δε) corresponds to the range (B_lin) assigned to the elastic behavior, to determine a new modulus of elasticity (Δσ / Δε) after a predefined period of time and to compare this again with at least one reference curve (602) in order to determine whether this newly determined modulus of elasticity (Δσ / Δε) corresponds to the range of this reference curve (602) assigned to the elastic behavior. [5] Shaft condition monitoring system (100) according to one of claims 1 to 4, characterized by that the evaluation unit (108, 208, 308) is designed to provide a warning signal if it is determined that the determined modulus of elasticity (Δσ / Δε) does not correspond to the range (B_lin) assigned to the elastic behavior. [6] Shaft condition monitoring system (100) according to one of claims 1 to 5, characterized bythat the measured value detection system (118, 508) has a further rotation angle sensor (112) which is arranged on the shaft (14) at a distance from the first rotation angle sensor (110) and is designed to detect the reference rotation position. [7] Shaft condition monitoring system (100) according to one of claims 1 to 6, characterized by that the measured value detection system (118, 508) has a further torque sensor (116) which is arranged on the shaft (14) at a distance from the first torque sensor (114) and is designed to detect the reference torque (Mr). [8] Shaft condition monitoring system (100) according to one of claims 1 to 6, characterized by that the evaluation unit (108, 208, 308) is designed to computationally determine the reference torque (Mr) on the basis of the detected torque (M) and a rotational speed of the shaft (14). [9] Shaft condition monitoring system (100) according to one of claims 1 to 8, characterized bythat at least one of the rotation angle sensors (110, 112) is a resolver or a perforated wheel sensor. [10] Shaft condition monitoring system (100) according to one of claims 1 to 9, characterized by that at least one reference curve (602) with which the determined modulus of elasticity (Δσ / Δε) is compared is a curve of a stress-strain diagram of the shaft (14). [11] Shaft condition monitoring system (100) according to one of claims 1 to 10, characterized by in that at least one reference curve (602) with which the determined modulus of elasticity is compared is a curve which represents a temporal progression of a modulus of elasticity (Δσ / Δε) determined during operation, wherein the region (B_lin) of the reference curve (602) assigned to the elastic behavior corresponds to that region of the curve which was determined during a start of a torque application to the shaft (14). [12] Shaft condition monitoring system (201) according to one of claims 1 to 11, comprising a synchronization unit designed such that at least the first rotational position and the first torque (M) are detected in a time-synchronous manner. [13] Shaft condition monitoring system (201) according to claim 12, characterized by that the synchronization unit has a clock line (218) and is designed to control the sensors of the measured value acquisition system (118, 508) simultaneously with a clock signal via the clock line (218). [14] Shaft condition monitoring system (301) according to claim 12, characterized bythat the synchronization unit has at least one A / D converter (318) which is connected via lines at least to the first rotation angle sensor (310) and the first torque sensor (314) for transmitting a first rotation position signal representing the first rotation position and a first torque signal representing the first torque (M) and is designed to sample the signals fed to the A / D converter (318) in a time-synchronized manner and then to transmit them to the evaluation unit (308). [15] Internal combustion engine (200) with a motor shaft (104, 204) of an engine (202) having a shaft condition monitoring system (100, 201, 301) according to one of claims 1 to 14. [16] Internal combustion engine (200) according to claim 15, characterized bythat the evaluation unit (208) of the shaft condition monitoring system (201) is designed to determine a total torque of the engine shaft (204) from a characteristic map of the internal combustion engine (200) and to derive the reference torque (Mr) from the total torque. [17] Electric generator (504) with a generator shaft (14, 506) having a shaft condition monitoring system (201) according to one of claims 1 to 14. [18] A method for monitoring a condition of a shaft of a shaft condition monitoring system (100), wherein the shaft condition monitoring system (100) comprises a shaft (14), a measured value acquisition system (118, 508) for acquiring a shaft parameter and an evaluation unit (108, 208, 308), wherein the measured value acquisition system (118, 508) is designed to acquire a shaft parameter and the method comprises the steps: - determining (S1) a first rotational position (φ) of the shaft (14) with respect to a reference rotational position (φr) to determine a rotational position deviation (Δσ) between the first rotational position (φ) and the reference rotational position (φr), wherein the rotational position deviation (Δσ) is assigned to a stress of a torsional state of the shaft (14) under load, - detecting (S2) a first torque (M) of the shaft (14) with respect to a reference torque (Mr) to determine a torque deviation (Δε) between the first torque (M) and the reference torque (Mr), wherein the torque deviation (Δɛ) is assigned to an extension of the torsional state of the shaft (14) under load, - determining (S3) a modulus of elasticity (Δσ / Δε) with a number of rotational position deviations and a number of torque deviations as a relationship between stress and strain of a torsional state of the shaft (14) under load, the method being further characterized by the steps: - comparing (S4) the elastic modulus (Δσ / Δε) with at least one reference curve (602) having a region (B_lin) associated with an elastic behavior of the shaft (14), - Determine (S5), whether the determined modulus of elasticity (Δσ / Δε) corresponds to a region (B_lin) assigned to the elastic behavior, wherein the region (B_lin) of the reference curve (602) assigned to the elastic behavior corresponds to an at least approximately linear relationship between stress and strain of the shaft (14), or whether the determined modulus of elasticity (Δσ / Δε) lies outside a range (606) assigned to the elastic behavior, wherein the reference curve (602) has, outside the range (606) assigned to the elastic behavior, a range assigned to a plastic behavior which corresponds to a non-linear relationship between stress and strain of the shaft (14).

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