Rotary Encoder and Method for Operating a Rotary Encoder

Description

[0001] The invention relates to a rotary encoder for a machine, in particular a lifting device, crane or the like, and to a method for operating a rotary encoder, wherein the rotary encoder can be connected to a shaft of a machine for detecting a rotation of the shaft, wherein the rotary encoder has a frame that can be attached to a machine with a sensor device arranged thereon for detecting a rotation of the encoder shaft, and a signal output device for outputting a rotary encoder signal and / or a speed signal, wherein the rotary encoder has a bearing device with which the encoder shaft is rotatably mounted on the frame.

[0002] Such rotary encoders and methods are well known in the art and are essentially used for position and speed detection of an axis or shaft. A rotary encoder comprises at least one encoder shaft that can be coupled to a machine and a mechanical, optical, capacitive, inductive, or magnetic encoder or detection device. The encoder device can, for example, be an incremental encoder or an absolute encoder. In a mechanical version, the encoder device can be a switch or a counter. The encoder device can acquire signals, such as an angle signal or a speed signal, for each revolution of the shaft. From these signals, a corresponding signal, which may be converted by the signal output device or adapted to a technical standard, can then be output.The signal output device is typically connected to an evaluation unit, machine control system, or similar device via a signal transmission cable or wirelessly. Such a rotary encoder is known from DE 10 2013 204 399 A1. Further rotary encoders are known from DE 10 2007 036271 A1 and DE 20 2013 102753 U1.

[0003] Rotary encoders are used, among other things, in large machines or systems and are subjected to high loads during operation. The housing of a rotary encoder is therefore usually made of metal, making the encoder relatively resistant to mechanical and thermal stresses. The encoder is then mounted by connecting the housing to the machine, for example, using screws. This connection to the machine creates the problem that compensating or shaft currents flow through the encoder connected to the shaft, potentially causing bearing damage, especially in rolling bearings. To prevent such bearing damage, it is known to connect so-called grounding contacts to a shaft. These contacts ensure grounding of the shaft or a controlled discharge of induced currents, essentially via the grounding contact instead of the bearings.Since the grounding contact is a separate component, its use is not always possible and incurs undesirable costs. Furthermore, high shaft currents result in undesirable power losses and higher operating temperatures. It is also known to electrically isolate the machine shaft from the encoder shaft via a coupling. However, such insulating couplings, corresponding insulating adapter shafts, or insulating bushings must be manufactured and assembled with precision to minimize potential runout errors. Sometimes, such solutions require more installation space, imposing corresponding restrictions on the design of mounting interfaces. Furthermore, the resulting forces can lead to increased bearing wear. Depending on their design, insulating couplings may also only be able to withstand low loads.

[0004] Furthermore, in such connections, contamination and moisture can reduce the resistance of the insulating connections and thus their protective function against shaft currents. Insulating bearings are also known, but they are not available for all standardized bearing sizes and designs. The different materials used in these so-called hybrid bearings, for example, steel and ceramic, have different coefficients of thermal expansion, which limits the operating temperature range. In hybrid bearings, the balls can be made of ceramic, or the insulation of an outer bearing shell can be formed by a ceramic layer. The present invention therefore aims to propose a rotary encoder, a rotary encoder arrangement, and a method for operating a rotary encoder that prevents bearing damage using simple means.

[0005] This problem is solved by a rotary encoder having the features of claim 1, a rotary encoder arrangement having the features of claim 8 and a method having the features of claim 9.

[0006] The rotary encoder according to the invention for a machine, in particular a hoist, crane, or the like, has a rotary encoder shaft that can be connected to a shaft of a machine to detect the rotation of the shaft. The rotary encoder has a frame that can be attached to a machine, with a sensor device arranged thereon for detecting the rotation of the rotary encoder shaft, and a signal output device for outputting an angular direction signal and / or a speed signal. The rotary encoder has a bearing device with which the rotary encoder shaft is rotatably mounted on the frame. The rotary encoder has an insulating device that electrically isolates the rotary encoder shaft and the bearing device from the frame. Accordingly, the rotary encoder shaft is rotatably connected to the shaft of the machine, which can, for example, be an electric motor. For the purposes of this invention, the term "shaft" also refers to an axle.The shaft can be directly coupled to a drive unit of the machine. Alternatively, the encoder shaft can also be rotatably connected to an axle. The frame serves to mount the encoder unit to the machine, with the encoder unit being arranged on the encoder shaft in such a way that rotation of the encoder shaft generates a rotational angle signal and / or a speed signal, which can be output and processed by the signal output device. The encoder unit and the signal output device can be designed like encoder units and signal output devices known from the prior art. Furthermore, the encoder shaft is rotatably mounted on the frame by means of the bearing assembly.Because the encoder has an insulating device that electrically isolates the encoder shaft and the bearing assembly from the frame, it prevents equalizing or shaft currents from flowing from the shaft and / or the encoder shaft into the frame or machine components via the bearing assembly. This eliminates the need for an insulated adapter shaft between the encoder shaft and the mounting shaft, as well as special bearings, couplings, or grounding contacts. While an electrical potential may arise between the frame and the encoder shaft or the bearing assembly, the insulating device prevents this potential from being easily equalized or flowing as current through the bearing assembly. The insulating device alone thus makes it possible to easily avoid bearing damage, for example, to the encoder or a machine, without the need for further complex technical measures.Furthermore, the insulating device enables the input and / or detection of an electrical signal and / or potential between the encoder shaft and the frame, between the shaft of a machine and the frame, between the bearing assembly and the frame, and / or between the bearing assembly and the encoder shaft. Using a measuring device, changes in the electrical signal and / or the electrical potential can then be measured, and a physical quantity, such as a damage value of a bearing on the encoder shaft, the shaft of a machine, and / or the bearing assembly, can be determined. In particular, a physical quantity or damage value of the encoder and / or an encoder attachment—including a coupling, an adapter shaft, or a torque arm—as well as, for example, a damage value of a machine bearing can be determined.By isolating the bearing device, all methods for electrical condition monitoring of an entire drive train can be integrated into the rotary encoder and reduced to a single mounting point.

[0007] The insulating device can therefore be designed such that the conduction of currents or voltages induced or supplied in the shaft and / or the encoder shaft into the frame is interrupted. Since the frame is usually grounded via the machine when mounted on it, the insulating device can prevent currents from flowing into the frame via the bearing assembly or the encoder shaft. This allows for condition monitoring of the encoder bearing assembly and / or condition monitoring of the rest of the drive train, including the machine bearings, and enables the monitoring of these components to be isolated from each other. If, for example, an insulated coupling or similar device is used between the encoder shaft and the machine shaft, contact with the machine shaft can be established using a further suitable device.

[0008] The frame can be designed as a housing that accommodates the encoder, the signal output device, and the bearing assembly. The housing can be a single, self-contained unit and / or a multi-part structure. For example, the housing can be designed with a flange for mounting to a machine. A receptacle for the bearing assembly can be integrated within the housing. The encoder can consist of a disk with increments surrounding the encoder shaft and a sensor for detecting these increments, thus enabling the acquisition of the angle signal and / or the speed signal. The signal output device can be a discrete circuit for processing and transmitting the respective signals. Both the encoder and the signal output device can be mounted to the housing.

[0009] The bearing device thus has at least one bearing, preferably a rolling bearing, particularly preferably two or more rolling bearings.

[0010] The essential point is that the rolling bearing is a standardized or normed, uninsulated rolling bearing that is inexpensive and readily available. For example, the rolling bearing could be a deep groove ball bearing. Alternatively, the bearing assembly could have at least one plain bearing, preferably two or more plain bearings.

[0011] The bearing or rolling bearing can be directly connected to the encoder shaft. A fit, such as a transition fit or press fit, can be formed between an outer diameter of the encoder shaft and an inner diameter of the bearing or rolling bearing. The bearing or rolling bearing can thus bear directly against the encoder shaft.

[0012] The bearing assembly comprises a bearing device that holds and at least partially surrounds the bearing or rolling bearing(s). The bearing device is designed as a sleeve into which the bearing(s) are inserted. The outer diameter of the bearing can be directly connected to the inner diameter of the sleeve by a fit, such as a transition fit or press fit, or by an adhesive bond. This significantly simplifies the mounting of the bearings independently of the frame. The bearing device or sleeve can itself form a flange by which it can be attached to the frame. The insulating device then makes it possible to electrically isolate the bearing device from the housing while still ensuring safe and easy mounting of the bearings.At the same time, it is also possible to use cost-effective rolling bearings, as no special bearing designs are required. The bearing assembly can enable a modular design of rotary encoders, allowing it to be used with various types of encoders. Furthermore, the bearing assembly significantly simplifies electrical connection to a line for signal input or potential measurement via the bearings.

[0013] The insulating device can be made of a dielectric material, which can be positioned between the frame and the bearing assembly. The dielectric material allows for a comparatively thin insulating device, so that it does not require significantly more installation space. The dielectric material can be plastic, insulating paper, mica, or ceramic. Other well-known dielectric materials, such as hard fabric or printed circuit board material, can also be used. The insulating device can also incorporate air gaps. The dielectric material can also form a surface coating, for example, as a lacquer or an anodized layer.

[0014] The insulating device can be formed from a plurality of insulating elements, whereby the bearing device can be rigidly connected to the frame via the insulating elements. The insulating elements can then be arranged at the points between the bearing device and the frame where the bearing device is held to the frame and would otherwise be in contact with the frame.

[0015] The insulating device can be designed as at least one sleeve and / or one disc. If the bearing assembly is designed at least partially in the form of a sleeve, the insulating device can then surround the bearing assembly. If the bearing assembly rests against the frame with an axial surface, the insulating device can also be designed partially as a disc that rests against the axial surface. If the insulating device comprises a plurality of insulating elements, these insulating elements can be designed as rings or as individual discs, for example, washers for screws or the like. This is particularly advantageous if the bearing assembly or a bearing assembly is bolted to the frame.

[0016] Alternatively, the insulating device can be made of a dielectric material, with the bearing assembly forming the insulating device. Accordingly, the bearing assembly can then be made entirely of the dielectric material, such as plastic or the like. The separate design of an insulating device or devices is then no longer necessary. This embodiment is particularly advantageous when no large forces are transmitted via the bearing assembly.

[0017] The rotary encoder arrangement according to the invention comprises a rotary encoder according to the invention and a machine, in particular a hoist, crane or the like, wherein the rotary encoder is connected to a shaft of the machine for detecting a rotation of the shaft. The shaft of the machine can be directly connected to a rotary encoder shaft of the rotary encoder without the need for adapter shafts or other means for mutual electrical insulation of the shafts.

[0018] In the inventive method for operating a rotary encoder for a machine, in particular a hoist, crane, or the like, a rotary encoder shaft connected to a shaft of the machine detects a rotation of the shaft. A sensor device of the rotary encoder is arranged on a frame of the rotary encoder attached to the machine and detects a rotation of the rotary encoder shaft. A rotary encoder signal and / or a speed signal is output by means of a signal output device of the rotary encoder. The rotary encoder shaft is rotatably mounted on the frame by a bearing device of the rotary encoder. The rotary encoder shaft and the bearing device are electrically insulated from the frame by means of an insulating device of the rotary encoder. For the advantages of the inventive method, reference is made to the description of advantages of the rotary encoder according to the invention.

[0019] Furthermore, an electrical signal and / or an electrical potential can be injected and / or detected between the encoder shaft and the frame, between the bearing assembly and the frame, between the machine shaft and the frame, and / or between the bearing assembly and the encoder shaft by means of a measuring device on the rotary encoder. The encoder's measuring device can, for example, be integrated into a housing formed by the frame. Since the encoder shaft and the machine shaft are electrically isolated from the frame by means of the insulating device, an electrical potential can develop between the encoder shaft or the machine shaft and the frame. The measuring device can then detect or measure a quantity of this electrical potential.The measuring device can also input and / or acquire an electrical signal, for example, a signal with a fixed or variable frequency or any signal pattern. An input signal, in this context, refers to a potential specifically generated by the measuring device. An input signal can be galvanically isolated from the machine's grounding. This prevents interference from signals with induced or coupled shaft voltages and can thus increase the accuracy and sensitivity of the measuring device. If the acquisition is performed for a signal routed between the bearing assembly and the frame, a measured value of the signal for the bearing assembly can advantageously be obtained. Furthermore, the acquisition can be performed for a signal routed between the machine shaft and the frame, advantageously yielding a measured value of the signal for the shaft bearings.The drive train can be monitored. By using different signals, a time-parallel measurement is possible. The measuring device can then be connected to the signal output device and output a corresponding measured value. This measured value can be evaluated, allowing the rotary encoder itself to be used as a measuring device for the electrical potential and / or signal. The electrical potential and / or signal can be used to determine the operating state of the machine and / or the rotary encoder.

[0020] The measuring device generates an electrical signal, which is then transmitted and measured via at least one bearing, preferably at least one rolling bearing, in the bearing assembly and / or a bearing on the machine shaft. This allows for simple monitoring of the operating condition of each bearing. The signal strength can be set so that the bearing is not damaged by the signal. The isolation of the bearing assembly from the frame allows for the simultaneous monitoring of individual bearings or all bearings within the assembly. The measuring device can then be directly electrically connected to individual bearings or to a bearing assembly within the assembly. For example, in the case of a rolling bearing, the signal can be transmitted via an inner ring, rolling elements, and an outer ring of the bearing.

[0021] The measuring device can detect and store changes in electrical potential or signal over an operating period. It can determine and output a physical quantity, such as a load-dependent damage value, from a bearing on the machine shaft, from the bearing assembly, and / or from a machine attachment, including all components involved in the attachment, such as couplings, adapter shafts, or torque arms. Depending on the condition of the bearings and / or related machine components, the signal or potential can change by varying degrees. The measuring device can generate the electrical signal continuously or at intervals. Changes in this signal, interference signals, or electrical potential can be easily detected by measuring it over an operating period.This measurement can be used to determine a damage value and thus predict potential damage to the machine and / or bearings. The measuring device can therefore also be used to monitor the machine's operating condition.

[0022] Further advantageous embodiments of the method result from the feature descriptions of the dependent claims relating to device claim 1.

[0023] A preferred embodiment of the invention is explained in more detail below with reference to the accompanying drawing.

[0024] The FigureFigure 10 shows a longitudinal sectional view of a rotary encoder 10, which essentially consists of a frame 11, a rotary encoder shaft 12, an encoder assembly 13, and a signal output device 14, shown only schematically here. The frame 11 is designed as a housing 15, which can be connected to a machine (not shown) via a flange of a first housing part 17. A second housing part 18 is screwed to the first housing part 17.

[0025] The rotary encoder 10 further comprises an insulating device 19 and a bearing device 20 for supporting the rotary encoder shaft 12. The insulating device 19 is designed such that the rotary encoder shaft 12 and the bearing device 20 are electrically insulated from the frame 11. The bearing device 20 includes two rolling bearings 21, which are directly connected to the rotary encoder shaft 12. The bearing device 20 further comprises a bearing assembly 22, which is partially sleeve-shaped and accommodates the rolling bearings 21. The rolling bearings 21 are directly connected to the bearing assembly 22 and spaced apart from each other by a ring 23. The bearing assembly 22 further forms a flange 24, via which the bearing assembly 22 is screwed to the first housing part 17 by means of screws 25.The insulating device 19 is made of a dielectric material, such as plastic, and consists of a first ring 26, a second ring 27, a disc 28, and a plurality of washers 29 for the screws 25. The bearing assembly 22 is thus completely electrically isolated from the frame 11. Any currents induced in a shaft of the machine (not shown) and / or the encoder shaft 12 into the frame 11 are therefore prevented. The design of the encoder assembly 13, here formed by a disc 30 with increments not shown, mounted on the encoder shaft 12, and a detector on a circuit board 31 (not shown in detail) for detecting the increments, is not further affected by the design of the bearing assembly 20 and the insulating device 19.

Claims

1. A rotary encoder (10) for a machine, in particular a hoist, crane or the like, the rotary encoder having a rotary encoder shaft (12) which is connectable to a shaft of a machine for detecting a rotation of the shaft, the rotary encoder having a frame (11) which is mountable on a machine, the frame (11) having an encoder element (13) disposed thereon for detecting a rotation of the rotary encoder shaft and a signal output element (14) for outputting a rotation angle signal and / or a speed signal, the rotary encoder having a bearing device (20) by means of which the rotary encoder shaft is rotatably mounted on the frame, the rotary encoder having an insulating device (19) which electrically insulates the rotary encoder shaft and the bearing device from the frame, the bearing device (20) having at least one bearing, preferably a rolling bearing (21), particularly preferably two or more rolling bearings, and the bearing device (20) comprising a support element (22) which supports and at least partially surrounds the bearing or a plurality of bearings, the support element (22) being at least formed as a sleeve, the sleeve forming a flange by means of which the support element is fastened on the frame, and the insulating device (19) surrounding the bearing device (20).

2. The rotary encoder according to claim 1, characterized in that the insulating device (19) can be formed such that currents induced in the shaft and / or the rotary encoder shaft (12) are interrupted from being discharged to the frame (11).

3. The rotary encoder according to claim 1 or 2, characterized in that the frame (11) is formed as a housing (15) in which the encoder element (13), the signal output element (14) and the bearing device (20) are accommodated.

4. The rotary encoder according to any one of the preceding claims, characterized in that the bearing is directly connected to the rotary encoder shaft (12).

5. The rotary encoder according to any one of the preceding claims, characterized in that the insulating device (19) is formed by a dielectric material which is disposed between the frame (11) and the bearing device (20).

6. The rotary encoder according to claim 5, characterized in that the dielectric material is plastic, insulating paper, mica or ceramic.

7. The rotary encoder according to any one of the preceding claims, characterized in that the insulating device (19) is formed by a plurality of insulating elements (26, 27, 28, 29), the bearing device (20) being rigidly connected to the frame (11) via the insulating elements.

8. A rotary encoder arrangement having a rotary encoder (10) according to any one of the preceding claims and a machine, in particular a hoist, crane or the like, the rotary encoder being connected to a shaft of the machine for detecting a rotation of the shaft.

9. A method for operating a rotary encoder (10) for a machine, in particular a hoist, crane or the like, a rotary encoder shaft (12) of the rotary encoder detecting a rotation of the shaft, said rotary encoder shaft (12) being connected to a shaft of a machine, an encoder element (13) of the rotary encoder being disposed on a frame (11) of the rotary encoder and detecting a rotation of the rotary encoder shaft, said frame (11) being fastened to the machine, a rotation angle signal and / or a speed signal being output by means of a signal output element (14) of the rotary encoder, the rotary encoder shaft being rotatably mounted on the frame via a bearing device (20) of the rotary encoder, the rotary encoder shaft and the bearing device being electrically insulated from the frame by means of an insulating device (19) of the rotary encoder, the bearing device (20) having at least one bearing, preferably a rolling bearing (21), particularly preferably two or more rolling bearings, and the bearing device (20) comprising a support element (22) which supports and at least partially surrounds the bearing or a plurality of bearings, the support element (22) being at least formed as a sleeve, the sleeve forming a flange by means of which the support element is fastened on the frame, and the insulating device (19) surrounding the bearing device (20).

10. The method according to claim 9, characterized in that at least an electric signal and / or an electric potential is detected between the rotary encoder shaft (12) and the frame (11), between the bearing device (20) and the frame, between the shaft of a machine and the frame, and / or between the bearing device and the rotary encoder shaft by means of a measuring element of the rotary encoder (10).

11. The method according to claim 10, characterized in that an electric signal is generated by means of the measuring element and is conducted and measured via at least a bearing, preferably at least a rolling bearing (21), of the bearing device (20) and / or a bearing of the shaft of the machine.

12. The method according to claim 10 or 11, characterized in that the measuring element detects a change in the electric signal over an operation period, the measuring element determining and outputting a physical quantity, preferably a load-dependent damage value, of a bearing of the shaft of the machine, of the bearing device (20) and / or of an attachment of the machine.