Inductor and device for inductive heating of a component and method therefor

Abstract

An inductor (10) is used for inductive heating of a metallic component and has at least one coil (10'), wherein the approximately annular coil has a channel (13) which passes through the coil (10') as a recess from the inner circumference (12) of the coil to the outer circumference (11) of the coil so that electromagnetic radiation (17) can pass through the channel (13) from the inside to the outside and be sensed in a measurement-technical manner. The channel (13) extends in an approximately radial direction. In a device (100) comprising such an inductor, it is provided that a pyrometer (16) is arranged relative to the channel (13) such that a lens (16') of the pyrometer (16) faces the outlet opening (13') of the channel (13) and is oriented coaxially with the longitudinal extension direction of the channel (13) via its optical axis. The radiation (17) sensed by the pyrometer (16) through the channel (13) and the temperature acquired thereby provide information about the development of a thermal process as a measurement variable.

Description

Technical Field

[0001] The invention relates to an inductor for inductive heating of a component, to a device comprising such an inductor and also to a method, in particular for operating such a device. Background Art

[0002] Such inductors are typically used for heat treatment of components, such as shafts or eccentrics, where increased structural strength or increased structural hardness is required to prevent wear. In this case, such inductors generate eddy currents via a magnetic field in the component or workpiece, which lead to a temperature increase in the component. The component geometry and the skin effect that occurs during heating lead to an inhomogeneous temperature distribution, especially over the surface area of ​​the component, such as in Figure 1A Reference is made to the components shown during the induction heat treatment phase and in Figure 1B As explained in the description with reference to the corresponding temperature development over time, this results in an increase in temperature of the process zone close to the surface relative to the region remote from the surface, which leads to different structural strengths within the microstructure of the correspondingly heat-treated component. Summary of the invention

[0003] An inductor having the features of claim 1 has the advantage that a more uniform temperature distribution can be set in the components treated thereby and components with a more uniform structural strength in terms of quality can thus be realized or produced. For this purpose, the approximately annularly shaped coil has a channel which, as a recess, passes through the coil from the inner circumference of the coil to the outer circumference of the coil so that electromagnetic radiation can pass through the channel from the inside to the outside and can be sensed in terms of measurement. It is thus possible to sense in terms of measurement outside the inductor the thermal radiation which reaches the outside through the channel from the component received in the interior of the annular induction coil of the inductor during the induction heat treatment and to assign a temperature to the sensed thermal radiation, which temperature provides information about the process development in the process zone close to the surface and thus allows a review of the process quality, unlike conventional inductors, in which the process zone is completely shielded and therefore inaccessible in terms of measurement.

[0004] The channel expediently extends approximately in radial direction, wherein the channel has an inlet opening on the inner circumference and, at its other end, an outlet opening on the outer circumference, so that reflection losses of the emitted thermal radiation on the wall of the channel are kept as low as possible.

[0005] Preferably, the channel extends approximately in a straight line and also has an approximately circular inner cross section in order to achieve an optimized radiation guidance.

[0006] A further development of the invention can be that the channel extends approximately at half the height with respect to the longitudinal axis of the inductor. The channel thus passes through the annular section of the inductor approximately in the center between the lower and upper limits of the inductor (seen in the axial direction), which provides the possibility of measuring the process zone, which is located in the influence region with a greater field strength than the lower and upper limits of the inductor, at which the field strength naturally drops significantly.

[0007] In a device including such an inductor, it is provided that the pyrometer is arranged relative to the channel so that the lens of the pyrometer faces the outlet opening of the channel. The thermal radiation emerging through the channel can reach the lens of the pyrometer and be imaged on the sensor of the pyrometer for detection.

[0008] In order to achieve an optimized light quantum yield, according to an advantageous embodiment of the invention, the optics of the pyrometer are oriented coaxially with their optical axis to the longitudinal extension of the channel.

[0009] An advantageous and preferred embodiment of the invention can be that the pyrometer is designed as a ratio pyrometer. In ratio pyrometers, often also referred to as two-color pyrometers, the incident thermal radiation is measured at two different wavelengths or wavelength ranges, so that knowledge of the emissivity of the measurement object or component generating the thermal radiation can be dispensed with for determining the temperature.

[0010] A suitable embodiment of the invention provides that the process computer is in signal and / or data transmission connection with the pyrometer in order to receive the transmitted measurement signals and / or measurement data from the pyrometer on the output side and process them. Furthermore, the process computer is in control connection with a generator for generating electrical power for the inductor, whereby the heat treatment process can be controlled. For this purpose, the process computer calculates parameters for controlling the induction heat treatment based on the temperature measurement signals and / or temperature measurement data received by the pyrometer.

[0011] A method particularly suitable for operating the device comprises the following method steps: a) activating the inductor, b) sensing the thermal radiation coming out of the region of the component received in the inductor through the channel of the inductor, wherein a temperature locally corresponding to the respective region is determined from the sensed thermal radiation, c) comparing the temperatures respectively determined for the respective region with a reference value, and d) readjusting a process parameter when a deviation between the sensed temperature and the reference value is determined in the comparison, wherein the readjustment is performed in accordance with the determined deviation. The temperature determined by a temperature distribution simulation for the component for the region based on the sensing according to method step b) is used as a reference value. The temperature distribution simulation is performed based on the calculation of the electromagnetic field generated by the inductor, the eddy currents induced by the component, the thermal energy generated thereby there, and the temperature distribution formed thereby in the component.

[0012] The electrical power supplied to the inductor during its activation and / or the duration of its activation and / or the feed speed by which the inductor moves during its activation duration along its longitudinal axis, i.e. relative to the respective component to be processed, are selected as process parameters. The method according to the invention advantageously enables very precise adjustment of the structural state in the component by direct measurement-technical examination of the process zone (via a channel formed in the inductor), since undesirable temperature increases in the process zone can be sensed in real time and can be reduced as much as possible and practically instantaneously by readjustment.

[0013] The geometry and / or material properties of the respective component to be processed are expediently taken into account in the simulation in order to be able to model the component as accurately as possible.

[0014] Further advantageous embodiments and refinements of the invention result from the measures listed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments of the present invention are explained in detail in the following description and drawings. The following drawings show schematic views:

[0016] Figure 1A Simulation of a 3D temperature distribution view of a component during an induction heat treatment phase,

[0017] Figure 1B A diagram with a plurality of temperature curves, wherein each temperature curve shows the development of the temperature over time for a corresponding region of the component plotted along the ordinate and in relation to the Figure 1A The 3D temperature distribution view shown in

[0018] Figure 2 A highly schematic perspective view of an approximately annular coil of an inductor for inductively heating a metal component and having a channel running radially through the coil from the inside to the outside,

[0019] Figure 3 A perspective view of a portion of the device according to the invention with the inductor of FIG. 1 , in the interior space of which a component is accommodated,

[0020] Figure 4 A block diagram for explaining the device according to the invention, comprising the inductor shown in FIG. 1 , a generator for electrically actuating the inductor, a pyrometer and a process computer in measurement data transmission connection with the pyrometer, and

[0021] Figure 5 With the device for operating according to the present invention Figure 4Flow chart of the main method steps of the method of the device. DETAILED DESCRIPTION

[0022] In reference Figures 2 to 5 Before explaining the main features of the inductor according to the invention and the device according to the invention together with a method suitable for operating the device, reference should first be made to Figure 1A and 1B Features of a sensor according to the prior art are explained.

[0023] Figure 1A The temperature distribution of a rotationally symmetrically constructed component during a typical heat treatment phase is shown in a three-dimensional illustration, which is calculated with the aid of a simulation based on an electromagnetic field generated by an induction coil of an inductor, which induces eddy currents in the component, and the calculation of the thermal energy generated due to eddy current losses in the component, taking into account the geometry and material properties of the component. Different temperature zones are formed in the simulated temperature distribution of the component, as shown by the loss temperature zones at different areas or positions 31 to 35 on the surface of the component, which partially lead to an inhomogeneous temperature distribution in the component; in areas of the component close to the surface, generally higher temperatures are present due to the eddy currents acting mainly close to the surface, while in contrast, significantly lower temperatures are present in the interior of the component due to the heat conduction taken into account in the simulation. For this purpose, Figure 1B A diagram is shown with a total of five temperature curves 31 '-35 ', wherein for each temperature curve the time t plotted along the abscissa is shown for the temperature curves in the embodiment of FIG. Figure 2 Temperature T of various regions or locations 31-35 of the component shown in A. The simulation shows that for the temperature profiles 33' to 35' assigned to the regions close to the surface of the component, after a correspondingly inclined rising edge at the start of the heat treatment at a time t≈2 s (on the time axis) a correspondingly significant temperature overshoot is obtained compared to the temperature profile 31' of the region 31 relatively far from the surface, which has a temperature peak of >1100°C.

[0024] Figure 2An inductor, designated overall by 10 , which is used for inductive heating of a metal component is shown in a highly schematic perspective view. The inductor 10 has a coil 10' which is designed in an annular or hollow-cylindrical manner due to an outer circumferential surface 11 and an inner circumferential surface 12 arranged coaxially thereto (with respect to a longitudinal center axis 10" of the coil 10') so that a rotationally symmetrical component can be received within its inner circumferential surface 11 and heated inductively. During the inductive heating phase, the temperature present on the surface of the component received in the coil 10' can be detected by measurement technology in that a channel 13 is formed in the coil 10' which passes through the coil 10' in a radial direction from the inside to the outside so that thermal radiation radiating from the interior of the coil 10' of the component can pass outward, where a pyrometer arranged in the vicinity of an outlet opening 13' of the channel 13 can detect the impinging radiation in order to thereby detect the temperature. Thus, the channel 13 extending straight in the radial direction has an outlet opening 13' on the outer circumferential surface 11 and, at the other end of the channel, has an inlet opening 13" on the inner circumferential surface 12 which is opposite to the outlet opening 13'.

[0025] In terms of production technology, in order to form the channel 13 when winding the coil, for example a small hollow cylindrical tube is placed or arranged on a support body at the beginning of the winding process and optionally removed again at the end of the winding process.

[0026] Figure 3 A perspective view shows a portion of a device 100 according to the invention for inductively heating a component 14, which is received rotatably about its axis of symmetry in the interior of an inductor 10. For this purpose, the component 14 is mounted on a rotatable holding device 20 and rotated about its axis of symmetry or longitudinal center axis during the heat treatment, thereby achieving a temperature distribution in the component 14 that is as uniform as possible. During the activation period of the inductor 10, the inductor is connected to the inductor 10 via electrical connections 15', 15". Figure 3 The generator (not shown) is electrically connected. A correspondingly arranged pyrometer (not shown) Figure 3 ) can sense the thermal radiation radiated onto the surface of the component 14 from the area directly adjacent to and radially facing the channel 13 via the channel 13 of the inductor 10 and thereby acquire the temperature existing there.

[0027] Figure 4The device 100 according to the invention is shown in a highly schematic view and comprises essentially: an inductor 10 according to the invention; a generator 15 for generating high-frequency electrical power for the inductor 10, which electrical power can be supplied to the coil 10' of the inductor 10 via electrical connecting lines 15', 15", a pyrometer 16 for detecting thermal radiation 17 which radiates from a component 14 received from the interior of the coil 10' of the inductor 10 and reaches the outside through the channel 13 of the inductor 10, and a process computing unit 18 which is connected to the output of the pyrometer 16 via signal and data transmission lines 19 in order to receive and process the temperature measurement data of the pyrometer. In this case, the pyrometer 16 is arranged or disposed in the inductor 10 in such a way that The pyrometer is placed near the sensor 10 so that the pyrometer and its lens or its incident lens 16' are aligned with the longitudinal extension direction of the channel 13, wherein the lens 16' of the pyrometer 16 and the output opening 13' of the sensor 10 face each other. The measuring axis of the pyrometer formed by the lens 16' and the sensor (not shown) runs coaxially with the longitudinal extension direction of the channel 13. As a result, the lens 16' of the pyrometer 16 captures the thermal radiation 17 that comes out of the output opening 13' to the sensor, which senses the radiation and converts it into an electrical signal. In a preferred embodiment, the pyrometer is constructed as a two-color pyrometer, so that the emissivity of the measuring object or component is not important when acquiring the temperature. Because the component is held during the induction heat treatment by means of a rotatably constructed holding device 20 ( Figure 3 ) rotates, so that the pyrometer 16 can scan the area of ​​the component passing by the input opening 13 ″ of the channel 13 during the rotation with the sensed thermal radiation 17.

[0028] Figure 5 A flow chart with the essential method steps of the method for operating the device 100 is shown. In a first method step 210, the inductor 10 is activated by supplying electrical power generated by the generator 15 to the inductor 10 via the electrical connecting lines 15', 15". Then, in a method step 220, the thermal radiation 17 radiated from the component 14 through the channel 13 is detected by the pyrometer 16 within a predetermined time period Δt and evaluated, i.e., assigned to the corresponding temperature on the basis of the Stefan Boltzmann law, which corresponds to the corresponding region on the surface of the component adjacent to the input opening of the channel 13 at the time of the measurement (seen in the radial direction), and converted into temperature measurement data.

[0029] According to a subsequent method step 230 , the temperature measurement data acquired by the pyrometer 16 are transmitted to the process computer 18 , where the transmitted temperature measurement data are then processed in a subsequent method step 240 .

[0030] In a further method step 250 , the temperatures respectively acquired by the pyrometer for a region on the surface of the component (at the respective measuring time) are compared in the process computing unit 18 with the temperatures from a simulated temperature distribution of the component, wherein the temperatures extracted from the simulated temperature distribution correspond to the same region on the surface which is also based on the respective measurement.

[0031] In a subsequent detection step 260, it is determined whether a deviation ΔT is obtained in the comparison between the temperature acquired with reference to the detected thermal radiation and the temperature extracted from the simulated temperature profile. In the negative case, i.e. if there is actually no deviation, a return is made to step 220, so that the pyrometer senses the radiation for the next time period and thereby acquires temperature measurement data. In the positive case, i.e. if there is a deviation ΔT, in a subsequent method step 270, a readjustment of the process is carried out based on the acquired temperature deviation ΔT, for example by tracking the electrical power of the generator and / or the treatment duration and / or the feed speed of the inductor within the control loop as a function of the deviation ΔT. Following the readjustment, a return is made to step 220 in a method step 280 until a predetermined heat treatment duration is reached.

[0032] Advantageously, in the method according to the invention, the electromagnetic radiation 17 sensed by the pyrometer 16 via the channel 13 and the temperature detected therefrom provide information as measured variables about the development of the thermal process.

[0033] In summary, the method 200 according to the invention comprises the following method steps: a) activating 210 the inductor 10, b) sensing electromagnetic radiation coming out of the region of the component 14 received in the inductor through the channel 13 of the inductor 10, wherein a temperature locally corresponding to the respective region is determined from the sensed radiation, c) comparing 220 the temperatures respectively determined for the respective region with a reference value, wherein as reference value a temperature is used which is determined by a temperature distribution simulation for the component for the region corresponding to the sensing according to method step b), wherein the temperature distribution simulation is based on a calculation of the electromagnetic field generated by the inductor 10, the eddy currents induced by the field in the component, the thermal energy generated therein and the temperature distribution formed in the component by heat conduction, and d) if a deviation ΔT is determined between the sensed temperature and the reference value during the comparison, re-regulating 280 a process parameter, wherein the re-regulation is performed in accordance with the determined deviation ΔT.

[0034] Physics-based simulation methods are used to model the temperature distribution in the component. The simulation methods are based on finite element simulations of electromagnetic thermal field equations. Data-based methods of machine learning, such as support vector machines or nearest neighbor algorithms, are used to classify the temperature field.

Claims

1. A device, comprising: An inductor (10) for inductively heating a component of metallic construction, the inductor having at least one coil, wherein the coil is of approximately annular design and has a channel (13) which passes through the coil as a recess from the inner circumference of the coil to the outer circumference of the coil in order to allow radiation to pass through the channel (13) from the inside to the outside, wherein the channel (13) has an inlet opening (13') on the inner circumference and, at the other end of the channel, an outlet opening (13") on the outer circumference, wherein the component can be received in the interior of the inductor (10) so as to be rotatable about an axis of symmetry or a longitudinal center axis of the component; and A pyrometer (16) is arranged outside the inductor (10) with respect to the channel (13) such that a lens (16') of the pyrometer (16) faces the output opening (13") of the channel (13).

2. The device according to claim 1, characterized in that The channel (13) extends in an approximately radial direction.

3. The device according to claim 1 or 2, characterized in that The channel (13) extends approximately in a straight line.

4. The device according to any one of claims 1 to 3, characterized in that The channel (13) has an approximately circular inner cross section.

5. The device according to any one of claims 1 to 4, characterized in that The channel (13) extends approximately at half the height relative to the longitudinal axis of the inductor (10).

6. The device according to any one of claims 1 to 5, characterized in that The lens (16') of the pyrometer (16) is oriented with its optical axis coaxially to the longitudinal extension direction of the channel (13).

7. The device according to any one of claims 1 to 6, characterized in that The pyrometer (16) is designed as a ratiometric pyrometer.

8. The device according to any one of claims 1 to 7, characterized in that A process computer (18) is in signal and / or data transmission connection with the pyrometer (16) in order to receive the transmitted measurement signals and / or measurement data from the pyrometer (16) on the output side and to process them.

9. The device according to claim 8, characterized in that The process computer (18) is in control connection with a generator for generating electrical power for the inductor (10).

10. The device according to claim 8 or 9, characterized in that The process computing device (18) calculates parameters for controlling the induction heat treatment based on the temperature measurement signal and / or the temperature measurement data received from the pyrometer (16).

11. A method for operating a device according to any one of claims 1 to 10, comprising the following method steps: a) activating (210) the sensor (10), b) sensing (220) electromagnetic radiation coming out of the region of the component (14) received in the inductor through the channel (13) of the inductor (10), wherein: The temperature corresponding to the corresponding area is obtained locally from the sensed radiation, c) comparing (240) the temperatures obtained for the respective regions with reference values, and, d) re-adjusting (280) the process parameter when a deviation between the sensed temperature and the reference value is detected during the comparison, wherein the re-adjustment is carried out in accordance with the detected deviation, wherein the component (14) is mounted on a rotatable holding device (20) and is rotated about an axis of symmetry or a longitudinal center axis of the component during the heat treatment, thereby achieving a temperature distribution in the component (14) that is as uniform as possible.

12. The method according to claim 11, characterized in that The temperature used as a reference value is that which is extracted from a temperature distribution simulation for the component for that region which is based in each case on the sensing ( 220 ) according to method step b).

13. The method according to claim 12, characterized in that The temperature distribution simulation is performed based on the calculation of the electromagnetic field generated by the inductor (10), the eddy currents induced by the field in the component, the thermal energy generated thereby there and the temperature distribution resulting thereby in the component.

14. The method according to any one of claims 11 to 13, characterized in that The electrical power supplied to the inductor (10) during the activation of the inductor and / or the duration of the activation of the inductor (10) and / or the feed speed by which the inductor (10) is moved along the longitudinal axis (10") of the inductor during its activation duration are selected as process parameters.

15. The method according to any one of claims 12 to 14, characterized in that The geometry and / or material properties of the respective component to be processed are taken into account in the simulation.

Images