Induction coil unit and method for controlling induction heating process of induction coil unit

Abstract

The invention relates to an induction coil unit having an induction coil, into which a sleeve part of a tool holder can be inserted, and to a method for controlling an induction heating process of an induction coil unit, in which a sleeve part of a tool holder is inserted into the induction coil of the induction coil unit. In order to increase the degree of automation and the operational safety of the induction coil unit, it is provided that during the induction heating of the sleeve part inserted into the induction coil, the sleeve part is inserted into the induction coil. A time curve or frequency curve of the coil current, and / or of the coil voltage, and / or of the input current, and / or of the input voltage is determined for the sleeve part inserted into the induction coil. In addition, a (coil current) curve and / or a (coil voltage) curve and / or a (input current) curve and / or a (input voltage) curve is then analyzed. On the basis of the analyzed curve or the evaluated curve, in particular on the basis of the curve behavior and / or curve change and / or curve change behavior, it is determined whether the heating process is continued or ended, in particular uninterrupted.

Description

[0001] The invention relates to an induction coil unit having an induction coil, into which a sleeve part of a tool holder can be inserted, and to a method for controlling an induction heating process of an induction coil unit, wherein the sleeve part of a tool holder is inserted into the induction coil of the induction coil unit.

[0002] Such a generic induction coil unit is known from the prior art, for example from EP 1 867 211 A1.

[0003] These known induction coil units are used to thermally expand a tool holder by means of an alternating magnetic field that can be generated by the induction coil and eddy currents thereby induced in a tool holder inserted into the induction coil of the induction coil unit, so that a tool can be inserted into the tool holder in this expanded state of the tool holder and then, after a cooling process of the tool holder, the tool is securely and symmetrically held by the tool holder. This process is also referred to (for short) as inductive shrink fit of a tool in a tool holder and is known as such.

[0004] For a more detailed description of the technology and the operating background, reference should therefore be made to the above-mentioned patent applications.

[0005] However, in such known induction coil units, the problem arises that, in order to operate them efficiently, that is to say to inductively shrink-fit the tool into the tool holder, in particular during the heating of the tool holder, the induction coil unit needs to be adjusted with respect to different operating parameters, such as in particular the heating time, in each case individually to the tool holder currently held therein, which requires a high degree of manual intervention and thus in some cases significantly prolongs the cycle time for changing tools in different types of tool holders. In addition to this, manual intervention is always a potential source of error.

[0006] On the other hand, if such adjustment is not performed or is performed incorrectly for the currently held tool holder, the operation of the induction coil unit may in some cases be inefficient, since the intended eddy currents are not properly induced in the tool holder. In particularly unfavorable cases, such as, for example, in the case of an excessively long heating time, the tool holder may even overheat and thus be destroyed.

[0007] The object of the present invention is therefore to provide an induction coil unit and a method for controlling an induction heating process of an induction coil unit which are able to overcome the above-mentioned disadvantages of such induction coil units known from the prior art, wherein the induction coil unit can in particular have an increased degree of automation and can therefore be operated with shorter cycle times while maintaining a high degree of operating safety.

[0008] This object is achieved by an induction coil unit and a method for controlling an induction heating process of an induction coil unit having the features of the respective independent claims. Advantageous developments of the invention are the subject matter of the dependent claims and of the following description and relate to both the induction coil unit and the method for controlling an induction heating process of an induction coil unit.

[0009] Unless expressly defined otherwise, any terms used (such as above, below, front, rear, left, or right) are to be understood according to common understanding, including with reference to the present drawings. Terms (such as radial and axial), when used and not expressly defined otherwise, are to be understood with respect to a central axis or axis of symmetry of a component / part described herein (including with respect to the present drawings).

[0010] The expression "substantially" when used can be understood (as understood by the Supreme Court) to mean "still to a substantial degree in practice". Thus, possible deviations from precision implied by this concept may occur unintentionally (that is to say without any functional basis) due to manufacturing or assembly tolerances, etc.

[0011] Induction coil unit together with method for controlling an induction heating process of an induction coil unit An induction coil is provided in the induction coil unit into which (in terms of arrangement) or into which (in terms of method) a sleeve part of a tool holder can be inserted.

[0012] method

[0013] In a method for controlling an induction heating process of an induction coil unit, such as a shrink device, in which a sleeve portion of a tool holder is inserted into an induction coil of the induction coil unit, it is provided that

[0014] During an in particular uninterrupted induction heating process in the sleeve section inserted into the induction coil, the time curve or frequency curve of the following is determined for the sleeve section inserted into the induction coil:

[0015] - coil current, in short, the amperes produced in a coil or coil circuit as a function of time or frequency, and / or

[0016] - coil voltage, in short, the voltage varying with time or with frequency of the coil current present at the coil or capable of being tapped in the coil circuit, and / or

[0017] Input current and / or input voltage, in short, the amperage and / or voltage of a current generated upstream of the coil or upstream of the coil circuit, for example in an input circuit or an intermediate circuit, which varies over time or with frequency.

[0018] A time curve or a frequency curve (sometimes also referred to as a frequency characteristic) may be understood here illustratively and simply as in particular a mapping or a relationship, wherein the mapping variable of a mapping rule is time or frequency, and the mapping rule maps the mapping variable to a second mapping variable. Thus, in this case, the mapped second variable may be the above-mentioned coil current and / or coil voltage and / or input current and / or input voltage, or a variable that can be derived or obtained / calculated therefrom, such as a phase or a phase shift.

[0019] Mathematically, this can be expressed in simplified form as follows:

[0020] (coil current / coil voltage / input current / input voltage (or derived variable)) = f (time or frequency)

[0021] Where: f = mapping rule / relationship.

[0022] Furthermore, the (coil current) curve and / or the (coil voltage) curve and / or the (input current) curve and / or the (input voltage) curve or the resulting variables are then analyzed.

[0023] Based on the analyzed or evaluated curve, in particular based on the curve behavior and / or the curve change and / or the curve change behavior, it is decided whether the in particular uninterrupted heating process is to be continued or ended.

[0024] Analysis in this case may therefore mean, in particular, determining or investigating the curve behavior and / or the curve profile and / or the curve profile behavior of a time or frequency curve based on ascertainable parameters.

[0025] Here, a curve behavior may be understood as meaning in particular a change in the curve (e.g. an increasing, decreasing and / or constant curve) and also the curvature behavior of the curve, while a curve change / behavior is understood as meaning a change in the curve itself or as a whole; for example, there is a change in the curve over time and / or the heating temperature of the sleeve part inserted into the induction coil, that is to say a change in the third dimension overall.

[0026] The present invention is based on the following discovery: depending on the heating or heating temperature of the sleeve part inserted into the induction coil, there is a change in the magnetic properties (such as magnetic permeability) of the sleeve part inserted into the induction coil, and therefore there is a change in the inductance and / or electrical properties (such as the resistance of the entire system) of the entire system (also including the induction coil and the sleeve part inserted therein).

[0027] As has been recognized, in this case, the change in magnetic permeability or inductance is more significant, the closer the heating temperature of the sleeve portion inserted into the induction coil is to its Curie temperature Tc. On the other hand, below the Curie temperature Tc, far from the Curie temperature Tc (such as at the beginning of heating), the change in electrical characteristics (such as resistance) is dominant.

[0028] This means, in turn, that temperature-related changes in the permeability, inductance and / or electrical properties or resistance can be identified with the aid of the “dynamics” in the curve or the curve changes / curve change behavior, or that these changes are reflected there, in particular having different influences or dominance in different temperature ranges.

[0029] It has also been recognized here that this is reflected in particular in the coil current, the coil voltage and the input current and input voltage and therefore also in the variables that can be derived or obtained / calculated therefrom, such as the phase or the phase shift.

[0030] In simplified and briefly described terms, in the lower temperature range, in particular, changes in resistance will be reflected in the coil current, coil voltage, and input current and input voltage, or variables that can be derived or obtained / calculated therefrom (such as phase or phase shift), and when approaching or approaching the Curie temperature Tc, changes in permeability / inductance will be reflected therein.

[0031] In other words, the curves that most reliably describe / map / track the (heating) state of the inserted sleeve part or that most reliably describe / map the identified temperature-related effects are the curves of coil current, coil voltage and input current and input voltage or variables derived therefrom.

[0032] Identifying / mapping these dynamics or this varying parameter (or parameters) makes this variation accountable / understandable (analytically) - and therefore allows its use in defining decision criteria regarding the heating of the inserted sleeve portion.

[0033] Such a parameter (describing the curve dynamics or curve behavior or curve change / curve change behavior) can, for example, map or represent a change in amplitude (value), in particular a change in amplitude extreme values, in particular a change in amplitude maximum values, such as an ampere or voltage dropping / decreasing or remaining constant or increasing / rising, in particular in the case of a time curve.

[0034] Such parameters (describing the curve dynamics or the curve behavior or the curve change / curve change behavior) can, for example (particularly in the case of a frequency curve) also be amplitude extremes, in particular the resonant frequency, amplitude extreme value changes, variance or curve width / bandwidth or variance / curve width / bandwidth change and / or resonant frequency change.

[0035] In other words, in simple and illustrative terms, such a parameter (describing the curve dynamics or curve behavior or curve change / curve change behavior) is not just a simple characteristic variable that statically describes a certain state during power transmission or power consumption (such as a certain ampere / voltage value at a certain time or in a time curve), but a broader characteristic variable that goes beyond this range and maps the "dynamics" in the time or frequency curve / frequency curve change.

[0036] Simply put (mathematically speaking), the (mathematical) characteristic variables or higher-order derivatives in the time curve or frequency curve / frequency curve change.

[0037] It is therefore particularly advantageous to describe the curve dynamics, for example, using derivatives or tangents of the curve or the curve change and / or derivatives or tangents connecting curves, which connect the amplitude values ​​(especially the amplitude maximum) of the curves (especially the time curves). In short, the parameter in this case would be the tangent.

[0038] In other words, the parameter may (conveniently mathematically) be a derivative or tangent of the curve (particularly the time curve) and thus map the variation (particularly the time variation) of the coil current or coil voltage or input current or input voltage.

[0039] This derivative or one or more tangents (in particular using a change in one or more slopes of the one or more tangents) can then be used in particular to decide whether the heating process should be continued or ended.

[0040] In particular, a change in the slope of a tangent can be of decisive importance here, for example a change from a falling tangent to a horizontal tangent or vice versa, or a change from a horizontal tangent to a rising tangent or vice versa.

[0041] For example, if the parameters of the time curve of the coil current, coil voltage and / or input current and / or input voltage thus exhibit a horizontal curve or a rising curve or a transition from a falling tangent to a horizontal tangent or from a horizontal tangent to a rising tangent, the heating process can be terminated when such behavior occurs ("termination behavior").

[0042] This also applies in the same way to the curvature and / or curvature behavior of the curve.

[0043] In particular, a termination can be performed, for example, as soon as only one or the first of the (curve) parameters exhibits a defined, described termination behavior (in time), or alternatively only when several or all (curve) parameters (here the parameters of coil current, coil voltage, input current and input voltage) exhibit a predeterminable termination behavior ((predefinable) "termination criterion").

[0044] In this case, separate stop criteria can also be defined individually on a sleeve section specific basis in each case for one or more specific sleeve sections, for example, so that for the diameter of a larger sleeve section several or all parameters have to exhibit stop behavior, while for the diameter of a smaller sleeve section only one parameter has to exhibit stop behavior.

[0045] It can be particularly advantageous here to determine the effective current or voltage curve of the determined time / frequency curve and if this is used as a further basis for the parameter determination, the effective curve reproduces the actual current or voltage curve more realistically.

[0046] The same applies when the determined time / frequency curve is measured, smoothed, averaged, filtered and / or normalized.

[0047] In particular, it may also be advantageous to normalize these curves to a reference voltage, for example to the German reference mains voltage.Such a normalization allows the method to be independent of any specific country with a corresponding mains voltage.

[0048] Furthermore, it may be advantageous to also base the decision on the geometry or other physical properties (such as material or mass) of the sleeve part inserted into the induction coil of the induction coil unit. Such geometry may be, for example, the outer diameter of the inserted sleeve part.

[0049] This is based on the fact that the variable to be measured (apart from the temperature) depends decisively on the extent to which the sleeve portion fills the center or so-called core of the induction coil, that is to say whether the sleeve portion in question has a smaller or larger (outer) diameter or a larger or smaller mass.

[0050] In particular, in the case of an inductive shrink-fit device or shrink device, the insertion of the tool holder into a sleeve portion circumferentially surrounded by an induction coil ring forms an essential component of the magnetic circuit. In particular, the sleeve portion forms the metal core of the induction coil. The range of the inductance to be measured therefore depends decisively on the extent to which the sleeve portion fills the center or so-called core of the induction coil, that is to say, whether the sleeve portion in question has a smaller or larger (outer) diameter or a larger or smaller mass.

[0051] In this respect, it is advantageous to determine the geometry or outer diameter of the sleeve part inserted into the induction coil before starting (in particular in an automated manner) and thus "identify" the inserted sleeve part. This is described, for example, in German patent applications 10 2015 016 831.2 and 10 2019 112 521.9 and European patent application 19 17 6562.7. The contents of these documents are hereby incorporated into the subject matter of the present application.

[0052] If the inserted sleeve part is then identified, heating parameters for the inserted sleeve part or its heating process can be determined or defined.

[0053] Such heating parameters may in particular be the contraction / heating frequency and / or the contraction / heating temperature and / or the time of the heating process and / or the maximum time and / or the energy (current integral) of the heating process.

[0054] Therefore, it is also particularly advantageous to define the frequency of the (heating) current (that is to say the contraction / heating frequency) close to the resonance frequency, for example "just" below or above the resonance frequency, in particular "just" above the resonance frequency; as the contraction / heating frequency approaches the resonance frequency, the efficiency / effectiveness of the heating increases. It should be avoided to define the contraction / heating frequency equal to the resonance frequency, otherwise the resonance effect may lead to overloading of components in the induction coil unit.

[0055] Furthermore, it may also be advantageous to determine the curve or the time curve and / or the frequency curve by measurement. Suitable measuring means (or functionally equivalent circuits) or suitable measuring means (or circuits) may be provided in the induction coil unit.

[0056] If measuring amperage in this manner, it is advantageous to use a current (amperage) measuring tool such as an ammeter or multimeter, or even a measuring coil, connected in series; if measuring voltage, it is advantageous to use a voltmeter connected in parallel.

[0057] In this case, such a measurement of the curve can be carried out in an input circuit of the circuit of the induction coil unit and / or in an intermediate circuit and / or an output circuit of the induction coil unit or on the induction coil.

[0058] These measurements may also be performed in parallel (in time) at the above-mentioned several points of the circuit.

[0059] unit

[0060] In the induction coil unit for carrying out the method, a circuit is also provided, by means of which the induction coil can be supplied with power.

[0061] It may be advantageous if the circuit has at least one power semiconductor component, in particular at least one insulated gate bipolar transistor (IGBT) and / or metal oxide semiconductor field effect transistor (MOSFET), which has good forward behavior, high reverse voltage and robustness and can also be driven with almost no power required.

[0062] Furthermore, in the induction coil unit, a control unit is provided, by means of which the induction coil and the circuit can be controlled. The control unit is also configured such that, in short, the method (in terms of its essential features, in particular also in terms of all embodiments and developments described above) can be carried out.

[0063] This also means in particular that the control unit controlling the induction coil and the circuit is configured such that

[0064] During an in particular uninterrupted induction heating process in a sleeve part inserted into the induction coil, a time curve or a frequency curve of the coil current and / or the coil voltage and / or the input current and / or the input voltage can be determined for the sleeve part inserted into the induction coil, and the (coil current) curve and / or the (coil voltage) curve and / or the (input current) curve and / or the (input voltage) curve, possibly including variables derived therefrom, can be analyzed, and based on the analyzed curves or evaluated curves, in particular based on the curve behavior and / or the curve change and / or the curve change behavior, it can be determined whether the in particular uninterrupted, heating process is to be continued or ended.

[0065] It is also advantageous if one or more measuring devices are provided, by means of which the one or more time curves or the one or more frequency curves can be measured.

[0066] Preferably, in this case the measuring device is a current measuring device or a voltage measuring device.

[0067] Also preferably, the measuring device can be installed in the input circuit and / or in the intermediate circuit and / or in the output circuit of the electrical circuit.

[0068] Preferably, the method (together with the induction coil unit) can also be used to identify an already warmed sleeve part of the tool holder which is inserted into the induction coil. The determined parameters are used here to identify the preheated state of the sleeve part.

[0069] If, for example, a parameter of the time curve already exhibits a horizontal curve or a rising curve at the beginning of the heating process of the inserted sleeve part, this indicates that the sleeve part has been preheated.

[0070] Since, by means of the method and also in the case of the induction coil unit, a largely automatic or automated operation is possible, that is to say the inductive shrink-fitting of the tool into the tool holder, in particular the heating of the tool holder, manual intervention for the purpose of setting the operating parameters becomes superfluous in this case for the respective tool holder just inserted into the induction coil unit, which means on the one hand that the time previously required for this is saved and on the other hand that the automatic / automated operation also makes it possible to meet high standards in terms of operating safety and tolerances so that the unit can ensure operation in accordance with regulations. By means of the method and in the case of the induction coil unit, an effective protection against overheating of the tool holder to be heated / expanded can also be achieved.

[0071] The description of advantageous configurations of the invention given so far includes many features which are reproduced in the individual dependent claims, in some cases together. However, these features can also be advantageously considered individually and combined into suitable further combinations.

[0072] In particular, these features may be combined individually and in any suitable combination with the method according to the invention.

[0073] Even if some terms are used in the singular form or in combination with numbers in the specification and / or claims, the scope of the present invention is not intended to be limited to the singular form of these terms or the corresponding numbers. In addition, the word "a" or "an" should not be understood as a number, but an indefinite article.

[0074] The above-mentioned characteristics, features and advantages of the present invention and the manner of achieving these will become clearer and can be more clearly understood in conjunction with the following description of exemplary embodiments of the present invention, which will be explained in more detail in conjunction with the accompanying drawings / figures (in the accompanying drawings / figures, the same parts / components and functions are represented by the same markings).

[0075] The exemplary embodiments are used to explain the invention without limiting the invention to the combinations of features specified therein, including combinations of functional features. For this purpose, suitable features of each exemplary embodiment may also be explicitly considered separately, removed from one exemplary embodiment, introduced into another exemplary embodiment in order to supplement the latter and combined with any one of the claims.

[0076] In the figure:

[0077] Figure 1 shows a longitudinal middle section of an induction coil unit according to one embodiment;

[0078] Figure 2 A circuit diagram showing a circuit for powering an induction coil that can be used in an induction coil unit;

[0079] Figure 3 shows a time curve of the coil current in a case where the sleeve is partially inserted into the induction coil of the induction coil unit during contraction;

[0080] Figure 4 Shown according to Figure 3 Idealized time curve of the RMS coil current.

[0081] Automatic heating control of the shrinking process using a shrinking device

[0082] Figure 1 The basic structure of an induction coil unit is shown, which is also referred to here as a retraction device due to its intended function (hereinafter).

[0083] like Figure 1 As shown, the retraction device provides an induction coil 1 with individual turns 2, in the center of which a tool holder 4 is inserted in order to retract a holding shaft H of a tool W, here for example a milling cutter, into or release it from a sleeve part HP.

[0084] The operating principle on which the contraction and release are based is described in more detail in German patent application DE 199 15 412 A1, the content of which is hereby incorporated into the subject matter of the present application.

[0085] The induction coil 1 is provided with a first sheath 3 made of an electrically non-conductive but magnetically conductive material on its outer circumference.

[0086] Typically, the first sheath 3 is composed of ferrite or metal powder or metal sintered material, the individual particles of which are isolated from each other in an electrically insulating manner and are therefore substantially magnetically conductive and electrically non-conductive as a whole.

[0087] The first sheath 3 is also designed so that it is completely self-enclosed in the circumferential direction, that is, it completely covers the outer peripheral surface of the induction coil 1, so that in theory, there are no remaining "magnetic gaps" except for irrelevant local penetrations (such as individual and / or small local holes, etc.).

[0088] In addition, if Figure 1 It is also shown that in the retractable device the shielding element made of magnetically conductive but electrically non-conductive material does not end with the first sheath 3 .

[0089] Instead, the magnetic covers 3 a , 3 b made of said material abut at least one, and better still both, end faces of the first sheath 3 and are generally in contact with the first sheath 3 .

[0090] On the end face of the induction coil 1 facing away from the tool holder 4 , the magnetic cover 3 a is preferably designed as a completely or preferably partially replaceable pole shoe, that is to say as an annular structure with a central opening forming a channel 7 for clamping or releasing the tool W.

[0091] On the end face of the induction coil 1 facing the tool holder 4 , the magnetic cover 3 b is preferably designed as an intrinsically planar annular disk which ideally fully engages with the winding of the induction coil 1 and has a central passage for the sleeve part HP.

[0092] To improve the shielding even further, e.g. Figure 1 As also shown, the induction coil 1 and its first sheath 3 are surrounded on their periphery by a second sheath 9 , in particular such that the first sheath 3 and the second sheath 9 are in contact with each other, ideally over most or all of their mutually facing peripheral surfaces.

[0093] The second sheath 9 is made of a non-magnetic but conductive material (such as aluminum).

[0094] “Electrically conductive” is to be understood here as meaning materials which are not only locally (“grain-wise”, as it were) electrically conductive, but also materials which allow the formation of eddy currents to a relevant extent.

[0095] A special feature of the second sheath 9 is that it is preferably designed, and preferably designed to be sufficiently thick in the radial direction, so that under the influence of the stray field of the induction coil 1 eddy currents are generated in the second sheath, which eddy currents lead to an undesired stray field attenuation.

[0096] The second jacket 9 is also surrounded on its outer circumference by power semiconductor components 10 , which are explained in greater detail below, and which are arranged directly on the outer circumference of the second jacket 9 in recesses 11 (only indicated) there.

[0097] These power semiconductor components 10 have two large main surfaces and four small side surfaces. The large main surface is preferably more than four times as large as each of the individual side surfaces.

[0098] The power semiconductor components 10 are arranged such that one of their large main surfaces is in thermally conductive contact with the second jacket 9 generally on the periphery thereof, wherein the relevant large main surface of the power semiconductor components 10 is adhesively bonded to the peripheral surface of the second jacket 9 by means of a thermally conductive adhesive.

[0099] Each of the power semiconductor components 10 has different power supply terminals.

[0100] In addition, if Figure 1It is also shown that capacitors 14a, 14b are grouped together around the induction coil 1 on the periphery of the induction coil.

[0101] The capacitors 14a are preferably smoothing capacitors which are directly part of the power supply circuit; the capacitors 14b are preferably resonant circuit capacitors which are likewise directly part of the power supply circuit.

[0102] In order to electrically connect the capacitors 14 a , 14 b , a plurality of circuit boards 15 a , 15 b are provided here, each of which is joined around the outer circumference of the induction coil 1 .

[0103] Each of these circuit boards 15a, 15b is preferably formed as an annular disk. Each of the circuit boards 15a, 15b is preferably composed of FR4 or a similar material commonly used for circuit boards.

[0104] As in Figure 1 It can also be seen in FIG. 1 that the rotational symmetry axis of each of the two printed circuit boards 15 a , 15 b (designed here as printed circuit board annular disks) is coaxial here with the longitudinal axis L of the induction coil (and also of the tool holder 4 / tool ​​W).

[0105] The upper circuit board 15a of the two circuit boards carries smoothing capacitors 14a whose connecting tabs penetrate the upper circuit board 15a or are connected to the upper circuit board 15a using SMD technology so that the smoothing capacitors 14a are suspended from the upper circuit board 15a.

[0106] The lower circuit board 15 b of the two circuit boards is designed accordingly, from which the resonant circuit capacitor 14 b protrudes upward.

[0107] In summary, the power semiconductor 10 forms a first imaginary cylinder around the induction coil 1; the capacitors 14a, 14b form a second imaginary cylinder around the first imaginary cylinder; the capacitors 14a, 14b, which are only less sensitive to stray fields, form an imaginary outer cylinder, while the power semiconductor components 10, which rely on an installation space with as little stray fields as possible, form an imaginary inner cylinder.

[0108] like Figure 1 As also shown, the induction coil 1 is not "fully wound" over its entire length in the direction of its longitudinal axis L. Instead, the induction coil is composed of two substantially cylindrical winding packages. These winding packages each form an end face of the induction coil 1. The winding packages are kept at a certain distance from each other, for example, the distance is approximately at least 1.5 times the extent of each winding package in the direction of the longitudinal axis L of the induction coil 1.

[0109] Such an induction coil 1 contributes to a reduction in reactive power, since the induction coil has no windings in the “central region” which are not necessarily necessary from the point of view of achieving the most efficient possible heating of the sleeve portion HP of the tool holder, but which, if present, tend to generate additional reactive power without making a really significant contribution to the heating.

[0110] In order to supply power to the induction coil 1 with as little loss as possible, a Figure 2 The circuit is shown in more detail.

[0111] like Figure 2 As shown, for this purpose, the circuit has a resonant circuit SKS (see Figure 2 ).

[0112] In the resonant circuit SKS, most of the required energy oscillates periodically (at high frequency) back and forth between the induction coil 1 and the capacitor units 14a, 14b. This means that, in each cycle or periodically, only the energy extracted from the resonant circuit SKS through its heating power and its other power losses needs to be fed back. Therefore, the previous very high losses no longer occur.

[0113] like Figure 2 The power electronics shown, which supply the induction coil 1 , are supplied on the input side with the commonly available mains current NST, which in Europe (three-phase current, 3f) is 400 V / 50 Hz (corresponding values ​​in other countries).

[0114] like Figure 2 As shown, the current drawn from the grid is converted by a rectifier G21 into a DC current which is in turn smoothed by one or more smoothing capacitors 14a (not shown).

[0115] In addition, if Figure 2 It is also shown that this direct current is supplied to the actual resonant circuit SKS.

[0116] The backbone of the resonant circuit SKS is formed by the power semiconductor components 10 , the resonant circuit capacitor 14 b and the induction coil 1 for contraction and release.

[0117] The resonant circuit SKS is controlled or regulated by the control electronics SEK, which are supplied with a direct current from the rectifier G.

[0118] The power semiconductor component 10 is preferably implemented by an insulated gate bipolar transistor (IGBT for short).

[0119] The control electronics SEK switches the power semiconductor components 10 / IGBTs at a frequency which specifies the operating frequency set at the resonance circuit SKS.

[0120] It is important that the resonant circuit SKS never operates completely resonantly.

[0121] This would lead here to rapid destruction of the power semiconductor components 10 due to voltage peaks. In contrast, the control electronics SEK are designed such that they operate the power electronics or their resonant circuits SKS within a predefinable operating range which only approaches the resonant frequency or natural frequency of the system.

[0122] Preferably, the resonant circuit is controlled or adjusted (by the controller 20) such that exist Values ​​in the range φ 0.1 to φ 1 are particularly advantageous. This again results in avoiding voltage peaks and thus provides further support for miniaturization.

[0123] In order to operate the shrinking device 1 with a certain degree of operational safety (in a manner that is as automated as possible), the shrinking device is equipped with an automatic heating controller / regulator that enables automated shrinking operation.

[0124] The heating controller / regulator is implemented by a corresponding controller or regulator 20 in the retraction device, which is essentially based on an analysis of the (measured) coil current M-SpA, coil voltage M-SpV and / or input current M-EA and / or input voltage M-EV or their time curves.

[0125] To measure the coil current (M-SpA), coil voltage (M-SpV), input current (M-EA) and input voltage (M-EV), as Figure 2 It is also shown that the circuit accordingly provides current / voltage measuring devices M-SpA (coil current), M-SpV (coil voltage) or M-EA (input current) or M-EV (input voltage), which are accordingly installed at the correspondingly shown positions in the circuit.

[0126] If in this case, in the case of an induction coil for retraction, the measured variables or their curves also depend on the temperature of the inserted sleeve part of the tool holder, then this can advantageously be used for the (automated) heating control in order to thus increase the safety of the retraction device while avoiding "manual" error sources (because it is automated).

[0127] (A) (Automatic) identification of the tool holder / sleeve part currently inserted into the retraction device or its induction coil

[0128] At the beginning of the heating, insert the induction coil (1, see Figure 1 and Figure 2 ) in the sleeve part (HP, see Figure 1), firstly the geometry or the outer diameter of the sleeve part inserted into the induction coil is determined (in an automated manner) and the inserted sleeve part is thus "identified".

[0129] This is described, for example, in German patent applications 10 2015 016 831.2 and 10 2019 112 521.9 and in European patent application 19 17 6562.7. The contents of these documents are hereby incorporated into the subject matter of the present application.

[0130] If the inserted sleeve part is then identified, (previously) defined heating parameters such as, in particular, the (individual) shrinking / heating frequency can be defined for the inserted sleeve part or its heating process.

[0131] The heating process of the inserted sleeve part is then started with its individual shrinking / heating frequency, wherein, while starting to supply power to the induction coil, the outputs of coil current, coil voltage, input current and input voltage are also measured (in this respect, reference is made to the method according to Figure 2 circuit).

[0132] (B) (Automated / Automatically controlled) shrinkage process Figure 3 and Figure 4 )

[0133] Figure 3 (and idealized forms Figure 4 ) shows how the heating process of the inserted sleeve part can be controlled (20) based on the time curve 22 of the coil current M-SpA. Figure 4 Corresponds to Figure 3 , where an idealized representation of the coil current M-SpA (RMS amperes, filtered and smoothed) is shown.

[0134] The control (20) presented here based on the coil current curve 22 can also be carried out accordingly using the coil voltage M-SpV and / or the input current M-EA and / or the input voltage M-EV or variables derived therefrom (such as phase and phase shift) (because their curves correspond qualitatively to the curve of the coil current).

[0135] like Figure 3 and Figure 4 It is shown that during the heating process the coil current M-SpA is measured continuously over a time curve (T (time)) using the current measuring device M-SpA (coil current) mentioned.

[0136] Figure 3 and Figure 4A typical (curve) curve 22 of the (measured) coil current M-SpA during heating of an inserted sleeve part is shown in each case (starting from a cold sleeve part until it is annealed, phases 1 to 4).

[0137] If it is relevant to the control, the following can be inferred from the coil current curve 22 .

[0138] like Figure 3 and Figure 4 As shown, the coil current M-SpA first decreases at the beginning (and in this case a cold sleeve portion), and then decreases over time and during the initial heating of the sleeve portion (phase 1). In other words, the slope of the coil current curve is negative, or the tangent applied to the coil current curve has a falling curve.

[0139] After the initial reduction, the coil current M-SpA then remains approximately constant in a further time / heating curve (that is, the slope of the coil current curve is zero or the tangent applied to the coil current curve has a horizontal curve) (phase 2), wherein the coil current M-SpA then increases or rises again in this further time curve and during further heating (phase 3) (until the sleeve part is annealed, phase 4) (that is, the slope of the coil current curve is positive or the tangent applied to the coil current curve has a rising curve). This rise occurs here with an increasing slope / gradient (phases 3 and 4).

[0140] The curvature behavior of the coil current curve 22 is also obtained from the descending curve, the ascending curve and the horizontal curve of the slope or tangent.

[0141] The coil controller 20 exploits this expected coil current curve 22 by configuring its control based on this curvature behavior.

[0142] In this case, if the measured coil current M-SpA is continuously transmitted to the controller 20 , the controller 20 continuously determines the slope of the coil current curve 22 or the tangent of the coil current curve 22 , as well as the curvature behavior thereof.

[0143] If the coil current curve M-SpA then changes from its horizontal constant phase to a rising curve (phase 2 to phase 3), that is, the tangent starts to rise again (from the horizontal direction) or the slope (and curvature) of the coil current curve 22 becomes positive ("termination criterion" 23), the controller 20 (automatically) switches off the heating process; the heating state of the inserted sleeve part has here reached a critical phase / temperature.

[0144] As an alternative, if it is desired to allow higher heating temperatures, a slope limit value can also be predefined as a "stop criterion" (slope / tangent in phase 4) (alternative stop / alternative stop criterion 24). If the coil current curve then reaches this predefined limit slope, the controller 20 will (automatically) shut down the heating process.

[0145] The controller can thus be retracted automatically or automatically to a large extent. In this case, manual intervention for the purpose of setting the operating parameters is superfluous, which means on the one hand that the time previously required for this is saved, and on the other hand, the automatic / automatic operation also makes it possible to comply with high standards in terms of operating safety and tolerances, so as to be able to ensure that the unit is operated in accordance with regulations. An efficient protection against overheating of the sleeve parts is also achieved.

[0146] Although the present invention has been shown and described in detail by means of preferred exemplary embodiments, the present invention is not limited to the disclosed examples and other variations may be derived from these examples without departing from the scope of protection of the present invention.

Claims

1. A method for controlling an induction heating process of an induction coil unit, wherein: The sleeve portion of the tool holder is inserted into the induction coil of the induction coil unit, in, - determining at least one time curve or frequency curve of a coil current and / or a coil voltage and / or an input current and / or an input voltage for the sleeve part inserted into the induction coil during an in particular uninterrupted induction heating process in the sleeve part inserted into the induction coil, - Analyze the (coil current) curve and / or the (coil voltage) curve and / or the (input current) curve and / or the (input voltage) curve, possible variables derived therefrom, and based on the analyzed curve or the evaluated curve, in particular based on the curve behavior and / or the curve change and / or the curve change behavior, decide whether the heating process, in particular uninterrupted, is to continue or to end.

2. A method for controlling an induction heating process according to the preceding claim, in, The time curve of the coil current, the time curve of the coil voltage, the time curve of the input current and the time curve of the input voltage are determined, the curves of all determined time curves are analyzed, and based on all analyzed curves it is decided whether the heating process is to be continued or ended, and / or wherein the variable obtained is a phase or a phase shift.

3. A method for controlling an induction heating process as claimed in any one of the preceding claims, in, The time curve or the frequency curve is mapped using the RMS current value or the voltage value.

4. The method for controlling an induction heating process according to claim 1, wherein: When analyzing the time curve, the curve behavior and / or the curve change and / or the curve change behavior is determined, and / or when analyzing the frequency curve, extreme values, in particular resonance frequencies, and / or (bandwidth) widths or variances are determined.

5. Method for controlling an induction heating process according to one of the preceding claims, in, When analyzing the time curve, in particular the current values ​​or voltage values, in particular RMS, at different times of the induction heating process are analyzed, in particular compared, using a tangent line or a slope line of the time curve, and / or wherein: When analyzing the frequency curve, the frequency curve to be analyzed is compared with a reference curve, in particular using the extreme values ​​and / or the (bandwidth) width or the variance.

6. Method for controlling an induction heating process according to one of the preceding claims, in, When analyzing the time curve, a plurality of tangent lines are applied to the time curve, and determination is made in consideration of changes in the slopes of the tangent lines.

7. Method for controlling an induction heating process according to one of the preceding claims, in, When making the decision, the geometric shape and / or other physical characteristics of the sleeve portion inserted into the induction coil of the induction coil unit are also taken into account.

8. Method for controlling an induction heating process according to one of the preceding claims, in, Before and / or during the analysis, the time curve or the frequency curve to be analyzed is smoothed, averaged, filtered and / or, in particular, normalized to a reference mains voltage, in particular a German or European reference mains voltage.

9. Method for controlling an induction heating process according to one of the preceding claims, in, The time curve or the frequency curve is determined using a measurement result of the current or voltage, in particular a measurement result of the measured RMS current or RMS voltage.

10. Method for controlling an induction heating process according to one of the preceding claims, in, The input current and / or the input voltage is measured in the intermediate circuit, in particular downstream of the rectifier, or in the input circuit, in particular upstream of the rectifier and / or at the connection section.

11. Method for controlling an induction heating process according to one of the preceding claims, For identifying an already warmed sleeve portion of a tool holder inserted into the induction coil of the induction coil unit, the preheating state of the sleeve portion is identified based on an analyzed time curve or an evaluated time curve or an analyzed frequency curve or an evaluated frequency curve, in particular based on the curve behavior and / or curve change and / or curve change behavior of the time curve or the extreme values ​​and / or (bandwidth) width or variance of the frequency curve.

12. An induction coil unit for carrying out the method according to at least one of the preceding method claims, the induction coil unit having an induction coil into which a sleeve part of a tool holder can be inserted, It is characterized in that - an electric circuit by means of which the induction coil can be supplied with power, and - a control unit, by means of which the induction coil and the electrical circuit can be controlled and which is configured such that the method according to at least one of the preceding method claims can be carried out.

13. An induction coil unit as claimed in at least the preceding claim, It is characterized in that One or more measuring devices, by means of which the one or more time curves or the one or more frequency curves of the coil current and / or of the coil voltage and / or of the input current and / or of the input voltage can be measured.

14. An induction coil unit as claimed in at least the preceding claim, in, The measuring device is a current measuring device or a voltage measuring device and / or wherein the measuring device is installed in an input circuit and / or in an intermediate circuit and / or in a coil circuit of the electrical circuit.

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