Device and method for magnetizing a tool holder of an electric hand-held power tool, electric hand-held power tool and tool holder

Abstract

A device (1) for magnetizing a tool holder (2) of an electric hand-held power tool (28), in particular a rotary impact wrench (28), has a rotary motor (3), a translational motor (6), and an electromagnet (10). The rotary motor (3) is designed to be connected to the tool holder (2). The tool holder (2) can be rotated about a longitudinal axis (4) of the tool holder (2) by means of the rotary motor (3). The translational motor (6) is designed to move the rotary motor (3) along a lateral direction (7) running perpendicular to the longitudinal axis (4). As a result, the tool holder (2) can be moved linearly towards or away from poles (11) of the electromagnet (10). The electromagnet (10) is arranged such that the poles (11) are arranged one above the other with respect to a vertical direction (13) running perpendicular to the longitudinal axis (4) and the lateral direction (7).As a result, the tool holder (2) can be arranged in a magnetic field of the electromagnet (10) in such a way that the longitudinal axis (4) is arranged perpendicular to magnetic field lines of the magnetic field.

Description

The present invention relates to a device and a method for magnetizing a tool holder of an electric hand-held power tool and an electric hand-held power tool, in particular a rotary impact wrench, and a tool holder.Rotary impact screwdrivers are based on the principle that when a bolt or a screw is tightened or loosened, a torque is built up on a wrench on an impact-by-impact basis, as when a bolt or a screw is tightened or loosened with hammer impacts. In rotary impact screwdrivers, the impacts or the impact operation are provided by a rotary impact mechanism. The rotary percussion mechanism has a rotary percussion hammer which is connected to a motor via shaft and gear elements and is designed to transmit kinetic energy to an anvil of a tool holder. Since the reaction torque is not larger than that required for accelerating the hammer, the reaction force transmitted back to an operator is very small. Furthermore, impact screwdrivers are of compact design and have a low mass. As a result, they are particularly flexible and easy to operate.An object of the present invention is to provide a device for magnetizing a tool holder of an electric hand-held power tool, to specify a method for magnetizing a tool holder of an electric hand-held power tool and to provide an improved tool holder and electric hand-held power tool. These objects are achieved by a device and a method for magnetizing a tool holder of an electric hand-held power tool, and by an electric hand-held power tool and a tool holder having the features of the respectively independent claims. Advantageous further developments are specified in dependent claims.A device for magnetizing a tool holder of an electric hand-held power tool, in particular a rotary impact wrench, has a rotation motor, a translation motor and an electromagnet. The rotation motor is designed for connection to the tool holder. The tool holder is rotatable about a longitudinal axis of the tool holder by means of the rotation motor. The translation motor is designed to move the rotation motor along a lateral direction running perpendicular to the longitudinal axis of the tool holder in the connected state of the tool holder with the rotation motor. As a result, the tool holder is designed to be movable linearly toward poles of the electromagnet or away from the poles of the electromagnet. The electromagnet is arranged in such a way that the poles of the electromagnet are arranged one above the other with respect to a vertical direction running perpendicular to the longitudinal axis of the tool holder and perpendicular to the lateral direction in the connected state of the tool holder to the rotary motor. As a result, the tool holder can be arranged in a magnetic field of the electromagnet in such a way that the longitudinal axis of the tool holder is arranged perpendicular to magnetic field lines of the magnetic field of the electromagnet.The electric hand-held power tool, which can be designed in particular as a rotary impact wrench, has a drive motor, a drive shaft connected to the drive motor, a transmission connected to the drive shaft, an intermediate shaft connected to the transmission, and the tool holder connected to the intermediate shaft. The tool holder has a cylindrically shaped section which can be fully cylindrical or hollow cylindrical. The tool holder also includes a receiving member for receiving a tool and an anvil disposed on opposite sides of the cylindrical portion extending along the longitudinal axis of the tool holder. The receiving element, the cylindrical section and the anvil are firmly connected to one another and can be formed monolithically, for example. In the installed state, the anvil of the tool holder protrudes into a housing of the electric hand-held power tool and is coupled to a rotary impact hammer mechanism arranged around the intermediate shaft. The receiving element of the tool holder protrudes from the housing. The tool holder is rotatably mounted about its longitudinal axis. However, the anvil and the rotary impact hammer mechanism can be omitted if the electric hand-held power tool is not designed as a rotary impact wrench or if the electric hand-held power tool generally does not have a rotary impact hammer mechanism for generating rotary impacts acting on the tool holder.The device for magnetizing the tool holder of the electric hand-held power tool is based on the idea of magnetizing at least a part of the tool holder, whereby the tool holder can be used for measuring a torque applied to the tool holder. For this purpose, a part of the cylindrical section must be magnetized. The tool holder must therefore be ferromagnetic at least in the part of the cylindrical section to be magnetized.The device advantageously makes it possible to provide a magnetized tool holder which makes it possible to measure torque on the basis of the inverse magnetostrictive effect, which is also known as the Villiari effect. The Villiari effect is a magnetoelastic effect which describes a change in a magnetic susceptibility of a material as a result of deformation or as a result of mechanical stresses and stress. In other words, magnetization of a material changes when it is subjected to mechanical stress and deformation. This change in magnetization can be measured by means of a magnetic field sensor.A further advantage of the device is that a tool holder can be provided which has sections which are annularly magnetized about the longitudinal axis. This is made possible in that the tool holder can be rotated in the magnetic field of the electromagnet about its longitudinal axis, while the tool holder is arranged in such a way that its longitudinal axis is arranged perpendicular to the magnetic field lines of the magnetic field of the electromagnet.For example, it is possible to magnetize a tool holder in such a way that its cylindrical section has two sections which are magnetized annularly about the longitudinal axis and are polarized in opposite directions. A total magnetization in this case can be formed by a difference in the magnetizations of the annularly magnetized sections. The magnetizations of the annularly magnetized sections are each formed by a sum of a change in magnetization as a result of an acting torque and a contribution from stray fields or external magnetic fields. The contributions of the stray fields or external magnetic fields compensate each other in the total magnetization. The contributions of the actual measurement signals, on the other hand, add up since the change in the magnetization in oppositely magnetized sections have different signs. In this way, the change in the magnetization as a result of the applied torque can be measured particularly accurately. In addition, this reduces the computational effort required to compensate for the influence of external magnetic fields on measured values.A torque sensor of an electric hand-held power tool with a tool holder magnetized in this way can advantageously be used to provide torque predictions in real time and to implement a tool control with a closed loop. Feature extraction and predictions based on features extracted from torque data can be carried out by an internal tool electronics.Typically, the torque exerted is measured with a manual wrench with a torque indicator or a transducer on a power wrench. However, this is impractical when using large torque wrench sensors for common applications and in inaccessible locations. The device for magnetizing a tool holder makes it possible to provide a compact electric hand-held power tool with a torque sensor which displays immediate feedback to the user about a work progress.Advantageously, the device enables a series of parameters to be controlled within the framework of the magnetization of the tool holder in order to achieve a desired, uniform and stable magnetization of sections of the tool holder to be magnetized. This will be explained below in connection with a method for magnetizing a tool holder of an electric hand-held power tool.Within the scope of the method for magnetizing a tool holder of an electric hand-held power tool, in particular a rotary impact wrench, the tool holder is first connected to the rotation motor and positioned with respect to poles of the electromagnet. In this case, the tool holder is arranged in such a way that its longitudinal axis is arranged perpendicular to the lateral direction, the tool holder has a predeterminable first distance from the poles of the electromagnet in the lateral direction, and the tool holder is arranged in the region of the poles of the electromagnet in the vertical direction. In this case, a section of the tool holder to be magnetized is arranged opposite the poles of the electromagnet in the lateral direction. By applying a predeterminable direct current to the electromagnet, a magnetic field is generated. The tool holder is moved toward the poles of the electromagnet, wherein the tool holder is moved along the lateral direction at a predefinable first speed until the tool holder has a predefinable second distance from the poles of the electromagnet. The tool holder is rotated in the magnetic field of the electromagnet, wherein a predeterminable first number of revolutions of the tool holder about the longitudinal axis takes place at a predeterminable first rotational speed. The tool holder is moved away from the poles of the electromagnet, wherein the tool holder is moved along the lateral direction at a predefinable second speed until the tool holder has a predefinable third distance from the poles of the electromagnet.For moving the tool holder along the lateral direction, the device has, for example, a linear guide. The rotation motor to which the tool holder is connected can be arranged, for example, on a platform, wherein the translation motor is designed to move the platform with rotation motor and tool holder by means of the linear guide in the lateral direction, i.e. in the connected state of the tool holder to the rotation motor perpendicular to the longitudinal axis of the tool holder. The electromagnet or the poles of the electromagnet are arranged at one end of the linear guide. As a result, the tool holder can be moved away towards the poles of the electromagnet and away from the poles of the electromagnet. A precise linear guidance of the tool holder is important in order to achieve a uniform and stable magnetization of the tool holder, since the tool holder is moved along the lateral direction in the magnetic field of the electromagnet.Advantageously, the device makes it possible that various parameters can be controlled precisely during the method for magnetizing a tool holder. For example, different distances of the tool holder to the poles of the electromagnet can be selected precisely with respect to the lateral direction. In addition to the initial first distance and the final third distance, which may be identical to the first distance, the second distance of the tool holder to the poles of the electromagnet, which distance represents a minimum distance of the tool holder to the poles of the electromagnet, may also be controlled with a high accuracy.If the tool holder reaches this minimum second distance within the scope of the method, the tool holder is located in the range of maximum field strengths of the magnetic field of the electromagnet. In this region, the tool holder is rotated in order to achieve an annular magnetization of the tool holder about its longitudinal axis. In this case, the longitudinal axis of the tool holder is arranged perpendicular to the magnetic field lines of the magnetic field of the electromagnet. The degree of magnetization can be controlled by specifying the first number of revolutions and the first rotational speed of the tool holder. The second distance of the tool holder from the poles of the electromagnet can be, for example, 0.2 mm and should be consistent, i.e. as equal as possible, for both poles of the electromagnet. A distance between the poles of the electromagnet, which also influences the result of the magnetization, may be, for example, 5 mm. By polarity reversal of the magnetic field or of the direct current applied to the electromagnet, the direction of magnetization of the tool holder can be changed. In this way, oppositely magnetized sections of the tool holder can be produced. In addition, the first and the second speed of the tool holder can also influence the result of the magnetization when the tool holder is moved along the lateral direction.In one embodiment, the tool holder is rotated at a predefinable second rotational speed and / or third rotational speed when moving in the direction of the electromagnet and / or away from the electromagnet. Advantageously, a particularly uniform magnetization of the tool holder can be achieved if the tool holder is rotated not only in the region of the electromagnet, i.e. if it has the minimum, second distance from the poles of the electromagnet, but also if a rotation of the tool holder takes place when the tool holder is moved toward the electromagnet and / or away from the electromagnet. A number of revolutions when moving the tool holder toward the electromagnet is given by a distance between the first distance and the second distance and the second rotational speed. A number of revolutions in moving the tool holder away from the electromagnet is given by a distance between the second distance and the third distance and the third rotational speed. In order to achieve a particularly uniform and stable magnetization, it may be expedient that a direction of rotation of the tool holder is not changed within the scope of the method.In one embodiment, the direct current is increased and / or reduced when the tool holder is moved in the direction of the electromagnet and / or away from the electromagnet. Alternatively, instead of varying the speeds of the tool holder as it moves toward or away from the electromagnet, the direct current applied to the electromagnet to generate the magnetic field may be varied. For example, it is possible to increase the direct current when moving the tool holder toward the electromagnet according to a ramp instead of increasing the first speed. It is also possible, for example, to reduce the direct current when moving the tool holder away from the electromagnet according to a ramp, instead of reducing the second speed.In one embodiment, after the tool holder is moved away from the electromagnet and is at the third distance from the poles of the electromagnet, the direct current is reduced and the tool holder is rotated at a fourth rotational speed. In this case, a predeterminable second number of revolutions of the tool holder about the longitudinal axis takes place at a predeterminable fourth rotational speed. Advantageously, a particularly uniform and stable magnetization of the tool holder can be achieved. A rate of reduction of the direct current can be given, for example, by a quotient of a maximum direct current and the second number of revolutions in order to uniformly reduce the current intensity while the tool holder is still rotating.In one embodiment, the device has a displacement device for displacing the rotary motor along a direction which, in the connected state of the tool holder to the rotary motor, runs parallel to the longitudinal axis of the tool holder. Advantageously, the tool holder can be positioned in such a way that a further section of the tool holder can be magnetized. However, the apparatus does not necessarily have to have the displacement device. Alternatively, the rotation motor can be repositioned and mounted on the platform parallel to the longitudinal axis of the tool holder, for example, in order to magnetize a further section of the tool holder.In one embodiment, the method has the following additional method steps. The tool holder is displaced along the longitudinal axis, wherein a further section of the tool holder to be magnetized is arranged opposite the poles of the electromagnet in the lateral direction. A further magnetic field is generated by applying a predeterminable further direct current to the electromagnet, wherein the magnetic field and the further magnetic field are oppositely poled. The tool holder is moved toward the electromagnet at a predefinable further first speed until the tool holder has a predefinable further second distance from the poles of the electromagnet. The tool holder is rotated in the further magnetic field of the electromagnet, wherein a predeterminable further number of revolutions of the tool holder about the longitudinal axis takes place at a predeterminable further first rotational speed. The tool holder is moved away from the electromagnet at a predefinable further second speed until the tool holder has a predefinable further third distance from the poles of the electromagnet. Advantageously, the magnetized sections of the tool holder are magnetized annularly in opposite directions around the longitudinal axis, whereby a particularly efficient torque sensor or an electric hand-held power tool with an efficient torque sensor can be provided. The further distances, the further speeds, the further first rotational speed, the further first number of revolutions and the further direct current can be identical to the distances, speeds, the first rotational speed, the first number of revolutions and the direct current, which is not absolutely necessary, however.When magnetizing the further section of the tool holder, the tool holder can also be rotated at a predefinable rotational speed during movement in the direction of the electromagnet and / or away from the electromagnet. Likewise, the further direct current can be increased and / or reduced when the tool holder is moved in the direction of the electromagnet and / or away from the electromagnet.An electric hand-held power tool, in particular a rotary impact wrench, has a tool holder with at least one annularly magnetized section encircling a longitudinal axis of the tool holder and a magnetic field sensor arranged in the region of the annularly magnetized section. The tool holder is rotatable about its longitudinal axis. The annularly magnetized section and the magnetic field sensor arranged on the tool holder in the region of the annularly magnetized section advantageously form a magnetic field sensor which is based on the Villiari effect.In one embodiment, the portion which is magnetized annularly circumferentially about the longitudinal axis comprises a ferromagnetic, nanocrystalline, metallic glass. The metallic glass can be glued, for example, to the tool holder or its cylindrical section. Cyanoacrylate or an epoxy can be used as the adhesive, for example. The metallic glass can comprise, for example, Fe 78 B 13 Si 9 or another metallic glass. The metallic glass has a nanocrystalline structure. A nanocrystalline structure is intended to mean a polycrystalline structure whose average grain size is, for example, in the submicrometer range. The nanocrystallineity can be achieved, for example, by a thermal treatment of an initially amorphous metallic glass. For example, the thermal treatment of the metallic glass can be carried out at a temperature between the Curie temperature and the crystallization temperature of the metallic glass. For Fe 78 B 13 Si 9 the values for the Curie temperature are 410° C. and the crystallization temperature are 535° C. For example, the thermal treatment can be carried out at 525° C. in an inert atmosphere.The nanocrystalline structure induced by the thermal treatment offers the advantage that the metallic glass has a high magnetostrictive coefficient, as a result of which the inverse magnetostriction can be utilized more efficiently. Advantageously, it is also possible to adjust the responsiveness of the torque sensor by varying an amount of the material of the metallic glass. An efficiency of a magnetostrictive effect can be changed by, for example, varying a thickness of the metallic glass. However, the tool holder does not necessarily have to comprise the ferromagnetic, nanocrystalline, metallic glass. Alternatively, the tool holder can have a different ferromagnetic material at least in sections to be magnetized. However, the tool holder can also be designed as such at least in sections ferromagnetic.The magnetic field sensor can be designed, for example, as a fluxgate sensor or as a Hall sensor. The magnetic field sensor may alternatively be based on the anisotropic magneto-resistance, the tunnel resistance or the giant magneto-resistance or on another effect. The magnetic field sensor is not in contact with the tool holder, as a result of which the torque sensor of the electric hand-held power tool is embodied non-invasively or contactless. The magnetic field sensor can be arranged, for example, on a printed circuit board which is arranged in the region of the tool holder.In one embodiment, the tool holder has at least two portions arranged one behind the other along the longitudinal axis and magnetized annularly circumferentially about the longitudinal axis. Immediately adjacent magnetized portions are magnetized in opposite directions. A magnetic field sensor is arranged in each case in the region of a ring-shaped magnetized section. Advantageously, contributions of external magnetic fields and stray fields can be compensated for in the measurement of a torque applied to the tool holder.A tool holder for an electric hand-held power tool, in particular for a rotary impact wrench, has at least one portion which is magnetized annularly in a circumferential manner about a longitudinal axis of the tool holder.The device and the method for magnetizing a tool holder of an electric hand-held power tool, in particular of a rotary impact wrench, are explained in more detail in the following description in conjunction with schematic drawings. The following are shown: FIG. 1 : shows a device for magnetizing a tool holder of an electric hand-held power tool; FIG. 2 : a method for magnetizing a tool holder of an electric hand-held power tool; FIG. 3 : a rotary impact wrench with a torque sensor with a magnetized tool holder; and FIG. 4 : shows a magnetized tool holder with example measurements with a torque sensor.FIG. 1 schematically shows a device 1 for magnetizing a tool holder 2 of an electric hand-held power tool, which are designed, for example, as a rotary impact wrench. However, the electric hand-held power tool can also be designed as another electric device which has at least one tool holder 2 designed for rotation.The device 1 has a rotation motor 3. The rotation motor 3 is designed for connection to the tool holder 2. The tool holder 2 is rotatable about a longitudinal axis 4 of the tool holder 2 by means of the rotation motor 3. The rotary motor 3 can be arranged, for example, on a platform not shown in FIG. 1. For driving the rotary motor 3, the device 1 has a first motor driver 5, which is connected to the rotary motor 3.In addition to the rotation motor 3, the device 1 has a translation motor 6. The translation motor 6 is designed to move the rotation motor 3 along a lateral direction 7 which runs perpendicular to the longitudinal axis 4 of the tool holder 2 in the connected state of the tool holder 2 with the rotation motor 3. In order to enable a linear movement of the tool holder 2, the device 1 has a linear guide 8. The translation motor 6 is designed to move the rotation motor 3 with the tool holder 2 along the linear guide 8. For driving the translation motor 6, the device 1 has a second motor driver 9, which is connected to the translation motor 6.The device 1 further comprises an electromagnet 10. The electromagnet 10 has two magnetic poles 11 and is connected by means of a supply source 12 which is provided to apply a direct voltage or a direct current to the electromagnet 10, whereby a magnetic field can be generated between the poles 11 of the electromagnet 10. The electromagnet 10 is arranged in such a way that its poles 11 are arranged at one end of the linear guide 8 and opposite the translation motor 6. As a result, the tool holder 2 is designed to be movable linearly toward the poles 11 of the electromagnet 10 or away from the poles 11 of the electromagnet 10.The electromagnet 10 is also arranged in such a way that the poles 11 of the electromagnet 10 are arranged one above the other with respect to a vertical direction 13 which runs perpendicular to the longitudinal axis 4 of the tool holder 2 and perpendicular to the lateral direction 8 in the connected state of the tool holder 2 with the rotary motor 3, whereby the tool holder 2 can be arranged in the magnetic field of the electromagnet 10 in such a way that the longitudinal axis 4 of the tool holder 2 is arranged perpendicular to magnetic field lines of the magnetic field of the electromagnet 10. As a result, the tool holder 2 can be magnetized in such a way that it has a section which is magnetized annularly in a circumferential manner about the longitudinal axis 4. In order to be able to magnetize a plurality of sections of the tool holder 2, the device 1 can have, for example, a displacement device for displacing the rotation motor 3 along a direction running parallel to the longitudinal axis 4 of the tool holder 2 in the connected state of the tool holder 2 with the rotation motor 3.The motor drivers 5, 9 of the device 1 are connected to a common controller 14. The controller 14 can be designed, for example, as a so-called Arduino platform. An Arduino platform is a platform made of soft and hardware. The hardware has at least one microcontroller and analog and digital inputs and outputs. However, the controller 14 does not necessarily have to be designed as an Arduino platform. In another embodiment, the motor drivers 5, 9 can also be formed as a component of the controller 14. In this case, the controller 14 is directly connected to the rotation motor 3 and the translation motor 6. The controller 14 can be activated and deactivated, for example, using a switch 15 of the device 1. As a result, a method for magnetizing the tool holder 2 can be started or ended.FIG. 2 schematically shows method steps of the method 16 for magnetizing the tool holder 2.In a first method step 17, the tool holder 2 is connected to the rotary motor 3 and positioned or aligned with respect to the poles 11 of the electromagnet 10. Here, the tool holder 2 is arranged in such a way that its longitudinal axis 4 is arranged perpendicular to the lateral direction 7, the tool holder 2 has a predeterminable first distance from the poles 11 of the electromagnet 10 in the lateral direction 7, and the tool holder 2 is arranged in the region of the poles 11 of the electromagnet 10 in the vertical direction 13. A section of the tool holder 2 to be magnetized is arranged opposite the poles 11 of the electromagnet 10 in the lateral direction 7.In a second method step 18, a magnetic field is generated by applying a predefinable direct current to the electromagnet 10. In a third method step 19, the tool holder 2 is moved toward the poles 11 of the electromagnet 10, wherein the tool holder 2 is moved along the lateral direction 7 at a predefinable first speed until the tool holder 2 has a predefinable second distance from the poles 11 of the electromagnet 10.In a fourth method step 20, the tool holder 2 is rotated in the magnetic field of the electromagnet 10, wherein a predefinable first number of revolutions of the tool holder 2 about the longitudinal axis 4 takes place at a predefinable first rotational speed. In a fifth method step 21, the tool holder 2 is moved away from the poles 11 of the electromagnet 10, wherein the tool holder 2 is moved along the lateral direction 7 at a predefinable second speed until the tool holder 2 has a predefinable third distance from the poles 11 of the electromagnet 10. The tool holder 2 can additionally be rotated at a predefinable second rotational speed and / or third rotational speed when moving in the direction of the electromagnet 10 and / or away from the electromagnet 10, i.e. within the scope of the third and fifth method steps 19, 21. After the tool holder 2 has been moved away from the electromagnet 10 and has the third distance from the poles 11 of the electromagnet 10, the direct current can be reduced in an optional sixth method step 22 and the tool holder 2 can be rotated at a fourth rotational speed, wherein a predeterminable second number of revolutions of the tool holder 2 about the longitudinal axis 4 takes place at a predeterminable fourth rotational speed.The first, second and third distances are set and set prior to performing the method. The first speed, the second speed, the first rotational speed, the first number of revolutions and optionally the second, third and fourth rotational speeds and the second number of revolutions must be provided to the controller 14 in order to actuate the rotational motor 3 and the translation motor 6 in accordance with the provided parameters. All parameters can be predefined on the basis of measurements of a magnetic field strength of the magnetic field of the electromagnet 10. For example, the mentioned distances of the tool holder 2 to the poles 11 of the electromagnet 10 and the mentioned speeds and rotational speeds of the tool holder 2 can be expediently selected on the basis of the measured magnetic field strength in order to achieve a uniform and stable magnetization of the tool holder 2. Instead of the speeds being adjusted, the direct current can alternatively be increased and / or reduced when the tool holder 2 is moved in the direction of the electromagnet 10 and / or away from the electromagnet 10.In an optional seventh method step 23, the tool holder 2 is displaced along the longitudinal axis 4, wherein a further section of the tool holder 2 to be magnetized is arranged opposite the poles 11 of the electromagnet 10 in the lateral direction 7. In an optional eighth method step 24, a further magnetic field is generated by applying a predeterminable further direct current to the electromagnet 10, wherein the magnetic field and the further magnetic field are oppositely poled. In an optional ninth method step 25, the tool holder 2 is moved again toward the electromagnet 10 at a predefinable further first speed until the tool holder 2 has a predefinable further second distance from the poles 11 of the electromagnet 10. In an optional tenth method step 26, the tool holder 2 is rotated in the further magnetic field of the electromagnet 10, wherein a predeterminable further number of revolutions of the tool holder 2 about the longitudinal axis 4 takes place at a predeterminable further first rotational speed. In an optional eleventh method step 27, the tool holder 2 is moved away from the electromagnet 10 at a predefinable further second speed until the tool holder 2 has a predefinable further third distance from the poles 11 of the electromagnet 10.Because the magnetic field and the further magnetic field are oppositely poled, the section magnetized in the context of the method and the further magnetized section have an opposite magnetization. In another embodiment, however, the magnetic field and the further magnetic field can also be polarized in the same way, as a result of which the magnetized sections can be magnetized in the same direction.FIG. 3 schematically shows a part of a rotary impact wrench 28 in a lateral sectional view.The rotary impact wrench 28 has the magnetized tool holder 2. The tool holder 2 projects into a housing 32 of the rotary impact wrench 28. In addition, the tool holder 2 has a receiving element 34 for receiving a tool which projects out of the housing 32. The anvil 33 and the receiving element 34 are connected to each other by a cylindrical portion 35 of the tool holder 2. In the cylindrical section 35, the tool holder 2 has a magnetized section 31, within which the tool holder 2 is magnetized annularly about the longitudinal axis 4. Merely by way of example, the tool holder 2 of FIG. 3 has only one magnetized section 31. A plurality of magnetized portions 31 may also be provided.The rotary impact wrench 28 also has a magnetic field sensor 29 which is arranged in the region of the magnetized section 31. The magnetized portion 31 of the tool holder 2 and the magnetic field sensor 29 form a torque sensor 30, and the magnetic field sensor 29 is configured to measure a change in a magnetic field of the magnetized portion 31 due to a torque acting on the tool holder 2. The torque sensor 30 is thus based on a magnetostrictive effect, more precisely on the Villi effect.FIG. 4 schematically shows a tool holder 2 in a side view, which has two annularly magnetized sections 31 arranged one behind the other along the longitudinal axis 4. The annularly magnetized sections 31 are magnetized in opposite directions, which is indicated by arrows in the region of the magnetized sections 31. In this case, in the rotary impact screwdriver 28, a magnetic field sensor 29 is arranged in each case in the region of a annularly magnetized section 31.FIG. 4 also shows exemplary magnetic field changes of the magnetic fields of the oppositely magnetized sections 31 of the tool holder 2, wherein a magnetic field strength in mT is plotted against a time duration in each case. It can be seen that the magnetic field changes during a rotation of the tool holder 2 and during the impact operation of the rotary impact wrench 28 have different signs for the sections 31 magnetized in different directions. A positive change in the magnetic field strength of a magnetized section 31 occurs when a direction of rotation of the tool holder 2 during operation of the rotary impact wrench 28 corresponds to the direction of the annular magnetization of the tool holder 2, which is shown in the right-hand diagram in FIG. 4. A negative change in the magnetic field strength occurs when the direction of rotation of the tool holder 2 during operation of the rotary impact wrench 28 does not correspond to the annular magnetization of the tool holder 2 and is opposite, which is shown in the left-hand diagram in FIG. 4. The diagrams of FIG. 4 show maxima of the magnetic field strengths of the magnetized sections 31. These indicate a striking operation of the torque sensor 28.

Claims

Device (1) for magnetizing a tool holder (2) of an electric hand-held power tool (28), in particular a rotary impact wrench (28), having a rotation motor (3), a translation motor (6) and an electromagnet (10), wherein the rotation motor (3) is designed for connection to the tool holder (2) and the tool holder (2) is rotatable by means of the rotation motor (3) about a longitudinal axis (4) of the tool holder (2), wherein the translation motor (6) is designed to move the rotation motor (3) along a lateral direction (7) which runs perpendicular to the longitudinal axis (4) of the tool holder (2) in the connected state of the tool holder (2) with the rotation motor (3), as a result of which the tool holder (7) can be moved linearly toward poles (11) of the electromagnet (10) or away from the poles (11) of the electromagnet (10), wherein the electromagnet (10) is arranged such that the poles (11) of the electromagnet (10) are arranged one above the other with respect to a vertical direction (13), which runs perpendicular to the longitudinal axis (4) of the tool holder (2) and perpendicular to the lateral direction (7) in the connected state of the tool holder (2) to the rotary motor (3), whereby the tool holder (2) can be arranged in a magnetic field of the electromagnet (10) such that the longitudinal axis (4) of the tool holder (2) is arranged perpendicular to magnetic field lines of the magnetic field of the electromagnet (10).Device (1) according to claim 1, comprising a displacement device for displacing the rotation motor (3) along a direction running parallel to the longitudinal axis (4) of the tool holder (2) in the connected state of the tool holder (2) to the rotation motor (3).Method (16) for magnetizing a tool holder (2) of an electric hand-held power tool (28), in particular a rotary impact wrench (28), by means of a device (1) according to one of the preceding claims, having the following method steps (17, 18, 19, 20, 21): - connecting the tool holder (2) to the rotary motor (3) and positioning the tool holder (2) with respect to the poles (11) of the electromagnet (10), wherein the tool holder (2) is arranged in such a way that its longitudinal axis (4) is arranged perpendicular to the lateral direction (7), the tool holder (2) has a predeterminable first distance from the poles (11) of the electromagnet (10) in the lateral direction (7), and the tool holder (2) is arranged in the region of the poles (11) of the electromagnet (10) in the vertical direction (13), wherein a section of the tool holder (2) to be magnetized is arranged opposite the poles (11) of the electromagnet (10) in the lateral direction (7), - generating a magnetic field by applying a predefinable direct current to the electromagnet (10), - moving the tool holder (2) toward the poles (11) of the electromagnet (10), wherein the tool holder (10) is moved along the lateral direction (7) at a predefinable first speed until the tool holder (2) has a predefinable second distance from the poles (11) of the electromagnet (10), - rotating the tool holder (2) in the magnetic field of the electromagnet (10), wherein a predefinable first number of rotations of the tool holder (2) about the longitudinal axis (4) takes place at a predefinable first rotational speed, - moving the tool holder (2) away from the poles (11) of the electromagnet (10), wherein the tool holder (10) is moved along the lateral direction (7) at a predefinable second speed until the tool holder (2) has a predefinable third distance from the poles (11) of the electromagnet (10).Method (16) according to claim 3, wherein the tool holder (2) is rotated at a predeterminable second rotational speed and / or third rotational speed when moving in the direction of the electromagnet (10) and / or away from the electromagnet (10).Method (16) according to claim 4, wherein the direct current is increased and / or reduced when the tool holder (2) is moved in the direction of the electromagnet (10) and / or away from the electromagnet (10).Method (16) according to one of Claims 3 to 5, wherein, after the tool holder (2) has been moved away from the electromagnet (10) and has the third distance from the poles (11) of the electromagnet (10), the direct current is reduced and the tool holder (2) is rotated at a fourth rotational speed, wherein a predeterminable second number of revolutions of the tool holder (2) about the longitudinal axis (4) takes place at a predeterminable fourth rotational speed.Method (16) according to one of Claims 3 to 6, having the following additional method steps: - displacing the tool holder (2) along the longitudinal axis (4), wherein a further section of the tool holder (2) to be magnetized is arranged opposite the poles (11) of the electromagnet (10) in the lateral direction (7), - generating a further magnetic field by applying a predeterminable further direct current to the electromagnet (10), wherein the magnetic field and the further magnetic field are polarized in opposite directions, - moving the tool holder (2) towards the electromagnet (10) at a predeterminable further first speed until the tool holder (2) has a predeterminable further second distance from the poles (11) of the electromagnet (10), - rotating the tool holder (2) in the further magnetic field of the electromagnet (11), wherein a predeterminable further number of revolutions of the tool holder (2) about the longitudinal axis (4) takes place at a predeterminable further first rotational speed, - moving the tool holder (2) away from the electromagnet (10) at a predeterminable further second speed until the tool holder (2) has a predeterminable further third distance from the poles (11) of the electromagnet (10).Electric hand-held power tool (28), in particular a rotary impact wrench (28), having a tool holder (2) having at least one section (31) which is magnetized annularly in a circumferential manner about a longitudinal axis (4) of the tool holder (2), and a magnetic field sensor (29) which is arranged in the region of the annularly magnetized section (31), wherein the tool holder (2) is rotatable about its longitudinal axis (4).Electric hand-held power tool (28) according to Claim 8, wherein the annularly magnetized section (31) comprises a ferromagnetic, nanocrystalline, metallic glass.Electric hand-held power tool (28) according to Claim 8 or 9, wherein the tool holder (2) has at least two magnetized sections (31) which are arranged one behind the other along the longitudinal axis (4) and which run circumferentially in a ring-shaped manner about the longitudinal axis (4), wherein directly adjacent magnetized sections (31) are magnetized in opposite directions, wherein in each case one magnetic field sensor (29) is arranged in the region of a ring-shaped magnetized section (31).Tool holder (2) for an electric hand-held power tool (28), in particular for a rotary impact wrench, having at least one section (31) which is magnetized annularly in a circumferential manner about a longitudinal axis (4) of the tool holder (2).

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