Electric hand tool

Abstract

An electric hand-held power tool (1) has a tool holder (2) and an attachment (11). The tool holder (2) has a longitudinal axis (6) and is rotatable about the longitudinal axis (6). Either the attachment (11) is plugged onto the tool holder (2) and fastened to a housing (7) of the electric hand-held power tool (1), and the tool holder (2) has at least one section (10) magnetized in a ring shape around its longitudinal axis (6), or a socket adapter (20) is plugged onto the tool holder (2) and fastened to the housing (7), wherein a socket adapter (21) is arranged on the socket adapter (20) and connected to the tool holder (2) and has at least one further section (22) magnetized in a ring shape around the longitudinal axis (6), and the attachment (11) is plugged onto the socket adapter (21) and fastened to the socket adapter (20).The attachment (11) has at least one magnetic field sensor (12) which is arranged in the region of the magnetized section (10) or in the region of the further magnetized section (22).

Description

The present invention relates to an electric hand-held power tool, in particular a rotary impact wrench.It is known from the prior art to determine an applied torque when tightening or loosening screws and nuts with a manual wrench with a torque indicator or with a converter on a power wrench. Time, labor and cost for setting up external torque sensors is very high for measurement of torque in common or repetitive tasks as well as in industrial-level production. Moreover, carrying out a working step with large torque keys is made difficult for daily use in locations that are difficult to access.It is an object of the present invention to provide an improved electric hand-held power tool, in particular an improved rotary impact wrench. This object is achieved by an electric hand-held power tool having the features of the independent claim. Advantageous further developments are specified in dependent claims.An electric hand-held power tool has a tool holder and a fixture. The tool holder has a longitudinal axis and is rotatable about the longitudinal axis. Either the attachment is plugged onto the tool receptacle and fastened to a housing of the electric hand-held power tool and the tool receptacle has at least one portion which is magnetized annularly around its longitudinal axis, or a socket wrench adapter is plugged onto the tool receptacle and fastened to the housing, wherein a socket wrench attachment is arranged on the socket wrench adapter and is connected to the tool receptacle and has at least one further portion which is magnetized annularly around the longitudinal axis, and the attachment is plugged onto the socket wrench attachment and fastened to the socket wrench adapter. The attachment has at least one magnetic field sensor. The magnetic field sensor is arranged in the region of the magnetized section of the tool holder or in the region of the further magnetized section of the socket wrench attachment.The electric hand-held power tool can be designed as any desired electric device, the tool holder of which is designed for rotation, for example as a rotary impact wrench. In any case, the electric hand-held power tool has a drive motor which is designed to rotate the tool holder about its longitudinal axis in order to perform a task, for example in order to tighten or loosen a screw or a nut. The drive motor can be connected to the tool holder, for example, via a drive shaft, a transmission connected to the drive shaft and an intermediate shaft connected to the transmission.The tool holder has a receiving element for receiving a tool. For example, the receiving element of the tool holder can be designed to receive a helical bit or a nut. In the case of a rotary impact wrench, the tool holder additionally has an anvil. The receiving element and the anvil are arranged along the longitudinal axis of the tool holder on opposite sides of the tool holder and are connected to one another via a cylindrical section of the tool holder. In the installed state, the tool holder protrudes partially into the housing of the electric hand-held power tool, wherein the receiving element of the tool holder protrudes from the housing. In a rotary impact screwdriver, the anvil is arranged in the housing and connected to a rotary impact hammer mechanism. The rotary percussion hammer mechanism can be arranged, for example, in the region of the intermediate shaft. The rotary impact hammer mechanism is designed to generate rotary impacts acting via the anvil on the tool holder in order to be able to build up a tightening torque in a pulsed and stepwise manner.The socket wrench attachment can also be referred to as a socket. Since the socket is connected to the tool holder, the socket is likewise rotatable about the longitudinal axis of the tool holder or about a further longitudinal axis of the socket. The attachment, on the other hand, is non-rotatable, since it is fastened either to the housing or to the socket key adapter. The fact that the attachment or the socket wrench adapter is plugged onto the tool receptacle therefore does not mean that the attachment or the socket wrench adapter is connected to the tool receptacle. Rather, the tool holder protrudes either from the attachment or from the socket adapter and is spaced apart from the attachment or from the socket adapter so that it can rotate freely. More specifically, the receiving element protrudes either from the attachment or from the socket adapter and can either be connected to a tool or is connected to the socket adapter.In the case of the electric hand-held power tool, either the tool holder has the section which is magnetized annularly around its longitudinal axis, or the socket has the further magnetized section which is likewise magnetized annularly around the longitudinal axis of the tool holder or annularly around the further longitudinal axis of the socket. The magnetized section of the tool holder or the further magnetized section of the socket forms, together with the magnetic field sensor of the attachment, a torque sensor for measuring a torque applied to the tool holder or to the socket during operation of the electric hand-held power tool on the basis of a magnetoelastic effect.The underlying magnetoelastic effect is the inverse magnetostrictive effect, which can also be referred to as the Villi effect. During operation of the electric hand-held power tool, the tool holder rotates and, in the variant with the socket wrench attachment, also the socket wrench attachment. This causes mechanical stresses and deformations in the magnetized section or in the further magnetized section, as a result of which a magnetization of the magnetized section or of the further magnetized section changes. By measuring a change in a magnetic field of the magnetized section or of the further magnetized section as a result of the rotation of the tool holder by means of the magnetic field sensor, it is thus possible to infer the torque which is present at the tool holder or at the socket wrench attachment during operation of the electric hand-held power tool.The electric hand-held power tool is advantageously designed to be particularly compact due to its structure. However, the underlying principle can be scaled, i.e. reduced or enlarged, to different requirements, in order to be able to use different socket sizes for different sized screws, for example. Overall, the integrated torque sensor advantageously allows the electric hand-held power tool to reduce the expenditure of time, labor and costs for carrying out a working step. In addition, the torque can be ascertained very reliably and quickly and can be provided directly to a user, for example, in order to indicate a work progress. In addition, the integrated torque sensor makes it possible to make predictions about the torque or to make statements about a state of a screw connection, for example.In one embodiment, the attachment or the socket wrench adapter is decoupled from the tool holder by a ball bearing. This reduces contact between the rotatable tool holder and the attachment or socket adapter fastened to the housing. Advantageously, this also allows a wobble movement of the tool holder and, if appropriate, of the socket wrench attachment to be reduced during operation of the electric hand-held power tool, as a result of which the tool holder and the socket wrench attachment can rotate in a stable manner.In one embodiment, the magnetic field sensor is arranged on an outer side of the attachment facing away from the tool holder or on an outer side of the attachment facing away from the socket. Advantageously, a torque applied to the tool holder and, if applicable, to the socket wrench attachment can be measured contactless by this construction. The magnetic field sensor does not necessarily have to be arranged on the outer side of the attachment. In any case, however, the magnetic field sensor is arranged at a distance from at least the magnetized section of the tool holder or from the further magnetized section of the socket wrench attachment. The magnetic field sensor can be designed, for example, as a fluxgate or as a Hall sensor. However, the magnetic field sensor can alternatively be designed as another sensor, for example it can be based on an anisotropic magnetic resistance, a magnetic tunnel resistance or on the giant magnetic resistance.In one embodiment, a printed circuit board (PCB) is disposed on the exterior of the attachment, and the magnetic field sensor is disposed on the printed circuit board and electrically connected to the printed circuit board. Advantageously, the electric hand-held power tool thereby has a particularly compact torque sensor, wherein, for example, a control and an evaluation electronics for the magnetic field sensor can be provided on the printed circuit board. The printed circuit board can optionally be flexible. As a result, the printed circuit board can be arranged in a space-saving manner, for example on a mount of hollow cylindrical design, wherein the printed circuit board can be arranged at least in sections annularly circumferentially around the mount. However, the printed circuit board can also be rigid.In one embodiment, the attachment has at least one through opening formed in the region between the magnetized section of the tool holder and the magnetic field sensor or between the further magnetized section of the socket wrench attachment and the magnetic field sensor. In one embodiment, the printed circuit board has a further through opening formed in the region between the magnetized section of the tool holder and the magnetic field sensor or between the further magnetized section of the socket wrench attachment and the magnetic field sensor. At least one through-opening and / or at least one further through-opening can be provided.Advantageously, a magnetic field change of the magnetic field of the magnetized section or of the further magnetized section as a result of a torque applied to the tool holder can thereby be measured without the attachment and optionally the printed circuit board impairing the measurement, since the through-opening is provided in the attachment and optionally the further through-opening is provided in the printed circuit board. However, the through-opening and / or the further through-opening can also be omitted, for example if a cap and a printed circuit board are used, which each have a material, at least in the region between the magnetic field sensor and the magnetized section or the further magnetized section, which does not influence the measurement, or only insignificantly.In one embodiment, the attachment has two segments. The segments are connected to one another along a plane running along the longitudinal axis of the tool holder. In this case, the attachment is fastened to the housing of the electric hand-held power tool in that the attachment has a first projection which extends annularly around the longitudinal axis of the tool holder and radially protrudes with respect to the longitudinal axis, and the housing has a second projection which extends annularly around the longitudinal axis of the tool holder and radially protrudes away from the longitudinal axis. The second protrusion is disposed between the first protrusion and the magnetic field sensor with respect to the longitudinal axis, and the first protrusion abuts the second protrusion along the longitudinal axis. This advantageously prevents the attachment plugged onto the tool holder from being able to become detached from the electric hand-held power tool. Alternatively, the attachment can be fastened to the housing, for example, by means of screws or, for example, by means of a latching mechanism.In one embodiment, the attachment has a spacer arranged either between the magnetized section of the tool holder and the magnetic field sensor or between the further magnetized section of the socket wrench attachment and the magnetic field sensor. Advantageously, this determines a distance between the magnetized section of the tool holder or between the further magnetized section of the socket wrench attachment and the magnetic field sensor, which influences a measurement of the torque.In one embodiment, the tool holder has at least two portions which are arranged one behind the other along the longitudinal axis and are magnetized annularly around the longitudinal axis, or the socket wrench attachment has at least two portions which are arranged one behind the other along the longitudinal axis and are magnetized annularly around the longitudinal axis. Immediately adjacent magnetized portions or immediately adjacent other magnetized portions are magnetized in opposite directions. A magnetic field sensor is arranged in each case in the region of a magnetized section of the tool holder or of a further magnetized section of the socket wrench attachment.In this variant, the electric hand-held power tool has at least two torque sensors which are based on the Villiari effect. The magnetizations of the magnetized sections or of the further 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. A total magnetization is given by a difference of the magnetizations of the at least two magnetized sections, whereby the contributions of the stray fields or external magnetic fields in the total magnetization are compensated. 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 can be measured particularly accurately.In one embodiment, the magnetized portion or the further magnetized portion comprises a ferromagnetic, nanocrystalline, metallic glass. The metallic glass can comprise, for example, Fe 78 B 13 Si 9 or another metallic glass. A nanocrystalline structure is intended to refer to a polycrystalline structure whose average grain size is, for example, less than 1 μm. The nanocrystallineity can be induced, for example, by a thermal treatment of an amorphous metallic glass, it being possible for the glass to be heated, for example, in the range between its Curie temperature and its crystallization temperature, which are 78 B 13 Si 9410 ° C. and 535° C., respectively.Advantageously, the metallic glass has a high magnetostrictive coefficient, whereby the Villiari effect can be utilized efficiently. A sensitivity of the torque sensor can be influenced, for example, by arranging the glass with different thicknesses on the tool holder or on the socket wrench attachment. For example, the glass can be adhesively bonded to the tool holder or the socket, for example by means of cyanoacrylate or an epoxy.In an alternative embodiment, the tool holder or the socket wrench attachment has another ferromagnetic material which is arranged on the tool holder. The ferromagnetic material is arranged in each case on the cylindrical section of the tool holder or on a cylindrical section of the socket wrench attachment. In another embodiment, the tool holder or the socket wrench attachment is ferromagnetic at least in sections. In this case, therefore, no ferromagnetic material needs to be arranged on the tool holder or on the socket wrench attachment. For example, a monolithically formed tool holder or a monolithically formed socket wrench attachment can be formed ferromagnetically. If a plurality of magnetized sections or a plurality of further magnetized sections are provided, the tool holder or the socket can have identical or different ferromagnetic sections or materials.The electric hand-held power tool is explained in more detail in the following description in conjunction with schematic drawings. The following are shown: FIG. 1 : shows an electric hand-held power tool according to a first embodiment in a lateral sectional view; FIG. 2 : shows a top part of the electric hand-held power tool in a perspective view; FIG. 3 : shows an electric hand-held power tool according to a second embodiment in a lateral sectional view; FIG. 4 : method steps for mounting the electric hand-held power tool of FIG. 3 ; FIG. 5 : shows a side sectional view of a hand-held electric machine tool according to a third embodiment; FIG. 6 : shows the electric hand-held power tool of FIG. 5 in an exploded illustration; and FIG. 7 shows a front view and an enlarged view of a part of the attachment of the electric hand-held power tool of FIG. 5.FIG. 1 schematically shows a hand-held electric power tool 1 according to a first embodiment in a lateral sectional view. By way of example, the electric hand-held power tool 1 is designed as a rotary impact wrench 1. For this reason, the electric hand-held power tool 1 is referred to below as a rotary impact wrench 1. However, the electric hand-held power tool 1 can also be configured as another electric device that has a tool holder 2 that is configured to be rotatable in order to carry out a work. The electric hand-held power tool 1 is based on the idea of providing an integrated torque sensor which makes it possible to reliably measure a torque present at the rotating tool holder 2 during operation of the electric hand-held power tool 1 or, for example, to make a prediction with respect to the torque.The tool holder 2 has a receiving element 3, a cylindrical section 4 and an anvil 5. The cylindrical portion 4 of the tool holder 2 connects the receiving member 3 to the anvil 5. A longitudinal axis 6 of the tool holder 2 is defined by a longitudinal axis of the cylindrical section 4 or corresponds to it. The receiving element 3 is designed to receive a tool and protrudes from a housing 7 of the rotary impact wrench 1. the anvil 5 is arranged in the housing 7 and coupled to a drive motor and a rotary impact hammer mechanism 8. The rotary percussion hammer mechanism 8 is arranged in the region of a shaft 9 and is coupled to the shaft 9. The shaft 9 may also be referred to as an intermediate shaft 9. The intermediate shaft 9 is connected to a drive motor via a transmission and a further shaft, which is not explained in more detail in connection with FIG. 1, however. The drive motor is designed to set the tool holder 2 in rotation about its longitudinal axis 6. The anvil 5 of the tool holder 2 is a component of the rotary impact hammer mechanism 8 and is designed to transmit rotary impacts to the tool holder 2 in addition to the rotation of the tool holder 2. The rotary impact hammer mechanism 8 will also not be explained in more detail in connection with FIG. 1, since rotary impact hammer mechanisms 8 are known from the prior art. If the electric hand-held power tool 1 is not designed as a rotary impact screwdriver 1, the anvil 5 and the rotary impact hammer mechanism 8 can also be omitted.The cylindrical section 4 of the tool holder 2 has a section 10 which is magnetized annularly in a circumferential manner about the longitudinal axis 6. An exemplary magnetization direction is indicated in FIG. 1 by means of an arrow. The tool holder 2 can also have a plurality of sections 10 which are annularly magnetized circumferentially about the longitudinal axis 6 and are arranged one behind the other along the longitudinal axis 6. Directly adjacent magnetized sections 10 can have an opposite magnetization. The magnetized portion 10 can be produced, for example, by rotating the tool holder 2 about its longitudinal axis 6 in a magnetic field of an electromagnet. The magnetized section 10 can have, for example, a ferromagnetic, nanocrystalline, metallic glass or another ferromagnetic material which is arranged on the tool holder 2, more precisely on the cylindrical section 4 of the tool holder 2, and is magnetizable. Alternatively, however, the tool holder 2 can also be ferromagnetic. The magnetized portion 10 can thus be produced either by magnetizing a ferromagnetic material arranged on the tool holder 2 or by magnetizing a part of the cylindrical portion 4.The rotary impact wrench 1 also has a top 11. The attachment 11 is plugged onto the tool holder 2 and fastened to the housing 7 of the rotary impact wrench 1. The attachment 11 has a magnetic field sensor 12. The magnetic field sensor 12 is arranged in the region of the magnetized section 10 of the tool holder 2, wherein the magnetic field sensor 12 is arranged on an outer side of the attachment 11 facing away from the tool holder 2 and is spaced apart from the magnetized section 10. The magnetic field sensor 12 is designed to measure a magnetic field change of a magnetic field of the magnetized section 10 during operation of the rotary impact wrench 1. A rotation of the tool holder 2 causes deformations and stresses in the magnetized section 11, which in turn cause a change in the magnetization of the magnetized section 11. As a result, a measurement signal at the magnetic field sensor 12 changes depending on the applied torque, as a result of which a torque applied to the tool holder 2 can be determined. The magnetized portion 10 and the magnetic field sensor 12 thus form a contactless torque sensor 13 of the rotary impact wrench 1, which is based on the inverse magnetostrictive effect.FIG. 2 schematically shows the attachment 11 with the magnetic field sensor 12 in a perspective view. Reference numerals used so far are retained.The attachment 11 has a hollow cylindrical section 14, a holder 15 and a flange 16. The attachment can be plugged onto the tool holder 2 by the hollow cylindrical section 14. The holder 15 is arranged on a casing outer surface of the hollow cylindrical section 14 and is designed to receive a battery for the electrical supply of the rotary impact wrench 1. The holder 15 can also be omitted. The flange 16 is arranged at one end of the hollow cylindrical section 14 and is provided for fastening the attachment 11 to the housing 7. For this purpose, the flange 16 has bores, as a result of which the attachment 11 can be fastened to the housing by means of screws. Flange 16 may also be omitted if other means are provided for securing attachment 11 to housing 11.A printed circuit board 17 is arranged on the outer side of the attachment 11, more precisely on the outer surface of the hollow cylindrical section 14. The magnetic field sensor 12 is disposed on the circuit board 17 and electrically connected to the circuit board 17. The printed circuit board 17 comprises, for example, a control and an evaluation electronics for the rotary impact wrench 1 and in particular for the magnetic field sensor 12. The printed circuit board 17 can be flexible, for example.The attachment 11 has at least one through-opening 18 formed in the region between the magnetized section 10 of the tool holder 2 and the magnetic field sensor 12. In addition, the printed circuit board 17 has at least one further through-opening 19, which is arranged in the region between the through-opening 18 and the magnetic field sensor 12. Merely by way of example, FIG. 1 shows that a total of three through-openings 18 are provided in the attachment 11 and correspondingly three further through-openings 19 are provided in the printed circuit board 17. Another number of through-openings 18 and further through-openings 19 can also be provided. The through-openings 18 and / or the further through-openings 19 can also be omitted entirely, but they offer the advantage that the magnetic field of the magnetized section 10 can be measured undisturbed.FIG. 3 schematically shows a rotary impact wrench 1 according to a second embodiment in a lateral sectional view. The rotary impact wrench 1 according to the second embodiment exhibits similarities with the rotary impact wrench 1 according to the first embodiment. In the following description, the differences of the impact wrench 1 according to the second embodiment from the impact wrench 1 according to the first embodiment will be substantially described. Reference numerals used so far are retained for similar and identical elements.In the rotary impact wrench 1, the attachment 11 is not plugged onto the tool holder 2 and fastened to the housing 7, but a socket adapter 20. The socket wrench attachment 21 is connected to the receiving element 3 of the tool holder 2. As a result, the socket wrench attachment 21 is likewise rotatable about the longitudinal axis 6 of the tool holder 2. A longitudinal axis of the socket wrench attachment 21 and the longitudinal axis 6 of the tool holder 2 lie on a straight line. The socket wrench adapter 20 is designed to be non-rotatable, as is the attachment 11 in the rotary impact wrench 1 according to FIG. 1. The socket wrench adapter 20 can be decoupled from the tool holder 2 by a ball bearing, for example. The ball bearing is not shown in FIG. 3 for simplicity. This makes it possible to prevent a wobbling movement of the tool holder 2 and the socket 21. In the rotary impact wrench 1 according to the first embodiment, a ball bearing can also be provided, which, however, decouples the attachment 11 from the tool holder 2. This can prevent a wobbling movement of the tool holder 2, in particular in the case of long tool holders 2.In the rotary impact wrench 1 according to FIG. 3, the tool holder 2 also does not have a magnetized section 10. Instead, the socket wrench adapter 21 has at least one further section 22 which is magnetized annularly around the longitudinal axis 6 of the tool holder 2. For example, the socket key adapter 21 has only one further magnetized section 22. The further magnetized section 22 of the socket 21 of the rotary impact wrench 1 of FIG. 2 can have a ferromagnetic, nanocrystalline and magnetized glass like the magnetized section 10 of the tool holder 2 according to FIG. 1. Alternatively, the socket key attachment 21 can have a different ferromagnetic material in the further magnetized section 22 or can itself be formed ferromagnetic at least in sections. The socket key attachment 21 can also have a plurality of further magnetized sections 22 arranged one behind the other along the longitudinal axis 6, wherein directly adjacent further magnetized sections 22 can be magnetized in opposite directions, for example.In the rotary impact wrench 1 according to the second embodiment, in contrast to the attachment 11 of the rotary impact wrench 1 according to the first embodiment, the attachment 11 is not plugged onto the tool holder 2, but is arranged so as to lie against the socket adapter 20 along the longitudinal axis 6 and is fastened to it, for example by means of flange structures 16 of the socket adapter 20 and the attachment 11 facing each other, which flange structures are screwed together. As a result, the attachment 11 is in each case mounted non-rotatably in the rotary impact screwdriver 1 according to the first and second embodiments.The magnetic field sensor 12 is arranged in the region of the further magnetized section 22 of the socket 21 and forms a torque sensor 13 with the further magnetized section 22, The magnetic field sensor 12 is arranged at a distance from the further magnetized section 22 by being arranged on an outer side of the socket 11 facing away from the socket 21.On the outside of the socket 21, a printed circuit board 17 can also be arranged, which can be flexible or rigid. The magnetic field sensor 12 is arranged on the printed circuit board 17 and electrically connected thereto. The attachment 11 can also have at least one through-opening 18 in the region between the further magnetized section 22 of the socket 21 and the magnetic field sensor 12. The printed circuit board 17 can have a further through-opening 19 arranged in the region between the through-opening 18 of the attachment 11 and the magnetic field sensor 12. The through-opening 18 and / or the further through-opening 19 can also be omitted. In the variant of the rotary impact wrench 1 according to FIG. 2, the attachment 11 likewise has the holder 15 for receiving a battery or an accumulator, which can, however, also be omitted.FIG. 4 schematically shows steps for assembling the rotary impact wrench 1 of FIG. 3, wherein perspective views are shown in each case.In a first step, the socket wrench adapter 20 is plugged onto the tool holder 2 and fastened to the housing 7. In a second step, the socket 21 is arranged on the socket adapter 20 and connected to the tool holder 2. In a third step, the attachment 11 is plugged onto the socket 21 and fastened to the socket adapter 20, wherein the magnetic field sensor 12 of the attachment 11 is arranged in the region of the further magnetized section 22. In an optional fourth step, a cover 23 is plugged onto the attachment 11, covering and thereby protecting the printed circuit board 17 and the magnetic field sensor 12. The cover 23 can be screwed to the attachment 11 on a front side 24 of the socket 21 facing away from the socket adapter 20 in order to fasten it, as is shown by way of example in FIG. 4. The cover 23 can also be omitted.FIG. 5 schematically shows a rotary impact wrench 1 according to a third embodiment in a lateral sectional view. The rotary impact wrench 1 according to the third embodiment exhibits similarities with the rotary impact wrench 1 according to the first embodiment. In the following description, the differences of the impact wrench 1 according to the third embodiment from the impact wrench 1 according to the first embodiment will be substantially described. Reference numerals used so far are retained for similar and identical elements.The rotary impact wrench 1 according to the third embodiment has an attachment 11 which, as in the rotary impact wrench 1 according to the first embodiment, is plugged onto the tool holder 2 and fastened to the housing 7. A socket adapter 20 and a socket 21 are likewise not provided in the rotary impact wrench 1 according to the third embodiment.In contrast to the rotary impact wrench 1 according to the first embodiment, the rotary impact wrench 1 according to the third embodiment has, for example, two sections 10 which are arranged one behind the other along the longitudinal axis 6 and are magnetized annularly around the longitudinal axis 6 and are magnetized in opposite directions. A magnetic field sensor 12 of the attachment 11 is arranged in the region of a magnetized section 10 of the tool holder 2. As a result, the torque sensor 13 of the rotary impact wrench 1 has two sensor segments, each of which comprises a magnetized section 10 and a magnetic field sensor 12 and contributes to a measurement signal. The rotary impact wrench 1 according to the third embodiment can also have more than two sensor segments, i.e. more than two magnetized sections 10 and more than two magnetic field sensors 12, wherein the magnetized sections 10 are arranged one behind the other along the longitudinal axis 6 and adjacent magnetized sections 10 can be oppositely magnetized. A separate magnetic field sensor 12 can be provided for each magnetized section 10, which is arranged in the region of a magnetized section 10.Due to the different directions of the magnetizations of the magnetized sections 10, a measurement signal corrected by an influence by external magnetic fields and stray fields can be provided in a differential operation of the sensor segments, since undesired contributions compensate each other, while actual magnetoelastic contributions add each other. For example, a rotary impact on the tool holder 2 caused by the rotary impact mechanism 8 generates a magnetization change which has different signs in the magnetized sections 10. Since a total signal in differential operation is given by a difference of the measured changes in the magnetizations, their amounts are added. The rotary impact screwdrivers 1 according to the first and second embodiments can also each have at least two magnetized sections 10 or further magnetized sections 22 arranged one behind the other along the longitudinal axis 6, wherein adjacent magnetized sections 10 or further magnetized sections 22 can be magnetized in opposite directions. Correspondingly, the attachments 11 according to FIG. 1 can each have at least two magnetic field sensors 12 in order to provide a torque sensor 13 with a plurality of sensor segments.The attachment 11 of the rotary impact wrench 1 according to FIG. 5 has a first projection 25 which extends annularly around the longitudinal axis 6 of the tool holder 2 and projects radially with respect to the longitudinal axis 6. In addition, in this variant, the housing 7 has a second projection 26 which extends annularly around the longitudinal axis 6 of the tool holder 2 and projects radially away from the longitudinal axis 6. The second protrusion 26 is arranged between the first protrusion 25 and the magnetic field sensor 12 with respect to the longitudinal axis 6. The first projection 25 abuts the first projection 25 along the longitudinal axis 6. As a result, the attachment 11 is fastened to the housing 7, since the attachment 11 is not removed from the housing 7 due to the abutment of the first protrusion 25 on the second protrusion 26.In order that the attachment 11 can be fastened to the housing 7 in this way, the attachment 11 has two segments 27. FIG. 6 schematically shows a part of the rotary impact wrench 1 according to the third embodiment of FIG. 5 in an exploded representation in order to clarify the segmentation of the attachment 11. The segments 27 of the attachment 11 are connected to one another along a plane running along the longitudinal axis 6 of the tool holder 2. In FIG. 6, the segments 25 are screwed together by way of example.In this embodiment, the attachment 11 has two holders 28, which are, for example, a component of only one segment 27. Alternatively, a respective holder 28 can also be a component of a respective segment 27. The holders 28 are arranged one above the other with respect to the connecting plane of the segments 27. However, the holders 28 can also be arranged differently, for example the holders 28 can be arranged next to one another with respect to the connecting plane of the segments 27 along a direction running perpendicular to the longitudinal axis 6 and perpendicular to the connecting plane of the segments 27. The holders 28 are provided for receiving a respective printed circuit board 17. The printed circuit boards 17 each have a magnetic field sensor 12.FIG. 7 schematically shows a part of the rotary impact wrench of FIGS. 5 and 6 in a front view of the receiving element 3 of the tool holder 2, which projects from the attachment 11. The attachment 11 has two spacers 29. The spacers 29 are each arranged between the magnetized sections 10 of the tool holder 2 and the magnetic field sensors 12 and each define a radial distance 30 of the magnetic field sensors 12 from the tool holder 2 and in particular from the magnetized sections 10 of the tool holder 2. The distances 30 can be selected, for example, depending on the magnetization of the magnetized sections 10 in order to ensure reliable measurements.The holders 28 for the printed circuit boards 17 are designed such that they are open toward the tool holder 2. As a result, no components of the attachment 11 are arranged between the tool holder 2 and the magnetic field sensors 12 that could influence torque measurements. In order that the spacers 29 also do not influence the torque measurements, the spacers 29 are C-shaped with reference to FIG. 6. In other words, the spacers 29 each have an exception in a region between the tool holder 2 and the magnetic field sensors 12, as a result of which the magnetic field sensors 12 are at least partially uncovered by the spacers 29. The rotary impact screwdrivers 1 of FIGS. 1 and 3 can also each have spacers 29 which are each arranged between a magnetic field sensor 12 and a magnetized section 10 or a further magnetized section 22 of the tool holder 2.

Claims

Electric hand-held power tool (1), in particular a rotary impact wrench (1), having a tool holder (2) and a top piece (11), wherein the tool holder (2) has a longitudinal axis (6) and is rotatable about the longitudinal axis (6), wherein the top piece (11) is plugged onto the tool holder (2) and fastened to a housing (7) of the electric hand-held power tool (1) and the tool holder (2) has at least one section (10) which is magnetized annularly in a circumferential manner about its longitudinal axis (6) or wherein a socket wrench adapter (20) is plugged onto the tool holder (2) and fastened to the housing (7), a socket wrench attachment (21) is arranged on the socket wrench adapter (20) and connected to the tool holder (2) and has at least one further portion (22) which is magnetized annularly around the longitudinal axis (6) of the tool holder (2) and the attachment (11) is plugged onto the socket wrench attachment (21) and fastened to the socket wrench adapter (20), wherein the attachment (11) has at least one magnetic field sensor (12), wherein the magnetic field sensor (12) is arranged in the region of the magnetized portion (10) of the tool holder (2) or in the region of the further magnetized portion (22) of the socket wrench attachment (21).Electric hand-held power tool (1) according to Claim 1, wherein the attachment (11) or socket wrench adapter (20) is decoupled from the tool holder (2) by a ball bearing.Electric hand-held power tool (1) according to Claim 1 or 2, wherein the magnetic field sensor (12) is arranged on an outer side of the attachment (11) facing away from the tool holder (2) or on an outer side of the attachment (11) facing away from the socket (21).The electric hand-held power tool (1) according to claim 3, wherein a printed circuit board (17) is arranged on the outside of the attachment (11), and the magnetic field sensor (12) is arranged on the printed circuit board and electrically connected to the printed circuit board (17).Electric hand-held power tool (1) according to one of the preceding claims, wherein the attachment (11) has at least one through opening (18) formed in the region between the magnetized section (10) of the tool holder (2) and the magnetic field sensor (12) or between the further magnetized section (22) of the socket wrench attachment (21) and the magnetic field sensor (12).Electric hand-held power tool (1) according to Claim 4 or 5, wherein the printed circuit board (17) has a further through opening (18) formed in the region between the magnetized section (10) of the tool holder (2) and the magnetic field sensor (12) or between the further magnetized section (22) of the socket wrench attachment (21) and the magnetic field sensor (12).Electric hand-held power tool (1) according to Claim 1, wherein the attachment (11) has two segments (27), wherein the segments (27) are connected to one another along a plane running along the longitudinal axis (6) of the tool holder (2), wherein the attachment (11) has a first projection (25) which runs annularly around the longitudinal axis (6) of the tool holder (2) and projects radially with respect to the longitudinal axis (6), and the housing (7) has a second projection (26) which runs annularly around the longitudinal axis of the tool holder (2) and projects radially away from the longitudinal axis (6), wherein the second projection (26) is arranged between the first projection (1) and the magnetic field sensor (12) with respect to the longitudinal axis (6), and the first projection (25) bears against the second projection (26) along the longitudinal axis (6).Electric hand-held power tool (1) according to one of the preceding claims, wherein the attachment (11) has a spacer (29) arranged between the magnetized section (10) of the tool holder (2) and the magnetic field sensor (12) or between the further magnetized section (22) of the socket wrench attachment (21).Electric hand-held power tool (1) according to one of the preceding claims, wherein the tool holder (2) has at least two sections (10) which are arranged one behind the other along the longitudinal axis (6) and are magnetized annularly around the longitudinal axis (6), or the socket (21) has at least two further sections (22) which are arranged one behind the other along the longitudinal axis (6) and are magnetized annularly around the longitudinal axis (6), wherein directly adjacent magnetized sections (10) or further magnetized sections (22) are magnetized in opposite directions, wherein a magnetic field sensor (12) is arranged in each case in the region of a magnetized section (10) of the tool holder (2) or of a further magnetized section (22) of the socket (21).Electric hand-held power tool (1) according to one of the preceding claims, wherein the magnetized section (10) or the further magnetized section (22) comprises a ferromagnetic, nanocrystalline, metallic glass.

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