Electric hand tool and method for measuring torque in electric hand tool

Abstract

The invention relates to an electrodynamic hand tool and a method for measuring a torque in an electrodynamic hand tool. The electric hand tool includes: a drive unit for driving a shaft of the electric hand tool and driving a socket of the electric hand tool or a socket connectable to the electric hand tool through the shaft; a magnetostrictive torque sensor for measuring a torque applied to the shaft by the driving unit, the magnetostrictive torque sensor including a magnetized torque transmitting element and a three-dimensional magnetic field sensor configured to measure a total magnetic field including a magnetic field generated by the magnetized portion of the shaft and an interfering external magnetic field; and a processor for at least partially correcting the total magnetic field for an interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized torque transmitting element, and for determining a torque applied to the shaft by the drive unit based on the corrected magnetic field.

Description

Technical Field

[0001] The invention relates to an electric hand-held tool with a torque sensor. Background Art

[0002] The torque adjustment of nuts or bolts in a vehicle, for example for attaching a wheel, can be done manually by a workshop mechanic using a mechanical torque wrench. The corresponding maximum torque is set via a mechanical slip clutch or by pneumatic pressure.

[0003] In addition, there are electric hand tools, such as impact wrenches, in which the required torque can be preset. A specific type of such electric hand tools can have a magnetostrictive torque measuring sensor / magnetoelastic torque measuring sensor, as described in EP 4 173 753 A1. Sensors based on the magnetoelastic principle usually use one or more coils to measure the magnetic flux. However, external magnetic fields may interfere with the measurement signal of the sensor. Such external magnetic fields may be caused by the earth's magnetic field, strong electric currents, electromagnetic radiation, for example from nearby electric motors or magnetized components. Summary of the invention

[0004] It is an object of the present invention to overcome at least some of the above mentioned disadvantages.

[0005] This object is achieved by the electric hand tool according to the present invention.

[0006] The electric hand tool according to the present invention, in particular an impact wrench or a screwdriver or an electric drill, comprises: a drive unit, which is used to drive a shaft of the electric hand tool and is configured to drive a socket of the electric hand tool or a socket that can be connected to the electric hand tool via the shaft; a magnetostrictive torque sensor, which is used to measure the torque applied to the shaft by the drive unit; wherein the magnetostrictive torque sensor comprises a magnetized torque transmission part and a three-dimensional magnetic field sensor, the magnetized torque transmission part is, for example, a magnetized part of the shaft, and the three-dimensional magnetic field sensor is, in particular, a magnetoresistive sensor, such as an AMR sensor (Anisotropic magnetoresistance) magnetic field sensor, TMR (Tunnel magnetoresistance) magnetic field sensor, CMR (Colossal magnetoresistance) magnetic field sensor, GMR (Giant magnetoresistance) magnetic field sensor or EMR (Extraordinary magnetoresistance) magnetic field sensor, wherein the three-dimensional magnetic field sensor is configured to measure a total magnetic field, the total magnetic field including a magnetic field generated by a magnetizing torque transfer part and an interfering external magnetic field; and a processor for at least partially correcting the total magnetic field for the interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetizing torque transfer part, and the processor for determining the torque applied to the shaft by the drive unit based on the corrected magnetic field.

[0007] The measurements made by the magnetostrictive torque sensor can therefore be corrected for the disturbing effects of external magnetic fields that are not generated by the magnetized portion of the shaft. In particular, the effects of magnetic fields that have a direction different from that of the magnetic field generated by the magnetized shaft due to the magnetostrictive effect can be compensated. As a result, the torque applied to the shaft can be determined more accurately.

[0008] According to a refinement, the torque may be generated as a result of a rotational force acting on the shaft via the drive unit and a counter-rotational force acting on the shaft via the socket.

[0009] The external magnetic field can be measured by the three-dimensional magnetic field sensor in the torque-free state of the shaft, in which the counter-rotational force acting on the shaft through the socket is zero. This has the advantage that there is no effect (magnetic field) from the magnetostrictive torque sensor, so that the external magnetic field alone can be determined. The shaft can be stationary or can rotate at a constant rotational speed due to being driven by an electric motor.

[0010] In another development, the electric hand tool may further comprise an angle sensor for determining the rotation angle of the shaft.

[0011] The external magnetic field can be measured by a three-dimensional magnetic field sensor as a function of the rotation angle of the shaft determined by the angle sensor. This has the advantage that an external magnetic field from a source that is rotationally asymmetric relative to the shaft rotation can be determined. For example, a magnetized nut attached to a socket can be pre-magnetized in a manner that is not rotationally symmetric.

[0012] The electric handheld tool may also include a memory in communication with the processor, wherein the memory may be configured to store a relationship between a three-dimensional value of the external magnetic field and a rotation angle of the axis, and wherein the processor may be configured to obtain an interfering external magnetic field according to the rotation angle based on the stored relationship.

[0013] In another refinement, the socket may be configured to receive a fastening element, such as a nut, bolt or screw.

[0014] In a further refinement, the external magnetic field can be generated by an electric current, electromagnetic radiation - for example from an electric motor - or a magnetized component, in particular by at least one of the group consisting of a socket, a tool or fastening element connected to the socket, an electric motor of an electric hand tool and the Earth's magnetic field.

[0015] The above-mentioned objects are also achieved by the method according to the invention.

[0016] The method for measuring torque in an electric hand tool, in particular an impact wrench or a screwdriver or an electric drill, comprises the following steps: driving a shaft of the electric hand tool and driving a socket of the electric hand tool or a socket connected to the electric hand tool via the shaft; measuring the torque applied to the shaft via a drive unit using a magnetostrictive torque sensor; wherein the magnetostrictive torque sensor comprises a magnetized torque transfer portion, such as a magnetized portion of the shaft, and a three-dimensional magnetic field sensor, in particular a magnetoresistive sensor, such as a TMR magnetic field sensor, a CMR magnetic field sensor, a GMR magnetic field sensor, an AMR magnetic field sensor or an EMR magnetic field sensor; and measuring a total magnetic field by using the three-dimensional magnetic field sensor, the total magnetic field comprising a magnetic field generated by the magnetized torque transfer portion and an interfering external magnetic field; and at least partially correcting the total magnetic field for the interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized torque transfer portion, and determining the torque applied to the shaft via the drive unit based on the corrected magnetic field.

[0017] According to an improved scheme of the method according to the present invention, the torque can be generated due to the rotational force acting on the shaft through the drive unit and the reverse rotational force acting on the shaft through the socket, and the method can also include the following steps: measuring the external magnetic field by a three-dimensional magnetic field sensor in the torque-free state of the shaft, and in the torque-free state of the shaft, the reverse rotational force acting on the shaft through the socket is zero.

[0018] In another improved solution, the method may further include determining a rotation angle of the shaft; and measuring the external magnetic field by the three-dimensional magnetic field sensor according to the determined rotation angle of the shaft.

[0019] The method may further include the steps of storing a relationship between the three-dimensional value of the external magnetic field and the rotation angle of the shaft in a memory, and obtaining the disturbing external magnetic field according to the rotation angle based on the stored relationship.

[0020] In a further development, the socket can receive a fastening element, such as a nut, a bolt or a screw.

[0021] In a further refinement, the external magnetic field can be generated by an electric current, electromagnetic radiation - for example from an electric motor - or a magnetized component, in particular by at least one of the group consisting of a socket, a tool or fastening element connected to the socket, an electric motor of an electric hand tool and the Earth's magnetic field.

[0022] Other features and exemplary embodiments and advantages of the present invention will be explained in more detail below with the aid of the accompanying drawings. It is clear that the embodiments do not exhaust the scope of the present invention. It is also clear that some or all of the features described below may also be combined with each other in different ways. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 An embodiment of an electric hand tool according to the present invention is shown. DETAILED DESCRIPTION

[0024] If torque sensors based on the magnetoelastic effect are used in power tools / machine tools (e.g. impact wrenches), external fields can lead to measurement errors or make measurement impossible. Impact wrenches often use slip-on nuts or other slip-on tools that are pre-magnetized by the manufacturer. Furthermore, these machines are often driven by powerful electric motors that, due to the high power consumption and currents involved, generate strong magnetic fields that are superimposed on the (desired) magnetic field caused by inverse magnetostriction.

[0025] Sensors based on the magnetoelastic principle usually use one or more coils to perform magnetic flux measurement. However, the coils can only measure the value of the magnetic flux, but not the direction of the magnetic flux (no 3D measurement).

[0026] An AMR sensor, TMR sensor, GMR sensor, CMR sensor or EMR sensor (3D resolution) can detect the magnetic flux direction. By using such a sensor instead of an induction coil, the field direction of the magnetic flux can be detected. Thus, it can be distinguished whether the signal is generated by the earth's magnetic field, by a magnetized component (e.g. a static or rotating wrench socket), or by an applied torque (to be measured) in the shaft of an impact wrench due to the magnetoelastic effect. Therefore, the present invention relates to the use of a direction-resolving element, such as an AMR sensor, in particular for use in a machine tool to correct / compensate for errors due to external magnetic fields.

[0027] Figure 1 An embodiment of a power hand tool 100 according to the present invention is shown.

[0028] The electric hand tool 100 includes a drive unit (electric motor) 10 for driving a shaft 20 of the electric hand tool 100, and the drive unit 10 is configured to drive a socket 30 that can be connected to the electric hand tool 100 through the shaft 20. The electric hand tool 100 also has a magnetostrictive torque sensor 40, which is used to measure the torque applied to the shaft 20 through the drive unit 10; wherein the magnetostrictive torque sensor 40 includes a magnetized portion 41 of the shaft 20 and an AMR magnetic field sensor, a TMR magnetic field sensor, a GMR magnetic field sensor, a CMR magnetic field sensor, or an EMR magnetic field sensor 42, wherein the AMR magnetic field sensor, the TMR magnetic field sensor, the GMR magnetic field sensor, the CMR magnetic field sensor, or the EMR magnetic field sensor 42 is configured to measure the total magnetic field, which includes the magnetic field generated by the magnetized portion of the shaft and the interfering external magnetic field. In addition, the processor 50 is configured to at least partially correct the total magnetic field for an interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized portion 41 of the shaft 20, and the processor 50 is configured to determine the torque applied to the shaft 20 by the drive unit 10 based on the corrected magnetic field.

[0029] The external magnetic field can be measured by the AMR magnetic field sensor, TMR magnetic field sensor, GMR magnetic field sensor, CMR magnetic field sensor or EMR magnetic field sensor 42 in the torque-free state of the shaft 20, in which the counter-rotational force acting on the shaft 20 through the socket 30 is zero. This has the following result: there is no effect (magnetic field) from the magnetostrictive torque sensor, so that the external magnetic field can be determined alone. The shaft 20 can be stationary or can rotate at a constant rotational speed due to being driven by the electric motor 10.

[0030] The electric hand tool 100 also includes an angle sensor 11 for determining the rotation angle of the shaft 20. The external magnetic field can be measured by an AMR magnetic field sensor, a TMR magnetic field sensor, a GMR magnetic field sensor, a CMR magnetic field sensor, or an EMR magnetic field sensor 42 according to the rotation angle of the shaft determined by the angle sensor 11. Thus, an external magnetic field from a source that is rotationally asymmetric relative to the shaft rotation can be determined. For example, a magnetized nut attached to the socket 30 can be pre-magnetized in a manner that is not rotationally symmetric.

[0031] The electric hand tool 100 also includes a memory 51 (volatile or permanent) in communication with the processor 50. The memory 51 stores the current relationship between the three-dimensional value of the external magnetic field and the rotation angle of the shaft 20, and the processor 50 can obtain the disturbing external magnetic field according to the rotation angle based on the stored relationship. The relationship can depend on the orientation of the electric hand tool 100 when the effect of the earth's magnetic field is compensated, for example. In addition, the relationship can depend on the specific magnetized fastening element 31 or magnetized socket 30 attached.

[0032] In this embodiment, the electric hand tool 100 has a rechargeable battery unit 91 attached to the housing 90 to supply power to the drive unit 10. In this example, the battery unit 91 is attached to a handle 92 of the housing 90.

[0033] The socket 30 can receive a fastening element 31, such as a nut, bolt or screw, which can be driven and fixed to an object. The processor 50 receives the measurement signal from the magnetostrictive torque sensor 40 and controls the drive unit 10 to adjust the applied torque value by increasing the torque until the torque value is within a predetermined tolerance range around a predetermined value for the current fastening process. The predetermined value and / or tolerance range is stored in a permanent memory 65 of the electric hand tool 100.

[0034] The torque sensor 40 is a magnetostrictive torque sensor and includes a magnetized portion 41 of the shaft 20 and an AMR magnetic field sensor, a TMR magnetic field sensor, a GMR magnetic field sensor, a CMR magnetic field sensor or an EMR magnetic field sensor 42 for detecting a change in a magnetic field from the magnetized portion 41 outside the shaft 20 .

[0035] The driven shaft 20 is magnetized and an AMR magnetic field sensor, a TMR magnetic field sensor, a GMR magnetic field sensor, a CMR magnetic field sensor or an EMR magnetic field sensor 42 is arranged close to the magnetized portion 41 to determine the change in magnetic field when a torque is applied, which causes a torsion of the shaft 20 and thereby produces a change in magnetic field at the location of the magnetic field sensor due to the inverse magnetostrictive effect. The magnetization of the shaft 20 can be set during the manufacture of the electric hand tool 100, and the calibration of the magnetic field sensor signal related to the applied torque can be stored in the permanent memory 65 of the electric hand tool 100.

[0036] A torque sensor based on the principle of the inverse magnetostrictive effect is described, for example, in EP 3 050 790 B1. A magnetized shaft (as the primary sensor part) generates a magnetic field outside the shaft as a function of the applied torque, which can be detected contactlessly by a magnetic field sensor (as the secondary sensor part). The magnetic field variation is generally proportional to the applied torque. A corresponding one-time calibration is performed during the manufacturing phase of the torque sensor in order to correlate the magnetic field variation with the applied torque.

[0037] Other magnetized torque transmission parts based on the inverse magnetostrictive effect are described in EP 4 116 688 A1, which can be used in the electric hand tool 100 instead of the magnetized part 41 of the shaft 20. These torque sensors include: a disk, which includes a magnetostrictive material, a pre-magnetized material or a magnetizable material; and a magnetic field sensor device; wherein a torque acting around the rotation axis of the disk can be applied to the disk, and the magnetostrictive material is designed to generate a magnetic field that changes outside the disk according to the applied torque; wherein the magnetic field sensor device is designed to output a signal based on the magnetic field generated by the magnetostrictive material; and wherein the torque sensor is configured to determine the value of the applied torque based on the output signal. The disk used as a torque transmission part is used to measure the applied torque by pre-magnetizing at least a part of the disk. In particular, the disk can have spokes connecting the inner part and the outer part of the disk, and one or more spokes can be magnetized. In this way, the disk - rather than the shaft on which the disk can be placed - is used as the main sensor.

[0038] The embodiments are exemplary only, and the full scope of the invention is defined by the claims.

Claims

1. An electric hand-held tool, in particular an impact wrench or a screwdriver or an electric drill, comprising: a drive unit for driving a shaft of the electric hand tool and configured to drive a socket of the electric hand tool or a socket connectable to the electric hand tool via the shaft; A magnetostrictive torque sensor, the magnetostrictive torque sensor is used to measure the torque applied to the shaft by the drive unit; wherein the magnetostrictive torque sensor comprises a magnetized torque transfer portion and a three-dimensional magnetic field sensor, the magnetized torque transfer portion is, for example, a magnetized portion of the shaft, the three-dimensional magnetic field sensor is particularly an anisotropic magnetoresistive magnetic field sensor, a tunnel magnetoresistive magnetic field sensor, a giant magnetoresistive magnetic field sensor, a colossal magnetoresistive magnetic field sensor or an abnormal magnetoresistive magnetic field sensor, wherein the three-dimensional magnetic field sensor is configured to measure a total magnetic field, the total magnetic field comprising a magnetic field generated by the magnetized torque transfer portion and an interfering external magnetic field; and A processor is used to at least partially correct the total magnetic field for the interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetizing torque transfer portion, and the processor is used to determine the torque applied to the shaft by the drive unit based on the corrected magnetic field.

2. The electric hand tool according to claim 1, wherein: The torque is generated due to a rotational force acting on the shaft through the drive unit and a counter-rotational force acting on the shaft through the socket.

3. The electric hand tool according to claim 2, wherein: The external magnetic field is measured by the three-dimensional magnetic field sensor in a torque-free state of the shaft, in which the counter-rotational force acting on the shaft through the socket is zero.

4. An electric hand tool according to any one of claims 1 to 3, further comprising an angle sensor for determining the angle of rotation of the shaft.

5. The electric hand tool according to claim 4, wherein: The external magnetic field is measured by the three-dimensional magnetic field sensor according to the rotation angle of the shaft determined by the angle sensor.

6. The electric hand tool of claim 5, further comprising a memory in communication with the processor, wherein: The memory is configured to store a relationship between a three-dimensional value of the external magnetic field and the rotation angle of the shaft, and wherein the processor is configured to obtain the disturbed external magnetic field according to the rotation angle based on the stored relationship.

7. The electric hand tool according to any one of claims 1 to 6, wherein: The socket is configured to receive a fastening element, such as a nut, bolt or screw.

8. The electric hand tool according to any one of claims 1 to 7, wherein: The external magnetic field is generated by electric current, electromagnetic radiation, for example from an electric motor, or a magnetized component, in particular by at least one of the group consisting of the socket, a tool or fastening element connected to the socket, an electric motor of the electric hand tool, and the Earth's magnetic field.

9. A method for measuring torque in an electric hand-held tool, in particular an impact wrench or a screwdriver or an electric drill, the method comprising: driving a shaft of the electric hand tool and, via the shaft, driving a socket of the electric hand tool or being connected to a socket of the electric hand tool; The torque applied to the shaft by the drive unit is measured using a magnetostrictive torque sensor; wherein the magnetostrictive torque sensor comprises a magnetized torque transmission part and a three-dimensional magnetic field sensor, the magnetized torque transmission part is, for example, a magnetized part of the shaft, and the three-dimensional magnetic field sensor is particularly an anisotropic magnetoresistance magnetic field sensor, a tunnel magnetoresistance magnetic field sensor, a giant magnetoresistance magnetic field sensor, a colossal magnetoresistance magnetic field sensor or an abnormal magnetoresistance magnetic field sensor; and by using the three-dimensional magnetic field sensor, a total magnetic field is measured, the total magnetic field comprising a magnetic field generated by the magnetized torque transmission part and an interfering external magnetic field; and The total magnetic field is at least partially corrected for the interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetizing torque transfer portion, and the torque applied to the shaft by the drive unit is determined based on the corrected magnetic field.

10. The method according to claim 9, wherein: The torque is generated due to the rotational force acting on the shaft through the drive unit and the reverse rotational force acting on the shaft through the socket, and the method also includes the following steps: measuring the external magnetic field by the three-dimensional magnetic field sensor when the shaft is in a torque-free state, and when the shaft is in a torque-free state, the reverse rotational force acting on the shaft through the socket is zero. 11 . The method according to claim 9 , further comprising determining a rotation angle of the shaft, and measuring the external magnetic field by the three-dimensional magnetic field sensor according to the determined rotation angle of the shaft. 12 . The method according to claim 11 , further comprising storing a relationship between the three-dimensional value of the external magnetic field and the rotation angle of the shaft in a memory, and obtaining the disturbed external magnetic field according to the rotation angle based on the stored relationship.

13. The method according to any one of claims 9 to 12, wherein: The socket receives a fastening element, such as a nut, bolt or screw.

14. The method according to any one of claims 9 to 13, wherein: The external magnetic field is generated by electric current, electromagnetic radiation, for example from an electric motor, or a magnetized component, in particular by at least one of the group consisting of the socket, a tool or fastening element connected to the socket, an electric motor of the electric hand tool, and the Earth's magnetic field.

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