Powered hand tools with torque sensor and external magnetic field compensation

Abstract

To solve the problem that since a magnetostrictive / magnetoelastic torque measurement sensor, in most cases, uses one or more coils for magnetic flux measurement, external magnetic fields may interfere with a measurement signal of the sensor.SOLUTION: An electric hand tool includes: a drive unit for driving a shaft of the electric hand tool, where the drive unit is configured to drive a socket via the shaft; a magnetostrictive torque sensor for measuring torque applied to the shaft via the drive unit, where the magnetostrictive torque sensor includes a magnetized torque transfer component and a 3D magnetic field sensor, where the 3D magnetic field sensor is configured to measure a total magnetic field, where the total magnetic field includes magnetic field generated by a magnetized portion of the magnetized shaft and interfering external magnetic field; and a processor for at least partially correcting the total magnetic field with respect to the interfering external magnetic field and acquiring the corrected magnetic field corresponding to the magnetic field generated by the magnetized torque transfer component.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electric power tool provided with a torque sensor.

Background Art

[0002] Torque adjustment of nuts or bolts of a vehicle, such as wheel attachment, is manually performed by a mechanic at a workplace using a mechanical torque wrench. Each maximum torque is set by a mechanical slip clutch or pneumatically.

[0003] Furthermore, there are also electric power tools such as impact wrenches that can preset the required torque. A specific type of such an electric power tool has a magnetostrictive / magnetoelastic torque measurement sensor as described in Patent Document 1. Sensors based on the magnetoelastic principle often use one or more coils for magnetic flux measurement. However, there is a possibility that an external magnetic field interferes with the measurement signal of the sensor. Such an external magnetic field is caused by the Earth's magnetic field, for example, a strong current from a nearby electric motor or magnetized parts, or electromagnetic radiation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to overcome at least some of the above-mentioned drawbacks.

Means for Solving the Problems

[0006] This object is achieved by the electric power tool according to claim 1.

[0007] The electric hand tool according to the present invention, in particular an impact wrench, screwdriver, or electric drill, includes a drive unit for driving the shaft of the electric hand tool, configured to drive a socket of the electric hand tool or a socket connectable to the electric hand tool via the shaft, and a magnetostrictive torque sensor for measuring the torque applied to the shaft via the drive unit, wherein the magnetostrictive torque sensor is configured to drive a magnetized torque transmission part such as a magnetized portion of the shaft, and a 3D magnetic field sensor, in particular a magnetoresistance sensor, e.g., AMR (anisotropic magnetoresistance), TMR (tunnel magnetoresistance), CMR (colossal magnetoresistance), GMR (giant magnetoresistance), or EMR (extraordinary magnetoresistance). A magnetoresistance (anomalous magnetoresistance) magnetic field sensor is provided, and the 3D magnetic field sensor is configured to measure the total magnetic field, the total magnetic field including the magnetic field generated by the magnetized torque transmission unit and interfering external magnetic fields; and a processor is provided to at least partially correct the total magnetic field for the interfering external magnetic fields to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized torque transmission unit, and to determine the torque applied to the shaft via the drive unit based on the corrected magnetic field.

[0008] Therefore, measurements using a magnetostrictive torque sensor can compensate for the effects of interference from external magnetic fields not originating from the magnetized portion of the shaft. In particular, it can compensate for the effects of magnetic fields having a different direction from the magnetic field generated from the magnetized shaft due to the magnetostrictive effect. Consequently, the torque applied to the shaft can be determined more accurately.

[0009] According to one theory, torque is due to a rotational force acting on the shaft via the drive unit and a counter-rotational force acting on the shaft via the socket.

[0010] The external magnetic field is measured by a 3D magnetic field sensor when there is no torque on the shaft, and the counter-rotational force acting on the shaft via the socket is zero. This has the advantage that the external magnetic field can be determined individually because there is no influence (magnetic field) from the magnetostrictive torque sensor. The shaft may be stationary or rotating at a constant rotational speed because it is driven by an electric motor.

[0011] In another development, the powered hand tool would further incorporate an angle sensor to determine the rotation angle of the shaft.

[0012] The external magnetic field is measured by a 3D magnetic field sensor according to the rotation angle of the shaft, which is determined by an angle sensor. This has the advantage of being able to determine the external magnetic field from a source that is rotationally asymmetric with respect to the rotation of the shaft. For example, a magnetized nut attached to a socket is pre-magnetized so that it is not rotationally symmetric.

[0013] The powered hand tool further includes memory that communicates with a processor, the memory being configured to store the relationship between the 3D value of an external magnetic field and the rotation angle of the shaft, and the processor being configured to obtain an interfering external magnetic field according to the rotation angle based on the stored relationship.

[0014] In another configuration, the socket is configured to accept fastening elements such as nuts, bolts, or screws.

[0015] In further developments, the external magnetic field is generated by, for example, electric current from an electric motor, electromagnetic radiation, or magnetized components, particularly sockets, tools or fastening elements connected to sockets, electric motors of powered hand tools, and the Earth's magnetic field, among others.

[0016] The above-mentioned objective can also be achieved by the method described in claim 9.

[0017] A method for measuring torque in an electric hand tool, particularly an impact wrench, screwdriver, or electric drill, includes the steps of: driving the shaft of the electric hand tool and driving the 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 transmission part such as a magnetized portion of the shaft, and a 3D magnetic field sensor, particularly a magnetoresistive sensor, such as a TMR, CMR, GMR, AMR, or EMR magnetic field sensor, and by using the 3D magnetic field sensor, the total magnetic field is measured, wherein the total magnetic field includes the magnetic field generated by the magnetized torque transmission part and an interfering external magnetic field; and correcting the total magnetic field at least partially for the interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized torque transmission part, and determining the torque applied to the shaft via the drive unit based on the corrected magnetic field.

[0018] According to one development of the method according to the present invention, torque is due to a rotational force acting on the shaft via a drive unit and a reverse rotational force acting on the shaft via a socket, and the method further includes the step of measuring an external magnetic field by a 3D magnetic field sensor when there is no torque on the shaft and the reverse rotational force acting on the shaft via the socket is zero.

[0019] In another development, the method further includes the steps of determining the rotation angle of the shaft and measuring the external magnetic field using a 3D magnetic field sensor according to the determined rotation angle of the shaft.

[0020] The method further includes the steps of storing in memory the relationship between the 3D value of the external magnetic field and the rotation angle of the shaft, and obtaining an interfering external magnetic field according to the rotation angle based on the stored relationship.

[0021] In another configuration, the socket can accept fastening elements such as nuts, bolts, or screws.

[0022] In a further development, the external magnetic field is generated by at least one from the group of, for example, a current from an electric motor, electromagnetic radiation, or a magnetized component, in particular 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.

[0023] Further features and exemplary embodiments and advantages of the present invention will be explained in more detail hereinafter in this specification by means of the following drawings. It is clear that the embodiments do not cover the entire field of the present invention. Furthermore, it is clear that some or all of the features described hereinafter can also be combined with each other in different ways.

Brief Description of the Drawings

[0024] [Figure 1] Shows an embodiment of an electric hand tool according to the present invention.

Embodiments for Carrying out the Invention

[0025] When a torque sensor that measures based on the magnetoelastic effect is used in an electric tool / machine tool (for example, an impact wrench), an external magnetic field may cause a measurement error or make the measurement impossible. Impact wrenches often use a slip-on nut or other slip-on tool that is pre-magnetized by the manufacturer. Furthermore, these machines are often driven by a powerful electric motor, and due to the high power consumption and the associated current, a powerful magnetic field is generated that is superimposed on the (desired) magnetic field caused by magnetostriction.

[0026] Sensors based on the magnetoelastic principle often use one or more coils for magnetic flux measurement. However, the coil can only measure the value of the magnetic flux and cannot measure the magnetic flux direction (3D measurement is not possible).

[0027] AMR, TMR, GMR, CMR, or EMR sensors (3D resolution) can detect the direction of magnetic flux. By using such sensors instead of induction coils, the field direction of the magnetic flux can be detected. Thus, it is possible to distinguish whether a signal was generated by the Earth's magnetic field, by a magnetizing component (e.g., a stationary or rotating wrench socket), or by torque applied to the shaft of an impact wrench (which can be measured) due to the magnetoelastic effect. Therefore, the present invention relates in particular to the use of direction-resolving elements such as AMR sensors for use in machine tools to correct / compensate for errors caused by external magnetic fields.

[0028] Figure 1 shows one embodiment of the electric hand tool 100 according to the present invention.

[0029] The powered hand tool 100 includes a drive unit (electric motor) 10 for driving the shaft 20 of the powered hand tool 100, and the drive unit 10 is configured to drive a socket 30 connectable to the powered hand tool 100 via the shaft 20. The powered hand tool 100 further includes a magnetostrictive torque sensor 40 for measuring the torque applied to the shaft 20 via the drive unit 10, the magnetostrictive torque sensor 40 comprising a magnetized portion 41 of the shaft 20 and an AMR, TMR, GMR, CMR, or EMR magnetic field sensor 42, the AMR, TMR, GMR, CMR, or EMR magnetic field sensor 42 being configured to measure the total magnetic field, the total magnetic field including the magnetic field generated by the magnetized portion of the shaft and interfering external magnetic fields. In addition, a processor 50 is provided for at least partially correcting the total magnetic field for interfering external magnetic fields to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized portion 41 of the shaft 20, and for determining the torque applied to the shaft 20 via the drive unit 10 based on the corrected magnetic field.

[0030] The external magnetic field can be measured by an AMR, TMR, GMR, CMR, or EMR magnetic field sensor 42 when there is no torque on the shaft 20, in which case the reverse rotational force acting on the shaft 20 via the socket 30 is zero. This results in the absence of influence (magnetic field) from the magnetostrictive torque sensor, allowing the external magnetic field to be determined individually. The shaft 20 may be stationary or may be rotating at a constant rotational speed driven by the electric motor 10.

[0031] The powered hand tool 100 further includes an angle sensor 11 for determining the rotation angle of the shaft 20. The external magnetic field is measured by an AMR, TMR, GMR, CMR, or EMR magnetic field sensor 42, depending on the rotation angle of the shaft determined by the angle sensor 11. This makes it possible to determine the external magnetic field from a source that is rotationally asymmetric with respect to the rotation of the shaft. For example, a magnetized nut attached to a socket 30 is pre-magnetized so as not to be rotationally symmetric.

[0032] The powered hand tool 100 further includes a memory 51 (volatile or persistent) that communicates with the processor 50. The memory 51 stores the current relationship between the 3D value of the external magnetic field and the rotation angle of the shaft 20, and the processor 50 can obtain an interfering external magnetic field depending on the rotation angle based on the stored relationship. This relationship depends, for example, on the orientation of the powered hand tool 100 when the effects of the Earth's magnetic field are compensated for. Furthermore, this relationship depends on the specific magnetized fastening element 31 or magnetized socket 30 to which it is attached.

[0033] In this embodiment, the power hand tool 100 has a rechargeable battery unit 91 mounted on the housing 90 to supply electrical energy to the drive unit 10. In this embodiment, the battery unit 91 is mounted on the handgrip 92 of the housing 90.

[0034] The socket 30 can receive fastening elements 31 such as nuts, bolts, or screws that can be driven and secured to an object. The processor 50 receives a 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 it falls within a predefined tolerance range near a predetermined value used in the current fastening process. The predetermined value and / or tolerance range is stored in the persistent memory 65 of the power hand tool 100.

[0035] The torque sensor 40 is a magnetostrictive torque sensor and includes an AMR, TMR, GMR, CMR, or EMR magnetic field sensor 42 for detecting changes in the magnetic field from the magnetized portion 41 of the shaft 20 and from the magnetized portion 41 outside the shaft 20.

[0036] The driven shaft 20 is magnetized, and an AMR, TMR, GMR, CMR, or EMR magnetic field sensor 42 is positioned near the magnetized portion 41 to determine the change in the magnetic field when torque is applied, as this torque causes twisting of the shaft 20, thereby generating a change in the magnetic field at the position of the magnetic field sensor due to the inverse magnetostrictive effect. The magnetization of the shaft 20 may be provided during the manufacture of the power hand tool 100, and the calibration of the magnetic field sensor signal related to the applied torque is stored in the persistent memory 65 of the power hand tool 100.

[0037] A torque sensor based on the principle of the inverse magnetostrictive effect is described, for example, in European Patent No. 3050790 B1. A magnetized shaft (as the primary sensor) generates a magnetic field outside the shaft in response to the applied torque, and this magnetic field can be detected non-contact by a magnetic field sensor (as the secondary sensor). The change in the magnetic field is usually directly proportional to the applied torque. During the manufacturing process of the torque sensor, a corresponding one-time calibration is performed to correlate the change in the magnetic field with the applied torque.

[0038] Other magnetized torque transmission units based on the inverse magnetostrictive effect are described in European Patent Application Publication No. 4116688 A1 and can be used as a substitute for the magnetized portion 41 of the shaft 20 in a power hand tool 100. These torque sensors comprise a disk containing a magnetostrictive material, a pre-magnetized or magnetizable material, and a magnetic field sensor arrangement, wherein a torque acting around the axis of rotation of the disk is applied to the disk, the magnetostrictive material is designed to generate a magnetic field outside the disk that changes in response to the applied torque, the magnetic field sensor arrangement is designed to output a signal based on the magnetic field generated by the magnetostrictive material, and the torque sensor is configured to determine the value of the applied torque based on the output signal. The disk acting as a torque transmission unit is used to measure the applied torque by pre-magnetizing at least a portion of the disk. In particular, the disk has spokes connecting an inner portion and an outer portion of the disk, and one or more spokes are magnetized. In this way, the disk, rather than the shaft on which the disk is arranged, is used as the primary sensor.

[0039] The embodiments described herein are illustrative only, and the full scope of the invention is defined by the claims.

Claims

1. It is an electric hand tool, A drive unit for driving the shaft of the electric hand tool, the drive unit configured to drive the socket of the electric hand tool or a socket connectable to the electric hand tool via the shaft, A magnetostrictive torque sensor for measuring the torque applied to the shaft via the drive unit, wherein the magnetostrictive torque sensor comprises a magnetized torque transmission unit and a 3D magnetic field sensor, the 3D magnetic field sensor is configured to measure the total magnetic field, and the total magnetic field includes the magnetic field generated by the magnetized torque transmission unit and interfering external magnetic fields, A processor for correcting the entire magnetic field at least partially with respect to the interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized torque transmission unit, and for determining the torque applied to the shaft via the drive unit based on the corrected magnetic field. Equipped with, The torque is due to a rotational force acting on the shaft via the drive unit and a reverse rotational force acting on the shaft via the socket. The external magnetic field is measured by the 3D magnetic field sensor when there is no torque on the shaft, and the reverse rotational force acting on the shaft via the socket is zero. Electric hand tools.

2. The electric hand tool according to claim 1, further comprising an angle sensor for determining the rotation angle of the shaft.

3. The electric hand tool according to claim 2, wherein the external magnetic field is measured by the 3D magnetic field sensor in accordance with the rotation angle of the shaft determined by the angle sensor.

4. The electric hand tool according to claim 3, further comprising a memory that communicates with the processor, wherein the memory is configured to store a relationship between the 3D value of the external magnetic field and the rotation angle of the shaft, and the processor is configured to obtain the interfering external magnetic field according to the rotation angle based on the stored relationship.

5. The electric hand tool according to claim 1, wherein the socket is configured to receive a fastening element.

6. The powered hand tool according to claim 1, wherein the external magnetic field is generated by an electric current, electromagnetic radiation, or a magnetized component.

7. A method for measuring torque in an electric hand tool, The steps include driving the shaft of the electric hand tool and driving the socket of the electric hand tool or a socket connected to the electric hand tool via the shaft, A step of measuring the torque applied to the shaft via the driving step using a magnetostrictive torque sensor, wherein the magnetostrictive torque sensor comprises a magnetized torque transmission unit and a 3D magnetic field sensor, and by using the 3D magnetic field sensor, the total magnetic field is measured, and the total magnetic field includes the magnetic field generated by the magnetized torque transmission unit and interfering external magnetic fields. The steps include: correcting the entire magnetic field at least partially with respect to the interfering external magnetic field to obtain a corrected magnetic field corresponding to the magnetic field generated by the magnetized torque transmission unit; and determining the torque applied to the shaft via the driving step based on the corrected magnetic field. Includes, The torque is due to a rotational force acting on the shaft via the driving step and a reverse rotational force acting on the shaft via the socket, and the method further includes the step of measuring the external magnetic field by the 3D magnetic field sensor when there is no torque on the shaft, and the reverse rotational force acting on the shaft via the socket is zero. method.

8. The method according to claim 7, further comprising the steps of determining the rotation angle of the shaft and measuring the external magnetic field with the 3D magnetic field sensor according to the determined rotation angle of the shaft.

9. The method according to claim 8, further comprising the steps of: storing in memory the relationship between the 3D value of the external magnetic field and the rotation angle of the shaft; and obtaining the interfering external magnetic field according to the rotation angle based on the stored relationship.

10. The method according to claim 7, wherein the socket receives a fastening element.

11. The method according to claim 7, wherein the external magnetic field is generated by an electric current, electromagnetic radiation, or a magnetized component.

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