Induction of a magnetic field for amplifying a measurement signal of a magnetostrictive torque sensor

Abstract

Magnetostrictive torque sensors essentially consist of two components, on the one hand a magnetized region of the shaft and on the other hand a magnetic field sensor for detecting the magnetic field from the magnetized region under load. Especially at low torques, the strength of the generated magnetic field is low only at the measurement points, which in combination with a corresponding uncertainty of the torque measurement of the torque sensor can result in a low signal-to-noise ratio.SOLUTION: The torque sensor 100 comprises a shaft 10 having a first magnetized region 11, the first magnetized region generating a first magnetic field B1 in response to a torque applied to the shaft, a first magnetic field sensor 21 for detecting a first magnetic field, the first magnetic field sensor being adapted to output a signal in response to a strength of the first magnetic field at a location of the first magnetic field sensor, and a first magnetic field guiding device 3132 for guiding the first magnetic field to the location of the first magnetic field sensor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a torque sensor based on the effect of magnetostriction, and in particular to the induction of a magnetic field for amplifying the measurement signal of a magnetostrictive torque sensor. [Background technology]

[0002] Torque sensors are known in the prior art. An example of such a torque sensor based on the principle of the inverse magnetostrictive effect is disclosed in U.S. Pat. No. 5,623,999. Here, a magnetized shaft generates a corresponding magnetic field outside the shaft in response to applied torque, which can be detected without contact using a magnetic field sensor. Thus, such a magnetostrictive torque sensor essentially consists of two components: on the one hand, a magnetized region of the shaft, and, on the other hand, a magnetic field sensor for detecting the magnetic field from the magnetized region under load.

[0003] The measurement of the magnetic field changes caused by the torque can be performed by a measuring coil in the measurement circuit, which is affected by the changing magnetic field. In another variant, a magnetic field sensor based on the magnetoresistive effect is used, which can detect not only the strength of the magnetic field but also the direction of the magnetic field.

[0004] These measuring coils or magnetic field sensors are attached contactlessly to the magnetized shaft (e.g., parallel to the axis of rotation) and detect the magnetic field changes that occur under load due to inverse magnetostriction. The magnetic field changes are usually directly proportional to the external force and establish a relationship with the torque. For this purpose, a calibration is performed during the manufacturing stage of the torque sensor.

[0005] Especially at low torques, the strength of the magnetic field generated is low only at the point of measurement, which, combined with the corresponding uncertainty in the torque measurement of the torque sensor, can result in a low signal-to-noise ratio. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent No. 3050790 Summary of the Invention [Problem to be solved by the invention]

[0007] The invention is based on the object of at least partially resolving the above-mentioned drawbacks. [Means for solving the problem]

[0008] This problem is solved by a torque sensor according to claim 1.

[0009] According to claim 1, the torque sensor according to the invention comprises the following features: a shaft having a first magnetized region that generates a first magnetic field in response to a torque applied to the shaft; a first magnetic field sensor for detecting the first magnetic field, the first magnetic field sensor being designed to output a signal in response to the strength of the first magnetic field at the location of the first magnetic field sensor; and a first magnetic field guiding arrangement for guiding the first magnetic field to the location of the first magnetic field sensor.

[0010] By guiding the magnetic field to the measurement point, the magnetic signal in this area is focused and amplified, thereby improving the accuracy of the torque sensor.

[0011] The torque sensor according to the invention can be further developed as follows.

[0012] A further development is for the torque sensor to further comprise a second magnetized region that generates a second magnetic field in response to torque applied to the shaft, the magnetization of the second magnetized region being opposite to the magnetization of the first magnetized region; a second magnetic field sensor for detecting the second magnetic field, the second magnetic field sensor adapted to output a signal in response to the strength of the second magnetic field at the location of the second magnetic field sensor; and a second magnetic field guiding device for guiding the second magnetic field to the location of the second magnetic field sensor.

[0013] By providing a second magnetized region whose magnetization is opposite to that of the first magnetized region, it is possible to effectively correct the signal for external magnetic fields. In this way, it is possible to improve accuracy, and in particular to compensate for constant external magnetic disturbance fields that are independent of the applied torque. The magnetic field is directed from the second region with the second magnetic field guiding device to the position of the second magnetic field sensor, where it is amplified.

[0014] However, one or more further magnetized regions, such as a third magnetized region, may also be provided.

[0015] According to another further development, the first magnetic field guiding device can comprise first and second magnetic field guiding elements, which are arranged on different, in particular opposite, sides of the first magnetic field sensor, thereby improving the focusing of the magnetic field from both sides of the first region at the location of the first magnetic field sensor.

[0016] Another further development is that the second magnetic field guiding device can comprise third and fourth magnetic field guiding elements, whereby the third and fourth magnetic field guiding elements are arranged on different, in particular opposite, sides of the second magnetic field sensor. Accordingly, the aforementioned advantages also apply here, i.e., at the location of the second magnetic field sensor, the magnetic fields from both sides of the second region are focused.

[0017] This can be further developed so that second and third magnetic field guiding elements are provided between and integrally formed with the first and second magnetic field sensors.

[0018] According to another further development, each of the magnetic field guiding elements can comprise a metal sheet, which allows the magnetic field to be guided precisely to the magnetic field sensor, and the magnetic field in the metal sheet essentially follows the direction of the sheet and can reappear at the edges or bends to reach the magnetic field sensor.

[0019] This can be further developed so that each metal sheet is flat or so that the end section of each metal sheet adjacent the first magnetic field sensor is sloped, which allows the magnetic field guided / conducted by the metal sheet to reach the magnetic field sensor.

[0020] Another further development is that each metal sheet is rectangular in the plane of the sheet or tapered towards the magnetic field sensor, in other words wedge-shaped in the direction of the magnetic field sensor, which further strengthens the focusing of the magnetic field at the location of the magnetic field sensor.

[0021] According to another further development, the material of the first or first and / or second magnetic field guiding device can comprise a soft magnetic or paramagnetic material, which is advantageous in that permanent magnetization and hysteresis effects that may occur in metal sheets can be avoided.

[0022] This can be further developed in that the material of the first or first and / or second magnetic field guiding device can comprise a metal or ceramic material or a plastic material with magnetizable metal particles.

[0023] Another further development is that the first and / or second magnetic field sensor comprises one or more coils or is a sensor based on the magnetoresistive effect, in particular an AMR sensor, a CMR sensor, a GMR sensor, a TMR sensor or a sensor based on the planar Hall effect, which have proven advantageous for measuring magnetic fields, in particular due to their relatively high sensitivity.

[0024] The first and / or second magnetic field sensors may be disposed on a printed circuit board.

[0025] Further features and exemplary embodiments and advantages of the present invention are described in more detail below with reference to the drawings. It should be understood that the embodiments are not exhaustive of the scope of the present invention. It should also be understood that some or all of the features described below may be combined in other ways. [Brief explanation of the drawings]

[0026] [Figure 1] 1 shows an embodiment of a torque sensor according to the invention with a metal sheet as a magnetic field guide. [Figure 2] 2A-2C show various embodiments of the metal sheet according to FIG. [Figure 3] 3 shows a further embodiment of the metal sheet according to FIG. 1 or 2; [Figure 4] 1 shows an embodiment with vertically positioned sensors. DETAILED DESCRIPTION OF THE INVENTION

[0027] FIG. 1 shows an embodiment 100 of a torque sensor according to the present invention.

[0028] The torque sensor 100 according to the present invention comprises a shaft 10 having a first magnetized region 11 which generates a first magnetic field B1 in response to torque applied to the shaft 10, a first magnetic field sensor 21 for detecting the first magnetic field B1, the first magnetic field sensor 21 being designed to output a signal in response to the strength of the first magnetic field B1 at the position of the first magnetic field sensor 21, and first magnetic field guiding devices 31, 32 for guiding the first magnetic field B1 to the position of the first magnetic field sensor 21.

[0029] The torque sensor 100 further comprises a second magnetized region 12 that generates a second magnetic field B2 in response to torque applied to the shaft 10, the magnetization of the second magnetized region 12 being opposite to the magnetization of the first magnetized region 11. The magnetizations are imprinted in opposite circumferential directions on the shaft 10 by pre-magnetization. A second magnetic field sensor 22 is provided for detecting the second magnetic field B2 and is configured to output a signal corresponding to the strength of the second magnetic field B2 at the location of the second magnetic field sensor 22. Second magnetic field guiding devices 33, 34 guide the second magnetic field B2 to the location of the second magnetic field sensor 22.

[0030] The first and second magnetic field sensors are disposed on a printed circuit board 40 .

[0031] The first magnetic field guiding devices 31, 32 comprise a first magnetic field guiding element 31 and a second magnetic field guiding element 32. The second magnetic field guiding devices 33, 34 comprise a third magnetic field guiding element 33 and a fourth magnetic field guiding element 34.

[0032] The magnetic field guiding elements are formed as metal sheets 31, 32, 33, 34.

[0033] FIG. 2 shows various embodiments of the metal sheet according to FIG.

[0034] The metal sheets can be formed in one plane (first figure) or can be tilted downwards (second figure) or upwards (third figure) at the sensors 21, 22.

[0035] In the fourth figure, the second and third metal sheets 32, 33 are integrally formed from above.

[0036] In the fifth figure, the second and third metal sheets 32, 33 are formed only in a plane perpendicular to the printed circuit board.

[0037] FIG. 3 shows a further embodiment of the metal sheet according to FIG. 1 or FIG.

[0038] In the upper illustration, the metal sheets 31, 32, 33, 34 are rectangular in the plane of the sheets, and in the lower illustration they are wedge-shaped in the direction of the sensors 21, 22, which causes the magnetic field (or magnetic field lines) to be more strongly concentrated at the sensors 21, 22.

[0039] FIG. 4 shows an embodiment with vertically arranged sensors.

[0040] In this arrangement of sensors 21, 22 on PCB 40, the magnetic field lines can also be guided through metal sheets 31, 32, 33, 34 to improve the signal.

[0041] The illustrated embodiments are merely exemplary, the full scope of the invention being defined by the claims.

Claims

1. a shaft having a first magnetized region, the first magnetized region generating a first magnetic field in response to torque applied to the shaft; a first magnetic field sensor for detecting the first magnetic field, the first magnetic field sensor adapted to output a signal in response to a strength of the first magnetic field at a location of the first magnetic field sensor; a first magnetic field guiding device for guiding the first magnetic field to the position of the first magnetic field sensor; A torque sensor comprising:

2. a second magnetized region that generates a second magnetic field in response to torque applied to the shaft, the magnetization of the second magnetized region being opposite to the magnetization of the first magnetized region; a second magnetic field sensor for detecting the second magnetic field, the second magnetic field sensor adapted to output a signal in response to a strength of the second magnetic field at a location of the second magnetic field sensor; a second magnetic field guiding device for guiding the second magnetic field to the position of the second magnetic field sensor; The torque sensor of claim 1 further comprising:

3. 3. The torque sensor according to claim 1, wherein the first magnetic field guiding device comprises first and second magnetic field guiding elements, the first and second magnetic field guiding elements being arranged on different sides, in particular opposite sides, of the first magnetic field sensor.

4. 4. The torque sensor according to claim 3, wherein the second magnetic field guiding device comprises third and fourth magnetic field guiding elements, the third and fourth magnetic field guiding elements being respectively arranged on different, in particular opposite, sides of the second magnetic field sensor.

5. The torque sensor according to claim 4 , wherein the second and third magnetic field guiding elements are disposed between and integrally formed with the first and second magnetic field sensors.

6. The torque sensor of claim 3 , wherein each of the magnetic field guiding elements comprises a metal sheet.

7. 7. The torque sensor of claim 6, wherein each metal sheet is formed flat or an end section of each metal sheet adjacent the first magnetic field sensor is formed at an angle.

8. 7. The torque sensor of claim 6, wherein each of the metal sheets is rectangular in the plane of the metal sheet or tapered towards the magnetic field sensor.

9. 3. The torque sensor according to claim 1 or 2, wherein the material of the first or first and / or second magnetic field guiding device comprises a soft magnetic or paramagnetic material.

10. 10. The torque sensor of claim 9, wherein the material of the first or first and / or second magnetic field guiding device comprises a metal or ceramic material or a plastic material with magnetizable metal particles.

11. 3. The torque sensor according to claim 1 or 2, wherein the first and / or the second magnetic field sensor comprises one or more coils or one or more sensors based on the magnetoresistive effect, in particular AMR, CMR, GMR, TMR sensors or one or more sensors based on the planar Hall effect.

12. 3. The torque sensor according to claim 1, wherein the first and / or the second magnetic field sensor is arranged on a printed circuit board.

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