KR20080043007A - Solenoid magnetometer - Google Patents

Abstract

A solenoid magnetometer is provided to measure a magnetic field generated by a torque transducer element, by using bobbin and common coil winding schemes. A solenoid magnetometer includes at least one inner coil, at least one outer coil, and at least one magnetic strip(42). The inner coils are arranged around an axis. The outer coils are concentrically arranged around the inner coils. The magnetic strips are arranged to be parallel to the axis between the inner and outer coils. A first inner coil(34) and a first outer coil(36) are concentrically arranged and electrically contacted to each other. A second inner coil(38) and a second outer coil(40) are concentrically arranged and electrically contacted to each other.

Description

Solenoid Magnetic Meter {SOLENOID MAGNETOMETER}

1 is a partial cutaway view of a portion of an exemplary torque sensor in accordance with the present invention.

2 is a perspective view of an exemplary magnetic meter in accordance with the present invention.

3 is a schematic cross-sectional view of an exemplary magnetic meter in accordance with the present invention.

* Description of the symbols for the main parts of the drawings *

10: torque detector assembly 12: torque transducer element

14: shaft 18: shaft

21, 23: upper and lower shaft portion 22: magnetic meter

24: bobbin 28: intermediate flange

32: notch 42: magnetic strip

34, 38, 36, 40: internal and external coils

The present invention relates generally to magnetic sensors for torque sensors. In particular, the invention relates to a magnetometer comprising several coils arranged in association with each other for measuring branch magnetic fields associated with torque.

Conventional torque detectors include a torque transducer element that responds to the application of torque by generating a magnetic field. The generated or changed magnetic fields are detected by a magnetometer. The torque transducer element typically includes a magnetoelastic material that responds to the application of torque by creating a magnetic field. Applying torque to the magnetoelastic material creates shear stress stresses in the magnetization regions such that the direction of the magnetic field generated by the torque transducer element moves substantially from the circumferential direction to the helical direction. The helical movement of the magnetic field is detected as an axial component of the magnetic field. The axial component of the magnetic field is proportional to the torque applied and provides an accurate and reliable indication of the torque applied to the torque element.

The detection of the axial components of the magnetic field and in particular the magnetic field distortion generated by the torque is achieved through the use of magnetic field detectors. Commonly used magnetic field detectors are flux gate detectors, which are manufactured as fine wire coils surrounding a core of magnetically saturable material and are supplied with alternating current. Alternating current provides periodic magnetic saturation of the magnetic elements. The magnetic field formed by the torque transducer movement is superimposed on the periodic magnetic field generated by the coils. Superposition of the magnetic field generated by the torque transducer movement creates asymmetry upon magnetic saturation of the coils. Inductance changes in the coils due to magnetic saturation generate a voltage induced in the coils. This voltage is measured to determine the torque amplitude and direction applied to the torque transducer element.

Known prior art magnetic field detectors include bobbins having an upper axis section and a lower axis section provided by a central flange. The upper and lower coils are insulated from each other and alternating current is induced to form a magnetic field. Magnetically saturable strips are disposed between the coil and the torque transducer element. These magnetic strips are magnetically saturated by alternating currents formed in the coils. The magnetic strips are arranged parallel to the shaft and the axis of rotation. Magnetic strips are made of a material having very rapid magnetic saturation properties, which means that the magnetic strips can be rapidly saturated in the presence of the magnetic field and quickly demagnetize in the absence of the magnetic field.

Undesirably, prior art magnetic field detectors require a precise arrangement to remove the distortion caused by impinging the magnetic fields. The constant and precise arrangement required increases cost and complexity and reduces the durability and reliability of the torque detector.

Accordingly, it is an object of the present invention to design and develop an easy to produce, durable and precise magnetic field detector that can be used in torque transducer elements having a shaft supporting a magnetoelastic material.

An exemplary magnetometer according to the invention comprises first and second internal coils supported on a common bobbin and connected to the first and second external coils. There are a number of magnetic strips between the inner and outer coils. Magnetic strips are alternately magnetized and demagnetized to form a magnetic field used to measure the distortion generated by the torque applied to the torque transducer element.

The magnetometer assembly according to the invention comprises a bobbin divided into an upper shaft portion and a lower shaft portion. The upper and lower shaft portions are divided by an intermediate flange. Each shaft portion includes an inner coil and an outer coil. The inner and outer coils are electrically connected. The inner and outer coils are wound in a correspondingly opposite direction and form magnetic fields of equal magnitude.

There are a number of magnetic streams between the inner and outer coils. Each magnetic strip includes a very large length to diameter ratio that is magnetically saturable and extends axially the length of the upper and lower coils. The intermediate flange includes a corresponding plurality of notches, allowing the magnetic strips to extend over the entire length of the bobbin.

The magnetic field is formed by applying alternating energy to the coils to periodically saturate the magnetic strips at the positive and negative peaks of the alternating current waveform. When torque is applied to the torque transducer element, a branching magnetic field is created. The branch magnetic field is superimposed on the magnetic strips in different ways in the upper and lower portions of the magnetometer assembly. Each of the upper and lower coils is in electrical communication with a central node. The voltage at the central node is observed and indicates the magnitude and amplitude difference of the magnetic field between the upper and lower coils, which in turn indicate the torque applied to the shaft.

Thus, the magnetometer of the present invention simply, efficiently and economically senses the magnetic fields formed by the torque transducer elements of the bobbin assembly which are simple and economical.

These and other features of the present invention can be best understood from the following specification and drawings, and the following summary.

Referring to FIG. 1, a torque sensor assembly 10 according to the invention comprises a torque transducer element 12 shown and supporting a magnetoelastic ring 16. The torque transducer element 12 includes a shaft 14 supporting the magnetoelastic ring 16. The torque transducer element 12 is rotatable about an axis 18. The torque in the torque transducer element 12 is transmitted to the magnetoelastic ring 16. The magnetoelastic ring 16 has a magnetic field along the circumferential magnet in the direction indicated by arrow 20 when in the default non-torque condition.

The torque detector assembly 10 includes a magnetometer 22. The magnetometer 22 includes a bobbin 24 having an upper shaft portion 21 and a lower shaft portion 23 separated by an intermediate flange 28. Each of the upper and lower portions 21, 23 includes an inner coil and an outer coil. The upper portion 21 includes an inner coil 34 and an outer coil 36. The lower portion 23 includes an inner coil 38 and an outer coil 40. The inner coils 34 and 38 are electrically connected to the central node 50 (FIG. 3). In addition, each of the inner coils 34, 38 is electrically connected to the outer coils 36, 40. A plurality of axial magnetic strips 42 are disposed between each of the inner coils 34, 38 and the outer coils 36, 40.

Magnetic strips 42 are disposed axially along the length of the bobbin 24. Magnetic strips 42 are preferably wires or streams with a very large length to diameter ratio.

The inner coils 34 and 38 form a magnetic field opposite the magnetic field formed by the outer coils 36 and 40 upon the provision of an alternating current. The oppositely formed magnetic fields of the inner coils 34 and 38 and the outer coils 36 and 40 provide a desired low inductance that cannot be generated in the individual coils.

Each of the inner coils 34, 38 and the outer coils 36, 40 is wound using approximately 200 turns of magnetic wire. The specific size of the magnetic wire and the number of turns used to form the coil are specifically applied and those skilled in the art understand how to size the coil to provide the desired magnetic properties for the particular application. In the embodiment shown in FIG. 1, each of the inner and outer coils 34, 38, 36, 40 has approximately 200 windings. In addition, the internal coils 34, 38 are disposed radially adjacent to the shaft 14 of the transducer element 12. Positioning the internal coils 34, 38 in close relationship with the torque transducer element 12 to provide the desired accuracy and detection of any magnetic field distortion formed by the torque applied to the torque transducer element 12. It is preferable.

In addition, no matter how many turns are provided to form and configure the respective inner coils 34, 38 and the outer coils 36, 40, each coil will have the same number of turns. The advantage of this construction means is that the use of a single bobbin to support the same number of turns and turns reduces complexity and increases durability.

Referring to FIG. 2, the magnetometer assembly 22 includes a plurality of magnetic strips 42 that are shown in perspective without the torque transducer 12 and are arranged equally at an angle about the bobbin 24. The same angular distribution of the magnetic strips provides uniform magnetic saturation for each of the magnetic strips 42. This same angular distribution is produced by a corresponding number of identical angular distribution notches 32 in the intermediate flange 28. As will be appreciated, the specific number and spacing of magnetic strips 42 is a sensitivity issue. The number of magnetic strips 42 provides a desired sensitivity alignment means that can be adjusted by varying the number and spacing between each of the magnetic strips 42.

2 shows the same angular distribution and spacing between the respective magnetic strips 42. The spacing between the magnetic strips 42 is represented by radial lengths 44 arranged such that the respective magnetic strips 42 are disposed parallel to the axis 18.

Referring to FIG. 3, the magnetometer assembly 22 is schematically shown in cross section to illustrate the relationship to the various electrical connections between the coils and the magnetic strips 42 disposed between the coils. With reference to the upper portion 21 of the bobbin 26, the inner coil assembly 34 is electrically connected to the outer coil assembly 36. However, each of the inner coil assemblies 34 and outer coil assemblies 36 is wound to form magnetic fields in opposite directions. In addition, each of the upper coil assemblies 34, 36 is formed with exactly the same number of windings to form magnetic fields of the same size.

With reference to the lower portion 23 of the magnetometer assembly 22, the lower inner coil assembly 38 is electrically connected to the outer coil assembly 40. The electrical connections are shown as node 48. Again, inner coil 38 and outer coil 40 are manufactured using wires of the same size and grade with the same number of turns. The inner coil 38 and outer coil 40 form the same but opposite magnetic field.

Magnetic strips 42 are disposed between the inner and outer coil assemblies 34, 38, 36, 40 of both the upper portion 21 and the lower portion 23 of the magnetometer assembly 22.

Coils 34, 36, 38, 40 are attached to an alternating current source, indicated at 52. The alternating current source 52 provides the alternating current used to form the periodic saturation of the magnetic strips 42. Alternating current is formed by the application of a square wave voltage to form positive and negative peaks in which the magnetic strips 42 are magnetically saturated.

1 and 3, in operation, the coils 34, 36, 38, 40 generate a magnetic field superimposed with the magnetic field generated by the torque transducer element 12. The magnetic field generated by the torque transducer element 12 will naturally diverge and be detected differently in the other axial portions of the magnetic strips 28. When the magnetic fields in the upper and lower portions 21, 23 of the magnetometer 22 are identical; Another saturation of the magnetic strips 42 in the upper and lower portions 21, 23 of the magnetometer assembly 22 will be detected as one voltage at the common node 50.

Thus, at the common node or connection point 50 between the upper and lower portions 21, 23 of the magnetometer assembly 22, a pulse voltage wave shape with a frequency different from that used to drive the coils can be detected. will be. The phase and amplitude of the voltage signal generated and detected at node 50 indicates and is related to the amplitude and direction of the branched magnetic field and thus to the torque applied to the torque transducer element 12.

Thus, in operation, each of the coils 34, 36, 38, 40 is excited by alternating current at a magnitude that produces saturation of the magnetic strips 42. Each of the magnetic strips 42 is magnetically saturated at the positive and negative peaks of the alternating current waveform. When torque is applied to the torque transducer element 12, the branched magnetic field by the magnetoelastic ring 16 overlaps the magnetic field formed in the magnetic strips 42. The overlapping addition of the magnetic field on the magnetically saturated strips 42 forms an asymmetry of magnetic saturation between the upper and lower portions 21, 23 of the magnetometer 22. The voltage waveform formed by the asymmetry can be observed at the common node 50 and will even include even harmonics. Even harmonics of the voltage waveform include frequency and phase in addition to the characteristics used equally to determine the magnitude of the magnetic field, and thus the torque provided to the transducer element 12.

Accordingly, the magnetometer 22 developed and described in the present invention provides accurate and durable measurement of the magnetic field formed by the torque transducer element 12 using bobbin and common coil winding techniques.

Although preferred embodiments of the invention have been described, those skilled in the art will recognize that certain variations are within the scope of the invention. For this reason, the following claims should be considered to determine the true scope and content of this invention.

The magnetic field detector of the present invention is easy to produce, durable and precise for use in torque transducer elements having a shaft supporting a magnetoelastic material.

Claims (14)

As a magnetometer assembly, One or more internal coils disposed about an axis; At least one outer coil disposed coaxially about the at least one inner coil; And One or more magnetic strips disposed parallel to the axis between the one or more inner coils and the one or more outer coils, Magnetometer assembly. 2. The apparatus of claim 1, further comprising: a first inner coil and a first outer coil coaxially disposed and electrically connected to each other, and a second inner coil, and a coaxially disposed and electrically connected to the second inner coil. Including two external coils, Magnetometer assembly. The bobbin according to claim 2, wherein the first inner coil, the first outer coil, the second inner coil and the second outer coil include a bobbin wound thereon. Magnetometer assembly. 4. The apparatus of claim 3, comprising a separate axial compartment separating the first inner and outer coils from the second inner and outer coils. Magnetometer assembly. The method of claim 1, wherein the magnetic strip comprises a wire having a length greater than the cross-sectional area, Magnetometer assembly. The magnetic coil of claim 1, wherein the inner and outer coils are provided to coaxially surround a magnetic region of the magnetoelastic device. Magnetometer assembly. A magnetoelastic torque detector assembly A torque element supporting a magnetoelastic material; And A magnetometer comprising at least one inner coil electrically coupled to at least one outer coil and a magnetic strip disposed between the at least one inner coil and the at least one outer coil, Magnetoelastic torque detector assembly. 8. The magnetic meter of claim 7, wherein the magnetometer includes a second inner and outer coil disposed axially with respect to the first inner and outer coil and the torque element, and the first inner and outer coil and the second inner and outer coils. Comprising a plurality of magnetic strips disposed between the outer coil, Magnetoelastic torque detector assembly. 9. The apparatus of claim 8, comprising bobbins supporting the first inner and outer coils and the second inner and outer coils, the bobbin shafting the first inner and outer coils from the second inner and outer coils. Including the middle flange separating in the direction, Magnetoelastic torque detector assembly. 10. The method of claim 9, wherein the intermediate flange comprises a plurality of angularly spaced notches, the corresponding plurality of magnetic strips extending axially. Magnetoelastic torque detector assembly. 8. The magnetic strip of claim 7 wherein the magnetic strip comprises a wire. Magnetoelastic torque detector assembly. The torque sensor detects torque. a) applying alternating current to the first inner and outer coils and the second inner and outer coils, the second inner and outer coils being disposed in parallel with the axis of the torque element between the inner and outer coils; Spaced axially at a determined level to form a saturated magnetic field in the strip; And Detecting a distortion of a magnetic field generated in the magnetic strip indicating a torque applied to the torque element, Torque sensing method. 13. The method of claim 12, comprising observing a voltage on a waveform indicating torque applied at a common node between the first inner and outer coils and the second inner and outer coils. Torque sensing method. The method of claim 13, wherein the voltage waveform comprises a frequency and an amplitude indicating the magnitude of the magnetic field generated by the torque applied to the torque element. Torque sensing method.

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