JP2748044B2 - Magnetic torque sensor and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic torque sensor suitable for use in detecting torque under high load and high temperature conditions such as construction machines and machine tools, and a method for manufacturing the same. In particular, the present invention relates to adjustment of impedance balance of a plurality of coils used in the magnetic torque sensor.

[Problems to be solved by conventional technology and invention]

Japanese Patent Application Laid-Open No. 1-170823 discloses a magnetic torque sensor that detects a shaft torque by utilizing the magnetostriction characteristics of a ferromagnetic material.

In this prior art, for example, as shown in FIG. 3, magnetically anisotropic parts 2, 3 are formed on a measured shaft 1 made of a magnetic metal or the like having a magnetostrictive effect. The magnetic anisotropic part 2 has a left-handed helical magnetic anisotropy, and the magnetically anisotropic part 3 has a right-handed helical magnetic anisotropy. When a torque is applied to the shaft 1, the isotropic portions 2 and 3 change their magnetic permeability in these portions more than in other portions.

Around such an axis 1, four detection coils L1,
L2, L3, and L4 are provided around the coil. In particular, the coils L2 and L3 are provided around the magnetic anisotropic parts 2 and 3, respectively, and these coils L2 and L3 function for torque detection. Other coil
L1 and L4 function as temperature compensating coils for compensating for temperature variations in the axial direction of the shaft 1.

In such a configuration, the torque generated on the shaft 1 is measured using, for example, a bridge circuit as shown in FIG. That is, in this case, the impedances of the coils L2 and L3 are set equal, the impedances of the coils L1 and L4 are set equal, and the impedance of the coils L1 and L4 is a / b of the impedance of the coils L2 and L3. It is set to double (a and b are the distances between the coils shown in FIG. 3).

In such a configuration, when the AC power supply 4 is applied,
When no torque is applied to shaft 1, torque measurement circuit 4
However, when the torque in the direction of arrow A is applied to the shaft 1, the impedance of the coil L2 increases and the impedance of the coil L3 decreases. The signal of the specified magnitude is input. Conversely, when a torque is applied to the shaft 1 in the direction of arrow B, the torque measurement circuit 4
, A signal having a negative value corresponding to the torque is input. Therefore, the torque measuring circuit 4 can detect the torque generated on the shaft 1 by measuring the output of the bridge circuit.

By the way, in such a torque sensor, since the input signal to the torque measuring circuit 4 changes only at a very small level, it is necessary to first accurately balance the impedance of each coil. Each coil was wound by hand with extreme care in order to remove the coil. That is, in the prior art, as shown in FIG. 5, the coils L1 to L4 are carefully wound around the hollow bobbin 5 integrally formed with the plurality of yoke portions 6 so that the coils L1 to L4 are not always unevenly wound with the same tension. Since the winding balance is used to balance the bridge, there is a problem that the accuracy is not improved yet, and there is no mass productivity, the cost is high, and the yield is poor. The bobbin 5 detects the torque of the shaft 1 to be measured by being fitted to the shaft 1 to be measured.

[Problems to be solved by the invention]

The present invention has been made in view of such circumstances,
The coil balance can be easily adjusted accurately,
It is an object of the present invention to provide a magnetic torque sensor that improves mass productivity and a method for manufacturing the same.

[Means and actions for solving the problem]

According to the present invention, the torque is detected by providing a plurality of coils around the axis of the ferromagnetic material along the axial direction and detecting magnetic distortion of the axis due to torsional torque applied to the axis by the plurality of coils. Magnetic torque sensor,
Shield rings are provided on both sides of the coil so as to sandwich the plurality of coils, respectively, and the impedance of the coils is balanced by adjusting the electromagnetic characteristics of the shield rings.

That is, in the magnetic torque sensor of the present invention, the electromagnetic properties such as the magnetic permeability of the shield rings disposed on both sides of each coil are changed by, for example, changing the material, material, surface roughness, shape, and number of plates of the shield rings. Adjust to balance the coil.

Further, in the present invention, a plurality of coils are provided around the axis of the ferromagnetic material along the axial direction, and the magnetic distortion of the axis due to a torsional torque applied to the axis is detected by the plurality of coils to reduce the torque. In the method of manufacturing a magnetic torque sensor for detecting, a step of preparing a plurality of shield rings made of the plurality of coils and the ferromagnetic material in advance, and alternately forming the plurality of coils and the plurality of shield rings on a hollow bobbin. A magnetic torque sensor is manufactured by a mounting step and a step of adjusting the electromagnetic characteristics of the plurality of shield rings to balance the impedance of the coil.

That is, according to the manufacturing method, a plurality of coils and a plurality of shield rings are prepared in advance, and the plurality of coils and the plurality of shield rings are mounted on a hollow bobbin to manufacture a magnetic torque sensor. Then, a shield ring whose electric and magnetic properties are adjusted before the mounting step is prepared, or the impedance of the coil is balanced by adjusting the electric and magnetic properties of the shield ring after the mounting step. To Of course, it is possible to achieve the balance up to this point, but in some cases, the final adjustment of the coil can be easily analogized from this patent.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of a magnetic torque sensor according to the present invention.
To detect the torque of the shaft 1 to be measured. In this embodiment, four coils are used for temperature compensation. In this magnetic torque sensor, even if temperature compensation is not performed, at least two coils are required to know the direction of torque, and the measurement sensitivity can be improved by increasing the number of coils.

In FIG. 1, ring-shaped shield rings (yoke) Y1 to Y4 made of Fe—Ni alloy or the like are provided on the left and right of coils L1 to L4.
Y5 is provided. These shield rings Y1 to Y5 are intended to reduce the loss in the magnetic circuit and improve the detection sensitivity, but in this device,
The coils are balanced by slightly changing the electro-magnetic characteristics such as the magnetic permeability of the yokes Y1 to Y5. That is, in the present apparatus, the coil balance is achieved by changing the electromagnetic characteristics of the yokes Y1 to Y5 instead of the conventional winding method of the coil. These coils L1 to L4 and shield rings Y1 to Y5 are made of Fe-Ni
It is covered with an outer shield body 10 made of an alloy or the like to improve detection characteristics.

Hereinafter, the manufacturing process of the magnetic torque sensor and the adjustment of the coil balance will be described with reference to FIG.

First, the coils L1 to L4 used for the magnetic torque sensor,
The shield rings Y1 to Y5 and the bobbin 20 are created before combining them.

A fusion coil is used for the coils L1 to L4, and the fusion coil is wound by a required number of turns using a high-precision automatic winding machine. The coils L1 to L4 shown in FIG.

On the other hand, a large number of shield rings Y1 to Y5 in which electric and magnetic properties such as magnetic permeability are slightly changed are prepared in advance (see FIG.
Figure (a). Here, this point is a big difference from the conventional one.However, the shield rings Y1 to Y5 are not integrally formed with the bobbin 20 for winding the coils L1 to L4. Y1 to Y5 and the bobbin 20 are configured separately.

The parameters that change the electromagnetic characteristics of the shield rings Y1 to Y5 include the following.

Change the material (composition).

Materials to change include silicon steel, mild steel, permalloy, and the like.

Change the material (heat treatment).

 Change the way of tempering and quenching.

Change the surface roughness.

Change the shape.

Change the shape of the shield ring to a circle, square, polygon, or any other shape.

The number of plates constituting one shield ring is changed.

One shield ring composed of one plate, 2
Various kinds are prepared, such as a laminate of three plates and a laminate of 3 to n plates, and an appropriate one is used. However, no matter how many plates constitute one shield ring, the thickness itself of one shield ring does not change.

The above method is common in that the AC permeability is changed by changing the volume in which the magnetic flux enters the shield ring.

In the present embodiment, any one of the above methods is selected, or the above methods are appropriately combined to change the electromagnetic characteristics of the shield ring. Prepare a large number of shield rings, each of which is slightly changed.

In other words, by arranging a number of shield rings having the same magnetic permeability, a number of shield rings having slightly different magnetic permeability are prepared in advance, and an appropriate shield ring is appropriately selected from these during assembly. Try to balance the coil.

Further, the coils L1 to L4 and the shield rings Y1 to
A hollow bobbin 20 made of nonmagnetic Teflon or the like to which Y5 is to be mounted is also prepared in advance (FIG. 2 (a)).

When these preparations are completed, the coils L1 to L4 and the appropriately selected shield rings Y1 to Y5 are alternately and sequentially inserted into the bobbin 20, as shown in FIG. 2 (b), and as shown in FIG. 2 (c). A magnetic torque sensor having such four coils L1 to L4 and five shield rings Y1 to Y5 provided around the bobbin 20 is created.

When the above steps are completed, for example, the impedance balance of the coil is checked with an LCR tester or the like shown in FIG. 4, and if the balance is not obtained, the shield rings Y1 to Y5 are appropriately replaced to thereby adjust the coil balance. Make adjustments.

When this adjustment is completed, the coils L1 to L4 and the shield ring are connected by the external yoke 10 as shown in FIG.
The magnetic torque sensor is completed by coating Y1 to Y5. The magnetic torque sensor thus produced is provided around the shaft 1 to be measured, on which the magnetic anisotropic portion is appropriately formed, and detects the torque.

In the magnetic torque sensor of the present invention, the number of coils is not limited to four, but may be at least two as described above, and an arbitrary number of two or more may be selected. Further, the connection mode of the bridge circuit formed by each coil of the magnetic torque sensor is not limited to that shown in FIG. 4, and any connection may be made. Further, the output of each coil of the magnetic torque sensor may be extracted by a differential amplifier instead of a bridge circuit to detect the torque. In the embodiment, the measured shaft 1 is made of a ferromagnetic material. However, a magnetostrictive material such as an amorphous material is applied to the surface of the measured shaft 1 made of a ferromagnetic material or a non-ferromagnetic material. You may make it stick. Also,
The shield ring may also be configured by covering or sandwiching a nonmagnetic material with a ferromagnetic material.

Further, in FIG. 4, each coil is operated by combining both functions of the excitation coil and the detection coil. However, the excitation coil and the detection coil are separately provided.
For example, two detection coils may be wound on the excitation coil. Also in this case, a shield ring is provided between the two detection coils, and the coil balance in which the electromagnetic characteristics of the shield ring are adjusted is achieved.

〔The invention's effect〕

As described above, according to the present invention, the coil balance is adjusted by appropriately adjusting the electromagnetic characteristics of the shield ring as the magnetic shield body disposed on both sides of each coil, so that the adjustment work can be easily performed. At the same time, mass productivity is improved.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, FIG. 2 is a view for explaining a manufacturing process of the magnetic torque sensor of the present invention, FIG. 3 is a view for explaining the principle of the magnetic torque sensor, and FIG. FIG. 5 is a diagram showing the structure of a conventional magnetic torque sensor. 1 ... Axes to be measured, 2, 3 ... Magnetic anisotropic parts L1-L4 ... Coils, Y1-Y5 ... Shield rings, 10 ...
Outer shield body 20 bobbin

Claims (2)

(57) [Claims] 1. A plurality of coils are provided around an axis having a surface on which a ferromagnetic material or a magnetostrictive material is disposed, and a plurality of coils are provided along an axial direction, and magnetostriction of the axis caused by torsion torque applied to the axis is controlled by the plurality of coils. In a magnetic torque sensor that detects the torque by detecting, a shield ring is disposed on both sides of the coil so as to sandwich the plurality of coils, and the impedance of the coil is adjusted by adjusting the electromagnetic characteristics of these shield rings. A magnetic torque sensor having a balance. 2. A plurality of coils are provided around an axis of a ferromagnetic material along an axial direction, and a magnetic distortion of the axis due to a torsional torque applied to the axis is detected by the plurality of coils to reduce the torque. In the method of manufacturing a magnetic torque sensor for detecting, a step of previously forming the plurality of coils and a plurality of shield rings mainly made of a ferromagnetic material; and alternately forming the plurality of coils and the plurality of shield rings thus formed on a hollow bobbin. A method of manufacturing a magnetic torque sensor, comprising: a step of mounting; and a step of adjusting the electromagnetic properties of the plurality of shield rings to balance the impedance of the coil.