JP2697842B2 - Torque sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the invention]

(Industrial application field) The present invention relates to a magnetostrictive torque sensor used for detecting a torque applied to a shaft to be measured. (Prior art) Conventionally, as this type of magnetostrictive torque sensor,
For example, there is a structure shown in FIG. The magnetostrictive torque sensor 21 shown in FIG. 4 has a gap 23 between the measured shaft 22 and the outer periphery of the measured shaft 22 made of a magnetic material having a magnetostrictive effect. Yoke 24 made of high permeability material of
In the yoke 24, an exciting coil 25 as exciting means for forming a magnetic circuit in which the measured shaft 22 is part of a magnetic path,
It has a structure provided with a detection coil 26 as detection means for detecting a magnetostrictive component passing through the shaft 22 to be measured. In the magnetostrictive torque sensor 21 having such a structure, when the excitation coil 25 is energized, the magnetic flux emitted from the excitation coil 25 causes the measured magnetic flux 22 → the gap 23 → the yoke 24 →
A magnetic circuit is formed that passes from the gap 23 to the shaft 22 to be measured. At this time, an induced electromotive force is generated in the detection coil 26. In the state where the induced electromotive force is generated, when a torsional torque is applied to the measured shaft 22, the magnetic permeability of the measured shaft 22 itself changes due to the magnetostrictive effect of the measured shaft 22. Since a change occurs in the magnetic flux density and the induced electromotive force generated in the detection coil 26 due to self-induction changes, by detecting the change in the induced electromotive force, the torsional torque applied to the measured shaft 22 is detected. be able to. (Problems to be Solved by the Invention) However, in the magnetostrictive torque sensor 21 having the structure as shown in FIG. 4, a normal mechanical structural steel (JIS SC, SCr, SCM, SNCM, etc.) is used as the shaft 22 to be measured. ), There is a problem that the detection amount of the magnetostriction effect is small and sufficient detection sensitivity cannot be obtained. (Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and aims to solve the above problems by providing a torque sensor capable of obtaining a sufficient detection sensitivity. And

Configuration of the Invention

(Means for Solving the Problems) The present invention detects an axis to be measured, exciting means for forming a magnetic circuit having the axis to be measured as a part of a magnetic path, and detecting a magnetostrictive component passing through the axis to be measured. In a torque sensor provided with a detecting means for detecting, at least a part of the shaft to be measured, in particular, a part or the whole forming the magnetic path, contains Al by 1% by weight.
1.0 to 15.0%, C is 0.01 to 0.50%, Cr, M
One or two selected from o, W, V, Nb, Ta, Ti, Zr, Hf
B, Si, Ge, Sn, Pb, P,
Fe containing one or more elements selected from Sb, Cu, Ni, Co, Mn, Be, Sc, Y, and rare earth elements in a total amount of 0.01 to 5.0%, with the balance being substantially Fe -It is characterized by using an Al alloy as a material. As described above, a torque sensor according to the present invention detects an axis to be measured, an exciting unit that forms a magnetic circuit having the axis to be measured as a part of a magnetic path, and detects a magnetostrictive component generated in the axis to be measured. In this case, for example, the exciting means and the detecting means can be constituted by separate coils, that is, an exciting coil and a detecting coil, or a common coil. It is also possible to adopt a configuration in which a change in inductance due to a change in magnetic permeability of the coil is detected. Further, the measured shaft may be formed with a concavo-convex portion forming a predetermined angle with respect to the axial direction thereof so as to impart a shape with magnetic anisotropy. The present invention is not limited to this, and various other configurations can be adopted. In the magnetostrictive torque sensor according to the present invention, at least a part of the shaft to be measured, in particular, a portion forming a magnetic path, or the entirety of the shaft to be measured is made of a Fe-Al alloy having the above-described specific component. The reason for limiting the component composition (% by weight) will be described below. Al: 11.0 to 15.0% Al has a feature of enhancing the magnetostriction effect of the axis to be measured, enhancing the detection sensitivity of the magnetostrictive component, and reducing the hysteresis. However, if the amount of Al is too large, the toughness is reduced, and when the power transmission shaft itself is used as the shaft to be measured, there is a problem of strength, and processing such as forging and cutting becomes difficult. , And the detection sensitivity of the magnetostrictive component decreases, and the hysteresis also increases. Conversely, if the Al content is too small, the detection sensitivity of the magnetostrictive component is lowered, and the problem that the hysteresis increases further occurs.
The range was 15.0%. B, Si, Ge, Sn, Pb, P, Sb, Cu, Ni, Co, Mn, Cr, Mo, W, V, Nb, Ta, Ti,
Zr, Hf, Be, Sc, Y, one or more of the rare earth elements selected in total: 0.01 to 5.0% These elements act as deoxidizing and desulfurizing agents during melting, In addition, it forms a solid solution with Fe-Al-based alloys to increase strength, improve strength by precipitation hardening, promote crystal grain refinement, improve toughness, and improve C, W, Cr, etc. It is an element that is effective for suppressing diffusion movement and improving malleability, but if it is too much, it reduces workability, reduces toughness, and lowers the sensitivity of detecting magnetostrictive components, resulting in hysteresis. Therefore, one or more of these elements are limited to 0.01 to 5.0% or less in total because of problems such as an increase in the number of elements. C: 0.01 to 0.50% and a total of one or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, and Hf: 0.01 to 5.0
% C and Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf form carbides and disperse in the dough to form a power transmission system such as a drive shaft or a column shaft. It is an element effective for securing the strength required as a shaft structure of the above, and it is desirable to include it in a Fe-Al-based alloy as necessary. However, if the content is too large, the workability is adversely affected. Therefore, C is 0.01 to 0.50% and Cr, Mo, W,
The total of one or more selected from V, Nb, Ta, Ti, Zr, and Hf is preferably in the range of 0.01 to 5.0%. (Embodiment) FIG. 1 shows a torque sensor according to an embodiment of the present invention. The torque sensor 1 shown in the figure uses a shaft 2 to be measured which is entirely made of an Fe-Al alloy having a composition shown in Table 1 below, and the surface of the shaft 2 to be measured is The concave portions 3a, 3b and the convex portions 4a, which make a predetermined angle with respect to the axial direction of the shaft 2,
4b are formed integrally with the shaft to be measured 2 at an appropriate interval, and the concave portions 3a and 3b and the convex portions 4a and 4b have a shape magnetic anisotropy. In this case, the one concave portion 3a and the convex portion 4a and the other concave portion 3b and the convex portion 4b have the same inclination angle (for example, 45 ° in this embodiment) with respect to the axial direction and are mutually opposite. They are provided as a pair in a state inclined in the opposite direction. In addition, the torque sensor 1 faces the concave portion 3a and the convex portion 4a formed on the measured shaft 2 and the concave portion 3b and the convex portion 4b formed on the measured shaft 2 in addition to the shaft 2 to be measured. And a pair of coils 5a and 5b arranged
A cylindrical yoke 7 made of a material having a high magnetic permeability is provided outside the a and 5b and with a gap 6 between the shaft 2 to be measured and the shaft 2 to be measured. In this case, the coils 5a and 5b are used in common for excitation means for forming a magnetic circuit with the measured shaft 2 as a part of a magnetic path and for detecting means for detecting a magnetostrictive component passing through the measured shaft 2. It is something to be done. In the torque sensor 1 having such a structure, the coil 5
As shown in FIG. 2, a and 5b are combined with resistors 11 and 12 to form a bridge circuit. The bridge circuit is provided with a variable resistor 13 for balance, and a connection point A of the bridge circuit. , C, an excitation oscillator 14 is connected to adjust the excitation direction to the same direction, and a differential amplifier 15 is connected between the connection points B, B ′.
Are connected so that the detection output can be taken out from the output terminals 16 and 17. Next, the operation when the torque sensor 1 shown in FIG. 1 is connected to the electric circuit shown in FIG. 2 will be described. First, upon operation, the excitation oscillator 14
An alternating current having a constant amplitude (V) and a frequency (f) is applied to 5a and 5b. Due to this energization, the lines of magnetic force having the magnetic path of the measured shaft 2 → the gap 6 → the yoke 7 → the gap 6 → the measured shaft 2 are generated so as to surround the coils 5a and 5b. By the way, when the frequency (f) of the alternating current to be energized is increased, the eddy current increases in the shaft 2 to be measured. The distribution of the eddy current is stronger as it is closer to the center of the shaft 2 to be measured, and becomes zero on the surface. Therefore, even if the magnetization on the surface can follow the change in the external magnetic field, the change in the magnetization is hindered on the inside. Therefore, the magnetic field lines flow on the surface portion of the shaft 2 to be measured, and the concave portions 3a and 3b are formed on the shaft 2 to be measured.
Is formed so as to form a predetermined angle with respect to the axial direction of the shaft, and this becomes a magnetic resistance and flows mainly through the convex portions 4a and 4b. Therefore, the effect of shape magnetic anisotropy due to the concave portions 3a, 3b and the convex portions 4a, 4b appears. The angles of the concave portions 3a, 3b and the convex portions 4a, 4b with respect to the axial direction are such that one concave portion 3a and the convex portion 4a and the other concave portion 3b and the convex portion 4b are in opposite directions and equal to each other. Although it is assumed that the axis has an angle, it is most preferable that the angle is in the main stress direction when torque is applied to the measured shaft 2, that is, in the right 45 ° direction and the left 45 ° direction. is there. The reason for this is that the lines of magnetic force mainly flow in the main stress direction, and the convex portions 4a and 4b are the outermost surface portions of the shaft 2 to be measured. This is because it can be extracted most effectively. When a torque is applied to the shaft 2 to be measured in the direction T shown in FIG. 1, the one convex portion 4a is formed in the right 45 ° direction, so that the maximum tensile stress + σ acts, Conversely, since the other convex portion 4b is formed in the left 45 ° direction, the maximum compressive stress −σ acts. Here, if the measured shaft 2 has a positive magnetostriction effect, the magnetic permeability of one convex portion 4a increases as compared to when the torque is zero, and conversely, the magnetic permeability of the other convex portion 4b increases. The permeability decreases as compared to the case where the torque is zero. Therefore, the inductance of one coil 5a increases and the inductance of the other coil 5b decreases,
The balance of the bridge circuit shown in FIG. 2 is lost, and an output corresponding to the torque is generated between the output terminals 16 and 17. Further, when the torque is applied in the opposite direction, the inductance of one coil 5a decreases and the inductance of the other coil 5b increases due to the action opposite to that described above. The balance of the bridge circuit is lost, and an output corresponding to the torque is generated between the output terminals 16 and 17. More specifically, the inductances of the coils 5a and 5b are L ₁ and L ₂ , the resistance values of the resistors 11 and 12 are R, the voltage of the excitation oscillator 14 is V, and the frequency is f. When the current flowing through the bridge circuit ABC is i ₁ and the current flowing through the circuit AB′-C is i ₂ , , And the potential V ₁ of the point B, the potential V ₂ of _{V 1 = i 1 · R B} ' point, the V ₂ = i ₂ · R. Therefore, the potential difference of BB ′ is | V ₁ −V ₂ | Is obtained by the differential amplifier 15 to detect the torque. In the torque sensor 1 of this embodiment, the concave portions 3a, 3
b and the convex portions 4a and 4b have a pair of opposite inclinations, the coils 5a and 5b are respectively opposed to each other, and the difference in magnetic change between the concave portions 3a and 3b and the convex portions 4a and 4b is determined. Since the detection is performed by the bridge circuit, even if the magnetic permeability of the shaft 2 to be measured changes with the temperature, the zero point of the output can be fixed and the detection accuracy of the torque can be high. It is possible. In this embodiment, the shaft 2 to be measured is made of an Fe-Al alloy having the chemical components shown in Table 1. And
Each of the 50 kg Fe-Al alloys was melted in a vacuum induction furnace, forged, machined into a shape to be measured shaft 2, and then subjected to a heat treatment under the conditions shown in Table 1 as well. The measurement axis 2 was produced. The shaft to be measured 2 is formed on a surface portion of a shaft having a diameter of 20 mm by forming concave portions 3 a and 3 b having a predetermined angle (45 ° in this embodiment) with a predetermined angle (45 ° in this embodiment), a step portion having a width of 1 mm, and a convex portion. 4a and 4b form a structure integrally formed. Next, in the torsion sensor 1 using the above-mentioned shaft 2 to be measured, an AC having a frequency of 30 KHz and a current of 30 mA is supplied to the coils 5a and 5b from the excitation oscillator 14 of the electric circuit diagram shown in FIG. Shaft 2 → Spacing 6 → Yoke 7 → Spacing 6
→ A magnetic circuit is formed with the measured shaft 2 as a magnetic path,
In this state, when a torque of 1 kgf · m is applied in each of the left and right rotation directions, the change in the magnetic permeability of the shaft 2 to be measured is measured by the coils 5 a and 5.
When the change in inductance is detected by the AC bridge shown in FIG. 2 at b, the output of each torque sensor 1 at this time becomes as shown in FIG. 3, and the output sensitivity (the angle θ in FIG. 3) at this time was examined. . These results are also shown in Table 1. Table 1 also shows the results of the tensile strength when a tensile test was performed on the same material to evaluate the mechanical properties. As is clear from the results shown in Table 1, the Al content was 11.0 to
15.0%, and further, C is 0.01 to 0.50% and C
N is an embodiment containing one or more selected from r, Mo, W, V, Nb, Ta, Ti, Zr, and Hf in a total amount of 0.01 to 5.0%.
o.1,2, B, Si, Ge, Sn, Pb, P, Sb, Cu, Ni, Co, Mn, Be, S
In the case of Nos. 3 to 6, which are examples including at least one of c, Y, and rare earth elements, C and at least one of Cr to Hf, the sensitivity is 1.3
2.22.2 V / Kgf · m, and the sensitivity is much higher than that of Comparative Example No. 13 using JIS S30C which is a normal steel for machine structure. A case where the measured shaft 2 made of a Fe-Al-based alloy to which a suitable amount of one or more of the above B to rare earth elements and / or C and one or more of Cr to Hf are added is substantially used. Al and
For example, in comparison with the case of Comparative Example No. 10 using the shaft to be measured 2 made of a Fe-Al-based alloy consisting of Fe only, the case of Comparative Example No. 10 has a slightly higher sensitivity, The properties were inferior, and it was confirmed that, as shown in Table 1, strength, toughness, workability, etc. could be improved by adding the above elements to the Fe-Al alloy. However, when the addition amount of the above elements exceeds an appropriate amount, for example, in the case of Comparative Examples Nos. 11 and 12, the sensitivity is 0.7 V / Kgf
m, 0.5V / Kgf · m. In the above embodiment, the torque sensor 1 in which the coils 5a and 5b are commonly used for the coil for the excitation means and the coil for the detection means has been described as an example.
As in the torque sensor 21 illustrated in the figure, a yoke 24 made of a material having high magnetic permeability is disposed around the measured shaft 22 with a gap 23 between the measured shaft 22 and the yoke 24. In
It is also possible to form a structure provided with an exciting coil 25 as exciting means and a detecting coil 26 as detecting means,
There is no particular limitation.

【The invention's effect】

As described above, the present invention provides an axis to be measured, exciting means for forming a magnetic circuit having the axis to be measured as a part of a magnetic path, and detecting means for detecting a magnetostrictive component passing through the axis to be measured. Wherein at least a part of the shaft to be measured contains Al in an amount of 11.0 to 15.0% by weight, and further contains 0.01 to 0.50% of C, Cr, Mo, W, V, Nb, and Ta. , Ti, Zr, Hf, at least one element selected from the group consisting of B, Si, Ge, Sn, Pb, P, Sb, Cu, Ni, Co, Mn, Be, Sc,
Y, one or two or more elements selected from rare earth elements are contained in a total amount of 0.01 to 5.0%, and the balance is substantially made of Fe-Al-based alloy,
The output sensitivity of the torque sensor can be made sufficiently good while the strength of the shaft to be measured is sufficiently secured, and the torque can be accurately detected. In the case where a rotating shaft having a large load, such as a power transmission shaft, is used as the shaft to be measured and the torque applied to the rotating shaft is detected, the strength of the rotating shaft is sufficiently secured. The detection sensitivity of the sensor can be increased, and a very excellent effect that the detection of torque can be performed with a very simple configuration and accurately can be achieved.

[Brief description of the drawings]

FIG. 1 is an axial cross-sectional explanatory view showing a structural example of a torque sensor to which the present invention is applied, FIG. 2 is an explanatory view illustrating the configuration of an electric circuit connected to the torque sensor of FIG. 1, and FIG. FIG. 4 is a graph showing an output characteristic of the torque sensor, and FIGS. 4 (a) and 4 (b) are an explanatory diagram in an axial direction and an explanatory diagram in a direction perpendicular to the axis, respectively, showing other structural examples of the torque sensor. 1,21 ... Torque sensor, 2,22 ... Measured axis, 5a, 5b ...
Coil (excitation means and detection means), 25 ... excitation coil (excitation means), 26 ... detection coil (detection means).

Claims (2)

(57) [Claims] 1. A torque sensor comprising: an axis to be measured; exciting means for forming a magnetic circuit having the axis to be measured as a part of a magnetic path; and detecting means for detecting a magnetostrictive component passing through the axis to be measured. , At least a part of the axis to be measured is, by weight%,
Containing 11.0 to 15.0% of Al, and 0.01 to 0.50% of C;
Fe-Al comprising one or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, and Hf in a total amount of 0.01 to 5.0%, and the balance substantially consisting of Fe A torque sensor using a base alloy as a material. 2. A torque sensor comprising: a shaft to be measured; exciting means for forming a magnetic circuit having the shaft to be measured as a part of a magnetic path; and detecting means for detecting a magnetostrictive component passing through the shaft to be measured. , At least a part of the axis to be measured is, by weight%,
Containing 11.0 to 15.0% of Al, and 0.01 to 0.50% of C;
One or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf and B, Si, Ge, Sn, Pb, P, Sb, Cu, Ni, Co , Mn, B
e, Sc, Y, one or two or more elements selected from the rare earth elements are contained in a total amount of 0.01 to 5.0%, and the remainder is substantially made of Fe-Al-based alloy. Characteristic torque sensor.