JPH0758811B2 - Torque detector - Google Patents

Description

The present invention relates to a magnetostrictive torque detection device used for torque detection, and reduces a rotational fluctuation of output and a hysteresis. The present invention relates to a torque detection device that achieves both of the above.

(Prior Art) It is known that when torque is applied to a shaft to be measured, such as a rotating shaft or a fixed shaft, the strain of the shaft material becomes larger at the surface portion of the shaft than at the center portion of the shaft.

Further, for example, when a torque T is applied clockwise toward the axial cross section of the shaft to be measured, tensile stress + σ is generated around the shaft in the right direction inclined by 45 degrees with respect to the axial direction, as shown in FIG. 45
A compressive stress −σ occurs in the leftward direction inclined.

On the other hand, the magnetic substance has a so-called magnetostriction characteristic in which the magnetic permeability changes when stress is applied, and the stress acting on the magnetic substance can be magnetically measured by utilizing the characteristic of this magnetic substance.

That is, a magnetic substance having a positive magnetostriction has a property of increasing magnetic permeability in the tensile stress direction, and a magnetic substance having a negative magnetostriction has a property of decreasing magnetic permeability in the tensile stress direction.

To detect the torque applied to a shaft such as a rotating shaft or a fixed shaft by using this property, it is possible to concentrate the magnetic flux generated from the exciting coil on the surface part of the shaft, that is, the part where large distortion occurs. It is possible to obtain the detection output.

9 (a) and 9 (b) are views showing a conventional torque detecting device. In this torque detecting device 51, a yoke 54 formed of, for example, a high magnetic permeability material such as permalloy is arranged on the outer periphery of a shaft to be measured 52 made of a magnetic material in close proximity to the shaft to be measured 52 with a predetermined space 53. , An exciting coil 55 as an exciting means for forming a magnetic circuit having the measured shaft 52 as a part of a magnetic path on the yoke 54, and a detection means for detecting a magnetostrictive component passing through the measured shaft 52. The coil 56 is provided, and the magnetic flux emitted from the exciting coil 55 forms a magnetic circuit having the shaft to be measured 52 and the yoke 54 as magnetic paths.

In this torque detecting device 51, for example, as shown in FIG. 8, when a torque T is applied in the clockwise direction toward the axial cross section of the shaft to be measured 52, the tensile stress in the right direction inclined by 45 degrees with respect to the axial direction. The output is the sum of the increase in magnetic permeability due to + σ and the decrease in magnetic permeability due to the compressive stress -σ in the left direction inclined at 45 degrees.

In this way, in the torque detection device 51, for example,
An output characteristic as shown in FIG. 10 is obtained, whereby torque is detected by making the applied torque correspond to the detected output (Japanese Patent Laid-Open No. 60-79238).

(Problems to be solved by the invention) However, the rotating shaft and fixed shaft used for torque measurement are often subjected to local stress due to heat treatment such as machining or quenching. The domain wall is moved and fixed by the stress. Therefore, as shown in FIG. 11, the distribution state has a local anisotropy of magnetic permeability. When the torque is measured in this state, the torque T = 0 kgf · m shown in FIG. Output (hereinafter, referred to as “zero torque”) appears as a variation depending on the rotational position of the shaft 52 to be measured. Then, the distribution state having the local anisotropy of magnetic permeability is preserved in the torque region to be measured without disappearing.
The relationship between the torque T and the output shown in the figure appears as an output fluctuation due to the rotational position of the shaft 52 to be measured even when the torque T increases, and the torque T acting on the shaft 52 to be measured can be accurately measured. There was a problem that I could not do it.

Therefore, in the conventional case, in the measured shaft 52, in order to eliminate the distribution state having the local anisotropy of magnetic permeability described above, the measured shaft 52 is heated to a high temperature, and strain relief annealing is performed. It was customary to perform more processing.

However, when high-temperature annealing treatment is applied to the shaft to be measured 52, the material is softened and easily plastically deforms. Moreover, as shown in Fig. 13, hysteresis appears largely and torque detection is performed. However, there is a problem in that the accuracy of is reduced.

That is, in the conventional torque detection device 51, the hysteresis becomes large when trying to eliminate the output fluctuation due to the rotation of the shaft to be measured 52, and the output fluctuation due to the rotation becomes large when trying to keep the hysteresis small. I had a problem.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and the entire circumference of the shaft to be measured can be obtained without picking up the local anisotropy of magnetic permeability of the shaft to be measured. By detecting the change in magnetic permeability as a total, it is possible to obtain a stable torque output that does not change the torque detection output characteristics depending on the rotational position of the shaft to be measured, even when the shaft to be measured is used in a rotating state. It is an object of the present invention to provide a highly accurate torque detection device which can be made extremely small in hysteresis.

[Structure of the Invention] (Means for Solving Problems) The present invention has a shaft to be measured and a coil forming a magnetic circuit having the shaft to be measured as a part of a magnetic path. In the torque detection device for detecting a magnetostrictive component passing through the shaft, the measured shaft is a disordered phase single phase, or Fe ₃ Al type ordered phase,
An iron-aluminum based alloy consisting of a mixed phase containing two or more of FeAl-type ordered phase and disordered phase and having an Fe ₃ Al-type ordered phase degree of 0.9 or less is part or all of the material. It is characterized by.

In an embodiment of the present invention, the measured shaft has a shape magnetic field formed by forming a concave portion and / or a convex portion at appropriate intervals on the surface portion so as to form a constant angle with the axial direction of the measured shaft. Anisotropy can be imparted, and specifically, for example, the shape magnetic anisotropy due to the uneven portion can be formed as a pair in which the directions are reversed, and further, the pair of A configuration in which a pair of coils facing the uneven portion is wound can be used. In the case of winding a pair of coils, the coils can be connected to an exciting oscillator and the exciting directions can be aligned with each other. Furthermore, it is also possible to adopt a configuration in which a change in magnetic permeability in the pair of concavo-convex portions due to a torque load is detected as a change in the inductance of the opposing coils via the differential amplifier by the AC bridge.

In the torque detection device according to the present invention, as the shaft to be measured,
Iron-aluminum alloy consisting of disordered phases as part or all of the material, or Fe ₃ Al with an order of 0.9 or less
-Type ordered phase, FeAl-type ordered phase and a mixed phase containing two or more kinds of disordered phases are used as a part or all of an iron-aluminum alloy,
In this case, the aluminum content is 8% by weight or more and 18% by weight
It is particularly desirable to have the following.

That is, the present inventor investigated the relationship between the aluminum concentration in the iron-aluminum alloy and the output sensitivity and hysteresis in various experimental studies, and the results shown in FIG. 6 were obtained. This FIG. 6 shows the experimental results when the shaft to be measured having the shape shown in FIG. 1 which will be described later is formed by hot working → cooling using iron-aluminum engaging metal. As shown in FIG. 6, the sensitivity becomes zero when the aluminum concentration exceeds 18% by weight, and the hysteresis decreases as the aluminum concentration increases, and becomes zero near 14% by weight.

Therefore, although it depends on the accuracy required for the torque detection device, it is usually desirable that the hysteresis satisfies the accuracy within 10%, and the aluminum concentration is 8% by weight or more. Further, if the aluminum concentration exceeds 18% by weight, it becomes nonmagnetic at room temperature and the sensitivity becomes zero, so it is preferable to set it to 18% by weight or less.

When the relationship between the order of the Fe ₃ Al type ordered phase and the hysteresis was examined, the results shown in FIG. 7 were obtained. As shown in FIG. 7, the order of the Fe ₃ Al type ordered phase was 0.9. , And the hysteresis increases to approach the perfect ordered phase and exceeds 10%, the ordering degree of the Fe ₃ Al type ordered phase was set to 0.9 or less.

The order of the Fe ₃ Al type ordered phase can be adjusted by cooling the material after the completion of casting, hot forging, hot rolling, hot extrusion, or the like, a quenching method after heating to an irregular region, or the above-mentioned quenching. This can be done by selecting the temperature and the holding time when reheating below the transformation point of the Fe ₃ Al type ordered phase / disordered phase.

In this way, as the material of the shaft to be measured, an iron-aluminum alloy consisting of a disordered phase, or an F degree of order of 0.9 or less.
e ₃ Al type ordered phase, FeAl type ordered phase and disordered phase 2
By using the iron-aluminum alloy composed of a mixed phase containing at least one kind, it is possible to obtain a torque detection device having high sensitivity and excellent output characteristics in both of the antinomy characteristics with extremely small hysteresis.

Further, according to another experiment conducted by the present inventor, it has been confirmed that the iron-aluminum alloy used for at least a part of the shaft to be measured has an electric resistivity of 75 μΩ-cm or more. This means that the higher the cooling rate after manufacturing the measured shaft by casting or hot forging, the larger the electrical resistivity of the manufactured measured shaft and the more irregular phases, and the lower the hysteresis. by.

(Embodiment) FIG. 1 is a sectional explanatory view showing a configuration of a torque detecting device according to an embodiment of the present invention.

A torque detection device 1 shown in the figure has at least a surface to be measured 2 made of an iron-aluminum alloy, and as the iron-aluminum alloy, those having an irregular phase and a single phase, and a regularity degree. A mixed phase containing two or more of Fe ₃ Al-type ordered phase, FeAl-type ordered phase and disordered phase of 0.9 or less is used. Then, on the surface of the shaft to be measured 2, concave portions 3a and 3b and convex portions 4a and 4b forming a predetermined angle with respect to the axial direction of the shaft to be measured 2 are provided at appropriate intervals. It is formed integrally with No. 2 and has a shape magnetic anisotropy by these concave portions 3a, 3b and convex portions 4a, 4b.

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 (45 ° in this embodiment) with respect to the axial direction and opposite directions. It is provided as a pair in a tilted state.

In addition to the measured shaft 2, the torque detecting device 1 faces one of the concave portion 3a and the convex portion 4a formed on the measured shaft 2 and the other concave portion 3b and the convex portion 4b. Has a pair of coils 5a, 5b arranged in
A cylindrical yoke 7 made of a high magnetic permeability material is provided outside the a and 5b and with a gap 6 between the shaft 2 and the measured shaft 2.

In the torque detection device 1 having such a structure, the coil 5
As illustrated in FIG. 2, a and 5b are combined with resistors 11 and 12 to form a bridge circuit, and a variable resistor 13 for balancing is provided in the bridge circuit, and a connection point A of the bridge circuit is provided. An excitation oscillator 14 is connected between C and C to align the excitation direction in the same direction, and a differential amplifier 15 is connected between connection points B and B '.
Is connected so that the detection output can be taken out from the output terminals 16 and 17.

Next, the operation when the torque detector 1 shown in FIG. 1 is connected to the electric circuit shown in FIG. 2 will be described.

First, when operating, the excitation oscillator 14
An alternating current of constant amplitude (V) and frequency (f) is applied to a and 5b. Due to this energization, the magnetic force lines whose magnetic path is the shaft to be measured 2 → gap 6 → yoke 7 → gap 6 → shaft to be measured 2
It occurs so as to surround 5a and 5b.

By the way, if the frequency (f) of the alternating current to be energized is increased,
The eddy current increases on the measured shaft 2. 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 will be hindered inside.

Therefore, the magnetic force lines flow on the surface portion of the shaft to be measured 2, and the concave portions 3a and 3b are formed on the shaft to be measured 2 so as to form a predetermined angle with the axial direction of the shaft 2 to be measured. For,
This serves as a magnetic resistance, and flows mainly through the convex portions 4a and 4b. Therefore, the concave portions 3a, 3b and the convex portion 4a,
The effect of shape magnetic anisotropy due to 4b appears.

The angles of the concave portions 3a, 3b and the convex portions 4a, 4b with respect to the axial direction are the concave portion 3a and the convex portion 4a on one side and the concave portion on the other side.
The angles of 3b and the convex portion 4b are opposite to each other and have the same angle, but the most desirable direction is the principal stress direction when torque is applied to the shaft to be measured 2, that is, the right 45 ° direction and the left 45 ° direction. It is to make a direction. The reason for this is
The lines of magnetic force mainly flow in the principal stress direction, and the convex portions 4a, 4
This is because b is the outermost surface portion of the shaft to be measured 2 where the strain is the largest, and the change in the magnetic permeability of the magnetic body due to this strain can be most effectively extracted.

When a torque is applied to the shaft 2 to be measured in the T direction shown in FIG. 1, 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 shaft 2 to be measured has a positive magnetostrictive 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. The magnetic susceptibility decreases compared to when the torque is zero.

Therefore, the inductance of one coil 5a increases and the inductance of the other coil 5b decreases,
The bridge circuit shown in FIG. 2 is out of balance, 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 effect opposite to that described above, so that it is shown in FIG. The balance of the bridge circuit is lost, and an output corresponding to the torque is generated between the output terminals 16 and 17.

In this embodiment, as described above, the concave portions 3a, 3b and the convex portions 4a, 4b are a pair of which the inclinations are opposite to each other, and the coils 5a, 5b are opposed to each other, and the concave portion 3 is formed.
Since the bridge circuit detects the difference in magnetic change between a and 3b and convex portions 4a and 4b, the measured shaft 2
The zero point of the output can be kept stationary even if the magnetic permeability of is changed by temperature, and the torque detection accuracy can be improved.

More specifically explaining this, 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 A-B-C is i ₁ and the current flowing through the circuit A-B'-C is i ₂ , Therefore, the potential V _{1 at the} point B becomes V ₁ = i ₁ · R and the potential V _{2 at the} point B ′ becomes V ₂ = i ₂ · R.

Therefore, the potential difference at the point BB ′ is | V ₁ −V ₂ | Which is determined by the operational amplifier 15.

In the electric circuit shown in FIG. 2, the frequency (f) of the alternating current supplied from the exciting oscillator 14 to the coils 5a and 5b is 1 kHz to 100.
It is more preferable to set the frequency to about kHz, whereby high-sensitivity and low-hysteresis output characteristics can be obtained.

In the torque detection device 1 according to the present invention, the measured shaft 2
As at least the surface portion is used iron-aluminum-based alloy, in particular, the alloy is composed of a disordered phase single phase, the order of 0.9 or less Fe ₃ Al type ordered phase, F
As described above, the mixed phase containing two or more kinds of the eAl type ordered phase and the disordered phase is used, and in this embodiment, the concave portion is formed on the surface of the shaft having a diameter of 20 mm.
3a, 3b and convex portions 4a, 4b were formed. In this case, the steps of the concave portions 3a, 3b and the convex portions 4a, 4b formed on the measured shaft 2 are
Although it was formed to be 1 mm, this step depends on the influence degree of the eddy current, but if the frequency of the alternating current supplied by the excitation oscillator 14 is about 1 KHz to 100 KHz as described above, 0.5 mm to A step of about 1.5 mm is sufficient.

On the other hand, the distance between the concave portions 3a, 3b and the convex portions 4a, 4b may be such that the shape magnetic anisotropy is sufficiently obtained, and in this embodiment, the concave portions 3a, 3b and the convex portions 4a, 4a, Same as 4b 2m
It was formed at m intervals.

On the other hand, when the cross-sectional shapes of the concave portions 3a, 3b and the convex portions 4a, 4b are R-shaped as shown in FIG. 3 as a model cross-section, the influence of the notches can be reduced and the workability is improved It can be anything.

In FIG. 3, the concave portions 3a and 3b have an R shape, and the convex portions 4a and 4b
Is flat, but it is also desirable if the convex portions 4a, 4b are also R-shaped as necessary. By making both R-shaped in this way, the notch when torque is applied is formed. It is also possible to prevent breakage due to the effect.

In the torque detection device 1 shown in this embodiment, the number of turns of the coils 5a and 5b is set appropriately, but here, it is assumed that the coils 5a and 5b are made by winding 44 turns of a copper wire having a wire diameter of 0.6 mm. . Regarding the method of connecting the copper wires in the coils 5a and 5b, the exciting magnetic field is shared by connecting the coils 5a and 5b so that the directions of the magnetic fields are the same. The sensitivity can be increased. In this example, the torque was measured at an AC excitation frequency of 10 KHz and a current of 100 mA supplied from the excitation oscillator 14 of the electric circuit shown in FIG.

As a result, in the torque detection device 1 according to this embodiment, the torque-output characteristic when the shaft 2 to be measured is fixed at a fixed position is shown in FIG. Here, the output at zero torque is the variable resistor of the electric circuit shown in FIG.
Balance at 13 and set to zero, the zero point does not change thereafter. And, in this case, it showed an extremely excellent characteristic of zero hysteresis.

The output when the shaft 2 to be measured was rotated was as shown in FIG. As shown in FIG. 5, in the torque detecting device 1 according to the present invention, since the averaged magnetic permeability change in the entire circumference of the shaft to be measured 2 is captured, there is no rotation fluctuation of the zero point, and therefore, when torque is applied. Even in the above, no rotational fluctuation of the output corresponding to the applied torque occurred. Note that FIG. 5 shows 14% by weight.
Fe-Al-based alloy containing Al, which contains an Fe ₃ Al type ordered phase and a disordered phase, and the Fe ₃ Al type ordered phase has an ordering degree of 0.3.
7 shows an experimental result when a shaft to be measured is formed using a system alloy.

In the torque detection device 1 according to the embodiment of the present invention, the output sensitivity is improved by using the yoke 7 made of a high magnetic permeability material, for example, an iron-nickel alloy to reduce leakage of magnetic force lines. This yoke 7 does not necessarily have to be used in consideration of the exciting current.

Further, the change in the magnetic permeability of the pair of concave portions 3a, 3b and the convex portions 4a, 4b due to the torque applied to the shaft to be measured 2 is recognized as the change in the inductance of the pair of coils 5a, 5b, and the differential amplifier 15 by the AC bridge. However, the shaft to be measured 2 having the above-described configuration can be applied to a torque detecting device provided with an exciting coil and a detecting coil.

As described above, the present invention has the shaft to be measured and the coil forming the magnetic circuit having the shaft to be measured as a part of the magnetic path, and passes through the shaft to be measured. In the torque detection device for detecting a magnetostrictive component, the measured shaft is composed of a disordered phase single phase or a mixed phase containing two or more of Fe ₃ Al type ordered phase, FeAl type ordered phase and disordered phase. , Fe ₃ Al-type ordered phase having an ordering degree of 0.9 or less is used as the material, the hysteresis is extremely small, the accuracy of torque detection can be significantly improved, and Since the magnetic change due to the torque of the measurement shaft is captured over the entire circumference of the shaft to be measured, there is no change in the output due to the rotation of the shaft to be measured, and the torque of the shaft rotating at high speed can be accurately measured. Excellent effect on Obtained. Also, when a concave portion and / or a convex portion is formed on the shaft to be measured so as to have a formed magnetic anisotropy, the inclination of the concave and convex portions is opposite to each other, and the difference in magnetic change between the two is considered. It is possible to keep the zero point of the output stationary even when the magnetic permeability of the shaft to be measured changes due to temperature change. Since it can be used directly as an axis,
It is possible to provide a torque detection device having a remarkably excellent effect that the torque detection means can be configured very compactly without using a coupling or the like.

[Brief description of drawings]

1 is a cross-sectional explanatory view showing the structure of a torque detection device according to an embodiment of the present invention, FIG. 2 is an explanatory view illustrating the configuration of an electric circuit connected to the torque detection device of FIG. 1, and FIG. A model explanatory view illustrating the cross-sectional shapes of the concave portion and the convex portion formed on the shaft to be measured, FIG. 4 and FIG. 5 are each a fixed shaft of the shaft to be measured in the torque detecting device according to the embodiment of the present invention. Fig. 6 is a characteristic explanatory diagram showing the relationship between the torque and the output when the rotation is performed, and a characteristic explanatory diagram showing the stability of the detection output when the shaft to be measured is rotated once. Fig. 6 is an irregular phase single phase or Fe ₃ Al type In a torque detection device using a shaft to be measured composed of an iron-aluminum alloy consisting of a mixed phase containing two or more of an ordered phase, an FeAl type ordered phase and a disordered phase, aluminum in the iron-aluminum based alloy is used. Output sensitivity and Graph illustrating the results of examining the influence of the Hysteresis, graph Figure 7 is an example of the results of examining the influence of the hysteresis due to the degree of order of the Fe ₃ Al type ordered phase, torque FIG. 8 is applied to the shaft FIG. 9A and FIG. 9B are explanatory views of a slope showing a relationship between (T) and stress (σ).
FIG. 10 is a schematic front view and a schematic side view, respectively, for explaining the structure of the conventional torque detection device, and FIG. 10 is a characteristic showing the relationship between torque and output when the shaft to be measured is fixed at a fixed position in the conventional torque detection device. Explanatory drawing, FIG. 11 is a conceptual explanatory view showing a locally anisotropic distribution state of the magnetic permeability of the shaft surface portion in a normal shaft, and FIG. 12 is one rotation of the shaft to be measured in the conventional torque detecting device. Fig. 13 is a characteristic explanatory diagram showing the fluctuation of the detected output when the measured shaft is heated to a high temperature and strain-relieved and annealed to reduce the fluctuation of the output rotation in the conventional torque detection device. It is a characteristic explanatory view showing the relation between torque and output when there is. 1 ... Torque detection device, 2 ... Measured shaft, 5a, 5b ... Coil.

Claims (1)

[Claims] 1. A torque detection device for detecting a magnetostrictive component passing through the shaft to be measured, comprising: a shaft to be measured; and a coil forming a magnetic circuit having the shaft to be measured as a part of a magnetic path. At least a part of the measuring axis is irregular phase single phase, or
Fe ₃ Al type ordered phase, FeAl type ordered phase and disordered phase 2
A torque detection device comprising a mixed phase containing at least one kind and an iron-aluminum alloy having a Fe ₃ Al type ordered phase with an ordering degree of 0.9 or less.