JPS63297545A - Axis to be measured for torque sensor - Google Patents

Abstract

PURPOSE:To execute the detection of a large torque applied to an axis to be measured with high accuracy by providing a specific Fe-Al alloy layer on the partial surface of the axis to be measured. CONSTITUTION:An Fe-Al alloy layer 3 is provided on the partial surface of the axis 2 to be measured by a thermal spraying method and the torque applied to the axis to be measured is detected. The above-mentioned Fe-Al alloy layer 3 is formed from mixed phase. Said mixed phase contains >=2 kinds among an irregular phase, Fe3Al type regular phase having <=0.9 regularity and FeAl type regular phase. A torque applied to the axis 2 to be measured, particularly a large torque, can be detected with high accuracy by the above-mentioned torque sensor 1.

Description

[Detailed description of the invention]

[Objective of the invention] (Industrial application field) The present invention relates to a torque sensor used to detect torque applied to a shaft to be measured, and in particular to detect large torques with high accuracy without any trouble. The present invention relates to a shaft to be measured for a torque sensor that is capable of (Prior Art) Conventionally, as a torque sensor used to detect torque applied to a shaft to be measured, there has been one shown in FIG. 6, for example. This torque sensor 51 is of a magnetostrictive type, and two excitation coils 53 and a detection coil 54 are disposed on the surface of a shaft 52 to be measured made of a material having a magnetostriction effect. It has a structure in which a yoke 56 made of a high magnetic permeability material is provided on the outer periphery of the yoke 54 with a gap 55 between it and the shaft 52 to be measured. When operating this magnetostrictive torque sensor 51,
By energizing the excitation coil 53, the shaft to be measured 52
A magnetic circuit passing through the gap 55 and the yoke 56 is formed. At this time, an induced electromotive force is generated in the detection coil 54. In such a state, when a screw torque is applied to the shaft to be measured 52, the magnetic permeability of the shaft to be measured 52 itself changes due to the magnetostrictive effect of the shaft to be measured 52.
The magnetic flux density passing through the magnetic circuit changes, and the induced electromotive force generated in the detection coil 54 also changes accordingly, and by reading the change in this induced electromotive force,
The value of the torsional torque applied to the shaft 52 to be measured can be known. However, when considering the case where the shaft to be measured is a commonly used power transmission shaft (for example, a drive shaft or a column shaft), this type of power transmission shaft has a small magnetostrictive effect, so it does not exhibit sufficient torque detection ability. I can't. Therefore, by taking advantage of the large magnetostrictive effect of an amorphous magnetic ribbon, a torque sensor has been proposed in which the amorphous magnetic ribbon is wound around a rotating shaft and fixed with an adhesive (Japanese Unexamined Patent Publication No. 58-9034). ). However, this torque sensor has the problem that it can only be manufactured using fairly complicated means, such as the need to heat-treat the amorphous magnetic ribbon to provide an axis of easy magnetization with a predetermined angle. Therefore, in order to easily obtain magnetic anisotropy, a large number of sleeves (57a, 5) are formed in the 45° direction as shown in FIG.
A torque sensor 51 has been proposed which has a structure as shown in FIG. 8, in which an amorphous short strip-shaped magnetostrictive magnetic thin strip 57 having a diameter 7b is adhered and fixed to a shaft to be measured (rotating shaft) 52 with an adhesive. (Japanese Unexamined Patent Publication No. 166827/1982). (Problems to be Solved by the Invention) However, in the conventional torque sensor 51 as described above, the amorphous magnetic ribbon 57 is fixed to the shaft 52 to be measured using an adhesive. Save,
There is a problem in that it is difficult to uniformly adhere the amorphous magnetic ribbon 57 to the shaft 52 to be measured, and variations in characteristics tend to become large. Also, as shown in Figure 9,
The one that outputs the characteristics shown by the line ■ in the initial stage may have a large torque, e.g. 10 kgf, due to the creep phenomenon of the adhesive.
After applying a torque of about @m, a shift in the output occurs as shown by the line ■ in the same figure, and there is a problem in that high accuracy cannot be maintained. Furthermore, with respect to temperature changes, as the temperature rises, the adhesive softens and the output shifts as described above, and also because the difference in thermal expansion between the amorphous magnetic ribbon 57 and the shaft 52 to be measured is large. However, there was a problem in that stable output could not be obtained against changes in temperature. (Purpose of the Invention) The present invention was made by focusing on the above-mentioned conventional problems, and since no adhesive is used, the characteristics cannot be changed due to large torque application or temperature changes, which are caused by the use of conventional adhesives. To provide a shaft to be measured for a torque sensor, which has almost no variation, exhibits stable output characteristics even with large torque application and temperature changes, and is capable of performing highly accurate torque measurements with high sensitivity and low hysteresis. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) The present invention relates to the measured shaft of a torque sensor that detects torque applied to the measured shaft, and the present invention relates to at least a part of the surface or the entire surface of the measured shaft. It is characterized by having a structure in which an Fe-AM alloy layer formed by thermal spraying is provided on the surface of the Fe-A
The present invention is characterized in that the n-based alloy layer is formed on the surface of the shaft to be measured by a thermal spraying method, thereby solving the problems encountered in the conventional method of fixing a ribbon using an adhesive. In this case, the bonding strength of the Fe-A alloy layer to the surface of the shaft to be measured can be selected by selecting various thermal spraying methods and thermal spraying conditions, so the thermal spraying method corresponding to the maximum stress applied to the shaft to be measured can be selected. and thermal spraying conditions. In addition, in the Fe-An alloy layer formed by thermal spraying, the A concentration in the Fe-A alloy layer and the metallurgical phase (Fe3A alternating ordered phase, FeAl ordered phase, irregular phase) By selecting a mixed phase of 1" e3Al type ordered phase (0 order degree, etc.), it is possible to obtain a highly accurate torque sensor with high sensitivity and low hysteresis.Adjustment of this metallurgical phase The selection of the thermal spraying method and thermal spraying conditions, as well as the post-spraying heat treatment method and heat treatment conditions (
This can be done by selecting the heating temperature, heating holding time, cooling rate after heating, etc. In a more desirable embodiment of the shaft to be measured for a torque sensor according to the present invention, the Fe-Al1-based alloy layer has an irregular circumferential phase single phase, or an Fe3 AJL type regular phase circumferential phase eA.
The iron-aluminum alloy is made of a mixed phase containing two or more of an L-type ordered phase and an irregular circumferential phase, and the degree of order of the Fe5Ai-type ordered phase is 0.9 or less. good. Further, in an embodiment of the present invention, the axis to be measured is
Shape magnetic anisotropy is imparted by forming Fe-An alloy layers by thermal spraying on the surface at appropriate intervals so as to form a constant angle with the axial direction of the measured axis. Specifically, for example, the shape magnetic anisotropy due to the Fe-AM alloy layer can be formed as a pair with the directions reversed, and further, It can be configured by winding a pair of coils facing each other in the layer. In the case of winding a pair of coils, the coils can be connected to an excitation oscillator so that the excitation directions are aligned in the same direction. Furthermore, the pair of F e due to torque load
- It is also possible to adopt a configuration in which a change in magnetic permeability in the AJL alloy layer is detected as a change in inductance of an opposing coil using an AC bridge via a differential amplifier. In another embodiment of the present invention, it is also possible to use the shaft as the measured shaft of a so-called magnetic head type torque sensor in which an excitation coil and a detection coil are placed facing each other in a 45° direction on the surface of the measured shaft. be. In the shaft to be measured for a torque sensor according to the present invention, Fe-A9. It is particularly desirable that the An content in the alloy layer is 8% by weight or more and 18% by weight or less.In other words, the influence of the An content on sensitivity is significantly reduced when the A content exceeds 18% by weight. This is because the influence on hysteresis decreases as the An content increases and becomes zero near 14% by weight. Therefore, although it depends on the accuracy required of the torque sensor, in normal cases it is desirable to satisfy the accuracy within 10% of hysteresis, and the An content in the Fe-An alloy layer is 8% by weight. % or more, and I
If the Q content exceeds 18% by weight, it becomes non-magnetic at room temperature and the sensitivity becomes zero, so it is preferably 18% by weight or less. In addition, when we investigated the relationship between the regularity of the Fe3An-type ordered phase and hysteresis, we found that when the regularity of the FeBAl-type ordered phase exceeds 0.9 and approaches a completely regular phase, the hysteresis increases to 10%. Since it tends to exceed Fe3 Af
It is particularly desirable that the degree of order of the L-shaped ordered phase be 0.9 or less. The degree of regularity of this l"e3AR type ordered sum can be adjusted by selecting the thermal spraying method and the cooling method (including reheating) after the thermal spraying is completed.Furthermore,
The Fe-An alloy layer has an electrical resistivity of 75 μΩ.
-0 m or more is particularly preferred. As described above, as a shaft to be measured for a torque sensor, at least a portion of its surface is preferably an Fe-AfL alloy layer consisting of an irregular circumferential phase, or an Fe5An type ordered phase with a degree of order of 0.9 or less. By using a Fe-AfL alloy layer formed by a thermal spraying method, the Fe-AfL alloy layer is made of a mixed phase containing two or more of the FeAl-type ordered phase and the irregular circumferential phase. It is possible to obtain a torque sensor that has extremely low hysteresis and has excellent output characteristics in both of the tradeoff characteristics. FIG. 1 is an explanatory cross-sectional view showing the configuration of a torque sensor according to an embodiment of the present invention. The torque sensor 1 shown in the figure has a shaft 2 to be measured made of, for example, structural carbon steel or alloy steel. is 0.9 or less, an Fe3 An-type regular periodic phase FeAfJ, a mixed phase containing two or more types of a washin periodic phase and an irregular periodic phase,
The e-AM gold alloy layer 3 is formed by thermal spraying. Fe-
AJI alloy layer 3 Strips 3a and 3b forming a predetermined angle with respect to the axial direction of the shaft 2 to be measured are formed at appropriate intervals, and these strips 3a and 3b improve the shape magnetic anisotropy. It's like it lasts. In this case, the one band-shaped portion 3a and the other band-shaped portion 3b
A pair of blades are inclined at the same angle of inclination (45° in this embodiment) with respect to the axial direction and in opposite directions. In addition to the shaft to be measured 2, this torque sensor 1 also includes:
A pair of coils 4 are arranged to face each other on one strip 3a and the other strip 3b formed on the shaft 2 to be measured.
a, 4b, and a cylindrical yoke 6 made of a high magnetic permeability material is provided outside the coils 4a, 4b and with a gap 5 between it and the shaft 2 to be measured. It is something that does. In the torque sensor 1 having such a structure, the coil 4a
, 4b are combined with a resistor 7.8 to form a bridge circuit, as illustrated in FIG. An excitation oscillator 10 is connected between C and the excitation direction is aligned in the same direction, and a differential amplifier 11 is connected between connection points B and B' to extract the detection output from output terminals 12 and 13. It is possible to do so. When such a torque sensor 1 operates, an excitation oscillator 10 supplies an alternating current with a constant amplitude (V) and frequency (f) to the coils 4a and 4b. By this energization,
Lines of magnetic force whose magnetic path is the axis to be measured 2 → gap 5 → yoke 6 → gap 5 → axis to be measured 2 are generated so as to surround the coils 4a and 4b. The magnetic lines of force flow on the surface of the shaft 2 to be measured, and the belt-shaped parts 3a and 3b are formed on the shaft 2 to be measured so as to form a predetermined angle with the axial direction of the shaft 2 to be measured. The effect of shape magnetic anisotropy appears. Therefore, for the measured axis 2! When torque is applied in the T direction shown in Fig. s1, the maximum tensile stress +σ acts on one of the strips 3a since it is formed in the right 45° direction, and on the other hand, the other strip 3b is formed in the left 45° direction. Since it is formed in the ° direction, the maximum compressive stress -σ acts on it. Therefore, the inductance of one coil 4a increases and the inductance of the other coil 4b decreases, causing the bridge circuit shown in FIG. occurs. Furthermore, when torque is applied in the opposite direction, the inductance of one coil 4a decreases and the inductance of the other coil 4b increases due to the opposite effect to that described above. The bridge circuit is unbalanced, and an output corresponding to the torque T is generated between the output terminals 12 and 13. As a result, output characteristics as shown in FIG. 3 can be obtained. In this embodiment, as described above, the strip portion 31L
, 3b are used as a pair with opposite inclinations, and the coils 4a * 4b are placed opposite to each other, so that the difference in magnetic change in the strips 3a and 3b is detected by a bridge circuit. Fe-A liberal arts alloy layer 3
Even if the magnetic permeability of the magnet changes with temperature, the zero point of the output can remain unchanged, making it possible to increase the accuracy of torque detection. In the embodiment described above, the change in magnetic permeability of the pair of strips 3a, 3b due to the application of torque to the shaft 2 to be measured is treated as a change in the inductance of the pair of coils 4a, 4b, and is detected via the operational amplifier 11 by an AC bridge. Although the torque sensor uses a self-excitation method that utilizes changes in self-inductance, as shown in Figure 6, there are also torque sensors that use an external excitation method that uses changes in so-called mutual inductance, in which an excitation coil and a detection coil are provided. It is possible to apply the measured axis 2 having the above configuration. FIGS. 4(a) and 4(b) are diagrams showing other embodiments of a torque sensor to which the shaft to be measured for a torque sensor according to the present invention is applied. This torque sensor 21 has a shaft to be measured 22.
In this case, the shaft 22 to be measured is made of structural carbon steel, structural alloy steel, or stainless steel, and has an Fe-A alloy layer 23 formed by thermal spraying on the surface. A predetermined interval 24 is placed on the outer periphery of the measured shaft 22, and
For example, a yoke 25 made of a high magnetic permeability material such as permalloy is arranged close to the yoke 25, and the shaft 5 to be measured is connected to the yoke 25.
An excitation coil 26 as an excitation means forming a magnetic circuit as a part of the Fe-AfL alloy layer 23 provided in 2.
and F e-A! provided on the shaft 52 to be measured. ; A detection coil 27 is provided as a detection means for detecting the magnetostriction component passing through the L-based alloy layer 23, and the magnetic flux emitted from the excitation coil 26 is applied to the Fe-A1-based alloy layer 2 provided on the shaft 22 to be measured.
3 and the yoke 25 form a magnetic circuit. In this torque sensor 21, for example, when torque is applied clockwise toward the shaft cross section of the shaft 22 to be measured, the magnetic permeability increases due to the tensile stress +σ in the right direction inclined at 45 degrees with respect to the axial direction, and The sum of the leftward compressive stress and the decrease in magnetic permeability due to σ is taken as an output, and torque is detected from this. Fe on the surface of at least a part of the shaft to be measured as described above.
- The shaft to be measured for a torque sensor according to the present invention in which an AfL alloy layer is formed by a thermal spraying method uses the above-mentioned excitation detection method (magnetic head detection method, detection method using a change in self-inductance, mutual inductance The present invention can be applied without being limited to the type of detection method (detection method using change). (Example) Example 1 In this example, stainless steel (SUS 304) with an outer diameter of 18 mm was selected as the base material of the shaft to be measured, and plasma spraying was performed using Fe-An alloy powder as the spraying material. , an Fe-AM alloy layer was formed on the surface of the base material. At this time, the thickness of the Fe-An alloy layer was 1 mm, and the outer diameter of the shaft to be measured was 20 mm.
1 width 2mm, depth 1mm, 8 on one side on the surface of the shaft to be measured
The shaft to be measured (2) was machined to form a groove with an angle of 45° to form a band-shaped portion (3a, 3b) as shown in Figure 1.
prepared. Next, as shown in Table 1, some of the shafts to be measured (2) were left as thermal sprayed, and some of the other shafts to be measured (2) were heated and held at 600°C x thr in vacuum. Heat treated with oil cooling. The An content in the Fe-An alloy layer (3) thus formed was 13.2%, and the Fe-An alloy layer (3) formed in this manner was 13.2%.
-Fe5A type regularity of A-type alloy layer (3) is 0
．． 81, and when the above heat treatment is applied, it is 0.2
It was 3. Next, as shown in Table 1, the first
The number of turns of the coils (4a, 4b) shown in the figure is 44 each.
turn, the measurement frequency by the excitation oscillator (10) is 30KHz, and the measurement current is loOmA.
A torque of Kgf-m was applied to the shaft to be measured (2). As a result, as shown in Table 1, the sensitivity [S] in the output characteristics shown in Figure 5 is ±3.2V/
Kgf@m, ±4.3V/Kgf when heat treated
The hysteresis [H] was 4% when as-sprayed and 1% when heat treated, giving excellent results. In this example, a shaft to be measured similar to that in Example 1 was prepared and applied to the magnetic helad type torque sensor (21) shown in FIG. In this case, the axis to be measured in Example 1 is the one in which the AfL content in the Fe-A alloy layer (23) is 12.7%, and the AfL content in the Fe-A alloy layer (23) as sprayed. The regularity of the Fe5A sentence pattern regularity phase is 0.62.
The difference is that when heat treatment is applied, it is 0.22. Next, using the magnetic head method, as shown in Table 1,
The excitation coil (26) shown in Fig. 4 has 100 turns, the detection coil (27) has 100' turns, the measurement frequency is 10KHz, and the measurement current is 200mA.
A torque of 11 kgf was applied to the shaft to be measured (22). The results were also good as shown in Table 1. Example 3 In this example, the base material of the shaft to be measured has an outer diameter of 20 mm (
7) Select stainless steel (SUS 304) and perform plasma spraying using Fe-AfL alloy powder as a thermal spraying material to form an Fe-An alloy layer on the surface of the base material. In the same way, grooves with an angle of 45° are machined to create band-shaped parts (3a, 3b) as shown in Figure 1.
) A shaft to be measured (2) was prepared. Next, as shown in Table 1, the mixture was heated and held at 800° C. for 1 hr, cooled in oil, then kept at 400° C. for 1 hr, and then cooled in a continuous furnace. Fe-AJI alloy layer (3) formed in this way
The AfL content therein was 11.9%, and the Fe5An type rule compatibility degree was 0.37. Next, under the conditions also shown in Table 1, torque detection was performed using the self-excitation method and torque detection using the external excitation method, and the torque detection results also shown in Table 1 were obtained, and the sensitivity [S ] and a small hysteresis [H], good detection results were obtained. Example 4 In this example, an induction hardened and tempered mechanical structural alloy steel (S CM 440) with an outer diameter of 10 mm was selected as the base material of the shaft to be measured, and an Fe-An alloy wire was used as the thermal spray material. By performing wire blast spraying, F is applied to the surface of the base material.
An e-AfL alloy layer was formed. Next, as shown in Table 1, heat treatment was performed under the same conditions as in Example 3. The A'fL content in the Fe-A alloy layer thus formed was 14.1%, and the Fe5A
The degree of compatibility and affinity of the i-type rule was 0.42. Next, the number of each coil was set using the same magnetic head method as in Example 2, and the measurement frequency was set to 10 KHz. 1 to the axis to be measured (22) with the measurement current set to 50mA.
Torques of Kgf11m and loKgflllm were applied. As a result, torque detection sensitivity [S] and hysteresis [
H] showed a good value as shown in the same <81 table.

【Effect of the invention】

As explained above, according to the present invention, in the shaft to be measured of the torque sensor that detects the torque applied to the shaft to be measured, the surface of at least a part of the shaft to be measured is formed by thermal spraying. Since the structure is equipped with a Fe-AJI alloy layer, it is difficult to apply large torque due to the use of the adhesive or due to temperature changes, as in the case where a magnetic thin film is bonded and fixed using a conventional adhesive. It is possible to eliminate the occurrence of defects, obtain stable output characteristics even when large torques are applied or large temperature changes, and perform highly accurate torque measurements with high sensitivity and low hysteresis. This brings about a very good effect of making it possible.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional explanatory diagram of a torque sensor in one embodiment of the present invention, Fig. 2 is an electric circuit diagram connected to the torque sensor of Fig. 1, Fig. 3 is an output characteristic diagram of the torque sensor, and Fig. 4 (a) and (b) are respectively a front explanatory view and a side explanatory view of the torque sensor in other embodiments, and FIG. 5 is a sensitivity [5
] and an explanatory diagram showing the measurement procedure of hysteresis [H],
Fig. 6 is a vertical cross-sectional view of a conventional torque sensor, Fig. 7 is a developed view of a magnetic thin film attached to a shaft to be measured for a conventional torque sensor, and Fig. 8 is a 75! Longitudinal cross-sectional view of a torque sensor using a shaft to be measured to which a magnetic thin film of J is attached with adhesive, No. 9
The diagram shows the output characteristics of a conventional torque sensor. 1.21...Torque sensor. 2.22... Axis to be measured, 3.23... Fe-AfL alloy layer.

Claims (2)

[Claims] (1) In the measured shaft of the torque sensor that detects the torque applied to the measured shaft, an Fe-Al alloy layer formed by thermal spraying is provided on at least a part of the surface of the measured shaft. A shaft to be measured for a torque sensor, characterized in that: (2) The Fe-Al alloy layer has a disordered phase or Fe
_3Al-type ordered phase, FeAl-type ordered phase, and disordered phase. The shaft to be measured for a torque sensor according to item (1).