JPS589034A - Torque sensor by thin amorphous magnetic strip - Google Patents

Abstract

PURPOSE:To make the non-contact detection of torque possible by fixing a thin amorphous magnetic strip having a large magnetostriction constant by winding and fixing it to a revolving shaft. CONSTITUTION:Two magnetic heads 18, 19 are disposed in symmetrical positions with inclination at an equal angle with respect to the axial direction of a revolving shaft 4 spacially slightly from a thin amorphous magnetic strip 1. An easy- to-magnetize axis is applied to the strip 1 in the axial or rotating direction by a heat treatment. When the two heads 18, 19 are excited by a high frequency power source 14 via a diode 20, the inductance of either of the magnetic heads is increased by a magnetostrictive effect and that of the other is decreased on exertion of torque thereupon, thus producing a difference between the excition currents. If the difference in the excitation currents is drawn out as a DC differential output Vout 23, the direction and magnitude of the torque are detected from the code and magnitude thereof.

Description

[Detailed Description of the Invention] Torque is the most fundamental variable when controlling rotary drive parts such as electric motors and automobiles, and can also be used for failure diagnosis as a parameter indicating the degree of bubbling in the system. You can also do it. Torque detection requires a non-contact method, is capable of detecting torque in forward rotation, reverse rotation, and at rest, and is required to be highly accurate and reliable.

Until now, there have been indirect methods that use light or magnetism to detect torque from the screw angle of the shaft, and direct methods that use magnetostriction and phenomena of the rotating shaft to directly detect torque.
Neither method has taken hold. The reasons for this are that the indirect method requires a special torsion bar to convert torque into torsional displacement, and that the use of light poses a problem in terms of environmental resistance.

On the other hand, the direct method that utilizes the magnetostriction phenomenon of the shaft is simple and has excellent reliability, but originally, attention has been paid only to the mechanical strength of rotating shafts, and the magnetic properties of the shaft are The detection output is uniform in the direction of rotation (uneven rotation occurs), and the output is dependent on the rotation speed, which are considered to be major drawbacks.

The object of the present invention is to provide an amorphous magnetic ribbon sensor in order to eliminate such drawbacks. That is, an amorphous magnetic ribbon that has been appropriately heat-treated and has remarkable magnetostrictive properties is wound and fixed around a rotating shaft, and the shaft strain stress due to torque is introduced into the amorphous magnetic ribbon, so that the magnetostrictive phenomenon can be induced. This is a direct method for detecting sitorque by externally and non-contactly detecting changes in the magnetic properties of an amorphous magnetic ribbon.

FIG. 1 is a diagram showing the principle of the present invention. Figure 1(a) shows that an amorphous magnetic ribbon (1) wound into a ring shape has an easy axis of magnetization Ku (3) uniformly tilted at an angle α with respect to its length direction (2) by heat treatment. It was given. To simplify the explanation, let α〉45・, and the magnetostriction constant λg
)O. Figure 1 (b) shows this amorphous magnetic ribbon (1) wrapped around a rotating shaft (4) and fixed, and when torque (5) is applied to the rotating shaft (4) as shown in Figure 1 (6). The amorphous magnetic ribbon (1) has ±
Strain stress σ(6) is generated in the 45° direction, and sea-axis magnetic anisotropy is induced also in the positive direction of σ due to the magnetostrictive effect, resulting in the synthesized easy axis of magnetization from Ku(3). K
M(η). Figure 1(c) shows the torque in the opposite direction (8
) is added, in which case the acidified easy axis of magnetization K
19) has an opposite relationship to Ku(7) in FIG. 1(b). Generally, the permeability of a magnetic material changes depending on the direction of the axis of easy magnetization with respect to the excitation direction, so if the axis of easy magnetization is changed by torque as shown in Figure 1, the permeability of the amorphous magnetic ribbon changes. Torque can be detected from

FIG. 2 is an explanatory diagram of a simplified display method for displaying the winding method of the coil. As shown in Fig. 2(a), the winding (10) wound around the amorphous magnetic ribbon (1) is shown in Fig. 2(b).
) is expressed by the abbreviation of the winding (11).

FIG. 3 shows a method of detecting changes in magnetic permeability as changes in inductance. FIG. 3(a) shows a method of measuring inductance with an impedance measuring device (13) using a detection winding (12) placed around an amorphous magnetic ribbon (1). Figure 3 6) is a high frequency power supply (1
4) Change the inductance using the excitation winding (15)
This method uses an AC voltmeter (l) to detect changes in induced voltage due to mutual induction between the detection winding (12) and the detection winding (12).
Figure (c) shows a method in which a change in inductance is detected by an impedance measuring device (13) using a magnetic head (17) placed slightly away from the amorphous magnetic ribbon (1). In the above three methods, the excitation frequency 1 needs to be high so that the rotation axis (4) is hardly magnetized. The rotation speed dependence of the method shown in Figure 3 (e) can be removed. According to any of the three methods shown in Figure 3, it is possible to detect the magnitude of torque and also to distinguish between forward and reverse rotation of torque. It is possible to select the detection value based on the detected value when torque is applied and it is dangerous, and to determine based on the magnitude relationship between the detected value when torque is applied and the reference value. In addition, since the magnetostrictive phenomenon is unrelated to the rotation of the shaft, torque can be detected regardless of whether the shaft is stationary or rotating.

In order to obtain high stability and good accuracy during actual torque detection, it is desirable to use a differential configuration as a method for obtaining the output. This will be explained below using examples.

1st Embodiment Figure 4 shows the basic configuration of a torque sensor that extends the principle of Figure 3(c) to obtain a differential output. The amorphous magnetic ribbon (1) is placed at a symmetrical position tilted at an equal angle with respect to the axial direction of (4), and slightly separated from the amorphous magnetic ribbon (1). Alternatively, if the two magnetic heads (18) and (19) are excited by a high frequency power source (14) through the diode (2), when the torque (5) is not applied, , 2-), the inductances of the magnetic heads are equal due to symmetry, and the excitation currents are also equal, but when torque is applied, the inductance of one of the magnetic heads increases due to the magnetostrictive effect, and the inductance of the other decreases, so there is a gap between the excitation currents. It makes a difference. This difference in excitation current is calculated by the output resistance (21
) and smoothing capacitor (22), DC differential output %Vo
If it is extracted as ut (23), the direction and magnitude of the torque can be detected from its sign and magnitude.

Second Embodiment FIG. 6 shows the basic configuration of a magnetic circuit. An excitation magnetic head (24) and a detection magnetic head (25) are installed slightly apart from the amorphous magnetic ribbon (1) and at right angles to each other. The excitation magnetic head (24) excites the amorphous magnetic ribbon (1) with high frequency using a high frequency power supply (14) and an excitation winding (2).The excitation direction is relative to the axial direction of the rotating shaft (4). Parallel or perpendicular, and the easy axis of magnetization is also applied parallel or perpendicular to the axial direction. When no torque is applied, the magnetic resistance between AIBI and low magnetic resistance B2 is equal due to symmetry, Also, the magnetic resistance between A2B1 and A2B
Since the magnetic resistance between the two is also equal≠, the magnetic circuit bridge is balanced and the magnetic flux from the excitation magnetic head (24) does not pass through the detection magnetic head (25) and no output appears. . On the other hand, as shown in Figure 5, the torque (5
) is applied, due to the magnetostrictive effect -p AlB1
The magnitude of the magnetic resistance between AlB2 and A2B2, and the thickness of the magnetic resistance between AlB2 and A2B1.

Since the magnetic fluxes change in opposite directions, the bridge balance of the magnetic circuit is broken, magnetic flux passes through the detection magnetic head, and an induced voltage is generated in the detection winding (27). If this voltage is extracted as a direct current by the synchronous rectifier (28), the direction and magnitude of the torque can be detected from its sign and magnitude.

Compared to the conventional method that uses the ferromagnetic properties of the rotating shaft, it uses an amorphous magnetic ribbon, so there is no non-uniformity in magnetic properties in the rotation direction, and high-frequency excitation is performed using a minute excitation current. This is the advantage of this method.

The third practical example, Figure 6, applies the principle shown in Figure 3(b) and uses two amorphous magnetic ribbons (1) of the same composition to extract output differentially. This is the basic configuration of a torque sensor. The detection winding (12) is connected in such a way that the induced voltages cancel each other out. The small black circle (29) attached to the winding indicates the polarity of the winding. The easy axis of magnetization Ku (3) of the amorphous magnetic ribbon (1) is provided by heat treatment so that the inclination angle α shown in FIG. 1 is at an angle of ±α degrees with respect to the longitudinal direction of the amorphous magnetic ribbon.

When no torque is applied, the permeability of the two amorphous magnetic ribbons (1) is equal, so the two sensing windings (
12) Since the induced voltages are equal and have opposite polarities, they cancel each other out, so no output is produced. When the torque (5) is applied, taking as an example the case where the magnetostriction constant λB of the amorphous magnetic ribbon (1) is positive, the axis of easy magnetization is as shown in FIG. 7) and KuC9), the magnetic permeability on the right side becomes larger than the magnetic permeability of the amorphous magnetic ribbon on the left side, and as a result, the induced voltage in the detection winding on the right side becomes larger. This difference in induced voltage is outputted as a DC voltage by a synchronous rectifier (28).

Even if the direction of torque is reversed, the same principle applies to the synchronous rectifier (28) in which the induced voltage on the left side is larger.
The sign of the DC output voltage is reversed. Therefore, the direction and magnitude of torque can be detected. In the case where the magnetostriction constant λ8<0, the torque sensor is constructed according to the same principle as above.

The fourth embodiment, FIG. 7, applies the principle of FIG. 3(a) to use two amorphous magnetic ribbons (1) of the same composition so that the torque detection output is differentially output. The basic configuration of the torque sensor is the same as the circuit system of the first embodiment shown in FIG. Easy magnetization axis Ku of amorphous magnetic ribbon (1)
(3) is provided in the same manner as in the case of the third embodiment in FIG.

In this case, the change in magnetic permeability of the amorphous magnetic ribbon (1) when torque (5) is applied as shown in Figure 7 is shown in Figure 6.
This is the same as in the embodiment. Torque can be detected by detecting the change in magnetic permeability due to this torque (5) by changing the excitation current in the same manner as in the first embodiment in FIG.

5th Embodiment FIG. 8 shows that in the first embodiment shown in FIG. 4, one amorphous magnetic ribbon (1) is used and two detection magnetic heads (
18) , (19) are arranged obliquely along the plane of the rotating shaft (4), two amorphous magnetic ribbons (1) are used for detection as in the third and fourth embodiments. This is a torque sensor that makes it easy to install the magnetic head (No. 3).

The easy axis of magnetization Ku(3) is provided in the same manner as in the third embodiment of FIG. 6 and the fourth embodiment of FIG. 7. The circuit system is the same as that of the first embodiment shown in FIG. Therefore, torque can be detected by detecting changes in magnetic permeability due to torque (mu) based on changes in excitation current.

Embodiment 6 FIG. 9 shows that in the third embodiment of FIG. Alternatively, two amorphous magnetic ribbons (1) and (31
), and FIG. 6 shows the basic configuration of a torque sensor using the same circuit system as the third embodiment. Easy axis of magnetization Ku (3
) direction is the uniaxial magnetic anisotropy induced by the magnetostrictive effect caused by the strain stress due to zero torque (5) applied in the same direction as shown in Figure 9. Since the directions of are opposite to each other, a differential output proportional to torque (5) appears. According to this method, if the two types of amorphous magnetic ribbons (t) and (31) can be heat-treated at the same time, it has the advantage that the direction of the easy axis of magnetization Ku (3) can be precisely aligned. The method of using a combination of amorphous magnetic ribbons having different magnetostrictive characteristics can be similarly applied to each of the fourth and fifth embodiments.

As described above, the present invention eliminates the need for a dedicated torsion bar for once converting torque into screw displacement, and stabilizes and accurately converts not only static torque but also forward and reverse rotation torque. A simple and industrially suitable torque sensor that can be detected by contact is obtained.

[Brief explanation of drawings]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is an explanatory diagram regarding the abbreviation of windings, Fig. 3 is an explanatory diagram regarding the magnetic permeability detection method, and Fig. 4 is an explanatory diagram of the first embodiment of the present invention. 5 is a principle diagram of a torque sensor according to a second embodiment of the present invention, FIG. 6 is a principle diagram of a torque sensor according to a third embodiment of the present invention, and FIG. 7 is a principle diagram of a torque sensor according to a third embodiment of the present invention. 〇(1) Amorphous magnetic ribbon (2) Length direction of amorphous magnetic ribbon (3) Axis of easy magnetization imparted by heat treatment (4) Axis of rotation (5) Direction of torque (6) Distribution of strain and stress due to torque (7) Torque Axis of easy magnetization (8) Direction of torque (9) Axis of easy magnetization (lO
) Winding (11) Winding written in abbreviated notation (I2) Detection winding (13) Impedance measuring device (14) High frequency power supply (15) Excitation winding (16) AC voltmeter (17) Magnetic head (18 ) Magnetic head (19) Magnetic head (20) Diode (21) Resistor (22) Capacitor (23) Output voltage (24) Magnetic head for excitation (25) Magnetic head for detection (26) Winding for excitation (27) Detection Winding (28) Synchronous rectifier (29) Symbol indicating the polarity of the winding (30) Magnetic head (31) Amorphous magnetic ribbon with negative magnetostriction constant Patent applicant: Kosuke Harada and one other person Change the content L) (bl (cl Figure 1 Figure 2 fc) Figure 3 Figure 4 Figure 5 Figure 6 Figure 3 Figure 7 Figure 8 Figure 9 Procedural amendment (method) % formula % 1. Indication of the case Patent Application No. 108542 filed in 19822. Name of the invention 3. Relationship with the case by the person making the amendment Patent applicant address 2-4-6-4 Sakurazaka, Chuo-ku, Fukuoka-shi, Fukuoka Prefecture.
Date of amendment order: November 5, 1980 Engraving of drawings (no change in content)

Claims (1)

[Claims] Non-contact detection of torque is possible by wrapping an amorphous magnetic ribbon with a large magnetostriction constant around a rotating shaft and fixing it, and using the fact that the magnetic properties of the amorphous magnetic ribbon change due to the torque applied to the rotating shaft. Torque sensor using amorphous magnetic ribbon.