JPS62185136A - Magnetostrictive type torque sensor - Google Patents

Abstract

PURPOSE:To enable a highly accurate torque detection stably for a long time, by providing a groove at a specified angle to the direction of center axis on a surface of a shaft having a magnetic distortion effect. CONSTITUTION:A torque sensor 1 provided with a plurality of grooves 3 on the surface of a shaft 2 having a magnetic distortion effect at 45 deg. to the direction of the center axis in a horizontal symmetry. Moreover, two exciting coils 4 and 5 are arranged near this shaft 2 and a yoke 7 comprising material of a high magnetic permeability on the circumference thereof with a clearance 6 between it and the shaft 2. With such an arrangement, a magnetic flux flowing in the direction at a specified angle to the direction of the center axis can be generated thereby eliminating a factor of adverse effect on the detection accuracy of torque due to adhesion between the shaft and a magnetic film. This enables a highly accurate torque detection for a long time.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention utilizes the magnetostrictive effect to reduce the torque by Δ11.
This invention relates to a magnetostrictive torque sensor that is used to perform constant measurement.

(Prior Art) Examples of conventional structures of this type of magnetostrictive torque sensor include those shown in FIGS. 7 and 8 (
A similar prior art is disclosed in JP-A-59-77326. ). This magnetostrictive torque sensor 10
1 has a magnetostrictive film 104 as shown in FIG. 102, and this magnetostriction n
'Two excitation coils 105, 106 around A 104
is arranged on the outer periphery of the excitation coil 105, 106,
Magnetostriction 11! It has a structure in which a yoke 108 made of a high magnetic permeability material is provided with a gap 107 between it and J 104. In this case, the magnetostrictive film 104 has a magnetostrictive effect as described above, and is made of, for example, Fe-based amorphous metal.

Next, the magnetostrictive torque sensor 101 having such a structure will be described.
The procedure for detecting torque using the following will be explained. First, torque detection←Previously, two excitation coils 105,
A constant alternating current voltage is applied to each of the terminals 106. In this way, the magnetostrictive film 104, the gap 107. A magnetic circuit passing through the yoke 108 is formed around the excitation coil 105 and IO2, respectively. As the detection circuit connected to this magnetostrictive torque sensor 101, the one illustrated in FIG. 9 is used. This detection circuit consists of inductances L, L2 formed by each excitation coil 105, 106, and a resistance (R).
111 and 112 constitute a bridge, and the shaft 102
Inductance L due to the addition of torsional torque to
I.

Using the current change caused by the change in L2, the resistor 111
．． Torque output is obtained as the potential difference between 112 and 112.

Next, the inductance L due to the addition of torsional torque,
, L2 will be explained. When torsional torque is applied to the shaft 102 of the magnetostrictive torque sensor 101 shown in FIG. 7 in the right direction, the magnetostrictive torque sensor 11Q 104
Along the direction 03, the left portion undergoes tensile deformation, and the right portion undergoes compressive deformation. for example,
Magnetostriction constant > Magnetostriction n to the right of 0! ,! When 104 is used, the magnetic permeability increases under tensile deformation, and the magnetic permeability decreases under compressive deformation. As a result, the inductance L of one excitation coil 105 increases, and the inductance L2 of the other excitation coil 106 decreases.

Note that when a leftward twisting torque is applied to 'hh 102, the above case is reversed.

Therefore, when the AC power supply 113 is connected and the bridge is driven at the voltage V1 frequency f, the currents in the circuits ABC and AB'C shown in FIG. 9 are respectively + 1 =
v +4 π 2 f 2
Ll 2 ... ... (1) i7=
v R+4π2f2L22-(2).

That is, from the above equations (1) and (2), the currents 11 and 12 flowing through the circuits ABC and AB'C decrease if the inductances L, , L2 increase, and conversely, if the inductances L, , L2 decrease To increase.

The potentials V, V2 at points B and B' are as follows.

V, = i, e R・−・−(3) V2 = +2 e R・・・・・・(4), and the potential difference V is:
(5), which becomes the torque output. Incidentally, in reality, a differential amplifier 10 114 is used as shown in FIG. In this case, the torque output V is linear with respect to the torque until the amount of strain applied to the magnetostriction 104 is about 10-4.

Next, each potential V associated with the addition of torque to the shaft 102
, V2, and V will be explained based on FIGS. 10 and 11. Figure 1O(a).

(b) shows changes in potentials vl and v2 caused by changes in inductance L' I + L2 in excitation coils 105 and 106, respectively, due to torque application. Further, the potential difference V, which is the torque output, is as shown in FIG.

(Problems to be Solved by the Invention) If the magnetostrictive torque sensor 101 having such a structure is used, by measuring the potential difference V.

Although it is possible to detect the direction and magnitude of the torque applied to the shaft 102, such a conventional magnetostrictive torque sensor 101 has the following problems.

That is, normally, the magnetostrictive film 104 is provided on the surface of the shaft 102 by adhesion, and in this case, the adhesion process is essential. However, the shaft 10
The adhesive layer that adheres the surface of the shaft 102 and the magnetostrictive film 104 tends to deteriorate due to repeated torque applied to the magnetostrictive film 104, changes in the temperature applied to the shaft 102 due to changes in the surrounding environment, changes over time, etc. As a result, the amount of deformation of the magnetostrictive film 104, which deforms in response to the torque applied to the shaft 102, changes, causing a problem that the torque detection 4ti changes or the accuracy deteriorates.

This invention was made in view of the above-mentioned conventional problems, and does not cause changes in the amount of deformation of the magnetostrictive film due to deterioration of the adhesive layer, and can stably detect torque with high precision over a long period of time. The purpose of the present invention is to provide a magnetostrictive torque sensor that can be used.

[Structure of the Invention] (Means for Solving the Problems) The structure of the magnetostrictive torque sensor according to the present invention for achieving the above object includes a plurality of coils disposed near a shaft having a magnetostrictive effect. In the magnetostrictive torque sensor, the magnetic flux generated by the coil forms a magnetic circuit passing through the shaft, and the torque is detected using magnetostriction caused by deformation of the shaft due to torsional torque applied to the shaft. , characterized in that the surface of the shaft is provided with a groove and/or a non-magnetic material that forms a predetermined angle with the oil direction of the center of the shaft, and applies the skin effect when electromagnetic waves are incident on a substance. It is.

The skin effect applied to the magnetostrictive torque sensor according to the present invention is expressed by equation (6).

However, the island is the magnetic permeability of the material, σ is the electrical conductivity of the material, δ is called the penetration depth, and the amplitude of the electromagnetic wave is 1/e
gives the depth attenuated to.

(Embodiment 1) FIGS. 1 and 2 are diagrams showing an embodiment of the present invention, and FIG. 1 is a diagram showing the structure of a magnetostrictive torque sensor.

That is, in this magnetostrictive torque sensor 1, as the shaft 2,
As shown in Fig. 2 (&), a Fe-13% by weight Al alloy having a magnetostrictive effect is used to form a plurality of grooves 3 symmetrically on the left and right sides at an angle of 45 degrees with the central axis direction. In the vicinity of this M2, two excitation coils 4 and 5 are disposed in the same manner as shown in FIG. 6 and a yoke 7 made of a high magnetic permeability material.

Next, the operation of this magnetostrictive torque sensor 1 is the same as that of the conventional one, so the explanation thereof will be omitted, but the operation when detecting the torque applied to the shaft 2 will be explained.

That is, under the condition of the penetration depth δ expressed by the above equation (6), the high-intensity electromagnetic wave penetrates within δ shown in FIG. 2(c). In this embodiment, since the depth of the groove 3 is set to be deeper than the above-mentioned penetration depth δ, the groove 3 is
It became possible to generate magnetic flux along the direction of .

Therefore, if a rightward torsional torque is applied to shaft 2,
In the Fe-13 wt% A cross alloy, the magnetostriction constant is 〉O, and the magnetic permeability in the groove 3 direction increases due to tensile deformation in the right side part, and the groove 3 direction increases due to compressive deformation in the left side part.
It was found that the magnetic permeability in this direction was reduced, making it possible to measure torque in the same manner as before.

In addition, Fe used as the material of the shaft 2 in this Example 1
l The penetration depth δ of the 3.1% An alloy is determined by input frequency f = lO' (Hz), magnetic permeability g = 4w x 105 (H
/m), electrical conductivity cr=lO"(Ω-'m'), from equation (6) above, δayO, 6 (mm), but the magnetic flux in the central axis direction that does not contribute to torque detection To prevent the flow of.

The greater the depth of the groove 3, the higher the torque detection sensitivity. Further, when the input frequency f is lowered until the penetration depth δ becomes larger than the depth of the groove 3, the flow of magnetic flux in the direction of the central axis increases, and the torque detection sensitivity decreases significantly.

That is, FIG. 3 is a diagram showing the relationship between torque and output obtained by this Example 1, and f! It was confirmed that even when the groove 3 described above was provided in II2, torque could be measured mainly due to the skin effect.

Furthermore, Fig. 4 shows the relationship between the actually measured input frequency f and torque detection sensitivity, and shows that as the input frequency f increases, the skin effect becomes more pronounced and the torque detection sensitivity increases. It could be confirmed.

Furthermore, in this embodiment, since the shaft is not provided with a magnetostrictive film or adhesive layer that is made of different materials, torque detection accuracy may be reduced due to the difference in thermal expansion coefficient between different materials. Conventional problems have also been resolved.

(Example 2) Figure m5 is a diagram showing another embodiment of the present invention.

In this Embodiment 2, the car 2 is the same F as in Embodiment 1.
Using an e-13% by weight An alloy, 1ti grooves were formed on its surface in the same manner as the grooves 3 provided on the shaft 2 in Example 1, as shown in FIGS. 5(a) and 5(b). A non-magnetic electrically conductive material with a thickness and width greater than the penetration depth δ mentioned above, such as a thin layer of copper +1! J 1 G is provided by plating, and the structure other than this shaft 2 is the same as that of the first embodiment.

In this magnetostrictive torque sensor 1, most of the magnetic flux flows within the penetration depth δ shown in FIG. Since a magnetic flux flow occurs in the three directions of the groove of Embodiment 2, the same characteristics as shown in FIGS. 7 and 8 are obtained.
Also, it is possible to constant the torque Δ11I.

(Embodiment 3) FIG. 6 is a diagram showing an embodiment of a pond according to the present invention.

In this Example 3, as shown in FIGS. 6(a) and 6(b), copper 20, which is a non-magnetic good electrical conductor, is placed in the groove 3 of the sleeve 2 used as the shaft 2 in Example 1. The structure other than the shaft 2 is the same as that of the first and second embodiments.

In this magnetostrictive torque sensor 1, due to the skin effect shown in equation (6) above, the flow of magnetic flux in the central axis direction is further reduced compared to each of the embodiments 1.2, and the flow of magnetic flux in the direction of the groove 3 is reduced. As a result, the torque detection sensitivity is improved.

The shaft 2 shown in Examples 1 and 2.3 may be made of any material that has a magnetostrictive effect, and the Q film 10 may be made of a non-magnetic material, more preferably a non-magnetic material with good electrical conductivity. A similar effect can be obtained in the body.

[Effects of the Invention] As explained above, according to the present invention, a plurality of coils are arranged near a shaft having a magnetostrictive effect, and a magnetic circuit is formed in which the magnetic flux generated by the coils passes through the shaft. In a magnetostrictive torque sensor that detects the torque using magnetostriction caused by deformation of the shaft due to torsional torque applied to the shaft, the surface of the shaft is provided with a predetermined angle with respect to the central axis direction of the shaft. By adopting a configuration that includes a groove and/or a non-magnetic material, it is possible to generate a magnetic flux flowing in a direction that makes a predetermined angle with the direction of the central axis, which eliminates the problem of conventional problems between the axis and the magnetostrictive film. It is possible to eliminate the adverse effect F that affects the accuracy of torque detection due to the adhesion of the adhesive, and it is possible to obtain an extremely excellent effect that it is possible to perform torque detection with extremely high precision over a long period of time when measuring torque.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional explanatory diagram showing a structural example of a magnetostrictive torque sensor according to an embodiment of the present invention, Fig. 2 (a), (b),
(c) is a front view, a side cross-sectional view, and an enlarged cross-sectional view of the groove portion of the shaft used in the magnetostrictive torque sensor shown in Fig. 1, and Fig. 3 is an enlarged sectional view of the shaft used in the magnetostrictive torque sensor shown in Fig. 1. Figure 4 is an explanatory diagram showing the relationship between the input frequency and torque detection sensitivity actually measured from the magnetostrictive torque sensor having the structure shown in Figure 1, and Figure 5 is an explanatory diagram showing the relationship between torque and output.
a), (b), and (c) are a front view, a side sectional view, and an enlarged sectional view of a thin film portion, respectively, showing the structure of a shaft according to another embodiment of the present invention, and FIG. 6(a). (b) and (c) are a front view, a side sectional view, and an enlarged sectional view of a groove portion showing the structure of a shaft according to still another embodiment of the present invention, and FIG. 7 is a structure of a conventional magnetostrictive torque sensor. An explanatory cross-sectional diagram showing an example, FIG. 8 is a developed explanatory diagram of a model of magnetostriction used in the magnetostrictive torque sensor of FIG. 7, and FIG. 9 is a diagram of the detection circuit of the magnetostrictive torque sensor of FIGS. 1 and 7. -・Explanatory diagram showing examples, Figures 10(a) and (b) are similar to Figures 1 and 7.
Explanatory diagram showing changes in potentials V1 and V2 caused by changes in intufftances L, L2 due to torque application in each excitation coil of the magnetostrictive torque sensor shown in the figure.
Figure 1 also shows the potential difference V (= lV+
FIG. 2 is an explanatory diagram showing changes in V2 1). DESCRIPTION OF SYMBOLS 1... Magnetostrictive torque sensor, 2... Shaft, 3... Groove, 4.5... Excitation coil, 6... Gap, 7... Yoke, 10... Thin film (non-magnetic good conductor of electricity). 20...Copper (non-magnetic good electrical conductor). Patent applicant: Kushio Jidosha Co., Ltd. Attorney, Patent Attorney: Fumi Koshio Figure 1 Figure 2 (.) Figure 2 (b) Figure 2 (c) Figure 5 (a) Figure 5 (b) Figure 5 Fig. (C) Fig. 6 (0) Fig. 6 (b) Fig. 6 (C) Fig. 9 Fig. 10 (0) Fig. 10 (b) Fig. 11 left rotation Chi-rotation procedure amendment book 1986 October 17th, Commissioner of the Japan Patent Office, Kuro 1) Mr. Akihiro 1, Indication of the case, 1985 Patent Application No. 28364, 2, Name of the invention, Magnetostrictive torque sensor 3, Person making the amendment, Relationship to the case, Name of patent applicant (name) ) (399) Nissan Motor Co., Ltd. 4, Agent Address (Residence) Kobikikan Ginza Building, 2-8-9 Ginza, Chuo-ku, Tokyo 104 Phone: 03 (5B?) 2781 (Representative) 6, Increase due to amendment Number of inventions 7, Figure 1 of drawings subject to amendment 8, Contents of amendment

Claims (1)

[Claims] (1) A plurality of coils are disposed near a shaft having a magnetostrictive effect, and the magnetic flux generated by the coils forms a magnetic circuit passing through the shaft, and the shaft is deformed by torsional torque applied to the shaft. In the magnetostrictive torque sensor that detects the torque using magnetostriction caused by, the surface of the shaft is provided with a groove and/or a non-magnetic material that forms a predetermined angle with the direction of the central axis of the shaft. Features of magnetostrictive torque sensor.