JPS60123078A - Torque sensor - Google Patents

Abstract

PURPOSE:To obtain a torque sensor having excellent linearity in the detection of torque extending over a wide range by fixing a magnetic metallic thin band, a saturation magnetostriction constant lambdas thereof is kept within a specific range, to a shaft and detecting the change of the magnetic characteristics of the thin band in a non-contact manner. CONSTITUTION:A magnetic metallic thin band 22 having magnetostriction, a saturation magnetostriction constant lambdas thereof satisfies the relationship of formula 1X10<-6=¦lambdas¦<20X10<-6>, is fixed to a shaft 21, and torque is measured by detecting a change by torque applied to the shaft 21 of the magnetic characteristics of the thin band in a noncontact manner. An amorphous alloy consisting of a composition such as one of (Co1-a-bFeaMb)zSixBy (where M represents one kind or more of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Ru, Ir, Pd, Pt, Ag, Au, Cu, Zn, Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Y, and a rare-earth metal and 0.05<= a<=0.5, 0<=b<=0.15, 0<=x<=20, 4<=y<=35, x+y+z=100) is used as said magnetic metal thin band 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a torque sensor that detects torque without contact.

[Technical background of the invention and its problems]

Torque is a basic quantity when controlling a rotational drive system, and in order to accurately detect it, a non-contact structure is required.

Recently, a torque sensor that uses the magnetostrictive properties of amorphous magnetic alloys to detect torque without direct contact has been proposed (IEE of Japan Magnetics Study Group Materials MAG
-81-71).

This is achieved by wrapping an amorphous magnetic ribbon with large magnetostrictive properties around a rotating shaft and fixing it, and detecting the strain stress of the rotating shaft caused by torque by detecting changes in the magnetic properties of the amorphous alloy caused by magnetostriction. This is a non-contact detection method.

This torque sensor will be explained in more detail with reference to FIG. In Fig. 1, reference numeral 1 denotes a nine-ring magnetic core formed from a ribbon of amorphous magnetic alloy.
Induced magnetic anisotropy Ku '3 in the direction of inclination of angle θ with respect to
is provided and wound around the rotating shaft 4 and fixed. For ease of explanation.

Assume that θ>45° and saturation magnetostriction constant λ8>0. When a torque 5 is applied to the rotating shaft 4, a tension a is applied to the annular magnetic core 1 in the +45° direction, and a compressive stress -a is applied in the -45° direction, and the induced magnetic anisotropy Ku'- is applied to the annular magnetic core 1 due to the magnetostrictive effect. 3λ
S-a is guided in the +45° direction. As a result, the induced magnetic anisotropy changes to Ku6 as a combination of Ku' and Ku'. In general, the magnetic permeability of a magnetic material changes depending on the direction of induced magnetic anisotropy with respect to the excitation direction, so as shown in Figure 1, the induction of the annular magnetic core of the amorphous magnetic alloy ribbon by the torque applied to the axis of rotation is as shown in Figure 1. If the magnetic anisotropy changes, a detection coil is placed close to the annular magnetic core, and the detection circuit outputs the change in magnetic permeability as a change in voltage, thereby detecting torque. be able to.

In addition, in the above description of the torque sensor, a case was described in which an amorphous magnetic alloy was used as the magnetic material constituting the annular magnetic core, but the present invention is not limited to this, and any material exhibiting soft magnetism may be used, such as permalloy (Fe-N1 alloy). , Sendust (
Other magnetic materials such as Fe-A7-81 alloy) Fe-8t alloy can be used.

In this way, torque is detected using magnetostrictive properties, but generally when using magnetostrictive properties, a magnetic material with a saturation magnetostrictive constant of as large as possible, for example 3°XIO' or more, is used to increase the output. It is common to use

However, conventional methods often have a problem in that the linearity of output with respect to torque is poor, and measurements can only be made within a narrow torque range.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a torque sensor with excellent linearity in wide-range torque detection.

[Summary of the invention]

The present invention measures torque by non-contact detecting changes in the magnetic properties of a magnetostrictive magnetic metal ribbon (saturation magnetostriction constant λS) fixed to a rotating shaft due to torque applied to the rotating shaft. The torque sensor is characterized in that λS of the magnetic metal ribbon satisfies the relationship of 1 x 1o-'(lλSl<20 x 10-e. Such a torque sensor has very high linearity. It will be excellent.

This change in surface stress is converted into a magnetic change in the magnetic metal for measurement.
If the value is less than ', the conversion efficiency is extremely poor.

Although the linearity is good, there is a problem that the sensor output is low. Therefore, λS>lxz□−a. Furthermore, when λS exceeds 20×10 − ”, the linearity deteriorates significantly.

Therefore, the range is as described above.

The inventor of the present invention has conducted intensive research on the linearity of torque sensors, and has found a way to guarantee this linearity.

The present invention was achieved by discovering that the saturation magnetostriction constant (λ8) and induced magnetic anisotropy (Kua) of a magnetic metal ribbon are significantly related.

According to the research of the present inventor, Kuo73・λS・GA)2
(Kuo: induced magnetic anisotropy, λS: saturation magnetostriction constant, σA
: surface stress of magnetic metal ribbon], (T: torque, d
It has been found that excellent linearity can be obtained within the range of: diameter of the torque transmission shaft (rotating shaft), GT: rigidity of the torque transmission shaft, GA: rigidity of the magnetic gold 4 ribbon.

That is, Good linearity can be obtained within the range of .

As is clear from the above equation, the value of Ku6/λS is an important factor in ensuring linearity over a wide range of torque. I understand.

The physical meaning of this equation is that there are two different types of anisotropy K
In the competition between u6 and 3λSσ, Kuox3λSσA
Easily causes instability in the magnetization direction in the vicinity.

Ku, 1 because it causes a saturation phenomenon.

If it is sufficiently larger than 3λSσA, this saturation phenomenon does not occur and the easy magnetization direction changes only by a small amount in the vicinity of K11o. The critical value of this linear phenomenon is Kuo/λ5==2
That is to say.

As described above, according to the research conducted by the present inventors, it has been found that the larger K u,/λS is, the more linearity is guaranteed over a wide range of torque.

Conventionally, in stress sensors using magnetostriction.

The focus was on achieving larger saturation magnetostriction values. This is to increase the efficiency in converting stress into magnetic change.

When linearity is considered here, as mentioned above (Ku, /λ
Since the larger S is, the better, Ku6 also needs to increase as λS increases. However, K u 6 ni has a limit (~15 x 10 S 6170 m”),
If λS is increased, linearity will be degraded. For example, the maximum torque of an automobile engine shaft is 100k
In order to guarantee linearity up to this range, it is necessary to take into consideration the shaft diameter, etc.
It is necessary to impart a Ku exceeding `` by treatment in a magnetic field. However, this value exceeds the limit value and is not possible.

Therefore, the above relationship < I X 1 o−@<1λS l
In the range <20 XIO'', excellent linearity can be obtained.

Furthermore, when Kuo is applied to a magnetic metal ribbon by treatment in a magnetic field, a certain amount or more of Ku6 is required to impart more ideal uniaxial magnetic anisotropy. Therefore, Ku6) I XI O” ertt/cm” T!
It is desirable that there be.

Examples of the magnetic metal ribbon used in the present invention include Permalloy (Fe-'Ni alloy), Sendust (Fe-AJ-
Examples include magnetic materials such as 8i alloy)' and Fe-81 alloy. However, it is possible to provide a larger amount of Ku6,
It is preferable to use a large amorphous alloy with a variable range of Kuo/λS.

Also as an amorphous alloy.

(COt-a bFeaMb) zsi xByMet
Ti, Zr, Hf, V, Nb, Ta, Cr, Me.

W, Mn, Re, Ru, Ir, Pd, Pt, AJ.

Au, Cu, Zn, AJ, Ga, In, Ge, 8n.

At least one element selected from Pb, 8b, Bi, Y, rare earth metals
By using an amorphous alloy expressed as 04≦y×35x10y1z-100, a torque sensor with extremely excellent linearity can be obtained.

Here, Fe is an essential component to obtain a large value of induced magnetic anisotropy and to control the saturation magnetostriction value. is small, and at a) 0.5, the saturation magnetostriction value becomes large and the linearity deteriorates.

Therefore, 0.05 (a (range of 0.5).

M increases the crystallization temperature of the amorphous alloy, improves thermal stability, and can adjust the thickness of the thermal expansion coefficient, making it possible to match the thermal expansion coefficient of the rotating shaft material, making it reliable. This element is effective in obtaining a torque sensor with high performance, but its size is b −0,15
If it exceeds this value, it becomes difficult to make it amorphous. Therefore, b(0, 15).

Although the effect of M starts to appear when added in a small amount, it is practically preferable to set the content to 0.01(b(0,12.).

Si is an element that is effective in raising the crystallization temperature, but the reason why its content is limited to the above range is that X is 20
This is because the production of amorphous alloys becomes difficult if the Also, is B an essential element for the production of amorphous alloys?
This is because if y di is less than 4 or more than 35, it becomes difficult to manufacture an amorphous alloy.

A practically preferable lower limit value of 8i is 1<Sl.

This is because the inclusion of Sl increases the manufacturability of the amorphous alloy.

In this way, lXl0−”<Iλs l(20X 10−
It shows excellent linearity in the range of 5×1 (T6
If <1λSl<18 XI O-6, it will be more practically excellent.

〔Effect of the invention〕

As explained above, according to the present invention, a torque sensor having good linearity can be obtained, and it is effective when used in a system where torque changes over a wide range.

In a torque sensor, it is necessary to impart induced magnetic anisotropy to a magnetic metal ribbon. Created.

After heat-treating to remove internal stress, it is wound around the rotating shaft and bonded with the shaft twisted.

A method of untwisting the shaft is known.

(Materials MAG-81-
71).

Furthermore, as previously filed by the present inventors, there is also a method of imparting induced magnetic anisotropy to an amorphous magnetic alloy ribbon in advance, and then winding the ribbon around a rotating shaft and fixing it. No. 57-171347). One specific method is to heat the amorphous magnetic alloy ribbon while applying an external DC magnetic field in a direction having a certain angle θ with respect to the longitudinal direction.

However, the former method has the problem of complicating the process, such as the need to prepare an annular magnetic core that matches the diameter of the shaft in advance and the need to twist the rotating shaft. is more practical.

[Embodiments of the invention]

The present invention will be explained in detail below.

Amorphous alloy ribbon (approximately 5 mm wide) having the composition shown in Table 1
, average plate thickness 30 μm) was produced by a single roll method. This amorphous alloy ribbon was heat treated in a magnetic field at 300°C.

After imparting induced magnetic anisotropy by IH furnace cooling (applied magnetic field direction, 45° to the longitudinal direction of the ribbon, 20000e), it was fixed in the circumferential direction of the torque transmission shaft.

The configuration of the torque sensor is shown in FIG.

Reference numeral 21 in FIG.
22. is fixed. These annular magnetic cores 22, . 22
．． A thin ribbon of the amorphous magnetic alloy mentioned above is wound around the torque transmission shaft 21 and fixed thereto. Moreover, these annular magnetic cores 22. ．． At 22°, induced magnetic anisotropy is imparted in directions inclined at an angle of 45° and an angle of −45° with respect to the local direction, respectively. A detection head constituted by a pair of U-shaped magnetic cores 231m23t made of oxide magnetic material is disposed above the annular magnetic cores 221 and 22 with a gap of 1 mm between them. These magnetic cores 23. ．． 23
．． There is a primary winding (excitation winding) 2 as shown in Figure 2 1b+.
4 and 'g secondary winding (detection winding) 25 are arranged in a sister manner.

This detection head detects the annular magnetic core 22. ．． 22. The magnet can be excited in the circumferential direction. Although such excitation can be performed in the width direction depending on the configuration, it is more effective to excite in the circumferential direction where the demagnetizing field coefficient is smaller due to the shape of the ribbon because the excitation current can be smaller. Also.

The secondary winding (detection winding) 25 is differentially connected.

The torque of the torque transmission shaft 21 is detected using the torque sensor. Its characteristics are also shown in Table 1.

In Table 1, the saturation magnetostriction value (λ3) is the value determined by the strain gauge method, and the induced magnetic anisotropy (Ku) is the value obtained by heat-treating the amorphous alloy by applying a magnetic field in the length and width directions. This is a value calculated from the area surrounded by two magnetization curves falling in the first quadrant of the magnetization curve.

Linearity is defined as the 2σ value for the least squares straight line of the output, which is 70
kg, m) The least squares linear approximation value (represented by straight line (@)) for the torque value.

(Hereafter, white) As is clear from Table 1, λS is lXl0”≦1λs
It can be seen that the second embodiment of the lower body invention, which satisfies the relationship l<20X10', has better linearity.

Therefore, it is very effective when used in systems where torque varies over a wide range, such as automobile engine shafts.

[Brief explanation of drawings]

FIG. 1 is a principle diagram explaining a torque sensor, and FIG. 2 is a configuration diagram of the torque sensor. Representative Patent Attorney Noriyuki Chika (and 1 other person) Figure 1

Claims (1)

[Scope of Claims] (Non-contact detection of changes in the magnetic properties of a magnetostrictive magnetic metal ribbon (saturation magnetostriction constant λS) that is fixed to the rotating shaft) due to a torque applied to the rotating shaft. According to
A torque sensor for measuring torque, characterized in that λS of the magnetic metal ribbon satisfies the relationship lX10-'(lλ5l(20X10'). (2) An amorphous alloy is used as the magnetic metal ribbon. The torque sensor according to claim 1, characterized in that an amorphous alloy having a composition of (Co, -a-bFelMb)zsixBy is used as the amorphous alloy. The torque sensor according to claim 3. (4) As the amorphous alloy, from the composition of 0.01(b(0,12 1(X(20 1 ■■■ The torque sensor according to claim 3, characterized in that an amorphous alloy is used.