JPH0943070A - Magnetostrictive torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetostrictive torque sensor including a shield case which is easy to mold, can be mass-produced and is inexpensive. SOLUTION: A magnetostrictive torque sensor comprising coils 14, 15 placed around a magnetically anisotropic part 12 formed on a surface of a torque transmission shaft 11 has a shield case 31 for receiving the coils 14, 15 wherein a plurality of divided pieces 32 in a peripheral direction of press-molding are assembled into a cylindrical structure with both ends closed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque sensor.

[0002]

2. Description of the Related Art As a known magnetostrictive torque sensor, a pair of magnetic anisotropic portions are formed on the outer circumference of a torque transmission shaft, and the magnetic permeability of each magnetic anisotropic portion when torque is applied to this shaft is measured. The change is detected by a pair of detection coils arranged along the outer circumference of these magnetic anisotropic parts, and the magnitude of the torque acting on the shaft is converted into an electric signal from the difference between the detection signals. There is.

In this type of magnetostrictive torque sensor, the detection coil and this detection coil are arranged so that the detected value does not include disturbance and the magnetic flux is efficiently passed through the magnetic anisotropic portion of the torque transmission shaft. It is customary to arrange an exciting coil for exciting in a cylindrical shield case.

7 and 8 show an example of a conventional magnetostrictive torque sensor of this type. Here, 11 is a shaft for transmitting torque, and a pair of magnetic anisotropic parts 12, 12 are formed on the outer periphery of the shaft 11 and are inclined in directions opposite to each other at an angle of ± 45 degrees with respect to the axial direction of the shaft 11. , Each of which is formed by a large number of knurling grooves and the like.

An excitation coil 14 and a detection coil 15 wound around a bobbin 13 are arranged around each magnetic anisotropic portion. The detection coil 15 can detect a change in magnetic permeability of the magnetic anisotropic portion when torque is applied to the shaft 11. The exciting coil 14 is provided to excite the detecting coil 15.

The coil 14 wound around the bobbin 13 in this way,
15 is housed inside a cylindrical shield case 16. In other words, the shield case 16 is a cylindrical body in which the circumferential direction is divided into halves each of 180 degrees, and the accommodating portion 17 for each bobbin 13 is formed on the inner periphery thereof. At the same time, both ends thereof are closed by the inner peripheral flange 18. Through holes 19 are formed in the shield case 16 every 180 degrees along the circumferential direction, and the circuit board 20 is provided inside one of the through holes 19.
Is housed. The circuit board 20 is provided with a terminal 21 for wiring to the outside. The shield case 16 is formed by cutting a permalloy-based steel material and then heat-treating it.

In FIG. 7, reference numeral 22 is a line of magnetic force generated around the coils 14 and 15, and the line of magnetic force 22 is the magnetic anisotropy portion 12.
Of the shield case 16 and a portion of the shield case 16 around the accommodating portion 17 are passed.

[0008]

However, if the shield case 16 is formed by such a cutting process, it takes a lot of time to manufacture the shield case 16, and therefore it is not suitable for mass production and the manufacturing cost is high. There is a point.

Therefore, an object of the present invention is to solve the above problems and to obtain a magnetostrictive torque sensor having a shield case that is easy to mold, mass-produces, and is inexpensive.

[0010]

In order to achieve this object, the present invention provides a magnetostrictive torque sensor in which a coil is arranged around a magnetic anisotropic portion formed on the surface of a torque transmission shaft. A shield case for housing,
A plurality of divided pieces formed by press molding in the circumferential direction are assembled into a cylindrical shape having a structure in which both ends are closed.

As described above, since the press-formed circumferentially divided plural pieces are assembled in a cylindrical shape with both ends closed, the molding is easy, and thus mass production can be performed at low cost. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIGS. 1 to 3, a shield case 31 of a magnetostrictive torque sensor according to the present invention comprises:
It is configured by assembling a divided piece 32, which is divided into four in the circumferential direction, into a cylindrical shape. Each divided piece 32 is
It is a soft magnetic plate material such as permalloy, soft magnetic stainless steel, electromagnetic steel plate, etc. that is press-molded, and has a shield case 31
A main body portion 33 in the axial direction, a pair of radial end plate portions 34 formed at both ends of the main body portion 33, and a pair extending outward in the axial direction from the inner peripheral ends of the end plate portions 34. Sleeve part 35
And are integrally formed. With such a circumferentially divided structure, press molding can be easily performed, and thus the shield case, that is, the torque sensor can be mass-produced at low cost.

Holes 36 used for wiring to the outside are formed in the shield case 31 at positions every 180 degrees along the circumferential direction. Each of the divided pieces 32, which is divided into four in the circumferential direction as described above, is configured such that the center position in the circumferential direction of the hole 36 forms the dividing line. That is, a cutout 37 having a size half that of the hole 36 is formed in each of the divided pieces 32 so that one hole 36 is formed by the pair of divided pieces 32. With this configuration, the shield case 31 can be configured with only one type of divided piece 32.

After the divided pieces 32 are assembled into a cylindrical shape, a holding member 38 for holding the cylindrical state is arranged on the outer circumference of the cylindrical body. The holding member 38 is formed of, for example, a magnetic metal pipe that functions as a further shield. During stress relief annealing after forming the divided pieces 32 by press working, in a state of final shape in which a plurality of divided pieces 32 are cylindrically held by such a holding member 38 made of a metal pipe, these are placed in an annealing furnace. You can put it in. By doing so, deformation of the divided pieces 32 during the annealing heat treatment is prevented. It should be noted that the holding member 38 may be formed in a band shape wound around the outer circumference of the cylindrical body instead of the pipe shape.

When it is not necessary to perform the annealing heat treatment in the state where the divided piece 32 and the holding member 38 are integrated as described above, or when the required shielding effect is obtained only by the divided piece 32, The holding member 38 may be made of a material using other material. For example, the holding member 38 can be configured by a rubber band or the like.

In the magnetostrictive torque sensor thus constructed, the shield case is used as in the conventional case shown in FIG.
In 31, the magnetic force lines pass mainly in the axial direction and the magnetic force lines do not substantially pass in the circumferential direction, so the required performance is not impaired even with a structure divided in the circumferential direction. There is an advantage. Leakage of magnetic field lines to the outside due to the existence of a gap between the divided pieces 32, and the risk of magnetic field lines entering from the outside are eliminated by providing the holding member 38 that functions as a shield body as described above. can do.

In the above description, the torque sensor having a pair of the magnetic anisotropy portion 12 and the corresponding coils 14 and 15 is shown, but the number of these can be increased or decreased depending on the type of the torque sensor. Correspondingly, the shape of the shield case 31, that is, the divided piece 32 can be changed.

FIG. 4 shows another form of the shield case according to the present invention. That is, each divided piece 32 has a pair of large diameter portions 39 for accommodating the pair of bobbins 13 around which the exciting coil 14 and the detection coil 15 are wound, corresponding to each magnetic anisotropic portion 12, and these large diameter portions 39. It is formed to have a small diameter portion 40 formed between the diameter portions 39. With such a configuration, since the magnetic flux passage 41 in the radial direction is formed between the pair of bobbins 13, a favorable magnetic flux is generated and the performance of the torque sensor is improved.

5 and 6 show another form of the shield case according to the present invention. Here, the split piece
32 is divided into six in the circumferential direction. When the number of divisions is increased in this way, press forming becomes easier accordingly. Therefore, it is particularly advantageous when molding a large-diameter shield case. When divided into 6 parts as shown in the drawing, the first part has a notch 37 corresponding to the hole 36.
The shield case 31 can be composed of only two kinds of divided pieces 32A and the second divided piece 32B corresponding to a portion where it is not necessary to form a hole.

[0020]

As described above, according to the present invention, a shield case for accommodating a coil in a magnetostrictive torque sensor has a cylindrical shape in which a plurality of divided pieces are press-formed in the circumferential direction and both ends are closed. Since the shield case is assembled, the shield case can be easily molded and can be mass-produced at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a magnetostrictive torque sensor according to the present invention.

FIG. 2 is a side view of the shield case shown in FIG.

FIG. 3 is a perspective view of the shield case shown in FIG.

FIG. 4 is a cross-sectional view of a main part of another example of the shield case.

FIG. 5 is a perspective view of still another example of the shield case.

6 is a side view of the shield case shown in FIG.

FIG. 7 is a sectional view of a main part of a conventional magnetostrictive torque sensor.

8 is a side view of the shield case shown in FIG. 7. FIG.

[Explanation of symbols]

 12 Magnetic anisotropy section 14 Excitation coil 15 Detection coil 31 Shield case 32 Divided piece 32A Divided piece 32B Divided piece 38 Holding member

Claims (6)

[Claims] 1. A magnetostrictive torque sensor in which a coil is arranged around a magnetic anisotropy portion formed on the surface of a torque transmission shaft, and a shield case for housing the coil is press-molded. A magnetostrictive torque sensor having a structure in which a plurality of divided pieces are assembled in a circumferential direction in a cylindrical shape with both ends closed. 2. The magnetostrictive torque sensor according to claim 1, further comprising means arranged around a divided piece assembled in a cylindrical shape to hold the cylindrical state. 3. The magnetostrictive torque sensor according to claim 2, wherein the holding means constitutes a further shield case. 4. A pair of magnetic anisotropic portions are formed along the axial direction of the torque transmission shaft, and a pair of coils corresponding to the magnetic anisotropic portions are arranged. The magnetostrictive torque according to any one of claims 1 to 3, further comprising a pair of large-diameter portions for accommodating the coil and a small-diameter portion formed between the large-diameter portions. Sensor. 5. The shield case has a length of 180 along the circumferential direction.
There is a hole at every position, and each divided piece is configured to be divided into four at intervals of 90 degrees along the circumferential direction, and the center position in the circumferential direction of the hole forms the dividing line. The magnetostrictive torque sensor according to any one of claims 1 to 4, wherein the magnetostrictive torque sensor is configured as described above. 6. A method for manufacturing the magnetostrictive torque sensor according to claim 2 or 3, wherein the divided piece is held in a cylindrical state by a holding means, and then the divided piece is heat-treated. And