JP2003121275A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection accuracy by eliminating magnetic loss in a coil yoke part. SOLUTION: In this torque sensor, an input shaft 1 is connected to an output shaft 3 through a torsion bar 3, a magnetic path member 7 having a plurality of projections 8 on its circumference is attached to the output shaft 2, and detection coils 9 and 10 are disposed at positions facing to each other from the shaft direction on the side face of the path member 7. A magnetism limiting member 11 is attached to the input shaft 1, and shielding walls 12 and 13 having a plurality of windows 14 and 15 for the limiting member 11 are disposed between the detection coils 9 and 10 and the path member 7. An overlapping amount between the windows 14 and 15 of the shielding walls 12 and 13 and the projections 8 of the path member 7 produced by torsion of the coil spring 3 is detected as impedance variation of the detection coils 9 and 10. In the torque sensor, a coil yoke 18 of the detection coils 9 and 10 is integrally formed in a U-shaped half-cross-sectional shape with one axial end facing to the path member 7 opened, and a bobbin 17 is inserted from an opening 18a at the axial one end of the coil yoke 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor used for an electric power steering device of a vehicle,
In particular, the present invention relates to a torque sensor that converts a twist amount of an elastic body such as a torsion bar provided on a rotating shaft into impedance change and detects the impedance change by a detection coil.

[0002]

2. Description of the Related Art As a torque sensor of this type, Japanese Patent Laid-Open No.
A device described in Japanese Patent Laid-Open No. 1011212 has been devised.

In this torque sensor, the input-side and output-side shaft elements of the rotary shaft are connected by a torsion bar, and a magnetic path member made of a magnetic material having an uneven outer peripheral surface is integrally rotatable with one of the shaft elements. It is provided and on the other shaft element,
A cylindrical magnetic limiting member that surrounds the circumference of the magnetic path member is also provided so as to be integrally rotatable. A detection coil is attached to a housing that rotatably accommodates the rotating shaft so as to face the outer peripheral surface of the magnetic path member with the magnetic limiting member interposed therebetween, and allows passage of magnetism on the peripheral wall of the magnetic limiting member. Windows are formed. Therefore, in the case of this torque sensor, when the torsion bar is twisted and deformed by the torque acting on the rotating shaft, the overlap amount of the unevenness of the window of the magnetic limiting member and the magnetic path member changes accordingly, and the change is referred to as impedance change. It is detected by the detection coil.

Further, in the detection coil mounted on the housing, a bobbin around the coil body is housed in an annular coil yoke, and the magnetic entrance / exit end of the coil yoke faces the magnetic path member on the inner peripheral side. However, since the coil yoke accommodates the bobbin inside, the coil yoke has a structure in which the bobbin is sandwiched between a plurality of magnetic parts and the magnetic parts are joined together in that state.

[0005]

However, in this conventional torque sensor, since the coil yoke forming the magnetic path on the detection coil side is composed of a plurality of magnetic parts, magnetic loss occurs at the joint between the magnetic parts. Occurs,
For that reason, the detection accuracy is likely to be lowered.

Therefore, the present invention is intended to provide a torque sensor capable of improving the detection accuracy by eliminating the magnetic loss in the coil yoke portion.

[0007]

As a means for solving the above-mentioned problems, a first aspect of the present invention is directed to a rotating shaft formed by connecting two shaft elements by an elastic body, and the one shaft element. A magnetic path member made of a magnetic material, which is provided so as to be able to rotate integrally with each other and is provided with irregularities along the circumferential direction, and a bobbin around which the coil body is wound are housed in an annular coil yoke. A detection coil attached to the housing so that the inlet / outlet faces the magnetic path member in the axial direction, and provided integrally rotatably on the other shaft element so as to shield between the magnetic path member and the detection coil. And a magnetic limiting member made of a non-magnetic material having conductivity, in which a window for permitting the passage of magnetism is provided in a shielding wall located between the magnetic path member and the detection coil, and the elastic deformation is twisted and deformed. Magnetic limit associated with In a torque sensor for detecting the amount of overlap between a window of a material and unevenness of a magnetic path member as a change in impedance of a detection coil, a coil yoke of the detection coil is opened at one end in the axial direction facing the magnetic path member. The bobbin is integrally formed in a U-shaped half-section shape, and the bobbin is inserted through an opening at one end of the coil yoke in the axial direction.

In the case of the present invention, the bobbin can be housed inside the coil yoke simply by inserting the bobbin from one end side in the axial direction of the coil yoke, and the coil yoke is integrally formed as a whole. Since there is no joint, no magnetic loss occurs in the coil yoke.

It is desirable that the coil yoke and the bobbin be provided with a locking structure for locking them. In this case, it is possible to eliminate the positional deviation and the rattling of the bobbin with respect to the coil yoke.

As the locking structure, a through hole may be formed in the bottom wall of the U-shaped half cross section of the coil yoke, and the bobbin may be provided with a locking projection fitted into the through hole. In this case, since it is only necessary to form a through hole along the axial direction with respect to the coil yoke, the coil yoke can be easily molded. Also, when the bobbin is assembled to the coil yoke, It suffices to fit the locking projections into the through holes as they are in accordance with the insertion operation when inserting into.

It is preferable to form a plurality of through holes in the coil yoke at equal intervals in the circumferential direction. In such a case, the magnetic resistance can be balanced in the circumferential direction.

Further, a bobbin terminal insertion hole may be formed in the bottom wall of the coil yoke together with the through hole. In this case, the coil yoke can be easily formed, and the entire coil yoke can be easily designed in consideration of the change in the magnetic resistance due to the formation of the bobbin terminal insertion hole.

Further, the locking projection may be projected from the through hole of the coil yoke, and the projection may be crushed and deformed. In this case, the locking projection is surely prevented from coming off from the through hole, and the positional displacement and rattling of the bobbin with respect to the coil yoke are more reliably prevented.

Further, the locking projection is formed of resin, the coil yoke is press-fitted and fixed in the housing, and the tip of the locking projection protruding from the through hole of the coil yoke is abutted against the bottom wall of the housing portion of the housing. You can In this case, since the coil yoke can be fixed to the housing in a state where the elastic locking projection made of resin is brought into contact with the bottom wall of the housing portion, rattling of the coil yoke with respect to the housing is eliminated and the detection accuracy of the detection coil is improved. It is possible to raise it.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, one embodiment of the present invention is shown in FIG.
~ It demonstrates based on FIG.

FIG. 1 shows an embodiment in which a torque sensor according to the present invention is applied to a power steering device for a vehicle. In FIG. 1, reference numeral 1 denotes one axial element of a steering shaft (rotating shaft in the present invention). Is an input shaft, 2 is an output shaft which is the other shaft element of the same shaft, 3
Is a torsion bar as an elastic body that connects the input shaft 1 and the output shaft 2. The input shaft 1 and the output shaft 2 are rotatably supported by a housing 4 via bearings (not shown), and a large-diameter sleeve 5 is formed at the end of the input shaft 1 on the output shaft 2 side. A small diameter portion 6 whose distal end is inserted into the sleeve 5 is formed at the end portion on the input shaft 1 side.

An annular magnetic path member 7 made of a magnetic material is press-fitted and fixed to the root portion of the small diameter portion 6 of the output shaft 2. In this magnetic path member 7, a plurality of projections 8 projecting in the radial direction are provided on the outer peripheral surface at equal intervals as shown in FIG.
As a result, irregularities are formed on the outer peripheral edge portion.

A first detection coil 9 and a second detection coil 10 which will be described later and are fixedly installed in the housing portion of the housing 4 are arranged at positions facing both sides in the axial direction of the magnetic path member 7. Further, on the outer peripheral surface of the sleeve 5 of the input shaft 1,
A magnetic limiting member 11 made of a non-magnetic material having conductivity is attached.

As shown in FIGS. 1 to 3, the magnetic limiting member 11 has a cylindrical mounting base 11a fitted to the outer peripheral surface of the sleeve 5 and a magnetic path member 7 connected to the mounting base 11a. A surrounding portion 11b that covers from one axial side surface to the other axial side surface in a non-contact state is provided, and one disk-shaped side wall of the surrounding portion 11b has a magnetic path member 7 and a first detection coil 9. The first shield wall 12 is arranged between them, and the other side wall is arranged between the magnetic path member 7 and the second detection coil 10 to form a second shield wall 13.

On the first shield wall 12 and the second shield wall 13, a plurality of windows 14 ..., 15 ... Allowing passage of magnetism are formed at equal intervals in the circumferential direction. The windows 14 and 15 are formed to have the same width and the same number as the projections 8 of the magnetic path member 7, and the windows 14 of the one shield wall 12 and the windows 15 of the other shield wall 13 are formed with a set phase shift in the rotation direction. Has been done.

Reference numeral 30 in FIGS. 1 and 3 is attached from the general portion of the output shaft 2 to the root portion of the magnetic path member 7 to prevent the magnetism from wrapping around from the outer peripheral surface side of the output shaft 2. 11 is a magnetic limiting member made of the same material.

Here, the first detection coil 9 and the second detection coil 10 have a symmetrical structure with the magnetic path member 7 interposed therebetween, and the difference between impedance changes detected by the detection coils 9 and 10 is obtained. The change of self-inductance due to temperature etc. can be canceled.
Therefore, in the following, only the structure of the first detection coil 9 will be described in detail, and regarding the second detection coil 10, the same parts as those of the first detection coil 9 will be denoted by the same reference numerals and description thereof will be omitted. .

The detection coil 9 comprises a Korui body 16 and a resin bobbin 17 around which the coil body 16 is wound.
And a coil yoke 18 made of a magnetic material that accommodates the bobbin 17 therein. As shown in FIGS. 1 and 4, the coil yoke 18 (in FIG. 4, the coil body 16 is
Are not shown. ) The whole is formed in an annular shape, but its longitudinal half-section is integrally formed so as to form a U-shape with one end side in the axial direction opened. The bobbin 17 is housed inside the coil yoke 18 from the opening 18a on the one end side. Then, three through-holes 19 penetrating in the axial direction are formed at equal intervals in the circumferential direction in a portion of the coil yoke 18 corresponding to the bottom wall 18b of the U-shaped half cross section. One arcuate insertion hole 20 is formed while avoiding the formation position of the through hole 19.

Further, the bobbin 17 has three cylindrical locking projections 21 formed at equal intervals in the circumferential direction on the end surface of the bobbin 17 which is inserted into the Cory yoke 18, and the bobbin terminal 22 is provided outside on the same end surface. Substantially arcuate reinforcing protrusion 2 for pulling out
3 is formed. These protrusions 21 and 23 together with the through hole 19 and the insertion hole 20 of the coil yoke 18 form the bobbin 1.
7 and the coil yoke 18, and the bobbin 17 is provided in the axial opening 1 of the coil yoke 18.
8a when inserting it into the inside of the coil yoke 18 from FIG.
As shown in FIG. 3, the through hole 19 and the insertion hole 20 are fitted respectively. Then, as shown in FIG. 5, the tip end portions of the locking protrusions 21 protruding from the respective through holes 19 of the coil yoke 18 are crushed and deformed by heat staking or the like to be firmly fixed to the bottom wall 18b of the coil yoke 18. ing.

Each of the detection coils 9 and 1 thus configured
0 is press-fitted and fixed in the housing portion of the housing 4, and
The bobbin terminal 22 is connected to a circuit board (not shown) including an AC current supply section and an impedance detection section. At this time, at least one detection coil 9 projects the tip end of the locking projection 21 into the housing section bottom wall 24. Housing 4 when applied
Has been pressed into. Therefore, the coil yoke 18 is supported by the housing 4 with the elasticity of the resin-made locking projections 21, which prevents the coil yoke 18 from rattling.

Since the torque sensor has the above-described structure, when a torque is input between the input shaft 1 and the output shaft 2, the torsion bar 3 is twisted according to the torque, and the torsion bar 3 is twisted according to the twisted amount. Each window 14 ..., 15 ... of the magnetic restricting member 11
And the amount of overlap between the protrusion 8 of the magnetic path member 7 changes,
As a result, the impedance change corresponding to the overlap amount is detected by the detection coils 9 and 10.

In the case of this torque sensor, the coil yoke 18 of each of the detection coils 9 and 10 is integrally formed in a U-shaped half cross-sectional shape having an opening at one end in the axial direction, and the opening 18a is formed.
Since the bobbin 17 is inserted into the inside of the yoke 18, it is extremely easy to assemble the detection coils 9 and 10, and since the coil yoke 18 is completely seamless, Magnetic loss does not occur.
Therefore, in this sensor, the torsion bar 3
It is possible to detect the impedance change according to the twist of the with high accuracy.

Further, in this torque sensor, since each bobbin 17 and the coil yoke 18 can be locked by the locking structure composed of the locking projections 21 and the through holes 19, a plurality of them can be locked as in the conventional one. Although it is not a structure in which the bobbin 17 is sandwiched by the magnetic material, it is possible to prevent the bobbin 17 from being displaced with respect to the coil yoke 18 and rattling. In particular, in the case of this embodiment, since the tip end portion of the locking projection 21 protruding from the through hole 19 is crushed and deformed, it is possible to more reliably prevent the bobbin 17 from being displaced or rattling.

Further, as the locking structure for the bobbin 17 and the coil yoke 18, various structures other than this embodiment can be adopted, but as in this embodiment, the bottom wall 18b of the coil yoke 18 has a shaft. Forming a through hole 19 along the direction,
When the locking projection 21 is fitted into the through hole 19, the locking projection 21 and the through hole 19 can be fitted at the same time when the bobbin 17 is inserted into the coil yoke 18. Assembly work can be performed efficiently. Further, when a plurality of through holes 19 are formed at equal intervals in the circumferential direction as in this embodiment, the magnetic resistance on the coil yoke 18 can be balanced in the circumferential direction.
It is possible to further improve the detection accuracy of the detection coils 9 and 10. Further, as in this embodiment, the coil yoke 18
When the insertion hole 20 of the bobbin terminal 22 is also formed in the bottom wall 18b of the above, the manufacturing of the coil yoke 18 is facilitated because the directions of the holes 19 and 20 are the same, and the coil yoke is also formed. When manufacturing 18, each hole 19,
There is an advantage in that it is possible to design by comprehensively considering the change in magnetic resistance due to the provision of 20.

Further, in this embodiment, the resin bobbin 17 protruding from the through hole 19 of the coil yoke 18 is used.
By making the protrusion 21 contact the bottom wall 24 of the housing portion of the housing 4 so that the rattling of the coil yoke 18 can be absorbed by the elasticity of the resin, the detection coils 9 and 10 are always in a stationary state. Therefore, there is an advantage that the detection accuracy of the coils 9 and 10 can be further improved.

The embodiment of the present invention is not limited to the one described above. For example, as shown in FIG. 6, the locking protrusion 121 formed on the bobbin 17 has a tapered retaining portion 121a at the tip thereof. Alternatively, the retaining portions 121a may be bulged, and the retaining portions 121a may be pushed into the corresponding through holes 19 of the coil yoke 18 to make the through holes 19 submerge.

[0032]

As described above, the invention described in claim 1 is
The coil yoke of the detection coil is integrally formed in a U-shaped half-section shape in which one end in the axial direction facing the magnetic path member is open,
Since the bobbin is inserted from the opening at one end in the axial direction of the coil yoke, the joint loss in the Cory yoke eliminates the magnetic loss in the yoke and facilitates the assembly of the detection coil. You can Therefore, according to the present invention, it is possible to reliably improve the detection accuracy and reduce the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing the same embodiment.

FIG. 3 is a perspective view showing the same embodiment.

FIG. 4 is an exploded perspective view showing the same embodiment.

FIG. 5 is a perspective view showing the same embodiment.

FIG. 6 is a perspective view showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Input axis (one axis element) 2 ... Output shaft (other shaft element) 3. Torsion bar (elastic body) 7 ... Magnetic path member 8 ... Protrusions (unevenness) 9 ... 1st detection coil (detection coil) 10 ... Second detection coil (detection coil) 11 ... Magnetic limiting member 12 ... First shielding wall (shielding wall) 13 ... Second shielding wall (shielding wall) 14, 15 ... Windows 16 ... Coil body 17 ... Bobbin 18 ... Coil yoke 18a ... Opening 18b ... bottom wall 19 ... Through hole 20 ... Insertion hole 21, 121 ... Locking protrusion 22 ... Bobbin terminal 24 ... Housing bottom wall

Claims (7)

[Claims] 1. A rotating shaft formed by connecting two shaft elements with an elastic body, and a magnetic body made of a magnetic material, which is integrally rotatably provided on the one shaft element and is provided with irregularities along a circumferential direction. A path member and a bobbin around which the coil body is wound are housed in an annular coil yoke, and a detection coil attached to the housing so that the magnetic entry / exit portion of the coil yoke faces the magnetic path member in the axial direction. A window that is integrally rotatably provided on the other shaft element so as to shield between the magnetic path member and the detection coil, and has a window that allows passage of magnetism is provided in a shielding wall located between the magnetic path member and the detection coil. And a magnetic limiting member made of a non-magnetic material having electrical conductivity, and the impedance variation of the detection coil is determined by determining the amount of overlap between the window of the magnetic limiting member and the unevenness of the magnetic path member due to the torsional deformation of the elastic body. When And a coil yoke of the detection coil, wherein the coil yoke of the detection coil is integrally formed in a U-shaped half cross-sectional shape with one end in the axial direction facing the magnetic path member open, and the bobbin is provided with a shaft of the coil yoke. A torque sensor characterized by being inserted from an opening at one end in the direction. 2. The torque sensor according to claim 1, wherein a locking structure for locking the coil yoke and the bobbin is provided. 3. A through hole is formed in the bottom wall of the U-shaped half cross section of the coil yoke, and a locking projection to be fitted into this through hole is provided on the bobbin. The torque sensor according to claim 2, wherein the torque sensor has a stop structure. 4. The torque sensor according to claim 3, wherein a plurality of the through holes are formed at equal intervals in the circumferential direction. 5. The torque sensor according to claim 3, wherein a bobbin terminal insertion hole is formed together with the through hole in the bottom wall of the U-shaped cross section of the coil yoke. 6. The torque sensor according to claim 3, wherein the locking projection is projected from a through hole of the coil yoke, and the projection is crushed and deformed. 7. The locking protrusion is formed of resin, the coil yoke is press-fitted and fixed in the housing, and the tip of the locking protrusion protruding from the through hole of the coil yoke is abutted against the bottom wall of the housing portion of the housing. The torque sensor according to any one of claims 3 to 6, characterized in that.