JP2008203176A - Torque sensor and electric power steering apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a magnetization of multiple poles in a magnet, improve the measurement accuracy of a torque sensor, and surely prevent contact between the magnet and magnetic materials. <P>SOLUTION: The torque sensor comprises first and second rotating shafts 1, 2 coaxially coupled via an elastic member 3 so as to relatively rotate; the magnet 6 coupled to the first rotating shaft 1, and axially magnetized to N and S poles; a pair of magnet side magnetic materials 7a, 7b axially disposed on both sides of the magnet and having a plurality of magnetic legs on the outer circumference; a pair of the magnetic materials 14, 15 coupled to the second rotating shaft 2 and having a plurality of magnetic legs, facing the magnetic poles in the magnet side magnetic materials 7a, 7b; and a magnetic detecting section 18 for detecting a magnetic flux density generated in a magnetic circuit of the magnetic materials 14, 15. When one magnetic leg 7c in the magnet side magnetic materials 7a, 7b faces one magnetic leg 14b in the magnetic materials 14, 15, the other magnetic leg 7d in the magnet side magnetic materials 7a, 7b is set so as to face the other magnetic leg 15b in the magnetic materials 14, 15. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  In the present invention, an elastic member that twists itself when a torsional torque is input is inserted between the first shaft and the second shaft, and the change in magnetic flux density generated by the magnet is caused by the torsion of the elastic member. The present invention relates to a torque sensor to be detected and an electric power steering apparatus using the torque sensor.

  As this type of torque sensor, for example, a first shaft body rotatably supported by a housing, a multi-pole magnetized permanent magnet fixed to the first shaft body, and the housing A second shaft body that is pivotally supported and disposed opposite to the first shaft body, and a tooth shape that is fixed to the second shaft body and corresponds to the multipolar magnetization number A relative displacement detection device comprising: a magnetic core having a body; and a magnetic sensor fixed to the housing and sandwiched by a magnetic member disposed in the vicinity of the outer peripheral surface of the magnetic core, The change in magnetic flux caused by the relative displacement between the permanent magnet and the magnetic core is defined as the direction of the relative position change and the amount of displacement around the rotation axis of the first shaft body and the second shaft body. In order to be detected by a sensor, the number of teeth corresponding to the number K is in the radial direction between the angle θ. And the magnetic sensor is a pair of first magnetic sensor and second magnetic sensor, and the first magnetic sensor and the second magnetic sensor are mutually angled in the radial direction {(2K + 1) / 2} θ−. There is known a relative displacement detection device provided with a 360 ° separation (see, for example, Patent Document 1).

A torque sensor comprising a torsion bar that coaxially connects the input shaft and the output shaft, a pair of magnetic yokes attached to the end of the input shaft, and a magnetic sensor that detects the magnetic flux density generated in the magnetic yoke. In the shaft yoke, the same number (12) of claws as the N pole and S pole of the magnet are provided at equal intervals on the entire circumference, and the torsion bar is not twisted. The magnetic sensor is placed so that the boundary between the N pole and S pole of the magnet coincides, and the magnetic sensor is inserted into a gap provided between the magnetic yokes facing each other in the axial direction to detect the magnetic flux density A torque sensor configured to do this is known (see, for example, Patent Document 2).
Japanese Patent No. 2741388 JP 2003-149062 A

However, in the conventional examples described in Patent Documents 1 and 2, it is necessary to magnetize the multipolar magnet in the circumferential direction, and the number of magnetizing steps is required. There is a problem that the magnetization intensity varies, and as a result, the measurement accuracy as a torque sensor deteriorates, and improvement is demanded.
Also, since it is necessary to narrow the gap between the magnetized surface of the magnet and the opposing magnetic body, a protective layer cannot be provided on the magnet surface, and contact between the magnet and the magnetic body due to poor assembly, etc. Therefore, there is a problem that the surface of the magnet is easily damaged, and there is a demand for improvement.

  Therefore, the present invention has been made paying attention to the problems of the conventional example described above, and eliminates the multipolar magnetization of the magnet to improve the measurement accuracy as a torque sensor and to make contact between the magnet and the magnetic body. An object of the present invention is to provide a torque sensor that can be reliably prevented and an electric power steering device using the torque sensor.

  In order to achieve the above object, a torque sensor according to claim 1 includes a first and a second rotating shaft that are connected so as to be rotatable relative to each other via an elastic member that is twisted when a twisting torque is transmitted coaxially. A magnet connected to either the first rotating shaft or the first rotating shaft side of the elastic member and magnetized in the NS in the axial direction, and disposed on both sides of the magnet in the axial direction on the outer peripheral surface. A pair of magnet side magnetic bodies having a plurality of magnetic legs, and the second rotation shaft and the elastic member are connected to any one of the second rotation shaft sides, and are formed by the magnet and the magnet side magnetic body. One magnet side magnet is provided with a pair of magnetic bodies having a plurality of magnetic legs arranged in a magnetic field to form a magnetic circuit, and a magnetic detector for detecting a magnetic flux density generated in the magnetic circuit of the magnetic body. When the magnetic leg of the body is opposed to the magnetic leg of one of the magnetic bodies To is characterized in that the magnetic leg of the other magnet-side magnetic bodies are disposed so as to face the magnetic leg of the other of the magnetic body.

The torque sensor according to a second aspect is the invention according to the first aspect, wherein each of the pair of magnet side magnetic bodies has a plurality of magnetic legs each having irregularities repeated at predetermined intervals on the outer peripheral surface, and one magnet The magnetic leg of the other magnet side magnetic body is disposed between the adjacent magnetic legs of the side magnetic body.
In the invention according to the first or second aspect, the magnets are simply magnetized with one of the N poles in the axial direction and the other with the S poles, and the magnetic poles of the magnetic body are relative to each other between the first rotating shaft and the second rotating shaft. Changes in the magnetic flux density due to rotation can be detected, and the magnetic flux density change can be detected by the magnetism detection unit. Magnetization of the magnet is easy, the number of magnetizing steps can be reduced, and the intensity of magnetization can be reduced. Variations can be reduced, the accuracy of magnetization can be improved, and there is no need to provide opposing parts on the outer surface of the magnet, so the surface of the magnet can be protected with a protective layer, and the magnet can be damaged. The problem can be improved.

Furthermore, the torque sensor according to a third aspect is the invention according to the first or second aspect, wherein the torque sensor is disposed in the vicinity of the magnetic body, guides the magnetic flux from the magnetic body, and includes a pair of magnetic collecting portions that collect the magnetic flux. The magnetic detection unit is arranged so as to detect a magnetic flux density generated in the auxiliary magnetic body via a magnetic collecting unit.
In the invention according to claim 3, even if the positional relationship between the magnetic detection element and the magnetic body changes, the influence on the magnetic circuit can be reduced and the magnetic flux can be concentrated on the magnetic detection element. Therefore, the influence of eccentricity and the like can be reduced and strong against magnetic disturbance.

  Furthermore, the torque sensor according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the pair of magnetic bodies is composed of a pair of yokes facing each other with a predetermined interval in the axial direction. Each yoke has an annular portion, a radial extension portion extending radially inward from the inner peripheral surface of the annular portion, and the other magnetic body in the axial direction from the tip of the radial extension portion. It has a magnetic leg composed of an axially extending portion, and the magnetic leg of the other magnetic body is disposed between the adjacent magnetic legs of one magnetic body.

In the invention according to claim 4, any of the magnet-side magnetic bodies disposed at different positions in the axial direction can constitute a magnetic circuit, and the direction of the magnetic flux induced to the magnetic detection element can be reversed. it can.
Still further, a torque sensor according to a fifth aspect is the invention according to any one of the first to fourth aspects, wherein the pair of magnet-side magnetic bodies are configured to cover the entire magnetized surface of the magnet. It is characterized by being.

In the invention according to claim 5, the magnetic flux generated from the magnet can be guided to the magnetic circuit without leakage, and the torque detection accuracy can be improved.
A torque sensor according to a sixth aspect is the invention according to any one of the first to fifth aspects, wherein the pair of magnet-side magnetic bodies is a center position between adjacent magnetic legs of one magnet-side magnetic body. In addition, the center of the magnetic leg of the other magnet-side magnetic body is disposed.

In the invention according to claim 6, the circumferential distance between the magnetic pole of one magnet-side magnetic body and the magnetic pole of the other magnet-side magnetic body can be increased, and the twist angle can be increased.
Furthermore, the torque sensor according to a seventh aspect is the invention according to any one of the first to sixth aspects, wherein each of the pair of magnet-side magnetic bodies is configured in an axisymmetric shape. Yes.

In the invention according to claim 7, since the magnetic poles of the magnet-side magnetic body are disposed at positions symmetrical with respect to the axis, the influence of eccentricity or the like can be reduced.
Furthermore, the torque sensor according to claim 8 is the invention according to any one of claims 1 to 7, wherein each of the pair of magnet-side magnetic bodies has magnetic legs arranged at equal intervals. It is a feature.

In the invention according to the eighth aspect, the distance between the magnetic legs of the magnet-side magnetic body can be increased, and the twist angle can be increased.
Still further, a torque sensor according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein the pair of magnetic bodies is located at a center position between adjacent magnetic legs of the one magnetic body. The magnetic body is arranged so that the center of the magnetic leg is located.

In the invention according to the ninth aspect, the circumferential distance between the magnetic pole of one magnetic body and the magnetic pole of the other magnetic body can be increased, and the twist angle can be increased.
A torque sensor according to a tenth aspect is characterized in that, in the invention according to any one of the first to eighth aspects, each of the pair of magnetic bodies is configured in an axisymmetric shape.

In the invention according to the tenth aspect, since the magnetic legs of the magnetic material are disposed at positions symmetrical with respect to the axis, the influence of eccentricity or the like can be reduced.
Furthermore, the torque sensor according to an eleventh aspect is characterized in that, in the invention according to any one of the first to tenth aspects, each of the pair of magnetic bodies has the magnetic legs arranged at equal intervals. .

In the invention according to claim 11, the distance between the magnetic legs of the magnetic material can be increased, and the twist angle can be increased.
Furthermore, in a torque sensor according to a twelfth aspect of the invention according to any one of the fourth to eleventh aspects, the pair of auxiliary magnetic bodies are formed in a ring shape, and each of the pair of magnetic bodies is provided with respect to the pair of magnetic bodies. They are close to each other in the radial direction, and the axial dimension is set longer than the axial dimension of the annular portion of the magnetic body.

In the invention according to the twelfth aspect, it is possible to reduce the influence of the machining error of the component parts and to reduce the influence of the eccentricity, the axial fluctuation, and the like.
Still further, a torque sensor according to a thirteenth aspect is the invention according to any one of the third to tenth aspects, wherein the pair of auxiliary magnetic bodies are closely opposed to the pair of magnetic bodies in the radial direction, and Each of the magnetic bodies is configured to be sandwiched in the axial direction.

In the invention according to the thirteenth aspect, it is possible to reduce the influence of the machining error of the component parts and to reduce the influence of the eccentricity, the axial fluctuation and the like.
According to a fourteenth aspect of the present invention, in the torque sensor according to the fourteenth aspect, the pair of auxiliary magnetic bodies includes a pair of yokes facing each other at a predetermined interval in the axial direction and having a width narrower than a width of the annular portion of the magnetic body. It has a belt-like portion, and the belt-like portion is opposed to the magnetic body in the axial direction.

In the invention according to the fourteenth aspect, it is possible to reduce the influence of the machining error of the component parts, and to reduce the influence of the eccentricity and the axial fluctuation.
The torque sensor according to a fifteenth aspect is the invention according to any one of the first to fourteenth aspects, wherein the magnetic detection unit has a plurality of magnetic detection elements, and the magnetic flux detected by the plurality of magnetic detection elements. An abnormality detection circuit for detecting an abnormality of the magnetic detection element based on the density is provided.

In the invention according to the fifteenth aspect, since two magnetic detection elements are used, the torque detection circuit can be configured in a double system.
The torque sensor according to a sixteenth aspect is the invention according to any one of the first to fourteenth aspects, wherein the magnetic detection unit includes three or more magnetic detection elements and is detected by each magnetic detection element. And an abnormality detection circuit that detects an abnormality of the magnetic detection element based on the magnetic flux density.

In the invention according to claim 16, since there are three or more magnetic detection elements, when the output values of the plurality of magnetic detection elements are equal and the output values of the remaining magnetic detection elements are different, the abnormal magnetic detection element Can be specified.
Still further, the torque sensor according to claim 17 is the invention according to any one of claims 3 to 16, wherein the magnet side magnetic body, the magnetic body, and the auxiliary magnetic body have a nickel content of 40 wt% or more, It is characterized by being set to 80 wt% or less.

According to the seventeenth aspect of the present invention, the magnetic properties of the magnet-side magnetic body, magnetic body and auxiliary magnetic body can be improved.
An electric power steering apparatus according to claim 18 uses the torque sensor according to any one of claims 1 to 17, and an input shaft connected by a torsion bar of a steering shaft connected to a steering wheel. The steering torque transmitted to the steering wheel is detected using the output shaft as the first or second rotating shaft, respectively.

  According to the seventeenth aspect of the present invention, highly accurate steering assist control can be performed using a highly accurate torque sensor.

  According to the present invention, since it is only necessary to magnetize the magnet in the N direction and the S pole in the axial direction, magnetization is easy, the number of magnetization steps can be reduced, and there is little variation in magnetization strength. Therefore, it is possible to improve the magnetization accuracy, and further, it is not necessary to provide a part facing the outer peripheral surface of the magnet, so that the surface of the magnet can be protected with a protective layer, and problems such as breakage of the magnet are improved. The effect that it can be obtained.

  Further, by configuring the electric power steering device using the torque sensor having the above-described effect, an effect that highly accurate steering assist control can be performed is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing the overall configuration of an embodiment of the present invention, FIG. 2 is a perspective view of the main part of FIG. 1, FIG. 3 is an exploded perspective view of FIG. 2, and FIG. FIG. 5 is a plan view and a side view showing the phase of the magnetic leg of the body and the phase of the magnetic leg of the magnetic body being matched, and FIG. 5 is a diagram illustrating the rotation of the magnetic body by 15 ° from FIG. FIG. 6 is a plan view showing a state in which the phase of the center of the adjacent magnetic leg of the magnetic body and the center position between the magnetic legs of the magnetic body coincide with each other. FIG. 2) A plan view and a side view of a state in which the phases of the magnetic leg of the magnet-side magnetic body and the magnetic leg of the magnetic body coincide with each other by rotating.

  In the figure, reference numeral 1 denotes a first rotating shaft connected to, for example, a steering wheel (not shown), and 2 denotes an electric motor of an electric power steering device that is coaxial with the first rotating shaft 1 and spaced apart by a predetermined distance. A second rotating shaft that is assisted and connected to a rack and pinion mechanism that steers the steered wheels via a universal joint (not shown) and an intermediate shaft. The first shaft 1 and the second shaft 2 are connected via a torsion bar 3 as an elastic member.

  A disc-shaped mounting flange 4 is formed at the end of the first shaft 1 on the torsion bar 3 side. The mounting flange 4 has a cylindrical shape and a flange portion 5a at the upper end, and is made of a nonmagnetic material such as an aluminum alloy. A configured support cylinder 5 is attached. An annular permanent magnet 6 and a pair of magnet-side magnetic bodies 7a and 7b made of, for example, an iron-based metal material sandwiching the permanent magnet 6 from both ends in the axial direction are attached to the outer peripheral surface of the support cylinder 5. It has been.

Here, as shown in FIG. 1, the permanent magnet 6 is magnetized so that one NS pole is arranged in the axial direction so that the upper half in the axial direction is an N pole and the lower half is an S pole. Has been.
Further, as is apparent from FIGS. 2 and 3, each of the magnet-side magnetic bodies 7a and 7b includes annular plate portions 8a and 8b that cover all axial ends of the permanent magnet 6, and these annular plate portions 8a and 8b. Rectangular magnetic legs 9a and 9b projecting from the outer peripheral surface of 8b by a predetermined length L at predetermined intervals, for example, 60 ° intervals (when the number of magnetic legs is 6) are formed, and these magnetic legs 9a and 9b are formed. 9b is arranged in axial symmetry.

  The magnet-side magnetic bodies 7a and 7b are arranged so that one magnet-side magnetic body, for example, the center position between the adjacent magnetic legs 9a of one magnet-side magnetic body 7a, that is, the center position of the recess 9c, Similarly, the magnetic leg 9b is positioned so that the central position between the magnetic legs 9b in the other magnet-side magnetic body 7b, that is, the central position of the recess 9d is positioned at the center position of the magnetic leg 9a in one magnet-side magnetic body 7a. The circumferential direction phase between the concave portion 9c and the magnetic leg 9b and the circumferential phase phase between the concave portion 9d and the magnetic leg 9a are arranged to coincide with each other. That is, the other magnet side magnetic body 7b is arranged with a phase difference of 30 ° (when the number of magnetic legs is 6) in the circumferential direction with respect to one magnet side magnetic body 7a. A protective layer 10 made of a synthetic resin material is formed on the outer peripheral cylindrical surface of the permanent magnet 6.

On the other hand, a support disk 11 extending outward from the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b is attached to the end of the second rotating shaft 2 on the torsion bar 3 side. A cylindrical magnetic body support portion 13 is disposed on an annular base portion 12 formed on the outer peripheral edge side of the upper surface of the magnetic body so as to surround the permanent magnet 6 and the magnet side magnetic bodies 7a and 7b.
The magnetic support 13 is provided with a first magnetic body 14 made of, for example, an iron-based metal material on the upper end side in the axial direction, and a second magnetic material 14 made of an iron-based metal material in the same manner on the lower end side. A magnetic body 15 is provided, and the first magnetic body 14 and the second magnetic body 15 constitute a pair of yokes. The first magnetic body 14 includes an annular portion 14a having a small axial thickness disposed on the outer peripheral side of the upper end surface of the magnetic support portion 13, and an inner circumferential surface of the annular portion 14a spaced by 60 °. (In the case where the number of magnetic legs is 6) and the magnetic legs 14b formed to project inward in the radial direction. The magnetic leg 14b is radially inward from the inner circumferential surface of the annular portion 14a with respect to the radius R1 from the center of the axis of the torsion bar 3 to the tips of the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b. A radially extending portion 14c extending to the position of the long radius R2, and an axially extending portion 14d extending axially downward from the inner end of the radially extending portion 14c to the lower side of the magnet side magnetic body 7b. The magnetic legs 14b are arranged in an axisymmetric manner.

  Similarly, the second magnetic body 15 includes an annular portion 15a having a small axial thickness disposed on the outer peripheral side of the lower end surface of the magnetic support portion 13, and an inner peripheral surface of the annular portion 15a. The magnetic legs 15b are formed so as to protrude radially inward at intervals of 60 ° (when the number of magnetic legs is 6). The magnetic leg 15b is radially inward from the inner peripheral surface of the annular portion 15a with respect to the radius R1 from the center of the axis of the torsion bar 3 to the tips of the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b. A radial extension 15c extending to the position of a long radius R2, and an axial extension 15d extending axially upward from the inner end of the radial extension 15c to the upper side of the magnet-side magnetic body 7a. The magnetic legs 15b are arranged symmetrically about the axis.

Then, the magnetic legs 14b and 15b of the first magnetic body 14 and the second magnetic body 15 are 30 ° in the circumferential direction so that the center of the other magnetic leg is located at the center position between one adjacent magnetic leg. The phase difference (when the number of magnetic legs is 6) is arranged.
The magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b and the magnetic legs 14b and 15b of the first and second magnetic bodies 14 and 15 are flat when the torsion bar 3 is not twisted. As shown in FIG. 5, the magnetic leg 14b of the first magnetic body 14 is positioned between the magnetic leg 9a of the magnet-side magnetic body 7a and the magnetic leg 9b of the magnet-side magnetic body 7b on the counterclockwise direction. The center is positioned so that the center of the magnetic leg 15b of the second magnetic body 15 is positioned at an intermediate position between the magnetic leg 9a of the magnet-side magnetic body 7a and the magnetic leg 9b of the magnet-side magnetic body 7b on the clockwise side. Is set.

In the figure, the setting is made as described above. However, the magnetic field of the second magnetic body 15 is intermediate between the magnetic leg 9a of the magnet-side magnetic body 7a and the magnetic leg 9b of the magnet-side magnetic body 7b on the counterclockwise direction. The center of the leg 15b may be positioned.
In addition, a cylindrical auxiliary magnetic body support portion 19 having a pair of upper and lower auxiliary magnetic bodies 17a and 17b fixed to the fixing portion and spaced apart by a predetermined distance and a magnetic detection portion 18 is disposed outside the magnetic body support portion 13. The auxiliary magnetic bodies 17a and 17b constitute a pair of yokes. Each of the auxiliary magnetic bodies 17a and 17b is made of, for example, an iron-based metal material, faces the annular portions 14a and 15a of the first and second magnetic bodies 14 and 15, and has an annular length in the axial direction. Cylindrical portions 17c and 17d that are long with respect to the portions 14a and 15a, and magnetism collecting portions 17e and 17f that extend outward from part of the circumferential direction of the cylindrical portions 17c and 17d and face each other.

  And the magnetism detection part 18 is provided between the magnetism collection parts 17e and 17f which mutually oppose. The magnetic detection unit 18 includes a required number of magnetic detection elements including any one of a Hall element, an MR (Magneto Resistance) element, an MI (Magneto Impedance) element, and an IC using these elements. However, in this embodiment, as shown in FIG. 3, two magnetic detection elements 20a and 20b serving as a main and a sub are provided.

Next, the operation of the first embodiment will be described.
Now, the torsional torque is transmitted to the second rotating shaft 2 with respect to the first rotating shaft 1 and rotated in the clockwise direction while twisting the torsion bar 3, so that FIG. As shown, the axial extensions 14d and 15d of the magnetic legs 14b and 15b of the first and second magnetic bodies 14 and 15 are opposed to the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b. Shall.

  In this state, the magnetic flux emitted from the N pole of the permanent magnet 6 passes through the magnet-side magnetic body 7a, and extends in the axial direction 14d of the magnetic leg 14b of the first magnetic body 14 facing the magnetic leg 9a. The magnetic detection elements 20a and 20b are reached from the annular portion 14a through the extension portion 14c through the cylindrical portion 17c and the magnetism collecting portion 17e of the auxiliary magnetic body 17a, and from the auxiliary magnetic body 17b to the annular portion 15a of the second magnetic body 15. A magnetic path that reaches the S pole of the permanent magnet 6 through the magnetic leg 9b of the other magnet side magnetic body 7b is formed via the magnetic leg 15b.

Therefore, the magnetic detection elements 20a and 20b detect the magnetic flux in the magnetic circuit formed by the permanent magnet 6, and the maximum voltage Vmax at the point A shown in FIG. 7 is obtained from the magnetic detection elements 20a and 20b. Output voltage is output.
When the torsional torque with respect to the second rotating shaft 2 is weakened from this state and the second rotating shaft 2 is returned in the counterclockwise direction, for example, the magnetic legs 9a and 9b of the magnet side magnetic bodies 7a and 7b are The axial extensions 14d and 15d of the magnetic legs 14b and 15b of the first magnetic body 14 and the second magnetic body 15 are gradually shifted counterclockwise, and the magnetic flux passing between them is gradually reduced. As a result, the amount of magnetic detection detected by the magnetic detection elements 20a and 20b decreases, and the output voltage gradually decreases from the maximum voltage Vmax as shown in FIG.

  Thereafter, in a state where the torsion bar 3 is no longer twisted due to the torsional torque disappearing in the first rotating shaft 1 and the second rotating shaft 2, as shown in FIG. 5, the magnetic legs 9a of the magnet-side magnetic bodies 7a and 7b. And 9b are intermediate positions of the magnetic legs 14b and 15b of the first and second magnetic bodies 14 and 15, so that the output voltage output from the magnetic detection elements 20a and 20b is as indicated by point B in FIG. The neutral voltage Vn is obtained.

  When the second rotary shaft 2 is further rotated counterclockwise while twisting the torsion bar 3 from this state, the magnetic leg 9a of the magnet-side magnetic body 7a is axially directed to the magnetic leg 15b of the second magnetic body 15 Since the magnetic leg 9b of the magnet side magnetic body 7b approaches the extension part 15d and approaches the axial extension part 14d of the magnetic leg 14b of the first magnetic body 14, the output output from the magnetic detection elements 20a and 20b. The voltage gradually decreases from the neutral voltage Vn as shown in FIG.

  Thereafter, the second rotating shaft 2 is further rotated counterclockwise so that the magnetic leg 9a of the magnet-side magnetic body 7a faces the axial extension 15d of the magnetic leg 15b of the second magnetic body 15, and the magnet When the magnetic leg 9b of the side magnetic body 7b is in the state shown in FIG. 6 facing the axial extension 14d of the magnetic leg 14b of the first magnetic body 14, the output voltages output from the magnetic detection elements 20a and 20b are as shown in FIG. 7, the minimum voltage Vmin is obtained.

  As described above, when no torsional torque is applied between the first rotating shaft 1 and the second rotating shaft 2 and the torsion bar 3 is not twisted, the output voltages of the magnetic detection elements 20a and 20b are neutral. When the second rotary shaft 2 is rotated while twisting the torsion bar 3 in the clockwise direction with respect to the first rotary shaft 1 from this state, the output voltage increases from the neutral voltage Vn, and conversely When the second rotating shaft 2 is rotated counterclockwise while twisting the torsion bar 3 with respect to the first rotating shaft 1, the output voltage of the magnetic detection elements 20a and 20b decreases from the neutral voltage Vn. The torsion torque applied to the first rotating shaft 1 and the second rotating shaft 2 from the magnetic detection elements 20a and 20b can be calculated using the torsional rigidity of the torsion bar 3, and the first rotating shaft 1st and 2nd round It is possible to obtain a twist output voltage corresponding to the torque is transmitted to one of the shaft 2.

As described above, according to the first embodiment, since the permanent magnet 6 only needs to be magnetized NS in the axial direction, there is no need to perform multipolar magnetization in the circumferential direction as in the conventional example described above. Therefore, it is possible to reliably prevent the magnetization intensity from being varied, and to improve the measurement accuracy as a torque sensor.
Moreover, both end surfaces of the permanent magnet 6 in the axial direction are completely covered with the magnet-side magnetic bodies 7a and 7b, and the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b and the magnetic legs 14b of the magnetic bodies 14 and 15 and Since the permanent magnet 6 and the magnetic bodies 14 and 15 do not need to face and face each other, the protective layer 10 can be formed on the outer peripheral surface of the permanent magnet 6 so that the permanent magnet 6 can be reliably protected from being damaged. Since both end surfaces in the axial direction of the permanent magnet 6 are completely covered with the magnet-side magnetic bodies 7a and 7b, the permanent magnet 6 can be protected from the permanent magnet 6. The generated magnetic flux can be guided to the magnetic circuit without leakage, and the torque detection accuracy can be improved.

  Further, the magnetic fluxes of the magnetic bodies 14 and 15 are guided to the auxiliary magnetic bodies 17a and 17b arranged in the fixed part, and the magnetic fluxes flowing through the auxiliary magnetic bodies 17a and 17b are collected by the magnetic flux collecting parts 17e and 17f, and the magnetic detection element 20a. Therefore, even if the positional relationship between the magnetic detection elements 20a and 20b and the magnetic bodies 14 and 15 changes, the influence on the magnetic circuit can be reduced and the magnetic flux can be reduced to the magnetic detection elements 20a and 20b. Therefore, it is possible to reduce the influence of eccentricity and the like, and to strengthen the magnetic disturbance.

  Further, since the axially extending portions 14d and 15d constituting the magnetic legs 14b and 15b of the magnetic bodies 14 and 15 are extended so as to face both the magnet side magnetic bodies 7a and 7b, they are at different positions in the axial direction. A magnetic circuit can be constituted by both the magnet-side magnetic bodies 7a and 7b arranged, and the direction of the magnetic flux induced to the magnetic detection elements 20a and 20b can be changed.

  Furthermore, since the magnet-side magnetic bodies 7a and 7b are arranged so that the center of the other magnetic leg 9b is located at the center position between one adjacent magnetic legs 9a, the magnet-side magnetic body 7a has a magnetic field. The circumferential distance between the leg 9a and the magnetic leg 9b of the other magnet-side magnetic body 7b can be increased. Similarly, the magnetic bodies 14 and 15 are also arranged so that the center of the other magnetic leg 15b is positioned at the center position between one adjacent magnetic leg 14b, so that one of the magnetic legs 14b and the other magnetic leg. The circumferential distance from 15b can be increased.

  Still further, since the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b are arranged axially symmetrically, the influence of eccentricity can be reduced, and the magnetic legs 9a and 9b are arranged at equal intervals. The distance between the adjacent magnetic legs 9a and 9b can be increased. Similarly, since the magnetic legs 14b and 15b are arranged symmetrically with respect to the magnetic bodies 14 and 15, the influence of eccentricity can be reduced, and by arranging the magnetic legs 14b and 15b at equal intervals, The distance between the adjacent magnetic legs 14b and 15b can be increased.

The axial lengths of the cylindrical portions 17c and 17d of the auxiliary magnetic bodies 17a and 17b facing the annular portions 14a and 15a of the magnetic bodies 14 and 15 are the axial lengths (thicknesses) of the annular portions 14a and 15a. ), The influence of machining errors of components can be reduced, and the influence of eccentricity and axial fluctuation can be reduced.
Further, when the magnetic detection element is composed of two magnetic detection elements 20a and 20b, the magnetic detection elements 20a and 20b are substantially the same according to the torsional torque transmitted from the magnetic detection elements 20a and 20b to the first rotary shaft 1 or the second rotary shaft 2. Since the output voltage of the value is output, the torque detection system can be duplicated by using one of these, for example, the magnetic detection element 20a as a main sensor and the magnetic detection element 20b as a sub sensor. At the same time, the abnormality of any of the magnetic detection elements 20a or 20b can be detected by comparing the output voltages of the two. In this case, if three or more magnetic detection elements are arranged, when the output voltages of the plurality of magnetic detection elements are equal and the output voltage of the remaining one magnetic detection element is different, this output voltage is Different magnetic detection elements can be identified as the magnetic detection elements in which an abnormality has occurred. Moreover, by making the magnetic flux detection directions of the magnetic detection elements 20a and 20b opposite to each other, a differential output can be obtained, and the output of the torque sensor can be a differential output. Furthermore, the reliability of the entire torque sensor can be further improved by providing a separate dedicated power source for each magnetic detection element.

  Furthermore, although the case where the protective layer 10 is provided on the outer peripheral surface of the permanent magnet 6 has been described in the first embodiment, the present invention is not limited to this, and the permanent magnet 6 and the magnet-side magnetic bodies 7a and 7b are provided. You may make it mold with a synthetic resin material. In this case, even when an inexpensive ferrite sintered magnet is used in terms of cost, the whole is molded with a synthetic resin material, so that the magnet can be reliably prevented from cracking.

Furthermore, although the number of magnetic legs of the magnet-side magnetic bodies 7a and 7b and the magnetic bodies 14 and 15 is six, the number of magnetic legs is not limited to this, and the number of both magnetic legs can be set to an arbitrary number.
Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, the configuration of the auxiliary magnetic bodies 17a and 17b is simplified.

  That is, in the second embodiment, as shown in FIGS. 8 and 9, the auxiliary magnetic bodies 17a and 17b are arranged such that a part of the annular portions 14a and 15a of the magnetic bodies 14 and 15 is disposed on the upper surface from the outer peripheral side. Except that the magnetic flux introducing portions 31a and 31b having a U-shaped cross section facing each other so as to sandwich the outer peripheral surface and the lower surface are arranged at predetermined intervals in the circumferential direction via the magnetic collecting portions 31c. The configuration is the same as that of the first embodiment described above, and the same reference numerals are given to the corresponding parts to the first embodiment, and the detailed description thereof will be omitted. Here, the magnetism collecting portion 31c connects the magnetic flux introducing portions 31a and 31b, and also connects the connecting plate portion 31d protruding in the outer peripheral direction and the axial direction between the magnetic bodies 14 and 15 from the outer peripheral edge of the connecting plate portion 31d. An axial extension 31e toward the center and a radial extension 31f extending radially outward from the axial extension 31e. Magnetic detection elements 20a and 20b are interposed between the radial extension portions 31f of the auxiliary magnetic bodies 17a and 17b.

  According to the second embodiment, in addition to the same effects as those of the first embodiment described above, the auxiliary magnetic bodies 17a and 17b are opposed to each other with the annular portions 14a and 15a of the magnetic bodies 14 and 15 sandwiched therebetween. Since it is comprised by the introduction parts 31a and 31b and the magnetism collection part 31c, while being able to set it as a simple structure, even if it receives a mechanical disturbance, the effect that the influence on a magnetic circuit can be made small is effective. can get.

Next, a third embodiment of the present invention will be described with reference to FIGS.
In the third embodiment, the structures of the auxiliary magnetic bodies 17a and 17b are simplified as in the second embodiment described above.
That is, in the third embodiment, as shown in FIGS. 10 to 12, the auxiliary magnetic bodies 17a and 17b are band-shaped with the same curvature and a width W2 narrower than the width W1 of the annular portions 14a and 15a of the magnetic bodies 14 and 15. The first and second embodiments described above except that the magnetic flux introducing portion 41a is configured by a magnetic flux collecting portion 41b extending in a radial direction from a substantially central position in the circumferential direction of the magnetic flux introducing portion 41a. It has the same configuration as that of the embodiment, and the same reference numerals are given to corresponding parts with the first and second embodiments, and the detailed description thereof will be omitted.

Here, the magnetic flux introducing portion 41a of the auxiliary magnetic body 17a is fixed to a fixing portion (not shown), and is disposed opposite to the annular portion 14a of the magnetic body 14 by a predetermined distance in the axial direction as shown in FIG. Similarly, the magnetic flux introducing portion 41a of the auxiliary magnetic body 17b is also disposed opposite to the annular portion 15a of the magnetic body 15 by a predetermined distance in the axial direction.
The magnetic flux collecting portion 41b includes a radially extending portion 41c that extends radially outward from a substantially central position in the circumferential direction of the magnetic flux introducing portion 41a, and the magnetic body 14 and the axial direction from the tip of the radially extending portion 41c. It is comprised by the axial direction extension part 41d which goes to the center position between 15, and the radial direction extension part 41e which goes to a radial direction outward from the lower end of this axial direction extension part 41d.

And the magnetic detection elements 20a and 20b are inserted between the radial direction extension parts 41e of the magnetism collection part 41b in the auxiliary magnetic bodies 17a and 17b.
In the third embodiment, the same effect as that of the second embodiment described above can be obtained, and the width W2 of the belt-like magnetic flux introduction portion 41a is set to the width of the annular portions 14a and 15a of the magnetic bodies 14 and 15. By making it shorter than W1, the influence on the magnetic circuit can be reduced even when subjected to mechanical disturbance such as eccentricity.

In addition, in the said 1st-3rd embodiment, although the case where the magnetic legs 9a and 9b of the magnet side magnetic bodies 7a and 7b were formed in the rectangle was demonstrated, it is not limited to this, A triangle, circular arc It may be a shape or the like, and a tip shape that provides the required output characteristics can be selected as appropriate.
In the first to third embodiments, the case where the magnet side magnetic bodies 7a and 7b, the magnetic bodies 14 and 15 and the auxiliary magnetic bodies 17a and 17b are formed of an iron-based metal material has been described. The magnet side magnetic bodies 7a and 7b, the magnetic bodies 14 and 15 and the auxiliary magnetic bodies 17a and 17b may be formed using an alloy containing nickel. Here, by setting the nickel content of the nickel alloy to 40% by weight or more, the hysteresis can be remarkably reduced as compared with a general iron-based metal material, and the hysteresis characteristics can be obtained to a level where there is no practical problem. Can be improved. In order to further reduce the hysteresis, it is preferable to use an alloy containing 70% by weight or more of nickel content. However, since nickel is expensive, the nickel content is set to 80% by weight or less depending on required performance. It is preferable to do.

  Further, in the first to third embodiments, the case where the same output voltage is obtained from the magnetic detection elements 20a and 20b has been described. However, the present invention is not limited to this, and the magnetic detection elements 20a and 20b. By setting the output characteristics in the opposite directions, the differential between the two magnetic detection elements 20a and 20b can be obtained, and the sensitivity can be improved by a factor of two.

  In the first to third embodiments, the case where the magnetic legs 14b and 15b of the magnetic bodies 14 and 15 are formed in an L shape having a radial extension portion and an axial extension portion has been described. However, the present invention is not limited to this, and the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b are formed in an L shape extending radially outward, and the magnetic legs of the magnetic bodies 14 and 15 are accordingly formed. 14b and 15b can be configured to extend only in the radial direction.

  In the first to third embodiments, the case where the annular portions 14a and 15a of the magnetic bodies 14 and 15 are arranged on the upper end surface and the lower end surface of the magnetic body support portion 13 has been described. Although not limited, as shown in FIG. 13, the annular portions 14 a and 15 a are arranged at positions closer to the center of the magnetic material support portion 13 in the axial direction and spaced apart by a predetermined distance in the axial direction. 14a and 15a are provided with magnetic legs 14b and 15b extending in the axial direction so as to face the magnetic legs 9a and 9b of the magnet-side magnetic bodies 7a and 7b from the inner peripheral edges of the magnetic bodies 14 and 15, respectively. You may cover with the support part 13. FIG.

Moreover, in the said 1st-3rd embodiment, although the magnetic leg 9a and 9b of the magnet side magnetic bodies 7a and 7b and the magnetic leg 14b and 15b of the magnetic bodies 14 and 15 were demonstrated, the case where it was six, The number of magnetic legs is not limited to this, and the number of magnetic legs can be appropriately set according to the twist angle.
Next, a fourth embodiment of the present invention will be described with reference to FIG.

In the fourth embodiment, the torque sensor according to the present invention is applied to an electric power steering apparatus.
That is, in the fourth embodiment, as shown in FIGS. 1 to 13, any one of the torque sensors described in the first to third embodiments is applied to the electric power steering apparatus.

In the figure, reference numeral 51 denotes an electric power steering device. The electric power steering device 51 includes a steering mechanism 52 that is steered by a driver.
The steering mechanism 52 has a steering shaft 54 in which an input shaft 54a to which a steering force applied by a driver is transmitted to a steering wheel 53 and an output shaft 54b are connected by a torsion bar (not shown). One end of the input shaft 54 a is connected to the steering wheel 53. And the torque sensor 55 which has any one structure in the 1st-3rd embodiment mentioned above is inserted between the input shaft 54a and the output shaft 54b.

The steering force transmitted to the output shaft 54 b is transmitted to the lower shaft 57 via the universal joint 56 and further transmitted to the pinion shaft 59 via the universal joint 58. The steering force transmitted to the pinion shaft 59 is transmitted to the tie rod 61 via the steering gear 60, and turns a steered wheel (not shown).
Here, the steering gear 60 is configured in a rack and pinion type having a pinion 60a connected to the pinion shaft 59 and a rack 60b meshing with the pinion 60a, and the rotational motion transmitted to the pinion 60a is linearly moved by the rack 60b. It has been converted to movement.

A steering assist mechanism 62 that transmits a steering assist force to the output shaft 54 b is connected to the output shaft 54 b of the steering shaft 54. The steering assist mechanism 62 includes a worm reducer 63 connected to the output shaft 54 b and an electric motor 64 that generates a steering assist force connected to the worm reducer 63.
The electric motor 64 has a measured value of the steering torque applied to the steering wheel 53 detected by the steering torque sensor 55 and transmitted to the input shaft 54a, and a vehicle speed detection value output from the vehicle speed sensor 65 that detects the vehicle speed. Is controlled by the control device 66.

  The control device 66 calculates a steering assist command value by referring to a control map that stores the relationship between the steering torque and the steering assist command value using the vehicle speed detection value as a parameter, and calculates the calculated steering assist command value and the electric motor 64. The motor current command value is calculated by performing feedback control based on the motor current flowing through the motor, and the calculated motor current command value is supplied to a motor drive circuit 67 configured by an inverter circuit. A motor drive current is formed based on the current command value, and the motor drive current is supplied to the electric motor 64, whereby the electric motor 64 generates a steering assist force according to the steering assist command value, thereby the steering wheel. 53 can be steered with a light steering force.

  Thus, by applying the torque sensor 55 having any one of the configurations in the first to third embodiments described above to the electric power steering device 51, the torque sensor 55 can be reduced in size and torque can be reduced. Highly accurate steering assist control can be performed with high detection accuracy.

It is a schematic sectional drawing which shows 1st Embodiment of the torque sensor which concerns on this invention. It is a perspective view of the principal part of FIG. FIG. 3 is an exploded perspective view of FIG. 2. It is explanatory drawing which shows the rotation state at the time of a maximum output, Comprising: (a) is a top view, (b) is a side view. It is a top view which shows the rotation state at the time of a neutral voltage. It is a top view which shows the rotation state at the time of the minimum output. It is a characteristic line figure which shows the output characteristic of a magnetic detection element. It is a perspective view of the principal part which shows the 2nd Embodiment of this invention. It is a disassembled perspective view which shows an auxiliary | assistant magnetic body. It is a perspective view of the principal part which shows the 3rd Embodiment of this invention. It is a disassembled perspective view which shows an auxiliary | assistant magnetic body. It is a bottom view which shows an auxiliary | assistant magnetic body. It is a schematic sectional drawing similar to FIG. 1 which shows the other example of a magnetic body. It is a schematic block diagram which shows embodiment at the time of applying the torque sensor of this invention to an electric power steering apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st rotating shaft, 2 ... 2nd rotating shaft, 3 ... Torsion bar, 6 ... Permanent magnet, 7a, 7b ... Magnet side magnetic body, 9a, 9b ... Magnetic leg, 10 ... Protective layer, 11 ... Support Discs: 13 ... magnetic material support, 14 ... first magnetic material, 14a ... annular portion, 14b ... magnetic legs, 14c ... radial extension, 14d ... axial extension, 15 ... second magnetic material 15a ... Annular part, 15b ... Magnetic leg, 15c ... Radial extension part, 15d ... Axial extension part, 17a, 17b ... Auxiliary magnetic body, 17c, 17d ... Cylindrical part, 17e, 17f ... Magnetic collecting part, 18 ... Magnetic detection part, 20a, 20b ... Magnetic detection element, 31a, 31b ... Magnetic flux introducing part, 31c ... Magnetic collecting part, 41a ... Magnetic flux introducing part, 41b ... Magnetic collecting part, 51 ... Electric power steering device, 52 ... Steering mechanism 53 ... Steering wheel, 54 Steering shaft DOO, 54a ... Input shaft, 54b ... Output shaft, 55 ... torque sensor, 60 ... steering gear, 63 ... worm reduction gear, 64 ... electric motor, 66 ... controller, 67 ... motor driving circuit

Claims (18)

  First and second rotating shafts connected to be rotatable relative to each other via an elastic member that is twisted when torsional torque is transmitted on the same axis, and the first rotating shaft and the first shaft of the elastic member. A magnet connected to one of the rotating shafts and magnetized in the axial direction NS; a pair of magnet-side magnetic bodies disposed on both axial sides of the magnet and having a plurality of magnetic legs on the outer peripheral surface; A plurality of magnetic legs that are connected to either the rotating shaft of the elastic member or the second rotating shaft side of the elastic member and are arranged in a magnetic field formed by the magnet and the magnet-side magnetic body to form a magnetic circuit. A pair of magnetic bodies and a magnetic detection unit for detecting a magnetic flux density generated in a magnetic circuit of the magnetic body, wherein a magnetic leg of one of the magnet-side magnetic bodies faces a magnetic leg of the one magnetic body The magnetic leg of the other magnet-side magnetic body becomes the magnetic leg of the other magnetic body. A torque sensor, characterized in that it is arranged so that direction.   The pair of magnet-side magnetic bodies each have a plurality of magnetic legs with irregularities repeated at predetermined intervals on the outer peripheral surface, and between the adjacent magnetic legs of one magnet-side magnetic body, the magnetic legs of the other magnet-side magnetic body The torque sensor according to claim 1, wherein the torque sensor is disposed.   The magnetic sensor includes a pair of auxiliary magnetic bodies that are disposed in proximity to the pair of magnetic bodies and guide a magnetic flux from the magnetic bodies and have a magnetic flux collecting section that collects the magnetic flux, and the magnetic detection section is interposed via the magnetic flux collecting section. The torque sensor according to claim 1, wherein the torque sensor is arranged so as to detect a magnetic flux density generated in the auxiliary magnetic body.   The pair of magnetic bodies includes a pair of yokes facing each other at a predetermined interval in the axial direction, and each yoke extends radially inward from an annular portion and an inner peripheral surface of the annular portion. A magnetic leg having a radial extension and an axial extension extending from the tip of the radial extension toward the other magnetic body in the axial direction, and the other between the adjacent magnetic legs of the one magnetic body; The torque sensor according to any one of claims 1 to 3, wherein a magnetic leg of the magnetic material is disposed.   The torque sensor according to any one of claims 1 to 4, wherein the pair of magnet-side magnetic bodies are configured to cover the entire magnetized surface of the magnet.   The pair of magnet-side magnetic bodies are arranged such that the center of the magnetic leg of the other magnet-side magnetic body is positioned at the center position between adjacent magnetic legs of one magnet-side magnetic body. The torque sensor according to any one of claims 1 to 5.   The torque sensor according to any one of claims 1 to 6, wherein each of the pair of magnet-side magnetic bodies is configured in an axisymmetric shape.   8. The torque sensor according to claim 1, wherein each of the pair of magnet-side magnetic bodies has magnetic legs arranged at equal intervals.   The pair of magnetic bodies are arranged such that the center of the magnetic leg of the other magnetic body is located at the center position between adjacent magnetic legs of one magnetic body. 9. The torque sensor according to any one of items 8.   9. The torque sensor according to claim 1, wherein each of the pair of magnetic bodies has an axisymmetric shape. 10.   11. The torque sensor according to claim 1, wherein the magnetic legs are arranged at equal intervals in each of the pair of magnetic bodies.   The pair of auxiliary magnetic bodies are formed in a ring shape, are close to each other in the radial direction with respect to the pair of magnetic bodies, and the axial dimension is set longer than the axial dimension of the annular portion of the magnetic body. The torque sensor according to claim 3, wherein the torque sensor is provided.   The pair of auxiliary magnetic bodies are configured so as to be close to and opposed to the pair of magnetic bodies in the radial direction and to sandwich the magnetic bodies in the axial direction, respectively. The torque sensor according to claim 1.   The pair of auxiliary magnetic bodies is composed of a pair of yokes facing each other at a predetermined interval in the axial direction, and has a band-shaped portion having a width narrower than the width of the annular portion of the magnetic body, The torque sensor according to any one of claims 3 to 11, wherein the torque sensor is opposed to the magnetic body in an axial direction.   The magnetic detection unit includes a plurality of magnetic detection elements, and includes an abnormality detection circuit that detects abnormality of the magnetic detection elements based on magnetic flux density detected by the plurality of magnetic detection elements. Item 15. The torque sensor according to any one of Items 1 to 14.   The magnetic detection unit includes three or more magnetic detection elements, and includes an abnormality detection circuit that detects an abnormality of the magnetic detection element based on the magnetic flux density detected by each magnetic detection element. The torque sensor according to any one of claims 1 to 14.   The torque according to any one of claims 3 to 16, wherein the magnet-side magnetic body, the magnetic body, and the auxiliary magnetic body have a nickel content set to 40 wt% or more and 80 wt% or less. Sensor.   The torque sensor according to any one of claims 1 to 17, wherein an input shaft and an output shaft connected by a torsion bar of a steering shaft connected to a steering wheel are respectively used for the first and second rotations. An electric power steering apparatus characterized by detecting a steering torque transmitted to the steering wheel as a shaft.

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