JP2005265593A - Torque detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque detecting apparatus which is hardly affected by magnetic fields from the outside. <P>SOLUTION: The torque detecting apparatus is provided with a first shaft 1 and a second shaft 2 connected to each other by a connecting shaft 3; a permanent magnet 5 fixed to the first shaft 1; a plurality of soft magnetic bodies 4a and 4b, fixed to the second shaft 2 and arranged in a magnetic field of the permanent magnet 5 to form a magnetic circuit; a plurality of auxiliary soft magnetic bodies 8 and 8, each coupled magnetically with the soft magnetic bodies 4a and 4b for inducing magnetic flux from the soft magnetic bodies 4a and 4b and having flux concentrating parts 19 and 19 for concentrating the induced magnetic flux, and detectors 6 and 6 for detecting the magnetic flux concentrated by the flux concentrating parts 19 and 19. When a torque is added to the first shaft 1 or the second shaft 2, the torque is detected, on the basis of output of the detectors 6 and 6 in the torque detection apparatus. The torque detection apparatus is provided with a magnetic shielding part 18 for shielding the magnetic flux concentrating parts 19 and 19 and the detectors 6 and 6 from magnetism from the outside. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is suitably used for an electric power steering device of a vehicle, and the like. The first shaft and the second shaft are coaxially connected by a connecting shaft, the permanent magnet fixed to the first shaft, and the second shaft. A plurality of soft magnetic bodies fixed and arranged in a magnetic field of a permanent magnet to form a magnetic circuit; a plurality of auxiliary soft magnetic bodies magnetically coupled to the soft magnetic bodies to induce magnetic flux from the soft magnetic bodies; and an auxiliary The present invention relates to a torque detection device that detects a magnetic flux based on an output of a detector when a torque is applied to a first shaft or a second shaft. .

  As a vehicle steering apparatus, there is an electric power steering apparatus that assists steering by driving an electric motor to reduce a burden on a driver. This includes an input shaft connected to a steering member (steering wheel, steering wheel), an output shaft connected to a steering wheel by a pinion, a rack, and the like, and a connecting shaft that connects the input shaft and the output shaft. The torque detection device detects the steering torque applied to the input shaft based on the angle, and drives and controls the steering assist electric motor linked to the output shaft based on the detected steering torque value. Conventionally, a magnetic detection resolver that detects a rotational position using a coil, an optical encoder detection device that detects transmission of light, or the like is used as a torque detection device of such an electric power steering device.

Patent Document 1 discloses an input shaft 1 and an output shaft 2 that are coaxially connected by a torsion bar 3 and an input shaft 1 as shown in an exploded perspective view (a) and a longitudinal sectional view (b) of FIG. And a magnetic yoke comprising a plurality of soft magnetic bodies 4a and 4b which are fixed to the output shaft 2 and are arranged in the magnetic field of the permanent magnet 5 to form a magnetic circuit. And two magnetic flux collecting rings 8 and 8 that are magnetically coupled to the magnetic yokes 4a and 4b and induce magnetic flux from the magnetic yokes 4a and 4b, and the magnetic flux collecting rings 8 and 8 provided on the magnetic flux collecting rings 8 and 8 are inducted. Magnetic flux collectors 19 and 19 for collecting the magnetic flux collected, and two magnetic sensors 6 and 6 (Hall ICs) for detecting the magnetic flux collected at the magnetic flux collectors 19 and 19, and torque is applied to the input shaft 1. Torque is detected based on the output of the magnetic sensors 6 and 6 Rukusensa has been proposed.
JP 2003-149062 A

  In the torque sensor as described above, the magnetic yokes 4a and 4b and the magnetic flux collecting rings 8 and 8 sometimes pick up a magnetic field from the outside, which affects the detection values of the magnetic sensors 6 and 6, and causes the torque value to be incorrect. There is a problem of detecting. In particular, the magnetic flux collecting rings 8 and 8 have a small magnetic flux density, so that the influence of an external magnetic field is large.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a torque detection device that is less affected by an external magnetic field.

  The torque detection device according to the present invention includes a first shaft and a second shaft that are coaxially coupled by a coupling shaft, a permanent magnet fixed to the first shaft, a fixed to the second shaft, and the permanent magnet A plurality of soft magnetic bodies that are arranged in the magnetic field of the magnetic field to form a magnetic circuit, and are magnetically coupled to the soft magnetic bodies to induce magnetic flux from the soft magnetic bodies, and to collect the induced magnetic flux A plurality of auxiliary soft magnetic bodies each having a portion and a detector for detecting the magnetic flux collected in the magnetic flux collecting portion, and when the torque is applied to the first shaft or the second shaft, the detector In the torque detection device that detects the torque based on the output of the magnetic field, the torque detection device includes a magnetic shielding unit that shields magnetism from the outside to the magnetism collecting unit and the detector.

  According to the torque detection device of the present invention, since the external magnetic field to the magnetism collecting portion having a relatively large surface area is shielded among the auxiliary soft magnetic bodies that are largely affected by the external magnetic field, the external magnetic field It is possible to realize a torque detection device that is less affected by

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
FIG. 1 is an explanatory view showing a configuration of an embodiment of a torque detection device according to the present invention, in which (a) is an exploded perspective view and (b) is a longitudinal sectional view. In this torque detector, an input shaft 1 (first shaft) and an output shaft 2 (second shaft) are coaxially connected via a small-diameter torsion bar 3 (connecting shaft). The input shaft 1 and the output shaft 2 are connected to the torsion bar 3 by pins 9 respectively.

  A cylindrical permanent magnet 5 in which 24 poles (12 poles each of N and S) are magnetized at equal intervals in the circumferential direction is fixed coaxially on the input shaft 1. On the output shaft 2, two magnetic yokes 4a and 4b (soft magnetic material) surrounding the permanent magnet 5 with an appropriate gap in the radial direction are fixed coaxially. In the magnetic yokes 4a and 4b, twelve isosceles triangular claws 10 extending in one direction perpendicular to the plate surface are provided around a plate-like ring at equal intervals. The two magnetic yokes 4a and 4b are opposed to each other so that the respective claws 10 are displaced at appropriate intervals in the circumferential direction.

  The magnetic yokes 4 a and 4 b are arranged in a magnetic field formed by the permanent magnet 5, and in a neutral state where no torque is applied to the input shaft 1, the tips of the respective claws 10 are the N pole and S pole of the permanent magnet 5. Arranged to point to the boundary. Around the magnetic yokes 4a, 4b, two magnetic flux collecting rings 8, which are magnetically coupled to the magnetic yokes 4a, 4b, respectively, induce magnetic fluxes from the magnetic yokes 4a, 4b, and are arranged in parallel at equal intervals. 8 (auxiliary soft magnetic material) is provided. The magnetism collecting rings 8 and 8 have flat magnetism collecting portions 19 and 19 that are closer to each other than the other portions, a gap is formed by the adjacent portions, and the induced magnetic fluxes gather at the magnetizing portions 19 and 19, respectively. It is formed as follows.

Two Hall ICs 6 (Hall elements, detectors) are inserted in the gaps between the magnetic collectors 19 and 19. The magnetism collecting rings 8 are fixed to a housing (not shown) in a magnetically insulated state. The Hall IC 6 is fixed to a housing (not shown), and each lead wire 7 of the Hall IC 6 is soldered to a substrate (not shown), supplying power for operating the Hall IC 6, and obtaining an output detected by the Hall IC 6. .
The magnetism collecting portions 19 and 19 are fitted into a cylindrical magnetic shield 18 (magnetic shielding portion) having a quadrangular cross section with the two Hall ICs 6 interposed therebetween, and are magnetically shielded by the side portions of the magnetic shield 18. Has been.

  FIG. 2 is a longitudinal sectional view showing a configuration example when the torque detection device having the above-described configuration is mounted on an electric power steering device. In this electric power steering apparatus, the input shaft 1 is connected to a steering (handle) (not shown), the upper half of the torsion bar 3 is loosely fitted in the hollow portion of the input shaft 1, and the upper end portion of the torsion bar 3 is pin 9a. To the input shaft 1. The lower half portion of the torsion bar 3 is loosely fitted in the hollow portion of the output shaft 2, the lower end portion of the torsion bar 3 is connected to the output shaft 2 by a pin 9b, and the input shaft is disposed above the hollow portion of the output shaft 2. The lower part of 1 is loosely fitted. The output shaft 2 is connected to a steering mechanism (not shown).

The input shaft 1 is rotatably supported by the housing 17 of the electric power steering apparatus by the bearing 13, and the output shaft 2 is rotatably supported by the housing 17 by the bearings 11 and 12.
A worm wheel 15 is fixed to the output shaft 2, and a worm 14 connected to a motor shaft of a steering assist motor (not shown) is engaged with the worm wheel 15.

A permanent magnet 5 is coaxially fixed to the input shaft 1, and two magnetic yokes 4 a and 4 b surrounding the permanent magnet 5 are provided coaxially to the output shaft 2 by providing an appropriate gap in the radial direction. Yes. Around the magnetic yokes 4a and 4b, there are disposed two magnetic flux collecting rings 8 and 8 that are magnetically coupled to the magnetic yokes 4a and 4b, respectively, and are arranged in parallel at equal intervals. Two Hall ICs 6 are inserted between the magnetic collecting portions 19 and 19 of the magnetic collecting rings 8 and 8.
The magnetism collecting portions 19 and 19 are magnetically shielded by being fitted into a cylindrical magnetic shield 18 having a quadrangular cross section made of a magnetic material with the two Hall ICs 6 being sandwiched therebetween.

  The magnetic yokes 4a and 4b are integrally molded with a synthetic resin 24, the magnetism collecting rings 8 and 8, the two Hall ICs 6 and the magnetic shield 18 are integrally molded with a synthetic resin 28, and the synthetic resin 28 is an electric power steering. It is fixed to the housing 17 of the device. In the Hall IC 6, each lead wire 7 is soldered to the substrate 16, and the substrate 16 supplies power for operating the Hall IC 6 to obtain an output detected by the Hall IC 6.

  Below, operation | movement of the torque detection apparatus of such a structure is demonstrated. When no torque is applied to the input shaft 1 or the output shaft 2, the claws 10 of the magnetic yokes 4a and 4b have areas facing the N pole and S pole of the permanent magnet 5, as shown in FIG. Since the magnetic flux entering from the N pole is equal to the magnetic flux exiting from the S pole, no magnetic flux is generated between the magnetic yoke 4a and the magnetic yoke 4b.

  When a one-way torque is applied to the input shaft 1 or the output shaft 2, the torsion bar 3 is twisted, and the relative positions of the claws 10 and the permanent magnets 5 of the magnetic yokes 4a and 4b change. At this time, for example, as shown in FIG. 3A, the area of the magnetic yoke 4a facing the claws 10 is larger in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole Becomes larger than the magnetic flux that goes out to the south pole. Further, the area of the magnetic yoke 4b facing the claws 10 is smaller in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole is smaller than the magnetic flux exiting to the S pole. As a result, a magnetic flux is generated from the magnetic yoke 4a to the magnetic yoke 4b, and this magnetic flux density increases as the difference in area between the N pole and the S pole facing each claw 10 increases.

  On the other hand, when a torque in the other direction is applied to the input shaft 1 or the output shaft 2, the torsion bar 3 is twisted in the opposite direction to the above, and the claws 10 of the magnetic yokes 4a and 4b and the permanent magnet 5 The relative position changes. At this time, for example, as shown in FIG. 3C, the area of the magnetic yoke 4a facing the claws 10 is smaller in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole Becomes smaller than the magnetic flux exiting the S pole. In addition, the area of the magnetic yoke 4b facing each claw 10 is larger in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole is larger than the magnetic flux exiting to the S pole. As a result, a magnetic flux is generated from the magnetic yoke 4b to the magnetic yoke 4a, and this magnetic flux density increases as the difference in the area between the N pole and the S pole facing each claw 10 increases.

  The change in the magnetic flux density generated in the gap between the magnetic yoke 4a and the magnetic yoke 4b described above is represented by the electric angle −180 to 180 deg. If it is shown corresponding to (mechanical angle-15-15 deg.), It becomes a sine wave shape as shown in FIG. The range actually used is -90 to 90 deg. From the rigidity of the torsion bar 3. Never exceed.

  In accordance with the magnetic flux density of the gap between the magnetic yoke 4a and the magnetic yoke 4b described above, the magnetic flux generated in the magnetic yokes 4a and 4b is induced by the magnetic flux collecting rings 8 and 8, respectively. 8 and 8 are concentrated on the magnetic collecting parts 19 and 19 and detected by the Hall ICs 6 and 6. The magnetic flux collecting rings 8 and 8 allow the Hall ICs 6 and 6 to detect the average of the magnetic flux density generated on the entire circumference of the magnetic yokes 4a and 4b.

It is explanatory drawing which shows the structure of embodiment of the torque detection apparatus which concerns on this invention. It is a longitudinal section showing an example of composition at the time of mounting a torque detection device concerning the present invention in an electric power steering device. It is explanatory drawing which shows the operation example of the torque detection apparatus which concerns on this invention.

Explanation of symbols

1 Input shaft (first axis)
2 Output shaft (second shaft)
3 Torsion bar (connection shaft)
4a, 4b Magnetic yoke (soft magnetic material)
5 Permanent magnet 6 Hall IC (Hall element, detector)
7 Lead wire 8 Magnetic flux collecting ring (auxiliary soft magnetic material)
10 claw 16 substrate 17 housing 18 magnetic shield (magnetic shielding part)
19 Magnetic collector

Claims (1)

A first shaft and a second shaft connected coaxially by a connecting shaft, a permanent magnet fixed to the first shaft, and a magnetic circuit fixed to the second shaft and disposed in the magnetic field of the permanent magnet And a plurality of auxiliary soft magnets that are magnetically coupled to the soft magnetic body, induce magnetic flux from the soft magnetic body, and each have a magnetic collecting portion for collecting the induced magnetic flux. And a detector for detecting the magnetic flux collected in the magnetic flux collector, and when the torque is applied to the first shaft or the second shaft, the torque is detected based on the output of the detector. In the torque detection device that has been made,
A torque detection device comprising a magnetic shielding unit that shields magnetism from the outside to the magnetism collecting unit and the detector.

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