JP2005265580A - Torque detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque detector dispensing with working on input and output shafts in order to provide them with stoppers, and dispensing with aligning the relative positions of stoppers with that of a permanent magnet or of a magnetic yoke for assembly. <P>SOLUTION: This torque detector is equipped with first and second shafts 1 and 2 coaxially connected to each other by a connecting shaft 3, the permanent magnet 5 of cylindrical shape firmly installed coaxially with the first shaft 1 at a prescribed position thereof, soft magnetic bodies 4a and 4b fixed on the second shaft 2 and disposed within the magnetic field of the permanent magnet 5 to form a magnetic circuit, and a detector 6 for detecting magnetic flux produced in the magnetic bodies 4a and 4b. This detector detects torque based on an output of the detector 6 when the torque is applied to the first shaft 1 or the second shaft 2. This device is equipped with contact parts 13 and 12 on an end face of the permanent magnet 5 and at a region of the magnetic body 1b confronting this end face, respectively. The contact parts 13 and 12 contact with each other when the connecting shaft 3 is distorted by a prescribed angle, thereby limiting the torsion of the connecting shaft 3 to or less than the prescribed angle. <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 that are fixed and arranged in a magnetic field of a permanent magnet to form a magnetic circuit, and a detector that detects a magnetic flux generated in the soft magnetic body, and torque is applied to the first axis or the second axis. The present invention relates to a torque detection device that detects torque based on the output of a detector when added.

  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. In Patent Document 1, an input shaft and an output shaft that are coaxially connected by a torsion bar, a ring-shaped permanent magnet fixed to the input shaft, and fixed to the output shaft are arranged in a magnetic field of the permanent magnet. A magnetic yoke made of a plurality of soft magnetic bodies forming a magnetic circuit and a magnetic sensor for detecting a magnetic flux generated in the magnetic yoke, based on the output of the magnetic sensor when torque is applied to the input shaft. A torque sensor for detecting torque is described.
JP 2003-149062 A

  In the torque sensor as described above, in order to prevent the torsion bar from being twisted too much and being damaged, a stopper that mechanically stops twisting beyond a predetermined angle is necessary. There is a problem that it is necessary to process the shaft and the output shaft, and it is necessary to assemble the stopper with the relative position of the permanent magnet or the magnetic yoke, which is troublesome.

  The present invention has been made in view of the circumstances as described above, and it is not necessary to process the input shaft and the output shaft in order to provide the stopper, and the relative position of the stopper and the permanent magnet or magnetic yoke is aligned. It is an object of the present invention to provide a torque detector that does not need to be assembled.

  A torque detection device according to a first aspect of the present invention includes a first shaft and a second shaft that are coaxially coupled by a coupling shaft, a cylindrical permanent magnet that is coaxially fixed at a predetermined position of the first shaft, A plurality of soft magnetic bodies fixed to two axes and arranged in a magnetic field of the permanent magnet to form a magnetic circuit, and a detector for detecting a magnetic flux generated in the soft magnetic bodies, the first axis or In the torque detection device for detecting the torque based on the output of the detector when torque is applied to the second shaft, the soft magnet facing the one end surface of the permanent magnet and the one end surface The body is provided with contact portions that should contact each other when the connecting shaft is twisted by a predetermined angle, and the twist of the connecting shaft is limited to the predetermined angle or less. .

  In this torque detector, the first shaft and the second shaft are coaxially connected by a connecting shaft, a cylindrical permanent magnet is coaxially fixed at a predetermined position of the first shaft, and a plurality of soft magnetic bodies are provided. Fixed to the second axis and disposed within the magnetic field of the permanent magnet to form a magnetic circuit. The detector detects the magnetic flux generated in the soft magnetic material, and detects the torque based on the output of the detector when torque is applied to the first axis or the second axis. The abutting portions of the one end surface of the permanent magnet and the portion of the soft magnetic material facing the one end surface are in contact with each other when the connecting shaft is twisted by a predetermined angle, and the twist of the connecting shaft is limited to a predetermined angle or less. .

  The torque detector according to a second aspect is characterized in that the contact portion of the permanent magnet is subjected to a surface treatment in order to increase the strength or to protect the surface.

  A torque detector according to a third aspect of the present invention includes a first shaft and a second shaft that are coaxially coupled by a coupling shaft, a cylindrical permanent magnet that is coaxially fixed at a predetermined position of the first shaft, A plurality of soft magnetic bodies fixed to two axes and arranged in a magnetic field of the permanent magnet to form a magnetic circuit, and a detector for detecting a magnetic flux generated in the soft magnetic bodies, the first axis or In the torque detection device for detecting the torque based on the output of the detector when torque is applied to the second shaft, the permanent magnet is made of a material different from the permanent magnet on one end surface. Each of which has a contact portion that should be in contact with each other when the connecting shaft is twisted by a predetermined angle at the portion and the portion of the soft magnetic body facing the portion. It should be limited to the predetermined angle or less.

  In this torque detector, the first shaft and the second shaft are coaxially connected by a connecting shaft, a cylindrical permanent magnet is coaxially fixed at a predetermined position of the first shaft, and a plurality of soft magnetic bodies are provided. Fixed to the second axis and disposed within the magnetic field of the permanent magnet to form a magnetic circuit. The detector detects the magnetic flux generated in the soft magnetic material, and detects the torque based on the output of the detector when torque is applied to the first axis or the second axis. The permanent magnet has a portion made of a different material on one end surface, and the contact portions of the different material portion and the portion of the soft magnetic material facing the portion are contacted with each other when the connecting shaft is twisted by a predetermined angle. The twist of the connecting shaft is limited to a predetermined angle or less.

  According to the torque detection device of the present invention, it is not necessary to process the input shaft and the output shaft in order to provide the stopper, and it is not necessary to assemble the stopper and the permanent magnet or the magnetic yoke in matching positions. A torque detection device capable of reducing the cost can be realized.

  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. As shown in the bottom view of FIG. 3, the permanent magnet 5 has 12 fan-shaped convex portions 13 and 12 concave portions 14 formed alternately on the lower end surface.

  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. As shown in FIG. 2 (a), the lower magnetic yoke 4b is provided with a bottom having a hole through which the torsion bar 3 passes, and a convex portion is formed on the bottom surface from each claw 10 to the hole. 12 (FIG. 2B, a contact portion of the magnetic yoke) and a concave portion 11 (FIG. 2C) excluding the convex portion 12 are formed.

  Each convex portion 12 of the magnetic yoke 4 b is loosely fitted into each concave portion 14 of the permanent magnet 5, and this play portion serves as a twisting allowance of the torsion bar 3. That is, when the torsion bar 3 is twisted, the side surface of each convex portion 13 (permanent magnet contact portion) of the permanent magnet 5 comes into contact with the side surface of each convex portion 12 shown in FIG. Prevent twisting.

  As shown in FIG. 5A, if the surface 15 of each convex portion 13 and concave portion 14 of the permanent magnet 5 is subjected to surface treatment such as quenching or coating with resin, the strength of each convex portion 13 is increased. Can also protect the surface. The range to which the surface treatment is performed can be limited to the side surface of the convex portion 13. Moreover, as shown in FIG.5 (b), if the surface 16 of each convex part 13 and the recessed part 14 of the permanent magnet 5 is covered with another metal, the intensity | strength of each convex part 13 can be increased. It is also possible to limit the range covered with metal to the side surface of the convex portion 13. Further, as shown in FIG. 5C, if another metal 17 (another material) is embedded in the permanent magnet 5 and the protrusion 13 and the recess 14 are formed on the lower end surface of the other metal 17, the protrusion The strength of the portion 13 can be increased.

  The magnetic yokes 4a and 4b are arranged in a magnetic field formed by the permanent magnet 5, and one or a plurality of Hall ICs 6 (Hall elements, detectors) for detecting a magnetic flux generated in the gap between them are inserted into the gap. Has been. The Hall IC 6 is fixed to a housing (not shown), and the 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 magnetic yokes 4 a and 4 b are arranged in a neutral state where no torque is applied so that the tips of the respective claws 10 point to the boundary between the N pole and the S pole of the permanent magnet 5.

  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. 6A, 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 the 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. 6C, 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 the magnetic flux density increases as the difference in 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 illustrated 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. (Mechanical angle -7.5 to 7.5 deg.) Is not exceeded (the actual range used is mechanical angle -5 to 5 deg.), And the magnetic flux density corresponding to the applied torque is detected. I can do it. That is, the applied torque can be known based on the detected magnetic flux density.

  On the other hand, torque is applied to the input shaft 1 or the output shaft 2 to twist the torsion bar 3, and the twist angle thereof is, for example, 5 deg. Is reached, the side surfaces of the respective convex portions 13 of the permanent magnet 5 are brought into contact with the side surfaces of the respective convex portions 12 of the magnetic yoke 4b, thereby preventing the torsion bar 3 from being further twisted and broken.

It is explanatory drawing which shows the structure of embodiment of the torque detection apparatus which concerns on this invention. It is explanatory drawing which shows one magnetic yoke of the torque detection apparatus which concerns on this invention. It is a bottom view which shows the permanent magnet of the torque detection apparatus which concerns on this invention. It is explanatory drawing which shows one magnetic yoke of the torque detection apparatus which concerns on this invention. It is explanatory drawing which shows the example of the other permanent magnet of the torque detection apparatus which concerns on this invention. It is explanatory drawing which shows operation | movement 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 10 Claw 11 Recess (recess of magnetic yoke)
12 Convex part (contact part of magnetic yoke)
13 Convex part (contact part of permanent magnet)
14 Recessed part (permanent magnet recessed part)
15, 16 Surface 17 Different metal (different material)

Claims (3)

A first shaft and a second shaft connected coaxially by a connecting shaft; a cylindrical permanent magnet fixed coaxially at a predetermined portion of the first shaft; and a second permanent shaft fixed to the second shaft. A plurality of soft magnetic bodies arranged in a magnetic field to form a magnetic circuit, and a detector for detecting a magnetic flux generated in the soft magnetic bodies, when torque is applied to the first axis or the second axis In addition, in the torque detection device adapted to detect the torque based on the output of the detector,
One end surface of the permanent magnet and a portion of the soft magnetic body facing the one end surface are provided with contact portions that should contact each other when the connection shaft is twisted by a predetermined angle, and the connection shaft is twisted. A torque detection device characterized by being limited to the predetermined angle or less.   The torque detection device according to claim 1, wherein the contact portion of the permanent magnet is surface-treated in order to increase strength or protect the surface. A first shaft and a second shaft connected coaxially by a connecting shaft; a cylindrical permanent magnet fixed coaxially at a predetermined portion of the first shaft; and a second permanent shaft fixed to the second shaft. A plurality of soft magnetic bodies arranged in a magnetic field to form a magnetic circuit, and a detector for detecting a magnetic flux generated in the soft magnetic bodies, when torque is applied to the first axis or the second axis In addition, in the torque detection device adapted to detect the torque based on the output of the detector,
The permanent magnet includes a portion made of a material different from that of the permanent magnet on one end surface, and abuts the portion and the portion of the soft magnetic body facing the portion when the connecting shaft is twisted by a predetermined angle. The torque detecting device according to any one of the preceding claims, wherein the torque detecting device has a contact portion to be controlled, and limits the twist of the connecting shaft to the predetermined angle or less.

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