JP2009020064A - Torque sensor and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor and an electric power steering device that are reduced in size and have significantly improved material efficiency. <P>SOLUTION: The torque sensor has: first and second shafts coaxially connected together through a connection shaft; a ring-shaped permanent magnet fixed to the second shaft and circumferentially magnetized with multiple poles; a sensor yoke fixed to the first shaft and forming a magnetic circuit together with the permanent magnet; a magnetism collecting yoke placed on the other side, in the axial direction, of the sensor yoke from the permanent magnet and forming a magnetic circuit together with the permanent magnet and the sensor yoke; and a magnetic flux sensor for sensing magnetic flux induced by the sensor yoke and the magnetism collecting yoke. The torque sensor senses, based on an output of the magnetic flux sensor, torque applied to either of the first and second shafts. The sensor yoke is constructed from claw poles arranged on the same or substantially the same plane, and at least some of the claw poles are formed separated from each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a torque detector and an electric power steering device (EPS), and is suitable for application to an electric power steering device of an automobile, for example.

Conventionally, what was indicated by patent documents 1-patent documents 3 is known as a torque detector. The torque detector disclosed in Patent Document 1 is provided with a pair of ring-shaped sensor members so as to face the circumferential side surface of a ring-shaped permanent magnet that is multipolarly magnetized along the circumferential direction. Torque generated on the permanent magnet side or on the sensor member side is detected based on the magnetic flux detected by the magnetic flux detector (magnetic sensor) disposed therebetween. Moreover, the torque detector disclosed in Patent Document 2 has a configuration in which, in the torque detector described in Patent Document 1, two magnetic flux detectors are used to detect magnetic flux.
JP-A-2-162221 Japanese Patent Laid-Open No. 2-141616 Japanese Patent No. 3874642

  However, in the torque detector having the configuration disclosed in Patent Document 1 or Patent Document 2, in order to detect the torque based on the output of the magnetic flux detector, the sensor member receives a certain amount of magnetic flux generated by the permanent magnet. Therefore, it is necessary to increase the area where the sensor member and the permanent magnet face each other.

  For this reason, in the torque detector having the configuration disclosed in Patent Document 1 and Patent Document 2, the sensor member and the permanent magnet have to be configured to be long in the axial direction. As a result, the torque detector itself and eventually the torque There has been a problem that it is difficult to reduce the size of an electric power steering apparatus including a detector.

  In Patent Document 3, a sensor yoke is formed by bending a claw pole portion from an annular member having a claw pole inside. However, since the inside of the annular member is discarded, there is a problem that the economy is poor.

  The present invention has been made in view of the above points, and an object of the present invention is to propose a torque detector and an electric power steering device that can be miniaturized and can dramatically improve material efficiency.

  In order to solve such a problem, in the present invention, the first and second shafts are coaxially connected via the connecting shaft, and are fixed to the second shaft, and are multipolarly magnetized along the circumferential direction. A ring-shaped permanent magnet; a sensor yoke fixed to the first shaft and forming a magnetic circuit with the permanent magnet; and the permanent magnet disposed on the axially opposite side of the permanent magnet with respect to the sensor yoke. And a magnetic flux collecting yoke that forms the magnetic circuit together with the sensor yoke, and a magnetic flux detector that detects the magnetic flux induced by the sensor yoke and the magnetic flux collecting yoke, and includes a first axis and a second axis. A torque detector for detecting a torque applied to any one of the magnetic flux detectors based on an output of the magnetic flux detector, wherein the sensor yokes are arranged on the same or substantially the same plane and at least part of them are separated from each other. Formation Characterized in that it is composed of a plurality of claw poles which.

  As a result, according to the torque detector of the present invention, the entire sensor yoke formed by the claw pole is not integrated, but the claw poles can be individually manufactured and appropriately combined, so that the material efficiency is high. Moreover, since the claw poles are arranged on the same or substantially the same plane, the axial length of the entire torque detector can be shortened. In addition, by doing so, the amount of the molding material may be small when they are integrated with the molding material such as resin.

  Further, in the present invention, in the electric power steering apparatus that generates auxiliary steering torque from the electric motor in response to the steering torque applied to the steering wheel, decelerates by the speed reducer, and transmits it to the output shaft of the steering mechanism, The torque detector is provided.

  By incorporating a torque detector for the electric power steering device, the manufacturing cost of the electric power steering device can be reduced.

  According to the present invention, since the sensor yoke does not have an annular portion, the inner portion of the annular portion is not wasted, and the size can be reduced and the material efficiency can be dramatically improved.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  1 to 5, reference numeral 1 denotes a torque detector according to the present embodiment as a whole. The torque detector 1 includes first and second shafts 3A and 3B connected via a torsion bar (connection shaft) 2 that is a torsion element. 1st and 2nd axis | shaft 3A, 3B is comprised by the column shape, The central axis and the central axis of the torsion bar 2 are extended on the straight line.

  A flat sensor yoke 4 positioned on the outer side in the radial direction is attached to the first shaft 3A in a state of being molded with a resin 5. Further, on the second shaft 3B, a ring-shaped permanent magnet 6 magnetized in the circumferential direction so that the end surfaces thereof are alternately N-pole and S-pole polarities is arranged via a back yoke 7 through a sensor yoke. 4 and the one side of the magnet 6 in the axial direction are fixedly arranged so as to face each other.

  The sensor yoke 4 includes first and second sensor yoke portions 4A and 4B. As shown in FIG. 2, the first sensor yoke portion 4A is formed of a plurality of first claw poles 4AX arranged in an annular shape. The first claw pole 4AX is a trapezoidal flat plate member made of a magnetic material, and a total of eight first claw poles 4AX are arranged with one end on the narrow side facing radially inward and the other end on the wide side facing radially outward. ing. The second sensor yoke portion 4B is formed of a plurality of second claw poles 4BX arranged in an annular shape. The second claw pole 4BX is a trapezoidal flat plate member made of a magnetic material. The first claw pole has one end on the narrow side facing radially inward and the other end on the wide side facing radially outward. A total of eight are arranged so as to alternate with 4AX. The number of the first and second claw poles 4AX, 4BX is selected to be the same as half the number of poles of the magnet 6 described later.

  As shown in FIG. 3, all the first and second claw poles 4AX and 4BX are molded by the resin 5 and integrated. Since the first and second claw poles 4AX, 4BX are arranged on the same or substantially the same plane, the thickness dimension can be formed small, and these can be integrated with a small amount of resin 5, Cost can be reduced.

  The first and second claw poles 4AX and 4BX are formed in a flat plate shape having the same or substantially the same thickness. Thus, by forming the first and second claw poles 4AX, 4BX in a flat plate shape, the length of the first and second claw poles 4AX, 4BX in the axial direction can be shortened, and accordingly, the apparatus The overall size can be reduced.

  Further, the first and second claw poles 4AX and 4BX are formed longer than the radial width of the magnet 6, so that the magnet 6 in the first and second claw poles 4AX and 4BX will be described later. When receiving the magnetic flux generated from the magnetic field, leakage of the magnetic flux can be reduced.

  In addition, the manufacturing method of 1st and 2nd claw pole 4AX, 4BX of this embodiment is shown in FIG. The first and second claw poles 4AX and 4BX are each formed by punching from a flat plate material 15 alternately in different directions. The soft magnetic material described in Patent Document 3 is manufactured by bending a claw pole portion from an annular member having a claw pole inside, but the inside is discarded. In the present embodiment, the use efficiency of the material 15 can be drastically increased because there is no annular portion that is discarded inside.

  The magnet 6 is configured by magnetizing an annular hard magnetic material alternately to the north or south pole at a predetermined angular interval in the circumferential direction. In the case of the present embodiment, the magnet 6 is magnetized to the N pole and the S pole at intervals of 22.5 [°]. Therefore, the magnet 6 has a total of 16 poles. In FIG. 5, the shaded portion represents the N pole. In addition, as a magnet material which comprises the magnet 6, a ferrite magnet, a rare earth magnet, a metal magnet, a sintered magnet, a plastic magnet, a rubber magnet, etc. can be used.

  On the opposite side of the magnet 6 with respect to the sensor yoke 4, a magnet collecting yoke 8 is arranged. The magnetism collecting yoke 8 has a ring-shaped first magnetism collecting yoke portion 8A and a smaller diameter than the first magnetism collecting yoke portion 8A, and is arranged coaxially and on the same plane as the first magnetism collecting yoke portion 8A. And the second magnetism collecting yoke portion 8B.

  In the magnetism collecting yoke 8, the first magnetism collecting yoke portion 8A is opposed to the wide side of each first claw pole 4AX constituting the first sensor yoke portion 4A, and the second magnetism collecting yoke portion 8B is The second claw pole 4BX that constitutes the second sensor yoke part 4B is fixed to a stationary part (not shown) so as to face the narrow side. In this way, by arranging the magnetic flux collecting yoke 8 over the entire circumference of the first and second sensor yoke portions 4A and 4B, a measurement error caused by a relative angle variation between the sensor yoke 4 and the magnetic flux collecting yoke 8 is achieved. Can be prevented.

  Further, the magnetic flux collecting yoke 8 is provided with a magnetic flux concentrating portion 9. More specifically, a magnetic flux concentrating portion constituting portion 9A, which is a half of the magnetic flux concentrating portion 9, is formed from a part of the first magnetic flux collecting yoke portion 8A toward the outside in the radial direction. A magnetic flux concentrating portion constituting portion 9B, which is the other half of the magnetic flux concentrating portion 9, is formed from the second magnetic collecting yoke portion 8B toward the radially outer side so as to face each other. And the magnetic flux detector 10 is arrange | positioned between the magnetic flux concentration part structure part 9A of 8 A of 1st magnetism collection yoke parts, and the magnetic flux concentration part structure part 9B of the 2nd magnetism collection yoke part 8B.

  By providing the magnetic flux concentrating portion 9 in the magnetic flux collecting yoke 8 in this way, the magnetic flux passing through the magnetic collecting yoke 8 can be concentrated on the magnetic flux concentrating portion 9, and the magnetic flux detector 10 as described later can detect the magnetic flux. It can make it easier to do. In addition, by providing the first and second magnetic flux concentrating portions 9A and 9B, the magnetic flux detector 10 can be easily installed.

  Furthermore, if three or more magnetic flux detectors 10 are used, even if one magnetic flux detector 10 fails, highly reliable data can be obtained by the remaining two or more normal magnetic flux detectors 10. Can do.

  As the magnetic flux detector 10, one that can detect the strength of magnetic flux, such as a Hall element, an MR element, or an MI element, is used. In the case of this embodiment, two magnetic flux detectors 10 are used. This is because by using the two magnetic flux detectors 10, the sensitivity can be doubled by taking the difference in output, and the zero point drift can be canceled. Further, by using two magnetic flux detectors 10, the sensor signal can be duplicated and the reliability can be improved.

  As shown in FIG. 1, the first and second magnetic flux collecting yoke portions 8A and 8B and the magnetic flux detector 10 are molded with a resin 5 and integrated. Alternatively, only the magnetic collecting yoke 8 may be molded so as to provide a hole into which the magnetic flux detector 10 can be inserted, and the magnetic flux detector 10 may be inserted into the hole after molding.

  Next, the operation of the torque detector 1 will be described. A schematic diagram of a magnetic circuit in the torque detector 1 is shown in FIG.

  In the torque detector 1, as shown in FIG. 7A, when the relative angle between the sensor yoke 4 and the magnet 6 is “0”, the center line of each of the first and second claw poles 4AX and 4BX is The first and second sensor yoke portions 4A and 4B are fixed to the first and second shafts 3A and 3B so as to coincide with the boundary between the N pole and the S pole on the end face of the magnet 6 in the axial direction. Therefore, when the relative angle between the sensor yoke 4 and the magnet 6 is “0”, the area of the first and second sensor yoke portions 4A and 4B facing the north pole of the magnet 6 and the first and second The area of the part facing the south pole of the magnet 6 in the two sensor yoke parts 4A and 4B is the same.

  In this state, the magnetic flux emitted from the N pole of the magnet 6 passes through the first and second claw poles 4AX and 4BX that constitute the first and second sensor yoke portions 4A and 4B, respectively, and the magnet 6 Enter the S pole. That is, when the relative angle between the sensor yoke 4 and the magnet 6 is “0”, the number of magnetic fluxes entering the first and second sensor yoke portions 4A and 4B is the same as the number of outgoing magnetic fluxes. The magnetic flux emitted from the magnetic flux does not pass through the magnetic flux detector 10.

  On the other hand, in the torque detector 1, as shown in FIG. 7B, the sensor yoke 4 is relative to the magnet 6 in the right direction indicated by the arrow x from the state of FIG. The first sensor yoke portion 4A (each first claw pole 4AX) rotates to the left and faces only the N-pole portion or the S-pole portion of the magnet 6, respectively, and the second sensor yoke portion 4B (each The relative angle between the sensor yoke 4 and the magnet 6 is maximized when the second claw pole 4BX) faces only the S pole portion or the N pole portion of the magnet 6 respectively.

  In this state, when the number of magnetic fluxes entering and exiting the first and second sensor yoke portions 4A and 4B loses balance and the sensor yoke 4 rotates relative to the magnet 6 in the right direction, the magnet 6 The magnetic flux emitted from the N pole of the first sensor yoke portion 4A (each first claw pole 4AX) from the first magnetic collecting yoke portion 8A, the first magnetic flux concentrating portion constituting portion 9A, the magnetic flux detector 10, The second magnetic flux concentrating portion constituting portion 9B, the second magnetic flux collecting yoke portion 8B, and the second sensor yoke portion 4B (each second claw pole 4BX) are sequentially entered into the S pole of the magnet 6. When the sensor yoke 4 rotates in the left direction relative to the magnet 6, the magnetic flux emitted from the N pole of the magnet 6 is second from the second sensor yoke portion 4B (each second claw pole 4BX). Magnetic flux collecting yoke portion 8B, second magnetic flux concentrating portion constituting portion 9B, magnetic flux detector 10, first magnetic flux concentrating portion constituting portion 9A, first magnetic collecting yoke portion 8A and first sensor yoke portion 4A (each 1 claw pole 4AX) and sequentially enters the south pole of magnet 6.

  When the sensor yoke 4 rotates in the right direction relative to the magnet 6 and the relative angle between the sensor yoke 4 and the magnet 6 is between “0” and the maximum angle, the distance between the sensor yoke 4 and the magnet 6 is The magnetic flux corresponding to the relative angle of the first sensor yoke portion 4A (each first claw pole 4AX) to the first magnetic flux collecting yoke portion 8A, the first magnetic flux concentration portion constituting portion 9A, the magnetic flux detector 10, The magnetic flux enters the south pole of the magnet 6 via the second magnetic flux concentrating portion constituting portion 9B, the second magnetic flux yoke portion 8B, and the second sensor yoke portion 4B (each second claw pole 4BX) sequentially. Further, when the sensor yoke 4 rotates to the left relative to the magnet 6 and the relative angle between the sensor yoke 4 and the magnet 6 is between “0” and the maximum angle, the distance between the sensor yoke 4 and the magnet 6 is The magnetic flux corresponding to the relative angle flows from the second sensor yoke portion 4B (each second claw pole 4BX) to the second magnetic flux collecting yoke portion 8B, the first magnetic flux concentration portion constituting portion 9B, the magnetic flux detector 10, and the second. The magnetic flux concentrating portion constituting portion 9A, the first magnetism collecting yoke portion 8A, and the first sensor yoke portion 4A (each first claw pole 4AX) enter the S pole of the magnet 6 sequentially.

  In this case, in the torque detector 1, the sensor yoke 4 and the magnet 6 are fixed to the first or second shaft 3A, 3B, respectively, and the first and second shafts 3A, 3B serve as the torsion bar 2. Therefore, when torsional torque acts between the first and second shafts 3A and 3B, the magnitude (torsional torque amount) and direction of the torsional torque are between the sensor yoke 4 and the magnet 6. It will appear as a relative angle (including orientation). Therefore, the magnitude and direction of the torsion torque acting between the first and second shafts 3A and 3B can be detected based on the number of magnetic fluxes detected by the magnetic flux detector 10 and the direction thereof.

  As described above, in the torque detector 1 according to the present embodiment, the magnitude and direction of the torsion torque acting between the first and second shafts 3A and 3B are determined by the relative angle between the sensor yoke 4 and the magnet 6. It is detected as the number of magnetic fluxes passing through the magnetic flux detector 10 along with the change and its direction. In this case, in the torque detector 1 according to the present embodiment, the first and second sensor yoke portions 4A and 4B (each of the first and second claw poles 4AX and 4BX) have a flat plate shape, and an annular shape. Therefore, the material efficiency can be drastically improved and the economic efficiency can be improved. Furthermore, since the axial length can be shortened, the torque detector 1 can be constructed in a small size.

  Further, in the torque detector 1 according to the present embodiment, the sensor yoke 4 is alternately arranged with the first sensor yoke portion 4A composed of the plurality of first claw poles 4AX arranged in an annular shape and the first claw pole 4A. The first and second claw poles 4AX and 4BX are shown in the figure by being constituted by the second sensor yoke portion 4B composed of a plurality of second claw poles 4BX arranged annularly so as to be positioned. As shown in FIG. 6, it can be formed by punching the plate-like material 28 alternately in different directions. As a result, the sensor yoke 4 does not have an annular portion whose inside is wasted, and the material efficiency can be dramatically improved. In particular, when an expensive metal containing a large amount of nickel is used as a material, the effect of low cost is great.

  In the above-described embodiment, the case where the first and second claw poles 4AX and 4BX are formed in a trapezoidal shape has been described. However, the present invention is not limited to this, and is formed in a triangular shape or a rectangular shape. You may make it do.

  In the above-described embodiment, the case where the number of poles of the magnet 6 is 16 has been described. However, the present invention is not limited to this, and a permanent magnet having a number of poles other than 16 is applied. May be.

  Furthermore, in the above-described embodiment, the case where half the number of poles of the magnet 6 and the number of the first and second claw poles 4AX and 4BX are set to the same number has been described. Not limited to this, these numbers may be varied.

  Furthermore, in the above-described embodiment, the case where the back yoke 7 is attached to effectively use the magnetic flux has been described. However, the present invention is not limited to this, and the magnet 6 is directly attached to the second shaft 3B. You may do it.

  Further, in the above-described embodiment, the case where two or more magnetic flux detectors are used as the magnetic flux detector 10 has been described. However, the present invention is not limited to this, and only one magnetic flux detector 10 is used. You may do it.

  Furthermore, in the above-described embodiment, the case where the resin yoke is used to integrate the sensor yoke 4 and the magnetism collecting yoke 8 has been described. However, the present invention is not limited to this, and the nonmagnetic material such as plastic or aluminum is used. A body may be incorporated to form an integral structure.

  Further, in the above-described embodiment, the case where all the first and second claw poles 4AX and 4BX are individually created has been described, but the present invention is not limited to this, and the first and / or second The claw poles 4AX and 4BX may be partly connected to each other. Specifically, for example, 2 to 4 claw poles 4AX and 4BX may be integrally connected.

  Furthermore, as shown in FIG. 8, the second sensor yoke 30 has a configuration in which protrusions 30A having substantially the same shape as the second claw pole 4BX are formed at regular intervals on the outer peripheral side of the annular coupling portion 30B (that is, The narrow side of each second claw pole 4BX is integrally connected by the connecting portion 30B), or as shown in FIG. 9, the first claw pole 4AX is formed on the inner peripheral side of the annular connecting portion 31B. The protrusions 31A having substantially the same shape as that of the first claw pole 4AX may be formed so as to protrude at a constant interval (that is, a shape in which the wide side of each first claw pole 4AX is integrally connected by the connecting portion 31B). By doing so, it is possible to increase the mechanical strength of the sensor yoke 4 and further facilitate assembly.

It is an end view which shows typically schematic structure of the torque detector by this embodiment. It is a principal part perspective view of the torque detector. It is a perspective view after mold of the torque detector. It is a back side perspective view of the same torque detector. It is a disassembled perspective view of the torque detector. It is the figure shown about the manufacturing method of the claw pole with which the same torque detector is equipped. It is the schematic of a magnetic circuit for demonstrating operation | movement of the torque detector. It is a disassembled perspective view which shows typically schematic structure of the torque detector by other embodiment. It is a disassembled perspective view which shows typically schematic structure of the torque detector by other embodiment.

Explanation of symbols

  1 ... Torque detector, 2 ... Torsion bar, 3A, 3B ... Shaft, 5 ... Resin, 6 ... Permanent magnet, 4 ... Sensor yoke, 4A, 4B ... Claw pole, 17 ... Back yoke , 25... Magnetic collecting yoke, 30 B... Connection portion, 31 B.

Claims (3)

A first and a second shaft connected coaxially via a connecting shaft; a ring-shaped permanent magnet fixed to the second shaft and multipolarly magnetized along a circumferential direction; A sensor yoke fixed to a shaft and forming a magnetic circuit together with the permanent magnet, and disposed on the opposite side of the permanent magnet in the axial direction with respect to the sensor yoke, and forms the magnetic circuit together with the permanent magnet and the sensor yoke. A magnetic flux collecting yoke, a magnetic flux detector for detecting the magnetic flux induced by the sensor yoke and the magnetic flux collecting yoke, and a torque applied to either one of the first shaft and the second shaft; A torque detector for detecting based on the output of the magnetic flux detector,
The sensor yoke is
A torque detector comprising a plurality of claw poles arranged on the same or substantially the same plane and formed at least partially separated from each other. The sensor yoke is
A first sensor yoke portion composed of a part of the plurality of claw poles;
A second sensor yoke portion composed of the remaining claw poles,
The first and second sensor yoke portions are
The torque detector according to claim 1, wherein each of the claw poles constituting the first or second sensor yoke portion is formed so as to be integrally connected. In the electric power steering device that generates auxiliary steering torque from the electric motor in response to the steering torque applied to the steering wheel, decelerates by the reducer, and transmits it to the output shaft of the steering mechanism.
An electric power steering apparatus comprising the torque detector according to claim 1.

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