JP5024648B2 - Torque detection method and torque detection device - Google Patents

Description

  The present invention relates to a torque detection method and a torque detection apparatus for measuring, for example, a torque generated by a magnetic field of a magnet for a voice coil motor with high sensitivity.

  For example, in a voice coil motor for a hard disk drive, miniaturization and high performance of the voice coil motor are required, and the performance of the magnet to be incorporated is being improved. For example, rare earth sintered magnets such as neodymium iron boron-based sintered magnets have high magnetic properties, and thus contribute to the miniaturization and high performance of the voice coil motor.

  On the other hand, in the magnet used for the voice coil motor, it is necessary to smoothly operate the actuator on which the magnetic head is mounted, and it is desired to accurately evaluate the torque that appears due to the magnetic field generated by the magnet.

  Torque measurement is widely performed in various directions, for example, rotation angle sensors and torque detection sensors used in automobile power steering, torque sensors for measuring liquid viscosity and wettability, torque sensors for drill punchers, etc. Is a typical example (see, for example, Patent Document 1, Patent Document 2, etc.).

  The invention described in Patent Document 1 relates to a rotation angle sensor incorporated in an electric power steering apparatus. A pair of gears are combined via a torsion bar, the rotation angle of each gear is magnetically read, and the torsion bar is twisted. Discloses a magnetic detection method for detecting the rotational torque of the operating shaft from the deviation generated by the above.

  The invention described in Patent Document 2 relates to a torque detection device for a rotational viscometer, and discloses a method for magnetically reading a twist angle of a rotating shaft generated by rotating a sample and undergoing flow deformation.

  In addition, a method of reading a change in permeability due to twisting of a magnetostrictive material, a method of reading a frequency, a propagation speed, a refractive index, and the like that change due to stress by applying ultrasonic waves or light have been proposed.

As a torque measurement in the field of magnetic recording, the applicant of the present invention has proposed a method and apparatus for measuring the running torque of a disk-shaped magnetic recording medium (see Patent Document 3). Japanese Patent Application Laid-Open No. H10-260260 discloses a traveling torque measuring apparatus having means for measuring the load current of a spindle motor for a disk-shaped magnetic recording medium and a micrometer head that supports the magnetic head and can adjust its height. It is disclosed to precisely measure the torque of a disc.
Japanese Patent Laid-Open No. 11-194007 JP 2005-55410 A Japanese Patent Laid-Open No. 6-137773

  However, all of the conventional techniques represented by the above-mentioned patent documents are torques generated by the rotation of the object to be measured, and no investigation has been made on detecting the torque generated by the magnetic field. In addition, a technique for measuring a minute level of torque with high sensitivity has not yet been established.

  Torque measurement in the prior art uses twisting of a transmission shaft such as a torsion bar generated by torque and changes in physical properties, and is applied to detect minute torque changes such as torque generated by a voice coil motor. It is difficult to make use of conventional technology. In addition, since the torque generated by the interaction with the magnetic field is measured, in the magnetic detection method and the method using magnetostriction, there is a concern that the magnetic field causes noise and an error due to noise increases. Furthermore, in the technique of measuring with ultrasonic waves or light, there remains a problem that the apparatus becomes large and the running cost is also generated.

  Therefore, the present invention has been proposed in view of such a conventional situation, and a novel torque capable of accurately detecting the torque generated by the interaction with the magnetic field while having a simple configuration and structure. It is an object to provide a detection method and a torque detection device, and to provide a torque detection method and a torque detection device capable of accurately measuring a minute torque generated by interaction with a magnetic field by improving sensitivity. Objective.

In order to achieve the above-mentioned object, a torque detection method of the present invention is a torque detection method for detecting torque generated by interaction with a magnetic field of a magnet for a voice coil motor, the mutual detection with the magnetic field of the magnet. A torque generating unit having a coil or magnetic body that generates torque by action is attached to the rotating shaft , and the torque is converted to a force to rotate the rotating shaft by transmitting the torque to the rotating shaft , and the converted force Is measured by a load cell, and the position where the coil or the magnetic body and the magnet are opposed to each other is relatively moved, and the distribution of the torque generated by the magnet with respect to the relative rotation angle is measured. The torque detection device of the present invention is a torque detection device that detects torque generated by interaction with a magnetic field of a magnet for a voice coil motor, and is disposed opposite to the magnet, and is magnetically coupled to the magnet. A torque generating unit having a coil or a magnetic body that generates torque by interaction; a rotating shaft on which the torque generating unit is mounted at one end; and a load cell that measures a force to rotate the rotating shaft; The coil or the magnetic body and the magnet are moved relative to each other, and the distribution of the torque generated by the magnet with respect to the relative rotation angle is measured.

  In the present invention, the torque generated by the magnetic field is directly transmitted to the rotating shaft, and the force to rotate the rotating shaft is directly detected using the load cell to detect the torque. Therefore, the force generated by the torque is transmitted to and measured by the load cell with almost no loss due to frictional resistance or the like, so that the detection accuracy is improved and the minute torque can be detected. Further, since it is not magnetic detection or magnetostriction detection, there is no influence of the magnetic field. In addition, a simple structure that only includes a rotating shaft and a load cell is sufficient, and the apparatus does not become large as in the technique of measuring with ultrasonic waves or light, and there is no running cost.

  According to the present invention, it is possible to accurately detect torque generated by a magnetic field while having a simple configuration and structure, and it is possible to measure minute torque generated by a magnetic field with high sensitivity and high accuracy. It is. Further, the problem of noise does not occur due to the magnetic field, and there is no need to make the equipment large. Furthermore, it is possible to perform measurement at a low cost without requiring a running cost or the like.

  Hereinafter, a torque detection method and a torque detection apparatus to which the present invention is applied will be described in detail with reference to the drawings. In the following description, a torque detection method and a torque detection device for measuring torque generated by a magnetic field of a magnet for a voice coil motor will be described as an example, but it goes without saying that the present invention is not limited to this. In addition, it can be used for torque measurement of magnets for various purposes.

(First embodiment)
The torque detection device of the present embodiment is intended to measure torque generated by the magnetic field of a magnet (arc-shaped so-called fan-shaped magnet) for a voice coil motor (VCM). The voice coil motor combines a fan-shaped magnet and an actuator equipped with a drive coil, and the drive coil is arranged opposite to the fan-shaped magnet so as to generate a magnetic field generated by the drive coil supplied with the magnetic field of the fan-shaped magnet and the drive current. A structure is employed in which torque is generated by mechanical interaction and an actuator mounted with a magnetic head is rotationally driven. On the other hand, hard disk drives (HDDs) are being reduced in size and thickness, and the fan-shaped magnets are also required to be reduced in size and thickness. Under such circumstances of miniaturization and thinning, it is important to directly grasp the minute torque generated between the fan-shaped magnet and the coil in order to smoothly operate the HDD head. . The torque detection device of the present embodiment measures a minute torque generated between the fan-shaped magnet and the coil directly and with high accuracy.

  1 and 2 are schematic diagrams showing a schematic configuration of the torque detection device of the present embodiment. The torque detection device of the present embodiment has a coil unit (corresponding to a torque generation unit) disposed opposite to the sector-shaped magnet 1 and has a coil that generates torque by interaction with the magnetic field of the magnet. A voice coil motor actuator) 2, a rotating shaft 3 to which the coil unit 2 is attached, a support base 4 that supports the rotating shaft 3, and a load cell 5 that measures torque (force) transmitted to the rotating shaft 3. Has been.

  The rotary shaft 3 is inserted through the bearing 6 so as to be substantially perpendicular to the support base 4 and freely rotatable, and the rotation of the rotary shaft 3 is designed so that there is no friction or resistance as much as possible. The rotating shaft 3 plays a role of transmitting torque generated by the interaction between the fan-shaped magnet 1 and the coil unit 2 to the load cell 5, and when, for example, a frictional force acts on the rotation of the rotating shaft 3, This may result in loss and make accurate measurement difficult. Therefore, in the case of this embodiment, the friction and resistance applied to the rotating shaft 3 by the bearing 6 are reduced.

  In addition, the load cell (load converter) 5 installed on a fixed base 7 that is stably fixed is coupled to a base portion of the rotating shaft 3 (a position below the support base 4). Is configured to detect the force of rotation acting on the rotary shaft 3. The load cell 5 converts “force” into “electric output”, and the conversion is generally performed by a strain gauge.

  The load cell 5 couples the rotary shaft 3 and the load cell 5 via, for example, an arm or the like in order to efficiently transmit the force to be rotated acting on the rotary shaft 3 to the load cell 5. In the case of this example, the load cell 5 is coupled to the arm 8 provided on the rotating shaft 3. The arm 8 also needs to have a high rigidity that can withstand this because, for example, if the arm 8 is bent or deformed by the force of the rotating shaft 3 to rotate, it causes a loss.

  On the other hand, the coil unit 2 is attached to the tip (upper end) on the opposite side of the rotating shaft 3 at a substantially right angle to the rotating shaft 3. The coil unit 2 is firmly fixed to the rotating shaft 3 so as not to move carelessly. If the coil unit 2 and the rotary shaft 3 are misaligned when torque is generated, it will also lead to a loss. For example, the coil unit 2 is mechanically firmly fixed to the rotary shaft 3 by screwing or the like.

  The coil unit 2 includes a coil 2a wound in a magnet facing surface in order to generate torque by interaction with the fan-shaped magnet 1, and a fan-shaped magnet is caused by passing an electric current through the coil 2a. Torque is generated by the magnetic interaction with 1.

  Here, as the coil unit 2, an actuator of a voice coil motor is preferably used as the coil unit 2 as it is. If the actuator is used as the coil unit 2 as it is, measurement according to the actual voice coil motor can be performed, and the torque actually generated by the voice coil motor can be measured as it is.

  In the case of this embodiment, a pair of the fan-shaped magnets 1 are installed substantially in parallel with the coil unit 2 interposed therebetween. However, the fan-shaped magnets 1 can be disposed only on one side so as to face the coil unit 2. It is. In any case, it is preferable that the fan-shaped magnet 1 is arranged in accordance with an actual voice coil motor.

  Although not shown, the fan-shaped magnet 1 is held by a support mechanism so as to be movable relative to the coil unit 2 in a plane facing the coil unit 2. This support mechanism enables the fan-shaped magnet 1 to rotate with respect to the rotation direction of the coil unit 2 by the rotating shaft 3. By attaching the support mechanism to the support base 4, The relative positional relationship can be changed while keeping the interval between the coil units 2 constant.

  The above is the configuration of the torque detection device of the present embodiment. In detecting the torque, a current is passed through the coil 2a of the coil unit 2 to generate torque due to the magnetic interaction between the sector magnet 1 and the coil 2a. . The generated torque becomes a force to rotate the coil unit 2, and this becomes a force to rotate the rotating shaft 3. The force for rotating the rotating shaft 3 is transmitted to the load cell 5 coupled to the rotating shaft 3 via the arm 8, and the torque generated by measuring the magnitude of the force by the load cell 5 is calculated. .

  When measuring the torque, the load of the load cell 5 when no current is passed through the coil 2a is set to zero. Therefore, when a predetermined current is passed through the coil 2a, the load becomes a relative load, so that measurement variations can be suppressed. In addition, the current flowing through the coil 2a during measurement may be constant. For example, the generated torque can be grasped with higher accuracy by reading the torque each time the current value is changed.

  In the torque measurement, a force to rotate the coil unit 2 is transmitted to the rotating shaft 3 by the generated torque, but the rotating shaft 3 itself is not rotated because it is coupled to the load cell 5. Only the force to rotate is transmitted to the load cell 5. Therefore, the torque measurement can be performed in a state where the relative positional relationship between the sector-shaped magnet 1 and the coil unit 2 is fixed.

  As described above, in the torque detection device of the present embodiment, the torque is measured in a state where the relative positional relationship between the sector magnet 1 and the coil unit 2 is fixed. By utilizing this fact, it is also possible to measure the distribution of the torque generated in the plane of the sector magnet 1 with respect to the relative rotation angle. That is, the fan-shaped magnet 1 is attached to be rotatable with respect to the rotation direction of the coil unit 2 by a support mechanism. Therefore, the fan-shaped magnet 1 is rotated in-plane using this support mechanism, and the torque is measured while changing the angle θ formed by the center line C1 of the sector-shaped magnet 1 and the center line C2 of the coil 2a shown in FIG. For example, the distribution of the torque relative to the relative rotation angle can be measured. Considering the driving of the voice coil motor, if the distribution of the torque with respect to the relative rotation angle can be grasped, it will be extremely useful information for designing the apparatus.

(Second Embodiment)
The configuration of the torque detection device is the same as that in the first embodiment. In this embodiment, a magnetic body (iron plate or the like) is placed on the coil portion, and a bulge is provided on the magnet end portion for VCM, and the force (torque) that attracts the iron plate and the magnet end portion is measured. .

  By arranging a magnetic material, for example, an iron piece instead of the coil, the torque generated by the interaction between the magnet and the iron piece can be measured. In this case, no current flows through the coil. For example, as shown in FIG. 4, a nonmagnetic plate-like member 9 is arranged instead of the coil unit 2, and a magnetic body 10 such as an iron piece is attached to the end of the plate-like member 9, so that the upper end 1 a is raised. Thus, an interaction occurs with the substantially fan-shaped magnet 1 having a different shape, and so-called latch torque can be measured. Therefore, in this embodiment, the plate-like member 9 to which the magnetic body 10 is attached corresponds to a torque generating unit.

Actually, an attempt was made to measure the latch torque generated by the interaction between the magnetic body 10 and the substantially sector-shaped magnet 1 having a shape in which the upper end portion 1a is raised. In the measurement, a substantially sector-shaped magnet 1 having the dimensions shown in FIG. 5 was used. Magnetic properties of the substantially fan-shaped magnet 1, the residual magnetic flux density Br1384mT, Hcb1070kA / m, Hcj1376kA / m, a (BH) max372kJ / ^{m 3.} A point where the center position of the magnetic body 10 coincides with the center position of the upper end portion 1a of the substantially sector-shaped magnet 1 was set to an angle θ = 0 °, and the torque was measured by changing the angle θ. The results are shown in FIG. It can be seen that the torque generated gradually decreases as the angle θ increases (the distance between the magnetic body 10 and the upper end portion 1a increases).

(Third embodiment)
In the torque detection device of the first embodiment, the rotating shaft 3 is supported by the support 5 via the bearing 6. Here, for example, when the fan-shaped magnet 1 is further downsized and the generated torque becomes smaller, the friction and resistance of the bearing 6 may also become a problem. The bearing 6 is not completely free of friction and resistance, and if the torque becomes very small, loss due to it becomes a problem and accurate measurement may be difficult.

  Therefore, in the present embodiment, a balance plate supported by a knife edge, a pin, or the like is used to eliminate friction and resistance applied to the rotating shaft 3 as much as possible, and a minute torque can be accurately measured. Therefore, the torque detection device according to the present embodiment can be referred to as a “yajirobe method”.

  Hereinafter, the configuration of the torque detection device of the present embodiment will be described. 7 and 8 are diagrams showing a schematic configuration of the torque detection device of the present embodiment. The torque detection device of this embodiment includes a balance plate 12 supported by a blade-like fulcrum 11 having a knife edge 11a, and a rotating shaft 3 is attached to the balance plate 12.

  The balance plate 12 is supported only by the knife edge 11a of the blade-like fulcrum 11, and is rotatably installed with the knife edge 11a as a fulcrum as if it is a jar. The support mechanism for the balance plate 12 is not limited to the knife edge 11a, and may be a plurality of pin-shaped fulcrums, for example.

  In the balance plate 12 having the knife edge 11a as a fulcrum, the resistance to rotation is almost zero, and the resistance due to friction or the like is greatly increased even when the bearing 6 is used as in the first embodiment. Can be reduced.

  In the present embodiment, the rotation shaft 3 is attached so that the center axis coincides with the rotation center of the balance plate 12. Therefore, in this embodiment, the attachment direction of the rotating shaft 3 is a horizontal direction. Moreover, since the rotating shaft 3 is attached to the balance plate 12, resistance to rotation is almost zero.

  Other configurations are basically the same as those in the first embodiment. For example, the coil unit 2 corresponding to the torque generating unit is attached to the tip of the rotating shaft 3. In this case, the coil unit 2 is attached in a substantially vertical direction and is firmly fixed to the rotating shaft 3 so as not to move carelessly.

  A pair of fan-shaped magnets 1 are installed substantially vertically with the coil unit 2 in between. Although not shown, the fan-shaped magnet 1 is held by a support mechanism so that it can move relative to the coil unit 2 in a plane facing the coil unit 2. This support mechanism enables the fan-shaped magnet 1 to rotate with respect to the rotation direction of the rotating shaft 3 of the coil unit 2, and the fan-shaped magnet 1 faces the coil unit 2 at a predetermined distance. By fixing the support mechanism as described above, it is possible to change the relative positional relationship while keeping the interval between the fan-shaped magnet 1 and the coil unit 2 constant.

  On the other hand, the load cell 5 is coupled to a position near one of the ends of the balance plate 12 with the fulcrum (knife edge 11a) interposed therebetween. The load cell 5 is stably fixed so as not to move by any fixing means.

  Here, when the load cell 5 is coupled to one end side of the balance plate 12, for example, when the rotary shaft 3 tries to rotate in the direction of arrow A in FIG. However, when attempting to rotate in the direction of arrow B, no force is applied to the load cell 5 and torque measurement cannot be performed. Therefore, in this embodiment, a balancer (weight) 13 is installed on the opposite side of the fulcrum of the balance plate 12 to eliminate such inconvenience.

  That is, when setting is made such that force F1 is applied to the load cell 5 by the installation of the balancer 13, when the force to rotate in the direction of arrow A is applied to the rotary shaft 3 by the generated torque, A force (F1 + F2) is applied which is a combination of the force F1 by the balancer 13 and the force F2 to rotate the rotating shaft 3. On the other hand, when a force to rotate in the direction of arrow B is applied to the rotary shaft 3 due to the generated torque, the load cell 5 has a force F2 to rotate the rotary shaft 3 from a force F1 by the balancer 13. The force (F1-F2) obtained by subtracting is added. Therefore, if the force F1 applied to the load cell 5 due to the installation of the balancer 13 is set larger than the force F2 to be transmitted to the rotating shaft 3 by the generation of torque, a load is always applied to the load cell 5. Thus, the torque can be measured regardless of which of the rotating shaft 3 rotates.

  Also in the torque detection device of the present embodiment, torque is detected by transmitting torque generated by the magnetic field of the sector-shaped magnet 1 to the rotary shaft 3 and directly detecting the force to rotate using the load cell 5. At this time, since the structure in which the rotary shaft 3 is directly attached to the fulcrum of the balance plate 12 is adopted, the force generated by the torque is transmitted to the load cell 5 with almost no loss due to the frictional resistance, and as a result, the detection accuracy is improved. This greatly improves the detection of minute torque.

FIG. 9 shows a torque measurement result (a measurement result of a distribution with respect to a relative rotation angle of torque generated in the plane of the fan-shaped magnet 1) by the torque detection device of the present embodiment and the torque detection device of the first embodiment. It is. From FIG. 9, it can be seen that torque can be measured by either method of the present embodiment or the first embodiment. Further, it can be seen that the resolution of the torque detection device of the present embodiment is improved compared to the torque detection device of the first embodiment. The resolution in the torque detection device of this embodiment is better than 0.001 mNm, whereas the torque detection device (bearing system) in the first embodiment has a resolution of 0.005 mNm. In the measurement, a sector-shaped magnet 1 having the dimensions shown in FIG. 10 was used. Magnetic properties of the substantially fan-shaped magnet 1, the residual magnetic flux density Br1370mT, Hcb1062kA / m, Hcj1393kA / m, a (BH) max365kJ / ^{m 3.} Further, the position where the center line of the coil 2a and the sector-shaped magnet 1 coincides is an angle θ = 0 °, and the torque generated in the plane of the sector-shaped magnet 1 in the range of −20 ° to 20 ° with respect to the relative rotation angle. Was measured. The current passed through the coil is 50 mA.

  As described above, in the torque detection device and the torque detection method of the present invention, it is possible to measure the torque generated by the magnetic field with a simple device configuration and measurement method. Further, in the present invention, since the relative comparison with the value before the current is passed, the signal loss due to friction can be reduced. Furthermore, by performing measurement while changing the current value, it is possible to reduce the influence of measurement variation and further increase the measurement accuracy. In particular, with regard to friction loss, by adopting the “Yajirube method” as in the second embodiment, the friction loss occurs only at the fulcrum of the balance plate 12 and is almost zero. Therefore, sensitivity and resolution can be increased.

It is a typical side view which shows the structure of the torque detection apparatus of 1st Embodiment. It is a typical top view which shows the structure of the torque detection apparatus of 1st Embodiment. It is a schematic plan view which shows the positional relationship of a fan-shaped magnet and a coil unit. It is a typical top view showing torque detection in a 2nd embodiment. It is a typical top view which shows the dimension of the substantially sector shaped magnet 1 in the case of torque measurement, and the positional relationship of the substantially sector shaped magnet 1 and a magnetic body. It is a characteristic view which shows a latch torque measurement result. It is a typical side view which shows the structure of the torque detection apparatus of 3rd Embodiment. It is a typical front view which shows the structure of the torque detection apparatus of 3rd Embodiment. It is a characteristic view which compares and shows the torque measurement result by the torque detection apparatus of 3rd Embodiment, and the torque detection apparatus of 1st Embodiment. FIG. 10 is a schematic plan view showing the dimensions of the substantially sector-shaped magnet 1 used in the measurement of FIG. 9 and the positional relationship between the substantially sector-shaped magnet 1 and the coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fan-shaped magnet, 2 coil unit, 2a coil, 3 rotating shaft, 4 support stand, 5 load cell, 6 bearing, 7 fixed stand, 8 arm, 9 plate member, 10 magnetic body, 11 blade-shaped fulcrum, 11a knife edge , 12 Balance plate, 13 Balancer (weight)

Claims (9)

A torque detection method for detecting a torque generated by an interaction with a magnetic field of a magnet for a voice coil motor, wherein a torque generating unit having a coil or a magnetic body that generates a torque by an interaction with the magnetic field of the magnet is rotated. The coil or the magnetic body and the magnet are mounted on a shaft , converted into a force to rotate the rotating shaft by transmitting the torque to the rotating shaft, and the converted force is measured by a load cell. The torque detection method is characterized by measuring the distribution of the torque generated by the magnet with respect to the relative rotation angle. The torque detection method according to claim 1, wherein measurement is performed by changing a value of a current flowing through the coil . The torque detection method according to claim 1, wherein a pair of magnets are installed with the torque generation unit interposed therebetween. 4. The load cell measures the force to rotate the balance plate by attaching the center axis of the rotation axis so as to substantially coincide with the rotation center of the balance plate balanced at the fulcrum . The torque detection method according to claim 1. A torque detection device for detecting torque generated by interaction with a magnetic field of a magnet for a voice coil motor ,
A torque generating unit having a coil or a magnetic body that is disposed opposite to the magnet and generates torque by magnetic interaction with the magnet;
A rotating shaft to which the torque generating unit is attached at one end;
A load cell for measuring the force of the rotating shaft to rotate ,
A torque detection device characterized by measuring a distribution of a torque generated by the magnet with respect to a relative rotation angle by relatively moving a facing position between the coil or the magnetic body and the magnet . The rotating shaft is inserted into a support base through a bearing, and the torque generating unit is attached to the tip of the rotating shaft at a substantially right angle to the rotating shaft, and the other end side of the rotating shaft is The torque detection device according to claim 5, wherein the torque detection device is coupled to the load cell via an arm. A balance plate balanced at a fulcrum is provided, the rotation axis of the balance plate is substantially aligned with the center axis of the balance plate, and the rotation axis is attached in a substantially horizontal direction. ,
6. The torque detecting device according to claim 5 , wherein the load cell is coupled to one side across the fulcrum of the balance plate, and a weight is installed on the other side. 8. The torque detection device according to claim 5, further comprising a mechanism for moving the magnet relative to the torque generation unit in a plane facing the torque generation unit. 9. 9. The torque detection device according to claim 6, wherein the torque generation unit is an actuator of a voice coil motor.

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