JP6536880B2 - Magnet, pickup device using the magnet, method of manufacturing the magnet - Google Patents

Description

  The present invention is a magnet in which the surfaces facing in the first direction are magnetized with the same polarity, and the surface facing in the second direction is magnetized with the opposite polarity to the magnetic pole, and a pickup device using this magnet, And a method of manufacturing the magnet.

  Patent Document 1 describes a Halbach magnetic circuit used for a linear motor.

  This Halbach magnetic circuit is composed of a first sintered magnet and two second sintered magnets located on both sides thereof. The first sintered magnet is magnetized in a direction orthogonal to the main surface, and each of the second sintered magnets is magnetized such that the orientation direction of the magnetization is inclined toward the main surface. As a result, the magnetic flux is concentrated in front of the main surface of the first sintered magnet to generate a magnetic field generating space with a high magnetic flux density.

  In the Halbach magnetic circuit described in Patent Document 1, although the second sintered magnet is fixed to both sides of the first sintered magnet with an adhesive, the magnetization direction of the second sintered magnet is inclined, When the second sintered magnet is disposed on both sides of the first sintered magnet, a force to move the second sintered magnet acts to position each magnet and fix it firmly with an adhesive. Work is difficult. Therefore, expensive and strong adhesives and fixtures have to be used, and since the bonding operation is required, the production efficiency of magnets also decreases.

  Patent Document 2 also describes a permanent magnet used for a linear actuator. The permanent magnet is composed of one magnet, and the two opposing surfaces are both magnetized to the S pole, and the surface orthogonal to the two surfaces is magnetized to the N pole.

  The first magnetizing means for forming the permanent magnet has magnetic anisotropy in advance so that the axis of easy magnetization matches the orientation of the magnetic pole in the manufacturing process of the permanent magnet, and then the magnetizing is performed. ing. In the second magnetization means, an isotropic magnet which is not magnetically anisotropic is used to orient the magnetization direction by magnetization.

Unexamined-Japanese-Patent No. 2010-50440 JP 2002-369492 A

  Unlike the one described in Patent Document 1, the permanent magnet described in Patent Document 2 does not have to fix a plurality of magnets with an adhesive.

  However, in the first magnetization means, it is necessary to use a magnetic block having a magnetic anisotropy in which the axis of easy magnetization conforms to the direction of the magnetic pole. Since this magnetic block is injection-molded in a magnetic field, it is necessary to use an orientation mold having a special structure for injection molding, which increases the manufacturing cost.

  In the second magnetizing means, an isotropic magnet which is not magnetically anisotropic is used. However, the isotropic magnet has the direction of the magnetization easy axis of each of the fine magnetic substance crystal grains inside. Because they are randomly fixed, the residual magnetic flux density after magnetization is lower than that of an anisotropic magnet in which the magnetization easy axes of all the crystal grains are oriented in the same direction. In general, a magnet magnetized with an isotropic magnetic material may have a residual magnetic flux density of 1/2 or less as compared with a magnet magnetized with a magnetic material having anisotropy.

  The present invention solves the above-mentioned conventional problems, can be constituted by a single magnet, and does not require complicated anisotropy, and a general uniaxial anisotropic magnet can be used, and also the generated magnetic flux density It is an object of the present invention to provide a magnet that can be increased in height, a pickup device using the magnet, and a method of manufacturing the magnet.

According to the present invention, a magnetic field has a first surface and a second surface facing each other in a first direction, and a third surface and a fourth surface facing each other in a second direction intersecting the first direction. In the magnet in which each of the faces of the body block is magnetized,
In the magnetic block, the magnetization easy axis is oriented in a first direction,
The first surface and the second surface are magnetized to the same polarity, and the third surface and the fourth surface are magnetized to the opposite polarity to the first surface and the second surface. Yes,
The magnetic flux density at positions separated by the same distance from each of the third surface and the fourth surface is characterized in that the third surface is higher than the fourth surface. .

  In the magnet of the present invention, for example, the magnetic body block is a bond block in which a powdery magnetic body is fixed by a resin material.

  The pickup apparatus according to the present invention comprises: a movable portion having the magnet and an objective lens facing the recording medium; a support member for movably supporting the movable portion; and a coil provided on the fixed side and facing the magnet , And is characterized in that

Further, the pickup apparatus of the present invention, the support portion where previous SL support member for supporting the movable part is one that is misaligned to the fourth side of the center of gravity of the movable portion.

  In the pickup device of the present invention, a first drive coil for moving the movable portion in the optical axis direction of the objective lens faces at least one of the first to fourth surfaces, and the first drive coil The second drive coil, which moves the movable portion in the direction intersecting the optical axis, is supplied with current in the direction intersecting the optical axis direction, and at least a plurality of corner portions where the faces of the magnet intersect. One of the corner portions may be opposed, and in the second drive coil, current may flow in the optical axis direction.

Next, according to the method of manufacturing a magnet of the present invention, a first surface and a second surface facing in a first direction, and a third surface facing in a second direction intersecting the first direction, and Using a magnetic block having a fourth surface, the easy axis of magnetization being oriented in a first direction,
A first yoke faces the first surface, a second yoke faces the second surface, and the respective yokes face the first surface and the second surface in opposite directions. The first magnetic field and the second surface are magnetized with the same polarity, and the third surface and the fourth surface are divided into the first surface and the second surface. It is characterized in that the magnetic pole different from that of the above is magnetized.

In the method of manufacturing a magnet according to the present invention, a third yoke is opposed to the third surface, and a magnetizing magnetic field which circulates between the first yoke and the third yoke; Forming a magnetizing magnetic field that circulates between the second yoke and the third yoke;
Magnetizing the magnetic flux density at a position separated by the same distance from each of the third surface and the fourth surface such that the third surface is higher than the fourth surface It is possible.

  In the magnet of the present invention, a magnetic substance block having magnetic anisotropy in which the axis of easy magnetization is oriented in one direction is magnetized, and the opposing surfaces are the same magnetic pole. Since a magnetic block in which the easy axis of magnetization is oriented in one direction is used, as described in Patent Document 2, a magnetic block of a special structure in which magnetic anisotropy is given in the magnetization direction is converted to a magnetic field. There is no need to mold in the middle, and a magnetic block that is a general commercially available product can be used. Furthermore, in the present invention, since the magnetic anisotropic magnetic block is used, the magnetic force to be held can be made stronger than a magnet in which the magnetic isotropic magnetic block is magnetized. It is also possible to configure the magnetic flux density emanating from the third surface to be high by the third and fourth surfaces magnetized to the same magnetic pole.

  The pickup apparatus of the present invention can realize a so-called moving magnet system by configuring at least a part of the movable portion with the magnet. In this method, the coil wiring need not be connected to the movable portion, so the structure can be simplified.

  Next, in the method of manufacturing the magnet according to the present invention, since the opposite surfaces are magnetized to the same magnetic pole by magnetizing the magnetic material block whose easy axis of magnetization is oriented in one direction, special magnetic A magnet of high magnetic property can be manufactured by a relatively simple process without using a magnetic block having a magnetic property.

A perspective view showing a magnet according to an embodiment of the present invention; An end view of the magnet shown in FIG. (A) is an explanatory view of a magnetizing device for magnetizing the magnet shown in FIG. 1, (b) is a conceptual view of an excitation pulse voltage waveform for magnetizing, (A) is a diagram showing the magnetic flux density perpendicular to the third surface and the fourth surface of the magnet shown in FIG. 1, (b) is the third surface and the fourth surface of the magnet of the first comparative example. A diagram showing the flux density perpendicular to the plane of the plane, A diagram showing the magnetic flux density perpendicular to the third and fourth surfaces of the magnet of the second comparative example; Diagram for explaining the difference between the magnetization state in the direction of easy magnetization and the direction of hard magnetization in the magnet having magnetic anisotropy, A perspective view showing a pickup device according to an embodiment of the present invention; FIG. 8 is a plan view of the pickup device shown in FIG. FIG. 8 is a side view showing the main part of the pickup device shown in FIG. 7; FIG. 8 is a perspective view showing a facing state of a magnet of a movable part of the pickup device shown in FIG.

  1 and 2 show a magnet 1 according to an embodiment of the present invention. In this specification, the state before being magnetized is referred to as a magnetic body block 10, and the one obtained by magnetizing the magnetic body block 10 is referred to as a magnet 1. In the embodiment of the present invention, since the magnet 1 is a bonded magnet, the pre-magnetized magnetic block 10 is a bonded block.

  The bond block is obtained by solidifying magnetic powder, which is a powdery magnetic body, with a binder resin. The magnetic powder is a Sm-Fe-N system (Samarium-Iron-Nitrogen system) or an Nd-Fe-B system (Neodymium-Iron-boron system). Or two or more kinds of magnetic powder may be mixed and used. The binder resin is PA (polyamide resin). The magnetic body block 10 can be called a rare earth block, and the completed magnet 1 is a rare earth magnet.

  The magnetic body block 10 shown in FIG. 1 and FIG. 2 is a rectangular parallelepiped, and the planar shape is 24 mm in length L, 12 mm in width W, and 6 mm in height H. In the magnetic body block 10, the X direction is a first direction, and the Z direction is a second direction. The first surface 11 and the second surface 12 face in the first direction (X direction), and the third surface 13 and the fourth face face in the second direction (Z direction) 14

  The magnetic block 10 has magnetic anisotropy, and the easy axis EA is oriented in the X direction substantially throughout the block. The magnetic body block 10 can be molded by injecting a mixture of magnetic powder and a binder resin into the inside of a mold, and at this time, by molding in a magnetic field oriented in the X direction, the magnetization easy axis EA A magnetic block 10 of magnetic anisotropy is formed in which X is oriented in the X direction. Alternatively, the magnetic body block 10 can be formed by so-called compacting in which magnetic powder mixed with a binder resin is pressurized with a mold. In this case, the magnetic powder is compressed in the Z direction in a magnetic field oriented in the X direction, thereby forming the magnetically anisotropic magnetic block 10 in which the easy axis of magnetization EA is oriented in the X direction.

  The magnetic body block 10 is a bond block and can be formed by injection molding using a mold, so that there is a degree of freedom in the shape. For example, the third surface 13 may be formed into a convex surface, a protrusion protruding in the Z direction may be formed on a part of the third surface 13, or a step may be formed so that the central portion of the third surface 13 is high. It can also be done. This is also true for the fourth surface 14. In the present specification, even if the third surface 13 or the like is formed into a shape having a protrusion as described above, the whole surrounded by L × W is defined as the third surface 13 or the like.

A magnetizing device 20 is shown in FIG. 3 (a).
The magnetizing device 20 has a magnetizing yoke 21. The magnetizing yoke 21 is formed of a soft magnetic material such as a Ni-Fe alloy (nickel-iron alloy). The magnetizing yoke 21 has a first yoke 21 a facing the first surface 11 of the magnetic body block 10, a second yoke 21 b facing the second surface 12, and a third facing the third surface 13. It has three yokes 21c. The first yoke 21a, the second yoke 21b, and the third yoke 21c are integrally formed.

  As shown in FIG. 3A, the first exciting coil 22a is wound around the first yoke 21a, the second exciting coil 22b is wound around the second yoke 21b, and the third yoke 21c is wound around the third yoke 21c. The excitation coil 22c is wound. The respective excitation coils 22a, 22b, 22c are connected in series, and the drive circuit 25 is connected to the excitation coils 22a, 22b, 22c.

  The drive circuit 25 has a DC power supply 26 and a switch 27. The switch 27 is composed of an active element such as a transistor, and is turned on and off at a predetermined cycle. When the switch 27 is ON, a drive voltage having a waveform shown in FIG. 3B is generated by a time constant determined by the capacitor C, the choke coil L, and the fixed resistor R, and this is generated in the excitation coils 22a, 22b, 22c. Given. The half width T of the drive voltage shown in FIG. 3B is about 130 μs.

  At the moment when the switch 27 of the drive circuit 25 is switched from OFF to ON, an exciting current which rapidly rises flows through the exciting coils 22a, 22b and 22c based on the voltage waveform of FIG. By this excitation current, within the magnetization yoke 21, the excitation magnetic flux 11 circulates between the first yoke 21a and the third yoke 21c, and between the second yoke 21b and the third yoke 21c. The excitation magnetic flux 22 circulates.

  By repeatedly applying the excitation magnetic fluxes 11 and Φ2, as shown in FIG. 2, the first surface 11 and the second surface 12 of the magnetic body block 10 are magnetized to the S pole, and the third surface 13 The fourth surface 14 is magnetized to the N pole to complete the magnet 1.

  The magnetic substance block 10 shown in FIGS. 1 and 2 has magnetic anisotropy, and the easy magnetization axis EA is oriented in the first direction (X direction) throughout the block, and the entire block is in the second direction. (Z direction) is the hard axis direction of magnetization.

  FIG. 6 shows an M-H curve when magnetizing a magnetic block having a side of 5 mm. The horizontal axis indicates the magnitude of the excitation magnetic field externally applied to the magnetic body block. The horizontal axes (+) and (-) mean the difference in the direction of the magnetic field. The vertical axis is the intensity of magnetization when the magnetic substance block is magnetized. The solid line in FIG. 6 shows the change in the magnetization of the magnetic body block when the exciting magnetic field is applied in the direction of the easy axis EA, and the broken line is the magnetic when the exciting magnetic field is applied in the direction of the hard axis HA The change of the magnetization of the body block is shown.

  As shown in FIG. 6, when an excitation magnetic field is applied from the outside, inside the magnetic substance block, it is easy to be magnetized in the direction of the easy axis EA, but it is extremely difficult to magnetize the hard axis HA.

  As shown in FIG. 2, the magnetization easy axis EA of the magnetic body block 10 is oriented in the first direction (X direction), so that the exciting magnetic field directed from the first yoke 21a to the first surface 11 When an exciting magnetic field directed from the second yoke 21b to the second surface 12 is simultaneously applied, inside the magnetic body block 10, magnetization is performed from the first surface 11 to the left in the drawing and from the second surface 12 It is magnetized in the right direction as shown. In the central portion of the magnetic body block 10, the magnetic field from the first surface 11 and the magnetic field from the second surface 12 are confined to form a cusped magnetic field. At this time, the third yoke 21c is also excited at the same time, and a magnetic field directed from the third surface 13 toward the third yoke 21c is generated. Therefore, the cusp magnetic field at the center of the magnetic body block 10 is the third yoke 21c. It is oriented in the direction.

  In the magnet thus magnetized, the first surface 11 and the second surface 12 opposed in the first direction (X direction) are magnetized to the S pole, and the magnet is magnetized in the second direction (Z direction). The opposing third surface 13 and fourth surface 14 are magnetized to the N pole. However, since the cusp magnetic field at the center of the inside of the magnetic body block 10 is attracted to the third yoke 21c, the magnetic force of the N pole on the third surface 13 is N on the fourth surface 14 after magnetization. It becomes stronger than the magnetic force of the pole.

  Fig.4 (a) is the diagram which measured the magnetic flux density emitted from the magnet 1 of embodiment of this invention, FIG.4 (b) is a line which measured the magnetic flux density emitted from the magnet in a 1st comparative example. FIG. FIG. 5 is a diagram in which the magnetic flux density emitted from the magnet in the second comparative example is measured.

  The same magnetic body block 10 is used in the embodiment of the present invention and the first comparative example and the second comparative example. Magnetic powder is a mixture of Sm-Fe-N and Nd-Fe-B, and the binder resin is PA. A rectangular magnetic body block 10 was formed by injection molding, and the length L was 24 mm, the width W was 12 mm, and the height H was 6 mm.

  The magnetic substance block 10 of the embodiment of the present invention, the result of which is shown in FIG. 4A, is one in which the magnetization easy axis EA is oriented in the first direction (X direction). In Comparative Examples 1 and 2, the magnetization easy axis EA is oriented in the second direction (Z direction), and the first direction (X direction) is the direction of the hard magnetization axis.

  FIG. 4A uses the magnetic body block 10 in which the first direction is the easy axis of magnetization EA, and the magnetizing device 20 shown in FIG. It is an actual measurement value of the magnet 1 which is magnetized by facing the second surface 12 to the second yoke 21 b and facing the third surface 13 to the third yoke 21 c.

  FIG. 4 (b) uses the magnetic body block whose second direction is the easy axis of magnetization EA, and uses the magnetizing apparatus 20 shown in FIG. 3 (a) to form the first surface 11 as the first surface. By the actual measurement value of the magnet of the second comparative example which is magnetized so as to face the yoke 21a, the second surface 12 to the second yoke 21b, and the third surface 13 to face the third yoke 21c. is there.

  FIG. 5 shows a third comparative example in which an excitation magnetic field directed in the Z direction is applied to a magnetic substance block whose second direction (Z direction) is the easy axis of magnetization EA to magnetize in the same state as a normal magnet. The actual value of the magnet of In FIG. 5, the third surface 13 is magnetized to the N pole and the fourth surface 14 is magnetized to the S pole.

  The horizontal axes in FIGS. 4 (a) and 4 (b) and FIG. 5 are the midpoints in the length direction L of the magnetic substance block 10 shown in FIG. 1 and indicate the distance on the X axis from the origin (0). There is. The vertical axes in FIGS. 4 (a) and 4 (b) and FIG. 5 are the magnetic flux density, the value of (+) is the magnetic flux density of the magnetic flux directed upward in the figure, and the value of (-) is downwardly directed in the figure It is the flux density of the magnetic flux.

  The diagrams shown by black circles in each of FIGS. 4A and 4B and FIG. 5 show the third surface 13 to Z in the magnet 1 of the embodiment of the present invention and the magnets of Comparative Example 1 and Comparative Example 2. It represents the magnetic flux density measured at a position 4 mm above the direction. A white circle indicates a magnetic flux density measured at a position 4 mm below the fourth surface 14 in the Z direction.

  As shown in FIG. 4A, in the magnet 1 of the embodiment, the magnetic force of the N pole on the third surface 13 is larger than the magnetic force of the N pole on the fourth surface 14 I understand.

  Comparing FIGS. 4A and 4B, the first yoke 21a and the second yoke 21b apply a magnetizing magnetic field to the magnetic body block 10 in the direction of the easy magnetization axis EA to magnetize the third yoke 21c. It is preferable to magnetize it as shown in FIG. 3A, facing the direction perpendicular to the easy axis EA.

  Further, comparing FIG. 4A with FIG. 5, in the embodiment of the present invention, as compared with the second comparative example in which the Z direction is the magnetization easy axis direction and is magnetized by the magnetization magnetic field of the Z direction, It can be seen that the magnetic force of the N pole at the surface 13 of 3 can be made stronger.

  The magnet 1 according to the embodiment of the present invention uses a general magnetic anisotropy magnetic block in which the first direction is the easy axis of magnetization EA, and it is only necessary to magnetize the yoke so as to face each other from three directions. The magnetic force of the third surface 13 can be strengthened more than the fourth surface. Moreover, since the magnet 1 is comprised from the one magnetic body block 10, it is not necessary to join a several magnet, and it becomes the thing excellent in mass productivity.

  Therefore, it becomes possible to use the magnet 1 of the said embodiment for a small linear actuator etc.

  In FIGS. 2 and 3A, the fourth yoke also faces the fourth surface 14 to generate an excitation magnetic field in the Z direction opposite to each other between the third yoke 21c and the fourth yoke. You may In this case, if the number of turns of the fourth excitation coil wound around the fourth yoke is made equal to that of the third excitation coil 22c, the magnetic force of the N pole at the third surface 13 and the fourth surface 14 The magnetic force of the N pole can be set to the same strength.

  Alternatively, the yoke may not be opposed to the third surface 13 and the fourth surface 14 but may be opposed to the first surface 11 and the second surface 12 to magnetize the magnetic block 10. The first surface 11 and the second surface 12 can form an S pole, and the third surface 13 and the fourth surface 14 can form an N pole magnet.

  Further, if the winding directions of the exciting coils 22a, 22b, 22c of the magnetizing device 20 are reversed, the first surface 11 and the second surface 12 are magnetized to the N pole, and the third surface 13 and the fourth surface It is also possible to form a magnet in which the face 14 of the is magnetized to the S pole.

  7 to 10 show a pickup device 30 as an example of use of the magnet 1.

  The pickup device 30 is for facing the recording surface of a disc such as a DVD or a CD as a recording medium, and reading information recorded on the recording surface or writing information on the recording surface.

  The pickup device 30 has a pickup base 31 on the fixed side. The fixing portion 32 is fixed to the pickup base 31, and the central portion of the suspension support member 33 is fixed to the back of the fixing portion 32. Suspension wires 34, which are elastic support members, are fixed to both ends of the suspension support member 33 as support members. Two suspension wires 34 are provided at intervals in the radial direction (R direction), for a total of four.

  As shown in FIG. 7 and FIG. 10, the movable portion 40 is provided at the tip of the suspension wire 34. The movable portion 40 has a magnet 41, a holder 42 fixed to the upper portion of the magnet 41, and an objective lens 43 fixed to the central portion of the holder 42.

  Connecting portions 42a are bent and formed on both sides in the radial direction (R direction) of the holder 42, and tips of four suspension wires 34 are inserted into the connecting holes of the connecting portions 42a for soldering or the like. It is fixed by an adhesive. In FIG. 8 and FIG. 9, the connection portion of the suspension wire 34 and the connection portion 42a is shown as a support portion 42s. The support point 42s is located closer to the suspension support member 33 than the position where the center of gravity G of the movable portion 40 exists. The center of gravity G is located on the optical axis O of the objective lens 43.

  The magnet 41 is formed with a through hole directly below the objective lens 43 in the direction of the optical axis O of the lens. In the pickup device 30, an inclined mirror such as a prism is provided on the lower side of the movable portion 40, and the through hole is opposed on the inclined mirror. The detection light emitted from the light emitting element is reflected by the tilt mirror, passes through the inside of the through hole, and is given to the objective lens 43. Further, the return light reflected by the recording surface of the disc returns along the same path, is reflected by the tilt mirror, and is received by the light receiving element.

  As shown in FIGS. 8 and 10, in the magnet 41, the side surfaces on both sides in the radial direction (R direction) are the first surface 41a and the second surface 41b, and the side surfaces on both sides in the tangential direction (T direction) Are the third surface 41c and the fourth surface 41d. The magnetic substance block forming the magnet 41 is the same rare earth bond block as that used to manufacture the magnet 1 shown in FIGS. 1 and 2, and the magnetization easy axis EA is directed in the radial direction (R direction).

  The magnetic block is magnetized by a magnetizing device 20 of the same type as shown in FIG. In the magnetic block, the first surface 41a faces the first yoke 21a, the second surface 41b faces the second yoke 21b, and the third surface 41c faces the third yoke 21c. The excitation coils 22a, 22b and 22c are energized and magnetized.

  In the magnet 41 after magnetization, the first surface 41 a and the second surface 41 b are magnetized to the S pole, and the third surface 41 c and the fourth surface 41 d are magnetized to the N pole. However, the magnetic force of the N pole of the third surface 41 c is stronger than the magnetic force of the N pole of the fourth surface 41 d.

  As shown in FIGS. 7 and 8, a pair of first coil yokes 35 is fixed to the pickup base 31, and a first drive coil (focus drive coil) 51 is provided to each of the first coil yokes 35. It is rolled. The first drive coil 51 is opposed to the third surface 41c and the fourth surface 41d of the magnet 41 of the movable portion 40, and as shown in FIG. 10, in the portion opposed to the respective surfaces 41c and 41d The drive current Ia flows in a radial direction (R direction) which is a direction orthogonal to the optical axis O. The movable portion 40 is driven in the focus direction (F direction) by the drive current Ia.

  Second coil yokes 36 are fixed at four positions of the pickup base 31, and second drive coils (tracking drive coils) 52 are supported by the respective second coil yokes 36. The second drive coil 52 is opposed to the corner of the magnet 41 of the movable unit 40. In the second drive coil 52 positioned in the front of FIG. 10, the drive current I1 flowing in the direction of the optical axis O at the portion facing the third surface 41c and the light at the portion facing the second surface 41b. The driving current I2 flowing in the direction of the axis O is reversed. Also in the other three second drive coils 52, the flow of current is the same or symmetrical as described above, and as a result, the movable portion 40 is driven in the radial direction (R direction).

  In the pickup device 30, the movable portion 40 is driven in the focus direction (direction F) by the drive current Ia flowing through the first drive coil 51, whereby the detection light emitted from the objective lens 43 is the recording surface of the disc. It is corrected to be able to focus on the The movable portion 40 is driven in the radial direction (R direction) by the drive currents I1 and I2 flowing to the second drive coil 52 so that the focusing spot of the detection light follows the recording track on the recording surface of the disk Corrected to

  As shown in FIG. 9, the support location 42 s, which is the connection portion between the suspension wire 34 and the connection portion 42 a, is set so as to be displaced closer to the fourth surface 41 d of the magnet 41 than the center of gravity G of the movable portion 40. It is done. As a result, a counterclockwise moment M by its own weight always acts on the movable portion 40, and when the movable portion 40 is driven in the focus direction (F direction), the third surface 41d of the magnet 41 This tends to cause a delay in the followability of the face 41c. However, since the magnetic force of the N pole of the third surface 41c is stronger than the magnetic force of the N pole of the fourth surface 41d, even if the drive current Ia flowing through the pair of first drive coils 51 is the same, The correction driving force F3 generated on the third surface 41c side is larger than the correction driving force F4 generated on the surface 41d side of # 4. Therefore, it is possible to correct the delay of the response due to the positional deviation between the center of gravity G and the support portion 42s.

  When the center of gravity G and the support portion 42s are not so far apart, the third magnetic surface 41c and the fourth surface 41d of the magnet 41 may be magnetized so that the magnetic force of the N pole is substantially the same.

  The pickup device 30 of the above-described structure is a so-called moving magnet type in which a coil is not provided in the movable portion 40. Therefore, wiring to the movable portion 40 is unnecessary, and the wiring structure can be simplified.

DESCRIPTION OF SYMBOLS 1 Magnet 10 Magnetic material block 11 1st surface 12 2nd surface 13 3rd surface 14 4th surface 20 Magnetization apparatus 21 Magnetization yoke 21a 1st yoke 21b 2nd yoke 21c 3rd yoke 22a First Excitation Coil 22b Second Excitation Coil 22c Third Excitation Coil 25 Drive Circuit 30 Pickup Device 34 Suspension Device 40 Suspension Wire 40 Movable Part 41 Magnet 41a First Face 41b Second Face 41c Third Face 41d Fourth Surface 43 objective lens 51 first drive coil 52 second drive coil EA easy axis of magnetization Ia drive current I1, I2 drive current

Claims (7)

A magnetic body block having a first surface and a second surface facing each other in a first direction, and a third surface and a fourth surface facing each other in a second direction intersecting the first direction, In the magnet in which each surface is magnetized,
In the magnetic block, the magnetization easy axis is oriented in a first direction,
The first surface and the second surface are magnetized to the same polarity, and the third surface and the fourth surface are magnetized to the opposite polarity to the first surface and the second surface. Yes,
A magnet characterized in that the magnetic flux density at positions separated by the same distance from each of the third surface and the fourth surface is higher in the third surface than in the fourth surface . The magnet according to claim 1 , wherein the magnetic body block is a bond block in which a powdery magnetic body is fixed by a resin material. A movable part having a magnet according to claim 1 and an objective lens facing the recording medium, a support member for movably supporting the movable part, and a coil provided on the fixed side and facing the magnet And a pick-up device characterized by having. 4. The pickup device according to claim 3 , wherein a support location at which the support member supports the movable portion is displaced to the fourth surface side with respect to a center of gravity of the movable portion. A first drive coil for moving the movable portion in the optical axis direction of the objective lens faces at least one of the first to fourth surfaces, and intersects the first drive coil with the optical axis direction. Current in the direction of
A second drive coil for moving the movable portion in a direction intersecting the optical axis faces at least one corner of a plurality of corner portions where the faces of the magnet intersect, and the second drive coil 5. The pickup device according to claim 3 , wherein a current flows in the optical axis direction. A magnetization easy axis having a first surface and a second surface facing each other in a first direction, and a third surface and a fourth surface facing each other in a second direction intersecting the first direction; Using a magnetic block oriented in the first direction,
A first yoke faces the first surface, a second yoke faces the second surface, and the respective yokes face the first surface and the second surface in opposite directions. The first magnetic field and the second surface are magnetized with the same polarity, and the third surface and the fourth surface are divided into the first surface and the second surface. A method of manufacturing a magnet, comprising: magnetizing a magnetic pole different from the surface of the magnet. A third yoke is opposed to the third surface, and a magnetizing magnetic field that circulates between the first yoke and the third yoke, and between the second yoke and the third yoke Form a magnetizing magnetic field that
Claims a flux density at a position the same distance away from each of the third surface and the fourth surface, towards the third surface is magnetized so as to be higher than the fourth surface The manufacturing method of the magnet of 6 statement.

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