JP4726689B2 - Objective lens drive - Google Patents

Description

  The present invention relates to an objective lens driving device having a configuration in which a hollow drive coil body is mounted on a lens holder to which an objective lens is attached, and a counter yoke is disposed in the drive coil body.

  As is well known, in an objective lens driving device in an optical head that optically reads or writes signals on a signal recording medium such as a disc, the lens holder to which the objective lens is attached is displaced with respect to the actuator frame. By mounting the focus coil and tracking coil, or tilt coil as necessary on the lens holder, and arranging the effective area of these drive coils in a predetermined magnetic field formed by a magnetic circuit. The objective lens is driven according to a signal supplied to each drive coil.

  By the way, as an objective lens driving device, a pair of focus coils, or a focus coil and a tilt coil are wound around a hollow structure in a rectangular shape on both sides of the objective lens sandwiched in the tracking direction of a lens holder in which the objective lens is arranged in the center. A configuration is known in which a drive coil body to be mounted is mounted and a pair of magnets that form a magnetic circuit on both sides of the lens holder are opposed to each other in a direction orthogonal to the tracking direction (for example, Patent Documents) 1).

  In this case, the tracking coil is wound in a substantially rectangular shape so that the winding center axis is in a direction orthogonal to the tracking direction and the focus direction, and the magnetic pole surfaces of the magnets are mutually opposite at two opposite sides that are effective areas of the tracking coil. The reverse polarity is set, thereby increasing the effective area of the tracking coil and enhancing the drive sensitivity in the tracking direction.

  The objective lens driving apparatus having such a configuration can perform focus driving using the driving force generated by the driving coil body on each side, and drive coils on each side of the lens holder against the magnetic field generated by the magnetic circuit. Considering the magnitude and direction of the drive signal flowing through the body, the radial tilt drive can be performed by making the drive force generated by the drive coil body on each side different according to the tilt in the radial direction of the disk.

In recent optical pickups corresponding to higher recording signal density, an objective lens with a high aperture ratio is used as the density increases, but if an objective lens with a high aperture ratio is used, the disc The coma aberration is significantly deteriorated with respect to the inclination in the radial direction. For this reason, an optical pickup objective lens drive device using a high aperture ratio objective lens requires radial tilt control. As described above, tilting is performed by the driving force generated in the drive coil body on each side of the lens holder. In many cases, an objective lens driving device configured to perform control is used.
JP 2001-118269 A

By the way, in the objective lens driving device configured to perform tilt control by the driving force generated in the driving coil body on each side of the lens holder described above, each driving coil body is generally configured in a rectangular hollow structure, Opposite yokes are arranged on the inner side of the coil body so as to face each pair of magnets, the density of the effective magnetic flux acting on the effective area of each drive coil body is increased, and the drive sensitivity is increased.

  Moreover, since there is a demand for high sensitivity in the objective lens driving device, it is desired to increase the number of turns of the drive coil constituting the drive coil body to achieve high sensitivity.

  However, there is a problem that the phase characteristics of the actuator deteriorate due to the opposing yoke disposed inside the drive coil body.

  Since the coil inductance is affected by the volume of the magnetic body in the coil, the inductance of the drive coil constituting the drive coil body is affected by the opposing yoke arranged inside the driving coil body, and the volume of the opposing yoke is large. As a result, the phase delay of the actuator occurs. This phase lag of the actuator reduces the phase margin at the higher-order resonance frequency and becomes a factor that deteriorates the stability of the servo characteristics in driving the actuator.

  For this reason, when the phase margin is not sufficient, it is necessary to take measures by some method, and it is necessary to reduce the size of the opposing yoke or reduce the weight of the actuator movable portion to ensure the phase margin.

  However, reducing the size of the opposing yoke in a dark manner causes a reduction in sensitivity, and it is difficult to reduce the weight of the lens holder due to the rigidity in order to reduce the weight of the actuator moving part. If this happens, the sensitivity will decrease. Therefore, it has been difficult for the objective lens driving device to ensure a sufficient phase margin while meeting high sensitivity requirements.

In the present invention, the drive coil is wound around a hollow structure so that it is opposed to the tracking direction of the lens holder .
A pair of drive coil bodies mounted on both sides of the object lens and the same corresponding to each drive coil body on both sides of the lens holder together with the pair of drive coil bodies in the direction orthogonal to the tracking direction a pair of magnets pole face of is arranged to be opposed, the are respectively disposed in the respective drive coil body and a pair of opposed yokes portion opposite to each of the pair of magnets, the pair each A notch is provided in the central portion of the opposing yoke portion by a through hole . While thereby achieving a reduction in the volume of the opposing yoke portion, thereby suppressing the influence of the density reduction of the effective magnetic flux acting on the effective area of the respective drive coil body due to volume contraction of the opposing yoke portions.

In the objective lens driving device of the present invention, since the notch is provided by the through hole in the central portion where the magnetic flux density of the opposing yoke portion is lower than that of the other portion, while reducing the volume of the opposing yoke portion, The effect of the decrease in the density of the effective magnetic flux acting on the effective area of each drive coil body due to the volume reduction of the counter yoke is suppressed, which is advantageous in ensuring a sufficient phase margin while meeting high sensitivity requirements.

In the case of an objective lens drive device in which a pair of hollow drive coil bodies are mounted on the lens holder on both sides of the objective lens in the tracking direction, the opposing yoke portion is provided separately in each drive coil body. The volume of the opposing yoke portion in each drive coil body can be reduced, and the phase delay of the actuator can be reduced .

  In the objective lens driving device in which the cover of the metal steel plate having magnetism is covered on the upper surface, the auxiliary opposing yoke portion is included in the opposing yoke in each driving coil body by forming the auxiliary opposing yoke portion on the cover. The volume reduction of the opposing yoke portion can be easily achieved.

1 is a perspective view showing a completed state of an example of a state in which the cover of the objective lens driving device according to the present invention is removed, and FIG. 2 is an exploded perspective view showing a lens holder portion of the objective lens driving device of FIG.

  External yoke portions 2 and 3 are integrally formed on the actuator frame 1 by sheet metal processing of a soft iron metal plate, and a pair of magnets are provided on the external yoke portions 2 and 3 so as to face each other with the lens holder 4 interposed therebetween. 5 and 6 are attached respectively.

  The lens holder 4 is configured by combining an upper piece 7 and a lower piece 8. The upper piece 7 and the lower piece 8 are formed by molding with a synthetic resin material mainly composed of liquid crystal polymer or polyphenylene sulfide, and the lens holder 4 is bonded by combining them while reducing the weight by a frame-like form. By configuring, the rigidity of the lens holder 4 is improved.

  The upper piece 7 has a lens mounting portion 10 to which the objective lens 9 is mounted on the central upper surface, a first bobbin portion 7a (first facing the magnet 6) in the center of each side wall facing the magnets 5 and 6 parallel to the tracking direction. The bobbin portion 7a is integrally formed. On the other hand, the lower piece 8 is sandwiched so as to avoid the side wall where the first bobbin portion 7a of the upper piece 7 below the objective lens 9 is formed, and the two second bobbins having a rectangular shape so as to be aligned in the tracking direction. The portions 8a and 8b are provided by being connected on the lower surface by a connecting portion 8c in which an optical path hole 11 to the objective lens 9 is formed.

  The upper piece 7 is formed with side walls 7c and 7d on both sides in the tracking direction so as to cover both outer side surfaces of the two second bobbin portions 8a and 8b of the lower piece 8, respectively. In the tracking direction, three fixing portions 19 for fixing each support wire 18 serving as an elastic support member that elastically supports the lens holder 4 so as to be displaceable on the actuator frame 1 are arranged on the side walls 7c and 7d at substantially equal intervals. Are formed symmetrically with respect to a virtual plane on the optical axis of the objective lens 9 perpendicular to the objective lens 9.

  Before the upper piece 7 and the lower piece 8 are joined to form the lens holder 4, as shown in FIG. 2, each first bobbin portion 7a on each side wall parallel to the tracking direction of the upper piece 7 has a tracking coil. 12 are wound, and focus coils 13a and 13b and tilt coils 14a and 14b are coaxially wound around the two second bobbin portions 8a and 8b of the lower piece 8, respectively.

  The upper piece 7 and the lower piece 8 are meshed with the side walls of the upper piece 7 where the first bobbin portion 7a is formed in the tracking direction and the two second bobbin portions 8a and 8b of the lower piece 8. 3 to form a lens holder 4 as shown in FIG. 3, and in the state in which the lens holder 4 is formed by combining the pieces, the lens holder 4 includes a tracking coil 12, focus coils 13a and 13b, and a tilt coil. The drive coils 14a and 14b are mounted.

  By the way, on the side walls 7c and 7d perpendicular to the tracking direction of the upper piece 7, flange-shaped protrusions 15a and 15b that are integrally formed in the vicinity of a predetermined end at an intermediate height protrude in the tracking direction. The strands of the tracking coil 12 that are continuously wound around the first bobbin portions 7a are subjected to terminal processing by the protrusions 15a and 15b.

The tracking coil 12 wound around each first bobbin portion 7a has a copper wire with an insulating film on its surface, for example, an end (starting end) from which the film is peeled off by using an enameled wire as a bare wire, and protruding portions 15a and 15b. The wire is wound around one of the first bobbins 7a and the other end of the first bobbin portion 7a in a direction opposite to each other for a predetermined number of times, and then the end of the wire from which the film has been peeled off ( The end of the projections 15a and 15b is engaged with the other end of the projections 15a and 15b, and the other ends of the projections 15a and 15b are engaged.

  On the upper and lower frame portions of the second bobbin portions 8a and 8b of the lower piece 8, hook-shaped upper protrusions 16a and 16b and lower protrusions 17a, which are integrally formed from the vicinity of a predetermined corner, respectively. 17b protrudes in the tracking direction, and the strands of the focus coils 13a and 13b continuously wound around the second bobbin portions 8a and 8b by the upper protrusions 16a and 16b are subjected to terminal processing, and each lower protrusion The strands of the tilt coils 14a and 14b continuously wound around the second bobbin portions 8a and 8b are subjected to terminal processing by the portions 17a and 17b.

  The focus coils 13a and 13b wound around the second bobbin portions 8a and 8b are, like the tracking coil 12, a copper wire whose surface is coated with an insulating film, for example, an enameled wire made of a bare wire, and the film peeled off. (Starting end) is entangled with one of the upper protrusions 16a, 16b and locked, and the element wire is wound around one and the other of the second bobbin portions 8a, 8b in the opposite directions, respectively, for a predetermined number of times, Thereafter, the end (terminal) of the strand from which the film is peeled off is entangled with the other end of the upper protrusions 16a and 16b that are not locked, and locked.

  Further, the tilt coils 14a and 14b wound around the second bobbin portions 8a and 8b, respectively, are coated with a copper wire having an insulating film on the surface, for example, enameled wire, as with other drive coils. The peeled terminal (starting end) is entangled with one of the lower protrusions 17a and 17b and locked, and the strands of the terminal are connected to one and the other of the second bobbin portions 8a and 8b in the same direction, respectively. The ends (terminal ends) of the strands that have been wound the same number of times on the same axis and then peeled off are entangled with the other ends of the lower projections 17a and 17b that are not locked. Stopped.

  The lens holder 4 constituted by combining the upper piece 7 and the lower piece 8 has six ends each fixed to a fixed substrate 21 fixed together with the auxiliary member 20 to the cut-and-raised portion 1 a of the actuator frame 1. The support wires 18 are fixed to the fixing portions 19 of the side walls 7c and 7d of the upper piece 7, and are erected by six support wires 18 of three on each side.

  Thus, the lens holder 4 is elastically supported by the actuator frame 1 by the six support wires 18 so as to be displaceable in the focus direction, the tracking direction, and the radial tilt direction.

  The other end portions of the six support wires 18 that are not the end portions that are fixed to the fixed substrate 21 are arranged in contact with or close to the predetermined protrusions, and the drive coils are entangled with the predetermined protrusions. A predetermined support wire 18 and a predetermined drive coil are associated with each other and connected by soldering to the end of the element wire.

  Further, the six support wires 18 are respectively surrounded by a dumping agent filled in the auxiliary member 20 to suppress vibration.

  By the way, the magnetic circuit has the configuration shown in FIG. 4 and will be described with reference to FIG. 5 in which the magnetic poles of the magnetic circuit are shown in a plane. The magnets 5 and 6 are divided into the opposite magnetic poles in the center in the tracking direction. The same polarity is opposed between the magnets 5 and 6. In this case, the magnets 5 and 6 may be separated at boundaries where the magnetic poles are different from each other, or the integral magnets 5 and 6 may be divided into opposite magnetic poles at the center by magnetization.

Further, since each of the second bobbin portions 8a and 8b is formed in a rectangular parallelepiped shape and has a hollow structure, opposing yokes 22 and 23 are disposed in the hollow portions of the second bobbin portions 8a and 8b, respectively. Each of the opposing yokes 22 and 23 is formed integrally with the actuator frame 1 by sheet metal processing and planted as shown in the partial sectional view of the magnetic circuit (covered with the actuator cover 28) shown in FIG. In the drive coil body constituted by the focus coil 13a and the tilt coil 14a, and in the drive coil body constituted by the focus coil 13b and the tilt coil 14b, notches by circular through holes 29 are respectively located. Is formed.

  If the through holes 29 are not formed in the opposing yokes 22 and 23, the magnetic fluxes of the opposing yokes 22 and 23 are transmitted from the magnetic pole surfaces of the magnets 5 and 6 as shown in FIG. After going to the center of the left and right direction, head to divide up and down. Therefore, the magnetic flux density is lower than the other portions in the upper, lower, left and right central portions of the opposing yokes 22, 23, and the through holes 29 are formed in the portions where the magnetic flux density is small. Accordingly, it is possible to reduce the inductance of the magnetic circuit while suppressing the decrease in the effective magnetic flux amount due to the volume of the opposing yokes 22 and 23 being reduced by the through hole 29. Therefore, it is advantageous to ensure a sufficient phase margin while meeting high sensitivity requirements.

  With such a magnetic circuit, each tracking coil 12 facing the magnets 5 and 6 has a driving current flowing in each effective region in the magnetic field of the magnetic poles that are bisected from the magnets 5 and 6 in the left and right directions. When the tracking coil 12 is arranged so that the winding direction of each tracking coil 12 is the same as viewed from the opposing magnets 5 and 6 and a tracking error signal is supplied to the tracking coil 12, A driving force is generated in the same tracking direction. For this reason, the lens holder 4 is driven in the tracking direction by a displacement amount corresponding to the current amount of the tracking error signal in a direction corresponding to the polarity of the tracking error signal.

  The tracking error signal is supplied to each tracking coil 12 via the terminals of the tracking coils 12 entangled with the protrusions 15a and 15b by the left and right support wires 18 installed in the middle in the vertical direction.

  The focus coils 13a and 13b are wound a predetermined number of times in opposite directions, and the opposing magnetic poles of the magnets 5 and 6 sandwiched between the focus coils 13a and 13b are different from each other. , 13b, a driving force is generated in the same focus direction in each of the focus coils 13a, 13b. Therefore, the lens holder 4 is driven in the focus direction in a direction corresponding to the polarity of the focus error signal and with a displacement amount corresponding to the current amount of the focus error signal.

  The focus error signal is supplied to the focus coils 13a and 13b via the terminals of the focus coils 13a and 13b entangled with the protrusions 16a and 16b by the left and right support wires 18 installed on the top. Done.

  The tilt coils 14a and 14b are wound a predetermined number of times in the same rotational direction, and the opposing magnetic poles of the main magnets 5 and 6 sandwiched between the tilt coils 14a and 14b are different. , 14b is supplied with a tilt error signal, a driving force is generated in each of the tilt coils 14a, 14b in opposite focus directions. Therefore, the lens holder 4 is driven in the radial skew direction in the direction corresponding to the polarity of the tilt error signal and by the amount of displacement corresponding to the amount of current of the tilt error signal.

  The supply of the tilt error signal to each of the tilt coils 14a and 14b is via the terminals of the respective tilt coils 14a and 14b entangled with the protrusions 17a and 17b by the left and right support wires 18 installed at the bottom. Done.

  A lens holder 4 having the objective lens 9 mounted on a virtual plane including the optical axis of the objective lens 9 perpendicular to the tracking direction and on a virtual plane including the optical axis of the objective lens 9 parallel to the tracking direction; The actuator movable part consisting of each drive coil is substantially plane symmetric, and the magnetic circuit is also plane symmetric, which makes it difficult to generate torsional vibrations, which is advantageous for countermeasures against phase shifts in focus high-order resonance and tracking high-order resonance. It has a configuration.

  Next, another embodiment in which the configuration of the magnetic circuit is different from the above-described embodiment will be described.

  FIG. 8 is a perspective view of a completed state of another embodiment of the objective lens driving device according to the present invention, and FIG. 9 is a perspective view showing a magnetic circuit portion with the lens holder 4 of FIG. 8 removed. In addition, the same number is attached | subjected to the member same as the above-mentioned Example.

  A soft iron metal plate is integrally formed on the actuator frame 1 by sheet metal processing, and the opposing yokes 31a, 31b and 32a, 32b disposed between the pair of magnets 5, 6 and facing the magnets 5, 6 are in the vertical direction. It is planted separated by slits. The tips of the opposing yokes 31a, 31b and 32a, 32b are intermediate in the height direction of the drive coil body constituted by the focus coil 13a and the tilt coil 14a and the drive coil body constituted by the focus coil 13b and the tilt coil 14b. It becomes the position.

  The upper part of the magnetic circuit is covered with a cover 33 made of a metal steel plate having magnetism, for example, SPCC (cold rolled steel plate and steel strip). The cover 33 is open at the center so that the objective lens 9 is exposed, and is arranged to correspond to the opposing yokes 31a, 31b and 32a, 32b so as to be vertically connected to each other. , 34b and 35a, 35b are bent downward from the central portion and formed integrally. Therefore, the opposing yokes 31a, 31b and 32a, 32b and the auxiliary opposing yoke portions 34a, 34b and 35a, 35b correspond to each other as shown in FIG. 10 showing a cross section taken along the broken line A with the drive coil body of FIG. 9 omitted. The comrades to be arranged are arranged in a line.

  By the way, the auxiliary opposing yoke portions 34a, 34b and 35a, 35b are each formed with a notch 36 having an oblique cut shape at the tip, and a drive coil body whose tip is constituted by the focus coil 13a and the tilt coil 14a, and It arrange | positions in the corresponding drive coil body of the drive coil body comprised by the focus coil 13b and the tilt coil 14b. That is, in the drive coil body, the respective opposing yokes 31a, 31b and 32a, 32b and the auxiliary opposing yoke portions 34a, 34b and 35a, 35b are opposed to each other.

  Therefore, the opposing yokes 31a, 31b and 32a, 32b are separated, the auxiliary opposing yoke portions 34a, 34b and 35a, 35b are separated, and the auxiliary opposing yoke portions 34a, 34b and 35a, 35b are separated. Coupled with the formation of the notch 36 at the tip, the opposing yokes 31a, 31b and 32a, 32b in the internal space of each drive coil body are opposed to each other including the auxiliary opposing yoke portions 34a, 34b and 35a, 35b. The volume of the yoke portion can be reduced, whereby the inductance of the magnetic circuit corresponding to each drive coil body can be reduced, and the decrease in the density of the effective magnetic flux acting on the effective area of each drive coil body can be suppressed. Therefore, it is advantageous to ensure a sufficient phase margin while meeting high sensitivity requirements.

When the notch 36 is formed at the tip of each of the auxiliary opposing yoke portions 34a, 34b and 35a, 35b, and when the notch 36 is not formed, the thrust and inductance are measured when the notch 36 is not formed. Are 16.39 (mN) and 25.1 (μH), respectively, but when the notch 36 is formed, the thrust and inductance are 16.38 (mN) and 22.9 (μH), respectively, while suppressing a decrease in actuator sensitivity. This proves that the inductance of the magnetic circuit can be reduced.

  In the above description, the notch formed in the opposing yoke portion is cut at the tip of each of the embodiments in which the circular through holes 29 of the opposing yokes 22 and 23 are formed, and the auxiliary opposing yoke portions 34a and 34b and 35a and 35b. Although the example which formed the notch 36 was given, the notch formed in the opposing yoke part of the present invention is not limited to these examples, and various modes and changes are made without departing from the spirit of the present invention. Is possible. For example, it is preferable not only to form the notches 36 in the auxiliary opposing yoke portions 34a, 34b and 35a, 35b, but also to form notches at the upper ends of the opposing yokes 31a, 31b and 32a, 32b. Further, the shape of the notch is not limited to the circular through hole 29 or the oblique cut.

FIG. 1 is a perspective view showing an example of a completed state in which the cover of the objective lens driving device according to the present invention is removed. It is the disassembled perspective view which showed the lens holder part of the objective lens drive device of FIG. FIG. 4 is a perspective view showing a state in which a lens holder 4 is configured by combining an upper piece 7 and a lower piece 8. It is a perspective view explaining the structure of a magnetic circuit. It is a top view explaining the magnetic pole of a magnetic circuit. 3 is a partial cross-sectional view of a magnetic circuit in a state where an actuator cover is covered. FIG. It is explanatory drawing explaining the direction of the magnetic flux which generate | occur | produces in the opposing yoke in which the notch is not formed. It is a perspective view of the completion state which shows another Example of the objective lens drive device which concerns on this invention. It is the perspective view which removed the lens holder 4 of FIG. 8, and showed the magnetic circuit part. It is a perspective view which shows the cross section in the broken line which excluded the drive coil body of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Actuator frame 4 Lens holder 5,6 Magnet 7 Upper piece 7a 1st bobbin part 8 Lower piece 8a, 8b 2nd bobbin part 9 Objective lens 12 Tracking coil 13a, 13b Focus coil 14a, 14b Tilt coil 18 Support wire 22, 23, 31a, 31b, 32a, 32b Counter yoke 34a, 34b, 35a, 35b Auxiliary counter yoke portion 29 Through hole (notch)
36 Notch

Claims (3)

An objective lens driving device in which a lens holder to which an objective lens is attached is elastically supported so as to be displaceable on an actuator frame, and a driving coil is wound around a hollow structure to sandwich the objective lens in the tracking direction of the lens holder A pair of drive coil bodies mounted on both sides and the same magnetic pole surface face each other corresponding to each drive coil body on both sides of the lens holder together with the pair of drive coil bodies in a direction orthogonal to the tracking direction. a pair of magnets arranged to be, the are respectively disposed in the respective drive coil body and a pair of opposed yokes portion opposite to each of the pair of magnets, the pair of the center of each opposing yoke portions An objective lens driving device characterized in that a notch is provided in a portion by a through hole . An objective lens driving device in which an objective lens is arranged in the center of a lens holder and a pair of hollow drive coil bodies are mounted on the lens holder on both sides of the objective lens in the tracking direction, and is orthogonal to the tracking direction. A pair of magnets arranged so that the same magnetic pole faces are opposed to each other on both sides of the lens holder together with the pair of drive coil bodies in the direction, and the drive coil bodies And a pair of opposing yoke portions respectively opposed to the pair of magnets, wherein the pair of opposing yoke portions are separated from each other in the drive coil bodies so as to face each pair of magnets. An objective lens driving device characterized by being provided. An objective lens driving device in which a metal steel plate cover having magnetism is covered on an upper surface, and an auxiliary opposing yoke portion disposed in the driving coil body is integrally formed on the cover, and the inside of the driving coil body is formed. 請 in place and the auxiliary counter yoke portion and the opposing yoke portions by relatively each tip comrades, you and characterized by forming a notch at the tip of the upper and or the auxiliary counter yoke portion of said opposing yoke The objective lens driving device according to claim 2.

Images