JP3328059B2 - Optical head drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head driving device for moving an optical head so as to face a predetermined position on an information recording medium such as an optical disk and a magneto-optical disk.

[0002]

2. Description of the Related Art An objective lens actuator is movably supported in a radial direction of an information recording medium in order to follow an information track formed on the information recording medium. The mechanism for supporting this optical head is simple, compact, and compact.
The combination of a shaft and a plain bearing is adopted because it is lightweight and inexpensive.

[0003] Such a supporting mechanism is disclosed in Japanese Patent Application Laid-Open No. 62-129.
No. 978, JP-A-63-184967 and the like.

FIG. 7 is a schematic sectional view of the support mechanism described in Japanese Patent Application Laid-Open No. 63-184967 as viewed from the direction in which the shaft extends. The movement direction of the carriage 6 on which various optical elements (not shown) are mounted is regulated by the main shaft 1 and the driven shaft 2 having a perfect cross section.

The carriage 6 is formed with a main bearing 61 and a driven bearing 62 through which the main shaft 1 and the driven shaft 2 are inserted. The main bearing 61 is a perfect circle bearing whose cross section is slightly larger in diameter than the main shaft 6. The driven bearing 62 has a cross section formed as a long hole having a linear portion in the Y direction, and a short axis of the long hole,
Both major shafts are larger than two driven shaft diameters. Driven bearing
The shape on the 62 side is a long hole having a linear portion in the Y-axis direction in order to cope with the deviation of the axial spacing and parallelism between the main shaft 1 and the driven shaft 2.

Further, since the bearing is an oil-impregnated bearing, good sliding properties can be obtained even with a metal shaft, and the speed at which the shaft and the bearing are worn can be reduced. FIG.
FIG. 1 is a perspective view of a support mechanism described in JP-A-1229978. The shaft supporting the carriage 6 is formed of ceramic. Unlike a metal shaft, the shaft is made of ceramic, so it has excellent slidability and abrasion resistance, prolongs the life of the head part, and it is hard to deform and lightweight, enabling stable head sliding .

[0007]

However, the above-mentioned various prior arts have the following disadvantages. First, JP 63
In the technology described in JP-A-184967, since the cross-sectional shapes of the main bearing 61 and the driven bearing 62 are different, the state of contact with the main shaft 1 and the driven shaft 2 is also different. The contact state between the main shaft 1 and the main bearing 61 is surface contact, and the driven shaft 2 and the driven bearing 6
The contact state with 2 is line contact.

Line contact has a smaller contact area than surface contact,
The load per unit area applied to the shaft and bearing on the driven shaft side increases. For this reason, the driven shaft 2 and the driven bearing 62 are more likely to be worn than the main shaft 1 and the main bearing 61, and the sliding characteristics of the shaft and the bearing are deteriorated after long-term use. Further, since an oil-impregnated bearing is used, oil may be scattered around and the oil may adhere to optical components.

In the case where the surfaces of the main shaft 1 and the driven shaft 2 are coated with a solid lubricant without using an oil-impregnated bearing, the wear on the driven shaft side is larger than the wear on the main shaft side as described above. As shown in (1), only a part of the contact portion of the driven shaft is worn and becomes flat.

[0010] For this reason, the contact portion between the shaft and the bearing, that is, the sliding portion is different from the initial one, and the sliding characteristics are far apart from the initial state. In addition, when the coated portion is worn, a gap is generated between the shaft and the bearing, which causes deterioration of the resonance characteristics of the carriage 6. Furthermore, the remarkable deterioration of the sliding characteristics makes the carriage immovable and completely unusable.

Further, in the technique described in Japanese Patent Application Laid-Open No. 62-129978, ceramic is used as the material of the shaft. However, ceramic has a drawback that it is expensive, and accordingly, the apparatus becomes expensive. Since reliability and low cost are listed as selling points in the optical head driving device, it is very problematic that reliability is lowered and manufacturing / assembly costs are increased due to such deterioration of sliding characteristics.

An object of the present invention is to solve the above-mentioned problems and to provide an inexpensive optical head driving device which maintains stable sliding characteristics for a long period of time by a support mechanism using a shaft and a slide bearing.

[0013]

According to the present invention, there is provided an optical head driving apparatus comprising: a main shaft; a driven shaft disposed in parallel with the main shaft;
A carriage provided with a main bearing through which the main shaft is inserted and movably supporting the carriage in the direction in which the main shaft extends, and a driven bearing which abuts the driven shaft and movably supports the carriage; and In an optical head drive device equipped with an objective lens actuator, the contact area between the driven shaft and the driven bearing is smaller than the contact area between the main shaft and the main bearing, and the main bearing and the driven bearing Are made of the same synthetic resin, and the surface hardness of the driven shaft is larger than the surface hardness of the main shaft.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 4 show a first embodiment of the present invention. FIG. 1 is an overall perspective view of an optical head driving device, FIG. 2 is an exploded perspective view thereof, and FIG. FIG. 4 is a perspective view of the objective lens actuator.

In FIG. 1, FIG. 2, and FIG. 3, the optical head driving device mainly includes a movable pickup A and an access magnetic circuit.
It consists of B and support shaft C (spindle 1 and driven shaft 2). A main shaft 1, a driven shaft 2, and two access magnetic circuits B, B are fixed to a deck base (not shown).
The surface of the spindle 1 is coated with a solid lubricant having excellent slidability. The driven shaft 2 is made of stainless steel.

The access magnetic circuits B, B include an access coil 7, 7 described later, an inner yoke 3, 3 penetrating the access coil 7, 7, an access magnet 4, 4 opposed thereto, and an access coil magnet 4, , 4 are mounted on the outer yokes 5, 5. The movable pickup is a carriage 6,
It comprises a reflecting mirror 8, a position sensor 9, and an objective lens actuator 10, and has the above-described access coils 7, 7
Is fixed.

The carriage 6 is made of a synthetic resin containing carbon fiber having good slidability, for example, polyphenylene sulfide containing 30% of carbon fiber. Carriage 6
Since it contains this carbon fiber, it has conductivity and does not carry static electricity. This carriage 6 has a spindle 1
Bearing 61 through which the shaft is inserted and driven shaft 2 through which the driven shaft 2 is inserted
A carriage 62 is formed, and the carriage 6 is movable in the axial extending direction via the main bearing 61 and the driven bearing 62. The main bearing 61 has a perfect circular circular cross section, and the diameter of this circle is slightly larger than the diameter of the main shaft 1, for example, the main shaft.
If 1 is a shaft having a fitting tolerance h6, the main bearing 61 is a bearing having a fitting tolerance G6. The driven bearing 62 is a long hole having a plane portion parallel to the recording medium surface, that is, a long hole having a plane parallel to the XY plane. The distance between these two planes is slightly larger than the diameter of the driven shaft 2, for example, if the driven shaft 2 is an axis having a fitting tolerance h6, the fitting tolerance G6
The distance is equivalent to that of the bearing. Since the driven bearing 62 comes into contact with the driven shaft 2 on its plane, the main bearing 1
In addition, the displacement of the shaft spacing and the parallelism of the driven shaft 2 in the XY plane can be absorbed, thereby preventing the sliding characteristics from being degraded due to these factors.

The carriage 6 has an access coil 7,
A reflection mirror 8 and a position sensor 9 are mounted, and an objective lens actuator 10 is mounted. The objective lens actuator 10 will be described with reference to FIG. A magnetic circuit 102 for the objective lens actuator is bonded and fixed to the base 101 of the objective lens actuator 10. The magnetic circuit 102 for the objective lens actuator includes a yoke 105 and a permanent magnet 106 bonded thereto so as to sandwich one side of the two tracking coils 103 and 103 and the focus coil 104.
It is composed of In order for the objective lens 107 to drive the objective lens 107 correctly, it is necessary to prevent resonance within the control frequency band. Here, the movable portion of the objective lens actuator 10, that is, the objective lens 107, the objective lens holder 108 for holding the objective lens 107, the two tracking coils 103, 103, and the focus coil 104, the center of gravity position in the Y direction is two tracking positions. It is the center of the coils 103,103. As a result, the drive point applied to the movable part during tracking driving coincides with the center of gravity of the movable part, so that unnecessary resonance does not occur.

Considering the focus driving, however, the position of one side 104a of the focus coil 104 and the two tracking coils 103, 103 sandwiched by the magnetic circuit 102 for the objective lens actuator are different from each other. Resonance occurs because the center of gravity of the movable part does not match. To prevent this, one side 104a of the focus coil 104
A leakage magnetic flux of the objective lens actuator magnetic circuit 102 is applied to the side 104b opposite to the above, so that the focus driving point is shifted to the position of the two tracking coils 103 in the movable portion. Magnetic circuit for objective lens actuator 102
The direction of the magnetic flux from the side in the Y direction is the same on the sides 104a and 104b of the focus coil 104. However, since the direction of the flowing current is opposite, a force opposite to the side 104a receiving the driving force in the main focus direction acts on the side 104b. These two sides
The resultant force of the forces acting on 104a and 104b is a position opposite to the side 104b on which the opposite force acts from the side 104a receiving the main driving force in the Y direction,
That is, it works on the two tracking coils 103 and 103 side.

Here, two sides 104 of the focus coil 104
a, 104b only, but actually focus coil 1
In consideration of all four sides of 04, the magnetic circuit 102 for the objective lens actuator, and the magnetic flux B of the access magnetic circuit B and B, the tracking coil 10 having two focus driving points is used.
3,103 side so as to coincide with the center of gravity of the movable part. At this time, two side yokes 105a and 105b are provided on the yoke 105 of the magnetic circuit 102 for the objective lens actuator so as to cover both ends of the permanent magnet 106 in the X direction in order to adjust the leakage magnetic flux reaching the focus coil 104. I have. The two side yokes 105a and 105b can effectively adjust the amount of leakage magnetic flux by optimizing the length in the Y direction, and the focus driving point and the tracking driving point and the center of gravity of the movable portion can be adjusted. Can be matched. As a method of adjusting the amount of leakage magnetic flux, it is conceivable to enlarge the yoke itself in the X direction. However, by providing a side yoke, the leakage magnetic flux is optimized with a smaller yoke.

Since the access coil 7, the reflection mirror 8, and the position sensor 9 are already known, detailed description thereof will be omitted. The contact between the main shaft 1 and the main bearing 61 is a surface contact as described above. Therefore, since only a part of the main shaft 1 does not wear, it is better to make the main shaft 1 from the viewpoint of improving the sliding characteristics of the shaft rather than improving the wear resistance of the shaft. On the other hand, since the driven shaft 2 is in linear contact with the driven bearing 62, a load is applied to only a part of the shaft and a problem occurs in that the shaft is worn only there. In general, solid lubricants applied to shafts have poor abrasion resistance.
It is better to make the shaft for the purpose of improving the wear resistance of the shaft rather than the sliding characteristics of the shaft.

In the present embodiment, in consideration of the above, stainless steel is used as the material of the driven shaft 2 so that the surface hardness of the driven shaft 2 is higher than the surface hardness of the main shaft 1. Therefore, the wear resistance is improved, and the movable pickup can be driven stably for a long time. In addition, since stainless steel is inexpensive, there is an effect that the optical head driving device can be manufactured at low cost.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the present embodiment, the same shaft as that of the first embodiment is used for the main shaft 1, and a ceramic shaft is used for the driven shaft 2. According to this embodiment, since the ceramic having extremely high hardness is used only for the driven shaft, the movable pickup can be driven stably for a long time with excellent wear resistance. Further, although ceramic is expensive, since it is used only for a driven shaft requiring hardness, the manufacturing cost of the optical head driving device can be minimized.

(Third Embodiment) Next, a third embodiment of the present invention will be described. In this embodiment, the same shaft as that of the first embodiment is used for the main shaft 1, and the surface of the driven shaft is coated with a high-hardness poly (4-fluoroethylene) resin so as to be higher than the surface hardness of the main shaft 1. . Poly 4 applied to the surface of this driven shaft
The ethylene fluoride resin has higher hardness than the solid lubricant applied to the main shaft 1 and has excellent wear resistance. For example, the poly4fluoroethylene resin coated on the main shaft has a hardness equivalent to pencil hardness of 2H, and the poly4fluoroethylene resin coated on the driven shaft has a pencil hardness of 3H.
Considerable hardness.

In this embodiment, the driven shaft is superior in slidability as compared with the case where the shaft surface is the shaft material itself as in the driven shaft 2 described in the first embodiment. Further, in this embodiment, since there is no problem if the surface of the driven shaft is coated with polytetrafluoroethylene resin having a surface hardness higher than that of the main shaft, the material of the driven shaft has some rigidity even if it is inexpensive. If it is enough, it can be applied.

Therefore, according to the structure of this embodiment, the optical head driving device can be manufactured at low cost while improving the sliding characteristics while ensuring the wear resistance of the driven shaft. The same effect can be obtained by applying not only polytetrafluoroethylene resin but also, for example, molybdenum disulfide or graphite to the driven shaft as the solid lubricant applied to the driven shaft. The first to third
Although the embodiment has been described, the present invention is not limited to these. For example, even if the shape of the driven bearing of the carriage is not a hole but a notch as shown in FIG. As shown in FIG. 6, the effect of each of the above-described embodiments can of course be achieved even if the shape is such that it simply contacts the driven shaft, and the access magnetic circuit is provided only on one side, for example, only on the main bearing side. It is the same even if it is.

Further, if the driven shaft is made of a material having magnetism, the movable pickup is attracted by the leakage magnetic flux of the actuator magnetic circuit of the objective lens actuator, so that the driven bearing and the driven shaft are always in contact with each other, and the movable pickup is loose. It does not stick and stable driving becomes possible.

[0028]

According to the present invention, it is possible to provide an inexpensive optical head driving device in which the abrasion of the driven shaft is suppressed, and as a result, stable sliding characteristics are maintained over a long period of time.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of an optical head driving device according to the present invention.

FIG. 2 is an exploded perspective view of the optical head driving device of the present invention.

FIG. 3 is a cross-sectional view of the optical head driving device according to the present invention as viewed from an axial extension direction.

FIG. 4 is a perspective view of an objective lens actuator of the optical head driving device according to the present invention.

FIG. 5 is a cross-sectional view showing an example of a bearing shape of the optical head driving device of the present invention, as viewed from an axial extending direction.

FIG. 6 is a cross-sectional view showing an example of a bearing shape of the optical head driving device of the present invention, as viewed from an axial extending direction.

FIG. 7 is a cross-sectional view of a carriage viewed from an axial extension direction of a conventional optical head driving device.

FIG. 8 is an overall perspective view of a conventional optical head driving device.

FIG. 9 is a diagram showing a problem of a conventional optical head driving device.

[Explanation of symbols]

 Reference Signs List A movable pickup B access magnetic circuit C support shaft 1 main shaft 2 driven shaft 3 inner yoke 4 permanent magnet 5 outer yoke 6 carriage 61 main bearing 62 driven bearing 7 access coil 8 reflection mirror 9 position sensor 10 objective lens actuator

Claims (1)

(57) [Claims] A main shaft, a driven shaft disposed in parallel with the main shaft, a main bearing through which the main shaft is inserted and which supports the carriage so as to be movable in a direction in which the main shaft extends, and a driven shaft which is in contact with the main shaft. A carriage including a driven bearing that movably supports the carriage, and an optical head driving device including an objective lens actuator mounted on the carriage, wherein a contact area between the driven shaft and the driven bearing is equal to the main shaft, the main bearing, The main bearing and the driven bearing are both made of the same synthetic resin, and the surface hardness of the driven shaft is larger than the surface hardness of the main shaft. An optical head driving device characterized by the above-mentioned.