JPH0589496A - Lens actuator - Google Patents

Abstract

PURPOSE:To improve the slidability of a bearing by forming a shaft of a metal having no resin coating, forming the front surface as a specular surface and subjecting the inner and outer peripheries of a sleeve to an anodic oxide coating treatment. CONSTITUTION:One end of the shaft 2 is fixed perpendicularly to a base 1 and the sleeve 3 is freely turnably and slidably fitted onto the outer periphery of the shaft 2. The shaft 2 is made of a stainless steel without having a resin coating and is worked by polishing to <=0.3 micron surface roughness. An aluminum material is used for the sleeve 3 in order to reduce its weight. The bore of the sleeve is polished to <=1 micron roughness. The inner and outer peripheries thereof are subjected to the anodic oxide coating treatment contg. ethylenetetrafluororesin powder of <=1 micron grain size at 1 to 30% by weight to 3 to 10 micron thickness. The coefft. of friction between the shaft 2 and the sleeve 3 is lowered about half the coefft. of friction of the conventional actuators. In addition, both the shaft and the sleeve have proper hardness and obviate the biting of metallic projections into their surfaces. Good sliding is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens actuator used in an optical disk device and a magneto-optical disk device, and having a bearing having excellent sliding performance in the center.

[0002]

2. Description of the Related Art In recent years, optical and magneto-optical disk devices have been
As the recording density increases, the number of revolutions of the disc also becomes 2-3 times faster, and the lens actuator for the purpose of finely moving the lens in the tracking direction and the focusing direction while irradiating the disc with laser light is accompanied by high speed and high precision. It is necessary to use a lens actuator that can be moved slightly, that is, a bearing-supported lens actuator having a structure having a bearing in the center, which has good high-speed response, has been widely used.
As a method other than the bearing support type, there is a leaf spring support type (not shown), which has a natural frequency and thus is slightly inferior in high speed response.

An example of the conventional lens actuator described above will be described below with reference to the drawings. Figure 3
It is sectional drawing of the conventional lens actuator. In FIG. 3, 11 is a base, and the shaft 11 is fixed to the center by a method such as press fitting. Reference numeral 13 denotes a sleeve, which is rotatably and slidably positioned on the outer circumference of the shaft 12, and a bobbin 14 is adhesively fixed to the outer circumference of the sleeve 13. Magnets 15A and 15B are attached to the base 11, and a Z for moving a movable part including the bearing 13, the bobbin 14, and the lens 18 in the Z direction in FIG. 3 near the outer circumference of the bobbin 14.
The axis drive coil 16 and the R axis drive coil for rotating in the R direction are wound. Reference numerals 14A and 11A are light transmitting holes (not shown) for passing laser light therethrough. In FIG. 4, the shaft 12 has tetrafluoroethylene resin (hereinafter referred to as PTFE)
The lubricating coating 12A, which is composed of a resin-based adhesive with a volume ratio of about 50% and the rest being a thickness of about 10 micrometers (hereinafter abbreviated as micron), is coated.

The operation of the lens actuator constructed as above will be described below. First, a disc as a recording medium (not shown) starts to rotate, laser light (not shown) reflected from the disc passes through the lens 18, hits a light receiver (not shown), and an electric signal is output from the light receiver. At this time, when the Z-axis drive coil 16 is energized, a magnetic field is generated to generate the two magnets 15A and 15B.
The coil 16 sandwiched between the coils generates a force in the Z direction in the figure, and the lens 18 is displaced in the Z direction in the figure together with the sleeve 13 and the bobbin 14 while being guided by the shaft 12 and the sleeve 13. The lens 18 is focused, increasing the output of the receiver. When the R-axis drive coil 17 is energized, the two magnets 15A and 15A
The coil 17 scissored by B generates a force to rotate slightly in the R direction in the figure, and optimizes the position of the lens 18 to increase the output of the light receiver. By continuously optimizing the positions in both the Z-axis direction and the R-axis direction in this manner, the output of the light receiver can be maximized.

[0005]

However, the above-mentioned structure has the following problems. The coating layer 12A of the shaft 12 is a resin material, and its surface roughness is limited to 1 micron. Also, the sleeve 13 is made of a material such as aluminum for the sake of weight reduction and has an inner diameter as small as 1 to 1.5 mm. Therefore, the surface roughness of the inner diameter is limited to about 1 micron. Therefore, the friction coefficient between the shaft 12 sleeve 13 is 0.2 to 0.3.
Indicates a slightly larger value.

This is because the shaft and the sleeve have insufficient roughness, and a metal projection of, for example, 1 micron remaining on the inner circumference of the sleeve 13 bites into the surface resin layer of the shaft 12 to prevent sliding. It is believed that When the coefficient of friction is large as described above, when the lens actuator is used in a horizontal attitude, the lens cannot be aligned because the lens is not aligned and the output cannot be obtained from the light receiver (not shown). In addition, the performance was insufficient even when used with the axis vertical.

[0007]

In order to solve the above problems, the lens actuator of the present invention has an alumite treatment containing PTFE powder in a weight ratio of 1 to 30% on the entire circumference of an aluminum sleeve, and the shaft is resin-coated. The surface roughness is made to be 0.3 μm or less by using a metal that does not have the above-mentioned property, and sliding is improved.

[0008]

According to the present invention, since the friction coefficient between the shaft and the sleeve can be reduced to about 0.1, which is half of the conventional value, the present invention can be used even when the shaft is horizontal and is used when the shaft is vertical. Time performance is also improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A lens actuator according to an embodiment of the present invention will be described below with reference to FIGS.

An example of the above-mentioned conventional lens actuator will be described below with reference to the drawings. Figure 1
It is sectional drawing of the lens actuator of the Example of this invention. In FIG. 1, reference numeral 1 is a base, and a shaft 2 is fixed to the center by a method such as press fitting. Reference numeral 3 denotes a sleeve, which is rotatably and slidably positioned on the outer circumference of the shaft 2. A bobbin 4 is adhesively fixed to the outer circumference of the sleeve 3. Magnet 5 on the base 1
A and 5B are attached, and a movable portion including a bearing 3, a bobbin 4, and a lens 8 is provided near the outer periphery of the bobbin 4 as shown in FIG.
Axis drive coil 6 for sliding in the Z direction at
The R-axis drive coil 7 for rotating in the R direction is wound. Reference numerals 1A and 4A are light transmitting holes (not shown) for passing a laser beam. In FIG. 2, the shaft 2 is made of stainless steel and has a surface roughness of 0.3 μm or less by polishing. Aluminum material is used for the sleeve 3 to reduce the weight, but the inner diameter is processed to a roughness of 1 micron or less,
The inner and outer circumferences of the sleeve 3 are alumite-treated to contain PTFE powder having a particle diameter of about 1 micron in a weight ratio of 1 to 30% to a thickness of 3 to 10 micron.

The operation of an example of the lens actuator constructed as described above will be described below. First, when the Z-axis drive coil 6 is energized, the two magnets 5
Generates a coil magnetic field sandwiched between A and 5B, and Z in the figure
The lens 8 is guided by the shaft 2 and the sleeve 3 and is slightly displaced in the Z direction in the figure together with the sleeve 3 and the bobbin 4 by generating a force in the direction, whereby the lens 8 is focused and the output of the light receiver is output. Increase. Further, when the R-axis drive coil 7 is energized, the coil 7 pinched by the two magnets 5A and 5B will generate a force to rotate slightly in the R direction in the figure in the future to optimize the position of the lens 8. By doing so, the output of the light receiver is increased. In this way, by continuing to optimize the positions in both the Z-axis direction and the R-axis direction, the output of the photodetector can be maximized.

In FIG. 2, since the surface of the shaft 2 is not coated with lubrication, it is possible to finish the mirror surface with a surface roughness of 0.3 micron or less without catching and with good slidability, and to make the sleeve 3 entirely. A lubrication coating is applied to the circumference, but since it is a coating by alumite treatment instead of the conventional resin coating method by spraying or brushing, it can be coated to a uniform thickness and its roughness can be less than 1 micron. As a result, the coefficient of friction between the shaft 2 and the sleeve 3 can be maintained at about 0.1 or less, which is about half the conventional value. In this way, the coefficient of friction can be reduced by the PTF coated on the sleeve.
E has slidability, the surface of the shaft is smooth, and the shaft and the sleeve also have appropriate hardness, and good sliding can be obtained without the metal projections biting into the surface. Conceivable.

The sleeve 3 is adhesively fixed to the bobbin 4. However, since the surface coating of the sleeve 3 contains PTFE, it may be difficult to obtain adhesive strength.
By making the surface roughness of the outer circumference of the core 3 or more rough, sufficient adhesive strength between the sleeve 3 and the bobbin 4 can be obtained.

As described above, according to this embodiment, the performance can be obtained even when the lens actuator is axially horizontal, and even when the lens actuator is used vertically, a light output (not shown) can be larger than the conventional output. In addition, since the shaft is not coated with resin, the roundness and cylindricity of the shaft can be processed well. Therefore, the clearance between the shaft and the sleeve can be reduced to 5 to 8 μm to prevent backlash. Shorten,
The entire lens actuator can be made thin.

[0015]

As described above, according to the present invention, the outer circumference of the shaft is made of steel material having a roughness of 0.3 micron or less, and the inner circumference of the aluminum alloy sleeve is 1 micron or less, and PTFE is used.
By subjecting the powder to the alumite treatment having a weight ratio of 1 to 30%, it is possible to obtain a lens actuator in which the bearing slides well and the performance is excellent.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a lens actuator of the present invention.

FIG. 2 is a block diagram of the main part of the same.

FIG. 3 is a sectional view of a conventional lens actuator.

FIG. 4 is a block diagram of the main part of the same.

[Explanation of symbols]

 1 Base 2 Axis 3 Sleeve 4 Bobbin 5A, 5B Magnet 6 Z Axis Drive Coil 7 R Axis Drive Coil 8 Lens 1A, 4A Transparent Hole

Claims (2)

[Claims] 1. A shaft has one end fixed substantially at a right angle, a sleeve is rotatably and slidably inserted into the outer periphery of the shaft, and a bobbin and a Z-axis drive coil are coaxially provided on the outer periphery of the sleeve. Is attached, an R-axis drive coil is attached in the vicinity of the Z-axis drive coil, and a magnet fixed to the base is located in the vicinity of the two coils.
A lens is fixed to the bobbin, the shaft is made of steel, the surface roughness is 0.3 μm or less, the material of the sleeve is aluminum alloy, and the inner circumference is made of tetrafluoroethylene powder in a weight ratio. A lens actuator containing 1-30% of alumite and having a surface roughness of 1 micrometer or less. 2. The lens according to claim 1, wherein the outer circumference of the sleeve is treated with alumite containing 1 to 30% by weight of tetrafluoroethylene powder, the surface roughness of which is 3 μm or more, and which is adhesively fixed to the bobbin. Actuator.