JPS6310330A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To improve the characteristic of an actuator and to miniaturize it and to reduce the number of processes by providing an objective lens holding cylinder with a magnetic body piece and providing a lateral pressure means using the magnetic force due to interaction between this magnetic body piece and a magnetic circuit. CONSTITUTION:An objective lens 2, a focusing coil 3, and a tracking coil 4 are attached to an objective lens holding cylinder 1, and a round bar-shaped magnetic body piece 8 is fitted and adhered to the attaching hole 1-b of the objective lens holding cylinder 1 so that its axial line B is orthogonal to a supporting shaft 5 and the center line of the objective lens 2. The supporting shaft 5 and a magnet 6 are attached to a yoke 7, and the magnetic circuit is formed with the magnet 6 and the yoke 7. They are so arranged that the axial line B of the magnetic body piece 8 is orthogonal to the magnetic pole surface of the magnet 6 and the magnetic body piece 8 is in the center of the magnet 6 when the objective lens holding cylinder 1 is in a neutral position in focusing and tracking directions. Thus, the lateral pressure means is obtained simultaneously with a tracking-direction neutral position holding means to reduce the number of constituting parts and processes.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an actuator for an optical pickup. More specifically, the present invention relates to a side pressure means for suppressing rattling due to the clearance between a bearing hole and a support shaft in a shaft sliding/shaft rotation type actuator.

(Summary of the Invention) In a shaft-sliding/shaft-rotating actuator for an optical pickup, a magnetic piece is provided in the objective lens holding cylinder, and the interaction between the magnetic piece and the magnetic circuit causes the shaft to move relative to the objective lens holding cylinder. By generating a magnetic force in the direction perpendicular to the axis of the object lens and preventing rattling within the clearance between the bearing hole of the objective lens holding tube and the spindle, the actuator's characteristics can be improved, made smaller, lowered in cost, reduced in process, and warmer. This has been improved.

(Prior Art) Conventionally, a rubber spring has generally been used as a track neutral holding and side pressure means in a shaft-sliding/shaft-rotating actuator. In FIG. 2, the bearing hole 1-a of the objective lens holding cylinder 1 and the support shaft 5 are fitted with a certain clearance. Further, one end of the rubber spring 20 is fixed to a pin 21 set up on a fixed part such as a yoke, and the other end is fixed to the objective lens holding cylinder 1, which is a movable part, via a pin 1-b. With this structure, the objective lens holding tube 1 is held at a neutral position in the track direction, and the objective lens holding tube 1 is pulled in the A direction by the rubber spring 20, thereby suppressing rattling in the clearance during focusing and tracking operations. The characteristics are being improved.

In addition, as shown in Fig. 3, there is a shaft sliding type without side pressure means.
In a shaft rotation type actuator, a rubber spring 30 is attached to the tip of the support shaft 5, and the rubber spring 30 is further attached to the support shaft 5.
A cap 31 is removed to prevent it from coming off. The holes at both ends of the rubber spring 30 are formed integrally with the objective lens holding cylinder 1 or can be removed from the objective lens holding cylinder 1.
-b, forming spring means. In this type of shaft-sliding/shaft-rotating actuator that does not have a lateral pressure means, the bearing hole 1-a and the support shaft 5 have a clearance, so that the posture of the objective lens holding cylinder 1 due to wobbling within the clearance is reduced. It is desirable to have a lateral pressure means because it cannot suppress fluctuations, tends to generate a rigid body resonance mode, and tilts the optical axis. Further, the direction of the lateral pressure is preferably a direction connecting the support axis and the center of the objective lens, taking into consideration the symmetry of the tracking direction.

(Problem to be solved by the invention) However, the conventional method using rubber springs requires extra parts and space for installing the rubber springs, which is very disadvantageous in reducing the cost and size of the pickup. It is a structure.

Furthermore, since the neutral position in the track direction is determined using a rubber spring, there is a drawback that adjustment work is required during assembly.

Furthermore, due to the material properties of rubber, there are drawbacks regarding IT characteristics and drawbacks in environmental resistance and durability.

Therefore, in order to solve these conventional drawbacks, the present invention has the following features:
The object of the present invention is to obtain an actuator that has a structure that does not require any parts or space for forming a rubber spring, can be easily manufactured by kneading, and has excellent temperature characteristics.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a magnetic piece in the objective lens holding tube and utilizes the magnetic force generated by the interaction between the magnetic piece and the magnetic circuit. By providing a lateral pressure means, it is possible to improve the characteristics of actuators, reduce their size, reduce costs,
The aim is to reduce process steps and improve temperature characteristics.

(Operation) It is based on the principle that when a magnetic material is placed in a magnetic field where the magnetic field distribution is not uniform, the magnetic material receives a force in a direction that reduces its potential energy. The idea is to use this force as a lateral pressure means.

Specifically, magnetic pieces are attached to the objective lens holding cylinder, and these magnetic pieces are placed inside the magnetic circuit. A magnetic circuit has a magnetic field distribution determined by its shape, and forms a non-uniform magnetic field.

In a non-uniform magnetic field, the magnetic piece generates a force in the tracking direction, that is, a force that attempts to return the objective lens holding tube to the neutral position when it rotates around the spindle, and at the same time connects the spindle and the center of the objective lens. Generates a directional force. The bearing hole of the objective lens holding cylinder is pressed against the support shaft by the force in the direction connecting the support shaft and the center of the objective lens, and a lateral pressure effect is obtained.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the objective lens holding tube 1 includes an objective lens 2,
A focus coil 3 and a track coil 4 are attached, and a round bar-shaped magnetic piece 8 is attached to the attachment hole 1-b of the objective lens holding cylinder 1, and its axis -〇-B is attached to the support shaft 5 and the objective lens 2. are fitted and bonded perpendicularly to the center line of the The yoke 7 has a spindle 5 and a magnet 6.
is attached, and the magnet 6 and yoke 7 form a magnetic circuit. When the objective lens holding cylinder 1 is at the neutral position in the focusing and tracking directions, the axis B of the magnetic piece 8 is perpendicular to the magnetic pole face of the magnet 6, and the magnetic piece 8 is arranged so as to be in the center of the magnet 6. ing.

FIG. 4 shows the magnetic field distribution of this magnetic circuit viewed from the side. The arrow lines represent lines of magnetic force, and the intensity of the lines of magnetic force is the magnetic field strength. The magnetic field distribution is shown by connecting points with equal magnetic field strength at large stocks. It can be seen from this distribution that the magnetic field strength decreases as the distance from the magnet 6 increases. Therefore, a force is generated in the magnetic piece 8 placed opposite the magnet 6 in the direction of the larger magnetic field strength, that is, in the direction of the magnet 6.
This force becomes lateral pressure. FIG. 5 shows h applied to the magnetic piece 8 when the objective lens holding cylinder 1 moves in the focusing direction while maintaining the neutral position in the tracking direction. There is a nearly flat force region centered around the neutral position, and fluctuations in side pressure are sufficiently suppressed within the range of movement necessary for focusing operation.

FIG. 6 shows the magnetic field distribution seen from the top. When the objective lens holding tube 1 rotates in the tracking direction,
The magnetic piece 8 moves on the orbit A. At this time, the magnetic piece 8 is
The force is applied in the direction where the magnetic field strength gradient at that position is maximum, and the force consists of a tangential component to the trajectory, a normal component to the trajectory,
That is, it is divided into tracking direction neutral holding force and side pressure. Figure 7 shows objective lens held! It shows the relationship between the tracking direction neutral holding force and the rotation angle of i11. As will be seen, the magnetic force exerted on the magnetic piece 8 is maximum at the end of the magnet, and at its peak darkness, the magnetic force is approximately linear. Further, the relationship between the rotation angle of the objective lens holding cylinder 1 and the side pressure is similar to the relationship between the focusing direction and the side pressure shown in FIG. 5, and a substantially constant side pressure is obtained within the movable range in the tracking direction.

By combining the magnetic piece 8 and the magnetic circuit in this manner, it is possible to apply a substantially constant side pressure to the objective lens holding cylinder 1 within the movable range of tracking and focusing.

Further, even in an actuator having a magnetic circuit having a configuration different from this example, it is possible to obtain a lateral pressure means using a magnetic piece. An example is shown in FIG. In FIG. 8, a magnetic circuit consisting of a magnet 6, an outer yoke 7-a1, and an inner yoke 7-b is arranged in a direction perpendicular to a direction A connecting the center of the support shaft 5 and the objective lens 2. The round rod-shaped magnetic piece 8 is attached to the objective lens holding cylinder 1 so as to be disposed near the end of the magnet in the magnetic circuit and symmetrically with respect to the forward direction. A force is generated in each of the left and right magnetic pieces 8 to draw them into the magnetic circuit, thereby maintaining neutrality in the track direction. In addition, all the resultant forces generated on the magnetic piece 8 become a force in the direction toward the objective lens holding cylinder 1 as side pressure.
It acts on

(Effects of the Invention) As described above, according to the present invention, the side pressure means can be obtained at the same time as the tracking direction neutral holding means by a simple method of adding a magnetic piece to the objective lens holding cylinder. Therefore, the number of component parts and culms can be reduced compared to conventional rubber spring means, and an inexpensive actuator can be realized.

Also, unlike rubber spring means, it does not require extra space,
This is very advantageous in reducing the size of the actuator.

Furthermore, since it uses magnetic force, it also has excellent temperature characteristics compared to rubber springs.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of an actuator according to the present invention. FIG. 2 is an exploded perspective view of an actuator using a conventional rubber spring and having lateral pressure means. FIG. 3 is an exploded perspective view of an actuator that uses a conventional rubber spring and has no lateral pressure means. FIG. 4 is a side sectional view showing the magnetic field distribution of the magnetic circuit according to the present invention. Figure 5 is for explaining the side pressure applied to the present invention-1
− This is a graph of FIG. 6 is a top view showing the magnetic field distribution of the magnetic circuit according to the present invention. FIG. 7 is a graph for explaining the tracking direction holding force according to the present invention. FIG. 8 is a top view of another embodiment of the invention. 8... Magnetic piece 1... Objective lens holding cylinder 2... Objective lens 5... Support shaft 6... Magnet 7... Yoke Applicant Seiko Electronics Co., Ltd. Foi Shin 7° direction Displacement amount and (fl, 7i sword's seki f thread Fig. 5, magnetic field 1!17 and net top view Fig. 6) On the other hand, 100 rotation angle and neutral guard's sekihe Fig. 7 This invention ( (Top view of 3X different embodiments Fig. 8)

Claims (3)

[Claims] (1) An objective lens holding tube configured to be rotatable around a support shaft and slidable in the axial direction of the support shaft, and an objective lens provided in the objective lens holding tube at a distance from the support shaft. and a coil means for focus adjustment and a coil means for track adjustment provided in the objective lens holding tube, and a magnet or a yoke and a magnet provided inside or outside the objective lens holding tube, or inside and outside the objective lens holding tube. In an objective lens drive device having a magnetic circuit, one or more magnetic pieces are provided in a portion of the peripheral portion of the objective lens holding cylinder that exists inside the magnetic circuit, so that the supporting shaft and the support shaft are connected to the objective lens holding cylinder. An objective lens driving device characterized in that a magnetic force is generated in a direction connecting the centers of the objective lenses. (2) A patent claim characterized in that the magnetic circuit is composed only of magnets and is arranged in a direction connecting the support shaft and the center of the objective lens, and the magnetic piece is provided at a position facing the magnet. The objective lens driving device according to item 1. (3) The objective lens driving device according to claim 1 or 2, wherein the magnetic piece is rod-shaped, and its longitudinal direction is arranged perpendicular to the axial direction of the support shaft.