JPS6310493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing external scattering of brake lubricant in a voice coil type electromagnetic drive system, and in particular, a round washer-shaped outer non-magnetic material is attached to the upper surface of a permanent magnet, and a round Attach the washer-shaped inner circumferential non-magnetic material to the top surface of the magnetic material.
When the voice coil is driven at high speed, the braking lubricating oil scattered from the permanent magnet hollow part is collected on both sides of the non-magnetic hollow part, and the permanent magnet hollow part is formed by its own weight. The present invention relates to a method for preventing external scattering of braking oil in a voice coil type electromagnetic drive system, characterized in that the braking oil is prevented from scattering to the outside by causing the braking oil to drop to the outside.

Conventionally, a so-called voice coil type electromagnetic drive system has been used as an electromagnetic drive system for optical pickup actuators, speakers, and other control equipment.

As an example, an actuator for an optical pickup will be explained based on FIG. A permanent magnet gap 3 is formed as a channel, and a circular voice coil 4 is arranged in the permanent magnet gap 3. The voice coil 4 is suspended and supported by a voice coil suspension disk 7 that protrudes from a lens barrel 6 on which an objective lens 5 is attached.
is supported by upper and lower parallel leaf springs 8 so as to be freely movable in the vertical direction. and,
Since the magnetic flux of the permanent magnet 1 and the current flowing through the voice coil 4 are perpendicular to each other, according to Fleming's left hand rule, the voice coil 4, which is a movable part, receives a force in the vertical direction, and the lens barrel 6 and the objective This is to move the lens 5 in the vertical direction. Here,
If lubricating oil is not put into this permanent magnet cavity 3, a characteristic with a large resonance peak (solid line) is obtained as shown in Figure 2, but in this case, the resonance frequency may shift slightly due to temperature changes, etc. In this case, the control system becomes unstable, so a characteristic (dotted line) with as small a resonance peak as possible is preferable. Therefore, as shown in Fig. 3, a magnetic fluid having the effect of improving magnetic efficiency is used as a braking oil 9 between the permanent magnet hollow part 3 and the voice coil 4, and its capillary phenomenon is utilized. It is inserted.

However, in this prior art, in the case of low-speed drive, the brake lubricant 9 does not scatter, but in the case of high-speed drive (large amplitude and high frequency), the brake lubricant 9 is placed outside, for example, by a permanent magnet 1. , scattering on the upper surface of the magnetic body 2. As a result, the braking oil 9
If there is a shortage, there is a problem that the resonance peak becomes large and the control system becomes unstable.

The present invention has been made by focusing on the problems of the prior art, and includes attaching a round washer-shaped outer non-magnetic material to the upper surface of the permanent magnet, and attaching a round-shaped washer-shaped inner non-magnetic material to the upper surface of the permanent magnet. A body is attached to the upper surface of the magnetic body to form a non-magnetic hollow part, and when the voice coil is driven at high speed, the braking oil that is scattered from the permanent magnet hollow part is absorbed by the non-magnetic hollow part. The object of the present invention is to solve the above-mentioned problems by collecting the magnets on both sides of the permanent magnet and letting them fall into the hollow part of the permanent magnet by its own weight.

The present invention will be explained below based on the drawings.

FIG. 4 is a sectional view showing an embodiment of the present invention.

10 is a non-magnetic material gap, and the outer peripheral side non-magnetic material 11
It is formed at an intermediate portion between the inner peripheral non-magnetic material 12 and the inner peripheral non-magnetic material 12 . The outer non-magnetic material 11 has a round washer shape and is attached to the upper surface of the permanent magnet 1. The inner non-magnetic body 12 has a round washer shape and is attached to the upper surface of the magnetic body 2. The height H of the outer non-magnetic material 11 and the inner non-magnetic material 12 is high enough to prevent the braking oil 9 from scattering to the outside even if it is scattered from the permanent magnet gap 3 when the voice coil is driven at high speed. It is determined that

When both sides of the non-magnetic material gap 10, that is, the inner peripheral surface of the outer peripheral non-magnetic material 11 and the outer peripheral surface of the inner peripheral-side non-magnetic material 12, are cut out in a semicircular shape as shown in FIG. Since the area for collecting the brake oil 9 becomes larger, it becomes easier to collect the brake oil 9.

Outer non-magnetic material 11 and inner non-magnetic material 12
The reason why is made of a non-magnetic material is to fill only the permanent magnet gap 3, which is a magnetic path, with the braking oil 9, which is a magnetic fluid. This is also to allow the collected braking oil 9 to fall into the permanent magnet cavity 3 due to its own weight.

With this configuration, even if the braking oil 9 filled in the permanent magnet cavity 3 is scattered when the voice coil 4 is driven at high speed, the scattered amount is absorbed by the non-magnetic material air. It is collected on both sides of the outer part 10 and falls into the permanent magnet empty part 3 due to its own weight. Therefore, the brake lubricant 9 does not scatter to the outside.

As explained above, this invention prevents the braking oil from scattering to the outside by forming a non-magnetic cavity above the permanent magnet cavity, thereby reducing the resonance peak and controlling the The effect is that the system can be stabilized.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the voice coil type electromagnetic drive system in an optical pickup, Fig. 2 is a diagram showing the relationship between frequency and gain, Fig. 3 is a diagram showing braking oil in the cavity, and Fig. 4 is a diagram showing the relationship between frequency and gain. The figure is a sectional view showing one embodiment of the invention, and FIG. 5 is a sectional view showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Permanent magnet, 2... Magnetic body, 3... Permanent magnet cavity, 4... Voice coil, 5... Objective lens, 6... Lens tube, 7... Voice coil hanging disk, 8... ... Parallel leaf spring, 9 ... Braking oil, 10
... Non-magnetic material gap, 11 ... Non-magnetic material on the outer peripheral side,
12... Inner peripheral non-magnetic material.

Claims (1)

[Claims] 1. A magnetic fluid is disposed between a permanent magnet cavity, which is a magnetic path formed by a permanent magnet and a magnetic body, and a voice coil disposed in the permanent magnet cavity. In a voice coil type electromagnetic drive system filled with lubricating oil for braking, a round washer-shaped outer non-magnetic body is attached to the top surface of the permanent magnet, and a round washer-shaped inner non-magnetic body is attached to the top of the magnetic body. It is attached to the top surface to form a non-magnetic hollow part, and when the voice coil is driven at high speed, the braking lubricant that is scattered from the permanent magnet hollow part is collected on both sides of the non-magnetic hollow part. A method for preventing external scattering of brake lubricant in a voice coil type electromagnetic drive system, characterized in that the brake lubricant is prevented from scattering to the outside by causing the brake lubricant to fall into the hollow part of the permanent magnet by its own weight. 2. A method for preventing external scattering of braking oil in a voice coil type electromagnetic drive system according to claim 1, wherein both side surfaces of the non-magnetic hollow portion are formed in a semicircular shape.