JPS63119075A - Optical head feeder - Google Patents

Abstract

PURPOSE:To reduce the accelerating/decelerating time in positioning an optical head by using a R-Fe-B magnet for a linear motor being a drive actuator of the optical head. CONSTITUTION:The R-Fe-B magnet is adopted for the linear motor of the drive actuator. That is, the optical head 1 is arranged in opposition to a disk 8 and the optical head is driven by the linear motor 2. In this case, the velocity of the optical head is detected by a position detector 3 in the linear motor and a position speed detection circuit 4 and inputted to a linear motor control circuit 5. A track error signal from a servo signal detection circuit 6 is inputted to the linear motor control circuit via a low pass filter 7 to apply the control of the linear motor at the recording and reproduction. Thus, the miniaturization, high speed and low cost are attained for the feeder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Public Expenses for Industrial Use] The present invention relates to an optical head feeding device for an optical memory device.

[Summary of the invention]

The present invention provides an optical head feeding device for an optical memory device in which the basic composition is R.
A linear motor using a permanent magnet consisting of -F e -B is used, a double-sided reflector is fixed to a moving coil that moves within the gap of the magnetic circuit of the linear motor, and two reflectors fixed to the yoke of the magnetic circuit are used. A photoelectric interrupt sensor enables detection of the position of the optical head, and a differential circuit obtains a speed signal to provide a speed feedback loop, making it possible to create a small, lightweight, and low-cost optical head feeder with excellent control characteristics. It is something to do.

[Conventional technology]

Conventionally, a rotary DC motor or a step motor has been used in an optical head feeding device for an optical memory, but a linear motor may be used for the purpose of shortening access time, and some embodiments have been proposed.

Typical permanent magnets for linear motors include alnico magnets, ferrite magnets, and rare earth cobalt magnets. ◇Permanent magnets for motors have a residual magnetic flux density of 1 Br,
It is desirable that both coercive forces Ha be large. Since alnico magnets have a small Ha value and ferrite magnets have a small Br value, rare earth cobalt magnets have been developed and are used as permanent magnets with excellent magnetic properties.

Further, as a means for detecting the speed of the optical head, a means using an N linear tachometer has been considered.

[Problem that the invention seeks to solve]

However, in the conventional technology, the above-mentioned rare earth cobalt magnets are expensive compared to alnico magnets and 7-layer light magnets.
This is due to the use of samarium (i9m) as a rare earth element and the use of extremely expensive cobal (Co), which results in high performance but extremely expensive products when used for linear motors. turn into. Further, the method of using a linear tachometer to detect the speed of the optical head has problems with the device size, leakage magnetic flux, etc., and in particular, restrictions are placed on component arrangement in order to avoid the adverse effects of leakage magnetic flux from the linear motor.

Therefore, the present invention is intended to solve these problems, and its purpose is to develop a rare earth permanent magnet (with a basic composition of R-IF e -B) that can obtain excellent magnetic properties at a low cost. A small, lightweight linear motor with excellent thrust characteristics is realized using R-'W e-B magnets. A position detector is added using the space of the magnetic circuit, and a speed signal is detected by a differential circuit. By doing so, it is possible to construct an optical head feeding device that does not require a new speed detector in the movable part.

[Means for solving problems]

The optical head feeding device of the present invention is an optical head feeding device for an optical memory device in which information is recorded and reproduced by an optical head using a disk. A linear motor using permanent magnets is used, a moving coil arranged in the gap of the magnetic circuit of the linear motor is fixed to the optical head, a double-sided reflector fixed to the moving coil, and a yoke of the linear motor are fixed to the optical head. A position signal of the optical head is detected by two fixed reflective photoelectric type interrupt sensors, and a speed signal of the optical head is detected from the position signal by a differential circuit to drive the linear motor during recording and reproduction. [Operation] According to the above configuration of the present invention, the linear motor, which is the drive actuator of the optical head, is provided with an R-type motor having excellent magnetic properties.
By using the -IF e -B magnet, the acceleration/deceleration time when positioning the optical head is shortened, and the position of the optical head can be detected by a position detector installed in the linear motor during recording and reproduction, and a differential circuit is used. Since a speed signal is obtained and a speed feedback loop is provided, it is possible to move the optical head with small size, low cost, and excellent stability. Figure 1 is a block diagram of the optical head feeding device of the present invention.
An optical head 1 is arranged facing the disk 8. The optical head is driven by a linear motor 2. At this time, a position detector 3 in the linear motor and a position speed detection circuit 4
The speed of the optical head is detected and inputted to the 1-line monitor control circuit 5. A track error signal from the servo signal detection circuit 6 is inputted to the linear motor control circuit via the low buzz coil motor 7, and the linear motor is controlled during recording and reproduction.

FIG. 2 is a perspective view of the main mechanism, in which an e-coil 201 is fixed to the optical spatula 1. The optical head is supported by two shafts 101, 102. A double-sided reflector 301 is fixed to the movable coil, and two interrupt sensors 3021305 (see FIG. 3) are placed on both sides of the double-sided reflector.

Figure 3 is a side view of the linear motor, with magnets 202 and 203
is fixed to the back yoke 206 and the magnet 204.
205 is fixed to the back yoke 207, and is coupled by side yokes 208 and 209 to form a magnetic circuit. The movable coil 201 is integrated with a double-sided reflector 301 and placed within the magnetic circuit gap. @Interrupt sensors 302 and 303 are placed on both sides of the double-sided reflector to detect the position of the optical head. Figure 4 shows a linear motor. Plan view of (back yoke 206,
4 of the moving coil (with magnets 202 and 203 removed).
Two of the sides that are on the magnets 204 and 205 generate thrust by the interaction of the magnetic field and current. R-? Used in linear motors? Compared to conventional rare earth cobalt magnets, s-B magnets have a larger maximum energy product B Hmaz, so higher performance and smaller linear motors can be realized, and the magnet cost is lower, so costs can be reduced. Furthermore, since the R-IF e -B magnet has excellent mechanical strength, handling during assembly becomes easier.

Next, we will explain how to detect the position of the optical head.
Figure 5 is an interrupt sensor layout diagram, in which the interrupt sensor 3 is moved because the double-sided reflector moves with the optical head.
02. Gap a1 between 303 and double-sided reflector. a2 changes. At this time, ((11+(12) remains constant.

Figure 6 is a position speed detection circuit diagram, and the interrupt sensor is L.
It consists of an ED and a phototransistor, and the phototransistor output of two interrupt sensors is connected to an operational amplifier 6.
After obtaining the position signal by differential amplification with 01, operational amplifier 609
The velocity signal is obtained using a differentiator. The operational amplifier 602 compares the reference voltage generated by the Zener diode 605 with the output addition signal C of the phototransistor, and drives the LEDs (two) to keep the amount of light from the LEDs constant.

The inverter 604S605 is for detecting the movable limit, and is provided on each side of the double-sided reflector as shown in Fig. 8 (α).
By providing non-reflective portions 607 and 608 as shown in (c), it becomes possible to detect the movable limit of the optical head.

Figure 7 is a differential output characteristic diagram, and the advantages of differential detection are:
For example, even if the output characteristics of A and B change as shown by the dashed-dotted line due to a temperature change or the like, the differential output V hardly changes and remains at 1. In addition, if the light intensity of the LED does not change, the output sum signal C of A and E is kept constant, so it is possible to drive the LID in feedback by comparing it with the reference voltage using an operational amplifier. With this configuration, the position (movable IJ) and speed of the optical head can be detected using a double-sided reflector and two reflective photoelectric interrupt sensors, and speed feedback control of the air motor is possible when the optical head is being fed. In addition, due to the driving method that keeps the light intensity of the LED constant, it is possible to suppress changes in output characteristics due to deterioration of the LID, which is a problem with interrupt sensors, and excellent long-term stable operation can be expected. ] As described above, according to the present invention, the linear motor of the drive actuator of the optical head feeding device is equipped with an R-XF e.
-By using the B magnet, the feeding device can be made smaller, faster, and lower in cost. Furthermore, the optical head position detector can be assembled into a linear motor, and the speed of the optical head can be detected by a differential circuit. As a result, speed feedback control of the linear motor can be realized and optical head feed control during recording and playback can be stabilized. Further, the speed detection characteristics are not affected by leakage magnetic flux of the linear motor. Note that if the optical head position is detected differentially as shown in the embodiment, the detection characteristics will be affected by temperature changes, etc., and the interrupt sensor's III! Since it is possible to configure the LID drive circuit so as to keep the light amount of the iD constant, there is an advantage that the characteristics of the detection system are less likely to change due to deterioration of the I and ID. Furthermore, since the detection of the movable IJ of the optical head is realized by an extremely simple process of providing a non-reflective part at the end of the double-sided reflector, it is necessary to separately provide a detector to prevent collisions when moving the optical head. Since there are no holes, the device can be made smaller and lower in cost.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the optical head feeding device of the present invention. Fig. 2 is a perspective view of the main mechanism of the optical head feeding device of the present invention. Fig. 3 is a side view of the near motor. Fig. 4 is a plan view of the linear motor. Figure 5 is an interrupt sensor layout diagram. Figure 6 is a position/velocity detection circuit diagram. Figure 7 is a differential output characteristic diagram. σ Head No. 1 Figure 2Q2~λ...Dotaite 20G, ■7...Ba °γ7-7-7mg, 2D
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Claims (1)

[Claims] Using a disk-shaped optical recording medium (hereinafter referred to as a disk),
In an optical head feeding device for an optical memory device in which information is recorded and reproduced by an optical head, as a drive actuator for the optical head, a linear magnet using a permanent magnet having a basic composition of R-Fe-B is used as a drive actuator for the optical head. A motor is used, a movable coil arranged in the gap of the magnetic circuit of the linear motor is fixed to the optical head, a double-sided reflector is fixed to the movable coil, and two reflective photoelectrons are fixed to the yoke of the linear motor. A position signal of the optical head is detected by a type interrupt sensor, a speed signal of the optical head is detected from the position signal by a differential circuit, and the linear motor is controlled by a servo loop having speed feedback during recording and reproduction. An optical head feeding device characterized by: