JPH0766638B2 - Information recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to head movement control in an information recording / reproducing apparatus, and more particularly to a method for preventing head runaway when control is inappropriate.

[Conventional technology]

In an information recording / reproducing apparatus such as an optical disk, a laser beam is used to narrow a laser beam to about 1 μm by an objective lens, and information is recorded or reproduced by this minute spot as one information memory.

Conventionally, a method of moving an optical head by a voice coil type linear motor or the like has been generally used in order to increase the information retrieval speed. In this type of device, at the time of information retrieval, the current head position is known from the address information of the optical disk, the distance to the target information track is calculated, and the linear motor is controlled so as to move the distance at high speed. In order to position the optical head at high speed and precision, the speed or position of the linear motor is controlled by using an external linear encoder or the reflected diffracted light when the light beam crosses the track as the position information of the linear motor. The method is taken. At this time, if the signal of the linear encoder becomes unsuitable for some reason, or if the focus of the light spot deviates from the disk surface and the position information of the linear motor cannot be obtained, the linear motor becomes uncontrollable and runs out of control. To do. In this case, since the linear motor has a working distance of a finite length, the linear motor normally collides with a mechanical stopper and stops. Since the optical head is composed of precision parts, excessive vibration and shock will cause performance deterioration, and in severe cases it will be broken and the function as a device will be lost.
It's a problem. Further, also during information recording / reproduction, the linear motor is driven so that the light spot is along the information track, and the linear motor is driven by the tracking error signal or the position information of the tracking actuator. Also in this case, if the normal control state is deviated due to an unexpected disturbance or the like, the linear motor will run out of control, and the same problem as described above will occur.

[Object of the Invention]

The present invention has been made in view of the problems of the above-described conventional example, and an object thereof is to prevent the head from colliding with a stopper by detecting the runaway of the linear motor and stopping the linear motor.

[Summary of Invention]

The purpose described above is to record and / or record information on an information recording medium.
Alternatively, a head for reproducing information recorded on the medium, moving means for moving the head relative to the medium, and speed detecting means for detecting a moving speed of the head,
An information recording / reproducing apparatus comprising stop means for applying a stop driving force to a head when the speed detected by the speed detecting means exceeds a limit value, and position detecting means for detecting the position of the head, and the limit value. And a memory means for storing a velocity curve set so that the absolute value monotonically increases from both end points of the operating range of the head, and the memory means is based on the position of the head detected by the position detecting means. The limit value at that position is further derived, the derived limit value is compared with the speed detected by the speed detecting means at that time, and when the detected speed exceeds the limit value, the stopping means is used. This is achieved by an information recording / reproducing apparatus characterized by applying a stop driving force according to the moving direction of the head.

Further, as one embodiment of the present invention, if the head moving means uses an electromagnetic action by a fixed magnetic field and a current flowing in a linear motor coil as in a linear motor as means for detecting the speed of the head, There is a method of detecting the speed by the counter electromotive voltage generated in the linear motor coil.

[Action]

According to the information recording / reproducing apparatus as described above, various internal causes,
It is possible to detect the runaway of the head due to an external cause and stop it immediately.

〔Example〕

Hereinafter, specific embodiments of the information recording / reproducing apparatus of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view of a mechanical portion of an embodiment according to the present invention.

In FIG. 1, reference numeral 1 denotes an optical disc which is an information carrier, and the optical disc 1 is provided with a recording medium layer for recording information, a guide groove for guiding a light spot, and address information indicating a position on the disc. ing. The address information is provided over the range of the shaded portion 1a. The optical disc 1 is rotated by a spindle motor 2, and information is recorded or reproduced by a laser beam from the optical head 3. The optical head 3 is provided with a focus servo mechanism for positioning the focal position of the laser spot on the information recording surface of the optical disc 1 and a tracking servo mechanism for controlling the irradiation position of the laser spot on the guide groove. Note that 3a schematically represents the laser light from the optical head 3.

Reference numeral 4 denotes a coil of the linear motor, which works to move the optical head 3 in the radial direction (indicated by an arrow in the figure) of the optical disk 1 by the electromagnetic action of the magnetic flux between the magnet 5 and the yoke 6 and the current flowing through the linear motor coil 4. There is.

At the time of information retrieval, the address of the track to which the light spot is currently radiated is reproduced, the distance to the target track is calculated by a microcomputer (not shown), and control is performed according to the characteristics of the linear motor, for example, as shown in FIG. A curve is created and the current flowing through the linear motor coil 4 is controlled so as to follow the control curve. At this time, the detector for detecting the position of the linear motor, that is, the position of the optical head 3 is performed by counting the tracking error signal obtained when the light spot crosses the track.

Further, this detector detects the speed of the optical head 3 and outputs it as a speed signal. When detecting the speed of the head, for example, the speed signal can be obtained by differentiating the position information of the head obtained by counting the tracking error signal.

The linear motor is equipped with another speed detector in addition to the speed detector based on the counting of the tracking error signal. The speed detector can be obtained by detecting a counter electromotive voltage generated in the linear motor coil 4, for example.

FIG. 4 is a block diagram showing an example of such a detection circuit.

In the figure, 4 is a linear motor coil, which is equivalently expressed as an inductance L and an internal resistance r '. 7 is a voltage detector a for detecting the voltage across the linear motor coil 4,
Reference numeral 8 is a current detection resistor R connected in series with the linear motor coil, 9 is a voltage detector b for detecting the voltage across the current detection resistor 8, and 10 is an amplifier having a gain r '/ R times.

The output of the voltage detector b due to the amplifier 10 becomes a voltage drop in the linear motor coil due to the current flowing in the linear motor coil 4. By taking the difference between the voltage and the output of the voltage detector a, the counter electromotive voltage of the linear motor coil 4 can be obtained. The back electromotive force is a signal proportional to the linear motor speed.

In the detection circuit of FIG. 4, accurate speed detection can be performed only when the current flowing through the linear motor coil 4 is direct current. However, in order to detect a more accurate speed, the characteristics of the amplifier 10 should be set to the inductance of the linear motor coil 4. Including up to minutes It should have a gain of.

Further, in this embodiment, the output of the speed detector is integrated to obtain a position signal of the linear motor.

In the following description, in order to avoid confusion, the detection speed and the detection position by the tracking error signal are the first speed signal and the first position signal, respectively, and the detection speed and the detection position by the back electromotive voltage of the linear motor coil are respectively set. Are the second velocity signal and the second position signal.

As described above, the linear motor control for information retrieval is performed by the first speed signal or the first position signal.

A linear motor that can stop at the end point of the operating range of the linear motor when the maximum driving force is applied in the stop direction, taking into consideration the acceleration characteristics of the linear motor, the acceleration resistance of the optical head, and the operating range of the linear motor. The maximum moving speed of is calculated at each point of the position of the linear motor, and a speed curve is created.

This is a velocity curve in which the absolute value monotonically increases from both end points of the operating range of the head, as indicated by a and b in FIG. 3, and is tabulated in ROM as described later.

In FIG. 3, the horizontal axis represents the linear motor position and the vertical axis represents the speed.

This curve represents the limit speed at which the moving linear motor can be stopped without colliding with the stopper at the end point. For example, in a linear motor that generates maximum α acceleration, the curve is v: speed, s: distance Becomes

Therefore, the limit speed at each position of the linear motor becomes a curve such as a or b in FIG. 3 depending on the direction of the speed. If the speed is in the area between these two curves, collision with the stopper is avoided. it can.

When it is judged that the limit curve is exceeded, the maximum driving force in the deceleration direction is applied to the linear motor, and the application of the driving force is stopped when the speed of the linear motor becomes zero. This operation will be described with reference to FIGS. 3 and 5.

FIG. 5 is a block diagram showing an example of a circuit for controlling the above operation. In the figure, 13 is a ROM table, 14 is an A / D converter for converting a linear motor position into a digital signal, and 15 is a linear. Addition points for monitoring the absolute position and speed of the motor, 16 and 21 are ROM tables, 17 and 22 are D / A converters, 18 and 23 are switches, and 19 and 24 are comparators.

At the time of access, the address at the start of access is read, the distance to the target track is calculated, and a target speed curve corresponding to the distance is created. This corresponds to FIGS. 3C-3C.

Also, the start address is input to the ROM table 13 and converted into the absolute position of the linear motor. This corresponds to the access start position in FIG. Also, the integrator 12 in FIG. 5 is reset.

When the linear motor starts to move, the first speed and position signals drive the linear motor along the target speed curves C to C '. On the other hand, the second speed and position signals are calculated as the access start position in FIG. 5 to obtain the absolute position of the linear motor. That is, the output of the addition point 15 that monitors the absolute position and speed of the linear motor becomes the absolute position of the linear motor. The absolute position, that is, the linear motor position corresponding to the horizontal axis in FIG. 3 is input to the ROM table 16 and converted into a limit speed, and a limit speed curve a in FIG. 3 is obtained by D / A conversion. Similarly, the ROM table 21 and the D / A conversion 22 are used to obtain b in FIG.

That is, the ROM tables 16 and 21 store speed curves such as a and b in FIG. 3, and the position signal of the linear motor is input to this to read the limit speed corresponding to the position.

At this point, if the focus servo is disengaged at point d and the tracking error signal, that is, the first speed and position signal becomes unsuitable, the linear motor runs out of control and follows the curve of C ″. This state is the second speed signal. Detected immediately,
Compared with the output of the D / A converters 17 and 22 described above, if the speed of the linear motor exceeds the limit speed curve, the comparator 19 or
The access control of a linear motor (not shown) is turned off by 24, and the maximum driving force in the reverse direction corresponding to the moving direction is applied to the linear motor to stop the linear motor.

When the limit speed is detected by switching the input switches of the comparators 19 and 24, the speed of the linear motor is compared with the ground level, that is, zero speed, so stop driving force is applied until the speed of the linear motor becomes zero. It

Next, the operation at the time of recording or reproducing information will be described. The linear motor slowly moves along the track helix during recording or playback. For this reason, the limit speed curve shown in FIG. 6 is used to compare the limit speed with the speed of the linear motor and stop the linear motor as in the above-described access operation. At this time, as the address corresponding to the start address in FIG. 5, the address read at the time of recording or reproducing information is input each time, and the integrator is reset.

When the linear motor is driven by the eccentric frequency component of the disk, that is, when the track follows the track in synchronization with the rotation, the output of the second speed detector is passed through the band limiting filter as shown in FIG. Rotation frequency ω
_It suffices to suppress _n .

The present invention is not limited to the above embodiment, but various modifications can be made.

For example, the end points of the limit speed curve may be set at a certain distance from the stopper of the linear motor with some allowance.

Further, the ROM table and the like in FIG. 5 can be operated by a computer.

Further, in FIG. 3, when the limit speed is set by the acceleration characteristics of the linear motor, not only the mechanical conditions such as the weight and friction of the linear motor are included, but also the respective cases of various runaway modes of the linear motor are considered. It is necessary to set it. Although there is a simple method of setting in consideration of the worst case of the runaway mode, the limit speed may be changed and set in each case. For example, there is a case where the limit speed is changed between information retrieval and information recording / reproduction.

Further, as described above, the limit speed is determined by the acceleration resistance characteristic of the head (when the structural strength of the head cannot withstand the impact generated by the linear motor driving force or another stopping means such as a mechanical brake). It is also possible to set.

Further, in the above embodiment, the case where the speed of the head is detected by the second moving speed signal through the moving means of the head has been described.
A means for directly detecting the moving speed of the head itself may be used. However, in this case, it is necessary to provide the speed detecting means independently as compared with the above embodiment.

Further, in the embodiment shown in FIG. 1, the case where the recording medium is disk-shaped has been shown, but the information recording of the present invention is also applicable to an apparatus for processing information on a recording medium having another shape such as a card through a head. It is obvious that a reproducing device can be applied.

Further, it is apparent that the information recording / reproducing apparatus of the present invention can be applied not only to the optical means but also to the information recording medium by the magnetic, electric or chemical means.

〔The invention's effect〕

As described above, according to the information recording / reproducing apparatus of the present invention, damage to the head and the linear motor is prevented and the reliability of the apparatus is improved by controlling the runaway of the linear motor so as to stop it immediately. be able to. In addition, since the limit value for judging runaway is set as a speed curve that monotonically increases from the end point of the operating range of the linear motor, runaway due to exceeding the limit value immediately after starting movement from the other end point False positives can also be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a mechanical portion of an information recording / reproducing apparatus according to the present invention, FIG. 2 is a diagram showing a speed curve of a linear motor at the time of information retrieval, FIG. 3 is a diagram showing a limit speed curve, and the like. FIG. 5 is a block diagram of the speed detector, and FIG. 5 is a block diagram of a circuit for detecting and controlling the runaway of the linear motor. FIG. 6 is a diagram showing a limit velocity curve at the time of recording / reproducing information,
The figure is a frequency characteristic diagram. 1 ... Optical disc, 2 ... Motor, 3 ... Optical head, 4
...... Linear motor coil, 5 …… Magnet, 6 …… Yoke,
12 …… Integrator, 13,16,21 …… ROM table, 14 …… A / D converter, 15 …… Addition point, 17,22 …… D / A converter, 19,24 ……
Comparator, 18, 23 ... Switch.

Claims (1)

[Claims] 1. A head for recording information on an information recording medium and / or reproducing information recorded on the medium, moving means for moving the head relative to the medium, and moving speed of the head. In the information recording / reproducing apparatus, the position of the head is detected in the information recording / reproducing apparatus, which comprises a speed detecting means for detecting and a stop means for applying a stop driving force to the head when the speed detected by the speed detecting means exceeds a limit value. The head detected by the position detecting means includes a position detecting means and a memory means that stores a speed curve set so that the absolute value monotonically increases from both end points of the operating range of the head as the limit value. Based on the position, the limit value at that position is derived from the memory means, and the derived limit value is compared with the speed detected by the speed detecting means at that time to detect the limit value. An information recording / reproducing apparatus, wherein when the speed exceeds a limit value, a stop driving force is applied by the stopping means according to the moving direction of the head.