JPH03241502A - Magnetic head rotation control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic head rotation control device for applying a magnetic field to an optical disk device using a recordable optical disk such as a magneto-optical disk.

Prior Art Conventionally, this type of optical disk device was disclosed in Japanese Patent Application Laid-open No. 63-2.
There is one shown in Japanese Patent No. 66602.

FIG. 9 shows the principle of this method, in which an external magnetic field is applied to a recordable optical disk (magneto-optical disk) 1 by a magnetic head 2, and an optical pickup 3 (objective lens 4 and actuator 5) is picked up from the opposite side. (representative) irradiates with laser light. The coercive force of the portion heated by this laser beam irradiation decreases, and the magnetization 6 is reversed in the direction of the external magnetic field from the magnetic head 2. Depending on the direction of this magnetization 6, “
1” or “OI+” information is recorded. Here,
The magnetic head 2 includes a magnet 8 that is rotatable around a rotating shaft 7 parallel to the disk surface (extending in the front and back directions of the paper), and is provided surrounding the magnet 8 to selectively drive the magnet 8 to rotate. It consists of a coil 9 that provides a driving force to That is, recording/erasing is performed by rotating the magnet 8 and switching the magnetic pole relative to the disk surface between the S pole and the N pole.

Furthermore, magnetic field sensors 10a and 10b using, for example, Hall elements are provided around the magnet 8, and the position of the magnet 8 is detected by detecting the magnetic field strength.

Problems to be Solved by the Invention During recording and erasing, it is desired to apply a desired magnetic pole to the optical disc 1, so the position (state) of the magnet 8 is set to Oo and 18.
0', and the magnet 8 may be rotated 180' between the two. On the other hand, during playback, the N pole or S pole is connected to the optical disc 1.
When a magnetic field is applied by the poles, the state is the same as that during recording or erasing, so the reliability of recorded data deteriorates, causing problems such as errors in reproduced signals. Therefore, during reproduction, it is necessary to hold the optical disc 1 in a state in which no magnetic poles are opposed to it (the position of the magnet 8 is 9°). However, in the case of the conventional method shown in FIG. 9, it is not possible to hold the magnet 8 in a state where no magnetic field is applied to the surface of the optical disk (the position of the magnet 8 is 90 degrees).

Also, according to the same publication, when rotating 180 degrees between the recording and erasing positions, the servo loop is entered after 90'' to perform position control, but the control gain is set high. Therefore, it cannot be said that efficient rotation control is being performed.

Means for Solving the Problems The invention according to claim 1 includes: a magnet that faces the surface of a recording type optical disk and is rotatable about a rotation axis that is parallel to the disk surface;
In a magnetic head rotation control device for applying a magnetic field, which includes a coil that is disposed surrounding the magnet and rotates the magnet in a specific direction depending on the direction of energization, a plurality of magnetic field sensors are provided around the magnet. and calculating means for calculating the zero-crossing point of any one of the addition signal, subtraction signal, or calculation signal of the addition signal and the subtraction signal of the magnetic field strength detection signals from these magnetic field sensors, It is arranged to detect that the magnet has reached an intermediate point between the starting position and the target rotational position.

In addition, in the invention according to claim 2, a time measuring means is provided for measuring the time required for the magnet to reach the intermediate point from the starting starting position, and a current is applied to rotate the magnet in a desired direction from the starting starting position. A current is applied to the coil to gradually accelerate the rotation while starting the rotation, and when reaching an intermediate point is detected by the output of the magnetic field sensor, the polarity of the current to the coil is reversed to reduce the rotational speed of the magnet, and the time measuring means The current supply to the coil is stopped when a time equivalent to the required time measured by the above has passed since passing the halfway point.

Since the timing when the working magnet reaches the midpoint between the rotation start position and the desired rotational attainment position is detected, switching control from acceleration to deceleration can be performed accurately, and stop control can be performed at the desired rotational attainment position. can be done efficiently. In this case, by setting the desired rotational arrival position to the 90° position, it is possible to perform a good reproducing operation.

By the way, if switching control from acceleration to deceleration is performed based only on detecting the timing of reaching the intermediate point, the desired rotational position may not be reached at the end of rotation due to the influence of variations in the torque of the drive coil. This may place a burden on the hold servo control system. In this regard, according to the second aspect of the invention, the time required from the rotation start position to the intermediate point is measured, and the rotation of the magnet is stopped when a time equivalent to this required time has elapsed from the intermediate point. It is possible to reduce the influence of such variations and reduce the burden on the hold servo control system.

Embodiment An embodiment of the invention set forth in claim 1 will be described with reference to FIGS. 1 to 4. The basic configuration is similar to that shown in FIG. 9, and the same parts are indicated using the same reference numerals. This embodiment is characterized by a rotation control system for the magnet 8. In FIG. 1, the position of the magnet 8 is detected by two magnetic sensors 10a,
This is done using a lob. Here, these magnetic field sensors 10a and 10b are provided at positions separated by 30 degrees with respect to a vertical line passing through the center of the magnet 8, as shown in FIG. Then, the rotation angle of the magnet 8 and the magnetic field strength detection signals Sa, Sb of each magnetic sensor 10a, 10b
is as shown in FIG. 2(b). Now, in this example,
As shown in FIG. 2(a), the state position where the magnet 8 is perpendicular to the surface of the optical disk is O' 180°,
The state position where the optical disc is horizontal to one surface is defined as 90°. These two magnetic field strength detection signals Sa and Sb
is input to the subtracter 11 on the one hand to form a subtraction signal Sc, and on the other hand to the adder 12 to form a sum signal Sd. Furthermore, these signals Sc and Sd are input to the arithmetic unit 13 and are made into a calculation signal Se.

On the other hand, the coil 9 is supplied with a drive current by a power amplifier 14, and its operation is controlled by a controller 15. First, the power amplifier 14 is connected to a first switch 16 that is controlled by the controller 15, and allows selection between a rotation mode in which the magnet 8 is rotated and a hold mode in which the magnet 8 is held in a predetermined position and state after rotation. It will be done. The hold mode side is connected to the hold control circuit 17, and receives the subtraction signal Sa and addition signal sb.
This is done by servo control using

In addition, on the rotation mode side, a power amplifier 14 is used to apply a current in a specific direction to the coil 9 to give rotational driving force to the magnet 8, and the direction of the driving current is controlled by a controller 15.
This is done by a second switch 18 which is switched and controlled by. That is, it is switched to connection to the power supply or -V, z source.

To control the rotation of the magnet 8, a driving current is applied to the coil 9 so that the magnet 8 rotates in a desired direction, and the rotation speed of the magnet 8 is gradually accelerated from the time when the rotation starts (see a in Fig. 3). ), the rotation speed is decelerated by reversing the polarity of the current flowing through the coil 9 when the intermediate point P18 between the rotation start position P and the desired desired rotation position P is reached. This is performed using a control method as shown in (see b in the figure). At this time, when the speed of the magnet 8 at the desired rotational attainment position P8 becomes zero and the rotation is completed, by switching the switch 16, servo control to efficiently hold the magnet 8 is immediately possible. The relationship between rotation time and rotation speed at this time is shown in FIG. 3(b). Further, the drive current flowing through the coil 9 is divided into an acceleration pulse C and a deceleration pulse d, as shown in FIG. 3(a). That is, the controller 15 applies the acceleration pulse C to the coil 9 at the rotation start position P 2 , and switches the switch 18 at the intermediate point P 4 to apply the deceleration pulse d. For such rotational drive control, it is necessary to detect whether the magnet 8 has reached the intermediate point P1 or not. Therefore, in this embodiment, the subtraction signal Sc, the addition signal Sd, or the calculation signal S
The zero cross comparator (calculating means) 19 is used for any of the signals e, the zero cross signal Sf is detected, the zero cross timing is detected as the magnet 8 is located at the intermediate point P11 position, and acceleration-deceleration switching control is performed. It was designed to be used for

Such a detection operation will be specifically explained.

First, detection of a 90° position will be explained. This detection method changes the rotation angle of the magnet 8 from 0° to 1800° or
Used to invert the 1806 state from 00 to Oo. That is, 90' is the intermediate point position, and this intermediate point position is detected based on the zero cross point of the subtraction signal Sc. When the subtraction signal Sc shown in FIG. 4(a) is passed through a zero-cross comparator 19a, a zero-cross signal Sf as shown in FIG. 4(b) is obtained. This zero cross signal S
By detecting the rise and fall of f, the controller 5 can detect the 90° position of the magnet 8. After that, the controller 15 switches and controls the switch 18,
Control as shown in FIG. 3 is performed by changing the polarity of the applied current.

Next, a control method for 90' inversion will be explained. This method moves the magnet 8 from 00 to 90'' and from 900 to 18''.
to 0°, 90' to 00, ]80° to 90',
It is used when each rotation is 90'. Detection of the midpoint between 45° and 135° in these operations is performed by calculating the subtraction signal Sc and addition signal Sd. First, the detection of 45° is the detection of the intermediate point when the magnet 8 is rotated 90° from Oo to 90' or from 90° to 06. In this case, by taking the difference between the subtraction signal Sc and addition signal Sd shown in FIG.
A signal that crosses zero at ° is obtained.

The controller 15 passes this signal through the zero-cross comparator 19b and detects the rise and fall of the zero-cross signal Sf, thereby detecting the 45° point which is the intermediate point.

Also, for 135° detection, the magnet 8 is moved from 90'' to 180'
This is the detection of the intermediate point when rotating 90 degrees from 180 degrees to 906 degrees. By adding the subtraction signal Sc and addition signal Sd shown in FIG. 4(a), a signal that crosses zero at 135° is obtained. The controller 15 converts this signal into a zero cross comparator 19b.
By detecting the rise and fall of the zero cross signal %Sf, the intermediate point 135' can be detected.

By the way, intermediate position detection of both 45° and 135° will be explained. This moves magnet 8 from 06 to 90',
Or when rotating the magnet 8 by 90' from 90° to Oo, or from 90' to 180° or from 180' to 90
It is possible to detect the midpoint (45° to 135°) in any case when rotating 900 degrees to '. In this case, as shown in FIG. 5, the subtraction signal Sc is converted into an absolute value signal Sg using the absolute value circuit 20,
is used to subtract the addition signal Sd. FIG. 6 shows the state of the signal at this time. The absolute value signal Sg of the subtraction signal Sc is shown by a solid line in FIG. This absolute value signal Sg
By taking the difference between and the addition signal Sd (indicated by a broken line), we get Fig. 6 (
As shown in b), a subtracted signal sh that crosses zero at points 45° and 135° is obtained. The controller 15 can detect the intermediate points of 45° and 135° by detecting the rise and fall of the zero-cross signal obtained by passing the subtraction signal sh through the zero-cross comparator 19.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8.

First, in the case of the above embodiment method, acceleration is switched to deceleration at the detected intermediate point position arrival timing, and then, when the desired rotational position is reached, the hold mode is entered and position control is performed by a servo loop. More specifically, control is performed so that the hold mode is entered at a timing when a specific period of time has elapsed from the rotation start point. However, if variations occur in the torque of the driving coil 9, the desired rotational position may not be reached at the end of rotation, which may place a burden on the servo control system. This situation will be explained with reference to FIG.

Figure (a) shows the relationship between the elapsed time of magnet rotation and the rotation angle, and Figure (b) shows the relationship between the rotation angle and the magnetic field sensor such as a Hall element.
The relationship between the addition signal sb and the subtraction signal Sa of the detection signals from oa and 10b is shown, and FIG. The solid lines in (a) and (c) of the same figures show the characteristics when using the coil 9 with a torque equal to the design value, and the broken lines show the characteristics when using the coil 9 with the torque less than the design value. As can be seen from FIG. 6(a), when a small torque coil is used as indicated by the broken line, the desired rotational position (rotational angular position) is not reached even after a specific time T has elapsed. Although not particularly shown in the figure, if the torque is larger than the design value, the desired rotational position (
It can be understood that the rotation angle position) is exceeded. If the hold servo mode is entered in such a state that the servo has not been reached or has gone too far, the load on the servo control system will be heavy and the servo settling time will become long.

This embodiment is designed to eliminate the influence of such variations in torque and the like. The circuit configuration of this embodiment is also as shown in FIG. 1, but the controller 15 of this embodiment also has the function of time measuring means. First, the timing at which the magnet 8 reaches the intermediate point from the rotation start position to the rotation end position is determined by the magnetic field sensor 1 as described in the previous embodiment.
0a.

It is detected based on the detection signal of 10b. At this time, in this embodiment, the timing signal for detecting the arrival at the intermediate point is also sent to the controller 1.
5, the time T1 required from the rotation start position to the intermediate point is measured, and the polarity of the current applied to the coil 9 is switched to slow down the rotation of the magnet 8. After passing the halfway point, the hold mode is entered after a time T has elapsed, but this time T2 is set as the above required time T.
The timing is controlled so that it is the same as 1. When the time T has elapsed from the intermediate point, the magnet 8 is located at the desired rotational attainment position, so it can immediately enter the hold mode, making it possible to hold the position efficiently.

The state of such control will be explained with reference to FIGS. 7(d) and (e). Figure (d) shows the relationship between the elapsed time of magnet rotation and the rotation angle similarly to figure (a), and figure (e) shows the relationship between the rotation angle and the elapsed time of magnet rotation.
Similarly to c), the relationship between the elapsed time of magnet rotation and the addition signal sb and subtraction signal Sa is shown. In this case as well, the solid line shows the characteristics when using the coil 9 with a torque equal to the design value, and the broken line shows the characteristics when using the coil 9 with the torque less than the design value. According to this, the rotation starting position P
The required time T from 1 to intermediate point P, 2 is the same time T as (Tr in the case of a broken line), (T in the case of a broken line, ') is the intermediate point P1. It can be seen that the magnet 8 is located at the desired rotational attainment position P2 after the lapse of time. Therefore, the rotation control can deal with variations in torque.

Effects of the Invention As described above, the present invention provides a signal that is either an addition signal, a subtraction signal, or a calculation signal of an addition signal and a subtraction signal of magnetic field strength detection signals provided by a plurality of magnetic field sensors provided around a magnet. A zero-crossing point is calculated by the calculation means, and it is detected by this zero-crossing point that the magnet has reached the intermediate point between the starting starting position and the desired rotational reaching position. Since the timing at which the motor reaches the halfway point is detected, switching control from acceleration to deceleration in magnet rotation drive can be performed accurately, and stopping control at the desired rotational position can be efficiently performed. , for example, set the desired rotational position to 90
' position, it is possible to perform a good regeneration operation. In addition, in the invention according to claim 2, the time required for the magnet to reach the intermediate point from the starting position is measured by the time measuring means. Then, a current is applied to the coil to rotate the magnet in the desired direction from the starting position, and the magnet is gradually accelerated while starting rotation. When the reaching of the halfway point is detected by the magnetic field sensor output, the polarity of the current to the coil is reversed. Since the magnet's rotational speed is slowed down and the current to the coil is stopped when a time equivalent to the measured time has passed after passing the halfway point, the influence of variations in the drive coil's torque etc. can be reduced. This reduces the burden on the hold servo control system and enables efficient position control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing the relationship between the state of the magnet and each signal, Figure 3 is an explanatory diagram showing the relationship between elapsed rotation time, applied current, and rotation speed, and Figure 4 is an explanatory diagram showing examples of generation of various zero-cross signals. 5 is a block diagram showing a modified example, FIG. 6 is an explanatory diagram showing an example of an absolute value signal, and FIG. 7 is a diagram showing a second embodiment of the present invention. FIG. 8 is an explanatory diagram showing the relationship between elapsed rotation time, applied current, and rotational speed. FIG. 9 is a schematic diagram showing a conventional example.

Claims (1)

[Claims] 1. A magnet that faces the surface of a recordable optical disk and is rotatable about a rotation axis parallel to the disk surface; In a magnetic head rotation control device for applying a magnetic field, which includes a coil that is rotationally driven, a plurality of magnetic field sensors are provided around the magnet, and an addition signal, a subtraction signal, or Calculating means is provided for calculating a zero-crossing point of any one of the calculated signals of the addition signal and the subtraction signal, and the magnet reaches an intermediate point between the starting starting position and the target rotational position at this zero-crossing point. What is claimed is: 1. A magnetic head rotation control device, characterized in that the magnetic head rotation control device detects whether 2. A time measuring means is provided to measure the time required for the magnet to reach an intermediate point from the starting position, and a current is applied to the coil to rotate the magnet in a desired direction from the starting position while starting the rotation. When the magnetic field sensor output detects that the intermediate point has been reached by gradually accelerating, the polarity of the current to the coil is reversed to slow down the rotational speed of the magnet so that the time required is equivalent to the time measured by the time measuring means. 2. The magnetic head rotation control device according to claim 1, further comprising: stopping energization of said coil when time has elapsed from passing through an intermediate point.