JP2576972B2 - Head access device - Google Patents

Description

The present invention relates to a head access device in an electronic still camera or a magnetic disk device.

[Prior Art] Conventionally, a head for transmitting and receiving information to and from a disk-shaped recording medium such as an electronic still camera or a magnetic disk device has a displacement for moving the head between tracks formed on the medium. Various head access devices have been devised. In general, this type of head access device supports a head 1 as shown in a principle diagram of FIG. 4 and converts a displacement of a cam or a screw or the like driven by a motor 3 to a head carriage 2 provided movably by itself. It is configured to operate by giving a predetermined displacement by the element 4. In the illustrated apparatus, the rotational displacement by the motor 3 is converted by the cam 4 and the cam follower 5 into a linear displacement along the moving direction of the head carriage 2, that is, the radial direction of the disc-shaped recording medium 6. Accordingly, the head 1 supported by the head carriage 2 moves in response to the rotation of the motor 3 to form a plurality of tracks formed on the disc-shaped recording medium 6.
Move between 7,7. Conventionally, the cam 4 as the displacement conversion element
A type in which the distance from the center to the peripheral surface that comes into contact with the cam follower linearly increases according to the rotation angle from the reference position has been applied. Therefore, the amount of displacement of the head 1 obtained in accordance with the rotation angle of the motor 3, that is, the rotation angle of the cam 4, has a linear relationship as shown in FIG. On the other hand, in recent years, a pulse motor has been actively used as a motor capable of controlling the rotation angle with an open loop relatively accurately. However, when a pulse motor is applied as the motor 3 of the above-described device, the following problem occurs. That is, as shown in FIG. 6, the relationship between the number of pulses supplied to the pulse motor and the corresponding rotation angle is not a strict step-like relationship, but a characteristic in which a dynamic component is superimposed. Is shown.
Therefore, the head carriage 2 does not stop at a regular position corresponding to the number of supply pulses, and it is difficult to accurately track the head 1 on a desired track on the medium 6. As a countermeasure against this, instead of changing the peripheral surface shape of the cam 4 to a smooth continuous shape obtaining a linear characteristic as shown in FIG. 5, a step-like characteristic as shown in FIG. When the head is at a predetermined track position, the carriage is stopped and unnecessary displacement is exerted on the head by the rotation of the motor when the head is at a predetermined track position. A technique for preventing such a situation has already been proposed (JP-A-59-3754).

[Problems to be Solved by the Invention] However, when a displacement conversion element (cam) having a characteristic as shown in FIG. 7 is applied, in a section where a change corresponding to the rotation of the motor does not occur (hereinafter referred to as a pause section), a motor is provided. Even if the rotation angle is slightly changed, a new problem arises because the head position does not change. That is, generally, in this type of apparatus, when information is reproduced by a head from a recording track formed on a medium, in order for the head to accurately trace the track, the head position is determined based on an envelope of a reproduction signal or the like. Delicate control,
So-called tracking control is required. However, as described above, when the motor is at the rotation position in the pause section as shown in FIG. 7, delicate control of the head position cannot be performed, and therefore, tracking control becomes difficult. On the other hand, if the characteristics of the displacement conversion element are set so that the output displacement changes substantially linearly as a whole in small steps in accordance with the supply pulse to the motor as shown in FIG. 9, a relatively accurate tracking control can be performed. (In FIG. 9, the horizontal axis indicates the number of rotation steps of the pulse motor, that is, the rotation angle of the cam, and the vertical axis indicates the output displacement by the track position on the medium). However, in this case, in order to move the head from a certain track (the n-th track to the next track (the (n + 1) -th track)), it is necessary to provide a large amount of input displacement (the number of input pulses) without providing a large amount of input displacement (number of input pulses). This means that the head access speed becomes extremely slow.The slow head access speed is a serious defect in a device as a storage unit of an electronic camera or an information device. .

The present invention has been made in view of the above points, and eliminates the above-described problems in the related art. This kind of head access that enables high-accuracy tracking control and high-speed head access at the same time is also possible. It is intended to provide a device.

[Means for Solving the Problems] The configuration of the present invention as means for solving the above problems will be described below. A head for transmitting and receiving information to and from a disk-shaped recording medium on which information is recorded on a plurality of annular tracks; a head carriage for supporting the head so as to be displaceable in a direction transverse to the tracks; A motor as a displacement drive source, and a displacement conversion mechanism for converting a rotational displacement by the motor into a displacement along a moving direction of the head carriage, wherein the displacement conversion mechanism is driven by the motor. A feed portion for generating a predetermined feed displacement is formed in its own predetermined portion; and a feed displacement is received in contact with the feed portion of the displacement conversion element, and the feed displacement is received. And a follower member for transmitting to the head carriage. The portion is formed so as to give a relatively large feed displacement to the follower member in accordance with the driven displacement of the displacement conversion element by the motor, and a displacement corresponding to a section in which the head moves between the plurality of annular tracks. A plurality of rough pitch feed portions provided corresponding to each driven section of the conversion element, and a plurality of relatively small steps of step-shaped feed displacements in accordance with the driven displacement of the displacement conversion element by the motor; The head is shaped to give the follower member with an intervening feed pause and the head corresponds to each driven position of the displacement conversion element corresponding to each position of the plurality of annular tracks. And a fine-pitch feeder provided as described above. .

[Operation] According to the head access device of the present invention, when the rough pitch feed portion of the displacement conversion element is at a position where the operation is performed in accordance with the rotation angle of the motor, the head carriage (accordingly, the head) is rotated by the rotation amount of the motor. Is relatively large, i.e., at a high speed, and is displaced between the tracks, thereby providing high-speed head access. On the other hand, when the fine pitch feed portion of the displacement conversion element is at the position where the operation is performed, the head makes a relatively small displacement with respect to the rotation of the motor, so that fine tracking can be performed with high precision.

Embodiment FIG. 1A is a diagram showing a main part of a head access device as an embodiment of the present invention. In FIG. 1A, the head 10 has a head chip 11 supported by a head base 12. The head 10 is mounted on a head carriage 20 movably guided by two guide rods 21, 21. A cam 41 as a displacement conversion element is provided so as to be rotationally driven by the stepping motor 30, and the cam 41 forms a displacement conversion mechanism 40 together with a roller-shaped cam follower 42 provided on the carriage 20 so as to be in contact with the cam 41. ing. The right ends of the two guide rods 21, 21 in the drawing are fitted and fixed to the structural member 100 of the apparatus. Although not shown, each left end is similarly fixed. The two guide rods 21, 21 penetrate through an insertion hole provided in the head carriage 20, and guide and support the head carriage 20 movably. Between the right side surface of the head carriage 20 in the drawing and the left side surface of the structural member 100 facing the head carriage 20, compressible coil springs 22, 22 are provided substantially along the outer circumferences of the guide rods 21, 21. Constant cam 41 for head carriage 20
A biasing force toward is provided. Therefore, the cam follower 42 provided on the carriage 20 is always in elastic contact with the cam 41. Further, a disc-shaped recording medium 60 such as a floppy disk, which is rotationally driven by a spindle motor (not shown), is arranged as shown by a two-dot chain line, and an annular information recording track 70, The head 10 is configured to trace on 70. In the present invention, the cam 41 as the conversion element has a characteristic pattern as shown in FIG. 1 (b) which is an enlarged view of a part b of the peripheral surface. That is, in the cam follower 41, the distance r from the center of rotation O to the portion P of the cam peripheral surface that comes into contact with the peripheral surface of the cam follower 42 increases in small steps according to the counterclockwise rotation angle of the cam 41. At the same time, the pattern is formed so as to increase in a relatively large step-like manner at predetermined intervals. This small step-like portion is a fine pitch feed section for giving the head 10 a relatively small displacement for tracking control for performing normal tracking for a single track, and The large step-like portion is a rough pitch feed portion for giving the head 10 a relatively large sudden displacement for movement between tracks. The characteristics of the cam 41 will be more easily understood from the characteristic diagram of FIG. In FIG. 2, the horizontal axis represents the rotation angle of the stepping motor 30 by the number of steps, and the vertical axis represents the displacement of the head (this corresponds to the aforementioned distance r) by the track number on the medium. On the vertical axis, for example, the distance from the n-th track to the next (n + 1) -th track, that is, the interval between adjacent tracks is a so-called track pitch. In the case of an electronic still camera, this is set to 100 μm according to the standard.

The operation of the apparatus of the present invention configured as described above will be described below.

When the head chip 11 of the head 10 traces the normal position of the n-th track on the recording medium 60, the rotation position of the cam 41 is the rotation reference position, that is, the position where the number of steps is zero in FIG. Assume that In order for the head 10 to be able to properly trace the n-th track of the recording medium 60 while the head 10 is rotating, the positional tolerance of the recording apparatus when recording the same track and the eccentricity of rotating the medium in the reproducing apparatus are required. It is necessary to perform tracking control to dynamically control the head by slightly displacing the head in response to the track being dynamically displaced from its intended normal position due to the influence of deviation or the like. As described above. In this example, in order to perform tracking control on the n-th track, a drive pulse from the servo circuit (not shown) to the pulse motor 30 is, for example, one step or two steps in the normal rotation direction (counterclockwise in FIG. 1). (1, 2 on the horizontal axis in FIG. 2) or one or two steps in the reverse direction (−1, -2 on the horizontal axis in FIG. 2). Fine tracking control can be properly performed by the operation of 41 phi pitch feeding sections. On the other hand, when the head 10 is caused to access the head from the n-th track to the next (n + 1) -th track, the rough pitch provided corresponding to the rotation angle of the pulse motor 30 and therefore the cam 41 between the second and third steps is used. The feed portion acts to give a relatively steep displacement to the head 10, and the head 10 moves quickly from the n-th track position to the (n + 1) -th track position. Of course, the tracking control for the (n + 1) th track is performed in the same manner as described above for the nth track. The head access to the (n + 2) th track and the (n + 3) th track and the tracking control for each of those tracks are performed in the same manner as described above. In other words, the cam 41 serving as a displacement conversion element having such an operation can be used for tracking control centering on the regular position of each track (the position of step numbers 0, 5, 10,... In FIG. 2). It can be said that it is provided over a required predetermined section (a section of ± 2 steps in FIG. 2), and a rough pitch feed section is provided between each of these fine pitch feed sections. As described above, in this example, in each fine pitch feed section, since the same section is formed by a plurality of minute steps each having a feed pause section, the action of the pause section causes the motor 30 (that is, the cam 41) to operate. Even if a rotation component includes a passive component, its influence can be suppressed to a minimum, and stable tracking is realized. Note that the effect of quick head access by the rough pitch feed portion of the displacement conversion element in the present invention can be seen by comparing the characteristics of FIG. 9 with the characteristics of FIG. 2 by the cam formed only by the fine pitch feed portion. It will be clearly understood how remarkable it is.

The present invention is not limited to the technical idea described in the above embodiments, and various modifications and changes can be made within the scope of the present invention. For example, instead of using the cam 41 and the cam follower 42 as shown in FIG. 1 as the displacement conversion mechanism 40, a grooved cam 41 'having a spiral groove and a pin-shaped cam follower corresponding to the groove as shown in FIG. 42 'may be applied. The groove cam 41 'as a displacement conversion element in FIG. 3 is mounted in exactly the same manner as the cam 41 in FIG. Correspondingly, a pin-shaped cam follower 42 'is also provided at a position corresponding to the cam follower 42 on the head carriage 20 in FIG. In this case cam follower 4
It goes without saying that the positional relationship between the groove cam 41 'and the cam follower 42' should be adjusted so that the tip of 2 'can properly trace the groove of the groove cam 41'. In the groove cam 41 'as a displacement conversion element in FIG. 3, the relationship between the distance from the center of rotation to the portion where the cam follower 42' fits into and slides into the cam groove and the rotation angle with the cam 41 'are as follows. The cam groove is configured to include a fine pitch feed portion and a rough pitch feed portion so as to be exactly the same as that shown in FIG. Therefore, when the element as shown in FIG. 3 is applied as the displacement conversion mechanism in the apparatus of the present invention, the same operation and effect as in the embodiment described above with reference to FIGS. In particular, if an element as shown in FIG. 3 is applied as the displacement conversion mechanism, the configuration and the size of the groove are appropriately selected to provide a structure which does not necessarily require the urging means 22 as shown in FIG. 1 (a). can do.

[Effects of the Invention] As described above, in the head access device of the present invention, when performing a head access operation of moving the head from a position corresponding to one track to a position corresponding to another track, the head is moved by the displacement conversion element. The rough pitch feed section works effectively to perform quick operation, while the fine pitch feed section of the displacement conversion element is effective for tracking operation to accurately align the head position with one specific track. By acting, highly accurate tracking control is performed. Further, since the fine pitch feed section is formed so that a relatively small number of steps of step-like feed displacement are present in a form including a feed stop section between each step, the feed pause section is provided. In the case where a pulse motor is used as a drive source, the variation in the stop position of the motor and the positioning error of the head due to the pulsating displacement can be effectively suppressed by the action of (1).

[Brief description of the drawings]

1 (a) is a diagram showing a main part of an embodiment of the present invention, FIG. 1 (b) is an enlarged view of a main part of the apparatus of FIG. 1 (a), and FIG. 2 is a characteristic of the apparatus of the present invention. FIG. 3 is a diagram showing a displacement conversion mechanism in another embodiment of the present invention, FIG. 4 is a principle diagram showing a conventional device, and FIG. 5 is a diagram showing a displacement conversion element in a conventional device. FIG. 6 is a diagram showing the relationship between the rotation angle of the cam and the output displacement, FIG. 6 is a diagram showing the relationship between the number of input pulses of the pulse motor and the rotation angle, FIG. 7 is a diagram showing a step-like cam characteristic; FIG. 8 is a diagram showing a cam having the characteristics of FIG. 7, and FIG. 9 is a diagram showing the characteristics of a cam having a small step shape. 10: Head, 20: Head carriage 3, 30: Motor, 40: Displacement conversion mechanism 41, 41 ': Displacement conversion element 6, 60: Recording medium, 7, 70: Track

Claims (1)

(57) [Claims] A head for transmitting and receiving information to and from a disk-shaped recording medium on which information is recorded on a plurality of annular tracks; a head carriage for supporting the head so as to be displaceable in a direction transverse to the tracks; A head access device comprising: a motor serving as a displacement drive source of the head carriage; and a displacement conversion mechanism that converts a rotational displacement by the motor into a displacement along a moving direction of the head carriage. A displacement conversion element in which a feed portion for being driven by a motor and generating a predetermined feed displacement is formed in its own predetermined portion,
And a follower member for receiving the feed displacement in contact with the feed portion of the displacement conversion element and transmitting the feed displacement to the head carriage. The feed portion of the displacement conversion element includes a displacement conversion element driven by the motor. For each driven section of the displacement conversion element formed so as to give a relatively large feed displacement to the follower member with the driven displacement of the follower member and corresponding to a section in which the head moves between the plurality of annular tracks. A plurality of rough-pitch feed units provided correspondingly, and a pause portion of a plurality of relatively small step-like step-like feed displacements is generated between each step with the driven displacement of the displacement conversion element by the motor. And the head corresponds to each position of the plurality of annular tracks. Head access device which is characterized in that which has been molded into a shape having a fine pitch feed portion provided so as to correspond to respective driven position of the position conversion element.