1. Field of the Invention
This invention relates to a seek control device and a seek control method used in a floppy disk apparatus to perform a return-to-zero (RTZ) operation when a seek error occurs.
2. Description of the Related Art
In the prior art floppy disk apparatus, as shown in FIG. 1, a magnetic head mounted on carriage 10 is driven in a radial direction along a magnetic recording medium (disk) by means of lead screw mechanism 13 for converting the rotational motion of stepping motor 12 to a linear motion. The disk is rotated while it is clamped on spindle hub 11 of a spindle mechanism. When a seek command is generated, the magnetic head is moved to a destination track with respect to an outermost track used as a reference track. That is, when the seek command is generated, a return-to-zero (RTZ) operation is first performed such that the magnetic head seeks the zero track in an outer direction along the recording medium, and the destination track is then sought by the magnetic head from an inner direction along the recording medium, after the zero track is detected.
In the prior art floppy disk apparatus, when the power source is turned on, the seek command is also generated, and the RTZ seek operation is performed to seek the zero track using a step signal from a host side (which includes a Floppy Disk Controller, FDC). The position of the magnetic head when the power is turned on is not previously determined, and for this reason, the RTZ seek operation is performed. Whether the magnetic head has reached the zero track is detected by track zero detector 20 shown in FIG. 2. When track zero (TZ) detection tab 21 attached to carriage 10 is detected by detector 20 during the RTZ operation, track zero detector 20 generates a TZ detection signal. The control circuit Floppy Disk Mechanism Controller, (FDMC) of the floppy disk apparatus generates and supplies a track zero signal to the host side in response to the TZ detection signal from detector 20. Then, the host side interrupts generation of the step pulse signal required for the RTZ operation.
As described above, the seek control is performed with respect to the zero track as the reference track. In a case where a seek error occurs, carriage 10 is driven further outwardly (- direction) along the disk from the zero track. In order to prevent the carriage 10 from being driven past the zero track, as shown in FIG. 1, a track zero (TZ) stopper 14 is mounted on lead screw mechanism 13 of the prior art floppy disk apparatus. More specifically, carriage 10 is mechanically prevented from being further driven in the - direction from the zero track by means of TZ stopper 14, even when a seek error has occurred. However, a position adjusting step is necessary to properly mount TZ stopper 14, and the step of mounting TZ stopper 14 increases the number of the assembling steps of the floppy disk apparatus. Further, mechanical distortion will occur due to the overshooting of the carriage each time the RTZ seek operation is performed, thereby adversely affecting positioning precision.