The present invention generally relates to a head carriage apparatus, and more particularly to a head carriage apparatus in which a head carriage is driven and moved by rotation of a lead-screw shaft and the movement of the head carriage is guided by a guide shaft.
A head carriage in a head carriage apparatus is driven and moved by rotation of a lead-screw shaft for recording and reproducing information on a disk by mans of a head carried by the head carriage. A description of this head carriage apparatus will be given by referring to FIGS. 1 and 2. In FIG. 1, a head carriage apparatus 1 includes a head carriage 10 carrying a head 11, a guide shaft 5 for guiding movement of the head carriage 10 in a direction as indicated by an arrow X1 or X2 in FIG. 1, and a drive part 4 having a lead-screw shaft 2 which is coupled to the head carriage 10 and a stepping motor 3 which rotates the lead-screw shaft 2 so as to move the head carriage 10 in the direction as indicated by the arrow X1 or X2 in FIG. 1. The guide shaft 5 is fixed to a disk unit (not shown) which is provided separately from the head carriage 10. The lead-screw shaft 2 is threaded so as to form a lead screw including a thread ridge 2b and a thread groove 2a on the threaded part of the lead-screw shaft 2.
This head carriage 10 has a carriage body 15 which is provided with an extension 12 extending transversely from a left-hand rear end of the carriage body 15 so that the extension 12 is brought in contact with a top of the lead-screw shaft 2, as shown in FIG. 2. This extension 12 is formed integrally with the head carriage 10 through a molding process of synthetic resin, and includes a downwardly projecting connecting portion 13 on bottom of the extension 12. The connecting portion 13 is fitted in the thread groove 2a of the lead-screw shaft 2 so as to apply a drive force from the thread ridge 2b to the connecting portion 13 of the carriage body 15 in a direction perpendicular to a flank of the threaded part of the lead-screw shaft 2 when the lead-screw shaft 2 is rotated. The axial direction of the lead-screw shaft 2 substantially accords with the direction as indicated by the arrow X1 or X2 in FIG. 1.
The carriage body 15 of the head carriage lo is provided on the opposite side (the right-hand side thereof) with a guide portion 16 extending longitudinally in parallel to the direction as indicated by the arrow X1 or X2 in FIG. 1, and this guide portion 16 is inserted into and guided by the guide shaft 5 in the axial direction of the guide shaft 5. Therefore, the head carriage 10 is moved in the direction as indicated by the arrow X1 or X2 in FIG. 1, by the above drive force exerted by the lead-screw shaft 2 when the shaft 2 is rotated.
The above movement of the head carriage 10 in the direction as indicated by the arrow X1 or X2 is guided by the guide shaft 5 and supported at two supporting portions 16a and 16b of the guide portion 16. In order to stabilize this movement of the head carriage 10 in the direction as indicated by the arrow X1 or X2 in FIG. 1, the supporting portions 16a and 16b of the guide portion 16 are arranged apart from each other by an appropriate distance Lab which is large enough for stable movement of the head carriage 10. An intermediate portion of the guide portion 16 between the supporting portions 16a and 16b is formed into a hollow part.
As apparent in from FIG. 2, the head carriage 10 is provided with a leaf spring 14 on the bottom of the carriage body 15, and this leaf spring 14 is fixed at one end portion thereof to the carriage body 15 by means of a machine screw 17. The other end of the leaf spring 14 is a free end and the leaf spring 14 at this free end is brought into contact with an outer peripheral surface of the lead-screw shaft 2. The leaf spring 14 serves to apply an upwardly biasing force to the lead-screw shaft 2 against the extension 12 of the carriage body 15. In accordance with the upwardly biasing force by the leaf spring 14, a downward force from the connecting portion 13 is exerted onto the lead-screw shaft 2 against the leaf spring 14, thus preventing the connecting portion 13 from being easily separated from the thread groove 2a of the lead-screw shaft 2. As described above, the head carriage 10 of the conventional apparatus is supported by the guide shaft 5 at two supporting points A and B, corresponding to the supporting portions 16a and 16b of the guide portion 16, and also supported by the lead-screw shaft 2 at a supporting point C, corresponding to the connecting portion 13 of the carriage body 15.
Recently, downsizing a disk drive unit in which the above described head carriage apparatus is accommodated is becoming important for a manufacturer of disk drive products. One attempt to downsize a disk drive unit can be made by changing the relative position of a connector 13 in the disk drive unit, as shown in FIG. 3A, into a position, as shown in FIG. 3B. For this purpose the relative position of the guide portion 16 provided within the head carriage apparatus must be changed or displaced into the relative position shown in FIG. 3B. In the head carriage apparatus shown in FIG. 3B, the supporting point B of the guide portion 16 is moved to a position which is located on the same side as the supporting point A with respect to a line D passing through the supporting point C and being perpendicular to the axial line of the guide shaft 5. On the other hand, in the head carriage apparatus shown in FIG. 3A, the supporting point B is located on the side opposite to the supporting point A with respect to the perpendicular line D.
In the case in which the supporting point B of the guide portion of the head carriage is simply moved in a forward direction to the position, as shown in FIG. 3B, for downsizing the disk drive unit, there is a problem in that the head carriage is slightly rotated around an axis perpendicular to the horizontal plane of the head carriage and the head is erroneously placed at a position deviating from an intended accurate position relative to the disk. This may cause a malfunction to occur in the disk recording and reproducing performed by the disk drive unit.