JPH0416290Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a head feeding mechanism for step-feeding a magnetic head with high precision.

[Conventional technology]

Electronic still cameras and so-called floppy disk devices are equipped with a magnetic head feeding mechanism for tracking a recording or reproducing magnetic head in the radial direction of a magnetic sheet or floppy disk.

As such a head feeding mechanism, one using a microstep cam in which a stepped receiving surface is formed on the outer periphery of a spiral cam is known. That is, the microstep cam is rotated via a motor and a gear train, and a cam follower fixed to the head carriage is brought into contact with one of the receiving surfaces of the microstep cam. Then, a cam follower provided on a head carriage holding a magnetic head is brought into contact with one of the receiving surfaces, and the cam follower is positioned by contacting a different receiving surface each time the microstep cam is rotated. It's becoming like that.

[Problem that the invention attempts to solve]

By the way, in the conventional head feeding mechanism as described above, the backlash that exists in the driving force transmission system for transmitting the driving force of the motor to the microstep cam becomes difficult when trying to improve the feeding accuracy of the magnetic head. , is a major cause of hindering this.

The present invention was developed in view of the above-mentioned drawbacks of the conventional head feeding mechanism, in which the accuracy of feeding the magnetic head deteriorates due to backlash occurring in the drive power transmission system from the motor to the microstep cam. It is an object of the present invention to provide a magnetic head feeding mechanism which prevents this and enables highly accurate head feeding.

[Means for solving problems]

In order to achieve the above object, in the magnetic head feeding mechanism of the present invention, the receiving surface at the starting point position and the receiving surface at the end point position of the microstep cam, which has a receiving surface formed in a step-like manner on the outer periphery, are connected by a guide surface. contact me,
The microstep cam is rotated in only one direction to send the magnetic head to any desired track position. Further, a biasing means is provided in the driving force transmission system between the microstep cam and the motor, and is configured to bias the microstep cam to rotate in a direction opposite to the one direction.

In a preferred embodiment of the present invention, the microstep cam is connected to a face gear coaxially provided with a coil spring, and the coil spring applies a rotation biasing force to the microstep cam in the opposite direction. ing. The face gear is formed with directional engagement teeth that follow the microstep cam when it rotates in the one direction, and the face gear has directional engagement teeth that follow the microstep cam when it rotates in the one direction. They are configured to mesh with each other by the biasing force of a coil spring.

An embodiment of the present invention will be described below with reference to the attached drawings.

〔Example〕

In FIG. 3, which schematically shows an example of a magnetic recording apparatus embodying the present invention, a still video floppy 1 includes a magnetic sheet pack 2 and a magnetic sheet 3 rotatably housed therein. A center core 4 is fixed to the center of the magnetic sheet 3, and a pulley 5 fits into the hole 4a of the center core 4. The pulley 5 is fixed to the tip of a spindle 7 of a motor 6, and when the motor 6 is driven, the magnetic sheet 3 is rotated.

A window 2a is formed in the magnetic sheet pack 2, and a magnetic head 8 is inserted through the window 2a and comes into contact with the recording surface of the magnetic sheet 3. The magnetic head 8
is fixed to a head carriage 10 via a support plate 9. When performing magnetic recording, in order to feed the magnetic head 8 to a predetermined track position, the head carriage 10 is moved parallel to the magnetic sheet 3 by a head feeding mechanism 11.
and is adapted to be moved in its radial direction.

In FIG. 1 showing the structure of the head feeding mechanism 11, the head carriage 10 is slidably supported by a pair of guide rods 13 and 14. As shown in FIG.
A stop pin 15 that acts as a cam follower is fixed to the head carriage 10, and one end of the stop pin 15 is pushed around the outer periphery of the microstep cam 18 by the urging force of a spring 16 that urges the head carriage 10 in one direction. is in contact with.

As shown in FIG. 2, the microstep cam 18 is a spiral cam with a stepped receiving surface 18a formed on the outer periphery thereof. and,
When the stepping motor 20 is driven, a gear 23 integrated with the microstep cam 18 rotates via a gear train 21 and an interlocking gear 22, so that the microstep cam 18 is rotated. Note that the stepping motor 20 is driven in only one direction so that the microstep cam 18 always rotates clockwise.

The number of stages of the receiving surface 18a formed on the microstep cam 18 corresponds to the number of magnetic tracks formed on the magnetic sheet 3, and the rotation angle α per step is 6°, and the total number of stages is 50. In this case, the microstep cam 18 is formed with a stepped receiving surface 18a over a range of 300°, and when the microstep cam 18 is rotated 300° clockwise from the position shown in FIG. 15. The magnetic head 8 is moved from the outermost track position (home position) of the magnetic sheet 3 to the innermost track position via the head carriage 10.

The remaining 60° portion of the microstep cam 18 where the stepped receiving surface 18a is not formed is used as a guide surface 18b. That is,
A receiving surface formed at the starting point position of the microstep cam 18 and a receiving surface formed at the ending point position are connected by a guide surface 18b formed in a substantially straight line. Therefore, when the microstep cam 18 is rotated one turn clockwise from the position shown in FIG.
The head is fed through the head carriage 10 from the outermost track position on the magnetic sheet 3 to the innermost track position, and then returns to the outermost track position.

Note that if the angle β between the guide surface 18b and the perpendicular line drawn from the end point of the receiving surface 18a to the line connecting the starting point of the receiving surface 18a and the center of rotation is 45° or less, the angle β between the starting point and the rotation center will change from the ending point to the starting point. The abutment pin 15 can be moved very smoothly until Further, similar head feeding can be performed by rotating the microstep cam 18 counterclockwise, but as in the illustrated embodiment, the contact surface 18a formed as a stepped cam is moved from the contact pin 15. It is preferable to set the direction in which the microstep cam 18 sequentially descends as the direction of rotation of the microstep cam 18.

A movable face gear 25 is provided to rotate coaxially with the microstep cam 18, and a coil spring 26 is suspended between the movable face gear 25 and the microstep cam 18. The microstep cam 18 and the movable face gear 25 are attached to an E-ring 28 through a shaft 27 implanted in a fixed portion, and rotate around this shaft 27. Directional engagement teeth are formed on the lower surface of the movable face gear 25, and are engaged with the fixed face gear 30 attached to the fixed part together with the shaft 27 by the urging force of the coil spring 26. It's becoming like that. The directionality of the engaging teeth allows the movable face gear 25 to easily rotate clockwise.

When the stepping motor 20 is driven and the microstep cam 18 is driven clockwise, the head carriage 10 is moved via the receiving surface 18a and the abutment pin 15, so that the magnetic head 8 moves along the microstep cam 18. The head is fed to a position corresponding to the amount of rotation.

When feeding the head, the microstep cam 18
When the coil spring 26 is rotated clockwise, the coil spring 26 is initially charged. That is, the movable face gear 25 and the fixed face gear 30 are
being crimped with a coil spring 26;
Since there is resistance in the meshing part between movable teeth,
Even if the microstep cam 18 rotates clockwise, the movable face gear 25 does not rotate immediately. After the coil spring 26 is charged to some extent, the movable face gear 25 is rotated in the same direction as the microstep cam 18.
Note that the extent to which the coil spring 26 is charged to rotate the movable face gear 25 depends on the movable face gear 25 and the fixed face gear 3.
It can be adjusted by the tooth profile of the engagement teeth formed at zero and the strength of the biasing force of the coil spring 26 in the axial direction.

After the head feeding is completed, the stepping motor 20
When the driving of the microstep cam 18 stops, the microstep cam 18 stops rotating while the coil spring 26 remains charged. That is, the movable face gear 25 is biased clockwise by the charge of the coil spring 26, but as described above, since there is resistance between the movable face gear 25 and the engaging teeth of the fixed face gear 30, the movable face gear 25 is pressed against the fixed face gear 30 and stopped. As a result, the charging force of the coil spring 26 applies a biasing force to the microstep cam 18 in a counterclockwise direction.

In this manner, when the stepping motor 20 is stopped, the microstep cam 18 is biased in the direction opposite to the direction of rotation for feeding the head, so that the gear train 21 and the interlocking gear 2
2, and the bumps occurring between the gears of the gear 23 are eliminated. Therefore, when driving the stepping motor 20 for the next head feed, the microstep cam 18 can be immediately rotated without play due to the backlash described above.

It should be noted that when the charging force of the coil spring 26 increases when the vehicle is stopped, the backlash removing action also extends to the first stage side of the gear train 21. Therefore, the charging force of the coil spring 26 may be set appropriately, taking into consideration the required accuracy, the torque of the stepping motor, and the like. Further, in the above-described embodiment, the backlash is removed at the final stage of the head feed drive system, but instead of this, for example, a structure may be provided in which the backlash is removed for the interlocking gear 22. Further, in order to keep the coil spring 26 in a charged state when head feeding is stopped, a clutch mechanism such as a friction plate may be used instead of the movable face gear 25 and fixed face gear 30. Of course, the above-mentioned bump crash removal mechanism can equally be applied not only to the above-mentioned gear coupling but also to a driving force transmission system including, for example, a chain.

[Effect of idea]

As explained above, according to the removal head feeding mechanism of the present invention, the microstep cam is configured to rotate in only one direction to feed the head, and when the head feeding is stopped, the microstep cam is biased in the opposite direction. Therefore, the influence of backlash in the drive force transmission system that drives the microstep cam can be suppressed, and the accuracy of head feeding can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts showing an embodiment of the present invention. FIG. 2 is a plan view showing an example of a microstep cam. FIG. 3 is an explanatory diagram showing an outline of a magnetic recording device using the present invention. DESCRIPTION OF SYMBOLS 1... Still video floppy, 3... Magnetic sheet, 8... Magnetic head, 10... Head carriage, 15... Retaining pin, 18... Microstep cam, 18a... Receiving surface, 18b... Guide surface, 20... Stepping motor, 21... Gear train, 22... Interlocking gear, 25... Movable face gear, 26... Coil spring, 30... Fixed face gear.

Claims (1)

[Claims for Utility Model Registration] (1) A cam follower is provided on a head carriage holding a magnetic head, and this cam follower is brought into contact with a microstep cam having a stepped receiving surface formed on its outer periphery. In a magnetic head feeding mechanism in which the magnetic head is rotated by a motor to step feed the magnetic head in the radial direction of the magnetic sheet, a receiving surface formed at a starting point position and a receiving surface formed at an ending point position of the microstep cam are provided. The microstep cam is rotated in one direction to feed the head, and the microstep cam is connected in the one direction and in the driving force transmission system between the motor and the microstep cam. A magnetic head feeding mechanism characterized in that it is provided with a biasing means for biasing in the opposite direction. (2) The biasing means is a coil spring hung between the microstep cam and a rotating member that slides in contact with the rotation regulating member and follows the microstep cam, and the coil spring is The magnetic head according to claim 1, wherein the magnetic head stores energy by rotating the microstep cam when the rotation of the rotating member is restricted by the regulating member. Feeding mechanism. (3) The rotating member and the rotation regulating member each include a movable face gear and a fixed face gear in which engaging teeth are formed, and the movable face gear is biased by the coil spring in a direction to mesh with the fixed face gear. 2. A magnetic head feeding mechanism according to claim 2, characterized in that: