JPH0579713U - Cam groove and magnetic recording / reproducing apparatus using the same - Google Patents

Abstract

(57) [Summary] [Purpose] To make it possible to easily and quickly cut a cam groove with high dimensional accuracy and good surface roughness, and to reduce damage to the cutter. Further, by using such a cam groove, play (rattle) of the head portion during helical scanning is reduced. [Structure] A groove surface 1a against which a ball contact of the cam groove 1 abuts
Are two included angles θ ₁ and θ ₂ with a narrow bottom side and a wide opening side.
After machining the V-shaped groove on the bottom side with a narrow angle, it is possible to machine the V-shaped groove on the opening side with a wide angle. Enables precise cam groove machining.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improved cam groove structure and a magnetic recording / reproducing apparatus using the cam groove. More specifically, the present invention is applicable to a helical scan type magnetic recording / reproducing apparatus such as a VTR (video tape recorder) or a DAT (digital audio tape recorder) which performs a helical scan by a helical traveling of a head without twisting a magnetic tape. The present invention relates to a cam groove used in a cam mechanism or the like that gives axial displacement to the head for helical traveling.

[0002]

[Prior Art]

 The conventional helical scan type magnetic recording / reproducing device used for VTRs and DATs is installed with some guide posts and drums tilted to the reference plane of the chassis or other component that is the mounting partner, and the tape is wound diagonally around the drums. Helical scanning recording / playback is performed by moving the vehicle in three dimensions. Then, the running position (height) of the tape was mechanically and forcibly regulated by a regulating flange provided on each post and a lead of the drum.

However, when the tape is twisted three-dimensionally by an inclined post or drum and the position of the tape is regulated by the flange of the post or the lead of the drum, the tension in the tape width direction becomes not constant, When the winding irregularity of the tape supply reel is large, non-linear friction is likely to occur at the regulated edge portion. As a result, the running of the tape becomes unstable, which may cause jitter or damage the tape edge. This phenomenon became more noticeable as the tape became thinner, and some tapes could not run. Further, this method has a limit in reducing the thickness of the entire device.

Therefore, the applicant of the present invention forms a slit 104 obliquely intersecting the rotation shaft 103 between the upper drum 101 and the lower drum 102 as shown in FIGS. A helical scan type magnetic recording / reproducing device of a VTR (so-called rotary head device) provided so that the head 105 is rotationally moved inside is proposed (Japanese Patent Application No. 1-5210-4). This rotary head device supports a head 105 movably in the drum axial direction by a linear guide 106 attached to a rotary shaft 103, and an annular cam 107 that gives the head 105 the same axial displacement as the slit 104. The rotary shaft 103 is arranged in the center, and the head 105 is rotated together with the linear guide 106 in accordance with the rotation of the rotary shaft 103, and the cam 107 reciprocates in the axial direction to rotate the head 105 along the slit 104. I have to. Here, a ball 108 is used as a contactor on the side of the linear guide 106 that supports the head 105, and is provided so that sliding on the cam 107 can be performed smoothly.

However, since the ball attached to the tip of the linear guide 106 side and constantly pressed against the cam 107 includes a force to move in the tangential direction as well as the rotating direction, the ball on the cam 107 moves. There is a risk that unstable movement such as wobbling may be caused and scanning accuracy may be reduced. Therefore, it has been considered to form a V-shaped groove for receiving the ball on the cam 107 and move the ball in this groove.

Here, conventionally, the V-shaped cam groove is generally one as shown in FIGS. 7A and 7B. The groove 109 shown in (A) is cut by, for example, a cutting tool. The groove 109 shown in (B) is formed by cutting the rectangular groove 110 at the bottom with, for example, a thin blade bit, and then widening the groove with a V-shaped bit to finish only the slope contacted by the ball. ..

[0007]

[Problems to be solved by the device]

 However, in the case of the groove of FIG. 7 (A), since there is no escape of the tip of the cutting tool, the cutting resistance becomes large and so-called chatter occurs on the cutting surface, so that there is a problem that the dimensional accuracy decreases and the surface roughness also becomes rough. However, it is unsuitable to be applied to a cam for helically scanning the head in a rotary head device such as a VTR or DAT that requires accuracy in the order of μm.

Further, in the case of the groove of FIG. 7B, since the deep and narrow groove 110 has to be cut, the cutter is easily broken and the cutting process is not easy. In order to proceed with cutting so as not to cause breakage of the cutter, it is necessary to significantly slow down the processing speed and feed, which causes a problem of extra work time.

An object of the present invention is to provide a cam groove that can be easily and quickly cut, has less damage to the cutter, has high dimensional accuracy, and has good surface roughness. It is another object of the present invention to provide a magnetic recording / reproducing apparatus which has a small play (rattle) at the head portion and is capable of accurate helical scanning.

[0010]

[Means for Solving the Problems]

 In order to achieve such an object, the cam groove of the present invention is configured such that the groove surface for contacting the ball contact member is formed by two slopes having a small included angle on the bottom side and a large included angle on the opening side. Further, preferably, the cam groove of the present invention is finished only on the slope near the opening.

Further, in the magnetic recording / reproducing apparatus of the present invention, a slit obliquely intersecting the axial center lines of the fixed upper drum and the fixed lower drum is provided between the fixed upper drum and the fixed lower drum. In a magnetic recording / reproducing apparatus for forming a helical track pattern on a tape running on a drum by rotating so as to be oblique to the axis center line, a rotating body which rotates about the axis center line of the drum. A cam mechanism that applies the same axial displacement as the slit to the head mounted via the linear guide slidable in the axial direction.

[0012]

[Action]

 Therefore, if a V-shaped groove with a wide angle is processed after processing a V-shaped groove with a narrow angle, the tip of the cutting tool that processes a wide V-shaped groove will fit into the groove with a narrow angle and will not receive cutting resistance, and the ball will Only the contacting slope part can be finished with precision by reducing the cutting resistance.

Further, according to the magnetic recording / reproducing apparatus that uses the cam groove to give the axial displacement to the rotating head, the cam groove gives the precise displacement while keeping the follower on the head side without rattling. ..

[0014]

【Example】

 Hereinafter, the configuration of the present invention will be described in detail based on the embodiments shown in the drawings. It should be noted that this embodiment is a case where the rotary head is applied to a cam mechanism for causing the head to perform a helical scan.

FIG. 2 shows an example of a rotary head to which the cam groove of the present invention is applied. In this rotary head device, a fixed upper drum 2 and a fixed lower drum 3 are arranged concentrically with an axis perpendicular to the rotary head mounting surface, for example, a drum shaft 6, and a head 4 is rotationally moved between them. A head 5 is mounted on a rotating body 7 that rotates around a drum shaft 6 via a linear guide 8 and the linear guide 8 is mechanically moved up and down in the width direction of the tape by a cam groove 1. Thus, the tape wound around the drums 2 and 3 and running parallel to the mounting surface of the rotary head is helically scanned.

The rotating body 7 is rotatably attached to a drum shaft 6 which is fixed to the center of the fixed lower drum 3 and is perpendicular to a reference plane, via radial bearings 9, 9. Between the rotating body 7 and the drum shaft 6, transformer coils are embedded in the outer peripheral surface of the transformer ring 10 fixed to the drum shaft 6 and the inner peripheral surface of the rotating body 7 facing the transformer ring 10, respectively. The transformer 11 is configured. Further, the stator coil 12 is provided on the drum shaft 6, and the rotor magnet 13 is provided on the rotating body 7, so that the drive motor 14 is configured.

A linear guide 8 that slides in the generatrix direction parallel to the center of rotation is attached to the rotating body 7. This linear guide 8 is, for example, a fixed holder member 8a having a guide groove formed in the generatrix direction of the rotating body 7 and a projection which is fitted in the groove of the holder member 8a and is slidable in the generatrix direction of the rotating body 7. The sliding member 8b has a linear ball bearing interposed between the sliding member 8b and the sliding member 8b, and the structure has no rattling in the rotating direction of the rotating body 7. The head 4 is mounted on the head base and is attached to the sliding member 8b of the linear guide 8 so as to project from the slit 5 toward the outer peripheral surface side of the drums 2, 3. Further, a ball contact 15 as a follower that constitutes a cam mechanism is attached to the linear guide 8 so as to project in the radial direction of the rotating body 7. For example, the ball contactor 15 is held by a holder 17 containing a spring 16 that applies a biasing force toward the cam groove 1. Further, in the case of the present embodiment, the cam is composed of a V-shaped groove 1 provided on the peripheral surface of a fixed cylinder, for example, the inner peripheral surface of the fixed lower drum 3, so that the desired axial displacement of the linear guide 8 can be obtained. It is given to the sliding member 8b.

With the above-described configuration, when the rotating body 7 supported by the drum shaft 6 is rotated by the drive motor 14, the linear guide 8 integrated with the rotating body 7 moves around the drum shaft 6 as a center. Rotate around the drum center. At the same time, since the sliding member 8b of the linear guide 8 is engaged with the cam groove 1 via the ball contactor 15, the sliding member 8b is moved up and down by following the cam groove 1 to move the head 4 in the axial direction. Gives the displacement of. Therefore, the head 4 realizes a helical scan along the slit 5.

FIG. 3 shows another embodiment. In this embodiment, an external motor is used to rotate the head 4. For example, a cam groove 1 is formed on the inner peripheral surface of one of the fixed upper drums 2, and a linear guide is provided on a rotary shaft 20 rotated by the external motor. 8 is attached. The rotary shaft 20 is rotatably supported by the fixed lower drum 3, and a fixing disk 21 is press-fitted on the upper end side thereof. The rotary transformer 11 is formed between the fixing disk 21 and the lower drum 3. A linear guide 8 is attached to the fixing disk 21, and a ball contact 15 and a head 4 are attached to a sliding member 8b of the linear guide 8.

FIG. 4 shows another embodiment. In this embodiment, an external motor is used to rotate the head. A fixed cylinder 30 having a cam groove 1 is provided inside the fixed drum 3 and a ball contactor 15 is located outside the fixed cylinder 30. The linear guide 8 is arranged in this manner. The linear guide 8 is attached to a disk 21 fixed to a rotary shaft 20 that is rotated by an external motor. The fixed cylinder 30 forming the cam groove 1 is arranged concentrically with the fixed lower drum 3 and fixed to the lower drum 3.

As shown in FIG. 1, the cam groove 1 used in each of the above-described embodiments has two included angles θ included in different sizes.₁, Θ₂The V-shape is composed of the slopes that compose the. This included angle θ₁, Θ ₂ Is bisected in the groove direction of the cam groove 1. Cam groove 1 has an included angle θ on the bottom side ₁ Is narrow and the included angle θ on the opening side₂Is set wide, and at least the slope 1a on the opening side is finished with a required roughness accuracy. For example, in the present embodiment, the angle θ on the bottom side is not particularly limited.₁Is about 76 ° ± 1 °, the included angle θ on the opening side₂Is formed at about 90 ° ± 4 '. The cam groove 1 has a narrow angle θ of, for example, about 76 °.₁Cutting or rough finishing by cutting, and then a wide angle θ of about 90 °₂Then, the slope 1a is finished by grinding. In order to improve dimensional accuracy and surface roughness, when using a material with good workability, such as aluminum or brass, wear resistance and lubricity of the surface of the cam groove 1, especially the slope 1a In order to improve the quality, surface treatment such as Ni-P-BN plating is appropriately applied as necessary.

[0022]

[Effect of the device]

 As is clear from the above description, in the cam groove of the present invention, the groove surface that abuts the ball contact is made up of an inclined surface composed of two included angles with a small included angle on the bottom side and a large included angle on the opening side. Therefore, if a V-shaped groove with a narrow angle is machined and then a V-shaped groove with a wide angle is machined, the tip of the cutting tool that processes a wide V-shaped groove will fit into the groove with a narrow angle and will not be subject to cutting resistance. For this reason, only the V-shaped cutter can be used to precisely finish only the beveled surface on which the ball hits without causing chattering on the groove surface, without using a cutter that has a rectangular cutting edge and is thin and easily broken. ..

Further, when the head of the magnetic recording / reproducing apparatus is made to perform a helical scan in this cam groove, the follower / ball contact is held by the V-shaped groove so that movement in a direction other than the rotational direction is restricted. As a result, the ball contactor, and thus the head, are prevented from unstable movements and the scanning accuracy is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a cam groove of the present invention.

FIG. 2 is a central longitudinal sectional view showing an example of a magnetic recording / reproducing apparatus to which the cam groove of the present invention is applied.

FIG. 3 is a central longitudinal sectional view showing another embodiment of the magnetic recording / reproducing apparatus to which the cam groove of the present invention is applied.

FIG. 4 is a central longitudinal sectional view showing still another embodiment of the magnetic recording / reproducing apparatus to which the cam groove of the present invention is applied.

FIG. 5 is an explanatory diagram showing an outline of a helical scan type magnetic recording / reproducing apparatus using a cam.

6 is a central longitudinal sectional view showing the structure of the magnetic recording / reproducing apparatus of FIG.

FIG. 7 is a diagram showing a conventional cam groove shape.

[Explanation of symbols]

1 Cam groove 1a Slope θ ₁ Narrower included angle θ ₂ Wider included angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichitoshi Muto 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the broadcasting technology research institute of Japan Broadcasting Corporation (72) Inventor Tsunegen Hashizume 5329 Shimosuwa-cho, Suwa-gun, Nagano Prefecture Sankyo Seiki Co., Ltd.

Claims (3)

[Scope of utility model registration request] 1. A cam groove having a V-shaped groove formed in contact with a ball contactor, the V-shaped groove having two included angles having a small included angle on the bottom side and a large included angle on the opening side. 2. The cam groove according to claim 1, wherein only the inclined surface near the opening is finished. 3. A slit obliquely intersecting the axial center lines of the fixed upper drum and the fixed lower drum is provided between the fixed upper drum and the fixed lower drum so that the head is diagonally intersected with the axial center line in the slit. In a magnetic recording / reproducing apparatus that forms a helical track pattern on a tape that is rotated and runs on a drum, a linear guide that is slidable in the axial direction is provided on a rotating body that rotates about an axis center line of the drum. 2. A magnetic recording / reproducing apparatus comprising a cam groove according to claim 1, which is a cam mechanism that gives a head mounted via the same axial displacement as the slit.