JPH08115546A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE: To make tape touch good to a head at the time of fast reverse reproducing by providing a 1st reel base equipped with a clutch mechanism of dependence on speed and a 2nd reel base equipped with a clutch mechanism of independence of speed. CONSTITUTION: When the T-side reel base 3 is to rotate counterclockwise in an REV mode, a brake is applied to lock a reel gear 3a, and when the reel base 3 is rotate clockwise at the time of a play or a fast forward reproducing mode, the brake is released so that the rotation of the reel gear 3a can not be prevented. Driving force is transmitted by a driving system in the REV mode via a rotor gear of a capstan motor, a driving gear, its coaxially integrated driving pulley, a timing belt 12, a driven pulley 13, its coaxially integrated driven gear 13a, an indler gear 14, a reel gear 2a and a belt 2c to the S-side reel base 2. Thus, the tape touch to the head at the REV time is improved, and miniaturization of a capstan and stabilization of tape traveling are attained, thus achieving high performance of the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus provided with different clutch mechanisms on both reel stands.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus such as a video tape recorder (hereinafter referred to as VTR) or a digital audio tape recorder (hereinafter referred to as DAT), as shown in FIG. The rotation of the capstan motor 1 (or the reel dedicated motor) is transmitted to the reel base 2 and the take-up side (hereinafter referred to as the T side) reel base 3 by the rotation of the idler gear mechanism 13. It is generally carried out through. Here, each reel stand 2, 3
Is equipped with a clutch mechanism whose rotation speed changes according to the winding diameter of the tape. A felt clutch type and a magnet clutch type are typical as the clutch mechanism, and the clutch mechanism is incorporated in a reel base or an intermediate gear meshing with the reel base gear.

FIG. 4 shows a felt clutch type reel stand, and FIG.
A sectional view of the magnetic clutch type reel stand is shown in FIG. The felt clutch type reel stand has the most basic structure,
It is inexpensive and lightweight and is widely used.
On the other hand, the magnetic clutch type reel stand has a non-contact structure in which the magnet 3c and the hysteresis plate 3d are combined in the clutch mechanism part, and the structure is a little complicated, but excellent in torque stability and durability, and Used for purposes.

Considering the operation during reverse fast-forward reproduction (hereinafter referred to as REV), there is a method of using a dedicated REV brake as a method of giving a tape back tension at the time of REV. In DAT, a method of locking the T-side reel stand 3 and substituting the slip torque generated in the clutch mechanism is often used. By the way, the tape back tension T for the reel stand is determined by a value T = Q / r obtained by dividing the reel stand slip torque Q by the tape winding radius r (FIG. 6).
reference).

[0005]

Focusing on the tape back tension T of the reel base in the above-mentioned felt clutch type and magnet clutch type, first, when the felt clutch type reel base is adopted, the torque depends on the speed. , When the tape winding diameter is large and the rotation speed is small,
That is, the slip torque becomes small at the beginning of tape winding, and becomes large when the tape winding diameter is small and the number of rotations is large, that is, at the end of tape winding. Therefore, Tmin = Qmin / rmax, Tmax = Qmax / rmin
Becomes

This indicates that Tmax >> Tmin, and the tape back tension becomes very large when the tape winding diameter is small, which causes an increase in power consumption of the capster motor and a tape damage due to the tension difference. It has become.

When the magnet clutch type reel stand is adopted, the torque is constant regardless of the speed, so the tension difference depending on the winding diameter is small, but the torque on the S side reel stand is also constant regardless of the speed. That is, there is a drawback that the tape tension near the cylinder at the beginning of tape winding in the REV mode becomes small, the contact between the tape and the head deteriorates, and it becomes difficult to obtain a good reproduction envelope.

[0008]

In the present invention, therefore, a speed-dependent felt clutch mechanism is used for the supply-side reel stand and a speed-independent magnet clutch mechanism is used for the take-up reel stand. This improves the contact between the tape and the magnetic head in the reverse fast-forward reproduction (review) mode.

[0009]

With the above structure, the head touch on the tape is improved even during REV, and a good reproduction envelope can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of both reel stands, FIG. 2 is a plan view in REV mode, and FIG. 3 is a diagram showing the speed dependence of slip torque. In addition, the feature of this plan is that
This is because a "felt clutch type reel mechanism having torque speed dependency" is adopted as the S-side reel base mechanism, and a "magnet clutch type mechanism having torque independent speed" is adopted as the T-side reel base mechanism.

1 and 2, 1 is a capstan motor having a rotor gear 1a on the outer periphery and a capstan shaft 1b at the center, 2 is an S side reel stand, 3 is a T side reel stand, 4
Is a cylinder, 5 and 6 are inclined guides, 7 is a pinch roller,
8 is a chassis, 9 is a tape, and 10 is a one-way clutch brake. When the T-side reel stand 3 tries to rotate counterclockwise (hereinafter referred to as CCW) in REV mode, a brake is applied to lock the reel gear 3a. However, when the reel base 3 rotates in the clockwise direction (hereinafter, referred to as CW) in the PLAY and fast forward reproduction (CUE) modes, the brake is released, and the rotation of the reel gear 3a is not hindered.
The one-way clutch brake is functionally the same as that described in Japanese Patent Laid-Open No. 64-86351.

The drive system in the REV mode includes a rotor gear 1a of the capstan motor 1, a drive gear 11a, a coaxial drive pulley 11, a timing belt 12, a driven pulley 13, a coaxial drive gear 13a, and an idler gear 14.
It is transmitted to the reel stand 2 via the reel gear 2a and the felt 2c.

As shown in FIG. 1, the S-side reel stand 2 has a felt clutch in the S-side reel stand 2. A felt 2c is attached to the reel base flange 2b, and the reel gear 2a, which makes surface contact with and slides on the felt 2c, is pressed downward so that a predetermined slip torque is generated by the compression spring 2d via the washer 2e. It is energized. When the reel gear 2a rotates, parts other than the reel gear 2a rotate integrally via the felt clutch mechanism, and the wing 2f engaging with the hub (not shown) of the cassette winds up the tape. The reel base 2 is press-fitted into the reel base flange 2b, and the wings 2f are press-fitted into the reel base 2 so as to be integrated, and the shaft 8a is rotatable.

The T-side reel stand 3 has a magnet clutch in the reel third. Reel stand boss 3
A yoke plate 3e is fixed to b, and a magnet 3c is stuck to the yoke plate 3e. Reel gear 3a
A hysteresis plate 3d is embedded in the magnet 3c.
It becomes a non-contact clutch mechanism by the suction force between and. The reel gear 3 is provided with a slight gap in order to obtain a predetermined slip torque and to make it non-contact, without the magnet 3c and the hysteresis plate 3d sticking to each other.
The boss 3a 'of a and the reel stand boss 3b are the washers 3g.
Are in sliding contact with each other. Wings 3f are press-fitted onto the upper portion of the reel stand 3. The reel base 3 is also rotatable on the shaft 8b on the chassis 8.

Here, the speed dependence of the torque of the felt clutch type and the magnet clutch type will be described. As shown in the measured values in FIG. 3, the felt clutch type torque has speed dependency, that is, even if the slip torque increases as the speed increases, the magnet clutch type torque does not have speed dependency. .

The reason why the felt clutch type has speed dependency is that the reel gear 2a, which is a counterpart member of the felt 2c.
Is a resin material such as polyacetal, which is a soft material together with the felt, and thus has a feature that the friction coefficient μ increases as the sliding speed increases. The reason why the friction coefficient increases has not yet been clearly theorized, but the shear stress generated on the slip surface, which causes friction, increases in proportion to the sliding speed due to the effect of viscous flow. The theory that is said is influential.

On the other hand, the magnetic clutch type does not have speed dependence because it is non-contact. Strictly speaking, the boss portion 3a ′ of the reel gear 3a and the reel base boss 3b shown in FIG. 1 are in surface contact with each other in the circumferential direction and are in sliding contact with each other through the washer 3g in the axial direction. It is almost negligible because the device such as applying a lubricating oil is elaborated to remove it.

Next, the tape tension condition for smoothly operating the REV mode in the small mechanism will be described. In the tape running system shown in FIG. 2, the tape tension between the S-side reel stand 2 and the entrance side tilt guide 5 is T1, the tape tension between the exit side tilt guide 6 and the capstan shaft 1b is T2, and the capstan shaft 1b and T. The tape tension between the side reel bases 3 is T3. In reality, the S side reel stand 2
There is another guide or a plurality of guides between the inclining guide 5 and the inclining guide 5, the inclining guide 6 and the capstan shaft 1b, and between the capstan shaft 1b and the T-side reel stand 3. However, since they are rotation guides and the load applied to the tape is small, they can be ignored when discussing the tape tension in the present invention, and therefore the drawings and the description thereof are omitted.

Preferred conditions in the REV mode include the following three items.

[0020] For the convenience of tape running, T1> T2 and T3 ≧ T2.

[0021]. T2 is large because of the contact between the head and tape (head touch).

.. Due to the miniaturization of the capstan shaft, T3
Is small. Is. On the other hand, and are contradictory conditions.

FIG. 3 is a graph showing the speed dependence of the felt clutch type and magnet clutch type reel stand of the present invention. For example, when the tape winding diameter variation range of the small cassette is the minimum winding diameter φ11.7 mm to the maximum winding diameter φ29 mm and the tape speed is 18831 mm / s, the number of rotations of the reel bases 2 and 3 is 30.6 to 12 in the PLAY mode. .6 rpm
Becomes However, in the PLAY mode, the S-side reel base 2 rotates integrally without slipping, but the T-side reel base 3 has a clutch mechanism.

Rotational speed of reel stand 30.6 to 12.6 rpm
In order to cope with the above, the reel gear 3a must rotate at a higher rotation speed. In the mechanism of the present invention shown in FIG. 2, the rotation speed of the reel gear 3a is designed to be 35.6 rpm. Therefore, the slip rotation speed of the clutch portion is 35.6- (30.6 to 12.6) = 5 to 2
It is 3 rpm. Since the transmission system of the S-side reel stand 2 is also the same, the slip rotation speed is 5 to 23 at the 1x REV.
rpm.

The minimum necessary value of the slip torque generated in the clutch portion of the T-side reel stand 3 is a torque value at which the tape can be smoothly wound during PLAY, and when the slip rotation speed is 5 rpm, which is the most disadvantageous situation. In addition, it is designed to be 9 grcm. This is always 9 gcm in the "magnet clutch type without torque speed dependence" adopted in the T-side reel stand 3 in the present invention, and changes depending on the number of rotations in the "felt clutch type with torque speed dependence", It means that it will be 9 grcm or more.

The minimum necessary value of the slip torque generated in the clutch portion of the S-side reel stand 2 is a value at which the tape can be smoothly wound during REV, and is designed by design to be 13 grcm. Since this mechanism uses a 16x REV, the slip speed of the clutch part is 16 x
(5-23) rpm, that is, 80-368 rpm. In the "felt clutch type with torque speed dependency" adopted for the S-side reel stand 2 in the present invention, the design is determined to be 13 grcm at 80 rpm, which is the most disadvantageous situation. At this time, when the reel gear 3a is rotationally locked by the one-way clutch brake, the slip rotation speed of the T-side reel stand 3 is 16 × (30.6 to 12.6) r.
pm, that is, 490 to 202 rpm. From the speed dependence of the torque shown in FIG. 3, the slip torque at the clutch part slip rotation speed in the mechanism of the present invention is summarized as shown in Table 1.

[0027]

[Table 1]

Further, as shown in FIG. 6, the value obtained by dividing the slip torque Q by the tape winding diameter r is the tape tension T, which is shown in Table 2.

[0029]

[Table 2]

The tape tension on the S side at REV is T1 as shown in FIG. 2, and the tape tension on the T side is T3. T2 is determined by the friction between the tape on the entrance side tilt guide 5, the cylinder 4, and the exit side tilt guide 6 and the tape tension on the T side T3. With this mechanism, T2 = T1 / 3.6 both in terms of design and actual measurement. Table 3 shows the change values of T1, T2, and T3 according to the type of clutch.

[0031]

[Table 3]

Therefore, when the preferable conditions of the REV described above are evaluated relative to each other, the combination of the S-side reel stand 2 of the present invention of the felt clutch type and the T-side reel stand 3 of the magnet clutch type is totally obtained. It is well balanced and clearly superior.

In the present embodiment, the 16-speed REV is taken as an example, but the effect of the present invention becomes more remarkable as the double speed increases. Further, as an example of the method of locking the T-side reel stand 3 by using the one-way clutch brake, the use of the one-way clutch brake is not necessarily a prerequisite of the present invention, and the hard gear brakes the reel gear of the T-side reel stand 3. 3a may be locked.

[0034]

According to the present invention, reverse fast forward reproduction (REV) is performed.
At this time, the conditions for good tape touch to the head, miniaturization of the capstan, and stable tape running are satisfied, and miniaturization and high performance of the device can be achieved. In addition, for the frequently used recording / playback mode, a magnetic clutch type with excellent durability is adopted as the clutch mechanism of the winding side reel stand, and for the REV mode that is rarely used, the supply side reel As the clutch mechanism of the stand,
By adopting a lightweight and inexpensive felt clutch type, it is possible to design a device with high cost performance.

As can be seen from the embodiment, the required slip torque of the take-up reel stand is usually smaller than the required slip torque of the supply reel stand, so that the magnet used can be made smaller, that is, lighter. Alternatively, a magnet having a weak magnetic force can be adopted, and an inexpensive magnet such as ferrite can be adopted. Further, since the take-up reel stand has no speed dependence of torque, the lock torque of the one-way clutch brake can be made small (in the embodiment of the present invention, a value exceeding 9 grcm is sufficient). This means that the strength of the brake mechanism can be reduced, and the structure can be simplified.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of both reel stands.

FIG. 2 is a plan view in REV mode.

FIG. 3 is a diagram showing speed dependence of slip torque of a felt clutch type reel stand.

FIG. 4 is a cross-sectional view of a felt clutch type reel stand.

FIG. 5 is a cross-sectional view of a magnet clutch type reel stand.

FIG. 6 is a schematic diagram showing the relationship between slip torque and tape tension.

[Explanation of symbols]

 2 Supply side reel stand (first reel stand) 2e Felt 3 Winding side reel stand (second reel stand) 3c Magnet

Claims (3)

[Claims] 1. A magnetic recording / reproducing apparatus comprising a first reel stand having a speed-dependent clutch mechanism and a second reel stand having a speed-independent clutch mechanism. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the first reel stand is a supply-side reel stand and the second reel stand is a take-up reel stand. 3. The magnetic recording / reproducing apparatus according to claim 1, wherein the first reel base is a felt clutch mechanism, and the second reel base is a magnet clutch mechanism.