JPS6147077B2 - - Google Patents

Description

[Detailed Description of the Invention] Conventionally, tape recorders have generally been driven by a method in which a single electric motor drives the capstan and reel stand, but in recent years, as the characteristics required by the market have improved, A plurality of electric motors for driving the reel stand are used for different functions, and so-called two-motor systems and three-motor systems are becoming more common. Looking at the mechanical mechanism of tape recorders, in order to improve cost and reliability, the transmission mechanism has been simplified, and belts, slip mechanisms, and speed reduction mechanisms have been avoided as much as possible. Therefore, the rotation speed of the motor for driving the reel stand will be as low as the reel stand rotation speed, so the cogging of the motor, which would not be a problem when the motor rotates at high speeds, will be directly transmitted to the reel stand. However, the conventional transmission mechanism has the drawback of poor wow and flutter characteristics. As a solution to this drawback, a coggingless electric motor such as a coreless or slotless motor is used. Reduce cogging as much as possible by adjusting the magnetization angle of the motor stator and increasing the number of poles of the rotor. If the cogging cannot be suppressed no matter what you do, it is unavoidable to add a deceleration mechanism,
Efforts have been made to increase the rotational speed of the electric motor for driving the reel stand, but no matter which method is used, the cost increases and it is by no means the best method.

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide a reel drive device for a tape recorder that can improve the wow and flutter characteristics of a reel stand even when using an electric motor having the same cogging as the conventional one.

The feature of the present invention is that the cogging frequency F of the reel stand is
The number of revolutions of the reel stand, the reduction ratio that reduces the number of revolutions of the motor, and the number _of poles of the motor were selected so that the resonant frequency F _T of _C and the cassette tape was such that F _C ≠ F T .

The present invention will be explained below with reference to illustrated embodiments. FIG. 1 shows the tape running system of a tape recorder. A tape 2 wound on a supply reel 1 is taken up through a running path of a guide roller 3, a head 4, a capstan 5, a pinch roller 6, and another guide roller 7. It is wound onto reel 8. Take-up reel 8
A reel stand 9 that rotates the reel stand 9 and an electric motor 1 for driving the reel stand
0, a pulley 11 and an idler pulley 12 are provided with deceleration means.

As shown in FIG. 2, the electric motor 10 for driving the reel stand is constituted by a small current motor with a core having a slot and a rotor 13 wound around a core having a plurality of salient poles 13a and a slot 13b. There is.

Next, the cogging frequency F _C generated in the reel stand when the reel stand is driven by the reel stand driving electric motor 10 can be obtained as follows: F _C = _NR ·α/60·2K (1).

In equation (1), N _R is the rotational speed of the take-up reel stand 9, α
is the reduction ratio when the rotation is transmitted from the reel stand driving electric motor 10 to the reel stand 9 via the pulley 11 and the idler pulley 12, and K is the reel stand driving electric motor 1
The number of salient poles 13a of the rotor 13 is 0. The rotational speed N _R is a rotational speed that constantly changes depending on the amount of tape being wound on the reel stand, that is, the diameter of the wound tape during the period from the start of tape winding to the end of winding. . For example, with commercially available cassette tape C-60 that lasts 30 minutes on one side, the rotation speed at the beginning of winding is approximately 42 rpm, but at the end of winding it is approximately
Changes to 18rpm. Therefore, the cogging frequency F
_C is constantly changing while the tape is being wound.

On the other hand, the cassette tape, in its running route,
It has many vibration types, and as a result of experimental confirmation, it is known that a resonance point exists at a resonance frequency F _T of 12 to 14 Hz. This resonant frequency is a value unique to each tape and does not change while the tape is running.

Next, a numerical example will be shown when the reduction ratio α and the number of poles K are selected so that the cogging frequency F _C satisfies F _C ≠ F _T. When the tape is run at 4.76 cm/sec, the cogging frequency F _C of the reel stand at the beginning of winding is obtained from the above equation (1), F _C = N _R・α/60・2K=42×2.7/60×2 ×
3=11.34 Cogging frequency of the reel stand at the end of winding F _C
is F _C =18×2.7/60×2×3=4.86, and the cogging frequency F _C of the reel stand changes from 11.34 Hz to 4.86 Hz while the tape is running. However, since this cogging frequency F _C is always deviated from the cassette tape's resonant frequency of 12 Hz to 14 Hz, the two do not resonate, and the wow and flutter characteristics do not deteriorate. FIG. 3 shows this state using measured values, and the wow and flutter always shows a low value.

Next, to show the case where the number of selections is bad and F _C = F _T , α
=5, K=3, the cogging frequency F _C of the reel stand at the beginning of winding is F _C =42×5/60×2×3=21 The cogging frequency F _C of the reel stand at the end of winding
becomes F _C =18×5/60×2×3=9. Therefore, since the cogging frequency F _C of the reel stand changes from 21Hz to 9Hz while the tape is running, there will always be a point in the middle of tape winding where it will be the same as the resonance frequency of the cassette tape, causing resonance at that point and worsening the wow and flutter characteristics. do. FIG. 4 shows this state, and it can be seen that the wow and flutter characteristics deteriorate in a period of about 10 minutes after the start of winding, and even after that, the values are higher than in FIG. 3.

Figure 5 shows the relationship between the reduction ratio α, the cogging frequency F _C of the reel stand, and the resonant frequency F _T of the cassette tape, where straight line A indicates the beginning of tape winding, that is, when the reel stand speed is 42 rpm, and straight line B is the end of tape winding, that is, the reel speed is 18 rpm
It shows the state when . two parallel lines C, C
The region is the resonant frequency F _C band. The two-dot chain line D shows the cogging frequency line range when the selected value example is good, and the two-dot chain line E shows the cogging frequency range when the selected value example is bad.

From the selection value example of the reduction ratio α and the number of poles K and FIG. 5, if the reduction ratio _α is constant, the cogging frequency F of the reel stand will change as the tape runs.
_C becomes smaller. Therefore, when using cassette tape C-60 and the number of poles K = 3, the reduction ratio α at the beginning of winding is F _C = 12 = 42 × α / 60 × 2 × 3, so α = 2.86 Reduction ratio at the end of winding α becomes α=7.78 from F _C =14=18×α/60×2×3, and if the reduction ratio α is chosen to be less than 2.86 or more than 7.78, any cassette can be used as long as the cassette tape is wound at 4.75 cm/sec. Even with Tape C-60, the cogging frequency of the reel stand is never the same as the resonant frequency of the cassette tape, and since the two do not resonate, the wow and flutter characteristics do not deteriorate.

In the above explanation, the cassette tape is commercially available C-
If the tape winding diameter is smaller than C-60 like 45, the rotational speed of the reel stand will also be faster at the end of winding.
Since the value is larger than 18 rpm, the optimum value will be different. Similarly, the tape speed is 4.76cm/
It is different if it is not sec but 2.4cm/sec or 9.5cm/sec,
The optimum state can be found by selecting the rotational speed N _R of the reel stand, the optimum reduction ratio α and the number of poles K for this rotational speed using the above equation (1). In the case of other large cassette halves or small cassette halves, the resonance frequency of the cassette tape is different, so the cogging frequency, reduction ratio, and number of poles may be selected in accordance with these values.

Since the present invention is configured as described above, even if a motor with cogging is used, characteristics equivalent to those using a non-cogging motor can be obtained, and the cost is reduced from about 70% to 50% compared to using a non-cogging motor. can do. Furthermore, even if there is some cogging, there is no need to increase the number of rotor poles or add a speed reduction mechanism, and it is possible to obtain a tape recorder reel drive device that exhibits excellent effects such as large manufacturing and cost advantages.

[Brief explanation of the drawing]

The drawings show an embodiment of a reel drive device for a tape recorder according to the present invention, FIG. 1 is an explanatory diagram of a tape running system of a tape recorder, FIG. 2 is an explanatory diagram of a rotor,
Figure 3 is a wow and flutter characteristic diagram when each constant value selection is good, Figure 4 is a wow and flutter characteristic diagram when each constant value selection is poor, and Figure 5 is the reduction ratio, cogging frequency of the reel stand, and resonance frequency of the cassette tape. FIG. 1... Supply reel, 2... Tape, 8... Take-up reel, 9... Reel stand, 10... Reel stand driving motor (small electric motor with commutator), 11...
Pulley, 12... Idler pulley, 13... Rotor, 13a... Salient pole, 13b... Slot, F _C
... Cogging frequency of the reel stand, F _T ... Resonance frequency of the cassette tape, α ... Reduction ratio, N _R ...
Rotation speed of the reel stand, K...number of poles.

Claims (1)

[Scope of Claims] 1. A motor with a core and a small commutator having a slot, means for reducing the rotational speed of the motor, and a reel stand that rotates while being decelerated by the means, the rotation of the reel stand being reduced by the means. If the number is N _R , the reduction ratio of the speed reduction means is α, the number of poles of the motor is K, and the cogging frequency of the reel stand is F _C , the value shown as F _C =N _R・α/60・2K is the value of the cassette tape. A reel drive device for a tape recorder in which each of the above constants is set so that, when the resonance frequency is F _T , F _C ≠ F _T .