JPS59193522A - Drum for video tape recorder - Google Patents

Abstract

PURPOSE:To eliminate the need for attachment of aheater and to miniaturize a drum for video tape recorder by using a coil contained in a direct drive type motor as a heater as well. CONSTITUTION:A drum is constituted with a monolithic structure of an upper drum 1, a lower drum 2 and a motor 5. The motor 5 contains a stator coil 6 and a rotary magnet 7. This motor 5 of a direct drive type drum is not generally energized when the operation of a video tape recorder is stopped since it is originally intended to revolve the drum 1. While, the coil 6 can be energized even when the operation of the video tape recorder is stopped and can generate heat. Thus the coil 6 can substitute a conventional heater 3. Furthermore the coil 6 has a large surface area and can heat up quickly the entire part of the drum in comparison with the heater 3. Then the coil 6 can defrost more quickly than the heater 3 when the condensation is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drum for a video tape recorder, and more particularly to an improvement in heater means for preventing dew condensation.

If the video tape recorder is suddenly moved outdoors or from a cold room to a cold room, immediately after a cold room has been heated suddenly, or if it is used in a humid place, condensation or frost may form around the drum, causing may stick to the surface of the drum and damage the tape. For this reason, conventionally, a heater made of, for example, a positive coefficient thermistor has been attached to the fixed portion of the drum. An example of this will be explained with reference to FIG. 1. 1 is an upper drum (rotating drum), 2 is a lower drum (fixed drum), and a heater 3 is fixed to this lower drum 2 with screws 4.

Such a heater 3 is always energized, and the heat generated by the heater 3 raises the temperature of the entire drum, causing dew condensation, and when dew condensation occurs, the dew can be quickly removed.

As described above, in the conventional apparatus, the purpose has been achieved to some extent by attaching the heater to the fixed part of the drum. However, in recent years, there has been a demand for downsizing of video tape recorders, and along with this, it has become necessary to downsize the drum as well. This imposes restrictions on the part to which the heater can be attached, and it has even become impossible to find a part on the drum to which the heater can be attached. There are cases where it is unavoidable to indirectly attach the heater to other parts attached to the drum (for example, various fixtures), but in this case, the effect of the heater is reduced,
I don't like it very much. Furthermore, since the degree of freedom in the mounting location of the heater is reduced, there is also the disadvantage that ease of installation is sacrificed.

This invention was made in order to eliminate the drawbacks of the conventional motors as described above. When the drum of the rotating head is driven by a direct drive method, this direct drive motor has a built-in coil. In view of this, an object of the present invention is to provide a drum for a videotape recorder that eliminates the need to attach a heater to the outside of the drum by using this coil as a heating element.

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

FIG. 2 shows a cross-sectional view of an example of the structure of a direct drive type drum.

In FIG. 2, the upper drum 1 and the lower drum 2 are
It is similar to the figure. 5 is a motor, and the upper drum 1, the lower drum 2, and this motor 5 together constitute a drum. The motor 5 includes a stator coil 6 and a rotor magnet 7. In this example, the stator coil 6 is attached to the lower drum 2 side, the rotor magnet 7 is attached to the rotating shaft 8, and the rotor magnet 7 is connected to the upper drum via the rotating shaft 8. Rotation is transmitted to 1.

Originally, the motor 5 of the direct drive type drum was
Since its purpose is to rotate the upper drum 1, it is generally not energized when the video tape recorder is stopped. However, since the stator coil 6 is wired even in such a stopped state, it generates heat when energized and can function in place of the conventional heater 3 (FIG. 1). Furthermore, since the stator coil 6 has a larger surface area than the heater 3 shown in FIG. It has the advantage of being tidy.

However, if the stator coil 6 is simply energized, the upper drum 1 will rotate. Even in this case, it is effective as a heater, but if the drum continues to rotate even when the operation is stopped, it is not favorable for the life of the drum.
Therefore, it is preferable that the drum not be rotated while the operation is stopped. Therefore, the following method is available as a method for preventing the drum from rotating while the operation is stopped.

The first step is to lower the voltage supplied to the motor 5.

That is, if a voltage is applied to the stator coil 6 while the operation is stopped so that the starting torque of the motor 5 is smaller than the rotational load of the drum, the stator coil 6 generates heat and acts as a heater. Since it does not rotate, adverse effects on the lifespan are prevented.

Further, as a direct drive type motor, the use of a transistor motor has become common. In the case of a transistor motor, a position sensor such as a Hall element is used, and if this operation is stopped, the motor 5 will not rotate even though it is energized. That is, when the video tape recorder is in operation, the position sensor is normally operated to rotate the drum, and when the video tape recorder is stopped, the operation of the position sensor is stopped while the stator coil 6 remains energized. According to this latter method, since the voltage supplied to the stator coil 6 is not limited, there is an advantage that a sufficient amount of heat generation can be obtained. In addition,
Of course, even in this latter case, the voltage supplied to the stator coil 6 when the operation is stopped is
It may be lower than during normal operation.

Although the motor 5 shown in FIG. 2 is of a flat type, similar effects can be expected with other types.

As described above, according to the present invention, since the coil included in the direct drive motor is also used as a heater, there is no need to install a separate heater, and therefore a space for installing the heater is provided on the drum surface. Since this is no longer necessary, it is possible to downsize the drum, that is, to downsize the drum for a video chip recorder.

[Brief explanation of drawings]

FIG. 1 is an external view showing a conventional drum for a video tape recorder. FIG. 2 is a sectional view showing an example of the structure of a direct drive drum according to an embodiment of the present invention. In the figure, 1 is an upper drum, 2 is a lower drum, 5 is a motor, and 6 is a stator coil. Agent Masu Oiwa Figure 1

Claims (3)

[Claims] (1) In a drum for a videotape recorder in which a motor is formed in the drum and the drum is rotated by a direct drive method, the motor is energized and the coils of the motor are turned on even when the videotape recorder is stopped. A drum for a video tape recorder, characterized in that the drum is configured to generate heat. (2) The drum for a video tape recorder according to claim 1, wherein the voltage supplied to the motor is set so that the starting torque of the motor is smaller than the rotational load of the motor. (3) While the video tape recorder is not operating,
2. The drum for a video tape recorder according to claim 1, wherein the operation of the position sensor of the motor is stopped.