JPH01137425A - Rotary drum device for vtr - Google Patents

Abstract

PURPOSE:To prevent the rise of a drum driving current at the time of a low temperature by forming a heating means, which heats an operating fluid at the time of a low temperature, to reduce the viscosity of the operating fluid. CONSTITUTION:The heating means which is fixed to a lower drum 1 and heats the operating fluid at the time of a low temperature, namely, a heating heater 11 used as a dew sticking preventing heater is provided. At the time of a low temperature, for example, <=10 deg.C, a switch SW1 for this heating heater which is arranged besides an already provided switch SW2 for dew sticking preventing heater is turned on. Thus, the dew sticking preventing heater is operated as the heating heater 11 to reduce the viscosity of the operating fluid without using special devices neither special materials, and the rise of the drum driving current is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rotating drum device for a VTR, and particularly to a rotating drum device for a VTR using a dynamic pressure type fluid bearing.

[Conventional technology]

Conventional rotating drums for VTRs using dynamic pressure fluid bearings are not equipped with a heating beater to raise the temperature of the working fluid, and even if equipped with a heater, it is insufficient to prevent dew build-up. This heater was used to remove dew when it adhered to the drum surface of the rotating drum.

The conventional rotary drum using a hydrodynamic bearing as described above has the disadvantage that since it is not heated at low temperatures, the viscosity of the working fluid increases, which causes an increase in drum drive current. there were.

[Problem to be Solved by the Invention 1] As described above, in the conventional example, when the temperature is low, the viscosity of the working fluid supporting the rotating body increases, and the rotational load increases, so the drum drive current increases. There was a problem.

This invention was made to solve the problems of the prior art as described above, and its purpose is to reduce the viscosity of the working fluid and prevent the drum drive current from increasing at low temperatures.

[Means for Solving the Problems] Therefore, in the present invention, the above-mentioned problems are solved by forming a heating means H for heating the working fluid at low temperatures in a rotating drum for a VTR equipped with a hydrodynamic fluid bearing. The goal is to solve problems and achieve goals.

[Effect]

The working fluid of the rotary drum for a VTR in this invention is heated by the heating means H at low temperatures to reduce its viscosity.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic side sectional view of a rotary drum for a VTR using a hydrodynamic bearing, which is an embodiment of the present invention, and FIG.
These are electrical circuit diagrams of the heating means H of the rotary drum for VTR shown in the figure, and FIG. 2(a) is a circuit diagram when the heating operation is performed in this embodiment, and FIG. 2(b) is the circuit diagram when the heating operation is automatically performed. FIG. Furthermore, FIG. 3 is a characteristic line diagram showing the relationship between the temperature of a rotating drum and drum drive current using the hydrodynamic bearing of the present invention, and FIG. 4 is a hydrodynamic bearing according to another embodiment of the present invention. 1 is a schematic side cross-sectional view of a rotating drum for a VTR using a VTR. In FIG. The shaft, 3 is a rotary transformer fixed to the lower drum 1, 4 is a sleeve rotatably loosely fitted to the center shaft 2, and 2a is formed on either the center shaft 2 or the sleeve 4 (in the figure, it is formed on the center shaft 2). ), and a working fluid (not shown) is provided in the loose fitting gap between the central shaft 2 and the sleeve 4.
A fishbone-shaped power generation pattern in which L is filled, 5 is a rotary transformer fixed to the sleeve 4 facing the rotary transformer 3, 6 is an upper drum fixed to the sleeve 4, and 7 is fixed to the upper drum 6. 8 is a thrust bearing plate fixed to the sleeve 4, 9 is a central shaft 2
9a is a fixing screw for fixing the oil cover 9 to the central shaft 2, and a spiral groove (not shown) is formed on one of the facing surfaces of the thrust bearing plate 8 and the oil cover 9. The gap between the thrust bearing plate 8 and the oil cover 9 is filled with a working fluid (not shown) similar to that filled in the gap between the central shaft 2 and the sleeve 4.
is fulfilled. 1 is a motor coil located opposite the rotor magnet 7 and fixed to the oil cover 9; 11 is a heating means H fixed to the lower drum 1 for heating the working fluid at low temperatures; In Fig. 2, 2S is the power supply for the heater 1, SW is the heating means H, which is a switch for the heater 11 that heats the working fluid at low temperatures, and SW2 is the switch for heating the heater 11 when there is dew on the rotating drum. Heater 1 to heat! switch for
For example, 2b is a temperature sensor (
2C is a Dua sensor (not shown) for detecting dew on the drum surface of a rotating drum, 2d, 2e
is an amplifier; in Fig. 3, the horizontal axis is the temperature of the rotating drum, the vertical axis is the rotating drum drive current, 3a is the characteristic curve, and in Fig. 4, 1' 1a is the temperature near the central axis. heating means H arranged to heat the working fluid at low temperatures;
This is a heater that also serves as a dew prevention heater.

In each figure, the same reference numerals indicate the same or equivalent parts.

Next, the operation of a rotary drum device for a VTR according to an embodiment of the present invention will be explained with reference to FIG.

By applying a certain current to the motor coil 10 of the VTR rotary drum shown in FIG. 1, a force in the rotational direction is generated in the rotor magnet 7, and the rotor magnet 7, the sleeve 4. Rotary transformer5. The upper drum 6 and the thrust bearing plate 8 (the parts to which these are fixed are hereinafter collectively referred to as the rotating body M) begin to rotate. Pressure is generated in this rotary body M by a dynamic pressure generation pattern 2a carved on the central shaft 2 or the sleeve 4, and the pressure restricts the rotary body M in the radial direction (radial wheel bearing).

In addition, a force in the thrust direction is exerted by a spiral groove (not shown) carved in either the thrust bearing plate 8 or the oil cover 9, and the three forces of gravity acting on the rotating body M and the suction force of the motor are exerted. Due to the force, the rotating body M floats up from the stationary side via the working fluid and rotates.

Next, an embodiment of the heating means H for heating the working fluid of the rotary drum for a VTR according to the present invention when the temperature is low will be described with reference to FIGS.

Characteristic curve 3 of rotating drum temperature and drum drive current in Figure 3
As shown in a, when the temperature is low, for example 10°C or lower,
The viscosity of the working fluid supporting the rotating body M increases, and as a result, the rotational load increases, and as a result, the drum drive current increases.

As can be seen from the characteristic curve 3a in Figure 3, the drum drive current is approximately 150 mA when the temperature of the rotating drum is 30°C.
On the other hand, at 0° C., approximately 450 mA is required, which is approximately three times as much current.

At such low temperatures, for example below 10 t', as shown in Figure 2 (
When the switch SW, which is the heating means H in a), is turned on and electricity is supplied to the heater 11, the rotating drum is warmed, the temperature of the working fluid increases due to heat transfer, and the viscosity of the working fluid decreases. To prevent dew buildup, switch sw
2 is turned ON and the dew adhesion prevention heater (heater) is energized and heated.

In addition, when the heating operation is performed automatically as shown in FIG. 2(b), the output of the temperature sensor 2b is passed through the amplifier 2d, and when the voltage becomes higher than a certain predetermined voltage VPafl, the analog switch SW1 is turned on and the heater 11 is energized. and heated.

On the other hand, when the UJ force of the Du@sensor 2c passes through the amplifier 2e and becomes higher than a certain predetermined voltage V Pafl, the analog switch sw2 is turned on and the heater 1°1 is energized and heated. As a result, the rotating drum drive current value can be lowered according to characteristic curve -38 in FIG.

Next, a rotary drum device for a VTR, which is another embodiment of the present invention, will be described with reference to FIG.

FIG. 4 shows a rotating drum device in which a heater lla, which is a heating means H for heating the working fluid at low temperatures, is placed near the center axis 2. The heater lla of this embodiment heats the area near the center axis 2. Therefore, heat transfer to the working fluid is fast.
The temperature rise time of the working fluid is faster than in the embodiment shown in FIG.

However, in this case, if the switch SW2 is turned on and the heater lla is used as a dew prevention heater, it will take a longer time for the dew to disappear than in the case of the above embodiment.

The heater which is the heating means H in the above embodiment is the lower drum! Alternatively, the size and location of the heater should be selected so that the current consumption of the heater is smaller than the decrease in current value due to a decrease in the viscosity of the working fluid. It is possible to suppress the increase in current value at low temperatures.

As described above, in a rotating drum device for a VTR using a hydrodynamic bearing, when the temperature is low, for example, 10° C. or lower, the heating heater of the present invention is installed in addition to the existing dew deposition prevention heater switch SW2. By turning on the switch SW1, the dew adhesion prevention heater is operated as a heating heater, and the rotating drum drive current value at low temperatures can be lowered without using any special equipment or special materials.

(Effects of the Invention) As explained above, according to the present invention, in a rotating drum for a VTR equipped with a hydrodynamic fluid bearing, at low temperatures,
By forming a heating means H for heating the working fluid,
This has the effect of reducing the viscosity of the working fluid and preventing an increase in drum drive current.

[Brief explanation of the drawing]

FIG. 1 is a schematic side sectional view of a rotary drum for a VTR using a hydrodynamic bearing, which is an embodiment of the present invention, and FIG.
2 is an electric circuit diagram of the heating means of the rotary drum for VTR shown in the figure, FIG. 2(a) is a circuit diagram when heating operation is performed in this embodiment, and FIG. 2(b) is a circuit diagram when heating operation is performed automatically. FIG. Furthermore, FIG. 3 is a characteristic curve diagram showing the relationship between the temperature of a rotating drum and drum drive current using the hydrodynamic bearing of the present invention, and FIG. 4 is a hydrodynamic bearing according to another embodiment of the present invention. 1 is a schematic side sectional view of a rotary drum for a VTR using a VTR. 1 - Lower drum 2 - Center shaft 3.5 - Rotary transformer 4 - Sleeve 6 - Upper drum 7 - Rotor magnet 8 - Thrust bearing plate 9 - ...-Oil cover 10--Motor coil 11.1la-shaft/-heater

Claims (3)

[Claims] (1) In a rotating drum for a VTR equipped with a hydrodynamic fluid bearing, a heating means is formed to heat the fluid arranged in the bearing at low temperatures, and the heating means lowers the viscosity of the working fluid. A VTR characterized by the following configuration:
Rotating drum device. (2) The VT according to claim 1, wherein the heating means is a means for heating the working fluid by operating a dew deposition prevention heater at a low temperature.
Rotating drum device for R. (3) The rotating drum device for a VTR according to claim 1 or 2, wherein the heating means operates when the temperature of the rotating drum is 10° C. or lower.