JPS62146447A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording and reproducing device simple in constitution, reduced in power consumption and effectively prevented from dew condensation by providing grooves for forming air layers around a cylinder for guiding a tape, and arranging linear heat generating bodies to be driven in accordance with an external signal in the grooves. CONSTITUTION:A magnetic head is arranged on a proper position of the peripheral edge of the lower surface of a rotary upper cylinder 21 and a lead surface 23 for guiding the traveling of the tape is formed on the periphery of a lower cylinder 22 arranged coaxially with the upper cylinder 21. The thin grooves 24 are formed on the peripheral surface of the cylinder 21 rectangularly to the axis and sheath heaters 25 are embedded in the thin grooves 24. A humidity sensor 26 is formed adjacently and oppositely to the peripheral surface of the cylinder. When the humidity detecting value of the sensor 26 exceeds a prescribed value, current is supplied to the heater 25 in accordance with an output signal and the periphery of the cylinder is directly and rapidly heated, so that the tape traveling system can be previously prevented from harmful dew condensation.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a magnetic recording/reproducing device, in particular, a magnetic recording/reproducing device having a cylinder for running a tape-shaped recording medium along a predetermined range of its circumferential surface. For example, a video tape recorder (hereinafter referred to as a VTR) is configured to record and reproduce information on the tape-shaped recording medium using a rotary magnetic head that rotates so that its locus roughly follows the outer periphery of the cylinder.
It relates to magnetic recording and reproducing devices such as.

[Prior Art] In recent years, magnetic recording and reproducing devices such as VTRs that run a tape-shaped recording medium (hereinafter referred to as tape) along a guide cylinder and record and reproduce information on this tape have been made smaller and lighter. is progressing significantly. The tape running system in such an apparatus is constructed as shown in FIG. 3, for example.

That is, the tape 3 drawn out from the supply reel 2 in the tape cassette 1 is transferred from the tension post 4 to each guide post group 5 to the full width erasing head 6 to the cylinder 7 to the audio erasing head 8 to the audio control head 9 to the capstan 10 and Pinch roller 11, then take-up reel 12
As shown in the figure, the tape 3 runs along a predetermined tube on the surface of the cylinder 7 in a state of road contact,
During this time, information is recorded on and reproduced from the tape 3 by a rotating head (not shown).

[Problems to be Solved by the Invention] In the magnetic recording/reproducing device as described above, if the device is placed in a humid atmosphere or if it is suddenly brought into a warm room after being placed in a cold room. In this case, condensation occurs on the cylinder circumferential surface. If you try to wind or run a tape around a cylinder with dew condensation on its outer surface in this way, a so-called tape sticking phenomenon will occur, causing abnormal fluctuations in tape tension and running speed, or causing the tape to stop running. There is a risk. For this reason, various countermeasures have been proposed in the past in order to deal with dew condensation in cylinders. For example, a condensation sensor is used to detect that there is a risk of condensation on the cylinder, and forcibly removes the tape from its running system and rewinds it onto the reel.
No. 282 Publication), and one in which the cylinder is vibrated in the direction of rotation in order to prevent problems in tape running due to the influence of humidity (Japanese Patent Laid-Open No. 1141-1983)
51 Publication) etc. In addition, the above-mentioned special public service No. 54-2428
Publication No. 2 also discloses the idea of removing dew condensation on the cylinder by heating the cylinder with a heater provided inside the cylinder. However, if a situation where there is a risk of condensation is detected and the tape is removed from its running system,
If the cylinder is configured to be photographed in its rotational direction, the device will become complicated and have to be larger.
This does not suit the design philosophy of this type of device, which aims to reduce size and weight. Additionally, devices that heat the cylinder using an internal heater increase power consumption, which causes the problem that the operating duration becomes more limited, especially in portable type VTRs that are powered by batteries. .

The present invention has been made in view of the above points, and it is an object of the present invention to provide a magnetic recording/reproducing device of this type that has a simple configuration, consumes little power, and can effectively prevent dew condensation.

[Means for Solving the Problems] The present invention provides a groove for forming an air layer on the circumferential surface of a cylinder that guides the tape, and a linear heating element that responds to an external signal is disposed within the groove. This is what I did.

[Function] In response to switch operations by the operator, external signals from humidity sensors, temperature sensors, etc., the linear heating element made of, for example, an ultra-fine wire sheathed heater is made to generate heat, directly warming the outer peripheral surface of the cylinder. By creating a dry atmosphere near the cylinder, condensation can be effectively prevented with low power consumption.

[Embodiment] FIG. 1(A) is an enlarged cross-sectional view of a main part of a magnetic recording/reproducing apparatus as an embodiment of the present invention, FIG. 1(B) is a side view corresponding to FIG. 1(A), Figure 2 shows Figure 1 (A) and Figure 1 (B).
) is a front view of the cylinder of the device of the embodiment shown in FIG. The magnetic recording/reproducing apparatus of this embodiment has a tape running system similar to that described with reference to FIG. 3, but its cylinder 20 is particularly unique. As shown in FIG. 2, the cylinder 20 has a generally similar external shape to a known cylinder of this type, and includes a rotary upper cylinder 21 and a fixed lower cylinder 22 arranged coaxially. As is well known, a magnetic head (not shown) is disposed at a suitable position on the outer periphery of the lower surface of the upper cylinder 21, and a lead surface 2 is provided on the outer periphery of the lower cylinder 22 to guide the running of the tape.
3 is formed. A thin groove 24, 24 is formed on the outer peripheral surface of the upper cylinder 21 in a direction perpendicular to the axis of the cylinder. As shown more clearly in FIGS. 1(A) and 1(B), an ultra-thin wire sheath heater as a linear heating element is inserted into these grooves 24.24.
It is embedded closely at or near the bottom of the In the Vt position of this embodiment, as shown in FIG. 2, a sensor 26 is arranged so as to closely face the circumferential surface of the upper cylinder 21. This sensor 26 is, for example, a humidity sensor.

As is well known, the above-mentioned cylinder (especially the upper cylinder) used as a tape guide in this type of magnetic recording/reproducing device usually has an air layer created between the tape and the circumferential surface of the cylinder to reduce friction. A groove having a V-shaped cross section is formed on the same peripheral surface in a direction perpendicular to the axis of the cylinder. The multi-grooves 24, 24 of the present invention may be of exactly the same type as such grooves.

In the device of the present invention configured as described above, the humidity sensor 2
When the humidity detected by the sensor 6 exceeds a predetermined value, the linear heating element 25 is driven in response to the output signal of the sensor, and the circumferential surface of the upper cylinder 21 is heated very quickly. That is, when the sensor 26 detects that there is a risk of condensation, the linear heating element 25 is activated immediately.
Since a sufficiently dry atmosphere is created in the space near the circumferential surface of the upper cylinder 21, the formation of dew condensation, which is extremely harmful to the tape running system, is prevented. Furthermore, in the present invention, only the peripheral surface of the cylinder necessary to obtain the dew condensation prevention effect is directly heated, so loss due to heat conduction is minimized, wasteful power consumption is small, and response is quick.

Incidentally, the cylinder in this type of device is generally made of aluminum, and therefore sufficient consideration must be given to deformation due to heating. Generally, in order to keep the deformation below the allowable value, it is necessary to keep the upper limit of the cylinder temperature to about 200°C or less, but this is the temperature required to create a dry atmosphere around the cylinder surface as in the present invention. Lower temperature (
It is not necessary to take any special measures against thermal deformation of the cylinder, since the temperature (for example, 100° C. or considerably lower) is sufficient to achieve the purpose. In addition, through experiments, the inventors used the well-known air introduction groove as described above to reduce friction with the tape as the groove 24 on the circumferential surface of the cylinder, and installed an ultra-fine wire heater in this groove. It was confirmed that even if the grooves were buried, the effect of forming an air layer by those grooves would not be affected.

In the above embodiment, a humidity sensor is used as the sensor 26, but a temperature sensor may also be used as the sensor. As mentioned above, if the device is placed in a cold room and the cylinder is cold, then the device is suddenly brought into a warm room, causing condensation on the circumferential surface of the cylinder.

Therefore, in order to prevent such condensation, a temperature sensor is used to detect the temperature at a suitable location near the cylinder, and a temperature change detection circuit (for example, a circuit commonly used in process control systems, etc.) is used to detect the temperature. If a change is detected and the detected temperature suddenly rises, the linear heating element may be immediately driven to perform dehumidification. In this case as well, it is possible to obtain substantially the same effect as in the case where a humidity sensor is applied as described above.

[Effects of the Invention] As described above, according to the present invention, by directly heating the circumferential surface of the cylinder, dew condensation can be prevented very quickly and effectively. Further, a sufficient dew condensation prevention effect can be obtained with extremely low power consumption.

[Brief explanation of drawings]

FIG. 1(A) is a sectional view showing the main part of the present invention, FIG. 1(B)
) is a side view corresponding to Fig. 1(A), and Fig. 2 is a side view corresponding to Fig. 1(A).
A) and FIG. 1(B) are front views of the cylinder of the apparatus of the embodiment, and FIG. 3 is a diagram showing the tape running system of a general magnetic recording/reproducing apparatus. 20...Cylinder 24.24...Groove 21.
... Upper cylinder 25 ... Linear heating element 22 ...
Lower cylinder Figure 1 (A)! Figure 1 (B) Figure 3

Claims (3)

[Claims] (1) A rotary magnetic head that has a cylinder for running a tape-shaped recording medium along a predetermined range of its circumferential surface and rotates so that the rotation locus of its tip approximately follows the outer circumferential surface of the cylinder In a magnetic recording and reproducing device configured to record and reproduce information on a tape-shaped recording medium, the cylinder has a groove on its circumferential surface for forming an air layer, and has a groove in the groove that responds to an external signal. A magnetic recording/reproducing device characterized in that a linear heating element is provided. (2) The magnetic recording/reproduction according to claim 1, wherein the linear heating element is adapted to respond to an output signal from a humidity sensor provided at a suitable location near the cylinder. Device. (3) The magnetic recording/reproduction according to claim 1, wherein the linear heating element is adapted to respond to an output signal from a temperature sensor provided at a suitable location near the cylinder. Device.