JPH04195757A - Magnetic recorder/reproducer - Google Patents

Abstract

PURPOSE:To bring two types of magnetic tapes having different thicknesses into contact with a rotary head in a stable state by opening or closing a second opening of an air flow hole in response to the type of the tape to be wound on a rotating drum. CONSTITUTION:A moving air layer passing a gap between a recesslike annular groove 44b and a magnetic tape 32 is formed from the outside of a plurality of annular groove sectional area reducing members 45a reduced at a gap from the tape to a rotary head vicinity window 47 increased at a gap from the tape, and a negative pressure is generated upon increase in the gap from the tape thereat. This negative pressure relates to the opening or closing state of a second opening of an air flow hole 63 arranged inside a rotating drum from the window 47. If the tape having specifications of large rigidity and large thickness is employed, the negative pressure in the window is increased, and a decrease in the pressure to the atmospheric pressure outside the tape is increased. Thus, a deforming amount of the tape wound outside the window to the bottom of the groove is increased, and a rotary head is stably brought into contact with the tape.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention mainly relates to a magnetic recording/reproducing apparatus for recording (or reproducing) bite signals on a magnetic tape, hereinafter referred to as a VTR. 〉Regarding.

Conventional technology In recent years, VTRs have become capable of longer recording times and higher image quality, and the ability to record (play) data by changing the thickness of the magnetic tape and the magnetic material of the magnetic tape built into the same size cassette is also required. . A conventional VTR will be described below with reference to the drawings.

FIG. 11 shows a sectional view of a rotary head device of a conventional VTR, in which numeral 1 denotes a rotary head, which is capable of reproducing recorded signals from a magnetic tape (not shown). The rotary head 1 is adhesively fixed to the tip of a spatula base 2, and is fixed to the lower end of the rotary drum 4 with screws 3. Reference numeral 5 designates a fixed lower drum, and its outer peripheral surface is provided with a tape lead 5a and a magnetic tape contact running surface 5b for helically guiding the running height position of the wound magnetic tape. Next, reference numeral 6 denotes a rotating disk, which is fixed to a rotating shaft 7 at the center and is rotatable by being supported by bearings 8.8'. Reference numeral 9 indicates a thrust stopper which is fastened to the lower end of the rotating shaft 7 with a screw 10, 11 is an electric motor rotor that is fastened to the thrust stopper 9 with a screw 12, and 13 is glued to the rotor 11 of the electric motor. The fixed magnet 14 is a stator coil of an electric motor, and when energized, rotational force is generated in the rotor 11. 15 is a spacer between the rotating disk 6 and the bearing 8; 16 is a screw that tightens and fixes the rotating drum 4 to the rotating disk 6; 17 is the primary core of the rotating transformer adhesively fixed to the lower part of the rotating disk 6. , 180° with respect to rotating head 1 and rotating head 1
A primary winding for transmitting a recording (or reproduction) signal to each of the rotary heads 1' (not shown) provided at a distance is provided in the groove.

Reference numeral 18 denotes a secondary core of the rotary transformer which is adhesively fixed inside the fixed lower drum 5 opposite to the primary core 17 of the rotary transformer, and a secondary winding is provided in the groove. 19
is a slip ring mounting tool that is fastened to the upper end of the rotating disk 6 with a screw 21 via a spacer 20;
22 are slip ring electrodes 23, 24, 23e, 24
This is a slip ring holder for insulating and holding e, and the slip ring attachment is fixed to the tool 19 with adhesive. 25°26
．． 25e, 26e are slip ring electrodes 23°, 24.
The brushes 27, which are in contact with the brushes 23e and 24e, are brush holders that insulate and hold the brushes 25, 26, 25e, and 26e, and the brushes on the VTR body are adhesively fixed to a plate 28. 29 is a circuit board fixed to the upper part of the rotary drum 4 with screws 30; 31 is a preamplification means configured on the circuit board 29, which amplifies the reproduced signals from the rotary heads 1 and 1'individually; It is added to the primary winding of the primary core 17 of the rotating transformer.

Next, FIG. 12 shows a plan view of essential parts of a conventional VTR.

32 is a magnetic tape, and tape guide 33. Erase head 3
4. Tape guide 359 A rotary head device consisting of a rotary drum 4 with a built-in rotary head 1°1' and a fixed lower drum 5, tape guide 36° audio control head 37. The tape is guided by each of the capstans 38 to form a tape running path. 39 indicates a pinch roller.

Next, the operation of the conventional example shown in FIGS. 11 and 12 is that when the VTR is put into the playback state, the 14 electric motor stator coils are energized, a rotational force is generated in the rotor 13, and a thrust stop is applied to the rotor 13. Parts fixed to the rotating shaft, such as the tool 92 rotating shaft 7, rotating disk 6, primary core 172 of the rotating transformer, rotating drum 42, rotating heads 1, 1', rotate in the direction of arrow 40. Subsequently, when the capstan 38 is rotated and the pinch roller 39 is pressed with the magnetic tape 32 sandwiched therebetween, the magnetic tape 32 starts running in the direction of the arrow 41 due to the cooperative action of the capstan 38 and the pinch roller 39.

Then, the power of +Vcc and GND is supplied to the preamplifier means 31 through the brushes 25.26 in contact with the electrodes 23.24 of the slip ring, and the preamplifier means 31
reaches the operating state, amplifies the reproduced signals from the rotating heads 1 and 1' individually, applies them to the primary winding of the primary core 17 of the rotary transformer, and amplifies the corresponding secondary winding of the secondary core 18. line and is applied to the subsequent signal processing circuit.

Problems to be Solved by the Invention As described above, in the conventional VTR described above, when two types of magnetic tapes having different thicknesses are used, for example, the contact between the thin first magnetic tape 32a and the rotary head 1 is limited. As shown in FIG. 13, a stable state with no gaps is reached; however, as shown in FIG. A gap will be created above and below the rotating head 1.

The reason for this is that there is a difference in deformation characteristics between the first magnetic tape 32a and the second magnetic tape 32b due to their increased thickness, and the thinner second magnetic tape 32b has greater rigidity and rotation. It doesn't fit well with the R shape of the tip of the head 1.

As a result, as shown in FIG.
When the contact state b is reached, a gap is generated on the upper and lower sides of the rotating head 1, and as shown by the solid line 1a in FIG.
The magnetization track is narrower than the magnetization track 1b formed on the magnetic tape 32a. Furthermore, as shown by the solid line 1c in FIG. 16, the reproduction signal from the rotary head 1 has a lower spacing output than the reproduction signal 1d from the first magnetic tape 32a, and the S/N ratio of the reproduction signal deteriorates. There was a problem.

As a means to solve this problem, when using the second magnetic tape 32b of the original specification, the tape tension is increased, and the amount of deformation of the magnetic tape on the upper and lower sides of the rotary head 1 shown in FIG. Generally, measures are taken to increase the amount of the rotary head 1 and to increase the amount of protrusion of the rotary head 1 with respect to the outer circumferential surface 4a of the rotary drum 1.

However, if the tape tension of the second magnetic tape 32b is increased or the protrusion of the rotary head 1 is increased, the contact pressure with the rotary head 1 will also increase, causing new problems such as accelerated wear of the magnetic tape and the rotary head 1. This led to a number of problems.

The present invention eliminates the conventional problems and brings the contact between two types of magnetic tapes with different thicknesses and a rotating head into a stable state without increasing the tension of the magnetic tape or increasing the amount of protrusion of the rotating head. , V at which a highly reliable reproduced signal can be obtained.
The purpose is to provide TR.

Means for Solving the Problems In order to achieve the above object, the magnetic recording and reproducing apparatus of the present invention includes a rotating drum having a concave annular groove arranged in the rotational direction of the outer circumferential surface around which a magnetic tape is wound, and a rotating drum. between a plurality of annular groove cross-sectional area reducing members disposed to reduce the cross-sectional area of the concave annular groove and a plurality of annular groove cross-sectional area reducing members disposed in the concave annular groove; Airflow passing through a rotating head temporary window facing the rotating head, a first opening provided in the rotating head temporary window, and a second opening provided inside the rotating drum. and an airflow hole opening opening/closing means for opening and closing the second opening of the airflow hole in conjunction with the type of magnetic tape wound on the rotating drum.

Operation Since the present invention has the above-described configuration, when the VTR is in operation, the magnetic tape is wound around the outer magnetic tape winding surface of the rotating drum and starts running.

[Rotating Drum Ray] The gap between the concave annular groove provided on the outer circumferential surface of the magnetic tape winding and the magnetic tape wound on the outside is reduced by a plurality of annular groove cross-sectional area reducing members, and the rotating head is The rotating head is enlarged outside the temporary window. The moving air layer around the magnetic tape winding outer peripheral surface of the rotating drum passes through the gap between the partially concave annular groove and the magnetic tape.

The moving air layer passing through the gap between the concave annular groove and the magnetic tape continues to the outside of the plurality of annular groove cross-sectional area reducing members where the gap with the magnetic tape is reduced, and the gap with the magnetic tape is expanded. The rotary head reaches the temporary window, where negative pressure is generated as the gap with the magnetic tape increases. This negative pressure is related to the opening/closing state of the second opening of the air flow hole arranged inside the rotating drum from the temporary window of the rotating head.
By detecting the type of magnetic tape, the second opening of the airflow hole is closed through the airflow hole opening opening/closing means, and the rotating head temporary window is sealed with the outer magnetic tape. , the negative pressure at the rotating head temporary window increases,
The pressure drop to the atmosphere outside the magnetic tape will increase. As a result, the amount of deformation of the magnetic tape wound outside the rotary head temporary window portion toward the annular groove bottom side increases, and the rotary head and the magnetic tape are brought into stable contact.

Embodiment Below, an embodiment of a VTR according to the present invention will be described in FIGS. 1 to 10.
This will be explained using figures. It should be noted that the same reference numerals and numerals as in the conventional example shown in FIGS. 11 to 16, and the parts not directly related to the present invention will not be described repeatedly.

FIG. 4 shows a side view of a rotary head device of a VTR according to an embodiment of the present invention, in which 43 is an annular rotary drum, and a first magnetic tape winding outer surface 43a for winding and guiding a magnetic tape is provided on the outside. It is configured.

Reference numeral 44 designates an annular body that is provided below the first magnetic tape winding outer surface 43 a and rotates together with the rotating drum 43 .

At the lower end of the annular body 44, there is a second magnetic tape winding having an outer diameter approximately the same as the outer diameter Du of the first magnetic tape winding outer peripheral surface 43a of the rotating drum 43, and for guiding the winding of the magnetic tape on the outside. A supination peripheral surface 44a is provided.

44b is a first magnetic tape winding outer circumferential surface 44b having a wide width between the first magnetic tape winding outer circumferential surface 43a and the second magnetic tape winding outer circumferential surface 44a.
shows a concave annular groove. 45 and 46 are concave annular groove sections formed in close contact with the side and bottom surfaces of the first concave annular groove 44b so as to reduce the cross-sectional area of the first concave annular groove 44b in the vicinity of the rotary head 1. Figure 3 shows an area reducing member. The rotating head 1 is spaced 18cm apart from the rotating head 1.
Similarly, a concave annular groove 18 cm apart from the cross-sectional area reducing member 45, 46 is formed near the concave annular groove 45 (not shown). Cross-sectional area reducing members 45° and 46° (not shown) are arranged. 47 and 47' (not shown) arranged 18 centimeters apart from 47 indicate a rotary head killing window for temporarily arranging the rotary heads 1, 1', and have a first concave annular groove. Concave annular groove cross-sectional area reducing member 4
5 and 46 and 45 and 4 spaced 18 cm apart.
It is constructed by partitioning between 6゛. 4
Reference numeral 8 indicates a second annular groove provided on the upper side of the magnetic tape winding outer peripheral surface 43a. Reference numeral 49 denotes a fixed lower drum, which has a tape lead 50 on the lower side that regulates the running height position of the magnetic tape in a helical shape, and a diameter slightly smaller than the diameter Du of the first magnetic tape winding outer peripheral surface 43a of the rotating drum 43. A magnetic tape contact running surface 51 is configured. As shown in the figure, the tape lead 50 of the fixed lower drum 49 comes into contact with the lower edge of the magnetic tape 32 midway through the winding of the magnetic tape 32 wound around the rotating drum 43, and reaches the running height of the magnetic tape 32. As shown in the figure, the lower edge portion 32a of the magnetic tape 32 at the start portion of the magnetic tape winding from the tape guide 35 to the rotating drum 43 is
The magnetic tape is wound and guided by a second magnetic tape winding outer circumferential surface 44a provided at 4. Further, the upper edge portion 32b of the magnetic tape 32 at the end portion of the magnetic tape winding from the rotating drum 43 to the tape guide 36 has a first concave annular groove 44b.
and the second annular groove 48 .
It is wound and guided by a. Reference numeral 52 denotes a motor that is constructed at the lower part of the fixed lower drum 49 and rotates the five-rotation drum 43. Reference numerals 53 and 53' indicate a helad base, and a rotary head 1,1' is fixed to the tip with adhesive.

FIG. 5 is an enlarged plan view showing the structure of the rotary head and the concave annular groove cross-sectional area reducing member arranged 180" apart in a rotary head device of a VTR according to a large embodiment of the present invention, and FIG.
The figure shows a sectional view of a rotary head section of a rotary head device for a VTR according to an embodiment of the present invention, which will be explained next with reference to FIGS. 5 and 6. 44c indicates the lower surface of the first concave annular groove 44b formed in the annular body 44. 45a and 46b indicate the outer peripheral surfaces of the concave annular groove cross-sectional area reducing members 45 and 46;
The respective outer diameters Di and Do are set to be several tens of μm smaller than the outer diameter Du of the second magnetic tape winding outer peripheral surface 44a. The upper surfaces 45t, 46t of the concave annular groove cross-sectional area reducing members 45, 46 are configured to be in close contact with the lower lower surface 43b of the rotating drum 43, as shown in FIG.

54 is a screw for tightening and fixing the helad base 53 to the annular body 44; 55a and 55b are screws for tightening and fixing the concave annular groove cross-sectional area reducing member 45.46 to the annular body 44; 56.
57 is a concave annular groove cross-sectional area facing the rotating head 1;
Screws 55a and 5 installed on small members 45 and 46, respectively.
The tightening of 5b indicates the guide surface.

As shown in the figure, the inner peripheral side of the concave annular groove cross-sectional area reducing member 45, 46 is configured to be in close contact with the lower surface 44c of the first concave annular groove 44b. Therefore, the rotating head temporary window 47 is
The concave annular groove 44b is connected to the concave annular groove cross-sectional area reducing member 4.
5.4'6 partitions. The rotary head 1 is disposed approximately in the middle of the rotary head temporary window 47, and the tip of the rotary head 1 is connected to the rotary drum 43 as shown in FIG.
The distance IO with respect to the first magnetic tape outer surface 43a of
configured on the inside.

Next, 43e and 44e in FIG. 6 indicate the lower end of the first magnetic tape winding outer peripheral surface 43a and the second magnetic tape winding outer peripheral surface 44.
The chamfered portions formed at the upper ends of a are shown.

Reference numeral 58 indicates a screw for tightening and fixing the annular body 44 to the lower lower surface 43b of the rotating drum 43. Reference numeral 63 indicated by a broken line indicates an air flow hole formed by passing through the rotary head temporary window 47 to the inside of the rotary drum 43.

Next, FIG. 1 shows a main part configuration diagram of a VTR according to an embodiment of the present invention, and 73 detects the types of magnetic tapes having different thicknesses or different magnetic materials, and 3 shows magnetic tape type detection means that outputs a control signal. A piezoelectric element 111 74 amplifies a control signal from the magnetic tape type detection means 73 to control a piezoelectric element to be described later.
Eight circuits, 75a and 75b, represent brushes that contact the rotating rings 76a and 76b and supply the output of the piezoelectric element control circuit 74 to the piezoelectric element built in the rotating drum 43.

77 is a piezoelectric element made of piezoceramic, and when an electric signal is supplied, the mechanical position of the free end changes.

78 is a screw that fixes one end of the piezoelectric element 77 to the inside of the rotating drum 43; 79 is a screw that fixes one end of the piezoelectric element 77 to the inside of the rotating drum 43;
The base is shown to be adhesively fixed to the free end of 7. As shown in the figure, the airflow type pressing member 80 has an airflow hole configured to penetrate from a first opening provided in the rotating head temporary window 47 to a second opening provided inside the rotating drum 43. 63 is configured to open and close the second opening. These magnetic tape type detection means 73. Piezoelectric element control circuit 74
．． Brushes 75a, 75b, rotating rings 76a, 76b,
The piezoelectric element 77 and the airflow type pressing member 80 constitute a means for opening and closing the second opening of the airflow hole 63.

An area surrounded by a dotted line 81 indicates a portion configured in the rotary head device.

Next, the operation of the VTR in one embodiment of the present invention will be explained using FIGS. 1 to 10. When the VTR is in use, the motor 52 is energized and the rotating drum 43 is moved to the fifth position.
If the magnetic tape 32 is rotated in the direction of arrow 40 in the figure, the magnetic tape 32 is wound around the rotary head device, and high-speed transfer is started, the fourth
As shown by the dotted line in the figure (the running height position of the magnetic tape 32 is regulated on the upper side by the limiters of the tape guides 35 and 36, and on the lower side by the tape lead 50 of the fixed lower drum 49. In this state For example, if the magnetic tape used is the second magnetic tape 32b of the original specification, the magnetic tape type detection means 73 detects this and outputs a control signal Vt in conjunction.The control signal Vt is generated by a piezoelectric element. The control circuit 74 amplifies the brushes 75a, 75b and the rotating ring 7.
6a and 76b to the piezoelectric element 77, the free end of the piezoelectric element 77 is urged downward as shown in FIG.
The second opening of the rotary head is closed, and the rotating head temporary window 47 is sealed with the magnetic tape 32 of the external bond.

On the other hand, a moving air layer is generated around the first magnetic tape winding outer circumferential surface 43a of the rotating rotary drum 43 and the second magnetic tape winding outer circumferential surface 44a of the annular body 44 due to the rotation, and the magnetic tape The outer surface of the magnetic tape at the start of winding and the second
and the magnetic tape 32b. The moving air layer that has flowed into the gap between the outer circumferential surface of the magnetic tape winding and the second magnetic tape 32b is transferred to the annular groove portion 44, a part of which is concave.
b and the second magnetic tape 32b.

The moving air layer passing through the gap between the concave annular groove 44b and the second magnetic tape 32b moves through the concave annular groove in which the gap with the second magnetic tape 32b decreases, as shown by arrow 59 in FIG. Continuing from the outside of the groove cross-sectional area reducing member 45, the arrow 6
As shown in o, the rotating head moves to the temporary window 47. Since the second opening of the air inflow hole 63 is closed in the rotating head temporary window 47, the gap between the second magnetic tape 32b and the rotating head temporary window 47 will be enlarged by the flowing moving air layer. An accompanying negative pressure Pi is generated, and the second magnetic tape 3
There will be a pressure drop with respect to the atmospheric pressure PO outside 2b. As a result, the second magnetic tape 32b wound around the outside of the concave annular groove 44b is deformed in the direction of the bottom surface 44c of the concave annular groove at the rotary head temporary window 47. The rotary head 1 and the second magnetic tape 32b, which are disposed approximately in the middle, are in contact with each other, and the second magnetic tape 32b is attached to the rotary head 1 along the broken lines 61 and 62 in FIG. Each transforms as shown.

The rotary head 1 and the second magnetic tape 32 in this state
The second magnetic tape 32b comes in contact with the negative pressure Pi generated in the rotary head temporary window 47 and the atmospheric pressure P outside, as shown in an enlarged view in FIG.

As a result of this action, the rotary head 1 is deformed so as to come into close contact with the upper and lower sides of the rotating head 1.

If the magnetic tape used in the VTR according to the embodiment of the present invention is, for example, the first magnetic tape 32a with thin specifications, the magnetic tape type detection means 74 detects this and outputs a control signal in conjunction with the magnetic tape type detection means 74. When the free end of the piezoelectric element 77 is urged upward through the second opening opening/closing means of the airflow hole 63 as shown in FIG. 2, the second opening of the airflow hole 63 opens ( This reduces the generation of negative pressure caused by the moving air layer flowing into the rotating head temporary window.In the VTR according to the embodiment of the present invention, when the thin first magnetic tape 32a is used, The contact between the first magnetic tape 32a and the rotary head 1 reaches a stable state with no gaps (the distance 1o between the first magnetic tape winding outer peripheral surface 43a and the tip of the rotary head 1 in FIG. 6, the concave shape, etc.) The diameters of the outer peripheral surfaces 45a and 46a of the annular groove cross-sectional area reducing members 45 and 46 are set.

Therefore, the contact between the thin first magnetic tape 32a and the rotary head reaches a stable state with no gap, as shown in FIGS. 2 and 7.

As described above (in the VTR of one embodiment of the present invention, the thin first magnetic tape 32a and the thin second magnetic tape 32a have different rigidities).
Each of the magnetic tapes 32b and the rotary head 1 come into stable contact with no gaps, and as shown in FIG. As shown in the figure (a stable state is reached with no output drop).

In the rotary head device for a VTR according to one embodiment of the present invention described above, the rotary head is fixed to the rotary drum and rotates integrally with the rotating drum. The present invention can also be applied to a rotary head device of an intermediate drum having a structure in which a rotary head is arranged in a protruding manner, or to a rotary head device of a VTR that uses a metal magnetic tape and an iron oxide magnetic magnetic tape having different rigidities. It works the same way.

Effects of the Invention As described above, according to the present invention, in a VTR that shares a rigid magnetic tape, it is possible to maintain stable contact between the magnetic tape and the rotary head without any gaps, and the recording mode This reduces the formation of perfect magnetized tracks and the reduction in the S/N ratio of the reproduced signal in the reproduction mode, which contributes to improving the reliability and popularizing this type of VTR.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main part of a VTR according to an embodiment of the present invention.
Fig. 2 is an operating state diagram of the air flow hole opening/closing means, for example, corresponding to a thin magnetic tape with low rigidity. 4 is a side view of the rotary head device, and FIG. 5 is a plane view showing the configuration of the rotary head and the concave annular groove cross-sectional area reducing member arranged 180 degrees apart in the rotary head device. 6 is a sectional view of the rotary head section of the rotary head device; FIG. 7 is an enlarged view of the state of contact between the rotary head and, for example, a thin magnetic tape with low rigidity;
Figure 8 is an enlarged view of the contact between the rotary head and a thin magnetic tape with high rigidity, Figure 9 is a recording magnetization pattern diagram of the rotary head, Figure 10 is a reproduction signal waveform diagram of the rotary head, and Figure 10 is a diagram of the reproduction signal waveform of the rotary head. Figure 11 is a sectional view of a conventional rotary head device;
Fig. 12 is a plan view of the main parts of a VTR with a built-in rotary head device, Fig. 13 is an enlarged view of the contact between the rotary head and, for example, a thin magnetic tape with low rigidity, and Fig. 14 is a diagram of the rotary head. For example, FIG. 15 is an enlarged view of the state of contact between a highly rigid thin magnetic tape and a rotary head, FIG. 15 is a recording magnetization pattern diagram of the rotary head, and FIG. 16 is a reproduction signal waveform diagram of the rotary head. 1.1'... Rotating head, 32... Magnetic tape, 43... Rotating drum, 43a...
...First magnetic tape winding outer peripheral surface, 44...
Annular body, 44a... Second magnetic tape winding outer circumferential surface, 45a... Outer circumferential surface of concave annular groove cross-sectional area reducing member, 47... Rotating head temporary window , 49...
... Fixed lower drum, 63 ... Air flow hole, 7
5a, 75b...Brush, 76a. 76b...Rotating ring, 77...Piezoelectric element, 80...Air flow type pressing member. Name of agent: Patent attorney Akira Koeji and 2 others + 1″--3
To the eaves-tν ua! x Tedery -■ Turn around゛ram 輯-fl [Ji body 47'---11811mut to・V′Kyōkanfuyuki,・V【
Surpassed Kuroishi-q Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 1゜ Fig. 9 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15

Claims (1)

[Claims] A rotating drum having a concave annular groove disposed in the rotational direction of an outer peripheral surface around which a magnetic tape is wound, and a plurality of concave annular grooves disposed in the rotating drum so as to reduce the cross-sectional area of the concave annular groove. an annular groove cross-sectional area reducing member; a rotating head temporary window in which the rotating head is disposed facing between the plurality of annular groove cross-sectional area reducing members disposed in the concave annular groove; and a rotating head temporary window disposed in the rotating head temporary window. an airflow hole passing through a first opening provided therein and a second opening provided inside the rotating drum; and a second opening of the airflow hole being wound around the rotating drum. What is claimed is: 1. A magnetic recording and reproducing apparatus comprising an airflow hole opening opening/closing means that opens and closes in conjunction with the type of magnetic tape being used.