JPS6160630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotation speed switching device for a rotary head, and is used to selectively switch and record and reproduce video signals having different field frequencies, such as NTSC color video signals and PAL color video signals. Another object of the present invention is to provide a device that has a simple configuration using a one-way clutch and is configured to be able to switch the rotational speed of a rotary head without being limited to a specific mode during switching operation.

Traditionally, the rotation speed of the rotary head is changed by switching according to the NTSC and PAL formats (or by detecting the field frequency and switching automatically), and recording and playing back color video signals of both formats.
There are VTR devices (VTR devices that can record and play back PAL video signals and NTSC video signals). The rotational speed switching device for the rotating head of such a VTR device has a configuration in which a motor dedicated to the NTSC system and a motor dedicated to the PAL system are installed separately, or pulleys of different diameters are installed side by side and the mounting position of a single belt is changed as appropriate. The configuration is such that the rotation speed of the rotating head can be switched.

However, the former has the disadvantage that it is not suitable for general home use because the VTR device as a whole becomes expensive and the weight of the VTR device increases. Further, in the latter case, the rotational speed switching operation is limited to only when the rotary head is rotating, such as during play, and the belt mounting position cannot be changed in the stop mode. For this reason, the rotary head cannot be rotated at the originally switched speed, and a magnetic tape recorded using a predetermined method cannot be normally reproduced from the beginning.

The present invention eliminates the above-mentioned drawbacks, and one embodiment thereof will be described below with reference to the drawings. 1 and 2 show a plan view and a front view, respectively, of an embodiment of the rotation speed switching device for a rotary head according to the present invention, and FIG. 3 shows a rotation transmission in the device shown in FIGS. 1 and 2. FIG. 3 is a diagram showing a route in block form.

In FIGS. 1 and 2, a guide drum assembly 1 and a motor 2 are disposed on a chassis 3, and the lower side of the chassis 3 includes a rotation speed switching device for a rotating head, which will be described later according to the present invention. A rotation transmission mechanism is provided.

The motor 2 is always rotated at a constant speed regardless of the PAL color video signal recording/reproducing mode (hereinafter referred to as PAL mode) or the NTSC color video signal recording/reproducing mode (hereinafter referred to as NTSC mode). A pair of pulleys 4 and 5 fixed to the motor shaft are rotated integrally by the motor 2, and the pulley 4
The rotation of another pulley 5 is transmitted to a pulley 7 dedicated to the PAL system via a square belt 6, and the rotation of another pulley 5 is transmitted to a pulley 9 dedicated to the NTSC system via a square belt 8. Rotate at different speeds depending on the specific. In the PAL mode, the rotation of the pulley 7 is directly transmitted to the pulley 10 via a one-way clutch mechanism (described later), and is further transmitted to the pulley 10 in the guide drum assembly 1 via the flat belt 11, pulley 12, and rotary head rotation shaft 13. A rotating magnetic head (not shown) is rotated at a speed corresponding to a field frequency of 50 Hz and is rotated against a magnetic tape (not shown).
Recording and playback of PAL color video signals is performed. On the other hand, in the NTSC mode, another one-way clutch mechanism is operated by the operation of the solenoid 14 as described later, and the pair of pulleys 7 and 9 and the pulley 10 are connected to each other.
The rotation transmission path between the pulley 1 and
0 is rotated integrally with another pulley 9 (that is, rotates independently of the pulley 7), and furthermore, a flat belt 11,
A rotating magnetic head (not shown) is rotated via a pulley 12 etc. at a speed corresponding to a field frequency of 60Hz, and the magnetic tape (not shown) is
A color video signal is recorded and/or played back.

Next, the configuration and operation of the main parts of the rotation speed switching device will be explained with reference to FIGS. 4 to 6. FIG. A partially longitudinal front view is shown. Also,
Figures 5A and 5B show the operating states of the one-way clutch in PAL mode, respectively.
FIGS. 6A and 6B are arrow views in the X and YY directions, and FIGS. 6A and B are arrows XX and YY in FIG.
It is an arrow view of a direction. The rotation transmission path switching mechanism uses a one-way clutch that is activated or deactivated by the action of centrifugal force generated by rotation, as described later, and the field frequency (60Hz) of the NTSC system is the same as the field frequency of the PAL system. (50Hz).

In the rotation transmission path switching mechanism 15 shown in FIG. 4, a shaft 16 to which a pulley 9 exclusively for the NTSC system is fixed is rotatably supported by a pair of bearings 18 and 19 in a holder 17. Further, the pulley 10 located below the pulley 9 and the pulley 7 exclusively for the PAL system are fitted into bearing sleeves 20 and 21, which are fitted onto the rotating shaft 16, respectively, and are supported so as to be freely rotatable independently.

Reference numeral 22 denotes a pin bent into an L-shape, and its hanging portion 22a is rotatably supported on the inner circumferential side of the pulley 7 exclusively for the PAL method.
b is fitted into an annular cam groove 23 bored on the lower surface side of the pulley 10. Note that the outer peripheral wall of the cam groove 23 has stepped portions 24a and 2 as shown in FIG. 5A.
A cam 24 having a diameter 4b is formed. here,
The pin 22 and cam 24 constitute a first one-way clutch.

In addition, 25 is an L-shaped bent pin, and its hanging portion 2
5a is rotatably supported at a predetermined radius position of the pulley 10, and its vertical portion 25b is fitted into an annular cam groove 26 formed on the lower surface side of the pulley 9 exclusively for the NTSC system. The outer peripheral wall surface of the cam groove 26 forms a circular cam 27, while the inner peripheral wall surface forms a cam 28 having a plurality (six) of hook-shaped locking portions 28a.
is formed. Here, the L-shaped bent pin 2
5 and the cam 28 constitute a second one-way clutch.

Next, we will explain the operation of the above mechanism in PAL mode and NTSC mode.
In this mode, the solenoid 14 shown in FIGS. 1 and 2 is inactive. Therefore, it is connected to the solenoid 14 via the connecting pin 30,
The switching lever 33, which is pivotally supported by a pin 32 installed in the holder 31, is rotated counterclockwise by a spring (not shown) and is at the position shown by the solid line in FIG. A locking lever 35 is attached to the switching mechanism section 15 and is installed so as to extend from the tip side thereof and is disposed at a height opposite to the gap section 34 between the NTSC system dedicated pulley 9 and the pulley 10.
located in a more remote location.

In this state, when motor 2 is driven
The pulley 7 dedicated to the PAL system rotates at a rotation speed N ₁ and the pulley 9 dedicated to the NTSC system rotates at a rotation speed N ₂ (>N ₁ ) in the same direction. As the pulley 7 dedicated to the PAL system rotates, the pin 22 rotates in the outer circumferential direction (counterclockwise in FIG. 24 and rotates clockwise at a rotational speed N ₁ . Due to the pairwise rotation of the pin 22 with the pulley 7, the vertical portion 22b of the pin 22 aligns with one stepped portion 24a of the cam 24 as shown in FIG. 5A.
Or 24b is locked, and the pulley 10 rotates clockwise together with the pulley 7 at a rotational speed _N1 .

Further, the pulley 9 exclusively for the NTSC system rotates clockwise in FIG. 5B at a rotational speed _N2 . At this time, due to the integral rotation of the pulley 10 and the pulley 7, the L-shaped bending pin 25 is rotated in the outer circumferential direction (counterclockwise in FIG. 5B) due to the action of centrifugal force, and the vertical portion 25b is engaged. It rotates clockwise at a rotational speed N ₁ while actively abutting against the circular cam 27 of the pulley 9 without being stopped by the stop lever 35. Therefore, pin 2
5 actively contacts the circular cam 27 of the pulley 9, and freely slides on the cam surface according to the difference between the rotational speeds N ₁ and N ₂ . As a result, the pulley 10 is not mechanically interfered with by the rotation of the pulley 9 exclusively for the NTSC system, and is operated via the first one-way clutch consisting of the pin 22 and the cam 24.
It rotates integrally with the PAL method exclusive pulley 7 at a rotational speed of _N1 .

As a result of the above-mentioned rotation of the pulley 10, the rotating magnetic head in the guide drum assembly 1, together with the upper rotating drum (both not shown), is rotated at 50 Hz via the flat belt 11, pulley 12, and rotating head rotating shaft 13 in FIG. It is rotated at a speed corresponding to the field frequency, and PAL color video signals are recorded and reproduced on a magnetic tape (not shown).

Next, the operation of switching the PAL mode to the NTSC mode of the apparatus will be described. This switching operation is carried out by operating the solenoid 14 for a predetermined period of time, conveniently utilizing the relationship N ₂ >N ₁ . For example, a rotating magnetic head (not shown)
When rotating in PAL mode, solenoid 1
4 is actuated, the switching lever 33 and the locking lever 35 are rotated clockwise in FIG. The vertical portion 25b is connected to the gap portion 34.
The locking lever 35 is locked by the circular arc portion 35a of the locking lever 35, and is rotated against the centrifugal force. As a result, the pin 25 is pressed against the cam 28 of the pulley 9 as shown in FIG. 6B, and the vertical portion 25b of the pin 25 is locked with one hook-shaped locking portion 28a of the cam 28.

At this time, the pulley 9 dedicated to the NTSC system is the pulley 1.
The cam 28 rotates in the same direction at a slightly higher speed (faster by the relative speed difference of N ₂ - _{N 1} ) than the cam 28.
is rotating in the direction in which it advances at the above-mentioned relative speed with respect to the pin 25, so when the pin vertical portion 25b is locked with the hook-shaped locking portion 28a of the cam 28, the pulley 10 is rotated.
It is rotated integrally with the pulley 9 exclusively for the NTSC system at a speed N ₂ faster than the current rotation speed N ₁ in the same direction. After this, the solenoid 14 is deactivated,
Even when the locking lever 35 is retracted to the position shown by the solid line in FIG. The pulley 10 continues to rotate at a rotational speed _N2 .

In addition, since the pulley 10 rotates at a speed N ₂ - N ₁ faster than the PAL-dedicated pulley 7, the engagement between the pin vertical portion 22b and the cam stepped portion 24a or 24b is released, as shown in FIG. 6A. As shown, the pin 22 contacts the cam surface with its vertical portion 22b, and
Slide the cam surface of No. 4 counterclockwise at a speed equal to the relative speed difference between the two. This operation does not adversely affect the rotation of the pulley 10 at the rotational speed _N2 .

As a result of the above-mentioned rotation of the pulley 10, the rotating magnetic head in the guide drum assembly 1, together with the upper rotating drum (both not shown), has a field frequency of 60 Hz via the flat belt 11, pulley 12, and rotating shaft 13 in FIG. NTSC color video signals are recorded or reproduced on a magnetic tape (not shown).

In addition, the solenoid 14 is activated in advance during the stop mode in which the motor 2 is stopped, the motor is started in this state, and the solenoid 14 is deactivated after the motor starts, so that the pulley 10
rotates integrally with the pulley 9 exclusively for the NTSC system from the beginning, and can start recording and reproducing the NTSC system color video signal from the first part of the magnetic tape.

Next, we will explain the operation when canceling the NTSC mode and returning to the original PAL mode. Momentarily lowers the rotation speed below the rated value. When you operate the switch and temporarily cut off the power to motor 2,
The rotational speed of the motor 2 immediately decreases below the rated value and then returns to the rated value again. As a result, the pulley 7 dedicated to the PAL system and the pulley 9 dedicated to the NTSC system, which are coupled to the motor by a belt, rotate rapidly following the rotation of the motor 2. On the other hand, since the pulley 10 is belt-coupled to an upper rotating guide drum (both not shown) having a rotating magnetic head and a large inertial force, the rotational speed does not immediately drop even when the motor 2 is cut off. It continues to rotate at a rotational speed of approximately _N2 due to the inertial force of the upper rotating guide drum (not shown). Here, when the rotational speed of the pulley 9 dedicated to the NTSC system becomes lower than the rotational speed of the pulley 10, the engagement between the vertical portion 25b of the pin 25 and the hook-shaped locking portion 28a of the cam 28 is released in FIG. 6B. , the pin 25 rotates counterclockwise in the figure due to the action of centrifugal force, and the pin 25 rotates counterclockwise in the figure.
As shown in Figure B, the vertical portion 25b is a circular cam 27.
It comes into contact with. This releases the second one-way clutch formed by pin 25 and cam 28.

When the motor 2 is energized again and starts rotating at the rated speed, the pin 22 engages the cam 24 as shown in FIG. Then, a rotating magnetic head (not shown) is rotated at a speed corresponding to the PAL mode, and the apparatus enters a mode for recording or reproducing PAL color video signals.

In the above explanation, solenoid operation used to switch from PAL mode to NTSC mode, NTSC
Motor 2 for switching from mode to PAL mode
If you momentarily cut off the power to the PAL by turning on and off a single switch,
mode, start in NTSC mode, change from PAL mode to NTSC mode while playing, or
All operation selections for switching from NTSC mode to PAL mode are possible with a single switch.

In the above embodiment, the rotational speed of the rotating magnetic head is configured to be switched to suit the PAL mode and the NTSC mode, but the configuration is not limited to this, and the rotational speed of the rotating magnetic head can be changed to suit other systems. It is also possible to configure the rotation speed to be switchable.

As described above, according to the rotational speed switching device for a rotary head according to the present invention, the rotational speed of the rotary head is changed so that the rotary head is selectively rotated at specific different speeds depending on the field frequency of the video signal to be recorded and reproduced. This device includes first and second rotary driving bodies 7 and 9 that are rotated by a single motor at specific different speeds depending on the field frequency, and a rotary body 10 that rotates the rotary head by their rotation. and the rotating body and the first and second
a first unidirectional centrifugal clutch 22 which is provided between the rotary drive body and whose coupling member 22 can be engaged with a clutch engaging portion 24 by centrifugal force;
- 24 and second unidirectional centrifugal clutches 25 to 28 whose coupling members 25 are disengaged from the clutch engagement portion 28 by centrifugal force, and in connection with this second unidirectional centrifugal clutch, separately. , switching means 14, 3 for forcibly engaging the engaging member 25 with the clutch engaging portion 28 against the centrifugal force;
3, 35, and when the rotary head rotates at a constant speed (PAL), the switching means is not operated and the engaging member 22 of the first unidirectional centrifugal clutch and the clutch engaging portion 24 are substantially connected. Upon engagement, the rotary head is driven through a first unidirectional centrifugal clutch, resulting in high speed rotation (NTSC) of the rotary head.
When the rotary head is driven through the second unidirectional centrifugal clutch by operating the switching means, the coupling member of the first unidirectional centrifugal clutch and the clutch engaging portion are engaged with each other. position, and the configuration is such that there is no substantial clutch engagement due to the opposite relative velocities between the rotary body and the first rotary drive body 7, so that only a single motor is used. It is easy to configure, and the rotation speed of the rotary head can be changed not only when the motor is rotating, but also when the motor is stopped. Therefore, the rotary head can be set to the field frequency of the recording/playback method from the start of recording/playback. The one-way clutch can be rotated at a speed according to It has the advantage that it is not necessary to provide each one-way clutch, and the overall configuration can be simplified.

[Brief explanation of the drawing]

1 and 2 are a plan view and a front view, respectively, of an embodiment of the rotational speed switching device for a rotary head according to the present invention, and FIG. 3 shows a rotation transmission mechanism in the device shown in FIGS. 1 and 2. 4 is a partial vertical sectional front view of the rotation transmission switching mechanism taken along the line - in FIG. 1, and FIGS. A Y-Y direction arrow view and FIGS. 6A and 6B are respectively X-X and YY direction arrow views in FIG. 4 in the NTSC mode. 1...Guide drum assembly, 2...Motor,
6, 8...Square belt, 7...Pulley for PAL system, 9...Pulley for NTSC system, 10...Pulley, 14...Solenoid, 15...Rotation transmission path switching mechanism section, 22, 25...L Letter-shaped bending pin, 2
2b, 25b... Vertical portion, 24... Cam, 24
a, 24b...Step part, 27...Circular cam, 28...
...Cam, 28a...Hook-shaped locking portion, 28b...Rotation direction extending surface, 33...Switching lever, 34...Gap portion, 35...Latching lever, 35a...Circular arc portion.

Claims (1)

[Claims] 1 In a device that switches the rotation speed of a rotary head so as to selectively rotate the rotary head at specific different speeds depending on the field frequency of the video signal to be recorded and reproduced, a single motor rotates the rotating head at specific different speeds depending on the field frequency of the video signal to be recorded and reproduced. first and second rotary drives that rotate at different speeds, a rotary body that rotates the rotary head by the rotation thereof, and a rotary body that is provided between the rotary body and the first and second rotary drive bodies. a first unidirectional centrifugal clutch whose coupling member is brought into engagement with the clutch engagement portion by centrifugal force; and a second unidirectional centrifugal clutch whose coupling member is disengaged from the clutch engagement portion by centrifugal force. a one-way centrifugal clutch; and, in connection with the second one-way centrifugal clutch, a switching means for forcibly engaging the engaging member with the clutch engaging portion against the centrifugal force; When the rotating head rotates at a constant speed,
By not operating the switching means and by substantially engaging the engagement member of the first unidirectional centrifugal clutch with the clutch engagement portion, the rotating head is moved through the first unidirectional centrifugal clutch. When the rotary head rotates at a high speed, the switching means is actuated so that the rotary head is driven through the second unidirectional centrifugal clutch and the coupling of the first unidirectional centrifugal clutch is activated. Rotation characterized in that the member and the clutch engaging portion are in the engaged position such that no substantial clutch engagement occurs due to opposite relative speeds between the rotary body and the first rotary drive body. Head rotation speed switching device.