JP2551778B2 - Drive mode switching device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive mode switching device in a magnetic recording / reproducing device such as a VTR (video tape recorder).

(Prior Art) Generally, in a magnetic recording / reproducing apparatus such as a VTR, recording,
There are various drive modes (hereinafter simply referred to as modes) such as playback, fast forward, rewind, stop, and pause. To support them, the positional relationship between the pinch roller and capstan, the position of the soft brake, and the main brake It is necessary to switch the position of the member for each of the other modes.

FIG. 3 is a plan view of an essential part showing an example of such a conventional mode switching device.

In the figure, reference numeral 1 denotes a mode motor capable of rotating in the forward and reverse directions. A first gear 2 which rotates integrally and is fixed to a rotation shaft of the mode motor, has a second gear 3a meshed with the first gear 2 and 3b.
Is a worm gear that is coaxially and integrally formed with it.

The worm gear 3b is meshed with a third gear having large and small gears 4a, 4b coaxially, and the small gear 4b is meshed with the cam gear 5. On one surface of the cam gear 5, there are formed concentric circles whose inner wall radii from the center are R ₁ , R ₂ , R _3, ... And a cam groove 5a in which their arcs are smoothly connected.

Reference numeral 6 is a main rod in which a cam follower pin 6a is implanted, and the cam follower pin 6a is slidably engaged with a cam groove 5a formed in the cam gear 5. Therefore, as the cam gear 5 rotates, the main rod 6, which receives the driving force from the cam follower pin 6a, can slide in the arrow FF 'direction by a slide guide (not shown).

Further, several cam surfaces are formed on the outer circumference or inside of the main rod 6, and the positions of the pinch roller, capstan, brake, etc. described above are changed by these surfaces.

In such a configuration, the mode motor 1 rotates in the A direction, and the small gear 4b of the third gear 4 passes through a series of gear trains.
Rotates in the C direction, the cam gear 5 meshing therewith rotates in the D direction, and along with this, the cam follower pin 6a is biased in the E direction along the cam groove 5a formed on the cam gear 5, The main rod 6 slides in the F direction.

The main rod 6 stops at the portion where the radius of curvature of the cam groove 5a is constant, and slides at the portion where the radius of curvature increases or decreases. Therefore, by controlling the position of the main rod 6 that corresponds to the position of the required drive mode to the position of the main rod 6 that stops and slides intermittently when it is stopped and feeds back the detection signal of the position of the main rod 6 to the mode motor 1. Then, each mode state is created and the drive mode is switched.

(Problems to be Solved by the Invention) In such a mode switching device, the number of the concentric circle portions (R ₁ , R ₂ , R ₃ ...) Of the cam groove 5a formed in the cam gear 5, that is, the main rod 6 is large. The number of modes is limited because the number of modes that can be formed is the number corresponding to the number of times when the modes stop. In order to increase this, it is necessary to increase the area of the cam gear 5, which hinders the downsizing of the mechanism.

In order to deal with this, it is conceivable to reduce the radius of the cam gear 5 to reduce the curvature radii R ₁ , R ₂ , R _3, ... Of the cam groove 5a, but this reduces the sliding stroke of the main rod 6. . On the other hand, a certain amount of sliding stroke is required to form the mode, and there is a limit to the reduction of the cam gear 5.

Further, since the driving member of the main rod 6 is the cam gear 5, a large transmission loss occurs as sliding resistance between the cam follower pin 6a and the cam groove 5a, and in order to compensate for it, sliding of the main rod 6 on the mode motor 1 is performed. Therefore, a larger sliding driving force is required than necessary, and the power consumption increases as the mode motor 1 grows stronger.

Further, when the transmission efficiency is low as described above, it is necessary to generate a large torque in the mode motor 1, so that a large force acts between the cam follower pin 6a and the cam groove 5a, and the reliability of the mechanism is improved. Also had a problem.

In view of various problems of the conventional example described above, the present invention does not mechanically increase the size even if the number of modes is increased or the stroke of the cam follower pin is freely set, and the driving force transmission efficiency is improved. It is an object of the present invention to provide a mode switching device which can be improved to improve reliability or reduce current consumption.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention employs a Geneva mechanism as a driving means for giving intermittent motion to a main rod for switching modes.

(Operation) In the present invention, a predetermined mode is set to correspond to an appropriate intermittent stop state that can theoretically be infinitely produced by rotating the Geneva without increasing the size by the Geneva mechanism. The number of modes can be increased by using the drive mode switching device, the size of the drive mode switching device is not increased even when the stroke is sufficiently taken, and the power transmission efficiency is high due to the meshing of gears. It can be provided.

(Examples) Hereinafter, the present invention will be described by examples with reference to the drawings.

FIG. 1 is a plan view of an essential part showing an embodiment of the present invention.
4 to 4 are the same as the description of the conventional example shown in FIG. That is, 1 is a mode motor capable of rotating in the forward and reverse directions, a first gear 2 which is integrally rotated is fixed to its rotation shaft, 3a is a second gear meshing with it, and 3b is coaxial with it. It is a worm gear that is formed integrally with the
A third gear 4 coaxially having 4a and 4b is meshed. 6 is a main rod.

Reference numeral 7 is a large geneva characterized by the present invention, which is connected to the small geneva 8 and meshes with the small gear 4b included in the third gear.
The small Geneva 8 meshes with the main rod 6 having a rack gear 6b formed in part. The main rod 6 is a drive source that moves a brake, a pinch roller, or the like (not shown) for driving a video tape to a predetermined position at a predetermined time, and forms a drive mode necessary for each state. 6
A mode switch (not shown) is provided for feeding back the position detection output of (1) to the mode motor 1 to stop its rotation and form the instructed mode.

FIG. 2 is a partially exploded view of the large Geneva 7 and the small Geneva 8. The large Geneva 7 has a gear 7c that meshes with the worm gear 3b shown in FIG. A gear 7b having two meshing teeth 7e provided only at a diameter end is coaxially integrated. Similarly, it has a Geneva 7a that is coaxially integrated with the gear 7c or 7b and has a notch 7d formed at a portion that is opposed to and fitted with the meshing tooth 7e.

On the other hand, the small Geneva 8 has a gear 8e fitted with the gear 7b and having meshing teeth engraved on the entire circumference, and has a Geneva 8b which is coaxially integrated with the gear 8e and meshes with the Geneva 7a. ing.
This Geneva 8b has a cam section 8d for every 90 ° about the axis of the gear 8e.
4 portions, and a curved portion 8c is formed between these portions along the circumferential portion 7f of the Geneva 8b and the Geneva 7a.

Further, a gear 8a, which is coaxially integrated with the gear 8e and the geneva 8b and has mesh teeth formed on the entire circumference, is provided on the upper surface of the geneva 8b, and the gear 8a is the main rod 6 shown in FIG. And slide it in the FF 'direction.

In the present invention configured as above, the mode motor 1 is
When rotated in the direction, the small gear 4b of the third gear 4 rotates in the direction of arrow C via a series of gear trains (Fig. 1). Next, in FIG. 2, the rotation of the small gear 4b is the gear of the large Geneva 7.
Drive 7c and rotate it in direction D.

When the large Geneva 7 rotates in the D direction, the meshing tooth 7e is moved to the gear 8e.
When it does not mesh with, the large Geneva 7 rotates, but it does not rotate because the rotational driving force is not transmitted to the gear 8e, and the circumferential portion 7f of the Geneva 7a follows the curved portion 8c of the Geneva 8b. The small Geneva 8 has a curved portion 8c and a circumferential portion 7f because it is rotating.
Positioned by and stopped. When the large Geneva 7 rotates further and the meshing teeth 7e mesh with the gear 8e, the notch
The cam portion 8d is fitted to 7d, and the driving force transmitted to gear 7c
It is transmitted to 8e and the small Geneva 8 rotates 90 °. That is,
The small Geneva 8 intermittently makes one rotation with four rests, while the large Geneva 7 has two rotations.

The intermittent rotational movement of the small Geneva 8 in the E direction as described above intermittently gives the main rod 6 a movement in the F direction in FIG. Therefore, if a predetermined mode is set correspondingly to an appropriate rest position where the main rod 6 rests, it becomes easy to detect the mode by the above-mentioned mode switch,
The detection signal can be fed back to the mode motor 1 and stopped to determine the position where each member of the recording or reproducing unit such as the pinch roller or the brake operates.

As described above, the Geneva mechanism used in the present invention is not limited to the one shown in FIG. 2, but any other Geneva mechanism may be used as long as it is a mechanism that gives intermittent motion to the driven system. Of course.

As described above, according to the present invention, the small Geneva 8 makes one rotation intermittently resting four times with respect to the two rotations of the large Geneva 7, and the main rod 6 makes an intermittent sliding motion in synchronization therewith. Therefore, it is possible to increase the number of rotations of the mode motor 1 to form a large number of intermittent motion stoppages. If the stoppages are appropriately selected and a predetermined operation of the recording or reproducing unit is performed, the mode switching can be performed. Mode operation can be formed without increasing the size of the device in accordance with the number of modes.

Further, since the main rod 6 and the small Geneva 8 are interlocked with each other by the meshing of the gear and the rack gear, the transmission efficiency is extremely good, the mode motor 1 can be downsized, and the mechanism does not require excessive force. It will be possible to contribute to the improvement of the reliability of.

(Effects of the Invention) As will be apparent from the detailed description given above, the present invention transfers the rotational force of the mode motor of the drive source to the main rod by the Geneva mechanism to move the member to a predetermined position. Since this is a device, the number of modes can be increased or the stroke of the main rod can be freely set without increasing the size, which contributes to downsizing and weight saving of the magnetic recording / reproducing device.

Furthermore, since the driving force is transmitted to the main rod via the gear, the transmission efficiency is extremely good, which allows the mode motor to have a small output and thus reduce power consumption. Since the drive system does not require much force, the reliability of the mechanism can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part showing an embodiment of the present invention, FIG. 2 is an exploded perspective view of the same part, and FIG. 3 is a schematic plan view showing a conventional example. 1 ... Mode motor, 2 ... First gear, 3a ... Second gear, 3b ... Worm gear, 4 ... Third gear, 4a ... Large gear, 4b ... Small gear, 5 ... Cam gear, 6 ...... Main rod, 6a ...... Cam follower pin, 6b ...... Rack gear, 7 ...
… Large Geneva, 7a …… Geneva, 7b, 7c …… Gear, 7d …… Notch part, 7e …… Mating tooth, 7f …… Circular part, 8 …… Small Geneva, 8a, 8e …… Gear, 8b ...... Geneva, 8c ...... Curved section, 8d
...... Cam section.

Claims (2)

(57) [Claims] 1. In a magnetic recording / reproducing apparatus, a mode motor power source, a recording or reproducing section having a plurality of operating position states, and a predetermined movement amount when switching from any of the operating position states to another operating position state. And a Geneva mechanism arranged so as to intermittently transmit the driving force of the mode motor power source to the main rod. And a drive mode switching device. 2. The drive mode switching according to claim 1, wherein the rotary motion intermittently transmitted by the Geneva mechanism is transmitted to a rack gear portion formed in a part of the main rod. apparatus.