JPS61274140A - Gear change-over mechanism - Google Patents

Abstract

PURPOSE:To facilitate the change-over between the transmission and isolation of torque of a gear mechanism with a small force, by providing a means for moving a primary gear in the direction parallel to the rotary shaft of the gear, and by forming projections on a part of teeth of a primary gear, which are projected laterally of the gear. CONSTITUTION:Projections 4a are formed on a gear 4 so that the gear 4 may be surely meshed with the associated gear 2a even by a small spring force when the gear 4 is depressed downward by the force of a spring 19 and therefore it meshes with the gear 2a. The projections 4a formed on the gear 4 are arranged at intervals such that the number of them is less than the number of meshing teeth of the drive gear 2a. With this arrangement, even if teeth of two gears are not yet meshed, the gear 2a always abuts against one of the projections 4a so that the gear 4 is initiated to rotate, and therefore normal meshing may be at once made.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a connection of a rotating force transmission mechanism,
The present invention relates to a mechanism for shutting off, and in particular to a switching mechanism that can perform a gear switching operation with a small operating force and can be constructed in a small size.

[Background of the invention]

In a transmission mechanism using gears, some of the gears may be moved parallel to the shaft to interrupt power transmission.

2. Description of the Related Art Transmission devices for automobiles and the like are well known as mechanisms for switching rotational speeds. However, since such a device is a complicated and large mechanism, it is not suitable for a mechanism that is required to be miniaturized, such as a magnetic tape drive mechanism of a magnetic recording/reproducing device. In order to obtain a simple gear switching mechanism in such a small device, it is conceivable to simply move one gear in a spur gear meshing mechanism parallel to the shaft. In such cases, when shifting from a disengaged state to a engaged state, the gears must be moved with a fairly large operating force in order for the gears to mesh properly, but if the switching operating force is increased, a large noise may be generated during switching This may cause problems such as the occurrence of an error or a decrease in rotational speed. It is also conceivable to widen the pitch between the teeth so that the teeth can mesh more easily, but if this is done, there is a problem in that noise increases when the teeth are meshed and rotated.

Although this is not a normal operation for connecting and disengaging teeth, an example of how to smoothly mesh teeth when assembling a small gear mechanism is disclosed in Japanese Patent Application Laid-Open No. 55-54914. There is an example.

[Purpose of the invention]

An object of the present invention is to provide a gear switching mechanism that can easily and reliably switch between transmitting and blocking the rotational force of a gear mechanism with a small operating force and is suitable for downsizing.

[Summary of the invention]

In order to achieve the above object, the present invention solves the problem that when the teeth of gears are meshed, the reason why the teeth of the gears cannot be meshed smoothly is that the teeth of the moving gear remain on top of the teeth of the other gear, causing rotation. Focusing on one point, the present invention is characterized in that a protrusion is provided on the side surface of a part of the teeth of at least one of these gears. This protrusion is, for example,
The tooth surface of the tooth on which this is provided may be extended toward the side surface of the gear.

[Embodiments of the invention]

The present invention will be explained in detail below with reference to Examples.

1 and 2 are diagrams showing the main parts of one embodiment of the present invention, and FIGS. 5 and 4 show the present invention in a magnetic recording/reproducing device such as a video tape recorder or an audio tape recorder. An example of application will be shown.

In FIGS. 6 and 4, 1 is a base that holds the drive mechanism, and 2 is a flywheel that serves as a power source for the drive mechanism. A gear 2α is provided at the end of the flywheel 2, and a one-way portion 2h is provided at the bottom. The flywheel rotates 20 times from the pulley part 2b to the pulley gear 1 via the belt 6.
4, and further to gear 11 and gear 15. A rotating arm 24 is pressed against the gear 11 by a spring 18 via a felt 17 provided therebetween, and as the gear 110 rotates, a torque corresponding to the direction of rotation is applied to the rotating arm 24.

As a result, the rotating arm rotates, and the gear 15 becomes the gear 50.
Alternatively, it contacts the gear 55 and transmits rotation. Gears 50° and 55 each have felt '51. Gears 7゜8 are coaxially provided via ``5''5, and springs 52゜54, respectively.
As a result, the rotation of gears 50, 55 is transmitted to gear 7.8 in a slippery manner. Reel stand 56 for gear 7
However, a reel stand 9 is meshed with the gear 8, and the 140 rotations of the pulley gear are transmitted to the reel stand 9 or 36 via a slip mechanism depending on the direction of rotation, and the magnetic tape (not shown) is applied to the reel stand 9 with appropriate tension. taken up on the reel.

This operation occurs when the magnetic recording/reproducing device is in the recording or reproducing operation state, and at this time, the gear 4 is
) at the 4' position shown by the dashed line.

It does not mesh with the gear 2α at the upper end of the flywheel 2.

When performing operations such as fast forwarding and rewinding, in which the magnetic tape is run faster than the normal operating speed, the switching arm 15 is rotated and the gear holder 16 (FIG. 2, Figure 4 (h) is lowered and the spring 19
Gear 4 is pushed down with zero force. Therefore, the gear 4 and the gear 2a of the flywheel 2 mesh with each other as 5, and the gear 4
rotates. The gear 4 is provided with holes (not shown) into which the plurality of legs 5α of the gear 5 are inserted, and the rotation of the gear 40 is transmitted to the gear 5 through the legs 5α. The 50 rotations of the gear are transmitted to the gear 6 and the gear 10.

Similar to the configuration of the rotating arm 24 and the gear 11 described above, another rotating arm 25 is pressed against the side surface of the gear 10 by a spring 18 via a felt 22, and rotates in the direction of rotation of the gear 10. Torque is applied to the rotating arm 25 accordingly. End 1/C of rotating arm 25
A gear 12 that meshes with the gear 10 is held, and the gear 12 meshes with the gear 7 or 8 depending on the rotating direction of the rotating arm 23. Gears 7 and 8 mesh with gears on reel stands 56 and 9, respectively, and rotation of flywheel 2 is transmitted to reel stand 56 or 9. Transmission of this rotation, i.e. gear 2α - gear 4 - gear 5 - gear 6 - gear 10 - gear 12 - gear 7 or 8 - reel stand 36 or 9
Since the 0 rotation transmission does not involve a slip mechanism in the middle, the 60 rotations of the reel stand 9 or the filter are faster than the rotations transmitted via the googly gear 14 described above. Therefore, a fast forward or rewind operation is obtained in which the magnetic tape is wound onto the reel at a slow speed.

This switching of the engagement of gear 4 is performed as follows:
C is beaten. When the tip of the switching arm 15 shown in Fig. 2 is pushed to the left by the rotation of the switching arm 27 (Fig. 5) supported by the fulcrum 27cL fixed on the base 1, the switching arm axis 15α rotates, its arm 15C rotates clockwise (Fig. 2), and the holding shaft 16h, which is engaged with the elongated hole 15b provided in this arm 15C, is pushed upward, and the holding shaft 16h is rotated. The fixed gear holder 16 is pushed up and the gear 4 is pushed up against the spring 19 to the position shown at 4'. Therefore, gear 4 and flywheel 2
is disengaged from gear 2CL. Switching arm 27
When the gear 4 is rotated in the opposite direction, the gear 4 is pushed downward by the force of the spring 190 and meshes with the gear 2α, thereby realizing switching between the two types of rotation of the reel stand 9,560 as described above.

1 (α
I, (A protrusion 4C as shown in A+ is provided.

The protrusions 4α provided on the gear 4 are provided at intervals of a smaller number of teeth than the number of meshing teeth with the gear 2α on the drive side. In this way, even when the two teeth do not mesh, the gear 2α always comes into contact with one of the protrusions 4α of the gear 4, and the gear 4 starts rotating, so that normal meshing is immediately achieved. . Therefore, the force (spring force) that moves the gear 4 in the direction of meshing with the gear 2a only needs to be a weak force, so that the two rotate with their teeth overlapping on the sides, like when they are pressed with a strong force. Therefore, there is no problem that the mesh cannot be properly adjusted. The protrusion 4a may have a shape, for example, in which some teeth of the gear 4 are extended toward the side surface of the gear. Figure 1 (α1,
In the example shown in (b), there is a protrusion 4 on the gear 4 which is the driven side.
Although this is an example in which tL is provided, the same effect can be obtained by providing a protrusion on the gear 2α of the flywheel 2 on the drive side. In this case, the number of protrusions may be small regardless of the number of meshing teeth between the two. Furthermore, although a protrusion may be provided on both sides, if the protrusion is used in a small and thin device, a sufficient effect can be obtained by providing the protrusion on only one side.

In FIG. 3, the winding-side inhibit arm 25 supported at a fulcrum 25α and the supply-side inhibit arm 26 supported at a fulcrum 26α rotate gear 120 rotations to gear 7 or 8, the rotation arm 2 is rotated so that the rotation of the gear 130 transmitted by the rotation of the pulley gear 14 is not transmitted to the gear 50 or 35.
This is to regulate 4. In addition, in order to fix the rotating arm 25 holding the gear 12 and prevent the gear 12 from meshing with the gear 7 or 8 during operations other than fast forwarding and rewinding, an inhibit arm supported on the fulcrum 57α is provided. 57, and a pin 37b provided at one end of the pin 37b is engaged with a cam groove 25α of the rotating arm 25. Needless to say, these inhibit arms can be rotated according to each mode of operation.

〔Effect of the invention〕

As described above, according to the present invention, in a mechanism for switching the meshing of two gears by moving one gear in the axial direction of the gears, a protrusion is provided on the side surface of the teeth of at least one gear, so that the meshing can be changed. When switching to the gear position, the protrusion meshes with the other tooth at the same position at the beginning of meshing and starts rotating, resulting in meshing at the normal position, which slows down the movement of the gear. A small gear switching mechanism that can be operated by force and has little noise can be obtained.

[Brief explanation of the drawing]

Figure 1 (α), (bl is a bottom view and side view showing the main parts of an embodiment of the present invention, Figure 2 is a sectional view of the main parts showing an example of a gear switching mechanism to which the present invention is applied, FIG. 3 is a plan view showing an example of a main part of a magnetic recording/reproducing apparatus to which the present invention is applied;
Figure 4 (α) and (h) are A of the apparatus shown in Figure 5.
-C or AB sectional view and a bottom view of essential parts. 2...Flywheel, 2α...Gear, 4-8.10 to 15.50.55...Gear, 4α...
・Protrusion, 9.56... Reel stand, 1B, 19, 52, 54... Spring, 25, 2
4... Rotating arm, j5.27... Switching arm. Conclusion 1 Figure a (shi) 5ku 15t) /l, b

Claims (1)

[Claims] In a transmission mechanism that transmits and interrupts rotational force by bringing engagement and separation between two gears into contact, there is provided a means for moving at least one gear in a direction parallel to the rotation axis, and a gear to be moved, or a means for moving at least one gear in a direction parallel to the rotation axis. A gear switching mechanism characterized by comprising a protrusion provided on a part of the teeth of at least one of the gears in mesh with each other in the side direction of the gear.