JPH05126218A - Belt transmission mechanism - Google Patents

Abstract

PURPOSE:To provide a mechanism in which transmission torque loss is little and small in size in a belt transmission mechanism used in a magnetic recording and reproducing device. CONSTITUTION:Idler pulleys 23 and 24 are provided between a driving pulley 1 and a driven pulley 4 at the positions from the outer circumference of winding of a belt 6 with this belt held between them. The idler pulleys 23 and 24 are rotatably mounted $ the end of a V-shaped pulley lever 21. The idler pulleys 23 and 24 are automatically moved to the position where a difference in tension between the tense side and the loose side becomes small all the time according to the change in the tension of the belt 6 opposed to the rotation direction of the pulley 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt transmission mechanism used in video tape recorders, digital audio tape recorders and the like.

[0002]

2. Description of the Related Art In recent years, video tape recorders (VTRs)
In digital audio tape recorders (DAT) and the like, there is a strong demand for downsizing, thinning, and low power consumption. Along with this, the belt transmission mechanism used for transmitting torque from the capstan motor to the load side such as the tape reel also has a small torque transmission loss,
And small things are required.

A belt transmission mechanism used in a conventional VTR or DAT tape transport device will be described. FIG. 7 is a top view of a conventional belt transmission mechanism, and FIG. 8 is a side view thereof, a part of which is cut away. 7 and 8, the drive pulley 1 is fixed to a rotor shaft 3 which is a rotation shaft of a capstan rotor 2 as a drive source. The driving pulley 1 and the driven pulley 4 are rotatably held at positions separated from each other on the chassis 5, and an endless belt 6 is stretched between them. Triangular teeth, for example, are formed on the inner circumference of the winding of the belt 6, and tooth grooves that mesh with the teeth of the belt 6 are also provided on the outer peripheral portions of the driving pulley 1 and the driven pulley 4.

Next, a center gear 7 and a swing lever 8 are coaxially attached to the driven pulley 4. The center gear 7 has the swing lever 8 scissors between it and the driven pulley 4, and rotates integrally with the driven pulley 4. A gear is formed on the outer peripheral side surface of the center gear 7. The swing lever 8 is a lever that rotates independently of the driven pulley 4, and has support arms 8a and 8b that project in a V shape from the central disk portion. A pair of pendulum gears 9 is provided on the support arms 8a and 8b.
A and 9b are rotatably supported. Pendulum gear 9a
Reference numeral 9b serves as an idler gear that swings to the left and right as the swing lever 8 rotates. Pendulum gears 9a, 9b
Both mesh with the outer peripheral side surface of the center gear 7, and selectively mesh with the gears of the supply reel base 10 or the take-up reel base 11 as the swing lever 8 swings.

On the driven pulley 4 side of the swing lever 8,
An annular friction plate 12 is fixed. The other surface of the friction plate 12 is in contact with the driven pulley 4, and the back surface of the driven pulley 4 is pressed by the clutch spring 13 provided in the annular groove on the lower surface of the center gear 7. On the other hand, the idler pulley 14 is a pulley that is rotatably attached to the chassis 5 and bends the belt 6 inward from the outer circumference of the winding to give an appropriate initial tension.

The operation of the conventional belt drive mechanism constructed as above will be described. FIG. 9 is a plan view showing the meshing state of the belt 6 on the driving pulley 1. As shown in FIGS. 7 and 8, when the capstan rotor 2 rotates clockwise (direction of arrow A), the tension of the belt 6 on the idler pulley 14 side is equal to the tension corresponding to the driving torque of the driving pulley 1. Although it becomes lower, the idler pulley 14 has a belt 6
Since the belt 6 is fixed by applying an appropriate initial tension to the belt 6, the belt 6 can transmit the rotational power in the clockwise direction to the driven pulley 4 with almost no loosening. As a result, the swing lever 8 receives the tension from the belt 6 and rotates clockwise,
The pendulum gear 9b meshes with the take-up reel stand 11 to rotate the take-up reel stand 11.

[0007]

However, in such a conventional structure, when the capstan rotor 2 rotates in the counterclockwise direction (the direction of arrow B in FIG. 7), the tension of the belt 6 on the idler pulley 14 side is driven. Since the tension corresponding to the torque increases, the friction loss in each bearing and the friction loss between the idler pulley 14 and the belt 6 increase. Further, since the belt 6 is circular in the unloaded state without being wound, the belt 6 swells to the outer circumference side of the winding as shown in 6A of FIG. 9 on the side where the tension is low. Therefore, the meshing ratio between the teeth of the belt 6 and the tooth grooves of the driving pulley 1 or the driven pulley 4 is reduced, and finally the meshing is disengaged.
However, there was a drawback that the sliding power might not be transmitted.

On the other hand, if the initial tension of the belt 6 is increased in order to prevent this, the friction loss between the belt 6 and the drive side pulley 1 or the driven side pulley 4 and the friction loss in the bearing are further increased, and the transmission torque is lost. Will grow. In addition, when the initial tension of the belt 6 is increased, the thickness of the chassis 5 supporting the drive side pulley 1 and the driven side pulley 4 is increased to secure the strength, and the belt 6 is prevented from being broken. Due to the large size, there is a problem that the entire belt transmission mechanism becomes large.

The present invention has been made in view of the above conventional problems, and it is an object of the present invention to provide a small belt transmission mechanism in which the loss of the transmission torque between the driving pulley and the driven pulley is small. To aim.

[0010]

According to the present invention, a drive pulley directly connected to a drive source that rotates in a forward or reverse direction, a driven pulley that applies a rotational force to a load, and a driven pulley and a drive pulley are wound. Between the rotated belt, the drive side pulley and the driven side pulley, a plurality of idler pulleys that are rotatably provided at positions that press the belt from the outer circumference of the belt, and a plurality of idler pulleys are rotatably supported. And a support member that moves according to a change in the tension of the belt.

[0011]

According to the present invention having such a feature, when the driving pulley rotates, the support member rotates under the tension of the belt, and the tension difference between the tension side and the slack side acting on the belt is always maintained. Move multiple idler pulleys to smaller positions. Therefore, the tension of the belt is automatically adjusted so as to be constant on both sides, and the belt transmission mechanism has a small loss of the transmission torque and a small size.

[0012]

1 to 3 are top views showing a belt transmission mechanism according to a first embodiment of the present invention. FIG. 1 shows a state during clockwise rotation, FIG. 2 shows a state during rotation stop, and FIG. 3 shows a state during counterclockwise rotation. FIG. 4 is a side view showing the structure of the belt transmission mechanism in this embodiment. The same parts as those in FIGS. 7 and 8 showing the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

Also in this embodiment, as in the conventional example, the tape conveying device includes a drive side pulley 1, a capstan rotor 2, a driven side pulley 4, a belt 6, a center gear 7, a swing lever 8, and pendulum gears 9a and 9b. A belt transmission mechanism including is provided.

Now, in this embodiment, the pulley lever 21
Is rotatably attached coaxially with the center gear 7. The pulley lever 21 is coaxially rotatably supported so that it can be rotated independently of the driven pulley 4, and a left idler pulley 23 and The right idler pulley 24 is pivotally supported. The left and right idler pulleys 23, 24 have belt grooves and urge the belt 6 from the outer circumference of winding. By rotating the pulley lever 21 independently of the driven pulley 4,
The positions of the idler pulleys 23 and 24 are changed so that the belt 6 is bent from the left and right. Other configurations are the same as those of the conventional example. Here, the pulley lever 21 rotatably supports the idler pulleys 23 and 24, and constitutes a support member that moves in response to changes in the tension of the belt 6.

The operation of the belt transmission mechanism thus constructed will be described. As shown in FIG. 1, when the capstan rotor 2 rotates in the direction of arrow A, the tension on the left idler pulley 23 side of the belt 6 becomes higher than the tension on the right idler pulley 24 side by the amount corresponding to the drive torque. Therefore, the left idler pulley 23 is pushed out by the tension of the belt 6 to the outside of the belt winding. Along with this, the pulley lever 21 slightly rotates counterclockwise, and the right idler pulley 24 presses the belt 6 inward. Therefore, the looseness of the belt 6 does not occur on the left and right.

When the driving pulley 1 stops rotating, the tension imbalance corresponding to the driving torque does not occur in the belt 6, so that the left idler pulley 23 and the right idler pulley 24 are in a substantially neutral position as shown in FIG. It is in.

On the other hand, as shown in FIG. 3, when the capstan rotor 2 rotates in the direction of arrow B, the tension of the belt 6 on the right idler pulley 24 side corresponds to the drive torque rather than the tension on the left idler pulley 23 side. As the tension increases, the right idler pulley 24 is pushed out of the belt winding by the belt 6. Along with this, the pulley lever 2
1 rotates slightly clockwise, and the left idler pulley 23 also moves so as to press the belt 6 inward.
Does not occur.

In this way, the left and right idler pulleys 23 and 24 are always stabilized at positions where the tension of the belt 6 is kept balanced, regardless of the direction and the torque of the capstan rotor 2. Therefore, it becomes unnecessary to apply an initial tension higher than necessary to the belt 6. Therefore, the belt 6 can surely transmit the power without slipping with each pulley, and the loss of the transmission torque is reduced. Although the pulley lever 21 is rotatably supported coaxially with the driven pulley 4 in this embodiment, it may be rotatably supported coaxially with the drive pulley 1.

Next, FIGS. 5 and 6 are a plan view and a side view of the belt transmission mechanism in the second embodiment of the present invention. In this embodiment, as shown in FIG. 5, the pulley lever 31 is provided so as to be slidable with respect to the chassis 5. The pulley lever 31 has a long plate shape, and is a support member that rotatably supports a right idler pulley 32 and a left idler pulley 33 at both ends thereof. Then, the ends of the shafts 32a and 33b of the pulleys are provided with a guide groove 34 which is cut into the chassis 5 in an elongated linear shape.
And to fit in this groove.

Also in this case, when the driving pulley 1 rotates in the A direction, the tension on one side of the belt 6 increases and the right idler pulley 32 is pushed out in the arrow C direction. Therefore, the left idler pulley 33 also moves in the C direction, and holds the tension of the belt on the side meshing with this pulley. When the drive pulley 1 rotates in the opposite direction, the left idler pulley 33
Are pushed out of the belt 6, and the tension balance of the belt 6 is maintained.

Although the belt transmission mechanism of the present invention is constituted by a toothed belt, it may be constituted by a toothless rubber belt or a belt having another shape, and is not limited to the belt, but may be another endless flexible member (for example, a belt). Similar effects can be obtained even with a chain).

[0022]

As described above, according to the present invention, between the drive side pulley and the driven side pulley, a plurality of idler pulleys are provided at positions sandwiching the belt from the winding outer circumference of the belt, and the tension of the belt is reduced. I try to move according to changes. For this reason, the tension is automatically adjusted so that the difference between the tension side and the slack side of the tension acting on the belt is always small, so that it is possible to realize a small belt transmission mechanism with little loss of conduction torque. Its practical effect is great.

[Brief description of drawings]

FIG. 1 is a top view (during clockwise rotation) of a belt transmission mechanism according to an embodiment of the present invention.

FIG. 2 is a top view (when rotation is stopped) of the belt transmission mechanism in the present embodiment.

FIG. 3 is a top view (during counterclockwise rotation) of the belt transmission mechanism in the present embodiment.

FIG. 4 is a side view of a belt transmission mechanism according to this embodiment.

FIG. 5 is a top view of a belt transmission mechanism according to another embodiment of the present invention.

FIG. 6 is a side view of a belt transmission mechanism according to another embodiment.

FIG. 7 is a top view of a conventional belt transmission mechanism.

FIG. 8 is a side view of a conventional belt transmission mechanism.

FIG. 9 is a partially enlarged view of a conventional belt transmission mechanism.

[Explanation of symbols]

 1 Drive Pulley 2 Capstan Rotor 3 Rotor Shaft 4 Driven Pulley 5 Chassis 6 Belt 7 Center Gear 8 Swing Lever 8a, 8b Support Arm 9a, 9b Pendulum Gear 12 Friction Plate 13 Clutch Spring 14 Idler Pulley 21, 31 Pulley Lever 22 , 32a 33a Shaft 23 32 Left idler pulley 24 33 Right idler pulley 34 Guide

Claims (1)

[Claims] 1. A drive-side pulley that is directly connected to a drive source that rotates in a forward or reverse direction, a driven-side pulley that applies a rotational force to a load, a belt that is wound around the driven-side pulley and the drive-side pulley, Between the drive-side pulley and the driven-side pulley, a plurality of idler pulleys that are rotatably provided at positions that press the belt from the outer circumference of the belt, and rotatably support the plurality of idler pulleys. And a support member that moves according to a change in the tension of the belt, the belt transmission mechanism.