JPH0672090A - Mechanical power transmission device - Google Patents

Abstract

PURPOSE:To surely transmit mechanical power without being influenced by load in the device of the large-sized endless sheet part of the indication part in an electric blackboard by always press-contacting at least a pair of guide members by an elastic body, providing the same in the arbitrary position of a transmission member and movably constituting the elastic member so that the pushing amount of the transmission member depending on the guide member is changed. CONSTITUTION:A timing belt 8 is stretched between a driving roller and a motor pulley 9. A pair of rollers 14, 14 are freely rollingly press-contacted to the outsides of the traveling faces 8a, 8b thereof and provided. The rollers 14, 14 are freely rotatably supported in the respective tip parts of a forked spring 13. The forked spring 13 is formed into a torsion spring wherein a torsion part is provided in the fulcrum part of the center. The rollers 14, 14 are pushed to the inside as shown by the arrows. When tensile force of the timing belt 8 is fluctuated by load fluctuation and tension of the traveling faces 8a, 8b is fluctuated, the spring 13 is extended and contracted to the inside and the outside and the rollers 14, 14 are moved and tension fluctuation is absorbed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device for conveying and driving a large endless sheet used for a display portion of an electronic blackboard, and more particularly to a torque transmission member (timing belt or flat belt) for transmitting torque from the driving portion. ) Relates to the improvement of the device for transmitting to the driven part.

[0002]

2. Description of the Related Art FIG. 6 (a) is a plan view showing the structure and principle of a conventional electronic blackboard having an endless sheet for multi-sided writing, in which a driving roller 1 and driven rollers 21, 22, 23 are endless sheets. 3 is wound on the path shown in the drawing, and at the position where the endless sheet 3 is folded back by the driven roller 21, the surface (the portion where characters are written) is illuminated by the light source 4, and the reflected light is received by the mirror 5. The lens 6 collects the light, and the line sensor 7 photoelectrically converts the image information on the sheet 3. The driving roller 1 for conveying the sheet 3 is connected to a motor pulley 9 by a timing belt 8, and a driving force is transmitted to the motor pulley 9 by a motor (not shown), and the driving force is transmitted via the timing belt 8 to the driving roller 1 Then, the endless sheet 3 is conveyed.

FIG. 6 (b) is a plan view showing a sheet driving portion of a conventional electronic blackboard, and FIG. 7 is a partial front view. Figure 6
In (b) and FIG. 7, the output shaft of the stepping motor (not shown) is fixed to the shaft 9a of the motor pulley 9. The driven portion that receives the transmission of the driving force from the motor pulley 9 includes a driving pulley 1a integrated with the lower end portion of the driving roller 1 in the axial direction, and a shaft 1b that is press-fitted and positioned in the axial center portion of the driving pulley 1a. The shaft 1b is rotatably supported by a bearing 11 fixed to the support plate 10.

The support plate 10 is provided with the shaft 1b of the drive roller 1 as shown in FIG.
Each axis of the driven rollers 21, 22, 23 shown in (a) (not shown)
Are rotatably positioned and supported via bearings 11, respectively. The support plate 10 is similarly arranged on the upper portion, and supports each bearing that axially supports the shaft of the upper end portion of each roller. An endless sheet 3 which constitutes a writing sheet of an electronic blackboard is wound around the outer periphery of the driving roller 1. A timing belt 8 as a transmission member is wound around the drive unit side motor pulley 9 and the driven unit side drive pulley 1a with a certain tension. When a drive signal is input to a stepping motor (not shown) from a controller (not shown), the motor is excited and starts rotating, and as a result, the motor pulley 9 rotates. Then,
Power is transmitted to the drive pulley 1a by the timing belt 8 to rotate the drive roller 1 and convey the endless sheet 3.

In order to reduce the sheet carrying load,
It is preferable to use rolling bearings as bearings, but it is essential to use sliding bearings in consideration of cost durability, and it is necessary to bear the slight increase in transport load, which is a drawback caused by using sliding bearings. There is. Further, because of such a state, there is a strong demand to make the carrying force as large as possible and the motor small. For that purpose, it is necessary to increase the reduction ratio, but it is necessary to reduce the number of reduction stages and increase the reduction ratio for reasons of space and cost.
That is, it is important to reduce the number of teeth of the motor pulley by one step deceleration and increase the number of teeth of the drive pulley as much as possible to increase the reduction ratio.

By the way, if the endless sheet 3 is conveyed in the state as shown in FIGS. 6 (b) and 7, the following problems will occur. That is, in the endless sheet 3 having an endless shape, as shown in FIG. 8, since the endless sheet 3 is joined by heat welding to form an endless sheet, the seam is usually formed from other portions. It's getting harder. Therefore, the conveyance load becomes large at the time of approaching the driven rollers 21, 22, 23. Especially, when the transportation speed is high, the transportation load becomes extremely large. In addition, the load increases when the user who uses the electronic blackboard presses the endless sheet with his or her hand or a writing instrument. In such a state, tooth jumping of the belt occurs at the meshing portion between the timing belt 8 and the motor pulley 9, and accurate reading and printing cannot be performed.

If the distance between the motor pulley 9 and the drive pulley 1a is set to be large so that sufficient tension is applied to the timing belt 8 in order to prevent tooth jumping, the motor may lose synchronization due to load fluctuations. Therefore, accurate reading and printing cannot be performed. Further, at the time of starting the motor, a high torque is generated due to the characteristics of the motor, and due to the large rising torque, the vibration is transmitted to the timing belt 8 via the motor pulley 9, and the vibration is transmitted from the drive pulley 1a to each part, resulting in an audible noise It makes me feel uncomfortable. Since it is necessary to prevent such tooth jump, motor step-out, and noise, belt tension adjustment is performed in order to keep the axial distance between the drive pulley 1a and the motor pulley 9 constant.
The adjustment range is very narrow and the adjustment is time consuming, but the effect is not good.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to reliably transmit power to a large endless sheet wound around a plurality of rollers and run without being influenced by a load, and to make various adjustments to reduce noise. It is an object to provide a transmission device that does not.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a drive unit,
In a power transmission device including a driven portion and a transmission member for transmitting the power from the driving portion to the driven portion, at least one pair of guide members slidably contacting any position of the transmission member are provided. An elastic member that constantly elastically presses each of the guide members is provided, and the elastic member is configured to be movable so that the pushing amount of the transmission member by each guide member is different, based on the output from the drive unit. It is characterized in that the driven portion is capable of forward and reverse rotation.

[0010]

According to the power transmission device having the structure of the present invention, the transmission member is constantly pressed by the elastic member, and the pressing position (pushing amount) of the guide portion is made variable by the rotation around the fulcrum of the elastic member. Since the load is not suddenly applied to the drive unit even when the motor starts up, falls, and when other load fluctuations are extremely large, it is possible to reliably transmit the torque without stepping out of the motor. Therefore, there is no tooth skipping due to the timing belt, and reading and printing can be performed with high accuracy. Further, according to the present invention, it is possible to reduce the noise when the motor starts up, when it falls down, or in the normal state. Further, according to the structure of the present invention, the power transmission device can be rotated forward and backward, and the previously written endless sheet can be recalled again without any trouble.

[0011]

The present invention will be described in detail below with reference to the drawings. [Embodiment 1] FIG. 1 is a plan view showing a configuration of an embodiment of a seat driving portion of an electronic blackboard according to the present invention, FIG. 2 is a partial front view thereof, and FIG. 3 is a plan view showing an operation. is there. The arrangement and configuration of the motor pulley 9 that constitutes the drive unit, the drive roller 1 that constitutes the driven unit, the drive pulley 1a, and the configuration related to the timing belt 8 that is the transmission member are shown in FIG.
Since it is the same as FIG. 7, duplicated description will be omitted. Each running surface 8 of the timing belt (transmission member) 8 facing each other
A roller (guide member) 14 rotatably pressed to the outside of a, 8b is rotatably supported by two tip portions 13a of a bifurcated spring 13 (elastic member) which is an elastic member. The stopper 15 prevents the roller 14 from falling off the tip portion 13a of the spring 13.

The elastic member spring 13 is a torsion spring in which a central fulcrum portion 13b is provided with a twisted portion, and each roller 14 is pressed in the direction of the arrow (inward) in FIG. 1 about the torsional fulcrum portion. . A set screw 12 is inserted into the hollow inside of the fulcrum of the spring 13, and the set screw 12 is attached to the support plate 10. The spring 13 is loosely fitted in the set screw 12 so as to be rotatable around its fulcrum portion 13b. Normally, when the power from the stepping motor (not shown) is not transmitted, or when the timing belt 8 is moving at a constant speed,
As shown in FIG. 1, the rollers 14 press the outer sides of the central portions of the two traveling surfaces 8a, 8b of the timing belt 8 which face each other, with a uniform pressure toward the inner side, which is a stable state.

As shown in FIG. 3, at the moment when the stepping motor is driven and the motor pulley 9 starts to rotate in the forward direction, the upstream side 8a of the two running surfaces of the timing belt 8 facing each other becomes the tension side and the opposite side 8b. Becomes the loose side instantly. At that time, one roller 14a is pushed upward by the tension of the tension side 8a in FIG. Since the rollers 14a and 14b press the timing belt 8 inward by the contracting force of the spring 13 and rotate about the fulcrum, the other roller 14b
Is for correcting looseness of the running surface 8b of the timing belt 8 (bending the running surface 8b as shown to maintain tension)
While moving up. Then it stops in a stable position. When the motor pulley 9 rotates in the reverse direction, the above operation is reversed. Therefore, at the moment when the motor starts, the timing belt 8 does not suddenly stretch, so that the load on the motor at the moment when the motor starts is eliminated. In addition, the load is not instantaneously applied even when the motor falls.

When the drive roller 1 is rotating at a constant speed and the load caused by the seam of the endless sheet 3 (see FIG. 8) is instantaneously applied to the drive pulley 1a, the timing belt 8 is rotated as shown in FIG. Since it is in contact with 14 in a bent state, the traveling surfaces 8a and 8b of the timing belt 8 try to expand in the stretching direction (outside) in accordance with the load variation. However, since the traveling surfaces 8a and 8b are both pressed inward by the roller 14 and the spring 13, the load is absorbed as tension. Therefore, the motor pulley 9
Therefore, a sudden load change is not transmitted to the shaft of the stepping motor. Therefore, there will be no step out. Even when the motor rises and falls as described above, the stroke of the timing belt 8 shifting from the bent state to the stretched state becomes slow due to the pressing force of the spring 13 and does not instantaneously shift. The load on the stepping motor shaft is not suddenly applied.

The distance between the fulcrum portion 13b of the spring 13 and the roller 14 is increased, and the spring can be rotated around the fulcrum portion, so that the spring constant is made as small as possible and a constant pressing force is always applied. This is to obtain a constant pressure and to apply a constant pressing force instantly when rotating in either forward or reverse directions. The roller 14 is rotatable and reduces the load at the time of contact with the timing belt 8. Also, in FIG.
With the configuration shown in FIGS. 2 and 3, the power transmission device can smoothly rotate forward and backward, and the previously written endless sheet can be recalled again without any trouble.

In the above embodiment, the driving and driven deceleration is one stage, but this is only an example, and the present invention is irrelevant to the number of deceleration stages and may be installed at any position. Further, although the example in which the driving side is constituted by the stepping motor and the driving pulley is shown, the invention is not limited to this. Further, since the timing belt 8 is pressed by the roller 14, the belt 8 is not in a tension state. Further, the roller 14 and the spring 13 cause vibration due to an increase in torque when the motor rises or falls, but the mechanism of this power transmission device absorbs the vibration and prevents transmission to the drive pulley 1a. In addition, spring 13
It becomes possible to fix the distance between each axis of the motor pulley 9 and the drive pulley 1a by adjusting the pressing force of (4) and setting it appropriately.

[Embodiment 2] In Embodiment 1, the rollers 14 are supported on the respective tips of the bifurcated torsion spring 13 to press both traveling surfaces of the timing belt 8 inward, but elastic members other than the torsion spring are used. (For example, coil spring, leaf spring)
May be used. For example, as shown in FIG. 4, if it is possible to secure a constant pressing force and positioning on the belt running surfaces 8a and 8b, the elastic member 13 is a spring as shown and a fulcrum for newly rotating the spring is provided. You may do it. This is because the tension as shown in FIG. 3 can be adjusted for the first time by rotating the spring.

[Third Embodiment] In the first embodiment, the roller 14
Although the belt running surfaces 8a and 8b facing each other are pressed from both outsides to the inside, as shown in FIG. 5, a fixed side roller 14b having an axial center fixed to one running surface 8b side is rotatably provided. The other running surface 8a may be pressed by the movable roller 14a. That is, in the example shown in FIG. 5, one of the arms of the torsion spring 13 is made short and fixed, and the roller 14a is rotatably supported at the tip of the long other arm. In this case, it is effective against load fluctuation at the time of rising when rotating in the direction of the arrow.

[0019]

According to the present invention, the following effects can be obtained. (1) There is no tooth skipping due to the timing belt, and transmission is performed reliably. Therefore, reading and printing can be performed with high accuracy. Further, since the motor pulley can be made as small as possible and the reduction ratio can be made large, it is possible to perform one-step reduction, reduce parts, reduce costs, and establish a drive system with space saving. (2) Even when the load fluctuation is extremely large at the time of starting and falling of the motor, the load is not suddenly applied to the drive unit by this configuration, and the motor can be surely transmitted without step-out. . (3) Noise is reduced when the motor starts up, falls, or in a normal state. (4) Since it is not necessary to adjust the distance between the shafts of the motor pulley and the drive pulley, workability is improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an endless sheet driving unit of an electronic blackboard of the present invention.

FIG. 2 is a partial front view showing an endless sheet driving unit of the electronic blackboard of the present invention.

FIG. 3 is a plan view showing an operating state of the present invention.

FIG. 4 is a diagram showing an example in which a spring is used as an elastic member.

FIG. 5 is a diagram showing that one of two rollers provided on the elastic member may be a fixed side and the other may be a movable pressing side.

6A and 6B are views showing an electronic blackboard having a conventional multi-sided writing endless sheet and a plan view showing an endless sheet driving unit of the conventional electronic blackboard.

FIG. 7 is a partial front view showing an endless sheet driving unit of a conventional electronic blackboard.

FIG. 8 is a diagram showing a state of a joint of an endless sheet.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 drive roller, 2a drive pulley, 2b bearing shaft, 21 driven roller, 22 driven roller, 23 driven roller, 3 endless sheet, 4 light source, 5
Mirror, 6 lenses, 7 line sensor, 8
Timing belt, 9 motor pulley, 10 support plate, 11 bearing, 12 set screw, 13 elastic member, 14
Roller, 14a roller, 14b roller, 15 stopper

Claims (2)

[Claims] 1. A power transmission device comprising a drive unit, a driven unit, and a transmission member for transmitting power from the drive unit to the driven unit, and a guide member slidingly contacting an arbitrary position of the transmission member. At least one pair of elastic members are provided, and elastic members that constantly elastically press each of the guide members against the transmission member are provided, and the elastic members are configured to be movable so that the pushing amounts of the transmission members by the guide members are different. Power transmission device characterized by. 2. The power transmission device according to claim 1, wherein the driven portion is capable of forward and reverse rotations based on an output from the drive portion.