JPH09104545A - Driving gear for paper feed roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an attraction type electromagnet from generating heat by eliminating necessity for operating a control means during the time with a paper feed roller left stopping. SOLUTION: A device has a drive gear 32 connected to a drive source, driven gear 33 connected to a paper feed roller, idle gear 41 arranged between the drive gear 32 and the driven gear 33 to take the first/second positions with power transmitted from the drive gear 32 to the driven gear 33 in the first position and transmission of power interrupted from the drive gear 32 to the driven gear 33 in the second position and a position switching means selectively placing the idle gear 41 in the first/second positions. The position switching means, by instantaneously attracting a movable core 47 of an attraction type electromagnet 45, performs switching of the first/second positions. A time for attracting the movable core 47 of the attraction type electromagnet 45 is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feed roller driving device.

[0002]

2. Description of the Related Art Conventionally, in a page printer, a paper feed roller is arranged to convey a paper. The paper feed roller feeds paper by hopping it, and is driven for a certain period of time until the leading edge of the paper is detected by the entrance sensor and then hits the registration roller, and then stopped. The drive of the paper feed roller is controlled by firmware.

FIG. 2 is an exploded perspective view of a conventional paper feed roller driving device. In the figure, 10 is a paper feed roller, and 1 is
Reference numeral 1 is a drive gear in which an internal gear 12 is coaxially formed, and the drive gear 11 is rotated by receiving power from a drive motor (not shown). Further, 13 is a driven gear, 1
Reference numeral 4 denotes a planetary gear, and the rotation shaft 15 of the planetary gear 14 is formed on the driven gear 13.

Reference numeral 16 is a ratchet wheel, on which a gear 17 is coaxially formed. The drive gear 1
1, the driven gear 13, and the gear 17 are all rotatably supported by the shaft 21. Further, the planetary gear 14 meshes with the internal gear 12, and also meshes with the gear 17. Further, a ratchet lever 18 is detachably attached to the ratchet wheel 16.

The ratchet lever 18 is engaged with the ratchet wheel 16 by the urging force of the spring 22 to fix the gear 17. Further, 19 is an attraction type electromagnetic magnet having a solenoid and a movable iron core (not shown), and the ratchet lever 1 is provided only when the solenoid is energized by a control means (not shown) to attract the movable iron core.
8 and the ratchet wheel 16 are released so that the gear 17 is rotatable.

In the paper feed roller driving device having the above-described structure, when the attracting electromagnetic magnet 19 releases the movable iron core, the gear 17 is fixed by the ratchet lever 18, so that the drive gear 11 rotates through the planetary gear 14. Is transmitted to the driven gear 13 to rotate the paper feed roller 10 connected to the driven gear 13. When the attracting electromagnetic magnet 19 attracts the movable iron core, the rotation transmitted through the drive gear 11 causes the gear 17 to rotate through the planetary gear 14, so that the rotation is not transmitted to the driven gear 13.
The paper feed roller 10 is stopped.

As described above, the paper feed roller 10 is stopped when the solenoid of the attraction type electromagnetic magnet 19 is energized, and is rotated when it is not energized.

[0008]

However, in the above-mentioned conventional paper feed roller driving device, while the paper feed roller 10 is stopped, the solenoid of the attraction type electromagnetic magnet 19 is energized to attract the movable iron core. I have to continue. Therefore, during that time, it is necessary to keep the control means in operation. Further, during that time, current continues to flow through the solenoid, so that the attraction type electromagnetic magnet 19 generates heat.

The present invention solves the problems of the conventional paper feed roller driving device described above, and it is not necessary to operate the control means while the paper feed roller is stopped, and the attraction type electromagnetic magnet An object of the present invention is to provide a drive device for a paper feed roller that does not generate heat.

[0010]

Therefore, in the paper feed roller driving device of the present invention, a drive gear connected to the drive source, a driven gear connected to the paper feed roller, and the drive gear and the driven gear. It is placed between the gear and takes the first position and the second position. At the first position, the power is transmitted from the driving gear to the driven gear, and at the second position, the transmission of the power from the driving gear to the driven gear is cut off. The idle gear and the position switching means for selectively placing the idle gear in the first position and the second position.

The position switching means switches between the first position and the second position by momentarily attracting the movable iron core of the attraction type electromagnetic magnet.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view of a drive device for a paper feed roller according to the first embodiment of the present invention. In the figure, 31 is a drive shaft, which is rotated at a substantially constant speed in the direction of arrow a by the power transmitted from a drive source (not shown). A drive gear 32 is arranged at the left end of the drive shaft 31 in the figure, and is rotated together with the drive shaft 31.

A driven gear 33 has the same outer diameter as that of the drive gear 32, is coaxially arranged, and is fixed to the right end of the shaft 34 in the figure. A paper feed roller (not shown) is connected to the shaft 34. The drive shaft 3
The shaft 1 and the shaft 34 are rotatably supported by a frame (not shown). A drum 35 is fixed to the drive shaft 31, and a left-hand spiral groove 36 and a right-hand spiral groove 37 are formed side by side on the surface of the drum 35. The left-hand spiral groove 36 and the right-hand spiral groove are formed. The spiral pitch, groove width, etc. are made substantially equal to the groove 37.

Reference numeral 41 denotes an idle gear which is disposed parallel to the drive shaft 31 and is rotatably supported and movably in the left and right directions in the drawing.
No. 1 selectively takes a first position and a second position, and meshes with the drive gear 32 at the first position, and meshes with the drive gear 32 and the driven gear 33 at the second position. A drum 42 is fixed to the left side of the idle gear 41 coaxial with the support shaft 49, and annular grooves 43 and 44 are formed at two positions on the surface of the drum 42. The idle gear 41 and the drum 42 are integrally formed.

Reference numeral 45 denotes an attraction type electromagnetic magnet, which is composed of a solenoid 46 and a movable iron core 47. Normally, when the solenoid 46 is not energized, the movable iron core 47 is released and the solenoid 4
When 6 is energized, the movable iron core 47 is attracted. The solenoid 46 of the attraction type electromagnetic magnet 45 is fixed to a frame or the like (not shown). When the movable iron core 47 is released, the tip of the movable iron core 47 is pressed against the surface of the drum 42 by the urging force of the spring 48, and the groove 43,
It is fitted to one side of 44. As a result, the axial movement of the idle gear 41 is restricted. On the other hand, when the movable iron core 47 is sucked, the tip of the movable iron core 47 is pulled out from the grooves 43 and 44 of the drum 42. As a result, the idle gear 41 becomes movable in the axial direction.

To this end, push springs 57 and 58 are provided at both left and right ends of the idle gear 41 in the figure so as to surround the support shaft 49. Energize to move in the direction.
By the way, the support shaft 49 has a substantially U-shaped support base 50.
The support base 50 is movably supported by the frame or the like in the left-right direction in the drawing, that is, parallel to the drive shaft 31. An arm 51 is swingably supported on the right end of the support base 50.

Reference numeral 53 is a tension spring for selectively detenting the arm 51 to a first swing position on the left side or a second swing position on the right side in the drawing.
Has one end fixed to a spring fulcrum 61 formed above the support shaft 52 of the arm 51, and the other end fixed to a fulcrum 54 formed on a frame (not shown) below the support shaft 52. The tip of the arm 51 is branched in two directions,
1 is detented to the first swing position, the first protrusion 55 fitted to the left-handed spiral groove 36, and the arm 51 to the second swing position, the right-handed spiral groove 37. A second protrusion 56 is formed to be fitted with the second protrusion 56. Further, the protrusions 59 and 60 are provided so that the swinging of the arm 51 is restricted at the positions where the first protrusion 55 and the second protrusion 56 are engaged with the left-hand spiral groove 36 and the right-hand spiral groove 37, respectively. Formed respectively.

Therefore, when the drive shaft 31 is rotated in the direction of the arrow a in the state where the first protrusion 55 is engaged with the left-handed spiral groove 36, the left-handed spiral groove 3 is formed.
The first protrusion 55 moves in the inside of 6, and the arm 51 and the support base 50 supporting the arm 51 move leftward in the figure against the biasing force of the push spring 57.

As a result, when the movable iron core 47 of the attraction type electromagnetic magnet 45 is momentarily attracted while the support base 50 is moved to the left in the figure, the push spring 57 causes the idle gear 41 to move to the left in the figure. Move it to the second position. On the other hand, when the drive shaft 31 is rotated in the direction of arrow a in the state where the second protrusion 56 is engaged with the right-handed spiral groove 37, the second protrusion 56 is formed in the right-handed spiral groove 37. Moves, and as a result, the arm 51 and the support base 50 supporting the arm 51 move rightward in the drawing against the biasing force of the push spring 58.

Therefore, when the movable iron core 47 of the attraction type electromagnetic magnet 45 is momentarily attracted while the support base 50 is moved to the right in the figure, the push spring 58 causes the idler gear 41 to move to the right in the figure. And move it to the first position. By the way, the idle gear 41
Is placed in the first position, and the protrusion of the movable iron core 47 is fitted in the groove 43, the idle gear 41 moves to the drive gear 3
When the idle gear 41 is placed in the second position and the protrusion of the movable iron core 47 is fitted in the groove 44, the idle gear 41 meshes with the drive gear 32 and the driven gear 33. Therefore, the idle gear 41 is set to the first
The paper feed roller connected to the shaft 34 can be intermittently rotated by setting the position and the second position.

Incidentally, the drum 35, the attraction type electromagnetic magnet 45, the support base 50, the arm 51 and the pressing springs 57 and 58.
The position switching means is constituted by. Next, the operation of the paper feed roller driving device having the above-described configuration will be described. FIG.
FIG. 4 is a first state diagram of the paper feed roller drive device according to the first embodiment of the present invention; FIG. 4 is a second state diagram of the paper feed roller drive device according to the first embodiment of the present invention; FIG. 5 is a third state diagram of the paper feed roller drive device according to the first embodiment of the present invention, and FIG. 6 is a fourth state of the paper feed roller drive device according to the first embodiment of the present invention. It is a figure.

First, as shown in FIG. 3, it is assumed that the tip of the movable iron core 47 of the attraction type electromagnetic magnet 45 is engaged with the left side groove 43 formed on the drum 42. At this time, the idle gear 41 meshes only with the drive gear 32, and the rotation of the drive gear 32 is not transmitted to the shaft 34. Further, the support base 50 is stopped at a balanced position by the action of the pressing springs 57 and 58.

In this state, the fulcrum 54 formed on the frame (not shown) is located to the left in FIG. 3 from the line connecting the fulcrum 52 of the arm 51 and the upper spring fulcrum 61, so that the arm 51 is located. Is detented to the first swing position. At this time, the arm 51 contacts the protrusion 59 to maintain the first swing position, and the first protrusion 55 of the arm 51 is engaged with the left-hand spiral groove 36 formed on the drum 35. It is pressed by the detent force of the tension spring 53.

When the drive shaft 31 is rotated in the direction of arrow a from this state, the first protrusion 55 of the arm 51 moves leftward in the left-hand spiral groove 36. In this embodiment, when the drive shaft 31 rotates about 1.5 times, the first protrusion 55 of the arm 51 reaches the left end of the left-hand spiral groove 36. The left end of the left-handed spiral groove 36 constitutes an annular groove closed in the circumferential direction. Therefore, the left-handed spiral groove 36
The first protrusion 55 that has reached the left end portion of the above will be repeatedly moved in the annular groove even if the drive shaft 31 is continuously rotated in the direction of the arrow a.

During this time, since the support base 50 restricts the swing of the arm 51 by the protrusion 59 and the support shaft 52, the support base 50 moves to the left in the drawing, and the pressing spring 57 compresses as shown in FIG. Then, the idle gear 41 is urged. However, since the idle gear 41 is restricted in the axial direction unless the movable iron core 47 of the attraction type electromagnetic magnet 45 is attracted, the support base 50 is biased to the right by the action of the push spring 57.

In this state, the fulcrum 54 for fixing the lower part of the detent tension spring 53 is located to the right of the line connecting the support shaft 52 of the arm 51 and the upper spring fulcrum 61, The detent force acts to place the arm 51 in the second swing position, but as described above, the support base 50 is biased to the right by the action of the push spring 57, and the arm 51 is pressed to the right. Therefore, a frictional force that tries to restrain the first protrusion 55 in the left-hand spiral groove 36 is generated, and the detent force of the tension spring 53 alone causes
The arm 51 cannot be placed in the second swing position.

As a result, from the state shown in FIG.
When is rotated about 1.5 times in the direction of arrow a, the state shown in FIG. 4 is obtained, and this state is maintained thereafter. Next, in the state shown in FIG. 4, when the movable iron core 47 of the attraction type electromagnetic magnet 45 is momentarily attracted and the tip of the movable iron core 47 is released from the groove 43, due to the urging force of the contracted push spring 57,
The idle gear 41 moves leftward. As a result, FIG.
As shown in, the tip of the movable iron core 47 is engaged with the groove 44 by the urging force of the spring 48 toward the drum 42. Then, the movement of the idle gear 41 in the left-right direction is restricted again.

By the way, in the state shown in FIG. 5, the idle gear 41 meshes with both the drive gear 32 and the driven gear 33. Therefore, the rotation transmitted to the drive gear 32 is transmitted to the shaft 34. At the same time, the biasing force of the push spring 57 is released, so that the support base 50 does not push the arm 51 to the right. Therefore, the frictional force that tries to restrain the first protrusion 55 in the left-hand spiral groove 36 disappears, so that the arm 51 swings by the detent force of the tension spring 53 and hits the protrusion 60 formed on the support base 50. Contacted and placed in the second swing position.

The second projection 56 of the arm 51 is fitted into the left end of the right-hand spiral groove 37 formed on the drum 35 by the detent force. At this time, since the drive shaft 31 continues to rotate in the direction of arrow a, when the drive shaft 31 rotates about 1.5 times, the second protrusion 56 moves in the right-hand spiral groove 37 in the right direction in FIG. , Reaches the right end of the right-hand spiral groove 37. The right end portion of the right-handed spiral groove 37 constitutes an annular groove closed in the circumferential direction. Therefore, the second protrusion 56 reaching the right end of the right-hand spiral groove 37 will repeatedly move in the annular groove thereafter even if the drive shaft 31 is continuously rotated in the direction of arrow a.

During this time, since the support base 50 regulates the swing of the arm 51 by the projection 60 and the support shaft 52, the support base 50 moves to the right in FIG. 6 and the pressing spring 58 is compressed to idle the gear 41. Energize. However, since the idle gear 41 is restricted in the axial direction unless the movable iron core 47 of the attraction type electromagnetic magnet 45 is attracted, the support base 50 is biased to the left by the action of the push spring 58.

In this state, the fulcrum 54 for fixing the lower part of the detent tension spring 53 is located to the left of the line connecting the support shaft 52 of the arm 51 and the upper spring fulcrum 61, The detent force acts to place the arm 51 in the first swing position, but as described above, the support base 50 is biased to the left by the action of the pressing spring 58, and the arm 51 is pressed to the left. To do. Therefore, since a frictional force that tries to restrain the second protrusion 56 in the right-hand spiral groove 37 is generated, the arm 51 cannot be placed in the first swing position only by the detent force of the tension spring 53. .

As a result, from the state shown in FIG.
When is rotated about 1.5 times in the direction of arrow a, the state shown in FIG. 6 is obtained, and this state is maintained thereafter. Next, in the state shown in FIG. 6, when the movable iron core 47 of the attraction type electromagnetic magnet 45 is momentarily attracted and the tip of the movable iron core 47 is released from the groove 44, by the urging force of the contracted push spring 58, The idle gear 41 moves to the right. as a result,
As shown in FIG. 3, the tip of the movable iron core 47 is engaged with the groove 43 by the urging force of the spring 48 toward the drum 42. Then, the movement of the idle gear 41 in the left-right direction is restricted again.

By the way, in the state shown in FIG. 3, the idle gear 41 meshes only with the drive gear 32. Therefore, the transmission of power from the drive gear 32 to the driven gear 33 is cut off, and the rotation transmitted to the drive gear 32 is not transmitted to the shaft 34. At the same time, the biasing force of the push spring 58 is released, so that the support base 50 does not push the arm 51 to the left. Therefore, the second protrusion 56 is formed in the right-hand spiral groove 3
Since the frictional force for restraining the inside of the armature 7 disappears, the arm 51 swings by the detent force of the tension spring 53, abuts on the protrusion 59 formed on the support base 50, and is placed in the first swinging position.

The detent force causes the first protrusion 55 of the arm 51 to fit into the right end of the left-handed spiral groove 36 formed on the drum 35, and returns to the state shown in FIG. As described above, by momentarily attracting the movable iron core 47 of the attraction type electromagnetic magnet 45 only once, it is possible to transmit power from the drive gear 32 to the driven gear 33.
Then, the power transmission from the drive gear 32 to the driven gear 33 can be interrupted by momentarily attracting the movable iron core 47 of the attraction type electromagnetic magnet 45 only once. The control means can be simplified.

In addition, the solenoid 46 of the attracting electromagnetic magnet 45 is used both when the power is transmitted and when the power is cut off.
Since it is not necessary to keep the current flowing through the device, the attracting electromagnetic magnet 45 does not generate heat, and it is not necessary to continue operating the control means. Furthermore, attraction type electromagnetic magnet 4
Since the power of 5 is not used to transmit the power itself, a large amount of power can be transmitted and cut off only by sucking the movable iron core 47 with a small amount of electric power.

Further, in the present embodiment, the drive shaft 3
When 1 is rotated about 1.5 times, the operation is switched to the next operation. However, by changing the pitch of the left-hand spiral groove 36 and the right-hand spiral groove 37, the operation is switched to the next operation even after one rotation or less. be able to. In addition, in the present embodiment, the drive device of the paper feed roller for conveying the single sheet or the like is described, but the present invention can be applied to other devices such as a document reading device that requires intermittent operation. .

Further, in the present embodiment, it may not be known whether power is transmitted or cut off in the initial state, but the idle gear 41 is detected by the sensor.
It is also possible to monitor whether power is being transmitted or cut off by detecting the position of. In the figure, 49 is a support shaft for supporting the idle gear 41.

Next, a second embodiment of the present invention will be described. FIG. 7 is a side view of the drive device for the paper feed roller according to the second embodiment of the present invention. In the figure, 3
Reference numeral 2 is a drive gear connected to a drive source (not shown), 33 is a driven gear connected to a paper feed roller (not shown), 64 is an attracting electromagnetic magnet, 65 is a solenoid, and 66 is a solenoid 65 which is moved forward and backward by energizing the solenoid 65. The movable iron core 41 is disposed between the drive gear 32 and the driven gear 33, and is constantly meshed with the drive gear 32.
An idle gear 71 that selectively meshes with the idle gear 41, a drum disposed adjacent to the idle gear 41, a spiral groove 72 formed on the surface of the drum 71, and fitted with the tip of the movable iron core 66. is there.

Reference numeral 67 is a push spring for applying a thrust force to the idle gear 41, and 49 is a support shaft for supporting the idle gear 41. The movable iron core 66 is
It also functions as a stopper for the idle gear 41 that is about to move due to the biasing force of the push spring 67. The support shaft 49 and the solenoid 65 are fixed to a frame (not shown), and the support shafts of the drive gear 32 and the driven gear 33 are rotatably supported by the frame.

The attraction type electromagnetic magnet 64, the pressing spring 67 and the drum 71 constitute a position switching means. Next, the operation of the paper feed roller driving device having the above-described configuration will be described. First, the drive gear 32 is rotated by receiving power from the drive source, and the idle gear 41 is rotated by being driven by the drive gear 32. Next, when the solenoid 65 attracts the movable iron core 66 and retracts it in the direction of arrow C, the stopper function of the idle gear 41 by the movable iron core 66 is released, and the idle gear 41 is moved in the direction of arrow A by the urging force of the push spring 67. It is moved and placed in the second position.

As a result, the idle gear 41 becomes the driven gear 3
3, the power of the drive gear 32 is transmitted to the driven gear 33. Since the driven gear 33 is connected to the paper feed roller, the paper feed roller is rotated while power is being transmitted. Further, the solenoid 65 has a movable iron core 66.
When the movable core 66 is released, the movable iron core 66 moves forward and its tip is fitted into the spiral groove 72 at the end of the idle gear 41. Therefore, as the idle gear 41 rotates, the tip of the movable iron core 66 moves in the spiral groove 72. As a result, the idle gear 41 moves in the direction of arrow B and is placed at the first position, disengaged from the driven gear 33, the transmission of power is interrupted, and the paper feed roller is stopped.

That is, when a certain period of time elapses after the attracting electromagnetic magnet 64 releases the movable iron core 66, the transmission of power from the drive gear 32 to the driven gear 33 is cut off. The time until the transmission of power from the drive gear 32 to the driven gear 33 is cut off can be arbitrarily set by changing the lead angle of the spiral groove 72. In this way, the transmission and interruption of power to and from the paper feed roller can be controlled by turning the solenoid 65 on and off without the need for a software drive source for the paper feed roller. The control means can be simplified.

Further, since it is not necessary to keep the current flowing through the solenoid 65 of the attraction type electromagnetic magnet 64 when the power is shut off, the attraction type electromagnetic magnet 64 does not generate heat and it is not necessary to continue operating the control means. Further, since the attraction force of the attraction type electromagnetic magnet 64 itself is not used to transmit the power, a large amount of power can be transmitted and blocked by only attracting the movable iron core 66 with a small electric power.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0045]

As described in detail above, according to the present invention, in the drive device for the paper feed roller, the drive gear connected to the drive source, the driven gear connected to the paper feed roller, and The first gear is provided between the drive gear and the driven gear.
The idle gear and the idle gear, which take the position and the second position, transmit power from the drive gear to the driven gear at the first position, and block transmission of power from the drive gear to the driven gear at the second position. And a position switching means for selectively setting the position and the second position.

Then, the position switching means switches between the first position and the second position by instantaneously attracting the movable iron core of the attraction type electromagnetic magnet. In this case, when power is transmitted to the drive gear when the idle gear is in the first position, power is not transmitted to the driven gear and the driven gear does not rotate. In this state, when the position switching means momentarily attracts the movable iron core of the attraction type electromagnetic magnet, the idle gear moves to the second position, power is transmitted to the driven gear, and the paper feed roller is rotated. To be

Next, when the idle gear is in the second position and the position switching means momentarily attracts the movable iron core of the attraction type electromagnetic magnet, the idle gear moves to the first position and the driven gear receives power. The transmission is stopped and the paper feed roller is stopped. In this way, the first position and the second
Since the position can be switched, the time for attracting the movable iron core of the attraction electromagnetic magnet is shortened. Therefore, it is not necessary to operate the control means while the paper feed roller is stopped, and the attraction type electromagnetic magnet does not generate heat.

[Brief description of the drawings]

FIG. 1 is a side view of a drive device for a paper feed roller according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of a conventional paper feed roller driving device.

FIG. 3 is a first state diagram of the paper feed roller driving device according to the first embodiment of the present invention.

FIG. 4 is a second state diagram of the drive device for the paper feed roller according to the first embodiment of the present invention.

FIG. 5 is a third state diagram of the paper feed roller driving device according to the first embodiment of the present invention.

FIG. 6 is a fourth state diagram of the paper feed roller driving device according to the first embodiment of the present invention.

FIG. 7 is a side view of a paper feed roller driving device according to a second embodiment of the present invention.

[Explanation of symbols]

 32 drive gear 33 driven gear 35, 42, 71 drum 36 left-handed spiral groove 37 right-handed spiral groove 41 idle gear 45, 64 attractive electromagnetic magnet 47, 66 movable iron core 50 support base 51 arm 55 first protrusion 56 second protrusion Part 57, 58, 67 Push spring 72 Spiral groove

Claims (4)

[Claims] 1. (a) a drive gear connected to a drive source;
(B) a driven gear connected to the paper feed roller; and (c) disposed between the drive gear and the driven gear to take the first position and the second position. At the first position, the drive gear moves to the driven gear. An idle gear for transmitting power to the drive gear and for cutting off power transmission from the drive gear to the driven gear in the second position;
And a position switching means for selectively placing the idle gear at the first position and the second position. (E) The position switching means instantaneously attracts the movable iron core of the attraction type electromagnetic magnet to generate the first A drive device for a paper feed roller, characterized in that switching between a position and a second position is performed. 2. The driving gear and the driven gear are coaxially arranged, and the idle gear is movably arranged along an axis parallel to the axes of the driving gear and the driven gear. The drive device for the paper feed roller according to claim 1. 3. The position switching means is fixed coaxially with the drive gear, and has a drum having a left-handed spiral groove and a right-handed spiral groove formed on the surface thereof, and selectively the left-handed spiral groove and the right-handed spiral groove. An arm having a protrusion fitted to the arm, a support that supports the arm and is moved by rotating the drive gear, and a contraction that accompanies the movement of the support to attach to the idle gear. A push spring that applies power,
2. The drive device for a paper feed roller according to claim 1, further comprising: an attraction type electromagnetic magnet that allows the idle gear to move by constantly regulating the axial movement of the idle gear and attracting a movable iron core. 4. (a) a drive gear connected to a drive source,
(B) a driven gear connected to the paper feed roller; and (c) disposed between the drive gear and the driven gear to take the first position and the second position. At the first position, the drive gear moves to the driven gear. An idle gear for transmitting power to the drive gear and for cutting off power transmission from the drive gear to the driven gear in the second position;
And a position switching means for selectively placing the idle gear at the first position and the second position. (E) The position switching means is fixed coaxially with the idle gear and has a spiral groove formed on its surface. A drum, a pressing spring for urging the idle gear along with the axial movement of the idle gear, and an attraction type electromagnetic magnet having a movable iron core selectively fitted in the spiral groove. Characteristic paper feed roller drive device.