JP2024068551A - Gear mechanism, tension control device and image forming apparatus - Google Patents

Abstract

A gear mechanism that is small and has a simple configuration and that switches the drive torque of a roll medium is provided.
[Solution] The gear mechanism has a sun gear fixed to an input shaft, at least one planetary gear arranged tangent to the pitch circle of the sun gear, an internal gear arranged tangent to the pitch circle of the planetary gears, a carrier that holds the planetary gears freely rotatable, a first gear fixed to the carrier, a second gear fixed to an output shaft, a bidirectional clutch that drivingly connects the first gear to the first gear on the input side and drives and connects the second gear to the output side, a first torque limiter that connects the carrier to the output shaft, and a second torque limiter that connects the output side of the bidirectional clutch to the output shaft.
[Selected Figure] Figure 6

Description

The present invention relates to a gear mechanism, a tension control device, and an image forming device.

There is known an image forming device that is configured to form an image on a continuous sheet-like medium (hereinafter referred to as "medium") fed from a roll media, which is a roll of medium, and to wind up the medium with the image formed on it onto the roll media. When the image forming device conveys the medium fed from the roll media in a predetermined direction, it is necessary to apply a predetermined tension to the medium. Therefore, a tension control device for appropriately applying tension to the medium being conveyed in the conveying device provided in the image forming device is also known.

Tension control in tension control devices can be performed by controlling the torque applied when rotating the roll media in a roll media holding mechanism that holds the media so that it can be fed out and wound up from the roll media.

Known mechanisms for controlling torque to apply tension to the media include a configuration that uses frictional drive transmission to change the reduction ratio (see Patent Document 1), and a configuration that controls the rotation speed of multiple motors to vary the reduction ratio and thereby vary the torque transmitted to the rotating shaft of the roll media (see Patent Document 2).

When varying the drive torque by friction, as in the configuration described in Patent Document 1, it is necessary to generate a large frictional force. In that case, a small drive mechanism cannot obtain sufficient frictional force. Therefore, when varying the drive torque by friction, the drive mechanism becomes large. In addition, when controlling the rotation speed of multiple motors, as in the configuration described in Patent Document 2, the control configuration of the drive source (motor) becomes complex.

Therefore, according to conventional technology, when the drive torque is varied to control the tension applied to the roll media, the mechanical configuration of the control mechanism becomes large and the electrical configuration becomes complex.

The present invention aims to provide a gear mechanism that is small and has a simple configuration and can switch the drive torque of roll media.

In order to solve the above technical problems, one aspect of the present invention is a gear mechanism having an input shaft and an output shaft, characterized in that it has a sun gear fixed to the input shaft, at least one planetary gear arranged so as to be tangent to the pitch circle of the sun gear, an internal gear arranged so as to be tangent to the pitch circle of the planetary gear, a carrier that holds the planetary gears rotatably, a first gear fixed to the carrier, a second gear fixed to the output shaft, a bidirectional clutch that drivingly connects the first gear to the first gear on the input side and drives the second gear to the output side, a first torque limiter that connects the carrier to the output shaft, and a second torque limiter that connects the output side of the bidirectional clutch to the output shaft.

The present invention is compact and has a simple configuration that allows the drive torque of roll media to be switched.

1 is a partially perspective view of a schematic configuration of an embodiment of an image forming apparatus according to the present invention; FIG. 2 is a schematic diagram showing the image forming apparatus from a side view. FIG. 2 is a partially perspective plan view of the image forming apparatus. FIG. 2 is a side view of a roll holding device included in the image forming apparatus. 1 is a side cross-sectional view showing one embodiment of a tension control device according to the present invention. 1 is a side cross-sectional view showing an embodiment of a gear mechanism according to the present invention; FIG. 4 is a diagram showing torque transmission from an input shaft side in the above gear mechanism. 4 is a diagram showing torque transmission from an output shaft side in the above gear mechanism. FIG.

Below, an embodiment of the present invention will be described with reference to the drawings. First, an inkjet printer 100, which is an embodiment of a liquid ejection device and image forming device equipped with a transport device for transporting an object according to the present invention, will be described with reference to Figs. 1 to 3. Fig. 1 is a perspective view illustrating an example of the appearance of the inkjet printer 100. Fig. 2 is a schematic diagram showing a side view of the inkjet printer 100. Fig. 3 is a plan view showing the main parts of an image forming unit 104 as a liquid ejection device equipped in the inkjet printer 100.

As shown in FIG. 1, the inkjet printer 100 is a serial type image forming device, and includes a device body 101, a paper feeder 102 disposed below the device body 101, and a winding device 103 disposed opposite the paper feeder 102.

In the inkjet printer 100 shown in FIG. 1, the paper feeder 102 is separate from the device main body 101. The paper feeder 102 may be disposed below the device main body 101 as shown in FIG. 1, or on the side. The device main body 101 and the paper feeder may be integrated as shown in FIG. 2. The winding device 103 is similar to the paper feeder 102, and may be disposed so as to be able to wind up the medium after it has been fed to the device main body 101. Therefore, as shown in FIG. 1 and FIG. 2, the paper feeder 102 and the winding device 103 may be disposed opposite each other with the device main body 101 in between.

Note that both the paper feeder 102 and the winder 103 correspond to embodiments of the transport device according to the present invention. Therefore, both the paper feeder 102 and the winder 103 include the tension control device according to the present invention.

The device main body 101 shown in FIG. 2 includes a paper feeder 102 as a medium supply device that feeds roll paper 112 in which the medium is wound around the outer circumference of a core member, a winding device 103 as a medium winding device that winds up the roll paper 112, and an image forming unit 104 that forms an image on the roll paper 112.

The image forming unit 104 is configured such that a carriage 5 supported by a guide rod 1 and a guide stay 2, which are guide members suspended between both side plates, can move in the direction of arrow A in FIG. 3 (main scanning direction, carriage movement direction).

As shown in FIG. 3, the image forming unit 104 has a main scanning motor 8, which is a drive source for reciprocating the carriage 5, disposed on one side in the main scanning direction. A timing belt 11 is wound around a drive pulley 9, which is driven and rotated by the main scanning motor 8, and a driven pulley 10 disposed on the other side in the main scanning direction. A belt holder of the carriage 5 is fixed to the timing belt 11, and the carriage 5 is reciprocated in the main scanning direction by driving the main scanning motor 8.

The carriage 5 is equipped with multiple recording heads 6a-6d, which are integrated with a liquid ejection head as a liquid ejection mechanism for ejecting liquid onto a medium to form an image, and a head tank that supplies liquid to the liquid ejection head. In the following description, when there is no need to distinguish between the multiple recording heads 6a-6d, they will simply be referred to as "recording head 6."

Here, recording head 6a and recording heads 6b to 6d are positioned one head (one nozzle row) apart in the sub-scanning direction (arrow B direction), which is perpendicular to the main scanning direction. In addition, recording head 6 has a nozzle row made up of multiple nozzles that eject droplets arranged in the sub-scanning direction perpendicular to the main scanning direction, and is mounted with the droplet ejection direction facing downward.

Each of the recording heads 6a to 6d has two nozzle rows. The recording heads 6a and 6b eject black droplets, which are the same color, from both nozzle rows. The recording head 6c ejects cyan (C) droplets from one nozzle row, and the other nozzle row is an unused nozzle row. The recording head 6d ejects yellow (Y) droplets from one nozzle row, and magenta (M) droplets from the other nozzle row.

As a result, for monochrome images, recording heads 6a and 6b can be used to form an image with a width equivalent to two heads in one scanning operation (one main scan), while for color images, recording heads 6b to 6d can be used to form the image. Note that the head configuration is not limited to this, and multiple recording heads may all be arranged side by side in the main scan direction.

An encoder sheet 12 is arranged along the movement direction of the carriage 5, and the carriage 5 is provided with an encoder sensor 13 that reads the encoder sheet 12. The encoder sheet 12 and the encoder sensor 13 form a linear encoder 14, and the position and speed of the carriage 5 are detected from the output of the linear encoder 14.

In the recording area of the main scanning area of the carriage 5, roll paper 112 is fed from a paper feeder 102 and intermittently transported by a transport means 15 (see FIG. 2) in a direction perpendicular to the main scanning direction of the carriage 5 (sub-scanning direction, paper transport direction: direction of arrow B in FIG. 3). As shown in FIG. 1, ink of each color is supplied to the head tank of the recording head 6 via a supply tube from an ink cartridge 60, which is a main tank that is replaceably mounted in the device main body 101. In addition, a maintenance and recovery mechanism 80 that maintains and recovers the recording head 6 is arranged on one side of the carriage 5 in the main scanning direction, beside the transport guide member 18 (see FIG. 1).

As shown in FIG. 2, the conveying means 15 has a conveying roller 16 that conveys the roll paper 112, which is a roll-shaped medium fed from the paper feeder 102, and a pressure roller 17 that is disposed opposite the conveying roller 16. The conveying roller 16 and the pressure roller 17 correspond to the conveying member. Downstream of the conveying roller 16, there is a conveying guide member 18 with multiple suction holes formed therein, and a suction fan 19 as a suction means that draws in suction through the suction holes of the conveying guide member 18.

A cutter is disposed downstream of this conveying means 15 as a cutting means for cutting the roll paper 112 on which an image has been formed by the recording head 6 to a predetermined length.

The roll paper 112 loaded in the paper feeder 102 is a long rolled medium, a sheet 120 (corresponding to the above-mentioned "roll media as a continuous sheet-like medium") wound in a roll shape around a hollow shaft 114, such as a paper tube, which is a core member. In this embodiment, the roll paper 112 may be one in which the end of the roll paper 112 is fixed to the hollow shaft 114 by gluing or other bonding, or one in which the end of the roll paper 112 is not fixed to the hollow shaft 114 and is not bonded to it.

As already shown in FIG. 2, a guide member 130 and a paper discharge guide member 131 are arranged on the device main body 101 side. The guide member 130 guides the roll paper 112 that is pulled out from the paper feeder 102. The paper discharge guide member 131 guides the roll paper 112 after suction downstream of the guide member 130 and the transport guide member 18.

The winding device 103 has a hollow shaft 115 such as a paper tube that serves as a core member. The tip of the roll paper 112 is attached to the hollow shaft 115 with tape or the like.

When the inkjet printer 100 configured in this way is performing an image formation process, the carriage 5 is moved in the main scanning direction, and the roll paper 112 fed from the paper feeder 102 is intermittently fed by the transport means 15. The recording head 6 is then driven in accordance with image information (print information) to eject droplets, forming a desired image on the roll paper 112. The roll paper 112 on which this image has been formed is guided by the paper discharge guide member 131 and taken up on the hollow shaft 115 in the winding device 103. The roll paper 112 on the transport roller 16 is transported while tension is applied from both the paper feeder 102 side and the winding device 103 side. Each of these tensions affects the transport accuracy.

[Embodiment of the conveying device]
Next, a roll body holding device 20 will be described as an embodiment of a conveying device according to the present invention. Fig. 4 is a side view illustrating an example of an overall image of the roll body holding device 20. As illustrated in Fig. 1, the roll body holding device 20 is configured to hold both side end portions of the roll paper 112. Therefore, the roll body holding device 20 is configured by being disposed opposite each other as a pair.

The roll body holding devices 20 are configured as a pair, one equipped with a drive source that applies a driving force and the other driven by it. In the following explanation, only one of the roll body holding devices 20 is shown, and its structure and operation are explained. By arranging devices with a similar configuration in positions to hold both side end portions of the roll paper 112, the roll paper 112 can be sent out and transported by the transport means 15 as a transport mechanism.

As shown in FIG. 4, the roll body holding device 20 is a box body with an approximately rectangular prism-shaped appearance in a side view, and a core holding member 22 is provided on a part of the outer wall surface of the housing, the wall surface facing the roll paper 112. The roll body holding device 20 includes a plurality of sliders (not shown) and a lock lever 27. The roll body holding device 20 is held by a guide rail 24 as a guide member so as to be slidable in only one direction via a slider provided on the bottom surface of the housing. As shown in FIG. 1, the guide rail 24 constitutes a part of the paper feeder 102 and the winding device 103, and holds the roll body holding device 20 so as to be movable along a direction parallel to the direction of arrow A in FIG. 1.

The core holding member 22 is fitted into the hollow shaft at both ends of the paper roll 112. The paper roll 112 with the core holding member fitted is held in a rotatable state by the roll body holding device 20. When the paper roll 112 rotates, the core holding member 22 also rotates around its axis.

The lock lever 27 is a movement restriction member that restricts the movement of the roll body holding device 20 that is held on the guide rail 24 by the slider. When the lock lever 27 is operated, the slider transitions from a state in which it is not pressed against the inner wall of the groove of the guide rail 24 to a state in which it is pressed against the inner wall. The movement of the roll body holding device 20 is restricted by friction between the slider and the inner wall.

In addition, by reversing the operation of the lock lever 27, the slider of the roll body holding device 20 is released from the state where it is pressed against the inner wall, eliminating friction, and allowing movement along the guide rail 24. The lock lever 27 is provided on the side opposite the side on which the core holding member 22 is provided. In other words, the lock lever 27 is located on the side opposite the side on which the roll paper 112 is held, and on the side that is easier for the user to operate.

The guide rail 24 is included in the paper feeder 102 and the winding device 103 shown in FIG. 1, and is arranged along the longitudinal direction of the hollow shaft 114 fixed to the paper feeder 102 and the hollow shaft 115 fixed to the winding device 103. The guide rail 24 is longer than the width dimension of the roll paper 112, and is provided at a position that connects the bottom surfaces of the paper feeder 102 and the winding device 103.

When fixing the roll paper 112 using the roll body holding device 20, one of the roll body holding devices 20 provided in the paper feeder 102 is made to hold one side end portion of the hollow shaft 114, which is the hollow portion of the roll paper 112. Then, the other roll body holding device 20 is moved to a holding position on one side end portion of the hollow shaft 114, and the lock lever 27 is operated to fix the position of the width direction W of the roll paper 112. At this time, the roll body holding device 20 can be moved and fixed so as to fix the axial center position of the roll paper 112, so that the axial center position of the roll paper 112 can be fixed and held by simple operations.

[Embodiments of tension control device]
Next, details of the drive mechanism 21 as an embodiment of the tension control device will be described. As already described, the drive mechanism 21 corresponds to a part of the configuration included in the roll body holding device 20. Fig. 5 is a schematic diagram showing the configuration of the drive mechanism 21 included in the roll body holding device 20.

As shown in FIG. 5, the drive mechanism 21 has a configuration including, as part of a housing, a first plate 201 and a second plate 202 that support a core rotating shaft 208 having a core holding member 22 fixed to one end thereof. The core rotating shaft 208 is disposed so as to pass through the first plate 201 and the second plate 202, and is rotatably supported by the first plate 201 and the second plate 202 via bearings.

The drive mechanism 21 includes a planetary gear mechanism 200 as a gear mechanism provided in a space surrounded by a first panel 201 and a second panel 202, a structure for transmitting a rotational driving force to the core holding member 22 via the planetary gear mechanism 200, and a motor 203 as a driving source for providing a rotational driving force to the planetary gear mechanism 200.

A first drive gear 204 is fixed to the drive shaft of the motor 203. The first drive gear 204 rotates with the rotation of the drive shaft.

The planetary gear mechanism 200 is located between the output shaft 230 and the input shaft 220, and a second drive gear 205 is fixed to the output shaft 230. The second drive gear 205 meshes with the first drive gear 204. In other words, the output shaft 230 is a shaft that rotates when driven by the motor 203.

A third drive gear 206 is fixed to the input shaft 220 of the planetary gear mechanism 200. The third drive gear 206 meshes with a fourth drive gear 207 fixed to the core rotation shaft 208. That is, the rotation of the drive shaft of the motor 203 is transmitted to the core rotation shaft 208 via the planetary gear mechanism 200, causing the core holding member 22 to rotate.

In the drive mechanism 21, the drive force (rotational force) of the motor 203 is transmitted to the core rotation shaft 208 via the planetary gear mechanism 200. In this configuration, a combination of multiple gears is illustrated, but the configuration of the transmission mechanism is not limited to being composed of gears, and may be configured to be connected using a belt or the like.

The core holding member 22 is configured to rotate by the driving force of the motor 203 via the drive mechanism 21, so the torque when feeding or winding the sheet 120 is controlled by the planetary gear mechanism 200 provided in the drive mechanism 21.

By controlling the torque transmitted to the core holding member 22 in the drive mechanism 21, the tension on the feed side and winding side of the sheet 120 can be controlled.

[Embodiment of Gear Mechanism]
Next, details of the planetary gear mechanism 200 as an embodiment of the gear mechanism according to the present invention will be described with reference to Figs. 6 to 8. Fig. 6 is a side cross-sectional view of the planetary gear mechanism 200. The planetary gear mechanism 200 has an input shaft 220 and an output shaft 230. As shown in Fig. 5, the output shaft 230 is connected to a motor 203 serving as a drive source. The input shaft 220 is connected to the core holding member 22. As a result, the drive force from the motor 203 is transmitted to the input shaft 220 via the planetary gear mechanism 200, causing the core holding member 22 to rotate.

The planetary gear mechanism 200 corresponds to a torque switching mechanism that switches the drive torque between the drive from the input shaft 220 and the drive from the output shaft 230.

A sun gear 221 is fixed to the input shaft 220. The sun gear 221 is fixed so that it cannot rotate relative to the input shaft 220 (relative rotation). The sun gear 221 is also arranged so that it is coaxial with the input shaft 220.

A planetary gear 222 is arranged around the sun gear 221. An internal gear 223 is arranged around the planetary gear 222. The internal gear 223 is fixed to a housing 228. At least one planetary gear 222 is arranged so that the pitch circle of the planetary gear 222 is tangent to the pitch circle of the sun gear 221. The internal gear 223 is arranged so that the pitch circle of the internal gear 223 is tangent to the pitch circle of the planetary gear 222. Therefore, due to the rotational force generated when the input shaft 220 rotates, the planetary gear 222 arranged between the sun gear 221 and the internal gear 223 rotates (revolves) around the input shaft 220 (around the sun gear 221) while rotating on its own axis.

The planetary gear 222 is held rotatably relative to the carrier shaft 231. The carrier shaft 231 is mounted on the carrier 232, which is a planetary carrier. In other words, when the planetary gear 222, which is in a state where it can rotate relative to the carrier shaft 231 (relatively rotatable), revolves due to the rotation of the input shaft 220, the carrier 232 rotates.

The carrier 232 is held by the output shaft 230 via a first torque limiter 233. A first gear 234 is fixed to the side of the carrier 232 opposite the side where the first torque limiter 233 is located.

The first gear 234 is fixed in a state where it cannot rotate relative to the carrier 232 (relative rotation is not possible). The first gear 234 is not in contact with the output shaft 230. The rotation axes of the input shaft 220 and the output shaft 230 are concentric.

A second gear 235 is fixed to the output shaft 230 at a position spaced apart from the first gear 234. The second gear 235 is fixed so as not to rotate relative to the output shaft 230. In other words, when the second gear 235 rotates, the output shaft 230 rotates, and the second gear 235 rotates as the output shaft 230 rotates.

A bidirectional clutch 210 having an axis parallel to the axial direction of the output shaft 230 is disposed between the first gear 234 and the second gear 235. An input gear 211 is fixed to one axis of the bidirectional clutch 210 so as not to rotate relative to the output shaft 230, and an output gear 212 is fixed to the other axis so as not to rotate relative to the input gear 211.

The first gear 234 fixed to the carrier 232 is connected to the input gear 211 of the bidirectional clutch 210. The second gear 235 fixed to the output shaft 230 is connected to the output gear 212 of the bidirectional clutch 210. When the first gear 234 rotates, the input gear 211 rotates. When the second gear 235 rotates, the output gear 212 rotates.

The bidirectional clutch 210 is configured so that the rotation of the input gear 211 causes the output gear 212 to rotate. The bidirectional clutch 210 is also configured so that the rotation of the output gear 212 does not cause the input gear 211 to rotate (spin). In other words, when torque is applied to the input gear 211, the output gear 212 rotates due to the rotation of the input gear 211. However, even if torque is applied to the output gear 212 and it rotates, the input gear 211 does not rotate due to the rotation of the output gear 212.

The number of teeth of the input gear 211 and output gear 212 of the bidirectional clutch 210, and the first gear 234 and second gear 235 are set so that the direction and speed of rotation of the carrier 232 are the same as the direction and speed of rotation of the output shaft 230.

The outer ring of the second torque limiter 236 is fixed to the second gear 235. And the inner ring of the second torque limiter 236 is fixed to the output shaft 230.

The manner in which rotational force is transmitted from the input shaft 220 to the output shaft 230 in the planetary gear mechanism 200 having the above configuration will be explained using the driving force transmission diagram in Figure 7. When the input shaft 220 rotates due to the rotational force Tf, that is, when the rotational force Tf is applied to the input shaft 220, the torque causes the sun gear 221 to rotate, and this rotation causes the planetary gear 222 to rotate. As a result, the carrier shaft 231 rotates concentrically with the input shaft 220 due to the transmission of torque from the rotational force Tf, which causes the carrier 232 to rotate. This rotation is transmitted to the bidirectional clutch 210 via the first gear 234 and the input side gear 211.

The bidirectional clutch 210 transmits the rotation of the input gear 211 to the output gear 212, so that the rotation caused by the rotational force Tf is transmitted to the output gear 212, causing the second gear 235 to rotate.

The rotation of the second gear 235 is transmitted to the output shaft 230 via the second torque limiter 236.

Here, the slip torque of the second torque limiter 236, i.e., the upper limit torque at which the torque applied to the outer wheel of the second torque limiter 236 is transmitted to the inner wheel side (output shaft 230), is defined as the "second slip torque T2."

The torque of the input gear 211 of the bidirectional clutch 210 is transmitted to the output gear 212 up to a maximum torque equivalent to the "allowable transmission torque Ta". Therefore, as shown in FIG. 7, when the torque at which the input gear 211 rotates due to the rotational force Tf is the "allowable transmission torque Ta", the torque has the same value as the allowable transmission torque Ta.

When considering the relationship between the "second slip torque T2" which is the slip torque of the second torque limiter 236 and the "allowable transmission torque Ta" of the bidirectional clutch 210, slip occurs when either of the two values is smaller. In other words, when "second slip torque T2 < allowable transmission torque Ta", the second torque limiter 236 slips.

Therefore, by setting the respective values so that "second slip torque T2 < allowable transmission torque Ta", a torque of the same value as the slip torque of the second torque limiter 236 (second slip torque T2) is transmitted to the output shaft 230. This becomes the driving force Tm.

As described above, the upper limit (limit) of the rotational force Tf transmitted from the input shaft 220 to the output shaft 230 is determined by multiplying the "second slip torque T2" as the slip torque of the second torque limiter 236 by the "primary first reduction ratio" as the reduction ratio from the second torque limiter 236 to the input shaft 220. Based on the value obtained by this multiplication, the rotational force Tf transmitted to the input shaft 220 is output as a driving force Tm at the output shaft 230.

By using the planetary gear mechanism 200 via the bidirectional clutch 210, the rotation direction of the input shaft 220 and the rotation direction of the output shaft 230 are the same, and the rotation speeds are also the same. In addition, by making the rotation of the output shaft 230 and the rotation of the carrier 232 the same, it is possible to prevent the first torque limiter 233 from slipping, thereby preventing unnecessary consumption of driving force due to a load.

As described above, the planetary gear mechanism 200 allows the drive torque to be switched between drive from the input shaft 220 and drive from the output shaft 230.

Next, the manner in which rotational force is transmitted from the output shaft 230 to the input shaft 220 in the planetary gear mechanism 200 will be described using the driving force transmission diagram in FIG. 8. When the output shaft 230 rotates due to the rotational force Tf, that is, when the rotational force Tf is applied to the output shaft 230, the rotational force Tf rotates the carrier 232 from the output shaft 230 via the first torque limiter 233. This rotation causes the carrier shaft 231 to rotate concentrically with the input shaft 220, causing the planetary gear 222 to rotate. The torque of this rotation causes the sun gear 221 to rotate, causing the input shaft 220 to rotate.

In this case, the torque due to the rotational force Tf applied to the output shaft 230 is transmitted to the output side gear 212 via the second gear 235, but since it is transmitted to the output side of the bidirectional clutch 210, the second gear 235 rotates idly due to the idling torque Tb of the bidirectional clutch 210, so there is no slippage in the second torque limiter 236 and no load is generated.

The torque of the rotational force Tf applied to the output shaft 230 is transmitted from the first torque limiter 233 to the input shaft 220. In other words, the rotational force Tf is determined by multiplying the "first slip torque T1" as the slip torque of the first torque limiter 233 by the "input side reduction ratio" as the reduction ratio from the first torque limiter 233 to the input shaft 220. Based on the value obtained by this multiplication, the rotational force Tf transmitted to the output shaft 230 is output as a driving force Tm at the input shaft 220.

However, the idling torque Tb must be set smaller than the second slip torque T2 of the second torque limiter 236.

As described above, by setting the required torques in the first torque limiter 233 and the second torque limiter 236, torque switching can be performed using the planetary gear mechanism 200.

The planetary gear mechanism 200 according to this embodiment is driven by gears, so the layout does not become large and it can be driven by only one drive source (motor 203).

The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist of the invention. All technical matters included in the technical ideas described in the claims are covered by the present invention. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims.

22 : Winding core holding member 200 : Planetary gear mechanism 201 : First face plate 202 : Second face plate 203 : Motor 204 : First drive gear 205 : Second drive gear 206 : Third drive gear 207 : Fourth drive gear 208 : Winding core rotating shaft 210 : Bidirectional clutch 211 : Input side gear 212 : Output side gear 220 : Input shaft 221 : Sun gear 222 : Planetary gear 223 : Internal gear 228 : Housing 230 : Output shaft 231 : Carrier shaft 232 : Carrier 233 : First torque limiter 234 : First gear 235 : Second gear 236 : Second torque limiter

JP 2019-163116 A JP 2021-157122 A

Claims (4)

A gear mechanism having an input shaft and an output shaft,
A sun gear fixed to the input shaft;
At least one planetary gear arranged tangent to a pitch circle of the sun gear;
an internal gear arranged tangent to a pitch circle of the planetary gear;
A carrier that rotatably holds the planetary gear;
A first gear fixed to the carrier;
A second gear fixed to the output shaft;
a bidirectional clutch that drivably connects the first gear to the first gear at an input side and drivably connects the second gear to the second gear at an output side;
a first torque limiter connecting the carrier and the output shaft;
a second torque limiter connecting an output side of the bidirectional clutch and the output shaft;
A gear mechanism comprising: an allowable transmission torque of the bidirectional clutch is greater than both a first slip torque T1 of the first torque limiter and a second slip torque T1 of the second torque limiter;
The idling torque of the bidirectional clutch is smaller than both the first slip torque T1 of the first torque limiter and the second slip torque T1 of the second torque limiter.
2. A gear mechanism according to claim 1. A tension control device that rotates a rolled medium attached to a rotating shaft and controls tension applied to a sheet-like medium that is fed out or wound up from the rolled medium,
A drive source that rotates an output shaft;
an input shaft that transmits torque from the drive source to the rotating shaft;
a torque switching mechanism that is interposed between the output shaft and the input shaft and that switches the torque from the drive source,
The torque switching mechanism includes the gear mechanism according to claim 1 or 2.
A tension control device characterized by: a conveying mechanism that conveys a sheet-like medium to which tension is applied by the tension control device according to claim 3;
a liquid ejection mechanism that ejects liquid onto the medium;
An image forming apparatus comprising: