JP6217354B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device that fixes an image on a sheet by conveying and heating the sheet sent from an image forming unit, and a motor that generates a driving force for driving the fixing device.

  2. Description of the Related Art Conventionally, an image forming apparatus configured to maintain a slack amount of a sheet conveyed between an image forming unit and a fixing unit within a certain range is known (for example, Patent Document 1). reference). The image forming apparatus includes a motor for generating a driving force for driving the fixing device, a sensor for detecting a slack amount of a sheet provided between the image forming unit and the fixing unit, and a motor based on a detection result of the sensor. And a control unit that controls the rotation speed and adjusts the conveyance speed of the fixing unit.

JP 2009-134120 A

  However, in order to simplify the control operation, it is desirable to be able to adjust the sheet conveyance speed in the fixing device without changing the rotation speed of the motor.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of adjusting a sheet conveyance speed in a fixing unit without changing a rotation speed of a motor.

In order to achieve the above-described object, an image forming apparatus of the present invention includes an image forming unit that forms an image on a sheet, and a fixing that fixes the image on the sheet by conveying and heating the sheet sent from the image forming unit. , A motor for generating a driving force for driving the fixing device, a speed change mechanism, and a control means.
The speed change mechanism has a first drive train whose speed transmission ratio is a first value and a second drive train whose speed transmission ratio is a second value larger than the first value. A first mode in which the driving force is transmitted to the fixing device via one of the first driving train and the second driving train, and the control means transmits the driving force of the motor to the fixing device via the first driving train; Selection control is performed to select one of the second modes in which the driving force of the motor is transmitted to the fixing device via the second drive train.

  Here, the speed transmission ratio is a value obtained from the angular velocity on the driving side / the angular velocity on the driven side.

  According to the image forming apparatus configured as described above, it is possible to adjust the sheet conveyance speed in the fixing unit without changing the rotation speed of the motor. Accordingly, the amount of sheet slack between the image forming unit and the fixing device can be set within a certain range.

The image forming apparatus described above may include a sheet conveying unit for conveying the sheet.
In this case, the driving force of the motor can be transmitted to the sheet conveying means.

  According to this, the motor can be used not only for the fixing device but also for driving the sheet conveying means. Since the rotation speed of the motor does not change as described above, the conveyance speed by the sheet conveyance means can be kept constant.

In the image forming apparatus described above, the image forming unit may include a photoconductor on which a developer image is formed.
In this case, the driving force of the motor can be transmitted to the photoconductor.

  According to this, the motor can also be used for driving the photosensitive member. Since the rotation speed of the motor does not change as described above, the rotation speed of the photoconductor can be kept constant.

In the above-described image forming apparatus, the fixing unit includes a heating unit heated by a heat source, a pressure roller that sandwiches the sheet between the heating units and rotates while being in contact with the heating unit, and a heating unit and a pressure roller. Biasing means for biasing one toward the other.
In this case, the speed change mechanism can be configured to transmit the driving force of the motor to the pressure roller.

  The heating unit described above may have an endless belt that contacts the pressure roller and rotates following the driving force of the pressure roller.

  In the above-described image forming apparatus, the speed change mechanism has a connection state in which the input unit to which the driving force is input from the motor and the output unit that outputs the driving force to the fixing unit, and the input unit and the output unit rotate together. And a connection mechanism capable of selecting a disconnected state in which the output unit does not rotate, and the control unit can select a connection state and a disconnected state of the connection mechanism.

  In this case, the connection mechanism described above may be an electromagnetic clutch.

  In the image forming apparatus in which the speed change mechanism includes a connection mechanism, the first drive train has the connection mechanism, and the second drive train transmits the drive force when the drive force is input from the fixing device side. The control means may be configured to place the connection mechanism in the connected state in the first mode and to disconnect the connection mechanism in the second mode.

  According to this, when the connection mechanism is in the connected state, the driving force of the motor is transmitted to the fixing device via the first drive train. At this time, the driving force is input from the fixing device side to the one-way clutch of the second driving train, but the driving force input from the fixing device side to the one-way clutch is not transmitted from the one-way clutch to the motor side, The driving force input to the one-way clutch from the motor side is not transmitted from the one-way clutch to the fixing device side. When the connection mechanism is in the disconnected state, the driving force of the motor is not transmitted via the first drive train, but is transmitted to the fixing device via the second drive train.

  In the image forming apparatus in which the transmission mechanism includes a connection mechanism, the connection mechanism includes a first connection mechanism provided in the first drive train and a second connection mechanism provided in the second drive train, and a control unit. In the first mode, the first connection mechanism is set to the connected state, the second connection mechanism is set to the disconnected state, and in the second mode, the first connection mechanism is set to the disconnected state, and the second connection mechanism is set to the connected state. It may be configured as follows.

  In this case, at least one of the first drive train and the second drive train has a one-way clutch that does not transmit the drive force when the drive force is input from the fixing device side between the connection mechanism and the fixing device. can do.

  According to this, since the driving force from the fixing device side is not transmitted to the connection mechanism by the one-way clutch, it is possible to suppress problems caused by the rotation of the input unit and the output unit in the disconnected connection mechanism.

  In the above-described image forming apparatus, the speed change mechanism is a planetary gear mechanism having three elements of a sun gear, a carrier, and a ring gear, and outputs the driving force to the first element to which the driving force is input from the motor. A planetary gear mechanism having a second element and a third element is provided, and the control means can be configured to select a rotation state and a stop state of the third element.

  According to this, when the third element is stopped, the driving force of the motor is transmitted to the fixing device via the first element and the second element. When the third element is in the rotating state, the driving force of the motor is not transmitted to the fixing device via the first element and the second element. Thereby, a planetary gear mechanism can be functioned as a connection mechanism mentioned above, for example.

  In the case where the speed change mechanism includes a planetary gear mechanism, the image forming apparatus includes a lock mechanism that stops the third element, and the lock mechanism engages the third element in the radial direction; And a drive unit that moves the engagement unit in the radial direction.

  In the image forming apparatus in which the speed change mechanism includes a planetary gear mechanism, the first element may be one of a sun gear and a ring gear, the second element may be a carrier, and the third element may be the other of the sun gear and the ring gear. .

  According to this, since the speed transmission ratio of the speed change mechanism can be increased as compared with the case where the first element or the third element is used as a carrier, the driving force of the motor is amplified to the fixing device by amplifying the torque. Can communicate.

  The planetary gear mechanism described above includes a first planetary gear mechanism provided in the first drive train and a second planetary gear mechanism provided in the second drive train, and the control means is the first planetary gear in the first mode. The third element of the gear mechanism is stopped, the third element of the second planetary gear mechanism is rotated, the third element of the first planetary gear mechanism is rotated in the second mode, and the second planetary gear is rotated. The third element of the gear mechanism may be configured to be in a stopped state.

  According to this, in the first mode, the driving force of the motor is transmitted to the fixing device via the first element and the second element of the first planetary gear mechanism. At this time, the driving force of the motor is not transmitted to the fixing device via the first element and the second element of the second planetary gear mechanism. In the second mode, the driving force of the motor is transmitted to the fixing device via the first element and the second element of the second planetary gear mechanism. At this time, the driving force of the motor is not transmitted to the fixing device via the first element and the second element of the first planetary gear mechanism.

  The first element of the first planetary gear mechanism and the first element of the second planetary gear mechanism can be configured to rotate integrally on the same axis.

  In the above-described image forming apparatus, the speed change mechanism is a planetary gear mechanism having three elements of a sun gear, a carrier, and a ring gear, and outputs the driving force to the first element to which the driving force is input from the motor. The first drive train includes a planetary gear mechanism having a second element and a third element, and the first drive train is a fixing device via a first one-way clutch to which the drive force is input from the second element and the second element. And the second drive train transmits the driving force of the motor to the fixing device via the third element and the second one-way clutch to which the driving force is input from the third element. The third element can be in a stopped state, the second element can be in a rotating state, the third element can be in a rotating state, and the second element can be in a stopped state in the second mode.

  According to this, in the first mode, since the third element is in the stopped state, the second element rotates upon receiving the driving force from the first element, and the driving force of the motor passes through the first driving train. It is transmitted to the fixing device. Since the second one-way clutch is provided between the third element and the fixing device, the driving force input from the fixing device side to the second one-way clutch is not transmitted to the stopped third element. In the second mode, since the second element is in a stopped state, the third element rotates upon receiving the driving force from the first element, and the driving force of the motor is applied to the fixing device via the second driving train. Communicated. Since the first one-way clutch is provided between the second element and the fixing device, the driving force input from the fixing device side to the first one-way clutch is not transmitted to the stopped second element.

  In the image forming apparatus described above, the control unit can be configured to switch between the first mode and the second mode when the fixing device is not transporting the sheet.

  According to this, since the conveyance speed does not fluctuate when fixing the sheet, the fixing operation can be stabilized.

  In the image forming apparatus described above, the control unit can select the first mode when the speed at which the sheet is conveyed through the fixing device is smaller than the first threshold value.

  According to this, when the sheet conveyance speed by the fixing device becomes slow, the speed transmission ratio can be changed in response to the change, so that the conveyance speed of the fixing device can be kept within a certain range.

  In the above-described image forming apparatus, the control unit may select the second mode when the speed at which the sheet is conveyed through the fixing device is larger than the second threshold value.

  According to this, when the sheet conveying speed by the fixing device is increased, the speed transmission ratio can be changed in response to the change, so that the conveying speed of the fixing device can be kept within a certain range.

The image forming apparatus described above may be provided with a sensor that is disposed at a position adjacent to the fixing device in the sheet conveyance path and detects the conveyance of the sheet.
In this case, the control means can be configured to execute the selection control using the detection result of the sensor.

  In the image forming apparatus including the above-described sensor, the sensor is disposed on the downstream side of the conveyance path from the fixing device, and the control unit is configured to perform the first mode when the time for the sheet to pass through the sensor is greater than the third threshold. Can be selected.

  According to this, when the time for the sheet to pass through the sensor becomes long, that is, when the sheet conveying speed by the fixing device becomes slow, the speed transmission ratio can be changed in accordance with the change. The conveyance speed can be within a certain range.

  In the image forming apparatus including the above-described sensor, the sensor is disposed on the downstream side of the conveyance path with respect to the fixing device, and the control unit performs the second mode when the time for the sheet to pass through the sensor is smaller than the fourth threshold value. Can be selected.

  According to this, when the time for the sheet to pass through the sensor is shortened, that is, when the conveying speed of the sheet by the fixing device is increased, the speed transmission ratio can be changed according to the change. The conveyance speed can be within a certain range.

  The control means described above has a counting means for counting the number of printed sheets in a fixed time. When the number of printed sheets is smaller than the fifth threshold, the first mode is selected, and when the number of printed sheets is equal to or larger than the fifth threshold. The second mode can be selected.

  When a plurality of sheets are printed in a certain period of time, a member for conveying the sheet such as a pressure roller expands due to the influence of heat of the fixing device, and the conveying speed of the fixing device becomes faster. By increasing the speed transmission ratio when the number of sheets equal to or greater than the fifth threshold is printed within a certain time, the conveyance speed of the fixing device can be kept within a certain range.

  The control means described above has counting means for counting the number of rotations of the motor in a fixed time, selects the first mode when the number of rotations of the motor is smaller than a sixth threshold, and the number of rotations of the motor is sixth. The second mode may be selected when the value is equal to or greater than the threshold value.

  According to this, since the speed transmission ratio can be increased when the motor is rotated more than the sixth threshold value within a certain time, that is, when a predetermined number of sheets are printed, the conveyance speed of the fixing device is kept within a certain range. Can be.

  According to the present invention, the sheet conveyance speed in the fixing device can be adjusted without changing the rotation speed of the motor. Accordingly, the amount of sheet slack between the image forming unit and the fixing device can be set within a certain range.

1 is a diagram illustrating a schematic configuration of a color printer according to an embodiment of the present invention. It is sectional drawing of a fixing device. It is a figure which shows the speed change mechanism when the 1st mode is selected. It is sectional drawing which shows the structure of an electromagnetic clutch, Comprising: The figure (a) which shows a disconnection state, and the figure (b) which shows a connection state. It is the front view (a) and side view (b) of a one-way clutch. It is a figure which shows the speed change mechanism when the 2nd mode is selected. It is a flowchart which shows the control by a control apparatus. FIG. 5A is a diagram illustrating a speed change mechanism when a first mode is selected in the first modification, and FIG. 5B is a diagram illustrating a speed change mechanism when a second mode is selected. In the 2nd modification, it is a sectional view (a) and a front view (b) of the speed change mechanism when the first mode is selected. In a 2nd modification, it is sectional drawing (a) of the speed change mechanism when the 2nd mode is selected, and a front view (b). In a 3rd modification, sectional drawing (a) of the speed change mechanism when the 1st mode is selected, and sectional view (b) of the speed change mechanism when the 2nd mode is selected. It is a flowchart which shows control of the control apparatus in a 4th modification. It is a flowchart which shows control of the control apparatus in a 5th modification.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the overall configuration of the color printer 1 as an example of an image forming apparatus will be described, and then the details of the features of the present invention will be described.

  In the following description, the direction will be described with reference to the user when using the color printer 1. That is, in FIG. 1, the right side toward the paper surface is “front side”, the left side toward the paper surface is “rear side”, the back side toward the paper surface is “right side”, and the front side toward the paper surface is “left side”. To do. In addition, the vertical direction toward the page is defined as the “vertical direction”.

  As shown in FIG. 1, the color printer 1 includes, in the apparatus main body 10, a paper feeding unit 20 that supplies paper P as an example of a sheet, and an image forming unit 30 that forms an image on the fed paper P. A fixing device 100 that fixes the image on the paper P, a paper discharge unit 90 that discharges the paper P on which the image is formed, and a motor M are provided.

  The sheet feeding unit 20 is a sheet conveying mechanism as an example of a sheet conveying unit including a sheet feeding tray 21 that accommodates the sheet P, and a plurality of rollers that convey the sheet P from the sheet feeding tray 21 to the image forming unit 30. 22.

  The image forming unit 30 includes a scanner unit 40, four process cartridges 50, a holder 60, and a transfer unit 70.

  The scanner unit 40 is provided in an upper part of the apparatus main body 10 and includes a laser light emitting unit, a polygon mirror, a lens, a reflecting mirror, and the like (not shown). In the scanner unit 40, the laser beam is irradiated on the surface of each photosensitive drum 51 by high-speed scanning through a path indicated by a two-dot chain line in the drawing.

  The process cartridge 50 is arranged in the front-rear direction above the paper supply unit 20 and includes a photosensitive drum 51 as an example of a photosensitive member, a known charger (not shown), a developing roller 53, a toner storage chamber, and the like. Has been.

  The holder 60 holds four process cartridges 50, and is configured to be movable in the front-rear direction through an opening 10A formed by opening the front cover 11 disposed on the front surface of the apparatus main body 10.

  The transfer unit 70 is provided between the paper feeding unit 20 and the four process cartridges 50 and includes a driving roller 71, a driven roller 72, a transport belt 73, and a transfer roller 74.

  The driving roller 71 and the driven roller 72 are spaced apart and arranged in parallel in the front-rear direction, and a conveyor belt 73 is stretched therebetween. In addition, four transfer rollers 74 that sandwich the conveyor belt 73 between the photosensitive drums 51 are arranged inside the conveyor belt 73 so as to face the photosensitive drums 51.

  In the image forming unit 30 configured as described above, first, the surface of each photosensitive drum 51 is uniformly charged by a charger and then exposed by the scanner unit 40. Thereby, an electrostatic latent image based on the image data is formed on each photosensitive drum 51. Thereafter, the toner in the toner storage chamber is supplied to the electrostatic latent image on the photosensitive drum 51 by the developing roller 53, so that the toner image is carried on the photosensitive drum 51.

  Next, the paper P supplied on the conveyance belt 73 is formed on each photosensitive drum 51 by passing between each photosensitive drum 51 and each transfer roller 74 while being conveyed rearward by each photosensitive drum 51. The transferred toner image is transferred onto the paper P.

  The fixing device 100 is disposed on the rear side of the four process cartridges 50 and the transfer unit 70, and is configured to fix the image on the paper P by conveying and heating the paper P sent from the image forming unit 30. ing. A detailed configuration of the fixing device 100 will be described later.

  Note that a paper passing sensor 310 as an example of a sensor that detects the passage of the paper P that has come out of the fixing device 100 is located at a position adjacent to the fixing device 100 on the downstream side of the conveyance path of the paper P from the fixing device 100. Has been placed. For example, the sheet passing sensor 310 continues to output a signal to the control device 300 as an example of a control unit provided in the apparatus main body 10 while the sheet P is passing over the sheet passing sensor 310, When the paper P does not pass over the paper sensor 310, a signal is not output to the control device 300.

  The paper discharge unit 90 mainly includes a plurality of transport rollers 91 that transport the paper P. The sheet P on which the toner image has been transferred and heat-fixed is transported by the transport roller 91 and discharged outside the apparatus main body 10.

  The motor M is a driving source that generates a driving force for driving the paper transport mechanism 22, each photosensitive drum 51, the fixing device 100, and the like.

Next, the configuration of the fixing device 100 will be described in detail.
As shown in FIG. 2, the fixing device 100 mainly includes a heating unit HU, a pressure roller 150 in contact with the heating unit HU, and a guide member 170 that supports the heating unit HU.

  The heating unit HU mainly includes a fixing belt 110 as an example of a belt, a halogen lamp 120 as an example of a heat source, a nip plate 130, a reflection plate 140, a stay 160, and a guide member 170.

  The fixing belt 110 is an endless belt having heat resistance and flexibility, and both ends thereof are guided by a guide member 170 (only one side is shown).

  The halogen lamp 120 is a known heating element that heats the toner on the paper P by heating the nip plate 130 and the fixing belt 110. Inside the fixing belt 110, a predetermined amount of heat is supplied from the inner surfaces of the fixing belt 110 and the nip plate 130. They are arranged at intervals.

  The nip plate 130 is a plate-like member that is heated by receiving radiant heat from the halogen lamp 120, and is disposed so as to be in sliding contact with the inner surface of the fixing belt 110. The nip plate 130 is made of a sheet metal such as an aluminum plate having a higher thermal conductivity than a steel stay 160 described later.

  The reflection plate 140 is a member that reflects the radiant heat from the halogen lamp 120 (mainly radiant heat radiated in the front-rear direction and the upward direction) toward the nip plate 130, and the halogen lamp 120 is reflected inside the fixing belt 110. It is arranged at a predetermined interval from the halogen lamp 120 so as to surround it.

  The reflection plate 140 is formed by curving an aluminum plate or the like in a substantially U shape in cross section, for example, having a high infrared and far infrared reflectance.

  The stay 160 is a member that secures the rigidity of the nip plate 130 by supporting the nip plate 130 via the reflection plate 140, and is arranged to cover the reflection plate 140.

  The pressure roller 150 is an elastically deformable member and is disposed below the heating unit HU. The pressure roller 150 forms a nip portion N by sandwiching the fixing belt 110 with the nip plate 130 in an elastically deformed state.

  As shown in FIG. 1, the pressure roller 150 is configured to be rotationally driven by a driving force transmitted from a motor M via a speed change mechanism 200 provided in the apparatus main body 10.

  As shown in FIG. 2, the guide members 170 are arranged one by one on both ends in the left-right direction of the fixing belt 110, guide the inner peripheral surface of the fixing belt 110, and support the halogen lamp 120, the stay 160, and the like. ing. The guide member 170 is urged downward by a spring S as an example of urging means disposed between a part of the fixing frame 180 provided above the heating unit HU and the guide member 170. Thereby, the heating unit HU is urged toward the pressure roller 150.

  In the fixing device 100 configured in this way, the fixing belt 110 is driven to rotate by the frictional force with the fixing belt 110 (or the paper P) when the pressure roller 150 is rotationally driven. That is, the fixing belt 110 rotates upon receiving the driving force of the pressure roller 150. As a result, the paper P onto which the toner image has been transferred is conveyed between the pressure roller 150 and the heated fixing belt 110 from the front to the back, whereby the toner image is thermally fixed.

Next, a detailed configuration of the speed change mechanism 200 will be described.
As shown in FIG. 1, the speed change mechanism 200 is a mechanism for transmitting the driving force of the motor M to the pressure roller 150 of the fixing device 100. As shown in FIG. 3, the speed change mechanism 200 includes a first drive train 201 whose speed transmission ratio is a first value, and a second drive whose speed transmission ratio is a second value larger than the first value. The driving force of the motor M is transmitted to the pressure roller 150 via one of the first driving row 201 and the second driving row 202. In FIG. 3, each gear is indicated by a pitch circle.

  Here, the speed transmission ratio is a value obtained by the angular speed on the driving side / the angular speed on the driven side, that is, in this embodiment, the speed transmission ratio is the angular speed of the first transmission gear 210 that is the most upstream gear of each drive train. / An angular velocity of the pressure roller gear 150G which is the most downstream gear of each drive train.

  The first drive train 201 meshes with the first transmission gear 210 that meshes with the drive gear G that rotates integrally with the rotation shaft of the motor M, the first intermediate gear 220 that meshes with the first transmission gear 210, and the first intermediate gear 220. The electromagnetic clutch 230, the second intermediate gear 240 that meshes with the electromagnetic clutch 230, the first drive input gear 250 that meshes with the second intermediate gear 240, and the first drive input gear 250 that rotates together with the pressure roller 150. And a pressure roller gear 150G.

  The second drive train 202 includes the first transmission gear 210, the first intermediate gear 220, the first drive input gear 250, and the pressure roller gear 150G, and the third intermediate gear 260 that meshes with the first intermediate gear 220. It has a one-way clutch 270 that meshes with the third intermediate gear 260 and the first drive input gear 250.

The motor M is also connected to a third drive train 203 for transmitting the driving force of the motor M to each photosensitive drum 51 and the paper transport mechanism 22.
The third drive train 203 mainly includes a second transmission gear 280 that meshes with the drive gear G and a second drive input gear 290 that meshes with the second transmission gear 280. The second drive input gear 290 is connected to each photosensitive drum 51 and each roller of the paper transport mechanism 22 via a plurality of gears (not shown). That is, in the present embodiment, the driving force of the motor M is transmitted to each photosensitive drum 51 and the paper transport mechanism 22.

  The third drive train 203 applies the driving force of the motor M not only to the photosensitive drum 51 and the paper transport mechanism 22 but also to, for example, each roller (drive roller 71 and transfer roller 74) of the transfer unit 70 and the paper discharge unit 90. It may be configured to be transmitted to other sheet conveying means for conveying the paper P such as the conveying roller 91.

  The electromagnetic clutch 230 has a connection state in which the driving force from the motor M can be transmitted to the pressure roller gear 150G via the first driving train 201, and the driving force from the motor M via the first driving train 201. It is an example of the connection mechanism which can select the cutting state which cannot be transmitted to 150G.

  As shown in FIG. 4A, the electromagnetic clutch 230 includes an input gear 231 as an example of an input portion that meshes with the first intermediate gear 220, and an output gear 232 as an example of an output portion that meshes with the second intermediate gear 240. The movable iron core 233 and the fixed iron core 234 are provided. The electromagnetic clutch 230 is configured to be able to select a connected state where the input gear 231 and the output gear 232 rotate together and a disconnected state where the output gear 232 does not rotate.

  The output gear 232 has a rotating shaft 232A, and the input gear 231 is assembled so as to be rotatable with respect to the rotating shaft 232A via a bearing (not shown).

  The movable iron core 233 is disposed between the input gear 231 and the output gear 232, and is wound with a coil. The movable iron core 233 is engaged with the rotation shaft 232A of the output gear 232 via a spline or serration, can move in the axial direction with respect to the rotation shaft 232A, and can rotate integrally with the rotation shaft 232A. ing. The movable iron core 233 is urged in a direction away from the input gear 231 by an urging member (not shown).

  The fixed iron core 234 is fixed to the end surface of the input gear 231 on the movable iron core 233 side. For this reason, when the movable iron core 233 is energized, the movable iron core 233 moves to the input gear 231 side by the electromagnetic attraction force and is attracted to the fixed iron core 234 as shown in FIG. As a result, the movable iron core 233 and the input gear 231 are integrated, and the electromagnetic clutch 230 enters a connection state in which the input gear 231 and the output gear 232 rotate integrally, and the driving force from the motor M transmitted to the input gear 231 is reduced. It is transmitted to the second intermediate gear 240.

  As shown in FIG. 4A, when the movable iron core 233 is not energized, the movable iron core 233 and the fixed iron core 234 are not attracted, and the electromagnetic clutch 230 is integrated with the input gear 231 and the output gear 232. The cutting force is not rotated, and the driving force from the motor M transmitted to the input gear 231 is not transmitted to the second intermediate gear 240.

  As shown in FIG. 3, the one-way clutch 270 can rotate only in one direction for transmitting the driving force from the motor M to the pressure roller gear 150G, and does not rotate by the driving force from the pressure roller gear 150G. It is configured. Specifically, as shown in FIG. 5A, the one-way clutch 270 is disposed between an annular outer ring 271, an inner ring 272 partially disposed inside the outer ring 271, and the outer ring 271 and the inner ring 272. A plurality of rollers 273 and an urging member 274 provided corresponding to each roller 273.

  The outer ring 271 has gear teeth (not shown) on the outer periphery and meshes with the third intermediate gear 260. The outer ring 271 has pockets 271 </ b> A that are recessed outward at a plurality of locations on the inner peripheral surface. The bottom portion of the pocket 271A is inclined so as to approach the inner ring 272 side from the center toward the outside in the rotation direction of the outer ring 271.

  As shown in FIG. 5B, the inner ring 272 is provided at an inner portion 272A disposed inside the outer ring 271, and at a position offset in the axial direction with respect to the outer ring 271, and can rotate integrally with the inner portion 272A. And a gear portion 272B. The gear part 272 </ b> B is provided with gear teeth (not shown) on the outer periphery and meshes with the first drive input gear 250.

  As shown in FIG. 5A, each roller 273 is disposed in the pocket 271 </ b> A of the outer ring 271. The roller 273 is urged by the urging member 274 toward the upstream end in the rotation direction of the outer ring 2271 of the pocket 271A (counterclockwise direction in FIG. 5A).

  In the one-way clutch 270 configured as described above, when the outer ring 271 rotates counterclockwise in FIG. 5A with respect to the inner ring 272, the roller 273 is fitted between the bottom of the pocket 271A and the inner ring 272. The outer ring 271 and the inner ring 272 are engaged with each other. At this time, the inner ring 272 rotates counterclockwise together with the outer ring 271. On the other hand, when the inner ring 272 rotates counterclockwise with respect to the outer ring 271, the roller 273 moves to the downstream side in the rotation direction by the frictional force between the roller 273 and the inner ring 272, and the engagement between the inner ring 272 and the outer ring 271 is released. . At this time, the inner ring 272 and the outer ring 271 rotate separately.

  As shown in FIG. 3, the electromagnetic clutch 230 and the second intermediate gear 240 constituting the first drive train 201 and the third intermediate gear 260 and the one-way clutch 270 constituting the second drive train 202 are the second The number of teeth is set so that the speed transmission ratio of the drive train 202 becomes a second value larger than the first value that is the speed transmission ratio of the first drive train 201.

  Thus, the driving force of the motor M is greater than the angular velocity of the first driving input gear 250 when the driving force of the motor M is transmitted via the third intermediate gear 260 and the one-way clutch 270. 2 The angular velocity of the first drive input gear 250 when it is transmitted via the intermediate gear 240 becomes faster.

  In the speed change mechanism 200 configured as described above, switching between the connected state and the disconnected state of the electromagnetic clutch 230 is controlled by the control device 300 (see FIG. 1), and the driving force of the motor M is used as the first driving train. It can be transmitted to the pressure roller 150 of the fixing device 100 via one of the 201 and the second drive train 202.

Here, the operation of the speed change mechanism 200 when the electromagnetic clutch 230 is in the connected state and the disconnected state will be described.
As shown in FIG. 3, when the motor M is driven while the electromagnetic clutch 230 is in a connected state, each gear constituting the first drive train 201 rotates, and the driving force of the motor M is applied via the first drive train 201. The pressure roller 150 is transmitted to the pressure roller gear 150G, and the pressure roller 150 rotates at the first speed.

  At this time, the driving force of the motor M is also transmitted to the outer ring 271 of the one-way clutch 270 of the second drive train 202. However, the driving force of the motor M is higher than the angular velocity of the first driving input gear 250 when the driving force of the motor M is transmitted via the third intermediate gear 260 and the one-way clutch 270. Since the angular velocity of the first drive input gear 250 when it is transmitted via the intermediate gear 240 is faster, the inner ring 272 of the one-way clutch 270 rotates by receiving the driving force from the first drive input gear 250, and the inner ring The angular velocity of 272 becomes faster than the angular velocity of the outer ring 271. Thereby, the meshing of the outer ring 271 and the inner ring 272 in the one-way clutch 270 is released, and the outer ring 271 rotates idly with respect to the inner ring 272. Therefore, the driving force of the motor M is not transmitted to the pressure roller gear 150G via the second driving train 202.

  As shown in FIG. 6, when the motor M is driven while the electromagnetic clutch 230 is in a disconnected state, the driving force of the motor M is transmitted to the input gear 231 of the electromagnetic clutch 230, but not transmitted to the output gear 232. As a result, the driving force of the motor M is not transmitted from the first drive train 201 to the pressure roller gear 150G. On the other hand, the gears constituting the second drive train 202 rotate and the outer ring 271 and the inner race 272 in the one-way clutch 270 mesh with each other, so that the driving force of the motor M is transmitted to the pressure roller gear 150G via the second drive train 202. The pressure roller 150 rotates at a second speed that is slower than the first speed. Note that the output gear 232 of the electromagnetic clutch 230 rotates upon receiving a driving force from the first drive input gear 250, but rotates idly with respect to the input gear 231.

Next, the control device 300 will be described in detail.
As shown in FIG. 1, the control device 300 includes a CPU, a RAM, a ROM, and the like (not shown), and controls the speed change mechanism 200 according to a detection result input from the paper passing sensor 310 and a preset program. Is configured to do.

  The control device 300 uses the detection result of the paper passing sensor 310 to transmit the driving force of the motor M to the fixing device 100 via the first driving train 201 and the driving force of the motor M to the second. Selection control for selecting any one of the second mode transmitted to the fixing device 100 via the drive train 202 is executed.

  Specifically, when the time during which the paper P having a predetermined length passes through the paper passing sensor 310 is longer (larger) than the first time T1 as an example of the third threshold value, the control device 300 performs the electromagnetic clutch 230. And the first mode is selected. Then, when the time during which the paper P having a predetermined length passes through the paper passing sensor 310 is shorter (smaller) than the second time T2 as an example of the fourth threshold, the control device 300 causes the electromagnetic clutch 230 to move. In the disconnected state, the second mode is selected. Further, the control device 300 maintains the currently selected mode as it is when the time during which the paper P having a predetermined length passes through the paper passing sensor 310 is not less than the first time T1 and not more than the second time T2. Is configured to do.

  In this way, by selecting the first mode and the second mode based on the time for which the paper P passes the paper passing sensor 310, it is possible to perform control according to the conveyance speed of the paper P in the fixing device 100. That is, when the time for which the paper P passes the paper passing sensor 310 is longer than the first time T1, this corresponds to the case where the speed at which the paper P is conveyed through the fixing device 100 is smaller than the first threshold. Further, when the time for which the paper P passes the paper passing sensor 310 is shorter than the second time T2, this corresponds to the case where the speed at which the paper P is conveyed through the fixing device 100 is larger than the second threshold.

  In the present embodiment, the first time T1 is set to be greater than the second time T2, but the first time T1 and the second time T2 may be set to be the same time. Further, the first time T1 and the second time T2 can be appropriately changed according to the size of the paper P, and can be appropriately set by inputting the size of the paper P by the user. Further, the first time T1 and the second time T2 may be set from the time passing through the second paper passing sensor 311 arranged on the upstream side of the transport path from the paper passing sensor 310. At this time, the second sheet passing sensor 311 may be disposed between the sheet transport mechanism 22 and the image forming unit 30.

  The control device 300 performs selection control when the fixing device 100 is not transporting the paper P. Specifically, for example, the control device 300 executes selection control after the sheet passing sensor 310 located downstream of the fixing device 100 detects the passage time of the sheet P and before the next sheet P is conveyed. . Thereby, since the conveyance speed does not fluctuate when fixing the paper P, the fixing operation can be stabilized.

  In addition, the control device 300 selects the first mode when performing the first printing after the power is turned on, and at the time of printing the first first sheet when the print job is input, The selected mode is to be executed.

The operation of the control device 300 will be described with reference to FIG.
When starting the control operation, the control device 300 first determines whether or not a print job has been received (S1). At this time, if a print job has not been received (S1, No), the control device 300 ends the control operation. On the other hand, when the print job is received (S1, Yes), the control device 300 determines whether or not the passage of the paper P is detected by the paper passing sensor 310 (S2).

  In step S2, when the passage of the paper P is not detected (S2, No), the control device 300 stands by until the paper P is detected.

  If the passage of the paper P is detected in step S2 (S2, Yes), it is determined whether or not the time during which the paper P passes the paper passing sensor 310 is longer than the first time T1 (S3). At this time, if it is determined that the time during which the paper P passes the paper passing sensor 310 is longer than the first time T1 (S3, Yes), the control device 300 places the electromagnetic clutch 230 in the connected state and sets the first mode. Select (S4).

  On the other hand, if it is determined in step S3 that the time during which the paper P passes the paper passing sensor 310 is equal to or shorter than the first time T1 (S3, No), the control device 300 causes the paper P to pass the paper passing sensor 310. It is determined whether or not the passing time is shorter than the second time T2 (S5). At this time, if it is determined that the time during which the paper P passes through the paper passing sensor 310 is shorter than the second time T2 (S5, Yes), the control device 300 sets the electromagnetic clutch 230 to the disconnected state and sets the second mode. Select (S6).

  In step S5, it is determined that the time during which the paper P passes through the paper passage sensor 310 is equal to or longer than the second time T2 (S5, No). That is, the paper P passes through the paper passage sensor 310. If it is determined that the currently running time is the second time T2 or more and the first time T1 or less, the control device 300 maintains the currently selected mode.

  After the mode is selected, one sheet is printed in that mode, and it is determined whether or not the print job is completed (S7). At this time, if the print job has ended (S7, Yes), the control device 300 stores the current mode and ends the control operation. On the other hand, if the print job has not ended in step S7 (S7, No), the control device 300 returns to step S2 and continues the control operation.

The operation and effect of the color printer 1 configured as described above will be described.
First, when the color printer 1 receives a print job for the first time after being turned on, the control device 300 performs print control in the first mode.

  In the first mode, since the electromagnetic clutch 230 is in a connected state, as shown in FIG. 3, as the motor M is driven, each gear constituting the first drive train 201 rotates, and the driving force of the motor M is increased. The pressure is transmitted to the pressure roller 150 through the first drive train 201. Thereby, the conveyance speed of the paper P in the fixing device 100 becomes a predetermined speed.

  When a plurality of sheets are continuously printed, in the fixing device 100, each member is heated by the radiant heat of the halogen lamp 120. At this time, since the pressure roller 150 expands, the peripheral speed becomes faster than when the pressure roller 150 is initially cooled, and the conveying speed of the fixing device 100 becomes faster than a predetermined speed.

  Thus, when the conveyance speed of the paper P in the fixing device 100 increases, the time during which the paper P passes the paper passing sensor 310 becomes shorter than the second time T2. At this time, the control is performed by the control device 300 in the second mode.

  When the second mode is selected, as shown in FIG. 6, the electromagnetic clutch 230 is in a disconnected state, so that the driving force of the motor M is transmitted to the pressure roller 150 via the second driving train 202. The As a result, the angular velocity of the pressure roller 150 becomes slower than when the first mode is selected, and the peripheral speed of the expanded pressure roller 150 can be suppressed from becoming too fast. The conveyance speed can be brought close to a predetermined speed.

  When there is sufficient time until the print job is completed and the next print job is input, the pressure roller 150 is cooled, and the diameter of the pressure roller 150 becomes smaller than that during expansion. At this time, when printing is started again, the peripheral speed of the pressure roller 150 becomes slower than that at the end of the previous print job, and the conveyance speed of the paper P in the fixing device 100 becomes slower than a predetermined speed. As a result, the time during which the paper P passes the paper passing sensor 310 is longer than the first time T1, so that the control control is performed by the control device 300 in the first mode. As a result, the angular speed of the pressure roller 150 becomes faster than when the second mode is selected, and the peripheral speed of the pressure roller 150 can be suppressed from becoming too slow. Can be set to a predetermined speed.

  As described above, in this embodiment, the conveyance speed of the fixing device 100 can be changed without changing the rotation speed of the motor M. Thereby, the slack of the paper P between the image forming unit 30 and the fixing device 100 can be kept within a certain range.

  Since the rotation speed of the motor M is not changed, the transport speed of the paper P in the photosensitive drum 51 and the paper transport mechanism 22 can be kept constant.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention. In the following description, components that are substantially the same as those in the above-described embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the embodiment, the first drive train 201 has the electromagnetic clutch 230 and the second drive train 202 has the one-way clutch 270. However, the present invention is not limited to this. For example, as shown in FIG. 8A, in the speed change mechanism 400, both the first drive train 401 and the second drive train 402 may have electromagnetic clutches 430, 460 and one-way clutches 440, 470. .

  Specifically, the first drive train 401 includes the first transmission gear 210, the first intermediate gear 220, the first drive input gear 250, and the pressure roller gear 150G in the above embodiment, as an example of the first connection mechanism. A first electromagnetic clutch 430 and a first one-way clutch 440 are provided. The second drive train 402 includes the first transmission gear 210, the first intermediate gear 220, the first drive input gear 250, and the pressure roller gear 150G in the above embodiment, and a second connection mechanism as an example of the second connection mechanism. An electromagnetic clutch 460 and a second one-way clutch 470 are provided.

  The first electromagnetic clutch 430 and the second electromagnetic clutch 460 have substantially the same configuration as the electromagnetic clutch 230 of the above embodiment, and the input gear 431 of the first electromagnetic clutch 430 and the input gear 461 of the second electromagnetic clutch 460 are , Each meshing with the first intermediate gear 220.

  The first one-way clutch 440 and the second one-way clutch 470 have substantially the same configuration as the one-way clutch 270 of the above-described embodiment. The outer ring 441 of the first one-way clutch 440 meshes with the output gear 432 of the first electromagnetic clutch 430, and the inner ring 442 of the first one-way clutch 440 meshes with the first drive input gear 250. The outer ring 471 of the second one-way clutch 470 is engaged with the output gear 462 of the second electromagnetic clutch 460, and the inner ring 472 of the second one-way clutch 470 is engaged with the first drive input gear 250. That is, the first one-way clutch 440 is disposed between the first electromagnetic clutch 430 and the pressure roller gear 150G, and the second one-way clutch 470 is disposed between the second electromagnetic clutch 460 and the pressure roller gear 150G.

  The first electromagnetic clutch 430 and the first one-way clutch 440 and the second electromagnetic clutch 460 and the second one-way clutch 470 have a speed transmission ratio of the second drive train 402 that is equal to the speed transmission ratio of the first drive train 401. The number of teeth is set so as to be a second value larger than a certain first value.

  In the first mode, the control device 300 sets the first electromagnetic clutch 430 in the connected state, sets the second electromagnetic clutch 460 in the disconnected state, and in the second mode sets the first electromagnetic clutch 430 in the disconnected state, 2 The electromagnetic clutch 460 is configured to be in a connected state.

  In the speed change mechanism 400 configured as described above, when the first mode is selected, the first electromagnetic clutch 430 is in the connected state and the second electromagnetic clutch 460 is in the disconnected state. Thus, the driving force of the motor M is transmitted to the pressure roller gear 150G.

  At this time, the inner ring 472 of the second one-way clutch 470 that meshes with the first drive input gear 250 rotates, but the inner ring 472 slides relative to the outer ring 471, so the outer ring 471 of the second one-way clutch 470 The drive force from the 150G side does not rotate, and the drive force of the first drive input gear 250 is not transmitted to the second electromagnetic clutch 460. Thereby, in the 2nd electromagnetic clutch 460 of a disconnection state, the malfunction by which both the input gear 461 and the output gear 462 rotate together can be suppressed.

  On the other hand, when the second mode is selected, the first electromagnetic clutch 430 is in a disconnected state and the second electromagnetic clutch 460 is in a connected state, and therefore, as shown in FIG. The driving force of the motor M is transmitted to the pressure roller gear 150G.

  At this time, the inner ring 442 of the first one-way clutch 440 that meshes with the first drive input gear 250 rotates, but the inner ring 442 slides with respect to the outer ring 441. Therefore, the outer ring 441 of the first one-way clutch 440 The drive force from the 150G side does not rotate, and the drive force of the first drive input gear 250 is not transmitted to the first electromagnetic clutch 430. Thereby, in the cut | disconnected 1st electromagnetic clutch 430, the malfunction by both of the input gear 431 and the output gear 432 rotating can be suppressed.

  In the above-described modification, both the first drive train 401 and the second drive train 402 are provided with the one-way clutches 440 and 470, but only one of the first drive train 401 and the second drive train 402 is provided. A configuration including a one-way clutch may be employed, or a configuration in which both the first drive train 401 and the second drive train 402 are not provided with a one-way clutch may be employed.

  In the embodiment, the speed change mechanism 200 includes the electromagnetic clutch 230, but the present invention is not limited to this. For example, as shown in FIGS. 9A and 9B, the speed change mechanism 500 may include planetary gear mechanisms 510 and 520 without including an electromagnetic clutch.

  Specifically, in the speed change mechanism 500, the first drive train 501 includes the first transmission gear 210, the first intermediate gear 220, the first drive input gear 250, and the pressure roller gear 150G in the above embodiment, as well as the first intermediate gear. A first planetary gear mechanism 510 is provided between the gear 220 and the first drive input gear 250. The second drive train 502 includes the first transmission gear 210, the first intermediate gear 220, the first drive input gear 250, and the pressure roller gear 150G in the above embodiment, as well as the first intermediate gear 220 and the first drive input. A second planetary gear mechanism 520 is provided between the gears 250. Further, a lock mechanism 503 acting on each planetary gear mechanism 510 520 is provided in the apparatus main body 10.

  The first planetary gear mechanism 510 includes a first sun gear 511 as an example of a first element to which driving force is input from the motor M, a first ring gear 512 as an example of a third element, and a plurality of first planetary gears 513. And a first carrier 514 as an example of a second element that outputs a driving force to the fixing device 100.

  The first sun gear 511 has a gear body 511A and a rotation shaft 511B provided integrally with the gear body 511A. Gear teeth are formed on the outer peripheral surface of the gear body 511A and the outer peripheral surface of the rotation shaft 511B. The first sun gear 511 is meshed with the first intermediate gear 220 so that when the motor M is driven, a driving force is input from the motor M.

  The first ring gear 512 is provided so as to be rotatable with respect to the rotation shaft 511B, and includes an annular inner tooth portion 512A centering on the rotation axis, and an outer tooth portion 512B provided to be shifted from the inner tooth portion 512A in the axial direction. Have. The inner tooth portion 512A has gear teeth on the inner peripheral surface, and the outer tooth portion 512B has gear teeth on the outer peripheral surface.

  The first planetary gear 513 is a gear disposed between the first sun gear 511 and the first ring gear 512, and the gear teeth of the rotation shaft 511B of the first sun gear 511 and the gear teeth of the inner tooth portion 512A of the first ring gear 512 are included. It meshes with both.

  The first carrier 514 includes a shaft support portion 514A that supports each first planetary gear 513 and is rotatably provided with respect to the rotation shaft 511B of the first sun gear 511. The first carrier 514 has gear teeth formed on the outer peripheral surface thereof, meshes with the first drive input gear 250, and outputs a driving force to the pressure roller gear 150G.

  The second planetary gear mechanism 520 has substantially the same configuration as the first planetary gear mechanism 510, and includes a first sun gear 511 as an example of the first element, and a third element having an inner tooth portion 522A and an outer tooth portion 522B. A second ring gear 522 as an example, a plurality of second planetary gears 523, and a second carrier 524 as an example of a second element having a shaft support portion 524 </ b> A for supporting the second planetary gear 523. That is, the first element of the first planetary gear mechanism 510 and the first element of the second planetary gear mechanism 520 are the same first sun gear 511, and can rotate integrally on the same axis.

  In addition, the first planetary gear mechanism 510 and the second planetary gear mechanism 520 have a second value in which the speed transmission ratio of the second drive train 502 is larger than the first value that is the speed transmission ratio of the first drive train 501. The number of teeth is set so that

  As shown in FIG. 9B, the first planetary gear mechanism 510 and the second planetary gear mechanism 520 configured as described above are connected to the first ring gear 512 and the first planetary gear mechanism 503 by a lock mechanism 503 provided in the apparatus body 10. The two-ring gear 522 can be switched between a rotating state and a stopped state.

  The lock mechanism 503 includes a solenoid 540 as an example of a drive unit, and an arm member 550 that is provided so as to be swingable and whose proximal end is pushed by the solenoid 540.

  The arm member 550 extends from the swing center to the external tooth portion 512B side of the first ring gear 512, and has a first arm 551 having a claw 551A (engagement portion) at the tip, and an external tooth of the second ring gear 522 from the swing center. And a second arm 552 having a claw 552A (engaging portion) at the tip thereof. As the arm member 550 swings, the claw 551A of the first arm 551 moves in the radial direction with respect to the first ring gear 512, and the claw 552A of the second arm 552 moves in the radial direction with respect to the second ring gear 522. Configured to move to. In the arm member 550, when the solenoid 540 is not operated, the claw 551A of the first arm 551 is engaged with the outer tooth portion 512B of the first ring gear 512, and the claw 552A of the second arm 552 is engaged with the second ring gear. It is biased by a spring (not shown) so as to be separated from 522.

  In the arm member 550, the claw 551A of the first arm 551 is engaged with the external tooth portion 512B of the first ring gear 512 from the radial direction in the state shown in FIG. The ring gear 512 is stopped. At this time, the claw 552A of the second arm 552 is separated from the external tooth portion 522B of the second ring gear 522, and the second ring gear 522 is in a rotating state. Further, in the state shown in FIG. 10B in which the solenoid 540 is operated, the arm member 550 engages the outer teeth 522B of the second ring gear 522 from the radial direction with the claw 552A of the second arm 552, and the second ring gear. 522 is set to the stop state. At this time, the claw 551A of the first arm 551 is separated from the external tooth portion 512B of the first ring gear 512, and the first ring gear 512 is in a rotating state.

  When the first mode is selected, the control device 300 is configured not to actuate the solenoid 540 so that the first ring gear 512 is stopped and the second ring gear 522 is rotated. In addition, when the second mode is selected, the control device 300 is configured to operate the solenoid 540 so that the first ring gear 512 is rotated and the second ring gear 522 is stopped.

  In the speed change mechanism 500 configured as described above, when the first mode is selected, the first ring gear 512 is stopped as shown in FIG. The driving force of the motor M is transmitted to the first carrier 514 via the first planetary gear 513, and the first carrier 514 rotates. On the other hand, since the second ring gear 522 is in a rotating state, the driving force of the motor M is not transmitted to the second carrier 524. Thus, in the first mode, the driving force of the motor M is transmitted to the pressure roller gear 150G via the first drive train 501.

  When the second mode is selected, as shown in FIG. 10A, the second ring gear 522 is in a stopped state, so the first sun gear 511 passes through the second planetary gear 523 to the second carrier 524. The driving force of the motor M is transmitted, and the second carrier 524 rotates. On the other hand, since the first ring gear 512 is in a rotating state, the driving force of the motor M is not transmitted to the first carrier 514. Thus, in the second mode, the driving force of the motor M is transmitted to the pressure roller gear 150G via the second drive train 502.

  In the first planetary gear mechanism 510 and the second planetary gear mechanism 520, the first element and the third element are constituted by the first sun gear 511, the first ring gear 512, and the second ring gear 522. Alternatively, the speed transmission ratio of the speed change mechanism 500 can be increased as compared with the case where the third element is the first carrier 514 or the second carrier 524. Thereby, the driving force of the motor M can be transmitted to the fixing device 100 by amplifying the torque.

  In the modified example described above, the sun gear 511 of the planetary gear mechanisms 510 and 520 is the first element to which the driving force is input from the motor M, and the ring gears 512 and 513 of the planetary gear mechanisms 510 and 520 are the third element. However, the configuration of the planetary gear mechanism is not limited to this. For example, the planetary gear mechanism may be configured such that the sun gear functions as the third element and the ring gear functions as the first element.

  In the above-described modification, the speed change mechanism 500 includes the two planetary gear mechanisms 510 and 520. However, as illustrated in FIG. 11A, the speed change mechanism 600 is configured to include one planetary gear mechanism 600A. There may be.

  In the speed change mechanism 600, the first drive train 601 includes the first transmission gear 210, the first intermediate gear 220, the first drive input gear 250, and the pressure roller gear 150G in the above embodiment, as well as the first intermediate gear 220 and the first intermediate gear 220. A planetary gear mechanism 600A and a third one-way clutch 650 are provided between the one drive input gear 250, and the second drive train 602 includes the first transmission gear 210, the first intermediate gear 220, and the first drive input in the embodiment. In addition to the gear 250 and the pressure roller gear 150G, a planetary gear mechanism 600A and a fourth one-way clutch 660 are provided between the first intermediate gear 220 and the first drive input gear 250. The third one-way clutch 650 and the fourth one-way clutch 660 have the same configuration as the one-way clutch 270 in the embodiment. Further, the lock mechanism 503 in the above-described modification is provided in the apparatus main body 2.

  The planetary gear mechanism 600A includes a sun gear 610 as an example of a second element that outputs a driving force to the fixing device 100, a ring gear 620 as an example of a third element that outputs a driving force to the fixing device 100, and a plurality of planetary gears 630. And a carrier 640 as an example of a first element to which a driving force is input from the motor M.

  The sun gear 610 includes a large-diameter portion 611, a small-diameter portion 612, and a shaft portion 613 that can rotate integrally with the large-diameter portion 611 and the small-diameter portion 612. The large-diameter portion 611, the small-diameter portion 612, and the shaft portion 613 each have gear teeth on the outer peripheral surface. The large diameter portion 611 meshes with the outer ring 651 of the third one-way clutch 650. Note that the inner ring 652 of the third one-way clutch 650 is engaged with the first drive input gear 250, and the driving force input from the sun gear 610 to the outer ring 651 is transmitted to the first drive input gear 250. That is, a driving force can be output from the sun gear 610 to the pressure roller gear 150G via the third one-way clutch 650.

  The sun gear 610 can be switched between a stopped state and a rotating state by engaging and separating the claw 551A of the first arm 551 of the lock mechanism 503 with respect to the small diameter portion 612.

  The ring gear 620 is rotatably provided with respect to the shaft portion 613 of the sun gear 610, and has a main body portion 621 that is formed in an annular shape, and a locking portion 622 that is provided to be offset in the axial direction with respect to the main body portion 621. ing. The main body 621 has gear teeth on the inner peripheral surface and the outer peripheral surface. The engaging portion 622 has gear teeth on the outer peripheral surface. The main body 621 of the ring gear 620 meshes with the outer ring 661 of the fourth one-way clutch 660. The inner ring 662 of the fourth one-way clutch 660 meshes with the first drive input gear 250 so that the driving force input from the ring gear 620 to the outer ring 661 is transmitted to the first drive input gear 250. That is, a driving force can be output from the ring gear 620 to the pressure roller gear 150G via the fourth one-way clutch 660.

  The ring gear 620 can be switched between a stopped state and a rotating state when the claw 552A of the second arm 552 of the lock mechanism 503 is engaged / separated from the engaging portion 622.

  Each planetary gear 630 is disposed between the shaft portion 613 of the sun gear 610 and the main body portion 621 of the ring gear 620, and meshes with the gear teeth of the shaft portion 613 and the gear teeth of the main body portion 621.

  The carrier 640 includes a shaft support portion 641 that supports the planetary gear 630 and is provided so as to be rotatable with respect to the shaft portion 613 of the sun gear 610. Gear teeth are formed on the outer peripheral surface of the carrier 640, meshing with the first intermediate gear 220, and driving force is input from the motor M to the carrier 640.

  When the control device 300 selects the first mode, the claw 551A of the first arm 551 is separated from the sun gear 610, the sun gear 610 is rotated, and the claw 552A of the second arm 552 is engaged with the ring gear 620. Then, the ring gear 620 is brought into a stopped state. Further, when selecting the second mode, the control device 300 engages the claw 551A of the first arm 551 with the sun gear 610 to stop the sun gear 610 and separate the claw 552A of the second arm 552 from the ring gear 620. The ring gear 620 is rotated.

  In the speed change mechanism 600 configured as described above, when the first mode is selected, the sun gear 610 is in the rotating state and the ring gear 620 is in the stopped state, as shown in FIG. The driving force input to 640 is transmitted to the sun gear 610 via the planetary gear 630. Thereby, the driving force of the motor M is transmitted to the pressure roller gear 150G via the first drive train 601.

  When the second mode is selected, as shown in FIG. 11B, since the sun gear 610 is stopped and the ring gear 620 is rotated, the driving force input to the carrier 640 causes the planetary gear 630 to be driven. To the ring gear 620. Thereby, the driving force of the motor M is transmitted to the pressure roller gear 150G via the second drive train 602.

  In the embodiment, the control device 300 executes the selection control based on the passage time of the paper P at the position of the paper passing sensor 310, but the present invention is not limited to this. For example, the paper passing sensor 310 is a speed sensor that measures the transport speed of the paper P, and the control device 300 receives the transport speed of the paper P transported by the fixing device 100 from the paper pass sensor 310 and the transport speed is the first. The first mode is selected when it is smaller than the conveyance speed V1 as an example of the threshold value, and the second mode is selected when it is larger than the conveyance speed V2 as an example of the second threshold value. Good. Note that the transport speed V1 and the transport speed V2 do not need to be changed according to the size of the paper P, and can be set as appropriate through experiments, simulations, and the like.

  In the embodiment, the control device 300 executes the selection control using the detection signal of the paper passing sensor 310. However, the present invention is not limited to this, and the selection control is performed based on the number of printed sheets in a fixed time. May be executed. As the number of printed sheets in a certain time increases, the temperature of the fixing device 100 increases and the diameter of the pressure roller 150 increases. As the diameter of the pressure roller 150 changes, the conveyance speed of the paper P in the fixing device 100 changes. For this reason, as in this modification, by performing selection control based on the number of printed sheets in a fixed time, the slack amount of the paper P conveyed between the fixing device 100 and the image forming unit 30 is set in a fixed range. Can do.

  Specifically, the control device 300 includes a counting unit that counts the number of printed sheets within a predetermined time from the last printing time, and the number of printed sheets is smaller than a predetermined number of sheets as an example of the fifth threshold value. The first mode is selected, and when the number of printed sheets is equal to or greater than the predetermined number, the second mode is selected. In addition, the control device 300 records the printing time after printing one sheet of paper. The number of prints within a certain time is determined by counting the times recorded within the certain time. Note that the fixed time and the predetermined number can be set as appropriate by experiments, simulations, or the like.

The operation of the control device 300 will be described with reference to FIG.
When starting the control operation, the control device 300 first determines whether or not a print job has been received (S11). At this time, if a print job has not been received (S11, No), the control device 300 ends the control operation. On the other hand, when a print job is received (S11, Yes), the control device 300 counts the number of printed sheets within a certain time (S12), and determines whether the number of printed sheets within a certain time is less than a predetermined number (S13). .

  At this time, if the number of printed sheets within a predetermined time is less than the predetermined number (S13, Yes), the control device 300 selects the first mode (S15) and executes printing for one sheet (S16). On the other hand, when it is determined in step S13 that the number of printed sheets within a predetermined time is equal to or larger than the predetermined number (S13, No), the control device 300 selects the second mode (S14) and executes printing for one sheet. (S16).

  After printing one sheet in step S16, the control device 300 records the current time (S17), and determines whether or not the print job is completed (S18).

  At this time, if it is determined that the print job is completed (S18, Yes), the control device 300 ends the control operation. On the other hand, if it is determined in step S18 that the print job is not completed (S18, No), the control device 300 returns to step S12 and continues print control.

  In the color printer 1 configured in this way, when a predetermined number of sheets or more are printed within a certain period of time, when the temperature of the fixing device 100 exceeds a certain value and the diameter of the pressure roller 150 increases, the controller 300 is Since the second mode is selected and the rotation speed of the pressure roller 150 is decreased, the conveyance speed of the fixing device 100 can be set within a certain range.

  Further, the counting means described above may be configured to count the number of rotations of the motor M within a certain time from the last printing time. As the number of rotations of the motor M within a certain time increases, the number of printed sheets within a certain time increases and the diameter of the pressure roller 150 increases. As the diameter of the pressure roller 150 changes, the conveyance speed of the fixing device 100 changes. Therefore, as in this modification, by performing selection control based on the number of rotations of the motor M in a certain time, the amount of slackness of the paper P conveyed between the fixing device 100 and the image forming unit 30 is in a certain range. Can be.

  Specifically, the control device 300 selects the first mode when the number of rotations is smaller than a predetermined number as an example of the sixth threshold, and selects the second mode when the number of rotations is equal to or larger than the predetermined number. Control to do. Further, the control device 300 records the printing time after printing one sheet of paper, as in the embodiment in FIG. The number of rotations of the motor M within a certain period of time is determined by the product of the number of rotations of the motor M considered necessary for printing one sheet and the number of printed sheets within a certain period of time (a plurality of times corresponding to the number of printed sheets). . Note that the predetermined time and the predetermined number of times can be set as appropriate by experiment, simulation, or the like.

The operation of the control device 300 will be described with reference to FIG.
The processing in step S11 is the same as that in FIG. 12, and when it is determined that there is a print job (S11, Yes), the control device 300 rotates the motor M within a certain time from the last printing time. The number of times (the product of the number of rotations of the motor M for one print and a plurality of times corresponding to the number of prints) is counted (S22), and it is determined whether or not the number of rotations is smaller than a predetermined number (S23).

  In step S23, when the number of rotations of the motor M is smaller than the predetermined number (S23, Yes), the control device 300 selects the first mode (S25), and when the number of rotations of the motor M is equal to or larger than the predetermined number (S23, No), the second mode is selected (S24). After Step S24 or Step S25, the processes after Step S16 are the same as those in FIG.

  In the color printer 1 configured as described above, the motor M rotates a predetermined number of times or more within a predetermined time, that is, a plurality of sheets are printed at short intervals, so that the temperature of the fixing device 100 becomes a predetermined value or more. When the diameter of the pressure roller 150 increases, the control device 300 selects the second mode and slows down the rotation speed of the pressure roller 150, so that the conveyance speed of the fixing device 100 can be kept within a certain range. .

  In the embodiment, the electromagnetic clutch 230 is illustrated as an example of the connection mechanism. However, the present invention is not limited to this, and the configuration of the connection mechanism may be changed as appropriate. For example, the connection mechanism may be configured to be in a connected state and a disconnected state by moving a swing gear using a solenoid.

  Moreover, you may employ | adopt a planetary gear mechanism as a connection mechanism. For example, in the above embodiment, the first planetary gear mechanism 510 in the above-described modification may be provided in place of the electromagnetic clutch 230. In this case, the control device 300 sets the connection mechanism to a connection state in which the first sun gear 511 (input unit) and the first carrier 514 (output unit) rotate together by stopping the first ring gear 512. Can do. Moreover, the control apparatus 300 can make a connection mechanism into the cutting | disconnection state which the 1st carrier 514 does not rotate by making the 1st ring gear 512 into a rotation state.

  In the embodiment, the heating unit HU includes the fixing belt 110 and the halogen lamp 120 provided on the inner side of the fixing belt 110. However, the present invention is not limited to this, and a cylindrical heating roller and A halogen lamp 120 disposed inside the heating roller may be provided.

  In this case, the first drive input gear 250 of the transmission mechanism 200 may be configured to mesh with a gear that rotates integrally with the heating roller, and the transmission mechanism 200 may be configured to transmit the driving force of the motor M to the heating roller. .

  In the embodiment, the heating unit HU is urged toward the pressure roller 150. However, the present invention is not limited to this, and the pressure roller 150 is urged toward the heating unit HU by a spring or the like. May be.

  In the embodiment, the paper passing sensor 310 is disposed at an adjacent position on the downstream side of the fixing device 100, but may be disposed at an adjacent position on the upstream side of the fixing device 100.

  In the embodiment, the paper P such as a thick paper, a postcard, and a thin paper is used as an example of the sheet. However, the present invention is not limited to this, and may be an OHP sheet, for example.

  In the above embodiment, the present invention is applied to the color printer 1. However, the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.

DESCRIPTION OF SYMBOLS 1 Color printer 22 Paper conveyance mechanism 30 Image formation part 40 Scanner unit 51 Photosensitive drum 100 Fixing device 110 Fixing belt 120 Halogen lamp 150 Pressure roller 200 Transmission mechanism 201 1st drive train 202 2nd drive train 230 Electromagnetic clutch 231 Input gear 232 Output gear 270 One-way clutch 300 Control device 310 Sensor HU Heating unit M Motor P Paper

Claims (28)

An image forming unit for forming an image on a sheet;
A fixing device for fixing the image to the sheet by conveying and heating the sheet sent from the image forming unit;
A motor for generating a driving force for driving the fixing device;
A first drive train whose speed transmission ratio is a first value; and a second drive train whose speed transmission ratio is a second value larger than the first value; and the driving force of the motor, A transmission mechanism for transmitting to the fixing device via one of the first drive train and the second drive train;
Either the first mode in which the driving force of the motor is transmitted to the fixing device via the first driving train or the second mode in which the driving force of the motor is transmitted to the fixing device via the second driving train. Control means for executing selection control for selecting one of them ,
The speed change mechanism is a planetary gear mechanism having three elements of a sun gear, a carrier, and a ring gear, and includes a first element that receives a driving force from the motor and a second element that outputs the driving force to the fixing device. A planetary gear mechanism having a third element,
The planetary gear mechanism comprises a first planetary gear mechanism provided in the first drive train and a second planetary gear mechanism provided in the second drive train,
The control means puts the third element of the first planetary gear mechanism in a stopped state in the first mode, turns the third element of the second planetary gear mechanism in a rotating state, and turns the third element of the second planetary gear mechanism in the second mode. An image forming apparatus characterized in that the third element of the first planetary gear mechanism is set in a rotating state and the third element of the second planetary gear mechanism is set in a stopped state. The image forming apparatus according to claim 1 , wherein the first element of the first planetary gear mechanism and the first element of the second planetary gear mechanism rotate coaxially and integrally. A lock mechanism for bringing the third element into a stopped state;
The said locking mechanism is provided with the engaging part engaged with the said 3rd element from radial direction, and the drive part which moves the said engaging part to radial direction, The Claim 1 or Claim 2 characterized by the above-mentioned. Image forming apparatus. 4. The device according to claim 1, wherein the first element is one of a sun gear and a ring gear, the second element is a carrier, and the third element is the other of the sun gear and the ring gear . 2. The image forming apparatus according to item 1 . An image forming unit for forming an image on a sheet;
A fixing device for fixing the image to the sheet by conveying and heating the sheet sent from the image forming unit;
A motor for generating a driving force for driving the fixing device;
A first drive train whose speed transmission ratio is a first value; and a second drive train whose speed transmission ratio is a second value larger than the first value; and the driving force of the motor, A transmission mechanism for transmitting to the fixing device via one of the first drive train and the second drive train;
Either the first mode in which the driving force of the motor is transmitted to the fixing device via the first driving train or the second mode in which the driving force of the motor is transmitted to the fixing device via the second driving train. Control means for executing selection control for selecting one of them ,
The transmission mechanism is a planetary gear mechanism having three elements of a sun gear, a carrier, and a ring gear, and includes a first element that receives a driving force from the motor, a second element that outputs the driving force to the fixing device, and A planetary gear mechanism having a third element;
The first drive train transmits the driving force of the motor to the fixing device through the second element and a first one-way clutch to which the driving force is input from the second element.
The second drive train transmits the driving force of the motor to the fixing device via the third element and a second one-way clutch to which the driving force is input from the third element.
The control means puts the third element in a stopped state in the first mode, turns the second element in a rotating state, turns the third element in a rotating state in the second mode, and moves the second element Is stopped. Wherein, when said fixing device does not convey the sheet, an image as claimed in any one of claims 5, characterized in that switching the second mode to the first mode Forming equipment. Wherein, when the rate at which the sheet is conveyed to the fixing unit is less than the first threshold from claim 1 characterized by selecting said first mode to any one of claims 6 The image forming apparatus described. Wherein, when the rate at which the sheet is conveyed to the fixing device is greater than the second threshold from claim 1 characterized by selecting said second mode to any one of claims 7 The image forming apparatus described. The sensor is disposed at a position adjacent to the fixing device in the sheet conveyance path, and includes a sensor for detecting sheet conveyance.
It said control means, the image forming apparatus according to any one of claims 1 to 8, characterized in that by utilizing the detection result of the sensor to perform the selection control. The control means includes
Having a counting means for counting the number of printed sheets in a certain period of time;
The first mode is selected when the number of printed sheets is smaller than a fifth threshold, and the second mode is selected when the number of printed sheets is equal to or larger than the fifth threshold. The image forming apparatus according to any one of 6 . An image forming unit for forming an image on a sheet;
A fixing device for fixing the image to the sheet by conveying and heating the sheet sent from the image forming unit;
A motor for generating a driving force for driving the fixing device;
A first drive train whose speed transmission ratio is a first value; and a second drive train whose speed transmission ratio is a second value larger than the first value; and the driving force of the motor, A transmission mechanism for transmitting to the fixing device via one of the first drive train and the second drive train;
Either the first mode in which the driving force of the motor is transmitted to the fixing device via the first driving train or the second mode in which the driving force of the motor is transmitted to the fixing device via the second driving train. Control means for executing selection control for selecting one of them ,
The sensor is disposed at a position adjacent to the fixing device in the sheet conveyance path, and includes a sensor for detecting sheet conveyance.
The sensor is disposed on the downstream side of the conveyance path with respect to the fixing device,
The control means executes the selection control using a detection result of the sensor, and selects the first mode when a time for the sheet to pass through the sensor is larger than a third threshold value. Image forming apparatus. Before SL control means, when the time the sheet passes through the sensor is less than the fourth threshold image forming apparatus according to claim 11, characterized by selecting said second mode. An image forming unit for forming an image on a sheet;
A fixing device for fixing the image to the sheet by conveying and heating the sheet sent from the image forming unit;
A motor for generating a driving force for driving the fixing device;
A first drive train whose speed transmission ratio is a first value; and a second drive train whose speed transmission ratio is a second value larger than the first value; and the driving force of the motor, A transmission mechanism for transmitting to the fixing device via one of the first drive train and the second drive train;
Either the first mode in which the driving force of the motor is transmitted to the fixing device via the first driving train or the second mode in which the driving force of the motor is transmitted to the fixing device via the second driving train. Control means for executing selection control for selecting one of them ,
The control means includes
Having a counting means for counting the number of rotations of the motor in a fixed time;
The first mode is selected when the rotational speed of the motor is smaller than a sixth threshold value, and the second mode is selected when the rotational speed of the motor is greater than or equal to the sixth threshold value. Forming equipment. The speed change mechanism includes an input unit to which driving force is input from the motor, and an output unit that outputs driving force to the fixing device, and a connection state in which the input unit and the output unit rotate together, A connection mechanism capable of selecting a cutting state in which the output unit does not rotate;
It said control means, the image forming apparatus according to any one of claims 13 claim 11, characterized by selecting a disconnected state and the connected state of the connecting mechanism. The image forming apparatus according to claim 14 , wherein the connection mechanism is an electromagnetic clutch. The first drive train has the connection mechanism,
The second driving train has a one-way clutch that does not transmit driving force when driving force is input from the fixing device side,
16. The image forming apparatus according to claim 14 , wherein the control unit sets the connection mechanism in a connected state in the first mode, and sets the connection mechanism in a disconnected state in the second mode. The connection mechanism includes a first connection mechanism provided in the first drive train and a second connection mechanism provided in the second drive train,
The control means sets the first connection mechanism in the connected state in the first mode, sets the second connection mechanism in a disconnected state, sets the first connection mechanism in the disconnected state in the second mode, and 16. The image forming apparatus according to claim 14, wherein the second connection mechanism is in a connected state. At least one of the first drive train and the second drive train has a one-way clutch that does not transmit a drive force when the drive force is input from the fixing device side between the connection mechanism and the fixing device. The image forming apparatus according to claim 17 , wherein the image forming apparatus is an image forming apparatus. The speed change mechanism is a planetary gear mechanism having three elements of a sun gear, a carrier, and a ring gear, and includes a first element that receives a driving force from the motor and a second element that outputs the driving force to the fixing device. A planetary gear mechanism having a third element,
Said control means, the image forming apparatus according to any one of claims 13 claim 11, characterized by selecting a stop state and the rotation state of said third element. A lock mechanism for bringing the third element into a stopped state;
The image forming apparatus according to claim 19 , wherein the lock mechanism includes an engagement portion that engages with the third element in a radial direction, and a drive portion that moves the engagement portion in the radial direction. Wherein the first element is in one of the sun gear and the ring gear, the second element is the carrier, the third element of claim 19 or claim 20, characterized in that the other of the sun gear and the ring gear Image forming apparatus. The planetary gear mechanism comprises a first planetary gear mechanism provided in the first drive train and a second planetary gear mechanism provided in the second drive train,
The control means puts the third element of the first planetary gear mechanism in a stopped state in the first mode, turns the third element of the second planetary gear mechanism in a rotating state, and turns the third element of the second planetary gear mechanism in the second mode. 22. The device according to claim 19 , wherein the third element of the first planetary gear mechanism is set in a rotating state, and the third element of the second planetary gear mechanism is set in a stopped state. The image forming apparatus described in 1. 23. The image forming apparatus according to claim 22 , wherein the first element of the first planetary gear mechanism and the first element of the second planetary gear mechanism rotate integrally on the same axis. The transmission mechanism is a planetary gear mechanism having three elements of a sun gear, a carrier, and a ring gear, and includes a first element that receives a driving force from the motor, a second element that outputs the driving force to the fixing device, and A planetary gear mechanism having a third element;
The first drive train transmits the driving force of the motor to the fixing device through the second element and a first one-way clutch to which the driving force is input from the second element.
The second drive train transmits the driving force of the motor to the fixing device via the third element and a second one-way clutch to which the driving force is input from the third element.
The control means puts the third element in a stopped state in the first mode, turns the second element in a rotating state, turns the third element in a rotating state in the second mode, and moves the second element the image forming apparatus according to any one of claims 13 claim 11, characterized in that the stopped state. A sheet conveying means for conveying the sheet;
25. The image forming apparatus according to claim 1, wherein a driving force of the motor is transmitted to the sheet conveying unit. The image forming unit includes a photoreceptor on which a developer image is formed,
26. The image forming apparatus according to claim 1, wherein a driving force of the motor is transmitted to the photoconductor. The fixing device includes a heating unit that is heated by a heat source, a pressure roller that sandwiches a sheet between the heating unit and rotates while being in contact with the heating unit, and one of the heating unit and the pressure roller. Biasing means for biasing toward the other,
The transmission mechanism, an image forming apparatus according to any one of claims 26 claim 1, characterized in that for transmitting the driving force of the motor to the pressure roller. 28. The image forming apparatus according to claim 27 , wherein the heating unit has an endless belt that contacts the pressure roller and rotates following the driving force of the pressure roller. .

Images