JP6477599B2 - Image forming apparatus and conveyance control method - Google Patents

Description

  The present invention relates to an image forming apparatus capable of forming an image by an electrophotographic method, and a conveyance control method executed by the image forming apparatus.

  An image forming apparatus such as a printer capable of forming an image by an electrophotographic method includes an image forming unit including a photosensitive drum, a transfer unit, and a fixing unit. A toner image is formed on the surface of the photosensitive drum. The transfer unit is provided in contact with the photosensitive drum, transfers the toner image formed on the photosensitive drum to the surface of the sheet, and conveys the sheet onto which the toner image has been transferred to the fixing unit. The fixing unit fixes the toner image transferred to the sheet to the sheet, and conveys the sheet on which the toner image is fixed to the paper discharge unit. For example, in this type of image forming apparatus, the transfer unit is driven at a higher speed than the fixing unit. In this case, the sheet is bent between the transfer portion and the fixing portion. In this type of image forming apparatus, the fixing unit is arranged above the transfer unit (see Patent Document 1). In this case, the transfer unit conveys the sheet on which the toner image is transferred upward.

JP 2001-92337 A

  When the transfer unit conveys the sheet in the upward direction, the leading edge of the sheet may fluctuate, and the conveyance posture of the sheet between the transfer unit and the fixing unit may become unstable. On the other hand, by using a part of the airflow of the blower fan used for cooling in the apparatus, it is possible to stabilize the conveying posture of the sheet conveyed from the transfer unit to the fixing unit. Specifically, a part of the air flow of the blower fan is transferred from the exhaust port to the sheet conveyance path by using a duct having an exhaust port opposed to the sheet conveyance path conveyed between the transfer unit and the fixing unit. By guiding toward the sheet, it is possible to stabilize the conveying posture of the sheet.

  In the image forming apparatus, when the temperature inside the apparatus rises, the control unit of the image forming apparatus may increase the output of the blower fan. Here, when a part of the airflow of the blower fan is used to stabilize the sheet conveying posture, when the output of the blower fan is increased, the momentum of the airflow guided by the duct becomes strong. In this case, a portion of the sheet conveyed between the transfer unit and the fixing unit where the deflection is formed may be blown by the air current, and the toner image transferred to the sheet may be disturbed.

  An object of the present invention is to provide an image forming apparatus and a conveyance control method capable of suppressing the disturbance of a toner image transferred to a sheet between a transfer unit and a fixing unit.

  An image forming apparatus according to an aspect of the present invention includes a transfer unit, a fixing unit, a conveyance control unit, a blower fan, a first duct unit, an air volume control unit, and a temperature detection unit. The transfer unit transfers the toner image formed on the image carrier to a sheet and conveys the sheet onto which the toner image has been transferred upward. The fixing unit fixes the toner image on a sheet conveyed from the transfer unit, and conveys the sheet on which the toner image is fixed to a paper discharge unit. The transport control unit drives the transfer unit at a predetermined first transport speed, and drives the fixing unit at a second transport speed that is slower than the first transport speed. The blower fan generates an airflow used for cooling in the machine. The first duct unit has an exhaust port formed at a position facing a conveyance path of a sheet conveyed from the transfer unit to the fixing unit, and a part of the airflow generated by the blower fan is Guidance from the exhaust port toward the transport path. The air volume control unit controls the air volume of the blower fan. The temperature detection unit detects an in-machine temperature. Moreover, the said air volume control part increases the air volume of the said ventilation fan, when the said in-machine temperature detected by the said temperature detection part is more than the preset threshold value. The conveyance control unit drives the fixing unit at a third conveyance speed faster than the second conveyance speed when the in-machine temperature detected by the temperature detection unit is equal to or higher than the threshold value.

  A conveyance control method according to another aspect of the present invention includes a transfer unit that transfers a toner image formed on an image carrier to a sheet and conveys the sheet onto which the toner image has been transferred; A fixing unit that fixes the toner image on the conveyed sheet and conveys the sheet on which the toner image is fixed to a paper discharge unit, a blower fan that generates an airflow used for cooling in the machine, and the transfer unit A discharge port formed at a position opposite to a conveyance path of a sheet conveyed to the fixing unit; and a part of the air flow generated by the blower fan is guided from the exhaust port toward the conveyance path. And a first duct unit, and includes the following first step, second step, and third step. In the first step, the transfer unit is driven at a predetermined first transport speed, and the fixing unit is driven at a second transport speed that is slower than the first transport speed. In the second step, the in-machine temperature is detected. In the third step, the air volume of the blower fan is increased when the in-machine temperature detected in the second step is equal to or higher than a preset threshold value. In the fourth step, when the in-machine temperature detected in the second step is equal to or higher than the threshold value, the fixing unit is driven at a third transport speed that is faster than the second transport speed.

  According to the present invention, it is possible to prevent the toner image transferred to the sheet from being disturbed between the transfer portion and the fixing portion.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration around the conveyance guide unit in the image forming apparatus according to the embodiment of the present disclosure. FIG. 3 is a diagram showing a configuration of the first duct in the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a block diagram showing a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a flowchart illustrating an example of a conveyance control process executed by the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a flowchart showing an example of the first speed change process executed by the image forming apparatus according to the embodiment of the present invention. FIG. 7 is a flowchart illustrating an example of the second speed change process executed by the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

[Configuration of Image Forming Apparatus 10]
First, the configuration of the image forming apparatus 10 according to the embodiment of the present disclosure will be described with reference to FIGS. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10. FIG. 2 is a schematic cross-sectional view showing the configuration around the transport guide portion 45. 3 is a cross-sectional view taken along the line III-III in FIG. In FIG. 2, the conveyance path R of the sheet S is indicated by a broken line.

  For convenience of explanation, the vertical direction is defined as the vertical direction D1 in the installation state in which the image forming apparatus 10 can be used (the state shown in FIG. 1). Further, the front-rear direction D2 is defined with the front surface of the image forming apparatus 10 shown in FIG. Further, the left-right direction D3 is defined with reference to the front of the image forming apparatus 10 in the installed state.

  The image forming apparatus 10 is a multifunction machine having a plurality of functions such as a facsimile function and a copy function, as well as a scan function for reading image data from a document and a print function for forming an image based on the image data. The present invention can also be applied to image forming apparatuses such as printers, facsimile machines, and copiers.

  As shown in FIGS. 1 and 4, the image forming apparatus 10 includes a housing 10A, an ADF (automatic document feeder) 1, an image reading unit 2, an image forming unit 3, a sheet supply unit 4, a control unit 5, and an operation. The display part 6 and the ventilation part 7 are provided.

  The housing 10A is formed in a substantially rectangular parallelepiped shape. As illustrated in FIG. 1, the housing 10 </ b> A accommodates the components of the image forming unit 3, the sheet supply unit 4, the control unit 5, and the blower unit 7. An image reading unit 2 is provided on the top of the housing 10A. In addition, an ADF 1 is provided above the image reading unit 2. An operation display unit 6 is provided at the front end of the image reading unit 2.

  The ADF 1 includes a document setting unit, a plurality of conveyance rollers, a document pressing unit, and a paper discharge unit, and can read a document passing through a reading position by the image reading unit 2. The image reading unit 2 includes a document table, a light source A plurality of mirrors, an optical lens, and a CCD, and can read the image data of the document placed on the document table.

  The control unit 5 includes control devices such as a CPU, ROM, RAM, and EEPROM (registered trademark) (not shown). The CPU is a processor that executes various arithmetic processes. The ROM is a non-volatile storage medium in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage medium, and the EEPROM is a nonvolatile storage medium. The RAM and the EEPROM are used as a temporary storage memory (working area) for various processes executed by the CPU. In the control unit 5, various control programs stored in advance in the ROM are executed by the CPU. As a result, the image forming apparatus 10 is comprehensively controlled by the control unit 5. The control unit 5 may be an electronic circuit such as an integrated circuit (ASIC), and is a control unit provided separately from the main control unit that controls the image forming apparatus 10 in an integrated manner. May be.

  The operation display unit 6 is a display unit such as a liquid crystal display that displays various types of information in response to control instructions from the control unit 5, and an operation key or touch panel that inputs various types of information to the control unit 5 in response to user operations. And so on.

  The image forming unit 3 can form an image by electrophotography based on the image data read by the image reading unit 2. The image forming unit 3 can also form an image based on image data input from an information processing apparatus such as an external personal computer.

  Specifically, as illustrated in FIG. 1, the image forming unit 3 includes a photosensitive drum 31, a charging device 32, an optical scanning device 33, a developing unit 34, a transfer roller 35, a cleaning device 36, and a fixing unit 37. . Further, the image forming unit 3 includes a temperature sensor 3A, a first motor 3B, and a second motor 3C, as shown in FIG.

  The photosensitive drum 31 has an electrostatic latent image formed on the surface. The photosensitive drum 31 is rotatably supported by a rotating shaft 31A shown in FIG. 2 by an internal frame of the housing 10A. The photosensitive drum 31 receives the rotational driving force transmitted from the first motor 3B (see FIG. 4) and rotates in the rotational direction D4 shown in FIGS. Here, the photosensitive drum 31 is an example of an image carrier in the present invention.

  The charging device 32 charges the surface of the photosensitive drum 31. The optical scanning device 33 forms an electrostatic latent image on the surface of the photosensitive drum 31. The developing unit 34 develops the electrostatic latent image formed on the surface of the photosensitive drum 31 using toner. The developing unit 34 is supplied with toner from a toner container 34 </ b> A (see FIG. 1) that can be attached to and detached from the image forming unit 3.

  The transfer roller 35 is disposed in contact with the photosensitive drum 31, and transfers the toner image formed on the photosensitive drum 31 to the sheet S that passes the transfer position P <b> 1 (see FIG. 1) in contact with the photosensitive drum 31. To do. The transfer roller 35 is supported so that the rotation shaft 35A shown in FIG. 2 can be rotated by the internal frame of the housing 10A. The transfer roller 35 receives the rotational driving force transmitted from the first motor 3B (see FIG. 4) and rotates in the rotational direction D5 shown in FIG. Here, the transfer roller 35 is an example of a transfer portion in the present invention.

  The cleaning device 36 cleans the surface of the photosensitive drum 31 after the transfer of the toner image by the transfer roller 35. For example, as shown in FIG. 2, the cleaning device 36 includes a blade-shaped cleaning member 362, a polishing roller 363, and a housing 361 for housing them.

  The fixing unit 37 fixes the toner image transferred to the sheet S by the transfer roller 35 on the sheet S. As shown in FIGS. 1 and 2, the fixing unit 37 is disposed above the transfer roller 35. As shown in FIG. 2, the fixing unit 37 includes a fixing belt 372, a pressure roller 373, and a housing 371 that accommodates them.

  The fixing belt 372 is provided in contact with the pressure roller 373 and heats the toner image transferred to the sheet S at a fixing position P2 (see FIG. 2) in contact with the pressure roller 373 to fix it on the sheet S. The pressure roller 373 presses the sheet S that passes through the fixing position P2. For example, in the fixing unit 37, the fixing belt 372 receives the rotational driving force transmitted from the second motor 3C (see FIG. 4) and rotates in the rotational direction D6 shown in FIG. Note that the pressure roller 373 may rotate by receiving the rotational driving force transmitted from the second motor 3C.

  The temperature sensor 3 </ b> A detects the temperature of the developing unit 34. For example, the temperature sensor 3 </ b> A is an electric circuit including a thermistor provided inside the developing unit 34. The temperature sensor 3 </ b> A outputs an electrical signal indicating the temperature of the developing unit 34 to the control unit 5. The first motor 3 </ b> B supplies a rotational driving force to the photosensitive drum 31 and the transfer roller 35. The second motor 3 </ b> C supplies a rotational driving force to the fixing belt 372.

  The sheet supply unit 4 supplies the sheet S to the image forming unit 3. Specifically, as shown in FIG. 1, the sheet supply unit 4 includes a first conveyance path 40A, a second conveyance path 40B, a paper feed cassette 41, a pickup roller 42, a feed roller 43A, a retard roller 43B, and a registration roller 44. , A conveyance guide unit 45, a discharge roller 46, a discharge tray 47, and a switching member 48.

  The first conveyance path 40 </ b> A is a movement path of the sheet S formed between the paper feed cassette 41 and the paper discharge tray 47. For example, the first transport path 40A is formed by a pair of transport guide members provided in the housing 10A. As shown in FIG. 1, the first transport path 40A is provided to extend in the up-down direction D1 on the right side in the left-right direction D3 of the housing 10A.

  As shown in FIG. 1, a registration roller 44 and a discharge roller 46 are arranged in the first transport path 40A. The registration roller 44 and the discharge roller 46 convey the sheet S along the conveyance direction D7 shown in FIG. Further, as shown in FIG. 1, a transfer roller 35 is disposed in the first transport path 40A. The transfer roller 35 is rotated by the driving force generated by the first motor 3B, and thereby conveys the sheet S to which the toner image has been transferred upward. Further, as shown in FIG. 1, a fixing unit 37 is disposed on the first conveyance path 40 </ b> A on the downstream side in the conveyance direction D <b> 7 from the transfer roller 35. The fixing belt 372 of the fixing unit 37 is rotated by the driving force generated by the second motor 3 </ b> C, and thereby conveys the sheet S on which the toner image is fixed to the paper discharge tray 47. Here, the paper discharge tray 47 is an example of a paper discharge unit in the present invention.

  Here, the transfer roller 35 is driven at a faster rotational speed than the fixing belt 372. As a result, the sheet S is bent between the transfer position P1 (see FIG. 2) and the fixing position P2 (see FIG. 2).

  The paper feed cassette 41 accommodates a sheet S on which an image is formed by the image forming unit 3. For example, the sheet cassette 41 contains sheet members such as paper, coated paper, postcards, envelopes, and OHP sheets. The sheet feeding cassette 41 has a lift plate (not shown) that lifts the uppermost sheet S to a contact position with the pickup roller 42 among the plurality of sheets S accommodated.

  The pickup roller 42 conveys the uppermost sheet S out of the plurality of sheets S accommodated in the paper feed cassette 41 from the paper feed cassette 41 to the feed roller 43A. The feed roller 43A conveys the sheet S conveyed from the paper feed cassette 41 by the pickup roller 42 to the first conveyance path 40A. The retard roller 43B separates the uppermost sheet S from the other sheets S when a plurality of sheets S are conveyed from the paper feed cassette 41 by the pickup roller 42. The registration roller 44 conveys the sheet S in the conveyance direction D7 by rotating in response to a rotational driving force transmitted from a motor (not shown).

  The conveyance guide unit 45 guides the sheet S to the fixing unit 37. As shown in FIGS. 1 and 2, the conveyance guide unit 45 is downstream in the conveyance direction D7 from the transfer position P1 in the first conveyance path 40A, and is conveyed in the conveyance direction from the fixing position P2 of the toner image by the fixing unit 37. Provided upstream of D7. As shown in FIG. 2, the conveyance guide unit 45 is opposite to the first surface (the surface on the side in contact with the photosensitive drum 31) on which the toner image on the sheet S conveyed by the transfer roller 35 is transferred. It is provided facing the second surface.

  For example, the conveyance guide unit 45 includes a first guide member 451 and a second guide member 452 as shown in FIG. As shown in FIG. 2, the first guide member 451 is disposed to be inclined to the upper right, and guides the sheet S that has passed the transfer position P1 to the downstream side in the transport direction D7. The second guide member 452 is disposed to be inclined to the upper left on the downstream side in the transport direction D7 from the first guide member 451 in the first transport path 40A, and the sheet S guided by the first guide member 451 is fixed to the fixing unit 37. To guide. For example, the first guide member 451 and the second guide member 452 are formed of resin.

  The discharge roller 46 discharges the sheet S on which the toner image is fixed by the fixing unit 37 to the discharge tray 47. The sheet S on which an image is formed by the image forming unit 3 is discharged to the paper discharge tray 47.

  The second transport path 40B is provided on the right side of the first transport path 40A in the housing 10A. The second conveyance path 40B includes a first position P3 (see FIG. 1) downstream in the conveyance direction D7 from the fixing position P2 in the first conveyance path 40A, and an upstream in the conveyance direction D7 from the registration rollers 44 in the first conveyance path 40A. The second position P4 (see FIG. 1) on the side is connected. For example, the second transport path 40B is formed by a pair of transport guide members provided in the housing 10A. A plurality of transport rollers are provided in the second transport path 40B.

  The switching member 48 opens the first transport path 40A and closes the second transport path 40B (the state shown in FIG. 1), and opens the second transport path 40B and opens the first transport path 40A. It is possible to change the posture between the second posture and the second posture. The switching member 48 is rotatably provided at the first position P3 of the first transport path 40A, and is rotated by a driving force supplied from a driving source (not shown). Thereby, the switching member 48 changes its posture between the first posture and the second posture.

  In the image forming unit 3, an image is formed on the sheet S supplied by the sheet supply unit 4 according to the following procedure. First, the surface of the photosensitive drum 31 is uniformly charged to a predetermined potential by the charging device 32. Next, the light scanning device 33 irradiates the surface of the photosensitive drum 31 with light based on the image data. Thereby, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 31. The electrostatic latent image formed on the surface of the photosensitive drum 31 is developed (visualized) as a toner image by the developing unit 34. The toner image formed on the surface of the photosensitive drum 31 is conveyed to the transfer position P1 (see FIG. 1) by the transfer roller 35 by the photosensitive drum 31 rotating in the rotation direction D4.

  On the other hand, the sheet supply unit 4 supplies the sheet S to the transfer position P1 (see FIG. 1) in parallel with the image forming operation by the image forming unit 3. Specifically, in the paper feed cassette 41, the sheet S lifted to the contact position with the pickup roller 42 by the lift plate is conveyed to the registration roller 44 by the pickup roller 42 and the feed roller 43A. The registration roller 44 conveys the sheet S to the transfer position P1 in synchronization with the timing at which the toner image is conveyed to the transfer position P1 (see FIG. 1) by the photosensitive drum 31. As a result, the toner image conveyed by the photosensitive drum 31 is transferred to the surface of the sheet S conveyed to the transfer position P1 at the conveyance timing, and an image is formed on the sheet S. The toner remaining on the surface of the photosensitive drum 31 is removed by the cleaning device 36.

  The sheet S on which the toner image is transferred at the transfer position P <b> 1 is conveyed by the rotation of the transfer roller 35 and guided to the fixing unit 37 by the conveyance guide unit 45. In the fixing unit 37, the toner image transferred to the sheet S is heated by the fixing belt 372 and the pressure roller 373. As a result, the toner image is fixed on the sheet S. The sheet S on which the toner image is fixed by the fixing unit 37 is conveyed to the discharge roller 46 by the rotation of the fixing belt 372. When an image is formed only on one side of the sheet S, the discharge roller 46 discharges the sheet S after image formation conveyed from the fixing unit 37 to the discharge tray 47.

  On the other hand, when images are formed on both surfaces of the sheet S, the sheet S after image formation conveyed from the fixing unit 37 is conveyed to the second conveyance path 40B. Specifically, the control unit 5 uses the discharge roller 46 and the switching member 48 to send the sheet S having an image formed on the surface thereof to the second conveyance path 40B. The sheet S sent to the second transport path 40B is sent from the second position P4 to the first transport path 40A in a state where the front surface and the back surface are reversed. Thereafter, the sheet S sent from the second position P4 to the first conveyance path 40A is formed on the back surface at the transfer position P1 and the fixing position P2, and is discharged to the paper discharge tray 47.

  The air blower 7 cools the inside of the housing 10A. Specifically, as shown in FIG. 1, the blower unit 7 includes a blower fan 71, a first duct 72, a second duct 73, a third duct 74, and a fourth duct 75.

  The blower fan 71 generates an airflow used for cooling in the machine. As shown in FIG. 1, the blower fan 71 is provided in an opening 10B formed on the left side surface of the housing 10A. For example, the opening 10B is formed in a substantially square shape. The blower fan 71 is rotationally driven by electric power supplied from a power source (not shown). Thereby, air is taken in from the outside of the housing 10A, and an air flow along the air blowing direction D8 shown in FIG. 1 is generated inside the housing 10A. Note that the blower fan 71 may be a blower that blows air on a principle different from the blown air by rotation of the fan.

  The first duct 72 guides the airflow generated by the blower fan 71 to the inside of the housing 10A. Specifically, as shown in FIG. 3, the first duct 72 has a left end connected to the opening 10 </ b> B, and has a width extending in the front-rear direction D <b> 2 from the left end toward the right. As shown in FIG. 1, the first duct 72 branches up and down at the right end. The lower side of the right end portion of the first duct 72 is connected to the second duct 73. The upper side of the right end portion of the first duct 72 is connected to the third duct 74.

  The second duct 73 guides part of the airflow generated by the blower fan 71 to the toner container 34 </ b> A and the developing unit 34. Specifically, as shown in FIG. 1, the second duct 73 tilts downward from the right end portion of the first duct 72 in the right direction, and then, in the left-right direction below the toner container 34 </ b> A and the developing unit 34. It extends along D3. For example, a part of the second duct 73 positioned below the toner container 34A is formed by a lower surface of the toner container 34A and a guide member provided on the lower surface of the toner container 34A. A part of the second duct 73 located below the developing unit 34 is formed by a lower surface of the developing unit 34 and a guide member provided on the lower surface of the developing unit 34. A part of the airflow generated by the blower fan 71 is guided to the lower surface of the toner container 34 </ b> A and the lower surface of the developing unit 34 by the second duct 73. As a result, the toner stored in the toner container 34A and the toner stored in the developing unit 34 are cooled. The airflow guided by the second duct 73 is discharged to the outside of the housing 10A from an exhaust port (not shown) provided on the back surface of the housing 10A. Here, the second duct 73 is an example of the second duct portion in the present invention.

  A part of the airflow generated by the blower fan 71 may be guided to other components of the image forming apparatus 10 such as a control board (not shown) provided with the control unit 5 by a duct (not shown).

  By the way, when the transfer roller 35 conveys the sheet S upward, the leading edge of the sheet S fluctuates, and the conveying posture of the sheet S between the transfer position P1 (see FIG. 2) and the fixing position P2 (see FIG. 2). May become unstable. On the other hand, by using a part of the airflow generated by the blower fan 71, it is possible to stabilize the conveying posture of the sheet S conveyed from the transfer position P1 to the fixing position P2. Specifically, by using a duct having an exhaust port facing the conveyance path R of the sheet S conveyed from the transfer position P1 to the fixing position P2, a part of the airflow generated by the blower fan 71 is reduced to the exhaust port. By guiding toward the transport path R of the sheet S, the transport posture of the sheet S can be stabilized.

  In the image forming apparatus 10, the control unit 5 increases the output of the blower fan 71 when the in-machine temperature increases. Here, when a part of the airflow of the blower fan 71 is used to stabilize the conveying posture of the sheet S, when the output of the blower fan 71 is increased, the momentum of the airflow guided by the duct becomes strong. In this case, the portion of the sheet S that is conveyed between the transfer position P1 and the fixing position P2 is bent, and the toner image transferred to the sheet may be disturbed by the airflow. Further, when the sheet S conveyed by the transfer roller 35 is guided to the fixing unit 37 by the conveyance guide unit 45 as in the image forming apparatus 10, if the momentum of the air flow guided by the duct becomes strong, the sheet S The portion where the deflection is formed and the conveyance guide portion 45 may come into strong contact with each other. In this case, frictional charging may occur between the sheet S and the conveyance guide unit 45, and the toner on the sheet S may be scattered from the sheet S.

  In contrast, in the image forming apparatus 10 according to the embodiment of the present invention, as described below, the toner image transferred to the sheet S is disturbed between the transfer position P1 and the fixing position P2. It is possible to suppress.

  The third duct 74 guides part of the airflow generated by the blower fan 71 to the fourth duct 75. Specifically, as shown in FIG. 1, the third duct 74 is inclined upward from the right end portion of the first duct 72 in the right direction, and then the optical scanning device 33, the charging device 32, and the cleaning device 36. Is extended along the left-right direction D3.

  The fourth duct 75 is connected to the right end portion of the third duct 74. As shown in FIG. 2, the fourth duct 75 is opposed to the conveyance guide portion 45 across the conveyance path R (see FIG. 2) of the sheet S conveyed from the transfer position P1 to the fixing position P2. It has an exhaust port 75A formed in (see FIG. 2). The fourth duct 75 guides part of the airflow generated by the blower fan 71 from the exhaust port 75A toward the transport path R. The 4th duct 75 is an example of the 1st duct part in this invention here.

  For example, as shown in FIG. 2, the fourth duct 75 includes an upper guide portion 371 </ b> A provided on the lower surface of the housing 371 of the fixing portion 37 and a lower guide portion provided on the upper surface of the housing 361 of the cleaning device 36. 361A. For example, the upper guide portion 371A is formed integrally with the housing 371, and the lower guide portion 361A is formed integrally with the housing 361. The upper guide portion 371A may be a separate member from the housing 371, and the lower guide portion 361A may be a separate member from the housing 361.

  A part of the airflow generated by the blower fan 71 is sent out from the exhaust port 75A to the surface of the sheet S (the transfer surface of the toner image) conveyed along the conveyance path R by the fourth duct 75. Thereby, the conveyance posture of the sheet S conveyed between the transfer position P1 (see FIG. 2) and the fixing position P2 is stabilized. By stabilizing the conveyance posture of the sheet S, occurrence of a paper jam of the sheet S between the transfer position P1 and the fixing position P2 is suppressed. Further, contact between the surface of the sheet S and the housing 361 of the cleaning device 36 is prevented.

  The first duct portion in the present invention has an exhaust port provided to face the back surface (contact surface with the transfer roller 35) of the sheet S conveyed from the transfer position P1 (see FIG. 2) to the fixing position P2. You may have. For example, the exhaust port in the present invention may be provided on the surface of the first guide member 451 of the transport guide portion 45 that faces the transport path R. In this case, the blower fan 71 and the opening 10B may be provided on the back surface or the right side surface of the housing 10A.

  The ROM of the control unit 5 stores in advance a conveyance control program for causing the CPU to execute a conveyance control process (see the flowchart of FIG. 5) described later. The conveyance control program is recorded on a computer-readable recording medium such as a CD, a DVD, or a flash memory, and is read from the recording medium and installed in the EEPROM of the control unit 5. Also good.

  And the control part 5 contains the temperature detection part 51, the air volume control part 52, and the conveyance control part 53, as FIG. 4 shows. Specifically, the control unit 5 executes the transport control program stored in the ROM using the CPU. As a result, the control unit 5 functions as the temperature detection unit 51, the air volume control unit 52, and the conveyance control unit 53.

  The temperature detector 51 detects the in-machine temperature. For example, the temperature detection unit 51 detects the internal temperature when the image forming apparatus 10 performs a printing process. For example, the temperature detection unit 51 detects the temperature of the developing unit 34 based on the electrical signal output from the temperature sensor 3A.

  Note that the temperature detection unit 51 may detect the temperature at a location different from the development unit 34. For example, the temperature detection unit 51 may detect the temperature of the control board. In this case, the temperature sensor 3A may be provided on the control board.

  The air volume control unit 52 controls the air volume of the blower fan 71. For example, the air volume control unit 52 controls the air volume of the blower fan 71 when the printing process is executed. Specifically, the air volume control unit 52 increases the air volume of the blower fan 71 when the in-machine temperature detected by the temperature detection unit 51 is equal to or higher than a preset threshold value.

  For example, the air volume control unit 52 controls the output of the power supply that supplies power to the blower fan 71 while the in-machine temperature detected by the temperature detection unit 51 is less than the threshold value, and sets the blower fan 71 in advance. Rotate at a predetermined first rotation speed. In addition, the air volume control unit 52 controls the output of the power supply that supplies power to the blower fan 71 when the in-machine temperature detected by the temperature detection unit 51 is equal to or higher than the threshold value, thereby controlling the blower fan 71. It is rotated at a second rotation speed that is faster than the first rotation speed. For example, the air volume control unit 52 rotates the blower fan 71 at the second rotation speed until the in-machine temperature detected by the temperature detection unit 51 becomes less than the threshold value.

  The air volume control unit 52 may change the air volume of the airflow generated by the blower fan 71 continuously or stepwise in accordance with the change in temperature detected by the temperature detection unit 51.

  The conveyance control unit 53 controls driving of the transfer roller 35 and the fixing unit 37. For example, the conveyance control unit 53 controls driving of the transfer roller 35 and the fixing unit 37 when the printing process is executed. Specifically, the transport control unit 53 drives the transfer roller 35 at a predetermined first transport speed, and drives the fixing unit 37 at a second transport speed that is slower than the first transport speed. Further, when the in-machine temperature detected by the temperature detection unit 51 is equal to or higher than the threshold value, the conveyance control unit 53 drives the fixing unit 37 at a third conveyance speed that is faster than the second conveyance speed.

  For example, the second transport speed is 99.93% of the first transport speed. When the fixing unit 37 is driven at the second transport speed that is slower than the first transport speed, the sheet S passing through the transfer position P1 (see FIG. 2) is pulled toward the fixing unit 37, and the toner image is transferred. Occurrence of defects that shift the position is avoided. The third transport speed is slower than the first transport speed. The third transport speed may be faster than the first transport speed. Even if the third conveyance speed is higher than the first conveyance speed, the sheet S is in a section from the transfer position P1 to the fixing position P2 while the fixing unit 37 is driven at the second conveyance speed. Therefore, the above-mentioned problem does not occur immediately.

  For example, the conveyance control unit 53 controls the driving of the first motor 3B to drive the transfer roller 35 at the first conveyance speed. Further, the conveyance control unit 53 controls the driving of the second motor 3 </ b> C so that the fixing belt 372 of the fixing unit 37 is moved to the second level while the in-machine temperature detected by the temperature detection unit 51 is less than the threshold value. Drive at the conveyance speed. Further, the conveyance control unit 53 controls the driving of the second motor 3C when the in-machine temperature detected by the temperature detection unit 51 is equal to or higher than the threshold value, so that the fixing belt 372 of the fixing unit 37 is moved to the first level. Drive at 3 transport speeds. For example, the conveyance control unit 53 drives the fixing belt 372 of the fixing unit 37 at the third conveyance speed until the in-machine temperature detected by the temperature detection unit 51 becomes less than the threshold value.

  In addition, the conveyance control part 53 respond | corresponds to the fluctuation | variation of the airflow of the airflow by the airflow control part 52, when the airflow control part 52 changes the airflow of the airflow which generate | occur | produces with the ventilation fan 71 continuously or in steps. The conveyance speed of the sheet S by the fixing unit 37 may be changed continuously or stepwise.

  Here, the conveyance control unit 53 moves the fixing unit 37 when the internal temperature detected by the temperature detection unit 51 is equal to or higher than the threshold value and the thickness of the sheet S is equal to or lower than a predetermined reference value. Drive at the third transport speed.

  For example, in the image forming apparatus 10, any one of a normal mode in which printing is performed using a sheet having a thickness of the sheet S exceeding the reference value and a thin paper mode in which printing is performed using a sheet having a thickness of the sheet S equal to or less than the reference value. The printing process is executed in the printing mode. For example, the control unit 5 sets the print mode to the normal mode or the thin paper mode in accordance with a user operation on the operation display unit 6. The conveyance control unit 53 determines that the thickness of the sheet S is equal to or less than the reference value when the printing mode is set to the thin paper mode.

  Note that an optical sensor or an ultrasonic sensor capable of detecting the thickness of the sheet S conveyed on the first conveyance path 40A is provided upstream of the registration rollers 44 in the first conveyance path 40A in the conveyance direction D7. Good. In this case, the conveyance control unit 53 may determine whether the thickness of the sheet S is equal to or less than the reference value based on an electrical signal output from the optical sensor or the ultrasonic sensor.

[Transport control processing]
Hereinafter, an example of the procedure of the conveyance control method according to the present invention will be described together with an example of the procedure of the conveyance control process executed by the control unit 5 in the image forming apparatus 10 with reference to FIG. Here, steps S11, S12,... Represent the numbers of processing procedures (steps) executed by the control unit 5. The control unit 5 executes the transport control process when the printing process is executed.

<Step S11>
First, in step S11, the control unit 5 drives the transfer roller 35 at the first transport speed, and drives the fixing unit 37 at the second transport speed. For example, the control unit 5 controls the driving of the first motor 3B to drive the transfer roller 35 at the first transport speed. The control unit 5 controls the driving of the second motor 3C to drive the fixing belt 372 of the fixing unit 37 at the second transport speed. Here, the process of step S <b> 11 is an example of a first step in the present invention, and is executed by the transport control unit 53 of the control unit 5.

<Step S12>
In step S <b> 12, the control unit 5 rotates the blower fan 71. For example, the control unit 5 controls the output of the power supply that supplies power to the blower fan 71 to rotate the blower fan 71 at the first rotation speed. Here, the process of step S <b> 12 is executed by the air volume control unit 52 of the control unit 5.

<Step S13>
In step S13, the control unit 5 determines whether or not the printing process has been completed.

  Here, when the control unit 5 determines that the printing process is completed (Yes in S13), the control unit 5 ends the conveyance control process. If the printing process has not been completed (No in S13), the control unit 5 shifts the process to step S14.

<Step S14>
In step S14, the control unit 5 detects the in-machine temperature. For example, the control unit 5 detects the temperature of the developing unit 34 based on the electrical signal output from the temperature sensor 3A. Here, the process of step S14 is an example of the second step in the present invention, and is executed by the temperature detection unit 51 of the control unit 5.

<Step S15>
In step S15, the control unit 5 determines whether or not the in-machine temperature detected in step S14 is equal to or higher than the threshold value.

  Here, if the control part 5 judges that the said in-machine temperature detected by step S14 is more than the said threshold value (Yes side of S15), it will transfer a process to step S16. If the in-machine temperature detected in step S14 is less than the threshold value (No side in S15), the control unit 5 shifts the process to step S13, and the end of the printing process or the in-machine temperature is equal to the above-described temperature. Wait for the threshold to be exceeded.

<Step S16>
In step S16, the control part 5 performs the 1st speed change process demonstrated below.

[First speed change process]
Here, an example of the procedure of the first speed change process executed in step S16 of the transport control process will be described with reference to FIG. Note that the processing after step S17 of the transport control processing will be described after the description of the first speed change processing is completed.

<Step S31>
First, in step S <b> 31, the control unit 5 increases the air volume of the blower fan 71. For example, the control unit 5 controls the output of the power supply that supplies power to the blower fan 71 to change the rotational speed of the blower fan 71 from the first rotational speed to the second rotational speed. Here, the process of step S31 is an example of a third step in the present invention, and is executed by the air volume control unit 52 of the control unit 5.

<Step S32>
In step S32, the controller 5 determines whether or not the thickness of the sheet S is equal to or less than the reference value. For example, the control unit 5 determines that the thickness of the sheet S is equal to or less than the reference value when the print mode is set to the thin paper mode. Here, the process of step S <b> 32 is executed by the transport control unit 53 of the control unit 5.

  Here, when the control unit 5 determines that the thickness of the sheet S is equal to or less than the reference value (Yes side of S32), the control unit 5 shifts the process to step S33. Further, if the thickness of the sheet S exceeds the reference value (No side of S32), the control unit 5 ends the first speed changing process.

<Step S33>
In step S33, the control unit 5 drives the fixing unit 37 at the third transport speed that is faster than the second transport speed. For example, the control unit 5 controls the driving of the second motor 3C to drive the fixing belt 372 of the fixing unit 37 at the third transport speed. Here, the process of step S33 is an example of the fourth step in the present invention, and is executed by the transport control unit 53 of the control unit 5.

  Above, description of the said 1st speed change process is complete | finished, and description of the process after step S17 of the said conveyance control process is restarted.

<Step S17>
In step S <b> 17, the control unit 5 determines whether or not the printing process has been completed, similarly to step S <b> 13.

  Here, when the control unit 5 determines that the printing process has been completed (Yes in S17), the control unit 5 ends the conveyance control process. If the printing process has not been completed (No in S17), the control unit 5 shifts the process to step S18.

<Step S18>
In step S18, the control part 5 detects the said in-machine temperature similarly to step S14. Here, the process of step S <b> 18 is executed by the temperature detection unit 51 of the control unit 5.

<Step S19>
In step S19, the control unit 5 determines whether or not the in-machine temperature detected in step S18 is less than the threshold value.

  Here, if the control part 5 judges that the said in-machine temperature detected by step S18 is less than the said threshold value (Yes side of S19), it will transfer a process to step S20. If the in-machine temperature detected in step S18 is equal to or higher than the threshold value (No side in S19), the control unit 5 shifts the process to step S17, and the end of the printing process or the in-machine temperature is the above-described temperature. Wait for it to fall below the threshold.

<Step S20>
In step S20, the control part 5 performs the 2nd speed change process demonstrated below. And the control part 5 makes a process transfer to step S13 after completion | finish of the said 2nd speed change process.

[Second speed change process]
Here, an example of the procedure of the second speed change process executed in step S20 of the transport control process will be described with reference to FIG.

<Step S41>
First, in step S <b> 41, the control unit 5 decreases the air volume of the blower fan 71. For example, the control unit 5 controls the output of the power supply that supplies power to the blower fan 71 to change the rotational speed of the blower fan 71 from the second rotational speed to the first rotational speed. Here, the process of step S <b> 41 is executed by the air volume control unit 52 of the control unit 5.

<Step S42>
In step S42, the control unit 5 determines whether or not the thickness of the sheet S is equal to or less than the reference value, as in step S32 of the first speed change process. Here, the process of step S <b> 42 is executed by the transport control unit 53 of the control unit 5.

  Here, if the control part 5 judges that the thickness of the sheet | seat S is below the said reference value (Yes side of S42), it will transfer a process to step S43. If the thickness of the sheet S exceeds the reference value (No side of S42), the control unit 5 ends the second speed change process.

<Step S43>
In step S43, the control unit 5 drives the fixing unit 37 at the second transport speed. For example, the control unit 5 controls the driving of the second motor 3C to drive the fixing belt 372 of the fixing unit 37 at the second transport speed. Here, the process of step S <b> 43 is executed by the conveyance control unit 53 of the control unit 5.

  As described above, in the conveyance control process, when the in-machine temperature is equal to or higher than the threshold value, the amount of airflow generated by the blower fan 71 is increased and the conveyance speed of the sheet S by the fixing unit 37 is increased. . As a result, the sheet S is pulled toward the fixing unit 37, so that the flexure formed on the sheet S is reduced. Accordingly, it is possible to suppress the toner image transferred to the sheet S from being disturbed by a portion where the deflection of the sheet S is formed by the airflow. Further, contact between the sheet S and the conveyance guide unit 45 is avoided, and generation of frictional charging between the sheet S and the conveyance guide unit 45 is avoided. Therefore, the toner on the sheet S is prevented from scattering from the sheet S.

1 ADF
2 Image reading unit 3 Image forming unit 4 Sheet supply unit 5 Control unit 6 Operation display unit 7 Blower unit 10 Image forming device 31 Photosensitive drum 32 Charging device 33 Optical scanning device 34 Development unit 35 Transfer roller 36 Cleaning device 37 Fixing unit 45 Conveyance guide section 51 Temperature detection section 52 Air volume control section 53 Conveyance control section 71 Blower fan 75 Fourth duct

Claims (5)

A transfer unit that transfers the toner image formed on the image carrier to a sheet and conveys the sheet onto which the toner image has been transferred;
A fixing unit that fixes the toner image on a sheet conveyed from the transfer unit and conveys the sheet on which the toner image has been fixed to a paper discharge unit;
A transfer controller that drives the transfer unit at a predetermined first transfer speed and drives the fixing unit at a second transfer speed that is slower than the first transfer speed;
A blower fan that generates an airflow used for cooling in the machine;
An exhaust port formed at a position opposite to a conveyance path of a sheet conveyed from the transfer unit to the fixing unit, and a part of the airflow generated by the blower fan is transferred from the exhaust port to the conveyance path; A first duct portion to be directed toward,
An air volume control unit for controlling the air volume of the blower fan;
A temperature detector for detecting the temperature inside the machine;
With
The air volume control unit increases the air volume of the blower fan when the in-machine temperature detected by the temperature detection unit is equal to or higher than a preset threshold value,
The conveyance control unit drives the fixing unit at a third conveyance speed faster than the second conveyance speed when the in-machine temperature detected by the temperature detection unit is equal to or higher than the threshold. Conveyance that is provided opposite to the second surface opposite to the first surface on which the toner image is transferred on the sheet conveyed by the transfer unit and guides the sheet conveyed by the transfer unit to the fixing unit. A guide portion;
The image forming apparatus according to claim 1, wherein the exhaust port is provided to face the conveyance guide unit with the conveyance path interposed therebetween. A developing unit for developing the electrostatic latent image formed on the surface of the image carrier;
A second duct portion for guiding a part of the air flow generated by the blower fan to the developing portion;
The image forming apparatus according to claim 1, wherein the temperature detection unit detects a temperature of the developing unit.   The conveyance control unit moves the fixing unit to the third conveyance speed when the in-machine temperature detected by the temperature detection unit is equal to or higher than the threshold value and the thickness of the sheet is equal to or less than a predetermined reference value. The image forming apparatus according to claim 1, wherein the image forming apparatus is driven by a motor. A toner image formed on the image carrier is transferred to a sheet, a transfer unit that conveys the sheet on which the toner image is transferred upward, and the toner image is fixed to the sheet conveyed from the transfer unit; A fixing unit that conveys the sheet on which the toner image has been fixed to the paper discharge unit, a blower fan that generates an airflow used for cooling in the apparatus, and a conveyance path of the sheet that is conveyed from the transfer unit to the fixing unit. A first duct portion that has an exhaust port formed at an opposing position and guides a part of the airflow generated by the blower fan from the exhaust port toward the transport path. A transport control method comprising:
A first step of driving the transfer unit at a predetermined first transport speed and driving the fixing unit at a second transport speed that is slower than the first transport speed;
A second step of detecting the in-machine temperature;
A third step of increasing the air volume of the blower fan when the in-machine temperature detected by the second step is equal to or higher than a preset threshold;
A fourth step of driving the fixing unit at a third transport speed faster than the second transport speed when the in-machine temperature detected by the second step is equal to or higher than the threshold;
A conveyance control method including: