JP2012133084A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a recording medium from being pulled farther than necessary to a sheet discharging section side and from being bent more sharply than necessary on a conveyance path between a fixing section and a sheet discharging section when the recording medium is held and conveyed by both of a nip portion of a roller pair of the sheet discharging section and a nip portion of a roller pair of the fixing section.SOLUTION: A pressure roller 3 of a fixing section 13 is provided with a first thermistor 7 for detecting temperature of a core bar. A controller 16 has registered a rotational speed correction table beforehand. In a case where the temperature of the core bar of the pressure roller 3 detected by the first thermistor 7 is not within a specified temperature range during a printing of a paper sheet P, the controller 16 reads out a correction value corresponding to the temperature of the core bar from the rotational speed correction table and performs change control of a rotational speed so as to increase a predetermined rotational speed of a drive motor 15 of a sheet discharging roller pair 14 by a percentage based on the correction value, or decrease the predetermined rotational speed thereof by the percentage based thereon.

Description

  The present invention relates to an image forming apparatus including a printer, a facsimile machine, a copying machine, and a complex machine thereof.

2. Description of the Related Art Image forming apparatuses including printers, facsimiles, copiers, and complex machines thereof include a fixing device that fixes a toner image formed on an image carrier onto a recording medium.
The fixing device as described above includes a roller fixing method and a belt fixing method.

  A roller fixing type fixing device includes a heating roller maintained at a predetermined temperature and a pressure roller pressed against the heating roller, and a recording medium is formed by a nip formed by the pressure roller and the heating roller. (Paper, transfer material, etc.) is nipped and carried, and the unfixed toner image on the recording medium is pressed by the pressure roller and the heat of the heating roller is applied to the toner image on the recording medium. This is a fixing device.

  The fixing device of the belt fixing system includes a fixing roller disposed opposite to the pressure roller, and an endless fixing belt stretched between the fixing roller and the heating roller. The nip formed by the pressure contact is held while the recording medium is nipped and conveyed. The unfixed toner image on the recording medium is pressed by the pressure roller and the heat of the heating roller via the fixing belt. Is applied to the recording medium, and the toner image is fixed on the recording medium.

In the above-described roller fixing type or belt fixing type fixing device, there is a case where the recording medium nipping and conveying speed fluctuates in the fixing device depending on the temperature state of components such as the fixing roller and the heating roller.
For example, in the case of the belt fixing type fixing device, when the fixing roller is driven to rotate, the paper conveyance speed varies due to slip between the fixing roller and the fixing belt. The recording medium is nipped and conveyed by the nip portion while the belt is driven to rotate.

  However, while the recording medium is nipped and conveyed by the nip portion, if the heat of the fixing belt is transferred to the pressure roller and the temperature of the pressure roller rises, the pressure roller formed of the rubber material etc. The outer diameter of the roller increases and the outer diameter of the roller increases, and even if the pressure roller is driven at a constant rotational speed, the outer diameter increases as the pressure roller becomes hot and the peripheral speed (rotation) of the pressure roller increases. Speed).

  As a result, the nipping / conveying speed of the recording medium in the fixing device becomes faster than the conveying speed of the recording medium from the image transfer unit upstream of the fixing device (before the fixing device in the recording medium conveying direction). However, the recording medium is pulled, and there is a problem that the image is shifted due to the transfer in the image transfer portion.

On the other hand, when the recording medium being nipped and conveyed is deprived of heat by the nip portion and the temperature of the pressure roller is lowered, the outer diameter of the pressure roller may be reduced. In this case, the nipping and conveying speed of the recording medium is It becomes slower than the conveyance speed of the recording medium from the transfer section, causing an unnecessary loop (sag) on the recording medium, making the incident angle of the recording medium to the fixing device unstable, and causing an offset in the fixing device. There was a problem to do.
Such pressure roller diameter variation due to pressure roller temperature variation is a phenomenon that appears prominently in fixing devices of recent high-speed full-color image forming apparatuses.

In particular, a belt fixing type fixing device suitable for use in a color image forming apparatus that performs high-speed processing uses a large-diameter pressure roller with a thick rubber layer. Become prominent.
The change in the nipping / conveying speed in the fixing device is the same in the roller fixing type fixing device, and there is the same problem as described above.

  Therefore, conventionally, an endless fixing belt stretched between a heating roller containing a heater lamp and a fixing roller, a pressure roller arranged in pressure contact with the fixing belt, and the temperature of the fixing belt are detected. And a driving means having a motor for rotationally driving the pressure roller, and a controller for controlling the rotation of the driving means, and the number of rotations of the driving means is controlled based on the detected temperature of the thermistor, and the heating roller There is an image forming apparatus (see, for example, Patent Document 1) that sets the pressure roller to a predetermined peripheral speed regardless of the temperature.

  Also provided is a loop amount detecting means for detecting the amount of loop formed by the transfer material between the image transfer unit and the fixing device in a state where the transfer material (recording medium) is simultaneously held by the image transfer unit and the fixing device. In order to switch and control the nipping and conveying speed of the transfer member at the nip portion of the fixing device according to the detection result of the loop amount detecting means, the rotation speed of the fixing motor that rotates the pressure roller is switched and the pressure roller An image forming apparatus in which a thermistor is arranged on the surface and the nipping and conveying speed of the fixing device is set in consideration of the thermal expansion of the pressure roller according to the temperature of the pressure roller surface detected by the thermistor (for example, Patent Document 2) See).

  However, in the conventional image forming apparatus described above, it is not possible to adjust the conveyance speed of the recording medium by the paper discharge unit downstream of the fixing apparatus in accordance with the change in the nipping conveyance speed of the recording medium in the fixing apparatus.

  In the paper discharge unit downstream of the fixing device, the conveyance of the recording medium is controlled at a predetermined constant speed, so that the recording medium is nipped and conveyed by both the roller pair of the paper discharge unit and the nip portion of the roller pair of the fixing device. When the nipping conveyance speed of the recording medium in the fixing device becomes slower than the conveyance speed of the paper discharge unit in the fixed state, the paper discharge unit pulls the recording medium. There has been a problem that the toner image is rubbed and the image is disturbed and stained.

  In addition, when the nipping conveyance speed of the recording medium in the fixing device becomes faster than the conveyance speed of the paper discharge unit, a loop of the recording medium becomes large in the conveyance path between the paper discharge unit and the fixing device, and the recording medium is bellows. And the image surface may be rubbed against the fixing belt (or fixing roller) or the separation plate (separating claw) of the pressure roller to disturb the image or cause jamming (JAM, paper jam). There was a problem.

  In order to eliminate such image defects and conveyance problems between the paper discharge unit and the fixing device, fixing is performed so that the recording medium is conveyed in an appropriate loop along the conveyance path between the paper discharge unit and the fixing device. It is necessary to adjust the nipping / conveying speed of the recording medium in the paper discharge unit in accordance with the change in the nipping / conveying speed of the recording medium in the apparatus, and to maintain the difference between the nipping and conveying speeds in an appropriate state.

  The present invention has been made in view of the above points. The recording medium is sandwiched and conveyed by a roller for fixing a toner image on the recording medium, and the recording is performed by a roller for discharging the recording medium after the toner image is fixed. The object is to maintain the difference from the medium nipping and conveying speed in an appropriate state.

  In order to achieve the above-mentioned object, the present invention is arranged in such a manner that a heating roller having a heat source, a fixing roller having an elastic layer on the outer periphery of the core metal, and a pressing roller are arranged in pressure contact with the outer surface of the core metal. A pressure roller provided with no heat source therein, an endless fixing belt stretched between the heating roller and the fixing roller, and a pressure roller driving means for driving the pressure roller to rotate. A fixing unit provided; a discharging unit provided with a discharging roller pair downstream of the fixing unit in the recording medium conveyance direction; and a discharging roller pair driving unit that rotationally drives the discharging roller pair. And a pressure roller drive control means for controlling the rotation speed of the pressure roller drive means, and a paper discharge roller pair drive control means for controlling the rotation speed of the paper discharge roller pair drive means. The pressure roller between the fixing roller and the pressure roller A toner image is heated and fixed on a recording medium through a recording medium carrying an unfixed toner image in a nip formed by the fixing belt formed by the pressure roller and the pressure roller. In the image forming apparatus that sandwiches and conveys the paper by the pair of paper discharge rollers, a core metal temperature detecting unit that detects the temperature of the core of the pressure roller is provided, and the discharge roller pair drive control unit includes the above-mentioned Provided is an image forming apparatus provided with a correcting means for correcting the number of rotations of the discharge roller pair driving means based on the detected temperature detected by the core metal temperature detecting means.

  Also, a heating roller having a heat source, a fixing roller having an elastic layer on the outer periphery of the cored bar, and a pressure roller are disposed in pressure contact with the outer surface of the cored bar, and an elastic layer is not provided inside. A fixing unit comprising: a pressure roller; an endless fixing belt stretched between the heating roller and the fixing roller; and a pressure roller driving unit that rotationally drives the pressure roller; and the fixing unit A discharge section provided with a discharge roller pair and a discharge roller pair driving means for rotationally driving the discharge roller pair on the downstream side in the conveyance direction of the recording medium. A pressure roller drive control means for controlling the rotation speed; and a paper discharge roller pair drive control means for controlling the rotation speed of the paper discharge roller pair drive means, the fixing roller and the pressure roller of the fixing unit. The fixing belt formed by pressure contact with A toner image is heated and fixed on the recording medium through a recording medium carrying an unfixed toner image in a nip formed by the pressure roller, and is nipped and conveyed by the pair of discharging rollers of the discharging section. In the image forming apparatus for discharging the paper, a core metal temperature detecting means for detecting the temperature of the core metal of the pressure roller and a pressure roller surface temperature detecting means for detecting the surface temperature of the pressure roller are provided. Based on the detected temperature, an average temperature of the temperature detected by the core metal temperature detecting means and the temperature detected by the pressure roller surface temperature detecting means is set to the discharge roller pair drive control means. Provided is an image forming apparatus provided with a correcting means for correcting the rotational speed of the discharge roller pair driving means.

  Further, a heating roller having a heat source, a fixing roller having an elastic layer on the outer periphery of the cored bar, and a pressure roller are arranged in pressure contact with the outer surface of the cored bar, and an elastic layer is not provided inside. A fixing unit comprising: a pressure roller; an endless fixing belt stretched between the heating roller and the fixing roller; and a pressure roller driving unit that rotationally drives the pressure roller; and the fixing unit A discharge section provided with a discharge roller pair and a discharge roller pair driving means for rotationally driving the discharge roller pair on the downstream side in the conveyance direction of the recording medium. A pressure roller drive control means for controlling the rotation speed; and a paper discharge roller pair drive control means for controlling the rotation speed of the paper discharge roller pair drive means, the fixing roller and the pressure roller of the fixing unit. The fixing belt formed by pressure contact with A toner image is heated and fixed on the recording medium through a recording medium carrying an unfixed toner image in a nip formed by the pressure roller, and is nipped and conveyed by the pair of discharging rollers of the discharging section. In the image forming apparatus for discharging paper, the core roller temperature detecting means for detecting the temperature of the core metal of the pressure roller and the heating roller temperature detecting means for detecting the temperature of the heating roller are provided, and the paper discharge roller In the pair drive control means, an average temperature of the temperature detected by the core metal temperature detection means and the temperature detected by the heating roller temperature detection means is set as a detection temperature, and the discharge roller pair drive is based on the detected temperature. An image forming apparatus provided with a correcting means for correcting the number of rotations of the means is provided.

  Further, in the image forming apparatus as described above, when the detected temperature is higher than a predetermined temperature, the correction unit is configured such that the number of rotations of the discharge roller pair driving unit is set to the discharge roller pair driving unit at the predetermined temperature. When the detected temperature is lower than a predetermined temperature, the rotation speed of the paper discharge roller pair driving means is set to be higher than the rotation speed of the paper discharge roller pair driving means at the predetermined temperature. It is preferable to use an image forming apparatus as a means for correcting so as to reduce the amount.

  Further, in the image forming apparatus as described above, when the recording medium is continuously passed through the nip portion through the correction unit, the discharge roller pair driving unit increases as the number of sheets passed increases. It is preferable to provide means for correcting the rotational speed so as to approach the rotational speed of the discharge roller pair driving means at the predetermined temperature.

  Further, in the image forming apparatus as described above, when the discharge roller pair drive unit causes the correction roller to continuously rotate the pressure roller, the discharge roller is increased as the rotation drive time increases. It is preferable to provide means for correcting the rotational speed of the pair driving means so as to approach the rotational speed of the paper discharge roller pair driving means at the predetermined temperature.

  In the image forming apparatus according to the present invention, when the recording medium is nipped and conveyed by both the roller pair of the paper discharge unit and the nip portion of the roller pair of the fixing unit, the conveyance speed by the roller pair of the paper discharge unit and the roller pair of the fixing unit are Depending on the temperature change, the conveyance speed of the roller pair of the fixing unit and the conveyance speed of the roller pair of the paper discharge unit differ, and the recording medium is pulled more than necessary to the paper discharge unit side, or the recording medium is pulled between the fixing unit and the paper discharge unit. It is possible not to bend more than necessary in the transport route.

FIG. 2 is a block diagram illustrating a main configuration inside a fixing unit illustrated in FIG. 1 and a functional configuration relating to a discharge roller pair and driving thereof. FIG. 2 is a waveform diagram illustrating an example of a change in a cored bar temperature of a pressure roller and a conveyance speed difference between a paper discharge unit and a fixing unit illustrated in FIG. 1. 1 is a block diagram illustrating a functional configuration of a multifunction machine according to an embodiment of the invention. FIG.

FIG. 3 is a flowchart showing a control process for rotational driving of a pair of paper discharge rollers in the multifunction machine shown in FIG. 1. FIG. 2 is a waveform diagram illustrating an example of a change in an average value of a core metal temperature and a surface temperature of a pressure roller illustrated in FIG. 1 and a conveyance speed difference between a paper discharge unit and a fixing unit. FIG. 9 is a flowchart showing another control process for rotationally driving the paper discharge roller pair in the multifunction machine shown in FIG. 1.

FIG. 2 is a waveform diagram illustrating an example of a change in an average value of a core metal temperature of a pressure roller and a temperature of a heating roller illustrated in FIG. 1 and a conveyance speed difference between a paper discharge unit and a fixing unit. FIG. 10 is a flowchart showing another control process for rotationally driving the paper discharge roller pair in the multifunction machine shown in FIG. 1.

FIG. 6 is a diagram illustrating an example of a table in which rotation speed correction values for a pair of paper discharge rollers corresponding to the number of continuous sheets are registered. It is a figure which shows an example of the table which registered the rotation speed correction value of the discharge roller pair according to the continuous rotation time of a pressure roller.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
FIG. 3 is a block diagram showing a functional configuration of a multifunction machine according to an embodiment of the present invention.
The multifunction machine 20 is an image forming apparatus capable of digital color printing, and includes a paper feeding unit 21, a document conveying unit 22, a document reading unit 23, and an image forming unit 24.

The paper feeding unit 21 feeds the paper P to the image forming unit 24 during printing and copying.
The document conveying unit 22 conveys the document to the document reading unit 23 when reading an image.
The document reading unit 23 has a plurality of components including a light source and a mirror inside, and is a scanner mechanism unit that reads an image of a document fed from the document transport unit 22 and inputs the image data. Since each of the above components is known, a detailed description thereof will be omitted.

  The image forming unit 24 is a unit composed of a plurality of known parts. First, an intermediate transfer belt 25 is provided, and around the photosensitive drums 26Y to 26K are arranged side by side. The photoconductor drum 26Y is a photoconductor for transferring a yellow toner image, the photoconductor drum 26M is a photoconductor for transferring a magenta toner image, and the photoconductor drum 26C transfers a cyan toner image. The photosensitive drum 26K is a photosensitive member for transferring a black toner image.

  Around each of the photosensitive drums 26Y to 26K, the charging devices 27Y to 27K for charging the surface of the respective photosensitive drums, and the electrostatic latent images formed on the surfaces of the respective photosensitive drums to the respective colors. The developing devices 28Y to 28K that visualize with the toner of the toner and the toner images (visible images) on the respective photosensitive drums are transferred onto the intermediate transfer belt 25 and then remain on the photosensitive drums 26Y to 26K. Each cleaning device for collecting the toner is provided.

  Above the digital color copying machine 20, an exposure device 29, which is a unit including an exposure unit including a plurality of mirrors and lenses for forming an electrostatic latent image on the surface of the photosensitive drum, is provided. The paper (transfer paper) P transported by the transport means 31 from the tray section 30 of the paper feed section 21 is temporarily stopped at the registration roller section 32, and is re-feeded in synchronization with the image on the photosensitive drum, and transferred. The toner image on the intermediate transfer belt 25 is transferred to the paper P by the roller unit 33. The sheet P on which the toner image has been transferred is subjected to a fixing process of the toner image on the sheet P by pressurization and heating by a fixing unit (also referred to as “fixing device”) 13. 34 is discharged.

The control unit 16 is realized by a microcomputer, and controls the entire multifunction device 20 and executes control processing according to the present invention.
The multi-function device 20 has a plurality of functions including an image reading function, a printing function, a copying function, and a communication function including facsimile communication and Internet communication, and detailed operations thereof are omitted because they are well-known techniques. .

FIG. 1 is a block diagram illustrating a main configuration inside the fixing unit 13 illustrated in FIG. 3 and a functional configuration relating to driving of the discharge roller pair 14 and the discharge roller pair 14.
The fixing unit 13 is a belt fixing type fixing device, and the heating roller 1, the fixing roller 2, and the pressure roller 3 are arranged in the direction indicated by the arrow in the longitudinal direction of the casing (not shown) of the fixing unit 13. A fixing belt 4 is wound around the heating roller 1 and the fixing roller 2.

In the hollow of the heating roller 1, a heater lamp is provided as a heat source for the fixing unit 13.
The fixing roller 2 is a rubber roller having an elastic layer on the outer periphery of the cored bar.
The pressure roller 3 is a rubber roller that is disposed in pressure contact with the fixing roller 2 and includes an elastic layer on the outer periphery of the core metal and does not include a heat source therein.

  The fixing roller 2 and the pressure roller 3 are disposed so as to face each other, and the pressure roller 3 presses the fixing roller 2 toward the center of the fixing roller 2 via the fixing belt 4 (this pressure is not shown). By being performed by a pressure depressurization mechanism that drives pressure depressurization, a nip portion indicated by an arrow 14 is formed between the pressure roller 3 and the fixing belt 4.

The fixing belt 4 is an endless belt stretched between the heating roller 1 and the fixing roller 2, for example, an endless belt formed of a polyimide layer (PI layer) having a thickness of 90 μm. Is coated with an offset preventive agent such as a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) film.
The tension roller 5 is formed of a cylindrical aluminum tube and applies tension to the fixing belt 4.

  The drive motor 6 is controlled in rotational speed (rotational speed) by the control unit 16 and rotationally drives the pressure roller 3 in the arrow direction shown in FIG. That is, it functions as a pressure roller driving unit that rotationally drives the pressure roller 3. By the rotation of the pressure roller 3, the fixing roller 2 and the fixing belt 4 that are in pressure contact with the pressure roller 3 are rotated at the same speed in the directions of arrows shown in FIG.

When the fixing belt 4 is rotated by the pressure roller 3 (in the direction indicated by an arrow A in the figure), the heating roller 1 is heated by a heater that is an internal heat source, thereby contacting the heating roller 1. Is also heated all around.
The heating roller 1, the fixing roller 2, the pressure roller 3, the fixing belt 4, the drive motor 6, and the control unit 16 constitute a fixing unit.

The paper discharge roller pair 14 is a roller pair that is provided downstream in the conveyance direction of the paper P with respect to the fixing unit 13, and sandwiches and conveys the paper P conveyed from the fixing unit 13.
The drive motor 15 is controlled in rotational speed (rotational speed) by the control unit 16 and rotationally drives one roller of the paper discharge roller pair 14 in the arrow direction shown in FIG. The other roller rotates as the roller driven to rotate is rotated. The paper discharge roller pair 14 and the drive motor 15 constitute a paper discharge unit.

The control unit 16 is realized by a microcomputer including a CPU, a ROM, and a RAM. The control unit 16 controls the entire multi-function machine and controls the rotational driving of the drive motors 6 and 15. As a process according to the invention, the first thermistor 7, the rotational speed of the drive motor 15 is corrected based on the detected temperature of the second thermistor 8 or the third thermistor 9.
That is, the function of each means of the pressure roller drive control means for controlling the rotation speed of the pressure roller drive means, the paper discharge roller pair drive control means for controlling the rotation speed of the paper discharge roller pair drive means, and the correction means. Fulfill.

  The first thermistor 7 is disposed in the cored bar portion of the pressure roller 3, detects the temperature Ts (° C.) of the cored bar part of the pressure roller 3 (referred to as “core metal temperature”), and the cored bar temperature. Ts (° C.) is sent to the control unit 16. That is, it corresponds to a core temperature detecting means for detecting the temperature of the core of the pressure roller.

  The second thermistor 8 is disposed outside the pressure roller 3 and in the vicinity of the surface portion of the pressure roller 3, and detects the temperature Tm (° C.) of the surface of the pressure roller 3 (referred to as “surface temperature”). The surface temperature Tm (° C.) is sent to the control unit 16. That is, it corresponds to a pressure roller surface temperature detecting means for detecting the surface temperature of the pressure roller.

  The third thermistor 9 is disposed outside the fixing belt 4 and in the vicinity of the surface portion of the heating roller 1. The third thermistor 9 detects the temperature Tp (° C.) of the heating roller 1 via the fixing belt 4 and detects the temperature Tp (° C.). Is sent to the control unit 16. That is, it corresponds to a heating roller temperature detecting means for detecting the temperature of the heating roller.

Then, under the control of the control unit 16, when the paper P on which the toner image is formed is inserted between the fixing belt 4 and the pressure roller 3 and is nipped and conveyed by the nip unit 12, the heating from the fixing belt 4 is performed. The toner image on the paper P is fixed on the paper surface by the heat melting by the pressure and the pressure by the pressure roller 3.
Further, at the end of the fixing belt 4 in the conveying direction, the separation plate 10 separates the paper P from the fixing belt 4, or the separation plate 11 separates the paper P from the pressure roller 3.

  Thereafter, the paper P is transported to a transport roller pair 14 disposed on the downstream side in the paper transport direction, and the rotation speed of the transport roller pair 14 is controlled by the control unit 16 (this control includes correction processing according to the invention). Driven by the drive motor 15 (included), it is rotationally driven in the direction of the arrow shown in FIG. 1, and the paper P is discharged to the paper discharge portion (discharge tray) 34 of FIG.

  In this multifunction device, the detection temperature of the first thermistor 7, the detection temperature of the third thermistor 9, and the detection temperature of the thermistor (not shown) provided for the fixing belt 4 are used. The temperature of the nip portion 12 related to the fixing of the toner image is controlled. Since the control is a known technique, the description thereof is omitted.

  By this control, the difference between the nipping and conveying speed of the sheet P in the nip portion 12 and the nipping and conveying speed of the sheet P of the paper discharge roller pair 14 is maintained in an appropriate state, so that the sheet P is separated from the nip portion 12. In a state in which both of the paper discharge rollers 14 are nipped and conveyed, the nipping and conveying speed of the paper P in the nip portion 12 is slower than the conveyance speed of the paper discharge roller pair 14, and the paper P is discharged from the paper discharge roller pair 14. The toner image on the paper P is rubbed by the fixing unit 13 and the image is not disturbed or smeared.

  Further, when the paper P is nipped and conveyed by both the nip portion 12 and the discharge roller pair 14, the nipping and conveying speed of the paper P in the nip portion 12 becomes faster than the conveyance speed of the paper discharge roller pair 14. In addition, there is a problem that the loop of the paper P becomes large in the conveyance path between the fixing unit 13 and the paper discharge roller pair 14, and the image surface is rubbed against the separating plates 10 and 11 to disturb the image or cause a jam. You don't have to wake up.

Next, a description will be given of a process for controlling the rotational drive of the paper discharge roller pair in this multifunction machine.
As described above, when the sheet P is nipped and conveyed by the nip portion 12, when the heat of the fixing belt 4 is transmitted to the pressure roller 3 and the temperature of the pressure roller 3 rises, the rubber material of the roller expands and the roller When the outer diameter is increased, the peripheral speed of the pressure roller 3 is increased, and the paper P is nipped and conveyed by both the roller pair 14 of the paper discharge unit and the nip portion 12 of the fixing unit 13, the paper P is nipped by the fixing unit 13. The transport speed becomes faster than the transport speed of the pair of paper discharge rollers 14 in the paper discharge section, and the paper P may be slack more than necessary, which may cause a jam.

  Further, when the sheet P being nipped and conveyed is deprived of heat by the nip portion 12 and the temperature of the pressure roller 3 is lowered and the outer diameter of the pressure roller 3 is reduced, the nipping and conveying speed of the sheet P in the fixing unit 13 is increased. Therefore, there is a possibility that the image becomes slower than the conveyance speed of the paper discharge roller pair 14 of the paper discharge unit, and the image at the time of fixing is disturbed by the paper discharge roller pair 14 pulling the paper P.

FIG. 2 is a waveform diagram showing an example of a change in the temperature of the core of the pressure roller 3 and the difference in transport speed between the paper discharge unit and the fixing unit.
The horizontal axis of FIG. 2 shows changes in the core metal temperature (core metal temperature) Ts (° C.) of the pressure roller 3, and the vertical axis shows the conveyance speed of the paper discharge roller pair 14 in the paper discharge unit and the nip of the fixing unit 13. The change of the difference with the conveyance speed of the part 12 is shown. A waveform indicated by a thick line in the figure is a waveform showing an example of a change in the temperature of the core metal of the pressure roller 3 and a difference in conveyance speed between the paper discharge unit and the fixing unit.

  The target speed difference a (mm / s) on the vertical axis is such that the sheet P is not bent or pulled toward the sheet discharge unit in the conveyance path of the sheet P between the sheet discharge unit and the fixing unit 13. Difference between the conveyance speeds of the paper discharge unit and the fixing unit to be maintained, and an allowable error of ± 2 (mm / s) above and below the target speed difference a and an allowable speed difference centered on the target speed difference a The range is k.

In the example shown in FIG. 2, when the core metal temperature Ts of the pressure roller 3 is lower than 55 ° C., the lower limit value a-2 (mm / s) of the allowable speed difference range k of the target speed difference a (mm / s). As the temperature decreases, the difference in transport speed between the paper discharge unit and the fixing unit spreads rapidly.
Further, the core temperature Ts of the pressure roller 3 is 55 to n (an arbitrary value greater than 55) ° C. is a specified temperature range A in which the allowable speed difference range k of the target speed difference a (mm / s) is maintained. is there.

Furthermore, when the core metal temperature Ts of the pressure roller 3 exceeds n ° C., the upper limit value a + 2 (mm / s) of the allowable speed difference range k of the target speed difference a (mm / s) is exceeded, and as the temperature increases The transport speed difference between the paper part and the fixing part gradually widens.
As described above, when the core metal temperature Ts of the pressure roller 3 is lower than the specified temperature range A, the conveyance speed of the fixing unit 13 is decreased, and the conveyance speed of the paper P on the fixing unit 13 side becomes slow. When the core temperature Ts is higher than the specified temperature range A, the conveyance speed of the paper P on the fixing unit 13 side tends to increase.

Therefore, in this multi-function machine, an experiment is performed in advance, and the discharge roller pair 14 is rotated according to a change in temperature when the core metal temperature Ts of the pressure roller 3 is lower and higher than the specified temperature range A. A correction value for the rotational speed of the drive motor 15 to be driven is obtained, and a rotational speed correction table in which the change in temperature is associated with the correction value is created.
This rotation speed correction table is stored in advance in the ROM or RAM (nonvolatile memory) of the control unit 16.

  In the above-described experiment, the difference in the conveyance speed between the paper discharge unit and the fixing unit 13 for each change in temperature decrease and increase depending on whether the core temperature Ts of the pressure roller 3 is lower or higher than the specified temperature range A. Is determined to be within a permissible speed difference range k of the target speed difference a (mm / s), and the ratio% of the number of rotations to be added to or subtracted from the predetermined number of rotations of the discharge roller pair 14 is obtained. The correction value.

FIG. 4 is a flowchart showing the control process of the rotational drive of the paper discharge roller pair 14 in this multifunction machine.
In this process, the control unit 16 corrects the number of rotations of the discharge roller pair driving unit based on the detected temperature detected by the cored bar temperature detecting unit that detects the temperature of the cored bar of the pressure roller. Fulfills the function.

  When the paper P is printed, the control unit 16 detects the core temperature of the pressure roller 3 (the temperature of the core metal by the first thermistor 7 at step S1 in FIG. 4). When Ts (corresponding to temperature) is detected, it is determined in step 2 whether or not the core metal temperature Ts is within the specified temperature range A. If it is within the specified temperature range A, the drive motor for the paper discharge roller pair 14 is determined in step 4. The number of rotations of 15 is maintained and controlled at a predetermined number of rotations, and this process is terminated.

On the other hand, if it is determined in step 2 that the core metal temperature Ts is not within the specified temperature range A, the correction value corresponding to the core metal temperature Ts is read in step 3 by referring to the rotation speed correction table, and the paper discharge roller The predetermined number of rotations of the pair of drive motors 15 is controlled to be changed to a number of rotations that is increased or decreased by a percentage based on the correction value, and this process is terminated.
In the change control described above, when the core metal temperature Ts falls below the lower limit value of the specified temperature range A, the conveyance speed on the fixing unit 13 side is decreased. The conveyance speed on the part side is also reduced. When the core temperature Ts exceeds the upper limit value of the specified temperature range A, the conveyance speed on the fixing unit 13 side is increased. Also increases the transport speed.

  When the temperature of the pressure roller 3 hardly exceeds the upper limit value n of the specified temperature range A, the control unit 16 recognizes that the core metal temperature Ts is lower than the lower limit value of the specified temperature range A. The correction value corresponding to the core metal temperature Ts is read with reference to the correction table, and the rotation number is controlled to be changed from the predetermined rotation number of the drive motor 15 of the paper discharge roller pair 14 by a percentage% based on the correction value. Good.

  In this way, even in the pressure roller 3 having a thick rubber layer that does not include a heat source, the change in the conveyance speed of the fixing unit 13 is estimated based on the temperature of the core metal of the pressure roller 3, and the paper discharge roller The rotational speed of the drive motor 15 is changed and controlled so that the pair 14 is rotated at a predetermined peripheral speed.

  Accordingly, the pressure roller 3 is heated and the rubber layer is thermally expanded, or the temperature is decreased and contracted to change the roller diameter, and the peripheral speed of the pressure roller 3 is changed due to the change of the roller diameter. Even in this case, the rotation speed of the paper discharge roller pair 14 is corrected in accordance with the change, and the difference in nipping and conveying speed between the fixing unit and the paper discharge unit can be maintained constant. Therefore, it is possible to prevent the occurrence of image defects and jamming of the paper P due to cosmetics and the like.

Next, another control process for rotationally driving the paper discharge roller pair in this multifunction machine will be described.
FIG. 5 is a waveform diagram showing an example of changes in the average value of the temperature obtained by adding the core metal temperature and the surface temperature of the pressure roller 3 and the difference in transport speed between the paper discharge unit and the fixing unit.
The horizontal axis of FIG. 5 shows the change of the average value ((Tm + Ts) / 2) of the core metal temperature (core metal temperature) Ts (° C.) and the surface temperature (surface temperature) Tm (° C.) of the pressure roller 3. The vertical axis shows the change in the difference between the conveyance speed of the paper discharge roller pair 14 of the paper discharge section and the conveyance speed of the nip section 12 of the fixing section 13.
A waveform indicated by a thick line in the figure is a waveform showing an example of a change in the average value of the temperature of the cored bar and the surface temperature of the pressure roller 3 and the difference in transport speed between the paper discharge unit and the fixing unit. is there.

  The target speed difference a (mm / s) on the vertical axis is such that the sheet P is not bent or pulled toward the sheet discharge unit in the conveyance path of the sheet P between the sheet discharge unit and the fixing unit 13. Difference between the conveyance speeds of the paper discharge unit and the fixing unit 13 to be maintained, and the allowable speed is about ± 2 (mm / s) above and below the target speed difference a and the target speed difference a is the center. The difference range is k.

In the example shown in FIG. 5, when the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3 is lower than 105 ° C., the lower limit value a of the allowable speed difference range k of the target speed difference a (mm / s). -2 (mm / s), and the difference in transport speed between the paper discharge unit and the fixing unit gradually increases as the temperature decreases.
Further, when the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3 is 105 to n (an arbitrary value greater than 105) ° C., the allowable speed difference range k of the target speed difference a (mm / s) is maintained. The specified temperature range B.

Further, when the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3 exceeds n ° C., the upper limit value a + 2 (mm / s) of the allowable speed difference range k of the target speed difference a (mm / s) is set. As the temperature rises, the conveyance speed difference between the paper discharge unit and the fixing unit gradually increases.
As described above, when the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3 is lower than the specified temperature range B, the conveyance speed of the fixing unit 13 is the conveyance speed of the paper P on the fixing unit 13 side. When the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3 is higher than the specified temperature range B, the conveyance speed of the paper P on the fixing unit 13 side tends to increase.

Therefore, in this multifunction machine, an experiment is performed in advance, and the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3 is lower and higher than the specified temperature range B according to the change in temperature. A correction value for the rotation speed of the drive motor 15 that rotationally drives the paper discharge roller pair 14 is obtained, and a rotation speed correction table that associates the change in the average value with the correction value is created.
This rotation speed correction table is stored in advance in the ROM or RAM (nonvolatile memory) of the control unit 16.

  In the experiment described above, the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3 is lower and higher than the specified temperature range B. A ratio% of the number of rotations to be added to or subtracted from the predetermined number of rotations of the paper discharge roller pair 14 so that the conveyance speed difference of the fixing unit 13 is within the allowable speed difference range k of the target speed difference a (mm / s). The ratio% is determined as the correction value.

FIG. 6 is a flowchart showing another control process for rotationally driving the paper discharge roller pair 14 in this multifunction machine.
In the case of this processing, the control unit 16 detects the temperature detected by the core metal temperature detecting means that detects the temperature of the core metal of the pressure roller 3 and the pressure roller surface temperature detection that detects the surface temperature of the pressure roller 3. The average temperature of the temperatures detected by the means is used as a detected temperature, and based on the detected temperature, the function of correcting means for correcting the rotation speed of the discharge roller pair driving means is achieved.

  When printing the paper P, the control unit 16 performs the core temperature of the pressure roller 3 (the core metal inside the pressure roller 3) by the first thermistor 7 in step (indicated by “S” in FIG. 6) 11 in FIG. When the surface temperature of the pressure roller 3 (which is the temperature of the roller surface) Tm is detected by the second thermistor 8, the average value of both temperatures (core metal temperature Ts + surface temperature Tm) / 2 is obtained, and the average value is set as the detected temperature. In step 12, it is determined whether (Ts + Tm) / 2 of the detected temperature is within the specified temperature range B. If it is within the specified temperature range B, the paper is discharged in step 14. The rotational speed of the driving motor 15 of the roller pair 14 is maintained and controlled at a predetermined rotational speed, and this process is terminated.

  On the other hand, if (Ts + Tm) / 2 of the detected temperature is not within the specified temperature range B in the determination in step 12, the rotational speed correction table is referred to in step 13 and the correction value corresponding to the above (Ts + Tm) / 2 is obtained. The reading and control of changing the rotational speed from the predetermined rotational speed of the drive motor 15 of the paper discharge roller pair 14 to a rotational speed that is increased or decreased by a percentage based on the correction value is completed, and this processing is terminated.

  In the above change control, when the detected temperature (Ts + Tm) / 2 falls below the lower limit value of the specified temperature range B, the conveyance speed on the fixing unit 13 side decreases, so the number of rotations of the discharge roller pair 14 is reduced. As a result, the conveyance speed on the paper output side is also reduced. Further, when the detected temperature (Ts + Tm) / 2 exceeds the upper limit value of the specified temperature range B, the conveyance speed on the fixing unit 13 side is increased, so that the number of rotations of the discharge roller pair 14 is increased and discharged. The conveyance speed on the part side is also increased.

  When the detected temperature (Ts + Tm) / 2 hardly exceeds the upper limit value n of the specified temperature range B, the control unit 16 recognizes that the detected temperature (Ts + Tm) / 2 is lower than the lower limit value of the specified temperature range B. Then, with reference to the rotation speed correction table, the correction value corresponding to the detected temperature (Ts + Tm) / 2 is read, and the rotation speed is calculated by a percentage based on the correction value from the predetermined rotation speed of the drive motor 15 of the discharge roller pair 14. It is better to control the change with less.

In this way, by using the average value of the inside and surface temperatures of the pressure roller 3, the conveyance speed on the fixing unit 13 side more accurately reflecting the change in the roller diameter than when only the internal temperature is used. Can be estimated.
Therefore, even if the peripheral speed of the pressure roller 3 changes due to a change in the roller diameter of the pressure roller 3, the rotational speed of the paper discharge roller pair 14 is more accurately corrected according to the change, and the fixing unit and paper discharge Therefore, it is possible to prevent the occurrence of image defects and jamming of the paper P due to a squeeze between the separation plates 10 and 11 of the paper P and the like.

Next, another control process for the rotational drive of the paper discharge roller pair in this multifunction machine will be described.
FIG. 7 is a waveform diagram showing an example of changes in the average value of the temperature obtained by adding the core metal temperature of the pressure roller 3 and the temperature of the heating roller 1 and the difference in transport speed between the paper discharge unit and the fixing unit. .

  The horizontal axis in FIG. 7 represents the average value of the core metal temperature (core metal temperature) Ts (° C.) of the pressure roller 3 and the temperature of the heating roller 1 (in this case, the surface temperature) Tp (° C.) (( Tm + Tp) / 2), and the vertical axis shows the change in the difference between the conveyance speed of the paper discharge roller pair 14 of the paper discharge section and the conveyance speed of the nip section 12 of the fixing section 13. A waveform indicated by a thick line in the drawing shows an example of a change in the average value of the temperature of the core metal of the pressure roller 3 and the temperature of the heating roller 1 and the difference in transport speed between the paper discharge unit and the fixing unit. It is a waveform.

  The target speed difference a (mm / s) on the vertical axis is such that the sheet P is not bent or pulled toward the sheet discharge unit in the conveyance path of the sheet P between the sheet discharge unit and the fixing unit 13. Difference between the conveyance speeds of the paper discharge unit and the fixing unit 13 to be maintained, and the allowable speed is about ± 2 (mm / s) above and below the target speed difference a and the target speed difference a is the center. The difference range is k.

In the example shown in FIG. 7, if the average value of the core metal temperature Ts of the pressure roller 3 and the temperature Tp of the heating roller 1 is lower than 105 ° C., the allowable speed difference range k of the target speed difference a (mm / s). It becomes slower than the lower limit value a-2 (mm / s), and the conveyance speed difference between the paper discharge unit and the fixing unit gradually increases as the temperature decreases.
Further, the average value of the core metal temperature Ts of the pressure roller 3 and the temperature Tp of the heating roller 1 is 105 to n (any value larger than 105) ° C. is an allowable speed difference range of the target speed difference a (mm / s). This is the specified temperature range C in which k is maintained.

Further, when the average value of the core metal temperature Ts of the pressure roller 3 and the temperature Tp of the heating roller 1 exceeds n ° C., the upper limit value a + 2 (mm / s) of the allowable speed difference range k of the target speed difference a (mm / s). As the temperature rises, the difference in transport speed between the paper discharge unit and the fixing unit gradually increases.
Thus, the conveyance speed of the fixing unit 13 is also affected by changes in the roller diameters of the heating roller 1 and the fixing roller 2, and the average value of the core metal temperature Ts of the pressure roller 3 and the temperature Tp of the heating roller 1 is If the temperature is lower than the specified temperature range C, the conveyance speed of the paper P on the fixing unit 13 side becomes slow, and the average value of the core metal temperature Ts of the pressure roller 3 and the temperature Tp of the heating roller 1 is lower than the specified temperature range C. If it is high, the conveyance speed of the paper P on the fixing unit 13 side tends to increase.

Therefore, in this multi-function machine, an experiment is performed in advance, and the change in temperature of the average value of the core metal temperature Ts of the pressure roller 3 and the temperature Tp of the heating roller 1 is lower and higher than the specified temperature range C. Accordingly, a correction value of the rotation speed of the drive motor 15 that rotationally drives the paper discharge roller pair 14 is obtained, and a rotation speed correction table in which the change of the average value is associated with the correction value is created.
This rotation speed correction table is stored in advance in the ROM or RAM (nonvolatile memory) of the control unit 16.

  In the experiment described above, the average value of the cored bar temperature Ts of the pressure roller 3 and the temperature Tp of the heating roller 1 is lower than the specified temperature range C and higher when the temperature is decreased and increased. The number of rotations to be added to or subtracted from the predetermined number of rotations of the discharge roller pair 14 so that the conveyance speed difference between the paper part and the fixing part 13 is within the allowable speed difference range k of the target speed difference a (mm / s). A percentage is obtained, and the percentage is used as the correction value.

FIG. 8 is a flowchart showing another control process of the rotational drive of the paper discharge roller pair 14 in this multifunction machine.
In the case of this process, the control unit 16 is detected by the temperature detected by the core metal temperature detecting means for detecting the temperature of the core metal of the pressure roller 3 and the heating roller temperature detecting means for detecting the temperature of the heating roller 1. The average temperature of the detected temperatures is set as a detected temperature, and based on the detected temperature, a function of a correcting unit that corrects the number of rotations of the discharge roller pair driving unit is achieved.

  When printing the paper P, the control unit 16 performs the core temperature of the pressure roller 3 (the core metal inside the pressure roller 3) by the first thermistor 7 in step 21 (indicated by “S” in the figure) in FIG. When the temperature of the heating roller 1 (detected temperature via the fixing belt 4) Tp is detected by the third thermistor 9, the average value of both temperatures (the core metal of the pressure roller 3) is detected. The temperature Ts + the temperature Tp of the heating roller 1) / 2 is obtained, and the average value is used as the detected temperature. In step 22, it is determined whether or not the detected temperature (Ts + Tp) / 2 is within the specified temperature range C. If it is within C, in step 24, the rotational speed of the drive motor 15 of the paper discharge roller pair 14 is maintained and controlled at a predetermined rotational speed, and this process ends.

  On the other hand, if (Ts + Tp) / 2 of the detected temperature is not within the specified temperature range C in the determination of step 22, the rotational speed correction table is referred to in step 23 and the correction value corresponding to the above (Ts + Tp) / 2 is obtained. The reading and control of changing the rotational speed from the predetermined rotational speed of the drive motor 15 of the paper discharge roller pair 14 to a rotational speed that is increased or decreased by a percentage based on the correction value is completed, and this processing is terminated.

  In the above change control, when the detected temperature (Ts + Tp) / 2 falls below the lower limit value of the specified temperature range C, the conveyance speed on the fixing unit 13 side decreases, so the number of rotations of the discharge roller pair 14 is reduced. As a result, the conveyance speed on the paper output side is also reduced. When the detected temperature (Ts + Tp) / 2 exceeds the upper limit value of the specified temperature range C, the conveyance speed on the fixing unit 13 side is increased. The conveyance speed on the part side is also increased.

  When the detected temperature (Ts + Tp) / 2 hardly exceeds the upper limit value n of the specified temperature range C, the control unit 16 recognizes that the detected temperature (Ts + Tp) / 2 is lower than the lower limit value of the specified temperature range C. Then, with reference to the rotation speed correction table, the correction value corresponding to the detected temperature (Ts + Tp) / 2 is read, and the rotation speed is calculated by a percentage based on the correction value from the predetermined rotation speed of the drive motor 15 of the paper discharge roller pair 14. It is better to control the change with less.

In this way, by using the average value of the internal temperature of the pressure roller 3 and the temperature of the heating roller 1, fixing is performed in consideration of the change in the roller diameter of the pressure roller 3 and the change in the roller diameter of the heating roller 1. The change in the conveyance speed of the paper P on the side of the section 13 can be estimated more accurately.
Therefore, even if the peripheral speed of the pressure roller 3 changes due to a change in the roller diameter of the pressure roller 3, the rotational speed of the paper discharge roller pair 14 is more accurately corrected according to the change, and the fixing unit and paper discharge Therefore, it is possible to prevent the occurrence of image defects and jamming of the paper P due to a squeeze between the separation plates 10 and 11 of the paper P and the like.

  Next, when the number of sheets passing through the nip portion 12 of the fixing unit 13 increases, the core metal temperature Ts of the pressure roller 3, the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3, the pressure roller 3 The average values of the core metal temperature Ts and the temperature Tp of the heating roller 1 are stabilized, and the difference in the conveyance speed between the fixing unit 13 and the paper discharge unit approaches the target speed difference a.

Therefore, the control unit 16 executes the above-described correction process when the paper P starts to pass through the fixing unit 13. After that, when the paper P is continuously passed through the nip portion 12, the control unit 16 passes the fixing unit 13. The number of rotations of the discharge roller pair 14 may be further corrected based on the number of sheets.
In this case, when the recording medium is continuously passed through the nip portion 12, the control unit 16 sets the number of rotations of the paper discharge roller pair driving means as the number of paper discharge roller pairs at a predetermined temperature as the number of passed sheets increases. It functions as a means for correcting the rotational speed of the driving means so as to approach it.

FIG. 9 is a diagram illustrating an example of a table in which the rotation speed correction values of the paper discharge roller pair 14 corresponding to the continuous sheet passing number are registered.
The correction values in the table shown in FIG. 9 are obtained in advance by experiments, and this table is also registered in advance in the ROM or RAM of the control unit 16.

  The control unit 16 performs the above-described correction processing after printing is started, and also counts the number of continuously passing sheets during printing. In the table shown in FIG. The corresponding discharge roller pair rotation speed correction value is read out. For example, when the number of passing sheets is 0 to 500, when the rotation speed of the discharge roller pair 14 is corrected, the rotation speed is increased to 1.00%. Is corrected so as to be close to the rotation speed of the discharge roller pair driving means at a predetermined temperature (specified temperature range A, B, or C) that falls within the target speed difference range k centered on the target speed difference a. To correct.

Further, when the rotational speed is lowered, the rotational speed is corrected by adding the rotational speed of 1.00%.
Similarly, the correction is made with the speed correction value of 0.50% of the paper discharge roller pair 14 for the sheet passing number 501 to 1000, and is not corrected for the sheet passing number 1001 or more.
In this way, when the number of sheets to be passed increases, the pressure roller 3 approaches a temperature corresponding to a predetermined temperature. Therefore, the rotation speed of the paper discharge roller pair 14 is brought close to the initial rotation speed before correction, and the sheet is passed. Regardless of the number of sheets, the difference in nipping and conveying speed between the fixing unit and the paper discharge unit can be made constant.

  Next, when the rotation driving time of the pressure roller 3 of the fixing unit 13 becomes longer, the core metal temperature Ts of the pressure roller 3, the average value of the core metal temperature Ts and the surface temperature Tm of the pressure roller 3, the pressure roller 3 The average values of the core metal temperature Ts and the temperature Tp of the heating roller 1 are stabilized, and the difference in the conveyance speed between the fixing unit 13 and the paper discharge unit approaches the target speed difference a.

Therefore, the control unit 16 executes the above-described correction process when the paper P starts to pass through the fixing unit 13, and when the rotation driving time of the pressure roller 3 becomes long after that, based on the rotation driving time. The number of rotations of the paper discharge roller pair 14 may be further corrected.
In this case, when the discharge roller pair driving means continuously rotates the pressure roller 3, the control unit 16 sets the rotation speed of the discharge roller pair driving means at a predetermined temperature as the rotation drive time increases. It functions as a means for correcting the paper discharge roller pair so that it approaches the rotational speed of the drive means.

FIG. 10 is a diagram illustrating an example of a table in which the rotation speed correction value of the paper discharge roller pair 14 corresponding to the continuous rotation time of the pressure roller 3 is registered.
The correction values in the table shown in FIG. 10 are obtained in advance by experiments, and this table is also registered in advance in the ROM or RAM of the control unit 16.

  The control unit 16 performs the above-described correction processing after printing is started, monitors the driving time of the driving motor 6 that rotates the pressure roller 3 during printing, and continuously rotates the pressure roller 3 according to the driving time. The time is measured, and the discharge roller pair rotation speed correction value corresponding to the column of the continuous rotation time range in the table shown in FIG. 10 is read. For example, when the continuous rotation time is 0 to 300 (seconds), the discharge is performed. When the rotational speed of the roller pair 14 is corrected, when the rotational speed is increased, the rotational speed is corrected to a rotational speed obtained by subtracting the rotational speed of 1.00%, and a predetermined temperature that falls within the target speed difference range k centered on the target speed difference a. Correction is made so as to approach the number of rotations of the discharge roller pair driving means in the (specified temperature range A, B, or C).

Further, when the rotational speed is lowered, the rotational speed is corrected by adding the rotational speed of 1.00%.
Similarly, when the continuous rotation time is 301 to 600 (seconds), correction is made with the speed correction value of 0.50% of the discharge roller pair 14, and when the continuous rotation time is 601 (seconds) or more, no correction is made.
In this way, when the rotation driving time of the pressure roller 3 increases, the pressure roller 3 approaches a temperature corresponding to a predetermined temperature, so that the rotation speed of the paper discharge roller pair 14 is set to the initial rotation speed before correction. Accordingly, the difference in the nipping and conveying speed between the fixing unit and the paper discharge unit can be made constant regardless of the number of sheets to be passed.

  The image forming apparatus according to the present invention can also be applied to a printer, a facsimile machine, a copying machine, and a complex machine thereof.

1: Heating roller 2: Fixing roller 3: Pressure roller 4: Fixing belt 5: Tension roller 6, 15: Drive motor 7: First thermistor 8: Second thermistor 9: Third thermistor 10, 11: Separating plate 12: Nip part 13: Fixing part 14: Paper discharge roller pair 16: Control part 20: Digital color copying machine 21: Paper feeding part 22: Original conveying part 23: Original reading part 24: Image forming part 25: Intermediate transfer belts 26Y to 26K : Photosensitive drums 27Y to 27K: Charging devices 28Y to 28K: Developing devices 29: Exposure devices 30: Tray portions 31: Conveying means 32: Registration roller portions 33: Transfer roller portions 34: Paper discharge storage portions P: Paper

JP 2009-163038 A JP 2007-72289 A

Claims (6)

A heating roller with a heat source, a fixing roller with an elastic layer on the outer periphery of the cored bar, and a pressure roller that is arranged in pressure contact with the fixing roller and has an elastic layer on the outer periphery of the cored bar and no heat source inside A fixing unit comprising: a roller; an endless fixing belt stretched between the heating roller and the fixing roller; and a pressure roller driving unit that rotationally drives the pressure roller; A discharge section having a discharge roller pair and a discharge roller pair driving means for rotationally driving the discharge roller pair on the downstream side in the conveyance direction of the recording medium, and the number of rotations of the pressure roller driving means. Pressure roller drive control means for controlling the paper discharge roller pair drive control means for controlling the rotation speed of the paper discharge roller pair drive means, and the fixing roller and pressure roller of the fixing unit, The fixing belt formed by pressure contact with the A toner image is heated and fixed on a recording medium through a recording medium carrying an unfixed toner image in a nip formed by a pressure roller, and is nipped and conveyed by the pair of discharging rollers of the discharging section. In an image forming apparatus that discharges paper,
Providing a core metal temperature detecting means for detecting the temperature of the core of the pressure roller;
An image characterized in that the discharge roller pair drive control means is provided with a correction means for correcting the rotation speed of the discharge roller pair drive means based on the detected temperature detected by the core metal temperature detection means. Forming equipment. A heating roller with a heat source, a fixing roller with an elastic layer on the outer periphery of the cored bar, and a pressure roller that is arranged in pressure contact with the fixing roller and has an elastic layer on the outer periphery of the cored bar and no heat source inside A fixing unit comprising: a roller; an endless fixing belt stretched between the heating roller and the fixing roller; and a pressure roller driving unit that rotationally drives the pressure roller; A discharge section having a discharge roller pair and a discharge roller pair driving means for rotationally driving the discharge roller pair on the downstream side in the conveyance direction of the recording medium, and the number of rotations of the pressure roller driving means. Pressure roller drive control means for controlling the paper discharge roller pair drive control means for controlling the rotation speed of the paper discharge roller pair drive means, and the fixing roller and pressure roller of the fixing unit, The fixing belt formed by pressure contact with the A toner image is heated and fixed on a recording medium through a recording medium carrying an unfixed toner image in a nip formed by a pressure roller, and is nipped and conveyed by the pair of discharging rollers of the discharging section. In an image forming apparatus that discharges paper,
A core temperature detecting means for detecting the temperature of the core of the pressure roller;
A pressure roller surface temperature detecting means for detecting the surface temperature of the pressure roller;
Based on the detected temperature, an average temperature of the temperature detected by the core metal temperature detecting means and the temperature detected by the pressure roller surface temperature detecting means is set to the discharge roller pair drive control means. An image forming apparatus, comprising: a correcting unit that corrects the rotation speed of the discharge roller pair driving unit. A heating roller with a heat source, a fixing roller with an elastic layer on the outer periphery of the cored bar, and a pressure roller that is arranged in pressure contact with the fixing roller and has an elastic layer on the outer periphery of the cored bar and no heat source inside A fixing unit comprising: a roller; an endless fixing belt stretched between the heating roller and the fixing roller; and a pressure roller driving unit that rotationally drives the pressure roller; A discharge section having a discharge roller pair and a discharge roller pair driving means for rotationally driving the discharge roller pair on the downstream side in the conveyance direction of the recording medium, and the number of rotations of the pressure roller driving means. Pressure roller drive control means for controlling the paper discharge roller pair drive control means for controlling the rotation speed of the paper discharge roller pair drive means, and the fixing roller and pressure roller of the fixing unit, The fixing belt formed by pressure contact with the A toner image is heated and fixed on a recording medium through a recording medium carrying an unfixed toner image in a nip formed by a pressure roller, and is nipped and conveyed by the pair of discharging rollers of the discharging section. In an image forming apparatus that discharges paper,
A core temperature detecting means for detecting the temperature of the core of the pressure roller;
A heating roller temperature detecting means for detecting the temperature of the heating roller;
An average temperature of the temperature detected by the core metal temperature detection means and the temperature detected by the heating roller temperature detection means is set as a detection temperature in the discharge roller pair drive control means, and the discharge temperature is determined based on the detection temperature. An image forming apparatus comprising correction means for correcting the number of rotations of the paper roller pair drive means.   When the detected temperature is higher than a predetermined temperature, the correction unit corrects the rotation speed of the discharge roller pair driving unit to be higher than the rotation number of the discharge roller pair drive unit at the predetermined temperature. When the detected temperature is lower than a predetermined temperature, the correction unit corrects the rotation speed of the discharge roller pair driving unit to be lower than the rotation number of the discharge roller pair drive unit at the predetermined temperature. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   When the recording medium is continuously passed through the nip portion to the correction means, the number of rotations of the paper discharge roller pair driving means is increased at the predetermined temperature as the number of sheets passed therethrough increases. 5. The image forming apparatus according to claim 4, further comprising means for correcting so as to approach the rotational speed of the pair drive means.   When the paper discharge roller pair drive means causes the correction roller to continuously rotate the pressure roller, the rotation speed of the paper discharge roller pair drive means is increased at the predetermined temperature as the rotation drive time increases. 5. The image forming apparatus according to claim 4, further comprising means for correcting so as to approach the rotational speed of the discharge roller pair driving means.

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