JP5856940B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and more particularly, to an image forming apparatus that continuously fixes a plurality of recording media.

  Conventionally, in an image forming apparatus, a toner image is transferred to a recording medium by an image forming unit, and the toner image transferred to the recording medium is fixed to the recording medium by a fixing device. The fixing device supplies heat to the unfixed toner on the recording medium by a heating roller at a nip formed between a heating roller heated by a heating means such as a heater and a pressure roller pressed against the heating roller. As a result, the toner is melted, whereby the melted toner is fixed on the surface of the recording medium.

  Further, the image forming apparatus can print recording media of various sizes in the width direction orthogonal to the conveyance direction of the recording medium. In the fixing device, since the length in the width direction of the heating roller is set in accordance with the size of the recording medium having the maximum width to be printed, the heating roller is used when fixing the recording medium having a small size in the width direction. In the paper passing area in contact with the recording medium, the heat of the heating roller is taken away by the recording medium, while in the non-paper passing area in which the recording medium does not contact, the temperature of the heating roller becomes high. In particular, when a recording medium having a small width is continuously printed, the temperature of the non-sheet passing area gradually increases with respect to the temperature of the sheet passing area, and a temperature difference occurs on the surface of the heating roller, so that fixing performance cannot be secured. .

  Therefore, when the image forming apparatus described in Patent Document 1 continuously performs printing on a recording medium having a small width, a predetermined number of prints per unit time is specified for the number of continuous prints, and the number of continuous prints is determined. Accordingly, the conveyance interval of the recording medium having a small width is set. As the number of continuously printed sheets increases, the recording medium conveyance interval increases. As a result, the temperature distribution in the width direction of the heating roller is made uniform to ensure fixing performance.

JP 2007-193109 A (paragraphs [0028], [0035], [0036], FIG. 2)

  In the image forming apparatus described in Patent Document 1, the continuous printing number is divided into a plurality of areas such as 2 to 5, 11 to 20, and the recording medium conveyance interval is set for each area. . When the number of continuous prints in each region is at or near the median value, fixing performance is ensured, and the number of prints per unit time is appropriately set to obtain printing productivity. However, in a region where the number of continuous prints is relatively small in each region, the temperature of the non-sheet passing region of the heating member does not become so high that the fixing performance deteriorates, and the number of prints per unit time becomes too small. Productivity may be reduced. On the other hand, in a portion where the number of continuous prints is relatively large in each region, the temperature of the non-sheet passing region of the heating member excessively increases, and it may be difficult to ensure the fixing performance.

  The present invention has been made to solve the above-described problems. When a recording medium is continuously printed regardless of the size of a small width, the fixing performance is ensured and the printing productivity is reduced. An object of the present invention is to provide an image forming apparatus that does not occur.

  In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a heating member that is heated by a heating unit, a pressure member that forms a nip portion by being pressed against the heating member, and a nip portion. A first temperature detection unit for detecting a surface temperature of a sheet passing area of the heating member formed when a recording medium having a width smaller than a maximum width recording medium is passed; A second temperature detection unit configured to detect a surface temperature of a non-sheet passing region of the heating member formed when the medium is passed through the nip portion, and when the recording medium passes through the nip portion. A fixing device that fixes an unfixed toner image on the recording medium, a transport unit that transports the recording medium to the fixing device, and a transport interval setting unit that sets a transport interval of the recording medium of the transport unit when performing continuous printing. The first temperature detection unit detects Control means for controlling the heating means and the conveyance interval setting means based on a first surface temperature and a second surface temperature detected by the second temperature detection unit, the control means comprising continuous printing At the start, the heating means is controlled based on the first surface temperature to maintain the first surface temperature at the first fixing temperature, and the conveyance so that the recording medium is conveyed at a first conveyance interval. When the interval setting means is controlled and the second surface temperature rises to a limit temperature at which fixing performance can be ensured, the heating means is controlled so as to maintain the second surface temperature at the limit temperature, When the one surface temperature is lower than the first fixing temperature by a predetermined temperature, the conveyance interval setting unit is controlled so that the recording medium is conveyed at a second conveyance interval that is larger than the first conveyance interval. To be characterized by To have.

  According to the first invention, when continuously printing a recording medium having a small width, at the start of continuous printing, the heating means is controlled based on the first surface temperature to maintain the first surface temperature at the first fixing temperature. At the same time, the recording medium is conveyed at the first conveyance interval, whereby the recording medium is continuously fixed. When the fixing process is continuously performed on a recording medium having a small width, when the temperature of the non-sheet passing region of the heating member gradually increases and the second surface temperature rises to the limit temperature, the second surface temperature is set to the limit temperature. Hold. Subsequently, when a recording medium having a small width is continuously printed in a state where the second surface temperature is maintained at the limit temperature, the first surface temperature is lowered. Therefore, when the first surface temperature is lower than the first fixing temperature by a predetermined temperature, the conveyance interval setting unit is controlled so that the recording medium is conveyed at the second conveyance interval that is larger than the first conveyance interval. To do. By this control, the recording medium conveyance interval is increased, so that the temperature of the pressure member rises, and the temperature of the nip portion rises via the pressure member, so that fixing performance can be ensured. As a result, good fixing performance is ensured regardless of the width size of the recording medium, and it is not necessary to provide a sensor for detecting the width size of the recording medium, which simplifies the apparatus. Furthermore, when the continuous printing is performed at the initial stage or when the number of continuous printing is relatively small, the conveyance interval can be set small, so that the printing productivity is not lowered.

Sectional drawing which shows the structure of the image forming apparatus which concerns on 1st Embodiment of this invention. 1 is a side cross-sectional view illustrating a configuration of a fixing device used in an image forming apparatus according to a first embodiment. FIG. 2 is a cross-sectional plan view illustrating a configuration of a fixing device according to the first embodiment and its periphery. The figure which shows the temperature control of the control part which concerns on 1st Embodiment. 6 is a flowchart showing an image forming procedure of the control unit according to the first embodiment. The figure which shows the structure of the paper length calculation part which concerns on 2nd Embodiment of this invention, and its periphery. A flowchart showing a procedure of image formation of a control unit according to the second embodiment.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Further, the use of the invention and the terms shown here are not limited thereto.

  FIG. 1 is a cross-sectional view illustrating the overall configuration of an image forming apparatus including a fixing device according to an embodiment of the present invention, and the right side is illustrated as the front side of the image forming apparatus. The image forming apparatus 1 is a printer, and a paper feeding device 20 is disposed below the apparatus main body 1 a of the image forming apparatus 1. The paper feeding device 20 includes a paper feeding cassette 22 that stores paper P that is a recording medium, and a manual feed tray 41 on which the paper P can be placed. The paper feed cassette 22 is provided so that it can be pulled out from the front of the apparatus main body 1a to store the paper P. The manual feed tray 41 is disposed above the paper feed cassette 22. A sheet conveyance path 4 extending from the lower side to the upper side of the apparatus main body 1a and reaching the paper discharge unit 3 formed on the upper surface of the apparatus main body 1a is formed behind the paper supply device 20. A pickup roller 29, a paper feed roller 30, a registration roller pair 8, an image forming unit 9, a fixing device 10, and a discharge roller pair 11 are arranged in this order along the paper conveyance path 4 from the upstream side.

  The paper feed cassette 22 is provided with a paper stacking plate 28 that is rotatably supported with respect to the paper feed cassette 22. When the paper P stacked on the paper stacking plate 28 is sent out toward the paper transport path 4 by the pickup roller 29, and when a plurality of papers P are simultaneously sent by the pickup roller 29, the paper P is separated from the paper feed roller 30. The sheet P is rolled by the pad 35 and only the topmost sheet is sent out. The paper P delivered to the paper transport path 4 is transported to the registration roller pair 8, and the timing is adjusted by the registration roller pair 8 and supplied to the image forming unit 9.

  The manual feed tray 41 feeds paper P of a size, envelope, cardboard, etc. not loaded in the paper feed cassette 22 to the image forming unit 9 via the registration roller pair 8, and the paper P is the main body of the apparatus. It is placed on the manual feed tray 41 from the front of 1a.

  The image forming unit 9 forms a predetermined toner image on the paper P by an electrophotographic process. The photoconductor 14 is an image carrier that is pivotally supported in a clockwise direction in FIG. 1, and the photoconductor. 14, a charging device 15, a developing device 16, a cleaning device 17, a transfer roller 18 disposed so as to face the photoconductor 14 across the paper conveyance path 4, and a photoconductor 14. The exposure apparatus 19 is configured.

  The charging device 15 is provided with a conductive rubber roller 15 a connected to a power source (not shown), and the conductive rubber roller 15 a is disposed so as to contact the photoreceptor 14. When the photosensitive member 14 rotates, the conductive rubber roller 15a comes into contact with the surface of the photosensitive member 14 and is driven to rotate. At this time, by applying a predetermined voltage to the conductive rubber roller 15a, The surface is charged uniformly.

  Next, an electrostatic latent image based on image data input from the outside of the image forming apparatus 1 is formed on the photosensitive member 14 by the beam light emitted from the exposure device 19, and toner is formed on the electrostatic latent image by the developing device 16. Adheres to form a toner image on the surface of the photoreceptor 14. Then, the paper P is supplied from the registration roller pair 8 between the photoconductor 14 and the transfer roller 18 (transfer position) at a predetermined timing, and the toner image on the surface of the photoconductor 14 is transferred onto the paper P by the transfer roller 18. Is done.

  The sheet P on which the toner image is transferred is separated from the photoreceptor 14 and conveyed toward the fixing device 10. The fixing device 10 is disposed on the downstream side of the image forming unit 9 with respect to the paper transport direction, and the paper P on which the toner image is transferred in the image forming unit 9 is pressed with a heating roller provided in the fixing device 10. The toner image heated and pressed by the roller and transferred onto the paper P is fixed.

  The paper P on which the image has been formed is discharged to the paper discharge unit 3 by the discharge roller pair 11. On the other hand, the toner remaining on the surface of the photoconductor 14 after the transfer is removed by the cleaning device 17, the photoconductor 14 is charged again by the charging device 15, and image formation is performed in the same manner.

  2 and 3 are views showing the fixing device 10 used in the image forming apparatus 1, FIG. 2 is a side sectional view of the fixing device 10, and FIG. 3 shows a configuration of the fixing device 10 and its periphery. FIG. In FIG. 3, “PA” indicates a sheet passing area when a sheet P having a size smaller than the maximum sheet passing width is passed, and “PB” indicates a sheet P having a size smaller than the maximum sheet passing width. The non-sheet passing area is shown. In FIG. 3, the pressure roller 52 is not shown.

  As shown in FIG. 2, the fixing device 10 is a roller fixing method, and includes a heating roller 51 that is a heating member, a pressure roller 52 that is a pressure member, a heater 53 that is a heating unit, and a first temperature detection. Unit 71 and a second temperature detection unit 72.

  As the heating roller 51, a cylindrical cored bar made of a metal such as aluminum or iron excellent in thermal conductivity is coated with a fluororesin coating or a tube. A heater 53 such as a halogen lamp or a xenon lamp is provided inside the core of the heating roller 51.

  The pressure roller 52 is formed by forming an elastic layer such as silicon rubber on a cylindrical base material made of synthetic resin, metal or other material, and coating the surface of the elastic layer with a fluororesin coat. .

  The pressure roller 52 is brought into pressure contact with the heating roller 51 at a predetermined pressure, and the heating roller 51 is rotationally driven by a driving source (not shown). As the heating roller 51 rotates, the pressure roller 52 is driven to rotate. A nip portion N is formed at a portion where the heating roller 51 and the pressure roller 52 come into contact with each other. The pressure roller 52 may be driven to rotate by a driving source, and the heating roller 51 may be driven to rotate.

  The first temperature detection unit 71 and the second temperature detection unit 72 are each formed of a thermistor, and detect the surface temperature of the heating roller 51. The first temperature detection unit 71 and the second temperature detection unit 72 are close to or in contact with the surface of the heating roller 51 and in the paper conveyance direction. On the other hand, it is arranged in the vicinity of the upstream side of the nip portion N. The first temperature detection unit 71 detects the surface temperature of the central portion of the heating roller 51 in the axial direction, that is, the sheet passing area PA (see FIG. 3), while the second temperature detection unit 72 is the end of the heating roller 51. The surface temperature of the portion side, that is, the non-sheet passing region PB (see FIG. 3) is detected. As a result, the surface temperature of the heating roller 51 can be controlled to a fixing temperature necessary for the fixing process.

  The paper P is transported from the upstream side in the paper transport direction (the lower side in FIG. 2) to the nip portion N, and heated and pressed by the heating roller 51 and the pressure roller 52 in the nip portion N. The powdered toner is melted and fixed. The paper P after the fixing process is separated from the surface of the heating roller 51 by a separation claw (not shown) and then conveyed downstream of the fixing device 10 in the paper conveying direction.

  As shown in FIG. 3, the first temperature detection unit 71 and the second temperature detection unit 72 are connected to a control unit 81 which is a control means. Further, a power source 69 for driving the heater 53, a motor 85 for rotationally driving the registration roller pair 8 (see FIG. 1), and a memory for storing data on the fixing temperature on the surface of the heating roller 51 and the conveyance interval of the paper P during the fixing process. The unit 82 is connected to the control unit 81. The registration roller pair 8 and the motor 85 constitute a conveyance interval setting unit.

  The control unit 81 includes a microcomputer and storage elements such as a RAM and a ROM, and is set from the outside of the image forming apparatus 1 and data related to temperatures detected by the first temperature detection unit 71 and the second temperature detection unit 72. Further, referring to the data stored in the storage unit 82 based on the print data and the like, the on / off of energization to the heater 53 by the power source 69 is controlled and the rotational drive of the motor 85 is controlled.

  The heater 53 is disposed so as to extend to both end portions in the axial direction of the heating roller 51, and an area corresponding to the maximum width of paper P that can pass through the nip portion N (see FIG. 2) (the paper passing area PA and the non-passing area). It is possible to heat up to the paper area PB). Accordingly, when a paper P having a small width such as A5T is passed through the nip portion N, the surface temperature of the heating roller 51 is high in the non-paper passing area PB where the paper P does not contact. In particular, when the paper P having a small width is continuously printed, the temperature of the non-paper passing area PB where the paper P is not in contact with the paper passing area PA where the paper P is in contact gradually increases, and the axial direction of the heating roller 51 A difference in surface temperature occurs, and fixing performance cannot be secured.

  Therefore, the control unit 81 refers to a correlation table described later in the storage unit 82 and controls the surface temperature of the heating roller 51 as shown in FIG. 4 and also controls the conveyance interval of the paper P for continuous printing. FIG. 4 is a graph with time (unit: sec) on the horizontal axis and temperature (unit: ° C.) on the vertical axis. 4 is the temperature (first surface temperature) of the sheet passing area PA of the heating roller 51 detected by the first temperature detector 71 (see FIG. 3), and the TB line is the second temperature. This is the temperature (second surface temperature) of the non-sheet passing region PB of the heating roller 51 detected by the detection unit 72 (see FIG. 3). The TL line is a limit temperature at which the fixing performance can be ensured. For example, temperature data of 220 ° C. is stored in the storage unit 82. TF1 is a first fixing temperature for controlling the first surface temperature TA for fixing the paper P. For example, temperature data of 185 ° C. is stored in the storage unit 82. TF2 is a second fixing temperature for controlling the first surface temperature TA in order to fix the paper P. For example, temperature data of 180 ° C. lower than the first fixing temperature TF1 is stored in the storage unit 82. Further, a third fixing temperature TF3 (for example, 175 ° C., not shown) lower than the second fixing temperature TF2 and a fourth fixing temperature TF4 (for example, 170 ° C., not shown) lower than the third fixing temperature TF3 are stored in the storage unit 82. Has been. The TP line is the surface temperature of the pressure roller 52 (see FIG. 2).

The storage unit 82 (see FIG. 3) stores the data of the first to fourth fixing temperatures TF1 to TF4 in correspondence with the temperature detected by the first temperature detection unit 71, and the conveyance interval D of the paper P. Is saved. Table 1 shows the relationship between the correlation amounts. In Table 1, with respect to the first surface temperature TA detected by the first temperature detector 71, for example, four transport intervals D and fixing temperatures TF from group 1 to group 4 are set. When the first surface temperature TA of the first temperature detector 71 decreases in the order of group 1 to group 4, the conveyance interval D of the paper P increases in the order of D1 to D4, and the fixing temperature TF is the first as described above. The fixing temperature TF1 is set lower in the order from the fourth fixing temperature TF4. Based on the surface temperature of the heating roller 51 detected by the first temperature detection unit 71 and the second temperature detection unit 72, the control unit 81 refers to the correlation table in Table 1 and controls the conveyance interval D and the fixing temperature TF. .

  When a main switch (not shown) of the image forming apparatus 1 is turned on, the power source 69 (see FIG. 3) is turned on and the heater 53 is heated. The first surface temperature TA detected by the first temperature detection unit 71 (see FIG. 3) rises, and the second surface temperature TB detected by the second temperature detection unit 72 (see FIG. 3) rises. As the temperature of the roller 51 rises, the surface temperature of the pressure roller 52 rises. Information on the number of prints is input to the image forming apparatus 1, and a sheet P of a predetermined size is placed on the manual feed tray 41 (see FIG. 1). Here, it is assumed that paper P having a small width such as A5T is continuously printed.

  When the heating roller 51 rises in temperature and the first surface temperature TA reaches the first fixing temperature TF1 at time T0, continuous printing is started. By passing the paper P through the nip portion N, the heat of the heating roller 51 and the pressure roller 52 is transmitted to the paper P through the nip portion N, and the surface temperature of the pressure roller 52 is lowered. Is heated and the first surface temperature TA is maintained at the first fixing temperature TF1.

  In the section from time T0 to time T1, the controller 81 controls the energization of the heater 53 so that the first surface temperature TA is maintained at the first fixing temperature TF1. At the start of continuous printing, the conveyance interval is set to D1 based on the correlation table (see Table 1) in the storage unit 82. In a state where the first surface temperature TA is maintained at the first fixing temperature TF1, the paper P is sequentially conveyed to the nip portion N at the conveyance interval D1 and continuously subjected to fixing processing. Note that the conveyance interval D of the paper P is determined by setting the timing for starting the rotation of the registration roller pair 8. That is, the registration roller pair 8 is rotationally driven to convey the paper P, and when the conveyance of the paper P is completed, the rotation of the registration roller pair 8 is stopped. The time from the stopped state to the next rotation of the registration roller pair 8 is the sheet conveyance interval D. By repeating the rotation and stop of the registration roller pair 8 at a predetermined timing, the paper P is continuously conveyed at a predetermined conveyance interval. Further, the conveyance interval D of the paper P can be changed by changing the rotation start timing of the registration roller pair 8. The registration roller pair 8 is rotationally driven by a motor 85 (see FIG. 3), and the conveyance interval D is changed by changing the driving and stopping timing of the motor 85.

  When the paper P having a small width is continuously fixed, the second surface temperature TB of the non-sheet passing region PB (see FIG. 3) of the heating roller 51 gradually increases, and the second surface temperature TB becomes the limit temperature TL. (Time T1 in FIG. 4). When the second surface temperature TB rises to the limit temperature TL, the control unit 81 controls energization to the heater 53 so that the second surface temperature TB does not exceed the limit temperature TL.

  When the paper P having a small width is continuously printed in a state where the second surface temperature TB is maintained at the limit temperature TL, the first surface temperature TA is decreased (section from the time T1 to the time T2). When the first surface temperature TA is lower than the first fixing temperature TF1 by a predetermined temperature, for example, 3 ° C., the control unit 81 refers to the correlation table (Table 1) and transports the transport interval larger than the transport interval D1. Control is performed so that the sheet P is conveyed to the nip portion N at the interval D2. That is, the control unit 81 changes the interval between the rotational drive and stop of the motor 85 to increase the conveyance interval of the paper P by the registration roller pair 8. By increasing the conveyance interval of the paper P, the time during which the heating roller 51 is in contact with the pressure roller 52 is lengthened, so that the temperature of the pressure roller 52 rises (after time T2), and the pressure roller 52 As a result, the temperature of the nip portion N rises, and as a result, fixing performance can be ensured.

  When the first surface temperature TA is lower than the first fixing temperature TF1 by a predetermined temperature, for example, 3 ° C., the control unit 81 controls the conveyance interval to D2 and refers to the correlation table (Table 1). Thus, the power supply to the heater 53 is controlled so that the first surface temperature TA becomes the second fixing temperature TF2 lower than the first fixing temperature TF1. By this control, the fixing process of the paper P is performed at the second fixing temperature TF2. In this case, the second surface temperature TB gradually decreases after time T2.

  In the section after time T2, the same processing as that in the section from time T0 to time T2 is executed. Specifically, the first surface temperature TA is held at the second fixing temperature TF2, and the conveyance interval is set to D2. When the paper P having a small width is sequentially conveyed to the nip portion N at the conveyance interval D2 and is continuously fixed at the second fixing temperature TF2, the temperature of the non-sheet passing area PB (see FIG. 3) of the heating roller 51. Gradually increases, and the second surface temperature TB rises to the limit temperature TL. When the second surface temperature TB rises to the limit temperature TL, the control unit 81 controls energization to the heater 53 so as to maintain the second surface temperature TB at the limit temperature TL. When the second surface temperature TB is maintained at the limit temperature TL, the first surface temperature TA decreases, and when the first surface temperature TA becomes lower than the second fixing temperature TF2 by a predetermined temperature, for example, 3 ° C., the control unit 81 Referring to the correlation table (Table 1), the sheet P is conveyed to the nip portion N at the conveyance interval D3 which is larger than the conveyance interval D2, and the first surface temperature TA is lower than the second fixing temperature TF2. Control is performed so that the fixing temperature is TF3. By this control, the conveyance interval of the paper P is increased, so that the temperature of the pressure roller 52 rises, the temperature of the nip portion N rises via the pressure roller 52, and the paper P at the third fixing temperature TF3. Can be fixed.

  The above is a procedure for continuously fixing the paper P having a small width. However, when fixing the paper P having the maximum width that can be passed, the correlation table (Table 1) in the storage unit 82 is displayed at the start of printing. Based on the above, energization to the heater 53 is controlled so that the first surface temperature TA is maintained at the first fixing temperature TF1, and the conveyance interval is set to D1. Since the sheet P is also passed through the non-sheet passing area PB of the heating roller 51, the second surface temperature TB becomes a temperature in the vicinity of the first fixing temperature TF1, and does not rise to the limit temperature TL continuously. Fixing treatment can be performed.

  With the above configuration, good fixing performance is ensured regardless of the width size of the paper P, and it is not necessary to provide a sensor for detecting the width size of the paper P, and the apparatus becomes simple. Furthermore, since the conveyance interval can be set small at the initial stage of continuous printing or when the number of continuous prints is relatively small, printing productivity is not lowered. In particular, the present embodiment is preferably applied to an image forming apparatus such as a simple printer that includes a manual feed mode and does not include a sensor that detects the width size of the paper P. In the above-described printer or the like, even if the width size of the paper P conveyed from the manual feed tray 41 is not detected, good fixing performance is ensured, and printing productivity is not lowered.

  In the above embodiment, when the first surface temperature TA decreases while the second surface temperature TB is held at the limit temperature TL, the control unit 81 increases the conveyance interval D and sets the first surface temperature TA. Although the configuration for performing the control for lowering the fixing temperature TF to be controlled is shown, the present embodiment is not limited to this, and the control unit 81 performs only the control for increasing the conveyance interval D to ensure the fixing performance. Good.

  Specifically, according to the procedure shown in FIG. 5, the control unit 81 controls the conveyance interval of the paper P and the surface temperature of the heating roller 51. FIG. 5 is a flowchart showing an image forming procedure of the control unit 81.

  In step 1, when a main switch (not shown) of the image forming apparatus 1 is turned on, the power source 69 is turned on. Print data such as the number of printed sheets, setting of a print image, and setting of a paper feed destination of the paper P are input from the outside of the image forming apparatus 1. Here, the small size paper P is placed on the manual feed tray 41, and the paper feed destination of the paper P is set to the manual feed mode.

  In step 2, group 1 is selected from the correlation table (table 1) in the storage unit 82. In Step 3 and Step 4, the control unit 81 controls the energization to the heater 53 so that the first surface temperature TA becomes the first fixing temperature TF1 based on the data of Group 1 of the correlation table. The motor 85 is controlled so that 8 conveys the paper P at the conveyance interval D1.

  In step 5, the second surface temperature TB is examined while the first surface temperature TA is maintained at the first fixing temperature TF1. If the second surface temperature TB has not risen to the limit temperature TL, it is checked in step 6 whether or not the set number of prints has been reached. If the set number of prints has been reached, printing is terminated. (Step 7). If the set number of prints has not been reached, the second surface temperature TB is continuously checked and printing is continued.

  In Step 5, when the second surface temperature TB rises to the limit temperature TL for 3 seconds, in Step 8, the energization to the heater 53 is controlled so that the second surface temperature TB maintains the limit temperature TL.

  In a state where the second surface temperature TB is held at the limit temperature TL, in Step 9, it is checked whether or not the first surface temperature TA is 3 ° C. lower than the first fixing temperature TF1. If the first surface temperature TA has not decreased to the above temperature, in step 6 ′, it is checked whether or not the set number of prints has been reached. If the set number of prints has been reached, printing is terminated. (Step 7 '). If the set number of prints has not been reached, the first surface temperature TA is continuously checked and printing is continued.

  In step 9, when the first surface temperature TA is lowered by 3 ° C. from the first fixing temperature TF1, in step 10, it is checked whether or not the group 4 of the correlation table (Table 1) in the storage unit 82 is input. Since group 1 of the correlation table is selected this time, in step 11, group 1 is changed to group 2. Returning to Step 2, in Step 2, Group 2 is selected from the correlation table (Table 1) in the storage unit 82. Thereafter, the routine from step 3 to step 11 is executed in the same manner, and printing is executed in a state where the conveyance interval of the paper P and the surface temperature of the heating roller 51 are controlled.

  When the control of the conveyance interval of the paper P and the surface temperature of the heating roller 51 based on the group 4 of the correlation table (Table 1) is completed (YES in Step 10), the temperature of the non-sheet passing area PB rises to the limit temperature TL. Therefore, in order to lower the surface temperature of the heating roller 51, in step 12, the conveyance of the paper P is stopped and the power source 69 of the heater 53 is turned off. In step 13, the conveyance of the paper P is stopped and the power supply 69 is turned off until the first surface temperature TA decreases to 150 ° C. (NO in step 13).

  When the first surface temperature TA reaches 150 ° C. (YES in step 13), in step 14, the first surface temperature TA is controlled to be held at the fourth fixing temperature TF4, and in step 15, the paper P is moved to the conveyance interval D4. Control to be. Then, printing is executed.

  In step 16, if the second surface temperature TB is not equal to or lower than the limit temperature TL (NO in step 16) with the fixing process of the small size paper P, that is, the second surface temperature TB is 3 seconds until the limit temperature TL. If so, return to step 12. Returning to step 12, after performing aging (step 13), the first surface temperature TA is held at the fourth fixing temperature TF4 (step 14), and the printing interval is set as the conveyance interval D4 of the paper P (step 15). . In step 17, it is checked whether or not the set number of prints has been reached. If the set number of prints has been reached, printing is terminated (step 18).

(Second Embodiment)
In the second embodiment, the conveyance interval D and the fixing temperature TF can be set according to the length of the sheet P being conveyed. FIG. 6 is a diagram illustrating the configuration of the length calculation unit and its periphery, and FIG. 7 is a flowchart illustrating the image forming procedure of the control unit 81. In the second embodiment, a configuration that includes a length calculation unit that calculates the length of the paper P and a configuration that selects a group in the correlation table of the storage unit 82 according to the length of the paper P will be mainly described. Description of the same part as 1 embodiment is abbreviate | omitted.

  As shown in FIG. 6, a conveyance roller pair 90 is disposed in the sheet conveyance path 4, and a detection sensor 88 is disposed in the vicinity of the conveyance roller pair 90.

  The detection sensor 88 detects the passage of the paper P, and includes a light emitting unit having an LED and a light receiving unit having a photodiode, and receives light reflected from and reflected by the paper P from the light emitting unit. The passage of the paper P is detected by receiving the light. The light from the light emitting part is received by the light receiving part for the time until the trailing edge of the paper P passes the detection sensor 88 after the leading edge of the paper P passes the detection sensor 88. The received light amount data corresponding to the received time is output from the detection sensor 88 to the length measuring unit 89. In the detection sensor 88, the light emitting unit and the light receiving unit are provided facing the left and right sides of the paper conveyance path 4, and when the paper P passes between the light emitting unit and the light receiving unit, the light from the light emitting unit to the light receiving unit is emitted. The configuration may be such that data is output by being blocked by the paper P. Further, one end of the cantilever may be arranged in the paper transport path 4 using a cantilever type photodetector. In this case, the leading end of the sheet P is detected when one end of the cantilever comes into contact with the sheet P, and the trailing end of the sheet P is detected when one end of the cantilever is separated from the sheet P.

  The length calculation unit 89 includes a microcomputer, a storage element such as a RAM and a ROM, etc., and receives a received light amount data from the detection sensor 88 and rotates a drive source such as a motor (not shown) that rotates the transport roller pair 90. Enter the rotation speed data. The length calculation unit 89 calculates the time required for the leading and trailing ends of the paper P to pass based on the received light amount data, and calculates the rotation speed of the transport roller pair 90 based on the rotation speed data. The length calculation unit 89 calculates the length of the paper P in the transport direction based on the passage time of the leading edge and the rear edge of the paper P and the rotation speed of the transport roller pair 90.

  The length calculation unit 89 may be configured as a part of the control unit 81 (see FIG. 3). Also, the length calculation unit 89 calculates the length in the transport direction of the paper P based on the driving time for the registration roller pair 8 to rotate to transport the paper P and the rotational speed of the range roller 7. Good. As described above, the length in the conveyance direction of the paper P can be obtained by using a general-purpose member of the paper conveyance path 4 such as the conveyance roller pair 90 and the detection sensor 88 or the range roller pair 8 without providing a special member. Is detected.

  As shown in FIG. 7, based on the length of the sheet P calculated by the length calculation unit 89 and the correlation table stored in the storage unit 82 (see FIG. 3), the control unit 81 performs the conveyance interval of the sheet P. And the surface temperature of the heating roller 51 is controlled.

  In step 21, when a main switch (not shown) of the image forming apparatus 1 is turned on, the power source 69 is turned on. Print data such as the number of printed sheets, setting of a print image, and setting of a paper feed destination of the paper P are input from the outside of the image forming apparatus 1. Here, the small size paper P is placed on the manual feed tray 41, and the paper feed destination of the paper P is set to the manual feed mode.

  In step 22, the length L in the conveyance direction of the sheet P conveyed from the manual feed tray 41 is calculated by the length calculation unit 89, and the conveyance direction length L is input from the length calculation unit 89.

In step 23, a correlation table group corresponding to the conveyance direction length L of the paper P is selected with reference to the correlation table stored in the storage unit 82. The correlation table is shown in Table 2.

  In the correlation table shown in Table 2, the group 4 is deleted from the correlation table (Table 1) of the first embodiment, and the paper length L is added instead of the first surface temperature TA of the first temperature detection unit 71. It is a thing. That is, in the order of group 1 to group 3, the conveyance interval D of the paper P increases in the order of D1 to D3, and the fixing temperature TF is set to be lower in the order of the first fixing temperature TF1 to the third fixing temperature TF3.

  The paper length L is classified according to the length in the transport direction regardless of the width of the paper P. Group 1 includes paper P having a relatively short length L in the paper transport direction. Group 2 includes paper P having a length L in the paper transport direction longer than that of group 1, and group 3 includes paper P having a length L in the paper transport direction longer than that of group 2. For example, in group 1, the smallest paper size is A6 (length L = 148 mm in the paper conveyance direction, paper width W = 105 mm) to B5T (L = 257 mm, W = 182 mm) as the largest paper size. Including. In Group 2, the smallest paper size is 8.5 × 11T (L = 279.4 mm, W = 215.9 mm) to the largest paper size is A4T (L = 297 mm, W = 210 mm). In addition, in group 3, the smallest paper size includes Folio (L = 330 mm, W = 210 mm) to the largest paper size 11 × 17 (L = 431.8 mm, W = 279.4 mm). .

  In step 23, when the conveyance direction length L of the paper P is included in the group 1 of the correlation table (Table 2), in step 24, the first surface temperature TA is controlled to be the first fixing temperature TF1, and The motor 85 is controlled so that the registration roller pair 8 conveys the paper P at the conveyance interval D1. Next, an interruption is performed between step 4 and step 5 in the flowchart (see FIG. 5) of the first embodiment, and the steps after step 5 are executed until printing is completed.

  In step 23, when the conveyance direction length L of the paper P is not included in the group 1 of the correlation table (Table 2), it is checked in Step 25 whether it is included in the group 2 of the correlation table (Table 2). When the conveyance direction length L of the sheet P is included in the group 2 of the correlation table (Table 2), in step 26, the first surface temperature TA is controlled to be the second fixing temperature TF2, and the registration roller pair 8 is also controlled. Controls the motor 85 so as to transport the paper P at the transport interval D2. Next, an interruption is performed between step 4 and step 5 in the flowchart (see FIG. 5) of the first embodiment, and the steps after step 5 are executed until printing is completed.

  In step 25, when the conveyance direction length L of the paper P is not included in the group 2 of the correlation table (Table 2), it is checked in Step 27 whether it is included in the group 3 of the correlation table (Table 2). When the conveyance direction length L of the paper P is included in the group 3 of the correlation table (Table 2), in step 28, the first surface temperature TA is controlled to be the third fixing temperature TF3, and the registration roller pair 8 is also controlled. Controls the motor 85 so as to transport the paper P at the transport interval D3. Next, an interruption is performed between step 4 and step 5 in the flowchart (see FIG. 5) of the first embodiment, and the steps after step 5 are executed until printing is completed.

  In step 27, when the conveyance direction length L of the paper P is not included in the group 3 of the correlation table (Table 2), an interruption is performed between step 13 and step 14 in the flowchart (see FIG. 5) of the first embodiment. Steps after step 14 are executed until printing is completed.

  With the above configuration, good fixing performance is ensured regardless of the width size of the paper P, and it is not necessary to provide a sensor for detecting the width size of the paper P, and the apparatus becomes simple. Furthermore, since the conveyance interval can be set small at the initial stage of continuous printing or when the number of continuous prints is relatively small, printing productivity is not lowered. In particular, the present embodiment is preferably applied to an image forming apparatus such as a simple printer that includes a manual feed mode and does not include a sensor that detects the width size of the paper P. In the above-described printer or the like, even if the width size of the paper P conveyed from the manual feed tray 41 is not detected, good fixing performance is ensured, and printing productivity is not lowered.

  In the first and second embodiments, the example applied to the roller fixing method has been described. However, the present invention is not limited to this, and is applied to a belt fixing method and a method of heating a heating roller or a belt by electromagnetic induction. May be.

  The present invention can be used for an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and in particular, can be used for an image forming apparatus that continuously fixes a plurality of recording media.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4 Paper conveyance path (conveyance part)
8 Registration roller pair (conveyance interval setting means)
10 Fixing Device 41 Manual Tray 51 Heating Roller (Heating Member)
52 Pressure roller (Pressure member)
53 Heater (heating means)
69 Power Supply 71 First Temperature Detection Unit 72 Second Temperature Detection Unit 81 Control Unit (Control Unit)
82 storage unit 85 motor (conveyance interval setting means)
88 detection sensor 89 length calculation unit 90 transport roller pair D1 to D4 1st to 4th transport interval Di ith transport interval N nip PA PA paper passing area PB non-paper passing area TA first surface temperature TB second surface temperature TF1 ~ TF4 1st to 4th fixing temperature TFi ith fixing temperature TL Limit temperature TP Pressure roller temperature

Claims (5)

A heating member heated by a heating means;
A pressure member that forms a nip portion by being pressed against the heating member;
A first temperature detection unit that detects a surface temperature of a sheet passing region of the heating member that is formed when a recording medium having a width smaller than a maximum width recording medium that can pass through the nip portion is passed;
A second temperature detection unit that detects a surface temperature of a non-sheet passing region of the heating member formed when the recording medium having a small width is passed through the nip portion;
A fixing device for fixing an unfixed toner image on the recording medium when the recording medium passes through the nip portion;
A transport unit for transporting a recording medium to the fixing device;
A length calculation unit for calculating the length in the conveyance direction of the recording medium conveyed to the conveyance unit;
A conveyance interval setting means for setting a conveyance interval of the recording medium of the conveyance unit when continuously printing;
A storage unit that stores a correlation amount between the conveyance interval and the fixing temperature with respect to the length of the recording medium in the conveyance direction;
Control means for controlling the heating means and the conveyance interval setting means based on the first surface temperature detected by the first temperature detection unit and the second surface temperature detected by the second temperature detection unit;
With
The control means controls the heating means based on the first surface temperature at the start of continuous printing to maintain the first surface temperature at the first fixing temperature, and the recording medium is conveyed at a first conveyance interval. The transporting interval setting means is controlled so that when the second surface temperature rises to a limit temperature at which fixing performance can be ensured, the heating means is maintained so that the second surface temperature is maintained at the limit temperature. When the first surface temperature is lower than the first fixing temperature by a predetermined temperature, the recording medium is conveyed at a second conveyance interval that is larger than the first conveyance interval. Controlling the conveying interval setting means, and controlling the heating means to maintain the first surface temperature at a second fixing temperature lower than the first fixing temperature,
The control unit is configured to set the recording medium at a predetermined conveyance interval based on the conveyance direction length of the recording medium calculated by the length calculation unit and the correlation amount of the storage unit before fixing processing for continuous printing. An image forming apparatus characterized by controlling the conveying interval setting means so as to be conveyed, and controlling the heating means so as to maintain the first surface temperature at a predetermined fixing temperature . The control means controls the heating means so as to maintain the first surface temperature at the second fixing temperature, and the conveyance interval setting means is configured so that the recording medium is conveyed at the second conveyance interval. And when the second surface temperature rises to the limit temperature, the heating means is controlled so as to keep the second surface temperature at the limit temperature, and the first surface temperature is set higher than the second fixing temperature. When the temperature becomes lower than the second transport interval, the transport interval setting means is controlled to transport the recording medium at a third transport interval that is larger than the second transport interval, and the first surface temperature is set to the first surface temperature. the image forming apparatus according to claim 1, wherein the controller controls the heating means so as to hold lower than 2 fixing temperature third fixing temperature. The correlation amount stored in the storage unit is configured such that when the length of the recording medium in the transport direction increases, the fixing temperature for controlling the first surface temperature decreases and the transport interval increases. The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. The correlation amount stored in the storage unit has a group in which the length in the conveyance direction of the recording medium is divided according to the area of the length, and the conveyance interval and the fixing temperature are set for each group. The image forming apparatus according to claim 3 . The transport unit includes a registration roller pair that transports the recording medium to the image forming unit in synchronization with the timing of transferring the toner image to the recording medium.
The conveyance interval setting means, the resist roller pair by changing the timing of starting the rotation, the image of any one of claims 1 to 4, characterized in that to change the conveyance interval of the recording medium Forming equipment.