JP2009216731A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recording apparatus, preventing deterioration of fixability by conducting the paper sheet carrying control according to the surface temperature of a pressure roller. <P>SOLUTION: This image forming apparatus includes a thermistor 38 for detecting the surface temperature of the pressure roller 33 coming into contact with a fixing roller 28, wherein the surface temperature data is obtained based on a detection signal from the thermistor 38 while the pressure roller is rotated. In a setting section 403, the paper carrying speed is set according to the detected surface temperature, so that when the surface temperature is low, the carrying speed is low, and when the surface temperature is high, the carrying speed is high. A carrying control part 404 conducts the carrying control based on the set carrying speed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

  In the above-described image forming apparatus, an electrostatic latent image is formed on the surface of the photosensitive drum and visualized with toner, the formed toner image is transferred to a sheet to form an image, and the toner transferred to the sheet The toner image is fixed on the sheet in the fixing device. In the fixing device, a sheet is carried into a nip portion with a press roller while rotating a heated fixing roller, and a fixing operation is performed by thermally fusing toner.

  In such a fixing device, the surface temperature of the fixing roller is constantly detected, and heating of the fixing roller is started when the surface temperature falls below a predetermined temperature. Then, heating control is performed so that heating is stopped when the surface temperature reaches a predetermined temperature so that the surface temperature of the fixing roller is maintained at the predetermined temperature. Since the fixing roller is deprived of heat by contacting the paper, it is necessary to consider this point.

  In Patent Document 1, in an electronic image recording apparatus, when a print command is issued, the fixing roller is heated, and when the temperature of the fixing roller reaches a temperature that can be fixed by low-speed conveyance, paper feeding is started by low-speed conveyance. A technique is disclosed in which when printing is performed and the temperature of the fixing roller further rises and reaches a temperature at which fixing can be performed by high-speed conveyance, paper feeding is started and printing is performed by high-speed conveyance.

  In Patent Document 2, to save energy, a high-speed printing mode, a medium-speed printing mode, and a low-speed printing mode can be set, and printing is performed when the fixing roller is heated to a temperature suitable for each printing mode. The technique made to do is disclosed.

  In Patent Document 3, based on the temperature of the fixing roller, printing is started at a low speed even when the temperature of the fixing roller is about the energy saving mode, thereby shortening the time from the printing instruction to the end of printing and the consumption. A technology of an image forming apparatus that saves electric power is disclosed.

Patent Document 4 discloses a printer in which the printing speed is made variable in order to achieve both high speed during continuous printing and shortening the time until printing of the first sheet, and the printing speed is controlled based on the temperature of the fixing roller. The technology is disclosed.
Japanese Patent Laid-Open No. 2005-3818 JP-A-2005-25041 JP 2004-145086 A JP 2000-137407 A

  When the heating control of the fixing roller is performed, it is necessary to consider the surface temperature of the press roller because the press roller pressed against the fixing roller takes heat from the fixing roller.

  In the state where the press roller is cooled, such as the same temperature as the room temperature where the image recording apparatus is installed, the fixability of the first and second sheets is not sufficient, and the image quality deteriorates. In the conventional technique described above, the temperature of the fixing roller is measured, and the printing speed is controlled based on the measurement result, but the deterioration of the image quality due to the press roller is not taken into consideration.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can prevent deterioration in fixability by controlling conveyance of a sheet according to the surface temperature of a press roller.

  An image forming apparatus according to the present invention includes an image forming unit that forms an electrostatic latent image on the surface of a photosensitive drum, develops the electrostatic latent image, and transfers a toner image onto a sheet, and a sheet on which the toner image is transferred. A fixing unit that fixes a toner image by being sandwiched between a fixing roller and a press roller and heated and pressed, a temperature detection unit that detects a surface temperature of the press roller, and a conveyance based on a detection signal from the temperature detection unit And a conveyance control unit that controls the operation. Furthermore, the conveyance control unit controls the conveyance speed of the sheet based on a detection signal from the temperature detection unit. Furthermore, the conveyance control unit controls sheet feeding timing based on a detection signal from the temperature detection unit.

  With the above-described configuration, it is possible to perform an optimal fixing process by controlling the conveyance of the sheet according to the surface temperature of the press roller.

  That is, when the press roller is cold, heat is easily taken from the heated fixing roller, and therefore, the amount of heat taken by the paper is suppressed by the paper conveyance control. For example, by lowering the sheet conveyance speed than usual, the amount of contact between the fixing roller and the sheet per unit time is reduced, and the amount of heat taken away can be suppressed. Therefore, it is possible to suppress a decrease in fixability. Further, the amount of heat transmitted from the fixing roller to the press roller increases, and the press roller is warmed quickly. In the present invention, the sheet conveyance speed is the number of sheets on which image forming processing is performed per unit time.

  If the paper feeding timing is set to be slower than usual, the interval between the conveyed papers is vacant and the time during which the paper is not in contact with the paper becomes longer. Therefore, the lowering of the surface temperature of the fixing roller can be suppressed accordingly. . In addition, the time during which the fixing roller and the press roller are in direct contact with each other becomes longer, and the press roller can be warmed quickly.

  When the press roller is warm, the amount of heat taken away from the fixing roller to the press roller is small. Therefore, even if it is controlled to increase the paper conveyance speed, the fixing property is not deteriorated.

  As described above, by controlling the conveyance of the sheet according to the surface temperature of the press roller, it is possible to perform a fine image forming process while suppressing a decrease in fixability.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic view of an entire image forming apparatus including a fixing device according to an embodiment of the present invention. A document reading unit 1 that conveys a document and reads the document is disposed at an upper part of the image forming apparatus, and a recording unit 2 that records an image, a sheet transport unit 3 that transports a sheet on which an image is recorded, and a paper feeding unit 4 is arranged.

  The document reading unit 1 includes a cover unit 10 having a document feeder (ADF) therein and a reading body unit 12 having a scanner 11. On the upper surface of the reading main body 12, a platen glass 13 is disposed at a portion for reading the conveyed document, and a placement bed 14 made of a transparent glass material is disposed at a portion for placing and reading the document or book. Yes. When reading a transported document, the scanner 11 is stopped at a position facing the platen glass 13 to perform a reading operation. When reading a document placed on the mounting bed 14, the scanner 11 reads a document or the like. Are scanned to perform a reading operation.

  A document retainer 15 is attached to the surface of the cover portion 10 facing the placement bed 14, and a document tray 16 on which a plurality of documents are placed is provided above the document retainer 15. A document placed on the document tray 16 is carried into the ADF by a pickup roller 17 and a separation roller 18, conveyed to a reading position facing the platen glass 13 by a feed roller 19, read by a scan 11, and read by a discharge roller 20. It is discharged to the document discharge tray 21.

  In the recording unit 2, a developer 22, a charging brush 23, a photosensitive drum 24, a transfer roller 25, an exposure head 26, and a memory removal brush 27 are used as an image forming unit in order to record on the sheet conveyed by the sheet conveying unit 3. It has. Further, the fixing unit includes a fixing roller 28 and a press roller 33. First, the surface of the photosensitive drum 24 is uniformly charged by the charging brush 23, and the electrostatic latent image is formed by exposing the charged surface of the photosensitive drum 24 according to the image recording signal by the exposure head 26. . Next, the toner in the developing device 22 is transferred to the electrostatic latent image formed on the photosensitive drum 24 by the supply roller and the developing roller to be visualized, and formed on the surface of the photosensitive drum 24 by the transfer roller 25. Transfer the toner image onto the paper. The transferred toner image is heated and pressed by the fixing roller 28 and fixed on the paper.

  In this way, a series of processes such as charging on the photoreceptor, exposure, development, transfer to paper and fixing are performed, and an image is formed on the paper. The toner remaining on the surface of the photosensitive drum 24 after the transfer is weakened in adhesion by a memory removal brush (ERS brush) 27 and dispersed on the surface of the photosensitive drum 10. The residual toner is collected on the developing roller of the developing device 22.

  A plurality of sheets are stacked and set in the sheet feeding cassette 5 in the sheet feeding unit 4, and are fed one by one by the sheet feeding roller 29 to the sheet conveying unit 3. The fed paper is conveyed by the feed roller 30 and is sandwiched between the feed rollers 31 and 32. Then, the sheet is conveyed to the recording unit 2 by the feed roller 31 to form an image, and the sheet subjected to the image forming process is sandwiched between the fixing roller 28 and the press roller 33 to perform the fixing process, and then the sheet discharge roller 34 and It is carried out to the paper discharge tray 36 by the press roller 35.

  FIG. 2 is a schematic sectional view of a fixing unit in which a fixing mechanism including the fixing roller 28 and a paper discharge mechanism including the paper discharge roller 34 are unitized. In the fixing unit, a fixing roller 28 and a paper discharge roller 34 are attached to the unit frame 6. A press roller 33 is provided on the lower frame 7 so as to face the fixing roller 28, and a press roller 35 is attached so as to face the paper discharge roller 34. It is assembled by fixing the lower frame 7 to the lower part of the unit frame 6.

  The thermistor 37 for detecting the surface temperature is in contact with the surface of the fixing roller 28, and the thermistor 37 is attached to the unit frame 6 and is urged toward the fixing roller 28. The thermistor 37 may be set at any position as long as the sheet conveyed to the surface of the fixing roller 28 is in contact with the surface. The thermistor 38 for detecting the surface temperature is in contact with the surface of the press roller 33, and the thermistor 38 is attached to the unit frame 7 and urged toward the press roller 33. The contact position of the thermistor 38 with the press roller 33 is set on the upstream side in the rotation direction of the press roller 33 in the vicinity of the nip position with the fixing roller 28.

  FIG. 3 is a schematic diagram illustrating a circuit configuration in the recording unit 2. The recording control unit 40 that controls the entire recording operation includes an image formation control unit 401, a fixing control unit 402, a setting unit 403, and a conveyance control unit 404.

  The image formation control unit 401 transmits a control signal to a charging voltage application circuit 41 that applies a charging voltage to the charging brush 23 and a development voltage application circuit 42 that applies a development voltage and a supply voltage to the development roller and the supply roller of the developing device 22. Thus, voltage control of each member is performed. Similarly, a control signal is transmitted to a distributed voltage application circuit 43 that applies a distributed voltage to the memory removal brush 27 and a transfer voltage application circuit 44 that applies a transfer voltage to the transfer roller 25 to control the voltage of each member. The recording control unit 40 controls the exposure of the LED head 26 based on the image signal, and forms an electrostatic latent image on the surface of the photosensitive drum 24 that is uniformly charged by the charging brush 23.

  The fixing control unit 402 performs fixing control by transmitting an on / off control signal to a heater driving circuit 46 that is driven by energizing a heater built in the fixing roller 28. At that time, a detection signal relating to the surface temperature of the fixing roller 28 from the temperature detection circuit 47 provided with the thermistor 37 is received and fixing control is performed.

FIG. 4 is a graph showing the transition of the surface temperature related to the heating control of the fixing roller by energizing the heater. The vertical axis represents the surface temperature (T), and the horizontal axis represents time (t). The surface temperature of the fixing roller is T _{0 when the} apparatus is not energized with the power off. When the power is turned on at time t ₀ , the heater is energized and heating control is started.

By starting the heating control, the fixing roller is heated and the surface temperature rises. When the set temperature (standby temperature) T ₁ in the standby state of the apparatus is reached at time t ₁ , the heater energization is controlled to be kept at the standby temperature T ₁ . Therefore, the surface temperature of the fixing roller will be the temperature change at a predetermined amplitude about the standby temperature T _1.

When a recording start signal is input at time t ₂ in the standby state of the apparatus, heating control by continuous energization of the heater is started, and the surface temperature of the fixing roller is increased again. Then, when the driving start temperature T ₂ is reached at time t ₃ , driving of the main motor is started and rotation driving of the fixing roller is started. Further, when the surface temperature rises and reaches the pickup temperature T ₃ at time t ₄ , the pickup roller is driven to rotate to start the paper feeding operation.

When the surface temperature further rises from the pickup temperature T ₃ and reaches the fixing temperature T ₄ at time t ₅ , the heater energization is controlled to be kept at the fixing temperature T ₄ . Therefore, the surface temperature of the fixing roller changes with a predetermined amplitude around the fixing temperature T ₄ .

  A temperature detection circuit 48 including a thermistor 38 as a temperature detection unit detects the surface temperature of the press roller 33. The detection start timing of the surface temperature may be performed from the time when the fixing roller 28 is driven to rotate and the press roller 33 starts to rotate. Then, the surface temperature is sampled at a predetermined time interval and a detection signal is transmitted to the recording control unit 40.

The setting unit 403 sets data for transport control based on the detection signal from the temperature detection circuit 48. FIG. 5 is a graph showing an example of setting data. The vertical axis represents the sheet conveyance speed (PV; the number of sheets subjected to image formation processing per minute), and the horizontal axis represents the surface temperature (T _P ) of the press roller. In this example, a predetermined conveyance speed is set corresponding to a surface temperature within a predetermined range. For example, in the range of the surface temperature T _P1 ° C. to T _P2 ° C., the sheet conveyance speed is set to ₁ PV / min. In the range of the surface temperature T _P2 ° C to T _P3 ° C, the paper conveyance speed is set to ₂ sheets / minute of PV, and the paper conveyance speed is set to increase as the surface temperature increases.

In this example, the paper transport speed is set, but the paper feed timing may be set. Also in this case, the sheet feeding timing is set for each surface temperature T _P within a predetermined range. For example, when the surface temperature is low, the paper feed timing is set later than usual so that the paper feed interval is widened, and the paper feed timing is advanced so that the paper feed interval becomes narrower as the surface temperature becomes higher. Set to.

  Regarding the surface temperature of the press roller, for example, the average value of the surface temperature for each rotation of the press roller is used, or the paper conveyance speed or the paper feeding timing is set using the temperature difference between the maximum temperature and the minimum temperature for each rotation. May be.

  The setting unit 403 previously registers setting data corresponding to the surface temperature as a setting table, and reads the corresponding data from the setting table in accordance with the detected surface temperature.

  The transport control unit 404 transmits a control signal to the main motor (RX) 45 to perform rotational drive control. The main motor 45 rotationally drives the pickup roller 29, the feed roller 31, the photosensitive drum 24, the supply roller and the developing roller of the developing device 22, the transfer roller 25, and the fixing roller 28 based on a control signal from the recording control unit 40. Let

  The conveyance control unit 404 controls the rotation of each roller at the sheet conveyance speed set based on the detection signal from the temperature detection circuit 48. When the paper feed timing is set, the rotation of the pickup roller 29 is controlled. The rotation of the pickup roller is controlled by turning on and off the clutch 50 that contacts and separates the drive of the main motor 45 at a set paper feed timing.

  FIG. 6 is a flow relating to the case where the paper transport speed is set when performing the recording process. First, it is checked whether or not a recording signal has been input (S100), and when the recording signal is input, the fixing roller is heated and rotated (S101). Then, the surface temperature of the press roller is detected (S102), the corresponding setting data is read based on the detected surface temperature, and the conveyance speed is set (S103).

  Next, the paper feeding operation is started (S104), and the paper is fed, whereby the rotation of each roller is controlled based on the set conveyance speed, and the image forming process is performed (S105). When the image forming process is completed, it is checked whether or not the next recording signal is input (S106). If there is a next recording signal, the process returns to step S102 to detect the surface temperature of the press roller and The transport speed is set.

  In this way, the sheet conveyance speed is adjusted according to the surface temperature of the press roller, and a satisfactory fixing process can be performed even when the press roller is cold. Further, when the press roller is warmed, the paper conveyance speed is increased and the processing speed can be increased.

  FIG. 7 is a flow relating to the case where the paper feed timing is set when performing the recording process. First, it is checked whether a recording signal is input (S200). When the recording signal is input, the fixing roller is heated and rotated (S201). Then, the surface temperature of the press roller is detected (S202), the corresponding setting data is read based on the detected surface temperature, and the paper feed timing is set (S203).

  Next, the sheet feeding operation is started based on the set sheet feeding timing (S204), and when the sheet is fed, rotation control of each roller is performed and an image forming process is performed (S205). When the image forming process is completed, it is checked whether or not the next recording signal is input (S206). If there is a next recording signal, the process returns to step S202 to detect the surface temperature of the press roller, and the paper feed timing. Is set.

  In this way, the interval between the fed sheets is adjusted according to the surface temperature of the press roller, and a satisfactory fixing process can be performed even when the press roller is cold. Further, when the press roller is warmed, the paper feed interval can be narrowed to increase the processing speed.

1 is a schematic view of an entire image forming apparatus including an embodiment according to the present invention. It is a schematic sectional drawing regarding a fixing unit. It is a whole block diagram regarding the embodiment concerning the present invention. 6 is a graph showing a transition of the surface temperature of the fixing roller with respect to heating control of the fixing roller. It is a graph which shows the conveyance speed of the paper set with respect to the surface temperature of a press roller. It is a flow relating to the case of setting the paper conveyance speed when performing the recording process. This is a flow relating to a case where paper feed timing is set when performing a recording process.

Explanation of symbols

1 Document Reading Unit 2 Recording Unit 3 Paper Conveying Unit 4 Paper Feeding Unit
28 Fixing roller
33 Press roller
34 Paper discharge roller
35 Press roller
37 Thermistor
38 Thermistor

Claims (3)

  An image forming unit that forms an electrostatic latent image on the surface of the photosensitive drum, develops the electrostatic latent image, and transfers the toner image onto a sheet, and the sheet on which the toner image is transferred is sandwiched between a fixing roller and a press roller. A fixing unit that fixes the toner image by heating and pressurizing; a temperature detection unit that detects a surface temperature of the press roller; and a conveyance control unit that controls a conveyance operation based on a detection signal from the temperature detection unit. An image forming apparatus comprising the image forming apparatus.   The image forming apparatus according to claim 1, wherein the transport control unit controls a paper transport speed based on a detection signal from the temperature detection unit.   The image forming apparatus according to claim 1, wherein the conveyance control unit controls sheet feeding timing based on a detection signal from the temperature detection unit.

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