JP2007139916A - Image forming apparatus and fixing control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a fixing control method which are capable of more appropriately predicting a temperature of a pressure roller in fixing processing after at least extension of a paper interval to achieve proper temperature control of a heating member. <P>SOLUTION: During extension of the paper interval when the interval between a plurality of transfer papers to be consecutively fed is longer than a prescribed time, the heating member is controlled to a target temperature for extension of the paper interval, and prediction of a first predictive temperature for setting a target temperature for paper feed is stopped, and only prediction of a second predictive temperature for setting a temperature allowing paper feed is executed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and in particular, includes a fixing device that fixes a toner image formed and transferred on a transfer paper to the transfer paper using heat and pressure. The present invention relates to an image forming apparatus and a fixing control method thereof.

  For example, in order to obtain a hard copy with a printer device or the like, first, the video controller receives document image data to be printed such as text and figures from an external device such as a host computer. The video controller develops the received image data and converts it into a video signal. When the image development is completed, the video controller transmits a signal for starting a printing operation (hereinafter referred to as a print command) to the engine controller and also transmits an image video signal. Upon receiving the print command, the engine controller irradiates a laser beam onto the photosensitive drum to form an electrostatic latent image, and develops the toner image by attaching toner to the electrostatic latent image on the photosensitive drum. The image is transferred onto transfer paper and thermally fixed by a fixing device. A hard copy is obtained by such a series of printing operations.

  When image data transferred from the outside such as a printer or a facsimile is received and image formation is continuously performed on a plurality of transfer sheets, the interval between the transfer sheet and the next transfer sheet in the fixing device (hereinafter referred to as the “transfer sheet”). The time between papers) may vary depending on the print mode or the like, but becomes more indefinite depending on the amount and type of image data. For example, if the amount of image data is large and it takes time to transfer the image data or expand the data in the video controller, or if the image data such as a graphics image is complex and requires time to process, the time between papers Becomes longer.

  When the temperature of the heating member between the sheets is kept the same as or slightly lower than that during the passage of the transfer paper through the fixing nip (hereinafter referred to as “passing paper”), if the time between the sheets becomes longer, The temperature of the pressure roller rises more than necessary. For example, if the temperature is kept at a high temperature until the image development is completed during the paper interval, the amount of heat held by the pressure roller increases and the temperature rises.

  As a defect in this case, for example, when a film is used as a heating member, when the transfer paper passes through the nip portion where the pressure roller and the film are in contact, the moisture contained in the transfer paper evaporates all at once, Will be released. This water vapor forms a layer between the pressure roller and the transfer paper, and the frictional force between the transfer paper and the pressure roller is reduced. Since the transfer paper is driven and conveyed by the frictional force, if the frictional force is reduced, the transfer paper cannot be slid and conveyed, and a slip phenomenon occurs.

  In order to avoid the occurrence of such a slip phenomenon, the target temperature of the heating member is set low during the period when the paper interval time is longer than the predetermined time (intermediate paper extension period), and the pressure roller temperature is set higher than necessary. Control so as not to increase. However, if the image development of the video controller is finished when the pressure roller temperature is too low, immediately restarting the printing operation cannot secure the amount of heat necessary to fix the toner image on the transfer paper, resulting in poor fixing. .

  Thus, the temperature of the pressure roller affects the fixability. In particular, when a film is used as the heating member, the heat capacity of the pressure roller is larger than that of the heating member, and the temperature of the pressure roller at the time when the fixing operation is started has a great influence on the fixability. For this reason, it is necessary to detect the temperature of the pressure roller during the interval between sheets and reset the target temperature of the heating member based on the detected temperature. However, if a sensor for directly detecting the temperature of the pressure roller is provided, the configuration becomes complicated and the cost increases.

In Patent Document 1, when proportional control is performed according to the difference between the surface temperature of the heating roller and the target temperature, the pressure roller temperature has a deviation from the target temperature in proportion to the heat radiation amount of the heating roller. A technique for predicting the temperature of the pressure roller from the temperature of the heating roller without using a sensor for directly detecting the temperature of the pressure roller is disclosed.
JP-A-8-262896

  There are various situations (such as the number of continuous sheets to be passed, paper size, paper type, etc.) before the inter-paper extension, and the prediction of the temperature of the pressure roller during the inter-paper extension may not always be accurate. In particular, when the fixing device is extended at a relatively low temperature, when the predicted temperature of the pressure roller becomes higher than the actual temperature of the pressure roller, the target temperature of the heating member is lower than the original temperature. Become. As a result, a situation occurs in which the target temperature of the heater is not high although the actual temperature of the pressure roller is low, and fixing failure occurs. On the other hand, if the paper is kept waiting longer than necessary, there is also a problem that the start of paper feeding immediately after the inter-paper extension period is delayed more than necessary.

  The present invention has been made in such a background, and an object thereof is to realize a prediction of a more appropriate pressure roller temperature in a fixing process after extending between papers, and thus an appropriate temperature control of a heating member. Another object of the present invention is to provide an image forming apparatus and a fixing control method.

  An image forming apparatus according to the present invention includes an image forming device that forms a toner image on transfer paper based on image information subjected to image processing, a fixing member in which a heating member having a heater and a pressure roller are pressed against each other. A fixing device that heat-fixes the toner image on the transfer paper by passing the transfer paper through a nip portion; and a control unit that controls the fixing device. The control unit controls the temperature of the pressure roller. Predicting pressure roller temperature predicting means, paper passing target temperature setting means for setting a paper passing target temperature of the heating member based on the pressure roller predicted temperature obtained by the pressure roller temperature predicting means, A paper passage permission temperature setting means for setting a paper passage permission temperature of the heating member, which may allow the transfer paper to pass through the fixing nip based on the predicted pressure roller temperature obtained by the pressure roller temperature prediction means; The And, the control means to manage separately the second predicted temperature for the first predicted temperature and passed permission temperature settings for sheet passing target temperature setting.

  The pressure roller temperature predicting means manages the first predicted temperature for setting the sheet passing target temperature and the second predicted temperature for setting the permitted sheet passing temperature separately as the predicted temperature of the pressure roller, thereby allowing The paper target temperature and the paper passing permission temperature can be set based on different conditions. Therefore, for example, it is possible to control the fixing device suitable for a special state such as extension between sheets.

  For example, the pressure roller temperature predicting unit stops the prediction of the first and second predicted temperatures during the passing of the transfer paper to the fixing nip portion, and between the plurality of transfer papers that are continuously passed. During the inter-paper extension when the inter-paper period is longer than a predetermined time, only the prediction of the second predicted temperature is executed. This is because it is not necessary to stop the prediction of the first and second predicted temperatures while the transfer paper passes through the fixing nip portion. Also, by executing only the prediction of the second predicted temperature during the paper interval extension, the first predicted temperature can be kept low, thereby preventing the sheet passing target temperature from becoming lower than necessary. it can. This functions to prevent the occurrence of fixing failure. Furthermore, by predicting the second predicted temperature, it is possible to prevent the paper passing permission temperature from becoming higher than necessary. This functions so as not to delay the fixing start time after the extension between sheets more than necessary.

  The control means adjusts the temperature of the heating member at a predetermined target temperature for a paper interval between a plurality of transfer papers that are continuously passed, and for the paper interval during the extension of the paper interval. The temperature of the heating member is controlled at the target temperature during the inter-paper extension period lower than the target temperature. By setting the target temperature during the interval between papers to be lower, it is possible to prevent the occurrence of a slip phenomenon at the time of resuming paper feeding, and the present invention is suitable for application to such fixing control.

  Temperature detecting means for detecting the temperature of the heating member may be provided, and the control means may determine the second predicted temperature during the extension of the interval according to the detected temperature of the heating member. As a result, the second predicted temperature during the inter-paper extension can be easily determined.

  When the heating member is formed of a film member, the influence of the temperature of the pressure roller on the fixing property is increased, and the present invention is suitable for application to such a configuration.

  The fixing control method according to the present invention is a fixing control method for heating and fixing a toner image formed on a transfer paper to the transfer paper, and includes a pressure roller temperature prediction step for predicting the temperature of the pressure roller, Based on the pressure roller predicted temperature obtained in the pressure roller temperature prediction step, the paper passing target temperature setting step for setting the paper passing target temperature of the heating member, and the pressure obtained in the pressure roller temperature prediction step. A paper passage permission temperature setting step for setting a paper passage permission temperature of the heating member, which may allow the transfer paper to pass through the fixing nip based on the pressure roller prediction temperature. In the pressure roller temperature prediction step, The first predicted temperature for setting the paper passing target temperature and the second predicted temperature for setting the paper passing permission temperature are managed.

  More specifically, in the pressure roller temperature predicting step, the prediction of the first and second predicted temperatures is stopped while the transfer sheet is passing through the fixing nip portion, and a plurality of transfers in which continuous sheet passing is performed. During the inter-paper extension when the inter-paper period between papers is longer than a predetermined time, only the prediction of the second predicted temperature is executed.

  According to the present invention, the first predicted temperature of the pressure roller for setting the paper passing target temperature and the second predicted temperature of the pressure roller for setting the paper passing permission temperature are managed separately, respectively. Accordingly, it is possible to appropriately set the sheet passing target temperature and the sheet passing permission temperature in accordance with the temperature state of the pressure roller corresponding to the pressure roller. As a result, it is possible to at least predict the temperature of the pressure roller more appropriately in the fixing process after extending the interval between sheets, and thus to achieve appropriate temperature control of the heating member. That is, it is possible to satisfy the fixability and to suppress the decrease in throughput while preventing the occurrence of slip at the fixing nip portion of the transfer paper at least after the inter-paper extension period.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. Hereinafter, a printer will be described as an example of an image forming apparatus. However, the present invention is not limited to a printer, and can be applied to other image forming apparatuses such as a copying machine and a facsimile.

  FIG. 1 is a diagram showing a schematic configuration of a printer system according to the present embodiment. The printer 1 receives commands and image data necessary for image output from an external device such as a host computer.

  The printer 1 analyzes data such as character information, image (graphic) information, or vector information as image data sent from an external device, converts the data into a video signal in units of pages, and this video. The laser is modulated in accordance with the signal, and an image forming device 7 for forming a visible image such as a character or an image on the transfer paper with toner, a transport device 6 for feeding and conveying the transfer paper, and a toner image on the transfer paper. It is composed of a fixing device 5 for fixing by heat and pressure, and an engine controller 4 for controlling them. In FIG. 1, the present invention relates to the fixing device 5 and its control.

  FIG. 2 is a flowchart showing a flow from reception of an image formation instruction in the printer 1 to completion of image formation. First, the video controller 3 receives image data such as texts and diagrams from an external device (S1). The video controller 3 that has received the image data transmits a preheat command for preheating the fixing device 5 to the engine controller 4 and starts image processing of the image data, and also issues a print command when the image processing is completed. Transmit (S2). The engine controller 4 starts up the high pressure, the scanner, and the fixing device when the preheat command is received (S3). In particular, the fixing device 5 starts energization of the heater and adjusts the temperature at a target temperature to be controlled. The engine controller 4 receives the print command from the video controller 3 and starts the printing operation when the preparation of the printer 1 is completed (S4, Yes) (S5).

  FIG. 3 shows a schematic configuration of the fixing device 5. The fixing device 5 includes a pressure roller (pressure member) 8 that applies pressure to the transfer paper 12, a heater 10 that heats the pressure roller 8 and applies heat to the transfer paper 12, and a temperature detection diagram. A thin-walled heating member 9 having a built-in thermistor (temperature detection means) is provided, and a transfer paper 12 carrying a toner image is passed through a fixing nip 11 formed by the heating member 9 and the pressure roller 8. The toner image is fixed on the transfer paper 12. The heating member 9 controls the output value to the heater 10 based on the temperature detected by the thermistor (hereinafter, thermistor detection temperature) TH (° C.) so that the pressure roller 8 can maintain the temperature necessary for heat fixing. ing.

  In the fixing operation of the transfer paper 12 by the fixing device 5, the set temperature of the heating member 9 is set to the paper target temperature. In particular, when a film member is used as the heating member 9, the heat capacity of the pressure roller 8 is larger than that of the heating member 9, and the temperature of the pressure roller 8 at the time of starting the fixing operation greatly affects the fixing property. The setting of the sheet passing target temperature is changed according to the temperature held by the pressure roller 8. Regarding the relationship between the paper passing target temperature and the temperature of the pressure roller 8, when the temperature of the pressure roller 8 (hereinafter referred to as pressure roller temperature) is low, the amount of heat applied from the pressure roller 8 to the transfer paper 12 is small. Increase the target temperature. On the other hand, when the pressure roller temperature is high, the amount of heat given from the pressure roller 8 to the transfer paper 12 is large, so the sheet passing target temperature is set low.

  As disclosed in Patent Document 1, conventionally, the temperature of the pressure roller is determined from the detection result of the temperature detection means for detecting the surface temperature of the heating member 9 without separately providing a means for detecting the temperature of the pressure roller. To be predicted. However, in the present invention, the specific method of the prediction is not particularly limited, and an arbitrary prediction method can be used.

  FIG. 4 shows an example of a data table (first data table) 40 that represents the relationship between the pressure roller predicted temperature and the set value of the paper passing target temperature, obtained by experiment. The pressure roller temperature predicted to set the sheet passing target temperature is set as the pressure roller predicted temperature PT1 (° C.). As can be seen from this figure, the lower the pressure roller predicted temperature PT1, the higher the sheet passing target temperature. This is because the lower the temperature of the pressure roller, the smaller the amount of heat it holds and the less it contributes to fixing.

  Actually, even if the predicted pressure roller temperature PT1 is the same, the selected print mode (normal, thick paper, OHP, postcard, etc.), the number of continuous paper passes in one job, and the size of the transfer paper 12 to be used. Since the paper passing target temperature may change depending on the case, it may be reflected in the data table. For this purpose, for example, a data table 50 in which an appropriate sheet passing target temperature value corresponding to the range of the pressure roller predicted temperature PT1 is set for each print mode as illustrated in FIG. 5 can be used.

  FIG. 6 shows a data table 60 in which an appropriate sheet feeding target temperature corresponding to the range of the pressure roller predicted temperature PT1 is set according to the number of continuous sheets of transfer paper to be fixed. ing. According to the data table 60, it is possible to set an appropriate paper passing target temperature more finely according to the number of continuous paper passing. The data table shown in FIG. 5 and the data table shown in FIG. 6 can be combined to form one data table.

  Further, at the time of fixing, it is necessary to raise the pressure roller temperature to a minimum temperature that can satisfy the fixing property. This temperature is set as “paper passing permission temperature”. At the time of fixing, the transfer paper 12 is transported to the fixing nip 11 by the transport device 6 when the thermistor detection temperature TH reaches the paper passage permission temperature. Let the pressure roller predicted temperature for setting the paper passing permission temperature be PT2. For example, as shown in a data table (second data table) 70 of FIG. 7, the paper passing permission temperature (° C.) is determined based on the predicted pressure roller temperature PT2. The numerical values in the data table 70 are obtained by experiments. As can be seen from this figure, the lower the pressure roller predicted temperature PT2, the higher the paper passing permission temperature.

In the present embodiment, prediction processing is executed for the pressure roller predicted temperatures PT1 and PT2 (° C.) in the following cases.
(1) When the printer 1 is in a standby state where it can accept a job,
(2) From receiving the preheat command to receiving the print command,
(3) When printing is started and the fixing device 5 is in a high temperature state, during a waiting time when waiting for the pressure roller temperature to fall to an appropriate temperature in order to prevent high temperature offset,
(4) If the interval between papers is longer than the specified time during continuous paper feeding,

  In states other than the above (when the transfer paper 12 is being fed and when a jam / error occurs), the pressure roller temperature prediction stops, and the pressure roller predicted temperatures PT1 and PT2 hold the values before the stop. Further, the prediction method of the pressure roller temperature in the cases (1) to (3) is exactly the same for both PT1 and PT2, and is different only in the case (4) as described later.

  Next, the pressure roller temperature prediction execution process will be described with reference to the flowchart of FIG. The program representing the execution procedure of this process is realized by the CPU in the engine controller 4 reading and executing a control program stored in the memory.

  In the process of FIG. 8, when the printer main body 1 is turned on, the heating member and the pressure roller of the fixing device 5 initially rotate (S10). During this time, the fixing device 5 performs idle rotation with temperature control at a predetermined temperature (for example, 90 ° C.), and thereafter performs idle rotation with temperature control at 0 ° C. (heater not lit) for a predetermined time (for example, 4 seconds). When the initial rotation is completed (S11, Yes), the pressure roller temperature prediction (1) is executed (S12). The pressure roller temperature prediction (1) is executed until the preheat command is received. When the preheat command is received (S13, Yes), the preheat temperature is adjusted (S14), and the pressure roller temperature prediction is performed as the pressure roller temperature prediction. Switch to (2) (S15).

  When the print command is received (S16, Yes), if the pressure roller predicted temperature PT2 is not an appropriate temperature (that is, high temperature) (S17, No), the pressure roller 8 is cooled until it falls to the appropriate temperature (S18). ). During this time, the pressure roller temperature prediction executes the pressure roller temperature prediction (3) (S19). When the predicted pressure roller temperature PT2 falls to an appropriate temperature, the pressure roller temperature prediction is stopped for both PT1 and PT2 (S20), and the temperature adjustment for passing paper is started (S21).

  Next, when there is a paper interval instruction indicating that the paper interval period has been entered (S23, Yes), temperature control for the paper interval is started (S24). At this time, the pressure roller temperature prediction is stopped, and the values of PT1 and PT2 are held. However, if the paper interval time is extended (S25, Yes), the temperature adjustment during the paper interval extension is performed (S32), and the pressure roller temperature prediction for PT2 is performed while the prediction of PT1 is stopped (4). Is executed (S33). Next, if there is a sheet passing instruction (S34, Yes), the process returns to step S20, and the prediction for both PT1 and PT2 is stopped (S20), and the temperature adjustment for sheet passing is started (S21). During continuous paper feeding, the above-mentioned temperature regulation during paper feeding and temperature regulation between papers are repeated.

  When the printing is finished and the post-rotation instruction is received (S22, Yes), the post-rotation process is executed (S27). After the post-rotation process is completed (S28, Yes), the process shifts to a standby state waiting for the preheat instruction. At this time, pressure roller temperature prediction (1) is started (S29). Thereafter, if there is a preheat instruction (S31, Yes) until the power is turned off (S30, Yes), the process returns to step S14.

  Next, a method for predicting the pressure roller temperature in the case of the pressure roller temperature prediction (4) will be described. When the image development in the video controller 3 is not completed during continuous paper feeding and a print command is not issued, or when the conveyance preparation of the transfer paper 12 by the conveyance device is slow, the inter-paper time is extended. As a result, the inter-paper temperature control is continuously executed, so that the pressure roller temperature becomes high and slipping may occur. In order to prevent this, the heating member 9 is controlled so as not to raise the temperature of the pressure roller 8 more than necessary by lowering the temperature between the papers to a predetermined temperature (for example, 100 ° C.). The pressure roller predicted temperature PT2 at this time is determined by the thermistor detection temperature TH as shown in the data table 80 of FIG. Further, the temperature prediction is stopped (that is, not executed) for the pressure roller predicted temperature PT1. The data table 80 operates to fix the predicted temperature PT2 to a predetermined temperature if the thermistor detection temperature is lower than a certain threshold temperature (105 ° C.), and to equalize the thermistor detection temperature if the temperature is equal to or higher than the threshold. This data table 80 is meaningful in relation to the data table 70 shown in FIG. The data table 80 not only defines the lower limit value of the predicted temperature PT2 of the pressure roller when the thermistor detection temperature is lower than the threshold value, but also predicts the predicted temperature PT2 higher than the actual temperature of the pressure roller when the temperature is equal to or higher than the threshold value. To do. This works for the data table 70 of FIG. 7 so as not to raise the sheet passing target temperature more than necessary. According to the data table 80 of FIG. 10, the prediction of the predicted temperature PT2 during the inter-paper extension can be performed very simply. Further, since the prediction of PT2 during the paper interval extension works on the relatively rough three-stage PT2 temperature range of the data table 70 of FIG. 7, the data table 70 having a simple configuration as shown in FIG. But it ’s enough.

  The reason for performing such control for the predicted temperatures PT1 and PT2 is as follows. As described above, since the temperature of the heating member 9 is lowered from the temperature adjustment temperature between the sheets to a lower temperature during the extension between the sheets, the temperature of the pressure roller is also decreased. Therefore, when the actual temperature of the pressure roller is lower than the predicted temperature of the pressure roller, the target temperature of the heating member is set low, resulting in a fixing failure. Therefore, during the paper interval extension, the prediction of PT1 for setting the sheet passing target temperature is not executed, and the predicted value of time t1 that has been maintained up to time t2 is maintained as it is. As a result, it is possible to avoid a situation in which the temperature of the pressure roller is overestimated and the sheet passing target temperature set based on the temperature is too low. The predicted value of the pressure roller predicted temperature PT1 at this time is likely to be lower than the actual temperature of the pressure roller, but since it is after the paper interval extension period, it is temporarily after the paper interval extension period. It is considered that there is no possibility of slipping even if the paper passing target temperature becomes higher than necessary.

  On the other hand, the reason for executing the prediction of the pressure roller predicted temperature PT2 for setting the paper passing permission temperature during the paper interval extension period is that the predicted value of the time point t2 is also maintained for the predicted value of PT2. Since the predicted value of PT2 is likely to be lower than the actual temperature of the pressure roller, the paper passing permission temperature is set higher than necessary. In such a case, the sheet passing is not permitted until the thermistor detection temperature reaches the sheet passing permission temperature set higher than necessary, resulting in a delay in the sheet passing timing immediately after the inter-paper extension period.

  For the reasons described above, prediction is executed for the pressure roller predicted temperature PT2 during paper interval extension, and for the pressure roller predicted temperature PT1, prediction is stopped and the predicted value held immediately before is used. It is a thing. As a result, it is possible to prevent a delay in processing more than necessary while preventing the occurrence of fixing failure immediately after the inter-paper extension period.

  Next, an example of setting each of the sheet passing target temperature and the sheet passing allowable temperature using the pressure roller predicted temperatures PT1 and PT2 will be described with reference to a specific temperature change graph of FIG.

  A case will be described in which the sheet passing is started in the state where the fixing device 5 is cooled and the time between sheets becomes longer. When the printer 1 is in a standby state where a job can be received, the pressure roller temperature prediction (1) described above is executed. When the engine controller 4 receives the preheat command from the video controller 3, the engine controller 4 starts energizing the heater 10 and simultaneously switches the pressure roller temperature prediction to the pressure roller temperature prediction (2) described above. Next, when a print command is received from the video controller 3 at time t1, the temperature prediction is stopped while the predicted pressure roller predicted temperatures PT1 and PT2 are maintained.

  When a print command is received, first, a sheet passing target temperature and a sheet passing permission temperature are set for the first sheet of the transfer sheet 12 based on the pressure roller predicted temperatures PT1 and PT2. At this time, since the fixing device 5 is cold, it is assumed that the predicted pressure roller temperatures PT1 and PT2 are 50 ° C., for example. According to the example of the data table 40 of FIG. 4, the paper passing target temperature is set to 206 ° C., and the paper passing permission temperature is set to “paper passing target temperature −21 ° C.”, that is, 185 ° C. from the data table 70 of FIG. The

  The transfer paper 12 is kept waiting in front of the registration roller (registration) until the thermistor detection temperature TH reaches the paper passing permission temperature. During this time, the output value to the heater 10 is controlled to raise the temperature of the heating member 9 by a target of 206 ° C. When the thermistor detection temperature TH reaches the paper passage permission temperature (= 185 ° C.), the transfer paper 12 that has been waiting before the registration is transported to the fixing nip 11 by the transport device 6 and thermally fixed.

  The temperature is adjusted at the target temperature between pages (between papers). The inter-paper time Ti can vary depending on the print mode, paper size, and the like. It also varies depending on the time required for image development.

  After the immediately preceding transfer paper 12 has passed through the fixing nip at time t2, it is determined that it has entered the paper extension period if the print command cannot be received from the video controller, and the fixing device 5 controls the heater 10 to control the heating member 9 The temperature is controlled at a target temperature of 100 ° C., which is the target temperature during the paper interval extension. At this time, the temperature prediction for obtaining the pressure roller predicted temperature PT1 for setting the sheet passing target temperature is stopped, and only the prediction of the pressure roller predicted temperature PT2 is resumed.

  For example, when a print command is received from the video controller 10 seconds after a predetermined time between papers has elapsed (time point t3), the temperature of the pressure roller at the pressure roller predicted temperature PT2 The prediction is stopped and the pressure roller predicted temperature PT2 is obtained. (The predetermined time between papers may vary depending on the print mode, paper size, etc.) At this time, the temperature adjustment time at 100 ° C. between the papers is long. For example, if the thermistor detection temperature is less than 105 ° C., FIG. According to the example of the data table 80, the pressure roller predicted temperature PT2 = 80 ° C. Since the pressure roller predicted temperature PT1 is not updated, PT1 = 50 ° C. remains.

  Based on these pressure roller predicted temperatures PT1 and PT2, the sheet passing target temperature and the sheet passing permission temperature for the next transfer sheet 12 are determined. At the pressure roller temperature, the set value is the same as that of the immediately preceding transfer sheet 12. Further, the transport sequence of the next transfer sheet 12 is also transported at the same timing as the immediately preceding transfer sheet 12, and image formation is performed. After the post-rotation is finished, the pressure roller temperature prediction (1) of PT1 and PT2 is resumed at time t4.

  When a print command is received immediately after a predetermined time has elapsed as a time between one transfer sheet and the next transfer sheet, the time for turning off the heater 10 is short, and the actual temperature of the pressure roller does not decrease. The predicted roller temperature PT2 is equal to or higher than the threshold value 105 ° C. in the data table 80 of FIG. 10, and PT2 is determined to be equal to the thermistor detection temperature. Here, taking the case of 145 ° C. as an example, the paper passing target temperature is set to 206 ° C. from the data table 40 (FIG. 4) based on the pressure roller predicted temperature PT1 = 50 ° C., and the pressure roller predicted temperature PT2 Based on = 145 (° C.), the paper passing permission temperature is set to 140 ° C. from the data table 70 (FIG. 7). At this time, since the paper passing permission temperature is 140 ° C. and the thermistor detection temperature TH is 145 ° C., it is assumed that the actual temperature of the pressure roller has reached the temperature satisfying the fixing property, and the next transfer paper is immediately Transport to the fixing nip.

  Note that when stopping in an abnormal state, such as when a jam occurs, the effectiveness of the predicted value is not guaranteed, so both PT1 and PT2 stop prediction.

The preferred embodiment of the present invention has been described above, but various modifications and changes other than those mentioned above can be made.
For example, the configurations and specific numerical values of the various data tables described above are merely illustrative examples, and the present invention is not limited to them.

1 is a system configuration schematic diagram of a printer according to an embodiment of the present invention. 2 is a flowchart illustrating a flow from reception of an image formation instruction to completion of image formation in the printer illustrated in FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. It is a figure which shows the data table showing the relationship between the setting value of predicted pressure roller temperature and paper passing target temperature calculated | required by experiment in embodiment of this invention. It is a figure which shows the data table which set the appropriate paper passing target temperature value corresponding to the range of pressurization roller estimated temperature PT1 for every printing mode in embodiment of this invention. A data table in which an appropriate sheet passing target temperature corresponding to the range of the predicted pressure roller temperature PT1 is set in accordance with the number of continuous sheets to be transferred in the embodiment of the present invention. FIG. It is a figure which shows the data table for determining paper passing permission temperature (degreeC) based on pressurization roller estimated temperature PT2 in embodiment of this invention. It is a flowchart which shows the prediction execution process of pressure roller temperature in embodiment of this invention. It is a figure for demonstrating each setting example of paper passing target temperature and paper passing permission temperature using pressurization roller prediction temperature PT1, PT2 in embodiment of this invention. It is a figure which shows the data table of the setting value of pressurizing roller estimated temperature PT2 in the embodiment of this invention during the time extension between paper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus main body 3 Video controller 4 Engine controller 5 Fixing apparatus 6 Conveying apparatus 7 Image forming apparatus 8 Pressure roller 9 Heating member (film member)
DESCRIPTION OF SYMBOLS 10 Heater 11 Fixing nip 12 Transfer paper 40, 50, 60, 70, 80 ... Data table

Claims (10)

An image forming device that forms a toner image on transfer paper based on image information subjected to image processing;
A fixing device that heats and fixes the toner image on the transfer paper by passing the transfer paper through a fixing nip formed by a heating member having a heater and a pressure roller pressed against each other; and
Control means for controlling the fixing device,
The control means includes
Pressure roller temperature prediction means for predicting the temperature of the pressure roller;
A paper passing target temperature setting means for setting a paper passing target temperature of the heating member based on the predicted pressure roller temperature obtained by the pressure roller temperature predicting means;
Based on the estimated pressure roller temperature obtained by the pressure roller temperature predicting means, the sheet passing permission temperature setting means for setting the sheet passing permission temperature of the heating member, which allows the transfer sheet to pass through the fixing nip. And
The image forming apparatus, wherein the control unit separately manages a first predicted temperature for setting a sheet passing target temperature and a second predicted temperature for setting a permitted sheet passing temperature.   The pressure roller temperature predicting unit stops the prediction of the first and second predicted temperatures during the passing of the transfer sheet to the fixing nip portion, and the interval between the plurality of transfer sheets that are continuously passed The image forming apparatus according to claim 1, wherein only the prediction of the second predicted temperature is executed during a paper interval extension when the period is longer than a predetermined time.   The control means adjusts the temperature of the heating member at a predetermined target temperature for a paper interval between a plurality of transfer papers that are continuously passed, and for the paper interval during the extension of the paper interval. The image forming apparatus according to claim 2, wherein the temperature of the heating member is controlled at a target temperature during a paper interval extension period lower than the target temperature.   The control means sets a sheet passing target temperature immediately after a sheet extending period using a first data table that defines a sheet passing target temperature corresponding to a first predicted temperature. 2. The image forming apparatus according to 2 or 3.   The control means sets a paper passage permission temperature immediately after the inter-paper extension period using a second data table that defines a paper passage permission temperature corresponding to the second predicted temperature. The image forming apparatus according to any one of 2 to 4. A temperature detecting means for detecting the temperature of the heating member;
The image forming apparatus according to claim 2, wherein the control unit determines the second predicted temperature during the inter-paper extension according to a detected temperature of the heating member.   The image forming apparatus according to claim 1, wherein the heating member is a film member. A fixing control method when heat-fixing a toner image formed on a transfer paper to the transfer paper,
A pressure roller temperature prediction step for predicting the temperature of the pressure roller;
A paper passing target temperature setting step for setting a paper passing target temperature of the heating member based on the predicted pressure roller temperature obtained in the pressure roller temperature predicting step;
A paper passage permission temperature setting step for setting a paper passage permission temperature of the heating member, which allows the transfer paper to pass through the fixing nip based on the predicted pressure roller temperature obtained in the pressure roller temperature prediction step. And
In the pressure roller temperature prediction step, a first predicted temperature for setting a sheet passing target temperature and a second predicted temperature for setting a sheet passing permission temperature are managed.   In the pressure roller temperature prediction step, the prediction of the first and second predicted temperatures is stopped while the transfer sheet is passing through the fixing nip portion, and the interval between the plurality of transfer sheets that are continuously passed is stopped. 9. The fixing control method according to claim 8, wherein only the prediction of the second predicted temperature is executed during the inter-paper extension when the period is longer than a predetermined time. An image forming device that forms a toner image on transfer paper based on image information;
A fixing device that heats and fixes the toner image on the transfer paper by passing the transfer paper through a fixing nip formed by a heating member having a heater and a pressure roller pressed against each other; and
Control means for controlling the fixing device,
The control means includes
When the temperature of the heating member is controlled at a predetermined target temperature for the interval between the plurality of transfer sheets that are continuously passed, and the interval between the sheets becomes longer than a predetermined time During the extension, the temperature of the heating member is controlled at the target temperature during the paper extension period lower than the target temperature for the paper interval,
At least during the inter-paper extension, based on the predicted temperature of the pressure roller, the heating member may start conveying the transfer paper to the fixing nip and the target temperature of the heating member at the time of the next paper passing. Set the paper passage permission temperature of the member,
During the inter-paper extension when the inter-paper period between the plurality of transfer papers that are continuously passed is longer than a predetermined time, the temperature prediction of the pressure roller is executed for setting the permissible paper passing temperature. The temperature of the pressure roller is not predicted for setting the sheet passing target temperature.

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