JP2010262035A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which sets a threshold value for determining a conveying speed to a printing mode which a user requests, and selects an optimum paper sheet-conveying speed with respect to the number of printings, which the user wants, to increasingly contribute to improvement in convenience. <P>SOLUTION: When a fixing unit 112 heats and fixes a toner image, a temperature of the fixing unit is controlled at a prescribed temperature according to the temperature of a fixing means 120 detected by a first temperature-detecting means 118, a second temperature-detecting means 119 monitors the temperature of a fixing heater 116, threshold-value information on the number of recording materials P can be updated on the basis of the result of the temperature monitoring, an updated threshold value is stored in a nonvolatile memory 312 as the latest threshold value, and information on the number of the printings in a printing mode newly instructed by a printer controller is compared with the latest threshold value stored in the nonvolatile memory to determine a recording material-conveying speed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a function of switching a plurality of recording material conveyance speeds according to a printing form and a threshold value.

  Conventionally, an electrophotographic printer is known as an example of an image forming apparatus.

  In an electrophotographic image forming apparatus, a toner image formed on each photosensitive drum is transferred to a transfer medium, and then an unfixed toner image formed on a recording material is heated and fixed by a fixing unit. Form.

  As a fixing unit used in such an image forming apparatus, an on-demand fixing unit that has a low cost and a short warm-up time has been proposed.

  A schematic configuration of such an on-demand fixing unit is shown in FIG. The fixing unit 112 of the present example is a heating device of a fixing belt heating method and a pressing rotary member driving method.

  Reference numeral 120 denotes a fixing belt as a first rotating body, which is a cylindrical member in which an elastic layer is provided on the belt-like member. Reference numeral 122 denotes a pressure roller as a second rotating body.

  Reference numeral 117 denotes a heater holder as a heating body holding member, and reference numeral 116 denotes a fixing heater as a heating body, which is disposed on the lower surface of the heater holder 117 along the longitudinal direction.

  By pressing both ends of the heater holder 117 against the pressure roller 122 by a pressure mechanism (not shown), the lower surface of the fixing heater 116 is applied to the elastic layer of the pressure roller 122 via the fixing belt 120 with a predetermined pressing force. We are pressing and holding. As a result, a fixing nip 127 having a predetermined width necessary for heat fixing is formed.

  Reference numerals 118 and 119 denote main and sub thermistors as first temperature detection means and second temperature detection means. The main thermistor 118 as the first temperature detecting means is disposed in a non-contact manner with the fixing heater 116 as a heating body. In this example, the inner surface of the fixing belt 120 is elastically contacted above the heater holder 117, the temperature of the inner surface of the fixing belt 120 is detected, and the temperature of the fixing heater 116 is set to a desired temperature by a control unit (not shown). It is controlled to become.

  The sub-thermistor 119 as the second temperature detecting means is disposed closer to the fixing heater 116 as a heat source than the main thermistor 118, and detects the back surface temperature at the end of the fixing heater 116 as a heat source.

An image forming apparatus including such a fixing unit 112 generally determines the recording material conveyance speed uniformly based on the type and size of the recording material P. For example, when printing thick paper (paper having a basis weight of about 120 g / m ² ), the amount of heat capacity of the paper is larger than when printing plain paper (paper having a basis weight of about 75 g / m ² ). Requires a lot of heat. Therefore, in addition to the full speed mode for printing plain paper as the recording material conveyance speed, a half speed mode for printing thick paper is prepared. In the thick paper mode, plain paper can also be printed.

  In such an image forming apparatus, for example, when the user requests a job for switching the printing mode alternately from plain paper → thick paper → plain paper → thick paper, the conveyance speed is determined as full speed → half speed → full speed → half speed. Each time, the paper conveyance speed was changed repeatedly for printing.

  However, in such a method, after the printing of one sheet is completed, the mechanism of the electrophotographic process is restarted at a different paper conveyance speed, and then the next printing is performed, so that the printing interval is increased and the job execution time is increased. There was a problem that would become longer. Therefore, in such a case, depending on the printing mode and the number of prints requested by the user, the printing time is shorter when printing is performed at a low conveyance speed.

  Therefore, for example, in the technique disclosed in Patent Document 1, in an image forming apparatus having at least two different printing modes and at least two different paper conveyance speeds corresponding to the printing modes, a user print A threshold is set for the request. There has been proposed an image forming apparatus that improves the performance for the user by appropriately switching between two different paper conveyance modes depending on the number of prints with respect to the threshold value.

JP 2003-122071 A

  However, in the above-described conventional example, the recording material conveyance speed is not switched by the threshold value when the same size recording material is fed by the same method and continuously printed. Also, the speed switching control based on the temperature detection of the fixing heater 116 by the sub-thermistor 119 is not performed. For this reason, when a small-sized recording material is continuously conveyed by a conventional image forming apparatus, there are the following problems.

  First, when continuously printing a small size recording material, it is conveyed as follows. However, the small-size paper referred to here is general recording paper whose length in the direction orthogonal to the conveyance direction of the recording material is shorter than the maximum sheet passing width of the fixing heater 116. For example, in the case of the fixing heater 116 shown in FIG. 10, the maximum sheet passing width is designed to be a size that can convey LETTER size paper (vertical 279.4 mm, horizontal 215.9 mm) in parallel in the vertical direction. In the fixing unit 112, a recording material having a size smaller than 216 mm in the direction orthogonal to the direction in which the recording material is conveyed is handled as a small size paper. However, A4 size paper (height 297 mm, width 210 mm) has a maximum sheet passing width of 210 mm when transported in parallel in the vertical direction, and is almost the same size as the LETTER size. Treat as. A recording material smaller than the A4 size, for example, a B5 size paper (257 mm long and 182 mm wide) is handled as a small size paper.

  First, when a small-size recording material is conveyed, heat is removed from the small-size sheet passing area of the fixing heater 116 due to the passage of the paper. However, since the main thermistor 118 controls the passing area of the small-size paper so as to have a constant temperature, electric power for supplementing the deprived heat is input to the fixing heater 116. As a result, the fixing heater 116 generates heat uniformly. However, since the heat is not taken away from the small size non-sheet passing area with respect to this heat generation, the temperature rises to a set temperature or more than the small size sheet passing area. When the number of sheets to be passed increases, this process is repeated to further increase the temperature of the small size non-sheet passing area. As a result, the temperature of the non-sheet passing area of the fixing heater 116 exceeds the heat resistance temperature of the heater holder or the like, and the fixing unit 112 is damaged.

  Therefore, when the small-size recording material is continuously conveyed, the temperature of the small-size non-sheet passing area is monitored by the sub-thermistor 119, and when the temperature reaches a predetermined temperature or more, the recording material supply timing is delayed. By increasing the recording material conveyance interval, the throughput is reduced to prevent the temperature of the non-sheet passing area of the fixing heater 116 from rising. The throughput in this case is the number of recording materials conveyed per minute and is expressed in ppm (page per minute).

  For example, when B5 size plain paper is continuously passed through the fixing device in the full speed mode as a small size recording material, the following throughput reduction is performed.

  First, when the paper feeding is started, the recording material is conveyed at a throughput of 40 ppm immediately after the start. Then, the temperature of the small size non-sheet passing area starts to rise (FIG. 11).

  When the number of continuously printed sheets increases, the temperature of the small size non-sheet passing area detected by the sub-thermistor 119 eventually reaches a predetermined temperature (250 ° C.). Then, the recording interval of the recording material is widened by the printer controller, and the throughput is reduced to 10 ppm (FIG. 12).

  In this fixing device, the temperature of the small-size non-sheet passing region reaches a predetermined temperature when approximately six sheets are passed, and the throughput after the seventh sheet is reduced to 10 ppm. As a result, when the number of sheets to be printed is large, the throughput is reduced by increasing the temperature, so that it takes a long time to execute the job.

  On the other hand, as the second recording material conveyance speed, the throughput when paper is fed in the half-speed mode is as follows.

  First, when transporting the recording material in the half-speed mode, the time required for the recording material to pass through the fixing nip is longer because the transport speed is slower than when the fixing is performed in the full-speed mode. However, a good fixed image can be obtained. Therefore, the temperature control temperature can be set lower in the half speed mode than in the full speed mode. As a result, the recording material conveyance speed becomes slower, but the temperature rise in the small size non-sheet passing area is less likely to occur, and the throughput of a larger number of recording materials is reduced compared to when the sheet is passed in the full speed mode. Can be transported without any problems.

  In this fixing device, the temperature control temperature in the half speed mode can be set to be approximately 20 ° C. lower than that in the full speed mode. As a result, as shown in FIG. Fifteen sheets can be transported before reaching.

  As described above, when a small-sized recording material is continuously conveyed, if printing is performed in the full speed mode, the job is executed in a short time when the number of printed sheets is small (in this example, six or less). However, when the number of printed sheets is large (in this example, seven or more), throughput reduction cannot be avoided, and as a result, it takes a considerable amount of time.

  On the other hand, when printing is performed in the half speed mode, the required time is short when the number of printed sheets is large, but it takes time when the number of printed sheets is small.

  The present invention has been made paying attention to the above-mentioned problems. The object of the present invention is to provide a threshold value for determining the recording material conveyance speed for the printing form, and the number of prints designated by the user is equal to or more than the threshold value. If there is, the throughput is avoided by printing in the low speed mode. On the other hand, if the number of prints instructed by the user is less than or equal to the threshold value, printing is performed in the full speed mode, and the job is completed quickly, thereby contributing to improvement in usability.

  In order to achieve the above object, the present invention has the following configuration.

A printer controller for instructing the printing mode;
A non-volatile memory for storing threshold information of the number of recording materials for determining the conveying speed of the recording material for the instructed printing mode;
A fixing unit having a heater for heating and fixing the toner image on the recording material; a first temperature detecting unit for detecting a temperature of the fixing unit; and a second temperature detecting unit for detecting a temperature of an end of the heater. A fixing unit having
In an image forming apparatus capable of heating and fixing at a plurality of recording material conveyance speeds,
When the fixing unit heat-fixes the toner image on the recording material, the temperature of the fixing unit is controlled to a predetermined temperature by the temperature detected by the first temperature detecting unit,
And the temperature of the heater is monitored by the second temperature detecting means,
The threshold information can be updated based on the result of the temperature monitoring, the updated threshold is stored as the latest threshold in the nonvolatile memory, and the number information of the printing form newly designated by the printer controller and the An image forming apparatus, wherein a recording material conveyance speed is determined by comparison with a latest threshold value stored in a nonvolatile memory.

  According to the present invention, by providing a threshold value for determining the conveyance speed for the instructed printing mode, the optimum recording material conveyance speed for selecting the number of sheets to be printed by the user is selected and executed. Is possible. As a result, it is possible to provide an image forming apparatus that can greatly contribute to the improvement of convenience for the user.

Schematic cross-sectional view of the printer mechanism in the first or second embodiment of the present invention Block diagram of the printer control unit in the first embodiment Graph of the number of sheets passed and time required for printing in the first embodiment Flowchart showing print mode discrimination control in the first embodiment Block diagram of the printer control unit in the second embodiment Schematic cross-sectional view of the printer mechanism in the third embodiment Block diagram of the printer control unit in the third embodiment Flowchart showing print mode discrimination control in the third embodiment (A) Cross-sectional view of the fixing device of the prior art and the embodiment, (b) Perspective view showing the positional relationship of the fixing heater, main thermistor, and sub-thermistor. The figure which shows the relationship between the maximum sheet passing width and the small size sheet passing area in the fixing heaters of the prior art and the embodiment. Temperature rise profile of small size paper non-passage part of fixing device Graph showing the relationship between the number of sheets passed and the required time when printing in full speed mode Graph showing the relationship between the number of sheets passed and the required time when printing in half-speed mode and full-speed mode

  Hereinafter, the form for implementing this invention is demonstrated in detail by an Example.

  FIG. 1 is a schematic view of a cross section of the image forming apparatus in the first embodiment.

  Here, 1 is a photosensitive drum for forming an electrostatic latent image, 2 is a charging roller for uniformly charging the photosensitive drum 1, and 3 is a static image formed on the photosensitive drum 1 by a laser beam 6. It is a developing device for developing an electrostatic latent image with toner. Reference numeral 4 denotes a transfer roller charger for transferring the toner image on the photosensitive drum 1 to a predetermined recording material, 5 an optical unit for scanning the laser beam 6 on the photosensitive drum 1, and 6 from the optical unit 5. This is a emitted laser beam. Reference numeral 7 denotes a fixing device that melts the toner image on the recording material and heat-fixes it on the recording material (hereinafter referred to as “paper”). This fixing device has the same configuration as the fixing unit shown in FIG.

  As described above, reference numerals 118 and 119 in FIG. 9 denote main and sub thermistors as the first temperature detecting means and the second temperature detecting means. The main thermistor 118 as the first temperature detecting means is disposed in a non-contact manner with the fixing heater 116 as a heating body. The sub-thermistor 119 monitors the temperature of the fixing heater. Further, it is installed at a position about 100 mm away from the center so that it is easy to detect the temperature rise at the end of the fixing heater 116 that is orthogonal to the conveyance direction when passing small-size paper.

  Reference numeral 8 is a standard cassette for loading sheets to be printed, 9 is a standard cassette paper feed roller for picking up paper from the standard cassette 8, 10 is a manual tray (MP tray), and 11 is a manual tray paper feed roller. Reference numeral 12 denotes a discharge roller for discharging the paper to the outside of the apparatus, and reference numeral 13 denotes a registration roller for taking the leading edge resist for printing the conveyed paper. Reference numeral 14 denotes a paper discharge sensor for confirming whether or not the paper has normally been discharged from the fixing device 7, 15 a sensor for detecting the presence or absence of paper in the standard cassette 8, and 16 paper in the manual feed tray (MP tray) 10. It is a sensor which detects the presence or absence of.

  FIG. 2 is a block diagram of the printer control unit in the first embodiment (FIG. 10).

  Reference numeral 300 denotes a printer control unit having the following configuration.

  301 receives image data through communication with the host computer 311, develops the received image data into a print form that can be printed by the printer, and exchanges signals with an engine control unit 302 described later. It is a printer controller that performs serial communication.

  Reference numeral 302 denotes an engine control unit that exchanges signals with the printer controller 301 and controls the units 303 to 309 of the printer engine via serial communication. It has.

  Reference numeral 303 denotes a paper transport control unit that feeds and transports paper to be printed and performs paper transport from the engine control unit 302 to paper discharge after printing. An optical system control unit 304 executes driving of the scanner motor and laser ON / OFF control based on an instruction from the engine control unit 302. Reference numeral 305 denotes a high voltage system control unit that executes a high voltage output necessary for an electrophotographic process such as charging, development, and transfer based on an instruction from the engine control unit 302. Reference numeral 306 denotes a fixing unit 7 based on an instruction from the engine control unit 302. It is a fixing device temperature control part which performs temperature control of this.

  The engine control unit 302 controls the paper transport of the electrophotographic printer and the mechanism unit of the electrophotographic process via the units 303 to 309 of the printer engine.

  A host computer 311 transfers image data to the printer controller 301 and sets printer printing conditions in the printer controller 301 in response to a request from the user.

  Reference numeral 312 denotes a rewritable nonvolatile memory in the printer controller 301 in which threshold information that is a condition for switching between the low speed transport speed and the high speed transport speed is stored. Further, the print mode determination unit 313 of the paper transport speed control unit compares the print mode instructed by the print job control unit 315 with threshold information for determining the paper transport speed in the non-volatile memory 312, and Determines at what speed the requested job is printed. Then, the information is transmitted to the serial communication control unit 314. Reference numeral 314 denotes a serial communication control unit that performs serial communication of the video interface with the engine control unit 302, and issues a high-speed conveyance speed designation command and a low-speed conveyance speed designation command based on information from the print mode determination unit 313. Reference numeral 315 denotes a print job control unit that analyzes a print job command from the host computer 311 and instructs the print mode determination unit 313 about a print form.

  A video interface control unit 316 analyzes serial communication from the printer controller 301. Reference numeral 317 denotes a transport speed switching control unit that receives transport speed switching information in the command analysis result from the video interface control unit 316 and instructs the paper transport control unit 303 to perform speed switching.

  In a printer system having such a printer control unit 300, various print job requests are issued from the host computer 311 to the printer controller 301. The present invention provides an image forming apparatus that improves usability and performance by selecting and executing an optimal sheet conveyance speed for these jobs.

  Next, the effect of using the form of the present embodiment will be described using experimental results.

First, the throughput when continuous paper (CLC: basis weight 80 g / m ² product number: 5548A004) of B5 size (length: 257 mm, width: 182 mm) as a small size paper from the standard cassette 8 is continuously conveyed in parallel in the vertical direction. This is similar to FIG. 12 already shown. In the figure, the horizontal axis represents the number of prints and the vertical axis represents the time required for printing. The slope of the graph represents the printing speed (ppm), and the smaller the slope, the faster the printing speed. Looking at this graph, when printing is started in the full speed mode (40 ppm), the 6 sheets immediately after the start of paper feeding are output within a short time, but the slope of the graph increases when the number of printed sheets exceeds 7 sheets. It can be seen that the print speed is reduced to 10 ppm.

  As described above with reference to FIG. 11, the temperature of the non-sheet passing area of the fixing heater 116 rises when six small-size sheets are conveyed at 40 ppm, and the detection temperature of the sub-thermistor 119 is set to a predetermined temperature (250 It is because it will reach above. In order to prevent an excessive temperature rise beyond that, it becomes necessary to delay the paper feeding timing of paper conveyance or to pause for a certain period of time. As a result, the throughput is reduced to 10 ppm. For this reason, when there are a large number of sheets to be continuously passed, if the printing is started in the full speed mode, the throughput is reduced halfway, and it takes time to execute the print job.

  On the other hand, when printing is started in the half speed mode from the beginning as shown in FIG. 3, the temperature control temperature of the fixing heater 116 can be lowered. As a result, the temperature of the non-sheet passing area of the fixing heater 116 is unlikely to rise above a predetermined temperature, and throughput is unlikely to decrease. Therefore, when the number of printed sheets is greater than 7, the printing is started in the full speed mode. The time required to execute the job is shorter than that.

  Therefore, in such a case, a threshold value N is provided for the number of printed sheets (FIG. 3), and when the number of printed sheets is smaller than the threshold value N, the full-speed mode is started and the job is executed quickly. On the other hand, when the number of printed sheets is greater than or equal to the threshold value N, it starts in the half-speed mode, and prevents excessive temperature rise where the temperature of the non-sheet passing area of the fixing heater exceeds a predetermined temperature, thereby avoiding throughput reduction Shorten total print time. At this time, a determination as to which paper conveyance speed is used for printing is performed by the print mode determination unit 313 using a comparison result with a threshold value N of the number of continuous prints stored in the nonvolatile memory 312 in advance.

  For example, assuming that the threshold N for the number of continuous prints of small-size paper is 7, if the number of continuous prints of small-size paper specified by the user is less than 7, the paper is conveyed at full speed. On the other hand, when the number of continuous prints of small size paper specified by the user is 7 or more, printing is started in the half speed mode.

  FIG. 4 is a flowchart showing the control of the print mode determination unit 313.

  First, it waits for a print request from the host computer 311 (S401).

When there is a print request, the print mode determination unit 313 analyzes the requested print job content (S402) and determines whether the job is a small size paper. (S403)
In the case of a small-size paper job, the threshold value N for paper conveyance speed switching is read (S405), the number of prints of the job is analyzed (S406), and if the threshold value (N = 7 sheets) is small, the paper is used in full speed mode. (S408) and send the job to serial communication.

  If it is equal to or greater than the threshold (N = 7 sheets), a setting is made to start printing in the half speed mode (S407), and the job is sent to serial communication.

  The threshold value of 7 sheets is stored in advance in the non-volatile memory 312 in the printer controller 301. By reading the information in this memory (S405), the print mode determination unit 313 makes a comparison determination.

  This threshold value N is uniformly set as a default value (N = 7 sheets) when the printer is shipped from the factory. Rather than printing in full speed mode in advance and reducing throughput, it is set to the number of prints at the boundary where printing time is shortened by starting in half speed mode, but in reality the environment where the printer is used and the user It varies depending on the type of paper used.

  This is because, for example, when the temperature of the environment in which the user prints is 15 ° C. and when it is 25 ° C., the temperature of the paper used also changes by 10 ° C. Then, when fixing is performed in an environment of 15 ° C., the sheet P absorbs more heat when passing through the fixing nip portion 127, so that more power is supplied to the fixing heater 116. As a result, in a low temperature environment, the temperature of the non-sheet passing area for small size paper tends to rise. Also, even when different types of paper of the same size are transported, a thick paper with a smooth surface (eg, CLC cardboard B5 product number: NS-700) takes a lot of heat in the fixing nip, A large amount of electric power is input to the fixing heater, and the temperature of the non-sheet passing area is easily increased. However, in the case of a thin recording material with a rough surface (eg, Office Planner (registered trademark) B5, product number 5553A014), since the amount of heat received in the fixing nip is small, the non-sheet passing region is difficult to increase in temperature and the threshold value N changes. To do.

  The threshold value N is also affected by a difference in temperature increase speed due to manufacturing variations among the fixing units 112. The following manufacturing variations that affect the heating speed of the fixing unit are considered.

  Variation in the amount of heat generated due to variation in the resistance value of the heating element of the fixing heater, variation in the pressing force of the pressure mechanism (pressure spring) for forming the fixing nip, and variation in the hardness of the pressure roller 122 The variation in the width of the fixing nip 127 due to the above can be considered. Therefore, it is necessary to reset the optimum threshold value N specific to the printer used by the user. This will be described below.

  Immediately after the printer is shipped from the factory and started to be used by the user, the paper conveyance speed is determined based on the threshold value N as a default value in advance. That is, if the number information of the requested job is less than N sheets, printing is performed in the full speed mode, and if it is more than N sheets, printing is performed in the half speed mode.

  On the other hand, when the number information of the requested job is exactly N, printing is performed at full speed, and the time T1 required for executing the job is measured and stored in the printer controller. When the same job is requested next time, this time, printing is performed in the half speed mode, and the time T2 required for executing the job is stored.

  By repeating the above steps for a certain period after the printer starts to be used, or for a certain number of times, the average time of T1 and the average time of T2 are obtained. From the comparison result of the obtained average times, when T1> T2, the threshold for switching the sheet conveyance speed is reset from N to N−1 sheets. Conversely, when T1 <T2, the resetting is performed from N to N + 1.

  After the resetting, the above-described process is repeated for the updated new threshold value N again after a certain period of time or after a fixed number of times of use, thereby updating to the latest threshold value N.

  The threshold value N eventually converges to an optimum value, but there is a possibility that the operating status of the image forming apparatus itself may change depending on the change of paper frequently used by the user, the change of the installation location, or the age of use. N is continuously updated.

  In this way, by continuously updating the paper transport speed threshold to the latest threshold, it is possible to always switch the paper transport speed under the optimum conditions for the user, especially when the number of prints is small. Can print faster.

  Since the configuration of the printer mechanism in the second embodiment is the same as that of the first embodiment shown in FIG. 1, the same portions are denoted by the same reference numerals and description thereof is omitted.

  FIG. 5 is a block diagram of the printer control unit 300 ′ in the second embodiment. In the second embodiment, the printer controller 301 ′ uses as data the number of small-size sheets that have been continuously passed, the conveyance speed at that time, the temperature rise rate of the fixing heater 116, the time required for job execution, and the like. Store in the nonvolatile memory 321.

  This data is information on what type of paper is frequently used by the user who uses the printer and in what environment the printer is used. Further, this corresponds to information regarding whether the fixing unit is likely to increase in temperature due to variations in manufacturing of the printer, or conversely, whether the fixing unit is difficult to increase in temperature.

  Based on this information, the recording material conveyance speed switching threshold value N is updated by the print mode determination unit 320 to a unique threshold value N optimum for the printer used by the user, as in the first embodiment.

  Hereinafter, the updating of the threshold value N specific to the printer will be described.

  Immediately after the printer is shipped from the factory and started to be used by the user, the paper transport speed is determined based on the threshold value N as a default value in advance. That is, if the number information of the requested job is N or less, printing is performed in the full speed mode, and if it is more than N sheets, printing is performed in the half speed mode.

  At this time, if the number information of the requested job is N or less, the printing speed is increased in the full speed mode and at the same time the temperature rise rate of the non-sheet passing area of the fixing heater 116 detected by the sub-thermistor 119. Keep monitoring. Then, even when the number of continuously printed sheets is small, it is possible to predict how much the temperature of the non-sheet passing area of the fixing heater 116 will rise when the number of continuously printed sheets increases further from the data of the temperature increase rate.

  As a result, it is possible to predict the number of sheets at which the fixing heater 116 will reduce the throughput after the sheet is passed, and further, it is possible to calculate the predicted value T3 of the time when the printing of N sheets is completed.

  On the other hand, when printing is performed in the half speed mode, a throughput reduction does not normally occur. Therefore, the time T4 required for printing N sheets can be obtained from the sheet conveyance speed in the half speed mode and the number N of printed sheets.

  The print mode determination unit 320 compares T3 and T4. If T3> T4, the threshold for switching the sheet conveyance speed is changed from N to N-1, and if T3 <T4, the nonvolatile memory 321 is changed from N to N + 1. Update the threshold information. When the required number of printed sheets is equal to or less than the threshold value N, the sub-thermistor 119 detects the temperature of the non-sheet passing area of the fixing heater 116 when printing in the full speed mode, and predicts the temperature rise to convey the sheet. The speed switching threshold can be updated at any time. As a result, it is possible to always switch the sheet conveyance speed under the optimum conditions for the user. In particular, when the number of prints is small, printing can be performed more quickly.

  In this way, by switching the paper conveyance speed according to the number of prints designated for printing in the requested job, it is possible to print faster when the number of prints is small.

  The configuration of the printer mechanism in the third embodiment is almost the same as in the first and second embodiments. However, as shown in FIG. 6, an environmental sensor 220 that can measure the temperature of the environment where the printer is used is installed, and the threshold N for switching the paper conveyance speed is determined for each environmental temperature. . The environmental sensor 220 is installed near the standard cassette 208 inside the printer, and can detect the temperature of the paper used. In addition, the same code | symbol is attached | subjected to the same location and description is abbreviate | omitted.

  When a printer is used by a user, even if the same user uses the same paper, the temperature of the environment may vary depending on the season and time. For example, when the temperature fluctuation of the environment is 5 ° C., the paper temperature also changes accordingly. If small-size paper having a temperature of 10 ° C. is conveyed under such conditions, only the small-size paper passing area of the fixing heater 116 is deprived of more heat. However, since the temperature of the fixing unit 112 is controlled by the main thermistor 118 so as to be maintained at a constant temperature, more electric power is supplied, and as a result, the temperature of the small size non-sheet passing area tends to rise. .

  Therefore, a method for determining the optimum sheet transport speed switching threshold N based on the detection result of the environmental temperature by the environmental sensor 220 will be described below.

  First, a threshold value is prepared every 10 ° C. according to the temperature of the environment. In this embodiment, thresholds N1, N2, N3, and N4 are set for each of the temperature ranges for cases where the environmental temperature is 5 ° C. or lower, 5 ° C. to 15 ° C., 15 ° C. to 25 ° C., and 25 ° C. or higher. The optimum threshold value is determined.

  The method for determining the optimum threshold values N1 to N4 for each temperature range is the same as the method described in the first embodiment or the second embodiment, and thus the description thereof is omitted.

  A block diagram of the printer control unit 300 ″ is shown in FIG. 7. The printer mechanism unit in the third embodiment is provided with an environment sensor input unit 330 for detecting the temperature of the environment.

  FIG. 8 is a flowchart showing the control of the print mode determination unit 320 that determines the optimum threshold N based on the detection result of the environmental temperature by the environmental sensor 220.

  First, it waits for a print request from the host computer 311 (S501).

  When there is a print request, the environmental sensor 220 reads the room temperature (T ° C.) (S503).

  The print mode determination unit 320 analyzes the contents of the print job (S502), and determines whether there is a small size paper job (S504).

  If the job is a small size paper, one of the threshold values N1 to N4 corresponding to the temperature read by the environmental sensor 220 is read (S506), and the number of prints is analyzed (S507).

  If the number of prints is small on the basis of the threshold value N, a setting is made to carry the paper in the full speed mode (S509), and the job is sent to serial communication.

  If the number of prints is large based on the threshold value N, a setting is made to start printing in the half speed mode (S508), and the job is sent to serial communication.

  As described above, based on the detection result of the environmental temperature by the environmental sensor 220, the print mode determination unit 320 appropriately sets the threshold N for switching the paper conveyance speed at the time when the printer is used in accordance with the environmental temperature. Thus, the control can be performed with higher accuracy.

112 Fixing unit 116 Ceramic heater (corresponding to the heater)
117 Heater holder 118 Main thermistor (corresponding to the first temperature detecting means)
119 Sub thermistor (corresponding to the second temperature detection means)
120 Fixing belt 127 Fixing nip 122 Pressure roller 220 Environmental sensor 300 Printer controller 301 Printer controller 302 Engine controller 312 Non-volatile memory 313 Print mode determination unit 314 Serial communication controller 315 Print job controller 317 Conveyance speed switching controller

Claims (4)

A printer controller for instructing the printing mode;
A non-volatile memory for storing threshold information of the number of recording materials for determining the conveying speed of the recording material for the instructed printing mode;
A fixing unit having a heater for heating and fixing the toner image on the recording material; a first temperature detecting unit for detecting a temperature of the fixing unit; and a second temperature detecting unit for detecting a temperature of an end of the heater. A fixing unit having
In an image forming apparatus capable of heating and fixing at a plurality of recording material conveyance speeds,
When the fixing unit heat-fixes the toner image on the recording material, the temperature of the fixing unit is controlled to a predetermined temperature by the temperature detected by the first temperature detecting unit,
And the temperature of the heater is monitored by the second temperature detecting means,
The threshold information can be updated based on the result of the temperature monitoring, the updated threshold is stored as the latest threshold in the nonvolatile memory, and the number information of the printing form newly designated by the printer controller and the An image forming apparatus, wherein a recording material conveyance speed is determined by comparison with a latest threshold value stored in a nonvolatile memory. A printer controller for instructing the printing mode;
A non-volatile memory for storing threshold information of the number of recording materials for determining the conveying speed of the recording material for the instructed printing mode;
A fixing unit having a heater for heating and fixing the toner image on the recording material; a first temperature detecting unit for detecting a temperature of the fixing unit; and a second temperature detecting unit for detecting a temperature of an end of the heater. A fixing unit having
In an image forming apparatus capable of heating and fixing at a plurality of recording material conveyance speeds,
When the fixing unit heat-fixes the toner image on the recording material, the temperature of the fixing unit is controlled to a predetermined temperature by the temperature detected by the first temperature detecting unit,
And according to the conveyance speed of the recording material controlled based on the result of the temperature monitor by the second temperature detecting means and the time required for printing,
The threshold information can be updated, the updated threshold value is stored as the latest threshold value in the nonvolatile memory, and the number information of the printing form newly instructed by the printer controller and the latest information stored in the nonvolatile memory. An image forming apparatus, wherein a recording material conveyance speed is determined by comparison with a threshold value.   The second temperature detection means is arranged at a position where an excessive temperature rise at the end of the heater can be detected when recording materials of different sizes are conveyed. The image forming apparatus according to 2.   When the monitored temperature of the heater detected by the second temperature detection unit exceeds a predetermined value, the temperature of the fixing unit is prevented from being excessively increased by changing the recording material conveyance speed. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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