JP2021185404A - Image forming apparatus - Google Patents

Abstract

To prevent damage to a fuser and a reduction in usability after printing on small-size paper.SOLUTION: An image forming apparatus comprises: a transfer roller 106 that transfers a toner image on a photoconductor drum 122 to a sheet; a paper feed tray 140 that feeds the sheet to which the toner image is transferred; a fuser 130 that fixes the transferred toner image to the sheet; and an engine control unit 202 that controls the feeding and conveyance of the sheet. The fuser 130 has a fixing film 133 that heats the toner image on the sheet and a pressure roller 134 that is in contact with the fixing film 133 to form a nip part and applies pressure to the toner image on the sheet. When the sheet on the paper feed tray 140 is replaced between the completion of a print job for printing a small-size sheet and execution of the next print job, the engine control unit 202 extends the drive time of the pressure roller 134 in a state in which it does not pass a sheet through the nip part compared with the drive time of the pressure roller 134 when the sheet is not replaced (S401-S404).SELECTED DRAWING: Figure 4

Description

The present invention relates to an image forming apparatus using an electrophotographic process.

Among image forming devices using an electrophotographic process, there is an image forming device provided with a film heating type fixing device capable of suppressing power supply during standby. In the film heating type fuser, the paper on which the toner image is transferred is conveyed to the nip portion between the fixing film containing the heater and the pressurizing roller, and the conveyed paper is heated and pressed at the nip portion to heat and pressurize the toner. Fix the image on the paper. In such a fuser, when paper having a narrow width (length in the direction orthogonal to the paper transport direction) such as A5 size (hereinafter referred to as small size paper) passes through the nip portion, the end of the pressure roller The part does not come into contact with the passing paper. As a result, the temperature of the end portion of the pressure roller becomes larger than that of the paper passing portion of the pressure roller whose temperature drops when it comes into contact with the passing paper. Therefore, if the temperature of the pressure roller continues to rise due to continuous printing of small size paper, parts such as the pressure roller may exceed the heat resistant temperature and be damaged by heat.

In order to prevent such heat damage, during continuous printing, when the paper width sensor provided on the transport path detects that the paper being continuously printed is small size paper, the paper is fed. Increase the interval to reduce throughput. As a result, in the non-passing section (non-passing period) in which the paper does not pass through the fuser, the temperature of the end of the pressurizing roller and the temperature of the passing section are equalized, and the temperature of the end of the pressurizing roller rises. Suppress. As the length of the paper in the transport direction is shorter, the amount of temperature rise at the end of the pressurizing roller per sheet of paper is smaller, so that the amount of throughput reduction can be reduced. That is, while continuously printing A5 size paper, it is assumed that the paper that is conveyed to the fuser and then transferred to the fuser is also A5 size, and the A5 size paper is continuously transferred to the fuser. Set the throughput in anticipation of the amount of temperature rise at the end of the pressurizing roller when the paper is transported. As a result, the optimum throughput can be realized within the range where the heat resistant temperature of the component is not exceeded.

In addition, wide paper such as A4 size paper (hereinafter referred to as large size paper) with the temperature of the end where the paper of the pressurizing roller of the fuser does not pass and the temperature of the paper passing part through which the paper passes are non-uniform. When the paper is transported, a phenomenon called hot offset may occur. In order to prevent the occurrence of hot offset in which the image formed on the edge of the paper is over-fixed, the image forming apparatus performs the following post-processing operation. That is, when printing on small-sized paper is finished, the fuser is driven (backward rotation) for a certain period of time with the power supply to the heater of the fuser stopped in preparation for the next printing job. Lowers the temperature of the end of the pressurizing roller. For example, in the image forming apparatus described in Patent Document 1, the paper size of the print job currently being executed is compared with the paper size of the print job to be executed next, and the back rotation time for suppressing the occurrence of hot offset is set. We are optimizing.

JP-A-2018-774403

Since the next print job cannot be executed during the period during which the post-rotation is performed after the print job is completed, the shorter the post-rotation time, the better the usability. Therefore, if the post-rotation time after continuous printing of small-sized paper is determined assuming that the length of the paper used in the next print job is the same as that of the immediately preceding print job, at the start of the next print job. Can be optimally set within the range that does not exceed the heat resistant temperature of the parts. However, if the paper used in the next print job is longer in the transport direction than the paper used in the previous print job, the amount of temperature rise at the end of the pressurizing roller per sheet of paper is higher than expected. May also damage the parts of the fuser. In order to prevent damage, if the back rotation time is set to the time assuming the longest paper that can be introduced into the fuser, the next print job assumes the same length as the previous print job. It will be longer than the post-rotation time. As a result, when the next print job uses the same size paper as the previous print job, unnecessary waiting time increases and usability deteriorates.

The present invention has been made under such circumstances, and an object of the present invention is to prevent damage to the fuser and deterioration of usability after printing small size paper.

In order to solve the above-mentioned problems, the present invention has the following configurations.

(1) An image forming unit having a photosensitive drum and transferring a toner image formed on the photosensitive drum to a sheet, a paper feeding means for feeding a sheet on which the toner image is transferred, and a transferred toner image. The fixing means is provided with a fixing means for fixing the sheet to the sheet and a control means for controlling the feeding and transporting of the sheet. The fixing means has a heating member for heating the toner image on the sheet and a nip in contact with the heating member. It has a pressurizing member that forms a portion and pressurizes a toner image on the sheet, and the control means ends a preceding printing job of printing a small-sized sheet in which the width of the sheet is smaller than a predetermined width. When the sheet accommodated in the paper feeding means is replaced between the time when the sheet is executed and the time when the next printing job is executed, the time for driving the pressurizing member without allowing the sheet to pass through the nip portion is set. An image forming apparatus, characterized in that, when the sheet accommodated in the paper feeding means is not replaced, the time for driving the pressurizing member is extended.

According to the present invention, it is possible to prevent damage to the fuser and deterioration of usability after printing small size paper.

Sectional drawing which shows the structure of the image forming apparatus of Example 1. A block diagram showing a system configuration of the image forming apparatus of Examples 1 to 3. Flow chart showing the control sequence of the paper feed operation of Examples 1 to 3 A flowchart showing a control sequence of the backward rotation operation of the first embodiment. Sectional drawing which shows the structure of the image forming apparatus of Examples 2 and 3. A flowchart showing a control sequence of idle rotation operation before printing in the second embodiment. A flowchart showing a control sequence of the backward rotation operation of the third embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Structure of image forming apparatus]
FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus of the first embodiment. In this embodiment, a laser beam printer 100 (hereinafter referred to as a printer 100) is used as an image forming apparatus. In FIG. 1, the photosensitive drum 122 is made of an organic photosensitive member or an amorphous silicon photosensitive member, and is rotationally driven at a predetermined peripheral speed (process speed) in the clockwise direction in the drawing. The charging roller 123 uniformly charges the surface of the photosensitive drum 122 with a potential of a predetermined polarity. The scanner 108 scans the photosensitive drum 122 with a laser beam modulated according to image data input from an image reader (not shown), an external computer (not shown), or the like. Then, the laser beam output from the scanner 108 according to the image data is applied to the photosensitive drum 122 to form an electrostatic latent image on the surface of the photosensitive drum 122. The electrostatic latent image formed on the photosensitive drum 122 (on the photosensitive drum) is developed by the adhesion of toner by the developing roller 121, and the toner image is formed. The photosensitive drum 122, the charging roller 123, the developing roller 121, the scanner 108, and the transfer roller 106 described later constitute an image forming unit.

The printer 100 has a paper feed tray 140 in which a paper (also referred to as a sheet) P as a recording material is housed. The paper feed roller 101 feeds paper P from the paper feed tray 140, and the registration sensor 105 detects that the paper feed has reached the registration roller 104. The registration sensor 105 is turned on when the paper P is detected, and turned off when the paper P is not detected. The paper presence / absence sensor 141, which is a sheet detecting means, detects the presence / absence of paper P housed in the paper feed tray 140. Further, the transport paper width sensor 107 (hereinafter referred to as a width sensor 107) is arranged on the downstream side of the paper P of the registration sensor 105 in the transport direction, and is a length of the paper P in a direction orthogonal to the transport direction of the paper P. Detect the width. The width sensor 107 is turned on when the width of the paper P is 190 mm or more, and turned off when the width of the paper P is less than 190 mm. After that, the paper P is conveyed to the nip portion between the transfer roller 106 and the photosensitive drum 122 by the registration roller 104. A voltage having a polarity opposite to that of the toner is applied to the transfer roller 106, and a voltage having a polarity opposite to that of the toner is applied from the back surface of the paper P, so that the toner image on the photosensitive drum 122 is displayed on the paper P (on the sheet). Transferred.

The paper P on which the toner image is transferred is separated from the photosensitive drum 122 and conveyed to the fixing device 130. The fuser 130 is composed of a fixing film 133, a heater 132 that heats the fixing film 133, a thermistor 131 that detects the temperature of the heater 132, and a pressing roller 134 that forms a fixing nip portion together with the fixing film 133 and pressurizes the paper P. Has been done. The paper P on which the toner image is transferred is introduced into the fixing nip portion of the fixing film 133 which is a heating member and the pressure roller 134 which is a pressure member, and is pressurized and heated, and the toner image is fixed to the paper P. Will be done. The fixing / discharging sensor 109 detects the feeding state of the paper P conveyed from the fixing device 130. The fixing / discharging sensor 109 is turned on (ON) when the paper P is detected, and turned off (OFF) when the paper P is not detected. In the case of single-sided printing, the paper P that has passed through the fixing / discharging sensor 109 is conveyed by the discharging roller 111 and discharged to the discharging tray 112. On the other hand, in the case of double-sided printing, the paper P that has passed through the fixing / discharging sensor 109 is provided on both sides in the direction indicated by the arrow D in the figure by the discharging roller 111 whose rotation direction is switched by the reversing solenoid (not shown). It is transported to the transport path 114. The paper P conveyed to the double-sided transfer path 114 is conveyed by the double-sided transfer roller 113. After that, the paper P reaches the registration roller 104 again, is conveyed to the nip portion of the transfer roller 106 and the photosensitive drum 122, and the toner image is transferred to the opposite surface of the paper P, and the toner image is transferred to the fuser 130. The toner image is fixed on the paper P. Then, the paper P that has passed through the fuser 130 is discharged to the discharge tray 112 by the discharge roller 111 whose rotation direction has been restored by the reversing solenoid (not shown).

[System configuration of image forming device]
Next, the system configuration of the printer 100 will be described. FIG. 2 is a block diagram showing a system configuration of the printer 100. In FIG. 2, the printer 100 includes a controller unit 201 and an engine control unit 202. The controller unit 201 can communicate with the engine control unit 202 via the host computer 200, which is an external device, and the video interface unit 203.

The host computer 200 transmits print conditions, image data to be printed, and print commands to the controller unit 201 of the printer 100. The controller unit 201 converts the image data received from the host computer 200 into exposure data that can be output from the scanner 108, and creates print reservation information for each print page based on the received print conditions. Here, the print reservation information is, for example, a paper feed tray 140 indicating a supply source for supplying the paper P, a size of the paper P, and a print mode (single-sided printing, double-sided printing, etc.).

The controller unit 201 transmits a print reservation instruction including print reservation information of each print page to the engine control unit 202 via the video interface unit 203. Then, when the conversion from the image data to the exposure data is completed, the controller unit 201 transmits a print start instruction to the engine control unit 202. Upon receiving the print start instruction from the controller unit 201, the engine control unit 202 controls each unit of the printer 100 to start the image forming operation. The engine control unit 202 has a CPU (not shown) as a control means, a ROM (not shown) and a RAM (not shown) as storage means, and controls the image forming operation of the printer 100. Further, the CPU has a timer for measuring the time. The CPU performs image formation control according to a control program stored in the ROM. In addition, data and parameters required for various controls are also stored in the ROM. The RAM temporarily stores the control data acquired from each device in the printer 100, and is also used as a work area for arithmetic processing accompanying the execution of the control program.

The drive control unit 209 controls the main motor 204, the paper feed clutch 214, and the reversing solenoid 215 to rotate and drive each roller inside the printer 100 by the main motor 204. The main motor 204 rotates and drives the above-mentioned paper feed roller 101, registration roller 104, photosensitive drum 122, transfer roller 106, pressure roller 134, discharge roller 111, and double-sided transfer roller 113. The main motor 204 and the paper feed roller 101 are connected to each other via the paper feed clutch 214. When the paper P is fed from the paper feed tray 140, the drive control unit 209 controls the paper feed clutch 214 for a predetermined time to connect the main motor 204 and the paper feed roller 101, and the paper feed roller 101. Is driven to rotate. Further, the reversing solenoid 215 switches the rotation direction of the discharge roller 111 according to the control of the drive control unit 209.

The exposure control unit 208 rotates the scanner motor (not shown) provided in the scanner 108 and corrects the exposure amount of the laser that emits the laser beam in response to the instruction from the engine control unit 202. Further, the exposure control unit 208 controls the irradiation of the photosensitive drum 122 with the laser beam according to the exposure data received from the controller unit 201 via the video interface unit 203. The high voltage control unit 210 controls a high voltage power supply device that applies a DC voltage or an AC voltage to a member in the printer 100 to which a high voltage is applied, for example, a charging roller 123, a developing roller 121, and a transfer roller 106.

The fixing control unit 211 detects the surface temperature of the heater 132 by the thermistor 131 provided in the fixing device 130, and controls the power supply to the heater 132 according to the detected surface temperature. The sensor input unit 212 acquires the detection information of the registration sensor 105, the width sensor 107, the paper presence / absence sensor 141, and the fixing / discharging sensor 109 described above, and outputs the detection information to the engine control unit 202. The paper exchange detection unit 220 detects whether or not the paper P in the paper feed tray 140 has been exchanged based on the detection information acquired from the paper presence / absence sensor 141. The end temperature estimation unit 221 which is an estimation means estimates the temperature of the end of the pressurizing roller 134 of the fuser 130 according to the state of the fuser 130. The paper exchange detection unit 220 and the end temperature estimation unit 221 may have functions of the engine control unit 202 instead of the device provided inside the printer 100.

[Image formation operation]
Subsequently, the image forming operation of the printer 100 described above will be described. The image forming operation is started when the engine control unit 202 receives a print start instruction from the controller unit 201. First, in preparation for printing, the engine control unit 202 controls the drive control unit 209 to drive the main motor 204, controls the high voltage control unit 210, and uses the charging roller 123 to cover the surface of the photosensitive drum 122. It is charged to the same potential. Further, the engine control unit 202 controls the fixing control unit 211 to start supplying electric power to the heater 132 as a start-up operation of the fixing device 130. The engine control unit 202 determines that the fuser 130 is ready when a predetermined time has elapsed from the start-up of the fuser 130, controls the drive control unit 209, and drives the paper feed roller 101 via the paper feed clutch 214. Then, the paper P is fed from the paper feed tray 140. When the engine control unit 202 acquires the detection information of the tip of the paper P from the registration sensor 105 via the sensor input unit 212, the engine control unit 202 instructs the controller unit 201 to output the exposure data to the scanner 108 after a predetermined time has elapsed. Pixel signal to output the start signal.

The engine control unit 202 controls the exposure control unit 208 to irradiate the photosensitive drum 122 with laser light corresponding to the pixel signal output from the controller unit 201 by the scanner 108, and creates an electrostatic latent image on the photosensitive drum 122. To form. Toner is adhered to the electrostatic latent image formed on the photosensitive drum 122 by the developing roller 121, and a toner image is formed. The toner image formed on the photosensitive drum 122 is fed from the paper feed tray 140 and transferred to the paper P conveyed to the nip portion between the photosensitive drum 122 and the transfer roller 106.

The paper P passes through the nip portion between the photosensitive drum 122 and the transfer roller 106, is peeled from the photosensitive drum 122, and then is conveyed to the fixing device 130. Then, the paper P is pressed and heated in the fixing nip portion formed by the fixing film 133 and the pressure roller 134, so that the toner image is fixed to the paper P. Then, in the case of single-sided printing, the paper P that has passed through the fuser 130 is discharged onto the discharge tray 112 on the upper part of the printer 100 via the discharge roller 111 with the printing side facing down. On the other hand, in the case of double-sided printing, the engine control unit 202 detects that the paper P has passed through the fixing / discharging sensor 109 by the fixing / discharging sensor 109 via the sensor input unit 212. Then, the engine control unit 202 controls the drive control unit 209, switches the rotation direction of the discharge roller 111 by the reversing solenoid 215, and transports the paper P to the double-sided transport path 114 in the direction indicated by the arrow D in FIG. .. Then, the paper P is conveyed through the double-sided transfer path 114 by the double-sided transfer roller 113, then reaches the registration roller 104 again, and is conveyed to the nip portion of the transfer roller 106 and the photosensitive drum 122. Then, at the nip portion between the transfer roller 106 and the photosensitive drum 122, the toner image is transferred to the surface opposite to the paper P, and the toner image is fixed to the paper P by the fixing device 130. Then, the paper P that has passed through the fuser 130 is discharged to the discharge tray 112 by the discharge roller 111 whose rotation direction has been restored by the reversing solenoid (not shown).

[Temperature change in pressure roller]
In the following, paper P having a narrow width (length in the direction orthogonal to the paper transport direction) such as A5 size is described as small size paper, and paper P having a wide width such as A4 size is described as large size paper. I decided to. The width of the pressure roller 134 of the fuser 130 (the length in the direction orthogonal to the transport direction of the paper P) is a size corresponding to the width of the large-sized paper. Therefore, when the small-sized paper passes through the fuser 130, the temperature of the passing portion where the small-sized paper of the pressurizing roller 134 comes into contact is lowered due to the heat being taken away by the small-sized paper, and the small-sized paper becomes The temperature of the non-passing paper part (hereinafter referred to as the end part) that does not come into contact does not drop. As a result, the temperature of the end portion of the pressure roller 134 rises higher than that of the paper passing portion. Therefore, in order to prevent heat damage to the pressure roller 134, the interval at which small size paper is fed from the paper feed tray 140 is made longer than in the case of large size paper, and the temperature at the end of the pressure roller 134 is increased. Lower. Therefore, it is necessary to secure the idle rotation time of the fuser 130 (pressurizing roller 134) for a longer time than in the case of large size paper.

Table 1 is a table showing the amount of temperature change per unit time (100 msec (milliseconds) in Table 1) of the end portion of the pressurizing roller 134 in each state of the fuser 130. The left column of Table 1 shows the "state" of the fuser 130. In "small size paper passing", small size paper to which the toner image formed at a process speed of 170 mm / sec is transferred passes through the pressure roller 134 while power is being supplied to the heater 132 of the fuser 130. It refers to the state of being. Further, in "idle rotation" and "stop", the fuser 130 (pressurizing roller 134) is driven (idle rotation) and stopped with the power supply to the heater 132 of the fuser 130 stopped, respectively. Refers to the state of Further, "other" refers to a state excluding the above-mentioned state of the fuser 130, that is, a state in which power is being supplied to the heater 132 of the fuser 130 and the paper P does not pass through the pressurizing roller 134. pointing. On the other hand, the right column of Table 1 shows the amount of temperature change (unit: ° C.) of the pressurizing roller 134 per unit time according to the state of the fuser 130 shown in the left column, and "-" in Table 1. Indicates a decrease in temperature. From Table 1, the temperature per unit time (100 msec) of the pressurizing roller 134 in "small size paper passing" increased by 1.4 ° C, and the temperature per unit time in "idle rotation" and "stop" was changed. It decreases by 0.3 ° C and 0.1 ° C, respectively. Further, in the "other" state, the temperature of the pressure roller 134 per unit time rises by 1.4 ° C.

［加圧ローラの端部温度の推定］
図３は、プリンタ１００において、用紙Ｐへの印刷ジョブ実行時の用紙Ｐの給紙動作の制御シーケンスを示すフローチャートである。図３（ａ）は、端部温度推定部２２１（図２）が、加圧ローラ１３４の端部の温度を定着器１３０の状態に応じて算出する制御シーケンスを示すフローチャートである。図３（ａ）に示す処理は、プリンタ１００の電源がオンされると起動され、端部温度推定部２２１により、エンジン制御部２０２が画像形成動作の制御を行っているか否かによらず、常時実行される。なお、端部温度推定部２２１は、エンジン制御部２０２により実行される機能であり、上述した表１のデータは、エンジン制御部２０２内のＲＯＭに格納されているものとする。 ステップ（以下、Ｓとする）３２１では、端部温度推定部２２１は、センサ入力部２１２を介して、サーミスタ１３１が検知したヒータ１３２の温度情報を取得し、加圧ローラ１３４の端部の温度（以下、端部温度ともいう）とする。Ｓ３２２では、端部温度推定部２２１は、後述する図３（ｂ）の処理で設定される定着器１３０の状態に応じて、ＲＯＭに格納された表１より対応する状態における単位時間あたりの温度変化量に基づいて、加圧ローラ１３４の端部の温度を更新する。Ｓ３２３では、端部温度推定部２２１は、タイマをリセットしてスタートさせ、タイマが加圧ローラ１３４の端部の温度を更新する単位時間である１００ｍｓｅｃ（ミリ秒）が経過したかどうか判断する。端部温度推定部２２１は、タイマを参照して１００ｍｓｅｃが経過したと判断すると処理をＳ３２２に戻し、１００ｍｓｅｃが経過していないと判断すると処理をＳ３２３に戻す。なお、更新された加圧ローラ１３４の端部の温度が、サーミスタ１３１により検知されるヒータ１３２の温度を下回っていた場合には、端部温度推定部２２１は、サーミスタ１３１の検知温度と同じ温度に補正する。

[Estimation of end temperature of pressure roller]
FIG. 3 is a flowchart showing a control sequence of the paper feeding operation of the paper P when the print job is executed on the paper P in the printer 100. FIG. 3A is a flowchart showing a control sequence in which the end temperature estimation unit 221 (FIG. 2) calculates the temperature of the end of the pressurizing roller 134 according to the state of the fuser 130. The process shown in FIG. 3A is started when the power of the printer 100 is turned on, and regardless of whether or not the engine control unit 202 controls the image forming operation by the end temperature estimation unit 221. Always run. The end temperature estimation unit 221 is a function executed by the engine control unit 202, and it is assumed that the data in Table 1 described above is stored in the ROM in the engine control unit 202. In the step (hereinafter referred to as S) 321, the end temperature estimation unit 221 acquires the temperature information of the heater 132 detected by the thermistor 131 via the sensor input unit 212, and obtains the temperature of the end of the pressurizing roller 134. (Hereinafter, also referred to as end temperature). In S322, the end temperature estimation unit 221 is the temperature per unit time in the corresponding state from Table 1 stored in the ROM according to the state of the fuser 130 set in the process of FIG. 3 (b) described later. The temperature at the end of the pressurizing roller 134 is updated based on the amount of change. In S323, the end temperature estimation unit 221 resets and starts the timer, and determines whether or not 100 msec (milliseconds), which is a unit time for the timer to update the temperature of the end portion of the pressurizing roller 134, has elapsed. The end temperature estimation unit 221 refers to the timer and returns the process to S322 when it is determined that 100 msec has elapsed, and returns the process to S323 when it determines that 100 msec has not elapsed. When the temperature of the end of the updated pressure roller 134 is lower than the temperature of the heater 132 detected by the thermistor 131, the end temperature estimation unit 221 has the same temperature as the detection temperature of the thermistor 131. Correct to.

[Relationship between the end temperature of the pressure roller and the paper feed interval]
Table 2 shown below is a table showing the relationship between the temperature at the end of the pressurizing roller 134 and the paper feeding interval. In Table 2, the left column shows the temperature of the end of the pressurizing roller 134 estimated by the process of FIG. 3A, and the right column shows the supply according to the temperature of the end of the pressurizing roller 134. The paper feed interval (unit: msec (millisecond)) for feeding paper P from the paper tray 140 is shown. According to Table 2, when the temperature of the end of the pressure roller 134 is 0 ° C. or higher and lower than 190 ° C., 190 ° C. or higher and lower than 200 ° C., and 200 ° C. or higher and lower than 210 ° C., 3000 msec and 5000 msec, respectively. A paper feed interval of 6500 msec is required. Similarly, when the temperature of the end of the pressure roller 134 is 210 ° C. or higher and lower than 220 ° C., 220 ° C. or higher and lower than 230 ° C., and 230 ° C. or higher and lower than 240 ° C., 8000 msec, 13000 msec, and 15000 msec, respectively. A paper feed interval is required. Further, when the temperature of the end of the pressurizing roller 134 is 240 ° C. or higher, a feeding interval of 30,000 msec is required.

［用紙の給紙制御］
続いて、図３（ｂ）に示すフローチャートにおける処理について説明する。図３（ｂ）は、用紙Ｐへの印刷時における、給紙トレイ１４０からの用紙Ｐの給紙動作を制御する制御シーケンスを示すフローチャートである。図３（ｂ）に示す処理は、エンジン制御部２０２がコントローラ部２０１から印刷ジョブ（先行の印刷ジョブ）のプリント開始指示を受信すると起動され、エンジン制御部２０２により実行される。後述するように、エンジン制御部２０２は、画像形成動作中に、図３（ａ）において加圧ローラ１３４の端部温度を推定するための定着器１３０の状態の設定を行い、推定された加圧ローラ１３４の端部温度に応じて、用紙Ｐの給紙間隔を制御する。

[Paper Feed Control]
Subsequently, the processing in the flowchart shown in FIG. 3B will be described. FIG. 3B is a flowchart showing a control sequence for controlling the paper feeding operation of the paper P from the paper feed tray 140 at the time of printing on the paper P. The process shown in FIG. 3B is started when the engine control unit 202 receives a print start instruction of a print job (preceding print job) from the controller unit 201, and is executed by the engine control unit 202. As will be described later, the engine control unit 202 sets the state of the fuser 130 for estimating the end temperature of the pressurizing roller 134 in FIG. 3A during the image forming operation, and the estimated addition is performed. The paper feeding interval of the paper P is controlled according to the temperature at the end of the pressure roller 134.

In S301, the engine control unit 202 controls the fixing control unit 211 to supply electric power to the heater 132, and the state of the fixing device 130 referred to in the process of S322 in FIG. Set to "Other". In S302, the engine control unit 202 controls the drive control unit 209 to drive the paper feed roller 101 via the paper feed clutch 214, and starts paper feeding from the paper feed tray 140. In S303, the engine control unit 202 acquires the state of the registration sensor 105 via the sensor input unit 212. When the engine control unit 202 detects that the registration sensor 105 is in the ON state, the process proceeds to S304, and when it detects that the registration sensor 105 is not in the ON state (is in the OFF state), the process is performed. Return to S303. In S304, the engine control unit 202 resets the timer and starts the paper P after calculating the time for the paper P to be transported on the transport path from the registration sensor 105 to the width sensor 107. Then, the engine control unit 202 waits while referring to the timer until the calculated time elapses and the paper P is conveyed to the width sensor 107 and the width of the paper P is detected, and when the calculated time elapses. , Proceed to processing to S305.

In S305, the engine control unit 202 acquires the state of the width sensor 107 via the sensor input unit 212. When the engine control unit 202 detects that the registration sensor 105 is in the off state, the engine control unit 202 determines that the paper P being conveyed is small size paper, and proceeds to process with S306. On the other hand, when the engine control unit 202 detects that the width sensor 107 is in the on state (not in the off state), the engine control unit 202 determines that the paper P being conveyed is a large size paper, and processes the paper P in S313. Proceed.

In S306, the engine control unit 202 acquires the state of the fixing / discharging sensor 109 via the sensor input unit 212. When the engine control unit 202 detects that the state of the fixing / discharging sensor 109 is on, it determines that the paper P is passing through the pressurizing roller 134 of the fixing device 130, and sets the process to S307. Proceed. On the other hand, when the engine control unit 202 detects that the state of the fixing / discharging sensor 109 is not in the on state (off state), the engine control unit 202 determines that the paper P has not reached the fixing device 130, and performs processing. Return to S306. In S307, the engine control unit 202 sets the state of the fuser 130 referred to in the process of S322 of FIG. 3A to “in small size paper passing” in Table 1.

In S308, the engine control unit 202 acquires the state of the fixing / discharging sensor 109 via the sensor input unit 212. When the engine control unit 202 detects that the state of the fixing / discharging sensor 109 is in the off state, the engine control unit 202 determines that the paper P has passed through the pressurizing roller 134 of the fixing device 130, and proceeds to the process to S309. On the other hand, when the engine control unit 202 detects that the state of the fixing / discharging sensor 109 is not in the off state (is in the on state), the paper P is passing through the pressurizing roller 134 of the fixing device 130. Judgment is made, and the process is returned to S308. In S309, the engine control unit 202 controls the fixing control unit 211 to stop the power supply to the heater 132, and the fixing device 130 (pressurizing roller 134) referred to in the process of S322 in FIG. 3A. Set the state to "idle rotation" in Table 1.

In S310, the engine control unit 202 determines whether the print job being executed is double-sided printing, proceeds to S311 if it is determined to be double-sided printing, and determines that it is not double-sided printing (single-sided printing). The process proceeds to S312. In S311 the engine control unit 202 controls the fixing control unit 211 to supply electric power to the heater 132, and sets the state of the fixing device 130 to “Other” in Table 1. Then, the engine control unit 202 controls the drive control unit 209, switches the rotation direction of the discharge roller 111 by the reversing solenoid 215, transfers the paper P to the double-sided transfer path 114, and returns the process to S303.

In S312, the engine control unit 202 acquires the temperature of the end portion of the pressure roller 134 from the end temperature estimation unit 221 and supplies the temperature corresponding to the temperature of the end portion of the pressure roller 134 based on Table 2 described above. Determine the paper spacing. The engine control unit 202 resets and starts the timer, and stops the paper feeding until the determined paper feeding interval elapses. When the engine control unit 202 refers to the timer and determines that the determined paper feed interval has elapsed, the engine control unit 202 stops the timer and advances the process to S314.

In S313, the engine control unit 202 resets and starts the timer, and stops the paper feeding until the paper feeding interval of the large size paper (in this embodiment, 30 msec) elapses. When the engine control unit 202 refers to the timer and determines that the feeding interval of the large-sized paper has elapsed, the engine control unit 202 stops the timer and advances the processing to S314.

In S314, the engine control unit 202 determines whether or not there is a print job (next print job) to be executed subsequently (no next job?), And if there is a next print job, returns the process to S301, and returns the process to S301. If there is no next print job, the process proceeds to S315. In S315, the engine control unit 202 drives the fuser 130 to rotate and cool the pressurizing roller 134, and executes a "rear rotation operation". In S316, the engine control unit 202 stops the drive of the pressurizing roller 134 of the fuser 130, sets the state of the fuser 130 to "stop" in Table 1, and ends the process.

By setting the paper feed interval shown in Table 2 according to the temperature at the end of the pressurizing roller 134, the paper P is started to be fed and the printing is completed before the next paper P to be printed is fed. The end temperature of the pressurizing roller 134 at the time point is controlled to be 230 ° C. or lower. As described above, when the temperature at the end of the pressure roller 134 exceeds the predetermined temperature of 230 ° C., the pressure roller 134 may be damaged. Therefore, by performing the paper feed control of the paper P described above, the print job can be executed without damaging the pressure roller 134.

[Amount of temperature rise of the pressure roller due to the printing mode of small size paper]
Subsequently, a control sequence of the present embodiment in which the post-rotation time after printing small-sized paper using the configuration described above is changed according to the detection result of the paper exchange detection unit 220 will be described.

In Table 3 shown below, single-sided printing and double-sided printing of A5 size paper and special size paper with A5 width and long paper length are performed based on the amount of change in the end temperature of the pressure roller 134 shown in Table 1 described above. It is a table showing the amount of temperature rise (unit: ° C.) at the end of the pressurizing roller 134 in the case of. The A5 size paper has a width of 148 mm and a length (length in the paper transport direction) of 210 mm. On the other hand, the special size paper (hereinafter referred to as long narrow paper) has a width of 148 mm and a length of 356 mm. In Table 3, the left column shows the types of small size paper, that is, A5 size paper and long narrow paper. In the right column, the amount of temperature rise at the end of the pressure roller 134 per sheet of paper during single-sided printing and double-sided printing is shown according to the type of paper. The amount of temperature increase in the case of single-sided printing is determined based on the value of the amount of temperature change shown in Table 1 and the length of the paper P. On the other hand, the temperature increase amount in the case of double-sided printing is the temperature increase amount when printing on both sides of the paper P based on the value of the temperature change amount shown in Table 1 and the length of the paper P, and the temperature during the reversing operation. It is determined by the amount of decrease. Here, the inverting operation is an operation in which after printing on the first side of the paper P is completed, the paper P is inverted by the discharge roller 111, conveyed on the double-sided transfer path 114 by the double-sided transfer roller 113, and then transferred to the fixing device 130 again. Pointing to. In this embodiment, the distance at which the paper P is conveyed during the reversing operation is 430 mm.

［加圧ローラの端部温度と後回転時間との関係］
以下に示す表４は、加圧ローラ１３４の端部の温度と、後回転時間との関係を示す表である。表４において、左側の列は、図３（ａ）の処理により推定された加圧ローラ１３４の端部の温度を示し、右側の列は、加圧ローラ１３４の端部の温度に応じた後回転時間（単位：ｍｓｅｃ（ミリ秒））を示している。なお、後回転時間は、「（ａ）用紙交換なし」と「（ｂ）用紙交換あり」とに分かれている。「（ａ）用紙交換なし」は、後回転動作中に給紙トレイ１４０に収容された用紙Ｐの交換が行われなかった場合の後回転時間を示しており、本実施例では、上述した表２に示す給紙間隔と同じ時間としている。一方、「（ｂ）用紙交換あり」は、後回転動作中に給紙トレイ１４０に収容された用紙Ｐの交換が行われた場合の後回転時間を示している。上述した表３より、用紙交換により給紙トレイ１４０に収容された用紙Ｐがロングナロー紙であり、実施される印刷ジョブがロングナロー紙への両面印刷の場合には、加圧ローラ１３４の温度上昇量は５１℃となる。本実施例の構成では、用紙交換が行われた場合の交換後の用紙Ｐのサイズは、幅センサ１０７が検知するため、用紙Ｐの給紙を行わないと用紙Ｐのサイズを検知することができない。そのため、表４に示す「（ｂ）用紙交換あり」の後回転時間は、ロングナロー紙への両面印刷の場合を想定した時間となっている。

[Relationship between end temperature of pressure roller and back rotation time]
Table 4 shown below is a table showing the relationship between the temperature at the end of the pressure roller 134 and the post-rotation time. In Table 4, the left column shows the temperature of the end of the pressurizing roller 134 estimated by the process of FIG. 3 (a), and the right column shows the temperature of the end of the pressurizing roller 134. The rotation time (unit: msec (millisecond)) is shown. The back rotation time is divided into "(a) without paper replacement" and "(b) with paper replacement". “(A) No paper replacement” indicates the back rotation time when the paper P stored in the paper feed tray 140 is not replaced during the back rotation operation, and in this embodiment, the above-mentioned table is shown. The time is the same as the paper feed interval shown in 2. On the other hand, "(b) with paper replacement" indicates the back rotation time when the paper P stored in the paper feed tray 140 is replaced during the back rotation operation. From Table 3 above, when the paper P accommodated in the paper feed tray 140 by paper replacement is long narrow paper and the printing job to be performed is double-sided printing on long narrow paper, the temperature of the pressure roller 134 is reached. The amount of increase is 51 ° C. In the configuration of this embodiment, since the width sensor 107 detects the size of the paper P after the paper replacement when the paper is replaced, the size of the paper P can be detected if the paper P is not fed. Can not. Therefore, the post-rotation time of "(b) With paper replacement" shown in Table 4 is a time assuming the case of double-sided printing on long narrow paper.

［小サイズ紙の印刷後の後回転動作］
図４は、図３（ｂ）のＳ３１５で実行される後回転動作の制御シーケンスを示すフローチャートであり、図３（ｂ）と同様に、図４に示す処理はエンジン制御部２０２により実行される。以下では、図４に示す処理について、表４等を参照しながら、本実施例における後回転動作について具体的に説明する。そのため、小サイズ紙であるＡ５サイズ紙を連続印刷し、図３（ｂ）のＳ３１４の処理において、印刷ジョブが終了した時点での加圧ローラ１３４の端部温度が２０９℃である場合を例にして、図４の処理について説明する。

[Post-rotation operation after printing small size paper]
FIG. 4 is a flowchart showing a control sequence of the back rotation operation executed in S315 of FIG. 3 (b), and the process shown in FIG. 4 is executed by the engine control unit 202 as in FIG. 3 (b). .. Hereinafter, the back rotation operation in this embodiment will be specifically described with reference to Table 4 and the like for the processing shown in FIG. Therefore, an example is a case where A5 size paper, which is a small size paper, is continuously printed, and the end temperature of the pressure roller 134 at the time when the printing job is completed in the process of S314 in FIG. 3 (b) is 209 ° C. Then, the process of FIG. 4 will be described.

In S401, the engine control unit 202 acquires the end temperature of the pressurizing roller 134 at the start of the backward rotation operation from the end temperature estimation unit 221, and based on the acquired end temperature, "(( The corresponding time of "a) No paper replacement" is determined as the back rotation time (first idle rotation time). Then, the engine control unit 202 resets the timer and starts it. Since the end temperature of the pressurizing roller 134 at the start of the back rotation is 209 ° C., the back rotation time is determined to be 6500 msec based on Table 4 (a). In S402, the engine control unit 202 determines whether or not the paper P in the paper feed tray 140 has been replaced (paper replacement detected?) By the paper replacement detection unit 220 based on the detection information from the paper presence / absence sensor 141. If the engine control unit 202 determines that the paper P in the paper feed tray 140 has been replaced, the process proceeds to S403, and if it determines that the paper P in the paper feed tray 140 has not been replaced, the process proceeds to S404. Proceed.

First, processing when the paper P of the paper feed tray 140 has not been replaced will be described. If the replacement of the paper P in the paper feed tray 140 is not detected in the processing of S402, the processing of S404 is performed next. In S404, the engine control unit 202 refers to the timer, determines whether or not the rotation time has elapsed after the determination in S401, and if it determines that the rotation time has not elapsed, returns the process to S402, and the post-rotation time. If it is determined that the elapse has passed, the post-rotation process is terminated. The post-rotation time determined in the processing of S401 is 6500 msec. From Table 1 above, the temperature at the end of the pressurizing roller 134 when the state of the fuser 130 (pressurizing roller 134) on which the backward rotation operation is executed is "stopped" is lowered by 0.3 ° C. per 100 msec. do. Therefore, the temperature at the end of the pressure roller 134 when the post-rotation time has elapsed is 6500 msec is 189.5 ° C. (= 209 ° C. − (6500 msec × 0.3 ° C./100 msec)).

If the next print job is started immediately, the paper P in the paper feed tray 140 has not been replaced, so that the next print job is a print job for A5 size paper P, which is a small size paper. .. From Table 3 above, the temperature at the end of the pressure roller 134 increases by 17.3 ° C. when single-sided printing is performed on A5 size paper P, and increases by 27.0 ° C. when double-sided printing is performed. .. As a result, for example, in the next printing job, double-sided printing is performed on the A5 size paper P, and the temperature at the end of the pressure roller 134 at the time when the paper P is ejected rises by 27.0 ° C., 216.5. The temperature is (= 189.5 ° C + 27.0 ° C). If the end temperature of the pressure roller 134 exceeds 230 ° C, the pressure roller 134 may be damaged, but since the end temperature of the pressure roller 134 is 216.5 ° C, pressure is applied. No damage occurs to the roller 134.

Subsequently, the processing when the paper P of the paper feed tray 140 is replaced will be described. When the replacement of the paper P in the paper feed tray 140 is detected in the processing of S402, the processing of S403 is performed next. In S403, the engine control unit 202 sets the corresponding time of “(b) Paper replacement” in Table 4 as the post-rotation time based on the end temperature of the pressurizing roller 134 at the start of post-rotation acquired in S401. (Second idle rotation time) is determined. Since the end temperature of the pressurizing roller 134 at the start of the back rotation is 209 ° C., the back rotation time is changed from 6500 msec to 17,000 msec and extended based on Table 4 (b). In S404, the engine control unit 202 refers to the timer, determines whether or not the rotation time has elapsed after being changed in S403, and if it determines that the rotation time has not elapsed, returns the process to S402 and returns the post-rotation time. If it is determined that has passed, the backward rotation operation is terminated.

The post-rotation time after resetting in the process of S403 is 17,000 msec. From Table 1 above, the temperature at the end of the pressurizing roller 134 when the state of the fuser 130 (pressurizing roller 134) on which the backward rotation operation is executed is "stopped" is lowered by 0.3 ° C. per 100 msec. do. Therefore, the amount of decrease in the end temperature of the pressurizing roller 134 when the post-rotation time elapses is 51.0 ° C. (= 17000 msec × 0.3 ° C./100 msec). Therefore, the end temperature of the pressure roller 134 when the post-rotation time has elapsed 17,000 msec is 158.0 ° C. (= 209 ° C.-51.0 ° C.).

Since the paper P of the paper feed tray 140 has been replaced, the paper P may be replaced from A5 size paper of small size paper to long narrow paper, and the next printing job may be a printing job on long narrow paper. be. From Table 3 described above, the temperature at the end of the pressure roller 134 increases by 29.3 ° C. when single-sided printing is performed on long narrow paper, and increases by 51.0 ° C. when double-sided printing is performed. As a result, for example, in the next printing job, double-sided printing is performed on one sheet of long narrow paper, and the temperature at the end of the pressure roller 134 at the time when the long narrow paper is ejected rises by 51.0 ° C., 209. The temperature is (= 158.0 ° C + 51.0 ° C). If the end temperature of the pressure roller 134 exceeds 230 ° C, the pressure roller 134 may be damaged, but since the end temperature of the pressure roller 134 is 209 ° C, the pressure roller 134 Does not cause any damage.

Even if the paper P in the paper feed tray 140 is replaced, if the back rotation time (6500 msec) is the same as when the paper P is not replaced, the back rotation time has elapsed. The end temperature of the pressure roller 134 is 189.5 ° C. Then, in this state, double-sided printing is performed on one sheet of long narrow paper in the next printing job, and the temperature at the end of the pressure roller 134 at the time when the long narrow paper is ejected rises by 51.0 ° C. It reaches 240.5 ° C (= 189.5 ° C + 51.0 ° C). If the temperature at the end of the pressure roller 134 exceeds 230 ° C., the pressure roller 134 may be damaged. Therefore, even when the paper P of the paper feed tray 140 is replaced, the pressure roller 134 may be damaged in the same post-rotation time as when the paper P is not replaced. Therefore, when the paper P is replaced, damage to the pressure roller 134 can be prevented by performing the process of switching the post-rotation time of S403 described above. The values shown in Tables 1 to 4 described above are examples, and it is desirable to experimentally obtain and determine the optimum value.

As described above, in this embodiment, when the paper P is replaced during the back rotation, the back rotation time after printing the small size paper is larger than the time determined at the start of the back rotation. It is changed so that the rotation time will be after increasing it. As a result, when the user does not replace the paper P before and after the print job, the post-rotation time, which is a waiting time for the user, can be relatively shortened. Further, when the user replaces the paper P before and after the print job, the next print job can be executed without causing damage to the pressure roller 134 regardless of the paper size. It will be possible.

As described above, according to the present embodiment, it is possible to prevent damage to the fuser and deterioration of usability after printing small size paper.

In the first embodiment, a method of changing the back rotation time when the paper is changed during the back rotation operation after printing the small size paper has been described. In the second embodiment, even if the paper is not replaced during the back rotation operation and the paper is changed between the end of the back rotation operation and the start of the next print job, the pressurizing roller is used. Describes how to execute a print job without causing damage. Specifically, in this embodiment, when the paper is replaced and it is determined that the temperature at the end of the pressure roller needs to be lowered, the fuser is idled before the start of the print job. , Performs a process to lower the temperature at the end of the pressurizing roller.

[Structure of image forming apparatus]
FIG. 5A is a schematic cross-sectional view showing the configuration of the printer 100 which is the image forming apparatus of this embodiment. The configuration of the printer 100 of this embodiment is different from that of the printer 100 of the first embodiment shown in FIG. , The width sensor 150) is provided. The configuration of the printer 100 is the same as that of the first embodiment except for the width sensor 150, and the description of other configurations will be omitted.

[Paper width sensor]
5 (b) is a diagram showing the configuration of the width sensor 150 when the paper feed tray 140 is viewed from the right side to the left in the figure of FIG. 5 (a). The operation of the width sensor 150 when the user sets the paper P in the paper feed tray 140 and moves the side regulation plate 82R to the width position of the paper P in the direction of the arrow A in the drawing will be described. The side regulation plates 82 (82R, 82L) have a pair of left and right sides. When one side regulation plate 82 (82R, 82L) is moved, the other side regulation plate 82 (82L, 82R) is also symmetrically moved by the pinion (not shown), and the width direction of the paper P is regulated simultaneously on the left and right sides. can do. When the side regulation plate 82R moves, the sensor rack 154 connected to the side regulation plate 82R also moves in the direction of arrow A via the groove portion and the protrusion 82Ra of the sensor rack 154. As a result, the gear of the sensor gear 153 that meshes with the teeth of the sensor rack 154 rotates in the direction of arrow Z, and accordingly, the protrusion shaft portion 156 also rotates in the direction of arrow Z, depending on the angle of the protrusion shaft portion 156. The width sensor 150 detects the voltage output from the sensor (not shown). The engine control unit 202 calculates the width of the paper P based on the voltage output from the width sensor 150 according to the angle of the protrusion shaft unit 156.

[Control sequence from the end of the backward rotation operation to the execution of the print job]
Using the configuration of the printer 100 described above, the present embodiment according to the detection result of the paper exchange detection unit 220 from the end of the post-rotation operation after printing the small size paper to the execution of the next print job. The control sequence will be described below.

FIG. 6A is a flowchart showing a control sequence from the end of the back rotation operation after printing the small size paper to the execution of the next print job, and FIG. 6A shows the control sequence. The process shown is executed by the engine control unit 202. At the time when the process of FIG. 6A is started, the pressure roller 134 is in the following state. That is, in Example 1, A5 size paper, which is a small size paper, was continuously printed, and the end temperature of the pressure roller 134 at the time when the printing job was completed in S314 of FIG. 3B was 209 ° C. do. Then, it is assumed that the back rotation operation shown in FIG. 4 is executed and immediately after the back rotation time of 6500 msec when the end temperature of the pressure roller 134 shown in Table 2 is 209 ° C. has elapsed. The temperature at the end of the pressure roller 134 at this point is 189.5 ° C (= 209.0 ° C-6500 msec × 0.3 ° C / 100 msec), and the paper P is replaced during the post-rotation operation. Was not done.

In this embodiment, an example in which the paper P is replaced 1000 msec after the end of the post-rotation time and the print job is started after 5000 msec will be described. The end temperature at the end of the rear rotation of the pressure roller 134 is 189.5 ° C. The state of the pressurizing roller 134 until 6000 msec (= 5000 msec + 1000 msec) elapses is the "stopped" state shown in Table 1. Since the end temperature of the pressurizing roller 134 in the "stopped" state shown in Table 1 decreases by 0.3 ° C. per 100 msec, the end temperature of the pressurizing roller 134 after 6000 msec has elapsed is 183.5 ° C. (= 189.5 ° C.-6000 msec x 0.1 / 100 msec).

In S601, the engine control unit 202 detects whether or not the paper has been replaced. When the engine control unit 202 executes the process of S601, the process of FIG. 6B is activated in order to detect the presence or absence of paper replacement.

FIG. 6B is a flowchart showing a control sequence for detecting whether or not the paper P stored in the paper feed tray 140 has been replaced. The process shown in FIG. 6B is activated when the engine control unit 202 executes the process of S601, and is executed by the paper exchange detection unit 220.

In S611, the paper exchange detection unit 220 stores the width of the paper P according to the voltage output by the width sensor 150. At this time, in this embodiment, since the paper P housed in the paper feed tray 140 is A5 size paper of small size paper, the paper width is 148 mm. After that, the paper exchange detection unit 220 determines whether or not the voltage value corresponding to the paper width output by the width sensor 150 has changed. If the paper exchange detection unit 220 determines that the voltage value has not changed, the process returns to S612, and if it determines that the voltage value has changed, the process proceeds to S613. In S613, the paper exchange detection unit 220 stores that the exchange of the paper P in the paper feed tray 140 is detected, and ends the process. In this embodiment, the paper replacement detection unit 220 detects the paper replacement by the change in the width of the paper P detected by the width sensor 150. For example, as in the first embodiment, the paper presence / absence sensor 141 It may be detected by the change of the presence / absence of the paper P based on the input signal value.

In this embodiment, 1000 msec after the detection of paper replacement in the paper feed tray 140 is started, the voltage value output by the width sensor 150 is calculated by the user operating the side regulation plate 82R to replace the paper P. Change. As a result, the paper exchange detection unit 220 remembers that the paper exchange has been detected, and ends the paper exchange detection process shown in FIG. 6 (b).

Returning to the description of the process shown in FIG. 6A, in S602, the engine control unit 202 determines whether or not there is a print job to be executed. If there is a print job to be executed, the engine control unit 202 advances the process to S603, and if there is no print job to be executed, the engine control unit 202 returns the process to S602. The above-mentioned process of FIG. 6B is performed by the paper exchange detection unit 220 in parallel with the process of S602, and when the exchange of the paper P of the paper feed tray 140 is detected, the process of FIG. 6B is performed. Is finished.

In S603, the engine control unit 202 determines whether or not the paper exchange is detected in the process shown in FIG. 6B. When the engine control unit 202 detects that the paper has been replaced, the engine control unit 202 advances the process to S604. On the other hand, if it is not detected that the paper exchange has been performed, the engine control unit 202 advances the process to S608. In this embodiment, since the print job is started 6000 msec after the end of the post-rotation time, the end temperature of the pressure roller 134 at this time is 183.5 ° C. as described above. Since the paper has not been replaced, the temperature at the end of the pressure roller 134 when double-sided printing of A5 size paper is performed in the printing job rises by 27.0 ° C. from Table 3. Therefore, the temperature at the end of the pressure roller 134 after executing the print job is 210.5 ° C (= 183.5 ° C + 27.0 ° C), but the situation does not exceed 230 ° C. It is not necessary to perform idle rotation of (pressurizing roller 134).

In S604, the engine control unit 202 determines whether the first sheet of the print job is double-sided printing. If the engine control unit 202 determines that the first sheet of paper is double-sided printing, the process proceeds to S605. On the other hand, when the engine control unit 202 determines that the first sheet is not double-sided printing (single-sided printing), the process proceeds to S608. When the first sheet of paper is A5 size paper and long narrow paper, the temperature at the end of the pressure roller 134 increases by 17.3 ° C and 29.3 ° C, respectively, from Table 3. The end temperature of the pressure roller 134 at the time of starting the printing job is 183.5 ° C., and when single-sided printing of A5 size paper is performed, the end temperature of the pressure roller 134 is 200.8 ° C. (= 183.5 ° C + 17.3 ° C). Similarly, when single-sided printing of long narrow paper is performed, the end temperature of the pressure roller 134 becomes 212.8 ° C. (= 183.5 ° C. + 29.3 ° C.). When single-sided printing of A5 size paper and long narrow paper is performed, the temperature at the end of the pressure roller 134 does not exceed 230 ° C. Therefore, the fuser 130 (pressure roller 134) is idle. There is no need to do.

In S605, the engine control unit 202 determines whether or not the width of the paper P detected by the width sensor 150 is less than a predetermined value (in this embodiment, the width of the A4 size paper, which is a large size paper, is 190 mm). When the engine control unit 202 determines that the width of the paper P is less than a predetermined value (less than 190 mm) and the paper P is not a large-sized paper, the process proceeds to S606. On the other hand, when the engine control unit 202 determines that the width of the paper P is 190 mm or more and a predetermined value or more (a predetermined width or more), the paper P is a large size paper and the end temperature of the pressurizing roller 134 is high. Since there is no situation in which the temperature rises as compared with the paper-passing area, the process proceeds to S608.

In S606, the engine control unit 202 acquires the current end temperature of the pressurizing roller 134 from the end temperature estimation unit 221, and based on the acquired end temperature, “(b) Paper replacement” in Table 4 The corresponding time of "Yes" is determined as the idle rotation time (third idle rotation time). In S607, the engine control unit 202 resets the timer and starts it. Then, the engine control unit 202 drives the fuser 130 to start the rotation operation of the pressurizing roller 134, and while referring to the timer, performs the idle rotation operation of the fuser 130 until the idle rotation time elapses, and is empty. When the rotation time elapses, the process proceeds to S608. In S608, the engine control unit 202 starts a print job.

The end temperature of the pressure roller 134 at the time of starting the processing of S606 is 183.5 ° C. From "(b) With paper replacement" in Table 4 described above, the post-rotation time (idle rotation time) corresponding to the end temperature of the pressure roller 134 is 10,000 msec. As a result, the end temperature of the pressurizing roller 134 after the idle rotation time has elapsed becomes 153.5 ° C. (= 183.5 ° C.-10000 msec × 0.3 ° C./100 msec). Therefore, in the printing job, double-sided printing of long narrow paper is performed, and when the end temperature of the pressure roller 134 rises by 51.0 ° C. as shown in Table 3, 204.5 ° C. (= 153.5 ° C. + 51). It becomes 0.0 ° C.). Since the end temperature of the pressure roller 134 after double-sided printing of the long narrow paper does not exceed 230 ° C., the pressure roller 134 is not damaged and double-sided printing can be performed.

As described above, in this embodiment, if the paper replacement is detected after the post-rotation operation after printing the small size paper is completed, there is a possibility that the pressure roller may be damaged by the execution of the print job. If necessary, idle rotation of the fuser is performed before the start of the print job. As a result, when the idle rotation of the fuser is unnecessary, the execution of the print job can be started immediately without waiting for the user, so that it is possible to prevent the usability from deteriorating. On the other hand, when idle rotation of the fuser is required, the print job can be executed without damaging the pressurizing roller by performing idle rotation.

In this embodiment, the paper replacement is detected by the change in the width of the paper P detected by the width sensor 150. For example, when the width sensor 150 is provided in the printer 100 of the first embodiment as in the present embodiment, the paper exchange detection by the paper exchange detection unit 220 of S402 in FIG. 4 is not the paper presence / absence sensor 141 but the detection of the paper exchange. It may be performed based on the detection information by the width sensor 150.

As described above, according to the present embodiment, it is possible to prevent damage to the fuser and deterioration of usability after printing small size paper.

In Examples 1 and 2, a method of determining the back rotation time and the idle rotation time of the fuser when the paper is replaced after printing the small size paper has been described. In the third embodiment, when the paper is replaced with the large size paper after printing the small size paper, the method of stopping the rear rotation operation of the fuser and executing the print job will be described.

Generally, in a pressure roller, in a non-uniform state where there is a temperature difference between the temperature of the edge portion, which is a non-passing portion where paper does not pass, and the temperature of the central portion, which is a paper passing portion through which paper passes. When printing on large size paper, a phenomenon called hot offset may occur. The hot offset is a phenomenon in which an image formed in a region corresponding to the position of the end portion of the pressurizing roller is overfixed on a large-sized paper due to a temperature difference between the end portion and the central portion of the pressurizing roller. Whether or not hot offset occurs is determined by the physical characteristics of the toner used. In the image forming apparatus of this embodiment, the backward rotation operation of the fuser 130 when a toner that does not generate hot offset is used will be described. The printer 100, which is the image forming apparatus of this embodiment, has the same configuration as the printer 100 shown in FIG. 5 of the second embodiment, and the description of the configuration of the printer 100 will be omitted.

[Post-rotation operation after printing small size paper]
FIG. 7 is a flowchart showing a control sequence of the back rotation operation executed in S315 of FIG. 3B of the first embodiment in the present embodiment, and the process shown in FIG. 7 is executed by the engine control unit 202. In the following, the back rotation operation in this embodiment will be specifically described with reference to Table 4 and the like for the processing shown in FIG. 7. Therefore, in the case where A5 size paper, which is a small size paper, is continuously printed and the end temperature of the pressure roller 134 is 209 ° C. at the time when the printing job is completed in the process of S314 in FIG. 3 (b). As an example, the process of FIG. 7 will be described.

In S701, the engine control unit 202 acquires the end temperature of the pressurizing roller 134 at the start of the backward rotation operation from the end temperature estimation unit 221, and based on the acquired end temperature, "(( The corresponding time of "a) No paper change" is determined as the back rotation time. Then, the engine control unit 202 resets the timer and starts it. Since the end temperature of the pressurizing roller 134 at the start of the back rotation is 209 ° C., the back rotation time is determined to be 6500 msec based on Table 4 (a). In S702, the engine control unit 202 determines whether or not the paper P in the paper feed tray 140 has been replaced (paper replacement detected?) Based on the detection information from the paper presence / absence sensor 141 by the paper replacement detection unit 220. When the engine control unit 202 determines from the detection information from the paper presence / absence sensor 141 that the paper P in the paper feed tray 140 has been replaced, the engine control unit 202 advances the process to S703. On the other hand, if the detection information from the paper presence / absence sensor 141 has not changed since the start of the reverse rotation, the engine control unit 202 determines that the paper P in the paper feed tray 140 has not been replaced, and sets the process to S706. Proceed.

In S703, the engine control unit 202 sets the corresponding time of “(b) with paper replacement” in Table 4 as the post-rotation time based on the end temperature of the pressurizing roller 134 at the start of post-rotation acquired in S701. To decide. Since the end temperature of the pressurizing roller 134 at the start of the back rotation is 209 ° C., the back rotation time is changed from 6500 msec to 17,000 msec based on Table 4 (b).

In S704, the engine control unit 202 determines whether or not the width of the paper P detected by the width sensor 150 is less than a predetermined value (in this embodiment, the width of the A4 size paper, which is a large size paper, is 190 mm). When the engine control unit 202 determines that the width of the paper P is less than a predetermined value (less than 190 mm) and is not a large size paper, the process proceeds to S706. On the other hand, when the engine control unit 202 determines that the width of the paper P is equal to or larger than a predetermined value (190 mm or more) and is a large-sized paper, the process proceeds to S705. In S705, the engine control unit 202 determines whether or not there is a print job to be executed. If there is a print job to be executed, the engine control unit 202 ends the back rotation operation of the fuser 130 even before the back rotation time elapses. As described above, the reason why the rear rotation operation of the fuser 130 can be completed is that the toner used in this embodiment has the physical properties that hot offset does not occur, and the paper P used in the next printing job is a large size paper. If so, the temperature at the end of the pressurizing roller 134 does not rise. On the other hand, if there is no print job to be executed, the engine control unit 202 advances the process to S706.

In S706, the engine control unit 202 refers to the timer to determine whether or not the rotation time has elapsed after being determined by the processing of S701 or the processing of S703, and if it is determined that the rotation time has not elapsed, the processing is performed. Return to S702. On the other hand, when the engine control unit 202 determines that the rear rotation time has elapsed, the engine control unit 202 ends the rear rotation operation of the fuser 130.

As described above, when the printer 100 uses toner that does not generate hot offset, the paper is replaced with the large size paper during the post-rotation operation after printing the small size paper, and the printing job is started. In, the running back-rotation operation can be stopped. As a result, when the small size paper is used after printing the small size paper, the next printing job can be executed without damaging the pressure roller 134 by performing the back rotation operation. In addition, if the paper is changed from small size paper to large size paper during the back rotation operation and there is a print job during the back rotation time, the back rotation operation can be stopped and the print job can be executed. The waiting time can be shortened and usability can be improved.

As described above, according to the present embodiment, it is possible to prevent damage to the fuser and deterioration of usability after printing small size paper.

106 Transfer roller 122 Photosensitive drum 130 Fuser 133 Fixing film 134 Pressurized roller 140 Paper feed tray 202 Engine control unit

Claims (14)

An image forming unit having a photosensitive drum and transferring a toner image formed on the photosensitive drum to a sheet.
A paper feed means for feeding the sheet to which the toner image is transferred, and
A fixing means for fixing the transferred toner image on the sheet,
Control means for controlling the paper feeding and feeding of sheets, and
Equipped with
The fixing means includes a heating member that heats the toner image on the sheet, and a pressurizing member that contacts the heating member to form a nip portion and pressurizes the toner image on the sheet.
The control means is housed in the paper feed means between the end of the preceding print job for printing a small size sheet whose sheet width is smaller than a predetermined width and the execution of the next print job. When the sheet is replaced, the time for driving the pressurizing member without passing the sheet through the nip portion is used, and when the sheet accommodated in the paper feeding means is not replaced, the pressurizing member is driven. An image forming apparatus characterized by extending from time. The heating member is a fixing film and is
The pressurizing member is a rotating pressurizing roller.
The image forming apparatus according to claim 1, wherein the driving time is an idle rotation time of the pressurizing roller in a state where the sheet does not pass through the nip portion. The image forming apparatus according to claim 2, wherein the width of the pressure roller is larger than the width of the small-sized sheet. The image forming apparatus according to claim 3, further comprising an estimation means for estimating the temperature of the end portion of the pressure roller that the sheet does not come into contact with when the small-sized sheet passes through the pressure roller. .. The fixing means has a heater for heating the fixing film, and the fixing means has a heater.
The fourth aspect of the present invention is characterized in that the estimation means estimates the temperature of the end portion of the pressure roller based on the presence or absence of power supply to the heater and the state of rotation or stop of the pressure roller. The image forming apparatus according to the description. A sheet detecting means for detecting the presence or absence of a sheet accommodated in the paper feeding means is provided.
The image forming apparatus according to claim 4, wherein the control means detects replacement of a sheet accommodated in the paper feeding means based on the detection result of the sheet detecting means. A sheet detecting means for detecting the width of the sheet accommodated in the paper feeding means is provided.
The image forming apparatus according to claim 4, wherein the control means detects replacement of a sheet accommodated in the paper feeding means based on the detection result of the sheet detecting means. The pressurizing roller has a first idle rotation determined based on the temperature of the end portion of the pressurizing roller when the preceding printing job estimated by the estimation means is completed after the preceding printing job is completed. Carry out idle rotation of time,
If the sheet detecting means detects the replacement of the sheet of the feeding means while the idle rotation of the first idle rotation time is being carried out, the addition when the preceding printing job is completed. The image formation according to claim 6 or 7, wherein the idle rotation of the second idle rotation time longer than the first idle rotation time is performed based on the temperature of the end portion of the compression roller. Device. The temperature of the end portion of the pressurizing roller after performing the idle rotation of the second idle rotation time has the same width as the small size sheet and is longer in the transport direction than the small size sheet. The image forming apparatus according to claim 8, wherein the temperature of the end portion of the pressure roller, which rises when double-sided printing of a long sheet is performed, is a temperature that does not exceed a predetermined temperature. The toner for forming a toner image in the image forming portion has a physical property that does not cause over-fixing of the toner image.
In the control means, when the pressurizing roller is performing idle rotation in the second idle rotation time, the next printing job prints a large-sized sheet in which the width of the sheet is equal to or larger than the predetermined width. The image forming apparatus according to claim 8, wherein in the case of a print job to be performed, the idle rotation of the pressurizing roller is stopped and the next print job is executed. The control means detects the sheet between the time when the idle rotation time for cooling the end of the pressure roller after the completion of the preceding print job has elapsed and the time when the next print job is executed. The means detects the replacement of the sheet of the paper feeding means,
When the next print job is a print job that performs double-sided printing on the small-sized sheet, before the next print job is executed, before the next print job estimated by the estimation means is executed. The image forming apparatus according to claim 6 or 7, wherein the image forming apparatus is subjected to idle rotation of a third idle rotation time of the pressurizing roller, which is determined based on the temperature of the end portion of the pressurizing roller. If the sheet detecting means does not detect the replacement of the sheet of the feeding means before the next printing job is executed, the pressurizing roller performs single-sided printing on the small size sheet by the next printing job. When the print job or the next print job is a print job for printing a large-sized sheet having a sheet width equal to or larger than the predetermined width, the third idle rotation time is not idle. The image forming apparatus according to claim 11. The temperature of the end portion of the pressurizing roller after performing the idle rotation of the third idle rotation time has the same width as the small size sheet and is longer in the transport direction than the small size sheet. The image forming apparatus according to claim 11, wherein the temperature of the end portion of the pressure roller, which rises when double-sided printing of a long sheet is performed, is a temperature that does not exceed a predetermined temperature. Any of claims 1 to 13, characterized in that a double-sided transport path for transporting the sheet on which the toner image is transferred to one side of the sheet to the image forming unit is provided again for printing on both sides of the sheet. The image forming apparatus according to item 1.

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