JP2009069605A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient image forming apparatus configured to change a time to switch a set temperature for a heat roller from a fixation temperature to a standby temperature in accordance with the warm-up degree of the apparatus, so that unnecessary heat is not supplied to the heat roller. <P>SOLUTION: Next, when the surface temperature Tp detected at a step S101 is equal to or higher than a prescribed temperature T3, that is, when Tp≥T3 is established (Yes at S102), the set temperature for the heat roller 27 is switched by a printer controller 11 as a first control means from the fixation temperature T1 to the standby temperature T2 while adjusted to a first timing of turning off a PDS 33 (S103). On the other hand, when Tp≥T3 is not established at the step S102 (No at S102), the turning-off of the PDS is detected based on a detection signal from the PDS 33 (S106). Next, the set temperature for the heat roller 27 is switched by the printer controller 11 as a second control means from the fixation temperature T1 to the standby temperature T2 while adjusted to a second timing of stopping a motor 34 after a lapse of prescribed time from the first timing (S107). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus.

  An electrophotographic image forming apparatus includes a fixing device that fixes a toner image transferred to a recording sheet by heating and pressurizing the recording sheet. This fixing device includes a heat roller, a press roller that is placed so as to be opposed to the heat roller by being pressed and contacted, a heater built in the heat roller, and a temperature that is placed in contact with the surface of the heat roller. And a sensor. For example, a halogen lamp is used as the heater. In order to stabilize the fixing property of the toner image, the surface temperature of the heat roller is controlled so that the surface temperature of the heat roller is maintained at a predetermined fixing temperature. The surface temperature of the heat roller is controlled by heater on / off control using heat supplied from the heater (see, for example, Patent Document 1). Specifically, the heater is stopped when the surface temperature of the heat roller detected by the temperature sensor becomes higher than the fixing temperature, and the heater is operated when the temperature becomes lower than the fixing temperature. When a series of image forming processes is completed, the set temperature with respect to the surface temperature of the heat roller is switched from the fixing temperature to the standby temperature. The standby temperature is a temperature lower than the fixing temperature for reducing energy consumption during standby. The timing for switching the set temperature from the fixing temperature to the standby temperature is after a lapse of a predetermined time after a series of image forming processes. For example, the motor that rotates the heat roller and the press roller is switched according to the timing when the motor stops.

JP 2001-228744 A

  In the conventional image forming apparatus as described above, the set temperature with respect to the surface temperature of the heat roller is switched from the fixing temperature to the standby temperature after a lapse of a certain time after a series of image forming processes, regardless of whether the apparatus is warm or not. It has been. If the device is not warmed, if the set temperature is switched to the standby temperature after a while after the series of image forming processes is completed, heat is continuously supplied to the heat roller even after the series of image forming processes is completed. The surface temperature begins to fall after a predetermined time has elapsed. For this reason, it is possible to prevent the so-called FCOT (First Copy Output Time) from the time when the copy start button is pressed until the trailing edge of the first recording sheet is discharged to the tray. However, when the apparatus is warm, the set temperature is maintained at the fixing temperature for a while even after a series of image forming processes is completed, and unnecessary heat is supplied to the heat roller for a predetermined time. Further, the heat causes the device to warm up more than necessary.

  The present invention has been made to solve the above-described problems.In accordance with the warming condition of the apparatus, the time for switching the set temperature of the heat roller from the fixing temperature to the standby temperature is changed, and unnecessary heat is generated. An object of the present invention is to provide an efficient image forming apparatus that does not supply heat rollers.

  In order to achieve the above object, a first invention is an image forming apparatus in which an image forming process is performed by fixing a toner image transferred to a recording paper by heating and pressurizing the recording paper. A roller, a heater built in the heat roller, supplying heat to the heat roller, a press roller installed in contact with the heat roller, and installed on the heat roller and the recording paper discharge side of the press roller. A recording paper discharge sensor for detecting passage, temperature detecting means for detecting the surface temperature of the press roller, and when the detected surface temperature is higher than a predetermined temperature, the last recording paper passes through the series of image forming processes. First control means for switching the set temperature of the heat roller from the fixing temperature to the standby temperature in accordance with the first timing when the recording paper discharge sensor is turned off, and the detected surface temperature It is lower than the temperature, in which a second control means for switching to the standby temperature set temperature from the fixing temperature from the first timing after a predetermined time has elapsed.

  With this configuration, when the apparatus is warmed, the surface temperature of the heat roller starts to decrease immediately after the end of a series of image forming processes. In addition, when the apparatus is not warmed, the surface temperature of the heat roller starts to decrease after a predetermined time has elapsed after a series of image forming processes has been completed.

  The second invention further comprises a motor for rotating the heat roller and the press roller in the configuration of the first invention, and the second control means is set in accordance with the second time when the motor stops after the first time. The temperature is switched from the fixing temperature to the standby temperature.

  With this configuration, when the apparatus is not warmed, the surface temperature of the heat roller starts to decrease in accordance with the stop of the motor after a lapse of a predetermined time after the end of a series of image forming processes.

  According to a third aspect of the present invention, in the configuration of the first or second aspect of the present invention, the temperature sensor further includes a temperature sensor installed in contact with the surface of the press roller, and the temperature detecting means is a surface directly from the surface of the press roller by the temperature sensor. It detects temperature.

  If comprised in this way, the warming condition of an apparatus will be judged using the temperature sensor which contacts the surface of a press roller directly.

  As described above, the first invention does not supply unnecessary heat to the heat roller because the surface temperature of the heat roller starts to decrease immediately after the end of the series of image forming processes when the apparatus is warm. An efficient image forming apparatus is obtained. In addition, since unnecessary heat is not supplied to the heat roller after a series of image forming processes, the apparatus can be prevented from being heated more than necessary, and energy consumption can be reduced. When the apparatus is not warmed, the heat roller surface temperature starts to decrease after a lapse of a predetermined time after a series of image formation processes are completed, so that heat is supplied to the heat roller for a predetermined time even after the completion of the series of image formation processes. Since the apparatus is continuously heated, it is possible to prevent the FCOT from becoming long.

  According to the second invention, in addition to the effect of the first invention, when the apparatus is not warmed, the surface of the heat roller is adjusted to stop the motor after a lapse of a predetermined time after a series of image forming processes are completed. Since the temperature starts to decrease, the image forming apparatus becomes more efficient.

  In the third aspect of the invention, in addition to the effects of the first or second aspect of the invention, since the degree of warming of the apparatus is determined using a temperature sensor that directly contacts the surface of the press roller, a more efficient image forming apparatus It becomes.

  Next, embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

  Referring to FIG. 1, for example, an image forming apparatus 10 incorporated in a facsimile machine or a copier is provided with a transfer roller 13 installed so as to be in contact with and face the photosensitive drum 12 across the recording paper conveyance path. A fixing device 15 installed on the downstream side of the recording paper conveyance direction, a developing device 14 installed around the photosensitive drum 12, and a printer controller 11 for controlling each part of the image forming apparatus 10. .

  The photosensitive drum 12 is a photosensitive member that is charged by exposure, and is rotated by a driving source (not shown). Around the photosensitive drum 12, a charging brush 16 as a brush roller type charger, an LED print head 18 as an exposure unit, and a memory removal brush 19 are installed. A predetermined bias voltage is applied to the charging brush 16 by a charging bias application circuit 17. The charging brush 16 to which the bias voltage is applied charges the outer peripheral surface of the photosensitive drum 12 uniformly while rotating. The LED print head 18 is configured by arranging a large number of LEDs in parallel, irradiates light to the outer peripheral surface of the photosensitive drum 12 based on input image information, and an electrostatic latent image corresponding to the image information on the outer peripheral surface. Form. A predetermined bias voltage is applied to the memory removal brush 19 by the memory removal brush voltage application circuit 20. The memory removal brush 19 to which the bias voltage is applied removes the toner image remaining along the contour of the image on the outer peripheral surface of the photosensitive drum 12 after the transfer.

  The transfer roller 13 is rotated following the rotation of the photosensitive drum 12, and transfers a toner image formed on the outer peripheral surface of the photosensitive drum 12 as a transfer unit onto a recording sheet. A predetermined bias voltage is applied to the transfer roller 13 by a transfer bias application circuit 21. A current detection unit 22 is installed between the transfer roller 13 and the transfer bias application circuit 21, detects a current that flows when the transfer bias voltage is applied, and sends a signal to the printer controller 11.

  The developing device 14 includes a supply roller 23, a developing roller 24, and a blade 25. The supply roller 23 supplies the toner to the developing roller 24 while charging the toner from a toner case (not shown) containing the toner. The developing roller 24 is placed between the supply roller 23 and the photosensitive drum 12 so as to contact both, and transfers the toner to the photosensitive drum 12. The blade 25 is elastically brought into contact with the outer peripheral surface of the developing roller 24 and makes the layer pressure of the toner layer attached to the outer peripheral surface of the developing roller 24 uniform. A predetermined bias voltage is applied to the supply roller 23, the developing roller 24, and the blade 25 by a developing device bias applying circuit 26.

  The fixing device 15 includes a heat roller 27, a press roller 28 installed so as to be opposed to the heat roller 27 under pressure and contact, and a heater 29 built in the heat roller 27 and supplying heat to the heat roller. I have. A temperature sensor 30 is installed in contact with the surface of the heat roller 27, and a temperature sensor 32 is installed in contact with the surface of the press roller 28. For example, a halogen lamp is used as the heater 29. A heater operation circuit 31 is connected to the heat roller 27, and the heater operation circuit 31 operates based on a control signal from the printer controller 11 to operate the heater 29. Further, the heat roller 27 and the press roller 28 rotate when the motor 34 is driven based on a control signal from the printer controller 11. The photosensitive drum 12, the supply roller 23, the developing roller 24, and the like also rotate when the motor 34 is driven.

  The printer controller 11 transmits a signal to the heater operation circuit 31 based on the detection signal of the temperature sensor 30 to control on / off of the heater 29, and the surface temperature of the heat roller 27 stabilizes the toner image fixability. A predetermined fixing temperature (for example, 190 ° C.) is maintained. Specifically, the heater 29 is stopped when the surface temperature of the heat roller 27 detected by the temperature sensor 30 becomes higher than the fixing temperature, and the heater 29 is operated when the temperature becomes lower than the fixing temperature. After a series of image forming processes is completed after the copy start button is pressed, the set temperature for the surface temperature of the heat roller 27 is switched from the fixing temperature to the standby temperature (for example, 110 ° C.). As a result, the heat supplied to the heat roller 27 is reduced, and energy consumption during standby of the image forming process is reduced. A series of image forming processes, for example, in a copying machine, is a single image forming process when copying only one sheet, and an image forming process for all multiple sheets when copying a plurality of sheets continuously. That is. The printer controller 11 detects the surface temperature of the press roller 28 based on the detection signal of the temperature sensor 32.

  The recording sheets are conveyed one by one along a recording sheet conveyance path from a sheet feeding cassette (not shown) to the fixing device 15 via the transfer roller 13. A recording paper discharge sensor PDS 33 is installed on the recording paper discharge side of the heat roller 27 and the press roller 28 of the fixing device 15 to detect the passage of the recording paper. Specifically, the PDS 33 is turned on while the recording paper passes through the PDS 33 along the recording paper conveyance path, and the PDS 33 is turned off otherwise. The on / off state of the PDS is detected by the printer controller 11 based on a detection signal from the PDS 33.

  Next, the surface temperature control of the heat roller 27 when a series of image forming processes is completed will be described.

  FIG. 2 is a flow chart showing the contents of the surface temperature control of the heat roller in the first embodiment of the present invention.

  Referring to FIG. 2, in the series of image forming processes, the last recording sheet is passing PDS 33 and PDS 33 is turned on (S100). At this time, the set temperature of the heat roller 27 is the fixing temperature T1. After the PDS 33 is turned on, the printer controller 11 detects the surface temperature Tp of the press roller 28 by receiving a signal from the temperature sensor 32 by the temperature detecting means (S101). Next, if the surface temperature Tp detected in step S101 is equal to or higher than the predetermined temperature T3, that is, if Tp ≧ T3 (Yes in S102), the printer controller 11 serves as a first control means as a detection signal from the PDS 33. Based on this, it is detected that the PDS 33 is turned off, and the set temperature of the heat roller 27 is switched from the fixing temperature T1 to the standby temperature T2 in accordance with the first time when the PDS 33 is turned off (S103). When the trailing edge of the recording paper passes through the PDS 33, the PDS 33 is turned off. Next, the printer controller 11 stops the motor 34 after a predetermined time has elapsed from the first time (S104). Next, the image forming apparatus 10 enters a standby state (S105).

On the other hand, if Tp ≧ T3 is not satisfied in step S102 (No in S102), the printer controller 11 detects that the PDS 33 is turned off based on the detection signal from the PDS 33 (S106). Next, as a second control means, the printer controller 11 stops the motor 34 after a predetermined time has elapsed from the first time when the PDS 33 is turned off, and sets the heat roller 27 in accordance with the second time when the motor 34 stops. The temperature is switched from the fixing temperature T1 to the standby temperature T2 (S107). Next, the image forming apparatus 10 enters a standby state as in the case of Tp ≧ T3 (Yes in S102) (S105).
In the above control, the degree of warming of the device is determined based on the surface temperature of the press roller 28. If the surface temperature of the press roller 28 is higher than a predetermined temperature T3 set in advance, it is determined that the apparatus is warm. Conversely, if the temperature is lower than the predetermined temperature T3, it is determined that the apparatus is not warmed. The timing for switching the set temperature of the heat roller 27 from the fixing temperature T1 to the standby temperature T2 is changed according to the warming condition of the apparatus.

  Next, the relationship between the surface temperature Tr of the heat roller 27, the set temperature, the PDS 33, and the motor 34 in the above-described surface temperature control of the heat roller 27 will be described.

  FIG. 3 is a time chart in the image forming apparatus shown in FIG. 1 showing the relationship between the surface temperature Tr of the heat roller, the set temperature, the PDS, and the motor, and FIG. 3A is a time chart when Tp ≧ T3. FIG. 3B is a time chart when Tp <T3.

  Referring to FIG. 3A, FIG. 3A is a time chart when the surface temperature Tp of the press roller 28 detected in step S101 described above is equal to or higher than a predetermined temperature T3, that is, Tp ≧ T3 (Yes in S102). FIG. 3A shows a case where it is determined that the apparatus is warm. Elapsed time is taken on the horizontal axis, and the change in the surface temperature Tr of the heat roller 27, the set temperature with respect to the surface temperature Tr of the heat roller 27, the on / off state of the PDS 33, and the on / off state of the motor 34 are shown from the top. ing. The on / off state of the PDS 33 and the on / off state of the motor 34 are the same as those in FIGS. 3A and 3B.

  Looking at the time chart of the PDS 33 and the motor 34, the motor 34 is stopped after a predetermined time has elapsed from the first time when the PDS 33 is turned off. The first time when the PDS 33 is turned off is a time when the trailing edge of the last recording sheet passes through the PDS 33 when printing is performed on a plurality of recording sheets in a series of image forming processes. Next, looking at the time chart of the set temperature and the PDS 33, the set temperature is switched from the fixing temperature T1 to the standby temperature T2 in accordance with the first time when the PDS 33 is turned off. Further, in the time chart of the surface temperature Tr of the heat roller 27, a temperature ripple is formed around the fixing temperature T1 until the set temperature is switched from the fixing temperature T1 to the standby temperature T2, and thereafter, the standby temperature T2 gradually decreases. Inclined towards

  Referring to FIG. 3B, FIG. 3B is a time chart when the surface temperature Tp of the press roller 28 detected in step S101 described above is lower than the predetermined temperature T3, that is, when Tp <T3 (No in S102). FIG. 3B shows a case where it is determined that the device is not warmed. The structure of the time chart of FIG. 3B is the same as that of FIG. 3A.

  Looking at the set temperature and the time chart of the motor 34, the set temperature is switched from the fixing temperature T1 to the standby temperature T2 in accordance with the second time when the motor 34 stops. Looking at the time chart of the surface temperature Tr of the heat roller 27, a temperature ripple is formed around the fixing temperature T <b> 1 until the set temperature switches from the fixing temperature T <b> 1 to the standby temperature T <b> 2. The slope is inclined toward the standby temperature T2.

  When the apparatus is warm, the press roller 28 installed in contact with the heat roller 27 is also warmed, so that the apparatus does not cool suddenly, and the heat roller 27 is heated by the entire press roller 28 and the fixing device 15. It is hard to be deprived of. Therefore, even if the set temperature is switched from the fixing temperature to the standby temperature at an earlier time than when the apparatus is not warmed, the FCOT does not become long. On the other hand, when the apparatus is not warmed, the set temperature is switched from the fixing temperature to the standby temperature after a lapse of a predetermined time after a series of image forming processes. Therefore, since heat is supplied to the heat roller 27 for the predetermined time, even if the surface temperature Tr of the heat roller 27 cools down more rapidly than when the apparatus is warmed, the FCOT is less likely to become longer.

  In the image forming apparatus 10 in which the surface temperature Tr of the heat roller 27 is controlled as described above, the surface of the press roller 28 when the last recording sheet passes and the PDS 33 is turned on in a series of image forming processes. If the temperature Tp is higher than the predetermined temperature T3, it is determined that the device is warm. When the apparatus is warmed, the set temperature is switched from the fixing temperature T1 to the standby temperature T2 in accordance with the timing when the PDS 33 is turned off immediately after the end of the series of image forming processes. Therefore, when the apparatus is warm, the surface temperature Tr of the heat roller 27 starts to decrease immediately after the end of the series of image forming processes, and therefore unnecessary heat after the end of the image forming process is not supplied to the heat roller 27. An efficient image forming apparatus can be obtained. In addition, since unnecessary heat is not supplied to the heat roller 27 after the series of image forming processes, the apparatus can be prevented from being heated more than necessary, and energy consumption can be reduced. The unnecessary heat is heat for maintaining the surface temperature Tr of the heat roller 27 at the fixing temperature T1.

  On the other hand, if the surface temperature Tp of the press roller 28 is lower than the predetermined temperature T3 when the PDS 33 is on as described above, it is determined that the apparatus is not warmed. If the apparatus is not warmed, the set temperature is switched from the fixing temperature T1 to the standby temperature T2 in accordance with the timing when the motor 34 stops after a predetermined time has elapsed after the end of a series of image forming processes. When the apparatus is not warmed, the surface temperature of the heat roller starts to decrease after a predetermined time elapses after the series of image forming processes is completed and the motor is stopped. Therefore, when the apparatus is not warmed, heat continues to be supplied to the heat roller 27 for a predetermined time even after a series of image forming processes is completed, and the apparatus is warmed, so that it is possible to prevent FCOT from becoming long. . The heat continuously supplied here is heat for maintaining the surface temperature Tr of the heat roller 27 at the fixing temperature T1. Further, since the warming condition of the apparatus is determined using the temperature sensor 32 that directly contacts the surface of the press roller 28 that takes away the heat supplied to the heat roller 27, a more efficient image forming apparatus is obtained.

  In the above embodiment, the surface temperature of the press roller is detected by using a temperature sensor installed in contact with the surface of the press roller as the temperature detecting means, but this relates to the surface temperature of the press roller. If it can be detected, it may be detected using a temperature sensor arranged in the vicinity of the press roller. Alternatively, the surface temperature of the heat roller may be indirectly detected using other temperatures such as the temperature inside the heat insulating wall when the press roller is surrounded by the heat insulating wall.

  In the above embodiment, the set temperature of the heat roller is switched from the fixing temperature to the standby temperature in accordance with the timing when the motor stops when the apparatus is not warmed. If time has passed, you may switch to another time.

1 is a block diagram showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. It is the flowchart which showed the content of the surface temperature control of the heat roller in 1st Embodiment of this invention. FIG. 3A is a time chart in the image forming apparatus shown in FIG. 1 showing the relationship between the surface temperature Tr of the heat roller, the set temperature, the PDS, and the motor. FIG. 3A is a time chart when Tp ≧ T3, and FIG. It is a time chart in case of Tp <T3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 27 Heat roller 28 Press roller 29 Heater 32 Temperature sensor 33 PDS
34 Motor

Claims (3)

An image forming apparatus in which an image forming process is performed by fixing a toner image transferred to the recording paper by heating and pressurizing the recording paper,
A heat roller,
A heater built in the heat roller and supplying heat to the heat roller;
A press roller installed in contact with the heat roller;
A recording paper discharge sensor installed on the recording paper discharge side of the heat roller and the press roller to detect the passage of the recording paper;
Temperature detecting means for detecting the surface temperature of the press roller;
When the detected surface temperature is higher than a predetermined temperature, the heat roller is adjusted to the first time when the last recording sheet passes and the recording sheet discharge sensor is turned off in a series of the image forming processes. First control means for switching the set temperature from the fixing temperature to the standby temperature;
An image forming apparatus comprising: a second control unit configured to switch the set temperature from the fixing temperature to the standby temperature after a predetermined time has elapsed from the first time when the detected surface temperature is lower than the predetermined temperature. A motor for rotating the heat roller and the press roller;
The image forming apparatus according to claim 1, wherein the second control unit switches the set temperature from the fixing temperature to the standby temperature in accordance with a second timing when the motor stops after the first timing. A temperature sensor installed in contact with the surface of the press roller;
The image forming apparatus according to claim 1, wherein the temperature detection unit detects the surface temperature directly from the surface of the press roller by the temperature sensor.

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