JP2010122448A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the convenience and energy saving of an image forming apparatus by determining the timing of shifting into a power saving mode in consideration of the time required for recovery from the power saving mode. <P>SOLUTION: The image forming apparatus is shifted into the power saving mode, when the temperature of a fixing part 40 after the formation of an image is completed is decreased below a predetermined temperature. The predetermined temperature is such a temperature that the predicted time required to reach a fixing target temperature from the detected temperature of the fixing part 40 is not shorter than the rising time of a controller 202 in recovery from the power saving mode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that heats and fixes a sheet, and particularly to control of shifting to a power saving mode.

  In recent years, energy saving of electrophotographic apparatuses such as printers, copiers, facsimiles and the like has been proposed in view of environmental problems.

For example, Patent Document 1 is configured so that the user can grasp the power consumption value by having a power consumption calculation function in the image forming apparatus. Then, the user can schedule power supply based on the power consumption information, and can set the power saving mode according to the operating environment. For example, the user can grasp the operation status of the image forming apparatus for one week and set the time to shift to the energy saving mode.
JP 2002-225395 A

  However, the conventional image forming apparatus is configured such that the user sets the conditions for shifting to the energy saving mode. In other words, since each user uses to determine the condition setting, it is necessary for the user to make settings after understanding the convenience and energy saving effect. Trial and error are necessary for effective setting, and operability is poor. .

  Even if scheduling is performed, the expected energy saving effect may not be obtained, for example, the mode is shifted to the power saving mode immediately after mass printing, or the mode is not easily shifted to the low power mode after printing a small amount. In addition, if the fixing device is deprived of heat on the recording paper after a large number of prints, and immediately shifts to the power saving mode, the first print time after returning from the power saving mode becomes longer. It can get worse.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus that automatically controls operations that achieve both convenience and energy saving in accordance with usage conditions in an image forming apparatus equipped with a power saving mode. It is said.

  In order to solve the above problems, an image forming apparatus according to the present invention includes an image forming unit that forms an image on a sheet in an image forming apparatus having a power saving mode for reducing power consumption in a state where image formation is not performed. A fixing unit that fixes the sheet on which the image is formed, a temperature detection unit that detects the temperature of the fixing unit, a temperature control unit that controls the temperature of the fixing unit to be a target temperature, and completion of image formation And a control unit that shifts the image forming apparatus to the power saving mode when a temperature detected by the temperature detecting unit later becomes lower than a predetermined temperature.

  According to the present invention, by changing the time for shifting to the power saving mode according to the expected return time from the power saving mode, the mode is shifted to the power saving mode at an optimal timing without deteriorating the convenience of the image forming apparatus. It becomes possible.

(First embodiment)
The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus according to an embodiment of the present invention.

  This image forming apparatus is an electrophotographic color image forming apparatus in which a plurality of image forming units are arranged in parallel.

  The image forming apparatus includes an image forming unit 10, a paper feeding unit 20, an intermediate transfer unit 30, and a fixing unit 40.

  The image forming unit 10 is configured as described below. Photosensitive drums 11a, 11b, 11c, and 11d as image carriers are pivotally supported at their centers and are driven to rotate in the direction of the arrow. The primary chargers 12a, 12b, 12c, 12d, the laser scanner unit 13, and the developing devices 14a, 14b, 14c, 14d are arranged in order in the rotation direction so as to face the outer peripheral surfaces of the photosensitive drums 11a to 11d. The primary chargers 12a to 12d respectively apply a uniform charge amount to the surfaces of the photosensitive drums 11a to 11d. Next, the laser scanner unit 13 irradiates the photosensitive drums 11a to 11d with light beams such as a laser beam modulated according to the recording image signal, and thereby electrostatic latent images are respectively formed on the photosensitive drums 11a to 11d. Form.

  Further, the developing devices 14a to 14d respectively containing developer of four colors such as yellow, cyan, magenta and black (hereinafter referred to as “toner”) visualize the electrostatic latent image. The visualized visible image is transferred to the intermediate transfer belt 31 in the image transfer areas Ta, Tb, Tc, and Td. The cleaning devices 15a, 15b, 15c, and 15d clean the drum surface by scraping off toner remaining on the photosensitive drums 11a to 11d without being transferred to the intermediate transfer belt 31. Through the process described above, the four color toner images are transferred onto the intermediate transfer belt 31 in an overlapping manner.

  The sheet feeding unit 20 includes cassettes 21 a and 21 b for storing sheets P and a manual feed tray 27. The sheets P stored in the cassettes 21a, 21b or the manual feed tray 27 are sent out one by one by the pickup rollers 22a, 22b, 26, and conveyed to the registration roller 25 by the pair of paper feed rollers 23a, 23b, 23c. Then, the registration roller 25 is driven in accordance with the image formation timing of the image forming unit 10 to send out the sheet P to the secondary transfer region Te.

  In the primary transfer areas Ta to Td where the photosensitive drums 11 a to 11 d and the intermediate transfer belt 31 face each other, primary transfer chargers 35 a to 35 d are disposed on the back side of the intermediate transfer belt 31. A secondary transfer roller 36 is disposed so as to face the driven roller 34, and a secondary transfer region Te is formed by a nip with the intermediate transfer belt 31. The secondary transfer roller 36 is pressed against the intermediate transfer belt 31 with an appropriate pressure.

  The fixing unit 40 includes a fixing film having a heat source such as a ceramic heater substrate therein, and a pressure roller (which may be provided with a heat source in some cases) that presses the film across the ceramic heater substrate. Further, a guide 43 for guiding the recording material P to the nip portion of the 40 rollers of the fixing unit is provided upstream of the fixing unit 40. In addition, an outer paper discharge roller 45 is provided for guiding the recording material P that has passed through the fixing unit 40 to the outside of the apparatus.

  Next, the operation of the image forming apparatus will be described.

  When an instruction to start an image forming operation is input from an operation unit (not shown) or an external device, the sheet P is fed from a paper feed stage corresponding to the selected sheet size. For example, a case where paper is fed from the cassette 21a will be described. First, the sheet P is sent out one by one from the cassette 21a by the pickup roller 22a. The sheet P is guided between the sheet feeding guides 24 by the pair of sheet feeding rollers 23c and conveyed to the registration rollers 25. At that time, the registration roller 25 is stopped, and the leading edge of the sheet P hits the nip portion of the registration roller 25. Thereafter, the registration roller 25 starts rotating in accordance with the timing at which the toner image transferred to the intermediate transfer belt 31 by the image forming unit 10 reaches the secondary transfer region Te.

  On the other hand, when an image forming operation start signal is issued in the image forming unit 10, the toner image formed on the photosensitive drum 11 d that is the most upstream in the rotation direction of the intermediate transfer belt 31 is transferred to the intermediate transfer belt in the primary transfer region Td. 31 is transferred. The transferred toner image is conveyed to the next primary transfer region Tc. In the primary transfer area Tc, image formation is delayed by the time taken to convey the toner image from the primary transfer area Td to the primary transfer area Tc, and the next toner is aligned with the previous image. The image is transferred. The same process is repeated for the primary transfer area Tb and the primary transfer area Ta, and the four color toner images are finally transferred onto the intermediate transfer belt 31.

  Thereafter, when the sheet P enters the secondary transfer region Te and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the sheet P. Then, the four-color toner images formed on the intermediate transfer belt 31 by the above-described process are transferred onto the surface of the sheet P. Thereafter, the sheet P is accurately guided to the nip portion of the fixing unit 40 by the conveyance guide 43. The toner image is fixed on the surface of the sheet P by the heat and nip pressure in the fixing unit 40. Thereafter, the sheet P is conveyed by the inner discharge roller 44 and the outer discharge roller 45 and discharged outside the apparatus.

  FIG. 2 is a block diagram of the control unit of the image forming apparatus.

  Reference numeral 201 denotes a module control unit that controls each module of the entire image processing apparatus. The module control unit 201 includes a CPU (not shown), a ROM (not shown) storing control programs and data, a RAM used as a work storage area, etc., a driver (not shown) for each load, and the like. The program is executed according to an instruction from 202. The driving loads 208 are configured by a motor, a clutch, a solenoid, and the like that drive a paper feeding system, a transport system, and an optical system. Sensors 210 include a paper detection sensor for detecting the conveyed paper, a toner residual detection sensor for detecting the amount of toner in the developing unit, a home position for each load, a switch for detecting the open / closed state of the door, and the like. Consists of. The high voltage unit 213 outputs a high voltage to the primary charger 113, the developing device 118, the pre-transfer charger 121, the transfer charger 133, and the separation charger 134 in accordance with an instruction from the module control unit 201. The fixing unit 40 includes an on-demand heater, a temperature detection unit, a heater driving unit, and the like (the fixing unit configuration will be described later), and is a temperature that controls the temperature of the fixing unit to a target temperature by an on / off signal from the module control unit 201. Key control is performed.

  An operation unit 220 includes a key operated by the operator, a liquid crystal display that displays the state of the apparatus, and an LED.

  The main controller 202 includes a CPU 250, a ROM 251, and a communication unit 204, and communicates with the operation unit 220, the external device 106, the module control unit 201, and the power control unit 203. Note that the communication unit 204 can monitor an instruction to return from the power saving mode from the operation unit 220 and an input of an image forming job from the outside even when the power is not supplied to the CPU 250. That is, the communication unit functions as a monitoring unit. Further, the power consumption of the communication unit 204 is lower than that of the CPU 250. The main controller 202 performs various image processing on image signals from an image reading unit of the image forming apparatus and an external device. Further, the power control unit 203 controls power supply to the module control unit 201 and the main controller 202 in accordance with an instruction from the main controller 202.

  The image forming apparatus of the present embodiment has a power saving mode and a standby mode as operation modes when the image forming operation is not executed. The transition from the standby mode to the power saving mode and the return from the power saving mode to the standby mode are performed by instructing the power control unit 203 from the communication unit 204. The standby mode in the present embodiment refers to a state in which power can be supplied to each module of the image forming apparatus and printing can be started immediately when an image forming request is made from the operation unit, the network, or a FAX (however, The temperature control of the fixing unit is not performed. The power saving mode is a state in which power is supplied to the operation unit 220 and the communication unit 204 and power is not supplied to the CPU 250 and the ROM 251 in order to reduce power consumption in a state where image formation is not executed. It refers to a state that consumes less power than in the mode. The transition control flow from the standby mode to the power saving mode will be described later.

  Further, when the main controller 202 returns from the power saving mode to the standby mode, the main controller 202 performs a rising operation (initialization operation) so that each unit in the main controller 202 operates normally. Only after the start-up operation is completed, the main controller 202 starts up in a state where the image forming apparatus can be controlled. In this embodiment, the time required for the main controller to rise is 10 seconds.

  Next, the fixing unit 40 and its drive circuit will be described with reference to FIGS.

  FIG. 3 is a configuration diagram of the fixing unit 40 of FIG. Reference numeral 701 denotes a ceramic heater, 702 a fixing film, 703 a pressure roller, 711 a sheet metal, 712 a temperature detection thermistor, 713 a holder, and 714 a self-bias circuit. The ceramic heater 701 is a heater (see FIG. 4) in which a heat generation pattern is printed on ceramic, and is a highly responsive heater that rises by about 50 ° C. in one second. The fixing film 702 is made of a metal as a base material, a film having a rubber layer of about 300 μm, and a fluorine surface treatment. The fixing film 702 has a very small heat capacity and transmits the heat of the heater only to the nip portion. The pressure roller 703 is a roller having a hardness of about 60 ° and frictionally drives the fixing film 702. The sheet metal 711 has a U-shape and presses the fixing film 702 against the pressure roller 703 from the inside, and the pressure is about 180N. The thermistor 712 has a main thermistor and a sub-thermistor, and detects the temperature of the heater 701, respectively. The main thermistor is disposed at the center of the heater 701 in the front and back direction (the axial direction of the pressure roller 703), and detects the temperature for fixing temperature control. The sub-thermistor is disposed at the end of the heater 701 in the axial direction of the pressure roller 703, and detects a temperature rise in a non-sheet passing portion when a small size paper such as A4R or B5 size is passed.

  FIG. 4 is a plan view of the heater 701 in FIG. In the figure, 704 is a heating element and 705 is an electrode. The heating element 704 generates heat by applying a voltage to both ends of the electrode 705. The heating element pattern of the heater is an example, and may be determined according to the characteristics of the fixing unit 40.

  FIG. 5 is a circuit diagram (detailed circuit diagram of the module control unit 201 and the fixing unit 40 shown in the control block diagram of FIG. 2) showing the configuration of the heater drive control circuit that controls the drive of the heater 701. Reference numeral 901 denotes an AC power source such as a commercial power source that supplies power to the entire image forming apparatus. Power is supplied to the AC power source 901 via the AC filter 902. A triac 904, resistors 905 and 906, and a phototriac coupler 907 connected in series between the resistors 905 and 906 are connected between the AC filter 902 and the ceramic heater 701. Resistors 905 and 906 are bias resistors for the triac 904. The phototriac coupler 907 is a device for ensuring a creepage distance between the electrical primary and secondary circuits. One end of the phototriac coupler 907 on the light emitting unit side is connected to the power supply Vcc via a resistor 908. The resistor 908 is a resistor for limiting the current of the phototriac coupler 907. The other end of the phototriac coupler 907 on the light emitting unit side is connected to the collector terminal of the transistor 909. A CPU 920 (arranged in the module control unit 201 in the control block diagram of FIG. 2) is connected to the base terminal of the transistor 909 via a resistor 910.

  The AC power source 901 causes the ceramic heater 701 to generate heat by supplying power to the ceramic heater 701 via the AC filter 902. The triac 904 controls energization and interruption of the power supplied to the ceramic heater 701. It is. The transistor 909 controls ON / OFF of the light-emitting diode of the phototriac coupler 907, and the triac 904 is turned on when the light-emitting diode emits light. The transistor 909 operates according to the heater ON signal from the CPU 920 via the resistor 910. The CPU 920 has an analog input detection unit, and detects the temperature of the heater 701 by comparing the voltage generated by dividing the voltage with the thermistor 712 in contact with the ceramic heater 701 and the table in the CPU 920.

  With the configuration described above, temperature control is performed so that the fixing unit 40 is maintained at a predetermined temperature during printing or standby.

  FIG. 6 is a diagram showing a temperature transition of the fixing unit 40 after printing (after the temperature control of the fixing unit is finished). When the standby mode is set after the image formation is finished, the temperature control of the fixing unit 40 is finished. Since the amount of heat accumulated in the fixing unit 40 varies depending on the time during which image formation has been performed, the temperature change of the fixing unit 40 after the completion of temperature control varies depending on conditions such as the time during which image formation has been performed. FIG. 6 shows the temperature transition after 500 images are formed and then 50 images are formed. Since heat is accumulated in the fixing unit 40 (particularly the pressure roller 703) after printing 500 sheets, the temperature decrease rate after image formation is relatively low. It takes about 300 seconds to decrease to 100 ° C. On the other hand, after printing 50 sheets, the rate of temperature decrease is relatively high, and it takes only about 60 seconds to decrease to 100 ° C. As described above, this is due to the accumulation of heat in the fixing unit 40, and thus varies depending on the temperature of the fixing unit 40 and the time required for image formation. Shows a good temperature curve.

  FIG. 7 is a diagram illustrating the relationship between the fixing unit temperature when the temperature control of the fixing unit 40 is not performed and the arrival time from the temperature control start to the target temperature (200 ° C.). Data indicating this relationship is stored in the ROM 251. When the temperature of the fixing unit 40 is controlled in the standby mode, the temperature is always controlled to the target temperature (temperature necessary for image formation). However, when the temperature control is not performed even in the power saving mode or in the standby mode, the temperature of the fixing unit 40 must be raised to the target temperature when an instruction to start image formation is given. In this case, when the fixing unit 40 is warmed due to the influence of the previous image formation, the time until the target temperature is reached varies. For example, as described above with reference to FIG. 6, the fixing unit 40 reaches 100 ° C. when 300 seconds have elapsed after forming 500 images. If an image formation start (temperature control start) command is issued at that time, it is understood that 10 seconds are required until the fixing unit 40 reaches the target temperature (200 ° C.). When the temperature of the fixing unit 40 is lower, the time to reach the fixing target temperature is further increased.

  It is assumed that the activation time of elements other than the fixing unit 40, for example, the time required for the main controller 202 (CPU 250) to rise to a controllable state (rise time) is 10 seconds. If the time until the fixing unit 40 reaches the target temperature is shorter than the rise time of the main controller 202 (CPU 250) when an image formation start command is received in the power saving mode, immediately after the main controller 202 rises. Image formation can be started. That is, if the temperature of the fixing unit 40 is equal to or higher than a predetermined temperature (100 ° C. in this example), the time until the target temperature is reached is 10 seconds or less, so that image formation can be started immediately after the main controller 202 is activated. . However, when the temperature of the fixing unit 40 is less than 100 ° C., even if the main controller 202 is started up, the fixing unit 40 has not reached the target temperature, so that image formation cannot be started immediately. That is, when the temperature of the fixing unit 40 decreases to less than 100 ° C. after the image formation is completed, the time until the image formation can be started even when the mode is shifted to the power saving mode or the standby mode is maintained. Be the same.

  With reference to the flowchart of FIG. 8, the control for shifting to the power saving mode in the present embodiment will be described. This flowchart is executed according to a program stored in the ROM 251 by the CPU 250 arranged in the main controller 202.

  When the power source of the image forming apparatus is turned on or restored from the power saving mode and the main controller 202 (CPU 250) is started up, the CPU 250 controls the module control unit 201 to perform the initial operation of the image forming unit such as pre-multi rotation. (1002). When the initial operation ends, the CPU 250 shifts to the standby mode and waits for a print request (1003). If there is no print request, the CPU 250 detects the temperature of the fixing unit 40 based on the output of the thermistor 712 (1005). The CPU 250 compares the target temperature arrival time of the fixing unit 40 calculated from the detected temperature with the time required for returning from the power saving mode (the startup time of the main controller 202 is 10 seconds) (1006). This comparison is performed based on a table (FIG. 7) stored in the ROM 251. The CPU 250 determines whether the target temperature arrival time of the fixing unit 40 is 10 seconds or less, that is, whether the temperature of the fixing unit 40 is 100 ° C. or higher (1007). Repeat 1007). The CPU 250 always monitors the temperature of the fixing unit 40 during the standby mode, performs a process of shifting to the power saving mode when the temperature becomes less than 100 ° C., regardless of the elapsed time after the end of image formation, and the image forming apparatus. Is shifted to the power saving mode (1008). The temperature of 100 ° C. is a temperature (detection temperature) at which the time required for the fixing unit 40 to reach the target temperature from the detection temperature is not shorter than the rise time when the main controller 202 returns from the power saving mode. .

  If the CPU 250 determines in step 1003 that a print request has been made, the CPU 250 performs a printing operation (1004), and performs the processing in and after step 1005 described above even after finishing the temperature control of the fixing unit 40 after the printing. If, for example, 500 images are formed in the printing operation in step 1004, the temperature of the fixing unit 40 decreases to 100 ° C. after about 5 minutes, so that the mode is shifted to the power saving mode. If 50 images are formed in the printing operation in step 1004, the mode is shifted to the power saving mode after about 1 minute. In either case, before shifting to the power saving mode, that is, in the standby mode, it is possible to output the first print within 10 seconds after inputting the instruction to start image formation.

  When the mode is shifted to the power saving mode, the CPU 250 controls the power control unit so as to supply power only to the communication unit 204 in order to monitor the start-up request (print request or the like) from the operation unit or the network. 1008). Thereafter, the power supply to the CPU 250 is cut off. During the power saving mode, the communication unit 204 monitors whether or not the image forming apparatus is requested to start up from the operation unit or the network. When the startup request is received, the power supply unit 203 supplies power to start up the CPU 250 and the like. Is output. As a result, power is supplied to the main controller 202 including the CPU 250, and the image forming apparatus is brought into a state where image formation is possible.

  This control is repeatedly performed until the image forming apparatus is turned off or shifted to the power saving mode.

  As described above, by considering the time required for the main controller 202 to rise and the time required for the fixing unit 40 to return to the fixable temperature, the timing for shifting to the power saving mode is determined. Can be efficiently performed. That is, it is possible to prevent the first print time after returning from the power saving mode from becoming long because the fixing device is in a warm state after a large amount of printing.

  In this embodiment, the case where a ceramic heater (resistor) is used as the heater unit of the fixing unit 40 has been described as an example. However, a fixing unit using a halogen heater, an IH heater, or the like may be used.

In addition, the startup request from the power saving state may be a device that can be connected by FAX or USB in addition to a request from the operation unit or the network.
In this embodiment, a table that predicts the target temperature from the temperature of the fixing unit 40 is used. However, a table for predicting the target temperature arrival time from the plurality of falling characteristics of the fixing unit 40 after the end of image formation and the measured temperature of the fixing unit 40 shown in FIG. 6 may be used. For example, the table shown in FIG. 7 may be provided separately for the case where the number of image formations in the immediately preceding image formation job is greater than or equal to the predetermined number. That is, the target temperature arrival time of the fixing unit 40 is changed according to the duration of the immediately preceding image forming job. For example, when the detected temperature of the fixing unit is 100 ° C., the target temperature arrival time when the duration of the immediately preceding image forming job is the first time T1 is the second duration of the immediately preceding image forming job. It becomes shorter than the target temperature arrival time at time T2 (<T1). This is because the amount of heat stored in the pressure roller 703 when the duration of the immediately preceding image forming job is T1 is greater than when the duration is T2. Therefore, the temperature for shifting to the power saving mode when the duration of the immediately preceding image forming job is T1 is set lower than when the duration is T2. The same applies even if the duration of the image forming job is replaced with the number of images formed.

  In the present embodiment, the timing for shifting to the power saving mode is determined by comparing the target temperature arrival time of the fixing unit 40 and the return time of the main controller 202 from the power saving mode. However, in addition to this, the user may be able to set the transition time to the power saving mode. Thus, for example, even when a large amount of image formation is performed, the temperature drop of the fixing unit 40 is delayed, and the timing of shifting to the power saving mode is delayed, the mode is changed to the power saving mode with the transition time set by the user. By shifting, the transition time to the power saving mode does not become too long.

1 is a side sectional view of an image forming apparatus. 2 is a control block diagram of the image forming apparatus. FIG. It is a block diagram of a fixing unit. It is a top view of a heater. It is a figure which shows a heater drive circuit. It is a figure which shows the temperature transition of a fixing part. FIG. 6 is a diagram illustrating a relationship between a fixing unit temperature and a target temperature arrival time after returning from a power saving mode. It is a flowchart which shows transfer control to a power saving mode.

Explanation of symbols

40 Fixing Unit 202 Main Controller 203 Power Control Unit 204 Communication Unit 250 CPU
712 thermistor

Claims (5)

In an image forming apparatus having a power saving mode for reducing power consumption when image formation is not performed,
Image forming means for forming an image on a sheet;
A fixing unit for fixing a sheet on which an image is formed; and
Temperature detecting means for detecting the temperature of the fixing unit;
Temperature control means for controlling the temperature of the fixing unit to be a target temperature;
A control unit that shifts the image forming apparatus to the power saving mode when the temperature detected by the temperature detecting unit after image formation is lower than a predetermined temperature;
An image forming apparatus comprising:   The predetermined temperature is such that the time required to reach the target temperature from the temperature detected by the temperature detection means is longer than the time required for the controller to start up when returning from the power saving mode. The image forming apparatus according to claim 1, wherein the image forming apparatus is a temperature.   The image forming apparatus according to claim 2, wherein the control unit includes a table storing data indicating a relationship between a temperature of the fixing unit and a time required to reach the target temperature from the temperature. .   The image according to claim 1, further comprising a monitoring unit that monitors an instruction to start image formation, wherein in the power saving mode, power is supplied to the monitoring unit and power is not supplied to the control unit. Forming equipment.   When the duration of the immediately preceding image forming job is the first time, the control unit performs the predetermined time more than when the duration of the immediately preceding image forming job is the second time shorter than the first time. The image forming apparatus according to claim 1, wherein the temperature is lowered.

Images