JP5625861B2 - Image forming apparatus and fixing control method - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus (copying machine, printer, multifunction machine, etc.) that performs a power saving operation, and more specifically, wastes a heating means (heater) for fixing a toner image on a recording medium. The present invention relates to an image forming apparatus and a fixing control method that realize power saving by controlling not to drive.

In recent years, thorough power saving has been demanded even in electrophotographic image forming apparatuses due to increasing awareness of environmental problems. In an electrophotographic image forming apparatus, toner is thermally fixed on a printing paper, and it is necessary to keep the fixing device at a high temperature during printing. Therefore, most of the power consumption in the image forming apparatus is occupied by the power supplied to the heater as the heating unit of the fixing device.
Many technologies have been developed for power saving of the fixing device, and an on-demand fixing method, an IH (electromagnetic induction heating) fixing method, and the like have already been put into practical use.

In addition to the power saving of the fixing device, a control method for driving the fixing heater unnecessarily so as not to generate an excessive amount of heat is a technique necessary for power saving.
The control method employed in many image forming apparatuses is such that when there is no print request to be processed during printing in which the heater is driven at a temperature at which proper fixing is possible (hereinafter referred to as “fixable temperature”), the heater is used. The power supply to the printer is stopped, and then the system shifts to power saving control (hereinafter also referred to as “standby control”) that maintains the temperature of the fixing device (hereinafter referred to as “fixing temperature”) in the standby state. In this control method, when a print request is received at the time of printing, the control is returned to the control at the time of printing driven at the fixing possible temperature.

In addition, when performing the power saving control described above, the temperature at which the fixing device can be fixed is estimated by predicting the time from the temperature rising gradient of the fixing device until the fixing device reaches the fixable temperature after the start of printing of the print request received during standby. For example, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 2010-128465), it is already known to control the image recording medium to enter the fixing device at the timing to become.
The waiting time after the fixing device reaches the fixable temperature by predicting the time to reach the required fixing temperature from the temperature rise characteristics of the fixing device and starting image formation at the timing determined according to the prediction result The heater is driven wastefully so as not to generate an excessive amount of heat.

However, according to the conventional control method described above, the fixing temperature detected for obtaining the temperature rising gradient is the temperature of the surface of the fixing roller, and is not detected because the ambient temperature in the fixing device is not detected. Even if the temperatures are equal, the amount of heat required for the fixing device to be ready for printing may differ. For example, the required amount of heat differs between when the temperature in the fixing device is sufficiently high, such as after the end of continuous printing, and when the time has elapsed due to standby control. In addition, since the time to reach the fixing possible temperature is predicted from the temperature rise characteristic and the image forming start timing is determined according to the prediction result, the image forming start timing is after the prediction and cannot be before the prediction.
Therefore, when the temperature in the fixing device is sufficiently high, such as after the end of continuous printing, the fixing temperature is reached immediately after the start of the fixing device, so that a waiting time occurs until the image recording medium reaches the fixing device. In the meantime, heat is released from the fixing device, and a new amount of heat is required.

Here, with reference to FIGS. 8 and 9, the control operation of the prior art that intends the printing paper to enter the fixing device at the timing when the fixing possible temperature is reached will be described in more detail.
FIG. 8 is a diagram for explaining a change in the fixing temperature in one operation example of the heater drive control corresponding to the print request at the time of power saving (standby) in this prior art.
FIG. 8 is a diagram illustrating the relationship between the control and the transition of the fixing temperature when the printing operation is performed from the state where the image forming apparatus is in a standby state for a certain time or more and the heating roller is maintained at a certain standby temperature. is there.
In the following description, the hardware configuration of the image forming apparatus according to the prior art is common to the configurations of FIGS. 1 to 3 according to the present invention, which will be described later. Reference shall be made to the constituent elements to be referred to.

As shown in FIG. 8, when a print request is received (job reception) while the standby temperature control is being performed by the standby control, the fixing driving unit 27 (FIG. 3) is operated in response to this request, and heating is performed. The roller 23 and the pressure roller 24 (FIGS. 1 and 2) are rotated, and the heater lamp 26 is turned on. At this time, since the pressure roller 24 is heated by the heat of the heating roller 23, the temperature detected by the thermistor 25 that detects the surface temperature of the heating roller 23 is temporarily lowered.
After the operation of the fixing drive unit 27 is started, first, t1 is calculated from the gradient (ΔT / Δt) of the fixing temperature change until the fixing temperature reaches the fixable temperature, and the image forming drive unit 29 and the intermediate transfer drive unit 30 are operated. Start image formation. This image formation start timing can be determined as follows. That is, the time t2 from the start of image formation until the first print sheet enters the fixing device 18 can be obtained in advance from the operating conditions of the paper feed drive unit 28, and therefore is predicted based on the gradient of the fixing temperature change. The time t2 is calculated backward from the time point after t1, and the calculated time point is determined as the image formation start timing.
By doing so, it is possible to control the paper feed drive unit 28 and transport the printing paper so that the first printing paper enters the fixing device 18 at the timing when the fixing temperature reaches the fixing possible temperature. Thus, the heater lamp 26 is not turned on unnecessarily and no extra heat is generated.

Incidentally, the control operation example of FIG. 8 is a case where a print request is received during a control period for maintaining the standby temperature. However, the print request is made at any time and, as shown below, the initial stage of transition to standby control, that is, standby There is a case where a print request is accepted at a timing before entering a control for maintaining the temperature. Next, an operation example in the case where the control method is the same as that shown in FIG. 8 will be described.
FIG. 9 is a diagram for explaining changes in the fixing temperature in the heater drive control of this operation example.

As shown in FIG. 9, when a print request is made at the beginning of the transition to the standby control, the fixing driving unit 27 is operated in response to the request to rotate the heating roller 23 and the pressure roller 24, and the heater lamp 26 is turned on.
At this time, shortly after printing, the fixing device 18 has sufficient heat, the pressure roller 24 is also at a high temperature, and the decrease in the fixing temperature is small, that is, the fixing temperature enters a control for maintaining the standby temperature. The temperature is higher than the previous standby temperature. From this state, the control is switched to printing control, the fixing driving unit 27 is operated, and the temperature is raised to the fixing possible temperature.

Control is switched to printing control, and the fixing driving unit 27 starts to operate. Similar to the operation example of FIG. 8, the time t1 until the fixing temperature reaches the fixable temperature is obtained from the temperature change gradient (ΔT / Δt). .
However, in the case of this operation example, t1 is shorter than the time t2 from the start of image formation until the printing paper enters the fixing device 18, so that the time t1 is based on the gradient of the fixing temperature change as shown in FIG. Even if the image forming drive unit 29 and the intermediate transfer drive unit 30 are operated immediately, even if the temperature of the fixing device 18 reaches the fixable temperature, the first printing paper does not enter, As a result, this printing paper enters after time t3.
As described above, according to the conventional heater drive control, when the next print request is received in a state where the fixing device 18 has sufficient heat immediately after printing, the temperature of the fixing device 18 is increased. After reaching the fixable temperature, the printer waits for the entry of the print paper for a time t3 until the print paper reaches the fixing device 18 without being used for the fixing operation. The heat to keep is wasted.

  The present invention has been made in view of the above-described problems of the prior art. The purpose of the present invention is to fix printing paper at the timing when the temperature of the fixing unit reaches the fixable temperature, regardless of when a print request is made during standby. In order to prevent the heating means of the fixing unit from being driven wastefully.

The present invention has an image forming unit that forms an image on a recording medium in a transported state, and a heating unit that can control driving on / off, and is on the recording medium in a transported state formed by the image forming unit. A fixing unit that heats the image by the heating unit and fixes the image on a recording medium; a fixing temperature detection unit that detects a temperature of the fixing unit; and the operation of the image forming unit is stopped in the absence of a print request, and the heating The driving of the fixing unit is turned off, and the heating unit is turned on / off based on the fixing temperature detected by the fixing temperature detecting unit to perform the standby control to keep the fixing unit at the standby temperature. As a return operation performed in response to a print request, the image forming unit in a stopped state is started, and the fixing unit is switched from the standby control to maintain the fixing temperature at the time of paper passing. An image forming apparatus having a control means for a change in temperature gradient calculating means for calculating a temperature change gradient descending direction at predetermined time intervals based on the fixing temperature detected by the fixing temperature detecting means, wherein A temperature change gradient storage means for storing a rise time at which the fixing temperature rises to a fixable temperature from the start of the heating means in relation to the temperature change gradient in the downward direction calculated by the temperature change gradient calculation means and the fixing temperature; The control unit acquires the start-up time from the temperature change gradient storage unit based on the fixing temperature and the temperature change gradient at that time when the image forming apparatus is powered on or returned from standby control. The start-up time is compared with the entry time from the start of the image forming unit until the first recording medium enters the fixing unit. Is shorter, the image forming unit is immediately activated in response to a print request made during standby, and the timing of activation of the heating unit is set at the timing when the recording medium enters the fixing unit. The temperature is determined so as to reach a fixing temperature .

  According to the present invention, it is possible to allow the printing paper to enter the fixing device at a timing when the temperature of the fixing unit reaches the fixable temperature, and wasteful heating means of the fixing unit, regardless of when a print request is made during standby. Power can be saved by avoiding driving.

1 is a diagram illustrating an outline of a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a fixing device provided in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a block diagram showing a schematic configuration of an image forming control system of the image forming apparatus shown in FIG. 1. It is a figure explaining the change of the fixing temperature in the operation example (embodiment 1) of the heater drive control corresponding to the print request at the time of standby. It is a table of the prediction time t4 which makes variable the elapsed time from the last printing and the number of printed sheets. It is a table of prediction time t4 which makes temperature change gradient value and fixing temperature variable. It is a figure explaining the application conditions of heater drive control (Embodiment 1) corresponding to the printing request at the time of standby. It is a figure explaining the change of the fixing temperature in 1 operation example of the heater drive control corresponding to the printing request | requirement at the time of the power saving (standby) based on a prior art. FIG. 9 is a diagram for explaining a change in fixing temperature in another operation example of heater drive control corresponding to a print request during standby in FIG. 8.

Hereinafter, embodiments of an image forming apparatus according to the present invention will be described.
The present invention relates to an electrophotographic image forming apparatus (a copying machine, a printer, a multifunction machine, etc.) that performs a power saving operation, and does not wastefully drive a heating unit (heater) for fixing a toner image on a recording medium. By doing so, control is performed to realize power saving.
The heater drive control intended for this power-saving operation is to first perform standby control, but when the print request is received during standby (when standby control is being performed), the temperature can be fixed. When performing the control operation of returning to the drive-time printing control, the printing paper is caused to enter the fixing device at the timing when the temperature of the fixing unit reaches the fixable temperature regardless of the time when the print request is made during standby. Thus, the operation of preventing the heating means of the fixing unit from being driven wastefully is characterized.
The heater drive control of the present embodiment, which is intended for power saving operation, will be described below with reference to the accompanying drawings. Prior to detailed description of the heater drive control, first, the image forming apparatus of the present embodiment. The outline of will be described.

[Configuration of Image Forming Apparatus]
FIG. 1 is a diagram illustrating an outline of a configuration of an image forming apparatus according to the present embodiment.
Here, with reference to FIG. 1, the configuration of the operation unit directly related to image formation and the outline of the operation of the operation unit related to the image forming apparatus will be described. In the figure, a tandem type color image forming apparatus is illustrated, but a toner image is formed on a printing paper in the conveyance process, and image formation is performed according to a series of image forming processes in which the formed toner image is thermally fixed. An electrophotographic image forming apparatus may be a color / monochrome machine, or may be an image forming system other than the embodiment described below.
Further, the configuration of the control system that controls the operation unit directly related to image formation, the drive unit, and the like will be described later in [Configuration of control system].

As shown in FIG. 1, the image forming apparatus 1 has a configuration in which AIO (All In One) cartridges having the number of color components are arranged along an intermediate transfer belt 12. The AIO cartridge is a module in which the electrophotographic process unit is integrated so that it can be handled as a replacement part.
The intermediate transfer belt 12 is an endless belt and rotates counterclockwise (indicated by an arrow in FIG. 1), and the AIO cartridges 2A, 2B, 2C, and 2D of the respective color component colors are sequentially arranged from the upstream side in the rotation direction. Are arranged in a so-called tandem type configuration.
Among these AIO cartridges 2A, 2B, 2C, and 2D, 2A forms a black image, 2B forms a cyan image, 2C forms a magenta image, and 2D forms a yellow image.
However, each AIO cartridge has the same internal configuration except that the color of the toner image to be formed is different. Therefore, in the following description, the AIO cartridge 2A will be described in detail, but for the other AIO cartridges 2B, 2C, and 2D, the description of the AIO cartridge 2A to be described later will be referred to and description thereof will be omitted.

The intermediate transfer belt 12 is an endless belt wound around a drive roller 3 and a transfer belt tension roller 4 that are rotationally driven. The drive roller 3 is rotationally driven by a drive motor (not shown), and the drive motor, the drive roller 3, and the transfer belt tension roller 4 function as drive means for moving the intermediate transfer belt 12.
An AIO cartridge 2A as an electrophotographic process section includes a photoconductor 5A having a drum outer periphery as a photosensitive surface, a charger 6A, an exposure device 7, a developing device 8A, a cleaner blade 9A, and the like disposed around the photoconductor 5A. It is configured.
The exposure unit 7 is configured to irradiate laser beams 10A, 10B, 10C, and 10D that are exposure lights corresponding to the color component colors formed by the AIO cartridges 2A, 2B, 2C, and 2D.

When forming an image, the outer peripheral photosensitive surface of the photoconductor 5A is uniformly charged by the charger 6A in the dark, and then emitted from the exposure device 7 having a laser light source that is controlled to be turned on with image data corresponding to the black image. Exposure with the laser beam 10A forms an electrostatic latent image on the outer peripheral photosensitive surface. The developing unit 8A visualizes the electrostatic latent image with black toner, that is, forms a black toner image on the photoreceptor 5A.
The formed toner image is transferred onto the intermediate transfer belt 12 by the action of the primary transfer roller 11A at a position (primary transfer position) where the photoreceptor 5A and the intermediate transfer belt 12 are in contact with each other. By this transfer, an image of black toner is formed on the intermediate transfer belt 12.
After the transfer of the toner image, the photoreceptor 5A waits for the next image formation after the unnecessary toner remaining on the outer peripheral surface is wiped off by the cleaner blade 9A.
As described above, the black toner image is conveyed to the next AIO cartridge 2B by the intermediate transfer belt 12 by the AIO cartridge 2A.

In the AIO cartridge 2B, a magenta toner image is formed on the photoconductor 5B by a process similar to the image forming process in the AIO cartridge 2A, and the toner image is superimposed on the black image formed on the intermediate transfer belt 12. And is transcribed.
The intermediate transfer belt 12 is further conveyed to the downstream AIO cartridges 2C and 2D one after another, and a cyan toner image formed on the photoconductor 5C and a yellow toner image formed on the photoconductor 5D by the same operation. The toner image is transferred while being superimposed on the intermediate transfer belt 12. Thus, a full-color image is formed on the intermediate transfer belt 12. The intermediate transfer belt 12 on which the full-color superimposed image is formed is conveyed to the position of the secondary transfer roller 13.
In the case of printing with black only, the primary transfer rollers 11B, 11C, and 11D are retracted to positions separated from the photoreceptors 2B, 2C, and 2D, respectively, and the above-described image forming process is performed only when black. Do.

During the paper transport operation during image formation, the printing paper 15 stored in the paper feed tray 14 is sequentially sent out by rotating the paper feed roller 16 counterclockwise from the top, and is moved to the registration roller 17 position. And wait.
The driving of the registration roller 17 is started at the timing when the toner image conveyed by the intermediate transfer belt 12 and the secondary transfer roller 13 overlap the position of the toner image and the printing paper 15. At this time, the registration roller 17 is driven to rotate counterclockwise to feed out the printing paper 15.

The printing paper 15 sent out by the registration roller 17 transfers the toner image on the intermediate transfer belt 12 to the printing paper 15 by the secondary transfer roller 13, and then the toner image by a fixing device 18 (detailed later). Is fixed by heat and pressure, and is discharged to the outside of the image forming apparatus 1 by a discharge roller 19 that is driven to rotate counterclockwise.
When performing double-sided printing, the paper discharge roller 19 is driven to rotate clockwise before the print paper 15 passes through the paper discharge roller 19, and the print paper 15 is conveyed to the double-side conveyance path 22. The printing paper 15 conveyed to the duplex conveyance path 22 is conveyed again to the registration roller 17 via the duplex roller 20. The printing paper 15 that has reached the registration roller 17 is fed again from the registration roller 17, and after the toner image is transferred to the opposite side of the paper surface by the secondary transfer roller 13, the toner image is heated by the fixing device 18. Then, the toner is fixed by the pressure and discharged from the image forming apparatus by a discharge roller 19 that is rotated counterclockwise.

[Configuration of Fixing Device]
The fixing device 18 related to the characteristic part of the present invention will be described in more detail.
FIG. 2 is a diagram showing a configuration of the fixing device 18 provided in the color image forming apparatus 1 of FIG.
As shown in FIG. 2, the fixing device 18 detects a heating roller 23, a pressure roller 24, a heater lamp 26 as a heating unit provided in the heating roller 23, and a temperature provided on the surface of the heating roller 23. A thermistor 25 is provided.
The heating roller 23 and the pressure roller 24 can be rotated while being in pressure contact with each other. By rotating the heating roller 23 and the pressure roller 24, heat generated by the heater lamp 26 in the heating roller 23 is applied to the pressure roller. The paper is transported in the direction of the broken line arrow in FIG. 2 while fixing the toner on the printing paper and fixing the toner on the printing paper.

The heater lamp 26 is controlled to be turned on / off (on / off) so that the surface temperature of the heating roller 23 becomes a target temperature according to the temperature detected by the thermistor 25.
The temperature of the fixing device 18 (surface temperature of the heating roller 23) needs to be maintained at a temperature for properly fixing the toner image when the printing paper is passed. In addition, the heater lamp 26 is turned on / off to control the temperature of the fixing device 18 so as to maintain the target fixing temperature. As will be described in detail later, on / off control of the heater lamp 26 is performed so that the standby temperature (target temperature) is maintained even in the power saving operation performed when there is no print request.
In FIG. 2, the heater lamp 26 as a heating unit is provided in the heating roller 23, but a heating method provided in the pressure roller 24 may be used, and a control method described later is applied as the heating method employed. A heating means other than the heater lamp may be used as long as it can be used.

[Control system configuration]
A configuration of a control system (hereinafter referred to as “image formation control system”) such as an operation unit directly related to image formation of the image forming apparatus 1 (FIG. 1) will be described.
FIG. 3 is a block diagram showing a schematic configuration of an image forming control system according to the image forming apparatus of the present embodiment.
In this embodiment, an example in which one of the control functions of the image forming control system is controlled by the fixing device is shown as an example. Therefore, the heater drive control system of the fixing device 18 is included in this control system. .
The image forming control system shown in FIG. 3 operates under the control of the main controller 103 that controls the entire image forming apparatus.

As shown in FIG. 3, the image forming control system of the present embodiment has a CPU (Central Processing Unit) 100 and a ROM (Read Only Memory) as control means (controller) that controls image forming control under the control of the main controller 103. 101, and a computer or ASIC (Application Specific Integrated Circuit) configured by each element of a RAM (Random Access Memory) 102 as hardware.
The ROM 101 stores a control program for realizing control of the fixing device according to the present embodiment, and the CPU 100 reads and executes the program stored in the ROM 101. The RAM 102 is used as a work memory for storing data necessary for executing a program.
The main controller 103 and the CPU 100 are connected by a bus, and exchange the mode instruction state such as an error occurrence state and power saving (energy saving) of the image forming apparatus, and a user I / F (interface) or network I / F. A print instruction is notified based on the print request received through

The CPU 100 receives detection results of the thermistor 25 and sensors 31, and under the control of the CPU 100, operating units such as a heater lamp 26, a fixing driving unit 27, a paper feeding driving unit 28, and an image forming driving unit 29 are provided. Connecting.
The thermistor 25 detects the surface temperature of the heating roller 23, and the sensors 31 detect the operation state of the device such as the conveyance state of the printing paper. The CPU 100 turns on / off the heater lamp 26 so that the surface temperature of the heating roller 23 becomes a predetermined temperature according to the temperature result detected by the thermistor 25 (see the description of FIG. 2).
The fixing drive unit 27 is a mechanism for driving the fixing device 18, the paper feed drive unit 28 is a mechanism for driving the paper feed roller 16 and the registration roller 17, and the image forming drive unit 29 is the photoconductor 5, the charger 6, and the developer 8. The driving mechanism and the intermediate transfer driving unit 30 are mechanisms for driving the driving roller 3 of the intermediate transfer belt 12, and the CPU 100 controls on / off and the number of rotations, respectively.

[Power saving operation]
In the power saving operation in this embodiment, the operation of the image forming unit is stopped in a state where there is no print request, and standby control is performed to keep the fixing device 18 at a standby temperature. The state where there is no print request is based on the condition that there is no print request from the device status and there is no problem even if the control mode is changed, and the main controller 103 checks whether this condition is satisfied. Is done. The main controller 103 instructs the CPU 100 of the image forming control system to shift to standby control according to the confirmation result.
This standby control is an on / off operation in which the driving of the heater lamp 26 as a heating unit is turned off and the heater lamp 26 is turned on again when the detected temperature decreases until the standby temperature is reached based on the fixing temperature detected by the thermistor 25. Is a control to keep the fixing device 18 at a standby temperature by repeating the above.

In addition, as a return operation performed in response to a print request performed during standby, the stopped image forming unit is activated, and the fixing device 18 is switched from the standby control so as to maintain the fixing possible temperature during sheet passing. Control during printing. It should be noted that the generation of a print request is based on the input operation of an operation unit (not shown) as a user I / F and the acceptance of a print request in a network I / F (not shown). Confirmed by the main controller 103. The main controller 103 instructs the CPU 100 of the image formation control system to return to the printing control according to the confirmation result.
To return to the control at the time of printing, the heater lamp 26 as a heating unit is turned on, and based on the fixing temperature detected by the thermistor 25, the fixing temperature is increased until the fixing possible temperature at the time of paper passing is reached. It is control which maintains 18 at the temperature.

The temperature control of the fixing device 18 that repeats the transition to the standby control and the return to the printing control is basically an existing power saving operation.
However, in this embodiment, the conventional technique based on the power saving operation is based on a technique intended to solve a problem that may occur. For this technique, the following [Heater corresponding to printing request during standby] Control] will be described later.

[Heater control to respond to printing requests during standby]
As described above, the drive control of the heater lamp 26 that is intended to save power repeats the transition to the standby control and the return to the printing control to save power in the standby state.
However, as described in the above [Problems to be Solved by the Invention], when switching the control operation of receiving a print request during standby and returning to the control at the time of printing driven at a fixing temperature, as described above, According to the technology, a printing paper fixing device can be used even if the temperature is raised to a fixing temperature when a printing request is made immediately after printing and before a fixing temperature is set to a control for maintaining a standby temperature. The approach to 18 is not in time, and power is consumed wastefully.
Therefore, even when the print request is made at any time during standby, particularly at the above time that causes unnecessary power consumption according to the prior art, the sheet is fed at the timing when the temperature of the fixing device 18 reaches the fixable temperature. Is allowed to enter the fixing device 18.

“Embodiment 1”
For this purpose, an image forming unit (an operation unit that performs image formation, transfer, or the like) is immediately activated in response to a print request made during standby, and a change in the fixing temperature detected by the thermistor 25 at the time of the print request is The change gradient value is obtained, and based on the obtained temperature change gradient value, the timing for switching from the standby control to the printing control, that is, the driving timing of the heater lamp 26 to make the fixing possible temperature at the time of paper passing is determined.
Here, the temperature change gradient value at the time of the print request indicates that the fixing temperature detected by the thermistor 25 is at least the driving timing of the heater lamp 26 (from the time of printing to the time of printing control). It is obtained by a process of calculating in a form such as an average value at a predetermined time interval until a control switching timing) is determined.

As will be described in detail later, for example, the larger the temperature change gradient value calculated at the time of the print request, the earlier the start timing of the heater lamp 26 for changing the fixing device 18 from the standby temperature to the fixable temperature at the time of passing paper. The heater lamp 26 starts to be driven at the determined start timing.
In this switching operation from standby to printing, an image forming unit (an operation unit that performs image formation or transfer) that is activated in response to a print request has the first printing paper loaded from the fixing device 18 at the time of activation. The time required to enter the printer is almost constant, but the time required from the start of the heater lamp 26 to the rise to the fixing temperature may be shorter than this time. If the operation is to immediately start the image forming unit in response to this, it is possible to match the rise to the fixable temperature when the first printing paper enters the fixing device 18, and it can be done in the shortest time.
Hereinafter, the present embodiment for performing heater control corresponding to a printing request during standby based on a temperature change gradient will be described with reference to the accompanying drawings.

FIG. 4 is a diagram for explaining a change in the fixing temperature in the operation example of the heater drive control corresponding to the standby print request according to the present embodiment.
As shown in FIG. 4, in this operation example, when the print request (job reception) is made at the beginning of the transition to the standby control, that is, the print request time is not shortly after the print, and the fixing device 18 Is in a state where there is sufficient heat, the pressure roller 24 is also at a high temperature, and the decrease in the fixing temperature is small, higher than the standby temperature before entering the control for maintaining the fixing temperature at the standby temperature, and in the heater off state. An example is shown.
The feature of the operation shown in the figure is that a temperature change gradient is obtained at the time of a print request performed during standby, and at the same time, an image forming unit (an operation unit that performs image formation, transfer, etc.) is activated.
When the fixing device 18 is sufficiently heated at the beginning of the transition to the standby control as in the operation example of FIG. 4, the time until the fixing temperature rises is shortened. Therefore, the image is compared with the time required for the starting. The time from the start of the forming unit to the time when the first printing paper enters the fixing device 18 usually takes longer. In this embodiment, a configuration of a control system that enables the image forming unit to be activated at the time of request for a print request during standby is employed.
Therefore, in order to output the first print sheet in the shortest time in response to the print request, the image forming unit is immediately activated at the time of the request.

Even in a high state before entering the control for maintaining the fixing temperature at the standby temperature, the time taken for the temperature to rise to the fixing temperature becomes longer as the gradient of the temperature change that decreases with the passage of time gradually increases. Depending on the conditions, this time may exceed the time from the start-up of the image forming unit to the entry.
Therefore, in order to output the first print sheet in the shortest time in such a case, it is desirable to obtain the temperature change gradient immediately upon the print request in response to the print request. If the temperature change gradient can be acquired earlier, the driving timing of the heater lamp 26 described later can be determined earlier, and the time required for starting up to the fixable temperature can be shortened.

For this reason, a predetermined time interval is determined based on the fixing temperature detected by the thermistor 25 until the driving timing of the heater lamp 26 (switching timing to the printing control) is determined at least after the transition from the printing control to the standby control. Then, the temperature change gradient value (ΔT / Δt) is calculated, and this value can be used immediately in response to a print request (job reception).
Specifically, the fixing temperature detected by the thermistor 25 is acquired at a predetermined cycle (for example, 500 msec), the temperature change gradient in each cycle is calculated from the acquired fixing temperature, and the obtained temperature change gradient in each cycle is calculated. Based on this, a temperature change gradient value (ΔT / Δt; ° C./sec) is calculated every predetermined time interval (for example, 10 sec). At this time, the temperature change gradient value for each predetermined time interval is calculated as an average temperature change gradient value of the temperature change gradient of each cycle included in the predetermined time interval.
If the print request time is less than the predetermined time interval (in the above example, the print request time point is less than 10 sec), the temperature change gradient value is calculated using the fixing temperature acquired so far.

The temperature change gradient (ΔT / Δt) is obtained as described above, and the fixing temperature reaches the fixable temperature by the method shown in the following <Starting time t4 to fixable temperature t4> based on the obtained temperature change gradient. Calculate the estimated time t4.
At this time, t2> t4, that is, the first print sheet from the start of the image forming unit (the operation unit that performs image formation, transfer, etc.) to the fixing device 18 from the estimated time t4 required to reach the fixable temperature. When the estimated time t2 required for entering the vehicle becomes long, the fixing device 18 is not operated, only the image forming unit is operated, and the image forming operation is started.
After that, the fixing is started from the scheduled time when the first printing paper entered into the fixing device 18 in advance by the estimated time t <b> 2 that is required from when the image forming unit is activated until the first printing paper enters the fixing device 18. The timing for starting the operation of the fixing device 18 is determined by back-calculating the estimated time t4 minutes required for the temperature to reach the fixing possible temperature.
When the timing for starting the operation of the fixing device 18 is reached, the fixing driving unit 27 is operated, the heating roller 23 and the pressure roller 24 are rotated, and the heater lamp 26 is turned on.

<Rise time to fixing temperature t4>
Here, a method for obtaining the predicted time t4 required for the fixing temperature to rise to the fixable temperature based on the temperature change gradient value obtained at the time of the request in response to the print request (job reception) during standby will be described.
The predicted time t4 varies depending on the temperature change gradient value and also on the fixing temperature at the time when the temperature change gradient is calculated.
As for the temperature change gradient value, the larger the temperature change gradient value, the longer it takes to rise to the fixable temperature. Regarding the fixing temperature, the lower the fixing temperature, the longer it takes to rise to the fixing possible temperature.

When the temperature change gradient value and the fixing temperature are variables, as a method for obtaining the predicted time t4 immediately in response to a print request, a table of predicted times t4 (hereinafter referred to as “variables”) using the temperature change gradient value and the fixing temperature as variables. (Predicted time t4 table (1) ") is created and stored, and when this predicted time t4 is obtained, a method of obtaining this value by referring to the predicted time t4 table (1) is applied.
FIG. 5 is an explanatory diagram showing an example of the predicted time t4 table (1). In the table shown in the figure, the temperature change gradient value is changed in four steps in the horizontal direction and the fixing temperature is changed in six steps in the vertical direction, and numerical values (at the intersections of the selected values in the vertical and horizontal directions ( Here, it is obtained as the predicted time t4.

For example, when a printing request during standby is received, if the fixing temperature at the time of the request is 165 ° C. and the temperature change gradient value obtained at that time is −0.05 ° C./sec, the estimated time t4 table (1) The predicted time t4 obtained by referring to is 12 seconds.
In addition, an image forming unit (an operation unit that performs image formation or transfer) is immediately activated in response to a print request (job reception), and a prediction that occurs from the time when the first print sheet enters the fixing device 18 is started. When the time t2 is 20 seconds, the predicted time t2> the predicted time t4, which corresponds to the operation example shown in FIG.
Therefore, the operation of the fixing device 18 is started 8 seconds after starting the image forming unit, the heating roller 23 and the pressure roller 24 are rotated, and the heater lamp 26 is turned on. By turning on the heater lamp 26 at such a timing, the time when the fixing device 18 rises to the fixable temperature can be matched with the entry timing of the first printing paper into the fixing device 18.

The predicted time t4 table (1) described above is created by acquiring experience values in advance by performing a test or the like.
In addition, when applied to a low-cost device that does not require high performance, the predicted time t4 corresponding to a change in temperature change gradient value that is most suitable for the device state and the use state without considering the change in the fixing temperature. A simple method of finding the rise time t4 to the fixable temperature only by the temperature change gradient value may be employed.

By the way, the predicted time t4 is influenced by the outside air temperature. That is, when the outside air temperature is high, the heat generated by the heater lamp 26 is small, so the temperature rises relatively quickly and the predicted time t4 is shortened. On the other hand, when the outside air temperature is low, the heater lamp Since the release of heat generated by 26 increases, it takes time to rise to the fixable temperature, and the predicted time t4 becomes longer.
In order to optimize the operation in response to the change in the outside air temperature, a means for detecting the outside air temperature is provided, and the predicted time t4 can be changed in accordance with the detected outside air temperature. For example, a method of preparing a predicted time t4 table (1) having a value that guarantees an appropriate operation for each changing outside air temperature, selecting a table that adapts to the current state of the outside air temperature, and changing the table to be used. Is adopted. By taking such measures, the activation timing of the heater lamp 26 can be optimized.

<Responding to when the power is turned on>
The above-described operation in the present embodiment is performed at predetermined time intervals in a situation where the fixing temperature is higher than the standby temperature and the fixing temperature changes in the descending direction when the heater is turned off before entering the control for maintaining the fixing temperature at the standby temperature. It is assumed that the temperature change gradient value is obtained. For this reason, the operation for calculating the temperature change gradient value is from the time when the control is shifted to the standby control until the heater lamp 26 drive timing (switching timing to the printing control) is determined.
Therefore, the heater start timing control based on the temperature change gradient value cannot be executed because there is no temperature change gradient value when the power of the image forming apparatus 1 is turned on or the control for keeping the fixing temperature at the standby temperature is entered.

Therefore, the heater start-up timing control of this embodiment can be executed by the following method even when the power is turned on or the control for keeping the fixing temperature at the standby temperature is entered.
This method is a method that can be executed by diverting the temperature change gradient value calculated at predetermined time intervals in the above-described operation described with reference to FIG. 4 in the present embodiment.
Specifically, the temperature change gradient value calculated at a predetermined time interval is recorded in the nonvolatile RAM in association with the detected fixing temperature and stored in a format that can be referred to.
In such a format, the image forming apparatus 1 grasps the state of the device that has occurred so far, and is detected at the time when the image forming apparatus 1 having no temperature change gradient value is turned on or returned from standby (sleep). Based on the fixing temperature, the temperature change gradient value of the closest device state recorded in the nonvolatile RAM is referred to.
In this way, the temperature change gradient value referenced from the history of the device state is diverted to the operation at the time of power-on or return from standby (sleep), so that the heater of the present embodiment is also activated in this operation. Timing control can be implemented.

  As described above, according to the first embodiment, when performing the control operation for returning to the print time control in response to the print request in the standby state, the print request is performed at any point in the standby time, particularly after the print. Even if it is performed immediately before the control for maintaining the fixing temperature at the standby temperature, the printing paper is caused to enter the fixing device at the timing when the temperature of the fixing unit reaches the fixing possible temperature. The power saving operation can be performed without driving the heating means wastefully.

“Embodiment 2”
In the first embodiment, the embodiment in which the start time t4 to the fixable temperature is obtained based on the temperature change gradient value and the heater start timing control is performed is shown.
However, when the control shifts to standby control and enters the control to maintain the fixing device 18 at the standby temperature from the initial stage of transition (see the operation example in FIG. 4), and the state continues for a while thereafter, the device conditions of the image forming apparatus 1 are reached. The temperature change characteristic changes considerably depending on the ambient environment of the equipment, and the predicted time t4 predicted by the predicted time t4 table (1) in the method of the first embodiment (hereinafter referred to as “temperature change gradient method”) is not necessarily appropriate. Instead, the intended result may not be obtained.

Therefore, instead of the temperature change gradient method, it is possible to obtain an appropriate prediction time t4 by the following method.
The method of this embodiment is based on the time at the end of printing performed in response to a print request last time, the number of printed sheets, and the current temperature state of the fixing device 18 determined by the elapsed time from the end of previous printing. Assuming that there is a certain relationship, a startup time t4 to a fixable temperature that is suitable for the recognized temperature state of the fixing device 18 is predicted, and the activation control of the heater lamp 26 is performed at a timing determined according to the prediction result. It is a technique to do.

Specifically, at the end of printing performed in response to a print request, the print end time and the number of prints are recorded as print information in a nonvolatile RAM and stored in a format that can be referred to.
If there is no print request after storing the print information at the end of printing, the process shifts to standby control, and then enters control for keeping the fixing device 18 at a standby temperature.
When a print request is received under the operation state of the standby control, the standby control is switched to the print control for raising the fixing device 18 to a fixable temperature in response to the print request.

At this time, in this embodiment, the previous print information recorded in the nonvolatile RAM is referred to, and the current state of the fixing device 18 is recognized based on the print end time and the number of prints of the acquired print. That is, it is recognized in the form of the elapsed time from the end of the previous printing (obtained from the current time and the previous printing end time) and the state of the fixing device 18 at the end of the previous printing represented by the number of printed sheets.
Further, based on the recognition result, it takes from the start of the heater lamp 26 to the fixing possible temperature, which is adapted to the current state of the fixing device 18 by the method shown in <Starting time t4 to fixing possible temperature> described later. The predicted time t4 is obtained.
The timing of starting the operation of the fixing device 18 after obtaining the predicted time t4, that is, the control operation of the activation timing of the heater lamp 26 to the fixing possible temperature at the time of paper passing is the same as that described in the first embodiment. There is no explanation here.

<Rise time to fixing temperature t4>
Here, with respect to the standby print request, the fixing temperature rises to the fixable temperature based on the state of the fixing device 18 recognized at the time of the request, that is, the elapsed time from the end of the previous print and the previous number of prints. A method for obtaining the predicted time t4 required for the increase will be described.
Regarding the relationship between the elapsed time from the end of the previous print, the previous number of printed sheets, and the estimated time t4, the longer the elapsed time from the end of the previous print, the more the fixing device 18 cools down. It takes a long time to launch. In addition, the smaller the number of previous prints, the lower the temperature of the fixing device 18 at the end of printing. Therefore, it takes a longer time for the temperature to rise to the fixable temperature.

As a method for obtaining the predicted time t4 in response to a print request when the elapsed time from the previous print end and the previous number of printed sheets are variables, the elapsed time from the previous print end and the previous time A table of predicted time t4 (hereinafter referred to as “predicted time t4 table (2)”) with the number of printed sheets as a variable is created and stored, and when calculating the predicted time t4, refer to the predicted time t4 table (2). To apply this method. The predicted time t4 table (2) is created by acquiring an experience value in advance by performing a test or the like.
In addition, when applied to low-cost equipment that does not require advanced performance, the change in elapsed time from the end of the previous printing, which is most suitable for the equipment state and usage state, without considering the number of previous prints. A simple method may be employed in which the predicted time t4 corresponding to is found, and the rise time t4 to the fixable temperature is predicted based only on the elapsed time from the end of the previous printing.

  FIG. 6 is an explanatory diagram showing an example of the predicted time t4 table (2). In the table shown in the figure, the previous number of prints is changed in four steps in the horizontal direction, and the elapsed time from the end of the previous printing is changed in four steps in the vertical direction. A numerical value (indicated here by the number of seconds) written at the intersection is obtained as the predicted time t4. This table is a predicted time t4 when a predetermined number of sheets are printed from a cold start and printed after a lapse of a predetermined time, and the numerical values shown here are not shown as long as they are used within the specification range of the image forming apparatus 1. It will never be longer than the number in the table.

For example, when a printing request in standby is received, if the elapsed time from the end of the previous printing is 20 seconds and the previous number of printed sheets is 8, the predicted time t4 table (2) is referred to. The predicted time t4 obtained by this is 7 seconds.
In addition, an image forming unit (an operation unit that performs image formation or transfer) is activated immediately in response to a print request, and an estimated time t2 that is required from the time of activation until the first print sheet enters the fixing device 18 is 20. In the case of seconds, the operation of the fixing device 18 is started 13 seconds after the image forming unit is activated, the heating roller 23 and the pressure roller 24 are rotated, and the heater lamp 26 is turned on. By turning on the heater lamp 26 at such a timing, the time when the fixing device 18 rises to the fixable temperature can be matched with the entry timing of the first printing paper into the fixing device 18.

By the way, the predicted time t4 is influenced by the outside air temperature. That is, when the outside air temperature is high, the heat generated by the heater lamp 26 is small, so the temperature rises relatively quickly and the predicted time t4 is shortened. On the other hand, when the outside air temperature is low, the heater lamp Since the release of heat generated by 26 increases, it takes time to rise to the fixable temperature, and the predicted time t4 becomes longer.
In order to optimize the operation in response to the change in the outside air temperature, a means for detecting the outside air temperature is provided, and the predicted time t4 can be changed in accordance with the detected outside air temperature. For example, a method of preparing a predicted time t4 table (2) having a value for guaranteeing proper operation for each changing outside air temperature, selecting a table that adapts to the current state of the outside air temperature, and changing the table to be used. Is adopted. By taking such measures, the activation timing of the heater lamp 26 can be optimized.

<Responding to when the power is turned on>
Further, the method of the present embodiment is applicable to a print request at the time of power-on or return from standby (sleep) in which the temperature change gradient method cannot be applied to the first embodiment (in these cases, the temperature change gradient value is not calculated). Correspondingly, the present invention can also be applied when starting timing control of the heater lamp 26 is performed.
That is, by recording the previous print end time and the previous number of prints in the nonvolatile RAM as print information, even when responding to the current print request performed through the power-off or standby (sleep) control process The heater activation timing control can be executed by the method of the present embodiment based on the elapsed time from the end of the previous printing that can be obtained from the printing information recorded in the nonvolatile RAM and the previous number of printed sheets. it can.

  As described above, according to the second embodiment, when performing the control operation to return to the print time control in response to the print request at the standby time, the print request is performed at any point in the standby time, particularly after the print. Even after a long time has passed since the start of the control to keep the fixing temperature at the standby temperature, or at each time when the power is turned on or when returning from the standby (sleep) mode, the temperature of the fixing unit can be fixed. Thus, it is possible to perform the operation of causing the printing paper to enter the fixing device at the timing of reaching, so that the heating means of the fixing unit is not driven wastefully, and the power saving operation can be performed.

“Embodiment 3”
In the second embodiment, as a method that can replace the first embodiment based on the temperature change gradient method, the rise time t4 to the fixable temperature is obtained based on the elapsed time from the end of the previous printing and the previous number of printed sheets, and the heater An embodiment is shown in which the start timing control of the lamp 26 is performed (hereinafter, the method of Embodiment 2 is referred to as “previous print information reference method”).
However, the temperature change gradient method and the previous printing information reference method are suitable for the former when the fixing temperature is sufficiently high soon after printing and before entering the control to maintain the fixing temperature at the standby temperature. The latter is suitable for the time when a considerable amount of time has passed after printing and the control for keeping the fixing temperature at the standby temperature is entered, and the areas suitable for application are divided.
Therefore, the present embodiment shows an embodiment intended to be applied in combination with the temperature change gradient method and the previous print information reference method.

In this embodiment, two examples in which the temperature change gradient method and the previous print information reference method are combined will be described as <Example 1> and <Example 2>.
<Example 1>
In this embodiment, only when the print request is received does not reach the predetermined elapsed time determined from when the image forming apparatus is turned on or when the image forming apparatus is returned from the standby (sleep) control, the previous print information is referred to. The method is applied, and in other cases, the temperature change gradient method is applied.
The predetermined elapsed time is a time for determining a time point at which the temperature change gradient value can be obtained as an appropriate value starting from power-on or a return from standby control without a temperature change gradient value. In this way, the predetermined elapsed time is determined, and the start timing control of the heater lamp 26 is appropriately performed by using the previous printing information reference method in this period.
As a control procedure, when a print request is received, it is confirmed whether or not the reception time point has reached a predetermined elapsed time starting from when the power is turned on or when returning from standby control. Select either the gradient method or the previous print information reference method.

<Example 2>
In this embodiment, the previous printing information reference method is used only when the power-on of the image forming apparatus or the return from the standby (sleep) control has reached a predetermined elapsed time determined from the end of the previous printing. In other cases, the temperature variation gradient method is applied.
The predetermined elapsed time is based on the premise that the time when the power is turned on or the return from the standby control is shortly after printing, and the fixing temperature is sufficiently high and before the control for maintaining the fixing temperature at the standby temperature is started. Therefore, the time when the temperature change gradient method can be applied is determined. In this way, the predetermined elapsed time is determined, and the start timing control of the heater lamp 26 is appropriately performed by using the previous print information reference method only when the predetermined elapsed time is reached.

As a control procedure, when returning from standby control when the power is turned on or accepting a print request, etc., check whether the return time has reached the specified elapsed time starting from the end of the previous print. According to the result, either the temperature change gradient method or the previous print information reference method is selected.
Note that when the temperature change gradient method is applied, depending on the conditions for a print request made immediately after power-on or return from standby control, the <return to power-on etc. It is necessary to adopt the method shown in [Action].

  As described above, according to the third embodiment, when performing the control operation for returning to the printing-time control in response to the printing request at the time of standby, the temperature change gradient method The wasteful power consumption of the heating unit of the fixing device can be further reduced by selecting a method that can obtain an appropriate operation from the previous printing information reference method.

“Embodiment 4”
This embodiment demonstrates embodiment which set the application condition for optimizing the control action by a temperature change gradient method.
In this embodiment, four different setting examples will be described below as <application condition 1> to <application condition 4>.
FIG. 7 is a diagram illustrating a change in fixing temperature in the process of performing standby control after the end of printing. In the figure, the vertical axis represents the fixing temperature, and the horizontal axis represents time. In the figure, heater on / off states and temperature states are added to explain the application conditions of the temperature change gradient method of the present embodiment.

<Applicable condition 1>
When printing is completed (at the beginning of the time in FIG. 7), the image forming apparatus 1 once stops the operation of the fixing device 18 and waits for the next print request. During this time, since the heat is not supplied by the heater lamp 26, the fixing temperature is lowered. If there is no print request in this state, the control is switched to the standby control. However, as shown in the state (1) of FIG. 7, the heater lamp 26 starts to be driven next in order to maintain the standby temperature ( The decrease continues until the first heater is turned on in FIG.
In the process of performing standby control after the end of printing, the fixing temperature is detected in the above-mentioned state where the fixing temperature continues to change in the downward direction until reaching the standby temperature, the temperature change gradient is obtained, and control by this temperature change gradient method is performed. Doing is the state where the results intended by the method are most effectively obtained.

Therefore, control by the temperature change gradient method is performed only at this time, that is, from the end of printing until the first drive control of the heater lamp 26 in the process of performing standby control (state (1) in FIG. 7). By adopting as an application condition, the control can be simplified and the power saving effect can be enhanced.
If a print request is received (print job received) after the first drive control of the heater lamp 26, the heat in the fixing device is regarded as insufficient and the conventional technique (see FIG. 8). As shown in FIG. 8, after the printing request is received, the fixing device 18 may be controlled to operate immediately.

<Applicable condition 2>
As shown in <Applicable condition 1> above, from the end of printing until the first heater lamp 26 is turned on, heat is not applied to the fixing device 18, and the temperature change gradient in the downward direction is shown in FIG. The predicted time t4 can be obtained by referring to the predicted time t4 table (1) shown. However, when the heater lamp 26 is turned on in order to maintain the standby temperature by the standby control, the state shown in the state (2) in FIG. As described above, since the temperature rising portion occurs, it is necessary to exclude the temperature rising portion from the calculation target of the temperature change gradient.

The temperature change gradient calculation target range is a range that is not affected by the lighting of the heater lamp 26. For example, as shown in a state (3) in FIG. It is appropriate to acquire the fixing temperature after 10 seconds.
Therefore, the application condition is to set this period as a temperature change gradient calculation target.
The temperature change gradient is obtained according to the application conditions thus determined, and the obtained temperature change gradient is used as the temperature change gradient for referring to the predicted time t4 table (1) shown in FIG. Even during the control, it is possible to determine the lighting start timing of the heater lamp 26 and perform heater drive control intended to save power.

<Applicable condition 3>
As described in <Applicable Condition 1> and <Applicable Condition 2>, it is effective to execute the temperature change gradient method based on fixing temperature detection at a limited time in the process of performing standby control after the end of printing. In order to immediately respond to the printing request, it is desirable that the temperature change gradient method can be applied in the same manner at a time other than the above limited time.
Therefore, in the operation of <Applicable Condition 1> or <Applicable Condition 2> described above, this is a method that can be executed by diverting the temperature change gradient value calculated at a limited time.
Specifically, the temperature change gradient value calculated at the limited time is recorded in the nonvolatile RAM in association with the detected fixing temperature and stored in a format that can be referred to. In consideration of the compatibility with the predicted time t4 table (1) shown in FIG. 5, the timing of <applicable condition 1>, that is, the first heater lamp 26 in the process of performing standby control after the end of printing. It is better to adopt the period until the on-drive control (state (1) in FIG. 7).

The fixing temperature / temperature change gradient value recorded in the non-volatile RAM in such a format is arbitrary, including a time period during which the temperature change gradient value cannot be calculated during the standby control, for example, the on-period of the heater lamp 26. The temperature change gradient method can be applied regardless of the time. When the recorded fixing temperature / temperature change gradient value is used, the temperature change gradient value of the nearest device state recorded in the nonvolatile RAM is referred to based on the fixing temperature detected at that time.
However, when the fixing temperature / temperature change gradient value is recorded in the nonvolatile RAM by adopting the time until the first turn-on control of the heater lamp 26 (state (1) in FIG. 7), the device state changes over time. Therefore, it is necessary to manage the application limit until the recorded fixing temperature / temperature change gradient value becomes incompatible and cannot be used. Specifically, starting from the first on-drive control of the heater lamp 26 in the process of performing the standby control, the fixing temperature / temperature change gradient value recorded in the nonvolatile RAM reaches a predetermined elapsed time at which the compatibility is lost. It is confirmed whether or not application is possible according to the confirmation result.

In addition, when applied to a low-cost device that does not require high performance, the prediction time t4 table finds the prediction time t4 corresponding to the change in temperature change gradient value that is most suitable for the device state and use state, A simple method for predicting the rise time t4 to the fixable temperature only by the temperature change gradient value can be adopted.
When this simple method is adopted, in this <application condition 3>, information indicating the device (temperature) state of the fixing device 18 recorded in the nonvolatile RAM for use in referring to the predicted time t4 table is the temperature change gradient value. The fixing temperature is unnecessary.

<Applicable condition 4>
The application limit of the temperature change gradient method of this embodiment is set, and the intended operation is guaranteed by checking whether the set condition is satisfied.
In the standby control, control is performed to keep the fixing temperature at the standby temperature. In this control, as shown in FIG. 7, the heater lamp 26 is repeatedly turned on and off in order to maintain the standby temperature, and the fixing temperature is repeatedly raised and lowered with this on and off.
However, the repetition of the temperature increase / decrease is not constant, and the device state changes with time due to the release of heat accumulated during the previous printing, and the on-control time of the heater lamp 26 for maintaining the standby temperature. The temperature gradually increases and also appears as a change in the temperature state in the off control time of the heater lamp 26.
As described above, the temperature change gradient method of the present embodiment is adapted to the state (1) shown in FIG. 7, that is, the operating condition (prediction) until the first heater lamp 26 is turned on. Time t4 table value etc.) is determined. Therefore, the change appearing in the temperature state means a deviation from the determined operating condition, and gradually loses compatibility and becomes the limit of application.

Therefore, the change in the temperature state in the fixing device 18 is detected based on the on-control time of the heater lamp 26, and the application limit is managed by a method in which an application limit is determined in advance and confirmed with respect to the detected on-control time. To do.
Specifically, each time the heater lamp 26 is turned on, the turn-on control time is detected, whether or not the detected turn-on control time has reached a predetermined application limit time, and is applied according to the confirmation result. Determine whether or not. Here, if it is determined that application is possible, the temperature change gradient method is applied to a print request to be performed thereafter, the lighting start timing of the heater lamp 26 is determined, and heater drive control intended for power saving is performed. .
When the above determination is made and it is determined that the application limit has been reached, it is assumed that the heat in the fixing device is insufficient, and when the print request is received (print job reception) after that, the conventional technique (FIG. 8). As shown in FIG. 4), the control of operating the fixing device 18 may be performed immediately after receiving this print request.

  1..Image forming device, 2A, 2B, 2C, 2D, ..AIO cartridge, 5A, 5B, 5C, 5D..Photoconductor, 12..Intermediate transfer belt, 15..Printing paper, 18..Fixing device, 23 .. Heating roller, 25 .. Thermistor, 26 .. Heater lamp, 100 .. CPU, 103 .. Main controller.

JP 2010-128465 A

Claims (7)

An image forming unit that forms an image on a recording medium in a transport state;
A fixing unit having a heating unit capable of controlling on / off of driving, and heating the image on the recording medium formed by the image forming unit in a conveying state to fix the image on the recording medium by the heating unit;
Fixing temperature detecting means for detecting the temperature of the fixing unit;
The operation of the image forming unit is stopped in the absence of a print request, the driving of the heating unit is turned off, and the driving of the heating unit is turned on / off based on the fixing temperature detected by the fixing temperature detecting unit. While the standby control is performed to keep the fixing unit at the standby temperature, the stopped image forming unit is started and the fixing unit is set to the standby as a return operation performed in response to a print request performed during standby. An image forming apparatus having a control unit that performs control during printing by switching from time control and maintaining a fixing temperature at the time of paper passing,
A temperature change gradient calculating means for calculating a temperature change gradient in a descending direction at predetermined time intervals based on the fixing temperature detected by the fixing temperature detecting means ;
Temperature change gradient storage means for storing a rise time at which the fixing temperature rises to a fixable temperature from the start of the heating means in relation to the temperature change gradient in the downward direction calculated by the temperature change gradient calculation means and the fixing temperature. ,
The control unit acquires the start-up time from the temperature change gradient storage unit based on the fixing temperature and the temperature change gradient at that time when the image forming apparatus is powered on or returned from standby control. When the start-up time is shorter than the entry time when the start-up time is compared with the entry time from the start of the image forming unit until the first recording medium enters the fixing unit, The image forming unit is immediately activated in response to a print request to be made, and the timing of the heating unit is activated so that the temperature of the fixing unit reaches the fixable temperature when the recording medium enters the fixing unit. image forming apparatus characterized by determining the. The image forming apparatus according to claim 1,
Means for detecting the outside air temperature;
Temperature change gradient storage means for storing a temperature change gradient in the downward direction calculated for each outside air temperature by the temperature change gradient calculation means in relation to the fixing temperature, and
When the image forming apparatus is powered on or returned from standby, the control unit is configured to perform the heating from the temperature change gradient storage unit according to the outside air temperature based on the fixing temperature at that time and the temperature change gradient in the descending direction. an image forming apparatus comprising Rukoto define the activation timing means. The image forming apparatus according to claim 1 or 2 ,
The control means starts the heating means based on the temperature change gradient or the fixing temperature and the temperature change gradient only after the printing is completed until the first drive control of the heating means in the process of performing standby control. An image forming apparatus that performs the control operation performed by determining The image forming apparatus according to claim 1 or 2 ,
Immediately before the first drive control of the heating unit in the process of performing the standby control after the end of printing, the standby transition temperature change gradient storage unit stores the temperature change gradient in the downward direction calculated by the temperature change gradient calculation unit. Prepared,
The control means is the temperature transition gradient storage means at the time of standby transition until a predetermined elapsed time is reached from the time when the heating means is turned off in the first drive control of the heating means in the process of performing the standby control. The start-up timing of the heating means is determined on the basis of the temperature change gradient in the downward direction stored in the printer and the fixing temperature detected by the fixing temperature detecting means when printing is requested. The image forming apparatus according to any one of claims 1 to 3 ,
Immediately before the first drive control of the heating unit in the process of performing the standby control after the end of printing, the temperature transition gradient in the standby transition that stores the temperature change gradient in the downward direction and the fixing temperature calculated by the temperature change gradient calculator A storage means,
The control means is the temperature transition gradient storage means at the time of standby transition until a predetermined elapsed time is reached from the time when the heating means is turned off in the first drive control of the heating means in the process of performing the standby control. The start-up timing of the heating unit is determined on the basis of the temperature change gradient in the downward direction and the fixing temperature stored in the image forming apparatus. An image forming apparatus according to any of claims 1-5,
An on-drive control time measuring means for measuring the on-drive control time of the heating means each time in the process of performing standby control after the end of printing,
The control unit starts the heating unit based on a temperature change gradient or a fixing temperature and a temperature change gradient until the on-drive control time of the heating unit measured by the on-drive control time measuring unit reaches a predetermined time or more. An image forming apparatus that performs the control operation performed at a predetermined timing. An image forming unit that forms an image on a recording medium in a transport state;
A fixing unit having a heating unit capable of controlling on / off of driving, and heating the image on the recording medium formed by the image forming unit in a conveying state to fix the image on the recording medium by the heating unit ;
Fixing temperature detecting means for detecting the temperature of the fixing unit;
It stops the operation of the image forming unit in the absence of a print request, and turns off the driving of the heating means, on / off driving of the heating means based on the fixing temperature before Kijo deposition temperature detecting means for detecting While performing standby control to keep the fixing unit at a standby temperature, the image forming unit in a stopped state is activated and the fixing unit is operated as a return operation performed in response to a print request performed during standby. A fixing control method in an image forming apparatus having a control unit that performs control during printing by switching from the standby control and maintaining a fixing possible temperature during paper passing ,
A temperature change gradient calculating step of calculating a temperature change gradient in the downward direction at predetermined time intervals based on the fixing temperature detected by the fixing temperature detecting means;
A step of storing in the temperature change gradient storage means a rise time at which the fixing temperature rises to a fixable temperature from the start of the heating means in relation to the temperature change gradient in the downward direction calculated in the temperature change gradient calculating step and the fixing temperature. When,
In the control unit, the control unit starts up from the temperature change gradient storage unit based on the fixing temperature and the temperature change gradient at that time when the image forming apparatus is turned on or returned from standby control. Time is acquired, and the start-up time is shorter than the entry time by comparing the start-up time with the entry time from the start of the image forming unit until the first recording medium enters the fixing unit. The image forming unit is immediately activated in response to a print request made during standby, and the temperature of the fixing unit is fixed at the timing when the heating unit is activated, when the recording medium enters the fixing unit. And a fixing control method in an image forming apparatus , comprising: a step of determining the temperature so as to reach a possible temperature .

Images