JP4116950B2 - Control device, image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a power saving mode, and more particularly, when a temporal change in the amount of heat necessary to return the temperature of a fixing unit to a fixing temperature and when the fixing unit is heated from an environmental temperature to a fixing temperature. From this amount of heat, a reasonable time is set for shifting to the power saving mode from the end of the printing process.

  A fixing device included in an image forming apparatus configured as a copying machine, a printer, a facsimile, or a complex machine thereof heats a toner image transferred to a sheet such as transfer paper or pressurizes a sheet to which the toner image is attached. Thus, the toner image is fixed on the sheet. As a method of fixing a toner image on a sheet with this fixing device, there are a heat fixing method, a pressure fixing method, and the like. Among these methods, a heat roller fixing method belonging to the heat fixing method is widely used recently. It is.

  A heat roller fixing method (hereinafter, referred to as a heat fixing method) includes a fixing roller having a built-in heating source such as a heater, and a pressure roller having a pressure mechanism that is paired with the fixing roller. In a fixing device that employs a thermal fixing method, when a sheet with toner adhered to the surface passes between the fixing roller and the pressure roller, the toner is melted by the heat of the fixing roller, and the melted toner adheres. The pressed roller is pressed by the pressure roller to fix the toner to the sheet.

  In an image forming apparatus that employs the above-described heat fixing method in a fixing device, the proportion of power consumption in a heating source such as a heater built in a fixing roller is very high in the power consumption in the entire image forming apparatus. For this reason, in recent years, many image forming apparatuses having a so-called power saving mode in which power consumption in the heater is suppressed by stopping energization of the heater while the printing process is not performed have been manufactured. For example, Patent Literature 1, Patent Literature 2, and Patent Literature 3 include devices that have the power saving mode.

In the apparatus disclosed in Patent Document 1, the timer incorporated in the apparatus causes a transition from the ready mode in which the heater temperature is maintained at the ready temperature after the end of the printing process to the power saving mode in which energization of the heater is stopped. Is measured. In this apparatus, first, the timer starts counting with the end of the printing process, and the heater is energized with less power than during the fixing operation within a predetermined time period after the printing process counted by the timer is not performed. Therefore, the heater temperature is maintained at a predetermined ready temperature lower than the fixing temperature (ready mode). After that, when the timer count reaches a predetermined time, a power saving signal is output from the device main body side control unit to the heater side control unit, and energization to the heater is completely stopped (power saving mode). The amount of power consumed by the heater while processing is not performed is reduced.
Further, in the apparatus disclosed in Patent Document 2, as in the apparatus disclosed in Patent Document 1, energization to the heater is stopped or fixed when the time during which printing processing is not performed reaches a predetermined time. By controlling the heater so that the control temperature is lower than normal, the amount of power consumed by the heater while the printing process is not performed is reduced.

Here, in Patent Document 1 or Patent Document 2, the time for shifting to the power saving mode after the end of the printing process (hereinafter referred to as mode transition preparation time) is stored in an internal storage unit such as a semiconductor memory included in the image forming apparatus. It is set to a predetermined time stored in advance.
In this case, if the mode transition preparation time is shortened, the time for energizing the heater after the end of the printing process is shortened, so that the power consumption in the heater is reduced. However, for example, when continuous printing is performed, there is a possibility that the mode transition preparation time may be reached after the printing process is completed and before the next printing process is started. In addition, when reprinting is performed after shifting to the power saving mode, it is necessary to raise the temperature of the heater to the fixing temperature, but the mode transition preparation time is shortened rapidly, that is, the power saving mode is frequently entered. If this setting is made, a waiting time until the temperature of the heater is raised to the fixing temperature is generated, and there is no denying the problem that the working efficiency is lowered.
Conversely, simply increasing the mode transition preparation time setting decreases the number of times of waiting for printing as described above, but the printing process is not performed because it takes longer to energize the heater after the printing process is completed. Nevertheless, the heater is energized, and there is a problem that power is wasted.

Such a problem arises from setting the mode transition preparation time to be constant without a reasonable reason. Therefore, in order to solve such a problem, as shown in Patent Document 3, an apparatus in which the mode transition preparation time is variable has been proposed. In this apparatus, the mode transition preparation time is set based on the time from the end of the print process to the start of the next print process (that is, the interval at which the print signal is sent). The device disclosed in Patent Document 3 has also been proposed as a device capable of setting the mode transition preparation time according to the work time zone at that time. This makes it possible to set the mode transition preparation time according to the frequency of use of each time zone of the image forming apparatus, thereby reducing the power consumed while printing is not being performed and improving the work efficiency. Is also planned.
JP 58-40573 A JP-A-3-221984 Japanese Patent Laid-Open No. 7-251550

However, in the apparatus disclosed in Patent Document 3, the mode transition preparation time is simply set according to the time from the end of the printing process to the start of the next printing process or the work time zone. Therefore, it is far from the demand for optimal power saving following the changes in the four seasons and the subtle changes in the ambient temperature such as the temperature change between daytime and nighttime.
SUMMARY OF THE INVENTION An object of the present invention is to provide a rational image forming apparatus capable of calculating and setting an optimal mode transition preparation time from moment to moment in accordance with such a subtle change in environmental temperature.

Therefore, in order to achieve the above object, the present invention takes into account characteristics such as specific heat and volume of a fixing unit such as a fixing roller constituting a fixing device, and an environmental temperature at each time, and after the end of the printing process. The amount of heat required to maintain the temperature of the fixing unit at the ready temperature and the amount of heat when the fixing unit is heated from the environmental temperature to the fixing temperature are calculated and calculated from the end of the printing process. The period up to the time is set as the mode transition preparation time.
This rationalizes the balance between the request to suppress the waiting time by making the mode transition preparation time as long as possible and the request to suppress the waste of power consumption by making the mode transition preparation time too long. The limit time from the end of the printing process to the transition to the power saving mode can be calculated. That is, it is possible to obtain a mode transition preparation time in which there is no excess or deficiency in power consumed from the end of the printing process.

In order to achieve the above object, the present invention provides at least an image forming mode in which an image forming operation is performed in a fixing unit provided in an image forming apparatus based on a predetermined fixing temperature, and the temperature of the fixing unit is lower than the fixing temperature. Saving from the start of the ready mode in an image forming apparatus having three modes: a ready mode that maintains a predetermined ready temperature that is higher than the ambient temperature, and a power saving mode that stops energization of the fixing unit and waits for an image forming operation instruction. In a control device of an image forming apparatus that controls a mode transition preparation time until a transition to a power mode, a ready temperature arrival time detection that detects a time until the temperature of the fixing unit reaches a ready temperature from a fixing temperature by natural cooling. Means, an integrated heat dissipation amount calculating means for calculating an integrated value of the heat dissipation amount based on the passage of time from the fixing unit maintained at the ready temperature, A first return heat amount calculating means for calculating an amount of heat required for returning the fixing portion at the temperature to the fixing temperature, and an amount of heat required for returning the fixing portion at the environmental temperature to the fixing temperature. Computation of integrated heat dissipation after elapse of time until the temperature of the fixing unit detected by the second return heat amount calculating means for calculating and the ready temperature arrival time selecting means reaches the ready temperature by natural cooling from the fixing temperature. The integrated value of the heat dissipation amount based on the passage of time from the fixing unit maintained at the ready temperature calculated by the means, and the fixing unit at the ready temperature calculated by the first return heat amount calculating unit The sum of the amount of heat required to return to the fixing temperature is the amount of heat required to return the fixing unit at the environmental temperature calculated by the second return heat amount calculating means to the fixing temperature. The mode transition preparation time is set based on the sum of the saturation time calculation means for calculating the time until the operation is completed and the time detected by the ready temperature arrival time detection means and the time calculated by the saturation time calculation means. It is constituted by a mode transition preparation time setting unit, the control unit of the image forming apparatus having a.

  In this case, it is desirable that the calculation of the heat radiation amount from the fixing unit by the integrated heat radiation amount calculation means is based on Newton's cooling law.

  Note that any one of the control devices described above may be one of the control devices provided in the image forming apparatus.

As described above, according to the present invention, in the control device for controlling the mode transition preparation time provided in the image forming apparatus having the image forming mode, the ready mode, and the power saving mode, the mode transition preparation time is provided. However, a temporal change in the amount of heat necessary for returning the temperature of the fixing unit to the fixing temperature after an appropriate elapsed time from the start of the ready mode (the amount of heat released when the fixing unit is naturally cooled, and the above (Calculated from the amount of heat required to raise the fixing unit from the ready temperature to the fixing temperature) and the amount of heat when the fixing unit is heated from the environmental temperature to the fixing temperature.
That is, according to the present invention, the temperature of the fixing unit is maintained at the ready temperature after the completion of the printing process, taking into consideration the characteristics such as the specific heat and volume of the constituent members of the fixing unit and the environmental temperature at that time. The time required for the amount of heat required to be equal to the amount of heat when the fixing unit is heated from the environmental temperature to the fixing temperature is calculated, and the period from the end of the printing process to the calculated time is referred to as the mode transition preparation time. To do.

  From this, it is possible to set a reasonable mode transition preparation time that can satisfy both the request for minimizing the occurrence of waiting time and the cost reduction by reducing power consumption.

  Embodiments and examples of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. The following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention. FIG. 1 is a schematic sectional view of an image forming apparatus A according to an embodiment of the present invention (hereinafter referred to as an embodiment), and FIG. 2 is an outline of a main part of the image forming apparatus A according to the embodiment. FIG. 3 is a functional block diagram showing the configuration, FIG. 3 is a flowchart showing a mode transition preparation time calculation process performed by the CPU 32 in the control device 31 included in the image forming apparatus A according to the above embodiment, and FIG. 4 is in the above embodiment. FIG. 5 is a graph showing a change in surface temperature (Y axis) with the elapsed time (X axis) in the fixing roller 1 provided in the fixing device X, and FIG. 5 shows the fixing roller 1 provided in the fixing device X according to the embodiment. FIG. 6 is a graph showing each elapsed time (X axis) and the power (Y axis) consumed when the temperature is raised from the current temperature to the fixing temperature, and FIG. 6 is a fixing roller provided in the fixing device X according to the embodiment. Keep 1 temperature at ready temperature FIG. 7 is a graph showing the power consumed during printing (Y axis). FIG. 7 shows the elapsed time from the end of the printing process to the transition to the power saving mode in the fixing roller 1 provided in the fixing device X according to the embodiment. It is the graph which showed the relationship between (X-axis) and the electric power consumed (Y-axis).

  Here, it is considered that the temperature state of the fixing roller 1 provided in the fixing device X of the image forming apparatus A shown in this embodiment has the following three stages. That is, the temperature when the fixing roller 1 is performing the fixing process, that is, the fixing temperature (corresponding to the image forming mode in the present invention), and the temperature of the fixing roller 1 is maintained in a ready state within a predetermined time from the end of the printing process. Temperature when ready, that is, ready temperature (corresponding to the ready mode in the present invention), temperature after sufficient time has passed since the heater is turned off, that is, environmental temperature (corresponding to power saving mode in the present invention) ).

  First, the overall configuration of the image forming apparatus A according to the embodiment of the present invention will be described with reference to FIG. The image forming apparatus A is a multifunction machine having a copying function and a printer function. The image forming apparatus A shown in the present embodiment is related to a monochrome developing apparatus, but may be related to color development.

The image forming apparatus A includes a sheet feeding unit for mounting a plurality of cassettes 5 below, a duplex unit 6 disposed above the sheet feeding unit, and an image forming unit 7 disposed above the sheet unit. A fixing device X that fixes toner onto a sheet such as transfer paper is provided beside the image forming unit 7, and a scanner 8 that reads an image and an automatic document feeder (hereinafter referred to as ADF) 9 are attached to the upper portion of the fixing device X. ing. A display operation unit 3 such as a liquid crystal touch panel is disposed on the upper surface of the main body of the image forming apparatus A, and the user operates the display operation unit 3 to select one of the image quality mode selection and the plurality of cassettes 5. Or start reading the image.

  The image forming unit 7 is provided with an image forming unit 15 in which a charging device 12, a developing device 13, and a cleaning device 14 are arranged around the photosensitive drum 11, and is opposed to the photosensitive drum 11 below. A transfer device 16 is arranged. The photosensitive drum 11 has a photosensitive layer formed on the surface of an aluminum cylinder having a diameter of 84 mm, for example, and is driven to rotate clockwise in FIG. The charging device 12 charges the surface of the rotating photosensitive drum 11 to several hundred volts by corona discharge. On the downstream side of the charging device 12 on the surface of the photosensitive drum 11 in the rotational direction, the surface of the photosensitive drum 11 is exposed by an exposure device 18 including an LED array head and a Selfoc lens to form an electrostatic latent image. Is done.

Image data used for controlling the light emission output of the exposure device 18 is input from the image processing unit 4. That is, the original image light guided by the mirror from the scanner 8 is incident on a CCD (Charge-Coupled Device) 10 where A /
D-converted and input to the image processing unit 4 as digital image data (original image data). Further, the document image data is subjected to predetermined image processing in the image processing unit 4, and then the document image data is input to the exposure device control unit 19, and the document image data after the image processing is performed by the exposure device control unit 19. The exposure device 18 is controlled so that the exposure is performed according to the above.

In the developing device 13, the developing roller rotates so that the magnetic brush formed on the surface of the developing roller comes into contact with the surface of the photosensitive drum 11, and a charged toner is attached to the electrostatic latent image to form a toner image. The toner image is conveyed in the transfer device 16 in a state where the sheet conveyed from one of the cassettes 5 is sandwiched between the photosensitive drum 11 and the transfer belt 17 that moves at the same speed as the peripheral speed. While being charged, the toner image is transferred onto the sheet. Further, a cleaning device 14 is disposed on the downstream side of the transfer device 16, and toner and other deposits remaining on the surface of the photosensitive drum 11 are removed. The sheet on which the toner image is transferred by the transfer device 16 is conveyed to the fixing device X provided on the downstream side in the conveyance direction.
Note that the transfer device 16 of the image forming apparatus A employs a transfer belt, but this can be replaced with a transfer roller.

The fixing device X includes a fixing roller 1 which is an example of a fixing unit, and a pressure roller 2 provided with a pressure mechanism facing the fixing roller 1. The fixing roller 1 incorporates a heater such as a halogen heater, for example, and its temperature is controlled by a control device provided in the image forming apparatus. Here, the fixing device X is consumed by a fixing roller temperature sensor 20 that detects the temperature of the fixing roller 1 described later, an environmental temperature sensor 21 that detects the environmental temperature, and a heater that raises the temperature of the fixing roller 1. A heater wattmeter 22 for measuring electric power is provided, and while the image forming apparatus is in operation, the fixing roller temperature sensor 20, the environmental temperature sensor 21, and the heater wattmeter 22 are always in operation. ing.
The fixing roller 1 is cited as an example of a fixing unit in the present invention.

  The toner image adhering to the sheet conveyed from the transfer device 16 by the transfer belt or the transfer roller is caused by the heat of the fixing roller 1 while the sheet passes between the fixing roller 1 and the pressure roller 2. The image is fused and fixed, and the sheet is pressed against the fixing roller 1 by the pressure roller 2 to be fixed on the sheet. The sheet on which the toner image has been fixed by the fixing device X is then sent to the sheet processing device B side, subjected to predetermined processing, and then discharged from the sheet discharge port.

Next, a schematic configuration of a main part of the image forming apparatus A according to the present embodiment will be described with reference to FIG.
The image forming apparatus A includes a fixing device X including a fixing roller 1 heated by a heater 30 and a control device 31 that controls internal mechanisms such as the heater 30 and the fixing roller 1 in the fixing device X. The control device 31 includes a CPU 32 that manages control of the apparatus body, a non-volatile memory 41 such as a ROM, and a print control unit 39 that includes a heater power supply circuit 40 that controls the heater 30. 39 and the CPU 32 and the nonvolatile memory 41 are connected to each other by a predetermined bus.

Further, the fixing roller temperature sensor 20 that detects the temperature of the fixing roller 1, and the sensor unit 23 and the control device 31 that include the environmental temperature sensor 21 that detects the environmental temperature are further consumed by the heater 30. The heater wattmeter 22 for measuring the power to be measured and the control device 31 are connected to each other by a predetermined bus. That is, data is transmitted between the control device 31 (specifically, the CPU 32), the fixing roller temperature sensor 20, the environmental temperature temperature sensor 21, and the heater wattmeter 22 via buses connected to each other. Signals are being sent and received.
As shown in the figure, the ready temperature arrival time detection means 33, the integrated heat release amount calculation means 34, the first return heat amount calculation means 35, the second return heat amount calculation means 36, the saturation time calculation means 37, the mode transition. The CPU 32 executes a control program that realizes each function of the preparation time setting unit 38, thereby calculating the mode transition preparation time.

  Here, the non-volatile memory 41 stores in advance the fixing temperature and the ready temperature in the fixing roller 1. Furthermore, characteristic data such as parameter values or fixed values of functions for calculating and setting the mode transition preparation time, such as the specific heat of the devices constituting the fixing device and the volume of the fixing roller 1, regarding the setting of the mode transition preparation time. Is also stored in advance. Based on the fixing temperature, the ready temperature, the characteristic data, and the environmental temperature detected by the environmental temperature sensor 21 stored in the nonvolatile memory 41, the CPU 32 executes a process for realizing each of the functions described above. Thus, various setting data including the mode transition preparation time are calculated. The calculated various setting data is stored in the nonvolatile memory 41.

  In addition, during the time from the end of printing to the transition to the power saving mode, that is, during the mode transition preparation time calculated by the above-described series of processing, the temperature of the fixing roller 1 is changed from the CPU 32 to the heater power supply circuit 40 to the ready temperature. An instruction to control the temperature of the heater 30 is held. After that, when the mode transition preparation time is reached, an instruction to stop energization of the heater 30 is issued from the CPU 32 to the heater power supply circuit 40, thereby shifting to the power saving mode.

  Next, using the graphs of FIGS. 4 to 7, the concept for calculating the mode transition preparation time performed by the CPU 32 provided in the control device 31 of the image forming apparatus A according to the present embodiment will be described. .

First, the graph of FIG. 4 will be described. FIG. 4 is a graph showing the temperature change of the fixing roller 1 with the passage of time from the end of the printing process.
For example, when the fixing roller 1 is naturally cooled from the fixing temperature A to the environmental temperature Ts by stopping energization of the heater 30 at the end of the printing process, the temperature of the fixing roller 1 is set to Newton's temperature as time passes. There is a change as shown in the curve of T2 according to the cooling law. That is, when the elapsed time is 0 at the end of the printing process, it takes time for the fixing roller temperature to decrease from the fixing temperature A to the environmental temperature Ts by the elapsed time tsp.
Further, as shown in the figure, when the temperature of the fixing roller 1 decreases from the fixing temperature A to the environmental temperature Ts, the state of the ready temperature TR is passed. In this case, if the temperature of the fixing roller 1 after the elapsed time tRP is maintained at the ready temperature TR without being lowered to the environmental temperature TR, naturally, the temperature of the fixing roller 1 after the elapsed time tRP is a straight line T1. Will be kept constant.

Here, according to Newton's law of cooling, the rate at which an object cools is approximately proportional to the difference between the temperature of the object and the ambient temperature, and this can be expressed by a mathematical model T = AeBt + C (T: The temperature of the heater 30, t: elapsed time, A: fixing temperature, B: constant determined by the material such as specific heat between the heater 30 and the fixing roller 1, and C: environmental temperature). From this, by performing an exponential regression analysis on the temperature drop data of the fixing roller 1 where the temperature of the fixing roller 1 decreases from the fixing temperature A to the ready temperature TR, and calculating a regression equation and a correlation coefficient. The relationship between the temperature of the fixing roller 1 and the elapsed time when the temperature drop of the fixing roller 1 shows the curve T2 can be calculated.
Thus, an example of means for detecting the elapsed time tRP from the end of the printing process until the temperature of the fixing roller 1 reaches the ready temperature TR is the ready temperature arrival time detecting means 33 in the present invention.

Based on the relationship between the temperature of the fixing roller 1 and the elapsed time according to the Newton's cooling law calculated by the method as described above, the temperature of the fixing roller 1 that has decreased with the elapsed time is raised from the temperature of the fixing roller 1 to the fixing temperature A. Is calculated.
The relationship between the power consumption and the elapsed time is represented by a curve rising to the right as shown in the graph of FIG. Here, when the temperature of the fixing roller 1 shown by the straight line T1 in FIG. 4 is kept constant, the temperature of the fixing roller 1 is raised from the ready temperature TR to the fixing temperature A as shown by the straight line T4 shown in FIG. It can be seen that PRP power is required. Similarly to the straight line T1, as indicated by the straight line T2 in FIG. 4, the temperature of the fixing roller 1 becomes the environmental temperature TS after the elapsed time tSP, and the temperature of the fixing roller 1 is fixed from the environmental temperature TS. In order to increase the temperature to A, PSP power is required.

  Here, as indicated by the straight line T1 in FIG. 4 described above, in order to keep the temperature of the fixing roller 1 at the ready temperature TR, the temperature of the fixing roller 1 is increased from the ready temperature TR to the fixing temperature A. Apart from the consumed electric power, electric power represented by a straight line rising to the right as shown in FIG. 6 is required.

  FIG. 7 is a summary of FIGS. 4 to 6 described above. The calculation of the mode transition preparation time tp in the image forming apparatus A will be described with reference to FIG. In FIG. 7, a power consumption curve T6 when returning to the fixing temperature again after a lapse of a certain time after stopping energization of the heater 30 at the fixing temperature corresponds to T3 in FIG. Further, the power consumption straight line T7 when the temperature of the fixing roller 1 after the elapsed time tRP is held at the ready temperature TR is in a standby state, the integrated value of T4 in FIG. 5 and T5 in FIG. This is the sum of the power PRP consumed when the temperature is raised from the ready temperature TR to the fixing temperature A and the power PR consumed when the temperature of the fixing roller 1 is held at the ready temperature TR.

  As described above, an example of means for calculating the integrated value of heat dissipation amount (that is, PSP-PRP) based on the passage of time until the temperature of the fixing roller 1 reaches the environmental temperature TS from the ready temperature TR is an integration according to the present invention. It is a heat radiation amount calculation means. An example of means for calculating the power consumption (that is, PRP) required to return the temperature of the fixing roller 1 from the ready temperature TR to the fixing temperature A is the first return heat amount calculation means in the present invention. Further, an example of means for calculating power consumption (that is, PSP) required to return the temperature of the fixing roller 1 from the environmental temperature TS to the fixing temperature A when the temperature of the fixing roller 1 is the environmental temperature TS is as follows. It is the 2nd return calorie | calculation means in invention.

Here, as shown in FIG. 7, the amount of heat (electric energy) for raising the temperature of the fixing roller 1 in the natural heat dissipation state to the fixing temperature A after the end of the printing process in the image forming apparatus A is a curve. The amount of heat (electric energy) for maintaining the ready temperature TR from the time tRP when reaching the ready temperature TR and raising the temperature of the fixing roller 1 from the ready temperature TR to the fixing temperature A at an arbitrary time is represented by T6. It is represented by a straight line T7.
Therefore, since the straight line T7 exceeds the curve T6 at time tP, if the mode transition preparation time is made longer than time tP, the straight line T7 consumes more power than the curve T6, which is uneconomical. In order to shorten the waiting time for returning to the fixing temperature A, the time tP should be as long as possible. However, as described above, it can be seen that the time tP is the limit from the economical aspect. The present invention achieves balanced control by automatically calculating such a reasonable time tP.

  The time required from the time tRP when the temperature of the fixing roller 1 reaches the ready temperature TR to the intersection P (that is, the mode transition preparation time tP) between the curve T6 and the straight line T7 (that is, the mode transition preparation time tP−time). One example of means for calculating (tRP) is the saturation time calculating means in the present invention.

Hereinafter, the calculation procedure of the mode transition preparation time tP performed by the CPU 32 in the control device 31 provided in the image forming apparatus A according to the above embodiment will be described with reference to FIG. Here, a case will be described in which parameters necessary for the calculation of the mode transition preparation time tP are acquired in the printing process stage or when the power is turned on. In FIG. 3, reference numerals S1, S2,... Indicate step numbers.
S1: First, it is determined whether either the initial operation when the image forming apparatus A is turned on or the printing process in the image forming apparatus A is started. If it is determined that it has started, the process proceeds to step S2, and this step is repeated while it has not started.
S2: An instruction to turn on the heater 30 from the CPU 32 to the heater power circuit 40 when either the initial operation when the image forming apparatus A is turned on or the printing process in the image forming apparatus A is started. The temperature rise of the fixing roller 1 of the fixing device X is started. After the temperature rise of the fixing roller 1 starts, the process proceeds to step S3.
S3: Power consumption required while the temperature of the fixing roller 1 is raised from the environmental temperature TS to the fixing temperature A by the heater 30 is detected in relation to the temperature at each time point (hereinafter referred to as power consumption when rising from a predetermined temperature). And the process proceeds to step S4.
S4: The power consumption during the temperature rise from the predetermined temperature detected in step S3 is stored in the nonvolatile memory 41, and the process proceeds to step S5.
For example, the power for raising the temperature from the environmental temperature TS to the ready temperature TR, the power for raising the temperature from the ready temperature TR to the fixing temperature A, and the like are measured at small time intervals. If the electric power to raise the temperature from one temperature to another temperature is known, the reverse cooling curve shown in FIG. Therefore, the procedure in step S4 is synonymous with the procedure for drawing the cooling curve T in FIG. 4, and this also corresponds to the processing procedure for drawing the power consumption curve in T3 in FIG. In this way, a curve of T3 is obtained. Further, since the specific heat of the fixing roller 1 is known, the power consumption for maintaining the fixing roller 1 at a predetermined ready temperature TR, that is, the slope of the straight line T5 in FIG. 6 is also calculated.
S5: When the above calculation is completed, it is determined whether the initial operation when the image forming apparatus A is turned on or the printing process in the image forming apparatus A is completed. If it is determined that the printing process has ended, the process proceeds to step S6, and this step is repeated while the printing process has not ended.
S6: When an initial operation upon power-on of the image forming apparatus A or the end of the printing process in the image forming apparatus A is detected, a timer provided therein is started and measurement of elapsed time is started. Then, the process proceeds to step S7.
S7: Here, the curve T6 and the straight line T7 stored in S4 are reproduced. Since this data is collected in step S3 and stored in advance in the nonvolatile memory 41, it may be reproduced in relation to the time at which it is collected at the same time. In this case, the time elapses based on the characteristic data such as the specific heat of the apparatus constituting the fixing device X, the characteristic data such as the volume, the environmental temperature TS detected by the environmental temperature sensor 21, and the Newton's cooling law. Accordingly, the relationship between the temperature drop of the fixing roller 1 and the amount of heat released spontaneously at that time may be calculated (T2 in FIG. 4).
S8: From the integrated value of power consumption calculated in step S7 (curve T6 in FIG. 7) and the integrated value of power consumption calculated in step S8 (straight line T7 in FIG. 7), FIG. The intersection point P as shown is obtained, and the mode transition preparation time tP is calculated.
S9: Setting the mode transition preparation time tP in the image forming apparatus A by storing the mode transition preparation time tP calculated in the step S8 in an internal storage unit provided in the image forming apparatus A. Thereafter, the mode transition preparation time is set using the mode transition preparation time tP. Therefore, it is desirable to repeat this procedure at appropriate time intervals, for example, at the end of the printing process, and to set the preparation time after the optimum mode following the change in environmental temperature.
An example of means for setting the mode transition preparation time tP in the image forming apparatus A in this step is the mode transition preparation time setting means in the present invention.

  As described above, the mode transition preparation time tP is determined by performing the series of processes described above. Therefore, when the count of the timer activated in step S6 reaches the mode transition preparation time tp calculated in step S9, the CPU 32 issues an instruction to turn off the heater 30 to the heater power supply circuit 40. As a result, energization of the fixing roller 1 is stopped, and a transition is made to a power saving mode in which an instruction for the next image forming operation is awaited.

1 is a schematic sectional view of an image forming apparatus A according to an embodiment of the present invention. 1 is a functional block diagram illustrating a schematic configuration of a main part of an image forming apparatus A according to an exemplary embodiment. 6 is a flowchart showing a mode transition preparation time calculation process performed by a CPU 32 in a control device 31 provided in the image forming apparatus A according to the present embodiment. 6 is a graph showing a change in surface temperature (Y axis) with an elapsed time (X axis) in the fixing roller 1 provided in the fixing device X according to the embodiment. 6 is a graph showing each elapsed time (X axis) in the fixing roller 1 provided in the fixing device X according to the present embodiment and electric power (Y axis) consumed when the temperature is raised from the temperature at that time to the fixing temperature. 6 is a graph showing electric power (Y axis) consumed when the temperature of the fixing roller 1 included in the fixing device X according to the embodiment is held at a ready temperature. In the fixing roller 1 provided in the fixing device X according to this embodiment, the relationship between the elapsed time (X axis) from the end of the printing process to the transition to the power saving mode and the consumed power (Y axis) is shown. Graph.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fixing roller 2 ... Pressure roller 3 ... Display operation part 4 ... Image processing part 5 ... Cassette 6 ... Duplex unit 7 ... Image forming part 8 ... Scanner 9 ... Automatic document feeder (ADF)
10 ... CCD
DESCRIPTION OF SYMBOLS 11 ... Photoconductor drum 12 ... Charging device 13 ... Developing device 14 ... Cleaning device 15 ... Image forming unit 16 ... Transfer device 17 ... Transfer belt 18 ... Exposure device 19 ... Exposure device control means 20 ... Fixing roller temperature sensor 21 ... Environment Temperature sensor 22 for heater ... Wattmeter for heater 23 ... Sensor unit 30 ... Heater 31 ... Control device 32 ... CPU
33 ... Ready temperature arrival time detection means 34 ... Integrated heat release amount calculation means 35 ... First return heat amount calculation means 36 ... Second return heat amount calculation means 37 ... Saturation time calculation means 38 ... Mode transition preparation time setting means 39 ... Print Control unit 40 ... heater power supply circuit 41 ... nonvolatile memory

Claims (3)

At least an image forming mode in which an image forming operation is performed in a fixing unit provided in the image forming apparatus based on a predetermined fixing temperature, and the temperature of the fixing unit is maintained at a predetermined ready temperature lower than the fixing temperature and higher than the environmental temperature. Mode transition preparation time from the start of the ready mode to the transition to the power saving mode in the image forming apparatus having the three modes of the ready mode and the power saving mode in which the energization to the fixing unit is stopped and the image forming operation is instructed In the control device of the image forming apparatus for controlling
A ready temperature arrival time detecting means for detecting a time until the temperature of the fixing portion reaches the ready temperature by natural cooling from the fixing temperature;
An integrated heat dissipation amount calculating means for calculating an integrated value of the heat dissipation amount based on the passage of time from the fixing unit maintained at the ready temperature;
First return heat amount calculating means for calculating the amount of heat required to return the fixing unit at the ready temperature to the fixing temperature;
A second return heat amount calculating means for calculating an amount of heat necessary for returning the fixing unit at the environmental temperature to the fixing temperature;
The temperature of the fixing unit detected by the ready temperature arrival time selecting means is maintained at the ready temperature calculated by the integrated heat radiation calculating means after the time from the fixing temperature until reaching the ready temperature by natural cooling. The integrated value of the heat dissipation amount based on the passage of time from the fixing unit and the amount of heat necessary for returning the fixing unit at the ready temperature calculated by the first return heat amount calculating means to the fixing temperature. Saturation time calculation means for calculating a time until the sum reaches a heat amount necessary for returning the fixing unit at the environmental temperature calculated by the second return heat amount calculation means to the fixing temperature;
Mode transition preparation time setting means for setting a mode transition preparation time based on the sum of the time detected by the ready temperature arrival time detection means and the time calculated by the saturation time calculation means;
A control apparatus for an image forming apparatus, comprising: 2. The control device for an image forming apparatus according to claim 1 , wherein the calculation of the heat radiation amount from the fixing unit by the integrated heat radiation amount calculation means is based on Newton's cooling law. An image forming apparatus including a control device according to claim 1 or 2.

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