JP2016024323A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing FPOT (first printout time) while saving power.SOLUTION: An image forming apparatus is configured to execute a power saving mode for limiting power consumed by each part of the image forming apparatus when a prescribed time has lapsed after a power control part that controls power supply to each part of the image forming apparatus enters a standby period for waiting for the start of image formation. The power control part executes a preheating mode for supplying power to a fixation part to maintain a preheating temperature when, at the time when the temperature of the fixation part detected by a temperature detection part lowers to a prescribed preheating temperature after the start of the standby time, the residual time from the time to the start of the power saving mode is a prescribed residual threshold time or more.SELECTED DRAWING: Figure 3

Description

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

  In recent years, image forming apparatuses such as copying machines, printers, and facsimiles have been increased in speed and color. In the case of such a high-speed printer or color printer, there is a tendency that the control target temperature of the fixing device when the toner image formed on the recording paper (recording material) is heated and fixed is increased. Further, it is preferable that a so-called first printout time (hereinafter referred to as “FPOT”) from when an image formation request is input to when the first recording sheet is discharged is as short as possible. Therefore, in an image forming apparatus that requires a certain amount of heating time from the time when the printer receives a print job to the control target temperature of the fixing device (fixing unit), control is performed to preheat the fixing device to some extent during standby in order to shorten the heating time Has been implemented. On the other hand, in recent years, there has been a demand for power saving of image forming apparatuses, and when a standby mode continues for a certain period of time, it is common to have a function of automatically shifting to a power saving mode that consumes less power than the standby mode. It has become. Therefore, for the purpose of reducing the preheating power during standby for power saving, Patent Document 1 determines whether or not to perform preheating according to the user set time for transition from the standby state to the power saving mode. The invention is disclosed.

Japanese Patent No. 5058669

  In recent years, since the recovery time for the image forming apparatus to return from the power saving mode has been reduced, the time for the image forming apparatus to automatically transition from the standby mode to the power saving mode is often set to be short. ing. Therefore, the time that the image forming apparatus stays in the standby mode is shortened, and even if the image forming apparatus performs preheating in the standby mode, the print job is not received and the power saving mode is changed, and the preheating power is reduced. There arises a problem that it is not used for shortening FPOT. On the other hand, if the preheating in the standby mode of the fixing device is cut off, the FPOT becomes large and the usability is deteriorated. Therefore, the preheating of the fixing device cannot be simply cut off.

  An object of the present invention is to provide an image forming apparatus capable of reducing power consumption while reducing FPOT.

In order to achieve the above object, an image forming apparatus of the present invention includes:
An image forming unit for forming a developer image on a recording material;
A fixing unit that heat-fixes the developer image on the recording material;
A temperature detection unit for detecting the temperature of the fixing unit;
A power control unit that controls power supply to each unit of the image forming apparatus;
With
The power control unit is configured to execute a power saving mode for limiting power consumed by each unit of the image forming apparatus when a predetermined time has elapsed after entering a standby period for waiting for the start of image formation. In the image forming apparatus,
When the temperature detected by the temperature detection unit has decreased to a predetermined preheating temperature after entering the standby period, the power control unit has a predetermined remaining time from the time until the start of the power saving mode. When the time is equal to or longer than the threshold time, a preheating mode for supplying electric power to the fixing unit is executed to maintain the preheating temperature.
In order to achieve the above object, the image forming apparatus of the present invention includes:
An image forming unit for forming a developer image on a recording material;
A fixing unit that heat-fixes the developer image on the recording material;
A temperature detection unit for detecting the temperature of the fixing unit;
A power control unit that controls power supply to each unit of the image forming apparatus;
With
The power control unit executes a power saving mode for limiting power consumed by each unit of the image forming apparatus when a predetermined time has elapsed after entering a standby period for waiting for the start of image formation, and the standby period In the image forming apparatus configured to execute a preheating mode in which power is supplied to the fixing unit so as to maintain a predetermined preheating temperature of the fixing device.
A first state in which the temperature detected by the temperature detection means decreases from the first temperature to the second temperature at the time when the standby time is entered, between the start of the power saving mode after the start of the standby period; The second state maintained at the second temperature, and the temperature transition state that transitions in the order of the third state that decreases from the second temperature to the third temperature at the start of the power saving mode can be taken. It is characterized by.

  According to the present invention, it is possible to save power while reducing FPOT.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. Flowchart of preheating control of embodiment 1 Timing chart of preheating control of embodiment 1 Flowchart of preheating control of embodiment 2 Timing chart of preheating control of embodiment 2 Flow chart of preheating control of embodiment 3 Timing chart of preheating control of embodiment 3 FIG. 10 is a diagram illustrating the relationship between the fixing device temperature and the fixing ready time of the image forming apparatus according to the third exemplary embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

Example 1
<Overall configuration and image formation process>
With reference to FIG. 1A, an outline of the overall configuration of an electrophotographic image forming apparatus (hereinafter referred to as an image forming apparatus) according to an embodiment of the present invention will be described. FIG. 1A is a schematic cross-sectional view illustrating the overall configuration of the image forming apparatus according to the present embodiment. As an image forming apparatus according to this embodiment, a color laser printer using an electrophotographic image forming process will be described here.

An image forming apparatus 100 (hereinafter referred to as a printer 100) according to this embodiment includes process stations (process cartridges) 5Y, 5M, 5C, and 5K that can be attached to and detached from the apparatus main body. The four process stations 5Y, 5M, 5C, and 5K have the same structure, but toners (developer) of different colors, that is, yellow (Y), magenta (M), cyan (C), and black (K). Is different in that an image is formed. Except for the case where a specific process station is described, the YMCK code is omitted hereinafter. Each process station 5 includes a toner container 23, a photosensitive drum 1 as a photoreceptor, a charging roller 2, a developing roller 3, a cleaning blade 4, and a waste toner container 24. An exposure device 7 is disposed below the process station 5 and performs exposure based on the image signal to the photosensitive drum 1.

  The photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the charging roller 2 during the rotation process. The photosensitive drum 1 is subjected to image exposure by the exposure device 7 so as to correspond to the first to fourth color component images (yellow, magenta, cyan, black component images) of the target color image. An electrostatic latent image is formed. The charging roller 2 is driven to rotate as the photosensitive drum 1 rotates. The exposure apparatus 7 used in the present embodiment is a polygon scanner using a laser diode, and forms an electrostatic latent image by forming an image of a laser beam modulated according to image information on the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is developed by the developing rollers 3 of the first to fourth process stations Y, M, C, and K. Each color toner is attached to the electrostatic latent image on the photosensitive drum 1 via the developing roller 3 and developed as a toner image (developer image). The toner in each toner container 23 is a negatively charged non-magnetic one-component toner, and development of the electrostatic latent image is performed by a non-magnetic one-component contact development method. A developing bias is applied to the developing roller 3 by a developing bias power source (not shown), thereby developing.

  The intermediate transfer belt unit includes an intermediate transfer belt 8, a driving roller 9, and a secondary transfer counter roller 10. Further, a primary transfer roller 6 is disposed inside the intermediate transfer belt 8 so as to face each photosensitive drum 1, and a positive primary transfer bias is applied by a primary transfer bias power source (not shown). When the driving roller 9 is rotated by a motor (not shown), the intermediate transfer belt 8 is rotated, and the secondary transfer counter roller 10 is also rotated accordingly. Each photosensitive drum 1 rotates in the arrow direction, the intermediate transfer belt 8 rotates in the arrow A direction, and a positive primary transfer bias is applied to the primary transfer roller 6. As a result, the toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 8 sequentially from the toner image on the photosensitive drum 1Y. Thereafter, the four color toner images are conveyed to the secondary transfer roller 11 in an overlapping state. The cleaning blade 4 of the photosensitive drum 1 is in pressure contact with the photosensitive drum 1 and removes residual toner remaining on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 8 and other residues on the photosensitive drum 1.

  The feeding / conveying device 12 includes a feeding roller 14 that feeds the recording material P from the inside of the paper feeding cassette 13 that stores the recording material (recording medium such as recording paper, an OHP sheet, and cloth), and the fed recording material. A conveying roller pair 15 for conveying P; Then, the recording material P conveyed from the feeding / conveying device 12 is conveyed to the secondary transfer roller 11 by the registration roller pair 16. In the transfer from the intermediate transfer belt 8 to the recording material P, a positive bias is applied to the secondary transfer roller 11 so that the four color toner images on the intermediate transfer belt 8 are transferred to the conveyed recording material P. Transfer (secondary transfer). The cleaning blade 21 is in pressure contact with the intermediate transfer belt 8, removes residual toner remaining on the surface of the intermediate transfer belt 8 without being subjected to secondary transfer and other residues on the intermediate transfer belt 8, and collects them in a waste toner container 22. To do. The apparatus configuration relating to the process of forming a toner image on the recording material in the above configuration corresponds to the image forming unit of the present invention.

  The recording material P after the toner image is transferred is conveyed to a fixing device (fixing unit) 17. The fixing unit 17 includes a fixing heater 30 and a cylindrical fixing film 18 in which a temperature detection sensor 31 for detecting the temperature of the fixing heater 30 is disposed on the inner peripheral side, and a fixing nip portion by pressing against the outer peripheral surface of the fixing film 18. It is a film heating type fixing device provided with a pressure roller 19 to be formed. The recording material P is heated and pressed at the fixing nip portion to heat and fix the toner image, and is discharged out of the printer 100 (outside of the apparatus) as an image formed product (printed paper or the like) by the discharge roller pair 20. .

Reference numeral 50 denotes an operation panel for notifying the user of the apparatus status and setting the apparatus by the user, and an operation switch, an LED display, and the like are arranged. The power supply device 35 connected to the commercial power supply 36 has a fixing power supply circuit to the fixing device 17 and a rectifying action from AC to DC, and the power consumed in the above-described image forming process is a power supply that is usually a main power supply. It is supplied from the apparatus 35 to each part of the laser beam printer.

<Control block diagram>
FIG. 1B is a control block diagram of the image forming apparatus according to the present embodiment. The printer control unit 101 includes a circuit such as a CPU 104, a ROM, and a RAM (not shown), and executes a program for controlling each device in the printer 100 as an image forming apparatus. The CPU 104 in the printer control unit 101 controls the fixing power supply circuit 37 in the power supply device 35 to turn on / off the fixing heater 30 and adjust the temperature. The CPU 104 monitors the temperature detection result of the fixing heater 30 by the temperature detection sensor (temperature detection unit) 31 and fixes the fixing power so as to keep the temperature of the fixing heater 30 constant in order to achieve the target temperature necessary for the fixing device 17. The supply power to the fixing heater 30 is controlled by the supply circuit 37.

  The controller 102 is connected to the printer control unit 101, and issues a print instruction to the printer control unit 101 according to the settings of the operation panel 50 and the host computer 102 connected via a network, a printer cable, or the like. The controller 102 receives image information and a print command from the host computer 103. The controller 102 analyzes the received image information and converts it into bitmap data. During printing, the controller 102 transmits the bitmap data to the printer control unit 101 in synchronization with the TOP signal transmitted from the printer control unit 101. . Each function of the printer control unit 101 may be realized by the CPU 104 executing various control programs, or a part or all of the function may be performed by a dedicated circuit (ASIC) for a specific application. good.

<Power saving transition process>
Next, a process for shifting to the power saving mode (power saving control) of the image forming apparatus will be described. After the printer 100 is turned on and the preparatory operation when the power is turned on is completed, and after the printing is completed, the printer 100 shifts to a standby mode (standby control) waiting for a print job. In the image forming apparatus according to the present exemplary embodiment, when a predetermined time has elapsed after entering a standby period for waiting for the start of image formation, a power saving mode for limiting power consumed by each unit of the image forming apparatus is executed. That is, the controller 102 counts the elapsed time in the stern mode, and compares the power saving transition time Tsleep stored in the controller 102 with the standby standby time Tstby. When the standby standby time Tstby becomes longer than the power saving transition time Tsleep, the controller 102 automatically shifts to the power saving mode. At the time of shifting to the power saving mode, the controller 102 reduces power consumption by turning off the backlight of the operation panel 50 or cutting off the power supply to some circuits inside the controller 102. The controller 102 also issues a power saving instruction to the printer control unit 101. In accordance with the instruction, the printer control unit 101 reduces power consumption by stopping the power supply of the fixing power supply circuit 37 or stopping the power supply to some circuits output from the power supply device 35. In the above configuration, the configuration related to the control of power supply to each unit of the apparatus corresponds to the power control unit in the present invention.

The transition time Tsleep to the power saving mode can be set by the user from the operation panel 50 or the host computer 103. The transition time that can be set by the user is 1 minute, 5 minutes, 15 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes, etc., but generally it is initially set to comply with international programs such as Energy Star Has been. However, when the printer 100 shifts to the power saving mode, a return time from the power saving mode is required for printing, and the wait time becomes longer than when printing in the standby mode. Therefore, a user who is worried about the wait time due to the power saving return of the printer can reduce the frequency at which the printer enters the power saving mode by setting the power saving transition time large.

<Standby temperature control>
In the standby mode, the printer control unit 101 waits for a print job from the controller 102, sets the target temperature of the fixing unit 17 to a temperature lower than the temperature during printing, supplies power to the fixing heater 30, and fixes the fixing job. The vessel 17 is maintained at a predetermined preheat temperature. Hereinafter, this preheating in the standby mode is referred to as standby temperature control (preheating mode). If the fixing device 17 is cooled too much during the standby mode, it takes a long time to input an amount of power necessary for preheating the fixing device 17 after receiving a print job. That is, the time (fixing ready time) from when a print job is received until toner image formation can be started increases. In recent years, FPOT, that is, the time from when a print job is received until the first sheet is ejected, has been attracting attention for improving usability. As the fixing ready time increases, the FPOT also increases. It will be. Further, performing standby temperature control leads to power consumption. Therefore, it is necessary to reduce the standby temperature control time for power saving while maintaining FPOT as much as possible.

<Flowchart of this embodiment>
FIG. 2 is a flowchart that best represents the characteristics of the present embodiment, and is a flowchart for describing processing for switching the fixing preheating control during print standby according to the setting of the power saving mode transition time Tsleep according to the present embodiment. . FIG. 2A is a flowchart of the printer control unit 101, and FIG. 2B is a flowchart of the controller 102.

  The controller 102 executes the control shown in FIG. 2B in parallel with the processing of the flowchart of the printer control unit 101 shown in FIG. The controller 102 sets a reference time for counting the elapsed time in the standby mode after printing is finished (S151). Then, the controller 102 monitors whether or not the elapsed time in the standby mode has become equal to or longer than the power saving mode transition time Tsleep in order to determine whether or not to shift the printer 100 to the power saving mode (S152). When the controller 102 determines to shift to the power saving mode, the controller 102 transmits an instruction to shift to the power saving mode to the printer control unit 101. In that case, the printer control unit 101 exits the process of the flowchart and starts the transition to the power saving mode even in the middle of the flowchart of FIG.

  Next, the operation of the printer control unit 101 will be described based on the flowchart shown in FIG. When the printer control unit 101 finishes printing and shifts to the standby mode, the printer control unit 101 first sets the reference of the elapsed time Estby in the standby mode to the time at this time (S101). Next, the printer control unit 101 makes an inquiry to the controller 102 and acquires the transition time Tsleep to the power saving mode (S102). Thereafter, the printer control unit 101 monitors the temperature detection sensor 31 to start standby temperature adjustment, and determines whether a condition for starting standby temperature adjustment is satisfied. In this embodiment, when the temperature detected by the temperature detection sensor 31 falls below a predetermined standby temperature adjustment temperature (preheating temperature) or when the temperature is lowered to the standby temperature adjustment temperature, it is determined that the standby temperature adjustment is started, and the difference is made. If this is the case, the monitoring is continued (S103).

When it is determined that the standby temperature adjustment is started, first, the remaining time Trest (= Tsleep-Estby) until the transition to the power saving mode is calculated from the standby mode elapsed time Estby and the power saving mode transition time Tsleep at this time (S104). Next, the remaining time Trest until the transition to the power saving mode is compared with the remaining threshold time Trest_thr (S105). When Trest is less than Trest_thr (shorter than the remaining threshold time), the fixing device 1 does not adjust the standby temperature until the transition to the power saving mode and the print job comes.
7 is determined not to be overcooled, and standby temperature control is not executed (S106). If Trest is equal to or greater than Trest_thr (more than the remaining threshold time), it is determined that if the standby temperature adjustment is not performed for a long time until the transition to power saving, the fixing device 17 will be overcooled, and standby temperature adjustment is performed ( S107). If it is determined that standby temperature adjustment is necessary, the process returns to step S104 until the power saving mode is entered, and it is determined whether standby temperature adjustment is to be executed. As a result, the standby temperature adjustment is performed until the remaining time Trest has the same length as the remaining threshold time Trest_thr. The remaining threshold time Trest_thr is a predetermined threshold temperature when the standby temperature adjustment is not executed from the time point before the remaining threshold time Trest_thr before the start time of the power saving mode. It sets so that it may become above. The threshold temperature is set from the viewpoint of maintaining the fixing device 17 in a temperature range that does not affect the FPOT when a print job comes later.

  FIG. 3 is a diagram showing a difference in standby temperature adjustment operation due to a difference in heat storage state of the fixing device 17. 3A is an example of a cold state (first temperature transition state) in which the heat storage of the fixing device 17 is small in the standby mode transition state, and FIG. 3B is a fixing unit in the standby mode transition state. It is an example (2nd temperature transition state) of a hot state with the large heat storage of 17. FIG. In this embodiment, the standby temperature control temperature Fstby is set to 120 ° C., and the power saving mode transition time Tsleep is set to 1 minute. The remaining threshold time Trest_thr is set to 15 seconds.

  In FIG. 3A, since the heat storage of the fixing device is small, the temperature decreases quickly and the fixing device temperature decreases from the standby shift to the standby temperature adjustment temperature at an early timing (first state: first temperature → second temperature), The printer control unit 101 performs standby temperature adjustment. Then, the standby temperature adjustment is stopped at the timing when the remaining time Trest until the transition to the power saving mode falls below the remaining threshold time Trest_thr (second state). After the standby temperature control is stopped (third state: second temperature → third temperature), the fixing device temperature prediction is slight, and even if a print job comes in the meantime, the wait time becomes so large that the usability is impaired. There is no end. On the other hand, in FIG. 3B, at the timing when the fixing device temperature decreases to the standby temperature adjustment temperature, the remaining time Trest until the transition to the power saving mode is less than the remaining threshold time Trest_thr, and thus the standby temperature adjustment is not executed. .

  Although the remaining threshold time Trest_thr is set to 15 seconds in the present embodiment, the remaining threshold time Trest_thr is changed depending on whether the power saving mode transition time Tsleep set by the user is larger or smaller than the factory setting value, and is set to the user setting. You may comprise so that the printer operation according to it may be implemented. For example, when the power saving mode transition time Tsleep by the user is longer than the factory default value, it may be determined that the user has given priority to the wait time, and a small value may be set as the remaining threshold time Trest_thr. In addition, when the power saving mode transition time Tsleep by the user is smaller than the factory-set value, a threshold value that prioritizes power saving may be used.

  As described above, according to the present embodiment, the standby temperature adjustment is stopped at the timing when the remaining time for shifting to the power saving mode is reduced, thereby reducing the power required for the standby temperature adjustment. I can do it. Whether or not standby temperature control is performed is determined based on the remaining time for transition to the power saving mode, and does not affect FPOT. In the present embodiment, the case of the film heating system has been described as the configuration of the fixing device, but it goes without saying that the present invention can also be applied to a heat roller type fixing device.

(Example 2)
An image forming apparatus according to Embodiment 2 of the present invention will be described. The apparatus configuration of the image forming apparatus according to this embodiment and the schematic configuration of the control system are the same as those in the first embodiment. Those explanations are omitted, and different points from the first embodiment will be mainly described below using the same reference numerals.

  The fixing device 17 has a characteristic of accumulating heat according to the heating time during printing. When the transition to the standby mode is performed in the cold state where the heat storage amount is small, the cooling speed of the fixing device 17 is fast, and when the transition is made to the standby mode in the hot state where the heat storage amount is large, the cooling speed of the fixing device 17 is slow. In particular, since the heat storage capacity of the film heating type fixing device is smaller than that of the heat roller type fixing device, there is a difference in the cooling speed of the fixing device in the standby mode between the cold state and the hot state. In Example 1, regardless of the amount of heat stored in the fixing unit 17, whether or not standby temperature control is appropriate is determined using a uniform time as a threshold value. In this embodiment, in order to take into account the cooling speed due to the difference in the heat storage amount of the fixing device 17, the change in the fixing device temperature corresponding to the heat storage condition of the fixing device 17 is predicted from the temperature change per unit time, and the change is Based on the above, the existence of standby temperature control was judged.

  FIG. 4 is a flowchart illustrating the control of the printer control unit 101 in this embodiment. When the printer control unit 101 finishes printing and shifts to the standby mode, the printer control unit 101 first sets the reference for the elapsed time Estby in the standby mode to the time T at this time (S201). Next, the printer control unit 101 inquires of the controller 102 and acquires the transition time Tsleep to the power saving mode (S202). In the present embodiment, a method is adopted in which the temperature detection sensor 31 is monitored and the temperature transition is predicted based on the change in temperature detected by the temperature detection sensor 31 for the latest one second. In the above configuration, the configuration related to the prediction of the temperature transition corresponds to the temperature transition prediction unit in the present invention. In S203, the reference time for monitoring the temperature detection sensor 31 and the temperature at the start of monitoring are recorded. Then, in S204, it is determined whether 1 second has elapsed since the previous temperature transition measurement. If it has elapsed, the transition temperature Tdelta per second is updated based on the temperature of the temperature detection sensor 31 at this time (S205). ). In addition, the printer control unit 101 monitors the temperature detection sensor 31 to start standby temperature adjustment, and determines whether a condition for starting standby temperature adjustment is satisfied. In this embodiment, it is determined that the standby temperature adjustment starts when the temperature detected by the temperature detection sensor 31 falls below the predetermined standby temperature adjustment temperature or when the temperature falls to the standby temperature adjustment temperature, and monitoring is continued if the temperature is different (S206). . While monitoring the start of standby temperature control, the transition temperature per second is continuously updated (S204 and S205).

When it is determined that the standby temperature adjustment is started (S206), first, the remaining time Trest (= Tsleep-Estby) until the transition to the power saving mode is calculated from the standby mode elapsed time Estby and the power saving mode transition time Tsleep at this point ( S207). Next, the temperature Fsleep of the temperature detection sensor 31 at the power saving mode transition timing is predicted from the remaining time Trest and the transition temperature Tdelta per second (S205). That is, the temperature transition from when the detected temperature decreases to the preheating temperature to when the power saving mode starts when the standby temperature adjustment is not executed is predicted. The prediction is calculated by the following formula.
Fsleep = Fstby-Trest × Tdelta

Then, the predicted temperature Fsleep of the fixing device is compared with a predetermined threshold temperature Fsleep_thr (S209). If Fsleep is equal to or higher than Fsleep_thr (threshold temperature or higher), it is determined that the fixing device 17 is not overcooled even when a print job comes in a state where the standby temperature is not adjusted before the transition to the power saving mode. Standby temperature control is not executed (S210). If Fsleep is less than Fsleep_thr, it is determined that the remaining time until the power saving shift is large and the standby temperature adjustment is not executed, and it is determined that the fixing device 17 is cooled too much, and the standby temperature adjustment is executed (S211). If it is determined that standby temperature adjustment needs to be performed, the process returns to step S207 until the power saving mode is entered, and it is determined whether standby temperature adjustment is to be executed. As a result, the standby temperature adjustment is ended at the standby temperature adjustment end timing in the predicted temperature transition at which the predicted temperature Fsleep at the start of the power saving mode is equal to or higher than the threshold temperature Fsleep_thr.

  FIG. 5 is a diagram illustrating a difference in standby temperature control operation due to a difference in heat storage state of the fixing device 17. The standby temperature control temperature Fstby is set to 120 ° C., and the power saving mode transition time Tsleep is set to 1 minute. The threshold temperature Fsleep_thr is set to 100 ° C. In FIG. 5, in order to show the calculation process, a graph of the fixing device transition prediction after the start of standby temperature control is shown in several points.

  FIG. 5A is an example of a cold state in which the heat storage of the fixing device 17 is small in the standby mode transition state. In this example, the predicted temperature at the power saving mode transition timing is lower than Fsleep_thr at the time of Pnt1 at which standby temperature adjustment is started, and standby temperature adjustment is executed. At the subsequent timing, the situation where the predicted temperature Fsleep is lower than the threshold temperature Fsleep_thr continues, and at the time of Pnt4, the predicted temperature Fsleep becomes equal to or higher than the threshold temperature Fsleep_thr, and the standby temperature adjustment is stopped. On the other hand, in FIG. 5B showing the hot state, the standby temperature adjustment is stopped at the timing of Pnt3 earlier than that in the hot state because the temperature transition gradually decreases compared to the cold state.

  In this embodiment, a method of predicting the temperature transition of the fixing device 17 based on the latest temperature decrease amount of the fixing device 17 is adopted. As another method, a heat storage counter is prepared, the counter is counted up according to the power supply to the heater of the fixing device 17 during printing, and the counter is counted down at regular intervals while the heater power supply is stopped. A method is mentioned. In this method, the amount of heat storage is simulated, and the temperature decrease amount of the fixing device 17 is determined according to the value of the heat storage counter. In this embodiment, in order to reflect the heat storage amount of the fixing device 17, a method of predicting the fixing device temperature at the time of shifting to the power saving mode is adopted. The same effect can be obtained by setting the value of the remaining threshold time Trest_thr described in the first embodiment according to the heat storage amount of the fixing device 17.

  As described above, according to the present embodiment, it is possible to determine the timing for stopping the standby temperature adjustment during the transition from the standby mode to the power saving mode according to the heat storage amount of the fixing device 17. The power required for standby temperature control can be further reduced.

(Example 3)
An image forming apparatus according to Embodiment 3 of the present invention will be described. The apparatus configuration of the image forming apparatus according to the present embodiment and the schematic configuration of the control system are the same as those in the first and second embodiments. Those explanations are omitted, and different points from the first and second embodiments will be mainly described below using the same reference numerals.

  In the second embodiment, the timing for stopping the standby temperature adjustment is switched in accordance with the heat storage condition of the fixing device 17. Further, in this embodiment, the influence on the user wait time due to the stop of the standby temperature adjustment is calculated, and the presence or absence of the standby temperature adjustment is determined from the degree of the influence.

FIG. 6 is a flowchart illustrating the control of the printer control unit 101 in this embodiment. When the printer control unit 101 finishes printing and shifts to the standby mode, the printer control unit 101 first sets a reference for the elapsed time Estby in the standby mode to the time T at this time (S301). Next, the printer control unit 101 makes an inquiry to the controller 102 and acquires the transition time Tsleep to the power saving mode (S302). In the present embodiment, a method of predicting a temperature transition based on a change in the temperature detection sensor 31 in the nearest one second of the temperature detection sensor 31 is employed as in the second embodiment. Therefore, in S303, the reference time for monitoring the temperature detection sensor 31 and the temperature at the start of monitoring are recorded. In S304, it is determined whether 1 second has elapsed since the previous temperature transition measurement. If it has elapsed, the transition temperature Tdelta per second is updated based on the temperature of the temperature detection sensor 31 at this time (S305). ). In addition, the printer control unit 101 monitors the temperature detection sensor 31 to start standby temperature adjustment, and determines whether a condition for starting standby temperature adjustment is satisfied. In this embodiment, if the temperature detection sensor 31 falls below a predetermined standby temperature adjustment temperature, it is determined that standby temperature adjustment starts, and if it is different, monitoring is continued (S306). While monitoring the start of standby temperature control, the transition temperature per second is continuously updated (S304 and S305).

  When it is determined that the standby temperature adjustment is started (S306), first, the remaining time Trest (= Tsleep-Estby) until the transition to the power saving mode is calculated from the standby mode elapsed time Estby and the power saving mode transition time Tsleep at this point ( S307). Next, the predicted temperature Fsleep of the temperature detection sensor 31 at the power saving mode transition timing is predicted from the remaining time Trest and the transition temperature Tdelta per second in the same manner as in the second embodiment (S305).

  Next, based on the predicted temperature Fsleep, a time Trdy required for the fixing device ready at the power saving mode transition timing is obtained (S309). The fixing ready time is a time during which a sheet on which a toner image has been transferred can be passed through the fixing device 17 from the timing when the pre-heating of the fixing device 17 is started after receiving a print job in the standby mode (fixing preparation time). Refers to that. That is, in this embodiment, when the image forming operation is started at the start of the power saving mode based on the predicted temperature Fsleep, the time from the start of the image forming operation until the heat fixing process of the fixing device 17 becomes possible. (Estimated preparation time for fixing). In this embodiment, normal FPOT can be achieved if it is 4 seconds or less. The printer control unit 101 has experimental data on the relationship between the fixing device temperature and the fixing ready time shown in FIG. 8 in the ROM. Therefore, the fixing ready time Trdy is determined from the predicted temperature Fsleep based on this graph.

  Then, the fixing ready time Trdy is compared with a predetermined threshold ready temperature Trdy_thr (S310). If Trdy is equal to or less than Trdy_thr (less than the threshold preparation time), it is determined that the fixing device 17 is not cooled excessively even if a print job comes in a state where the standby temperature is not adjusted before the transition to the power saving mode. The standby temperature control is not executed (S311). If Trdy is larger than Trdy_thr, it is determined that the remaining time until the transition to power saving is large and the standby temperature adjustment is not executed, and it is determined that the fixing device 17 is cooled too much, and the standby temperature adjustment is executed (S312). If it is determined that standby temperature adjustment is to be executed, the process returns to step S104 until the power saving mode is entered, and it is determined whether standby temperature adjustment is to be executed. As a result, when the image forming operation is started at the time of starting the power saving mode, the standby temperature adjustment is ended at the standby temperature adjustment end timing in the predicted temperature transition in which the fixing ready time Trdy is equal to or less than the threshold ready temperature Trdy_thr.

  FIG. 7 is a diagram illustrating a difference in standby temperature adjustment operation due to a difference in heat storage state of the fixing device 17. The standby temperature control temperature Fstby is set to 120 ° C., and the power saving mode transition time Tsleep is set to 1 minute. The threshold ready temperature Trdy_thr is set to 4.3 seconds. The horizontal axis of the graph represents the elapsed time in standby, the axis related to the fixing device temperature corresponds to the left vertical axis, and the axis related to the fixing ready time corresponds to the right vertical axis. In the figure, in order to show the calculation process, a graph of several point transition predictions after the start of standby temperature control and a fixing ready prediction time are shown.

FIG. 7A is an example of a cold state in which the heat storage of the fixing device 17 is small in the standby mode transition state. In this example, the predicted temperature at the power saving mode transition timing is about 70 ° C. at the time of Pnt1 at which standby temperature control is started, and the fixing ready predicted time Trdy is about 4.7 seconds, which is longer than the threshold ready time Trdy_thr. Perform standby temperature control greatly. At the subsequent timing, the situation in which the estimated ready ready time Trdy is longer than the threshold ready time Trdy_thr continues, and at the time of Pnt3, the estimated ready ready time Trdy becomes less than or equal to the threshold ready time Trdy_thr, and the standby temperature adjustment is stopped. On the other hand, in FIG. 7B showing the hot state, the estimated fixing ready time at the timing when the fixing device temperature is lowered to the standby temperature control temperature is about 4.0 seconds, which is already less than the threshold ready time Trdy_thr. The standby temperature control is not performed and the process is finished.

  In this embodiment, the fixing ready time is stored in the ROM of the print control unit 101, and the presence / absence of standby temperature control is determined from the fixing ready time. Of course, the data stored in the ROM of the print control unit 101 may include FPOT data instead of the fixing ready time.

  As described above, the present embodiment is a method for determining the timing for stopping the standby temperature adjustment during the transition from the standby mode to the power saving mode based on the estimated FPOT value. According to the present embodiment, it is possible to make a determination based on the actual influence on the user, so that both usability and power saving can be realized more effectively.

  DESCRIPTION OF SYMBOLS 17 ... Fixing device, 18 ... Fixing film, 19 ... Pressure roller, 30 ... Fixing heater, 31 ... Temperature detection sensor, 35 ... Power supply device, 36 ... Commercial power supply, 37 ... Fixing power supply circuit, 50 ... Operation panel, 100 ... Laser beam printer, 101 ... Printer control unit, 102 ... Controller, 103 ... Host computer, 104 ... CPU

Claims (12)

An image forming unit for forming a developer image on a recording material;
A fixing unit that heat-fixes the developer image on the recording material;
A temperature detection unit for detecting the temperature of the fixing unit;
A power control unit that controls power supply to each unit of the image forming apparatus;
With
The power control unit is configured to execute a power saving mode for limiting power consumed by each unit of the image forming apparatus when a predetermined time has elapsed after entering a standby period for waiting for the start of image formation. In the image forming apparatus,
When the temperature detected by the temperature detection unit has decreased to a predetermined preheating temperature after entering the standby period, the power control unit has a predetermined remaining time from the time until the start of the power saving mode. An image forming apparatus that executes a preheating mode in which power is supplied to the fixing unit in order to maintain the preheating temperature when the time is longer than a threshold time.   The power control unit, when the remaining time is longer than the remaining threshold time, executes the preheating mode until the remaining time becomes the same length as the remaining threshold time. The image forming apparatus according to 1.   The remaining threshold time is a predetermined temperature at the start of the power saving mode when the preheating mode is not executed from a time before the remaining threshold time before the start of the power saving mode. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to be equal to or higher than a threshold temperature.   The image forming apparatus according to claim 1, wherein the power control unit does not execute the preheating mode when the remaining time is shorter than the remaining threshold time. A temperature transition prediction unit that predicts a temperature transition of the fixing device based on a change per unit time in temperature detected by the temperature detection unit;
The temperature transition prediction unit predicts the temperature transition from the end of the preheating mode to the start of the power saving mode,
The power control unit ends the preheating mode at an end timing of the preheating mode in the temperature transition in which the predicted temperature at the start time of the power saving mode predicted by the temperature transition prediction unit is equal to or higher than a predetermined threshold temperature. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The temperature transition prediction unit predicts the temperature transition from the time when the temperature detected by the temperature detection unit decreases to the preheating temperature to the start time of the power saving mode when the preheating mode is not executed. ,
The said electric power control part does not perform the said preheating mode, when the estimated temperature at the time of the start of the said power saving mode in this temperature transition becomes more than predetermined threshold temperature. Image forming apparatus. A temperature transition prediction unit that predicts a temperature transition of the fixing device based on a change per unit time in temperature detected by the temperature detection unit;
The temperature transition prediction unit predicts the temperature transition from the end of the preheating mode to the start of the power saving mode,
The power control unit is a case where the preheating mode is started when the temperature detected by the temperature detection unit is lowered to the preheating temperature after entering the standby period, and the power saving is included in the end timing. When the image forming operation is started at the start time of the mode, an end timing at which the estimated fixing preparation time from the start of the image forming operation until the heat fixing process of the fixing unit becomes possible is equal to or less than a predetermined threshold preparation time The image forming apparatus according to claim 1, wherein the preheating mode is terminated. The temperature transition prediction unit predicts the temperature transition from the time when the temperature detected by the temperature detection unit decreases to the preheating temperature to the start time of the power saving mode when the preheating mode is not executed. ,
The power control unit does not execute the preheating mode when the estimated fixing preparation time when the image forming operation is started at the start time of the power saving mode in the temperature transition is equal to or shorter than the threshold preparation time. The image forming apparatus according to claim 7. An image forming unit for forming a developer image on a recording material;
A fixing unit that heat-fixes the developer image on the recording material;
A temperature detection unit for detecting the temperature of the fixing unit;
A power control unit that controls power supply to each unit of the image forming apparatus;
With
The power control unit executes a power saving mode for limiting power consumed by each unit of the image forming apparatus when a predetermined time has elapsed after entering a standby period for waiting for the start of image formation, and the standby period In the image forming apparatus configured to execute a preheating mode in which power is supplied to the fixing unit so as to maintain a predetermined preheating temperature of the fixing device.
A first state in which the temperature detected by the temperature detection means decreases from the first temperature to the second temperature at the time when the standby time is entered, between the start of the power saving mode after the start of the standby period; The second state maintained at the second temperature, and the temperature transition state that transitions in the order of the third state that decreases from the second temperature to the third temperature at the start of the power saving mode can be taken. An image forming apparatus.   The temperature detected by the temperature detection means does not include the temperature transition state and the state in which the temperature is maintained constant during the period from the start of the standby period to the start of the power saving mode. The image forming apparatus according to claim 9, wherein the image forming apparatus is configured to be in any one of a second temperature transition state that changes from the first temperature to the third temperature.   11. The second temperature according to claim 9, wherein the second temperature is a temperature when the power control unit executes a preheating mode in which less power is supplied to the fixing unit than during an image forming operation. Image forming apparatus.   When the image forming operation is started at the start time of the power saving mode, the third temperature is a predetermined fixing preparation time from the start of the image forming operation until the heat fixing process of the fixing unit is enabled. The image forming apparatus according to claim 9, wherein the temperature is equal to or lower than a threshold preparation time.