JP2013186196A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of minimizing fluctuations in recovery time required to shift from a power saving mode back to a ready state in which image formation is available which are caused by environmental variations.SOLUTION: At a start of a power saving mode (time point tb), power supply to a heater in a fixing part is variably controlled over a time tp so that the temperature of a fixing roller is maintained at a reference standby temperature Tw0 corresponding to a reference environment. When a power supply value at this time is larger than a power value necessary for maintaining the standby temperature Tw0 in the reference environment, it is decided that a heat outflow from the fixing roller is larger than in the reference environment due to environmental variations, and the standby temperature is set at Twu which is higher for the heat outflow than the Tw0 (time point tc), and the temperature of the fixing roller is raised to the standby temperature Twu thereafter. Subsequently, power supply to the heater is controlled so that the standby temperature Twu is maintained (time point tc-te), and warming up is started from a state of the standby temperature Twu (time point te).

Description

  The present invention relates to an image forming apparatus that thermally fixes an image on a sheet by a fixing member heated by a heat generating portion.

Conventionally, in an image forming apparatus, when an image forming job such as printing is not executed, the temperature of a fixing member such as a fixing roller heated by a heat generating portion such as a halogen heater is lower than a fixing temperature necessary for heat fixing. A device that saves power by shifting to a power saving mode in which the temperature is maintained at a standby temperature and suppressing power supplied to the heat generating portion has become widespread.
In this image forming apparatus, when a mode release instruction is received in the power saving mode, the power supplied to the heat generating portion is increased to raise the temperature of the fixing member, and when the temperature of the fixing member reaches the fixing temperature, the image forming job Transitions to an executable ready state (warm-up).

When the power saving function using the power saving mode is adopted, it is desirable that the recovery time (warm-up time) required from when the mode release instruction is received to when the mode is changed to the ready state is constant. It tends to vary due to fluctuations in the temperature inside the machine.
Specifically, for example, when the image forming apparatus has been placed in a low temperature environment for a long time in the power saving mode, the inside of the apparatus is often lowered to a low temperature, and the heat generated when the fixing member is heated by warm-up. Since it becomes easy to escape from the fixing member to its peripheral members, the recovery time may take longer than the normal temperature environment. Conversely, in a high temperature environment, the heat of the fixing member is difficult to escape and the recovery time is shortened.

  In order to suppress such variation in return time, Patent Document 1 discloses that an actual return time is measured during warm-up, and if the measured time is longer than, for example, a target value, A configuration is disclosed in which the standby temperature in the next power saving mode is set to a temperature higher than the standby temperature in the previous power saving mode so that the deviation is eliminated.

JP 2004-70064 A

  However, in the configuration of Patent Document 1, since the standby temperature set based on the measurement result of the return time in the past environment is used, the current installation environment of the image forming apparatus is not reflected. Therefore, for example, if the environment is different between the past and the present, even if the standby temperature set based on the past environment is applied in the current power saving mode, the return time does not always match or approach the target value. In some cases, it may vary greatly.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reducing variations in return time as much as possible.

  In order to achieve the above object, an image forming apparatus according to the present invention maintains a fixing member heated by a heat generating portion at a standby temperature lower than a fixing temperature necessary for thermally fixing an image on a sheet. When an instruction to cancel the mode is received at this time, the power supplied to the heat generating part is increased to raise the temperature of the fixing member, and when the temperature of the fixing member reaches the fixing temperature, the printer enters a ready state in which an image forming job can be executed. An image forming apparatus that obtains information indicating a target return time from when a mode release instruction is received to when the mode is changed to a ready state; and a heat outflow amount that flows from the fixing member to the periphery thereof. The detection means for detecting the index value and the time until the temperature of the fixing member reaches the fixing temperature due to the temperature rise after receiving the mode release instruction are reduced so as to coincide with the acquired return time. Characterized in that it comprises a determination means for determining the standby temperature to be applied to the power saving mode in accordance with the magnitude of the detected index value of the heat outflow when entering the force mode.

  The power supply unit that supplies power to the heat generating unit, and the power supply unit so that the temperature of the fixing member is maintained at a predetermined reference standby temperature for a predetermined time after entering the power saving mode. Control means for varying the power supplied to the heat generating part, the detecting means detects the amount of power supplied to the heat generating part as an index value of the heat outflow amount, and the determining means The standby temperature may be determined according to the magnitude of power during the predetermined time.

Here, the determining means determines the standby temperature by an amount corresponding to the difference if the detected power is greater than a predetermined reference amount with respect to a target return time. A value higher than the temperature may be determined. If the value is smaller, an amount corresponding to the difference may be determined as a value lower than the reference standby temperature.
Further, the control unit acquires a target standby temperature transition time required for the temperature of the fixing member to reach the determined standby temperature after the predetermined time has elapsed in the power saving mode, and the determined When the standby temperature is higher than the reference standby temperature, when the acquired standby temperature transition time elapses, the power supply unit is configured so that the temperature of the fixing member reaches the standby temperature due to the temperature increase. The first power control is performed to vary the power supplied to the heat generating unit, and when the determined standby temperature is lower than the reference standby temperature, the temperature of the fixing member is reduced by the temperature when the acquired standby temperature transition time elapses. Second power control may be performed on the power supply unit so that the power supplied to the heat generating unit is variable so that the standby temperature is reached.

Here, the first power control is a control for gradually increasing the power supplied to the heat generating part as time elapses, and the second power control is the power supplied to the heat generating part as time elapses. The control may be gradually reduced.
Here, when the determined standby temperature is higher than the reference standby temperature, the control unit performs the first power control before executing the first power control, so that the power supplied to the heat generating unit is increased. If it is determined that the maximum value is reached halfway until the target standby temperature transition time elapses, instead of the first power control, the power supplied to the heat generating portion is initially set to a maximum value or a value close to the maximum in advance. Third power control may be performed in which the power value is determined and then gradually reduced with time.

  In addition, the apparatus includes a receiving unit that receives the designation of the return time from a user, the acquisition unit acquires a user-specified time that is received by the receiving unit, and the determination unit uses the specified waiting temperature as the reference standby temperature. In the case where the recovery temperature is the first length, the first temperature predetermined for the recovery time of the first length is used, and the second length is shorter than the first length. Alternatively, a second temperature higher than the first temperature may be used, which is predetermined with respect to the recovery time of the second length.

Further, after the determination of the standby temperature to be applied to the power saving mode, the determination means replaces the determined standby temperature, and the magnitude of the index value of the heat outflow amount detected again during the power saving mode. Accordingly, the standby temperature to be applied thereafter may be determined again and updated to the newly determined standby temperature.
Moreover, it is good also considering it as the maximum value of the range which can supply the supply electric power to the said heat_generation | fever part before changing to the said ready state from the said mode cancellation | release.

  According to the above, the standby temperature can be determined based on the amount of heat flow out of the fixing member according to the current environment when the power saving mode is entered. It is possible to suppress variations in recovery time as compared with the configuration in which the temperature is set.

1 is a block diagram illustrating an overall configuration of an image forming apparatus. FIG. 6 is a schematic diagram illustrating how the surface temperature of the fixing roller changes with time in a normal mode and a power saving mode. It is a figure which shows the relationship between return time tu and reference | standard standby temperature Tw0. It is a figure which shows the relationship between the reference | standard standby temperature Tw0 and the reference | standard supply electric power P0. It is a figure which shows the integrated value (predicted value) of the electric power supplied to a heater between the time tb-td in a power saving mode. It is a figure which shows the relationship between integrated electric power (predicted value) Pw and standby temperature Tw. It is a figure which shows transition of the surface temperature of a fixing roller when the standby temperature transition time tr in power saving mode is short. It is a flowchart which shows a part of control content of a power saving mode. It is a flowchart which shows the remaining part of the control content of a power saving mode.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
(1) Overall Configuration FIG. 1 is a block diagram showing the overall configuration of the image forming apparatus 10.
As shown in FIG. 1, the image forming apparatus 10 includes a document conveying unit 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, a fixing unit 5, an operation unit 6, and a control unit 7. And a power supply unit 8 and a heater power supply 9 and execute an image forming job such as printing (hereinafter referred to as “job”). Further, it is configured to be able to switch between a normal mode in which a job can be executed and a power saving mode in which power consumption is less than that in the normal mode when the job is not executed.

The document conveying unit 1 conveys a set document to the reading position of the image reading unit 2.
The image reading unit 2 reads the original conveyed by the original conveying unit 1 at a reading position to obtain image data.
The image forming unit 3 uses a known electrophotographic method to transfer the image on a recording sheet (such as paper) fed from the paper feeding unit 4 based on the image data read by the image reading unit 2. Forming, here, a toner image formed on the photosensitive drum is transferred to a sheet at a transfer position.

The paper feeding unit 4 feeds the set sheet and conveys it to the transfer position of the image forming unit 3.
The fixing unit 5 heat-fixes the image transferred on the sheet S in the image forming unit 3 to the sheet S. The fixing unit 5 is pressed against the cylindrical fixing roller 51 (fixing member) and the fixing roller 51. A roller 52, an elongated heater 53 (heat generating part) inserted through the fixing roller 51, and a temperature detection sensor 54 for detecting the surface temperature of the fixing roller 51 are provided.

The heater 53 generates heat due to the power supplied from the heater power source 9, and the fixing roller 51 is heated by the heat generated from the heater 53 and rotates between the fixing roller 51 and the pressure roller 52 that rotate in the direction indicated by the arrow in FIG. When the sheet S passes through the pressure contact portion (fixing nip), the image on the sheet S is thermally fixed to the sheet S by the heat of the fixing roller 51.
The power supply unit 8 converts the AC power from the commercial power supply 90 to the control unit 7 and the heater power supply 9 and converts them into DC power necessary for them.

The heater power supply 9 functions as a power supply unit that converts DC power from the power supply unit 8 into AC power having a magnitude indicated by the control unit 7 and supplies the converted AC power to the heater 53. In addition, not only alternating current power but direct current power is supplied if the heater 53 generate | occur | produces with direct current | flow.
When the power supplied from the heater power source 9 to the heater 53 increases, the amount of heat generated by the heater 53 increases and the temperature of the fixing roller 51 increases. Conversely, when the power supplied decreases, the amount of heat generated by the heater 53 decreases and the fixing roller 51 Since the temperature decreases, the control unit 7 can control the surface temperature of the fixing roller 51 by instructing the heater power supply 9 the magnitude of the power supplied to the heater 53.

  The operation unit 6 includes a start key for receiving a job execution instruction from a user, a numeric keypad for receiving an instruction for the number of prints by the job, a power saving mode key for receiving an instruction to enter a power saving mode, and an instruction for canceling the power saving mode. Release key to be accepted, return time designation key to accept designation of a warm-up (return) time tu that is a target from the release of the power saving mode to the ready state where the job can be executed, standby temperature transition time tr in the power saving mode A standby temperature transition time input key for receiving a setting input (described later) is provided. When an instruction input by each key is received, input information indicating the received content is notified to the control unit 7. In the above description, the user can arbitrarily specify the return time tu, but it may not be specified, and a fixed value for use in such a case is stored in advance.

The control unit 7 is operated by direct current power from the power supply unit 8, and comprehensively controls the document conveying unit 1 to the operation unit 6 based on input information of the operation unit 6 by the user, and executes a smooth job. In addition, when the user instructs the power saving mode, the mode is switched from the normal mode to the power saving mode. After that, when the user instructs to cancel the power saving mode, the power saving mode is canceled and the warm-up returns to the ready state. Perform the action.
(2) Normal Mode and Power Saving Mode The normal mode is a mode for maintaining the surface temperature of the fixing roller 51 at a fixing temperature (for example, 170 ° C.) necessary for heat fixing, and the power saving mode executes a job. In this mode, the surface temperature of the fixing roller 51 is maintained at a standby temperature (for example, 160 ° C.) lower than the fixing temperature.

  The transition from the normal mode to the power saving mode is performed when the user operates the power saving mode key. However, the transition is not limited to this, and may be performed automatically when the job ends, for example. The power saving mode is released when the user operates the release key. However, the power saving mode is not limited to this. For example, detection of a new document set on the document conveying unit 1 is used as a cancellation instruction. It may be performed upon receipt of a release instruction.

The fixing temperature is determined in advance, but the standby temperature is determined according to the installation environment of the image forming apparatus 10 every time the power saving mode is executed. For this reason, a different standby temperature may be determined for each power saving mode.
FIG. 2 is a schematic diagram showing how the surface temperature of the fixing roller 51 changes with time in the normal mode and the power saving mode.

  In the same figure, when the fixing temperature is Ts, the standby temperature is Tw, the time point ta is when the job is finished, the time point tb is when the power saving mode is started, and the time point te is when the user receives a cancel instruction during the power saving mode. When the surface temperature of the fixing roller 51 reaches the fixing temperature Ts due to warm-up and transitions to a ready state (a job executable state) by the warm-up, the target value tu of the return time is determined from the acceptance of the release instruction by the user. Time required for transition to the ready state (warm-up). In the warm-up, the supply power to the heater 53 is fixed, and here, the maximum value that can be supplied to the heater 53, for example, 1200 [W] is set. The power value is not limited to the maximum value, and may be a predetermined power value that is slightly lower than the maximum value, for example.

  As shown in the figure, during the execution of the job, the surface temperature of the fixing roller 51 is maintained at the fixing temperature Ts as the normal mode, and when the job is finished (time point ta), preparation for shifting to the power saving mode is performed. A standby state is entered (time points ta to tb). In the standby state, the surface temperature of the fixing roller 51 is lowered from the fixing temperature Ts to a predetermined standby temperature Tw0 (reference value). Specifically, when the job is completed, the power supplied to the heater 53 is reduced as compared to when the job is being executed, and the temperature of the fixing roller 51 is lowered.

  When the surface temperature of the fixing roller 51 reaches the standby temperature Tw0, a transition is made to the power saving mode (time tb), and the power supplied to the heater 53 is maintained to maintain the standby temperature Tw0 for a predetermined time tp (time tb to tc). It is assumed that the supply power at the predetermined time tp is variably detected as a heat outflow amount from the fixing roller 51, and the standby temperature Tw is determined based on the detected value. The reason why the standby temperature Tw is determined by detecting the amount of heat flow is to allow the warm-up to be completed within the designated recovery time tu and to suppress variations in the recovery time.

That is, as described above, when the temperature inside the apparatus increases or decreases depending on the surrounding environment of the image forming apparatus 10, the amount of heat flow from the fixing roller 51 per unit time also changes.
For example, when trying to maintain the surface temperature of the fixing roller 51 at the standby temperature Tw0, if the amount of heat flowing from the fixing roller 51 to the surroundings is large, it is necessary to increase the power supplied to the heater 53 as compared to the case where the amount of heat is small. If the amount of heat flowing out of the fixing roller 51 is large, the amount of heat that escapes from the surrounding members (such as the pressure roller 52) from the fixing roller 51 (see the arrows indicating the heat flow in and out in FIG. 1) is replenished by increasing the supply power. Because it is necessary to do.

  The amount of heat flow is greatly affected by fluctuation factors such as the surrounding environment of the image forming apparatus 10, particularly temperature. For example, in a low temperature environment, the temperature of each part inside the apparatus is often lowered. Even when the fixing roller 51 is heated, the temperature of the peripheral member is low, so that the heat of the fixing roller 51 flows out (stolen) into the peripheral member, and the amount of heat outflow tends to increase more than the normal temperature environment. Conversely, in a high temperature environment, the temperature of each part inside the apparatus also rises to some extent, and the amount of heat outflow tends to be smaller than in a normal temperature environment.

  If this state of large (or small) heat outflow continues during the warm-up through the power saving mode, the power supplied to the heater 53 is fixed at the maximum value in the warm-up, and the fixing roller from the heater 53 is fixed. Since the amount of heat supplied to unit 51 per unit time is the same regardless of the environment, the more heat flows out of fixing roller 51, the longer it takes to raise the temperature of fixing roller 51, and vice versa. The temperature of the fixing roller 51 is increased quickly, and the return time is likely to vary.

  Therefore, warm-up is completed at the return time tu for each target return time tu (for example, 10 seconds, 11 seconds, 12 seconds,...) In a standard environment (for example, room temperature). The relationship between the reference standby temperature (reference temperature) Tw0 that can be performed and the reference supply power (reference amount) P0 of the heater 53 that is assumed to be necessary to maintain the reference standby temperature Tw0 is determined in advance.

  When the actual supply power P (corresponding to the heat outflow amount) at the predetermined time tp when entering the power saving mode is larger than the reference supply power P0 determined in advance with respect to the return time tu, The standby temperature Tw is determined to be Twu that is higher than the reference standby temperature Tw0 by an amount corresponding to the difference, that is, an amount that heat outflow is assumed to increase during the warm-up compared to the reference standby temperature Tw0. On the contrary, when the supply power P is lower than the reference supply power P0, the standby temperature Tw is set to be lower than the reference standby temperature Tw0 by the amount that heat is likely to flow out during the warm-up compared to the reference standby temperature Tw0. By determining a low Twd, an attempt is made to suppress variations in recovery time as much as possible. A method for determining the standby temperature Tw will be described later.

If the heat outflow amount (supplied power P) is equal to the reference, the standby temperature is determined as Tw0, and after time tc, the surface temperature of the fixing roller 51 is in the power saving mode as shown by the solid line in FIG. The power supplied to the heater 53 is controlled so as to be maintained at the standby temperature Tw0.
On the other hand, if the amount of heat outflow is larger than the reference, the standby temperature is determined as Twu, and the surface temperature of the fixing roller 51 gradually increases from the standby temperature Tw0 to Twu during the power saving mode as shown by the broken line in FIG. (Time tc to td) After time td, the power supplied to the heater 53 is controlled so as to be maintained at the standby temperature Twu.

  On the other hand, if the amount of heat flow is less than the reference, the standby temperature is determined as Twd, and the surface temperature of the fixing roller 51 is gradually increased from the standby temperature Tw0 to Twd in the power saving mode as shown by the one-dot chain line in FIG. The electric power supplied to the heater 53 is controlled so as to be maintained at Twd after the time td. The time tr (time tc to td) required for the standby temperature Tw to reach the determined temperature is referred to as standby temperature transition time. The standby temperature transition time tr can be set and input from the operation unit 6 by the user as described above.

When a cancel instruction from the user is received in the power saving mode (time te), the power supplied to the heater 53 is maximized to raise the temperature of the fixing roller 51 from the standby temperature Tw (warm up), and the temperature of the fixing roller 51 is fixed. When the temperature Ts is reached (time tf), a transition is made to a ready state in which an image forming job can be executed.
Since the warm-up is started from the standby temperature Tw determined based on the magnitude of the heat outflow detected when entering the power saving mode, the recovery time can be set regardless of whether the heat outflow of the fixing roller 51 is large or small. There is no significant difference in tu, and variations in recovery time can be suppressed. Hereinafter, returning to FIG. 1, the configuration of each unit of the control unit 7 will be specifically described.
(3) Configuration of Control Unit 7 The control unit 7 includes a power detection unit 71, a standby temperature determination unit 72, a reference standby temperature determination unit 73, a return time determination unit 74, a power control unit 75, and an overall control unit. 76, standby temperature transition time determination unit 77, standby temperature transition time storage unit 78, temperature detection unit 79, fixing temperature storage unit 80, power saving mode time history storage unit 81, timer 82, and reference supply A power determination unit 83 and a return time storage unit 84 are provided.

Each unit except the overall control unit 76 is responsible for temperature control of the fixing roller 51, and the overall control unit 76 is responsible for overall control of the operation of the image forming job and switching control between the normal mode and the power saving mode. .
The temperature detection unit 79 receives the detection signal of the temperature detection sensor 54, detects the current surface temperature (current temperature) Ta of the fixing roller 51, and sends the detected value to the power control unit 75.

  The power control unit 75 acquires the detection temperature Ta by the temperature detection unit 79, acquires the target temperature Tx of the fixing roller 51 from the overall control unit 76, and the current surface temperature Ta of the fixing roller 51 is higher than the target temperature Tx. If the temperature is lower, the heater power supply 9 is instructed to increase the power supplied to the heater 53 in order to increase the temperature to the target temperature Tx. If the temperature is higher than the target temperature Tx, the temperature is decreased to the target temperature Tx. An instruction is given to reduce the power supplied to the heater 53. Specifically, when the power value P1 is currently instructed as the power supplied to the heater 53, the power value P2 is switched to a power value P2 that is larger (or smaller) by a predetermined amount corresponding to the temperature difference.

  In the power saving mode, instead of the above, the surface temperature Ta of the fixing roller 51 is changed to the target temperature Tx (standby temperature Tw) when the standby temperature transition time tr determined by the standby temperature transition time determination unit 77 elapses as described later. ) Is commanded to the heater power source 9 so as to control the supply power to the heater 53. Further, during warm-up, the heater power supply 9 is instructed to supply the maximum power to the heater 53. The acquisition of the detected temperature Ta and the target temperature Tx and the instruction of the power supply to the heater power supply 9 are repeatedly executed at a constant time, for example, at an interval of 100 milliseconds.

  In the normal mode, the overall control unit 76 sends the information on the fixing temperature Ts stored in the fixing temperature storage unit 80 as the target temperature Tx of the fixing roller 51 to the power control unit 75. The information of the reference standby temperature Tw0 determined by the reference standby temperature determination unit 73 is sent to the power control unit 75 as the target temperature Tx until the elapse of the predetermined time tp after entering the power mode, and (b) for the predetermined time tp. After the elapse of time, information indicating the standby temperature Tw determined by the standby temperature determination unit 72 is sent to the power control unit 75 as the target temperature Tx.

  The return time determination unit 74 determines the return time tu. Here, when the user designates the return time tu with the return time designation key, the designated time information (information indicating the return time) is stored in the return time storage unit 84, and the return time determination unit 74. When the time information specified by the user is stored in the return time storage unit 84, the time information is acquired from the return time storage unit 84 and determined as the return time tu specified by the user. If not specified by the user, time information by the user is not stored in the return time storage unit 84. In this case, a time indicating a predetermined fixed value, for example, 15 seconds, etc. Information is acquired from the return time storage unit 84 and determined as the return time tu.

  The reference standby temperature determination unit 73 determines the reference standby temperature Tw0 in the power saving mode based on the return time tu determined by the return time determination unit 74. Specifically, as shown in FIG. 3, information indicating a correspondence relationship between the return time tu and the reference standby temperature Tw0 is obtained from an experiment or the like and stored in the control unit 7 in advance for each device. Referring to the reference standby temperature Tw0 corresponding to the return time tu.

The return time tu can be arbitrarily specified by the user as the target value of the warm-up time as described above, and may be set to a long time or a short time.
While the return time tu is variable, the power supplied to the heater 53 during the warm-up is fixed at a maximum value, so that the heat supply amount per unit time from the heater 53 to the fixing roller 51 is also increased. It becomes constant.

  Since the heat supply amount per unit time from the heater 53 to the fixing roller 51 is constant, the temperature increase rate of the fixing roller 51 should also be constant. Therefore, the fixing is performed just after the return time tu has elapsed from the release of the power saving mode. In order for the temperature of the roller 51 to reach the fixing temperature Ts, the shorter the return time tu, the higher the standby temperature Tw at the time of canceling the power saving mode is set so as to approach the fixing temperature Ts. Conversely, if the return time tu is long, the standby temperature Tw when the power saving mode is released may be determined to be lower than the fixing temperature Ts.

That is, the recovery time and the standby temperature have a relationship that the standby temperature becomes higher when the recovery time is shorter than when the recovery time is long, and this correspondence is the same regardless of the installation environment.
Therefore, in the present embodiment, for example, when the return time tu is set to a different time on the basis of the normal temperature environment, the reference standby temperature Tw0 with respect to each return time tu is indicated as information indicating the corresponding relationship (the return time is the first time). The first temperature corresponds to the reference standby temperature in the case of the length, and the second temperature higher than the first temperature corresponds to the second length shorter than the first length. ) In advance from experiments and the like, and every time the power saving mode is entered, the reference standby temperature Tw0 for the set return time tu is determined. FIG. 3 shows an example in which the return time tu and the reference standby temperature Tw0 are in a proportional relationship. However, if the device configuration is different, there may be a different correspondence relationship.

Returning to FIG. 1, when determining the reference standby temperature Tw0 in the power saving mode, the reference standby temperature determination unit 73 sends information on the determined reference standby temperature Tw0 to the overall control unit 76 and the reference supply power determination unit 83.
When acquiring the reference standby temperature Tw0, the overall control unit 76 uses the reference standby temperature Tw0 as the target temperature Tx of the fixing roller 51 during the predetermined time period tp after entering the power saving mode.

The reference supply power determination unit 83 determines a reference supply power P0 corresponding to the acquired reference standby temperature Tw0. Specifically, as shown in FIG. 4, information indicating a correspondence relationship between the reference standby temperature Tw0 and the reference supply power P0 is stored in the control unit 7 in advance for each device, and the reference standby is performed with reference to the information. A reference supply power P0 corresponding to the temperature Tw0 is determined.
Since the reference standby temperature Tw0 is high, it is necessary to maintain the surface temperature of the fixing roller 51 at a higher temperature, so that the supply power to the heater 53 also increases. When it is high, there is a relationship that requires more power supply than when it is low, and this correspondence is the same regardless of the installation environment.

  Therefore, in the present embodiment, for example, when the reference standby temperature Tw0 is set to a different temperature on the basis of the normal temperature environment, the reference supply power P0 necessary for maintaining each temperature Tw0 is information indicating the correspondence relationship. As the reference supply power P0 for the determined reference standby temperature Tw0 every time the power saving mode is entered. FIG. 4 shows an example in which the reference standby temperature Tw0 and the reference supply power P0 are in a proportional relationship. However, if the device configuration is different, there may be a different correspondence relationship.

Returning to FIG. 1, when the reference supply power determination unit 83 determines the reference supply power P0 for the reference standby temperature Tw0, the reference supply power determination unit 83 sends information on the determined reference supply power P0 to the standby temperature determination unit 72.
The standby temperature determination unit 72 determines the standby temperature Tw to be applied to the power saving mode based on the detected power P by the power detection unit 71 and the reference supply power P0 determined by the reference supply power determination unit 83. A method for determining the standby temperature Tw will be described with reference to FIGS.
(4) Method for Determining Standby Temperature Tw FIG. 5 is a diagram showing an integrated value (predicted value) of the power supplied to the heater 53 between time points tb and td in the power saving mode, and a solid line graph P0 is a reference. The transition of the integrated power in an environment with a broken line, and the broken line Pu indicates the transition of the integrated power in an environment where the heat flow from the fixing roller 51 is large with respect to the reference (corresponding to a low temperature environment). It shows the transition of the integrated power in an environment where Pd is less than the standard for heat outflow (equivalent to a high temperature environment). Note that the fact that the heat outflow is less than the reference means that the fixing roller 51 absorbs heat (heat absorption) from the periphery when the temperature around the fixing roller 51 is higher. included.

  As indicated by the broken line graph, when the power supplied to the heater 53 is higher than the reference, it means that the heat outflow amount is higher than the reference as described above. In this case, the amount of heat outflow per unit time does not change significantly unless the surrounding environmental fluctuations are large, so if the amount of heat outflow per unit time is the same up to time td, the power supplied to the heater 53 The state in which Pu is increased by the difference ΔP from the reference supply power P0 is continued.

Assuming that the supply power continues to increase by the difference ΔP, the difference ΔP from the reference supply power P0 is found from the value of the supply power P detected when the power saving mode is entered, and the time point when the difference ΔP is found. The integrated power Pwu when reaching the time point td from the time between tb and td can be calculated and predicted in advance at the previous time points tb to tc (heat detection amount detection time tp).
A value obtained by dividing the difference between the predicted integrated power Pwu and the reference integrated power Pw0 by the time between time points tb to td corresponds to the increase amount ΔS of the heat outflow amount per unit time with respect to the reference, and the heat outflow amount is the reference If it continues during the warm-up after the time point td, a larger amount of heat than the reference by the amount of heat obtained by multiplying the return time tu by the increase amount ΔS is generated during the warm-up. It should flow out around 51.

If the standby temperature Tw is determined to be a temperature Twu higher than the reference Tw0 by the amount corresponding to the amount of heat flowing out, even if the heat outflow exceeds the reference, it does not deviate significantly from the set return time tu. The warm-up can be completed.
Therefore, when the amount of heat outflow per unit time, that is, the integrated power (predicted value) Pw is larger than the reference, if the warm-up is just finished at the return time tu, the standby temperature Tw is set higher than the reference standby temperature Tw0. If it is determined in advance how much it should be increased, the integrated power Pwu is estimated by estimating the integrated power Pwu based on the detected power P at the detection time tp of the heat outflow amount when entering the power saving mode. The corresponding standby temperature Tw can be obtained.

  On the contrary, as shown by the one-dot chain line graph, when the power supply Pd of the heater 53 is smaller than the standard, the integrated power is also Pwd smaller than the standard Pw0, and the heat outflow amount is smaller than the standard. Will be less. In this case, if the warm-up is just finished at the return time tu, the standby temperature Tw will be lower than the reference standby temperature Tw0, and if it is determined in advance how much lower it is necessary, As in the case where the amount of outflow is larger than the reference, by calculating the integrated power Pwd based on the power P detected when the power saving mode is entered, the standby temperature Tw corresponding to the integrated power Pwd can be obtained.

  FIG. 6 is a diagram showing the relationship between the accumulated power (predicted value) Pw and the standby temperature Tw when the return time tu is set to a certain value, and the reference standby temperature Tw0 corresponds to the reference accumulated power Pw0. An example in which a standby temperature Twu higher than the reference corresponds to the integrated power Pwu greater than the reference, and conversely, a standby temperature Twd lower than the reference corresponds to the integrated power Pwd lower than the reference. Is shown. If the relationship between the integrated power Pw and the standby temperature Tw is used, when the integrated power Pw increases or decreases with respect to the reference, the standby temperature Tw corresponding to the increase / decrease amount can be obtained.

The correspondence relationship between the integrated power Pw and the standby temperature Tw is obtained in advance through experiments or the like, and the information (standby temperature information) is stored in the control unit 7 and read when the standby temperature Tw is determined. In addition, although the example in case integrated electric power Pw and standby temperature Tw have a proportional relationship was demonstrated in FIG. 6, it may become a different relationship depending on an apparatus structure.
Further, as shown in FIG. 5, if the difference ΔP of the power P supplied to the heater 53 with respect to the reference due to heat outflow is constant over time, the amount of heat outflow is replaced with calculation of the integrated power Pw. The difference ΔP between the detected power P and the reference power P0 at the detection time tp can also be used as an index value of the heat outflow amount. In this case, if the correspondence between the power difference ΔP and the standby temperature Tw as shown in FIG. 6 is obtained as standby temperature information in advance, the heat outflow in the power saving mode is calculated without calculating the integrated power Pw. The difference ΔP is detected at the amount detection time tp, and the standby temperature Tw corresponding to the detected difference ΔP can be determined as the standby temperature Tw in the power saving mode.

  Note that the time tp is set in advance for each device by a time suitable for detection of the amount of heat outflow, for example, 30 seconds, and is stored in the control unit 7. In some cases, it may be switched to a longer time than normal temperature. When the amount of heat outflow is higher or lower than at normal temperature at high or low temperatures, the state of heat outflow can be detected more accurately over a longer time than at normal temperature.

In addition, in FIGS. 3 to 7 described above, relationships such as time and temperature are shown by graphs. However, the present invention is not limited to this, and information such as mathematical formulas and table formats may be used. Further, FIG. 3 and FIG. 4 may be combined to have information for associating the return time with the reference supply power.
Returning to FIG. 1, each time the standby temperature determination unit 72 enters the power saving mode, the power P detected by the power detection unit 71 during the detection time tp of the heat outflow amount and the reference supply power determination unit 83 The supplied power P0 is acquired, the integrated power Pw is predicted from the acquired power P and P0, the standby temperature Tw corresponding to the predicted integrated power Pw is read from the standby temperature information shown in FIG. The temperature Tw is sent to the overall control unit 76 as the standby temperature Tw in the power saving mode.

The standby temperature transition time storage unit 78 stores information indicating the set standby temperature transition time tr when the user inputs the standby temperature transition time tr from the operation unit 6.
The power saving mode time history storage unit 81 stores a history of the power saving mode time (from time tb to te) from when the power saving mode is entered until the power saving mode is canceled in the past power saving mode. Here, for each power saving mode, the time from when the power saving mode is entered to when it is released is counted by the timer 82, and the time measured as a history of the past power saving mode time is used as the power saving mode time history. Stored in the storage unit 81.

The standby temperature transition time determination unit 77 determines the standby temperature transition time tr. Specifically, when the standby temperature transition time tr is set by the user from the operation unit 6, information indicating the standby temperature transition time is read from the standby temperature transition time storage unit 78, and the read standby temperature transition time is read out. Is determined as the standby temperature transition time tr.
If not set by the user, the history of the past power saving mode time is read from the power saving mode time history storage unit 81, and the shortest time is determined as the standby temperature transition time tr. Information indicating the determined standby temperature transition time tr is sent to the power control unit 75 via the overall control unit 76.
(5) Variable control of power supplied to heater 53 in power saving mode The power control unit 75 uses the standby temperature transition time tr determined by the standby temperature transition time determination unit 77 in the power saving mode as a target standby temperature transition time. Based on the acquired standby temperature transition time tr, the heater power supply 9 is instructed to variably control the power supplied to the heater 53.

Here, when the time point td when the standby temperature transition time tr has elapsed, the surface temperature Ta of the fixing roller 51 reaches the target temperature Tx (corresponding to the determined standby temperature Tw). Gradually increase or decrease the supply power.
Specifically, the temperature difference ΔT between the surface temperature Ta of the fixing roller 51 and the standby temperature Tw, and the surface temperature Ta of the fixing roller 51 are kept on standby for the standby temperature transition time tr in order to eliminate the temperature difference ΔT. The relationship with the power supply P that is assumed to be required to raise or lower the temperature to the temperature Tw is obtained in advance from experiments or the like.

  Here, when the temperature difference ΔT is positive (Ta <Tx), the supplied power P becomes a value that gradually increases with time. For example, in increments of 0.5 seconds, the target power value is increased by 10 [W]. When the temperature difference ΔT is negative (Ta> Tx), the relationship is opposite to that of the positive case. The reason why the supply power is gradually increased or decreased in this way is to make it easier to stabilize the temperature of the fixing roller 51.

  In other words, the surface temperature of the fixing roller 51 increases and decreases as the power supplied to the heater 53 increases and decreases, but a certain amount of delay is inevitably caused before the heat of the heater 53 is transmitted to the surface of the fixing roller 51. For this reason, for example, when the maximum power is supplied from the beginning in order to increase the surface temperature of the fixing roller 51, the amount of heat supplied to the fixing roller 51 is also maximized, and the rate of temperature increase is also maximized. If the power supply is suppressed when the surface temperature of the fixing roller 51 reaches the standby temperature Twu, the temperature rise can be suppressed, but the amount of heat that has been supplied so far is transmitted to the surface of the fixing roller 51 with a delay. The surface temperature of the fixing roller 51 is likely to exceed the standby temperature Twu.

In that case, if the supplied power is drastically reduced in order to quickly lower the temperature to the standby temperature Twu, the temperature tends to drop below the standby temperature Twu. As a result, the temperature of the fixing roller 51 fluctuates up and down and becomes stable. It becomes difficult.
Therefore, by taking into account the delay in heat transfer from the heater 53 to the fixing roller 51 in advance, the supply temperature is increased little by little, so that the rate of temperature rise becomes moderate to some extent, and the surface temperature of the fixing roller 51 becomes the standby temperature Twu. The surface temperature of the fixing roller 51 can be made stable at the standby temperature Twu just after the standby temperature transition time tr has elapsed.

  The same applies to the case where the surface temperature of the fixing roller 51 is lowered. If the supply power is cut off, the surface speed of the fixing roller 51 can be reduced in a short time, but the electric power after the temperature falls below the standby temperature Twd. Even if the supply is resumed, it takes a certain amount of time to raise the temperature, so that it is difficult to stabilize the standby temperature Twu. Therefore, by gradually reducing the supply power, the surface temperature of the fixing roller 51 is set to the standby temperature transition time tr. It is possible to achieve a stable state at the standby temperature Twd during the lapse of time.

When the temperature difference ΔT is set in units of 1 ° C., such as +1 [° C.], +2 [° C.], −1 [° C.], −2 [° C.],. The power value for the temperature difference ΔT (a value that gradually changes with time: for example, +10 W, +20 W,..., Etc. every 0.5 seconds with reference to the power supplied at the time point tc) is determined in advance.
By storing information indicating the relationship between the temperature difference ΔT and the supplied power P (standby temperature transition time power information) in advance, if the magnitude of the temperature difference ΔT is known, the supplied power P corresponding to the ΔT is waited. Read from the temperature transition time power information, know how many seconds after the variable control start, how much power should be supplied before starting the control, when the control is started, the determined power can be determined By supplying in time, the surface temperature of the fixing roller 51 can be raised or lowered toward the determined standby temperature. When the temperature difference ΔT is 0, the current supply power is the supply power P.

  Hereinafter, in the power saving mode, (a) when the temperature difference ΔT is positive, the surface temperature of the fixing roller 51 becomes the determined standby temperature Tw when the standby temperature transition time tr elapses due to the temperature rise of the fixing roller 51. After the power supplied to the heater 53 is gradually increased so as to reach the first temperature control, the surface temperature of the fixing roller 51 is maintained at the standby temperature Tw, and (b) the temperature difference ΔT is negative. In this case, the power supplied to the heater 53 is gradually reduced so that the surface temperature of the fixing roller 51 reaches the determined standby temperature Tw when the standby temperature transition time tr elapses due to the temperature decrease of the fixing roller 51. After that, the second power control is used to control the surface temperature of the fixing roller 51 to maintain the standby temperature Tw. (C) When the temperature difference ΔT is 0, the power supplied to the heater 53 is maintained and the fixing is performed. The control for maintaining the surface temperature of Ra 51 to the current temperature of the reference power control.

  Then, a temperature difference ΔT between the actual surface temperature Ta of the fixing roller 51 detected at the time tc after entering the power saving mode and the determined standby temperature Tw (target temperature Tx) is detected, and the detected temperature If the difference ΔT is positive, the first power control is performed. If the difference ΔT is negative, the second power control is performed. If the difference ΔT is 0, the reference control is performed. That is, the supply power P corresponding to the temperature difference ΔT is read. Is supplied to the heater 53, the power value is instructed to the heater power supply 9.

Note that, depending on the magnitude of the heat flow from the fixing roller 51, the supply of the power value assumed in advance may cause the temperature increase / decrease of the fixing roller 51 not to be as expected, and therefore within the standby temperature transition time tr Thus, the temperature difference ΔT at that time may be obtained every few seconds, and the supply power P for the obtained temperature difference ΔT may be updated each time.
FIG. 7 is a diagram showing the transition of the surface temperature of the fixing roller 51 when the standby temperature Tw in the power saving mode is Twu higher than the reference Tw0 and the standby temperature transition time tr is shorter than the example shown in FIG. is there. The duration of one power saving mode (time points tb to te) is not fixed because the cancellation of the power saving mode is due to a job execution instruction or a canceling operation by the user, and may be short or long. .

  If the standby temperature transition time tr is determined to be longer and the duration time of the power saving mode is shortened, the power saving mode is canceled halfway until the surface temperature of the fixing roller 51 reaches the standby temperature Tw. May occur. In such a case, the warm-up is not started from the determined standby temperature Tw, and the warm-up cannot be completed at the designated return time tu, and the return time varies.

In order to suppress such variation as much as possible, it is preferable that the standby temperature transition time tr is set to a shorter time by the user. However, if the standby temperature transition time tr is too short, the power saving mode time is long. If there are many times, the time during which the surface temperature of the fixing roller 51 is maintained at Twu higher than the standby temperature Tw0 also becomes longer, so that the total power consumption of the heater 53 in the power saving mode increases. Therefore, it is more desirable for the user to set the standby temperature transition time tr to a suitable time in consideration of the variation in the return time and the power consumption of the heater 53.
(6) Control of Power Saving Mode by Control Unit 7 FIG. 8 and FIG. 9 are flowcharts showing the contents of control of the power saving mode by the control unit 7, which are started every time the standby mode is entered.

As shown in FIG. 8, it is determined whether or not the return time tu is designated by the user (step S1). This determination is handled by the return time determination unit 74. If information indicating the return time tu specified by the user is stored in the return time storage unit 84, it is determined that it has been specified, and if not stored, it is determined that it has not been specified.
If it is determined that it is designated by the user (“YES” in step S1), the target return time tu is determined as the user designated time (step S2), and the process proceeds to step S4. This determination is performed by the return time determination unit 74.

If it is determined that it is not specified by the user (“NO” in step S1), the target return time tu is determined to be a fixed value (step S3), and the process proceeds to step S4.
A configuration in which the user can selectively input from the operation unit 6 whether the time specified by the user or a fixed value is used and the time previously selected by the user is determined as the return time tu. It may be taken.

In step S4, it is determined whether or not the standby temperature transition time tr has been set by the user. This determination is made by the standby temperature transition time determination unit 77, and if the information indicating the standby temperature transition time tr is stored in the standby temperature transition time storage unit 78, it is determined that the standby temperature transition time has been set and stored. If not, it is determined that it is not set.
If it is determined that it is set by the user (“YES” in step S4), the standby temperature transition time tr is determined as the user set time (step S5), and the process proceeds to step S7.

If it is determined that it is not set by the user (“NO” in step S4), the standby temperature transition time tr is determined as the shortest time in the past history (step S6), and the process proceeds to step S7. This determination of the shortest time is performed by reading the shortest time among the power saving mode times stored as a history in the power saving mode time history storage unit 81.
In step S7, a reference standby temperature Tw0 corresponding to the determined return time tu is determined. This determination is performed by the reference standby temperature determination unit 73.

Then, the reference supply power P0 corresponding to the determined reference standby temperature Tw0 is determined (step S8). This determination is handled by the reference supply power determination unit 83.
Then, control is performed to reduce the power supplied to the heater 53 so that the surface temperature of the fixing roller 51 decreases to the determined reference standby temperature Tw0 (step S9).
When the temperature falls to the reference standby temperature Tw0, it is determined that the power saving mode has been entered (corresponding to the time point tb in FIG. 2), and time measurement by the timer 82 is started (step S10). This time measurement is executed to measure the elapsed time since entering the power saving mode.

Then, control is performed to vary the power supplied to the heater 53 so that the surface temperature of the fixing roller 51 is maintained at the standby temperature Tw0 until the time tp elapses after entering the power saving mode. (Step S11). The power control unit 75 takes charge of this variable control.
As described above, if the heat outflow from the fixing roller 51 is about the same as the reference, supplying the same power as the reference supply power P0 to the heater 53 can maintain the standby temperature Tw0. If there are more, the standby temperature Tw0 can be maintained by supplying more power than the reference supply power P0.

The electric power actually supplied to the heater 53 over the time tp is detected (step S12). This detection is performed by the power detection unit 71. Here, the average value of the supplied power during the time tp is calculated as the detected value P.
Based on the difference between the detected supply power (actual measurement) P to the heater 53 and the reference supply power P0, the integrated power Pw when the power P is supplied to the heater 53 over the standby temperature transition time tr is obtained. Prediction is made (step S13). This prediction is handled by the standby temperature determination unit 72, and as shown in FIG. 5, for example, when the heat outflow is larger than the reference, it is set as Pwu, and when it is lower than the reference, it is set as Pwd.

Turning to FIG. 9, in step S14, a standby temperature Tw for the predicted integrated power Pw is determined. This determination is performed by the standby temperature determination unit 72. As shown in FIG. 6, for example, if the predicted value of the integrated power is Pwu, the standby temperature is Twu, and if the predicted value is Pwd, the standby temperature is Twd. The
Then, it is determined whether or not the determined standby temperature Tw is Tw0 (step S15). If the standby temperature Tw is not Tw0 (“NO” in step S15) and is Thu higher than Tw0 (“YES” in step S16), the standby temperature transition time tr has elapsed and the surface of the fixing roller 51 When the surface temperature of the fixing roller 51 reaches the standby temperature Twu by gradually increasing the power supplied to the heater 53 so that the time when the temperature rises to Twu coincides with the first temperature, the first power maintained at that temperature Control is performed (step S17).

  On the other hand, when the determined standby temperature Tw is Twd lower than Tw0 (“NO” in step S16), the standby temperature transition time tr elapses and the surface temperature of the fixing roller 51 decreases to Twd due to the temperature decrease. When the surface temperature of the fixing roller 51 reaches the standby temperature Twd by gradually reducing the power supplied to the heater 53 so as to coincide with the time point, the second power control is performed to maintain the temperature (step S18).

If the determined standby temperature Tw matches Tw0 (“YES” in step S15), the reference power control is performed to maintain the current power supplied to the heater 53 and maintain the temperature Tw0 (step S19). ). The first power control, the second power control, and the reference power control are handled by the power control unit 75 as described above.
When the power control in the standby temperature transition time tr is started, it is determined whether or not an instruction to cancel the power saving mode has been received (step S20). If it is determined that the release instruction has not been received (“NO” in step S20), it is determined whether or not the update time of the standby temperature Tw has been reached (step S21).

The standby temperature Tw is updated by re-determining the standby temperature Tw initially determined when the power saving mode is entered, and then the standby temperature Tw at that time every predetermined time, for example, every 15 minutes. It is. The standby temperature Tw is updated for the following reason.
That is, when the power saving mode continues for a long time, for example, 30 minutes or more, if the surrounding environment changes greatly between the time when the power saving mode is entered and the time when the power saving mode ends, the state of heat outflow is also Often changes to some extent. If the state of heat outflow changes during the power saving mode, the temperature rise time of the fixing roller 51 during warm-up also changes depending on the amount of change, so the state of heat outflow when entering the power saving mode If the standby temperature Tw determined based on the above is applied as it is, the difference between the designated return time tu and the actual warm-up time is more likely to occur as the amount of change in heat flow increases.

Here, it is determined that the update time has been reached every time a predetermined time has elapsed since the last determination of the standby temperature Tw, and the count value of the timer 82 is referred to as to whether or not the predetermined time has elapsed. It is judged by.
If it is determined that it is not time to update the standby temperature Tw (“NO” in step S21), the process returns to step S20. When it is determined that the update time of the standby temperature Tw has been reached (“YES” in step S21), the power supplied to the heater 53 is controlled so that the surface temperature of the fixing roller 51 becomes the reference standby temperature Tw0 ( In step S22), the process returns to step S11, and the processes in steps S11 to S14 are executed again to determine the standby temperature Tw again.

  If the update time is the time tg shown in FIG. 7, the surface temperature of the fixing roller 51 is the standby temperature Twu (> Tw0), so the power supplied to the heater 53 is reduced and the fixing roller 51 The surface temperature is lowered to the reference standby temperature Tw0 (step S22), and when the reference standby temperature Tw0 is reached, the processing after step S11 is executed. If the surface temperature of the fixing roller 51 is Twd (<Tw0) at the time of update, the power supplied to the heater 53 is increased to raise the temperature to the reference standby temperature Tw0 (step S22).

The standby temperature Tw to be applied later is re-determined according to the state of heat outflow at that time, which is detected again during the power saving mode by the processing in steps S11 to S14, and the standby is re-determined. The temperature can be updated to Tw.
After the standby temperature Tw is updated, the processing of steps S15 to S19 is executed. In this case, the standby temperature transition time tr may be the same length as described above, or may be a different time, for example, a shorter time. It is good also to switch to. If the standby temperature transition time tr is set to a shorter time tr1, the transition to the updated standby temperature becomes faster, so that the power saving mode may be canceled immediately before the time tr elapses from the update. However, if the elapsed time tr1 is earlier (past) than the release time, the updated standby temperature can be maintained before the release, and the standby temperature transition time tr can be maintained. The variation in the return time can be reduced as compared with the case where it is left as it is.

  Note that when the cancellation is performed during the power saving mode varies depending on the frequency of the job instruction by the user, etc., and the power saving mode may continue for a long time, such as outside business hours. In such a case, the standby transition time tr may be lengthened. A configuration is also possible in which the user can set and input a different standby transition time tr for different time zones such as business hours and non-business hours, and the corresponding standby transition time tr is automatically switched for each time zone. it can.

If the cancellation instruction is not accepted during the power saving mode (“NO” in step S20) and if it is not the time for updating the standby temperature Tw (“NO” in step S21), the determinations of steps S20 and S21 are repeatedly executed. To do.
If a release instruction is accepted before reaching the update time (“YES” in step S20), the timer 82 is stopped and the count value of the timer 82 is added to the past history as the power saving mode time. After storing in the mode time history storage unit 81 (step S23), the timer 82 is reset to zero (step S24).

Then, in order to start the warm-up, the control to switch the supply power to the heater 53 to the maximum, that is, the heater power supply 9 is instructed to set the supply power to the maximum value (step S25), and the process ends. . The power control unit 75 takes charge of this instruction.
In the warm-up, the maximum power is supplied to the heater 53, and when the surface temperature of the fixing roller 51 reaches the fixing temperature Ts, the state transitions to the ready state. At the start of the warm-up (time point te in FIG. 2), the surface temperature Ta of the fixing roller 51 is maintained at the standby temperature Tw determined according to the heat outflow state.

  Therefore, even if the same heat outflow state as in the power saving mode is continued during the warm-up, the warm-up can be terminated in accordance with the elapse of the designated return time tu, and the return time It is possible to prevent the user from feeling inconvenience for the user who has specified the return time, while improving the accuracy of the return time closer to the specified time by suppressing the variation of It becomes like this.

In the above description, the configuration example in which the process of updating the standby temperature is repeated every predetermined time in the middle of the power saving mode has been described. However, the configuration is not limited thereto, and a configuration in which the standby time is not updated may be employed. . This is because it may not be necessary to perform the update when the power saving mode time is short as a whole or when the change in the surrounding environment is relatively small.
In such a case, for example, if the change in the surrounding environment after entering the power saving mode, for example, the temperature change is smaller than a predetermined value, the standby time is not updated (prohibited), and when the predetermined value is exceeded. The standby time may be updated, and thereafter, the process of repeatedly updating the standby time may be executed only when the temperature change from the update becomes a predetermined value or more. It is possible to execute only when it is assumed that the update of the waiting time is necessary. The predetermined value can be obtained in advance by experiments or the like in accordance with the upper limit when the variation in recovery time exceeds the upper limit of the allowable range due to a change in the state of heat outflow caused by a temperature change.

  In addition, the user can designate the return time tu, but the present invention is not limited to this, and a configuration having only a fixed value may be used. This is because it is not desirable that the time required for warm-up after returning from the power saving mode varies even with a configuration having only a fixed value. In the case of this configuration, the reference standby temperature Tw0 and the reference supply power P0 with respect to the return time tu as fixed values are determined in advance through experiments and simulations and associated with each other.

  The present invention is not limited to the image forming apparatus, and may be a method of supplying power to the heater in the power saving mode. The method may be a program executed by a computer. The program according to the present invention includes, for example, a magnetic disk such as a magnetic tape and a flexible disk, an optical recording medium such as a DVD-ROM, DVD-RAM, CD-ROM, CD-R, MO, and PD, and a flash memory recording medium. It can be recorded on various computer-readable recording media, and may be produced, transferred, etc. in the form of the recording medium, wired and wireless various networks including the Internet in the form of programs, In some cases, the data is transmitted and supplied via broadcasting, telecommunication lines, satellite communications, or the like.

(Modification)
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the above-described embodiment, the example in which the power supplied from the heater 53 is used as the index value of the heat outflow amount of the fixing roller 51 has been described. However, the index value may indicate the state of heat outflow. For example, it is not limited to this.

For example, the temperature transition of the surface temperature of the fixing roller 51 when a constant power is supplied to the heater 53 over a certain time can be used as an index value of the heat outflow amount.
Specifically, first, a reference temperature gradient when a constant power is supplied to the heater 53 when the surface temperature of the fixing roller 51 is at the reference standby temperature Tw0 in a reference environment is obtained in advance. Thereafter, when the same constant power is supplied from the reference standby temperature Tw0 when the power saving mode is entered, the temperature gradient of the fixing roller 51 at that time is detected, and the detected temperature gradient, the reference temperature gradient, The state of heat outflow is determined from the difference between the two.

For example, when the reference temperature gradient is positive, if the detected temperature gradient is smaller than the reference temperature gradient, it means that the rate of temperature increase is lower than the reference due to heat outflow. It turns out that the heat outflow is increasing. If the detected temperature gradient is larger than the reference temperature gradient, the opposite is true.
If the standby temperature Tw is increased or decreased with respect to the reference Tw0 with respect to the magnitude of the difference between the detected temperature gradient and the reference temperature gradient, the warm-up can be completed within the designated recovery time tu. It is possible to determine the standby temperature Tw suitable for the power saving mode by obtaining in advance through experiments or simulations and storing the corresponding information (corresponding to FIG. 6).

(2) In the above embodiment, the fixing roller is configured to perform the first power control or the second power control for gradually increasing or decreasing the power supplied to the heater 53 over the standby temperature transition time tr in the power saving mode. Although the surface temperature of 51 is gradually raised to the standby temperature Twu or lowered to Twd, this is not restrictive.
For example, when the surface temperature of the fixing roller 51 is increased, it is possible to perform power control in which the maximum power is supplied at the beginning of the standby temperature transition time tr and the supply power is gradually reduced. When the power value is gradually increased as described above, if the power value reaches the maximum value in the middle, the power cannot be increased beyond the maximum value, so the maximum power is fixed from the middle. As a result, when the entire standby temperature transition time tr is viewed, the power supply at the initial point of the standby temperature transition time tr is small, so that the temperature rise of the fixing roller 51 is delayed. When the standby temperature transition time tr elapses, it is likely that the temperature has not been raised to the target standby temperature Twu.

Since the supply power P of the heater 53 during the standby temperature transition time tr can be known from the standby temperature transition time power information before the start of control if the temperature difference ΔT is known as described above, before the start of the first power control, In the first power control to be executed from now on, it can be determined that the supplied power P reaches the maximum value in the middle of the standby temperature transition time tr and reaches its peak.
Therefore, if the first power control is performed before the execution of the first power control, if it is determined in advance that the supply power P reaches the middle during the standby temperature transition time tr, the above supply power is gradually increased. Instead of increasing the first power control, the temperature of the fixing roller 51 is increased by performing the third power control in which the supply power is first set to the maximum value and then the supply power is gradually reduced as time elapses. Temperature control can be performed so that the surface temperature of the fixing roller 51 reaches the standby temperature Twu when the standby temperature transition time tr elapses while preventing delay.

Note that the maximum power supply time and the rate at which the power is reduced from the maximum value can be determined in advance from experiments, simulations, and the like for each different temperature difference ΔT. Further, the power is not limited to the maximum value, and for example, as a relatively large (predetermined) power value close to the maximum value, the power may be input first, and gradually reduced.
Further, the supply time and supply power are determined before the start of control, and the power supply is performed as determined. However, the speed at which the surface temperature of the fixing roller 51 changes during the temperature increase or decrease is too high. If it is determined that it is too late, the supplied power may be changed to a suitable value at any time. For example, when it is determined that the rate of temperature increase is slow, the subsequent power supply is changed to a power value obtained by adding a predetermined value to a predetermined power value, so that the rate of temperature increase is corrected. You can also take a method.

(3) In the above embodiment, the type of the heater 53 as the heat generating part is not particularly described, but in addition to a heating wire, a halogen heater, a resistance heating element and the like that generate heat directly by energization of supplied power, An electromagnetic induction type in which the induction heating layer generates heat by electromagnetic induction by magnetic flux generated by energization of the coil can also be used.
Moreover, although the example which uses the fixing roller 51 as a fixing member heated by a heat generating part was demonstrated, it is not restricted to a roller-shaped thing, For example, a belt-shaped thing can also be used.

  The image forming apparatus according to the present invention cancels the mode in the power saving mode in which the fixing member heated by the heat generating unit is maintained at a standby temperature lower than the fixing temperature necessary for thermally fixing the image on the sheet. When an instruction is received, the power supply to the heat generating unit is increased to raise the temperature of the fixing member, and when the temperature of the fixing member reaches the fixing temperature, the image forming apparatus generally transitions to a ready state in which an image forming job can be executed. The present invention can be applied to a copying machine, a printer, a multifunction machine (MFP), a facsimile machine, and the like.

  The contents of the above embodiment and the above modification may be combined.

  The present invention can be applied to an image forming apparatus capable of executing a power saving mode.

DESCRIPTION OF SYMBOLS 5 Fixing part 6 Operation part 7 Control part 9 Heater power supply 10 Image forming apparatus 51 Fixing roller 71 Power detection part 72 Standby temperature determination part 74 Return time determination part 75 Power control part 76 Overall control part 77 Standby temperature transition time determination part 79 Temperature Detection unit tu Recovery time Ts Fixing temperature Tw Standby temperature

Claims (9)

When an instruction to cancel the mode is received in the power saving mode in which the fixing member heated by the heat generating unit is maintained at a standby temperature lower than the fixing temperature necessary for heat fixing the image on the sheet, An image forming apparatus that raises the power supply to raise the temperature of the fixing member and transitions to a ready state in which an image forming job can be executed when the temperature of the fixing member reaches the fixing temperature.
An acquisition means for acquiring information indicating a return time that is a target until a transition to the ready state after receiving an instruction to cancel the mode;
Detecting means for detecting an index value of the amount of heat flowing out from the fixing member to the periphery thereof;
The amount of heat flow detected when entering the power saving mode so that the time from when the mode release instruction is received until the temperature of the fixing member reaches the fixing temperature due to the temperature rise matches the acquired recovery time. Determining means for determining a standby temperature to be applied to the power saving mode according to the index value of
An image forming apparatus comprising: A power supply unit for supplying power to the heat generating unit;
Control means for varying the power supplied to the heat generating unit so that the temperature of the fixing member is maintained at a predetermined reference standby temperature for a predetermined time after entering the power saving mode for the power supply unit;
With
The detection means includes
As an index value of the heat outflow amount, the magnitude of electric power supplied to the heat generating part is detected,
The determining means includes
The image forming apparatus according to claim 1, wherein the standby temperature is determined according to a magnitude of electric power during the predetermined time. The determining means includes
If the detected temperature is greater than a predetermined reference amount for a target recovery time, the standby temperature is determined to be an amount corresponding to the difference, a value higher than the reference standby temperature, The image forming apparatus according to claim 2, wherein if it is smaller, an amount corresponding to the difference is determined to be a value lower than the reference standby temperature. The control means includes
Obtaining a target standby temperature transition time required for the temperature of the fixing member to reach the determined standby temperature after the predetermined time has elapsed in the power saving mode;
When the determined standby temperature is higher than the reference standby temperature, the power supply unit is configured so that the temperature of the fixing member reaches the standby temperature due to a temperature rise when the acquired standby temperature transition time elapses. On the other hand, the first power control is performed to vary the power supplied to the heat generating part,
When the determined standby temperature is lower than the reference standby temperature, the power supply unit is configured so that the temperature of the fixing member reaches the standby temperature due to a decrease in temperature when the acquired standby temperature transition time elapses. 4. The image forming apparatus according to claim 2, wherein second power control is performed to vary power supplied to the heat generating unit. 5. The first power control is:
It is a control to gradually increase the power supplied to the heat generating part over time,
The second power control is
The image forming apparatus according to claim 4, wherein the control is to gradually reduce the power supplied to the heat generating portion as time elapses. The control means includes
When the determined standby temperature is higher than the reference standby temperature, if the first power control is performed before the execution of the first power control, the power supplied to the heat generating unit is changed to the target standby temperature transition time. If it is determined that the maximum value is reached in the middle of the passage, instead of the first power control, the power supplied to the heat generating portion is first set to a maximum value or a predetermined power value close to the maximum value, and then The image forming apparatus according to claim 5, wherein third power control is performed to gradually reduce with time. Receiving means for accepting designation of the return time from a user;
The acquisition means includes
Obtaining a user-specified time accepted by the accepting means;
The determining means includes
As the reference standby temperature, when the designated return time is the first length, the first temperature predetermined for the return time of the first length is used, and the reference standby temperature is set to be longer than the first length. The second temperature higher than the first temperature, which is predetermined for the return time of the second length in the case of the short second length, is used. The image forming apparatus according to claim 1. The determining means includes
After the determination of the standby temperature to be applied to the power saving mode, instead of the determined standby temperature, it is applied later according to the magnitude of the index value of the heat outflow amount detected again during the power saving mode. The image forming apparatus according to claim 1, wherein the standby temperature to be determined is re-determined and updated to the re-determined standby temperature.   9. The maximum value in a range in which power supplied to the heat generating unit can be supplied during the period from the mode cancellation to the ready state transition, is set forth in claim 1. Image forming apparatus.

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