JP2011191628A - Fixing control method, fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method to perform stable fixing even immediately after the linear velocity of a print job is switched by suppressing fluctuation of fixing property due to a temperature change when the linear velocity of the print job is switched. <P>SOLUTION: A fixing heater 53 is controlled, by calculating heater initial correction DUTY on a heating side: ΔD by ΔD=Cd(Sf/Si)Di (15% in this example), adding Di (30% in this example), being DUTY just before changing the linear velocity, to the calculated result, and forcibly deriving DUTY (45% in this case), being D=Di+ΔD as performance DUTY:D, in a first control period after changing the linear velocity (forcibly using it as control DUTY), wherein the linear velocity before switching is defined as Si, the linear velocity after switching is defined as Sf, an addition ratio is defined as Cd, and DUTY of a heater before switching is defined as Di. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device control method, a fixing device, and an image forming apparatus used in an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system.

  In a conventional image forming apparatus using an electrophotographic system, a recording medium on which an unfixed toner image is transferred is conveyed while being sandwiched between a fixing member and a pressure member, and unfixed toner is applied by applying heat and pressure. A thermal fixing device that fixes an image on a recording medium is widely used. In the fixing process in this type of fixing device, the unfixed image is heated while nipping and pressing the recording medium carrying the unfixed image, and the developer contained in the unfixed image, in particular, the toner is softened and melted. By allowing the recording medium to penetrate, the toner is fixed on the recording medium.

  On the other hand, an image forming apparatus configured so that the linear speed can be switched is well known. However, in such an apparatus, the fixing property fluctuates due to a temperature change when the linear speed is switched in the fixing process.

  That is, when the linear velocity is switched, the temperature becomes unstable because the contact distance with an object to be heated (such as a fixing belt or a pressure roller) that must be heated for a certain time changes. For example, if the linear velocity increases, the contact distance with the object to be heated per unit time becomes longer, so the temperature temporarily drops. If the recording medium reaches the fixing device before recovering from this temporary drop in temperature, the amount of heat becomes insufficient, and the fixability deteriorates.

  Conventionally, the target temperature on the heating side (fixing member side) has been set so as to ensure fixability even when the pressure side temperature is low. Therefore, the target temperature on the heating side is the pressure side that changes from moment to moment. The setting does not reflect the temperature, which causes a change in fixing property. Furthermore, when the pressure side temperature is high, more heat than necessary is consumed.

  In Japanese Patent Laid-Open No. 6-337614 (Patent Document 1), an energization control unit variably controls a temperature control target temperature of a heating member while a sheet of recording material passes through the nip. A fixing device is disclosed that prevents fixing unevenness and offset due to temperature changes.

  However, the apparatus described in Patent Document 1 cannot cope with the above-described change in fixability when output with different print job line speeds is performed, and the fixability is caused by a temperature change when the line speed is switched. The problem of fluctuations cannot be solved.

  The present invention solves the above-described problem that the fixing property fluctuates due to a temperature change when the linear speed is switched, and a fixing device and an image forming apparatus that can perform stable fixing even immediately after the linear speed is switched. It is an issue to provide.

  According to the present invention, the above-described problem is caused by passing a recording medium holding an unfixed toner image through a fixing nip formed by a fixing member heated by a fixing heater and a pressure member pressed against the fixing member. In a fixing device control method for fixing an unfixed toner image on a recording medium, the target temperature of the next control cycle is determined based on temperature information obtained from a detecting means for detecting the temperature of the fixing member, and the DUTY of the fixing heater is controlled. In addition, when the factor affecting the fixability changes, the problem is solved by changing the DUTY of the fixing heater.

In addition, it is preferable that the factor affecting the fixability is a change in linear velocity.
Further, the control for calculating the DUTY of the fixing heater with reference to the past DUTY is used, and when the linear speed is switched, the initial correction DUTY corresponding to the linear speed ratio before and after the switching is one cycle before the linear speed is switched. It is preferable to add to the DUTY that has been displayed in the above and forcibly use it as the reference DUTY in the first control cycle after the linear velocity is switched.

  Also, the linear velocity before switching is Si, the linear velocity after switching is Sf, the addition ratio Cd, the heater DUTY before switching is Di, and the heater initial correction DUTY: ΔD is calculated as ΔD = Cd (Sf / Si) Di. It is preferable.

In addition, it is preferable that the factor affecting the fixability is temperature information obtained from a detection unit that detects the temperature of the pressure member.
Further, it is preferable that the DUTY of the fixing heater can be set independently for each paper thickness based on the paper thickness information indicating the thickness of the recording medium.

  Further, the reference temperature Ts on the pressure side during paper passing, the current pressure side temperature Tr, the correction coefficient for each paper thickness is Cp, and the target temperature correction value: ΔT on the heating side is calculated as ΔT = Cp (Ts−Tr). It is preferable.

In addition, when Tr is less than Ts, it is preferable that the number of output sheets per unit time can be reduced by widening the space between recording media.
In addition, it is preferable to have an exclusion time during which DUTY control of the fixing heater is not performed based on temperature information obtained from a detection unit that detects the temperature of the pressure member.

In addition, it is preferable that an upper limit value and a lower limit value of ΔT can be set.
In addition, when Tr exceeds Ts, it is preferable that the number of output sheets per unit time can be increased by narrowing the gap between the recording media.

  If the Tr exceeds Ts, whether the number of output sheets per unit time is increased by narrowing the space between the recording media, or the heating side target temperature is corrected based on the Tr to suppress power consumption. It is preferable that, can be selected.

Moreover, it is preferable that Ts can be changed according to the environmental temperature.
In addition, it is preferable that the Cp can be changed according to the environmental temperature.
According to the present invention, the above problem is solved by a fixing device controlled by the fixing control method according to any one of claims 1 to 14.

  Further, according to the present invention, the above problem is solved by an image forming apparatus provided with the fixing device according to claim 15.

  According to the fixing control method, the fixing device, and the image forming apparatus of the present invention, it is possible to cope with a change in factors that affect the fixing property, and for example, the influence of a change in temperature of the fixing member is suppressed as much as possible to be stable. A fixing operation can be performed.

  According to the method of the second aspect, it is possible to perform appropriate DUTY control in response to the temperature change of the fixing member caused by the change of the linear velocity, and it is possible to stabilize the fixing member temperature immediately after the linear velocity is switched. .

According to the method of the third aspect, it is possible to eliminate the control delay associated with the feedback control and stabilize the fixing member temperature immediately after the linear speed is switched.
According to the method of claim 4, by setting an appropriate DUTY capable of suppressing a temporary drop in the fixing member temperature due to the switching of the linear speed, the fixing member temperature immediately after the switching of the linear speed can be stabilized.

According to the method of claim 5, more appropriate DUTY control can be performed by correcting the target temperature on the fixing member side with the temperature on the pressure member side.
According to the method of claim 6, since the influence of the temperature on the pressure side varies with the paper thickness, the fixing condition can be kept optimal by setting the target temperature on the heating side according to the paper thickness. Thereby, the fixing process can be performed with a minimum amount of energy.

According to the method of the seventh aspect, the target temperature on the heating side can be set more appropriately, and the fixing conditions can be further optimized.
According to the method of claim 8, when the pressure side temperature Tr falls below the reference temperature Ts due to voltage drop or the like, the space between the papers is widened, and the contact time between the heating side and the pressure side is lengthened, whereby the temperature on the pressure side is increased. By pulling up, it is possible to satisfy the temperature condition necessary for fixing on the pressure side and the heating side and to secure the fixing property.

  According to the method of claim 9, in a model in which the pressurization temperature gradually decreases after the paper feeding is started (in many high-productivity machines), the fixing unit is in a period until the maximum decrease temperature on the pressurization side is reached. There is a desire to increase the temperature by storing as much heat as possible. In such a model, when the temperature on the pressure side is high, heat is stored as much as possible by providing a time during which the temperature correction on the heating side is not performed, and after passing through the maximum drop temperature on the pressure side, looking at the temperature on the pressure side By correcting the target temperature on the heating side, power consumption can be suppressed without deteriorating fixability and productivity.

  According to the method of claim 10, when the contribution of the temperature to the heating side on the pressure side is not linear and the fixability is lowered, the temperature correction value ΔT reaches a peak within a range in which the fixability can be satisfied. To do. That is, fixability can be ensured by avoiding temperature correction below the minimum temperature required on the heating side.

According to the method of the eleventh aspect, when the pressure side temperature Tr becomes higher than the reference temperature Ts that can secure the fixability, the productivity can be improved by narrowing the gap between the sheets.
According to the method of the twelfth aspect, the convenience of the user can be improved by enabling the user to select whether to maximize the productivity or to save the electric power within a range where the fixing property can be satisfied.

According to the method of the thirteenth aspect, the fixing property can be ensured even if the use environment of the machine changes.
According to the method of the fourteenth aspect, since the correction coefficient Cp for each paper thickness can be changed according to the environmental temperature, it is possible to suppress the power consumption while ensuring the fixing property even when the use environment of the machine is changed.

1 is a cross-sectional view illustrating a schematic configuration of a color printer which is an example of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional configuration diagram of a fixing device. FIG. 3 is a perspective view of a main part of the fixing device. FIG. 6 is a schematic diagram showing the amount of heat generated by the fixing heater and the arrangement of temperature sensors. It is a graph which shows the mode of the heating side target temperature correction | amendment by pressurization side temperature.

Hereinafter, a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of a color printer which is an example of an image forming apparatus according to the present invention. The color printer shown in this figure is a color printer that can form a full-color image by adopting a tandem method, and four image forming units 1 (a, b, c, d) are arranged at substantially the center of the apparatus main body. Has been established. Each image forming unit 1 (a, b, c, d) has the same configuration except that the color of the toner to be handled is different from yellow, cyan, magenta, and black. In the following description, a, b, c in reference numerals are used. , D will be omitted as appropriate.

  Each image forming unit 1 includes a photosensitive drum 2 as an image carrier. Around the photosensitive drum 2, a charging unit 3, a developing device 4, a cleaning unit 5, and the like are disposed. Further, a transfer as a primary transfer unit is provided inside the intermediate transfer belt 7 so as to face each photosensitive drum 2. A roller 8 is provided. In each image forming unit 1, a part including the photosensitive drum 2, the charging unit 3, and the cleaning unit 5 is detachably provided as a process cartridge in the printer main body.

  The intermediate transfer belt 7 is stretched around the support rollers 15a and 15b and is driven to run counterclockwise in the drawing. A cleaning device 70 for cleaning the intermediate transfer belt is disposed outside the left support roller 15a. In the upper space of the intermediate transfer belt 7, toner bottles 20 (a, b, c, d) that store toners of yellow, cyan, magenta, and black are arranged.

An optical writing device 6 is disposed below the tandem image forming unit in which the four image forming units 1 are arranged. The optical writing device 6 includes appropriate components such as a light source, a polygon mirror, an f-θ lens, and a reflection mirror, and applies laser light to the surface of each photoconductor 1 based on image data of each color toner. Irradiate while scanning.
Is provided with a paper feed tray 17 for loading paper.

  The lowermost part of the apparatus main body is configured as a paper feed unit, and a paper feed tray 30 for storing a recording medium is arranged. On the right side of the paper feed tray 30 is a paper feed roller 31 that feeds the papers stacked on the paper feed tray, and separates the papers one by one using a separation pad or the like. A registration roller 35 is provided above the paper feed roller 31 (on the downstream side in the paper transport direction). Above the registration roller 35, a transfer roller 18 as a secondary transfer unit is provided to face a support roller 15b as a transfer counter roller, thereby forming a secondary transfer portion.

  A fixing device 50 is provided above the secondary transfer unit. Although the fixing device will be described in detail later, the fixing is performed by heating and pressurizing the recording medium on which the unfixed toner image is transferred in the secondary transfer unit. A paper discharge roller 60 is provided above the fixing device 50.

An image forming operation in the color printer configured as described above will be briefly described.
The photosensitive drum 2 of the image forming unit 1 is rotated in the clockwise direction in the figure by a driving unit (not shown), and the surface of the photosensitive drum 2 is uniformly charged to a predetermined polarity by the charging unit 3. The charged photoconductor surface is irradiated with laser light from the optical writing device 6, whereby an electrostatic latent image is formed on the photoconductor drum 2 surface. At this time, the image information exposed on each photosensitive drum 2 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. Each color toner is applied from the developing device 4 to the electrostatic latent image formed in this manner, and visualized as a toner image.

  Further, the intermediate transfer belt 7 is driven to run counterclockwise in the figure, and the respective color toner images are sequentially transferred from the photosensitive drum 2 to the intermediate transfer belt 7 by the action of the primary transfer roller 8 in each image forming unit 1. In this way, the intermediate transfer belt 7 carries a full-color toner image on its surface.

  Note that any one of the image forming units 1 can be used to form a single-color image or a two-color or three-color image. In the case of monochrome printing, image formation is performed using the rightmost black unit 1d in the drawing among the four image forming units.

  The residual toner adhering to the surface of the photosensitive drum after the toner image is transferred is removed from the surface of the photosensitive drum by the cleaning unit 5, and then the surface potential is initialized by the action of the static eliminator. Prepare for the next image formation.

  On the other hand, the sheet is fed from the sheet feeding tray 30 and is sent out toward the secondary transfer position by the registration roller pair 35 in timing with the toner image carried on the intermediate transfer belt 7. The toner image on the surface of the intermediate transfer belt is collectively transferred onto the sheet by the secondary transfer roller 18 to which the transfer bias is applied. When the sheet on which the toner image is transferred passes through the fixing device 50, the toner image is fused and fixed to the sheet by heat and pressure. The fixed paper is discharged by a paper discharge roller 60 to a paper discharge tray formed on the upper surface of the apparatus main body.

Next, the fixing device will be described with reference to FIGS.
The fixing device 50 of this example is a belt fixing device that uses a belt as a fixing member, and includes a fixing roller 51, a pressure roller 52, a heating roller 54, a fixing belt 55, and the like inside the unit. The heating roller 54 includes a fixing heater 53 including a plurality of heaters, a fixing belt 55 made of a heat-resistant elastic material is stretched between the heating roller 54 and the fixing roller 51, and a pressure roller facing the fixing roller 51. 52 forms a nip. A tension roller 57 is in contact with the inner surface of the fixing belt 55, and appropriate tension is applied to the fixing belt 55.

  The fixing heater 53 in the heating roller 54 is divided into a central heater 53a and an end heater 53b, which are controlled using temperature sensors 56A and 56B, respectively. By varying the lighting DUTY of the heater depending on the size of the transfer paper, an increase in end temperature (in the roller axis direction) can be suppressed and wasteful power can be saved. In addition, it is effective as a countermeasure against flicker by dividing it into two instead of one heater. For large size paper, the central heater 53a and the end heater 53b are used in the same DUTY, but for small size transfer paper, the DUTY of the end heater is remarkably lowered to suppress heating and power consumption of useless portions. be able to. In this example, heating is performed from the inside of the fixing belt 55 by the heating roller, but non-contact heating (radiant heat such as halogen heater) may be performed from the outside of the belt. In this example, the number of heaters is two, but three or more heaters may be used.

  In the present embodiment, as shown in FIG. 4, the temperature sensor 56A is provided at a position corresponding to the heat generating electric resistance portion 53aw of the central heater 53a, and the position corresponding to the heat generating electric resistance portion 53bw on one side of the end heater 53b. The temperature sensors 56B are arranged respectively. In this example, a thermopile is used as the temperature sensor 56A, and a non-contact thermistor is used as the temperature sensor 56B. That is, the temperature of the fixing heater 53 is controlled by a thermopile and the end heater is controlled by a non-contact thermistor.

  A thermopile is a sensor with good time response that generates an electromotive force according to the temperature difference from the cold junction by condensing the infrared rays radiated from the object at the hot junction where many thermocouples are connected in series. is there. It has an atmosphere sensor to compensate for changes in the temperature of the thermopile itself (especially the temperature at the cold junction).

  The non-contact thermistor is a thermistor pair whose resistance value varies with temperature, and includes a detection sensor that detects the temperature of the object and an atmosphere sensor that detects the ambient temperature of the detection sensor. The detection temperature of the detection sensor can be corrected by the detection value of the atmosphere sensor. Non-contact thermistors are less expensive than thermopiles but are less responsive.

  In this example, since two fixing heaters are used, two temperature sensors are provided. However, when the number of heaters is further increased, the number of temperature sensors may be increased. Further, if there is a temperature sensor that can maintain the fixing property without using a thermopile or a non-contact thermistor, it may be used. If the distance between the fixing member and the non-contact sensor changes due to component tolerances and the deviation from the set value of the ambient temperature is unacceptable, adjust the distance between the non-contact sensor and the fixing member so that the ambient temperature falls within the set value. A spacer or the like may be inserted when the non-contact sensor is screwed.

  The fixing roller 51 and the pressure roller 52 are made of an elastic material such as rubber or a foamed material such as sponge so as to have an appropriate surface pressure and nip width. In this embodiment, the fixing roller 51 is a sponge roller and has a hardness of about 35 HS, and the pressure roller 52 uses a rubber having a thickness of about 3 mm on the surface and a hardness of about 60 Hs. Both diameters are about 40 mm.

  A typical configuration of the fixing belt 55 is a polyimide resin of 80 μm as a base material, a silicone rubber of 200 μm, and a PFA of 10 μm. Rubber is necessary to follow the unevenness of the recording medium, and PFA on the surface is unnecessary if the release property of the rubber to toner and paper powder is excellent.

  The fixing belt 55 has a side guide for preventing the climbing by the end, and the side guide contacts the end of the heating roller 54 when the fixing belt 55 is moved to either side, and the side is further shifted. It has a structure that regulates.

  In the fixing device 50 having the above configuration, the temperature control necessary for the fixing process is performed by controlling the lighting rate of the fixing heater 53 according to the output of the non-contact temperature sensor 56 (A, B). .

Since the contact time of the fixing belt 55 with the heating roller 54 changes depending on the linear velocity, the temperature temporarily becomes unstable when the linear velocity changes.
If the heater DUTY (the amount of power per unit time or lighting time) is calculated by PID control and the DUTY of the previous cycle is referenced during the calculation, the DUTY required after the line speed is switched In order to achieve the required DUTY, control is performed in stages. If the control period is 600 ms, it takes about 3 to 4 seconds to settle to the required DUTY. During this time, the temperature becomes unstable. Further, since the feedback control is performed, the temperature drops due to the switching of the linear velocity, and is calculated by the PID control in a direction in which the heater DUTY is changed after the temperature sensor senses the temperature. Therefore, it is influenced by the reaction time of the sensor. Assuming that the sensor reaction time is 300 ms, the sensor reacts 300 ms after the temperature of the fixing belt actually drops, and calculation starts in the direction of changing the heater DUTY. In particular, in a sensor with a slow reaction speed such as a non-contact thermistor (typical reaction speed is about 4 seconds), the influence of temperature fluctuation due to a change in linear speed is large, and it takes time until the temperature settles (7 to 8 seconds). degree). In a machine having a first print time of several seconds, the paper reaches the fixing belt before the temperature change due to the switching of the linear speed is recovered, and the fixing property is affected.

  Therefore, when the linear velocity is switched, the initial correction DUTY corresponding to the linear velocity ratio before and after the switching is added to the DUTY that was output one cycle before the linear velocity is switched, and the first time after the linear velocity is switched. By forcibly outputting in the control cycle, the temperature immediately after switching is stabilized.

  As an example, if the DUTY is 30% before the line speed is switched and the required DUTY is 45% after the line speed is switched, the DUTY is 45% in the cycle of the first round after the line speed is switched. Forcibly. From there, the PID calculation after changing the linear velocity is started.

At this time, the DUTY required after the linear speed change is estimated from the linear speed ratio. If the linear speed before switching is Si, the linear speed after switching is Sf, the addition ratio Cd, and the heater DUTY before switching is Di, Heater-side heater initial correction DUTY: ΔD is ΔD = Cd (Sf / Si) Di
(15% in this example), and Di (30% in this example) immediately before the linear speed change is added to this, and execution DUTY: D is set as D = Di + ΔD
DUTY (45% in this case) is forcibly output in the first control cycle after changing the linear velocity (forcibly used as control DUTY).

A method for calculating the addition ΔD (in this case, 15%) will be described later.
If the information that the line speed is switched before the line speed is switched can be obtained, D% (45% in this case) may be output in the control cycle before the line speed is switched.

  In addition, since the fixing process is performed by feeding paper into a fixing nip composed of a fixing belt and a pressure roller, there is a correlation between the temperature on the heating side and the temperature on the pressing side necessary for fixing, and the temperature on the pressing side is When the temperature on the pressure side is lower than when it is high, the temperature on the heating side needs to be higher.

  In the conventional control method, the target temperature setting on the heating side is set so that the fixing property can be secured even when the temperature on the pressure side is the lowest. When the temperature on the pressure side is high, more heat is applied to the paper and toner. It was.

  In this embodiment, by setting the target temperature on the heating side corresponding to the paper thickness by looking at the pressurization temperature (setting the target temperature independently for each paper thickness), the fixing conditions are optimally maintained and the minimum energy is set. With this, the fixing process can be completed.

Here, a method of calculating the addition ΔD (in this case, 15%) will be described.
As described above, in this embodiment, when the linear velocity before switching is Si, the linear velocity after switching is Sf, the addition ratio Cd, and the heater DUTY before switching is Di, the heater initial correction value ΔD on the heating side is ΔD. = Cd (Sf / Si) Di
And is added to DUTY immediately before the line speed is switched.

  An example in which the linear speed can be switched to three linear speeds S1, S2, and S3, the ratio of the respective linear speeds is 1: 2: 3, the addition ratio Cd is 0.25, and the heater DUTY before switching is 30%. When the linear speed increases from S1 to S2, 15% is added as the heater DUTY. When the linear velocity increases from S1 to S3, 22.5% of DUTY is added. The addition ratio Cd is determined to a value at which the temperature is most stable when the linear velocity is switched.

  When the temperature transition immediately after the linear speed is changed depending on the temperature of the pressure roller, the value of the addition ratio Cd may be changed depending on the pressure roller temperature. In this embodiment, this control is not applied when the line speed is switched to the slower one. When the linear velocity decreases, the addition ratio Cd may be set to a negative value to reduce DUTY. In addition, although the linear speed is increased, if the target temperature becomes low and the target temperature can be reached earlier when this control is not performed, a limiting condition such as not being applied when the target temperature is low may be set.

Further, assuming that the pressure side reference temperature Ts, the current pressure side temperature Tr, and the correction coefficient for each paper thickness during paper passing are Cp, the heating side target temperature correction value ΔT is ΔT = Cp (Ts−Tr).
And the target temperature on the heating side is corrected.

  The pressurization reference temperature Ts is the temperature at which the pressurization temperature becomes the lowest during paper feeding, and there is a margin in the fixability by the increase in the pressurization temperature from there, so the target temperature on the heating side is corrected accordingly. To do. Thus, the fixing process is completed without supplying more power than necessary when the pressurization temperature is high. In FIG. 5, the heating side target temperature correction | amendment by pressurization side temperature is shown with a graph.

  The paper thickness coefficient Cp is determined by how much the pressure roller temperature contributes to the fixing belt temperature. In the case of 55K paper, the contribution of the pressure roller is large and contributes about 1/2 to the fixing belt side. However, the contribution becomes smaller as the paper becomes thicker and hardly contributes when the paper becomes 180K or more.

When the pressurization temperature falls below the pressurization reference temperature Ts, the space between the sheets is widened to increase the temperature of the pressurization roller in order to ensure fixability.
For models in which the pressurization temperature gradually drops after the start of paper feeding (often in high-productivity machines), as much heat as possible is stored in the fixing unit until the maximum drop temperature on the pressurization side is reached. There is a desire to keep the temperature high. In such a model, when the temperature on the pressure side is high, heat is stored as much as possible by providing a time during which the temperature correction on the heating side is not performed, and after passing through the maximum drop temperature on the pressure side, looking at the temperature on the pressure side By correcting the target temperature on the heating side, power consumption can be suppressed without deteriorating fixability and productivity. In such a model, it is better to provide an exclusion time and not perform the temperature correction of the fixing belt, but correct the temperature after the pressure roller temperature reaches the maximum drop temperature.

  When there is a margin in the pressure roller temperature, the paper interval may be narrowed to increase the CPM (number of output sheets per unit time). By correcting the maximum productivity mode and the target temperature on the heating side, it is possible to select a power saving print mode that suppresses power consumption, thereby improving convenience.

It is preferable that an upper limit value and a lower limit value of the temperature correction value ΔT on the heating side can be set.
That is, when the temperature change on the pressurization side does not affect the heating side linearly and the fixability deteriorates, the temperature correction value ΔT reaches a peak within a range where the fixability can be satisfied. As a result, it is possible to prevent the temperature from being corrected below the minimum temperature required for the heating side.

  When the image forming apparatus includes a unit that can acquire the temperature of the environment in which the image forming apparatus is installed, the pressure reference temperature Ts may be changed according to the environmental temperature obtained from the environmental temperature acquiring unit. . Further, the paper thickness coefficient Cp may be changed according to the acquired environmental temperature. As a result, even if a change occurs in the use environment of the image forming apparatus, it is possible to suppress power consumption while ensuring fixability.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, the number of heaters and heater positions (inside and outside) can be set as appropriate. Moreover, you may have a heating means in the pressurization side. The numerical value of the control DUTY is an example. The number of linear speed switching stages and the linear speed ratio in that case can also be set as appropriate. In addition, the presence or absence of a separation claw or a separation plate is also arbitrary.

  In the image forming apparatus, the configuration of the image forming unit is also arbitrary, and the order of colors in the tandem image forming unit is arbitrary. Configurations other than the tandem method are also possible. Further, the present invention can be applied not only to a color image forming apparatus but also to a monochrome apparatus. Of course, the image forming apparatus is not limited to a printer, and any form such as a copying machine, a facsimile machine, or a multifunction machine having a plurality of functions can be adopted.

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Photoconductor drum 7 Intermediate transfer belt 50 Fixing device 51 Fixing roller 52 Pressure roller 53 Fixing heater 53a Central heater 53b End heater 54 Heating roller 55 Fixing belt 56 Temperature sensor P Recording medium

JP-A-6-337614

Claims (16)

The recording medium holding the unfixed toner image is passed through a fixing nip formed by a fixing member heated by a fixing heater and a pressure member pressed against the fixing member, and the unfixed toner image is fixed to the recording medium. In the fixing device control method,
While determining the target temperature of the next control cycle based on the temperature information obtained from the detecting means for detecting the temperature of the fixing member and controlling the DUTY of the fixing heater,
A fixing control method, wherein a duty factor of the fixing heater is changed when a factor affecting the fixing property changes.   The fixing control method according to claim 1, wherein the factor affecting the fixing property is a change in linear velocity. Using a control for calculating the DUTY of the fixing heater with reference to the past DUTY,
When the line speed is switched, the initial correction DUTY corresponding to the linear speed ratio before and after switching is added to the DUTY that was output one cycle before the line speed is switched, and the first control period after the line speed is switched The fixing control method according to claim 2, wherein the fixing duty is forcibly used as the reference DUTY. The linear velocity before switching is Si, the linear velocity after switching is Sf, the addition ratio Cd, and the heater DUTY before switching is Di,
Heater initial correction DUTY: ΔD is ΔD = Cd (Sf / Si) Di
The fixing control method according to claim 3, wherein the fixing control method is calculated by:   The fixing control method according to claim 1, wherein the factor affecting the fixing property is temperature information obtained from a detection unit that detects the temperature of the pressure member.   The fixing control method according to claim 1, wherein the DUTY of the fixing heater can be set independently for each paper thickness based on paper thickness information indicating the thickness of the recording medium. Cp is the reference temperature Ts on the pressure side during paper passing, the current pressure side temperature Tr, and the correction coefficient for each paper thickness.
Target temperature correction value on the heating side: ΔT is ΔT = Cp (Ts−Tr)
The fixing control method according to claim 1, wherein the fixing control method is calculated by:   The fixing control method according to claim 7, wherein when the Tr is less than the Ts, the number of output sheets per unit time can be reduced by widening a gap between sheets of the recording medium.   9. The apparatus according to claim 5, further comprising an exclusion time during which DUTY control of the fixing heater is not performed based on temperature information obtained from a detection unit that detects a temperature of the pressure member. Fixing control method.   The fixing control method according to claim 5, wherein an upper limit value and a lower limit value of the ΔT can be set.   8. The fixing control method according to claim 7, wherein when the Tr exceeds the Ts, the number of output sheets per unit time can be increased by narrowing a gap between sheets of the recording medium.   If the Tr exceeds Ts, whether to increase the number of output sheets per unit time by narrowing the gap between the recording media, or to correct the heating target temperature based on the Tr to suppress power consumption. The fixing control method according to claim 7, wherein the fixing control method is selectable.   The fixing control method according to claim 7, wherein the Ts can be changed according to an environmental temperature.   The fixing control method according to claim 7, wherein the Cp can be changed according to an environmental temperature.   A fixing device controlled by the fixing control method according to claim 1. An image forming apparatus comprising the fixing device according to claim 15.

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