JP6813330B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming device for fixing a toner image formed on paper.

In recent years, the heat storage effect has been reduced due to the thinning of the fixing roller due to energy saving. Therefore, the surface temperature of the fixing roller becomes unstable during continuous paper passing, and the temperature of the fixing roller may drop during paper passing. In particular, in a state where the fixing member has not sufficiently stored heat, such as immediately after warming up (warming up), there is a problem that the temperature of the fixing roller drops remarkably, which causes deterioration of image quality such as occurrence of fixing failure.

Therefore, it is conceivable to start paper passing after sufficient heat storage during warm-up, but this will increase the waiting time from the start of warm-up to the start of paper passing, and this waiting time will be shortened. It will be a new issue.

In order to deal with this problem, in Patent Document 1, the CPM down rate and the reload determination temperature are determined from the paper size, the paper type, the number of continuous paper sheets, and the temperature of the pressurizing roller, and the processing (paper passing) is started. The fixing device of the configuration is disclosed. Here, CPM (Cop Per Minutes) is the number of sheets to be passed per minute (sheets / minute).

Japanese Unexamined Patent Publication No. 2001-282041

As described above, the surface temperature of the fixing roller is often unstable due to the thinning, and factors other than the judgment factors (paper size, paper type, number of continuous sheets to be passed, temperature of the pressurizing roller) shown in Patent Document 1. It is often affected by. Further, even if the fixing member can sufficiently store heat during paper passing, the processing is performed at a constant CPM, and there is a problem that the printing efficiency is lowered more than necessary.

The present invention was devised to solve such a problem, and an object of the present invention is to gradually confirm the effect of temperature decrease due to paper passing at the start of JOB at a relatively early stage after the start of warm-up. By increasing the CPM, the waiting time from the start of warm-up to the start of JOB can be shortened, and the occurrence of fixing defects due to the temperature drop of the fixing member can be prevented, and a fixing device and an image forming device equipped with the fixing device. Is to provide.

In order to solve the above problems, the fixing device of the present invention is a fixing device that heats the paper sandwiched between the nip portions provided between the fixing member and the pressurizing member to fix the toner image formed on the paper. The fixing member temperature detection unit that detects the temperature of the fixing member, the fixing member temperature determination unit that determines the fixing temperature detected by the fixing member temperature detection unit, and the determination result of the fixing member temperature determination unit. A transfer control unit that controls the transfer of paper to the nip portion is provided based on the above, and at the start of a job, the transfer control unit controls CPM down to increase the paper passing interval from a predetermined paper passing interval. While controlling and executing the job, the CPM down control is performed stepwise from CPM down control having a large CPM down rate to CPM down control having a small CPM down rate based on the determination result of the fixing member temperature determination unit. When the transfer control unit passes a specified number of sheets at a predetermined CPM down rate and the determination result of the fixing member temperature determination unit does not indicate that the fixing temperature is rising. Is characterized in that the CPM down control at the predetermined CPM down rate is executed again .

Further, according to the fixing device of the present invention, after the transfer control unit has passed a predetermined number of sheets at a predetermined CPM down rate, the determination result of the fixing member temperature determination unit indicates that the fixing temperature is rising. If that shows may be configured to migrate to the CPM down control small next stage of C PM-down rate.
It is characterized by being said to be.

Further, the fixing device of the present invention is a fixing device that heats the paper sandwiched between the nip portions provided between the fixing member and the pressurizing member to fix the toner image formed on the paper. Based on the determination results of the fixing member temperature detection unit that detects the temperature of the fixing member, the fixing member temperature determination unit that determines the fixing temperature detected by the fixing member temperature detection unit, and the determination result of the fixing member temperature determination unit. A transfer control unit that controls the transfer of paper to the nip unit is provided, and at the start of the job, the transfer control unit performs CPM down control, which is a control to increase the paper passing interval from a predetermined paper passing interval, to perform a job. Is executed, and the CPM down control is executed while gradually changing from the CPM down control having a large CPM down rate to the CPM down control having a small CPM down rate based on the determination result of the fixing member temperature determination unit. After passing a predetermined number of sheets of paper at a predetermined CPM down rate, the transport control unit has a CPM down rate when the determination result of the fixing member temperature determination unit indicates that the fixing temperature is rising. It is characterized by shifting to the next stage of CPM down control with a small temperature .

Further, the image forming apparatus of the present invention is characterized by including the fixing apparatus having each of the above configurations.

The present invention has a configuration in which the CPM is gradually increased while confirming the effect of the temperature decrease due to paper passing at the start of JOB after the start of warm-up. As a result, it is not necessary to wait for the fixing member to sufficiently store heat and enable high-speed paper passing, so that the waiting time from the start of warm-up to the start of JOB can be shortened. In addition, it is possible to prevent the occurrence of fixing defects due to a decrease in the temperature of the fixing member. Further, by increasing the CPM step by step, the influence of the CPM reduction, that is, the decrease in printing efficiency can be suppressed to the minimum necessary.

It is schematic cross-sectional view of the image forming apparatus provided with the fixing apparatus which concerns on embodiment of this invention as seen from the side. It is the schematic of the fixing device. It is a functional block diagram which shows the electrical structure of an image forming apparatus. It is a chart which shows an example of the CPM down rate of each stage. It is a chart which shows the condition (specified value) for shifting to each stage. It is a flowchart which shows the processing procedure of the CPM down control which concerns on Example 1. FIG. It is a flowchart which shows the processing procedure of the CPM down control which concerns on Example 1. FIG. It is a graph which shows the state of the temperature change (undershoot) of a fixing roller and a pressure roller when the CPM down control by Example 1 is not performed when a job is started at an early stage after the start of warm-up. It is a graph which shows the state of the temperature change (undershoot) of a fixing roller and a pressurizing roller when the CPM down control by Example 1 is performed when a job is started at an early stage after the start of warm-up. It is a flowchart which shows the processing procedure of the CPM down control which concerns on Example 2. It is a flowchart which shows the processing procedure of the CPM down control which concerns on Example 2. It is a flowchart which shows the processing procedure of the CPM down control which concerns on Example 3. FIG. It is a flowchart which shows the processing procedure of the CPM down control which concerns on Example 3. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus including the fixing apparatus according to the embodiment of the present invention as viewed from the side.

The image forming apparatus 1 has a copying function of reading a document and forming an image on paper, and includes an image reading device C, a document conveying device (ADF) B provided above the image reading device C, and an image reading device C. It includes an image forming unit A, a paper feed cassette 10, and a loading tray 15 provided on the lower side.

The document transport device B is supported so as to be openable and closable with respect to the image reading device C. When the document transfer device B is opened, the upper part of the image reading device C is opened so that the document can be placed by hand. Further, the document transporting device B automatically transports the placed document onto the image reading device C. The image reading device C reads the placed document or the document transported from the document transporting device B to generate image data.

In the image forming apparatus 1, image data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (for example, black). Is treated. The image forming unit A is provided with four developing devices 2, a photoconductor drum (image carrier) 3, a drum cleaning device 4, and a charger 5 for forming four types of toner images, each of which is black. , Cyan, magenta, and yellow, and four image stations Pa, Pb, Pc, and Pd are configured.

The drum cleaning device 4 removes and recovers residual toner on the surface of the photoconductor drum 3. The charger 5 uniformly charges the surface of the photoconductor drum 3 to a predetermined potential. The optical scanning device 6 exposes the surface of the photoconductor drum 3 to form an electrostatic latent image. The developing device 2 develops an electrostatic latent image on the surface of the photoconductor drum 3 to form a toner image on the surface of the photoconductor drum 3. By the series of operations described above, toner images of each color are formed on the surface of each photoconductor drum 3.

An intermediate transfer belt 7 is arranged on the upper side of the photoconductor drum 3. The intermediate transfer belt 7 orbits in the direction of arrow D, residual toner is removed and recovered by the belt cleaning device 9, and toner images of each color formed on the surface of each photoconductor drum 3 are sequentially transferred and superposed. Therefore, a color toner image is formed on the surface of the intermediate transfer belt 7.

The transfer roller 11a of the secondary transfer device 11 has a transfer nip portion formed between the transfer roller 11a and the intermediate transfer belt 7, and sandwiches and conveys the paper conveyed through the paper transfer path S in the transfer nip portion. When the paper passes through the transfer nip portion, the toner image on the surface of the intermediate transfer belt 7 is transferred and conveyed to the fixing device 12.

The fixing device 12 includes a fixing roller 34 and a pressure roller 36 that rotate with the paper in between. The fixing device 12 sandwiches the paper on which the toner image is transferred into the fixing nip portion between the fixing roller 34 and the pressure roller 36, heats and pressurizes the paper, and fixes the toner image on the paper. The fixing device 12 will be described in detail later with reference to FIG.

The paper feed cassette 10 is a cassette for storing paper used for image formation, and is provided under the optical scanning device 6. The paper is drawn out from the paper feed cassette 10 by the pickup roller 16, conveyed through the paper conveying path S, and carried out to the loading tray 15 via the paper ejection roller 17 via the secondary transfer device 11 and the fixing device 12. Will be done. In the paper transport path S, the paper is temporarily stopped, the tips of the paper are aligned, and then the paper is aligned with the transfer timing of the color toner image at the transfer nip portion between the intermediate transfer belt 7 and the transfer roller 11a. A registration roller 14, a pre-registration roller 19, a transfer roller 13 for urging the transfer of paper, and a paper discharge roller 17 are arranged.

Further, when forming an image not only on the front surface of the paper but also on the back surface, the paper is conveyed from the paper ejection roller 17 to the reversing path Sr in the opposite direction, the front and back sides of the paper are inverted, and the paper is transferred to the resist roller 14. The image is formed on the back surface in the same manner as on the front surface, and the paper is carried out to the loading tray 15.

FIG. 2 shows a schematic view of the fixing device 12.

The fixing device 12 is composed of a heating roller 31, a fixing roller 34, a pressure roller 36, a fixing belt 33, and the like. The fixing belt 33 is an endless belt, and is stretched between a heating roller 31 and a fixing roller 34. The fixing roller 34 has a fixing nip portion formed by pressurizing the pressure roller 36 from the inner peripheral surface side of the fixing belt 33 via the fixing belt 33 by an elastic member (spring or the like) (not shown). .. By passing the paper on which the unfixed toner image is formed through the fixing nip portion, the toner is melted and pressed against the paper, and the image is fixed on the paper.

The heating roller 31 has a halogen lamp 32 installed as a heating source inside the hollow core metal. Hollow aluminum is used for the core metal, but the material is not limited to this, and may be made of a metal such as iron. Further, in order to efficiently transfer the heat from the heating source inside the core metal to the fixing belt 33, it is preferable to use a core metal having a wall thickness as thin as possible. Further, a mold release layer may be formed on the surface layer of the core metal for the purpose of reducing the frictional force between the fixing belt 33 and the heating roller 31 and reducing the leaning force due to meandering. The material of the release layer may be any material having excellent heat resistance and durability and a low coefficient of friction, such as PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene). You may use a fluoromaterial such as. In the vicinity of the heating roller 31, a fixing member temperature detecting unit 42 composed of a temperature detecting element such as a thermistor that detects the surface temperature of the fixing belt 33 is arranged in contact with the fixing belt 33. However, the fixing member temperature detection unit 42 may be a non-contact type sensor such as a thermocouple temperature sensor or an infrared temperature sensor. The fixing temperature is controlled to a predetermined temperature by controlling ON / OFF of the halogen lamp 32 based on the detection temperature of the fixing member temperature detecting unit 42.

The fixing roller 34 has a heat insulating elastic layer formed on the core metal. Hollow aluminum is used for the core metal, but the material is not limited to this, and may be made of a metal such as iron. Further, a solid core metal may be used. The heat-insulating elastic layer needs to secure a wide nip width in the fixing nip portion and prevent heat from escaping from the inner peripheral surface of the belt. For example, silicon sponge rubber having heat resistance can be used. Although not shown, the fixing roller 34 applies a predetermined load to the pressurizing roller 36 by springs from both ends thereof. As a result, a fixing nip portion is formed between the pressing roller 36 and the fixing belt 33 via the fixing belt 33.

The fixing belt 33 has an elastic layer of, for example, 150 μm and a release layer (PTFE) of, for example, 10 μm formed on a polyimide having an outer diameter of 50 mm and a thickness of 70 μm. However, the thickness and material of the belt are not limited to these, and a metal belt such as Ni, stainless steel, or iron may be used. As the material of the elastic layer, any material having heat resistance and elasticity may be used, and silicon rubber can be used. The material of the release layer may be any material as long as it has excellent heat resistance and durability and excellent releasability with toner, such as PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) and PTFE (poly). Fluorine-based materials such as tetrafluoroethylene) can be used.

In the pressure roller 36, an elastic layer and a release layer are formed on the core metal in this order. Hollow aluminum is used for the core metal, but the material is not limited to this, and may be made of a metal such as iron. As the elastic layer, for example, a silicon rubber having a heat resistance of 1 mm in thickness can be used. The material of the release layer may be any material as long as it has excellent heat resistance and durability and excellent releasability with toner, such as PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE. Fluorine-based materials such as (polytetrafluoroethylene) can be used. Further, in the pressure roller 36, a pressure member temperature detection unit 44 composed of a temperature detection element such as a thermistor that detects the surface temperature of the pressure roller 36 comes into contact with the pressure roller 36 in the vicinity of the fixing nip portion. Is arranged. However, the pressurizing member temperature detection unit 44 may be a non-contact type sensor such as a thermocouple temperature sensor or an infrared temperature sensor.

FIG. 3 is a functional block diagram showing an electrical configuration of the image forming apparatus 1 having the above configuration.

As described above, the image forming apparatus 1 transfers the paper supplied from the paper feeding unit (paper feed cassette 10) to the image forming unit A (particularly, the secondary transfer device) via the paper conveying unit (paper conveying path S). It is configured to be transported to 11 and the fixing device 12).

In addition to the above-mentioned fixing roller 34, pressure roller 36, fixing member temperature detection unit 42, and pressure member temperature detection unit 44, the fixing device 12 includes a transfer control unit 41, a fixing member temperature determination unit 45, and a pressure member temperature determination. It is configured to include a unit 46 and a print rate calculation unit 47. A drive unit (not shown) is connected to the fixing roller 34, and the fixing roller 34 is rotationally driven by the drive unit. The pressurizing roller 36 is driven by the fixing roller 34 to rotate. The halogen lamp 32 is a lamp that heats the fixing roller 34, and is built in the heating roller 31 so that the output is controlled based on the duty ratio. The fixing member temperature detection unit 42 and the pressurizing member temperature detection unit 44 are configured to periodically detect the temperature, and in the present embodiment, the temperature is detected, for example, every 0.2 seconds. For the sake of explanation below, the surface temperature of the fixing roller 34 (more specifically, the fixing belt 33) detected by the fixing member temperature detecting unit 42 is referred to as a fixing surface temperature Tf, and is detected by the pressure member temperature detecting unit 44. The surface temperature of the pressure roller 36 may be referred to as a pressurized surface temperature Tp.

The fixing device 12 includes a CPU 40. The CPU 40 stores the transport control unit 41, the fixing member temperature determination unit 45, the pressurizing member temperature determination unit 46, and the print rate calculation unit 47 as a program incorporated in advance, and by executing the stored program, the CPU 40 stores the program. Execute the process described later. The image forming apparatus 1 may be controlled by the CPU 40. That is, the CPU 40 common to the image forming apparatus 1 and the fixing apparatus 12 may be used.

The fixing member temperature determination unit 45 determines the fixing temperature (fixing surface temperature Tf) detected by the fixing member temperature detection unit 42. The pressurizing member temperature determination unit 46 determines the pressurization temperature (pressurized surface temperature Tp) detected by the pressurizing member temperature detecting unit 44. The print rate calculation unit 47 calculates the print rate of the paper from the received job information.

The transfer control unit 41 controls the transfer of the paper to the fixing nip unit based on the determination results of the fixing member temperature determination unit 45 and / or the pressurizing member temperature determination unit 46. That is, the transfer control unit 41 controls the operations of the resist roller 14, the pre-resist roller 19, the transfer roller 13, and the paper ejection roller 17 to control the start and stop of transfer of the paper.

Further, when the pressurizing temperature detected by the pressurizing member temperature detecting unit 44 at the start of the job is equal to or less than a preset threshold temperature, the transport control unit 41 sets the paper passing interval from a predetermined paper passing interval. The job is executed by performing CPM down control, which is a control for increasing the temperature. The CPM down control at this time is performed in stages from CPM down control having a large CPM down rate to CPM down control having a small CPM down rate based on the determination results of the fixing member temperature determination unit 45 and / or the pressurizing member temperature determination unit 46. It is configured to be executed while changing the target. The CPM down control performed when the job is started immediately after the warm-up is completed will be described in detail later.

In the fixing device 12, the target temperature Tg is instructed by the CPU 40, and the output of the halogen lamp 32, which is a heating source, is controlled so that the fixing surface temperature Tf detected by the fixing member temperature detecting unit 42 approaches the target temperature Tg. .. The target temperature Tg is appropriately changed according to the operation of the image forming apparatus 1. For example, in the standby state in which the operation is stopped, the target temperature Tg is set to a low temperature and the image forming is instructed. , The temperature is set high so that the fixing surface temperature Tf is suitable for image formation.

Next, an example of CPM down control when the job is started immediately after the completion of warm-up, which is a feature of the present invention, will be described.

(Example 1)
In the first embodiment, three stages shown in FIG. 4 are prepared as the down rate of CPM. In this example, the image forming apparatus 1 illustrates a case where the CPM is a high-speed machine of 61 sheets / minute. Then, in stage 1, the CPM down rate is set to 60% (that is, CPM 40% (24 sheets / minute)), and in stage 2, the CPM down rate is set to 40% (that is, CPM 60% (37 sheets / minute)). In stage 3, the CPM down rate is set to 20% (that is, CPM 80% (49 sheets / minute)). However, the number of stages, the down rate at each stage, and the like may be appropriately set to an optimum value by, for example, an experiment, and the above setting example is an example and is not limited to this. Further, in the first embodiment, as shown in FIG. 5, the fixing surface temperature Tf is set as a condition (specified value) for shifting from the stage 1 to the stage 2, from the stage 2 to the stage 3, and from the stage 3 to the normal CPM. And the pressurized surface temperature Tp are set. That is, in stage 1, the fixing surface temperature Tf is set to the target temperature Tg-7 ° C., and the pressurized surface temperature Tp is set to 100 ° C. as specified values. Further, in the stage 2, the fixing surface temperature Tf is set to the target temperature Tg-5 ° C. and the pressurized surface temperature Tp is set to 90 ° C. as specified values. Further, in the stage 3, the fixing surface temperature Tf is set to the target temperature Tg-7 ° C. and the pressurized surface temperature Tp is set to 80 ° C. as specified values. Here, the target temperature Tg of the fixing surface temperature Tf is, for example, 170 ° C. It should be noted that these values are suitable values obtained by experiments and the like with less undershoot of the fixing temperature, but these values differ depending on the model (for example, high-speed machine, medium-speed machine, etc.). , Not limited to the above values.

In the first embodiment, the print rate calculation unit 47 shown in FIG. 3 is not used. That is, in the first embodiment, the print rate calculation unit 47 is not an indispensable constituent requirement.

6A and 6B are flowcharts showing a processing procedure of CPM down control according to the first embodiment. Hereinafter, the CPM down control process of the first embodiment will be described with reference to the flowchart.

When printing (job start) of the job is instructed based on the job data read and saved in the image forming apparatus 1 or the job data transmitted via a communication line (not shown) and saved internally, the transfer is performed. The control unit 41 first determines whether or not the printing of the instructed job is in the color mode (step S1). As a result, when it is not in the color mode (that is, in the monochrome mode: it is determined as No in step S1), the job is executed at the normal CPM (that is, the paper passing interval of 61 sheets / minute) as before (step). S17). That is, in the monochrome mode, since the toner is easily fixed by only one layer, the fixing temperature is extremely lowered (that is, the fixing temperature is large) even if printing is started in a state where the fixing roller 34 does not sufficiently store heat. There is no undershoot), and even if the CPM down control is not performed, the print quality is hardly deteriorated (that is, fixing failure occurs). Therefore, in the monochrome mode, printing is started at a normal CPM as before.

On the other hand, when the printing is in the color mode (when it is determined to be Yes in step S1), the transport control unit 41 then presses the surface temperature (pressurization) of the pressure roller 36 detected by the pressure member temperature detection unit 44. It is confirmed whether or not the temperature) is equal to or lower than the preset threshold value Y ° C. (for example, 120 ° C.) (step S2).

When the image forming apparatus 1 starts the job from the standby state, the fixing roller 34 and the pressurizing roller 36 are sufficiently heated and stored. For example, the fixing roller 34 is heated to 170 ° C., which is the target temperature Tg, and the pressurizing roller 36 is heated to, for example, 120 ° C. or higher. Therefore, the temperature of the pressurizing roller 36 sufficiently exceeds the threshold value Y ° C. On the other hand, when the image forming apparatus 1 starts warming up by turning on the power from the power off state, the detected surface temperature of the pressurizing roller 36 is close to the atmospheric temperature of the installation place, and is naturally equal to or less than the threshold value Y ° C. Therefore, by confirming whether the surface temperature of the pressurizing roller 36 is Y ° C. or lower at the start of the job, whether the image forming apparatus 1 starts the job from the standby state or warms up first in the power off state. It is possible to determine whether to start the job after it has started. It should be noted that this determination may be made not by the surface temperature of the pressurizing roller 36 but by the surface temperature of the fixing roller 34, and the ambient temperature (atmospheric temperature) of the fixing roller 34 and the pressurizing roller 36 is separately provided. It may be detected by a temperature detection sensor and determined based on the detected ambient temperature.

As a result, when the surface temperature of the pressurizing roller 36 exceeds Y ° C. (when it is determined to be Yes in step S2), the job is started from the standby state, so the process proceeds to step S17. The job is executed at a normal CPM (that is, a paper passing interval of 61 sheets / minute) as before.

On the other hand, when the surface temperature of the pressurizing roller 36 does not exceed Y ° C. (when it is determined as No in step S2), the transfer control unit 41 lowers the CPM when the job is started immediately after the warm-up is completed. Control is started (step S3).

That is, the transport control unit 41 first starts the CPM down control under the condition of stage 1 (step S4). That is, the CPM down rate is set to 60% (CPM rate 40% (24 sheets / minute)), and the CPM down control is started.

Then, in the CPM down control in stage 1, it is confirmed whether or not a predetermined number of sheets have been passed through in advance (step S5). Here, the specified number of sheets is an arbitrarily set number of sheets, and is set to, for example, 6 sheets in the first embodiment.

Then, when the specified number of sheets have been passed (if it is determined to be Yes in step S5), the transport control unit 41 then determines whether or not the fixing surface temperature Tf is equal to or higher than the specified value (target temperature Tg-7 ° C.). (Step S6) and whether or not the pressurized surface temperature Tp is equal to or higher than the specified value (100 ° C.) (step S7).

As a result, if any one of them does not exceed the specified value (No in step S6 or No in step S7), the process returns to step S4 and the process of stage 1 is executed again.

On the other hand, when both the fixing surface temperature Tf and the pressurized surface temperature Tp exceed the specified values (when it is determined to be Yes in step S6 and Yes in step S7), the process proceeds to step S8. The transport control unit 41 then starts CPM down control under the condition of stage 2. That is, the CPM down rate is set to 40% (CPM rate 60% (37 sheets / minute)), and the CPM down control is started.

Then, in the CPM down control in the stage 2, it is confirmed whether or not a predetermined number of sheets have been passed through in advance (step S9). Here, the specified number of sheets is an arbitrarily set number, and in the first embodiment, it is set to, for example, five.

Then, when the specified number of sheets have been passed (when it is determined to be Yes in step S9), the transport control unit 41 next determines whether or not the fixing surface temperature Tf is equal to or higher than the specified value (target temperature Tg-5 ° C.). (Step S10) and whether or not the pressurized surface temperature Tp is equal to or higher than the specified value (90 ° C.) (step S11).

As a result, if any one of them does not exceed the specified value (No in step S10 or No in step S11), the process returns to step S8 and the process of stage 2 is executed again.

On the other hand, when both the fixing surface temperature Tf and the pressurized surface temperature Tp exceed the specified values (when it is determined to be Yes in step S10 and Yes in step S11), the process proceeds to step S12. The transport control unit 41 then starts CPM down control under the condition of stage 3. That is, the CPM down rate is set to 20% (CPM rate 80% (48 sheets / minute)), and the CPM down control is started.

Then, in the CPM down control in the stage 3, it is confirmed whether or not a predetermined number of sheets have been passed through in advance (step S13). Here, the specified number of sheets is an arbitrarily set number of sheets, and is set to, for example, 6 sheets in the first embodiment.

Then, when the specified number of sheets have been passed (if it is determined to be Yes in step S13), the transport control unit 41 then determines whether or not the fixing surface temperature Tf is equal to or higher than the specified value (target temperature Tg-7 ° C.). (Step S14) and whether or not the pressurized surface temperature Tp is equal to or higher than the specified value (80 ° C.) (step S15).

As a result, if either one does not exceed the specified value (No in step S14 or No in step S15), the process returns to step S12 and the process of stage 3 is executed again. Become.

On the other hand, when both the fixing surface temperature Tf and the pressurized surface temperature Tp exceed the specified values (when it is determined to be Yes in step S14 and Yes in step S15), the process proceeds to step S16. The transport control unit 41 will continue the subsequent printing at the normal CPM (that is, the CPM down rate is 0%) as before.

7 and 8 show the temperature changes of the fixing roller 34 and the pressurizing roller 36 when the job is started immediately after the warm-up is completed, depending on whether the CPM down control according to the first embodiment is performed or not. It is a graph which shows the state of undershoot). FIG. 7 shows a case where the CPM down control is not performed, and FIG. 8 shows a case where the CPM down control is performed.

As shown in FIG. 7, when the job is started with a normal CPM, for example, 35.5 seconds after the warm-up is completed, the surface temperature of the fixing roller 34 is undershooted (temperature drop). In conjunction with this, undershoot (temperature drop) also occurs in the surface temperature of the pressurizing roller 36. Therefore, from FIG. 7, it can be seen that if the job is started at a normal CPM from a relatively early stage after the start of warm-up, there is a high possibility that fixing failure will occur.

On the other hand, as shown in FIG. 8, when the job is started by performing the CPM down control according to the first embodiment, for example, 31.7 seconds after the completion of the warm-up, the surface temperature of the fixing roller 34 is undershoot (temperature decrease). ), And in conjunction with this, the surface temperature of the pressurizing roller 36 is maintained at around 70 to 80 ° C. without undershooting (temperature drop). Therefore, from FIG. 8, it can be seen that when the CPM down control of the first embodiment is performed and the job is started from a relatively early stage after the warm-up is completed, the fixing defect does not occur. Note that "stage 4" in FIG. 8 means a CPM down rate of 0%, that is, paper passing at normal CPM.

As described above, according to the first embodiment, the JOB is started by the CPM down control after the warm-up, and the CPM down rate is gradually reduced while confirming the influence of the temperature drop (undershoot) due to the paper passing (undershoot). That is, by increasing the CPM to normal), it is not necessary to wait for the fixing member to sufficiently store heat and enable high-speed paper passing, so that the waiting time from the start of warm-up to the start of JOB can be shortened. it can. In addition, it is possible to prevent the occurrence of fixing defects due to a decrease in the temperature of the fixing member. Further, by increasing the CPM step by step, the influence of the CPM reduction, that is, the decrease in printing efficiency can be suppressed to the minimum necessary.

(Example 2)
In the first embodiment, the fixing surface temperature Tf shown in FIG. 5 is used as a condition (specified value) for shifting from stage 1 to stage 2, stage 2 to stage 3, and stage 3 to stage 4 (normal CPM). Although the pressurized surface temperature Tp is set, in the second embodiment, the stage 1 to the stage 2, the stage 2 to the stage 3, and the stage 3 to the stage 4 are set based on the determination result of the fixing member temperature determination unit 45. It is configured to sequentially shift to (normal CPM). In the second embodiment, the print rate calculation unit 47 shown in FIG. 3 is not used. That is, in the second embodiment, the print rate calculation unit 47 is not an indispensable constituent requirement.

9A and 9B are flowcharts showing a processing procedure of CPM down control according to the second embodiment. Hereinafter, the CPM down control process of the second embodiment will be described with reference to the flowchart.

When printing (job start) of the job is instructed based on the job data read and saved in the image forming apparatus 1 or the job data transmitted via a communication line (not shown) and saved internally, the transfer is performed. The control unit 41 first determines whether or not the printing of the instructed job is in the color mode (step S21). As a result, when it is not in the color mode (that is, in the monochrome mode: it is determined as No in step S21), the job is executed at the normal CPM (that is, the paper passing interval of 61 sheets / minute) as before (step). S37).

On the other hand, when the printing is in the color mode (when it is determined to be Yes in step S21), the transport control unit 41 then presses the surface temperature (pressurization) of the pressure roller 36 detected by the pressure member temperature detection unit 44. It is confirmed whether or not the temperature) is equal to or lower than the preset threshold value Y ° C. (for example, 120 ° C.) (step S22).

As a result, when the surface temperature of the pressurizing roller 36 exceeds Y ° C. (when it is determined to be Yes in step S22), the job is started from the standby state, so the process proceeds to step S37. The job is executed at a normal CPM (that is, a paper passing interval of 61 sheets / minute) as before.

On the other hand, when the surface temperature of the pressurizing roller 36 does not exceed Y ° C. (when it is determined as No in step S22), the transfer control unit 41 lowers the CPM when the job is started immediately after the warm-up is completed. Control is started (step S23).

That is, the transport control unit 41 first starts the CPM down control under the condition of stage 1 (step S24). That is, the CPM down rate is set to 60% (CPM rate 40% (24 sheets / minute)), and the CPM down control is started.

Then, in the CPM down control in the stage 1, it is confirmed whether or not a predetermined number of sheets (for example, 6 sheets) has been passed through in advance (step S25).

As a result, when the specified number of sheets have been passed (if it is determined to be Yes in step S25), the transport control unit 41 then determines whether the fixing surface temperature Tf has reached the target temperature Tg (for example, 170 ° C.). (Step S26) is confirmed. That is, the current fixing surface temperature Tf0 detected by the fixing member temperature detecting unit 42 and the target temperature Tg are compared.

As a result, in the case of [Tg−Tf0 ≦ 0] (when it is determined to be Yes in step S26), the surface temperature of the fixing roller 34 has reached the target temperature Tg. In this case, the process proceeds to step S36. And continue the job by returning to the normal CPM (that is, the paper passing interval of 61 sheets / minute) as before.

On the other hand, in the case of [Tg-Tf0> 0] (when No is determined in step S26), the fixing surface temperature Tf has not reached the target temperature Tg. In this case, the fixing member is next. The temperature determination unit 45 determines whether or not the fixing temperature (fixing surface temperature) is rising (step S27).

This determination is made using the current fixing surface temperature Tf0 of the fixing roller 34 detected by the fixing member temperature detecting unit 42 and the previous fixing surface temperature (for example, the temperature one second ago) Tf1.

As a result of the determination, when Tf0-Tf1 ≦ 0 (when it is determined as No in step S27), it is determined that the fixing roller 34 is not yet sufficiently heated and heat is stored, and the process returns to step S24 to perform the stage. The process of 1 is executed again.

On the other hand, as a result of the determination, when Tf0-Tf1> 0 (when it is determined to be Yes in step S27), it can be determined that the temperature of the fixing roller 34 is still rising even after the processing in stage 1 is completed. Then, in this case, the process proceeds to step S28, and the transfer control unit 41 then starts the CPM down control under the condition of stage 2. That is, the CPM down rate is set to 40% (CPM rate 60% (37 sheets / minute)), and the CPM down control is started.

Then, in the CPM down control in the stage 2, it is confirmed whether or not a predetermined number of sheets (for example, 5 sheets) has been passed through in advance (step S29).

As a result, when the specified number of sheets have been passed (if it is determined to be Yes in step S29), the transport control unit 41 then determines whether or not the fixing surface temperature Tf has reached the target temperature Tg (for example, 170 ° C.). (Step S30) is confirmed. That is, the current fixing surface temperature Tf0 detected by the fixing member temperature detecting unit 42 and the target temperature Tg are compared.

As a result, in the case of [Tg−Tf0 ≦ 0] (when it is determined to be Yes in step S30), the surface temperature of the fixing roller 34 has reached the target temperature Tg. In this case, the process proceeds to step S36. And continue the job by returning to the normal CPM (that is, the paper passing interval of 61 sheets / minute) as before.

On the other hand, in the case of [Tg-Tf0> 0] (when No is determined in step S30), the fixing surface temperature Tf has not reached the target temperature Tg. In this case, the fixing member is next. The temperature determination unit 45 determines whether or not the fixing temperature (fixing surface temperature) is rising (step S31). This determination is the same as the determination in step S27.

As a result of the determination, when Tf0-Tf1 ≦ 0 (when it is determined as No in step S31), it is determined that the fixing roller 34 is not yet sufficiently heated and heat is stored, and the process returns to step S28 to perform the stage. The process of 2 is executed again.

On the other hand, as a result of the determination, when Tf0-Tf1> 0 (when it is determined to be Yes in step S31), it can be determined that the temperature of the fixing roller 34 is still rising even after the processing in the stage 2 is completed. Then, in this case, the process proceeds to step S32, and the transfer control unit 41 then starts the CPM down control under the condition of the stage 3. That is, the CPM down rate is set to 20% (CPM rate 80% (49 sheets / minute)), and the CPM down control is started.

Then, in the CPM down control in the stage 3, it is confirmed whether or not a predetermined number of sheets (for example, 6 sheets) has been passed through in advance (step S33).

As a result, when the specified number of sheets have been passed (if it is determined to be Yes in step S33), the transport control unit 41 then determines whether the fixing surface temperature Tf has reached the target temperature Tg (for example, 170 ° C.). (Step S34) is confirmed. That is, the current fixing surface temperature Tf0 detected by the fixing member temperature detecting unit 42 and the target temperature Tg are compared.

As a result, in the case of [Tg−Tf0 ≦ 0] (when it is determined to be Yes in step S34), the surface temperature of the fixing roller 34 has reached the target temperature Tg. In this case, the process proceeds to step S36. And continue the job by returning to the normal CPM (that is, the paper passing interval of 61 sheets / minute) as before.

On the other hand, in the case of [Tg-Tf0> 0] (when No is determined in step S34), the fixing surface temperature Tf has not reached the target temperature Tg. In this case, the fixing member is next. The temperature determination unit 45 determines whether or not the fixing temperature (fixing surface temperature) is rising (step S35). This determination is the same as the determination in steps S27 and S31.

As a result of the determination, when Tf0-Tf1 ≦ 0 (when it is determined as No in step S35), it is determined that the fixing roller 34 is not yet sufficiently heated and heat is stored, and the process returns to step S32 to perform the stage. The process of 3 is executed again.

On the other hand, as a result of the determination, when Tf0-Tf1> 0 (when it is determined to be Yes in step S35), it is determined that the temperature of the fixing roller 34 is still rising even after the processing in the stage 3 is completed. Then, in this case, the process proceeds to step S36, and the transfer control unit 41 performs the subsequent transfer control with the normal CPM (that is, the CPM down rate is 0%) as before.

As described above, according to the second embodiment, the JOB is started by the CPM down control after the warm-up, and the CPM down rate is gradually reduced while confirming the influence of the temperature drop (undershoot) due to the paper passing (undershoot). That is, by increasing the CPM to normal), it is not necessary to wait for the fixing member to sufficiently store heat and enable high-speed paper passing, so that the waiting time from the start of warm-up to the start of JOB can be shortened. it can. In addition, it is possible to prevent the occurrence of fixing defects due to a decrease in the temperature of the fixing member. Further, by increasing the CPM step by step, the influence of the CPM reduction, that is, the decrease in printing efficiency can be suppressed to the minimum necessary.

(Example 3)
In the first embodiment, the fixing surface temperature Tf shown in FIG. 5 is used as a condition (specified value) for shifting from stage 1 to stage 2, stage 2 to stage 3, and stage 3 to stage 4 (normal CPM). The pressurized surface temperature Tp is set. In the third embodiment, the processing in each stage is the same as in the first embodiment, but in the third embodiment, the stages 1 and 2 are based on the print rate calculated by the print rate calculation unit 47 after the start of warm-up. , The stage corresponding to the print rate is selected from the stages 3, and the CPM down control is started from that stage to execute the job. That is, in the third embodiment, the print rate calculation unit 47 shown in FIG. 3 is an indispensable constituent requirement.

As described above, if the job is started when the fixing roller 34 immediately after the warm-up is completed and the heat is not sufficiently stored, the fixing temperature drops (undershoots), but the effect of the temperature drop is printed. It is possible to predict to some extent from the rate information. That is, when the amount of fixing toner is large (when the printing rate is high), the fixing temperature inevitably drops significantly, and when the amount of fixing toner is low (when the printing rate is low), the drop in fixing temperature is relatively small. Therefore, when the printing rate is low, there is almost no effect even if the job is executed as it is with a normal CPM. Therefore, in the third embodiment, in consideration of this point, the CPM down control is performed when the job is started immediately after the warm-up is completed.

10A and 10B are flowcharts showing a processing procedure of CPM down control according to the third embodiment. Hereinafter, the CPM down control process of the third embodiment will be described with reference to the flowchart.

When printing (job start) of the job is instructed based on the job data read and saved in the image forming apparatus 1 or the job data transmitted via a communication line (not shown) and saved internally, the transfer is performed. First, the control unit 41 determines whether or not the printing of the instructed job is in the color mode (step S41). As a result, when it is not in the color mode (that is, in the monochrome mode: it is determined as No in step S41), the job is executed at the normal CPM (that is, the paper passing interval of 61 sheets / minute) as before (step). S48).

On the other hand, when the printing is in the color mode (when it is determined to be Yes in step S41), the transfer control unit 41 then presses the surface temperature (pressurization) of the pressure roller 36 detected by the pressure member temperature detection unit 44. It is confirmed whether or not the temperature) is equal to or lower than the preset threshold value Y ° C. (for example, 120 ° C.) (step S42).

As a result, when the surface temperature of the pressurizing roller 36 exceeds Y ° C. (when it is determined to be Yes in step S42), the job is started from the standby state, so the process proceeds to step S48. The job is executed at a normal CPM (that is, a paper passing interval of 61 sheets / minute) as before.

On the other hand, when the surface temperature of the pressurizing roller 36 does not exceed Y ° C. (when No is determined in step S42), the transfer control unit 41 lowers the CPM when the job is started immediately after the warm-up is completed. Control is started (step S43).

That is, the transport control unit 41 calculates the printing rate of the paper based on the job data stored inside (step S44). The printing rate is the printing area of the toner (that is, the average printing area per page obtained by dividing the printing area of all pages by the number of pages, or when calculating the printing rate for each page, the toner is included in one page. It can be obtained by dividing (the area where the toner is attached) B by the area A of the paper used for printing.

However, when calculating the print rate for each page, if there is an image with a high print rate for each fixed number of sheets while executing a plurality of sheets job, the maximum print rate is assigned to each stage. For example, when the number of sheets judged in one stage is 5, the printing rate of the first sheet is 20%, the printing rate of the second and third sheets is 80%, and the printing rate of the fourth and fifth sheets is If it is 40%, the highest printing rate of 80% is applied as the printing rate.

Here, in the third embodiment, three print rates (print rate 1, print rate 2, print rate 3) corresponding to the stages 1, 2, and 3 are set in advance. Specifically, the print rate 1 is set to a high value of 70% or more, the print rate 2 is set to a print rate of 40 to 69%, and the print rate 3 is set to a high value. The print rate is set in the range of 20 to 39%. Therefore, the transport control unit 41 compares the calculated print rate with the preset print rates 1, 2, and 3.

As a result, when the calculated print rate is the print rate 1 (that is, 70% or more) (when it is determined to be Yes in step S45), the transfer control unit 41 controls the CPM down under the condition of stage 1. Is started (step S4). That is, when the printing rate is 70% or more, it is considered that the temperature drop of the fixing roller 34 due to the fixing operation is large. In this case, the CPM down control is started from the stage 1 having the largest CPM down rate. And run the job.

Since the processing after stage 1 is the same as the processing of steps S4 to S16 of the first embodiment, the same step numbers are assigned to the same steps here, and detailed description thereof will be omitted.

On the other hand, when the calculated print rate is a print rate of 2 (that is, a value in the range of 40 to 69%) (when it is determined as No in step S45 and Yes in step S46), the transfer control unit. 41 proceeds to step S8 and starts CPM down control under the condition of stage 2. That is, in this case, since the temperature drop of the fixing roller 34 due to the fixing operation is smaller than that in the case of the printing rate 1, it is determined that the fixing failure does not occur even if the stage 1 is skipped, and the CPM down control is started from the stage 2. And run the job.

On the other hand, when the calculated print rate is a print rate of 3 (that is, a value within the range of 20 to 39%) (when it is determined that No in step S45, No in step S46, and Yes in step S47). The transport control unit 41 proceeds to step S12 and starts CPM down control under the condition of stage 3. That is, in this case, since the temperature drop of the fixing roller 34 due to the fixing operation is smaller than that in the case of the printing rate 2, it is judged that the fixing failure does not occur even if the stage 1 and the stage 2 are skipped, and the CPM from the stage 3 Start down control and execute the job.

On the other hand, when the calculated printing rate does not correspond to any of the printing rates 1 to 3 (that is, the printing rate is 20% or less) (when it is determined as No in step S47), the fixing is performed by the fixing operation. Since it is considered that the temperature drop of the roller 34 is not enough to cause fixing failure, in this case, the process proceeds to step S48, and the normal CPM (that is, 61 sheets / minute paper passing interval) is continued as before. Run the job with.

As described above, according to the third embodiment, even if the warm-up is not completed, the JOB is started by the CPM down control after the warm-up, and the effect of the temperature drop (undershoot) due to the paper passing is confirmed stepwise. By reducing the CPM down rate (that is, increasing it to normal CPM), it is not necessary to wait for the fixing member to sufficiently store heat and enable high-speed paper passing, so JOB from the start of warm-up. The waiting time until the start can be shortened. In addition, it is possible to prevent the occurrence of fixing defects due to a decrease in the temperature of the fixing member. Furthermore, during CPM down control, by selecting the stage of the CPM down rate that starts according to the print rate, it is possible to shift to the normal CPM printing operation at an earlier stage while preventing the fixing temperature from undershooting. Therefore, the influence of CPM down, that is, the decrease in printing efficiency can be suppressed to the minimum necessary.

The fixing device of the present embodiment is a fixing device that heats the paper sandwiched between the nip portions provided between the fixing member and the pressurizing member to fix the toner image formed on the paper. A fixing member temperature detection unit that detects the temperature of the fixing member, a pressure member temperature detection unit that detects the temperature of the pressurizing member, and a fixing member temperature determination that determines the fixing temperature detected by the fixing member temperature detection unit. Based on the determination results of the section, the pressurizing member temperature determining section for determining the pressurizing temperature detected by the pressurizing member temperature detecting section, the fixing member temperature determining section and / or the pressurizing member temperature determining section. A transfer control unit that controls the transfer of paper to the nip portion is provided, and at the start of a job, the transfer control unit performs CPM down control, which is a control for increasing the paper passing interval from a predetermined paper passing interval. In addition to executing the job, the CPM down control changes from a CPM down control having a large CPM down rate to a small CPM down rate based on the determination results of the fixing member temperature determination unit and / or the pressurizing member temperature determination unit. It is configured to execute while changing the CPM down control step by step.
Further, according to the fixing device of the present embodiment, the transport control unit passes a predetermined number of sheets at a predetermined CPM down rate, and then the fixing member temperature determination unit and the pressurizing member temperature determination unit. If the determination result does not exceed at least one of the preset fixing member specified temperature and the pressure member specified temperature, the CPM down control at the predetermined CPM down rate may be executed again. ..
Further, according to the fixing device of the present embodiment, the transport control unit passes a predetermined number of sheets at a predetermined CPM down rate, and then the fixing member temperature determination unit and the pressurizing member temperature determination unit. If the determination result exceeds the specified temperature of the fixing member and the specified temperature of the pressurizing member, the configuration may shift to the CPM down control of the next stage in which the CPM down rate is small.
Further, the fixing device of the present embodiment is a fixing device that heats the paper sandwiched between the nip portions provided between the fixing member and the pressure member to fix the toner image formed on the paper. , A fixing member temperature detection unit that detects the temperature of the fixing member, a pressure member temperature detection unit that detects the temperature of the pressurizing member, and a fixing member that determines the fixing temperature detected by the fixing member temperature detection unit. A temperature determination unit, a pressurizing member temperature determination unit that determines the pressurization temperature detected by the pressurizing member temperature detection unit, a print rate calculation unit that calculates a paper print rate from received job information, and the fixing. A transfer control unit that controls the transfer of paper to the nip portion based on the determination result of the member temperature determination unit is provided, and at the start of the job, the transfer control unit sets the paper passing interval from a predetermined paper passing interval. The job is executed by performing CPM down control, which is a control for increasing, and the CPM down control changes from a CPM down control having a large CPM down rate to a small CPM down rate based on the determination result of the fixing member temperature determination unit. When the CPM down control is executed while changing to a plurality of stages, the CPM of the CPM down rate corresponding to the print rate is selected from the multiple stages of the CPM down control based on the print rate calculated by the print rate calculation unit. The configuration is such that the job is executed from the down control.
Further, according to the fixing device of the present embodiment, the transport control unit passes a predetermined number of sheets at a predetermined CPM down rate, and then the fixing member temperature determination unit and the pressurizing member temperature determination unit. If the determination result does not exceed at least one of the preset fixing member specified temperature and the pressurizing member specified temperature, the CPM down control at the predetermined CPM down rate may be executed again. ..
Further, according to the fixing device of the present embodiment, the transport control unit passes a predetermined number of sheets at a predetermined CPM down rate, and then the fixing member temperature determination unit and the pressurizing member temperature determination unit. If the determination result exceeds the specified temperature of the fixing member and the specified temperature of the pressurizing member, the configuration may shift to the CPM down control of the next stage in which the CPM down rate is small.
Further, according to the fixing device of the present embodiment, the fixing temperature is the surface temperature of the fixing member, and the pressurizing temperature is the surface temperature of the pressing member.
It should be noted that the embodiments disclosed this time are examples in all respects and do not serve as a basis for limited interpretation. Therefore, the technical scope of the present invention is not construed solely by the above-described embodiments, but is defined based on the description of the claims. It also includes all changes within the meaning and scope of the claims.

1 Image forming device A Image forming unit B Document transfer device (ADF)
C Image reader S Paper transport section (paper transport path)
10 Paper cassette 12 Fixing device 15 Loading tray 31 Heating roller 32 Halogen lamp (heating source)
33 Fixing belt (fixing member)
34 Fixing roller (fixing member)
36 Pressurized roller (pressurized member)
40 CPU
41 Transport control unit 42 Fixing member temperature detection unit 44 Pressurizing member temperature detection unit 45 Fixing member temperature determination unit 46 Pressurization member temperature determination unit 47 Printing rate calculation unit

Claims (4)

A fixing device that heats the paper sandwiched between the nip portions provided between the fixing member and the pressure member to fix the toner image formed on the paper.
A fixing member temperature detection section for detecting a temperature of said fixing member,
A fixing member temperature determination unit that determines the fixing temperature detected by the fixing member temperature detection unit,
A transfer control unit that controls the transfer of paper to the nip unit based on the determination result of the fixing member temperature determination unit is provided.
At the start of the job, the transport control unit executes the job by performing CPM down control, which is a control for increasing the paper passing interval from the predetermined paper passing interval.
The CPM down control is executed while stepwise changing from CPM down control having a large CPM down rate to CPM down control having a small CPM down rate based on the determination result of the fixing member temperature determination unit .
After passing a predetermined number of sheets of paper at a predetermined CPM down rate, the transport control unit performs the predetermined CPM when the determination result of the fixing member temperature determination unit does not indicate that the fixing temperature is rising. A fixing device characterized in that CPM down control at a down rate is executed again . The fixing device according to claim 1.
After passing a predetermined number of sheets of paper at a predetermined CPM down rate, the transport control unit determines the CPM down rate when the determination result of the fixing member temperature determination unit indicates that the fixing temperature is rising. A fixing device characterized by shifting to a small next-stage CPM down control. A fixing device that heats the paper sandwiched between the nip portions provided between the fixing member and the pressure member to fix the toner image formed on the paper.
A fixing member temperature detection unit that detects the temperature of the fixing member,
A fixing member temperature determination unit that determines the fixing temperature detected by the fixing member temperature detection unit,
A transfer control unit that controls the transfer of paper to the nip unit based on the determination result of the fixing member temperature determination unit is provided.
At the start of the job, the transport control unit executes the job by performing CPM down control, which is a control for increasing the paper passing interval from the predetermined paper passing interval.
The CPM down control is executed while stepwise changing from CPM down control having a large CPM down rate to CPM down control having a small CPM down rate based on the determination result of the fixing member temperature determination unit.
After passing a predetermined number of sheets of paper at a predetermined CPM down rate, the transport control unit determines the CPM down rate when the determination result of the fixing member temperature determination unit indicates that the fixing temperature is rising. A fixing device characterized by shifting to a small next-stage CPM down control. An image forming apparatus including the fixing apparatus according to any one of claims 1 to 3 .

Images