JP2018141959A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can prevent the occurrence of an image defect and can appropriately issue a warning for the life of a fixing unit, even when a difference in heat transfer occurs due to wear of a surface layer of a fixing member, such as a fixing film and when a variation in hardness of a pressure member occurs.SOLUTION: An image forming apparatus prints an image on a recording material, and comprises: a fixing unit that fixes the image formed on the recording material to the recording material; a temperature sensor that detects the temperature of a rotating body of the fixing unit; a wear amount acquisition part that acquires the amount of wear of a surface layer of the rotating body according to a detected temperature; and a control temperature setting part that sets a control temperature for a heater according to the amount of wear.SELECTED DRAWING: Figure 3

Description

  The present invention is an image forming apparatus adopting an image forming process such as an electrophotographic system or an electrostatic recording system, such as a copying machine or an LBP, and uses an unfixed toner image formed and supported on a recording material as a recording material. The present invention relates to an image forming apparatus including a heat fixing unit for heat fixing.

As a heat fixing unit (hereinafter, referred to as a fixing unit), for example, as described in Patent Document 1, there is a film heating type fixing unit excellent in rising of a heater from a sleep state. A film heating type fixing unit forms a fixing nip portion with a heater as a heating source and a pressure roller via a cylindrical fixing film. Since the fixing unit having this configuration can easily realize a reduction in heat capacity and a reduction in diameter, the fixing unit can be started up to a fixable state with less power.
Further, Patent Document 2 proposes a configuration in which a foamed rubber layer made of a sponge material or a balloon material is used as a rubber layer of the pressure roller as a configuration that further suppresses energy input to the fixing unit. By adopting these structures, the heat insulation effect in the thickness direction of the pressure roller is enhanced, so the amount of heat transferred from the heater to the pressure roller can be suppressed, and the heat energy of the heater can be used more efficiently. .
On the other hand, a configuration has been proposed in which the energy saving property is further improved by increasing the thermal conductivity of each component member in the path through which the thermal energy from the heater is transmitted to the toner on the recording material. For example, in the above-described film heating type fixing unit, an effect of lowering the control temperature of the heater can be obtained by using a material having higher thermal conductivity for the base layer or rubber layer of the fixing film.

JP-A-4-204980 JP 2002-148988 A

As described above, as the heat capacity of the entire fixing unit is reduced and the heat conductivity of the member is increased, the deterioration of the printing quality due to the wear of the surface layer of the fixing film and the change in the hardness of the pressure roller has become a problem. .
To shorten the thermal start-up time of the fixing unit, it is necessary to improve heat conduction or reduce the heat capacity. For this purpose, it is necessary to reduce the thickness of the heat transfer portion. However, if the heat transfer part is a frictional sliding part like a fixing film, the heat transfer method may change greatly depending on the degree of wear, and the situation where the original performance cannot be achieved may occur. is there.
For the surface layer of the fixing film, PFA or PTFE, which is a heat-resistant resin having good releasability, is used in order to prevent toner adhesion. However, these resins are difficult to conduct heat, and their thickness greatly affects the performance of the fixing unit.
When the surface layer of the fixing film is worn, the heat from the heater is more easily transmitted to the toner and the recording material. As a result, problems such as occurrence of hot offset and deterioration of paper curl after the fixing process occur. Further, depending on the paper type of the recording material, paper wrinkles may occur.
In addition, if the heat supply becomes excessive, the recording material contracts in the longitudinal direction of the fixing nip portion in the fixing nip portion. As a result, a drape (pleat) -like undulation is generated in the portion of the recording material before entering the fixing nip portion, and the portion may enter the fixing nip portion to cause paper wrinkling.
On the other hand, the pressure roller undergoes repeated stress due to heating and rotation, so that the rubber material deteriorates and the hardness decreases.
Problems such as hot offset and curling of the recording material occur not only when the surface layer of the fixing film is thin, but also when the hardness of the pressure roller is low. When the hardness of the pressure roller decreases, the width of the fixing nip portion in the recording material conveyance direction increases and the time for heating the recording material increases. This is because the heat supply to the toner and paper increases, resulting in excessive heat supply.

In order to deal with these problems, it is conceivable to change the fixing conditions in accordance with the usage status of the apparatus. For example, the conditions such as the control temperature are changed by a predetermined number.
However, the actual degree of wear varies depending on the use conditions. In some cases, the wear of the fixing film or the decrease in the hardness of the pressure roller progresses earlier than expected, and in this case, the above-described problem occurs. On the other hand, when the wear of the fixing film or the decrease in the hardness of the pressure roller does not progress more than expected, a problem due to insufficient heat supply occurs. For example, there is a paper jam due to poor fixing or toner accumulation in the fixing unit.
Also, the difference in the degree of wear of the fixing film and the degree of change in the hardness of the pressure roller depending on the use conditions affects the timing of issuing a life warning in addition to the problem of print quality.
The life of the fixing unit varies depending on the degree of wear of the fixing film and the degree of hardness reduction of the pressure roller. In the method of warning the life of the fixing unit using information such as the total number of printed sheets, the total driving time, and the total number of rotations, the fixing unit reaches the end of its life before issuing a warning. May cause a life warning.
An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of image defects even when a difference in heat transfer occurs due to wear of a surface layer of a fixing member such as a fixing film or when a hardness variation of a pressure member occurs. Is to provide.
It is another object of the present invention to provide an image forming apparatus capable of appropriately performing a life warning.

In order to achieve the above object, the present invention provides:
In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member having a surface layer, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and the rotating member A fixing unit having a heater for heating
A temperature sensor for detecting the temperature of the rotating body;
A wear amount acquisition unit that acquires the wear amount of the surface layer of the rotating body, and a wear amount acquisition unit that acquires the wear amount according to a temperature detected by the temperature sensor;
A control temperature setting unit for setting the control temperature of the heater according to the wear amount;
It is characterized by providing.

In addition, other inventions
In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member having a surface layer, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and the rotating member A fixing unit having a heater for heating
A temperature sensor for detecting the temperature of the rotating body;
A wear amount acquisition unit that acquires the wear amount of the surface layer of the rotating body, and a wear amount acquisition unit that acquires the wear amount according to a temperature detected by the temperature sensor;
A life calculation unit for calculating the life of the rotating body according to the wear amount;
It is characterized by providing.
In addition, other inventions
In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and heats the rotating member. A fixing unit having a heater;
A temperature sensor for detecting the temperature of the pressure member;
A hardness change amount acquisition unit for acquiring a hardness change amount of the pressure member, and a hardness change amount acquisition unit for acquiring the hardness change amount according to a detection temperature of the temperature sensor;
A control temperature setting unit for setting the control temperature of the heater according to the amount of change in hardness;
It is characterized by providing.
In addition, other inventions
In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and heats the rotating member. A fixing unit having a heater;
A temperature sensor for detecting the temperature of the pressure member;
A hardness change amount acquisition unit for acquiring a hardness change amount of the pressure member, and a hardness change amount acquisition unit for acquiring the hardness change amount according to a detection temperature of the temperature sensor;
A life calculation unit for calculating the life of the pressure member according to the hardness change amount;
It is characterized by providing.

  According to the present invention, even when a difference in heat transfer occurs due to wear of the surface layer of the fixing member, or when the hardness variation of the pressure member occurs, the occurrence of image defects is prevented, and a life warning is appropriately provided. It can be carried out.

1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic configuration diagram of a heat fixing unit. The schematic block diagram showing a heat fixing unit and a temperature sensor. FIG. 6 is a diagram illustrating member temperatures in continuous paper passing according to the first exemplary embodiment. FIG. 4 is a diagram illustrating member temperature in the case of intermittent paper feeding in the first embodiment. The figure which shows the relationship between the surface temperature of a fixing film, and the amount of wear. The figure which shows the relationship between the surface film thickness of a fixing film, and control temperature. The figure which shows the relationship between the surface temperature of a pressure roller, and hardness variation | change_quantity. The figure which shows the relationship between the surface temperature of a pressure roller, and hardness variation | change_quantity. The figure which shows the relationship between the usage time of a pressure roller, and hardness change. FIG. 3 is a schematic configuration diagram of an image forming apparatus according to a second embodiment. FIG. 2 is a schematic configuration diagram of a heat fixing unit. FIG. 6 is a diagram for explaining a member temperature when a sheet is passed in the second embodiment. The figure which shows the relationship between the surface film thickness of a fixing film, and control temperature. FIG. 3 is a diagram illustrating member temperatures in the case of continuous paper passing in the first embodiment. FIG. 4 is a diagram illustrating member temperatures in the case of intermittent paper feeding in the first embodiment. FIG. 3 is an explanatory diagram of member temperature of intermittent paper having a long interval in the first embodiment. FIG. 6 is a diagram illustrating member temperature in the case of continuous paper passing according to the second embodiment. FIG. 6 is a diagram for explaining member temperatures in the case of intermittent paper feeding in the second embodiment. Explanatory drawing of the member temperature of intermittent paper with a long space | interval in Example 2. FIG.

Hereinafter, the present invention will be described in detail based on illustrated embodiments. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention only to them.
[Example 1]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1 of the present invention.
(1) Description of Image Forming Apparatus In the figure, reference numeral 1 denotes a photosensitive drum, and a photosensitive material such as OPC, amorphous Se, or amorphous Si is formed on an aluminum cylinder. The photosensitive drum 1 is rotationally driven in the direction of the arrow. First, the surface is uniformly charged by a charging roller 2 as a charging device. Next, the photosensitive drum 1 is subjected to scanning exposure by the laser light L which is ON / OFF controlled according to image information from the laser scanner 3, and an electrostatic latent image is formed on the photosensitive drum 1. This electrostatic latent image is developed and visualized by the developing device 4.
The visualized toner image is transferred onto the recording material P by a voltage applied to a transfer roller 5 as a transfer device. Here, in order to match the image forming position of the toner image on the photosensitive drum 1 and the position of the recording material, the top sensor 8 detects the leading edge of the recording material, and the recording material conveyance timing is adjusted. The recording material P conveyed at a predetermined timing is nipped and conveyed between the photosensitive drum 1 and the transfer roller 5. The recording material P onto which the toner image has been transferred is conveyed to the fixing unit 6 and the toner image is fixed on the recording material as a permanent image.
On the other hand, residual toner remaining on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the cleaning device 7. A paper discharge sensor 9 provided in the fixing unit 6 is a sensor for detecting when a recording material causes a paper jam or the like between the top sensor 8 and the paper discharge sensor 9.

(2) Description of Fixing Unit 6 2-1) Cross-sectional Configuration of Fixing Unit Next, the fixing unit 6 will be described.
FIG. 2 is a schematic diagram showing a cross-sectional configuration of the central portion in the longitudinal direction of the fixing unit 6 representing the present embodiment.
The fixing unit 6 includes a heating unit 10 including a heater 11 as a heating source, a cylindrical fixing film (fixing rotator) 13, and a pressure roller 20 as a pressure member. . A fixing nip portion N is formed by pressing the heater 11 and the pressure roller 20 with a predetermined pressure through the fixing film 13. By heating while passing the recording material P carrying the unfixed toner image in the fixing nip N, the toner image is fixed on the recording material.
The heating unit 10 mainly includes a fixing film 13, a heater 11, a heat insulating holder 12 that holds the heater 11, a metal stay 14, and the like. The metal stay 14 receives pressure from a spring (not shown) and presses the heat insulating holder 12 toward the pressure roller 20.
The heater 11 is a low heat capacity plate-shaped member and is in contact with the inner surface of the fixing film 13. The heater 11 has an insulating ceramic substrate such as alumina or aluminum nitride. A heating resistance layer using a material such as Ag / Pd (silver palladium), RuO ₂ or Ta ₂ N is formed on the surface of the substrate along the longitudinal direction of the substrate by a printing technique such as screen printing. As shown in the figure, a protective layer 11a such as a glass layer that protects the heating resistance layer is provided on the surface where the heater 11 is in contact with the fixing film 13, as long as thermal efficiency is not impaired. The heat insulating holder 12 that holds the heater 11 is formed of a heat-resistant resin such as liquid crystal polymer, phenol resin, PPS, or PEEK, and also has a role of guiding the rotation of the fixing film 13.

The base layer of the fixing film 13 is a heat resistant film having a total thickness of 200 μm or less. By reducing the thickness (decreasing the heat capacity), it is possible to start up to a temperature at which fixing is possible in a short time. The fixing film 13 has a base layer made of a heat-resistant resin such as polyimide, polyamideimide, PEEK, or a pure metal or alloy such as SUS (steel use stainless), Al, Ni, Cu, Zn having heat resistance and high thermal conductivity. ing. On the other hand, in order to construct a long-life fixing unit, it is necessary to form a base layer having sufficient strength and excellent durability. For this reason, the base layer of the fixing film 13 needs to have a thickness of 20 μm or more. Therefore, the thickness of the base layer of the fixing film 13 is optimally 20 μm or more and 200 μm or less.
Further, in order to prevent offset and ensure separation of the recording material, the surface layer of the fixing film 13 is made of PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene hexa). Good releasability of fluororesin such as fluoropropylene copolymer), ETFE (ethylene tetrafluoroethylene copolymer), CTFE (polychlorotrifluoroethylene), PVDF (polyvinylidene fluoride), silicone resin, etc. A heat resistant resin is coated or mixed alone.
Further, a silicone rubber layer having a thickness of about 100 μm to 300 μm may be formed between the surface layer and the base layer as an intermediate rubber layer. By forming the intermediate rubber layer, the surface of the fixing film 13 can easily follow the unevenness of the surface of the recording material and the unevenness of the toner image, and it is possible to provide good image quality.

The pressure roller 20 is an elastic roller in which an elastic layer 22 is formed on the outer side of a metal core 21 made of SUS, SUM (steel use machinery), Al or the like, and a surface layer as shown in the drawing. 23 may be formed.
The elastic layer 22 is an elastic solid rubber layer formed of heat-resistant rubber such as silicone rubber or fluorine rubber, or a sponge rubber layer formed by foaming silicone rubber to provide a more heat-insulating effect, or hollow in the silicone rubber layer. A foam rubber layer or the like in which a filler (such as a microballoon) is dispersed and a gas portion is provided in the fired cured product to enhance the heat insulation effect.
For the surface layer 23, PFA, PTFE or the like is used.
Further, the pressure roller 20 obtains a driving force that rotates in the direction of the arrow in FIG. 2 via a driving gear (not shown) provided at the end of the cored bar 21. The driving force is transmitted from a motor (not shown) according to a command from a CPU (not shown) that controls the control means. As the pressure roller 20 is driven to rotate, the fixing film 13 is driven to rotate by a frictional force with the pressure roller 20. By interposing a lubricant such as fluorine-based or silicone-based heat resistant grease between the fixing film 13 and the heater 11, the frictional resistance can be kept low and the fixing film 13 can be smoothly rotated.
A thermistor 15 as a temperature sensor is provided on the back surface of the ceramic substrate. In accordance with a signal from the thermistor 15, the CPU controls the duty ratio of the electric power supplied to the heater 11 so that the heater 11 maintains the control temperature. Thereby, the temperature in the fixing nip N can be maintained at a desired temperature. The temperature sensor is not limited to the thermistor, and various sensors can be applied.
The fixing unit 6 includes a storage medium (NVRAM) serving as a storage unit or a storage unit. This storage medium 33 communicates with the CPU and stores the operating status of the fixing unit.
The product specification of the first embodiment is an image forming apparatus capable of printing 60 sheets per minute and printing A4 size by vertical feeding. The paper conveyance speed in the apparatus is 400 mm / second. The fixing film 13 and the pressure roller 20 that are in contact with the recording material P also rotate at the same peripheral speed as the paper conveyance speed. Further, the fixing unit 6 is replaceable with respect to the image forming apparatus, and is set to be replaced after printing 150k sheets (150,000 sheets).

Next, specific examples of each component in the fixing unit 6 are shown below.
The fixing film 13 has an outer diameter of 30 mm. The base layer is made of PI having a thickness of 60 μm, and carbon fiber is dispersed in order to improve heat conduction. On top of this, a silicone rubber layer having a thickness of 250 μm is provided as an elastic layer. The surface layer is a PFA layer having a thickness of 20 μm, and a tube made of PFA is covered with a silicone rubber layer.
The pressure roller 20 has an outer diameter of 30 mm. The core metal 21 is made of iron having an outer diameter of 23 mm, a solid silicone rubber layer having a thickness of about 3.5 mm is formed thereon as an elastic layer 22, and a PFA tube having a thickness of 50 μm is coated as the surface layer 23.
The pressure roller 20 is molded such that the hardness measured when the Asker C hardness meter is brought into contact with the surface (that is, the surface layer 23) with a load of 1 kg is 55 °. The hardness of the silicone rubber layer at this time is 17 ° under the same measurement conditions as described above.
The pressure applied between the pressure roller 20 and the fixing film 13 is 15 kgf.

2-2) Description of Temperature Sensor for Detecting Surface Temperature of Fixing Film 13 and Pressure Roller 20 FIG. 3 is a temperature sensor for measuring the surface temperature of fixing film 13 and the surface temperature of pressure roller 20 of fixing unit 6. The schematic block diagram of is shown.
Reference numeral 31 denotes a non-contact temperature sensor for detecting the surface temperature of the fixing film 13. Reference numeral 32 denotes a non-contact temperature sensor for detecting the surface temperature of the pressure roller 20. A temperature sensor suitable for 31 and 32 is a non-contact type thermistor such as a thermopile.
These temperature sensors 31 and 32 are installed in the image forming apparatus. When the fixing unit 6 is detachable from the image forming apparatus, a mechanism may be employed in which the temperature sensors 31 and 32 are retracted so as not to interfere with the fixing unit 6. Further, the temperature sensors 31 and 32 may be provided inside the detachable fixing unit 6.
The temperature of the surface of the fixing film 13 and the temperature of the surface of the pressure roller 20 measured by the temperature sensors 31 and 32 are stored in the storage medium 33 such as NVRAM shown in FIG. Once stored. These temperature information is reflected in the temperature control of the fixing unit 6 by being read into the CPU 100 as the control means. Alternatively, the measured temperature is directly transmitted to the CPU 100 each time, and then used for life management of the fixing unit 6. A specific control method will be described below. Note that the CPU 100 outputs a temperature control signal to the temperature control circuit 101 and a warning signal to the display panel 102.

(3) Explanation regarding the temperature of the fixing film and the amount of wear on the surface layer The surface layer of the fixing film 13 is worn by passing paper. The reason is that there is a slight difference in peripheral speed between the paper material of the recording material P and the fixing film 13.
The fixing unit 6 rotates following the rotation of the pressure roller 20. The pressure roller 20 conveys the recording material P, and the fixing film 13 is rotated by the frictional force between the recording material P and the fixing film 13. Since the surface of the fixing film 13 is made of a material having high releasability, the coefficient of friction is low. Further, since the inner surface of the fixing film 13 is rubbed against the heater 11 and the heat insulating holder 12, the peripheral speed of the fixing film 13 is slower than the conveying speed of the recording material P.
The paper material of the recording material P contains minerals such as calcium carbonate and kaolin as fillers to make the paper white and opaque. These fillers act as abrasives to scrape the surface layer of the fixing film 13.
The speed at which the surface layer of the fixing film 13 is worn is related to the temperature of the surface and the time during which the temperature is applied. Resins such as PFA and PTFE used for the surface layer of the fixing film 13 become soft as the temperature rises. For this reason, when the fixing film 13 and the recording material P are pressed at the fixing nip portion N, the paper filler bites into the fixing film 13 more deeply. In this state, it is considered that wear is accelerated by a difference in peripheral speed between the fixing film 13 and the recording material P.
In addition, the hardness of these resins changes with the time heated. These resins change in hardness due to elastic deformation due to external stress and viscous deformation due to the above-mentioned temperature, and the viscous deformation is related to the heating time. For this reason, it is hard at the beginning of heating and tends to become soft after a certain amount of heating time.

The relationship between the surface temperature of the fixing film 13 and the wear rate is shown in FIG.
In FIG. 6, the horizontal axis represents the temperature of the fixing film 13, and the vertical axis represents the wear rate of the surface layer of the fixing film 13, indicating the amount of wear per 1000 sheets.
When the temperature is low, the surface layer is not cut much, but when the temperature is high, the amount of wear increases. If the surface temperature is about 180 ° C., the wear amount per 1000 sheets is 0.07 μm, but at 200 ° C., it becomes 0.13 μm. FIG. 6 shows the amount of wear when both elastic deformation and viscous deformation are considered.
In this embodiment, when the surface temperature of the fixing film 13 reaches 160 ° C., wear due to viscous deformation starts. When the fixing unit 6 is cooled to about room temperature, energization to the heater 11 is started and the time required for the surface temperature of the fixing film 13 to reach 160 ° C. is about 4.8 seconds. For this reason, the amount of wear before 4.8 seconds is small, and is almost constant at 0.05 μm / 1000 sheets.
Further, the time until viscous deformation starts varies depending on the temperature of the member. In the structure of this embodiment, when the surface temperature of the fixing film 13 is 160 to 175 ° C., about 6 seconds, when it is 175 to 200 ° C., about 3.5 seconds, and when it is 200 ° C. or more, viscous deformation takes about 1 second. Begins.
The temperature of the heater 11 is controlled based on a signal from the thermistor 15 provided on the back surface of the heater 11. In this example, the power supplied to the heater is controlled so that the temperature detected by the thermistor 15 maintains the control temperature of 200 ° C.
When 60 sheets per minute are printed at a control temperature of 200 ° C. when the fixing film 13 is new, the temperature of the fixing film is 180 ° C.
When the film thickness of the surface layer of the fixing film 13 becomes small, the temperature of the fixing film surface becomes high even if the control temperature is the same. In order to prevent this, in this embodiment, the control temperature is changed according to the surface layer thickness of the fixing film 13. The relationship between the surface layer thickness and the control temperature is shown in FIG.
The horizontal axis in FIG. 7 is the surface layer thickness, and the vertical axis is the control temperature for maintaining the surface of the fixing film at 180 ° C. when printing is performed at a rate of 60 sheets per minute. When the surface layer thickness is 20 μm, the control temperature is 200 ° C., but 196 ° C. for 15 μm, 192 ° C. for 10 μm, and 188 ° C. for 5 μm. As will be described later, this control temperature is utilized for life notification timing and the like.

(4) Description of the temperature and hardness reduction amount of the pressure roller 20 When the hardness of the pressure roller 20 is smaller (softer), the time for the recording material P to pass through the fixing nip portion N becomes longer. Since the amount of heat transmitted to the toner increases, the effect of melting the toner is increased.
On the other hand, if the hardness is high (hard), a low-priced and small motor can be used, in which the load torque when driving the fixing unit 6 is small and the generated torque is small.
Since the hardness of the pressure roller 20 tends to gradually decrease with use, it is set in consideration of the above circumstances. In this embodiment, the pressure roller 20 has a hardness of 55 °. As the motor, a motor that can be driven when the lower limit of the hardness of the pressure roller is 50 ° was selected.
FIG. 8 is a graph showing the relationship between the surface temperature of the pressure roller 20 and the hardness reduction rate. The horizontal axis represents the surface temperature of the pressure roller 20, and the vertical axis represents the rate of hardness reduction per 100 hours of rotation time.
When the temperature of the pressure roller 20 is about 100 ° C., the hardness change per rotation time of 100 hours is about 1 °, and when the temperature is 180 ° C., it becomes 2.5 °.
Table 1 shows the relationship between the hardness of the pressure roller 20 in this embodiment, the width Ln of the fixing nip portion, and the control temperature necessary to obtain a fixed fixing property.
When the hardness of the pressure roller 20 is lowered by 2 degrees, the nip width is increased by 0.5 mm. In order to obtain a fixed fixing performance, the control temperature needs to be lowered by 3 °.

(5) Explanation regarding the Paper Passing Mode and the Temperature of the Fixing Film 13 The paper passing sequence based on the fixing unit 6 includes the following four steps.
Pre-rotation step: a preparation step, which is a step of stabilizing the potential of the photosensitive drum 1 and stabilizing the rotation of the laser scanner 3, an image formation on the photosensitive drum 1, and an image on the photosensitive drum 1 are transferred A conveyance process in which the recording material P is conveyed to the fixing unit 6 and a warm-up process for warming the fixing film 13 and the pressure roller 20 are included. The warm-up process overlaps with the preparation process and the transport process in terms of time.
Paper passing process: A process in which the recording material P on which unfixed toner is placed is passed through the fixing nip portion N to perform fixing. This is a period in which the recording material P exists in the fixing nip portion N.
Inter-paper step: Timing between the preceding recording material P and the next recording material P when continuous paper feeding is performed. This is a period in which the recording material P does not exist in the fixing nip portion N during continuous paper feeding.
Post-rotation step: a rotation time for taking out the recording material P out of the apparatus.
Each required time was set as follows.
Pre-rotation: 6 seconds Paper feed: 0.74 seconds (A4 size: 297 mm)
Between paper sheets: 0.25 seconds After rotation: 1 second The temperature of the fixing film 13 and the pressure roller 20 changes depending on the condition of passing paper. How these temperatures change under the above conditions, This will be described with reference to FIGS.
FIG. 4 shows the temperature transition of the fixing film 13 and the pressure roller 20 when printing is continuously performed. The horizontal axis is time, and the vertical axis is temperature. The solid line represents the surface temperature of the fixing film 13, and the broken line represents the surface temperature of the pressure roller 20. R1 on the time axis represents a pre-rotation period, R2 represents a paper passing process period, and R3 represents a paper interval period.
In the case of continuous sheet passing, the sheet passing process and the interval between sheets are repeated after the pre-rotation until the designated number of prints is completed (there is no post-rotation period in the middle). The temperature control of the fixing unit when the paper is passed is performed according to the temperature detected by the thermistor 15 on the back of the heater 11. The control temperature of the heater 11 is 200 ° C.
During the period of the pre-rotation step R1, a large amount of electric power is supplied to the heater 11 in order to set the temperature behind the heater 11 to a temperature necessary for fixing.
In the period of R1, when the temperature of the thermistor 15 reaches 200 ° C., an image is created in time so that the recording material P enters the fixing nip N.
During the period R2 of the sheet passing process and the period R3 between the sheets, the CPU 100 controls the energization of the heater 11 so that the temperature detected by the thermistor 15 becomes a constant temperature of 200 ° C.
When the sheet is continuously fed, the fixing film 13 is deprived of heat by the recording material P, and the surface temperature thereof is about 180 ° C.
The pressure roller 20 also decreases in temperature with the passage of paper and is stabilized at about 80 ° C.
In this way, when printing is performed at the fastest throughput of the product, the temperature of both the fixing film 13 and the pressure roller 20 is kept low.
Under this condition, when printing of 150 k sheets, which is the life of the fixing unit of this example, is performed, the surface layer of the fixing film 13 is cut by 12.6 μm.
On the other hand, when printing 150k sheets at a printing speed of 60 ppm, the rotation time of the pressure roller is about 41 hours, but the decrease in the hardness of the pressure roller 20 after rotating for 41 hours is about 0.5 °, which is a problem. Must not.

Next, FIG. 5 shows a case of intermittent paper feeding in which the temperature of the fixing unit 6 becomes high. The notations of the horizontal axis, the vertical axis, the solid line, and the broken line in FIG. 5 are the same as those in FIG.
FIG. 5 shows the temperature transition of the fixing film 13 and the pressure roller 20 when one sheet is printed every 8 seconds.
With the configuration of this embodiment, if printing is performed every 8 seconds, pre-rotation starts immediately after the completion of post-rotation of the first print. In this case, since the fixing unit 6 is warm, the heater 11 reaches the control temperature of 200 degrees immediately after the warm-up is started. However, since image formation and paper conveyance take 6 seconds, the heater 11 stands by while maintaining a temperature of 200 ° C. During the standby, the fixing film 13 and the pressure roller 20 are rotating. If the fixing film 13 and the pressure roller 20 are stopped and stand by while the heater 11 is at a high temperature, a local thermal history (deformation) remains in the fixing film 13 and the pressure roller 20, and this deformation is applied to the image. Because it affects.
During the pre-rotation period R1, since the time during which the heater 11 maintains 200 ° C. is long, the temperature of the fixing film 13 reaches 200 ° C., which is substantially equal to the control temperature. Since the pressure roller 20 rotates in contact with the fixing film 13 having a high temperature, the temperature of the pressure roller 20 also rises to about 160 ° C. In such a state that the temperature of the fixing film 13 and the pressure roller 20 is high, the wear of the fixing film 13 is accelerated, and the hardness of the pressure roller 20 is accelerated to decrease, so that the life of the fixing unit 6 (150 k) is increased. There is a possibility that problems such as hot offset, curl, and paper wrinkle may occur.
In the case of intermittent paper feeding shown in FIG. 5, the fixing film 13 may reach a temperature of 200 ° C. at the timing when the leading edge of the recording material P enters the fixing nip portion. The wear amount per 1000 (1k) sheets at this time is 0.13 μm from FIG. When 150k sheets are printed, the wear amount is 19.5 μm, and the surface layer is almost lost.
On the other hand, since the pressure roller 20 rotates at a temperature of 160 ° C., the hardness decreases by 1.7 ° per 100 hours until 100 k sheets are printed, and thereafter, the hardness decreases by 0.9 ° per 100 hours. Hardness decreases. When intermittently printing 150 k sheets, the rotation time of the pressure roller 20 and the fixing film 13 is 333 hours, so the hardness decreases at a hardness reduction rate (0.9 ° / 100 hours) in the latter 233 hours.
As a result, the hardness of the pressure roller 20 at the time of 150k sheets is about 51 °, and decreases to around 50 ° which is the lower limit hardness that can be driven, and the motor has no margin in terms of durability.
In the method of displaying the life warning of the fixing unit 6 on the operation panel of the product main body or the monitor of the PC by counting the number of printed recording materials, the timing for issuing the life warning with respect to the timing when the life of the fixing unit 6 is reached. Deviation occurs. As a result, the user cannot be warned properly. There was a risk of paper jams due to paper contamination and drive failure.

(6) Control of this embodiment Therefore, in this embodiment, the CPU 11 monitors the surface temperature of the fixing film 13 and the pressure roller 20 with the first temperature sensor 31 and the second temperature sensor 32 to obtain the surface temperature. The amount of wear on the surface layer of the fixing film 13 and the change in the hardness of the pressure roller 20 for each print are calculated to predict the film thickness of the surface layer of the fixing film 13 and the hardness of the pressure roller 20 at the time of temperature measurement. . The CPU 11 has a role of a wear amount acquisition unit that acquires the wear amount of the surface layer of the fixing film 13 and a role of a hardness change amount acquisition unit that acquires a hardness change amount per unit time of the pressure roller 20. Further, the CPU 11 functions as a control temperature setting unit for setting the heater control temperature in accordance with the amount of wear on the surface layer of the fixing film and the amount of change in hardness of the pressure roller, the amount of wear on the surface layer of the fixing film, and the change in hardness of the pressure roller. It has a role of a lifetime calculation unit that calculates the lifetime of the fixing film and the pressure roller according to the amount. Then, by setting the control temperature from the prediction information of the surface layer thickness of the fixing film and the hardness of the pressure roller, it is possible to prevent the occurrence of image defects and to issue a life warning at an appropriate timing.

Specifically, for the surface layer thickness of the fixing film 13, the coefficient corresponding to the surface wear amount corresponding to the surface temperature of the fixing film 13 is subtracted from the initial value for each sheet passing, and the calculation result Based on the above, change the control temperature and display the life.
For the pressure roller 20, the coefficient corresponding to the amount of change in hardness according to the surface temperature of the pressure roller 20 is subtracted from the initial value every unit time, and the control temperature is changed based on the calculation result. Displays the life.
The calculation result is stored in the storage medium 33 attached to the fixing unit 6.
The life display is performed by selecting one of the fixing film 13 and the pressure roller 20 that is closer to the life. Further, the display may be made when the life is reached, or may be made in the form of displaying the ratio used with respect to the length of the life.

[Specific Procedure for Estimating (Predicting) the Surface Layer Thickness of the Fixing Film 13]
Next, a procedure for calculating the film thickness of the surface layer of the fixing film 13 will be described. First, a film thickness coefficient T corresponding to the surface layer thickness of the fixing film 13 is calculated. The initial value of the film thickness coefficient T is 2,000,000. This initial value may be changed according to the initial thickness of the surface layer of the fixing film. In that case, it is increased or decreased at a rate of 100,000 per 1 μm thickness. This initial value is stored in the storage medium 33 of the fixing unit 6. Each time printing is performed, the film thickness coefficient T is updated by subtracting the coefficient from the film thickness coefficient T. As the subtraction coefficient, values shown in Table 2 are used in this embodiment. The subtraction coefficient is a surface layer wear amount corresponding to the surface temperature of the fixing film 13.
Every time one sheet is printed, the subtraction coefficient in Table 2 is subtracted from the initial value of the film thickness coefficient T, and the value is stored in the storage medium 33 of the fixing unit 6.
The amount of wear differs depending on how the heat history of the surface layer of the fixing film 13 is received, and it is necessary to assume the case of only elastic deformation and the case of considering viscous deformation. The subtraction coefficient shown in Table 2 is a case including both elastic deformation and viscous deformation. The subtraction coefficient at the timing of only elastic deformation is “5” in this embodiment. The period during which this elastic deformation-only subtraction coefficient is used varies depending on the surface temperature of the fixing film. Table 3 shows the relationship between the surface temperature and the time using “5” as the subtraction coefficient.
In the case of printing from room temperature with a surface temperature of 40 ° C. or lower, the subtraction coefficient “5” is used according to the time shown in Table 3 until the first second sheet.
For this reason, when printing is performed for three sheets, the fixing unit 6 is left until it is cooled, and then when the printing is performed again, the subtraction coefficient “5” is used.
When printing is performed continuously in the warm state of the fixing unit 6 as in the case of continuous printing, the influence of the subtraction coefficient in Table 2 is large and the influence of the subtraction condition in Table 3 is dependent on the number of sheets. Hardly appears.

Next, the control temperature of the heater 11 is determined from the value of the film thickness coefficient T corresponding to the surface layer thickness of the fixing film 13 (predicted information of the surface layer thickness). The control temperature is such that the film surface temperature is 180 ° C. during continuous paper feeding.
From FIG. 7, when the relationship between the surface layer thickness of the fixing film 13 and the control temperature at which the film surface is 180 ° C. is approximated in this example, the following equation 1 is obtained: Control temperature [° C.] = 0.8 × film surface layer thickness [μm] +184 [° C.] --- (Formula 1)
When this is used as a coefficient equation, the following equation 2 is obtained.
Control temperature [° C.] = 0.8 × film thickness coefficient T × 100,000 + 184 [° C.] (Equation 2)
In terms of control, this calculation may be performed, or control may be performed using a correspondence table as shown in Table 4 below.

Next, the life display of the fixing film 13 will be described. When performing the life display, set with some allowance. The reason is that image defects such as image contamination occur when the surface layer of the fixing film 13 disappears even a little.
In this embodiment, the lifetime is determined when the remaining surface layer of the fixing film 13 reaches 4 μm. That is, the remaining film thickness is set to 4 μm. This value is a film thickness coefficient and corresponds to 400,000.
When the life display is performed in a ratio, the initial value of the film thickness coefficient T is set to 100%, and the remaining film thickness coefficient 400000 is set to 0%. For example, when the initial film thickness coefficient T is 2,000,000, the life display may be decreased by 1% each time the film thickness coefficient T decreases by 16000.
When the ratio display is not performed, the life display of the fixing unit may be displayed when the film thickness coefficient reaches 400,000.

Next, the pressure roller 20 will be described. First, a hardness coefficient D corresponding to the hardness of the pressure roller 20 is calculated. In this embodiment, the pressure roller hardness when new is 55 °. Further, the hardness subtraction coefficient per hardness of 1 ° is treated as 10,000,000. For this reason, the initial value of the hardness coefficient D of the pressure roller 20 is 550,000,000. This value may be changed by the initial hardness of the pressure roller 20. In that case, the initial coefficient is increased or decreased at a rate of 10,000,000 with respect to the pressure roller hardness of 1 ° and stored in the storage medium 33 of the fixing unit 6.
The calculation is performed by subtracting the coefficient every time printing is performed. The subtraction of the hardness coefficient D of the pressure roller 20 is performed every 1 second of the rotation time of the pressure roller 20, and the coefficient is changed as shown in Table 5 according to the temperature. Table 5 shows a predetermined amount of change in hardness per rotation time corresponding to the surface temperature of the pressure roller 20.
As shown in FIG. 10, the change in hardness of the pressure roller 20 is large until the initial 100 hours of the rotation time, and thereafter, the amount of change decreases.
This is because the PFA tube covering the roller surface is stretched during the initial period, so that the surface tension is lowered and the hardness is lowered. For this reason, it is presumed that the amount of change in hardness in the initial period increases.
On the other hand, after the initial period, only a decrease in hardness due to rubber is caused, so that the amount of change in hardness is estimated to be relatively small.

Next, the control temperature is corrected from the value of the hardness coefficient D (hardness prediction information) of the pressure roller 20.
For the correction, the correspondence table of Table 6 is used. For example, when the film thickness coefficient T of the fixing film 13 is 1,000,000, the control temperature is 193 ° C., but when the hardness coefficient D of the pressure roller 20 is 535,000,000. The temperature is adjusted at 191 ° C., which is 2 ° C. lower than that temperature.

Next, the life display of the pressure roller 20 will be described. In the driving motor employed in the apparatus of this embodiment, when the hardness of the pressure roller 20 is less than 50 °, rotation failure occurs due to an increase in rotational load torque. Before that, it is necessary to issue a life warning. The lower limit hardness of the pressure roller 20 for the normal operation of the motor employed in the apparatus of this example is 51 °. This hardness is a hardness coefficient D and corresponds to 510,000,000.
When the life display is performed in a ratio, the initial value of the hardness coefficient D is set to 100%, and the lower limit hardness coefficient 510000000 is set to 0%. For example, when the initial hardness coefficient D is 550,000,000, the life display may be decreased by 1% every time the hardness coefficient D decreases by 400,000.
When the ratio display is not performed, the life display of the fixing unit may be displayed when the film thickness coefficient reaches 510,000,000.

(7) Effects of the present embodiment By following the procedure described above, the wear rate of the surface layer of the fixing film 13 or the hardness change rate of the pressure roller 20 changes depending on the use conditions. However, the control temperature can be set to an appropriate temperature. As a result, the temperature of the fixing nip portion can be maintained appropriately, and good printing can be performed without causing problems such as hot offset and curl.
Further, in terms of the life of the fixing unit 6, the life management can be performed according to the surface layer thickness of the fixing film 13 and the hardness of the pressure roller 20. The fixing unit can be used continuously without being discarded. Further, when used under severe conditions for the wear of the fixing film 13 and the hardness change of the pressure roller 20, a life warning can be appropriately given in accordance with the situation of these parts.

Hereinafter, specific calculations for determining an appropriate control temperature and specific calculations for performing appropriate life management will be described in the case where the use conditions are different. Moreover, the effect with respect to each use condition is also demonstrated.
First, FIG. 15 shows the temperature transition of the fixing film 13 and the pressure roller 20 when 60 sheets of printing per minute as shown in FIG. 4 are continuously performed (in the case of continuous paper feeding).
In FIG. 15, the horizontal axis indicates time, the vertical axis indicates temperature, the solid line indicates the temperature of the fixing film, the broken line indicates the temperature of the pressure roller, and K indicates the timing at which the apparatus is temporarily stopped for paper feeding. The graph shows the average temperature at 5 second intervals.
If continuous printing is continued in this way, the temperature of the pressure roller 20 gradually decreases until about the 50th page, but then gradually increases. It is assumed that the temperature of the pressure roller 20 gradually rises due to the heat supplied from the heater 11 to the pressure roller 20 between the sheets, and the pressure roller 20 warms up to the core.
Calculation of an appropriate control temperature corresponding to the decrease in the surface layer thickness of the fixing film 13 is as follows. Under this sheet passing condition, the temperature of the fixing film 13 changes at 180 ° C. The subtraction coefficient per sheet at this temperature is 9 based on Table 2.
If the film thickness coefficient T at the time of 10k sheets is calculated, it is as follows.
2,000,000-9 × 10,000 = 1,910,000
The control temperature when the film thickness coefficient T is 1,9110,000 is 200 ° C. from Table 4.
Further, calculation of an appropriate control temperature corresponding to the decrease in the hardness of the pressure roller 20 is as follows.
Under this sheet passing condition, the temperature of the pressure roller 20 does not reach 150 ° C. The subtraction coefficient at this temperature is 42 based on Table 5. The time when 10k sheets are continuously fed is 10,000 seconds. The hardness coefficient D of the pressure roller 20 at this time is as follows.
550,000,000-42 × 10,000 = 549,580,000
In this case, the control temperature is not changed due to the hardness of the pressure roller 20. Therefore, the control temperature at the time of 10k is 200 ° C.
The control temperature calculated from the viewpoint of reducing the surface layer thickness of the fixing film 13 described above is 200 ° C., and the control temperature calculated from the viewpoint of reducing the hardness of the pressure roller 20 is also 200 ° C. Therefore, it is determined that the control temperature suitable for the stage after passing 10k sheets is 200 ° C.

Next, the life of the fixing unit will be described. When the subtraction coefficient 9 is calculated until the film thickness coefficient T of the fixing film 13 is changed from 2,000,000 to 400,000, as shown below, the fixing film 13 prints 178 k sheets when 10 k sheets are printed. Is possible.
(2,000,000-400,000) ÷ 9≈178,000
For the pressure roller 20, the time required for the hardness coefficient D to reach 550,000,000 to 510,000,000 and the number of printable sheets after printing 10k sheets are as follows.
Pressure roller rotation time: (550,000,000-510,000,000) / 42 = 95380 [seconds] = 264 hours In this embodiment, the printing speed per minute is 60 sheets, and one sheet per second. Printing is performed.
That is, the number of printable sheets at the time of printing 10k sheets calculated from the lifetime of the pressure roller 20 is 952k sheets.
When the lifetimes of the fixing film 13 and the pressure roller 20 are compared based on the usable number (printable number) that is a value converted into the number of recording materials used (number of printed sheets), in this example, the fixing film 13 can be used. Since the number of sheets is less than the usable number of the pressure rollers 20, the life of the fixing film 13 is defined as the life of the fixing unit 6.
Therefore, the control temperature and life under this paper passing condition are as follows.
Control temperature when printing 10k sheets is 200 ° C
The usable number of sheets (printable number of sheets) until the life of the fixing unit at the time of printing 10k sheets is 178k sheets. Thus, in the case of continuous sheet passing, there is little wear of the fixing film 13 and the hardness of the pressure roller 20 The change is small. For this reason, the change amount of the control temperature is small, and the usable number of the fixing units 6 is 178k sheets longer than the assumed 150k sheets.

  Next, when the fixing unit 6 as shown in FIG. 5 is cooled and two prints are continuously repeated every 8 seconds (in the case of intermittent printing), the fixing film 13 and the pressure roller 20 are used. The temperature transition of is shown in FIG. The temperature rise of the pressure roller 20 is larger than that in the case of continuous paper feeding shown in FIG.

Under this paper passing condition, the temperature of the fixing film changes at 200 ° C. Based on Table 2, the subtraction coefficient per sheet at this temperature is 18.
If the film thickness coefficient T at the time of 10k sheets is calculated, it is as follows.
2,000,000-18 × 10,000 = 1,820,000
The control temperature when the film thickness coefficient T is 1,820,000 is determined to be 200 ° C. from Table 4.
Further, the temperature of the pressure roller 20 under this sheet passing condition is 175 ° C., and the subtraction coefficients at this temperature are 70 to 70 in Table 5. The time for passing 10k sheets is 80,000 seconds because it takes 8 seconds per sheet for intermittent printing. The hardness coefficient D of the pressure roller 20 at this time is as follows.
550,000,000-70 × 80,000 = 544,400,000
In this case, according to Table 6, the correction amount of the control temperature caused by the hardness reduction of the pressure roller 30 is 0 ° C.
Therefore, the control temperature at the time when 10k sheets are printed is 200 ° C.
Therefore, as described above, the control temperature calculated from the viewpoint of reducing the surface layer thickness of the fixing film 13 is 200 ° C. and the hardness of the pressure roller 20 is decreased even under such intermittent printing conditions. The control temperature calculated from this point of view is also 200 ° C. Therefore, the control temperature after passing 10k sheets is determined to be 200 ° C.
When the same calculation is performed at the time of passing 20k sheets, the control temperature determined based on the decrease in the surface layer thickness of the fixing film 13 is 200 ° C., and the control temperature determined based on the decrease in the hardness of the pressure roller 20 is 198 ° C. In this case, the control temperature determined by the decrease in the hardness of the pressure roller 20 is selected and controlled at 198 ° C.

A method for calculating the lifetime of the fixing unit in the case of intermittent printing will be described. First, the number of usable fixing films 13 at the time when 10k sheets are printed is as follows when the film thickness coefficient T of the fixing film is calculated with the subtraction coefficient 18 from 2,000,000 to 400,000. 89k.
(2,000,000-400,000) ÷ 18≈89,000
Next, the usable number of the pressure rollers 20 when 10k sheets are printed will be described. Calculation of the time required until the hardness coefficient D of the pressure roller reaches 550,000,000 to 510,000,000 and the number of printable sheets after printing 10k sheets are as follows.
Based on Table 5, the first 100 hours are calculated with a subtraction factor of 70.
After that, since the calculation is performed with the subtraction coefficient 35, the following calculation is performed.
100 × 60 × 60 + (550,000,000-510,000,000-70 × 100 × 60 × 60) ÷ 35
= 360000 + 422857
= 728857 [seconds] = 217 hours If the number of printable sheets is calculated from this, it takes 8 seconds per sheet, so the following is obtained.
782857 [seconds] ÷ 8 [seconds / sheet] = 97857 [sheets]
The number of printable sheets after printing 10k sheets is 98k sheets.
Considering the number of printable sheets of the fixing film 13 and the pressure roller 20, the number of printable sheets of the fixing film 13 is smaller, so the life of the fixing film 13 is defined as the life of the fixing unit 6.
Therefore, the control temperature and the life of the fixing unit under this paper passing condition are as follows.
Control temperature when printing 10k sheets is 200 ° C
The control temperature when printing 20k sheets is 198 ° C
The life of the fixing unit after printing 10k sheets is 89k sheets

As shown in FIG. 16, under severe use conditions in which the pressure roller temperature rises greatly, the timing for informing the life of the fixing unit is earlier than in the case where the present embodiment is not adopted. It is possible to prevent image defects due to a decrease in hardness of the image.
In addition, a warning can be issued before the apparatus is stopped due to image smear or paper jam due to wear of the fixing film 13 or a decrease in the hardness of the pressure roller 20. In this way, it is possible to notify the user or the administrator of the network printer of the life at an accurate timing and prompt the replacement of the fixing unit.

  In the above description, the control temperature determination method and the life notification calculation method, and the usage mode in which continuous printing is always continued as shown in FIG. 15 and the usage mode in which intermittent printing is always continued as shown in FIG. The effect of was explained. However, the actual usage form of the user is a complicated form in which continuous printing and intermittent printing are alternately mixed. Therefore, the calculation according to each usage pattern may be calculated for each print job, every predetermined time, or every predetermined number of sheets. Then, by accumulating and updating the results sequentially in the storage medium 33 included in the fixing unit 6, optimal control and accurate life count can be performed.

Further, FIG. 17 shows the temperature transition when printing one sheet at a time at intervals of 10 minutes. As described above, when a long stoppage occurs between operation of the apparatus, the fixing unit 6 is naturally cooled. Even if the printing is continued in this state, the temperature of the fixing film 13 and the pressure roller 20 is always lowered at the start of printing because it is not affected by the heat of the previous paper passing.
Although the pre-rotation operation is performed for each print, since the fixing unit 6 is not rotationally driven until the temperature of the heater 11 reaches 170 ° C., the number of rotations of the fixing unit 6 is small. In the case of such usage, when the present embodiment is applied, the rotation time of the pressure roller 20 is shortened. Therefore, the hardness reduction of the pressure roller 20 is smaller than that in the case of continuous paper feeding, and the control temperature is reduced. ,It does not affect.
Also, the fixing film 13 has a printing time of 8 seconds. In the printing process, the printing is finished before the surface PFA undergoes viscous deformation. Less than.
The lifetime (number of printable sheets) of the fixing film 13 when printing 10k sheets is about 320k.
From these circumstances, in such usage, the change in the control temperature is smaller and the durability is longer than when the apparatus is continuously operated.

(8) Other application examples of the present embodiment In the present embodiment, the temperatures of the fixing film 13 and the pressure roller 20 are measured by thermopile, but may be predicted based on the paper passing history. Good.
For example, in the configuration of this embodiment, the surface temperature of the fixing film 13 when continuous paper feeding is performed as shown in FIG. 4 is 190 ° C. for the first sheet, and then 180 ° C., as shown in FIG. When intermittent printing is performed, the temperature is the same as the control temperature.
As for the temperature of the pressure roller 20, a single printing process is divided into temporal segments such as a pre-rotation period, a paper passing period, an inter-paper period, and a post-rotation period. Then, the temperature of the pressure roller 20 may be estimated from the integrated value in consideration of the amount of heat supplied from the fixing film 13 to the pressure roller 20 in each period, heat radiation to the air, and the like. For example, the temperature of the pressure roller 20 is estimated as follows.
i) Divide the main body operation into segments for pre-rotation, paper-to-sheet, paper-passing, and standby. ii) Define the coefficient for each segment as shown in Table 7. iii) Coefficient every 100 msec for each segment Iv) The added coefficient is stored as an integrated count. V) The integrated count is treated as the temperature of each member. The initial value is determined from the temperature of the thermistor 15 on the back of the heater 11.

By performing such coefficient setting and integration, the temperature of the pressure roller 20 can be estimated.
The temperature of the fixing film 13 can also be estimated by providing a dedicated coefficient.
Further, in this embodiment, the film thickness coefficient T of the fixing film 13 and the hardness coefficient D of the pressure roller 20 are stored in the storage medium 33 attached to the fixing unit 6, but are stored in the storage medium on the apparatus main body side of the image forming apparatus. You may remember. For example, in the case of an image forming apparatus in which the fixing unit is not replaceable, the memory of the image forming apparatus main body may be used. Further, when the fixing unit is replaceable, the fixing unit has a plurality of electrodes, and an individual identification unit is provided for identifying the individual fixing unit according to open / short between the plurality of electrodes. In this case, the memory of the image forming apparatus main body may be used.
In this embodiment, the temperatures of both the fixing film 13 and the pressure roller 20 are monitored and utilized for the control temperature and the life detection, but either one may be used depending on the apparatus configuration. In consideration of the durability of the fixing film 13 and the pressure roller 20, it may be selected whether to use it for both control temperature and life detection or for either one of them.

[Example 2]
Next, a second embodiment of the present invention will be described. In the case of a small-sized image forming apparatus, it is often impossible to use an engine controller having a high processing capability in order to reduce the size of electric parts for main body control. Further, the fixing unit is fixed to the main body of the image forming apparatus, and is often not set as a replacement part. An example of implementing the proposed configuration in such an image forming apparatus will be described.
FIG. 11 shows an image forming apparatus according to the second embodiment. The same components as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted. The image forming apparatus according to the present exemplary embodiment is an image forming apparatus that prints 15 sheets by vertically feeding A4 size paper per minute. The paper conveyance speed in image formation is 100 mm / second. The configuration of the fixing unit 44 is different from that of the first embodiment.

FIG. 12 shows a cross-sectional view of the fixing unit 44. The fixing unit 44 includes a heating unit 34 including a heater 35 as a heating source, a cylindrical fixing film (fixing rotator) 38, and a pressure roller 40 as a pressure member. The fixing nip N is formed by pressing the heater 35 and the pressure roller 40 with a predetermined pressure through the fixing film 38.
The heating unit 34 mainly includes a fixing film 38, a heater 35, a heat insulating holder 36 that holds the heater 35, a metal stay 37, and the like. The metal stay 37 receives pressure from a spring (not shown) and presses the heat insulating holder 36 toward the pressure roller 40. A thermistor 39 is attached to the back of the heater 35 and detects the temperature of the heater 35.
The heater 35 is a ceramic heater having a thickness of 1 mm and a width of 5 mm. The heater 35 has a heat generating layer formed on an alumina substrate.
The outer diameter of the fixing film 38 is 18 mm, the base layer is 70 μm thick, and the material is PI (polyimide) in which carbon fibers are dispersed as a heat conductive filler. On top of that, PFA is coated with a thickness of 13 μm.
The diameter of the pressure roller 40 is 15 mm. The pressure roller 40 is configured by providing an elastic layer 42 and a 30 μm thick PFA tube layer on an aluminum cored bar 41. The elastic layer 42 is a foamed rubber layer. A load of 13 kgf is applied between the heating unit 34 and the pressure roller 40. The control temperature of the heater 35 during printing (during fixing processing) is 200 ° C.
The fixing unit 44 is fixed to the main body of the image forming apparatus and cannot be replaced. The lifetimes of the main body of the image forming apparatus and the fixing unit 44 are both 30,000 sheets.
In addition, the fixing unit 44 is reduced in size, and the temperature reacts quickly to energization of the heater 35.
The fixing film 38 has a surface layer formed of a coating. The coating is cheaper than the resin tube, and the range of material selection is widened, but the durability tends to be short. For this reason, it is often used in small machines with a short life.
The elastic layer 42 of the pressure roller 40 has a heat insulating structure in which bubbles are formed or bubbles are formed inside by adding a resin balloon. Further, by using foamed rubber, the hardness on the surface of the roller can be made about 40 °. By using the pressure roller 40 of this configuration, the heat insulation is high and the nip width of the fixing nip portion N can be widened. The nip width in this configuration is 6 mm.

Next, FIG. 13 shows the temperature transition of the fixing film and the pressure roller when the paper is passed in this configuration. FIG. 13A shows the case of continuous paper feeding, and FIG. 13B shows the case of intermittent paper feeding. The horizontal axis shown in FIG. 13 is time, and the vertical axis is temperature. The solid line is the temperature of the fixing film, and the broken line is the temperature of the pressure roller. First, the case of continuous paper feeding in FIG. The horizontal axis represents time, and the vertical axis represents temperature. The solid line indicates the temperature of the fixing film 38, and the broken line indicates the temperature of the pressure roller 40.
The period R5 in the figure is a pre-rotation period, the length of the period R5 is 3 seconds, the period R6 is a paper passing period, and the length of the period R6 when passing A4 size paper 297 mm is 3 seconds, the period R7 is a paper interval, and the length of the period R7 is 1 second. The control temperature is 200 ° C.
During the sheet passing, the surface temperature of the fixing film 38 is 195 ° C. for the first sheet. After that, the temperature decreases and the third sheet reaches 180 ° C. Thereafter, when the paper is continuously fed, the film temperature is maintained at 180 ° C. The reason why the temperature of the fixing film 38 is lower than the control temperature of 200 ° C. is that the release layer, which is the surface layer of the fixing film 38, has poor heat conduction, and therefore a temperature gradient can be formed on the front and back surfaces.
The reason why the temperature of the fixing film 38 is high in the first printed sheet is due to the heat storage effect that the fixing film 38 is warmed by the previous rotation.
Since the pressure roller 40 has a small heat capacity and stores a small amount of heat, the pressure roller 40 is maintained at a high temperature during non-sheet passing. However, when the sheet is passed, the recording material P is deprived of heat, and the temperature immediately decreases.

FIG. 13B shows the temperatures of the fixing film and the pressure roller in intermittent printing. In the figure, the period R8 is post-rotation, and shows an example of intermittent printing in which the next job is performed immediately after the completion of a single-sheet passing job. Also in the case of intermittent printing, the temperature transition of the fixing film 38 and the pressure roller 40 is the same as in the case of continuous printing. However, since heat is stored in the fixing film in the post-rotation period R8 and the pre-rotation period R5, the temperature of the film is high and becomes 195 ° C. every time.
As in this example, when the pressure roller 40 is an adiabatic system, there is no heat supply due to heat storage of the pressure roller 40, so when the recording material P enters the fixing nip portion N, Only the heat supply determines the temperature. Further, the pressure roller 40 also has a small heat capacity, so that when the recording material P enters the fixing nip portion N, the temperature decreases. Since the heat capacity is small, the temperature rise when printing is continued is slow.

Next, with reference to FIG. 18 to FIG. 20, a temperature transition when such printing is repeatedly performed will be described. FIG. 18 shows a case where 400 sheets are printed by continuous paper passing as shown in FIG. FIG. 19 shows a case where intermittent printing as shown in FIG. 13B is performed, and FIG. 20 shows a case where printing is performed one by one every 10 minutes.
As shown in FIG. 18, when continuous printing is continuously performed, the temperature of the fixing film 38 is stabilized at 180 ° C. The temperature of the pressure roller 40 gradually increases, but does not exceed 100 ° C.
As shown in FIG. 19, when intermittent printing is repeated, the pressure roller 40 gradually warms up, so that the control temperature is changed in anticipation of this. The initial temperature control is 200 ° C., and the film temperature at this time is 195 ° C. When the printing time exceeds 15 minutes, the control temperature is 195 ° C., and the film temperature at this time is 190 ° C. The temperature of the pressure roller exceeds 100 ° C. in 5 minutes.
As shown in FIG. 20, when printing one sheet from time to time, the temperature of both the fixing film 38 and the pressure roller 40 rises when printing, but the temperature does not continue to rise.
The amount of wear of the fixing film 38 becomes disadvantageous as the film diameter decreases. In addition, a film of a resin film formed by applying a resin to a base layer and then baking it, like a coating, rather than a film coated with a base layer after the resin is molded into a tube like a film with a tube coated on the base layer However, wear tends to progress faster.

Table 8 shows the relationship between the temperature and the amount of wear in Example 2. This table shows the amount of wear when the heating time is 7 seconds or more and the wear due to elastic deformation and the wear due to viscous deformation are combined.
Note that the time for considering viscous deformation is the same as in Table 3. The amount of wear due to elastic deformation is 0.07 μm / 1000 sheets (0.7 × 10 ⁻⁴ μm / sheet).

The hardness of the pressure roller 40 hardly changes when it is used between room temperature and 100 ° C. On the other hand, at 100 ° C. or higher, it decreases by about 1 ° in 20 hours.
FIG. 14 shows the relationship between the film thickness of the fixing film 38 and an appropriate control temperature. The relationship between the two can be expressed by the following equation.
Control temperature [° C.] = 0.9 × film surface layer thickness [μm] +188 [° C.]-(Formula 3)
Table 9 shows the correction amounts of the hardness, nip width, and control temperature of the pressure roller 40.

Based on the above conditions, in the second embodiment, the control temperature and the life are set as follows.
That is, for each paper passing, at least one of the paper interval time, which is interval time information from the previous paper passing time to the current paper passing time, rotation drive information, and recording material paper passing number information. Information is acquired at the same time. For the fixing film 38, the recording material passing sheet number information is obtained. For the pressure roller 40, the rotation time information is simultaneously obtained and stored as heat history information in a storage medium (not shown) provided in the control unit of the image forming apparatus. To do.
Then, according to the heat history information stored in the storage medium 33, the control temperature of the heater 11, the usable number information or the life warning information is used as a control value of the fixing unit 6 by a main body control unit (not shown) as a control means. It is supposed to change.
These calculations are performed based on the change in the thickness of the fixing film 38 and the change in the hardness of the pressure roller 40. These parameters are estimated as follows.

Case 1: When one sheet of recording material is printed at intervals of 10 minutes or more
The amount of film wear is 0.7 × 10 ⁻⁴ μm / sheet per recording material.
(Assuming wear due to elastic deformation only)
Pressure roller hardness change per rotation time 20 hours: 0.1 ° / 20 hours Case 2: Continuous printing of 20 or more recording materials
The film wear amount is 2 × 10 ⁻⁴ per recording material.
Change in pressure roller hardness per rotation time 20 hours: 0.1 ° / 20 hours Case 3: Cases other than above
Abrasion amount of film is 3 × 10 ⁻⁴ μm / sheet
Pressure roller hardness change is less than 5 minutes from the start of operation of the apparatus per 20 hours of rotation time: 0.1 ° / 20 hours
5 minutes or more from the start of operation of the apparatus: 1 ° / 20 hours For each print job, it is determined which of these cases corresponds, and the surface layer thickness of the fixing film 38 and the hardness of the pressure roller 40 are estimated.
As for the film thickness of the fixing film 38, the wear amount for each job is estimated and subtracted from the initial film thickness. About the hardness of the pressure roller 40, the hardness of the pressure roller 40 is estimated according to the rotation time for every job.

The change of the control temperature based on these pieces of information and the reflection on the remaining life (number of printable sheets) are performed as follows.
For the fixing film 38, the control temperature is calculated from the obtained film thickness using Equation (3), and the control temperature is changed. The life warning based on the fixing film 38 is made when the remaining film thickness reaches 4 μm.
Next, regarding the estimation of the hardness of the pressure roller 40, the hardness reduction rate for each case is estimated according to the rotation time for each job. The apparatus of this example issues a warning that the pressure roller has reached its end of life when the hardness of the pressure roller is reduced by 6 degrees from the initial value. Note that the foam type elastic layer hardly changes the load torque even if the hardness changes. Further, when the fixing unit is fixed to the main body of the image forming apparatus and the driving motor used in the fixing unit and the image forming unit including the photosensitive drum 1 is common as in this embodiment, there is a margin in driving torque. In many cases, the problem of drive failure is unlikely to occur. Because of these factors, the hardness change of the pressure roller is larger when the pressure roller of this example is used than when the pressure roller of Example 1 in which the elastic layer is a solid rubber layer is used. There is no problem even if a life warning is issued at that time.

A specific example is shown below. A job that continuously feeds paper as shown in FIG. The fixing film temperature at the time of paper passing does not exceed 180 ° C., and the temperature of the pressure roller does not exceed 100 ° C.
The control temperature and the life of the fixing unit (main body life) when 10,000 sheets are printed are as follows.
Control temperature when printing 10,000 sheets: 198 ° C
Fixing unit life at the time of printing 10,000 sheets: 45,000 sheets A job for performing intermittent paper feeding as shown in FIG. The film temperature during paper feeding is 195 ° C. to 190 ° C., and the temperature of the pressure roller exceeds 100 ° C. after 5 minutes.
The control temperature and the life of the fixing unit (main body life) when 10,000 sheets are printed are as follows.
Control temperature when printing 10,000 sheets: 195 ° C
Fixing unit life at the time of printing 10,000 sheets: 30,000 sheets In case 2, although the hardness of the pressure roller changes, it reaches the life of the fixing unit due to the film thickness of the fixing film, so the pressure roller is fixed. Does not affect the life of the unit.

A job that prints once every 10 minutes as shown in FIG.
The film temperature at the time of paper passing is 195 ° C., but the printing is finished before the surface layer of the fixing film reaches viscous deformation. Therefore, the wear amount per sheet is 0.7 × 10 ⁻⁴ μm. The temperature of the pressure roller does not exceed 100 ° C.
The control temperature and the life of the fixing unit (main body life) when 10,000 sheets are printed are as follows.
Control temperature when printing 10,000 sheets: 199 ° C
Fixing unit life at the time of printing 10,000 sheets: 12.8 thousand sheets or more In any application example, there is no image defect due to improper control temperature setting, and the life warning can be performed appropriately done.

  In actual usage, cases 1, 2, and 3 are likely to be mixed, but by adjusting the predicted values of film thickness and pressure roller hardness for each job, the control temperature setting and life warning can be set appropriately. Can be done.

1 Photosensitive drum 6 Fixing device (heat fixing device)
DESCRIPTION OF SYMBOLS 10 Fixing member 11 Heating heater 13 Fixing film, 15 Thermistor 20 Pressure roller 31, 32 Temperature detection sensor 100 CPU (control part)

Claims (11)

In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member having a surface layer, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and the rotating member A fixing unit having a heater for heating
A temperature sensor for detecting the temperature of the rotating body;
A wear amount acquisition unit that acquires the wear amount of the surface layer of the rotating body, and a wear amount acquisition unit that acquires the wear amount according to a temperature detected by the temperature sensor;
A control temperature setting unit for setting the control temperature of the heater according to the wear amount;
An image forming apparatus comprising: If the temperature sensor that detects the temperature of the rotating body is a first temperature sensor, the apparatus further includes a second temperature sensor that detects the temperature of the pressure member, and a detection temperature of the second temperature sensor. A hardness change amount acquisition unit that acquires the hardness change amount of the pressure member according to
The image forming apparatus according to claim 1, wherein the control temperature setting unit sets a control temperature of the heater according to the wear amount and the hardness change amount. In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member having a surface layer, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and the rotating member A fixing unit having a heater for heating
A temperature sensor for detecting the temperature of the rotating body;
A wear amount acquisition unit that acquires the wear amount of the surface layer of the rotating body, and a wear amount acquisition unit that acquires the wear amount according to a temperature detected by the temperature sensor;
A life calculation unit for calculating the life of the rotating body according to the wear amount;
An image forming apparatus comprising:   The wear amount acquisition unit acquires the wear amount per recording material, and the wear amount per recording material differs according to a temperature detected by the temperature sensor. The image forming apparatus according to any one of 1 to 3. In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and heats the rotating member. A fixing unit having a heater;
A temperature sensor for detecting the temperature of the pressure member;
A hardness change amount acquisition unit for acquiring a hardness change amount of the pressure member, and a hardness change amount acquisition unit for acquiring the hardness change amount according to a detection temperature of the temperature sensor;
A control temperature setting unit for setting the control temperature of the heater according to the amount of change in hardness;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, further comprising a storage unit that stores the control temperature. In an image forming apparatus that prints an image on a recording material,
A fixing unit that fixes an image formed on a recording material to the recording material, the rotating member, a pressure member that forms a fixing nip portion that sandwiches and conveys the recording material together with the rotating member, and heats the rotating member. A fixing unit having a heater;
A temperature sensor for detecting the temperature of the pressure member;
A hardness change amount acquisition unit for acquiring a hardness change amount of the pressure member, and a hardness change amount acquisition unit for acquiring the hardness change amount according to a detection temperature of the temperature sensor;
A life calculation unit for calculating the life of the pressure member according to the hardness change amount;
An image forming apparatus comprising:   The hardness change amount acquisition unit acquires the hardness change amount per unit time, and the hardness change amount per unit time differs according to a temperature detected by the temperature sensor. The image forming apparatus according to any one of 5 and 7.   The image forming apparatus according to claim 1, wherein the rotating body is a film.   The image forming apparatus according to claim 9, wherein the heater is in contact with an inner surface of the film.   The image forming apparatus according to claim 10, wherein the pressing member forms the fixing nip portion together with the heater via the film.