JP2020129021A - Image forming device - Google Patents

Abstract

To shorten FPOT and suppress the wear of a fixing unit.SOLUTION: When a printing indication is received from a user (Yes in S10), a control unit 80 determines required nip pressure that corresponds to a temperature difference T (S14). The control unit 80 also determines upper-limit nip pressure that corresponds to the total travel distance P of a fixing belt 51 (S16). When the required nip pressure is lower than or equal to the upper-limit nip pressure (Yes in S17), the control unit 80 sets nip pressure to the required nip pressure (S18) and starts conveyance of paper 21a, 21b to a nip unit N. Meanwhile, when the required nip pressure exceeds the upper-limit nip pressure (No in S17), the control unit 80 sets nip pressure to the upper-limit nip pressure (S19) and starts conveyance of paper 21a, 21b to the nip unit N after elapse of an additional time. Thereafter, when the temperature difference T becomes a prescribed value (Yes in S26), the control unit 80 changes nip pressure to small nip pressure.SELECTED DRAWING: Figure 14

Description

The present invention relates to an image forming apparatus.

An electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine having a combination of these functions includes a fixing unit that fixes a toner image transferred on a sheet. The fixing unit fixes the toner image on the sheet by applying heat and pressure to the sheet that passes through the nip formed. Generally, the time from when the user presses the print start button to when the sheet on which the toner image is formed is ejected from the image forming apparatus is called FPOT (First Print Output Time) or FCOT (First Copy Output Time). From the viewpoint of user convenience, there is a demand for shortening.

Looking at the details of FPOT or FCOT, it takes time to raise the temperature of the nip portion formed in the fixing portion to a temperature required to satisfy the image quality. Therefore, as a technique for shortening the FPOT, Patent Document 1 discloses a technique for increasing the pressure applied at the start of the fixing operation and increasing the pressure applied to the sheet passing through the nip portion formed in the fixing portion. ing. Specifically, in the technique described in Patent Document 1, at the start of the operation of fixing the transferred toner image on the paper, the pressure of the pressure roller is set to be greater than the pressure required to obtain a predetermined fixing strength. When a large pressure is applied and the nip portion is heated to a temperature required to obtain a predetermined fixing strength, the pressure of the pressure roller is controlled to be reduced to a pressure required to obtain a predetermined fixing strength.

Generally, the temperature of the nip required to satisfy the image quality can be lowered by increasing the pressure in the nip. According to the technique described in Japanese Patent Laid-Open No. 2004-284, at the start of the fixing operation, the pressure in the nip portion is made higher than a predetermined pressure, and the temperature in the nip portion required to satisfy the image quality is lowered to reduce the FPOT. Shorten.

JP, 2010-2670, A

However, generally, when the pressure in the nip portion is increased, the surface layer of the fixing belt is worn, and various members in the fixing portion including the fixing belt are deteriorated, and as a result, the life of the fixing portion is shortened. In the technique described in Japanese Patent Application Laid-Open No. 2004-242242, the pressure in the nip portion is increased at the start of the fixing operation without considering the degree of wear of the fixing portion, which may significantly shorten the life of the fixing portion.

The present invention has been conceived in view of such circumstances, and an object thereof is to shorten the FPOT and suppress the consumption of the fixing unit.

An image forming apparatus according to an aspect of the present invention is an image forming apparatus capable of forming a toner image on a recording medium, and includes a first rotating body that is heated by a heat source and a second rotating body that can be pressed against the first rotating body. The recording medium that includes a body and is conveyed to a nip portion formed between the first rotating body and the second rotating body is heated by the first rotating body and is heated by the second rotating body. A fixing unit that fixes the toner image by pressure contact with the first rotating body and a control unit that controls the pressure in the nip unit are provided, and the control unit, when receiving a printing instruction, the nip unit. The pressure in the nip portion is increased according to the temperature rising condition toward the temperature required for the above and the degree of wear of the fixing unit.

Preferably, the first rotating body is an endless fixing belt, the fixing unit further includes a pressing member inscribed in the fixing belt, and the second rotating body includes the pressing member via the fixing belt. The nip portion is formed between the fixing belt and the fixing belt by being pressed by the pressing member.

Preferably, the control means sets the temperature rising condition toward the temperature required for the nip portion as a difference between the temperature in the nip portion when the print instruction is received and the temperature required for the nip portion. It judges based on.

Preferably, the control means determines the temperature rise condition toward the temperature required for the nip portion based on the length of waiting time for waiting for a print instruction.

Preferably, the control unit further increases the pressure in the nip portion according to the voltage supplied to the image forming apparatus.

Preferably, the control unit determines the degree of wear of the fixing unit based on the total number of rotations of the first rotating body or the second rotating body.

Preferably, the control unit determines the consumption degree of the fixing unit based on the total number of printed sheets.

Preferably, the control unit determines the degree of wear of the fixing unit based on the driving torque of the fixing unit.

Preferably, the control means lowers the pressure in the nip portion when the number of printed sheets reaches a predetermined value after increasing the pressure in the nip portion.

Preferably, the control means increases the pressure in the nip portion, and then increases the pressure in the nip portion when the difference between the temperature in the nip portion and the temperature required for the nip portion reaches a predetermined value. Lower.

Preferably, the control unit determines the upper limit value of the pressure in the nip portion based on the degree of wear of the fixing unit.

According to the present invention, it is possible to shorten the FPOT and suppress the consumption of the fixing unit.

FIG. 3 is a diagram showing an image forming apparatus. FIG. 3 is a block diagram showing a hardware configuration of the image forming apparatus. It is a figure which shows a fixing part. FIG. 6 is a diagram showing a set temperature of a fixing unit in a print mode. FIG. 6 is a diagram showing a temperature change of a fixing unit when the print mode is changed to a standby mode. It is a figure which shows the relationship between a nip pressure and the temperature which can satisfy fixing strength. It is a figure which shows the temperature change of a nip part when nip pressure is normal nip pressure. It is a figure which shows the temperature change of a nip part when nip pressure is larger than normal nip pressure. It is a figure which shows the relationship between a nip pressure and the life of a fixing part. It is a figure which shows a required nip pressure. It is a figure which shows an upper limit nip pressure. FIG. 6 is a diagram showing a set value of a nip pressure in a print mode. It is a figure which shows the additional time until paper insertion. It is a flow chart which shows nip pressure determination processing. It is a figure showing an example of change of nip pressure in a printing mode. It is a figure which shows a required nip pressure. It is a figure which shows FPOT. It is a figure which shows a required nip pressure. It is a figure which shows FPOT. It is a figure which shows an upper limit nip pressure. It is a figure which shows an upper limit nip pressure. FIG. 6 is a diagram showing a set value of a nip pressure in a print mode.

Hereinafter, embodiments will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

FIG. 1 is a diagram showing the image forming apparatus 100. FIG. 2 is a block diagram showing the hardware configuration of the image forming apparatus 100. With reference to FIGS. 1 and 2, the configuration of the image forming apparatus 100 and a series of processes (hereinafter, also referred to as “printing process”) of forming, fixing, and discharging a toner image in the image forming apparatus 100 will be described. To do.

Referring to FIGS. 1 and 2, image forming apparatus 100 is a tandem type color printer. The image forming apparatus 100 includes a printer engine 10, paper feed cassettes 20a and 20b, a fixing unit 50, a control unit 80, a storage unit 90, and a communication unit 91.

The printer engine 10 is an electrophotographic printer engine, and includes an imaging station 1, an intermediate transfer belt 8, a pair of rollers 9a and 9b, a secondary transfer roller 11, and an intermediate transfer belt cleaner 12, and uses input image data as input image data. Based on this, a toner image is formed on the sheets 21a and 21b.

The imaging stations 1Y, 1M, 1C and 1K form four color toner images of yellow (Y), magenta (M), cyan (C) and black (K) in parallel. The imaging stations 1Y, 1M, 1C and 1K have a common configuration. Therefore, in the following, common constituent elements are indicated by the same reference numeral, and Y, M, C, and K are added to the reference numerals only when distinguishing them.

The imaging station 1 has a photoconductor 2, a charging charger 3, an exposure device 4, a developing device 5, a drum cleaner 6, and a primary transfer roller 7.

The photoconductor 2 is a rotating body on a drum on the surface of which an electrostatic latent image is formed. The charging charger 3 uniformly charges the surface of the photoconductor 2 in a negative polarity. The exposure device 4 is composed of a semiconductor laser or the like, and irradiates the photoconductor 2 with laser light based on print image data. As a result, an electrostatic latent image based on the print image data is formed on the surface of the photoconductor 2.

The developing device 5 contains a developer of each color component (for example, a two-component developer including a toner having a small particle size and a magnetic material), and allows the toner of each color component to adhere to the surface of the photoconductor 2. To visualize the electrostatic latent image to form a toner image. The toner images of the respective colors formed on the photoconductor 2 are sequentially transferred (primary transfer) from the photoconductor 2 onto the intermediate transfer belt 8 by the primary transfer roller 7 in the order of yellow, magenta, cyan, and black. The toner images of the respective colors are superposed on the transfer belt 8.

The intermediate transfer belt 8 is an endless belt and is wound around a pair of rollers 9a and 9b. The roller 9a is drivingly connected to a motor (not shown) and rotates based on the driving of the motor. The intermediate transfer belt 8 and the roller 9b that supports the intermediate transfer belt 8 rotate counterclockwise as the roller 9a rotates.

The drum cleaner 6 scrapes and removes the transfer residual toner remaining on the surface of the photoconductor 2 after the primary transfer.

The paper feed cassettes 20a and 20b can store papers 21a and 21b of different sizes. The sheets 21a and 21b are taken out from the sheet feeding cassettes 20a and 20b by the pickup rollers 15a and 15b and fed to the printer engine 10. The papers 21a and 21b are transported on the transport path R such that their long sides are parallel to the transport direction M1 and are even on the left and right.

The primary-transferred toner image is secondarily transferred by the secondary transfer roller 11 to the papers 21a and 21b conveyed from the paper feed cassettes 20a and 20b through the registration rollers 15c.

The intermediate transfer belt cleaner 12 scrapes off and removes the transfer residual toner remaining on the surface of the intermediate transfer belt 8 after the secondary transfer.

After the secondary transfer, the sheets 21a and 21b are conveyed to the fixing unit 50 along the conveyance route R. The fixing unit 50 heats and pressurizes the papers 21a and 21b to fix the untransferred toner images secondarily transferred onto the papers 21a and 21b. Details will be described later with reference to FIG.

The papers 21a and 21b on which the toner images have been fixed are conveyed along the conveyance path R and sent to the paper discharge tray 18.

The control unit 80 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, and the like. The CPU 81 reads various processing programs stored in the ROM 82 according to the instruction signal received by the communication unit 91, expands the programs in the RAM 83, and centrally controls the operation of each unit of the image forming apparatus 100 according to the expanded programs. To do.

The storage unit 90 is configured by a storage unit such as a DRAM (Dynamic Random Access Memory) or a HDD (Hard Disk Drive) which is a semiconductor memory, and stores image data and the like input from the outside via the communication unit 91.

The communication unit 91 transmits/receives data to/from an external device connected to a communication network such as a LAN (Local Area Network).

FIG. 3 is a diagram showing the fixing unit 50. With reference to FIG. 3, the configuration of the fixing unit 50 and the mechanism for fixing the toner image on the sheets 21a and 21b will be described.

The fixing unit 50 includes a fixing belt 51, pressure members 52a and 52b, a sliding member 53, a supporting member 54, a heat source 56, a heating member 57, a pressure roller 58, temperature sensors 60a and 60b, and a pressure varying device (illustration). Omitted).

The fixing belt 51 is an endless belt that rotates with pressure contact of a pressure roller 58, which will be described later. The fixing belt 51 includes a base layer, an elastic layer, and a release layer, and has an outer diameter of any value, but preferably 10 to 100 mm. The base layer is made of polyimide, SUS, Ni electroforming or the like, and has a thickness of 5 to 100 μm. The elastic layer is preferably made of a material having high heat resistance such as silicone rubber or fluororubber, and has a thickness of 10 to 300 μm. It is desirable that the release layer has a structure such as a fluorine tube or a fluorine-based coating that imparts releasability, and the thickness is 5 to 100 μm. The fixing belt 51 is heated by a heat source 56 described later.

The pressure members 52 a and 52 b are inscribed in the fixing belt 51 by being supported by the support member 54. The pressure member 52a forms a nip portion N together with a pressure roller 58 described later. The pressure members 52a and 52b are made of resin such as polyphenylene sulfide, polyimide, or liquid crystal polymer, metal such as aluminum or iron, and ceramic, and have any shape. The pressing members 52a and 52b may be composed of two parts such as a fixing member made of silicone rubber or fluororubber.

The sliding member 53 is arranged around the pressing member 52a. The sliding member 53 is generally composed of a glass cloth as a base material and its sliding surface is covered with a fluororesin, and a woven fabric of fluorofiber, a fluororesin sheet, a glass coat or the like is used. The sliding member 53 reduces the sliding resistance between the fixing belt 51 and the pressing member 52a and stabilizes the rotation of the fixing belt 51.

The heat source 56 is a halogen lamp heater, a resistance heating type heater, IH, or the like. The heat source 56 is supplied with electric power so that the temperature detected by the temperature sensor 60a described later becomes a preset temperature. As a result, the heating member 57 described below rises in temperature, and the fixing belt 51 also rises in temperature via the heating member 57.

The heating member 57 stretches the fixing belt 51 together with the pressure members 52a and 52b. The heating member 57 is a rotating body made of a metal cylinder such as aluminum or SUS. The outer shape is arbitrary, but is preferably 10 to 100 mm and the thickness is preferably 0.1 to 5 mm. When a halogen lamp heater is used as the heat source 56, it is desirable that the inner surface of the heating member 57 be black. In addition, in order to prevent scratches on the outer surface due to foreign matter or the like, the outer surface of the heating member 57 may be coated with polytetrafluoroethylene.

The pressure roller 58 is a rotating body provided at a position opposed to the pressure member 52 a via the fixing belt 51. The pressure roller 58 is rotated at a predetermined rotation speed by a fixing/conveying motor (not shown). The pressure roller 58 presses against the fixing belt 51 to press the fixing belt 51 against the pressure member 52 a and form a nip portion N between the pressure roller 58 and the fixing belt 51. The pressure roller 58 is composed of a core metal, an elastic layer, and a release layer, and the outer diameter is arbitrary, but 20 to 100 mm is preferable. The core metal is preferably a metal such as aluminum or iron, and has a pipe shape and a thickness of 0.1 to 10 mm. The cored bar is not limited to the pipe shape, and may be solid or may have a cross-sectional shape of three arrows. The elastic layer is preferably made of a material having high heat resistance such as silicone rubber or fluororubber, and the thickness is preferably 1 to 20 mm. The release layer preferably has a structure such as a fluorine tube or a fluorine-based coating that imparts releasability, and has a thickness of 5 to 100 μm.

The temperature sensors 60a and 60b are sensors that detect temperature. The temperature sensor 60a is a sensor that detects the temperature of the fixing belt 51 near the heat source 56. The temperature sensor 60b is a sensor that detects the temperature of the fixing belt 51 in the vicinity of the nip portion N separated from the heat source 56.

The pressing force varying device varies the pressure contact force of the pressure roller 58 to the fixing belt 51, that is, the contact pressure between the pressure member 52a and the pressure roller 58. The pressing force varying device is composed of, for example, a pressure spring. Under the control of the controller 80, the pressurizing force varying device switches the pressure in the nip portion N (hereinafter, also referred to as “nip pressure”) by changing the length of the pressure spring. Specifically, the pressurizing force variable device has one of a normal nip pressure (for example, 100 kPa), a nip pressure up1 (for example, 130 kPa), a nip pressure up2 (for example, 160 kPa), and a nip pressure up3 (for example, 190 kPa). You can switch to. Note that the magnitude of the nip pressure is not limited to these, and the magnitude relationship among the normal nip pressure, the nip pressure up1, the nip pressure up2, and the nip pressure up3 is as follows: normal nip pressure<nip pressure up1<nip pressure up2<nip pressure up3. More preferably, the nip pressure up1 is 30% higher than the normal nip pressure, the nip pressure up2 is 60% higher than the normal nip pressure, and the nip pressure up3 is higher than the normal nip pressure. The size may be increased by 90%.

In the fixing unit 50, the papers 21a and 21b are conveyed through the nip portion N with the surface on which the toner image is transferred facing the fixing belt 51. The sheets 21a and 21b are heated by the heat from the fixing belt 51 when being conveyed through the nip portion N, and are pressed by the pressure roller 58 pressing against the fixing belt 51. As a result, the toner image is fixed on the sheets 21a and 21b.

FIG. 4 is a diagram showing the set temperature of the fixing unit 50 in the print mode. In the image forming apparatus 100, the set temperature of the fixing unit 50 in the print mode (hereinafter referred to as “print set temperature”) is determined based on the paper type and the installation environment. Paper types include thin paper, plain paper, and thick paper, which are set by the user. Alternatively, when the image forming apparatus 100 includes a device that detects the paper type, the device identifies the paper type. The installation environment refers to the temperature and humidity in the installation area of the image forming apparatus 100, and is classified into a low temperature environment, a normal environment, or a high temperature environment. The image forming apparatus 100 is provided with a device that detects the temperature and humidity of the installation area, and the device determines whether the environment corresponds to a low temperature environment, a normal environment, or a high temperature environment. In the print mode, the print setting temperature is determined based on the specified paper type and the installation environment, and power is supplied to the heat source 56 so that the temperature detected by the temperature sensor 60a becomes the print setting temperature. The table shown in FIG. 4 is stored in the ROM 82 and is referred to in the nip pressure determination process shown in FIG.

FIG. 5 is a diagram showing a temperature change of the fixing unit 50 when the print mode is changed to the standby mode. The horizontal axis represents time and the vertical axis represents temperature. The standby mode is a mode started when the user does not perform an operation for a predetermined time. In the standby mode, the rotation of the fixing belt 51 is stopped.

Solid lines L1 and L2 indicate set temperatures of the fixing unit 50. The solid line L1 indicates the print setting temperature, and the solid line L2 indicates the setting temperature in the standby mode (hereinafter referred to as "standby setting temperature"). In the print mode, electric power is supplied to the heat source 56 so that the temperature detected by the temperature sensor 60a becomes the print setting temperature, whereas in the standby mode, the temperature detected by the temperature sensor 60a is the standby setting temperature. The electric power is supplied to the heat source 56 so that The dotted line L3 indicates the temperature of the fixing belt 51 near the heat source 56, and the alternate long and short dash line L4 indicates the temperature of the fixing belt 51 near the nip portion N away from the heat source 56.

As indicated by L3 in FIG. 5, the fixing belt 51 near the heat source 56 is maintained at the print setting temperature in the print mode and is maintained at the standby set temperature in the standby mode. On the other hand, the fixing belt 51 near the nip portion N, which is separated from the heat source 56, is maintained at the print setting temperature in the print mode as shown by L4 in FIG. Is decreasing. This is because the rotation of the fixing belt 51 is stopped in the standby mode and heat is not transmitted to the vicinity of the nip portion N. In the print mode in which the fixing belt 51 is rotating, heat spreads over the entire fixing belt 51, so that the fixing belt 51 prints even near the heat source 56 or near the nip N separated from the heat source 56. The set temperature is maintained, and the nip portion N is always warmed. On the other hand, in the standby mode in which the rotation of the fixing belt 51 is stopped, heat is not transferred to the vicinity of the nip portion N, which is separated from the heat source 56, so that the temperature of the fixing belt 51 near the nip portion N decreases with time. , The nip portion N also decreases with time.

FIG. 6 is a diagram showing the relationship between the nip pressure and the temperature at which the fixing strength can be satisfied. The horizontal axis represents the nip pressure, and the vertical axis represents the temperature at which the fixing strength can be satisfied. The temperature at which the fixing strength can be satisfied (hereinafter, also referred to as “fixing temperature”) is the temperature required for the nip portion N to fix the toner image.

As shown in FIG. 6, the nip pressure and the fixing temperature are in an inversely proportional relationship, and when the nip pressure is increased, the fixing temperature decreases. That is, if the nip pressure is increased, the fixing strength can be satisfied even if the temperature in the nip portion N is low. This is because when the nip pressure is increased, the force of the melted toner entangled with the papers 21a and 21b increases. In addition, as the nip pressure increases, the nip width increases, and the time that the melted toner is entangled with the sheets 21a and 21b increases.

7 and 8 are diagrams showing a temperature change in the nip portion N. FIG. 7 is a diagram showing a temperature change of the nip portion N when the nip pressure is the normal nip pressure, and FIG. 8 is a diagram showing a temperature change of the nip portion N when the nip pressure is higher than the normal nip pressure. Is. The horizontal axis represents the elapsed time after receiving the print instruction, and the vertical axis represents the temperature of the nip portion N.

As shown in FIGS. 7 and 8, when the nip pressure is higher than the normal nip pressure, the temperature (fixing temperature) at which the fixing strength can be satisfied is lower than when the nip pressure is the normal nip pressure. Takes less time to reach the fixing temperature. When the nip portion N reaches the fixing temperature, the "sheet loading possible time" is reached, and the sheets 21a and 21b are conveyed to the nip portion N, heated and pressurized, and then discharged to the sheet discharge tray 18. Therefore, when the nip pressure is high, the time from when the user issues a print instruction until the papers 21a and 21b on which the toner images are formed are discharged to the paper discharge tray 18, that is, FPOT becomes shorter.

FIG. 9 is a diagram showing the relationship between the nip pressure and the life of the fixing unit 50. The horizontal axis represents the nip pressure, and the vertical axis represents the life of the fixing unit 50.

As shown in FIG. 9, the nip pressure and the life of the fixing unit 50 are substantially in inverse proportion to each other, and increasing the nip pressure shortens the life of the fixing unit 50. This is because the wear of the surface layer of the fixing belt 51 progresses as the nip pressure increases. Further, if the nip pressure increases, the sliding member 53 deteriorates, and the driving torque of the fixing unit 50 increases.

As described above, when the nip pressure is increased, the fixing temperature is lowered and the FPOT is shortened, but the life of the fixing unit 50 is shortened. Therefore, in the image forming apparatus 100 according to the embodiment, when the print instruction is received from the user, the nip pressure is set based on the temperature rising condition toward the print setting temperature of the nip portion N and the degree of wear of the fixing portion 50. By raising it, the FPOT is shortened and the fixing unit 50 is prevented from being consumed.

FIG. 10 is a diagram showing the required nip pressure. The table shown in FIG. 10 is stored in the ROM 82 and is referred to in the nip pressure determination process shown in FIG. The required nip pressure is assigned based on the difference between the temperature of the nip portion N when the print instruction is received from the user and the print setting temperature (hereinafter, also referred to as “temperature difference T”). The temperature difference T is a value obtained by subtracting the print setting temperature from the temperature of the nip portion N.

As shown in FIG. 10, the required nip pressure is assigned such that it increases as the temperature difference T increases, that is, as the value of the temperature difference T decreases. Generally, when the temperature difference T is large, it takes a long time to raise the temperature of the nip portion N, and the FPOT becomes long. However, according to the allocation shown in FIG. 10, when the temperature difference T is large, the required nip pressure is determined to be a large nip pressure, so that the fixing temperature is lowered and the temperature raising time is shortened. As a result, FPOT is shortened.

FIG. 11 is a diagram showing the upper limit nip pressure. The table shown in FIG. 11 is stored in the ROM 82 and is referred to in the nip pressure determination process shown in FIG. The upper limit nip pressure is assigned based on the total travel distance P of the fixing belt 51. The total running distance P of the fixing belt 51 indicates the degree of wear of the fixing unit 50. When the total traveling distance P of the fixing belt 51 is long, it can be said that the wear of the surface layer of the fixing belt 51 is advanced.

As shown in FIG. 11, the upper limit nip pressure is assigned so that it becomes smaller as the total traveling distance P of the fixing belt 51 becomes longer. As shown in FIG. 9, when the nip pressure is increased, the abrasion of the surface layer of the fixing belt 51 is promoted. If the total traveling distance P of the fixing belt 51 is long, that is, if the surface layer of the fixing belt 51 is already worn, if the nip pressure is increased, the wear is spurred. However, according to the allocation shown in FIG. 11, when the wear of the surface layer of the fixing belt 51 is advanced, the upper limit nip pressure is determined to be a small nip pressure, so that the deterioration of the fixing belt 51 is suppressed.

Note that the nip pressure may be assigned based on the total number of revolutions of the fixing belt 51, the total number of revolutions of the pressure roller 58, or the total number of revolutions of the heating member 57 instead of the total traveling distance P of the fixing belt 51. Good. The total number of revolutions of the fixing belt 51, the total number of revolutions of the pressure roller 58, or the total number of revolutions of the heating member 57 also indicates the degree of wear of the fixing unit 50. When the total number of rotations of the fixing belt 51, the total number of rotations of the pressure roller 58, or the total number of rotations of the heating member 57 is large, the fixing unit 50 is being consumed, and therefore the nip pressure smaller than the upper limit nip pressure is reached. Is assigned to suppress the consumption of the fixing unit 50.

FIG. 12 is a diagram showing the set value of the nip pressure in the print mode. The table shown in FIG. 12 is stored in the ROM 82 and is referred to in the nip pressure determination process shown in FIG. In the image forming apparatus 100, by assigning the nip pressure as shown in FIG. 12, as the difference between the temperature of the nip portion N and the print setting temperature (temperature difference T) changes during the print mode, the nip pressure is changed. Change.

As shown in FIG. 12, a small nip pressure is assigned as the temperature difference T decreases, that is, as the value of the temperature difference T approaches a positive value, except when the nip pressure at the start of printing is the normal nip pressure. ing. As shown in FIG. 9, when the nip pressure is high, the fixing section 50 is worn out. When there is a large difference between the nip portion N and the print setting temperature, such as at the start of printing, it is necessary to increase the nip pressure to satisfy the fixing strength. However, when the difference between the print setting temperature and the print setting temperature decreases due to the temperature rise of the nip portion N, the nip portion N is close to the fixing temperature or is higher than the fixing temperature. Satisfies strength. With the allocation shown in FIG. 12, the nip pressure becomes weaker as the difference between the temperature of the nip portion N and the print setting temperature becomes smaller, so that the wear of the fixing portion 50 can be suppressed.

FIG. 13 is a diagram showing an additional time until the sheets 21a and 21b are loaded. The table shown in FIG. 13 is stored in the ROM 82 and is referred to in the nip pressure determination process shown in FIG.

Inserting the sheets 21a and 21b is to convey the sheets 21a and 21b to the nip portion N. In the image forming apparatus 100, the size of the nip pressure (“requested nip pressure”) assigned based on the difference (temperature difference T) between the temperature of the nip portion N and the print setting temperature when the print instruction is received from the user. Is larger than the size of the nip pressure (“upper limit nip pressure”) assigned based on the degree of wear of the fixing unit 50, the nip pressure is set to the upper limit nip pressure. Although such setting can suppress the wear of the fixing unit 50, the nip pressure becomes smaller than the required nip pressure, and the fixing strength may not be satisfied.

Therefore, in the image forming apparatus 100, as shown in FIG. 13, when the required nip pressure is larger than the upper limit nip pressure, the additional time until the sheets 21a and 21b are loaded is allocated. Accordingly, even if the set nip pressure is lower than the required nip pressure, the conveyance of the sheets 21a and 21b to the nip portion N can be delayed, so that the temperature rising time of the nip portion N is secured, The fixing strength can be satisfied.

FIG. 14 is a flowchart showing the nip pressure determination process. The nip pressure determination process is a process of determining the nip pressure when a print instruction is received from the user, and is realized by the control unit 80 (for example, the CPU 81) executing a predetermined program stored in the ROM 82. ..

First, the control unit 80 determines whether or not a print instruction has been received from the user (S10). The print instruction is sent to the control unit 80 when the user presses the print button. The control unit 80 repeats the process of S10 until the print instruction is received from the user, and when the print instruction is received from the user (YES in S10), moves to S11.

In S11, the control unit 80 detects the value of the temperature sensor 60b (S11). As a result, the temperature of the nip portion N when the print instruction is received from the user is specified. Next, the control unit 80 refers to the table shown in FIG. 4 to acquire the print setting temperature (S12). Next, the control unit 80 calculates a value obtained by subtracting the print setting temperature acquired in S12 from the value of the temperature sensor 60b (S13). As a result, the difference (temperature difference T) between the temperature of the nip portion N and the print setting temperature when the print instruction is received from the user described in FIG. 10 is specified. Next, the control unit 80 refers to the table shown in FIG. 10 to determine the required nip pressure according to the temperature difference T (S14).

Next, the control unit 80 acquires the total traveling distance P of the fixing belt 51 (S15). As a result, the degree of wear of the surface layer of the fixing belt 51 is specified. Next, the control unit 80 refers to the table shown in FIG. 11 to determine the upper limit nip pressure according to the total traveling distance P of the fixing belt 51 (S16).

Next, the control unit 80 determines whether the required nip pressure is less than or equal to the upper limit nip pressure (S17). When the required nip pressure is equal to or lower than the upper limit nip pressure (YES in S17), the control unit 80 sets the nip pressure to the required nip pressure (S18), and proceeds to S22. On the other hand, when the required nip pressure exceeds the upper limit nip pressure (NO in S17), the controller 80 sets the nip pressure to the upper limit nip pressure (S19), and proceeds to S20.

In S20, the control unit 80 refers to the table shown in FIG. 13 to determine the additional time until the paper is loaded. Next, the control unit 80 determines whether the additional time determined in S20 has elapsed (S21). This is because the conveyance of the sheets 21a and 21b to the nip portion N is delayed by the additional time. Since the nip pressure is set to the upper limit nip pressure lower than the required nip pressure in the processing of S19, the fixing strength may not be satisfied. However, by S20 and S21, the conveyance of the sheets 21a and 21b to the nip portion N can be delayed, and the temperature rising time of the nip portion N is secured, so that the fixing strength can be satisfied. The control unit 80 repeats the processing of S21 until the additional time determined in S20 has elapsed, and when the additional time determined in S20 has elapsed (YES in S21), moves to S22.

In S22, the control unit 80 controls the conveyance rollers to start the conveyance of the sheets 21a and 21b to the nip portion N. Next, the controller 80 determines whether the set nip pressure is other than the normal nip pressure (S23). If the set nip pressure is other than the normal nip pressure (YES in S23), the control unit 80 proceeds to S24. On the other hand, when the set nip pressure is the normal nip pressure (NO in S23), the control unit 80 proceeds to S28.

In S24, the control unit 80 detects the value of the temperature sensor 60b. After receiving the print instruction from the user, the temperature of the nip portion N rises with the rotation of the fixing belt 51, and the current temperature of the nip portion N is specified by the process of S24. Next, the control unit 80 calculates a value obtained by subtracting the print setting temperature acquired in S12 from the value of the temperature sensor 60b (S25). As a result, the difference (temperature difference T) between the temperature of the nip portion N and the print setting temperature described in FIG. 10 is specified. Next, the control unit 80 refers to the table shown in FIG. 12 and determines whether or not the temperature difference T has reached a predetermined value set for each nip pressure set in S18 or S19 (S26). When the temperature difference T reaches the predetermined value (YES in S26), the control unit 80 proceeds to S27. On the other hand, when the temperature difference T is not the predetermined value (NO in S26), the control unit 80 moves to S23.

In S27, the control unit 80 refers to the table shown in FIG. 12 and changes the nip pressure to a small nip pressure. Then, the control unit 80 determines whether or not the printing is completed (S28). When the printing is completed (YES in S28), the control unit 80 ends the process shown in FIG. On the other hand, when the printing is not completed (NO in S28), the controller 80 moves to S23.

FIG. 15 is a diagram showing an example of changes in the nip pressure during the print mode. The horizontal axis represents the elapsed time after receiving the print instruction, and the vertical axis represents the temperature of the nip portion N.

FIG. 15 shows the transition of the nip pressure after the print instruction is received from the user and the nip pressure is determined to be “nip pressure up3” in S18 or S19 of the nip pressure determination processing shown in FIG. ing.

As shown in FIG. 15, after the nip pressure is determined to be “nip pressure up3”, as the temperature of the nip portion N increases toward the print setting temperature, the nip pressure is gradually changed to a smaller nip pressure. Will be done. Specifically, the nip pressure is changed to “nip pressure up2” at the timing when the difference between the temperature of the nip portion N and the print setting temperature (temperature difference T) becomes −20, and the temperature difference T becomes −10. The nip pressure is changed to “nip pressure up1” at the timing when the temperature difference T becomes −5, and the nip pressure is changed to the “normal nip pressure” at the timing when the temperature difference T becomes −5.

As described above, in the image forming apparatus 100, when the difference between the temperature of the nip portion N and the print setting temperature is large, the nip pressure is increased to lower the fixing temperature, thereby shortening the paper inputtable time and reducing the FPOT. Realize shortening. On the other hand, when the difference between the temperature of the nip portion N and the print setting temperature becomes small, the nip pressure is weakened to suppress the wear of the fixing portion 50.

As described above, in the image forming apparatus 100 according to the embodiment, when determining the nip pressure when the print instruction is received from the user, the control unit 80 first sets the difference between the temperature of the nip portion N and the print setting temperature ( The required nip pressure is determined based on the temperature difference T), and the upper limit nip pressure is determined based on the total travel distance P of the fixing belt 51. After determining the required nip pressure and the upper limit nip pressure, the control unit 80 compares the required nip pressure with the upper limit nip pressure, and if the required nip pressure is equal to or lower than the upper limit nip pressure, sets the nip pressure to the required nip pressure. If the required nip pressure exceeds the upper limit nip pressure, the nip pressure is set to the upper limit nip pressure. The required nip pressure is determined to be larger as the temperature difference T is larger, and the upper limit nip pressure is determined to be smaller as the total traveling distance P of the fixing belt 51 is longer. Therefore, FPOT is shortened and Wear of the fixing unit 50 is suppressed.

In the image forming apparatus 100 according to the embodiment, when the required nip pressure exceeds the upper limit nip pressure, the conveyance of the sheets 21a and 21b to the nip portion N is delayed. As a result, the temperature rise time of the nip portion N is secured, so that the fixing strength is satisfied.

Further, in the image forming apparatus 100 according to the embodiment, when the print instruction is received from the user and the nip pressure is set higher than the normal nip pressure, the temperature rising state of the nip portion N, that is, the temperature of the nip portion N is set. And the print setting temperature (temperature difference T), the nip pressure is reduced. As a result, the consumption of the fixing unit 50 can be suppressed.

The fixing unit 50 in the embodiment has a structure as shown in FIG. However, the structure of the fixing unit 50 is not limited to this, and the fixing unit 50 does not have the pressing members 52a and 52b, the sliding member 53, and the supporting member 54, and the pressing roller 58 presses the heating member 57 to press A nip portion N may be formed between the roller 58 and the heating member 57.

Further, although the image forming apparatus 100 in the embodiment is a color printer, it is not limited to this. The image forming apparatus 100 may be mounted in any form such as a multi-function peripheral (MFP: Multi-Functional Peripheral), a copying machine, a facsimile, and a printer, or may be a monochrome machine. When the image forming apparatus 100 is a multifunction machine or a copying machine, it is possible to shorten FCOT in addition to shortening FPOT.

Hereinafter, some modified examples will be shown. In the modified example, only the points different from the above-described embodiment are described, and the description of the same points is omitted.

[Modification 1]
Modification 1 is a modification regarding determination of the required nip pressure. In the above-described embodiment, the required nip pressure is determined based on the difference (temperature difference T) between the temperature of the nip portion N and the print setting temperature when the print instruction is received from the user. On the other hand, in the first modification, the required nip pressure is determined based on the elapsed time from the standby mode.

FIG. 16 is a diagram showing the required nip pressure. The table shown in FIG. 16 is stored in the ROM 82 and is referred to in the process (S14) of determining the required nip pressure in the nip pressure determining process of FIG.

As shown in FIG. 16, the required nip pressure is assigned based on the elapsed time t from the standby mode. The elapsed time t from the standby mode is the time from the shift to the standby mode until the print instruction is received. The required nip pressure is assigned such that it increases as the elapsed time t from the standby mode increases. As described with reference to FIG. 5, in the standby mode, the temperature in the nip portion N decreases with time. Therefore, the longer the elapsed time t from the standby mode is, the larger the difference between the temperature of the nip portion N and the print setting temperature is, the longer it takes to raise the temperature of the nip portion N, and the longer the FPOT becomes. However, according to the allocation shown in FIG. 16, when the elapsed time t from the standby mode is long, the required nip pressure is determined to be a large nip pressure, so that the fixing temperature is lowered and the temperature raising time is shortened. As a result, FPOT is shortened.

[Modification 2]
Modification 2 is a modification regarding determination of the required nip pressure. In the above-described embodiment, the required nip pressure is determined based on the difference (temperature difference T) between the temperature of the nip portion N and the print setting temperature when the print instruction is received from the user. On the other hand, in the second modification, the required nip pressure is determined based on the temperature difference T and the voltage supplied to the image forming apparatus 100.

FIG. 17 is a diagram showing the FPOT. FIG. 18 is a diagram showing the required nip pressure. The tables shown in FIGS. 17 and 18 are stored in the ROM 82, and are referred to in the process (S14) of determining the required nip pressure in the nip pressure determining process of FIG. Specifically, the control unit 80 identifies the FPOT from the temperature difference T and the supplied voltage V with reference to FIG. 17, and determines the required nip pressure from the identified FPOT with reference to FIG.

As shown in FIG. 17, the FPOT becomes longer as the temperature difference T becomes larger, that is, the value of the temperature difference T becomes negative, and becomes longer as the supplied voltage V becomes smaller. A large temperature difference T means that it takes time to raise the temperature, and a small supplied voltage V also means that it takes time to raise the temperature. Further, as shown in FIG. 18, the required nip pressure is assigned to increase as the value of FPOT increases, that is, the temperature difference T increases and the supplied voltage V decreases. Thus, when the temperature difference T is large and the supplied voltage V is small, the required nip pressure is determined to be a large nip pressure, so that the fixing temperature is lowered and the temperature raising time is shortened. As a result, FPOT is shortened.

[Modification 3]
Modification 3 is a modification regarding determination of the required nip pressure. In the above-described embodiment, the required nip pressure is determined based on the difference (temperature difference T) between the temperature of the nip portion N and the print setting temperature when the print instruction is received from the user. On the other hand, in the third modification, the required nip pressure is determined based on the elapsed time t from the standby mode and the voltage V supplied to the image forming apparatus 100.

FIG. 19 is a diagram showing an FPOT. In the modified example 3, in the process (S14) of determining the required nip pressure in the nip pressure determination process shown in FIG. 14, the required nip pressure is determined with reference to FIG. 19 and FIG. 18 referred to in the modified example 2. .. The table shown in FIG. 19 is stored in the ROM 82. Specifically, the control unit 80 identifies the FPOT from the elapsed time t from the standby mode and the supplied voltage V with reference to FIG. 19, and the required nip pressure from the identified FPOT with reference to FIG. To decide.

As shown in FIG. 19, the FPOT becomes longer as the elapsed time t from the standby mode becomes longer, and becomes longer as the supplied voltage V becomes smaller. A long elapsed time t from the standby mode means that it takes time to raise the temperature, and a small voltage V supplied also means that it takes time to raise the temperature. Further, as shown in FIG. 18, the required nip pressure is assigned to increase as the value of FPOT increases, that is, as the elapsed time t from the standby mode increases and the voltage V supplied decreases. .. Accordingly, when the elapsed time t from the standby mode is long and the supplied voltage V is small, the required nip pressure is determined to be a large nip pressure, so that the fixing temperature is lowered and the temperature raising time is shortened. As a result, FPOT is shortened.

[Modification 4]
Modification 4 is a modification regarding determination of the upper limit nip pressure. In the above embodiment, the upper limit nip pressure is determined based on the total traveling distance P of the fixing belt 51. On the other hand, in the modified example 4, the upper limit nip pressure is determined based on the total number of printed sheets of the image forming apparatus 100.

FIG. 20 is a diagram showing the upper limit nip pressure. The table shown in FIG. 20 is stored in the ROM 82 and is referred to in the process of determining the upper limit nip pressure (S16) of the nip pressure determination process shown in FIG.

As shown in FIG. 20, the upper limit nip pressure is assigned based on the total number of printed sheets Q. The upper limit nip pressure is assigned so that it becomes smaller as the total number of printed sheets Q is larger. The total number of printed sheets Q indicates the degree of wear of the fixing unit 50. When the total number of printed sheets Q is large, it can be said that the wear of the surface layer of the fixing belt 51 is advanced. As described in FIG. 9, when the nip pressure is increased, the abrasion of the surface layer of the fixing belt 51 is promoted. If the total number of printed sheets Q is large, that is, if the surface layer of the fixing belt 51 has already been worn, increasing the nip pressure accelerates the wear. However, when the surface layer of the fixing belt 51 is abraded, the upper limit nip pressure is determined to be a small nip pressure, so that the abrasion of the fixing belt 51 is suppressed.

[Modification 5]
Modification 5 is a modification regarding determination of the upper limit nip pressure. In the above embodiment, the upper limit nip pressure is determined based on the total traveling distance P of the fixing belt 51. On the other hand, in the modified example 5, the upper limit nip pressure is determined based on the drive torque of the fixing unit 50.

FIG. 21 is a diagram showing the upper limit nip pressure. The table shown in FIG. 21 is stored in the ROM 82, and is referred to in the process of determining the upper limit nip pressure (S16) in the nip pressure determination process shown in FIG.

As shown in FIG. 21, the upper limit nip pressure is assigned based on the drive torque R of the fixing unit 50. The upper limit nip pressure is assigned such that the higher the drive torque R of the fixing unit 50, the smaller the upper limit nip pressure. The drive torque R of the fixing unit 50 indicates the degree of wear of the fixing unit 50. When the driving torque of the fixing unit 50 increases, it can be said that the sliding member 53 has deteriorated. As described with reference to FIG. 9, when the nip pressure is increased, deterioration of the sliding member 53 is promoted. If the driving torque R of the fixing unit 50 is high, that is, if the sliding member 53 has already deteriorated, increasing the nip pressure accelerates the deterioration. However, when the driving torque R of the fixing unit 50 is high, the upper limit nip pressure is determined to be a small nip pressure, so that deterioration of the sliding member 53 is suppressed.

[Modification 6]
Modification 6 is a modification relating to the change of the nip pressure during the print mode. In the above-described embodiment, when the print instruction is received from the user and the nip pressure is set higher than the normal nip pressure, the temperature rising state of the nip portion N, that is, the temperature of the nip portion N and the print setting temperature are The nip pressure was changed to a small nip pressure based on the difference (temperature difference T). On the other hand, in the modified example 6, when a print instruction is received from the user and the nip pressure is set to be higher than the normal nip pressure, the nip pressure is changed to a small nip pressure based on the number of printed sheets S after the setting. ..

FIG. 22 is a diagram showing the set value of the nip pressure in the print mode. The table shown in FIG. 22 is stored in the ROM 82, and is referred to in the nip pressure changing process (S27) of the nip pressure determining process shown in FIG.

As shown in FIG. 22, except that the nip pressure at the start of printing is the normal nip pressure, a smaller nip pressure is assigned as the number of printed sheets S increases. As shown in FIG. 9, when the nip pressure is high, the fixing section 50 is worn out. When there is a large difference between the nip portion N and the print setting temperature, such as at the start of printing, it is necessary to increase the nip pressure to satisfy the fixing strength. However, after the nip pressure is increased, as the number of printed sheets S increases, the nip portion N approaches the fixing temperature or becomes higher than the fixing temperature, so that the fixing strength can be satisfied even if the nip pressure is weakened. According to the allocation shown in FIG. 22, when the print instruction is received from the user and the nip pressure is set to be higher than the normal nip pressure, the nip pressure becomes smaller as the number of printed sheets S after setting increases. Since it is changed, consumption of the fixing unit 50 is suppressed.

The embodiment and the modification examples 1 to 6 have been described above. In the embodiment, the determination of the required nip pressure can be replaced with any one of the modified examples 1 to 3, and the determination of the upper limit nip pressure can be replaced with any one of the modified examples 4 and 5. Therefore, the modification 6 can be replaced with the modification of the nip pressure during the print mode. Therefore, in the embodiment, only the determination of the required nip pressure may be replaced with any one of the modified examples 1 to 3, and only the determination of the upper limit nip pressure may be performed in any one of the modified examples 4 and 5. Alternatively, the modification 6 may be replaced only with respect to the change of the nip pressure during the print mode. Further, in the embodiment, the determination of the required nip pressure may be replaced with any one of the modifications 1 to 3, and the determination of the upper limit nip pressure may be replaced with any one of the modifications 4 and 5. Further, in the embodiment, the determination of the required nip pressure may be replaced with any one of the modifications 1 to 3, and the modification 6 may be replaced with the modification of the nip pressure in the print mode. Further, in the embodiment, any one of the modified examples 4 and 5 may be substituted for determining the upper limit nip pressure, and the modified example 6 may be substituted for the change of the nip pressure during the print mode. Further, in the embodiment, the required nip pressure is determined by any one of Modifications 1 to 3, and the upper limit nip pressure is determined by any one of Modifications 4 and 5. Modification 6 may be substituted for the change in the nip pressure.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

10 printer engine, 20a, 20b paper feed cassette, 21a, 21b paper, 50 fixing unit, 51 fixing belt, 52a, 52b pressing member, 53 sliding member, 56 heat source, 57 heating member, 58 pressing roller, 60a, 60b Temperature sensor, 80 Control part, 81 CPU, 82 ROM, 100 Image forming apparatus.

Claims (11)

An image forming apparatus capable of forming a toner image on a recording medium,
A first rotating body that is heated by a heat source, and a second rotating body that can be pressed against the first rotating body, and is conveyed to a nip portion formed between the first rotating body and the second rotating body. Fixing means for fixing the toner image to the recording medium by heating by the first rotating body and pressure contact with the first rotating body by the second rotating body;
A control means for controlling the pressure in the nip portion,
When the control unit receives a print instruction, the control unit raises the pressure in the nip portion according to the temperature rising condition toward the temperature required for the nip portion and the degree of wear of the fixing unit. Forming equipment. The first rotating body is an endless fixing belt,
The fixing unit further includes a pressing member inscribed in the fixing belt,
The second rotating body is provided at a position facing the pressing member via the fixing belt, and presses the fixing belt against the pressing member to form the nip portion with the fixing belt. The image forming apparatus according to claim 1. The control means, based on the difference between the temperature required for the nip portion and the temperature required for the nip portion when the print instruction is received, The image forming apparatus according to claim 1, wherein the determination is performed. 4. The control unit according to claim 1, wherein the control unit determines a temperature rising state toward a temperature required for the nip portion based on a length of a waiting time for waiting for a print instruction. The image forming apparatus according to item. The image forming apparatus according to claim 3, wherein the control unit further increases the pressure in the nip portion according to the voltage supplied to the image forming apparatus. The image forming method according to claim 1, wherein the control unit determines the consumption degree of the fixing unit based on the total number of rotations of the first rotating body or the second rotating body. apparatus. The image forming apparatus according to claim 1, wherein the control unit determines the degree of wear of the fixing unit based on the total number of printed sheets. The image forming apparatus according to claim 1, wherein the control unit determines a consumption degree of the fixing unit based on a driving torque of the fixing unit. The image according to claim 1, wherein the control unit lowers the pressure in the nip portion when the number of printed sheets reaches a predetermined value after the pressure in the nip portion is increased. Forming equipment. The control means lowers the pressure in the nip portion when the difference between the temperature in the nip portion and the temperature required in the nip portion reaches a predetermined value after increasing the pressure in the nip portion. The image forming apparatus according to any one of claims 1 to 9. The image forming apparatus according to claim 1, wherein the control unit determines the upper limit value of the pressure in the nip portion based on the degree of wear of the fixing unit.

Images