JP2021149056A - Fixing device and image forming apparatus - Google Patents

Abstract

To accurately determine the life of a fixing device.SOLUTION: A fixing device has a rotatable first rotating body that has a release layer and an elastic layer in order from a surface, a second rotating body that rotates in contact with the first rotating body, and a heating body that heats the first rotating body, conveys a recording material on which an image is formed while sandwiching the recording material at a nip part formed between the first rotating body and the second rotating body, and heats the image. The fixing device comprises: a detection unit that detects a surface temperature of the release layer; a quantum type infrared sensor that detects a surface temperature of the elastic layer in a non-contact manner; and a determination unit that determines the life of the fixing device based on the temperature difference between the surface temperature of the release layer and the surface temperature of the elastic layer. The quantum type infrared sensor detects an infrared ray radiated from the surface of the elastic layer to detect the surface temperature of the elastic layer, and the infrared emissivity of the elastic layer in a wavelength region of the infrared ray detected by the quantum type infrared sensor is larger than the infrared emissivity of the release layer in the wavelength region of the infrared ray detected by the quantum type infrared sensor.SELECTED DRAWING: Figure 2

Description

The present invention relates to an image forming apparatus such as a copying machine or a printer, and a fixing device used in the image forming apparatus, which has a function of forming an image on a recording material such as a sheet.

Conventionally, in an image forming apparatus such as a copying machine or a printer, a recording material carrying an unfixed image formed of toner is heated while being in contact with a fixing roller to fix the unfixed image on the recording material. A fixing device is used. The fixing roller is heated by the heater.
In the fixing device, in order to control the temperature of the surface of the fixing roller, there is a method of arranging the temperature detecting member in close proximity to the fixing roller in a non-contact manner. As the temperature detecting means, there are those using a thermopile, those using a thermistor on an infrared absorbing film which is a film member, and the like. The temperature detecting means estimates and detects the temperature of the fixing roller by receiving or absorbing infrared rays radiated from the fixing roller that is the target of temperature detection.

Patent Document 1 discloses a method of reducing the infrared emissivity of the fixing roller in the wavelength region that can be detected by the temperature detecting means of the fixing device to be equal to or lower than the infrared emissivity of the toner. By using the method disclosed in Patent Document 1, even when the toner is offset to the surface of the fixing roller, which is the infrared radiation surface, during the use of the fixing device, it is possible to suppress the detection of the temperature of the fixing roller as a lower temperature than the actual temperature. can. Therefore, deterioration of the fixing device and the image forming device due to the abnormal temperature rise of the fixing roller can be suppressed.

Japanese Unexamined Patent Publication No. 2003-57987

Although the method disclosed in Patent Document 1 can suppress the deterioration of the fixing device, it is difficult to determine the life of the fixing device due to the deterioration of the fixing device. In view of the above problems, an object of the present invention is to accurately determine the life of the fixing device.

The fixing device of the present invention for solving the above-mentioned problems is
A rotatable first rotating body having a release layer and an elastic layer in order from the surface, a second rotating body that rotates in contact with the first rotating body, and a heating body that heats the first rotating body. A fixing device that heats the image by transporting the recording material on which the image is formed while sandwiching it between the nip portion formed between the first rotating body and the second rotating body.
A detector that detects the surface temperature of the release layer and
A quantum infrared sensor that detects the surface temperature of the elastic layer in a non-contact manner,
A determination unit that determines the life of the fixing device based on the temperature difference between the surface temperature of the release layer and the surface temperature of the elastic layer.
With
The quantum type infrared sensor detects the surface temperature of the elastic layer by detecting infrared rays radiated from the surface of the elastic layer.
The infrared emissivity of the elastic layer in the infrared wavelength range detected by the quantum infrared sensor is larger than the infrared emissivity of the release layer in the infrared wavelength range detected by the quantum infrared sensor. It is characterized by that.

The fixing device of the present invention for solving the above-mentioned problems is
A rotatable first rotating body having a release layer and an elastic layer in order from the surface, a second rotating body that rotates in contact with the first rotating body, and a heating body that heats the first rotating body. A fixing device that heats the image by transporting the recording material on which the image is formed while sandwiching it between the nip portion formed between the first rotating body and the second rotating body.
A quantum infrared sensor that detects the surface temperature of the elastic layer in a non-contact manner is provided.
The quantum type infrared sensor detects the surface temperature of the elastic layer by detecting infrared rays radiated from the surface of the elastic layer.
The infrared emissivity of the elastic layer in the infrared wavelength range detected by the quantum infrared sensor is larger than the infrared emissivity of the release layer in the infrared wavelength range detected by the quantum infrared sensor. It is characterized by that.

According to the present invention, the life of the fixing device can be accurately determined.

Schematic configuration diagram of the image forming apparatus according to the first embodiment Cross-sectional view of the fixing device according to the first embodiment An exploded perspective view of a film assembly unit used in the fixing device according to the first embodiment. Front view of the fixing device according to the first embodiment Cross-sectional view of the fixing device according to the first embodiment Block diagram of control unit and fixing heating drive circuit according to the first embodiment A graph showing the relationship between the difference in detected temperature and the thickness of the release layer according to Example 1. A graph showing the relationship between the thickness of the release layer and the remaining life of the fixing device according to the first embodiment. Flow chart for detecting the thickness of the release layer and the remaining life of the fixing device according to the first embodiment Cross-sectional view of the fixing device according to the second embodiment Enlarged view of the fixing nip portion when the fixing device according to the second embodiment is new and when it has reached the end of its life. A graph showing the relationship between the thickness of the release layer according to Example 3 and the correction value of the target control temperature.

Hereinafter, preferred embodiments of the present invention will be described in detail, exemplary, with reference to the drawings. However, the dimensions, materials, shapes, etc. of the components described in this embodiment should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, and the invention of the present invention. It is not intended to limit the scope to the following embodiments.

(Example 1)
(1) Image Forming Device The configuration of the image forming device according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the first embodiment. The image forming apparatus according to the first embodiment is, for example, a full-color printer of an intermediate transfer method using an electrophotographic method.

The image forming apparatus includes image forming units 1Y, 1M, 1C, and 1Bk that form yellow, magenta, cyan, and black images, respectively. These four image forming portions are arranged in a row at regular intervals. Hereinafter, when the image forming units 1Y, 1M, 1C, and 1Bk are collectively referred to, they are referred to as an image forming unit 1.

The photosensitive drums 2 as image carriers are attached to the image forming portions 1Y, 1M, 1C, and 1Bk, respectively.
a, 2b, 2c, and 2d are installed. Around each of the photosensitive drums 2a, 2b, 2c, and 2d, charging rollers 3a, 3b, 3c, 3d as charging means and developing devices 4a, 4b, 4c, 4d as developing means are installed, respectively. Further, transfer sheets 5a, 5b, 5c, 5d and drum cleaning devices 6a, 6b, 6c, 6d as transfer means are installed around the photosensitive drums 2a, 2b, 2c, 2d, respectively. Further, around each of the photosensitive drums 2a, 2b, 2c, 2d, there are exposure devices 7a, 7b, 7c, 7d above the charging rollers 3a, 3b, 3c, 3d and the developing devices 4a, 4b, 4c, 4d. Each is installed. Yellow toner, magenta toner, cyan toner, and black toner having negative charging characteristics are stored in each of the developing devices 4a, 4b, 4c, and 4d, respectively.

The photosensitive drums 2a, 2b, 2c, and 2d are negatively charged organic photoconductors, and have a photosensitive layer on a drum substrate made of aluminum. Hereinafter, when the photosensitive drums 2a, 2b, 2c, and 2d are collectively referred to, they are referred to as the photosensitive drum 2. The photosensitive drum 2 is rotationally driven in the direction of arrow R1 (counterclockwise) at a predetermined process speed by a driving device (not shown). A desired charging bias is applied to the charging rollers 3a, 3b, 3c, and 3d by a charging bias power supply (not shown). Hereinafter, when the charging rollers 3a, 3b, 3c, and 3d are collectively referred to, they are referred to as charging rollers 3. The charging roller 3 is in contact with the photosensitive drum 2 with a predetermined pressure contact force, and uniformly charges the surface of the photosensitive drum 2 to a predetermined potential. In Example 1, the photosensitive drum 2 is negatively charged by the charging roller 3.

The exposure device (laser scanner device) 7a, 7b, 7c, 7d emits laser light modulated in response to a time-series electric digital pixel signal of image information input from a host computer (not shown) to a laser output unit (laser output unit). Output from (not shown). The output laser beam exposes the surface of the photosensitive drum 2 as an image through a reflection mirror (not shown). As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 2 charged by the charging roller 3.

The developing devices 4a, 4b, 4c, and 4d use a contact developing method as a developing method. When the developing devices 4a, 4b, 4c, and 4d are collectively referred to, they are referred to as the developing device 4. The developing apparatus 4 has a developing roller as a developer carrier. The toner supported in a thin layer on the developing roller is supplied to the photosensitive drum 2 by the developing roller which is rotationally driven by a developing driving device (not shown). A development bias is applied to the developing rollers by a developing voltage applying means (not shown). The electrostatic latent image formed on the photosensitive drum 2 is developed (reversed and developed) as a toner image by the toner supplied from the developing roller, and the toner image is formed on the photosensitive drum 2.

In the full-color image forming mode, the developing rollers in the developing devices 4a, 4b, 4c, and 4d come into contact with the photosensitive drums 2a, 2b, 2c, and 2d2. In the monocolor image forming mode (for example, black-and-white image forming mode) described later, the developing roller in the image forming unit 1 in which the image forming operation is performed and the photosensitive drum 2 come into contact with each other, and the image forming unit 1 in which the image forming operation is not performed is not performed. The developing roller and the photosensitive drum 2 in the above are separated from each other. This is to suppress deterioration and consumption of the developing roller and toner.

The transfer sheets 5a, 5b, 5c, and 5d as the sheet-shaped transfer means are sheet members formed of a conductive resin. Further, the transfer pads 15a, 15b, 15c, 15d as the transfer sheet pressurizing member are elastic members formed of rubber or the like.

An intermediate transfer belt 20 which is an endless belt-shaped intermediate transfer body is installed facing the photosensitive drum 2. The intermediate transfer belt 20 is made of a semi-conductive resin. The intermediate transfer belt 20 is stretched by a drive roller 21, a tension roller 22, and a secondary transfer opposed roller 23. The intermediate transfer belt 20 is tensioned by a pressurizing means (not shown) on the tension roller 22, and is rotationally driven by the drive roller 21 in the direction of arrow R2.

The intermediate transfer belt 20 is in contact with the photosensitive drum 2a. The transfer sheet 5a is arranged on the inner peripheral surface side of the intermediate transfer belt 20 and is in contact with the intermediate transfer belt 20. The transfer sheet 5a is in contact with the transfer pad 15a and is pressed against the inner peripheral surface of the intermediate transfer belt 20 by the transfer pad 15a. Therefore, the transfer pad 15a presses the photosensitive drum 2a via the transfer sheet 5a and the intermediate transfer belt 20. A power supply for primary transfer (not shown) is connected to the transfer sheet 5a. The toner image formed on the photosensitive drum 2a is primarily transferred onto the rotating intermediate transfer belt 20 by the transfer sheet 5a to which the primary transfer voltage is applied.

The configuration described above is the configuration of the transfer unit of the image forming unit 1Y, and the same applies to the configuration of the transfer unit of the image forming units 1M, 1C, and 1Bk. The yellow and black toner images formed by the photosensitive drums 2c and 2d are sequentially superimposed on the yellow and magenta toner images superimposed and transferred on the intermediate transfer belt 20 at each transfer unit. As a result, a full-color toner image is formed on the intermediate transfer belt 20.

The secondary transfer roller 24 presses the secondary transfer opposed roller 23 from the outside of the intermediate transfer belt 20. Further, the secondary transfer roller 24 has a configuration capable of being in contact with the intermediate transfer belt 20 and being separated from the intermediate transfer belt 20. The recording material (recording medium) P is conveyed to the contact portion between the secondary transfer roller 24 and the intermediate transfer belt 20 by the paper feed roller (resist roller) 13. A power supply for secondary transfer (not shown) is connected to the secondary transfer roller 24. The toner image primaryly transferred onto the intermediate transfer belt 20 is secondarily transferred onto the recording material P being conveyed by the secondary transfer roller to which the secondary transfer voltage is applied.

A charging roller 25 (cleaning charging roller 25) as a cleaning charging member is provided on the outer peripheral surface side of the intermediate transfer belt 20. The cleaning charging roller 25 is in contact with the intermediate transfer belt 20 at a position downstream of the contact portion M between the intermediate transfer belt 20 and the secondary transfer roller 24 in the direction of rotation of the intermediate transfer belt 20. The cleaning charging roller 25 is a belt cleaning device for removing and recovering the transfer residual toner remaining on the surface of the intermediate transfer belt 20. A cleaning power supply (not shown) is connected to the cleaning charging roller 25. The transfer residual toner is removed by the cleaning charging roller 25 to which the cleaning voltage is applied.

On the outer peripheral surface side of the intermediate transfer belt 20, a sensor unit 50 for color registration correction and density correction is provided at a position facing the drive roller 21. Regardless of various conditions such as changes in the usage environment of the image forming apparatus and the number of images formed, stable color registration correction (alignment of toner images of each color on the intermediate transfer belt 20) or stable image density can be achieved. A sensor unit 50 is provided to obtain this. The sensor unit 50 includes a light emitting element such as an LED and a light receiving element such as a photodiode or CdS.

A fixing device (image heating device) 12 having a fixing film 30 which is a first rotating body and a pressure roller 33 which is a second rotating body is installed on the downstream side of the recording material P of the secondary transfer roller 24 in the transport direction. ing. The toner image is heated and pressurized by transporting the recording material P on which the toner image (image) is formed while being sandwiched between the fixing nip portions N formed between the fixing film 30 and the pressure roller 33. It is fixed as a fixed image on the surface of the recording material P. A guide member 42 is provided so that the tip of the recording material P is surely introduced into the fixing nip portion N.

Further, at the time of color registration correction and density correction, a toner image is formed on the intermediate transfer belt 20, and the portion of the intermediate transfer belt 20 that rotates and moves without the toner image and the toner image is irradiated with light from the light emitting element. The position and density of the toner image patch formed are measured by receiving the toner image on the intermediate transfer belt 20 and the reflected light from the portion without the toner image by the light receiving element. Color registration correction is performed by measuring the interval between the presence and absence of toner images. Further, the density is corrected by measuring the density of the toner image.

(2) Fixing device The fixing device 12 will be described. The fixing device 12 is a tensionless type film heating type image heating device. In the tensionless type film heating type fixing device 12, an endless belt-shaped (or cylindrical) heat-resistant film is used as the fixing film 30. At least a part of the peripheral length of the fixing film 30 is always tension-free (a state in which tension is not applied). When a rotational driving force is applied to the pressure roller 33, the pressure roller 33 comes into contact with the fixing film 30 and rotates, and the fixing film 30 is driven to rotate with respect to the pressure roller 33. When the heating method of the fixing device 12 is the film heating method, the heat capacity of the fixing device 12 becomes small, and the time until the temperature of the fixing device 12 reaches the fixable temperature is shortened. Therefore, when the heating method of the fixing device 12 is the film heating method, it is not necessary to perform standby temperature control when the fixing device 12 is in the standby state. Hereinafter, a case where the heating method of the fixing device 12 is a film heating method will be described.

FIG. 2 is a cross-sectional view of the fixing device 12 according to the first embodiment. Further, FIG. 3 is an exploded perspective view of the film assembly unit used in the fixing device 12. FIG. 4 is a front view of the fixing device 12. FIG. 4 shows a state in which a part of the fixing device 12 is cut out.

<Members of fixing device>
First, the main constituent members of the fixing device 12 will be described. The fixing device 12 includes a heater unit 29, a fixing film 30, a heater holder 31, and a reinforcing member 34. The heater unit 29 has a ceramic heater 32 that heats the fixing film 30. The heater holder 31 functions as a support member for supporting the ceramic heater 32, and guides the rotational running of the cylindrical fixing film 30. For the heater holder 31, a highly heat-resistant resin such as polyimide, polyamide-imide, PEEK, PPS, or liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass, or the like can be preferably used. The ceramic heater 32 as a heating body has an elongated plate shape and is in contact with the inner surface of the fixing film 30. The ceramic heater 32 has a resistance heating element 82 and electrodes printed on a ceramic substrate having high heat resistance. Further, a glass coat layer that protects the resistance heating element 82 is provided on the ceramic substrate. The resistance heating element 82 has two heating elements, and two electrodes are arranged on one side of the ceramic substrate. The glass coat layer is installed on the side in contact with the fixing film 30.

The fixing film 30 is a member provided with an elastic layer on the outside of an endless belt-shaped (or cylindrical) base layer, and further provided with a release layer on the outside. Therefore, the fixing film 30 has a release layer (first layer), an elastic layer (second layer), and a base layer (third layer) in this order from the surface. The release layer is a layer that prevents the offset phenomenon that occurs when the toner adheres to the surface of the fixing film 30 once and then moves to the recording material P again. As the release layer, a fluororesin such as perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene resin (FEP), which has a thickness of about 5 to 70 μm and has good releasability, is used. Can be used. By using a PFA tube having a thickness of 20 μm, a uniform fluororesin layer can be easily formed.

Since the fixing film 30 has an elastic layer, the fixing film 30 can heat the toner image t in a state of wrapping the toner image t regardless of the unevenness of the surface of the recording material P. For the elastic layer, for example, a silicone rubber layer having a thickness of 200 μm is used. The base layer is a layer in contact with the ceramic heater 32 on the innermost surface side of the fixing film 30. As the base layer, polyimide, polyamideimide, PEEK, SUS, Ni electroformed or the like having excellent heat resistance and flexibility is used. A base layer having a thickness of about 10 to 100 μm may be used. In Example 1, a cylindrical polyimide resin having a thickness of 50 μm and an inner diameter of 18 mm measured by a micrometer is used as a base layer.

<Structure of fixing device>
The configuration of the fixing device 12 will be described with reference to FIG. The reinforcing member 34 is made of a metal such as iron. The reinforcing member 34 is a member that maintains a strength that does not easily deform when the heater holder 31 is pressed toward the pressure roller 33 side. The ceramic heater 32 is pressed against the pressure roller 33 side by the pressing means described later via the heater holder 31 and the reinforcing member 34. The region (pressure contact region) in which the pressed pressure roller 33 and the fixing film 30 are in close contact with each other is the fixing nip portion N. In this way, the pressure roller 33 may form the fixing nip portion N together with the ceramic heater 32 via the fixing film 30.

Next, the film assembly unit used in the fixing device 12 will be described with reference to FIG. The heater holder 31 has a substantially gutter-shaped cross section, and the reinforcing member 34 fits inside the tub-shaped shape. A heater receiving groove is provided on the side of the heater holder 31 facing the pressure roller 33, and the ceramic heater 32 fits into the heater receiving groove and is fitted into a desired position. The fixing film 30 is fitted on the outside of the heater holder 31 to which the heater holder 31 and the ceramic heater 32 are assembled with a margin in peripheral length. Hereinafter, the axial direction of the cylindrical shape of the fixing film 30 (the direction of the arrow in which the fixing film 30 is inserted in FIG. 3) is referred to as a longitudinal direction. The overhanging portion of the reinforcing member 34 projects outward from both ends of the fixing film 30. The film assembly unit is assembled by fitting the flange members 36 to both ends of the overhanging portion of the reinforcing member 34. The power supply connector 35 is fitted to the power supply terminal of the ceramic heater 32 protruding from the end of the fixing film 30. Electric power is supplied to the ceramic heater 32 via the power supply connector 35. The pressure roller 33 includes a metal core metal, an elastic layer made of silicone rubber having elastic properties, and a mold release layer having releasability. A drive gear 44 is attached to one end of the core metal of the pressure roller 33. The pressurizing roller 33 rotates by receiving a rotational driving force from a driving means (not shown).

Next, the configuration of the fixing device 12 will be described with reference to FIG. The flange member 36 restricts the rotational movement of the rotating fixing film 30 in the longitudinal direction. Further, the flange member 36 regulates the position of the fixing film 30 during the operation of the fixing device 12. The distance between the left side and the right side of the flange (the portion that regulates the end portion of the fixing film 30) of the flange member 36 is longer than the length in the longitudinal direction of the fixing film 30. This is because the end portion of the fixing film 30 is not damaged during normal use. Further, the length of the pressure roller 33 in the longitudinal direction is about 10 mm shorter than that of the fixing film 30. This is to prevent the grease protruding from the end portion of the fixing film 30 from coming into contact with the pressure roller 33 and losing the grip force to cause slippage.

The film assembly unit is provided so as to face the pressure roller 33, and the movement in the left-right direction of FIG. 4 is restricted. The film assembly unit is supported by the top plate side housing 39 of the fixing device 12 so that the film assembly unit can be moved in the vertical direction. A pressure spring 38 is attached to the top plate side housing 39 of the fixing device 12 in a compressed state. The pressing force of the pressurizing spring 38 is received by the overhanging portion of the reinforcing member 34, the reinforcing member 34 is pressed toward the pressurizing roller 33 side, and the entire film assembly unit presses against the pressurizing roller 33 side. The pressing force in Example 1 is 200 N (20.4 kgf).

A bearing 37 that pivotally supports the core metal of the pressure roller 33 is provided. The bearing 37 receives the pressing force from the film assembly unit via the pressurizing roller 33. In order to rotatably support the core metal of the relatively high temperature pressure roller 33, the material of the bearing 37 is a material having heat resistance and excellent slidability. The bearing 37 is attached to the bottom housing 40 of the fixing device 12.

<Temperature detection device>
The configuration of the fixing device 12 will be described with reference to FIG. FIG. 5 is a cross-sectional view of the fixing device 12. The image forming apparatus includes a quantum type infrared sensor 83 and a thermopile type infrared sensor (hereinafter, referred to as thermopile) 84 as means for detecting the temperature of the fixing film 30. The infrared sensor 83 and the thermopile 84 are non-contact type sensors that detect the temperature of the fixing film 30 without contacting the fixing film 30. The infrared sensor 83 uses InSb (indium antimonide) as a detection element. The infrared sensor 83 is arranged so as to detect the temperature at a predetermined position M on the surface side of the fixing film 30 on the downstream side in the rotation direction of the fixing film 30 with reference to the fixing nip portion N. The infrared sensor 83 detects the temperature of the fixing film 30 after passing through the fixing nip portion N. Similarly, the thermopile 84 as a detection unit is also arranged so as to detect the temperature at the position M of the fixing film 30.

<Temperature control system>
A method of controlling the temperature of the fixing film 30 by the temperature detecting means will be described. Basically, the main control target is the detection temperature of the thermopile 84. Based on the detection temperature of the thermopile 84, the control unit described later controls the power supplied from the fixing heating drive circuit 60 to the ceramic heater 32 via the power line 61, and sets the temperature of the fixing film 30 to a desired temperature (control target temperature). ). The control target temperature (target temperature) may be a constant temperature or may be changed according to image information from the host computer. The details of temperature control will be described below.

FIG. 6 is a block diagram of a control unit 200 that controls an image forming device and a fixing device 12, and a fixing heating drive circuit 60. The fixing heating drive circuit 60 includes an AC power supply 204, a triac 205, and a zero cross detection circuit 206. The triac 205 is controlled by the control unit 200. The triac 205 energizes and shuts off the ceramic heater 32.

The AC power supply 204 sends a zero-cross signal to the control unit 200 via the zero-cross detection circuit 206. The control unit 200 controls the triac 205 based on the zero cross signal. By energizing the ceramic heater 32 from the fixing heating drive circuit 60, the temperature of the ceramic heater 32 rises. The outputs of the infrared sensor 83 and the thermopile 84 that detect the temperature of the fixing film 30 are taken into the control unit 200 via the A / D converters 201 and 202, respectively. Specifically, each temperature of the infrared sensor 83 and the thermopile 84 is monitored by the control unit 200 as a voltage value. The control unit 200 performs phase control, wave number control, and the like of the AC voltage energized by the triac 205 by the triac 205 based on the temperature information of the fixing film 30 from the infrared sensor 83 and the thermopile 84. That is, the control unit 200 controls the electric power supplied to the ceramic heater 32 so that the temperature of the surface of the fixing film 30 maintains a predetermined control target temperature (set temperature). In the image forming apparatus of the first embodiment, the set temperature of the fixing film 30 in the standard printing mode is 180 ° C.

The control unit 200 includes a CPU 210 such as a microprocessor, and a ROM 211 that stores control programs and data of the CPU 210. Further, the control unit 200 includes a RAM 212 that is used as a work area when the CPU 210 controls is executed and temporarily stores various data, an EEPROM 213 that non-volatilely stores control information and the like described later. The timer 214 measures the time after the rotation of the pressurizing roller 33 of the fixing device 12, which will be described later, and the start of energization of the ceramic heater 32. As described above, in addition to the power control and temperature detection of the fixing device 12 described above, the control unit 200 also detects the thickness of the release layer, which will be described later, and controls the driving means 203 for driving the fixing device 12. The control unit 200 controls the fixing device 12 and controls the overall operation of the image forming device. The control unit 200 may be provided in the fixing device 12, or may be provided in the image forming device.

PID control is used as the temperature control by the control unit 200. Further, as a power control method, there are control methods such as wave number control and phase control, and in the first embodiment, phase control is used. Specifically, the control unit 200 detects the temperature of the thermopile 84 every 2 μs, and the control unit 200 controls the ceramic heater 32 by PID control so that the surface temperature of the fixing film 30 is maintained at the set temperature. Determine the amount of power supplied to. For example, in order to specify the electric power in 5% increments, it is generally performed by using an energization angle in 5% increments with respect to one half wave of the AC waveform supplied from the Triac 205. This energization angle is obtained as the timing at which the triac 205 is turned on, starting from the time when the zero cross signal is detected by the zero cross detection circuit 206.

(3) Explanation of Detection of Thickness of Release Layer The release layer is used in the fixing film 30 to suppress the offset of toner, but the release layer wears when the recording material P continues to pass through. I will do it. The wear of the release layer is one of the factors that determine the life of the fixing device 12, and as the wear of the release layer progresses, the fixing film 30 cannot secure the releasability. Therefore, the performance of the fixing device 12 cannot be maintained, and the life of the fixing device 12 is reached. Against this background, it is desired to improve the life prediction accuracy of the fixing device 12 in order to improve the maintenance serviceability of the image forming device.

The degree of deterioration of the release layer varies depending on the usage state of the image forming apparatus by the user. This is because the degree of wear of the release layer differs depending on the type of recording material P used by the user. In the first embodiment, the thickness of the release layer is detected by the method described below, and the life of the fixing device 12 can be predicted more accurately.

A method of detecting the thickness of the release layer, which is the surface layer of the fixing film 30, by using the detection temperatures of the infrared sensor 83 and the thermopile 84 will be described. In the embodiment, a method of detecting the thickness of the release layer by using the PFA layer as the release layer will be described. However, even if a fluororesin layer such as a PTFE layer or a FEP layer is used as the release layer, the release layer is used. The method of detecting the thickness of is the same. As will be described later, since the thickness of the release layer is detected by using the temperature difference between the front and back surfaces of the release layer, the relationship between the temperature difference between the front and back surfaces of the release layer and the thickness of the release layer can be easily obtained. It is desirable to have. In the first embodiment, a state in which a sufficient amount of time has passed after the printing of the image forming apparatus is completed (a condition of the first printing after the power of the image forming apparatus is turned on, or a condition in which one hour or more has passed after the printing is completed). Then, the thickness of the release layer is detected. Further, the thickness of the release layer is detected after 4 seconds from the state in which the rotation of the pressurizing roller 33 of the fixing device 12 and the energization of the ceramic heater 32 (both are performed substantially at the same time) are started with the start of printing. Will be done. When the fixing device 12 is sufficiently cooled, a temperature difference between the front and back surfaces of the release layer is likely to occur. Further, when the heat transfer from the ceramic heater 32 as a heating source to the front and back surfaces of the release layer is the same transient state, the relationship between the temperature difference between the front and back surfaces of the release layer and the thickness of the release layer is stable. do. Therefore, the thickness of the release layer is detected under the above conditions.

FIG. 7A is a graph showing the relationship between the detection temperatures of the infrared sensor 83 and the thermopile 84 under the above conditions and the thickness of the release layer of the fixing film 30. Since the temperature is controlled so that the detection temperature of the thermopile 84 is 180 ° C., the detection temperature of the thermopile 84 is approximately 180 ° C. On the other hand, the detection temperature of the infrared sensor 83 becomes lower as the thickness of the release layer becomes thicker. Since this tendency is almost constant even when the control temperature of the thermopile 84 is different, the difference between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 has a correlation with the thickness of the release layer of the fixing film 30. it is conceivable that. FIG. 7B is a graph showing the relationship between the difference (temperature difference) between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 and the thickness of the release layer of the fixing film 30. As shown in FIG. 7B, as the thickness of the release layer decreases, the difference between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 decreases.

Next, a method of setting the life of the fixing device 12 will be described. In the thin-walled fixing film 30 used in Example 1, when the release layer is worn and the thickness of the release layer becomes 0 μm, the releasability of the fixing film 30 cannot be ensured. Therefore, the toner on the recording material P is transferred to the fixing film 30, and an offset occurs in which the toner adheres to the recording material P again after one rotation of the fixing film 30. As described above, the performance of the fixing device 12 cannot be maintained, and the life of the fixing device 12 is reached. However, in consideration of unevenness of the wear portion of the release layer of the fixing film 30 and variation in the progress of wear, a predetermined margin is set for notifying the user of the life of the fixing device 12. Specifically, the timing at which the thickness of the release layer of the fixing film 30 reaches 3 μm is defined as the notification timing of the life of the fixing device 12 (remaining life of 0%). Further, in the first embodiment, the median value (manufacturing center value) of the thickness of the release layer when the fixing film 30 is new is 20 μm, and the fixing device 12 when the thickness of the release layer is 20 μm. The remaining life of the product is 100%. In Example 1, between the point where the thickness of the release layer is 20 μm and the remaining life is 100% and the point where the thickness of the release layer is 3 μm and the remaining life is 0%. Is linearly interpolated to define the remaining life of the fixing device 12. FIG. 8 shows the relationship between the thickness of the release layer of the fixing film 30 defined in this way and the remaining life of the fixing device 12.

The control of detecting the thickness of the release layer of the fixing film 30 and the remaining life of the fixing device 12 described above will be described with reference to the flowchart of FIG. When printing starts (S1), driving of a motor, which is a driving means (not shown), starts, and energization from the fixing heating drive circuit 60 to the ceramic heater 32 starts (S2). The control unit 200 finishes printing based on whether it is the first print after the power of the image molding apparatus is turned on (condition 1) or the value of the timer 214 in a state where a certain time has elapsed after the printing of the image forming apparatus is completed. It is determined whether one hour or more has passed later (condition 2) (S3). If condition 1 or condition 2 is met, the process proceeds to the measurement step of S4. If neither condition 1 nor condition 2 is met, the process proceeds to the step of waiting for the completion of printing in S12.

In the measurement step, in order to measure the time after the heating of the ceramic heater 32 is started, the control unit 200 resets the timer 214 to set the count value to 0, and then starts the time counting of the timer 214 ( S4). The control unit 200 waits until 4 seconds have elapsed from the start of time counting of the timer 214 (S5), and after 4 seconds, acquires the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 (S6). The control unit 200 determines the relationship between the temperature difference obtained in advance in an experiment and the thickness of the release layer of the fixing film 30 based on the difference (temperature difference) between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84. The thickness of the release layer is calculated using (S7). Then, the control unit 200 calculates the remaining life X (%) of the fixing device 12 from the thickness of the release layer by using the relationship between the thickness of the release layer and the remaining life of the fixing device 12 (S8).

The control unit 200 functions as a determination unit and determines whether or not the value of the remaining life X of the fixing device 12 is equal to or less than a predetermined value (for example, 0%) (S9). If the value of the remaining life X of the fixing device 12 is not equal to or less than a predetermined value, the control unit 200 determines that the fixing device 12 has not reached the end of its life (S10). On the other hand, when the value of the remaining life X of the fixing device 12 is not more than a predetermined value, the control unit 200 determines that the fixing device 12 has reached the end of its life (a state in which the fixing device 12 needs to be replaced). (S11). In this case, the control unit 200 functions as a notification unit and notifies information regarding the life of the fixing device 12 via a communication interface or the like. Further, the control unit 200 may display information on the life of the fixing device 12 on a display unit such as a display. The information regarding the life of the fixing device 12 includes information indicating that the fixing device 12 has reached the end of its life and information indicating that the fixing device 12 needs to be replaced. The information regarding the life of the fixing device 12 may include information indicating that the fixing device 12 is near the end of its life and information indicating the replacement time of the fixing device 12.

Then, the control unit 200 waits until the end of printing (S12). In order to measure the time from the end of printing, the control unit 200 resets the timer 214 at the end of printing, sets the count value to 0, and then starts timing the timer 214 (S13). After that, the control unit 200 ends the control.

The control unit 200 acquires the difference temperature between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 at a predetermined timing. The predetermined timing is an arbitrary timing from the start of heating of the ceramic heater 32 to the entry of the recording material P into the fixing nip portion N. The predetermined timing is after a predetermined time (for example, 4 seconds) has elapsed from the start of heating of the ceramic heater 32, and even at an arbitrary timing until the recording material P rushes into the fixing nip portion N. good.

In S7 of FIG. 9, the control unit 200 functions as an acquisition unit and acquires the thickness of the release layer based on the difference (temperature difference) between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84. There is. In S8 and S9 of FIG. 9, the control unit 200 may compare the thickness of the release layer with a predetermined thickness, and determine the life of the fixing device 12 based on the comparison result. When the thickness of the release layer is smaller than a predetermined thickness (for example, 3 μm), the control unit 200 determines that the fixing device 12 has reached the end of its life (a state in which the fixing device 12 needs to be replaced). Further, the control unit 200 compares the difference (temperature difference) between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 with the predetermined temperature difference, and determines the life of the fixing device 12 based on the comparison result. May be good. When the difference (temperature difference) between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 is smaller than the predetermined temperature difference (for example, 2 ° C.), the control unit 200 is in a state where the fixing device 12 has reached the end of its life (for example, 2 ° C.). It is determined that the fixing device 12 needs to be replaced). In these cases, the control unit 200 notifies the information regarding the life of the fixing device 12.

(4) Action / Effect A mechanism capable of detecting the thickness of the release layer of the fixing film 30 by using the difference between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 will be described. First, the thickness of the release layer can be detected because the temperature difference between the front and back surfaces of the thickness of the release layer and the thickness of the release layer correspond to each other during the heating and heating of the fixing film 30. There is. As a result of heating by the ceramic heater 32, heat is transferred from the base layer of the fixing film 30 to the elastic layer and the release layer. Depending on the thermal resistance of each of the elastic layer and the release layer, the temperature is lowered in the order of the elastic layer and the release layer from the base layer of the fixing film 30 as compared with the temperature of the ceramic heater 32. Further, the temperature difference between the front and back surfaces of the elastic layer and the release layer also changes according to the thermal resistance of each of the elastic layer and the release layer. That is, the thicker the release layer (the larger the thermal resistance), the larger the temperature difference between the front and back surfaces of the release layer. The relationship between the temperature difference on the front and back surfaces of the release layer and the thickness of the release layer is a transient state in which the heat transfer from the ceramic heater 32 is the same (in Example 1, the rotation of the pressurizing roller 33 of the fixing device 12). When compared (4 seconds after the start), the relationship is unique. In this way, the temperature difference between the front and back surfaces of the release layer corresponds to the thickness of the release layer, so that the thickness of the release layer can be detected.

Next, a method of detecting the temperature difference between the front and back surfaces of the release layer will be described. The surface temperature of the release layer can be easily measured using a thermopile or a thermocouple. The temperature of the inner surface (the interface between the release layer and the elastic layer), which is the back surface of the release layer, can be detected by using the infrared sensor 83. Since the infrared sensor 83 uses a quantum type detection element, it has wavelength dependence on the infrared rays to be detected. The infrared sensor 83 used in Example 1 detects the temperature in a wavelength range of about 3 to 5 μm of infrared rays. It is known that the PFA resin used in the release layer is transparent in the wavelength range of about 3 to 5 μm of infrared rays. That is, the spectral emissivity of the PFA resin in the wavelength range of about 3 to 5 μm of infrared rays is small. Therefore, the infrared emissivity in the wavelength range of about 3 to 5 μm in the elastic layer is larger than the infrared emissivity in the wavelength range of about 3 to 5 μm in the PFA resin. As described above, the infrared emissivity of the elastic layer in the infrared wavelength region detected by the infrared sensor 83 is larger than the infrared emissivity of the release layer in the infrared wavelength region detected by the infrared sensor 83. As a result, the infrared sensor 83 is affected by the PFA resin that is transparent in the wavelength range of about 3 to 5 μm and emits infrared rays in the wavelength range of about 3 to 5 μm radiated from the surface of the elastic layer due to its wavelength characteristics. Measure without. Therefore, the infrared sensor 83 can directly detect the surface temperature of the elastic layer by detecting the infrared rays radiated from the surface of the elastic layer. On the other hand, the thermopile 84 has no wavelength dependence and detects the temperature by absorbing infrared rays in general (wavelength range of 1 to 1000 μm), so that the surface temperature of the release layer is detected. As described above, the thermopile 84 is used to measure the surface temperature of the release layer, and the infrared sensor 83 is used to measure the surface temperature of the elastic layer. Since the surface temperature of the elastic layer can be regarded as the same temperature as the back surface temperature of the release layer, the temperature of the front and back surfaces of the release layer can be measured. Therefore, it is possible to measure the temperature difference between the front and back surfaces of the release layer and detect the thickness of the release layer corresponding to the temperature difference.

(5) Experimental Results of Image Output in Example 1 and Comparative Example Next, the experimental results of image output in Example 1 will be described. First, the evaluation of wear of the release layer will be described. As described above, when the release layer is worn and the thickness of the release layer becomes 0 μm, the releasability of the fixing film 30 cannot be ensured. Therefore, a phenomenon that the toner on the recording material P is offset occurs, the performance as the fixing device 12 cannot be maintained, and the fixing device 12 has reached the end of its life.

Therefore, "wear of the release layer" was evaluated under the following conditions. From the state where the fixing device 12 is new, 5000 sheets are continuously printed per day, the release layer is worn away, and the PTA film thickness becomes 0 μm. The timing when the remaining life becomes 0%) was confirmed. Evaluation was performed using an A4 size recording material (manufactured by CANON, Red Label, basis weight 80 g / m ^2). As the fixing device 12, a fixing device A having a short device life and a fixing device B having a long device life are used. For the fixing device A, the pressing force is set to 220 N, and the thickness of the release layer is set to 15 μm. For the fixing device B, the pressing force is set to 180 N, and the thickness of the release layer is set to 25 μm.

The detection conditions for device life will be described. Example 1 is as described in "(3) Explanation of detection of thickness of release layer". Comparative Examples 1 and 2 use a method of determining the device life based on the number of prints of the image forming apparatus, and notify the device life when a predetermined number of sheets have been passed. In Comparative Example 1, a method of determining by adding a margin based on the verification result of the life of the fixing device A is adopted, and a method of notifying the life of the device by passing 220,000 sheets is used. Further, in Comparative Example 2, a method of determining by adding a margin based on the verification result of the life of the fixing device B is adopted, and a method of notifying the life of the device by passing 390000 sheets is used.

Relationship between the number of prints when an offset occurs in Example 1 and Comparative Examples 1 and 2 (hereinafter referred to as the number of offsets) and the number of prints when notifying the device life (hereinafter referred to as the number of life notifications). The confirmation results are shown in Table 1.

First, the result of Example 1 will be described. Regarding the fixing device A, the device life is notified when the number of sheets to be passed is 215,000, and an offset occurs when the number of sheets to be passed is 231 or 786. Therefore, with respect to the fixing device A, there is a margin of 16,786 sheets from the notification of the device life to the occurrence of the offset. Regarding the fixing device B, the device life is notified when the number of sheets to be passed is 385,000, and an offset occurs when the number of sheets to be passed is 403,441. Therefore, with respect to the fixing device B, there is a margin of 18,441 sheets from the notification of the device life to the occurrence of the offset.

Next, the result of Comparative Example 1 will be described. Regarding the fixing device A, there is a margin of 11,786 sheets before an offset occurs after the device life is notified when the number of sheets to be passed is 220,000, and there is an appropriate margin. On the other hand, with respect to the fixing device B, there is a margin of 183,441 sheets from the notification of the device life to the occurrence of the offset, and the margin is in an excessive state. The device life is notified at a very early timing with respect to the ability of the fixing device B, resulting in poor detection accuracy of the device life.

Next, the result of Comparative Example 2 will be described. Regarding the fixing device B, there is a margin of 13,441 sheets before the offset occurs after the notification of the device life is given when the number of sheets to be passed is 390,000, and there is an appropriate margin. On the other hand, with respect to the fixing device A, an offset occurs before the timing (number of sheets to be passed: 158,214 sheets) when the device life is notified, and the fixing device A cannot serve as a device life notification.

For the reason explained in (4) Action / Effect above, in Example 1 can determine the device life with higher accuracy than in Comparative Examples 1 and 2, as shown in the confirmation results in Table 1. , The device life can be notified at an appropriate timing.

(6) Summary As described above, in the first embodiment, the temperature of the release layer of the fixing film 30 is detected by using the thermopile 84, and the wavelength dependence of the infrared sensor 83 is detected by using the quantum infrared sensor 83. The temperature of the elastic layer of the fixing film 30 is detected by. Since the infrared emissivity of the elastic layer is larger than the infrared emissivity of the release layer, the quantum infrared sensor 83 can detect the temperature of the elastic layer without being affected by the release layer. By detecting the wear of the release layer based on the difference temperature between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84, the life of the fixing device 12 can be determined more accurately.

(Example 2)
In the second embodiment, the life estimation accuracy of the fixing device 12 is improved by accurately measuring the temperature of the elastic layer of the fixing roller by using the fixing roller type fixing device 12 in which the halogen heater is provided inside the fixing roller. The method will be described. The configuration of the image forming apparatus according to the second embodiment is the same as that of the first embodiment, as shown in FIG. Therefore, in the configuration of the second embodiment, the description of the configuration overlapping with the first embodiment will be omitted.

FIG. 10 shows a cross-sectional view of a fixing device 12 in which a halogen heater is provided inside a fixing roller. Since the configuration of the fixing device 12 according to the second embodiment has the same parts as those of the first embodiment, the description of the configuration overlapping with the first embodiment will be omitted, and the configuration of the parts different from the first embodiment will be described. The fixing roller 85 is a hollow roller, and a heater 86 as a heating element (heat source) is provided inside the fixing roller 85. As the heater 86, a lamp heater, a heating wire, a planar heating element provided with a resistance pattern, or the like is mainly used. In the second embodiment, a cylindrical halogen lamp is used as the heater 86.

The heater 86 is arranged substantially along the perpendicular line drawn with respect to the fixing nip portion N and in parallel with the fixing roller 85, and does not come into contact with the inner surface of the fixing roller 85. By heating by the heater 86, the inner surface of the fixing roller 85 absorbs heat, and the temperature of the fixing roller 85 rises. Further, the fixing roller 85 includes an elastic layer formed of silicone rubber having elastic properties on the outside of the hollow roller, and a releasable layer having releasability. The fixing roller 85 has hollow rollers as a release layer (first layer), an elastic layer (second layer), and a base layer (third layer) in this order from the surface. A drive gear 44 shown in FIG. 4 is attached to one end of a hollow roller (core metal) of the fixing roller 85, and the drive gear 44 receives a rotational driving force by a driving means (not shown) to receive the fixing roller 85. Is rotating. The roller hardness of the fixing roller 85 is 70 ° (measuring instrument: ASKE R-C hardness tester, condition: 1000 g load).

Further, the pressure roller 33 is pressed toward the fixing roller 85 by a pressing means (not shown). The region (pressure contact region) in which the pressed pressure roller 33 and the fixing roller 85 are in close contact with each other is the fixing nip portion N. The fixing nip portion N as the pressure contact portion receives the rotating force of the fixing roller 85 directly or with the recording material P sandwiched between them, and the pressure roller 33 rotates drivenly. The roller hardness of the pressure roller 33 is also 70 ° (measuring instrument: ASKE R-C hardness tester, condition: 1000 g load).

The image forming apparatus includes a quantum infrared sensor 83 as a means for detecting the temperature of the fixing roller 85. The infrared sensor 83 as the first temperature detecting means is arranged on the downstream side in the rotation direction of the fixing roller 85 with reference to the fixing nip portion N, and determines the temperature of the fixing roller 85 after passing through the fixing nip portion N. To detect. The control target in the second embodiment is the detection temperature of the infrared sensor 83, and the control unit 200 controls the power supplied from the fixing heating drive circuit 60 to the heater 86 based on the detection temperature of the infrared sensor 83, and the fixing roller 85. The temperature of is maintained at a predetermined control target temperature (set temperature).

In the fixing roller type fixing device 12, the heat capacity is large, and the response from the energization of the heater 86 to the rise in the detection temperature of the infrared sensor 83 is slow. Therefore, the fixing roller type fixing device 12 uses so-called on / off control in which the power is turned on when the temperature falls below the predetermined temperature and the power is turned off when the temperature exceeds the predetermined temperature. Specifically, the set temperature is set to 200 ° C., and when the temperature falls below the set temperature, the power is turned on, and when the temperature exceeds the set temperature, the power is turned off. Therefore, the temperature fluctuation of the fixing roller type fixing device 12 is larger than that of the on-demand type fixing device 12 used in the first embodiment, and the fixing device 12 is used depending on the difference in configuration due to the manufacturing tolerance of the fixing device 12 and the usage state. Differences in temperature are likely to occur.

Even in the fixing roller type fixing device 12 as shown in the second embodiment, it is important to detect the life of the fixing device 12. The fixing roller method generally has a higher pressing force than the fixing film 30 and has a long product life. Since the stress applied to the release layer, which is the outermost layer, is also large, a release layer having a sufficient thickness is used in advance. In Example 2, a 50 μm release layer is used. As a result, the wear of the release layer is no longer the main factor related to the life of the fixing device 12. The main factor that determines the life of the fixing roller type fixing device 12 is the hardening and deterioration of the elastic layer.

In the fixing roller type fixing device 12, both the fixing roller 85 and the pressure roller 33 are provided with an elastic layer and a release layer on a metal pipe, and a fixing nip portion N as a pressure contact portion is mainly provided by deformation of the elastic layer. Is forming. A thin rubber layer having a low hardness is used for the elastic layer of the fixing roller 85 in order to form the fixing nip portion N having a width that can be fixed and to reduce the heating rise time of the fixing device 12. In particular, since the rubber layer of the fixing roller 85 is on the heating side, thermal deterioration is likely to occur, and the fixing roller 85 is more likely to be cured and deteriorated than the pressure roller 33.

Specifically, in the fixing device 12 of the second embodiment, the hardness of the fixing roller 85 when new is 70 °, but the hardness of the fixing roller 85 after printing 500,000 sheets is 78 °. On the other hand, the hardness of the pressure roller 33 at the time of new product is 70 °, but the hardness of the pressure roller 33 after printing 500,000 sheets is 69 °. As the hardening and deterioration of the rubber layer of the fixing roller 85 progresses, the hardness of the fixing roller 85 becomes harder than that of the pressure roller 33. Therefore, regarding the shape of the fixing nip portion N, the rubber layer of the pressurizing roller 33 is greatly deformed, while the rubber layer of the fixing roller 85 is not deformed so much. When the fixing nip portion N has such a shape, the recording material P is discharged in a form that follows the cylindrical shape of the fixing roller 85, and as a result, the recording material P is likely to be wound around the fixing roller 85. As the number of prints increases and the elastic layer of the fixing roller 85 deteriorates due to hardening, the fixing device 12 is not in a state recommended to be used by the user from the viewpoint that wrapping is likely to occur, and the fixing device 12 has reached the end of its life. Reach. FIG. 11A shows an enlarged view of the initial fixing nip portion N of the fixing device 12 in the second embodiment, and FIG. 11B shows an enlarged view of the fixing nip portion N at the end of the life of the fixing device 12. show.

The operating temperature of the rubber layer of the fixing roller 85 has a great influence on the curing deterioration of the fixing roller 85. However, when detecting the temperature of the surface of the fixing roller 85, the temperature of the elastic layer of the fixing roller 85 cannot be accurately detected due to the influence of the PFA layer on the outermost surface of the fixing roller 85, so that the life of the fixing device 12 is extended. There is a problem that it cannot be detected accurately. Therefore, in the second embodiment, in the fixing device 12 using the infrared sensor 83, a method of directly detecting the temperature of the elastic layer of the fixing roller 85 is used. In the second embodiment, the principle that the temperature of the elastic layer can be directly detected is the same as that in the first embodiment, and thus detailed description thereof will be omitted.

The Arrhenius law is followed for the hardening and deterioration of the elastic layer. As a result of experimental verification in Example 2, if the fixing device 12 is continuously used under the condition that the temperature of the elastic layer is about 12 ° C. higher, the life of the fixing device 12 is halved. Specifically, in the fixing device 12 of the second embodiment, when 500,000 sheets are printed, the hardness of the fixing roller 85 becomes 78 ° and the hardness of the pressure roller 33 becomes 69 °. When 500,000 sheets are printed when the temperature of the elastic layer is 200 ° C., wrapping is likely to occur, so that the life of the fixing device 12 is set. Then, when 250,000 sheets are printed when the temperature of the elastic layer is 212 ° C., the state is the same as when the temperature of the elastic layer is 200 ° C., so that the life of the fixing device 12 is set. As described above, since the life of the fixing device 12 changes depending on the temperature of the elastic layer, the counting method as described below is used. The reference temperature of the life of the fixing device 12 is set to 200 ° C., the actual temperature of the infrared sensor 83 at the time of printing is set to T0 ° C., and the life counter per sheet is set to 2 ^ ((T0-200) / 12)). .. When the cumulative count value of the life counter reaches 500,000, the control unit 200 determines that the life of the fixing device 12 has been reached. When the temperature of the elastic layer is 200 ° C., the life counter per sheet is 1, and when the temperature of the elastic layer is 212 ° C., the life counter per sheet is 2. As described above, when the temperature of the elastic layer is 212 ° C. and 250,000 sheets are printed, the fixing device 12 reaches the end of its life, so that the control unit 200 can detect that the life of the fixing device 12 is halved.

As described above, in the second embodiment, the temperature of the elastic layer of the fixing roller 85 is detected by using the quantum infrared sensor 83. The control unit 200 functions as a cumulative unit, and each time the recording material P passes through the fixing nip portion N, the control unit 200 obtains a count value obtained by adding a weight according to the temperature of the elastic layer to the temperature of the elastic layer, and obtains the count value. Accumulate. The control unit 200 determines the life of the fixing device 12 based on the accumulated count value. As a result, the life of the fixing device 12 can be accurately detected regardless of the difference in configuration due to the manufacturing tolerance of the fixing device 12 and the usage state of the fixing device 12. Further, when the accumulated count value reaches a predetermined value, the control unit 200 notifies the information regarding the life of the fixing device 12. As a result, the user can be informed of information regarding the life of the fixing device 12. Further, the method for determining the life of the fixing device 12 described in the second embodiment may be applied to the film heating type fixing device 12 of the first embodiment.

(Example 3)
In Examples 1 and 2, the present invention has been described from the viewpoint of the life of the fixing device 12. In the third embodiment, a method of keeping the fixing performance of the fixing device 12 constant will be described. The configuration of the image forming apparatus according to the third embodiment is the same as that of the first embodiment, as shown in FIG. Further, the configuration of the fixing device 12 is the same as that of the first embodiment, as shown in FIG. Therefore, in the configuration of the third embodiment, the description of the configuration overlapping with the first and second embodiments will be omitted. The fixing performance differs depending on the thickness of the release layer. Specifically, the thicker the release layer, the lower the fixing performance. Here, the fixing performance means a fixing temperature at which an image can be fixed on the recording material P when a red image (toner image) is formed on the entire surface of the recording material P. The lower the fixable temperature, the higher the fixing performance.

The thicker the release layer, the thicker the release layer, even under the condition of controlling the electric power supplied to the ceramic heater 32 so that the surface temperature of the release layer becomes constant, that is, the detection temperature of the thermopile 84 becomes constant. Poor fixing performance. The reason for this is that the hardness of the release layer is harder than that of the silicone rubber of the elastic layer, and the thicker the release layer, the more the shape of the release layer does not follow the unevenness of the recording material P. Therefore, in the third embodiment, the thickness of the release layer is detected by the same method as in the first embodiment, and the temperature is basically controlled so that the detected temperature of the thermopile 84 becomes constant. Further, the temperature is controlled so that the detection temperature of the thermopile 84 becomes higher as the thickness of the release layer becomes thicker.

FIG. 12 shows the relationship between the thickness of the release layer and the correction value of the control target temperature. By using the control of the third embodiment, it is possible to set the optimum control target temperature as the fixing performance without being affected by the thickness of the release layer. When the fixing device 12 is new, a positive correction value is added to the control target temperature according to the thickness of the release layer, which differs depending on the manufacturing tolerance. The control unit 200 changes the control target temperature by adding a positive correction value according to the thickness of the release layer to the control target temperature. Then, as the thickness of the release layer gradually decreases with the continuous use of the fixing device 12, the positive correction value becomes smaller. Near the life of the fixing device 12, the correction value of the control target temperature becomes almost 0. If the thickness of the release layer is reduced, the difference temperature between the detection temperature of the infrared sensor 83 and the detection temperature of the thermopile 84 becomes smaller, so that the positive correction value becomes smaller as the difference temperature becomes smaller.

According to the third embodiment, the optimum control target temperature can be selected by selecting the correction value of the control target temperature according to the thickness of the release layer and correcting the control target temperature using the correction value. As a result, it is possible to suppress an error between the fixable temperature and the control target temperature. As a result, the life of the fixing device 12 can be extended as a secondary effect. For example, when the thickness of the release layer is unknown, it is necessary to set a high control target temperature in order to secure the fixing performance even when the actual thickness of the release layer is thick. As a result, the curing deterioration of the silicone rubber described in Example 2 is likely to proceed. again,
The progress of wear of the release layer described in Example 1 becomes faster. In such a case, the life of the fixing device 12 can be extended by selecting a correction value of the control target temperature according to the thickness of the release layer and correcting the control target temperature using the correction value.

(Other Examples)
In the second embodiment, a method of improving the accuracy of life detection by using the fixing roller type fixing device 12 has been described. However, other effects can be obtained by being able to directly detect the temperature of the elastic layer. For example, it is possible to improve the throughput when passing small size paper. Considering the heat resistance of the silicone rubber used for the elastic layer, it is possible to directly measure the surface temperature of the silicone rubber when the throughput is lowered when the temperature of the silicone rubber is high when passing small-sized paper. It is possible because it is. Since the PFA resin used for the release layer has a high heat-resistant temperature, it becomes the heat-resistant rate-determining factor of the silicone rubber used for the elastic layer.

Further, the configurations of Examples 1 to 3 may be applied to the induction heating type fixing device and the external heating type fixing device. The same effect can be obtained when the temperature of the elastic layer is directly measured or the thickness of the release layer is detected by the induction heating method or the external heating type fixing device to which the configurations of Examples 1 to 3 are applied. Can be done. Moreover, in Examples 1 to 3, it was described using the color image forming apparatus and the fixing apparatus provided in the color image forming apparatus. However, the configurations of Examples 1 to 3 may be applied to the monochrome image forming apparatus and the sheet heating apparatus. The same effect can be obtained in the monochrome image forming apparatus to which the configurations of Examples 1 to 3 are applied and the sheet heating apparatus.

Further, in Examples 1 and 3, a method using a thermopile 84 as a method for detecting the temperature of the surface of the release layer is described. However, even if the temperature of the surface of the release layer is detected by using, for example, a contact thermistor or a thermoelectric pair, the same effect as that of detecting the temperature of the surface of the release layer by using the thermopile 84 can be obtained. can. In that case, it is preferable to detect the temperature of the surface of the release layer more accurately. Therefore, when using the contact type temperature detection unit from the viewpoint of not depriving the surface temperature of the release layer, it is preferable to use the temperature detection unit having a smaller heat capacity. Further, in order to prevent toner stains and the like from occurring between the contact-type temperature detection unit and the surface of the release layer, it is preferable that the temperature detection unit has a surface with high releasability.

In Examples 1 and 3, a configuration in which a ceramic heater 32 is used as a heating body for heating the fixing film 30 is described. The structure is not limited to this, and in Examples 1 and 3, the heater 86 described in Example 2 may be used as the heating body for heating the fixing film 30. Further, in Examples 1 and 3, a heat transfer member for efficiently transferring the heat of the heater 86 to the fixing film 30 may be provided on the inner surface of the fixing film 30.

12 ... Fixing device, 30 ... Fixing film, 32 ... Ceramic heater, 33 ... Pressurizing roller, 83 ... Infrared sensor, 84 ... Thermopile, 85 ... Fixing roller, 200 ... Control unit, P ... Recording material

Claims (15)

A rotatable first rotating body having a release layer and an elastic layer in order from the surface, a second rotating body that rotates in contact with the first rotating body, and a heating body that heats the first rotating body. A fixing device that heats the image by transporting the recording material on which the image is formed while sandwiching it between the nip portion formed between the first rotating body and the second rotating body.
A detector that detects the surface temperature of the release layer and
A quantum infrared sensor that detects the surface temperature of the elastic layer in a non-contact manner,
A determination unit that determines the life of the fixing device based on the temperature difference between the surface temperature of the release layer and the surface temperature of the elastic layer.
With
The quantum type infrared sensor detects the surface temperature of the elastic layer by detecting infrared rays radiated from the surface of the elastic layer.
The infrared emissivity of the elastic layer in the infrared wavelength range detected by the quantum infrared sensor is larger than the infrared emissivity of the release layer in the infrared wavelength range detected by the quantum infrared sensor. A fixing device characterized by the fact that. The fixing device according to claim 1, further comprising a notification unit for notifying information on the life of the fixing device when the temperature difference is smaller than a predetermined temperature difference. Further provided with an acquisition unit for acquiring the thickness of the release layer based on the temperature difference,
The fixing device according to claim 1, further comprising a notification unit for notifying information on the life of the fixing device when the thickness of the release layer is smaller than a predetermined thickness. The fixing device according to claim 3, wherein the temperature difference decreases as the thickness of the release layer decreases. Further provided with a control unit that controls the electric power supplied to the heating body so that the temperature of the release layer maintains the control target temperature.
The control unit changes the control target temperature by adding a positive correction value to the control target temperature.
The fixing device according to any one of claims 1 to 4, wherein the correction value becomes smaller as the temperature difference becomes smaller. The fixing device according to any one of claims 1 to 5, wherein the detection unit is a thermopile type infrared sensor arranged in the release layer in a non-contact manner. The fixing device according to any one of claims 1 to 5, wherein the detection unit is a thermocouple or a thermistor arranged in contact with the release layer. Any of claims 1 to 7, wherein the determination unit acquires the temperature difference at an arbitrary timing from the start of heating of the heating body to the time before the recording material enters the nip portion. The fixing device according to one item. A rotatable first rotating body having a release layer and an elastic layer in order from the surface, a second rotating body that rotates in contact with the first rotating body, and a heating body that heats the first rotating body. A fixing device that heats the image by transporting the recording material on which the image is formed while sandwiching it between the nip portion formed between the first rotating body and the second rotating body.
A quantum infrared sensor that detects the surface temperature of the elastic layer in a non-contact manner is provided.
The quantum type infrared sensor detects the surface temperature of the elastic layer by detecting infrared rays radiated from the surface of the elastic layer.
The infrared emissivity of the elastic layer in the infrared wavelength range detected by the quantum infrared sensor is larger than the infrared emissivity of the release layer in the infrared wavelength range detected by the quantum infrared sensor. A fixing device characterized by the fact that. Each time the recording material passes through the nip portion, a weighting according to the temperature of the elastic layer is added to the temperature of the elastic layer to obtain a count value, and a cumulative portion that accumulates the count values and a cumulative portion.
A determination unit that determines the life of the fixing device based on the accumulated count values, and a determination unit.
9. The fixing device according to claim 9, further comprising. The fixing device according to claim 10, further comprising a notification unit for notifying information on the life of the fixing device when the count value reaches a predetermined value. The first rotating body is a tubular film that comes into contact with the recording material.
The fixing device according to any one of claims 1 to 9, wherein the heating body is in contact with the inner surface of the film. The fixing device according to claim 12, wherein the second rotating body is a pressure roller, and the nip portion is formed together with the heating body via the film. The first rotating body is a cylindrical roller that comes into contact with the recording material.
The fixing device according to claim 10 or 11, wherein the heating body is provided inside the roller. An image forming portion that forms the image on the recording material,
The fixing device according to any one of claims 1 to 14.
An image forming apparatus characterized by having.

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