JP7761871B2 - Fixing device and image forming apparatus - Google Patents

Description

This invention relates to a fixing device that heats a toner image to fix it to the surface of a sheet, and to an image forming device equipped with the fixing device, such as a copier, printer, facsimile, or a combination machine thereof.

Technology for detecting abnormal conditions in fixing devices in image forming devices such as copiers and printers has been widely known (see, for example, Patent Document 1).

More specifically, the fixing device has a fixing roller (fixing member) pressed against a pressure roller (pressure member), forming a nip (fixing nip) through which the sheet (paper) is transported. The fixing roller is heated by a heating means such as a heater, electromagnetic induction coil, or resistance heating element. The toner image on the sheet transported to the nip is then fixed onto the sheet by the heat received from the fixing roller and the pressure of the nip.

On the other hand, Patent Document 1 discloses technology that detects abnormal conditions in which a recording medium (sheet) is tightly wrapped around a heating roller or in which the recording medium is floating up, based on the temperature detection results of a contact thermistor and a non-contact thermistor that detect the surface temperature of the heating roller (fixing member).

Conventional fixing devices have many causes for malfunctions, but when an abnormality occurs, it is not possible to distinguish the cause of the abnormality. As a result, it is not possible to perform maintenance on the fixing device efficiently.

This invention was made to solve the above-mentioned problems, and aims to provide a fixing device and an image forming apparatus that allow for efficient maintenance.

The fixing device of the present invention is a fixing device comprising: a fixing member that is heated by a heating means and heats a toner image to fix it on the surface of a sheet; a pressure member that forms a nip portion through which a sheet is conveyed by being pressed against the fixing member; a first temperature detection means that detects the surface temperature of the fixing member; and a second temperature detection means that detects the surface temperature of the pressure member. The fixing device compares two temperature transitions detected by the first temperature detection means and the second temperature detection means during image formation with two temperature transitions that have been detected and stored in the past, and if both the temperature transitions detected by the first temperature detection means and the second temperature detection means are normal, the fixing device is determined to be in a normal state where it is operating normally, and if both the temperature transitions detected by the first temperature detection means and the second temperature detection means are abnormal, the fixing device is determined to be in a normal state where it is operating normally. and if the temperature change detected by the first temperature detection means is normal and the temperature change detected by the second temperature detection means is abnormal, it is determined to be a first non-heating system abnormality state in which an abnormality has occurred in a component other than the heating system component, that is, at least one of the pressure member, the second temperature detection means, and a nip portion forming mechanism for forming the nip portion; and if the temperature change detected by the first temperature detection means is abnormal and the temperature change detected by the second temperature detection means is normal, it is determined to be a second non-heating system abnormality state in which an abnormality has occurred in a component other than the heating system component, and the abnormality has occurred due to a cause different from the first non-heating system abnormality state ; and if it is determined to be the second non-heating system abnormality state, it issues a warning to encourage replacement of the fixing device itself .

The present invention provides a fixing device and an image forming apparatus that allow for efficient maintenance.

1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; FIG. 2 is a diagram illustrating a configuration of a fixing device. (A) A graph showing an example of the temperature trends of the first temperature sensor and the second temperature sensor in a normal state, and (B) a graph showing an example of the temperature trends of the first temperature sensor and the second temperature sensor in an abnormal state (heating system abnormal state). 10 is a table showing the relationship between the temperature transitions of the first and second temperature sensors and the determination results that distinguish between a normal state, a heating system abnormal state, and a non-heating system abnormal state. FIG. FIG. 10 is a diagram showing a display screen of an operation display panel as a specific example. 10 is a flowchart showing an example of control for determining an abnormal state.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that in each drawing, identical or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

First, the overall configuration and operation of an image forming apparatus 1 will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes a tandem color copier as an image forming apparatus, 2 denotes a writing unit that emits laser light based on input image information, 3 denotes a document transport unit that transports a document D to a document reading unit 4, and 4 denotes a document reading unit that reads the image information of the document D.
Also, 7 indicates a paper feed section in which sheets P such as paper are stored, 9 indicates a registration roller (timing roller) that adjusts the timing of conveying sheets P, and 11Y, 11M, 11C, and 11BK indicate photosensitive drums on which toner images of each color (yellow, magenta, cyan, and black) are formed.

Also, 12 denotes a charging section that charges the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK, 13 denotes a developing section that develops the electrostatic latent image formed on the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK, 14 denotes a primary transfer roller that transfers the toner image formed on the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK onto the surface of sheet P, and 15 denotes a cleaning section that collects untransferred toner remaining on the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK.
Also, 16 denotes an intermediate transfer belt cleaning section that cleans the intermediate transfer belt 17, 17 denotes the intermediate transfer belt onto which multiple color toner images are transferred in layers, 18 denotes a secondary transfer roller for transferring the color toner image on the intermediate transfer belt 17 onto the sheet P, and 20 denotes a fixing device that fixes the toner image (unfixed image) on the sheet P.

Hereinafter, the operation (printing operation) of the image forming apparatus during normal color image formation will be described.
First, the document D is transported from the document table by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

More specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating it with light emitted from an illumination lamp. The light reflected from the document D is then focused on the color sensor via a group of mirrors and a lens. The color image information of the document D is read by the color sensor in RGB (red, green, blue) color separation light, and then converted into electrical image signals. Furthermore, the image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, etc. based on the RGB color separation image signals, obtaining color image information in yellow, magenta, cyan, and black.

The image information for each color (yellow, magenta, cyan, and black) is then sent to the writing unit 2. Then, the writing unit 2 emits laser light (exposure light) based on the image information for each color toward the surface of the corresponding photosensitive drum 11Y, 11M, 11C, and 11BK.

Meanwhile, the four photoconductor drums 11Y, 11M, 11C, and 11BK each rotate counterclockwise in Fig. 1. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portions facing the charging unit 12 (charging process). In this way, a charging potential is formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK.
Thereafter, the surfaces of the charged photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams (exposure process). More specifically, in the writing unit 2, four light sources emit laser beams corresponding to image signals, one for each color. Each laser beam passes through a separate optical path for each color component: yellow, magenta, cyan, and black.

The laser light corresponding to the yellow component is irradiated onto the surface of the first photosensitive drum 11Y from the left side of the paper. At this time, the laser light of the yellow component is scanned in the direction of the rotation axis of the photosensitive drum 11Y (main scanning direction, width direction) by the polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y after it has been charged by the charging unit 12.

Similarly, the laser light corresponding to the magenta component is irradiated onto the surface of the photosensitive drum 11M, the second from the left on the paper, and an electrostatic latent image corresponding to the magenta component is formed. The laser light for the cyan component is irradiated onto the surface of the photosensitive drum 11C, the third from the left on the paper, and an electrostatic latent image for the cyan component is formed. The laser light for the black component is irradiated onto the surface of the photosensitive drum 11BK, the fourth from the left on the paper, and an electrostatic latent image for the black component is formed.

Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color have been formed reach positions facing the developing units 13. Then, toner of each color is supplied from each developing unit 13 to the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images formed on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (the developing process).
Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the development process each reach a position facing the intermediate transfer belt 17. Here, a primary transfer roller 14 is installed at each facing position so as to abut against the inner circumferential surface of the intermediate transfer belt 17. Then, at the position of the primary transfer roller 14, the toner images of each color formed on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred onto the intermediate transfer belt 17 in order, superimposed on top of each other (this is the primary transfer process).

After the transfer process, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK each reach a position facing the cleaning unit 15. The cleaning unit 15 then collects untransferred toner remaining on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK (this is the cleaning process).
Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK pass through a charge removal section, and a series of image forming processes on the photosensitive drums 11Y, 11M, 11C, and 11BK are completed.

Meanwhile, the intermediate transfer belt 17, onto which the toner of each color is transferred (carried) in layers on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK, travels clockwise in FIG. 1 and reaches a position facing the secondary transfer roller 18. Then, at the position facing the secondary transfer roller 18, the color toner images carried on the intermediate transfer belt 17 are transferred onto the sheet P (secondary transfer process).
Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhering to the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and the series of transfer processes on the intermediate transfer belt 17 is completed.

Here, the sheet P transported between the intermediate transfer belt 17 and the secondary transfer roller 18 (secondary transfer nip) is transported from the paper feed unit 7 via the registration rollers 9 and the like.
More specifically, the sheet P is fed by a paper feed roller 8 from a paper feed unit 7 that stores the sheet P, passes through a conveyance path, and is then guided to a registration roller 9. The sheet P that has reached the registration roller 9 is conveyed toward the secondary transfer nip in a timely manner.

Then, the sheet P onto which the full-color image has been transferred is guided by a conveyor belt to the fixing device 20. In the fixing device 20, the color image (toner image) is fixed to the surface of the sheet P at a nip portion (fixing nip) between a fixing roller and a pressure roller (fixing process).
After the fixing process, the sheet P is discharged as an output image to the outside of the apparatus main body 1 by a paper discharge roller, and a series of image forming processes (printing) is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIG. 2 and other figures.
As shown in Figure 2, the fixing device 20 is composed of a fixing roller 21 as a fixing member, a heater 25 as a heating means, a pressure roller 31 as a pressure member, a first temperature sensor 40 as a first temperature detection means for detecting the temperature (surface temperature) of the center of the width of the fixing roller 21, a second temperature sensor 41 as a second temperature detection means for detecting the temperature (surface temperature) of the center of the width of the pressure roller 31, and a pressure mechanism 55 as a nip portion forming mechanism for forming a nip portion.

Here, the fixing roller 21 (fixing rotor) as a fixing member is a multi-layer roller member in which a coating layer 21b (a laminate of an elastic layer and a release layer) is formed on a hollow core metal 21a made of a metal material such as stainless steel, and is pressed against a pressure roller 31 as a pressure member to form a nip portion (fixing nip).
The elastic layer in the coating layer 21b of the fixing roller 21 is made of an elastic material such as fluororubber, silicone rubber, or foamed silicone rubber. The release layer in the coating layer 21b of the fixing roller 21 is made of PFA (tetrafluoroethylene perfluoroalkylvinylether copolymer resin) or the like. By providing the release layer on the surface layer of the fixing roller 21, the release properties (peelability) of the toner image are ensured. The fixing roller 21 is rotated clockwise in FIG. 2 by a drive motor (not shown).

A heater 25 serving as a heating means is fixed inside the hollow fixing roller 21 (core metal 21a).
The heater 25 is a rod-shaped halogen heater, and both ends thereof are fixed to the side plates of the fixing device 20. When the main switch of the image forming apparatus main body 1 is turned on (power on), power is supplied to the heater 25 from the power supply unit 51. The fixing roller 21 is heated by radiant heat from the heater 25, whose output is controlled (PID controlled) by the control unit 50, and further heat is applied to the toner image T on the sheet P from the surface of the heated fixing roller 21.
The output of the heater 25 is controlled based on the detection result of the roller surface temperature by a first temperature sensor 40 (e.g., a thermopile or a non-contact thermistor) that faces the surface of the fixing roller 21 in a non-contact manner at the center of the width direction (the direction perpendicular to the plane of the paper in FIG. 2 ). That is, the heater 25, which serves as a heating means, is controlled based on the detection result of the first temperature sensor 40 that serves as a first temperature detection means. More specifically, an AC voltage is applied from a power supply unit 51 to the heater 25 for a current-carrying time that is determined based on the detection result of the first temperature sensor 40. By controlling the output of the heater 25 in this way, the temperature of the fixing roller 21 (fixing temperature) can be adjusted and controlled to a desired temperature (target control temperature).

The pressure roller 31 (pressure rotating body) as a pressure member is a roller member mainly composed of a core metal 32 and an elastic layer 33 as a coating layer that covers the outer circumferential surface of the core metal 32 .
The elastic layer 33 (covering layer) of the pressure roller 31 is made of a material such as silicone rubber, foamed silicone rubber, etc. It is also possible to provide a thin release layer made of PFA or the like on the surface of the elastic layer 33, and to configure the covering layer with the elastic layer 33 and the release layer.
The pressure roller 31 is then pressed against the fixing roller 21 by a pressure mechanism 55 serving as a nip forming mechanism. In this way, a desired nip is formed between the pressure roller 31 and the fixing roller 21. The pressure mechanism 55 (nip forming mechanism) can be configured, for example, with a rotatable lever that contacts shafts at both ends of the pressure roller 31, and a spring (biasing member) that biases the lever upward (toward the fixing roller 21).
The pressure roller 31 is rotated counterclockwise in FIG. 2 in accordance with the rotation of the fixing roller 21 .

In addition to the first temperature sensor 40 (first temperature detection means) that detects the surface temperature of the fixing roller 21, the fixing device 20 in this embodiment is also provided with a second temperature sensor 41 (second temperature detection means) that detects the surface temperature of the pressure roller 31. The second temperature sensor 41 may be a thermopile or a non-contact thermistor that faces the surface of the pressure roller 31 in the center in the width direction without contacting it.
The presence or absence of an abnormality in the fixing device 20 and the nature of the abnormality are detected based on the detection results of the first temperature sensor 40 and the second temperature sensor 41. These will be described in detail later. In this embodiment, in order to clearly distinguish between abnormal states, which will be described later, the widthwise positions of the first temperature sensor 40 and the second temperature sensor 41 are set so as not to coincide with each other at the center in the width direction.

The fixing device 20 configured as described above operates as follows.
When the main switch of the apparatus main body 1 is turned on, an AC voltage is applied (power is supplied) from the power supply unit 51 to the heater 25 .
When a print command (print request) is input, a drive motor (drive mechanism) (not shown) starts rotating the fixing roller 21 clockwise, and the pressure roller 31 starts rotating counterclockwise. Thereafter, a sheet P is fed from the paper feed unit 7, and at the position of the secondary transfer roller 18, the toner image on the intermediate transfer belt 17 is carried as an unfixed image on the sheet P. The sheet P carrying the unfixed image T (toner image) is transported in the direction of the arrow in FIG. 2 and sent into the nip between the fixing roller 21 and the pressure roller 31, which are in a pressure-contact state. The toner image T is then fixed to the surface of the sheet P by the heat of the fixing roller 21 and the pressure force of the fixing roller 21 and the pressure roller 31. After the fixing process, the sheet P is sent out of the nip in the direction of the arrow by the rotating fixing roller 21 and the pressure roller 31.

The following describes in detail the characteristic configuration and operation of the fixing device 20 (image forming apparatus 1) in this embodiment.
As previously explained using Figure 2 etc., the fixing device 20 in this embodiment is provided with a first temperature sensor 40 as a first temperature detection means for detecting the surface temperature of the fixing roller 21 as a fixing member, and a second temperature sensor 41 as a second temperature detection means for detecting the surface temperature of the pressure roller 31 as a pressure member.

In this embodiment, the two temperature trends detected by the first temperature sensor 40 (first temperature detection means) and the second temperature sensor 41 (second temperature detection means) during image formation (printing) are compared with two temperature trends (normal temperature trends) previously detected and stored to determine whether the state is a "normal state" in which the fixing device 20 is operating normally, a "heating system abnormal state" in which an abnormality has occurred in a heating system component involved in the control (heating control) of heating the fixing roller 21 (fixing member), or a "non-heating system abnormal state" in which an abnormality has occurred in a component other than a heating system component.

In other words, in this embodiment, the temperature changes (temperature transitions) of the fixing roller 21 and pressure roller 31 detected by the first and second temperature sensors 40, 41 during printing are compared with those detected and stored in the past under normal conditions (see graphs R1 and R2 in Figure 3(A)), and whether the fixing device 20 is in a normal or abnormal state is determined based on whether the changes are roughly similar to the normal state or whether they deviate significantly from the normal state. Then, when an abnormal state is determined, it is determined whether the cause of the abnormality is due to a heating system component or to another component.

Here, in this embodiment, the above-mentioned "heating system components" are the fixing roller 21 (fixing member), the heater 25 (heating means), the first temperature sensor 40 (first temperature detection means), and the power supply unit 51 that supplies power to the heater 25.
Specifically, if the surface of the fixing roller 21 is damaged or peeled off, the first temperature sensor 40 fails, the power supply unit 51 fails, or there is an abnormality in a component involved in the heating control of the fixing roller 21, not only will the temperature change detected by the first temperature sensor 40 become abnormal, but the temperature change detected by the second temperature sensor 41 will also become abnormal, and the state of such temperature change will be grasped and determined to be an "abnormal heating system state."

3A shows a "normal state" in which both the graph R1 showing the temperature change detected by the first temperature sensor 40 and the graph R2 showing the temperature change detected by the second temperature sensor 41 are normal. In contrast, FIG. 3B shows a "heating system abnormal state" in which both the graph S1 showing the temperature change detected by the first temperature sensor 40 and the graph S2 showing the temperature change detected by the second temperature sensor 41 are abnormal.
Then, data on temperature transitions in a normal state detected by the first and second temperature sensors 40, 41 (see FIG. 3A) is stored in the memory of the control unit 50 every time printing is completed.

In this way, in this embodiment, when an abnormality occurs in the fixing device 20, the cause can be identified to some extent in advance. This allows for efficient maintenance of the fixing device 20.

In particular, in this embodiment, it is further determined whether the "non-heating system abnormal state" is a "first non-heating system abnormal state" or a "second non-heating system abnormal state."
The "first non-heating system abnormal state" is an abnormal state in which an abnormality occurs in at least one of the pressure roller 31 (pressure member), the second temperature sensor 41 (second temperature detection means), and the pressure mechanism 55 (a nip portion forming mechanism for forming a nip portion). In other words, the "first non-heating system abnormal state" is an abnormality in a non-heating system component that is not involved in heater control (fixing temperature control), primarily a component on the pressure roller side. Specifically, if the surface of the pressure roller 31 is damaged or peeled, the second temperature sensor 41 breaks down, the pressure applied by the pressure mechanism 55 significantly increases or decreases, or there is an abnormality in a component on the pressure path roller side, the temperature transition detected by the first temperature sensor 40 will be normal, but the temperature transition detected by the second temperature sensor 41 will be abnormal. This temperature transition state is recognized and a "first non-heating system abnormal state" will be identified.
In contrast, the "second non-heating system abnormal state" is an abnormal state in which an abnormality occurs due to a cause different from that of the "first non-heating system abnormal state." In other words, the "second non-heating system abnormal state" is an abnormality that cannot be identified as either a "heating system abnormal state" or a "first non-heating system abnormal state." For example, such an abnormal state may occur when a cause that lowers the surface temperature of the fixing roller 21 and a cause that raises the surface temperature of the pressure roller 31 occur in combination. In such a case, the temperature change detected by the second temperature sensor 41 is normal, but the temperature change detected by the first temperature sensor 40 is abnormal. This temperature change state is recognized and determined to be a "second non-heating system abnormal state."
In addition, since the cause of the "second non-heating system abnormal state" is often not clearly identified, it is preferable to replace the fixing device 20 itself rather than replacing or maintaining some of the parts of the fixing device 20.

More specifically, in this embodiment, as shown in FIG. 4, if the temperature change detected by the first temperature sensor 40 is normal and the temperature change detected by the second temperature sensor 41 is also normal, the control unit 50 determines that the state is "normal."
On the other hand, if the temperature change detected by the first temperature sensor 40 is abnormal and the temperature change detected by the second temperature sensor 41 is also abnormal, the control unit 50 determines that the state is a "heating system abnormal state." Furthermore, if the temperature change detected by the first temperature sensor 40 is normal and the temperature change detected by the second temperature sensor 41 is abnormal, the control unit 50 determines that the state is a "first non-heating system abnormal state." Furthermore, if the temperature change detected by the first temperature sensor 40 is abnormal and the temperature change detected by the second temperature sensor 41 is normal, the control unit 50 determines that the state is a "second non-heating system abnormal state."

In this embodiment, whether the current temperature trend is normal or abnormal compared to normal past temperature trends is determined by whether the difference between the current and past temperature trends is within a predetermined reference range.
Specifically, when the difference in temperature transition is determined to be within a predetermined reference range (when the current temperature transition is roughly similar to that in normal times), the current temperature transition is determined to be normal. On the other hand, when the difference in temperature transition is determined to be outside the predetermined reference range (when the current temperature transition is significantly different from that in normal times), the current temperature transition is determined to be abnormal.
The reference range (temperature) "ΔT°C" can be, for example, a temperature range "ΔT = T±A°C" with a predetermined temperature range on both the high-temperature side and the low-temperature side centered around the target surface temperature (detected temperature) T°C. The calculation unit can then determine whether the average value (or maximum or minimum value) of the current temperature transition is within or outside the reference range ΔT°C set in this way. The reference range "ΔT°C" can also be set as the range of the temperature gradient (temperature change within a predetermined time) in the temperature transition.

In this embodiment, when the control unit 50 (calculation unit) determines that the "heating system abnormal state" or "non-heating system abnormal state" exists, and determines that the difference between the current and past temperature changes described above is outside a predetermined reference range ΔT°C by a predetermined value A (ΔT≦T±A°C) (when the difference is not significantly outside the reference range ΔT°C), a notification is issued to prompt maintenance to resolve the abnormal state without interrupting the subsequent image forming operation (printing operation). Specifically, a display such as that shown in FIG. 5(A) is displayed on the operation display panel 100.
On the other hand, when it is determined that the difference between the current and past temperature transitions described above is outside the range of a predetermined value A ((ΔT>T±A°C)) with respect to the predetermined reference range ΔT°C (when the temperature is significantly outside the reference range ΔT°C), the subsequent image forming operation (printing operation) is interrupted and the abnormal state is notified. Specifically, the display shown in Fig. 5(B) is displayed on the operation display panel 100.

In this embodiment, the above-mentioned "predetermined value A" can be changed to any value.
As a specific example, as shown in FIGS. 5(C) to (E), a serviceman or a user can operate the operation display panel 100 to change the predetermined value A for the set value of the temperature range (differential temperature) and temperature gradient as the reference range ΔT°C exemplified above.
By configuring in this way, for a user who gives priority to forming a good fixed image, the predetermined value A can be adjusted to be narrower so that maintenance can be performed earlier, and for a user who gives priority to avoiding downtime of the device, the predetermined value A can be adjusted to be wider so that maintenance can be performed when time is more flexible, thereby improving usability for the user.
In this embodiment, referring to Figures 5(C) to (E), the operation display panel 100 can be operated by a serviceman or a user to select whether or not to notify (display) the above-mentioned "abnormal state" and continue printing.

An example of control for determining an abnormal state will be described below with reference to FIG.
First, when the image forming apparatus 1 starts printing (image formation operation) from a standby state, the first and second temperature sensors 40, 41 acquire data on the surface temperatures (temperature transitions) of the fixing roller 21 and the pressure roller 31 during printing, and the data is stored in the memory unit (ROM) of the control unit 50 (steps S1 and S2). The data (current temperature transitions) stored in the memory unit is then compared with data on normal temperature transitions stored in the memory unit (ROM) (step S3), and it is determined whether the fixing device 20 is in an abnormal state (step S4). This determination is made based on whether the difference in the temperature transitions compared in step S3 is within a reference range ΔT°C.
If the printer is determined to be in a normal state, the printer is deemed to be in a normal state and printing is terminated. The data on the temperature change after printing that is determined to be in a normal state is stored in the memory unit as data from past normal times.
On the other hand, if an abnormality is determined in step S4, the abnormality is further determined in detail (step S5). That is, as described above with reference to Fig. 4, based on the combination of normal and abnormal temperature transitions detected by the first and second temperature sensors 40, 41, the abnormality is determined to be either a heating system abnormality, a first non-heating system abnormality, or a second non-heating system abnormality.
It is then determined whether to continue printing in the abnormal state (step S6). That is, as explained above, it is determined whether the difference between the current temperature change and the past (normal) temperature change is outside the range of a predetermined value A with respect to a predetermined reference range ΔT°C.
As a result, if the conditions for continuing printing are met, the operation display panel 100 displays a message urging maintenance such as part replacement (see FIG. 5A), while continuing printing (step S7), and the flow ends upon completion of the printing (step S8). On the other hand, if the conditions for continuing printing are not met in step S6, the printing is stopped, and a message indicating that there is an abnormality in the device is displayed on the operation display panel 100 (see FIG. 5B).

As described above, the fixing device 20 in this embodiment includes the fixing roller 21 (fixing member) that is heated by the heater 25 (heating means) to heat the toner image T and fix it on the surface of the sheet P, the pressure roller 31 (pressure member) that presses against the fixing roller 21 to form a nip portion through which the sheet P is conveyed, the first temperature sensor 40 (first temperature detection means) that detects the surface temperature of the fixing roller 21, and the second temperature sensor 41 (second temperature detection means) that detects the surface temperature of the pressure roller 31. Then, by comparing two temperature transitions detected by the first temperature sensor 40 and the second temperature sensor 41, respectively, during image formation with two temperature transitions detected and stored in the past, it is determined whether the fixing device 20 is in a normal state where it is operating normally, a heating system abnormal state where an abnormality has occurred in a heating system component related to the control of heating the fixing roller 21, or a non-heating system abnormal state where an abnormality has occurred in a component other than the heating system component.
This allows efficient maintenance of the fixing device 20.

In this embodiment, a fixing roller 21 is used as the fixing member and a pressure roller 31 is used as the pressure member, but the fixing member and the pressure member are not limited to these, and for example, a fixing belt can be used as the fixing member and a pressure belt can be used as the pressure member.
In addition, in this embodiment, a thermal heater type heating means is used as the heating means for heating the fixing member (fixing roller 21), but the heating means is not limited to this, and for example, an electromagnetic induction type (IH type) or a resistance heating element type can also be used.
In this embodiment, a second heating means (for example, a second heater installed inside the pressure roller 31) can be provided to actively heat the pressure roller 31. In this case, the second heating means is controlled based on the detection result of the second temperature sensor 41 (second temperature detection means). In addition, a second heating abnormality state in which an abnormality occurs in a second heating system component involved in controlling the heating of the pressure roller is added to the heating system abnormality state.
Furthermore, in this embodiment, non-contact temperature sensors are used as the first temperature sensor 40 and the second temperature sensor 41, but contact temperature sensors may also be used as the first temperature sensor 40 and the second temperature sensor 41.
In such cases, the same effect as that of this embodiment can be obtained.

It should be noted that the present invention is not limited to this embodiment, and it is clear that within the scope of the technical concept of the present invention, this embodiment may be modified as appropriate in ways other than those suggested in this embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to this embodiment, and may be any number, position, shape, etc. that is suitable for implementing the present invention.

In this specification, the term "width direction" is defined as a direction perpendicular to the sheet conveying direction.
In this specification, the term "sheet" is defined to include not only paper (sheet of paper) but also all sheet-like recording media such as coated paper, label paper, OHP sheets, and film sheets.

1. Image forming apparatus (image forming apparatus main body),
20 Fixing device,
21 Fixing roller (fixing member),
25 heater (heating means),
31 pressure roller (pressure member),
40 first temperature sensor (first temperature detection means),
41 second temperature sensor (second temperature detection means),
50 control unit,
51 Power supply section,
55 Pressurizing mechanism (nip forming mechanism),
P sheet (paper).

Japanese Patent Application Laid-Open No. 2007-219007

Claims (6)

a fixing member that is heated by a heating means and heats the toner image to fix it on the surface of the sheet;
a pressure member that forms a nip portion through which a sheet is conveyed by being pressed against the fixing member;
a first temperature detecting means for detecting a surface temperature of the fixing member;
a second temperature detection means for detecting the surface temperature of the pressure member;
A fixing device comprising:
comparing two temperature transitions detected by the first temperature detection means and the second temperature detection means during image formation with the two temperature transitions detected and stored in the past;
If both of the two temperature transitions detected by the first temperature detection means and the second temperature detection means are normal, the fixing device is determined to be in a normal state where it is operating normally,
If both of the two temperature transitions detected by the first temperature detection means and the second temperature detection means are abnormal, it is determined that an abnormality has occurred in a heating system component related to the control of heating the fixing member, and
If the temperature transition detected by the first temperature detection means is normal and the temperature transition detected by the second temperature detection means is abnormal, it is determined that a first non-heating system abnormal state has occurred in at least one of the components other than the heating system components, namely, the pressure member, the second temperature detection means, and a nip portion forming mechanism for forming the nip portion, and
If the temperature transition detected by the first temperature detection means is abnormal and the temperature transition detected by the second temperature detection means is normal, it is determined that an abnormality has occurred in a component other than the heating system component, and that the abnormality has occurred due to a cause different from that of the first non-heating system abnormal state , and
When it is determined that the second non-heating system is in the abnormal state, a notification is given to prompt replacement of the fixing device itself . 2. The fixing device according to claim 1, wherein the heating system components are the fixing member, the heating means, the first temperature detection means, and a power supply section that supplies power to the heating means. When it is determined that the abnormality state is one of the heating system abnormality state, the first non-heating system abnormality state, and the second non-heating system abnormality state,
When it is determined that the difference between the current temperature change and the past temperature change is outside a predetermined value range of a predetermined reference range, a notification is issued to prompt maintenance to eliminate the abnormal state without interrupting the subsequent image forming operation,
3. The fixing device according to claim 1, wherein when it is determined that the difference is outside the range of the predetermined value with respect to the predetermined reference range, the subsequent image forming operation is interrupted and the abnormal state is notified. 4. The fixing device according to claim 3, wherein the predetermined value can be changed to any value. 5. The fixing device according to claim 1, wherein the heating means is controlled based on the detection result of the first temperature detection means. An image forming apparatus comprising the fixing device according to any one of claims 1 to 5.