JP2024068349A - Fixing device and image forming device - Google Patents

Abstract

To eliminate a slip of a fixing belt without stopping a device as much as possible when detecting the slip of the fixing belt.SOLUTION: "A belt idle drive mode (a control mode)" brings a pressure roller 31 (a pressure rotor) in a separated state by a contact/separation mechanism 60 into contact with a fixing belt 21 for predetermined time R and then separates the pressure roller 31 again when a slip of the fixing belt 21 is detected first by first and second temperature sensors 41, 42 (first slip detection means) after starting execution, then completes the belt idle drive mode when the slip of the fixing belt 21 is not detected by the second temperature sensor 42 (second slip detection means), and repeats operation for returning to the separated state after bringing the pressure roller 31 in the separated state into contact with the fixing belt for the predetermined time R when detecting the slip of the fixing belt 21 by the second temperature sensor 42 (second slip detection means).SELECTED DRAWING: Figure 5

Description

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

Conventionally, in fixing devices installed in image forming devices such as copiers and printers, a fixing nip through which a sheet is transported is formed by pressing a pressure rotating body (pressure roller) against a nip forming member that contacts the inner peripheral surface of the fixing belt via the fixing belt (see, for example, Patent Document 1).

On the other hand, Patent Document 1 discloses a technology in which a temperature sensor that detects the surface temperature of the fixing belt and a temperature sensor that detects the surface temperature of the pressure roller are provided, and if the temperature difference between the two temperature sensors is large, it is determined that slippage has occurred in the fixing belt and heating of the fixing belt is stopped.

Even though the technology in Patent Document 1 can detect slippage of the fixing belt, it is necessary to stop the device once and perform separate maintenance to prevent slippage of the fixing belt, which reduces the productivity of the device.

This invention was made to solve the above-mentioned problems, and aims to provide a fixing device and an image forming device that, when slippage of the fixing belt is detected, can eliminate the slippage of the fixing belt without stopping the device as much as possible.

The fixing device in this invention includes a fixing belt that is heated by a heating means and heats and fixes a toner image on a sheet while traveling in a predetermined traveling direction, a nip forming member that slides against the inner peripheral surface of the fixing belt, a pressure rotating body that forms a fixing nip through which a sheet is transported by being pressed against the nip forming member via the fixing belt, and a contact/separation mechanism that moves the pressure rotating body relatively close to and away from the fixing belt, and a control mode in which the fixing belt is heated by the heating means and the fixing belt is caused to travel at a predetermined timing while the pressure rotating body is separated from the fixing belt by the contact/separation mechanism. The control mode is started, and when slippage of the fixing belt is first detected by the first slip detection means after the start of the control mode, the contact/separation mechanism brings the pressure rotor, which was in a separated state, into contact with the fixing belt for a predetermined time, and then returns the pressure rotor to the separated state. If slippage of the fixing belt is not detected by the second slip detection means, the control mode is terminated, and when slippage of the fixing belt is detected by the second slip detection means, the pressure rotor, which was in a separated state, is brought into contact for the predetermined time and then returned to the separated state, and the operation is repeated.

The present invention provides a fixing device and an image forming device that, when a slippage of the fixing belt is detected, can eliminate the slippage of the fixing belt without stopping the device as much as possible.

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. FIG. 2 is a diagram showing the fixing device in a state where the pressure roller is separated from the fixing device; 11A and 11B are diagrams illustrating an operation of the fixing device in a belt empty drive mode. 10 is a flowchart showing a control in a belt empty drive mode.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that in each drawing, the same or corresponding parts are given the same reference numerals, and the repeated 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 an image forming apparatus as a multifunction machine having a copy function and a printer function, reference numeral 2 denotes a writing unit that emits laser light based on input image information, reference numeral 3 denotes an original transport unit that transports an original D to an original reading unit 4, reference numeral 4 denotes an original reading unit that reads image information of the original D, and reference numeral 7 denotes a paper feed unit in which sheets P such as paper are stored.
Further, reference numeral 9 denotes a registration roller (timing roller) that adjusts the timing of transporting sheet P, 11Y, 11M, 11C, and 11BK denote photosensitive drums on which toner images of each color (yellow, magenta, cyan, and black) are formed, and 12 denotes a charging unit that charges each of the photosensitive drums 11Y, 11M, 11C, and 11BK.
Further, reference numeral 13 denotes a developing unit which develops the electrostatic latent images formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK, reference numeral 14 denotes a primary transfer bias roller which transfers the toner images formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK onto a sheet P in a superimposed manner, and reference numeral 15 denotes a cleaning unit which collects untransferred toner on each of the photosensitive drums 11Y, 11M, 11C, and 11BK.
In addition, reference numeral 16 denotes an intermediate transfer belt cleaning section that cleans the intermediate transfer belt 17, reference numeral 17 denotes the intermediate transfer belt onto which multiple color toner images are transferred in superimposed order, reference numeral 18 denotes a secondary transfer bias roller for transferring the color toner image on the intermediate transfer belt 17 onto the sheet P, and reference numeral 20 denotes a fixing device that fixes the toner image (unfixed image) on the sheet P.
Reference numeral 65 denotes an operation display panel for displaying information relating to the printing operation (image forming operation) and for performing operations.

A normal color image forming operation (printing operation) in the image forming apparatus will be described below.
When the image forming apparatus 1 is used as a copier, the user places an original D on the original platen, inputs necessary information such as printing conditions into the operation display panel 65, and presses the copy button.
As a result, the document D is transported from the document table in the direction of the arrow in the drawing 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 image information of the document D placed on the contact glass 5 is optically read by the document reading unit 4.

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 by the document D is then imaged 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 for each RGB (red, green, blue) color separation light, and then converted into an electrical image signal. Furthermore, based on the RGB color separation image signal, the image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, and other processing to obtain color image information of yellow, magenta, cyan, and black.

When the image forming device 1 is used as a printer, the user inputs necessary information such as image information and printing conditions from an external input device such as a personal computer that is communicatively connected to the image forming device 1, and the information is acquired by the control unit of the image forming device 1.

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 onto the corresponding photoconductor drums 11Y, 11M, 11C, and 11BK.

Meanwhile, the four photoconductor drums 11Y, 11M, 11C, and 11BK each rotate in the counterclockwise direction 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). Thus, a charging potential is formed on the photoconductor drums 11Y, 11M, 11C, and 11BK. Then, the charged surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK reach the respective laser light irradiation positions.
In the writing unit 2, laser beams corresponding to image signals are emitted from four light sources, one for each color. Each laser beam passes through a separate optical path for each color component (yellow, magenta, cyan, black) (exposure process).

The laser light corresponding to the yellow component is irradiated onto the surface of the first photoconductor 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 photoconductor 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 photoconductor 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 second photoconductor drum 11M from the left on the paper, forming an electrostatic latent image corresponding to the magenta component. The laser light of the cyan component is irradiated onto the surface of the third photoconductor drum 11C from the left on the paper, forming an electrostatic latent image of the cyan component. The laser light of the black component is irradiated onto the surface of the fourth photoconductor drum 11BK from the left on the paper, forming an electrostatic latent image of the black component.

Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13. Then, the toner of the respective colors is supplied from each developing unit 13 onto the photoconductor drums 11Y, 11M, 11C, and 11BK, and the latent images on the photoconductor drums 11Y, 11M, 11C, and 11BK are developed (this is the developing process).
Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the development process reach the portions facing the intermediate transfer belt 17. Here, primary transfer bias rollers 14 are provided at each of the facing portions so as to abut against the inner peripheral surface of the intermediate transfer belt 17. Then, at the positions of the primary transfer bias rollers 14, the toner images of each color formed on the photoconductor drums 11Y, 11M, 11C, and 11BK are transferred onto the intermediate transfer belt 17 in order, superimposed thereon (this is the primary transfer process).

After the transfer process, the surfaces of the photoconductor 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 photoconductor drums 11Y, 11M, 11C, and 11BK (this is the cleaning process).
Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK pass through a charge removing section, and a series of image forming processes on the photoconductor drums 11Y, 11M, 11C, and 11BK are completed.

Meanwhile, the intermediate transfer belt 17 onto which the toners of the respective colors on the photoconductor drums 11Y, 11M, 11C, and 11BK are transferred (carried) in an overlapping manner travels in a clockwise direction in the drawing and reaches a position facing the secondary transfer bias roller 18. Then, at the position facing the secondary transfer bias 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 a 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 bias roller 18 (secondary transfer nip) is transported from the paper feed section 7 via the registration rollers 9 and the like.
More specifically, the sheet P fed by a feed roller 8 from a feed unit 7 storing the sheet P passes through a transport guide and is then guided to a registration roller 9. The sheet P that has reached the registration roller 9 is transported in a timely manner toward the secondary transfer nip.

Then, the sheet P onto which the full-color image has been transferred is guided by a conveyor belt to a fixing device 20. In the fixing device 20, the color image (toner image) is fixed onto the sheet P at a fixing nip (nip portion) between a fixing belt 21 and a pressure roller 31 (fixing process).
After the fixing process, the sheet P is discharged by a discharge roller to the outside of the apparatus main body 1 as an output image, and a series of image forming processes (printing operations) 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 FIGS.
As shown in FIG. 2, the fixing device 20 is composed of a fixing belt 21, a heating roller 22, a nip forming member 23 (sliding pad), a lubricant supply roller 24, a tension roller 25, a heater 26 as a heating means, a reinforcing roller 27, temperature sensors 41 and 42, a pressure roller 31 as a pressure rotating body, and the like.

Here, the fixing belt 21 is a fixing rotating body that heats the toner image on the sheet P to fix it on the sheet P. The fixing belt 21 is an endless belt with a multi-layer structure in which an elastic layer and a release layer (surface layer) are sequentially laminated on a base layer made of a resin material such as polyimide. The elastic layer of the fixing belt 21 is formed of an elastic material such as fluororubber, silicone rubber, and foamed silicone rubber with a layer thickness of about 90 μm. The release layer of the fixing belt 21 is formed of PFA (tetrafluoroethylene perfluoroalkylvinylether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like with a layer thickness of about 20 μm. By providing a release layer on the surface layer of the fixing belt 21, the releasability (peelability) of the toner T (toner image) is ensured. The fixing belt 21 is stretched and supported by three roller members (a heating roller 22, a lubricant supply roller 24, and a tension roller 25) and a nip forming member 23, and runs (rotates) in the direction of the arrow (clockwise) in Fig. 2. By using the fixing belt 21 with a low heat capacity as the fixing member, the temperature rise characteristic of the device is improved.
In the present embodiment, the three roller members 22, 24, and 25 are used to support and stretch the fixing belt 21, but the number of roller members is not limited to this.

The heating roller 22 is a roller member with a hollow structure made of a metal material such as aluminum or stainless steel, and a heater 26 (heat source) is fixed inside the cylindrical body as a heating means without rotating. By setting the thickness of the heating roller 22 to be relatively thin, the heat capacity of the heating body is reduced and the temperature rise characteristics of the device are improved (the rise time is shortened).

The heater 26 (heating means) provided inside the heating roller 22 is a 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 is supplied to the heater 26 from a power supply unit (not shown). The heating roller 22 is heated by radiant heat from the heater 26, the output of which is controlled by the control unit 90, and further heat is applied to the toner image T on the sheet P from the surface of the fixing belt 21 heated by the heating roller 22.
The output control of the heater 26 is performed based on the detection result of the belt surface temperature by a first temperature sensor 41 that faces the surface of the fixing belt 21 without contacting it. More specifically, an AC voltage is applied to the heater 26 for a current-carrying time that is determined based on the detection result of the first temperature sensor 41 (thermopile). By controlling the output of the heater 26 in this way, the temperature of the fixing belt 21 (fixing temperature) can be adjusted and controlled to a desired temperature (target control temperature).
In this embodiment, one heater 26 is provided inside the heating roller 22, but a plurality of heaters may be provided.
In the present embodiment, the first temperature sensor 41 is disposed at a position facing the heating roller 22 with the fixing belt 21 interposed therebetween.
In addition, in this embodiment, in addition to the first temperature sensor 41, a second temperature sensor 42 is installed downstream of the first temperature sensor 41, so that the detection result of the belt surface temperature by the second temperature sensor 41 can also be used for the above-mentioned heater control.

2, the nip forming member 23 is in sliding contact with the inner peripheral surface (sliding surface) of the fixing belt 21, and is in pressure contact with the pressure roller 31 via the fixing belt 21 to form a fixing nip. The surface of the nip forming member 23 facing the pressure roller 31 (the surface that is in sliding contact with the fixing belt 21) is formed in a flat shape. This makes the shape of the nip portion approximately parallel to the image surface of the sheet P, and the adhesion between the fixing belt 21 and the sheet P is increased, thereby improving the fixing performance. Furthermore, the curvature of the fixing belt 21 at the exit side of the nip portion is large, so that the sheet P sent out from the nip portion can be easily separated from the fixing belt 21.
In this embodiment, the nip forming member 23 that forms the nip portion is formed in a flat shape, but the nip forming member 23 that forms the nip portion may also be formed in a concave shape. That is, the opposing surface of the nip forming member 23 (the surface that slides against the fixing belt 21) may also be formed in a concave shape so as to conform to the curvature of the pressure roller 31. In that case, the sheet P is sent out from the nip portion so as to conform to the curvature of the pressure roller 31, so that it is possible to prevent the sheet P from being attracted to the fixing belt 21 after the fixing process and not being separated.

In addition, the material for forming the nip forming member 23 may be a resin material or a metal material, but a resin material (such as a liquid crystal polymer, polyamideimide, polyimide, etc.) that has sufficient rigidity so as not to bend significantly even when subjected to the pressure of the pressure roller 31 and has heat resistance and heat insulation properties is preferred.
In addition, the opposing surface of the nip forming member 23 is preferably coated with a low-friction material (such as diamond-like carbon, PTFE, molybdenum disulfide, graphite, etc.) to reduce sliding resistance with the fixing belt 21.
In the present embodiment, the heater 26 is used as a heating means for heating the fixing belt 21. However, by using a ceramic heater or the like as the nip forming member 23, the nip forming member 23 that functions as a sliding contact member can also function as a heating means. In that case, the facing surface of the nip forming member 23 may be made of an inorganic material such as glass or ceramics, or may have a resin coating formed on the outermost surface.

In this embodiment, a reinforcing roller 27 that reinforces the strength of nip forming member 23 that forms the nip portion is fixed to the inner peripheral surface side of fixing belt 21. Although not shown, reinforcing roller 27 is formed so that its length in the width direction (the direction perpendicular to the paper surface of FIGS. 1 to 4) is equal to that of nip forming member 23, and both ends in the width direction are held non-rotatably by a frame (housing) of fixing device 20.
The reinforcing roller 27 abuts against the pressure roller 31 via the nip forming member 23 and the fixing belt 21, thereby preventing the nip forming member 23 from being significantly deformed by the pressure of the pressure roller 31 at the nip portion. In order to satisfy the above-mentioned functions, the reinforcing roller 27 is preferably made of a metal material having high mechanical strength, such as stainless steel or iron.

The lubricant supply roller 24 is positioned downstream of the heating roller 22 (downstream in the belt running direction) and upstream of the fixing nip (nip forming member 23) so as to abut against the inner surface of the fixing belt 21.
The lubricant supply roller 24 is impregnated with a lubricant (e.g., silicone oil, silicone grease whose base oil is silicone oil, fluorosilicone oil, fluorosilicone grease whose base oil is fluorosilicone oil, fluorine oil, fluorine grease whose base oil is fluorine oil, or a combination of any two or more of these). The lubricant is supplied (applied) from the lubricant supply roller 24 to the inner peripheral surface of the fixing belt 21, thereby reducing the sliding resistance between the nip forming member 23 and the fixing belt 21.
In this embodiment, the second temperature sensor 42 is disposed so as to face the lubricant supply roller 24 across the fixing belt 21 (so as to face the surface of the fixing belt 21 without contacting it).

The tension roller 25 is disposed downstream (in the belt running direction) of the fixing nip (nip forming member 23 ) and upstream of the heating roller 22 so as to abut against the inner surface of the fixing belt 21 .
Although not shown, the tension roller 25 is biased by a compression spring so as to apply tension to the fixing belt 21 .

The pressure roller 31 is a pressure rotating body that forms a fixing nip through which the sheet P is conveyed by pressing it against the nip forming member 23 via the fixing belt 21. The pressure roller 31 as a pressure rotating body mainly consists of a core 32 made of a metal material, an elastic layer 33 formed on the outer peripheral surface of the core 32 via an adhesive layer, and a surface layer 34 (release layer) formed on the outer peripheral surface of the elastic layer 33. The elastic layer 33 of the pressure roller 31 has a layer thickness of about several mm and is formed of an elastic material such as foamed silicone rubber, fluororubber, or silicone rubber that has insulating properties. The surface layer 34 of the pressure roller 31 has a layer thickness of about several tens of μm to several hundreds of μm and is formed of a low-friction material such as conductive PFA (PFA tube). By providing a conductive release layer as the surface layer 34 of the pressure roller 31, the release property (peelability) for the toner T (toner image) is guaranteed, and the problem of the sheet P being electrostatically attracted to the pressure roller 31 and reducing the separation property can be reduced.

Here, the fixing device 20 in the present embodiment is provided with a contact/separation mechanism 60 that brings the pressure roller 31 into contact with and separates the fixing belt 21. That is, the contact/separation mechanism 60 is provided that switches the pressure roller 31 from a contact state (or a spaced state) to a spaced state (or a contact state) with respect to the fixing belt 21.
More specifically, during a normal fixing process (printing operation), the pressure roller 31 is moved by the contact/separation mechanism 60 so as to be in pressure contact with the nip forming member 23 via the fixing belt 21. In this way, a desired fixing nip is formed between the pressure roller 31 and the fixing belt 21, and the fixing process can be carried out (the state shown in FIG. 2).
3, the pressure roller 31 is moved in the direction of the white arrow by the contact/separation mechanism 60 so as to separate from the fixing belt 21. In this way, the pressure roller 31 is not in pressure contact with the fixing belt 21 (nip forming member 23), thereby reducing problems such as the pressure roller 31, the fixing belt 21, and the nip forming member 23 being deformed by unnecessary pressure.
As such a contact/separation mechanism 60, a known mechanism can be used, for example, one that is composed of a lever member that supports the shaft portion of the pressure roller 31, a cam that raises and lowers the lever member, and a motor that rotates the cam.
In the present embodiment, the contact/separation mechanism 60 can be configured to adjust the pressure contact force of the pressure roller 31 against the fixing belt 21 in addition to the contact/separation of the pressure roller 31 against the fixing belt 21 .

In addition, in this embodiment, the driving means for driving the fixing device 20 is composed of a driving motor 70 connected to the shaft portion of the pressure roller 31, a gear train (not shown) that transmits drive from a driving gear installed on the motor shaft of the driving motor 70 to the shaft portion of the heating roller 22, and the like.
The drive motor 70 moves up and down together with the pressure roller 31 by the contact/separation mechanism 60. Also, the drive gear installed on the motor shaft of the drive motor 70 meshes with and disengages from the above-mentioned gear train in conjunction with the up and down movement by the contact/separation mechanism 60.
In addition, the driving means for driving the fixing device 20 is not limited to that in this embodiment, and for example, a driving motor for rotating the heating roller 22 can be provided separately from the driving motor for rotating the pressure roller 31.

The fixing device 20 configured as 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 to the heater 26 .
When a print command (job command) is input, the pressure roller 31 and the heating roller 22 are rotated in the direction of the arrow in FIG. 2 by the drive motor 70, and the fixing belt 21, the lubricant supply roller 24, and the tension roller 25 are rotated in the direction of the arrow in FIG. 2 (clockwise). After that, the sheet P is fed from the paper feed unit 7, and the toner image on the intermediate transfer belt 17 is carried on the sheet P as an unfixed image at the position of the secondary transfer bias roller 18. The sheet P carrying the unfixed image (toner image) is transported in the direction of the dashed arrow in FIG. 2 and is fed into the fixing nip between the fixing belt 21 and the pressure roller 31 in a pressure contact state. The toner image is fixed on the surface of the sheet P by the heating by the fixing belt 21 and the pressing force of the fixing belt 21 (nip forming member 23) and the pressure roller 31. After that, the sheet P sent out from the fixing nip by the rotating fixing belt 21 and pressure roller 31 is transported in the direction of the dashed arrow.

The characteristic configuration and operation of the fixing device 20 (image forming apparatus 1) in this embodiment will be described in detail below.
As previously described with reference to Figures 2 and 3, the fixing device 20 in this embodiment is provided with a fixing belt 21, a nip forming member 23, a pressure roller 31 as a pressure rotating body, a contact/separation mechanism 60, and the like.
The fixing belt 21 is heated by a heater 26 as a heating means, and heats and fixes the toner image on the sheet P while traveling in a predetermined traveling direction. The heater 26 as a heating means is provided inside a heating roller 22 that contacts the inner peripheral surface of the fixing belt 21.
The nip forming member 23 is in sliding contact with the inner circumferential surface of the fixing belt 21 .
The pressure roller 31 as a pressure rotating member is in pressure contact with the nip forming member 23 via the fixing belt 21 to form a fixing nip through which the sheet P is transported.
The contact/separation mechanism 60 moves the pressure roller 31 (pressure rotating body) relatively to and from the fixing belt 21. Specifically, in the present embodiment, the contact/separation mechanism 60 moves the pressure roller 31 up and down to contact and separate the pressure roller 31 from the fixing belt 21.

Here, the fixing device 20 in this embodiment is provided with first and second temperature sensors 41 and 42 .
The first temperature sensor 41 is a first temperature detection unit that detects the surface temperature of the fixing belt 21, and is disposed at a position facing the heating roller 22 with the fixing belt 21 interposed therebetween.
The second temperature sensor 42 is a second temperature detection means that is located downstream in the running direction from the first temperature sensor 41 (downstream in the running direction of the fixing belt 21) and upstream in the running direction from the fixing nip (nip forming member 23) and detects the surface temperature of the fixing belt 21.
The first temperature sensor 41, together with the second temperature sensor 42, functions as a first slip detection means for detecting a slip state of the fixing belt 21 after a control mode (a belt idle driving mode) described later is started. The second temperature sensor 42 functions as a second slip detection means for detecting whether or not the slip has been eliminated after the slip of the fixing belt 21 is detected by the first and second temperature sensors 41 and 42 (first slip detection means) and an operation is performed to eliminate the slip. In this way, the second temperature sensor 42 functions as both the first slip detection means and the second slip detection means. These first and second slip detection means will be described in detail later.

In this embodiment, a "control mode" in which the fixing belt 21 is caused to run while being heated by the heater 26 (heating means) in a state in which the pressure roller 31 (pressure rotating body) is separated from the fixing belt 21 by the contact/separation mechanism 60 is started to be executed at a predetermined timing during the non-fixing process. Hereinafter, such a control mode will be appropriately referred to as a "belt idle drive mode."
For more details, refer to FIG. 4A. In the "belt empty drive mode (control mode)," during warming-up before the start of printing operation, the control unit 90 controls the contact/separation mechanism 60, the power supply unit, and the drive motor 70 to separate the pressure roller 31 from the fixing belt 21 (separated state), turn on the heater 26, and operate the drive motor 70.
In this way, by executing the "belt idle drive mode (control mode)", it is possible to reduce wear caused by sliding with the fixing belt 21 by bringing the pressure roller 31 into contact with the fixing belt 21, while uniformly heating the fixing belt 21 in the circumferential direction. Therefore, in the subsequent fixing process (printing operation), a fixed image with good fixability can be formed on the sheet P.

In this embodiment, the "belt idle drive mode (control mode)" is set so that when slippage of the fixing belt 21 is detected by the first and second temperature sensors 41, 42 (slip detection means), the pressure roller 31 (pressure rotating body) that was in a separated state is brought into contact with the fixing belt 21 by the contact/separation mechanism 60.
That is, when the belt empty drive mode (control mode) is started, the pressure roller 31 is in a separated state as shown in Fig. 4A. However, after the belt empty drive mode is started, when the first and second temperature sensors 41 and 42 detect slippage of the fixing belt 21, the pressure roller 31 is shifted from the separated state shown in Fig. 4A to the contact state shown in Fig. 4B by the control of the contact/separation mechanism 60 by the control unit 90.

More specifically, the slippage of the fixing belt 21 is likely to occur when the belt idle driving mode is started after the fixing device 20 has not been driven and the pressure roller 31 has been in a separated state for a long period of time.
If the pressure roller 31 is separated from the fixing device 20 for a long period of time without the fixing device 20 being driven, the fixing belt 21 is likely to develop a bend (curl) at the positions of the heating roller 22, the lubricant supply roller 24, the nip forming member 23, and the tension roller 25. Even if the idle belt drive mode is started in such a state, the bend creates resistance and the fixing belt is likely to slip.
In response to this, by contacting the pressure roller 31 against the fixing belt 21 to form a fixing nip, the pressure roller 31 applies a propulsive force to move the fixing belt 21 at the fixing nip position, making it easier to eliminate slippage (making it easier for the fixing belt 21 to run normally).
In other words, when slippage of the fixing belt 21 is detected while the belt empty drive mode is being executed, the pressure roller 31 is transitioned from a separated state to a contact state, making it possible to eliminate the slippage of the fixing belt 21 without stopping the fixing device 20 (image forming apparatus 1).

Thus, in this embodiment, the "belt empty drive mode (control mode)" is a mode in which, when slippage of the fixing belt 21 is first detected by the first and second temperature sensors 41, 42 (first slip detection means) after execution of the belt empty drive mode has begun, the pressure roller 31 (pressure rotating body), which was in a separated state, is brought into contact with the fixing belt 21 by the contact/separation mechanism 60 for a predetermined time R, and then the pressure roller 31 is put into the separated state again.
Then, the "belt empty drive mode (control mode)" is terminated thereafter when the second temperature sensor 42 functioning as the second slip detection means does not detect slippage of the fixing belt 21. In contrast, when the second temperature sensor 42 (second slip detection means) detects slippage of the fixing belt 21, the pressure roller 31, which was in a separated state, is brought into a contact state for a predetermined time R and then returned to the separated state, and the operation is repeated.

Here, the first slip detection means (first and second temperature sensors 41, 42) detects that the fixing belt 21 has slipped when the temperature difference (T1-T2) between the first temperature T1 detected by the first temperature sensor 41 and the second temperature T2 detected by the second temperature sensor 42 after a predetermined time X has elapsed since the first temperature T1 was detected exceeds a predetermined value A (approximately 35°).
The above-mentioned "predetermined time X" is the time it takes for the part of the fixing belt 21 detected by the first temperature sensor 41 to reach the position of the second temperature sensor 42 when the fixing belt 21 runs normally without slipping. In other words, the "predetermined time X" is a value obtained by dividing the distance M from the detection position of the first temperature sensor 41 to the detection position of the second temperature sensor 42 on the fixing belt 21 by the linear velocity V of the fixing belt 21 (X=M/V).

In detail, when there is no slippage in the fixing belt 21, the portion detected by the first temperature sensor 41 reaches exactly the position of the second temperature sensor 42 after the predetermined time X has elapsed, so that the above-mentioned temperature difference (T1-T2) does not become very large (it becomes less than the predetermined position A).
On the other hand, if slippage occurs in the fixing belt 21, the portion detected by the first temperature sensor 41 will not reach the position of the second temperature sensor 42 after the specified time X has elapsed, and the above-mentioned temperature difference (T1-T2) will become large (exceed the specified position A).
In this embodiment, in consideration of the mechanism of slip detection by the first and second temperature sensors 41, 42 (first slip detection means) described above, the first temperature sensor 41 and the second temperature sensor 42 are installed at the same position in the width direction (the direction perpendicular to the paper surface of FIGS. 2 to 4). Specifically, the first temperature sensor 41 and the second temperature sensor 42 are each installed at a central position in the width direction.
In addition, in this embodiment, the first and second temperature sensors 41, 42 are temperature sensors that do not contact the fixing belt 21, so that slippage of the fixing belt 21 is less likely to occur compared to the case where a temperature sensor that contacts the fixing belt 21 is used.

In contrast, the second slip detection means (second temperature sensor 42) detects that the fixing belt 21 has slipped when the temperature difference (T2'-T2) between the second temperature T' detected by the second temperature sensor 42 at that time and the second temperature T2 detected by the second temperature sensor 42 when the first slip detection means (first and second temperature sensors 41, 42) first detects a slip after the mode execution starts does not exceed a predetermined value B.
The above-mentioned "predetermined value B" is a value that takes into account a margin of error between the normal value of the belt surface temperature at the position of the second temperature sensor 42 when the slippage of the fixing belt 21 is eliminated and the fixing belt 21 is running normally, and the abnormal value of the belt surface temperature at the position of the second temperature sensor 42 when slippage occurs in the fixing belt 21.

In this manner, in this embodiment, after the belt empty drive mode is started, slippage of the fixing belt 21 is detected by the first and second temperature sensors 41, 42 (first slip detection means), and operation is performed to eliminate the slippage. Then, the second temperature sensor 42 (second slip detection means) detects whether the slippage has been eliminated, and if slippage is detected, the pressure roller 31 is repeatedly brought into contact with and separated from the fixing belt 21 to eliminate the slippage.
Therefore, when slippage of the fixing belt 21 is detected, the slippage of the fixing belt 21 can be eliminated without stopping the fixing device 20 (image forming apparatus 1) as much as possible.

Here, in this embodiment, when slippage of the fixing belt 21 is detected by the second temperature sensor 42 (second slip detection means) and the number of times that the pressure roller 31 (pressure rotating body) is brought into contact and then returned to a separated state exceeds a predetermined number N, the printing operation scheduled to be performed after the belt empty drive mode (control mode) is stopped.
Then, when the number of interruptions (the number of times the printing operation has been interrupted) reaches a predetermined number H, a display prompting maintenance (call a serviceman) of the fixing device 20 is displayed on the operation display panel 65 (see FIG. 1). On the other hand, when the number of interruptions does not reach the predetermined number H, the main power supply of the image forming apparatus main body 1 in which the fixing device 20 is installed is turned off and on, and then the belt empty drive mode (control mode) is executed again.
In this way, when it is presumed that there is a reasonable possibility that the fixing device 20 will recover, an attempt is made to re-execute the belt empty drive mode after turning the main power off and on, and when it is presumed that there is an extremely low possibility that the fixing device 20 will recover, maintenance of the device is encouraged, thereby preventing the user from wasting time.

In addition, in carrying out such control, when slippage of the fixing belt 21 is no longer detected by the first and second temperature sensors 41, 42 (first slip detection means) or the second temperature sensor 42 (second slip detection means), the above-mentioned predetermined number of times N and the number of times of interruption H are reset to zero for control purposes.
This makes it easier to achieve the effects of carrying out the above-mentioned control.

An example of control in the belt empty drive mode will be described below with reference to the flowchart of FIG.
5, when the main power supply of the image forming apparatus 1 is turned on, the energy saving mode is released, or a print command is input, the belt idle drive mode is started in order to uniformly heat the fixing belt 21 in a cooled or semi-cooled state in the circumferential direction (step S1). That is, with the pressure roller 31 separated from the fixing belt 21, the heater 26 is turned on, and the fixing belt 21 is driven to rotate by the drive motor 70.
Then, the control unit 90 judges whether the temperature difference (T1-T2) between the first temperature T1 detected by the first temperature sensor 41 and the second temperature T2 detected by the second temperature sensor 42 exceeds a predetermined value A (step S2). As a result, if the temperature difference (T1-T2) does not exceed the predetermined value A, it is determined that the fixing belt 21 is not slipping (or the slippage has been eliminated), and after the belt idle drive mode ends, the pressure roller 31 is brought into contact and the desired printing operation is started (step S3). At this time, the number of times N that the pressure roller 31 has been in contact with and separated from the fixing belt 21, which was counted up in step S4, and the number of times H that the printing operation was stopped, which was counted up in step S9, are each reset to zero.
On the other hand, if the temperature difference (T1-T2) exceeds the predetermined value A in step S2, it is determined that the fixing belt 21 is slipping, and the belt empty drive mode is continued with the pressure roller 31, which was in a separated state, in a contact state (step S4). At this time, the number N of times the pressure roller 31 has been in contact and separated is counted up. Then, after the predetermined time R has elapsed, the pressure roller 31 is again in the separated state, and the belt empty drive mode is continued (step S5).
Then, the control unit 90 judges whether the temperature difference (T2'-T2) between the current second temperature T' detected by the second temperature sensor 42 and the second temperature T2 detected by the second temperature sensor 42 in step S2 exceeds a predetermined value B (step S6). If the temperature difference (T2'-T2) exceeds the predetermined value B, it is determined that the slippage of the fixing belt 21 has been eliminated, and after the belt idle drive mode ends, the pressure roller 31 is brought into contact and the desired printing operation is started (step S7). At this time, the number of times N that the pressure roller 31 has been in contact and separated, which was counted up in step S4, and the number of times H that the printing operation was stopped, which was counted up in step S9, are each reset to zero.

On the other hand, if it is determined in step S6 that the temperature difference (T2'-T2) does not exceed the predetermined value B, it is determined that the slippage of the fixing belt 21 has not been resolved, and if the number of contacts and separations of the pressure roller 31 is not equal to or greater than the predetermined number N, the flow from step 4 onwards is repeated (step S8).
On the other hand, if the number of contacts and separations of the pressure roller 31 is equal to or greater than the predetermined number N in step S8, the printing operation scheduled thereafter is stopped (step S9). At this time, the number of times the printing operation has been stopped is counted up (H). Then, it is determined whether the number of times the printing operation has been stopped is equal to or greater than the predetermined number H (step S10). As a result, if the number of times the printing operation has been stopped is equal to or greater than the predetermined number H, a display is displayed on the operation display panel 65 urging the user to perform maintenance on the device (step S11). On the other hand, if the number of times the printing operation has been stopped is not equal to or greater than the predetermined number H in step S10, a display is displayed on the operation display panel 65 urging the user to turn the main power off and on (step S12), and when the main power is turned off and on, the flow from step S1 onwards is repeated (step S13).

As described above, the fixing device 20 in this embodiment includes the fixing belt 21 that is heated by the heater 26 (heating means) and heats and fixes a toner image on the sheet P while traveling in a predetermined traveling direction, the nip forming member 23 that comes into sliding contact with the inner peripheral surface of the fixing belt 21, the pressure roller 31 (pressure rotating body) that forms a fixing nip through which the sheet P is conveyed by pressing the pressure roller 31 against the nip forming member 23 via the fixing belt 21, and the contact/separation mechanism 60 that moves the pressure roller 31 relatively close to and away from the fixing belt 21. Then, in a state in which the pressure roller 31 is separated from the fixing belt 21 by the contact/separation mechanism 60, a "belt idle drive mode (control mode)" in which the fixing belt 21 is caused to travel while being heated by the heater 26 is started to be executed at a predetermined timing. In the "belt empty drive mode (control mode)", when slippage of the fixing belt 21 is first detected by the first and second temperature sensors 41, 42 (first slip detection means) after the start of execution, the pressure roller 31, which was in a separated state, is brought into contact with the fixing belt 21 for a predetermined time R by the contact/separation mechanism 60, and then the pressure roller 31 is returned to the separated state. If no slippage of the fixing belt 21 is detected by the second temperature sensor 42 (second slip detection means), the belt empty drive mode is terminated, and when slippage of the fixing belt 21 is detected by the second temperature sensor 42 (second slip detection means), the pressure roller 31, which was in a separated state, is brought into contact for the predetermined time R and then returned to the separated state, and this operation is repeated.
As a result, when slippage of the fixing belt 21 is detected, the slippage of the fixing belt 21 can be eliminated without stopping the device as much as possible.

In this embodiment, the pressure roller 31 (roller member) is used as the pressure rotating body, but a pressure belt (belt member) can also be used as the pressure rotating body.
In addition, in this embodiment, the present invention is applied to a fixing device 20 of a thermal heater type that uses a heater 26 as a heating means, but the application of the present invention is not limited to this, and the present invention can also be applied, for example, to a fixing device of an electromagnetic induction type (IH type) that uses an electromagnetic induction coil as a heating means, or a fixing device of a resistance heating type that uses a resistance heating element as a heating means.
In addition, in this embodiment, the contact/separation mechanism 60 is configured so that the pressure roller 31 (pressure rotating body) contacts and separates from the fixing belt 21, but the contact/separation mechanism may be any mechanism that moves the pressure roller (pressure rotating body) relatively to and from the fixing belt, and the contact/separation mechanism may also be configured so that the fixing belt contacts and separates from the pressure roller (pressure rotating body).
In these cases, the same effects as those of the present embodiment can be obtained.

It is clear that the present invention is not limited to this embodiment, and 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 "sheet" is not limited to paper, but is defined to include all sheet-like recording media, such as coated paper, label paper, and OHP sheets.
In addition, in this specification, the term "slip state" of the fixing belt is defined to include not only a state in which the fixing belt, which should be running normally, has stopped, but also a state in which the fixing belt is running in a state different from the normal state, such as a state in which the fixing belt runs intermittently by repeatedly starting and stopping, or a state in which the fixing belt runs at a slower speed than normal.

1 Image forming apparatus (image forming apparatus main body),
20 Fixing device,
21 Fixing belt (fixing rotor),
22 heating roller,
23 nip forming member,
24 Lubricant supply roller,
25 tension roller,
26 heater (heating means),
27 Reinforcement roller,
31 Pressure roller (pressure rotating body),
41 First temperature sensor (first slip detection means),
42 second temperature sensor (first slip detection means, second slip detection means),
60 Contact mechanism (pressure adjustment mechanism),
70 Drive motor (drive means),
P sheet (recording medium).

In addition, the present invention can also be embodied in a combination of Supplementary Notes 1 to 7 as follows.
(Appendix 1)
a fixing belt that is heated by a heating means and that heats and fixes a toner image on a sheet while traveling in a predetermined traveling direction;
a nip forming member that is in sliding contact with an inner peripheral surface of the fixing belt;
a pressure rotating member that forms a fixing nip through which a sheet is conveyed by being pressed against the nip forming member via the fixing belt;
a contact/separation mechanism for relatively contacting and separating the pressure rotating body with respect to the fixing belt;
Equipped with
a control mode in which the fixing belt is caused to run while being heated by the heating means in a state in which the contact/separation mechanism separates the pressure rotator from the fixing belt, is started at a predetermined timing;
The control mode is
when slippage of the fixing belt is detected for the first time by the first slip detection means after the start of the operation, the pressure rotating body, which has been in a separated state by the contact/separation mechanism, is brought into contact with the fixing belt for a predetermined period of time, and then the pressure rotating body is brought into the separated state again;
Thereafter, when slippage of the fixing belt is not detected by the second slip detection means, the control mode is terminated, and when slippage of the fixing belt is detected by the second slip detection means, the fixing device repeats the operation of bringing the pressure rotating body, which was in a separated state, into a contact state for the predetermined time and then returning it to the separated state.
(Appendix 2)
a first temperature sensor that detects a surface temperature of the fixing belt;
a second temperature sensor that detects a surface temperature of the fixing belt downstream of the first temperature sensor in the traveling direction and upstream of the fixing nip in the traveling direction;
Equipped with
the first slip detection means detects that the fixing belt has slipped when a temperature difference between a first temperature detected by the first temperature sensor and a second temperature detected by the second temperature sensor after a predetermined time has elapsed since the first temperature was detected exceeds a predetermined value;
The fixing device described in Appendix 1, characterized in that the second slip detection means detects that the fixing belt has slipped when a temperature difference between a second temperature detected by the second temperature sensor at that time and a second temperature detected by the second temperature sensor when a slip is detected by the first slip detection means does not exceed a predetermined value.
(Appendix 3)
When slippage is detected by the second slip detection means and the number of times that the operation of returning the pressurizing rotator to a separated state after being brought into contact with the pressurizing rotator exceeds a predetermined number of times, a printing operation scheduled to be performed after the control mode is stopped,
The fixing device described in Appendix 1 or Appendix 2, characterized in that, when the number of interruptions reaches a predetermined number, a display is displayed prompting the user to perform maintenance on the fixing device, and, when the number of interruptions has not reached the predetermined number, the control mode is executed again after the main power supply of the image forming apparatus body in which the fixing device is installed is turned off and on.
(Appendix 4)
4. The fixing device according to claim 3, wherein the predetermined number and the number of interruptions are reset when the first slip detection means or the second slip detection means no longer detects slippage of the fixing belt.
(Appendix 5)
5. The fixing device according to claim 1, wherein the first temperature sensor and the second temperature sensor are disposed at the same position in a width direction.
(Appendix 6)
a heating roller having a heater disposed therein as the heating means and contacting the inner peripheral surface of the fixing belt;
6. The fixing device according to claim 1, wherein the first temperature sensor is disposed at a position facing the heating roller with the fixing belt interposed therebetween.
(Appendix 7)
7. An image forming apparatus comprising the fixing device according to claim 1.

Patent No. 5418913

Claims (7)

a fixing belt that is heated by a heating means and that heats and fixes a toner image on a sheet while traveling in a predetermined traveling direction;
a nip forming member that is in sliding contact with an inner peripheral surface of the fixing belt;
a pressure rotating member that forms a fixing nip through which a sheet is conveyed by being pressed against the nip forming member via the fixing belt;
a contact/separation mechanism for relatively contacting and separating the pressure rotating body with respect to the fixing belt;
Equipped with
a control mode in which the fixing belt is caused to run while being heated by the heating means in a state in which the contact/separation mechanism separates the pressure rotator from the fixing belt, is started at a predetermined timing;
The control mode is
when slippage of the fixing belt is detected for the first time by the first slip detection means after the start of the operation, the pressure rotating body, which has been in a separated state by the contact/separation mechanism, is brought into contact with the fixing belt for a predetermined period of time, and then the pressure rotating body is brought into the separated state again;
Thereafter, when slippage of the fixing belt is not detected by the second slip detection means, the control mode is terminated, and when slippage of the fixing belt is detected by the second slip detection means, the fixing device repeats the operation of bringing the pressure rotating body, which was in a separated state, into a contact state for the predetermined time and then returning it to the separated state. a first temperature sensor that detects a surface temperature of the fixing belt;
a second temperature sensor that detects a surface temperature of the fixing belt downstream of the first temperature sensor in the traveling direction and upstream of the fixing nip in the traveling direction;
Equipped with
the first slip detection means detects that the fixing belt has slipped when a temperature difference between a first temperature detected by the first temperature sensor and a second temperature detected by the second temperature sensor after a predetermined time has elapsed since the first temperature was detected exceeds a predetermined value;
2. The fixing device according to claim 1, wherein the second slip detection means detects that the fixing belt has slipped when a temperature difference between a second temperature detected by the second temperature sensor at that time and a second temperature detected by the second temperature sensor when a slip is detected by the first slip detection means does not exceed a predetermined value. When slippage is detected by the second slip detection means and the number of times that the operation of returning the pressurizing rotator to a separated state after being brought into contact with the pressurizing rotator exceeds a predetermined number of times, a printing operation scheduled to be performed after the control mode is stopped,
The fixing device according to claim 1 or claim 2, characterized in that, when the number of interruptions reaches a predetermined number, a display is displayed prompting the user to perform maintenance on the fixing device, and, when the number of interruptions has not reached the predetermined number, the control mode is executed again after turning off and on a main power supply of an image forming apparatus body in which the fixing device is installed. The fixing device according to claim 3, characterized in that the predetermined number of times and the number of times of interruption are reset when slippage of the fixing belt is no longer detected by the first slip detection means or the second slip detection means. The fixing device according to claim 1 or 2, characterized in that the first temperature sensor and the second temperature sensor are installed at the same position in the width direction. a heating roller having a heater disposed therein as the heating means and contacting the inner circumferential surface of the fixing belt;
3. The fixing device according to claim 1, wherein the first temperature sensor is disposed at a position facing the heating roller across the fixing belt. An image forming apparatus comprising the fixing device according to claim 1 or 2.

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