JP2022151529A - Fixing device and image forming apparatus - Google Patents

Abstract

To prevent wear of an inner surface of a fixing belt and a slide part over time.SOLUTION: A fixing device of the present invention comprises: a sleeve-like rotating member (fixing belt 310) that has flexibility; a slide member (resistance member 370) that slides with an inner surface of the rotating member; a pressure member (pressure roller 320) that is in pressure contact with a portion facing the slide member with the rotating member therebetween to form a nip part between the rotating member and the pressure member; and lubricant between the rotating member and the slide member. The consistency of the lubricant is set to 340 or less and the elastic power of a slide surface of the rotating member is set to 58% or more, or the consistency of the lubricant is set to 275 or less and the elastic power of the slide surface of the rotating member is set to 55% or more. The surface roughness in a slide direction of the slide surface of the rotating member is made larger than the surface roughness in the slide direction of a slide surface of the slide member.SELECTED DRAWING: Figure 7

Description

The present invention relates to a fixing device and an image forming apparatus, and more particularly to a fixing device and an image forming apparatus that improve the slidability of a fixing belt and suppress the generation of abnormal noise due to sliding.

Various types of fixing devices are known for use in electrophotographic image forming apparatuses. One of them is a sliding fixing method in which a thin fixing belt with a low heat capacity is heated by a heater member (see Patent Documents 1 and 2). A halogen lamp or a planar heater is used as the heater member. A fixing nip is formed by sandwiching the fixing belt between a pressure roller as a pressure member outside the fixing belt and a sliding portion that is in sliding contact with the inner peripheral surface of the fixing belt.

In the conventional sliding fixing method, a lubricant is applied to the sliding portion in order to suppress abrasion of the inner surface of the belt that is in sliding contact with the sliding portion and the planar heater. Japanese Patent Application Laid-Open No. 2002-200010, the surface roughness of the inner surface of the fixing belt in the sliding direction is made larger than the surface roughness of the sliding portion.

However, it has been found that it is difficult to maintain the inner surface roughness of the rotating fixing belt as in Patent Document 3 over time, and that the inner surface roughness of the fixing belt smoothes out due to wear over time. When the inner surface of the fixing belt is smoothed, the wear of the inner surface of the belt (sliding layer such as polyimide or PTFE) increases (surface deterioration), which causes abnormal noise due to stick-slip. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress wear of rotating members and sliding portions over time.

In order to solve the above-described problems, the fixing device of the present invention includes a flexible sleeve-shaped rotating member, a sliding member that slides on the inner circumference of the rotating member, and a sliding member that sandwiches the rotating member. A fixing device comprising: a pressure member that presses against a portion facing a member to form a nip portion with the rotating member; and a lubricant between the rotating member and the sliding member, wherein the lubricant is The consistency is 340 or less, the elastic power of the sliding surface of the rotating member is 58% or more, or the consistency of the lubricant is 275 or less, the elastic power of the sliding surface of the rotating member is 55% or more, and The surface roughness of the sliding surface of the rotating member in the sliding direction is made larger than the surface roughness of the sliding surface of the sliding member in the sliding direction.

ADVANTAGE OF THE INVENTION According to this invention, the abrasion of a rotating member and a sliding part can be suppressed over time.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 1 is a principle diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 1 is a cross-sectional view of a first fixing device according to an embodiment of the invention; FIG. FIG. 4 is a cross-sectional view of a second fixing device according to an embodiment of the invention; FIG. 5 is a cross-sectional view of a third fixing device according to an embodiment of the invention; FIG. 5 is a cross-sectional view of a fourth fixing device according to an embodiment of the invention; FIG. 4A is a plan view and a cross-sectional view (b) of a single resistance heating element having an electrode at one end; It is a plan view (a) and a cross-sectional view (b) of a dual resistance heating element having electrodes at both ends. 1 is a plan view of a multi-resistive heating element having electrodes at both ends; FIG. FIG. 3 shows a heating device, a power supply circuit and a controller; (a) to (d) are diagrams for explaining a method of measuring elastic power. FIG. 4 is a load-displacement diagram for explaining the difference between elastic power and return rate. FIG. 5 is a diagram showing inner surface wear ranks of a fixing belt according to elastic power. FIG. 4 is a diagram showing the correlation between elastic work rate and film thickness reduction; FIG. 5 is a diagram showing how a lubricant is held depending on the difference in surface roughness between a fixing belt and a heater; It is a figure explaining arithmetic mean roughness. FIG. 4 is a diagram showing a load curve; FIG. 4 is a diagram showing a load curve representing a solid portion and a space portion; It is a figure which shows height distribution by bias degree (skewness) Ssk, and shows height distribution when (a) Ssk>0 and (b) Ssk<0. It is a figure which shows the height distribution by the kurtosis (kurtosis) Sku, and shows the height distribution when (a) Sku>3 and (b) Sku<3. It is a figure which shows the relationship between an elastic work rate and a coefficient of friction. FIG. 5 is a diagram showing the relationship between elastic power and the occurrence of abnormal noise/vibration; It is a figure which shows the relationship between an elastic work rate and the difference of a friction coefficient. 1 is a schematic configuration diagram of an image forming apparatus of a different model; FIG. 3A and 3B are diagrams illustrating configurations of fixing devices of different types; FIG. 3 is a plan view of a heater member of the fixing device; FIG. It is an exploded perspective view of a heater member and a holder. 3 is an exploded perspective view of a heater member, terminals, guides, and stays; FIG. It is a figure which shows arrangement|positioning of a thermistor. It is explanatory drawing of the groove|channel of a guide.

Hereinafter, a heating device according to an embodiment of the present invention, and a fixing device and an image forming apparatus (laser printer) using the heating device will be described with reference to the drawings. In addition, the "heating device" in the present invention means a device for heating a sheet member with a heating element. Further, the term "fixing device" means that a sheet member is conveyed in a direction orthogonal to the longitudinal direction to a nip portion formed between a heating device and a pressurizing member, and unfixed toner on the sheet member is removed. means a device for fixing on. Further, the term "image forming apparatus" means an apparatus that includes a fixing device and forms an image by attaching a developer or ink to a sheet member, which is a recording medium for recording an image.

A laser printer is an example of an image forming apparatus, and the image forming apparatus is not limited to a laser printer. That is, the image forming apparatus can be configured as a copier, a facsimile machine, a printer, a printing machine, or an inkjet recording apparatus, or a multifunction machine combining at least two of these.

The same or corresponding parts in each figure are denoted by the same reference numerals, and redundant description thereof will be appropriately simplified or omitted. Also, the dimensions, materials, shapes, relative positions, and the like in the description of each component are examples, and are not intended to limit the scope of the present invention unless otherwise specified.

In the following embodiments, the "recording medium", which is the sheet member of the present invention, will be described as "paper", but the "recording medium" is not limited to paper. The "recording medium" includes not only paper but also OHP sheets, fabrics, metal sheets, plastic films, or prepreg sheets in which carbon fibers are previously impregnated with resin.

The term "recording medium" also includes media to which developer and ink can be applied, recording paper, and recording sheets. In addition to plain paper, "paper" includes thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like.

In addition, the term "image formation" used in the following description refers not only to imparting meaningful images, such as characters and figures, to a medium, but also to imparting meaningless images, such as patterns, to a medium. also means

(Configuration of laser printer)
FIG. 1A is a configuration diagram schematically showing the configuration of a color laser printer as an embodiment of an image forming apparatus 100 equipped with a heating device or fixing device 300 of the present invention. FIG. 1B also shows a simplified illustration of the principle of the color laser printer.

The image forming apparatus 100 includes four process units 1K, 1Y, 1M and 1C as image forming means. These process units form images with developers of respective colors of black (K), yellow (Y), magenta (M), and cyan (C) corresponding to color separation components of a color image.

Each of the process units 1K, 1Y, 1M and 1C has the same configuration except that they have toner bottles 6K, 6Y, 6M and 6C containing unused toner of different colors. Therefore, the configuration of one process unit 1K will be described below, and the description of the other process units 1Y, 1M, and 1C will be omitted.

The process unit 1K has an image carrier 2K (for example, a photosensitive drum), a drum cleaning device 3K, and a neutralizer. The process unit 1K further includes a charging device 4K as charging means for uniformly charging the surface of the image carrier, and a developing device as developing means for performing visible image processing on the electrostatic latent image formed on the image carrier. It has 5K and so on. The process unit 1K is detachably attached to the main body of the image forming apparatus 100, and consumable parts can be replaced at the same time.

The exposure device 7 is arranged above each of the process units 1K, 1Y, 1M, and 1C installed in this image forming apparatus 100 . The exposure unit 7 is configured to perform write scanning according to image information, that is, to irradiate the image carrier 2K with laser light LB from a laser diode, which is reflected by a mirror 7a based on image data.

The transfer device 15 is arranged below each of the process units 1K, 1Y, 1M and 1C in this embodiment. This transfer device 15 corresponds to the transfer means TM of FIG. 1B. The primary transfer rollers 19K, 19Y, 19M and 19C are arranged in contact with the intermediate transfer belt 16 so as to face the respective image carriers 2K, 2Y, 2M and 2C.

The intermediate transfer belt 16 circulates while being stretched over primary transfer rollers 19K, 19Y, 19M, 19C, a driving roller 18, and a driven roller 17. As shown in FIG. The secondary transfer roller 20 is arranged in contact with the intermediate transfer belt 16 so as to face the drive roller 18 . If the image carriers 2K, 2Y, 2M, and 2C are the first image carriers of each color, the intermediate transfer belt 16 is the second image carrier that synthesizes those images.

The belt cleaning device 21 is installed downstream of the secondary transfer roller 20 in the running direction of the intermediate transfer belt 16 . A cleaning backup roller is installed on the opposite side of the intermediate transfer belt 16 to the belt cleaning device 21 .

A sheet feeding device 200 having a tray for stacking sheets P is installed below the image forming apparatus 100 . The paper feeder 200 constitutes a recording medium supply section, and can accommodate a large number of sheets P as a recording medium in a bundle. unitized with.

The paper feeding device 200 is detachable from the main body of the image forming apparatus 100 in order to replenish paper and the like. The paper feed roller 60 and the roller pair 210 are arranged above the paper feeder 200 so as to convey the uppermost paper P of the paper feeder 200 toward the paper feed path 32 .

A pair of registration rollers 250 as a separating and conveying unit is arranged immediately upstream in the conveying direction of the secondary transfer roller 20 and can temporarily stop the paper P fed from the paper feeding device 200 . Due to this temporary stop, slack is formed on the leading end side of the paper P, and the skew of the paper P is corrected.

A registration sensor RS is disposed immediately upstream of the registration roller pair 250 in the conveying direction, and the passage of the leading edge of the sheet is detected by this registration sensor RS. After the registration sensor RS detects the passage of the leading edge of the paper, the paper hits the pair of registration rollers 250 and temporarily stops when a predetermined time elapses.

At the downstream end of the paper feeder 200, a transport roller 240 is arranged for upwardly transporting the paper transported from the roller pair 210 to the right side. As shown in FIG. 1A, the transport rollers 240 transport the paper upward toward the pair of registration rollers 250 .

The roller pair 210 is composed of a pair of upper and lower rollers. The roller pair 210 can be of the FRR separation type or the FR separation type.

In the FRR separation method, a separation roller (return roller) to which a constant amount of torque is applied in the direction opposite to the paper feed direction by a drive shaft via a torque limiter is brought into pressure contact with the feed roller to separate the paper at the nip between the rollers. In the FR separation method, a separation roller (friction roller) supported by a fixed shaft via a torque limiter is brought into pressure contact with a feed roller to separate the paper at the nip between the rollers.

In this embodiment, the roller pair 210 is constructed by the FRR separation method. That is, the roller pair 210 consists of an upper feed roller 220 that conveys the paper into the machine and a lower separation roller 230 that is driven by a drive shaft through a torque limiter in the direction opposite to the feed roller 220. consists of

The separating roller 230 is biased toward the feeding roller 220 by biasing means such as a spring. The feeding roller 60 rotates to the left in FIG. 1A by transmitting the driving force of the feeding roller 220 through the clutch means.

The paper P, which has been bumped against the pair of registration rollers 250 and has slack at its leading edge, is transferred to the secondary transfer roller 20 and the drive roller in time with the timing at which the toner image formed on the intermediate transfer belt 16 is suitably transferred. 18 (transfer nip N in FIG. 1B). Then, the toner image formed on the intermediate transfer belt 16 is electrostatically transferred to the desired transfer position with high precision by the bias applied at the secondary transfer nip. ing.

The post-transfer conveying path 33 is arranged above the secondary transfer nip between the secondary transfer roller 20 and the drive roller 18 . The fixing device 300 is installed near the upper end of the post-transfer conveying path 33 .

The fixing device 300 includes a fixing belt 310 as a rotating member containing a heating device, and a pressure roller 320 as a pressure member rotating while contacting the fixing belt 310 with a predetermined pressure. The fixing device 300 can be of various types as shown in FIGS. 2A to 2D, which will be described later, but the type shown in FIG. 2A will be described here.

The post-fixing transport path 35 is disposed above the fixing device 300 , and branches into a paper discharge path 36 and a reversing transport path 41 at the upper end of the post-fixing transport path 35 . A switching member 42 is arranged at this branched portion, and the switching member 42 swings around a swing shaft 42a. A paper discharge roller pair 37 is arranged near the opening end of the paper discharge path 36 .

The reverse transport path 41 joins the paper feed path 32 at the other end opposite to the branched portion. A reverse conveying roller pair 43 is arranged in the middle of the reverse conveying path 41 . The discharge tray 44 is installed on the upper portion of the image forming apparatus 100 so as to form a concave shape toward the inside of the image forming apparatus 100 .

A powder container 10 (for example, a toner container) is arranged between the transfer device 15 and the paper feeding device 200 . The powder container 10 is detachably attached to the main body of the image forming apparatus 100 .

The image forming apparatus 100 of the present embodiment requires a predetermined distance from the paper feed roller 60 to the secondary transfer roller 20 due to transfer paper transport. Then, the powder container 10 is installed in the dead space generated at this distance to reduce the size of the laser printer as a whole.

The transfer cover 8 is installed above the paper feeding device 200 and in front of the paper feeding device 200 in the pull-out direction. By opening the transfer cover 8, the inside of the image forming apparatus 100 can be inspected. The transfer cover 8 is provided with a manual paper feeding roller 45 for manual paper feeding and a manual paper feeding tray 46 for manual paper feeding.

(Operation of laser printer)
Next, the basic operation of the laser printer according to this embodiment will be described below with reference to FIG. 1A. First, the case of single-sided printing will be described.

The paper feed roller 60 is rotated by a paper feed signal from the control section of the image forming apparatus 100, as shown in FIG. 1A. Then, the paper feed roller 60 separates only the uppermost paper sheet from the stack of paper sheets P stacked on the paper feeder 200 and feeds it to the paper feed path 32 .

When the leading edge of the paper P sent out by the paper feed roller 60 and the roller pair 210 reaches the nip of the registration roller pair 250, it becomes slack and waits in that state. Then, the optimum timing (synchronization) for transferring the toner image formed on the intermediate transfer belt 16 to the paper P is obtained, and the tip skew of the paper P is corrected.

In the case of manual paper feeding, the stack of paper stacked on the manual feed tray 46 passes through a part of the reversing conveyance path 41 one by one from the uppermost paper by the manual paper feed roller 45 and is nipped by the registration roller pair 250 . transported to. The subsequent operations are the same as those for paper feeding from the paper feeding device 200 .

Here, as for the image forming operation, one process unit 1K will be described, and the description of the other process units 1Y, 1M, and 1C will be omitted. First, the charging device 4K uniformly charges the surface of the image carrier 2K to a high potential. Then, the exposing device 7 irradiates the surface of the image carrier 2K with the laser beam LB based on the image data.

On the surface of the image carrier 2K irradiated with the laser beam LB, the potential of the irradiated portion is lowered to form an electrostatic latent image. The developing device 5K has a developer carrier that carries a developer containing toner, and the unused black toner supplied from the toner bottle 6K is passed through the developer carrier to form an electrostatic latent image. is transferred to the surface portion of the image carrier 2K.

The image carrier 2K to which the toner has been transferred forms (develops) a black toner image on its surface. Then, the toner image formed on the image carrier 2K is transferred to the intermediate transfer belt 16. FIG.

The drum cleaning device 3K removes residual toner adhering to the surface of the image carrier 2K after the intermediate transfer process. The removed residual toner is transported to and collected by the waste toner conveying means to the waste toner storage section in the process unit 1K. Further, the static elimination device eliminates residual charges on the image carrier 2K from which the residual toner has been removed by the cleaning device 3K.

In the process units 1Y, 1M, and 1C of each color, toner images are similarly formed on the image carriers 2Y, 2M, and 2C, and transferred to the intermediate transfer belt 16 so that the toner images of each color are superimposed.

The intermediate transfer belt 16 onto which the toner images of the respective colors are transferred so as to overlap each other travels to the secondary transfer nip between the secondary transfer roller 20 and the driving roller 18 . On the other hand, the pair of registration rollers 250 sandwiches the sheet of paper that abuts against them and rotates at a predetermined timing. The sheet is conveyed to the secondary transfer nip of the secondary transfer roller 20 . In this manner, the toner image on the intermediate transfer belt 16 is transferred onto the paper P sent out by the registration roller pair 250 .

The paper P onto which the toner image has been transferred is transported to the fixing device 300 through the post-transfer transport path 33 . Then, the sheet P conveyed to the fixing device 300 is sandwiched between the fixing belt 310 and the pressure roller 320, and the unfixed toner image is fixed on the sheet P by applying heat and pressure. The paper P on which the toner image is fixed is sent from the fixing device 300 to the transport path 35 after fixing.

The switching member 42 is in a position where the vicinity of the upper end of the post-fixing transport path 35 is open as indicated by the solid line in FIG. 1A at the timing when the paper P is sent out from the fixing device 300 . Then, the sheet P sent out from the fixing device 300 is sent out to the discharge path 36 via the post-fixing transport path 35 . The paper discharge roller pair 37 pinches the paper P sent to the paper discharge path 36 and discharges it to the paper discharge tray 44 by being rotationally driven, thereby completing single-sided printing.

Next, the case of double-sided printing will be described. As in the case of single-sided printing, the fixing device 300 feeds the paper P to the paper discharge path 36 . When double-sided printing is performed, the pair of paper discharge rollers 37 conveys a portion of the paper P to the outside of the image forming apparatus 100 by rotational driving.

When the trailing edge of the paper P passes through the paper discharge path 36, the switching member 42 swings around the swing shaft 42a as indicated by the dotted line in FIG. do. Almost at the same time as the upper end of the post-fixing transport path 35 is closed, the paper discharge roller pair 37 rotates in a direction opposite to the direction in which the paper P is transported out of the image forming apparatus 100 , and sends the paper P to the reverse transport path 41 . .

The sheet P sent out to the reverse transport path 41 reaches the registration roller pair 250 via the reverse transport roller pair 43 . Then, the registration roller pair 250 finds the optimum timing (synchronization) for transferring the toner image formed on the intermediate transfer belt 16 to the toner image untransferred surface of the paper P, and feeds the paper P to the secondary transfer nip.

Then, the secondary transfer roller 20 and the drive roller 18 transfer the toner image to the toner image untransferred surface (back surface) of the paper P when the paper P passes through the secondary transfer nip. Then, the paper P onto which the toner image has been transferred is transported to the fixing device 300 through the post-transfer transport path 33 .

The fixing device 300 fixes the unfixed toner image on the back surface of the paper P by sandwiching the conveyed paper P between the fixing belt 310 and the pressure roller 320 and applying heat and pressure. In this way, the paper P having the toner images fixed on both sides thereof is fed from the fixing device 300 to the transport path 35 after fixing.

The switching member 42 is in a position where the vicinity of the upper end of the post-fixing transport path 35 is open as indicated by the solid line in FIG. 1A at the timing when the paper P is sent out from the fixing device 300 . Then, the paper P delivered from the fixing device 300 is delivered to the paper discharge path 36 via the fixing transportation path. The paper discharge roller pair 37 pinches the paper P sent to the paper discharge path 36, rotates, and discharges the paper P to the paper discharge tray 44, thereby completing double-sided printing.

After the toner image on the intermediate transfer belt 16 is transferred to the paper P, residual toner remains on the intermediate transfer belt 16 . A belt cleaning device 21 removes this residual toner from the intermediate transfer belt 16 . Further, the toner removed from the intermediate transfer belt 16 is conveyed to the powder container 10 by the waste toner conveying means and collected in the powder container 10 .

(● Fixing device)
Next, the heating device and the first to fourth fixing devices 300 according to the embodiment of the invention will be further described below. The heating device of this embodiment is for heating the fixing belt 310 of the fixing device 300 .

As shown in FIG. 2A, the first fixing device is composed of a thin fixing belt 310 with a low heat capacity and a pressure roller 320 . The fixing belt 310 has, for example, a cylindrical substrate whose main component is polyimide (PI) and has an outer diameter of 25 mm and a thickness of 40 to 120 μm. By using polyimide as the main component, it is possible to secure a high elastic work rate (eg, about 20 to 40% in the case of PAI). In addition, by using polyimide, the inner surface coating may be omitted if the base material is a PI system, and if the base material is other than PI, a PI-based paint may be applied.

As the outermost layer of the fixing belt 310, a release layer having a thickness of 5 to 50 μm is formed of a fluorine-based resin such as PFA or PTFE in order to increase durability and ensure release properties. An elastic layer made of rubber or the like having a thickness of 50 to 500 μm may be provided between the substrate and the release layer.

Alternatively, only the adhesive layer may be interposed between the substrate and the release layer without interposing the elastic layer. Since the polyimide substrate is highly flexible, the belt conforms well to the shape of the nip entrance, and capillary action facilitates the supply of grease to the belt.

Further, when the belt surface temperature is the same, the temperature of the inner surface of the belt, that is, the sliding surface must be increased due to the heat insulating effect of the elastic layer. Without the elastic layer, the heat conductivity from the inner surface to the outer surface of the belt is improved, so that the heater setting temperature can be lowered, which is advantageous against evaporation of the lubricant, and the life of the belt can be extended. Incidentally, Patent Document 5 (Japanese Patent No. 6061606) proposes a fixing device in which wear resistance is improved by using polyimide for the inner peripheral surface of the belt and by adjusting the loss elastic modulus of the polyimide. , sufficient wear resistance is not obtained.

Further, the substrate of the fixing belt 310 is not limited to polyimide, and may be a heat-resistant resin such as PEEK, or a metal substrate such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 310 may be coated with polyimide, PTFE, or the like as a sliding layer.

The pressure roller 320 has an outer diameter of 25 mm, for example, and includes a solid iron core 321, an elastic layer 322 formed on the surface of the core 321, and a release layer formed on the outer side of the elastic layer 322. 323. The elastic layer 322 is made of silicone rubber and has a thickness of 3.5 mm, for example.

In order to improve the releasability of the elastic layer 322, it is desirable to form a releasing layer 323 of a fluorine resin layer having a thickness of about 40 μm, for example. A pressure roller 320 is pressed against the fixing belt 310 by an urging means.

A roll-shaped heat soaking member 389 is arranged around the outer periphery of the fixing belt 310 so as to be rotatable and separable from the outer peripheral surface of the fixing belt 310 . The heat equalizing member 389 eliminates temperature unevenness in the axial direction of the fixing belt 310, and is made of a material such as aluminum or copper having high thermal conductivity in the axial direction.

If the surface of the heat equalizing member 389 is covered with a highly releasable material such as PTFE or PFA, toner fixation can be suppressed. Note that the heat soaking member 389 can also be arranged on the outer circumference of the pressure roller 320 .

The heat soaking member 389 may be configured to be driven to rotate by contact with the fixing belt 310, or may be rotated by a drive source. The soaking member 389 is brought into contact with the outer peripheral surface of the fixing belt 310 in the process of reducing the difference temperature (hereinafter referred to as the temperature difference reduction process), which will be described later, and the temperature unevenness of the fixing belt 310 is heat-transferred in the axial direction by the soaking member 389 . By doing so, difference temperature reduction processing is performed.

Since the heat soaking member 389 has a driving source, it is possible to provide a peripheral speed difference between the heat equalizing member 389 and the fixing belt 310 , and it is possible to impart a function of smoothing the surface properties of the fixing belt 310 . As a result, it is possible to reduce "paper edge damage" that occurs on the surface of the image due to wear of the fixing belt 310 at the paper edge. Therefore, it is desirable that the soaking member 389 is larger than the maximum sheet width and larger than the heating width of the resistance member 370, which is the heat source (heat soaking member 389 width>resistance member 370 width>maximum sheet width).

The temperature difference reduction process of the present invention includes all processes for reducing temperature unevenness in the longitudinal direction of the heating element 330 (fixing belt 310), and specifically includes the following processes.
(1) When the differential temperature detected by two thermistors in the longitudinal direction of the heating element 330 exceeds the permissible range, the paper conveyance is temporarily stopped.
(2) When the difference temperature exceeds the allowable range, the sheet conveying speed is temporarily reduced.
(3) When the differential temperature exceeds the allowable range, the heat soaking member 389 is temporarily brought into contact with the fixing belt 310 or the pressure roller 320 .

The allowable range can be freely set, for example, in the range of 5°C to 15°C. Depending on the degree of deviation from the allowable range, it is possible to increase or decrease the time during which the paper conveyance is temporarily stopped, the time during which the paper conveyance speed is temporarily reduced, or the time during which the heat soaking member 389 is temporarily contacted. can. Also, the rate at which the paper transport speed is reduced can be increased or decreased according to the degree of deviation from the allowable range.

If the heat soaking member 389 is always in contact with the fixing belt 310 or the pressure roller 320, the heat capacity will increase and the quick start-up will be impaired. Therefore, a contact/separation mechanism (not shown) is provided to detect the increase in temperature of the non-sheet-passing portion, and rotate the heat equalizing member 389 in contact with the fixing belt 310 or the pressure roller 320 when it is determined that heat equalization is necessary. It is desirable to control

In particular, as a feature of the heater, when the width of the resistance member 370 > the maximum paper width is configured to suppress the temperature drop at the edges at the time of start-up, even if the maximum paper size is used, the edges may Excessive temperature rise in a part of the paper tends to become apparent, and the temperature around the edge of the paper also rises excessively due to the influence of the excessively heated end, and gloss unevenness tends to become apparent. For this reason, in the single heater configuration, it is also effective to satisfy the width of the resistance member 370>maximum sheet width, and to dispose a monitoring thermistor TH2, which will be described later, outside the maximum sheet size to detect excessive temperature rise.

Regarding the placement of the monitoring thermistor TH2 in the cross-sectional direction, it is preferable to place the thermistor on the surface of the fixing belt 310 that contacts the transparent toner in terms of temperature detection. may be used to estimate overheating. Moreover, even if it is arranged on the surface of the pressure roller 320, the excessive temperature rise can be detected.

In particular, when a thermistor is arranged on the surface of pressure roller 320, an inexpensive sensor with lower heat resistance can be used. The control sensor may also be arranged behind the heater, or may be arranged on the surface of the fixing belt 310 or inside the fixing belt 310 .

A stay 350 and a heater holder 340 are arranged inside the fixing belt 310 in the axial direction. The stay 350 is made of a metal channel material, and both end portions thereof are supported by both side plates of the heating device. The stay 350 reliably receives the pressing force of the pressure roller 320 and stably forms the fixing nip SN as a nip portion.

A paper sheet P as a sheet member is conveyed to the fixing nip SN in a direction orthogonal to the longitudinal direction of the fixing belt 310 or the heating element 330 (or the longitudinal direction of the pressure roller 320). Here, the "perpendicular direction" does not have to form an angle of exactly 90° with the longitudinal direction. An angle of about 90° with respect to the longitudinal direction is also included in the "perpendicular direction". Here, the angle of about 90° is preferably 80° to 100°, more preferably 85° to 95°.

The heater holder 340 is for holding the base material 341 of the heating device and is supported by the stay 350 . The heater holder 340 is preferably made of a heat-resistant resin with low thermal conductivity, such as LCP, which reduces heat transfer to the heater holder 340 so that the fixing belt 310 can be efficiently heated.

The shape of the heater holder 340 is such that the heater holder 340 supports only two portions near both ends in the widthwise direction of the substrate 341 in order to avoid contact with the high-temperature portion of the substrate 341 . As a result, the amount of heat flowing to heater holder 340 can be further reduced, and fixing belt 310 can be efficiently heated.

The heating device has a resistance member 370 as a sliding member made of a resistance heating element. The resistance member 370 can be formed in multiple types as shown in FIGS. 3A-3C.

In either type, resistive member 370 is formed on substrate 341, which is an elongated sheet metal member coated with an insulating material. By directly heating the nip portion with the resistance member 370, the viscosity of the lubricant in the nip portion can be lowered to reduce oil film breakage and suppress wear.

Low-cost aluminum, stainless steel, or the like is preferable as the material of the base material 341 . The base material 341 is not limited to being made of metal, and can be made of ceramics such as alumina and aluminum nitride, or non-metallic materials such as glass and mica that are excellent in heat resistance and insulation.

In order to improve the heat uniformity of the heating device and improve the image quality, the substrate 341 may be made of a material with high thermal conductivity such as copper, graphite, or graphene. In this embodiment, an alumina substrate having a short width of 8 mm, a long width of 270 mm, and a thickness of 1.0 mm is used.

( ● Single type resistance material)
FIG. 3A shows a single-type resistance member 370 , and the resistance members 370 are formed in parallel two rows in the longitudinal direction of the substrate 341 in series. A positioning hole 330 a for positioning the base material 341 is formed on one end side of the base material 341 . One ends of the two rows of resistance members 370 are connected to power supply electrodes 370c and 370d through power supply lines 379a and 379c with small resistance values formed in the longitudinal direction on one end side of the base material 341, respectively. The electrodes 370c, 370d are connected to power supply means including an AC power supply 410 as shown in FIG.

The other end of the resistance member 370 is connected by folding back toward the opposite side of the base material 341 in the longitudinal direction via a feeder line 379b having a small resistance value formed in the short direction on the other end side of the base material 341. be done. The resistance member 370, the electrodes 370c and 370d, and the feeder lines 379a to 379c are formed with a predetermined line width and thickness by screen printing.

The material of the resistance member 370 can be formed by applying a paste prepared by mixing silver (Ag), silver palladium (AgPd), glass powder, or the like by screen printing or the like, and then firing the paste. The resistance value of the resistance member 370 can be set to 10Ω at room temperature, for example. The resistance material of the resistance member 370 may also be silver alloy (AgPt), ruthenium oxide (RuO2), or the like.

A thin overcoat layer or insulating layer 385 covers the surface of the resistive member 370 and the feeder lines 379a-379c. The insulating layer 385 ensures the slidability of the fixing belt 310, and also ensures the insulation between the fixing belt 310, the resistance member 370, and the power supply lines 379a to 379c. Therefore, the insulating layer 385 constitutes a part of the sliding member. By using a heat-resistant glass for the insulating layer 385, the lubricant of the fixing belt 310 does not impregnate the resistance member 370 as a sliding member, so it is possible to suppress oil film breakage on the nip surface.

As a material of the insulating layer 385, heat-resistant glass having a thickness of 75 μm, for example, can be used. The resistance member 370 heats the fixing belt 310 in contact with the insulating layer 385 side by heat transfer to increase the temperature thereof, and heats and fixes an unfixed image on the paper P conveyed to the fixing nip SN.

A thermistor TH1 as a first temperature detecting member is arranged within the range of the minimum sheet passing width. The thermistor TH1 can accurately detect the temperature of the fixing belt 310 in the area in contact with any size of paper. The temperature of the resistance member 370 is controlled based on the temperature T1 of the resistance member 370 or base material 341 detected by the thermistor TH1.

A monitoring thermistor TH2 serving as a second temperature detecting member is arranged near the edge of the smallest sheet out of the range of the smallest sheet and having a length (width) greater than the resistance member 370 . The thermistor TH2 has a function of monitoring temperature unevenness of the resistance member 370 or the fixing belt 310. FIG.

Then, based on the difference temperature (=T1-T2) between the temperature T1 detected by the thermistor TH1 and the temperature T2 of the central resistance member 370-1 or base material 341 detected by the thermistor TH2, the resistance A differential temperature reduction process is performed to uniformly heat the member 370 in the longitudinal direction. Further, the thermistor TH2 can detect an excessive temperature rise in the non-sheet passing portion. Thermistors TH1 and TH2 can be contact type thermistors with a thermal time constant of less than 1 second, and are arranged in a form of being pressed against the back side of substrate 341 by springs 387, as shown in FIGS. 2A-2D. be.

(Dual type resistance member)
FIG. 3B shows a dual-type resistance member consisting of a central resistance member 370-1 in the center in the longitudinal direction and a pair of left and right end resistance members 370-2 arranged on both sides of this central resistance member 370-1. It is configured. The opposing ends of the central resistance member 370-1 and the end resistance members 370-2 are formed to be inclined with respect to the widthwise direction of the substrate 341 (parallelogram). This inclination reduces the gap between the central resistance member 370-1 and the end resistance members 370-2 when viewed from the lateral direction of the base material 341, thereby reducing the temperature drop between them. .

Note that the central resistance member 370-1 is 215 mm for A4 paper, and the end resistance members 370-2 are 301 mm for A3 paper. By doing so, the A4 paper and the A3 paper can be prevented from overheating, and the productivity can be improved.

One end of the central resistance member 370-1 is connected to the left electrode 370e via a feed line 379d, and the other end is connected to the right electrode 370h via a feed line 379f. One end of the left end resistance member 370-2 is connected to the left electrode 370e through the feed line 379d, and the other end is connected to the left electrode 370f through the feed line 379e. One end of the right end resistance member 370-2 is connected to the left electrode 370e via a feed line 379d, and the other end is connected to the right electrode 370g via a feed line 379h.

The central resistance member 370-1 and the end resistance members 370-2 can generate heat independently, and when voltage is applied to the electrodes 370e and 370h, the central resistance member 370-1 generates heat. Similarly, when a voltage is applied to the electrodes 370e and 370f, the left end resistance member 370-2 generates heat, and when a voltage is applied to the electrodes 370e and 370g, the right end resistance member 370-2 generates heat.

By connecting the electrodes 370f and 370g in parallel outside, the left and right end resistance members 370-2 can be heated simultaneously. If the paper is center-based, the temperature becomes bilaterally symmetrical. Therefore, the thermistor is not provided for both ends of the end resistance member 370-2, but only for one side, so that the cost can be reduced.

The center resistance member 370-1 and the end resistance members 370-2 are covered with a thin insulating layer 385 similar to the series resistance members 370 (FIG. 3A) previously described. This insulating layer 385 can be made of, for example, heat-resistant glass with a thickness of 75 μm. The insulating layer 385 insulates and protects the central resistance member 370 - 1 , the end resistance members 370 - 2 and the power supply lines 379 d , 379 e , 379 f and 379 h and maintains the slidability with the fixing belt 310 .

A thermistor TH1 serving as a temperature detecting member is arranged within the range of the minimum sheet passing width. The temperature of the central resistance member 370-1 is controlled based on the temperature T1 of the central resistance member 370-1 or the substrate 341 detected by the thermistor TH1. Here, the temperature detection sensor (member) and the temperature control sensor (member) may be separate.

Outside the range of the minimum paper passing width and inside the smallest paper passing width among the papers that are larger than the total length (width) of the central resistance member 370-1 and the end resistance member 370-2, A thermistor TH3 is arranged as a temperature detection member. Then, based on the difference temperature (=T1-T3) between the temperature T1 detected by the thermistor TH1 and the temperature T3 of the central resistance member 370-1 or base material 341 detected by the thermistor TH3, the central A differential temperature reduction process is performed to equalize the temperature of the resistance member 370-1 in the longitudinal direction.

The thermistor TH3 is located outside the smallest paper and inside the inclined portion of the central resistance member 370-1 in order to detect excessive temperature rise in the non-paper-passing portion when the paper having a size smaller than the central resistance member 370-1 is passed. are provided. Since the slanted portion has a low heat generation density, it is preferable to dispose the thermistor TH3 at a position that does not interfere with the slanted portion.

Further, if it is arranged outside the largest sheet of paper whose width is smaller than that of the central resistance member 370-1 and inside the inclined portion, it is possible to detect an excessive temperature rise when printing on a sheet other than the smallest sheet, which is more preferable. Thermistor TH3 may be arranged to measure the outer peripheral temperature of pressure roller 320 without being arranged inside fixing belt 310 .

Since the temperature of the pressure roller 320, which is in contact with the fixing belt 310 and has a large heat capacity, is lower than that of the fixing belt 310 provided with a heat generating portion, an inexpensive thermistor can be used as the thermistor TH3. Further, since the thermistor is connected to a lead wire, which will be described later, a region for routing the lead wire is required when the thermistor comes into contact with a heater provided in the fixing belt 310 . As the number of thermistors increases, the number of lead wires also increases, so the diameter of the belt must be increased. can be reduced.

A thermistor TH2 as a temperature detecting member is arranged near the edge of the smallest sheet of paper that is larger than the combined length (width) of the central resistance member 370-1 and the end resistance member 370-2. The temperature of the end resistance member 370-2 is controlled based on the temperature T2 of the end resistance member 370-2 or the substrate 341 detected by the thermistor TH2.

The thermistor TH4 is arranged outside the width of the smallest sheet of paper that is larger than the combined length (width) of the central resistance member 370-1 and the end resistance members 370-2. Then, based on the differential temperature (=T2-T4), which is the difference between the temperature T2 detected by the thermistor TH2 and the temperature T4 of the substrate 341 detected by the thermistor TH4, the end resistance member 370-2 is adjusted. A differential temperature reduction process is performed to equalize the temperature in the longitudinal direction. Thermistors TH1-TH4 can be contact-type thermistors having a thermal time constant of less than 1 second, and are arranged in a form of being pressed against the back side of substrate 341 by springs 387, as shown in FIGS. 2A-2D. be.

Thus, in addition to the thermistors (TH1 in FIG. 3A, TH1 and TH2 in FIG. 3B) for controlling the heat source of the fixing device, the thermistors (TH2 in FIG. 3A, TH3 and TH4 in FIG. 3B) for monitoring temperature uniformity are used. By using , the transparent toner is fixed in a state of no temperature unevenness, and both quick start-up and prevention of transparent toner gloss unevenness can be achieved. In addition, the heat source of the planar heater (heating element 330) has a heating pattern that allows partial heating and control as shown in FIG. High productivity can be maintained.

In addition, even when a transparent or highly transparent toner whose glossiness is highly temperature dependent is used, uneven glossiness can be prevented from occurring in the formed image. That is, as shown in FIG. 3B, it is constantly monitored that the temperature deviation between the central portion and the end portion of each resistance member 370-1, 370-2 and the temperature deviation of each resistance member 370-1, 370-2 are within a predetermined range. to allow paper feeding. Thereby, gloss unevenness can be prevented from occurring.

FIG. 3B is an embodiment of up to three blocks in a symmetrical resistive member arrangement with respect to the center of the sheet. However, even if the resistance members are arranged more finely, such as 5 blocks or 7 blocks, by similarly arranging a plurality of thermistors in each resistance member, it is possible to provide a system that does not cause gloss defects even when transparent toner is used. .

(Multi-type resistance member)
As shown in FIG. 3C, the resistance member 370 may be of a multi-type configuration in which PTC elements 371 to 378 are electrically connected in parallel. The use of multiple types makes it easier to make the temperature uniform in the axial direction, so that the viscosity of the grease can be made uniform in the axial direction, and the amount of grease on the nip surface can be made uniform in the axial direction.

In this multi-type, the thermistors TH1 and TH2 in FIG. 3A and the thermistors TH1 to TH4 in FIG. 3B can be similarly arranged. If the resistance value between the electrodes 370c and 370d at both ends in FIG. 3C is assumed to be 10Ω, the resistance value of each of the PTC elements 371 to 378 increases to 80Ω due to the parallel connection.

The PTC element is made of a material having a positive temperature coefficient of resistance, and has the characteristic that the resistance value increases as the temperature T rises (current I decreases and the heater output decreases). A temperature coefficient of resistance (TCR) can be, for example, 1500 PPM (parts per million). The temperature resistance coefficient can be stored in a memory of the controller 400 (see FIG. 4), which will be described later.

The PTC elements 371 to 378 of FIG. 3C are arranged linearly and equally spaced in the longitudinal direction of the substrate 341 . On both sides of the PTC elements 371 to 378 in the short direction, feed lines 370a and 370b having small resistance values are arranged linearly parallel to each other, and both ends of the PTC elements 371 to 378 are connected to the feed lines 370a and 370b. It is A power supply means including an AC power supply 410 is connected to electrodes 370c and 370d formed at one end of each of the power supply lines 370a and 370b, as shown in FIG.

The PTC elements 371-378 and feed lines 370a, 370b are also covered with a thin insulating layer 385, similar to the series resistance member 370 (FIG. 3A) previously described. This insulating layer 385 can be made of, for example, heat-resistant glass with a thickness of 75 μm. The insulating layer 385 insulates and protects the PTC elements 371 to 378 and the feeder lines 370a and 370b, and maintains slidability with the fixing belt 310. FIG.

The PTC elements 371 to 378 can be formed by coating the substrate 341 with a paste prepared by, for example, silver palladium (AgPd) or glass powder by screen printing or the like, and then firing the substrate 341. can. In this embodiment, the resistance value of each of the PTC elements 371 to 378 is set to 80Ω at room temperature (the total resistance value is 10Ω).

As for the materials of the PTC elements 371 to 378, a silver alloy (AgPt) or ruthenium oxide (RuO2) resistance material may be used in addition to the materials described above. The power supply lines 370a and 370b and the electrodes 370c and 370d can be made of silver (Ag) or silver palladium (AgPd) by screen printing or the like.

The insulating layer 385 side of the PTC elements 371 to 378 contacts the fixing belt 310 and heats, heat transfer raises the temperature of the fixing belt 310, and the unfixed image conveyed to the fixing nip SN is heated and fixed.

By using the PTC elements 371 to 378, when the temperature of the PTC elements in the non-paper-passing area rises due to small size paper passing, etc., the heat generation amount of the PTC elements decreases due to the temperature resistance dependence of the resistance heating element. and suppress the temperature rise. Due to this feature, for example, when printing on paper narrower than the full width of the PTC elements 371 to 378 (for example, within the width of the PTC elements 373 to 376), the PTC elements 371, 372, 377, and 378 outside the paper width heat the paper. The temperature rises because it is not deprived. Then, the resistance values of these PTC elements 371, 372, 377 and 378 increase.

Since the voltage applied to the PTC elements 371 to 378 is constant, the outputs of the PTC elements 371, 372, 377, and 378 outside the paper width are relatively lowered, suppressing the edge temperature rise. When the PTC elements 371 to 378 are electrically connected in series, the only way to suppress the temperature rise of the resistance heating elements outside the paper width in continuous printing is to reduce the printing speed. By electrically connecting the PTC elements 371 to 378 in parallel, it is possible to suppress the temperature rise in the non-paper passing portion while maintaining the printing speed.

As the temperature of the fixing belt 310 increases, the strength of the fixing belt 310 decreases, and thus the fixing belt 310 is easily worn. However, by making the resistance member 370 multi-type, it is possible to suppress the excessive temperature rise in the non-sheet-passing portion even when the small-size paper is passed, thereby suppressing the wear of the fixing belt 310 and also obtaining the effect of suppressing the evaporation of the lubricant. .

The arrangement of the PTC elements 371 to 378 is not limited to the state shown in FIG. 3C(a). In FIG. 3C(a), since there are gaps extending in the width direction between the PTC elements 371 to 378, the amount of heat generated in the gaps is reduced, which tends to cause uneven fixing. Therefore, in FIGS. 3C(b) and (c), the ends of the PTC elements 371 to 378 are overlapped with each other in the longitudinal direction.

In FIG. 3C(b), the PTC elements 371 to 378 are formed with L-shaped notch steps at the ends thereof, and the stepped portions are overlapped with the stepped portions at the ends of the adjacent resistance heating elements. In FIG. 3C(c), the ends of the PTC elements 371 to 378 are formed with inclined portions by oblique cutouts, and the inclined portions are overlapped with the inclined portions of the ends of the adjacent resistance heating elements. By overlapping the ends of the PTC elements 371 to 378 with each other in this way, it is possible to suppress the influence of a decrease in the amount of heat generated in the gaps between the resistance heating elements.

The electrodes 370c and 370d may be arranged on both ends of the PTC elements 371 to 378, or may be arranged on one side of the PTC elements 371 to 378 as shown in FIGS. 3C(a) to 3C(c). By thus arranging the electrodes 370c and 370d on one side, it is possible to save space in the longitudinal direction.

Each of the resistance heating elements 371 to 378 in FIG. 3C is composed of a strip-shaped planar heating element. It can also be configured by electrically connecting PTC elements in parallel.

(Power supply circuit)
FIG. 4 shows a power supply circuit for supplying power to the heating device. This power supply circuit is normally arranged on the main body side of the image forming apparatus 100 .

The resistance members 370 of the heating device here use the center resistance member 370-1 and the end resistance members 370-2 of FIG. 3B. Below the heating device is shown the power supply circuitry that powers the central resistance member 370-1 and the end resistance members 370-2.

A power supply circuit as power control means comprises a control section 400 , an AC power supply 410 , a triac 420 , a current detection means 430 , heater relays 441 and 442 , and voltage detection means 451 and 452 . The control unit 400 and the triac 420 constitute power supply means.

An AC power supply 410, a current transformer CT of a current detection means 430, a triac 420, and heater relays 441 and 442 are arranged in series between an electrode 370e and opposite electrodes 370g and 370h. A voltage detecting means 451 is arranged between the electrode 370e on one side and the electrode 370f, and a voltage detecting means 452 is arranged between the electrode 370e on one side and the electrode 370h on the opposite side.

Temperatures detected by thermistors TH1 to TH4 are input to control unit 400. FIG. Based on the temperature obtained from the thermistor TH1, the control unit 400 supplies temperature to the electrodes 370e, 370g, and 370h by the triac 420 so that the central resistance member 370-1 and the end resistance members 370-2 reach predetermined target temperatures. Duty control the current.

Specifically, the triac 420 duty-controls the current flowing through the central resistance member 370-1 with a duty ratio corresponding to the temperature difference between the current temperature and the target temperature of the thermistor TH1. At a duty ratio of 0%, the current becomes zero, and at a duty ratio of 100%, the current becomes maximum.

Similarly, the triac 420 duty-controls the current flowing through the end resistance member 370-2 with a duty ratio corresponding to the temperature difference between the current temperature and the target temperature of the thermistor TH2. Here, the "duty" is the ratio of the energization time to the resistance member 370 per control cycle.

On the other hand, based on the differential temperature between the current temperatures of thermistors TH1 and TH3, the central resistance member 370-1 can be subjected to differential temperature reduction processing in the manner described above. Similarly, the left and right end resistance members 370-2 can be subjected to differential temperature reduction processing based on the differential temperature between the current temperatures of the thermistor TH2 and thermistor TH4.

The control unit 400 can be configured with a microcomputer including a CPU, ROM, RAM, I/O interface, and the like. When the paper passes through the fixing nip SN, heat removal (heat transfer to the paper) is generated due to the passage of the paper. By controlling, the temperature of the fixing belt 310 can be controlled to a desired temperature.

Current detection means 430 detects the sum of current values flowing through resistance member 370 . That is, the controller 400 reads the magnitude of the current flowing between the electrodes 370c and 370d via the voltage generated in the secondary resistance of the current transformer CT.

Further, the voltage detection means detects a voltage value E between the electrodes 370c and 370d of the resistance member 370, and the controller 400 reads the voltage E. FIG. Then, the controller 400 calculates the resistance value R (=E/I) of the resistance member 370 from the current value I and the voltage value E. FIG.

In FIG. 2A, when the paper P is passed through the fixing nip SN in the direction of the arrow, the paper P is heated between the fixing belt 310 and the pressure roller 320, and the toner image is fixed on the paper P. As shown in FIG. At this time, the fixing belt 310 is heated by heat from the resistance member 370 while sliding on the insulating layer 385 of the resistance member 370 .

(Other embodiments of the fixing device)
The fixing device 300 is not limited to the first fixing device of FIG. 2A. The second to fourth fixing devices will be described below with reference to FIGS. 2B to 2D. As shown in FIG. 2B, the second fixing device has a pressure roller 390 on the side opposite to the pressure roller 320, and the fixing belt 310 is sandwiched and heated between the pressure roller 390 and the heating device.

The above-described heating device is arranged inside the fixing belt 310 . An auxiliary stay 351 is attached to one side of the stay 350, and a nip forming member 381 is attached to the other side.

The heating device is held by this auxiliary stay 351 . The nip forming member 381 contacts the pressure roller 320 via the fixing belt 310 to form a fixing nip SN.

As shown in FIG. 2C, the third fixing device has a heating device inside the fixing belt 310 . In this heating device, instead of omitting the pressure roller 390 described above, the length of contact with the fixing belt 310 in the circumferential direction is lengthened. It is formed in an arc shape.

The resistance member 370 is arranged in the center of the arc-shaped base material 341 . Others are the same as the second fixing device in FIG. 2B.

The fourth fixing device, as shown in FIG. 2D, is divided into a heating nip HN and a fixing nip SN. That is, a nip forming member 381 and a stay 352 made of a metal channel material are arranged on the opposite side of the pressure roller 320 from the fixing belt 310 so as to enclose the nip forming member 381 and the stay 352 . A pressure belt 334 is arranged so as to be rotatable.

Then, the paper P is passed through the fixing nip SN between the pressure belt 334 and the pressure roller 320 to be heated and fixed. Others are the same as the first fixing device in FIG. 2A.

(Manufacturing method of fixing belt)
Next, a method for manufacturing the fixing belt 310 according to this embodiment will be described. The elastic power of the inner surface (sliding surface) of the fixing belt 310 used in this embodiment is prescribed to be 55% or more under environmental conditions of a temperature of 23° C. and a relative humidity of 50%.
◆Paint preparation (common)
・The coating solution is prepared by adding 80 g of NMP (N-methyl-pyrrolidone) to 100 g of polyimide varnish and mixing.
・U-imide varnish AR manufactured by Unitika Ltd. was used as the polyimide varnish.
・As NMP, special grade N-methyl-pyrrolidinone manufactured by Kanto Kagaku was used.
- Kneading is carried out by gradually adding a needle-like inorganic filler to the above prepared liquid A while carrying out blade agitation with a desk-top mixer.
- Add 20 g of acicular inorganic filler to 100 g of polyimide varnish.
・ Gradually add and knead the needle-like inorganic filler over about 10 to 15 minutes so that it does not form balls.・Tismo D manufactured by Otsuka Chemical Co., Ltd. was used as the acicular inorganic filler.
・This prepared liquid is designated as B.

◆ Painting (Common)
・Spray coating or dipping coating is used to coat the inner peripheral surface of the fixing belt.
・This time, spray paint is used.
・Pour prepared liquid B into the pumping tank.
・Rotate the fixing belt of the object to be coated in order to coat the inner peripheral surface of the fixing belt.
・Set the rotation speed of the fixing belt in the range of 900 to 1000 rpm.
・This time, set the speed to 900 rpm.

・The coating speed is set to 30 mm/s, and the coating weight for one coating on one side is in the range of 0.7 to 1.2 g.
・Adjustment of coating weight is carried out by the pressure at which preparation liquid B is pumped.
・This time, the pressure was 125 kPa, and the coating weight for one coating on one side at that time was 1.0 g.
・After application, pre-dry with hot air at 200°C, and apply multiple coats.
・Repeat painting and pre-drying 3 to 4 times.
- After finishing the coating, put it in a drying oven at 260°C and heat-treat it for 30 minutes to volatilize the NMP.
・The film thickness of the sliding layer is desirably 8 to 15 μm.
- This time, a total of 4.2 g of the prepared liquid B was applied, and the film thickness was 11 μm.

◆ Firing (common)
・Firing is carried out in a vertical far-infrared firing furnace.
・Far-infrared heaters are arranged on the left and right sides of the vertically arranged fixing belt, and the heater heats a range equal to or longer than the length of the fixing belt.
・Set the far-infrared heater temperature so that the fixing belt reaches the specified temperature.

◆ Firing temperature (when elastic power is relatively high)
- The far-infrared heater temperature was set so that the actual temperature of the fixing belt was 360°C.
・Baking time is 30 minutes.
- When the elastic work rate of the sliding layer after firing was measured, it was 70.0% at a room temperature of 23°C and 60.2% at a heating condition of 165°C.

◆ Firing temperature (when elastic power is relatively low)
- The far-infrared heater temperature was set so that the actual temperature of the fixing belt was 280°C.
・Baking time is 30 minutes.
- When the elastic work rate of the sliding layer after firing was measured, it was 60.4% under room temperature conditions of 23°C and 52.1% under 165°C heating conditions.

(Roughness of the belt and noise suppression effect)
Abnormal noise on the sliding surface is caused by insufficient lubricant on the sliding surface. In order to suppress abnormal noise, it is necessary to increase the amount of lubricant on the sliding surface.

By increasing the surface roughness of the inner surface of the fixing belt as in Japanese Patent Application Laid-Open No. 2009-14893, the amount of lubricant retained on the inner surface of the fixing belt can be increased. If the amount of lubricant retained on the inner surface of the fixing belt is increased, the amount of lubricant that newly flows into the sliding surface due to rotation can be increased, which is advantageous for noise suppression.

However, the roughness on the heater side is also related to securing a sufficient amount of lubricant for the sliding surface to suppress abnormal noise. As shown in FIG. 9A to be described later, when the surface roughness Sa2 of the sliding surface (insulating layer) of the heater is made larger than the surface roughness Sa1 of the inner surface of the fixing belt, the lubricant retained on the inner surface of the fixing belt is It flows into the sliding part.

However, the amount of lubricant that has flowed in as described above cannot fill the concave portions of the heater, and the oil film of the lubricant is cut off at the convex portions of the heater. As a result, abnormal noise and wear occur. In addition, the inner surface of the belt deteriorates in a streak-like manner due to sliding, and heat unevenness occurs in the image, resulting in abnormal images such as uneven glossiness and streaks in glossiness.

The larger the surface roughness Sa1 of the inner surface of the fixing belt, the larger the amount of grease retained by the fixing belt. When Sa1 is 0.2 .mu.m or more, the grease retention of the belt is stable, and it is desirable that the surface roughness Sa2 of the insulating layer of the heater, which is the opposed member, is 0.05 .mu.m or less. The "surface roughness Sa" referred to in this specification means the surface roughness Sa in the sliding direction (belt rotation direction) in which the fixing belt slides on the heater.

By setting the surface roughness Sa2 of the insulating layer of the heater to 0.05 μm or less, it is possible to prevent the grease conveyed from the fixing belt from entering the concave portions of the insulating layer of the heater and causing the grease to run out at the convex portions. . Although the surface roughness Sa2 is sufficient for retaining the grease in the fixing belt, it is more desirable that the space volume Vvv of the core portion, which will be described later, representing the volume of the concave portions of the irregularities, is 0.01 ml/m ² or more. As Vvv increases, the amount of grease retained by the fixing belt increases.

Lubricants can include fluorine greases or silicone oils. These lubricants can maintain lubricity over a long period of time between members sliding under high temperature and high surface pressure, and can suppress wear.

Further, when the fixing belt does not have an elastic layer such as rubber, the rigidity of the fixing belt is reduced and the belt easily conforms to the shape of the nip entrance. Then, the grease is easily supplied to the nip portion by capillarity.

(How to measure elastic power)
The elastic work mentioned above can be measured by a load-unload test (indentation test) of a microsurface hardness tester using a diamond indenter, and the closer to 1 (100%), the easier it is to judge that the material is elastically deformable. As shown in FIG. 5, the diamond indenter A is pushed in at a constant loading speed from the point (a) where the diamond indenter A comes into contact with the sample B (loading process), and is stopped for a certain period of time at the maximum displacement (b) when the set load is reached. . Then, the indenter is further pulled up at a constant unloading speed (unloading process), and the point at which the load is finally removed from the indenter is defined as plastic displacement (c).

At this time, the resulting curve of indentation depth and load is recorded as shown in FIG. 5(d). From this curve, the elastic work rate can be obtained by calculating the ratio of the work of elastic deformation We to the total work done by the indenter A on the surface layer (the work of plastic deformation Wt+the work of elastic deformation We).

The elastic work rate (%) can be expressed by a formula as follows.
Elastic work rate (%) = work amount of elastic deformation We × 100 / (work amount of plastic deformation Wt + work amount of elastic deformation We)

The elastic power measurement is performed under constant temperature and humidity, and in this embodiment, the elastic power indicates the measured value of the above test performed under environmental conditions of a temperature of 23° C. and a relative humidity of 50%. In this embodiment, a load is applied using a Fischerscope HM-2000 (manufactured by Fisher Instruments) and a Vickers indenter under the conditions of a set load of 20 mN, a time to reach the maximum load of 30 sec, and a creep time of 5 sec, and removed over 30 sec. Although the load was measured, the value measured by any device with equivalent performance is acceptable.

A sample was measured by suspending the fixing belt of the present embodiment on a metal substrate. Since the elastic power is affected by the spring characteristics of the substrate, a rigid metal plate, slide glass, or the like is suitable as the substrate.

Furthermore, since the hardness and elasticity of the underlying layer of the cross-linked surface layer (for example, the belt base material) also have an effect, a specified weight is applied so that the maximum displacement is 1/10 of the inner surface coating thickness in order to reduce these effects. adjusted. In order to eliminate the influence of the rubber and release layer on the surface layer of the base material, it is desirable to remove the rubber and release layer on the surface during measurement. In this measurement, the surface rubber and release layer were peeled off.

(Difference between elastic work rate and return rate)
There is a return rate as an index similar to the elastic power (see Patent Document 4: Japanese Patent No. 6036469). However, the return rates are all the same for return lines 1, 2 and 3, as shown in the load-displacement diagram of FIG. On the other hand, the return lines 1, 2, and 3 all have different values because the elastic power also has area information.

The area of the displacement-load curve at the time of pressurization and unloading represented by the elastic power is the energy loss, and the larger the difference, the larger the frictional force (torque). For example, even if the return rate is the same, the magnitude of the frictional force may differ depending on the unloading profile.

Therefore, as the characteristics of the sliding surface, the elastic power is more effective because it is possible to confirm the information of the frictional force in addition to the wear resistance. Since there is no area information, the presence or absence (magnitude) of frictional force cannot be determined by the return rate.

(Abrasion rank by elastic work rate)
As shown in FIG. 7, according to wear tests by the inventors of the present application, the elastic work rate of the inner surface (sliding surface) of the fixing belt is increased, and grease A with a consistency of 275, which has a consistency of 340 or less as a lubricant, The use of 340 Grease B was found to improve wear resistance. The elastic power can be measured by the indentation test in FIG. 5 described above, and it can be judged that the material is more elastically deformable as the power is closer to 1 (100%).

The lubricant enters the sliding surface with the sliding member together with the belt, but the amount of lubricant that can enter the sliding surface is suppressed by the nip pressure. A soft lubricant with a high consistency loses to the nip pressure and the amount of penetration decreases.

On the other hand, a hard (highly viscous) lubricant with a low consistency penetrates in a larger amount than a lubricant with a high consistency, and the effect of suppressing sliding wear is enhanced. When the elastic power of the inner surface of the belt is large, coupled with the reaction force generated by the lubricant with high viscosity and low consistency, a gap is likely to occur between the inner surface of the belt and the rubbing member, and more lubricant rubs. Abrasion resistance is improved by obtaining the effect of making it easier to enter the surface.

・ Verification configuration: [Nip forming member: Planar heater on the glass surface]
+ [fixing belt: inner PI-based paint] + [pressure roller]
・Lubricant: Fluorine Grease A (Consistency 275), Fluorine Grease B (Consistency 340)
・Test conditions: Repeated heating (belt temperature 180°C) until the actual life expectancy, rotational operation test ・Martens hardness measurement conditions: 1 μm indentation
・Belt hardness (H1): about 500 N/mm ²
・Heater glass surface hardness (H2): about 3500 N/mm ²

As an evaluation method, the surface film property tester Fisher Scope H-100 manufactured by Fisher Instruments is used to measure the elastic power and universal hardness, and the surface roughness shape measuring machine Surfcom 1400D manufactured by Tokyo Seimitsu is used. Point average roughness (Rz) was measured.

A durability test was carried out by varying the level of elastic power of the belt from 45% to 65% in the relationship of H1<H2 between the hardness H1 of the sliding surface of the fixing belt and the surface hardness H2 of the heater glass. investigated. The wear ranks shown in FIG. 7 are as follows: rank 1 is a state in which many lines of gloss unevenness (streaks) are clearly visible in a solid image in which the inner surface of the belt is abraded by wear; Rank 3 indicates a state in which gloss unevenness (streaks) is faintly visible on a solid image, Rank 4 indicates a state in which no gloss streaks are observed, and Rank 5 indicates a state in which there are no abrasion streaks on the inner surface of the belt. In this embodiment, the practically usable range is set to wear rank 3 or higher, and the range in which image quality is not affected at all is set to wear rank 4 or higher.

In general, when a soft lubricant with a high consistency is used, deterioration of the inner surface of the belt is accelerated, and deterioration is improved when a hard lubricant with a low consistency is used. However, if a hard lubricant is used, there is a risk that there will be no margin for the drive force limit of the device due to an increase in sliding resistance due to abrasion powder generated by sliding (torque over will stop the device).

When hard lubricants are used, expensive hard materials are selected for motors and gears to provide sufficient driving force to avoid torque over. Also, if the torque becomes high, the belt will not rotate smoothly with the pressure roller, causing paper wrinkles and even paper jams. do.

Even if the hardness H2 of the sliding surface of the sliding member is greater than the hardness H1 of the sliding surface of the fixing belt, the state of wear of the inner surface varies depending on the elastic power. From the test results of FIG. 7, it can be seen that by using grease A with an elastic power of 55% or more and a consistency of 275, practical wear resistance performance can be ensured. Further, it can be seen that by using the grease B having an elastic power of 58% or more and a consistency of 340, practical wear resistance performance can be ensured. Also, it can be seen that this state can be maintained when the elastic power is at least 63% or less. Practical wear resistance performance can be ensured by using a consistency of hardness H1 to hardness H2 of 340 to 265, but a consistency of hardness H3 up to 220 may also be used.

Further, when the elastic power is 58% or more, the grease A can secure high-quality wear resistance, and the grease B can secure practical wear resistance performance. Therefore, by using a belt with a high elastic work rate, it becomes possible to use a soft lubricant, and the selection range of grease is widened.

In the case of a hard lubricant, shear stress acts on the lubricant between the belt and the sliding member, increasing the sliding resistance. As a result, the driving torque of the pressure roller increases, and the load on the driving gear and motor increases. In order to cope with this, it is necessary to select drive system parts with high cost. If a soft lubricant can be used, it will be possible to reduce the cost of the drive system and suppress belt wear.

The elastic work rate indicates how much the applied stress can be relaxed when the stress is removed, and the larger the value, the higher the stress relaxation ability. It is desirable to formulate the inner surface of the belt so that the stress caused by sliding does not remain as permanent deformation.

( Printing durability)
FIG. 8 is a diagram showing the correlation between the elastic power and the amount of film reduction. A plurality of plotted points in the figure are the results of a printing endurance test using samples having different elastic powers on the inner surface of the belt. In the test, a character test chart was formed on 100,000 sheets of recording paper at the black image position for each photoreceptor in a normal/normal humidity environment with a temperature of 25° C. and a relative humidity of 50%.

The film thickness was measured at the start of the printing endurance test and after image formation on 100,000 sheets of recording paper to determine the amount of film reduction. The film thickness was measured using a film thickness measuring device (trade name: Fischer Scope MMS, manufactured by Fisher Instruments Co., Ltd.).

It was found that the larger the elastic power, the smaller the amount of film loss, and the better the printing durability. When the elastic power is 55% or more, the amount of film reduction becomes almost negligible.

(Lubricant holding state)
9(a) and 9(b) schematically show how the lubricant L is retained depending on the difference in surface roughness between the fixing belt and the heater. Let Sa1 be the surface roughness of the inner surface of the fixing belt, and Sa2 be the surface roughness of the sliding surface (insulating layer) of the heater. FIG. 9A shows cross sections of the fixing belt and the heater when Sa1<Sa2.

FIG. 9A shows that the lubricant tends to transfer from the belt to the heater because the surface roughness Sa2 of the heater is larger. On the other hand, FIG. 4B shows cross sections of the fixing belt and the heater when the surface roughness is reversed and Sa2<Sa1. FIG. 4B shows that the lubricant tends to transfer from the heater to the belt because the surface roughness Sa1 of the belt is larger.

From FIG. 9, it can be seen that in order to maintain the amount of lubricant L on the inner surface of the fixing belt, it is necessary to increase the surface roughness Sa1 of the belt so that Sa2<Sa1. Moreover, in order to maintain such a magnitude relationship of surface roughness over time, it was found that the elastic power should be 55% or more based on the results of the amount of film reduction shown in FIG.

(Types of surface shape parameters)
Surface shape parameters sensitive to abnormal noise and sliding include arithmetic mean roughness Sa, protruded valley space volume Vvv, skewness Ssk, and kurtosis Sku. Each parameter will be described below.

(Arithmetic mean roughness)
FIG. 10A is a diagram explaining arithmetic mean roughness. The arithmetic mean roughness Sa is a parameter obtained by three-dimensionally expanding the profile curve (line roughness) parameter Ra. FIG. 10A shows the average of absolute values of Z(x, y) (height difference from the average plane) in the measurement target area.

( Load curve)
The protruding trough space volume Vvv represents the void volume of the trough at a load area ratio of p %. FIG. 10B is a diagram showing a load curve.

In order to calculate the protruded valley space volume Vvv, a surface load curve is obtained, which is a curve representing the height at which the load area ratio is from 0% to 100%. The load area ratio represents the area of a region having a certain height c or more. The load area ratio at height c corresponds to Smr(c) in FIG. 10B.

From this load curve, the volume of the area where the load area ratio is p % or more and 100% or less is calculated as the protruded valley space volume Vvv. This time, p=80 is used to calculate the projecting valley space volume Vvv.

( body part and space part)
FIG. 10C is a diagram showing a load curve representing a solid portion and a void portion. As the protruded valley space volume Vvv increases, the volume of the valley increases, and thus more lubricant can be retained. As a result, the wear resistance is improved.

(Height distribution by degree of bias)
FIG. 10D shows the height distribution according to skewness Ssk. FIG. 10D(a) is the height distribution when the bias degree Ssk>0. FIG. 10D(b) is the height distribution when the deviation degree Ssk<0.

The degree of skewness (skewness) Ssk represents the symmetry of the height distribution, and is calculated by the following equation (Equation 1).

When Ssk=0, the height distribution is vertically symmetrical. When Ssk>0, the surface has many fine peaks as shown in FIG. 10D(a). When Ssk<0, the surface has many fine peaks as shown in FIG. 10D(b).

On the surface with many fine peaks as shown in FIG. 10D(b), since the contact area of the sliding surface increases, the wear resistance is improved. Since wear resistance is more advantageous as Ssk is smaller, it is desirable to set the surface shape characteristic value Ssk (degree of strain) of the sliding surface of the fixing belt to 0 or less.

( Kurtosis)
The kurtosis (kurtosis) Sku represents the sharpness of the height distribution, and is calculated by the following formula (Equation 2).

When Sku=3, the height distribution becomes a normal distribution. In the case of Sku>3, the surface has many sharp peaks and valleys as shown in FIG. 10E(a). In the case of Sku<3, the surface becomes flat as shown in FIG. 10E(b), and the contact area of the sliding surface increases, resulting in good wear resistance.

(Measurement method)
Surface shape parameters can be measured using VK-X100 (manufactured by Keyence) using a 50x objective lens. The sample was measured after setting the fixing belt of the present invention on a smooth surface and confirming that there was no large inclination or undulation at the observation position.

(Relationship between elastic power and coefficient of friction)
The area of the displacement-load curve at the time of pressurization and unloading in FIG. 5 explained in terms of elastic power is the energy loss, and the larger the difference, the larger the frictional force (torque). FIG. 11A shows that the friction coefficients (static friction coefficient and dynamic friction coefficient) of the fixing belt are different by changing the elastic power. The difference between the static friction coefficient and the dynamic friction coefficient becomes smaller as the elastic power increases.

FIG. 11B shows the state of occurrence of abnormal noise and vibration when the elastic power is changed (50%→55%→63%), confirmed by the following experiment.
<Measurement conditions>
Dynamic friction coefficient: A small amount of grease applied (Toray HP300: 50mg), 24h average value adopted Measurement device: Ring-on tester Cut out the belt and set it in the ring-on tester Contact: Glass φ10
Rotational speed (measuring part): 250mm/sec
Temperature: 23°C
Load: 1kg/ ^cm2

■ Coefficient of static friction: No grease application Contact: Glass φ10
Temperature: 23°C
Load: 1kg/ ^cm2

According to this experiment, even if the elastic power is changed (50%→55%→63%), it seems that there is no change in noise generation. However, since abnormal noise is generated when the vibration worsens, it was found that increasing the elastic power has the effect of suppressing the generation of abnormal noise and vibration of the fixing belt.

That is, by setting the elastic work rate to 55%, the elastic deformability of the fixing belt can be improved, stress during sliding can be relaxed, and practical wear resistance performance can be ensured (prevention of belt material deterioration). In addition, noise and vibration can be satisfactorily suppressed. Further, by setting the elastic work rate to 63%, the elastic deformability of the fixing belt can be further improved and the stress during sliding can be more alleviated, and high-quality wear resistance can be secured and there is no difference. Sound and vibration can be suppressed even better.

Merely increasing the hardness (Martens hardness) of the belt surface in order to improve the abrasion resistance of the belt cannot suppress deterioration of the member. By increasing the elastic power, the stress exerted on the surface material of the belt by the nip sliding portion is relieved, thereby obtaining the effect of suppressing the deterioration of the member structure.

FIG. 11C illustrates the difference between the static friction coefficient and the dynamic friction coefficient in FIG. 11A corresponding to changes in the elastic power. As is clear from the figure, the difference in the coefficient of friction is 0.14 or less when the elastic power is 55% or more. The smaller the difference between the friction coefficients, the more the stick-slip phenomenon can be suppressed, and the occurrence of abnormal noise and vibration can be suppressed.

(Other embodiments of the image forming apparatus)
The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1A, but may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile machine, or a multifunction machine of these.

For example, as shown in FIG. 12, the image forming apparatus 100 of the present embodiment includes an image forming unit 50 including a photosensitive drum and the like, a sheet conveying unit including a pair of timing rollers 15 and the like, a sheet feeding device 200, It includes a fixing device 300 , a paper ejection device 10 , and a reading section 51 . The paper feeder 200 has a plurality of paper feed trays, each of which accommodates paper of different sizes.

The reading unit 51 reads the image of the document Q. As shown in FIG. The reading unit 51 generates image data from the read image. The paper feeding device 200 accommodates a plurality of papers P and sends out the papers P to the transport path. The timing roller 15 conveys the paper P on the conveying path to the image forming means 50 .

The image forming means 50 forms a toner image on the paper P. As shown in FIG. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishing device, a transfer roller, a cleaning device, and a neutralizing device. The toner image indicates the image of the document Q, for example.

The fixing device 300 heats and presses the toner image to fix the toner image on the paper P. As shown in FIG. The paper P on which the toner image is fixed is conveyed to the paper discharge device 10 by a conveying roller or the like. The paper discharge device 10 discharges the paper P to the outside of the image forming apparatus 100 .

Next, the fixing device 300 of this embodiment will be described. The description of the configuration common to the fixing device of the above embodiment will be omitted as appropriate. As shown in FIG. 13, the fixing device 300 includes a fixing belt 310, a pressure roller 320, a heater 332, a heater holder 344, a stay 350, a thermistor TH, and the like.

A fixing nip N is formed between the fixing belt 310 and the pressure roller 320 . The nip width of the fixing nip N can be set to 10 mm, for example, and the linear speed of the fixing device 300 can be set to 240 mm/s, for example.

The fixing belt 310 has a polyimide substrate and a release layer and does not have an elastic layer. The release layer is made of a heat-resistant film material made of, for example, fluororesin. The fixing belt 310 can have an outer diameter of, for example, about 24 mm.

The pressure roller 320 includes a metal core 321 , an elastic layer 322 and a release layer 323 . The outer diameter of the pressure roller 320 can be, for example, 24-30 mm, and the thickness of the elastic layer 322 can be, for example, 3-4 mm.

The heater 332 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element and the like, and an insulating layer, and can be formed with a total thickness of 1 mm, for example. Also, the width Y of the heater 332 in the array crossing direction can be set to 13 mm, for example.

As shown in FIG. 14, the conductor layer of the heater 332 includes a plurality of resistance heating elements 31, power supply lines 133, and electrode portions 134A-134C. Also in this embodiment, as shown in the enlarged view of FIG. 13, divided regions are formed by dividing a plurality of resistance heating elements 31 in the arrangement direction (however, in FIG. 14, only the divided regions are shown in the enlarged view). are shown in the drawing, but in practice, divided regions are provided between all the resistance heating elements 31).

The resistance heating element 31 constitutes three heating portions 135A to 135C. By energizing the electrode portions 134A and 134B, the heat generating portions 135A and 135C generate heat.

By energizing the electrode portions 134A and 134C, the heat generating portion 135B generates heat. For example, the heat-generating portion 135B can be caused to generate heat when performing the fixing operation on small-size paper, and all the heat-generating portions can generate heat when performing the fixing operation on large-size paper.

As shown in FIG. 15, the heater holder 344 holds the heater 332 in its recess 344b. The recess 344b is provided on the heater holder 344 on the heater 332 side.

The recessed portion 344b is provided inside the heater holder 344 on both sides (or one side) in the arrangement direction of the heater holder 344, and a surface 344b1 that is recessed on the stay 350 side from the other surface of the heater 332 and is substantially parallel to the base material 30. and wall portions 344b3 provided inside the heater holder 344 on both sides in the arrangement cross direction. The heater holder 344 has a guide portion 344a. The heater holder 344 is made of LCP (liquid crystal polymer).

As shown in FIG. 16, the connector 65 includes a resin (for example, LCP) U-shaped housing and a plurality of contact terminals provided on the inner surface of the U-shaped housing. The connector 65 is attached so as to sandwich the heater 332 and the heater holder 344 together from the front side and the back side.

In this state, each contact terminal is brought into contact (pressure contact) with each electrode portion of the heater 332 , thereby electrically connecting the heat generating portion 35 and the power source provided in the image forming apparatus through the connector 65 . As a result, power can be supplied from the power supply to the heating unit 35 . At least a portion of each electrode portion 34 is exposed without being covered with an insulating layer in order to ensure connection with the connector 65 .

The flanges 53 that hold both ends of the fixing belt 310 are provided on both sides in the alignment direction of the fixing belt 310 and hold both ends of the fixing belt 310 from the inside of the belt. The flange 53 is fixed to the housing of the fixing device 300 . The flanges 53 are inserted into both ends of the stay 350 (see arrow directions from the flanges 53 in FIG. 16).

The direction in which the connector 65 is attached to the heater 332 and the heater holder 344 is the heater array intersecting direction (see the arrow direction from the connector 65 in FIG. 16). When the connector 65 is attached to the heater holder 344, a convex portion provided on one of the connector 65 and the heater holder 344 may be engaged with a concave portion provided on the other so that the convex portion relatively moves within the concave portion. Further, the connector 65 is attached to the heater 332 and the heater holder 344 on one side in the arrangement direction and on the side opposite to the side on which the drive motor of the pressure roller 320 is provided.

As shown in FIG. 17, a thermistor TH is provided on each of the center side and the end side of the fixing belt 310 in the arrangement direction so as to face the inner peripheral surface of the fixing belt 310 . The heater 332 is controlled based on the temperatures of the fixing belt 310 detected by the thermistor TH on the center side and the end side in the arrangement direction. One of these thermistors TH is provided at a position corresponding to the divided area between the resistance heating elements of the heater 332, as in the above-described embodiment.

Thermostats TS are provided on the center side and the end side of the fixing belt 310 in the alignment direction so as to face the inner peripheral surface of the fixing belt 310 . When the temperature of fixing belt 310 detected by thermostat TS exceeds a predetermined threshold value, power supply to heater 332 is stopped.

Flanges 53 that hold the ends of the fixing belt 310 are provided at both ends of the fixing belt 310 in the arrangement direction. The flange 53 is made of LCP (liquid crystal polymer).

As shown in FIG. 18, the flange 53 is provided with a slide groove 53a. The slide groove 53 a extends in the contact/separation direction of the fixing belt 310 with respect to the pressure roller 320 .

The engaging portion of the housing of the fixing device 300 is engaged with the slide groove 53a. The fixing belt 310 can move toward and away from the pressure roller 320 by relatively moving the engaging portion within the slide groove 53a.

Although the present invention has been described above based on the embodiments, it is needless to say that the present invention is not limited to the above embodiments and can be variously modified within the scope of the technical idea described in the claims. . For example, the pressure roller 320 as a pressure member of the fixing device 300 may be composed of a pressure belt stretched between two rotating bodies. Also, other heat generating elements such as a ceramic heater can be used as the heat generating element of the fixing device 300 .

1K, 1Y, 1M, 1C: Process unit 2K, 2Y, 2M, 2C: Image carrier
3K, 3Y, 3M, 3C: Drum cleaning device 4K, 4Y, 4M, 4C: Charging device
5K, 5Y, 5M, 5C: Developing device 6K, 6Y, 6M, 6C: Toner bottle 7: Exposure device 7a: Mirror 8: Transfer cover 10: Powder container 15: Transfer device 16: Intermediate transfer belt 17: Driven roller 18: drive roller
19K, 19Y, 19M, 19C: primary transfer roller 20: secondary transfer roller 21: belt cleaning device 31: resistance heating element 32: paper feed path 33: post-transfer transport path 35: post-fixing transport path 36: paper discharge path 37 : Discharge roller pair 41: Reversing conveying path 42: Switching member 42a: Swing shaft 43: Reversing conveying roller pair 44: Discharge tray 45: Paper feed roller 46: Tray 60: Paper feed roller 70: Connector 71: Housing 72 : Contact terminal 72a: Contact portion 73: Harness 74: High thermal conductivity member 100: Image forming apparatus 101: Protrusion 102: Hole 103: Image forming apparatus main body 200: Paper feeding device 210: Roller pair 220: Feeding roller 230: Separating roller 240: Conveying roller 250: Registration roller pair 300: Fixing device 310: Fixing belt 320: Pressure roller 321: Core metal 322: Elastic layer 323: Release layer 324: Drive transmission gear 330: Heat generating element 330a: Positioning hole 333a: electrode portion 333b: power supply line 334: pressure belt 334: conductor layers 340, 344: heater holder 341: base materials 350, 352: stay 351: auxiliary stay 370: resistance member 370-1: central resistance member 370-2: End resistance members 370a, 370b: Feed lines 370c to 370h: Electrodes 371 to 378: PTC elements 379a to 379h: Feed lines 381: Nip forming member 385: Insulating layer 387: Spring 389: Uniform heat member 390: Pressure roller 400: Control unit 400: Control unit 410: AC power supply 420: Triac 430: Current detection means 441, 442: Heater relays 451, 452: Voltage detection means P: Paper SN: Fixing nip TH, TH1 to TH4: Thermistor TS: Thermostat TM: Transfer means

Japanese Patent No. 6336026 JP 2015-194713 A JP 2009-14893 A Japanese Patent No. 6036469 Japanese Patent No. 6061606

Claims (14)

a flexible sleeve-shaped rotary member;
a sliding member that slides on the inner circumference of the rotating member;
a pressurizing member that presses against a portion facing the sliding member across the rotating member to form a nip portion with the rotating member;
In a fixing device including a lubricant between the rotating member and the sliding member,
The consistency of the lubricant is 340 or less, and the elastic power of the sliding surface of the rotating member is 58% or more, or the consistency of the lubricant is 275 or less, and the elastic power of the sliding surface of the rotating member is 55%. and above,
A fixing device, wherein the surface roughness of the sliding surface of the rotating member in the sliding direction is larger than the surface roughness of the sliding surface of the sliding member in the sliding direction. 2. A fixing device according to claim 1, wherein the sliding surface of said rotary member has an elastic power of 63% or more. 3. A fixing device according to claim 1, wherein said sliding member has a heater. 4. The fixing device according to any one of claims 1 to 3, wherein the lubricant contains fluorine grease or silicone oil. 5. The fixing device according to claim 1, wherein a material of the sliding surface of said rotating member contains polyimide. 6. The fixing device according to claim 1, wherein the surface roughness Sa (arithmetic mean height) of the sliding surface of the rotating member is 0.2 [mu]m or more. 7. The fixing device according to claim 1, wherein the sliding surface of the sliding member has a surface roughness of 0.05 [mu]m or less. The fixing device according to any one of claims 1 to 7, wherein a protruded valley space volume Vvv, which is a surface shape characteristic value of the sliding surface of the rotating member, is 0.01 ml/ ^m2 or more. 9. The fixing device according to claim 1, wherein a bias degree Ssk, which is a surface shape characteristic value of the sliding surface of the rotating member, is 0 or less. 10. The fixing device according to claim 1, wherein a sharpness Sku, which is a characteristic value of the surface shape of the sliding surface of the rotating member, is 3 or less. 11. The fixing device according to claim 1, wherein the sliding surface of the sliding member is made of glass. 12. The fixing device according to any one of claims 1 to 11, wherein the rotating member comprises a base material, a surface layer, and an adhesive layer. 13. The fixing device according to any one of claims 1 to 12, wherein the heating element of the heater is divided into a plurality of parts in the longitudinal direction. An image forming apparatus comprising the fixing device according to any one of claims 1 to 13.

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