JP7338412B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming apparatus.

Various types of fixing devices are known for use in electrophotographic image forming apparatuses. One of them is a type in which a thin fixing belt with a low heat capacity is heated by a halogen heater (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100003). In this type of fixing device, a nip plate is provided on the inside and a pressure roller is provided on the outside with the fixing belt interposed therebetween. A halogen heater heats the nip plate, and the nip plate heats the fixing belt. The nip plate is supported by a stay having a channel shape in cross section.

The paper passage area of the fixing belt must be sufficiently heated to the temperature required for fixing when the image forming apparatus starts printing. However, when there is a long job interval, printing starts immediately after returning from the sleep mode, so the paper passing area is often started up from a low temperature.

When the paper passage area of the fixing belt is started from a low temperature, the temperature rise becomes slow. In particular, since the heat escapes to the paper non-passage area, the end portion of the paper passage area is much slower to rise in temperature. As a result, the sleep recovery time is prolonged. The fixing device disclosed in Japanese Patent Application Laid-Open No. 2002-200002 extends the nip plate to the upstream side in the rotation direction of the fixing belt, and heats the extended portion by radiation, thereby shortening the sleep recovery time.

However, in the fixing device of Patent Document 1, the upstream side plate portion of the stay is shortened in the height direction to support the extended portion of the nip plate. For this reason, it has been difficult to accelerate the temperature rise at the end portion without lowering the strength of the stay.

SUMMARY OF THE INVENTION An object of the present invention is to accelerate the temperature rise at the ends without lowering the strength of the stay.

In order to solve the above-mentioned problems, the fixing device of the present invention comprises a rotatable endless fixing member, a heating element arranged in the longitudinal direction inside the fixing member, and sliding contact with the inner peripheral surface of the fixing member. a nip plate arranged in a longitudinal direction in a state of being held in place; a support member surrounding the heat generating element and supporting the heat generating element; and a pressure member arranged to face the nip plate and forming a fixing nip with the fixing member, wherein the nip plate is provided at least in the longitudinal direction of the fixing device. A heating portion located at an upstream end in the conveying direction of the fixing nip is provided at both ends, and an extended reflecting portion extending upstream facing the heating portion is formed at both ends in the longitudinal direction of the reflecting member. and

The present invention can speed up the temperature rise at the ends without lowering the strength of the stay.

1 is a principle diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 3A and 3B are a central cross-sectional view and a cross-sectional view of an end portion of the fixing device; FIG. 3A and 3B are a central cross-sectional view and a cross-sectional view of an end portion of the fixing device; FIG. It is a figure which shows edge heat distribution lifting at the time of using two halogen heaters. 4 is a perspective view of a stay of the fixing device; FIG. 4 is a perspective view of a nip plate of the fixing device; FIG. 4 is a perspective view of a reflecting member of the fixing device; FIG. It is a figure which shows edge heat distribution lifting at the time of using two halogen heaters. It is a figure which shows edge heat distribution lifting at the time of using one halogen heater. 8A and 8B are a cross-sectional view of an end portion of a fixing device according to Modified Embodiment 1, and FIG. 8B are views of a halogen heater; 8A and 8B are a sectional view of an end portion of a fixing device according to Modified Embodiment 2, and FIG. 8B is a diagram of a halogen heater; 8A and 8B are a cross-sectional view of an end portion of a fixing device according to Modified Embodiment 3 and FIG. 8B is a diagram of a halogen heater; FIG. 14A is a cross-sectional view of an end portion of a fixing device according to Modified Embodiment 4, and FIG. 11B is a diagram of a halogen heater; FIG. 14A is a cross-sectional view of an end portion of a fixing device according to Modified Embodiment 5, and FIG. 11B is a view of a halogen heater; FIG. 10A is a perspective view of a stay and FIG. 11B is a cross-sectional view of an end portion of a fixing device according to Modified Embodiment 6;

A fixing device and an image forming apparatus (laser printer) according to embodiments of the present invention will be described below with reference to the drawings. 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" is described as "paper", but the "recording medium" is not limited to paper (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. 1 is a principle diagram of a laser printer as one embodiment of an image forming apparatus 100 equipped with a fixing device 300 of the present invention. The image forming apparatus 100 has an image carrier 2 (for example, a photosensitive drum) and a drum cleaning device 3 . Further, a charging device 4 as charging means for uniformly charging the surface of the image carrier, a developing device 5 as developing means for performing visible image processing of the electrostatic latent image formed on the image carrier, and an image carrier. It has a transfer means TM disposed below the body 2, a static elimination device, and the like.

The exposure unit 7 is arranged above the image carrier 2 . The exposure unit 7 reflects a laser beam Lb from a laser diode on a mirror 7a and irradiates the image carrier 2 based on writing scanning according to image information, ie, image data.

A sheet feeding device 50 having a tray for stacking sheets P is installed below the image forming apparatus 100 . The paper feeder 50 can accommodate a large number of papers P as a recording medium in a bundle, and is unitized together with a paper feed roller 60 as paper P transport means.

A pair of registration rollers 250 as a separating and conveying means is arranged downstream of the paper feeding roller 60 . The paper P fed from the paper feeding device 50 is temporarily stopped by the registration roller pair 250 . 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.

The paper P, which has been abutted against the pair of registration rollers 250 and formed with slack at the leading end, is fed to the transfer nip N of the transfer means TM at the timing when the toner image on the image carrier 2 is appropriately transferred. Then, the toner image on the image carrier 2 is electrostatically transferred to a desired transfer position on the fed paper P by a bias applied at the transfer nip N. As shown in FIG.

A fixing device 300 is arranged on the downstream side of the transfer nip N. As shown in FIG. The fixing device 300 includes a fixing belt 310 as a fixing member containing a halogen heater as a heating element (to be described later), and a pressure roller 320 as a pressure member rotating while contacting the fixing belt 310 with a predetermined pressure. I have it.

(laser printer operation)
Next, the basic operation of the laser printer according to this embodiment will be described. Paper feed roller 60 rotates in response to a paper feed signal from the control section of image forming apparatus 100 . By the rotation of the paper feed roller 60, the uppermost sheet of the bundle of paper P stacked on the paper feeder 50 is separated and sent to the paper feed path.

When the leading edge of the sheet P reaches the nip of the pair of registration rollers 250, the sheet P becomes loose and waits in that state. Then, the optimum timing (synchronization) for transferring the toner image on the image carrier 2 to the paper P is obtained, and the leading edge skew of the paper P is corrected.

The charging device 4 uniformly charges the surface of the image carrier 2 to a high potential. Then, the exposing device 7 reflects the laser light Lb based on the image data on the mirror 7a and irradiates the surface of the image carrier 2 with the laser light Lb.

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

The image carrier 2 to which the toner has been transferred forms (develops) a toner image on its surface. Then, the toner image formed on the image carrier 2 is transferred onto the paper P by the transfer means TM.

The drum cleaning device 3 uses a cleaning blade 3a to remove residual toner adhering to the surface of the image carrier 2 after the transfer process. The removed residual toner is collected in the waste toner container.

The paper P onto which the toner image has been transferred is conveyed to the fixing device 300 . The paper 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 paper P by applying heat and pressure. The paper P on which the toner image is fixed is sent out from the fixing device 300 .

(fixing device)
Next, the fixing device 300 according to the embodiment of the invention will be further described. As shown in FIGS. 2A and 2B, the fixing device 300 includes a low heat capacity thin fixing belt 310 and a pressure roller 320 . The fixing belt 310 has, for example, a cylindrical substrate made of polyimide (PI) having an outer diameter of 25 mm and a thickness of 40 to 120 μm.

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.

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 release layer 323 of a fluorine resin layer having a thickness of, for example, about 40 μm. A pressure roller 320 is pressed against the fixing belt 310 by an urging means.

A stay 330 and a nip plate 380 (first heating unit) are arranged inside the fixing belt 310 in the axial direction. The stay 330 is formed of a metal channel material having a U-shaped cross section, and both end portions thereof are supported by both side plates of the fixing device 300 . The stay 330 reliably receives the pressing force of the pressure roller 320 and stably forms the fixing nip SN.

The nip plate 380 makes the temperature of the fixing belt 310 uniform in the width direction by transferring heat in the axial direction (width direction). The nip plate 380 is made of a material having high thermal conductivity such as copper, aluminum or silver in order to facilitate heat transfer in the width direction. In addition, it is desirable to use copper in consideration of cost, processing, and the like.

The nip plate 380 is supported by the downward open ends of the stays 330 at both lateral ends thereof. As shown in FIG. 4B, the upstream end of the nip plate 380, that is, the upstream end in the rotation direction of the fixing belt 310, extends along the inner peripheral surface of the fixing belt 310 in a substantially arc shape toward the upstream side in the rotation direction along the inner peripheral surface of the fixing belt 310. It has an extended extension portion 380a (second heating portion, a heating portion located at the upstream end of the fixing nip in the conveying direction). The extension portions 380a are formed at least at both ends in the longitudinal direction of the nip plate 380 for the purpose of lifting end heat distribution, which will be described later. The extension portion 380 a guides the fixing belt 310 entering the fixing nip SN and preheats the fixing belt 310 . Here, the “longitudinal direction” of the nip plate 380 is the same direction as the axial direction of the halogen heaters 361 and 362 .

The extension portion 380a may be formed over the entire longitudinal length of the nip plate 380. However, the central portion (intermediate portion) of the nip plate 380 in the longitudinal direction is sandwiched between the paper-passing areas and heat is difficult to escape. Temperature can be easily ensured. Therefore, it is sufficient that the extensions 380a are formed at both longitudinal ends as shown in FIG. 4B. Here, both ends in the longitudinal direction refer to portions outside the maximum sheet passing area.

At the downstream end of the nip plate 380, that is, at the rotational direction downstream end of the fixing belt 310, a lubricant regulating portion 380b is formed along the outer side of the downstream side plate portion of the stay 330 so as to be bent upward at a substantially right angle. The lubricant regulating portion 380b regulates the lubricant adhering to the inner peripheral surface of the fixing belt 310 from flowing into the upper surface of the nip plate 380 (the surface painted black or the like).

When the lubricant flows into the upper surface of the nip plate 380, the heating efficiency of the nip plate 380 is lowered. A decrease in heating efficiency can be prevented by the lubricant restricting portion 380b.

As shown in FIGS. 2A and 2B, the stay 330 is made of a channel material with a U-shaped cross section that opens downward. A nip plate 380 is supported at the downward open end of the stay 330 . A fixing nip SN is formed between the nip plate 380 and the fixing belt 310 by the pressure of the pressure roller 320 acting on the nip plate 380 via the fixing belt 310 .

The stay 330 has a downstream side wall 330a, a ceiling wall 330b and an upstream side wall 330c. Upper ends of the downstream side wall 330a and the upstream side wall 330c are connected by a ceiling wall 330b.

The nip plate 380 is fixed to the lower ends of the downstream side wall 330a and the upstream side wall 330c. Therefore, a space is formed inside the stay 330 in which all four sides are closed.

(halogen heater)
Halogen heaters 361 and 362 are arranged axially in a closed space inside the stay 330 . Both ends of the halogen heaters 361 and 362 are supported by both side plates of the fixing device 300 .

One halogen heater 361 has a heat generating portion h1 in the center in the axial direction as shown in FIG. The other halogen heater 362 (second heating element) is arranged upstream and adjacent to the one halogen heater 361 . The halogen heater 362 has heat generating portions h2 at both ends in the axial direction, and both width direction end portions of the fixing belt 310 are heated by radiant heat from the heat generating portions h2.

When small size paper P such as postcard size or A4 vertical size is passed through the fixing device, only the halogen heater 361 generates heat, and when large size paper P such as A3 size is passed , the halogen heaters 361 and 362 both generate heat. The heating regions of the halogen heaters 361 and 362 are provided with a width corresponding to the width L of the A3 size paper.

(reflective member)
A reflecting member (reflecting plate) 370 is arranged on the inner surface of the stay 330 . The reflecting member 370 has a partial shape of an ellipse in cross section, and the heating portion h1 of the halogen heater 361 is positioned at the focal point of the ellipse. The radiant heat radiated laterally and upward from the heat generating portion h1 of the halogen heater 361 is reflected by the reflecting member 370 and then radiated toward the upper surface of the nip plate 380 .

Both ends of the stay 330 and the reflecting member 370 in the axial direction are open toward the upstream side as shown in FIGS. 2A(b) and 2B(b). That is, inclined portions 330d that are inclined upstream as shown in FIG. 4A are provided at both ends of the stay 330 in the axial direction. The width of this inclined portion 330d can be the same width as that of the extension portion 380a described above.

A notch 330e cuts between the inclined portions 330d at both ends in the axial direction of the stay 330 and the upstream side wall 330c at the central portion in the axial direction. However, the ratio of the upstream side wall 330c to the total axial length of the stay 330 is considerably large. Therefore, the strength of the stay 330 against the pressing force of the pressure roller 320 can be sufficiently ensured, and the downsizing of the fixing device 300 can be easily accommodated. Note that the notch 330e may be closed with a wall to prevent heat escape.

Extended reflecting portions 370b are formed at both ends of the reflecting member 370 in the axial direction. A notch 370c cuts between the extended reflecting portion 370b and the central reflecting portion 370a in the central portion in the axial direction. The notch 370c may also be closed with a wall to prevent heat escape.

The extension reflecting portion 370b has the same width as the inclined portion 330d of the stay 330, and extends along the inner surface of the inclined portion 330d. The distal end of the extended reflecting portion 370b can be fixed to the distal end of the inclined portion 330d as required.

The radiation area of the halogen heater 362 is enlarged by the extended reflector 370b. That is, the upper surface of the nip plate 380 is directly irradiated with the radiant heat from the heat generating portions h2 at both ends in the axial direction of the halogen heater 362, and the radiant heat directed upward and upstream from the heat generating portions h2 is reflected by the extended reflecting portions 370b. , is projected onto the extension 380a.

(fixing operation)
In FIGS. 2A and 2B, when the paper P is passed through the fixing nip SN in the direction of the arrow, the paper P is heated at the fixing nip SN between the fixing belt 310 and the pressure roller 320, and the toner image is formed on the paper P. be established. At this time, the fixing belt 310 is heated by radiant heat from the halogen heaters 361 and 362 via the nip plate 380 . 2A and 2B differ only in the arrangement of the halogen heater 362. FIG.

As indicated by the dashed line in FIG. 3, the conventional fixing device tends to cause temperature drop near both ends of the paper width L, and sleep recovery time is prolonged in order to avoid fixing failure due to this temperature drop. In the embodiment of the present invention, as described above, the nip plate 380 is provided with extensions 380a at both ends, and the halogen heaters 362 heat the extensions 380a.

Therefore, the fixing belt 310 is preheated by the extension 380a before entering the fixing nip SN. By this preheating, as shown by the upward arrow in FIG. 3, the end heat distribution lifting effect can be obtained, and the time (sleep return time) for securing the temperature necessary for fixing in the paper passing area can be shortened.

The halogen heater 361 described above has a heat generating portion h1 in the center in the axial direction as shown in FIG. may be used. As a result, the watt density at both ends in the longitudinal direction of the halogen heaters 362 and 363 facing the extended portion 380a can be made higher than the watt density at the central portion in the longitudinal direction.

Here, the watt density is the power per unit surface, that is, the value obtained by dividing the heater power [W] by the heater surface area [cm ² ]. Watt density can be increased by increasing heater windings. By making the watt density at both ends of the halogen heaters 362 and 363 in the longitudinal direction higher than the watt density at the central part in the longitudinal direction, the heat distribution lifting effect at the ends can be ensured and the temperature rise at the ends can be accelerated. By doing so, the sleep return time can be further shortened.

As for the halogen heater, as shown in FIG. 7, it is also possible to use only one halogen heater 363 having a heat generating portion h3 that generates heat in the entire axial direction. That is, by preheating both ends of the fixing belt 310 by means of the extension part 380a as described above, even if only one halogen heater 363 is used, the end heat distribution lifting effect prevents the end temperature from dropping. Sleep recovery time can be shortened.

Next, modified embodiments 1 to 5 in which the type and position of the halogen heater used in the fixing device 300 are different will be described with reference to FIGS. 8A to 8E.
(Modified Embodiment 1)
FIG. 8A shows a modified embodiment 1. FIG. The halogen heater (first heating element) 363 used in this modified embodiment 1 is only one having a heat generating portion h3 that generates heat in the entire axial direction. Extension portions 380a (second heating portions) at both ends are extended upstream, and both longitudinal ends of the reflecting member (reflector) 370 are opened upstream so as to face the extension portions 380a, and the extension reflecting portions are heated. 370b. By doing so, both ends of the fixing belt 310 can be heated from the upstream side, and the temperature rise at the ends can be accelerated.

(Modified Embodiment 2)
FIG. 8B shows a modified embodiment 2. In this modified embodiment 2, in addition to the halogen heater 363 of FIG. are doing. The halogen heater 362 for end heating has heat generating portions h2 at both ends in the axial direction, and is arranged immediately upstream and adjacent to the halogen heater 363 for full width heating. By adding the halogen heater 362 for heating the end portion, the extension portion 380a of the nip plate 380 as the second heating portion can be heated more effectively, and the temperature rise of the end portion of the fixing belt 310 can be further accelerated. be able to.

(Modified Embodiment 3)
In the modified embodiment 2 of FIG. 8B, a halogen heater 363 that heats the entire width and a halogen heater 362 that heats only the ends are installed, but in the modified embodiment 3 of FIG. A halogen heater 361 having a heat generating portion h1 in the center in the axial direction is used. That is, it has a two-heater configuration of a halogen heater 361 for central heating and a halogen heater 362 for edge heating.

In this configuration as well, the extended portion 380a (second heating portion) of the nip plate 380 is extended upstream, and both longitudinal ends of the reflecting member (reflector) 370 are extended upstream so as to face the extended portion 380a. It is opened to form an extended reflecting portion 370b. By doing so, both ends of the fixing belt 310 can be heated from the upstream side, and the temperature rise at the ends can be accelerated.

(Modified Embodiment 4)
In the fourth modified embodiment shown in FIG. 8D, the halogen heater 362 for heating the end portion, which is installed in the second modified embodiment shown in FIG. 8B, is moved between the central portion of the reflecting member 370 in the conveying direction and the extended reflecting portion 370b. is. By moving the end heating halogen heater 362 upstream in the transport direction in this manner, the extension 380a of the nip plate 380 as the second heating portion can be heated more effectively, and the heating can be performed from further upstream. Both ends of the fixing belt 310 can be heated to speed up the temperature rise of the ends.

(Modified Embodiment 5)
The modified embodiment 5 of FIG. 8E uses a halogen heater 361 having a heating portion h1 in the center in the axial direction instead of the halogen heater 363 for full-width heating of the modified embodiment 4 of FIG. 8D. Also in this configuration, since the halogen heater 362 for heating the end portion is moved to the upstream side in the transport direction, the extension portion 380a as the second heating portion of the nip plate 380 can be heated more effectively. Both ends of the fixing belt 310 can be heated from upstream, and the temperature rise at the ends can be hastened.

(Modified Embodiment 6)
It should be noted that in the modified embodiments 1 to 5 described above, the inclined portion 330d of the stay 330 can be omitted. 9(a), cutout portions 330f are formed at both ends in the axial direction of the upstream side wall 330c of the stay 330, and from the cutout portions 330f, as shown in FIG. The extension reflecting portion 370b is projected outward.

Although the present invention has been specifically described above based on the embodiments, 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. Needless to say. For example, in the above embodiment, the fixing device provided with one or two halogen heaters 361, 362 (or 362, 363) has been described, but the number of halogen heaters to be used may of course be three or more. .

2: Image carrier 3: Drum cleaning device 3a: Cleaning blade 4: Charging device 5: Developing device 5a: Developer carrier 7: Exposure device 7a: Mirror 50: Paper feeding device 60: Paper feeding roller 100: Image forming Apparatus 250: Registration roller pair 300: Fixing device 310: Fixing belt (fixing member)
320: pressure roller (pressure member) 321: iron core metal 322: elastic layer 323: release layer 330: stay (support member) 330a: downstream side wall 330b: ceiling wall 330c: upstream side wall 330d: inclined portion 361 ~ 363: Halogen heater (heating element)
370: Reflecting member 370a: Central reflecting part 370b: Extension reflecting part 380: Nip plate (first heating part)
380a: Extension part (second heating part) 380b: Lubricant regulating part h1 to h3: Heat generating part L: Paper width Lb: Laser light N: Transfer nip P: Paper SN: Fixing nip TM: Transfer means

JP 2013-114057 A

Claims (3)

a rotatable endless fixing member;
a heating element longitudinally disposed inside the fixing member;
a nip plate arranged in the longitudinal direction in a state of sliding contact with the inner peripheral surface of the fixing member;
a support member that surrounds the heating element and supports the heating element;
a reflecting member disposed on the inner surface of the supporting member and reflecting heat generated by the heating element toward the nip plate;
A fixing device comprising: a pressure member arranged to face the nip plate and forming a fixing nip with the fixing member;
A heating portion located at an upstream end in the conveying direction of the fixing nip is provided at least on both ends of the nip plate in the longitudinal direction. Forming an extended reflecting part extending upstream with respect to the central part ,
A fixing device, wherein upstream side plate portions at both ends in the longitudinal direction of the support member are inclined upstream, and the extension reflecting portion is arranged inside the upstream side plate portions. 2. A fixing device according to claim 1 , wherein the watt density of both longitudinal ends of said heat generating element facing said extended reflecting portion of said nip plate is set higher than the watt density of a central portion of said heat generating element in the longitudinal direction. . An image forming apparatus comprising: a developing device for forming an image on a recording medium; and a fixing device according to claim 1 or 2 for fixing the image on the recording medium.

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