JP7447705B2 - Heating device, fixing device and image forming device - Google Patents

Description

The present invention relates to a heating device, a fixing device, and an image forming device, and more particularly to a heating device that adjusts the opening area of a cooling opening formed in a housing of the fixing device by opening and closing a shutter member, and a fixing device equipped with the heating device. The present invention relates to an apparatus and an image forming apparatus.

Various types of fixing devices are known for use in electrophotographic image forming apparatuses, and one of them is a surf fixing method that is excellent in energy saving and has a short warm-up time. In this surf fixing method, a thin fixing belt with a low heat capacity is contacted and heated from the inside with a planar heater, and a sheet member passing through a fixing nip is heated by the fixing belt to heat and fix an unfixed toner image carried on the sheet member.

When such a fixing device continuously prints small size paper, the temperature of the longitudinal end portion (non-sheet passing portion) of the fixing belt may rise excessively. If the edge temperature rises excessively, the durability of the fusing belt decreases, and when transitioning from printing on small-sized paper to large-sized paper, the edge temperature may rise excessively due to the excessive amount of fusing heat supplied to the edge. (high temperature) may cause problems such as offset or jams due to paper wrapping around the fixing belt.

Therefore, as in Patent Document 1 (Japanese Unexamined Patent Publication No. 2009-288275) and Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2017-44953), as a measure to suppress excessive temperature rise at the ends, both longitudinal ends of the fixing belt (non-passable) are proposed. The paper section) is cooled using a blower fan. The fixing devices of Patent Documents 1 and 2 are rack-and-pinion mechanisms in which shutter members are provided in openings formed at both ends of the device housing in the longitudinal direction, and the shutter members are provided in the center of the housing in the longitudinal direction. Adjust the cooling air volume by sliding in the longitudinal direction.

In the fixing devices of Patent Documents 1 and 2, when the temperature of the end portion of the fixing belt exceeds a high temperature threshold, the shutter member is fully opened to blow cooling air into the non-sheet passing portion of the fixing belt. For this reason, a phenomenon in which the cooling air wraps around to the end paper passing portion of the fixing belt and the temperature of the end paper passing portion becomes lower than the temperature of the central paper passing portion has become a problem. This is because if such a cooling air circulation phenomenon occurs, image defects will occur due to poor fixing. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a heating device that can prevent cooling air from flowing around the heating member.

In order to solve the above problem, the heating device of the present invention has a heating member and a pressure member that have a longitudinal direction and are in pressure contact with each other to form a nip, which are housed in a housing, and the housing crosses the longitudinal direction. In a heating device that has an inlet and an outlet facing each other in the direction, and transfers heat from the heating member to the sheet member by passing the sheet member conveyed from the inlet toward the outlet through the nip, the casing includes: a pair of openings opening toward both ends in the longitudinal direction of the heating member; and a pair of openings that are slidable in the longitudinal direction of the heating member, and closing the openings by moving toward the ends in the longitudinal direction. , a shutter member that opens the opening by moving toward the center in the longitudinal direction, and a cooling fan can blow cooling air from the opening toward the longitudinal end of the heating member; The shutter member is opened based on the detection results from a central temperature detection member that detects the temperature at the longitudinal center of the heating member and an end temperature detection member that detects the temperature at the longitudinal end of the heating member. temperature and the rotation speed of the blower fan are controlled by a control unit, and when the end temperature detection member detects a predetermined high temperature threshold, the control unit controls the blower fan to The heating member is characterized in that the number of rotations is increased and the shutter member is moved a predetermined length toward the longitudinal end of the heating member.

According to the present invention, it is possible to prevent cooling air from flowing around the heating member.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a principle diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a sectional view of a fixing device used in an image forming apparatus. In the fixing device according to the embodiment of the present invention, the shutter member is (a) a perspective view in an open state, (b) a perspective view in a closed state, and (c) a sectional view in a closed state. (a) and (b) are plan views of a heater connected in parallel to two electrodes at both ends. FIG. 3 is a plan view of a heater connected in parallel to three electrodes. FIG. 3 is a cross-sectional view showing the relationship between the position of the shutter member and the temperature distribution of the fixing belt. FIG. 3 is a cross-sectional view showing the relationship between the position of the shutter member and the temperature distribution of the fixing belt. FIG. 3 is a cross-sectional view showing the relationship between the position of a conventional shutter member and the temperature distribution of a fixing belt. FIG. 3 is a cross-sectional view of the shutter member in (a) position A and (b) position B; FIG. 6 is a diagram showing a change in the duty of the blower fan when moving the shutter member from position A to position B; It is a figure which shows the structure which controls a shutter member and the motor of a ventilation fan by a control part. FIG. 6A is a cross-sectional view similar to FIG. 6A using a shutter member having two upper and lower shutter members. It is a top view of the second shutter member. 6A is a cross-sectional view similar to FIG. 6A using a shutter member having a tip member. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 it goes without saying that the image forming apparatus is not limited to a laser printer. That is, the image forming apparatus can be configured as a copying machine, a facsimile machine, a printer, a printing press, and an inkjet recording apparatus, or as a multifunction device that combines at least two or more of these.

Note that the same or corresponding parts in each figure are denoted by the same reference numerals, and overlapping explanations thereof will be simplified or omitted as appropriate. In addition, the dimensions, materials, shapes, relative arrangement thereof, etc. in the description of each component are merely illustrative, and the scope of the present invention is not intended to be limited thereto unless specifically stated.

In the following embodiments, the sheet member (recording medium) will be described as a "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, and prepreg sheets in which carbon fibers are pre-impregnated with resin.

A medium to which a developer or ink can be attached, a recording paper, or a recording sheet are all included in the term "recording medium." In addition to plain paper, "paper" also includes cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like.

Furthermore, "image formation" used in the following description means not only adding images such as characters and figures to a medium, but also adding patterns such as patterns to the medium.

(Laser printer configuration)
FIG. 1A is a configuration diagram schematically showing the configuration of a color laser printer as an embodiment of an image forming apparatus 100 including a fixing device 300. Further, FIG. 1B illustrates the principle of the color laser printer in a simplified manner.

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

Each of the process units 1K, 1Y, 1M, and 1C has the same configuration except that it includes 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 descriptions of the other process units 1Y, 1M, and 1C will be omitted.

The process unit 1K includes an image carrier 2K (for example, a photosensitive drum), a drum cleaning device 3K, and a static eliminator. The process unit 1K further includes a charging device 4K as a charging device that uniformly charges the surface of the image carrier, and a developing device as a developing device that performs visible image processing of the electrostatic latent image formed on the image carrier. It has 5K etc. 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 the image forming apparatus 100. The exposure device 7 is configured to perform writing scanning according to image information, that is, to reflect laser light L from a laser diode on a mirror 7a and irradiate the image carrier 2K based on the image data.

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

The intermediate transfer belt 16 is configured to circulate around the primary transfer rollers 19K, 19Y, 19M, and 19C, the drive roller 18, and the driven roller 17. The secondary transfer roller 20 is disposed opposite to the drive roller 18 and in contact with the intermediate transfer belt 16 . Note that 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 combines those images.

Belt cleaning device 21 is installed downstream of secondary transfer roller 20 in the running direction of intermediate transfer belt 16 . Further, a cleaning backup roller is installed on the side opposite to the belt cleaning device 21 with respect to the intermediate transfer belt 16.

A paper feeding device 200 having a tray for stacking paper P is installed below the image forming apparatus 100. This paper feeding device 200 constitutes a recording medium supply section, and is capable of accommodating a large number of sheets P as recording media in a bundle, and includes a paper feeding roller 60 and a pair of rollers 210 as means for transporting the sheets P. It is unitized with.

The paper feeding device 200 can be inserted into and removed from the main body of the image forming apparatus 100 for purposes such as replenishing paper. The paper feed roller 60 and the roller pair 210 are arranged above the paper feed device 200 and are adapted to convey the uppermost sheet P of the paper feed device 200 toward the paper feed path 32.

The pair of registration rollers 250 serving as separation conveyance means are disposed immediately upstream of the secondary transfer roller 20 in the conveyance direction, and can temporarily stop the paper P fed from the paper feeding device 200. By this temporary stop, a slack is formed on the leading edge side of the paper P, and the skew of the paper P is corrected.

A registration sensor 31 is disposed immediately upstream of the pair of registration rollers 250 in the transport direction, and the registration sensor 31 detects passage of the leading edge of the paper. When a predetermined period of time has elapsed after the registration sensor 31 detects the passage of the leading edge of the paper, the paper abuts against the pair of registration rollers 250 and is temporarily stopped.

At the downstream end of the paper feeding device 200, a conveying roller 240 is provided to convey upwardly the sheet conveyed to the right side from the roller pair 210. As shown in FIG. 1A, the conveyance roller 240 conveys the paper toward the registration roller pair 250 above.

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 certain amount of torque is applied in the counter-feeding direction by a drive shaft via a torque limiter is brought into pressure contact with a feeding roller, and the paper is separated at the nip between the rollers. In the FR separation method, a separation roller (friction roller) supported by a fixed shaft is brought into pressure contact with a feeding roller via a torque limiter, and the paper is separated at the nip between the rollers.

In this embodiment, the roller pair 210 is constructed using an FRR separation method. That is, the roller pair 210 includes an upper feeding roller 220 that conveys the paper into the machine, and a lower separation roller 230 that is supplied with a driving force by a drive shaft in the opposite direction to the feeding roller 220 via a torque limiter. It is made up of.

The separation roller 230 is biased toward the feeding roller 220 by biasing means such as a spring. The paper feed roller 60 is configured to rotate counterclockwise in FIG. 1A by transmitting the driving force of the feed roller 220 via a clutch means.

The paper P, which has been abutted against the pair of registration rollers 250 and has a loose end, is moved between the secondary transfer roller 20 and the drive roller in accordance 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, on the fed paper P, the toner image formed on the intermediate transfer belt 16 is electrostatically transferred to a desired transfer position with high precision due to the bias applied at the secondary transfer nip. ing.

The post-transfer conveyance 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 conveyance path 33. The fixing device 300 includes a fixing belt 310 as a heating member containing a heat generating member, and a pressure roller 320 as a pressure member that rotates while contacting the fixing belt 310 with a predetermined pressure.

The post-fixing conveyance path 35 is disposed above the fixing device 300, and branches into a paper discharge path 36 and a reversal conveyance path 41 at the upper end of the post-fixing conveyance path 35. A switching member 42 is disposed at this branching portion, and the switching member 42 is configured to swing around a swing shaft 42a thereof. Further, a pair of paper discharge rollers 37 is arranged near the open end of the paper discharge path 36.

The reversing conveyance path 41 joins the paper feed path 32 at the other end on the opposite side to the branching portion. In the middle of the reversing conveyance path 41, a pair of reversing conveyance rollers 43 is disposed. The paper discharge tray 44 is installed at the upper part of the image forming apparatus 100 so as to form a concave shape toward the inside of the image forming apparatus 100 .

The 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 this embodiment requires a predetermined distance from the paper feed roller 60 to the secondary transfer roller 20 due to transfer paper conveyance. The powder container 10 is installed in the dead space created at this distance, thereby reducing the size of the entire laser printer.

The transfer cover 8 is installed on the top of the paper feeding device 200 and in front of the paper feeding device 200 in the drawing direction. By opening this transfer cover 8, the inside of the image forming apparatus 100 can be inspected. A manual paper feed roller 45 for manual paper feeding and a manual paper tray 46 for manual paper feeding are installed on the transfer cover 8.

(Principle of image forming device)
Next, a diagram of the principle of the image forming apparatus 100 described above will be explained with reference to FIG. 1B. The image forming apparatus 100 includes an image carrier 2 (for example, a photosensitive drum) and a drum cleaning device 3. Further, a charging device 4 as a charging means that uniformly charges the surface of the image carrier, a developing device 5 that performs visible image processing of an electrostatic latent image formed on the image carrier, and a lower part of the image carrier 2 are provided. It has a transfer means TM and a static eliminator, etc. arranged in the transfer unit TM.

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

A paper feeding device 200 having a tray for stacking paper P is installed below the image forming apparatus 100. This paper feeding device 200 is capable of accommodating a large number of sheets of paper P as a recording medium in the form of a bundle, and is integrated into a unit together with a paper feeding roller 60 as a means for conveying the paper P.

A pair of registration rollers 250 serving as separation and conveyance means are disposed downstream of the paper feed roller 60. The paper P fed from the paper feeding device 200 is temporarily stopped by a pair of registration rollers 250. By this temporary stop, a slack is formed on the leading edge side of the paper P, and the skew of the paper P is corrected.

The sheet P, which has been abutted against the pair of registration rollers 250 and has a loose end portion, is sent to the transfer nip N of the transfer means TM in synchronization with the timing at which the toner image on the image carrier 2 is suitably transferred. Then, the toner image on the image carrier 2 of the fed paper P is electrostatically transferred to a desired transfer position by a bias applied at the transfer nip N.

A fixing device 300 is disposed downstream of the transfer nip N. The fixing device 300 includes a fixing roller 310 that is heated by a heater, and a pressure roller 320 that rotates while contacting the fixing roller 310 with a predetermined pressure.

(Laser printer operation)
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 explained.

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

When the leading edge of the paper P sent out by the paper feed roller 60 and the pair of rollers 210 reaches the nip of the pair of registration rollers 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 determined, and the leading edge skew of the paper P is corrected.

In the case of manual paper feeding, a bundle of paper stacked on the manual paper tray 46 is passed through a part of the reversing conveyance path 41 one by one by the manual paper feed roller 45 starting from the topmost paper, and is passed through a part of the reversing conveyance path 41 by the manual paper feed roller 45 and passed through the nip between the pair of registration rollers 250. transported to. The subsequent operations are the same as those for feeding paper from the paper feeding device 200.

Here, the image forming operation will be explained for one process unit 1K, and the explanation for 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 exposure device 7 irradiates the surface of the image carrier 2K with laser light L based on the image data.

On the surface of the image carrier 2K irradiated with the laser beam L, the potential of the irradiated portion decreases, forming an electrostatic latent image. The developing device 5K has a developer carrier that carries a developer containing toner, and uses the unused black toner supplied from the toner bottle 6K via the developer carrier to form an electrostatic latent image. The image carrier 2K 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.

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 sent to a waste toner storage section in the process unit 1K and collected by the waste toner conveying means. Further, the charge eliminator removes the residual charge 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 the toner images of each color are transferred to the intermediate transfer belt 16 so as to overlap.

The intermediate transfer belt 16, onto which the toner images of each color have been transferred so as to overlap each other, travels to a secondary transfer nip between the secondary transfer roller 20 and the drive roller 18. On the other hand, the registration roller pair 250 rotates while sandwiching the sheet of paper abutted against it at a predetermined timing, and the toner images formed in the superimposed manner on the intermediate transfer belt 16 are suitably transferred. It is conveyed to the secondary transfer nip of the secondary transfer roller 20. In this way, the toner image on the intermediate transfer belt 16 is transferred onto the paper P sent out by the pair of registration rollers 250.

The paper P on which the toner image has been transferred is conveyed to the fixing device 300 through the post-transfer conveyance path 33 . Then, 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 to the paper P by heating and applying pressure. The paper P on which the toner image has been fixed is sent out from the fixing device 300 to the conveying path 35 after fixing.

At the timing when the paper P is sent out from the fixing device 300, the switching member 42 is in a position that opens the vicinity of the upper end of the post-fixing conveyance path 35, as shown by the solid line in FIG. 1A. Then, the paper P sent out from the fixing device 300 is sent out to the paper discharge path 36 via the post-fixing conveyance path 35. The pair of paper discharge rollers 37 sandwich the paper P sent to the paper discharge path 36 and are rotated to discharge the paper P to the paper discharge tray 44, thereby completing one-sided printing.

Next, the case of double-sided printing will be explained. As in the case of single-sided printing, the fixing device 300 sends out the paper P to the paper discharge path 36. When double-sided printing is performed, the paper ejection roller pair 37 transports a portion of the paper P to the outside of the image forming apparatus 100 by rotation.

Then, when the rear end of the paper P passes through the paper discharge path 36, the switching member 42 swings about the swing shaft 42a as shown by the dotted line in FIG. 1A, and closes the upper end of the post-fixing transport path 35. do. Almost at the same time as the upper end of the post-fixing conveyance path 35 is closed, the paper discharge roller pair 37 rotates in the opposite direction to the direction in which the paper P is conveyed out of the image forming apparatus 100, and sends out the paper P to the reversal conveyance path 41. .

The paper P sent out to the reversing conveyance path 41 passes through a pair of reversing conveyance rollers 43 and reaches a pair of registration rollers 250 . Then, the pair of registration rollers 250 achieves optimal 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 sends 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 sheet P when the sheet P passes through the secondary transfer nip. Then, the paper P onto which the toner image has been transferred is conveyed to the fixing device 300 through the post-transfer conveyance path 33 .

The fixing device 300 fixes the unfixed toner image on the back side of the paper P by sandwiching the transported paper P between the fixing belt 310 and the pressure roller 320 and applying heat and pressure. In this way, the paper P with the toner images fixed on both the front and back surfaces is sent out from the fixing device 300 to the post-fixing conveyance path 35.

At the timing when the paper P is sent out from the fixing device 300, the switching member 42 is in a position that opens the vicinity of the upper end of the post-fixing conveyance path 35, as shown by the solid line in FIG. 1A. Then, the paper P sent out from the fixing device 300 is sent out to the paper discharge path 36 via the fixing conveyance path. The paper discharge roller pair 37 pinches the paper P sent to the paper discharge path 36, is driven to rotate, and discharges the paper 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. Belt cleaning device 21 removes this residual toner from 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 is collected in the powder container 10.

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

The fixing device 300 may be of a type using a fixing belt 310 as shown in FIG. 2, or may be of a roller fixing type or a belt fixing type. In either fixing method, when heating and fixing a toner image formed on small-sized paper P, the heat of the heater is absorbed by the paper P in the area where the paper P passes, but the heat of the heater is absorbed in the area where the paper P does not pass. is not taken away by the paper P, so the temperature may rise excessively.

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

Further, the base of the fixing belt 310 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal base 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 outside of the elastic layer 322. 323. The elastic layer 322 is made of silicone rubber and has a thickness of, for example, 3.5 mm.

In order to improve mold releasability on the surface of the elastic layer 322, it is desirable to form a mold release layer 323 made of a fluororesin layer having a thickness of, for example, about 40 μm. A pressure roller 320 is pressed against the fixing belt 310 by a biasing means.

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 of the stay 350 are supported by both side plates of the fixing device 300. The stay 350 reliably receives the pressing force of the pressure roller 320 and stably forms the fixing nip SN.

The heater holder 340 is for holding the base material 341 of the heater 330 of the fixing device 300, and is supported by a stay 350. The heater holder 340 can preferably be formed of a heat-resistant resin with low thermal conductivity such as LCP, thereby reducing heat transfer to the heater holder 340 and efficiently heating the fixing belt 310.

The shape of the heater holder 340 is such that it supports only two locations near both ends of the base material 341 in the lateral direction in order to avoid contact with the high temperature portion of the base material 341. Thereby, the amount of heat flowing to the heater holder 340 can be further reduced, and the fixing belt 310 can be efficiently heated.

A thermistor TH1 serving as a central temperature detection member for detecting the temperature of a resistance member 370 of a heater 330, which will be described later, is disposed on the back surface of the base material 341. Thermistor TH1 is pressed against the back surface of base material 341 by spring 387, thereby making it possible to accurately detect the temperature of resistance member 370.

Further, the temperature of the inner surface of the fixing belt 310 on the downstream side of the fixing nip SN is configured to be detected by a thermistor TH2 as a central temperature detecting member and a thermistor TH3 as an end temperature detecting member. One thermistor TH2 is disposed at the center in the longitudinal direction of the heater 330 like the thermistor TH1, as shown in FIG. 6A. The other thermistor TH3 is disposed at the longitudinal end of the heater 330 (non-sheet passing section).

Thermistors TH1 and TH2 are arranged at the center in the width direction of the small size paper. Further, the thermistor TH3 is arranged in a non-paper passing portion outside the large size paper in the width direction. Based on the temperature information from the thermistors TH1 to TH3, the power supplied to the resistance member 370 and the drive mechanism (motor M1) of the shutter member 307 are controlled, as will be described later with reference to FIG. The rise can be effectively suppressed.

The thermistors TH1 to TH3 can also be replaced by thermistors disposed opposite to the outer peripheral surface of the pressure roller 320. By arranging the thermistor on the pressure roller 320 side outside the fixing belt 310, maintenance of the thermistor becomes easy. Note that the fixing device 300 can be of various types, and the fixing device shown in FIG. 2 described above is only one example.

(Fusing device housing)
Next, the structure of the casing 301 of the fixing device 300 according to the embodiment of the present invention will be described with reference to FIGS. 3(a) to 3(c). In this fixing device 300, the fixing belt 310 as a heating member and the pressure roller 320 as a pressure member are housed in a housing (cover) for insulation and heat retention as shown in FIGS. 3(a) to 3(c). It is housed in 301.

The shape of the casing 301 is a compact cross-sectional shape with two circular arcs facing each other in the horizontal direction so that there is no wasted space outside the fixing belt 310 and pressure roller 320 housed inside. An inlet 302 and an outlet 303 are formed in the upper and lower planar parts of the casing 301.

The inlet 302 and the outlet 303 face each other in a direction (in the vertical direction in FIG. 3) that traverses the longitudinal direction of the fixing belt 310 (in the axial direction perpendicular to the paper surface in FIG. 3). A sheet carrying a toner image enters through an entrance 302, passes through a fixing nip SN, and exits through an exit 303.

As shown in FIG. 3, a rectangular opening 304 is formed from half the height of one arcuate side surface of the housing 301 to the upper end. A pair of openings 304 are formed at both ends of the housing 301 in the longitudinal direction, and open toward both ends (non-sheet passing portion) of the fixing belt 310 in the longitudinal direction.

A blower fan 520 is disposed outside the opening 304 as described later. This blower fan 520 supplies cooling air to the opening 304. By combining the rotational speed of the blower fan 520 and the opening degree of the shutter member 307, it is possible to efficiently suppress the temperature rise in the non-sheet passing portion of the fixing belt 310.

(Shutter member)
As shown in FIGS. 3A and 3B, the amount of cooling air supplied can be adjusted by adjusting the opening degree of a pair of left and right shutter members 307 provided outside the opening 304. The shutter member 307 has a curved shape so as to cover the fixing belt 310.

In this embodiment, the shutter member 307 has an overall curved shape with the center of curvature at the rotation center position of the fixing belt 310, but the shutter member 307 may have a partially linear shape or a partially curved shape. May contain. By adopting such a curved shape, it is possible to enhance the heat retention effect of the fixing belt 310 by the shutter member 307 and to downsize the entire image forming apparatus.

3(a) shows a state in which the shutter member 307 is open, and FIG. 3(b) shows a state in which the shutter member 307 is closed. Further, FIG. 3(c) is a cross-sectional view of the shutter member 307 in a closed state. A pinion 308 is disposed at the center in the longitudinal direction of the housing 301, and the pinion 308 is driven by a motor.

A pair of left and right shutter members 307 are arranged to be slidable in the longitudinal direction of the housing of the fixing device 300, and a pinion 308 is engaged with a rack 307a extending from the shutter members 307 toward the center in the longitudinal direction. As the pinion 308 rotates, the left and right shutter members 307 approach and move away from each other, thereby opening and closing the opening 304.

The shutter member 307 can be a press-molded product of heat-resistant sheet metal. By making the shutter member 307 a press-molded product, the dimensional accuracy of the shutter member can be improved.

A heat insulating member (insulating member) such as felt or sponge may be attached to the inner surface of the shutter member 307 to improve heat insulating properties. Further, even when the shutter member 307 is made of heat-resistant resin, a heat retaining member (insulating member) can be attached to the back surface thereof.

Specifically, as shown in FIG. 3C, the area of the opening 304 is an area extending from the center of the arc-shaped side surface of the housing 301 in the height direction to the ceiling of the housing 301 in the height direction. Further, in the longitudinal direction of the housing 301, as shown in FIG.

Therefore, the opening 304 opens obliquely upward as shown in FIGS. 3(a) and 3(c). Although almost the entire opening 304 is visible when viewed from directly above the housing 301, it is not visible from directly below the housing 301. By opening upward or diagonally upward, excess heat that causes excessive temperature rise at the end of the fixing belt 310 can be efficiently discharged from the opening 304 to the outside of the housing 301 .

Even if the shutter member 307 is only opened half-open or fully open, the opening 304 can upwardly dissipate excess heat that causes excessive temperature rise at the end of the fixing belt 310. In this embodiment, in order to enhance the cooling effect of the end portion of the fixing belt 310, a blower fan 520 is disposed outside the shutter member 307 as shown in FIG. 6A.

By forcibly blowing cooling air into the housing 301 toward the end of the fixing belt 310 by the blower fan 520, the end of the fixing belt 310 is effectively cooled and excessive temperature rise at the end is suppressed. be able to. The air blown into the housing 301 is heated by the end of the fixing belt 310 and naturally exhausted upward.

The warm air exhausted upward in this way can be effectively used to prevent dew condensation from forming on the branch portion. That is, as shown in FIG. 1A, by arranging the switching member 42 above the fixing device 300, which branches into the paper reversing conveyance path 41 during double-sided printing, condensation can be prevented from adhering to the switching member 42. Can be done. In order to effectively prevent dew condensation from forming, it is preferable to arrange the switching member 42 vertically above the opening 304.

Conventionally, in order to deal with dew condensation on the paper conveyance path, the image forming apparatus has been idled (warmed up) until the dew condensation has disappeared, or an independent fan has been installed to eliminate the condensation. The former has the problem of long waiting time before printing, and the latter has the problem of complicating the mechanism due to the fan, increasing the size and cost of the device. By effectively utilizing the waste heat from the end of the fixing belt 310 and actively sending it to the dew condensation section, the above-mentioned problem can be solved.

(heater)
The fixing device 300 described above includes a heater 330 held in a heater holder 340 as shown in FIG. This heater 330 has a resistance member 370 formed of a resistance heating element (planar heater) on a base material 341. The resistance member 370 can be formed in a plurality of types, like a heater 330, an example of which is shown in FIGS. 4(a) and 4(b), which will be described later.

In either type, the resistance member 370 is formed on a base material 341 made of an elongated metal thin plate member coated with an insulating material. In the fixing method in which the fixing nip SN is heated by a planar heater, multiple types of paper widths can be uniformly heated by dividing the resistance member, which is a heating element, into a plurality of parts in the paper width direction and individually controlling the heating.

The material for the base material 341 is preferably low-cost aluminum, stainless steel, or the like. The base material 341 is not limited to metal, but may also be made of ceramic such as alumina or aluminum nitride, or non-metallic material with excellent heat resistance and insulation such as glass or mica.

In order to improve the thermal uniformity of the heater 330 and improve the image quality, the base material 341 may be made of a material with high thermal conductivity such as copper, graphite, and graphene. In this embodiment, an alumina base material having a transverse width of 8 mm, a longitudinal width of 270 mm, and a thickness of 1.0 mm is used.

As shown in FIGS. 4(a) and 4(b), the heater 330 can be constructed of a multi-type heater in which resistance heating elements 371 to 378 are electrically connected in parallel. The heater 330 has two electrodes 370c and 370d, and assuming that the resistance value between the electrodes 370c and 370d at both ends is 10Ω, the resistance value of each heating element 371 to 378 is as large as 80Ω because of the parallel connection.

PTC elements can be used for the resistance heating elements 371 to 378. The PTC element is made of a material having a positive temperature resistance coefficient, and has a characteristic that the resistance value increases as the temperature T increases (the current I decreases and the heater output decreases). The temperature coefficient of resistance (TCR) can be, for example, 1500 PPM (parts per million).

The heating elements 371 to 378 in FIGS. 4(a) and 4(b) are arranged linearly and at equal intervals in the longitudinal direction of the base material 341. Conductors 370a and 370b with small resistance values are arranged in a straight line parallel to each other on both sides of each heating element 371 to 378 in the transverse direction, and both ends of each heating element 371 to 378 are connected to these conductors 370a and 370b. There is. Then, AC power is supplied to electrodes 370c and 370d formed at one end of each of the conductors 370a and 370b.

The heating elements 371 to 378 and the conductors 370a and 370b are covered with a thin insulating layer 385. This insulating layer 385 can be made of heat-resistant glass with a thickness of 75 μm, for example. The insulating layer 385 insulates and protects the heating elements 371 to 378 and the conductors 370a and 370b, and maintains sliding performance with the fixing belt 310.

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

In addition to the materials described above, the heating elements 371 to 378 may be made of a resistive material such as silver alloy (AgPt) or ruthenium oxide (RuO ₂ ). The conductors 370a, 370b and the electrodes 370c, 370d can be made of silver (Ag) or silver palladium (AgPd) by screen printing or the like.

The insulating layer 385 side of the heating elements 371 to 378 contacts the fixing belt 310 and heats it, raising the temperature of the fixing belt 310 by heat transfer, thereby heating and fixing the unfixed image conveyed to the fixing nip SN. When PTC elements are used as the heating elements 371 to 378, when the temperature of the heating element in the non-paper passing area increases due to passing small size paper, the heat generation amount of the PTC element decreases due to its temperature resistance dependence. Temperature rise can be suppressed.

Due to this feature, for example, when printing on paper that is narrower than the entire width of the heating elements 371 to 378 (for example, within the width of the heating elements 373 to 376), the heating elements 371, 372, 377, and 378 outside the paper width apply heat to the paper. Since it is not taken away, the temperature rises. Then, the resistance values of the heating elements 371, 372, 377, and 378 by the PTC elements increase.

Since the voltage applied to the heating elements 371 to 378 is constant, the output of the heating elements 371, 372, 377, and 378 outside the paper width is relatively reduced, and the rise in temperature at the edge portion is suppressed. When the heating elements 371 to 378 are electrically connected in series, there is no other way than reducing the printing speed to suppress the temperature rise of the heating elements 371, 372, 377, and 378 outside the paper width during continuous printing. do not have. By electrically connecting the heating elements 371 to 378 in parallel, it is possible to suppress the temperature rise in the non-paper passing area while maintaining the printing speed.

If there is a gap between the heating elements 371 to 378 that continues in the lateral direction, the amount of heat generated decreases in the gap, which tends to cause fixing unevenness. Therefore, in FIGS. 4(a) and 4(b), the ends of the heating elements 371 to 378 are overlapped with each other in the longitudinal direction.

In FIG. 4(a), stepped portions formed by L-shaped notches are formed at the ends of the heating elements 371 to 378, and the stepped portions are overlapped with the stepped portions of the adjacent element ends. In FIG. 4(b), inclined portions formed by diagonal notches are formed at the ends of the heating elements 371 to 378, and the inclined portions are overlapped with the inclined portions of the adjacent element ends. By causing the ends of the heating elements 371 to 378 to overlap with each other in this manner, it is possible to suppress the effect of a reduction in the amount of heat generated in the gaps between the elements.

Further, the electrodes 370c and 370d can be arranged at both ends of the heating elements 371-378, or on one side of the heating elements 371-378. By arranging the electrodes 370c and 370d on one side in this way, it is possible to save space in the longitudinal direction. Each of the heating elements 371 to 378 in FIGS. 4(a) and 4(b) is composed of a rectangular planar heating element, but in order to obtain the desired output (resistance value), the line width is made thinner and a serpentine shape is formed. It can also be constructed by electrically connecting a plurality of heating elements formed in parallel in parallel.

(Modified example of heater)
Next, a modified example of the heater 330 is shown in FIG. The heater 330 of this modification has three electrodes 370h, 370i, and 370j arranged at both ends of the base material 341, and seven heating elements 371 to 377 arranged between the electrodes in the longitudinal direction of the base material 341. . The following three heat generation patterns are selectable.
Heat generation pattern 1: Only central heating elements 372 to 376 generate heat (small size A4 paper heated)
Heat generation pattern 2: All heating elements 371 to 377 generate heat (large size A3 paper heating)
Heat generation pattern 3: Only the edge heating elements 371 and 377 generate heat (prevents edge temperature drop when heating A3 paper)

Five heating elements 372 to 376 at the center in the longitudinal direction of the heater 330 are connected in parallel to a first electrode 370h and a second electrode 370i via conductors 370e and 370f having a lower resistance than the heating elements. Further, two resistance heating elements 371 and 377 at both ends in the longitudinal direction are connected in parallel to a second electrode 370i and a third electrode 370j via conductors 370f and 370g having a lower resistance than the heating elements 371 and 377. .

The second electrode 370i on the right side is always connected to the AC power source, and the first electrode 370h and the third electrode 370j on the left side are selectively connected to the AC power source by switching a switch. Thereby, the three heat generation patterns 1 to 3 described above can be selected.

In the heater 330 in which three heating patterns can be selected, for example, the longitudinal length of the five successive heating elements 372 to 376 in the longitudinal center of the heater 330 is A4 width, and the total seven heating elements including both ends are Make the longitudinal length of 371 to 377 the same as A3 size. By appropriately controlling the heating states of the heating elements 371 to 377, A4 size and A3 size paper can be heated uniformly.

For heating control of the heating elements 371 to 377, a control method is generally used in which an appropriate amount of heat is obtained by varying the lighting time (lighting duty) of the heating elements within a predetermined control time. The lighting duty is adjusted by controlling the phase of the AC power source using a triac as a control means. When the duty ratio is 0%, the current is zero, and when the duty ratio is 100%, the current is maximum.

(Opening degree of shutter member)
FIG. 6A is a cross-sectional view when the shutter member 307 is moved a predetermined distance toward the longitudinal end of the fixing belt 310 when the thermistor TH3 detects a predetermined high temperature threshold. The high temperature threshold is, for example, 180°C. The detection information of the thermistor TH3 is input to the control unit 400, which will be described later with reference to FIG. 7C, and the rotation speed of the blower fan 520 is increased compared to before the detection of the high temperature threshold value, and at the same time, the shutter member 307 is moved outside the paper passing width of the paper P. Deploy.

As shown in FIG. 6B, the "predetermined length" by which the shutter member 307 is moved is preferably within 50% of the distance to the peak position of the end temperature distribution of the fixing belt 310. That is, starting from the end in the width direction perpendicular to the conveying direction of the paper P (direction perpendicular to the paper surface of FIG. 6B), the temperature distribution at the end of the fixing belt 310 reaches the peak position toward the end in the longitudinal direction of the fixing belt 310. Set the distance to 100%.

In this case, it is preferable to set less than half (50%) of the distance as the limit at which the tip end 307b of the shutter member 307 moves toward the end in the longitudinal direction. If the tip portion 307b of the shutter member 307 is moved by more than 50%, the cooling air from the blower fan 520 is throttled by the shutter member 307, making it difficult to suppress excessive temperature rise at the end portion.

In the case of FIG. 6A, compared to the conventional case of FIG. 6C, the amount of air flowing into the non-sheet passing area is reduced due to the influence of the shutter member 307 (diaphragm effect). Therefore, in order to compensate for the throttling effect, the blower fan 520 is driven at high rotation speed and high output. By doing so, it is possible to prevent an excessive temperature rise at the end portion and also to prevent a temperature drop due to wraparound (a drop in the temperature distribution in FIG. 6C) due to the aperture effect of the shutter member 307.

The shutter member 307 need not always move to the same position in FIG. 6A when thermistor TH3 senses a predetermined high temperature threshold. Depending on the number of sheets passed and the continuous operation time of the machine, it may be slid a predetermined distance from the position shown in FIG. 6A in the opening direction or the closing direction. By appropriately moving in this way, it is possible to further suppress the rise in temperature at the end and achieve high productivity of the machine.

For example, the position of the shutter member 307 is shifted inward (in the opening direction) depending on the temperature detected by the thermistor TH3 provided in the non-paper passing portion or the continuous operating time from the start of paper passing. By doing so, it is possible to increase the amount of air from the blower fan 520 that hits the paper non-passing portions at both ends of the fixing belt 310, and to suppress a decrease in the number of printed sheets (a decrease in productivity).

That is, as shown in FIG. 6B, in the initial stage of paper passing, the shutter member 307 is moved to a position 50% of the peak position where the temperature rises, thereby preventing a drop in temperature within the paper passing area. However, when the temperature in the end region increases, the shutter member 307 is moved inward (in the opening direction) to blow air over a wider area, thereby suppressing the temperature rise in the non-sheet passing portions at both ends.

At this time, when the shutter member 307 is in position A as shown in FIG. 7A(a), the blower fan 520 is used at the maximum air volume (duty: 100%) as shown in FIG. 7B. However, depending on the temperature detected by the thermistor TH3 or the continuous operating time of the machine, the shutter member 307 is moved to position B as shown in FIG. 7A(b), and at the same time, control is performed to suppress the air volume of the blower fan 520 as shown in FIG. 7B. (Duty: 80%) may be performed.

When the shutter member 307 moves in the opening direction, cooling air may flow around the edges of the paper, causing a decrease in temperature in the paper passing area. Therefore, the air volume may be temporarily suppressed at a duty of 80% to prevent a temperature drop, and then control may be performed to maximize the air volume (duty of 100%) to prevent a further temperature rise.

(control unit)
FIG. 7C shows a control system for the motor M1 that drives the shutter member 307 to open and close and the motor M2 that rotates the blower fan 520. The two motors M1, M2 are controlled by a control section 400 of the machine. The detection information of the three thermistors TH1 to TH3 described above is input to the control unit 400. Then, the motors M1 and M2 are controlled so that excessive temperature rise at the end of the fixing belt 310 does not occur. Further, the temperature of the heater 330 or the fixing belt 310 is controlled by the control unit 400 to a fixing target temperature (for example, 170° C.).

The speed of the motor M1 that drives the shutter member 307 to open and close can be increased as appropriate depending on the degree of deviation of the temperature detected by the thermistor TH3 from the end high temperature threshold of the fixing belt 310. Thereby, the shutter member 307 can be opened and closed quickly to effectively suppress excessive temperature rise at the end and cooling air circulation. Further, the rotational speed of the motor M2 that rotates the blower fan 520 may be similarly increased as appropriate, thereby effectively suppressing excessive temperature rise at the end portions and cooling air circulation. Further, the rotation speed or duty of the motor M2 that rotates the blower fan 520 may be continuously increased or decreased in inverse proportion to the opening degree of the shutter member 307.

(Two-piece shutter member)
If the shutter member 307 is in position A in FIG. 7A(a), the outer region (ventilation inlet region) of the shutter member 307 is narrow, and the non-sheet passing region of the fixing belt 310 may not be sufficiently cooled. Therefore, as shown in FIG. 8A, a two-piece structure is used, including an upper (outer) shutter member 307-1 and a lower (inner) shutter member 307-2. In FIG. 8A, the shutter member 307-2 is at position A in FIG. 7A(a), and the distal end portion 307-1b of the shutter member 307-1 is slightly retreated from position A in the opening direction (to the left).

The lower (inner) shutter member 307-2 has a slit S as a notch through which the air from the blower fan 520 can pass, as shown in FIG. 8B. Note that the slit S portion only needs to be able to pass the air from the blower fan 520, and can be changed to another shape that allows ventilation, such as a louver shape.

In this way, by providing the second shutter member 307-2 with the slit S, the flow of cooling air to the end sheet passing area of the fixing belt 310 increases, thereby suppressing the temperature drop in the end sheet passing area. The effectiveness of this decreases. However, since the amount of air hitting the non-sheet passing area increases through the slit S, it is possible to more effectively prevent the temperature rise in the non-sheet passing area.

Note that the two shutter members 307-1 and 307-2 can be configured to be slidable independently of each other. Then, the shutter members 307-1 and 307-2 are slid and arranged at a predetermined ratio according to the paper size.

However, as the continuous operating time of the machine passes, the cooling area may be increased or decreased by moving the first shutter member 307-1. Then, after a certain period of time has passed and the temperature within the paper passing area stops dropping, the second shutter member 307-2 remains in the position shown in FIG. 8A, and only the first shutter member 307-1 slides in the opening direction. However, it is desirable to increase the amount of air that hits the paper passing area at the end of the fixing belt 310.

Alternatively, as shown in FIG. 8C, the second shutter member 307-2 may be eliminated and a tip member 307-3 having a plurality of slits S may be fixed to the tip of the first shutter member 307-1. Unlike the two-piece shutter members 307-1 and 307-2, the movable area of one shutter member 307-1 is reduced and the cooling efficiency is reduced; however, only one driving member is required for the shutter member 307-1. Cost can be reduced.

Although the present invention has been described above based on the embodiments, it goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the technical idea described in the claims. . For example, in the embodiment described above, the blower fan 520 is arranged outside the shutter member 307, but the blower fan 520 may be arranged as a suction fan in an exhaust duct connected to the opening 304 on the upper surface of the housing 301. . When the air inside the housing 301 is sucked and exhausted by the suction fan, the outside air sucked in from the horizontal and lateral directions of the opening 304 cools the non-paper passing portions at both ends of the fixing belt 310 . The shutter member 307 adjusts the intake amount or intake range of the intake outside air.

Furthermore, although the shutter member 307 is arranged so as to be openable and closable outside the opening 304, it is also possible to arrange the shutter member 307 to be openable and closable inside the opening 304. Further, in the embodiment described above, the fixing belt 310 is used as the heating member, but instead of the fixing belt 310, it is also possible to use a fixing roller having an internal heating source.

In addition to being used in the fixing device 300 described above, the heating device of the present invention can also be used in a paper drying device of an inkjet printer. Further, as the heating element for heating the fixing belt 310, in addition to the heater 330 using a PTC element, other heating elements such as a ceramic heater can also be used.

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: Registration sensor 32: Paper feed path 33: Post-transfer transport path 35: Post-fixing transport path 36: Paper discharge path 37: Paper discharge roller pair 41: Reversing conveyance path 42: Switching member 42a: Swing shaft 43: Reverse conveyance roller pair 44: Paper discharge tray 45: Paper feed roller 46: Tray 60: Paper feed roller 100: Image forming apparatus 200: Paper Feeding device 210: Roller pair 220: Feeding roller 230: Separation roller 240: Conveying roller 250: Registration roller pair 300: Fixing device 310: Fixing belt 301: Housing (cover) 302: Entrance 303: Exit 304: Opening 307: Shutter member 307-1: First shutter member 307-2: Second shutter member 307-3: Tip member 307a: Rack 308: Pinion 320: Pressure roller 321: Core bar 322: Elastic layer 323: Separation Mold layer 330: Resistance member 334: Pressure belt 340: Heater holder 341: Base material 350: Stay 352: Stay 351: Auxiliary stay 370: Resistance member 370a, 370b: Conductor 370c, 370d: Electrodes 370e to 370g: Conductor 370h: No. 1 electrode 370i: Second electrode 370j: Third electrode 371 to 378: Resistance heating element 385: Insulating layer 387: Spring 400: Control unit 520: Blower fan L: Laser light N: Transfer nip P: Paper (sheet) Element)
SN: Fixing nip TH1 to TH3: Thermistor TM: Transfer section

JP2009-288275A JP 2017-44953 Publication

Claims (10)

A heating member and a pressure member having a longitudinal direction and press against each other to form a nip are housed in a housing, the housing has an inlet and an outlet facing each other in a direction transverse to the longitudinal direction, and the housing has an inlet and an outlet facing each other in a direction transverse to the longitudinal direction, and a In a heating device that transfers heat from the heating member to the sheet member conveyed toward the exit by passing the sheet member through the nip,
The casing has a pair of openings that are open toward both ends in the longitudinal direction of the heating member, and is slidable in the longitudinal direction of the heating member, and is configured to open the openings by moving toward the ends in the longitudinal direction. a shutter member that closes the opening and opens the opening by moving toward the center in the longitudinal direction;
A blower fan can blow cooling air from the opening toward the longitudinal end of the heating member,
The shutter member is opened based on the detection results from a central temperature detection member that detects the temperature at the longitudinal center of the heating member and an end temperature detection member that detects the temperature at the longitudinal end of the heating member. degree and the rotation speed of the blower fan are controlled by a control unit,
When the end temperature detection member detects a predetermined high temperature threshold, the control unit increases the rotation speed of the blower fan compared to before the detection of the high temperature threshold, and controls the shutter member to rotate the heating member. A heating device characterized in that it moves a predetermined length toward an end in a longitudinal direction. The limit for moving the shutter member a predetermined length toward the longitudinal end of the heating member is determined by starting from the end in the width direction perpendicular to the conveyance direction of the sheet member and moving toward the longitudinal end of the heating member. 2. The heating device according to claim 1, wherein the distance is within 50% of the distance to the peak position of the end temperature distribution of the heating member. The heating device according to claim 1 or 2, wherein the control unit adjusts the opening degree of the shutter member in accordance with a detection result of the end temperature detection member or in accordance with a continuous operating time of the heating device. . 4. The heating device according to claim 1, wherein the rotational speed of the blower fan increases or decreases in inverse proportion to the opening degree of the shutter member. When the end temperature detection member no longer detects the high temperature threshold, the shutter member is moved a predetermined length toward the center in the longitudinal direction of the heating member, and the rotation speed of the blower fan is reduced. The heating device according to any one of claims 1 to 4. 6. The heating device according to claim 5, wherein when the temperature detected by the end temperature detection member increases, the number of revolutions of the blower fan is increased. 7. The heating device according to claim 1, wherein the shutter member has a plurality of notches through which a portion of the cooling air can pass. The shutter member includes a first shutter member without the plurality of notches and a second shutter member with the plurality of notches, and the end temperature detection member detects a predetermined high temperature threshold. 8. The heating device according to claim 7, wherein the first shutter member and the second shutter member move toward the longitudinal ends of the heating member at a predetermined ratio. A fixing device comprising the heating device according to claim 1, wherein the toner image carried on the sheet member is heated and fixed by passing the toner image carried on the sheet member through the nip. An image forming apparatus comprising the fixing device according to claim 9.

Images