JP5609676B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes a toner image on a recording material at a nip formed by a fixing member and a pressure member, and an image forming apparatus including the fixing device.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, a latent image corresponding to an original is formed on a photosensitive member, and toner is applied to the latent image. Then, the visualized toner image is transferred onto the recording paper, and then the toner image transferred onto the recording paper is fixed and discharged.

  As a fixing device for fixing a toner image in this manner, a recording sheet onto which a toner image is transferred is sandwiched between a fixing roller having a built-in halogen heater and a pressure roller that presses the fixing roller. There is a fixing device of a heat roller fixing system that heats and pressurizes while conveying, and such a fixing device is widely used because of its simple configuration.

  In addition, an endless fixing belt is stretched between a heating roller having a halogen heater and the like and a fixing roller, and has a pressure roller that presses the fixing roller through the fixing belt. There is a belt-fixing type fixing device that heats and pressurizes while sandwiching and transporting the recording paper onto which the toner image is transferred at the nip formed by the above-mentioned fixing device, and since the fixing belt has a small heat capacity, This has the advantage of shortening the warm-up time and saving energy.

  Here, since the toner of the toner image on the recording paper is heated when passing through the nip portion, the toner has adhesive force, and the recording paper passing through the nip portion adheres to the surface of the fixing roller or the fixing belt. There is a risk of jamming due to wrapping and separation. In particular, when a small amount of paper (thin paper), especially a coated paper for printing with a small amount of paper is used as the recording paper, the separation performance is further deteriorated.

  On the other hand, the speed of image forming apparatuses is increasing, and if the fixing roller is made large to ensure a sufficiently long nip width, the roller curvature at the fixing nip outlet becomes small, so the separation performance Decreases.

  In order to make it easier to separate the recording paper from the fixing member, a heat-resistant resin having high releasability is used on the surface of the fixing member, a release agent such as silicone oil is applied, or the toner is melted by heating in the toner. Various measures have been taken, such as the inclusion of waxes that function as However, there are an increasing number of factors that decrease the separation performance, such as the image formation on the coated paper described above and the increase in the toner adhesive force due to the increase in the toner amount due to the addition of the toners of a plurality of colors forming the color image. Separation means for separating is essential.

  Separation means is provided with a separation claw coated with fluororesin having good releasability on the paper discharge side of the recording paper with respect to the nip portion, and its tip is brought into contact with the outer surface of the fixing roller or fixing belt, and the recording paper is There is a method of separating from a fixing roller or the like.

  However, since the tip of the separation claw is in contact with the surface of the fixing roller or the like, the surface layer formed of a fluororesin or the like covering the surface of the fixing roller or the like is rubbed and the wrinkle is also transferred to the image. There is a problem of end. In particular, in the case of a color image, since a glossy image is required, it tends to be noticeable.

  In order to cope with such a problem, a technique has been developed in which air is blown to the outlet side of the nip portion to separate the recording paper from a fixing roller or the like.

  As an example of this, there is known a fixing device that separates recording paper from a fixing roller by jetting compressed air generated by a compressor into a nip portion in a pulse shape (see Patent Document 1).

  In addition, a fixing device is known in which a separation claw is provided and air blown by a fan is blown to a nip portion to separate a recording sheet from a fixing roller (see Patent Document 2).

JP 2005-202033 A Japanese Utility Model Publication No. 63-140571

  As described above, for separating the recording paper, the compressed air generated by the compressor is discharged from the air nozzle, and the air blown by the fan is discharged from the air duct. At this time, it is desirable that the air nozzle and the air duct be as close to the nip as possible. Thereby, the air volume and wind speed of the air to discharge can be reduced, As a result, the ventilation source connected to an air nozzle or an air duct can be reduced in size.

On the other hand, recording sheets that can be fed are defined in the image forming apparatus and are described in an instruction manual or the like. Nevertheless, when the user uses non-standard recording paper, for example, thin paper of 60 g / m ² or less, if the separation is not reliably performed after fixing, the leading edge of the recording paper contacts the leading edge of an air nozzle or the like. Jam may occur on contact. If the jammed recording paper is caught in a narrow gap between the fixing belt or the fixing roller and the air nozzle, it is difficult to remove the recording paper. Even if the recording paper can be pulled out, the recording paper bent by the jam passes through a narrow gap between the fixing belt and the air nozzle, so that the surface of the fixing belt and the like may be wrinkled by the recording paper. .

  The present invention has been made in view of such problems, and relates to a fixing device that discharges air from an air nozzle or the like and sprays the recording material that has passed through a nip portion to separate the recording material from a fixing member such as a fixing belt. As described above, even if a jam occurs and the recording material is caught in the gap between the fixing member and the air nozzle, the surface of the fixing member is not wrinkled, and the recording material can be easily pulled out. It is an object of the invention to propose a fixing device and an image forming apparatus provided with the fixing member.

  The above object is achieved by the invention described below.

1. In a fixing device that fixes a toner image on a recording material at a nip formed by a heated fixing member and a pressure member that pressurizes the fixing member.
An air discharge means for discharging air to spray the recording material and separating the recording material from the fixing member;
The fixing device according to claim 1, wherein the air discharge unit includes a tubular member that circulates air and discharges the air from a discharge port, and the vicinity of the discharge port of the tubular member is formed of an elastic body.

  2. 2. The fixing device according to claim 1, wherein the air discharge unit discharges compressed air generated by a compressor, and the tubular member is an air nozzle.

  3. A flow hole through which the compressed air in the air nozzle circulates is gradually reduced from a large diameter to a small diameter as it advances to the discharge port, and then is formed to a constant diameter up to the discharge port, and the flow hole is reduced to a constant diameter. 3. The fixing device according to 2 above, wherein an elastic body is formed between the second portion and the discharge port which are separated from the first portion toward the discharge port by a predetermined length.

  4). The air nozzle is formed of an elastic body, and the flow hole through which the compressed air flows in the air nozzle is formed to have a constant diameter from the large diameter to the small diameter after gradually decreasing from the large diameter to the discharge opening. The outer circumference of the air nozzle except for the space between the discharge port and the second part separated from the first part by a predetermined length from the first part reduced to a constant diameter is covered with a rigid body. The fixing device according to 1.

  5. A flow hole through which the compressed air in the air nozzle circulates is gradually reduced from a large diameter to a small diameter as it advances to the discharge port, and then is formed to a constant diameter up to the discharge port, and the flow hole is reduced to a constant diameter. Between the second part separated by a predetermined length from one part to the discharge port side and the third part separated by a predetermined length from the discharge port to the second part side 3. The fixing device as described in 2 above, wherein the fixing device is formed of an elastic body.

  6). 6. The fixing device according to claim 1, wherein the elastic body includes a reinforcing member and has flexibility only in a thickness direction of the recording material.

7). The elastic body incorporates a reinforcing member and has flexibility only in the thickness direction of the recording material,
The fixing according to any one of 3 to 5, wherein the reinforcing member is a plurality of reinforcing yarns that annularly surround the flow hole, and each of the reinforcing members is disposed in a flow direction of the compressed air. apparatus.

  8). The fixing device according to 7 above, wherein the plurality of reinforcing yarns are unevenly distributed in a portion away from the discharge port.

  9. 8. The fixing device according to 7, wherein a spacing between the plurality of reinforcing yarns is arranged so as to be coarser as the distance from the ejection port is closer.

10. The elastic body incorporates a reinforcing member and has flexibility only in the thickness direction of the recording material,
The reinforcing member is a plurality of reinforcing yarns surrounding the flow hole, and the plurality of reinforcing yarns are arranged so that the interval between the reinforcing yarns is dense on the fixing member side and rough on the opposite side to the fixing member. The fixing device according to any one of 3 to 5, wherein:

  11. 11. The fixing device according to any one of 1 to 10, wherein the periphery of the discharge port is covered with a sheath-like member.

  12 2. The fixing device according to 1, wherein the air discharge unit discharges air blown by a fan, and the tubular member is an air duct.

13. 6. The fixing device according to any one of 2 to 5 , wherein an air duct for discharging air blown by a fan is provided in parallel with the air nozzle.

  14 14. The fixing device according to 13, wherein the vicinity of a discharge port for discharging air in the air duct is formed of an elastic body.

  15. 15. The fixing device according to any one of 1 to 14, wherein the elastic body is made of silicon rubber.

  16. 16. An image forming apparatus comprising the fixing device according to any one of 1 to 15.

  According to the fixing device and the image forming apparatus including the fixing member of the present invention, air is discharged from an air nozzle or the like and sprayed onto the recording material that has passed through the nip portion, and the recording material is separated from the fixing member such as a fixing belt. In the fixing device, even when a jam occurs and the recording material is caught in the gap between the fixing member and the air nozzle, the surface of the fixing member is not wrinkled, and the recording material can be easily pulled out. .

1 is a configuration diagram of an image forming apparatus. It is sectional drawing of a belt fixing apparatus. It is an enlarged vertical sectional view of an air nozzle. FIG. 5 is a diagram in which a recording paper jams between the fixing belt and an air nozzle. It is a perspective view of the air nozzle of the form 1 of reinforcement. It is a perspective view of the air nozzle of the form 2 of reinforcement. It is a perspective view of the air nozzle of the form 3 of reinforcement. It is a longitudinal cross-sectional view of the air nozzle of the form 1 of reinforcement. It is a longitudinal cross-sectional view of the air nozzle which coat | covered the front-end | tip with the protection member. It is a figure explaining the connection method of a nozzle main body and an elastic body. It is a longitudinal cross-sectional view of the air nozzle formed entirely with an elastic material. It is a longitudinal cross-sectional view of the air nozzle which has arrange | positioned the elastic body in the position a little away from the discharge outlet. It is a perspective view of the elastic body of an air duct. It is a longitudinal cross-sectional view of the air duct which mounted | wore the duct main body with the elastic body. It is a longitudinal cross-sectional view of the air duct which reinforced the joining of an elastic body and a duct main body. It is a perspective view of an air nozzle and a solenoid valve. It is a block diagram regarding an air nozzle or an air duct.

  Embodiments relating to the present invention will be described below with reference to the drawings.

  First, an example of an image forming apparatus using the present invention will be described with reference to the block diagram of FIG.

  The image forming apparatus includes an image forming apparatus main body GH and an image reading apparatus YS.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus. A plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer belt 5, a sheet feeding and conveying unit, a fixing device 8, and the like. Consists of.

  An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and one or both images of the document are scanned and exposed by the optical system of the document image scanning exposure device 202 and read into the line image sensor CCD. It is.

  A signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 7Y are arranged around the photosensitive drum 1Y. In the image forming unit 10M that forms a magenta (M) color image, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 7M are arranged around the photosensitive drum 1M. In the image forming unit 10C that forms a cyan (C) color image, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 7C are arranged around the photosensitive drum 1C. In the image forming unit 10K that forms a black (K) image, a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 7K are arranged around the photosensitive drum 1K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit.

  The developing units 4Y, 4M, 4C, and 4K include a two-component developer composed of a toner having a small particle size of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. The toner is composed of a pigment or dye serving as a color former, a wax that helps the toner peel from the fixing member after fixing, and a binder resin that holds these.

  The intermediate transfer belt 5 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 8 heats and pressurizes the toner image on the recording paper (recording material) P at a nip portion formed between the heated fixing belt 81 and the pressure roller 83 to fix the toner image.

  Thus, each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred to the rotating intermediate transfer belt 5 by the transfer means 6Y, 6M, 6C, and 6K (primary transfer), and color. A combined toner image is formed. The recording paper P stored in the paper feeding cassette 20 is fed by the paper feeding means 21 and is conveyed to the transfer means 6A through the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, etc. A color image is transferred to P (secondary transfer). The recording paper P to which the color image has been transferred is heated and pressurized by the fixing device 8 and the color toner image on the recording paper P is fixed. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the transfer unit 6A, the residual toner is removed by the cleaning unit 7A from the intermediate transfer belt 5 from which the recording paper P is separated by curvature.

  The image forming apparatus for forming a color image has been described above. However, an image forming apparatus for forming a monochrome image may be used, or an intermediate transfer belt may or may not be used.

  Next, the fixing device 8 according to the present invention will be described based on the sectional view of the belt fixing device of FIG.

  The fixing belt 81 (fixing member) is formed in an endless shape. For example, PI (polyimide) having a thickness of 70 μm is used as a base, and a heat-resistant silicon rubber (hardness JIS) having a thickness of 200 μm is used with an outer peripheral surface of the base as an elastic layer. -A15 °) and further covered with a tube of PFA (perfluoroalkoxy), which is a heat-resistant resin having a thickness of 30 μm. The outer diameter is, for example, 168 mm. Other configurations include using a metal substrate such as nickel electroforming as the substrate, using fluorine rubber as the elastic layer, and using a fluorine resin coating layer such as PFA or PTFE (polytetrafluoroethylene) as the surface release layer. May be.

  The heating roller 82 incorporates a halogen heater 82A as a heating means for heating the fixing belt 81. For example, the outer peripheral surface of a cylindrical metal core 82B having a thickness of 4 mm formed of aluminum or the like is formed on PTFE having a thickness of 30 μm. The resin layer 82C coated with The outer diameter is 90 mm, for example. The halogen heater 82A is composed of, for example, two of 1200 W, two of 750 W, and one of 500 W in order to cope with different paper widths, and generates different heat in the axial direction corresponding to different paper widths of the recording paper. They are arranged so that they are distributed.

  The fixing roller 83 is a solid core metal 83A formed of a metal such as iron, which is covered with a heat-resistant silicon rubber (hardness JIS-A 10 °) having a thickness of 17 mm as an elastic layer 83B, and further having a thickness of 30 μm. The resin layer 83C is coated with PTFE, which is a low friction and heat resistant resin. The outer diameter is 90 mm, for example.

  The pressure roller 84 (pressure member) incorporates a halogen heater 84A to shorten the temperature rising time immediately after the power supply to the image output apparatus is turned on, and is a cylindrical cored bar 84B having a thickness of 4 mm formed of aluminum or the like. The outer peripheral surface is covered with a heat-resistant silicone rubber having a thickness of 2 mm (hardness JIS-A 10 °) as an elastic layer 84C, and further covered with a resin layer 84D of a PFA tube having a thickness of 30 μm. The outer diameter is 90 mm. The halogen heater 84A is 700 W, for example.

  Then, the pressing roller 84 presses the fixing roller 83 via the fixing belt 81 by an urging means (not shown).

  In the above configuration, when the pressure roller 84 is rotated counterclockwise by a driving unit (not shown), the fixing belt 81 and the heating roller 82 are rotated clockwise, and the fixing roller 83 is also rotated clockwise. Note that the fixing roller 83 may be driven. In addition, the fixing belt 81 is heated by the halogen heater 82A through the heating roller 82 that abuts, and the pressure roller 84 is also heated by the halogen heater 84A. Since the pressure roller 84 is urged in the direction of the fixing roller 83 by an urging means (not shown), it is formed between the fixing belt 81 wound around the fixing roller 83 and the pressure roller 84. At the nip portion N, the fed recording material P is heated and pressurized, and the toner image on the recording material P is fixed.

  The fixing conditions are, for example, as follows.

Fixing load: 2000N
Fixing belt tension: 250N
Fixing belt control temperature: 160-200 ° C
Pressure roller control temperature: 80-120 ° C
Recording paper transport speed: 500 mm / s
Further, any heating means may be used as the heating means for heating the fixing belt 81. For example, an induction heating heating element using an excitation coil may be used. The position where the heating means is provided is not necessarily limited to the heating roller 82.

  Further, a tension roller that applies tension to the fixing belt 81 or a shift control roller that controls the meandering of the belt may be provided.

  In the fixing device 8 as described above, if the fixed recording material P is ejected from the nip portion N and then attached to the fixing belt 81 and wound, there is a risk of jamming. It is necessary to ensure separation from

  Accordingly, the fixing device 8 includes two types of air discharge means for discharging air in order to separate the recording material P from the fixing belt 81. The first air discharge means discharges compressed air generated by being compressed by a compressor, which will be described later, from an air nozzle 110 that is a tubular member formed in a tubular shape. The front end of the recording paper P is separated from the fixing belt 81 by spraying the front end of the recording paper P for a short time. The second air discharge means discharges air blown by the fan 151 continuously from an air duct 150 which is a tubular member formed in a tubular shape, and blows and fixes the recording paper P from which the leading end is separated. Avoid sticking to the belt 81. The air nozzle 110 and the air duct 150 are juxtaposed so that the discharge port 112B of the air nozzle 110 and the discharge port 162A of the air duct 150 are close to each other in the vicinity of the outlet side of the nip portion N.

  As an example, the blowing position is that the air from the air nozzle 110 is the outer peripheral surface of the fixing belt 81 located 25 mm from the exit of the nip N, and the air from the air duct 150 is located 10 mm from the exit of the nip N. This is the outer peripheral surface of the fixing belt 81.

  The air discharged from the air nozzle 110 needs to have a high wind speed because the leading end of the recording paper P is separated from the fixing belt 81. However, since the discharge can be performed in a short time, the air volume may be small. On the other hand, since the air discharged from the air duct 150 is after the leading end of the recording paper P has been separated, the air speed may be smaller than that of the air nozzle 110, but is continuously discharged until the entire recording paper P passes through the nip portion N. Therefore, the air volume is required to be larger than that of the air nozzle 110. The air volume from the air nozzle 110 may be about 1/10 of the air volume from the air duct 150. Since the air nozzle 110 and the air duct 150 thus supplement each other, the size and power are reduced to about 1/10 compared to the configuration in which only the compressed air is discharged from the air nozzle 110 without providing the air duct 150. Miniaturization and power saving.

  In this way, the recording paper P separated from the fixing belt 81 is guided and conveyed by the paper discharge guide plate 85. Since the separation claw 86 made of heat-resistant resin is in pressure contact with the pressure roller 84, the recording paper P is wound around the pressure roller 84 even when the recording paper P is pressed downward by the air from the air nozzle 110 or the air duct 150. It won't stick. Further, the separation claw 86 is coated with a fluororesin at a tip end of about 10 mm, for example, and has good lubricity and is pressed against the pressure roller 84 with a weak pressure of about 1 mN. There is no sticking. In addition, even when the toner image is located on the pressure roller 84 side during double-sided copying, the temperature of the pressure roller 84 is low, so the toner image does not melt and an image defect occurs due to the separation claw 86. There is nothing to do. As the separation claw 86, one used in a conventional fixing device can be applied.

On the other hand, recording sheets that can be fed are defined in the image forming apparatus and are described in an instruction manual or the like. Nevertheless, when the user uses recording paper that is not specified, for example, a thin paper of 60 g / m ² or less, the leading end of the recording paper is not separated from the fixing belt 81 after fixing. A jam may occur in contact with the portion. When the jammed recording paper is caught in a narrow gap between the fixing belt 81 and the air nozzle 110, it is difficult to remove the recording paper. Even if the recording paper can be pulled out, the recording paper bent by the jam passes through a narrow gap between the fixing belt 81 and the air nozzle 110, so that the surface of the fixing belt 81 may be wrinkled by the recording paper. is there. In the following, means for solving this problem will be described.

  FIG. 3 is an enlarged longitudinal sectional view of the air nozzle 110.

  The air nozzle 110 is formed long in the direction perpendicular to the paper surface, that is, in the width direction of the recording paper. Then, the compressed air is sent into the air nozzle 110 through the inner holes 121A of the plurality of pipes 121 through an electromagnetic valve or the like which will be described later.

  The air nozzle 110 is connected to an elastic body 112 made of silicon rubber or the like at the tip of a nozzle body 111 made of metal such as iron or aluminum. The nozzle main body 111 includes a plurality of (for example, five) nozzle holes 111A having a circular cross-sectional shape, a single first circulation hole 111B formed long in the vertical direction, and a vertical direction in the vertical direction. A plurality of (eg, 130) second flow holes 111C having a circular cross-sectional shape are provided. The elastic body 112 has a plurality of third flow holes 112A that are provided in a plurality in the direction perpendicular to the paper surface and have a circular cross-sectional shape and are arranged corresponding to the respective second flow holes 111C.

  The compressed air is sent into the air nozzle 110 through the inner holes 121A of the plurality of pipes 121, and flows into the single first flow hole 111B from the plurality of input holes 111A. Subsequently, the compressed air in the first flow hole 111B branches, flows through the plurality of second flow holes 111C and the third flow hole 112A, and is discharged from the discharge port 112B at the tip of the third flow hole 112A.

  As described above, when the recording paper P is caught in the narrow gap between the fixing belt 81 and the air nozzle 110 as shown in FIG. 4, the recording paper P is pulled out in the direction of arrow A. At this time, the elastic body 112 provided at the tip of the air nozzle 110 is deformed by receiving a force in the direction of arrow B. Accordingly, the force for pulling out the recording paper P in which the jam has occurred is small, and the surface of the fixing belt 81 is not wrinkled.

  In addition, since the 1st flow hole 111B in the air nozzle 110 is gradually reduced from a large diameter to a small diameter as it progresses to the discharge port 112B, the flow of compressed air is a turbulent flow. On the other hand, since the second circulation hole 111C and the third circulation hole 112A have a constant diameter up to the discharge port 112B, the flow of the compressed air is a laminar flow. Therefore, if the elastic body is formed to extend to the position of the first flow hole 111B, vibration is generated by turbulent flow, and the direction in which the compressed air is blown becomes unstable. Therefore, the position where the elastic body is provided is a portion where the flow hole is reduced to a certain diameter, that is, between the first portion 110X at the boundary between the first flow hole 111B and the second flow hole 111C and the discharge port 112B. A portion having a constant aperture is desirable. However, the wind pressure of the compressed air is maximum at the first portion 110X, and the wind pressure gradually decreases toward the discharge port 112B. Therefore, if the elastic body is formed up to the first portion 110X where the wind pressure is maximum, the diameter is widened due to the wind pressure, resulting in an unstable flow. This is avoided, and this is avoided from the first portion 110X toward the discharge port 112B. It is desirable to form an elastic body between the second portion 110Y and the discharge port 112B separated by a length of. However, if the length of the elastic body is short, it becomes difficult to deform, so that a reasonably long one is desirable.

  According to the experiment by the present inventor, when the length of the discharge port 112B from the first part 110X is 13 mm, the second part 110Y is preferably located 2 mm away from the first part 110X.

Further, the outer diameter of the fixing roller 83 may be increased in order to increase the width of the nip portion N as the speed increases. In such a case, since the curvature separation performance of the recording paper P is lowered, it is necessary to increase the discharge pressure from the air nozzle 110. However, when the discharge pressure increases, the flow hole of the elastic body expands to generate turbulent flow, and the discharge direction of the compressed air becomes unstable. In such a case, it is necessary to reinforce the elastic body by incorporating a reinforcing member in the elastic body, and the form of reinforcement will be described below.
・ Reinforcement form 1
Reinforcing form 1 for reinforcing the elastic body will be described with reference to FIG. 5 which is a perspective view of the air nozzle.

  In the elastic body 212 of the air nozzle 210, a plurality of reinforcing yarns 213 formed in an annular shape are juxtaposed in the flow direction of the compressed air as reinforcing members, and surround all the third flow holes 212A. Therefore, even if high-pressure compressed air flows, the third flow hole 212A does not expand and the discharge direction of the compressed air does not become unstable. In addition, since the plurality of reinforcing yarns 213 are arranged in parallel in the compressed air flow direction at a predetermined interval, the elastic body 212 has flexibility only in the thickness direction of the recording paper, that is, in the vertical direction in FIG. The reinforcing thread 213 does not hinder the elastic body 212 from being deformed.

The material of the reinforcing yarn 213 is desirably a synthetic fiber such as vinylon or polyester. In the case of vinylon, it is desirable that three 1200 denier yarns are twisted and the strength is about 7.5 g / d. Further, by making the pitch of the plurality of reinforcing yarns 213 equal, for example, 2 mm, the elastic body 212 can be easily manufactured.
・ Reinforcement form 2
Reinforcing form 2 for reinforcing the elastic body will be described with reference to FIG. 6 which is a perspective view of the air nozzle.

  In the elastic body 312 of the air nozzle 310, a plurality of annular reinforcing yarns 313 are juxtaposed in the compressed air discharge direction in the same manner as in the reinforcing mode 1, and the materials and the like are also the same.

  This embodiment is different from the reinforcement mode 1 in that the reinforcing yarn 313 is not provided in the vicinity of the discharge port 312B of the elastic body 312 and is unevenly distributed in a portion away from the discharge port 312B. This is because the wind pressure of the compressed air is higher at the part away from the discharge port 312B, and the vicinity of the discharge port 312B is at a low pressure. Because it does not.

Thereby, the total number of the reinforcing yarns 313 can be reduced.
・ Reinforcement form 3
Reinforcing form 3 for reinforcing the elastic body will be described with reference to FIG. 7 which is a perspective view of the air nozzle.

  In the elastic body 412 of the air nozzle 410, a plurality of annular reinforcing yarns 413 are arranged in parallel in the compressed air discharge direction in the same manner as in the reinforcing mode 1, and the material and the like are also the same.

  The difference between this embodiment and reinforcement embodiment 1 is that the pitches of the reinforcing yarns 413 are not evenly spaced, and are arranged roughly in parallel as they are closer to the discharge port 412B of the elastic body 412, and more closely in parallel as they are farther from the discharge port 412B. It is that. The reason for this is that the pressure of the compressed air is lower as it is closer to the discharge port 412B and higher as it is farther from the discharge port 412B.

Thereby, even if the number of the reinforcing yarns 413 is the same as that of the reinforcing form 1, higher pressure resistance characteristics can be obtained.
・ Reinforcement form 4
Reinforcing form 4 for reinforcing the elastic body will be described with reference to FIG. 8 which is a longitudinal sectional view of the air nozzle.

  Among the elastic bodies 512 of the air nozzle 510, a plurality of reinforcing yarns 513 are disposed, but some of them are not annular but may be formed in a concave shape or a reverse concave shape. The plurality of reinforcing yarns 513 are arranged so that the pitch is dense on the side of the fixing belt 81 as the fixing member (upper side in FIG. 8) and the opposite side is rough.

  Thereby, even if the reinforcing yarn is incorporated, deformation in the direction of the arrow becomes easier.

  In each reinforcing yarn 513, the reinforcing yarn 513A is formed in an annular shape, the reinforcing yarn 513B is formed in a concave shape, and the reinforcing yarn 513C is formed in a reverse concave shape. Moreover, the material etc. are the same as that of the form 1 of reinforcement.

  In addition, although not shown, the pitch of the reinforcing yarn is made the same on the fixing belt 81 side and the opposite side, a thick reinforcing yarn is arranged on the fixing belt 81 side, and a thin reinforcing yarn is arranged on the opposite side. It may be.

  In addition, the leading end of the recording paper that cannot be separated may come into contact with the leading end of the elastic body of the air nozzle, and the elastic body may be damaged. For such a problem, as shown in FIG. 9, the tip of the elastic body 112 may be covered with a sheath-like protective member 114 having a discharge port 114A. The protective member 114 is formed of a metal plate or resin.

  Next, means for connecting the elastic body 112 to the nozzle body 111 of the air nozzle 110 will be described with reference to FIG. The nozzle body 111 has a protruding fitting boss 111D, and the elastic body 112 has a fitting hole 112D having a diameter slightly larger than the outer diameter of the fitting boss 111D. Then, the fitting hole 112D is fitted into the fitting boss 111D, and both are joined with an adhesive.

  The nozzle body 111 may be provided with a fitting hole, and the elastic body 112 may be provided with a fitting boss.

  Further, the nozzle body 111 and the elastic body 112 in the air nozzle 110 may be formed by two-color molding or outsert molding.

  In each of the above embodiments, an elastic body is connected to the nozzle body of the air nozzle, but an air nozzle having a different configuration will be described.

  FIG. 11 is a cross-sectional view of an air nozzle in which the entire air nozzle is formed of an elastic material.

  In FIG. 11, the air nozzle 610 is configured such that the nozzle body 111 and the elastic body 112 in FIG. 3 are integrated, and the nozzle body 111 is also formed of silicon rubber or the like. Accordingly, the compressed air flows from the plurality of input holes 610A to the single first flow hole 610B, flows through the plurality of second flow holes 610C, and is discharged from the discharge port 610D. However, since the air nozzle 610 vibrates or deforms due to the wind pressure of the compressed air as it is, the portion excluding the vicinity of the discharge port 610D is covered with a rigid body 615 having rigidity such as metal or resin. The portion that is not covered with the rigid body 615 includes a second portion 610Y that is separated from the first portion 610X at the boundary between the first flow hole 610B and the second flow hole 610C by a predetermined length from the discharge port 610D. It is between the discharge ports 610D.

  In the above embodiments, the vicinity of the discharge port of the air nozzle is formed of an elastic body. However, the meaning of the vicinity of the discharge port does not necessarily mean that the discharge port is formed of an elastic body. That is, the discharge port itself does not necessarily need to be an elastic body, and may be a rigid body, and includes that the elastic body is located at a position slightly away from the discharge port, although it is in the vicinity of the discharge port. Such an air nozzle is shown in FIG.

  In the air nozzle 710, an elastic body 712 made of silicon rubber or the like is connected to a nozzle body 711 made of metal, and a protective member 713 made of metal or resin is further connected to the elastic body 712. That is, the second portion 710Y having a predetermined length from the first portion 710X to the discharge port 713A side, and the second portion from the discharge port 713A. The elastic body 712 may be disposed between the third portion 710Z separated by a predetermined length on the 710Y side.

  In addition, the above-mentioned connection method can be used for these connection methods.

  Accordingly, when a jam occurs in the recording paper, the air nozzle 710 can be deformed by the elastic body 712, and the air nozzle 710 is damaged by the protective member 713 even if the leading end of the recording paper comes into contact with the leading end of the air nozzle 710. There is nothing.

  Next, the air duct 150 will be described.

  The tip of the air duct 150 does not necessarily have the elastic body 112 like the air nozzle 110 but may be a rigid body. However, the elastic body 112 is deformed when a jam occurs in the recording paper P as shown in FIG. 4, but since the air duct 150 is close to the air nozzle 110, the elastic body 112 abuts against the tip of the air duct 150, The deformation amount of the elastic body 112 may be limited. Assuming such a case, the air duct 150 is also provided with an elastic body at the tip thereof, whereby the elastic body 112 of the air nozzle 110 is more easily deformed and handling when a jam occurs on the recording paper P is facilitated. .

  The air duct 150 having an elastic body will be described below.

  Similarly to the air nozzle 110, the air duct 150 also has a flow hole that gradually decreases from a large diameter to a small diameter as it goes to the discharge port, and a flow hole having a constant diameter. However, since the air duct 150 has a low wind pressure, the portion where the elastic body is provided is not limited to a portion having a flow hole having a constant diameter, and no problem occurs even if the diameter is applied to a portion where the diameter gradually decreases.

  A perspective view of the elastic body 162 of such an air duct 150 is shown in FIG.

  The elastic body 162 is made of silicon rubber or the like. Since the air duct 150 has a low wind pressure but a large air volume, its discharge port 162A is formed large. Therefore, even if the wind pressure is low, the frame is easily deformed only by the surrounding frame, and a plurality of ribs 162B are provided in the vertical direction for reinforcement.

  Further, in order to attach the elastic body 162 to the duct main body 161, as shown in the sectional view of the air duct in FIG. 14, the end of the elastic body 162 and the end of the duct main body 161 are fitted together with an adhesive. What is necessary is just to join.

  When high air pressure is required for the air duct 150, the reinforcing member 163 is used as shown in FIG. 15, and the reinforcing member 163 is fixed to the air duct 150 of FIG.

  Next, the air nozzle 110 and the related configuration will be described with reference to FIGS. 16 and 17. 16 is a perspective view of the air nozzle 110 and the electromagnetic valve 123, and FIG. 17 is a block diagram relating to the air nozzle 110 and the air duct 150.

  In FIG. 16, the air nozzle 110 is formed long in the width direction of the recording paper P, and the elastic body 112 of each air nozzle 110 is provided with 130 nozzle holes 112B having a diameter of 0.8 mm at a pitch of 2.5 mm.

  The nozzle body 111 of the air nozzle 110 is connected to two piping parts 122 by five pipes 121, and the two piping parts 122 communicate with two electromagnetic valves 123, respectively. As shown in FIG. 16, the electromagnetic valve 123 is connected to and integrated with an air tank 124, and the air tank 124 is connected to a compressor 125.

The solenoid valve 123 is a direct acting type, and has a capacity of 0.001 m ³ / s (100 kPa) and a response speed of 20 ms.

The capacity of the air tank 124 is 0.05 m ³ .

The compressor 125 is a reciprocating oil-free type, and has an electric power of 0.75 kW, a static pressure of 0.8 MPa, and an air volume of 0.00125 m ³ / s.

  In the image forming apparatus having the above configuration as shown in FIG. 1, the paper feed sensor 102 detects that the recording paper P accommodated in the paper feed cassette 20 has been fed by the paper feed means 21. Since the time from when the paper feed sensor 102 is detected until the leading end of the conveyed recording paper P reaches the exit of the nip portion N is constant and known in advance, the control means 101 comprising a CPU or the like is controlled by the timer 103. An open signal is transmitted to the solenoid valve 123 about 15 ms before reaching that time, and a close signal is transmitted after 50 ms. Since the compressed air compressed by the compressor 125 is stored in the air tank 124 in advance, the compressed air is discharged from the air nozzle 110 when the electromagnetic valve 123 is opened, and the front end of the recording paper P immediately after passing through the nip portion N. Spray against the part.

At this time, compressed air of about 0.8 MPa stored in the air tank 124 by the compressor 125 is decompressed by a regulator (not shown) and supplied to the air nozzle 110. The discharge pressure from the air nozzle 110 is 0.1 to 0.2 MPa, the discharge air volume is 100 to 160 m / s, and the discharge air volume is 0.005 to 0.008 m ³ / s.

  Further, since the electromagnetic valve 123 is fully opened about 20 ms after the opening signal is inputted, the maximum air volume is reached when the recording paper P is conveyed about 10 mm from the nip portion. Since the maximum discharge air volume of compressed air from the air nozzle 110 is 2 to 3 times the air volume necessary for separating the recording paper P, the recording paper P is discharged from the nip portion N before the maximum discharge air volume of the compressed air reaches the maximum. Separation begins before the transport amount reaches 10 mm. Thereafter, when a close signal is input to the solenoid valve 123, the discharge air volume of the compressed air discharged from the air nozzle 110 gradually decreases and is discharged until the leading end portion of the recording paper P reaches 25 to 30 mm from the nip portion N. Keep doing. The amount of air discharged at this time is the amount of air that can separate the recording paper P even if there is a toner image with the maximum amount of adhesion.

  In FIG. 16, three pipes 121B, 121C, and 121D branched from the piping portion 122A communicating with the electromagnetic valve 123A are connected to the center portion of the nozzle body 111 and branched from the piping portion 122B communicating with the electromagnetic valve 123B. The two pipes 121A and 121E are connected to the peripheral portion of the nozzle body 111.

  When the size of the recording paper on which an image is formed is input to the operation panel arranged at the top of the image forming apparatus, the recording paper size detection unit 104 detects the size and transmits it to the control unit 101. For example, when the A4 size recording paper is fed laterally, the control unit 101 transmits an open signal to both the potential valve 123A and the electromagnetic valve 123B. Thereby, the compressed air is discharged from all the discharge ports 112B. Further, when the A4 size recording paper is fed longitudinally, the control means 101 transmits an open signal only to the electromagnetic valve 123A and does not transmit an open signal to the potential valve 123B. Thereby, the compressed air is discharged from only the discharge port 112B near the center corresponding to the vertical dimension of approximately A4 size. As described above, by changing the discharge position of the compressed air according to the size of the recording paper, useless discharge of the compressed air can be suppressed and the power consumption of the compressor 125 can be reduced.

  At this time, the halogen heater 82A built in the heating roller 82 is also energized to the one corresponding to the paper passing area to suppress power.

  As described above, after the compressed air is discharged from the air nozzle 110 and the leading end of the recording paper P that has passed through the nip portion N is separated from the fixing belt 81, the discharge of the compressed air is stopped and the fan switch 152 is turned on. Instead, the air blown from the air duct 150 by the fan 151 is continuously discharged and blown onto the recording paper P to prevent the recording paper P from adhering to the fixing belt 81.

  Here, when the separation of the recording paper P proceeds to some extent and the leading end of the recording paper P is opened by 0.2 mm or more from the fixing belt 81, the air nozzle 110 causes the peeling force to act on all the open areas. Air that blows in a wide range with a large air volume even at low pressure is more desirable than air that blows in a narrow range at high pressure, such as compressed air to be discharged. Therefore, the discharge from the air nozzle 110 is stopped, and the air blown by the fan 151 from the air duct 150 is blown to the leading end of the recording paper P that is opened from the fixing belt 81. As a result, a force is applied to the recording paper P against the adhesive force of the toner without blowing from the air nozzle 110, and the recording paper P is reliably separated from the fixing roller 81.

On the other hand, the discharge port 162A of the air duct 150 is formed so that the thickness direction of the recording paper P is 1.6 mm. The air duct 150 is connected to the fan 151. The fan 151 is provided with five 97 × 33 mm sirocco fans and has a static pressure of 1280 Pa. Moreover, the discharge air volume is 160 × 10 ⁻⁵ m ³ / s.

  Note that the fan 151 is not limited to a sirocco fan, and may be an axial fan, a cross flow fan, a blower, or the like. In short, the recording paper P with the leading end separated from the fixing belt 81 can be continuously separated. What is necessary is just to have the conditions which have an appropriate air volume. The shape of the duct 150 is set according to the type of the fan 151.

  The fixing device described above has a configuration in which the recording paper is separated by using both the air nozzle and the air duct. However, the present invention is not limited to this, and the recording paper is formed by only one of the air nozzle and the air duct. The present invention can also be applied to a fixing device that performs this separation. For example, when the roller has a small diameter, the recording paper can be separated only by the air discharged from the air duct, and the vicinity of the discharge port of the air duct may be formed of an elastic body.

  The fixing device of the present invention is not limited to the belt fixing device, and can be applied to other types of fixing devices such as a heat roller fixing type fixing device.

DESCRIPTION OF SYMBOLS 8 Fixing device 81 Fixing belt 82 Heating roller 83 Fixing roller 84 Pressure roller 101 Control means 110,210,310,410,510,610,710 Air nozzle 110X 1st part 110Y 2nd part 111,711 Nozzle main body 111B 1st 1 flow hole 111C 2nd flow hole 114,713 Protection member 112,162,212,312,412,512,712 Elastic body 112A 3rd flow hole 112B, 162A Discharge port 123 Solenoid valve 125 Compressor 150 Air duct 151 Fan 163 Reinforcement member 213, 313, 413 Reinforcement thread 615 Rigid body P Recording material N Nip part

Claims (16)

In a fixing device that fixes a toner image on a recording material at a nip formed by a heated fixing member and a pressure member that pressurizes the fixing member.
An air discharge means for discharging air to spray the recording material and separating the recording material from the fixing member;
The fixing device according to claim 1, wherein the air discharge unit includes a tubular member that circulates air and discharges the air from a discharge port, and the vicinity of the discharge port of the tubular member is formed of an elastic body.   The fixing device according to claim 1, wherein the air discharge unit discharges compressed air generated by a compressor, and the tubular member is an air nozzle.   A flow hole through which the compressed air in the air nozzle circulates is gradually reduced from a large diameter to a small diameter as it advances to the discharge port, and then is formed to a constant diameter up to the discharge port, and the flow hole is reduced to a constant diameter. The fixing device according to claim 2, wherein an elastic body is formed between the second portion and the discharge port that are separated from each other by a predetermined length from the one portion to the discharge port side.   The air nozzle is formed of an elastic body, and the flow hole through which the compressed air flows in the air nozzle is formed to have a constant diameter from the large diameter to the small diameter after gradually decreasing from the large diameter to the discharge opening. The outer periphery of the air nozzle is covered with a rigid body except for a portion between the discharge port and the second portion separated by a predetermined length from the first portion reduced to a constant diameter. 3. The fixing device according to 2.   A flow hole through which the compressed air in the air nozzle circulates is gradually reduced from a large diameter to a small diameter as it advances to the discharge port, and then is formed to a constant diameter up to the discharge port, and the flow hole is reduced to a constant diameter. Between the second part separated by a predetermined length from one part to the discharge port side and the third part separated by a predetermined length from the discharge port to the second part side The fixing device according to claim 2, wherein the fixing device is formed of an elastic body.   The fixing device according to claim 1, wherein the elastic body includes a reinforcing member and has flexibility only in a thickness direction of the recording material. The elastic body incorporates a reinforcing member and has flexibility only in the thickness direction of the recording material,
The said reinforcement member is a some reinforcement thread | yen which encloses the said circulation hole cyclically | annularly, and each is arrange | positioned in the distribution direction of compressed air, The any one of Claims 3-5 characterized by the above-mentioned. Fixing device.   The fixing device according to claim 7, wherein the plurality of reinforcing yarns are unevenly distributed in a portion away from the discharge port.   The fixing device according to claim 7, wherein a plurality of the reinforcing yarns are arranged such that the interval between the reinforcing yarns becomes coarser as the distance from the discharge port becomes closer. The elastic body incorporates a reinforcing member and has flexibility only in the thickness direction of the recording material,
The reinforcing member is a plurality of reinforcing yarns surrounding the flow hole, and the plurality of reinforcing yarns are arranged so that the interval between the reinforcing yarns is dense on the fixing member side and rough on the opposite side to the fixing member. The fixing device according to claim 3, wherein the fixing device is a fixing device.   The fixing device according to claim 1, wherein a periphery of the discharge port is covered with a sheath-like member.   The fixing device according to claim 1, wherein the air discharge unit discharges air blown by a fan, and the tubular member is an air duct. The fixing device according to claim 2 , wherein an air duct that discharges air blown by a fan is provided in parallel with the air nozzle.   The fixing device according to claim 13, wherein the vicinity of the discharge port for discharging air in the air duct is formed of an elastic body.   The fixing device according to claim 1, wherein the elastic body is made of silicon rubber.   An image forming apparatus comprising the fixing device according to claim 1.

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