JP5418343B2 - 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.

  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 transporting, 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 presses the recording paper onto which the toner image has been transferred at the nip formed by the belt, and such a fixing device has a heat supply (heating roller) and pressurization. Since the function of (fixing roller) is separated, a wide rubber nip and durability can be achieved by using a thick rubber layer for the fixing roller. In the heat roller fixing method, it is necessary to provide a rubber layer on the fixing roller in order to obtain high image quality. However, since there is a heat source inside, the interface temperature between the cored bar and rubber is increased, and both durability and a wide nip width are achieved. Difficult to do.

  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) and a small amount of coated paper for printing are used as the recording paper, the separation performance is further deteriorated.

  On the other hand, the speed of the image forming apparatus has been increased, and if the fixing roller is enlarged in order to ensure a sufficiently long nip width, the roller curvature at the fixing nip outlet also becomes small, and the separation performance deteriorates.

  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 containing wax that functions as a material. 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.

  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, the compressed air generated by the compressor is stored in two air boxes, and the two solenoid valves connected to the air box are alternately opened and closed to inject compressed air, making it compatible with high-speed copying machines. A sheet separating apparatus is known (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 onto a nip portion (see Patent Document 2).

  There is also known a separation device in which a separation auxiliary plate is disposed in the vicinity of the nip portion and discharges pulsed compressed air from between the fixing roller and the separation auxiliary plate (see Patent Document 3).

  In addition, the compressed air generated from the compressor is discharged by two solenoid valves, and when the leading edge of the recording paper passes through the nip, high pressure compressed air is injected, and then low pressure compressed air is injected. An apparatus is known (see Patent Document 4).

JP-A-60-256180 Japanese Utility Model Publication No. 63-140571 Japanese Patent Application Laid-Open No. 2004-212954 JP 2007-86132 A

  When air is blown to separate the recording paper from the fixing roller, etc., if there is no toner image near the leading edge of the recording paper and there is a wide area where no adhesive force is generated, the recording paper may be damaged by its own “strain” or its own weight. Since the tip of the film peels off and receives air in the peeled area, a large peeling force can be applied. However, if there is an image near the leading edge of the recording paper, the recording paper is transported along the outer peripheral tangent direction of the fixing roller or the like, so the gap generated between the leading edge of the recording paper and the outer periphery of the fixing roller or the like is very small. . For example, when the outer diameter is 90 mm and the leading edge of the recording paper is 3 mm, the gap is only about 0.1 mm. In order to blow air into the gap and lift the leading edge of the paper, it is necessary to blow a high-speed air flow, in other words, high-pressure air, to the nip portion. For this purpose, compressed air generated at a high pressure by a compressor or the like is desirable.

  Further, the phenomenon that the recording paper that has passed through the nip portion does not separate and adheres to the surface of the fixing roller or the fixing belt does not occur only at the leading end portion of the recording paper but also after the leading end portion. Further, even if the leading end of the recording paper is pulled out by the paper discharge roller, uneven peeling occurs in the wound portion. Therefore, when air is blown to the outlet side of the nip portion to separate the recording paper from the fixing roller or the like, it is necessary to blow air continuously.

When compressed air is continuously blown in this way, compressed air close to 0.01 m ³ / s is required. Since a large amount of energy is required to generate compressed air, a high-power compressor of 5 to 10 Kw is required to generate compressed air of this air volume, and the size of the apparatus including the compressor and the air tank is 1 m. There is a risk that it will be as large as ^three .

  On the other hand, in the conventional patent documents, it is impossible to find a configuration that satisfies various performances while suppressing the increase in size of such an apparatus.

  That is, in patent document 1, there exists a possibility of having a high-power compressor as mentioned above and becoming a large sized apparatus.

  In Patent Document 2, air blown by a fan is used, but in this case, high-pressure air cannot be obtained and must be used in combination with a separation claw. Therefore, the problem that the surface of the fixing roller is rubbed by the separation claw cannot be solved.

  In Patent Document 3, since the recording paper is separated by a sharp peeling auxiliary plate after the leading end of the recording paper is peeled off with compressed air, there is a possibility that the image on the recording paper may be wrinkled.

  In Patent Document 4, the compressed air is kept at a low pressure after the leading edge of the recording paper is peeled off with compressed air. However, in order to form high-quality images on various recording papers at high speed and maintain separation performance. In order to obtain this air volume, there is a possibility that a large apparatus will be provided with a high-power compressor as described above.

  The present invention has been made in view of such a problem, and is a fixing device having a configuration in which the leading end portion of a recording material is peeled off by compressed air, and does not require a high-power compressor and the size of the device is not increased. In addition, it is an object of the present invention to propose a fixing device capable of efficiently blowing compressed air to a fixing member to reliably peel the recording material from the fixing member, and an image forming apparatus including the fixing device. To do.

  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.
A first spraying means and a second spraying means for discharging air and spraying the recording material to separate the recording material from the fixing member are provided in the vicinity of the outlet portion of the nip portion. A first valve for controlling the discharge of air by opening / closing the upstream side of the spraying means, and a second valve for controlling the discharge of air by opening / closing the inside of the second spraying means;
The pressure of the air discharged from the first blowing means is greater than the pressure of the air discharged from the second blowing means, and the air volume discharged from the first blowing means is discharged from the second blowing means. Less than the air volume,
The air flow supplied via the first valve is controlled by opening and closing the first valve, and the opening and closing operation of the second valve is performed by the controlled force of the air flow. Fixing device to do.

  2. When the pressure of the air supplied to the first blowing means becomes a predetermined value or more, the second valve is closed, and the pressure of the air supplied to the first blowing means becomes a predetermined value or less. 2. The fixing device according to 1 above, wherein the second valve is configured to open when the second valve is opened.

  3. The air discharged from the first blowing means is air compressed by a compressor, and the air discharged from the second blowing means is air blown by a fan. The fixing device described.

4). A cylinder in which an opening provided at one end communicates with the downstream side of the first valve;
A piston which is contained in the cylinder and slides in conjunction with the opening and closing operation of the second valve, and which is pressed by the air flowing from the first valve and passing through the opening;
A biasing member that biases the piston in the direction of the opening,
When the air pressure that presses the piston exceeds a predetermined value, the piston is pressed against the urging force of the urging member to close the second valve, and the air pressure that presses the piston is predetermined. 4. The fixing device according to claim 1, wherein when the pressure is equal to or less than the value, the piston is pressed by an urging force of the urging member to open the second valve.

5. A cylinder in which an opening provided at one end communicates with the downstream side of the first valve;
A piston which is contained in the cylinder and slides in conjunction with the opening and closing operation of the second valve, and which is pressed by the air flowing from the first valve and passing through the opening;
A weight member that presses the piston in the direction of the opening by gravity, and a drive mechanism,
When the air pressure that presses the piston becomes a predetermined value or more, the second valve is closed against the gravity applied to the weight member, and the air pressure that presses the piston becomes a predetermined value or less. The fixing device according to any one of 1 to 3, wherein the second valve is opened by gravity applied to the weight member.

6). A first cylinder in which a first opening provided at one end communicates with a downstream side of the first valve;
A first piston contained in the first cylinder and sliding in conjunction with the opening and closing operation of the second valve, and flowing from the first valve and pressed by the air passing through the first opening;
A second cylinder in which a second opening provided at one end communicates with an upstream side of the first valve;
The second cylinder has a head smaller in area than the head of the first piston and slides in conjunction with the opening / closing operation of the second valve, and flows from the first valve. A second piston pressed by the air that has passed through the opening,
The rod of the first piston and the rod of the second piston are arranged to face each other and connected to each other, and the two rods have a drive mechanism that slides in conjunction with the opening / closing operation of the second valve. ,
When the air pressure that presses the first piston exceeds a predetermined value, the air pressure that presses the first piston presses the second piston to close the second valve and presses the first piston. 4. The fixing device according to claim 1, wherein the second piston presses the first piston to open the second valve when a predetermined value or less is reached. 5. .

7). The second valve is opened by wind from the fan;
A cylinder in which an opening provided at one end communicates with the downstream side of the first valve;
And a piston that is included in the cylinder and slides in conjunction with the opening and closing operation of the second valve, and is pressed by the air that flows from the first valve and passes through the opening. ,
When the air pressure that presses the piston becomes a predetermined value or more, the piston is pressed against the force that the second valve opens by wind force from the fan, and the second valve is closed. When the air pressure that presses the piston becomes a predetermined value or less, the second valve and the piston are pressed by the wind force from the fan to open the second valve. The fixing device according to any one of the above.

  8). The fixing device according to any one of 4 to 7, wherein the driving mechanism is disposed in the vicinity of both sides in the width direction of the recording paper in the second spraying unit.

9. An opening is provided in a part of the wall constituting the flow path of the second spraying means, and the supply path for supplying an air flow to the opening and the first spraying means is communicated.
Forming the second valve with an elastic member having elasticity to cover the opening;
When the pressure of the air supplied to the first spraying means exceeds a predetermined value, the second valve is pressed by the pressure of the air to close the discharge port of the second spraying means. Any one of the above 1-3, wherein when the pressure of the air supplied to the first spraying unit becomes a predetermined value or less, the discharge port of the second spraying unit is opened. The fixing device according to Item.

10. From the start of closing the first valve to the completion of closing, the sum of the air volume of air discharged from the first spraying means and the air volume of air discharged from the second spraying means is the sum of the recording material . The fixing device according to any one of the above items 1 to 9, wherein the fixing device is at least a predetermined air volume capable of continuing separation from the fixing member.

  11. 11. The fixing device according to any one of 1 to 10, wherein the first valve of the first spraying unit is an electromagnetic valve.

  12 An image forming apparatus comprising the fixing device according to any one of 1 to 11 above.

  According to the fixing device and the image forming apparatus of the present invention, although the recording material is peeled off from the fixing member by compressed air, a high-power compressor is not required and the apparatus is not enlarged. In addition, since the air discharged from the second spraying unit does not become a resistance when the air is discharged from the first spraying unit, the recording material can be reliably peeled off from the fixing member.

1 is a configuration diagram of an image forming apparatus. It is sectional drawing of the belt fixing apparatus which made the 2nd valve the open state. It is sectional drawing of the belt fixing apparatus which made the 2nd valve closed. It is a perspective view of the 2nd air nozzle. It is a perspective view of the 1st air nozzle. It is sectional drawing of the drive mechanism which drives the 2nd valve in 1st Embodiment. It is a block diagram regarding a 1st air nozzle, a 2nd air nozzle, and its related member. It is a timing chart of the discharge of the air by the 1st air nozzle and the 2nd air nozzle. It is a figure which shows the air volume from a 1st air nozzle and a 2nd air nozzle. It is sectional drawing of the drive mechanism which drives the 2nd valve in 2nd Embodiment. It is sectional drawing of the drive mechanism of a different structure in 2nd Embodiment. It is sectional drawing of the drive mechanism which drives the 2nd valve in 3rd Embodiment, Comprising: It is the figure which open | released the 2nd valve. It is sectional drawing of the drive mechanism which drives the 2nd valve in 3rd Embodiment, Comprising: It is the figure which closed the 2nd valve. It is a block diagram in a 3rd embodiment. It is sectional drawing of the drive mechanism which drives the 2nd valve in 4th Embodiment. It is sectional drawing of the 2nd valve etc. in a 5th embodiment.

  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 device 3C, and the charging unit 2K and the exposure device 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 views of the belt fixing device shown in FIGS. FIG. 2 is a view in which the second valve is opened, and FIG. 3 is a view in which the second valve is closed, except for the second valve.

  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 and two of 750 W in order to correspond to different paper widths, and is arranged so as to have different heat generation distributions in the axial direction corresponding to different paper widths of the recording paper. It is. In addition to this, a 500 W one having a uniform light distribution for maintaining the temperature during standby is arranged.

  The fixing roller 83 is formed by covering a core metal 83A made of metal such as iron 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 low friction of 30 μm. And covered with a resin layer 83C coated with PTFE which is a 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, although a halogen heater with high heat generation efficiency is suitable as a heating means for heating the fixing belt 81, for example, electromagnetic induction heating using an exciting 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

  Therefore, in the present fixing device 8, as the separating means, a first air nozzle 111 (first spraying means) and a second air nozzle 121 (second spraying means) are provided in the vicinity of the exit side of the nip portion N. The first air nozzle 111 discharges compressed air generated by being compressed by a compressor. The first air nozzle 111 is sprayed for a short time to the vicinity of the front end of the recording paper P immediately after passing through the nip portion N, and the front end of the recording paper P The part is separated from the fixing belt 81. On the other hand, the second air nozzle 121 discharges air that has been blown by the fan 123 and passed through the duct 125, and is continuously blown to the recording paper P from which the leading end is separated so as not to adhere to the fixing belt 81. .

  As an example, the front end of the first air nozzle 111 is located at a distance of 25 mm from the outlet portion of the nip portion N, and the air from the first air nozzle 111 is located at 10 mm from the outlet portion of the nip portion N. It sets so that it may discharge toward an outer peripheral surface.

  In addition, a second valve 122 that opens and closes in order to discharge or stop the air blown by the fan 123 from the second air nozzle 121 is provided inside the end of the duct 125.

  Then, the air discharged from the first air nozzle 111 is blown into a very narrow gap between the leading end of the recording paper P and the fixing belt 81, that is, blown to a very small air receiving surface to peel off the recording paper P. Needs to be large, but only a small amount of air is needed because it requires only a short discharge. On the other hand, since the air discharged from the second air nozzle 121 is after the leading edge of the recording paper P has been separated, the wind speed may be smaller than that of the first air nozzle 111, but the entire recording paper P passes through the nip portion N. Therefore, the air volume per print is larger than that of the first air nozzle 111. A fan is difficult to obtain high pressure like a compressor, but it is relatively easy to obtain a large air volume with low power and small size, after the tip part separated and the wind receiving area of the paper became large It is suitable as an air supply source. Note that high-speed, that is, high-pressure air must be discharged from the first air nozzle 111. However, since the opening cross-sectional area of the discharge portion is small, the air volume per unit time is approximately 1 / of the air volume from the second air nozzle 121. 10 is sufficient. Since the first air nozzle 111 and the second air nozzle 121 supplement each other in this manner, the air compressor is compared with a configuration in which only the compressed air is discharged from the first air nozzle 111 without providing the second air nozzle 121. Therefore, the size and power are reduced to about 1/10, which reduces the size and saves power.

  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 pressurized even if the recording paper P is pressed downward by the air from the first air nozzle 111 or the second air nozzle 121. The roller 84 is not wound around. Further, the separation claw 86 is coated with a fluororesin at the tip of about 10 mm, for example, and has good lubricity, and is pressed against the pressure roller 84 with a weak pressure of about 5 to 10 mN. There will be no wrinkles. 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.

  In the image forming apparatus including the fixing device 8 having the first air nozzle 111 and the second air nozzle 121 as described above, the first air nozzle 111 ejects the leading end portion of the recording paper P beyond the exit portion of the nip portion N. The recording paper P is separated from the fixing belt 81 by blowing the air. At this time, if air is simultaneously blown from the second air nozzle 121 to the leading edge of the recording paper P, the air discharged from the second air nozzle 121 becomes resistance to the air discharged from the first air nozzle 111, and recording is performed. Experiments have revealed that the separation performance of the paper P with respect to the leading end may be deteriorated.

  The experimental results are shown in Table 1.

  In this experiment, the numerical value of the first air nozzle 111 is the discharge pressure, “Yes” of the second air nozzle 121 is a state in which air is discharged at a wind speed of 23 m / s, and “No” is a state in which no air is discharged. .

  As for the sign of the separation performance, が indicates very good separation performance, ◯ indicates good separation performance, Δ indicates separation but gloss unevenness occurs, and × does not separate and jam occurs. Specifically, under the conditions that occur at Δ and ×, the front end of the recording paper P is blown by the air from the second air nozzle 121 that flows around after the front end of the recording paper P is peeled off by the air from the first air nozzle 111. May be partially squeezed toward the fixing belt 81, or conversely squeezed toward the pressure roller 84, and the leading edge of the recording paper P may collide with the nozzle or may strike the conveyance guide at a deep angle. The paper bends and deforms, or a paper jam occurs.

  As described above, in order to prevent deterioration of the separation performance of the recording paper P, it is desirable that air is not discharged from the second air nozzle 121 as much as possible when the air is discharged from the first air nozzle 111. However, when the second air nozzle 121 is discharged after the discharge from the first air nozzle 111 is stopped, in other words, when the transfer from the first air nozzle 111 to the second air nozzle 121 is continued, the separation of the recording paper P is continued. It is necessary to maintain the airflow necessary for the operation.

  That is, when the leading edge of the recording paper P is peeled off, the air volume from the second air nozzle 121 must be a predetermined amount or less, and after the leading edge of the recording paper P is peeled off, the compressed air is supplied to the first air nozzle 111. In the process of stopping the process, before the separation of the recording paper P cannot be continued, the sum of the air volume from the second air nozzle 121 and the air volume from the first air nozzle 111 needs to reach an air volume capable of continuing the separation of the recording paper P. There is.

  At this time, the second valve 122 may be controlled using a motor or the like, but a high output stepping motor and a circuit for driving it are required to obtain high controllability and responsiveness. In addition, since the operation time of each valve must be controlled according to time, variations in response time of the first valve cannot be absorbed. In the present invention, the discharge of air from the second air nozzle 121, that is, the opening / closing operation of the second valve 122 is controlled by a change in the air pressure from the first air nozzle 111. That is, since the air discharge from the second air nozzle 121 is controlled according to the discharge conditions (wind pressure or air volume) of the first air nozzle 111, it is difficult to be affected by response variations, and it is possible to take over the stable separation auxiliary air blow. .

  Hereinafter, various embodiments relating to such a configuration will be described.

[First Embodiment]
A first embodiment will be described with reference to FIGS. 4 is a perspective view of the second air nozzle, FIG. 5 is a perspective view of the first air nozzle and the like, FIG. 6 is a sectional view of a driving mechanism for driving the second valve in the second air nozzle, and FIG. FIG. 8 is a timing chart of air discharge by the first air nozzle and the second air nozzle, and FIG. 9 is a view showing the air volume from the first air nozzle and the second air nozzle.

  As shown in FIG. 4, the second air nozzle 121 is formed long in the width direction of the recording paper to be fixed.

  As an example, the dimensions of the discharge port 121A of the second air nozzle 121 are 325 mm in the width direction of the recording paper P and 3 mm in the thickness direction of the recording paper P. The second air nozzle 121 is connected to a plurality of fans 123 by a duct 125 as shown in FIGS.

  As shown in FIG. 5, five first air nozzles 111 are arranged in the width direction of the recording paper, and each first air nozzle 111 is provided with 13 nozzle holes 111A having a diameter of 1 mm at a pitch of 5 mm. Accordingly, the total number of nozzle holes 111A is 65 with the five first air nozzles 111. The five first air nozzles 111 are connected to the two piping parts 117 by five pipes 116, respectively, and the two piping parts 117 communicate with the two first valves 112, which are electromagnetic valves, respectively. .

  The two piping parts 117 are also connected to two second valve drive mechanisms 150 that drive the second valve 122. Although the second valve drive mechanism 150 will be described later, it is disposed in the vicinity of both ends in the width direction of the recording paper in the second air nozzle 121.

  Next, the second valve drive mechanism 150 will be described with reference to FIG.

  In FIG. 6, the second air nozzle 121 is illustrated in an enlarged manner, and the second valve 122 is disposed inside the second air nozzle 121, and the second valve 122 is perpendicular to the paper surface, that is, the width of the recording paper. The support shaft 126 is rotatable about a support shaft 126 that is long in the direction. FIG. 6A is a diagram in a state in which the second valve 122 is opened, and FIG. 6B is a diagram in a state in which the second valve 122 is closed.

  One cylinder 151 is arranged in the vicinity of the outer end of the second air nozzle 121, that is, in the vicinity of both outer ends in the width direction of the recording paper P, and a piston 152 is fitted inside each cylinder 151 and slides. Arranged freely. The end of the rod 152A of the piston 152 protrudes outside the cylinder 151, and a drive shaft 153 is implanted at the end. In addition, drive levers 154 that are coaxial with the above-described support shaft 126 and rotate around the support shaft 126 are disposed in the vicinity of the outer end of the second air nozzle 121, and are elongated holes 154 </ b> A provided at one end of each drive lever 154. A drive shaft 153 is inserted into the shaft. Accordingly, the second valve 122 rotates and opens and closes in conjunction with the rotation of the drive lever 154.

  A compression coil spring 155 is disposed between the piston head 152B of the piston 152 and the bottom 151A of the cylinder 151, and the piston 152 is urged in the direction of the opening 151B of the cylinder 151. However, the sliding of the piston 152 is interlocked with the rotation of the second valve 122, and when the second valve 122 is opened as shown in FIG. 2 Since the piston 152 abuts against the inner wall of the air nozzle 121, the piston 152 does not slide in the direction of the opening 151B beyond the position shown in FIG. 6A even when urged by the compression coil spring 255. Further, an O-ring 156 is pressure-bonded to the rod 152A of the piston 152 so that air inside the cylinder 151 does not leak.

  In this embodiment, there is no problem even if some compressed air leaks from the cylinder 151, so that the O-ring 156 is fitted to the rod 152A so that the operation of the piston 152 is not hindered by the O-ring 156. Is usually set to be looser than that used for sealing.

  One end of a pipe 157 is connected to the outer peripheral surface of the opening 151B of the cylinder 151, and the other end of the pipe 157 is connected to the downstream side of the first valve 112 described later.

  As an example, the dimensions of the second valve 122 are 323 mm in the width direction of the recording paper P, 4.5 mm in the direction of air flow, and 0.8 mm in thickness, and are made of a heat resistant resin.

  The internal diameter of the cylinder 151 is 10 mm, the spring pressure of the compression coil spring 255 is 0.5 N / mm, and the amount of compression of the compression coil spring 255 from FIG. 6A to FIG. 6B is 10 mm. In the present embodiment, the compression coil spring 255 is installed in the cylinder 151 and is compressed when compressed air is supplied. For example, the compression coil spring 255 is arranged between the stopper provided on the rod 152A and the outside of the bottom portion 151A. A spring may be installed coaxially with the rod 152A so that the spring is extended when compressed air is supplied.

  Next, related members of the first air nozzle 111 and the second air nozzle 121 will be described with reference to FIG.

  The compressed air compressed by the compressor 115 is stored in advance in the air tank 114, adjusted to a predetermined pressure by the regulator 113, and then discharged from the first air nozzle 111 when the first valve 112, which is an electromagnetic valve, is opened. To do.

  As an example, each member has the following functions and performance.

The compressor 115 is a reciprocating oil-free type, and its output is 0.75 kW, the static pressure is 0.8 MPa, and the air volume is 0.00125 m ³ / s.

The capacity of the air tank 114 is 0.05 m ³ .

  The regulator 113 reduces the compressed air to about 0.15 MPa.

The first valve 112 is a direct acting solenoid valve, and has a capacity of 0.08 m ³ / s (100 kPa) and a response speed of 20 ms.

The discharge pressure from the first air nozzle 111 is 0.1 to 0.2 MPa, the discharge air speed is 100 to 160 m / s, and the discharge air amount is 0.005 to 0.008 m ³ / s.

  On the other hand, when the fan switch 124 is turned on, the fan 123 rotates and the path to the second valve 122 is preloaded by the fan 123. When the second valve 122 is driven and opened by the second valve driving means 150, air is blown from the second air nozzle 121.

  As an example, there are five fans 123, which are 70 mm axial fans. The power is 12 W and the static pressure is 500 Pa. However, the fan 123 is not limited to the axial flow fan, and may be a sirocco 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 requirements which have an appropriate air volume. The shape of the duct 125 is set according to the type of the fan 123.

The discharge pressure from the second air nozzle 121 is 500 Pa, the discharge air speed is 20 to 30 m / s, and the discharge air amount is 0.02 to 0.03 m ³ / s. However, the wind speed and the air volume are in accordance with conditions such as the paper conveyance speed of 500 mm / s, the paper sheet amount of 80 g / m ² and the roller configuration in the present embodiment, and are not limited thereto.

  The second valve driving means 150 is configured as shown in FIG. The first valve 112 communicates with the cylinder 151 by a pipe 157 in FIG. For this reason, when the first valve 112 is closed, the compressed air does not flow to the cylinder 151, and the piston 152 is urged by the compression coil spring 155 to be in the state shown in FIG. Therefore, the second valve 122 opens the second air nozzle 121. On the other hand, when the first valve 112 is opened, compressed air flows from the opening 151B to the cylinder 151, and the compressed air presses the piston 152 against the urging force of the compression coil spring 155, as shown in FIG. It becomes a state. Accordingly, the second valve 122 closes the second air nozzle 121.

  The control means 101, paper feed sensor 102, and timer 103 will be described later.

  Next, the process of discharging air from the first air nozzle 111 and the second air nozzle 121 will be described with reference to FIG. In this case, A4 recording paper P is fed at 100 ppm.

  When 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 in the image forming apparatus having the above-described configuration as shown in FIG. The control means 101 is configured to energize the fan switch 124. Since the sheet feeding operation itself is also controlled by the control unit 101, the control unit 101 refers to the timer 103 without using the sheet feeding sensor 102, manages the time interval between both operations, and energizes the fan switch 124. You may control. Thereby, each fan 123 starts rotation. At this time, since the first valve 112 is closed and the second valve 122 is open as shown in FIG. 6A, air is discharged from the second air nozzle 121 at, for example, 20 m / s.

  The reason why the fan switch 124 is energized before the recording paper P reaches the fixing device 8 is that there is a time lag until the maximum rotation speed is reached after the fan 123 starts rotating. Further, if the conveyance speed of the recording paper P is slow and the fan 123 can reach a wind speed sufficient to continue the separation described later before reaching the position where the recording paper P is to be separated, the recording is possible. The paper P may be energized after reaching the fixing device 8. Conversely, when the present invention is applied to a higher-speed image forming apparatus and a blower or the like that has a high output but takes a long time to start is used as the fan 123, the image forming apparatus starts feeding or further performs an image forming operation. Prior to the start, the energization timing of the fan switch 124 is appropriately selected, such as starting the blower.

Further, instead of blowing air from the fan 123 after paper feeding, the fan 123 is operated prior to paper feeding operation to cool the fixing belt 81 and create a temperature gradient from the heating part to the fixing part. If the temperature drop is reduced, fluctuations in image gloss due to temperature changes can be suppressed. In addition, since the electric power necessary to reduce the temperature drop can be reduced, the fixing power source capacity can be suppressed. For example, when 300 g / m ² of paper is passed without blowing before passing paper, the temperature of the fixing belt 81 is reduced by about 15 ° C. about 30 s after the start of passing paper. When operated, the temperature drop fell below 5 ° C.

  On the other hand, since the time from when the paper feed sensor 102 is detected until the leading edge 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 a timer. An open signal is transmitted to the first valve 112, which is an electromagnetic valve, for example, 15 ms before the time is reached by 103. Since the compressed air of about 0.8 MPa compressed by the compressor 115 is stored in the air tank 114 in advance, the pressure is reduced by the regulator 113 and the compressed air is discharged from the first air nozzle 111 when the first valve 112 is opened. Then, the recording paper P is blown against the leading edge of the recording paper P immediately after passing through the nip portion N, and the recording paper P is separated from the fixing belt 81.

  Further, since the first valve 112 is fully opened about 20 ms after the opening signal is inputted, the maximum pressure, for example, 0.15 MPa is reached when the recording paper P is conveyed about 10 mm from the nip portion, and the air volume is increased. Is maximized. Since the pressure of the compressed air from the first air nozzle 111 is 2 to 3 times the pressure necessary for separating the recording paper P, the recording paper P is discharged before the pressure of the compressed air reaches the maximum, that is, from the nip portion N. Separation begins before the transport amount reaches 10 mm. Thereafter, the closing signal is transmitted about 50 ms after the opening signal is input to the first valve 112. When a closing signal is input to the first valve 112, the pressure of the compressed air discharged from the first air nozzle 111 gradually decreases, and the air volume also decreases, while the leading end of the recording paper P moves from the nip N. Continue to discharge until it reaches 25-30 mm. The pressure at this time is a pressure at which the recording paper P can be separated even if there is a maximum amount of toner image.

  Here, when the first valve 112 starts to open and the pressure of the compressed air rises to 0.05 MPa or more, the pressure of the compressed air prevails due to the urging force of the compression coil spring 155 and the piston 152 starts to be pressed. That is, the second valve 122 of the second air nozzle 121 starts to close, and the flow rate of the air discharged from the second air nozzle 121 starts to decrease. Eventually, when the pressure of the compressed air reaches 0.15 MPa, the second valve 122 is completely closed. Therefore, when the signal is input to the first valve 112 and reaches 20 ms at which it is fully opened, no air is discharged from the second air nozzle 121 at all. Accordingly, only the compressed air from the first air nozzle 111 is blown onto the recording paper P at the leading edge of the recording paper P, and the vicinity of the leading edge of the recording paper P is separated from the fixing belt 81.

  In addition, when the pressure of compressed air becomes 0.05 MPa, the force applied to the piston 152 is 8 to 10N.

Further, according to an experiment, if the leading edge of the recording paper P protrudes 5 to 10 mm from the fixing belt 81, the thickness of about 80 g / m ² on which the solid image with the maximum adhesion amount is placed by blowing with a fan of about 20 m / s. It has been confirmed that even a thin coated paper for printing can be continuously separated.

  On the other hand, about 50 ms after the opening signal is input to the first valve 112, the leading edge of the recording paper P is separated from the fixing belt 81 by 10 mm or more. Accordingly, a close signal is transmitted to the first valve 112 at this time. Thereby, the first valve 112 starts to close, the pressure of the compressed air decreases, and the air volume also decreases. When the pressure of the compressed air falls below 0.15 MPa, the piston 152 starts to slide in the direction of the opening 151B by the urging force of the compression coil spring 255. That is, the second valve 122 of the second air nozzle 121 starts to open. Therefore, the air volume of the compressed air from the first air nozzle 111 decreases, and the air volume of the air from the second air nozzle 121 increases. And when the pressure of compressed air falls to 0.05 MPa, the piston 152 will be in the state of Fig.6 (a), and the 2nd valve 122 will open | release completely. Further, when the first valve 112 is completely closed, the compressed air is not discharged from the first air nozzle 111, so that the air pressure becomes zero and the opening of the second valve 122 is maintained. Thereafter, the recording paper P is separated only by the air discharged from the second air nozzle 121.

  In the above, there is a process in which the air volume of the compressed air from the first air nozzle 111 decreases and the air volume of the air from the second air nozzle 121 increases. In this case, the total air volume of both is a predetermined air volume required for separation ( Vc) must be set to be greater than or equal to Vc). This is shown in FIG. 9A and 9B, A1 is the air volume from the first air nozzle 111, A2 is the air volume from the second air nozzle 121, and A1 + A2 is the sum of the air volume from the first air nozzle 111 and the air volume from the second air nozzle 121. Indicates.

  On the other hand, as shown in FIG. 9B, when the total air volume of both is equal to or less than the predetermined air volume (Vc), sufficient separation cannot be performed, and paper jams and peeling unevenness occur due to poor separation.

In order to set the total air volume of the air volume from the first air nozzle 111 and the air volume from the second air nozzle 121 to be equal to or higher than a predetermined air volume (Vc) necessary for separation, the air pressure of the compressed air is illustrated. It is necessary to set appropriately the dimension of each member shown in FIG. The dimensions of each member described above are determined by the cylinder diameter (pressure and cross-sectional area determine the force that pushes the rod so that the total air volume from the two air nozzles exceeds the predetermined air volume at the compressed air pressure of the configuration of the present embodiment. ) And spring configuration. In this example, Vc was about 0.003 m ³ / s, and it was configured to exceed this.

  Further, according to an experiment, when the recording paper P is peeled after the leading end of the recording paper P is wound by 10 mm or more, image unevenness caused by a change in the peeling state occurs as the winding amount increases, and the image quality is lowered. I know that. As described above, if separation is started before the amount of wrapping is reached, the occurrence of image unevenness can be suppressed.

  With the configuration of the present embodiment, a thin paper separation performance and a high productivity can be achieved in combination with a fan while being a small-sized and low-power compressor. In addition, when the leading end portion of the recording paper P is peeled off from the fixing belt, the leading end portion avoids a paper jam caused by the irregular behavior of the leading end portion that occurs across the wind from the fan, and from the compressor. By switching to the fan by the supplied compressed air, it is possible to maintain the air volume necessary for continuing the separation and reliably continue the separation.

  Incidentally, instead of the compression coil spring 155 in FIG. 6, a torsion coil spring that urges the support shaft 126 counterclockwise, that is, urges the second valve 122 to open may be provided.

[Second Embodiment]
A second embodiment will be described with reference to FIG. FIG. 10 is a cross-sectional view of a drive mechanism that drives the second valve in the second air nozzle.

  10, a second valve 222 is arranged inside the second air nozzle 121 as in FIG. 6, and the second valve 222 is centered on a support shaft 226 that is long in the direction perpendicular to the paper surface, that is, in the width direction of the recording paper. Both the support shafts 226 are rotatable. However, in FIG. 6, the support shaft 226 is disposed in the vicinity of the upper portion of the inner wall of the second air nozzle 121, but in FIG. 10, the support shaft 226 is disposed in the vicinity of the lower portion of the inner wall of the second air nozzle 121. FIG. 10A is a view showing a state where the second valve 222 is opened, and FIG. 10B is a view showing a state where the second valve 222 is closed.

  One cylinder 251 is disposed near the outer end of the second air nozzle 121, and a piston 252 is fitted inside each cylinder 251 and is slidably disposed. The end of the rod 252A of the piston 252 protrudes above the cylinder 251, and a drive shaft 253 is implanted at the end. In addition, a drive lever 254 that is coaxial with the support shaft 226 and rotates around the support shaft 226 is disposed in the vicinity of the outer end of the second air nozzle 121, and is driven into a long hole 254 A provided at one end of each drive lever 254. A shaft 253 is inserted. Accordingly, the second valve 222 rotates and opens and closes in conjunction with the rotation of the drive lever 254.

  A heavy weight member 255 is fixed on the piston head 252B of the piston 252, and the piston 252 is urged toward the opening 251B of the cylinder 251 by gravity due to the weight member 255. The sliding of the piston 252 is interlocked with the rotation of the second valve 222. When the second valve 222 is opened as shown in FIG. 2 Since it abuts against the inner wall of the air nozzle 121, it does not slide in the direction of the opening 251B beyond the position shown in FIG. 10A even if gravity is applied to the piston 252 by the weight member 255. Further, an O-ring 256 is pressure-bonded to the rod 252A of the piston 252 so that air inside the cylinder 251 does not leak. As in the first embodiment, there is no problem even if some compressed air leaks from the cylinder 251, so that the O-ring 256 is fitted to the rod 252A so that the operation of the piston 252 is not hindered. Is set to be looser than that normally used for sealing.

  One end of a pipe 257 is connected to the outer peripheral surface of the opening 251B of the cylinder 251 and the other end of the pipe 257 is connected to the downstream side of the first valve 112 described above.

  As an example, the dimensions of the second valve 222 are 323 mm in the width direction of the recording paper P, 4.5 mm in the direction of air flow, and 1 mm in thickness, and are formed from a galvanized steel plate. The inner diameter of the cylinder 251 is 4 mm. The weight member 255 has a diameter of 3 mm, a length of 21 mm, is formed of STKM (carbon steel pipe for mechanical structure), and has a mass of 0.12 kg.

  The operation of this drive mechanism is the same as that of the drive mechanism in FIG.

  When the first valve 112 is closed, it is in the state of FIG. 10A, and the piston 252 is not pressed, so that it remains below due to the gravity of the weight member 255, via the drive lever 254. The second valve 222 is open.

  When the first valve 112 starts to open and the pressure of the compressed air rises to, for example, 0.05 MPa or more, the pressure of the compressed air prevails over the gravity of the weight member 255 and starts to press the piston 252. That is, the second valve 222 starts to close and the flow rate of the air discharged from the second air nozzle 121 starts to decrease. Eventually, when the pressure of the compressed air reaches 0.10 MPa, the second valve 222 is completely closed and no air is discharged from the second air nozzle 121 as shown in FIG. 10B. Accordingly, only the compressed air from the first air nozzle 111 is blown onto the recording paper P, and the recording paper P is separated from the fixing belt 81.

  When the closing signal is transmitted to the first valve 112, the first valve 112 starts to close, the pressure of the compressed air decreases, and the air volume also decreases. When the pressure of the compressed air drops below 0.10 MPa, the piston 252 starts to slide in the direction of the opening 251B due to the gravity of the weight member 255. That is, the second valve 222 of the second air nozzle 121 starts to open. Therefore, the air volume of the compressed air from the first air nozzle 111 decreases, and the air volume of the air from the second air nozzle 121 increases. When the first valve 112 is completely closed, the compressed air is not discharged from the first air nozzle 111, and the pressure of the compressed air becomes zero. Then, the piston 252 is in the state of FIG. 10A, and the second valve 222 is completely opened. Therefore, thereafter, the recording paper P is separated only by the air discharged from the second air nozzle 121.

  The above is a configuration in which compressed air is blown from the lower side of the cylinder 251 and the piston 252 is moved upward against the gravity of the weight member 255. However, compressed air is blown from the upper side of the cylinder and the piston is moved to the gravity of the weight member. It can also be configured to move downward against the above. Such a configuration will be described with reference to FIG.

  Since FIG. 11 is similar to FIG. 6, only the main part will be described. The drive lever 264 rotates around the support shaft 266 in conjunction with the rod 262A of the piston 262. A weight member 265 is fixed to the end of the drive lever 264. Therefore, as shown in FIG. 11A, when the compressed air is not blown into the cylinder 261, the drive lever 264 rotates counterclockwise due to the gravity of the weight member 265, so that the second valve 222 is opened. At the same time, the piston 262 is moved upward via the rod 262A. On the other hand, when the pressure of the compressed air becomes equal to or higher than the predetermined pressure as described above, the compressed air presses the piston 262 and moves the drive lever 264 clockwise against the gravity of the weight member 265 as shown in FIG. And the second valve 222 is closed.

[Third Embodiment]
A third embodiment will be described with reference to FIGS. FIG. 12 is a sectional view of the driving mechanism in which the second valve in the second air nozzle is opened, and FIG. 13 is a sectional view of the driving mechanism in which the second valve in the second air nozzle is closed.

  12 and 13, a second valve 322 is arranged inside the second air nozzle 121 as in FIG. 6, and the second valve 322 is a support shaft 326 that is long in the direction perpendicular to the paper surface, that is, in the width direction of the recording paper. The support shaft 326 is rotatable about the center.

  One first cylinder 351 is disposed near the outer end of the second air nozzle 121, and a first piston 352 is fitted and slidably disposed inside each first cylinder 351. The end portion of the rod 352 </ b> A of the first piston 352 protrudes below the first cylinder 351.

  Further, an O-ring 356 is pressure-bonded to the rod 352A of the first piston 352 so that air inside the first cylinder 351 does not leak.

  One end of a pipe 357 is connected to the outer peripheral surface of the first opening 351B of the first cylinder 351, and the other end of the pipe 357 is connected to the downstream side of the first valve 112 described above.

  One second cylinder 361 is also arranged below the two first cylinders 351, and a second piston 362 is fitted inside each second cylinder 361 and is slidably disposed. The end of the rod 362 </ b> A of the second piston 362 protrudes above the second cylinder 361.

  The cross-sectional area inside the second cylinder 361 is set to 2/3 of the cross-sectional area inside the first cylinder 351. That is, the sectional area of the piston head 362A of the second piston 362 is set to 2/3 of the sectional area of the piston head 352A of the first piston 352. As an example, the inner diameter of the second cylinder 361 is 8 mm.

  Further, an O-ring 366 is pressure-bonded to the rod 362A of the second piston 362 so that air inside the second cylinder 361 does not leak.

  One end of a pipe 367 is connected to the outer peripheral surface of the second opening 361B of the second cylinder 361, and the other end of the pipe 367 is connected to the upstream side of the first valve 112 described above.

  The end of the rod 352A of the first piston 352 and the end of the rod 362A of the second piston 362 are joined, and a drive shaft 353 is implanted in this joined part. A drive lever 354 that is coaxial with the support shaft 326 and rotates about the support shaft 326 is disposed in the vicinity of the outer end of the second air nozzle 121, and is driven into a long hole 354 A provided at one end of each drive lever 354. A shaft 353 is inserted. Accordingly, the second valve 322 rotates and opens and closes in conjunction with the rotation of the drive lever 354.

  The operation of this drive mechanism is the same as that of the drive mechanism in FIG.

  When the first valve 112 is closed, it is in the state of FIG. 12, and no pressing force is applied to the first piston 352, but a pressing force by compressed air is applied to the second piston 362.

  When the first valve 112 starts to open, a pressing force by compressed air is applied to both the first piston 352 and the second piston 362. When the pressure of the compressed air rises to, for example, 0.1 MPa or more with the opening of the first valve 112, the pressing force of the first piston 352 having a larger cross-sectional area is applied with a pressure of 0.15 MPa. It exceeds the pressing force of the second piston 362 having a cross-sectional area of only 2/3. Therefore, the first piston 352 presses the second piston 362, and the drive shaft 353 moves toward the second cylinder 361. Therefore, the drive lever 354 rotates, the second valve 322 starts to close, and the flow rate of the air discharged from the second air nozzle 121 starts to decrease. Eventually, as shown in FIG. 13, when the pressure of the compressed air reaches 0.15 MPa, the second valve 322 is completely closed and no air is discharged from the second air nozzle 121. Accordingly, only the compressed air from the first air nozzle 111 is blown onto the recording paper P, and the recording paper P is separated from the fixing belt 81.

  When the closing signal is transmitted to the first valve 112, the first valve 112 starts to close, the pressure of the compressed air decreases, and the air volume also decreases. When the pressure of the compressed air drops below 0.1 MPa, the second piston 362 presses the first piston 352 and the drive shaft 353 moves toward the first cylinder 351. Accordingly, the drive lever 354 rotates and the second valve 322 of the second air nozzle 121 starts to open. Therefore, the air volume of the compressed air from the first air nozzle 111 decreases, and the air volume of the air from the second air nozzle 121 increases. When the first valve 112 is completely closed, the compressed air is not discharged from the first air nozzle 111, and the pressure of the compressed air becomes zero. Then, it will be in the state of FIG. 12, and the 2nd valve 322 will open | release completely. Therefore, thereafter, the recording paper P is separated only by the air discharged from the second air nozzle 121.

  The block diagram showing the present embodiment is the same as in FIG. 7 except that the compressed air flows into the second valve driving means 150 from the two upstream and downstream flow paths of the first valve 112. FIG. 14 shows a block diagram clarifying this.

[Fourth Embodiment]
A fourth embodiment will be described with reference to FIG. FIG. 15 is a cross-sectional view of a drive mechanism for driving the second valve in the second air nozzle.

  15, a second valve 422 is disposed inside the second air nozzle 121 as in FIG. 6, and the second valve 422 is centered on a support shaft 426 that is long in the direction perpendicular to the paper surface, that is, in the width direction of the recording paper. Both the support shafts 426 are rotatable. Similarly to FIG. 10, the support shaft 426 is disposed in the vicinity of the lower portion of the inner wall of the second air nozzle 121. FIG. 15A is a diagram in a state in which the second valve 422 is opened, and FIG. 15B is a diagram in a state in which the second valve 422 is closed.

  One cylinder 451 is disposed near the outer end of the second air nozzle 121, and a piston 452 is fitted inside each cylinder 451 so as to be slidable. The end of the rod 452A of the piston 452 protrudes above the cylinder 451, and a drive shaft 453 is implanted at the end. In addition, a drive lever 454 that is coaxial with the support shaft 426 and rotates about the support shaft 426 is disposed near the outer end of the second air nozzle 121, and is driven into a long hole 454 </ b> A provided at one end of each drive lever 454. A shaft 453 is inserted. Accordingly, the second valve 422 rotates and opens and closes in conjunction with the rotation of the drive lever 454.

  Further, an O-ring 456 is pressure-bonded to the rod 452A of the piston 452 so that air inside the cylinder 451 does not leak.

  One end of a pipe 457 is connected to the outer peripheral surface of the opening 451B of the cylinder 451, and the other end of the pipe 457 is connected to the downstream side of the first valve 112 described above.

  As an example, the dimensions of the second valve 422 are 323 mm in the width direction of the recording paper P, 12 mm in the direction of air flow, and 0.8 mm in thickness, and are made of a heat resistant resin. In this embodiment, since the second valve 422 is opened by the blowing pressure from the fan 123, the length in the direction in which air flows is larger than that of the second valve 122 of the first embodiment. The wind area is secured.

  The inner diameter of the cylinder 451 is 10 mm.

  In the present embodiment, the opening / closing operation of the second valve 422 is performed by the balance between the wind pressure from the fan 123 and the wind pressure of the compressed air from the first valve 112.

  That is, when the first valve 112 is closed, the state is as shown in FIG. 15A, and the air is blown from the fan 123 without applying a pressing force to the piston 452, so the second valve 422 is Pressed by wind pressure and opened.

  On the other hand, when the first valve 112 is opened, the piston 452 is pressed by compressed air, and the force to close the second valve 422 is greater than the wind force by the fan 123, and the second valve 422 as shown in FIG. The valve 422 is closed.

  Then, when a close signal is input to the first valve 112 and the pressure of the compressed air to the piston 452 is reduced to, for example, 0.12 MPa, the second valve 422 starts to open due to the wind pressure from the fan 123, and 0.1 MPa It becomes fully open. Since the separation of the recording paper is continued when the wind pressure is about 0.05 MPa, the separation from the first air nozzle 111 to the second air nozzle 121 is performed without the separation becoming unstable, and stable separation becomes possible.

  In the above first to fourth embodiments, the second valves 122 to 422 are opened / closed around the support shaft, but may be formed as a sliding door if necessary.

[Fifth Embodiment]
A fifth embodiment will be described with reference to FIG. FIG. 16 is a sectional view of the second valve and the like in the second air nozzle.

  The second valve in the present embodiment is formed of an elastic member having elasticity, unlike the valve that rotates around the support shaft in the above-described embodiment. FIG. 16A is a diagram showing a state in which the second valve is opened, and FIG. 16B is a diagram showing a state in which the second valve is closed.

  In the present embodiment, the first air nozzle 111 and the second air nozzle 121 are disposed adjacent to each other. Then, a part of the side wall of the first air nozzle 111 and a part of the side wall of the second air nozzle 121 are opened, and the flow path 111A and the flow path 121A communicate with each other. Is covered by a second valve 522 formed of an elastic member such as elastic rubber.

  The opening / closing operation of the second valve 522 is performed by the balance between the wind pressure of the compressed air from the first valve 112 and the wind pressure from the fan 123.

  That is, when the first valve 112 is closed, as shown in FIG. 16A, only air is blown from the fan 123 to the discharge hole 121A, and is not blown to the discharge hole 111A. Therefore, the second valve 522 is not pressed by compressed air and is open.

  On the other hand, when the first valve 112 is opened, the second valve 522 is pressed by compressed air. Accordingly, as shown in FIG. 16B, the second valve 522 extends to abut against the inner wall 121B of the discharge hole 121A, and closes the discharge hole 121A of the second air nozzle 121.

  The pressure of the compressed air is about 0.5 MPa, which is a discharge pressure necessary for separation. At 0.08 MPa, the second valve 522 is extended by about 8%, and swells to a position substantially equal to the inner wall of the discharge hole 121A. Further, when the pressure of the compressed air increases, the second valve 522 swells inside the discharge hole 121A, contacts the inner wall 121B of the discharge hole 121A, and closes the discharge hole 121A. When the maximum pressure is 1.5 MPa, the inner wall 121B and the second valve 522 are pressed within a predetermined range as shown in FIG.

  Conversely, when the pressure of the compressed air decreases, the second valve 522 contracts accordingly and opens the discharge hole 121A.

  As an example, the second valve 522 is made of silicone rubber and has an elastic modulus of 40 MPa and a thickness of 1.2 mm.

  The opening of the discharge hole 111A is 323 mm × 20 mm. At this time, the length with which the second valve 522 contacts the inner wall 121B is 3 to 5 mm.

  Also in this embodiment, since the separation of the recording paper is continued at about 0.05 MPa, the separation from the first air nozzle 111 to the second air nozzle 121 is performed without the separation becoming unstable, and the stable separation is achieved. Is possible.

  Most rubbers function well even with an elongation of about 100%, but deterioration is accelerated. Therefore, in consideration of durability, it is most desirable that the second valve 522 is set so as to extend about 50% at maximum by compressed air. In the present embodiment, sufficient durability performance can be ensured by setting it to extend up to about 15%.

  Further, since the second valve 522 is disposed in the vicinity of the high-temperature fixing belt, it is desirable to use heat-resistant silicone rubber. However, if the cooling state of the first air nozzle 111 and the second air nozzle 121 is good. A rubber having poor heat resistance may be used.

  In the second to fifth embodiments described above, as in the first embodiment, the relationship between the air volumes discharged from the first air nozzle 111 and the second air nozzle 121 satisfies FIG. 9A. .

  In the above description, the number of the first air nozzles 111 has been described as five, but the number is not limited. Further, nozzles having different sizes may be combined according to the paper width, or the nozzles may be integrally formed to divide the flow path inside.

  Further, the fixing device using the first air nozzle 111 and the second air nozzle 121 is not limited to the belt fixing device as described above, and any fixing device may be used. For example, a recording material on which a toner image is transferred at a nip formed by a fixing roller (fixing member) incorporating a heating means such as a halogen heater and a pressure roller (pressure member) that presses the fixing roller. There may be a heat roller fixing type fixing device that heats and pressurizes while sandwiching and conveying.

  By the way, louvers are provided in the front and rear of the image forming apparatus as shown in FIG. 1, and the outside air sucked from the opening of the louvers is located on the outlet side of the fixing device via an air duct arranged at the upper portion of the fixing device. Guided by fans. The air duct is maintained at a low temperature by the outside air, and suppresses a temperature rise in the toner storage portion or the like due to thermal diffusion from the fixing device.

  The air discharged from the first air nozzle 111 and the second air nozzle 121 is guided to an opening provided at the end of the image forming apparatus on the fixing device outlet side by a duct having a part of the recording paper conveyance guide as a wall, and is discharged. The Further, if an exhaust fan is provided in the opening, the exhaust can be efficiently performed, and thermal contamination in the apparatus due to the air that has been blown to the fixing apparatus and has risen in temperature can be minimized. When a post-processing device or the like is connected to the image reading device, the image forming device is evacuated by providing openings on the upper surface and the rear surface.

DESCRIPTION OF SYMBOLS 8 Fixing apparatus 81 Fixing belt 82 Heating roller 83 Fixing roller 84 Pressure roller 101 Control means 102 Paper feed sensor 103 Timer 111 1st air nozzle 112 1st valve 113 Regulator 114 Air tank 115 Compressor 121 2nd air nozzle 122,222,322 422, 522 Second valve 123 Fan 124 Fan switch 125 Duct 126, 226, 266, 326, 426 Support shaft 151, 251, 261, 451 Cylinder 152, 252, 262, 452 Piston 154, 254, 264, 354 454 Drive lever 155 Compression coil spring 255, 265 Weight member 351 First cylinder 352 First piston 361 Second cylinder 362 Second piston N Nip part P Recording paper

Claims (12)

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.
A first spraying means and a second spraying means for discharging air and spraying the recording material to separate the recording material from the fixing member are provided in the vicinity of the outlet portion of the nip portion. A first valve for controlling the discharge of air by opening / closing the upstream side of the spraying means, and a second valve for controlling the discharge of air by opening / closing the inside of the second spraying means;
The pressure of the air discharged from the first blowing means is greater than the pressure of the air discharged from the second blowing means, and the air volume discharged from the first blowing means is discharged from the second blowing means. Less than the air volume,
The air flow supplied via the first valve is controlled by opening and closing the first valve, and the opening and closing operation of the second valve is performed by the controlled force of the air flow. Fixing device to do.   When the pressure of the air supplied to the first blowing means becomes a predetermined value or more, the second valve is closed, and the pressure of the air supplied to the first blowing means becomes a predetermined value or less. 2. The fixing device according to claim 1, wherein the second valve is configured to open when the second valve is opened.   The air discharged from the first blowing means is air compressed by a compressor, and the air discharged from the second blowing means is air blown by a fan. 3. The fixing device according to 2. A cylinder in which an opening provided at one end communicates with the downstream side of the first valve;
A piston which is contained in the cylinder and slides in conjunction with the opening and closing operation of the second valve, and which is pressed by the air flowing from the first valve and passing through the opening;
A biasing member that biases the piston in the direction of the opening,
When the air pressure that presses the piston exceeds a predetermined value, the piston is pressed against the urging force of the urging member to close the second valve, and the air pressure that presses the piston is predetermined. 4. The fixing device according to claim 1, wherein when the pressure is equal to or less than the value, the piston is pressed by an urging force of the urging member to open the second valve. 5. . A cylinder in which an opening provided at one end communicates with the downstream side of the first valve;
A piston which is contained in the cylinder and slides in conjunction with the opening and closing operation of the second valve, and which is pressed by the air flowing from the first valve and passing through the opening;
A weight member that presses the piston in the direction of the opening by gravity, and a drive mechanism,
When the air pressure that presses the piston becomes a predetermined value or more, the second valve is closed against the gravity applied to the weight member, and the air pressure that presses the piston becomes a predetermined value or less. The fixing device according to claim 1, wherein the second valve is opened by gravity applied to the weight member. A first cylinder in which a first opening provided at one end communicates with a downstream side of the first valve;
A first piston contained in the first cylinder and sliding in conjunction with the opening and closing operation of the second valve, and flowing from the first valve and pressed by the air passing through the first opening;
A second cylinder in which a second opening provided at one end communicates with an upstream side of the first valve;
The second cylinder has a head smaller in area than the head of the first piston and slides in conjunction with the opening / closing operation of the second valve, and flows from the first valve. A second piston pressed by the air that has passed through the opening,
The rod of the first piston and the rod of the second piston are arranged to face each other and connected to each other, and the two rods have a drive mechanism that slides in conjunction with the opening / closing operation of the second valve. ,
When the air pressure that presses the first piston exceeds a predetermined value, the air pressure that presses the first piston presses the second piston to close the second valve and presses the first piston. The fixing according to any one of claims 1 to 3, wherein when the pressure becomes equal to or less than a predetermined value, the second piston presses the first piston to open the second valve. apparatus. The second valve is opened by wind from the fan;
A cylinder in which an opening provided at one end communicates with the downstream side of the first valve;
And a piston that is included in the cylinder and slides in conjunction with the opening and closing operation of the second valve, and is pressed by the air that flows from the first valve and passes through the opening. ,
When the air pressure that presses the piston becomes a predetermined value or more, the piston is pressed against the force that the second valve opens by wind force from the fan, and the second valve is closed. 2. The second valve is opened by pressing the second valve and the piston by wind force from a fan when the air pressure that presses the piston becomes a predetermined value or less. 4. The fixing device according to any one of 3 above.   8. The fixing device according to claim 4, wherein the driving mechanism is disposed in the vicinity of both sides in the width direction of the recording paper in the second spraying unit. 9. An opening is provided in a part of the wall constituting the flow path of the second spraying means, and the supply path for supplying an air flow to the opening and the first spraying means is communicated.
Forming the second valve with an elastic member having elasticity to cover the opening;
When the pressure of the air supplied to the first spraying means exceeds a predetermined value, the second valve is pressed by the pressure of the air to close the discharge port of the second spraying means. The discharge port of the second spraying means is opened when the pressure of the air supplied to the first spraying means becomes a predetermined value or less. The fixing device according to Item 1. From the start of closing the first valve to the completion of closing, the sum of the air volume of air discharged from the first spraying means and the air volume of air discharged from the second spraying means is the sum of the recording material . The fixing device according to claim 1, wherein the fixing device has a predetermined airflow amount or more capable of continuing separation from the fixing member.   The fixing device according to claim 1, wherein the first valve of the first spraying unit is an electromagnetic valve.   An image forming apparatus comprising the fixing device according to claim 1.

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