JP3844198B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device including a separating member that separates a sheet-like medium such as a sheet from a rotating member such as a fixing belt and a heating roller, and an image forming apparatus such as a copying machine, a facsimile, and a printer having the separating member.
[0002]
[Prior art]
Image forming apparatuses such as copying machines, facsimile machines, and printers generally have a fixing device for fixing a toner image onto a sheet-like medium on which a toner image as a fixed image is formed.
[0003]
The fixing device includes a heating roller as a rotating member that has a heat source therein and is driven to rotate, and a pressure roller that is pressed against the heating roller and is driven to rotate by the heating roller, and a nip formed by both rollers. As a rotating member for conveying a sheet-like medium on which toner is fixed, a sheet-type medium is passed through the rotation of both rollers and heated and pressed to fix the toner image. A so-called belt fixing device of a type including an endless fixing belt, a heating roller and a fixing roller around which the fixing belt is wound, a pressure roller disposed so as to face the fixing roller via the fixing belt, and the like is known. ing.
[0004]
In any type of fixing device, the toner image is fixed on the sheet-like medium conveyed by the rotation of the rotating member by melting by heating. At the time of fixing, the toner image usually comes into contact with the sheet-like medium. However, since the toner image is highly viscous in a molten state, the sheet-like medium may be wound around the rotating member. Therefore, normally, the fixing device has means for forcibly separating the sheet-like medium from the rotating member, such as a separation claw, and prevents the sheet-like medium from being wound around the rotating member.
[0005]
However, since the separating member is only partially in contact with the surface of the rotating member, the surface of the rotating member is subjected to uneven pressing force by the separating member in the direction of the rotation axis, and the surface of the rotating member is unevenly worn, You may get hurt. In order to solve such problems, Japanese Patent Application Laid-Open No. 11-184300 discloses a fixing device that separates paper using a plastic release sheet.
[0006]
This fixing device includes a fixing roller as a rotating member, a pressure roller that rotates in contact with the fixing roller, and a rotation direction of the fixing roller rather than a nip portion as a facing position where the fixing roller and the pressure roller are in contact with each other. And a release sheet as a separating member that is disposed on the downstream side and separates the sheet that has passed through the nip portion from the fixing roller. The release sheet is arranged so that the edge thereof contacts the surface of the fixing roller with a uniform pressing force.
[0007]
[Problems to be solved by the invention]
However, in such a fixing device, the release sheet separates the paper that has passed through the nip while preventing uneven wear of the fixing roller due to the non-uniform pressing force, but the toner image on the paper does not adhere to the release sheet. Since the toner is conveyed while being rubbed against the tip or the portion after the tip, the toner adheres to the release sheet. As a result, there is a problem in that the toner adheres to the release sheet over time, and the fixed toner may be sandwiched between the release sheet and the fixing roller, causing damage to the fixing roller. Further, since the image is rubbed against the release sheet, there is a problem that the image may be disturbed.
[0008]
The present invention solves the above problems and provides a fixing device and an image forming apparatus having the same that prevent the toner from adhering to the separation member to prevent the fixing roller from being damaged or causing image disturbance. The purpose is to do.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, the invention according to claim 1ShiMediaFixing memberSeparating member for separating fromTheDisplace the separating memberMakeWith displacement meansIn the fixing device, the displacing unit displaces the separation member in a direction away from the sheet-like medium when the leading end of the sheet-like medium is separated from the fixing member by the separation member.It is characterized by that.
[0010]
  According to a second aspect of the present invention, there is provided the fixing device according to the first aspect, wherein the fixing device is a sheet-like medium.Toner image detecting means for detecting the position of the toner image, and the displacing means is arranged in accordance with the length from the leading edge of the sheet-like medium to the leading edge of the toner image detected by the toner image detecting means. DisplaceIt is characterized by that.
[0011]
  The invention described in claim 3Claim 1In the fixing device described above, on the sheet-like mediumToner amount detection means for detecting the toner amountAnd the displacement means isToner amount detecting meansSheet media detected byToner amount onDepending on the displacement of the separating memberMakeIt is characterized by that.
[0012]
  The invention according to claim 4Claim 1In the fixing device described above, a sheet-like mediumThe type ofDetectPaper type detection meansAnd the displacement means isPaper type detection meansSheet media detected byType ofDepending on the displacement of the separating memberMakeIt is characterized by that.
[0013]
  The invention according to claim 5Claim 1In the fixing device described in the above, the sheet-like mediumjamJam detection means for detecting, the displacement means,When the jam detecting means detects a jam of the sheet-like medium, the separating member is displaced away from the fixing member.It is characterized by that.
[0014]
  The invention according to claim 6 is the invention according to claim 1.Or any one of 5In the fixing device described in,UpThe displacement means isThe separation member is displaced in the rotation direction of the fixing member.It is characterized by that.
[0015]
  According to a seventh aspect of the present invention, there is provided the fixing device according to any one of the first to sixth aspects.In an image forming apparatus.
[0018]
【Example】
FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus may be any known apparatus such as a copying machine, a facsimile machine, or a printer, but the image forming apparatus in this embodiment is a copying machine that forms a color image. The image forming apparatus 20 includes plain paper generally used for copying and the like, 90K paper such as an OHP sheet, a card, and a postcard, and a basis weight of about 100 g / m.²Any of so-called special sheets having a larger heat capacity than plain paper, such as considerably thicker paper or envelopes, can be used as the sheet-like medium.
[0019]
The image forming apparatus 20 is disposed to face the image forming apparatuses 21C, 21Y, 21M, and 21BK that form an image for each color, that is, a toner image according to the document image, and the image forming apparatuses 21C, 21Y, 21M, and 21BK. A transfer device 22 having a belt 61 as a transfer belt as an intermediate transfer member and rollers 62, 63, 31 that span the belt 61.
[0020]
The image forming apparatus 20 also supplies a sheet as a sheet-like medium supply unit that supplies various sheet-like media to a transfer area that is a facing area between the belt 61 and the image forming apparatuses 21C, 21Y, 21M, and 21BK in the transfer apparatus 22. Resist for supplying the sheet-like media conveyed from the cassettes 23 and 24 and the paper feeding cassettes 23 and 24 by the paper feeding rollers 56 and 58 in accordance with the timing of image formation by the image forming devices 21C, 21Y, 21M, and 21BK. And a roller 30.
[0021]
The image forming apparatus 20 also includes a separation device 14 that separates the transferred sheet-like medium from the belt 61, a neutralization device 15 that neutralizes the belt 61 after the transfer, and a cleaning that cleans the belt 61 that has been neutralized by the neutralization device 15. A cleaning device 28 as a unit, a fixing device 1 that fixes a sheet-like medium on which a toner image is transferred in a transfer area, and a fixed sheet-like medium discharged from the fixing device 1 The apparatus includes a discharge roller 13 that discharges to the outside of the main body of the forming apparatus 20 and a discharge tray that serves as a sheet stacking unit (not shown) that stacks the sheet-like medium discharged by the discharge roller 13.
[0022]
Each of the image forming devices 21C, 21Y, 21M, and 21BK develops each color of cyan, yellow, magenta, and black, and uses different toner colors, but the configuration is almost the same. The configuration of 21C will be described as a representative of the image forming devices 21C, 21Y, 21M, and 21BK. In addition, when it is not necessary to distinguish, C, Y, M, and BK attached to the end are abbreviate | omitted.
[0023]
The image forming device 21C has a photosensitive drum 25C as an electrostatic latent image carrier, a charging device 27C sequentially arranged in the rotation direction A of the photosensitive drum 25C, a developing device 26C as a developing device, and a belt 61. It has a transfer device 17C as a transfer charger disposed to face the photosensitive drum 25C, and has a well-known configuration for receiving exposure light 29C from the exposure device 19C between the charging device 27C and the developing device 26C. .
[0024]
The photosensitive drum 25 is negatively charged by the charging device 27, and the portion receiving the exposure light 29 is reversely developed with the negatively charged toner. The charging device 27 is of a type such as corotron or scorotron, which generates a charge by corona discharge and spreads it on the surface of the photosensitive drum 25. In the arrangement of the developing devices 26, yellow, cyan, magenta, and black toners are used in order from the paper supply side, and the overlapping transfer is sequentially performed in this order by a positive corona.
[0025]
The belt 61 is made of a dielectric material such as a polyester film, is positively charged by the transfer device 17, and is neutralized by the static eliminator 15 after the sheet-like medium is separated. The static eliminator 15 performs negative AC corona discharge with a charger from both sides of the belt 61, neutralizes the accumulated charge in the belt 61, neutralizes the charge, and initializes the belt 61.
[0026]
The separation device 14 performs negative AC corona discharge with a charger from the upper surface of the sheet-like medium, neutralizes the accumulated charge on the transfer paper, and removes discharge when the sheet-like medium is separated from the belt 61. To prevent toner dust. The photoconductor drum 25 has photoconductivity and is an organic photoconductor, but may be an inorganic photoconductor. The photosensitive drums 25 are arranged in the same plane. The electrostatic latent image carrier may be a belt shape instead of a drum shape.
[0027]
A document reading unit 12 is disposed on the upper part of the image forming apparatus 20. The image forming apparatus 20 performs image formation by a color separation superposition transfer method generally used for full-color image forming apparatuses, and the document reading unit 12 has three colors of blue, red, and green via an optical system 51. The image information light that has undergone color separation is read by the CCD 11 to read the original 50.
[0028]
Based on the light intensity level detected by each CCD 11, image calculation processing is performed to create write image data to be developed in each color of yellow, cyan, magenta, and black, and each exposure apparatus according to the written image data 19 irradiates the photosensitive drum 25 with exposure light 29, and optical writing is performed.
[0029]
The toner used in the image forming apparatus 20 contains at least a binder resin, a colorant, and a wax, and contains 5 to 20 parts by weight of either wax represented by carnauba or oil represented by dimethylsiloxane. It contains. By using such a toner, even in the oilless fixing device 1, a color image can be fixed without the sheet-like medium being wound around the fixing belt 2.
[0030]
As shown in FIG. 2, the fixing device 1 includes an endless fixing belt 2 as a rotating member for conveying a sheet-like medium on which toner is fixed, a heating roller 3 around which the fixing belt 2 is wound, and a fixing roller. 4 and the fixing roller 4 via the fixing belt 2, and rotates in the same direction C as the rotation direction B of the fixing belt 2 in the fixing portion 16 as a nip portion that is a position facing the fixing belt 2. A pressure roller 5 as a pressure member, a heating roller 3, and heaters 6 and 7 as heating means provided inside the pressure roller 5 are provided.
[0031]
The fixing device 1 is also disposed so as to face the heating roller 3 via the fixing belt 2 and thermistor 8 as temperature detecting means for detecting the temperature of the fixing belt 2 and the pressure roller 5 to be pressed. A thermistor 18 as temperature detecting means for detecting the temperature of the roller 5, a separation plate 70 as a separation member for separating the sheet-like medium that has passed through the fixing unit 16 from the fixing belt 2, and a sheet-like shape carrying a toner image. A guide plate 52 or the like as guide means for guiding the medium P toward the fixing unit 16 is provided. The heating roller 3 is urged away from the fixing roller 4 in order to give an appropriate predetermined tension to the fixing belt 2.
[0032]
In FIG. 2, the toner constituting the toner image is carried on the sheet-like medium P. However, this illustration is omitted in FIGS. 2 and 3 to 7, and only the signs T in FIGS. This is illustrated. As will be described later, the separation plate 70 to which the present invention is applied is displaced, but in this embodiment, the front end of the separation plate 70, that is, the end on the rotating member side becomes the rotating member when the separating plate 70 is displaced to the rotating member side. In order to make contact, FIG. 2 shows a state in which the separation plate 70 is in contact with the fixing belt 2. However, the distal end of the separation plate 70 only needs to be close to the rotating member when displaced toward the rotating member, and does not necessarily need to contact.
[0033]
The fixing belt 2 is formed by forming a release layer made of 200 μm high release silicone rubber on the surface layer of a 100 μm-thick polyimide resin, which is a heat-resistant resin, and has a small heat capacity and thermal response. Have been good. As the heat-resistant resin, the substrate may be polyamide resin, polyether ketone (PEEK), or the like, in addition to polyimide resin, and may be made of metal such as stainless steel or nickel, or rubber. In consideration of flexibility and the like, the thickness is desirably 100 μm or less.
[0034]
The release layer is preferably excellent in heat resistance and durability in addition to releasability. Therefore, it is desirable that the release layer be a heat-resistant release layer using fluorine resin or the like in addition to high release silicone rubber. In the case of a fluororesin, the release layer is formed by coating the substrate surface by spraying or the like and then heat-sealing. Further, the high release silicone rubber layer is desirable as a condition for obtaining good fixability and thermal responsiveness when the rubber height is 25 to 65 degrees (JIS A hardness meter) and the thickness is in the range of 100 to 300 μm.
[0035]
On the surface of the fixing belt 2, an elastic layer such as silicon rubber is provided on the base, and a release layer such as a fluororesin and a PFA tube is provided on the elastic layer, whereby an OHP sheet is formed as a sheet-like medium. Transparency when used can be secured, and a good fixed image can be obtained by uniformly fixing.
[0036]
The fixing roller 4 has a diameter of 40 mm and a cored bar 9 as a base made of a steel metal pipe, and covers the cored bar 9 to make the width of the fixing unit 16 sufficiently wide. And an elastic layer 10. The elastic body layer 10 is made of heat-resistant porous foamed silicon rubber, and is soft and heat insulating.
[0037]
Since the material of the elastic body layer 10 is a heat-resistant porous elastic body having a low thermal conductivity and a heat insulating function, it reduces the heat loss of the belt, reduces the temperature drop after the start-up, and recovers the temperature. The pre-rotation time is shortened. Further, since the elastic layer 10 has a relatively low hardness, a sufficient nip width can be obtained even when the pressure contact force of the pressure roller 5 is small, and a good fixing performance can be obtained even under relatively low temperature and low pressure conditions. Obtainable.
[0038]
Although the pressure roller 5 has a diameter of 40 mm and is not shown in the figure, an aluminum core as a base made of a steel metal pipe, and a heat-resistant porous silicon covering the core And a rubber release layer having a thickness of 2 mm. The core metal can be made of stainless steel, carbon steel, etc. in addition to aluminum. The release layer can be composed of fluorine resin as well as high release silicone rubber.
[0039]
A heater 7 is built in the center of the cored bar. In order to improve the releasability of the sheet-like medium from the fixing belt 2, the pressure roller 5 is made harder than the fixing roller 4 and the fixing portion 16 is formed downward. The pressure roller 5 is urged in a direction to come into pressure contact with the fixing roller 4 by an elastic body (not shown) such as a spring.
[0040]
The heating roller 3 has a diameter of 50 mm, and the core metal is a thin-walled aluminum roller pipe having good thermal conductivity to prevent temperature unevenness in the longitudinal direction, and has a thickness of 5 mm. The core metal surface is anodized to prevent wear due to friction with the fixing belt 2. A heater 6 is built in the center of the cored bar. The core metal may be carbon steel, stainless steel, copper or the like.
[0041]
As described above, the heating roller 3 and the pressure roller 5 are each made of a thin cylindrical cored bar, so that the heat capacity is reduced. The heat capacity of the heating roller 3 is 26 cal / ° C. or less, and the pressure roller 5 The heat capacity is 36 cal / ° C. or less. By making the heating roller 3 and the pressure roller 5 have low heat capacities, even when the fixing belt 2 rotates, the heat is hardly taken away, and adverse effects on fixing and a rise time are prevented. Furthermore, even if the temperature is lowered due to continuous fixing or the like, the time until the recovery is shortened. The heaters 6 and 7 heat the fixing belt 2 through the heating roller 3, the pressure roller 5, and the rollers 3 and 5.
[0042]
The guide plate 52 is disposed upstream of the fixing unit 16 in the sheet medium conveyance direction D. On the downstream side of the sheet-like medium conveyance direction D of the fixing unit 16, the sheet-like medium P that is expanded toward the fixing unit 16, is fixed, and is conveyed along with the rotation of the fixing belt 2 is fixed. (1) An outlet upper guide and an outlet lower guide (not shown) that are guided toward the outside of the main body are disposed. Further, on the downstream side of the outlet upper guide and the outlet lower guide in the sheet medium conveyance direction D, the outlet upper guide and the outlet lower guide are provided. A paper discharge roller (not shown) for discharging the sheet medium P guided by the guide to the outside of the fixing device 1 main body is provided.
[0043]
Although not shown, the heaters 6 and 7 are connected to a power source as a voltage applying means, and generate heat when a voltage is applied by the power source. The power supply and the thermistors 8 and 18 are connected via control means. When the power of the image forming apparatus 20 is turned on or when the image forming apparatus 20 shifts from the standby state to the operating state, the control unit applies a voltage to the power source and starts heating by the heaters 6 and 7. To do.
[0044]
Separation plate 70 includes a stainless steel base material having a thickness of 0.2 mm, and a fluorine resin layer having a thickness of 15 μm coated on the front and back surfaces of the base material and an edge facing fixing belt 2. Yes. A heat resistant resin may be used for the substrate. The arrangement of the separation plate 70 in the state shown in FIG. 2 is an angle formed by the direction in which the tip of the separation plate 70 faces and the direction in which the tip of the separation plate 70 and the rotation center of the fixing roller 4 are connected. Occupies a position where the angle becomes 90 degrees or more.
[0045]
Also, the separation plate 70 is disposed at a position close to the exit of the fixing unit 16 so that the image area on the sheet-like medium P can come into contact with the front end of the sheet-like medium P before the fixing unit 16 comes out. Yes. The width of the separation plate 70 is wide enough to contact the entire fixing belt 2 in the axial direction, that is, the direction perpendicular to the paper surface.
[0046]
The toner image on the sheet-like medium P causes an adhesive force to the fixing belt 2 with respect to the sheet-like medium P at the exit of the fixing unit 16, but the tip of the sheet-like medium P is separated from the fixing belt 2 to some extent. After the conveyance, the sheet-like medium P can be separated from the fixing belt 2 by the strain of the sheet-like medium P itself.
[0047]
Therefore, the separation plate 70 only needs to be separated from the fixing belt 2 at the leading end of the sheet-like medium P, and the above-described arrangement position occupies such a position. However, if the separation plate 70 always occupies such an arrangement position, the toner image on the sheet-like medium P is conveyed while being rubbed against the leading edge of the separation plate 70 or the portion after the leading edge. It will stick. As a result, the toner adheres to the separation plate 70 over time, and the fixed toner may be sandwiched between the separation plate 70 and the fixing roller 4 to damage the fixing roller 4. Further, since the image is rubbed against the separation plate 70, the image may be disturbed.
[0048]
Therefore, the fixing device 1 can displace the separation plate 70. As is apparent from FIGS. 2 and 3, the displacement plate 70 is displaced in the rotation direction B of the fixing belt 2, and as is apparent from FIGS. And those that are displaced in the transport direction D of the medium P.
[0049]
The shape of the separating plate 70 is not limited to a flat plate shape as shown in FIGS. 2 to 4, but the rear end side of the separating plate 70 is bent in a direction away from the conveyance path of the sheet-like medium P as shown in FIG. It may have a letter shape, or may have a shape in which the rear end side is curved away from the conveyance path of the sheet-like medium P as shown in FIG. By adopting such a shape, the sheet-like medium P is separated from the fixing belt 2 at the leading end, and the toner image on the sheet-like medium P is separated because the sheet-like medium P being conveyed does not come into contact. It is possible to prevent the toner from adhering to the separation plate 70 by rubbing against the plate 70 or causing image disturbance.
[0050]
As shown in FIG. 7, as a configuration for performing such displacement of the separation plate 70, the fixing device 1 has a displacement means 64 that displaces the separation plate 70. The displacement means 64 is integrated with the separation plate 70 and can be moved in the G direction by a guide (not shown), a pulley 72 rotatably supported on a shaft 73 integral with the separation plate holder 71, and one end thereof. A tension spring 74 is fixed to the shaft 73 and the other end is fixed to a stationary member on the fixing device 1 main body side.
[0051]
The displacement means 64 is also fixed to a shaft 75 fixed at one end to the fixing device 1 main body side, and fixed at the other end to a stationary member on the fixing device 1 main body side, and a wire 68 wound around a pulley and a shaft 75. , A gear 77 meshed with the gear 76, a motor 55 for driving the gear 77, and a one-way clutch for transmitting the drive of the motor 55 to the gear 77 and rotating the gear in the E direction. 69.
[0052]
The displacement means 64 also includes a sheet-shaped medium separation detection sensor 78 as a detection means for detecting that the leading edge of the sheet-shaped medium P has been separated from the fixing belt 2 by the separation plate 70, and a sheet-shaped medium separation detection sensor 78. It has an MPU 53 as a control means for receiving a signal, and a driver 54 for transmitting a control signal generated by the MPU 53 to the motor 55.
[0053]
The displacing means 64 displaces the separation plate 70 in the G direction substantially parallel to the rotation direction B of the fixing belt 2 at the tip portion of the separation plate 70, and the guide displaces the separation plate holder 71 only in the G direction. In addition to supporting the tension spring 74, the tensioning direction of the tension spring 74, between the stationary member and the pulley 72, and the tensioning direction of the wire 68 on the pulley 72 and the shaft 75 are substantially parallel to the G direction. The G direction includes a G1 direction in which the tip of the separation plate 70 is displaced downstream in the B direction and a G2 direction in which the tip of the separation plate 70 is displaced upstream in the B direction.
[0054]
When the sheet-like medium P passes through the fixing unit 16 and the leading end is separated by the separating plate 70 by the displacement means 64, that is, the leading end of the sheet-like medium P passes the end of the separating plate 70 on the fixing belt 2 side. When the sheet-like medium separation detection sensor 78 detects the leading end of the sheet-like medium P and issues a detection signal to the MPU 53, the MPU receives this signal and issues a drive control signal for the motor 55, and the driver The motor 55 is driven via 54.
[0055]
When the motor 55 is driven, the gear 77 is rotationally driven in the E direction via the one-way clutch 69, and the gear 76 is rotationally driven in the F direction, and the pulley 72 moves the wire 68 against the urging force of the tension spring 74. , The separation plate holder 71 is displaced in the G1 direction, and the separation plate 70 is also moved from the home position for separating the sheet-like medium P from the fixing belt 2 shown in FIGS. As shown in FIG. 3, it is displaced in the G1 direction. As a result, the separation plate 70 does not come into contact with the sheet-like medium P ejected from the fixing unit 16 and conveyed, and the toner image on the sheet-like medium P is rubbed against the separation plate 70 and the toner T is applied to the separation plate 70. There is no sticking or image distortion.
[0056]
On the other hand, when the sheet-like medium separation detection sensor 78 detects the rear end of the sheet-like medium P, the MPU 53 stops the drive control signal of the motor 55. Then, due to the urging force of the tension spring 74 and the action of the one-way clutch 69, the gear 77 rotates in the opposite direction to the E direction and the gear 76 rotates in the opposite direction to the F direction, and the pulley 72 and the separation plate holder 71 are moved in the G2 direction. Accordingly, the separation plate 70 is also displaced in the G2 direction and returned to the home position shown in FIGS. Then, the separation plate 70 stands by in this state until the sheet-like medium P passes through the fixing unit 16.
[0057]
The timing at which the MPU 53 displaces the separation plate 70 in the G1 direction is such that the separation plate 70 does not come into contact with the sheet-like medium P discharged from the fixing unit 16 and conveyed, and the toner image on the sheet-like medium P is separated from the separation plate 70. When the leading edge of the sheet-like medium P passes the end of the separation plate 70 on the fixing belt 2 side within a range in which the toner T does not adhere to the separation plate 70 and the image is not disturbed. Or later.
[0058]
The sheet-like medium separation detection sensor 78 can be used as a jam detection unit that detects a jam of the sheet-like medium P. In this case, when the sheet-like medium separation detection sensor 78 does not detect the sheet-like medium P within the set time after the sheet-like medium P is sent out in the main body of the image forming apparatus 20, the MPU 53 causes a jam in the fixing device 1. It is determined that this occurs, and the motor 55 is driven to displace the separation plate 70 in the G1 direction, which is the direction away from the fixing unit 16. In this way, when the jam occurs, the separation plate 70 is moved away from the exit of the fixing unit to improve the workability of the jam processing.
[0059]
FIG. 8 shows a displacement means 64 ′ for displacing the separation plate 70 in accordance with the toner image on the sheet-like medium P. That is, the displacement means 64 ′ is different from the displacement means 64 in terms of displacing the separation plate 70. For this reason, the displacement means 64 ′ replaces the sheet-like medium separation detection sensor 78 as the detection means in the displacement means 64 with an output image recognition means 79 for detecting the position of the toner image on the sheet-like medium P as the detection means. Have. Note that the same components as those shown in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
[0060]
The output image recognition means 79 is disposed so as to face the upper surface of the guide plate 52, that is, the conveyance surface side of the sheet-like medium P. The output image recognition means 79 detects the presence or absence of the sheet-like medium P, the position of the toner image on the sheet-like medium P, and the amount of toner T constituting the toner image. Therefore, the output image recognition means 79 is a toner image detection means in that it detects the position of the toner image on the sheet-like medium P, and is a toner amount detection means in that it detects the amount of toner T.
[0061]
The output image recognition means 79 detects the toner image on the sheet-like medium P, and the length from the leading edge of the sheet-like medium P to the toner constituting the leading edge of the toner image on the sheet-like medium P, that is, the sheet-like medium P The margin length at the leading edge of the toner and the amount of toner T near the leading edge of the toner image are detected. These are detected when the margin length is short or when the amount of toner near the tip is large, the adhesive force of the sheet medium P to the fixing belt 2 is large, and the sheet medium P is applied to the fixing belt 2. This is because it is easy to wind. The displacement means 64 ′ displaces the separation plate 70 in accordance with the length of the margin and the amount of toner.
[0062]
When the output image recognition unit 79 recognizes that the margin is small or the amount of toner near the tip is large, the output image recognition unit 79 transfers the information to the MPU 53. Based on the information, the MPU 53 determines that the leading edge of the sheet-like medium P has a strong adhesive force to the fixing belt 2 and sets the separation plate 70 at the home position shown in FIGS. Separate from belt 2.
[0063]
When the separation plate 70 detects that the leading edge of the sheet-like medium P has been separated from the fixing belt 2 after a predetermined time has elapsed after the output image recognition means 79 senses the leading edge of the sheet-like medium P, the MPU 53 causes the motor 55 to be turned on. By driving, the separating plate 70 is displaced in the G1 direction as shown in FIG. As a result, the separation plate 70 does not come into contact with the sheet-like medium P ejected from the fixing unit 16 and conveyed, and the toner image on the sheet-like medium P is rubbed against the separation plate 70 and the toner T is applied to the separation plate 70. There is no sticking or image distortion. When the MPU 53 has driven the motor 55 and a predetermined time has elapsed, the driving of the motor 55 is stopped assuming that the conveyance of the sheet-like medium P is finished, and the separation plate 70 returns to the home position shown in FIGS.
[0064]
On the other hand, when the output image recognition means 79 recognizes that the margin is large or the amount of toner near the leading edge is small, the information is transferred to the MPU 53. The MPU 53, based on this information, transfers the leading edge of the sheet-like medium P. It is determined that the adhesive force to the fixing belt 2 is small, and the motor 55 is driven to displace the separation plate 70 in the G1 direction as shown in FIG.
[0065]
The sheet-like medium P is not separated from the fixing belt 2 by the action of the separation plate 70, but has a low adhesive force to the fixing belt 2, so that the fixing belt 2 is bent by the curvature of the fixing belt 2 and the sheet-like medium P. Separate from 2. Also in this case, the separation plate 70 does not come into contact with the sheet-like medium P discharged from the fixing unit 16 and conveyed, and the toner image on the sheet-like medium P is rubbed against the separation plate 70 so that the toner T is applied to the separation plate 70. There is no sticking or image distortion.
[0066]
Even after the leading edge of the sheet-like medium P is separated, if the amount of toner after the leading edge of the toner image is large, if the separation plate 70 is displaced from the home position, the sheet-like medium P is wound around the fixing belt 2 again. It may end up. Therefore, the output image recognizing means 79 also detects the toner image after the leading edge, and transfers the information to the MPU 53 when it recognizes that the toner amount is large.
[0067]
Based on the information, the MPU 53 determines that the leading edge of the sheet-like medium P has a strong adhesive force to the fixing belt 2 and sets the separation plate 70 at the home position shown in FIGS. Separate from belt 2. This prevents the sheet-like medium P from being wound around the fixing belt 2 again after the leading edge is separated.
[0068]
Note that the output image recognition unit 79 may detect only one of the position of the toner image on the sheet-like medium P and the amount of toner T constituting the toner image. That is, the output image recognition unit 79 may function as either a toner image detection unit that detects the position of the toner image on the sheet-like medium P or a toner amount detection unit that detects the amount of toner T. .
[0069]
FIG. 9 shows a displacement means 64 ″ for displacing the separation plate 70 in accordance with the type of the sheet-like medium P. That is, the displacement means 64 ″ displaces the separation plate 70 as compared with the displacement means 64 and 64 ′. The conditions to be made are different. For this reason, the displacement means 64 ″ replaces the sheet-like medium separation detection sensor 78 as the detection means in the displacement means 64 and the output image recognition means 79 as the detection means in the displacement means 64 ′ with the sheet-like medium P as the detection means. A paper type detecting means 80 for detecting the upper type is provided.
[0070]
Further, the displacement means 64 ″ differs in the direction in which the separation plate 70 is displaced compared to the displacement means 64, 64 ′. The displacement means 64 ″ moves the separation plate 70 in the transport direction D of the sheet-like medium P. And the guide supports the separation plate holder 71 so as to be displaceable only in the H direction, and the tensioning direction of the tension spring 74, between the stationary member and the pulley 72, and The extending direction of the wire 68 on the pulley 72 and the shaft 75 is substantially parallel to the H direction. The H direction includes an H1 direction in which the separation plate 70 is displaced downstream in the D direction and an H2 direction in which the tip of the separation plate 70 is displaced upstream in the D direction. The same components as those in FIGS. 7 and 8 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
[0071]
The paper type detection unit 80 is disposed on the upstream side of the guide plate 52 in the conveyance direction D of the sheet medium P. The paper type detection unit 80 detects the presence or absence of the sheet-like medium P and the type of the sheet-like medium P. The reason for detecting the paper type is that it is possible to estimate the wrapping property around the fixing belt 2 depending on the type of the sheet-like medium P. That is, when the paper type of the sheet-like medium P is thin, the sheet-like medium P is easily wound around the fixing belt 2, and when the paper type of the sheet-like medium P is thick, the sheet-like medium P is used. Is difficult to wind around the fixing belt 2. The displacement means 64 ″ displaces the separation plate 70 in accordance with the paper type.
[0072]
The paper type detection unit 80 detects the paper type and transfers the information to the MPU 53. When the MPU 53 determines that the sheet type of the sheet-like medium P is thin and easily wound around the fixing belt 2 based on the information, the separation plate 70 is set to the home position shown in FIGS. 2 and 9, and the leading end of the sheet-like medium P is fixed. Separate from belt 2. When the separation plate 70 detects that the leading edge of the sheet-like medium P has been separated from the fixing belt 2 after a predetermined time has elapsed since the paper type detection means 80 detected the leading edge of the sheet-like medium P, the MPU 53 turns the motor 55 on. By driving, the separation plate 70 is displaced in the H1 direction as shown in FIG.
[0073]
As a result, the separation plate 70 does not come into contact with the sheet-like medium P ejected from the fixing unit 16 and conveyed, and the toner image on the sheet-like medium P is rubbed against the separation plate 70 and the toner T is applied to the separation plate 70. There is no sticking or image distortion. When the MPU 53 has driven the motor 55 and a predetermined time has passed, the driving of the motor 55 is stopped assuming that the conveyance of the sheet-like medium P is finished, and the separation plate 70 is displaced in the H2 direction and returned to the home position shown in FIGS. To do.
[0074]
On the other hand, when the paper type detection unit 80 recognizes that the paper type of the sheet-like medium P is thick, the information is transferred to the MPU 53, but the MPU 53 winds the sheet-like medium P around the fixing belt 2 based on the information. The motor 55 is driven and the separation plate 70 is displaced in the H1 direction as shown in FIG.
[0075]
The sheet-like medium P is not separated from the fixing belt 2 by the action of the separation plate 70, but since the winding property to the fixing belt 2 is small, the fixing belt 2 is caused by the curvature of the fixing belt 2 and the strain of the sheet-like medium P. Separate from 2. Also in this case, the separation plate 70 does not come into contact with the sheet-like medium P discharged from the fixing unit 16 and conveyed, and the toner image on the sheet-like medium P is rubbed against the separation plate 70 so that the toner T is applied to the separation plate 70. There is no sticking or image distortion.
[0076]
In the present exemplary embodiment, when the power of the image forming apparatus 20 is turned on by a predetermined operation by the operator or when the state is changed from the standby state to the operation state, the control unit controls to rise to a predetermined set temperature. Is completed, and image formation and fixing are possible. When the operator performs a well-known operation for starting image formation, the photosensitive drum 25 is charged by the charging device 27 as the photosensitive drum 25 rotates in the direction A, and the exposure light 29 causes a static image corresponding to the original image. An electrostatic latent image is formed, the electrostatic latent image is developed by the developing device 26, and the toner image formed on the photosensitive drum 25 is transferred onto a sheet-like medium conveyed on the transfer device 22.
[0077]
The sheet-like medium on which the yellow toner is transferred by the image forming device 21Y is transferred to the cyan, magenta, and black toner images by the image forming devices 21C, 21M, and 21BK, as appropriate, while being conveyed to the transfer device 22. After all the toner images necessary for image formation are transferred, the toner image is transferred from the transfer device 22 to the fixing device 1 and guided to the fixing unit 16 by the guide plate 52.
[0078]
While the sheet-like medium is conveyed by the movement of the fixing belt 2, the toner constituting the toner image is heated and pressed in the fixing unit 16 and melted and fixed on the sheet-like medium. The heating by the heaters 6 and 7 does not cause a temperature drop to the extent that the fixing belt 2 starts to rotate, and the fixing is interrupted even when continuous fixing is performed. There is no need to reheat, heat is supplied to such an extent that hot offset does not occur, and good fixing is performed with respect to glossiness and the like. The sheet-like medium after fixing is conveyed by a paper discharge roller 13 and discharged to a paper discharge tray outside the main body of the image forming apparatus 20.
[0079]
At the time of such fixing, the fixing device 1 is provided with a displacing means, so that the separation plate 70 is appropriately displaced and does not come into contact with the sheet-like medium discharged from the fixing unit 16 and conveyed. The toner image is not rubbed against the separation plate 70, and the toner does not adhere to the separation plate 70 and the image is not disturbed. Further, when the displacement means includes the jam detection means, when a jam occurs in the fixing device 1, the separation plate 70 is displaced in a direction away from the fixing unit 16, and the jam processing is easily performed.
[0080]
Although the fixing device and the image forming apparatus to which the present invention is applied have been described above, the heater as the heating unit is not limited to the heating roller and the pressure roller, and may be disposed on the fixing roller. Regardless of the heater, the rotating member is directly or indirectly heated by the heater, so that the heater is heated.
[0081]
The case where the present invention is applied to a belt fixing device has been described above, but the present invention can also be applied to a heat roller pair type fixing device as shown in FIG. Hereinafter, the same components as those in the above-described example are denoted by the same reference numerals, detailed description thereof will be omitted, and different portions will be mainly described. The illustration of the toner constituting the toner image is omitted.
[0082]
The fixing device includes a heating roller 59 as a fixing roller as a rotating member for heating and conveying the sheet-like medium P on which the toner image is fixed, and a pressure roller 60 pressed against the heating roller 59. Have. The heating roller 59 has an aluminum cored bar 65, a 2 mm thick elastic layer 66 formed on the surface of the cored bar 65, and a 50 μm thick PFA tube 67 coated on the elastic layer. A heater 6 is disposed inside the cored bar 65. The on-axis hardness of the heating roller 59 is Asker C67Hs. The core metal 65 of the heating roller 59 is not limited to aluminum but may be made of stainless steel, carbon steel, or the like. The pressure roller 60 is a roller having the same configuration as the heating roller 59. Although not shown, this fixing device has the above-described displacement means.
[0083]
Since the tip of the separation plate 70, that is, the end on the rotating member side contacts the rotating member when the separating plate 70 is displaced toward the rotating member, FIG. 10 shows a state where the separating plate 70 contacts the fixing belt 2. However, the distal end of the separation plate 70 only needs to be close to the rotating member when displaced to the rotating member side, and does not necessarily need to contact.
[0084]
The arrangement of the separation plate 70 in the state shown in FIG. 10 is an angle formed by the direction in which the tip of the separation plate 70 faces and the direction in which the tip of the separation plate 70 and the rotation center of the heating roller 59 are connected. Occupies a position where the angle becomes 90 degrees or more. Also, the separation plate 70 is disposed at a position close to the exit of the fixing unit 16 so that the image area on the sheet-like medium P can come into contact with the front end of the sheet-like medium P before the fixing unit 16 comes out. Yes. The width of the separation plate 70 is wide enough to contact the entire fixing belt 2 in the axial direction, that is, the direction perpendicular to the paper surface.
[0085]
In this fixing device, a sheet-like medium P carrying a toner image conveyed from the main body side of the image forming apparatus 20 is passed between a heating roller 59 and a pressure roller 60 and heated and pressurized to thereby form toner. The image is melted and fixed on the sheet-like medium P. At the time of fixing, the fixing device is provided with a displacing means, so that the separation plate 70 is appropriately displaced and does not come into contact with the sheet-like medium P that is discharged from the fixing unit 16 and conveyed. Thus, the toner image is not rubbed against the separation plate 70 and the toner is fixed to the separation plate 70 and the image is not disturbed. Further, when the displacement means is provided with a jam detection means, when a jam occurs in the fixing device, the separating plate 70 is displaced in a direction away from the fixing portion 16, and the jam processing is easily performed.
[0086]
The configuration of the various fixing devices has been described above, but in which direction the displacement means is displaced, under which conditions, in which shape, the fixing device is any type of fixing device. It can be appropriately selected and combined. The image forming apparatus of the present embodiment forms a color image, but may form a single color image.
[0087]
【The invention's effect】
  The present inventionShiMediaFixing memberSeparating member for separating fromTheDisplace the separating memberMakeWith displacement meansIn the fixing device, the displacement unit displaces the separation member in a direction away from the sheet-like medium when the leading end of the sheet-like medium is separated from the fixing member by the separation member.SoFixing memberBy separating the separation member that separates the sheet-like medium from the toner and preventing the toner from adhering to the separation member,Fixing memberIt is possible to provide a fixing device capable of preventing damage to the image and causing image disturbance.
  In addition, since the separating member is displaced after separating the sheet-like medium from the fixing member, the sheet-like medium can be reliably separated from the fixing member, and toner can be prevented from adhering to the separating member to damage the fixing member or image. It is possible to provide a fixing device capable of preventing the occurrence of disturbance.
[0088]
  According to the length from the leading edge of the sheet-like medium to the leading edge of the toner image detected by the toner image detecting means, the toner image detecting means for detecting the position of the toner image on the sheet-like medium. Displace the separating memberIf it is,When the length is short, the adhesive force of the sheet medium to the fixing member is large, so that the separation member is brought close to the fixing member, and the sheet medium is reliably separated from the fixing member, and in other cases, the separation member is kept away from the fixing member. Fixing member by preventing toner from adhering to the separation memberIt is possible to provide a fixing device capable of preventing damage to the image and causing image disturbance.
[0089]
  On sheet mediaToner amount detection means for detecting the toner amountAnd the displacement means isToner amount detection meansSheet media detected byToner amount onDepending on the displacement of the separating memberMakeIf it is,When the toner amount is large, the fixing memberBecause the adhesive strength of the sheet-like medium to theFixing memberClose the sheet mediaFixing memberTo ensure separation from theFixing memberBy preventing the toner from adhering to the separation member away fromFixing memberIt is possible to provide a fixing device capable of preventing damage to the image and causing image disturbance.
[0090]
  Sheet mediaThe type ofDetectPaper type detection meansDisplacement meansIs paper type detection meansSheet media detected byType ofDepending on the displacement of the separating memberMakeIf it is,When the sheet-like medium is thin, the sheet-like medium is weak and difficult to separate from the fixing member.Separation memberFixing memberClose the sheet mediaFixing memberSurely separate from theWhen the sheet-like medium is thick, the sheet-like medium is strong and easily separated from the fixing member.By preventing the toner from adhering to the separation member away fromFixing memberIt is possible to provide a fixing device capable of preventing damage to the image and causing image disturbance.
[0091]
  Of sheet mediajamDetectjamHaving detecting means and displacing meansWhen the jam detecting means detects a jam of the sheet-like medium, the separating member is displaced away from the fixing member.If it is,When the jam occurs, the separation member is displaced away from the fixing member, and the jam processing is easily performed.It is possible to provide a fixing device that can perform the above operation.
[0092]
  Displacement means displaces the separation member in the rotation direction of the fixing member.If it is,Displacement of the separation member in the rotation direction of the fixing member prevents the toner from adhering to the separation member by moving the separation member away from the fixing member, and prevents damage to the fixing member and image distortion.It is possible to provide a fixing device that can perform the above operation.
[0093]
  Since the present invention is an image forming apparatus having the fixing device according to any one of claims 1 to 6, the image forming apparatus includes the fixing device having the above-described effects, and performs good fixing over time. Image formationbe able toImage forming apparatusCan be provided.
[Brief description of the drawings]
FIG. 1 is a side view showing an outline of a fixing device to which the present invention is applied and an image forming apparatus having the same.
2 is a side view of a fixing device provided in the image forming apparatus shown in FIG.
3 is a side view showing a state in which a separating member provided in the fixing device shown in FIG. 2 is displaced in the rotation direction of the rotating member.
4 is a side view showing a state in which a separation member provided in the fixing device shown in FIG. 2 is displaced in the sheet-like medium conveyance direction. FIG.
FIG. 5 is a side view showing an example when the separating member has a bent shape.
FIG. 6 is a side view showing an example when the separating member has a curved shape.
7 is a side view illustrating a configuration example of a displacement unit included in the fixing device illustrated in FIG. 2;
FIG. 8 is a side view showing another configuration example of a displacement unit included in the fixing device shown in FIG. 2;
9 is a side view showing still another configuration example of the displacement means included in the fixing device shown in FIG. 2. FIG.
10 is a side view showing another example of a fixing device provided in the image forming apparatus shown in FIG.
[Explanation of symbols]
1 Fixing device
2 Rotating member
5 Pressure member
6 Heating means
7 Heating means
16 Opposing position of rotating member and pressure member
20 Image forming apparatus
59 Rotating member
60 Pressure member
64 Displacement means
64 'displacement means
64 "displacement means
70 Separation member
78 Toner image detection means
78 Jam detection means
79 Toner image detection means
79 Toner amount detection means
80 Paper type detection means
B Rotation direction of rotating member
D Transport direction of sheet media
P sheet media
T Toner

Claims (7)

A separating member for separating the sheet over preparative like medium from the fixing member, the fixing device having a displacement means for causing displacement of the separating member,
The fixing device is characterized in that when the leading edge of the sheet-like medium is separated from the fixing member by the separating member, the separating member is displaced in a direction away from the sheet-like medium . The fixing device according to claim 1.
A toner image detecting means for detecting the position of the toner image on the sheet-like medium;
The fixing device is characterized in that the separation member displaces the separation member in accordance with the length from the leading edge of the sheet-like medium to the leading edge of the toner image detected by the toner image detection means . The fixing device according to claim 1 .
A toner amount detecting means for detecting the toner amount on the sheet-like medium;
The fixing device is characterized in that the displacement means displaces the separation member in accordance with the toner amount on the sheet-like medium detected by the toner amount detection means . The fixing device according to claim 1 .
Having paper type detection means for detecting the type of sheet-like medium;
The fixing device is characterized in that the displacement means displaces the separation member in accordance with the type of the sheet-like medium detected by the paper type detection means . The fixing device according to claim 1 ,
Having jam detecting means for detecting jam of a sheet-like medium;
The fixing device is configured to displace the separation member in a direction away from the fixing member when the jam detecting unit detects a jam of the sheet-like medium . In the fixing device according to any one of claims 1 to 5 ,
Upper Symbol displacement means, the fixing device characterized by displacing the separating member in the rotational direction of the fixing member. An image forming apparatus comprising the fixing device according to claim 1 .

Images