JP2007086132A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the separability of a recording material and to prevent dew condensation. <P>SOLUTION: Air is blown to a separating section by using a blowing means for jetting high pressure air while a recording material is passed through the separating section and jetting low pressure air when the recording material is not passed through the separating section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Like a heating roller and a pressure roller, the recording material is nipped and conveyed between the heating member and the pressure member, and the toner image is heated and melted when the recording material passes through the nip formed by the heating member and the pressure member. A fixing device that fixes the toner image is widely used in an electrophotographic image forming apparatus, but various separation techniques are used to reliably separate the recording material carrying the toner image from the heating member. .

  That is, a technique using a separation claw, a technique that strongly bends the recording material at the separation point, a technique that uses the straightness of the recording material, a technique that blows air to the separation position, and the like have been conventionally used, and these are used in combination. Things are also done.

  In the method using the separation claw, the surface of the heating member may be damaged by the separation claw, and the method of strongly bending the recording material has problems such as low reliability.

  As an air blowing technique, for example, Patent Document 1 proposes that pulsed compressed air is blown when a recording material front end passes through a nip between a heating member and a pressure member.

On the other hand, in the fixing device, high humidity air containing water evaporated from the recording material due to heating causes condensation of water droplets to the fixing device and its nearby components, which adheres to the recording material and degrades the image quality. Patent Document 2 proposes that a wind flow is formed in the vicinity of the fixing device, and that the high humidity air in the vicinity of the fixing device is removed by being carried on the wind flow.
Japanese Patent Application Laid-Open No. 2004-212954 JP-A-5-27534

  Condensation occurs most prominently in a paper discharge unit of a fixing device that contains a lot of moisture and high-temperature air is rapidly cooled. However, as in Patent Document 2, the air in the vicinity of the fixing device is sucked as a whole. With this method, it is difficult to sufficiently prevent dew condensation in the paper discharge unit.

  The present invention aims to solve the problem of dew condensation in the paper discharge unit while ensuring separation of the recording material with a simple structure by using a blowing unit that generates compressed air for separating the recording material. And

The object is achieved by the following invention.
1.
A heating member, a pressure member, and a blowing unit that blows air in the vicinity of a sheet discharge side of a nip formed by the heating member and the pressure member;
Fixing the toner image on the recording material by passing the recording material through the nip, and separating the recording material from the heating member by blowing air from the blowing means when the leading edge of the recording material passes through the nip. In the device
The fixing device is characterized in that the blowing means blows high-pressure air during the time when the leading edge of the recording material passes through the nip, and blows low-pressure air during the time other than the time.
2.
2. The fixing according to claim 1, further comprising: a control unit configured to control at least one of the air flow rate at the time and the air flow rate at times other than the time by controlling the air blowing unit. apparatus.
3.
3. The air blower according to the above 1 or 2, wherein the air blowing means controls at least one of the air flow rate at the time and the air flow rate at times other than the time by changing an area of the air blowing opening. Fixing device.
4).
4. The fixing device according to any one of items 1 to 3, further comprising a heating unit that raises a temperature of air blown from the blowing unit.

  According to the present invention, reliable separation of the recording material and prevention of condensation are achieved by a simple mechanism.

  FIG. 1 is an overall view of an image forming apparatus incorporating a fixing device according to an embodiment of the present invention.

  The image forming apparatus includes an automatic document feeder A, an image reading unit B, and an image forming unit C. In the image forming portion C, reference numeral 1 denotes a photoconductor, and the photoconductor is preferably an organic photoconductor having a photosensitive layer in which an organic photoconductor is dispersed in a resin from the viewpoints of environment and cost, but is not limited thereto. Any known photoreceptor can be used.

  The photosensitive member 1 is not limited to the drum-shaped photosensitive member illustrated, and may be a belt-shaped photosensitive member. Reference numeral 2 denotes a charging device that charges the photoreceptor 1 and forms a uniform potential on the photoreceptor 1. The charging device 2 is preferably a scorotron charger having a control grid and a discharge electrode or a contact charging type charger using a roller to which a voltage is applied.

  Reference numeral 3 denotes an exposure apparatus that exposes the photoreceptor 1. The exposure apparatus is preferably a scanning exposure apparatus having a scanning optical system comprising a laser diode as a light source and comprising a polygon mirror, a lens and a mirror, and a scanning optical apparatus having a light emitting diode array and an imaging optical element. Any known exposure apparatus can be used. The exposure device 3 performs dot exposure of the photoreceptor 1 according to the image data.

  A developing device 4 accommodates a two-component developer or a one-component developer, develops an electrostatic latent image on the photoreceptor 1, and forms a toner image on the photoreceptor 1. A transfer device 5 includes a corona charger. The transfer device 5 charges the recording material P with a polarity opposite to that of the toner on the photoreceptor 1, and transfers the toner image to the recording material P. Reference numeral 6 denotes a separation device including a corona charger, which performs AC corona charging on the recording material P to remove the charge from the recording material P and separate it from the photoreceptor 1.

  Reference numeral 7 denotes a fixing device, which includes a heating roller 71 as a heating member, a heating roller 72 as a pressure member in pressure contact with the heating member, and a heater 73.

  Reference numeral 8 denotes a cleaning device. Untransferred toner and untransferred toner adhere to the photoreceptor 1 after the transfer, and it is necessary to clean the photoreceptor 1 in order to perform the next image formation. The cleaning device 8 has a cleaning blade made of an elastic blade such as urethane rubber.

  Reference numeral 9 denotes a recording material storage unit for storing the recording material P. The recording material storage unit 9 includes a tray or a cassette, and can be pulled out from the image forming apparatus to supply the recording material P.

  FIG. 2 is a view showing a fixing device according to the embodiment of the present invention.

  The pressure roller 72 is brought into pressure contact with the heating roller 71, and the heating roller 71 rotates as indicated by an arrow, whereby the recording material P is nipped and conveyed by a nip NP between the heating roller 71 and the pressure roller 72. A heater 73 such as a halogen lamp is disposed inside the heating roller 71, and the recording material P is heated when passing through the nip NP, and the toner image T is fixed.

  As a heating member, a hard roller in which a release layer such as a fluorine resin is formed on a metal core, a heat resistant elastic layer such as silicon rubber on a metal core, and a soft in which a release layer is formed on the heat resistant elastic layer A roller can be used, and a belt can be used instead of the roller.

  As the pressure member, a metal cored bar formed with a heat-resistant elastic layer such as silicon rubber, a roller having a release layer formed on the heat-resistant elastic layer, and a belt instead of the roller may be used. it can.

  As the heater, a resistance heating element, an induction heating element or the like can be used in addition to the halogen lamp.

  74 is a plate-shaped peeling member whose tip is disposed close to the heating roller 71, and 75 is a nozzle that sends air toward a separation unit that separates the recording material P from the heating roller 71. 76 and 77 are discharge guide plates, and 78 is a fixing discharge roller.

  When the leading end of the recording material P passes through the nip NP, compressed air is blown from the nozzle 75 and the recording material P is separated from the heating roller 1. Further, the recording material P is reliably separated from the heating roller 71 by separating the leading end of the recording material P by the peeling member 74 on the downstream side in the fixing roller rotation direction at the position where the compressed air is blown.

  In the paper discharge unit of the fixing device, high-humidity and high-temperature air stays as a result of evaporation of water from the recording material P heated in the nip NP. As a result of the high humidity and high temperature air being cooled in the paper discharge section, the vapor pressure is reduced and the water is separated, and the peeling member 4, paper discharge guide plates 76 and 77, fixing paper discharge roller 78, etc. Condensation on the surface occurs.

  In the present invention, such condensation is prevented by blowing air from the nozzle 75.

  The separation and prevention of condensation of the recording material P by blowing air from the nozzle 75 will be described with reference to FIGS.

  FIG. 3 is a block diagram of a control system for air blowing, FIG. 4 is a graph showing a change in pressure of air ejected from the nozzle 75, and FIG. 5 is a diagram showing air flow in the paper discharge unit.

  Air is sent to the nozzle 75 from the compressor 21 via the electromagnetic valves 22A and 22B. The electromagnetic valve 22A is a valve through which a large amount of air passes, and the electromagnetic valve 22B is a valve through which a small amount of air passes.

  The control means 20 controls on / off of the electromagnetic valves 22A and 22B to control the amount of air ejected from the nozzle 75, and the air showing the pressure change shown in FIG. 4 is discharged from the recording material separating unit, that is, the nip NP. It sprays on the paper side end (the right end of the nip NP in FIG. 2).

  In FIG. 4, ta corresponds to the time for the leading edge of the recording material to pass through the nip NP, which is a short time of several tens of msec, for example, about 20 msec to 90 msec, and tb passes through the nip NP. When a plurality of recording materials P are continuously fixed, the time ta and the time tb are formed as shown in the figure. In FIG. 4, the time tc is the interval between the recording materials P that are continuously conveyed.

  At time ta, air is sent from the electromagnetic valve 22A, and at time tb, air is sent from the electromagnetic valve 22B. As a result, as shown in FIG. 4, when the recording material front end passes through the nip NP, high-pressure air is ejected at the front end of the nozzle 75 facing the paper discharge unit, and the recording material P is separated from the heating roller 1.

  The nip passage time at the front end of the recording material, that is, the time tb other than the high pressure air blowing time ta is the time for the recording material to pass through the nip NP, and includes the time excluding the front end passage time ta. A predetermined amount of time following the time may be included. As described above, in the process of fixing the recording material P that is continuously conveyed, a continuous time is formed by the time ta and the time tb, but the rear end of the recording material P has passed through the nip NP. The time until the predetermined time is included in the time tb, and then the air blowing for preventing condensation stops.

  At a time tb other than when the recording material leading edge passes through the nip, since low-pressure air is ejected from the nozzle 5, the recording material P does not flutter by this air.

  The air pressure in the vicinity of the nozzle 75 at time ta is about 0.1 MPa to 0.3 MPa, and the air pressure at time tb is slightly higher than atmospheric pressure.

  As shown in FIG. 5, the air ejected from the nozzle 75 is blocked by the nip NP, flows in the axial direction of the heating roller 71 along the discharge side end of the nip NP, and is discharged outside the fixing device. As a result, the air staying in the paper discharge unit is reliably discharged out of the fixing device by the air flow shown in FIG. 5, and the high-humidity air is reliably removed from the paper discharge unit.

  The air discharged to the outside of the fixing device is discharged to the outside of the image forming apparatus by an air exhaust device that discharges air in the entire image forming apparatus.

  By blowing air as described above, recording materials of various types of paper are reliably separated, and reliable separation is performed against changes in the environment such as temperature and humidity, and condensation is well prevented. be able to.

  As shown in FIG. 3, it is preferable that a heater 23 is provided in the flow of intake air between the electromagnetic valves 22A and 22B of the compressor 21, so that high-temperature air is ejected from the nozzle 5 and discharged. As a result, the vapor pressure of the air increases, so that dew condensation can be prevented more effectively, and temperature reduction of the heating roller 1 and the pressure roller 2 can be suppressed.

  As shown in FIG. 4, the control means 20 controls the blowing pressure according to the time when the leading edge of the recording material passes. However, the control means 20 changes the environment such as humidity and temperature, or the properties of the recording material P used (paper thickness, paper type). ), It is preferable to perform control to change the air pressure at time ta and time tb. By such control, reliable separation is performed on various recording materials, and stable recording material separation is also performed against environmental changes. Further, dew condensation is reliably prevented without being influenced by environmental changes or the like.

  FIG. 6 is a view showing another example of the fixing device according to the embodiment of the present invention.

  In this example, a fixed air flow restricting plate 79A and a movable air flow restricting plate 79B are provided as air flow restricting members that form a flow of air blown to the heating roller 71.

  The air flow restricting plate 79B is in the position of the solid line during the time when the leading edge of the recording material P passes through the nip NP (time ta in FIG. 4), and forms a small area air discharge port. (Time tb in FIG. 4), it recedes to the position of the dotted line to form a large area waste outlet. As a result, the airflow indicated by the arrow W is blown to the recording material separating portion at a high pressure during the time when the recording material P passes through the nip NP, and is blown at a low pressure at times other than the above time. Therefore, the leading edge of the recording material P is reliably separated and condensation is prevented. Further, when the rear end portion of the recording material P passes through the paper discharge portion, low-pressure air is sent to the paper discharge portion, so that the recording material is prevented from flapping.

1 is an overall view of an image forming apparatus incorporating a fixing device according to an embodiment of the present invention. 1 is a diagram illustrating a fixing device according to an embodiment of the present invention. It is a block diagram of a control system of air blowing. It is a graph which shows the pressure change of the air which ejects from the nozzle. It is a figure which shows the flow of the air in a paper discharge part. It is a figure which shows the other example of the fixing device which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating roller 2 Pressure roller 3 Heater 4 Separation member 5 Nozzle 20 Control means 21 Compressor 22A, 22B Solenoid valve

Claims (4)

A heating member, a pressure member, and a blowing unit that blows air in the vicinity of a sheet discharge side of a nip formed by the heating member and the pressure member;
Fixing the toner image on the recording material by passing the recording material through the nip, and separating the recording material from the heating member by blowing air from the blowing means when the leading edge of the recording material passes through the nip. In the device
The fixing device is characterized in that the blowing means blows high-pressure air during the time when the leading edge of the recording material passes through the nip, and blows low-pressure air during the time other than the time. The control unit according to claim 1, further comprising: a control unit configured to control at least one of the air flow rate during the time period and the air flow rate other than the time period by controlling the air blowing unit. Fixing device. 3. The air blower according to claim 1 or 2, wherein the air blowing means controls at least one of the air flow rate at the time and the air flow rate at times other than the time by changing an area of the air blowing opening. The fixing device described. The fixing device according to claim 1, further comprising a heating unit that raises a temperature of air blown from the blowing unit.

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