JP2006030876A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a fixing member from being wound by curling and discharging a recording member in a direction opposite to the adhesive force of toner at a nip portion, thereby eliminating a time and a conveying distance for lowering the temperature of the toner, and reducing the temperature of the fixing belt. A fixing device without energy loss is provided.
A recording medium having a fixing belt stretched around a fixing roller and a pressure belt stretched around a pressure roller, and carrying a toner image in a nip formed by the fixing belt and the pressure belt. In the fixing device for fixing the toner image to the recording member by passing the member, the nip portion is formed by a plurality of fixing rollers and pressure rollers facing each other, and the plurality of fixing rollers and pressure rollers Means for displacing.
[Selection] Figure 2

Description

  The present invention relates to a fixing device for fixing a toner image on a recording member, and an image forming apparatus such as a laser beam printer, a digital copying machine, and a plain paper facsimile including the fixing device.

In a fixing device that fixes toner transferred to a sheet-like recording member such as paper and OHP by heating, there is a problem that the recording member is wound around the fixing belt and the fixing roller by the adhesive force of the toner. Therefore, in order to avoid this problem, conventionally, in a fixing device in which a fixing member made of a fixing belt is wound around a plurality of guide rollers and a pressure member made of a pressure roller is pressed against the fixing belt, the fixing belt is separated from the fixing belt. A technique for applying a mold is known.
However, various problems still remain when applying a release agent to the fixing belt. Therefore, in order to eliminate the need for the application of a release agent, the recording member that has passed through the nip portion between the fixing member composed of the fixing belt and the pressure member composed of the pressure roller is conveyed as it is in close contact with the fixing member. After the recording member passes between the fixing member and the conveying roller, the recording member is peeled off from the fixing member, and the surface linear velocity of the conveying roller and the surface linear velocity of the fixing member are made different. A method has been proposed. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 2003-076202

However, in the technique disclosed in Patent Document 1, first, the fixing belt and the recording member are in close contact with each other, and the temperature of the fixing belt also decreases as the toner temperature decreases. This takes time and energy, making it inefficient and uneconomical. In addition, a long transport distance is required until the toner temperature is lowered, which is disadvantageous in terms of layout.
Secondly, when double-sided printing or backing paper is used, there is a problem that the toner on the back side that has already been fixed melts and wraps around the pressure roller instead of the fixing belt instead of the front side. .
The present invention has been made in view of the above-described circumstances, and an object thereof is to prevent winding by the curl and discharge angle of the paper at the nip exit.
More specifically, by curling and discharging the recording member in the direction opposite to the adhesive force of the toner at the nip portion, the fixing member is prevented from being wound, and there is no need for a time and a conveying distance for lowering the toner temperature. It is an object of the present invention to provide a fixing device that does not lose energy due to a temperature drop.
In addition, when toner is also present on the back surface of the recording member such as double-sided printing or backing paper, the curling direction and the toner adhesive force may coincide with each other, which may cause winding. Therefore, the amount of toner on the back side of the paper is detected and compared with the amount of toner on the front side of the paper with an arithmetic unit, and the arrangement of the fixing roller and the pressure roller in the nip portion is changed according to the toner amount difference, and the discharge direction An object of the present invention is to provide an image forming apparatus capable of preventing winding by changing the curl direction and the curl amount.
Further, even if the nip shape is the same, the amount of curl varies depending on the thickness of the recording member. Therefore, the nip shape is determined by detecting the thickness of the recording member. To provide an image forming apparatus capable of preventing winding by changing the discharge direction, curl direction, and curl amount by changing the arrangement of the fixing roller and the pressure roller according to the thickness of the recording member. Objective.

In order to solve the above problems, a fixing device according to a first aspect of the present invention includes a fixing belt stretched around a fixing roller and a pressure belt stretched around a pressure roller, and the fixing belt And a fixing device for fixing the toner image to the recording member by passing the recording member carrying the toner image through the nip formed by the pressure belt, wherein the nip portion includes a plurality of fixing rollers and a plurality of pressures. The rollers are formed by facing each other one-on-one, and have displacement means for displacing the plurality of fixing rollers and pressure rollers.
An image forming apparatus according to a second aspect of the invention includes the fixing device according to the first aspect.
According to a third aspect of the present invention, there is provided an image forming apparatus according to the second aspect, further comprising: a detection unit that detects toner amount information on the back side of the recording member; an arithmetic unit that processes the detection information; and a control unit. The control means controls the displacement means according to information on the toner amount difference between the front surface and the back surface of the recording member to displace the plurality of fixing rollers and pressure rollers.
According to a fourth aspect of the present invention, in the second or third aspect, the recording member thickness detection unit and an arithmetic unit for processing the detection information are further provided, and the control unit is configured to perform the recording unit according to the thickness information of the recording member. A plurality of fixing rollers and pressure are displaced.

According to the present invention, since the nip shape is changed by displacing the arrangement of the plurality of fixing rollers and the pressure rollers, the discharge direction, the curl direction, and the curl amount of the recording member are changed. The winding of the member can be prevented.
Since the image forming apparatus of the present invention includes the fixing device described above, it is possible to prevent the recording member from being wrapped around the fixing device.
The image forming apparatus of the present invention has a detecting means for detecting toner image information on the back side of the recording member and an arithmetic unit for processing the toner image information, and detects toner amounts on the front side and the back side of the recording member. A comparison is made with an arithmetic unit, and the arrangement of the fixing roller and the pressure roller is displaced according to the assumed adhesive force of the toner to change the discharge direction, curl direction, and curl amount. Even during double-sided fixing, it is possible to completely prevent the recording member from being wrapped around the fixing device.
In the image forming apparatus of the present invention, the thickness of the recording member is detected, and the detection information is processed by the arithmetic unit to determine the optimum nip shape, and the arrangement of the fixing roller and the pressure roller is displaced to curl. Since the direction and the curl amount are changed, even when the recording member is thick paper, the winding of the recording member in the fixing device can be prevented without unnecessarily increasing the curl.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The monochrome printer shown in FIG. 1 includes an image forming unit 1 that forms a toner image on a recording member P such as paper or OHP, and a fixing device 2 that fixes the toner image on the recording member P. The image forming means 1 will be described below.
First, the drum-shaped photoconductor 3 is rotationally driven in a clockwise direction in FIG. 1 by a driving device (not shown), and the surface of the photoconductor 3 is uniformly charged to a predetermined polarity by the charging roller 4. A transfer belt 5 is disposed opposite to the photoreceptor 3, and the transfer belt 5 is stretched around a driving roller 6 and a driven roller 7 and is driven to rotate counterclockwise. A laser beam L that is light-modulated based on image forming information received from a PC (not shown) is irradiated from the laser writing unit 8 to the charging surface on the photosensitive member 3. As a result, an electrostatic latent image is formed on the photosensitive member 3, and the electrostatic latent image is visualized as a toner image by the developing device 9.
On the other hand, the recording member P is conveyed from the paper supply unit 10 by the conveyance roller 11. The recording member P is fed between the photosensitive member 3 and the transfer belt 5 as indicated by an arrow A, and is carried by the transfer belt 5 and conveyed. A transfer roller 12 is disposed at a position facing the photoconductor 3 across the transfer belt 5, and a voltage having a polarity opposite to the charging polarity of the toner on the photoconductor 3 is applied to the transfer roller 12. 3 is transferred onto the recording member P. The transfer residual toner that is not transferred to the recording member P and remains on the photosensitive member 3 is removed by the cleaning device 13. Then, the recording member P to which the unfixed toner image is transferred is sent to the fixing device 2 as indicated by an arrow B, and the toner image is fixed on the recording member P. The recording member P that has passed through the fixing device 2 is conveyed in the direction of arrow C and discharged onto a paper discharge tray (not shown). Control of each part is performed by a control means (not shown).

Next, the fixing device 2 according to the present invention will be described. FIG. 2 is an enlarged cross-sectional view of the fixing device 2 shown in FIG. Endless fixing belt 24 stretched between heating roller 21a, tension roller 22a and fixing rollers 23a, 23b, and 23c, and endless stretched between heating roller 21b, tension roller 22b, and pressure rollers 25a, 25b, and 25c The pressure belt 26 is rotationally driven in the directions of arrows E and F by driving devices (not shown). The tension rollers 22a and 22b tension the fixing belt 24 and the pressure belt 26 with appropriate tension by tension springs 27a and 27b, respectively.
The fixing rollers 23a, 23b, 23c and the pressure rollers 25a, 25b, 25c are respectively connected to electric actuators (displacement means) 29a, 29b, 29c, 29d, 29e via springs 28a, 28b, 28c, 28d, 28e, 28f. 29f are attached. The mechanism for displacing the fixing rollers 23a, 23b, and 23c and the pressure rollers 25a, 25b, and 25c may be an electric motor, a piezo element, or the like in addition to the electric actuator. Heaters 30a and 30b are arranged in the heating rollers 21a and 21b as heating sources for heating the heating rollers 21a and 21b, and the thermistors 31a and 31b as temperature detecting means are provided on the surfaces of the fixing belt 24 and the pressure belt 26. Is arranged. The thermistors 31a and 31b detect the temperatures of the surfaces of the fixing belt 24 and the pressure belt 26, and the heaters 30a and 30b are turned on and off by a temperature control circuit (not shown). Is maintained within a predetermined range suitable for fixing the toner image.
The unfixed toner image is transferred onto the recording member P by the heated fixing belt 24 and the pressure belt 26 at the nip N formed between the fixing rollers 23a, 23b, and 23c and the pressure rollers 25a, 25b, and 25c. To be established. At this time, the fixing rollers 23a, 23b, 23c and the pressure rollers 25a, 25b, 25c are connected to the electric actuators 29a, 29b, according to the amount of toner on the recording member P obtained from image forming information received from a PC (not shown). The shape (pressing force) of the nip N is determined by displacing with 29c, 29d, 29e, and 29f.
As an example of the shape of the nip N, when the amount of toner on the recording member P is small, the fixing rollers 23a, 23b, 23c and the pressure rollers 25a, 25b, 25c are arranged in parallel as shown in FIG. The member P is discharged straight in parallel with the arrow C. When the amount of toner on the recording member P is large, the fixing-side electric actuators 29a, 29b, and 29c are contracted and the pressure-side electric actuators 29d, 29e, and 29f are extended, thereby fixing rollers 23a, 23b, and 23c. The pressure rollers 25a, 25b, and 25c are arranged so that the pressure roller side bites into the fixing roller side as shown in FIG.
At this time, the electric actuators 29b and 29e are displaced more than the other electric actuators 29a, 29c and 29d, 29f, thereby bending the nip N. As a result, the recording member P curls to the pressure side and is discharged at an angle α inclined to the pressure side, so that the toner adhesive force generated between the fixing belt 24 and the recording member P is canceled, and the recording member P is fixed to the fixing belt 24. It is discharged without being wrapped around.

Next, a second embodiment of the present invention will be described. In recent years, a backing paper already printed on the back surface is sometimes used as a recording member due to environmental considerations. As shown in FIG. 5, the CCD 14 is disposed between the paper feeding unit 10 and the transfer belt 5 so as to face the back side of the recording member P (back side with respect to the fixing surface), and the toner amount information on the back side of the recording member P. Get. Further, toner amount information on the surface (fixing surface) of the recording member P is obtained from image forming information received from a PC (not shown). A central processing unit (not shown) calculates the toner amount difference between the back surface and the front surface of the recording member P, and moves the electric actuators 29a, 29b, 29c, 29d, 29e, 29f according to the toner amount difference, thereby Determine the shape.
For example, when the amount of toner on the surface is large, the fixing-side electric actuators 29a, 29b, and 29c are contracted, and the pressing-side electric actuators 29d, 29e, and 29f are extended to thereby fix the fixing rollers 23a, 23b, and 23c and the pressurizing rollers. The rollers 25a, 25b, and 25c are arranged such that the pressure roller side bites into the fixing roller side as shown in FIG. At this time, the electric actuators 29b and 29e are displaced more than the other electric actuators 29a, 29c, 29d, and 29f, so that the nip N is curved so that the fixing roller side is concave. Conversely, when the amount of toner on the back surface of the recording member is large, the electric actuators 29a, 29b, 29c on the fixing side are extended and the electric actuators 29d, 29e, 29f on the pressing side are contracted, so that the nip N is moved to the pressure roller side. Curve to be concave. The above mechanism is also effective when performing duplex printing.
Next, a third embodiment of the present invention will be described. In the third embodiment, as shown in FIG. 6, the thickness of the recording member P is detected by a thickness sensor 15 provided between the paper feeding unit and the transfer belt. The thicker the recording member P, the less likely it is to wind, and the more likely it is to curl. Therefore, the nip shape is changed according to the thickness of the recording member P. When the recording member P is thick, the fixing rollers 23a, 23b and 23c and the pressure rollers 25a, 25b and 25c are arranged in parallel as shown in FIG. 3, and the recording member P is discharged straight in parallel with the arrow C. Conversely, when the recording member P is thin, the recording members P are curled and discharged at an inclined angle by displacing the electric actuators 29a, 29b, 29c, 29d, 29e, and 29f to curve the nip.

FIG. 3 is an explanatory diagram of an image forming apparatus including the fixing device of the present invention. FIG. 2 is an enlarged cross-sectional view of the fixing device shown in FIG. 1. FIG. 4 is an explanatory diagram for explaining an example of the shape of a nip N when the amount of toner on the recording member P is small. FIG. 3 is an explanatory diagram for explaining an example of the shape of a nip N when the amount of toner on a recording member P is large. Explanatory drawing about 2nd Example of this invention. Explanatory drawing about 3rd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming means, 2 Fixing device, 3 Photoconductor, 4 Charging roller, 5 Transfer belt, 6 Driving roller, 7 Driven roller, 8 Laser writing unit, 9 Developing device, 10 Paper feed part, 11 Conveyance roller, 12 Transfer roller , 13 Cleaning device, 14 CCD, 15 Thickness sensor, 21a, 21b Heating roller, 22a, 22b Tension low, 23a-c Fixing roller, 24 Fixing belt, 25a-c Pressure roller, 26 Pressure belt, 27a, 27b Tension spring, 28a-f spring, 29a-f Electric actuator, 30a, 30b Heater, 31a, 31b Thermistor, A, B, C Transport direction, E, F Belt rotation direction, P recording member, L laser beam, N nip, α discharge angle

Claims (4)

  A fixing belt stretched around the fixing roller and a pressure belt stretched around the pressure roller are provided, and a recording member carrying a toner image is passed through a nip formed by the fixing belt and the pressure belt. Thus, in the fixing device for fixing the toner image to the recording member, the nip portion is formed by a plurality of fixing rollers and a plurality of pressure rollers facing each other one-to-one, and the plurality of fixing rollers and A fixing device having displacement means for displacing a pressure roller.   An image forming apparatus comprising the fixing device according to claim 1.   A detecting unit that detects toner amount information on the back side of the recording member; an arithmetic unit that processes the detection information; and a control unit. The image forming apparatus according to claim 2, wherein the plurality of fixing rollers and the pressure roller are displaced by controlling the displacement unit according to the above. The recording member thickness detecting means and an arithmetic device for processing the detected information are further provided, wherein the control means displaces the plurality of fixing rollers and pressure according to the recording member thickness information. The image forming apparatus according to claim 2.

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