JP2001092295A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device, capable of improving image quality and energy saving and preventing paper from being wrinkled. SOLUTION: This fixing device is provided with a fixing roller, having a heat source for fixing an unfixed image transferred to the paper by an image- forming device, and a pressure roller arranged to be opposed to the fixing roller and pressurized. In the device, pressure applied between the fixing roller and the pressure roller can be varied according to the number of sheets of consecutively passing paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed image on paper in an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses (copiers, laser printers, facsimile machines, etc.) include:
In order to fix a toner image on paper (transfer paper), a fixing device in which a fixing roller having a fixing heater (heat source) and a pressure roller are combined is provided. Generally, the fixing temperature control of such a fixing device is a temperature control that alternately supplies and non-supplies power to a heater before and after a reference set temperature (fixing temperature) necessary for fixing. There are known an off control method and a proportional control method in which the pulse width and the interval between pulses of a pulse signal for controlling the energization of the heater are changed proportionally as the temperature approaches the fixing temperature. A control method for compensating for the disadvantages of the on / off control method and the proportional control method is also well known. As such a control method, the fixing device is proportionally started by heating by full energization without turning on / off the heater. After launching straight to the point,
There is known a control method in which a necessary temperature for fixing is maintained by transitioning to a temperature necessary for fixing while maintaining thermal equilibrium by a proportional control method.

In such a fixing device, the fixing roller is maintained at a predetermined set temperature during standby (during warm-up), and then the sheet conveyed by the "copy start signal" is transferred to the fixing roller and the pressure roller. The toner image on the sheet is thermally fused by applying a pressure between the two. Here, since the heat of the fixing roller is transferred to the sheet during the fixing and is taken away, the temperature of the fixing roller temporarily drops to a temperature at which the fixing cannot be performed when continuous paper feeding is performed. It is possible. In particular, with the shortening of the warm-up time in recent years, the thickness of the fixing roller itself has been reduced, so that it is difficult to obtain the heat storage effect of the fixing roller, and if the temperature of the fixing roller is extremely lowered by continuous paper passing, While the fixing temperature is restored to the set temperature, there arises a problem that the copying operation cannot be performed. In order to shorten or eliminate such temperature recovery time and save energy, the amount of fixing supply heat per sheet in continuous paper passing is minimized.
Further, it is necessary to prevent a decrease in heat storage of the fixing roller by increasing the number of continuous sheets. For this reason, conventionally, the temperature of the fixing roller is sequentially detected, and the pressure applied to the sheet passing is controlled in accordance with the temperature transition of the fixing roller.

[0004] For example, Japanese Patent Application Laid-Open No. 57-79976 discloses a "heat roller fixing device" in which the pressurizing time is controlled by detecting the surface temperature of the fixing roller. That is, in this publication, the surrounding temperature of the fixing roller is detected, and the pressing force of the fixing device is controlled according to the detected temperature and the temperature fluctuation. When the surrounding temperature of the fixing roller decreases, the pressing force is increased. Let's deal with it. However,
In this publication example, particularly when a fixing roller having a small amount of heat storage is used with a thin fixing roller, if the fixing is in a state immediately after warm-up, heat is taken off by the pressure roller in a low temperature state, or during the paper passing, However, there is a problem that the temperature of the surface of the fixing roller changes due to the amount of heat taken by the sheet, which tends to cause an unstable state.

FIG. 16 is a diagram for explaining the temperature distribution of a conventional fixing roller. The temperature distribution of the fixing roller shown in FIG. 16 indicates a transition of a decrease in the surface temperature of the fixing roller. That is, in FIG. 2A, heat is taken from the fixing roller when the fixing roller rotates while being in contact with the pressure roller before the paper is conveyed to the paper feeding section and reaches the fixing section in FIG. The state at the time when the surface temperature of the pressure roller changes is shown immediately after warm-up, which is started from the room temperature state. FIG. 3B shows the temperature distribution of the surface temperature of the fixing roller maintained at the control temperature and in the state where the temperature of the pressure roller is high. Also,
FIG. 3C shows a temperature distribution in which the set temperature is raised from the “low power mode” in which the control temperature of the fixing roller is controlled to be low in order to save energy during standby.

Since the surface temperature of the fixing roller is not stable when the first copy is started by the copying operation, the method of detecting the temperature of the fixing roller and changing the pressing force is not shown in FIG. As shown in Fig. 16, when the surface temperature of the fixing roller is unstable, the pressing force of the fixing device changes drastically while the paper is being conveyed, which may cause problems such as wrinkling of the paper. Is desired.

[0007]

However, in the case of the above-described conventional fixing device, the heat storage effect is reduced due to the reduction in thickness of the fixing roller due to energy saving, so that the surface temperature of the fixing roller becomes unstable during continuous paper feeding. Therefore, there is a possibility that the temperature of the fixing roller during the sheet passing may be reduced, and this may cause a deterioration in image quality such as occurrence of fixing failure. Further, in the case of Japanese Patent Application Laid-Open No. 57-79976, only the ambient temperature of the fixing roller is used for pressure control as described above. The pressure control based on only the ambient temperature of the fixing roller is unreliable, especially when the paper is not plain paper but a different paper type such as tracing paper. May occur. In addition, when a long sheet is passed, the temperature of the fixing roller is reduced due to a longer time required to pass the paper in the fixing device, and deterioration of image quality such as defective fixing is particularly likely to occur. There's a problem. Furthermore, since the standby power is reduced in accordance with energy saving, when the power saving mode or the heat source off mode is set during the standby, the fixing roller and the pressure roller are in a cold state. In the state, the temperatures of the fixing roller and the pressure roller are increased. As a result, the temperature of the fixing roller and the temperature of the pressure roller become unstable, so that the pressure control becomes unstable, which also causes deterioration of image quality such as defective fixing.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional fixing device, and to switch and change the pressing force with respect to the sheet passing in advance according to the amount of temperature decrease of the fixing roller due to the number of sheets passing. Image quality (fixability)
Another object of the present invention is to provide a fixing device capable of improving energy saving and reducing paper wrinkles.

[0009]

According to an aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus. In a fixing device having a pressure roller disposed opposite to the fixing roller and being pressed, and in which a pressing force applied between the fixing roller and the pressure roller can be changed, continuous feeding of paper is performed. The pressure is switched according to the number of sheets.

The invention according to a second aspect is characterized in that, in the invention according to the first aspect, the pressing force is switched according to the continuous paper passing time or the paper passing distance.

According to a third aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus, and a pressing roller disposed opposite to the fixing roller and pressed. In a fixing device having a pressure roller and a variable pressure applied between the fixing roller and the pressure roller, the pressure is adjusted according to the number of continuous paper sheets, the continuous paper passing time or the paper passing distance. The pressure can be switched,
The present invention is characterized in that the amount of pressurizing force or the amount of pressurizing is varied according to the sheet size and the type of the sheet, and that a pressurizing control means for changing the timing is provided.

According to a fourth aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus, and a pressing roller disposed opposite to the fixing roller and pressed. A fixing roller having a pressure roller and capable of changing the pressure applied to the paper passing between the fixing roller and the pressure roller, in accordance with the number of continuous papers passed, the continuous paper passing time, or the paper passing distance. The pressure can be switched,
Detect the fixing roller temperature or the pressure roller temperature before passing the paper,
A fixing roller having a heat source for fixing an unfixed image transferred to a transfer sheet by an image forming apparatus by changing a switching amount of the pressing force based on the detected temperatures, and a fixing roller facing the fixing roller. And a pressure roller having a pressure roller arranged in a manner such that the pressure applied to the paper passing between the fixing roller and the pressure roller is variable. Is switched.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the fixing device of the present invention will be described in detail with reference to the drawings. Here, FIG. 1 is a configuration diagram of an embodiment of a digital copying machine equipped with a fixing device of the present invention, and FIG. 2 is a perspective view illustrating a configuration of an automatic document feeder. FIG. 3 is a perspective view showing an arrangement state of the document size detection sensor with respect to the contact glass, and FIG. 4 is a perspective view showing a configuration of the document size detection sensor. FIG. 5 is a perspective view showing a configuration of each tray, and FIG. 6 is a block diagram showing a control system of the digital copying machine. FIG. 7 is an overall block diagram showing the configuration of an image processing circuit in a digital copying machine, and FIG. 8 is a perspective view showing the configuration of a fixing device.

As shown in FIG. 1, the digital copying machine has a copying machine main body 1, an automatic document feeder (ADF) 100, and a paper feed unit 300. The originals stacked thereon are fed one by one onto a contact glass 10 on the copying machine main body 1 side, and are discharged onto a discharge tray 105 after reading the image data. The document placed on the document feeder 101 is aligned in the width direction of the paper by a side fence (not shown).
The document is separated from the lowermost document by the paper feed roller 102 and fed, and is conveyed onto the contact glass 10 by the conveyance belt 103. Further, the feeding unit 107 is provided with a document width detection sensor 118 and a document length detection sensor 119, and the document size (B5, A4) of the document conveyed from the automatic document feeder 100 by these detection sensors 118, 119 is provided. , B4) can be detected. Then, the document on the contact glass 10 is conveyed to the transport belt 103 after reading of the image data is completed.
Then, the paper is discharged onto the paper discharge tray 105 by the paper discharge roller 104, and a series of operations is completed.

At the time of double-sided copying, the original is fed by the feed roller 102, passes over the contact glass 10 by the conveyor belt 103, is inverted by the inversion claw 106, and is again fed onto the contact glass 10, The back side of the document is read. Next, after reading the back surface of the document on the contact glass 10, the document is conveyed by the conveyance belt 103, is inverted by the reversing claw 106, is conveyed again to the contact glass 10, and the front surface of the document is read. Then, the original after both sides of the original have been read is discharged onto the discharge tray 105 by the transport belt 103 and the discharge rollers 104.

As shown in FIG. 2, the automatic document feeder 100
Is opened and closed about hinges 81, 82 provided on the left and right sides, and a nail is provided on the upper surface of the copying machine main body 1 near the hinge 81.
The claw 83 is inserted into a hole 84 formed on the lower surface of the automatic document feeder 100 at the opposing position when the automatic document feeder 100 is closed. Inside the automatic document feeder 100 adjacent to the hole 84, there are provided a lift-up detection sensor 85 and a document detection timing sensor 86 for detecting the presence or absence of a claw 83 inserted through the hole 84. The lift-up detection sensor 85 detects the claw 83 when the automatic document feeder 100 is completely closed (lift-down) and turns on, and turns off when the automatic document feeder 100 is open (lift-up). Become. Here, the state in which the automatic document feeder 100 is completely closed is a state in which a part of the lower surface of the automatic document feeder 100 is in contact with the upper surface of the copying machine main body 1.

On the other hand, a document detection timing sensor 86 is provided for controlling the timing of detecting the size of the document on the contact glass 10 based on the detection results of the document size detection sensors 91 to 93 (see FIG. 3). When the opening angle of the automatic document feeder 100 falls within a predetermined angle, the claw 83 is detected and turned on. The predetermined angle is a slight angle, and when the automatic document feeder 100 is manually opened by the operator, the lift-up detection sensor 85 and the document detection timing sensor
Both 86s are turned off. Reference numerals 87 and 88 denote end-face scales for positioning the document.

As shown in FIG. 3, original size detection sensors 91 to 93 are arranged below the contact glass 10. As shown in FIG. 4, these original size detection sensors 91 to 93 disperse the light emitted from one light emitting diode 91a into three beams and irradiate the three beams with three light receiving elements 91b inside the optical system. Is a reflective sensor that receives light at
The tact glass 10 is seen through the optical system, and only the reflected light from the document surface is received to detect the presence or absence of the document. The document size detection sensors 91 to 93 are always operating, and each light receiving element 91b is turned on when a document on the contact glass 10 is detected, and is turned off when no document is detected. I have. Such a document size detection sensor 91
93 are arranged so as to correspond to various types of originals placed at predetermined positions on the contact glass 10, so that the presence / absence of an original set can be determined and various original sizes can be accurately detected. be able to.

Referring again to FIG. 1, the copying machine main body 1 has a scanner for reading a document, an image processing section, a plotter, and the like. The scanner has a contact glass 10 for placing a document thereon and an optical scanning system. The optical scanning system includes an exposure lamp 11, first, second, third mirrors 12, 13, and 14, a full-color CCD 16, and the like. . The exposure lamp 11 and the first mirror 12 are mounted on a first carriage, and the first carriage is moved in the sub-scanning direction at a constant speed by a stepping motor when reading a document. The second and third mirrors 13 and 14 are mounted on a second carriage, and the second carriage is moved by a stepping motor at approximately half the speed of the first carriage when reading a document. And
The image surface of the original is optically scanned by the movement of the first and second carriages, and the read data is imaged by the lens 15 on the light receiving surface of the full-color CCD 16 and photoelectrically converted.

Next, the image data photoelectrically converted into each of red (R), green (G), and blue (B) by the full-color CCD 16 is A / D-converted by an image processing circuit and then variously processed by an image processing unit 604. Image processing is performed. Then, as described later, at the time of copying, the image is copied onto a sheet by the writing unit 607. This writing unit includes a laser output unit 20, an fθ lens 21, and a mirror 22,
The laser output unit 20 has a laser diode (LD) as a laser light source, a polygon mirror and a polygon motor. The laser output unit 20 emits laser light of a black signal modulated according to an image read by a scanner at the time of copying, and forms a laser latent image on the photoconductor 30. Around the photoconductor 30, a black developing device 32, an LED writing unit 31 for writing a red signal image, a red developing device 33, a transfer device and a separator (not shown) are arranged.
The transfer device transfers the toner image formed on the photoconductor 30 to a sheet. The paper is supplied to the duplex unit 40 and the first tray 50 in the copying machine body 1 and the second
One of the tray 310, the third tray 320, and the fourth tray 330 is selected, and the sheet is fed by the feed roller 42, the separation roller 43, and the first, second, third, and fourth sheet feeding devices 51, 311, 321, and 331. . Note that, as shown in FIG.
The sheet size and the setting direction of the sheets set up to the tray 330 can be detected by a combination of the position adjustment of the size lever 400 and the on / off of the push switches 401 in a plurality.

On the other hand, the paper after front-side printing during double-sided printing is
The sheet is guided to the two-sided conveyance path 41 by the switching claw 57, is inverted by the feed roller 42 and the separation roller 43, and is accumulated (stocked) on the two-sided unit 40. The sheet in the double-sided unit 40 is raised by the tray and hits the feed roller 42, and is sent to the vertical transport unit 60 by the rotation of the feed roller 42 to form an image on the back surface. As shown in the circuit block diagram of FIG. 6, the operation unit controller 500 performs screen display control of the liquid crystal display of the scanning unit, lighting control of various LEDs, and various key input controls, and the system controller 501 (SCU) supplies power. It performs paper, conveyance, fixing, double-sided printing, process control, etc. For this reason, the system controller 501 is connected to the printer controller 506 (PCU) and input / output signal paths of various loads and various sensors. Further, the image processing controller 502 performs image control and scanner reading control, and the ADF controller 503 performs overall control of the automatic document feeder 100. A paper feed tray controller 504 controls the paper feed tray, and a facsimile controller 505.
Manages printer data reception and file management.

Hereinafter, the operation of the present embodiment will be described with reference to the flowcharts of FIGS. First, the original 600 on the contact glass 10 is illuminated by the exposure lamp 11,
This reflected light is read by the full-color CCD 16 as image data. Next, the analog image signal separated into each color of red (R), green (G), and blue (B) by the full-color CCD 16 is amplified by the signal processing circuit 601 and light quantity correction is performed. Further, the analog image signal is supplied to the A / D converter 60.
The image signal is converted into a digital image signal by 2, subjected to shading correction by a shading correction circuit 603, and transmitted to an image processing unit 604. The image processing unit 604 performs image quality processing such as MTF correction, γ correction, black image generation, color image generation, binary processing, and multi-value processing on the image data. Is the selector 605
Is output to In the selector 605, the image signal is changed by the scaling unit 606.
Alternatively, switching to send to the image memory controller 608 is performed. The scaling unit 606 scales up and down the image signal in accordance with the scaling factor and sends it to the writing unit 607. On the other hand, between the image memory controller 608 and the selector 605, an image signal can be input and output in both directions, and a CPU 609 for setting the image memory controller 608 and controlling a reading unit and a writing unit is provided. ROM 610 for storing the programs and data, and a RAM 611 for working. The CPU 609 writes and reads data in the image memory 612 via the image memory controller 608.

The image memory controller 608 compresses the input image data of the original by an internal image compression device or the like, and then sends it to the image memory 612. This image data compression allows the image memory 61 having a limited memory capacity to be used.
2 can be used effectively. Further, since it is possible to store a large amount of document image data at a time, it is possible to output the image of the stored document image data in page order. In this case, when outputting the image, the data in the image memory 612 is transferred to the image memory controller 6.
Output while performing decompression processing sequentially by the decompression device in 08. On the other hand, during “FAX transmission”, the selector 605 transfers the black data to the FAX image memory 613.
At the time of “FAX reception”, data received from the line is demodulated and decompressed, then expanded by the FAX image memory 613, and then output to the writing unit 607 by the selector 605 via the scaling unit 606. As described above, when the “printer data” is received, after the image data is expanded in the printer image memory 614, the image data is transmitted to the writing unit 607 by the selector 605.

As shown in FIG. 8, the fixing device 55 according to the present invention has a fixing roller 700 and a pressure roller 701 that is in pressure contact with the fixing roller 700. The fixing roller 700 has a surface PF.
It is coated with a heat-resistant release layer such as A, PTFE, etc., and a heat source 702 for heating is provided inside.
As the heat source 702, a halogen heater, an infrared heater (Nichrome wire), or the like is used. Further, temperature sensors 703 and 703 are provided on the surface portions of the fixing roller 700 and the pressure roller 701, respectively.
A heat source 702 is controlled based on the temperature detection signals from the temperature sensors 703 and 704 so that the temperatures of the fixing roller 700 and the pressure roller 701 become constant, and the transfer paper ( The pressure mechanism is controlled so that the nip width between the fixing roller 700 and the pressure roller 701 for controlling the amount of heat supplied to the sheet (paper) P can be changed. That is,
The fixing roller 700 is rotationally driven by a driving mechanism (not shown), and applies heat and pressure to the sheet P to perform a fixing process while conveying the sheet P in conjunction with the pressure roller 701.
The surface of the pressure roller 701 is made of a heat-resistant rubber layer such as silicon.

The pressure roller 701 is rotatably supported at both ends of the shaft, and is constantly urged in a direction away from the fixing roller 700 by urging means (not shown).
On the other hand, the pressure roller 701 is cantilevered from below the shaft by a pressure mechanism and is pressed against the lower side of the fixing roller 700. The pressurizing mechanism has a stepping motor 710. When the stepping motor 710 rotates forward (direction A), the driving force is transmitted from a gear 711 provided coaxially to a gear 713 via an idler gear 712. here,
A shaft 714 having a feed screw at the tip is connected to the gear 713, and the anchor 715 can be pulled in the horizontal direction (C direction). The end of a spring 716 is attached to the anchor 715, and the other end is attached to a link 717. Therefore, with the horizontal movement of the anchor 715, the link 717 rotates around the fulcrum 718. A substantially triangular lever 719 is fitted to one end of the link 717, and the lever 719 rotates around the fulcrum 720, so that the pressure roller 701 is pushed upward, thereby fixing the image. A pressing force is applied to the roller 700. on the other hand,
When the stepping motor 710 rotates in the reverse direction (direction B), the anchor 715 is pushed back in the horizontal direction (direction D), so that the lever 719 rotates downward around the fulcrum 720, and the pressure roller 701 is pulled down. Pressure is released. In addition, a home position detection unit 721 is provided below the anchor 715, and the home position detection unit 721 is turned on and off by a detection piece formed below the anchor 715. By adjusting the amount, the specified pressure can be applied to the pressure roller 701. Such a mechanism is provided on both sides of the pressure roller 701.

Hereinafter, functions and operations of each embodiment of the present invention will be described in detail. In the fixing device configured as described above, when the power is turned on, the heat source 702 generates heat and starts heating in the fixing roller 700, and the temperature sensors 703 and 704 determine the surface temperatures of the fixing roller 700 and the pressure roller 701. Start detection. Then, when the surface temperature of the fixing roller 700 and the pressure roller 701 reaches a temperature at which an unfixed image on the sheet P can be fixed, the warm-up is completed and copying is possible.

FIG. 9 shows a first embodiment of the present invention. First, in the first embodiment, the paper size (step S1) and paper type (step S2) of the paper are checked. Based on this check, the pressing force on one side of the sheet passing between the fixing roller and the pressure roller is switched and changed during continuous sheet feeding, and the number of continuous sheets N1, N2 and the pressing force P0, P1 at the time of the change. , P2 are each a “setting table”
Select according to That is, as shown in FIG. 10, the "setting table" stores the number of continuous sheets N1, N2 and the pressing force P0, P1, P2, for example, the pressing force P0, P1, P2.
100N, 150N, 200
N is a table set in advance. Also figure
As shown in Fig. 11, paper type A (thin paper), type B (thick paper)
For each of the paper sizes 1, 2, and 3 (for example, B5, A4, and B4) of the type C (tracing paper), the value of the continuous sheet number N1, N2 is a numerical value (for example, A
N1 is 30, 50, 10 for paper sizes 1, 2, 3 of (thin paper)
0, and N2 is 50, 100, and 150). Then, after the process of step S2, the pressing force is set to P0 (steps S3 and S3).
4, S5). In this case, the size of the paper is set to satisfy the relationship of size 1 <size 2 <size 3. Thereafter, continuous paper passing is started, and the number N of continuous paper passing is counted (step S6). Next, when the number of continuous paper sheets reaches N1, the pressing force is increased from P0 to P1 (steps S7, S8,
S9). Subsequently, when the number of continuous sheets reaches N1, the pressing force is changed from P1 to P2 (step S10). And
When the continuous paper feeding is completed by the copying operation, the set pressure returns to P0 (step S11).

Next, in the second embodiment of the present invention, the digital copying machine shown in FIG. 1 is configured such that long paper can be passed by a manual paper feed unit (not shown). in this case,
Even if only one long sheet is passed, the temperature of the fixing roller may drop when the sheet is passed, which may cause problems such as poor fixability. For this reason, in the case of the first embodiment, since the change control for switching the pressurizing force is performed according to the number of continuous sheets, the control may not be executed when one long sheet is passed. Therefore,
In the second embodiment, even when a long sheet is passed, the pressure is switched and the paper passing time is counted so as to control the change, and the pressure is applied to the fixing roller by the paper passing distance corresponding to the count. The change control is performed by switching the pressure applied to the paper passing between the pressure roller and the pressure roller.

FIG. 12 is a flowchart showing a processing procedure of the operation (continuous paper passing distance / pressure) of the second embodiment.
FIG. 13 is a diagram for explaining paper types, paper sizes, and continuous paper passing distances. As shown in FIG. 12, first, the paper size and the paper type are checked (steps S20 and S21), and then the continuous paper passing distances L1 and L2 and the pressure P0, P1, and P2 are each selected and determined. Next, the pressing force is set to P0 as an initial setting (steps S22, S23, S24). FIG. 10 shows the value of the one-sided pressure as the value of the pressure. Further, as shown in FIG. 13, paper types A (thin paper), type B (thick paper) and type C (tracing paper)
Paper size 1, 2, 3 (for example, B
5, A4, B4), the values of the continuous paper passing distances L1, L2 are set to the numerical values in the figure (for example, the paper size 1, A (thin paper)).
In 2 and 3, L1 is 3m, 5m and 10m, and L2 is
Are 5 m, 11 m, and 15 m).
Here, the paper size has a relationship of size 1> size 2> size 3. Continuous paper passing is started, and the paper passing distance is counted (step S25). When the paper passing distance reaches L1, the pressing force is increased from P0 to P1 (steps S26, S27, S28). Subsequently, the paper passing distance is L
When the pressure becomes 1, the pressure changes from P1 to P2 (step S29). Then, when the continuous paper passing is completed, the pressing force returns to P0 (step S30).

FIG. 14 is a flowchart showing the processing procedure of the operation of the third embodiment, and FIG. 15 is a diagram for explaining the temperatures and pressurizing forces of the fixing roller and the pressure roller. In the third embodiment of the present invention, various states such as a state started from the "low power mode" of energy saving, and a state in which fixing is maintained at the control temperature and the temperature of the pressure roller is high, etc. Corresponding to That is, in order to reduce standby power consumption by recently saving energy of the image output apparatus, the power supply is set to off during standby or the fixing control is controlled at a low temperature to reduce the power consumption. A reduced low power mode is employed. Therefore, the temperature of the fixing roller and the pressure roller at the time of starting continuous paper feeding may be the state immediately after warm-up started from room temperature state, the state started from low power mode during standby, or the control temperature In various states such as a state where the temperature of the pressure roller is high. In the third embodiment, the temperature of the fixing roller and the temperature of the pressure roller are detected before the start of sheet feeding,
The pressing force in the pressurization control is switched and changed based on the two detection states. As a result, it is possible to prevent image quality (fixing property) and occurrence of paper wrinkles.

As shown in FIG. 14, first, the paper size and paper type are checked (steps S40 and S41). After this check is completed, the temperatures of the fixing roller and the pressing force are detected before starting the sheet feeding (step S42). The number of continuous sheets N1, N2 for switching and changing the pressing force during continuous sheet feeding.
And the pressures P0, P1, P2 are determined (step S
43, S44). The pressing force is set to P0 as an initial setting (step S45). See Table 15 (a),
(b) shows the value of the pressing force on one side of the paper passing between the fixing roller and the pressure roller. Referring to FIG. 15 (a), three pressing roller temperatures T2 (T2 <50 ° C., 50 ° C. ≦ 50) with respect to the fixing roller temperature T1 (140 ° C. <T1> 160 ° C.).
T2 <100 ° C., 100 ° C. ≦ T2). Further, the pressures P0, P0 for each of these three pressure roller temperatures T2,
The continuous sheet number N for each of P1 and P2 is set. For example, when T2 <50 ° C., 100
N, 150N, 200N are indicated, and at 50 ° C ≦ T2 <100 ° C,
80 N, 120 N, and 160 N are set as the number of continuous sheets, and 10
When 0 ° C. ≦ T2, the number of continuous sheets 70N, 105N, and 400N is set.

In FIG. 15B, a temperature different from the fixing roller temperature T1 shown in FIG. 15A is set, and three pressure roller temperatures T2 are shown for this temperature. I have. Further, pressures P0, P1, and P2 are shown for each of the three pressure roller temperatures T2. Then, as shown in FIG. 12 described above, the values of the number N1, N2 of continuous paper passing are determined according to the type and size of the paper, and the continuous paper feeding is started, and as shown in FIG. The number of passed sheets is counted (step S46). The number of continuous paper passing is N1
Is reached, the pressure is increased from P0 to P1 (steps S47, S48, S49). Subsequently, when the number of continuous sheets passed reaches N2, the pressing force is changed from P1 to P2 (step S2).
50), when the continuous paper feeding is completed, the pressing force returns to P0 (step S51). Here, in the processing procedure of FIG. 14, the change control for switching the pressing force is performed according to the number of continuous sheets passed, but the change control for switching the pressing force according to the sheet passing distance shown in FIG. The temperature of the roller and the pressure roller may be detected, and the pressure may be more finely changed and controlled.

[0033]

The present invention is as described above. According to the first aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus; In a fixing device having a pressure roller that is disposed to face the roller and is pressed, a pressing force applied between the fixing roller and the pressure roller is variable.
Since the pressing force is switched according to the number of sheets continuously passed, the switching of the pressing force makes it possible to apply the necessary minimum amount of heat to the paper, thereby improving energy saving and fixing failure. This has the effect of preventing deterioration of image quality and generation of paper wrinkles during conveyance.

According to a second aspect of the present invention, in the first aspect of the present invention, since the pressing force is switched according to the continuous paper passing time or the paper passing distance of the paper, the paper passing time is counted, and The continuous length of the paper (paper passing distance) is read, and the pressure applied to the paper passing is switched and changed according to the paper passing distance, so that the minimum amount of heat required can be given to the paper. In addition to this, there is an effect that even when the long paper is a paper, it is possible to prevent a deterioration in image quality such as a fixing failure and the occurrence of paper wrinkles during conveyance.

According to a third aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus, and a pressing roller which is disposed opposite to the fixing roller and is pressurized. In a fixing device having a pressure roller and a variable pressure applied between the fixing roller and the pressure roller, the pressure is adjusted according to the number of continuous paper sheets, the continuous paper passing time or the paper passing distance. The pressure can be switched,
It has a pressure control means for varying the amount of pressurizing force or the amount of pressurization depending on the paper size and paper type of the paper, and has a pressure control means for changing the timing, so that it can be finely continuous according to the paper type and size of the paper. Since the pressing force during paper passing can be changed by switching, it is possible to apply the minimum required amount of heat to the paper, thereby improving energy saving and further preventing paper wrinkles during transportation. There is an effect that can be.

According to a fourth aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus, and a pressure roller disposed and opposed to the fixing roller. In a fixing device having a pressure roller and capable of changing the pressure applied to the paper passing between the fixing roller and the pressure roller, according to the number of continuous papers or the continuous paper passing time or the paper passing distance. The pressing force can be switched, and the fixing roller temperature or the pressure roller temperature before the paper passing is detected, and the amount of switching of the pressing force is changed based on these detected temperatures. The switching can be finely controlled, whereby the transition of the fixing temperature can be determined and the minimum amount of heat can be supplied, so that more effective energy saving can be achieved. Further, there is an effect that deterioration of image quality such as fixing failure and occurrence of paper wrinkles during conveyance can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an example of a digital copying machine equipped with a fixing device of the present invention.

FIG. 2 is a perspective view showing a configuration of the automatic document feeder.

FIG. 3 is a perspective view showing an arrangement state of the original size detection sensor.

FIG. 4 is a perspective view showing a configuration of the original size detection sensor.

FIG. 5 is a perspective view showing the configuration of the paper feed tray.

FIG. 6 is an overall block diagram showing a control system of the digital copying machine in the embodiment.

FIG. 7 is a block diagram illustrating a configuration of the image processing circuit.

FIG. 8 is a perspective view illustrating an internal configuration of the fixing device.

FIG. 9 is a flowchart illustrating a processing procedure according to the first embodiment.

FIG. 10 is a table showing a pressing force value on one side of a sheet.

FIG. 11 is a table showing values of the same paper type, paper size, and number of sheets passed.

FIG. 12 is a flowchart illustrating a processing procedure according to the second embodiment.

FIG. 13 is a table showing values of each paper type, paper size, and paper passing distance.

FIG. 14 is a flowchart illustrating a processing procedure according to the third embodiment.

15A is a table showing a relation value between the temperature of the fixing roller and the pressure roller and the pressing force at a low temperature when the temperature is high; FIG.

FIG. 16 is a diagram showing a conventional temperature distribution on the surface of a fixing roller.

[Explanation of symbols]

 1 Copier body 30 Photoconductor 50 First tray 55 Fixing device 86 Document detection timing sensor 91, 92, 93 Document size detection sensor 101 Document feeder 118 Document width detection sensor 119 Document length detection sensor 310 Second tray 320 3 tray 330 4th tray 501 System controller 502 Image processing controller 503 ADF controller 504 Feed tray controller 604 Image processing unit 608 Image memory controller 700 Fixing roller 701 Pressure roller 702 Heat source 703, 704 Temperature sensor 710 Stepping motor

Continued on front page F term (reference) 2H027 DA35 DA45 DC02 EA12 ED25 EF06 2H033 AA32 BA59 BB34 CA05 CA12 CA16 CA17 CA19 CA20 CA39

Claims (4)

[Claims] A fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus;
In a fixing device having a pressure roller which is disposed opposite to the fixing roller and is pressurized, and in which a pressing force applied between the fixing roller and the pressure roller is variable, continuous paper passage is performed. A fixing device, wherein the pressing force is switched according to the number of sheets. 2. The fixing device according to claim 1, wherein the pressing force is switched according to a continuous paper passing time or a paper passing distance of the paper. 3. A fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus;
In a fixing device having a pressure roller which is disposed opposite to the fixing roller and is pressurized, and in which a pressing force applied between the fixing roller and the pressure roller is variable, continuous paper passage is performed. The pressing force can be switched according to the number of paper sheets, the continuous paper passing time or the paper passing distance, and the amount of pressure or the amount of pressure can be changed according to the paper size and paper type of the paper, and the timing can be changed. A pressure control unit for performing the fixing operation. 4. A fixing roller having a heat source for fixing an unfixed image transferred to a sheet by an image forming apparatus;
In a fixing device having a pressure roller which is arranged opposite to the fixing roller and is pressurized, and in which a pressing force with respect to a paper passing between the fixing roller and the pressure roller is variable, continuous paper passage is performed. The pressing force can be switched according to the number of sheets, the continuous paper passing time or the paper passing distance, and the temperature of the fixing roller or the pressure roller before the paper is detected is detected, and the pressure is switched based on the detected temperatures. A fixing device wherein the amount is changed.