JP2004013058A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the temperature of the end part of a heat roller is continuously raised, so that bearings made of resin that support the shaft of a heat roller are melted when small sized papers such as post cards or the like are continuously printed. <P>SOLUTION: A first thermistor 31 is positioned at the center section of a heat roller 7, while a second thermistor 32 is positioned at the tip end section of the roller 7. When the temperature detected by the thermistor 32 is raised to a heating prohibiting temperature T1, a lamp heater 9 which heats the roller 7 is turned off, image forming operations are stopped and the roller 7 is cooled off. When the temperature detected by the thermistor 32 is reduced to a heating allowable temperature T2, the heater 9 is turned on and heating of the roller 7 is resumed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for fixing a toner image by heating and melting a toner image transferred onto a sheet by a heat roller.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, the surface of a photoconductor drum is charged by a charger, toner is superimposed on an electrostatic latent image on the surface of the photoconductor drum by an LED head, and a visible image is formed. And a recording material such as a sheet of paper or an OHP sheet is conveyed, and a potential having a polarity opposite to that of the toner is applied to the transfer roller. Then, the toner moves from the photosensitive drum to the paper in a uniform electric field formed between the photosensitive drum and the transfer roller, and the transfer is performed.
Then, the transferred paper is conveyed to a fixing device, where the paper is pressed toward a heat roller by a press roller, and the toner transferred onto the paper is heated and melted by the heat roller to be fixed.
[0003]
[Problems to be solved by the invention]
Here, the heat roller of the fixing device has a built-in heater, and a device that uniformly heats the heat roller in the width direction is often adopted. Therefore, the surface of the heat roller is set at a substantially uniform temperature in the width direction, and the toner image transferred onto the sheet is heated at a uniform temperature. The heat roller is provided with temperature detecting means for detecting the surface temperature of the heat roller, and the temperature of the heat roller surface is controlled to be constant based on the temperature detected by the temperature detecting means. The temperature detecting means is disposed substantially at the center of the heat roller.
The heat roller is formed so as to match the width of the sheet of the maximum size on which an image can be formed, and when a sheet of a size smaller than the width of the heat roller, for example, a sheet of postcard or the like passes, the heat roller is A portion where the paper abuts (paper passing portion) and a portion where the paper does not abut (non-paper passing portion) are generated on the surface of the heat roller. It has been done based on.
In this case, the heat is removed at the time of fixing the toner image in the paper passing portion of the heat roller, but the heat is not taken away by the paper in the non-paper passing portion. When the temperature control is performed based on the above, heat is accumulated at both ends of the heat roller which is a non-sheet passing portion, and the temperature rises.
As described above, when printing is continuously performed such that only the central portion of the heat roller comes into contact with the sheet, the both ends of the heat roller are abnormally heated, and the temperature is extremely increased. was there. In addition, there has been a problem that the resin bearing that supports the heat roller is damaged due to the temperature rise.
Conversely, if the position of the temperature detecting means does not come into contact with the sheet and the sheet passes through other portions, the sheet is fed to the heat roller (fixing device) at a temperature lower than the fixing temperature. In this case, the fixing property of the toner is deteriorated, and the paper is wasted.
Accordingly, an object of the present invention is to provide a temperature detecting unit in a non-sheet passing portion of a heat roller, separately from a temperature detecting unit provided in a sheet passing portion of a heat roller as in a conventional image forming apparatus, By detecting the temperature of the paper portion, the heating control of the heat roller is performed within a predetermined limit temperature (heating inhibition temperature).
[0004]
[Means for Solving the Problems]
The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.
That is, according to the first aspect of the present invention, there is provided an image forming apparatus for fixing a toner image by heating and melting a toner image transferred onto a sheet by a heat roller, and detecting a temperature of a non-sheet passing portion of the heat roller. When a temperature detection unit is provided, and when the detected temperature reaches a preset heating inhibition temperature, the heater for heating the heat roller is turned off and the image forming operation is stopped, and the detected temperature becomes the heating allowable temperature. In such a case, the heater is turned on.
[0005]
According to a second aspect, the suspension of the image forming operation is a suspension of sheet feeding.
[0006]
According to a third aspect of the present invention, the apparatus further comprises a second temperature detecting means for detecting a temperature of a sheet passing portion of the heat roller, and when the temperature detected by the second temperature detecting means reaches a preset target fixing temperature, This is to restart paper feeding.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of an image forming apparatus according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view of a multifunction peripheral adopting the present invention, FIG. 2 is a schematic block diagram showing the configuration of an image forming apparatus, FIG. 3 is a diagram showing the arrangement of first and second thermistors on a heat roller, and FIG. Is a timing chart of control by the controller.
[0008]
As shown in FIG. 1, a main body of a multifunction peripheral 1 having a facsimile function and a copy function according to the present invention is mounted and fixed on a paper feed cassette 5, and includes an image reading device 3 and The image forming apparatus 2 is arranged vertically.
An ADF device (automatic document feeder) 4 is attached above the image reading device 3, and an outer cover 6 is provided in front of the ADF device 4 (in the direction of arrow A in FIG. 1). She is being dressed.
[0009]
As shown in FIG. 2, a paper transport path 12 is formed inside the image forming apparatus 2, and along the paper transport path 12, a developing device 14, a photosensitive device 15, and a fixing device 16 are arranged rearward. Are located. The image forming apparatus 2 is configured by these devices, and transfers image information to a sheet taken in from the sheet feeding cassette 5 and performs fixing.
[0010]
The developing device 14 includes a toner chamber 19 that stores toner, a developing roller 20 that supplies toner to the photosensitive drum 22, and a supply roller 21 that supplies toner to the developing roller 20.
[0011]
The photosensitive device 15 includes a photosensitive drum 22 that contacts the sheet to transfer the toner, a transfer roller 17 that is disposed to face the photosensitive drum 22, and a charger 18 that negatively charges the surface of the photosensitive drum 22. It has. Above the photosensitive drum 22, an LED head 30 that is a light emitting body that forms an electrostatic latent image on the photosensitive drum 22 is arranged.
[0012]
The fixing device 16 includes a heat roller 7 and a press roller 8 arranged to face the heat roller 7, which will be described in detail later.
[0013]
At the downstream side of the fixing device 16 and at the end of the sheet transport path 12, a discharge roller 25 for feeding out a sheet onto a discharge tray 27 and a press roller 26 facing the discharge roller 25 are arranged.
[0014]
Next, the configuration of the fixing device 16 will be described with reference to FIGS.
The fixing device 16 is configured by a fixing heat roller system, and the heat roller 7 and the press roller 8 nip and convey the paper holding the toner image along the paper conveyance path 12 while applying heat and pressure. Fix the image to the paper.
[0015]
As shown in FIG. 2, the heat roller 7 and the press roller 8 are arranged to face each other with the sheet conveyance path 12 interposed therebetween. The hollow heat roller 7 is formed of a metal having good heat conductivity such as aluminum, and a lamp heater 9 such as a halogen lamp is inserted coaxially. The heat generated by turning on the lamp heater 9 is transmitted to the outer peripheral portion of the heat roller 7 to heat the heat roller 7. When the lamp heater 9 is turned off, the heat roller 7 is cooled by ambient air. However, the means for heating the heat roller 7 is not limited to a halogen lamp, but may be a hot cathode fluorescent lamp or the like. Further, in this embodiment, one lamp heater 9 is provided inside the heat roller 7, but a plurality of lamp heaters 9 may be provided.
[0016]
On the other hand, the press roller 8 is formed by press-fitting a rubber body made of silicon rubber, ethylene propylene rubber, or the like to a rotation shaft core so as to be relatively non-rotatable. Heated indirectly by
[0017]
As shown in FIG. 3, both ends of the heat roller 7 are rotatably supported by resin bearings 11 fixed to the main body frame 10. A first thermistor 31 as a temperature detecting means is provided in contact with the surface of the central portion (paper passing section) of the heat roller 7, and the temperature detected by the first thermistor 31 is transmitted to a controller 33 as a control means. Is output.
[0018]
When the detected temperature of the first thermistor 31 is lower than the preset target fixing temperature T3, the controller 33 energizes the lamp heater 9 to heat the heat roller 7, and the detected temperature of the first thermistor 31 becomes lower than the target fixing temperature T3. If it exceeds, the controller 33 cuts off the power of the lamp heater 9 and prohibits the heating of the heat roller 7. That is, when fixing the toner image on the sheet, the controller 33 controls the lamp heater 9 to turn on and off so that the surface temperature at the center of the heat roller 7 maintains the target fixing temperature T3.
[0019]
Further, a second thermistor 32 as a temperature detecting means different from the first thermistor 31 is provided in contact with the surface of one end of the heat roller 7 (in the vicinity of the bearing 11 at the non-sheet passing portion). The temperature detected by the controller 32 is also output to the controller 33. As described above, the temperature at the end of the heat roller 7 is measured when the narrow paper such as a postcard is printed continuously, and the temperature at the end is considerably higher than that at the center. This is for detecting a temperature difference (a temperature difference between an end portion and a center portion) due to a position on the heat roller 7 because it is conceivable. The second thermistor 32 may be arranged not only at one end of the heat roller 7 but also at both ends.
[0020]
When the temperature detected by the second thermistor 32 exceeds a preset heating inhibition temperature T1, the controller 33 turns off the lamp heater 9 and inhibits the heating of the heat roller 7. Thus, the heat roller 7 is no longer heated by the lamp heater 9, and the heat roller 7 is cooled by the ambient air, and its temperature decreases. Note that the heating inhibition temperature T1 is set lower than the heat resistant temperature of the resin of the bearing 11.
In addition to this, the controller 33 controls the paper feed clutch 24 that cuts off the transmission of the rotational power of the motor M to the paper feed roller 23 to cut off the transmission of power to the paper feed roller 23, The paper feed by the roller 23 is stopped. Thus, the image forming (printing) operation is stopped.
That is, the controller 33 permits the printing process if the temperature of the end portion of the heat roller 7 does not exceed the heating prohibition temperature T1, and prohibits the printing if it exceeds.
[0021]
FIG. 4 shows the change over time in the detected temperatures of the first and second thermistors 31 and 32 when printing continuously continuous paper such as a postcard having a smaller paper width than that of the standard A4 / B5 and the like. 4 shows a timing chart of the operation of the lamp heater 9 and the paper feed clutch 24 under the control of the control unit.
As shown in FIG. 4, during the printing operation, the controller 33 supplies power to the lamp heater 9 if the temperature at the center of the heat roller 7 is lower than the target fixing temperature T3, and the temperature at the center of the heat roller 7 becomes the target fixing temperature. If T3 is exceeded, the lamp heater 9 is turned off, and control is performed such that the temperature at the center of the heat roller 7 maintains the target fixing temperature T3. While the target fixing temperature T3 is maintained, the controller 33 turns on the paper feed clutch 24 and supplies the driving force of the motor M when the print trigger (one-shot pulse) is turned on and the start of printing is instructed. The paper is transmitted to the paper roller 23 and the paper in the paper feed cassette 5 is sent out to the developing device 14. During this time, the heat at the end of the heat roller 7 is not deprived by the paper passing therethrough, so the temperature at the end of the heat roller 7 rises above the target fixing temperature T3.
[0022]
When the temperature at the end of the heat roller 7 exceeds the heating prohibition temperature T1 as at time t1, the controller 33 shuts off the lamp heater 9 even if the temperature at the center of the heat roller 7 is lower than the target fixing temperature T3. The heating of the heat roller 7 is prohibited. Thereafter, the controller 33 cools the heat roller 7 without energizing the lamp heater until time t2 when the temperature at the end of the heat roller 7 becomes equal to or lower than the allowable heating temperature T2. In this manner, the temperature of the end of the heat roller 7 is suppressed to the heating inhibition temperature T1 or lower, so that the resin bearing 11 is not damaged.
[0023]
Further, even if the print trigger is turned on after time t1 (after the heating of the heat roller 7 is prohibited), the controller 33 continues to turn off the paper feed clutch 24 and feeds the paper in the paper feed cassette 5. Ban. This is because if the surface temperature of the heat roller 7 is equal to or lower than the target fixing temperature T3, good fixability cannot be obtained, so that paper feeding is prohibited and waste of paper and toner is prevented.
[0024]
Eventually, when the temperature at the end of the heat roller 7 becomes equal to or lower than the allowable heating temperature T2, the controller 33 energizes the lamp heater 9, and after the time t3 when the temperature at the center of the heat roller 7 reaches the target fixing temperature T3, this temperature is maintained. The energization to the lamp heater 9 is controlled so as to maintain T3.
[0025]
The controller 33 inhibits sheet feeding when the temperature at the end of the heat roller 7 is equal to or higher than the allowable heating temperature T2 and equal to or lower than the heating prohibition temperature T1, and when the temperature at the center of the heat roller 7 becomes close to the target fixing temperature T3. The paper feed clutch 24 is turned on in response to the print trigger being turned on, and the paper is sent to the developing device 14.
Thereafter, the controller 33 repeats the above-described operation control.
[0026]
Note that if the print trigger is turned on before time t4 (before the heating of the heat roller 7 is prohibited), even if the heating of the heat roller 7 is prohibited, the supply of the power to the print trigger on is prohibited. For the paper, the paper supply clutch 24 is turned on, the paper is sent to the developing device 14, and the image forming process is performed. Then, feeding of the next sheet is stopped. In this way, the state in which the sheet stops in the sheet transport path 12 does not occur.
[0027]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
More specifically, an image forming apparatus for fixing a toner image by heating and melting a toner image transferred onto a sheet by a heat roller as described in claim 1, wherein the temperature of a non-sheet passing portion of the heat roller is detected. When the detected temperature reaches a preset heating inhibition temperature, the heater for heating the heat roller is turned off and the image forming operation is stopped, and the detected temperature becomes the heating allowable temperature. In such a case, since the heater is turned on, an inappropriate rise in the temperature of the non-sheet passing portion of the heat roller can be suppressed near the heating prohibition temperature, and deterioration of the resin bearing that supports the heat roller can be prevented. .
[0028]
Since the image forming operation is stopped by stopping the sheet feeding, the sheet is not fed to the heat roller (fixing device) at a temperature lower than the fixing temperature, and the sheet is wasted. Can be reduced.
[0029]
According to a third aspect of the present invention, there is provided a second temperature detecting means for detecting a temperature of a sheet passing portion of the heat roller, and when a temperature detected by the second temperature detecting means reaches a preset target fixing temperature. Since the sheet feeding is restarted, the image forming process can be performed at a temperature of the heat roller suitable for fixing the toner, and the toner image can be reliably fixed on the sheet.
[Brief description of the drawings]
FIG. 1 is a perspective view of a multifunction peripheral that employs the present invention.
FIG. 2 is a schematic block diagram illustrating a configuration of an image forming apparatus.
FIG. 3 is a diagram showing an arrangement configuration of first and second thermistors on a heat roller.
FIG. 4 is a timing chart of control by a controller.
[Explanation of symbols]
2 Image forming apparatus 7 Heat roller 8 Press roller 9 Lamp heater 16 Fixing device 23 Feed roller 24 Feed clutch 31 First thermistor 32 Second thermistor 33 Controller

Claims (3)

An image forming apparatus for fixing a toner image by heating and melting a toner image transferred onto a sheet by a heat roller, comprising a temperature detecting unit for detecting a temperature of a non-sheet passing portion of the heat roller, and detecting the temperature. When the temperature reaches the preset heating prohibition temperature, the heater for heating the heat roller is turned off and the image forming operation is stopped, and when the detected temperature reaches the allowable heating temperature, the heater is turned on. An image forming apparatus, comprising: The image forming apparatus according to claim 1, wherein the stop of the image forming operation is a stop of sheet feeding. A second temperature detecting means for detecting the temperature of the paper passing portion of the heat roller is provided, and when the temperature detected by the second temperature detecting means reaches a preset target fixing temperature, paper feeding is restarted. The image forming apparatus according to claim 2, wherein:

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